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Engine Electrical

Engine Electrical

MEMO

1 Chonan Technical Service Training Center

Engine Electrical

PrefaceAs the electric devices of the vehicles are the same with the nervous systems of the human body, any

malfunction of them will result to the defected vehicles. Therefore, it is necessary to understand the basic

knowledge about the electric devices.

Recently, the mechanical structure becomes to more complicate in order to protect the environments from

the harmful exhausted gases and especially, the most parts of vehicles are comprised of the new electric

devices for enhancing the performance of vehicles. Therefore, the scopes of the electrical knowledge to study

shall be more enlarged and more.

This book is composed of the engine electrical generals varying for these situations.


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Contents1. Battery

1.1 The Principle of the battery 7

1.2 Purpose of battery 7

1.3 The Kinds of the battery 8

1.4 The structure of the lead-acid battery and the charging and discharging operation 9

1.5 Various characteristics of the lead-acid battery 16

1.6 Life time of the lead-acid battery 20

1.7 Charge of the lead-acid battery 20

1.8 MF battery 24

2. Starting System

2.1 The principles and kinds of the DC motor 25

2.2 Start motor 29

2.3 Structure and operation of the start motor 30

2.4 Starting-system trouble diagnosis 42

3. Charging System

3.1 Purpose of the charging system 45

3.2 Single phase alternating current and 3-phase alternating current 45

3.3 Direct current alternator 48

3.4 Alternating current alternator 52

3.5 Alternator regulator 56

4. Ignition System

4.1 Purpose of ignition system 61

4.2 Computer control type ignition system 63

4.3 DLI (Distributor less Ignition) 75

4.4 Performance of the ignition system 80

5. The Micro 570 analyzer

5.1 Key pad 83


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5.2 Battery test procedures 83

5.3 Starter test procedures 85

5.4 Charging test procedures 86

MEMO


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1. Battery1.1 The Principle of the Battery

The Battery is an electrochemical device

converting a chemical energy to the electrical energy

through the chemical operations of the electricity. It

is classified into the primary cell and the secondary

cell.

1.1.1 The Primary Cell

When a copper plate and a zinc plate are put

into a dilute sulfuric acid solution, the zinc will be

melted by the sulfur to be zinc ion (Zn++) having the

positive (+) electricity, therefore, the negative (-)

electric charge will be collected to the zinc plate

side. And the hydrogen ion (H+) will move to the

copper plate from repulsing by the zinc ion.

Therefore, the hydrogen ion will give the positive (+)

charge to the copper plate, so the copper plate will

have the positive charge. Consequently, a voltage

difference will be occurred between the zinc plate

and the copper plate.

By connecting an external load (resistor)

between the copper plate and the zinc plate, an

electric current will flow from the copper plate to the

zinc plate through the external load. Using this

device, the chemical energy will be changed to the

electrical energy. For the primary cell, after it is

discharged at once, it is impossible to be recharged

again.

Fig. 1-1. The Principle of the Primary cell

1.1.2 The Secondary Cell

This type is generally called as the storage

battery. It can be recovered the battery function by

recharging after it is discharged. In the vehicles, this

secondary cell is mostly used. When electric loads

are connected to the battery terminals, a voltage will


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be generated by the chemical reaction between the

electrode plates and the electrolyte in the battery.

The storage battery, generally, is the lead-acid

battery in which the dilute sulfuric acid is used for

the electrolyte, the lead peroxide is used for the

positive plate (anode) and the pure lead is used for

the negative plate (cathode).

Fig. 1-2 The Principle of the Lead-acid Battery

1.2. Purpose of Battery

The battery can make the electrical energy from

the chemical energy in the materials used for the

electrode plates and the electrolyte (This is called

the discharging). It can also store the electrical

energy as the chemical energy (this called the

charging). The requirements for the battery are like

that.

It should be small in size and light in

weight, and it should have long lifetime.

It should be endure against the hard

vibrating conditions, and it should be easy to

control.

It should have large capacity and it should

have cheap cost.

The functions of the battery for the vehicle

shall satisfy the following conditions.

It should cover full electrical load capacity

of the operating devices.

When the alternator malfunctions, the

battery should be used for the electric source

during running of the vehicles.

It should control the balance between the

output of the alternator and the load according

to the running status.

However, the battery is not the main source of

the electric devices of the vehicles. It just has an

auxiliary role when the engine is started and when

the electric output of the alternator is smaller than

the output of the battery. Therefore, the most

required important role of the battery is to start the

engine with optimized condition.

1.3 The Kinds of the Battery

The battery used in the most vehicles is the

secondary cell (storage battery or galvanic battery)

possible to be charged and discharged of which

kinds are like the followings.

1.3.1 Lead-Acid Battery

This kind battery is comprised of the lead

peroxide (PbO2) as the positive (+) electrode

(anode) plate, the discharge lead (Pb) as the

negative electrode (cathode) plate and the dilute

sulfuric acid (H2SO4) as the electrolyte. The

advantages and disadvantages of this are like the

followings.


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(1) The advantages of the lead-acid battery

It is less dangerous than other types

because the chemical reaction of it occurs in

the room temperature.

It has high reliabilities and low cost

respectively.

(2) The disadvantages of the lead-acid battery

The energy density is about 40Wh/kgf,

lower than others.

It has shorter lifetime and longer charging

time than others do.

1.3.2 Alkali Battery (Ni-Cd Battery)

In the alkali battery, there are Ni-Fe battery and

Ni-Cd battery. The di-nickel-hydroxide [2NiO(OH)]

and iron (Fe) are used in Ni-Fe battery and the di-

nickel-hydroxide [2NiO(OH)] and cadmium (Cd) are

used in Ni-Cd battery as the anode (+) plate and the

cathode (-) plate, respectively. The potassium

hydroxide (KOH) is used for the electrolyte. The

electrolyte is only used for moving the electrons and

not used in the chemical reaction for charging and

discharging, so the specific gravity shall not be

changed almost. The case is made of the steel sheet

coated with nickel or the plastic.

The rated voltage is about 1.2V per cell, and

the voltage in the charging state is about 1.35V per

cell. The voltage will be decreased down to the 1.1V

at discharging operation, however, it will be

increased up to the 1.4~1.7V at charging operation.

The advantages and disadvantages of the alkali

battery are like the followings.

(1) The advantages of the alkali battery

It can endure under the hard working

conditions such as over charging, over

discharging and leaving for long times.

It has good high rate discharging

performances.

It has large output density.

It has long lifetime (10~20 years).

It has short charging time.

(2) The disadvantages of the alkali battery

It has low energy density, about

25~35Wh/kgf.

The cost of the metal used for the

electrode is so expensive.

It is hard to supply for mass product.

1.4 The structure of the lead-acid battery

and the charging and discharging

operation

1.4.1 The structure of the lead-acid battery

The basic compositions of the lead-acid battery

are the two kinds of metal electrode having the

different ionization characteristics each other and

the electrolyte in the case. There is an electric

voltage difference between the anode (+) and

cathode (-). As shown in Fig 1-3, when an electrical

load is connected between these electrodes, the

sequential electrical currents will flow from the (+)

electrode having the higher electrical voltage value


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to the (-) electrode having the lower electrical

voltage by occurring the chemical reaction between

the electrodes and the electrolyte.

Fig. 1-3. The basic schematic diagram of the

lead-acid battery

In the lead-acid battery used for the vehicles,

the lead peroxide (PbO2) is used for the anode, the

discharge lead (Pb) is used for the cathode and the

dilute sulfuric acid (H2SO4) solution is used for the

electrolyte. Actually, in order to get larger electrical

energy from smaller volume as possible, the area of

the electrode plates contacting with the electrolyte

should be as large as possible. To do so, the

electrode plate should be a plate group consisted of

the multiple thin metal plates in parallel. These plate

groups of anode and cathode electrodes are

installed facing each other.

Fig 1-4. The structure of the storage battery

(1) Electrode Plate

The electrode consists of an anode plate and a

cathode plate. They are made of lead peroxide and

discharge lead at the anode and cathode plate,

respectively after a paste of lead powder or lead

oxide powder with dilute sulfuric acid solution is

spread on a metal-alloyed grid plate, dried and

metamorphosed.

Fig. 1-5. Electrode Plate

The grid should be easy to treat, have a good

electrical conductivity and mechanical strength, be

compatible with the reacting materials and have

high resistance against the acid. Generally, the grid

is made of the alloy of lead (Pb) and antimony (Sb).

The lead peroxide, dark brown colored, is easily


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percolated by the electrolyte because it is porous,

however, it can be easily torn off from the plate

because it has weak bonding energy of the

molecules. The discharge lead, gray colored porous,

is not torn off from the grid because it has strong

bonding energy and reactivity, however, the particle

of the powder shall be grew up as the battery is

used so the porosity is reduced.

As the crystallized particles of the lead peroxide

are torn off from the plate or the porosity of the

negative plate is reduced, the capacity of the battery

is reduced; at last its lifetime will be terminated. The

anode plate is more activated so that the cathode

plate consists of one more plate in order to enhance

the capacity and protect the negative plate.

(2) Separator

The separators are inserted among the multiple

of the anode plates and the cathode plates to protect

the short of them. If the electrode plates are shorted

each other by damaged separator, then the electrical

energy charged in the battery will be leaked out.

The material of the separator is the reinforced

fiber made of resin, or the rubber or plastic having

tiny percolates. The grooved face of the separator is

facing to the anode electrode to protect the

corrosion by the lead peroxide and to accelerate the

diffusion of the electrolyte. The requirements of the

separator are like the followings.

It should be a nonconductor.

It should be porous to accelerate the

diffusion of the electrolyte.

It has good mechanical strength and

should not be corroded by the electrolyte easily.

It should not emit any harmful material

against the electrodes.

(3) Plate Group

The plate group is made by assembling the

multiple of electrodes and separators alternatively,

welding the electrode with connecting piece and

connecting to the terminal pole, the (+) terminal pole

for the anode plate and the (-) terminal pole for the

cathode plate.

The one plate group made by this method is

called the one cell. For the 12V storage battery,

there are six cells in one case connected by

connector in serial. Each cell can generate

electromotive force of 2.1~2.3V. As increasing the

number of cell, the surface area contacting with the

electrolyte is also increased, so the capacity of the

battery will be increased.

(4) Battery Case

The case is generally made of plastic resin.

For the 12V battery, the case is divided into 6

sectors for containing the six cells. At the bottom of

the each cell, there is an element rest to protect

from being shortage resulted from the slugs or

deposits of the reacting materials torn off from the

plates. Using a sodium carbonate and water or

ammonia water performs the cleaning for the case

and cover of the battery.


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Fig. 1-6. Plate group

(5) Cover & Vent plug

The cover is also made of plastic resin and

adhered to the case to secure from penetrating of air

or moisture. At the center of the cover, there are a

hole for injecting the electrolyte or distilled water and

inserting the spoid for measuring the specific gravity

or the thermometer, and a vent plug for closing this

hole. There is also a small hole near the vent plug to

emit the oxygen or hydrogen gases generated from

the inside of the battery. In the case of MF battery

recently used, there is no vent plug.

Fig. 1-7. The structure of the vent plug

(6) Electrolyte

The electrolyte is a dilute sulfuric acid solution

having the high degree of purity by mixing the

distilled water with sulfuric acid. The electrolyte

stores the electrical energy when the battery is

charged in which the electrolyte contacts with the

electrode plates, and it emits the electrical energy

when the battery is discharged. It also conducts the

electrical current in the cell. The specific gravity of

the electrolyte is bout 1.280 when the battery is fully

charged at 20 , and it is treated as the standard℃

value.

At the standard specific gravity, the conductivity of

the sulfur is the highest value. When the battery is

fully discharged, the specific gravity is about 1.050.

Actually, the electrolyte of battery has a lot higher

specific gravity than the standard value to increase

the electromotive force and to reduce the internal

resistance when the battery is discharged. The

manufacturing process of the electrolyte is like that.

The vessel should be insulator (such as

ebonite or plastic) when the electrolyte is

mixed.

The sulfuric acid is mixed into the distilled


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water slowly. The mixing ratio of distilled water

and sulfuric acid (1.400) is 60% and 40%.

The mixing should be performed slowly by

stirring with glass stick and then cooling.

Control the specific gravity of the

electrolyte as the 1.280 at 20 . ℃

1.4.2 The charge and discharge operation of

the lead-acid battery

To connect an electric load between (+) and (-)

terminal poles of the battery to flow the current is the

discharge. Reversely, to supply a current to the

battery by connecting the direct current source such

as recharges or alternator is the charge. When the

battery is charged or discharged, the anode (+) and

the cathode (-) plates and the electrolyte react

chemically. That is, the charge and discharge

operation of the battery is performed by the lead

peroxide of the anode plate, the discharge lead of

the cathode plate and the sulfuric acid solution of

the electrolyte. The chemical reaction of the charge

and discharge operation of the battery is like the

followings.

* The chemical reaction at the charge operation

Anode Electrolyte Cathode Anode Electrolyte CathodePbO2 + 2H2SO4 + Pb → PbSO4 + 2H2O + PbSO4

Lead peroxide

Dilute sulfuric acid

Discharge lead

Lead sulfate

Water Lead sulfate

* The chemical reaction at the discharge operation

Anode Electrolyte Cathode Anode Electrolyte CathodePbSO4 + 2H2O + PbSO4 → PbO2 + 2H2SO4 + Pb

Lead peroxide

Water Lead sulfate

Lead peroxide

Dilute sulfuric acid

Discharge lead

(1) Discharge of the Lead-Acid Battery

Fig. 1-8 The chemical reaction of the discharge operation


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The lead peroxide of the anode plate is

converted into water by which the oxygen in the lead

peroxide is combining with the hydrogen of the

sulfuric acid of the electrolyte. The lead in the lead

peroxide is combined with the sulfuric acid to form

the lead sulfate.

The discharge lead of the cathode is converted into

the lead sulfate as the anode. As the discharge is

progressing, the anode and the cathode are

converted into the lead sulfate and the electrolyte is

diluted more and more by the increasing water.

Therefore, the specific gravity of the electrolyte will

be lowered and the internal resistance of the battery

will be increased, so the current can not flow as time

goes.

A. Specific Gravity of Electrolyte and

Discharge status

The specific gravity of the electrolyte is

decreased proportional to the amount of the

discharge. The figure 1-9 shows the changes of the

specific gravity according to the discharged amount

from the 1.280, the value at the full charged status,

to the 1.080, the value at the full discharged status.

By measuring the specific gravity of the electrolyte, it

is possible to detect how much the battery is

discharged.

Fig. 1-9 The specific gravity of electrolyte

and the discharged amount of the battery

If the battery is left not using for a long time,

then the electrodes may be the lead sulfate

permanently or various defects can be occurred, so

the battery will not work any more.

If the specific gravity is 1.200 (20 ), the℃

battery should be recharged. If a battery is stored

for a long time, the battery should be recharged at

least one time for 15 days. The formula for acquiring

the amount of discharge from the specific gravity is

like following.

Specific Gravity at full charged - Specific Gravity at measuredDischarge Rate (%)= X 100

Specific Gravity at full charged - Specific Gravity at full discharged

B. Temperature conversion of the specific

gravity of electrolyte

The specific gravity of the electrolyte is

changed by the temperature. The reason is that the

volume of the sulfuric acid is shrunk or expanded by

the temperature, so the weight per unit volume is

changed. That is, if the temperature is increased,

the specific gravity of electrolyte will be decreased,


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and if the temperature is decreased, the specific

gravity of electrolyte will be increased. The variation

is 0.0007 per 1 . Therefore, when the charge and℃

discharge status is determined, the specific gravity

should be converted into the specific gravity at the

standard temperature (20 ). The specific gravity of℃

the standard temperature is acquired from the

following formula.

Fig. 1-10 The variations of the specific gravity

according to the temperature of electrolyte

S20 = St + 0.0007x(t-20)

Here, S20: Specific gravity converted at the standard temperature (20),

St: Specific gravity measured at the temperature of t℃

0.0007: Temperature coefficient

t: Temperature of electrolyte at measuring the specific gravity

C. Method for measuring the specific gravity of

electrolyte

The charging status of the battery can be

determined from the measuring the specific gravity

of electrolyte (because the specific gravity will be

lowered as the dilute sulfuric acid solution will be

changed into water). The kinds of devices for

measuring the specific gravity are suction type

gravimeter shown in the Fig. 1-11 and optical

refraction gravimeter shown in the Fig. 1-12. The

suction type gravimeter comprises of the rubber

bulb, the glass tube having a float and the suction

tube. To measure the specific gravity, open the vent

plug at the cover of battery, insert the suction tube

into the hole to suck the electrolyte, and read the

scale at the stopping position of the float. The

electrolyte surface contacting with the float is

convex by the surface tension of the electrolyte, so

the scale pointed by the convex portion should be

read.


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Fig. 1-11 The suction type gravimeter

Fig. 1-12 The Optical refraction gravimeter

For the optical refraction gravimeter, open the

light refraction cover, take some of electrolyte using

the measuring rod, paste it on the measuring glass,

close the refraction cover, turn the cover toward the

light side, see through the lens with leveling the

gravimeter, and read the scale pointing the boundary

between the dark side and the bright side.

(2) Charging in lead-acid battery

By flowing charging current to the discharged

battery from the external direct current source

(charger or alternator), the reaction material of the

anode and cathode dissolved into the lead sulfate

during the discharge operation will be changed into

the lead and sulfuric radicals.

The distilled water is dissolved into the oxygen

and hydrogen. The sulfuric radical dissolved from

the lead sulfate is combined with the hydrogen to

make the sulfuric acid finally it will resolve into the

sulfuric acid. Therefore, the density of the sulfuric

acid is increased and the specific gravity will be

increased, too. Then the anode plate is converted

into the lead peroxide and the cathode plate is

converted into the discharge lead. The figure 1-14

represents the curve showing the relationship

between the voltage and specific gravity of

electrolyte according to the charging time.


Rubber bulb

Lens (for magnifying

the measuring scale)

Measuring window

Electrolyte

Scale

Antifreeze

Float

Suction tube

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Fig. 1-13 Chemical changes during the charge operation

Fig. 1-14 Charging Characteristic Curve

A. Changes of terminal voltage

To charge the battery with constant current, the

voltage applied to the terminal shall be increased as

shown in Fig. 1-14. At the beginning of the charge

operation, the increasing curve of the voltage is

slack; however, at the end of the charge operation,

the curve will be increased sharply, so when the

voltage is reached at about 2.7V per cell and the


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terminal voltage of the 12V battery is reached at

about 16V, the voltage has the constant values. At

the end of the charge operation, the anode will

generate plentiful of oxygen and the cathode will

generate plentiful of hydrogen. These gases cover

the plates and then the internal resistance will be

increased. Therefore, in order to flow constant

current, the terminal voltage should be increased.

After the charge operation is completed, only the

distilled water is dissolved by electrolysis, so that the

amount of gases will be saturated and the voltage is

stabilized. The terminal voltage during charge

operation is like the following equation.

Et = Eo + Ic x r

Here, Et : Voltage applied to the

terminal,

Eo : Electromotive Force

Ic : Discharged current

r : Internal Resistance

As we know from the upper equation, when the

charge operation is performed at the lower

temperature in which the internal resistance is high,

the terminal voltage will be increased. This means

that the charge current will be reduced, as the

temperature is low, when the battery is charged with

constant current using a charger or alternator.

B. Charge the battery installed at the vehicle

The electric source for the battery installed at

the vehicle is an alternator controlled its output

voltage uniformly by the voltage regulator to charge

with uniform voltage. However, there are some

electro devices such as illuminators, wiper motor

and heater, so the alternator shall supply the

electric power to these devices and battery at the

same time when the vehicle is running. If the engine

is in the idling state, then the output of the alternator

will be reduced. Furthermore, if the electrical load is

higher than the output of the alternator, then the

battery will start to discharge for supplying an extra

electric power to the electric devices.

In this case, the amount of the charge and

discharge current will be decided by the discharging

state (remained electric capacity) and the other

conditions such as setting voltage, kinds of load,

running status and ambient temperature. When the

recharging device operates normally and the load is

not overloaded, if the vehicle is continued to drive,

then the battery will be charged and the average

recharging current will be reduced.

1.5 Various characteristics of the lead-

acid battery

1.5.1 Electromotive of the lead-acid battery

The electromotive of the lead-acid battery is

about 2.1~2.3V per cell and this varies according to

the specific gravity and temperature of the electrolyte

and the discharging status. The electromotive will be

reduced when the temperature of electrolyte is

lowered. The reason is that, at that time, the

chemical reaction in the battery will go slowly and

the resistance of the electrolyte will be increased.


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Fig. 1-15 Relationship between the electromotive

and the specific gravity of the electrolyte

Fig. 1-16 Relationship between the electromotive

and the temperature of the lectrolyte

1.5.2 Final voltage

The terminal voltage of the lead-acid battery will

decrease according to the progression of the

discharge because the internal resistance is

increased. At the limitation value, the terminal voltage

will be drop abruptly. If the discharge operation is

continued over this limitation value, then the voltage

will be too low to be used and the battery

performances will be degraded. This limitation value

is called the final voltage or the test end voltage.

The voltage drop-down of the battery, at the

starting of the discharge operation, is occurred by

the lead sulfate on the surface of the electrode

plate, which hinders the electrolyte from reacting

with the electrode plate. As the discharge is

continued, the lead sulfate will block the contacting

of the electrolyte to the electrode materials. At last,

the discharge is not performed. Therefore, the

voltage is dropped down abruptly.

The final voltage is different according to the

kind of the battery. Generally, it is 1.7 ~ 1.8(1.75) V

per cell and 10.5V (1.75 x 6) for the 12V battery.

Fig. 1-17 Discharging Curve of the lead-acid

battery

1.5.3 Capacity of the lead-acid battery

The battery capacity is the electrical capacity,

which can be discharged until the terminal voltage

reaches to the nominal final voltage when the fully

charged battery is continuously discharged with the

uniform current. The elements for deciding the

capacity are the size (or area), thickness and


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(Ampere Hour rate) represented by the following

equation.

Ampere Hour rate (AH) = Discharging current

(A) X Continuous Discharging time till Final

voltage (H)

(1) Relationship between the discharging rate

and the capacity

The discharging rate of battery is the amount of

discharging which influence to the battery capacity

directly. As the battery capacity is represented by the

discharging current X discharging time, the

discharging rate may be represented by the amount

of the discharged current (this is called as the current

rate), or the discharging time (this is called as the

time rate). Other methods for representing the battery

capacity are the 20-Hour rate capacity, 25-Ampere

rate and Cold discharge rate.

A. 20-Hour rate (or 10-hour rate) capacity

The 20-hour rate capacity is the total amount of

current, which can be discharged during 20 hours (for

10-Hour rate, during 10 hours) when the uniform

current is discharged continuously until the final

voltage of a cell reaches to 1.75V. This is used as the

typical discharging rate.

For example, the 20-Hour rate 100AH capacity

means that it needs 20 hours to discharge

continuously with 5A until reaching to the final

voltage.

Fig. 1-18 Discharge rate and battery capacity

The battery capacity will be reduced as easily

as it discharges with large current. The reason is

that the chemical reaction progresses faster than

the diffusion of the electrolyte so the required

sulfuric acid is not supplied enough to the electrode

when the battery is discharging with large current

(for example, at starting the engine). That is, when

the discharge operation performed with large

current, the amount of electrode material on the

surface is used for chemical reaction only, so the

capacity will be reduced. In this status, if the

discharge operation is stopped temporary, the

electrolyte can diffuse into the electrode, the

discharge operation can be recovered. This

capacity is called the surplus capacity. That the

using time for battery at starting engine is limited

within 10~15 seconds is respected to these

characteristics of chemical reaction of battery.

Table The discharge rate and the discharged current rate▶▶▶

Discharge Rate 20 Hours 10 Hours 5 Hours 3 Hours 1 Hour

Capacity (AH) 100 92 80 75 68


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Amount of Discharged Current (A) 5 9.2 16.0 25.0 68.0

Discharged current Rate 1.0 1.84 3.2 5.0 13.6

B. 25-Ampere Rate

The 25-Ampere rate is the time until a cell

reaches to the 1.75V when the battery is discharged

with uniform current (25A) at 26.6 .This represents℃

the performance of battery for supplying current to

the electro device when the alternator is malfunction.

C. Cold discharge rate

The cold discharge rate is the time that is

required until the voltage of a cell is dropdown to 1V

when the battery is discharged with 300A at -17.7 .℃

(2) Relationship between the temperature and the

capacity in the electrolyte

The battery capacity is mainly decided by the

temperature of electrolyte. That is, when the

discharge operation is performed with constant

discharging rate, if the temperature is high, then the

capacity is large however if the temperature is low,

then the capacity is small. Therefore, when the

capacity is represented the temperature should be

mentioned. At standard, the temperature is 25℃

(here, the standard temperature of electrolyte specific

gravity is 20 ). ℃

This relationship influences to the engine

starting in the winter season. The battery

performance is also regulated by this relationship. If

the electrolyte temperature is high, then the chemical

reaction will be progressing actively so the battery

capacity will be increased.

(3) The specific gravity of electrolyte and the

capacity

It is theoretically clear that the amount of sulfur

in the electrolyte is directly related to the capacity.

Furthermore, the capacity is varied by the amount

of the electrode material, amount of using rate and

the area, thickness and number of the electrode

plate. However, if the conditions of the electrode

material are the same, the capacity is decided by

the specific gravity of the electrolyte.

(4) Variations of capacity and voltage

according to the connection type of battery

A. For the serial connection

The serial connection is to connect the (+)

terminal of one battery to the (-) terminal of another

battery when two or more batteries having the same

capacity are connected each other. The voltage will

be increased as the number of connected batteries;

however the capacity is the same with one battery.

B. For the parallel connection

The parallel connection is to connect the (+)

terminals of two batteries and the (-) terminals of

two batteries, respectively each other. The capacity

is increased as the number of connected batteries;

however the voltage is the same with one battery. At

the start of the engine, if the starting is impossible

from the battery discharging operation, the extra

battery shall be connected for starting. At this time,

the extra battery should be connected parallel to the


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origin battery of vehicle.

[Example] if three batteries of 12V-100AH are connected in serial then they will be a battery of

36V-100AH; if they are connected in parallel then they will be a battery of 12V-300AH.

Fig. 1-19 The connecting type for batteries

1.5.4 Self-discharge of the lead-acid battery

The self-discharge is a phenomenon of which

the battery capacity is gradually reduced in nature

when the battery is left being not used. The reasons

for the self-discharge are like followings.

The material (discharge lead) of cathode

plate reacts with the sulfur and then it converted

into the lead sulfate and the hydrogen gases are

generated. - It is necessitated by its structure.

The foreign materials (lead (Pb), nickel (Ni)

or copper (Cu)) are flown into the electrolyte so

a localized cell is formed with the cathode plate

that the self-discharge will be progressed.

Additionally, another localized cell can be

formed between the grid and the anode material

(lead peroxide).

The torn off materials from the plate are

stacked at the bottom and side of the case, or

the separator would be damaged, so the

electrode plates may be shorted that the self-

discharge will be progressed.

The current leakage through the electrolyte

or dust adhered on the cover of the battery is

also one reason of self-discharge.

To take a care especially of the self-discharge

is the over discharge resulted from the self-

discharge by being left for a long time. If the battery

is over discharged, then the electrodes may be turn

into the lead sulfate permanently so the battery will

not be recovered.

The amount of the self-discharge is

represented by the percentage (%) about the

battery capacity Generally, it is 0.3~1.5% about the

actual capacity for 24 hours. The amount of self-

discharge is related to the followings.

The amount of the self-discharge will be

increased, as the temperature and specific

gravity of electrolyte and the battery capacity are


Engine Electrical

high. The figure 1-20 shows that the self-

discharge amount is varying to 1.6 at 1.280, and

to 0.6 at 1.200, in accordance that the amount is

1 at 1.240 (20 ) of specific gravity.℃Fig. 1-20 Specific Gravity and Self-discharge

The amount of self-discharge is increased

as the time is gone, but the rate is lowered, as

the time is gone after the charge operation is

performed.

The relationship between the temperature

and the self-discharge is like following table.

Table ▶▶▶ Electrolyte temperature, Self-discharging rate for 24-Hour and

Reduced amount of the specific gravity

Temperature( )℃ Self-discharging amount

(% per 24 hour)

Reduced amount of the specific

gravity (per 24hour)

30 1.0 0.002

20 0.5 0.001

5 0.25 0.0005

1.6 Life time of lead-acid battery

As the time is passing away, the battery

performance will be degraded, the battery capacity

will be reduced and the amount of discharge will be

increased so, at last, the battery will not be used any

more. The main factor for deciding the life time of

battery is the tearing off of materials from electrodes.

As the volume of these materials will enlarged or

reduced according to the progressing of charge and

discharge, the lead peroxide having the weak

bonding force will be torn off form the electrode

easily. The porosity of lead of the cathode is

degraded so it will be a cause of reducing the life

time. Furthermore, the temperature increasing

during charging and the carelessness of treatment

are also the reasons of reducing life time. The

reasons can be listed to the bellow.

The permanent transformation into the

lead sulfate of the electrode by the over

discharge or insufficient charge.

The increased temperature of electrolyte

by the over discharge.

The deterioration of the separators and

electrodes and the crack of the grid.


Engine Electrical

The exposure of the electrode by the lack

of electrolyte.

The specific gravity of electrolyte, which is

being too high or low.

The foreign materials flown into the

electrolyte.

The short or the tear off of electrodes in

the case.

1.7 Charge of lead-acid battery

1.7.1 Method for charging the lead-acid battery

The discharged battery should be charged with

the direct current (DC) so the charger rectifying the

alternating current should be used. Generally, the

charger is the silicon charger using the silicon (Si)

as a rectifier.

The figure 1-20 is the basic diagram of a

charger comprising of the transformer, the rectifier

and the voltage selection switch. In this figure, the

AC is a connector to the alternating current. There

are transformer and voltage selection switch for

output required DC voltage according to the amount

of the electric load connected to the DC terminal.

The transformed AC current is transferred to the

rectifier through the selection switch and then

rectified by the rectifying circuit consisting of 4

diodes to form into a single phase current. At (+) and

(-) terminal, a direct current for charging is output.

Fig. 1-20 The basic diagram of a charger

The connecting method for battery is to

connect the (+) terminal of the battery to the (+)

terminal of the charger and the (-) terminal of the

battery to the (-) terminal of the charger, and to

control the output voltage using the selection switch

according to the regulated current for the battery. To

charge the multiple of batteries using one charger at

the same time, there are the serial charging and the

parallel charging as shown in the Fig. 1-21.

Fig. 1-21 Method for connecting

batteries at charge operation

(1) Serial charging

The batteries having the same capacity are

connected as shown in the Fig. 1-21 (a) to charge at

the same time. In this case, the charging may

perform with the output current the same current for

one cell. However, as the same current is applied to

each battery, it is impossible to control the charge

current according to the discharged status of each


Engine Electrical

battery. For this method, the connectable battery

number is decided by the rated voltage of the

charger.

When the number of battery connectable to the

charger is decided, as the 2.7V is needed for one

cell of battery, for the 12V battery, the minimum

rated voltage of charger should be 16V. That is, for

the charger having the 75V of the maximum rated

voltage, in order to charge the 12V battery in serial

connection, the number of connectable battery is 4.

(2) Parallel charging

The plurality of batteries of which capacity or

discharged status is different is connected as shown

in Fig. 1-21 (b) to charge. At this time, the same

charging voltage is applied to the each individual

battery, so variable resistor should be attached to

supply different voltage according to the discharged

status. In this method, the charging may performed

with the output voltage having the same voltage of

one cell; however, the charging current is the

summation of the currents for each battery.

Therefore, the number of connectable battery is

decided by the rated current of the charger. In this

method, if there is no variable resistor, the charge in

parallel connection prefers not to be performed as

possible. Because the required current for charging

may be so large that the life time of battery will be

reduced quickly.

There are many methods for charging the

battery using the charger. The all currents for

charge operation are not used only for the charging.

There are some amounts of losing in current such

as the heat generated during charging process and

the gas generated by the electrolysis of distilled

water. Here, it is important problem how to reduce

the current loss. There are various methods for

charging operation such as the initial charge, the

maintenance charge, the recovery charge, and the

equalizing charge.

1.7.2 Initial charge

The initial charge is performed at first after the

battery is manufactured and the electrolyte is

supplied before it is used. The purpose of the initial

charge is to activate the cathode plate by resolving

the lead oxide or the lead carbide formed from the

reaction of the lead cathode with oxide or carbon in

the atmosphere, into the discharge lead again.

Recently, there is newly developed battery, which

can be used just after the electrolyte is supplied.

1.7.3 Maintenance charge

The maintenance charge is the charging

operation for supplement the consumed capacity by

the normal usage or the self-discharge. The battery

for vehicles can be supplemented the consumed

capacity at starting of the engine by the alternator

and regulator of alternator during running of the

vehicle. Furthermore, in the following conditions, the

discharged current is larger than the charged

amount, so the maintenance charge is also needed.

When the running time is too short to

perform the supplement enough.

When the charging amount by the running

of vehicle is not sufficient by the over discharge

or leakage current in the electric circuit.

When the charge operation is not

performed by the malfunction of the alternator

or regulator of the alternator, or by the defects

on the control.

There are two methods in the maintenance


Engine Electrical

charge, the normal charge in which the charging

time is relatively long, and the quick charge in

which the charging time is relatively short by using

large current. Furthermore, the normal charge is

classified into the constant current charge, the

constant voltage charge and the variable current

charge according to the charging condition.

(1) Constant current charge

This charging method is to charge with the

constant current from the starting to end of the

charge operation. The range of current is roughly

like that;

The standard charge current: 10% of the

battery capacity

The minimum charge current: 5% of the

battery capacity

The maximum charge current: 20% of

the battery capacity

And the charge characteristic in the constant

current charge is like that;

a. The terminal voltage during the charge

operation is increased sharply at the beginning

and it is increased slowly after that. And then, at

the near of 2.4V, it is increased sharply again,

and at the 2.6~2.7V, it is maintained with the

constant value.

b. The specific gravity of electrolyte is slowly

increased because it is not moved until the gas

is generated. When the gas is generated, it will

be increased sharply and then it maintained

with constant value at about 1.280.

c. If the voltage of a cell reaches at 2.3~2.4V after

the charge operation is started, a plentiful of

gas is generated. The reason is that the current

supplied after the full charging is completed is

used for the electrolysis of the distilled water. At

the anode (+) plate, the oxygen is generated

and the hydrogen is generated at the cathode

(-) plate. The status of gas generation during

charge operation is also used as the means for

deciding the completion of the charge

operation. Here, the hydrogen gas is

dangerous because it is explosive gas, so it

should be careful not to contact with any flame.

d. When the charge operation is completed, if the

specific gravity of electrolyte conversed to

20 is over 1.280, then more distilled water℃

should be supplied to control the specific

gravity to the 1.280.

Fig. 1-22 Characteristics of charge current and

voltage in the constant current charge

(2) Constant voltage charge

This method is to charge with constant voltage


Engine Electrical

over all charging process. The charge characteristic

is shown in Fig. 1-23; at the beginning of charge,

large current is applied. As charging time is gone,

the current will be decreased. At last, the current will

not be flown at the end of the charging. Therefore,

there is no gas generation, so the charge

performance is superior, however, the large current

may influence to reduce the life time.

Fig. 1-23 Characteristics of charge current and

voltage in the constant voltage charge.

(3) Variable current charge

This charge method is to charge with variable

current as the charge is progressed. In this method,

the charge efficiency is very high and the electrolyte

temperature is slowly increased. At the end of the

charge process, the current will be decreased, so it

is possible to reduce the current loss and to protect

damages from the gas generation.

(4) Quick charge

This method is generally used with a quick

charger when the charging time is not enough. As

the quick charge does not make chemical reactions

with deep portion of electrode material, the

maintenance charge should be performed after the

quick charge is completed.

Fig. 1-24 Quick charger


Engine Electrical

When the quick charge is performed, the

followings should be considered.

a. If user wants to perform quick charge in which

the battery is not removed from vehicle, the all

cable should be separated from the terminal

poles of (+) and (-). And then the clip of

charger is installed thereat (this is for

protecting the diode of alternator).

b. The charge current should be 50% of the

capacity even it is decided by the discharging

status of battery and charge time.

c. The quick charge should be performed within a

short time as possible.

d. If the electrolyte temperature is over 45 , the℃

charge current should be reduced or the

charge operation should be delayed and

continued after the temperature is lowered

1.7.4 Recovery charge

The recovery charge is for recovering the

electrode plate surface, which is sulfated by the

continued discharge operation. This is performed by

the constant current charge and with small current

for 40~50 hours. And then, this charged amount

should be re-discharged and re-charged it again

with the same manner. This process is performed

some times.

1.7.5 Equalizing charge

The equalizing charge is performed when the

specific gravity of each cell’s electrolyte is not same.

This is for equalizing the specific gravity of

electrolyte in each cell by increasing the current up

to 20~25% of normal current and performing the

overcharging. This uses the constant current

charge.

1.7.6 Cautions for charging battery

The place in which the charge operation is

performed should have ventilation system.

The discharged battery should not be left

without use but be performed by the

maintenance charge.

The electrolyte temperature should not be

over 45 . ℃

The battery, which is processing the

charge operation, should not be closed to any

flame.

The battery should not be over charged

because the anode (+) plate of the over-

charged battery will be oxide.

When two more batteries are charged at

the same time, they should be charged in

serial connection.

The charger and the battery should not be

connected reversibly.

A counteractive material such as

ammonia water or sodium carbonate should be

prepared.

All vent plug of each cell should be


Engine Electrical

opened.

1.8 MF battery

The MF (Maintenance Free) battery is also

lead-acid battery developed normal battery to

protect the electrolyte from being reduced by the

gas generated at self-discharge or chemical

reaction, and to reduce the check and maintenance

process. The main features are like that;

It is not necessary to check or replace the

distilled water.

The self-discharge rate is very low.

It can be stored for a long time.

The typical differences between the MF battery

and normal battery are the material, manufacturing

method and shape of the grid. The material of the

grid is the alloy of lead-antimony having less

antimony (Sb) or the alloy of lead-calcium. The

antimony, used for the grid of normal battery, is for

enhancing the mechanical strength of grid and

making the manufacturing process to be easy. It can

be extracted from the electrode surface so that a

localized battery is formed. And then, the self-

discharge may be accelerated and the charge

voltage shall be reduced. When the constant

voltage charge is used in vehicles, the charge

current will be increased gradually so that the

electrolysis of the distilled water will be more

activated. To prevent these phenomena, if the MF

battery is made of alloy including less antimony or

lead-calcium alloy, then the reducing electrolyte and

self-discharge will be prevented. The manufacturing

method for the grid is to make iron grid plate by a

mechanical process such as punching a steel

sheet, so the quality and productivity are enhanced.

By adopting a catalyst plug for resolving the oxygen

and hydrogen gases to the distilled water again, it is

not necessary to supplement the distilled water.

Fig. 1-25 Structure of catalyst plug

2. Starting SystemThe vehicle engine operates with the four

strokes including intake stroke, compression stroke,

explosion stroke and exhaust stroke. Among them,

the energy for moving is generated at the explosion

stroke only, and this energy is transformed to the


Engine Electrical

flywheel and output through the continuous

rotational movement by the inertia force of the

flywheel. At the starting of the engine, the force

needed for the initial intake and compression strokes

should be supplied externally to rotate the

crankshaft. At this time, the battery, the starting

motor, the ignition switch and the wiring are needed.

Fig. 2-1 Starting Circuit Diagram

2.1 The Principles and Kinds of the DC

Motor

2.1.1 The principles of the DC motor

As shown in Fig. 2-2, after a conductor

(armature) which can be freely rotate in the

magnetic field is installed, a commutator for

supplying the current source is installed, a brush

contacting to the commutator to supply the current

to the conductor is attached and then the current is

applied, a force is generated to a direction

according to the Fleming's left hand law. At that

time, the current is flowing from the conductor A to

the conductor B (Refer to Fig. 2-3). Therefore, the

conductor A near the N pole has the force to

downward direction, and the conductor B near the S

pole has the force to upward direction. So, it will

rotate in left turn. This generated rotational force is

proportional to the multiplication of the strength of

the magnetic field and current flowing through the

conductor. Considering the situation after the

conductor rotates 180 degree, the conductor A and

B are located in the reversed position. Therefore,

the rotation direction will be reversed, so it can not

rotate continuously. In order to prevent this conflict,

the supplying direction of the current should be

maintained in the one direction about the magnetic

field so that the rotation direction is not reversed.

Fig. 2-2 The principle of motor


Engine Electrical

Fig. 2-3 The force activated to the armature

The electromagnetic force applied to the

armature located in the magnetic field, when a DC

current is applied to the armature thorugh the brush

and commutator, will be described using the Figs. 2-

3 (a), (b) and (c).

Case of figure (a): As the current is flown from

the coil B of armature to the coil A, the

electromagnetic force at the coil A is applied to

upward and that of coil B is applied to downward.

Therefore, the armature will rotate in left (counter-

clockwise) direction.

Case of figure (b): When the armature turns

90 degrees to the center of coil, the current is not

flown through the armature. However, the armature

continues to rotate by the inertia of its moving.

Case of figure (c): As the armature is rotating,

the coil A and coil B are located in reversed position

about the figure (a). However, the direction of

current is not changed by the brush, so the direction

of electromagnetic force is the same with the figure

(a) even while the current is flown from the coil A to

the coil B. Therefore, the armature will be rotating in

left (counter-clockwise) direction continuously.

2.1.2 The Kinds of Direct Current motor

According to the connecting method between

the armature coil and the field (yoke) coil, the series

winding type, the shunt winding type, and the

compound winding type are used for the direct

current motor comprising of armature coil, field

(yoke) coil, commutator and brush. Recently, the

permanent magnetic type is also used.

(1) Series winding type motor

This type is that the armature coil and the field

(yoke) coil are connected in serial. The constant

current flows through each coil. The feature of this

type is that it can make large rotational force but not

make over current at high load because the rotation

speed can be controlled automatically according to

the variation of the load. However, without load, the

rotation speed will be very high so that the motor

should be treated no to be damaged. Due to that,

this type is used for the starting motor. The

characteristic of this type is like that;


Engine Electrical

Fig. 2-4 Electric diagram of

the series winding dc motor

A. Characteristic of relationship between the

armature current and rotation force

The rotation force of the motor is proportional

to the multiplying of the armature current and the

strength of the magnetic field. The strength of the

magnetic field is decided by the yoke current and

the armature current. The character graph is shown

in figure 2-5. As the armature current is high, the

rotation force will be increased.

B. Characteristic of relationship between the

armature current and speed

The armature current is reversely proportional

to the reverse electromotive force made by the

motor. The reverse electromotive force is

proportional to the speed of the motor. Therefore,

the armature current is reversely proportional to the

speed. The character graph is shown in figure 2-5.

As shown in the graph, when the speed is low, that

is, the load is high, the rotation force is high because

of the increased armature current, and so the series

winding dc motor is generally used for starting

motor.

Fig. 2-5 Characteristic graph of

each type of dc motor

(2) Shunt winding type motor

This type is that the armature coil and the field

coil are connected in parallel. The source voltage is

applied at each coil. According to the current flown

through the field coil, the rotation speed can be

controlled with the wide range easily. It can be used


Engine Electrical

for the motor of constant speed operation in which

the rotation speed is not changed when the load is

varied, or for the motor of acceleration or

deceleration in which the rotation speed is varied by

the yoke current. This motor is used for the window

washer, cooling fan, power window, and so on.

Fig 2-6 Electric diagram of

the shunt winding dc motor

A. Characteristic of relationship between the

armature current and rotation force

Like the series winding type, the rotation force

is proportional to the multiplying of the armature

current and the yoke field strength. However, the

strength of the magnetic field can not be changed in

this type, so the characteristic graph will be as

shown in Fig 2-5. That is, as the armature current is

large (the load is high), the rotation force is

increased, but the increased ratio is less than that

of series winding type.

B. Characteristic of relationship between the

armature current and speed

The rotation speed of the motor is proportional

to the voltage and reversely proportional to the field

yoke strength. Therefore, when the power source is

the battery, the voltage is constant and the yoke

field is not changed. Consequently, when the

armature current is increased, the voltage is

lowered little but the rotation speed is almost

constant, as shown in figure 2-5.

(3) Compound winding type motor

This type is that the armature coil and one field

coil are connected in serial and these are connected

another field coil in parallel. The pole directions of

these two field coils are the same. This type shows

the neutral characteristic of the series winding type

and the shunt winding type.

That is, when the motor is starting, it has large

rotating force like the series winding type. After it is

started, it has constant rotation speed like the shunt

winding type. So, it has more complicated structure

than series winding type. This type is used for

windshield wiper motor.

Fig. 2-7 Electric diagram of

the compound winding dc motor

(4) Permanent magnetic motor

The ferrite magnet is the permanent magnet


Engine Electrical

made by pressing an oxide powder including barium

and iron and sintering at high temperature. The main

feature of it is light and to have a strong magnetic

force. This magnet is served as the field york coil

and pole core. In this case, the current is only

supplied to the armature coil, so if the direction of

current is changed then the rotation direction is also

changed. The reason is that the pole direction of the

ferrite magnet is not changed; however, pole

direction of the armature, the electromagnet, can be

changed according to the direction of the current.

This type is used for wind shield wiper motor, servo

motor for controlling the idling speed of the ECU

engine, step motor, fuel pump and so on.

Fig. 2-8 Electric diagram of the permanent

magnetic motor

2.2 Start motor

Nowadays, the most vehicle engine uses the

series winding type motor of which source is battery,

for the start motor. The series winding type motor

generates the low speed and large force with a load.

When the load is reduced, the rotating force is

decreased but the rotation speed is increased. That

is, the rotation speed will be remarkably varied. The

start motor should generate the rotation force,

which can be against the compressing force of the

engine cylinder and the frictional force of all parts,

so the rotation force should be large. The most

suitable type for these requirements is the series

winding type motor, therefore the required condition

is like that;


Engine Electrical

The rotational force for starting should be

large.

It should be small and light as possible

and have large output.

It should be operated with small current

capacity.

It should endure against vibrations.

It should endure against mechanical

shocks.

2.2.1 Rotation force for starting

The required rotation force and speed of the start

motor for starting of the engine depends on the kind

of engine (cylinder volume, compression ratio, and

ignition type) or temperature (ambient temperature

or lubricant oil temperature). The starting

performance is mainly affected by the status of

battery, the electrical source. Therefore, when the

starting performance is concerned, the requirement

for engine, characteristic of the start motor and

performance of battery should be included. The

rotational resistance of the engine is decided by the

forces needed for compressing the air and fuel

mixture in the cylinder and the frictional forces of the

cylinder, the piston ring, each bearing and gear.

When the engine is starting, the rotation force

needed that the start motor rotates the crank shaft

against the rotational resistance is called as the

starting rotation force. The starting rotation force of

start motor can be increased by enlarging the ratio

between the flywheel ring gear and the pinion gear

(to about 10~15:1). This ratio can be acquired by

following equation. This starting rotation force will

be large as the cylinder volume or the compression

ratio is large as well as it shall be affected by the

ambient temperature.

2.2.2 Initial rpm for engine starting

To start engine, the rotation speed and force

should be larger than those for rotating the

crankshaft. If the rotation speed is too low, then the

compressed gas between the cylinder and piston

will be leaked, so the compression pressure for

starting can not be acquired. For gasoline engine, if

the voltage supplied to the ignition coil is too low,

then the ignition shall be failed. For diesel engine, if

the adiabatic compression is not sufficiently

performed, then the temperature for igniting the fuel

shall not be acquired. The lowest limitation value of

speed of rotation for engine starting is called the

minimum starting rotation speed.

This rotation speed of diesel engine is little

larger than that of gasoline engine. Generally, the

minimum rotation speed will be large as the

temperature is high. It is also varied according to

the cylinder number, cycle number, shape of

combustion chamber, ignition type and so on.

For the 2-cylce engine, the minimum starting

rotation speed is about 150~200 rpm at -15 . For℃

the 4-cycle engine, it is more than 100rpm for the

gasoline engine, or 180 rpm for the diesel engine.

(Rotation Resistance of engine) x (Tooth number of pinion gear)

Rotating force = —————————————————————————————


Engine Electrical

(Tooth number of flywheel ring gear)

2.2.3 Starting performance of the engine

The output of the start motor is varied by the

capacity of the battery and the difference of the

temperature. The figure 2-9 shows one example of

the characteristic variations according to the various

batteries having different capacity for operating the

start motor.

Fig. 2-9 Variations of Characteristics of

start motor according to the variations

of the battery capacity

When the battery capacity is small, the terminal

voltage will be greatly drop down and the rotation

speed will be slow at the engine starting, so the

output will be decreased. Furthermore, as shown in

Fig. 2-10, the actual capacity is also lowered as the

temperature is lowed, so the output of the start

motor is also reduced. Therefore, at any case, the

starting performance will be degraded.

The figure 2-11 shows the relationship

between the rotation speeds of the engine started

by the start motor and the rotation force operating

the engine through the pinion gear and flywheel ring

gear. When the temperature is lowered, the

viscosity of the lubricant oil is increased, so the

rotational resistance of the engine is increased.

However, the driving rotation force will be reduced

by the dropdown of the battery capacity.

Fig. 2-10 Variations of Characteristics of

start motor according to the variations

of the temperature


Engine Electrical

Fig. 2-11 Characteristics for the engine starting

2.3 Structure and operation of start

motor

The start motor comprises of three main parts in

accordance with the operation.

The part for generating rotational force

The part for transmitting the rotational

force to the engine fly-wheel ring gear

The part for contacting the pinion to the

flywheel ring gear using sliding motion.

According to the source voltage or the output, these

three main parts are different in size and the

number of poles and brushes. However, the

structure and operation are similar.


Engine Electrical

Fig. 2-12 Structure of the start motor

2.3.1 Electromotor part

The electromotor part is comprised of the

rotating part (armature, commutator, etc) and the

fixed part (field coil, pole core, brush, etc.).

(1) Rotating Part

A. Armature

The armature is consisting of a shaft and an

iron core, a plurality of armature coil wound in

isolated state around them, and commutator. The

both ends of shaft are supported by bearing and

rotating within the yoke iron core. The shaft of the

armature is made of special steel to prevent from

being broken, deformed or bent because it is

affected under large forces. The shaft has a spline

on which the pinion is sliding. The shaft should be


Engine Electrical

annealed to prevent from being worn.

The iron core of armature comprises of multiple

of thin steel sheet isolated and stacked in order to

flow the magnetic flux well and to reduce the eddy

current. The material is iron, nickel, or cobalt having

large magnetic permeability. At the outer

circumference, slot for armature coil is formed for

preventing the iron core from overheating. The iron

core of armature will be a magnetic circuit for the

magnetic field generated form the pole core and

converts the electromagnetic force generated

between the magnetic force of the pole core and the

armature coil to the rotational force. Therefore, the

larger is the armature coil, the larger is the rotation

force.

Fig. 2-13 Structure of armature

Fig. 2-14 Structure of armature coil

The armature coil should have large current so

that it should be made of the rectangular conductor

with wave winding method. The coil is inserted into

the slot with being isolated in which the one end of

the coil is connected to the N pole and the other

end is connected to the S pole. The both ends of

the coil are soldered to the commutator. Therefore,

the rotational forces generated from each coil, when

the current is flown at the same time, are rotating

the armature. The shapes of iron core are shown in

figure 2-15. Generally, two coils are inserted into

one slot, so the cross sectional shapes are like as

shown in figure 2-15 (a), (b) and (c). For isolating

the armature coil, the mica paper, the fiber or the

plastic is used.

Fig. 2-15 Slot shape of the armature iron core

B. Commutator

As shown in figure 2-16, multiple of copper

commutator plates are arranged in cylindrical shape

with insulator (mica) between them. The armature


Pinion

ArmatureOverrunning

Clutch

Reduction Gear

Engine Electrical

coil is soldered with each commutator plate. It

makes the current from brush flow in one direction to

the armature coil.

The inner part of the commutator is thinner than

the outer part of it. To prevent from seceding, it is

joined with V-shaped mica or V-shaped clamp ring.

The each piece of commutator plate is isolated by

the mica of which thickness is about 1mm and of

which diameter is 0.5~0.8mm (max 0.2mm) smaller

than the outer diameter of commutator. This small

amount is called the under cut having a vital role of

protect the commutator from discontenting, inferior

in rectifying, or being damaged by vibration. The

pieces of commutator are always connected with the

brush during rotation, so there are large current or

sparks between the brush and commutator.

Therefore it can have high temperature so it can be

easily damaged. It is important part for determining

the life time of the start motor.

(2) Fixed part

The fixed part of the start motor is comprised of

a yoke generating the magnetic field for rotating the

armature, a pole core, a field coil, a brush sending

the current from the field coil to the armature coil

through the commutator, a brush holder, and front

and rear end frames supporting the armature shaft.

A. Yoke & Pole core

The yoke is the path of the magnetic field as

well as the frame of the start motor. Inside surface

of it, the pole core, which has a role of magnetic

pole supporting the field coil, is fixed with screws.

As the field coil is wound around the pole core,

the pole core will be an electromagnet when the

current is flow in the field coil. The number of

electromagnet is decided by the number of pole

core. If the number of pole core is 4 then the

electromagnet has 4 poles.

B. Field coil

This is the coil being wound around the pole

core to generate magnetic field. As a large current

should be flown through it, it should be made of

rectangular copper wire.


Fig. 2-16 Commutator and Undercut

Engine Electrical

C. Brush & brush holder

The four brushes transmitting the current to the

armature coil through the commutator are installed.

Two of them are supported by the insulated holder

and connected to the commutator (these are called

(+) brushes), and the other two are supported by the

grounded holder and connected to the commutator

(these are called (-) brushes). The brush is made of

carbon, graphitic carbon, electrical graphitic carbon,

or metallic graphitic carbon having good lubricating

and applying electric current abilities. The start

motor has large current and is operated within a

short time period, so the metallic graphitic carbon for

low voltage and large current is generally used for

start motor.

The metallic graphitic carbon brush is made of

powder of copper and graphite in which the ratio of

copper is about 50~90%. The resistivity and contact

resistance are very low. In order that the brush

supplies the current to the armature coil through the

commutator, the brush should contact to the

commutator using spring tension to slide within the

holder in up and down. The spring tension of the

brush is about 0.5~1.0 kgf/㎠ . If the brush is worn

over 1/3 of the standard length, then it should be

replaced.

D. Bearing

As the start motor is heavy and used within a short

time, the bushing type bearing is used for the start

motor. There are slots at the bearing for lubrication.

Preferably, the oil-less bearing is used.

(3) Solenoid switch

This is also called as a magnetic switch. It

does a role of the switch doing ON-OFF operation

for the large current flown from the battery to the

start motor and of the joint connecting the pinion of

the start motor and engine flywheel ring gear.

The solenoid switch, as shown in 2-20,

comprises of a hollow core, a plunger, a contact

disk, two contacting terminals [one is for connecting

to the (+) terminal of battery when the contact disk

is closed, the other is for supplying current to the

start motor] and two excite coils wound on the

hollow core. The two excite coils are comprised of a

pull-in coil and a hold-in coil. The start part of the

winding of each coil is connected to the switch

terminal of the start motor (S terminal or St

terminal). The pull-in coil is grounded to the start

motor terminal (M terminal) and the hold-in coil is

grounded to the housing.


Fig. 2-17 Pole core and Field

coil

Fig 2-18 Installation of brush and commutator

Engine Electrical

In order that it is easy for the pinion of starting

motor and engine fly wheel ring gear to joint each

other and it is smooth for the operation for rotating

the start motor and operation of plunger to work, the

pull-in coil has thick coil wound around itself, and it

is connected to the battery in serial. The hold-in coil

has thinner coil than that the pull-in coil, so less

current is flown through it. However, it is connected

to the battery in parallel so that it makes magnetic

field regardless of open/close state of the two

contact points.

Fig. 2-20 Structure of the solenoid switch

The operation of excite coil is to generate the

magnetic force by flowing the battery current

according to the closing of the start switch (or

ignition switch; key) at the driving seat, and to pull

up the plunger. By the movement of the plunger, the

contact disk is operated to contact the two contact

points, at the same time; the shift lever is pulled to

slide the pinion so that the pinion joints to the engine

fly wheel ring gear. The working of the solenoid is

like that;

When the starting switch is closed, the current

flows from the starting switch to pull-in coil so that

the plunger is suddenly pulled and then the contact

disk is closed to the two contact points. At the same

time, by pulling the plunger, the pinion is pushed to

the flywheel ring gear. At that time, a big current

flows from the (+) terminal of the battery to the start

motor terminal (M terminal) via the battery terminal

(B terminal) of the solenoid switch. The current from

the start motor terminal flows through the ways of

field coil → (+) brush → commutator → armature

coil → commutator → (-) brush → ground to rotate

the armature and then the engine is cranked.

As the plunger is pulled and the two contact


Fig 2-19 Brush and brush holder

Engine Electrical

points are connected to the contact disk, the pull in

coil is opened by the contact disk so that the current

does not flow through the pull in coil and the pulling

force of the pull-in coil becomes to zero. Therefore,

the plunger will be back to the original position by

the tension of the return spring so that the joint of

the pinion and ring gear will be released. At this

time, the hold-in coil will hinder the plunger from

being return to the original position by the return

spring and the pinion from being separated from ring

gear by the vibration generated during cranking of

the engine.

After the engine is started, if the ignition switch

is released, then the contact disk is closed at that

moment, therefore, the current of pull-in coil is

reversely flowing from the start motor terminal (M

terminal). So, the direction of the pull-in coil's

magnetic field is also reversed and then the

magnetic forces of the hold-in coil and pull-in coil are

cancelled each other. Therefore, the plunger is

return by the tension of the return spring, the pinion

is separated from the ring gear and the contact disk

is opened. As the pull-in coil is connected in serial

with the battery and the start motor, it is called serial

soil or current coil. As the hold-in coil is connected

in parallel, it is called shunt coil or voltage coil.

Fig. 2-21 Structure of solenoid switch

(4) Overrunning clutch

When the engine is started, the pinion of the

start motor and the flywheel ring gear are jointed

each other so that the start motor is driven in high

speed by the flywheel. Therefore, the armature,

bearing, commutator and brush can be damaged. To

protect these parts, this clutch makes pinion rotate in

idle state after engine starting to prevent the start

motor form being driven by the engine. There are the

roller type, the multi-plate type and the Sprag type.

A. Roller type overrunning clutch

This type comprises of sleeve (spline tube)

installed on the spline of the armature shaft and

outer race having wedge shaped groove, which are

combined each other. In side of the outer race,

there is an inner race composing the one body with

the pinion. The wedge shaped groove at the outer

race includes rollers and springs, in which the

rollers are pushed to narrow side by the springs.


Outer race Inner race

Engine Electrical

Fig 2-22 Overrunning clutch

The operation of the roller type is like that;

according to the rotation of the armature shaft, the

outer race is rotate along the direction of arrow

shown in Fig 2-22, however, the inner race is not

moving so that the roller is moving along the outer

circumference of the outer race. At this time,

according to the difference of the rotational speed

between of the outer race and of the inner race, the

rollers are pushed to the narrow side in the groove

so that the inner race and outer race is fixed.

Therefore, the rotation force of the armature shaft

will be transmitted to the pinion to crank the engine.

After the engine is started, as the pinion ring is

jointed with the ring gear during the operation of the

solenoid, the pinion is rotated by the fly wheel. At

this time, the speed of the inner race is faster than

that of the outer race, so the rotation direction of the

rollers is reversed. Therefore, the rollers will be

move to the wide side of the groove, and the gap

between the inner race and outer race will be

enlarged so that they are sliding each other and the

rotation force of the fly wheel transmitted to the

pinion will not be transmitted any more,

The roller type uses about 4~5 roller. As this

type has lightweight and small size, the inertia

generated when the both gears are joined is small

so that the pinion or ring gear is less damaged.

However, as the contact surface of the roller for

transmitting the driving force is small, partial wear

will be often generated so that this type can make a

fault when big driving force shall be transmitted.

B. Multi-plate type overrunning clutch

This type is used for the armature movable

type start motor, and the structure is shown in Fig 2-

23. The spline is formed at the armature shaft to

combine with the spline formed inside of the

advance sleeve and then they can make a sliding

movement. The driving clutch plate is combined to

the groove of the advance sleeve. Pinion is formed

as one boy with the outer case including a driven

clutch plate at the groove formed inside of the case.


Roller Spring

Engine Electrical

Fig 2-23 Structure of the multi-plate type

The operation of the multi-plate type clutch is

like that; the pinion of the start motor is jointed to the

fly wheel ring gear by pushing of the shift lever. In

this state, if the pinion is stopped, the rotation of the

armature shaft is transmitted to the advance sleeve

so that the advance sleeve is pushed to the pinion

through the spline. This pushing force is transmitted

from the advance sleeve to the driving spring via the

clutch plate so the driving spring is bent. The

bending of the driving spring generates a pressure

on the surfaces of both clutches and transmits the

rotation force by the friction force there-between.

After the engine is started, the rotation force of the

pinion is faster than that of the armature shaft, so

the advance sleeve will be rotating. Therefore, due

to the operation of spline, the advance sleeve will

rotate in reverse direction with the pinion and the

both clutch plates are sliding so that the rotation

force of the engine can not be transmitted to the

armature shaft.

C. Sprag type overrunning clutch

This type is generally used for heavy weight

engines, and its operation is like that; the outer race

is driven by the start motor. When the engine is

started, the outer race and the inner race are joined

to be one body. As the fly wheel drives the pinion by

the starting of the engine, the inner race is rotating

faster than outer race, so that the jointing between

the inner and outer races will be released to prevent

the engine from driving the start motor.

Fig 2-24 Structure of Sprag type


Engine Electrical

2.3.2 Power Train

The power train is a method for joining the

pinion of the start motor to the fly wheel ring gear

and divided in to following types.

1. Bendix type

2. Pinion perturbation type

a. Manual type b. Electric type

3. Armature perturbation type

(1) Bendix type

This type is a method using the character that

the inertia of pinion and the series start motor are

rotating in high speed with no load.

The operation is like that; as current is flowing,

the start motor will rotate in high speed. However,

due to the inertia force, the pinion is not rotating with

the armature shaft but rotating on the spline and

moving toward the fly wheel ring gear to joint with it.

As the pinion reaches at the end part of the

spline and joints with the ring gear, the rotation

force of the armature is transmitted to the pinion via

the driving spring and spline so that the pinion will

drive the fly wheel with a large driving force.

Because the rotation force of the armature is

transmitted to the pinion via the driving spring, the

shock form the joining of both gears will be reduced

sot that the damages of armature and gear are also

prevented. The teeth of pinion and ring gear have

some chamber to ensure the fixing of them. After

the engine is started, the pinion is rotated by the

ring gear.


Fig 2-25 Structure and circuit diagram of Bandix type

Engine Electrical

Therefore, it slides on the spline in opposite

direction so that the fixed gear joint is released and

returned back to original position. As the start motor

is not rotated by the fly wheel ring gear after the

engine is started, the overrunning clutch is not

needed.

Fig 2-26 Jointing between the pinion and ring gear

(2) Pinion perturbation type

Figure 2-26 Structure of pinion perturbation type

In this type, there are the manual type and the

electrical type. Nowadays, only the electrical type is

used, so we will explain about this type only. The

electrical type is the method using a solenoid switch,

and the operation likes followings.

A. When the start motor is rotating;

a. Turn on the ignition switch.

b. The current flows from the start motor switch

terminal (S terminal) of the solenoid switch to

the pull-in coil and the hold-in coil.

c. The current into the pull-in coil flows to the field

coil, brush, commutator and armature coil of

the start motor via the start motor terminal (M

terminal) of the solenoid switch and the


Engine Electrical

armature starts to rotate.

d. The plunger of solenoid switch is pulled in so

that it pulls the shift lever, and then the pinion

of the start motor is pushed by the shift lever to

joint with the fly wheel ring gear.

e. By the pulling of the plunger, the contact plate

of the solenoid switch closes to the two contact

points.

f. As a current flows from the battery to the field

coil and armature coil via the cable, the start

motor start to rotate with a big power to crank

the engine.

B. When the engine is cranked;

a. As the contact plate closes to the two contact

points, the current flowing in the pull-in coil is

shored so that the magnetic force applied to

the plunger will be reduced.

b. At this time, the magnetic force generated by

the hold-in coil hinders the pinion from returning

to the original position by the return spring to

prevent the joint between the pinion and ring

gear from being released.

C. After the engine is cranked;

a. When the pinion of the start motor is rotated by

the fly wheel ring gear, the armature is

protected by the overrunning clutch.

b. At the moment of ignition switch off, the

contact plate is still closed so that the current

from battery is flowing from the start motor

terminal of the solenoid switch to the pull-in coli

in opposite direction and then flows into the

hold-in coil.

c. The magnetic force generated by the pull-in

coil is reversed to set off the magnetic force of

hold-in coil, so that the pulling force is reduced.

Therefore, by the tension of the return spring,

the plunger and the pinion return and separate

from the ring gear, and the contact plate is

opened. The current flowing to the start motor

will be broken and then the start motor is

stopped.

(3) Armature perturbation type


Engine Electrical

Fig 2-27 Structure and circuit diagram of the armature perturbation type

This type has been used in diesel engine. As

shown in Fig 2-27, the pinion is installed at the front

end of the armature and the center of the armature

core and the center of the pole (yoke) core are off set

each other. The solenoid switch is installed over the

body of the start motor and driven by the start switch

and the movement of the armature. The field coil

comprises of the primary field coil for generating the

rotation force and the auxiliary field coil for moving

the armature.

a. When the start switch is closed (ON), the

solenoid switch is driven and the upper contact

point of movable contact plate is closed.

b. At the upper contact point, as current flows to

the auxiliary field coil so the pole core is

magnetized, the armature core is pulled to the

center of the pole core by this magnetic force.

c. At this time, as current also flows in the

armature coil, the armature starts to rotate and

move to joint the pinion and the ring gear.

d. By completing the movement of the armature,

the lower contact point of the solenoid switch and

the movable contact plate are closed.

e. In the circuit formed by the closing the movable

contact plate, current from battery flows to the

primary field coil and armature coil to crank the

engine.

f. After the engine is cranked, the pinion is rotated

by the fly wheel ring gear. At this time, the

transmission of the engine rotation force to the

armature is broken by the multi-plate type

overrunning clutch.

g. As the load on the start motor is lightened by the

breaking down of the rotation force of the engine,

the field current is also reduced and the force is

also weakened so that the armature returns back

to the original position by the return spring and

the pinion and the ring gear are separated each

other.

In this type start motor, as the pinion and

armature are moved as the one body, so the shock

applied to the fly wheel ring gear is very large.


Engine Electrical

Therefore, the both gear are easy to be broken. To

prevent these damages, the pinion should be made

of soft material to protect the ring gear and it could be

replaced.

(4) Reduction gear type

There are the electrical indentation type and the

oil gear reduction type. The oil gear reduction type is

generally used for the 2-wheel vehicle. We will

explain about the electrical indentation type

generally used for the small size and lightweight

requirements.

The Fig 2-28(a) shows the structure of the

electric indentation type, in which the start motor

part is the same as the pinion perturbation type,

however, the power transmission comprises of

solenoid switch pulling the reduction gear and the

pinion and intermitting the main current. At the front

end of the armature shaft, a driving pinion is

installed on the spline so the driving pinion and

idling gear, the idle gear and the clutch gear are

always jointed.

Due to these gears, the rpm of the armature is

reduced to 1/3 and transmitted to the pinion. In

other words, the rotational force is enhanced up to 3

times and transmitted to the pinion by these gears.

a. As the ignition switch is on, current flows in the

pull-in coil and hold-in coil of the solenoid

switch so that the armature starts to rotate and

the plunger is pulled.

b. By the moving of the plunger, the plunger shaft

is pushed and the pinion is jointed to the ring


Fig. 2-28 Electric indentation reduction gear type start motor

Engine Electrical

gear.

c. At this time, the overrunning clutch is joined

with the clutch gear. Therefore, only the pinion

moves through the spline on the pinion shaft.

d. As the pinion and the ring gear is jointed, the

contact plate of the solenoid switch is closed

and the main current flows into the start motor.

Then the engine is cranked by the strong

rotation force of the start motor.

e. As the contact plate of the solenoid switch is

closed, current dose not flow into the pull-in

coil so that the plunger will be maintained by

the magnetic force generated by the hold-in

coil.

f. After the engine is cranked, the pinion is rotated

by the ring gear; however, the rotation force

into the armature is blocked by the overrunning

clutch.

g. When the start switch is opened, the operation

of the solenoid switch is the same in the case

of pinion perturbation type. However, as this

type is for high speed motor, it can be stopped

by small rotational resistance. So, it can be

stopped by the friction force between the brush

and the commutator without any additional

brake system.

2.4 Starting-system trouble diagnosis

2.4.1 Starting-system Troubles

Three basic starting-system complaints are:

a. The engine does not crank.

b. The engine cranks slowly but does not start.

c. The engine cranks normally but does not start.

This condition is not caused by the starting

system. It indicates a problem in the fuel or

ignition system, or in the engine.

The chart in Fig. 2-29 shows various possible

causes of these and other starting-system troubles,

and the checks or corrections to make.

2.4.2 No cranking, Lights stay bright

Current is not getting to the starting motor. Use

a voltmeter to check for voltage at the ignition switch

and starting motor terminals with the ignition key

turned to START. Battery voltage up to the starting

motor terminal indicates trouble in the starting

motor. Trouble is indicated in the relay or solenoid if

it has battery voltage but the starting motor terminal

does not.

2.4.3 No cranking, Lights dim heavily

Recharge or replace a discharged battery. The

battery is less efficient at low temperatures and

engine oil gets thicker. The starting motor cannot

always crank the engine with a low battery. These

symptoms may also indicate advancing spark

timing, excessive starter draw, and loose or dirty

connections.

2.4.4 No cranking, Lights dim slightly

The drive pinion may not be engaging with the

ring gear. If the starting-motor armature spins, then

the overrunning clutch is slipping. Also, there may

be high resistance or an open circuit in the starting

motor.


Engine Electrical

2.4.5 No cranking, Lights go out

There is a poor connection, probably at the

battery. Wiggle the cable connections at the battery.

If they are tight, make a voltage-drop test. If the

meter shows voltage, the connection has excessive

resistance. Clean the cable clamp and battery

terminal. Install and tighten the clamp.

2.4.6 No cranking, No lights

Either the battery is dead or there is an open in

the battery insulated circuit or ground circuit.

Possibilities include a loose connection at the

battery, relay, or solenoid. An open fusible link

indicates a short circuit.

2.4.7 Engine cranks slowly but does not start

The battery may be run down or the

temperature is very low. A defective starting motor

crank the engine too slowly to start it. Trouble in the

engine may prevent normal cranking. Also, the

driver may have run the battery down trying to start.

2.4.8 Engine cranks at normal speed but does

not start

When the engine cranks at normal speed, the

starting system is okay. The trouble is elsewhere.

Item 7 in Fig. 2-29 lists possible causes.

2.4.9 Relay or solenoid chatters

If this happens when the key is turned to start,

the battery is probably low. Charge the battery. The

contacts in the relay or solenoid switch may be

burned. Replace the relay or the contact plate.

Another cause is a defective solenoid hold in

winding. Replace the solenoid.

2.4.10 Pinion disengages slowly after starting

Item 9 in Fig. 2-29 lists four possible causes.

Also listed are the checks and corrections to make.

2.4.11 Unusual Noise

A high-pitched whine can result if there is too

much or too little clearance between the

overrunning-clutch pinion and the ring gear. The

procedure for adjusting the clearance is in the

manufacturer's service manual.

Condition Possible Cause Check or Correction

1. No cranking, lights stay bright

a. Open circuit in ignition switchb. Open circuit in starting motorc. Open in control circuitd. Open fusible link

Check switch contacts and connectionsCheck commutator, brushes, and connectionsCheck solenoid, or relay, switch, and connectionsCorrect condition causing link to blow; replace link

2. No cranking, lights dim heavily

a. Trouble in engineb. Battery lowc. Very low temperature

d. Frozen armature bearings, short in starting motor

Check engine to find troubleCheck, recharge, or replace batteryBattery must be fully charge, with engine, wiring

circuit, and starting motor in good conditionRepair staring motor

3. No cranking, lights dim slightly

a. Faulty or slipping driveb. Excessive resistance or open

circuit in starting motor.

Replace partsClean commutator, replace brushes; repair poor

connections4. No cranking, lights go Poor connection, probably at battery Clean cable clamp and terminal; tighten clamp


Engine Electrical

Condition Possible Cause Check or Correction

out5. No cranking, no lights a. Battery dead

b. Open circuitRecharge or replace batteryClean and tighten connections; replace wiring

6. Engine cranks slowly but does not start

a. Battery run downb. Very low temperature

c. Starting motor defectived. Undersized battery cables or

batterye. Mechanical trouble in enginef. Driver has run battery down trying

to start.

Check, recharge, or replace batteryBattery must be fully charged, with engine, wiring

circuit, and starting motor in good conditionTest starting motorInstall cables or battery of adequate size

Check engineSee item 7

7. engine cranks at normal speed but does not start

a. Ignition system defectiveb. Fuel system defective

c. Air leaks in intake manifold or carburetor

d. Engine defective

Make spark test; check timing and ignition systemCheck fuel pump, line, carburetor or fuel injection

systemTighten mounting; replace gaskets as needed

Check compression, valve timing, etc.8. Relay or solenoid

chattersa. Hold-in winding openb. Low batteryc. Burned contacts

Replace solenoidCharge batteryReplace

9. Pinion disengages slowly after starting

a. Sticky solenoid plungerb. Overrunning clutch sticks on

armature shaftc. Overrunning clutch defectived. Shift-lever return spring weak

Clean and free plungerClean armature shaft and clutch sleeve

Replace clutchInstall new spring

10. Unusual noises a. High-pitched whine during cranking (before engine fires)

b. High-pitched whine after engine firs as key is released

c. Loud whoop, buzzing, or siren sound after engine fires but while starter is engaged-sounds like a siren if engine is revved.

d. Rumble, growl, or knock as starter is coasting to a stop after engine starts

Too much clearance between pinion and ring gear

Too little clearance between pinion and ring gear

Defective overrunning clutch

Bent or unbalanced armature

Fig. 2-29 Starting-system trouble-diagnosis chart.

MEMO


Engine Electrical


Engine Electrical

3. Charging System3.1 Purpose of the charging system

There are two kinds of alternator used for

vehicle, the direct current (DC) alternator and the

alternating current (AC) alternator. In any case, the

charging system for vehicle should output the

electric signal in serial for charging the battery. That

is, the DC alternator makes the output by rectifying

the alternating current made in armature coil using

the commutator and brush, whereas the AC

alternator gets the alternating current output from

the stator coil and this alternating current is

converted into the direct current by rectifying through

silicon diodes.

3.2 Single phase AC AND 3- phase AC

3.2.1 Single phase Alternating Current

(1) Generating single phase alternating current

As shown in Fig 3-1, the DC alternator makes

the current by rotating a conducting wire in a

magnetic field, whereas, the AC alternator makes

the current by rotating the magnetic field with fixing

the conducting wire.

Fig 3-1 Generation of the single phase AC.

(2) Relationship between the rotation number

and the frequency

As shown in Fig 3-2, the one cycle is the

change of electromotive force from a to a' and the

frequency is the repetition number of this change for

one second. In the Fig 3-1, when the magnet

rotates one turn during one second, the frequency

is one cycle. In the Fig 3-2, if 4-pole magnet is

used, then the same change is repeated in every

1/2 turn, so 2-cycle is occurred at every one turn of

magnet. As the number of magnetic pole is

increased or the rotation speed is increased, the

frequency is also increased. This relationship is

represented by the following equation.

120602 PNNp

f×=

×=

Fig 3-2 The electromotive force of the single

phase AC

3.2.2 3-phase Alternating Current

(1) Purpose of the 3-phase AC


Engine Electrical

The alternator for vehicle, at first, was the

single-phase AC alternator and made the DC by

rectifying the AC using commnutaor and brush.

Nowadays, due to the development of the high

performance silicon diode, 3-phase AC alternator is

used.

(2) Generation of the 3-phase AC

As shown in Fig 3-3, after the 3 groups of coil

having the same windings, A-A', B-B' and C-C', are

wound in 120° arraying, when a magnet is rotating

within the coil array, then the 3-phase AC voltage is

generated as shown in 3-4. The coil B generates

the voltage in 120° lag behind the voltage

generation at coil A, and the coil C generates the

voltage in 120° lag behind the voltage generation at

coil C. These AC waveforms generated at the A, B

and C groups are called 3-phase AC.

Fig 3-3 Arraying diagram of 3-phase coil

Fig 3-4 The 3-phase AC voltage

Fig. 3-5 Connecting method of 3-phase coil

(3) Connecting method of 3-phase coil

In the commercial 3-phase AC alternator, the 3

pairs of coil are connected as shown in Fig 3-5. The

figure (a) shows the Y-connection (or star

connection) in which each one end of A, B and C

coil is each outer terminal and the each other end is

connected at one point, while, the figure (b) shows

the tri angle connection (or delta connection) in


Engine Electrical

which one start point of each coil is connected to

other end point of each coil and each connected

point is three outer terminals.

Here, the voltage and current generated at

each coil are called the phase voltage and the phase

current, respectively. The voltage between the outer

terminals and the current flowing at the outer

terminal are called the line voltage and the line

current, respectively. There are some relationships

between Y-connection and the tri angle connection

as followings.

In the case of Y-connection IpIlEpEl −⋅= ,3

In the case of tri angle connection IpIlEpEl ⋅== 3,

here, El: Line voltage Ep: Phase voltage

Il: Line current Ip: Phase current

Fig 3-6 Line voltage

In the case of the Y-connection, the line voltage

is √3 times of the phase voltage, and in the case

of tri angle connection, the line current is √3 times

of phase current. Therefore, if the coil winding is

the same with the alternator having same

capacity, then the Y-connection can make higher

electromotive force than the tri angle connection.

So, AC alternator for vehicle can get high voltage

in low speed and generally uses the Y-connection,

which can utilize middle voltage point. However,

for large output, the tri angle connection is used.

3.2.3 Rectifier

The current made form the rotary type

alternator rotated by mechanical force is alternating

current so it should be converted into direct current

to use as the vehicle power source. To convert the

alternating current into the direct current is the

"rectify" and the device for rectifying is the "rectifier."

The rectifier is made of various material such as

mineral, metal, semiconductor, and vacuum tube for

the purpose.

In the rectifier for vehicle, there are the silicon


Engine Electrical

diode for the AC alternator, the germanium diode for

the voltage regulator, and the tungar bulb rectifier,

selenium rectifier and the silicon rectifier for the

battery charger.

(1) Tungar bulb rectifier

This rectifier has the structure as shown in Fig

3-7. When AC current is supplied between the two

electrodes, the filament is heated and current flows

from the anode (+) to the cathode (-), however, it can

not flow in opposite direction. As a result, the half

rectifier is performed. When 2 bulbs are used, the

full rectifier is possible. The tungar bulb rectifier is

usually used for battery charger. It is easy to be

utilized and not expensive, however, it has small

capacity and low efficiency, so nowadays, it is rarely

used.

(2) Selenium rectifier

Forming the metallic film by melting selenium

on the iron or nickel plate, as shown in Fig 3-8, the

current can flow from the iron plate to selenium film

but it can not flow in opposite direction. Using this

character, the selenium rectifier is made by deciding

the number and size of the selenium film according

to the voltage and current.

Fig 3-7 Tungar bulb rectifier Fig 3-8 Selenium rectifier

(3) Silicon diode

In the current direction, the silicon diode can

flow current with a small voltage of under 1V,

however, it cannot flow current in reverse direction.

As shown in 3-9, there are two kinds of silicon diode

according to the current direction; therefore, it is

careful when wiring or test is performed. Fig 3-9 Current direction of silicon diode

3.3 Direct Current Alternator

3.3.1 Principle of the direct current alternator


Engine Electrical

As shown in Fig 3-10, installing and rotating a

conducting wire (armature coil) in the magnetic field

(Pole core) of the fixed N and S poles, an

electromotive force is induced at the conducting wire

by the electromagnetic induction law. At this time,

the direction of electromotive force is the same with

the arrow in figure according to the Fleming right

hand law. The direction of the voltage generated at

the rotating armature coil is changed at every 1/2

(180°) turn. When the armature turns in one turn,

then the 1 cycle of AC voltage is generated.

Therefore, the DC alternator is formed by connecting

a commutator comprising of half cylindrical pieces of

commutator to the terminal of the armature coil in

order to be rotated with the armature coil and

connecting brushes on the commutator pieces.

At the load connected to the brush, the direct

current, as shown in Fig 3-11, will flow. In the actual

DC alternator, the armature coil is wound by

overlapped somewhat with neighbored coil, so the

electromotive force of each coil is overlapped,

therefore, the output has less microseism.

Fig 3-11 Waveform of rectified output

3.3.2 Types of Direct Current Alternators

There are a number of different types of

alternators. Several of these alternator types will be

discussed briefly. Study their similarities as well as

their differences. Alternators can be distinguished

by their method of excitation. Self-excited

alternators can be separated further into the

categories of shunt, series, and compound.

One feature that separates alternators is the

excitation method, the method that is used to start

the alternator running. Some alternators require a

separate power source during the starting of the

alternator. These are called separately excited field

alternators. Other alternators use the alternators

own leftover magnetism in place of that power

source. These are self-excited alternators.

(1) Separately Excited Field Alternator

Alternator output is determined by the strength

of the magnetic field and the speed of rotation. Field

strength is measured in ampere-turns. So, an

increase in current in the field windings will increase

the times the speed of rotation. Therefore, most

output regulating devices depend on varying the

current in the field.


Fig. 3-10 Principle of the direct current alternator

Engine Electrical

The field windings can be connected to a

separate, or independent, source of dc voltage,

Figure 3-12. This is the separately excited field

alternator. With the speed constant, the output may

be varied by controlling the exciting voltage of the dc

source. This is done by inserting resistance in series

with the source and field windings.

Figure 3-12. A separately excited field alternator

(2) Self Excited Alternator

A self-excited alternator uses no separate

source of voltage to excite the alternator field

winding. The self-excited alternator produces a small

voltage when the armature windings cut across a

weak magnetic field.

This weak magnetic field is caused by

magnetism left over in the pole shoes or field coil

cores after the voltage and current have ceased to

flow. The magnetism left in a magnet after the

magnetizing force has been removed is called

residual magnetism.

Look ahead to the diagram of the shunt

alternator shown in figure 3-13. A residual magnetic

field will cause a small voltage to be produced as the

armature conductors rotate past the field poles. The

small voltage produced will, in turn, cause the

current to increase through the field poles. An

increase in field pole magnetism will cause a further

increase in output voltage. The relationship of the

current produced by the armature directly

increasing the amount of magnetism in the field

poles is how the self-excited alternator works. The

magnetism produced by the armature voltage will

increase until the field poles reach saturation, the

point where the poles cannot contain any more

magnetic lines of force.

Figure 3-13. A shunt alternator

A. Shunt alternator

The shunt alternator derives its name from the

way the field pole coils are connected in parallel to

the armature, Figure 3-13. Another way of saying

parallel is the term shunt. The field windings consist

of many turns of small wire. They use only a small

part of the generated current produce the magnetic

field in the pole's windings. The total current

delivered to the load. Thus, the output current can

be thought of as varying according to the applied

load. The field flux does not vary to a great extent.

Therefore, the terminal voltage remains constant

under varying load conditions. This type of


Engine Electrical

alternator is considered a constant voltage machine.

All machines are designed to do a certain

amount of work. If overloaded their lives are

shortened. As with any machine, the life of a

alternator can be shortened by an overload

condition. When overloaded, the shunt alternator

terminal voltage drops rapidly. Excessive current

causes the armature windings to heat up. The heat

can cause the alternator to fail by destroying the thin

coat of insulation covering the armature wires.

B. Series alternator

The series alternator is so named because its

field windings are wired in series with the armature

and the load. Such a alternator is sketched in

Figure 3-14. A series winding by itself will provide a

fluctuating voltage to the alternator load.

As the current increases or decreases through

the load, the voltage at the alternator output

terminals will greatly increase or decrease. Because

of the wide difference in output voltage, it is not a

very practical alternator to use if the load varies.

Figure 3-14. A series wound alternator

C. Compound alternator

The compound alternator uses both series and

shunt windings in the field. The series windings are

often a few turns of large wire. The wire size of the

series windings is usually the same size as the

armature conductors.

These windings must carry the same amount of

current as the armature since they are in series with

each other. The series windings are mounted on the

same poles with the shunt windings. Both windings

add to the field strength of the alternator field poles.

If both act in the same direction or polarity, an

increase in load causes an increase of current in

the series coils. This increase in current would

increase the magnetic field and the terminal voltage

of the output. The field are said to be additive. The

resulting field would be the sum of both coils.

However, the current through the series winding can

produce magnetic saturation of the core. This

saturation results in a decrease of voltage as the

load increases.

The way terminal voltage behaves depends on

the degree of compounding. A compound alternator,

which maintains the same voltage either at no-load

or full-load conditions, is said to be a flat-

compounded alternator. An over compounded

alternator will have a decreased voltage at full-load

current.

A variable load may be placed in parallel with

the series winding to adjust the degree of

compounding. Figure 3-15 shows schematic

diagrams of the shunt, the series, and the

compound alternator.


Engine Electrical

Figure 3-15 Compare these wiring diagrams of

the shunt, series, and compound alternator

3.3.3 Structure of Direct Current alternator

(1) Armature

The armature is the device for generating a

current by rotating in the field. As shown in 3-16, it

comprises of armature core, armature coil, and

commutator shaft. The armature core is made of

multiple of thin silicon steel and wound by coil

having insulating cover at the slit of the outer

circumference. The winding methods of the

armature coil are the wave winding type and the lap

winding type. The lap winding type is most used.


Engine Electrical

Fig 3-16 Structure of Armature

Fig 3-17 Unfold diagram of armature coil

Fig 3-18 Connection between brush and armature coil

By comparing with the armature of the start

motor, that of alternator has less current, so the coil

is made of thinner wire. However, to get large

electromotive force, the coil includes a lot of winding

number and multiple of wire is inserted in one slit.

The both ends of the armature are soldered on the

commutator. The alternating current generated at the

armature coil is rectified to convert into a direct

current by the commutator and the brush sliding on

the commutator. As the armature of the DC

alternator is continuously rotating during the

operation of the engine, the both ends should be

supported at the end frame by the ball bearing, and

at one end, there is a screw for fixing a pulley.

(2) Pole core & Field coil

The pole core supporting the field coil in the

yoke is installed by screws. The pole core becomes

an electromagnet to form N and S pole when a

current flows into the field coil. The field coil is the

coil wound around the pole core and magnetizes

the pole core when a current flow therein.

The DC alternator has little residual magnetism at

pole core even the current does not flow in the field

coil so that the electric generation is started basis

on this residual magnetism. The field coil and the

armature coil are connected in serial (shunt winding

type).

According to the grounding method of the end

of these coils, there are internal grounding type and

external grounding type.

For the internal grounding type, the start of the

coil winding is connected to the voltage regulator of

the alternator regulator and the end of the coil is


Engine Electrical

connected to the internal space of the pole core. For

the external grounding type, the start of the coil is

connected to the armature terminal and the end of

coil is grounded via alternator voltage regulator.

Fig 3-19 Wiring of the direct current alternator

(3) Brush

The brush of DC alternator rectifies the

alternating current generated at the armature by

connecting with the commutator and sends to out.

As the brush is always working with the engine

operation and has wide range of rotation speed, it

should be made of carbon material having good

rectifying performance and less wearing character.

Despite that the brush of start motor is contacted to

the commutator in perpendicular, the brush of

alternator is contact is contacted to the commutator

with some angle.

3.4 Alternating current alternator

3.4.1 Purpose for AC alternator

The alternating current alternator is 3-phase AC

alternator and it can get the direct current output

using rectifying silicon diode. It has good endurance

at high speed and charging performance in low

speed so that it is widely used for charging system

for vehicle's battery. This alternator is driven by the

driving belt connected with the engine crankshaft

pulley and comprises of voltage regulator, charging

relay, and yoke relay. The characteristics are like

that;

It has small size and lightweight, it makes

output voltage chargeable in low speed.

Having not commutator in the rotation

part, the limit of the permeable rotating speed

is very high.

As it rectifies with silicon diode, it has

large electric capacity.

The lifetime of brush is long.

3.4.2 Structure and operation of the AC

alternator

The AC alternator comprises of stator the fixed

part, rotor the rotating part, and end frame

supporting the both ends of rotor. The stator coil

fixed by the stator generates output current of the

alternator. The rotor and the rotor coil rotate in the

stator to induce the electromotive force at the stator

coil.


Engine Electrical

The alternating current generated in stator coil is

rectified by the rectifier (silicon diode) installed at the

end frame into direct current and supplied out. The

brush is not to get output current but to excite the

rotor coil by supplying current to rotor coil from

battery. The silicon diode not only rectifies the

alternating current generated from the stator coil but

also prevents the reverse current from battery to

alternator. Therefore, it does not need any cut out

relay unlike the DC alternator. If the generated

voltage from the alternator is higher than the terminal

voltage of battery, then the battery charging will be

automatically started.

(1) Stator

The stator acts as the armature of the DC

alternator. As shown in Fig 3-21, separated three

coils are individually wound around the steel core

consisting of multiple layers. The 3-phase AC will be

induced in these coils.

Fig 3-21 Structure stator

To reduce the core loss (phenomena in which

the hysteresis loss and the loss of eddy current are

occurred because of a lot of changes of magnitude

of flux around the steel core), the stator steel core

comprises of the lagged thin silicon steel plates,

and inside of it there are some slits for installing the

stator coil. During operation, it becomes the

pathway for the magnetic flux generated from the

pole of the rotor.

The one group of stator coil is made by

winding the copper wire covered with insulating

material into the slit as shown in Fig 3-22. The coil

pitch matches to the gap of the pole (pole pitch).

The three groups of this coil are arrayed in 120°

(2/3 of pole pitch) and formed into 3-phase

connection. For the coil connection method, there

are the Y-connection and the tri angle connection,

as mentioned in former chapter.

Fig 3-22 Appearance of the stator coil

(2) Rotor

The rotor, like the field coil and the pole core of

the DC alternator, makes the magnetic flux. It


Fig 3-20 Structure of the AC alternator

Engine Electrical

comprises of rotor core, rotor coil, shaft, and slip ring.

For the type of rotor, there are the Randle type and

the pole type. The pole type has small outer

diameter, however, winding method is complicated.

This type is used for large capacity alternator. For the

vehicle AC alternator, the Randle type having simple

structure and good strength is widely used. As shown

in Fig 3-24, the Randle type comprises of combined

4~6 steel cores inserted on shaft from the both ends

of cylindrical rotor coil. The winding start and the

end of rotor coil are connected to the two slip rings

installed on the shaft with being insulated.

Fig 3-23 Structure of rotor

Fig 3-24 Types of rotor

The operation of the rotor is like that; when the

current flows in the rotor coil through the brush

contacting to the slip ring, a magnetic flux is formed

in the direction of shaft so that one side of core is

magnetized into N pole and the other side is

magnetized into S pole. Therefore, each pole pieces

facing each other is also magnetized and the 8~12

of N poles and S poles are arrayed. The material of

rotor core is made by forging or imprinting the low

carbon steel. The slip is made of good conducting


Engine Electrical

material such as copper or stainless steel.

(3) Brush

The two brushes are inserted into a brush

holder fixed on a bracket and contacts to the slip

ring by a spring. One brush is connected to the

insulated outer terminal, and the other brush is

grounded through the brush holder. As the rotor is

rotating, the brush sequentially slides and contacts

to the slip ring, therefore, it should be made of metal

carbon material for good wear resistance and low

contact resistance.

(4) Rectifier

The rectifier comprises of diode. As shown in

Fig 3-25, 6 diodes are installed at the rear part of

the end frame to rectify the 3-phase AC generated

at the stator coil to convert into the direct current.

When current flows to the diodes, the

temperature of diodes is increased, so that they are

installed with heat sink (cooling plate). Generally,

three diodes of negative side are indented to the

back end frame and three diodes of positive side

are indented to the heat sink with being insulated.

Otherwise, each three diodes of (+) and (-) side are

soldered to heat sink, respectively. In other hand,

six diodes are installed on the printed board having

a heat sink.

Fig 3-25 Connection of diodes

3.4.3 Operation of AC alternator

Using the Fig 3-27, this type will be explained.

At first, when the ignition switch is on, current of

about 2~3A flows through the path of terminal F →

(+) brush → slip ring → rotor coil → slip ring → (-)

brush → terminal E (ground). Due to this current, the

rotor coil is magnetized to make a magnetic flux.

The AC alternator works as a separate excited

alternator at the beginning of operation. After the

engine is cranked, the rotor is rotated by the driving

belt, and the stator shut down the magnetic flux of

rotor, so that the 3-phase alternating current is

generated at the stator coil. This AC voltage is

rectified into direct current by the 6 silicon diodes

and output via the B terminal.

When the rotation speed of the rotor is

1,000rpm, the voltage of this AC current is higher

than the battery terminal voltage. Therefore, the


Engine Electrical

output current is supplied form the B terminal to the

each electro device and to the battery as a charging

current. Additionally, some amounts of the output

current from the B terminal are supplied to the rotor

coil. The DC alternator works as the self excited

alternator at the beginning of the operation.

However, in AC alternator, as the current does not

flow when the voltage supplied to the silicon diodes

is less than 0.5V, if the AC alternator works as the

self excited alternator at the beginning of the

operation, than the time for making output voltage is

delayed, so that it should work as the separate

excited alternator at first. The N terminal output half

voltage of the B terminal output. This voltage is

used for working the voltage regulator.

Fig 3-26 Operation of AC alternator

3.5 Alternator regulator

The output of the alternator is decided by the

winding number of armature (or stator) coil, the

strength of field and the number of intermitting the

magnetic flux per time (rotation speed). Therefore,

as the rpm of engine is increased, the voltage and

current made at alternator are also increased.

Therefore, the generated voltage and current should

be controlled to protect the all elector devices and

alternator. The alternator regulator works this role. It

can control the generated current by regulating the

magnitude of the current flown the field coil using

any method.

3.5.1 Direct current alternator regulator

The DC alternator regulator comprises of the

cut out relay, the voltage regulator and the current

limiter.


Engine Electrical

Fig 3-27 Direct current alternator regulator

(1) Cut out relay

This is one of switch using electromagnetic

force. It protects the reverse current from battery to

alternator when the alternator is stopped or the

generated voltage is lower than battery voltage.

When the current flows to the battery, the contact

point should be closed. This action is cut-in and the

voltage for this action is cut-in voltage. Generally, the

cut-in voltage for 12V battery is 13.8~14.8V.

A. Structure of the cut-out relay

As shown in Fig 3-28, the cut-out relay

comprises of the electromagnet having two coils,

one is wound with thin wire and the other is wound

with thick wire, and the contact point. The thin wire

coil is called the voltage coil, and the thick wire coil

is called current coil. They are wound in the same

direction. The contact point is opened by the

armature adjusting spring. When the magnetic force

of the electromagnet is stronger than tension of this

spring, the contact point is closed.

Fig 3-28 Structure of the cut-out relay

B. Operation of the cut-out relay

If the current generated by rotation of the

alternator meets to the cut-in voltage (charging

voltage), then the core will be magnetized by the

magnetic force formed by the voltage coil, and then

the contact point will be closed. At this time, the

current coil has current, so that the contact point

can be completely closed by the magnetic force

generated by the two coils. Therefore, the charging

current will flow into the battery. So, the contact

point will not be separated by any vibration but

maintain the contacting condition during driving.

In comparison, when the rotation speed of

alternator is to be slowed and the voltage of

alternator is to be lowed, the current will flow

through the current coil in opposite direction.

As a result, the magnetic force of the core will

be weakened suddenly. At that time, by the tension

of the spring, the contact point will be opened and

then the charging circuit is also opened. So, the

reverse current from the battery to the alternator can

be protected.

(2) Voltage regulator

The voltage regulator is to ensure that the

generated voltage maintains a constant value. If the

generated voltage is higher than regulated value,


Engine Electrical

the exciting current will be reduced by connecting an

additional resistor to the field coil in serial in order to

cut down the generated voltage. If the voltage is

lower than the regulated value, then some resistor

will be disconnected from the field coil to recover the

generated voltage.

In the voltage regulator, there are the vibration

contacting type, the carbon pile type, the transistor

type and the IC type. Nowadays, the IC type is only

used. It will be explained in the section of AC

alternator regulator with the transistor type.

Fig 3-29 Structure of the voltage regulator

(3) Current limiter (Current regulator)

The current limiter plays role of protecting the

alternator from the over current by controlling the

current made by the DC alternator. That is, the

current limiter prevents an electric load higher than

the regulated value from being applied to the

alternator.

A. Structure of the current limiter

Like the voltage regulator, the current limiter

comprises of armature, the armature adjusting

spring, and the contact point. Only that the

electromagnet coil (or current coil) is excited by the

charging current is the different thing.

Fig 3-30 The current limiter

B. Operation of the current limiter

As shown in Fig 3-30, before the output current

of the alternator meets to the regulated current, the

contact point is closed. As the output current of the

alternator is increasing, if it reaches to the limitation

value at last, then the contact point will be opened

by the magnetic force of the electromagnet. When

the contact point is opened, the serial resistor is

connected to the field circuit so that the generated

voltage will be decreased. Therefore, the load

current is reduced. As the load current is reduced,

the pulling force of the electromagnet is reduced so

that the contact point will be closed again by the

spring.


Engine Electrical

3.5.2 Alternating current alternator regulator

As the AC alternator uses silicon diodes as the

rectifier, it is not possible for any reverse current to

occur. Additionally, it has the current limiting function

so there are no worries about over current.

Therefore, the AC alternator regulator does not need

any cut-out relay and current limiter unlike the DC

alternator. That is, the voltage regulator is the only

thing to be required. The charging alert lamp relay

shall be connected to the voltage regulator in order

to operate the charging alter lamp.

(1) Transistor type voltage regulator

Using a transistor as a switch instead of the

contact point in the contacting type regulator, the

transistor type voltage regulator changes the

average value of the field current to control the

generating voltage. In this type, there are the semi-

transistor type in which transistors and relays are

combined and the full transistor type in which all

mechanical parts are removed. Furthermore, the IC

regulator includes the full transistor type into the

alternator body using IC circuit. In the Fig 3-31, the

Tr2 is the transistor for intermitting the field current,

and the base current of the Tr2 is controlled by the

transistor Tr1 and the Zener diode Dz. The alternator

terminal voltage Et is divided by resistor R1 and R2.

To the Zener diode Dz, the voltage E1 represented

by following equation is applied in reverse direction.

21

11 RR

REtE

+=

Here, Et = E1 + E2.

As the Dz has no current when the Et is low,

the Tr1 is OFF and the Tr2 is ON so that the current

flow to the yoke. When the E1 is higher than the

Zener voltage as the generated voltage is

increasing, the current flows through the Zener

diode so that Tr1 is ON and the Tr2 is OFF.

Therefore, the yoke current will be blocked. That is,

the yoke current can be controlled using the

operation in which the Tr2 is OFF when the Et is

high, and the Tr2 is ON when the Et is low, rapidly.

Fig 3-31 The basic circuit of the full transistor

type regulator

As the transistor regulator has not contact

point, there is no spark, which can be a reason of

EMI or EMC. As it has not mechanical parts, it has

long lifetime and good resistance against vibrations.

However, it is weak in high voltage and heat so it

should be carefully treated.

(2) IC voltage regulator

A. Purpose of IC voltage regulator

The charging circuit of the IC voltage regulator

comprises of the semiconductor circuits to intermit

the rotor coil current and then it can regulate the

voltage generated at the AC alternator. Basically, its

operating principle is same with that of transistor


Engine Electrical

type. However, it can be made in tiny size so that it

can be embodied into the alternator. Therefore, the

charging circuit of this type can be made simply and

this type many merits like those;

The wiring will be simple.

The voltage is not varied by vibration and

this type has good endurance.

The accuracy for controlling the voltage is

very high.

It has high heat resistance and high

output.

It can be minimized in size easily so that it

can be installed into the alternator.

The charging performance can be

enhanced, and the electric power can be

distributed to each electric load properly.

B. Operation of the IC voltage regulator

Fig 3-32 Circuit diagram of IC voltage regulator

a. When the ignition switch is ON during stop

state of the engine

When the ignition switch is ON, the current

flows from the L terminal of the AC alternator to the

base of transistor Tr1 through the IG terminal of the

AC alternator, the charging alert lamp relay IG

terminal and terminal A, and then the Tr1 is ON.

When the Tr1 is ON, as the battery current (field

current) flows from the rotor coil to the Tr1 through

the L terminal and the IG terminal of the AC

alternator, the rotor will be excited. At this time, the

current flows to the coil of the charging alert lamp


Engine Electrical

relay to close the contact point by the magnetic force

generated at the coil, so that the alter lamp turns

ON. As the initial exciting resistor (R4) has high

resistance (about 100Ω), the discharge of battery

can be protected by controlling the current which

flows to the rotor coil when the ignition switch is not

OFF.

b. When the AC alternator starts to work after

the engine is starting

If the generated voltage of the AC alternator is

higher than battery terminal voltage (13.8~14.8V),

then battery charge will be started from B terminal.

At this time, the voltage at the L terminal of the AC

alternator is increased, and at last it is not different

from that of the IG terminal of the charging alter

lamp relay. Then current at the charging alter lamp

relay coil is cut off so that the contact point is

opened. And then the alert lamp is OFF. Due to the

diode (D2) for hindering the reverse current, the

current flowed through the exciting diode by the

voltage of the stator coil flows not to the battery or

electric load but to the rotor coil and the L terminal

of the regulator.

c. When the generated voltage at the AC

alternator is over the regulated value by

high rotation of the engine.

At that time, as the current flow from the S

terminal of the voltage regulator via the resistor R2

and the Zener diode (ZD) to the base of the

transistor Tr2, the Tr2 is ON. Here, the voltage at

point P is to maintain the voltage for supplying the

base current of the transistor Tr1. However, when

the Tr2 is ON, the voltage is drop down suddenly

and then the base current of the Tr1 is cut off and

the Tr1 is OFF. Therefore, as the exciting current of

the rotor coil is cut off, the voltage from the AC

alternator is lowered.

When the voltage from the AC alternator is lower

than the regulated voltage, the current does not flow

to the Zener diode, so that the Tr2 is OFF and the

Tr1 is ON again. The voltage generating is restarted.

Like this, by repeating the ON and OFF operation of

the transistors Tr1 and Tr2 due to the operation of

the Zener diode, the exciting current which flow the

rotor coil can be intermitted and the voltage from

alternator can be maintained constantly.


Engine Electrical

4. Ignition System4.1 Purpose of ignition system

This system is a set of devices for combusting

the mixture of fuel compressed in the combustion

chamber of gasoline engine using an electrical spark

generated from a high voltage. In the ignition

system, there are the battery ignition type (uses

direct current electric power) using the battery as the

electric power and the high voltage magnet ignition

type (uses alternating current electric power) using

the high voltage alternator as the electric power. In

automobile, the battery ignition type is generally

used. In recent, due to the development of

semiconductor, there are the full transistor ignition

type, the high-energy ignition (HEI), and the

distributor less ignition (DLI).

4.1.1 The interrupter contacting type and the

transistor ignition type

The transistor ignition type uses the method in

which the current flown in the first coil of the ignition

coil is interrupted (intermitted) by switching

operation of the transistor to induce high voltage at

the second coil. In the interrupt contacting type, as

the first current of the ignition coil is directly

intermitted by opening/closing the contact point, the

arc can be made when the contact point is opened.

To prevent these arcs, the interrupter contact

point and battery are connected in serial. However,

at the low speed, as the speed for opening the

contact point is slow, it is easy to make an arc.

Therefore the second voltage generating will be not

stable and the misfiring will be occurred easily.

In comparison, for the transistor ignition type,

the first current is electrically intermitted by a

transistor so that the interruption of current is stable

at low speed and the second coil can make the high

voltage in stable.


Engine Electrical

Recently, as a countermeasure to the emission

gases, it is required to increase the flame energy of

ignition plug in order to make an accurate ignition

without any misfire at low speed even at high speed.

To do so, the first current should be increased. In the

interruption contact type, it is hard to increase the

first current, but in the transistor type, it is possible.

Additionally, in order to enhance the ignition

performance at high speed, the winding number of

the first ignition coil should be reduced so that the

inductance and resistance of the first coil can be

lowered.

As the result, the first current needs to be

increased as quickly as possible. That is, in order

that the energy supplied to the first ignition circuit

reduces the inductance but the flame energy is not

reduced, the first current should be enlarged.

Interrupter contacting type Full transistor type Computer control type

Due to the chattering of the interrupter contact point at high speed, the engine has incongruity in ignition.

The performances at low and high speed are safe.

The performances at low and high speed are very safe.

As the interrupter contact point has sparks, the contact point should be checked and replaced periodically.

Not having interrupt contact point, the checking and controlling are not needed.

Not having interrupt contact point, the checking and controlling are not needed.

Due to the abnormal operation of the vacuum and centrifugal timing control device, the engine has incongruity in ignition.

There are similar phenomena with the interrupter contacting type.

As the ignition timing is controlled by computer, it is the most efficiency.

In the interrupter contact type, due to the limitation

by the arc at the contact point, the magnitude of the

first current has a limit; however, in the transistor

type, it is possible to enlarge the first current

enormously.

Therefore, the ignition coil can comprise of the

first coil having low inductance and large winding

number ratio so that it can get better performance at

high speed than in the case of external resistor

ignition coil.

The characteristics of the transistor type are like

followings.

The performance at low speed is stable.

The performance at high speed is

enhanced.

The ignition performance is enhanced by

increasing the flame energy.

The reliability of ignition system is

enhanced.


Engine Electrical

The various electric control units for

improving the engine performance (ignition

timing and cam angle control) can be attached.

It is possible to reduce the winding

number ratio of ignition coil.

Fig 4-1 The intermitted waveform of the first current and the waveform of the second voltage

Fig 4-2 Speed characteristic of the second voltage

4.2 Computer control type ignition

system

4.2.1 Purpose of the computer control type

ignition system

This type uses the method in which by

detecting the status of engine using sensors and

input to computer (ECU), the computer calculates

the ignition timing and sends the intermittent signal

for the first current to the power transistor to induce

the high voltage at the second ignition coil.

The mold type ignition coil is used. There are


Engine Electrical

the high-energy ignition (HEI) type and the

distributor-less ignition (DLI) type. The merits of

these types are like that;

The ignition flame is very stable at low and

high speed.

When knocking is occurred, the ignition

timing is automatically delayed to suppress the

knocking.

Sensing the operating status of the

engine, the engine is controlled by optimized

ignition timing.

As it uses the high output ignition coil, the

complete combustion is possible.

Table ▶▶▶ Comparing the structure of each ignition system

Interrupter contacting type Full transistor type Computer control type

The first current is intermitted by the interrupter contact point.

The first current is intermitted by the switching of the transistor.

The first current of the power transistor is intermitted by computer.

Battery is needed. Battery is not needed. Battery is not needed.

The open magnetic circuit type ignition coil is used.

The open magnetic circuit type ignition coil is used.

Mold type ignition coil is used.

The opening/closing the interrupter contact point is performed by the cam fixed on the distributor shaft.

The intermittence of the first current is performed by the rotation of the signal rotor fixed on the distributor shaft.

The signal is generated by intermitting the light by rotating of a disk installed on the distributor shaft between the LED and photo diode.

4.2.2 HEI (High Energy Ignition) type

■ Ignition coil The ignition coil is the boosting transformer


Fig 4-3 Structural diagram of HEI

Engine Electrical

generating the current of the high voltage (about

20,000 ~ 25,000V) used for making an arc at ignition

plug.

(1) Principal of the ignition coil

The ignition coil uses the magnetic induction

effect and the mutual induction effect. The Fig 4-4

shows this principle. Of the two coils wound around

the core, the input side is called the first coil, and the

output side is called the second coil. The first coil is

magnetized by flowing of low current from battery;

however, this current is direct current so that the

induced voltage is not generated. When this low

current is interrupted by the power transistor, at the

first coil, the voltage E1 higher than battery voltage

is generated by the magnetic induction effect. The

induced voltage E1 at the first coil is determined by

the winding number of the first coil, the magnitude of

the current, the speed of current changing and the

core material. At the second coil, the voltage E2

proportional to the winding number ratio is

generated by the mutual induction effect.

(2) Structure of the ignition coil

The ignition coil makes the magnetic flux flow

through the mold type core to prevent the magnetic

flux generated by the magnetic induction effect from

being radiated out.

By thickening the diameter of the first coil wire,

the resistance can be reduced and the larger

magnetic flux can be generated so that the high

voltage can be made. The structure is simple and

the heat resistance is very high.

(3) Performance of the ignition coil

The important things for the performance of the

ignition coil are the speed characteristic, the

temperature characteristic and the insulation

characteristic.

a. Speed characteristic: The discharging

gap should be larger than 6mm, when the

distributor shaft is rotating with 1,800rpm at the test

of ignition coil flame.

b. Temperature characteristic: During

working of the engine, the temperature will be

increased by the heat by the current.


E: Battery voltage E1: First voltage

E2: Second voltage 11

22 E

N

NE =

N1: winding number of the first coil

N2: winding number of the second coil

Fig 4-4 Principle of ignition coil

Engine Electrical

As the temperature is increased, the resistance

of the first coil becomes larger so the first

intermitted current will be reduced.

Consequently, the discharging gap of the

second side will be reduced so the performance

at 80 should be regulated.℃

c. Insulation characteristic: The insulation

resistance and the withstanding voltage are

reduced according to the increasing of

temperature, however, it should be more than

10 ㏁ at 80 , and it should be more than℃

50 ㏁ at room temperature (20 ).℃

■ Power Transistor

The power transistor plays role of intermitting

the first current, which flow in the ignition coil

according to the signal from the computer. The

structure of the power TR is the NPN type

comprising of the base controlled by computer, the

collector connected to the (-) terminal of the ignition

first coil and the emitter connected to the ground.

The operation of the power transistor is like that;

a. When the ignition switch is ON, the battery

voltage is applied to the ignition primary coil.

b. According to the rotation of the disk in the

distributor, the ignition signal of the crank shift

angle sensor from the computer makes the

shorting-grounding signals repeatedly to the

power transistor.

c. The ignition signal repeats the shoring-

grounding operation of the current which flow

the ignition primary coil through the power

transistor by interrupting the power transistor.

d. The ignition timing is calculated by the

computer. When the current on the base of the

power transistor is interrupted, the ignition first

current is also interrupted. Therefore, the high

voltage is induced at the ignition second coil

and this high voltage is applied to the ignition

plug by the rotor of the distributor.

■ Waveform of the ignition voltage

As the time flows, the voltage applied to the

first and the second circuit of the ignition system will

be often varied. To indicate this varying voltage on

the engine scope screen continuously with the time

in plane is the voltage waveform of the ignition

system.

By observing this voltage waveform, it is

possible to check the engine performance as well

as the function and the malfunction status of each

part of the ignition system. So, the engine scope is

widely used for investigating the malfunction when

the engine performance is checked and serviced.


Fig.4-5 The structure of mold type ignition coil

Engine Electrical

Fig 4-6 Appearance and circuit diagram of the power transistor

The waveform of the ignition voltage of the

ignition system includes the first voltage waveform

and the second voltage waveform.

The Fig 4-7 shows the basic waveform of the

second voltage at the normal state. The voltage

waveform is divided into the firing section, the

intermediate section, and the Dwell section. The

firing section is the section for observing the output

of the ignition coil, the capacitor discharging voltage,

the induced discharging voltage and the duration

time.

The intermediate section shows the waveform from

after the discharging flame is extinguished to until

the voltage is ON at the ignition first coil. Just after

the discharging flame is extinguished, the 4~5 turn

of oscillating waveform is occurred. Then until the

voltage of the ignition first coil is ON, the stabilized

waveform is shown. The Dwell section shows the

waveform from when the voltage is ON at the

ignition first coil to when the voltage is OFF. In this

section, the Dwell angle %, the variations of the

Dwell angle according to the speed variation and so

on can be observed. The detail explanation for the

second waveform is like the followings.

(1) Firing section: A → D section

This section shows the firing status at the ignition

plug. It comprises of the firing line and the spark


Fig 4-7 The second waveform

1(ECU) 3(Ignition coil)

2(Ground)

Engine Electrical

line.

Firing line: The fire is the flame generated

at the ignition plug when the first current is

interrupted. The fire line is the vertical line

indicating the voltage needed for discharging

over the rotor gap of the distributor and the plug

gap by inducing the high voltage at the ignition

coil.

Spark line: The spark line is the horizontal

line indicating the voltage needed for inducing

the flame.

Point A: This is the point for forming the

high voltage at the ignition coil when the

voltage of the ignition first coil is interrupted.

Point B: The point at which the ignition

plug makes fire by inducing the high voltage at

the ignition coil (the height of this point is the

ignition voltage).

Point C: After the spark is generated, the

high voltage is down to this point. During the

ignition, it maintains a constant value.

Point D: This is the point for terminating

the flame at the ignition plug.

(2) Intermediate section: D → E section

This section is continuously showing in the ignition

section. The residual voltage inside the ignition coil

is reduced gradually in this section.

(3) Dwell section: E → A' section

This section indicates the time interval in which the

ignition first coil is ON, that is, the electric current

flows to the power transistor during the interval.

a. Point E: The point on which the voltage at the

ignition first coil is ON. As a magnetic field is

formed at the ignition coil, a waveform is

occurred. The waveform is shown under the

zero line by the vibration from the reverse

electromotive force induced ignition coil when

the voltage of ignition first coil is ON.

b. Point A': The point on which the voltage of the

ignition first coil is OFF.

■ Distributor

(1) Distributor cap and rotor

The distributor cap and the rotor distribute the

high voltage induced from the ignition coil to each

ignition plug according to the ignition order.


Engine Electrical

Distributor cap

At the distributor cap, there is central terminal

connected to the ignition coil, and ignition plug

terminals of the same number with the engine

cylinder number are arrayed around the ignition coil.

In the central terminal, a carbon piece connecting to

the rotor head is installed with a spring. The

distributor cap is made of resin material, its

withstanding voltage should be more than 25,000V

and it has good heat and magnetic resistance and

high mechanical strength.

* Rotor

The rotor is installed at the top of the distributor

shaft. It distributes the high voltage received from

the central terminal of the distributor cap to each

ignition plug terminal. The rotor is inserted from one

side of the distributor shaft. There is a gap of

0.3~0.4mm between the front end of the rotor and

the ignition plug terminal in the cap.

(2) Type of distributor

A. Optical type

● Distributor for 4-cylinder engine

The distributor for 4-cylinder engine comprises

of the crank shift angle sensor, the first cylinder top

dead center (TDC) sensor, the disk rotating with the

distributor shaft, and the rotor distributing the high

voltage induced from the ignition coil according to

the ignition order.

In the unit assembly, there are two set of the

LED and photo diode to detect the two kind slits, to

make pulse signals and to send to the computer.

The crank shift angle sensor and the first cylinder

TDC sensor comprise of the disk and unit assembly.

The disk made of metal includes 4 slits for passing

the light arrayed around the circumference of the

disk with 90° and used for crank shift angle sensor,

and inside of these 4 slits, there is one slit used for

the first cylinder TDC sensor.


Fig 4-8 Distributor cap and rotor

Engine Electrical

Fig 4-9 Structure of the unit assembly

Between the LED and the photo diode, as the disk

rotates, the light from the LED is transmitted to the

photo diode through the slits on the disk or

interrupted.

At this time, if the photo diode receives the light, then

the current flow in opposite direction and this current

can be detected by input to the comparator with 5V,

and then 5V is applied to the computer from the

terminal shown in Fig 4-9. In this state, if the disk②

rotates more and the light to the photo diode is

interrupted, then the voltage applied to the terminal

will be 0V. By repeating this operation, the pulse②

signal from the unit assembly is transmitted to the

computer.

The signal acquired from the 4 slits for sensing the

crank angle is the standard signal for calculating the

engine speed. By detecting whether the piston of

each cylinder is upper point of the compression

stroke, according to the signal acquired from the slit

for the first cylinder TDC sensor, the standard signal

for the first cylinder is distinguished so that the

computer can decide the distribution order using

these signals.

Fig 4-10 Operation of the crank shift angle sensor and the No.1 cylinder TDC sensor


Engine Electrical

Fig 4-11 Structure of TDC and crank shift angle sensor in the 6-cylinder engine

● For 6-cylinder engine

The TDC sensor of the distributor for 6-cylinder

engine detects not only the TDC of the first cylinder

but also the TDC of the first, third and fifth cylinder

and converts into pulse signal and transmits to the

computer so that the order for fuel injecting is

decided according these signals. There are two kinds

of disk, one includes the 360 slits for detecting the 1°

of TDC sensor at the circumference of the disk and 6

slits for crank shift angle sensor inside of the disk, the

other includes 6 slits for crank shift angle sensor at

the circumference of the disk and 4 slits for TDC

sensor inside of the disk.

The operation is the same in the 4-cylinder

engine as the photo diode detects the emitted light

from the LED according to the rotation of the

distributor shaft. Basis on the signal detected from

the crank shift angle sensor, the engine speed can

be calculated and the fuel injecting timing and the

ignition timing can be controlled.

B. Induction type

The induction type uses the ton wheel and the

permanent magnet. In this type, the ton wheel of the

first cylinder TDC sensor and the crank shift angle

sensor is installed at the back of the crank shaft

pulley or the fly wheel side, and the engine rotation

speed and the first cylinder TDC are detected

according to the rotation of the crank shaft. By

receiving these signals, the computer distinguishes

the basic signal of the first cylinder and decides the

order for fuel injection. As the structure of the first

cylinder and crank shift angle sensor is like that a

coil is wound around a permanent magnet, when

the ton wheel is rotating, pulse signals are induced


Engine Electrical

according to the variations of the air gap. Input these

signals into the computer, the first cylinder TDC and

engine speed are detected.


Fig 4-12 Structure of the induction type

Engine Electrical

Fig 4-13 Pulse generated by the rotation of the crank shaft

C. Hall sensor type

In this type, a Hall sensor is installed at the

distributor and the voltage variation occurred by the

Hall effect is input to the computer. By converting

this pulse to digital waveform using an analog-digital

converter the computer detects the crank angle. The

Hall device is a semiconductor device comprising of

thin film of germanium (Ge), potassium (K) and

arsenic (As), as shown in Fig 4-14.

As shown in figure, if a Hall device is installed

between two permanent magnetic poles and current

(Iv) is supplied, then the electrons in the Hall device

are refracted in perpendicular direction with the

current and magnetic flux direction. As the result, to

the cross sectional surface A1, the electrons are

plentiful and to the cross sectional surface A2, the

electrons are rare. Therefore, a voltage difference is

occurred between A1 and A2 and voltage (UH) is

generated. When the current (Iv) is constant, the

voltage (UH) is proportional to the magnetic flux

density. As the output voltage is very small, it should

be amplified by the OP AMP, as shown in Fig 4-15,

in order to be used as a signal.


Engine Electrical

Fig 4-14 Hall effect Fig 4-15 Structure of the Hall sensor

4.2.3 Spark plug cable (Hi-tension cord)

This cable is an insulated high voltage wire

connecting the second terminal of the ignition coil to

the central terminal of distributor cap, and the

ignition plug terminal of the distributor to the ignition

plug. One end of the spark plug cable is jointed with

the ignition plug terminal by the brass tag and the

other end is jointed with the ignition plug terminal of

the distributor cap, and then they are secured by

rubber cap.

The structure is, as shown in Fig 4-16, like that

the central conductor is insulated by rubber and its

surface is covered by plastic material. The cable in

which the central conductor is made by multiple of

copper wire or carbon implanted fiber to have

constant resistance is called the TVRS (Television

Radio Suppression) cable. This has about 10 ㏀

unit resistance over the all cable to prevent noises

according to the high frequency at the ignition circuit.

(1) Carbon wire

As shown in Fig 4-18, the resistance conductor

is the glass fiber made by implanting carbon into the

glass fiber to get constant resistance. The external

cover is the ethylene propylene rubber (EPDM),

which has good heat and cold resistances.

(2) Double wire wound type resistance cable

As shown in Fig 4-19, the resistance cable

comprises of the thin metallic core wire which is

wound around tetron core with tetron separator in

certain gap. The thickened wire core is surrounded

by insulator. Additionally, a special heat resistant

vinyl is used for the external cover considering the

state of the engine room. The resistance of the wire

is about 16 ㏀ /m.


Engine Electrical

4.2.4 Spark (Ignition) plug

The spark plug, as shown in Fig 4-20, is

installed at the combustion chamber of the cylinder

head and ignites the fuel mixture in the cylinder by

generating an electric spark between the central

electrode and ground electrode using the high

voltage generated at the ignition second coil.

Fig 4-20 Installation position of the spark plug

(1) Structure of the spark plug

The spark plug, as shown in Fig 4-21,

comprises of the three major parts including the

electrode, the insulator, and the shell.


Fig 4-18 Carbon line

Fig 4-19 Double wire wound type cable

Fig 4-16 Spark plug cable

Engine Electrical

Fig 4-21 Structure of the spark plug

* Electrode

The electrode comprises of the central

electrode and the ground electrode. As the high

voltage induced from the ignition coil is applied to

the central electrodes via the central shaft, a spark

will be generated at the gap with the ground

electrode. Between the central and ground

electrodes, the gap is 0.7~1.1mm. The material of

electrodes should have good endurance against the

damage and good heat resistance and corrosion

resistance so it is made of nickel alloy or platinum

alloy. In some cases, considering the heat radiation

performance, the central electrode can comprises of

copper. The diameter of central electrode is

generally 2.5mm. Recently, in order to prevent the

spark voltage from being lowered and to enhance

the ignition performance, some central electrodes

shall have the thin central diameter down to 1mm or

the ground electrode shall have U-shaped groove.

* Insulator

The insulator works in hindering the leakage of

voltage by surrounding the core or central electrode,

so it plays an important role in deciding the

performance. Therefore, it should have good

electrical insulation performance, heat conduction

performance and heat resistance, and mechanical

strength and it should be stable in chemical. The

insulator is made of ceramic having good insulation

performance and has a rib for prevent the flashover

of high voltage current.

* Shell

The shell is the metal part surrounding the

insulator and has a screw part for installing itself at

the cylinder head. The ground electrode is soldered

at the end of the screw. According to the diameter of

the screw, there are 4 kinds of the screw, 10mm,

12mm, 14mm and 18mm. The length (reach) of the

screw is decided by the diameter. For the screw of

length 14mm, there are 3 kind screws, 9.5mm,

12.7mm and 19mm. The gap between the insulator

and the core wire or the shell is caulked by filling a

special sealant, using a glass seal (after the glass

and copper powder are filled in the joint part of the

central electrode and core and melted to attach the

insulator and the metal) or melting them with spark.

(2) Requirement for the spark plug

The spark plug has the simple structure in

which two electrodes of ignition circuit are facing

each other to make a spark. However, the ambient

condition for working is very tough so it should have

performances satisfying the following conditions.

* It should have good heat resistance

The spark plug is exposed in combustion gas

having temperature of 2,000 and is cooled℃

suddenly at the intake stroke by the injected gas.

Therefore, it should endure the sudden change of

temperature.


Engine Electrical

* It should have good mechanical strength

The spark plug is influenced by a large vibration

according to the change of pressure of the vacuum

pressure at the intake stroke and of about 35~45kgf/

㎠ at the expansion stroke. It should have

mechanical strength enough to endure this change

of pressure.

* It should have good corrosion resistance

The electrodes of the spark plug are exposed in

the combustion gas so they can be chemically

attacked by the carbon and so on. Therefore, it is

needed to endure the corrosion. Generally, they are

made of Ni-Cr alloy.

* It should have good airtight-ness

The spark plug should have the airtight-ness

enough to endure the pressure applied from the

compression and expansion strokes. Especially,

there is no gas leakage at the high temperature.

* It should keep the self-cleaning temperature

If the temperature of the electrode is extremely

increased, then it will be a reason of the advancing

spark, otherwise if it is too low then carbon slug will

be stacked and current leakage will be occurred.

These are the main reason of misfire. Therefore,

during the engine operation, the temperature of the

electrode should be maintained in 500~600 .℃

* It should have good electric insulation

performance.

The spark plug should endure against the high

voltage of 15,000~20,000V during engine operation

and maintain good insulation property under sudden

change of temperature. It generally is made of

alumina (AlO3) or other magnetic insulating

materials.

* The spark should have strong energy

As the end part of the electrode is sharp as

possible, the spark will be easily made. If the end

part of the electrode is too sharp, then it has short

lift time. Therefore, it should have proper shape to

make the spark smoothly.

* It should have good ignition performance

Even the electrode makes a spark, if the

energy is not sufficient, then the firing is not

accomplished. Therefore, the shape of electrode

should be considered to make sufficient energy in

the lean mixture of fuel gas.

* It should have good heat conduction

If the heat from the combusted gas is not

radiated, the electrode could have short life time

from the melting or corrosion. Therefore, it has heat

conduction enough to maintain the temperature

being under 950 . Especially, at the high℃

temperature, it has high heat conduction efficiency.

(3) The self cleaning temperature and the heat

value of the spark plug

During engine operation, as the spark plug is

exposed in the high temperature by the combustion

of the fuel mixture, the electrode should maintain

proper temperature. If the operating temperature of

the electrode of the spark plug is lower than 400 ,℃

then the carbon made from the combustion will

attach to the electrode so that the insulation

property will be degraded and the spark will be

weakened, finally the misfiring is occurred. If its

temperature is over 800~950 , then the firing time℃

will be advanced so that the engine output will be


Engine Electrical

lowered. Therefore, the most proper temperature of

the electrode is 500~600 . This temperature is℃

called the self-cleaning temperature of spark plug.

The self-cleaning temperature is decided by the

applied heat capacity and the radiated heat capacity.

The applied heat capacity is varied by the type of

engine and driving status, and the radiated heat

capacity is varied by the structure of spark plug. As

the spark plug has different radiated heat capacity

property contrast in its structure, it should be

carefully selected for the engine. The numerical

expression of the radiation heat capacity is the heat

value. The heat value is decided by the length from

the part just below of the insulator to the lower seal.

The used heat value of spark plug is very important

and varied by the style of combustion chamber of

engine, the position of intake-exhaust valve, the

compression ratio, and the rotation speed. With the

same material, when the area exposed to the

combustion gas is large and the radiation path

(length of the all part of insulator) of the heat is long,

the radiation property is inferior and it is easy for the

temperature to increase. This type is called hot

type.

The characteristic of the hot type spark plug is

large resistance against the damage but low

resistance for the advancing ignition. Therefore, it is

proper to the low speed and low load engine. The

cold type has high heat radiation property and low

temperature increasing. The characteristic of the

cold type is that this type has high resistance against

the advancing ignition but it has low damage

resistance. Therefore, it is proper to the high speed

and high load engine.

Fig 4-22 Heat value of the spark plug

Recently, the wide range spark plug which can

maintain the self cleaning temperature in wide

range of driving condition is used. Generally, the


Engine Electrical

heat value is shown by number in the marks

indicating the type and size of the spark plug. The

number indicating the heat value is varied by the

manufacturer. The large number means the cold

type, and the low number means the heat type.

Fig 4-23 Radiation of the spark plug

4.3 DLI (Distributor less Ignition)

4.3.1 Purpose of the DLI

In all ignition type including transistor ignition

type, the high voltage is induced using one ignition

coil and supplied to the spark plug through the rotor

installed on the distributor shaft and the spark plug

cable. However, because this high voltage is

distributed by mechanical method, the voltage drop

down or current leakage may be occurred. As the

voltage should go through the air gap (0.3~0.4 mm)

between the rotor of distributor and segment of cap,

energy will be loss or this is the reason of noise of

the electromagnetic wave. The ignition method for

overcoming these problems is the DLI (Distributor

Less Ignition).

4.3.2 Kind and characteristic of DLI

Classifying the DLI according to the electric

control method, there are the ignition coil

distribution type and the diode distribution type. The

ignition coil distribution type is that the high voltage

is directly distributed from the ignition coil to the

spark plug, and there are two kinds, the

synchronous spark type and the individual spark

type. The synchronous type distributes the high

voltage to two cylinders with one ignition coil. That

is, when the first and fourth cylinders are ignited at

the same time, the first spark plug is discharged

when the first cylinder is at the upper position, while


Engine Electrical

the fourth spark plug makes invalid discharging

because the fourth cylinder is exhausting the gas.

The individual spark type uses the method in

which the each cylinder has individual ignition coil

and spark plug to make the spark directly.

The diode distribution type is one of synchronous

type in which the direction of the high voltage is

controlled by the diode. DLI has many merits such

as followings.

The distributor doesn't make any current

leakage.

There is no energy loss of high voltage

between the rotor and the cap of distributor.

The cap of distributor doesn't have any

radio wave noise.

There is no limitation in advancing angle

range of the ignition

Even if the output of high voltage is

reduced, the discharge effective energy is not

reduced.

It has good endurance.

As it has no electromagnetic wave

interruption, it doesn't make influence to other

electro devices.

Fig 4-24 Various DLI types

4.3.3 Parts of DLI and operation

The DLI comprises of the power transistor

operated by the signal from the ECU controlling the

ignition timing and the ignition coil inducing the high

voltage according to the intermitting operation of the

power transistor. The induced high voltage from the

ignition coil is sent to the spark plug through each

spark plug cable to make spark and the


Engine Electrical

compressed fuel mixture will be fired in the

combustion chamber.

(1) Ignition coil and power transistor

The ignition coil is attached at the cylinder head

after the two mold types are combined to the one

coil. This ignition coil has separated terminal to

supply the high voltage from one ignition coil to two

cylinders. The first current of the ignition coil is

controlled by the power transistor. This power

transistor performs the intermittence operation by

the computer signal. Fig 4-25 Structure of the ignition coil

Fig 4-26 Basic circuit of power transistor

(2)CAS (Crank Shift Angle Sensor)

The CAS is installed at the body of the sensor

with the TDC sensor and driven by the camshaft at

the cylinder head. The body of the sensor comprises

of unit assembly and disk. The operation of sensor is

like followings. The CAS is used for detecting the

crank shift angle of each cylinder using the 4 slits

arrayed at the outer circumference of the disk. When

this signal is sent to the computer, the computer

calculates the rotation speed of the engine, the air

amount injected per stroke and the ignition timing

and sends the signal for intermitting the first current

of the ignition coil to the power transistor.

The TDC sensor is used for detecting the

upper point at the compression stroke of the first

and fourth cylinder using the two slit arrayed at the

inner side of the disk and send these data to the

computer. The computer decides, basis on these

signals, the fuel injecting signal and the cylinder for

making ignition.


No.3 No.2 No.1 No.4

Capacitor(Condenser)

Engine Electrical

Fig.4-27 Crankshaft angle sensor

4.3.4 Control for the ignition timing of DLI

To control the ignition timing at DLI, the

computer receiving the signals from various sensors

detecting the operating status of the engine

compares with the predetermined data in the

computer and calculates the best ignition timing.

After that, the computer sends the results to the two

power transistor. By the switching operation of the

power transistors, the first current which flows to the

two ignition coils is intermitted. The induced high

voltage to the second coil from this intermitting

operation is distributed with the ignition order of 1(4)

- 3(2) - 4(1) - 2(3) to fire the mixture in cylinder

(here, the number in parenthesis indicates the

cylinder ignited synchronously).


Fig 4-28 Operation of the CAS and TDC sensor

Engine Electrical

In the Fig 4-29, as the power transistor isⓐ

ON, the current flow to the first coil of the ignition coil

and when the power transistor is OFF, highⓐ ⓐ

voltages of (+) and (-) are induced at the second coil

of the ignition coil . At this time, the induced highⓐ

voltage is sent to the first and fourth cylinder through

the two terminals, the (-) high voltage is induced to

the first cylinder and the (+) high voltage is induced

to the fourth cylinder. When the first cylinder is in the

compression stroke, the fourth cylinder is in the

exhaust stroke, inversely, when the fourth cylinder is

in the compression cylinder, the first cylinder is in the

exhaust stroke.

Therefore, the valid spark is made at the

compression stroke of any one cylinder between the

two cylinders. As the air density is very high in the

compression stroke, the voltage needed for engine

should be high. As the current is discharged with

almost no load in the exhaust stroke, most high

voltages of (+) and (-) is applied to the spark plug in

the compression stroke. Therefore, by comparing

with the case of discharge with one spark plug in the

conventional ignition system, the discharged voltage

of the dual high voltages is similar with the

conventional system.

(1) Spark distribution control

The computer decides the cylinder which will be

fired basis on the TDC (No.1 and No.4 cylinder TDC)

signal, calculates the ignition timing basis on the

CAS signal and sends the first current intermitting

signal of the ignition coil to the power transistor.

When the High signal (Logic 1) of the crank shift

angle sensor and the TDC sensor are input to the

computer, the computer decides that the first

cylinder is in the compression stroke, interrupts the

current to the power transistor and then the highⓐ

voltage will be sent to the first and fourth cylinder.

When the High signal of the CAS and the Low

(logic 0) signal of the TDC sensor are input, the

computer decides that the third cylinder is

compressed stroke (at that time, the second

cylinder is in the exhaust stroke) and interrupts the

current of the power transistor and then the highⓑ

voltage is sent to the third and second cylinder. Like

these, as the computer selects the power

transistors and alternately according to theⓐ ⓑ

CAS and TDC sensor, the computer can interrupt

the electric current to distribute the spark.

(2) Ignition timing control

The computer measures the frequency T of CAS

signal and calculates the time (t) for one turn of

crank shaft about the T.

180

Tt =

When the signal frequency T of the CAS is

acquired, the ignition timing T1 is calculated basis

on the 75° signal before the upper point and the


Fig 4-29 Circuit for DLI ignition

Engine Electrical

interruption signal of the first current is sent to the

power transistor.

T1 = t x (75 - θ)

Here, θ: Ignition advancing angle

calculated by the computer

(3) Ignition advancing angle

The computer stores the standard ignition

advancing angle optimized in accordance with the air

amount per one cycle of one cylinder and the engine

speed. By the input signal from each sensor, this

standard ignition advancing angle is compensated

additionally. When the engine is start, the ignition

timing is controlled with the stored value.

a. Ignition advancing angle in the normal

operation

Standard ignition advancing angle: The

map value predetermined according to the

intake air amount per one cycle at one cylinder

and the engine speed is the standard ignition

advancing angle. Here, the map value is the

value stored in ROM (Read Only Memory) in the

computer.

Engine temperature compensation:

According to the signal of the water sensor, when

the cooling water is low, the ignition timing should

be advanced to enhance the driving

performance.

Atmospheric pressure compensation:

According to the signal of the atmospheric

pressure sensor, when the pressure is low, the

ignition timing should be advanced to enhance

the driving performance in the high land area.

b. Ignition advancing angle when the engine is

cranking

During the cranking of engine, by synchronizing

with the CAS signal, the fixed ignition timing (5°

before upper point) is made.

c. Control when the ignition timing is regulated

At this time, as the terminal for control the crank

shift angle sensor, the ignition timing synchronized

to the signal of the crank shift angle sensor (5°


Fig. 4-30

Spark distribution

of each cylinder

Engine Electrical

before TDC) is formed. If it is need to control the

ignition timing, release the fixing nut of the crank shift

angle sensor and control by turning to left or right in

order that the CAS signal is controlled to meet the

standard ignition timing.

Fig 4-31 Ignition advancing angle control

4.4 Performance of the ignition system

The purpose of the ignition system is to form

the spherical flame kernel in the mixture gas by

making the spark from a spark plug at the most

proper time. Especially, adopting the emission

purification system, it is necessary for the

performance to combust completely without any

misfire under all driving conditions. Therefore, the

second voltage of the ignition system should

maintain high voltage value from low speed to the

high speed of the engine. Furthermore, the flame

energy from the spark plug should be large. Here,

we will explain about conditions influencing to the

ignition performance basis on the operation of the

high voltage circuit in the ignition system.

4.4.1 Ignition spark voltage

As the voltage generated at the second ignition

coil is increased, when it reaches to the spark

voltage (discharging start voltage), the spark is

generated at the electrode gap of spark plug. This

spark voltage is low in the easy condition for making

the spark; otherwise, the spark voltage is high in the


Engine Electrical

hard condition for making the spark. As the voltage

acquired from the ignition coil has a limitation, in

order to get perfect ignition without misfire under all

driving condition, the spark voltage should be rater

low than high. The elements influencing to the

magnitude of the spark voltage are the shape of the

spark plug electrode, the polarity, the gap of the

electrode, the pressure of the fuel mixture around

the electrode, the temperature of the electrode and

fuel mixture, the mixing ratio, moisture, movement of

gas. Among them, the gap of electrode and the

pressure and temperature of the fuel mixture are the

most important.

A. The influence from the shape and the gap of

the electrode of the spark plug

The Fig 4-32 shows the relation between the

electrode gap and spark voltage in the atmosphere

pressure. It shows that the spark voltage is

increasing proportional to the gap of the electrode.

In the same gap value, when the end portion of the

electrode has rounded shape as , it is hard toⓐ

discharge, and when the end of the electrode has

sharpened shape as , it is easy to discharge.ⓑ

Therefore, in the actual cases, the brand new spark

plug having a sharpened shape electrode has a

good discharging performance at first. After time is

passed, as the electrode wears more and more, at

last, the shape of the electrode will be rounded so

that it is hard to discharge. The spark voltage will be

increased.

Fig 4-32 Spark voltage and gap of electrode

B. Influence from the pressure and temperature

of the fuel mixture


pressure of fuel mixture around the electrode and

the spark voltage. As the pressure of the mixture is

increasing, the spark voltage is also increased. With

the same pressure, when the temperature of the

mixture is high, the spark voltage will be lowered.


temperature of the electrode and the spark voltage.

As the electrode temperature is increasing, the

spark voltage will suddenly be lowered because the

electrode will be easy to discharge from the surface

of the electrode. The electrode gap of the spark

plug is generally about 0.7~0.9mm. In the

atmosphere pressure, the spark is discharged with

2~3kV. When it is attached at the cylinder head, the

spark voltage will be higher than 10kV because the

pressure of the mixture around the electrode is

about 10kgf/ ㎠ during the compression stroke.

When the mixture injected into the cylinder at

room temperature is compressed, its temperature

will be higher than 200 . Furthermore, in the℃

engine driving state, the temperature of the spark


Engine Electrical

plug is higher than 500 , so the spark voltage will℃

be lowered as the increased temperature. The spark

can be discharged at about 10kV. Contrarily, when

the engine is started in the cold weather, the spark

voltage will be increased. Additionally, when the

engine is accelerated, the intake efficiency is

enhanced and the compression pressure is

increased so that the spark voltage will be increased

temporarily.

Fig 4-33 Spark voltage and the pressure of the

mixture

Fig 4-34 Spark voltage and the temperature of

electrode

C. Other influences

Even the spark voltage is lower in the air than

in the mixture, the spark voltage tends to be

increased as the mixture is lean. When the moisture

is high, the electrode temperature of the spark plug

is lowered so that the spark voltage will be high

somewhat. With the different shape of the electrode,

according to the polarity that is, which electrode is

connected to the (+), there is a difference in the

spark voltage. This is called the polarity effect. If the

central electrode has cylindrical shape and the

ground electrode has flat shape, as shown in Fig 4-

35, when the electrode gap is in small range, then

the central electrode is applied with (-) and the

ground electrode is applied with (+) to make spark

easily.

Fig 4-35 Spark voltage and polarity

In actual spark plug, there is no extremely

different shape in the electrode shapes like needle

electrode and flat electrode. As shown in Fig 4-35,

the central electrode is corresponding to the needle

electrode and the ground electrode is

corresponding to the flat electrode. In the aspect of

temperature of electrode, the central electrode has

high temperature.

4.4.2 Spark energy and ignition performance

The purpose of the ignition system is to ignite

the mixture in the combustion chamber completely.

When the ignition is failed, it is called the misfire.

This includes the cases in which there is no spark


Engine Electrical

between the electrodes of the spark plug (it is called

miss spark) and in which the mixture is not fired

even the spark is made (it is called miss fire).

Recently, as the countermeasure of the emission

gas, the ignition system is required high

performance in which even the lean fuel mixture can

be fired.

Therefore, various spark plugs which can meet

this requirement are developed. That the mixture is

combusted within a short time period by the spark of

the spark plug is called the explosion and this is

processing as the following procedure.

As shown in Fig 4-36, when the spark is

generated at the electrode gap of the spark plug in

the compressed mixture, then a small sphere flame

kernel is formed at first. This flame kernel can be

cooled by the ambient mixture and electrode.

However, if the heat capacity of this flame kernel is

enough large, then the combustion reaction will be

accelerated and grown and then the flame surface

will be spread into the mixture even after the flame

kernel is extinguished. The main role of the ignition

system is to generate a sphere flame kernel which

can spread into the mixture. However, the

combustion followed from this kernel is mainly

decided by the status of the mixture and the flame

does not govern the spread of the combustion.

Fig 4-36 Formation of flame kernel by the spark

When the heat capacity of the flame kernel is

low and the flame kernel is easy to be cooled by the

electrode of the spark plug, the flame can not

spread so that the ignition can not be completed.

Extinguish effect of the electrode is lessen as the

electrode is thinner and the gap electrode is larger.

Therefore, recently, the spark plug has larger

electrode gap and thinner central electrode or a

groove on the ground electrode in order to enhance

the ignition performance.


Engine Electrical

5. The Micro 570 analyzerThe Micro 570 analyzer provides the ability to

test the charging and starting systems, including the

battery, starter and alternator.

Fig 5-1 Micro 570 analyzer

Caution: Because of the possibility of

personal injury, always use extreme caution and

appropriate eye protection when working with

batteries.

5.1 Key pad

The Micro 570 button on the key pad provide

the following functions:


Use the arrow buttons to scroll to main menu.

Press the ENTER button to make selection

Press the CODE button to generate a warranty code

Press the MENU button to print and view the last test result, set the time, use the voltmeter, and export data to a PC.

Engine Electrical

Fig 5-2 Micro 570 analyzer switch

5.2 Battery Test procedures

1) Connect the tester to the battery

Caution: Connect clamps securely. If “ CHECK

CONNECTON” message is displayed on the

screen, reconnect clamps securely.

2) The tester will ask if the battery is connected “IN A

VEHICLE” or “ OUT OF VEHICLE”. Make your

selection by pressing the arrow buttons: then

press “ENTER” button.

3) Choose either CCA or CCP and press the

“ENTER” button.

* CCA: Cold cranking amps, is an SAE specification

for cranking batteried at –18 .℃

* CCP: Cold cranking amps, is an SAE specification

for Korean manufacturer’s for cranking

batteried at –18 .℃

4) Set the CCA value displayed on the screen to the

CCA value marked on the battery label by

pressing up and down buttons and press

“ENTER” button.

The battery ratings (CCA) displayed on the tester

must be identical to the ratings marked on

battery label.

5) The tester displays battery test results including

voltage and battery ratings. A relevant action

must be given according to the test results by

referring to the battery test results as shown in

the table below.

6) To conduct starter test, continuously, press

“ENTER” button.


Engine Electrical

Result on printer Remedy

Good battery No action is required.

Good recharge Battery is in a good state.

Recharge the battery and use.

Charge & Retest Battery is not charged properly.

Charge and test the battery again (Failure to charge the battery fully may read

incorrect measurement value)

Replace battery Replace battery and recheck the charging system.(Improper connection between

battery and vehicle cables may cause “REPLACE BATTERY”, retest the battery

after removing cable and connecting the tester to the battery terminal directly prior

to replacing the battery)

Bad cell-replace Charge and retest the battery. And than, test results may cause “REPLACE

BATTERY”, replace battery and recheck the charging system.

5.3 Starter test procedure

1) After the battery test, press the “ Enter” button immediately for the starter test.


Engine Electrical

2) After pressing “ENTER” button, start the engine.

3) Cranking voltage and starter test results will be

displayed on the screen. Take a relevant action

according to the test results by referring to the

starter test results as given below.

4) To continue charging system test, press “ENTER”

button.


Cranking voltage

normal

System shows a normal starter draw.

Cranking voltage low Cranking voltage is lower than normal level.

Check the battery and retest.

Charge battery The state of battery charge is too low to test.

Check the battery and retest.

Replace battery Replace battery.

If the vehicle is not started though the battery condition of “Good and fully

charged” is displayed.

Check wiring for open circuit, battery cable connection, starter and repair or

replace as necessary.


Engine Electrical

If the engine does crank, check fuel system.

5.4 Charging system test procedure

1) Press “ENTER” button to begin charging system

test.

2) If “ENTER” button is pressed, the tester displays

the actual voltage of alternator. Press, “ENTER”

button to test the charging system.

3) Turn off all electrical load and rev engine for

5seconds with pressing the accelerator pedal.

4) Press “ENTER” button.

5) The Micro 570 analyzer charging system output

at idle for comparison to other readings.


Engine Electrical

6) Take a relevant action according to the test results

by referring to the table below after shutting off

the engine and disconnect the tester clamps

from the battery.


Charging system

normal / Diode ripple

normal

Charging system is normal

No charging voltage Alternator does not supply charging current to battery.

Check belts, connection between alternator and battery.

Replace belts or cable or alternator as necessary.

Low charging voltage Alternator does not supply charging current to battery and electrical load to system

fully.

Check belts and alternator and replace as necessary.

High charging voltage The voltage from alternator to battery is higher than normal limit during voltage

regulating.

Check connection, ground and replace regulator as necessary.

Check electrolyte level in the battery.

Excess ripple detected One or more diodes in the alternator are not functioning properly.

Check alternator mounting, belts and replace as necessary.


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