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Service Training
Meeting Guide 757 SERV1757
March 2002
TECHNICAL PRESENTATION
D6R SERIES II
TRACK-TYPE TRACTORS
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31
Torque Divider Group
The D6R Series II Track-type Tractors are equipped with a power shift
transmission and use a torque divider (1) to transfer engine power to the
transmission. The torque dividers on these machines are similar to the
torque dividers on other Caterpillar Track-type Tractors.
The torque divider provides both a hydraulic and a mechanical connection
from the engine to the transmission. The torque converter provides the
hydraulic connection while the planetary gear set provides the mechanical
connection. During operation, the planetary gear set and the torque
converter work together to provide an increase in torque as the load on the
machine increases.
The torque converter outlet relief valve (2) is mounted on the torqueconverter case.
The torque converter outlet pressure tap (3) is located on the back of the
torque converter relief valve.
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Torque divider group:
1. Torque divider
2. Torque converter
outlet relief valve
3. Torque converter
outlet pressure tap
3
2
1
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Priority valve
components:
1. Torque converter
inlet pressure tap
2. Torque converter
inlet relief valve
3. Priority valve group
32
The torque converter inlet pressure tap (1) is located on the side of the
torque converter inlet relief valve (2), which is contained in the priority
valve group (3).
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1
2
3
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33
SUN GEAR
HOUSING
IMPELLER
TURBINE
OUTLET
PASSAGE
OUTPUT SHAFT
STATOR
PLANET CARRIER
PLANET GEARS
ENGINE FLYWHEEL
INLET
PASSAGE
RING GEAR
TORQUE DIVIDER
This illustration shows a typical torque divider. The impeller, rotating
housing, and sun gear (shown in red) are mechanically connected to the
engine flywheel. The turbine and ring gear (blue) are connected and the
planet carrier and output shaft (yellow) are connected.
The sun gear and the impeller always rotate at engine speed. As the
impeller rotates, it directs oil against the turbine blades, causing the
turbine to rotate. Turbine rotation causes the ring gear to rotate. During
NO LOAD conditions, the planet gears (green) and planet carrier rotate asa unit with the planet gears stationary on their shafts.
Torque divider
operation:
- During NO LOAD
condition
components rotate
as unit
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As the operator loads the machine, the output shaft slows down. A
decrease in output shaft speed causes the rpm of the planetary carrier to
decrease. Decreasing the planetary carrier rotation causes the relative
motion between the sun gear and the planet carrier to cause the planet
gears to rotate. Rotating the planet gears decreases the rpm of the ringgear and the turbine. At this point, the torque splits with the torque
converter multiplying the torque hydraulically, and the planetary gear set
multiplying the torque mechanically.
An extremely heavy load can stall the machine. If the machine stalls, the
output shaft and the planetary carrier will not rotate. This condition
causes the ring gear and turbine to slowly rotate in the opposite direction
of engine rotation. Rotating the ring gear and turbine in the opposite
direction provides maximum torque multiplication.
During all load conditions, the torque converter provides 70% of the
output and the planetary gear set provides the remaining 30% of the
output. The size of the planetary gears establishes the torque split
between the hydraulic torque and mechanical torque.
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- During stall, turbine
and ring gear rotate
in opposite
directions
- Torque converter
provides 70% of
output
- Planetary gear set
provides 30% of
output
- Under load, relative
motion slows turbine
rotation
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Component locations:
1. Power train filter
2. SOS tap
3. Power train oil
pump supply
pressure tap
4. Power train oil filter
bypass switch
34
Opening the hinged cover of the compartment on the right fender allows
access to the power train filter (1) for the the D6R Series II. On top of the
power train filter housing are the power train SOS tap (2) and the pump
supply pressure tap (3). The power train filter drain plug is below the
filter housing.
The filter bypass pressure switch (4) opens during cold start-ups and
when the filter is plugged.
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1
4
2
3
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Component locations:
1. Power train oil fill
tube
2. Power train oil
dipstick
35
The power train oil fill tube (1) and dipstick (2) are located at the rear of
the left side engine compartment.
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12
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Power train oil pump:
1. Torque converter
and lube section
2. Transmission and
controls section
3. Transmission and
torque converter
scavenge section
4. Check valve
36
The three section gear-type power train oil pump is located at the right
front of the main case below the floor plate and is driven by a shaft
extending from the rear of the flywheel housing.
The three sections are the torque converter charging section (1), the
transmission charging section (2), and the torque converter and
transmission scavenge section (3).
Under certain conditions, the torque converter charging section and the
transmission charging section combine flow through the check valve (4)
to provide more oil to the transmission and brakes. This will be covered
in more detail later in this presentation.
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1
2 3
4
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3F/3R planetary power
shift transmission
Pressure taps:
1. Transmission main
relief valve
2. Transmission
lubrication
37
Transmission
The three speed FORWARD, three speed REVERSE planetary power
shift transmission transfers power from the engine to the final drives. The
transmission contains three hydraulically controlled speed clutches and
two hydraulically controlled directional clutches. The transmissionshifting function is controlled by the Power Train Electronic Control
System. The Power Train ECM responds to operator shifting requests by
controlling the electrical current to the transmission clutch solenoids. The
solenoid current controls the hydraulic circuits that engage the
transmission clutches.
The Power Train ECM selects the transmission clutches to be engaged
and the clutch pressure is modulated electronically. Solenoid valves
control the modulation of the clutch pressure. The Power Train ECM
uses the transmission speed, engine speed, and the power train oiltemperature signals to control smooth engagement of the clutches. Each
transmission clutch in the planetary group has a corresponding solenoid
valve on the transmission hydraulic control group.
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The Power Train ECM uses the transmission solenoid valves to directly
modulate the oil pressure to each transmission clutch. The solenoid
valves are proportional. The Power Train ECM modulates the electrical
current to the solenoid valves. Modulating the solenoid valves controls
the power train oil flow to the transmission clutches. Electronic clutchmodulation allows the Power Train ECM to control the time required to
fill a clutch with oil and the rate of the clutch pressure modulation.
The pressure setting for the transmission main relief valve may be
checked using the transmission main relief valve pressure tap (1).
Transmission lubrication pressure may be checked using the transmission
lubrication pressure tap (2). These two pressure taps are located at the
rear of the machine and at the top of the cover for the transmission case.
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38
TEST PORT
FROM
PUMP
BALLVALVE
SPOOL SPRINGORIFICE
SOLENOID PIN
TO
CLUTCH
D6R SERIES II
TRANSMISSION MODULATING VALVE
The transmission clutches are hydraulically engaged and spring released.
The transmission modulating valve solenoid is energized to engage the
clutch.
As current is applied to the solenoid, the pin extends to the right and
moves the ball closer to the orifice. The ball begins to restrict the amount
of oil to drain, increasing the pressure on the left end of the spool. As the
pressure at the left end of the spool increases, the spool shifts to the right,
blocking the drain passage. Oil is now directed to the clutch. When theclutch fills, pressure begins to increase, engaging the clutch.
As clutch pressure increases, the pressure plus the spring force moves the
spool back to the left. When maximum clutch pressure is reached a
balance is maintained between clutch pressure and the solenoid, holding
the spool in a metering position.
Transmission
modulating valve
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De-energizing the solenoid returns the pin to the left. The pressure on the
left end of the spool forces the ball away from the orifice, which relieves
pressure on the left end of the spool. This, in turn, allows the spool to
shift to the left, due to the spring force plus the clutch oil pressure. Clutch
pressure is then directed to drain, and the clutch is disengaged.
When the transmission is in NEUTRAL, the modulating valve, which
controls engagement of the No. 3 clutch, allows flow to the clutch. The
other modulating valves stop flow to the clutches, thereby allowing the
clutches to be released by spring force. Since the No. 1 or 2 directional
clutch is not engaged, no power is transmitted to the output shaft of the
transmission.
When the transmission is in FIRST SPEED FORWARD, the modulating
valves which control flow to the No. 2 and 5 clutches receive a signal
from the Power Train ECM to allow flow to the clutches and, therefore,
allow the clutches to engage.
NOTE: The transmission modulating valves must be recalibrated
when any of the following procedures are performed:
- Transmission modulating valve and/or solenoid is replaced.
- Transmission is serviced or replaced.
- Power Train ECM is replaced.
For the calibration procedure, refer to the Power Train Electronic
Control System Service Manual (Form SENR8367).
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FIRST FORWARD
NEUTRAL
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39
Transmission clutch
locations:
1. Reverse
2. Forward
3. Third
4. Second
5. First
POWER SHIFT TRANSMISSION
INPUT SHAFT
OUTPUT SHAFT
OUTPUT
SUN GEARS
RING GEARS
INPUT SUN
GEARS
PLANETARY
CARRIER
RING
GEARS
1 2 3 4 5
This illustration shows a sectional view of a typical transmission group.
The planetary group has two directional and three speed clutches which
are numbered in sequence (1 through 5) from the rear of the transmission
to the front. Clutches No. 1 and 2 are the reverse and forward directional
clutches. Clutches No. 3, 4, and 5 are the third, second and first speed
clutches. The No. 5 clutch is a rotating clutch.
In this sectional view of the transmission, the input shaft and input sun
gears are shown in red. The output shaft and output sun gears are blue.The ring gears are shown in green. The planetary carrier is brown. The
planet gears and shafts are shown in orange. The clutch discs, clutch
plates, pistons, springs and bearings are shown in yellow. The stationary
clutch housings are shown in gray.
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The input sun gears are splined to the input shaft and drive the directional
gear trains. The output shaft is driven by output sun gears No. 3 and 4
and rotating clutch No. 5. When the No. 2, 3, or 4 clutches are engaged,
their respective ring gears are held stationary. The No. 1 planetary carrier
is held when the No. 1 clutch is engaged. When engaged, the No. 5rotating clutch locks the output components (for FIRST gear) to the
output shaft.
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Priority valve group:
1. Priority valve
2. Torque converter
inlet relief valve
3. Solenoid valve
4. Priority valve
pressure tap
40
Priority Valve
The priority valve group on the D6R Series II contains the priority valve
(1) and the torque converter inlet relief valve (2). A solenoid valve (3)
receives an output signal from the ECM to operate the priority valve at
either high or low pressure. A pressure tap (4) is also installed on the
priority valve to test priority valve pressure.
The priority valve ensures that the steering clutch and brake control valve
receives supply oil along with the transmission control group before
supplying oil to the torque converter circuit. The priority valve only
operates at high pressure during certain conditions to improve efficiency.
The solenoid valve, when DE-ENERGIZED, allows the priority valve to
operate at high pressure or 2930 kPa (425 psi). The solenoid isde-energized for the following conditions: When the oil temperature is
less than 40C (104F), during a speed or directional change, and when
the engine speed is below 1300 rpm.
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4
1
2
3
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The solenoid valve, when ENERGIZED, allows the priority valve to
operate at low pressure or 1100 kPa (160 psi) maximum. The solenoid
valve is energized for the following conditions: When the above
conditions are not fulfilled and when the parking brake is ENGAGED,
regardless of oil temperature or engine speed.
Oil from the torque converter flows through the torque converter outlet
relief valve to the oil cooler. By maintaining oil pressure in the torque
converter, the outlet relief valve ensures efficient power transfer between
the engine and transmission, and also prevents cavitation in the torque
converter.
Oil from the oil cooler lubricates the steering clutches and brakes and the
transmission planetaries before returning to the power train sump. The
implement and winch pump drive gears and bearings receive lubrication
oil from the inlet side of the torque converter.
The torque converter inlet relief valve maintains adequate oil pressure to
the torque converter while the torque converter outlet relief valve prevents
the pressure from becoming too high in the torque converter.
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41
TO TORQUE CONVERTER
SUPPLY
SOLENOID
VALVE
PRIORITY
VALVE
PRIORITY VALVEPRIORITY MODE
The Priority Valve makes sure that oil pressure is first available for
steering, braking, and transmission control, and then for torque converter
operation and lubrication of the steering clutches, brakes, and
transmission. The priority valve has two modes of operation, Priority
Mode and Normal Mode. In Normal Mode, oil flow to the torque
converter, the lubrication system, and controls is separate. In Priority
Mode, priority is given to oil flow for steering, braking, and transmission
control.
This illustration shows the priority valve operating in the Priority Mode.
Oil enters the slug chamber on the left end of the spool, through the small
hole in the center of the valve stem. It then passes through the orifice in
the center of the check valve where it forces the slug against the stop.
Pressure then builds in the slug chamber, moving the valve to the right
against the valve spring, acting like a relief valve. The valve is held in a
metering position so that a pressure of 2965 kPa (430 psi).
Priority Valve:
- Two modes:
- Priority Mode
- Normal Mode
Priority Mode
operation
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During operation in the Priority Mode, the solenoid valve is de-energized,
which results in the valve spool being shifted to the left, as previously
described. The result is a restriction of supply oil to the torque converter
and lube system.
With the spool shifted to the left, supply pressure increases. The increase
in supply pressure causes oil flow to be restricted to the torque converter
and lubrication sections of the power train oil system. This oil combines
with the flow from the transmission and charging pump section through
the check valve (illustration 36, item 4), giving increased flow, or priority,
to steering, braking, and transmission control.
Three conditions will put the system in the Priority Mode: Engine speed
below 1350 rpm, power train oil temperature below 40C (104F), and
during transmission shifts.
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42
TO TORQUE CONVERTER
SUPPLY
SOLENOIDVALVE
PRIORITY
VALVE
PRIORITY VALVENORMAL MODE
This visual shows the priority valve in Normal Mode.
The coil of the solenoid valve is ENERGIZED when in the Normal Mode
of operation, opening up the passage for supply oil to pressurize the
chamber to the left of the slug. Since the left end of the valve spool has a
greater effective area than the right, the valve spool is shifted to the right.
This condition allows more supply oil to be directed to the torque
converter, lube system, and controls.
The increased flow to the torque converter now decreases the upstreamsupply pressure, which allows the check valve to close off. The oil from
the torque converter charging section of the pump is no longer combined
with the oil from the transmission and charging section of the pump, and
the flows from these two sections are once again separate.
Normal Mode
operation
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The priority valve only operates in the Normal Mode when engine speed
is above 1350 rpm, power train oil temperature is above 40C (104F),
and when transmission clutches are engaged.
The pressure tap for testing priority valve pressure is located at the top,
front of the priority valve group (illustration 40, item 4).
The pressure tap for testing the torque converter inlet pressure is located
on the side of the priority valve group (see illustration 32, item 1).
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Pressure tap for
priority valve
Pressure tap for
torque converter inlet
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43
Three section pump:
1. Torque converter
charging section
2. Transmission
charging section
3. Scavenge section
3
4
2
5
1
FROM
CONVERTER
SCAVENGE
PRIORITY
VALVE
TO TORQUE
CONVERTER
FROM OILCOOLER
STEERING AND
BRAKE VALVE
TRANSMISSION
CONTROL
GROUP
POWER TRAIN HYDRAULIC SYSTEMD6R SERIES II WITH FINGER TIP CONTROL
3 2 1
PUMP SECTIONS
1. TORQUE CONVERTER CHARGING SECTION
2. TRANSMISSION CHARGING SECTION
3. TRANSMISSION AND TORQUE CONVERTER
SCAVENGE SECTION
This illustration shows the power train oil system components on the D6R
Series II machines equipped with steering clutches and brakes.
The power train oil system uses a three section gear pump. The scavenge
section (3) returns oil from the torque converter and transmission sumps
to the bevel gear case. The center section (2) sends oil at the same time to
the steering and brake control valve and the transmission control group.
The torque converter charging section (1) directs oil from the case to the
priority valve, the torque converter and, during certain conditions, sends
oil to the steering and brake control valve and the transmission control
group.
NOTE: For more information on the steering and brake controls,
refer to the Technical Instruction Module "Electronically Controlled
Steering and Brake System--D5M/D6M/D6R/D6R Track-type
Tractors" (Form SEGV2628).
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44
Differential steer
power train hydraulic
schematic
3
4
2
5
1
FROM
CONVERTER
SCAVENGE
PRIORITY
VALVE
TO TORQUE
CONVERTER
FROM OILCOOLER
BRAKE
VALVE
TRANSMISSION
CONTROL
GROUP
TO TRANSMISSION
CASE
POWER TRAIN HYDRAULIC SYSTEMD6R SERIES II WITH DIFFERENTIAL STEERING
3 2 1
PUMP SECTIONS
1. TORQUE CONVERTER CHARGING SECTION
2. TRANSMISSION CHARGING SECTION
3. TRANSMISSION AND TORQUE CONVERTER
SCAVENGE SECTION
This illustration shows the power train oil system components on the D6R
Series II machines equipped with differential steering.
The only difference is that the differential steer machine does not have
steering clutches and uses only one proportional solenoid on the brake
valve.