7 injection pump

8/12/2019 7 Injection Pump

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The main aim of the fuel injection pump isto deliver accurately metered quantity of fuel

under high pressure ranging from 110 bar to

200 bar at the correct instant to the injector

fitted on each cylinder of diesel engine.

Injection pump generally classified into

two categories namely

(1) Jerk type pump (e.g. Bosch pump)(2) distributor type pump (e.g. Roosa

master pump)


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JERK TYPE PUMP

(a) Sketch of typical plunger is shown. (b) Schematic diagram of the plunger within the

barrel is shown. Port A The fuel is always available under relatively

low pressure in side the barrel.

The plunger is driven axially along the barrel by acamshaft and can be rotated about its axis by means ofRack D.

The moment of which is controlled by the fuel controllever.

Port B is the orifice through which fuel is delivered to theinjector after passing through a spring loaded checkvalve.

Port C is the outlet port.


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Fig (b)

Shows the position of the plunger there is nofuel injection to combustion chamber.

Plunger is below port A, the fuel is filled above of

barrel by port A.

Plunger rises and close off port A, the liquid fuelmay passes through Port B or port C.

Overcome The Spring Force of Check Valve fuelwill leave from port C.


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FIG (c)

Plunger is rotated by fuel control lever in order to injectmaximum quantity of fuel per stroke.

Plunger moves upward past port A and traps the fuelin the barrel, it also closes of port C.\

The Trapped Fuel has no alternative except to oneescape through check valve.

This is the beginning of the injection it will continue

until helical indentation on the plunger uncovers theport C,


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FIG (D)

If plunger reaches port C fuel will escape

through port C. The Check Valve will close the Orifice B and fuel

injection ceases at the effective stroke ends.

The effective stroke of the plunger is defined as,

The axial distance traversed between the time port A is

closed off by the plunger, and the time port C

uncovered by the helix

In the effective stroke relative quantity of fuel

injected and depicted.


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Fig (e) & (d)

Another position of the Plunger rotated by

rack to inject the less than maximum

quantity of fuel injected by following the

above sequences of events.

Port C uncovers soon and the effectivestroke is shortened resulting in small

quantity of fuel is injected.


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Construction details

Shows individual BOSCH Injection pump. The

pump is positive displacement type.All individual high pressure pumps are placed in

one housing.

The plunger of which are activated by individual

cam which are arranged in line. High pressure line start at the pump and terminate

at the injector which is located in the cylinder head.

The amount of fuel is controlled by a horizontal

movement of the rack, which in turn rotates the

plunger and thus varies the effective stroke.


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The pump consists of two plungers

moving away from each other

moving towards each other

When the pump plunger moves away from eachother,

The fuel is drawn into the central rotor passage fromthe inlet port

When the pump plunger moves towards eachother,

Pressure is generated

With the rotation of rotor wherever the radial

delivery passage in the rotor coincides with the delivery

port the fuel is injected

7 injection pump

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