A. M-injection pump With pneumatic governor
Operation of Injection Pump and RPM GovernorA. M-injection pump with pneumatic governor
The injection pump with pneumatic governor is provided with a mechanical starting and stopping device, as well as with a valve governor (venturi governor) mounted on intake manifold.
The injection pump has a separate oil lubrication system and should be serviced at regular maintenance intervals.
Layout and operation of pneumatic governor
The vacuum originating in intake manifold of engine is routed to vacuum chamber (26) of governor by means of a vacuum line attached to throttle valve housing. The atmospheric pressure chamber (25) of the governor is connected to atmosphere by way of the air cleaner.
Both pressure chambers are hermetically separated from each other by a diaphragm. Control rod (8) attached to diaphragm is displaced under influence of differential pressure between the atmospheric pressure chamber (25) and the vacuum chamber (26) and controls the injected quantity. The control spring pushes the diaphragm and the attached control rod (8) in direction of "full load" at the most up against double lever (9, full load), which rests with its other end against full load stop. The full load stop adjusts the max. permissible injection quantity.
The full load stop is resiliently supported, so that the lever can still be pulled by way of bowden wire beyond full load position into starting position when starting. When starting, the engine is provided with an injected fuel quantity, which is higher than the full load quantity. In addition to the control spring, the vacuum chamber (26) also houses the idle speed auxiliary spring (18, poppet). The idle speed auxiliary spring is connected to throttle valve on throttle valve housing by means of regulating linkage. As a result the poppet cam (15) is adapted to the respective throttle valve position.
The idle speed auxiliary spring serves the purpose of limiting the vibrations of control rod (B) in lower rpm and load range, as well as at idle to prevent any hunting of engine. At idle and in partial load range the control rod of the injection pump is therefore in balance between the forces of the vacuum, the control spring and the idle speed auxiliary spring (poppet).
Starting of engine
For starting, the stopping and starting lever is actuated in direction of starting. As a result, the spring-loaded stop bolt (17) in full load stop is pushed via double lever (9) into adjusting screw and the control spring can displace the diaphragm and thereby the control rod in direction of start (a). This means, that the engine is receiving more fuel while starting than during full load operation.
Idle range of engine
With the engine running at idle, the adjusting lever of the throttle valve rests against adjustable idle speed stop, and the venturi tube is almost completely closed. A vacuum will be established in vacuum chamber already at idle speed, which is enough to pull the control rod (8) into its idle speed position against the pressure of control spring (13). At reducing load, the engine accelerates and the vacuum increases. Consequently, the diaphragm will displace the control rod still further in direction of "stop": The engine will again run more slowly.
If, on the other hand, the load is increasing, the engine speed goes down and the vacuum decreases; the control spring will therefore displace the control rod in direction of "full" and the engine is again running faster. The governor is thereby limiting the idle speed in upward and downward direction, that is, it is controlling the idle speed.
Between idle and final speed
The governor keeps any speed between idle and final speed constant. The more the accelerator pedal, (or control flap respectively) is adjusted in direction of "FULL" (d) the higher the engine speed.
Maximum speed range of engine (full-load speed regulation)
To obtain nominal speed (full output) completely depress accelerator pedal; the adjusting lever of the throttle valve will then rest against its (adjustable) end stop (full load stop (2). The throttle valve is fully open. At first, the vacuum in vacuum chamber will be low; the vacuum required for max. speed control will be attained at nominal speed only.
When the nominal speed is exceeded, the control rod (8) will move away from its full load stop and will be displaced in direction of stop until the delivered fuel quantity has become so small that the upper idle speed can no longer be exceeded.
Stopping the engine
For stopping engine, the control rod (8) is pushed to stop by means of start and stop cable control. No more fuel will then be injected.