Timing control for fuel pump - using angularly adjustable cam ring controlled by hydraulically actuated piston with pressure correlated with engine speed

摘要

The fuel injection pump includes a charge pump for delivering discrete pulses of high pressure liquid fuel sequentially tp the several cylinders of an associated engine and has an angularly adjustable cam ring to control the timing of the pumping strokes. The position of the cam ring is controlled by an advance piston, the position of which is controlled by a hydraulic pressure correlated with engine speed. A load sensing piston, engageable with one end of the advance piston above a fixed amount of timing advance, is subjected to the pressure of the metered fuel downstream of the metering valve. This controls the quantity of fuel delivered by the pump to urge the advance piston in a direction to retard the timing of the pumping strokes. This results in a timing control system in which the timing is more advanced at high speeds and light load than it is at high speeds and full load.