The invention relates to a fuel injection pump including a stepped plunger movable by a cam drive and having a reduced diameter portion for executing suction and delivery strokes and an end face for limiting the pump working space. The end face has a damping space connected with the suction space of the pump and whose volume can be changed. DE-OS 3,144,277 has already disclosed a fuel injection pump which, in order to increase the power by increasing the delivery rate of the pump plunger, has a hydraulic cushioning device in order to compliment the restoring forces required to decelerate the oscillating pump plunger, which restoring forces can no longer be produced by the helical springs which are supposed to hold the pump plunger in contact with the face cams. The known hydraulic cushioning device requires a restriction groove on the pump plunger in order to limit the outflow of the fuel from a damping space. The formation of the restriction groove on the pump plunger requires additional and, furthermore, cost-intensive operations since the restriction groove must usually be produced by erosion. Furthermore, the braking effect affects the majority of the pump plunger movement, with the result that the driving forces required are higher than necessary.
USPTO Backgrounds
USPTO Backgrounds