Variable displacement high pressure pump for fuel injection systems

摘要

A variable displacement high pressure pump having a plurality of high pressure pumping units which receive fuel from a low pressure fuel pump. A rotary cam-driven roller tappet, for producing pumping displacement of the pumping plunger of a respective pumping element, is connected to the pumping plunger by a separated link in a manner permitting the pumping plunger to float relative to the roller tappet during at least a portion of each pumping cycle. As a result, the capacity of the pumping chamber can be limited to an extent that is less than the full stroke achievable by the pumping plunger being retracted to the maximum extent which is permitted by the driving cam. In this way, the quantity of fuel to be pressurized and injected into the common rail does not have to be determined by a cutting-off of a spilling flow of excess metered fuel during the compression stroke of the pumping plunger, so that a low pressure solenoid valve can be used, in the case of time-stroke and time-pressure metering, and no solenoid is required to control metering in the case of pressure-time metering.