High pressure fuel injection system for an internal combustion engine.

摘要

A high pressure fuel injection system for an internal combustion engine having a high pressure fuel pump (36) for delivering fuel to an accumulator type fuel injector (45). The output pressure of the fuel pump (36) is sensed by a pressure sensor which generates a voltage output to a control unit (48). The control unit (48) compares a reference voltage indicating the appropriate pressure for a given engine running condition, such as load and speed, with the voltage representing actual fuel pressure and operates a first release valve (46) for reducing the pressure in a conduit (42) connecting the fuel pump (36) with the fuel injector (45). A second release valve (51) operated by the control unit (48) controls a release passage (49) provided in the fuel pump (36) at a point intermediate the ends of the stroke of the pump plunger (37). Fuel relieved from the pumping chamber via the release passage (49) further limits the maximum pressure developed by the fuel pump (36) for certain engine running conditions. In its pumping stroke the pump plunger (37) closes the release passage (49) so that even if the second relief valve (51) fails and stays open the pump plunger (37) will still generates sufficient pressure to run the engine adequately.