Direct acting fuel injector

Abstract

An electrically controlled hydraulic actuated fuel injector wherein the amount of return fuel flow is substantially reduced without adversely affecting injection valve operation. An improved control valve armature valve disk of faster acting construction is also included. In one embodiment, dual pressurizing passages of differing diameters provide lower total fuel flow to a control chamber than the outflow through a depressurizing passage controlled by a control valve. Upon full opening of the injection valve, all return fuel flow is supplied to the control chamber through the smaller pressurizing passage, thereby reducing the requirement for pressure fuel flow. Upon closing of the control valve, cutting off discharge through the depressurizing passage, both of the dual pressurizing passages help fill the control chamber to quickly close the injection valve. The improved control valve armature is a small magnetically responsive disk fixed to a metal guide shim having a periphery clamped in the injector housing. Integral fingers of the shim are fixed to the disk, guiding its opening and closing motion free from rubbing on the housing. The fingers lie near the periphery of the shim and disk, allowing room for fuel flow between the disk and an associated solenoid to which the disk is attracted when the control valve is open. Hydraulic resistance to closing of the control valve is thus reduced.