Unit injector for internal combustion engines

Abstract

A unit injector for an internal combustion engine has a solenoid valve for closing a fuel overflow passage to determine the injection timing and the injection quantity. A pumping plunger has its outer peripheral surface formed with first and second longitudinal slits both communicating with the plunger chamber, and a circumferentially extending suction slit communicating with the first longitudinal slit and registrable with a fuel intake passage when the plunger is in an extreme position remote from the plunger chamber. The plunger can assume selectively a normal operating position, a starting position, and an emergency stopping position, at respective different circumferential positions thereof. In the normal operating position, the plunger chamber communicates with the fuel intake passage through alignment of the first longitudinal slit or the suction slit with the fuel intake passage, and also communicated and with the fuel overflow passage via the second longitudinal slit. In this position, the fuel injection rate may be reduced by a leakage groove continuous with the first longitudinal slit. In the starting position the plunger chamber communicates with the fuel intake passage through alignment of the first longitudinal slit or the suction slit with the fuel intake passage, but is disconnected from the the fuel overflow passage. In the emergency stopping position, the plunger chamber is dsconnected from both the fuel intake passage and the fuel overflow passage, or the plunger chamber is communicated with the fuel intake passage through the first longitudinal slit during the pressure delivery stroke of the plunger.