Electrically controlled unit fuel injector for fuel injection in diesel

Abstract

The unit fuel injector has a pump piston driven at a constant stroke length, which pumps fuel at injection pressure to an injection nozzle as long as an electrically actuated overflow valve blocks the flow of the fuel flowing from the pump work chamber to a low-pressure chamber via an overflow conduit. The overflow valve is inserted between a first section which communicates continuously with the pump work chamber and a second section leading to the low-pressure chamber of the overflow conduit and is secured to a housing part laterally projecting from the pump housing. The first section of the overflow conduit comprises a connecting bore leading away from the pump work chamber, a control conduit controlled by the overflow valve, and a transverse conduit connecting these two. The transverse conduit extends from the housing side remote from the projecting housing part to the control conduit, crossing through the cylinder bore and in every stroke position of the pump piston is sealed off, without additional sealing means, by the jacket face of the pump piston. The unit fuel injector is particularly suitable for high-pressure injection in Diesel engines.