Combined fuel injection pump and injector - uses hollow plunger, spring pressurised needle and helical by=pass passages in plunger body

摘要

The injector housing contains a hollow plunger (2), inside which is the injector needle (3). This is held against the nozzle (8) by a spring (4) bearing against the inside back wall of the plunger. A thin plate (6) limits the backward movement of the needle with respect to the plunger. Fuel is delivered to the pressure chamber through a channel (9) in the housing. On its downward stroke, the plunger first shuts off the fuel supply opening (10) and then pressurises the fuel sufficiently for it to unseat the needle and atomise through the nozzle. On the return plunger stroke, the increased spring pressure rapidly slams the needle shut against the nozzle. Rotation of the plunger body by an electric stepping motor (14) allows inclined pressure release passages (11,12) to regulate the fuel injection quantity. By-pass fuel re-enters the fuel line through passages (15,16) and a sealing ring (17) prevents fuel leakage outside the injector housing. ADVANTAGE - Space-saving; rapid shut-off at end of working stroke.