Pump nozzle

摘要

A pump nozzle (1) for a fuel injection device, especially of diesel internal combustion engines with direct fuel injection, is described, which has a pump piston (9), which can be driven by at least one drive (8, 13) and generates the injection pressure, the pump working chamber (17) of which can be connected by way of a fuel pressure line (24) to a pressure admission chamber (25), which is assigned to a nozzle needle (26), closing the spray apertures (31) and loaded by a closing spring (27). In order to divide the injection in a pump nozzle of the said type into a pre-injection of small quantity and a main injection succeeding this at an interval for the purpose of reducing the combustion noise, it is proposed that means be provided for briefly reducing the pressure generated in the pump working chamber (17) below the opening pressure of the nozzle needle (26) during the pressure stroke of the pump piston (9). At the same time, it is proposed that the timing and/or the duration of the pressure reduction be controllable as a function of the operating state and that the pressure reduction be achieved by briefly connecting the pump working chamber (17) to a pressure relief chamber (37).