HIGH PRESSURE UNIT FUEL INJECTOR WITH TIMING CHAMBER PRESSURE CONTROL VALVE

摘要

A high pressure unit fuel injector includes a timing chamber formed between upper and lower plungers of the injector for controlling the timing of injection. A timing chamber relief valve is provided for performing at least one of the functions of (1) draining timing fluid from the timing chamber during an injection stroke responsive to pressure in the timing chamber for maximizing the pressure of fuel in the injection chamber under low speed operating conditions without exceeding a pressure capability of the injector under high speed operating conditions, and (2) for collapsing the timing chamber in a controlled manner at termination of injection so as to prevent secondary injection from occurring. The relief valve structure is wholly formed above the lower plunger, preferably within the upper plunger above the timing chamber. Thereby, assembly and maintenance operations on the valve are facilitated. Also, by providing the relief valve structure in an upper part of the plunger, the timing chamber assembly can be easily adapted for use on different types of injectors, including open and closed nozzle injectors.