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A fuel injector includes an injector housing having a plunger assembly disposed within a central axial bore and including a lower plunger, an intermediate plunger, and an upper plunger. The lower plunger reciprocates within the central bore to meter a variable quantity of fuel and to inject this fue

A fuel injector includes an injector housing having a plunger assembly disposed within a central axial bore and including a lower plunger, an intermediate plunger, and an upper plunger. The lower plunger reciprocates within the central bore to meter a variable quantity of fuel and to inject this fuel during downward portions of the reciprocating motion. A timing chamber formed between the upper and intermediate plungers receives an amount of timing fluid to create a variable length hydraulic link between the plungers. The fluid is drained from the chamber through a drain passage at the end of the injection cycle. The timing chamber has associated with it a mechanism for changing the effective flow function of the drain passage, at a point in the cycle following fuel injection, to maintain a large downward pressure on the lower plunger to hold the lower plunger down and thus prevent additional, undesired fuel flow into the combustion chamber. In a preferred embodiment, the drain passage is located along the central axis of the intermediate plunger, and the upper plunger is provided with a projecting portion which moves into position as the timing chamber collapses to effectively constrict the drain passage, thus changing the timing fluid flow function to a function which provides greater fluid pressure in the timing chamber.

대표청구항 ▼

A fuel injector of a type driven by a cam to operate in an injector cycle which includes an initial high cam speed portion and a subsequent lower cam speed portion at the end of the cycle to periodically inject fuel into the combustion chamber of an internal combustion engine during successive injec

A fuel injector of a type driven by a cam to operate in an injector cycle which includes an initial high cam speed portion and a subsequent lower cam speed portion at the end of the cycle to periodically inject fuel into the combustion chamber of an internal combustion engine during successive injector cycles, comprising: a) an injector body having a central bore and an injection orifice communicating between said central bore and the combustion chamber; b) upper and lower plungers mounted for reciprocating movement within said central bore between retracted and advanced positions during each injector cycle; c) hydraulic timing means for varying the timing of fuel injection during successive injector cycles, said hydraulic timing means including: i) a variable volume timing chamber formed between said upper plunger and said lower plunger; ii) timing fluid supply means for supplying timing fluid to said timing chamber to control the volume of said timing chamber during successive injector cycles; d) blowdown force generating means for creating a blowdown force on said lower plunger tending to hold said lower plunger in its advanced position following termination of fuel injection during each injection cycle, said blowdown force generating means including: (i) a drain passage through which timing fluid is expelled from said timing chamber following termination of fuel injection during each injector cycle, and (ii) multistage drain force varying means including a flow constricting portion with a central control orifice in said drain passage, and a projecting surface moving with at least one of said plungers and interacting with said drain passage for varying a backpressure of said timing chamber fluid according to a first function during a first period following the injection portion of the injector cycle, and according to a second, different function during a subsequent period following the injection portion of the injector cycle, the diameter of said central control orifice determining the flow of said timing fluid from said timing chamber during said high cam speed portion of the cycle, and the first and second functions determining the flow of said timing fluid from said timing chamber during said low cam speed portion of the cycle.