High pressure unit fuel injector with timing chamber pressure control

A fuel injector, adapted to be mounted within the head of an engine containing a fluid passageway for draining fluid, for periodically injecting fuel of a variable quantity on a cycle to cycle basis as a function of the pressure of fuel supplied to the injector from a source of fuel and at a variable time during each cycle as a function of the pressure of a timing fluid supplied to the injector from a source of timing fluid, comprising:

• an injector body containing a central bore and an injector orifice at the lower end of the body;
• a reciprocating plunger assembly including an upper plunger and a lower plunger mounted within said bore, a variable volume injection chamber being defined between said lower plunger and the lower end of said injector body containing said injector orifice, said variable volume injection chamber communicating during a portion of each injector cycle with the source of fuel, and a variable volume timing chamber located below said upper plunger, said timing chamber communicating for a portion of each injector cycle with a source of timing fluid;
• and
• pressure-responsive valve means for opening a timing chamber draining passage means in response to an opening pressure produced by a predetermined pressure of the timing fluid in said timing chamber being exceeded, said valve means being wholly formed above said lower plunger, and said draining passage means including a passage extending through said injector body which terminates at a sidewall of said injector body for providing communication with the fluid passageway provided in the engine head.

A fuel injector for periodically injecting fuel of a variable quantity on a cycle to cycle basis as a function of the pressure fuel supplied to the injector from a source of fuel and at a variable time during each cycle as a function of the pressure of a timing fluid supplied to the injector from a source of timing fluid, comprising:

• an injector body containing a central bore and an injector orifice at the lower end of the body;
• a reciprocating plunger assembly including an upper plunger and a lower plunger mounted within said central bore, a variable volume injection chamber being defined between said lower plunger and the lower end of said injector body containing said injector orifice, said variable volume injection chamber communicating during a portion of each injector cycle with the source of fuel, and a variable volume timing chamber located below said upper plunger, said timing chamber communicating for a portion of each injector cycle with a source of timing fluid;
• valve means for opening a timing chamber draining passage means in response to an opening pressure corresponding to a predetermined pressure of the timing fluid in said timing chamber, said valve means opening to allow drainage of the timing chamber during an injection stroke 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;
• first biasing means for upwardly biasing said lower plunger to control metering of timing fluid into said timing chamber;
• and
• second biasing means for controlling opening of said valve means independently of said first biasing means, whereby an opening force of said valve means is unaffected by the stroke of and biasing force on said lower plunger.