Stanadyne Corporation

Mark Duquette

Kenneth H Klopfer

A hydraulically actuated servo piston and hydraulic advance piston are integrated into the cam follower of a unit pump or injector to provide variable advance for an injection event produced by the pump or injector. The servo piston is nested in the advance piston with fluid passageways in the advance piston selectively opened or closed by movement of the servo piston. The full pressure of a hydraulic pump is available to the advance piston for powering the advance function, while stepwise reduced levels of hydraulic pressure from the same hydraulic pump are applied to control movement of the servo piston. A damping orifice restricts flow of hydraulic fluid to and from the servo piston.

Servo controlled timing advance for unit pump or unit injector

A fuel injector unit pump, driven by a cam function to supply fuel to an injector for an injection event. The fuel injector unit pump includes a body and a pumping plunger reciprocably disposed within the body and has a driven end. A cam follower assembly is provided for engaging the cam and includes an advance piston that engages the driven end of the pumping plunger for advancing or retarding the timing of the injection event. The advance piston is movable in response to fluid pressure controlled by an advance control. A follower return spring is disposed between the body and the cam follower assembly and a plunger return spring is mounted coaxially with the follower return spring and between the body and the advance piston. The advance piston includes a main cavity and the cam follower assembly includes a housing and the fuel injector unit pump may also include a balance spring disposed between the main cavity of the advance piston and the housing of the cam follower assembly.

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Andover, CT, United States of America

Mark Duquette