Servo control synchronous advancing device for unit pump or unit oil sprayer

Abstract

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.

Description

technical field [0001] The present invention relates to a timing advance for use in fuel injection systems of the type commonly used in vehicle engines. Specifically, the present invention is an improvement over hydraulically actuated synchro advancer technology described in U.S. Patent Application Serial No. 09 / 638,758, "Synch Advancer for Unit Pump or Unit Injector" filed August 14, 2000 "Timing Advance Piston for Unit Pump or Unit Injector and Method Therefor," the disclosure of which is incorporated herein by reference. Background technique [0002] The automotive industry is under constant pressure to reduce unnecessary fuel injection from the internal combustion engines that power nearly all vehicles currently in use throughout the world. Although the engine has low emissions during steady state operation (such as while cruising), the fuel injection quantity is still high during non-steady state processes of the engine, such as start-up, accele...

AI Technical Summary

Problems solved by technology

Although the engine has low emissions during steady state operation (such as when cruising), the fuel injection vo

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