Force balanced electronically controlled fuel injector

Abstract

A unit fuel injector is provided comprising an injector body containing a pumping chamber and a valve element provided for movement between (i) an advanced position wherein a supply passage communicates with the pumping chamber through a transfer passage and (ii) a retracted position wherein communication between the supply passage and the pumping chamber is blocked to allow fuel to flow from the pumping chamber through the transfer passage and out the discharge orifice. In one embodiment the valve element includes a control valve integrally formed with a tip valve, and a force balancing element for tending to balance the forces acting on the valve element by reducing the effective cross-sectional area upon which fluid pressure operates. The control valve, whether formed integral with or separate from the tip valve, extends through the solenoid to engage a valve seat formed adjacent the pumping chamber. The armature of the solenoid assembly is sized to be operatively positioned adjacent the stator inner pole without extending to a position adjacent the outer pole. The fuel transfer passage may be at least partially formed in the control valve.