Hydraulically-actuated fuel injector with rate shaping spool control

Abstract

A hydraulically-actuated fuel injector includes an injector body that defines an actuation fluid inlet, a first actuation fluid cavity, a second actuation fluid cavity and a nozzle outlet. A piston is positioned in the injector body and is moveable between a retracted position and an advanced position. The piston has a primary hydraulic surface exposed to fluid in the first actuation fluid cavity, and an opposing hydraulic surface exposed to fluid in the second actuation fluid cavity. A control valve includes a spool valve member that is moveable a distance between a first position and a second position. The first actuation fluid cavity is closed to the actuation fluid inlet when the spool valve member is in its first position. The first actuation fluid cavity is open, but the second actuation fluid cavity is closed, to the actuation fluid inlet when the spool valve member is moving through a first portion of the distance. The first actuation fluid cavity and the second actuation fluid cavity are open to the actuation fluid inlet when the spool valve member is moving through a second portion of the distance. The first actuation fluid cavity is open to the actuation fluid inlet when the spool valve member is in its second position.