PISTON AND BARREL ASSEMBLY WITH STEPPED TOP AND HYDRAULICALLY-ACTUATED FUEL INJECTOR UTILIZING SAME

摘要

A hydraulically actuated fuel injector has an injector body (11) including a barrel (12) and defining a nozzle chamber (39), a needle control chamber (31), and a nozzle outlet (40) that opens to the nozzle chamber (39). The injector body (11) further includes an actuation fluid inlet (20) and an actuation fluid drain (21). A barrel (12) defines an actuation fluid cavity (22) and a piston bore (70), which includes an upper bore (72) and a lower bore (71). Fuel is hydraulically pressurized in the nozzle chamber (39). A piston (80) with a stepped top slides in the piston bore (70) and moves in between a retracted position and an advanced position. A needle valve member (44) in the nozzle chamber (39) moves between an open position and a closed position. The needle valve member (44) includes a closing hydraulic surface (49) exposed to pressure in the needle control chamber (31). A needle control valve including an actuator (15, 115). The needle control valve is attached to the injector body (11) and moves in between an off position in which the needle control chamber (31) is opened to a source of high pressure fluid (20) and an on position in which the needle control chamber (31) is opened to a low pressure passage (26). An actuation fluid control valve opens and choses the actuation fluid cavity (22).