Hydraulically-actuated fuel injector with direct control needle valve

A fuel injection system comprising a plurality of hydraulically actuated fuel injectors with direct control needle valves, each injector comprising:

• an injector body defining an actuation fluid inlet, a fuel supply passage, and a needle control chamber;
• a piezo-electric actuator disposed in the injector body;
• a needle valve member moveably disposed in the injector body;
• a closing hydraulic surface exposed to pressure in the needle control chamber;
• a relatively slow moving actuation fluid control valve member moveable in response to the piezo-electic actuator;
• and
• a relatively fast moving needle control valve member moveable in response to the piezo-electric actuator,
• the system further comprising:
• a common source of low pressure fluid connected with the fuel supply passages of the plurality of hydraulically actuated fuel injectors;
• and
• a source of high pressure fluid connected to the actuation fluid inlets of the plurality of hydraulically actuated fuel injectors.

A hydraulically actuated fuel injector comprising:

• an injector body defining an actuation fluid inlet, an actuation fluid cavity, and a needle control chamber;
• a piezo-electric actuator attached to the injector body;
• a relatively slow moving actuation fluid control valve member disposed in the injector body and moveable in response to the actuator to open and close the actuation fluid inlet to the actuation fluid cavity;
• a needle valve member moveably disposed in the injector body and having a closing hydraulic surface exposed to pressure in the needle control chamber;
• and
• a relatively fast moving needle control valve member disposed in the injector body and moveable in response to the actuator to open and close the needle control chamber to a source of high pressure fluid.