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 having an injector body defining an actuation fluid inlet, a fuel supply passage and a needle control chamber;
• a single solenoid attached to said injector body;
• a needle valve member movably mounted in said injector body and having a closing hydraulic surface exposed to pressure in said needle control chamber;
• a source of relatively low pressure fuel connected to said fuel supply passage;
• a source of relatively high pressure actuation fluid connected to said actuation fluid inlet;
• and
• a computer in communication with and capable of controlling said solenoid.

A hydraulically actuated fuel injector comprising:

• an injector body defining an actuation fluid inlet, an actuation fluid cavity, and a needle control chamber;
• a single solenoid attached to said injector body and being movable between a first position and a second position;
• a first valve member mounted in said injector body and being movable by said solenoid and operable to open and close said actuation fluid inlet to said actuation fluid cavity;
• a needle valve member movably mounted in said injector body and having a closing hydraulic surface exposed to pressure in said needle control chamber;
• and
• a second valve member mounted in said injector body and being movable by said solenoid and being operable to open and close said needle control chamber to a source of high pressure fluid.