Patent ID: 7353806

Claim:
A piezoelectric-actuated fuel injector device for injecting fuel into a combustion chamber of an internal combustion engine, the fuel injector device comprising: an elongate injector body with an injector cavity, an injector orifice communicating with one end of the injector cavity, and a fuel supply circuit adapted to supply fuel for injection through the injector orifice; a nozzle valve element in the injector cavity, the nozzle valve element adapted to move between an open nozzle position, in which fuel flows from the fuel supply circuit through the injector orifice into the combustion chamber, and a closed nozzle position, in which fuel flow through the injector orifice is blocked; a control chamber adapted to receive fuel from the fuel supply circuit and hold fuel at a control chamber pressure, the control chamber positioned to cause movement of the nozzle valve element between the open nozzle position and the closed nozzle position according to the control chamber pressure; a low pressure drain; a control valve closably connecting the control chamber to the low pressure drain to change the control chamber pressure, the control valve comprising: a valve chamber with a first end, a second end, and a fuel entrance positioned between the first and second ends for receiving fuel from the control chamber, the first end being a closable opening leading to the low pressure drain; a valve seat positioned at the first end of the valve chamber; a valve plunger movable along a first axis within the valve chamber between a closed plunger position, where the valve plunger is engaged with the valve seat to close the first end and block connection between the valve chamber and the low pressure drain, and an open plunger position, where the plunger is disengaged from the valve seat to open the first end and allow connection between the valve chamber and the low pressure drain; and an annular chamber within the valve chamber created by an annular indentation formed on the valve plunger, with a first annular surface and a second annular surface opposing the first annular surface, the fuel entrance being positioned between the first and second annular surfaces, and the first and second annular surfaces adapted to balance pressure acting on the plunger along the first axis from fuel entering through the fuel entrance; a passageway leading from the control chamber to the fuel entrance of the valve chamber, the passageway intersecting the valve chamber along a second axis transverse to the first axis of the valve chamber; a piezoelectric actuator adapted to move the valve plunger between the open valve position and the closed valve position; and a hydraulic linkage adapted to operably connect, at least partially, the piezoelectric actuator with the second end of the valve plunger and to compensate for dimensional changes between the piezoelectric actuator and the second end of the valve plunger.