Hydraulic control valve and fuel injector using same

A fuel injector comprising:

• a fuel spray mechanism working to spray fuel;
• and
• a hydraulic control valve including a piezoelectric actuator and a hydraulic valve mechanism working to actuate said fuel spray mechanism, said piezoelectric actuator including a deformable element made of a material which produces a mechanical deformation under application of a voltage, said hydraulic valve mechanism working to convert the deformation of said piezoelectric actuator into a hydraulic pressure to move a valve member hydraulically for opening and closing a fluid port selectively, thereby controlling a second hydraulic pressure serving to actuate said fuel spray mechanism, said hydraulic valve mechanism being so designed that said piezoelectric actuator produces a maximum output force working to develop the hydraulic pressure when opening the fluid port through the valve member, the maximum output force decreasing after the fluid port is opened and being set smaller than one-half of a maximum possible output force of said piezoelectric actuator under application of a maximum working voltage to said piezoelectric actuator.

A hydraulic control valve comprising:

• an actuator working to be deformed mechanically under application of an electric energy;
• and
• a hydraulic valve mechanism working to convert deformation of said actuator into a hydraulic pressure and to change the hydraulic pressure as a function of the deformation of said actuator to move a valve member for closing either of a high-pressure port leading to a high-pressure passage and a low-pressure port leading to a low-pressure passage, when the electric energy is applied to said actuator, said hydraulic valve mechanism working to open the low-pressure port through the valve member while closing the high-pressure port, when the electric energy is released from said actuator, said hydraulic valve mechanism working to open the high-pressure port while closing the low-pressure port, said hydraulic valve mechanism being so designed that the electric energy to be applied to said actuator when opening the low-pressure port is greater than or equal to an electric energy required to close the high-pressure port.

A fuel injector comprising:

• a fuel spray mechanism working to spray fuel;
• and
• a hydraulic control valve including an actuator and a hydraulic valve mechanism working to actuate said fuel spray mechanism, said actuator working to be deformed mechanically under application of an electric energy, said hydraulic valve mechanism working to convert deformation of said actuator into a hydraulic pressure and to change the hydraulic pressure as a function of the deformation of said actuator to move a valve member for closing either of a high-pressure port leading to a high-pressure passage and a low-pressure port leading to a low-pressure passage to control a second hydraulic pressure serving to actuate said fuel spray mechanism, when the electric energy is applied to said actuator, said hydraulic valve mechanism working to open the low-pressure port through the valve member while closing the high-pressure port, when the electric energy is released from said actuator, said hydraulic valve mechanism working to open the high-pressure port while closing the low-pressure port, said hydraulic valve mechanism being so designed that the electric energy to be applied to said actuator when opening the low-pressure port is greater than or equal to an electric energy required to close the high-pressure port.