Patent ID: 7458525

Claim:
A common rail injector for injecting fuel supplied from a common rail through a high-pressure channel, comprising: a control chamber for applying a pressure in a valve-closing direction to a nozzle needle; a control valve having a three-way valve structure for switching between communication and interruption of said control chamber with said high-pressure channel and a low-pressure channel, thereby increasing and decreasing the pressure of said control chamber; and a drive unit for driving a valve element of said control valve to selectively set the valve element on a low-pressure side seat, which communicates between said control chamber and said low-pressure channel, or a high-pressure side seat, which communicates between said control chamber and said high-pressure channel, wherein said drive unit has an actuator for causing a displacement when electrically energized, and a slide pin member for sliding inside a slide hole to transmit a driving force in accordance with the displacement of said actuator, said slide pin member having a pin-shaped extremity in contact with said valve element of said control valve accommodated in a valve chamber, a space formed around said pin-shaped extremity disposed between a sliding portion of said slide pin member and said low-pressure side seat is always communicated with said low-pressure channel through a throttle portion, which has a passage cross-sectional area smaller than a passage cross-sectional area of a portion of an adjacent channel that is located adjacent to said throttle portion on a low-pressure channel side of said throttle portion, and has a longitudinal axis generally parallel to a longitudinal axis of the throttle portion, to communicate between said throttle portion and said low-pressure channel, a diameter of an opening, which is surrounded by said low-pressure seat and is communicated with said low-pressure channel, is less than or equal to a diameter of an opening, which is surrounded by said high-pressure seat and is communicated with said high-pressure channel, and the pressure in said control chamber in communication with said valve chamber is exerted as an assistance force, so that a high-pressure side seat closing load becomes less than or equal to a low-pressure side seat opening load.