Patent ID: 7204233

Claim:
A common rail fuel injection system for an internal combustion engine comprising: a high-pressure pump that feeds a high-pressure fuel; a common rail that accumulates the high-pressure fuel fed by the high-pressure pump; an injector that injects the high-pressure fuel accumulated in the common rail; a target common rail pressure calculator that calculates a target common rail pressure in accordance with a driving state of the internal combustion engine; a valve device that opens when an actual common rail pressure in the common rail exceeds a predetermined valve-opening pressure to flow the high-pressure fuel in the common rail to a low-pressure system; and a valve-opening pressure changer that changes the valve-opening pressure of the valve device into the target common rail pressure, wherein: the valve device is provided with a fixing member having a high-pressure passage communicated with the common rail, a valve body capable of blocking the high-pressure passage, and a spring urging the valve body to block the high-pressure passage; the valve-opening pressure changer is provided with an actuator that varies a spring force of the spring, and an actuator controller that controls the actuator to change the valve-opening pressure into the target common rail pressure; the valve device and the actuator are integrally provided as a pressure-reduction valve; and the actuator comprises a direction transformer for changing a compression amount of the spring and a motor for driving the direction transformer.