Patent ID: 7305971

Claim:
A fuel injection apparatus for an engine comprising: a common rail accumulating fuel under a given pressure; a rail pressure sensor disposed to measure pressure of the fuel in said common rail and provide an output indicative thereof; fuel injectors each including an injector body, an injection valve, a pressure chamber, a control valve, a spring, and an actuator, the spring urging the control valve to close the pressure chamber, so that pressure in the pressure chamber acts on the injection valve to close a spray hole formed in the injector body, the actuator being supplied with electricity to move the control valve to open the pressure chamber, so that the pressure in the pressure chamber changes to move the control valve to open the spray hole for initiating injection of fuel into a corresponding one of cylinders of an engine; a controller working to control the electricity supplied to the actuator of each of said fuel injectors using the output from said rail pressure sensor for controlling the injection of the fuel into the engine and also monitor an operation state of said rail pressure sensor, when having determined that the operation state of said rail pressure sensor is unusual, said controller changing a value of the electricity supplied to the actuator to determine whether a resulting change in a preselected operation characteristic of the engine has appeared or not, when it is determined that the resulting change has appeared, said controller calculating a value of the rail pressure using the changed value of the electricity and a physical property of balance among forces acting on the control valve on one of said fuel injectors which has induced the change in operation characteristic of the engine.