Patent ID: 8670916

Claim:
A fuel injection system which supplies fuel to an internal combustion engine, comprising: a pump for pressurizing and feeding fuel, as stored in a fuel tank; an injector for spraying and supplying the fuel existing in a high-pressure fuel path communicating with an outlet of said pump into the internal combustion engine; pressure detecting means which is disposed in a portion of the high-pressure fuel path which is closer to the injector than to the outlet of the pump and is for detecting pressure of the fuel in the high-pressure fuel path; and discharge pressure calculating means for calculating a discharge pressure of the pump based on the pressure, as detected by the pressure detecting means, wherein the discharge pressure calculating means includes: propagation time calculating means for adding a time elapsing from detection of a detection pressure, as detected by the pressure detecting means before a start time of calculation of the discharge pressure, to the start time of the calculation to a time required for pressure to propagate from the outlet of the pump to the pressure detecting means to calculate a pressure variation consideration time; fuel increase/decrease amount calculating means for calculating a change in amount of the fuel existing in the high-pressure fuel path within the pressure variation consideration time; conversion means for converting the change in amount, as calculated by the fuel increase/decrease amount calculating means, into a change in pressure; and discharge pressure calculating means for calculating the discharge pressure of the pump based on the change in pressure, as converted by said conversion means, and the detection pressure.