Patent ID: 8789511

Claim:
A controller for a pressure reducing valve applied to a fuel injection system which is provided with an accumulator accumulating a fuel which is supplied from a fuel pump to a fuel injector; a pressure reducing valve reducing an internal fuel pressure in the accumulator; and a fuel pressure sensor detecting a fuel pressure in a fuel supply passage from the accumulator to an injection port of the fuel injector, the controller controlling an operation of the pressure reducing valve in such a manner that the internal fuel pressure in the accumulator agrees with a target fuel pressure, the controller comprising: a fuel-pressure-variation detecting means for detecting a fuel pressure variation timing at which a detection value of the fuel pressure sensor is varied due to an opening operation or a closing operation of the pressure reducing valve, and a response-delay-time computing means for computing a response delay time from a time when a command signal is outputted until a time when the pressure reducing valve start opening or closing, based on a command timing at which the command signal is outputted to open or close the pressure reducing valve and the fuel pressure variation timing detected by the fuel-pressure-variation detecting means, wherein the fuel pressure sensor is provided to a plurality of fuel supply passages of which path length are different from each other, the controller further comprising: a time-difference computing means for computing a time difference between the fuel pressure variation timings detected by the fuel pressure sensors; a propagation-velocity computing means for computing a fuel pressure propagation-velocity in the fuel supply passage based on the time difference; and a propagation-delay computing means for computing a propagation delay time from a time when the pressure reducing valve starts opening or closing until the time of the fuel pressure variation timing, wherein the response-delay-time computing means for computing the response delay time by subtracting the propagation delay time from a specified time which corresponds a time period from the command timing until the fuel pressure variation timing.