Fuel injection system

A fuel injection system including an accumulator container configured to accumulate fuel in a high-pressure state, and a fuel injection valve configured to inject high-pressure fuel in the accumulator container to a cylinder of an internal combustion engine, wherein

• the fuel injection valve includes
• a control chamber configured to be supplied with the high-pressure fuel from the accumulator container through a high-pressure fuel passage,
• a needle valve configured to move in an axial direction according to a fuel pressure inside the control chamber to open an injection hole to inject the fuel, and
• a pressure adjusting valve placed in a fuel passage connected to the control chamber and configured to allow and to shut off an outflow of the fuel from the control chamber to adjust the fuel pressure inside the control chamber,
• the fuel passage includes a first fuel passage having a first orifice and a second fuel passage having a second orifice that is configured to limit a flow rate of the fuel through a flow passage area different from a flow passage area of the first orifice,
• the pressure adjusting valve includes a first on-off valve placed in the first fuel passage and a second on-off valve placed in the second fuel passage, and
• the system comprising:
• a pressure detection unit configured to detect the fuel pressure in the high-pressure fuel passage;
• a drive control unit configured to control opening and closing of the pressure adjusting valve based on a drive command signal output to the fuel injection valve;
• an acquisition unit configured to acquire an inflection point of the fuel pressure detected by the pressure detection unit and an inclination of the fuel pressure after the inflection point appears, after an output of the drive command signal;
• and
• a delay time computation unit configured to compute a response delay time of the pressure adjusting valve with respect to the drive command signal for each of the first on-off valve and the second on-off valve based on the inflection point and the inclination acquired by the acquisition unit.