Patent ID: 8739764

Claim:
A method for correcting a fuel injection amount in a common-rail-type fuel injection control device, the method comprising: injecting a minute amount of fuel a plurality of times when a fuel injection valve is in a non-injection state; estimating an injection amount based on an amount of variation in an engine speed generated during the injection of the minute amount of fuel; determining a difference between a reference energizing time and an energizing time at the time of injection the minute amount of fuel, the reference energizing time corresponding to the estimated injection amount and a rail pressure during the injection of the minute amount of fuel, and acquired from a reference energizing time map, generated at the time of mounting the fuel injection valve, having a rail pressure and a fuel injection amount as input parameters; storing the difference between the reference energizing time and the energizing time at the time of injection the minute amount of fuel; correcting a subsequent energizing time based on the stored difference; correcting a deviation of a fuel injection amount caused by a deviation of an injection characteristic of the fuel injection valve; calculating an engine speed based on an amount of variation in a frequency component of an engine rotational signal; further correcting the corrected energizing time based on the presence or absence of an operation of an exhaust brake and a magnitude of a supercharging pressure; and further correcting the calculated engine speed based on the presence or absence of the operation of an exhaust brake and the magnitude of the supercharging pressure.