Method for correcting fuel injection amount in common-rail-type fuel injection control device and common-rail-type fuel injection control device

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;
• correcting a calculated, based on a magnitude of a supercharging pressure, prescribed number of times to inject the minute amount of fuel based on the presence or the absence of an operation of an exhaust brake, and
• updating the difference between a reference energizing time and an energizing time at the time of injection the minute amount of fuel when the estimated injection amount converges with a predetermined threshold calculated based on a magnitude of the supercharging pressure and corrected based on the presence or the absence of the operation of the exhaust brake.

A common-rail-type fuel injection control device having an electronic control unit which executes an operation control of an internal combustion engine, the electronic control unit configured to:

• inject a minute amount of fuel a plurality of times when a fuel injection valve is in a non-injection state;
• estimate an injection amount based on an amount of variation in an engine speed generated during the injection of the minute amount of fuel;
• determine 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;
• store the difference between the reference energizing time and the energizing time at the time of injection the minute amount of fuel;
• correct a subsequent energizing time based on the stored difference;
• correct a deviation of a fuel injection amount caused by a deviation of an injection characteristic of the fuel injection valve;
• calculate an engine speed based on an amount of variation in a frequency component of an engine rotational signal;
• further correct 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 correct the calculated engine speed based on the presence or absence of the operation of an exhaust brake and the magnitude of the supercharging pressure.

A common-rail-type fuel injection control device having an electronic control unit which executes an operation control of an internal combustion engine, the electronic control unit being configured such that minute injection which is fuel injection of a minute injection amount is performed plural times when a fuel injection valve is in a non-injection state;

• an estimated injection amount which is estimated to be injected at the time of performing the minute injection is calculated based on an amount of variation in an engine speed generated in the minute injection;
• the difference between a reference energizing time corresponding to the estimated injection amount and a rail pressure at the time of performing the minute injection which is acquired from a reference energizing time map from which an energizing time acquired at the time of mounting the fuel injection valve with respect to various rail pressures and fuel injection amounts is readable as the reference energizing time using a rail pressure and a fuel injection amount as input parameters and an energizing time at the time of performing the minute injection is calculated,
• a result of calculation of the difference is stored as a learnt value in an updatable manner, and
• at the time of performing fuel injection subsequently, a value acquired by correcting the reference energizing time with the learnt value is set as an energizing time,
• so that the deviation of a fuel injection amount caused by the deviation of an injection characteristic of the fuel injection valve is correctable, and the amount of variation in the engine speed is calculated based on a rotational variation frequency component which is an amount of variation in a frequency component of an engine rotation signal, wherein
• the electronic control unit is configured such that a prescribed number of times of injection of the minute injection calculated based on the magnitude of a supercharging pressure is corrected based on the presence or the non-presence of an operation of an exhaust brake, and
• updating of the learnt value is allowed when the estimated injection amount is converged to a predetermined threshold value, and the predetermined threshold value calculated based on the magnitude of the supercharging pressure is corrected based on the presence or the non-presence of the operation of the exhaust brake.