Engine fuel injection control device

1. An engine fuel injection control device equipped with a solenoid-type fuel injector, comprising:

a voltage sensor configured to detect a voltage of a solenoid in the fuel injector; and

a controller configured to set a valve-open period of the fuel injector based on a fuel injection amount according to an operation state of the engine, in order to control the fuel injector based on the set valve-open period,

wherein the controller is configured to correct the set valve-open period so that said valve-open period becomes shorter as the voltage detected by the voltage sensor at the time of opening the fuel injector becomes larger, in order to control the fuel injector based on the corrected valve-open period,

wherein the controller is configured to derive an attenuation characteristic of a residual voltage of the solenoid in the fuel injector based on a variation of the voltage detected by the voltage sensor, and to estimate the residual voltage at the timing of fuel injection, from the derived attenuation characteristic, in order to correct the set valve-open period based on the estimated residual voltage, and

wherein the attenuation characteristic is a relationship between an elapsed time from a completion of fuel injection and the voltage of the solenoid detected by the voltage sensor, which corresponds to the residual voltage of the solenoid.

2. An engine fuel injection control device equipped with a solenoid-type fuel injector, comprising:

a voltage sensor configured to detect a voltage of a solenoid in the fuel injector; and

a controller configured to derive an attenuation characteristic of a residual voltage of the solenoid in the fuel injector based on a variation of the voltage detected by the voltage sensor, and configured to set a valve-open period of the fuel injector based on an fuel injection amount according to an operation state of the engine, in order to control the fuel injector based on the set valve-open period,

wherein the attenuation characteristic is a relationship between an elapsed time from a completion of fuel injection and the voltage of the solenoid detected by the voltage sensor, which corresponds to the residual voltage of the solenoid, and

wherein the controller is configured to estimate the residual voltage at the timing of fuel injection, from the derived attenuation characteristic, and is configured to correct the set valve-open period based on the estimated residual voltage.

3. The engine fuel injection control device according to claim 2 ,

wherein the controller is configured to correct the set valve-open period so that the said valve-open period becomes shorter as the residual voltage becomes larger.

4. The engine fuel injection control device according to claim 1 ,

wherein the controller is configured to control the fuel injector to perform fuel injection two times or more for each combustion event in a cylinder of the engine, and is configured to correct the valve-open period of the fuel injector at the time of a second or subsequent fuel injection.

5. The engine fuel injection control device according to claim 1 ,

wherein the controller is configured to perform the setting correcting of the valve-open period, and the control of the fuel injector based on said valve-open period, when an injection interval between fuel injections from the fuel injector is less than a predetermined time.

6. The engine fuel injection control device according to claim 1 ,

wherein the controller is configured to control the fuel injector to perform fuel injection two times for each combustion event in a cylinder of the engine, and is configured to correct the valve-open period of the fuel injector based on the voltage detected by the voltage sensor at the start of a second fuel injection.

7. The engine fuel injection control device according to claim 2 ,

wherein the controller is configured to control the fuel injector to perform fuel injection two times or more for each combustion event in a cylinder of the engine, and is configured to correct the valve-open period of the fuel injector at the time of a second or subsequent fuel injection.

8. The engine fuel injection control device according to claim 2 ,

wherein the controller is configured to perform the correcting of the valve-open period, and the control of the fuel injector based on said valve-open period, when an injection interval between fuel injections from the fuel injector is less than a predetermined time.

9. The engine fuel injection control device according to claim 2 ,

wherein the controller is configured to control the fuel injector to perform fuel injection two times for each combustion event in a cylinder of the engine, and is configured to correct the valve-open period of the fuel injector based on the voltage detected by the voltage sensor at the start of a second fuel injection.

10. The engine fuel injection control device according to claim 1 ,

wherein the attenuation characteristic is configured such that the voltage of the solenoid is attenuated in accordance with an exponential function after the elapsed time becomes a first given value until the elapsed time becomes a second given value larger than the first given value.

11. The engine fuel injection control device according to claim 2 ,

wherein the attenuation characteristic is configured such that the voltage of the solenoid is attenuated in accordance with an exponential function after the elapsed time becomes a first given value until the elapsed time becomes a second given value larger than the first given value.

12. The engine fuel injection control device according to claim 1 ,

wherein the attenuation characteristic is configured such that the voltage of the solenoid is maintained at a constant value when the elapsed time is less than a first given value, and the voltage of the solenoid is maintained at a constant value when the elapsed time is equal to or greater than a second given value larger than the first given value.

13. The engine fuel injection control device according to claim 2 ,

wherein the attenuation characteristic is configured such that the voltage of the solenoid is maintained at a constant value when the elapsed time is less than a first given value, and the voltage of the solenoid is maintained at a constant value when the elapsed time is equal to or greater than a second given value larger than the first given value.

14. The engine fuel injection control device according to claim 1 ,

wherein the controller is configured to:

control the fuel injector to perform fuel injection two times or more for each combustion event in a cylinder of the engine;

acquire an injection pattern for injecting fuel from the fuel injector, according to an operation state of the engine;

obtain an injection interval between a first fuel injection and a second fuel injection, from the injection pattern, in order to determine whether or not the injection interval is less than a given time period;

control the fuel injector according to the injection pattern, when the injection interval is less than the given time period; and

control the fuel injector according to an injection pattern in which an injection period for the second fuel injection is corrected based on the residual voltage, when the injection interval is equal to or greater than the given time period.

15. The engine fuel injection control device according to claim 2 ,

wherein the controller is configured to:

control the fuel injector to perform fuel injection two times or more for each combustion event in a cylinder of the engine;

acquire an injection pattern for injecting fuel from the fuel injector, according to an operation state of the engine;

obtain an injection interval between a first fuel injection and a second fuel injection, from the injection pattern, in order to determine whether or not the injection interval is less than a given time period;

control the fuel injector according to the injection pattern, when the injection interval is less than the given time period; and

control the fuel injector according to an injection pattern in which an injection period for the second fuel injection is corrected based on the residual voltage, when the injection interval is equal to or greater than the given time period.

16. The engine fuel injection control device according to claim 14 ,

wherein the controller is configured to:

convert a crank angle at which the second fuel injection is to be started, into a time period from completion of the first fuel injection, based on a current engine speed, in order to set the time period as a criterion time period;

determine whether or not the criterion time period has elapsed after a completion of the first fuel injection;

control the fuel injector according to the injection pattern in which the injection period for the second fuel injection is corrected based on the residual voltage, when the criterion time period has elapsed after the completion of the first fuel injection; and

repeat determining whether or not the criterion time period has elapsed after the completion of the first fuel injection, until the criterion time period has elapsed, in order to restrict controlling the fuel injector according to the injection pattern in which the injection period for the second fuel injection is corrected based on the residual voltage, when the criterion time period has not elapsed after the completion of the first fuel injection.

17. The engine fuel injection control device according to claim 15 ,

wherein the controller is configured to:

convert a crank angle at which the second fuel injection is to be started, into a time period from completion of the first fuel injection, based on a current engine speed, in order to set the time period as a criterion time period;

determine whether or not the criterion time period has elapsed after a completion of the first fuel injection;

control the fuel injector according to the injection pattern in which the injection period for the second fuel injection is corrected based on the residual voltage, when the criterion time period has elapsed after the completion of the first fuel injection; and

repeat determining whether or not the criterion time period has elapsed after the completion of the first fuel injection, until the criterion time period has elapsed, in order to restrict controlling the fuel injector according to the injection pattern in which the injection period for the second fuel injection is corrected based on the residual voltage, when the criterion time period has not elapsed after the completion of the first fuel injection.