Detecting a predetermined opening state of a fuel injector having a solenoid drive

1. An engine controller for a vehicle, which engine controller is configured to perform instructions for:

applying a predetermined electrical voltage profile to a solenoid drive of the fuel injector;

detecting the temporal profile of the current strength of a current flowing through the coil of the solenoid drive;

detecting the temporal profile of the voltage across the coil;

determining a function based on the temporal profile of the current strength and the temporal profile of the voltage, wherein the function represents one of the interlinked magnetic flux and a temporal derivative of the interlinked magnetic flux in the solenoid drive; and

determining the time as the time at which the function has a characteristic feature.

2. The engine controller of claim 1 , wherein the characteristic feature is one of: a maximum, a minimum, a threshold value and an inflection point.

3. The engine controller of claim 1 , wherein the function comprises a calculation of f(t)=u(t)−R*i(t), wherein u(t) is the temporal profile of the voltage across the coil, R the electrical resistance of the coil, and i(t) the temporal profile of the current strength of the current flowing through the coil.

4. The engine controller of claim 3 , wherein the function comprises calculation of the interlinked magnetic flux by integration of f(t) and calculation of the temporal derivative of the interlinked magnetic flux.

5. The engine controller of claim 1 , wherein at least one of the function and time are determined using numerical methods.

6. The engine controller of claim 1 , wherein the predetermined opening state of the fuel injector is one of: the start of an opening phase, the end of the opening phase, the start of a closing phase and the end of the closing phase.

7. A method for determining a time at which a fuel injector for an internal combustion engine of a motor vehicle is in a predetermined opening state comprising:

applying a predetermined electrical voltage profile to a solenoid drive of the fuel injector;

detecting the temporal profile of the current strength of a current flowing through the coil of the solenoid drive;

detecting the temporal profile of the voltage across the coil;

determining a function based on the temporal profile of the current strength and the temporal profile of the voltage, wherein the function represents one of the interlinked magnetic flux and a temporal derivative of the interlinked magnetic flux in the solenoid drive; and

determining the time as the time at which the function has a characteristic feature.

8. The method of claim 1 , wherein the characteristic feature is one of: a maximum, a minimum, a threshold value and an inflection point.

9. The method of claim 1 , wherein the determination of the function comprises a calculation of f(t)=u(t)−R*i(t), wherein u(t) is the temporal profile of the voltage across the coil, R the electrical resistance of the coil, and i(t) the temporal profile of the current strength of the current flowing through the coil.

10. The method of claim 9 , wherein the function is equal to f(t).

11. The method of claim 9 , wherein the determination of the function comprises calculation of the interlinked magnetic flux by integration of f(t) and calculation of the temporal derivative of the interlinked magnetic flux.

12. The method of claim 1 , wherein at least one of the function and time are determined using numerical methods.

13. The method of claim 1 , wherein the predetermined opening state of the fuel injector is one of: the start of an opening phase, the end of the opening phase, the start of a closing phase and the end of the closing phase.

14. A method for actuating a fuel injector having a solenoid drive comprising:

applying a predetermined electrical voltage profile to a solenoid drive of the fuel injector;

detecting the temporal profile of the current strength of a current flowing through the coil of the solenoid drive;

detecting the temporal profile of the voltage across the coil;

determining a function based on the temporal profile of the current strength and the temporal profile of the voltage, wherein the function represents one of the interlinked magnetic flux and a temporal derivative of the interlinked magnetic flux in the solenoid drive; and

determining the time the fuel injector is in a predetermined open state as the time at which the function has a characteristic feature;

actuating the fuel injector based on the determined time, wherein a duration between the application of a boost voltage for opening the fuel injector and the application of a voltage for closing the fuel injector is changed when it is determined that the time occurs one of later and earlier than a reference time.

15. The method of claim 14 , wherein the characteristic feature is one of: a maximum, a minimum, a threshold value and an inflection point.

16. The method of claim 14 , wherein the determination of the function comprises a calculation of f(t)=u(t)−R*i(t), wherein u(t) is the temporal profile of the voltage across the coil, R the electrical resistance of the coil, and i(t) the temporal profile of the current strength of the current flowing through the coil.

17. The method of claim 16 , wherein the function is equal to f(t).

18. The method of claim 16 , wherein the determination of the function comprises calculation of the interlinked magnetic flux by integration of f(t) and calculation of the temporal derivative of the interlinked magnetic flux.

19. The method of claim 14 , wherein at least one of the function and time are determined using numerical methods.

20. The method of claim 14 , wherein the predetermined opening state of the fuel injector is one of: the start of an opening phase, the end of the opening phase, the start of a closing phase and the end of the closing phase.