Method for determining the opening point in the time of a fuel injector

1. A method for determining an opening point in time of a control valve of an indirectly controlled diesel fuel injector of a combustion engine of a motor vehicle, which control valve comprises a coil drive, the method comprising:

determining a progression with respect to time of a current strength of a current flowing through the coil drive,

calculating a current integral based on the determined current strength as a function of time commencing at a predetermined starting time, and

determining a point in time at which the current integral achieves a predetermined current integral reference value, wherein the determined point in time is the opening point in time of the control valve.

2. The method of claim 1 , further comprising determining the predetermined current integral reference value, which comprises:

detecting a point in time at which a pressure drops in a fuel line configured to supply fuel to the fuel injector, and

measuring the current integral at the detected point in time, wherein the measured current integral is the predetermined current integral reference value.

3. The method of claim 2 , wherein the predetermined current integral reference value is dependent upon the pressure in the fuel line, and wherein the process of determining the predetermining current integral reference value moreover comprises steps of:

measuring the pressure in the fuel line, and

storing the measured current integral and the measured pressure in a memory device of an engine control unit of the motor vehicle, wherein the measured current integral for the measured pressure is the pressure-dependent predetermined current integral reference value.

4. The method of claim 3 , comprising performing the process of determining the predetermined pressure-dependent current integral reference value for different pressures in the fuel line.

5. The method of claim 1 , comprising influencing the coil drive by a voltage corresponding to the battery voltage of a battery of the motor vehicle, in order to generate the current flowing through the coil drive.

6. A method for controlling an indirectly controlled diesel fuel injector of a combustion engine of a motor vehicle, wherein the fuel injector comprises a control valve having a coil drive, the method comprising:

determining an opening point in time of the control valve:

determining a progression with respect to time of a current strength of a current flowing through the coil drive,

calculating a current integral based on the determined current strength as a function of time commencing at a predetermined starting time, and

determining a point in time at which the current integral achieves a predetermined current integral reference value, wherein the determined point in time is the opening point in time of the control valve,

optimizing a time period for controlling the coil drive based on the determined opening point in time, and

controlling the indirectly controlled fuel injector wherein by influencing the coil drive with a voltage pulse having a duration equal to the optimized time period.

7. A device for determining an opening point in time of a control valve of an indirectly controlled diesel fuel injector of a combustion engine of a motor vehicle, which control valve comprises a coil drive, the device comprising:

a sensing device configured to determine the progression with respect to time of a current strength of a flow that flows through the coil drive,

a calculating unit configured to calculate a current integral based on the determined current strength as a function of time commencing at a predetermined starting time, and

a comparator unit configured to determine a point in time at which the current integral achieves at least a predetermined current integral reference value, wherein the determined point in time is the opening point in time of the control valve.

8. The device of claim 7 , further configured to:

detecting a point in time at which a pressure drops in a fuel line configured to supply fuel to the fuel injector, and

measuring the current integral at the detected point in time, wherein the measured current integral is the predetermined current integral reference value.

9. The device of claim 8 , wherein the predetermined current integral reference value is dependent upon the pressure in the fuel line, and wherein the process of determining the predetermining current integral reference value moreover comprises:

measuring the pressure in the fuel line, and

storing the measured current integral and the measured pressure in a memory device of an engine control unit of the motor vehicle, wherein the measured current integral for the measured pressure is the pressure-dependent predetermined current integral reference value.

10. The device of claim 9 , configured to perform the process of determining the predetermined pressure-dependent current integral reference value for different pressures in the fuel line.

11. The device of claim 7 , further configured to influence the coil drive by a voltage corresponding to the battery voltage of a battery of the motor vehicle, in order to generate the current flowing through the coil drive.

12. A computer program for determining the opening point in time of a control valve of an indirectly controlled diesel fuel injector of a combustion engine of a motor vehicle, which control valve comprises a coil drive, wherein the computer program comprises computer-readable instructions stored in non-transitory media and executable by a processor to:

determine a progression with respect to time of a current strength of a current flowing through the coil drive,

calculate a current integral based on the determined current strength as a function of time commencing at a predetermined starting time, and

determine a point in time at which the current integral achieves a predetermined current integral reference value, wherein the determined point in time is the opening point in time of the control valve.

13. The computer program of claim 12 , further comprising instructions for determining the predetermined current integral reference value by:

detecting a point in time at which a pressure drops in a fuel line configured to supply fuel to the fuel injector, and

measuring the current integral at the detected point in time, wherein the measured current integral is the predetermined current integral reference value.

14. The computer program of claim 13 , wherein the predetermined current integral reference value is dependent upon the pressure in the fuel line, and wherein determining the predetermining current integral reference value moreover comprises:

measuring the pressure in the fuel line, and

storing the measured current integral and the measured pressure in a memory device of an engine control unit of the motor vehicle, wherein the measured current integral for the measured pressure is the pressure-dependent predetermined current integral reference value.

15. The computer program of claim 14 , comprising instructions for performing the process of determining the predetermined pressure-dependent current integral reference value for different pressures in the fuel line.

16. The computer program of claim 12 , further comprising instructions for influencing the coil drive by a voltage corresponding to the battery voltage of a battery of the motor vehicle, in order to generate the current flowing through the coil drive.