Method and device for operating an injection valve

1. A method for operating an indirectly-driven injection valve having a longitudinal axis, a nozzle needle in a valve space, a control valve in a control space and an actuator which is embodied as a solid actuator in an actuator space, wherein the actuator is designed to act on the control valve, and the control valve is designed to act on the nozzle needle, wherein the nozzle needle is designed to prevent, in a closed position, a flow of fluid through at least one injection opening and otherwise to enable the flow of fluid, the method comprising:

feeding different predefined quantities of electrical energy to the actuator in a plurality of adaptation passes in order to change an axial length of the actuator,

for each respective adaptation pass:

after the predefined quantity of electrical energy which is assigned to the respective adaptation pass has been fed in, detecting a first and second voltage value across the actuator,

determining a voltage difference value as a function of the first and second voltage values, and

comparing the voltage difference value with a predefined threshold value for that respective adaptation pass,

determining, for a particular adaptation pass, that the voltage difference value is less than the predefined threshold value, which indicates that axial position of the nozzle needle remains unchanged throughout the feeding of the predefined quantity of electrical energy, and in response to such determination, discharging the actuator and executing a subsequent adaptation pass using a different predefined quantity of electrical energy, such that the particular adaptation pass involves electrically charging and discharging the actuator without causing an axial movement of the nozzle needle, and

determining, for the subsequent adaptation pass, that the voltage difference value is greater than or equal to the predefined threshold value, and in response to such determination:

determining an energy offset value based on the predefined quantity of electrical energy assigned to that respective adaptation pass, and

adapting at least one actuation of the actuator for injecting fluid as a function of the determined energy offset value.

2. The method according to claim 1 , wherein, in a way which correlates with the respective adaptation pass, in succession

during a charging phase the predefined quantity of electrical energy which is assigned to the respective adaptation pass is fed to the actuator,

during a holding phase for a predefined time period the feeding in of a further quantity of electrical energy is stopped, wherein the first and second voltage values are detected during the holding phase, and

the actuator is discharged during a discharge phase.

3. The method according to claim 1 , wherein the first voltage value is detected at a first time which is directly after the charging phase.

4. The method according to claim 1 , wherein the second voltage value is detected at a second time at which an oscillation of a movement of the control valve which is excited by means of the actuator has essentially decayed during the holding phase.

5. The method according to claim 1 , wherein a fault in the actuator is detected if the determined voltage difference is smaller in absolute value than the predefined threshold value and if the quantity of electrical energy which is fed to the actuator is larger in absolute value than a predefined maximum energy value.

6. The method according to claim 1 , wherein, during or after the adaptation pass in which the predefined threshold value is reached or exceeded in absolute value, an energy offset value is determined as a function of the quantity of electrical energy which is assigned to this adaptation pass, which energy offset value is taken into account for the actuation of the actuator in order to inject fluid and/or for the actuation of the actuator during subsequent adaptation passes.

7. The method according to claim 1 , wherein the quantity of electrical energy which is respectively fed to the actuator is increased in successive adaptation passes.

8. The method according to claim 1 , wherein the injection valve is coupled hydraulically to a high pressure accumulator in order to feed in fluid, wherein the adaptation passes are started if the pressure at which the fluid is stored in the high pressure accumulator has a predefined pressure.

9. The method according to claim 8 , wherein, during the adaptation passes, the pressure in the high pressure accumulator remains constant.

10. The method according to claim 8 , wherein the threshold value is predefined as a function of the predefined pressure.

11. A device for operating an injection valve having a longitudinal axis, a nozzle needle in a valve space, a control valve in a control space and an actuator which is embodied as a solid actuator in an actuator space, wherein the actuator is designed to act on the control valve, and the control valve is designed to act on the nozzle needle, wherein the nozzle needle is designed, in a closed position, to prevent a flow of fluid through at least one injection opening and otherwise to enable the flow of fluid, wherein the device is configured

to feed different predefined quantities of electrical energy to the actuator in a plurality of adaptation passes, in order to change an axial length of the actuator,

for each respective adaptation pass:

to detect a first and second voltage value across the actuator in a way which correlates with the respective adaptation pass after the predefined quantity of electrical energy which is assigned to the respective adaptation pass has been fed in,

to determine a voltage difference value as a function of the first and second voltage values,

to compare the voltage difference value with a predefined threshold value for that respective adaptation pass,

to determine, for a particular adaptation pass, that the voltage difference value is less than the predefined threshold value, which indicates that axial position of the nozzle needle remains unchanged throughout the feeding of the predefined quantity of electrical energy, and in response to such determination, to discharge the actuator and executing a subsequent adaptation pass using a different predefined quantity of electrical energy, such that the particular adaptation pass involves electrically charging and discharging the actuator without causing an axial movement of the nozzle needle, and

to determine, for the subsequent adaptation pass, that the voltage difference value is greater than or equal to the predefined threshold value, and in response to such determination:

to determine an energy offset value based on the predefined quantity of electrical energy assigned to that respective adaptation pass, and

to adapt at least one actuation of the actuator for injecting fluid as a function of the determined energy offset value.

12. The device according to claim 11 , wherein, in a way which correlates with the respective adaptation pass, the device is further configured in succession

to feed during a charging phase the predefined quantity of electrical energy which is assigned to the respective adaptation pass to the actuator,

to stop during a holding phase for a predefined time period the feeding in of a further quantity of electrical energy, wherein the first and second voltage values are detected during the holding phase, and

to discharge the actuator during a discharge phase.

13. The device according to claim 11 , wherein the first voltage value is detected at a first time which is directly after the charging phase.

14. The device according to claim 11 , wherein the second voltage value is detected at a second time at which an oscillation of a movement of the control valve which is excited by means of the actuator has essentially decayed during the holding phase.

15. The device according to claim 11 , wherein a fault in the actuator is detected if the determined voltage difference is smaller in absolute value than the predefined threshold value and if the quantity of electrical energy which is fed to the actuator is larger in absolute value than a predefined maximum energy value.

16. The device according to claim 11 , wherein, during or after the adaptation pass in which the predefined threshold value is reached or exceeded in absolute value, an energy offset value is determined as a function of the quantity of electrical energy which is assigned to this adaptation pass, which energy offset value is taken into account for the actuation of the actuator in order to inject fluid and/or for the actuation of the actuator during subsequent adaptation passes.

17. The device according to claim 11 , wherein the quantity of electrical energy which is respectively fed to the actuator is increased in successive adaptation passes.

18. The device according to claim 11 , wherein the injection valve is coupled hydraulically to a high pressure accumulator in order to feed in fluid, wherein the adaptation passes are started if the pressure at which the fluid is stored in the high pressure accumulator has a predefined pressure.

19. The device according to claim 18 , wherein, during the adaptation passes, the pressure in the high pressure accumulator remains constant.

20. The device according to claim 18 , wherein the threshold value is predefined as a function of the predefined pressure.