Circuit arrangement and method for operating an injector arrangement

1. A circuit arrangement for operating an injector arrangement for injecting fuel in an internal combustion engine of a motor vehicle,

wherein the injector arrangement comprises one or more injectors each formed from an electrically actuatable actuator and a fuel valve designed to be activated by means of the actuator wherein the fuel valve comprises a valve body arranged movably relative to a valve seat,

wherein the circuit arrangement is formed to optionally supply an actuation voltage to each of the injectors for actuating the actuator via a conductor arrangement,

and wherein the circuit arrangement is designed to superimpose a measuring signal onto the actuation voltage, such that the actuation voltage and superimposed measuring signal are applied to the actuator, and such that a sensing signal is formed which is representative of the position of the valve body relative to the valve seat, wherein an evaluation of the sensing signal comprises determining, a runtime delay of sound waves generated by the actuator and reflected at a nozzle needle of the fuel valve.

2. The circuit arrangement according to claim 1 , wherein the measuring signal contains one or more signal portions with a respectively fixed frequency which is larger than the maximum actuation frequency to be expected during the operation of the injector arrangement.

3. The circuit arrangement according to claim 2 , wherein the fixed frequency is at least tenfold of the maximum actuation frequency to be expected during the operation of the injector arrangement and/or larger than a resonance frequency of the actuator.

4. The circuit arrangement according to claim 1 , wherein the measuring signal contains signal pulses, the duration of which is considerably shorter than the reciprocal of the maximum actuation frequency to be expected during the operation of the injector arrangement.

5. The circuit arrangement according to claim 1 , wherein the actuator is a piezoelectric actuator.

6. The circuit arrangement according to claim 1 , wherein measuring signal is superimposed by means of a frequency-selective coupling network.

7. The circuit arrangement according to claim 1 , wherein the measuring signal to be superimposed is guided over a switch to perform the superposition at predetermined points in time and/or periods.

8. The circuit arrangement according to claim 1 , wherein the evaluation of the electric properties of the actuator comprises a frequency filtering of a voltage tapped by the conductor arrangement.

9. The circuit arrangement according to claim 1 , wherein the evaluation of the electrical properties of the actuator comprises a Fourier analysis of a voltage tapped by the conductor arrangement.

10. The circuit arrangement according to claim 1 , wherein during the operation of the injector arrangement, the sensing signal is used with the control or regulation of a fuel injection quantity.

11. A method for operating an injector arrangement for injecting fuel in an internal combustion engine of a motor vehicle, wherein the injector arrangement comprises one or more injectors each formed of an electrically actuatable actuator and a fuel valve which is activated by means of the actuator wherein the fuel valve comprises a valve body which can be moved relative to a valve seat, the method comprising, for at least one actuator:

generating an actuation voltage for actuating the actuator via a conductor arrangement,

superimposing a measuring signal onto the actuation voltage,

supplying the actuation voltage and superimposed measuring signal to the actuator,

wherein the measuring signal supplied to the actuator generates sound waves which are reflected at a nozzle needle of the fuel valve to form a sensing signal,

measuring said sensing signal, and

determining a position of the valve body relative to the valve seat by determining a runtime delay of the reflected sound waves.

12. A method for operating an injector arrangement for injecting fuel in an internal combustion engine of a motor vehicle, wherein the injector arrangement comprises one or more electrically actuatable injectors each comprising an actuator and a fuel valve, wherein the fuel valve comprises a valve body arranged movably relative to a valve seat, the method comprising, for at least one actuator:

generating an actuation voltage for actuating the actuator via a conductor arrangement,

superimposing a measuring signal onto the actuation voltage,

supplying the actuation voltage and the superimposed measuring signal to the actuator, and

wherein the measuring signal superimposed on the actuation voltage generates sound waves which are reflected at a nozzle needle of the fuel valve to form a sensing signal, and

determining a position of the valve body relative to the valve seat based on a runtime delay of the sensing signal.

13. The method according to claim 12 , wherein the measuring signal contains one or more signal portions with a respectively fixed frequency which is larger than the maximum actuation frequency to be expected during the operation of the injector arrangement.

14. The method according to claim 13 , wherein the fixed frequency is at least tenfold of the maximum actuation frequency to be expected during the operation of the injector arrangement and/or larger than a resonance frequency of the actuator.

15. The method according to claim 12 , wherein the measuring signal contains signal pulses, the duration of which is considerably shorter than the reciprocal of the maximum actuation frequency to be expected during the operation of the injector arrangement.

16. The method according to claim 12 , wherein the actuator is a piezoelectric actuator.

17. The method according to claim 12 , wherein measuring signal is superimposed by means of a frequency-selective coupling network.

18. The method according to claim 12 , wherein during the operation of the injector arrangement, the sensing signal is used with the control or regulation of a fuel injection quantity.