Method for injection valves

1. A method for operating an internal combustion engine with one or more injection valves having nozzle needles activated by a respective piezo actuator, the method comprising:

actuating a particular piezo actuator in a pulse-width-modulated manner;

recording the T on and/or T off switching times of the pulse-width-modulated piezo output stage of the particular piezo actuator;

evaluating the recorded switching times to derive a position of the nozzle needle of the injection valve associated with the particular piezo actuator; and

using the derived positions to control actuation of the particular piezo actuator during operation of the internal combustion engine.

2. The method as claimed in claim 1 , further comprising modifying the pulse-width by evaluating comparator thresholds.

3. The method as claimed in claim 1 , further comprising:

detecting a shift of voltage difference U DCDC −UP (terminal voltage minus piezo voltage) resulting from a non-uniform change in piezo voltage; and

evaluating the shift of voltage difference as a change in the switching times.

4. The method as claimed in claim 1 , wherein a prespecified value and/or a real voltage at the injector is mapped by measuring a T on time.

5. The method as claimed in claim 1 , further comprising measuring an ON (T on) time and an OFF (T off) time.

6. The method as claimed in claim 1 , further comprising measuring an ON (T on) time and an OFF (T off) time in the actuation path.

7. The method as claimed in claim 6 , wherein the ON and OFF times are measured upstream of the gate driver and/or directly at the gate of the power MOS.

8. The method as claimed in claim 6 , further comprising measuring the mean value of the actuation pulse.