Method of controlling an injection quantity of an injector of an internal combustion engine

1. A method of controlling the injection quantity of a chargeable and dischargeable injector of an internal combustion engine, in which an injector voltage and an injector charge are determined, by means of which an energy, which is stored in the injector and correlates with the injection quantity, as well as an injector capacity are calculated, the method comprising the steps of:

determining a charge value and a voltage value after the end of a charging phase of the injector, and calculating a first energy value and a first capacity value from said charge value and said voltage value,

if a time length of a retaining phase between the charging phase and the discharge phase is longer than a definable period of time:

determining a new voltage value and a new charge value of the injector,

calculating a second capacity value from said new charge value and said new voltage value,

calculating a second energy value based on a square of the charge value and the second calculated capacity value,

determining a correction value based on the first calculated energy value and the second calculated energy value, and

storing the correction value in a first characteristics map, and

controlling said injector based on the calculated second energy value.

2. The method according to claim 1 , wherein the instant of the second voltage measurement and of the second charge measurement is at the end of the retaining phase.

3. The method according to claim 1 , wherein for determining the second energy value the charge determined at the end of the charging phase is squared and divided by the calculated capacity at the end of the retaining phase and multiplied by the factor 0.5.

4. The method according to claim 1 , wherein the correction value is stored in a first characteristics map, in dependence upon an actuator temperature of the injector and a rail pressure.

5. The method according to claim 1 , wherein the actuator temperature is determined by determining a mean capacity value of all actuators over a definable number of injections, and by means of a stored second characteristics map the actuator temperature for the mean capacity value determined in each case is identified.

6. The method according to claim 1 , wherein when the correction values are stored in the first characteristics map, the values present in the characteristics map prior to storing are overwritten.

7. A method of controlling the injection quantity of a chargeable and dischargeable injector of an internal combustion engine, in which an injector voltage and an injector charge are determined, by means of which an energy stored at the injector is calculated, which correlates with the injection quantity, and an injector capacity, that the method comprising the steps of:

determining a mean charge value and a mean voltage value after the end of the charging phase of all injectors, and calculating a first energy value and a first capacity value from said mean charge value and said mean voltage value,

if the period of time of a retaining phase between the charging phase and the discharge phase is longer than a definable time period,

determining an instantaneous mean voltage and an instantaneous mean charge of all injectors at a definable instant,

calculating a second capacity value from said instantaneous mean charge and said instantaneous mean voltage,

calculating a second energy value based on a square of the mean charge value and the second calculated capacity value,

determining a correction value based on the first calculated energy value and the second calculated energy value, and

storing the correction value in a first characteristics map, and

controlling said injector based on the calculated second energy value.

8. The method according to claim 7 , wherein the instant of the second voltage measurement and charge measurement is at the end of the retaining phase.

9. The method according to claim 1 , wherein the chargeable and dischargeable injector, is a piezoelectric injector.

10. The method according to claim 7 , wherein the chargeable and dischargeable injector, is a piezoelectric injector.

11. A method for controlling the injection quantity of a chargeable and dischargeable injector of an internal combustion engine, comprising the steps of:

determining a charge value and a voltage value after the end of a charging phase of the injector, and calculating a first energy value and a first capacity value from said charge value and said voltage value,

if a time length of a retaining phase between the charging phase and the discharge phase is longer than a definable period of time:

determining a new voltage value and a new charge value of the injector

calculating a second capacity value from said new voltage value and said new charge value,

calculating a second energy value based on a square of the charge value and the second calculated capacity value,

determining a correction value based on the first calculated energy value and the second calculated energy value, and

storing the correction value in a first characteristics map, and

controlling said injector according to the determined second energy value.

12. The method according to claim 11 , wherein the instant of the second voltage measurement and of the second charge measurement is at the end of the retaining phase.

13. The method according to claim 11 , wherein for determining the second energy value the charge determined at the end of the charging phase is squared and divided by the calculated capacity at the end of the retaining phase and multiplied by the factor 0.5.

14. The method according to claim 11 , wherein the correction value is stored in a first characteristics map, in dependence upon an actuator temperature of the injector and a rail pressure.

15. The method according to claim 11 , wherein the actuator temperature is determined by determining a mean capacity value of all actuators over a definable number of injections, and by means of a stored second characteristics map the actuator temperature for the mean capacity value determined in each case is identified.

16. The method according to claim 11 , wherein when the correction values are stored in the first characteristics map, the values present in the characteristics map prior to storing are overwritten.

17. The method according to claim 11 , wherein the chargeable and dischargeable injector, is a piezoelectric injector.