Patent ID: 6847881

Claim:
A device for determining the injected fuel volume for pre- or post-injections, comprising: a fuel injection valve controlled by a piezo-actuator, a pulsator receiving control signals and signal parameters from which it generates a signal shape for an output current that is fed to the piezo-actuator, an analog/digital converter coupled with an input of the piezo-actuator, an arithmetic-logic unit coupled with said analog/digital converter and said pulsator, wherein the arithmetic-logic unit comprises a non-linear actuator model by means of which the temporal curve of force exerted on the fuel injection valve is determined from which the gradient of the drop-off in force after a force maximum is determined from which a threshold value is derived, a storage unit in which the gradient of each main fuel injection and the derived threshold value are continuously stored, and a comparator receiving the gradient determined for each pre- or post-injection and the threshold value stored in the storage unit for comparison, wherein a parameter correction is integrated in the comparator that corrects the signal parameters according to the result of the comparison.