Method and device for controlling piezo-driven fuel injection valves
AssigneeSiemens Aktiengesellschaft
InventorJoachim Melbert
Life of this patent
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Abstract
The force exerted on an injector valve (4, 5), by the piezo-actuator (3) on a main injection, is determined by means of a non-linear actuator model (8) and thus the gradient (−dFHdt) of the drop-off in force after the force maximum (FHmax) and a threshold value (G) are derived, with which a gradient (−dFV/dt) determined for the pre- or post-injection is compared and, depending on the result of the comparison, the signal parameter (p) for the subsequent pre- or post-injection(s) is corrected.
Claims12
A method for controlling a fuel injection valve by means of a piezo-actuator, particularly for determining the injected fuel volume for pre- or post-injections, comprising the steps of:
- determining, from the current fed to the piezo-actuator for a main fuel injection and the voltage then building up at it, the temporal curve of the force exerted on the fuel injection valve,
- determining, from this temporal curve, the gradient of the tangent of the drop-off in force occurring after the force maximum,
- specifying a threshold value derived from these gradients of the tangent,
- determining, from the current fed to the piezo-actuator for a post-injection or pre-injection of a subsequent injection process following the main fuel injection and the subsequent voltage building up at it, the temporal curve of the force exerted by it on the fuel injection valve,
- determining, from this temporal curve, the gradient of the tangent of the drop-off in force occurring after the force maximum, and
- comparing the amount of this determined gradient with the threshold value, in which case it is assumed that a post- or pre-injection has taken place if the amount of the gradient exceeds the threshold value and it is assumed that a post- or pre-injection has not taken place if the amount of the gradient is less than the threshold value.
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 with a downstream end stage wherein control signals and signal parameters are fed to the pulsator from which it generates a signal shape for an output current of the end stage that is fed to the piezo-actuator,
- an analog/digital converter in which electrical signals that can be picked up at an input of the piezo-actuator are converted into digital signals,
- an arithmetic-logic unit in which the digital signals are processed for signal parameters for the pulsator, wherein the arithmetic-logic unit comprises a non-linear actuator model by means of which from the signals that can be picked up at the input of the piezo-actuator for each fuel injection, the temporal curve of force exerted on the fuel injection valve by the piezo-actuator, is determined and from the temporal curve the gradient of the drop-off in force after a force maximum is determined arithmetically and from the gradient 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 in which the amount of the gradient determined for each pre- or post-injection is compared with the threshold value stored in the storage unit, wherein a parameter correction is integrated in the comparator that corrects the signal parameters that can be fed to the pulsator according to the result of the comparison.
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.
Dependencies are inferred from the claim text.