Abstract: A method and a device are described for detecting a fault current across a piezoelectric actuator (5) of an injector or its high voltage supply lead (6, 6a). Because the fault current upon contact with a person, for example, is relatively small compared to the useful current that charges or discharges the actuator, direct measurement of the current is not reliable. Therefore, it is suggested that, during the injection or in an injection pause, when the piezoelectric actuator (5) is charged, the voltage variation or a change in voltage (dU) be measured and the difference be compared to a predefined threshold value (S). When the threshold value (S) is exceeded, a fault message is produced, the voltage source is shut off, and/or the piezoelectric actuator (5) is discharged. The measured fault can be weighted using a counting algorithm. The method thus provides maximum protection upon contact, in particular for service personnel.

Abstract: Online optimization of injection systems having piezoelectric elements which are used, for example, as actuators in a fuel injection system of an internal combustion engine, wherein the piezoelectric element is activated by an activation voltage having a value set as a function of operating characteristics of the particular piezoelectric element, and based upon, for example, a correction value for injected fuel volume.

Abstract: A method is proposed for diagnosing the drive voltage for a piezoelectric actuator of an injector, in which the drive voltage is measured for the individual phases of the injection procedure. With respect to each control phase, a corresponding tolerance band is provided, which is set using the setpoint value of the drive voltage. The tolerance ranges are established as a function of operating and/or environmental conditions. If, for the individual drive cycles, the corresponding tolerance ranges are not reached, then, in response to repeated measurement, these erroneous measurements are counted. When a preestablished number for the erroneous measurements is exceeded, then an ongoing error is diagnosed. If, after a certain time, the number is not exceeded, then the counter is reset. In the case of an error, the error storage unit can be reset using a maintenance plug-in device during maintenance.

Abstract: The invention describes a method and an apparatus for a fuel injection system with a piezoelectric element for controlling the amount of injected fuel by charging and/or discharging the piezoelectric element, wherein the fuel injection system comprises a current flow controller for charging and/or discharging the piezoelectric element based upon the gradient of a voltage across the piezoelectric element due to a charge the piezoelectric element is carrying.

Abstract: A method of charging or discharging a piezoelectric element, in which electric charge carriers are transported back and forth between a supply voltage of a direct voltage source and a piezoelectric element in order to transmit an elastic deflection of the piezoelectric element to an actuator. An actuating movement of the actuator is modified as a function of the level of a voltage being applied to the piezoelectric element, a reduction of the level of the applied voltage being compensated for by at least one additional transmission of electric charge carriers during a holding phase of the piezoelectric element.

Abstract: According to the present invention, a method is proposed for determining the rail pressure of an injector having a voltage-controlled piezoelectrical actuator, the piezoelectrical actuator (2) actuating a nozzle needle (11) using hydraulic coupler (4). As a result of the pressure in the high-pressure channel (13), a coupler pressure (Pk) is built up via the hydraulic coupler (4), the coupler pressure inducing a piezovoltage (Ui) in the actuator (2). Because this voltage value is redundant with regard to the pressure value in the high-pressure channel (13), which is measured by a pressure sensor (D), the voltage value can be used for monitoring the functioning of the pressure sensor (D). In the event of the failure of the pressure sensor (D), emergency operation can be built up for the injector (1) with the assistance of the induced voltage (Ui). The injector (1) advantageously functions for injecting fuel in an internal combustion engine.

Abstract: A method of triggering a piezoelectric actuator which controls the injection of fuel into the combustion chamber of an internal combustion engine via a valve is described in which the operating situation of the engine is determined and the derivative with respect to time of the voltage, which can be picked off at the piezoelectric actuator, is selected as a function of the operating situation. Furthermore, a control unit for controlling a fuel injection system is described, in which a piezoelectric element is triggered in such a way that the derivative with respect to time of the voltage, which can be picked off at the piezoelectric actuator, is adjusted to the operating situation of the engine. Additionally described is a fuel injection system, having at least one piezoelectric actuator which is triggered accordingly.

Abstract: A method of calculating the voltage setpoint of a piezoelectric element as a function of a rail pressure is provided, in which a corrected voltage setpoint is formed by, among other adjustments, using a multiplier as a function of a temperature of the piezoelectric element. Additional adjustments for forming the corrected voltage setpoint includes adjusting the setpoint control voltage by multiplication by at least one correction value (multiplier) and/or by addition of at least one correction value (addend).

Abstract: The invention describes a method and an apparatus for detecting a load decrease when driving a piezoelectric element, for example, used as an actuator in a fuel injection system of an internal combustion engine. The method and apparatus are characterized in that an error signal is generated when the piezoelectric element reaches a target voltage more quickly than a predetermined minimum time interval during a charging or discharging operation.

Abstract: A fuel injection system for an internal combustion engine, in particular a diesel engine, having at least two cylinders, the fuel injection system having at least two actuator elements and at least one actuator element being assigned to each cylinder in order to inject fuel into the cylinder, and the fuel injection system having an injection control system for monitoring and/or resolving a conflict in triggering of the actuator elements.

Abstract: The invention describes a method and apparatus for operating a fuel injection system having a piezoelectric element (10, 20, 30, 40, 50 or 60) for controlling the amount of fuel injected into a combustion engine, characterized in that the piezoelectric element (10, 20, 30, 40, 50 or 60) is controlled based upon the charge it is carrying.

Abstract: The invention describes an apparatus and method for detecting a short circuit to a battery voltage when driving a piezoelectric element, for example, used as an actuator in a fuel injection system of an internal combustion engine. The apparatus and method are characterized in that separate switches are used for selecting a piezoelectric element to be operated and for selecting the operation that is to be performed on the piezoelectric element. A short circuit to battery voltage is detected by first activating the switches to select a piezoelectric element. For a predetermined time interval, the invention monitors for abnormal currents flowing in series with the piezoelectric element. If abnormal currents are detected, an error signal is generated indicating a short circuit to battery voltage.

Abstract: The invention describes a method and an apparatus for charging a piezoelectric element of a fuel injection system for, for example, an internal combustion engine. The apparatus is characterized in that the piezoelectric element is activated by an activation voltage having a value set as a function of measured fuel pressure in the fuel injection system.

Abstract: A method for determining the control voltage for a piezoelectric actuator of an injection valve in which at first the pressure in a hydraulic coupler is measured indirectly, before the next injection process. The pressure is measured since the piezoelectric actuator is mechanically coupled to the hydraulic coupler, so that the pressure induces a corresponding piezo voltage in the actuator. This induced voltage is used before the next injection process for correcting the control voltage for the actuator. Too low an induced voltage is valued as a fault for recognizing an intermittent injection operation. The injection valve may be used for a common rail system for fuel injection in a gasoline or diesel engine.

Abstract: The invention describes a fuel injection system comprising a piezoelectric element for controlling an amount of injected fuel, by charging and discharging the piezoelectric element using a driving circuitry, and a current diagnosis unit capable of detecting a fault of a current flowing in the driving circuitry within 10 &mgr;sec of the fault occurring.

Abstract: A method and a device for controlling a controller having a capacitive element. An ohmic resistor is connected in parallel to the capacitive element. The value of the ohmic resistor is determined at certain times, and then the type and/or temperature of the capacitive element is deduced on the basis of the value of the resistor.

Abstract: A method for determining the control voltage for a piezoelectric actuator of an injection valve in which at first the pressure in a hydraulic coupler is measured indirectly, before the next injection process. The pressure is measured since the piezoelectric actuator is mechanically coupled to the hydraulic coupler, so that the pressure induces a corresponding piezo voltage in the actuator. This induced voltage is used before the next injection process for correcting the control voltage for the actuator. Too low an induced voltage is valued as a fault for recognizing an intermittent injection operation. The injection valve may be used for a common rail system for fuel injection in a gasoline or diesel engine.