Abstract: The invention relates to a method and a device for actuating an injection valve, which has a piezo actuator and a nozzle needle, of a fuel injection system of an internal combustion engine, in which method a control unit, in a manner dependent on a setpoint stroke height of the piezo actuator in successive injection cycles, outputs a control signal for changing the actual stroke height of the piezo actuator, characterized in that the control unit changes the setpoint stroke height of the piezo actuator, for compensation of the temperature dependency of the capacitance of the piezo actuator, in a manner dependent on the temperature of said piezo actuator.

Abstract: The invention relates to a method and a device for actuating an injection valve, which has a piezo actuator and a nozzle needle, of a fuel injection system of an internal combustion engine, in which method a control unit, in a manner dependent on a setpoint stroke height of the piezo actuator in successive injection cycles, outputs a control signal for changing the actual stroke height of the piezo actuator, characterized in that the control unit changes the setpoint stroke height of the piezo actuator, for compensation of the temperature dependency of the capacitance of the piezo actuator, in a manner dependent on the temperature of said piezo actuator.

Abstract: A method is disclosed for determining the idle travel of a piezo-injector which has a piezo-actuator and a nozzle needle which is activated directly by the piezo-actuator. A test pulse is applied to the piezo-actuator, which pulse brings about a continuous increase in the piezo-travel. The time period is measured which passes between the starting of the test pulse and the time when the idle travel is overcome. The idle travel of the piezo-injector is then determined from the measured time period.

Abstract: An injection nozzle has a nozzle needle that suppresses metering of fluid in a closed position and otherwise allows the metering of fluid. Furthermore, the injection valve has a solid-state actuator that acts on the nozzle needle. A first operating phase is performed for a closing operation in a first operating mode, during which first operating phase the solid-state actuator is discharged to a predefined part charge. Furthermore, a second operating phase is performed, during which the solid-state actuator is operated as a sensor. An operating duration of the second operating phase is predefined such that the closed position of the nozzle needle is reached during the operating duration. A third operating phase is performed, during which the solid-state actuator is discharged further to a predefined reference state. In a second operating mode, the first and second operating phases are carried out and the third operating phase is omitted.

Abstract: A method for determining the actual start of injection is performed by an actuating device for a piezo fuel injection valve and includes the following steps. First, a test injection is carried out with such a short actuation duration that a start of shut-off takes place at a time so early that the nozzle needle does not reach the open end position. Said time is predefined by the actuation and is therefore precisely known. Next, the closing time of the nozzle needle is then determined by measurement and evaluation of an electrical variable of the piezo direct drive. Once the closing time and the time of the start of shut-off are known, the actual start of injection is calculated back from the closing time via the start of shut-off. This permits an adequately precise determination of the actual injection quantity in almost every operating state of the internal combustion engine.

Abstract: A method is disclosed for monitoring the state of a piezoelectric injector of the fuel injection system of an internal combustion engine, the piezoelectric injector having a piezoelectric actuator and a nozzle needle that can be moved by said piezoelectric actuator. The piezoelectric injector can be operated in a partial-stroke mode and a full-stroke mode. In the partial-stroke mode, the curve of an electrical parameter over time is recorded, the maximum value of the curve is determined, a constant parameter value that arises after the presence of the maximum value is determined, the duration between the presence of the maximum value and the reaching of the constant parameter value is determined, the difference between the maximum value and the constant parameter value is determined, and conclusions about the state of the piezoelectric injector are drawn on the basis of the determined duration and the determined difference.

Abstract: A method for monitoring an injection fluid quantity, which is injected through an injection nozzle, includes opening and closing said injection nozzle by a closure element guided in one movement, detecting at least three characteristic points of the movement of the closure element at which the closure element is located at a certain position, and calculating the injection quantity from the at least three detected characteristic points.

Abstract: A method is disclosed for determining the idle travel of a piezo-injector which has a piezo-actuator and a nozzle needle which is activated directly by the piezo-actuator. A test pulse is applied to the piezo-actuator, which pulse brings about a continuous increase in the piezo-travel. The time period is measured which passes between the starting of the test pulse and the time when the idle travel is overcome. The idle travel of the piezo-injector is then determined from the measured time period.

Abstract: A method is disclosed for monitoring the state of a piezoelectric injector of the fuel injection system of an internal combustion engine, the piezoelectric injector having a piezoelectric actuator and a nozzle needle that can be moved by said piezoelectric actuator. The piezoelectric injector can be operated in a partial-stroke mode and a full-stroke mode. In the partial-stroke mode, the curve of an electrical parameter over time is recorded, the maximum value of the curve is determined, a constant parameter value that arises after the presence of the maximum value is determined, the duration between the presence of the maximum value and the reaching of the constant parameter value is determined, the difference between the maximum value and the constant parameter value is determined, and conclusions about the state of the piezoelectric injector are drawn on the basis of the determined duration and the determined difference.

Abstract: A method for determining the actual start of injection is performed by an actuating device for a piezo fuel injection valve and includes the following steps. First, a test injection is carried out with such a short actuation duration that a start of shut-off takes place at a time so early that the nozzle needle does not reach the open end position. Said time is predefined by the actuation and is therefore precisely known. Next, the closing time of the nozzle needle is then determined by measurement and evaluation of an electrical variable of the piezo direct drive. Once the closing time and the time of the start of shut-off are known, the actual start of injection is calculated back from the closing time via the start of shut-off. This permits an adequately precise determination of the actual injection quantity in almost every operating state of the internal combustion engine.