The present invention relates to an injector for injecting fuel, comprising an injector housing, a movable nozzle needle which is arranged in the injector housing and has a nozzle needle tip, a nozzle needle seat for receiving the nozzle needle tip, and a mechanical switch which upon contact of the nozzle needle tip with the nozzle needle seat assumes a closed state and upon interruption of the contact assumes an open state, wherein the injector is provided with an input line and an output line for actuating a movement of the nozzle needle, and the switch includes a first terminal and a second terminal. The injector is characterized in that the first terminal of the switch is connected to the input line and the second terminal of the switch is connected to the injector housing.

Disclosed is a method for discharging the pressure in a fuel supply rail of an injection system of an engine, the fuel injection rail connected to a fuel tank by piezo-electric injectors, each including a needle and a piezo-electric actuator pressing on a servo valve of the injector. The injection system includes a fuel pressure sensor and an electrical generator transmitting electric current pulses to each actuator. When the accelerator is released, a first electrical command allows determination of a moment of opening of the respective servo valve without triggering an injection. A second electrical command triggers a discharge of fuel from the fuel supply rail to the tank and therefore to discharge the pressure of the supply rail without triggering an injection. The second electrical command charges the piezo-electric actuator between a first voltage level that opens the servo valve, and a second voltage level triggering an injection.

A fuel system includes an electronic control module (ECM), at least one injector coupled to the ECM, and a configurable output driver circuit coupled to the at least one injector. The configurable output driver circuit includes a channel that enables adaptation of ECM outputs. The configurable output driver circuit is configurable based on a value stored in a register circuit.

An internal combustion engine comprises a fuel injection valve which has a needle, wherein a valve opening speed of the needle during post injection is raised as compared with a valve opening speed of the needle during main injection if a pressure of the fuel is not more than a first predetermined pressure, while the valve opening speed of the needle during the post injection is lowered as compared with the valve opening speed of the needle during the main injection if the pressure of the fuel is not less than a second predetermined pressure that is a pressure larger than the first predetermined pressure, when a requested post injection fuel amount is larger than an injection amount threshold value.

Method for controlling a fuel injector with a piezoelectric actuator acting on a valve element, including the following steps, in the normal operation of the vehicle: (200): Estimating an engine parameter (Pj.sub.EST), representative of an actual play (J.sub.REEL) between the piezoelectric actuator and the valve element, (300): Comparing the engine parameter with the equivalent parameter (Pj.sub.ECU) representative of the original play (J.sub.INIT): if the engine parameter differs from the equivalent parameter in such a way that the actual play is greater than the original play: Applying an electrical polarization charge to the piezoelectric actuator, in order to polarize the piezoelectric actuator during the injection of the fuel, Commanding the closure of the injector.

A method is provided for determining the fuel temperature in the high-pressure zone of a fuel injection system of a motor vehicle. The fuel injection system has at least one injector operated by a servo valve which is actuated by means of a piezo actuator. After an injection process has been carried out, the piezo actuator is discharged after the injection has ended in such a way that the servo valve can close, but a non-positive connection remains between the piezo actuator and the servo valve. This condition of reduced charge is maintained. The pressure oscillation of the actuator voltage resulting from this is recorded and from this the hydraulic natural frequency of the enclosed high-pressure volume of fuel is deduced. The prevailing fuel temperature can be determined from the natural frequency.

An injection valve has a moveable nozzle needle that controls a dosing of fluid and a solid-state actuator that actuates the nozzle needle. To operate the injection valve, values of a characteristic for a load state of the actuator are detected at a predetermined sampling rate. A start reference time and end reference time are determined correlating in chronological terms to an operating phase in which the solid-state actuator is discharged to a predetermined reference state by absorbing the energy in a discharging resistor. A correction reference value is determined based on a detected value of the characteristic correlating to an end of the operating phase, and a predetermined reference value. A correction value pattern is determined based on the end reference time, the start reference time, and the correction reference value. The detected values of the characteristic for the load state are determined based on the correction value pattern.

A method for repolarizing a piezoelectric actuator associated with an injector mounted on an internal combustion engine of a vehicle, the piezoelectric actuator having undergone initial polarization before the vehicle was used, includes with the engine stopped: applying a first polarization voltage to the terminals of the piezoelectric actuator during a first specified time interval of not less than ten minutes, stopping the application of the first polarization voltage during a second time interval, following the first time interval and at least equal to the latter, applying a second polarization voltage to the terminals of the piezoelectric actuator during a third specified time interval, following the second time interval, stopping the application of the second polarization voltage to the terminals of the piezoelectric actuator after the third time interval,
the successive first, second and third time intervals defining a repolarization sequence of the piezoelectric actuator.

A method for operating an internal combustion engine including feeding a pilot quantity of gas fuel, into a prechamber before a piston reaches a top dead center position. The method comprises autoignition of the pilot quantity of gas fuel in the prechamber, feeding a main quantity of gas fuel into the prechamber after the autoignition, and ignition of the main quantity of gas fuel by the conditions in the prechamber that are brought about by the autoignited pilot quantity. The method makes it possible to operate an internal combustion engine purely with methane or some other gaseous fuel, by means of compression autoignition of the pilot quantity.

A capacitive actuator is connected to an output of an apparatus which is formed with a capacitor connected between an input and a reference potential, with a full bridge with four power switching elements connected in parallel with the capacitor. To charge the capacitive actuator, a control circuit first turns on the first and third power switching elements. Current then flows from the first capacitor via a coil connected between the bridge paths and energy is stored in the coil. When a maximum current value is reached, the first and third power switching elements are switched off and magnetic energy stored in the coil decays due to current flow via the diodes of the second and fourth power switching elements. This charges the capacitive actuator. The capacitive actuator is charged to a predefined voltage by possible repeated switching of the first and third power switching elements.