A method for monitoring an injector for common-rail injection systems includes detecting an electrical signal indicative of a deformation of a diaphragm of a head plate having a reaction surface facing a control chamber of the injector and processing the deformation signal to determine characteristic data of the operation of the injector.

A nozzle assembly of a fuel injector includes a nozzle body in which a needle member is adapted to translate. The nozzle assembly is further provided with an electrical circuit so that an electrical signal enabling contact detection is measurable between the needle member and the nozzle body. The nozzle assembly also includes a piezoresistive device which continuously varies the electrical signal during the final closing displacements, or the initial opening displacements, of the needle, the variations of the signal being a function of a differential pressure.

A nozzle assembly of a fuel injector includes a nozzle body in which a needle member is adapted to translate. The nozzle assembly is further provided with an electrical circuit so that an electrical signal enabling contact detection is measurable between the needle member and the nozzle body. The nozzle assembly also includes a piezoresistive device which continuously varies the electrical signal during the final closing displacements, or the initial opening displacements, of the needle, the variations of the signal being a function of a differential pressure.

A fuel injector includes an injector housing, a longitudinally movable nozzle needle, and a force sensing element. The injector housing defines a nozzle chamber, a pressure chamber, and a measuring chamber. The nozzle chamber is configured to be supplied with pressurized fuel via a feed line formed in the injector housing. The pressure chamber is configured to be hydraulically connected to the feed line. The nozzle needle is disposed in the nozzle chamber and is configured to open and to close at least one spray hole. The force sensing element is disposed in the measuring chamber and is configured to detect a pressure in the pressure chamber. The measuring chamber is separated from the pressure chamber by a diaphragm-like intermediate wall. The force sensing element supports the intermediate wall.

A method for operating a fuel injection system with pressure reduction, and a fuel injection system that includes a fuel injection valve with a servo valve are provided. The method for operating a fuel injection system includes performing a desired pressure reduction in the pressure accumulator using at least one fuel injection valve of the fuel injection system. This is achieved by opening a servo valve in the fuel injection valve, which is opened, during a pressure reduction phase, just wide enough that the actual closing element remains closed and as a result no fuel injection process takes place.

A fuel injector includes an injector housing, a longitudinally movable nozzle needle, and a force sensing element. The injector housing defines a nozzle chamber, a pressure chamber, and a measuring chamber. The nozzle chamber is configured to be supplied with pressurized fuel via a feed line formed in the injector housing. The pressure chamber is configured to be hydraulically connected to the feed line. The nozzle needle is disposed in the nozzle chamber and is configured to open and to close at least one spray hole. The force sensing element is disposed in the measuring chamber and is configured to detect a pressure in the pressure chamber. The measuring chamber is separated from the pressure chamber by a diaphragm-like intermediate wall. The force sensing element supports the intermediate wall.

An actuator unit for a fuel injection valve of a vehicle internal combustion engine. The actuator unit includes an electronic component formed as a stack. The component includes a plurality of electrode layers and a plurality of material layers which are arranged alternately and react to the application of an electric field. The component also has two outer electrodes electrically connected to respective electrode layers on at least one circumferential side of the component. Additionally, the actuator unit has a piezoelectric sensor coupled to the component in a force-fitting manner, in the stroke direction of the component. When the component is in operation, the sensor detects a force generated by the component, as a voltage or charge between two electrodes arranged on opposing end faces, of a sensor element. The electrodes are deposited from an electrically conductive material directly onto at least the end faces of the sensor element.