A fuel injector 100 includes a nozzle member 60 having a fuel passage 60a leading to an injection port 60b; a valve main body 51 adapted to reciprocate for opening and closing the fuel passage 60a; an elastic portion 56 elastically deformable in closing the fuel passage 60a by movement of the valve main body 51 in a closing direction, the elastic member being attached to one of the nozzle member 60 and the valve main body 51 and adapted to be abutted against the other of the nozzle member 60 and the valve main body 51 to close the fuel passage 60a by moving the valve main body 51 in the closing direction; and a stopper 70 adapted to restrict movement of the valve main body 51 in the closing direction by being abutted against the valve main body 51, the stopper 70 being formed of material different from the nozzle member 60.

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.

A method for detecting defective injectors includes operating an internal combustion engine in an idling mode and deactivating mixture control of the internal combustion engine. The method also includes switching off selectively each injector of the respective injection group, detecting the change in the characteristic value when the respective injector is switched off, and checking a fault criterion. The fault criterion is satisfied when the change in the characteristic value for the respective switched-off injector exceeds or undershoots a predetermined amount. The method also includes detecting a defect in the respective injector in response to the fault criterion being satisfied.

A fuel injection apparatus includes a valve element provided with a flow passage allowing a fuel to flow therethrough, a valve seat which the valve element will contact with or separate from, and a casing accommodating therein the valve element and the valve seat. During valve opening in which the valve element is separated from the valve seat, the fuel flowing through the flow passage is discharged through a gap between the valve element and the valve seat. A direction in which the valve seat is placed relative to the valve element is the same as a direction of the fuel flowing in the flow passage. The fuel injection apparatus further includes a discharge-side flow passage in which the fuel to be discharged during valve opening is allowed flow. The discharge-side flow passage is formed outside an outer peripheral portion of the valve seat.

A valve for metering a flowing medium, in particular a fluid, having a metering opening situated in the fluid flow and surrounded by a valve seat, a valve needle that controls the metering opening and that has a closing head that works together with the valve seat to close and release the metering opening, a piezoelectric actuator that acts on the valve needle to release the metering opening, and an elastic resetting element that acts on the valve needle to close the metering opening. To minimize the required stroke of the piezoelectric actuator for a required stroke of the closing head of the valve needle, the point of action of the resetting element on the valve needle is situated on or close to the end of the valve needle that bears the closing head.

A fuel injector for an internal combustion engine includes: an electromagnetic actuating element having a solenoid coil, a core and a valve casing as the outer solenoid circuit component, and a movable valve-closure body, which cooperates with a valve-seat surface assigned to a valve-seat body. The core and a connection pipe are fixedly connected in an inner opening of a thin-walled valve sleeve and the valve casing at the outer circumference of the valve sleeve is fixedly connected to the valve sleeve by being pressed in/on.

An injector drive device supplies driving electric power to injectors injecting fuel to cylinders of an internal combustion engine. The cylinders are grouped into multiple groups including at least a first cylinder group and a second cylinder group. The injector drive device includes: a booster circuit that boosts voltage of electric power supplied from an external power source; a first and second capacitors that accumulates electric power to be supplied to the injectors of the first cylinder group and the second cylinder group respectively; switch elements that selectively supply the output of the booster circuit to the capacitors; and a controller that, in the case where a charging amounts of the capacitors both are below a predetermined value, switches the switch elements to supply the output of the booster circuit preferentially to the capacitor that has a shorter period until a next planned fuel discharge start.

A fuel injection control apparatus is provided with a first valve opening timing determination portion that determines a first valve opening timing on the basis of a collision signal that is included in detected signals of an in-cylinder pressure sensor and indicates a collision between a movable core and a valve element and a second valve opening timing determination portion that determines a second valve opening timing on the basis of another collision signal that is included in the detected signals and indicates a collision between the movable core and a stationary core.

A fuel injector includes an injector body comprising an internal injector cavity, a flow passageway, and a drain conduit. The flow passageway is in fluid communication with at least one injector orifice. The fuel injector further includes a valve assembly comprising a valve seat and a valve member in fluid communication with the fuel circuit. The valve member is configured to move between an open position allowing fuel flow through the at least one injector orifice and a closed position inhibiting fuel flow through the at least one injector orifice. The fuel injector also includes a nozzle valve element fluidly coupled to the valve assembly, an actuator operably coupled to the valve assembly and the nozzle valve element, and a flexible member configured to elastically deform in response to pressure in the fuel injector. The flexible member is configured to inhibit flow to the drain circuit during an injection event.