The present disclosure provides a method for operating an injector of an internal combustion engine, the nozzle needle of said injector being operated by a piezo actuator by means of a servo valve. The method may include eliminating the idle travel of the piezo actuator by maintaining a permanent direct force connection between the piezo actuator and the servo valve, so that a change in force on the servo valve due to a change in pressure in the valve chamber when the servo valve is opened and closed and when the nozzle needle of the injector is closed is always transmitted to the piezo actuator as a change in force, detecting the resulting change in voltage and/or capacitance of the piezo actuator, and ascertaining parameters with which the injection quantity which is output by the injector is regulated based on the result of the detection.

The pressing part includes an abutment part capable of being in contact with the inner peripheral surface of the pressing passage, and a depressed opposite part that is opposed to the exhaust port at a position away from the exhaust port in a perpendicular direction perpendicular to the displacement direction due to an outer peripheral surface of the pressing part recessed from the abutment part even when the abutment part is in contact with the inner peripheral surface of the pressing passage. When the abutment part is in contact with the inner peripheral surface of the pressing passage, a depression dimension of the depressed opposite part relative to the abutment part is set, such that an amount of fuel discharged from the valve chest is defined by the exhaust throttle part instead of a gap between the depressed opposite part and the inner peripheral surface of the pressing passage.

A fuel injector for use in delivering fuel to an internal combustion engine includes a nozzle having a valve needle which is moveable with respect to a valve needle seating through a range of movement between a fully-closed position and a fully-open position to control fuel delivery through at least one nozzle outlet, whereby movement of the nozzle needle is controlled by fuel pressure within a control chamber. A nozzle control valve controls fuel flow into and out of the control chamber to pressurize and depressurize the control chamber, respectively. The fuel injector also includes a variable flow passage in communication with the control chamber through which fuel flows out of the control chamber at a variable rate throughout the range of movement of the valve needle so that movement of the valve needle is damped to a greater extent as it approaches the fully-open position.

An insert for use with a fuel injector comprises a shaft including a substantially cylindrical configuration defining a shaft cylindrical axis, a shaft radial direction, and a shaft diameter; and a head including a substantially cylindrical configuration defining a head cylindrical axis, a head radial direction, and a head diameter. The shaft and head may be attached to each other, the shaft cylindrical axis and the head cylindrical axis may be parallel to each other, the head diameter may be greater than the shaft diameter, and the shaft cylindrical axis may be spaced away from the head cylindrical axis.

An enclosure member includes a throughhole that penetrates a cover portion. The cover portion includes a blocking portion that receives an abutment by a wall portion to close an opening of an outflow passage with respect to spaces outside of the enclosure member. The blocking portion is provided so as to surround an opening of the throughhole, and the throughhole is in communication with the outflow passage even when the blocking portion is abutting the wall portion. Further, a spring is outside of a back pressure chamber to bias the enclosure member. The enclosure member itself blocks outside spaces from the back pressure chamber, so the expenditure of high pressure fuel may be controlled, and an injection hole may be opened and closed by a needle.

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.

An enclosure member includes a throughhole that penetrates a cover portion. The cover portion includes a blocking portion that receives an abutment by a wall portion to close an opening of an outflow passage with respect to spaces outside of the enclosure member. The blocking portion is provided so as to surround an opening of the throughhole, and the throughhole is in communication with the outflow passage even when the blocking portion is abutting the wall portion. Further, a spring is outside of a back pressure chamber to bias the enclosure member. The enclosure member itself blocks outside spaces from the back pressure chamber, so the expenditure of high pressure fuel may be controlled, and an injection hole may be opened and closed by a needle.