Various embodiments include a method for operating a fuel injector with a solenoid drive having a hydraulic stop at a predetermined fuel pressure comprising: applying a first current profile to the solenoid including a first holding current value prespecifying the current flowing during a holding phase; determining a resulting first flux; determining a first force based on the first flux corresponding to a hydraulic force exerted on the armature by fuel; determining a deviation between the first force and an optimal force corresponding to the predetermined fuel pressure; determining a second holding current based on the first holding current and the determined deviation; and applying a second current profile to carry out a second injection process using the second holding current value to apply a hydraulic force on the armature by the fuel adapted to the optimal force value.

A fuel injection system of an internal combustion engine includes: an injector having a hydraulic control chamber controlling the delivery of fuel through the injector, an actively controlled first valve system controlling the pressure relief from the control chamber, movable between: a first position in which the first valve system closes the injector by deterring the pressure from being relieved from the control chamber through the first relief circuit, and a second position in which the first valve system opens the injector by allowing the pressure to be relieved from the control chamber through the first relief circuit. A second relief circuit allows the pressure to be relieved from the control chamber through the second relief circuit. The second relief circuit includes a second valve system passively controlled by the fuel pressure and movable between two positions deterring or allowing the pressure to be relieved from the control chamber through the second relief circuit.

A fuel injection system of an internal combustion engine includes: an injector having a hydraulic control chamber controlling the delivery of fuel through the injector, an actively controlled first valve system controlling the pressure relief from the control chamber, movable between: a first position in which the first valve system closes the injector by deterring the pressure from being relieved from the control chamber through the first relief circuit, and a second position in which the first valve system opens the injector by allowing the pressure to be relieved from the control chamber through the first relief circuit. A second relief circuit allows the pressure to be relieved from the control chamber through the second relief circuit. The second relief circuit includes a second valve system passively controlled by the fuel pressure and movable between two positions deterring or allowing the pressure to be relieved from the control chamber through the second relief circuit.

A target injector valve opening period is calculated based on a target fuel injection amount, and an injector (2) is controlled by a current supply control unit (51) in accordance with an injector drive period acquired based on the target injector valve opening period. An actual valve closing delay period is calculated based on a drive waveform of the injector (2) at this time, and a difference between an actual valve closing delay period and a valve closing delay period calculated from a target injector valve opening period is learned. Then, the injector drive period is corrected by feedback control using a result of this learning.

Various embodiments include a method for operating a fuel injector comprising: applying a first current to a solenoid to perform a first injection process and inject a predefined injection quantity; determining a value of a system parameter indicating the relationship between the actual fuel quantity and the predefined quantity; determining, on the basis of the value of the system parameter, whether the actually injected fuel quantity is smaller than the predefined fuel quantity by a predefined amount corresponding to a disparity between a magnetic force exerted on the armature in the direction of the pole piece and an opposite hydraulic force exerted on the armature by fuel; and if it was determined that the quantities differ by enough, applying a second current to the solenoid to perform a second injection; wherein the second current exerts a lower magnetic force on the armature in the direction of the pole piece.

Various embodiments include a method for operating a fuel injector comprising: applying a first current to a solenoid to perform a first injection process and inject a predefined injection quantity; determining a value of a system parameter indicating the relationship between the actual fuel quantity and the predefined quantity; determining, on the basis of the value of the system parameter, whether the actually injected fuel quantity is smaller than the predefined fuel quantity by a predefined amount corresponding to a disparity between a magnetic force exerted on the armature in the direction of the pole piece and an opposite hydraulic force exerted on the armature by fuel; and if it was determined that the quantities differ by enough, applying a second current to the solenoid to perform a second injection; wherein the second current exerts a lower magnetic force on the armature in the direction of the pole piece.

A drive unit of a fuel injection device includes a driver circuit. The driver circuit opens and closes a valve element of the fuel injection device by supplying a drive current to the fuel injection device. The driver circuit supplies the drive current to open the valve element and sets the drive current to zero in an intermediate lift area. The intermediate lift area is an area is which a lift amount of the valve element is smaller than a maximum target lift amount.

A drive unit of a fuel injection device includes a driver circuit. The driver circuit opens and closes a valve element of the fuel injection device by supplying a drive current to the fuel injection device. The driver circuit supplies the drive current to open the valve element and sets the drive current to zero in an intermediate lift area. The intermediate lift area is an area is which a lift amount of the valve element is smaller than a maximum target lift amount.

A method for operating an internal combustion engine, which has at least one combustion chamber, at least one intake valve associated with the combustion chamber, and at least one injector associated with the combustion chamber, includes injecting fuel directly into the combustion chamber by the injector in order to operate the internal combustion chamber, where at least one partial stroke of the injector is performed while the intake valve is open.

A method of controlling a fuel injection device that can control a small amount of injection is provided. A fuel injection device for use in an internal combustion engine, includes: a valve body that can open and close a fuel passage, a needle that transfers a force with the valve body, and executes valve opening/closing operation, and an electromagnet that includes a coil and a magnetic core provided as a driver for driving the needle, and a cylindrical nozzle holder disposed on an outer periphery of the magnetic core and the needle, in which a current is supplied to the coil to exert a magnetic attractive force between the magnetic core and the needle to open the valve body.