SE1951116A1

SE1951116A1 - Fuel injector arrangement, high pressure injection system comprising the injector arrangement, fuel system comprising the high pressure injection system, vehicle comprising the fuel system, and a meth

Info

Publication number: SE1951116A1
Application number: SE1951116A
Authority: SE
Inventors: Andreas Andersson; Kim Kylstyröm
Original assignee: Scania Cv Ab
Priority date: 2019-10-01
Filing date: 2019-10-01
Publication date: 2021-04-02
Also published as: SE545024C2; DE102020125356A1

Abstract

The present disclosure relates to a fuel injector arrangement (100) which comprises a fuel injector (24) comprising a valve (114) comprising an electromagnetic actuator (120) moving an armature (123) connected to an armature plunger (123) to provide an open position and a closed position for the valve. A pilot valve (130) is connected to a nozzle plunger (117) arranged to open and/or close injector outlets (140) and being actuated by the movement of the armature plunger (115). The pilot valve (130) is connected with the nozzle plunger via a hydraulic coupling including a first volume (131) associated with the armature plunger (115), a second volume (134) associated with the nozzle plunger (117) and an orifice (132) between the first and second volumes. The armature plunger (115) and the nozzle plunger (117) are arranged in a respective cavity (116; 118) with a match clearance allowing a leakage flow past the match clearance during the movement of the armature plunger (115). The leakage flow is the return flow of the fuel injector.

Description

Fuel injector arrangement, high pressure injection system comprising the injectorarrangement, fuel system comprising the high pressure injection system, vehicle comprising the fuel system, and a method of operating the fuel injector arrangement TECHNICAL FIELD The present disclosure relates to a fuel injector arrangement for an internal combustionengine of a vehicle, a high pressure injection system and a fuel system comprising thehigh pressure injection system. The present disclosure further relates to a method of operating the fuel injector arrangement as defined in the appended claims.BACKGROUND ART Internal combustion engines, such as diesel engines, are used for example in trucks,buses, passenger cars, motor boats, vessels, ferries and ships. Internal combustionengines ofthe defined type are also used in industrial engines and/or engine drivenindustrial robots, power plants such as e.g. electric power plants comprising a dieselgenerator, and for example in locomotives. Such internal combustion engines areassociated with a fuel system adapted to transport fuel from one or more fuel tanks viaan injection system comprising one or more fuel injectors to the internal combustionengine. The fuel system comprises one or more fuel pumps, which may be drivenelectrically or mechanically by the internal combustion engine. The fuel pumps create afuel flow and pressure to transport the fuel to the injection system. The injection system then supplies fuel to the internal combustion engine at high pressure.

Internal combustion engines may be driven by different fuels, e.g. by diesel. The fuel issupplied to the engine by means of a fuel system comprising an injection system with oneor more fuel injectors. When fuel injector is opened, fuel is supplied with high pressure tothe injector. All fuel is however not injected to the engine, whereby a return of the fuelback to the fuel tank is normally arranged in the fuel system. The excessive supply of fuelto the injector causes parasitic losses of fuel, which is undesirable. Additionally, diesel often contains particulate matter which may cause wear in the sensitive injectors.

Therefore, there is a need to decrease both parasitic losses in the fuel systems and wear in the fuel injectors.

There have been attempts to provide more durable lifespan forfuel injectors, ofwhich US 2012/0291753 A1 discloses an example.

However, there is still a need for a solution by which both parasitic losses in the fuel systems and wear in the fuel injectors can be decreased.SUMMARY OF THE INVENTION The objective of the present invention is thus to decrease both parasitic losses in the fuel systems and wear in the fuel injectors.

Additionally, it is an objective to prevent operational disturbances in fuel injectors and fuel systems associated with an internal combustion engine.A further objective is to provide a robust fuel injector.

The objectives above are attained with a fuel injector arrangement as defined in theappended claims. Especially, the fuel injector arrangement according to the presentinvention is associated with an injection system of a fuel system configured to supply fuel from a fuel tank to an internal combustion engine.

The fuel injector arrangement comprises at least one fuel injector comprising an injectorbody comprising a fuel inlet, at least one injector outlet and a valve comprising anelectromagnetic actuator configured to move an armature to provide an open positionand a closed position ofthe valve. The armature is associated with an armature plunger,which is associated with a pilot valve. The pilot valve is connected to a nozzle plungerarranged to open and/or close the at least one injector outlet. The nozzle plunger isactuated by the movement of the armature plunger. The fuel injector arrangementfurther comprises a fuel return outlet for returning fuel to the tank. The pilot valve isconnected with the nozzle plunger via a hydraulic coupling including a first volumeassociated with the armature plunger, a second volume associated with the nozzleplunger and an orifice between the first and second volumes. The return outlet is connected to the armature plunger. The armature plunger and the nozzle plunger are arranged in a respective cavity of the injector body with a match clearance allowing aleakage flow past the match clearance when the armature plunger is moved, i.e. movedup and down in the cavity. This leakage flow corresponds to the return flow of the fuelinjector. The leakage flow can thus be reduced and the leakage flow past the matchclearance may be arranged to be the only return flow from the fuel injector. By thisconstruction, parasitic losses in the fuel systems and wear in the fuel injectors can bedecreased. Since less particulate matter, which is present in the fuel, passes through thecomponents ofthe fuel injector, it is possible to prevent operational disturbances in thefuel injectors and thus in fuel systems associated with an internal combustion engine. By the present valve structure, a robust fuel injector is thus provided.

A surface area ofthe armature plunger facing the first volume may be larger than asurface area of the nozzle plunger facing the second volume. By the hydraulic connectionand the different plunger areas, it is possible to obtain a gear ratio for the parts whilelifting, i.e. it is possible to lift the armature plunger less than the nozzle plunger. Thus, thevalve may be quickly controlled while the nozzle plunger may be positioned in the open/closed position in an accurate manner.

An opening and closing speed and/or force ofthe valve may be arranged to be controllable. ln this way, smooth operation can be provided.

The opening speed of the nozzle plunger may be arranged to be controllable by means ofthe size ofthe orifice. The size ofthe orifice affects the opening speed ofthe nozzle plunger.

The opening force of the armature plunger may be arranged to be controllable by meansof a preload of a spring connected to the armature. The spring may have a pre-determined spring force adapted to provide the desired opening speed, when a solenoidactuates the armature. Thus, a simple and robust control device for the valve can be provided.

The nozzle plunger may be connected to a spring at a surface facing the orifice. Also thisspring may have a pre-determined spring force adapted to provide the desired opening speed, whereby a simple and robust control device for the valve can be provided.

The present invention also re|ates to a high pressure injection system comprising a high pressure pump, an accumulator and a fuel injector arrangement as described above.

Additionally, the present invention re|ates to a fuel system configured to supply fuel to aninternal combustion engine associated with a vehicle, the fuel system comprising a mainfuel pipe connecting a low pressure fuel pump, a fuel tank upstream of the low pressurepump, and a high pressure injection system as mentioned above downstream of the low pressure pump.

Furthermore, the present invention re|ates to a vehicle comprising the fuel system as described above.

Additionally, the present invention re|ates to a method of operating a fuel injectorarrangement associated with an injection system of a fuel system and configured tosupply fuel from a fuel tank to an internal combustion engine. The fuel injectorarrangement comprises at least one fuel injector comprising an injector body connectedto a fuel inlet, at least one injector outlet, and a valve comprising an electromagneticactuator configured to move an armature to provide an open position and a closedposition for the valve, the armature being associated with an armature plunger, which isassociated with a pilot valve, the pilot valve being connected to a nozzle plunger arrangedto open and/or close the at least one injector outlet, wherein the nozzle plunger isactuated by the movement of the armature plunger, the fuel injector further comprising afuel return outlet for returning fuel from the fuel injector to the tank. The method comprises the following steps: - opening the valve by lifting the nozzle plunger to an open position bylifting the armature plunger by means of an electromagnetic actuator,wherein the armature plunger is connected with the nozzle plunger via ahydraulic coupling of the pilot valve including a first volume associatedwith the armature plunger, a second volume associated with the nozzleplunger and an orifice between the first and second volumes, - during the movement of the armature plunger, leading a leakage flow past a match clearance between the nozzle plunger, the armature plunger and a respective cavity ofthe injector body, in which the nozzle plungerand the armature plunger are respectively arranged, to the return channelto provide a return flow of the fuel injector, - closing the valve by pushing the nozzle plunger into a closed position bymoving the armature plunger towards the out|et openings, the nozzle plunger thereby blocking the out|et openings.

The method may comprise controlling an opening and closing speed and/or force of thevalve. The controlling the opening and closing speed may be done by means of controllingthe size of the orifice. Furthermore, the method may comprise controlling the opening force by means of controlling a preload of a spring connected to the armature.

Further features and advantages are described below in the detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 schematically illustrates a vehicle comprising a fuel system ofthe present disclosure; Fig. 2 schematically illustrates an example coupling scheme for the fuel system ofthe present disclosure; Fig. 3 schematically illustrates an example of a fuel injector according to the present disclosure in an open position Fig. 4 schematically illustrates an example of a fuel injector according to the present disclosure in a closed position.DETAILED DESCRIPTION The solution of the present disclosure will be described in more detail below withreference to the accompanying drawings, which schematically illustrate examples of thepresent disclosure in a way not limiting the scope defined in the appended claims. Thedrawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the present solution or features thereof.

Generally, the present disclosure relates to a fuel injector arrangement, which is a part ofa high pressure injection system, which may also be referred to as a high pressure circuitin a fuel system of a vehicle. The fuel system may comprise a fuel tank arranged upstreamof a low pressure pump, which is arranged to suck fuel from the tank. The low pressurepump is arranged to supply and pressurize fuel further to a high pressure pump, which isarranged downstream of the low pressure pump and associated with the internalcombustion engine. Before injecting the fuel to the engine, it is supplied to anaccumulator connected to the injection arrangement, which is configured to provide fuelto the internal combustion engine. The low pressure pump pressurizes the fuel to 9-14bar, but is not limited thereto. The low pressure pump may be mechanically driven by theinternal combustion engine or it may be electrically driven. The high pressure pump isassociated with and located in close proximity of an engine block ofthe internalcombustion engine and is arranged to pressurize the fuel to a high pressure, e.g. to 500-2400 bar, but is not limited thereto. Thus, the low pressure pump pressurizes the fuel to apressure, which is more than 10, or more than 20 or more than 30 times smaller than theoperating pressure ofthe high pressure pump. Further, the tank, the low pressure pumpand the high pressure pump are connected by a main fuel pipe or conduit. The fuelsystem also usually comprises one or more fuel filters for purifying the fuel from particulate matter and/or water.

Fig. fl. schematically shows a side view of a heavy vehicle 1, which is a truck, comprising aninternal combustion engine 2, tlvhiclﬁ is associated tvith a fuel system fi- coniprisiiﬁg a fuel tank 11. Generally, in the present disclosure besides the vehicle heing a truck, the vehiclecould he any other type of a heavy vehicle, such as a hus. The vehicle 1 further comprises a gearhox 6 connected to the driving vvheels 1G of the vehicle 1 via a propeller shaft 8.

Fig. 2 illustrates schematically an example of a fuel system 4, in which the fuel injectionarrangement ofthe present disclosure is used. The fuel system 4 comprises a fuel tank 11from which fuel is sucked by means of a low pressure pump 12 to a high pressureinjection system 25 comprising a high pressure pump 19, which supplies fuel at highpressure to an accumulator 20. The fuel system is further provided with a main fuel pipe18, which connects the tank 11, the low pressure pump 12 and the high pressure pump 19 ofthe fuel system 4. ln the shown example in Fig. 2, the fuel system also comprises a fuel filter 17 arranged in the main fuel pipe 18 downstream of the low pressure pump 12and upstream of the high pressure pump 19, i.e. on the pressurized side ofthe lowpressure pump 12. A further fuel filter may be provided in the suction side of the lowpressure pump 12, i.e. upstream of the low pressure pump and downstream of the tank11. The accumulator 20 may be associated with a fuel return pipe 22, through which fuel not supplied to the engine 2 is returned to the tank 11.

The accumulator 20, which can be ofthe type common rail, supplies fuel to fuel injectors24, which in turn inject fuel to the internal combustion engine 2. To allow any excess fuelto be recirculated back to the tank 11, a return flow pipe 22 comprising a check valve 21 can be associated with the fuel injectors 24 and/or accumulator 20. ln this way, fuel can be returned back to the fuel tank while the check valve 21 prevents flow back to the fuelinjectors/accumulator. The return flow pipe 22 may be directly connected to the tank 11.Alternatively, the return flow pipe may be connected to the main fuel pipe 18 of the fuel system.

Generally, in this description by ”electromagnetic actuator" is meant an electric devicewhich transforms input energy to output mechanical work. An example of anelectromagnetic actuator is a solenoid actuator, which converts an electrical signal into amagnetic field producing motion of a part, e.g. pushing and pulling motion of an armature in a valve.

By ”pilot valve” is generally in this description meant a part ofthe valve positionedbetween an armature plunger and a nozzle plunger and connecting the same by hydraulicconnection to each other. The pilot valve is configured to control the valve feed by means ofthe hydraulic connection in which only small feeds are involved.

By ”match clearance” is meant a distance by which one object clears another or a clear space between them.

Reference is now made to Fig. 3 and Fig. 4 in which an example construction of a fuelinjector 24 comprised in a fuel injector arrangement 100 is shown schematically. ln Fig. 3,the valve 24 is in an open position, and in Fig. 4, the valve is in a closed position. The fuel injector arrangement 100 may be associated with the high pressure injection system 25 of a fuel system 4 as illustrated in Fig. 2, which is configured to supply fuel from a fuel tank 11 to an internal combustion engine 2.

The fuel injector arrangement 100 comprises at least one fuel injector 24 comprising aninjector body 110. The injector body 110 comprises a fuel inlet 111, at least one injectoroutlet 140, and a valve 114. The valve 114 comprises or is connected to anelectromagnetic actuator 120, e.g. a solenoid. The actuator 120 is configured to move anarmature 123 up and down in respect to an end stop plate 122 and to provide an openposition and a closed position for the valve. The armature 123 is associated with anarmature plunger 115, which is associated with a pilot valve 130. The armature 123responds to an electromagnetic signal from the solenoid and provides a pushing or pullingmotion to the armature plunger 115. The armature 123 may be connected to an upperarmature end stop 122. ln the shown example, the armature 123 in the form of a plate isconnected to a spring 124 positioned in between the armature 123 and the stop 122. Thespring 124 may have a pre-determined preload or spring force and can thus provide a desired opening speed for the valve 114.

The pilot valve 130 is connected to a nozzle plunger 117 of the valve. The nozzle plungeris arranged to open and/or close at least one injector outlet 140 located in a tip 150 of theinjector body 110. ln Fig. 3 the nozzle plunger is not in contact with the injector outletopenings 140, and thus the valve is in an open position and fuel can be injected from thevalve as illustrated by the arrows. ln Fig. 4, the valve is in a closed position, in which thenozzle plunger 117 blocks the outlet openings 140 and thus provides a closed position for the valve.

The nozzle plunger 117 is connected to the armature plunger 115 via a hydraulic couplingofthe pilot valve 130 and is actuated by the movement of the armature plunger 115. Thehydraulic coupling includes a first volume 131 associated with the armature plunger 115,a second volume 134 associated with the nozzle plunger 117 and an orifice 132 betweenthe first and second volumes 131, 134. The orifice 132 in the shown example alsocomprises a channel 133, by which the size or volume ofthe orifice can be controlled. ltshould be noted that the size ofthe orifice and the channel are exaggerated to moreclearly illustrate the example construction. The nozzle plunger 117 is thus configured to provide the open and/or closed position ofthe valve 24.

The fuel injector arrangement 100 further comprises the fuel return outlet 112 forreturning fuel to the tank 11 shown in Fig. 2. The return outlet 112 is connected to thearmature plunger 115. The armature plunger 115 is arranged in a cavity 116 of theinjector body 110 with a match clearance, i.e. open space between the armature plunger115 and walls of the cavity 116. ln this way it is possible to allow a leakage flow illustratedby the arrows past the match clearance when the armature plunger is moved up anddown in the cavity. ln a similar manner, the nozzle plunger 117 is arranged in a cavity 118ofthe nozzle body 110 with a match clearance, i.e. open space between the nozzleplunger 117 and walls ofthe cavity 117. Thus, the fuel not injected via the outlet openings140 is pressed through the match clearances between the nozzle plunger 117 andarmature plunger 115 and the respective cavities 118, 116. This leakage flow correspondsto the return flow ofthe fuel injector. The leakage flow may be arranged to be the onlyreturn flow from the fuel injector. Thereby it is possible to substantially decrease theamount of fuel returned to the fuel tank. Thereby, parasitic losses in the fuel systems andwear in the fuel injectors can be decreased. Since there is a decreased amount of fuelreturned to the fuel tank, also less particulate matter present in the fuel passes throughthe components of the fuel injector. Therefore, it is possible to prevent operationaldisturbances in fuel injectors and thus in fuel systems associated with an internal combustion engine. By the present valve structure, a robust fuel injector is provided.

As schematically illustrated in Fig. 3 and 4, a surface area a1 ofthe armature plunger 115facing the first volume 131 may be larger than a surface area A2 ofthe nozzle plunger 134facing the second volume 134. By the hydraulic connection and the different plungerareas, it is possible to obtain a gear ratio for the parts while lifting, i.e. it is possible to liftthe armature plunger 115 less than the nozzle plunger 117. Thus, the valve can be quicklycontrolled while nozzle plunger may be positioned in the open/closed position in an aCCUFate mannef.

An opening and closing speed and/or force ofthe valve may be arranged to be furthercontrollable. For example, the opening speed ofthe nozzle plunger 117 may be arrangedto be controllable by means ofthe size or volume of the orifice 132, which may includethe orifice channel 133. Additionally, to further control the speed, the nozzle plunger 117 may be connected to a spring 135 at a surface facing the orifice 132. The spring 135 may have a pre-determined spring force adapted to provide the desired opening speed, whereby a simple and robust control device for the valve can be provided.

The opening force of the armature plunger 117 may also be arranged to be controllableby means of a preload or spring force of a spring 124 connected to the armature 123. Thespring 124 may have a pre-determined spring force adapted to provide the desiredopening speed, when a solenoid actuates the armature. Thus, a simple and robust control device for the valve can be provided.

The present disclosure also relates to an injection system 25 comprising the high pressure pump 19, accumulator 20 and fuel injector arrangement 100 as described above.

Additionally, the present disclosure relates to a fuel system 4 illustrated in Fig. 2configured to supply fuel to an internal combustion engine 2 associated with a vehicle 1,the fuel system comprising a main fuel pipe 18 connecting a low pressure fuel pump 12, afuel tank 11 upstream of the low pressure pump 12, and a high pressure injection system as described above downstream ofthe low pressure pump 12.

Furthermore, the present invention relates to a vehicle 1 illustrated in Fig. 1 comprising the fuel system 4 as described above.

Additionally, the present invention relates to a method of operating a fuel injectorarrangement 100 associated with an injection system 25 of a fuel system 4 andconfigured to supply fuel from a fuel tank to an internal combustion engine 2. The fuelinjector arrangement comprises at least one fuel injector as described above and asillustrated schematically in Fig. 3 and 4. The method comprises opening the valve 114 bylifting the nozzle plunger 117 to an open position by lifting the armature plunger 115 bymeans of an electromagnetic actuator 120. The armature plunger 115 is connected withthe nozzle plunger 117 via a hydraulic coupling of the pilot valve 130, the hydrauliccoupling including the first volume 131 associated with the armature plunger 115, thesecond volume 134 associated with the nozzle plunger 117 and an orifice 132 between the first and second volumes 131, 134.

The method further comprises leading, during the movement ofthe armature plunger, a leakage flow past the match clearance between the nozzle plunger 117 and the armature 11 plunger 115 and the respective cavity 118, 116 to the return channel 112 to provide a return flow of the fuel injector.

The method also comprises a step of closing the valve by pushing the nozzle plunger 117into a closed position, in which the outlet openings 140 are blocked by the nozzle plunger117. The closed position can be obtained by moving or pushing the armature plunger 115towards the outlet openings by means of the electromagnetic actuator 120 or byreleasing the magnetic force acting on the armature plunger 115 and by letting the spring124 force the armature plunger 115 downwards. Since the nozzle plunger 117 ishydraulically connected with the armature plunger 115, the nozzle plunger 117 will moveby the movement of the armature plunger 115 downwards towards the tip 115 of theinjector body 110 and block the outlet openings 140. When the nozzle plunger 117 blocksthe outlet openings, the fuel inlet 111 is also blocked and closed. Thus, no fuel is fed tothe valve 114. Thereby no return flow is provided in the match clearances 116, 118 and the return outlet 122 can also thus be blocked.

The foregoing description ofthe examples has been provided for illustration of thepresent invention. The examples are not intended to limit the scope of the inventiondefined in the appended claims and features from the embodiments may be combined with one another.

Claims

1.

2. CLAll\/IS 1. A fuel injector arrangement (100) associated with an injection system (25) of a fuel system (4) configured to supply fuel from a fuel tank (11) to an internalcombustion engine(2), the fuel injector arrangement (100) comprising at least onefuel injector (24) comprising an injector body (110) comprising a fuel inlet (111), atleast one injector outlet (140) and a valve (114) comprising an electromagneticactuator (120) configured to move an armature (123) to provide an open positionand a closed position of the valve (114), the armature (123) being associated withan armature plunger (115), which is associated with a pilot valve (130), the pilotvalve being connected to a nozzle plunger (117) arranged to open and/or close theat least one injector outlet (140), wherein the nozzle plunger (117) is actuated bythe movement ofthe armature plunger (115), the fuel injector arrangementfurther comprising a fuel return outlet (112) for returning fuel to the tank (11),characterized in that the pilot valve (130) is connected with the nozzle plunger(117) via a hydraulic coupling including a first volume (131) associated with thearmature plunger (115), a second volume (134) associated with the nozzle plunger(117) and an orifice (132) between the first and second volumes and in that thereturn outlet (112) is connected to the armature plunger (115), the armatureplunger (115) and the nozzle plunger (117) being arranged in a respective cavity(116; 118) of the injector body (110) with a match clearance allowing a leakageflow past the match clearance when the armature plunger is moved to provide a return flow of the fuel injector (24). Fuel injector arrangement according to claim 1 or 2, wherein the leakage flow is arranged to be the only return flow from the fuel injector (24). Fuel injector arrangement according to claim 1 or 2, wherein a surface area (A1) ofthe armature plunger (115) facing the first volume (131) is larger than a surface area (A2) of the nozzle plunger (117) facing the second volume (134). 10. 11. 13 Fuel injector arrangement according to any one of claims 1 to 3, wherein anopening and closing speed and/or force of the valve (114) is arranged to be controllable. Fuel injector arrangement according to any one of the preceding claims, whereinthe opening speed of the nozzle plunger (117) is arranged to be controllable by means ofthe size ofthe orifice (132). Fuel injector arrangement according to any one of the preceding claims, whereinthe opening force ofthe armature plunger (115) is arranged to be controllable by means of a pre|oad of a spring (124) connected to the armature (123). Fuel injector arrangement according to any one of the preceding claims, whereinthe nozzle plunger (117) is connected to a spring (135) at a surface facing the orifice (132). A high pressure injection system (25) comprising a high pressure pump (19), an accumulator (20) and a fuel injector arrangement (100) of any one of claims 1-7. A fuel system (4) configured to supply fuel to an internal combustion engine (2)associated with a vehicle (1), the fuel system comprising a main fuel pipe (18)connecting a low pressure fuel pump, a fuel tank (11) upstream ofthe lowpressure pump (12), and a high pressure injection system (25) according to claim 8 downstream of the low pressure pump (12). Vehicle (1) comprising the fuel system (5) of claim 9. Method of operating a fuel injector arrangement (100) associated with aninjection system of a fuel system (4) and configured to supply fuel to an internalcombustion engine(2), the fuel injector arrangement (100) comprising at least onefuel injector (24) comprising an injector body (110) comprising a fuel inlet (111), at least one injector outlet (140) and a valve (114) comprising an electromagnetic 14 actuator (120) configured to move an armature (123) to provide an open positionand a closed position of the valve, the armature (123) being associated with anarmature plunger (115), which is associated with a pilot valve (130), the pilot valve(130) being connected to a nozzle plunger (117) arranged to open and/or close theat least one injector outlet (140), wherein the nozzle plunger (117) is actuated bythe movement ofthe armature plunger (115), the fuel injector (24) furthercomprising a fuel return outlet (112) for returning fuel from the fuel injector (24) to the tank (11), the method comprising the steps of - opening the valve (114) by lifting the nozzle plunger (117) to an openposition by lifting the armature plunger (115) by means of anelectromagnetic actuator (120), wherein the armature plunger (115) isconnected with the nozzle plunger (117) via a hydraulic coupling of thepilot valve (130) including a first volume (131) associated with thearmature plunger (115), a second volume (134) associated with the nozzleplunger (117) and an orifice (132) between the first and second volumes(131, 134), - during the movement of the armature plunger (115), leading a leakageflow past a match clearance between the nozzle plunger (117), thearmature plunger (115) and a respective cavity (118, 116) of the injectorbody (110), in which the nozzle plunger (117) and the armature plunger(115) are respectively arranged, to the return channel (112) to provide areturn flow of the fuel injector (24), - closing the valve by pushing the nozzle plunger (117) into a closedposition by moving of the armature plunger (115) towards the outletopenings (140), the nozzle plunger (117) thereby blocking the outletopenings (140). 12. I\/|ethod according to claim 11 comprising controlling an opening and closing speed and/or force of the valve (114). 1

3. Method according to claim 12 comprising controlling the opening and closing speed by means of controlling the size ofthe orifice (132). 1

4. Method according to claim 12 or 13 comprising controlling the opening force by means of controlling a pre|oad of a spring (124) connected to the armature (123).