Fuel injection valve for an internal combustion engine

Abstract

 A fuel injection valve (1) for an internal combustion engine comprising a housing (2) with a cavity (6) and a nozzle orifice (7) is disclosed. A valve needle (3) is positioned in the cavity (6). A valve spring (10) is positioned in the cavity (6), the valve spring (10) being mechanically coupled to the valve needle (3) for urging the valve needle (3) towards a closing position. The fuel injection valve comprises a sleeve (24) positioned in the cavity (6) for modifying a total force on the valve needle (3).

Description

[0001] The disclosure relates to a fuel injection valve for an internal combustion engine.

[0002] Fuel injection valves which operate electromagnetically are well known. With the aid of a magnetic coil which is chargeable by electricity to generate a magnetic field, a magnetisable armature will be stimulated for movement. The armature is coupled to a valve needle so that the valve needle starts moving due to the movement of the armature in order to unseal a nozzle orifice of the fuel injection valve. When the nozzle orifice is open, a fuel quantity, positioned in the fuel injection valve, may flow through the nozzle orifice into a combustion chamber, normally a combustion chamber of an internal combustion engine.

[0003] A combustion process of the internal combustion engine depends among several other criteria, e.g. fuel quantity or fuel temperature or fuel pressure - on the opening and closing of the nozzle orifice. Therefore, an exactly defined opening and closing of the nozzle orifice are very important for reaching an advantageous power rate, fuel consumption and/or emissions of the internal combustion engine.

[0004] A problem of fuel injection valves in the state of the art is a hydraulic force of the fuel. In a so called "non pressure balanced" fuel injection valve, the hydraulic force either urges - together with the valve spring - the valve needle against the nozzle orifice. In this case, a magnetic coil has to provide a magnetic field which is strong enough to lift the valve needle against the forces of the valve spring and the fuel. Or the hydraulic force acts against the closing force of the valve spring, in particular in outward opening valve. In this case, the hydraulic force limits the operating pressure of the fuel injection valve.

[0005] "Pressure balanced" fuel injection valves are known in principle. An actuator of a such "pressure balanced" fuel injection valve has to provide a force which is strong enough to lift the valve needle only against the force of the valve spring. However, the closing of the nozzle orifice has to be ensured and usually, additional components like servo valves are required for actuating the valve. This may make additional components necessary which increase the costs of the fuel injection valve.

[0006] Further, due to the principle construction of a "pressure balanced" injector, balancing of the hydraulic pressure on the valve needle usually requires that an actuator - comprising, e.g. both the magnetic coil and the armature - has to be separated from the fuel path. For example, this is achieved with bellows which separate the actuator from the fuel path. Production costs due to such complex construction are high.

[0007] It is an object of the invention to specify an improved fuel injection valve.

[0008] This object is achieved by a fuel injection valve for an internal combustion engine with the features of the independent claim. Advantageous embodiments of the invention are given in the dependent claims.

[0009] A fuel injection valve for an internal combustion engine is specified. The fuel injection valve may be provided for a fuel injection device of the internal combustion engine. In particular, the fuel injection valve is provided for injecting fuel directly into a combustion chamber of the internal combustion engine.

[0010] The fuel injection valve comprises a housing and a valve needle. The valve needle preferably has a longitudinal needle axis which is in particular also a longitudinal axis of the housing.

[0011] The housing has a cavity and a nozzle orifice. The cavity in particular hydraulically connects a fluid inlet end of the housing to the nozzle orifice. The nozzle orifice is in particular positioned at a downstream end of the cavity, in particular opposite of the fluid inlet end. Fuel which is positioned in the cavity may flow out of the nozzle orifice.

[0012] The valve needle is movably received in the cavity such that it is displaceable in reciprocating fashion - in particular in longitudinal direction - relative to the housing for opening and closing the nozzle orifice. More specifically, the valve needle is operable to seal the nozzle orifice in a closing position and enables fuel flow through the nozzle orifice in further positions. In its closing position, a needle tip of the valve needle in particular rests against a valve seat which is comprised by the housing.

[0013] A valve spring is positioned in the cavity and mechanically coupled to the valve needle for urging the valve needle towards its closing position, in particular in longitudinal direction. In particular, the valve spring rests against a spring seat of the housing and against a spring seat of the valve needle to bias the valve needle into contact with the valve seat of the housing when the actuator is de-energized.

[0014] The fuel injection valve further comprises an actuator, the actuator comprising a magnetic coil and an armature. The armature is positioned in the cavity and displaceable in reciprocating fashion - in particular in longitudinal direction - relative to the housing. The coil is positioned outside of the cavity. The actuator activates the moving of the valve needle by means of an electric current which generates a magnetic field of the magnetic coil to displace the armature. The armature is mechanically coupled to the valve needle so that the valve needle is movable away from the closing position by means of an axial displacement of the armature. The armature can be fixed to the valve needle. Alternatively, the armature is displaceable relative to the valve needle along the longitudinal needle axis, the displaceability being limited by an armature retainer of the valve needle. Preferably, the armature is configured to establish a form-fit engagement with the armature retainer for moving the valve needle away from the closing position.

[0015] The fuel injection valve comprises a sleeve which is positioned in the cavity for modifying a total force on the valve needle. The sleeve is preferably an elastic reducing ring.

[0016] Preferably, the cavity has a step. For example, the housing has a ledge which shapes the step of the cavity. The valve needle preferably comprises a washer. The washer may expediently project radially outwards from a shaft of the valve needle. The washer is in particular fixed to the shaft or in one piece with the shaft. The sleeve is positioned between the ledge and the washer in such fashion that it sealingly rests against the step, a circumferential side surface of the cavity and a top surface of the washer so that the top surface and a bottom surface of the washer have different hydraulic diameters. The top surface and the bottom surface are in particular positioned at axially opposite sides of the washer. In other words, the top surface faces towards the step and the bottom surface faces away from the step.

[0017] In particular, the sleeve has a central opening and a sidewall extending circumferentially around the opening. The shaft of the valve needle extends through the central opening. The invention makes use of the idea that the sleeve reduces the wetted perimeter of the top surface of the washer relative to the wetted perimeter of the bottom surface. The top surface of the washer is wetted only in the area overlapping the central opening in top view along the longitudinal axis. The bottom surface is also wetted in a region overlapping the sidewall of the sleeve. Therefore, the hydraulic force of the fuel acting on the bottom surface is larger than the hydraulic force acting on the top surface. In this way, the fuel pressure of the fuel in the cavity effects a hydraulic net force on the washer in axial direction towards the step.

[0018] Expediently, the step, the sleeve and the washer may be positioned in such fashion that the hydraulic net force on the washer is directed in axial direction opposite to the direction of the hydraulic force exerted by the fuel on the needle tip in particular when the injection nozzle is sealed. In this way, the hydraulic force on the needle tip is partially or completely compensated by the hydraulic net force on the washer.

[0019] In the case of an outward opening fuel injection valve, the hydraulic net force preferably biases the valve needle towards the closing position whereas the hydraulic force on the needle tip biases the valve needle in axial direction away from the closing position. With advantage, the hydraulic net force on the washer depends on the fuel pressure in the same way as the hydraulic force on the needle tip, so that the operating pressure for the fuel is not restricted by a maximum pressure at which the valve spring no longer is strong enough to keep the valve closed as in conventional non pressure balanced fuel injection valves.

[0020] At the same time, a valve spring with a particularly small spring rate can be used with an outward opening fuel injection valve according to the present disclosure because the hydraulic net force on the washer contributes largely to retaining the valve closed when the actuator is de-energized. Such small spring rates are advantageous since they allow opening of the fuel injection valve also in low pressure operation modes such as so-called "limp home" failure modes.

[0021] In the case of an inward opening fuel injection valve the hydraulic net forces effected on the washer due to the sleeve preferably biases the valve needle in axial direction away from the closing position in order to compensate or partly compensate the hydraulic force on the needle tip which presses the needle tip against the valve seat. With advantage, the force which the actuator has to transfer to the valve needle for moving the valve needle out of the closing position can be particularly small so that an actuator which is particularly small and/or consuming particularly little energy can be used.

[0022] With advantage, a partially or completely pressure balanced fuel injection valve is achievable according to the invention with a particularly simple, robust and low-cost design. The advantageous behaviour of a pressure balanced fuel injection valve is achievable in combination with a wet actuator design in particular simple and cost-effective fashion.

[0023] A further advantage of the invention is that an improved combustion is achievable because due to the possible higher fuel pressure the spray properties of the fuel may be improved (e.g. the droplet size may be particularly small). Therefore, the preparation of an air-fuel mixture in the cylinder of the combustion engine needs a shorter time and/or a better homogeneity as in prior art. This effect may lead to reduced emissions.

[0024] In one embodiment, the housing comprises a first housing portion, a second housing portion and a third housing portion, which are sequentially arranged along the longitudinal axis. The nozzle orifice is comprised by the first housing portion, the valve spring is positioned in the second housing portion and the magnetic coil and the armature axially overlap the third housing portion. Preferably, the armature is arranged in the portion of the cavity which is comprised by the third housing portion and the coil is enclosed in a plastic body of the third housing portion. The plastic body in particular extends circumferentially around a tubular metal body of the housing, the metal body defining the cavity. The configuration according to this embodiment is particularly well suited for outward opening fuel injection valves.

[0025] In one development of this embodiment, the step is comprised by the second housing portion, the sleeve is positioned upstream of the valve spring in the second housing portion and the washer of the valve needle is positioned upstream of the valve spring. In this way, the hydraulic net force on the washer is advantageously directed in longitudinal direction away from the nozzle orifice so that it contributes to biasing the valve needle towards the closing position.

[0026] In one embodiment, the sleeve comprises a first sleeve element and a second sleeve element. The second sleeve element preferably has a smaller stiffness than the first sleeve element. The first and second sleeve elements are in particular fixed to one another. Preferably, the second sleeve element rests sealingly against the step and the circumferential side surface of the cavity and against the top surface of the washer.

[0027] Due to the combination of a first sleeve element and a second sleeve element, the possibility is offered to combine a first element having a high mechanical stability with a second element having a good sealing behaviour to reach dimensional stability and satisfactory sealing of the sleeve over a wide range of the fuel pressure and/or preload of the sleeve.

[0028] In a preferred embodiment the first sleeve element metallic, i.e. it comprises or consists of a metal or an alloy, and the second sleeve element is comprises or consists of an elastomer or an elastomer compound such as e.g. rubber.

[0029] In another embodiment the second sleeve element embraces the first sleeve element. For example, the second sleeve element extends partially or completely circumferentially around the first sleeve element. Preferably, the first and second sleeve elements are in direct contact with one another at a common, circumferential interface. In one development, the elastomeric second sleeve element is vulcanised to the metallic first sleeve element. In this way, the first sleeve element improves the axial stability of the second sleeve element. In this way, the risk that the second sleeve element separates partially from the circumferential sidewall is particularly small.

[0030] In one embodiment, the first sleeve element of the sleeve is in the shape of a corrugated cylinder shell or in the shape of a bellows, in particular a cylindrical metal bellows. While a bellows is in particular understood to have inner and outer circumferential surfaces with a correspondingly zigzag shaped or undulated cross-section, a corrugated cylinder shell is in particular understood to have a cylindrical outer (or inner) surface and an inner (or outer) surface with a zigzag shaped or undulated cross-section. By means of these shapes, the axial stiffness of the first sleeve element can be easily selected.

[0031] In another embodiment, the second sleeve element of the sleeve has a basic shape of a cylinder shell. This is in particular understood to include shapes where the outer circumferential surface of the first sleeve has zigzag shaped or undulated cross-section and the inner circumferential surface of the second sleeve element follows that shape at the common interface of the first and second sleeve elements.

[0032] In one embodiment, the sleeve is preloaded, in particular in axial and/or radial direction. In particular, the washer presses the sleeve against the step of the cavity by means of the spring force of the valve spring. In this way, loss of the sealing contact between the sleeve and the washer and between the sleeve and the step and the circumferential side surface of the cavity is particularly unlikely. Radial preload may be achieved by oversizing the sleeve with respect to the lateral dimensions of the cavity and press-fitting the sleeve into the cavity. Preferably, the second sleeve element is radially pressed against the circumferential surface of the cavity and axially pressed against the step and the washer due to the preload of the sleeve. In one embodiment, the axial dimension and/or the radial dimension of the sleeve is/are reduced by an amount between 10 % and 20 % - the limits being included - relative to the uncompressed dimension due to the preload.

[0033] In another preferred embodiment the washer of the valve needle has a groove supporting the flow of the fuel. Also an improved identification of the positioning of the washer is reached reducing wrong assembling. In one development, the grooves are comprised by the top surface and the washer is distanced from the sleeve in the region of the grooves. In this way, the wetted area of the top surface and, thus the hydraulic net force on the washer can be easily changed by modifying the number and/or size of the grooves without changing the overall geometry of the washer and the sleeve. In this way, small part-to-part variations of the hydraulic net force are achievable.

[0034] Further advantages, features and details of the invention may be derived from the following description of preferred exemplary embodiments as well as from the drawings. The features and feature combinations as previously mentioned in the description as well as the features and feature combinations which will be mentioned in the following description of the figures and/or which are solely illustrated in the figures are not only applicable in the respective indicated combination but also in other combinations or isolated, without departing from the scope of the invention. For the sake of clarity, only those features are identified by reference numerals in the figures, which are useful for the corresponding description of the figures. Thus, the items need not be identified by their reference numerals throughout all figures, without losing their assignments.

[0035] In the figures:

Figure 1 is a longitudinal sectional view of a fuel injection valve according to a first embodiment of the invention,

Figure 2 is a diagram showing forces on the valve needle of a conventional fuel injection valve ,

Figure 3 is a diagram showing a force on the valve needle of a fuel injection valve according to the first exemplary embodiment,

Figure 4 is a longitudinal sectional view of a cut-out of a valve needle tip of the fuel injection valve according to the first exemplary embodiment,

Figure 5 is a longitudinal sectional view of a cut-out of the fuel injection valve according to the first exemplary embodiment,

Figure 6 is a top view of a washer of the valve needle of the fuel injection valve according to the first exemplary embodiment,

Figure 7 is a longitudinal sectional view of a sleeve of the fuel injection valve according to the first exemplary embodiment, and

Figure 8 is a longitudinal sectional view of a fuel injection valve according to a second exemplary embodiment of the invention.

Figure 1 shows a fuel injection valve 1 according to a first exemplary embodiment. The fuel injection valve 1 of the first embodiment is an outward opening injection valve for an internal combustion engine. It is configured to inject fuel directly into a combustion chamber of the engine.

[0036] The fuel injection valve 1 comprises a housing 2, in which a valve needle 3 with a needle axis 4 is movably arranged. The valve needle axis 4 is also a central longitudinal axis of the housing 2.

[0037] The valve needle 3 is movably arranged in the housing 2, received in a cavity 6 of a first housing portion 5 of the housing 2. A needle tip 8 of the valve needle 3 cooperates with a valve seat 23 of the housing 2 to seal and unseal a nozzle orifice 7 of the housing 2. The nozzle orifice 7 is positioned at a downstream end of the cavity 6.

[0038] A second housing portion 9 of the housing 2 is affiliated to the first housing portion 5. The second housing portion 9 is arranged directly subsequent to the first housing portion 5 upstream of the first housing portion 5 and comprises a valve spring 10 in the portion of the cavity 6 which is comprised by the second housing portion 9. This valve spring 10 is surrounding a portion of the valve needle 3, specifically a portion of a shaft 16 of the valve needle 3.

[0039] The valve spring 10 is preloaded and mechanically coupled to the valve needle 3 and to the housing 2 in such fashion that it biases the needle tip 8 against the valve seat 23, i.e. into a closing position of the valve needle 3. In this way, the valve needle is operable to seal the nozzle orifice 7 in the closing position. The fuel injection valve 1 further comprises an electromagnetic actuator 11. The valve needle 3 is axially displaceable away from the closing position against the bias of the valve spring by the electromagnetic actuator for unsealing the nozzle orifice 7. The electromagnetic actuator 11 comprises a coil 12 and an armature 31.

[0040] The magnetic coil 12 is positioned in a - in particular plastic - coil housing 13 which is arranged in a third housing portion 14 of the housing 2 outside of the cavity 6. The third housing portion 14 is affiliated to the second housing portion 9, so that the second housing portion 9 is arranged between the first housing portion 5 and the third housing portion 14.

[0041] The third housing portion 14 comprises together with the actuator 11 a calibration spring 15 for calibrating a total spring force acting on the valve needle 3.

[0042] A shaft 16 of the valve needle 3 is generally cylindrically formed and has a first guide portion 17 and a second guide portion 18 for limiting a tilt of the valve needle 3 relative to the longitudinal axis 4. Between an inner circumferential surface 19 of the cavity 6 and the guide portions 17, 18, fluid channels are formed so the fuel may pass the guide sections 17, 18 in longitudinal direction.

[0043] The valve needle 3 further comprises a washer 21 which is fixed to the shaft 16. The washer 21 is placed in the second housing portion 9 between a step 22 of the cavity and the valve spring 10, upstream of the valve spring 10. In the present embodiment, the washer 21 has a spring seat for supporting the valve spring 10. The washer 21 is fixed to the valve needle 10 for example by means of a welded and/or crimped and/or press-fitted connection.

[0044] Figure 2 shows a diagram representing different forces F on the valve needle 3 in dependence on the fuel pressure p.

[0045] The dotted line represents the spring force SL of the valve spring 10 and the calibration spring 15. The dashed-dotted line represents the hydraulic force HL of the fuel on the needle tip 8 (see Figure 4). A sum of both represents a total needle load NL on the valve needle 3. The hydraulic force HL results in particular from the difference between the fuel pressure in the cavity 6 - typically in a range between 150 bar and 500 bar - and the - typically much smaller - pressure on the outside of the needle tip 8. The hydraulic force HL on the needle tip 8 increases with the fuel pressure, while the spring force SL is constant.

[0046] The valve spring 10 is calibrated to a preload, e.g. 100N to 200N, to bias the valve needle 3 into the closing position. When the hydraulic force HL compensates or overcompensates the spring force SL, the valve spring 10 is no longer operable to keep the valve closed against the hydraulic force HL of the fuel on the needle tip 8. Therefore, the operation pressure of conventional fuel injection valves is limited to a range in which the needle load NL as a sum of the hydraulic force HL on the needle tip 8 and the spring force SL is smaller than 0N, i.e. in which the absolute value of the spring force SL exceeds the absolute value of the hydraulic force HL on the needle tip 8.

[0047] This limitation can be overcome with the fuel injection valve 1 according to the invention Due to the arrangement of a sleeve 24 (see in particular Figure 5) in the housing 2 of the fuel injection valve 1, the total needle load NL may be modified.

[0048] The sleeve 24 is arranged upstream of the valve spring 10 in the second housing portion 9 in a second portion 25 of the cavity 6 which is comprised by the second housing portion 9. The sleeve 24 is positioned between a step 22 of the cavity 6 and the washer 21.

[0049] The sleeve 24 is realized as a composite elastic element comprising a first sleeve element 27 and a second sleeve element 28 which is fixed to the first sleeve element 27.

[0050] The first sleeve element 27 is formed like a bellows and is made of a metal or an alloy, in particular of a stainless steel such as a spring steel. The form of the pleats or waves and the number of the pleats or waves of the bellows depend on the load which has to be absorbed. For example, the first sleeve element 27 may be manufactured by a stamped process so that the undulation is realized by a permanent plastic deformation while also a comprehensive stiffness in axial direction is guaranteed.

[0051] The second sleeve element 28 is made of an elastomer or an elastomer compound. The elastomer or the elastomer compound must be applicable regarding a possible contact with the fuel and the operative temperature range of -40 to 150°C. For example, the second sleeve element 28 is made of rubber.

[0052] A penetration of the fuel between the two sleeve elements 27, 28 may be avoided. For example, the sleeve 24 may be produced by a vulcanization process. A metallic surface of the first sleeve element 27 which is arranged vis-à-vis an elastomer surface of the second sleeve element 28 to form a common interface between the first and second sleeve elements 27, 28 is in particular treated before bonding the two sleeve elements 27, 28 to promote the bonding. This can be done by mechanical and/or chemical treatment. For example, a contamination of the metallic surface may be removed so that the contact between the two sleeve elements 27, 28 is particularly stable.

[0053] The first sleeve element 27 defines a central opening of the sleeve 24 through which the shaft 16 of the valve needle 3 extends. The second sleeve element 28 extends completely circumferentially around the first sleeve element 27 and contacts the latter at the common interface.

[0054] The sleeve 24 is placed between the step 22 and the washer 21 in radially and axially compressed fashion. Due to the valve spring 10, the washer 21 presses the sleeve 24 in axial direction so that a permanent axial load is transferred to the sleeve 24. The axial load may shrink the axial dimension of the sleeve 24 by 10% to 20%, for example, as compared to an unstressed state of the sleeve 24. The sleeve 24 can also be manufactured with an oversize of e.g. 10% to 20% of the radial dimensions relative to the lateral size of the second portion 25 of the cavity 6. In this way, a radial preload may be assured when fitting the sleeve 24 into the second housing portion 9.

[0055] This axial and radial load guarantees a contact of the second sleeve element 28 with the washer 21 and the second housing portion 9, specifically with the step 22 and the circumferential surface 19 of the cavity 6. This contact ensures a sealing in axial and radial direction so that the top surface 32 of the washer 21 has a smaller wetted area than a bottom surface 33 of the washer 21. The top surface 32 faces towards the step 22 and the bottom surface. This is roughly indicated in Figure 6, where the portion outside the dashed circle corresponds to the area which is covered by the second sleeve element 28 in top view along the longitudinal axis 4 and the dashed area corresponds to the area of the top surface 32 which is sealed from the fuel by the second sleeve element 28. It has to be noted in this context that, in the present embodiment, the washer 21 has optional radial grooves 30 to support the fuel flow and to enable adjusting the size of the wetted portion of the top surface 32.

[0056] Contrary to the top surface 32, the bottom surface 33 - axially opposite the top surface 32 - is completely exposed to the fuel pressure, either directly or via the top end of the valve spring which transfers the fuel pressure to the bottom surface 33. The difference of the wetted areas of the top surface 32 and the bottom surface 33 of the washer 21 generates a hydraulic net force WL on the washer 21 which acts in axial direction from the bottom surface 33 to the top surface 32, i.e. towards the step 22.

[0057] Figure 3 shows the resulting situation for the fuel injection valve according to the first embodiment. The hydraulic net force WL on the washer is pressure dependent in the same way as the hydraulic force HL on the needle tip 8, but directed in opposite axial direction. Therefore, the spring load SL and the hydraulic net force WL together (see the line "SL+WL" in Fig. 3) compensate the hydraulic force HL on the needle tip 8 independent of the pressure and the total load NL on the valve needle 3 is pressure independent. In this way, the valve spring 10 is operable to retain the valve needle 3 in the closing position independently from the fuel pressure. Thus, the maximum fuel pressure is not limited by the spring rate of the valve spring 10. It is also conceivable that the hydraulic net load WL on the washer 21 only partly compensates the hydraulic load HL on the needle tip 8.

[0058] In this or any other embodiment, the sleeve 24, in particular the second sleeve element 28, may be operable to absorb a kinetic energy of the moving mass after the closing of the valve needle 3 so that a re-opening or uncontrolled opening of the nozzle orifice 7 caused by the inertia of the valve needle is avoided or at least reduced.

[0059] Figure 8 shows a second exemplary embodiment of a fuel injection valve 1 according to the invention. The fuel injection valve 1 is an inward opening fuel injection valve in this case.

[0060] In case of the fuel injection valve 1 according to the second exemplary embodiment, the step 22 is comprised by an armature hard stop element which is fixed to the housing 2 in the cavity axially between the armature 31 and the washer 21. Other positions and/or configurations of the step 22 and the washer 21 are also conceivable insofar as they do not revert the direction of the hydraulic net force WL on the washer 21.

[0061] In the present embodiment of an inward opening valve, the hydraulic load HL on the needle tip 8 presses the needle tip 8 against the valve seat 23. The actuator 11 has to overcome the hydraulic load HL in addition to the spring load SL for moving the valve needle 3 out of the closing position, i.e. out of contact with the valve seat 23. The hydraulic net load WL on the washer 21 compensates, partly compensates or even overcompensates the hydraulic load HL on the needle tip 8, so that the force which the actuator 11 has to transfer to the valve needle 3 via the armature 31 is particularly small. The spring load SL, and the hydraulic loads HL and WL are roughly indicated by the arrows on the right hand side of Fig. 8.

Claims

1. A fuel injection valve for an internal combustion engine, comprising

- a housing (2) with a cavity (6)and a nozzle orifice (7), wherein fuel which is positioned in the cavity (6) may flow through the nozzle orifice (7),

- a valve needle (3) being positioned in the cavity (6) and displaceable relative to the housing (2) for sealing the nozzle orifice (7) in a closing position and enabling fuel flow through the nozzle orifice (7) in further positions,

- an actuator (11) comprising a magnetic coil (12) being positioned outside of the cavity (6) and an armature (31) being positioned in the cavity (6), being displaceable relative to the housing (2) and being mechanically coupled to the valve needle (3) for moving the valve needle (3) away from the closing position in dependence of a magnetic field (20) generated by the magnetic coil (12),

- a valve spring (10) being positioned in the cavity (6), the valve spring (10) being mechanically coupled to the valve needle (3) for urging the valve needle (3) towards the closing position,
wherein

- a sleeve (24) is positioned in the cavity (6) for modifying a total force on the valve needle (3).

2. The fuel injection valve according to claim 1,
characterized in that
the cavity (6) has a step (22),
the valve needle (3) comprises a washer (21), and
the sleeve (24) is positioned between the step (22) and the washer (21) in such fashion that it sealingly rests against the step (22), a circumferential side surface of the cavity (6) and a top surface of the washer (21) so that the top surface and a bottom surface of the washer (21) have different hydraulic diameters.

3. The fuel injection valve according to one of the preceding claims, wherein the sleeve (24) is an elastic reducing ring.

4. The fuel injection valve according to one of the preceding claims,
characterized in that
the housing comprises a first housing portion (5), a second housing portion (9) and a third housing portion (14), which are sequentially arranged along a longitudinal needle axis (4), the nozzle orifice (7) is comprised by the first housing portion (5), the valve spring (10) is positioned in the second housing portion (9) and the magnetic coil (12) and the armature (31) axially overlap the third housing portion (14).

5. The fuel injection valve according to claims 2 and 4,
characterized in that
the step (22) is comprised by the second housing portion (9), the sleeve (24) is positioned upstream of the valve spring (10) in the second housing portion (9) and the washer (21) of the valve needle (3) is positioned upstream of the valve spring (10).

6. The fuel injection valve according to claim 2 or 5,
characterized in that
the top surface of the washer (21) has a groove (30).

7. The fuel injection valve according to one of the preceding claims,
characterized in that
the sleeve (24) comprises a first sleeve element (27) and a second sleeve element (28), wherein the second sleeve element (28) has a smaller stiffness than the first sleeve element (27).

8. The fuel injection valve according to claim 7,
characterized in that
the first sleeve element (27) of the sleeve (24) is made of metal and the second sleeve element (28) of the sleeve (24) is made of an elastomer.

9. The fuel injection valve according to one of claims 7 or 8,
characterized in that
the first sleeve element (27) of the sleeve (24) is in the shape of a corrugated cylinder shell or in the shape of a bellows.

10. The fuel injection valve according to one of claims 7 to 9,
characterized in that
the second sleeve element (28) of the sleeve (24) has a basic shape of a cylinder shell.

11. The fuel injection valve according to one of claims 7 to 10,
characterized in that
the second sleeve element (28) of the sleeve (24) embraces the first sleeve element (27) of the sleeve (24).

12. The fuel injection valve according to one of the preceding claims,
characterized in that
the sleeve (24) is preloaded.

13. The fuel injection valve according to claim 12 and one of claims 2, 5, and 6, wherein the second sleeve element (28) is radially pressed against the circumferential surface of the cavity (6) and axially pressed against the step (22) and the washer (21) due to the preload of the sleeve (24).

Drawing