Filter assembly for an injection valve, valve assembly and injection valve

The present invention relates to a filter assembly for a fluid injection valve, a valve assembly and a fluid injection valve. The fluid injection valve may in particular be an injection valve for injecting fuel into a combustion engine.

A valve assembly for a fluid injection valve comprises a valve body comprising a cavity with a fluid inlet portion and a fluid outlet portion and a valve needle axially moveable in the cavity. The valve needle prevents a fluid flow through the fluid outlet portion in a closing position and releases the fluid flow through the fluid outlet portion in further positions. The valve needle may be actuated by an electromagnetic actuation unit.

A filter assembly is provided at the fluid inlet portion of the valve assembly for filtering the fluid to be dosed.

The valve needle is biased towards a closing position by a preloaded calibration spring. The calibration spring can be preloaded by press-fitting the filter assembly or a adjustment tube located on top of the spring into the housing, the pole piece or another element of the injection valve as disclosed in US 6, 997, 404 B2. This, however, adds to the length of the injector.

In EP 2 949 917 Al, a fuel injector is disclosed. It comprises a valve with a needle that is movable along a longitudinal axis between an open position and a closed position, for opening or closing the valve; an actuator which comprises an armature and a pole piece, the armature is axially movable and operable to interact mechanically with the needle so that the needle is moved ^

towards the open position by a movement of the armature in axial direction towards the pole piece; and a first spring for biasing the armature in axial direction away from the pole piece. The first spring is configured and operable to stop said movement of the armature by means of its spring force when the needle is in the open position.

DE 102013225820 Al relates to a fuel injector for fuel injection systems of internal combustion engines, in particular for the direct injection of fuel into the combustion chamber of an internal combustion engine, comprising a magnetic coil, an armature which is acted upon by the magnetic coil in a closing direction by a restoring spring and a valve needle, which is non-positively connected to the armature for actuating a valve closing body which forms a sealing seat together with a valve seat surface. A setting element for adjusting the spring force of a restoring spring is arranged in a connection sleeve serving as a supply port on the supply side. The adjusting element has an integrated guide for the restoring spring which is designed as at least one projection of a sleeve on the base region of this sleeve 59) such that it radially outwardly overlaps the restoring spring which interacts with the base region in axial direction.

The fuel injection valve according to DE 10 2007 049 963 Al is characterized in that said valve has an excitable actuator in the form of an electromagnetic circuit, comprising a magnetic coil, an outer magnetic circuit component, and a movable armature for activating a valve closing body interacting with a valve seat provided on a valve seat body. A fitting is provided on the inflow side, which has a flow bore that allows the inflow of fuel in the direction of the valve seat, wherein an adjustment element is provided in the flow bore for adjusting a spring tension of a return spring tensioned on the adjustment element, said element comprising a fuel filter. The fuel filter has a cup-shaped base body, which ends at a filter base, wherein the filter base is configured in reverse in a bowl shape, and is suspended downstream in the fitting at the free base end thereof. It is an object of the present invention to provide a space-saving filter assembly for an injection valve, a valve assembly and an injection valve with such a valve assembly.

These objects are achieved by means of a filter assembly for an injection valve, a valve assembly and an injection valve ac ^¬ cording to claims 1, 13 and 15.

Advantageous embodiments and developments are objects of the dependent claims.

According to a first aspect of the invention, a filter assembly for a fluid injection valve is provided, the filter assembly having a fluid inlet portion and a fluid outlet portion, wherein at least one flow path for fluid flow with a flow direction is formed between the fluid inlet portion and the fluid outlet portion .

The filter assembly comprises a filter sleeve having a first part and a second part. The first part comprises a filter element. The second part is arranged downstream of the first part with respect to the flow direction and forms a receptacle for an upper part of a calibration spring of the fluid injection valve, wherein a circumferential side wall of the receptacle is arranged to surround the upper part of the calibration spring.

Hence, the area, where the element preloading the calibration spring and an element of the valve assembly, e.g. the pole piece, are in frictional contact with one another, does not extend upwards from the calibration spring but around its upper part or some distance downwards from the upper part, i.e. some distance towards its lower part. By this, the clamping area of the calibration spring is moved from above the spring to the spring area itself. This has the advantage, that the space above the spring is not required for the preloading of the spring. This space can be used differently, particularly for the reduction of pressure waves from the rail. Alternatively or additionally, the overall length of the injector can be reduced.

According to one embodiment, the receptacle comprises a ledge for supporting the calibration spring, the ledge protruding from the circumferential side wall and dividing the first part from the second part. According to this embodiment, the ledge provides support for the calibration spring. The ledge can be formed integrally with the filter sleeve. It protrudes from the circumferential side wall far enough to allow for a stable support of the calibration spring. Thus, the ledge makes an annular support for the calibration spring, which is typically a coil spring. The central opening of this annular support makes a passage for fluid flow.

According to one embodiment, the second part of the filter sleeve has, on an outer surface of the circumferential side wall, a first fitting area for press-fitting the filter assembly into a fuel inj ector .

A fitting area is hereby understood to be a contact area between e.g. two elements, where frictional forces between the two elements make a frictional locking connection between the two elements. To make this frictional locking connection between the filter sleeve and an element of the fuel injector, e.g. the pole piece, the dimensions of the filter sleeve are chosen ac- cordingly. In particular the diameter of the filter sleeve is chosen to make press-fitting the filter sleeve possible.

According to one embodiment, the filter sleeve is made in one piece, i.e. the first part and the second part are formed integrally. This simplifies the manufacture of the filter sleeves and saves costs.

According to one embodiment, a disk having at least one opening is arranged in the filter sleeve dividing the first part from the second part and providing a support for the calibration spring. The disk can be an annular disk with a central opening or with a number of openings making a passage for fluid flow. This has the advantage, that a dampening effect on pressure waves in the fuel is created.

It has been found that the dampening effect and the passage of fuel through the opening are both satisfactory if the opening (in the case of one central opening) has a diameter of 0,5 millimeters to 1 millimeters, more particularly of 0,7 millimeters to 0,9 millimeters .

The disk can, in particular, be supported by the ledge. Thus, the outer diameter of the disk is typically chosen to be only slightly smaller than the inner diameter of the filter sleeve but larger than the inner diameter of the ledge.

According to one embodiment, the second part of the filter sleeve has, on an inner surface of the circumferential side wall, a spring fitting region for fastening a calibration spring within the filter sleeve. The calibration spring may be fixed to the filter sleeve, but the fastening can also mean a guiding of the calibration spring. It is advantageous, if the calibration spring is guided only at its topmost and lowermost part, but not in between. Guidance in between exerts frictional forces on the calibration spring and disturbs its movement.

According to the described embodiment, the upper part of the calibration spring can be fitted into the receptacle such that the inner surface of the circumferential side wall having the spring fitting region provides guidance for the calibration spring. In order to achieve this, the inner diameter of the receptacle is only slightly larger than the outer diameter of the calibration spring, and the axial length of the receptacle is sufficient to provide reliable guidance. According to one embodiment, instead of the disk a cap is arranged in the filter sleeve, the cap having a side wall part arranged coaxially with the circumferential side wall of the second part and a disk shaped part with at least one opening, the disk shaped part dividing the first part of the filter sleeve from the second part and providing a support for the calibration spring.

According to this embodiment, the receptacle receives the calibration spring and the cap. Preferably, the axial length of the cap is not larger than that of the receptacle so that the cap does not protrude from the receptacle. The cap provides a particularly reliable guidance for the calibration spring.

To achieve this, the cap may, on an inner surface of the side wall part, have a spring fitting region for fastening the calibration spring within the cap. Here, too, "fastening" of the calibration spring may mean securely guiding the calibration spring.

According to one embodiment, the cap has, on an outer surface of the side wall part, a cap fitting region for joining the cap to the filter sleeve. The cap could be welded to the filter sleeve. Alternatively, the cap could be press-fitted into the filter sleeve. In particular, the outer diameter of the cap and the inner diameter of the filter sleeve are such that a connection between both is possible. This has the advantage, that the cap providing particularly secure guidance of the calibration spring can be inserted into the filter sleeve.

The filter assembly can be used with different types of filters. According to one embodiment, the filter element comprises a body part which may comprise a plastic material (e.g. Nylon) and is joined to the first part of the filter sleeve, for example by welding or press-fitting. The filter element further comprises a cap part comprising a metal and being joined to a fluid inlet portion of the filter element, for example by welding or press-fitting. The cap part may have one or more openings to make a passage for fluid flow. The diameter of the openings may be relatively small to provide a dampening effect on pressure waves. Alternatively, the filter assembly can comprise a different type of filter element. According to this embodiment, the filter element is formed by the first part of the filter sleeve comprising a number of through-holes forming the fluid inlet portion of the filter assembly. According to this embodiment, the first part of the filter sleeve is closed at its upper end and provided with through holes, which may e.g. be laser-drilled, electron beam-drilled or drilled mechanically. Thus, the first part of the filter sleeve constitutes the filter element. According to one embodiment, the filter sleeve and/or the cap comprise steel, particularly stainless steel, and/or a copper alloy. These materials have the necessary corrosion resistance and provide the suitable mechanical properties for a tight press-fit. The filter sleeve and/or the cap can be manufactured by a deep-drawing process.

According to one aspect of the invention, a valve assembly for an injection valve is provided, comprising a valve body com- prising a cavity with a fluid inlet portion and a fluid outlet portion, a valve needle axially moveable in the cavity, the valve needle preventing a fluid flow through the fluid outlet portion in a closing position and releasing the fluid flow through the fluid outlet portion in further positions. The valve assembly further comprises the described filter assembly and a preloaded calibration spring for biasing the valve needle, the calibration spring having a lower part which is allocated near one end of the valve needle and an upper part which is allocated at a distance from the needle, the upper part being received by the receptacle.

Thus, the circumferential side wall of the receptacle encloses a plurality of turns of the calibration spring which represent the upper part of the calibration spring. The pole piece of the valve assembly provides a rigid element suitable to receive the filter assembly. The pole piece typically has a central opening receiving the calibration spring. Into this central opening the spring with the filter assembly may be press-fitted. Thus, the first fitting area of the second part of the filter sleeve is in contact with the pole piece.

Frictional forces between the fitting area of the second part of the filter sleeve and the inner surface of the pole piece make a stable frictional locking connection between the two press-fitted parts.

According to one aspect of the invention, a fluid injection valve with the described valve assembly is provided. The injection valve has the advantages described above in connection with the filter assembly.

Further advantages, advantageous embodiments and developments of the filter assembly, the valve assembly for an injection valve and the fluid injection valve will become apparent from the exemplary embodiments which are described below in association with schematic figures.

Figure 1 shows a cross sectional overview of an injection valve according to one embodiment of the in ^¬ vention ;

Figure 2 shows a detail of an injection valve according to a first embodiment of the invention,

Figure 3 shows a detail of an injection valve according to a second embodiment of the invention,

Figure 4 shows a detail of figures 2 and 3,

Figure 5 shows a detail of an injection valve according to a third embodiment of the invention,

Figure 6 shows a detail of an injection valve according to a fourth embodiment of the invention,

Figure 7 shows a detail of figures 5 and 6, Figure 8 shows a detail of an injection valve according to a fifth embodiment of the invention,

Figure 9 shows a detail of an injection valve according to a sixth embodiment of the invention and Figure 10 shows a detail of figures 8 and 9.

Elements of the same design and function that appear in different illustrations are identified by the same reference character.

The fluid injection valve 1 shown in figures 1 to 10 is in particular suitable for dosing fuel to an internal combustion engine. However, the invention could be used in other types of injection valves, too.

The injection valve 1 comprises a valve assembly 3. The valve assembly 3 comprises a valve body 5 with a central longitudinal axis. The valve body 5 comprises a cavity 7. The cavity 7 has a fluid outlet portion 11. The fluid outlet portion 11 communicates with a fluid inlet portion 9 which is provided in the valve body 5. The fluid inlet portion 9 and the fluid outlet portion 11 are in particular positioned at opposite axial ends of the valve body 5.

The cavity 7 takes in a valve needle 13. The valve needle 13 comprises a needle shaft 12 and a sealing ball 14 welded to the tip of the needle shaft 12. The injection valve 1 comprises an electromagnetic actuator unit 17 for the valve needle 13. The actuator unit 17 comprises a solenoid 19, an armature 21 and a pole piece 27. The armature 21 is axially movable in the cavity 7. The armature 21 is separate from the valve needle 13 and is axially movable relative to the valve needle 13 and to the valve body 5. A lower retainer 23 and an upper retainer 25 are fixed to the valve needle 13.

This type of injector is sometimes called "free-lift" injector, because the armature travels upwards some distance (the free-lift gap) before engaging the needle. However, the invention can be used with different types of injectors, where the armature is fixed to the needle, for example. The valve needle 13 is preloaded by a calibration spring 15 which is arranged in the cavity 7 at the end of the valve needle 13 facing the fluid inlet portion 9. A lower part 29 of the calibration spring 27 is supported by the upper retainer 25. It could be supported by the valve needle 13 itself, too.

An upper part 31 of the calibration spring 27 is received by the receptacle 35 of a filter assembly 33, which is press-fitted with the pole piece 27. The receptacle 35 is formed by a circum ^¬ ferential side wall 45 of the filter assembly 33. This is explained in more detail with reference to figures 2 to 10. The embodiment shown in figure 1 is also shown in figure 8.

During the manufacturing process of the injection valve 1, the filter assembly 33 can be moved axially in the valve body 5 in order to preload the calibration spring 15 in a desired manner. By this the calibration spring 15 exerts the desired force on the valve needle 13 towards a fluid outlet portion 11 of the injection valve 1. In the closing position of the valve needle 13, a fluid flow through the fluid outlet portion 11 is prevented.

To move the valve needle 13 in an opening position, the solenoid 19 is energized, the magnetic force on the armature 21 overcomes the force exerted by the calibration spring 15 and the armature 21 moves upwards, taking with it the valve needle 13 by means of the upper retainer 25. The fluid outlet portion 11 is opened.

When the solenoid 19 is de-energized, the calibration spring 15 forces the valve needle 13 downwards towards the fluid outlet portion 11, until the fluid outlet portion 11 is closed by the ball 14.

As can be seen in figure 1, there is a space above the filter assembly 33, where according to the state of the art there would be an adjustment tube preloading the calibration spring 15. The filter assembly 33 only reaches a little way above the pole piece 27. Therefore, the space above the filter assembly 33 can be used to dissipate pressure waves. Alternatively, the injection valve 1 could be made shorter.

Figure 2 shows details of the injection valve 1 according to a first embodiment of the invention. The filter assembly 33 comprises a filter sleeve 37, which may be a cylindrical tube and which has a first part 39 near the fluid inlet portion 11 and a second part 41 further away from the fluid inlet portion 11. Thus, the second part 41 is arranged downstream from the first part 39. A ledge 47 formed by a protrusion of the sleeve 37 divides the first part 39 from the second part 41.

The first part 39 comprises a filter element 43, which in this embodiment is formed of the upper part of the filter sleeve 37 being perforated by a number of laser-drilled through-holes. In this embodiment, the upper end of the filter sleeve 37 is closed.

The second part 41 has a circumferential side wall 45, which forms a receptacle 35 for the upper part 31 of the calibration spring 15. The filter sleeve 37 is press-fitted into a central opening in the pole piece 27. When mounted, the outside of the second part 41 is in frictional contact with the inner surface of the pole piece 27. The area on the outside of the second part 41, where there is contact between the filter sleeve 37 and the pole piece 27, is the first fitting area 49. Frictional forces operating across this area 49 make a frictional locking connection between the filter assembly 33 and the pole piece 27. When the filter assembly 33 is inserted into the central opening in the pole piece 27, the calibration spring 15 is compressed and thereby preloaded. The calibration spring 15 is supported by the ledge 47 and received in and guided by the receptacle 35. Thus, the circumferential side wall 45 functions as a guide for the calibration spring 15.

Figure 3 shows details of the injection valve 1 according to a second embodiment of the invention. This embodiment differs from the first one only in the kind of filter element 43 used. According to the second embodiment, the filter element 43 has a body part 51 made of a plastic material and being press-fitted onto a fluid inlet portion of the filter element 43. The filter element 43 further comprises a cap part 53 made of a metal and being press-fitted onto the first part 39 of the filter sleeve 37.

Figure 4 shows details of the filter sleeve 37 according to the first and second embodiments . According to these embodiments, the filter sleeve 37 comprises a circumferential ledge 47 which protrudes from the circumferential side wall 45 and forms a support for the calibration spring 15.

A part of an inner surface of the circumferential side wall 45 serves as a guide for the calibration spring 15. This surface area, where the calibration spring 15 may be in contact with the circumferential side wall 45, is called the spring fitting region .

Figure 5 shows details of an injection valve 1 according to a third embodiment of the invention. This embodiment differs from the first one shown in figure 2 in that an additional disk 55 is arranged below the ledge 47, covering essentially the entire cross-section of the filter sleeve 37 and providing a stable support for the calibration spring 15. The disk 55 has a central opening which can be better seen from figure 7. The disk has the advantage that it functions as a throttle for passing fluid, reducing pressure waves.

Figure 6 shows details of an injection valve 1 according to a fourth embodiment of the invention. This embodiment differs from the third only in the kind of filter element 43 used. According to the fourth embodiment, a filter element 43 as described above with reference to figure 3 is used. Figure 7 shows a detailed view of the filter sleeve 37 with the disk 55 according to the third and fourth embodiments. The diameter of the central opening 59 in the disk can be chosen according to the desired throttle effect. Instead of a single central opening, a number of openings could be used.

Figure 8 shows details of an injection valve 1 according to a fifth embodiment of the invention. This embodiment differs from the first and third one shown in figures 2 and 5 in that a cap 57 is arranged below the ledge 47.

The cap 57 has a disk shaped part 61 which can be seen in more detail in figure 10 and which essentially corresponds to the disk 55 of the third and fourth embodiment. The disk shaped part 61 has at least one opening. It may have one central opening 63 as shown in figure 10. The disk shaped part 61 divides the first part 39 of the filter sleeve 37 from the second part 41 and provides a support for the calibration spring 15. The cap 57 further comprises a side wall part 65 arranged coaxially with the circumferential side wall 45 of the second part 41. On an inner surface 69 of the side wall part 65, the cap 57 has a spring fitting region 67 for fastening the calibration spring 15 within the cap 57.

On an outer surface 71 of the side wall part 65, a cap fitting region 73 for press-fitting the cap 57 into the filter sleeve 37 is defined as the area where frictional forces operate to form a frictional locking connection between the cap 57 and the filter sleeve 37, when the cap 57 is press-fitted into the filter sleeve 37. Alternatively, the cap 57 could be welded to the filter sleeve 37.

Figure 9 shows details of an injection valve 1 according to a sixth embodiment of the invention. This embodiment differs from the fifth only in the kind of filter element 43 used. According to the sixth embodiment, a filter element 43 as described above with reference to figures 3 and 6 is used.