Valve assembly for an injection valve and injection valve The present invention relates to a valve assembly for a fluid injection valve and to a fluid injection valve, e.g. a fuel injection valve of a vehicle. It particularly relates to solenoid injection valves. In order to keep contamination in the form of particles from entering the injection valve, a particle filter is usually arranged near a fluid inlet portion of the injection valve. However, this particle filter cannot prevent particles from internal contamination generated for example by component cleanliness, press-fitting operation and laser welding from entering the ceiling area of the valve. This creates a possible risk of injector stuck open.

The document US 2011/0006136 Al discloses an injection valve with a particle filter that is arranged directly above the valve seat surrounding the ball. This filter would be suitable to prevent particles from entering the sealing area. However, this injector comprises a special component, the ball guide or the ball stop to guide the ball in its upward and downward movement. The particle filter is integrated in the ball guide or ball stop.

New injector designs, however, employ and integrated ball guide. The integrated ball guide is implemented by a seat body, which is an integral part of the valve body and forms the valve seat and a ball guide. The seat body serving as a ball guide surrounds the ball closely in order to perform its guiding function. Therefore, it is not possible to use a particle filter as disclosed in US 2011/0006136 Al with an injection valve of the integrated ball guide design. It is an object of the present invention to provide a valve assembly for an injection valve and an injection valve that overcome the above-mentioned difficulties and/or provide a stable performance of the injection valve by minimizing the risk of injector stuck open.

These objects are achieved by means of a valve assembly for an injection valve and injection valve according to the independent claims .

Advantageous embodiments and developments are specified in the dependent claims, the following description and the figures.

According to an aspect of the invention, a valve assembly for an injection valve is provided comprising a valve body with a central longitudinal axis comprising a cavity with a fluid inlet portion and a fluid outlet portion. The cavity comprises a first portion extending from the fluid inlet portion to a bottom surface and a second portion extending from a central opening in the bottom surface down towards the fluid outlet portion.

The valve assembly further comprises a valve needle axially movable in the cavity, i.e. it is arranged in the cavity and axially displaceable relative to the valve body in reciprocating fashion. The valve needle comprises a shaft and a ball, the ball cooperating with the valve seat to prevent fluid flow through the fluid outlet portion in the closing position and to release fluid flow through the fluid outlet portion in further positions. The ball may be fixed to the shaft, e.g. by means of a welded connection. The ball also may be formed by shaping a tip of the shaft .

The valve assembly further comprises a seat body, the seat body being an integral part of the valve body and forming the valve seat and a ball guide. The valve assembly further comprises an armature of an electromagnetic actuator unit being designed to actuate the valve needle, the armature being arranged in the first portion of the cavity.

A particle filter is entirely arranged in the second portion of the cavity. The particle filter is denoted as "lower particle filter" in the following due to its position adjacent to the fluid outlet portion. The valve assembly may additionally comprise an upper particle filter adjacent to the fluid inlet portion, in particular upstream of the armature.

Preferably, the lower particle filter is spaced from the bottom surface in axial direction towards the fluid outlet portion. In one embodiment, the lower particle filter is positioned upstream of the seat body. In particular, the entire lower particle filter is positioned outside of the seat body. Expediently, the lower particle filter may be arranged adjacent to or adjoining the seat body. For example, the lower particle filter may bear on an upstream surface of the seat body in some embodiments.

By the seat body being an integral part of the valve body it is understood that the seat body forms a part of the valve body. The seat body usually is not formed in one piece with the part of the valve body surrounding the needle shaft. Instead, the seat body is a separate part joined to the part of the valve body surrounding the needle shaft for example by press-fitting. In the region of the valve seat, this seat body constitutes the valve body and therefore forms an integral part of the valve body.

This valve assembly has the advantage that the injector re ^¬ liability is improved by introducing an obstacle to contamination coming from external or internal sources that could cause the injector stuck open issue or jeopardize the sealing area in- creasing the leakage rate or occlude the seat holes totally or partially. Furthermore, the integrated ball guide provides a very stable and reliable guidance to the ball resulting in a valve assembly which can operate reliably and precisely even under high pressure conditions. With advantage, the ball guide is not provided by the lower particle filter which is comparably easily deformable, but by direct contact between the ball and the rigid seat body which can easily be manufactured with small tolerances. According to an embodiment of the invention, at least one element of the lower particle filter is fixed to the valve needle.

Basically, with the integrated ball guide design of the injector, the lower particle filter can either be fixed to the valve needle, or to the valve body, or to both. The lower particle filter can consist of only one element, but it can also comprise several collaborating elements.

According to a further embodiment, the lower particle filter is comprised of one element - in particular it consists of one element - which is fixed to the needle, wherein a clearance is formed between an outer rim of the lower particle filter and the valve body. In this case, the clearance may represent an annular gap between the lower particle filter and the valve body extending completely around the lower particle filter in circumferential direction .

According to this embodiment, the clearance is calculated in order to avoid the contact between the lower particle filter and the valve body without affecting the filtering efficiency.

It is an advantage of this embodiment that no mechanical in ^¬ teraction takes place between the lower particle filter and the valve body, which helps reduce wear of components. According to an alternative embodiment, the lower particle filter is comprised of one element - i.e. in particular consists of one element - which is fixed to the needle, wherein one section of the lower particle filter is resiliently supported by the valve body.

According to this embodiment, there is no clearance or gap between the lower particle filter and the valve body. Instead, the lower particle filter being resiliently supported by the valve body causes a close mechanical contact between the lower particle filter and the valve body. Because of the resilient force, the lower particle filter does not part from the valve body due to movement of the needle. The movement of the needle will take at least one section of the lower particle filter with it, while another section of the lower particle filter being resiliently supported by the valve body remains in contact with the valve body. In order to achieve this, the lower particle filter might be bent, for example bellow-shaped and preloaded during assembly. This embodiment has the advantage, that the lower particle filter covers the entire fuel passage.

According to an alternative embodiment, the lower particle filter is comprised of at least two elements, a first element being fixed to the valve needle and the second element being fixed to the valve body. In one development, the lower particle filter consists of the first element and the second element.

In this case, the first element and the second element may remain in contact with each other during opening and closing of the valve. To achieve this, the first element may be resiliently supported by the second element. This embodiment has the ad ^¬ vantage, that the lower particle filter covers the entire fuel passage . Alternatively, a clearance can be formed between the first element and the second element so that there is no mechanical interaction between the two elements. The clearance between the first element and the second element is calculated in order to avoid the contact between the two elements without affecting the filtering efficiency.

According to one aspect of the invention, a fluid injection valve with the described valve assembly is provided. The injection valve may particular be a fuel injection valve of a vehicle.

The injection valve has the advantage, that injector stuck open events and leakages due to contamination in the region of the sealing zone can be prevented. The injection valve operates particularly stable and reliably.

Further advantages, advantageous embodiments and developments of 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 the schematic figures.

Figure 1 shows a cross-section of an injection valve with an integrated ball guide; Figure 2 shows a cross-section through the lower part of an injection valve according to a first embodiment of the invention ;

Figure 3 shows a cross-section through the lower part of an injection valve according to a second embodiment of the invention ; Figure 4 shows a cross-section through the lower part of an injection valve according to a third embodiment of the present invention and Figure 5 shows a cross-section through the lower part of an injection valve according to a fourth embodiment of the present invention.

The fluid injection valve 1 shown in figures 1 and 2 is in particular suitable for dosing fuel to a 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 4 with a central longitudinal axis L. A housing 6 is partially arranged around the valve body 4.

The valve body 4 comprises a cavity 9. The cavity 9 has a fluid outlet portion 7. The fluid outlet portion 7 communicates with a fluid inlet portion 5 which is provided in the valve body 4. The fluid inlet portion 5 and the fluid outlet portion 7 are in particular positioned at opposite axial ends of the valve body 4. The cavity 9 takes in a valve needle 11. The valve needle 11 comprises a needle shaft 15 and a sealing ball 13 welded to the tip of the needle shaft 15.

In a closing position of the valve needle 11, it sealingly rests on a valve seat 17 having at least one injection nozzle con- stituting the fluid outlet portion 7. A preloaded calibration spring 18 exerts a force on the needle 11 towards the closing position. In the closing position of the valve needle 11, a fluid flow through the at least one injection nozzle is prevented. The inj ection nozzle may be, for example, an inj ection hole . However, it may also be of some other type suitable for dosing fluid.

The valve assembly 3 is provided with an electro-magnetic actuator unit 19. The electro-magnetic actuator unit 19 comprises a solenoid 21, which is preferably arranged inside the housing 6. Furthermore, the electro-magnetic actuator unit 19 comprises an armature 23. The housing 6, parts of the valve body 4 and the armature 23 form an electromagnetic circuit. The armature 23 is axially movable in the cavity 9 and fixed to the valve needle 11 by form fit.

The cavity 9 comprises a first portion 25 and a second portion 27. The first portion 25 extends from the fluid inlet portion 5 down towards a bottom surface 29 below the armature 23. The second portion 27 extends from a central opening 31, which accommodates the needle shaft 15, in the bottom surface 29 down towards the fluid outlet portion 7. As can be seen from the detailed drawing on the right-hand side of figure 1, the valve assembly 3 has an integrated ball guide. It comprises a seat body 33 which forms the valve body 4 in the region of the fluid outlet portion 7. The seat body 33 forms a valve seat 17 and it guides the ball 13 in an upward and downward movement. To achieve the guiding function, the seat body 33 has guiding surfaces 34. The guiding surfaces 34 in particular alternate in circumferential direction with fluid channels through which fluid may pass the ball 13 in axial direction towards the valve seat 17. One such fluid channel is shown on the right side of the ball 13 in the detail drawing on the right-hand side of figure 1.

Figure 2 shows a lower part of an injection valve 1 which corresponds to the injection valve 1 shown in figure 1 except that a lower particle filter 35 is added in the second portion 27 of the cavity 9.

According to the first embodiment shown in figure 2, the lower particle filter 35 comprises - and preferably consists of - a first element 37, which is press fitted to the valve needle 11, and a second element 39 which is press fitted to the valve body 4 and bears on an upstream surface of the seat body 33. Between the first element 37 and the second element 39 there is a clearance 41. Along the clearance 41 the first element 37 and the second element 39 overlap in axial direction. Both elements 37, 39 are spaced apart from the bottom surface 29 in downstream axial direction . When the needle 11 travels upwards to open the injection valve 1, the overlap a between the first element 37 and the second element 39 decreases during the travel of the needle 11, the clearance 41 between the first element 37 and the second element 39 remains. An overlap between the first element 37 and the second element 39 remains even when the needle 11 has travelled to its maximum. Thus, the maximum overlap a is larger than the maximum travel of the needle 11.

According to this first embodiment, there is no mechanical interaction between the first element 37 and the second element 39 of the lower particle filter 35. This has the advantage, that problems due to wear of components are avoided.

The lower particle filter 35 according to all embodiments shown in the drawings and other embodiments of the invention may comprise or consist of one or more turned or stamped elements with holes, the holes being in particular mechanically drilled or laser drilled. The element (s) may also be a braided net. Figure 3 shows a second embodiment of the present invention. According to this embodiment, the lower particle filter 35 comprises - and preferably consists of - a first element 37 and a second element 39. However, according to the second embodiment, there is no clearance between the two elements 37, 39. Instead, the first element 37, which is press fitted on the needle 11, is resiliently supported by the second element 39 which is press fitted in the valve body 4 and rests on the upstream surface of the seat body 33. Due to the shape of the two elements 37, 39 and the resilient force between them, they remain in contact during the travel of the needle 11.

Figure 4 shows a third embodiment of the present invention. According to this embodiment, the lower particle filter 35 comprises only one element which is bellow-shaped and

press-fitted to the needle 11. During assembly of the injection valve 1, the lower particle filter 35 is preloaded and one section 43 of the lower particle filter 35 resiliently rests against a section - in particular the upstream surface - of the seat body 33. The section 43 remains in contact with the seat body 33 during travel of the needle 11.

Figure 5 shows a fourth embodiment of the present invention. According to this embodiment, the lower particle filter 35 comprises only one element which is disc-shaped and press-fitted to the needle 11. Between the outer rim 44 of the lower particle filter 35 and the valve body 4, there is a clearance 45. The clearance 45 remains essentially constant during travel of the needle 11. Thus, there is no mechanical interaction between the lower particle filter 35 and the valve body, so that wear of components is reduced.