EP3047134A1

EP3047134A1 - Valve assembly for an injection valve and injection valve

Info

Publication number: EP3047134A1
Application number: EP14757938.7A
Authority: EP
Inventors: Mauro Grandi; Francesco Lenzi; Valerio Polidori
Original assignee: Continental Automotive Technologies GmbH
Current assignee: Aumovio Germany GmbH
Priority date: 2013-09-18
Filing date: 2014-09-01
Publication date: 2016-07-27
Also published as: WO2015039859A1

Abstract

A valve assembly (11) for an injection valve (10) comprises a valve needle (20), an armature (22) axially moveable relative to the valve needle (20), a stop device (50), and a flexible component (46). The stop device (50) is operable to limit the axial displacement of the armature (22) with respect to the valve needle (20). The flexible component (46) is in a generally cup-shaped form, is fixed to the armature (22) and is fixed to the stop device (50) and/or the valve needle (20). It has a bent-shaped profile and is preloaded by means of deformation of the bent-shaped profile such that it biases the armature (22) into contact with a surface of the stop device (50). It is deformable to allow axial displacement of the armature (22) in the first axial direction away from the stop element against the bias.

Description

VALVE ASSEMBLY FOR AN INJECTION VALVE AND INJECTION VALVE

The invention relates to a valve assembly for an injection valve and an injection valve.

Injection valves are in wide spread use, in particular for internal combustion engines where they may be arranged in order to dose the fluid into an intake manifold of the internal combustion engine or directly into the combustion chamber of a cylinder of the internal combustion engine.

Injection valves are manufactured in various forms in order to satisfy the differing needs for various types of

combustion engines. Therefore, for example, their length, their diameter and also various elements of the injection valve being responsible for the way the fluid is dosed may vary in a wide range. In addition to that, injection valves may accommodate an actuator for actuating a needle of the injection valve, which may, for example, be an

electromagnetic actuator or piezoelectric actuator.

It is an object of the invention to specify a valve assembly and an injection valve which facilitate a reliable and precise functioning of the injection valve.

This object is achieved by a valve assembly having the features of claim 1. Advantageous embodiments of the valve assembly and the injection valve are specified in the dependent claims, in the following description and in the drawings . According to a first aspect, a valve assembly for an

injection valve is specified. According to a second aspect, an injection valve comprising the valve assembly is

specified .

The valve assembly comprises a valve body. The valve body includes a central longitudinal axis and comprises a cavity with a fluid inlet portion and a fluid outlet portion.

The valve assembly further comprises a valve needle axially movable in the cavity. In particular, the valve needle is axially displaceable with respect to the valve body in reciprocating fashion. The valve needle is operable to prevent a fluid flow through the fluid outlet portion in a closing position and to release the fluid flow through the fluid outlet portion in other positions.

Furthermore, the valve assembly comprises an electro-magnetic actuator assembly being configured to actuate the valve needle. In particular, the actuator assembly is operable to displace the valve needle away from the closing position in a first axial direction.

The actuator assembly comprises an armature which is arranged in the cavity and which is axially moveable relative to the valve needle. Expediently, the armature is also axially displaceable with respect to the valve body. The valve assembly is in particular configured such that the armature is operable to mechanically interact with the valve needle for taking the valve needle with it in the first axial direction in order to move the valve needle away from the closing position. The valve assembly comprises a stop device which is

configured and arranged to limit the axial movement of the armature. In particular, the stop device is operable to limit the axial displacement of the armature in a second axial direction, opposite to the first axial direction. The stop device may expediently be arranged in the cavity axially between the armature and a step in a surface of the cavity downstream of the armature.

Furthermore, the valve assembly comprises a flexible

component. The flexible component is mechanically connected with the armature. In other words, it is fixed to the

armature. In addition, the flexible component is mechanically connected with the stop device and/or the valve needle. In other words, it is fixed to the stop device and/or the valve needle. For example, it has a first seam which is fixed to the armature and a second seam which is fixe to the stop device and/or the valve needle. The first seam is

positionally fix relative to the armature and the second seam is positionally fix to the stop device and the valve needle.

The flexible component is arranged to provide a force on the armature contributing to coupling the armature with the stop device. More specifically, the flexible component comprising a bent-shaped profile and is preloaded by means of

deformation of the bent-shaped profile, such that it biases the armature into contact with a surface of the stop device. In other words, the flexible component is in particular preloaded in the valve assembly by means of deformation of the bent-shaped profile out of its neutral position so that it forces the armature into contact with a first surface of the stop device. The first surface is in particular facing towards the armature. In particular, an axial distance between the first seam and the second seam of the flexible component is larger when the flexible component is preloaded in the valve assembly as compared to the axial distance in the stress-free neutral position.

Further the flexible component is deformable to allow axial displacement of the armature in the first axial direction away from the stop element against the bias of the flexible component. More specifically, the bent-shaped profile is in particular elastically deformable in addition to the

deformation for generating the preload to allow axial displacement of the armature in the first axial direction away from and in particular out of contact with the stop element against the bias of the flexible component. The additional deformation in particular leads to a further increase of the axial distance between the first and second seams of the flexible component.

The arrangement of the flexible component allows applying a recall force on the armature in order to pull it into the direction of the stop device. This has the advantage that a recall force on the armature can be achieved, which

contributes to coupling the armature with the stop device, by a single component. The flexible component has the effect that, in a resting state of the injection valve, the armature is held attached to the stop device. This allows a reliable and precise functioning of the injection valve. A recall spring clamped by an additional construction element is not necessary .

In one embodiment, the valve assembly further comprises an armature retainer. The armature retainer is operable to limit the axial displacement of the armature with respect to the valve needle in the first axial direction. The armature may be operable to take the valve needle with it in the first axial direction by means of mechanical interaction - e.g. a form-fit connection - with the armature retainer for

displacing the valve needle away from the closing position. The armature retainer may be in one piece with the valve needle. Alternatively, the armature retainer may be a

separate piece which is fixed to the valve needle. The armature retainer is in particular positioned upstream of the armature in the cavity.

In one embodiment, the armature is forced into mechanical contact with the stop element by means of the flexible component when the actuator assembly is de-energized and the armature is displaceable away from the stop element and into contact with the armature retainer against the bias of the flexible component by means of energizing the actuator assembly .

The flexible component allows keeping the armature constantly in contact with the stop device to always realize a "free lift" before opening the valve needle when the armature comes in contact with the armature retainer during its travel in the first axial direction. The initial impulse transferred to the valve needle by the armature may be particularly large in this way. Thus, valve assembly is advantageously suitable for operating at particularly large fluid pressures.

Preferably the preload of the flexible component is

significantly smaller than a load of a return spring for the valve needle. The preload is by at least 50% smaller than the load of the return spring. The return spring is in particular provided for forcing the valve needle into the closing position when the actuator assembly is de-energized. In one embodiment, the flexible component is fixed to the valve needle on a side of the stop device remote from the armature. For example, the flexible component is fixed to the valve needle within a given area of the valve needle between the stop device and an end of the valve needle facing the fluid outlet portion. In a further embodiment, the flexible component is fixed to the stop device on a second surface of the stop device, the second surface being axially oriented facing away from the armature. Alternatively or additionally, the flexible component is fixed to the valve needle along a peripheral surface of the valve needle. In a further

embodiment, the flexible component is fixed to the armature along a peripheral surface of the armature. Preferably, the armature comprises a notch for arranging the flexible

component, in particular for arranging its first seam. In one development, the flexible component, in particular its second seam, extends circumferentially around the stop device at least in places. In other words, the flexible component succeeds the stop device in radial direction away from the longitudinal axis at least in places.

By this, the valve assembly can easily be assembled. In particular, the flexible component can easily be fixed to the valve needle and/or the stop device. As a result, the bent- shaped profile and therefore the desired preload and

deformability can easily be achieved.

The flexible component is designed at least generally cup- shaped. In another embodiment, the flexible component

comprises at least one bent-shaped spoke. By this, a desired preload and deformability can easily be achieved. The valve assembly can easily be assembled. In one embodiment, the flexible component comprises steel or consists of steel. By this, a robust and fluid resistant construction is made possible.

In a further embodiment, the mechanical connections are welded connections. In other words, the flexible component is fixed to at least one of the valve needle, the stop device and the armature by means of a respective welded connection such as a weld seam or weld spot. By this, a secure coupling between the flexible component and the armature, the stop device and the valve needle, respectively, is made possible and the position of the flexible component may be defined very exactly.

Advantageous embodiments and developments of the valve assembly and the injection valve will become apparent from the exemplary embodiment described below in association with the figures.

In the figures:

Figure 1, shows an injection valve in a longitudinal section view, and

Figure 2, shows a first embodiment of a valve assembly in a longitudinal section view.

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

Figure 1 shows an injection valve 10 which is suitable for dosing fluids and which comprises a valve assembly 11 and an inlet tube 12. The injection valve 10 may in particular be suitable for dosing fuel to an internal combustion engine, in particular directly into a combustion chamber of the internal combustion engine.

The valve assembly 11 comprises a valve body 14 with a central longitudinal axis L. It further comprises a housing 16. The housing 16 is partially arranged around the valve body 14. A cavity 18 is arranged in the valve body 14 and hydraulically connects a fluid inlet portion 42 of the valve body 14 with a fluid outlet portion 40 of the valve body 40.

The cavity 18 accommodates a valve needle 20 and an armature 22. An armature retainer 23 is arranged axially adjacent to the armature 22 and upstream thereof. The armature retainer 23 is, for example, fixedly coupled to the valve needle 20. The armature retainer 23 is formed as a collar around the valve needle 20.

A return spring 24 is arranged in a recess 26 provided in a pole piece 37. The pole piece 37 is fixed to the valve body 14 in the region of the fluid inlet end 42. The recess 26 is part of the cavity 18. The return spring 24 is mechanically coupled to the armature retainer 23. The armature retainer 23 is in contact with an inner side of the pole piece 37 and can guide the valve needle 20 in the axial direction by means of interaction with the recess 26. A filter element 30 is arranged in the recess 26 and positionally fixed with respect to the pole piece 37. The filter element 30 forms a further seat for the return spring 24. Thus, the return spring 24 is preloaded so that it is operable to act on the valve needle 20 to bias the valve needle 20 in the axial direction into a closing position. In the closing position of the valve needle 20, it sealingly rests on a seat plate 32, thus preventing a fluid flow through an injection nozzle 34. The injection nozzle 34 may be, for example, an injection hole. However, it may also be of some other type suitable for dosing fluid.

The valve assembly 11 is provided with an actuator assembly 36, which is preferably an electro-magnetic actuator. The electro-magnetic actuator assembly 36 comprises a coil 38, which is preferably arranged inside the housing 16.

Furthermore, the electro-magnetic actuator assembly 36 comprises the armature 22, the pole piece 37 and the housing 16. The armature 22 is arranged in the cavity 18 and axially movable relative to the valve needle 20 and to the valve body 14. The housing 16, the valve body 14, the inlet tube 12, and the armature 22 together form an electromagnetic circuit.

The fluid outlet portion 40 is a part of the cavity 18 located near the seat plate 32. The fluid outlet portion 40 communicates hydraulically with the fluid inlet portion 42 provided in the valve body 14.

The valve assembly 11 comprises a stop device 50 being arranged in the cavity 18 axially between the armature 22 and a step surface 44 of the cavity 18. The armature retainer 23 and the stop device 50 are positioned such that the armature 22 has a given axial play. In other words, the armature 22 is axially displaceable between the armature retainer 23 and the stop device 50 relative to the valve needle 20. The armature retainer 23 is operable to limit the axial displacement of the armature 22 with respect to the valve needle in a first axial direction D_]_ . The stop device 50 is designed to limit the axial movement of the armature 22in a second axial direction D2 which is opposite to the first axial direction. The stop device 50 comprises for example a damping element 52 and a hard stop element 54. The damping element 52 comprises an elastomer or consists of an elastomer. The damping element 52 is embodied in a ring-shaped form. The damping element 52 effects a de-bouncing when the armature 22 strokes against the stop device 50.

The hard stop element 54 is designed as a protrusion which extends in radially outward direction from the valve needle 20. The protrusion is rigidly coupled to the valve needle 20. For example, the protrusion is shaped as a ring element.

Alternatively, the hard stop element 54 comprises a weld seam. The hard stop element 54 forms a rigid stop element for the armature 22.

The valve assembly 11 comprises a flexible component 46. The flexible component 46 is mechanically connected with the armature 22 and the stop device 50 and/or the valve needle 20. The flexible component 46 is arranged and preloaded to provide a force on the armature 22 contributing to coupling the armature 22 with the stop device 50. Specifically, the flexible component 46 comprises a given bent-shaped profile which is elastically deformed out of its neutral position, such that it exerts a given force on the armature 22 to bias the armature 22 in contact with the stop device 50..

The flexible component 46 allows keeping the armature

constantly in contact with the stop device to always realize a "free lift". The bent-shaped profile is elastically

deformable in such fashion that the armature 22 can decouple from the stop device 50 and travel axially towards the armature retainer 23 so that it comes in contact with the armature retainer 23 and engages into a form-fit connection with the armature retainer 23 for displacing the valve needle 20 away from the closing position.

The free lift is the relative movement which the armature 22 can perform in respect to the valve needle 20 before

impacting the armature retainer 23 and moving together with the valve needle 22. This free lift movement allows the armature 22 to accumulate kinetic energy to move the valve needle 22 faster in its opening position and to transfer a particular large initial impulse to the valve needle 20 for moving the latter out of the closing position against the fluid pressure.

Preferably, the flexible component 46 is mechanically coupled with the stop device 50 by fixing the flexible component 46 to the hard stop element 54. Alternatively or additionally, the flexible component 46 is mechanically connected with the valve needle 20, in particular by welding, within a given area of the valve needle 20 between the stop device 50 and an end of the valve needle 20 facing the fluid outlet portion 40.

The flexible component 46 is designed in a generally cup- shaped form. For instance, the flexible component 46

comprises at least one bent-shaped spoke, preferably a plurality of bent-shaped spokes. In other words, the cup- shape may have a plurality of longitudinal slits. The

flexible component 46 comprises, for example, steel or consists of steel. A first seam of the flexible component 46 is mechanically connected with the armature 22 along a peripheral surface of the armature 22 so that the first seam is positionally fix relative to the armature 46. Preferably, the armature 22 comprises a notch for arranging the first seam of the flexible component 46. The damping element 52 of the stop device 50 is arranged in an interior of the cup- shape .

The flexible component biases the armature 22 into contact with a first surface of the stop device 50. The first surface faces towards the armature 22. It is for example an upstream surface of the damping element 52.

A second seam of the flexible component 46 may be

mechanically connected with the stop device 50 on a second surface of the stop device 50, this second surface being axially oriented facing away from the armature 22. The second surface is for example a downstream surface of the hard stop element 54. Alternatively or additionally, the second seam of the flexible component 46 may be mechanically connected with the valve needle 20 along a peripheral surface of the valve needle 20. For instance, the mechanical connections are welded connections so that the second seam is positionally fix relative to the valve needle 20 and the stop device 50.

In the following, the function of the injection valve 10 is described in detail:

The fluid is led through the inlet tube 12 to the fluid inlet portion 42 of the valve assembly 11 and further towards the fluid outlet portion 40.

The valve needle 20 prevents a fluid flow through the fluid outlet portion 40 in the valve body 14 in a closing position of the valve needle 20. Outside the closing position of the valve needle 20, the valve needle 20 allows the fluid to flow through the fluid outlet portion 40. If the electro-magnetic actuator assembly 36 with the coil 38 is energized, the actuator assembly 36 may exert an electro^¬ magnetic force on the armature 22. The armature 22 is

attracted by the pole piece 37 and may move in the first axial direction D_]_, i.e. in the present embodiment away from the fluid outlet portion 40. The armature 22 takes along the armature retainer 23 and the valve needle 20 so that the valve needle 20 moves in the first axial direction D_]_ out of the closing position. Outside the closing position of the valve needle 20, a fluid path is formed between the seat plate 32 and the valve needle 20 and the fluid can pass through the injection nozzle 34.

In the case that the actuator assembly 36 is de-energized, the return spring 24 can force the valve needle 20 to move in the second axial direction D2 into its closing position. In particular, it depends on the force balance between the force exerted on the valve needle 20 by the actuator assembly 36 and the force exerted on the valve needle 20 by the return spring 24 whether the valve needle 20 moves into its closing position or not.

When the valve needle 20 reaches its closing position, the armature 22 may decouple from the armature retainer 23 due to its inertia and the bias of the flexible component 46.

The flexible component 46 is designed and arranged in

conjunction with the stop device 50 to limit the axial movement of the armature 22 relative to the valve needle 20, for instance, inside a range of elastic deformation of the flexible component 46.

The flexible component 46 is, for example, connected with either the stop device 50 or with the valve needle 20. The flexible component 46, for example, is designed to generate the free lift function, that means allowing a flexible movement of the armature 22 which allows the armature 22 to move in respect to the needle before impacting the armature retainer 23. Alternatively the flexible component 46 is designed to allow the armature 22 beginning the free lift movement but due to a lower flexibility of the flexible component 46, the valve needle 20 starts to move in its opening position before the armature 22 impacts the armature retainer 23. In this case there is a lower amount of kinetic energy accumulated by the armature 22 before the opening phase begins .

Claims

1. Valve assembly (11) for an injection valve (10),

comprising

- a valve body (14) including a central longitudinal axis (L) , the valve body (14) comprising a cavity (18) with a fluid inlet portion (42) and a fluid outlet portion (40),

- a valve needle (20) axially movable in the cavity (18), the valve needle (20) preventing a fluid flow through the fluid outlet portion (40) in a closing position and releasing the fluid flow through the fluid outlet portion (40) in other positions,

- an electro-magnetic actuator assembly (36) being operable to displace the valve needle (20) away from the closing position in a first axial direction, the

actuator assembly (36) comprising an armature (22) which is arranged in the cavity (18) and is axially moveable relative to the valve needle (20),

- a stop device (50) , the stop device (50) being operable to limit the axial displacement of the armature (22) with respect to the valve needle (20) in a second axial direction, opposite the first axial direction, and

- a flexible component (46) being in a generally cup- shaped form, being fixed to the armature (22) and being fixed to the stop device (50) and/or the valve needle (20), wherein the flexible component (46) comprises a bent-shaped profile and is preloaded by means of

deformation of the bent-shaped profile such that it biases the armature (22) into contact with a surface of the stop device (50) and that the flexible component (46) is deformable to allow axial displacement of the

armature (22) in the first axial direction away from the stop element against the bias.

2. The valve assembly (11) according to claim 1, further comprising an armature retainer (23) , the armature retainer being operable to limit the axial displacement of the armature (22) with respect to the valve needle (20) in the first axial direction.

3. The valve assembly (11) according to claim 2, wherein the armature (22) is forced into mechanical contact with the stop element (50) by means of the flexible component (46) when the actuator assembly (36) is de-energized and the armature (22) is displaceable away from the stop element (50) and into contact with the armature retainer (23) against the bias of the flexible component (46) by means of energizing the actuator assembly (36) .

4. Valve assembly (11) according one of the preceding

claims, wherein the flexible component (46) is fixed to the valve needle (20) on a side of the stop device (50) remote from the armature (22) .

5. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) comprises at least one bent-shaped spoke.

6. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) comprises steel or consist of steel.

7. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) is fixed to the armature (22) along a peripheral surface of the armature (22 ) .

8. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) is fixed to the stop device (50) on a second surface of the stop device (50), the second surface being axially oriented facing away from the armature (22) .

9. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) is fixed to the valve needle (20) along a peripheral surface of the valve needle (20) .

10. Valve assembly (11) according to one of the preceding claims, wherein the flexible component (46) is fixed to the valve needle (20) and/or to the stop device (50) and/or to the armature (22) by means of a welded connection .

11. Injection valve (10) with a valve assembly (11)

according to one of the preceding claims.