Valve Assembly for an Injection Valve and Injection Valve

Abstract

A valve assembly for an injection valve is disclosed, including a valve body with a cavity, a valve needle axially moveable in the cavity, the valve needle being fixedly connected to a retaining element which extends in radial direction and is arranged in an axial region of the valve needle facing away from the fluid outlet portion, and an armature being able to slide on the valve needle and acting on the needle by way of the retaining element. A conical spring is arranged between the retaining element and a top side of the armature facing the retaining element, biasing the armature away from the retaining element.

Claims

1. A valve assembly for an injection valve, comprising: a valve body with a central longitudinal axis comprising a cavity with a fluid inlet portion and a fluid outlet portion, a retaining element, 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 needle being fixedly connected to the retaining element which extends in a radial direction and is arranged in an axial region of the valve needle facing away from the fluid outlet portion, an armature for an electromagnetic actuator unit axially movable in the cavity, the armature comprising a central axial opening through which the valve needle extends, the armature being able to slide on the valve needle and acting on the needle by way of the retaining element, and a conical spring arranged around the central longitudinal axis between the retaining element and a top side of the armature facing the retaining element, biasing the armature away from the retaining element.

2. The valve assembly according to claim 1, wherein the armature has a flat surface which is operable to engage in form fit connection with the retaining element and which represents a seat for the conical spring.

3. The valve assembly according to claim 1, wherein the retaining element comprises a sleeve portion which axially overlaps the conical spring and a collar portion projecting in a radially outward direction beyond the sleeve portion and representing a seat for the conical spring.

4. The valve assembly according to claim 1, wherein the conical spring includes a plurality of windings, a diameter of the windings of the conical spring increases at least by 2d per turn, wherein d is the diameter of spring wire.

5. The valve assembly according to claim 1, wherein the conical spring includes a plurality of windings, the diameter of the windings of the conical spring is minimal at a first end of the spring facing the retaining element and maximal at a second end facing the armature and increases in the direction towards the armature.

6. The valve assembly according to claim 1, wherein the armature comprises a number of through holes forming fluid passages between the fluid inlet portion and the fluid outlet portion, wherein first ends of the through holes are disposed on the top side of the armature radially outside of an area covered by the conical spring.

7. The valve assembly according to claim 1, wherein the valve assembly is part of and is disposed in an injection valve, the injection valve further comprising an electromagnetic actuator unit operatively coupled to the valve assembly, the electromagnetic actuator unit including the armature.

8. An injection valve, comprising: an electromagnetic actuator unit including an armature; and a valve assembly operably coupled to the actuator unit, comprising: a valve body with a central longitudinal axis comprising a cavity with a fluid inlet portion and a fluid outlet portion, a retaining element disposed in the cavity, 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 needle being fixedly connected to the retaining element which extends in radial direction and is arranged in an axial region of the valve needle facing away from the fluid outlet portion, and a conical spring arranged around the central longitudinal axis between the retaining element and a top side of the armature facing the retaining element, biasing the armature away from the retaining element, wherein the armature of the electromagnetic actuator unit is axially movable in the cavity, the armature comprising a central axial opening through which the valve needle extends, the armature being able to slide on the valve needle and acting on the needle by way of the retaining element.

9. The injection valve of claim 8, wherein the armature has a flat surface which is operable to engage in form fit connection with the retaining element and which represents a seat for the conical spring.

10. The injection valve of claim 8, wherein the retaining element comprises a sleeve portion which axially overlaps the conical spring and a collar portion projecting in radially outward direction beyond the sleeve portion and representing a seat for the conical spring.

11. The injection valve of claim 8, wherein the conical spring includes a plurality of windings, a diameter of the windings of the conical spring increases at least by 2d per turn, where d is the diameter of spring wire.

12. The injection valve of claim 1, wherein the conical spring includes a plurality of windings, the diameter of the windings of the conical spring is at a smallest diameter at a first end of the spring facing the retaining element and at a largest diameter at a second end facing the armature and increases in the direction towards the armature.

13. The injection valve of claim 1, wherein the armature comprises a number of through holes forming fluid passages between the fluid inlet portion and the fluid outlet portion, wherein first ends of the through holes are located on the top side of the armature radially outside an area covered by the conical spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a sectional view of an injection valve with a valve assembly according to one embodiment of the invention and

[0026] FIG. 2 shows a detail of FIG. 1.

DETAILED DESCRIPTION

[0027] FIG. 1 shows an injection valve 1 that is in particular suitable for dosing fuel to an internal combustion engine. The injection valve 1 comprises in particular 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.

[0028] 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.

[0029] In a closing position of the valve needle 11, valve needle 11 sealingly rests on a seat plate 17 having at least one injection nozzle. A preloaded calibration spring 18 exerts a force on the needle 11 in axial direction towards the closing position. The fluid outlet portion 7 is arranged near the seat plate 17.

[0030] In the closing position of the valve needle 11, a fluid flow through the at least one injection nozzle is prevented. The injection nozzle may be, for example, an injection hole. However, the injection nozzle may also be of some other type suitable for dosing fluid.

[0031] The valve assembly 3 is provided with an electro-magnetic actuator unit 19. The electro-magnetic actuator unit 19 comprises a coil 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 actuator unit 19 further comprises a pole piece 25.

[0032] The armature 23 is axially movable in the cavity 9 and fixed to the valve needle 11 by form fit, this joint preventing movement of the armature 23 relative to the valve needle 11 in radial direction. The needle 11 extends through a central axial opening in the armature 23. The armature 23 is axially movable relative to the valve needle 11, i.e. the armature 23 may slide on the needle 11.

[0033] At an axial end of the valve needle 11, the valve needle 11 comprises an upper retaining element 24. The upper retaining element 24 has a sleeve portion—in the following denoted as base portion 27—extending circumferentially around the axial end of the valve needle 11 and further comprises a collar portion 26 extending in radial direction away from the valve needle 11 so that it projects in radial outward direction beyond the base potion 27. The upper retaining element 24 is an integrally formed, one-pieced part. In this embodiment, the upper retaining element 24 is a separate piece but fixedly connected to the axial end of the valve needle 11. In further embodiments, the upper retaining element 24 may be formed in one piece with the valve needle 11.

[0034] Between the upper retaining element 24 and a top side 28 of the armature 23 facing the upper retaining element 24, a conical spring 30 is arranged around the central longitudinal axis L and around the base portion 27 of the upper retaining element 24, biasing the armature 23 away from the upper retaining element 24.

[0035] The conical spring 30 rests on a flat surface of the armature 23 on the top side 28 of the armature 23 with first end of the conical spring 30, which has a large diameter. Conical spring 30 rests against the collar 26 of the upper retaining element 24 with its second end, which has a smaller diameter.

[0036] The conical spring 30 comprises a number of windings, the diameter of which increases by at least 2d per turn, where d is the diameter of the spring wire. Thus, the spring 30 may be compressed tightly, taking up comparatively little space. Consequently, the spring travel of the conical spring 30 is comparatively large.

[0037] The conical spring 30 enables a transmission of forces between the armature 23 and the upper retaining element 24. The dampening effect of the spring 30 enables that the wearing effects on the armature 23 and/or on the valve needle 11 may be kept small during the opening or closing process of the valve needle 11.

[0038] In the closing position of the valve 1, there is a gap between the upper retaining element 24 and the armature 23, also called the free-lift gap. When the coil 21 is energized, the armature 23 experiences a magnetic force and slides upwards towards the pole piece 25, moving in an axial direction away from the fluid outlet portion 7, thereby compressing the conical spring 30.

[0039] Only after having travelled the gap and after having taken up kinetic energy, the flat surface of the armature 23 on which the conical spring 30 is seated hits the base portion 27 of the upper retaining element 24 and takes the valve needle 11 with it via the form-fit connection with the upper retaining element 24 that is established in this way. Consequently, the valve needle 11 moves in an axial direction out of the closing position of the valve 1. When the armature 23 starts to travel upwards, a gap is formed between the armature 23 and a disc-shaped element 43 fixedly connected to the needle 11 on the side of the armature 23 remote from the upper retaining element 24. The disc-shaped element 43 represents a lower retaining element which limits axial displacement of the armature 23 relative to the valve needle 11 in direction away from the upper retaining element 24.

[0040] When the coil 21 is de-energized, the calibration spring 18 is able to force the valve needle 11 to move in an axial direction into its closing position. At the end of the closing transient, when the valve needle 11 hits the seat plate 17, the armature 23 detaches from the upper retaining element 24 and travels downwards towards the disc-shaped element 43, closing the gap between armature 23 and disc-shaped element 43.

[0041] FIG. 2 shows a detail of the injection valve 1. The armature 23 comprises a number of through holes 32, which form fluid passages between the fluid inlet portion 5 and the fluid outlet portion 7. First ends 34 of the through holes 32 are exposed on the top side 28 of the armature 23 outside the area 36 covered by the conical spring 30. The area 36 covered by the conical spring 30 is the inner area of the top side 28, where windings of the conical spring 30 are arranged. Hence, the area 36 is annular, extends around the base portion 27 of the upper retaining element 24 and has the outer diameter of the largest windings of the conical spring 30.

[0042] Embodiments have been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The description above is merely exemplary in nature and, thus, variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.