Valve Assembly and Fluid Injector

Abstract

A valve assembly for a fluid injector is disclosed. The valve assembly includes a valve body having a longitudinal axis, an armature, a valve needle having a needle tip and a damping element. The armature and the damping element include penetrating first openings in which the valve needle is arranged. The damping element is fixed to the valve needle and arranged between the armature and the needle tip with respect to the longitudinal axis to attenuate a movement of the valve needle relative to the valve body during the operation of the valve assembly.

Claims

1. A valve assembly for a fluid injector comprising: a valve body having a longitudinal axis and comprising a wall which forms a recess that enables a streaming fluid to pass through the assembly during an operation, an armature, a valve needle having a needle tip, and a damping element, wherein the armature and the damping element comprise penetrating first openings, in which the valve needle is arranged, the armature, the valve needle and the damping element are arranged axially movable in the recess with respect to the longitudinal axis and relative to the valve body, and the damping element is fixed to the valve needle and arranged between the armature and the needle tip with respect to the longitudinal axis to attenuate a movement of the valve needle relative to the valve body during the operation of the assembly.

2. The valve assembly according to claim 1, wherein the damping element substantially fills in the recess of the valve body in a radial direction to generate a fluid friction for attenuating the movement of the valve needle.

3. The valve assembly according to claim 1, wherein an outer circumferential outline of the damping element is arranged flush with an outer circumferential outline of the armature.

4. The valve assembly according to claim 1, wherein the damping element has an upper surface and the armature has a lower surface which face towards each other and which are spaced apart from one another apart from a region where the upper surface of the damping element has a substantially ring-shaped protrusion which is engageable with the armature so that the protrusion enters into a form-fit connection with the lower surface of the armature.

5. The valve assembly according to claim 1, wherein the damping element comprises at least one penetrating second opening to enable the fluid to pass through the valve assembly during the operation.

6. The valve assembly according to claim 5, wherein the armature comprises at least one penetrating second opening to enable the fluid to pass through the valve assembly during the operation.

7. The valve assembly according to claim 6, wherein an outlet aperture of the at least one second opening of the armature no more than partially overlaps an inlet aperture of the at least one second opening of the damping element from a top view along the longitudinal axis.

8. The valve assembly according to claim 7, wherein a number of second openings of the damping element differs from a number of second openings of the armature.

9. The valve assembly according to claim 1, wherein the valve needle comprises an axial channel to enable the fluid passing the assembly during the operation.

10. The valve assembly according to claim 1, wherein the damping element has the shape of a disc.

11. The valve assembly according to claim 1, wherein the valve assembly forms part of the fluid injector.

12. A valve assembly for a fluid injector, comprising: a valve body having a longitudinal axis and including a wall which forms a recess that enables fluid to flow through the assembly during an operation of the fluid injector; an armature; a valve needle having a needle tip; and a damping element; wherein each of the armature and the damping element includes a first opening through which the valve needle is arranged, wherein the armature, the valve needle and the damping element are axially movable in the recess with respect to the longitudinal axis and relative to the valve body, and wherein the damping element is fixed to the valve needle and arranged between the armature and the needle tip with respect to the longitudinal axis to attenuate a movement of the valve needle relative to the valve body during the operation of the assembly.

13. The valve assembly of claim 12, wherein the damping element has an upper surface and the armature has a lower surface which faces the upper surface of the damping element, a first portion of the upper surface and a first portion of the lower surface are spaced apart from one another, the damping element further including a protrusion disposed radially outwardly from the first portion of the upper surface, the protrusion is engageable with the lower surface of the armature so that the protrusion enters into a form-fit connection therewith.

14. The valve assembly of claim 12, wherein the damping element comprises at least one second opening defined through the damping element, the at least one second opening enabling the fluid to flow through the valve assembly during the operation.

15. The valve assembly according to claim 14, wherein the armature comprises at least one second opening defined through the armature, the at least one second opening enabling the fluid to flow through the valve assembly during the operation.

16. The valve assembly according to claim 15, wherein a number of the second openings of the armature is different from a number of the second openings of the damping element.

17. The valve assembly according to claim 16, wherein the number of the second openings of the armature is greater than the number of the second openings of the damping element such that during at least a portion of the operation, a first fluid flow path through the valve assembly is defined in a direction that is lateral to the longitudinal axis in a space between an upper surface of the damping element and a lower surface of the armature.

18. The valve assembly according to claim 15, wherein the at least one second opening of the armature no more than partially overlaps the at least one second opening of the damping element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Exemplary embodiments of the invention are explained in the following with the aid of schematic drawings and reference numbers. Identical reference numbers designate elements or components with identical functions. In the figures:

[0036] FIG. 1 shows an exemplary embodiment of a fluid injector;

[0037] FIG. 2 shows an exemplary embodiment of an assembly for the fluid injector of FIG. 1; and

[0038] FIG. 3 shows an exemplary embodiment of a damping element depicted in FIGS. 1 and 2.

DETAILED DESCRIPTION

[0039] FIG. 1 shows an exemplary embodiment of a fluid injector 30 which comprises an O-ring or a circlip 32 for locking a spacer ring to a valve body 3, a spring element 34 in the valve body 3 and a coil 36 in a housing which surrounds a portion of the valve body 3. The valve body 3 has a longitudinal axis L. The valve body 3 has a circumferential side wall 5 which defines a recess 7.

[0040] The injector 30 further comprises a valve needle 11 which is positioned in the recess 7. The valve needle 11 is connected to an armature 9 and is axially movable relative to the valve body 3 along the longitudinal axis L. In coaction with a nozzle 38, the valve needle 11 prevents a fluid flow through the injector 30 in a closed position and is axially displaceable away from the closed position to enable the fluid flow.

[0041] The valve needle 11 is displaced away from the closed position by means of a magnetic force generated by energizing the coil 36 and is displaced towards the closing position by means of an elastic force generated by the spring element 34. A hydraulic force generated by the streaming fluid also influences the opening and closing process during an operation of the injector 30, in particular when the valve needle 11 is close to the closing position. The valve needle 11 and the armature 9 are rigidly coupled or—as in the present embodiment—axially displaceable relative to one another. Specifically, the armature 9 is axially arranged between an armature retainer of the valve needle and a damping element 13 which is fixed to a shaft of the valve needle 11 so that it has an axial play. The armature 9, for example, is realized as a massive steel part from a magnetic steel.

[0042] A valve assembly 1 of the fluid injector 30 comprises the armature 9, the valve needle 11, the damping element 13 and the valve body 3. More detailed illustrations of the assembly 1 will be described below with respect to FIGS. 2 and 3.

[0043] In FIG. 2, one exemplary embodiment of the valve assembly 1 is illustrated wherein the armature 9, the damping element 13 and the valve needle 11 are arranged in the recess 7 of the valve body 3. The armature 9 further comprises a first opening 15 in which the valve needle 11 is arranged as well as the damping element 13 comprises a first opening 17 in which the valve needle 11 is arranged.

[0044] In this exemplary embodiment of the assembly 1, in a cross section view with respect to the longitudinal axis L, the armature 9 comprises two second openings 16 which penetrate the armature 9 axially from a first side—i.e., a lower surface 24 of the armature 9—to a second side—i.e., an upper surface 22 of the armature 9. A central axis of each of the second openings 16 is inclined to the longitudinal axis L.

[0045] The damping element 13 also comprises a second opening 18 which penetrates the damping element 13 from a first side—i.e., an upper surface 25 of the damping element 13—to a second side 28 of the damping element 13. A central axis of the second opening 18 is parallel to and radially offset from the longitudinal axis L so that the second opening 18 is radially spaced apart from the longitudinal axis L.

[0046] In this exemplary embodiment, the valve needle 11 also comprises an opening 19 which extends axially through a portion of the valve needle 11 and thus the valve needle 11 acts as a hollow needle to enable fluid to pass through the assembly 1 during the operation of the assembly 1 or the injector 30. Such a configuration of the valve needle 11 is advantageous if, for example, the damping element 13 comprises no second openings 18 to let streaming fluid pass through. Alternatively, the streaming fluid can flow outside the armature 9 and the damping element 13 if there is enough clearance left to the wall 5 of the valve body 3.

[0047] This exemplary embodiment describes a combination of the armature 9, the valve needle 11 and the damping element 13 each comprising penetrating openings 16, 18, and 19, respectively, to enable fluid to pass through the assembly 1 during the operation. Concerning further embodiments, there may only be second openings 16 and 18 of the armature 9 and the damping element 13, respectively, arranged whereas the valve needle 11 is substantially solid. Alternatively, there is only one or more second openings 16 arranged which penetrate the armature 9 whereas the valve needle 11 and the damping element 13 are substantially configured solidly. Hence, various combinations of the armature 9, the valve needle 11 and the damping element 13 are possible which do or do not comprise penetrating openings 16, 18, 19, respectively, to enable streaming fluid to pass through the assembly 1.

[0048] Furthermore, the damping element 13 comprises a shape of a disc and is fixedly mounted on the valve needle 11, for example by press fit, welding or machining. The damping element 13 further matches the armature 9 concerning a lateral dimension of these components. This means that in this embodiment, an outer outline of a circumferential side surface 21 of the armature 9 is flush with an outer outline of a circumferential side surface 23 of the damping element 13 in top view along the longitudinal axis L. In addition, the damping element 13 nearly fills the recess 7 of the valve body 3 in a radial direction substantially perpendicular with respect to the longitudinal axis L. Preferably, only a small circumferential gap having a width—i.e., a radial dimension—of 0.5 mm or less, preferably of 0.2 mm or less, is established between the outer side surface 23 of the damping element 13 and an inner surface of the wall 5 of the valve body 3. Such gap sizes are also useful for other embodiments of the valve assembly 1.

[0049] The upper surface 25 of the damping element 13 has a ring-shaped protrusion 27 which is engageable into a form-fit connection with the bottom surface 24 of the armature 9. When the protrusion 27 is in contact with the bottom surface 24 of the armature 9, the rest of the upper surface 25 of the damping element 13 is spaced apart from the bottom surface 24 of the armature 9 so that a gap 26 is established between the two surfaces 24, 25 in a region radially inward of the ring-shaped protrusion 27. The protrusion 27 realizes a small contact surface to the armature 9 in a shape of a slim ring. For example, in a closed position of the injector 30, the protrusion 27 of the damping element 13 contacts the bottom surface 24 of the armature 9. In this context, it is desirable that the contact surface is small enough to avoid hydraulic sticking of the armature 9 and the damping element 13, but big enough to enable sufficient stability of the contact surface of the damping element 13 to avoid damage due temporary contact between the armature 9 and the damping element 13.

[0050] In case of an opening transient, the armature 9 moves upwards with respect to the longitudinal axis L, i.e., away from the damping element 13 due to the magnetic force generated by the coil 36. For example, after a preferred free lift of the armature 9, the valve needle 11 and the connected damping element 13 are also moved upwards due to the impact of the armature 9 on the armature retainer. Thus, the valve needle 11 is displaced away from the closing position and the streaming fluid mainly passes through the openings 16, 18 and 19.

[0051] Regarding this exemplary embodiment, the armature 9 comprises two second opening 16 whereas the damping element 13 comprises one second opening 18. It is advantageous that the respective number of the second openings 16, 18 differs from one another, for example, to further avoid phasing and hydraulic sticking of the damping element 13 and the armature 9. For example, the two second openings 16 of the armature 9 are designed as penetrating channels and the one second opening 18 of the damping element 13 is designed as a penetrating hole. Hence, there is at least one channel which guides the fluid into the recessed area 26 and onto the upper surface 25 of the damping element 13 and not directly through the second opening 18. Due to this part of streaming fluid impacting on the upper surface 25 of the damping element 13 and being deflected in a lateral direction, fluid friction may be generated and/or the damping element 13 may be pushed away from the armature 9 so that a hydraulic sticking of the armature 9 and the damping element 13 is prevented.

[0052] The assembly 1 describes a simple, reliable and competitive possibility to reduce a velocity of the valve needle 11 during an operation of the assembly 1 in reference to an opening process of the injector 30, for example. The damping element 13 mounted on the valve needle 11 decelerates the velocity of the valve needle 11 due to enhanced flow resistance generated by the damping element 13 and the streaming fluid.

[0053] Hence, the deceleration is generated by a force which is induced by the velocity of the valve needle 11 itself. Therefore, using the assembly 1 enables a reliable and secure functioning of the injector 30 with improved controllability.

[0054] An absolute value of the decelerating force can be chosen by the configuration of the damping element 13, for example, concerning a design or a shape of the damping element 13. Furthermore, the damping element 13 may comprise one or more recesses or openings like the described second openings 18 to adjust the absolute value of the decelerating force. The damping element 13 is connected to the valve needle 11. It may reduce the velocity of the valve needle 11 during the opening and the closing transient. The injector 30 which comprises the valve assembly 1 exhibits an improved controllability in a ballistic phase of the opening transient or in a ballistic operation mode where the valve needle 11 returns to the closing position without hitting a hard stop at the end of the opening transient. Hence, such a configuration allows for a fast opening of the injector 30 also at high pressure combined with an enhanced controllability of the valve needle 11 and the functioning of the injector 30 which is advantageous to accurately dose the fluid, for example.

[0055] FIG. 3 shows an exemplary embodiment of the damping element 13 which is similar to the one illustrated in FIG. 2. The damping element 13 comprises five penetrating second openings 18 with circular shape which are arranged on a circle around the first penetrating opening 17 with respect to the longitudinal axis L. The second openings 18 have a smaller diameter than the first opening 17 which is arranged for assembling the valve needle 11 and which, for example, matches a diameter of the adjacent first opening 15 of the armature 9. In this perspective view, the contact surface between the damping element 13 and the armature 9 given by the protrusion 27 of the damping element 13 is apparent. This also concerns the upper surface 25 and its recessed area radially inward from the protrusion 27, which recessed area shapes the gap 26 between the damping element 13 and the armature 9.

[0056] Additionally, the damping element 13 enables a stabilisation effect by guiding the valve needle 11 in reference to the armature 9 with respect to the longitudinal axis L. This is in particular affected by the outer circumferential side surface 23 of the damping element 13 being in sliding contact with the wall 5 of the valve body 9. In this context, a large diameter of the disc shaped damping element 13 is advantageous because this enables a beneficial starting position of the connected valve needle 11 with respect to the armature 9 due to leverage induced by the contact surface between the protrusion 27 of the damping element 13 and the first side 24 of the armature 9. To enable the above mentioned guiding effect, the damping element 13 of this embodiment comprise a small contact surface to the armature 9 and nearly fills in the recess 7 of the valve body 3, e.g., to realize an advantageous leverage.

[0057] The foregoing description illustrates various aspects and examples of the invention. It is not intended to be exhaustive. Rather, it is chosen to illustrate the principles of the invention and its practical application to enable one of ordinary skill in the art to utilize the invention, including its various modifications that naturally follow. All modifications and variations are contemplated within the scope of the invention as determined by the appended claims. Relatively apparent modifications include combining one or more features of various embodiments with features of other embodiments.