Valve assembly and injection valve

Abstract

 Valve assembly (4) of an injection valve (2), the valve assembly (4) comprising a valve body (10) including a central longitudinal axis (L), the valve body (10) having a cavity (11) which comprises an inner guide surface (12) in a guide area of the valve body (10), the cavity (11) having a fluid inlet portion (42) and a fluid outlet portion (44), a valve needle (13) axially movable in the cavity (11), the valve needle (13) having an outer surface (32) and preventing a fluid flow through the fluid outlet portion (44) in a closing position and releasing the fluid flow through the fluid outlet portion (44) in further positions, and a guide element (34). The guide element (34) is ball-shaped. The guide element (34) is arranged in the cavity (11) coaxially to the valve needle (13) and extends radially from the outer surface (32) of the valve needle (13) to the inner guide surface (12) of the valve body (10).

Description

[0001] The invention relates to a valve assembly for an injection valve and an injection valve.

[0002] Injection valves are in widespread use, in particular for an internal combustion engine 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.

[0003] Injection valves are manufactured in various forms in order to satisfy the various needs for the various combustion engines. Therefore, for example, their length, their diameter, and all the 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 can accommodate an actuator for actuating a needle of the injection valve, which may, for example, be an electromagnetic actuator or a piezoelectric actuator.

[0004] In order to enhance the combustion process in view of degradation of unwanted emissions, the respective injection valve may be suited to dose fluids under high pressures. The pressures may be in case of a gasoline engine, for example, in the range of up to 200 bar.

[0005] The object of the invention is to create a valve assembly for an injection valve and an injection valve which is simple to be manufactured and which facilitates a reliable and precise function.

[0006] This object is achieved by the features of the independent claims. Advantageous embodiments of the invention are given in the sub-claims.

[0007] According to a first aspect the invention is distinguished by a valve assembly of an injection valve. The valve assembly comprises a valve body including a central longitudinal axis. The valve body has a cavity which comprises an inner guide surface in a guide area of the valve body. The cavity has a fluid inlet portion and a fluid outlet portion. The valve assembly comprises a valve needle. The valve needle is axially movable in the cavity. The valve needle has an outer surface and 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 assembly comprises a ball-shaped guide element which is arranged in the cavity coaxially to the valve needle and extends radially from the outer surface of the valve needle to the inner guide surface of the valve body.

[0008] This has the advantage that a good alignment of the valve needle relative to the valve body and a good guidance of the valve needle in the valve body can be obtained. Furthermore, the spherical geometry of the guide element results in a small contact area between the guide element and the inner guide surface of the valve body. Consequently, a low friction and abrasion of the ball-shaped guide element with respect to the valve body can be obtained. This can result in a good dynamic performance of the injection valve. Consequently, a high life-time of the valve assembly is possible. Furthermore, ball-shaped guide elements allow achieving a low cost solution for the valve assembly.

[0009] In an advantageous embodiment, the guide element is fixedly coupled to the valve needle. This has the advantage that good guiding properties of the valve needle in the valve body are possible.

[0010] In a further advantageous embodiment, the guide element is welded to the valve needle. This has the advantage that a simple and secure coupling between the guide element and the valve needle is possible.

[0011] In a further advantageous embodiment, the valve body comprises an inlet tube. The fluid inlet portion is arranged inside the inlet tube. The guide area is arranged in the inlet tube. The guide element thereby forms an upper guide element of the valve needle. This has the advantage that an excellent dynamic behavior of the valve needle due to the small coupling areas between the guide element and the inlet tube can be obtained.

[0012] According to a second aspect the invention is distinguished by an injection valve with an actuator unit and a valve assembly according to the first aspect the invention. The actuator unit comprises an armature. The armature is arranged in the cavity and is moveable relative to the valve needle and is designed to mechanically cooperate with the guide element.

[0013] In an advantageous embodiment of the second aspect of the invention, the armature and the guide element are forming an interlocking device. This has the advantage that the armature can simply mechanically cooperate with the guide element. Furthermore, it is possible that the armature acts as a driver for the guide element and the valve needle in a reliable manner

[0014] In a further advantageous embodiment of the second aspect of the invention, the armature comprises a recess which is designed to take up at least a part of the guide element. This has the advantage that the armature and the guide element are mechanically coupled in a simple manner. Furthermore, a movement of the armature can be transmitted to the guide element in a simple and secure manner.

[0015] In a further advantageous embodiment of the second aspect of the invention, the recess is partly shaped as a cone. The recess faces the ball-shaped guide element. This has the advantage that, as at least a part of the guide element is arranged in the recess of the armature, a cone-sphere contact between the armature and the guide element is possible. Thus, the guide element and the armature act together in a ball-and-socket joint. Thus, a high degree of freedom of the armature with respect to the inlet tube in which the ball-shaped guide element is arranged can be obtained. Consequently, a good alignment of the armature with respect to the inlet tube can be obtained and the contact surfaces between the armature and the inlet tube can fit very well to each other.

[0016] Exemplary embodiments of the invention are explained in the following with the aid of schematic drawings. These are as follows:

Figure 1,

an injection valve in a longitudinal section view,

Figure 2,

an enlarged and detailed view of an embodiment of a valve assembly of the injection valve in a perspec- tive view, and

Figure 3,

an enlarged and detailed view of an embodiment of the valve assembly of the injection valve in a lon- gitudinal section view.

[0017] Elements of the same design and function that appear in different illustrations are identified by the same reference characters.

[0018] An injection valve 2 (Figure 1) that is in particular suitable for dosing fuel to an internal combustion engine comprises a valve assembly 4 and an actuator unit 6.

[0019] The valve assembly 4 comprises a valve body 10 with a central longitudinal axis L and a cavity 11. In a guide area of the valve body 10 the cavity 11 forms an inner guide surface 12 for a valve needle 13 which is arranged in the cavity 11. The valve needle 13 can be moved in the cavity 11 in axial direction. Preferably, the valve needle 13 is hollow and comprises orifices 14 which enable a fluid flow between the inside and the outside of the valve needle 13.

[0020] The valve assembly 4 further comprises an inlet tube 15. Preferably, the inner guide surface 12 is arranged in the inlet tube 15.

[0021] The actuator unit 6 comprises an armature 16 which is arranged in the cavity 11. The armature 16 can be moved in relation to the valve needle 13. A recess 18 is provided in the armature 16. Preferably, the recess 18 of the armature 16 is partly shaped as a cone. An armature spring 19 is arranged in the cavity 11 and is coupled to the armature 16 to exert a force on the armature 16 in axial direction.

[0022] A recess 20 is provided in the inlet tube 15. A main spring 22 is arranged in the recess 20 of the inlet tube 15. The main spring 22 is mechanically coupled to the valve needle 13 to exert a force on the valve needle 13 in axial direction.

[0023] In a closing position of the valve needle 13, it sealingly rests on a needle seat 26 of a seat body 28. The seat body 28 may be made in one part with the valve body 10 or be a separate part. If the valve needle 13 sealingly rests on the needle seat 26 a fluid flow through at least one injection nozzle 30 is prevented. The injection nozzle 30 may be, for example, an injection hole. However, it may also be of some other type suitable for dosing fluid.

[0024] The valve needle 13 has an outer surface 32. Radially between the inner guide surface 12 of the valve body 10 and the outer surface 32 of the valve needle 13 a guide element 34 is arranged which is also named upper guide element. The upper guide element 34 is provided for guiding the valve needle 13 relative to the inlet tube 15. The upper guide element 34 is shaped as a ball having a central drill hole which may take in the valve needle 13. Preferably, the ball-shaped upper guide element 34 is fixedly coupled to the valve needle 13. In particular, the upper guide element 34 may be welded to the valve needle 13. Preferably, the ball-shaped upper guide element 34 is partially taken up in the partly cone-shaped recess 18 of the armature 16 thereby forming a cone-sphere contact. The ball-shaped upper guide element 34 and the armature 16 are forming an interlocking device. This means that in particular the armature 16 entrains the ball-shaped upper guide element 34 for an axial movement of the valve needle 13.

[0025] The main spring 22 rests on a spring seat being formed by the surface of the ball-shaped upper guide element 34. Furthermore, an adjusting tube 40 is provided in the recess 20 of the inlet tube 15. The adjusting tube 40 forms a further seat for the main spring 22 and may be axially moved during the manufacturing process of the injection valve 2 in order to preload the main spring 22 in a desired way.

[0026] A further guide element 35 is arranged between the valve body 10 and the valve needle 13 near the injection nozzle 30. Preferably, the further guide element 35 is disk-shaped and comprises a central aperture. The further guide element 35 is also named lower guide element and is provided for guiding the valve needle 13 relative to the valve body 10 near the injection nozzle 30.

[0027] The actuator unit 6 preferably comprises an electromagnetic actuator with a coil 36 which is preferably over-molded and which is arranged in a housing 38. The coil 36, the armature 16 and the inlet tube 15 are forming an electromagnetic circuit. The actuator unit 6 may, however, also comprise another type of actuator, which is known to persons skilled in the art for that purpose. Such an actuator may be, for example, a piezoelectric actuator.

[0028] The valve assembly 4 has a fluid inlet portion 42 which is provided in the valve body 10. In particular, the fluid inlet portion 42 is provided in the inlet tube 15.

[0029] Additionally, the valve assembly 4 has a fluid outlet portion 44 which is provided in the valve body 10 near the seat body 28. The fluid inlet portion 42 is in hydraulic communication with the fluid outlet portion 44 via the orifices 14.

[0030] The valve needle 10 comprises a seat part 46 being adjacent to the seat body 26. Preferably, the seat part 46 has a spherical shape. In the closing position of the valve assembly 4 the seat part 46 rests on the seat body 28.

[0031] The armature 16 has a front surface 48 which faces away from the fluid outlet portion 44 and which faces the inlet tube 15 (Figure 3 with an enlarged distance between the armature 16 and the inlet tube 15 for a better representation). Preferably, the front surface 48 of the armature 16 which faces the inlet tube 15 has a surface layer comprising chromium which enables a curing of the armature 16.

[0032] In the following, the function of the injection valve is described in detail:

[0033] The fluid is led from the fluid inlet portion 42 in the inlet tube 15 to the hollow valve needle 13 and then through the orifices 14 in the valve needle 13 to the fluid outlet portion 44 near the injection nozzle 30.

[0034] The main spring 22 forces the valve needle 13 in axial direction towards the set body 28. It is depending on the force balance between the force on the valve needle 13 caused by the actuator unit 6 and the force on the valve needle 13 caused by the main spring 22 whether the valve needle 13 is in its closing position or not.

[0035] In the case when the actuator unit 6 is de-energized, the actuator unit 6 does not exert a force on the valve needle 13, and the main spring 22 can exert a force on the guide element 34 and the valve needle 13. Thus, the valve needle 13 can move in axial direction in its closing position, and the seat part 46 of the valve needle 13 is forced to sealingly rest on the needle seat 26 of the seat body 28. The armature spring 19 reduces the velocity of the movement of the armature 16. Consequently, as the guide element 34 is directly coupled to the armature 16, the velocity of the movement of the valve needle 13 in axial direction towards the seat body 28 is also reduced. As the guide element 34 has the shape of a ball, the valve needle 13 is guided very well inside the inlet tube 15 with a minimum of friction and abrasion of the ball-shaped guide element 34 and/or the inlet tube 15. In the closing position of the valve needle 13 a fluid flow through the fluid outlet portion 44 and the injection nozzle 30 is prevented.

[0036] In the case that the actuator unit 6 gets energized, the actuator unit 6, in particular the armature 16, may exert a force on the ball-shaped guide element 34 which is transmitted directly to the valve needle 13. The force from the armature 16 on the guide element 34 is contrary to the force on the valve needle 13 caused by the main spring 22. Thus, the valve needle 13 is able to move in axial direction out of the closing position. The movement of the armature 16 is limited when the front surface of the armature 16 which faces away from the fluid outlet portion 44 and which faces the inlet tube 15 gets into contact with inlet tube 15. Outside of the closing position of the valve needle 13, there is a gap between the seat body 28 and the seat part 46 of the valve needle 13. This gap enables a fluid flow through the injection nozzle 30.

[0037] As the ball-shaped guide element 34 and the armature 16 act together in a ball-and-socket joint, the armature 16 has a high degree of freedom with respect to the inlet tube 15 in which the ball-shaped guide element 34 is arranged. Therefore, the armature 16 can be aligned with respect to the inlet tube 15. Thus, the contact surfaces between the armature 16 and the inlet tube 15 may fit well to each other and a surface deformation of the contact surfaces between the armature 16 and the inlet tube 15 can be prevented. The prevention of a surface deformation is supported by the curing of the surfaces of the armature 16 and the high hardness of the ball-shaped guide element 34.

[0038] In general, a good dynamic performance of the injection valve during the opening and the closing process can be obtained due to the ball-shaped guide element 34. Consequently, a high reliability and a long life-time of the valve assembly 4 and the injection valve 2 are possible. Furthermore, ball-shaped guide elements 34 are easy to be produced. Therefore, it is possible to obtain a low cost solution for the valve assembly 4 and the injection valve 2.

Claims

1. Valve assembly (4) of an injection valve (2), the valve assembly (4) comprising

- a valve body (10) including a central longitudinal axis (L), the valve body (10) having a cavity (11) which comprises an inner guide surface (12) in a guide area of the valve body (10), the cavity (11) having a fluid inlet portion (42) and a fluid outlet portion (44),

- a valve needle (13) axially movable in the cavity (11), the valve needle (13) having an outer surface (32) and preventing a fluid flow through the fluid outlet portion (44) in a closing position and releasing the fluid flow through the fluid outlet portion (44) in further positions, and

- a ball-shaped guide element (34) being arranged in the cavity (11) coaxially to the valve needle (13) and extending radially from the outer surface (32) of the valve needle (13) to the inner guide surface (12) of the valve body (10).

2. Valve assembly (80) in accordance with claim 1, wherein the guide element (34) is fixedly coupled to the valve needle (13).

3. Valve assembly (80) in accordance with claim 1 or 2, wherein the guide element (34) is welded to the valve needle (13).

4. Valve assembly (80) in accordance with one of the preceding claims, wherein the valve body (4) comprises an inlet tube (15) and the fluid inlet portion (42) is arranged inside the inlet tube (15), and the guide area is arranged in the inlet tube (15), the guide element thereby forming an upper guide element (34) of the valve needle (13).

5. Injection valve (2) with an actuator unit (6) and a valve assembly (4) according to one of the preceding claims, wherein the actuator unit (6) comprises an armature (16) which is arranged in the cavity (11) and is moveable relative to the valve needle (13) and is designed to mechanically cooperate with the guide element (34).

6. Injection valve (2) in accordance with claim 5, wherein the armature (16) and the guide element (34) are forming an interlocking device.

7. Injection valve (2) in accordance with claim 5 or 6, wherein the armature (16) comprises a recess (18) being designed to take up at least a part of the guide element (34).

8. Injection valve (2) in accordance with claim 7, wherein the recess (18) is partly shaped as a cone and the recess (18) faces the ball-shaped guide element (34).

Drawing