Valve assembly for refrigerant and vehicle refrigeration system comprising same

Abstract

The invention relates to a valve assembly for a refrigerant, comprising a drive unit (10) for generating a rotational movement of a drive shaft (11) in a valve body chamber (13), a valve unit (20) for guiding a closing body (22) wherein the closing body (22) is configured to be switched between a closed position and an open position by the rotational movement of the drive shaft (11) in the valve unit (20), the invention relates to a valve assembly (10) comprising a valve unit (20) having a closing body (22), a valve seat (26), a closed position in which the closing body (22) abuts against the valve seat (26) and an open position in which the closing body (22) and the valve seat (26) are spaced apart, a rod seal (39) for sealing the closing body (22) with respect to the valve unit (20) wherein the rod seal (39) is arranged at least partially between the valve unit (20) and the closing body (22) and thereby circumferentially around the closing body (22), wherein the closing body and / or the valve unit comprises a sealing geometry that interacts with the rod seal (39) such that the rod seal (39) is arranged in a sealing manner in a closed position of the closing body (22) and is mounted in a sliding manner in an open position between the closing body (22) and the valve unit (20).

Description

Invention Field

[0001] This invention relates to a valve assembly for refrigerants. Specifically, this invention relates to a valve or valve assembly for a vehicle refrigeration system. Furthermore, this invention relates to such a vehicle refrigeration system. Technical Background

[0002] Valve assemblies for vehicle refrigeration systems have numerous applications in motor vehicles, such as in vehicle interior air conditioning. Valve assemblies are used to influence, control, or regulate the flow of refrigerant in a refrigerant circuit. Such valve assemblies are known, for example, from applicant EP4264093A1.

[0003] Typically, a valve assembly includes an actuator, a valve unit, and a shut-off body. The actuator drives the shut-off body via a drive shaft. In this case, the rotational motion applied by the drive unit is converted into translational motion of the shut-off body. To keep the force actuating the shut-off body low, the shut-off body preferably has a hollow channel, allowing refrigerant to flow on both sides of the shut-off body. This achieves pressure compensation, making it easier to move the shut-off body translationally.

[0004] Due to this translational movement, the shut-off body is in the closed position within the valve unit, preventing refrigerant from flowing through the valve unit. Furthermore, the shut-off body is configured to move translationally to the open position, where it is spaced apart from the valve seat. Importantly, for the function of the shut-off body, specifically in the closed position, no refrigerant bypass flow flows from the drive side to the valve unit side. In this regard, known valve assemblies typically provide a sealing device fixed within the valve unit and translationally movable to seal against the shut-off body.

[0005] Typically, this sealing device consists of two parts. One part is an O-ring made of rubber material, which serves as the sealing element. The other part is usually formed by a slip ring, located between the O-ring and the outer surface of the rod seal. The slip ring is typically made of a material with low contact friction, allowing the closing body to slide well through the sealing device during its translational movement. PTFE (Teflon) is commonly used as the material for this slip ring due to its excellent friction-reducing properties.

[0006] PTFE belongs to the category of so-called perfluoroalkyl chemicals (PFAS), and its use in the EU will be restricted in the coming years due to its harmful environmental impact. Therefore, it is necessary to avoid the use of this type of chemical as much as possible. Summary of the Invention

[0007] Against this backdrop, the object of the present invention is to provide a valve assembly characterized by simultaneously avoiding environmentally harmful chemicals, specifically perfluoroalkyl chemicals, with high energy efficiency. Furthermore, the object of the present invention is to provide a vehicle refrigeration system including such a valve assembly.

[0008] According to the invention, this objective is achieved in terms of valve assemblies by the subject matter of claim 1, and in terms of vehicle refrigeration systems by the subject matter of claim 15.

[0009] Specifically, this invention provides a valve assembly for a refrigerant, comprising a drive unit for generating rotational movement of a drive shaft within a valve body chamber. Furthermore, the valve assembly includes a valve unit for guiding a closing body. The closing body is configured to switch between a closed position and an open position via rotational movement of the drive shaft within the valve unit, in which the closing body abuts against a valve seat, and in the open position, the closing body is spaced apart from the valve seat. Additionally, a rod seal is provided for sealing the closing body relative to the valve unit, wherein the rod seal is at least partially disposed between the valve unit and the closing body, and thereby circumferentially surrounds the closing body. According to the invention, the closing body and / or the valve unit includes a sealing geometry that interacts with the rod seal, such that the rod seal is disposed in a sealing manner in the closed position of the closing body and slidably mounted in the open position between the closing body and the valve unit.

[0010] The basic idea of ​​this invention is based on the understanding that sealing of any possible bypass channels on the shut-off body should be avoided only at the closed position of the shut-off body. Once the shut-off body leaves the valve seat, refrigerant is allowed to flow through the valve unit. The refrigerant flowing through the shut-off body, specifically between the shut-off body and the valve unit, is harmless. The function previously achieved by slip rings made of PTFE, allowing the shut-off body to be guided easily and with low friction through the valve unit, is now achieved through the sliding installation of a rod seal. However, the sealing geometry of the shut-off body and / or valve unit ensures that the rod seal is arranged in a sealing manner in the closed position of the shut-off body. Therefore, the sealing effect of the rod seal depends on the position of the shut-off body. For this purpose, a corresponding geometry is provided on the shut-off body and / or valve unit, which allows the rod seal to transition from a non-sealing but sliding state to a sealing state.

[0011] Specifically, this can be achieved, for example, by the sealing geometry including the side surface of the rod seal and / or the inner surface of the valve unit, wherein each of the side surface and / or the inner surface includes at least a first diameter portion and a second diameter portion. Preferably, there is a press fit between the first diameter portion and the rod seal in the closed position. There is a clearance fit between the second diameter portion and the rod seal in the open position. In other words, the geometry of the closing body and / or the valve unit such that the rod seal is sealed between the closing body and the valve unit in the closed position. Specifically, the rod seal can be squeezed or pressed to firmly abut against the inner surface of the valve unit and / or the side surface of the closing body, thereby ensuring a sufficient seal between the closing body and the valve unit. There is a clearance fit between the rod seal and the second diameter portion on the closing body and / or the valve unit in the open position. In other words, there is a clearance between the rod seal and the closing body and / or the valve unit, allowing the closing body to be guided through the valve unit with low friction.

[0012] In a preferred embodiment, the rod seal is positioned in the closed position of the closure body within the region of a first diameter portion. Therefore, preferably, the first diameter portion is the diameter portion that achieves the sealing effect, regardless of its position on the closure body or valve unit. In this regard, it is advantageous for the rod seal to be positioned in the region of a second diameter portion when the closure body is in the open position. The second diameter portion is preferably designed such that the rod seal is positioned within this portion, with a clearance fit between the closure body and the valve unit.

[0013] In a specific embodiment, the closing body may include a first diameter portion and a second diameter portion. In this embodiment, the first diameter portion is larger than the second diameter portion. This has the effect that when the closing body is switched to the closed position, the first diameter portion, with its relatively larger diameter, is effective for the rod seal, specifically by reducing the distance between the side surface of the closing body and the inner surface of the valve unit. Thus, the rod seal is pressed between the closing body and the valve unit, thereby achieving a seal.

[0014] In other embodiments, a first diameter portion and a second diameter portion may be formed on the valve unit. In this case, the first diameter portion, intended to achieve a sealing effect, is equipped with a smaller diameter than the second diameter portion. In these embodiments, the rod seal is fastened to the closing body and moves along the valve unit together with the closing body. Once the rod seal reaches the first diameter portion of the valve unit, the distance between the inner surface of the valve unit and the side surface of the closing body decreases, causing the rod seal to be pressed between the valve unit and the closing body, thus achieving a seal.

[0015] Combinations of a shut-off body with two different diameter portions and a valve assembly with two different diameter portions are also possible. Importantly, the gap between the shut-off body and the valve unit, specifically the annular gap, preferably comprises different widths so that the rod seal is pressed into the narrow annular gap in the closed position of the shut-off body, thus achieving a seal. When the closed position is released, i.e., when the valve assembly is switched to the open position, the rod seal preferably enters a region of the annular gap between the shut-off body and the valve unit, in which the annular gap is wider than the rod seal, such that the rod seal is at a distance from the shut-off body and / or the valve unit. In the open position, the shut-off body can therefore be guided within the valve unit with low friction.

[0016] The following preferred embodiment specifically relates to a variation in which a first diameter portion and a second diameter portion are formed on the closing body. In this case, it is particularly preferred that the first diameter portion, preferably including a larger cross-sectional diameter than the second diameter portion, is arranged on the portion of the closing body away from the valve seat in the longitudinal direction. Therefore, it is ensured that during the translational closing movement of the closing body, the first diameter portion, together with the rod seal, effectively seals only when the closing body reaches the closed position. Therefore, it is advantageous if the second diameter portion is arranged on the portion of the closing body closer to the valve seat in the longitudinal direction.

[0017] To reliably retain the stem seal in the valve assembly, the valve unit or shut-off body may be specified to include a container for the stem seal. If the stem seal is disposed within the container of the valve unit, preferably a first diameter portion and a second diameter portion are located on the shut-off body. If the stem seal is disposed within the container of the shut-off body, preferably the first diameter portion and the second diameter portion are formed on the valve unit. In this case, it is preferable that the first diameter portion is formed at the end of the valve unit near the valve seat. In both cases, the stem seal is preferably secured within the container.

[0018] If the stem seal is fixed to the closing body, it is preferable that the stem seal moves together with the closing body from the closed position to the open position. When the stem seal is fixed in the valve unit, it is preferable that the stem seal is stationary.

[0019] Specifically, if the rod seal is fixed in the valve unit and the first and second diameter portions are formed on the closing body, it is advantageous to form a transition portion with a smoothly changing diameter between the first and second diameter portions. Specifically, the transition portion can be formed as a truncated cone, allowing for a sliding transition between the first and second diameter portions. This facilitates sealing via the rod seal. Specifically, if the transition portion is arranged on the closing body, the rod seal can be moved from the second diameter portion to the first diameter portion with minimal force, thereby effectively sealing at the closed position of the closing body.

[0020] In another embodiment of the invention, at the closed position of the closing body, the rod seal is longitudinally axially arranged between the two first diameter portions of the closing body and the valve unit. Therefore, both the closing body and the valve unit can include first diameter portions. Preferably, the first diameter portion of the closing body has a larger diameter than the second diameter portion of the closing body. Conversely, the first diameter portion of the valve unit has a smaller cross-sectional diameter than the second diameter portion of the valve unit. The closing body and the valve unit form an annular flange or annular stop surface to a certain extent, and the rod seal can be clamped between the annular flange or annular stop surface. Therefore, a sealing effect can be achieved at the closed position of the closing body due to the movement of the stop surface of the rod seal extending radially outward or inward.

[0021] Preferably, the stem seal is PTFE-free for all embodiments. Therefore, the stem seal can be specifically formed from a single, integral component. To meet upcoming regulations from European legislators and to avoid climate-harmful chemicals, it is best to avoid using PTFE. The use of a single, integral component as the stem seal saves on component costs, thus enabling cost-effective production of the valve assembly.

[0022] In a preferred embodiment of the valve assembly according to the invention, the closing body, in the open position, fluidly connects a first fluid flow port to a second fluid flow port, wherein in the closed position, the closing body closes the first fluid flow port relative to the second fluid flow port. Furthermore, the closing body may include a hollow channel that, in the closed position, connects the first fluid flow port to the valve body chamber in a pressure-compensated manner. The hollow channel may extend through the closing body along a longitudinal axis. Pressure compensation between the valve body chamber and the valve flow chamber is ensured by the hollow channel. Therefore, equal pressure exists on both sides of the closing body, thereby reducing the force required to move the closing body.

[0023] One harmonic aspect of the invention relates to a vehicle refrigeration system comprising the valve assembly described above. Preferred embodiments and advantages associated with the valve assembly also apply accordingly to the vehicle refrigeration system. Attached Figure Description

[0024] The invention will now be explained in more detail with reference to the accompanying drawings and based on exemplary embodiments. Wherein:

[0025] Figure 1 This is a longitudinal sectional view of a valve assembly according to a preferred embodiment of the present invention;

[0026] Figure 2a It is based on Figure 1A detailed view of the valve assembly, with the shut-off body in the open position;

[0027] Figure 2b It is based on Figure 1 A detailed view of the valve assembly, with the shut-off body in the closed position;

[0028] Figure 3a This is a detailed view of a valve assembly according to another embodiment of the invention, wherein the closing body is in the open position; and

[0029] Figure 3b It is based on Figure 3a A detailed view of the valve assembly, with the shut-off body in the closed position. Detailed Implementation

[0030] According to Figure 1 In the longitudinal sectional view, the valve assembly can be seen, which includes an actuation unit 10, a valve unit 20, and a shut-off body 22. The shut-off body 22 is guided within the valve unit 20. Here, the shut-off body 22 engages in a valve flow chamber 18, in which a valve seat 26 is formed. The valve seat 26 is assigned to a first fluid flow port 14 of the valve unit 20. A second fluid flow port 15 is laterally arranged in the valve flow chamber 18, through which fluid can flow into or out of the valve flow chamber 18.

[0031] The shut-off body 22 can seal against the valve seat 26 to prevent fluid from flowing through the first fluid flow port 14. The shut-off body 22 can be moved or displaced along the longitudinal axis L by the drive unit 10, so that the shut-off body 22 can release or interrupt the fluid flow between the first fluid flow port 14 and the second fluid flow port 15.

[0032] The closing body 22 is substantially elongated and rotationally symmetrical. A hollow channel 36 extends inside the closing body 22, which allows fluid connection between the valve flow chamber 18 and the valve body chamber 13 formed in the drive unit 10.

[0033] The movement of the closing body 22 is achieved by the drive unit 10, which includes a rotor 31 and a stator. Figure 1 Not shown in the diagram. A containment shield 32 extends through the gap between the rotor 31 and the stator, located between the rotor and the stator. The containment shield 32 is connected to the valve unit 20 in a sealed and secure manner. Specifically, the connection can be made by welding.

[0034] The rotor 31 is connected to the drive shaft 11 via a coupling 25, which can be, for example, an Oldham coupling or a cross-slider coupling. At one end on the valve seat side, the drive shaft 11 includes an external thread that engages with the internal thread of the closing body 22. The threaded coupling 12 converts the rotational movement of the drive shaft 11 into a translational movement of the closing body 22 along the longitudinal axis L.

[0035] The drive shaft 11 is mounted in the valve unit 20 via a drive shaft bearing 24. Specifically, the drive shaft bearing 24 can be a roller bearing, preferably a ball bearing.

[0036] A valve flow chamber 18 is disposed within a valve housing 23, which may be integrally formed with the valve unit 20. In the exemplary embodiment shown herein, the valve housing 23 is configured as a separate component that is connected to the valve unit 20. The connection may be permanent, for example, by welding.

[0037] As described above, the closing body 22 can be moved from the open position to the closed position. For this purpose, a drive unit 10 is used, which guides the closing body 22 to perform a translational movement via the drive shaft 11. Figure 1 In the diagram, the closing body 22 is shown in the closed position. In the closed position, the closing body 22 is flush against the valve seat 26. The valve unit 20 includes a guide channel 21, the length of which determines the maximum translational movement of the closing body 22.

[0038] The hollow passage 36 in the shut-off body 22 allows fluid to enter the valve body chamber 13 formed in the containment shield 32 from the first fluid flow port 14 through the hollow passage 36. This achieves pressure compensation on both sides of the shut-off body 22. In this case, the hollow passage 36 could also extend through the drive shaft 11. However, it is preferred that the pressure-compensating fluid connection be made via a threaded coupling 12. The meshing threads of the drive shaft 11 and the shut-off body 12 preferably have such a large clearance that fluid, specifically refrigerant, can move through.

[0039] In the closed position, it is advantageous to ensure that fluid exchange occurs only through the hollow passage 36. Any bypass, such as flow around the shut-off body 22, should be avoided. Therefore, a rod seal 39 is provided in the valve assembly between the valve unit 20 and the shut-off body 22.

[0040] According to Figure 1 In an exemplary embodiment, specifically, the valve unit 20, specifically the valve housing 23, includes a container 29 for a stem seal 39. Preferably, the stem seal 39 is formed as a PTFE-free O-ring, for example, made of a rubber material. The stem seal 39 is secured in the container 29, specifically inserted in a form-fitting manner along the longitudinal axis.

[0041] exist Figure 1 In the closed position shown, the rod seal 39 seals between the valve unit 20 and the closing body 22. After leaving the closed position, i.e., during the transition to the open position of the closing body 22, the sealing effect may decrease because the refrigerant bypass flow is harmless in other positions outside the closed position of the closing body 22. In this case, it is advantageous that the invention provides reduced friction between the valve unit 20 and the closing body 22, friction generated by supporting the rod seal 39 in a position outside the closed position. This avoids wear and reduces the force applied by the drive unit 10 for moving the closing body 22.

[0042] according to Figure 2a and 2b The enlarged image makes it easy to see the data based on... Figure 1 The function of the valve assembly. Figure 2a The open position of the closing body 22 is shown, while Figure 2b The closed position of the closing body 22 is shown.

[0043] In the open position, the closing body 22 is removed from the valve seat 26, allowing fluid to flow into the pressure valve flow chamber 18 via the first fluid flow port 14 and exit the valve flow chamber 18 via the second fluid flow port 15. Therefore, fluid (preferably refrigerant) can flow from the first fluid flow port 14 to the second fluid flow port 15.

[0044] In the embodiment shown here, the shut-off body 22 includes a sealing geometry that interacts with the rod seal 39 such that the rod seal 39 is arranged in a sealing manner in the closed position of the shut-off body 22 and slidably mounted between the shut-off body 22 and the valve unit in an open position. In the exemplary embodiment shown here, this sealing geometry is achieved by two diameter portions with different cross-sectional diameters. Specifically, the shut-off body 22 includes a first diameter portion 28A with a cross-sectional diameter larger than that of a second diameter portion 28B. The second diameter portion 28B is formed on the valve seat side. The first diameter portion 28A is arranged on the drive side of the shut-off body 22.

[0045] The transition portion 28C is disposed between the first diameter portion 28A and the second diameter portion 28B. The transition portion 28C is substantially conical or truncated conical in shape, which results in a sliding transition between the first diameter portion 28A and the second diameter portion 28B.

[0046] like Figure 2aAs shown, in the open position of the closing body 22, the rod seal 39 is arranged in the region of the second diameter portion 28B. Due to the relatively small cross-sectional diameter in the second diameter portion 28B, a distance exists between the rod seal 39 and the closing body 22. Therefore, the rod seal 39 includes a clearance fit with the closing body 22 in the second diameter portion 28B. The distance or clearance between the rod seal 39 and the second diameter portion 28B produces the effect that the closing body 22 can be easily and with low friction moved through the guide channel 21 of the valve unit 20 by the drive unit 10.

[0047] During the transition from the open to the closed position, the closing body 22 is guided to the valve seat 26 along the longitudinal axis L. In this case, the transition portion 28C first contacts the stem seal 39. The tapered transition portion 28C contacts the stem seal 39 and pushes it into the container 29. Subsequently, in the closed position, the first diameter portion 28A reaches the stem seal 39 and pushes it into the container 29. In this way, the stem seal 39 is pressed between the valve unit 20 and the closing body 22, and therefore the seal between the valve unit 20 and the closing body is effective. In this way, any bypass fluid flow is prevented.

[0048] exist Figure 3a and 3b Another exemplary embodiment of the invention is shown in the figure, which is consistent with the one described in the figure. Figures 1 to 2b The difference in the exemplary implementation is that: Figures 1 to 2b In this configuration, the rod seal 39 provides a radial seal between the valve unit 20 and the closing body 22. According to... Figure 3a and 3b In one exemplary embodiment, the rod seal 39 is arranged such that it effectively provides an axial seal between the valve unit 20 and the shut-off body 22. However, as in the aforementioned exemplary embodiment, when the rod seal 39 is in the closed position of the shut-off body 22, bypass fluid flow between the valve flow chamber 18 and the valve body chamber 13 is prevented.

[0049] Figure 3a The closed body 22 in the open position is shown. In the closed body shown, a container 29 for the stem seal 39 is arranged at the drive-side end. The stem seal 39 is thus secured to the closed body 22 and moves together with the closed body 22 through the guide passage 21 of the valve unit 20. On the drive side, the container 29 is defined by a closed-body-side stop 17. Specifically, the closed body 22 includes a radially outwardly projecting annular flange at its drive-side end, which forms the closed-body-side stop 17. The closed-body-side stop 17 substantially forms a one-sided form-fit for the stem seal 39.

[0050] according to Figure 3a and 3bIn an exemplary embodiment, the drive-side annular flange defines a first diameter portion 28A. The closing body 22 includes a second diameter portion 28B along the container 29 in the direction of the valve seat 26. The first diameter portion 28A includes a larger cross-sectional diameter than the second diameter portion 28B.

[0051] Valve unit 20 also includes a first diameter portion 28A′. The first diameter portion 28A′ is formed substantially by the inner diameter of the guide channel 21. Specifically, the guide channel 21 includes an inner surface 27, which is arranged coaxially with the side surface 28 of the shut-off body 22. Furthermore, specifically, valve unit 20 includes a second diameter portion 28B′ in the region of valve housing 23. To distinguish the diameter portions 28A, 28B, 28A′, and 28B′ of shut-off body 22 and valve unit 20, in Figure 3a and 3b In the middle, a high point is added to each of the diameter portions of valve unit 20.

[0052] A shoulder is formed between the first diameter portion 28A′ and the second diameter portion 28B′ of the valve unit 20. The shoulder includes an annular surface that serves as a valve-side stop 16. In the open position, the rod seal 39 is arranged spaced apart from the valve-side stop 16. Preferably, the rod seal 39, formed as an O-ring, is relaxed in this state and can maintain a distance from the inner surface 27 of the guide channel 21. Therefore, the closing body 22 can move in an energy-efficient manner.

[0053] Figure 3b The shut-off body 22 in the closed position is shown. It can be seen that in the closed position, the shut-off body 22 abuts against the valve seat 26. Simultaneously, the stem seal 39 contacts the valve-side stop 26. Therefore, the stem seal 39 elastically deforms between the shut-off body-side stop 17 and the valve-side stop 16, and thus expands radially outward. This ensures a good and reliable seal in the closed position. Since the stem seal 39 is clamped between the two stops in the longitudinal direction L, according to… Figure 3a and 3b In an exemplary implementation, reference is made to the axial seal.

[0054] This applies to all embodiments, whereby the valve assembly may also include an outer seal 30 in the region of the first fluid flow port 14. The outer seal 30 allows the valve assembly to be inserted into the valve block in a sealing manner. Furthermore, in all exemplary embodiments shown herein, an inner seal 19 is provided, formed between the upper portion of the valve unit 20 and the valve housing 23. Since the valve unit 20 is composed of two parts and includes a separate valve housing 23 in the exemplary embodiments shown herein, a sealing connection between the two components of the valve unit 20 is advantageous. This seal is achieved through the inner seal 19.

[0055] List of reference numerals

[0056]

[0057]

Claims

1. Valve assembly for a refrigerant, comprising: a drive unit (10) for generating a rotational movement of a drive shaft (11) within a valve body chamber (13), a valve unit (20) for guiding a closing body (22), wherein the closing body (22) is configured to be shifted between a closed position, in which the closing body (22) abuts against a valve seat (26), and an open position, in which the closing body (22) is spaced apart from the valve seat (26), by a rotational movement of the drive shaft (11) in the valve unit (20), a stem seal (39) for sealing the closing body (22) against the valve unit (20), wherein the stem seal (39) is arranged at least partially between the valve unit (20) and the closing body (22) and thereby circumferentially around the closing body (22), wherein the closing body and / or the valve unit comprise a sealing geometry interacting with the stem seal (39) such that the stem seal (39) is arranged in a sealing manner in the closed position of the closing body (22) and in a sliding manner in the open position between the closing body (22) and the valve unit (20).

2. Valve assembly according to claim 1, wherein the sealing geometry comprises a lateral surface (28) of the closing body (22) and / or an inner surface (27) of the valve unit (20), and wherein the lateral surface (28) and / or the inner surface (27) each comprise at least a first diameter portion (28A) and a second diameter portion (28B), wherein in the closed position a press fit between the first diameter portion (28A) and the stem seal (39) exists and in the open position a clearance fit between the second diameter portion (28B) and the stem seal (39) exists.

3. Valve assembly according to claim 1 or 2, wherein in the closed position of the closing body (22) the stem seal (39) is arranged in the area of the first diameter portion (28A).

4. Valve assembly according to any of the preceding claims, wherein in the open position of the closing body (22) the stem seal (39) is arranged in the area of the second diameter portion (28B).

5. Valve assembly according to any of the preceding claims, wherein the first diameter portion (28A) is arranged on a portion of the closing body (22) facing away from the valve seat with respect to a longitudinal axis direction (L).

6. Valve assembly according to any of the preceding claims, wherein the second diameter portion (28B) is arranged on a portion of the closing body (22) facing the valve seat with respect to the longitudinal axis direction (L).

7. Valve assembly according to any of the preceding claims, wherein the valve unit (20) or the closing body (22) comprises a receptacle (29) for the stem seal (39).

8. Valve assembly according to any of the preceding claims, wherein between the first diameter portion (28A) and the second diameter portion (28B) a transition portion (28C) with a smoothly varying diameter is formed.

9. Valve assembly according to any of the preceding claims, wherein in the closed position of the closure body (22) the stem seal (39) is arranged longitudinally axially between the two first diameter portions (28A) of the closure body (22) and the valve unit (20).

10. Valve assembly according to any of the preceding claims, wherein the stem seal (39) is free of PTFE.

11. Valve assembly according to any of the preceding claims, wherein the stem seal (39) is formed by a single integral part.

12. Valve assembly according to any of the preceding claims, wherein in the open position the closure body (22) fluidly connects the first fluid flow port (14) to the second fluid flow port (15), and wherein in the closed position the closure body (22) closes the first fluid flow port (14) with respect to the second fluid flow port (15).

13. Valve assembly according to claim 12, wherein the closure body (22) comprises a hollow passage (36) which in the closed position communicates the first fluid flow port (14) to the valve body chamber (13) in a pressure compensated manner.

14. Valve assembly according to claim 13, wherein the hollow passage (36) extends through the closure body (22) in the longitudinal axial direction (L).

15. Vehicle refrigeration system comprising a valve assembly according to any of the preceding claims.

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