Vacuum pump

Abstract

A vacuum pump, in particular a 2-shaft rotor pump, comprising: a housing defining a pump chamber, an inlet and an outlet; two rotor shafts arranged in the pump chamber, where each pump shaft comprises at least one pump element interacting with each other, where each rotor shaft comprises a first end and a second end; a front cover connected to the housing at the second end of the rotor shaft; wherein the front cover comprises at least one cooling element having a radial symmetry.

Description

Technical Field

[0001] The object of the present invention is to provide a vacuum pump, and in particular a twin-shaft vacuum pump. Background Art

[0002] Conventional vacuum pumps include a housing that defines one or more pump chambers, an inlet, and an outlet. A rotor is rotatably disposed in the pump chamber and includes at least one pump element. The rotor is rotated by an electric motor. In the case of a twin-shaft rotor pump, at least one pump element interacts with the pump element of a stator or another rotor to transport a gaseous medium from the inlet to the outlet. There are different vacuum pumps, such as claw pumps, Roots pumps, or screw pumps. In particular, for claw pumps, the gas is compressed before entering the outlet, thereby releasing a large amount of heat and making the exhaust port the hottest component. This results in a non-uniform temperature distribution and deformation of this component. The front cover seals the pumping chamber axially and determines the gap (= axial gap) between the claws and the front cover. This gap should be as small as possible for optimal performance and as large as possible to meet the requirements of safe operation. The non-uniform axial gap caused by the high thermal deformation of the front cover will require a larger gap to avoid contact between the claws and the front cover, and thus reduce performance. Although described in connection with claw pumps, similar problems also exist in vacuum pumps different from the prior art. Summary of the Invention

[0003] Therefore, the object of the present invention is to provide a vacuum pump that is operated more reliably with improved pump performance.

[0004] This problem is solved by a vacuum pump according to claim 1.

[0005] The vacuum pump according to the present invention is in particular a twin-shaft rotor pump, such as a claw pump, a Roots pump, a screw pump, etc. The vacuum pump according to the present invention includes a housing that defines a pump chamber, an inlet, and an outlet. Two rotor assemblies are disposed in the pump chamber and rotatably supported, wherein the rotor assemblies are rotated by an electric motor. Each rotor assembly includes a rotor shaft and at least one pump element, and the at least one pump element is connected to the rotor shaft and interacts with each other to transport a gaseous medium from the inlet to the outlet. Wherein, the rotor shaft includes a first end and an opposite second end. In particular, the first end is oriented towards the electric motor or the gear of the vacuum pump, and the second end is oriented towards the exhaust port or the outlet of the vacuum pump or is located in the region of the exhaust port or the outlet of the vacuum pump, that is, the low vacuum / high pressure region.

[0006] Furthermore, the vacuum pump according to the present invention provides a front cover that is connected to the housing and disposed at the second end of the rotor assembly. Thus, the axial end of the rotor assembly is covered by the front cover, where the front cover can be part of the housing (i.e., integrally constructed with the housing) or releasably connected to the housing. Thus, the front cover covers the axial end of the rotor assembly. In particular, the front cover covers the entire cross-sectional area of the pump chamber and thus has dimensions of an area: the pump elements of the first shaft and the second shaft generate the area as a rotary surface, i.e., the combined diameter of the pump elements. Preferably, the front cover is larger than this area. The front cover includes at least one cooling element having radial symmetry. It has been proven that radial symmetry provides on the one hand sufficient heat dissipation and distribution, while on the other hand provides increased stiffness of the front cover. Thus, the non-uniform temperature distribution in the front cover and the deformation caused by this non-uniform temperature distribution can be minimized, where at the same time, the deformation of the front cover is further minimized by the increased stiffness. Thus, the axial clearance can be reduced without the risk of contact between the rotor assembly (and in particular, the pump elements) and the front cover, thereby improving the pumping performance of the vacuum pump.

[0007] Preferably, the cooling element is radially symmetric about the axis of rotation of one of the rotor assemblies. Thus, the center of radial symmetry is defined by the axis of rotation of the rotor shaft of the corresponding rotor assembly. Alternatively, two cooling elements are disposed at the front cover, where each cooling element is radially symmetric about the respective axis of rotation of each rotor assembly. Wherein, by arranging the cooling element relative to the axis of rotation, sufficient temperature distribution in the front cover is achieved to reduce the thermal stress and deformation of the front cover.

[0008] Preferably, the two cooling elements overlap each other. In particular, if the cooling element includes one or more cooling ribs, the cooling ribs can be wound around each other to provide sufficient heat dissipation and a sufficiently uniform temperature distribution across the front cover.

[0009] Preferably, the two cooling elements cover the rotor diameter of the pump element (the cross-sectional area of the pump element). Alternatively, the area of the cooling element is smaller than the corresponding area of the pump element. Alternatively, the area of the cooling element is larger than the corresponding area of the pump element.

[0010] Preferably, the two cooling elements are shaped differently or the same. By shaping the cooling elements differently, a specific and customized temperature distribution in the front cover can be achieved. In particular, the non-uniform temperature distribution caused by non-uniform heating in the vacuum pump can be minimized.

[0011] Preferably, the at least one cooling element includes one or more cooling ribs. In particular, for the two cooling elements, both of the two cooling elements can include one or more cooling ribs.

[0012] Preferably, the at least one cooling element includes one or more annular ribs. In particular, the annular ribs are arranged concentrically around the respective rotation axis of each rotor assembly.

[0013] Preferably, the cooling element includes two or more nested annular ribs.

[0014] Preferably, the diameter of the annular rib is between 2 cm and 15 cm, and preferably between 3 cm and 13 cm. If the cooling element includes two annular ribs, the diameter of the outer annular rib can be between 8 cm and 15 cm, and preferably between 10 cm and 13 cm. The diameter of the inner annular rib can be between 2 cm and 8 cm, and preferably between 3 cm and 5 cm (here and hereinafter, all the provided intervals are understood to also include the boundary values, i.e., "between 2 cm and 15 cm" should be understood as "between 2 cm and 15 cm and including 2 cm and 15 cm").

[0015] Preferably, the ratio between the diameter of the inner annular rib and the outer annular rib is between 1:2 and 1:5, and preferably between 1:2 and 1:4. These ratios have been proven to provide both sufficient temperature distribution and stiffness simultaneously.

[0016] Preferably, the height of the cooling rib is between 0.8 cm and 2 cm, and more preferably between 1 cm and 1.6 cm. Thus, due to the specific radial symmetry of the cooling element, the cooling height of the cooling rib can be limited, thereby reducing the manufacturing cost of such a cooling element without loss of the cooling function.

[0017] Preferably, the width or thickness of the cooling rib is between 3 mm and 1 cm, and more preferably between 4 mm and 6 mm.

[0018] Preferably, the cooling element includes more than one annular rib, wherein the annular ribs are connected by one or more radial webs. Among them, the webs can be evenly distributed around the annular rib. Preferably, the cooling element includes more than 3 webs, more preferably more than 4 webs, and most preferably 8 webs.

[0019] Preferably, the height of the web is between 0.8 cm and 2 cm, and more preferably between 1 cm and 1.6 cm.

[0020] Preferably, the width or thickness of the web is between 3 mm and 1 cm, and more preferably between 4 mm and 6 mm.

[0021] Preferably, the cooling element is integrally constructed with the front cover. Thus, the cooling element and the front cover can be manufactured in a single step, thereby reducing the complexity and cost of the manufacturing process.

[0022] Preferably, the cooling element and the front cover are made of the same material. Thus, the thermal stress caused by thermal expansion can be minimized between the cooling element and the front cover.

[0023] Preferably, the outlet is provided in the front cover. Thus, the front cover also forms the outlet or exhaust port of the vacuum pump.

[0024] Preferably, the outlet includes an outlet cooling element, wherein the outlet cooling element can overlap with one or more cooling elements of the front cover.

[0025] Preferably, the outlet cooling element may include linear cooling fins, which may extend perpendicular to the connecting line of the two rotational axes of the two rotor assemblies. Alternatively, the cooling fins of the outlet cooling element extend perpendicular to the connecting line between the two rotational axes of the two rotor assemblies. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

[0027] The drawings illustrate:

[0028] Figure 1 is a schematic view of a claw pump according to the present invention; and

[0029] Figure 2 is a detailed view of the front cover according to the present invention. DETAILED DESCRIPTION

[0030] Referring to Figure 1 , the vacuum pump 10 includes a housing 12 that defines a plurality of pump chambers 14 connected by channels (not shown). The vacuum pump 10 includes two rotor assemblies 16. Each rotor assembly 16 includes a rotor shaft 17, wherein the pump elements 18 are connected to the respective rotor shafts 17 and are arranged in the respective pump chambers. The rotor assemblies 16 are rotated synchronously with each other by an electric motor through gears 20. By the rotation of the rotor assemblies 16, the respective rotor elements 18 interact with each other to transport the gaseous medium from an inlet (not shown) to an outlet 22. The rotor assemblies 16 include a first end 24 facing the gear 20 and a second end 26 facing the outlet 22, i.e., in the high-pressure / low-vacuum region. At the second end 26 of the rotor assembly 16, a front cover 28 is connected to the housing 12. Among them, the front cover 28 may be configured as a separate element releasably connected to the housing 12 or may be configured as an integral element of the housing 12. Among them, the axial clearance between the front cover 28 and the rotor assembly 16 is minimized to improve the pumping performance of the vacuum pump.

[0031] Referring to Figure 2, which shows a detailed view of the front cover 28. The outlet 22 is connected to or integrally formed with the front cover 28. The front cover 28 includes a first cooling element 34 and a second cooling element 36. Each of the cooling elements 34, 36 is constructed radially symmetrically about the axis of rotation 32 (see Figure 1 ). Wherein, the areas of the first cooling element 34 and the second cooling element 36 may correspond to the area defined by the combined cross-sectional area of the pump element 18, that is, correspond to the size of the pump chamber 14 or may overlap with the pump chamber 14. The first cooling element 34 and the second cooling element 36 are constructed substantially identically. Therefore, only the first cooling element 34 will be described in more detail hereinafter. However, the same description also applies to the second cooling element 36. Alternatively, contrary to what is shown in Figure 2 , the first cooling element 34 and the second cooling element 36 may be shaped differently. The first cooling element 34 includes a plurality of cooling ribs arranged with radial symmetry. The first cooling element 34 includes a first annular cooling rib 38 and a second annular cooling rib 40 concentrically arranged. Wherein, the diameter of the first annular cooling rib 38 is between 2 cm and 8 cm, and preferably between 3 cm and 5 cm, and the diameter of the second annular cooling rib 40 is between 8 cm and 15 cm, and preferably between 10 cm and 13 cm. In addition, the first annular cooling rib 38 and the second annular cooling rib 40 are connected by webs 42, wherein in the example of Figure 2 , eight webs 42 are arranged between the first annular cooling rib 38 and the second annular cooling rib 40. Additional webs are arranged outside the second annular cooling rib 40. By the cooling ribs of the cooling elements 34, 36, heat is distributed across the front cover 28 to prevent or reduce the thermal stress and deformation of the front cover. Sufficient heat dissipation can be achieved by the cooling ribs. At the same time, it has been proven that due to the radial symmetry of the cooling elements 34, 36, the stiffness of the front cover 28 can be increased. Therefore, contact between the front cover 28 and the rotor assembly 16 can be avoided, thereby increasing the reliability and operational safety of the vacuum pump 10.

[0032] In addition, as shown in Figure 2 , linear cooling fins 44 are connected to the outlet 22. Wherein, the linear cooling fins 44 connected to the outlet 22 overlap with the cooling elements 34, 36.

[0033] List of Reference Numerals

[0034] 10 Vacuum pump

[0035] 12 Housing

[0036] 14 Pump chamber

[0037] 16 Rotor assembly

[0038] 17 Rotor shaft

[0039] 18 Pump element

[0040] 20 Gears

[0041] 22 Outlet

[0042] 24 First End

[0043] 26 Second End

[0044] 28 Front Cover

[0045] 32 Axis of Rotation

[0046] 34 First Cooling Element

[0047] 36 Second Cooling Element

[0048] 38 First Annular Cooling Rib

[0049] 40 Second Annular Cooling Rib

[0050] 42 Web

[0051] 44 Cooling Fins

Claims

1. A vacuum pump, in particular a two-shaft rotary pump, the vacuum pump comprising: a housing defining a pump chamber, an inlet and an outlet; two rotor assemblies arranged in the pump chamber, wherein each rotor assembly includes at least one pump element interacting with each other, and wherein each rotor assembly includes a first end and a second end; a front cover connected to the housing at the second end of the rotor assembly; wherein the front cover includes at least one cooling element having radial symmetry.

2. The vacuum pump according to claim 1, wherein, The cooling element is radially symmetric about the axis of rotation of one of the rotor assemblies.

3. The vacuum pump according to claim 1 or claim 2, wherein Two cooling elements are arranged at the front cover, wherein each cooling element is radially symmetric about the respective axis of rotation of each rotor assembly.

4. The vacuum pump according to claim 3, wherein, The two cooling elements overlap each other.

5. The vacuum pump according to claim 3 or 4, wherein, The two cooling elements are shaped differently or identically.

6. The vacuum pump according to any one of claims 1 to 5, wherein, The at least one cooling element includes one or more cooling ribs.

7. The vacuum pump according to any one of claims 1 to 6, wherein, The at least one cooling element includes one or more annular ribs.

8. The vacuum pump according to claim 7, wherein, The cooling element includes more than one annular rib, wherein the annular ribs are connected by one or more radial webs.

9. The vacuum pump according to any one of claims 1 to 8, wherein, The outlet is provided in the front cover.

10. The vacuum pump according to claim 9, wherein, The outlet includes an outlet cooling element, wherein the outlet cooling element overlaps with the one or more cooling elements of the front cover.

11. The vacuum pump according to any one of claims 1 to 10, wherein, The vacuum pump is a claw pump, a Roots pump or a screw pump.

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