WO2013107667A1

WO2013107667A1 - Turbomolecular pump

Info

Publication number: WO2013107667A1
Application number: PCT/EP2013/050172
Authority: WO
Inventors: Christian Beyer; Holger Dietz; Gerhard Wilhelm Walter
Original assignee: Oerlikon Leybold Vacuum Gmbh
Priority date: 2012-01-21
Filing date: 2013-01-08
Publication date: 2013-07-25
Also published as: US20140369809A1; JP2015504137A; DE202012000611U1; EP2805057A1

Abstract

A turbomolecular pump has a rotor element (18) in a housing (16). The rotor element (18) is arranged on a rotor shaft (10). The rotor shaft (10) is supported by two bearing elements (12, 14) in the housing (16). The bearing element (12) on the high-vacuum side is constructed as a roller bearing. In order to guarantee a pressure in the area of the bearing element (12) that is acceptable for the bearing element (12) constructed as a roller bearing, the bearing element (12) is arranged in a chamber (36). Said chamber is connected via a channel (46) to the pre-vacuum area (38) and sealed relative to the high-vacuum area (34) by a gasket.

Description

Turbo molecular pump

The invention relates to a turbomolecular pump.

Turbomolecular pumps have at least one rotor element in a housing. The rotor element has a plurality of rotor blades and is mounted on a rotor shaft. The rotor shaft is driven by means of an electric motor and is mounted via bearing elements in the housing. Furthermore, the turbomolecular pump has a stator element having a plurality of stator vanes. The stator element is arranged, for example, via stator rings in the housing, wherein the stator vanes project between the rotor vanes, so that stator vanes and rotor vanes are arranged alternately. Possibly. For example, the turbomolecular pump may include one or more of such rotor and stator elements. Furthermore, it is known that turbomolecular pumps have a Holweck stage downstream of the rotor element in the flow direction. For storage of the fast rotating rotor shaft two bearing elements are provided. In this case, usually one of the bearing elements is arranged at the fore-vacuum-side end of the rotor shaft. This bearing element is in a relatively low vacuum environment, so that both magnetic bearings and rolling bearings can be used in this area. Because of the relatively low vacuum, there is no risk of the lubricant, which is usually fat, outgassing hydrocarbons or other substances in excess. Provided At the high-vacuum-side end of the rotor shaft also a bearing element is arranged, this is always a magnetic bearing. Since very low pressures or a high vacuum prevail in this area, rolling bearings, even encapsulated rolling bearings, can not be used in this area, since due to the vacuum components of the lubricant, in particular hydrocarbons, outgas from the lubricant. Magnetic bearings, however, are expensive bearings. Furthermore, the construction is expensive.

In order to equip both bearing elements of a rotor shaft as a rolling bearing, it is known to store the rotor shaft flying. The high-vacuum side bearing element is thus offset in the direction of the fore-vacuum side, so that the rotor shaft protrudes. As a result, the bearing element is offset in a range in which outgassing of the lubricant due to the prevailing low pressure is no longer or only to an acceptable degree. However, floating rotor shafts have the disadvantage that they have a high weight in order to ensure sufficient stability. Furthermore, the projection length is limited.

The object of the invention is to provide a cost-effective storage of the rotor shaft of a turbomolecular pump.

The object is achieved according to the invention by the features of claim 1.

In the embodiment of the turbomolecular pump according to the invention, bearing elements are respectively arranged in the two end regions of the rotor shaft. In this case, it may be in the vorvakuumseitigen bearing element to a rolling bearing or a magnetic bearing, the cost-effective design is preferred as a rolling bearing. According to the invention, a rolling bearing is also provided on the high vacuum side despite the prevailing low pressure. This is inventively possible in that the High vacuum-side bearing element is arranged in a chamber. The substantially completely surrounding the bearing element chamber is connected via a channel with a pressure range in which there is higher pressure. The channel thus connects the provided in the region of high vacuum chamber with a region in which a slight vacuum prevails. This has the consequence that even in the chamber, despite the arrangement of the chamber in the high vacuum range, not the high pressure prevailing in the low pressure, but a higher pressure prevails. This corresponds essentially to the pressure prevailing in the pressure range to which the channel is connected. The inventive provision of a chamber which is connected via a channel with a corresponding pressure range, it is possible to store the rotor shaft also high vacuum side by means of a rolling bearing. As a result, the cost can be significantly reduced. In particular, it is no longer necessary, even with the provision of rolling bearings to store the rotor shaft flying and thus have to accept the disadvantages of a cantilever in purchasing.

Preferably, the channel with a pressure area is connected, in the pressure of at least 1 - 10 ^"5 mbar, in particular at least 1 - lCT ³ mbar prevails Preferably, the pressure is in this range between 1 mbar and 1 -.. LCT ⁵ mbar under high vacuum region can Pressures of less than 1 - lCT ³ , in particular less than 1-10 ^"5 mbar and particularly preferably less than 1-10 ^{" 7} mbar prevail.

The high-vacuum-side bearing element supports the rotor shaft in the pump housing. The chamber is therefore formed in a preferred embodiment of the invention of a directly or indirectly connected to the housing bearing receiving element. The bearing receiving element has a star-shaped support member or is preferably connected to a star-shaped support element, which with the Housing is connected. The particular star-shaped support member thus has openings through which the medium to be delivered is conveyed.

In a further preferred embodiment of the invention, which ensures in particular a simplified assembly, the chamber is closed high vacuum side of a lid. The lid is preferably connected to the bearing receiving element. Thus, in a preferred embodiment, the rotor shaft protruding into the chamber is spanned by the lid. The shaft end is thus arranged inside the chamber. This has the advantage that in this area no sealing between the shaft and the cover must be made.

In a preferred embodiment of the invention, a sealing element is arranged between the bearing receiving element and the rotor element. This is in a preferred embodiment, a non-contact seal such as a labyrinth seal. The sealing element is preferably arranged in an annular gap formed by the bearing receiving element and the rotor element. By a relatively long sealing length, a good tightness can be achieved. In a particularly preferred embodiment, a sealing gap of the sealing element has a smaller cross-section than the cross-sectional area of the channel. If a plurality of channels are provided, it is preferred that the sealing gap has a smaller cross-sectional area than the sum of the cross-sectional areas of the channels. In this way, a preferred pumping direction is ensured, since via the channel on one side of the sealing element, a pressure is applied, which substantially corresponds to the pressure in the region of the channel opening, that is in particular from a pre-vacuum region and rests on the other side of the sealing element high vacuum.

In a particularly preferred embodiment, the sealing element comprises an active sealing element. This results in a conveying of medium from the Lower pressure area in the higher pressure area. As an active sealing element can be provided for example in one or both of the annular gap forming walls, a spiral groove. This can be designed in particular according to a Hohlwegpumpe.

The invention will be explained in more detail with reference to a preferred embodiment with reference to the accompanying drawings.

1 shows a simplified schematic sectional view of a turbomolecular pump according to the invention ausgestalteter storage.

The turbomolecular pump shown in simplified form has a rotor shaft 10 which is rotatably mounted in a housing 16 via a high-vacuum-side bearing element 12 and a forevacuum-side bearing element 14. The rotor shaft 10 carries a rotor element 18 with a plurality of rotor blades 20. In each case between two adjacent rotor blades 20 stator blades 22 are arranged. The stator vanes 22 are fixed in the housing 16 via stator rings 24, so that in the illustrated embodiment the stator element is formed by the stator vanes 22 and the stator rings 24.

The rotor shaft is driven by an electric motor 26 in the illustrated embodiment.

The forevacuum-side bearing element 14 is supported by a holding element 28. The holding element is connected to the housing 16 and has an outlet 30 of the turbomolecular pump.

To evacuate a space connected to the turbomolecular pump, not shown, the medium is thus conveyed out of the space through an inlet 32 of the vacuum pump in the direction of the outlet 32. The bearing element 12, although it is arranged in the high vacuum region 34, designed according to the invention as a rolling bearing. This is possible because the Lagerelementl2 is arranged in a chamber 36. The chamber 36, in which the high vacuum-side end of the rotor shaft 10 projects, is formed by a bearing receiving element 38 in the illustrated embodiment. In the direction of the inlet 32, the chamber 36 is closed by a cover 40. The cover 40 spans the high-vacuum-side end of the rotor shaft 10 so that it does not protrude through the cover 40. The cover 40 is fixedly connected to the bearing receiving element 38 in the illustrated embodiment.

In order to carry the outer bearing ring of the high-vacuum-side position element 12, the bearing receiving element 38 must be connected to the housing 16. This is realized in the illustrated embodiment by a support member 42 having a star-shaped configuration. Due to the star-shaped configuration of the support element 42, these openings 44, through which the medium is sucked by the rotor blades 22 in the turbomolecular pump.

For arranging a roller bearing in the high vacuum region 34, not only one chamber 36 is provided according to the invention. Furthermore, the chamber 36 is connected to a pre-vacuum region 48 via a channel 46 which is arranged in the rotor element. Due to the connection of the chamber 36 via the channel 46 with the pre-vacuum region 48, it is ensured that substantially the same pressure prevails within the chamber 36 as in the pre-vacuum region 48. In order to avoid that the pressure in the chamber decreases and the lubricant of the rolling bearing outgasses, a sealing element 50 is also provided. For this purpose, the bearing receiving element has a shoulder or contact surface 52 extending in the longitudinal direction of the pump or parallel to the rotor shaft 10. The surface 52 is thus an outer surface of a cylinder. Opposite surface 52 is parallel to surface 52 on rotor element 18 likewise a cylindrical lateral surface 54 is formed. Through the two surfaces 52, 54 thus a ring-cylindrical annular gap 56 is formed. Within the annular gap 56, a labyrinth seal is arranged as a sealing element 50 in the illustrated embodiment. In addition to or instead of a labyrinth seal, an active seal, such as a hollow path step, can be formed in the annular gap 56, which conveys medium from the high-vacuum region 34 in the direction of the vacuum region 48.

Claims

claims

A turbomolecular pump having at least one rotor element (18) with a plurality of rotor blades (20) mounted in a housing (16) by means of a rotor shaft (10), at least one stator element (22, 24) arranged in the housing (16) with a plurality of rotor blades (20) projecting Statorflügeln (22), and two in end portions of the rotor shaft (10) arranged bearing elements (12, 14), wherein at least the high vacuum-side bearing element (12) is formed as a rolling bearing, and in a chamber (36) is arranged is connected via at least one channel (46) with a pressure region (48) in which a higher pressure than in the high vacuum region (34) prevails.

2. turbomolecular pump according to claim 1, characterized in that in the pressure region (48) with a higher pressure, a pressure of at least

1 - 10 ^"5 mbar, especially l - 10 ^{" 3} mbar prevails.

3. turbomolecular pump according to claim 1 or 2, characterized in that in the high vacuum region (34) a pressure of less than 1 - 10 ³ mbar, in particular 1-10 ^"5 mbar and more preferably less than 1-10 ^{" 7} mbar.

4. turbomolecular pump according to one of claims 1 to 3, characterized in that the chamber (36) is at least partially formed by a directly or indirectly with the housing (16) connected bearing receiving element (38).

5. turbomolecular pump according to one of claims 1 to 4, characterized in that the chamber (36) high vacuum side of a lid (40) which is preferably connected to the bearing receiving element (38) is closed.

6. turbomolecular pump according to claim 4 or 5, characterized in that the bearing receiving element (38) via a particular star-shaped support member (42) is connected to the housing (16).

7. turbomolecular pump according to one of claims 4 to 6, characterized in that between the bearing receiving element (38) and the rotor element (18) has a sealing element (50) is arranged.

8. turbomolecular pump according to claim 7, characterized in that the sealing element (50) in a by the bearing receiving element (38) and the rotor element (18) formed annular gap (56) is arranged.

9. turbomolecular pump according to claim 7 or 8, characterized in that the sealing element (50) has a labyrinth seal.

10. turbomolecular pump according to one of claims 7 to 9, characterized in that a sealing gap of the sealing element (50) has a smaller cross-sectional area than the cross-sectional area of the channel (46) or as the sum of the cross-sectional areas a plurality of channels (46).

Turbomolekularpumpe according to one of claims 7 to 10, characterized in that the sealing element has an active sealing element, wherein the active sealing element in particular comprises the hollow path stage or is designed as a hollow path stage.

12. turbomolecular pump according to one of claims 1 to 10, characterized in that the at least one channel (46) with the fore-vacuum region (48) is connected.