WO2009141222A1

WO2009141222A1 - Multi-stage vacuum pump

Info

Publication number: WO2009141222A1
Application number: PCT/EP2009/055397
Authority: WO
Inventors: Markus Henry; Peter Klingner
Original assignee: Oerlikon Leybold Vacuum Gmbh
Priority date: 2008-05-23
Filing date: 2009-05-05
Publication date: 2009-11-26
Also published as: EP2288812A1; DE102008024764A1; JP5560263B2; US20110135506A1; JP2011521161A

Abstract

The invention relates to a multi-stage vacuum pump, comprising a plurality of rotor elements (14, 16) disposed on a common shaft (10) in a pump housing (12) for configuring multiple pump stages (18, 24, 26). The shaft is driven by an electric motor (40). An inner bearing element (42) is disposed between two rotor elements (14, 16) such that a mechanically favorable bearing arrangement is implemented using a simple configuration of the bearing elements (42, 44) as roller bearings. This is possible in particular due to the separation into two rotor elements (14, 16).

Description

Our sign: 090160WO KB / cd

Your sign: P08.12 WHERE

30.04.2009

Multi-stage vacuum pump

The invention relates to a multi-stage vacuum pump,

Multi-stage vacuum pumps are, for example, multi-inlet vacuum pumps with at least two inlets and one outlet. The inlets are connected to different vacuum levels of the multi-inlet pump, with each inlet creating a different vacuum. Here, the highest vacuum is usually generated with the inlet connected to the first stage of the multi-inlet pump, and the second highest vacuum, etc. with the inlet connected to the second vacuum stage. Such vacuum pumps with a plurality of vacuum stages have a housing in a shaft which is driven by an electric motor usually surrounding the shaft.

Different types of bearing of the shaft are known from the prior art. In particular, it is known to support the shaft via two ball bearings, wherein the electric motor is arranged between the two ball bearings. Towards the first stage, the shaft has a wave approach. On the shaft approach the rotor element is arranged. The rotor is thus arranged on the projecting Weiienansatz and therefore stored on the fly. Since the entire force acting on the rotor forces are transmitted to the projecting end of the shaft to this, a high load on the bearings. This affects the life of the bearings. Femer is with such stored waves limits the length of the shaft, otherwise the forces occurring in the camps can not be intercepted or extremely complex and expensive bearings must be used. A disadvantage of this bearing arrangement is the relatively small bearing distance,

In a similar bearing arrangement, the electric motor is not arranged between the two bearings but outside of the bearing. The rotor is in turn disposed on the cantilever shaft approach and thus also has the disadvantages of flying storage. Furthermore, the bearing distance is also very low. This leads to an unfavorable center of gravity and the resulting high bearing loads.

Furthermore, it is known from DE 603 13 493 to support the shaft at both ends. Due to the thus realized large bearing distance, the forces occurring in the bearings can be made uniform and reduced. However, the bearing arranged on the suction side of the pump, ie in the region of the first stage, must be designed as a magnetic bearing due to the low pressure prevailing here. According to the state of the art, a grease-lubricated ball bearing can not be used here because the grease was sucked out of the bearing due to the low pressure. As is customary with magnetic bearings, another ball bearing serving as a safety bearing is additionally provided which, however, does not serve to absorb forces, but merely serves as a temporary support. Due to the required provision of a permanent Magnetiagers and an additional backup bearing storage is expensive. Furthermore, it is necessary to provide a star-shaped holding element for the permanent magnetic bearing, which has flow openings. Since this star-shaped end shield is located in the region of the high-vacuum stage, conductivity values occur at an extremely unfavorable point in the flow profile. This reduces the maximum power of the vacuum pump, The object of the invention is to provide a cost effective and effective storage arrangement for multi-stage vacuum pumps, in particular to be able to increase the overall length.

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

According to the invention, the rotor is separated into at least two rotor elements. The two rotor elements are thus separate, in particular connected to the Weüe. Depending on the configuration of the multi-stage vacuum pump, in particular the arrangement of the inlets, one but also several stages may be formed per rotor element. By separating the rotor according to the invention into two rotor elements, it is possible to arrange an inner bearing element, which is usually a roller bearing, such as a ball bearing, between the two rotor elements. Preferably, therefore, one of the two rotor elements, in particular the rotor element forming or forming the high-vacuum stage, is arranged outside the inner bearing element. The rotor element is thus arranged on a shaft projection projecting relative to the inner bearing element. However, unlike the prior art, since it is not the entire rotor located at the cantilevered end of the shaft but only one of the at least two rotor elements, the forces and moments introduced thereto at the cantilevered end of the shaft considerably lower. The second rotor element may for example be arranged between an inner and an outer bearing element, in particular fixedly connected to the shaft.

Since erfinduπgsgemäß the inner bearing element is preferably not located in the region of high vacuum, but is disposed within the outer, the high vacuum stage comprising rotor element, the bearing is not exposed to the extremely low pressures prevail in the high vacuum. This has the advantage according to the invention that In particular grease-lubricated bearings, such as ball bearings can be used. The arrangement of a ball bearing has the particular advantage that ball bearings have a significantly lower design. Furthermore, the provision of a particular grease-lubricated ball bearing in this area has the advantage that no additional emergency storage must be present. This is mandatory for magnetic bearings, otherwise no emergency running properties are guaranteed in case of failure of the magnetic bearing.

In particular, due to the relatively large bearing distance, the forces acting on the bearings distribute more favorably. This is advantageous in terms of rotor dynamics. Also occurring misalignments of the time are less, so that storage mechanical advantages exist. Due to the realizable lower misalignment narrower gaps can be realized, so that the efficiency of the pump is improved or higher final pressures can be achieved. In a particularly preferred embodiment, the inner bearing element is fixed by a Haiteelement. The holding element has at least one throughflow opening. For fixing the bearing, in particular the outer bearing shell when using rolling bearings, the retaining element is preferably connected to the pump housing. It is particularly preferred that the holding element has a plurality of throughflow openings and in particular is designed in the shape of a star. The individual, preferably regularly arranged and preferably identically designed through-flow openings are preferably part-ring segmented. Since the inner bearing element is arranged in the conveying direction within the Rotoreiements, which includes the high vacuum stage, the medium flows through the flow openings only when exiting the high vacuum stage or when entering the next stage. The conductance losses generated by the holding element are thus significantly lower than when such a holding element is provided in the region of the high-vacuum stage, ie in the region of the gas inlet of the high-vacuum stage. In a particularly preferred embodiment, at least two Rotoreiemente are provided, wherein both the inner bearing element and the retaining element between these two Rotoreiementen is arranged.

In a further particularly preferred embodiment, the inner Lagereiement is arranged in the axial direction at least partially within a Rotoreiements. In particular, this is the rotor element comprising the high-vacuum stage. In this embodiment as well, the rotor element is still arranged in front of the inner bearing element in the flow direction. The inner bearing element is furthermore arranged between two rotor elements, in particular between the two attachment areas of the rotor elements on the shaft , By overlapping at least partially in the axial direction of the inner bearing element by a Teii the Rotoreiements the projecting shaft extension can be shortened. This results in a further improvement of the storage mechanism.

Preferably, an outer bearing element is arranged such that arranged between the two bearing elements, a Rotoreiement, in particular fixedly connected to the shaft. When providing two rotor elements, the outer bearing element is thus preferably arranged outside of the lowest stage forming Rotoreiements. It is particularly preferred in this case that the drive element between the outer Lagereiement and the lowest vacuum stage forming rotor element is arranged. This has the advantage that the two bearing elements have a very large bearing distance, whereby the storage mechanism is improved.

In embodiments with, for example, three or more inlets and a corresponding number of vacuum stages, it is preferred that the outer bearing member is disposed between two rotor members. These are preferably the two rotor elements, which are the lowest Forming vacuum levels, wherein a Rotoreiement may optionally form a plurality of vacuum levels.

Particularly in the case of a multi-stage vacuum pump with more than two inlets and in the case of the preferred arrangement of the outer bearing element between two rotor elements, the outer bearing element is fixed via a retaining element. The holding element preferably has passage openings and is formed corresponding to the Haiteelement of the inner bearing element.

The inner Lagereiement is preferably a rolling bearing. However, it is also mögüch to provide a magnetic bearing, in particular a permanent magnetic bearing, which optionally additionally a fishing camp is provided.

In a particularly preferred embodiment, the multi-stage vacuum pump according to the invention is a multi-inlet vacuum pump. This has at least one additional inlet next to the main inlet. The additional inlets are in this case preferably arranged in each case between two adjacent vacuum stages. In the case of customary MuItI-Inlet vacuum pens, a pressure of IxIO ^"5 mbar to IxIO ^{" 9} mbar can be achieved on the high-vacuum side. At a first intermediate point, a pressure of IxIO ^"2 mbar to IxIO ^{" 5} mbar can be achieved. If a second interim intake is intended, a pressure of IxIO ^"2 mbar to SxIO ^'1 mbar can be reached at this.

The invention will be explained in more detail with reference to preferred embodiments.

Show it :

Fig. 1 is a sectional view of a schematic diagram of a first

Embodiment with two rotor elements, Fig. 2 is a Schnlttansicht a schematic diagram of a first

Embodiment with three rotor elements, and

Fig. 3 is a schematic plan view of a Haiteelements.

In the greatly simplified schematic representation of a first embodiment of the multi-stage vacuum pump according to the invention (FIG. 1), a WeNe 12 is arranged in a pump housing 10. The shaft 12 carries the two separate or separate rotor elements 14, 16 according to the invention. These are firmly connected to the shaft 12.

In the illustrated embodiment, the rotor element 14 forms a first vacuum stage 18, in which the highest vacuum is generated. The gas to be delivered is sucked in here through a first inlet opening 20. In the illustrated embodiment, the first vacuum stage is a vacuum stage formed by a turbomolecular pump. With the rotor 14, a stator 22 connected to the housing 10 cooperates.

By the second rotor element 16, two vacuum stages 24, 26 are formed in the illustrated embodiment. The second vacuum stage 24 is likewise formed by a turbomolecular pump, wherein a stator 28 is likewise connected to the housing 10. The third stage 26 is a Holweck stage, in which the helically shaped projection 30 engages in a corresponding helical recess. The second vacuum stage 24 draws in medium through an inlet opening 34 and the third vacuum stage 26 through an inlet opening 36. The aspirated medium is conveyed from all three stages 18, 24, 26 to the ejection opening 38.

In the illustrated embodiment, an electric motor 40 for driving the shaft 12 is provided in the region of the third stage. The electric motor 40 surrounds the shaft 12 in a preferred embodiment. In the axial direction, the Holweck stage preferably surrounds the electric motor 40.

The bearing of the shaft 12 via an inner Lagereiernent 42 and an outer bearing member 44. The inner bearing member 42 is disposed between the two Rotoreiementen 14, 16. If the inner bearing element 42 is a roller bearing, an inner bearing ring is pressed onto the shaft 12, for example. An outer bearing ring is fixed by a Haiteelement 46. The holding element 46 shown in plan view in FIG. 3 has a plurality of, in particular regularly arranged, partial-ring-segment-shaped passage openings 48 through which the medium conveyed by the first stage 18 flows.

The outer bearing element 44 is arranged in the illustrated Ausführungsbeispiei outside the lowest or third stage 26. The bearing element 44 is preferably also a roller bearing,

In the dargesteilten embodiment, the inner bearing member is disposed in the axial direction 50 within the rotor member 14. For this purpose, the rotor element 14 has a cross-sectionally substantially annular recess 52.

In the second preferred embodiment, similar or identical components are identified by the same reference numerals. For clarity, no pump housing is shown. The gas flow is shown by the arrows 54, 56, 58, 60. An alternative gas flow is shown by arrows 62, 64, 56, 58, 60

In the exemplary embodiment shown in FIG. 2, three rotor elements 14, 66, 68 are shown on the shaft 64. In the illustrated exemplary embodiment (FIG. 2), all rotor elements 14, 66, 68 are shown as rotor elements of moiekular pumps, wherein it is Of course, it can also be about other rotor elements. Furthermore, even in this embodiment, individual rotor elements can form a plurality of stages.

According to the exemplary embodiment illustrated in FIG. 1, the inner bearing element 42 is arranged between two rotor elements 14, 66 and likewise fixed by a holding element 46 (FIG. 3) or connected to the housing. In the illustrated embodiment, the drive motor 40 is disposed between the two rotor elements 14, 66.

The second or outer bearing element 44 is arranged between the two rotor elements 66, 68 (FIG. 2) and fixed in the illustrated embodiment via a holding element 46.

In a first flow path, which is represented by the arrows 54, 56, 58, 60, a flow through the individual pump stages formed by the rotor elements 14, 66, 68 occurs in succession.

In the second flow path, which is represented by the arrows 62, 64, 56, 58, 60, in addition, a suction of gas through a further inlet opening in the direction of the arrow 62. Via a Beipass or connecting channel (arrow 64) is in both Direction of the arrow 62 and in the direction of arrow 54 sucked gas to the next stage (rotor element 66) passed.

The arrows 54, 62, 56 and 68 correspond to inlet openings or intake openings. The arrow 60 corresponds to the ejection opening.

Claims

claims

1. Multi-stage vacuum pump, with

a plurality of rotor elements (14, 16; 14, 66, 68) arranged on a common shaft (10, 64) in a pump housing (10) for forming a plurality of pump stages (18, 24, 46),

a driving element (40) driving the while (10, 64) and

an inner, between two rotor elements (14, 16, 14, 66) arranged bearing element (42).

2. Multi-stage vacuum pump according to claim 1, characterized in that the inner bearing element (42) via a holding element (46) is fixed, which has at least one through-flow opening (48),

3. Multi-stage vacuum pump according to claim 2, characterized in that the inner bearing element (42) via the holding element (46) with the pump housing (10) is connected.

4. Multi-stage vacuum pump according to claim 2 or 3, characterized in that the holding element (46) is substantially round and preferably has a plurality, in particular part-ring-segment-shaped flow openings (48).

5. Multi-stage vacuum pump according to one of claims 2 to 4, characterized in that the holding element (46) between two rotor elements (14, 16, 14, 66) is arranged.

6. Multi-stage vacuum pump according to one of claims 1 to 5, characterized in that the inner bearing element (42) in the axial direction (50) at least partially within a rotor element (14) is arranged.

7. Multi-stage vacuum pump according to one of claims 1 to 6, characterized in that between the inner bearing element (42) and an outer bearing element (44) a Rotoreiement (16, 66) is arranged, preferably fixedly connected to the shaft (64) .

8. Multi-stage vacuum pump according to claim 7, characterized in that the outer bearing element (44) between two rotor elements (66, 68) is arranged and preferably via a holding element (46) with flow openings (48) is fixed.

9. Multi-stage vacuum pump according to claim 7, characterized in that the inner bearing element (42) and / or the outer Lagereiement (44) is designed as a rolling bearing, in particular as a ball bearing.

10. Multi-stage vacuum pump according to claim 9, characterized in that the rolling bearing is grease-lubricated.