WO2014023519A1

WO2014023519A1 - Vacuum pump

Info

Publication number: WO2014023519A1
Application number: PCT/EP2013/064891
Authority: WO
Inventors: Rainer Hölzer
Original assignee: Oerlikon Leybold Vacuum Gmbh
Priority date: 2012-08-09
Filing date: 2013-07-15
Publication date: 2014-02-13
Also published as: TW201410981A; DE202012007700U1

Abstract

In a pump housing (12), a vacuum pump, such as, in particular, a turbomolecular pump, has a rotor shaft (10) which is mounted by two bearing arrangements (14). One of the two bearing arrangements (14) has an anti-friction bearing (16). In order to make a radial movement (30) of the anti-friction bearing (16) possible, it is surrounded by a sleeve (22). The sleeve (22) is arranged such that it can be displaced radially in the pump housing (12) as a result of the provision of rolling bodies (28).

Description

vacuum pump

The invention relates to a vacuum pump, in particular a turbomolecular pump.

Vacuum pumps such as turbomolecular pumps have in a pump housing a rotor shaft carrying a pumping element such as a rotor. Particularly in turbomolecular pumps, the rotor shafts are operated at high speeds of, for example, 60,000 / min. The rotor shaft is supported by two bearing arrangements. The bearing assemblies each have a magnetic or rolling bearing. In such fast-rotating rotor shafts, the bearing assemblies require a high rigidity in the axial direction. Furthermore, there is a requirement that one of the two bearing arrangements has a direction perpendicular to the rotor longitudinal axis, i. Having in the radial direction pointing mobility. Usually, this radial mobility is realized in the pressure side bearing. In this bearing arrangement, vertically arranged rotor shafts are usually the lower bearing arrangement.

For example, from EP 2 126 365 the provision of elastomeric rings is known. In particular, due to the required axial stiffness occur relatively large radially acting forces due to shear stresses between the bearing outer ring and the adjacent components. Such radial forces have a negative effect. From EP 1 618 308 a vacuum pump with a rotor shaft mounted via two bearing arrangements is also known. The bearing arrangement described in EP 1 618 308 has a roller bearing supporting the shaft. The outer ring of the ball bearing is surrounded by an elastomer ring. The elastomeric ring is disposed in an annular groove of the housing. In addition to the radial movement of the rolling bearing enabling elastomeric ring a thrust bearing is provided. The balls of the thrust bearing are arranged axially to the outer bearing ring. The balls of this bearing are arranged between the plane of the outer bearing ring extending perpendicular to the longitudinal axis of the shaft and a surface of the housing which is likewise perpendicular to the longitudinal axis of the rotor shaft. Through these bearings thus takes place an axial support of the outer bearing ring, at the same time a radial movement of the outer bearing ring and thus of the entire bearing is possible. The provision of an axial support on the outer bearing ring of the rolling bearing described in EP 1 618 308 has the disadvantage that the ball diameter is limited for the axial support taking place due to the width of the end face of the outer ring of the rolling bearing. Furthermore, the seat of the axial ball bearing during assembly can not be controlled. Furthermore, the required stepped bore and the required undercut in the housing is difficult to machine and measure.

The object of the invention is to provide a vacuum pump, in particular a turbomolecular pump whose rotor shaft with high axial stiffness in at least one rotor shaft bearing bearing arrangement is a light and low-friction radial mobility allows.

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

The vacuum pump according to the invention, which is in particular a turbomolecular pump, has a pump housing, which usually consists of several parts. In the pump housing is a rotor shaft stored by means of two bearing arrangements. The rotor shaft carries a pumping element such as a rotor. At least one of the two bearing arrangements has a rolling bearing. This bearing arrangement is preferably the pressure-side bearing arrangement. This is usually the lower bearing assembly with vertically arranged rotor shaft. The suction side, usually vertical upper rotor shaft assembly can also have a rolling bearing. It is preferred that the suction-side bearing has a magnetic bearing.

The rolling bearing bearing arrangement preferably has a sleeve which surrounds the rolling bearing at least partially, in particular completely. The sleeve is designed or arranged such that a radial displacement of the rolling bearing is possible. This is possible by the provision of rolling elements, in particular balls. Due to the provision of rolling elements such as balls for realizing a radial mobility in conjunction with a sleeve surrounding the bearing, the rolling elements of this bearing are arranged on a relatively large radius. This has the advantage that the restoring moment is greater at, except centered or obliquely introduced to the shaft axis axial forces. As a result, a better return of the rotor shaft is improved in the starting position or the optimum position.

In a particularly preferred embodiment of the invention, the sleeve surrounds an outer ring of the rolling bearing. In particular, by the choice of material and the assignment of the sleeve to the outer ring of the rolling bearing, the sleeve itself may have a certain damping property and thus in particular to avoid vibration transmission of critical frequencies to the rotor shaft.

Further, it is possible to design the sleeve such that the sleeve itself forms the outer ring of the rolling bearing. The advantage of such an embodiment is that the bearing assembly radially less Space required. Such space could be further reduced by the fact that the inner ring of the rolling bearing is omitted and formed directly from the surface of the rotor shaft. In this radially very small-scale bearing arrangement, the rolling elements of the rolling bearing are thus arranged directly between the rotor shaft and the sleeve.

In order to provide a bearing arrangement which is as small as possible in the axial direction, it is preferred that the rolling elements which enable the radial movement are arranged in the axial direction within the rolling bearing.

In a preferred development of the invention, the sleeve has a rolling collar bearing the rolling elements. The rolling elements are thus arranged between the radially extending collar of the sleeve and a surface of the pump housing or a component connected to the pump housing. As a result, a radial movement of the usually lower bearing assembly and thus a kind of oscillating movement of the rotor shaft is made possible according to the invention simple manner.

Preferably, a surface of the collar is parallel to a housing surface of the pump housing. Due to the relatively small radial movement, the two surfaces can be formed flat. Since a kind of pendulum movement is performed by the rotor shaft, it is preferable to form at least one of the two opposing surfaces spherical. The radius of the sphere preferably corresponds to the radius of the pendulum motion.

In a preferred embodiment of the invention, the housing surface, against which the balls of the rolling bearing abut, of a used in the pump housing, in particular hardened disc is formed. This has the advantage that no damage such as impressions in the housing can be caused by the balls. Due to the provision of a particular hardened disc, the choice of material of the housing is independent of the surface properties. So can one relatively soft housing material can be selected to form the housing.

The rolling elements enabling a radial or pendulum movement of the rotor shaft are preferably arranged in a holding element, similar to a cage, so that the position of the rolling bodies is defined.

In a further particularly preferred embodiment of the invention, a damping element is arranged between the sleeve and the pump housing. The damping element is designed such that it defines the position of the bearing assembly in the unloaded state. Furthermore, the damping element serves to allow a radial movement of the corresponding bearing arrangement, although to attenuate. The damping element preferably surrounds the sleeve completely. In particular, the damping element is annular. The damping element may in this case be arranged partially in a recess of the pump housing. Preferably, the axial position of the damping element is selected such that it is arranged substantially at the height of the rolling elements of the rolling bearing.

In a further preferred embodiment, the sleeve has a radially inwardly facing retaining collar. At this holding collar is in the assembled state of the outer ring of the bearing. By the retaining collar thus the position of the outer ring of the rolling bearing is axially defined. In particular, the outer ring of the rolling bearing can be connected to the sleeve by pressing.

In a preferred embodiment, the sleeve thus has a radially inwardly facing, in particular ring-shaped retaining collar and a radially outwardly facing, preferably also annularly shaped collar. The preferred embodiment of the invention, in particular the lower bearing assembly allows an application of axial force, so that the rotor shaft is positioned with high axial rigidity in the pump housing. In a direction perpendicular to the shaft axis or in the radial direction, the bearing assembly and thus the rotor shaft is easy and low friction movable. A force that is required to move the bearing assembly perpendicular to the rotor shaft is not or only slightly dependent on the axial forces.

Another advantage of providing a sleeve surrounding the rolling bearing is that the bore in the pump housing without the formation of a step is possible. It is therefore a simple through hole. Furthermore, the housing surface against which the rolling elements that enable the radial movement can be manufactured with a low tolerance. Furthermore, there is the advantage that the housing surface can have a larger planing impact tolerance. This is due, in particular, to the fact that the balls of the axial bearing are arranged on a larger diameter than the balls arranged on the end face of a bearing outer ring, as described in EP 1 618 308. If the angle deviation is the same, the runout can be greater than the dimension in mm.

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

Show it :

Figure 1 is a schematic sectional view of a first preferred

Embodiment of the bearing assembly according to the invention and

Figure 2 is a schematic sectional view of a second preferred embodiment of the bearing assembly according to the invention. A rotor shaft 10 of a vacuum pump such as a turbomolecular pump carries a rotor, not shown. The rotor shaft 10 is mounted in a pump housing 12 via the particular lower bearing assembly 14. Another designed for example as a magnetic bearing upper bearing assembly is disposed above or on the other side of the rotor. The illustrated bearing assembly 14 is usually arranged on the pressure side with respect to the rotor.

The bearing assembly 14 has a designed as a ball bearing in the illustrated embodiment roller bearing 16 with an arranged on the shaft 10 inner ring 18 and an outer ring 20. The outer ring 20 is not disposed directly in the housing 10, but supported by a sleeve 22.

The sleeve 22 is Z-shaped in cross-section and has a radially extending collar 24. The collar extends radially outward relative to the substantially cylindrically shaped inner sleeve section and is of annular design. Between a surface 26 of the collar 24 and the housing 12 a plurality of circumferentially spaced rolling elements 28 are provided. Due to the provision of the rolling elements 28, a radial movement or oscillation of the rotor shaft 10, as indicated by the arrow 30, possible.

The rolling elements 28 are preferably arranged in a holding element 32 designed corresponding to a cage, so that the position of the individual rolling elements is clearly defined.

In the housing 12, an annular disc 34 can be arranged. As a result, the rolling elements 28 are not on an immediate housing surface, but on a formed by the disc 34 housing surface 36 at. Furthermore, the sleeve 22 has a retaining collar 38. This is also annular and has radially inward, so that the outer ring 20 is clearly defined in its relative position to the sleeve 22.

For damping the radial movement, a damping element 40 such as an O-ring is arranged between the sleeve 22 and the pump housing 12. The damping element 40 surrounds the sleeve 22 annularly and is preferably arranged in a groove 42 of the housing 12.

In the further preferred embodiment shown in FIG. 2, similar and identical components are identified by the same reference numerals.

The essential difference of this embodiment is that the bearing assembly 14 in the axial direction, i. thus builds shorter in the longitudinal direction. For this purpose, the sleeve 22 is formed such that the collar 24 is disposed axially within or adjacent to the rolling bearing 16.

In the exemplary embodiment illustrated in FIG. 2, furthermore, the disk 36, which consists in particular of hardened material, is not provided. Of course, the disc 36 could also be omitted in the embodiment shown in Figure 1 with appropriate choice of material of the pump housing.

Claims

claims

A vacuum pump, in particular a turbomolecular pump, having a rotor shaft (10) arranged in a pump housing (12) and mounted by two bearing arrangements (14), one of the bearing arrangements (14) having a roller bearing (16), characterized in that the rolling bearing (16) is surrounded by a sleeve (22) which is arranged in the pump housing (12) via a radial displacement of the rolling bearing (16) enabling rolling bodies (28).

2. Vacuum pump according to claim 1, characterized in that the sleeve (22) carries an outer ring (20) of the rolling bearing (16) or forms the outer ring of the rolling bearing.

3. Vacuum pump according to claim 1 or 2, characterized in that the sleeve (22) has a rolling body (28) bearing radial collar (24).

4. Vacuum pump according to claim 3, characterized in that an upper side (26) of the collar (24) parallel to a housing surface (36).

5. Vacuum pump according to claim 4, characterized in that the housing surface (36) by a in the pump housing (12) inserted, in particular hardened disc (34) is formed.

6. Vacuum pump according to one of claims 1 to 5, characterized in that between the sleeve (22) and the pump housing (12) a damping element (40) is arranged.

7. Vacuum pump according to claim 6, characterized in that the damping element (40) surrounds the sleeve (22) and is preferably annular.

8. Vacuum pump according to one of claims 1 to 7, characterized by a position of the rolling elements (28) defining retaining element (32).

9. Vacuum pump according to one of claims 2 to 8, characterized in that the sleeve (22) has a radially inwardly pointing on the outer ring (20) of the rolling bearing (16) adjacent retaining collar.

10. Vacuum pump according to claim 9, characterized in that the retaining collar (38) and the rolling elements (28) carrying the collar (24) are offset from one another axially.

11. Vacuum pump according to one of claims 1 to 10, characterized in that the rolling elements (28) are arranged axially within the rolling bearing (16).