EP3051141B1 - Rotor bearing - Google Patents

Description

The present invention relates to an arrangement for mounting a rotor relative to a stator, in particular for mounting the rotor of a vacuum pump, with a radially stabilizing permanent magnet bearing in the region of one of the two rotor ends and a further bearing in the region of the opposite rotor end according to the preamble of claim 1 The invention further relates to a vacuum pump, in particular a turbomolecular pump, with such a rotor bearing.

A vacuum pump with such an arrangement is out DE 28 25 551 A1 known.

Magnetic bearing rotors are used in vacuum pumps, among others. Vacuum pumps such as Turbomolecular pumps are used in different areas of technology to create a vacuum necessary for a particular process. Turbomolecular pumps comprise a stator with a plurality of stator disks which follow one another in the direction of a rotor axis and a rotor which is rotatably mounted about the rotor axis relative to the stator and which comprises a rotor shaft and a plurality of rotor disks arranged on the rotor shaft, which are arranged in the axial direction and are arranged between the stator disks, the stator disks and the rotor disks each have a pump-active structure.

The currently most frequently used mechanical / magnetic or hybrid rotor bearing in turbomolecular pumps comprises a permanent magnetic radial bearing at one rotor end and a roller bearing provided with lubricant on the opposite side. In order for such a hybrid rotor bearing To prevent destruction of the permanent magnetic radial bearing and the resulting destruction of the entire rotor, a safety bearing in the form of a dry, mechanical roller bearing forms a kind of stop, which should prevent the rotor from rotating in the area of the permanent magnetic radial bearing in the event of a stronger deflection of the rotor and touch the stator.

Single-axis or multi-axis active magnet-bearing rotors have also been proposed. These are single or multi-axis position controlled rotors. The currently most frequently used rotors are actively controlled in all five axes, which is associated with a relatively high level of complexity, particularly with regard to the sensors, the actuators, the electronics and the control algorithm. In the area of turbomolecular pumps, some uniaxially active bearings were also used in the 1980s and 1990s, which included a necessarily heavy iron disk on the rotor, electromagnets in the stator and contactless rotor position sensors for axial stabilization. Due to the relatively complex construction and the correspondingly high manufacturing costs, single-axis active bearings of this type were then replaced by 5-axis active systems. This brought with it a certain cost reduction. Particularly with regard to reliability, stability and precision, however, there is still a considerable difference between such 5-axis active systems and the mechanical / magnetic or hybrid rotor bearings mentioned above.

The invention has for its object to provide a rotor bearing and a vacuum pump of the type mentioned, with which the problems mentioned above are eliminated. The rotor bearing should have at least essentially the same reliability with a simpler construction and correspondingly cheaper manufacturing and operating costs and avoiding the disadvantages that arise in connection with the previous uniaxially active bearings. Stability and precision like mechanical / magnetic or hybrid rotor bearings.

The object is achieved by a rotor bearing with the features of claim 1 and a vacuum pump with the features of claim 10. Preferred embodiments of the rotor bearing according to the invention and the vacuum pump according to the invention result from the subclaims, the present description and the drawing.

The arrangement according to the invention for mounting the rotor in relation to a stator, in particular for mounting the rotor of a vacuum pump, comprises a radially stabilizing permanent magnet bearing in the region of one of the two rotor ends and a further bearing in the region of the opposite rotor end. The further bearing is designed as an axially active, radially stabilizing permanent magnet bearing which, for axial stabilization, comprises a stator-side bearing part which is assigned to an intermediate part which is axially movably mounted with respect to a fixed housing of the stator and, together with this, is axially movable relative to the stator housing. The intermediate part can be acted upon by an actuator unit in order to counteract a respective axial deviation of the rotor from a desired position.

The design according to the invention results in a rotor bearing arrangement which, with a simpler construction and correspondingly lower manufacturing and operating costs, in particular has at least essentially the same reliability, stability and precision as a conventional mechanical / magnetic or hybrid rotor bearing arrangement, and that without the connection with the disadvantages resulting from the previous uniaxial active bearings.

By replacing the rolling bearing of the previous mechanical / magnetic or hybrid rotor bearing with an axially active, radially stabilizing permanent magnet bearing the rotor is now completely radially stabilized. By providing a stator-side bearing part for axial stabilization, which is assigned to an intermediate part which is axially movably mounted with respect to a fixed housing of the stator and is axially movable together with this with the stator housing, the heavy iron disk on the rotor, which was previously required for uniaxially active bearings, is eliminated.

In addition, a respective deflection of the intermediate part can now also be detected by a touching sensor which is simpler in comparison to a contactless sensor. Finally, only the relatively light intermediate part has to be moved via the actuator unit in order to counteract a respective axial deviation of the rotor with respect to the desired position. The result is a magnetically mounted rotor with a simple, uniaxially active bearing without the problems associated with the previous uniaxially active bearings.

Furthermore, the arrangement according to the invention comprises a sensor unit for measuring a respective axial deflection of the intermediate part relative to the stator housing and a control device connected to the sensor unit and the actuator unit, by means of which the actuator unit can be controlled as a function of the measured axial deflection of the intermediate part.

If the rotor deviates axially from the desired position, an axial force results which is magnetically transmitted to the stator-side bearing parts of the permanent magnet bearings. The axial force in question is supported in the case of the radially stabilizing permanent magnet bearing in the region of one rotor end on the stator housing and in the case of the axially active radially stabilizing permanent magnet bearing in the region of the opposite rotor end on the intermediate part which is axially movable relative to the stator housing. This can deflect the intermediate part are detected by the sensor unit, as a result of which a respective axial deviation of the rotor from the nominal position can be determined.

The actuator unit can preferably be controlled via the control unit such that the axial deflection of the intermediate part relative to the stator housing is zero on average over time. This results in a stable axial working point on average over time.

According to a preferred practical embodiment of the arrangement according to the invention, the intermediate part is inserted resiliently and / or damped into the stator housing.

The system is dynamically stabilized by the resilient and / or damped installation of the intermediate part in the stator housing. The intermediate part can be inserted in the stator housing in a resilient and damped manner, for example via O-rings and / or the like.

The control device can in particular comprise control electronics which act upon the actuator unit more strongly when the intermediate part is detected in order to accelerate the intermediate part in the direction of rotor movement, so that the rotor is "overhauled" so to speak and the unstable point is exceeded so that a counterforce can then be built up , which brakes the rotor and accelerates in the opposite direction. The result is a stable axial working point on average, at which the deflection of the intermediate part relative to the stator housing is zero on average over time. The operating points in different operating situations (rotor weight) and at different operating temperatures (thermal rotor elongation) may differ slightly, but this is not a problem if the spring elements involved are chosen appropriately.

The actuator unit can in particular comprise at least one linear actuator.

According to a preferred practical embodiment of the arrangement according to the invention, the actuator unit comprises at least one electromagnet and / or at least one hydraulic actuator.

It is also particularly advantageous if the sensor unit for measuring a respective axial deflection of the intermediate part relative to the stator housing comprises a touching sensor.

The use of such a contacting sensor is easily possible for measuring a respective axial deflection of the intermediate part and is associated with less effort than the use of a contactless sensor. The structure of the rotor bearing is thus further simplified. The sensor unit for measuring a respective axial deflection of the intermediate part relative to the stator housing can comprise, for example, a strain gauge or the like.

It is also advantageous if an at least radially acting catch bearing is additionally provided in the area of the two rotor ends.

The catch bearing in the region of the opposite rotor end provided with the axially active, radially stabilizing permanent magnet bearing is preferably designed as an axially and radially acting catch bearing.

Compared to the conventional mechanical / magnetic or hybrid rotor bearings, the rotor bearing according to the invention above all has the advantages of a purely non-contact bearing, with which the restrictions associated with conventional rolling and sliding bearings are eliminated, which are due, among other things, to the fact that these rolling and Plain bearings with solid, liquid or gaseous lubricants on the contact surfaces between the fixed and movable bearing part work. In contrast, field force bearings, in which the bearing forces are generated by magnetic fields, work without contact and without contact medium. Corresponding field force bearings can be used with particular advantage where other bearings reach their limits due to lubricant problems. Thus, at high ambient temperatures and due to frictional heat at the bearing gap, the lubricant can overheat in rapidly rotating systems and thereby lose its function. At low temperatures, liquid lubricants can become tough and therefore unusable. The use of lubricants can also be undesirable in certain applications due to a physico-chemical incompatibility, as is the case in particular in vacuum technology and, inter alia, also in clean room, chemical, food and medical technology. In the rotor bearing arrangement according to the invention, the restrictions mentioned do not apply. It works without locks and maintenance and is free from friction-related energy losses.

With the rotor bearing according to the invention, there are also advantages over known multi-axis active and the previous single-axis active magnetic bearings. Compared to the previous 3-axis active magnetic bearings, this results in a significantly lower expenditure on actuators, sensors and electronics. Since no iron parts are required on the rotor, the rotor weight is reduced. The associated, on average, lower unbalance also results in a reduced risk of starting or a reduced risk of contact with the bearing and a reduction in noise. The actuators and sensors as a whole can be kept relatively compact and accommodated in the stator, since the force is transmitted to the rotor magnetically via the axially active, radially stabilizing permanent magnet bearing and the rotor position can be detected indirectly by deflections of the intermediate part from its central position.

The rotor bearing arrangement according to the invention can be used in particular in the case of rotary machines with low axial and radial loads in standard operating cases and in vacuum pumps, such as, in particular, turbomolecular pumps.

The vacuum pump according to the invention, in particular turbomolecular pump, is characterized in that its rotor is supported relative to its stator by a bearing according to the invention.

The vacuum pump preferably comprises a permanent magnet motor as a rotary drive for the rotor.

According to a preferred practical embodiment of the vacuum pump according to the invention, the permanent magnet motor is arranged axially between an axially and radially acting catch bearing and the axially active radially stabilizing permanent magnet bearing.

Fig. 1

eine schematische Darstellung einer herkömmlichen Vakuumpumpe mit einer herkömmlichen mechanischen/magnetischen oder Hybrid-Rotorlagerung,

Fig. 2

eine Prinzipskizze einer beispielhaften Ausführungsform einer erfindungsgemäßen Rotorlagerung, und

Fig. 3

eine detailliertere schematische Teildarstellung der erfindungsgemäßen Rotorlagerung gemäß Fig. 2, die hier beispielsweise in einer Vakuumpumpe, insbesondere Turbomolekularpumpe, integriert ist.

The invention is explained in more detail below using an exemplary embodiment with reference to the drawing; in this show:

Fig. 1

a schematic representation of a conventional vacuum pump with a conventional mechanical / magnetic or hybrid rotor bearing,

Fig. 2

a schematic diagram of an exemplary embodiment of a rotor bearing according to the invention, and

Fig. 3

a detailed schematic partial representation of the rotor bearing according to the invention Fig. 2 , which is integrated here, for example, in a vacuum pump, in particular a turbomolecular pump.

In the Fig. 1 The conventional vacuum pump 10 shown comprises a pump inlet 14 surrounded by an inlet flange 12 and a plurality of pump stages for conveying the gas present at the pump inlet 14 to an in Fig. 1 Pump outlet, not shown. The vacuum pump 10 comprises a stator with a static housing 16 and a rotor arranged in the housing 16 with a rotor shaft 20 mounted rotatably about an axis of rotation 18.

The vacuum pump 10 is designed as a turbomolecular pump and comprises a plurality of turbomolecular pump stages connected in series with one another with effective pumping, with a plurality of turbomolecular rotor disks 22 connected to the rotor shaft 20 and a plurality of turbomolecular stator disks 24 arranged in the axial direction between the rotor disks 22 and fixed in the housing 16 by spacer rings 26 are held at a desired axial distance from one another. The rotor disks 22 and stator disks 24 provide an axial pumping action in the direction of the arrow 30 in a scoop area 28.

The vacuum pump 10 also comprises three Holweck pump stages which are arranged one inside the other in the radial direction and have a pumping effect and are connected in series with one another. The rotor-side part of the Holweck pump stages comprises a rotor hub 32 connected to the rotor shaft 20 and two cylindrical jacket-shaped Holweck rotor sleeves 34, 36 fastened to and supported by the rotor hub 32, which are oriented coaxially to the rotor axis 18 and nested one inside the other in the radial direction. Furthermore, two cylindrical jacket-shaped Holweck stator sleeves 38, 40 are provided, which are also oriented coaxially to the axis of rotation 18 and are nested in one another in the radial direction. The pump-active surfaces of the Holweck pump stages are each formed by the radial jacket surfaces opposite each other, forming a narrow radial Holweck gap, each of a Holweck rotor sleeve 34, 36 and a Holweck stator sleeve 38, 40. It is In each case one of the pump-active surfaces is smooth, in the present case that of the Holweck rotor sleeve 34 or 36, and the opposite pump-active surface of the Holweck stator sleeve 38, 40 is structured with helical grooves around the axis of rotation 18 in the axial direction, in which the gas is propelled by the rotation of the rotor and thereby pumped.

The rotatable mounting of the rotor shaft 20 is effected by a roller bearing 42 in the area of the pump outlet and a permanent magnet bearing 44 in the area of the pump inlet 14.

The permanent magnet bearing 44 comprises a rotor-side bearing half 46 and a stator-side bearing half 48, each of which comprises an annular stack of a plurality of permanent magnetic rings 50, 52 stacked one on top of the other in the axial direction, the magnetic rings 50, 52 lying opposite one another to form a radial bearing gap 54.

Within the permanent magnet bearing 44 an emergency or catch bearing 56 is provided, which is designed as an unlubricated rolling bearing and idles without contact during normal operation of the vacuum pump and only comes into engagement with an excessive radial deflection of the rotor relative to the stator in order to make a radial stop for the To form a rotor that prevents a collision of the rotor-side structures with the stator-side structures.

In the area of the roller bearing 42, a conical spray nut 58 is provided on the rotor shaft 20 with an external diameter increasing toward the roller bearing 42, which is in sliding contact with a wiper of an operating medium reservoir comprising several absorbent disks 60 soaked with an operating medium, such as a lubricant , In operation, the equipment is opened by capillary action from the equipment storage via the wiper transfer the rotating spray nut 58 and, as a result of the centrifugal force, conveyed along the spray nut 58 in the direction of the increasing outer diameter of the spray nut 58 to the roller bearing 42, where it fulfills a lubricating function, for example.

The vacuum pump comprises a drive motor 62 for rotatingly driving the rotor, the rotor of which is formed by the rotor shaft 20. A control unit 64 controls the drive motor 62.

The turbomolecular pump stages provide a pumping action in the direction of the arrow 30 in the scoop region 28.

Fig. 2 shows a schematic diagram of an exemplary embodiment of a rotor bearing according to the invention. Fig. 3 shows a schematic partial representation of the rotor bearing according to the invention Fig. 2 , in particular the axially active radially stabilizing permanent magnet bearing is shown in more detail. Here is the in Figure 3 rotor bearing shown, for example, integrated into a vacuum pump, in particular turbomolecular pump.

The in the Fig. 2 and 3 The arrangement 66 shown for mounting a rotor 68 relative to a stator 70 is, for example, for mounting the rotor 68 of a vacuum pump 72, in particular a turbomolecular pump (cf. in particular Fig. 3 ), can be used.

The rotor bearing formed by the arrangement 66 comprises a radially stabilizing permanent magnet bearing 74 (cf. Fig. 2 ) in the area of one of the two rotor ends and a further bearing in the area of the opposite rotor end, which is designed as an axially active, radially stabilizing permanent magnet bearing 76.

For axial stabilization, the axially active, radially stabilizing permanent magnet bearing 76 comprises a stator-side bearing part 78 (cf. Fig. 3 ), which is associated with an axially movably mounted intermediate part 82 with respect to a fixed housing 80 of the stator 70 and, together with this, is axially movable relative to the stator housing 80.

The intermediate part 82 is connected via an actuator unit 84 (cf. Fig. 3 ) acted upon in order to counteract a respective axial deviation of the rotor 68 with respect to a desired position.

In addition, the arrangement or rotor bearing 66 comprises a sensor unit 86 (cf. Fig. 3 ) for measuring a respective axial deflection of the intermediate part 82 relative to the stator housing 80. Furthermore, a control device 88 is provided which is connected to the sensor unit 86 and the actuator unit 84 and by means of which the actuator unit 84 can be controlled as a function of the measured axial deflection of the intermediate part 82 is.

In this case, the actuator unit 84 can in particular be controlled via the control device 88 such that the axial deflection of the intermediate part 82 with respect to the stator housing 80 is zero on average over time.

The intermediate part 82 is inserted resiliently and damped into the stator housing 80, which is illustrated here by O-rings 90.

The actuator unit 84 can in particular comprise one or more linear actuators. One or more electromagnets and / or one or more hydraulic actuators can be used, for example. In the present case, the actuator unit 84 comprises, for example, two electromagnets 84 ′, 84 ″ for acting on the intermediate part 82 in opposite axial directions.

The sensor unit 86 for measuring a respective axial deflection of the intermediate part 82 with respect to the stator housing 80 can in particular comprise a touching sensor such as a strain gauge or the like.

A radially acting catch bearing 92, 94 can also be provided in the area of the two rotor ends. In particular, the catch bearing 92 can be designed as an axially and radially acting catch bearing in the region of the relevant rotor end provided with the axially active, radially stabilizing permanent magnet bearing 76.

With a respective axial deviation of the rotor 68 from the desired position, an axial force results which is magnetically transmitted to the stator-side bearing parts of the permanent magnet bearings 76, 76. These in turn are supported in the case of the radially stabilizing permanent magnet bearing 74 on the stator housing 80 and in the case of the axially active radially stabilizing permanent magnet bearing 76 on the intermediate part 82 suspended resiliently in the stator housing 80. As a result, the intermediate part 82 with the stator-side bearing part 78 of the axially active, radially stabilizing permanent magnet bearing is deflected relative to the stator housing 80 in accordance with the spring constant. This deflection can be measured by means of the sensor unit 86.

The relevant electromagnet 84 ′ or 84 ″ of the actuator unit 84 can be energized or energized via the control device 88 or a control electronics assigned to it, which accelerates the intermediate part 82 in the direction of rotor movement in order to accelerate this intermediate part 82 in particular to such an extent that it the rotor 68, so to speak, "overhauled", thereby exceeding the unstable point in order to then be able to build up a counterforce which brakes the rotor 68 and accelerates in the opposite direction.

An axial working point which is stable on average over time can thus be set, at which the deflection of intermediate part 82 with respect to stator housing 80 is zero on average over time.

Again Fig. 3 can be removed, the stator-side bearing part 78 arranged on the intermediate part 82 and the rotor-side bearing part 96 of the axially active radially stabilizing permanent magnet bearing 76 can each be formed by a magnet ring stack from a plurality of permanent magnet magnet rings. The magnetic rings of a respective stack can be stacked on one another in the axial direction and form an at least approximately cylindrical jacket-shaped basic shape of the respective stack. The essentially cylindrical jacket-shaped rotor stack and the substantially cylindrical jacket-shaped stator stack are arranged essentially coaxially to one another and essentially coaxially to the axis of rotation 98 of the vacuum pump 72. In the present case, the stator stack is positioned within the rotor stack, so that the essentially cylindrical outer radial surface of the rotor stack is opposite the likewise substantially cylindrical outer radial surface of the stator stack. Between the radial inner surface of the rotor stack and the radial outer surface of the stator stack or between the stator-side bearing part 78 and the rotor-side bearing part 96 of the axially active, radially stabilizing permanent magnet bearing 76, there is an at least approximately cylindrical jacket-shaped radial magnetic gap 100, which is limited by the magnetic rings.

The rotor 68 of the vacuum pump 72 comprises a rotor shaft 104 and rotor disks 106 arranged thereon. The rotor 68 can be driven, for example, by a permanent magnet motor 102. This permanent magnet motor 102 is in the present case, for example, axially between the axially and radially acting Catch bearing 92 and the axially active radially stabilizing permanent magnet bearing 76 is arranged.

The in the Fig. 2 and 3 The rotor bearing 66 according to the invention shown differs from that in FIG Fig. 1 The conventional mechanical / magnetic or hybrid rotor bearing shown is thus essentially replaced by the fact that the mechanical rolling bearing is replaced by the axially active, radially stabilizing permanent magnet bearing 76, which for axial stabilization comprises the stator-side bearing part 78, which is the intermediate part which is axially movably mounted with respect to the fixed stator housing 80 82 assigned and together with this is axially movable relative to the stator housing 80. The intermediate part 82 can be acted upon by the actuator unit 84 in the manner described above in order to counteract a respective axial deviation of the rotor 68 with respect to a desired position.

Apart from the rotor bearing arrangement according to the invention, the vacuum pump 72 or turbomolecular pump according to the invention can, for example, at least essentially again have the same structure as that in FIG Fig. 1 shown vacuum pump.

LIST OF REFERENCE NUMBERS

10

vacuum pump

12

inlet flange

14

pump inlet

16

casing

18

axis of rotation

20

rotor shaft

22

rotor disc

24

stator

26

spacer

28

adding area

30

arrow

32

rotor hub

34

Holweck rotor sleeve

36

Holweck rotor sleeve

38

Holweck stator

40

Holweck stator

42

roller bearing

44

Permanent magnetic bearings

46

half of the bearing on the rotor side

48

stator side bearing half

50

permanent magnetic ring

52

permanent magnetic ring

54

radial bearing gap

56

Emergency or catch camp

58

conical injection nut

60

absorbent disc

62

drive motor

64

control unit

66

Arrangement, rotor bearing

68

rotor

70

stator

72

vacuum pump

74

radially stabilizing permanent magnet bearing

76

axially active radially stabilizing permanent magnet bearing

78

stator side bearing part

80

stator

82

intermediate part

84

actuator

84 '

electromagnet

84 "

electromagnet

86

sensor unit

88

control device

90

O-ring

92

catch bearing acting axially and radially

94

radially acting catch bearing

96

rotor-side bearing part

98

axis of rotation

100

magnetic gap

102

Permanent magnet motor

104

rotor shaft

106

rotor disc

Claims (12)

1. An arrangement (66) for supporting a rotor (68) with respect to a stator (70), in particular for supporting the rotor (68) of a vacuum pump (72), having a radially stabilizing permanent magnet bearing (74) in the region of one of the two rotor ends and having a further bearing (76) in the region of the oppositely disposed rotor end,
   wherein the further bearing is designed as an axially active radially stabilizing permanent magnet bearing (76) which comprises, for axial stabilization, a stator-side bearing part (78) which is associated with an intermediate part (82) axially movably supported with respect to a fixed-position housing (80) of the stator (70) and which is axially movable together with said intermediate part (82) relative to the stator housing (80); and
   wherein the intermediate part (82) can be acted on via an actuator unit (84) to counteract a respective axial deviation of the rotor (68) with respect to a desired position,
   characterized in that
   a sensor unit (86) for measuring a respective axial deflection of the intermediate part (82) with respect to the stator housing (80) is provided and a control device (88) is provided which is in communication with the sensor unit (86) and with the actuator unit (84) and via which the actuator unit (84) can be controlled in dependence on the measured axial deflection of the intermediate part (82).
2. An arrangement in accordance with claim 1,
   characterized in that the actuator unit (48) can be controlled via the control device (88) such that the axial deflection of the intermediate part (82) with respect to the stator housing (80) is zero on average over time.
3. An apparatus in accordance with at least one of the preceding claims,
   characterized in that the intermediate part (82) is inserted into the stator housing (80) in a resilient and/or damped manner, in particular via O-rings (90).
4. An apparatus in accordance with at least one of the preceding claims,
   characterized in that the actuator unit (84) comprises at least one linear actuator.
5. An apparatus in accordance with at least one of the preceding claims,
   characterized in that the actuator unit (84) comprises at least one electromagnet (84') and/or at least one hydraulic actuator.
6. An apparatus in accordance with at least one of the preceding claims,
   characterized in that the sensor unit (86) for measuring a respective axial deflection of the intermediate part (82) with respect to the stator housing (80) comprises a contacting sensor.
7. An arrangement in accordance with claim 6,
   characterized in that the sensor unit (86) for measuring a respective axial deflection of the intermediate part (82) with respect to the stator housing (80) comprises a strain gauge.
8. An apparatus in accordance with at least one of the preceding claims,
   characterized in that an at least radially effective safety bearing (92, 94) is respectively additionally provided in the region of the two rotor ends.
9. An arrangement in accordance with claim 8,
   characterized in that that safety bearing (92) which is provided at the rotor end in the region of the axially active radially stabilizing permanent magnet bearing (76) is designed as an axially and radially effective safety bearing.
10. A vacuum pump (72), in particular a turbomolecular pump, comprising a rotor (68) and a stator (70), wherein the rotor (68) is supported with respect to the stator (70) by an arrangement (66) in accordance with any one of the preceding claims.
11. A vacuum pump in accordance with claim 10,
    characterized in that the vacuum pump (72) comprises a permanent magnet motor (102) as a rotary drive for the rotor (68).
12. A vacuum pump in accordance with claim 11,
    characterized in that the permanent magnet motor (102) is axially arranged between an axially and radially effective safety bearing (92) and the axially active radially stabilizing permanent magnet bearing (76).

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