EP3135919B1 - Vacuum pump - Google Patents

Description

The present invention relates to a vacuum pump, in particular a turbomolecular pump, comprising a housing which encloses a suction-side housing and a housing facing away from the suction side, a stator, a rotor having a rotor shaft, a first bearing supporting the rotor shaft in the region of the suction side of the housing, and a rotor shaft in the area of the opposite side of the housing supporting another camp.

Vacuum pumps, e.g. Turbomolecular pumps are used in various fields of technology to create a vacuum necessary for a particular process. Turbomolecular pumps comprise a stator having a plurality of stator disks successive in the direction of a rotor axis and a rotor mounted rotatably relative to the stator about the rotor axis, comprising a rotor shaft and a plurality of arranged on the rotor shaft, axially successive and arranged between the stator disks rotor disks, wherein the stator disks and the rotor disks each have a pump-active structure.

For example, in turbomolecular pumps, the rotor shaft on the suction side, ie in the vacuum or high vacuum range, (UHV) usually supported by a UHV-suitable permanent magnet bearing and on the opposite side by a lubricated rolling bearing. In certain cases, the highest possible temperature should prevail on the suction side or in the high vacuum region of the vacuum pump in order to prevent gases from condensing. In contrast, the pump section with the roller bearing should be relatively cold in order to prevent that provided for lubricating the bearing lubricant, in particular oil, his loses lubricating properties. In most cases, however, now consist of the suction-side housing portion and the ball bearing containing opposite housing portion of a relatively high thermal conductivity possessed aluminum or other material with good thermal conductivity.

In the EP 1 508 700 A2 a turbomolecular pump is described, the housing comprises a suction-side housing portion, a facing away from the suction side housing portion and an intermediate housing portion. Between the central housing portion and the housing portion facing away from the suction side of the heat insulating recesses are provided, wherein a vacuum applied to the recess is completed to the outside and another recess is attached from the outside and is in communication with the atmosphere. Although the recesses result in a reduced heat flow path in cross section. In this case, however, one of the recesses is displaced radially inwardly relative to the other and arranged at a radial distance from the inner circumference of the housing such that regions of the housing jacket remain radially inside and outside this recess, via which an axial heat flow on both sides of the recess is made possible ,

In the JP 2010 025 122 A1 there is described a composite molecular pump with integrated thread groove pump which includes a bearing housing disposed in the vacuum pump and provided at its outer periphery with a heat shield disposed in a corresponding small recess. Between the heat shield and an inner stator section, an exhaust passage is formed. In the base of the bearing housing, a recess is also provided, which opens at the outer periphery of the base.

In the EP 0 408 791 A1 a friction pump is described, whose housing comprises a first housing part and a second housing part. The first housing part comprises an outer cylinder with a flange, via which the friction pump can be connected either directly or via an attachment flange to the recipient to be evacuated. The second housing part serves to hold the rotor and the stator of the drive motor. In this case, the second housing part is provided with holes through which a purge gas can be introduced into the space leading to the rotor. The flushing gas flow is intended to prevent gases laden with dust particles from entering the engine and storage space. A cylinder portion of the housing part is guided in a further cylinder portion of the housing part. For this purpose, two relatively narrow Passführungsbereiche are provided in which are provided in corresponding grooves recessed sealing rings. The two cylinder sections are spaced apart by a gap to maintain a temperature gradient between these two sections. This is intended to prevent the bearing and motor parts provided in the second housing part from being exposed to excessive thermal load when the stator parts are heated in order to prevent the formation of dust.

There is now the problem
the two requirements mentioned above
to meet as possible a high-temperature suction-side high-vacuum area and after a possible relatively cold opposite area of the vacuum pump as possible without much energy.

The invention has for its object to provide a vacuum pump, in particular turbomolecular pump, of the type mentioned, with which the aforementioned problem is eliminated. It should be ensured with the least possible effort and the least possible use of energy as large a temperature difference between the suction-side housing portion and the opposite housing portion of the vacuum pump.

The object is achieved by a vacuum pump, in particular turbomolecular pump, with the features of claim 1. Preferred embodiments of the vacuum pump according to the invention will become apparent from the dependent claims, the present description and the drawings.

The vacuum pump according to the invention, in particular turbomolecular pump, comprises a housing enclosing a suction side and a part facing away from the suction side, a stator, a rotor with a rotor shaft, a first bearing supporting the rotor shaft in the region of the suction side of the housing and another rotor shaft in the region the opposite side of the housing supporting rolling bearing. In this case, to increase the thermal resistance between the suction-side housing section and a housing section containing the rolling bearing, the part of the housing facing away from the suction side is provided with material recesses which are introduced into the housing a labyrinthine, extended by several changes in direction heat flow path in the housing results.

Due to the inventive design a relatively large temperature difference between the suction-side housing portion and the opposite housing portion of the vacuum pump is achieved at a very low cost and use of energy through an extended heat flow path in the housing. Thus, the suction-side region or the high-vacuum region of the vacuum pump can be relatively strongly tempered, for example to avoid condensation of toxic gases, without the corresponding housing section being heated accordingly, in particular in the region of a bearing of the rotor shaft located there. The opposite housing section must therefore be cooled at least less or not at all. It is thus ensured with relatively little effort while minimizing the use of energy for cooling the opposite housing section, that a rolling bearing contained in the opposite housing section can be kept sufficiently cool, so that the lubrication required for this bearing lubricant maintains its lubricating properties. The labyrinth-type heat flow path, which is produced by the material recesses in the pump housing according to the invention and is extended by a plurality of changes in direction, results in a type of thermal barrier between the suction-side housing section and the opposite housing section.

The remote from the suction side, provided with the material recesses part of the housing generally has a limited by an inner wall central bore whose central axis coincides in particular with the axis of rotation of the rotor shaft. In this case, according to a preferred practical embodiment of the vacuum pump according to the invention, the material recesses are introduced both from the inner wall and from the outer peripheral surface of the housing into the housing.

Preferably, viewed in the axial direction of the housing, the material recesses are alternately introduced into the housing starting from the inner wall and starting from the outer peripheral surface of the housing. In this case, the material recesses can mesh in particular like a comb.

At least one and preferably a plurality of material recesses may extend at least partially in the radial direction. It is ensured in particular by a vote of the radial depth of the or each material recess on the housing diameter or on the wall thickness of the housing that no excessive mechanical weakening of the housing takes place and the so-called "crash safety" of the housing or the pump is guaranteed.

The radial thickness or wall thickness of the portion of the housing provided with the material recesses is expediently greater than three times the radial dimension or depth of a radially extending material recess.

It is also of particular advantage if a radially extending material recess introduced into the housing from the outer peripheral surface of the housing has a radial dimension or depth which ends at a diameter of the part of the housing provided with the material recesses which is smaller than 0, 75 times the outer diameter of this housing part and is greater than 1.1 times the inner diameter of this housing part.

The material recesses may extend at least partially in the axial direction. In this case too, it will again be ensured that no excessive mechanical weakening of the housing takes place. Also conceivable is a combination of radially extending and axially extending material recesses. The extension of the material recesses can eg run obliquely to the radial direction and / or axial direction and, for example, also have a skewed course with respect to the longitudinal axis of the housing or the axis of rotation of the rotor shaft.

The width and / or height measured transversely to a longitudinal and / or circumferential extent of e.g. formed as a recess or slot material recess, i. in a radially extending, lying in an axial plane slot, for example, its axial height or clear width, is preferably in a range of about 1mm to 6mm, but may in principle be less than 1mm or greater than 6mm.

According to a preferred practical embodiment of the vacuum pump according to the invention, the material recesses are at least partially introduced in the form of recesses, slots and / or holes in the housing.

According to an advantageous embodiment of the vacuum pump according to the invention at least one material recess is provided as completely, partially or in sections extending around a longitudinal axis of the housing around the recess or slot.

Such a groove or slot may e.g. be made by means of a disc cutter or the like.

In a comparatively simple case, the material recesses may at least partially form free spaces filled only with air or gas.

In other cases, however, it may be advantageous if at least partially a heat-insulating solid is introduced into the material recesses. In this case, the solid in question expediently has a lower thermal conductivity than the material of the housing and as air or gas.

In the area of the suction-side housing section, a heating device can be provided. Preferably, such a heating device comprises at least one heating tape or the like.

Fig. 1

eine schematische Darstellung einer beispielhaften Ausführungsform einer Vakuumpumpe, bei der die Erfindung anwendbar ist, und

Fig. 2

eine schematische Darstellung des von der Ansaugseite abgewandten, mit Materialaussparungen versehenen Teils des Gehäuses einer beispielhaften Ausführungsform einer erfindungsgemäßen Vakuumpumpe.

The invention will be explained in more detail below with reference to an embodiment with reference to the drawing; in this show:

Fig. 1

a schematic representation of an exemplary embodiment of a vacuum pump to which the invention is applicable, and

Fig. 2

a schematic representation of the side facing away from the suction, provided with material recesses part of the housing of an exemplary embodiment of a vacuum pump according to the invention.

In the Fig. 1 shown vacuum pump 10 comprises a pump inlet 14 surrounded by an inlet flange 12 and a plurality of pumping stages for conveying the gas present at the pump inlet 14 to a in Fig. 1 not shown pump outlet. 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 rotatably mounted about a rotation axis 18.

The vacuum pump 10 is designed as a turbomolecular pump and comprises a plurality of pump-connected with each other in series turbomolecular pumping stages with a plurality of connected to the rotor shaft 20 turbomolecular rotor disks 22 and a plurality of axially disposed between the rotor disks 22 and fixed in the housing 16 turbomolecular stator disks 24 by spacer rings 26 at a desired axial distance held each other. The rotor disks 22 and stator disks 24 provide in a scooping region 28 an axial pumping action directed in the direction of the arrow 30.

The vacuum pump 10 also comprises three Holweck pumping stages which are arranged one inside the other in the radial direction and which are pumpingly connected to one another in series. The rotor-side part of the Holweck pump stages comprises a rotor hub 32 connected to the rotor shaft 20 and two cylinder shell-shaped Holweck rotor sleeves 34, 36 fastened to and supported by the rotor hub 32, which are oriented coaxially with the rotor axis 18 and are nested in the radial direction. Furthermore, two cylindrical jacket-shaped Holweck stator sleeves 38, 40 are provided, which are also oriented coaxially to the rotor axis 18 and are nested in the radial direction. The pump-active surfaces of the Holweck pump stages are each formed by the radial lateral surfaces of a Holweck rotor sleeve 34, 36 and a Holweck stator sleeve 38, 40 opposite each other, forming a narrow radial Holweck gap. In each case, one of the pump-active surfaces is smooth, in the present case, for example, the Holweck rotor sleeve 34 and 36, wherein the opposite pump-active surface of the respective Holweck stator 38 and 40 a structuring with helical about the rotation axis 18 around in the axial direction extending grooves, in which the gas is driven 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 region of the pump outlet and a permanent magnet bearing 44 in the region 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 comprising a ring stack of a plurality of axially stacked permanent magnetic rings 50, 52, wherein the magnetic rings 50, 52 facing each other to form a radial bearing gap 54.

Within the permanent magnet bearing 44, an emergency or fishing camp 56 is provided, which is designed as an unlubricated rolling and idle in normal operation of the vacuum pump without touching and passes only at an excessive radial deflection of the rotor relative to the stator into engagement to a radial stop for to form the rotor, which prevents a collision of the rotor-side structures with the stator-side structures.

In the region of the rolling bearing 42, a conical injection nut 58 is provided on the rotor shaft 20 with an outer diameter increasing towards the rolling bearing 42, which with a scraper one more with a resource such. a lubricant, soaked absorbent disks 60 in operative resource storage is in sliding contact. In operation, the operating means is transferred by capillary action from the working fluid reservoir via the scraper to the rotating injection nut 58 and due to the centrifugal force along the injection nut 58 in the direction of increasing outer diameter of the injection nut 58 is conveyed to the rolling bearing 42, where it is e.g. fulfills a lubricating function.

The vacuum pump includes a drive motor 62 for rotatably driving the rotor whose rotor is formed by the rotor shaft 20. A control unit 64 controls the drive motor 62.

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

Fig. 2 shows a schematic representation of the side facing away from the suction, provided with material recesses 66, 68 part of the housing 16 of an exemplary Embodiment of a vacuum pump 10 according to the invention, which is in particular a turbomolecular pump in the Fig. 1 represented type can act.

Correspondingly, the vacuum pump 10 according to the invention also comprises a housing 16, a stator and a rotor, not shown here, with a rotor shaft which is supported by a first bearing provided in the region of the suction side of the housing 16 and a further bearing provided in the region of the opposite side of the housing 16 is. It may be in the two camps not shown here as shown in FIG Fig. 1 For example, again act around a suction-side permanent magnet bearing and a provided on the opposite side bearings. This rolling bearing can eg in the field of in Fig. 2 be shown central bore 76 arranged.

According to the invention, in order to increase the thermal resistance between the suction-side housing section and the housing section containing the rolling bearing, the part 70 of the housing 16 facing away from the suction side is provided with material recesses 66, 68 which are inserted into the housing 16 in such a way that they become labyrinth-like, by a plurality of changes in direction extended heat flow path 72 results.

Thereby, during the operation of the pump, a relatively large temperature difference between the suction-side housing portion and the opposite housing portion of the vacuum pump 10 can be maintained. As already mentioned, the invention is for example in a vacuum pump in the Fig. 1 shown applicable. Due to the material recesses according to the invention, the suction-side housing section of the vacuum pump can be correspondingly tempered to avoid condensation of gases, without thereby also heating the opposite housing section 70 of the pump containing the further bearing. The rolling bearing containing housing portion 70 can thus be kept sufficiently cold with minimal cooling or possibly even without cooling, to ensure that the oil required for lubrication of the bearing retains its lubricating properties. Accordingly, the energy required hitherto for cooling is at least reduced.

The side facing away from the suction, provided with the material recesses 66, 68 part 70 of the housing 16 has a limited by an inner wall 74 central bore 76. In this case, the material recesses 66, 68, as in the example of Fig. 2 shown, both starting from the inner wall 74 and starting from the outer peripheral surface 78 of the housing 16 may be introduced into the housing 16.

The material recesses 66, 68 can, as in the Fig. 2 shown, in the axial direction of the housing 16 viewed in particular alternately starting from the inner wall 74 and starting from the outer peripheral surface 78 of the housing 16 may be introduced into the housing 16. As also shown, the material recesses 66, 68 in this case, in particular comb-like mesh.

In principle, the material recesses 66, 68 may extend at least partially in the radial direction and / or at least partially in the axial direction. In this case, for example, a combination of extending in the radial direction and extending in the axial direction material recesses 66, 68 conceivable. I'm in the Fig. 2 In the case illustrated, the material recesses 66, 68 each extend in the radial direction, that is, they lie in different height planes with respect to the axis of rotation 18 of the rotor shaft, not shown.

The material recesses 66, 68 may be introduced into the housing 16 at least partially in the form of recesses, slots and / or bores. there For example, at least one material recess 66, 68 can be provided as a recess or slot extending completely around the axis of rotation 18. In the example of Fig. 2 Both recesses 66, 68 are each formed as such a recess or slot.

While in the presentation according to Fig. 2 the facing away from the suction side portion 70 of the housing 16 is provided only with two successive material recesses 66, 68 in the axial direction, more than two material recesses may be introduced into these facing away from the suction side portion 70 of the housing 16. In the latter case, the material recesses in the axial direction of the housing 16 can in particular also be alternately introduced, starting from the inner wall 74 and starting from the outer circumferential surface 78 of the housing 16, into the housing 16 and intermesh in a comb-like manner.

The material recesses 66, 68 can at least partially form only free spaces filled with air or gas, as shown in FIG Fig. 2 is shown in the recess 68 introduced from the outside. As in Fig. 2 in the other, introduced from the inside recess 66, however, at least partially, a heat-insulating solid may be introduced into the material recesses, which expediently higher thermal insulation than air or gas and as the material of which the housing 16 consists. The housing material is in particular aluminum.

The radial depths into which the in Fig. 2 shown recesses 66, 68 each are shown purely by way of example and are selected in concrete applications depending on eg the wall thickness of the housing portion 70 and the ratio of the inner diameter in the bore 76 and the outer diameter of the housing portion 70, in each case such that the "crash safety" of the pump remains guaranteed. Regarding possible Dimensions of the recesses 66, 68 is hereby also referred to the introduction part.

Incidentally, the vacuum pump 10 according to the invention can be designed, for example, as described with reference to FIG Fig. 1 has been described. In addition, a heating device may be provided in the region of the suction-side housing section. Such a heater may include, for example, at least one heater band or the like.

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

Rolling

44

Permanent magnetic bearings

46

Rotor-side bearing half

48

stator side half

50

permanent magnetic ring

52

permanent magnetic ring

54

radial bearing gap

56

Emergency or fishing camp

58

conical spray nut

60

absorbent disc

62

drive motor

64

control unit

66

material cut

68

material cut

70

remote from the suction side of the housing

72

Heat flow path

74

inner wall

76

central hole

78

Outer circumferential surface

Claims (13)

1. A vacuum pump (10), in particular a turbomolecular pump, having a housing (16) which comprises a suction-side housing section and a part (70) remote from the suction side; having a stator; having a rotor with a rotor shaft; having a first bearing supporting the rotor shaft in the region of the suction side of the housing (16); and having a further rolling element bearing supporting the rotor shaft in the region of the oppositely disposed side of the housing, wherein the part (70) of the housing (16) remote from the suction side is provided with material cut-outs (66, 68) to increase the thermal resistance between the suction-side housing section and a housing section including the rolling element bearing, characterized in that the material cut-outs (66, 68) are introduced into the housing (16) in such a manner that a labyrinth-like heat flow path (72) extended by a plurality of direction changes is produced in the housing (16).
2. A vacuum pump in accordance with claim 1,
   characterized in that the part (70) of the housing (16) remote from the suction side and provided with the material cut-outs (66, 68) has a central bore (76) bounded by an inner wall (74); and in that the material cut-outs (66, 68) are introduced into the housing (16) both starting from the inner wall (74) and starting from an outer peripheral surface (78) of the housing (16).
3. A vacuum pump in accordance with claim 2,
   characterized in that the material cut-outs (66, 68) are introduced into the housing (16) in an alternating manner starting from the inner wall (74) and starting from the outer peripheral surface (78) of the housing (16), viewed in an axial direction of the housing (16).
4. A vacuum pump in accordance with claim 3,
   characterized in that the material cut-outs (66, 68) engage into one another in the manner of a comb.
5. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that at least one material cut-out (66, 68) extends at least partly in a radial direction.
6. A vacuum pump in accordance with claim 5,
   characterized in that the radial wall thickness of the part (70) of the housing (16) provided with the material cut-outs (66, 68) is larger than three times the depth of a radially extending material cut-out.
7. A vacuum pump in accordance with claim 5 or claim 6,
   characterized in that a radially extending material cut-out (68) introduced into the housing (16) starting from the outer peripheral surface (78) of the housing (16) has a depth which ends at a diameter of the part (70) of the housing (16) provided with the material cut-outs (66, 68) which is smaller than 0.75 times the outer diameter and larger than 1.1 times the inner diameter of the part (70) of the housing (16) provided with the material cut-outs (66, 68).
8. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that the material cut-outs (66, 68) extend at least partly in the axial direction.
9. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that at least some of the material cut-outs (66, 68) are introduced into the housing (16) in the form of incisions, slits and/or bores.
10. A vacuum pump in accordance with at least one of the preceding claims,
    
    characterized in that at least one material cut-out (66, 68) is provided as an incision or a slit extending completely, partly or sectionally about a longitudinal axis of the housing (16).
11. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that at least some of the material cut-outs (66, 68) form free spaces filled only with air or gas.
12. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that a thermally insulating solid is at least partly introduced into the material cut-outs (66, 68).
13. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that a heating device is provided in the region of the suction-side housing section.

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