EP3096020A1 - Vacuum pump - Google Patents

Abstract

The invention relates to a vacuum pump, in particular a turbomolecular pump, with a rotor which is rotatably mounted in the vacuum pump and having a portion on which a plurality of rotor blades are arranged, and a stator which axially offset from the rotor blades having the part of the rotor in one Housing the vacuum pump is arranged and has at least one stator blade. Between the rotor blades having part and the stator, a spacer element is arranged, which is adapted to keep at least one stator blade at a distance to the rotor at a bending of the stator.

Description

The present invention relates to a vacuum pump, in particular a turbomolecular pump, with a rotor which is rotatably mounted in the vacuum pump and having a portion on which a plurality of rotor blades are arranged, and a stator which is axially offset from the rotor blades having the rotor part in a housing of the vacuum pump is arranged and has at least one stator blade.

Vacuum pumps in the form of turbomolecular pumps are basically known and are used, for example, in the semiconductor industry and in physical research in order to generate a high vacuum required there. The turbomolecular pump is characterized by a rotor, also referred to as a blade rotor, whose structure is reminiscent of the rotor of a turbine. The rotor cooperates with a stator, also referred to as a blade stator, and usually rotates at such a high speed that the tangential velocity of the individual rotor blades is of a similar magnitude to the average thermal velocity of particles to be conveyed. In a vertical pumping direction from top to bottom, the majority of the particles collide with a bottom surface of an angularly pitched rotor blade. By a preferred direction of the bottom of the rotor blade in the pumping direction creates a pumping action. The portion of the turbomolecular pump that includes the blade rotor and the blade stator is generally referred to as a turbomolecular pumping stage or turbo stage.

In order to reduce a vacuum generated by the vacuum pump, i. E. To introduce gas particles into a space placed under vacuum, a pressure equalization between a vacuum pressure and a higher pressure, e.g. Atmospheric pressure generated. However, for example due to improper operation too rapid pressure equalization and thus too heavy flood process can be generated. In such a violent flooding process, there is the danger that in particular a stator made of sheet metal bends through the load of the flood process and strikes with its stator blades against the rotating rotor. Furthermore, the part of the rotor having the rotor blades may also bend, which may cause the rotor blades to strike against the stator. The contact between the rotor and the stator may cause particles to detach from the stator and / or rotor, which may damage the stator and the rotor and cause further damage to the pump.

The invention has for its object to provide a vacuum pump to which in the case of a violent flooding less damage.

The object is achieved by a vacuum pump with the features of claim 1 and in particular by the fact that between the rotor blades having part and the stator, a spacer element is arranged, which is adapted to bending of the stator, in particular as a result of a flood, the at least Keep a stator blade at a distance from the rotor.

The invention is based on the general idea, especially in turbomolecular pumps with laminated or stamped stator discs to prevent contact between the stator blades and the rotating rotor and thereby avoid damage that would be generated by a collision of the stator blades and the rotor. This is achieved by that the stator blades during a flooding operation are held axially, ie in the extension direction of the axis of rotation of the rotor, spaced from the rotor by a spacer element between the stator and the rotor is connected.

Advantageous embodiments of the invention are described in the dependent claims, the description and the drawings.

According to one embodiment, the spacer element is formed integrally with the part having the rotor blades. This facilitates the assembly of the vacuum pump and ensures a stable connection between the rotor and the spacer element.

The spacer element can be designed in the form of a ring.

This ring may be designed as a closed ring surrounding the axis of rotation of the rotor. This allows a bent stator to slide on the spacer without snagging.

In order to avoid an imbalance on the rotor, it is advantageous if the ring is arranged concentrically around the axis of rotation of the rotor and in particular has a constant cross section.

The cross section may be, for example, rectangular, triangular, semicircular or trapezoidal.

The spacer element preferably has a constant maximum height when viewed in the circumferential direction. In other words, the height of the spacer in the direction of rotation of the rotor can remain the same. This avoids that the sliding along the spacer element stator due to varying heights moves the spacer element in the axial direction and is thereby vibrated.

Advantageously, the spacer element is formed in a radially inner portion of the rotor blades having part. In this case, the rotor blades are arranged radially spaced from the spacer element and positioned so that a smooth radially inner portion of the stator can come into contact with the spacer element. As a rule, such a smooth, radially inner section is provided in the case of laminated stator disks as a so-called inner ring in order to connect the stator blades to one another on the inner circumference of the stator disk. By the above-mentioned positioning of the spacer element ensures that in a contact between the stator and rotor only a smooth surface of the stator slides along the spacer element and thereby the damage to the rotor and stator is minimized.

To further minimize damage to the stator, a contact surface of the spacer element may be rounded. Alternatively or additionally, the contact surface can be adapted from the angular position to the angular position of a part of the stator bearing against the spacer element in the bent state. In other words, the contact surface of the spacer element is aligned in space so that the stator in the bent state plan, i. flat, abuts the contact surface of the spacer element.

According to one embodiment, the rotor blades having part of the rotor is formed as a separate rotor disk. In this embodiment, a plurality of such rotor disks may be secured to a rotor shaft extending in the axial direction. For example, the rotor disks may be shrunk onto the rotor shaft. This can achieve manufacturing advantages. Alternatively, the rotor blades having part of the rotor may be integrally formed with a shaft portion of the rotor. In this embodiment, in particular a plurality of rotor blades having parts may be formed in the form of a single component. Such a rotor, in which the part having the rotor blades is formed integrally with the rotor shaft, is also referred to as a solid rotor.

For reasons of symmetry may be provided on two opposite sides of the rotor blades having part in each case a spacer element. Two opposite sides of the part, which are essentially aligned parallel to one another and whose surfaces point in opposite directions, are considered to be "opposite".

Advantageously, the stator comprises a stator disc, which is made of a sheet metal and is produced in particular by stamping. Particularly in the case of such laminated stator disks, there is the risk that the stator blades come into contact with the rotor during a flooding process. This is due to the fact that in laminated stator discs, the stator blades are positioned so that they protrude from the main plane of the stator. Consequently, the present invention is particularly advantageous when using laminated stator disks.

Specifically, the spacer may have a height that is so high that upon bending of the stator, a smooth part of the stator abuts the spacer and the stator blades of the stator are spaced from the rotor, and at the same time is so small that in normal operation no Impairment of the relative movement between the rotor and stator takes place. As a result, the damage to the vacuum pump in uncontrolled flooding and at the same time the wear during normal operation can be minimized.

Fig. 1

eine Schnittansicht einer erfindungsgemäßen Vakuumpumpe;

Fig. 2

eine Skizze, die jeweils den Erstkontaktpunkt bei einer gesägten Statorscheibe (I), bei einer geblechten Scheibe ohne Distanzelement (II) und bei einer geblechten Scheibe, die gemäß der Erfindung mit einem Distanzelement zusammenwirkt (III), darstellt;

Fig. 3

verschiedene Querschnittsformen eines Distanzelements gemäß der Erfindung.

The invention will now be described by way of a purely exemplary embodiment with reference to the accompanying drawings. Show it:

Fig. 1

a sectional view of a vacuum pump according to the invention;

Fig. 2

a sketch, each of the first contact point in a sawn stator (I), in a laminated disc without spacer (II) and a laminated disc, which cooperates according to the invention with a spacer element (III) represents;

Fig. 3

various cross-sectional shapes of a spacer element according to the invention.

In the Fig. 1 The vacuum pump shown comprises a pump inlet 10 surrounded by an inlet flange 11 and a pump outlet 12 and a plurality of process gas pumping stages for conveying the process gas at the pump inlet 10 to the pump outlet 12. The vacuum pump comprises a housing 64 and a rotor 16 arranged in the housing 64 with one the rotational axis 14 rotatably mounted rotor shaft 15th

In the present exemplary embodiment, the pump is designed as a turbomolecular pump and comprises a plurality of turbomolecular pump stages connected to the rotor shaft 15 with a plurality of radial rotor disks 66 attached to the rotor shaft 15 and stator disks 68 arranged between the rotor disks 66 and fixed in the housing 64, one rotor disk 66 and one rotor disk 66 adjacent stator disk 68 each form a turbomolecular pumping stage. The stator disks 68 are held by spacer rings 70 at a desired axial distance from each other.

While thus the in Fig. 1 shown embodiment, a vacuum pump with rotor disks 66 which are designed as separate components, is also an embodiment of the rotor 16 as a solid rotor conceivable.

The vacuum pump also comprises four radially arranged pumping stages which are connected to one another in pumping fashion in series with each other. The rotor of Holweckpumpstufen comprises a rotor shaft 15 integrally formed with the rotor hub 72 and two fixed to the rotor hub 72 and carried by this cylinder jacket Holweckrotorhülsen 74, 76, which are coaxial with the axis of rotation 14 oriented and nested in the radial direction. Furthermore, two cylinder jacket-shaped Holweckstatorhülsen 78, 80 are provided, which are also coaxial with the axis of rotation 14 oriented and nested in the radial direction. A third Holweckstatorhülse is formed by a receiving portion 132 of the housing 64, which serves in the manner described below for receiving and fixing a drive motor 20.

The pump-active surfaces of the Holweckpumpstufen are formed by the lateral surfaces, ie the radial inner and outer surfaces of the Holweckrotorhülsen 74, 76, the Holweckstatorhülsen 78, 80 and the receiving portion 132. The radially inner surface of the outer Holweckstatorhülse 78 is opposite to the radial outer surface of the outer Holweckrotorhülse 74 to form a radial Holweckspalts 82 and forms with this the first Holweckpumpstufe. The radially inner surface of the outer Holweckrotorhülse 74 faces the radial outer surface of the inner Holweckstatorhülse 80 to form a radial Holweckspalts 84 and forms with this the second Holweckpumpstufe. The radially inner surface of the inner Holweckstatorhülse 80 is opposite to the radial outer surface of the inner Holweckrotorhülse 76 to form a radial Holweckspalts 86 and forms with this the third Holweckpumpstufe. The radially inner surface of the inner Holweckrotorhülse 76 is the radial outer surface of the Receiving portion 132 with formation of a radial Holweckspalts 87 opposite and forms with this the fourth Holweckpumpstufe.

The aforementioned pump-active surfaces of Holweckstatorhülsen 78, 80 and the receiving portion 132 each have a plurality of spiral around the axis of rotation 14 around axially extending Holwecknuten, while the opposite lateral surfaces of Holweckrotorhülsen 74, 76 are smooth and the gas in the operation of the vacuum pump in drive the Holwecknuten.

For rotatably supporting the rotor shaft 15, a rolling bearing 88 in the region of the pump outlet 12 and a permanent magnet bearing 90 in the region of the pump inlet 10 are provided.

In the region of the rolling bearing 88, a conical injection nut 92 with an outer diameter increasing toward the rolling bearing 88 is provided on the rotor shaft 15. The spray nut 92 is in sliding contact with at least one scraper of a resource storage. The resource storage comprises a plurality of stacked absorbent pads 94 impregnated with a rolling bearing bearing means 88, for example a lubricant. In operation of the vacuum pump, the operating medium is transferred by capillary action from the working fluid reservoir via the scraper to the rotating spray nut 92 and due to the centrifugal force along the injection nut 92 in the direction of increasing outer diameter of the injection nut 92 to the rolling bearing 88 promoted where it is e.g. fulfills a lubricating function. The rolling bearing 88 and the resource storage are enclosed by a trough-shaped insert 96 and a cover member 98 of the vacuum pump.

The permanent magnet bearing comprises a rotor-side bearing half 100 and a stator-side bearing half 102, which each have a ring stack of several in Axial direction stacked permanent magnetic rings 104 and 106 include. The magnetic rings 104, 106 are opposed to each other to form a radial bearing gap 108, wherein the rotor-side magnet rings 104 are arranged radially on the outside and the stator magnet rings 106 radially inward. The magnetic field present in the bearing gap 108 causes magnetic repulsive forces between the magnetic rings 104, 106, which cause a radial bearing of the rotor shaft 15.

The rotor-side magnetic rings 104 are carried by a support portion 110 of the rotor shaft, which surrounds the magnet rings 104 radially on the outside. The stator-side magnet rings are supported by a stator-side support portion 112 which extends through the magnet rings 106 and is suspended from radial struts 114 of the housing 64. Parallel to the axis of rotation 14, the rotor-side magnet rings 104 are fixed in one direction by a cover element 116 coupled to the carrier section 110 and in the other direction by a radially projecting shoulder section of the carrier section 110. The stator-side magnet rings 106 are parallel to the axis of rotation 14 in one direction by a fastening ring 118 connected to the carrier section 112 and a compensation element 120 arranged between the fastening ring 118 and the magnet rings 106 and in the other direction by a support ring 122 connected to the carrier section 112 established.

Within the magnetic bearing an emergency or fishing camp 124 is provided, which runs empty during normal operation of the vacuum pump without touching and only with an excessive radial deflection of the rotor 16 engages relative to the stator in engagement to a radial stop for the rotor 16 form, which prevents a collision of the rotor-side structures with the stator-side structures. The backup bearing 124 is formed as an unlubricated rolling bearing and forms with the rotor 16 and / or the stator a radial gap, which causes the backup bearing 124 is disengaged in the normal pumping operation. The radial deflection, in which the fishing camp 124 engages is sized large enough so that the fishing camp 124 is not engaged during normal operation of the vacuum pump, and at the same time small enough so that a collision of the rotor-side structures with the stator-side structures is prevented under all circumstances ,

The vacuum pump includes the drive motor 20 for rotationally driving the rotor 16. The drive motor 20 includes a motor stator 22 having a core 38 and having one or more in Fig. 1 only schematically illustrated coils 42 which are defined in provided on the radially inner side of the core 38 grooves 38 of the core.

The armature of the drive motor 20 is formed by the rotor 16, whose rotor shaft 15 extends through the motor stator 22 therethrough. On the extending through the motor stator 22 through portion of the rotor shaft 15, a permanent magnet assembly 128 is fixed radially on the outside. Between the motor stator 22 and the portion of the rotor 16 extending through the motor stator 22, a gap 24 is arranged, which comprises a radial motor gap, via which the motor stator 22 and the permanent magnet arrangement 128 influence magnetically for transmission of the drive torque.

The permanent magnet arrangement 128 is fixed to the rotor shaft 15 in the axial direction by a fastening sleeve 126 plugged onto the rotor shaft 15. An encapsulation 130 surrounds the permanent magnet arrangement 128 on its radial outer side and seals it with respect to the intermediate space 24.

The motor stator 22 is fixed in the housing 64 by the housing-fixed receiving portion 132, which surrounds the motor stator 22 radially on the outside and supports the motor stator 22 in the radial and axial directions. The recording section 132 defines together with the rotor hub 72, an engine compartment 18 in which the drive motor 20 is received.

The engine compartment 18 has an inlet 28 arranged on one side of the intermediate space 24 and gas-conductively connected to the inner, fourth Holweckpumpstufe and an outlet 30 arranged on the opposite side of the intermediate space 24 and gas-conducting to the pump outlet 12.

The core 38 of the motor stator 22 has at its radial outer side in the in Fig. 1 On the left, a recess 34, which together with the adjacent portion of the receiving portion 132 forms a channel 32 through which the process gas delivered into the engine compartment 18 is conveyed to the gap 24 from the inlet 28 to the outlet 30.

The gas path on which the process gas passes from the pump inlet 10 to the pump outlet 12 is in Fig. 1 . 2 and 3 illustrated by arrows 26. The process gas is first pumped from the pump inlet 10 sequentially through the turbomolecular pumping stages and then sequentially through the four Holweck pumping stages. The gas exiting the fourth Holweckpumpstufe enters the engine compartment 18 and is conveyed from the inlet 28 of the engine compartment 18 through the channel 32 to the outlet 30 of the engine compartment 18 and the pump outlet 12.

Having described in the foregoing the basic structure of a turbomolecular pump, will now be discussed in more detail on the invention.

In a flooding process and a concomitant sudden increase in pressure on the high-vacuum side flows in a short time against a high flow of the arrows 26. This volume flow generates a pressure wave which deforms or bends the stator disks 68 in the direction of the high-vacuum side, ie counter to the arrows 26.

In Fig. 2 Three different variants I, II, III of a turbomolecular pumping stage are shown, each comprising a rotor disk 66 ', 66 ", 66"' and a stator disk 68 ', 68 ", 68"'. However, the skilled person will understand that, as a rule, as in Fig. 1 shown, several similar turbomolecular pumping stages are arranged in a vacuum pump. Each rotor disk 66 is connected in a rotationally fixed manner to the rotor shaft 15 and is designed to rotate together with the rotor shaft 15 about an axis of rotation 14. Each rotor disk 66 has a radially inner portion 134 and a rotor blade portion 136. The stator disks 68 also each include a radially inner portion 138 and a stator blade portion 140.

The first variant shown under I shows a sawn stator disk 68 'in its position during normal operation 68a' and the same sawn stator disk 68 'in the bent state 68b'. It can be seen that a first contact 142 'between the rotor disc 66' and the bent stator disc 68b 'between the radially inner portion 138 of the stator disc 68' and the radially inner portion 134 of the rotor disc 66 'takes place. As a result, a distance between a stator blade 144 'of the stator disk 68' and the rotor disk 66 'is maintained even in the bent state of the stator disk 68b'.

The second variant shows a laminated stator disk 68 ", likewise in its position in normal operation 68a" and in the bent state 68b. "Here, in contrast to variant I, it can be seen that the radially inner section 138 the stator disk 68 "has a smaller dimension in the axial direction than the stator blade portion 140. As a result, a first contact 142" does not take place on the radially inner portion 138 of the stator disk 68 ", but between the stator blade 144" and the rotor disk 66 ". As a result, the stator blade 144" strikes the rotating rotor disk 66 "and damage may occur to the rotor disk 66" and the laminated stator disk 68 ".

In order to prevent this, in variant III, a spacer element 146 is arranged on the rotor disk 66 '", which is also in Fig. 1 is shown. The spacer element 146 is formed on the radially inner portion 134 of the rotor disk 66 '"in the form of a slip ring encircling the rotor shaft 15. The spacer element 146 is arranged so that a first contact 142"' between a bent laminated stator disk 68b '"and the first Rotor disc 66 '"between the radially inner portion 138 of the stator disc 68''and the spacer element 146. As a result, the stator blade 144''in the bent state 68b'" of the stator disc 68 '' spaced from the rotor disc 66 '''held Stator blade 144 '"does not bear against the rotor disk 66 during a flooding operation. In normal operation 68a'", the stator disk 68 "'is at a distance from the spacer element 146 so that the spacer element 146 is not in contact with the stator disk 68'".

Fig. 3 shows several embodiments of the spacer element 146. According to one embodiment A, the cross section of the spacer element 146 in the form of a rectangle, here a square formed. In this case, the end face, which represents a contact surface 148 and points in the direction of a stator disk (not shown), is arranged at least substantially parallel to a main plane defined by the rotor disk.

Embodiment B shows a spacer element 146 with a triangular cross-section. More specifically, the cross section has the shape of an isosceles triangle whose apex points toward a stator disk, not shown. Thus, in this embodiment, the contact between the stator disk and the spacer element 146 arises at the apex of the triangular cross section.

Embodiment C shows a spacer element 146 with a semicircular cross section. The stator disk, not shown, in this embodiment lies in the bent state on a convex outer surface of the spacer element 146.

Embodiment D shows a spacer element 146 with a trapezoidal cross-sectional shape. The spacer element 146 is in this case arranged radially spaced from the rotor 16 to form a rotor disk collar 150. The height of the spacer 146, i. So the dimension in the axial direction increases in the radial direction from the inside to the outside. The resulting inclined plane forms a contact surface 148 for the stator disk, not shown. The angle of the oblique plane is preferably selected so that the stator disc in the bent state is substantially flat against it.

Embodiment E shows a spacer element 146, which forms a geometric unit together with a rotor disk collar 150. The spacer 146 is formed in the form of a survey 152, the edge of which is a contact surface 148 for a stator, not shown.

Embodiment F shows a spacer element 146, which is designed in the form of a rotor disk collar 150. A difference to embodiment E is that the motor disc collar 150 merges into the elevation 152 without an intermediate recess. The contact surface 148 is thus substantially perpendicular to the axis of rotation 14. In the embodiment shown, the rotor disk collar 150 is formed on both sides of the rotor 16.

While in the embodiments shown, the spacer element 146 is formed on individual rotor disks, which are fixed to a rotor shaft 15, can the spacer element 146 may also be formed on corresponding parts of a solid rotor.

LIST OF REFERENCE NUMBERS

10

pump inlet

11

inlet flange

12

pump outlet

14

axis of rotation

15

rotor shaft

16

rotor

18

engine compartment

20

drive motor

22

motor stator

24

gap

26

Arrows, gas path

28

inlet

30

outlet

32

channel

34

recess

38

core

42

Kitchen sink

64

casing

66

rotor disc

68

stator

68a

sawed stator disc in normal operation

68b

Sawn stator in the bent state

70

spacer ring

72

rotor hub

74, 76

Holweckrotorhülse

78, 80

Holweckstatorhülse

82, 84, 86, 87

Holweckspalt

88

roller bearing

90

Permanent magnetic bearings

92

spray mother

94

absorbent disc

96

trough-shaped insert

98

cover element

100

Rotor-side bearing half

102

stator side half

104, 106

magnetic ring

108

bearing gap

110, 112

support section

114

strut

116

cover element

118

fixing ring

120

compensation element

122

support ring

124

safety bearing

126

mounting sleeve

128

Permanent magnet assembly

130

encapsulation

132

receiving portion

134

radially inner section (rotor disc)

136

Rotor blade section

138

radially inner section (stator disc)

140

Statorschaufelabschnitt

142

Erstkontaktpunkt

144

stator

146

spacer

148

contact area

150

Rotor disc Bund

152

survey

Claims (11)

Vacuum pump, in particular turbomolecular pump, with a rotor (16) rotatably mounted in the vacuum pump and having a part (66) on which a plurality of rotor blades are arranged, and a stator (68) axially offset from the rotor blades having part (66) of the rotor is arranged in a housing (64) of the vacuum pump and has at least one stator blade (144),
characterized in that between the rotor blades containing part (66) and the stator (68) a spacer element (146) is arranged, which is adapted to bending of the stator (68b), the at least one stator blade (144) at a distance to hold the rotor (16). Vacuum pump according to claim 1,
characterized in that the spacer element (146) is formed integrally with the rotor blades having part (66). Vacuum pump according to claim 1 or 2,
characterized in that the spacer element (146) is formed as a ring. Vacuum pump according to claim 3,
characterized in that the ring is arranged concentrically about the axis of rotation (14) of the rotor (16). Vacuum pump according to claim 3 or 4,
characterized in that the spacer element (146) seen in the circumferential direction has a constant maximum height. Vacuum pump according to at least one of the preceding claims,
characterized in that the spacer element (146) is formed on a radially inner portion (134) of the rotor blade containing part (66) and arranged so that a smooth radially inner portion (138) of the bent stator (68b) with the spacer element (66) 146) comes into contact. Vacuum pump according to at least one of the preceding claims,
characterized in that a contact surface (148) of the spacer element (146) is rounded and / or adapted from the angular position to the angular position of the spacer element (146) abutting portion (138) of the bent stator (68b). Vacuum pump according to at least one of the preceding claims,
characterized in that the rotor blades having part of the rotor is formed as a separate rotor disc (66). Vacuum pump according to at least one of the preceding claims,
characterized in that on two opposite sides of the rotor blades having part (66) each have a spacer element (146) is provided. Vacuum pump according to at least one of the preceding claims, characterized in that the stator comprises a stator disc (68), which is made of a sheet metal and in particular is produced by stamping. Vacuum pump according to at least one of the preceding claims, characterized in that the spacer element (146) has a height that is sufficiently high, so that upon bending of the stator (68b), a smooth section (138) of the stator (68) on the spacer element (68). 146) and the stator blade (144) of the stator (68) spaced from the rotor (16) is held, and which is sufficiently small, so that during normal operation (68 a) no impairment of the relative movement between the rotor (16) and stator (68) takes place through the spacer element (146).

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