EP2565463B1 - Vacuum pump - Google Patents

Description

The invention relates to a vacuum pump with a rotor according to the preamble of claim 1, a method for manufacturing a rotor according to the preamble of claim 10 and a section for a rotor according to the preamble of claim 15.

Vacuum pumps exploit various physical effects to produce pressure differentials. One such effect is the momentum transfer to gas molecules by a rapidly moving component. A special embodiment provides a rotating sleeve, which cooperates with a stationary, coaxially arranged stator sleeve. If this stator sleeve provided with thread-like channels and the pumping stage used in the molecular pressure range, is generally spoken of a Holweckstufe.

The vacuum capability of a Holweck stage depends, among other things, on the speed of the sleeve and the shape of the channels. An improvement of the vacuum technical efficiency is in the DE 196 32 375 presented in which a plurality of coaxial with each other and in the gas stream parallel to each other, rotating sleeves are used.

Another way to increase performance is speed. As the speed increases, the load on the sleeve increases due to inertial forces. In order to achieve a small deformation of the sleeve, are made possible by the vacuum technically advantageous narrow column, provides EP 1 408 237 A1 a sleeve of carbon fiber reinforced material. Similar devices are known from GB 2 420 379 A and US Pat. No. 6,419,444 B1 ,

The technical problem underlying the invention is to further increase the performance of a vacuum pump of the type described.

This technical problem is solved by a section having the features of claim 1, a vacuum pump having the features of claim 2 and a method having the features of claim 11. The dependent claims 3 to 10 and 12 to 15 indicate advantageous developments of the invention.

The vacuum pump according to the invention with a rotor, which at least a portion of a fiber composite material with at least one fiber direction, is characterized in that the section at least one helical arranged groove and fibers of the fiber composite material are aligned such that at least a portion of the fibers is aligned with the fiber direction parallel to the groove.

For manufacturing reasons, not all fibers lie exactly parallel with a fiber direction which is aligned parallel to the groove. Characterized in that at least a part of the fibers is aligned with the fiber direction such that the fiber direction is aligned substantially parallel to the groove, one obtains the required stability.

This means that the fiber direction is aligned substantially parallel to the groove.

Advantageously, the section has at least one helically arranged groove and the fiber direction is aligned parallel to the groove, so that the section resists the action of centrifugal forces during operation of the vacuum pump.

It has been found that a groove on a section of a rotor improves performance with respect to vacuum data, for example, increases compression. By aligning the groove and fiber layer together a high strength of the section is achieved. Due to the orientation, long fiber lengths in the rotor are also possible adjacent to the groove, which also results in high strength at these points. A high strength brings a long life with it, also allows a fast rotation of the rotor and thus an improvement in the performance of the vacuum generation. The low expansion of fiber composite materials under applied centrifugal forces allows close Column between section and associated stator, which also brings an improvement in performance.

According to a particularly preferred embodiment of the invention, the section comprises a sleeve. This means that the portion having at least one helically arranged groove is formed as a sleeve. This sleeve-like construction is used in particular Holweckpumpstufen.

A further advantageous embodiment of the invention provides that on an inner side of the sleeve, an inner groove and on an outer side of the sleeve, an outer groove are provided. This structure is achieved in that a further inner layer is disposed on an inner circumferential surface of the sleeve. By this additional layer, the stability of the sleeve is significantly increased.

A further advantageous embodiment of the invention provides that the groove extends completely over an axial extent of the section.

This is the best way to increase the pumping capacity.

According to a further particularly preferred embodiment of the invention, a wrap angle of the groove is more than 360 °. As a result, a very high stability of the sleeve is achieved.

According to a further advantageous embodiment of the invention, it is provided that the section comprises at least a first and a second layer, wherein the groove is arranged in one of the layers. By this construction it is achieved that the groove is arranged in a layer which reinforces the sleeve. The groove is not taken from the material of the sleeve, so that the stability of the sleeve is increased by the further layer. The groove in the layer ensures that the pumping power is also improved.

A further advantageous embodiment of the invention provides that the first layer comprises a first matrix and the second layer comprises a second matrix. The fibers of the fiber composite material are arranged in the matrix. The fibers are thus in a first fiber direction. The fibers forming the sleeve are substantially parallel to a terminal edge. This ensures that centrifugal forces occurring during rapid rotation thus generate forces acting essentially along the grain direction, so that the sleeve can withstand them very well.

The second layer advantageously has a second matrix. This makes it possible to allow the fibers forming a projection on the sleeve to extend at an acute angle to the terminal edge. As a result, the stability of the sleeve, that is the section is significantly increased.

Advantageously, the groove has a first groove portion and a second groove portion with mutually different geometries. This embodiment is advantageous in pumps with a gas inlet and two gas outlets. In this embodiment, since the conveying direction of the grooves is formed opposite and directed away from the gas inlet, it is advantageous to provide two groove sections, which have an opposite direction of rotation. This means that the groove sections have different geometries from each other.

According to a further advantageous embodiment of the invention, a groove running around the rotor is provided between the first and the second groove portion. Where the grooves of the opposing groove portions collide, the groove encircling the rotor is provided to ensure that the gas impinging from the gas inlet on the circumferential groove is conveyed in the direction of the two spirally formed grooves.

The invention further relates to a method for manufacturing a rotor of a vacuum pump, which comprises a sleeve in which the sleeve is wound from a fiber material having a fiber direction and the fiber material is embedded in a plastic matrix to form a fiber composite, which is characterized in that the fiber direction is wound at an angle to a terminal edge of the sleeve and a groove aligned with the fiber direction is formed. Ideally, the groove is formed parallel to the fiber direction.

This design ensures that the section resists the action of centrifugal forces during operation of the vacuum pump.

An advantageous embodiment of the method provides that the shaping of the groove comprises a milling along the fiber direction. This way of making the groove is relatively easy.

According to an alternative method, it is provided that the shaping of the groove takes place by winding the fiber material onto a negative mold. This ensures that the fiber material is not damaged on the one hand by a milling operation, on the other hand, this is a material-saving way of production, since the grooves are formed by the winding and thus later no material must be removed.

A particularly preferred embodiment of the method according to the invention provides that a first layer with a first fiber direction and a second layer with a second fiber direction are wound and the groove is formed in at least one of the layers. This embodiment has the advantage that the sleeve is very stable, since on the one hand the different layers are formed and on the other hand, the fiber directions differ from each other. The deviation means that, in the ideal case, an acute angle is included between the fiber direction of the first layer and the fiber direction of the second layer.

A further advantageous embodiment of the invention provides that the groove is formed with a first groove portion and a second groove portion with mutually different geometries. This embodiment is particularly advantageous in dual-flow pumps having a gas inlet and two gas outlets. In these pumps, it is necessary that the grooves of the two sections are arranged in opposite directions to each other.

According to the invention, furthermore, a section for a rotor of a vacuum pump is provided, which comprises a fiber composite with a fiber direction, which is characterized in that the section has a groove and fibers of the fiber composite are aligned such that at least a portion of the fibers is aligned with the fiber direction parallel to the groove. This ensures that the section resists the action of centrifugal forces during operation of the vacuum pump.

Fig. 1

einen Längsschnitt durch eine Vakuumpumpe mit einem Rotor, welcher eine Hülse aufweist;

Fig. 2

einen Schnitt durch einen Teil der Hülse zur Verdeutlichung der Lage von Nut und Faserrichtung;

Fig. 3

einen Schnitt durch eine Hülse mit innerer, äußerer und Umfangsnut;

Fig. 4

eine Seitenansicht auf eine Negativform;

Fig. 5

einen Querschnitt durch die Negativform zur Herstellung einer Hülse mit innerer Nut und Wickeln der Nutstege;

Fig. 6

einen Querschnitt durch die Negativform und Wickeln der mittleren Schicht;

Fig. 7

einen Längsschnitt durch eine doppelflutige Vakuumpumpe gemäß zweitem Beispiel;

Fig. 8

einen Rotor in Seitenansicht in einer Weiterbildung;

Fig. 9

einen Verlauf von Kompression über Ausstoßdruck zur Darstellung eines erreichten Vorteiles.

Reference to an embodiment and its developments, the invention will be explained in more detail and the representation of its benefits to be deepened. Show it:

Fig. 1

a longitudinal section through a vacuum pump with a rotor having a sleeve;

Fig. 2

a section through a part of the sleeve to illustrate the position of the groove and fiber direction;

Fig. 3

a section through a sleeve with inner, outer and circumferential groove;

Fig. 4

a side view of a negative mold;

Fig. 5

a cross section through the female mold for producing a sleeve with an inner groove and winding the Nutstege;

Fig. 6

a cross section through the negative mold and winding the middle layer;

Fig. 7

a longitudinal section through a double-suction vacuum pump according to the second example;

Fig. 8

a rotor in side view in a development;

Fig. 9

a course of compression over ejection pressure to represent an advantage achieved.

A longitudinal section through a vacuum pump shows Fig. 1 , A housing 2 has an inlet 4 through which gas enters the vacuum pump. This is ejected after compression by the pump-active elements through an outlet. 6

In the housing 2 is a rotor 12 which is rotatably supported by a permanent magnet bearing 8 and a rolling bearing 10. Alternative bearings include active magnetic bearings and gas bearings. A drive 18 rotates it about an axis of rotation 310, whereby the speed is measured according to the pumping principles used and in the case of molecular pumping it is several tens of thousands of revolutions per minute. A turbomolecular pump section 14 may be provided, a molecular pumping section 16 is provided, the latter downstream of the gas stream and compressed to higher pressures.

Part of the rotor 12 is a section 22 belonging to the molecular pumping section 16 which comprises a hub 20 and a sleeve 24 fastened to the hub 20. Furthermore, the section 22 comprises at least one web 28 extending in a helical manner on the outer surface of the sleeve. Between the webs 28 of adjacent turns there remains at least one helical groove 30 with a groove depth T, wherein between web 28 and a terminal edge 26 of the sleeve 24 is an acute angle 312. This groove 30 or plurality of grooves 30 together with a stator 40 generates a pumping action. The stator 40 may have a smooth inner circumferential surface 42 or have on this helical grooves.

In Fig. 2 is the structure of the section in the area of the dashed box off Fig. 1 shown in a partially sectioned, perspective partial view.

A first layer 50 comprises a fiber composite having fibers 60 embedded in a first matrix 62. The fibers 60 lie in a first fiber direction 314. This layer 50 forms the sleeve 24, therefore, the fibers lie substantially parallel to the end edge 26. With fast rotation occurring centrifugal forces thus substantially along the fiber direction 314 acting forces, so that the sleeve 24th can resist this very well.

A second layer 52 is bonded to the first layer 50 and includes a fiber composite having fibers 60 embedded in a second matrix 64. The fibers 60 of this layer 52 are mostly oriented in the angle 312 to the end edge 26, which also web 28 and end edge 26 together. In this way, a fiber direction 316 is aligned with the groove 30 such that the portion resists the action of centrifugal forces during operation of the vacuum pump. The web 28 loading centrifugal forces mainly have a force component along the fiber direction 316 of the second layer 52. A high stability is achieved when the wrap angle is more than 360 °. It is advantageous to carry out the winding over the entire axial length of the web 28.

The fiber composite material can be a carbon fiber composite, CFRP, since it can counteract the occurring forces sufficiently well. The temperature expansion and chemical resistance are also advantageous when used in vacuum pumps.

The groove depth T can correspond to a complete layer thickness S. A higher strength is achieved if it is slightly lower, ie T <S applies.

A development of the section is in a cut in Fig. 3 shown.

The portion shown there has three layers 50, 52 and 54. Layer 50 is the middle of the three layers and forms a supporting sleeve. On the outer surface, the layer 52 is provided, the helical groove 30 and web 28, as shown Fig. 2 described, owns.

On an inner circumferential surface of the layer 50, the third layer 54 is arranged. This layer 54 is constructed in terms of fiber layer and matrix according to the aspects of the second layer 52. It has a first inner groove 32 and a second inner groove 36 which have a different pitch. This is accomplished by having a first land 34 forming a first angle 320 with the end edge 26 and a second land 38 forming a second angle 322 with the end edge 26, where first and second angles 320, 322 are different. The sense of rotation of the helical grooves in the layers 52 and 54 may be the same or opposite.

The section of the rotor 12 is made after Fig. 1 and Fig. 2 and the outer layer 52 of the section Fig. 3 by first forming the first layer 50. This is created by winding fibers in such a way that they are mostly in the circumferential direction. These are embedded in a matrix. The second and outer layers 52 are now formed by winding fibers at an angle 320, 322 to the final edge 26 of the first layer 50 on the first layer 50 and then also embedded in a matrix. It is now possible to leave free space between fibers, that is to wind only the webs 28 in the second layer 52. It is more advantageous to provide a continuous second layer 52 in which, after curing, a groove 30 is pierced such that the angle 320, 322 corresponds to the end edge 26 substantially at the angle in which the fibers of the second layer 52 on the first layer 50 were wound. An advantage of this method is that the groove depth can be easily varied. For example, a deeper groove may be formed at one axial end of the portion than at the opposite axial end of the portion. This is desirable in terms of vacuum performance when the less deep groove end operates at the higher pressure range. In the area of the less deep groove, the second layer 52 is not completely removed and at the deepest point of the groove, the groove depth reaches at most the value of the layer thickness S. In this way, particularly high resistance to centrifugal forces is maintained.

It can groove depth T or groove width or both change over the length of the groove 30, thereby advantageously adapted to the geometry of the groove 30 to the working pressure range and the performance of the pump can be improved.

The preparation of the grooves on the inner circumferential surface of the sleeve is based on the 4 to 6 be explained in more detail.

A negative mold 70 has a cylindrical portion, on the lateral surface of a helical shape groove 72 is introduced. Ribbon-like fiber material 74 is now wound in this molding groove 72, so that the molding groove 72 is gradually filled up. Fig. 5 shows a half-filled state in cross section. When the forming groove 72 is filled and the matrix is created, the third layer 54 is finished. Now, fibers 76 are wound around the outer surface itself, cf. Fig. 6 , and so made the layer 50.

The molding groove 72 may be formed as a multi-thread helix.

If only the mold grooves 72 are filled and then the jacket surface is wound, a sleeve 24 is created which has a groove only on the inside. This creates a very stable structure.

After the completed winding process, the female mold 70 is removed by unscrewing from the sleeve 24 produced.

The vacuum technical efficiency of the arrangement is based on the Fig. 9 be occupied. In it, the pressure ratio between the inlet and outlet in the absence of gas flow, the so-called idle compression over represented the discharge pressure. The curve 300 shows a conventional arrangement in which only one stator has a helical groove, as used for example in so-called Holweckpumpstufen. The curve 302 shows an arrangement with a groove on the rotor. The idle compression is significantly increased.

The use of the invention is not limited to the case shown so far.

In Fig. 7 a double-flow vacuum pump is shown in section. It has a housing 202 which is equipped with a gas inlet 204 and two gas outlets 206. The gas outlets 206 may be combined by an inner channel provided in the housing 202. A rotor 212 is rotatably mounted in bearings 208 and 210 and is driven by a drive 218. The rotor 212 has a section with a sleeve 224, on the outer circumferential surface of which are formed two grooves 230a and 230b according to the above-described method. The conveying direction of the grooves 230a, 230b is opposite and directed away from the gas inlet 204, as the arrows in FIG Fig. 7 clarify. The grooves 230a, 230b have an opposite direction of rotation. The grooves on the portion cooperate with stator-side grooves 242a and 242b, which are also helically designed in opposite directions of rotation. The grooves 230a, 230b of the sleeve 224 are arranged opposite the stator-side grooves 242a, 242b.

Shows another design point of view Fig. 8 on. A portion 222 'has a helical groove having a first groove portion 250 and a second groove portion 254. The geometries, in particular the cross sections, of the groove sections 250, 254 are different. Thus, the first groove portion 250 has a semicircular cross section and the second groove portion 254 has a triangular cross section. Between the groove portions 250, 254, a circumferential groove 260 is provided. The cross sections allow adaptation to the pressure region in which the respective groove section is to act preferentially. Alternatively or additionally, the geometries may differ with respect to the pitch of the helix. The circumferential groove portion may be provided at the transition point between different flow areas.

reference numerals

2

casing

4

inlet

6

outlet

8th

Permanent magnetic bearings

10

Rolling

12

rotor

14

turbomolecular pump section

16

molecular pump section

18

drive

20

hub

22

Section of the molecular pumping section 16

24

shell

26

terminal edge

28

web

30

groove

32

an inner groove

34

first jetty

36

second inner groove

38

second bridge

40

stator

42

Lateral surface of the stator 40

50

first shift

52

second layer, middle layer

54

third layer

60

fibers

62

matrix

64

second matrix

70

negative form

72

forming groove

74

band-like fiber material

76

band-like fiber material

202

casing

204

gas inlet

206

gas outlets

208

warehouse

210

warehouse

212

rotor

218

drive

222 '

section

224

shell

230a

groove

230b

groove

242a

stator-side grooves

242b

stator-side grooves

250

groove

254

second groove section

260

groove

300

Curve

302

Curve

310

axis of rotation

312

corner

314

the grain

316

the grain

320

first angle

322

second angle

S

layer thickness

T

groove depth

Claims (15)

1. Part (22; 224; 222') for a rotor (12; 212) of a vacuum pump, which comprises a fibre composite material with a fibre direction (314, 316), characterised in that the part (22; 224; 222') has a groove (30; 32, 36; 230a; 230b; 250, 254) and fibres (60) of the fibre composite material are oriented such that at least a part of the fibres (60) is aligned with the fibre direction (314, 316) parallel to the groove (30; 32, 36; 230a; 230b; 250, 254), so that the part resists the influence of centrifugal forces during operation of the vacuum pump.
2. Vacuum pump with a rotor (12; 212), which comprises at least one part (22; 224; 222') according to the preamble of claim 1, made of a fibre composite material with at least one fibre direction (314, 316), characterised in that the part (22; 224; 222') comprises at least one helically arranged groove (30; 32, 36; 230a, 230b) and fibres (60) of the fibre composite material are oriented such that at least a part of the fibres (60) is aligned with the fibre direction (314, 316) parallel to the groove (30; 32, 36; 230a, 230b).
3. Vacuum pump according to claim 2, characterised in that the part (22; 224; 222') comprises a sleeve (24; 224).
4. Vacuum pump according to claim 3, characterised in that provided on an interior side of the sleeve (24; 224) is an inner groove (32, 36) and provided on an exterior side of the sleeve (24; 224) is an outer groove (30).
5. Vacuum pump according to one of the preceding claims, characterised in that the groove (30; 230a; 230b) extends completely over an axial extent of the at least one part (22; 224; 222').
6. Vacuum pump according to one of the preceding claims, characterised in that a wrap angle of the groove (30; 32, 36; 230a; 230b) is more than 360°.
7. Vacuum pump according to one of the preceding claims, characterised in that the part (22; 224; 222') comprises at least one first and one second layer (50, 52), wherein the groove (30; 32, 36; 230a; 230b) is arranged in one of the layers (50, 52).
8. Vacuum pump according to claim 7, characterised in that the first layer (50) comprises a first matrix (62) and the second layer (52) comprises a second matrix (64).
9. Vacuum pump according to one of the preceding claims, characterised in that the groove comprises a first groove portion (250) and a second groove portion (254) with mutually different geometries.
10. Vacuum pump according to claim 9, characterised in that a groove (260) encircling the rotor (12) is provided between the first and the second groove portion (250, 254).
11. Method for producing a rotor (12; 212) of a vacuum pump, which comprises a sleeve (24; 224; 222'), in which the sleeve (24; 224; 222') is wound from a fibre material with a fibre direction (314, 316) and the fibre material is embedded in a plastics matrix to form a fibre composite material, characterised in that the fibre direction (314, 316) is wound at an angle (312) to a termination edge (26) of the sleeve and a groove (30; 32, 36; 230a; 230b; 250, 254) is formed aligned to the fibre direction.
12. Method according to claim 11, characterised in that the formation of the groove (30; 32, 36; 230a; 230b; 250, 254) comprises a milling along the fibre direction (314, 316).
13. Method according to claim 11 or 12, characterised in that the formation of the groove (30; 32, 36; 230a; 230b; 250, 254) comprises the winding of the fibre material onto a negative mould (70).
14. Method according to one of the claims 11 to 13, characterised in that a first layer (50) is wound with a first fibre direction (314) and a second layer (52) is wound with a second fibre direction (316) and the groove is formed in at least one of the layers.
15. Method according to one of the claims 11 to 14, characterised in that the groove is formed with a first groove portion (250) and a second groove portion (254) with mutually different geometries.

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