EP2597313B1 - High speed rotor for a vacuum pump - Google Patents

Description

The invention relates to a fast-rotating rotor according to the preamble of claim 1.

Holweck molecular pumping stages have been successful for years in the field of vacuum technology. As a rule, they are used in turbomolecular pump stages as the fore-vacuum side pumping stage, so that the turbomolecular pump can eject against higher prevacuum pressures. After Holweck rotates a smooth sleeve in a provided with helical grooves stator. Several pods may be present, so the beats DE 196 32 375 A1 to allow cores of different axial length in the gas stream to act in parallel.

Particularly successful are sleeves of carbon fiber reinforced material, as this has a low expansion under the action of heat and centrifugal forces.

The disadvantage, however, is that the sleeve must be carried on the rotor and in this case a material is used in a carrier component, which is subject to a greater extent and thus generates high voltages in the sleeve. This disadvantage complicates the design of the rotor and limits the vacuum technical performance, for example by speed and temperature limits. Vacuum performance includes, for example, the compression achieved and the pumping speed.

It was in the EP-A 1 408 237 proposed to let pass the fiber-reinforced Holweckhülse in the support member and thereby exploit a special design of the fibers. However, this proposal has not yet led to market success, which could be due to the complexity of the fiber design and rotor geometry.

Furthermore, in the post-published document EP 2 722 528 A1 a fast rotating rotor is described having a first sleeve and a support structure in which a second sleeve is disposed within the first sleeve and the first and second sleeves form a composite.

It is therefore an object of the invention to provide a high-speed rotor for a vacuum pump having improved vacuum performance.

This object is achieved by a rotor having the features of claim 1.

The design with the features of claim 1 ensures that the voltage difference between the support structure and sleeve is reduced. Due to the lower voltage difference, the vacuum technical performance is improved because speed and working temperature can be selected higher.

In this case, the first sleeve can be supported directly by the support structure, while the second sleeve is supported by the first sleeve and thus only indirectly connected to the support structure via the first sleeve. Alternatively, the second sleeve connected to the support structure and the first sleeve of the second sleeve be worn. Furthermore, it is also possible that both sleeves are directly connected to the support structure. According to the invention, the composite formed by the two sleeves is designed in such a way that the forces generated by the second sleeve under the action of centrifugal forces on the first sleeve approximate those forces which are due to the expansion of the support structure, in particular a hub of the support structure, to the first Interact with the sleeve.

The dependent claims 2 to 15 indicate advantageous developments of the invention, which additionally increase the aforementioned advantage.
In particular, it may be provided that the first sleeve and the second sleeve with respect to the material from which the sleeves are made, differ from each other. In particular, the materials differ in terms of expansion under the action of heat and / or centrifugal forces.

In a further embodiment, the first sleeve and the second sleeve can be connected to one another over a wide area, in particular over the whole area.

In particular, the choice of material according to claims 4 and 5, in particular in combination of the features together, leads to particularly low voltage differences. The vacuum technical performance is further improved if, according to claim 6, a pump-active structure in the form of a helical groove is provided on the rotor side, for example in this way the pumping speed is improved.

The composite can be formed by forming the two sleeves an adhesive bond or a shrink joint. The shrink-fit connection is in particular produced such that the first sleeve and the second sleeve are brought to different temperatures and then arranged one inside the other, in particular into one another pushed or inserted into each other. Following this, ie when returning to "normal temperature", the previously relatively "cooled" sleeve expands again, while the previously relatively "heated" sleeve contracts. This creates a firm connection between the two sleeves, for which in particular no additional fastening means are needed. It is provided in particular that it is the inner sleeve, in this case the second sleeve, which is "cooled" while the first sleeve, ie the outer sleeve, is brought to an elevated temperature.

Alternatively, the composite can also be formed by pressing or pressing the two sleeves together so that the two sleeves are welded together, or by screwing the two sleeves together, the latter being achieved in particular by the outer sleeve being on its inside and the inner sleeve is threaded on each of its outer sides and the two sleeves are screwed by screwing the inner sleeve into the outer sleeve.

Generally, a cohesive connection can exist between the two sleeves to form the composite. Alternatively, it is possible that a positive or non-positive connection is made between the two sleeves.

Furthermore, it can be provided that the one sleeve forms a reinforcement or coating of the other sleeve, wherein the reinforcement or coating can be formed either by the first sleeve or by the second sleeve.

The increased vacuum performance results in combination with a turbomolecular pumping section according to claim 9 and optionally the claims related thereto to an improvement in the pumping action of the overall pump. For vacuum pumps with at least one additional inlet according to claim 14 due to the improved performance new applications are developed, for example, if previously unattainable pressure conditions between the chambers of a multi-chamber system or previously unattainable pumping speeds are required.
With reference to an embodiment and its developments, the invention will be explained in more detail and the representation of its benefits to be deepened.

Fig. 1:

Teilschnitt einer Vakuumpumpe mit schnell drehendem Rotor;

Fig. 2:

Teilschnitt von Rotor und Stator gemäß einer Weiterbildung;

Fig. 3:

Tragstruktur und Hülse eines Rotors im Schnitt;

Fig. 4:

Schematische Darstellung eines Rotors mit wenigstens einem turbomolekularen Pumpabschnitt;

Fig. 5:

Teilgeschnittene Ansicht einer Vakuumpumpe, in der die Hülse auf der Ansaugseite der Nabe gelegen ist.

Show it:

Fig. 1:

Partial section of a vacuum pump with fast rotating rotor;

Fig. 2:

Partial section of rotor and stator according to a development;

3:

Support structure and sleeve of a rotor in section;

4:

Schematic representation of a rotor with at least one turbomolecular pump section;

Fig. 5:

Partial sectional view of a vacuum pump in which the sleeve is located on the suction side of the hub.

It shows Fig. 1 a vacuum pump 2, which is detachably connected by means of a flange 4 with a container, not shown, to be evacuated. Gas enters through the suction port 6, is compressed in the vacuum pump and discharged through the gas outlet 8. As a rule, a backing pump is connected to the gas outlet.

Within the vacuum pump, a rotor 10 is provided which comprises a shaft 12. This is rotatably supported by a first bearing 34 and a second bearing 36. On the shaft, a drive magnet 32 may be provided, which cooperates with a drive coil 30 to enable the rotor in rapid rotation. The rotational speed is dimensioned such that a molecular pump effect is brought about by the interaction of the rotor and a stator 40. The stator has a helical groove 42 on a radially inner surface.

On the shaft of the rotor, a support structure is attached, which may be designed as a disc-like hub 14 designed. With this hub a first sleeve 16 is connected rotatably. Within this first sleeve 16, a second sleeve 18 is arranged and both sleeves form a composite. This composite is preferably chemically stable, heat and speed resistant. In this way, the first and second sleeves remain connected under the operating conditions. As the rotor rotates, centrifugal forces begin to act on the rotating parts, but especially on the hub and sleeves. The expansion of the second sleeve is impeded by the first sleeve, in particular if the first sleeve is formed from a fiber-reinforced material, for example a carbon-fiber-reinforced plastic. The second sleeve is now designed according to material and geometry such that the forces generated by them under the action of centrifugal forces on the first sleeve those forces come close, which act on the first sleeve by the extension of the hub. The goal is in particular, in design of hub and second sleeve, the voltages in the first To bring the sleeve to a level that is compatible with its material constants. As a result, an overload of the first sleeve is avoided. It is advantageous that can be achieved with a much larger amount of operating conditions by the additional design degrees of freedom using the second sleeve, the overload of the first sleeve, wherein an operating condition is determined by among other things temperature, speed and gas load.

Further design options are in the further developments on hand of Fig. 2 to 5 presented.

To Fig. 2 is connected to the shaft 12, a hub 14 to which the first sleeve 16 is attached. Within the first sleeve and with this a composite forming the second sleeve 18 is provided. As in the example below Fig. 1 a stator 40 is provided which cooperates with the outer surface of the first sleeve, so that the first stator and the first sleeve form a first pumping stage. In addition to this stator, there is provided a second stator 44 cooperating with an inner surface of the second sleeve so that the second sleeve and the second stator form a second pumping stage.

The pumping stages can be flowed through in series one behind the other, the gas then follows the arrow 100. It may be desirable to operate the pumping stages in parallel. For this purpose, at least one passage 52 can be provided in the hub, through which gas can pass through the hub into the second pumping stage along the dashed arrow 102.

An advantageous development may be a connection 50, are connected by the second sleeve and hub. Hub and second sleeve can be made in one piece at this point.

According to another advantageous development, it is proposed to mount a pump-active structure on the inner surface of the second sleeve. This may be, for example, at least one helical groove 20. This pump-active structure increases pumping speed and compression.

The training according Fig. 3 refers to the supporting structure. This is designed according to the development as a support plate 60. The support disk has an inner ring 66 with a shaft receiver 68, with which the support disk can be mounted on the shaft. Radially outside, a circumferential ring of blades 62 adjoins the inner ring, so that a disk of substantially turbomolecular design is formed. With at least a portion of the blades, a support ring 64 is connected or made in one piece, to which the first sleeve 16 is fixed, which forms a composite with the second sleeve 18.

In Fig. 4 It is shown that a rotor disk 82 of turbomolecular design for forming a turbomolecular pump section can still be provided on the shaft 12. A plurality of rotor disks may be disposed on the shaft and form a first disk portion 84 and a second disk portion 86. Other disc sections may be present. This creates a powerful vacuum pump for differential evacuation of a multi-chamber system.

The rotor after Fig. 4 In addition to a first sleeve 16 connected to the sleeve 16 has a third sleeve 78, which may also be attached to the hub 14 or on its own support structure.

A first stator 40 cooperates with the outer surface of the first sleeve to form a pumping stage. A second stator 44 creates a pumping action with the inner surface of the second sleeve and the outer surface of the third sleeve to create a second and a third pumping stage.

A gas inlet 88 may be provided to admit gas between the first and second stator in the second pumping stage.

The rotor after Fig. 4 can be rotatably mounted with a permanent magnet bearing 80 and a second bearing 36, which may be designed as a rolling bearing or active magnetic bearing.

In Fig. 5 Rotor and stator of a vacuum pump are shown schematically and cut, the gas flow is illustrated by arrows. The shaft 12 of the rotor is supported at its suction end by a permanent magnet bearing 80. Forevacuum side, a roller bearing 92 serves to support the shaft. Between the bearings, a disc-shaped hub 14 is connected to the shaft. At this hub, a first sleeve 16 mitrotierbar, chemical and heat resistant attached. The first sleeve extends from the hub toward the suction side 104. A second sleeve 18 disposed radially within the first sleeve forms a bond with the first sleeve. It may have on its radially inner surface a pump structure, for example at least one helical groove. The radially inner surface of the sleeve cooperates with a second stator 44 and forms with it a molecular pumping stage. The radially outer surface of the first sleeve, however, together with the stator 40 forms a molecular pumping stage. One or both of the stators may have a pumping structure. In this way, a compact molecular vacuum pump created. Due to the additional pumping structure on the inner surface of the second sleeve, a high pumping speed can be achieved in this pumping stage, whereby an advantageous Saugvermögensabstufung the pumping stages to each other is possible. The second sleeve may be integral with the hub.

The pumping speed of the vacuum pump after Fig. 5 can be further increased by a rotor disk 82 is mounted on the rotor on the suction side. A further increase results from a stator disk 90 following in the gas flow of the rotor disk.

The on hand of the developments according to Fig. 2 to 5 features shown can be combined or exchanged, as far as this does not technically contradict.

LIST OF REFERENCE NUMBERS

2

vacuum pump

4

flange

6

gas outlet

10

rotor

12

wave

14

hub

16

first sleeve

18

second sleeve

20

Groove in second sleeve

30

drive coil

32

Impeller

34

first camp

36

second camp

40

stator

42

groove

44

second stator

50

connection

52

passage

60

carrying disc

62

shovel

64

support ring

66

inner ring

68

shaft mount

78

third sleeve

80

PM-camp

82

rotor disc

84

first disc section

86

second disc section

88

gas inlet

90

stator

92

roller bearing

100

Arrow: serial gas flow

102

dashed arrow: parallel gas flow

104

suction

Claims (14)

1. A fast-rotating rotor (10) for a vacuum pump (2) comprising a first sleeve (16) and a support structure (14; 60), wherein a second sleeve (18) is arranged within the first sleeve (16) and wherein the first sleeve (16) and the second sleeve (18) form a combination,
   characterized in that
   the combination is adapted with respect to the material and/or to the geometry at least of the second sleeve (18) such that the forces on the first sleeve (16) generated by the second sleeve (18) under the effect of centrifugal forces come close to those forces which act on the first sleeve (16) due to the expansion of the support structure (14; 60), in particular a hub (14).
2. A rotor in accordance with claim 1,
   characterized in that
   the first sleeve (16) and the second sleeve (18) differ from one another with respect to the material from which they are manufactured, in particular with respect to the expansion under the effect of heat and/or centrifugal forces.
3. A rotor in accordance with claim 1 or claim 2,
   characterized in that
   the first sleeve (16) and the second sleeve (18) are areally connected to one another, in particular over their full area.
4. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the first sleeve (16) comprises a carbon fiber reinforced material.
5. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the second sleeve (18) comprises a metal alloy.
6. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the second sleeve (18) has a helical groove (20) at an inner surface.
7. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the first sleeve (16) and the second sleeve (18) form an adhesive connection or a shrink connection.
8. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the second sleeve (18) and at least some of the support structure (14; 60) are formed in one part; or
   in that the first sleeve (16) and at least some of the support structure (14; 60) are connected to one another by means of an adhesive join.
9. A rotor in accordance with any one of the preceding claims,
   characterized in that
   the rotor comprises a rotor disk (82) of a turbomolecular type of construction for forming at least one turbomolecular pump section.
10. A rotor in accordance with any one of the preceding claims,
    characterized in that
    the support structure comprises a hub (14).
11. A vacuum pump (2),
    characterized in that
    it comprises a fast-rotating rotor (10) in accordance with any one of the preceding claims.
12. A vacuum pump (2) in accordance with claim 11,
    characterized in that
    it comprises a first stator (40) which has a helical passage which cooperates with an outer surface of the first sleeve (16) such that the first stator and the first sleeve form a pump stage, in particular a first pump stage.
13. A vacuum pump (2) in accordance with claim 11 or claim 12,
    characterized in that
    it has a second stator (44) which cooperates with an inner surface of the second sleeve (18) such that the second sleeve (18) and the second stator (44) form a pump stage, in particular a second pump stage.
14. A vacuum pump (2) in accordance with any one of the claims 11 to 13,
    characterized in that
    it has a gas inlet (88) through which gas moves between the first stator (40) and a second stator (44) into a second pump stage comprising the second stator (44).

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