EP3133290A1 - Vacuum pump - Google Patents

Abstract

Vacuum pump, in particular turbomolecular pump, having at least one rotor having a rotor shaft and a plurality of arranged on the rotor shaft, axially along the rotor shaft spaced rotor sections each comprising a plurality of circumferentially distributed rotor blades, and at least one rotor associated stator, the at least a stator section having a plurality of stator blades distributed in the circumferential direction, the stator section being arranged in the axial direction between a first and a second rotor section and adjacent to these two rotor sections, wherein a first axial spacing is provided between the first rotor section and the stator section and a second axial distance is provided between the stator portion and the second rotor portion, and wherein the second axial distance is different from the first axial distance.

Description

The present invention relates to a vacuum pump, in particular turbomolecular pump, having at least one rotor having a rotor shaft and a plurality of arranged on the rotor shaft, axially along the rotor shaft spaced rotor sections, each comprising a plurality of circumferentially distributed rotor blades, and at least one rotor associated stator having at least one stator section with a plurality of circumferentially spaced stator blades, wherein the stator in the axial direction between a first and a second rotor portion and adjacent to these two rotor sections each adjacent, and wherein between the first rotor section and the stator a first axial distance is provided and a second axial distance is provided between the stator section and the second rotor section.

Typically, a plurality of rotor sections and a plurality of stator sections are provided, which are arranged alternately in the axial direction, wherein a respective stator section is located centrally between two respectively adjacent rotor sections. The rotor sections may each be formed either integrally with the rotor shaft or may be provided in the form of a separately manufactured and rotatably connected to the rotor shaft rotor disk.

It is an object of the invention to improve the performance of such a vacuum pump.

The object is achieved by a vacuum pump according to claim 1, and in particular by the fact that the second axial distance is different from the first axial distance.

By the invention, the arrangement of the rotor and stator sections can be adapted to the movement of the molecules to be delivered, so that the pumping action is improved. The operation of the invention is described below in particular with reference to Fig. 2 explained in more detail.

In addition, the invention allows an existing construction of a vacuum pump to be improved by merely changing the position of the stator sections relative to the rotor sections. This can e.g. be realized by changing spacers between individual stator sections in a particularly simple manner. The invention thus improves the performance of a vacuum pump using particularly simple means, without the overall construction of the vacuum pump has to be changed.

The stator section is arranged between two rotor sections adjacent to it. In other words, a stator portion and each of the two rotor portions adjacent to each other are arranged in the respective axial direction in direct succession. No further stator or rotor sections are arranged between the stator section and the adjacent rotor section. The stator section has in each case an adjacent rotor section in both axial directions.

In the prior art, it is believed that optimum performance of the vacuum pump is achieved when the stator section is located exactly midway between two adjacent rotor sections. According to the invention, however, it has been recognized that the first axial distance and the second axial distance may have a different influence on the pumping action, so that the Pump effect can be favorably influenced by different choice of the two distances.

The first rotor section can be arranged in the pumping direction in front of the stator section and the second rotor section can be arranged in the pumping direction downstream of the stator section. In this case, the first axial distance may be smaller than the second axial distance. In other words, therefore, the first axial distance in the pumping direction can be smaller than the second axial distance in the pumping direction. In this case, the first axial distance can be made as small as possible. In this case, a certain minimum distance greater than zero is maintained between a stator section and an adjacent rotor section. Although, by decreasing the first axial distance, the second axial distance may become relatively large, it has been found that the second axial distance does not exert so much an influence on the pumping power, so that overall pumping performance is improved as the first axial distance is reduced.

In one embodiment of the invention, the first axial distance is less than 0.7 times the second axial distance. In this embodiment, a particularly good pump performance has resulted. Even better pumping powers may result if, according to a further embodiment, the first axial distance is less than or equal to half of the second axial distance.

In a further embodiment, the rotor shaft is mounted on the inlet side, in particular in a high vacuum region, by means of a lubrication-free bearing, in particular a magnetic bearing. As a result, the inlet-side storage not only perform maintenance-free, but also a contamination of the vacuum by the storage is prevented due to lack of lubricants.

The rotor shaft can alternatively or additionally on the outlet side, in particular in a medium or low vacuum range, by a lubricated bearing, in particular a rolling bearing such as a ball bearing to be stored. This allows a cost-effective and with relatively little game afflicted storage, while eliminating the problem of contamination on the outlet side.

In one embodiment, at least one rotor section is integrally formed with the rotor shaft. In particular, all rotor sections are integrally formed with the rotor shaft. Such a designed rotor is also referred to as a solid rotor. In contrast, at least one rotor section can be formed by a rotor disk produced separately from the rotor shaft and fastened to the rotor shaft. In particular, all rotor sections can be formed by separately produced rotor disks. This is also referred to as a disk rotor.

In a further embodiment, at least one stator section is designed as a stator disk made of sheet metal. As a result, the production of the stator and thus also those of the vacuum pump is technically simplified and cheaper. In particular, the stator is stamped from sheet metal, which further simplifies the manufacturing process.

The rotor blades and the stator blades can each be inclined to an at least substantially perpendicular to a rotation axis extending plane, wherein the rotor blades have an angle and the stator blades have an angle and the sum of the angle of attack of the stator blades and the angle of attack of the rotor blades at least substantially 90th ° is. In other words, a respective stator blade, in particular with a radially outer region, can be aligned at least substantially perpendicular to a respective rotor blade, in particular to its radially outer region. The molecules to be conveyed move away from a respective blade surface of the rotor in the direction of the stator section, as shown below Fig. 2 explained in more detail. So if the stator blades are parallel to In this direction of movement of the molecules are aligned, they provide the molecules with minimal resistance and the pump power is optimized.

In one embodiment of the invention, the angle of attack of the rotor blades is at least substantially 45 °, whereby the performance of the pump can be further improved.

Further embodiments of the invention are indicated in the dependent claims, the description and the figures.

Fig. 1

zeigt eine erfindungsgemäße Anordnung zweier Rotorscheiben mit einer dazwischenliegenden Statorscheibe, und

Fig. 2

zeigt Rotor- und Statorschaufeln zur Veranschaulichung der Wirkungsweise der Erfindung.

The invention will now be described by way of example only with reference to the schematic drawing.

Fig. 1

shows an inventive arrangement of two rotor disks with an intermediate stator, and

Fig. 2

shows rotor and stator blades to illustrate the operation of the invention.

An exemplary turbomolecular pump vacuum pump (not shown), which may be further developed by the invention and also by at least one embodiment disclosed herein, includes an inlet surrounded by an inlet flange and a plurality of pumping stages for delivering the gas present at the inlet to an outlet , The turbomolecular pump may have a lateral tap. The turbomolecular pump comprises a stator with a static housing and a rotor arranged in the housing with a rotor shaft rotatably mounted about a rotation axis.

The turbomolecular pump comprises a plurality of pump-connected in series with each other in series turbomolecular pumping stages with a plurality of connected to the rotor shaft, formed as a turbomolecular rotor disks rotor sections and arranged in the axial direction between the rotor disks and fixed in the housing, designed as a turbomolecular stator disks stator sections formed by spacers in a desired axial distance are held to each other. The rotor discs and stator discs provide in a scoop area an axial pumping action directed in the pumping direction.

The turbomolecular pump also comprises three Holweck pump stages, which are arranged one inside the other in the radial direction and pump-connected with one another in series. The rotor-side part of the Holweck pump stages comprises two cylinder jacket-shaped Holweck rotor sleeves fastened to and carried by the rotor shaft, which are oriented coaxially to the axis of rotation and are nested one inside the other. Furthermore, two cylindrical jacket-shaped Holweck stator sleeves are provided, which are also oriented coaxially to the axis of rotation and nested in one another. The pump-active surfaces of the Holweck pump stages are each formed by the radial lateral surfaces opposite one another, forming a narrow radial Holweck gap, namely in each case a Holweck rotor sleeve and a Holweck stator sleeve. In each case, one of the pump-active surfaces is smooth, in the present case, for example, the Holweck rotor sleeve, wherein the opposite pump-active surface of the respective Holweck stator sleeve has a structuring with helically around the rotation axis in the axial direction extending grooves, in which by the rotation the rotor propelled the gas and thereby pumped.

The rotatable mounting of the rotor shaft is effected by a rolling bearing in the region of the outlet and a permanent magnet bearing in the region of the inlet. The permanent magnet bearing comprises a rotor-side bearing half and a stator-side bearing half, each comprising a ring stack of a plurality of stacked in the axial direction of permanent magnetic rings, the magnetic rings facing each other with formation of a radial bearing gap.

Within the permanent magnet bearing, an emergency or fishing camp 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 with a radial stop for the rotor to form, which prevents a collision of the rotor-side structures with the stator-side structures.

In the area of the rolling bearing, a conical injection nut is provided on the rotor shaft with an outer diameter increasing towards the rolling bearing, which is provided with a scraper of a plurality with a working medium, such as e.g. a lubricant, soaked absorbent discs containing operating fluid in sliding contact. In operation, the operating medium is transferred by capillary action from the working fluid reservoir via the scraper to the rotating injection nut and due to the centrifugal force along the injection nut in the direction of the increasing outer diameter of the injection nut to the rolling bearing promotes out, where, for example. fulfills a lubricating function.

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

Fig. 1 shows a rotor shaft 14 of a rotor of a turbomolecular pump according to the invention shown here only partially, with the rotor shaft 14, two rotor disks 16 formed as rotor sections are rotatably connected. A respective rotor disk 16 has a plurality of circumferentially spaced, not shown rotor blades.

Between the rotor discs 16 designed as a stator 22 stator section is arranged, which is not connected to the rotor shaft 14, but statically connected to a housing of the turbomolecular pump, not shown. The stator disc 22 has a plurality of circumferentially spaced, also not shown stator blades.

There is a first axial distance A1 between the upper rotor disk 16 and the stator disk 22 and a second axial distance A2 exists between the stator disk 22 and the lower rotor disk 16. The first axial distance A1 is smaller than the second axial distance A2. Here, the axial distance A1 is about 0.4 times the second axial distance A2. This distance ratio is purely exemplary and according to the invention can in principle assume any desired value.

In other words, the stator section is arranged outside an axial center between the first rotor section, in this case the upper rotor disk 16, and the second rotor section, here the lower rotor disk 16. In other words, in other words, the stator section in the axial direction, that is along the rotor shaft 14, viewed closer to one of the adjacent rotor sections, namely closer to the upper rotor disk 16, as arranged on the respective other rotor section.

A pumping direction P describes a desired direction of movement of gas molecules to be delivered during a pumping operation. The gap following in the pumping direction P directly on the upper rotor disk 16, which is assigned to the first axial distance A1, is smaller than the second gap in the pumping direction, which directly follows the stator disk 22 and the associated with the second axial distance A2. It may be desirable to make the first axial distance A1 as low as possible in order to further improve the pumping power of the turbomolecular pump.

The operation of the invention will now be described with reference to Fig. 2 and a simplified physical model.

In Fig. 2 For this purpose, rotor blades 18 and stator blades 24 are shown simplified, namely as a simplified developed view in the radial direction, ie in the direction of the rotor shaft 14 shown here only as a dashed line. The rotor blades 18 are part of a rotor disk, not shown in detail, which in the pumping direction P directly in front of a stator blades 24 comprehensive, also not shown stator is arranged.

The rotor blades 18 move at high speed during the pumping operation Fig. 2 to the right (direction of rotation) while the stator blades 24 are fixed, ie do not move. The rotor blades 18 and the stator blades 24 are arranged obliquely at a respective angle of attack of 45 °, wherein the stator blades 24 are oriented obliquely opposite to the rotor blades 18. The angle of attack is in each case measured starting from a plane perpendicular to the rotor shaft 14 extending plane.

A molecule to be delivered, which gets into the axial region of the rotor blades 18, is to a certain extent trapped by the obliquely downwardly directed surface of a rapidly moving rotor blade 18, the molecule being adsorbed to the surface. Subsequently, the molecule desorbs from the surface, moving away from the rotor blade. In this case, the molecule assumes a preferred direction, which is perpendicular to the surface from which the molecule has previously been desorbed. In Fig. 2 are also the stator blades 24 aligned perpendicular to the obliquely downward surfaces of the rotor blades 18, so that a molecule which moves in the preferred direction can pass parallel to the stator blades 24 and thus almost unhindered through the axially adjacent stator disk 22, with only the - relatively small thickness of the stator blades 24 precluding this movement.

However, the further the distance that the molecule has already traveled after desorption from the rotor blade 18 when entering the axial area of the following stator disk 22, the more likely its direction of movement deviates from the preferred direction mentioned above. This is for example due to impacts with the housing wall, the rotor shaft or other molecules and can also be referred to as "blurring". According to the invention, it has been recognized that the probability of penetration for a respective molecule to be conveyed increases when the stator disk is arranged as close as possible to the rotor disk and thus, with high probability, the molecule does not already have a direction of movement deviating from the preferred direction when it reaches the stator disk. In contrast, the axial distance between the stator disk and the rotor disk following in the pumping direction has less influence on the pumping power. For here, the molecule to be promoted can be actively captured by the rotor disk, essentially independently of its direction of movement, and thereby further transported. The pumping power of the turbomolecular pump is therefore improved, in particular in the molecular working range, by the invention.

LIST OF REFERENCE NUMBERS

14

rotor shaft

16

rotor disc

18

rotor blade

22

stator

24

stator

P

pumping direction

Claims (11)

Vacuum pump, in particular turbomolecular pump, with
at least one rotor having a rotor shaft (14) and a plurality of on the rotor shaft (14) arranged axially along the rotor shaft (14) spaced rotor sections (16), each comprising a plurality of circumferentially distributed rotor blades (18) comprise, and
at least one stator associated with the rotor, which has at least one stator section (22) with a plurality of stator blades (24) distributed in the circumferential direction,
the stator section (22) being arranged in the axial direction between a first and a second rotor section (16) and adjacent to these two rotor sections (16),
wherein a first axial distance (A1) is provided between the first rotor portion (16) and the stator portion (22) and a second axial distance (A2) is provided between the stator portion (22) and the second rotor portion (16),
and wherein the second axial distance (A2) is different from the first axial distance (A1). Vacuum pump according to claim 1,
characterized in that
the first rotor section (16) is arranged in the pumping direction (P) in front of the stator section (22) and the second rotor section (16) is arranged in the pumping direction (P) downstream of the stator section (22), the first axial spacing (A1) being smaller as the second axial distance (A2). Vacuum pump according to one of the preceding claims,
characterized in that
the first axial distance (A1) is less than 0.7 times the second axial distance (A2). Vacuum pump according to one of the preceding claims,
characterized in that
the first axial distance (A1) is less than half the second axial distance (A2). Vacuum pump according to one of the preceding claims,
characterized in that
the rotor shaft (14) on the inlet side by a lubrication-free bearing, in particular a magnetic bearing, is mounted. Vacuum pump according to one of the preceding claims,
characterized in that
the rotor shaft (14) on the outlet side by a lubricated bearing, in particular a roller bearing, is mounted. Vacuum pump according to one of the preceding claims,
characterized in that
at least one rotor section (16) is integrally formed with the rotor shaft (14). Vacuum pump according to one of the preceding claims,
characterized in that
at least one stator section (22) is designed as a stator disk made of sheet metal. Vacuum pump according to claim 8,
characterized in that
the stator disk is stamped from sheet metal. Vacuum pump according to one of the preceding claims,
characterized in that
the rotor blades (18) and the stator blades (24) are each inclined to an at least substantially perpendicular to a rotation axis (R) extending plane, wherein the rotor blades (18) have an angle and the stator blades (24) have an angle and the sum from the angle of attack of the stator blades (24) and the angle of attack of the rotor blades (18) is at least substantially 90 °. Vacuum pump according to claim 10,
characterized in that
the angle of attack of the rotor blades (18) is at least substantially 45 °.

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