EP3032107B1 - Turbomolecular pump - Google Patents

Description

The invention relates to a turbomolecular pump with at least one turbomolecular pump stage, which comprises at least one blade rotor which is rotatably mounted about an axis.

Such turbomolecular pumps are generally known and are e.g. used in the semiconductor industry and in physical research to generate the high vacuum required there. The turbomolecular pump is characterized by a blade rotor, also referred to below as a rotor, the structure of which is reminiscent of the rotor of a turbine. The blade rotor interacts with a blade stator, also referred to below as the stator, and usually rotates at such a high speed that the tangential speed of the individual rotor blades is of a similar order of magnitude to the average thermal speed of the particles to be conveyed. With a vertical pumping direction from top to bottom, the majority of the particles collide with an underside of an angled rotor blade. A pumping action results from a preferred direction of the underside of the rotor blade in the pumping direction.

The rotor must also be surrounded by a wall to prevent the particles from flowing back outside the rotor area. Such a wall is formed, for example, from the inside of a housing containing the turbomolecular pump stage or from the inside of stator spacer rings arranged between individual stator disks. This wall has a cylindrical inner surface which is arranged concentrically to the rotor and whose preferred direction points radially inward and thus in the pumping direction. Particles by themselves or after colliding with a rotor blade on the cylindrical inner surface of the wall, there is no longer any pumping action.

A turbomolecular pump according to the preamble of claim 1 is known from the EP 0 568 069 A2 known.

Against this background, it is the object of the invention to improve the performance of turbomolecular pumps.

This object is achieved by a turbomolecular pump having the features of claim 1, and in particular in that a wall which at least partially surrounds the blade rotor is provided with at least one depression on at least one pump-effective subarea of its side facing the blade rotor, the depression being a spiral or has a helical course and / or the pump-effective portion is designed as a Holweck stator.

From molecular pumps e.g. according to Gaede or Holweck, it is known that such a depression can itself give the particles to be conveyed a further preferred direction. It is advantageous for this if the particles already have a preferred direction before they enter the depression, so that the majority of the particles strike a surface of the depression with their normal in the pumping direction. This is generally the case with a blade rotor of a turbomolecular pump, which is arranged opposite a depression, since the rotation of the rotor blades means that a tangential speed component of the particles is generally not zero, but points in the direction of rotation with an amount greater than zero. As a result, the wall itself can become a pump-active sub-area.

The performance of the turbomolecular pump can be improved by giving particles that strike the wall a preferred direction in the pumping direction.

According to the invention, it is particularly simple and inexpensive to make such a depression in the side of the wall facing the blade rotor. Such an indentation can, for example, be simply made with an ordinary milling tool.

Furthermore, the pumping speed and the compression can be increased on an existing flange with an existing pump. In addition, the invention enables the technical adaptation of a static component of the turbomolecular pump. Static components are not exposed to such high mechanical loads like rotor components. They can therefore be changed and installed without qualification. For this reason, further developments of turbomolecular pumps are particularly advantageous in terms of development technology if they only relate to static components, as is possible here according to the invention.

According to the invention, the depression has a spiral or helical shape. The depression therefore has a thread course which corresponds to the course of the depression in Gaede thread pumps or molecular pumps according to Holweck. The depression can be designed as a helix. As a result, the desired preferred direction is imparted to the particles even more evenly. The spiral or screw-shaped course of the depression advantageously has the same direction of rotation as the blade rotor.

The pump-effective part of the wall is alternatively or additionally designed as a Holweck stator. The Holweck stator, which is known per se, is applied to a turbomolecular pump stage with a few constructive measures.

The pumping action is further improved if the depression has a course with an axial component and / or with a slope different from zero. This gives the particles a preferred direction, also with an axial component. The pumping action in the axial direction is thus improved.

The depression can furthermore be designed in the manner of a groove or channel. This further improves the guidance of the particles in their preferred direction. Such a groove or such a channel can be made particularly easily in an inside wall.

Furthermore, the pump-effective partial area is advantageously provided with a plurality of, in particular non-contiguous, depressions. The depressions can advantageously run parallel to one another. By providing several depressions according to the invention, the pumping action of the inside of the wall can be increased in particular in proportion to the number of depressions. Disjointed and / or parallel depressions can also be introduced particularly easily and prevent backflow between the depressions.

The wall can advantageously be formed by a housing surrounding the blade rotor. The pump-effective section is formed on the inside of the housing. This means that there is no need to insert an additional wall into the pump housing. The recess can also be made by casting the housing or by milling. In particular, the housing can represent the outer housing of the pump. As a result, even fewer individual parts are required.

However, the wall can also be formed, for example, by a ring element surrounding the blade rotor and the pump-effective partial area can be formed on the inside of the ring element. The ring element is easy to machine and assemble, but represents an additional part of the vacuum pump. The ring element can be designed to be arranged between two stator disks and thus to define their axial distance between them. The ring element can in particular be a spacer ring, a spacer ring, a spacer sleeve and / or a spacer sleeve.

It can therefore be provided according to the invention to use already existing elements such as ring or sleeve elements between successive stator disks to form pump-effective subareas which are provided with at least one recess on their side facing the blade rotor.

In an advantageous embodiment, the blade rotor comprises a plurality of rotor disks arranged axially one after the other, integrally connected to one another or separate. The pump performance of the turbomolecular pump can be further improved by several rotor disks.

It can advantageously be provided that the pump-effective partial area extends in the axial direction only over a subset of rotor disks, preferably comprising the rotor disk closest to the suction side of the pump, in particular over exactly one rotor disk. On the first rotor disk in the pumping direction, the pumping effect can be improved particularly effectively by the depression according to the invention.

At least some blades of a blade stator interacting with the blade rotor can be connected to the wall. This results in a simpler construction of the turbomolecular pump.

The pump-effective subarea can advantageously be located axially outside of blades of a blade stator interacting with the blade rotor. The pump-effective subarea is then only arranged opposite the blades of the blade rotor, that is to say not at the level of the stator.

Alternatively, a pump-effective region of the wall can extend at least substantially over the entire axial length of the turbomolecular pump.

It can also be advantageously provided that a blade stator which interacts with the blade rotor comprises a plurality of stator disks arranged axially one after the other, the pump-effective partial region being located only axially between the stator disks and / or axially adjacent to at least one of the stator disks. For example, the pump-effective subarea can be formed by the inner sides of stator spacer rings located between stator disks and thus at the level of a rotor disk. This facilitates the insertion of the depression.

It can also be advantageously provided that blades of a blade stator interacting with the blade rotor each have an angle of attack in a radially outer end region which is at least approximately equal to a slope of the depression. The depression extends at least substantially parallel to the alignment or the angle of attack of the stator blades. This further improves the forwarding of the particles.

In a further embodiment, the blades of the blade rotor each have an angle of attack in a radially outer end region which differs between 45 ° and 90 ° from an increase in the depression. The depression is arranged perpendicularly or at an acute angle to the rotor blades.

It can also advantageously be provided that the pump-effective sub-area has a plurality of parallel depressions which are separated from one another by webs, the number of webs being at least approximately equal to the number of blades per stator disk of a blade stator interacting with the blade rotor. It can be advantageous to provide the same number of depressions or as many webs as stator blades. Furthermore, the number of rotor blades can also be the same as the number of stator blades. The probability of passage of the individual particles can thereby be further improved.

The stator blades can be firmly connected to the webs on the inside of the wall, in particular they can be made of material. The stator blades can thus spring from the webs between the depressions. The depressions can also extend between the stator blades. The depressions can also extend continuously over several turbomolecular pump stages or over several alternately arranged rotor and stator disks. The depressions can be designed as multi-start internal threads. In this way, an improved continuous particle flow in the pump-effective sub-area can be achieved.

A depression according to the invention can also be arranged on the inside of a stator spacer ring. This facilitates the manufacture of turbomolecular pumps with several turbomolecular pump stages or with several alternating rotor and stator disks.

The object of the invention also achieves a turbomolecular pump with at least one turbomolecular pump stage, which is surrounded at least in a partial axial area by a Holweck stator, the pump-effective side of which faces the blade rotor of the turbomolecular pump stage.

As a result, the invention combines a turbomolecular pump stage with a Holweck pump stage or creates a hybrid pump stage from these two pump types.

Possible specific configurations of this pump are given above and in the dependent claims.

Further embodiments of the invention are specified in the dependent claims, the description and the drawings.

Fig. 1

zeigt eine Schnittansicht einer erfindungsgemäßen Turbomolekularpumpe.

Fig. 2

zeigt in Perspektivansicht eine erfindungsgemäße Pumpstufe einer Turbomolekularpumpe.

Fig. 3

zeigt in einer anderen Perspektivansicht einen Teil der Pumpstufe von Fig. 2.

Fig. 4

zeigt eine Prinzipdarstellung einer erfindungsgemäßen Vertiefungsanordnung.

Fig. 5

zeigt in einer Prinzipdarstellung den Schaufelrotor einer erfindungsgemäßen Turbomolekularpumpstufe im Querschnitt längs der Drehachse des Rotors.

The invention is explained below by way of example only with reference to the drawings.

Fig. 1

shows a sectional view of a turbomolecular pump according to the invention.

Fig. 2

shows a perspective view of a pump stage of a turbomolecular pump according to the invention.

Fig. 3

shows in a different perspective view a part of the pump stage of FIG Fig. 2 .

Fig. 4

shows a schematic diagram of a deepening arrangement according to the invention.

Fig. 5

shows a schematic representation of the blade rotor of a turbomolecular pump stage according to the invention in cross section along the axis of rotation of the rotor.

Fig. 1 shows, purely by way of example, a typical basic structure of a turbomolecular pump with a turbomolecular pump section 56 and a Holweck pump section 58. The turbomolecular pump comprises a rotor shaft 36 which is rotatable in a housing 38 by a ball or generally a roller bearing 30 on the discharge side and by a A radial bearing 32 designed as a permanent magnet bearing is mounted on the suction side 40 of the turbomolecular pump. A plurality of rotor disks 12 are seated on the rotor shaft 36 and rotate together with the rotor shaft 36 during operation. Stator disks 14 are arranged axially alternating with the rotor disks 12 between the rotor disks 12. The stator disks 14 are in their mutual axial distance by spacer rings 54 set. The spacer rings 54 each have a wall on their side facing the rotor disks 12, the wall according to the invention each having one or more depressions, for example according to the embodiment of FIG Fig. 5 , are provided.

The Fig. 2 shows a blade rotor 12 and a blade stator 14 of a turbomolecular pump stage. The blade rotor is surrounded by a wall 16 in the radial direction. The blade rotor 12 rotates about a concentric axis (not shown) with the direction of rotation 44. Rotor blades 18, which are twisted in themselves, extend from radially inward to radially outward. That is, the angle of attack, which relates to the radially outer ends of the stator blades, is steeper than the angle of the origin of the rotor blades. The blade rotor is also essentially designed as a disk, ie it extends essentially in the radial direction and has a thickness in the axial direction.

The blade stator 14 of the Fig. 2 is essentially the same as the blade rotor 12, but is, in a way, mirror-inverted. The stator blades 20 likewise originate radially on the inside of the blade stator 14. However, they can also originate radially on the outside, for example on the wall 16.

The wall 16 surrounds the blade rotor 12 in the radial direction. The wall 16 has depressions 22 on the inside, ie on the side facing the blade rotor. The depressions 22 are each designed as a groove and extend helically in the axial direction. Crosspieces 24 are formed between the depressions 22. There is a type of channel between the webs 24 in a pump-effective sub-area. The number of depressions 22 and the number of webs 24 are in each case equal to the number of stator blades 20 and equal to the number of rotor blades 18. The depressions 22 are arranged parallel to one another and parallel to the outer ends of the stator blades 20. The pump direction is in Fig. 2 from top to bottom, i.e. axially downwards.

The Fig. 3 shows an alternative view of the turbomolecular pump stage of FIG Fig. 2 . The blade rotor 12 and the blade stator 14 are arranged axially adjacent. The blade rotor is radially enclosed by the wall 16. The wall 16 has on its inside the depressions 22 and the webs 24 arranged between them. The blade rotor 12 rotates with its rotor blades 18 within the wall 16. The stator blades 20 of the blade stator 14 are arranged statically. The pump-effective partial area, that is to say the axial extent of the depressions 22, extends only over the axial width of the rotor blades 18.

The webs 24 between the depressions 22 run parallel to the depressions 22. They are narrower than the depressions 22. The depressions 22 are designed as channel-like, rectangular grooves on the inside of the wall 16. Accordingly, the webs 24 are also rectangular. The webs 24 and the depressions 22 extend parallel to the radially outer ends of the stator blades 20. The webs 24 are each arranged in the circumferential direction at the same location as the stator blades 20. The axially lower, i.e. in the Fig. 3 the rear ends of the depressions 22 are arranged between the stator blades 20 in the circumferential direction. A particle stream in a depression 22 can thereby flow freely between the stator blades 20. The axially lower ends of the depressions 22 face the blade stator.

The Fig. 4 shows a schematic diagram of two turbomolecular pump stages. A rotor region 26, a stator region 28, a further rotor region 26 and a further stator region 28 are arranged axially adjacent. A rotor region 26 and an adjacent stator region 28 arranged axially below each form a turbomolecular pump stage. So it's in Fig. 3 two turbomolecular pump stages are shown.

Instead of "steps" one can also speak of "disks", i.e. this exemplarily illustrated turbomolecular pump comprises two rotor and two stator disks, which together can also be referred to as a turbomolecular pump stage.

The pumping direction runs from top to bottom. In the rotor areas 26, the rotor blades 18 move from left to right. The stator blades 20 are arranged statically in the stator regions.

Inside on a wall 16, not shown (e.g. after Fig. 2 or 3rd ) depressions 22 are arranged. Crosspieces 24 are arranged between the depressions 22. In this embodiment, the webs 24 are made wider than the depressions 22. The depressions 22 as well as the webs 24 are arranged parallel to the stator blades 20. The angle of attack 46 of the stator blades 20 is therefore at their radially outer ends equal to the slope 48 of the depressions 22. The depressions 22 are also located centrally between the stator blades 20 in the circumferential direction. The depressions 22 thus extend in the pumping direction from an upper suction side to a lower discharge side continuously over both turbomolecular pump stages shown.

The angle of incidence 50 of the rotor blades 18 is 90 ° greater than the angle of incidence 46 of the stator blades 20. The rotor blades 18 and the stator blades 20 are therefore aligned perpendicular to one another at their radially outer ends. The radially outer ends of the rotor blades 18 are therefore also arranged perpendicular to the slope 48 of the depressions 22.

The Fig. 5 schematically shows some components of a turbomolecular pump according to the invention, specifically in a basic illustration a vane rotor 12 also known as a rotor disk with vanes 18, which is rotatably mounted on a rotor shaft 36 and of which only one rotor disk 12 is shown. Of the Blade rotor 12 rotates with rotor shaft 36 in rotor direction of rotation 44. As a result, it effects a pumping process in pumping direction 42 from an intake side 40 to an exhaust side 52. The rotor disk 12 is shown in section. The visible rotor blade 18 to the right of the axis of rotation 34 extends axially upward away from the viewer, while the visible rotor blade 18 to the left of the axis of rotation 34 extends axially upward to the viewer. The rotor shaft 36 and the rotor disk 12 rotate about their axis of rotation 34.

In Fig. 5 Furthermore, the rotor shaft 36 is mounted radially and preferably also axially on the ejection side 52 with a roller bearing 30. The roller bearing 30 can be designed, for example, as a ball bearing or as a cylindrical roller bearing. The rotor shaft 36 is supported on the suction side 40 with a contactless and lubrication-free radial bearing 32, preferably with a magnetic bearing.

The blade rotor 12 of the Fig. 5 is surrounded by a housing 38. The housing 38 has depressions 22 on its inner side facing the blade rotor 12. Instead of the housing 38, for example, a ring element, such as a spacer ring 54 (cf. Fig. 1 ) can be provided with depressions 22 according to the invention, ie component 38 in Fig. 5 then represents such a spacer ring which interacts with the rotor disk 12 in the manner according to the invention.

The depressions 22 are arranged helically around the blade rotor 12 in the form of grooves. The direction of rotation of the helical recesses 22 corresponds to the direction of rotation 44 of the blade rotor 12. In the Fig. 2 , 3rd and 5 the direction of rotation corresponds to that of a left-handed thread. Crosspieces 24 are formed between the depressions 22. The webs 24 are here just as wide as the depressions 22. The pump-active partial area of the inner wall of the housing 38 goes into Fig. 5 axially in both directions beyond the blade rotor 12. In Fig. 5 the depressions 22 have an incline which is less than 45 °. The depressions 22 are designed as vertically milled grooves.

A blade stator, also referred to as a stator disk, can be arranged axially below and / or above the blade rotor 12. Further turbomolecular pump stages can also be arranged axially above and below the blade rotor 12. The structure can therefore, for example, correspond to the turbomolecular pump section Fig. 1 be chosen.

Alternatively, it is also possible not to provide a stator disk adjacent to the rotor disk 12. For example, two or more rotor disks can be arranged axially in direct succession before another stator disk follows, ie there are then at least one pair of immediately successive rotor disks, between which no stator disk is arranged in each case. Only rotor disks can also be provided, ie stator disks can also be dispensed with entirely, at least for a turbomolecular pump section of the turbomolecular pump. For such a construction of one or more turbomolecular pump sections of a turbomolecular pump and for such a turbomolecular pump as a whole, which otherwise have a typical construction as for example in Fig. 1 protection can be shown separately. Axial areas of such a pump section, in which there is no stator disk, can then have, according to the present invention, one or more ring-shaped or sleeve-shaped elements, each of which forms a wall surrounding the rotor disks, which on at least one pump-effective partial area of its side facing the rotor disks at least one recess is provided, but this is not mandatory.

As can be seen from the exemplary embodiments, a Holweck stator can therefore be arranged around the blade rotor of a turbomolecular pump stage according to the invention. As a result, gas particles which are accelerated outwards by the rotor against the inner wall of the housing are deflected in an axial direction by a Holweck stator thread. This in turn makes the probability of passage increases in the conveying direction and thus improves the power density of a turbomolecular pump.

In the case of arrangements known from the prior art, the particles to be conveyed hit a smooth surface in the radial gap between the radially outer end of the rotor blades and the inner wall of the housing or the inside of the stator spacer ring. There the particles stuck briefly and left this surface again with a cosine distribution, whereby they did not experience any other preferred direction. By means of the invention and in particular the Holweck thread according to the invention, more particles can now leave the inner wall of the housing or the inside of a wall facing the blade rotor with an axial component which points in the direction of the pump outlet, ie in the pumping direction. Simulation results for a single-stage turbomolecular pump with nitrogen to be pumped resulted in the following: The starting point was a housing inner wall without depressions, a compression ratio of K ₀ = 8.1 and a pumping speed S ₀ = 2262 L / s. With Holweck thread, the compression ratio improved to K ₀ = 8.8 and the pumping speed to S ₀ = 2304 L / s.

Reference list

12th

Blade rotor, rotor disc

14

Blade stator, stator disc

16

wall

18th

shovel

20th

shovel

22

deepening

24th

web

26

Rotor area

28

Stator area

30th

roller bearing

32

Radial bearing (permanent magnet bearing)

34

Axis of rotation

36

Rotor shaft

38

casing

40

Suction side

42

Pump direction

44

Direction of rotor rotation

46

Angle of attack of the stator blades

48

Slope of the depression

50

Angle of attack of the rotor blades

52

Discharge side

54

Spacer ring

56

Turbomolecular pump section

58

Holweck pump section

Claims (12)

1. A turbomolecular pump comprising
   at least one turbomolecular pump stage which comprises at least one blade rotor (12) rotatably supported about an axis (34),
   wherein a wall (16) at least partly surrounding the blade rotor (12) is provided with at least one recess (22) at at least one pump-active part region of its side facing the blade rotor (12),
   characterized in that
   the recess (22) has a spiral or helical course; and/or in that the pump-active part region is configured as a Holweck stator.
2. A turbomolecular pump in accordance with claim 1,
   characterized in that
   the recess (22) has a course with an axial component and/or with a pitch which differs from zero.
3. A turbomolecular pump in accordance with one of the preceding claims,
   characterized in that
   the recess (22) is groove-like or channel-like.
4. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   the pump-active part region is provided with a plurality of recesses (22), in particular non-contiguous recesses (22), with the recesses (22) in particular extending in parallel with one another.
5. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   the wall (16) is formed by a housing (38) surrounding the blade rotor (12) and the pump-active part region is formed at the inner side of the housing (38), with the housing (38) in particular being the outer housing of the pump.
6. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   the wall (16) is formed by at least one ring element which surrounds the blade rotor (12) and which is in particular configured as a separate insert; and in that the pump-active part region is formed at the inner side of the ring element, with the ring element in particular being a distance ring (54), a spacer ring, a distance sleeve and/or a spacer sleeve, which is arranged between two stator disks (14) following one another in the axial direction.
7. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   the blade rotor (12) comprises a plurality of rotor disks which are arranged axially following one another, which are connected in one piece to one another or which are separate; and/or in that
   the pump-active part region extends in the axial direction only over a partial quantity of rotor disks, preferably comprising the rotor disk disposed closest to the suction side (40) of the pump, and in particular extends over exactly one rotor disk.
8. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   at least some blades (20) of a blade stator (14) cooperating with the blade rotor (12) are connected to the wall (16), and/or in that the pump-active part region is located axially outside blades (20) of a blade stator (14) cooperating with the blade rotor (12).
9. A turbomolecular pump in accordance with any one of the preceding claims,
   characterized in that
   a blade stator (14) cooperating with the blade rotor (12) comprises a plurality of stator disks (14) arranged axially following one another, with the pump-active part region only being present axially between the stator disks (14) and/or axially adjacent to at least one of the stator disks (14).
10. A turbomolecular pump in accordance with any one of the preceding claims,
    characterized in that
    blades (20) of a blade stator (14) cooperating with the blade rotor (12) each have a blade angle (46), which is at least approximately equal to a pitch (48) of the recess (22), in a radially outer end region.
11. A turbomolecular pump in accordance with any one of the preceding claims,
    characterized in that
    blades (18) of the blade rotor (12) each have a blade angle (48), which differs from a pitch (48) of the recess (22) by between 45° and 90°, in a radially outer end region.
12. A turbomolecular pump in accordance with any one of the preceding claims,
    characterized in that
    the pump-active part region has a plurality of recesses (22) which extend in parallel and which are separated from one another by webs (24), with the number of webs (24) being at least approximately equal to the number of blades (20) per stator disk (14) of a blade stator (14) cooperating with the blade rotor.

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