EP3032107A2 - Turbomolecular pump - Google Patents

Abstract

The invention relates to a turbomolecular pump having at least one turbomolecular pumping stage which comprises at least one blade rotor (12) rotatably mounted about an axis (34), a wall (16) at least partially surrounding the blade rotor (12) on at least one pumping effective portion of its blade rotor (12). 12) facing side is provided with at least one recess. Furthermore, the invention relates to a turbomolecular pump having at least one turbomolecular pumping stage, which is surrounded by a Holweckstator at least in a Teilaxialbereich whose pump effective side facing the blade rotor (12) of the turbomolecular pumping stage.

Description

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

Such turbomolecular pumps are basically known and are known e.g. used in the semiconductor industry and in physical research to generate a high vacuum needed there. The turbomolecular pump is characterized by a blade rotor, also referred to below as a rotor, whose structure is reminiscent of the rotor of a turbine. The blade rotor interacts with a blade stator, also referred to below as a stator, and usually rotates at such a high speed that the tangential velocity of the individual rotor blades is of a similar magnitude to the mean thermal velocity of particles to be conveyed. In a vertical pumping direction from top to bottom, the majority of the particles collide with a bottom surface of an angularly pitched rotor blade. By a preferred direction of the bottom of the rotor blade in the pumping direction creates a pumping action.

The rotor must also be surrounded by a wall to prevent backflow of the particles outside the rotor area. Such a wall is formed, for example, from the inside of a housing containing the turbomolecular pumping stage or from the insides of stator stator 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 that by themselves or after colliding with a rotor blade on the cylindrical inner surface of the wall meet there no pumping action more.

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 with the features of claim 1, and in particular in that a wall at least partially surrounding the blade rotor is provided on at least one pump effective portion of its blade rotor side facing with at least one recess.

From molecular pumps e.g. According to Gaede or Holweck, it is known that such a depression itself can give the particles to be conveyed a further preferred direction. It is advantageous if the particles already have a preferred direction before they enter the depression, so that the majority of the particles strike an area of the depression pointing with their normal in the pumping direction. This is generally the case with a blade rotor of a turbomolecular pump located opposite a recess, because, due to the rotation of the rotor blades, a tangential velocity component of the particles is generally not zero but with an amount greater than zero in the direction of rotation. As a result, the wall can effectively become a pump-active subarea itself.

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

It is inventively particularly simple and kostengrünstig to bring such a depression in the blade rotor facing side of the wall. A such depression can be easily introduced, for example, with an ordinary milling tool.

Further, this can be increased on an existing flange with an existing pump, the pumping speed and compression. 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 as rotor components. They can therefore be modified and installed without qualification. For this reason, further developments of turbomolecular pumps are particularly advantageous in terms of development if they merely relate to static components, as is possible according to the invention here.

The pumping action is further improved if the depression has a course with an axial component and / or with a non-zero pitch. As a result, the particles are given a preferential direction, likewise with an axial component. The pumping action in the axial direction is thus improved.

Advantageously, the recess may have a spiral or helical course. The recess may thus have a thread profile corresponding to the recess profile in Gaede'sche screw pumps or molecular pumps according to Holweck. The depression may be formed as a helix. As a result, the particles are taught even more uniformly the desired preferred direction. The spiral or helical course of the depression advantageously has the same direction of rotation as the blade rotor.

The recess may also be formed groove or channel-like. The guidance of the particles in their preferred direction is thereby further improved. Such a groove or channel can be particularly easily introduced into a wall inside.

Advantageously, the pump-effective portion is further provided with a plurality of, in particular unrelated, depressions. In this case, the depressions can advantageously extend parallel to one another. By providing a plurality of indentations according to the invention, the pumping action of the inside of the wall can be increased, in particular proportionally to the number of recesses. Disconnected and / or parallel wells are also particularly easy to introduce and prevent backflow between the wells.

Advantageously, the pump-effective portion of the wall is designed as Holweckstator. So can be applied to a Turbomolekularpumpstufe with a few design measures of the known Holweckstator.

The wall may advantageously be formed by a housing surrounding the blade rotor. The pump-effective portion is formed on the inside of the housing. This does not require an additional wall to be introduced into the pump housing. The recess can also be produced by casting casings or by milling. In particular, the housing may be the outer housing of the pump. As a result, even fewer items are needed.

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

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

In an advantageous embodiment, the blade rotor comprises a plurality of axially successively arranged, integrally connected or separate rotor disks. The pumping power of the turbomolecular pump can be further improved by a plurality of rotor disks.

Advantageously, it can be provided that the pump-effective portion extends in the axial direction only over a, preferably the suction side of the pump nearest rotor disk comprehensive, subset of rotor disks, in particular over exactly one rotor disk. At the first rotor disk in the pumping direction, the pumping effect can be improved particularly effectively by the recess according to the invention.

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

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

Alternatively, a pump-effective region of the wall may extend at least substantially over the entire axial length of the turbomolecular pump. Advantageously, it can further be provided that a blade stator interacting with the blade rotor comprises a plurality of stator disks arranged axially one after the other, wherein the pump-effective portion is only axially between the stator disks and / or axially adjacent to at least one of the stator disks. For example, the pump-effective portion may be formed by the inner sides of each of stator disks and thus located at the height of a rotor disk stator spacer rings. This facilitates the insertion of the recess.

Advantageously, it may further be provided that blades of a blade stator interacting with the blade rotor have in each case an angle of attack in a radially outer end region which is at least approximately equal to a pitch of the recess. The recess extends at least substantially parallel to the orientation or to the angle of attack of the stator blades. This further improves the transmission of the particles.

In a further embodiment, the blades of the blade rotor in each case have an angle of attack in a radially outer end region which is different between a pitch of 45 ° and 90 ° of a pitch of the recess. The recess is arranged perpendicular or at an acute angle to the rotor blades.

It may also be advantageously provided that the pump-effective portion has a plurality of parallel depressions, which are separated by webs, wherein the number of webs is at least approximately equal to the number of blades per stator of a cooperating with the blade rotor paddle stator. It may be advantageous to provide just as many depressions or as many webs as stator blades. Furthermore, the number of rotor blades can be equal to the number of stator blades. As a result, the passage probability of the individual particles can be further improved.

The stator blades can be fixedly connected to the webs of the inside of the wall, in particular designed to be material-locking. The stator blades can thus spring from the webs between the recesses. The recesses may also extend between the stator vanes. The recesses may also extend continuously over a plurality of turbomolecular pumping stages or over a plurality of alternately arranged rotor and stator disks. The depressions can be designed as multi-threaded internal thread. Thus, an improved continuous particle flow in the pump effective portion can be achieved.

A recess according to the invention can also be arranged on the inside of a stator spacer ring. This facilitates the production of turbomolecular pumps in particular with several turbomolecular pumping stages or with a plurality of alternately arranged rotor and stator disks.

The object of the invention also solves a turbomolecular pump having at least one turbomolecular pumping stage, which is surrounded at least in a Teilaxialbereich by a Holweckstator whose pump-effective side facing the blade rotor of the turbomolecular pumping stage.

The invention thereby combines a turbomolecular pump stage with a Holweck pump stage or creates a hybrid pump stage from these two pump types.

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

Further embodiments of the invention are indicated 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 will now be described 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 in perspective view a pumping stage of a turbomolecular pump according to the invention.

Fig. 3

shows in another perspective view a part of the pumping stage of Fig. 2 ,

Fig. 4

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

Fig. 5

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

Fig. 1 purely by way of example shows a turbomolecular pump having a typical basic structure with a turbomolecular pumping section 56 and a Holweck pumping section 58. The turbomolecular pump comprises a rotor shaft 36 rotatable in a housing 38 through a ball or generally rolling bearing 30 on the ejection side and through mounted as a permanent magnet bearing radial bearing 32 is mounted on the suction side 40 of the turbomolecular pump. On the rotor shaft 36 sit a plurality of rotor disks 12, which rotate in operation together with the rotor shaft 36. Between the rotor disks 12, stator disks 14 are arranged axially alternately with the rotor disks 12. The stator disks 14 are in their mutual axial distance by spacer or spacer rings 54 fixed. The spacer rings 54 have on their side facing the rotor disks 12 each have a wall, the invention in each case with one or more recesses, for example according to the embodiment of Fig. 5 , are provided.

The Fig. 2 shows a paddle rotor 12 and a blade stator 14 of a turbomolecular pumping stage. The blade rotor is surrounded by a wall 16 in the radial direction. The blade rotor 12 rotates about a not shown, concentric axis with the direction of rotation 44. From radially inward to radially outward extending rotor blades 18 which are twisted in itself. That is, the angle of attack, which refers to the radially outer ends of the stator blades, is steeper than the angle of origin of the rotor blades. The blade rotor is also designed substantially as a disc, ie it extends substantially in the radial direction and has a thickness in the axial direction.

The Schaufelstator 14 of Fig. 2 is essentially the same as the blade rotor 12, but to a certain extent mirror-inverted. The stator blades 20 also spring radially inward on the blade stator 14. However, they can also spring radially outward, for example on the wall 16.

The wall 16 encloses the blade rotor 12 in the radial direction. On the inside, ie on the side facing the blade rotor, the wall 16 recesses 22. The recesses 22 are each designed as a groove and extend helically in the axial direction. Between the recesses 22 webs 24 are formed. Between the webs 24 so there is a kind of channel in a pump effective portion. The number of depressions 22 and the number of webs 24 are each equal to the number of stator blades 20 and equal to the number of rotor blades 18. The depressions 22 are arranged parallel to each other and parallel to the outer ends of the stator blades 20. The pumping direction depends on Fig. 2 from top to bottom, ie axially downwards. The Fig. 3 shows an alternative view of the turbomolecular pumping stage of Fig. 2 , Axially adjacent the vane rotor 12 and the vane stator 14 are arranged. The blade rotor is radially enclosed by the wall 16. The wall 16 has on its inside the recesses 22 and the webs 24 arranged therebetween. 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 region, 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 extend parallel to the depressions 22. In this case, they are made narrower than the depressions 22. The recesses 22 are designed as channel-like, rectangular grooves on the inside of the wall 16. Accordingly, the webs 24 are also formed at right angles. 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, ie in the Fig. 3 the rear ends of the recesses 22 are arranged circumferentially between the stator blades 20. A particle flow in a depression 22 can thereby flow unhindered between the stator blades 20. The axially lower ends of the recesses 22 face the blade stator.

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

Instead of "stages", it is also possible to speak of "slices", i. This exemplified turbomolecular pump comprises two rotor and two stator disks, which together can also be referred to as turbomolecular pumping stage.

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

Inside on a wall 16, not shown (eg Fig. 2 or 3 ) depressions 22 are arranged. Between the recesses 22 webs 24 are arranged. 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 equal to the pitch 48 of the depressions 22 at their radially outer ends. The depressions 22 are also located centrally in the circumferential direction between the stator blades 20. The recesses 22 thus extend in the pumping direction from an upper intake side to a lower discharge side continuously over both illustrated turbomolecular pump stages.

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

The Fig. 5 schematically shows some components of a turbomolecular pump according to the invention, in a schematic diagram of a rotor blade designated as a blade rotor 12 with blades 18 which rotatably mounted on a rotor shaft 36 and of which only a rotor disk 12 is shown. Of the Blade rotor 12 rotates with the rotor shaft 36 in the rotor rotation direction 44. Thus, it causes a pumping action in the pumping direction 42 from a suction side 40 toward an ejection 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 on the left of the axis of rotation 34 extends axially up 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 on the discharge side 52 with a rolling bearing 30 radially and preferably also axially. The rolling bearing 30 may be embodied for example as a ball bearing or as a cylindrical roller bearing. On the suction side 40, the rotor shaft 36 is mounted with a non-contact and lubrication-free radial bearing 32, preferably with a magnetic bearing.

The paddle wheel 12 of the Fig. 5 is surrounded by a housing 38. The housing 38 has recesses 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 (see. Fig. 1 ), be provided with recesses 22 according to the invention, ie, the component 38 in Fig. 5 then represents such a spacer ring, which cooperates in the manner according to the invention with the rotor disk 12.

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

Axially below and / or above the blade rotor 12, a blade stator, also referred to as a stator disk, may be arranged adjacent. Axially above and below the blade rotor 12 further turbomolecular pumping stages may be further arranged. The structure can therefore, for example, according to the turbomolecular pumping section according to Fig. 1 be elected.

It is alternatively also possible to provide no stator disk 12 adjacent to the rotor disk. For example, two or more rotor disks may be arranged axially immediately following one another, before a stator disk follows again, ie at least one pair of immediately successive rotor disks is present, between which no stator disk is arranged in each case. It can also be provided exclusively rotor disks, ie on stator discs can be completely dispensed with, at least for a turbomolecular pumping section of the turbomolecular pump. For such a structure of one or more turbomolecular pumping sections of a turbomolecular pump and for such a turbomolecular pump as a whole, which otherwise has a typical structure such as in Fig. 1 may have shown, is also claimed separately protection. Axial areas of such a pump section, in which there is no stator, then according to the present invention, one or more annular or sleeve-shaped elements each having a surrounding the rotor disks wall on at least one pump effective portion of their rotor disks facing side at least one depression is provided, but this is not mandatory.

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

In known from the prior art arrangements, the particles to be conveyed in the radial gap between the radially outer end of the rotor blades and the housing inner wall and the stator spacer ring inside against a smooth surface. There, the particles remained briefly adhere and left this surface again with a cosine distribution, where they learned no other preferred direction. By means of the invention and in particular the Holweck thread according to the invention, it is now possible for more particles to leave the housing inner wall or the inner side of a wall facing the blade rotor with an axial component pointing in the pump outlet direction, ie in the pumping direction. Simulation results for a single-stage turbomolecular pump with nitrogen to be delivered have shown 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. Holweck threading improved the compression ratio to K ₀ = 8.8 and the suction to So = 2304 L / s.

LIST OF REFERENCE NUMBERS

12

Blade rotor, rotor disk

14

Paddle stator, stator disc

16

wall

18

shovel

20

shovel

22

deepening

24

web

26

rotor area

28

stator

30

roller bearing

32

Radial bearing (permanent magnet bearing)

34

axis of rotation

36

rotor shaft

38

casing

40

suction

42

pumping direction

44

Rotor rotation

46

Incident angle of the stator blades

48

Slope of the depression

50

Angle of attack of the rotor blades

52

discharge side

54

spacer

56

Turbo-molecular pump section

58

Holweck pumping section

Claims (15)

Turbomolecular pump with
at least one turbomolecular pump stage comprising at least one blade rotor (12) rotatably mounted about an axis (34),
wherein a wall (16) at least partially surrounding the blade rotor (12) is provided with at least one recess (22) on at least one pump-effective partial area of its side facing the blade rotor (12). Turbomolecular pump according to claim 1,
characterized in that
the recess (22) has a profile with an axial component and / or with a non-zero pitch. Turbomolecular pump according to claim 1 or 2,
characterized in that
the recess (22) has a spiral or helical course. Turbomolecular pump according to one of the preceding claims,
characterized in that
the recess (22) is groove-shaped or channel-shaped. Turbomolecular pump according to one of the preceding claims,
characterized in that
the pump-effective portion is provided with a plurality of, in particular unrelated, recesses (22), wherein in particular the recesses (22) extend parallel to each other. Turbomolecular pump according to one of the preceding claims,
characterized in that
the pump-effective portion is formed as Holweckstator. Turbomolecular pump according to 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-effective portion is formed on the inside of the housing (38), wherein in particular the housing (38) is the outer housing of the pump. Turbomolecular pump according to one of the preceding claims,
characterized in that
the wall (16) of at least one the blade rotor (12) formed, in particular designed as a separate insert, ring member and the pump effective portion is formed on the inside of the ring member, wherein in particular the ring member is a spacer ring (54), a spacer ring, a spacer sleeve and / or a spacer sleeve which is arranged between two axially successive stator disks (14). Turbomolecular pump according to one of the preceding claims,
characterized in that
the blade rotor (12) comprises a plurality of axially successively arranged, integrally connected or separate rotor disks, and / or
the pump-effective portion extends in the axial direction only over a, preferably the suction side (40) of the pump closest rotor disk comprehensive, subset of rotor disks, in particular over exactly one rotor disk. Turbomolecular pump according to 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
the pump-effective portion is located axially outside of blades (20) of a blade stator (14) cooperating with the blade rotor (12). Turbomolecular pump according to one of the preceding claims,
characterized in that
a vane stator (14) cooperating with the vane rotor (12) comprises a plurality of stator disks (14) arranged axially successively, wherein the pump effective portion is only axially between the stator disks (14) and / or axially adjacent to at least one of the stator disks (14) , Turbomolecular pump according to one of the preceding claims,
characterized in that
Blades (20) of a blade stator (14) interacting with the blade rotor (12) each have an angle of incidence (46) in a radially outer end region which is at least approximately equal to a pitch (48) of the recess (22). Turbomolecular pump according to one of the preceding claims,
characterized in that
Blades (18) of the blade rotor (12) in each case have a setting angle (48) in a radially outer end region which is different between 45 ° and 90 ° from a pitch (48) of the recess (22). Turbomolecular pump according to one of the preceding claims,
characterized in that
the pump-effective portion having a plurality of parallel recesses (22) which are separated by webs (24), wherein the number of webs (24) at least approximately equal to the number of blades (20) per stator disc (14) one with the blade rotor cooperating Schaufelstators (14). Turbomolecular pump with
at least one turbomolecular pump stage, which is surrounded at least in a Teilaxialbereich by a Holweckstator whose pump effective side facing the blade rotor (12) of the turbomolecular pumping stage.

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