Vacuum pump

Abstract

A vacuum pump has a working space, a bearing space, a dividing wall arranged between the working space and the bearing space and at least one rotor shaft which extends through the dividing wall and which forms a gap with the dividing wall and having a blocking device for blocking between the working space and the bearing space. The blocking device is formed by a Siegbahn pump stage which is configured for providing a pump action passing through the gap between the working space and the bearing space.

Claims

1. A vacuum pump, comprising: a working space (12), a bearing space (14), a dividing wall (16) arranged between the working space (12) and the bearing space (14), a blocking device for blocking between the working space (12) and the bearing space (14), at least one rotor shaft (18) extending through the dividing wall (16), and a bearing for rotationally supporting the at least one rotor shaft located in the bearing space (14), and a gap (20) between the at least one rotor shaft (18) and the dividing wall (16), wherein the blocking device is formed by a Siegbahn pump stage (22), the Siegbahn pump stage being configured to provide a pump action between the working space (12) and the bearing space (14), with the pumping action directed through the gap (20) to block the bearing space (14) from the working space (12), wherein the Siegbahn pump stage (22) comprises a stator member (24) and a rotor member (26), wherein the stator member (24) and the rotor member (26) each forms one of two mutually oppositely disposed surfaces (28, 30) acting as pumps of the Siegbahn pump stage (22), and a rotor hub of a Holweck pump stage which simultaneously forms the rotor member (26) of the Siegbahn pump stage (22).

2. The vacuum pump in accordance with claim 1, wherein the pump is one of a turbomolecular pump and a side-channel pump.

3. The vacuum pump in accordance with claim 1: wherein one surface (28) of the two mutually oppositely disposed surfaces (28, 30) acting as a pump is formed by a structured surface and another surface (30) of the two mutually oppositely disposed surfaces (28, 30) acting as a pump is formed by a planar surface.

4. The vacuum pump in accordance with claim 3, wherein the stator member (24) has the structured surface (28) acting as a pump.

5. The vacuum pump in accordance with claim 1: wherein the two mutually oppositely disposed surfaces (28, 30) acting as pumps bound at least one conveying passage (34) of the Siegbahn pump stage (22) and a sealing gap (32) for sealing the conveying passage (34).

6. The vacuum pump in accordance with claim 5, wherein a region of at least one surface (28, 30) of the two mutually oppositely disposed surfaces (28, 30) acting as a pump which bounds the sealing gap (32) is or can be produced at least by a material-removing machining.

7. The vacuum pump in accordance with claim 1, wherein at least one of the stator member (24) and the rotor member (26) is configured as substantially disk-shaped.

8. The vacuum pump in accordance with claim 1, wherein at least one of the stator member (24) and the rotor member (26) is configured as one of an injection molded part, a forged part and a shaped part.

9. The vacuum pump in accordance with claim 1, wherein at least one of the stator member (24) and the rotor member (26) at least partly or fully comprises a metal.

10. The vacuum pump in accordance with claim 9, wherein the metal is aluminum.

11. The vacuum pump in accordance with claim 1, wherein at least one of the stator member (24) and the rotor member (26) at least partly or fully comprises a plastic.

12. The vacuum pump in accordance with claim 1, wherein the stator member (24) is configured as a separate part which is carried by a static component (16, 48) of the vacuum pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in the following by way of example with reference to advantageous embodiments and to the enclosed drawings. The drawings show:

(2) FIGS. 1 to 4 a cross-sectional view of, respectively, a vacuum pump in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(3) The vacuum pump shown in FIG. 1 is configured as a turbomolecular pump and comprises a working space 12 and a bearing space 14, which are bounded by a pump housing 48 of the vacuum pump, a dividing wall 16 separating the working space 12 and the bearing space 14 from one another, and a rotor shaft 18 which extends through the dividing wall 16 into the working space 12 and into the bearing space 14 while forming a radial gap 20.

(4) The turbomolecular pump structure is accommodated in the working space 12. This pump structure comprises a plurality of turbomolecular rotor disks 42 fastened to the rotor shaft 18 and comprises turbomolecular stator disks 44 arranged between the rotor disks 42 and fixed in the housing 48. The pump structure provides a pump action for a process gas which is applied at a pump inlet 38 which is bounded by an inlet flange 58 of the housing 48. This pump action serves to convey the process gas from the pump inlet 38 to the pump outlet 40.

(5) A roller element bearing 46 which supports the rotor shaft 18 rotatably about the axis of rotation 19 is arranged in the bearing space 14. In principle, a magnetic bearing or a magnetic bearing cartridge could also be provided in the bearing space 14 for the rotatable support of the rotor shaft 18. Furthermore, a drive, not shown in FIG. 1 for the rotor shaft 18 can be provided in the bearing space 14.

(6) The vacuum pump comprises a Siegbahn pump stage 22 having a stator member 24 carried by the dividing wall 16 and a rotor member 26 carried by the rotor shaft 18. The stator member 24 and the rotor member 26 are each configured substantially in disk shape and are oriented radial to the direction of rotation of the axis of the rotor shaft 18.

(7) The stator member 24 and the rotor member 26 each have one of two mutually oppositely disposed surfaces 28, 30 acting as pumps which form the structure acting as a pump of the Siegbahn pump stage 22. Whereas the surface 30 acting as a pump of the rotor member is formed by a planar surface which is oriented perpendicular to the axis of rotation 19 of the rotor shaft 18, the surface 28 acting as a pump of the stator member 24 is structured.

(8) The surface 28 acting as a pump of the stator organ 24 comprises a depression which forms a conveying passage 34 of the Siegbahn pump stage 22, which extends spirally from internal to external in the radial direction, and an elevated portion 36 bounding the depression or the conveying passage 34. The surface region of the elevated portion 36 which faces toward the surface 30 acting as a pump of the rotor member 26 forms an axial sealing gap 32 with the surface 30 acting as a pump, said sealing gap sealing the conveying passage 34.

(9) In the operation of the vacuum pump, the gas present in the conveying passage 34 is driven by the structure acting as a pump in the direction of rotation of the rotor shaft 18 and is thereby conveyed outwardly along the spiral line shape of the conveying passage 34 from the inlet 30 of the Siegbahn pump stage 22 facing the gap 20 in the radial direction to the outlet 52 of the Siegbahn pump stage 22 facing the working space 12. A pump action directed through the gap 20 from the bearing space 14 into the working space 12 is thereby provided which is illustrated by arrows 54 in FIG. 1 and which blocks the bearing space 14 from the working space 12.

(10) The vacuum pumps shown in FIGS. 2 to 4 substantially correspond, with the exception of the special features described in the following, to the vacuum pump shown in FIG. 1, with the same reference numerals in FIGS. 1 to 4 each designating the same or mutually corresponding components.

(11) In the vacuum pump shown in FIG. 2, the rotor member 26 of the Siegbahn pump stage 22 and its surface 28 acting as a pump are formed by the last rotor disk 42 in the conveying direction. The section of the rotor disk 42 forming the surface 28 acting as a pump carries the vanes of the rotor disk 42 which extend outwardly in the radial direction starting from this section. The process gas is conveyed, following on from the last rotor disk 42, laterally past the bearing space 14 in the direction of the axis of rotation to the pump outlet 40.

(12) The drive 60 arranged in the bearing space 14 is also shown schematically in FIG. 2.

(13) The vacuum pump shown in FIG. 3 substantially corresponds to the vacuum pump shown in FIG. 2, with a Holweck pump stage having a Holweck rotor 62 and a Holweck stator 64 being provided instead of the last turbomolecular pump stage in the direction of flow of the pump shown in FIG. 2, said Holweck pump stage conveying the gas conveyed by the turbomolecular pump stages further to the pump outlet 40. The rotor member 26 of the Siegbahn pump stage 22 and its surface 28 acting as a pump are formed in this embodiment by the rotor hub of the Holweck pump stage connected to the rotor shaft 18 or by a planar surface thereof which is of disk shape and which is oriented in the radial direction toward the axis of rotation 19.

(14) The Holweck rotor 62 comprises a Holweck cylinder 66 carried by the rotor hub and having a smooth radial outer surface in the present embodiment which forms a surface acting as a pump of the Holweck pump stage and is disposed opposite a surface acting as a pump of the Holweck stator 64 formed by the radial inner surface of the sleeve-shaped Holweck stator 64 while forming a narrow radial Holweck gap 68. The surface acting as a pump of the Holweck stator 64 is structured and forms one or more conveying passages which extend spirally about the axis of rotation 19 in the axial direction. In the operation of the vacuum pump, the process gas conveyed by the turbomolecular pump stages to the inlet of the Holweck pump stage in conveyed in the conveying passages of the Holweck pump stage and through them to the pump outlet 40.

(15) The vacuum pump shown in FIG. 4 substantially corresponds, except for the special features described in the following, to the vacuum pump shown in FIG. 3.

(16) The vacuum pump shown in FIG. 4 comprises a larger number of turbomolecular pump stages each having a rotor disk 42 and a stator disk 44, with the stator disks 44 being held by spacer rings 70 at a predefined spacing from one another. The vacuum pump furthermore comprises three Holweck pump stages which follow one another in the radial direction nested in one another, which are connected to the turbomolecular pump stages and to one another in series in the direction of flow and which are each formed in the manner described above with respect to the Holweck pump stage shown in FIG. 2.

(17) The Holweck pump stages comprise a Holweck rotor 62 having an outer Holweck cylinder 72 and an inner Holweck cylinder 74 which are each carried by a common rotor hub which simultaneously forms the rotor member 26 and the surface 28 acting as a pump of the Siegbahn pump stage 22. The Holweck pump stages furthermore comprise an outer Holweck stator 76 and an inner Holweck stator 78 which are each formed in sleeve shape. The radial inner surface of the outer Holweck stator 76 forms a first Holweck pump stage having a Holweck gap 80 with the radial outer surface of the outer Holweck cylinder 72; the radial inner surface of the outer Holweck cylinder 72 forms a second Holweck pump stage having a Holweck gap 82 with the radial outer surface of the inner Holweck stator 78; and the radial inner surface of the inner Holweck stator 78 forms a third Holweck pump stage having a Holweck gap 84 with the radial outer surface of the inner Holweck pump stage 74.

(18) The vacuum pump shown in FIG. 4 comprises a drive 60 which is configured as an electric motor and which is brushless DC motor in the present embodiment. An electronic control unit 86 serves for the control and current feed of the drive 60.

(19) A conical splash nut 58 having an outer cross-section reducing toward the roller element bearing 46 is provided at the end of the rotor shaft 18 at the bearing space side. The splash nut 88 is in sliding contact with at least one wiper of an operating medium store which comprises a plurality of absorbent disks 90 which are stacked on one another and which are saturated with an operating medium for the roller element bearing 46, e.g. with a lubricant for the roller element bearing 46. In the operation of the vacuum pump, the operating medium is transferred from the operating medium store via the wiper through the capillary action onto the rotating splash nut 88 and is conveyed as a result of the centrifugal force in the direction of the outer diameter of the splash nut 88 increasing in size to the roller element bearing 46, where it satisfies its desired function. The roller element bearing 46 and the operating medium store are encompassed by a tub-shaped insert 92 and by a cover element 94 of the vacuum pump.

(20) The rotor shaft 18 is rotatably supported by a magnetic bearing, which is configured as a permanent magnetic bearing in the present embodiment, at the high vacuum side, i.e. in the region of the pump inlet 38. The magnetic bearing comprises a bearing half 96 at the rotor side and a bearing half 98 at the stator side which each comprise a ring stack of a plurality of permanently magnetic rings 100 and 102 respectively stacked on one another in the axial direction. The magnetic rings 100, 102 are disposed opposite one another while forming a narrow radial bearing gap 103, with the magnetic rings 100 at the rotor side being arranged radially outwardly and the magnetic rings 102 at the stator side being arranged radially inwardly. The magnetic field present in the bearing gap 103 effects magnetic repulsion forces between the rings 100, 102 which effect a radial support of the rotor shaft 18.

(21) The magnetic rings 100 at the rotor side are carried by a carrier section 104 of the rotor shaft 18, the carrier section surrounding the magnetic rings 100 at the radially outer side. The magnetic rings 102 at the stator side are carried by a carrier section 106 at the stator side which extends through the magnetic rings 102 and is suspended at radial struts 108 of the housing 48. The magnetic rings 100 at the rotor side are fixed in parallel with the axis of rotation 19 in the one direction by a cover element 110 coupled to the carrier section 104 and in the other direction by a shoulder section of the carrier section 104. The magnetic rings 102 at the stator side are fixed in parallel with the axis of rotation in the one direction by a fastening ring 112 connected to the carrier section 106 and by a compensation element 114 arranged between the fastening ring 112 and the magnetic rings 102 and are fixed in the other direction by a support ring 116 connected to the carrier section 106.

(22) An emergency bearing or safety bearing 118 is arranged within the magnetic bearing; it idles in the normal operation of the vacuum pump without contact and only moves into engagement on an excessive radial deflection of the rotor relative to the stator to form a radial abutment for the rotor shaft 18 which prevents a collision of the structures at the rotor side with the structures at the stator side. The safety bearing 118 is configured as a non-lubricated roller element bearing and forms a radial gap with the rotor and/or the stator, said gap having the effect that the safety bearing 118 is out of engagement in normal pump operation. The radial deflection at which the safety bearing 118 comes into engagement is dimensioned sufficiently large that the safety bearing 118 does not move into engagement in the normal operation of the vacuum pump and is simultaneously small enough that a collision of the structures at the rotor side with the structures at the stator side is avoided under all circumstances.

(23) The vacuum pump shown in FIG. 4 comprises a barrier gas inlet 122 which is closed by a closure element 120, which connects the bearing space 14 to the pump exterior and via which a barrier gas can be supplied to the bearing space 14. The barrier gas supplied to the bearing space 14 is conveyed via the Siegbahn pump stage 22 into the working space 12 in the operation of the vacuum pump, whereby the bearing space 14 is blocked with respect to the working space 12.