Vacuum pump with vortex damper

Abstract

The invention relates to a vacuum pump, in particular a turbo molecular vacuum pump, comprising a housing and a rotor shaft arranged within the housing and rotatably supported by at least one permanent magnet bearing. Wherein the magnetic bearing is disposed at one end of the rotor shaft, and wherein the magnetic bearing comprises a static bearing element and a swivel bearing element disposed radially adjacent to each other. The eddy current damper is provided with an electrically conductive disc connected to the static bearing element.

Description

Technical Field

[0001] The invention relates to a vacuum pump, in particular to a turbomolecular pump. Background Art

[0002] A common vacuum pump includes a housing having an inlet and an outlet. A rotor is disposed in the housing and rotatably supported by at least one bearing. The rotor includes a rotor shaft, wherein at least one pump element is connected to the rotor shaft. In the case of a turbomolecular vacuum pump, a plurality of blades are connected to the rotor shaft and interact with a plurality of blades of a stator connected to the housing. When the motor rotates the rotor, a gaseous medium is transported from the inlet to the outlet of the vacuum pump.

[0003] In particular, if the rotor shaft is rotatably supported by one or more magnetic bearings, radial vibrations of the rotor shaft need to be damped in order to stabilize the rotation of the rotor shaft and avoid contact between the pump elements and the housing. However, such a damper is an additional element that needs to be considered and usually increases the size of the vacuum pump. Summary of the invention

[0004] It is therefore an object of the present invention to provide a compact vacuum pump with a damper for radial vibrations.

[0005] This problem is solved by a vacuum pump according to claim 1 .

[0006] In a first aspect, a vacuum pump is provided, preferably configured as a turbomolecular pump. The vacuum pump comprises a housing and a rotor shaft, the rotor shaft being arranged in the housing and rotatably supported by at least one bearing. At least one pump element is connected to the rotor shaft and rotates with the rotor shaft through a motor. Wherein, the vacuum pump according to the present invention comprises at least one Holweck stage, wherein the pump element is composed of a cylinder connected to the rotor shaft and a stator connected to the housing around the cylinder. Wherein, the stator comprises a threaded groove for guiding gas molecules to the outlet of the vacuum pump. In order to achieve a compact design of the vacuum pump, an eddy current damper (ECD) is arranged in the cylinder of the Holweck stage to provide effective damping of radial vibrations without increasing the space requirements of the vacuum pump. Typically, the cylinder diameter of the Holweck stage is as large as possible in order to increase the circumferential speed. Therefore, an internal volume is formed in the cylinder of the Holweck stage. It is known to use this internal volume to place the motor. However, the present invention finds that it is beneficial to use this internal volume also for the eddy current damper, so as to minimize the space requirements and achieve such an ECD without increasing the size of the vacuum pump.

[0007] Preferably, the eddy current damper comprises a disk connected to the housing and at least one annular magnet connected to the rotor shaft, wherein the disk is arranged axially beside the annular magnet. Thus, eddy currents are induced into the disk made of a conductive material (e.g. copper, aluminum, etc.) by the magnetic field of the annular magnet rotating with the rotor shaft.

[0008] Preferably, the housing comprises an inner wall extending into the cylinder of the Holweck stage, wherein said disc is attached to said inner wall for connecting the disc to the housing.

[0009] Preferably, the rotor shaft is supported by two bearings, wherein the ECD is located between the two bearings. Wherein, at least one bearing is configured as a permanent magnetic bearing. Preferably, the bearing facing the inlet side or the high vacuum side of the vacuum pump is configured as a permanent magnetic bearing. Alternatively, both bearings are configured as permanent magnetic bearings.

[0010] Preferably, the ECD is arranged between the motor and the bearing of the exhaust side of the rotor shaft towards the vacuum pump outlet. Wherein, the motor can also be connected to the inner wall and placed in the cylinder of the Holweck stage.

[0011] Preferably, the disk is divided into at least two parts. The separation is performed along the circumferential direction of the disk. By dividing the disk into at least two or more parts, the disk can be assembled around the rotor shaft. Therefore, at least one annular magnet can be preassembled to the rotor shaft outside the housing, thereby providing the possibility of balancing the rotor shaft together with the at least one annular magnet. Subsequently, after balancing, the disk is assembled around the rotor shaft and the preassembled rotor shaft is inserted into the housing. In a final step, the disk is connected to the housing, i.e. the inner wall of the housing. Therefore, after the rotor is assembled in the housing, it is not necessary to connect the at least one annular magnet to the rotor shaft inside the housing.

[0012] Preferably, the EDC comprises a second annular magnet which is arranged opposite the first annular magnet with respect to the disk. Thus, a gap is formed by the first annular magnet and the second annular magnet, wherein the disk is arranged in the gap. Thus, by this arrangement, the magnetic field at the location of the disk is enhanced, thereby more effectively inducing eddy currents into the disk.

[0013] Preferably, the disk comprises a radially extending portion, preferably extending into the gap between the first annular magnet and the second annular magnet, and at least one axially extending portion, wherein the axially extending portion acts as a conductor in order to reduce the ohmic resistance of the disk and enhance the flow of eddy currents through the disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is described below with reference to the accompanying drawings.

[0015] The accompanying drawings show:

[0016] Figure 1 According to a first embodiment of the present invention,

[0017] Figure 2 A detailed view showing a second embodiment of the invention,

[0018] Figure 3 A detailed view showing another embodiment of the present invention,

[0019] Figure 4 A detailed view of another embodiment of the invention is shown. DETAILED DESCRIPTION

[0020] See also Figure 1 , a vacuum pump constructed as a molecular vacuum pump is shown. For simplicity, only half of the vacuum pump is shown, which is basically symmetrical around the center limit 11. The vacuum pump includes a housing 10, in which a rotor shaft 12 is arranged. The rotor shaft 12 is rotatably supported by a first bearing 16 configured as a permanent magnetic bearing and a second bearing 14 also configured as a permanent magnetic bearing. The first magnetic bearing 16 includes a static bearing element 22, which is connected to the housing via an ear shaft 18 extending into a groove of the rotor shaft 12. In addition, the first magnetic bearing 16 includes a rotating bearing element 24, which is connected to the rotor shaft 12. The static bearing element 22 and the rotating bearing element 24 each include a plurality of mutually repelling annular magnets 27 so as to generate radial support between the static bearing element 22 and the rotating bearing element 24. Similarly, the second magnetic bearing 14 also includes a static bearing element 26, which includes a plurality of annular magnets 27; and a rotating bearing element 28 connected to the rotor shaft 12, which also includes a plurality of annular magnets 27 that repel each other with the annular magnets 27 of the static bearing element 26. Figure 1 As shown, the static bearing element is also connected to the housing 10 via a trunnion 20 .

[0021] The rotor shaft 12 is rotated by the motor 29. A plurality of pump elements 32 configured as blades are connected to the rotor shaft 12 and interact with stator elements 34, which are arranged alternately to the pump elements 32 and interact in order to convey a gaseous medium. In addition, the vacuum pump comprises a Holweck stage 37, which comprises a cylinder 38, which is connected to the rotor shaft and rotates with the rotor shaft. In addition, the Holweck stage 37 comprises a Holweck stator 40, which has a threaded groove 41, in order to convey a gaseous medium from the inlet 30 to the outlet (not shown) of the vacuum pump. Therein, the housing 10 comprises an inner wall 36, wherein the stator of the motor 29 is connected to the inner wall. The inner wall 36 extends into the inner volume of the cylinder 38 of the Holweck stage 37.

[0022] Furthermore, according to the invention, the vacuum pump comprises an eddy current damper 100 (ECD). The ECD is arranged within the cylinder 38 of the Holweck stage 37 in order to provide a compact design of the vacuum pump.

[0023] The ECD includes a disk 102 made of a conductive material (e.g., copper or aluminum). The disk 102 is connected to the inner wall 36 of the housing 10 by connecting elements 104A and 104B. Therefore, the disk 102 is non-rotating. In addition, the ECD 100 includes a first annular magnet 106A and a second annular magnet 106B, which are axially arranged beside the disk 102. A gap is formed by the first annular magnet 106A and the second annular magnet 106B, wherein the conductive disk 102 of the ECD 100 extends into the gap. The first annular magnet 106A and the second annular magnet 106B are attached to the rotor shaft 12 and rotate with the rotor shaft 12. Therefore, due to the rotation and radial vibration of the rotor shaft 12, eddy currents are induced in the conductive disk 102 through the magnetic field at the location of the conductive disk 102, wherein the induced eddy currents generate a magnetic field that interacts with the magnetic fields of the first annular magnet 106A and the second annular magnet 106B, wherein the generated magnetic force is opposite to the motion of the vibration, thereby generating a restoring force on the rotor shaft 12 and suppressing the radial vibration of the rotor.

[0024] Among them, the conductive disk 102 can be divided into two parts along its circumferential direction. Therefore, the first annular magnet 106A and the second annular magnet 106B can be preassembled on the rotor shaft 12. Then, the conductive disk 102 is assembled around the rotor shaft 12. Subsequently, the rotor shaft 12 is inserted into the housing 10 and attached to the inner wall 36 of the cover element 101 of the housing 10 through the connecting elements 104A, 104B. Alternatively, the rotor shaft 12 is inserted into the first housing element, then the conductive disk 102 is assembled around the rotor shaft 12, and then the cover element 101 with the inner wall 36 is inserted into the housing, that is, inserted into the cylinder of the rotor. In the last step, the conductive disk 102 is connected to the inner wall 36.

[0025] Therefore, through Figure 1 The embodiment provides a compact design for a vacuum pump, wherein the space within the cylinder 38 of the Holweck stage 37 is effectively utilized to place the ECD to suppress radial vibration of the rotor.

[0026] refer to Figure 2 , showing a detailed view of the first magnetic bearing 16 on the inlet side of the vacuum pump, which can be connected with Figure 1 The vacuum pump is constructed similarly.

[0027] In the following, the same or similar elements are denoted by the same reference numerals.

[0028] exist Figure 2In the embodiment, the static bearing element 22 includes an adjustment element 110 so as to adjust the axial position of the static bearing element 22 by adjusting the position of the static bearing element 22 against the restoring force of the spring 114. Therein, the adjustment element 110 includes a radial protrusion 111, wherein the conductive disk 112 is connected to the radial protrusion 111. Therefore, through the radial protrusion 111, the conductive disk 112 is axially arranged next to the annular magnet 116 of the ECD connected to the rotor shaft 12. The annular magnet 116 of the ECD is separated from the annular magnet 27 of the rotating bearing element 24 by the non-magnetic annular element 118. Therefore, by this configuration, the ECD is integrated into the magnetic bearing, thereby providing a compact design. In particular, the ECD is located between the magnetic bearing and the end 119 of the rotor shaft 12. Therefore, effective damping of radial vibrations can be achieved. In addition, due to its position, the ECD can be constructed to be very small, but still effectively suppress radial vibrations.

[0029] Alternatively, Figure 2 The ECD can also be implemented in a second magnetic bearing on the exhaust side of the vacuum pump.

[0030] refer to Figure 3 , which shows that Figure 2 A similar configuration is provided in which a ferrite material element 120 is placed between the annular magnet 116 of the ECD and the non-magnetic material element 118, which separates the annular magnet 116 of the ECD from the annular magnet 27 of the rotary bearing element 24. Thus, a magnetic circuit is formed through the ferrite material element 120, which enhances the magnetic field at the location of the conductive disk 112. In particular, the adjustment element 110 is also made of a ferrite material, which further enhances the magnetic field at the location of the conductive disk 116 by forming a completely or nearly closed magnetic circuit.

[0031] although Figure 3 The ECD is shown implemented in a first magnetic bearing on the inlet side of the vacuum pump, but the ECD may alternatively or additionally be implemented in a second magnetic bearing on the exhaust side of the vacuum pump.

[0032] See also Figure 4 , which shows another embodiment of the invention, wherein the regulator 110 comprises a radial protrusion 111 as a separate element carrying a conductive disk 112. Therein, the conductive disk 112 is axially next to the outermost annular magnet 27 of the rotating bearing element 24. Thus, the outermost annular magnet 27 of the rotating bearing element 24 simultaneously facilitates supporting the rotor shaft 12 and simultaneously serves as an annular magnet for the ECD, inducing eddy currents when the rotor shaft vibrates. Thus, a compact design is achieved and an additional annular magnet just for the ECD can be avoided.

[0033] although Figure 4The ECD is shown implemented in a first magnetic bearing on the inlet side of the vacuum pump, but the ECD may alternatively or additionally be implemented in a second magnetic bearing on the exhaust side of the vacuum pump.

[0034] certainly, Figure 1 and Figures 2 to 4 The embodiments can be freely combined. The vacuum pump can include an eddy current damper placed in the cylinder 38 of the Holweck stage 37, and an additional eddy current damper integrated in one of the magnetic bearings 14, 16. In addition, the vacuum pump can include an ECD integrated in the first magnetic bearing 16 or the second magnetic bearing 14. Alternatively, the vacuum pump includes an ECD in the first magnetic bearing and the second magnetic bearing. Therein, the ECD can be constructed identically to one of the embodiments 2 to 4, or can be constructed according to Figures 2 to 4 One of the embodiments is constructed in a different way.

Claims

1. Vacuum pumps, in particular turbomolecular vacuum pumps, including: case; a rotor shaft disposed within the housing and rotatably supported by at least one bearing; A Holweck stage comprising a cylinder connected to a rotor shaft and a stator surrounding the cylinder connected to a housing; Eddy current dampers arranged inside the cylinder of the Holweck stage. 2 . The vacuum pump according to claim 1 , wherein the eddy current damper comprises a disk connected to the housing and at least one annular magnet connected to the rotor shaft, wherein the disk is arranged axially beside the annular magnet.

3. A vacuum pump according to claim 1 or 2, comprising an inner wall extending into the cylinder, wherein the disc is attached to the inner wall.

4. The vacuum pump according to any one of claims 1 to 3, wherein the rotor shaft is supported by two bearings, wherein the eddy current damper is arranged between the two bearings.

5. The vacuum pump according to any of claims 1 to 4, wherein at least one bearing and preferably all bearings are configured as permanent magnetic bearings.

6. The vacuum pump according to any one of claims 1 to 5, wherein the disc is divided into at least two parts.

7. A vacuum pump according to any one of claims 1 to 6, wherein the disc comprises a radially extending portion and at least one axially extending portion, wherein: The radial extension is arranged beside an axial face of the at least one ring magnet or in a gap formed by two ring magnets.

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