Vacuum pump with eddy current damper

Abstract

A vacuum pump, in particular a turbomolecular vacuum pump, comprises a housing and a rotor shaft which is arranged in the housing and is rotatably supported by at least one permanent magnet bearing. In that regard, the magnetic bearing is arranged at one end of the rotor shaft, and the magnetic bearing comprises a stationary bearing element and a rotating bearing element which are arranged radially adjacent to each other. An eddy current damper having a conductive disk coupled to the stationary bearing element is provided.

Description

Technical Field

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[0001] The present invention relates to a vacuum pump, and more particularly to a turbomolecular pump.

Background Art

[0002] A general vacuum pump includes a housing having an inlet and an outlet. A rotor is disposed within the housing and is rotatably supported by at least one bearing. The rotor includes a rotor shaft, and at least one pump element is coupled to the rotor shaft. In the case of a turbomolecular vacuum pump, a plurality of vanes are coupled to the rotor shaft and interact with a plurality of vanes of a stator coupled to the housing. Rotation of the rotor by an electric motor causes a gaseous medium to be conveyed from the inlet of the vacuum pump toward the outlet.

[0003] Specifically, when the rotor shaft is rotatably supported by one or more magnetic bearings, it is necessary to attenuate the radial vibration of the rotor shaft in order to stabilize the rotation of the rotor shaft and avoid contact between the pump element and the housing. However, such dampers are additional elements to be considered and usually increase the size of the vacuum pump.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention is to provide a compact vacuum pump provided with a damper for radial vibration.

Means for Solving the Problems

[0005] This problem is solved by the vacuum pump according to claim 1 and the vacuum pump according to claim 8.

[0006] In a first embodiment, a vacuum pump is provided, preferably constructed as a turbomolecular pump. The vacuum pump comprises a housing and a rotor shaft located within the housing and rotatably supported by at least one bearing. In this embodiment, at least one pump element is coupled to the rotor shaft, and a gaseous medium is transported from the inlet to the outlet of the vacuum pump by the rotation of the rotor shaft by an electric motor. In this embodiment, a magnetic bearing is located at one end of the rotor shaft, and the magnetic bearing comprises a static bearing element coupled to the housing of the vacuum pump and not rotating. Furthermore, the magnetic bearing comprises a rotating bearing element radially coupled to the rotor shaft and rotating relative to the static bearing element. The rotating bearing element is located adjacent to the static bearing element to support the rotor shaft by mutual magnetic repulsion between the static bearing element and the rotating bearing element.

[0007] The present invention provides an eddy current damper (ECD) having a conductive disk coupled to a stationary bearing element. Thus, the present invention integrates the eddy current damper for damping radial vibrations of the rotor shaft with the magnetic bearing, thereby reducing the required space. Furthermore, since the magnetic bearing is located at one end of the rotor shaft, radial vibrations of the rotor shaft due to tilting or nutation are greatest at the end of the rotor shaft. Therefore, damping this movement at the end of the rotor shaft is most efficient. Consequently, the ECD can be constructed in a compact size while maintaining damping efficiency.

[0008] Preferably, the stationary bearing element is coupled to a trunnion extending into a recess in the rotor shaft.

[0009] Preferably, the stationary bearing element and the rotary bearing element, each equipped with multiple ring magnets, repel each other. Therefore, the ring magnets of the stationary bearing element and the rotary bearing element create a repulsive magnetic force between them.

[0010] Preferably, the magnetic bearing includes an adjustment element coupled to the stationary bearing element to adjust the axial position of the stationary bearing element relative to the rotating bearing element, and the conductive disk is mounted on the adjustment element. Therefore, by inserting the adjustment element into the magnetic bearing during assembly, the ECD including the conductive disk is assembled simultaneously.

[0011] Preferably, the adjustment element is made of a ferrite material. Thus, in order to create a magnetic circuit and strengthen the magnetic field at the position of the conductive disk, the magnetic field of the static bearing element is transmitted through the ferrite adjustment element.

[0012] Preferably, the stationary bearing element includes a radial projection, and the conductive disk is coupled to the radial projection. Thus, the radial projection allows the conductive disk to be positioned axially adjacent to each ring magnet of the ECD coupled to the rotating bearing element in order to induce eddy currents into the conductive disk. In this regard, more preferably, the radial projection can be constructed by an additional element positioned between the outermost axial ring magnet of the stationary bearing element and the adjustment element, or it can be constructed as an integral part with the adjustment element to facilitate assembly.

[0013] Preferably, the conductive disk is positioned axially adjacent to the rotating bearing element such that eddy currents are induced in the conductive disk by the magnetic field of the rotating bearing element.

[0014] Preferably, the outermost ring magnet of the rotating bearing element is also the magnetic ring of the ECD, so that the magnetic field of the outermost ring element of the rotating bearing element induces eddy currents in the conductive disk. It is not necessary to add a ring magnet for the ECD, and the magnetic field of the rotating bearing element can also be used for the ECD. Alternatively, the ECD comprises an additional ring magnet coupled to the rotating bearing element and separated from the ring magnet of the rotating bearing element by a non-magnetic material. Thereafter, a magnetic circuit is created by the additional ring magnet across the gap between the rotating bearing element and a regulating element, preferably made of a ferrite-based material.

[0015] Preferably, the ECD is positioned at the outermost position of the rotor shaft, i.e., between the end of the rotor shaft and the magnetic bearing, in order to efficiently dampen radial vibrations of the rotor shaft.

[0016] Preferably, the eddy current damper (ECD) is located on the exhaust side of the rotor shaft. Alternatively, the ECD is located on the intake side or high vacuum side of the rotor shaft. More preferably, the ECDs are located at both ends of the rotor shaft. In this respect, the ECDs at both ends can have similar or different structures and can be constructed in detail as described above.

[0017] Therefore, a compact eddy current damper is provided that is incorporated into the magnetic bearing of the vacuum pump. In this regard, the ECD is positioned at the location where it experiences the greatest vibration due to the rotor shaft tilting around the center of gravity of the rotor shaft.

[0018] The present invention will be described in further detail below with reference to the attached drawings. [Brief explanation of the drawing]

[0019] [Figure 1] This is a first embodiment of the present invention. [Figure 2] This is a detailed diagram of a second embodiment of the present invention. [Figure 3] This is a detailed diagram of another embodiment of the present invention. [Figure 4] This is a detailed diagram of another embodiment of the present invention. [Modes for carrying out the invention]

[0020] Refer to Figure 1, which shows a vacuum pump constructed as a molecular vacuum pump. In this regard, for simplification, only half of the vacuum pump, which is substantially symmetrical around the central axis (excess) 11, is shown. The vacuum pump comprises a housing 10, within which a rotor shaft 12 is located. The rotor shaft 12 is rotatably supported by a first bearing 16, constructed as a permanent magnet bearing, and a second bearing 14, also constructed as a permanent magnet bearing. The first magnetic bearing 16 comprises a stationary bearing element 22 coupled to the housing via a trunnion 18 extending into a recess in the rotor shaft 12. Furthermore, the first magnetic bearing 16 comprises a rotating bearing element 24 coupled to the rotor shaft 12. Each of the stationary bearing element 22 and the rotating bearing element 24 comprises a plurality of ring magnets 27 that repel each other to create radial support between the stationary bearing element 22 and the rotating bearing element 24. Similarly, the second magnetic bearing 14 comprises a stationary bearing element 26 having a plurality of ring magnets 27, and a plurality of ring magnets 27 that repel each other from the ring magnets 27 of the stationary bearing element 26. In this respect, as shown in Figure 1, the stationary bearing element is similarly coupled to the housing 10 via a trunnion 20.

[0021] The rotor shaft 12 is rotated by an electric motor 29. Multiple pump elements 32, constructed as vanes, are coupled to the rotor shaft 12 and interact with stator elements 34, which are alternately arranged relative to the pump elements 32, to interact with each other and transport a gaseous medium. Furthermore, the vacuum pump includes a Holbeck stage 37 which includes a cylinder 38 coupled to the rotor shaft and rotating with the rotor shaft. Furthermore, the Holbeck stage 37 includes a Holbeck stator 40 having threaded grooves 41 for transporting the gaseous medium from the inlet 30 of the vacuum pump toward the outlet (not shown). In this regard, the housing 10 includes an inner wall 36 to which the stator of the electric motor 29 is coupled. The inner wall 36 extends into the internal volume of the cylinder 38 of the Holbeck stage 37.

[0022] Furthermore, according to the present invention, the vacuum pump includes an eddy current damper 100 (ECD). The ECD is disposed inside the cylinder 38 of the Holweck stage 37 to provide a compact design of the vacuum pump.

[0023] The ECD includes a disk 102 made of a conductive material such as copper or aluminum. The disk 102 is coupled to the inner wall 36 of the housing 10 via coupling elements 104A and 104B. Accordingly, the disk 102 does not rotate. Further, the ECD 100 includes a first ring magnet 106A and a second ring magnet 106B disposed axially adjacent to the disk 102. A gap is created between the first ring magnet 106A and the second ring magnet 106B, and the conductive disk 102 of the ECD 100 extends into the gap. The first ring magnet 106A and the second ring magnet 106B are attached to the rotor shaft 12 and rotate together with the rotor shaft 12. Accordingly, due to the rotation and radial vibration of the rotor shaft 12, eddy currents are induced in the conductive disk 102 by the magnetic field at the position of the conductive disk 102, and the induced eddy currents create a magnetic field that interacts with the magnetic fields of the first ring magnet 106A and the second ring magnet 106B. The generated magnetic force is opposite to the vibrating movement, thereby creating a restoring force against the rotor shaft 12 and damping the radial vibration of the rotor.

[0024] In that regard, the conductive disk 102 can be separated into two parts along its circumferential direction. Accordingly, the first ring magnet 106A and the second ring magnet 106B can be pre-assembled to the rotor shaft 12. Thereafter, the conductive disk 102 is assembled around the rotor shaft 12. Thereafter, the rotor shaft 12 is inserted into the housing 10 and attached to the inner wall 36 of the cap element 101 of the housing 10 by the coupling elements 104A, 104B. Alternatively, the rotor shaft 12 is inserted into the first housing element, and then the conductive disk 102 is assembled around the rotor shaft 12, and then the cap element 101 having the inner wall 36 is inserted into the housing, i.e., the cylinder of the rotor. In the last step, the conductive disk 102 is coupled to the inner wall 36.

[0025] Thus, according to the embodiment of FIG. 1, a compact vacuum pump design is provided in which the space within the cylinder 38 of the Holvex stage 37 is efficiently used to arrange an ECD that attenuates the radial vibration of the rotor.

[0026] Referring to FIG. 2, a detailed view of a first magnetic bearing 16 on the inlet side of a vacuum pump that can be constructed similarly to the vacuum pump of FIG. 1 is shown.

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

[0028] In FIG. 2, the stationary bearing element 22 includes an adjustment element 110 for adjusting the axial position of the stationary bearing element 22 by adjusting the position of the stationary bearing element 22 against the restoring force of the spring 114. In that regard, the adjustment element 110 includes a radially projecting portion 111, and the conductive disk 112 is coupled to the radially projecting portion 111. Thus, by the radially projecting portion 111, the conductive disk 112 is arranged axially adjacent to the ring magnet 116 of the ECD coupled to the rotor shaft 12. The ring magnet 116 of the ECD is separated from the ring magnet 27 of the rotary bearing element 24 by a non-magnetic ring element 118. Thus, with this configuration, the ECD is integrated into the magnetic bearing, providing a compact design. Specifically, the ECD is arranged between the magnetic bearing and the end 119 of the rotor shaft 12. Thus, efficient attenuation of radial vibration can be achieved. Furthermore, due to its position, the ECD can be constructed in a small size while efficiently attenuating radial vibration.

[0029] Alternatively, the ECD of FIG. 2 can also be mounted on a second magnetic bearing on the exhaust side of the vacuum pump.

[0030] Referring to Figure 3, which shows a configuration similar to that in Figure 2, a ferrite material element 120 is positioned between the ECD ring magnet 116 and a non-magnetic material element 118 that separates the ECD ring magnet 116 from the ring magnet 27 of the rotating bearing element 24. Thus, the ferrite material element 120 creates a magnetic circuit that enhances the magnetic field at the location of the conductive disk 112. In detail, the adjustment element 110 is also constructed from a ferrite material and further enhances the magnetic field at the location of the conductive disk 116 by creating a completely or nearly closed magnetic circuit.

[0031] Figure 3 shows that the ECD is mounted on the first magnetic bearing on the intake side of the vacuum pump, but the ECD can also be mounted on the second magnetic bearing on the exhaust side of the vacuum pump, either alternatively or additionally.

[0032] Referring to Figure 4, which illustrates another embodiment of the present invention, the adjustment element 110 includes a radial projection 111 as a separate element supporting the conductive disk 112. In this respect, the conductive disk 112 is axially adjacent to the outermost ring magnet 27 of the rotating bearing element 24. Thus, the outermost ring magnet 27 of the rotating bearing element 24 is used as a ring magnet for the ECD, which simultaneously facilitates support of the rotor shaft 12 and simultaneously induces eddy currents during vibration of the rotor shaft. This enables a compact design and avoids the need to add a ring magnet solely for the ECD.

[0033] Figure 4 shows that the ECD is mounted on the first magnetic bearing on the intake side of the vacuum pump; however, the ECD can also be mounted on the second magnetic bearing on the exhaust side of the vacuum pump, either as an alternative or additional measure.

[0034] Of course, the embodiments in Figures 1 and 2 through 4 can be freely combined. The vacuum pump may include an eddy current damper located in the cylinder 38 of the Holbeck stage 37 and an additional eddy current damper integrated into one of the magnetic bearings 14, 16. Furthermore, the vacuum pump may include an ECD integrated into the first magnetic bearing 16 or the second magnetic bearing 14. Alternatively, the vacuum pump may include ECDs in both the first and second magnetic bearings. In this regard, the ECD may be constructed similarly to one of embodiments 2 through 4, or differently from one of embodiments 2 through 4.

Claims

1. Housing and A rotor shaft is disposed within the housing and rotatably supported by at least one permanent magnet bearing, Equipped with, The magnetic bearing comprises a stationary bearing element and a rotating bearing element arranged radially adjacent to each other, an eddy current damper having a conductive disc coupled to the stationary bearing element, and an adjustment element coupled to the stationary bearing element for adjusting the axial position of the stationary bearing element relative to the rotating bearing element. The conductive disk is coupled to the radial projection of the adjustment element, A vacuum pump wherein the conductive disk is positioned axially adjacent to the rotating bearing element, and the magnetic field of the rotating bearing element can induce eddy currents in the conductive disk.

2. The vacuum pump according to claim 1, wherein each of the stationary bearing element and the rotary bearing element is provided with a plurality of ring magnets that repel each other.

3. The vacuum pump according to claim 1, wherein the adjustment element is made of a ferrite-based material.

4. The vacuum pump according to claim 2, wherein the eddy current damper comprises a ring magnet coupled to the rotating bearing element and separated from the ring magnet of the rotating bearing element by a non-magnetic material.

5. The vacuum pump according to any one of claims 1 to 4, wherein the eddy current damper is located at the end of the rotor shaft.

6. The vacuum pump according to any one of claims 1 to 4, wherein the eddy current damper is located on the exhaust side of the rotor shaft.

7. The vacuum pump according to any one of claims 1 to 4, wherein eddy current dampers are arranged at each end of the rotor shaft.

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