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 arranged at one end of the rotor shaft, and wherein the magnetic bearing comprises a static bearing element and a swivel bearing element arranged 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 and by a vacuum pump according to claim 8 .

[0006] In a first aspect, a vacuum pump is provided, which is preferably configured as a turbomolecular pump. The vacuum pump includes a housing and a rotor shaft, the rotor shaft is arranged in the housing and is rotatably supported by at least one magnetic bearing, and the magnetic bearing is configured as a permanent magnetic bearing. Wherein, at least one pump element is connected to the rotor shaft, and when the rotor shaft is rotated by the motor, the gaseous medium is transported from the inlet of the vacuum pump to the outlet of the vacuum pump. Wherein, the magnetic bearing is arranged at one end of the rotor shaft, and the magnetic bearing includes a static bearing element that is connected to the housing of the vacuum pump and does not rotate. In addition, the magnetic bearing includes a rotating bearing element, which is radially connected to the rotor shaft and rotates relative to the static bearing element. The rotating bearing element is arranged next to the static bearing element so as to support the rotor shaft by the mutual magnetic repulsion between the static bearing element and the rotating bearing element.

[0007] According to the present invention, an eddy current damper (ECD) is provided, which has a conductive disk connected to a static bearing element. Therefore, by the present invention, an eddy current damper for damping radial vibrations of a rotor shaft is integrated into a magnetic bearing, thereby reducing space requirements. In addition, since the magnetic bearing is arranged at one end of the rotor shaft, the radial vibration of the rotor shaft caused by the tilting or nutation of the rotor shaft is the largest at the end of the rotor shaft. Therefore, it is most effective to damp such movement at the end of the rotor shaft. Therefore, the ECD can be constructed to be small, but still maintain its damping efficiency.

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

[0009] Preferably, the static bearing element and the rotating bearing element include a plurality of mutually repelling annular magnets. Therefore, through the annular magnets of the static bearing element and the rotating bearing element, a repelling magnetic force is generated between them.

[0010] Preferably, the magnetic bearing comprises an adjustment element connected to the static bearing element to adjust the axial position of the static bearing element relative to the rotating bearing element, wherein the conductive disc is attached to the adjustment element. Thus, by inserting the adjustment element into the magnetic bearing during assembly, the ECD comprising the conductive disc is assembled simultaneously.

[0011] Preferably, the adjustment element is made of a ferrite material. Thus, the magnetic field of the static bearing element penetrates into the ferrite adjustment element, thereby forming a magnetic circuit and enhancing the magnetic field at the location of the conductive disk.

[0012] Preferably, the static bearing element comprises a radial protrusion, wherein the conductive disc is connected to the radial protrusion. Thus, via the radial protrusion, the conductive disc can be placed axially next to a corresponding annular magnet of the ECD connected to the rotating bearing element, so as to induce eddy currents into the conductive disc. More preferably, the radial protrusion can be constituted by an additional element arranged between the axially outermost annular magnet of the static bearing element and the adjusting element, or can be constituted as one piece together with the adjusting element for easy assembly.

[0013] Preferably, the electrically conductive disk is arranged axially next to the rotary bearing element, so that a magnetic field passing through the rotary bearing element can induce eddy currents in the electrically conductive disk.

[0014] Preferably, the outermost annular magnet of the rotating bearing element is at the same time the magnet ring of the ECD, so that the magnetic field of the outermost annular element of the rotating bearing element induces eddy currents into the conductive disk. There is no need to implement an additional annular magnet for the ECD, and the magnetic field of the rotating bearing element can also be used for the ECD. Alternatively, the ECD includes an additional annular magnet connected to the rotating bearing element and separated from the annular magnet of the rotating bearing element by a non-magnetic material. Therefore, a magnetic circuit is formed by the additional annular magnet on the gap between the rotating bearing element and the adjusting element, which is preferably made of a ferrite material.

[0015] Preferably, the ECD is arranged at an axial end of the rotor shaft, ie, between the magnetic bearing and the end of the rotor shaft, so as to position the ECD at an outermost position of the rotor shaft to effectively suppress radial vibrations of the rotor shaft.

[0016] Preferably, the eddy current damper is arranged on the exhaust side of the rotor shaft. Alternatively, the ECD is arranged on the intake side or high vacuum side of the rotor shaft. More preferably, the ECD is arranged at both ends of the rotor shaft. The ECDs at both ends may be constructed similarly or differently, in particular as described above.

[0017] Thus, a compact design of an eddy current damper integrated in a magnetic bearing of a vacuum pump is provided, wherein, at the same time, the ECD is placed at the location where the rotor shaft is subject to maximum vibrations due to tilting about the rotor shaft center of gravity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is described below with reference to the accompanying drawings.

[0019] The accompanying drawings show:

[0020] Figure 1 According to a first embodiment of the present invention,

[0021] Figure 2 A detailed view showing a second embodiment of the invention,

[0022] Figure 3 A detailed view showing another embodiment of the present invention,

[0023] Figure 4 A detailed view of another embodiment of the invention is shown. DETAILED DESCRIPTION

[0024] 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 .

[0025] 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.

[0026] 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.

[0027] 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 of the rotor shaft 12 and when the rotor shaft 12 radially vibrates, 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In the following, the same or similar elements are denoted by the same reference numerals.

[0032] exist Figure 2 In 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 small, but still effectively suppress radial vibrations.

[0033] Alternatively, Figure 2 The ECD can also be implemented in a second magnetic bearing on the exhaust side of the vacuum pump.

[0034] 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.

[0035] 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.

[0036] See also Figure 4 , which shows another embodiment of the invention, wherein the adjustment member 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 the support of 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 solely for the ECD can be avoided.

[0037] although Figure 4 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.

[0038] 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 in the second magnetic bearing. The ECD can be constructed in the same way as in 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, especially turbomolecular vacuum pumps, including case; a rotor shaft disposed in the housing and rotatably supported by at least one permanent magnetic bearing; in, The magnetic bearing is arranged at one end of the rotor shaft, and Therein, the magnetic bearing comprises a static bearing element and a rotating bearing element which are arranged radially adjacent to each other and an eddy current damper having a conductive disk connected to the static bearing element.

2. The vacuum pump of claim 1, wherein the static bearing element and the rotating bearing element each comprise a plurality of mutually repelling annular magnets.

3. A vacuum pump according to any one of claims 1 or 2, wherein the magnetic bearing comprises an adjustment element connected to the static bearing element to adjust the axial position of the static bearing element relative to the rotating bearing element, wherein the conductive disc is attached to the adjustment element.

4. The vacuum pump according to claim 3, wherein the regulating element is made of a ferrite material.

5. The vacuum pump according to any one of claims 1 to 4, wherein the static bearing element comprises a radial protrusion, wherein the conductive disc is connected to the radial protrusion.

6. The vacuum pump according to claim 5, wherein the conductive disk is arranged axially beside the rotating bearing element so that a magnetic field passing through the rotating bearing element can induce eddy currents in the conductive disk.

7. A vacuum pump according to any one of claims 1 to 6, wherein the eddy current damper comprises an annular magnet which is connected to the rotating bearing element and is separated from the annular magnet of the rotating bearing element by a non-magnetic material.

8. The vacuum pump according to any one of claims 1 to 7, wherein an eddy current damper is arranged at an axial end of the rotor shaft.

9. The vacuum pump according to any one of claims 1 to 8, wherein the eddy current damper is arranged on the exhaust side of the rotor shaft.

10. The vacuum pump according to any one of claims 1 to 9, wherein an eddy current damper is arranged at each end of the rotor shaft.

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