Vacuum pump and adjustment method

Abstract

To permit adjustment of a position of a still side magnet not only from a side surface but also an upper surface of a casing.SOLUTION: A vacuum pump 1 includes: a casing section 2 for housing a rotor 3; a magnetic bearing 32; and a magnet nut 46. The magnetic bearing 32 includes: a first permanent magnet 41 disposed around a magnet holder section 16; and a second permanent magnet 42 disposed in a rotor 3 while opposing the first permanent magnet 41 in a radial direction. The magnet nut 46 includes a body section 51 and a projecting section 52. The body section 51 adjusts the position of the first permanent magnet 41 relative to the second permanent magnet 42 by rotation relative to the magnet holder section 16. The projecting section 52 projects from an upper surface 51b of the body section 51, and has abutted surfaces 53a, 53b that can abut on a side of an outer periphery 51c by a first tool 61 for rotating the body section 51 from the side of an upper surface 51b of the body section 51, and by a second tool 62 for rotating the body section 51 from the side of the outer periphery 51c of the body section 51.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vacuum pump and a method for adjusting the same. [Background technology]

[0002] Turbomolecular pumps are used as vacuum pumps for ultra-high vacuums, vacuum pumps for leak detectors, etc. For example, the vacuum pump shown in Patent Document 1 houses a rotor inside a housing and performs evacuation by rotating the rotor at tens of thousands of revolutions per minute.

[0003] In the vacuum pump shown in Patent Document 1, a rotor is rotatably supported on a housing by a magnetic bearing and a rolling bearing. The magnetic bearing includes a rotor-side magnet arranged on the rotor and a stationary-side magnet arranged in a magnet holder fixed to the housing. The rolling bearing needs to be preloaded to reduce rattle and noise during rotation. By adjusting the position of the rotor-side magnet relative to the stationary-side magnet, an appropriate preload can be applied to the rolling bearing.

[0004] The position of the rotor-side magnet is adjusted by rotating the magnet nut that is screwed onto the magnet holder. An air intake is formed in the housing above the magnet nut, allowing the operator to rotate the magnet nut through the air intake. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-122529 Summary of the Invention [Problem to be solved by the invention]

[0006] In vacuum pumps used in leak detectors, the intake port is sometimes not located on the top of the magnetic nut, but on the side of the magnetic nut. Also, in vacuum pumps, the rotor may be housed in a separate housing (called an adjustment housing) from the vacuum pump housing to adjust the rotor's rotational balance. A stationary magnet is also provided in the adjustment housing, and even when the rotor is housed in the adjustment housing, the position of the stationary magnet is adjusted by the magnetic nut.

[0007] With conventional magnetic nuts, the jig used to rotate the magnetic nut could only hold the magnetic nut from the side or top, which meant that the same magnetic nut could not be used for both the vacuum pump housing and the adjustment housing.

[0008] An object of the present invention is to enable the position of a stationary side magnet in a vacuum pump having a stationary side magnet to be adjusted from either the side or the top of the housing. [Means for solving the problem]

[0009] A vacuum pump according to one aspect of the present invention includes a rotor, a housing, a magnetic bearing, and an adjustment member. The rotor is rotatable. The housing accommodates the rotor. The magnetic bearing has a first magnet arranged around a magnet holder fixed to the housing, and a second magnet arranged on the rotor radially opposite the first magnet. The adjustment member adjusts the position of the first magnet relative to the second magnet. The adjustment member includes a main body and a protrusion. The main body has a second threaded portion on its inner circumferential surface that fits into a first threaded portion formed around the magnet holder. When rotated relative to the magnet holder, the main body moves in a direction along the rotation axis of the rotor to adjust the position of the first magnet relative to the second magnet. The protrusion protrudes from the top surface of the main body. The protrusion has an abutment surface on the outer circumferential side of the adjustment member that can be abutted by a first jig that rotates the main body from the top surface side of the main body, and that can be abutted by a second jig that rotates the main body from the side surface side of the main body. [Effects of the Invention]

[0010] In the above vacuum pump, the adjustment member that adjusts the position of the first magnet has a protruding portion that protrudes from the top surface of the main body and has an abutment surface that is abutted by a jig that rotates the main body. This abutment surface is provided on the protruding portion on the outer periphery of the main body and can be abutted by either a first jig that rotates the main body from the top side or a second jig that rotates the main body from the side side. In this way, the adjustment member can be rotated using a jig from either the top side or the side side of the main body, so the position of the first magnet can be adjusted from either the top side or the side side of the adjustment member. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a vacuum pump. [Figure 2] FIG. 2 is a top perspective view of a vacuum pump. [Figure 3] FIG. 2 is an enlarged view of a portion S in FIG. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] 10A and 10B are diagrams illustrating the arrangement of protrusions on a magnetic nut. [Figure 7] FIG. 2 is a diagram showing a balance adjustment housing. [Figure 8] FIG. 2 is a diagram showing the configuration of a first jig. [Figure 9] 10 is a diagram showing a state in which the magnetic nut is held by a first jig. FIG. [Figure 10] FIG. 10 is a diagram showing the configuration of a second jig. [Figure 11] 10 is a diagram showing a state in which the magnetic nut is held by a second jig. FIG. [Figure 12] FIG. 10 is a diagram showing a first jig according to another embodiment. [Figure 13] 10 is a diagram showing a state in which the magnetic nut is held by a first jig according to another embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1. First embodiment <1-1. Vacuum pump configuration> 1 and 2, a vacuum pump 1 according to an embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the vacuum pump 1. FIG. 2 is a top perspective view of the vacuum pump 1. The vacuum pump 1 has a housing 2, a rotor 3, a motor 4, a plurality of stator blade units 5, and a stator cylindrical portion 6.

[0013] The housing 2 houses a rotor 3, a motor 4, a plurality of stator blade units 5, and a stator cylindrical portion 6. The housing 2 has a casing 7 and a base 8. The housing 2 is made of a metal such as an aluminum alloy or iron. The casing 7 is a cylindrical member.

[0014] The casing 7 houses a plurality of stator blade units 5 and a plurality of stages of rotor blade units 22 provided on the rotor 3. The casing 7 has a first end portion 11, a second end portion 12, and a side portion 13. The first end portion 11 is disposed so as to cover the rotor 3 perpendicular to the axis A of the rotor 3. Note that the first end portion 11 is omitted from FIG. 2 .

[0015] The second end 12 is located on the opposite side to the first end 11 in the direction of the axis A of the rotor 3. The second end 12 is connected to the base 8. The side surface portion 13 connects the first end 11 and the second end 12. A first intake port P11 and second intake ports P12 and P13 are formed in the side surface portion 13 of the casing 7. The first intake port P11 is formed near the first end 11 of the side surface portion 13. An exhaust target device including an exhaust target space is connected to the first intake port P11.

[0016] The base 8 is arranged to close the opening on the second end 12 side of the casing 7. The casing 7 and the base 8 house the stator cylindrical portion 6 and the rotor cylindrical portion 23 provided on the rotor 3. The base 8 has a base end portion 15. The base end portion 15 is connected to the second end portion 12 of the casing 7. Note that the connection between the casing 7 and the base 8 includes the joining of separate members, and also includes the joining of separate portions of an integrated member.

[0017] An exhaust port P21 is formed on the side of the base 8. An auxiliary pump is connected to the exhaust port P21. An exhaust path is formed in the internal space of the housing 2, extending from the first intake port P11 to the exhaust port P21. A plurality of second intake ports P12 and P13 are connected to this exhaust path. When the vacuum pump 1 is used as a leak detector, pipes from a test specimen are connected to the plurality of second intake ports P12 and P13, respectively. The second intake port P12 is formed between the turbine section T and the drag pump section D. The second intake port P13 is formed midway through the drag pump section D. The second intake ports P12 and P13 may not be formed depending on the application of the vacuum pump 1.

[0018] The rotor 3 has a shaft 21, multiple stages of rotor blade units 22, and a rotor cylindrical portion 23. The shaft 21 extends in the axial direction A of the rotor 3. In the following description, the direction from the base 8 toward the casing 7 in the axial direction A is referred to as a first direction A1, and the opposite direction is referred to as a second direction A2.

[0019] The vacuum pump 1 has a magnet holder portion 16. The magnet holder portion 16 is disposed inside the casing 7. The magnet holder portion 16 is disposed from the first end portion 11 of the casing 7 toward the base 8. The magnet holder portion 16 is formed integrally with the casing 7. "Formed integrally" means, for example, that the magnet holder portion 16 is formed by molding the same material in a mold or by cutting.

[0020] The magnet holder portion 16 has a cylindrical outer shape. A recess 16a is formed facing the first direction A1 at the end of the magnet holder portion 16 on the second direction A2 side. The end of the shaft 21 on the first direction A1 side is inserted into the recess 16a.

[0021] The magnet holder portion 16 has beam portions 16b. Three beam portions 16b are provided at equal intervals along the circumferential direction of the magnet holder portion 16. The beam portions 16b are formed to bridge the magnet holder portion 16 and the side surface portion 13 of the casing 7. This allows the beam portions 16b to support the magnet holder portion 16 on the side surface portion 13. In other words, the beam portions 16b fix the magnet holder portion 16 while maintaining a constant distance from the side surface portion 13.

[0022] A recess 8a is formed facing the first direction A1 in the center of the surface of the base 8 on the second direction A2 side. The vacuum pump 1 has a lid 9. The lid 9 is arranged to cover the recess 8a of the base 8.

[0023] A through hole 8b is formed along the axis A in a ceiling portion on the first direction A1 side of the recess 8a of the base 8. The shaft 21 is inserted into the through hole 8b, and the end of the shaft 21 on the second direction A2 side protrudes inside the recess 8a.

[0024] The vacuum pump 1 includes a protective bearing 31 , a magnetic bearing 32 , and a rolling bearing 33 . The protective bearing 31 is disposed between the magnet holder portion 16 and the shaft 21. The protective bearing 31 is disposed inside the recess 16a of the magnet holder portion 16. The protective bearing 31 functions as a touchdown bearing that limits radial runout of the shaft 21 in the first direction A1. When the shaft 21 is in a steady rotation state, the shaft 21 and the protective bearing 31 are not in contact with each other, but when a large disturbance is applied or when the whirling of the shaft 21 increases during acceleration or deceleration of the rotation, the shaft 21 comes into contact with the inner surface of the inner ring of the protective bearing 31. The protective bearing 31 can be, for example, a ball bearing.

[0025] The magnetic bearing 32 is disposed between the magnet holder portion 16 and the rotor 3. The magnetic bearing 32 supports the rotor 3 in a non-contact manner. The magnetic bearing 32 will be described in detail later.

[0026] The rolling bearing 33 is disposed between the shaft 21 and the base 8. The rolling bearing 33 rotatably supports the shaft 21 relative to the base 8. The rolling bearing 33 is disposed in the through hole 8b of the base 8. The rolling bearing 33 may be, for example, a ball bearing. The vacuum pump 1 has a thrust nut 34 fixed to the shaft 21. The thrust nut 34 is disposed on a portion of the shaft 21 that protrudes from the through hole 8b and is located inside the recess 8a. The thrust nut 34 is disposed on the second direction A2 side of the rolling bearing 33. When the magnetic bearing 32, which will be described later, is adjusted, a force is applied to the rotor 3 that moves toward the casing 7, and the thrust nut 34 applies a preload to the rolling bearing 33 in the first direction A1.

[0027] The multiple stages of rotor blade units 22 are each connected to the shaft 21. The multiple stages of rotor blade units 22 are arranged at intervals from one another in the direction of axis A. Each rotor blade unit 22 includes a plurality of rotor blades 25, and although not shown, each of the multiple rotor blades 25 extends radially from the shaft 21 as the center. Note that in the drawings, only one of the multiple stages of rotor blade units 22 and one of the multiple rotor blades 25 is labeled with a reference numeral, and the reference numerals for the other rotor blade units 22 and other rotor blades 25 are omitted.

[0028] The rotor cylindrical portion 23 is connected to the shaft 21. The rotor cylindrical portion 23 is disposed below the rotor blade unit 22. The rotor cylindrical portion 23 is cylindrical and extends in the direction of the axis A. The rotor cylindrical portion 23 is disposed on the outer periphery of the shaft 21 so as to surround the shaft 21. The outer periphery of the rotor cylindrical portion 23 is a cylindrical curved surface.

[0029] The motor 4 drives the rotor 3 to rotate. For example, a brushless motor is used as the motor 4. The motor 4 has a motor rotor 26 and a motor stator 27. The motor rotor 26 is attached to the shaft 21. The motor stator 27 is attached to the base 8. The motor stator 27 is disposed opposite the motor rotor 26.

[0030] The multiple stages of stator blade units 5 are connected to the inner surface of the casing 7. The multiple stages of stator blade units 5 are arranged at intervals from one another in the direction of the axis A. Each of the multiple stages of stator blade units 5 is arranged between the multiple stages of rotor blade units 22. Each of the stator blade units 5 includes a plurality of stator blades 28. Although not shown in the figure, the multiple stator blades 28 each extend radially from the shaft 21 as the center.

[0031] The multiple stages of rotor blade units 22 and the multiple stages of stator blade units 5 constitute a turbine section T (turbomolecular pump). Note that in the drawings, only one of the multiple stator blade units 5 and one of the multiple stator blades 28 are labeled with a reference numeral, and the reference numerals of the other stator blade units 5 and other stator blades 28 are omitted.

[0032] The stator cylindrical portion 6 is disposed radially outside the rotor cylindrical portion 23. The stator cylindrical portion 6 is connected to a base 8. The stator cylindrical portion 6 is disposed facing the rotor cylindrical portion 23 in the radial direction of the rotor cylindrical portion 23.

[0033] A spiral thread is provided on the inner peripheral surface of the stator cylindrical portion 6. The rotor cylindrical portion 23 and the stator cylindrical portion 6 constitute a drag pump portion D (thread groove pump). In this vacuum pump 1, gas from the space to be evacuated of the device to be evacuated is evacuated by the turbine portion T, then evacuated by the drag pump portion D and exhausted to the outside of the vacuum pump 1.

[0034] <1-2. Structure of magnetic bearing> The configuration of the magnetic bearing 32 will be described below with reference to Figs. 1 to 3. Fig. 3 is an enlarged view of portion S in Fig. 1. The magnetic bearing 32 has a first permanent magnet 41 (an example of a first magnet) and a second permanent magnet 42 (an example of a second magnet). The first permanent magnet 41 is disposed on the outer peripheral surface of the magnet holder portion 16. The second permanent magnet 42 is fixed to the inner peripheral surface of the rotor 3. The first permanent magnet 41 and the second permanent magnet 42 are disposed to face each other in the radial direction B.

[0035] The first permanent magnets 41 and the second permanent magnets 42 are ring-shaped. In Fig. 1, three first permanent magnets 41 and three second permanent magnets 42 are arranged in a row along the direction of axis A, but the numbers of the first permanent magnets 41 and the second permanent magnets 42 are not particularly limited.

[0036] A gap is formed between the first permanent magnet 41 and the second permanent magnet 42. Each ring-shaped magnet element constituting the first permanent magnet 41 and the second permanent magnet 42 is arranged so that one end in the axial direction is a north pole and the other end is a south pole. The stacked ring-shaped magnet elements of the first permanent magnet 41 are arranged so that their north poles or south poles face each other in the axial direction. The stacked ring-shaped magnet elements of the second permanent magnet 42 are arranged so that their north poles or south poles face each other in the axial direction. The first permanent magnet 41 and the second permanent magnet 42 are arranged so that the same poles generally face each other, but misalignment in the axial direction A applies a force to the shaft 21 that moves in the first direction A1 relative to the casing 7 and base 8, and a preload is applied to the rolling bearing 33 by the thrust nut 34. The preload can be adjusted by adjusting the misalignment of the first permanent magnet 41 with respect to the second permanent magnet 42 in the axial direction A.

[0037] The vacuum pump 1 further includes a fixing member 43, a disc spring 44, a spring support member 45, and a magnet nut .

[0038] The fixing member 43 is disposed on the surface of the second permanent magnet 42 on the first direction A1 side. The fixing member 43 is ring-shaped. The fixing member 43 is fixed to the rotor 3. The fixing member 43 is a pressing member for fixing the position of the second permanent magnet 42. The fixing member 43 is fixed to the rotor 3 by shrink fitting, cooling fitting, or the like.

[0039] A plurality of balance adjustment holes 43a are provided at the end of the fixed member 43 in the first direction A1, i.e., at the upper end of the fixed member 43. The plurality of balance adjustment holes 43a are provided along the circumferential direction of the fixed member 43. Each of the plurality of balance adjustment holes 43a has a thread for receiving a screw. By threading a screw into one of the plurality of balance adjustment holes 43a, the position of the center of gravity of the rotor 3 can be adjusted. Adjusting the position of the center of gravity of the rotor 3 can reduce vibrations when the rotor 3 rotates.

[0040] The disc spring 44 is disposed on the second direction A2 side of the first permanent magnet 41. The end of the disc spring 44 opposite the first permanent magnet 41 is supported by a spring support member 45 fixed to the magnet holder portion 16. The disc spring 44, which is an elastic body, elastically supports the first permanent magnet 41 between the spring support member 45 and a magnet nut 46 disposed on the surface of the first permanent magnet 41 on the first direction A1 side. A shim ring may be disposed between the disc spring 44 and the first permanent magnet 41.

[0041] <1-3. Magnetic nut configuration> The magnetic nut 46 (an example of an adjustment member) is ring-shaped. The magnetic nut 46 is disposed on the surface of the first permanent magnet 41 on the first direction A1 side. The magnetic nut 46 adjusts the position of the first permanent magnet 41 in the axial A direction. The magnetic nut 46 can be considered a pressing member for receiving the preload pressure caused by the repulsive force of the magnet applied to the rolling bearing 33. The magnetic nut 46 is disposed movably on the outer periphery of the magnet holder portion 16.

[0042] The specific configuration of the magnetic nut 46 will be described below with reference to Figures 4 to 6. Figure 4 is a perspective view of the magnetic nut 46. Figure 5 is a top view of the magnetic nut 46. Figure 6 is a diagram showing the arrangement of the protrusions 52 in the magnetic nut 46. The magnetic nut 46 has a main body 51 and protrusions 52.

[0043] The main body 51 is a portion of the magnet nut 46 that holds the first permanent magnet 41. The main body 51 is ring-shaped. An internal thread (an example of a second thread) is formed on the inner periphery 51a of the main body 51. An external thread (an example of a first thread) is formed on the outer periphery of the magnet holder 16. The internal thread of the main body 51 fits into the external thread on the outer periphery of the magnet holder 16. That is, the main body 51 is threadedly engaged with the magnet holder 16 and can move along the axis A by rotating circumferentially relative to the magnet holder 16. A spacer may be disposed between the main body 51 and the first permanent magnet 41 to protect the first permanent magnet 41.

[0044] When the main body 51 rotates around the axis A relative to the magnet holder 16, the main body 51 moves in the direction of the axis A. The movement of the main body 51 causes the first permanent magnet 41, which is elastically supported by the disc spring 44, to move along the direction of the axis A. In other words, by rotating the main body 51, the position of the first permanent magnet 41 relative to the second permanent magnet 42 can be adjusted.

[0045] The protrusions 52 protrude in the first direction A1 from the upper surface 51b of the main body 51. The protrusions 52 are formed with a first contacted surface 53a and a second contacted surface 53b on the outer periphery 51c side of the main body 51 (i.e., the side facing the rotor 3) that are contacted by jigs (first jig 61, second jig 62) that rotate the main body 51. In the present embodiment, six protrusions 52 are provided on the upper surface 51b of the main body 51 at equal intervals along the circumferential direction of the main body 51.

[0046] When viewed from the top surface 51b, the first abutted surface 53a extends from a portion corresponding to the vertex of the outer periphery 51c of the protruding portion 52 toward the vertex of one of the two protruding portions 52 adjacent to the protruding portion 52. The first abutted surface 53a extends obliquely on the top surface 51b of the main body portion 51 from the outer periphery 51c side of the main body portion 51 toward the inner periphery 51a side.

[0047] When viewed from the top surface 51b, the second abutted surface 53b is a surface that extends from a portion corresponding to the vertex of the outer periphery 51c of the protruding portion 52 toward the vertex of the other of the two protruding portions 52 adjacent to the protruding portion 52. The second abutted surface 53b extends obliquely on the top surface 51b of the main body portion 51 from the outer periphery 51c side of the main body portion 51 toward the inner periphery 51a side.

[0048] The second abutted surface 53b is adjacent to the first abutted surface 53a of the protruding portion 52 adjacent to the protruding portion 52 on which the second abutted surface 53b is provided. Therefore, the second abutted surface 53b and the adjacent first abutted surface 53a are arranged on one common side of the hexagon formed by the six protruding portions 52.

[0049] As shown in Figures 4 to 6, the protrusion 52 is small compared to the main body 51. In this way, by forming the contact surfaces 53a, 53b that the jig contacts into small protrusions 52, the magnetic nut 46 can be held by the jig and the magnetic nut 46 can be made smaller. By making the magnetic nut 46 smaller, the eigenvalue of the vacuum pump 1 does not decrease, and large vibrations are less likely to occur in the vacuum pump 1. Furthermore, because the proportion of the casing 7 that the magnetic nut 46 occupies can be reduced, a larger first permanent magnet 41 (and a larger second permanent magnet 42) can be used in the vacuum pump 1, and the pumping speed of the vacuum pump 1 can be increased.

[0050] In the present embodiment, six protrusions 52 are provided on the top surface 51b of the main body 51 at equal intervals along the circumferential direction of the main body 51. By providing the six protrusions 52 at equal intervals along the circumferential direction of the main body 51, the six protrusions 52 form part of a hexagon when viewed from the top surface 51b side of the main body 51, as shown in Fig. 6. Specifically, the vertices of the protrusions 52 on the outer periphery 51c side correspond to the vertices of the hexagon, and the first abutted surface 53a and the second abutted surface 53b formed on the protrusions 52 correspond to the sides extending from the vertices of the hexagon.

[0051] The reason why six (a multiple of six) protrusions 52 are provided on the upper surface 51b of the main body 51 will be explained below. As will be described later, a first jig 61 (FIG. 8) that rotates the magnetic nut 46 from the upper surface 51b side of the main body 51 has three abutment portions that abut against the abutment surfaces 53a, 53b of the protrusions 52 through three spaces formed by three beam portions 16b provided on the magnet holder portion 16. To stably hold the magnetic nut 46 with this first jig, it is preferable that each of the three abutment portions abut against the abutment surface 53a, 53b of at least one protrusion 52. For this reason, it is preferable that the number of protrusions 52 provided on the upper surface 51b of the main body 51 is a multiple of three.

[0052] On the other hand, a second jig 62 (FIG. 10) that rotates the magnetic nut 46 from the side surface (outer periphery 51c) of the main body 51 has two contact portions for contacting the contact surfaces 53a, 53b of the protrusions 52. To stably hold the magnetic nut 46 with this second jig, it is preferable that each of the two contact portions contacts the contact surface 53a, 53b of at least one of the protrusions 52. For this reason, it is preferable that the number of protrusions 52 provided on the upper surface 51b of the main body 51 is a multiple of two.

[0053] As a result, in order to stably hold the magnetic nut 46 by both the first jig and the second jig, it is preferable that the number of protrusions 52 provided on the upper surface 51b of the main body 51 is a multiple of 2 and a multiple of 3, that is, a multiple of 6 (a common multiple of 2 and 3).

[0054] <2. Balance adjustment housing> Next, the balance adjustment housing 70 will be described. In this embodiment, balance adjustment (adjustment of the center of gravity position) of the rotor 3 is performed with the rotor 3 housed in the balance adjustment housing 70. The configuration of the balance adjustment housing 70 will be described below with reference to FIG. 7. FIG. 7 is a diagram showing the balance adjustment housing 70.

[0055] The balance adjustment housing 70 has the same configuration as the vacuum pump 1 described above, except that the housing part 2' does not have a first end, and an opening OP that allows access to the internal space of the housing part 2' is provided on the top surface of the casing 7' of the housing part 2'. Therefore, a description of the other components of the balance adjustment housing 70 will be omitted.

[0056] By providing an opening OP in the casing 7', a user can access the multiple balance adjustment holes 43a from the top of the vacuum pump 1 through the opening OP and adjust the balance of the rotor 3 by inserting a screw into any of the balance adjustment holes 43a or removing a screw inserted into any of the balance adjustment holes 43a.

[0057] Furthermore, a first jig 61 can be inserted from an opening OP at the top of the vacuum pump 1, and the first jig 61 can hold and rotate the magnetic nut 46 from the upper surface 51b side of the main body 51.

[0058] In the following description, the portion of the balance adjustment housing 70 that corresponds to the first permanent magnet 41 of the vacuum pump 1 will be referred to as the "third permanent magnet 41'." Also, the portion of the balance adjustment housing 70 that corresponds to the magnet holder portion 16 of the vacuum pump 1 will be referred to as the "magnet holder portion 16'," and the portion that corresponds to the beam portion 16b will be referred to as the "beam portion 16b'."

[0059] <3. First jig> The first jig 61 will be described below with reference to Fig. 8. Fig. 8 is a diagram showing the configuration of the first jig 61. The first jig 61 is a jig used when rotating the main body 51 of the magnetic nut 46 from the upper surface 51b side of the main body 51. The first jig 61 has a first gripping portion 61a and three first contact portions 61b.

[0060] The first gripping portion 61a is a rod-shaped member that is long in one direction. The first gripping portion 61a has, for example, a cylindrical shape that is long in one direction. The first gripping portion 61a is gripped by a user when the main body portion 51 is rotated by the first jig 61.

[0061] The three first contact portions 61b each branch off from one longitudinal end of the first gripping portion 61a and extend in the longitudinal direction of the first gripping portion 61a. The three first contact portions 61b are arranged at equal intervals in the circumferential direction of the first gripping portion 61a. Each first contact portion 61b has a contact surface 611. When the first jig 61 is inserted from the top surface 51b side of the main body portion 51, the contact surface 611 comes into contact with the first contacted surface 53a and the second contacted surface 53b of the protrusion 52 of the magnetic nut 46.

[0062] The first jig 61 having the above configuration is used to adjust the position of the magnetic nut 46 after the rotor 3 is housed in the balance adjustment housing 70 and the magnetic nut 46 is attached. Specifically, the first jig 61 is inserted from the top surface 51b of the main body 51 through the opening OP of the housing 2′, and each first abutment portion 61b of the first jig 61 is inserted into a space formed between two adjacent beam portions 16b′. From each space into which each first abutment portion 61b is inserted, two adjacent protrusions 52 of the six protrusions 52 provided on the top surface 51b of the main body 51 of the magnetic nut 46 can be seen. Furthermore, as described above, the first abutment surface 53a of one of the two adjacent protrusions 52 and the second abutment surface 53b of the other protrusion are adjacent to each other and are located on one side of a hexagon formed by the six protrusions 52. Therefore, when the first contact portion 61b is inserted between the two beam portions 16b', as shown in Fig. 9, the contact surface 611 of the first contact portion 61b comes into contact with the first contacted surface 53a of one of the two adjacent protrusions 52 and the second contacted surface 53b of the other protrusion 52. Fig. 9 is a diagram showing the magnetic nut 46 held by the first jig 61.

[0063] 4 to 6, the first contact surface 53a of one of the two adjacent protrusions 52 and the second contact surface 53b of the other are spaced apart. Therefore, each first contact portion 61b of the first jig 61 can hold the main body 51 at two separate points by contacting the adjacent first contact surface 53a and second contact surface 53b. As a result, the first jig 61 can stably hold the main body 51 (magnetic nut 46).

[0064] <4. Second jig> The second jig 62 will be described below with reference to Fig. 10. Fig. 10 is a diagram showing the configuration of the second jig 62. The second jig 62 is a jig used when rotating the main body 51 of the magnetic nut 46 from the side surface (outer periphery 51c) of the main body 51. The second jig 62 has a second gripping portion 62a and two second contact portions 62b.

[0065] The second gripping portion 62a is a member that is long in one direction. The first gripping portion 61a is, for example, a plate-like member that is long in one direction. The second gripping portion 62a is gripped by a user when the main body portion 51 is rotated by the second jig 62.

[0066] The two second contact portions 62b each branch off from one longitudinal end of the second gripping portion 62a and extend in the longitudinal direction of the second gripping portion 62a. The two second contact portions 62b are larger in diameter than the inner periphery 51a of the main body 51 of the magnetic nut 46 and smaller in diameter than the outer periphery 51c. Each second contact portion 62b has a contact surface 621. When the second jig 62 is inserted from the outer periphery 51c side of the main body 51, the contact surface 621 comes into contact with the first contact surface 53a and the second contact surface 53b of the protrusion 52 of the magnetic nut 46.

[0067] The second jig 62 having the above configuration is used to adjust the position of the magnetic nut 46 when the rotor 3 is housed in the housing 2 of the vacuum pump 1 and the magnetic nut 46 is attached. Specifically, as shown in FIG. 11 , the second jig 62 is inserted from the outer periphery 51c side of the main body 51 through the first intake port P11 of the vacuum pump 1, and the four protrusions 52 are sandwiched between the two second abutment portions 62b of the second jig 62. By sandwiching the four protrusions 52 between the two second abutment portions 62b, the abutment surface 621 of each second abutment portion 62b of the second jig 62 abuts against the first abutted surface 53a of one of two adjacent protrusions 52 among the four sandwiched protrusions 52 and the second abutted surface 53b of the other protrusion 52. In this way, the second jig 62 can hold the magnetic nut 46 with the four protrusions 52 sandwiched between the two second abutment portions 62b. Figure 11 is a diagram showing the magnetic nut 46 held by the second jig 62.

[0068] As described above, each second contact portion 62b of the second jig 62 contacts the adjacent first contacted surface 53a and second contacted surface 53b, thereby holding the main body portion 51 at two separate points. As a result, the second jig 62 can stably hold the main body portion 51 (magnetic nut 46).

[0069] <5. How to adjust the vacuum pump> Next, we will explain how to adjust the vacuum pump 1. Adjusting the vacuum pump 1 includes balancing the rotor 3 and adjusting the vacuum pump 1 with the rotor 3 after balance adjustment housed in the housing 2. Hereinafter, we will explain the method of adjusting the vacuum pump 1 in detail.

[0070] First, to perform balance adjustment of the rotor 3, the rotor 3 is housed in the internal space of the balance adjustment housing 70. The magnetic nut 46 is attached to the magnet holder portion 16' of the balance adjustment housing 70. The magnetic nut 46 is then rotated relative to the magnet holder portion 16' to adjust the position of the third permanent magnet 41' of the balance adjustment housing 70 relative to the second permanent magnet 42 of the rotor 3. This allows the preload force applied to the rolling bearing 33' of the balance adjustment housing 70 to be adjusted. The preload force applied to the rolling bearing 33' can be measured, for example, using a force gauge attached to the thrust nut 34' of the balance adjustment housing 70.

[0071] As described above, the balance adjustment housing 70 has an opening OP on the top surface of the casing 7' of the housing part 2' to access the balance adjustment hole 43a of the rotor 3. Therefore, when adjusting the balance of the rotor 3, the first jig 61 that rotates the magnetic nut 46 attached to the magnet holder part 16' is used from the top surface 51b side of the main body part 51.

[0072] Specifically, the first jig 61 described above is inserted into the internal space of the balance adjustment housing 70 through the opening OP at the top of the balance adjustment housing 70, and the contact surfaces 611 of the first contact portions 61b of the first jig 61 are brought into contact with the contact surfaces 53a, 53b of the magnetic nut 46 housed in the internal space of the balance adjustment housing 70. Specifically, as described with reference to FIG. 9 , each first contact portion 61b of the first jig 61 is inserted into the space formed between two adjacent beam portions 16b′ of the balance adjustment housing 70, and the contact surfaces 611 of each first contact portion 61b are brought into contact with the first contact surface 53a of one of the two adjacent protrusions 52 and the second contact surface 53b of the other protrusion 52.

[0073] With the magnet nut 46 held by the first jig 61 as described above, the first gripping portion 61a of the first jig 61 can be rotated around the longitudinal axis to rotate the magnet nut 46 relative to the magnet holder portion 16', thereby adjusting the position of the third permanent magnet 41' relative to the second permanent magnet 42 of the rotor 3.

[0074] After adjusting the position of the third permanent magnet 41' relative to the second permanent magnet 42 of the rotor 3, the balance of the rotor 3 is adjusted. Specifically, a screw is inserted into one of the plurality of balance adjustment holes 43a provided in the rotor 3, or a screw inserted into one of the balance adjustment holes 43a is removed to adjust the position of the center of gravity of the rotor 3 in the radial direction (direction perpendicular to the axis A) and circumferential direction, so that the position of the center of gravity of the rotor 3 coincides with the central position of the rotor 3. Note that the position of the center of gravity of the rotor 3 can be estimated, for example, based on vibrations generated when the rotor 3 is rotated around the axis A.

[0075] After adjusting the balance of the rotor 3, the balanced rotor 3 and magnet nut 46 are assembled into the vacuum pump 1. Specifically, the balanced rotor 3 is housed in the housing 2 of the vacuum pump 1, and the magnet nut 46 is attached to the magnet holder 16 of the vacuum pump 1. The magnet nut 46 is then rotated relative to the magnet holder 16 to adjust the position of the first permanent magnet 41 of the vacuum pump 1 relative to the second permanent magnet 42 of the rotor 3. This makes it possible to adjust the preload force applied to the rolling bearing 33 of the vacuum pump 1. The preload force applied to the rolling bearing 33 can be measured, for example, using a force gauge attached to the thrust nut 34 of the vacuum pump 1.

[0076] As described above, in the vacuum pump 1, the top surface of the casing 7 of the housing 2 is closed by the first end 11. Therefore, when the rotor 3 is housed in the housing 2 of the vacuum pump 1, the magnetic nut 46 cannot be accessed using the first jig 61. On the other hand, a first intake port P11 is provided on the side surface 13 of the housing 2. The magnetic nut 46 is accessible from the side surface (outer periphery 51c) of the main body 51 through this first intake port P11. Therefore, when the rotor 3 after balance adjustment is assembled into the vacuum pump 1, the magnetic nut 46 attached to the magnet holder portion 16 is rotated using the second jig 62, which rotates the magnetic nut 46 from the outer periphery 51c of the main body 51.

[0077] Specifically, the second jig 62 described above is inserted into the internal space of the housing 2 through the first intake port P11 provided on the side surface 13 of the housing 2, and the contact surfaces 621 of the second contact portions 62b of the second jig 62 are brought into contact with the contact surfaces 53a, 53b of the magnetic nut 46 housed in the internal space of the housing 2. Specifically, as described with reference to FIG. 11 , the four protrusions 52 of the magnetic nut 46 are sandwiched between the two second contact portions 62b of the second jig 62, and the contact surfaces 621 of the second contact portions 62b are brought into contact with the first contact surface 53a of one of two adjacent protrusions 52 of the four sandwiched protrusions 52 and the second contact surface 53b of the other protrusion 52.

[0078] With the magnet nut 46 held by the second jig 62 as described above, the second gripping portion 62a of the second jig 62 can be moved horizontally to rotate the magnet nut 46 relative to the magnet holder portion 16, thereby adjusting the position of the first permanent magnet 41 relative to the second permanent magnet 42 of the rotor 3. In this manner, the rotor 3 and magnet nut 46 after balance adjustment can be assembled into the vacuum pump 1.

[0079] In the vacuum pump 1, the protrusion 52 of the magnetic nut 46, which adjusts the positions of the first permanent magnet 41 and the third permanent magnet 41′, protrudes from the upper surface 51b of the main body 51 and has contact surfaces 53a and 53b that come into contact with a jig that rotates the main body 51. The contact surfaces 53a and 53b are provided on the protrusion 52 on the outer periphery 51c side of the main body 51 and can be contacted by both a first jig 61 that rotates the main body 51 from the upper surface 51b side of the main body 51 and a second jig 62 that rotates the main body 51 from the side (outer periphery 51c) side of the main body 51. In this way, the magnetic nut 46 can be rotated from either the upper surface or the side of the main body 51, so that the positions of the first permanent magnet 41 and the third permanent magnet 41′ can be adjusted from either the upper surface or the side of the magnetic nut 46.

[0080] For example, when the rotor 3 is stored in a balance adjustment housing 70 having an opening OP at the top of the housing part 2', that is, when adjusting the balance of the rotor 3, the position of the third permanent magnet 41' can be adjusted from the top surface of the balance adjustment housing 70 using a first jig 61 that rotates the main body part 51 from the top surface 51b side of the main body part 51.

[0081] On the other hand, when the rotor 3 is stored in the housing part 2 of the vacuum pump 1, which has the first intake port P11 on the side part 13, i.e., when the rotor 3 is incorporated into the vacuum pump 1, the position of the first permanent magnet 41 can be adjusted from the side of the vacuum pump 1 using a second jig 62 that rotates the main body part 51 from the side (outer periphery 51c) side of the main body part 51.

[0082] 2. Other Embodiments Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0083] In the above embodiment, six protrusions 52 are provided on the upper surface 51b of the main body 51 of the magnetic nut 46, but this is not limited to this. The number of protrusions 52 may be any number that is a multiple of six, such as 12 or 18.

[0084] Depending on whether beam portions 16b are provided on the magnet holder portion 16, or the number of beam portions 16b (i.e., the number of spaces formed by the beam portions 16b), the number of protrusions 52 and / or the shape of the polygon formed by the protrusions 52 and the abutment surfaces 53a, 53b (the number of vertices) can be any number.

[0085] In the above embodiment, the plurality of (six) protrusions 52 are arranged at predetermined intervals on the upper surface 51b of the main body 51 so as to form part of a polygonal shape. However, this is not limiting, and one protrusion 52 having an overall polygonal shape may be arranged on the upper surface 51b of the main body 51.

[0086] The first jig 61 that rotates the magnetic nut 46 from the upper surface 51b side of the main body 51 is not limited to the configuration described using Figures 7 and 8. For example, the first jig 61' may have a configuration as shown in Figure 12. Figure 12 is a diagram showing a first jig 61' of another embodiment. The first jig 61' has a third gripping portion 61a' and three third abutment portions 61b'.

[0087] The third gripping portion 61a' is a rod-shaped member that is long in one direction and is held by the user when the main body portion 51 is rotated by the first jig 61'.

[0088] The three third contact portions 61b' each branch off from one longitudinal end of the third gripping portion 61a' and extend in the longitudinal direction of the third gripping portion 61a'. The three third contact portions 61b' are arranged at equal intervals in the circumferential direction of the third gripping portion 61a'. Each third contact portion 61b' has a contact surface 611'. The contact surface 611' has a shape corresponding to the vertex of the protrusion 52 of the magnetic nut 46. When the first jig 61' is inserted from the upper surface 51b side of the main body 51, the contact surface 611' comes into contact with a portion of the contact surface (first contact surface 53a, second contact surface 53b) of one protrusion 52 of the magnetic nut 46 that corresponds to the vertex of the hexagon. In other words, the contact surface 611' comes into contact with the vertex of one protrusion 52.

[0089] When using the first jig 61′ having the above configuration to hold and rotate the magnetic nut 46 attached to the balance adjustment housing 70, the first jig 61′ is inserted from the upper surface 51b side of the main body 51 through the opening OP of the balance adjustment housing 70, and each third abutment portion 61b′ of the first jig 61′ is inserted into the space formed between two adjacent beam portions 16b′. Next, as shown in FIG. 13, the abutment surface 611′ of the third abutment portion 61b′ is abutted against the first abutment surface 53a and the second abutment surface 53b present at the apex of one protrusion 52. FIG. 13 is a diagram showing the magnetic nut 46 held by the first jig 61′ of another embodiment.

[0090] As shown in FIG. 13, the third contact portion 61b' of the first jig 61' is thinner than the first contact portion 61b of the first jig 61 described in the first embodiment. Therefore, the third contact portion 61b' can move more widely in the space between two adjacent beam portions 16b'. As a result, once the first jig 61' is inserted into the balance adjustment housing 70, the first jig 61' can rotate the magnetic nut 46 over a wide angular range without having to re-hold the magnetic nut 46. In other words, the first jig 61' can adjust the position of the magnetic nut 46 (i.e., the position of the third permanent magnet 41') without having to re-hold the magnetic nut 46.

[0091] 3. Aspects It will be appreciated by those skilled in the art that the above-described exemplary embodiment is a specific example of the following aspects. (First aspect) A vacuum pump includes a rotor, a housing, a magnetic bearing, and an adjustment member. The rotor is rotatable. The housing accommodates the rotor. The magnetic bearing has a first magnet arranged around a magnet holder fixed to the housing, and a second magnet arranged on the rotor radially opposite the first magnet. The adjustment member adjusts the position of the first magnet relative to the second magnet. The adjustment member includes a main body and a protrusion. The main body has a second threaded shape on its inner circumferential surface that fits into a first threaded shape formed around the magnet holder. When rotated relative to the magnet holder, the main body moves in a direction along the rotation axis of the rotor, adjusting the position of the first magnet relative to the second magnet. The protrusion protrudes from the top surface of the main body. The protrusion has an abutment surface on the outer circumferential side of the adjustment member that can be abutted by a first jig that rotates the main body from the top surface side of the main body, and that can be abutted by a second jig that rotates the main body from the side surface side of the main body.

[0092] In the vacuum pump according to the first aspect, the adjustment member for adjusting the position of the first magnet has a protruding portion that protrudes from the top surface of the main body and has an abutment surface that is abutted by a jig that rotates the main body. This abutment surface is provided on the protruding portion on the outer periphery of the main body and can be abutted by either a first jig that rotates the main body from the top side or a second jig that rotates the main body from the side side. In this way, the adjustment member can be rotated using a jig from either the top side or the side side of the main body, so the position of the first magnet can be adjusted from either the top side or the side side of the adjustment member.

[0093] (Second Aspect) In the vacuum pump according to the first aspect, the protrusion may have a polygonal shape when viewed from the top surface side of the main body. In the vacuum pump according to the second aspect, the adjustment member can be stably held and rotated using a jig.

[0094] (Third Aspect) In the vacuum pump according to the second aspect, a plurality of protrusions may be arranged on the upper surface of the main body. In this case, the plurality of protrusions may form part of a polygonal shape. In the vacuum pump according to the third aspect, the protrusions can be made small, and the adjustment member can be stably held and rotated using a jig.

[0095] (Fourth Aspect) In the vacuum pump according to the third aspect, each of the plurality of protrusions may be disposed at a vertex of a polygon on the upper surface of the main body. In the vacuum pump according to the fourth aspect, the protrusions can be made small, and the adjustment member can be stably held and rotated using a jig.

[0096] (Fifth Aspect) In the vacuum pump according to the third or fourth aspect, the first and second jigs may abut against the abutment surface of one of the plurality of protrusions and the abutment surface of the protrusion adjacent to the protrusion. In the vacuum pump according to the fifth aspect, the jigs can hold the adjustment member at two separate points, so that the adjustment member can be stably held and rotated.

[0097] (Sixth Aspect) In the vacuum pump according to the fourth aspect, the first jig may abut against portions of the abutment surface of the protrusion that correspond to vertices of the polygonal shape. In the vacuum pump according to the sixth aspect, the first jig can be used to adjust the position of the adjustment member over a wide range without having to re-hold the adjustment member.

[0098] (Seventh Aspect) In the vacuum pump according to any one of the third to sixth aspects, the number of protrusions arranged on the upper surface of the main body may be a multiple of 6. In the vacuum pump according to the seventh aspect, for example, the protrusions can be stably held at three locations using a first jig, and the protrusions can be stably held at two locations using a second jig.

[0099] (Eighth Aspect) A method for adjusting a vacuum pump according to any one of the first to seventh aspects includes the following steps. A step of housing the rotor and the adjustment member in an adjustment housing having an opening at the top and a third magnet. ◎A step of inserting a first jig into the adjustment housing through the opening, abutting the first jig against the abutment surface of the adjustment member housed in the adjustment housing, rotating the adjustment member, and adjusting the position of the third magnet relative to the second magnet. A step of accommodating the rotor and the adjusting member in a vacuum pump housing having an intake port formed on the side. ◎A step of inserting a second jig into the housing portion from the air intake port, abutting the second jig against the abutting surface of the adjustment member housed in the housing portion, rotating the adjustment member, and adjusting the position of the first magnet relative to the second magnet.

[0100] In the method for adjusting a vacuum pump according to the eighth aspect, when the rotor and adjustment member are housed in an adjustment housing having an opening at the top, the position of the third permanent magnet can be adjusted from the top of the adjustment housing using a first jig that rotates the adjustment member from the top side of the main body. On the other hand, when the rotor and adjustment member are housed in a vacuum pump housing having an intake port on the side, the position of the first magnet can be adjusted from the side of the vacuum pump using a second jig that rotates the main body from the side side of the main body.

[0101] (Ninth Aspect) The adjustment method according to the eighth aspect may further include a step of adjusting the balance of the rotor after the step of adjusting the position of the third magnet relative to the second magnet. By adjusting the balance of the rotor, the adjustment method according to the ninth aspect can suppress vibration during operation of the vacuum pump. [Explanation of symbols]

[0102] 1: Vacuum pump 2, 2': Housing 3: Rotor 4: Motor 5: Stator blade unit 6: Stator cylindrical part 7, 7': Casing 8: Bass 8a: Recess 8b: Through hole 9: Lid 11: First end 12:Second end 13: Side part 15: Base end 16, 16': Magnet holder part 16a: recess 16b, 16b': Beam part 21: Shaft 22: Rotor blade unit 23: Rotor cylindrical part 25: Rotor blade 26: Motor rotor 27: Motor stator 28: Stator blade 31: Protective bearing 32: Magnetic bearing 33, 33': Rolling bearing 34, 34': Thrust nut 41: First permanent magnet 41': Third permanent magnet 42: Second permanent magnet 43: Fixing member 43a: Balance adjustment hole 44: Disc spring 45: Spring support member 46: Magnetic nut 51: Main body 51a: Inner circumference 51b:Top surface 51c: outer circumference 52:Protrusion 53a: First abutted surface 53b: Second abutted surface 61, 61': First jig 61a: 1st gripping part 61a': Third gripping part 61b: 1st contact part 61b': Third contact part 62: Second jig 62a: Second grip part 62b: Second contact part 70: Balance adjustment housing 611, 611', 621: Contact surface A: Axis A1: 1st direction A2 :Second direction B: Radial direction T: Turbine section D: Drag pump section P11: First air intake P12: Second air intake P13: Second air intake P21: Exhaust port OP: Opening

Claims

1. A rotatable rotor; A housing portion that houses the rotor; a magnetic bearing including a first magnet arranged around a magnet holder fixed to the housing and a second magnet arranged on the rotor radially opposite to the first magnet; an adjustment member for adjusting a position of the first magnet relative to the second magnet, The adjustment member is a main body having an inner circumferential surface with a second thread shape that fits into a first thread shape formed around the magnet holder portion, and which moves in a direction along the rotation axis of the rotor by rotating relative to the magnet holder portion to adjust the position of the first magnet relative to the second magnet; a protrusion protruding from an upper surface of the main body, The protrusion has an abutment surface on the outer periphery of the main body portion, the abutment surface being abuttable by a first jig that rotates the main body portion from the top surface side of the main body portion and abuttable by a second jig that rotates the main body portion from the side surface side of the main body portion. Vacuum pump.

2. The vacuum pump according to claim 1 , wherein the protrusion has a polygonal shape when viewed from the top surface side of the main body.

3. The protrusions are arranged on the upper surface of the main body, The vacuum pump of claim 2 , wherein a plurality of protrusions form part of the polygonal shape.

4. The vacuum pump according to claim 3 , wherein each of the plurality of protrusions is disposed at a vertex of the polygonal shape on the upper surface of the main body.

5. The vacuum pump according to claim 3 , wherein the first jig and the second jig abut against a contact surface of one of the plurality of protrusions and a contact surface of a protrusion adjacent to the one of the plurality of protrusions.

6. The vacuum pump according to claim 4 , wherein the first jig abuts against portions of the abutment surface of the protrusion that correspond to vertices of the polygonal shape.

7. 4. The vacuum pump according to claim 3, wherein the number of the protrusions arranged on the upper surface of the main body is a multiple of six.

8. 2. A method for adjusting a vacuum pump according to claim 1, comprising the steps of: housing the rotor and the adjustment member in an adjustment housing having an opening at an upper portion and a third magnet; a step of inserting a first jig into the adjustment housing from the opening, abutting the first jig against the abutted surface of the adjustment member housed in the adjustment housing, rotating the adjustment member, and adjusting a position of the third magnet relative to the second magnet; a step of housing the rotor and the adjustment member in the housing of the vacuum pump having an intake port formed on a side surface thereof; a step of inserting a second jig into the housing from the intake port, bringing the second jig into contact with the contact surface of the adjustment member housed in the housing, and rotating the adjustment member to adjust the position of the first magnet relative to the second magnet; The adjustment method includes:

9. 9. The method according to claim 8, further comprising the step of adjusting balance of the rotor after the step of adjusting a position of the third magnet relative to the second magnet.

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