magnetic bearing device

Abstract

To provide a magnetic bearing device that can correct an inclination of a rotor with a small magnetic attraction and support the rotor stably.SOLUTION: A magnetic bearing device includes: a non-magnetic ring 1 constituted of a non-magnetic material; and at least three axial magnetic poles 5 arrayed along a circumferential direction of the non-magnetic ring 1. Each of the axial magnetic poles 5 includes: a circular arc-shaped coil 10; and a coil housing 12 for storing the coil 10. The at least three axial magnetic poles 5 are fixed to the non-magnetic ring 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic bearing device capable of supporting a rotating body in a non-contact manner. [Background technology]

[0002] A magnetic bearing device is a device that levitates a rotating body using magnetic force generated by an electromagnetic coil. Because magnetic bearing devices can support a rotating body without mechanically contacting the rotating body, they do not cause wear or frictional heat on the rotating body. Therefore, magnetic bearing devices are suitable for supporting rotating bodies that rotate at high speeds, such as the turbine blades of turbomolecular pumps.

[0003] Fig. 10 is a schematic diagram showing an example of a conventional magnetic bearing device. As shown in Fig. 10, a magnetic bearing device typically includes upper radial magnetic poles 501A, 501B and lower radial magnetic poles 502A, 502B arranged along the axis of a rotating body 500. The upper radial magnetic poles 501A, 501B and lower radial magnetic poles 502A, 502B not only support the radial load of the rotating body 500 but also have the function of adjusting the tilt of the rotating body 500. That is, as shown in Fig. 11, when the rotating body 500 tilts, the upper radial magnetic poles 501A, 501B and lower radial magnetic poles 502A, 502B generate different magnetic attractive forces, thereby correcting the tilt of the rotating body 500. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-60754 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the rotating body 500 has a flattened shape, a large magnetic attractive force is required to correct the tilt of the rotating body 500. That is, since the distance L between the center of gravity O of the rotating body 500 and the point of action of the magnetic attractive force is short, the magnetic attractive force required to generate the required moment force is large. As a result, the power required for the radial magnetic poles 501A, 501B, 502A, and 502B increases.

[0006] Furthermore, when the rotor 500 rotates at high speed, the rotor 500 as a whole expands radially outward, resulting in an increase in the magnetic gap between the rotor 500 and the radial magnetic poles 501A, 501B, 502A, and 502B, which reduces the magnetic attractive force and causes unstable control.

[0007] Furthermore, although not shown, conventional axial magnetic poles have a magnetic pole core made of a magnetic material and a ring-shaped U-shaped cross section, with a coil wound with a predetermined number of turns. When a current is passed through the winding, a force is generated between the magnetic pole core and a magnetic pole target separately arranged on the rotor. However, when the rotor tilts, gaps with the axial magnetic pole are created in both close and far areas, with the force being stronger in the close areas and weaker in the far areas, causing the rotor to tilt more. In a heavy, vertically mounted rotor, the axial magnetic attractive force is larger, so the force tending to tilt the rotor when tilted is even stronger, causing interference with radial tilt control.

[0008] Therefore, the present invention provides a magnetic bearing device that can correct the tilt of a rotor with a small magnetic attractive force and can stably support the rotor. [Means for solving the problem]

[0009] In one aspect, a magnetic bearing device for supporting a rotating body in a non-contact manner is provided, comprising a non-magnetic ring made of a non-magnetic material and at least three axial magnetic poles arranged along the circumferential direction of the non-magnetic ring, each axial magnetic pole having an arc-shaped coil and a coil housing that accommodates the coil, and the at least three axial magnetic poles are fixed to the non-magnetic ring.

[0010] In one aspect, the coil housing has an arc-shaped outer wall around which the coil is wound, an arc-shaped inner wall arranged inside the outer wall, and a base plate connected to the upper ends of the outer wall and the inner wall, and the coil housing is fixed to the non-magnetic ring. In one embodiment, the coil housing has a flange that protrudes radially inward from the inner wall, and the flange is fixed to the non-magnetic ring by a fastener. In one embodiment, the wire connected to the coil is disposed along the flange. In one embodiment, the non-magnetic ring has at least one notch in its inner circumference, and the electric wire extends through the notch.

[0011] In one aspect, the coil housing has an arc-shaped inner wall around which the coil is wound, an arc-shaped outer wall arranged outside the inner wall, and a base plate connected to the upper end of the outer wall and the upper end of the inner wall, and the coil housing is fixed to the non-magnetic ring. In one embodiment, the coil housing has a flange that protrudes radially outward from the outer wall, and the flange is fixed to the non-magnetic ring by a fastener. In one embodiment, the wire connected to the coil is disposed along the flange. In one embodiment, the non-magnetic ring has at least one notch in its outer periphery, and the electrical wire extends through the notch.

[0012] In one embodiment, the magnetic bearing device further includes a plurality of positioning pins for fixing the relative positions of the non-magnetic ring and each of the axial magnetic poles. In one embodiment, the magnetic bearing device further includes a molding material that covers the coils of the at least three axial magnetic poles. In one embodiment, the upper surface of the coil housing is a flat surface that can come into surface contact with the heat dissipation member. [Effects of the Invention]

[0013] According to the present invention, the point of application of the magnetic attractive force generated by each axial magnetic pole can be separated from the center of gravity of the rotor, so the magnetic bearing device can correct the tilt of the rotor with a small magnetic attractive force. Furthermore, even when the rotor rotates at high speed and expands radially outward, the magnetic gap between the axial magnetic pole and the rotor does not change. Therefore, the magnetic bearing device can stably control the attitude of the rotor.

[0014] The multiple axial magnetic poles are fixed to a single non-magnetic ring, and the relative positions of these axial magnetic poles are fixed. Therefore, even when a large load of the rotating body is applied to the axial magnetic poles, the positions of the axial magnetic poles can be stabilized. As a result, the axial magnetic poles can accurately control the attitude of the rotating body. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of an embodiment of a magnetic bearing device as seen from above; [Figure 2] FIG. 2 is a perspective view of the magnetic bearing device shown in FIG. 1, as seen from below. [Figure 3] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 10 is a perspective view illustrating one embodiment of coil wiring. [Figure 5] FIG. 2 is a schematic diagram showing an embodiment of a rotary machine including the magnetic bearing device and a rotating body supported by the magnetic bearing device. [Figure 6] FIG. 10 is a cross-sectional view showing another embodiment of the magnetic bearing device. [Figure 7] FIG. 10 is a cross-sectional view showing still another embodiment of a magnetic bearing device. [Figure 8] FIG. 8 is a top view of the coil housing of FIG. 7. [Figure 9] FIG. 10 is a cross-sectional view showing still another embodiment of a magnetic bearing device. [Figure 10] FIG. 1 is a schematic diagram showing an example of a conventional magnetic bearing device. [Figure 11] 1A and 1B are diagrams illustrating how a conventional magnetic bearing device corrects the tilt of a rotor. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of one embodiment of a magnetic bearing device as seen from above, and Fig. 2 is a perspective view of the magnetic bearing device shown in Fig. 1 as seen from below. The magnetic bearing device comprises a non-magnetic ring 1 made of a non-magnetic material and four axial magnetic poles 5 arranged along the circumferential direction of the non-magnetic ring 1. Examples of non-magnetic materials that make up the non-magnetic ring 1 include austenitic stainless steel, resin-based non-magnetic materials (PTFE (polytetrafluoroethylene), fiber-reinforced plastic), etc.

[0017] Each axial magnetic pole 5 is detachably fixed to the non-magnetic ring 1 by a plurality of screws 7, which are a plurality of fasteners. The relative positions of these four axial magnetic poles 5 are fixed by the single non-magnetic ring 1. Each axial magnetic pole 5 has an arc-shaped coil 10 and a coil housing 12 that houses the coil 10. The coil housing 12 is fixed to the non-magnetic ring 1 by the plurality of screws 7. By removing these screws 7, the entire axial magnetic pole 5 can be removed from the non-magnetic ring 1.

[0018] In this embodiment, four axial magnetic poles 5 are provided, but the number of axial magnetic poles 5 is not limited to this embodiment. From the viewpoint of correcting the tilt of a rotating body (described later) supported by the magnetic bearing device, at least three axial magnetic poles 5 are provided. Therefore, in other embodiments, three axial magnetic poles 5, or five or more axial magnetic poles 5 arranged along the circumferential direction of the non-magnetic ring 1 may be provided.

[0019] Each coil housing 12 has an arc-shaped outer wall 15 around which the coil 10 is wound, an arc-shaped inner wall 16 arranged inside the outer wall 15, and a base plate 17 connected to the upper ends of the outer wall 15 and the inner wall 16. The coil housing 12 is fixed to the non-magnetic ring 1. More specifically, the coil housing 12 has a flange 20 that protrudes radially inward from the inner wall 16, and the flange 20 has an arc-shaped shape that follows the non-magnetic ring 1. The flange 20 has a through-hole (not shown) through which the screw 7 passes, and the non-magnetic ring 1 has a threaded hole (not shown) into which the screw 7 is screwed. The flange 20 is fixed to the non-magnetic ring 1 by screwing the screw 7 into the threaded hole of the non-magnetic ring 1.

[0020] The outer wall 15, the inner wall 16, and the base plate 17 are made of a metal such as iron. In this embodiment, the outer wall 15, the inner wall 16, and the base plate 17 are an integral structure. In another embodiment, the outer wall 15, the inner wall 16, and the base plate 17 may be separate structures. The coil 10 is wound around the entire circumference of the outer wall 15, which functions as the iron core of the coil 10. The inner wall 16 extends along the inside of the outer wall 15 and the coil 10. The radial gap between the outer wall 15 and the inner wall 16 is constant, and both the outer wall 15 and the inner wall 16 are curved to follow the curved shape of the coil 10. The coil 10 is in contact with the base plate 17, and heat generated in the coil 10 is transferred to the base plate 17, where it is released from the base plate 17, thereby cooling the coil 10.

[0021] The four axial magnetic poles 5 are arranged at equal intervals along the circumferential direction of the non-magnetic ring 1. The axial magnetic poles 5 are arranged with gaps between them. In other words, two adjacent axial magnetic poles 5 are spaced apart, making it difficult for magnetic interference to occur between the axial magnetic poles 5. The four axial magnetic poles 5 are fixed to the non-magnetic ring 1, but because the non-magnetic ring 1 is made of a non-magnetic material, magnetic interference between the axial magnetic poles 5 is difficult to occur.

[0022] 3 is a cross-sectional view taken along line AA in FIG. 1. As described above, the coil housing 12 has an outer wall 15 around which the coil 10 is wound, an inner wall 16 disposed radially inward of the outer wall 15, and a base plate 17 connected to the upper ends of the outer wall 15 and the inner wall 16. The outer wall 15 and the inner wall 16 are arranged in parallel and protrude downward from the base plate 17 parallel to the axis CL of the non-magnetic ring 1. The lower ends of the outer wall 15 and the inner wall 16 are exposed downward. When a current flows through the coil 10, a magnetic force is generated that passes through the outer wall 15 and the inner wall 16. The rotating body, which will be described later, is attracted upward by this magnetic force (magnetic attraction).

[0023] The magnetic bearing device further includes a plurality of positioning pins 26 that fix the relative positions of the non-magnetic ring 1 and the axial magnetic pole 5. Although only one positioning pin 26 is shown in FIG. 3 , a plurality of positioning pins 26 are provided for each axial magnetic pole 5. The coil housing 12 has a first hole 28 formed in the lower surface of the flange 20, and the non-magnetic ring 1 has a second hole 29 formed in the upper surface thereof. The positioning pin 26 is inserted into both the first hole 28 and the second hole 29.

[0024] The positioning pins 26 fix the relative positions of the multiple axial magnetic poles 5 and the non-magnetic ring 1, thereby also fixing the relative positions of the multiple axial magnetic poles 5. Although the multiple axial magnetic poles 5 are fixed to the non-magnetic ring 1 by screws 7 as fasteners shown in FIG. 1, the positioning pins 26 can fix the relative positions of the multiple axial magnetic poles 5 more precisely than the screws 7. Therefore, the axial magnetic poles 5 can accurately control the attitude of the rotating body, which will be described later.

[0025] FIG. 4 is a perspective view showing one embodiment of the wiring of the coil 10. As shown in FIG. 4, the electric wire 32 connected to the coil 10 is arranged along the upper surface of the flange 20 of the coil housing 12. More specifically, the electric wire 32 is arranged in the space above the flange 20. According to this embodiment, there is no need to provide a dedicated space for the electric wire 32, and the configuration of the magnetic bearing device can be simplified. The non-magnetic ring 1 has at least one notch 33 on its inner periphery, and the electric wire 32 connected to the coil 10 extends through the notch 33. Although one notch 33 is provided in FIG. 4, multiple notches 33 may be provided.

[0026] FIG. 5 is a schematic diagram showing an embodiment of a rotating machine including the magnetic bearing device described with reference to FIGS. 1 to 4 and a rotating body 100 supported by the magnetic bearing device. Four axial magnetic poles 5 are arranged around the axis RA of the rotating body 100 and adjust the axial displacement and inclination of the rotating body 100. The four axial magnetic poles 5 are located above the rotating body 100 and operate to pull up the rotating body 100 by magnetic attractive force. No axial magnetic poles 5 are provided below the rotating body 100. The rotating body 100 displaces downward due to its own weight. Because the magnetic bearing device does not have axial magnetic poles located below the rotating body 100, the entire magnetic bearing device can be made compact.

[0027] Although not particularly limited, a specific example of the rotating body 100 is a turbine blade of a turbomolecular pump. The rotating body 100 of the embodiment shown in Fig. 5 is a flat rotor having a diameter larger than its axial dimension.

[0028] The axial magnetic poles 5 and the non-magnetic ring 1 are fixed to the stator 42 by being sandwiched between the mounting cover 40 and the step portion 43 of the stator 42. That is, the mounting cover 40 is fixed to the upper surface of the stator 42 with screws (not shown), and the non-magnetic ring 1 fixed to the axial magnetic poles 5 is pressed against the step portion 43 of the stator 42 by the mounting cover 40. However, the mounting of the axial magnetic poles 5 and the non-magnetic ring 1 to the stator 42 is not limited to this embodiment.

[0029] The mounting cover 40 is made of a metal such as iron or aluminum, and is in surface contact with the coil housing 12 of each axial magnetic pole 5. More specifically, the top surface of the coil housing 12 (i.e., the top surface of the base plate 17) is flat, and this flat surface is in surface contact with the mounting cover 40, which also functions as a heat dissipation member. Heat generated in the coil 10 is transferred to the mounting cover 40 via the coil housing 12, and the coil 10 can be cooled by dissipating the heat from the mounting cover 40. A space S is formed between the mounting cover 40 and the flange 20, in which the electric wires 32 connected to the coil 10 are arranged.

[0030] The magnetic bearing device further includes a plurality of axial displacement sensors 47 that detect the axial displacement of the rotor 100, and a magnetic pole control unit 50 that issues commands to the axial magnetic poles 5 based on the axial displacement of the rotor 100, causing the axial magnetic poles 5 to adjust the axial position of the rotor 100 and the inclination of the rotor 100. The plurality of axial displacement sensors 47 are fixed to the stator 42.

[0031] The magnetic pole control unit 50 includes a storage device 50a that stores a program for controlling the position and inclination of the rotating body 100, and an arithmetic unit 50b that executes calculations according to instructions included in the program. The magnetic pole control unit 50 is composed of at least one computer. The storage device 50a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic unit 50b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the magnetic pole control unit 50 is not limited to these examples.

[0032] The multiple axial displacement sensors 47 and the axial magnetic poles 5 are electrically connected to the magnetic pole control unit 50. The axial position of the rotating body 100 and the inclination of the rotating body 100 can be determined from the measured values ​​of the axial displacement of the rotating body 100 sent from the multiple axial displacement sensors 47 to the magnetic pole control unit 50. Therefore, the magnetic pole control unit 50 issues commands to the axial magnetic poles 5 based on the measured values ​​of the axial displacement of the rotating body 100, and issues commands to the axial magnetic poles 5 so that the rotating body 100 is maintained at a target axial position and target inclination (including a vertical attitude).

[0033] According to this embodiment, the attitude (including tilt) of the rotating body 100 can be corrected (adjusted) by the multiple magnetic attractive forces generated by the multiple axial magnetic poles 5. As can be seen from FIG. 5 , the point of action of the magnetic attractive forces generated by each axial magnetic pole 5 can be moved away from the center of gravity of the rotating body 100, so the magnetic bearing device can correct the tilt of the rotating body 100 with a small magnetic attractive force. Furthermore, even when the rotating body 100 rotates at high speed and expands radially outward, the magnetic gap between the axial magnetic poles 5 and the rotating body 100 does not change. Therefore, the magnetic bearing device can stably control the attitude of the rotating body 100.

[0034] The magnetic bearing device further includes a plurality of radial displacement sensors 60 that detect the radial displacement of the rotating body 100, and a plurality of radial magnetic poles 62 that support the radial load of the rotating body 100. The plurality of radial displacement sensors 60 and the plurality of radial magnetic poles 62 are fixed to the stator 42. The plurality of radial displacement sensors 60 are electrically connected to the magnetic pole control unit 50. The radial position of the rotating body 100 can be determined from the measured values ​​of the radial displacement of the rotating body 100 sent from the plurality of radial displacement sensors 60 to the magnetic pole control unit 50. Therefore, the magnetic pole control unit 50 issues commands to the radial magnetic poles 62 based on the measured values ​​of the radial displacement of the rotating body 100, and issues commands to the radial magnetic poles 62 so that the rotating body 100 is maintained at a target radial position.

[0035] Since the multiple axial magnetic poles 5 are arranged around the axis RA of the rotating body 100, the magnetic pole control unit 50 can be configured to give commands to the multiple axial magnetic poles 5 to adjust not only the axial position of the rotating body 100 but also the radial position of the rotating body 100. In such a case, the radial displacement sensor 60 and the radial magnetic pole 62 may be omitted.

[0036] Figure 6 is a cross-sectional view showing another embodiment of a magnetic bearing device. The configuration and operation of this embodiment, unless otherwise specified, are the same as those of the embodiment described with reference to Figures 1 to 5, and therefore redundant description will be omitted. As shown in Figure 6, the magnetic bearing device includes a molding material 70 that covers the coil 10 of each axial magnetic pole 5. Specific examples of the molding material 70 include epoxy resin. The molding material 70 has the functions of fixing the coil 10, insulating and protecting the coil 10, protecting the coil 10 from corrosive gases and radicals, and extracting heat from the coil 10.

[0037] The molding material 70 not only covers the coils 10 of the four axial magnetic poles 5, but also fills the gaps between the axial magnetic poles 5. The molding material 70 can increase the mechanical strength of the four axial magnetic poles 5 whose relative positions are fixed by the non-magnetic ring 1.

[0038] Figure 7 is a cross-sectional view showing yet another embodiment of a magnetic bearing device. The configuration and operation of this embodiment, unless otherwise specified, are the same as those of the embodiment described with reference to Figures 1 to 5, and therefore redundant description will be omitted. As shown in Figure 7, the coil housing 12 has an arc-shaped inner wall 16 around which the coil 10 is wound, an arc-shaped outer wall 15 disposed outside the inner wall 16, and a base plate 17 connected to the upper ends of the outer wall 15 and the inner wall 16. The coil housing 12 is fixed to the non-magnetic ring 1.

[0039] The stator 42 has a hollow shape with an internal space, and the rotor 100 is disposed within the internal space of the stator 42. That is, the stator 42 is disposed so as to surround the rotor 100. The coil housing 12 has a flange 20 that protrudes radially outward from the outer wall 15. The flange 20 is fixed to the non-magnetic ring 1 with a fastener such as a screw (not shown). Furthermore, the non-magnetic ring 1 is fixed to the stator 42 with a fastener such as a screw (not shown). Therefore, the axial magnetic poles 5 fixed to the non-magnetic ring 1 are fixed to the stator 42.

[0040] Fig. 8 is a top view of the coil housing 12 of Fig. 7. As shown in Fig. 8, the electric wire 32 connected to the coil 10 is arranged along the upper surface of the flange 20. The non-magnetic ring 1 has at least one notch 33 on its outer periphery, and the electric wire 32 connected to the coil 10 extends through the notch 33. Although one notch 33 is provided in Fig. 8, multiple notches 33 may be provided.

[0041] As shown in FIG. 9, the molding material 70 shown in FIG. 6 can also be applied to the embodiment shown in FIG.

[0042] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0043] 1 non-magnetic ring 5 axial poles 7 screws 10 coils 12 Coil housing 15 Exterior Wall 16 Inner wall 17 Base plate 20 flange 26 Locating pin 28 Hole 1 29 2nd hole 32 Electric wire 33 Cutout 40 Mounting cover 42 Stator 43 Step part 47 Axial displacement sensor 50 Magnetic pole control section 60 Radial Displacement Sensor 62 radial magnetic poles 70 Molding material 100 Rotating Body

Claims

1. A magnetic bearing device for supporting a rotating body in a non-contact manner, a non-magnetic ring made of a non-magnetic material; At least three axial magnetic poles are arranged along the circumferential direction of the non-magnetic ring, Each axial magnetic pole includes an arc-shaped coil and a coil housing that accommodates the coil, the at least three axial magnetic poles are fixed to the non-magnetic ring; the coil housing has an arc-shaped outer wall around which the coil is wound, an arc-shaped inner wall disposed inside the outer wall, and a base plate connected to an upper end of the outer wall and an upper end of the inner wall, and the coil housing is fixed to the non-magnetic ring, The magnetic bearing device, wherein the coil housing has a flange protruding radially inward from the inner wall, and the flange is fixed to the non-magnetic ring by a fastener.

2. 2. The magnetic bearing device according to claim 1, wherein an electric wire connected to said coil is arranged along said flange.

3. 3. The magnetic bearing device according to claim 2, wherein said non-magnetic ring has at least one notch in its inner periphery, and said electric wire extends through said notch.

4. A magnetic bearing device for supporting a rotating body in a non-contact manner, comprising: a non-magnetic ring made of a non-magnetic material; At least three axial magnetic poles are arranged along the circumferential direction of the non-magnetic ring, Each axial magnetic pole includes an arc-shaped coil and a coil housing that accommodates the coil, the at least three axial magnetic poles are fixed to the non-magnetic ring; the coil housing has an arc-shaped inner wall around which the coil is wound, an arc-shaped outer wall disposed outside the inner wall, and a base plate connected to an upper end of the outer wall and an upper end of the inner wall, The magnetic bearing device, wherein the coil housing is fixed to the non-magnetic ring.

5. 5. The magnetic bearing device according to claim 4, wherein the coil housing has a flange that protrudes radially outward from the outer wall, and the flange is fixed to the non-magnetic ring by a fastener.

6. 6. The magnetic bearing device according to claim 5, wherein an electric wire connected to said coil is arranged along said flange.

7. 7. The magnetic bearing device according to claim 6, wherein said non-magnetic ring has at least one notch in its outer periphery, said electric wire extending through said notch.

8. 5. A magnetic bearing device according to claim 1, further comprising a plurality of positioning pins for fixing the relative positions of said non-magnetic ring and each of said axial magnetic poles.

9. 5. The magnetic bearing device according to claim 1, further comprising a molding material covering said coils of said at least three axial magnetic poles.

10. 5. The magnetic bearing device according to claim 1, wherein the upper surface of said coil housing is a flat surface that can come into surface contact with a heat dissipation member.

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