JPH04119222A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To simplify constitution by providing a permanent magnet so that energizing force to push a rotary member in the specified axial direction may increase in association with increase in its displacement in the specified direction, and providing the rotary member and a support member with a superconductive member and a permanent magnet. CONSTITUTION:A pair of annular permanent magnets 6, 7 are arranged at the relatively opposite positions at the inside of a turbo blade mounting part 3 and a fixation member 5, while even on a lower end side of a rotary shaft 2 a pair of annular permanent magnets 8, 9 are arranged at the relatively opposite position between the side of a shaft 2 and the side of the fixation member 5. These magnets 6...9 support a rotary member 1 in the axial direction with their repellent force. The lower permanent magnet 9 on the side of the fixation member 5 is mounted on a freely swinging member 11 which is mounted on the fixation member 5 through a damper 12 such as of rubber, magnetic fluid, vacuum grease and the like. It is thus possible to ensure rigidity in carrying out supporting in the axial direction while improving damping performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic magnetic receiving device used in a turbo-molecular pump or the like.

(Prior Art and its Problems) A conventional example of a magnetic bearing device for supporting a rotating member in a non-contact manner in a turbo molecular pump or the like is disclosed in, for example, Japanese Patent Laid-Open No. 2-125106.

In the second type, a configuration is adopted in which the rotating member is supported in the radial direction by using the reaction force of a pair of permanent magnets, while the rotating member is supported in the axial direction by an electromagnet.

In this conventional example, since it is a -axis control bearing,
Although the configuration has been simplified to some extent, electromagnets, sensors, and control circuits for axial control are still required, and the reality is that it cannot be said that the desire for a simplified configuration is fully satisfied. be.

For this reason, for example, Japanese Patent Laid-Open No. 2-125107 proposes a magnetic bearing device that utilizes the Meissner effect of superconductors.

However, since this magnetic bearing device is an uncontrolled bearing, although its structure can be simplified, it cannot achieve sufficient rigidity and damping capacity, and has not been put to practical use.

This invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to simplify the configuration because it is an uncontrolled type, and also ,
It is an object of the present invention to provide a magnetic bearing device having sufficient rigidity and damping ability for use in compressors and the like.

(Means for Solving the Problems) Therefore, the magnetic bearing device according to the first aspect is a magnetic bearing device for supporting a rotating member rotating around an axis in the radial and axial directions with respect to a supporting member. A pair of permanent magnets are disposed at positions that substantially face each other in the radial direction of the rotating member and the supporting member, and the reactive force of the permanent magnets supports the rotating member in the radial direction. The arrangement is such that a biasing force that pushes the member in a specific axial direction acts and this biasing force increases as the displacement of the rotating member increases in the specific direction. and a permanent magnet are arranged so that the rotating member is biased in a direction opposite to the specific direction by the magnetic flux pinning effect of the superconductor, and the superconductor is biased by the pair of permanent magnets. It is characterized by being cooled and made superconducting while the biasing force in the direction is forcibly reduced.

Further, in the magnetic bearing device according to the second aspect, one of the permanent magnets for radial support is attached to a free rocking body that can swing in the radial direction, and the free rocking body is supported via a damping material. It is characterized by being radially supported by a member.

Furthermore, the magnetic bearing device according to the third aspect is characterized in that it includes an electromagnet for forcibly reducing the biasing force in a specific direction by the pair of permanent magnets.

In the magnetic bearing device according to a fourth aspect of the invention, the superconductor is YBa-Cu-0 formed by a melt powder melt growth method.
It is characterized by being

(Function) The function of the magnetic bearing device according to the first aspect will be explained based on FIG. 4. First, in a state where there is little biasing force in a specific axial direction, for example, upward, by a pair of permanent magnets, that is, in a state where the N-N plane and S-3 plane of the pair of permanent magnets are forcibly brought close together (point pg). , cooling the Y-based superconductor
Become superconducting. Then, at these 22 points, the repulsive force due to the magnetic flux pinning effect of the superconductor becomes approximately zero. Then, when the above-mentioned forcing force is released, the upward biasing force caused by the permanent magnet increases as shown in Fig. 4f-g. On the other hand, the downward repulsive force due to the magnetic flux pinning effect of the superconductor increases in a curved manner. In other words, the rotating member is supported in the axial direction at a point q where the biasing force of the permanent magnet and the repulsive force of the superconductor are balanced.

Further, in the magnetic bearing device according to the second aspect, it is possible to improve damping performance while ensuring rigidity during radial support by permanent magnets.

The magnetic bearing device according to the third claim and the magnetic bearing device according to the fourth claim are intended to advantageously put the magnetic bearing device according to the first claim into practical use.

(Embodiments) Next, specific embodiments of the magnetic bearing device of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment in which the magnetic bearing device of the present invention is applied to a turbo molecular pump. In the figure, I indicates a rotating member, which includes a rotating shaft 2, a turbo blade attachment part 3 connected to the rotating shaft 2,
It is composed of turbo blades 4 and the like, which are rotatably supported by a fixed member 5 including a casing.

A pair of annular permanent magnets 6.7 are disposed at opposite positions between the inside of the turbo blade mounting portion 3 and the fixed member 5, and are also fixed to the shaft 2 side on the lower end side of the rotating shaft 2. A pair of annular permanent magnets 8J9 are arranged at positions opposite to the member 5 side. Each of these permanent magnets 6...9 is for supporting the rotating member 1 in the radial direction with its repulsive force. Further, the permanent magnet 9 on the fixed member 5 side on the lower side is attached to a free rocking body 11 arranged to be swingable in the radial direction with a ball 10, and this free rocking body 11 is made of rubber, magnetic fluid, etc. The structure is such that it is attached to the fixing member 5 via a damping material 12 such as vacuum grease. This is to improve damping performance while ensuring rigidity during radial support.

Further, a permanent magnet I3 is attached to the upper end of the rotating shaft 2, and a Y-based superconductor 14 is attached to the fixed member 5 opposite to this.

In the figure, 15 is a cooling casing, 16 is a coolant introduction path, 17 is a temperature sensor, 18 is an electromagnet, 19 is a protective bearing that determines the limit of radial movement, and 20.21 is a protective device that determines the limit of axial movement. Each bearing is shown, and a member 22 is attached to the upper surface of the permanent magnet 13 for concentrating the magnetic flux of the magnet 13, increasing the generated magnetic field gradient, and increasing the repulsive force described later.

The above-mentioned permanent magnets 6, . . . 9 of each month are used to support the rotating member l in the radial direction by the repulsive force between the same poles, but more specifically, as shown in Fig. 2, The magnetic poles are arranged in a slightly shifted state, that is, in a state in which each magnetic pole of one example of the outer rotating member is slightly shifted upward. As a result of this arrangement, not only a radially outward repulsive force but also an axially upward biasing force is exerted on the rotating member 1 mainly due to the repulsive force between the inner and outer members having the same polarity. This biasing force has a characteristic that it increases as the upward displacement of the rotating member 1 in the axial direction increases.

By the way, the Y-based superconductor 14 is a Y-based molten bulk (M compound-based high-temperature superconductor) produced by the MPMG (melt powder melt growth) method, for example, silver-treated YB.
aCuO in which YJaCuOs is finely dispersed is used. This Y-based superconductor 14 has the following characteristics. That is, as shown in FIG. 3, when a 4000 gauss permanent magnet from Mugenzo is brought close to the Y-based molten bulk superconductor 14 cooled to 77°K, the magnetic flux is gradually pinned, and the repulsive force becomes the curve a-
It becomes stronger like b. Conversely, when the permanent magnet is moved away from the light, the repulsive force suddenly weakens and becomes like the Z curve b-c. By the way, if a permanent magnet is placed at point e from the beginning and then cooled from this state to 77°K to become superconducting, the repulsive force at point e becomes approximately zero,
From there, when the permanent magnet is brought closer to the superconductor 14,
This shows a characteristic that the repulsive force increases according to the curve eb, and this invention utilizes this characteristic.

Next, a stabilizing operation in the axial direction based on the above principle will be explained. First, the electromagnet 18 is activated to lower the rotating member 1 to the lower end of the axial movable range defined by the protective bearings 20, 21 (point P2 in FIG. 4). Next, liquid nitrogen is introduced into the cooling casing 15 from the coolant introduction path 16 to cool the Y-based superconductor 14. Then, the operation of the electromagnet 18 is stopped when the temperature detected by the temperature sensor 17 reaches, for example, 77° and it is confirmed that superconductivity has been achieved. Then, the rotating member 1 has a permanent magnet 6
... 9 and the downward repulsive force due to the magnetic flux pinning effect of the Y-based superconductor 14 are balanced (point q in Figure 4).

For example, as the permanent magnets 6...9 for radial support, Sa
+ -Co@Earth-based permanent magnets are used, with the average diameter of the upper permanent magnet 6.7 being 49 an, and the lower permanent magnet 8.9.
The average diameter of 20. If the arrangement shown in FIG. 1 is adopted as m, the bearing rigidity in the radial direction can be approximately 1.5 Xlo'N/k. Note that the radial damping capacity is determined by the selection of the free rocking body 11 and the damping material 12.

Furthermore, the axial instability stiffness due to the permanent magnets 6, .
The upward force increases like a line.

On the other hand, Y-based molten bulk (diameter 30IIIlIl, thickness 2
0mm) becomes superconducting, the diameter is 20mm, 4000
The repulsive force with the Gauss permanent magnet is 80 at a distance of 0.1
Since it is about N, the repulsive force due to the above operation is shown in Figure 4 p2.
- It rises like the h line. Therefore, the rotating member l is f-
It becomes stable at the intersection q between the g line and the p2-h line. In this case, the axial stiffness is K=8ON÷(1,5Xl0-'m) -3Xl05N
/m#2X105N/m, which is a sufficient value.

(Effects of the Invention) As described above, since the first claim is an uncontrolled type, the configuration can be simplified, and the turbo-molecular pump,
It becomes possible to provide a magnetic bearing device having sufficient rigidity and damping ability to be applied to optical scanners, beam choppers, flywheels, compressors, etc.

Further, the magnetic bearing device according to the second aspect has the advantage that damping capacity can be improved while ensuring rigidity during radial support by permanent magnets.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment in which the magnetic bearing device of the present invention is applied to a turbo-molecular pump, Fig. 2 is an explanatory diagram of an example of the arrangement of the annular permanent magnets in the above, and Fig. 3 is an explanatory diagram of the magnetic flux of the Y-based superconductor. A graph to explain the repulsive force due to the bottle stopper effect,
FIG. 4 is a graph for explaining the axial stabilization operation of the rotating member. 1... Rotating member, 5... Fixed member, 6.7.8.9
．． 13... Permanent magnet, 11... Free rocking body, 12.
... Damping material, 14... Y-based superconductor, 18... Electromagnet. Patent applicant Nippon Ferrofluidics Co., Ltd.

Claims (4)

[Claims] 1. In a magnetic bearing device for radially and axially supporting a rotating member rotating around an axis relative to a supporting member,
A pair of permanent magnets are disposed at positions substantially facing each other in the radial direction of the rotating member and the supporting member, and the rotating member is supported in the radial direction by the reaction force of the permanent magnets, and both of the permanent magnets
A biasing force that pushes the rotating member in a specific axial direction acts on the rotating member, and the rotating member and the supporting member are arranged so that the biasing force increases as the displacement of the rotating member increases in the specific direction. A superconductor and a permanent magnet are arranged so that the rotating member is biased in a direction opposite to the specific direction by the magnetic flux pinning effect of the superconductor, and the superconductor is further arranged in a direction opposite to the specific direction. A magnetic bearing device characterized by being cooled and made superconducting while forcibly reducing the biasing force in a specific direction. 2. One of the permanent magnets for radial support is attached to a free rocking body that can swing in the radial direction, and the free rocking body is radially supported by the support member via a damping material. A magnetic bearing device according to claim 1. 3. The magnetic bearing device according to claim 1 or 2, further comprising an electromagnet to forcibly reduce the urging force in a specific direction by the pair of permanent magnets. 4. A first characterized in that the superconductor is Y-Ba-Cu-O produced by a melt powder melt growth method.
A magnetic bearing device according to claim 1, second claim, or third claim.