JPH10131966A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance radial restoring force with simple structure and prevent the generation of demagnetization with the lapse of time by forming the overlapped structure of a plurality of ring-like permanent magnets on both rotating side and fixed side, and piling the radially magnetized permanent magnets in such a way that the magnetized directions are reverse. SOLUTION: A pluraility of ring-like permanent magnets 26, 26, 26 are formed in an axially overlapped state on the fixed side. The respective ring-like permanent magnets are radially magnetized in the magnetic pole mangetizing direction of N-poles and S-poles. Ring-like permanent magnets 25, 25, 25 on the rotating side are also magnetized radially in the magnetic pole magnetizing direction of N-poles and Spoles. The inner peripheral surface of the fixed side permanent magnet and the outer peripheral surface of the rotating side permanent magnet are axially aligned so as to face each other with a void A. The facing magnetic poles in the A are therefore like-poles, so that magnetic repulsive force works, and a rotor receives radial force so as to be supported in a levitated state, thus constituting a radial magnetic bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive type magnetic bearing device, and more particularly, to a passive type magnetic bearing device having a structure in which a plurality of ring-shaped permanent magnets are superimposed on both a rotating side and a stationary side. The present invention relates to a repulsion-type magnetic bearing device in which magnetic poles are coaxially arranged so as to have the same polarity, so that the rotating side floats and is supported in the radial direction.

[0002]

2. Description of the Related Art Various types of radial passive magnetic bearing devices utilizing the repulsive force of a permanent magnet have been considered. The most basic configuration is a configuration in which a pair of permanent magnets magnetized in the axial or radial direction are coaxially opposed (see FIGS. 6A and 6B). However,
In this configuration, a large restoring force (bearing rigidity) in the radial direction cannot be obtained even if the magnet is enlarged.

Therefore, a structure is adopted in which ring-shaped permanent magnets that are magnetized in the axial direction on both the rotating side and the stationary side are stacked in the axial direction with a thin non-magnetic spacer interposed therebetween so that the magnetizing directions are reversed. By doing so, an attempt is made to increase the bearing rigidity in the radial direction. That is, in this structure, as shown in FIG. 7, ring-shaped axially magnetized permanent magnets 21 and 22 are stacked coaxially via a non-magnetic space 23. The magnetization directions of the individual permanent magnets 21 and 22 are axial directions, and are arranged such that the magnetization directions of the stacked adjacent ring-shaped permanent magnets are opposite to each other. Then, the magnetic pole polarities of the row of the rotating side permanent magnets 21 are arranged coaxially with the row of the fixed side permanent magnets 22 so as to face each other. That is, the fixed-side permanent magnet 2
The N poles in the second row oppose the N poles in the row of the rotating permanent magnets 21, and similarly, the S poles in the row of the fixed permanent magnets 22 face the S poles in the row of the rotating permanent magnets 21. Therefore, a repulsive force is generated between the magnetic poles of the same polarity via the gap A on the rotating side and the fixed side, and the rotating side receives a floating supporting force in the radial direction. Since the passive magnetic bearing having the configuration shown in FIG. 7 is configured by stacking a plurality of ring-shaped permanent magnets, a large bearing rigidity is obtained as compared with the magnetic bearing device shown in FIGS. Can be

[0004] In addition, a device has been devised for obtaining a larger radial restoring force by making the surface of the permanent magnet and the non-magnetic spacer in contact with each other a tapered shape. This is a passive magnetic bearing having the structure shown in FIG.
2A and the non-magnetic spacer 23A are each provided with a taper as shown. This taper is provided so as to expand with respect to the gap A between both the rotating side and the fixed side. Individual ring-shaped permanent magnet 21
Since the magnetization directions of A and 22A are axial directions,
Due to the non-magnetic enlarged portion toward the gap A, the flow of magnetic flux is improved, and the magnetic resistance is reduced (permeance coefficient is increased) as compared with the structure of FIG. This increases the magnetic bearing rigidity.

[0005]

However, in the magnetic bearing device shown in FIG. 7, the larger the non-magnetic spacer 23, the larger the radial restoring force can be obtained.
In this case, the poles of the two permanent magnets come close to each other and mutually apply opposite magnetic fields. As a result, the permanent magnet is used in a state of extremely low permeance (high magnetic reluctance). Not only is the performance of the permanent magnet insufficient, but if the temperature rises in this state, demagnetization will occur over time. As the process proceeds, the characteristics of the permanent magnet deteriorate.

In the case of the magnetic bearing device shown in FIG. 8, this tendency is slightly alleviated. However, the production of the tapered permanent magnet causes an increase in cost and also from the viewpoint of machining accuracy. There are many problems.

The present invention has been made in view of the above circumstances, and provides a passive type magnetic bearing device having a simpler structure, a large radial restoring force, and hardly causing demagnetization over time. The purpose is to:

[0008]

The magnetic bearing device of the present invention has a structure in which a plurality of ring-shaped permanent magnets are stacked on both the rotating side and the stationary side, and the magnetic force generated by the permanent magnets in the radial direction. In the passive type magnetic bearing device supporting the rotating shaft, ring-shaped permanent magnets, each magnetized in the radial direction, are stacked so that the magnetization directions are reversed.

According to the configuration of the present invention described above, the ring-shaped permanent magnet is magnetized in the radial direction and has a structure in which a plurality of ring-shaped permanent magnets are superposed, so that the structure is compact and the permeance coefficient is high. (Low magnetic resistance)
Magnetic lines of high density can be formed in the radial direction.
As a result, as compared with a passive magnetic bearing having a structure in which conventional ring magnets magnetized in the axial direction are overlapped with each other, a higher radial restoring force is obtained and stability over time is improved.

[0010] Further, the rotary machine device according to the present invention is characterized in that at least two sets of the above-described magnetic bearing device are arranged at positions separated in the axial direction of the rotary shaft of the rotary machine.

As described above, the magnetic bearing device of the present invention has a compact structure and high restoring force. Therefore, by providing two sets of this magnetic bearing device in the direction of the rotating shaft, a rotating mechanical device in which the rotating shaft is supported in a non-contact manner by a compact magnetic bearing with little change over time can be obtained.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional configuration along a rotation axis of a magnetic bearing according to an embodiment of the present invention. On the fixed side, a plurality of ring-shaped permanent magnets 26
It is configured to be overlapped in the axial direction via 3. Each of the ring-shaped permanent magnets 26, 26, 26 is magnetized such that the magnetization directions of the N-pole and S-pole magnetic poles are radial.

The permanent magnets 26, 26, 26 are fixed to the inner peripheral portion of a stator (not shown) having a cylindrical inner peripheral surface, and fix the radial magnetic bearing 17 for floatingly supporting the rotor by magnetic force. Make up side.

On the rotating side, ring-shaped permanent magnets 25 and 2 are also provided.
5 and 25 are configured to overlap in the axial direction via a non-magnetic spacer 10. As shown in the drawing, the ring-shaped permanent magnets 25, 25, 25 are also magnetized in the radial direction with the magnetization directions of the N pole and the S pole. The rotating permanent magnets 25, 25, 25 are fixed to an outer peripheral portion of a cylindrical rotor (not shown), and constitute a target side of a radial magnetic bearing 17 that repels and floats the rotor by magnetic force.

The inner peripheral surfaces of the fixed permanent magnets 26, 26, 26 and the outer peripheral surfaces of the rotating permanent magnets 25, 25, 25 are axially aligned so as to face each other with a gap A therebetween. I have. Therefore, as shown in the gap A,
Since the facing magnetic poles are the same, a magnetic repulsive force acts, and the rotor receives a radial force to be levitated and supported, thereby constituting a radial magnetic bearing.

FIG. 2 is a graph showing the difference in the radial restoring force between the radial magnetized magnetic bearing and the axial magnetized magnetic bearing. In the figure, the vertical axis shows the radial restoring force, the horizontal axis shows the displacement from the center of the rotating shaft, the solid line shows the radial restoring force of the radial magnetized magnetic bearing, and the dotted line shows the axial magnetized magnetism. 3 shows the radial restoring force of the bearing. This is a magnetic bearing with a structure in which the ring-shaped permanent magnets shown in FIGS. 1 and 6 are superposed in the axial direction. The dimensions, shape and magnetizing force are the same, and only the magnetization direction is different between the radial direction and the axial direction. This is a comparison. As shown in the figure, the results of the computer simulation show that the radial restoring force of the radial magnetized magnetic bearing is about 1.33 times that of the axial magnetized magnetic bearing.

FIG. 3 compares the permeance coefficients of the radially magnetized magnetic bearing and the axially magnetized magnetic bearing.
The permeance coefficient is the reciprocal of the magnetic resistance as viewed from the magnetic pole of the magnet, and a large coefficient means that the amount of magnetic flux (line of magnetic force) formed for the same magnetizing force increases. In the figure, the horizontal axis indicates the axial position, and the vertical axis indicates the permeance coefficient. The solid line in the figure indicates the permeance coefficient of the radial magnetized magnetic bearing,
The dotted line shows the permeance coefficient of the axially magnetized magnetic bearing.
In this comparison, as in FIG. 2, for a magnetic bearing having a structure in which a plurality of ring-shaped permanent magnets having exactly the same shape and dimensions are stacked, the magnetization direction is different between the radial direction and the axial direction with the same magnetizing force. It is a comparison. As is clear from the figure, the permeance coefficient of the radially magnetized magnetic bearing is considerably larger than the permeance coefficient of the axially magnetized magnetic bearing.

FIG. 4 shows an analysis result of the magnetic flux distribution between the radially magnetized magnetic bearing and the axially magnetized magnetic bearing. (A) shows the magnetic flux distribution of the axial magnetized magnetic bearing, and (b) shows the magnetic flux distribution of the radial magnetized magnetic bearing. Both have the same shape,
A plurality of permanent magnets having a structure are overlapped in the axial direction, and the only difference is the magnetization direction with the same magnetizing force. Comparing these figures, it can be seen that the magnetic flux distribution of the radial magnetized magnetic bearing is much denser than that of the axial magnetized magnetic bearing, and the ability of the permanent magnet can be used effectively.

FIG. 5 shows a rotary machine equipped with the magnetic bearing device of the present invention. This rotating machine is an example in which the passive radial magnetic bearing device of the present invention is applied to a turbo molecular pump. The main shaft 4 to which the impeller 6 is fixed via the disk 5 is rotated by a motor 13 while being supported by two sets of radial passive magnetic bearings 17a and 17b of the present invention.
That is, the stator 3 has the bottom plate 1 and the cylindrical portion 2 and the rotor 7
Has a main shaft 4, a disk portion fixed to the main shaft 4, and an impeller 6. The main shaft 4 is radially supported by two radially passive magnetic bearings 17a and 17b at its upper and lower portions, respectively.

The stator has a structure in which a plurality of ring-shaped permanent magnets 25 are overlapped with a spacer interposed therebetween, and a plurality of rotating-side ring-shaped permanent magnets 25 are stacked in the axial direction at positions opposed to these. Have been placed. These permanent magnets 25 and 26 are respectively magnetized in the radial direction as shown in FIG. Therefore, in this rotary machine, the magnetic bearings 17a, 1 which are compact and have a strong radial restoring force.
At 7b, the main shaft 4 with the impeller 6 is supported in the radial direction.

The main shaft 4 is supported by an active magnetic bearing 14 in the axial direction. A thrust plate 10 made of a magnetic material is fixed to the main shaft 4, and electromagnets 11 that generate a magnetic attractive force in the axial direction are arranged on the stator side so as to sandwich the thrust plate 10. A displacement sensor 14 is provided on the bottom plate 1.
a is disposed to detect the axial displacement of the main shaft 4 and control the excitation of the electromagnet 11 to control the floating position of the main shaft 4. The motor 13 includes an electromagnet 11 fixed to the stator and a magnetic material 8 fixed to the main shaft 4.
The rotation of the main shaft 4 is performed by a motor 13.

In the above-described embodiment, a plurality of ring-shaped permanent magnets are superimposed and arranged on the outer peripheral side as the fixed side, while the one arranged on the inner peripheral side is the rotating side. Conversely, the inner side may be the fixed side and the outer side may be the rotating side.

[0024]

As described above, by adopting a structure in which ring-shaped permanent magnets magnetized in the radial direction on both the rotating side and the fixed side are stacked in the axial direction so that the magnetizing directions are reversed, the permanent The permeance coefficient viewed from the magnet can be increased. As a result, not only can the bearing rigidity in the radial direction be increased with a compact structure,
It is possible to provide a magnetic bearing device that is stable in magnetic properties, that is, has little change over time and is less likely to be demagnetized even when the temperature of the use environment increases. Further, since the magnetic bearing device has a simple structure, its manufacture is also easy.

By using at least two of these magnetic bearing devices in combination for supporting the rotating shaft of a rotating machine, a rotating machine having a compact magnetic bearing device with excellent aging characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is a graph comparing the radial restoring force of a radially magnetized magnetic bearing and an axially magnetized magnetic bearing.

FIG. 3 is a graph comparing a permeance coefficient between a radially magnetized magnetic bearing and an axially magnetized magnetic bearing.

FIG. 4 is a diagram comparing magnetic flux distributions of a radially magnetized magnetic bearing and an axially magnetized magnetic bearing.

FIG. 5 is a cross-sectional view showing an example of a rotating machine equipped with the magnetic bearing device of the present invention.

6A and 6B are explanatory views of a conventional radial magnetic bearing composed of a pair of permanent magnets, wherein FIG. 6A shows an axial magnetization type and FIG. 6B shows a radial magnetization type.

FIG. 7 is an explanatory view of a conventional magnetic bearing device.

FIG. 8 is an explanatory view showing a modification of the magnetic bearing device of FIG. 7;

[Explanation of symbols]

 17 Magnetic bearing 23 Non-magnetic spacer 25, 26 Ring-shaped permanent magnet A Air gap

Claims (2)

[Claims] 1. A passive magnetic bearing device having a structure in which a plurality of ring-shaped permanent magnets are superposed on both a rotating side and a stationary side, and supporting a rotating shaft by a magnetic force generated by the permanent magnets in a radial direction. 2. The magnetic bearing device according to claim 1, wherein ring-shaped permanent magnets, each magnetized in the radial direction, are stacked so that the magnetization directions are reversed. 2. A rotary machine device comprising at least two sets of the magnetic bearing device according to claim 1 arranged at positions separated from each other in the axial direction of a rotary shaft.