JPS5829291Y2 - magnetic bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bearing device that is capable of preventing changes in the shape of a permanent magnet attached to a rotating body.

A magnetic bearing device is known as a bearing that supports the load in the radial direction of a high-speed rotating body.

Figure 1 shows a conventionally used device of this type.
It is structured as follows.

That is, 1 in the figure is a vertical rotating body, and this rotating body 1
An annular permanent magnet 3 magnetized with the polarity shown is fixed to the upper end of the magnet via a reinforcing ring 2.

The reinforcing ring 2 is made of a non-magnetic material, and is fitted onto the outside of the permanent magnet 3 by means of press fitting, shrink fitting, or the like.

On the other hand, at a position facing the upper end surface of the permanent magnet 3.

A permanent magnet 4 magnetized to the illustrated polarity is fixed to a stationary body 5.

Note that 6 in FIG. 1 indicates a screw for fixing the reinforcing ring 2 to the rotating body 1.

According to this device, the radial position of the permanent magnet 3 is restrained by the magnetic attraction force generated between the permanent magnets 3 and 4, thereby exerting its function as a bearing.

However, the conventional device having the above configuration has the following problems.

That is, as the rotational speed of the rotating body 10 increases, the centrifugal force applied to the permanent magnet 3 and the reinforcing ring 2 also increases, and this force causes the permanent magnet 3 and the reinforcing ring 2 to extend in the circumferential direction.

The permanent magnet 3 is generally made of a material with relatively low strength, such as ferrite, so when the rotational speed exceeds a certain value, it breaks into multiple pieces 3a and 3b as shown in FIG. be forced to.

Since the force of this pressing is sufficiently strong, there is no deviation in the axial direction in this state.

In this way, once the permanent magnet 3 is cracked and the rotation speed decreases, the permanent magnet 3 will shrink as the reinforcing ring 2 contracts.
tries to return to its original shape, but since the cracked surfaces 3c are uneven, unnatural contact between the cracked surfaces 3c is likely to occur.

If the rotational speed continues to decrease while the permanent magnet 3 remains in unnatural contact, the permanent magnet 3 is tightened by the reinforcing ring 2, causing secondary cracking, and as shown in FIG.

If such a cycle is repeated several times, the permanent magnet 3 will completely separate from the reinforcing ring 2, and will no longer function as a bearing.

The present invention was developed in view of these circumstances, and its purpose is to create a magnetic bearing that can always hold the permanent magnet on the rotating body in a fixed position and maintain its function as a bearing over a long period of time. The goal is to provide equipment.

The details of the present invention will be explained below based on the embodiment shown in FIG.

Note that the same parts as in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The device of the present invention differs from conventional devices in that a shape regulating body 11 is provided in place of the conventional reinforcing ring 2 that fits only on the outer peripheral surface of the permanent magnet 3.

This shape regulating body 11 has an inner cylindrical portion 12. It consists of an outer cylindrical part 13 and an upper base part 14, each of which is brought into close contact with the inner circumferential surface, outer circumferential surface, and upper surface of the permanent magnet 3, respectively.

The shape regulating body 11 is made of a non-magnetic material having a high specific resistance.

With such a configuration, when the rotating body 1 rotates at high speed,
Although the permanent magnet 3 will still break into multiple pieces due to the above-mentioned reasons, when the rotational speed decreases in this state and the shape regulating body 11 contracts and attempts to return to its original shape, the cracked surface will break. Even if the top surface of the permanent magnet 3 looms up due to unnatural contact between the unevenness and the secondary cracking caused by this, the top part 14 of the shape regulating body 11 is in close contact with the top surface, so the looming does not occur. In addition, peeling that occurs due to the development of secondary cracks can be avoided because the inner cylindrical portion 12 and outer casing portion 13 of the regulating body 11 are in close contact with the inner and outer circumferential surfaces of the permanent magnet 3, respectively.
Hair is definitely protected.

Therefore, the permanent magnet 3 can be prevented from leaving the shape regulating body 11, and as a result, stable bearing function can be achieved over a long period of time.

In addition, since the shape regulating body 11 is made of a non-magnetic material with a high specific resistance, there is no drawback that when rotational runout occurs, excessive eddy current flows and the rotational runout increases. .

That is, this is based on the following reasons.

Assume now that a disc-shaped conductor 31 is rotating together with a rotating body at an angular velocity of ω, as shown in FIG. .

Therefore, in the above state, the magnetic flux path 32
When the center of rotation O' of the conductor 31 is eccentric by ε from the center O of If the angle θ is taken as follows, then vX2rωsinθ vy=ω(rcosθ−ε).

If we calculate the average value VX t Vy of the velocity with respect to the magnetic flux at all points on the conductor cutting the magnetic flux, we get: l 2π vX=-f rωs i nθdθ202π 0 1 2π vy=yf.

(d(rcool-e)d 19 nee ec.

This means that when the conductor 31 is displaced in the +X direction, it has a relative velocity in the -y force direction, and the force applied to the conductor 31 by the eddy current generated in the conductor 31 is applied in the +y force direction, that is, in the rotational direction.

Since this force is proportional to the east eccentricity ε, the rotating body is supported by a spring that generates a forward force in a direction perpendicular to the direction of eccentricity.

Therefore, if the mass of the rotating conductor 31 is m, the position of the center of gravity is X (t), y (t), and the spring constant is k, the equation of motion for one rotating part is as follows.

mx=-ky my=kx becomes.

Substituting the solution of this equation of motion as x=Xe''.y=Ye'' and solving for λ, we get λ=X1(l±1).

This solution has a positive sign of the real part, so in the end,
Such a system is unstable and the vibrations will diverge.

Therefore, the presence of a conductor in the rotating part is not preferable (if a damping function due to eddy current is expected, a conductor must be provided on the stationary part side).

) Therefore, in the present invention, since the shape regulating body 11 is formed of a material with a high specific resistance, it is possible to prevent the occurrence of rotational runout, that is, whirling, due to eddy currents.

As detailed above, according to the present invention, it is possible to reliably prevent the peeling phenomenon from occurring on the surface of the permanent magnet provided on the rotating body side, and to prevent the permanent magnet from coming off and scattering, and to always maintain the permanent magnet in a fixed position. Therefore, it is possible to provide a magnetic bearing device that can maintain its function as a bearing over a long period of time.

[Brief Description of the Drawings] Fig. 1 is a partially cutaway side view of a conventional device, Fig. 2 is a partially cutaway plan view for explaining the problems of the same device, and Fig. 3 is a partially cutaway side view of the same device. FIG. 4 is a partially cutaway side view showing an embodiment of the present invention, and FIG. 5 is a diagram for explaining the meaning of forming the shape gauge from a material with a high specific resistance. 1...Rotating body, 3...Rotating body side permanent magnet, 4...Static soil side permanent magnet, 11...Shape regulating body.

Claims (1)

[Scope of utility model registration request] The position of the first permanent magnet in the radial direction is restrained by a magnetic attraction force generated between the first annular permanent magnet attached to the rotating body and the first permanent magnet attached to the stationary body. a second permanent magnet that is made of a non-magnetic material with a high specific resistance; and a shape regulation that is closely attached to the surface of the first permanent magnet to regulate shape variation of the first permanent magnet. A magnetic bearing device comprising: a body;