JPS631812A - Magnetic top bearing device for vertical type rotor - Google Patents

Abstract

PURPOSE:To obtain strong damping forces to match a rotor body by permitting a permanent magnet to move freely in the horizontal direction and to be held centripetally, under the condition that a minute liquid film is provided for the magnet. CONSTITUTION:A permanent magnet 13 is held by a support member 14 capable of making centripetal action, such as a spring or the like. The permanent magnet 13, magnetized in polarity, restricts the position of a permanent magnet 2 in the radial direction, i.e. the position of the top end of a rotor body 1 in the radial direction, due to magnetic repulsion caused against a permanent magnet 2. Further, the support member 14 forms a minute liquid film in the horizontal direction, which produces a shear effect between the bottom face of the permanent magnet 13 and the inside bottom wall of a liquid bath 11. Therefore, said magnet is held in such that a minute clearance 15 may exist to make it possible to obtain strong damping forces to match the rotor body 1.

Description

Detailed Description of the Invention [Object of the Invention (Field of Industrial Application) The present invention relates to an upper magnetic bearing device for a vertical rotating body, and particularly relates to an upper magnetic bearing device for a vertical rotating body.
, relates to a magnetic bearing device that allows vibration damping ability to be easily set.

(Prior Art) Various types of upper bearings for vertical rotating bodies have been considered in the past. Among these are magnetic bearings that utilize magnetic force. This magnetic bearing has the characteristic that it can perform its bearing function in a completely non-contact state.

Incidentally, such an upper magnetic bearing device for a vertical rotating body is usually constructed as shown in FIG. That is, an annular permanent magnet 2 magnetized with the illustrated polarity is fixed to the upper end of the vertical rotating body 1 coaxially with the rotating body 1, and an annular permanent magnet 2 magnetized with the illustrated polarity is fixed on the inner surface of the casing 3. A permanent magnet 4 is arranged to face the permanent magnet 2 and fixed coaxially with the permanent magnet 2 in a relationship such that a magnetic attraction force acts between them, and the surface of the permanent magnet 4 is further covered with a non-magnetic and highly conductive material 5. The structure is as follows.

The magnetic bearing device configured in this way has permanent magnets 2 and 4.
The upper end of the rotating body 1 is restrained by the magnetic attraction force generated between them, and when the rotating body 1 attempts to vibrate horizontally, the non-magnetic and highly conductive material An eddy current is generated in 5, and the energy consumed by this eddy current absorbs vibration energy and damps the vibration.

However, the conventional upper magnetic bearing device for a vertical rotating body configured as described above has the following problems. That is, the magnitude of the damping force in this magnetic bearing device increases as the change in the magnetic flux passing through the non-magnetic, highly conductive material 5 increases.

However, when a permanent magnet is used as a source of magnetomotive force,
Due to the nature of permanent magnets, it is difficult to greatly change the magnetic flux passing through the nonmagnetic conductive material 5 during vibration, and it is not possible to obtain a large damping force.

For this reason, for example, when attempting to rotate a rotating body at a speed higher than the critical speed, the balance of the rotating body must be adjusted sufficiently in order to safely pass the critical speed. There was a problem that required a lot of time. Also.

Since the damping force is small, there are also problems such as unstable self-excited vibrations that occur during high-speed rotation at the same frequency as the natural frequency of the rotating body.

(Problems to be Solved by the Invention) As mentioned above, unless the damping force is increased by some means, it is not possible to simplify the assembly and adjustment of the single-rotator body and to achieve stability during high-speed rotation. .

Therefore, the present invention can generate a large damping force without impairing the characteristics of the magnetic bearing.

It is an object of the present invention to provide an upper magnetic bearing device for a vertical rotating body that can eliminate problems caused by insufficient damping force.

[Structure of the Invention] (Means for Solving the Problems) The device according to the present invention includes a first permanent magnet fixed to the upper part of the vertical rotating body, and a magnet arranged to surround the first permanent magnet. A magnetic repulsion force generated between a liquid tank placed in a stationary state, a viscous fluid contained in the liquid tank, and the first permanent magnet contained in the liquid tank causes the first permanent magnet to An annular second permanent magnet for restraining the radial position of the magnet; Can be moved horizontally in the formed state.

and support means for centripetally supporting.

(Function) In the device of the present invention, the second permanent magnet is moved horizontally by the supporting means with a micro liquid film for shearing effect extending horizontally between the second permanent magnet and the liquid tank. K can be moved freely to
, and since it is centripetally supported, it is possible to set the mass of the second permanent magnet and the members added thereto, to set the thickness of the micro liquid film, to select the second viscous fluid, to set the centripetal restoring force of the support means, etc. This makes it possible to easily generate a strong damping force that corresponds to critical speeds and unstable self-excited vibrations of the rotating body.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an upper magnetic bearing device for a vertical rotating body according to an embodiment of the present invention, and the same parts as in FIG. 3 are designated by the same reference numerals. Therefore, explanation of the overlapping portion will be omitted.

In this embodiment, a liquid tank 11 is provided on the inner surface of the casing 3 so as to surround the permanent magnet 2 .

This liquid tank 11 is made of a non-magnetic and highly conductive material. A viscous fluid 12 such as oil is contained in the liquid tank 11 . Furthermore, an annular permanent magnet 13 is housed in the liquid tank 11 concentrically with the permanent magnet 2 so as to be submerged in the viscous fluid 12. Supported by Permanent magnet 13 is 2
It is magnetized with the illustrated polarity, and the radial position of the permanent magnet 2, that is, the radial position of the upper end of the rotating body 1, is restrained by the magnetic repulsion force generated between the permanent magnet 2 and the permanent magnet 2. And the support member 14 is.

The permanent magnet 13 is supported so that a minute gap 15 exists between the bottom surface of the permanent magnet 13 and the inner surface of the bottom wall of the liquid tank 11 to form a minute liquid film in the horizontal direction that exerts a shearing effect.

With such a configuration, it is possible to easily realize an upper magnetic bearing having a good vibration damping function.

The reason for this will be explained below.

Now, when the rotating body 1 vibrates in the horizontal direction, this vibration is transmitted to the permanent magnet 13 via the permanent magnet 2. Therefore, the permanent magnet 13 moves in the horizontal direction. When the permanent magnet 13 moves in the horizontal direction in this way, the liquid film within one gap 15 is sheared and a damping force is generated. The damping constant C at this time is.

The viscosity coefficient of the viscous fluid 12 is μ, the permanent magnet 13 and the liquid tank 11
Letting the gap length of the A2 gap 15 be δ, the area facing the inner surface of the bottom wall is C-(μA)/δ.

Therefore, if we model this vibration system and show it.

The result will be as shown in Fig. 2(a). In the figure, 1M is the mass of the rotating body 1, D is the spring constant of the magnetic bearing consisting of the permanent magnets 2 and 13, D is the damping constant of this magnetic bearing, and 1m is the total quality of the permanent magnet 13 and the members added to it. ff
i and k are the spring constants of the support member 14, and C is the damping constant described above. - Generally, K and D are very small compared to C, so there is no problem even if it is approximately D-0.

When the rotating body body 1 vibrates at the frequency ω, the rotating body body 1
The allocation effect received by is equivalently expressed by the following equation. That is, 9 equivalent spring constant ke is.

...(2) becomes. Therefore, using these ke and Ce.

This vibration system can be further represented by an equivalent vibration model as shown in FIG. 2(b).

In this vibration model, when we find the conditions that can maximize the 1-equivalent damping constant Ce, equation (1)...(3
), and Ce reaches its maximum value when m-(K+k)/ω2. This means that when the natural frequency or critical speed of the system including the rotating body 1 and the bearings to be damped is ωC.

(LIo 2- (K+k)/m ・
It is sufficient to set m and k to the relationship of = (4).

Therefore, if you look at the margin.

0.5ωc, ≦(k1K)/'m≦1.5ωc2...
It is sufficient to set m and k so that the relationship (5) is satisfied,
This setting is easy.

−, from equation (2).

...(6), and Ce is + C2- (-mω2 to K+) 2/
It is maximum at ω2.

When you sort this out.

...(7) becomes. Substituting ω-ωC and equation (4) into equation (7) yields.

C2 = (m2ωc2)/4 - (8), so in the end.

(2C)/m-ωC (9). In other words, C and m should be set so as to satisfy equation (q), taking into account a margin.

0.54L) C≦(2C)/m≦1.5 ωc −(
C and m may be set so as to satisfy the relationship (to).

By simply setting K, quality mm, spring constant, and damping constant C in the above-mentioned relationships, a large damping force can be generated under conditions that most require damping.

Generally, the vibration amplitude when a nine-rotating body passes through a critical speed is proportional to the unbalance amount of the one-rotating body and inversely proportional to the damping force of the bearing. Therefore, once the allowable vibration amplitude value for the strength or structure of one rotating body is determined, the relationship between the allowable unbalance amount for one rotating body and the damping force of the bearing is determined accordingly.

That is, the allowable unbalance amount is proportional to the damping force of the bearing, and if the bearing damping force can be doubled, the allowable unbalance amount can also be doubled. If the allowable unbalance amount can be increased, balance adjustment will be easier, which will contribute to a significant reduction in manufacturing costs. In addition, unstable vibrations such as self-excited vibrations in which the rotating body body swings at the same frequency as the natural frequency during high-speed rotation occur due to insufficient damping force, and do not appear in bearings with large damping force. In this embodiment, since the damping force can be easily increased, it is possible to easily manufacture the rotating body main body and achieve stability during high-speed rotation for the reasons described above.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways. Namely.

In the embodiment described above, the permanent magnet 13 is supported by a spring, but it may be supported by a bellows having the same function, or by a combination of a bearing and a magnet.

[Effects of the Invention] As described above, according to the present invention, a strong damping force can be exerted with only simple settings, which facilitates the production of the rotating body and improves stability during high-speed rotation. It is possible to provide an upper magnetic bearing device for a vertical rotating body that can contribute to improvement.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an upper magnetic bearing device for a vertical rotating body according to an embodiment of the present invention, FIG. 2 is a diagram for explaining an equivalent circuit of a vibration system incorporating the same bearing device, and FIG. The figure is a longitudinal sectional view of a conventional upper magnetic bearing device. 1...Rotating body main body, 2.13...Permanent magnet, 11.
...Liquid tank, 12...Viscous fluid, 14...Supporting member,
15... Gap for liquid film formation.

Claims (1)

[Claims] (1) A first permanent magnet fixed to the upper part of the vertical rotating body, a liquid tank disposed in a stationary state surrounding the first permanent magnet, and the liquid tank. an annular second magnet which restrains the radial position of the first permanent magnet by a magnetic repulsion force generated between the viscous fluid contained in the liquid tank and the first permanent magnet contained in the liquid tank; a permanent magnet, the second permanent magnet being movable in the horizontal direction with a micro liquid film for shearing effect extending in the horizontal direction being formed between the second permanent magnet and the liquid tank; 1. An upper magnetic bearing device for a vertical rotating body, comprising support means for centripetally supporting the body. (2) The upper magnetic bearing device for a vertical rotating body according to claim 1, wherein the liquid tank is made of a non-magnetic and highly conductive material. (3) The upper magnetic field of the vertical rotating body according to claim 1, wherein the supporting means is mainly composed of one type selected from springs, bellows, and magnets. Bearing device. (4) The critical speed of the rotating body body is ωc, the total mass of the second permanent magnet and the members added thereto is m, and the spring between the first permanent magnet and the second permanent magnet is When K is a constant and k is a spring constant of the supporting means, each part is set so as to satisfy the following relationship: 0.5ωc^2≦(k+K)/m≦1.5ωc^2 An upper magnetic bearing device for a vertical rotating body according to claim 1. (5) When the critical speed of the rotating body body is ωc, the total mass of the second permanent magnet and the members added thereto is m, and the damping constant due to the micro liquid film is C, 0.5ωc≦( 2C)/m≦1.5ωc. The upper magnetic bearing device for a vertical rotating body according to claim 1, wherein each part is set to satisfy the relationship: 2C)/m≦1.5ωc.