JPH0742735A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To sufficiently eliminate oscillations at a resonance point and eliminate oscillation energy to some extent even under high speed rotation. CONSTITUTION:When a rotor shows a rotational speed corresponding to resonance point thereof, a free oscillation body 14 is oscillated interlockingly with oscillations in a diameter direction of the rotor, and oscillation energy is eliminated by a viscoelastic body 17. When the rotational speed is further increased and far from the resonance frequency of the free oscillation body 14, the free oscillation body 14 which is in almost static condition is in an axial magnetic field prepared by rotational members 2 and 3, so that eddy current loss is generated in the free oscillation body 14 by diametral variation of the magnetic field interlocked with the oscillations of the rotor in the diameter direction. Oscillation energy is thus eliminated. This effect is distinguished increasingly as rotational speed becomes high resulting in resonance frequency where the free oscillation body 14 is hard to move. Oscillations are sufficiently eliminated at the resonance point by both the functions, and oscillation energy is eliminated to some extent even under high speed rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device, and more particularly to a uniaxial control type magnetic bearing device in which an active magnetic bearing is used only in a rotating shaft direction and a passive magnetic bearing is used in a radial direction.

[0002]

2. Description of the Related Art As shown in FIG. 3, which shows the relationship between the rotational frequency and the resonant frequency, the radial resonance frequency of the rotor in this type of magnetic bearing device is increased by the influence of the moment of inertia as the rotor rotational speed increases. Get higher The rotor vibrates most in the radial direction at the rotation speed corresponding to the point R (see FIG. 3) where the rotor rotation speed and the resonance frequency match. This is because most of the disturbance is vibration that is synchronized with the rotation speed due to unbalance of the rotor.

Usually, except for the number of revolutions that matches the resonance frequency, if there is any vibration absorption, the rotor will rotate stably. However, when the rotor rotates at high speed, energy loss on the side of the stator increases energy loss (internal friction, eddy current loss) inside the rotor, which acts in a manner opposite to vibration energy absorption of the rotor. Therefore, when the energy loss inside the rotor exceeds the energy loss on the stator side (corresponding to vibration absorption at zero rotation speed), the vibration damping factor becomes substantially negative, and even for extremely small disturbances, The rotor oscillates at the resonance frequency at the rotational speed.

Therefore, in order to stably rotate the rotor up to a certain steady rotation speed, in addition to effectively absorbing the vibration at the resonance point R (see FIG. 3), the energy inside the rotor is always kept up to the steady rotation speed. It is necessary to cause energy absorption (energy loss) on the stator side more than the loss.

Therefore, conventionally, as a method of absorbing vibration, an eddy current type vibration absorbing apparatus and a viscoelastic body supporting free oscillating body type vibration absorbing apparatus have been proposed. FIG. 2 is a diagram showing the relationship between the resonance frequency and the damping coefficient (vibration absorbing effect), and the curve (a) shows the case of the eddy current type vibration absorbing device. In the case of this eddy current type, it is possible to absorb vibration energy that is substantially constant regardless of the frequency.
In addition, the curve (b) in FIG.
The case of the vibration absorbing device of the viscoelastic body supporting free oscillating body method described in Japanese Patent Laid-Open No. 06 is shown, but in this method, a very high damping coefficient is obtained at a certain resonance point.

[0006]

By the way, in the eddy current type vibration absorbing device, as shown by the curve (a) in FIG. 2, since the vibration absorbing effect does not decrease even at high frequencies, the vibration energy absorbing at the stator side against high frequencies is absorbed. It is most suitable for, but if it tries to absorb enough vibration at the resonance point, it becomes a very large vibration absorber.

A viscoelastic body supporting free oscillating body type vibration absorber disclosed in Japanese Unexamined Patent Publication No. 2-125106 shows the resonance frequency of the free oscillating body as shown by the curve (b) in FIG. Matching with the resonance point of the rotor makes it possible to increase the vibration absorption at the resonance point and is convenient for passing through the resonance point, but at frequencies other than the resonance point, the effect is reduced, so vibrations occur when the rotor is rotated at high speed. Absorption may be inadequate.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object thereof is to be able to sufficiently absorb vibration at a resonance point and also to absorb a certain amount of vibration energy even at a high speed rotation. It is to provide a magnetic bearing device.

[0009]

Therefore, in the magnetic bearing device of the present invention, a pair of disk-shaped rotating members 2 and 3 made of a conductive material are provided at a predetermined interval on the outer periphery of a rotor shaft 1 for rotating the rotor. , On both sides of each of the rotating members 2 and 3,
Axial control electromagnets 8 and 9 composed of coils 11 and 13 and yokes 10 and 12 are arranged so as to be in non-contact with the rotating members 2 and 3, respectively, and made of a conductive material between the rotating members 2 and 3. The free oscillating body 14 is arranged in a non-contact manner, the free oscillating body 14 is supported on the stator side through a viscoelastic body 17, and the opposite surfaces of the rotating members 2 and 3 are magnetized in opposite directions. A plurality of ring-shaped permanent magnets 4 to 7 are arranged concentrically, and the permanent magnets 4 to 7 of the rotating members 2 and 3 facing each other are magnetized to have different polarities. , 9 of the yokes 10 and 12 are arranged so as to face the magnetic pole surfaces of the permanent magnets 4 to 7 of the rotary members 2 and 3, respectively, and the free oscillating body 14 is provided with one of the rotary members 2 and 3.
The permanent magnets 18 and 19 magnetized to have different polarities from the magnetic poles of the permanent magnets 4 and 5 of the permanent magnets 4 and 5 of FIG. , 18 and 19 are set so that the radial spring constant of the viscoelastic body 17 and the radial spring constant of the viscoelastic body 17 are set so that the resonance point of the free oscillating body 14 and the resonance point of the rotor substantially coincide with each other. .

[0010]

In the above magnetic bearing device, when the rotor passes through the number of revolutions corresponding to its resonance point, the free oscillating body oscillates in conjunction with the radial vibration of the rotor, effectively absorbing the vibration energy. It is absorbed by the elastic body 17. As the number of revolutions further increases and the resonance frequency of the rotor moves away from the resonance frequency of the free oscillating body 14 under the influence of the moment of inertia, the free oscillating body 14 does not move in conjunction with the rotor. Therefore, the absorption efficiency of the vibration energy by the viscoelastic body 17 decreases. On the other hand, since the free oscillating body 14 which is almost stationary is in the magnetic field in the axial direction created by the rotating members 2 and 3 and is a conductor, the diameter of the magnetic field interlocked with the radial vibration of the rotor. An eddy current loss occurs in the free oscillating body 14 due to the change in direction, and the vibration energy is absorbed. This effect becomes more effective as the resonance frequency at the time of high speed rotation in which the free oscillating body 14 becomes difficult to move becomes. Due to both of these actions, it is possible to configure a vibration absorbing device that can sufficiently absorb the vibration at the resonance point and can absorb the vibration energy to some extent even at high speed rotation.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED 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 of the magnetic bearing device. First, the active axial magnetic bearing mechanism will be described with reference to FIG. 1. Two rotary members 2 and 3 are integrally provided on the outer circumference of a rotor shaft 1 for rotating a rotor along the axial direction thereof at predetermined intervals. There is. The rotating members 2, 3
Is formed in a disk shape, and two ring-shaped permanent magnets 4, 5 and 6, 7 are concentrically provided on the opposite surfaces of both rotary members 2, 3, respectively. The magnets 5 and 6 and 7 are magnetized in the rotation axis direction, and their magnetizing directions are opposite to each other. In FIG. 1, the exposed surface of the outer permanent magnet 4 of the upper rotating member 2 is the S pole, the exposed surface of the inner permanent magnet 5 is the N pole, and the exposed surface of the outer permanent magnet 6 of the lower rotating member 3 is the N pole. , The exposed surface of the inner permanent magnet 7 is the S pole,
The permanent magnets 4, 5 and 6, 7 of the rotating members 2, 3 are magnetized so as to attract each other.

The axial direction control electromagnets 8 and 9 constituting the active type axial magnetic bearing mechanism are arranged so as to sandwich the rotating members 2 and 3 from above and below, and the axial direction control electromagnets 8 and 9 are arranged as follows. Approximately U-shaped yoke 10, 1 with a part cut away
2 and a coil 11 arranged in the yokes 10 and 12,
13 and 13.

Here, the yoke 10 is formed so that the magnetic pole surfaces of both ends of the yoke 10 of the axial control electromagnet 8 and the magnetic pole surfaces of the permanent magnets 4 and 5 of the rotary member 2 are concentrically opposed to each other. The yoke 1 of the other axial control electromagnet 9
2 is also the same. That is, the magnetic flux generated by the permanent magnets passes, for example, through the permanent magnets 5 and 7 inside the rotating members 2 and 3, then from the inner yoke 12a of the yoke 12 of the axial control electromagnet 9 to the outer yoke 12b, and further the rotating member 3 2 through the outer permanent magnets 6, 4 and finally the axial control electromagnet 8
Outer yoke 10b of inner yoke 10 to inner yoke 10a
To return to the permanent magnet 5 inside the rotary member 2 again. With such an arrangement, the bias magnetic fluxes of the permanent magnets 4, 5, 6, 7 can be modulated by the axial control electromagnets 8, 9 and the rotor position can be changed.
It will be possible to control in the axial direction.

Next, the passive radial magnetic bearing mechanism will be described. The inner portion of the ring-shaped free oscillating body 14 is disposed in a state of being loosely fitted between the rotating members 2 and 3, and the viscoelastic body 1 from the side of the fixing member 16 of the main body case 15.
It is supported by a suitable spring constant by 7. As the viscoelastic body 17, for example, rubber, magnetic fluid, vacuum grease, silicon gel material or the like is used. The rotating member 2 includes two ring-shaped permanent magnets 18 and 19 axially magnetized in an upper portion of the inside of the free oscillating body 14 so that the free oscillating body 14 and the rotating member 2 interlock with each other in a radial direction without contact. And the magnetic pole surfaces face each other, and are arranged coaxially so as to attract each other. With this arrangement, the rotor can be supported by the rotating member 2 with a certain radial spring constant.

Next, the operation principle of the vibration absorbing device of the present invention will be described. Here, the curve (c) shown by the broken line in FIG.
Is the vibration absorption method according to the present invention. First, the radial spring constant due to the attractive force of the permanent magnets 4, 5 and 18, 19 between the rotary member 2 and the free rocking body 14 and the radial spring constant of the viscoelastic body 17 supporting the free rocking body 14 are appropriately set. The resonance point of the free oscillating body 14 and the resonance point of the rotor are matched with each other. With this setting, when the rotor passes the number of revolutions corresponding to its resonance point, the free oscillating body 14 oscillates in conjunction with the radial vibration of the rotor, and the viscoelastic body 17 effectively absorbs the vibration energy. To do.

As the number of revolutions further increases and the resonance frequency of the rotor moves away from the resonance frequency of the free oscillating body 14 due to the influence of the moment of inertia, the free oscillating body 14 does not move in conjunction with the rotor. Therefore, the absorption efficiency of the vibration energy by the viscoelastic body 17 decreases. On the other hand, since the free oscillating body 14 which is almost stationary is in the magnetic field in the axial direction created by the rotating members 2 and 3 and is a conductor, the diameter of the magnetic field interlocked with the radial vibration of the rotor. An eddy current loss occurs in the free oscillating body 14 due to the change in direction, and the vibration energy is absorbed. This effect becomes more effective as the resonance frequency at the time of high speed rotation in which the free oscillating body 14 becomes difficult to move becomes. That is, as shown in FIG. 2, the vibration energy is absorbed by the eddy current loss generated in the free oscillating body 14 at the time of high speed rotation, and the damping coefficient is larger than that in the case of the conventional viscoelastic body supporting free oscillating body type vibration absorption. Can be increased. Due to both of these actions, it is possible to configure a vibration absorbing device that can sufficiently absorb the vibration at the resonance point and can absorb the vibration energy to some extent even at high speed rotation.

[0018]

As described above, in the magnetic bearing device of the present invention, when the rotor passes the rotation speed corresponding to its resonance point, the free oscillating body oscillates in conjunction with the radial vibration of the rotor, Vibration energy is absorbed by the viscoelastic body. As the number of revolutions further increases and the resonance frequency of the rotor moves away from the resonance frequency of the free oscillating body due to the influence of the moment of inertia, the radial change of the magnetic field linked to the radial vibration of the rotor causes the free oscillating body to move. Eddy current loss occurs at and absorbs vibration energy. Therefore, by both of these actions, it is possible to configure a vibration absorbing device that can sufficiently absorb the vibration at the resonance point and can absorb the vibration energy to some extent even at the high speed rotation.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a magnetic bearing device of the present invention.

FIG. 2 is a diagram showing a relationship between a resonance frequency and a damping coefficient (vibration absorbing effect).

FIG. 3 is a diagram showing a relationship between a rotation speed and a resonance frequency.

[Explanation of symbols]

 1 Rotor Shaft 2 Rotating Member 3 Rotating Member 4 Permanent Magnet 5 Permanent Magnet 6 Permanent Magnet 7 Permanent Magnet 8 Axial Control Electromagnet 9 Axial Control Electromagnet 10 Yoke 11 Coil 12 Yoke 13 Coil 14 Free Oscillator 17 Viscoelastic Body 18 Permanent Magnet 19 permanent magnet

Claims (1)

[Claims] 1. A pair of disk-shaped rotating members (2) (3) made of a conductive material are provided at a predetermined interval on the outer circumference of a rotor shaft (1) for rotating a rotor, and each rotating member (2) is provided. Axial control electromagnets (8) and (9) composed of coils (11) and (13) and yokes (10) and (12) are not in contact with the rotating members (2) and (3), respectively, on both sides of (3). And a free oscillating body (14) made of a conductive material is disposed between the rotating members (2) and (3) without contact, and the free oscillating body (14) is attached to the viscoelastic body (17). ), And a plurality of ring-shaped permanent magnets (4 to 7), which are magnetized in opposite directions to each other on opposite surfaces of the rotating members (2) and (3), are concentrically arranged. And the permanent magnets (4 to 7) of the rotating members (2) and (3) facing each other are magnetized to different polarities, respectively. Axial control electromagnet (8)
The magnetic pole surfaces of the yokes (10) and (12) of (9) are arranged so as to face the magnetic pole surfaces of the permanent magnets (4) to (7) of the rotary members (2) and (3), respectively, and the free rocker ( 14) the permanent magnets (18) (1) magnetized to have different polarities from the magnetic poles of the magnetic pole surfaces of the permanent magnets (4) and (5) of the rotating members (2) and (3).
9), and the permanent magnets (4) (5) (18) (1) between the rotating members (2) (3) and the free oscillating body (14).
9) Radial spring constant and viscoelastic body (17)
The magnetic bearing device is characterized in that the radial spring constant is set so that the resonance point of the free oscillating body (14) and the resonance point of the rotor substantially coincide with each other.