JP2000266117A - Rotary magnetic damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain vibration even to high order vibration other than resonance being a target by installing a magnet on a rotary shaft, arranging a rotary disk of an electric conductor by leaving proper clearance so as to be opposed to the magnet, and rotating the rotary disk in the opposite direction of the rotational direction of a shaft. SOLUTION: A high temperature superconducting disk 8 is placed in a cryostat bottom part, a permanent magnet disk 7 is installed in a lower end part of a shaft of a nonmagnetic material, a disk rotor 6 and a fan 5 are installed in the middle, and a permanent magnet 4 is installed in an upper end part. A permanent magnet 2 is installed so that an N pole and an S pole of the permanent magnet 4 are opposed, a disk 3 of an electric conductor is arranged between the permanent magnet 2 and the permanent magnet 4, and the disk 3 is rotated by a motor 1. At this time, the rotational direction of the shaft side permanent magnet 4 and the rotational direction of the conductor disk 3 are reversed to increase a relative speed to thereby restrain vibration even to high order vibration other than resonance being a target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to whirling vibration of a shaft, and more particularly to overrunning of a resonance. The present invention reduces vibration of a high-speed rotating shaft that generates vibration,
It can be used for various devices having a rotation axis. Particularly, since it is characterized by non-contact, it is used for suppressing vibration of non-contact rotating shafts such as magnetic bearings and high-temperature superconducting bearings.

[0002]

2. Description of the Related Art A shaft rotating at high speed usually jumps over several resonance points and rotates in a higher mode. At this time, a general method of jumping over the resonance point is to accelerate by using a powerful motor and quickly pass the resonance point. Nevertheless, near the resonance point, the vibration becomes considerably larger than at other rotational speeds. Therefore, a method of taking damping force from a bearing or the like has been used. However, in order to take in damping force sufficient for suppressing vibration, there is a disadvantage that the bearing interval must be reduced as necessary. On the other hand, a non-contact rotating shaft using a magnetic bearing and a high-temperature superconducting bearing can be rotated at tens of thousands of rpm because there is no bearing friction and no need for lubrication. However, in this case, since there is no contact, attenuation is small, and it is difficult to pass through the resonance point without control. Therefore , generally, a method of suppressing resonance by active control using a magnetic actuator is used. However, the active control has a complicated structure, is expensive, requires a running cost (energy), and has a drawback that maintenance is much more difficult than when no control is performed.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned disadvantages, and can easily provide a large damping without rotation loss by incorporating the damper. In particular, it is intended to control over the resonance of the non-contact rotary shaft without control, and to suppress vibration even for higher-order vibrations other than the target resonance.

[0004]

Means for Solving the Problems A magnet is attached to a rotating shaft, and a rotating disk of an electric conductor is arranged at an appropriate gap so as to face the magnet, and the rotating disk is oriented in a direction opposite to the rotating direction of the shaft. Rotate to. Alternatively, an electric conductor disk is attached to the rotating shaft, a magnet is arranged at an appropriate gap so as to face the disk, and the magnet is rotated in a direction opposite to the rotation direction of the shaft. With such a configuration, the relative speed of the shaft can be increased. When an electric conductor is placed slightly away from a magnet and the magnet or the conductor is moved, an eddy current flows in the conductor, and a magnetic field acts on the eddy current to generate a resistance called Lorentz force. That is, a resistance force is generated in the direction opposite to the direction in which the conductor or the magnet moves. When this magnetic damper is attached to a vibration system such as a rotating shaft, the resistance becomes a damping force of the vibrations. It is known that the damping force at this time is proportional to the speed. That is, as the speed increases, the resistance increases. Therefore, by adopting a configuration like this device, the damping force can be increased by increasing the rotation speed of the external magnet or the external disk regardless of the rotation speed of the shaft. In addition, the amount of attenuation can be controlled by controlling the number of rotations of the conductor disk.

[0005]

FIG. 1 shows a superconducting levitation shaft, in which a high-temperature superconducting disk 8 is placed at the bottom of a cryostat. The shaft is made of a non-magnetic material, and a permanent magnet disk 7 is attached to a lower end portion, a disk rotor 6, a fan 5 and a permanent magnet 4 are attached to an upper end portion in the middle. Further, the permanent magnet 2 is attached to the housing such that the north pole and the south pole of the magnet 4 face each other.
A disk 3 of an electric conductor is disposed therebetween, so that the disk 3 can be rotated by the motor 1. With such a configuration, the shaft floats in a non-contact manner by the pinning force of the high-temperature superconducting disc 8. At this time, the pinning force acts in two directions: an axial direction and a direction perpendicular to the axis. In addition, a restoring force in the direction perpendicular to the axis is applied to the upper end of the shaft by the attractive force of the magnet attached to the upper end of the shaft, and the unstable force in the axial direction is stabilized by the axial pinning force of the high-temperature superconductor. Therefore, this shaft floats stably without control and without contact. It is considered that the shaft is rotated by applying compressed air to the fan 5 of the shaft in a tangential direction to allow the fan to pass through a resonance point and accelerate to a steady rotation speed.

In FIG. 1, the magnet 2, the magnet 3, and the disk 4 of the electric conductor are structural diagrams of the present invention. That is, the motor 1
By rotating the conductor disk 3 in the direction opposite to the rotation direction of the shaft, the rotation direction of the magnet 4 on the shaft and the rotation direction of the conductor disk are reversed, and the relative speed increases. The shaft rotation speed ω at this time
Is c = c ₀ (1 + ω ¹ / ω) (1) where c is the equivalent damping coefficient of the present damper with respect to Here, c is the damping coefficient of the present damper, c ₀ is the damping coefficient due to magnetic attenuation when the conductor disk is not rotated, ω ′ is the rotation speed of the conductor disk, and ω is the rotation speed of the shaft. From the equation (1), it can be seen that the damping coefficient c increases by increasing the rotational speed of the conductor disk ω ′. In this experiment, the conductor disk 3 is arranged between the two magnets 2 and 4, so that the damping force is large. However, the magnet 4 and the conductor disk 3 alone cause rotation of the conductor disk. A damping effect is obtained.

[0007]

FIG. 2 shows the effect of the present invention. FIG. 2 shows the relationship between the displacement amplitude of the shaft and the rotation frequency of the conductor disk 3 at the primary resonance (6.5 Hz) in the direction perpendicular to the axis at the position of the upper end magnet 4 in FIG. From this figure, the vibration amplitude of the shaft at the resonance point decreases with the rotation speed (rotation in the direction opposite to the rotation direction of the shaft) of the conductor disk 3. The effect is great, and the shaft amplitude is about 30H
When rotated at z, it is suppressed to about 1/3 or less of that when not rotated. From this, the effects of the present invention are listed as follows. (1) The present damper can apply considerable damping to the whirling vibration of the rotating shaft without contact and without control. (2) If a disk or a cylindrical magnet in which the magnet is uniformly magnetized in the thickness direction is used by the present damper, the magnetic attenuation in the rotation direction is eliminated. Therefore, in principle, there is no rotational energy loss due to the damper. Of course, it has energy loss for whirling. (3) The present damper requires energy to rotate the conductor disk, but does not require any further energy by stopping the rotation after overcoming the desired resonance. In addition, even after the rotation of the disk is stopped, the conductor disk is interposed between the magnets, so that the whirling is damped as a normal magnetic damper. Therefore, high-order vibration suppression has a considerable damping effect even at rest.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus according to an embodiment of the present invention.

FIG. 2 shows the relationship between the resonance amplitude in the direction perpendicular to the axis at the point of the tip magnet 4 of the shaft of the apparatus and the rotational speed of the conductor disk 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Motor 2 Cylindrical permanent magnet 3 Conductor disk (made of aluminum) 2 Cylindrical permanent magnet 5 Fan 6 Disk rotor 7 Disk permanent magnet 8 High-temperature superconducting disk

Claims (1)

[Claims] 1. A magnet is attached to a rotating shaft, and a rotating disk of an electric conductor is arranged at an appropriate gap so as to face the magnet, and the disk is rotated in a direction opposite to the rotating direction of the shaft. Alternatively, an electric conductor disk is attached to the rotating shaft, a magnet is arranged with an appropriate gap facing the disk, and the magnet is rotated in the direction opposite to the rotation direction of the shaft, so that the shaft rotates. A magnetic damper characterized by suppressing vibration.