JPH076541B2 - Magnetic bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a magnetic bearing device for a rotating machine.

(Prior Art) A magnetic bearing device is a device that supports a rotating shaft in a non-contact manner by a repulsive force or an attractive force between magnets, and is of a contact type such as ultra-high speed operation or operation in a vacuum where mixing of lubricant is disliked. Suitable for fields where bearings cannot be used. The magnetic bearings according to the prior art include a repulsive permanent magnet type that uses the repulsive force of permanent magnets, and an attraction method that controls the attraction force between the electromagnet and the rotation axis by adjusting the current flowing in the electromagnet according to the vibration of the rotation axis. A typical type is the electromagnet type.

FIG. 7 is a vertical cross-sectional view for explaining the structure of a repulsive permanent magnet type radical bearing device, in which a cylindrical permanent magnet (2) having a magnetic flux in the radial direction is concentrically attached to the rotating shaft (1) and is provided outside thereof. A cylindrical permanent magnet (3) having a polarity opposite to that of the permanent magnet (2) is fixed to the stationary portion (7). At this time, since the two permanent magnets repel each other, the potential of the rotating shaft (1) becomes stable at the center (C) of the stationary side cylindrical permanent magnet (3), and the rotating shaft (1) is eccentric from the center (C). Then, since the magnetic force acts in the direction of pushing the rotating shaft (1) back to the center (C), the rotating shaft (1) is supported without contacting the stationary portion.

In contrast to the repulsive permanent magnet type magnetic bearing device, in the attraction type electromagnet type radical magnetic bearing device whose schematic structure is shown in FIG. 8, the exciting current is applied to the electromagnet (4) arranged on the outer periphery of the rotating shaft (1). When I is energized, the rotating shaft (1) has an electromagnet (4)
The magnetic attraction force is generated by the magnetic flux generated by, but if the exciting current I is constant, the rotating shaft (1) is in an unstable state and if displacement occurs, it is attracted in that direction. The circuit (6) adjusts the magnetic flux density generated by the electromagnet (4) by calculating the exciting current required to restore the displacement based on the displacement of the rotating shaft (1) measured by the position sensor (5). The stability of the rotary shaft (1) is maintained.

The above description relates to the radial bearing device, but the same applies to the thrust bearing device, and the repulsive type is the main type in the permanent magnet type and the suction type is the main type in the electromagnet type.

As described above, since the magnetic bearing device supports the rotating shaft in a non-contact manner, it is possible to operate at an extremely high speed, which cannot be used in rolling bearings or journal bearings due to seizure, and the bearing loss of the drive device becomes zero. Further, since a lubricant is unnecessary, operation in vacuum is extremely easy. In spite of having such excellent characteristics, there are problems to be solved in the prior art as described below, and their application to large machines is particularly hindered.

First, in the repulsive permanent magnet type magnetic bearing, the vibration of the rotating shaft cannot be controlled because the magnetic force of the permanent magnet cannot be adjusted. For this reason, the vibration of the rotating shaft becomes large due to imbalance when passing the dangerous speed, and therefore it is necessary to strictly balance the rotating shaft. Therefore, its application is limited to those that are small and have a relatively low rotational speed, and it is difficult to apply it to large machines with a large unbalanced force and ultra-high speed operation.

Next, in the attraction type electromagnet type magnetic bearing device, a very large exciting current must be supplied to the electromagnet in order to support the load of the rotating shaft. It consumes a lot of power. Furthermore, since this exciting current is controlled to maintain the stability of the rotating shaft, the control device also needs a large capacity capable of controlling a large current, and also in the event of a power failure or failure of the power supply device or control device. Since it becomes impossible to control the position of the rotating shaft, the rotating shaft may collide with the stationary part and damage the machine.Therefore, an auxiliary power supply, an auxiliary circuit, an auxiliary bearing that mechanically supports the rotating shaft, etc. It is necessary to install various security devices, and there are many problems with the suction type electromagnet type magnetic bearing in terms of the device and reliability.
And there is a limit to the size.

(Problems to be Solved by the Invention) As described above, in the magnetic bearing according to the prior art, in the repulsion type permanent magnet type, the vibration damping property of the rotating shaft is omitted, and in the attraction type electromagnet type, a large current There are problems with consumption, accompanying large-capacity power supply and control device, necessity of security device for failure, etc., and due to these problems, both types will increase the size of applicable models. Is very difficult.

In view of these problems in the prior art, the present invention provides a magnetic bearing device that consumes less power and therefore does not require a large-capacity power source and a security device and that can control vibration of a rotating shaft. With the goal.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the present invention, a magnet that is oppositely attached to a rotating shaft and a stationary portion that faces the rotating shaft via a gap, a stationary magnet and a stationary portion, respectively. An electrostrictive element provided between the position sensor for detecting the displacement of the rotating shaft, a displacement signal from the position sensor, and the power for deforming the electrostrictive element is supplied to move the position of the stationary magnet. There is provided a magnetic bearing device including a control device that changes the vibration of a rotating shaft to reduce the vibration.

(Operation) With this type of structure, the revolving force between the magnets or the attraction force keeps the rotating shaft in a predetermined position. The control device inputs the displacement signal from the position sensor to the control device, which deforms the electrostrictive element to change the position of the stationary magnet, adjusts the magnetic force, reduces the vibration of the rotating shaft, and stabilizes. The operation is continued.

(Example) Example 1 Hereinafter, a first example of the present invention will be described.

FIG. 1 is a vertical sectional view showing a schematic structure of a repulsive permanent magnet type radial magnetic bearing device according to a first embodiment, and FIG. 2 is a top view thereof. Two cylindrical permanent magnets (2) and (3) having magnetic flux directions of radial directions and opposite polarities are prepared. The permanent magnet (2) is attached to the rotary shaft (1) and the permanent magnet (3).
Is attached to the stationary part (7) which is a casing through the electrostrictive elements (4) equally distributed on the circumference. And the rotation axis (1)
The two position sensors (5) for detecting the displacement of (1) are arranged from the right angle direction toward the rotating shaft (1) and fixed to a mounting device (not shown). A control device (6) for inputting a displacement signal from the position sensor (5) and supplying electric power for deforming the electrostrictive element (4) to change the position of the stationary permanent magnet (3) to reduce vibration of the rotating shaft. ) Is provided.

Next, the operation of the first embodiment will be described. With the above, the two permanent magnets (2), due to the opposite polarities,
Although the repulsive magnetic force is generated between (3) and the rotating shaft (1) is supported in the air, the magnetic force F supporting the rotating shaft (1) is equal to the rotating side permanent magnet (2) and the stationary side permanent magnet (2). _Let 3 be the relative position of q _R and q _S , and let the proportional constant be K. Given in. By the way, since the stationary permanent magnet (3) can be moved in position by an electrostrictive element (4) provided as a positioning device, both permanent magnets (2) can be controlled by controlling the electrostrictive element (4). It is possible to control the vibration of the rotating shaft (1) by changing the relative position r of (3) and (3) to adjust the supporting force of the rotating shaft (1).
That is, there is an optimum supporting force F _{0 of} the rotary shaft that minimizes the vibration of the rotary shaft (1) with respect to the displacement of the rotary shaft (1) measured by the position sensor (5). 6) obtains the relative position r ₀ of the permanent magnets (2), (3) for obtaining F ₀ from the equation (101), controls the electrostrictive element (4) to that position, and controls the stationary side permanent magnet (3 ) Move. In this way, by controlling the position of the stationary side permanent magnet (3), a magnetic bearing capable of controlling the vibration of the rotating shaft (1) while being a permanent magnet type is formed.

Embodiment 2 FIG. 3 is a transverse sectional view of a repulsive permanent magnet type radial magnetic bearing device, which is the same as the stationary permanent magnet (3) in Embodiment 1 of FIG. In the second embodiment, the stationary permanent magnet (3) is equally divided into four pieces, each of which is attached to the electrostrictive element (4). The stationary permanent magnet (3) controls the relative position with respect to the rotating shaft (1) based on the displacement of the rotating shaft (1) individually measured by the position sensor (5). Others are the same as in the first embodiment.

By doing so, the stationary permanent magnet (3) can be moved for each divided portion, so that the position control can be performed precisely.

As a modification of the first and second embodiments, the polarities of the rotating permanent magnet (2) and the stationary permanent magnet (3) are the same as those of the above-described two repulsive permanent magnet radial magnetic bearings. In the same direction, in consideration of the fact that the supporting force acting on the rotary shaft (1) becomes the attraction force, the attraction type permanent magnet radial magnetic bearing device is formed by performing the same control.

Third Embodiment FIG. 4 is a vertical cross-sectional view for explaining the structure of the suction type electromagnet type radial magnetic bearing device of the third embodiment, in which the stationary side electromagnet (3a) is electrostricted to the stationary part (7) which is a casing. It is mounted such that position control is possible via the element (4). The stationary side electromagnet (3a) is supplied with a constant current to generate a constant magnetic flux, and the rotating side magnet iron core (2a) made of laminated silicon steel plate is attached to the rotating shaft (1) to avoid heat generation due to eddy current. Apply suction force.

In this way, the control device (6) can operate the position sensor (5).
By controlling the electrostrictive element (4) which is a positioning device for the stationary side electromagnet (3a) from the displacement of the rotating shaft (1) measured by, the electromagnetic attraction force acting on the rotating shaft (1) is adjusted. Stable support of the rotating shaft (1). And since it is an attraction type, only the iron core (2a) is required as the rotating side magnet.

Fourth Embodiment FIG. 5 shows an attraction type electromagnet type magnetic bearing device of a fourth embodiment. This is one in which the stationary magnet is composed of a superconducting electromagnet (3b) in order to support the rotating shaft (1) with a large load, and the other embodiment is a horizontal type bearing (see FIG. 4). It is the same as the one supported by the table (8).

By doing so, a strong magnetic flux can be obtained due to the use of the superconducting electromagnet (3b), and moreover, the electrostrictive element (4)
Since the superconducting magnet (3b) is positioned by, the superconducting magnet (3b) only needs to generate a constant magnetic flux, there is no fear of loss of superconductivity due to changes in magnetic flux, and it can be applied to large machines. .

Fifth Embodiment FIG. 6 is a vertical sectional view showing the structure of a repulsive permanent magnet type thrust magnetic bearing device according to a fifth embodiment. A disk-shaped permanent magnet (2) having a magnetic flux in the axial direction is concentrically attached to the rotary shaft (1), and is opposed to the permanent magnet (2) and has an annular shape opposite to the permanent magnet (2) on both sides thereof. The permanent magnet (3) is attached to the stationary portion (7) composed of a casing so as to be movable relative to the permanent magnet (2) via an electrostrictive element (4) which is a positioning device. A position sensor (5) provided at the shaft end of the rotary shaft (1) measures the position of the rotary shaft (1) and transmits it to the control device (6). The control device (6) calculates the position of the permanent magnet (3) at which a magnetic force that minimizes the vibration of the rotating shaft (1) is obtained, and controls the electrostrictive element (4) to control the permanent magnet (3). It is moved to the position and the rotary shaft (1) is stably supported.

〔The invention's effect〕

As described above, according to the present invention, since the relative position of the stationary side magnet to the rotation axis is determined by the electrostrictive element, the power consumption is small, and therefore a large-capacity power source and a security device are unnecessary, and A magnetic bearing device capable of controlling vibration of a rotating shaft can be provided.

[Brief description of drawings]

FIG. 1 is a longitudinal section showing a first embodiment of the magnetic bearing device of the present invention, FIG. 2 is a top view showing the arrangement of the parts shown in FIG. 1, and FIG. 3 is a part showing the second embodiment. 4 is a top view showing the arrangement of FIG.
FIGS. 6 to 6 are vertical sectional views showing the third to fifth embodiments, and FIGS. 7 and 8 are vertical sectional views showing different conventional examples. 1 ... Rotation axis, 2 ... Rotation side permanent magnet, 2a ... Rotation side magnet iron core, 3 ... Stationary side permanent magnet, 3a ... Stationary side electromagnet, 3b ... ... Superconducting electromagnet which is a stationary side magnet, 4 ... Electrostrictive element, 5 ... Position sensor, 6 ... Control device, 7 ... Casing which is a stationary part, 8 ... Bearing stand.

Claims (1)

[Claims] Claim: What is claimed is: 1. A magnet mounted opposite to a rotary shaft and a stationary portion facing the rotary shaft through a gap, an electrostrictive element provided between the stationary magnet and the stationary portion, and displacement of the rotary shaft detected. And a controller for inputting a displacement signal from the position sensor and supplying electric power for deforming the electrostrictive element to change the position of the stationary magnet to reduce vibration of the rotating shaft. Magnetic bearing device characterized by.