JPS58109719A - Magnetic bearing - Google Patents

Abstract

PURPOSE:To suppress the generation of eddy current to minimum and consequently reduce the generation of heat by a structure wherein a bias magnet is made annular and yet a U-shape in its axial cross section so as to produce no change of magnetic flux in the direction of rotation of a shaft. CONSTITUTION:The iron core 5a of the bias electromagnet is made annular and yet a U-shape in its axial cross section as illustrated in the accompanying figure. When a permanent magnet is employed as bias magnet, the magnet is magnetized so as to produce circumferentially same magnetic pole as shown in the figure. While, when an electromagnet 5b is employed as bias magnet, circumferentially same magnetic pole can be obtained by winding a coil as indicated in the figure. Owing to the structure as mentioned above, because no change of magnetic flux is produced circumferentially even under the rotation of the shaft 2, no eddy current is resulted to be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a controlled magnetic bearing, and more particularly to a controlled radial magnetic bearing having an ear magnet and a control magnet.

Controlled radial magnetic bearings, which levitate and support a shaft at a desired position by increasing or decreasing the magnetic flux generated by a bias magnet using the magnetic flux generated by a control electromagnet, have conventionally generally had magnets arranged as shown in Figure 1. There is. That is, the X and Y directions are each controlled by two magnets, and the bias coil 4 and control coil 3 are wound around the iron core 1. In this method, when the ferromagnetic shaft 2 rotates, it crosses the N and S magnetic poles generated by the magnet, resulting in a large eddy current, which generates a large amount of heat in the shaft 2 and the magnet.This method is particularly useful when the rotation speed is high. I can't stand it. Therefore, countermeasures have been taken, such as placing laminated plates not only on the magnet but also on the shaft to suppress eddy currents. However, when a laminated plate is used for the shaft, it is limited in terms of centrifugal strength, and there are problems such as not being able to increase the speed of the shaft very much.

An object of the present invention is to provide a magnetic bearing that does not have the problem of heat generation due to eddy current even when the shaft rotates, and does not require a laminated plate to be provided on the shaft.

Eddy currents occur in magnetic bearings because the magnetic flux changes as the ferromagnetic material rotates. Therefore, if the magnet arrangement 1 is used such that the magnetic flux does not change in the direction of rotation, the vortex '#L flow loss will be reduced.

In particular, in the magnetic bearing according to the present invention, since the bias electromagnet always generates a certain amount of magnetic flux, eddy current loss caused by this is a major problem. Therefore, the bias magnet is made in the shape of a loam,
Moreover, its axial cross section is U-shaped, so that the magnetic flux does not change in the rotational direction of the shaft.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an example of a bias electromagnet constituting the magnetic bearing of the present invention. As shown in the figure, the iron core 5 of the bias electromagnet
A is annular, and its axial cross-sectional shape is U-shaped as shown in the figure. If a permanent magnet is used as a bias magnet, it is magnetized so that it has the same magnetic poles in the circumferential direction as shown in the figure, and when using electromagnet 5bi, if the coil is wound as shown in the figure, it has the same magnetic poles in the circumferential direction. is obtained.

In this way, even when the shaft 2 rotates, there is no change in the magnetic flux in the circumferential direction, so no eddy current is generated. FIG. 3 is a top view of the arrangement of control electromagnets 6 constituting the magnetic bearing of the present invention, and FIG. 4 is a plan view showing the overall configuration. The control electromagnet 6 has an iron core 6a
and a coil 6b.

When the control magnet 6 operates, a change in magnetic flux will naturally occur in the circumferential direction, but if we consider that the shaft 2 is held at a neutral point, the eddy current will be significantly reduced compared to the method shown in Figure 1. Can be made smaller.

As described above, according to the present invention, the generation of eddy currents caused by the rotation of the shaft is suppressed to a minimum, heat generation is reduced, and there is no need to take measures such as using a laminated plate for the shaft. This eliminates problems such as the rotational speed of the shaft being limited.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the overall configuration of a conventional controlled radial hunting bearing, Fig. 2 is a perspective view partially showing a bias magnet that constitutes the magnetic bearing of the present invention, and Fig. 38 is a diagram showing the present invention. FIG. 4 is a partially sectional perspective view showing a combination of control magnets constituting a magnetic bearing, and FIG. 4 is a diagram showing the overall configuration of the magnetic bearing of the present invention. 2...Shaft, 5...Bias electromagnet, 6...
control electromagnet. Agent Patent Attorney Toshiyuki Usuda 1 Figure 5 Figure 4 Figure 6 &

Claims (1)

[Claims] A control electromagnet, a bias magnet that generates a constant magnetic flux, and a wire are used, and the magnetic flux generated by the control electromagnet increases or decreases the magnetic flux generated by the bias magnet.
Kuyafu) 1- In a controlled radial magnetic bearing that floats and supports at a desired position, the bias magnet is annular and is arranged to surround the shaft, and its axial cross section is U-shaped, and the bias magnet is arranged in the circumferential direction of the rotor. A magnetic bearing characterized in that the magnetic flux generated by the magnetic bearing does not change.