JPS59113317A - Axial magnetic bearing - Google Patents

Abstract

PURPOSE:To realize appropriate maintenance of a position of opposition between two magnets at all times with a simple structure by bringing about strong distribution of density of magnetic flux in either a fringe part or a central part of a disc in a face of opposition of a disc-shaped rotary shaft side magnet to a bearing side magnet. CONSTITUTION:A disc-like permanent magnet 16 is fitted on the tip of a rotary shaft 11 and an electromagnet 17, equipped with coil in its iron core so that the projecting end face and cylindrical end face in the center form different poles, is provided in opposition to said magnet 16. As for distribution of density of magnetic flux on the pole face of the permanent magnet 16, either a fringe part or a central part of the disc is magnetized so as to have strong distribution of density. Thus, in case a position of the rotary shaft side magnet 16 in opposition to the bearing side magnet 17 is shifted, repulsive force is generated for both magnets to return to the original position. Then, radial bearing effect is given to stabilize a position of the rotary shaft and a magnet sticking downward is omitted to simplify structure of the bearing.

Description

[Detailed description of the invention] The present invention relates to magnetic bearings.

A conventional attraction-type axial magnetic bearing has a disc-shaped magnetic material T attached to the rotating shaft/end as shown in Figure 3, and one pole is formed in the center opposite to this magnetic material B, and the other pole is formed on the outer periphery. A fixed annular electromagnet 7 is provided. In such conventional bearings, in order to increase the restoring force against deviation in the radial direction, that is, the radial bearing effect, the attractive force is increased, and a magnetic material g is also provided below the shaft, similar to the electromagnet 7 above. It was necessary to maintain balance by attracting the shaft from below using an electromagnet.

In order to eliminate the above-mentioned drawbacks, the present invention is configured such that the rotating shaft side magnet and the stationary side magnet opposing the rotating shaft side magnet generate a repulsive force that returns each other to the original state when the position of the rotating shaft side magnet facing the bearing side magnet shifts. This is a feature of the present invention, and the drawings will be described in detail below.

Fig. 2 shows an embodiment of the present invention, in which a disk-shaped permanent magnet /l is attached to the tip of the rotating shaft //, and a protrusion is provided at the center of a bottomed cylinder, which is provided opposite to the permanent magnet /l. It consists of an electromagnet/7 in which a coil is mounted in a provided iron core so that the central protrusion end face and the cylindrical end face form different poles. Figure 2 (b) shows the magnetic flux density distribution on the magnetic pole surface of permanent magnet/B.
The M-shape is symmetrical and lies in the range of the M-shape shown by the dotted line and the M-shape shown by the solid line from the center O in the radius r direction. Since the magnetic flux density at the outer periphery of the permanent magnet/B is high, the restoring force against displacement in the radial direction is increased. If the overall attractive force is set appropriately according to the weight and load, the height of the peaks at the periphery of the M-shaped magnetic flux density distribution and the bottom of the valley at the center have opposite polarities, as shown in Figure 1. There is no need to provide a separate downwardly pulling magnet as in conventional devices.

Figure 3 shows the magnetic pole of electromagnet 77' attached to the rotating shaft in an attraction type thrust bearing in which the electromagnet in Figure 2 is replaced by a single-pole electromagnet 77' with a coil provided on the outer periphery of the end of a cylindrical core. The magnetic flux distribution on the magnetic pole surface of a disc-shaped permanent magnet with a diameter slightly larger than that of the surface is shaped like a mountain with reverse polarity at the periphery, as shown in Figure 7 (b). This creates a suction force in the center and a repulsive force in the periphery, giving it a strong restoring force.

As described above, in the present invention, the rotating shaft-side magnet and the fixed-side magnet opposing it are configured to generate repulsive forces that return each other to their original positions when the position of the rotating shaft-side magnet facing the bearing-side magnet is misaligned. Since it provides a radial bearing effect, the position of the rotating shaft is stable, and the need for a magnet that attracts the bearing downward can be omitted, simplifying the bearing structure.

[Brief explanation of drawings]

Fig. 1 is a partial sectional view of a conventional attraction type ac/kill magnetic bearing, Fig. 2 shows an embodiment of the present invention, Fig. 2(a) is a sectional view, and Fig. 2(b) is a partial sectional view of a permanent magnet. Magnetic flux density distribution curve diagram, 3rd
The figures show other embodiments, where (a) is a sectional view and (b) is a sectional view.
) is a magnetic flux density distribution curve diagram of a permanent magnet. //...rotation axis, /1. , /ly'... rotating shaft side magnet, /7. /7'...Bearing side electromagnet. Designated Agent Ino Ilin (Kyu) C t) Figure 2 (Ku J tb
)Figure 3

Claims (1)

[Claims] In an attraction-type axial magnetic bearing in which a bearing-side electromagnet and a disc-shaped rotating shaft-side permanent magnet provided on the rotating shaft are arranged with different poles facing each other, the rotating shaft-side permanent magnet faces the surface facing the bearing-side electromagnet. An axial magnetic bearing characterized in that either the peripheral portion or the central portion of the disk is magnetized to have a strong magnetic flux density distribution.