JPH02113117A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To prevent heat generation and generation of internal damping due to eddy current in a magnetic bearing device in which a body of rotation arranged on the outer periphery of a stationary shaft and an active magnetic bearing supporting the body of rotation are provided by holding an electromagnet provided on the stationary shaft by two ring-shaped magnetic poles. CONSTITUTION:A bias magnet consisting of electromagnets (or permanent magnet) 5 sandwitched between ring-shaped magnetic poles 4 and magnetic poles 4 is provided on a stationary shaft 2 arranged in the center section. Further, ring-shaped poles 6 having U-shaped cross section in axis direction are arranged on a body 1 of rotation at the position opposed to the bias magnet. When the bias magnetic flux of a magnetic bearing is radially supplied by the electromagnet and distributed evenly in the circumferential direction, the bias magnetic flux flowing in the ring-shaped magnetic poles becomes equally in the circumferential direction. Thus, since eddy current generated during the rotation can be restricted to an extremely low level even while the body of rotation rotates, and thereby heat generation of the body of rotation and generation of internal damping due to the eddy current can be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a magnetic bearing device for a turbo machine, etc., which is equipped with an electromagnet for controlling magnetic attraction force in the radial direction and a magnet for supplying a bias magnetic flux, and is capable of rotating a rotating body. This invention relates to a magnetic bearing device that provides stable support without contact.

[Prior art]

FIG. 4 is a diagram showing the structure of a conventional magnetic bearing device of this type, and FIG. 5 is a diagram showing the distribution of its bias magnetic flux. As shown in the figure, a conventional magnetic bearing device has a structure in which a rotating body 1 is arranged around the outer periphery of a fixed shaft 2 arranged in the center.
Electromagnets 3 that generate bias magnetic flux are arranged at predetermined intervals around the circumference of the fixed shaft 2.

[Problem to be solved by the invention]

Normally, a bias magnetic flux is applied to the control magnetic pole in order to linearize the magnetic bearing control system, but in the case of the magnetic bearing with the conventional structure described above, the magnetic flux Φ generated from the electromagnet 3 rotates from the fixed shaft 2 as shown in Fig. 4. It flows forming a substantially circular magnetic path to the body 1. As a result, as shown in Fig. 5, the strength of the magnetic flux is generated in the circumferential direction of the rotating body 1 from ■ to Eddy currents occur on the first side. This eddy current becomes larger as the rotating body 1 rotates faster.

The generation of this eddy current may cause the rotating body 1 to generate heat or cause internal damping, making the support of the rotating body unstable. Generally, as a countermeasure to this problem, the generation of eddy currents is suppressed by using silicon steel plates for the magnetic poles or by suppressing the bias magnetic flux as much as possible, but it is difficult to reduce the eddy currents, and it is difficult to suppress the bias magnetic flux. There was a problem in that it also affected the rigidity of the bearing.

The present invention was made in view of the above-mentioned points, and it is an object of the present invention to provide a magnetic bearing device that stably supports a rotating body by suppressing the generation of vortices in the rotating body as much as possible.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a magnetic bearing device that includes a fixed shaft in the center and a rotating body arranged around its outer periphery, and includes at least one active magnetic bearing that supports the rotating body and controls the radial direction. The device is characterized in that a magnet for supplying a bias magnetic flux is provided on the fixed shaft side by sandwiching an electromagnet or a permanent magnet between two ring-shaped magnetic poles.

[Effect]

By configuring the magnetic bearing device as described above, the bias magnetic flux flowing through the ring-shaped magnetic pole becomes uniform in the circumferential direction, thereby suppressing the eddy current generated during rotation to an extremely small amount even when the rotating body rotates. This makes it possible to prevent the occurrence of heat generation and internal damping in the rotating body due to eddy currents, which are problems with conventionally structured magnetic bearing devices, and to stably support the rotating body.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing a bias magnet section of a magnetic bearing device according to the present invention. The arrangement structure of the fixed shaft and rotating body of the magnetic bearing device is approximately the same as in FIG. 4. As shown in FIG. 1, a bias magnet consisting of a ring-shaped magnetic pole 4 and an electromagnet (or permanent tombstone) 5 sandwiched between the magnetic poles 4 is provided on the fixed shaft 2 arranged in the center. ing. Also,
A ring-shaped magnetic pole 6 having a U-shaped axial cross section is disposed on the rotating body 1 at a position facing the bias magnet.

By configuring the bias magnet section as described above, the electromagnet (
As shown in FIGS. 1 and 2, the magnetic flux Φ from the permanent magnet 5 flows axially to the fixed shaft 2 and radially to the rotating body. That is, as shown in FIG. 3, the magnetic flux in the air gap between the magnetic pole 4 of the fixed shaft 2 and the magnetic pole 6 of the rotating body 1 is evenly distributed in the circumferential direction (1) to (2). As the magnetic flux in the gap between the magnetic poles is evenly distributed in the circumferential direction, the magnetic flux density does not change even when the rotating body 1 rotates, so no eddy current is generated in the rotating body 1, or Even if it occurs, it can be suppressed to an extremely small range.

Therefore, the present invention provides a magnetic bearing device with higher stability than conventional magnetic bearing devices.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

That is, a magnet for supplying a bias magnetic flux is provided on the fixed shaft side by sandwiching an electromagnet or a permanent magnet between two ring-shaped magnetic poles, and the bias magnetic flux of the magnetic bearing is supplied radially by the electromagnet or permanent magnet to spread around the circumference. By distributing the magnetic flux evenly in the direction, the bias magnetic flux flowing through the ring-shaped magnetic pole becomes even in the circumferential direction, which suppresses the eddy current generated during rotation to an extremely small amount even when the rotating body rotates. Therefore, it is possible to provide a highly stable magnetic bearing device that can prevent the occurrence of heat generation and internal damping of the rotating body due to eddy currents and stably support the rotating body.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the bias magnet part of the magnetic bearing device of the present invention, FIG. 2 is a diagram showing the structure of the magnetic bearing device of the present invention and the direction in which the bias magnetic flux flows, and FIG. 3 is the distribution of the bias magnetic flux. FIG. 4 is a diagram showing the structure of a conventional magnetic bearing device and the direction in which the bias magnetic flux flows, and FIG. 5 is a diagram showing the distribution of the bias magnetic flux. In the figure, 1... rotating body, 2... fixed shaft, 3...
・Electromagnet, 4...magnetic pole, 5...electromagnet (or permanent magnet), 6...magnetic pole.

Claims (1)

[Claims] A rotary body is disposed around the outer periphery of the rotary body with a fixed shaft in the center, and includes at least one active magnetic bearing that supports the rotary body and controls the radial direction, and the active magnetic bearing controls the magnetic attraction force in the radial direction. In a magnetic bearing device comprising a control magnet for linearizing control and an electromagnet or a permanent magnet for supplying bias magnetic flux for linearizing control, the electromagnet or permanent magnet supplies the bias magnetic flux with two ring-shaped magnetic poles on the fixed shaft side. A magnetic bearing device that is characterized by sandwiching.