JPS595174B2 - magnetic bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bearing, and more particularly to a magnetic bearing that can optimize the distribution of magnetic flux density within a nonmagnetic conductor.

Figures 1 and 2 show conventional magnetic bearings, with the rotation axis IVC
A rotor yoke 2 made of a magnetic material is fixed, and rotor teeth 3A and 3B are integrally provided on the outer circumference of the rotor yoke 2.

These rotor teeth 3A, 3B are stator yokes 4A, 4B.
It is sandwiched between stator teeth 5A, 5 and 5B, which are integrally protruded from each other, through gaps 6A and 6B. Non-magnetic conductors □A, 7B are attached to the stator yoke 4 so as to surround the rotor teeth 3A, 3B and the stator teeth 5A, 5B.

Additionally, permanent magnets 8 are attached to the stator yokes 4A and 4B.
is installed. As shown by the broken line, the magnetic flux 9 generated from the permanent magnet 8 is distributed between the stator yoke 4A-stator tooth 5A-
Rotor teeth 3A, 3B-Stator teeth 5BN Stator yoke 4B
15 through the path of the permanent magnet 8 (the direction of the magnetic flux 9 is opposite depending on the polarity of the permanent magnet 8).

Now, when the rotating shaft 1 vibrates, the rotor teeth 3A, 3B also vibrate integrally with the rotating shaft 1, so the magnetic path vibrates, and the magnetic flux 9 passing through the non-magnetic conductors IA, 7B changes by 20. Eddy currents 10 are generated within the non-magnetic conductors TA, TB.

The force exerted by this eddy current 10 on the rotor teeth 3A and 3B acts as a damping force on the rotor yoke 2 and the rotating shaft 1, so that the rotating shaft 1 is damped. 25 The magnitude of the rudder current 10 related to the damping effect is determined by the non-magnetic conductor TA,
It is determined by the amount of magnetic flux, such as the steep change in magnetic flux passing through the TB, but in particular, more magnetic flux 30 is passed through the concave portions IIA, 12A, IIB, and 12B provided in the nonmagnetic conductors 7A and 7B, respectively. This results in an increase in eddy current.

However, in conventional magnetic bearings as shown in Figures 1 and 2,
The magnetic flux is concentrated on the shortest path between the stator teeth 5A, 5B and the rotor teeth 3A, 3B, and the sagging portion I of the non-magnetic conductive body 35
The amount of magnetic flux passing through IA, 12A, IIB, and 12B was small.

Therefore, the generation of eddy current 10 is small and the vibration damping effect is also small, making it impossible to suppress the vibration of the rotating shaft 1 by a thousandth and making it impossible to stably operate the rotating shaft 1 up to high speeds. .

In addition, rotor tooth 3A. It was not possible to prevent the whirling phenomenon at low speeds that is promoted by the residual magnetism of 3B.

In addition, in the case of Figs. 1 and 2, as shown by curve P in Fig. 5, the change in thrust force with respect to the gears 6A and 6B is large, so when the rotating weight becomes lighter and the total length becomes longer, Due to the increased elongation of the rotating body, there was a risk that the rotating body would jump to the stator side and become unable to rotate.

Furthermore, since the thrust force varies greatly with respect to the gap, the load on the lower shaft that supports the rotating weight fluctuates greatly, which adversely affects the lower shaft and causes a reduction in the life of the lower shaft.

The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a magnetic bearing capable of optimizing the distribution of magnetic flux.

The magnetic bearing according to the present invention includes a rotor yoke attached to a rotating shaft, rotor teeth provided on the rotor yoke,
a stator yoke provided with stator teeth opposed to the rotor teeth via a gap; a magnet attached to the stator yoke; A magnetic bearing comprising a non-magnetic conductor attached to a child yoke, wherein at least one of the rotor teeth and the stator teeth has a shape whose cross-sectional area decreases toward the gap. .

The present invention will be explained below based on embodiments shown in the drawings.

In FIGS. 3 and 4, the same parts or equivalent parts as those of the conventional apparatus shown in FIGS. 1 and 2 are designated by the same reference numerals, and the rotor teeth 3A, 3B have a gap 6A. 6
The fixed five small teeth 5A, 5B facing each other via the gap B are tapered so that the cross-sectional area decreases toward the gaps 6A, 6B. The other configurations are similar to the conventional device shown in FIGS. 1 and 2. When the rotating shaft 1 vibrates, the rotor yoke 2 fixed to the rotating shaft 1 and having rotor teeth 3A and 3B also vibrates together.

Therefore, from the stator teeth 5A, 5B to the non-magnetic conductor 7A,
The magnetic flux passing through 7B also changes over time. At this time, an induced voltage is generated in the nonmagnetic conductors 7A and 7B in a direction that prevents changes in magnetic flux. This induced voltage causes the non-magnetic conductor 7 to
Eddy current flows through A and 7B, and vibration energy is consumed as eddy current loss. This provides a damping effect that suppresses vibrations of the rotating shaft 1. This damping effect, ie, the damping force, is generally proportional to the conductivity of the nonmagnetic conductor, the volume of the nonmagnetic conductor, and the square of the axial change in magnetic flux density within the nonmagnetic conductor. In this embodiment, stator teeth 5A, 5B
The cross-sectional area gradually decreases toward the gear teeth 6A and 6B, so compared to the conventional example, there is a gap between the stator tooth 5A and the rotor tooth 3A and between the stator tooth 5B and the rotor tooth 3B. The magnetic flux that passes through the shortest distance between them decreases, and as shown in FIG.
The magnetic flux passing through 2A, 11B, and 12B is increased compared to the conventional example. Therefore, the amount of change in magnetic flux density due to vibration of the rotating body 1 also increases. The eddy current loss (proportional to the square of the change in magnetic flux density) generated in each sagging portion also increases, and the vibration damping effect increases. A certain portion of the rotor teeth 3A, 3B may be magnetized during assembly or the like.

This amount of magnetization, that is, residual magnetism, creates opposing poles of magnetic N and S in the circumferential direction of the rotor, the center of the rotor shifts during rotation, and a rotational force is generated due to the residual magnetism of the rotor. This rotational force induces a whirling phenomenon of the rotating shaft 1,
Adversely affects high-speed rotating objects. However, in this embodiment, the energy of the whirling phenomenon can be absorbed by the nonmagnetic conductor. Therefore, the whirling phenomenon can be prevented. The thrust characteristics of this embodiment with respect to the gaps 6A and 6B in FIG. 4, as shown by the curve Q in FIG.

The reason why the change in thrust becomes smaller in this way is that in this embodiment, the cross-sectional area of the stator teeth becomes smaller toward the gap, as described above. That is, the thrust force is generally proportional to the square of the magnetomotive force and the change in axial permeance. In this embodiment, since the tips of the stator teeth are tapered, this is similar to expanding the gaps 6A and 6B, and the permeance value thereof becomes small. Therefore, the value of thrust force becomes small. When the weight of the rotating body (not shown) attached to the rotating shaft 1 becomes lighter and the total length of the rotating body becomes longer (the longer total length of the rotating body means that the amount of elongation of the rotating body in the axial direction increases) When the thrust force is large (that is, the rotor teeth of the magnetic bearing moves upward), the tips of the rotor teeth come into contact with the non-magnetic conductor in the case of a conventional example with a large thrust force.

However, in this embodiment, since the change in thrust force with respect to the gap is small, the tips of the rotor teeth do not come into contact with the non-magnetic conductor. The difference between the weight of the rotating body and the thrust force is the load that the lower shaft that supports the rotating body receives.

In a conventional bearing with a large change in thrust force, the load applied to the lower shaft fluctuates greatly due to variations in the gap, which shortens the life of the bearing. However, in this embodiment, since the change in thrust force with respect to the gap is small, the variation in the load applied to the lower shaft is small and the life of the bearing is extended. Figures 6 and 7 respectively show other embodiments of the magnetic bearing according to the present invention. show,
In Fig. 6, the rotor teeth 3A, 3B side are tapered instead of the stator teeth 5A, 5B side, so that the cross-sectional area decreases as it goes towards the gears 6A, 6B. Both 5A, 5B and rotor teeth 3A, 3B are tapered.

In these embodiments as well, the stator teeth 5A, 5B and the rotor teeth 3A, 3 are similar to the embodiments shown in FIGS.
It is possible to reduce the magnetic flux passing through the shortest distance between B and increase the magnetic flux passing through the non-magnetic recesses 11A, 12A, 11B, and 12B.

It goes without saying that the present invention can also be applied to a case where the shapes of the rotor yoke 2, stator yokes 4A, 4B and the non-magnetic material 7 are changed as shown in FIG.

Furthermore, rotor teeth 3A, 3B or stator teeth 4A, 4B
The shape is gap 6A. As long as the cross-sectional area decreases toward 6B, it does not necessarily have to be the shape shown in FIGS. 3, 4, 6 to 8, and may be, for example, the shape shown in FIG. 9 or 10. As described above, the magnetic bearing according to the present invention has an excellent effect in that the distribution of magnetic flux density can be made appropriate by forming at least one of the rotor teeth and the stator teeth into a shape in which the cross-sectional area decreases toward the gap. has.

[Brief explanation of the drawing]

FIG. 1 is a cutaway end view showing a conventional magnetic bearing, FIG. 2 is an enlarged cutaway end view showing the main parts of FIG. 1, and FIG. 3 is a cutaway end view showing an embodiment of the magnetic bearing according to the present invention. 4 is an enlarged cut-away end view showing the main part of FIG. 3; FIG. 5 is a characteristic diagram showing the change in thrust force with respect to the gap between the bearing in FIG. 1 and the bearing in FIG. 3; FIG. , 7 and 8 are cut-away end views showing other embodiments of the magnetic bearing according to the present invention, and Figs. 9 and 10 respectively show other embodiments of the shape of the rotor teeth or stator teeth according to the present invention. FIG. 1...Rotating shaft, 2...Rotor Yo Kazuhisa
3A, 3B...Rotor teeth, 4A, 4B...
...Rotor yoke, 5A. 5B...Stator tooth,
6A, 6B...Gap・7,7A,7B・
...Nonmagnetic conductor.

Claims (1)

[Claims] 1. A rotor yoke attached to a rotating shaft, rotor teeth provided on the rotor yoke, a stator yoke provided with stator teeth opposed to the rotor teeth via a gap, and this fixed A magnetic bearing comprising a magnet attached to a child yoke and a non-magnetic conductor attached to the stator yoke so as to wrap around the rotor teeth and the stator teeth. A magnetic bearing characterized in that at least one of the stator teeth has a shape whose cross-sectional area decreases toward the gap.