JPH07199095A - Magnetic bearing device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a magnetic bearing device capable of reducing uneven rotation of a rotating body that supports a shaft. According to the present invention, a magnetic bearing device 1 in which magnets 6 and 14 are arranged so as to face a rotating body 11 and a bearing portion, respectively, and the rotating body 11 is axially supported in a non-contact manner by magnetic force between the magnets 6 and 14. And the convex portion 1 is provided on one of the facing portions of the magnets 6 and 14.
5, the concave portion 1 into which the convex portion 15 is inserted in a non-contact state
4a is provided. With this configuration, the displacement of the rotating body 11 with respect to the bearing portion can be prevented by the non-contact magnetic action between the convex portion 15 and the concave portion 14a, and the uneven rotation of the rotating body can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device and an optical scanning device.

[0002]

2. Description of the Related Art In a conventional thrust magnetic bearing device,
The thrust bearing of the rotating body includes a repulsive magnetic bearing.
This is a magnet that uses two ring-shaped permanent magnets, one permanent magnet is connected to one end of the rotating body, and the other permanent magnet is connected to the rotating body to the box body that protects the rotating body. It is connected to the position opposite to the vertical direction.

The permanent magnet itself has different magnetic poles at both ends, but the permanent magnets on the rotor side and the box side are arranged such that their magnetic poles have the same direction (repulsion).

According to this magnetic bearing device, when an appropriate vibration and load are applied to the rotating body, the position of the rotating body tends to change up and down by a small amount. A repulsive action occurs between the attached permanent magnet and the rotating body can be kept at a constant position.

By arranging a total of four permanent magnets, one set each at both ends of the rotating body and the box body, it is possible to further improve the positioning accuracy with respect to load and vibration.

[0006]

In the case of the above-mentioned conventional magnetic bearing device, a force is exerted so that the permanent magnets always try to escape in the radial direction.

Therefore, for example, when the above-mentioned magnetic bearing device of the repulsion system is incorporated in an optical scanning device of a laser beam printer, the opposing permanent magnets always try to escape in the radial direction, so that the rotating body has uneven rotation. May occur,
Further, there often occurs a situation in which a galling phenomenon occurs between the rotating body and the fixed shaft to make it unusable.

Further, in order to improve the positioning accuracy, it is necessary to arrange a total of four permanent magnets, one set at each end of the rotating body and the box body, which causes a problem of increasing the number of parts.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic bearing device capable of reducing the rotation unevenness of a rotating body which is axially supported and reducing the number of parts.

It is another object of the present invention to provide an optical scanning device incorporating the magnetic bearing device and having less uneven rotation.

[0011]

The invention according to claim 1 is
A magnetic bearing device, in which magnets are arranged so as to face a rotating body and a bearing portion, respectively, and the rotating body is axially supported by a magnetic force between the magnets in a non-contact manner. On the other hand, a concave portion is provided in which the convex portion is depressed in a non-contact state.

According to a second aspect of the present invention, the thrust load of the rotating body is received by the magnets arranged to face the rotating body and the bearing portion, respectively, and the magnetic force between the convex portion and the concave portion of the facing portion of each magnet is increased. The action suppresses the radial movement of the rotating body.

According to a third aspect of the present invention, the radial load of the rotating body is received by the magnets arranged to face the rotating body and the bearing portion, respectively, and the magnetic force between the convex portion and the concave portion of the facing portion of the magnets is increased. The action suppresses the movement of the rotating body in the thrust direction.

According to a fourth aspect of the invention, the magnet on the side of the rotating body also serves as a rotor of a drive motor for driving the rotating body.

[0015]

The function of the present invention will be described below.

According to another aspect of the magnetic bearing device of the present invention, a convex portion is formed in one of the facing portions of the magnets arranged to face the rotating body and the bearing portion, and a concave portion is formed in the other portion so that the convex portion is depressed in a non-contact state. Since the position of the rotating body is prevented from being displaced with respect to the bearing portion by the magnetic action in a non-contact state between the convex portion and the concave portion, uneven rotation of the rotating body can be reduced.

According to another aspect of the magnetic bearing device of the present invention, the thrust load of the rotating body is received by the magnets arranged to face the rotating body and the bearing portion, and the convex portions of the facing portions of the magnets, Since the radial action of the rotating body is suppressed by the magnetic action between the concave portions, this magnetic bearing device can be made to function for thrust load, and uneven rotation of the rotating body in the radial direction can be reduced.

According to another aspect of the magnetic bearing device of the present invention, the radial load of the rotating body is received by the magnets arranged to face the rotating body and the bearing portion, and the convex portions of the facing portions of the magnets are Since the movement of the rotating body in the thrust direction is suppressed by the magnetic action between the concave portions, it is possible to make this magnetic bearing device function for a radial load and improve the positioning accuracy of the rotating body in the thrust direction. Become.

According to the magnetic bearing device of the present invention, since the magnet on the side of the rotating body also serves as the rotor of the drive motor for driving the rotating body, it is possible to eliminate the independent magnet facing the bearing portion. Therefore, the number of parts can be reduced.

[0020]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an optical scanning device 50 incorporating the magnetic bearing device 1 of this embodiment.

This optical scanning device 50 comprises a main body 5 consisting of a lower frame body 3 having an opening 2 through which laser light enters, and an upper frame body 4 for covering the lower frame body 3. A disk-shaped first magnet (permanent magnet) 6 forming a bearing portion of the magnetic bearing device 1 is arranged on the bottom portion of the lower frame body 3.

A fixed shaft 9 is attached in a vertical arrangement by screws 7 and 8 at a substantially central portion of an internal space formed by the lower frame body 3 and the upper frame body 4.

A rotating body 11 is rotatably mounted on the fixed shaft 9 through a bush 10, and a polygon mirror 12 as a reflector having a reflecting surface on the outer peripheral surface is attached to the rotating body 11. The reflecting surface of the polygon mirror 12 faces the opening 2.

Further, a magnet support plate 13 is arranged below the rotating body 11, and a disk-like structure which constitutes the magnetic bearing device 1 is arranged on the lower surface side of the magnet support plate 13 so as to face the first magnet 6. The second magnet (permanent magnet) 14 of is arranged.

On the upper surface of the first magnet 6, as shown in an enlarged view in FIG. 2, convex portions 15 having an acute angle mountain shape are provided in a circular arrangement.

Further, the lower surface of the second magnet 14 is provided with a concave portion 14a in which the convex portion 15 can be inserted without contact in a circular arrangement.

The concave portion 14a side of the second magnet 14 is, for example, S
The convex portion 15 side of the first magnet 6 is also magnetized to the pole, for example, to the S pole. As shown in FIG. 3, the convex portion 15 side may be the N pole and the concave portion 14a side may be the N pole.

When the convex portion 15 and the concave portion 14a are magnetized as described above, a repulsive force acts between them. If the convex portions 15 and the concave portions 14a are magnetized to have different magnetic poles, an attractive force acts on the convex portions 15 and the concave portions 14a.

Contrary to the above case, the second magnet 1
The convex portion may be provided on the fourth side and the concave portion may be provided on the first magnet 6 side.

A rotor 16 made of a disk-shaped magnet is fitted on the upper part of the rotating body 11, and a stator 17 is fixedly arranged around the rotor 16 so that the rotating body 11 is rotated.
A drive motor 18 for driving the Here, when a current flows through the stator 17, starting torque with the rotor 16 is sequentially generated, and the entire rotating body 11 in which the rotor 16 is fitted rotates.

According to the optical scanning device 50 incorporating the magnetic bearing device 1 described above, when the rotating body 11 having the polygon mirror 12 having the light reflecting surface on the outer peripheral surface is mounted to be rotationally driven by the drive motor 18. , The repulsive force acts between the first magnet 6 and the second magnet 14, and the rotating body 11 tries to escape in the radial direction, but since the repulsive action also acts between the convex portion 15 and the concave portion 14a, The amount of positional deviation in the radial direction can be regulated by the amount of the gap between the convex portion 15 and the concave portion 14a, whereby the rotational unevenness in the radial direction of the polygon mirror 12 and the rotating body 11 can be reduced.

4 and 5 show the convex portion 15 and the concave portion 14a.
As shown in FIG. 4, a rectangular convex portion 15a is provided on the first magnet 6 side, and a concave portion 14b corresponding to the convex portion 15a is provided on the second magnet 14 side. Can be implemented.

Also in this case, the magnetic poles of the convex portions 15a and the concave portions 14b can have the same or different polarities, and the convex portions 15a and the concave portions 14b can be arranged upside down. .

FIG. 5 shows a semi-circular convex portion 1 on the side of the first magnet 6.
5b shows a case in which a concave portion 14c corresponding to the convex portion 15b is provided on the second magnet 14 side.

Also in this case, the magnetic poles of the convex portions 15b and the concave portions 14c can have the same polarity or different polarities, and the convex portions 15b and the concave portions 14c can be arranged upside down. .

FIG. 6 shows a magnetic bearing device 20 in which the number of parts is reduced. This magnetic bearing device 20 is
The magnetic bearing device 1 that receives the thrust load of the rotating body 11.
The same first magnet 21 as in the above case is provided with the same convex portion 21a as in the above case, and at the center of the rotor 31 constituting the drive motor 30 mounted on the outer periphery of the rotating body 11,
A second magnet 33 having a recess 34 similar to that described above is concentrically arranged on the lower surface side, and a stator 32 constituting the drive motor 30 is fixedly arranged around the rotor 31. As shown in FIG. 7, the outer circumference of the rotor 31 is magnetized to N and S poles at a predetermined pitch.

Further, as a magnetic bearing device 60 for reducing the number of parts, there is a device shown in FIGS. 9 and 10.
Here, the stator 32 that constitutes the drive motor 30 is fixedly arranged around the first magnet 21, and the rotor 31 is attached to the N and S poles at a predetermined pitch as shown in FIG. is doing.

In such a magnetic bearing device 20, 60, the convex portion 21a side of the first magnet 21 and the concave portion 34 of the second magnet 33 are magnetized to the same magnetic pole or different magnetic poles. As a result, as in the case described above, it is possible to reduce uneven rotation of the rotating body 11 in the radial direction.

Further, according to the magnetic bearing device 20, the second magnet 33 on the side of the rotating body 11 is integrally constructed so as to also serve as the rotor 31 of the drive motor 30 for driving the rotating body 11. It is possible to eliminate an independent magnet that faces the magnet 21 of FIG. 1 and thus reduce the number of parts.

FIG. 8 shows a radial type magnetic bearing device 40, which is a rotating body 41 fitted around the fixed shaft 9.
The second magnet 44 having the convex portion 44a projecting laterally on the outer periphery of the second magnet 44 is arranged all around, and the convex portion 44a is in a non-contact state around the second magnet 44 on the main body 5 side. An annular first magnet 42 having a concave portion 42a that is recessed in is provided on the inner circumference.

According to this magnetic bearing device 40, the convex portion 44a side and the concave portion 42a side are magnetized to the same magnetic pole or different magnetic poles, thereby reducing the rotational unevenness of the rotating body 11 in the radial direction. be able to. Further, it is possible to improve the positioning accuracy in the thrust direction.

The present invention can be variously modified within the scope of its gist other than the above-mentioned embodiment.

For example, an electromagnet can be used as the first magnet 6 arranged in a fixed state.

[0045]

According to the present invention described in detail above, the following effects can be obtained.

According to the first aspect of the present invention, the displacement of the rotating body with respect to the bearing portion can be prevented by the magnetic action in the non-contact state between the convex portion and the concave portion, whereby uneven rotation of the rotating body is reduced. It is possible to provide a magnetic bearing device capable of performing the above.

According to the second aspect of the present invention, it is possible to provide a magnetic bearing device that functions as a thrust load and that can reduce uneven rotation of the rotating body in the radial direction.

According to the third aspect of the present invention, it is possible to provide a magnetic bearing device that functions as a radial load and that improves the positioning accuracy of the rotor in the thrust direction.

According to the invention described in claim 4, it is possible to eliminate an independent magnet facing the bearing portion.
A magnetic bearing device that can reduce the number of parts can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing an apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a convex portion and a concave portion in the device according to the embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of another example of the convex portion and the concave portion in the device of the embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view of still another example of the convex portion and the concave portion in the device of the embodiment of the present invention

FIG. 5 is an enlarged cross-sectional view of still another example of the convex portion and the concave portion in the device of the embodiment of the present invention

FIG. 6 is a partial sectional view of another example of the apparatus according to the present invention.

FIG. 7 is a perspective view showing a second magnet in another example of the apparatus according to the present invention.

FIG. 8 is a partial cross-sectional view of still another example of the apparatus according to the present invention.

FIG. 9 is a partial cross-sectional view of still another example of the apparatus according to the present invention.

FIG. 10 is a perspective view showing a second magnet of still another example of the apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic bearing device 5 Main body 6 First magnet 11 Rotating body 12 Polygon mirror 14 Second magnet 14a Recessed portion 15 Convex portion 50 Optical scanning device

Claims (4)

[Claims] 1. A magnetic bearing device in which magnets are arranged so as to face a rotating body and a bearing portion, respectively, and the rotating body is axially supported in a non-contact manner by magnetic force between the magnets. A magnetic bearing device comprising a convex portion on one side and a concave portion into which the convex portion is inserted in a non-contact state on the other side. 2. The thrust load of the rotating body is received by the respective magnets arranged to face the rotating body and the bearing portion, respectively, and the magnetic action between the convex portion and the concave portion of the facing portion of each magnet causes the rotating body to move. The magnetic bearing device according to claim 1, wherein the magnetic bearing device suppresses movement in a radial direction. 3. The radial load of the rotor is received by the magnets arranged to face the rotor and the bearing portion, respectively, and the magnetic action between the protrusions and recesses of the facing portions of the magnets causes the rotor to rotate. The magnetic bearing device according to claim 1, wherein the magnetic bearing device suppresses movement in the thrust direction. 4. The magnet on the rotating body side also serves as a rotor of a drive motor for driving the rotating body.
The magnetic bearing device according to any one of claims 1 to 3.