JPH11218713A - Magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive optical deflector having the reduced number of parts by reducing the number of components of a magnetic bearing and manufacturing cost. SOLUTION: A supporting shaft material 22 formed by a permanent magnet material is fixed on a housing 20 and a non-magnetic member 24 is formed on the outer periphery of the material 20. A non-magnetic member 28 is formed on the inner periphery of a sleeve 26 formed by a permanent magnet material and the sleeve 26 and the material 22 are rotatably engaged with each other through a bearing gap K between both the non-magnetic members 28, 24. A magnetic bearing for supporting the axial direction of the sleeve 26 is formed by floating the sleeve 26 to be a rotary member on a fixed position by suction force generated between the sleeve 26 and the material 22 which are magnetized in mutually reversed directions of the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing suitable for an optical deflector used in an image forming apparatus such as a laser beam printer and an electrophotographic copying machine.

[0002]

2. Description of the Related Art A conventional example of an optical deflector will be described below.

In a digital image forming apparatus, an image carrier is generally scanned by a light beam such as a laser beam from a light source to read the image, or a recording medium is scanned by a light beam modulated by an image signal or a character signal. Images are recorded.

As means for scanning a light beam, an optical deflector comprising a rotary polygon mirror having a plurality of reflection surfaces on its outer periphery and a drive motor for rotating the rotary polygon mirror is used. A rotating polygon mirror is configured to scan a recording member, which is a scanning object, with a laser beam at a constant speed to form a line image.

[0005] An optical deflector of this type is formed by a bearing such as a dynamic pressure air bearing or a ball bearing, a permanent magnet attached to a rotating member, and an electromagnetic coil wound around an annular core around a fixed member. There is known a drive motor that generates a rotational torque by a magnetic circuit to be provided and a magnetic motor that holds a rotating member in an axial direction.

FIG. 5 and FIG. 6 are views for explaining the schematic structure of a conventional optical deflector. As shown in FIGS. 5 and 6, a search coil 112 for detecting the number of rotations is formed on the circuit board 110, and the drive coil 38 and the magnetic pole detection element 11 are formed.
4 are arranged in plurality.

FIG. 5 shows the structure of a dynamic air bearing. That is, air dynamic pressure is generated in the bearing gap K between the dynamic pressure generating groove 122A formed in the support shaft 122 and the sleeve 124 rotating around the support shaft 122. Accordingly, when the rotating member such as the sleeve 124 rotates, the radial direction of the rotating member is supported in a non-contact manner.

A magnetic circuit required for rotation is formed between the permanent magnet 126 for rotational drive and the yoke 36. That is, the plurality of magnetic poles of the permanent magnet 126 are
And the drive member 38 is energized by predetermined timing logic to rotate the rotating member.
At this time, the rotational speed is controlled to be constant by using the fluctuation component of the voltage induced in the fixed-side search coil 112 by the permanent magnet 128 for detecting the rotational speed of the rotating member shown in FIG. 5 as a detection signal.

Further, FIG. 1 shows that the rotating member is fixed by an attractive force generated between the rotating permanent magnet 132 and the fixed permanent magnet 134, which are magnetized in the axial direction and opposite to each other. The structure of the magnetic bearing which floats at the position of and supports the rotating member in the axial direction is shown. In addition, there are a bearing composed of a magnet and a magnetic material, a bearing floated by the dynamic pressure action of air, and the like.

On the other hand, as conventional examples of a magnetic bearing for holding a rotating member along an axial direction, there are Japanese Patent Application Laid-Open Nos. 60-55316, 60-244913, and 62-8.
No. 5216 gazette.

That is, Japanese Patent Application Laid-Open No. Sho 60-55316 discloses a structure in which a plurality of permanent magnets are stacked on the rotating side and the fixed side, respectively, to increase the attraction force. Japanese Patent Application Laid-Open No. Sho 60-244913 discloses a structure in which an attractive force is generated between a magnetic body attached to the upper and lower surfaces of each permanent magnet on the fixed side and a magnetic body on the rotating side. ing. Japanese Patent Application Laid-Open No. 62-85216 discloses a structure in which a magnetic material is attached to the upper and lower surfaces of the rotating and fixed permanent magnets to increase the attraction force.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The structure disclosed in Japanese Patent Publication No. 316 is effective in that a plurality of permanent magnets are overlapped on the rotating side and the fixed side, respectively, so that the attractive force is increased and the axial vibration of the rotating member is prevented. However, it could not be said to be an appropriate structure from the viewpoint of manufacturing cost.

Further, an attraction force is generated between a magnetic material attached to the upper and lower surfaces of each permanent magnet on the fixed side and a magnetic material on the rotating side disclosed in Japanese Patent Application Laid-Open No. 60-244913. Japanese Patent Application Laid-Open No. Sho 62-85216 discloses a magnet in which an attractive force is generated between magnetic bodies attached to the upper and lower surfaces of the rotating and fixed permanent magnets. These can be said to be more magnetically efficient than the conventional example in terms of the magnetic permeability and the saturation magnetic flux density of the magnetic material.

However, these are also disclosed in Japanese Unexamined Patent Publication No.
As in the case of Japanese Patent No. 55316, the structure was not always appropriate from the viewpoint of manufacturing cost.

The present invention has been made in view of the disadvantages of the related art, and has as its object to provide a magnetic bearing that can reduce manufacturing costs.

[0016]

According to a first aspect of the present invention, there is provided a magnetic bearing comprising: a rotary polygon mirror having a plurality of reflection surfaces on its outer periphery; and a rotary polygon mirror having one of a shaft member and a sleeve fitted with each other. A dynamic pressure air bearing with the other rotating member and the other as a fixed member, a drive coil wound around the fixed member and installed, a driving permanent magnet attached to the rotating member and generating a rotational torque with the drive coil, A magnetic bearing used for an optical deflector having a shaft member and a sleeve formed of a permanent magnet material.

The magnetic bearing according to the second aspect is characterized in that the shaft member and the sleeve are respectively magnetized in the axial direction and in mutually opposite directions.

A magnetic bearing according to a third aspect is characterized in that a non-magnetic material is formed on the outer peripheral side of the shaft member and on the inner peripheral side of the sleeve, respectively.

A magnetic bearing according to a fourth aspect is characterized in that a driving permanent magnet is integrally formed on a rotating member of the shaft member and the sleeve.

A magnetic bearing according to a fifth aspect is characterized in that the shaft member is a fixed member, and the shaft member is formed by a hollow member.

The operation of the magnetic bearing according to claim 1 will be described below. An optical deflector to which the magnetic bearing of the present invention is applied,
There is a dynamic pressure air bearing in which one of the shaft member and the sleeve that are fitted to each other is a rotating member to which a rotating polygon mirror is attached, and the other is a fixed member. Further, each of the shaft member and the sleeve is formed of a permanent magnet material, and constitutes a magnetic bearing that levitates the rotating member by these magnetic forces.

A drive coil is wound around a fixed member, and a drive permanent magnet for generating a rotational torque with the drive coil is mounted on the rotary member.

Accordingly, the rotating member is rotated by the driving coil and the driving permanent magnet, and the rotating polygon mirror having a plurality of reflecting surfaces on the outer periphery is rotated, and functions as an optical deflector.

Accordingly, the shaft member and the sleeve are each formed of a permanent magnet material, and the rotating member is levitated by the shaft member and the sleeve. Therefore, the number of components of the magnetic bearing can be reduced, and the number of components of the magnetic bearing can be reduced. Manufacturing costs can be reduced.

The operation of the magnetic bearing according to claim 2 will be described below. The present invention has the same effect as the first embodiment. Further, the present invention has a configuration in which the shaft member and the sleeve are respectively magnetized in the axial direction and in mutually opposite directions.

Therefore, not only is the shaft member and the sleeve made of permanent magnet material, but also the shaft member and the sleeve are magnetized in the axial direction and opposite to each other. As a result, the rotating member can be floated more reliably, and similarly to the first aspect, the number of components of the magnetic bearing can be reduced, and the manufacturing cost of the magnetic bearing can be reduced.

The operation of the magnetic bearing according to claim 3 will be described below. The present invention also has the same effect as the first and second aspects. Further, the present invention has a configuration in which a nonmagnetic material is formed on the outer peripheral side of the shaft member and the inner peripheral side of the sleeve, respectively.

Therefore, the dynamic pressure air bearing can be easily manufactured by suppressing the attraction force of the shaft member and the sleeve due to the magnetic force in the radial direction with the non-magnetic material, and providing the groove portion in the non-magnetic material in which the groove is easily formed. And the manufacturing cost can be further reduced.

The operation of the magnetic bearing according to claim 4 will be described below. The present invention also has the same effect as the first to third aspects. Further, the present invention has a configuration in which a driving permanent magnet is formed integrally with a rotating member of the shaft member and the sleeve.

Therefore, by integrally forming the driving permanent magnet with the rotating member of the shaft member and the sleeve formed of the permanent magnet material, the number of assembling steps of the magnetic bearing can be reduced, and the manufacturing is completed. Costs can be further reduced.

The operation of the magnetic bearing according to claim 5 will be described below. The present invention has the same effect as the first embodiment. Furthermore, the present invention has a configuration in which the shaft is a fixed member, and the shaft is formed of a hollow member.

Therefore, the shaft material can be easily fixed to the housing by bonding or the like simply by applying an adhesive to the hollow inner peripheral side of the shaft material, and the manufacturing cost can be further reduced.

[0033]

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

FIG. 4 is a diagram for explaining the outline of image recording in the image forming apparatus. As shown in this figure,
A light beam emitted from a laser 12 such as a semiconductor laser or a gas laser is modulated by an image signal or the like by a modulation means (not shown), and is rotated by a driving motor 30 through a collimator lens 14 in a direction indicated by an arrow A. Is incident on the reflecting mirror surface of.

The light beam reflected by the reflecting mirror surface of the rotating polygon mirror 32 is deflected in the direction of arrow B with the rotation of the rotating polygon mirror 32 in the direction of arrow A, and is directed to the recording member 18 through the converging optical system 16 which is a lens. The projected image is scanned on the recording member 18.

Along with this, the sub-scanning is performed by the rotation of the recording member 18 in the direction of arrow C, and a two-dimensional image is written on the recording member 18.

FIGS. 1 and 2 show a schematic configuration of the present embodiment. As shown in FIGS. 1 and 2, a cylindrical support shaft member 22 made of a permanent magnet material is fixed to a housing 20 constituting a frame of the optical deflector 10 by, for example, an adhesive. A non-magnetic member 24 coated with a non-magnetic material is formed on the outer periphery of the shaft member 22. A groove 24 </ b> A for generating dynamic pressure is formed on the outer peripheral side of the non-magnetic member 24.

On the other hand, a non-magnetic member 28 coated with a non-magnetic material is formed on the inner periphery of a sleeve 26 formed of a permanent magnet material in a sleeve shape.
The sleeve 26 and the support shaft member 22 are rotatably fitted via a bearing gap K between the magnetic member 8 and the magnetic member 24.

Therefore, the support shaft member 22 and the sleeve 2
6 constitutes a dynamic pressure air bearing that generates dynamic pressure by rotation, the sleeve 26 is a rotating member, and the support shaft 22 is a fixed member.

As shown in FIG. 1, the sleeve 26, which is a rotating member, is moved by the attraction force generated between the sleeve 26 and the support shaft 22, which are magnetized in the axial direction and opposite to each other. Floating at a certain position, sleeve 2
6, a magnetic bearing for supporting in the axial direction is formed. That is, the magnetic deflector 10 can be reduced in size by moving the magnetic bearing to the inner peripheral side close to the dynamic pressure air bearing.

At this time, the non-magnetic member 24 and the non-magnetic member 2
8, a constant distance is provided between the support shaft member 22 and the sleeve 26, so that direct contact between the support shaft member 22 and the sleeve 26 due to the magnetic force in the radial direction can be eliminated, and the attraction force can be suppressed. Therefore, it is possible to form a dynamic pressure air bearing with less influence on the dynamic pressure generating action.

As described above, the magnetic bearing for floating the sleeve 26 and the dynamic pressure air bearing for radial support can be integrally formed.

As shown in FIG. 1, on the outer peripheral side of the sleeve 26, a permanent magnet portion 26A for rotation, which is a driving permanent magnet, is made of the same material as the permanent magnet material forming the sleeve 26. And are formed integrally with it.

As described above, the sleeve 26 and the permanent magnet 26
Compared with the assembly of the magnetic bearing formed separately from A, the man-hour for assembling the magnetic bearing can be reduced.

As shown in FIG. 3 showing the magnetization pattern of the sleeve 26 and the permanent magnet portion 26A, the sleeve 2 on the inner circumferential side
The six portions are magnetized to a single pole as a magnetic bearing, and the portion of the permanent magnet portion 26A extending in a flange shape on the outer peripheral side is magnetized to a plurality of poles (in this case, eight poles) based on rotation logic. .

That is, the sleeve 26 and the permanent magnet 2
6A has both the function of a magnetic bearing and the function of a drive motor 30 that drives and rotates the sleeve 26 by generating a rotational torque by a magnetic circuit while being integral.

A rotary polygon mirror 32 having a plurality of reflection surfaces is fitted on the outer peripheral side of the sleeve 26, and the leaf spring 3
4, the rotating polygon mirror 32 is fixed while being pressed against the permanent magnet portion 26A.

On the other hand, a circuit board 36 having a hole 36A in the center is disposed on the housing 20, and a drive coil 38 is provided between the circuit board 36 and the housing 20. Then, the housing 20 and the drive coil 3
A yoke 42 formed in a ring shape is disposed between the yoke 42.

That is, the drive coil 38 is arranged to face the permanent magnet portion 26A with the circuit board 36 interposed therebetween, and a plurality of magnetic poles for detecting a plurality of magnetic poles of the permanent magnet 26A are provided on the outer peripheral side of the permanent magnet portion 26A. A detection element 44 is provided.

Next, the operation of the magnetic bearing according to this embodiment will be described below. In the optical deflector 10 to which the magnetic bearing of the present embodiment is applied, the support shaft member 22 and the sleeve 26 of the sleeve 26 that are fitted to each other are used as rotating members to which the rotating polygon mirror 32 is attached, and the support shaft member It has a dynamic pressure air bearing with 22 as a fixing member. Furthermore, these support shaft members 22
And the sleeve 26 are each formed of a permanent magnet material, and the support shaft member 22 and the sleeve 26 are respectively magnetized in the axial direction and in mutually opposite directions, so that the magnetic force causes the sleeve 26 to float. I have.

A drive coil 38 is wound around the housing 20 as a fixed member, and a permanent magnet 26A that generates a rotational torque with the drive coil 38 is attached to the rotary member.

Accordingly, the drive coil 38 and the permanent magnet section 26
A causes the rotating member to rotate, so that the rotating polygon mirror 32 having a plurality of reflecting surfaces on the outer periphery is rotated, and functions as the optical deflector 10.

Accordingly, the support shaft 22 and the sleeve 26 are not only formed by the permanent magnet material, but also the support shaft 22 and the sleeve 26 are magnetized in the axial direction and opposite to each other. Therefore, the sleeve 26 itself is levitated by the support shaft member 22 and the sleeve 26. Therefore, the number of components of the magnetic bearing can be reduced, and the manufacturing cost of the magnetic bearing can be reduced.

In this embodiment, the non-magnetic materials 24, 2 are provided on the outer peripheral side of the support shaft member 22 and the inner peripheral side of the sleeve 26.
8 are formed respectively. Therefore, the nonmagnetic materials 24 and 28 suppress the attraction force of the support shaft member 22 and the sleeve 26 due to the magnetic force in the radial direction. The compressed air bearing can be easily manufactured, and the manufacturing cost can be further reduced.

Further, in the present embodiment, the support shaft 22
The permanent magnet portion 26A is formed integrally with the sleeve 26, which is a member on the rotating side of the sleeve 26.
Therefore, by integrally forming the rotating member of the support shaft member 22 and the sleeve 26 formed of the permanent magnet material with the permanent magnet portion 26A, the number of assembling steps of the magnetic bearing can be reduced, and the manufacturing is completed. Costs can be further reduced.

On the other hand, in the present embodiment, the support shaft 22 is used as a fixing member, and the support shaft 22 is formed of a cylindrical hollow member. The support shaft member 22 can be easily fixed to the housing 20 only by applying, and the manufacturing cost can be further reduced.

The present invention is not limited to the above embodiment. In this embodiment, the configuration in which the sleeve rotates is described. However, it is needless to say that the present invention can be applied to a case where the shaft is rotated.

That is, the support shaft member 22 constituting the magnetic bearing
Although the sleeve 26 of the sleeve 26 is used as a rotating member and the support shaft 22 is used as a fixed member, the structure may be reversed.

[0059]

As described above, according to the present invention, it is possible to provide a compact and low-cost optical deflector with a reduced number of components and a reduced number of components and a reduced number of components of a magnetic bearing. Become.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing one embodiment of the present invention, in which a groove for generating dynamic pressure is shown.

FIG. 3 is a configuration diagram showing a magnetization pattern according to one embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an image forming apparatus to which an embodiment of the present invention has been applied.

FIG. 5 is a schematic configuration diagram of a conventional optical deflector.

FIG. 6 is a schematic configuration diagram of rotation signal detection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Optical deflector 22 Support shaft material 26 Sleeve 26A Permanent magnet part 38 Drive coil 30 Drive motor 32 Rotating polygon mirror

Claims (5)

[Claims] A dynamic pressure having a rotating polygonal mirror having a plurality of reflecting surfaces on its outer periphery, one of a shaft member and a sleeve to be fitted to each other being a rotating member to which the rotating polygonal mirror is attached, and the other being a fixed member. A magnetic bearing used for an optical deflector comprising: an air bearing; a drive coil wound around a fixed member and installed; and a drive permanent magnet attached to a rotating member and generating a rotational torque by the drive coil. A magnetic bearing, wherein the shaft member and the sleeve are made of a permanent magnet material. 2. The magnetic bearing according to claim 1, wherein the shaft member and the sleeve are respectively magnetized in the axial direction and in mutually opposite directions. 3. A non-magnetic material is formed on an outer peripheral side of a shaft member and an inner peripheral side of a sleeve, respectively.
Alternatively, the magnetic bearing according to claim 2. 4. The magnetic bearing according to claim 1, wherein a driving permanent magnet is integrally formed on a rotating member of the shaft member and the sleeve. 5. The magnetic bearing according to claim 1, wherein the shaft member is a fixed member, and the shaft member is formed of a hollow member.