JPH0797184B2 - Rotation support device for polygon mirror - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary support device for a polygon mirror used in, for example, a laser printer, a bar code reader, a laser copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, many techniques relating to such a polygon mirror are known. Generally, the faster the rotation speed of the polygon mirror, the better the efficiency.
It rotates at a high speed like pm. When rotating at such a high speed, the polygon mirror, that is, the rotating body having a mirror surface is deformed by the centrifugal force. If the deformation is not uniform, the mirror surface becomes uneven, and the image is disturbed. In addition, when rotating at high speed, so-called rasping movements and shakes are likely to occur, and when such rasping movements occur, the image is naturally disturbed. Therefore, various supporting devices for the polygon mirror have been proposed.

For example, in the technique disclosed in Japanese Patent Laid-Open No. 59-28757, a metal is used for the sliding surface of the rotating body so that the thrust load is not applied. However, when the radial load increases at high speed rotation,
Normally, it is difficult to support the air film by the herringbone-shaped dynamic pressure generating groove, and the balance adjustment becomes difficult.

Therefore, the applicant of the present invention has proposed a Japanese Patent Application No. Sho 62/1987 which is capable of stable high speed rotation and capable of accurately reflecting a laser beam or the like.
-74496 (see Japanese Patent Laid-Open No. 63-241515).

In order to understand the present invention well, first, referring to FIG. 2, the prior art described in the above-mentioned Japanese Patent Laid-Open No. 63-241515 will be described.

For example, in a laser printer, laser light from a laser unit such as a semiconductor laser or a gas laser is reflected from a window 13 by a mirror 2 formed on the outer peripheral surface of a rotating body 3 and irradiates the surface of a photoconductor. And
A magnet 7 is attached to the rotor 3 as a backup ring 9
It is attached integrally with. The rotating body 3 receives a radial load by a fixed shaft 5 provided at its center, and its own weight is received by a thrust plate 10. Although not shown, there is also known one in which a thrust plate is provided on the upper part of the rotating body 3. The fixed shaft 5 and the thrust plate 10
A herringbone-shaped or spiral-shaped groove 11 is formed on the sliding surface thereof to support the thrust force by generating a dynamic pressure by an air film.

The fixed shaft 5 is fixed to the motor casing 4, and a stator coil 6 is provided on the motor casing so as to face the magnet 7.

In the prior art, since the mirror 2 is formed by vapor-depositing aluminum or the like, its accuracy (about several μ) is relatively difficult to obtain, and a plurality of circular magnets are used as a magnet, so that high speed is achieved. The magnet tended to deform during rotation. Therefore, the mirror surface of the rotating body is deformed, and the movement of the reflected light is disturbed.

It is also known to use an aluminum alloy formed in a polygonal shape to form a mirror surface (herein referred to simply as "made of aluminum"). However, aluminum alloys are relatively weak and easily deformed.

Further, Japanese Patent Laid-Open No. 224305/58 discloses a polygon mirror using a ceramic rotor, but does not disclose any countermeasure against the deformation of the polygon mirror due to high speed rotation.

Japanese Unexamined Patent Publication No. 62-27713 discloses a rotary support device for a polygon mirror, which is supported by a shaft sleeve provided on the outer periphery of a fixed shaft and thrust plates above and below the shaft sleeve. Since it is not a pressure bearing structure, stable rotation cannot be obtained.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 60-205523, since a rolling bearing is used, shake occurs during rotation, especially at high speed rotation, and as a result, a suitable image cannot be obtained.

[0013]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a polygon mirror rotation supporting device which does not cause non-uniform deformation due to high speed rotation and has no shake.

[0014]

[Observation] As a result of various researches by the present inventor, as described above, non-uniform deformation is not preferable, but when the rotor is uniformly deformed by centrifugal force, no problem occurs, and the deformation of the rotor is It has been found that non-uniform deformation can be prevented by the transmission path of the torque of the rotational force applied to the magnet.

[0015]

According to the present invention, a rotating body is provided on the outer periphery of a fixed shaft, a polygonal mirror surface is provided on the outer periphery of the rotating body, and a magnet for generating torque is integrated with the rotating body. In the rotation support device of the attached polygon mirror, a shaft sleeve is rotatably provided on the outer periphery of the fixed shaft,
The rotating body is supported by the shaft sleeve and upper and lower thrust plates, and the rotating body is a rotor made of ceramic rotatably provided on the outer periphery of the shaft sleeve,
An aluminum rotor, which is arranged on the outer circumference of the ceramic rotor and has a mirror-finished outer peripheral surface in the radial direction, and the ring-shaped magnet are adhered and fixed to the outer circumference of the ceramic rotor. And a yoke made of steel, wherein a dynamic pressure generating groove is formed on the outer circumference of the shaft sleeve, and a dynamic pressure generating groove is formed on the ceramic rotor side surface of the upper and lower thrust plates, The aluminum rotor and the yoke are attached by a holding bolt.

[0016]

Therefore, the rotation torque applied to the ring-shaped magnet is transmitted to the yoke to which the magnet is adhered. Since the aluminum rotor is attached to the yoke by the holding bolt, the aluminum rotor and the mirror surface formed on the outer peripheral surface thereof rotate. On the other hand, since the yoke is shrink-fitted to the ceramic rotor, the torque transmitted to the yoke is reliably transmitted to the ceramic rotor even during high speed rotation. The radial load of the ceramic rotor is supported by the shaft sleeve, and the axial thrust load is supported by the upper and lower thrust plates to rotate at high speed. Therefore, the ceramic rotor does not swing in the axial direction or the radial direction at the time of high speed rotation, and the aluminum rotor integrated with the ceramic rotor via the yoke, the holding bolt, etc. does not swing.

Therefore, the aluminum rotor having the mirror surface formed on the outer periphery does not have an unbalanced element, and if it is properly processed, it will not be unevenly deformed by rotation.

Although the aluminum rotor has a larger amount of deformation due to centrifugal force than the ceramic rotor, according to the present invention, the aluminum rotor is not shrink-fitted to the ceramic rotor and the centrifugal force is reduced. The difference in the deformation amount due to the force is relieved at the boundary surface between the ceramic rotor and the aluminum rotor, and the deformation of the aluminum rotor is prevented from becoming uneven due to the difference in the deformation amount.

Further, since the dynamic pressure generating groove is formed, when the ceramic rotor swings and the gap becomes narrow,
When the pressure in that portion becomes high and widens, the pressure becomes low, so that the ceramic rotor does not swing as a result.

As described above, the ceramic rotor whose yoke is shrink-fitted is rotated. However, the rotor made of ceramic is prevented from swinging, and the rotor made of aluminum is not constrained by the rotor made of ceramic. The rotor made of aluminum is uniformly deformed by the centrifugal force, and as a result, it is possible to obtain the rotation supporting device of the polygon mirror capable of rotating at a sufficiently high speed.

[0021]

Embodiments of the present invention will be described below with reference to FIG.

In FIG. 1, a rotation support device for a polygon mirror embodying the present invention comprises a motor casing 20, a coil substrate 21 is mounted on the upper surface of the motor casing 20 by retaining bolts 22, and a motor is formed therein. An iron core 23 and a coil 24 are installed. The fixed shaft 25 is provided at the center of the motor casing 20 with the lower stopper nut 2
The shaft sleeve 27 is provided with a herringbone-shaped dynamic pressure generating groove 27a on the outer periphery of the fixed shaft 25. On the outer circumference of the shaft sleeve 27, a ring-shaped ceramic rotor 28 that constitutes the rotating body R is rotatably provided. An upper thrust plate 29 and a lower thrust plate 30 made of ceramic are provided above and below the rotor made of ceramic 28 so as to receive the axial thrust load of the rotating body R. Spiral-shaped grooves 29a and 30a are formed on the ceramic rotor 28 side surfaces of the upper and lower thrust plates 29 and 30, respectively. A ring-shaped yoke 31 is formed on the outer periphery of the lower part of the ceramic rotor 28.
Has been shrunk. The yoke 31 is made of, for example, steel, and a ring-shaped magnet 33a is attached to the inside of a ring portion 32 extending downward by adhesion. Above the yoke 31, an aluminum rotor 33 having a polygonal plane shape from the outer peripheral surface and having a mirror surface M formed on the outer peripheral surface is arranged on the outer peripheral side of the ceramic rotor 28. Here, the rotor 28 made of ceramic
The aluminum rotor 33 and the aluminum rotor 33 are not shrink-fitted, and they are separated from each other at the boundary 34.

The yoke 31 and the rotor 33 made of aluminum are
The pressing bolt 35, the pressing ring 36, and an elastic plate member 37 made of rubber, for example, are used to integrally fix the members. In FIG. 1, reference numeral 38 denotes an upper lock nut for holding the shaft sleeve 27 and the ceramic rotor 28 between the upper and lower thrust plates 29 and 30.

In operation, the rotating torque is applied to the magnet 33a in a known manner by controlling the current flowing through the coil 24 of the motor by the coil board 21. This rotation torque is transmitted to the yoke 31, and the rotation torque of the yoke 31 is transmitted to the shrink-fitted ceramic rotor 28. Since the rotor 28 made of ceramic is supported by thrust plates 29, 30 having a shaft sleeve 27 inward in the radial direction in the up-down direction, that is, in the axial direction in the up-down direction, through an air film formed by a dynamic pressure generating groove, it substantially vibrates. Is less likely to occur.

On the other hand, the yoke 31 is a rotor 33 made of aluminum.
Since it is fixed integrally with the rotor 33 made of aluminum
And the mirror surface M formed on the outer peripheral surface also rotates. Here, as described above, since the ceramic rotor 28 is not shaken, the aluminum rotor 33 integrated with the ceramic rotor 28 by the yoke 31, the holding bolt 35, etc. also causes a shake or a rasping motion. Rotate without.

The amount of deformation caused by the centrifugal force of the high speed rotation is larger in the aluminum rotor 33 than in the ceramic rotor 28, but the difference is eased at the boundary 34. Therefore, the difference in the deformation amount due to the centrifugal force does not adversely affect the uniform deformation of the aluminum rotor 33.

The aluminum rotor 33 is fixed to the yoke 31 integrally with the pressing bolt 35, the pressing ring 36, and the elastic plate body 37 by applying a uniform fastening force over the entire circumference thereof. Therefore, the rotor 33 made of aluminum
In, there is no local stress due to uneven distribution of fastening force, and the deformation is relatively uniform due to centrifugal force.

Further, since the yoke 31 made of steel is shrink-fitted to the rotor 28 made of ceramics, and the difference between the two deformation amounts due to centrifugal force is relatively small, the shrink-fitting force is released even at high speed rotation. There is no such thing.

[0029]

As described above, the present invention has the following excellent effects.

(1) Since the aluminum rotor is not directly connected to the ceramic rotor, there is no influence due to the difference in deformation between the two rotors.

(2) Since the ceramic rotor is supported by the fixed shaft in the radial direction and the thrust plate in the vertical direction, there is no wobbling or rasping motion, and correct rotation can be performed at high speed.

(3) Since the aluminum rotor is not stressed by the ceramic rotor and the yoke, there is no uneven deformation due to centrifugal force.

(4) Balance adjustment may be performed by adding or deleting mass to the yoke, and it is not necessary to process both rotors, and balance adjustment is easy.

(5) Due to the dynamic pressure generating groove, the deflection of the ceramic rotor is reliably prevented because the pressure increases when the gap becomes narrower and decreases when the gap becomes wider.

(6) At the time of assembly, the aluminum rotor may be installed on the yoke and attached by bolts, and therefore the aluminum rotor can be easily attached and detached.

(7) Therefore, even if the polygon mirror is rotated at a high speed, the polygon mirror is not deformed unevenly and a correct image can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional front view showing an embodiment of a rotary support device for a polygon mirror of the present invention.

FIG. 2 is a sectional front view showing a prior art.

[Explanation of symbols]

25 ... Fixed shaft 27 ... Shaft sleeve 28 ... Ceramic rotor 29 ... Upper thrust plate 30 ... Lower thrust plate 31 ... Yoke 33a ... Magnet 33 ... Aluminum Of the rotor 34 ... Boundary between the rotor made of ceramic and the rotor made of aluminum 35 ... Pressing bolt 36 ... Pressing ring 38 ... Elastic plate M ... Mirror surface R ... Rotating body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiya Kanamori 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Inside the EBARA CORPORATION (56) References JP-A-63-48511 (JP, A) JP-A-SHO 63-81316 (JP, A)

Claims (1)

[Claims] 1. A rotary support device for a polygon mirror, wherein a rotating body is provided on the outer periphery of a fixed shaft, a polygonal mirror surface is provided on the outer periphery of the rotating body, and a magnet for torque generation is integrally attached to the rotating body. A shaft sleeve is provided on the outer circumference of the fixed shaft, the rotating body is supported by the shaft sleeve and upper and lower thrust plates, and the rotating body is made of a ceramic rotatably provided on the outer circumference of the shaft sleeve. A rotor, an aluminum rotor arranged on the outer circumference of the ceramic rotor and having the mirror surface processed on the outer circumferential surface in the radial direction, and the ring-shaped magnet are bonded to the rotor A dynamic pressure generating groove is formed on the outer periphery of the shaft sleeve, and a ceramic rotor-side surface of the upper and lower thrust plates. A rotary support device for a polygon mirror, wherein a dynamic pressure generating groove is formed, and the aluminum rotor and the yoke are attached by a holding bolt.