JPH085945A - Light deflecting device - Google Patents

Abstract

PURPOSE:To stabilize the rotation of a driving motor rotating a rotary polygon mirror against vibration or shock and to prevent the inertial force of a rotating body from getting large. CONSTITUTION:In addition to 3rd and 4th permanent magnets 44 and 45 provided at the lower parts of a rotating sleeve 33 and the fixed shaft 32 of the driving motor, a 1st permanent magnet 38 is provided at the upper end of the fixed shaft 32 and a 2nd permanent magnet 40 is provided at the center part of a cover member 39 provided at the upper end of the sleeve 33 so that they may repulse each other. An air accumulation 41 is formed between the rotating sleeve 33 and the upper end of the fixed shaft 32. Then, the rotation is stabilized by large repulsive force and the inertial force is prevented from getting large by making the 3rd magnet 44 small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector having a rotary polygon mirror for deflecting and scanning light.

[0002]

2. Description of the Related Art In a conventional optical deflector, as shown in FIG. 4, a rotor 5 is attached to a fixed shaft 4 made of a ceramic material which is raised from a housing 3 having a stator 2 of a drive motor 1.
A rotary sleeve 6 made of a ceramic material is rotatably fitted to the rotary sleeve 6. A rotary polygon mirror 7 is attached to the rotary sleeve 6, and a cover 8 is attached to the upper end and a permanent magnet 9 is attached to the lower end. On the other hand, the permanent magnet 10 is fixed to the housing 3 so that different kinds of magnetic poles face the permanent magnet 9, and the permanent magnets 9 and 10 repel each other so that the permanent magnet 10 is interposed between the fixed shaft 4 and the cover 8. It is known that the air pocket 11 is formed.

The cover 8 is provided with a hole 13 provided with a detachable plug 12, and when the fixed shaft 4 and the rotary sleeve 6 are fitted together, the plug 12 is fitted with the plug 12 removed.
The air in the rotary sleeve 6 flows out from the hole 13 and can be fitted easily. The rotary sleeve 6 is supported in the radial direction by the air film between the rotary sleeve 6 and the fixed shaft 4 during rotation, and the permanent magnet 9 It is supported in the thrust direction by the repulsive force of 10. Air reservoir 1 sealed by plug 12
The air in 1 acts so as to damp the vertical vibration of the rotary sleeve 6, and holds the rotary sleeve 6 in the floating position.

[0004]

However, as in the above-mentioned conventional example, in a ceramic bearing which has very good slidability and is suitable for high speed rotation, as a magnetic repulsive force and an air damper for regulating the thrust direction. In the case of using an air pocket that acts, a relatively large magnetic repulsive force and an air damper force that balances with the magnetic repulsive force are required to stabilize external forces such as vibration and shock. For that purpose, it is preferable to make the permanent magnet 9 provided under the rotating sleeve 6 large, but on the other hand, the inertial force of the rotating body becomes large,
It has the drawback of delaying the rise time of the drive motor.

An object of the present invention is that the rotation of a drive motor for rotating a rotary polygon mirror is stable against vibration and shock,
Moreover, it is an object of the present invention to provide an optical deflecting device in which the inertial force of the rotating body does not increase.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, an optical deflector according to the present invention is an optical deflector in which a rotary polygon mirror is rotationally driven to deflect light, and a fixed shaft and a rotary sleeve are made of a ceramic material. A cover member is attached to the upper end of the rotary sleeve so as to form an air pocket, a first permanent magnet is provided in the center of rotation above the fixed shaft, and the cover member is provided with the first permanent magnet. A second permanent magnet that repels the magnet is provided, a third permanent magnet is provided at an outer peripheral portion on the lower side of the fixed shaft, and a fourth permanent magnet that repels the third permanent magnet is provided at a lower end portion of the rotating sleeve. It is characterized by having a permanent magnet of.

[0007]

The optical deflecting device having the above-described structure has the first and second
The repulsive force between the permanent magnets and the repulsive force between the third and fourth permanent magnets repels with a large force so that the inertial force of the rotating body does not become large by providing the second permanent magnet in the rotation center part. To

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a schematic configuration diagram of the embodiment, in which a laser unit 21 is provided on a frame 20, the laser light emitted from the laser unit 21 is deflected and scanned by a rotary polygon mirror 22, and an imaging lens 23 is formed.
The photoconductor 24 is scanned via a and 23b.

FIG. 2 is a schematic view of the main part of a drive motor having a rotary polygon mirror. The motor housing 3 on the frame 20
1, the motor housing 31 is provided with a substantially vertical fixed shaft 32 made of a ceramic material. A rotary sleeve 33, which is also made of a ceramic material, is rotatably fitted to the fixed shaft 32, and a flange 34 made of a non-magnetic metal material such as aluminum or brass is fitted on the rotary sleeve 33 by, for example, shrink fitting. It is installed by. A drive magnet 35 is attached to the outer circumference of the flange 34 by adhesion or the like.

A motor board 36 having electric components is mounted on the upper surface of the motor housing 31, and a stator 37 having a coil facing the drive magnet 35 is arranged on the board 36 to form a drive motor. The rotary polygon mirror 22 is fitted on the upper surface of the flange 34 and fixed by a leaf spring.

A recess is provided at the center of rotation at the upper end of the fixed shaft 32, and a disk-shaped first permanent magnet 38 is fitted in this recess. In addition, a cover member 39 that closes the upper end is provided on the upper end of the rotary sleeve 33, and a second permanent magnet 38 and the second permanent magnet 38 repel each other through a hole provided in the center of the cover member 39.
The permanent magnet 40 of FIG. An air reservoir 41 is formed between the cover member 39 and the upper end of the fixed shaft 32. The cover member 39 is provided with an air vent hole 43 provided with a sealing plug 42 for fitting the fixed shaft 32 into the rotary sleeve 33.

A third permanent magnet 44 having the same shape as the cross section of the rotary sleeve 33 is attached to the lower end of the rotary sleeve 33, and a fourth permanent magnet 45 repulsive to the third permanent magnet 44 is formed in a ring shape. It is formed and attached to the bottom of the gap between the motor housing 31 and the fixed shaft 32.

In the optical deflecting device thus constructed, when the rotary sleeve 33 is rotated by the drive motor, the fixed shaft 3 is rotated.
An air film is formed on the mating surface with 2, and the radial direction is supported without contact. On the other hand, the thrust direction is the cover member 39.
And the upper surface of the fixed shaft 32, the damper effect by the air pocket 41 and the repulsive force between the first and second permanent magnets 38 and 40 and between the third and fourth permanent magnets 44 and 45. Due to the large repulsive force, the rotary sleeve 33 can obtain a stable floating amount in the thrust direction.

Here, of the permanent magnets provided on the rotary sleeve 33 side, the second permanent magnet 40 is located at the center of rotation and the third permanent magnet 44 is located near the outer circumference, so By decreasing the magnetic flux density of the permanent magnet 44 as much as possible and increasing the magnetic flux density of the second permanent magnet 40 instead, the inertial force during rotation can be reduced without changing the repulsive force.

There is no problem even if the air vent hole 43 of the cover member 39 is omitted and the second permanent magnet 40 has a sealing function and is removable as shown in FIG.

In the above-mentioned embodiment, the inner rotor type motor, which is advantageous for high-speed rotation, has been described as an example, but it is also applicable to an outer rotor type surface-opposed motor.

[0017]

As described above, in the optical deflector according to the present invention, in addition to the fixed shaft of the drive motor and the third and fourth permanent magnets provided below the rotary sleeve, the fixed shaft and the rotary sleeve. Since a permanent magnet that repels each other in the thrust direction is also provided at the upper end of the, rotation can be stabilized by a large repulsive force. Since the second permanent magnet is provided at the center of rotation, the magnetic flux density of the third permanent magnet provided at the outer peripheral portion is reduced as much as possible, and instead, the magnetic flux density of the second permanent magnet is increased. It is possible to prevent the inertial force of the rotating body from increasing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram.

FIG. 2 is a main part configuration diagram of an embodiment.

FIG. 3 is a schematic configuration diagram of a main part of another embodiment.

FIG. 4 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 17 rotating polygon mirror 32 fixed shaft 33 rotating sleeve 38 first permanent magnet 39 cover member 40 second permanent magnet 41 air reservoir 44 third permanent magnet 45 fourth permanent magnet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taku Butada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hirofumi Hori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Shin Mogi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideyuki Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] 1. An optical deflecting device for rotating a rotary polygon mirror to deflect light, wherein a fixed shaft and a rotary sleeve are made of a ceramic material, and a cover member is formed at an upper end of the rotary sleeve to form an air pocket. Mounting, a first permanent magnet is provided at the center of rotation above the fixed shaft, and a second permanent magnet that repels the first permanent magnet is provided at the cover member. And a fourth permanent magnet that repels the third permanent magnet at the lower end of the rotary sleeve.