JPH085951A - Light deflection device - Google Patents

Abstract

PURPOSE:To eliminate the delay in rising at the time of starting a driving motor and to reduce the cost. CONSTITUTION:A disk-shaped permanent magnet 30 is mounted at the inside of the top end of a revolving sleeve 23 of the driving motor mounted with a rotary polyhedral mirror 28 and a permanent magnet 31 facing this permanent magnet 30 is mounted at the top end of a stationary shaft 22 fixed to a housing 21 in such a manner that both repulse each other. The revolving sleeve 23 is floated by the repulsive force of the permanent magnets 30, 31 to form an air reservoir between the revolving sleeve 23 and the top end of the stationary shaft 22. The permanent magnet 30 smaller than the permanent magnet of the conventional device is used on the rotor side to make inertia force small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus using a laser beam or the like, and an optical deflector having a rotating polygon mirror for scanning a laser beam on a photosensitive member.

[0002]

2. Description of the Related Art In a conventional optical deflector, as shown in FIG. 7, a fixed shaft 4 made of a ceramic material raised from a housing 3 provided with a stator 2 of a drive motor 1 and a rotor 5 are provided.
A rotary sleeve 6 made of a ceramic material is rotatably fitted, a rotary polygon mirror 7 is attached to the rotary sleeve 6, a cover 8 is attached to the upper end of the rotary sleeve 6, and a permanent magnet 9 is attached to the lower end. ing. Further, the permanent magnet 10 is fixed to the housing 3 such that different magnetic poles face the permanent magnet 9, and due to the repulsive action of the permanent magnets 9 and 10, air is generated between the fixed shaft 4 and the cover 8. There is one in which the pool 11 is configured.

A removable plug 1 is attached to the cover 8.
When the fixed shaft 4 and the rotary sleeve 6 are fitted with the plug 12 removed when the fixed shaft 4 and the rotary sleeve 6 are fitted, the air in the rotary sleeve 6 flows out from the hole 13 and is easily fitted. When rotating, the rotating sleeve 6 is supported in the radial direction by the air film between the rotating sleeve 6 and the fixed shaft 4 and in the thrust direction by the repulsive force of the permanent magnets 9 and 10. The air in the air reservoir 11 sealed by the plug 12 acts to damp the vertical vibration of the rotary sleeve 6 and holds the rotary sleeve 6 in a stable floating position.

[0004]

However, in the above-mentioned conventional example, since the outer diameter of the permanent magnet 9 is large, the inertial force of the rotating portion is large, so that the rising time of the drive motor is delayed and the rising time is not delayed. If so, a large starting current is required, which increases the cost of the device,
There is a drawback that the running cost also rises.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a low-cost optical deflector that does not delay the start-up when the drive motor is started.

[0006]

An optical deflecting device according to the present invention for achieving the above object is a deflection scanning device for deflecting light by rotatably driving a rotary polygon mirror. Has a shaft and a cylindrical sleeve, and a first permanent magnet is fixed to the end of the shaft, and repels the first permanent magnet at a position facing the first permanent magnet in the sleeve or in the vicinity thereof. The second permanent magnet is fixed, and the diameter of the rotor-side permanent magnet of the first and second permanent magnets is smaller than or substantially equal to the outer diameter of the shaft.

[0007]

In the optical deflector having the above-mentioned structure, the permanent magnet on the rotor side has a diameter smaller than or substantially equal to the outer diameter of the shaft, so that the inertial force of the rotating portion becomes small.

[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 an embodiment of the present invention, in which a motor housing 21 is provided with a substantially vertical fixed shaft 22 made of ceramic. The fixed shaft 22 has a cylindrical rotary sleeve 23 made of ceramic.
Is rotatably fitted, and the flange 2 made of a non-magnetic metal material such as aluminum or brass is fitted to the rotary sleeve 23.
4 is attached by shrink fitting, for example.
A drive magnet 25 is attached to the outer periphery of the flange 24 by means such as adhesion.

A motor board 26 having electric components is mounted on the upper surface of the motor housing 21, and a stator 27 facing the drive magnet 25 is mounted on the board 26.
Is arranged to form a drive motor, and a rotary polygon mirror 28 is fitted on the upper surface of the flange 24 and fixed by a leaf spring 29.

A disk-shaped permanent magnet 30 is arranged on the upper end of the rotary sleeve 23 so as to close the upper end of the rotary sleeve 23, and the upper end of the fixed shaft 22 is slightly smaller than the outer diameter of the fixed shaft 22. The disk-shaped permanent magnet 31 is fixed with its magnetic poles arranged so as to repel each other with the permanent magnet 30, and the rotary sleeve 23 is levitated in the thrust direction by the repulsive force. The permanent magnet 30 is provided with an air vent hole 32 for assembly, and a sealing plug 33 is attached to the hole 32.

In the optical deflector thus constructed, when the sealing plug 33 is removed and the rotary sleeve 23 is fitted on the fixed shaft 22, the permanent magnets 30 and 31 repel each other and the permanent magnets 30 and 31 are reciprocated. The holes 32 are inserted with a space between them.
Is closed by a sealing plug 33 to form an air pocket, and the rotary sleeve 23 obtains a stable floating amount in the thrust direction due to the air damping effect of this air pocket. Then, when the drive motor is driven, the rotary sleeve 23 rotates, an air film is formed on the fitting surface between the rotary sleeve 23 and the fixed shaft 22, and the radial direction is supported in a non-contact manner. Rotate in a state of low.

When the weight of the rotating permanent magnet 30 of this embodiment is compared with that of the conventional example, if the radii of the fixed shaft 4 and the fixed shaft 22 are both r, the inner diameter of the conventional permanent magnet 9 is Since the outer diameter is about (2r + 1) and the outer diameter is about (2r + 7), and the outer diameter of the permanent magnet 30 of the present embodiment is about (2r-1), when the thickness is t,

The weight of the conventional permanent magnet 9 is {(2r +
7) ² − (2r + 1) ² } π · t = (24t + 48) π · t
Becomes

The weight of the permanent magnet 30 of this embodiment is (2r
−1) ² π · t, and if the radius r is 5, the conventional permanent magnet 9 becomes about twice as heavy. Therefore, in the conventional case, since the outer diameter is large and heavy, the inertial force of the permanent magnet 9 is large,
If the rise time of the scanner motor is delayed or the rise time is made to be the same as that of this embodiment, a large starting current is required. Further, since the cost of the permanent magnet increases in proportion to the weight, the cost is lower in this embodiment.

Here, the repulsive force of the opposing permanent magnets is approximately proportional to the magnetic flux area generated from the permanent magnets, but the end face 1 m
For about m, magnetic flux is not generated from the end face and does not contribute so much to the repulsive force, so if you consider that and compare the repulsive force,

In the conventional permanent magnets 9 and 10, {(2r +
7-2) ² − (2r + 1 + 2) ² } π = 8 (r + 2) π, and in the permanent magnets 30 and 31 of this embodiment, (2r−1−)
^{2) 2 π = (2r-} 3) becomes ² [pi, Now if the r = 5, the repulsive force becomes substantially equal.

Further, as in the second embodiment shown in FIG.
A disk-shaped ferromagnetic body 34 made of, for example, iron may be interposed between the permanent magnet 31 and the fixed shaft 22 in the first embodiment. The ferromagnetic body 34 has such a thickness that the magnetic flux from the permanent magnet 31 is not saturated in the ferromagnetic body 34.

As a result, since the magnetic flux emitted from the permanent magnet 31 increases and the repulsive force increases, the magnetic field becomes stronger against external vibration, and easily vibrates by receiving external vibration,
It is possible to prevent the inconvenience that the rotating body collides with the stator during rotation. In this case, since the ferromagnetic body 34 is attached to the fixed shaft 22 side, the inertial force of the rotor portion does not increase at all.

Further, as in the third embodiment shown in FIG. 3, a ferromagnetic material 35 may be attached to the permanent magnet 30 on the rotary sleeve 23 side as a so-called back yoke. This allows
The magnetic flux density in the gap can be increased and the repulsive force can be increased without increasing the cost by making the permanent magnets 30 and 31 thick. Also, the sealing plug 3
If 3 is made of a ferromagnetic material and has a sufficient size,
It can also serve as a back yoke.

Further, a ferromagnetic material 34 as a back yoke.
4 is provided without thickening only the permanent magnet 31 on the fixed shaft 22 side as in the fourth embodiment shown in FIG.
Even if the permanent magnet 30 on the third side is made thin, the same repulsive force can be produced, and the inertial force of the permanent magnet 30 on the rotating side can be reduced.

In each of the above-described embodiments, the shaft 22 and the rotary sleeve 23 are so-called ceramic bearings made of a ceramic material. As shown in FIGS. 5 and 6, air and oil SGB (spiral, group) are used. , Bearing) thrust receiver.

FIG. 5 shows a second embodiment of the housing 4
0 is fixed to the bottom plate 41 by press-fitting the lower end and the fixed shaft 4
2, a herring horn-shaped shallow groove 43 for generating dynamic pressure is formed on the outer periphery of the fixed shaft 42. A rotary sleeve 44 is rotatably fitted to the fixed shaft 42 through a bearing gap S between the fixed shaft 42 and the outer peripheral surface thereof, and a dynamic pressure is applied between the outer peripheral surface of the fixed shaft 42 and the inner peripheral surface of the rotary sleeve 44. A radial base bearing of the system is constructed. Further, a permanent magnet 45 is arranged at the upper end of the fixed shaft 42, and a permanent magnet 46 is also arranged above the rotary sleeve 44 facing the fixed shaft 42 so as to repel the permanent magnet 45 to receive thrust. Has become.

A rotor 47 is attached to the outer peripheral surface of the rotary sleeve 44, and a stator 48 is attached to the inner peripheral surface of the housing 40 so as to face the rotor 47 on the outer peripheral side of the rotor 47 to form a drive motor. A rotary polygon mirror 49 is attached to the upper part of the rotary sleeve 44.

FIG. 6 shows a sixth embodiment, in which a rotary shaft 52 is rotatably fitted in a sleeve 51 fixed in a housing 50 of a drive motor, and a herringbone-shaped shallow groove is formed on the outer peripheral surface of the rotary shaft 52. A dynamic pressure radial bearing is formed by engraving the groove 53. Also, the housing 50
The permanent magnet 55 is mounted on the fixed plate 54 which is attached to the bottom surface of the sleeve 51 and which fixes the lower end of the sleeve 51, while the permanent magnet 56 facing the permanent magnet 55 is arranged at the lower end of the rotary shaft 52. The thrust receivers are formed by repulsing each other.

Further, the flange 5 fixed to the rotary shaft 52
A yoke 59 having a drive magnet 58 is attached to the drive magnet 7, and a stator 60 is fixed to a portion of the housing 50 facing the drive magnet 58 to form a drive motor. The rotary polygon mirror 61 is fixed to the upper surface of the flange 57.

In these fifth and sixth embodiments, by using a permanent magnet for the thrust bearing, the shaft portion and the bearing portion are not in contact with each other, and the conventional shallow groove is used for repeated start and stop. More durable than dynamic pressure thrust bearings.

[0027]

As described above, in the optical deflecting device according to the present invention, the repulsive permanent magnets provided on the shaft of the drive motor and the sleeve have an outer diameter substantially equal to the outer diameter of the shaft, or Since it is less than that, it is possible to reduce the inertial force, there is no delay in the startup at the time of startup, and the cost can be reduced by downsizing the permanent magnet.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is a schematic configuration diagram of a second embodiment.

FIG. 3 is a schematic configuration diagram of a third embodiment.

FIG. 4 is a schematic configuration diagram of a fourth embodiment.

FIG. 5 is a schematic configuration diagram of a fifth embodiment.

FIG. 6 is a schematic configuration diagram of a sixth embodiment.

FIG. 7 is a schematic configuration diagram of a conventional example.

[Explanation of symbols]

 22, 42, 56 Fixed shaft 23, 44 Rotating sleeve 28, 49, 61 Rotating polygon mirror 30, 31, 45, 46, 55, 56 Permanent magnet 33 Sealing plug 34 Ferromagnetic material 51 Sleeve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Tomita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shizuka Saigawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Non non corporation

Claims (4)

[Claims] 1. A deflection scanning device for deflecting light by rotationally driving a rotary polygon mirror, comprising a shaft and a cylindrical sleeve which are rotatably fitted to each other, and a first permanent member at an end of the shaft. Of the first and second permanent magnets, a magnet is fixed and a second permanent magnet that repels the first permanent magnet is fixed at a position facing the first permanent magnet in the sleeve or in the vicinity thereof. An optical deflecting device, wherein the diameter of the permanent magnet on the rotor side is smaller than or substantially equal to the outer diameter of the shaft. 2. The optical deflector according to claim 1, wherein a ferromagnetic material is attached as a back yoke to at least one of the first and second permanent magnets. 3. The optical deflector according to claim 1, wherein the shaft and the sleeve are made of a ceramic material. 4. The optical deflector according to claim 1, wherein the permanent magnet on the rotor side is thin, and the permanent magnet on the stator side is thick.