JPH1184299A - Optical deflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate an increase in parts and to avert an increase in cost and an increase in the size of an optical deflector by providing a case for housing a rotary polyhedral mirror and a means for rotating this rotary polyhedral mirror at high speed with heat radiation fins. SOLUTION: The case 20 is internally provided with a rotating section mainly constituting the rotary polyhedral mirror 30 and a dynamic pressure bearing device 32 and a static section mainly consisting of a coil substrate 22, a coil 23, a shaft 26, etc. An upper cap 21 is fixed by means of screws to the case 20. Moltopren (R) 24 is inserted between the case 20 and the upper cap 21. The case 20 has the many heat radiation fins 201 in its lower part to escape the heat generated at the time of the high-speed rotation of the rotary polyhedral mirror 30. The outside surfaces of the case 20, i.e., the parts of the fins are subjected to a black anodizing treatment. The heat radiation effect is additionally enhanced by this black anodizing treatment. Further, the front surface of the upper cap 21 is also subjected to the anodizing treatment, by which the heat radiation effect is additionally enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light deflection device for light scanning in an image forming apparatus or image reading apparatus which performs light scanning by a laser beam to form or read an image.

[0002]

2. Description of the Related Art An optical deflector that has been widely used as an optical deflector for optical scanning by a laser light beam has a rotating polygon mirror attached to a rotating shaft of a motor that can rotate at a high speed, and the rotating polygon mirror is rotated. The rotating shaft of the motor was supported by ball bearings and rotated. The upper limit of the rotation speed of such a rotating body is relatively low, which has been one barrier when developing a high-speed digital copying machine or laser printer. In order to use the laser scanning optical system used in these high-speed digital copiers, printers, and the like, the present applicant has replaced a conventional ball bearing with an optical deflector having a rotating polygon mirror supported by an air bearing. We have been developing equipment. Such an air bearing is disclosed in, for example, JP-A-7-243439, JP-A-7-259849, JP-A-8-114219, and JP-A-8-1.
No. 21,471, and the like.

[0003] The adoption of an air bearing has made it possible to rotate a rotating polygon mirror at tens of thousands of rpm, and as a result, a high-speed digital copying machine or laser printer has been realized.

[0004]

In the light deflecting device having the rotator rotating at a high speed as described above, a large amount of heat is generated with the rotation, and the temperature of the light deflecting device and the device parts in the vicinity thereof is increased. Was found to be undesirable. If a cooling device is added to the light deflecting device as a countermeasure, the number of components of the device increases, which leads to an increase in the number of assembly steps and cost, and also causes an undesirable problem that the device becomes large. Accordingly, it is an object of the present invention to provide an optical deflector that suppresses a temperature rise during high-speed rotation of a rotary polygon mirror without increasing the number of parts and increasing the size of the device.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotary polygon mirror, a dynamic pressure bearing device rotatably supporting the rotary polygon mirror, an electromagnetic device for rotating the rotary polygon mirror, and the rotary polygon mirror. The present invention is achieved by an optical deflector having a container for accommodating the dynamic pressure bearing device and the electromagnetic device, wherein the container has a cooling fin as an integral component.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments, one of the laser beam scanning optical systems in which the optical deflection device of the present invention is used.
An example will be described with reference to FIG.

Laser light L emitted from semiconductor laser 1
Is oscillated by the light deflecting device 4 via the collimator lens 2 and is incident on the surface of the photoconductor 3 via the fθ lens 5 and the cylindrical lens 6. The light deflecting device 4 is a deflecting device for scanning and exposing the photoconductor 3 in the direction of its rotation axis.

Next, an embodiment will be described with reference to FIGS. FIG. 2 is a plan view of the light deflecting device 4. Incident light L
₁ is reflected by the reflecting surface 301 of the rotating polygon mirror 30, and L
₂ a, is emitted in the direction of the angle range between L ₂ b. The rotating polygon mirror 30 is made of aluminum, and an outer peripheral surface 301 forming a polygon is formed on a reflecting surface by mirror finishing.
FIG. 3 is a cross-sectional view of the light deflecting device 4 taken along line AA in FIG. The rotating polygon mirror 3 is mainly provided in the case 20.
0, a rotating part forming the structure of the dynamic pressure bearing device 32 and stationary parts such as the coil substrate 22, the coil 23, the shaft 26, and the like are provided. The rotary polygon mirror 30 has a flat plate shape as shown in the figure, and a concave portion 303 is formed on its lower surface, that is, a surface 302 orthogonal to its rotation axis, and a magnet 31 and a steel plate yoke 34 are bonded to the concave portion 303 with an adhesive. It is fixed at. The rotary polygon mirror 30 is supported by a dynamic pressure bearing device 32 such that it can rotate at high speed. The dynamic pressure bearing device 32 includes a rotor 321 integrated with the rotary polygon mirror 30, a radial shaft 322 integrated with the stationary shaft 26, an upper thrust plate 323, and a lower thrust plate 3.
24. Rotor 321 and radial shaft 322
The upper thrust plate 323 and the lower thrust plate 324 are formed so as to have a small gap therebetween, and the rotor is supported by air when the rotor 321 rotates. Such a dynamic pressure bearing device is disclosed in Japanese Unexamined Patent Application Publication No.
JP-A-243434, JP-A-7-259849,
JP-A-8-114219, JP-A-8-12147
The one disclosed in Japanese Patent Publication No. 1 and the like can be used. A yoke 25 made of a silicon steel plate and a coil substrate 22 are attached to the case 20. A coil 23 that forms a magnetic field for rotating the rotary polygon mirror 30 at high speed is fixed to the coil substrate 22. The rotating polygon mirror 30 rotates at high speed due to the electromagnetic action of the coil 23 and the magnet 31.
High-speed rotation of 0 rpm or more has become possible.

An upper lid 21 that forms a container such as a rotary polygon mirror together with the case 20 is fixed to the case 20 with screws 211. By inserting a moltoprene 24 between the case 20 and the upper lid 21, sound from the optical deflector is generated. The occurrence is prevented.

A window 201 for inputting and outputting light is provided at one corner of the substantially square case 20. In this window 201, a light transmitting plate (glass plate) 35 is fixed with an adhesive. A double-sided adhesive tape is used for bonding the light transmitting plate 35. As the double-sided adhesive tape, an acrylic foam bonding tape manufactured by 3M, Y-4905J is preferable. Case 2
Flanges 202 provided at the four corners 0 are attachment portions for attaching the optical deflector unit to the image forming apparatus main body, and holes 203 are screw holes for attachment.

A large number of radiating fins 201 are provided below the case 20 to release heat generated when the rotary polygon mirror 30 rotates at a high speed. Is subjected to black alumite plating, and the heat dissipation effect is further enhanced by the black alumite plating. The upper surface of the upper lid 21 is also alumite-plated to further enhance the heat radiation effect.

Next, the above-described embodiment of the present invention and, as a conventional example, an optical deflecting device having no cooling device and a device in which the cooling device is formed separately and attached to the optical deflecting device are operated. The temperature rise during high-speed rotation was compared. In the embodiment of the present invention, at a rotation speed of 16500 rpm, 20
Only at 30 ° C. at a temperature of 2 ° C. and a rotation speed of 25000 rpm, it was proved that the device could be used sufficiently even at a high speed. On the other hand, in the conventional example without the cooling device, the rotation speed was 16500 rpm at 40 ° C., and in the example in which the cooling device was separately mounted, the rotation speed was also 16500 rpm.
A temperature rise of 35 ° C. at m was found, indicating an undesirable temperature rise.

[0013]

A heat radiation fin is provided in a case for housing a rotating polygon mirror and a means for rotating the rotating polygon mirror at a high speed, and heat generated when the rotating polygon mirror is rotated at a high speed is provided.
Since the temperature of the light deflecting device is prevented from becoming high, the number of components does not increase even if the heat dissipating fins are provided, and the cost and the size of the light deflecting device are avoided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a laser scanning optical system in which an optical deflection device of the present invention is used.

FIG. 2 is a plan view of the light deflecting device according to the embodiment of the present invention.

FIG. 3 is a sectional view taken along AA in FIG. 2;

[Explanation of symbols]

20 case 21 lid 22 coil substrate 23 coil 24 moltopren 30 rotating polygon mirror 31 magnet 32 dynamic pressure bearing device L ₁ incident light L ₂ a, L ₂ b emitted light

Claims (9)

[Claims] 1. A rotary polygon mirror, a dynamic pressure bearing device rotatably supporting the rotary polygon mirror, an electromagnetic device for rotating the rotary polygon mirror, and the rotary polygon mirror, the dynamic pressure bearing device, and the electromagnetic device. A light deflecting device having a container for cooling, wherein the container has a cooling fin as an integral component. 2. The light deflecting device according to claim 1, wherein a coupling member for attaching the light deflecting device to a device in which the light deflecting device is incorporated is provided in the container. 3. The container according to claim 1, wherein the container is provided with a light entrance / exit window, and a light transmitting plate covering the entrance / exit window is fixed to the container with a double-sided adhesive tape. The light deflecting device according to claim 1. 4. The light deflecting device according to claim 1, wherein the container has a case and a lid. 5. The light deflecting device according to claim 4, wherein moltoprene is interposed between the case and the lid. 6. The apparatus according to claim 1, wherein the electromagnetic device has a magnet and a coil, the magnet is provided on the rotating polygon mirror side, and the coil is provided on the container side. 2. The light deflecting device according to claim 1. 7. The light deflecting device according to claim 4, wherein the case is made of aluminum, and a surface of the case is anodized. 8. The light deflecting device according to claim 4, wherein the lid is made of aluminum, and a surface thereof is alumite-treated. 9. The polygon mirror of the rotary polygon mirror has an outer peripheral surface formed on a reflection surface, and the magnet is fixed to a surface substantially perpendicular to a rotation axis of the rotary polygon mirror. Item 7. An optical deflecting device according to Item 6.