JPH1193943A - Dynamic pressure fluid bearing and deflection scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a dynamic pressure fluid bearing. SOLUTION: A shaft 2 integrally combined with a rotary polygon mirror 1 rotates in noncontact under the dynamic pressure of a fluid film formed between it and a sleeve 3. The dynamic pressure creating grooves 2a, 2b, etc., of the shaft 2 are formed by plating the main body 20 of the shaft 2 with a corrosion-resistant first plating layer 21, adhering a resist pattern to it, plating it with a second layer 22 and removing the resist pattern. The bottom faces of the dynamic pressure creating grooves 2a, 2b, etc., are constituted of the corrosion-resistant first plating layer 21, so that a bearing improves in its durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing and a deflection scanning device used for an image forming apparatus such as a laser beam printer and a laser facsimile.

[0002]

2. Description of the Related Art A deflection scanning device used in an image forming apparatus such as a laser beam printer or a laser facsimile reflects a light beam such as a laser beam (laser beam) by a rotating polygon mirror rotating at a high speed, and deflects and scans the beam. Then, the obtained scanning light is imaged on a photoreceptor on a rotating drum to form an electrostatic latent image. Next, the electrostatic latent image on the photoreceptor is visualized into a toner image by a developing device, transferred to a recording medium such as recording paper, sent to a fixing device, and printed by heating and fixing the toner on the recording medium ( Print) is performed.

FIG. 6A shows a main part of a conventional deflection scanning apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 5-44717, which rotates integrally with a rotary polygon mirror 101. It has a shaft 102 and a sleeve 103 in which the shaft 102 is rotatably fitted. The sleeve 103 is fitted to a boss of an outer cylinder 104, and the outer cylinder 104 is supported upright on a fixed plate 105. The fixed plate 105 includes a thrust plate 106 that supports the lower end of the shaft 102 in the thrust direction. Axis 102
A flange 107 is fixed to an upper end of the rotary polygon mirror 1.
Numeral 01 is supported on the upper surface of the flange 107 and is configured to rotate with the shaft 102.

A yoke 109 for holding a rotor magnet 108 is fixed to a lower surface of an outer peripheral portion of the flange 107. The rotor magnet 108 faces a stator coil 110 fixed to an outer peripheral surface of a boss portion of the outer cylinder 104. It is arranged to be. When the stator coil 110 is excited by a drive current supplied from a drive circuit (not shown), the rotor magnet 108 rotates at high speed together with the shaft 102 and the rotating polygon mirror 101.

[0005] The sleeve 103 forms a fluid film between itself and the shaft 102 by rotation of the shaft 102, and forms a hydrodynamic fluid bearing that supports the shaft 102 in a non-contact manner by the dynamic pressure of the fluid film. On the outer peripheral surface of the shaft 102, the first dynamic pressure generation grooves 102 a are sequentially spaced upward from the lower end of the shaft 102.
And a second dynamic pressure generating groove 102b and a spiral lubricating groove 102c for guiding a lubricating fluid are formed. Further, a groove (not shown) constituting a dynamic pressure thrust bearing is provided on a portion of the upper surface of the thrust plate 106 facing the lower end of the shaft 102.

The dynamic pressure generating grooves 102a and 102b of the shaft 102
And the lubrication groove 102c, as shown in FIG.
An opening of the plating layer 121 applied to the main body 120 of the shaft 102, which is formed by the following method. Using a known gravure offset printing machine, each groove 102a-102
A resist having a thickness equal to or greater than the depth of the c-groove is applied to each of the grooves 102.
Printing is performed on the outer peripheral surface of the main body 120 of the shaft 102 in a pattern of a to 102c. After the resist is baked and solidified, the plating layer 1 is adjusted so that the outer diameter of the shaft 102 becomes a design value.
21 is plated. The plating layer 121 is formed by electroless plating using a hard material having excellent wear resistance. If the resist is removed, each of the grooves 102a to 102
c is formed, but the shaft 10
The base material surface of the second main body 120 is exposed. The grooves 102a to 102c formed by such a method have a rectangular shape with an accurate longitudinal cross-section, and have a constant cross-sectional layer at any portion in the longitudinal direction of the groove. An advantage is that stable bearing performance without uneven rotation or shaft runout can be obtained without uneven pressure.

[0007]

However, according to the above prior art, as described above, the base material surface of the shaft is exposed on the bottom surface of the dynamic pressure generating groove and the lubrication groove, so that humidity, temperature, etc. However, there is an unsolved problem that corrosion tends to occur due to environmental changes and durability is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and provides a plating layer having excellent corrosion resistance so that the base material surface of the shaft is not exposed at the bottom of the dynamic pressure generating groove. A hydrodynamic fluid bearing and deflection scanning device that can improve corrosion resistance against environmental changes such as temperature and humidity by covering and have excellent durability and excellent bearing performance without rotation unevenness and shaft runout. It is intended to provide.

[0009]

In order to achieve the above object, a hydrodynamic bearing of the present invention comprises a shaft having a dynamic pressure generating groove, and a sleeve for rotatably fitting the shaft. The cylindrical surface of the main body of the shaft is covered with a first plating layer, and the dynamic pressure generating groove is formed by an opening of a second plating layer laminated on the first plating layer. It is characterized by.

The second plating layer is preferably a hard plating layer having wear resistance.

It is preferable that the first plating layer is a plating layer having excellent corrosion resistance.

It is preferable that the first and second plating layers are plated by electroless plating.

[0013]

A first plating layer having excellent corrosion resistance is plated on the surface of the main body of the shaft, a resist pattern having a shape of a dynamic pressure generating groove is applied, and a second plating layer is plated. A dynamic pressure generating groove is formed by removing the resist pattern. The dynamic pressure generating groove formed by such a method,
The shape accuracy is high, the dynamic pressure unevenness is small, and the bearing performance is excellent.

The bottom surface of the dynamic pressure generating groove is made of a first material having excellent corrosion resistance.
Therefore, for example, even if the shaft is made of a material whose shaft is easily rusted, its surface is not exposed, and the environmental resistance performance of the bearing can be greatly improved.

If the second plating layer is a hard plating layer having abrasion resistance, it has high durability against galling at the time of starting and stopping, and can greatly contribute to prolonging the life of the bearing.
By using such a hydrodynamic bearing for the bearing of a rotary polygon mirror, the optical characteristics and rotational performance of the deflection scanning device can be significantly improved.

[0016]

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

FIG. 1 shows a main part of a deflection scanning apparatus according to one embodiment. It has a rotary polygon mirror 1, a shaft 2 that rotates integrally with the rotary polygon mirror 1, and a bearing portion provided with a sleeve 3 for rotatably fitting the same. The outer cylinder 4 is supported upright on the fixed plate 5. The fixed plate 5 includes a thrust plate 6 that supports the lower end of the shaft 2 in the thrust direction. A flange 7 is fitted to the upper end of the shaft 2, and the rotary polygon mirror 1 is supported on the upper surface of the flange 7. It is configured to rotate with the shaft 2.

A yoke 9 for holding a rotor magnet 8 is fixed to a lower surface of an outer peripheral portion of the flange 7, and the rotor magnet 8 faces a stator coil 10 fixed to an outer peripheral surface of a boss portion of the outer cylinder 4. And constitutes a motor for rotating the rotary polygon mirror 1. When the stator coil 10 is excited by a drive current supplied from a drive circuit (not shown), the rotor magnet 8 rotates at high speed together with the shaft 2 and the rotary polygon mirror 1.

The sleeve 3 forms a fluid film between the shaft 2 and the shaft 2 by the rotation of the shaft 2, and constitutes a hydrodynamic bearing for rotatingly supporting the shaft 2 in a non-contact manner by the dynamic pressure of the fluid film. A first dynamic pressure generating groove 2a and a second dynamic pressure generating groove 2b are provided on the outer peripheral surface of the shaft 2 at intervals sequentially upward from the lower end of the shaft 2.
And a spiral lubricating groove 2c for guiding the lubricating fluid are formed. In addition, a groove (not shown) that constitutes a dynamic pressure thrust bearing is provided on the upper surface of the thrust plate 6 at a position facing the lower end of the shaft 2.

As for the shaft 2, a first plating layer 21 having excellent corrosion resistance is formed on an outer peripheral surface which is a cylindrical surface of a rod-shaped main body 20 serving as a base material, and a dynamic pressure generating groove 2a is formed on the surface thereof as in the conventional example. , 2
b and a second plating layer 22 having openings such as lubrication grooves 2c. Such a dynamic pressure generating groove 2
The shaft 2 provided with a, 2b and the lubrication groove 2c is formed by the following method. As shown in FIG. 2, a main body 20 having an outer diameter obtained by subtracting the depth of each of the grooves 2 a to 2 c and the thickness of the first plating layer 21 from a design value of the outer diameter of the shaft 2 is manufactured. The first plating layer 21 is plated on the whole (base material surface) using a plating material having excellent corrosion resistance.

The grooves 2a to 2c are formed on the surface of the first plating layer 21 by using a gravure offset printing machine M shown in FIG.
The resist pattern R having a thickness equal to or less than the depth of the groove is printed. Gravure offset printing machine M, a first plating layer of resist supply unit M ₂ from the resist supplied to the intaglio M ₄ of the gravure roll M ₃ by carrying the offset roll M ₅ axis 2 with a doctor blade M ₁ 21
Is to be printed on the surface of The resist pattern R is
As shown in FIG. 4, on the first plating layer 21 that covers the main body 20 of the shaft 2, the dynamic pressure generation grooves 2a and 2b and the lubrication groove 2c are attached.

FIG. 2A is an enlarged sectional view of a part of the shaft 2 on which the resist pattern R is printed. After baking and solidifying the resist, as shown in FIG. 2B, the second plating layer 22 is plated. The second plating layer 22 is preferably formed by electroless plating using a hard plating material having excellent wear resistance. It is desirable that the above-mentioned first plating layer is also formed by electroless plating.

Next, when the resist pattern R was removed, as shown in FIG. 2C, openings for forming the dynamic pressure generating grooves 2a and 2b and the lubricating grooves 2c were formed in the second plating layer 22. Axis 2 can be obtained. The bottom surface of each of the grooves 2a to 2c is not formed on the base material surface of the shaft as in the conventional example, but is formed on the first surface.
Is exposed. The grooves 2a to 2c formed by such a method have a rectangular shape with an accurate longitudinal cross-section, and have a constant cross-sectional layer at any portion in the longitudinal direction of the groove. It has excellent bearing characteristics that the pressure is not uneven.

As described above, if the second plating layer 22 is abrasion-resistant hard electroless plating, it is extremely excellent in abrasion resistance, and the shaft 2 and the sleeve 3 are likely to come into contact with each other when starting or stopping the motor. However, the durability can be greatly improved without causing significant wear.

Since the bottom surfaces of the grooves 2a to 2c are formed by the first plating layer 21 having excellent corrosion resistance, the bottom surfaces of the grooves 2a to 2c are more corrosion resistant than when the body 20 of the shaft 2 is exposed as in the conventional example. The performance is greatly improved. Even if a material that easily rusts is used for the main body 20 of the shaft 2, the durability (environmental resistance) against environmental changes such as humidity and temperature can be sufficiently enhanced.

As described above, by greatly improving the environmental resistance performance and the rotational performance of the hydrodynamic bearing that rotatably supports the rotary polygon mirror 1, it is possible to greatly contribute to extending the life and improving the performance of the deflection scanning device.

FIG. 5 shows the entire deflection scanning device, which is a light source 5 for generating a light beam (light flux) such as a laser beam.
1 and a cylindrical lens 51a for linearly condensing the laser beam on the reflecting surface 1a of the rotary polygon mirror 1, and deflects and scans the light beam by rotation of the rotary polygon mirror 1.
An image is formed on a photoreceptor 53 on a rotating drum via an imaging lens system 52. The imaging lens system 52 includes a spherical lens 52a, a toric lens 52b, and the like, and has a so-called fθ function of correcting a scanning speed and the like of a point image formed on the photoconductor 53.

When the rotary polygon mirror 1 is rotated by the motor, its reflection surface 1a rotates at a constant speed around the axis of the rotary polygon mirror 1. Generated from the light source 51 as described above,
The angle between the optical path of the light beam condensed by the cylindrical lens 51a and the normal to the reflecting surface 1a of the rotating polygon mirror 1, that is, the angle of incidence of the light beam on the reflecting surface 1a, changes with time as the rotating polygon mirror 1 rotates. And the reflection angle also changes, so that the point image formed by condensing the light beam on the photoconductor 53 moves (scans) in the axial direction (main scanning direction) of the rotating drum.

The imaging lens system 52 focuses the light beam reflected by the rotary polygon mirror 1 on the photosensitive member 53 into a point image having a predetermined spot shape, and scans the point image in the main scanning direction. Is designed to keep the speed constant.

The point image formed on the photoreceptor 53 is electrostatically generated by the main scanning by the rotation of the rotary polygon mirror 1 and the sub-scanning by the rotation of the rotating drum having the photoreceptor 53 around its axis. Form a latent image.

A corona discharge device for uniformly charging the surface of the photosensitive member 53 is provided around the photosensitive member 53, and an electrostatic latent image formed on the surface of the photosensitive member 53 is visualized as a toner image. And a transfer corona discharger (both not shown) for transferring the toner image to recording paper, etc., and recording information by a light beam generated from the light source 51 is printed on recording paper or the like.

The detection mirror 54 reflects the light beam on the upstream side in the main scanning direction from the optical path of the light beam incident on the recording information writing start position on the surface of the photoreceptor 53, and receives a light receiving element 55 having a photodiode or the like. To the light receiving surface of The light receiving element 55 outputs a scanning start signal for detecting a scanning start position (write start position) when the light receiving surface is irradiated with the light beam.

The light source 51 generates a light beam corresponding to a signal given from a processing circuit for processing information from a host computer. The signal given to the light source 51 corresponds to information to be written on the photoconductor 53, and the processing circuit represents information corresponding to one scanning line which is a locus formed by a point image formed on the surface of the photoconductor 53. The signal is given to the light source 51 as one unit. This information signal is transmitted in synchronization with a scanning start signal given from the light receiving element 55.

The rotary polygon mirror 1, the imaging lens system 52 and the like are housed in an optical box 50, and the light source 51 and the like are mounted on the side wall of the optical box 50. After assembling the rotary polygon mirror 1 and the imaging lens system 52 into the optical box 50, a lid (not shown) is attached to the upper opening of the optical box 50.

[0035]

Since the present invention is configured as described above, the following effects can be obtained.

Since the bottom surface of the dynamic pressure generating groove is formed of a plating layer having excellent corrosion resistance, not the surface of the base material of the shaft, the environmental resistance performance of the bearing against changes in temperature and humidity can be greatly improved. .

Further, since the dynamic pressure generating groove is constituted by an opening of a hard plating layer having abrasion resistance, it has sufficient durability against galling at the time of starting and stopping.
Moreover, the shape accuracy of the dynamic pressure generating groove is high, so that excellent bearing performance without rotation unevenness and shaft runout can be stably obtained.

By using such a hydrodynamic bearing for the bearing of a rotary polygon mirror, it is possible to greatly contribute to higher performance and longer life of the deflection scanning device.

[Brief description of the drawings]

FIGS. 1A and 1B show a deflection scanning apparatus according to an embodiment, in which FIG. 1A is a schematic cross-sectional view, and FIG. 1B is an enlarged partial cross-sectional view showing a part of a shaft.

FIG. 2 is a view showing a step of forming a groove in a shaft.

FIG. 3 is a diagram illustrating a gravure offset printing press.

FIG. 4 is a perspective view showing a shaft in a step shown in FIG.

FIG. 5 is a diagram illustrating the entire deflection scanning device.

FIG. 6 shows a conventional example, in which (a) is a schematic sectional view,
(B) is an enlarged partial sectional view showing a part of the shaft in an enlarged manner.

[Explanation of symbols]

 Reference Signs List 1 rotary polygon mirror 2 shaft 2a, 2b dynamic pressure generating groove 2c lubrication groove 3 sleeve 4 outer cylinder 5 fixing plate 6 thrust plate 8 rotor magnet 10 stator coil 20 main body 21 first plating layer 22 second plating layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Horie 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masayoshi Asami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (7)

[Claims] A shaft provided with a dynamic pressure generating groove, and a sleeve for rotatably fitting the shaft; a cylindrical surface of a body of the shaft is covered with a first plating layer; Wherein the dynamic pressure generating groove is formed by an opening of a second plating layer laminated on the plating layer. 2. An opening in a second plating layer, wherein a resist pattern having a shape of a dynamic pressure generating groove is provided on the first plating layer, and then the second plating layer is plated. 2. The hydrodynamic bearing according to claim 1, wherein the hydrodynamic bearing is formed by removing a resist pattern. 3. The method according to claim 1, wherein the second plating layer is a hard plating layer having wear resistance.
A hydrodynamic bearing as described. 4. The hydrodynamic bearing according to claim 1, wherein the first plating layer is a plating layer having excellent corrosion resistance. 5. The hydrodynamic bearing according to claim 1, wherein the first and second plating layers are plated by electroless plating. 6. A deflection scanning device in which a bearing of a rotary polygon mirror for deflecting and scanning a light beam includes a shaft having a dynamic pressure generating groove and a sleeve for rotatably fitting the shaft. That the cylindrical surface of the main body is covered by a first plating layer, and that the dynamic pressure generating groove is constituted by an opening of a second plating layer laminated on the first plating layer. Characteristic deflection scanning device. 7. An opening in the second plating layer is provided with a resist pattern having a shape of a dynamic pressure generating groove on the first plating layer, and then plating the second plating layer. 7. The deflection scanning device according to claim 6, wherein the deflection scanning device is formed by removing a resist pattern.