JP2002039185A - Dynamic pressure bearing and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Problem] To prevent wear during low-speed rotation. A shaft (3) integrated with a rotary polygon mirror (1) is fitted into a sleeve (2) having a dynamic pressure generating groove (2a) to form a dynamic pressure bearing. On the bearing surface of the sleeve 2, a composite electroless plating film 22 containing a solid lubricant is formed after the conductive treatment by the flash plating film 21. This is formed by a simple film forming process, and can greatly improve the wear resistance and lubricity of the bearing surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing for rotatingly supporting a rotary polygon mirror or the like of a deflection scanning device for scanning a light beam at a high speed in a laser beam printer, a bar code reader or the like, and a method of manufacturing the same. It is.

[0002]

2. Description of the Related Art A deflection scanning device used in a laser beam printer, a bar code reader and the like deflects and scans a light beam such as a laser beam by a rotating polygon mirror rotating at a high speed. 2. Description of the Related Art In an image forming apparatus such as a laser beam printer, a scanning light obtained by a rotating polygon mirror is formed on a photosensitive member on a rotating drum to form an electrostatic latent image, and the electrostatic latent image on the photosensitive member is developed by a developing device. The toner image is developed into a toner image, transferred to a recording medium of recording paper, sent to a fixing device, and heated (fixed) on the recording medium to perform printing (printing).

In recent years, the speed and accuracy of such a deflection scanning device have been further increased, and in order to cope with this, a non-contact type of low noise and high rotation accuracy is mounted on a bearing portion of a rotary polygon mirror. A hydrodynamic bearing is used.

FIG. 7 shows a conventional dynamic pressure bearing, which comprises a shaft 102 which rotates integrally with a rotary polygon mirror 101 having a plurality of reflecting surfaces 101a, and which is rotatably fitted thereto. The sleeve 103
Are integrated with the bearing housing 104. Sleeve 103
A thrust receiver 106 having a spherical portion 106a for supporting the lower end of the shaft 102 in the thrust direction is fixed to the lower end of the shaft 102, and a flange 107 is fixed to the upper portion of the shaft 102. The rotary polygon mirror 101 is configured to be pressed against the upper surface of the flange 107 by an elastic pressing mechanism 108 including a pressing spring or the like, integrated with the flange 107, and to rotate together with the shaft 102.

A yoke 109a for holding a rotor magnet 109 is fixed to an outer peripheral portion of the flange 107, and the rotor magnet 109 is attached to the bearing housing 104.
Coil 110 on base plate 105 fixed to
It is arranged so that it may face. A driving current supplied from a driving circuit (not shown)
Is excited, the rotor magnet 109 rotates at high speed together with the shaft 102 and the rotary polygon mirror 101.

The sleeve 103 forms a fluid film between the shaft 102 and the shaft 102 by the rotation of the shaft 102, and constitutes a dynamic pressure 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, a first dynamic pressure generating groove 102a and a second
Are formed. In addition, a shallow groove (not shown) that constitutes a dynamic pressure thrust bearing is provided also on the upper surface of the thrust receiver 106 at a position facing the lower end of the shaft 102.

[0007] With the rotation of the shaft 102, the sleeve 103
Of the dynamic pressure generating groove 102
a, 102b are sucked into the central portion to generate a high pressure region. The shaft 102 and the sleeve 103 are formed by this high pressure region.
Are supported in a non-contact state in the radial direction. Because of this non-contact rotation, not only characteristics such as low noise and high rotational accuracy can be obtained compared to a plain bearing with metal contact, for example, but also the number of assembly parts is lower than that of a rolling bearing. Therefore, there is an advantage that the size and cost can be reduced.

However, at the time of starting or stopping when the rotation speed of the shaft does not reach the steady state value, the shaft and the sleeve come into contact with each other to generate abrasion powder, and the rotation may not be possible due to an impact or the like.

Therefore, a technique has been developed to improve hardness, wear resistance, lubricity, etc. by providing an anodic oxide film such as a nickel plating or an alumite film or a sprayed lubricating coating film on the bearing surface of the shaft or sleeve. (See JP-A-63-235719 and JP-A-7-27131).

[0010]

However, according to the above prior art, a nickel plating film, an anodic oxide film, or a sprayed lubricating coating film is formed on a bearing surface of a shaft, a sleeve, or the like, so that wear resistance and lubricity are improved. Is effective to prevent the generation of abrasion powder at the time of starting or stopping, but it is difficult to ensure uniformity of the film, and furthermore, the cost is high due to measures against environmental pollution. There is an unsolved problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and forms a composite electroless plating film having lubricity and wear resistance on a shaft portion and a sleeve portion which are fitted to each other. Accordingly, it is an object of the present invention to provide an inexpensive and high-performance dynamic pressure bearing capable of avoiding generation of wear powder and maintaining excellent bearing performance for a long period of time, and a method of manufacturing the same.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, a dynamic pressure bearing according to the present invention has a shaft portion and a sleeve portion which are relatively rotatably fitted. A composite electroless plating film containing a solid lubricant is formed on at least one of them.

[0013] It is preferable that a composite electroless plating film containing a solid lubricant is formed after at least one of the shaft portion and the sleeve portion is subjected to a conductive treatment.

The surface roughness of the composite electroless plating film is 2.0
It is good to be below μm.

The dynamic friction coefficient of the composite electroless plating film is 0.1.
It is good to be 3 mu or less.

[0016]

[Function] By providing a composite electroless plating film containing a solid lubricant such as molybdenum disulfide and graphite on the fitting surface of the shaft portion and the sleeve portion, abrasion powder generated when the shaft portion and the sleeve portion come into contact with each other is reduced. Prevent outbreak.

Since the above composite electroless plating film is inexpensive and the film thickness can be easily controlled, the gap size of the bearing gap can be set to a predetermined value by changing the film thickness of the shaft portion and the sleeve portion. Can be adjusted.

By forming a wear-resistant lubricating film by a composite electroless plating film containing an inexpensive solid lubricant with a simple film forming process, abrasion powder is generated during low-speed rotation such as when starting or stopping. In this way, it is possible to realize an inexpensive dynamic pressure bearing with excellent bearing performance.

By using such a dynamic pressure bearing for the bearing portion, it is possible to contribute to higher performance and lower cost of the deflection scanning device.

[0020]

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

FIG. 1A shows a main part of a deflection scanning apparatus having a dynamic pressure bearing according to an embodiment as a bearing part.
The rotary polygon mirror 1 is a deflection scanning unit having a plurality of reflection surfaces 1a on the side surfaces of a polygonal prism, and a sleeve portion (bearing member) supported by a bearing housing integrated with the optical box 50 shown in FIG. , A shaft 3 that is a shaft (bearing member) rotatably fitted to the sleeve 2, a rotor boss 4 that is a rotating member fixed to the shaft 3, and integrally connected to a lower surface thereof. And a stator coil 7 fixed to a base plate 6 integral with the bearing housing, and the stator coil 7 together with the rotor magnet 5 supported inside the rotor frame 5a. The motor which rotates is comprised. The rotating polygon mirror 1 is pressed against the rotor boss 4 by the holding plate 8,
It is integrated with a rotating part including the rotor boss 4, the rotor frame 5a, the rotor magnet 5, and the like.

When the stator coil 7 is excited by the drive current supplied through the drive circuit and the control circuit on the base plate 6, the rotor magnet 5 rotates together with the shaft 3 and the rotary polygon mirror 1, and the rotary polygon mirror 1 The light beam such as a laser beam applied to the reflection surface 1a is deflected and scanned.

The thrust receiver 9 is fixed to the sleeve 2,
The spherical end 3a of the shaft 3 is arranged so as to abut, and forms a pivot bearing. As shown in FIG. 1B, the bearing surface, which is the fitting surface of the sleeve 2, has a dynamic pressure generating groove 2a.
Is engraved, and when the shaft 3 rotates, the fluid in the bearing gap is taken into the center of the dynamic pressure generating groove 2 a, and a high pressure state is caused to separate the shaft 3 from the sleeve 2.

The sleeve 2 having the dynamic pressure generating groove 2a is made of resin, and has a bearing surface, as shown in FIG.
After performing a so-called conductive treatment for providing a flash plating film 21, a composite electroless plating film 22 containing a solid lubricant is formed as a lubricating film. The flash plating film 21 is necessary to make the bearing surface conductive because the base material of the sleeve 2 is a nonmetallic resin, and may be a plating film formed by a general plating process. If the sleeve 2 is made of metal, the flash plating film 21 can be omitted.

The composite electroless plating film 22 containing a solid lubricant is formed by electroless plating by a chemical reaction by dispersing molybdenum disulfide or graphite for imparting lubricity to an electroless plating solution that can be plated. This is the lubricating film to be used.

As described above, by applying the composite electroless plating film 22 having lubricity to the bearing surface of the sleeve 2 having the dynamic pressure generating groove 2a, the lubricity and wear resistance of the bearing surface are improved. The generation of wear powder when the sleeve 2 and the shaft 3 come into contact with each other is prevented, and troubles such as poor rotation caused by wear powder on the bearing portion are avoided.

According to the present embodiment, it is possible to prevent poor rotation due to wear of the shaft of the dynamic pressure bearing and the bearing surface of the sleeve, and to maintain a stable and favorable rotation state for a long period of time. Further, there is no fear of peeling of the film during rotation, and the film forming process is simple because of the electroless plating, so that the cost is low. Further, it is easy to ensure the uniformity of the film.

Further, since it is easy to control the film thickness to change the film thickness, there is an advantage that the gap between the shaft and the sleeve, that is, the bearing gap can be easily corrected (adjusted).

In this embodiment, a composite electroless plating film containing a solid lubricant is provided on the inner surface of the sleeve, but a similar film is formed on the outer surface (fitting surface) of the shaft. Alternatively, a similar coating may be provided on both mating surfaces of the shaft and the sleeve.

The composite electroless plating film containing the above-mentioned solid lubricant is prepared by dispersing fine particles acting as a lubricating filler in an electroless plating solution that can be plated, and forming a metal or nonmetal bearing. Formed on the surface. Hereinafter, the process will be described in detail.

When the shaft or sleeve of the dynamic pressure bearing is made of a nonmetal such as a resin, a composite electroless plating is performed after a surface plating treatment such as a chemical plating treatment or a metal plating.

The electroless plating solution is prepared by mixing nickel sulfate, nickel chloride or the like as a nickel salt, sodium hypophosphite as a reducing agent, sodium acetate as a buffer, and sodium citrate as a stabilizer at specified concentrations. Molybdenum disulfide, graphite, boron nitride and the like are dispersed therein as a solid lubricant to form a plating solution.

The lubricating filler has an average particle size of 0.02.
Molybdenum disulfide of .about.0.5 .mu.m is preferred.

Next, the lubricity is represented by a coefficient of static friction (mu = μ), and L and H are obtained by a measuring method as shown in FIG. 2 and are calculated by μ = H / L.

The dynamic friction coefficient is evaluated using a surface performance tester (Haydon). The coefficient of kinetic friction is 0.
3 mu or less is preferable, and especially 0.1 mu or less is optimal.

As a working process, a generally known electroless plating method may be used.

The composite electroless plating film containing the above-mentioned solid lubricant has lubricity and has sufficiently high wear resistance,
It has excellent performance such as scratch resistance, high adhesion and high solvent resistance.

The surface roughness (Rz) of the composite electroless plating film containing a solid lubricant is preferably 2.0 μm or less.

Regarding the dispersion amount of the fine particles of the solid lubricant,
There is a correlation with the ratio to the amount of electroless plating, and when the amount of fine particles is excessive, the fine particles fall out and cause dust after completion of the product, and when the amount is small, the lubricity tends to be low, and preferably 100 parts by weight of the plating solution. On the other hand, the range is preferably 0.5 to 15 parts by weight, particularly preferably 1 to 7 parts by weight. The shape of the fine particles may be a fixed shape, and the fine particles are put together with a plating solution in a prescribed amount into a container and dispersed by a ball mill for 24 hours or more, and then diluted with demineralized water, preferably to 5 to 20% by weight, in particular, to 7%. Dilute to a solid content of ~ 17 wt%.

The above plating solution was placed in a beaker, and
It is heated to 00 ° C., charged with a bearing member that has been subjected to plating pre-treatment in advance, and plated for 30 minutes to complete it.

At this time, the thickness of the plating film is 0.2 to 5
An arbitrary film thickness of 0 μm can be obtained. The content of the fine particles having lubricity is preferably 1 to 7% by weight, particularly preferably 3 to 5% by weight.

As described above, by dispersing the fine particles of the solid lubricant in the plating solution to form a plating film, the lubricity can be remarkably improved by the eutectoid effect.

In terms of the physical properties of the film, in addition to the effect of preventing the seizure of the bearing by the improvement of the surface roughness and the wear resistance, there is no generation of dust due to the falling off of fine particles as seen in spray coating, for example. There was no problem, for example, the hardness was Vickers 500.

The eutectoid content of the fine particles is confirmed by an X-ray microanalyzer.

The surface roughness was measured by "Surfcom" (trade name, manufactured by Tokyo Seimitsu Co., Ltd.).

(Example 1) A composite electroless plating film containing a solid lubricant was formed on the inner surface of a sleeve made of a brass material and a phosphor bronze material by the following steps.

As a plating solution, 2 wt% of molybdenum disulfide particles was added to a mixed solution of nickel sulfate 30 g / l, sodium hypophosphite 10 g / l, sodium acetate 10 g / l, and sodium citrate 10 g / l. After dispersing in a ball mill for 24 hours, the solution was diluted with demineralized water so that the total volume became 2 liters, to produce a plating solution. Next, the sleeve was treated with an alkali cleaner (Pakna JY30, manufactured by Yuken Chemical Co., Ltd.) at 30 g / liter at 60 ° C. for 5 minutes, washed with water, and then subjected to flash plating as 50 g / liter of nickel chloride and 30 ml of hydrochloric acid.
/ Liter, 5 A / dm ² , room temperature for 5 minutes, and after washing with water, a composite electroless plating film was formed using the plating solution.

The conditions of the electroless plating were as follows: treatment at 98 ° C. for 30 minutes, washing with water, and drying in a drying oven at 100 ° C. for 15 minutes to complete the process.

When the characteristics of the coating film were incorporated in the apparatus shown in FIG. 1 and evaluated, it was found that the dynamic pressure bearing had high lubricity and high durability. FIG. 3 shows the result of measuring the surface roughness of the sleeve.

Example 2 The same process as in Example 1 was carried out except that a chemical conversion treatment of the aluminum surface was performed on the inner surface of the sleeve made of an aluminum material as a base material at 5 g / liter of sodium dichromate at 50 ° C. for 2 minutes. Non-decomposition plating was performed.

(Example 3) Flash plating of the stainless steel surface was performed on the inner surface of a sleeve made of stainless steel for 5 minutes in the same manner as in Example 1, and electroless plating was performed in the same process as in Example 1. .

(Comparative Example) Brass material, phosphor bronze material,
The inner surface of a sleeve made of an aluminum material or a stainless steel material was plated by a general electroless nickel plating process and an electroless composite plating process, and was assembled and evaluated in the apparatus of FIG. As shown in FIGS. 4 and 5, the surface roughness was large, and phenomena such as uneven rotation and image sticking occurred, and there were also defects in quality such as poor adhesion. Table 1 summarizes the film performance of the electroless nickel plating and the electroless composite plating of Examples 1 to 3 and Comparative Example.

[0053]

[Table 1]

From this table, it can be seen that the composite electroless plating film in which the fine particles of the solid lubricant are dispersed is a very effective lubricating film in preventing the generation of abrasion powder.

FIG. 6 shows the entire deflection scanning apparatus, which includes a light source 51 which is a light source device for generating a light beam (light flux) such as a laser beam and the like, and a reflecting surface 1a of the rotary polygon mirror 1 which emits the laser beam. Lens 51 for condensing light linearly
The light beam is deflected and scanned by the rotation of the rotary polygon mirror 1 to form an image on a photosensitive member 53 which is an image forming surface on a rotating drum via an image forming lens system 52 which is an image forming means.
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 formed 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.

Around the photosensitive member 53, a charging device for uniformly charging the surface of the photosensitive member 53, and a charging device for visualizing an electrostatic latent image formed on the surface of the photosensitive member 53 into a toner image. A developing device, a transfer device (not shown) for transferring the toner image to recording paper, and the like are arranged, 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 write 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 the 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.

[0063]

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

By providing a composite electroless plating film containing a solid lubricant having lubricity and abrasion resistance on the fitting surface of the dynamic pressure bearing, it is possible to avoid troubles due to generation of abrasion powder during low-speed rotation and to reduce the cost. In addition, a dynamic pressure bearing having excellent bearing performance and durability can be realized. By using such a dynamic pressure bearing for a bearing portion such as a rotary polygon mirror of a deflection scanning device, it is possible to contribute to higher performance and lower cost of the deflection scanning device.

[Brief description of the drawings]

FIG. 1 shows a main part of a dynamic pressure bearing and a deflection scanning device according to an embodiment, where (a) is a schematic cross-sectional view thereof,
(B) is a sectional view showing a dynamic pressure generating groove on the inner surface of the sleeve,
(C) is an enlarged partial sectional view showing a part of the inner surface of the sleeve in an enlarged manner.

FIG. 2 is a diagram illustrating a method for measuring a static friction coefficient representing lubricity.

FIG. 3 is a graph showing the results of measuring the surface roughness of the sleeve of Example 1.

FIG. 4 is a graph showing the results of measuring the surface roughness of an electroless nickel plating film.

FIG. 5 is a graph showing the results of measuring the surface roughness of an electroless composite plating film.

FIG. 6 is a diagram illustrating the entire deflection scanning device.

FIG. 7 is a schematic sectional view showing one conventional example.

[Description of Signs] 1 Rotating polygon mirror 2 Sleeve 2a Dynamic pressure generating groove 3 Axis 5 Rotor magnet 7 Stator coil 21 Flash plating film 22 Composite electroless plating film containing solid lubricant

Claims (6)

[Claims] 1. A composite electroless plating film containing a solid lubricant is formed on at least one of the shaft portion and the sleeve portion, wherein the shaft portion and the sleeve portion are relatively rotatably fitted. A dynamic pressure bearing. 2. The method according to claim 1, wherein a conductive treatment is performed on at least one of the shaft portion and the sleeve portion, and then a composite electroless plating film containing a solid lubricant is formed. Pressure bearing. 3. The composite electroless plating film having a surface roughness of 2.
The dynamic pressure bearing according to claim 1, wherein the diameter of the dynamic pressure bearing is 0 μm or less. 4. The dynamic pressure bearing according to claim 1, wherein a dynamic friction coefficient of the composite electroless plating film is 0.3 mu or less. 5. The dynamic pressure bearing according to claim 1, wherein the composite electroless plating film contains at least one of a molybdenum compound, a carbide compound, and a nitride compound. 6. A method of manufacturing a dynamic pressure bearing, comprising a step of forming a composite electroless plating film containing a solid lubricant on at least one of a shaft portion and a sleeve portion which are relatively rotatably fitted.