JPH1193942A - Dynamic pressure bearing, manufacture of dynamic pressure bearing, and deflection scanning device using dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing suitably used for a deflection scanning device by providing a fixed sleeve for making a rotating shaft a dynamic pressure bearing, the fixed sleeve is finish worked by cutting with a diamond tool. SOLUTION: A diamond tool 42 is formed of a shank 40 having an outer diameter slightly smaller than the bore diameter of a fixed sleeve 29 to be worked and a diamond tip 41 brazed to a U-shaped cut-out provided on the tip of the shank 40. The fixed sleeve 29 is chucked on a lathe and finished by cutting with the diamond tool. Consequently, the fixed sleeve 29 can be worked with precision of a cylindricity of 1 μm or less, a roundness of 0.5 μm or less, a dispersion of herringbone groove depth of ± 1 μm or less and a surface roughness of 0.3 μm or less. Thus, a dynamic pressure bearing improved in precision of cylindricity, roundness and surface roughness, and a method for manufacturing a dynamic pressure bearing for deflection scanning device can be provided.

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, a method for manufacturing a dynamic pressure bearing, and a deflection scanning apparatus having a dynamic pressure bearing used in an image forming apparatus such as a laser beam printer or a laser facsimile. is there.

[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 by a rotating polygon mirror rotating at a high speed. The scanning light of the rotating polygon mirror thus obtained is formed on a photosensitive member 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 and sent to a fixing device, and the toner on the recording medium is heated and fixed to perform printing. Done.

[0003] The bearing of a motor for rotating a rotary polygon mirror is required to have low rotation unevenness, noise and vibration, and therefore high processing accuracy is required. As one of means for ensuring such high bearing accuracy, a dynamic pressure bearing which is supported by a dynamic pressure of a fluid generated by rotation is used. The dynamic pressure bearing has at least one pattern of dynamic pressure generating grooves formed in the inner diameter of the fixed sleeve, and is configured to support an axial load by a pumping action of a relative motion between the rotating shaft and the fixed sleeve.

For example, FIG. 5 is a sectional view showing a main part of a deflection scanning apparatus according to a conventional example described in Japanese Patent Application Laid-Open No. 7-199105. The deflection scanning device includes a fixed sleeve 1
01, a flange 103 is integrated with a rotating shaft 102 to be fitted to the rotor frame 10.
4. The rotor magnet 105 is fixed and the rotating polygon mirror 10 is fixed.
6 is pressed against the flange member 103 to be integrally connected thereto, and the fixed sleeve 101 is attached to the housing 1.
07, the rotor magnet 105 and the rotating polygon mirror 106 are integrally rotated by exciting the stator coil 108 erected on the motor circuit board 110.

Reference numeral 109 denotes a herringbone-shaped groove provided on the inner peripheral surface of the fixed sleeve, and lubricating oil is injected into this groove to constitute a radial dynamic pressure bearing. On the lower end surface of the rotating shaft 102, a dynamic pressure thrust bearing constituted by a thrust plate 111 is formed. The fixed sleeve 101 is finished by performing ball sizing on the inner peripheral surface thereof by, for example, a configuration described in Japanese Patent Application Laid-Open No. 7-246436. There is also a method of finishing by roller burnishing with a configuration as disclosed in JP-A-2-80814.

[0006]

However, according to the above-mentioned prior art, the inner diameter of the rotary sleeve of the deflector in the deflection scanning device is finished by ball sizing or roller burnishing. As the depth of the groove fluctuates, the cylindricity of the inner diameter of the rotating sleeve and the true cylinder also deteriorate. Also, in the case of ball sizing, when the ball is passed through the inner diameter of the sleeve, the raised portion during groove processing on the inner surface of the sleeve is shaved by the ball and adheres to the ball surface and the inner peripheral surface, and the inner peripheral surface may be roughened. . Also, a predetermined accuracy of the bearing inner diameter may not be obtained due to wear of the tool, generation of scratches, and the like. When a radial dynamic pressure bearing in which the accuracy of each component is not obtained is used for a deflection scanning device, the bearing rigidity becomes unstable,
It causes deterioration of rotation unevenness, shaft runout, and increase in vibration. In addition, the durability is reduced.

It is an object of the present invention to provide a dynamic pressure bearing suitable for use in a deflection scanning device, and a method of manufacturing such a dynamic pressure bearing.

Another object of the present invention is to improve the bearing characteristics of the deflector in the deflection scanning device and improve the durability.

[0009]

In order to achieve the above-mentioned object, a hydrodynamic bearing of the present invention has a shallow groove formed in the inner diameter by ball rolling, and then is finished by cutting with a diamond cutting tool. And a fixed sleeve for dynamic bearing the rotating shaft.

Further, in the method of manufacturing a dynamic pressure bearing of the present invention, a shallow groove is formed by ball rolling in the inner diameter of a fixed sleeve for dynamic pressure bearing of a rotating shaft, and then finishing is performed by cutting with a diamond bite. It is characterized by the following.

Still further, the deflection scanning apparatus of the present invention comprises: a rotating shaft rotatably fitted to a fixed sleeve; a rotating polygon mirror supported by the rotating shaft; a rotor magnet supported by the rotating shaft; An oil dynamic pressure bearing having a drive unit provided with a stator facing the rotary shaft, a shallow groove for generating dynamic pressure provided on an inner peripheral surface of the fixed sleeve, and lubricating oil interposed in a gap between the rotating shaft and the rotating shaft. In the deflection scanning device, a shallow groove is formed in the inner diameter of the fixed sleeve by ball rolling, and thereafter, cutting is performed using a diamond bite for finishing.

Further, it is preferable to use a natural diamond single crystal cutting tool before machining the shallow groove. In addition, it is preferable that the shallow groove processing and the inner diameter processing using a single crystal tool of natural diamond be processed by a wax.

[0013]

In the deflection scanning device having the above-described configuration, the inner diameter of the bearing fixing sleeve is finished by cutting with the use of a natural diamond single crystal cutting tool capable of creating the shape of the blade tip with high precision. The dimensional accuracy of each part constituting the radial dynamic pressure bearing, such as the degree, surface roughness, and depth of the herringbone-shaped groove for generating dynamic pressure, is improved, and the bearing characteristics of the deflector are improved and the durability is also improved. .

Further, by cutting using a single crystal tool of natural diamond before machining the shallow groove, the cylindricity, roundness, and surface roughness in a blank state before the machining of the shallow groove are improved. In addition, the shape of the shallow groove is stabilized, and the machining allowance at the time of finishing can be reduced, and the accuracy of cylindricity, roundness, groove depth, and the like is further improved.

Further, by performing the groove processing and the inner diameter processing with one chuck, the coaxiality can be easily obtained at the time of the groove processing and at the time of the finishing processing with the diamond tool, and the variation in the groove depth can be reduced. Become.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiment shown in FIG. FIG. 1 is a schematic plan view of a deflection scanning device according to an embodiment of the present invention. A laser unit 22 is attached to a part of the optical box 21, and a cylindrical lens 23 and a deflector 24 are arranged inside the optical box 21 in a traveling direction of a laser beam from the laser unit 22. In the traveling direction of the laser beam deflected by the rotary polygon mirror 35 of the deflector 24, the lenses 25 and 26
1, and the photosensitive drum 27 is disposed outside the optical box 21.

In the deflector 24, a fixed sleeve 29 is erected on a motor circuit board 38 fixed to the optical box 21 as shown in the sectional view of FIG.
0 is rotatably fitted. A flange member 3 made of aluminum, brass or the like is provided on the outer periphery of the rotating shaft 30.
1 is fixed by shrink-fitting, press-fitting, or the like.
The drive magnet 34 is glued and fixed to the lower portion of the outer periphery of the flange member 31 by shrink fitting, bonding or the like, or integrally formed. A stator 50 is disposed on the upper surface of the motor circuit board 38 so as to face the drive magnet 34.

The inner diameter of the fixed sleeve 29 has herringbone grooves 36 and 37. Reference numeral 51 denotes a thrust plate which is in contact with a spherical portion (arc having a large radius) below the rotary shaft 30. 39 is fixed sleeve 29 and rotation 3
This is the lubricating oil that has been injected into gap 0. Here, the inner diameter of the fixed sleeve is subjected to plastic working while pressing a plurality of balls against the inner diameter surface of the fixed sleeve by a groove processing tool as disclosed in, for example, JP-A-54-84155.
Then, it is finished by cutting with a diamond tool as shown in the schematic diagram of FIG.

The diamond cutting tool 42 has a shank 40 having an outer diameter slightly smaller than the inner diameter of the fixed sleeve 29 to be machined, and a diamond brazed to a U-shaped cutout provided at the tip of the shank 40. It is composed of a chip 41 (see FIG. 3b). As a result of chucking the fixed sleeve 29 on the lathe and cutting and finishing with the diamond bite of this embodiment, the cylindricity is 1 μm or less, the roundness is 0.5 μm or less, the variation of the herringbone groove depth ± 1 μm or less, the surface Processing was possible with an accuracy of a roughness of 0.3 μm or less. In this test processing, natural diamond is used as the diamond tip 41.

Since natural diamond can create the shape of the cutting edge with higher precision than the ordinary cutting tool materials of high-speed copper steel and cemented carbide, the transferability of the blade shape to the object to be machined is good. Except for an additional element such as deformation due to the chuck, the "maternal principle" that the trajectory of the relative motion between the tool and the processing target is directly transferred to the processing target is substantially satisfied. At this time, the theoretical surface roughness A can be expressed as A = f ² / 8R where f is the feed speed and R is the tip radius of the blade. For example, feed rate 0.02mm / r
ev, the theoretical surface roughness 0.2 when the tip radius is 0.2 mm
5 μm is obtained.

On the other hand, in the oil dynamic pressure bearing used in the deflection scanning device of the present invention, the radial bearing surface during rotation is not in contact, but the rotation shaft 30 comes into contact with the fixed sleeve 29 when the rotation is stopped. For this reason, if the surface roughness of the inner peripheral surface of the fixed sleeve 29 is large, adhesion and wear occur due to repeated contact,
The durability against start / stop decreases. As a countermeasure, the herringbone-shaped groove 3 on the inner peripheral surface of the fixed sleeve 29 is used.
The surface roughness of the non-grooved portion where the rotating shaft 30 contacts at the time of stop other than 6 and 37 needs to be 1 μm or less. Generally, the bearing clearance of an oil dynamic pressure bearing is 3 to 20 μm,
The roundness of the non-grooved portion usually requires an accuracy of 1 μm or less. With the conventional ball sizing and roller burnishing, it is relatively easy to achieve the above-mentioned surface roughness if there is no partial peeling or peeling, but the roundness and cylindricity are largely lost. However,
According to the processing method of the present invention, good surface roughness and roundness can be simultaneously obtained.

Further, by cutting using a single crystal tool bit of natural tire diamond before machining the shallow groove, the cylindricity, roundness and surface roughness of the blank before the shallow groove machining are improved. Therefore, the shape of the shallow groove can be stabilized, and the machining allowance at the time of finishing can be reduced, and the accuracy of cylindricity, roundness, groove depth, and the like can be further improved.

Further, as shown in a modified example of FIG. 4, on the lathe, the above-mentioned shallow groove machining tool 52 with the ball and the finish machining with the diamond tool 42 and the inner diameter machining with the diamond tool 42 before the shallow groove machining are performed in one operation. By processing with the chuck, the coaxialness of the shallow groove processing and the finishing processing with the diamond bite can be accurately obtained, so that the variation in the groove depth can be further suppressed. The shallow groove machining tool 52 and the diamond tool 42 are
Attached to a stage movable in the X and Y directions, the coaxial finishing can be accurately performed, and the diamond bit 42 can be used in common both after and before shallow groove processing. .

With such a configuration, the rotation shaft 30 of the deflector 24 is supported and rotated by a part of the spherical portion at the lower end contacting the thrust plate 38. At this time, in the radial direction, the rotary shaft 30 floats by the pumping action of the lubricating oil injected into the herringbone-shaped groove provided on the inner diameter of the fixed sleeve 29 and can be rotated in a non-contact manner. And the laser beam from the laser unit 22 is
The light is condensed on the rotating polygon mirror 35 of the deflector 24 by the cylindrical lens 23 and is deflected and scanned by the rotating polygon mirror 35. The deflected laser beam is scanned at a constant speed while being focused on the photoconductor 27 by the lenses 25 and 26.

Since the inner diameter of the fixed sleeve 29 is precisely machined, a stable radial dynamic pressure can be generated with little variation in the pumping action generated by the herringbone-shaped groove. Less rotation unevenness, shaft tilt and vibration. In addition, since there is no unevenness due to scratches or adhesion peeling on the inner diameter of the fixed sleeve as in ball sizing or burnishing, durability such as wear and galling is improved.

[0026]

As described above, according to the present invention,
A dynamic pressure bearing with improved accuracy of cylindricity, roundness, and surface roughness, and a method of manufacturing such a dynamic pressure bearing can be obtained.

In the deflection scanning device according to the present invention, the inner diameter of a fixed sleeve provided with a herringbone-shaped groove constituting a radial dynamic pressure bearing is finished by cutting with a diamond tool. After cutting with a ball, a herringbone-shaped groove is provided by a ball, and cutting with a diamond bite is performed again as an inner diameter finish, so that each component such as the cylindricity of the fixed sleeve, roundness, and the depth of the herringbone-shaped groove And the stable radial dynamic pressure can be generated. Therefore, it is possible to improve the characteristics of the bearing, such as uneven rotation, shaft tilt, and vibration, and to stabilize the rotation of the rotary polygon mirror. Further, the contact between the shaft and the sleeve and galling are prevented to improve durability.

[Brief description of the drawings]

FIG. 1 is a plan view of a deflection scanning device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the deflection scanning device according to the embodiment of the present invention.

FIG. 3 is a diagram of a diamond bite used for machining a bearing used in a deflection scanning device, of which FIG.
Is a side view thereof, and FIG. 3b is an end view thereof.

FIG. 4 is a schematic diagram of a modification of the embodiment.

FIG. 5 is a main sectional view of a conventional deflection scanning device.

[Description of Signs] 21 Optical box 28 Motor circuit board 29 Fixed sleeve 30 Rotating shaft 31 Flange member 32 Pressing spring 34 Drive magnet 35 Rotating polygon mirror 36, 37 Herringbone-shaped groove 51 Thrust plate 39 Lubricating oil 40 Shank 41 Diamond chip 42 diamond bite

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayoshi Asami 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Fumihiro Kuzumi 2-4-1-19 Nakane, Meguro-ku, Tokyo Kyano N Seiki Co., Ltd.

Claims (9)

[Claims] 1. A hydrodynamic bearing having a fixed sleeve for forming a shallow groove on an inner diameter by ball rolling and then finishing by cutting with a diamond tool for hydrodynamic bearing a rotating shaft. bearing. 2. The dynamic pressure bearing according to claim 1, wherein cutting is performed using the diamond tool before rolling the ball, and the cylindricity, roundness, and surface roughness of the blank fixed sleeve are reduced. A dynamic pressure bearing characterized by improved accuracy. 3. A method of manufacturing a dynamic pressure bearing, comprising forming a shallow groove by ball rolling in the inner diameter of a fixed sleeve for dynamic pressure bearing of a rotating shaft, and then performing finishing by cutting with a diamond bite. . 4. The method of manufacturing a dynamic pressure bearing according to claim 3, wherein the ball is cut using the diamond tool before ball rolling, and the fixed sleeve in a blank state has a cylindricity, a roundness, and a surface roughness. A method for manufacturing a dynamic pressure bearing, characterized by improving the accuracy of the bearing. 5. A drive unit comprising: a rotary shaft rotatably fitted to a fixed sleeve; a rotary polygon mirror supported by the rotary shaft; a rotor magnet supported by the rotary shaft; and a stator opposed to the rotor magnet. Having a shallow groove for generating dynamic pressure on the inner peripheral surface of the fixed sleeve, the deflection scanning device constituting an oil dynamic pressure bearing in which lubricating oil is interposed in the gap between the rotating shaft, A deflection scanning device characterized in that a shallow groove is formed in the inner diameter of a fixed sleeve by ball rolling, and thereafter, cutting is performed using a diamond bite for finishing. 6. The deflection scanning apparatus according to claim 5, wherein cutting is performed using the diamond tool before a shallow groove is formed in the inner diameter of the fixed sleeve by ball rolling. 7. The deflection scanning device according to claim 5, wherein the groove processing by the ball rolling and the inner diameter processing by the diamond tool are performed by one chuck. 8. The deflection scanning device according to claim 5, wherein a single crystal of natural diamond is used as the diamond of the diamond cutting tool. 9. A non-grooved portion other than a shallow groove for generating dynamic pressure on the inner peripheral surface of the fixed sleeve has a roundness of 1 μm.
The deflection scanning device according to any one of claims 5 to 8, wherein the deflection scanning device has a surface roughness of 1 m or less.