JP2000009144A - Fluid dynamic pressure bearing and forming method for dynamic pressure generating groove and bearing surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid dynamic pressure bearing and a forming method for a dynamic pressure generating groove, which contribute to the enhancement of productivity and process performance because the dynamic pressure generating groove can be excellently and quickly formed in the thrust bearing surface or the radial bearing surface of the fluid dynamic pressure bearing by means of a laser processing method. SOLUTION: A thin film 2 made out of hydrogenated amorphous diamond is formed over the surface 1a of axial core material 1 by means of a CVD method or the like so as to be irradiated by laser L under an oxygen atmosphere, and a part of the film including residuals is thereby removed, so that a dynamic pressure generating groove is formed up. Raw material solution in which fine grains of hydrogenated amorphous diamond are dispersed in a solvent, is uniformly applied to the surface 1a of the axial core material 1 by means of printing, spraying or dipping so as to be dried and sintered to be formed into the film 2, so that the film is irradiated by laser L so as to be formed into a bearing surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a laser machining method in which a dynamic pressure generating groove can be formed on a thrust bearing surface or a radial bearing surface of a fluid dynamic pressure bearing satisfactorily and quickly, thereby improving productivity and processing. The present invention relates to a fluid dynamic pressure bearing that contributes to improvement in performance, and a method for forming a dynamic pressure generating groove and a bearing surface.

[0002]

2. Description of the Related Art A method of forming a dynamic pressure generating groove disclosed in Japanese Patent Application Laid-Open No. 5-44055 is capable of forming a bearing surface excellent in wear resistance, heat resistance and chemical resistance, and using a metal alkoxide-based inorganic material. Coating agents, ceramic inks and ceramic coating agents were printed on the surface of the shaft core material and cured to form bearing surfaces.

A method of forming a dynamic pressure generating groove disclosed in Japanese Patent Application Laid-Open No. 61-62477 engraves a dynamic pressure generating groove by irradiating a bearing metal with a laser beam to evaporate or sublimate the metal. There is a need for a high-power laser, and burrs are generated around the processed groove, and the groove bottom becomes rough, resulting in poor finishing accuracy. In rare cases, needle-like projections may remain on the groove bottom. This may cause breakage during operation, causing an accident of being jammed between bearing surfaces, and there is a disadvantage that processing distortion remains on the material surface.

A method of forming a dynamic pressure generating groove disclosed in Japanese Patent Application Laid-Open No. 63-238992 is to apply and form a corrosion-resistant film on a bearing surface, and to apply a portion corresponding to the dynamic pressure-generating groove of the corrosion-resistant film by laser light. Irradiation to remove or evaporate or sublimate, etching to etch the dynamic pressure generating groove on the bearing surface, and finally remove the corrosion-resistant coating with a solvent, requires a high-power laser, many processes, Many dynamic pressure generating grooves are not necessarily formed uniformly, side etching occurs, the vertical wall surface of the groove is not vertical, and the dynamic pressure during rotation causes uneven dynamic pressure, causing uneven rotation and shaft contact Difficult to control the depth of the
There is a disadvantage that it is expensive to treat the waste liquid of the etching solution.

A method of forming a dynamic pressure generating groove disclosed in Japanese Patent Application Laid-Open No. Sho 62-1886 is to form a film made of a material that easily absorbs laser light on a shaft core, and to form a part of the film by the laser light. Is a method of forming a dynamic pressure generating groove by evaporating or sublimating the resin, which requires a high-power laser, and has a disadvantage that residues generated when removing the coating material adhere to the coating material and are difficult to remove. is there.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a coating constituting a bearing surface formed on the surface of a shaft core material is formed by curing a coating film formed of a metal alkoxide-based inorganic coating agent, a ceramic ink or a ceramic coating agent. It is intended to provide a method for forming a bearing surface and a fluid dynamic pressure bearing, which are made of a material excellent in wear resistance, lubricity, heat resistance and chemical resistance, which is equal to or more than a coating film.

An object of the present invention is to provide a method of forming a bearing surface and a fluid dynamic bearing which can easily form a film having a uniform film thickness, has high productivity and is inexpensive to manufacture.

According to the present invention, a film having a uniform film thickness can be easily formed, the depth of the dynamic pressure generating groove can be easily controlled, and a desired surface roughness can be obtained without forming needle-like projections on the groove bottom surface. The present invention provides a method for forming a bearing surface, and a fluid dynamic pressure bearing having a stable dynamic pressure generating groove with a good balance of characteristic distribution, which enables the dynamic pressure generating groove to have a good shape. is there.

The present invention provides a bearing surface which has a dynamic pressure generating groove which can be processed by a low-power laser of several watts or less, and has no residue (carbide) which adheres to the bearing surface and the groove bottom surface and is difficult to remove. And a fluid dynamic pressure bearing. An object of the present invention is to provide a bearing surface forming method and a fluid dynamic pressure bearing capable of increasing the processing speed of a dynamic pressure generating groove by a low-power laser of several watts or less and securing high productivity.

[0010]

According to the present invention, a raw material solution in which fine particles of hydrogenated amorphous diamond are dispersed in a solvent is applied to the surface of a shaft core material by printing, spraying or dipping, and dried to dryness. An object of the present invention is to provide a method for forming a bearing surface, which comprises forming a hydrogenated amorphous diamond film on the bearing surface.

[0011] The present invention also relates to a method of printing, spraying or dipping a raw material solution in which fine particles of hydrogenated amorphous diamond are dispersed in a solvent, applying the solution to the surface of the shaft core material, drying and calcining the material, and applying hydrogen to the bearing surface. It is an object of the present invention to provide a method for forming a bearing surface, which comprises forming a coating of an amorphous diamond. The present invention also provides a method for forming a bearing surface, comprising forming a hydrogenated amorphous diamond film on a bearing surface by the above method, and further sliding the bearing surface to remove free fine particles. Is to do.

Further, according to the present invention, a film of hydrogenated amorphous diamond is formed on a bearing surface by the above method,
It is still another object of the present invention to provide a method of forming a bearing surface, wherein a dynamic pressure generating groove is formed by irradiating the bearing surface with laser in the air to partially remove the coating. The present invention also provides a method for forming a hydrogenated amorphous diamond film on a bearing surface by the method described above,
An object of the present invention is to provide a method for forming a bearing surface, wherein a dynamic pressure generating groove is formed by irradiating a laser in an atmosphere of a reactive gas to partially remove the coating.

Another object of the present invention is to provide a fluid dynamic bearing having a bearing surface formed by the above-described method of forming a bearing surface.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1A, 1B, 1C and 1C show a first embodiment of a fluid dynamic bearing and a method of forming a dynamic pressure generating groove according to the present invention. This will be described with reference to FIG. First, as shown in FIG. 1A, a surface 1a corresponding to a radial bearing surface or a thrust bearing surface of the shaft core 1 is provided.
The grindstone is polished so that the bottom surface of the processed dynamic pressure generating groove can be suppressed to a desired surface roughness or less, for example, a maximum of 0.8 μm or less, and the surface is activated by alkali degreasing and pickling.

Next, as shown in FIG. 1 (b), the activated surface 1a of the shaft core 1 is hydrogenated by a plasma CVD method, another CVD method, sputtering, or a combustion flame method. A thin film 2 of amorphous diamond is formed so that the film thickness is equal to the depth of the dynamic pressure generating groove. Next, as shown in FIGS. 1C and 2, after disposing the shaft core 1 on which the coating 2 is formed in the closed container 8,
After the inside of the closed vessel 8 is evacuated by a vacuum suction device (not shown), the valve of the oxygen cylinder 10 is opened and filled with oxygen.
A laser L is oscillated from a low-power laser (eg, an argon ion laser, a YAG laser, or a carbon dioxide laser) 11 having an output of several watts provided inside (or outside) of the sealed container, and the laser L cannot be irradiated by ultrasonic waves. After passing through an optical path deflecting device 12 that deflects the optical path at the time of (1), the light diameter is reduced by a condenser lens 13, and the main scanning (reciprocal swing) is performed by a galvano mirror 14 or a polygon mirror as shown by an arrow a, and The shaft material 1 on which the film is formed is sub-scanned (rotated) as shown by an arrow b, and the laser L is formed in a part of the film 2 formed on the shaft material to form a dynamic pressure generating groove pattern. The hydrogenated amorphous diamond at the same location is heated to 800 ° C. to 900 ° C. by the thermal energy of the laser L and thermally decomposed into carbon dioxide gas and water vapor to leave a residue (carbide). Required number of dynamic pressure generating grooves 4 and 4 are removed without, formed at equal arranged ....

Coating of hydrogenated amorphous diamond 2
Is completely burned in air with a low-power laser to form carbon dioxide gas and water vapor, and does not generate residues. However, when the processing speed is high, carbide powder is generated, and the coating 2 and the bottom portion 1 of the dynamic pressure generating groove are formed.
a, and the adhered powder cannot be easily removed. Therefore, as described above, when a portion of the hydrogenated amorphous diamond coating 2 is burned off by a low-power laser in an oxygen atmosphere to form a dynamic pressure generating groove, complete combustion can be achieved even if the processing speed is increased. And the generation of carbide powder is completely eliminated.

The gas filling the closed vessel 9 is not limited to oxygen but may be any reactive gas that can guarantee complete combustion. It may be a substrate mixed with oxygen or a gaseous hydrogen peroxide, ozone or other oxidizing gas.

(Second Embodiment) FIG. 3A shows a second embodiment of the method of forming a bearing surface and the fluid dynamic pressure bearing of the present invention.
This will be described with reference to (b), (c), and (d). First, in the step shown in FIG. 3A, similarly to the step shown in FIG. 1A of the first embodiment, after machining the radial bearing surface of the shaft core 1 or the surface 1a corresponding to the thrust bearing surface, The surface of the groove is ground or polished so that the bottom surface of the dynamic pressure generating groove can be suppressed to a desired surface roughness or less, and the surface is activated by degreased with alkali and pickled.

Next, as shown in FIG. 3B, a thin film 2 of hydrogenated amorphous diamond is formed on the activated surface 1a of the shaft core 1 so that the film thickness is equal to the depth of the dynamic pressure generating groove. It forms so that it may become. Next, as shown in FIG. 3 (c), the coating 2 is brought into sliding contact with a smooth and hard article 3 to perform a gloss treatment.

Next, as shown in FIG. 3 (d), the coating 2 is irradiated with a laser beam L in the atmosphere or in a reactive gas so as to form a dynamic pressure generating groove pattern, and a part of the coating 2 is removed by reaction. Then, a required number of dynamic pressure generating grooves 4, 4,... Are formed at regular intervals to form the bearing surface of the fluid dynamic bearing (see FIG. 2). The hydrogenated amorphous diamond coating 2 has a very small surface friction coefficient and a high Vickers hardness of 1200 to 2000, so there is no fear that the dynamic pressure generating groove 4 will be damaged.

As shown in FIG. 3 (b), in order to form the coating 2 on the surface 1a of the shaft core 1, fine powder of amorphous diamond having a particle size of 1 to 2 μm or less, preferably about 50 to 100 nm is used. The raw material liquid in which the particles are dispersed in the solvent is uniformly applied by printing, spraying, or dipping (a method of dipping in the raw material liquid and slowly pulling it up so as not to drool), and then dried for several minutes to tens of minutes. Bake after solidifying.

When the coating 2 is formed by printing,
Since the thickness of the raw material liquid to be applied becomes as thick as 10 to 100 μm, it is preferable to use a low melting point organic solvent (for example, an acrylic adhesive or a rubber adhesive) as a solvent constituting the raw material liquid. In this case, baking is performed at 200 to 350 ° C. for about 20 minutes.

In the screen printing, the thickness of the coating 2 is increased, and in the offset printing and the gravure printing, the thickness of the coating 2 can be controlled to be smaller than that in the screen printing. FIG. 4 shows how a raw material liquid for forming a film on the radial bearing surface is printed by gravure printing. In FIG. 4, reference numeral 5 denotes a gravure plate roll, reference numeral 6 denotes a container for storing the raw material liquid, reference numeral 7 denotes a furnisher roll for stirring the raw material liquid in the container 6 and attaching the raw material liquid to the gravure plate roll 5, reference numeral 8 Is a doctor. Reference numeral 1 denotes a shaft core, which is rolled onto the gravure plate roll 5. On the surface of the gravure plate roll 5, a gravure cell 5a is formed in a rectangular area corresponding to the developed surface of the circumferential surface of the shaft core 1. Gravure roll 5
Is rotated, the raw material adhering to the gravure plate roll 5 enters the gravure cell 5a, and excess raw material is scraped off by the doctor 8. The raw material in the gravure cell 5a is transferred to the shaft material 1 when it comes into contact with the shaft material 1. Accordingly, if the gravure cell 5a is not provided in a portion corresponding to the dynamic pressure generating groove, printing having the dynamic pressure generating groove can be performed. The gravure cell 5a is formed by an etching method,
Since the depth can be accurately controlled, printing of a desired thickness can be performed.

When the coating 2 is formed by dipping or spraying, the thickness of the raw material liquid to be applied is set to 20 μm.
m or less, and a volatile organic solvent (eg, a general organic solvent such as alcohol or acetone, an acrylic monomer, or a fluorine-containing long-chain alcohol) can be used. The firing temperature in this case can be 80 to 350 ° C.

Even when the coating film 2 is dried, the organic solvent exhibits a necessary and sufficient adhesive function and has a necessary and sufficient bonding force, adhesion force, hardness, lubrication performance, abrasion resistance and lubrication performance.
Sintering may be omitted. The sintered film is solidified firmly because more organic solvent is volatilized and removed than the non-sintered film, and the bonding strength, adhesion, hardness, abrasion resistance, and lubrication performance are more excellent.

As shown in FIG. 3 (c), when the coating 2 comes into sliding contact with the smooth and hard article 3, fine particles of the hydrogenated amorphous diamond on the surface layer of the coating 2 are rubbed and the surface becomes smooth. Is pressed inward to produce luster,
It is divided into those that are released. If the released fine powder particles are left as they are, they will be interposed between the bearing surfaces when assembling the bearing, causing an increase in the coefficient of friction and causing uneven rotation, and will become foreign matters that will scratch the coating 2 formed on the bearing surface. To be removed.

In this way, when the coating 2 is brought into sliding contact, the film thickness becomes dense, the rate of cracking decreases with the passage of time, and the fine particles of hydrogenated amorphous diamond are less likely to be released from the cracked portion. The method of forming the dynamic pressure generating grooves 4, 4,.
This is the same as the embodiment (see FIG. 2).

[0028]

The fluid dynamic pressure bearing of the present invention and the method of forming the dynamic pressure generating groove and the bearing surface have the following effects. (1) Since the coating constituting the bearing surface formed on the surface of the shaft core is made of hydrogenated amorphous diamond, the coating film is cured by applying a metal alkoxide-based inorganic coating agent, ceramic ink or ceramic coating agent. It has excellent abrasion resistance, lubricity, heat resistance, and chemical resistance equal to or higher than that of a film. (2) Since the raw material liquid in which fine particles of hydrogenated amorphous diamond are dispersed in a solvent is applied to the surface of the shaft core material by printing, spraying or dipping, the productivity is high and the manufacturing cost is low. (3) Since a raw material liquid in which fine particles of hydrogenated amorphous diamond are dispersed in a solvent is applied to the surface of the shaft core material by printing, spraying, or dipping, a film having a uniform film thickness can be easily formed. In the case of printing, when the pattern of the dynamic pressure generating grooves is formed on the plate, the dynamic pressure generating grooves can be formed simultaneously with the bearing surface.

(4) A bearing surface is formed from a hydrogenated amorphous diamond film, and a portion is removed by irradiating the bearing surface with laser in air or a reactive gas to form a dynamic pressure generating groove. , Because the thickness of the coating is easy to control,
The desired depth of the dynamic pressure generating groove is obtained in a good shape, no needle-like projections are formed on the groove bottom surface, and there is no fear that the needle-like projections are caught between the bearing surfaces and bite, and high quality reliability is achieved. Characteristics, a groove bottom with a desired surface roughness is obtained, and a stable dynamic pressure generating groove with a small balance of characteristic distribution is provided. (5) The bearing surface made of hydrogenated amorphous diamond is irradiated with a laser to partially remove it to form a dynamic pressure generating groove, and the hydrogenated amorphous diamond film has a temperature of 800 ° C. to 900 ° C. Since it can be easily burned off at a relatively low temperature, a low-power laser such as an argon ion laser of several watts or less, a YAG laser, or a carbon dioxide gas laser can be used, and residues that adhere to the bearing surface and groove bottom and are difficult to remove. There is no generation of (carbide). Since no residue is generated, the dynamic pressure generating groove can be formed, so that it is possible to produce a high-quality product with no machining residue attached to the bearing surface and the groove bottom surface. (6) A low-power laser of several watts or less is formed on the bearing surface made of hydrogenated amorphous diamond by irradiating a laser in a reactive gas atmosphere to remove a part and form a dynamic pressure generating groove. Decomposes hydrogenated amorphous diamond into carbon dioxide gas and water vapor, resulting in residue (carbide)
Can be removed quickly without leaving any residue.The speed of machining the dynamic pressure generating groove is extremely fast and there is no residue attached to the bearing surface, so the thrust bearing surface or radial bearing surface of the fluid dynamic pressure bearing can be quickly removed. In addition, it can be formed satisfactorily, can keep equipment costs and power consumption low, and is extremely effective as a practical technology that can ensure high productivity.

[Brief description of the drawings]

FIG. 1A is an enlarged sectional view showing a shaft core material, and FIG. 1B is an enlarged cross-sectional view showing a shaft core material according to an embodiment of a fluid dynamic pressure bearing and a method of forming a dynamic pressure generating groove according to the present invention. An enlarged sectional view showing a state in which a film made of amorphous diamond is formed,
(C) is an enlarged cross-sectional view showing a state where a dynamic pressure generating groove is formed by irradiating a laser to the coating.

FIG. 2 is a schematic perspective view of an entire apparatus showing a state in which a coating is irradiated with a laser to form a dynamic pressure generating groove, according to an embodiment of a method of forming a bearing surface of a fluid dynamic pressure bearing of the present invention.

3 (a) is an enlarged cross-sectional view showing a shaft core material, and FIG. 3 (b) is an enlarged sectional view showing a shaft core material according to an embodiment of a bearing surface forming method and a fluid dynamic bearing of the present invention. (C) An enlarged cross-sectional view showing a state in which a film made of
FIG. 4 is an enlarged cross-sectional view showing a step of sliding the coating to make it conform as a bearing surface, and FIG. 4D is an enlarged cross-sectional view showing a step of forming a dynamic pressure generating groove by irradiating a laser to the coating.

FIG. 4 is a schematic front view showing how a raw material liquid for forming a film on a radial bearing surface is printed by gravure printing according to the embodiment of the bearing surface forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft core material 1a Shaft core material surface 2 Thin film of hydrogenated amorphous diamond 3 Smooth and hard article 4 Dynamic pressure generating groove 5 Gravure plate roll 6 Container 7 Furnisher roll 8 Doctor 9 Closed container 10 Oxygen cylinder 11 Low output Laser 12 Optical path deflecting device 13 Condensing lens 14 Galvano mirror L Laser

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kimio Omata 1-8-1 Nakase, Mihama-ku, Chiba-shi Inside Seiko Instruments Inc. (72) Inventor Yutaka Koyama 1-8-chome Nakase, Mihama-ku, Chiba-shi, Chiba Inside Iko Instruments Co., Ltd. (72) Inventor Takashi Ishida 1-8-1, Nakase, Mihama-ku, Chiba City, Chiba Prefecture Inside Inko Instruments Co., Ltd. Inside the corporation

Claims (9)

[Claims] 1. A method for forming a dynamic pressure generating groove by forming a thin film of hydrogenated amorphous diamond on a surface of a shaft core material to form a bearing surface, and irradiating a laser to partially remove the film. Features fluid dynamic pressure bearings. 2. A thin coating of hydrogenated amorphous diamond is formed on the surface of the shaft core material at a depth equal to the depth of the dynamic pressure generating groove to form a bearing surface. A method for forming a dynamic pressure generating groove, comprising forming a generating groove. 3. The method according to claim 2, wherein the laser irradiation is performed in an atmosphere of a reactive gas. 4. A raw material liquid in which fine particles of hydrogenated amorphous diamond are dispersed in a solvent is applied to the surface of the shaft core material by printing, spraying or dipping, and dried to dryness.
A method for forming a bearing surface, comprising forming a film of hydrogenated amorphous diamond on the bearing surface. 5. The method for forming a bearing surface according to claim 4, wherein the raw material liquid is applied to a surface of the shaft core material, dried, and then fired. 6. A method according to claim 4, wherein a coating of hydrogenated amorphous diamond is formed on the bearing surface, and the bearing surface is slid to remove free fine particles. The method of forming the bearing surface. 7. A hydrodynamic amorphous diamond film is formed on the bearing surface according to claim 4, and a part of said film is reacted and removed by irradiating said bearing surface with a laser beam in the atmosphere. A method for forming a bearing surface, comprising forming a generation groove. 8. A method according to claim 4, wherein a coating of hydrogenated amorphous diamond is formed on the bearing surface, and the bearing surface is irradiated with a laser in an atmosphere of a reactive gas. A method for forming a bearing surface, characterized in that a dynamic pressure generating groove is formed by removing a part by reaction. 9. A fluid dynamic pressure bearing having a bearing surface formed by the method for forming a bearing surface according to claim 4.