JP2002256280A - Method for forming lubricant film and dynamic pressure bearing component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a lubricant film having an uniform desired thickness with less labor and in a short time, or homogeneously containing a solid lubricant and having low surface roughness. SOLUTION: This method comprises coating a substrate 155 with a lubricant solution S>=3,000 cP in viscosity comprising a solid lubricant, a thermosetting resin and a solvent to form a lubricant film F which is then heated and cured to form the objective lubricant film F. Alternatively, another version of this method comprises coating a substrate 15 with the lubricant solution S comprising the solid lubricant, the thermosetting resin and the solvent to form a lubricant film F followed by holding the substrate 15 at a specified temperature for a specified time and then heating and curing the film F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a lubricating film and a hydrodynamic bearing component, and more particularly, to a method for forming a lubricating film formed on a sliding surface of a substrate in order to prevent damage to the substrate and the like. The present invention relates to a dynamic pressure bearing part having a lubricating film formed thereon.

[0002]

2. Description of the Related Art For example, in a fluid dynamic pressure bearing, a working fluid such as oil is interposed between a rotating side member and a stationary side member, and a dynamic pressure in the working fluid generated at the time of rotation by a pumping action of a dynamic pressure generating groove. This is used to support the rotating member. In such a fluid dynamic pressure bearing, when the number of rotations is low, such as at the start and stop of rotation, it is not possible to generate sufficient dynamic pressure to support the rotating member, and the bearing surface forming the bearing May slide. In particular, in the upright state (the state in which the axis of the motor is installed so as to be in a direction parallel to the direction of gravitational force), it receives the weight of the rotating side member, and is further affected by the magnetic force at the time of magnetic bias. In the thrust bearing portion, when the sliding of the bearing surface occurs, the bearing surface is severely damaged and worn, and in some cases, seizure of the bearing is caused, which causes a reduction in durability and reliability of the bearing.

Therefore, in order to prevent such seizure of the bearing, it has heretofore been conventionally practiced to apply a solid lubricant such as molybdenum disulfide to the bearing surface, particularly the bearing surface constituting the thrust bearing portion, to form a lubricating film. It was done.

FIG. 4 shows a general method of forming a lubricating film so far. First, the rotating side member (rotor hub) 15 is preheated at about 140 ° C. for 30 minutes, and then turned upside down to cover portions other than the bearing surface with masking jigs C ₁ and C ₂ .
And mixed with molybdenum disulfide which is a solid lubricant,
A lubricant solution having a viscosity of about 1,500 cP is spray-applied from the upper center by an injector to form a lubricating film on the bearing surface 155. Next, in this state, the lubricating film was cured by heating at about 190 ° C. for 1 hour.

[0005]

However, in such a conventional method of forming a lubricating film, much labor and time are required to attach and detach the masking member. In addition, the lubricant attached to the used masking member must be removed. Further, it is difficult to control the thickness of the formed lubricating film by spray coating, and a thick and uniform lubricating film cannot be obtained.

On the other hand, since solid lubricants such as molybdenum disulfide contained in a lubricating solution have a large specific gravity, they may precipitate during the period from when the lubricant solution is applied to a base material to when it is heated and cured. . For this reason, the components of the cured lubricating film were non-uniform in the longitudinal section direction. In addition, fine bubbles contained in the lubricating film expand during heat curing and escape from the film surface. As a result of this, traces remained on the surface of the lubricating film as irregularities, resulting in an increase in the surface roughness of the lubricating film.

The present invention has been made in view of such conventional problems, and has as its object to provide a method capable of forming a uniform lubricating film having a desired thickness with a small amount of labor and time. is there.

It is another object of the present invention to provide a method for forming a lubricating film containing a solid lubricant uniformly and having a small surface roughness.

It is another object of the present invention to provide a highly dynamic and highly durable dynamic motor that has high productivity, does not suffer damage or wear even if the bearing surface slides, and does not cause seizing of the bearing. It is to provide a pressure bearing component.

[0010]

In order to achieve the above object, a method for forming a lubricating film according to the present invention is based on a lubricant solution containing a solid lubricant, a thermosetting resin and a solvent and having a viscosity of 3,000 cP or more. After forming a lubricating film by coating on a material, the lubricating film is heated and cured.

At this time, in order to form a lubricating film more uniformly and quickly, it is desirable to rotate the substrate and apply a lubricant solution thereto.

In order to achieve the above object, in the method for forming a lubricating film according to the present invention, a lubricating solution containing a solid lubricant, a thermosetting resin and a solvent is applied to a substrate to form a lubricating film. The substrate was held at a predetermined temperature for a predetermined time, and then the lubricating film was heated and cured.

Here, in order to more effectively prevent precipitation of the solid lubricant in the lubricating film formed on the base material and to more effectively release air bubbles from the film to the outside air without leaving any trace, The holding temperature of the substrate after the formation of the lubricating film is 50 to 6
It is preferable that the temperature is in the range of 0 ° C and the holding time is in the range of 0.5 to 2 hours.

Further, in order to achieve the above object, a dynamic pressure bearing part according to the present invention has a structure in which a lubricating film is formed on at least a part of the substrate surface by the forming method according to any one of claims 1 to 4. .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the first invention will be described. A major feature of the method for forming a lubricating film according to the present invention is that the viscosity of the lubricant solution applied to the base material is 3,000 cP or more.

The conventionally used lubricant solution has a low viscosity of 1,500 cP, and the lubricant solution may flow to portions other than the portion where a lubricating film is to be formed. It was necessary to attach a masking member. Therefore, the present inventors have repeatedly examined whether or not a lubricating film can be formed without using a masking member, and as a result, it is seemingly a simple idea that the viscosity of the lubricant solution should be increased, but it has never been overlooked. The present inventors have found new findings that have led to the present invention.

As a result of further experiments conducted by the present inventors, it has been found that the viscosity of the lubricant solution is preferably 3,000 cP or more. The viscosity of the lubricant solution is 3,000c
If the value is less than P, the lubricant solution may flow to an undesired portion of the base material when the solution is applied. A preferred upper limit of the viscosity of the lubricant solution is 10,000 cP. The more preferable lower limit of the viscosity is 2,000 cP, and the more preferable upper limit of the viscosity is 5,000 cP.

The lubricant solution used in the present invention contains a solid lubricant, a thermosetting resin, and a solvent. The specific state of this solution is a state in which the thermosetting resin is dissolved in the solvent and the solid lubricant is dispersed as a powder. The viscosity of the lubricant solution can be adjusted by, for example, the amount and type of the solvent used. As a simple method, there is a method of evaporating a solvent of a commercially available lubricant solution to increase the solution viscosity.

As the solid lubricant used here, conventionally known solid lubricants can be used. For example, molybdenum sulfide, tungsten sulfide, graphite, boron nitride, antimony trioxide, polytetrafluoroethylene (PTFE), sekiboku, ummo, talc , Soap stone, zinc flower, etc. or 2
More than one species can be used in combination. Of these, molybdenum sulfide, particularly molybdenum disulfide, can be suitably used. In order to uniformly disperse in the thermosetting resin and sufficiently reduce the friction coefficient, the solid lubricant has an average particle size of 15 μm or less, and more preferably 0.1 to 10 μm. In addition, the compounding amount is 10 to 150 w with respect to the thermosetting resin.
t%.

The thermosetting resin used is not particularly limited as long as it has heat resistance. Examples thereof include polyamide imide resin, epoxy resin, alkyd resin, phenol resin, and polyimide resin. Imide resins are particularly preferred.

The solvent used in the present invention is not particularly limited as long as it can dissolve the thermosetting resin. For example, when a polyamideimide resin is used as the thermosetting resin, a nitrogen-based solvent such as N-methyl-2-pyrrolidone; when an epoxy resin is used, a ketone-based solvent such as methyl ethyl ketone; an aromatic solvent such as toluene and xylene; Ethyl solvents such as butyl; aromatic solvents and ester solvents when alkyd resins are used; alcohol solvents and ketone solvents such as ethanol when phenol resins are used; ester solvents; when polyimide resins are used A nitrogen-based solvent or the like is preferably used.

The compounding amount of the solvent may be appropriately adjusted so that the viscosity as a lubricant solution is 3,000 cP or more. Generally, 50 to 300 vol% of the total amount of the solid lubricant and the thermosetting resin is used. Range.

The substrate on which the lubricating film is to be formed is not particularly limited. Examples thereof include iron, carbon steel, other alloy steels, copper and copper alloys, aluminum and aluminum alloys, other various metals, alloys, and Al. ₂ O ₃ , SiO
₂ , ceramics such as TiO ₂ , ZrO ₂ , and SiC, glass, and hard plastics.

The method of applying the lubricant solution is not particularly limited, and a conventionally known application method can be used. However, in order to achieve the object of the present invention of forming a lubricating film without using a masking member, it is necessary to use a rotating method. A spin coating method in which a lubricant solution is applied to a base material that is being used is particularly preferred. Specifically, the number of rotations of the substrate and the amount of the lubricant solution applied are adjusted so that the lubricant solution spreads evenly on the substrate while the substrate rotates several times (preferably three times or more). Is recommended.

FIG. 1 is a sectional view showing a state when a lubricant solution is applied to a substrate. FIG. 1A is a state diagram when the lubricant solution S is dropped on the bearing surface 155 of the rotating rotor hub (base material) 15. Due to the centrifugal force, the dropped lubricant solution S spreads radially outward on the bearing surface as shown in FIG. At this time, since the viscosity of the lubricant solution is higher than before, a uniform lubricating film is formed on the bearing surface.
In addition, because the peripheral edge of the lubricating film is rounded due to surface tension,
The lubricant solution does not spread to portions other than the bearing surface.

When a lubricating film is formed on the bearing surface without any gap, for example, the rotor hub is rotated a little faster,
Add a little more lubricant solution. Then, FIG. 2 (a)
As shown in (2), the lubricant solution moves a large amount in the radial direction outward due to centrifugal force and is blocked from going to the outer peripheral wall, and the lubricant film becomes thicker in the radial direction outside. After the lubricating film is cured in this state, the upper surface of the lubricating film is cut along with the inner surface of the outer peripheral wall as shown by the broken line in FIG. As a result, a lubricating film can be formed on the bearing surface without any gap, as shown in FIG.

The thickness of the lubricating film to be formed is not particularly limited, and may be appropriately determined in accordance with the use environment of the substrate on which the lubricating film is formed. However, according to the forming method of the present invention, it has been conventionally difficult. A thick film can be formed by one application. The film thickness that can be formed by one application is about 1 to 100 μm.

In order to form the lubricating film uniformly and quickly, it is preferable to preheat the base material before applying the lubricant solution. The conditions for this preheating are, for example, 100 to
150 ° C. for 0.5 to 1 hour. The curing conditions after the formation of the lubricating film may be appropriately determined based on the type of the thermosetting resin or the base material.
Conditions such as と い っ た 3 hours can be exemplified.

Next, the second invention will be described. A major feature of the method for forming a lubricating film according to the present invention is that after forming a lubricating film on a substrate, the substrate is held at a predetermined temperature for a predetermined time.

In the conventional method, after a lubricating film is formed on a base material, the lubricating film is cured by placing it in a heating furnace or the like. According to this method, since the hardening of the lubricating film proceeds from the outside to the inside, a solid lubricant having a high specific gravity precipitates before the inside is hardened, so that a uniform film cannot be formed, and the bubbles existing in the film are heated. When the film was expanded and escaped from the surface, the film surface had already begun to cure, leaving traces of air bubbles remaining, and the surface roughness of the film was large. On the other hand, according to the forming method of the present invention, since the lubricating film is heated from the base side before the lubricating film is put into a heating furnace or the like and the lubricating film is cured from the lower side, precipitation of the solid lubricant can be prevented. In addition, since the film surface has not yet been cured when the bubbles escape from the surface of the lubricating film, the surface roughness of the lubricating film can be kept small without leaving traces of air bubbles.

The holding temperature and the holding time of the substrate after the formation of the lubricating film may be appropriately determined based on the type of the thermosetting resin and the amount of the applied resin. The time is preferably in the range of 0.5 to 2 hours.

In order to hold the substrate, the substrate may be placed on a heating member such as a hot plate. In this case, heat is transmitted from the heating member to the lubricating film via the base material.

The method for applying the lubricant solution to the substrate is not particularly limited, and a conventionally known method can be used. For example, a spin coating method, a spray coating method, a flow coating method, a roll coating method, a dipping method and the like can be mentioned.
Among them, the method of applying a high-viscosity lubricant solution by a spin coating method as described above is recommended from the viewpoint of productivity and film thickness controllability. Further, similarly to the above-described method, it is preferable to preheat the base material before applying the lubricant solution. The preheating conditions are the same as described above.

When the holding of the substrate is completed, the lubricating film is heated and cured. The conditions for curing the lubricating film are the same as those described above, for example, 150 to 300 ° C. and 0.5 to 3 hours.

The substrate on which the lubricating film is formed by the forming method according to the first and second inventions can be suitably used as a sliding part in a motor or an engine. Among them, it can be more suitably used as a dynamic pressure bearing part of a motor. An example in which the substrate on which the lubricating film is formed by the above-described forming method is used as a dynamic pressure bearing component (specifically, the rotor hub 15) of the motor will be described below.

FIG. 3 is a sectional view showing an embodiment of a spindle motor having a fluid dynamic bearing. Bracket 1
Reference numeral 1 denotes a base 111 provided at the center,
Peripheral wall 112 provided in the outer peripheral direction of the
And a flange 113 extending further outwardly from
These are formed integrally and coaxially. A magnetic attraction member M made of a permanent magnet or a ferromagnetic material is provided below the peripheral wall 112 to magnetically attract the rotor hub 15 downward in the axial direction.

An annular projection 114 is formed at the center of the base 111, and the fixed sleeve (sleeve member) 2 is fitted and fixed thereto by, for example, press fitting. A through-hole 121 is formed in the center of the fixed sleeve 2 in the axial direction, and a groove 122 is formed at the lower end thereof and opens downward in the axial direction.

The shaft (shaft member) 1 is inserted into the through hole 121 of the fixed sleeve 2 through a predetermined gap, and a ring-shaped stopper 132 having a size that fits in the groove 122 is used to prevent the shaft 1 from coming off. Is fitted to the lower end of the shaft 1. The counter plate 14 is mounted so as to cover the retaining 132.

The substantially cylindrical rotor hub 15 is fixed to the shaft 1 by fitting a hole 151 formed at the center of the upper surface to the upper end of the shaft 1. On the inner peripheral surface of the rotor hub 15, a rotor magnet 16 that is multipolarly magnetized in the circumferential direction is disposed over the entire circumference. A stator 17 is disposed radially inward of the rotor magnet 16 on an annular protrusion 114 formed on the base 111 of the bracket 11 so as to face the rotor magnet 16. The fixation between the stator 17 and the annular projection 114 may be performed by press-fitting, or by fixing with an adhesive.

A flange 154 is provided on the lower side of the outer periphery of the rotor hub 15.
Is formed, and a hard disk is mounted therein. Specifically, one or a plurality of hard disks are mounted on the flange portion 154 by being positioned by the outer peripheral portion 152 of the rotor hub 15, and then screwed down by a clamp member or the like. It is held and fixed.

The shaft 131 of the shaft 1 and the fixed sleeve 2
And the inner ceiling surface 15 of the rotor hub 15
A minute gap is formed between the upper surface of the fixed sleeve 2 and the lubricating fluid 5 (not shown). In the upper and lower lubricating fluid holding portions of the inner peripheral surface of the fixed sleeve 2, herringbone-shaped dynamic pressure generating grooves 123 a and 123 for generating dynamic pressure in the lubricating fluid as the shaft 1 rotates.
b is formed. Dynamic pressure generating grooves 123a, 123b
Generates a supporting force for holding the shaft 1 in the radial direction when the motor rotates. A dynamic pressure generating groove 124 for generating a dynamic pressure in the lubricating fluid with the rotation of the rotor hub 15 that rotates together with the shaft 1 is also formed on the upper surface of the fixed sleeve 2. The dynamic pressure generating groove 124 generates a force for supporting the rotor hub 15 in the axial direction upward when the motor rotates. On the other hand, the rotor hub 15 is magnetically attracted downward in the axial direction by a magnetic attraction member M provided under the peripheral wall 112 of the bracket 11. The balance between the dynamic pressure generated in the dynamic pressure generating groove 124 and the magnetic attractive force generated by the magnetic attractive member M generates a supporting force for holding the rotor hub 15 in the axial direction during rotation of the motor.

The spindle motor having such a configuration is often mounted on a hard drive disk device or the like in a substantially horizontal state. In this case, in addition to the attractive force of the magnetic attraction member M in the axial direction below the rotor hub 15, Attraction by its own weight acts. For this reason, when the motor having a low rotation speed starts and stops, the motor slides easily on the upper surface of the fixed sleeve 2 to cause seizure. However, the rotor hub 15 opposed to the dynamic pressure generation groove 124 formed on the upper surface of the fixed sleeve 2 is formed. Since the lubricating film F is formed at the position of the inner ceiling surface 155 by the forming method of the present invention, image sticking is effectively prevented.

[0043]

In the forming method according to the first aspect of the invention, the viscosity of the lubricant solution applied to the base material is set to 3,000 cP or more, so that a uniform lubricating film having a desired thickness can be formed with little labor and time. Can be formed.

Further, in the forming method according to the second invention, after the lubricating film is formed on the base material, the base material is held at a predetermined temperature for a predetermined time, so that the solid lubricant is uniformly contained and the surface roughness is small. A lubricating film can be formed.

Further, in the hydrodynamic bearing part according to the present invention, since the lubricating film is formed on at least a part of the base material surface by the above-described forming method, high productivity is obtained and sliding of the bearing surface occurs. However, no damage or wear occurs and no seizure of the bearing occurs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a forming method according to a first invention.

FIG. 2 is a cross-sectional view showing another example of the forming method according to the first invention.

FIG. 3 is a sectional view showing an example of a spindle motor provided with the dynamic pressure bearing component of the present invention.

FIG. 4 is a cross-sectional view showing a conventional method for forming a lubricating film.

[Explanation of symbols]

 S Lubricant solution 15 Rotor hub (base material)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10M 103/06 C10M 103/06 F 107/38 107/38 145/20 145/20 145/22 145/22 149/18 149/18 F16C 17/00 F16C 17/00 A 33/10 33/10 D 33/12 33/12 Z 33/14 33/14 Z // C10N 10:04 C10N 10:04 10:10 10 : 10 10:12 10:12 20:02 20:02 30:06 30:06 40:02 40:02 50:02 50:02 50:08 50:08 F term (reference) 3J011 AA04 AA06 BA06 CA02 CA05 DA01 DA02 JA01 KA04 KA05 MA02 QA04 QA05 QA07 SC02 SC05 SC14 SC20 SE05 SE06 SE07 SE10 4H104 AA04A AA13A AA19A AA24A AA26A CB12C CB13C CD02A CE13C EA02Z FA02 FA05 FA06 LA03 PA01 QA08 QA12

Claims (5)

[Claims] 1. A lubricant solution containing a solid lubricant, a thermosetting resin, and a solvent and having a viscosity of 3,000 cP or more is applied on a substrate to form a lubricating film, and the lubricating film is heated and cured. Forming a lubricating film. 2. The method for forming a lubricating film according to claim 1, wherein the lubricant solution is applied onto a rotating base material. 3. A lubricant solution containing a solid lubricant, a thermosetting resin, and a solvent is applied on a substrate to form a lubricating film.
A method for forming a lubricating film, comprising: holding the substrate at a predetermined temperature for a predetermined time; and thereafter heating and curing the lubricating film. 4. The holding temperature of the substrate after forming the lubricating film is 50.
4. The method for forming a lubricating film according to claim 3, wherein the holding time is in a range of from 0.5 to 2 hours. 5. A hydrodynamic bearing component, wherein a lubricating film is formed on at least a part of the surface of a base material by the forming method according to claim 1.