JP2000346076A - Bearing device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly support a shaft member and a bearing member without causing troubles such as peeling or seizure by reducing load on resin coating by simplified configuration. SOLUTION: A resin coating is allowed to be somewhat brittle by reducing the bridging density of the resin coating formed on the surface of at least one side of a shaft member or a bearing member beyond the maximum density again, thus the resin coating in high temperature environment is prevented from being visco-elastic, and thereby sliding resistance between a shaft member and a bearing member can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device provided with a resin film for supporting a shaft member and a bearing member, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a bearing device for supporting a shaft member and a bearing member so as to be relatively movable, a pair of sliding surfaces opposed to each other is formed by the shaft member and the bearing member. A resin film for preventing seizure may be formed on at least one side by spray coating or the like. Further, as an improvement of the coating film, it has been proposed by the present inventors that a resin film is formed uniformly by electrodeposition coating.

[0003]

However, in a conventional bearing device having a resin film on at least one of the shaft member and the bearing member, the resin film may become viscous, especially in a high temperature environment. Viscoelasticity may increase the sliding resistance between the shaft member and the bearing member. For example, in a dynamic pressure bearing device in which a dynamic pressure is generated in a lubricating fluid and a shaft member and a bearing member are floated and supported relatively to each other, no dynamic pressure is generated at the time of a stop, so that a In this case, the shaft member and the bearing member come into contact with each other and rub against each other. However, in such a hydrodynamic bearing device, the contact resistance at the time of starting and stopping the shaft member and the bearing member is high when the operating environment is high as described above. It increases due to the viscous elasticity of the resin film when formed. As shown in FIG. 5, the increase in frictional resistance due to the viscoelasticity of the resin film is caused by the relationship between the operating temperature of the motor (horizontal axis) and the starting current (vertical axis). The environmental temperature is a predetermined temperature (70 in FIG. 5).
(° C.), the starting current rapidly increases.

If the resin film is left visco-elastic in such a high temperature environment, the load on the resin film increases, which may cause problems such as peeling and seizure. Wear may progress early and the life may be shorter than expected.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bearing device and a method of manufacturing the bearing device, which have a simple structure and which can favorably reduce contact wear between a shaft member and a bearing member in a high-temperature environment. I do.

[0006]

To achieve the above object, according to the first aspect of the present invention, a shaft member and a bearing member slidably mounted on the shaft member so as to be vertically slidable. In a bearing device in which a pair of sliding surfaces facing each other are formed, and a resin film is formed on at least one surface of the pair of sliding surfaces, the resin film is made of a thermoplastic resin. The sliding surface is formed by a resin film which is formed from a resin cross-linked by the above-mentioned method, and which is made brittle by the density of the cross-link being lowered again beyond the maximum cross-link density.

According to the second aspect of the present invention, the bearing member is slidably mounted on the shaft member, and at least one of a pair of sliding surfaces formed opposite to each other by the shaft member and the bearing member. In a method for manufacturing a bearing device in which a resin film is formed on a surface, the resin film is formed by electrodeposition coating using a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, and the resin film is heated. After being thermally cured by the treatment, the crosslink density is reduced again so as to exceed the maximum crosslink density, and the sliding surface is formed using a resin film embrittled by the decrease in the crosslink density. I have to.

Further, according to the third aspect of the present invention, a pair of bearing surfaces opposed by a shaft member and a bearing member rotatably or continuously rotated relative to the shaft member are formed. In a bearing device formed and formed with a resin film on at least one surface of the pair of bearing surfaces, the resin film is formed from a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, The bearing surface is formed by a resin film that has been embrittled by the crosslink density being lowered again beyond the maximum crosslink density.

Further, in the invention according to claim 4, the bearing surface according to claim 3 is a dynamic pressure surface for a dynamic pressure bearing using air as a lubricating fluid.

Further, in the invention according to claim 5, the resin film according to claim 1 or 3 is made of an electrodeposition coating film using an acrylic resin material, and the thermosetting resin for the crosslinking is , Urethane, melamine, or epoxy.

Furthermore, in the invention according to claim 6, the embrittled resin film according to claim 1 or 3 is subjected to a reheating treatment at a heating temperature higher than a heating temperature at which the maximum crosslinking density is generated, or an X-ray. Irradiation, or ozone irradiation,
Alternatively, the crosslink density is lower than the maximum crosslink density by any means of ultraviolet irradiation.

According to the present invention, the bearing member is mounted on the shaft member so as to be relatively rotatable, and at least one surface of a pair of bearing surfaces formed to be opposed to each other by the shaft member and the bearing member. In a method of manufacturing a bearing device in which a resin film is formed thereon, the resin film is formed by electrodeposition coating using a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, and the resin film is subjected to a heat treatment. After the thermosetting, the density of the crosslink is reduced again beyond the maximum crosslink density, and the bearing surface is formed using a resin film embrittled by the reduction of the crosslink density.

Further, in the invention according to claim 8, an acrylic resin material is used as the resin film according to claim 7, and any one of urethane, melamine, and epoxy is used as the thermosetting resin for the crosslinking. One that includes one is used.

According to the first, second, third, or seventh aspect of the present invention having the above-described structure, the resin film which has been slightly embrittled within an appropriate range can make the resin film viscoelastic under a high-temperature environment. Is prevented, and the sliding resistance between the shaft member and the bearing member is reduced.

Such an effect can be easily and reliably obtained by selecting the resin film and the crosslinking agent thereof as in the invention of the fifth or eighth aspect.

Each of the above-mentioned effects is particularly remarkably obtained in the pneumatic bearing device according to the fourth aspect of the present invention.

Furthermore, the treatment for lowering the crosslink density is performed according to claim 6.
It is easily and reliably performed by performing the method as described in the invention.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. Prior to that, the structure of a shaft-rotating polygon mirror driving motor having an air dynamic pressure bearing to which the present invention is applied will be described with reference to the drawings. It is explained based on.

FIG. 4 shows an example of an outer rotor type motor having a fixed shaft type air dynamic pressure bearing device for rotating and driving a polygon mirror. This air dynamic pressure bearing motor includes a stator set 20 as a fixing member assembled on the frame 10 side,
And a rotor set 30 as a rotating member fitted so as to be fitted from the upper side in the figure. Among these, the stator set 20 is a fixed shaft (shaft) mounted to stand substantially at the center position of the frame 10. ) And a bearing holder 22 that surrounds the outer periphery of the fixed shaft 21 in a cylindrical shape at a certain distance in the radial direction. A stator core 23 is fitted on the outer periphery of the bearing holder 22, and a driving coil 24 is wound around each salient pole of the stator core 23.

A resin film as described later is formed on the outer peripheral surface of the fixed shaft 21, and a herringbone type dynamic pressure generating groove 25 is divided into two blocks in the axial direction to form a ring. The rotor cylinder body (bearing member) of the rotor set 30 is provided outside the fixed shaft 21 which is recessed so as to be parallel to each other and provided with the dynamic pressure generating grooves 25, 25.
31 are rotatably mounted with a gap of several μm to several tens μm. A radial dynamic pressure bearing for generating air dynamic pressure is formed between the outer peripheral surface of the fixed shaft 21 and the inner peripheral surface of the rotor cylindrical body 31. In the fixed shaft 21, an air supply hole 26 extends in the axial direction from a tip portion (upper end in the figure) of the fixed shaft 21, and the air supply hole 26 is used for generating the dynamic pressure of the two blocks. Grooves 25, 25
The opening is open toward the outside of the fixed shaft 21 at the portion between the two.

Further, an outer peripheral wall portion 21a of the fixed shaft 21 is axially projected at a distal end portion (upper end portion in the figure) of the fixed shaft 21 by a predetermined amount.
A fixed-side magnet 27 for floating the thrust is annularly mounted on the inner peripheral side. On the other hand, the rotor cylindrical body 31
A closed air end orifice 32 having a predetermined air flow resistance is provided at the center of the closed end portion on the upper end side in the drawing.
Are formed in the axial direction as damper means, and the shock in the axial direction to the rotor set 30 is reduced by the damper action due to the ventilation resistance of the air orifice 32. The air inside the rotor set 30 is supplied to the dynamic pressure generating grooves 2 by the air supply holes 26.
5 and 25, the dynamic pressure generating grooves 25
Is caused to flow in the axially outward vertical direction in the drawing and discharged to the outside.

Further, the air orifice 32 is provided at a closed end portion on the upper end side of the rotor cylindrical body 31 in the figure.
A thrust floating rotation side magnet 33 is annularly mounted so as to surround the periphery of the rotor. The rotating magnet 33 is magnetized in the axial direction (vertical direction in the drawing) so as to mutually generate magnetic attraction with the fixed magnet 27 on the fixed shaft 21. , The rotor set 30 is held in a state of floating by a predetermined amount in the thrust direction.

On the other hand, a flat hexagonal polygon mirror 34 as a rotating plate is fitted on the outer periphery of the rotor cylindrical body 31 on the upper end side in the drawing so as to constitute the rotating plate. The polygon mirror 34 is mounted on a holding portion 38 extending radially outward from the rotor cylindrical body 31 in the axial direction.
Is fixed from the outside in the axial direction.

A rotor flange portion 35 extends radially outward from the holding portion 38. The rotor flange portion 35 includes the cylindrical body portion 31 and the holding portion 3.
8, and is arranged so as to separate a space inside the rotor where the drive coil 24 is arranged and a space outside the rotor where the polygon mirror 34 is arranged.

Further, a drive magnet 37 is provided on the inner peripheral wall surface of an annular mounting plate 36 projecting from the outer peripheral portion of the rotor flange portion 35 in the axial direction (downward in the drawing) via a back yoke made of a magnetic material. It is mounted in a ring.
The drive magnet 37 is connected to the stator core 23 described above.
Is arranged so as to face the outer peripheral surface in the radial direction,
It constitutes a motor drive unit.

Incidentally, in the embodiment of FIG.
8, cylindrical body portion 31, rotor flange portion 35 and mounting portion 3
6 are formed integrally, but each may be formed separately.

When a predetermined drive voltage is applied to the drive coil 24, the polygon mirror 34 rotates together with the rotor cylindrical body 31, and the laser light converged on the polygon mirror 34 by the rotation of the polygon mirror 34. Scans on an image recording medium (not shown). At this time, the rotor cylindrical body 31 is supported in the radial direction by the dynamic pressure of the air generated between the rotor cylindrical body 31 and the fixed shaft 21, and the rotor cylinder body 31 and the fixed side magnet 27 Due to the magnetic attraction, the rotor set 30 is held in a state of floating by a predetermined amount in the thrust direction.

Here, the above-mentioned fixed shaft 21 is made of an aluminum material such as aluminum or an aluminum alloy, and the outer peripheral surface 21a of the fixed shaft 21 including the dynamic pressure bearing surface is formed by electrodeposition coating as described below. A lubricating resin film is formed. That is, in manufacturing the fixed shaft 21, first, a blank material of the fixed shaft 21 is formed by casting using aluminum, an aluminum alloy material or a magnesium alloy, a die casting method, or another processing method. The dynamic pressure generating groove 25 is first processed and formed by performing masking printing on a portion other than the portion where the dynamic pressure generating groove 25 is formed and performing an etching process or the like.

Next, the entire outer surface of the blank material of the fixed shaft 21 is subjected to electrodeposition coating to form a lubricating resin film. In performing the electrodeposition coating, the outer surface of the blank material of the fixed shaft 21 is subjected to a base treatment such as a chromate treatment (alodine treatment) for improving corrosion resistance and coating adhesion, and thereafter, Is immersed in an electrodeposition tank (not shown), and the entire surface of the blank material is coated by electrodeposition (electric swimming). In this electrodeposition coating, a blank material is put into a paint dispersed in water, and the paint is applied by passing an electric current so that the blank material and the other metal body become both poles.

The lubricating resin film according to the present embodiment, which is electrodeposited on the entire outer surface of the fixed shaft 21 in this manner, is formed by coating a thermoplastic resin material such as an acrylic resin with a thermosetting resin for crosslinking. Is formed from a resin containing any one of urethane, melamine, and epoxy, and is cured by a heat treatment at 190 ° C. for 30 minutes, for example. This heat treatment is to cure the film by promoting the above-mentioned crosslinking. For example, when the acrylic resin is cross-linked with urethane, as shown in FIG. The two are cross-linked by urethane.

As described above, the lubricating resin film is used in a state of being hardened by crosslinking, but if it is simply hardened by heating, it may become viscoelastic, especially in a high temperature environment. Due to the viscoelasticity, the contact sliding resistance between the fixed shaft 21 as the shaft member and the rotor cylindrical body 31 as the bearing member increases. That is, in the air dynamic pressure bearing device of the present embodiment, in particular, no dynamic pressure is generated at the time of stoppage. Therefore, at the time of start / stop, the fixed shaft 21 and the rotor cylindrical body 31 come into contact with each other and rub against each other. But
The contact sliding resistance between the fixed shaft 21 and the rotor cylindrical body 31 at the time of starting / stopping is sharply increased due to the viscous elasticity of the lubricating resin film in the high temperature environment described above.

Therefore, in the present embodiment, the lubricating resin film cured by the above-described heat treatment is further subjected to a reheat treatment at 220 to 340 ° C. (for example, 250 ° C.) for 30 minutes. Slightly embrittled. That is, as shown in FIG. 2, the heat treatment for promoting cross-linking is performed at 190 ° C., so that the cross-linking density is almost maximized (accurately at 215 ° C.). By subjecting the lubricating resin film to a reheating treatment to cause thermal decomposition, the crosslinks of the lubricating resin film are partially cut, and the density of the crosslinks is reduced again beyond the maximum crosslink density. In the case of FIG. 1 described above, a part of the bond between the acrylic main chain and the urethane that is the cross-linking part is cut, whereby the lubricating resin film becomes slightly more brittle than at the time of maximum cross-linking. It will be. In addition, 3
When reheating is performed at 00 ° C. or higher, the crosslinked portion is completely thermally decomposed.

As described above, in this embodiment, the reheating treatment for making the lubricating resin film slightly brittle is performed at a temperature higher than the heating temperature (about 215 ° C. in FIG. 2) at which the maximum crosslink density is reached (250 ° C. in this embodiment). C), but other methods such as X-ray irradiation, ozone irradiation, and ultraviolet irradiation can also be used.

According to such an embodiment, first, the lubricating resin film is uniformly coated on a general surface such as the hydrodynamic bearing surface of the fixed shaft 21 by an electrodeposition coating operation. Can be obtained easily. The lubricating resin film composed of the electrodeposition coating formed portion is formed to have extremely good lubricity because lubricating particles float on the surface of the coating at the time of electrodeposition coating, so that the bearing characteristics are improved. Is improved. Furthermore, in this electrodeposition coating, even if there is a defect such as a nest in the material of the coating partner, the coating enters the inside, so that the formed lubricating resin film must have strong adhesion. Becomes The use of the fixed shaft 21 having a lubricating resin film formed by electrodeposition coating having good lubrication as described above improves wear resistance on the hydrodynamic bearing surface, and significantly reduces generation of wear powder. At the same time, the maintenance of the bearing gap and the prevention of seizure are achieved.

Further, in this embodiment, the resin film which has been slightly embrittled within an appropriate range prevents the resin film from being viscous and elastic in a high-temperature environment, and allows the fixed shaft 21 and the rotor cylindrical body 31 to be in contact with each other. The contact sliding resistance is reduced. This point is apparent from the relationship between the operating environment temperature (horizontal axis) and the relative value of the static friction coefficient (vertical axis) in the air dynamic bearing device as shown in FIG. 3, for example. That is, in this figure, a standard cured product was prepared at a basic curing condition of 190 ° C. for 30 minutes, and the standard cured product was reheated under the conditions described in FIG. The results obtained by using the starting torque of the above as a substitute are shown, and the static friction coefficient on the vertical axis is shown based on the measurement result of the standard cured product.

As shown in FIG. 3, the temperature of the reheating treatment is 2
Up to about 40 ° C, the friction load tends to increase with the use environment temperature, but if the reheating temperature exceeds 250 ° C, the friction load is almost constant regardless of the use environment temperature. It turns out to be. This is because the slightly embrittled resin film prevented the resin film from being viscous and elastic in a high temperature environment, and reduced the contact sliding resistance between the fixed shaft 21 and the rotor cylindrical body 31. Conceivable.

Such an effect can be easily and surely obtained by selecting a crosslinking agent containing any one of urethane, melamine and epoxy for the acrylic resin as in the present embodiment.

Further, each of these functions is particularly remarkably obtained in the air dynamic pressure bearing device as in the above-described embodiment.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say. For example, the present invention can be applied to a shaft sliding member such as an objective lens holder of an optical pickup in which a bearing member rotates and slides up and down with respect to the shaft member.

[0040]

As described above, the first, second or third aspect of the present invention is described.
Or the invention according to 7, the cross-link density of the resin film formed on at least one surface of the shaft member or the bearing member, by lowering again beyond the maximum cross-link density, to make the resin film somewhat brittle, Since the resin film is configured to prevent viscoelasticity in a high-temperature environment and reduce the sliding resistance between the shaft member and the bearing member, the load on the resin film from start to stop is reduced. It is possible to smoothly support the shaft member and the bearing member without causing problems such as peeling and seizure in the resin film,
The reliability of the bearing device can be improved.

Further, since the invention described in claim 4 applies the present invention to an air dynamic pressure bearing device, the above-described effects can be particularly remarkably obtained.

According to the fifth or eighth aspect of the present invention, the above-described effects can be obtained easily and reliably by appropriately selecting the resin film and the thermosetting resin for crosslinking the resin film.

According to the sixth aspect of the present invention, the treatment for lowering the crosslink density is performed by an appropriate means.
The effects described above can be obtained easily and reliably.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a structural example of a resin film used in the present invention.

FIG. 2 is a diagram showing a temperature change of a bonding degree in a cross-linking portion.

FIG. 3 is a diagram showing a temperature change of friction of a resin film for each reheat treatment.

FIG. 4 is a half-cross sectional explanatory view showing an example of a polygon mirror drive motor including an air dynamic pressure bearing device to which the present invention is applied.

FIG. 5 is a diagram showing a temperature change of a driving current of a motor using a conventional bearing device having a resin film.

[Explanation of symbols]

 Reference Signs List 21 fixed shaft (shaft member) 21a outer peripheral wall of fixed shaft 25 groove for generating dynamic pressure 31 rotor cylindrical body

Claims (8)

[Claims] 1. A pair of sliding surfaces facing each other are formed by a shaft member and a bearing member slidably mounted on the shaft member, and at least one side of the pair of sliding surfaces is formed on the surface. In the bearing device having a resin film formed thereon, the resin film is formed from a resin obtained by cross-linking a thermoplastic resin with a thermosetting resin, and the density of the cross-link is reduced again beyond the maximum cross-link density. A bearing device, wherein the sliding surface is formed of a resin film which has been embrittled by the above. 2. A bearing member is slidably mounted on a shaft member, and a resin film is formed on at least one surface of a pair of sliding surfaces formed by the shaft member and the bearing member. In the method of manufacturing a bearing device as described above, using a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, the resin film is formed by electrodeposition coating, and after the resin film is thermally cured by a heat treatment, The cross-link density is reduced again so as to exceed the maximum cross-link density, and the sliding surface is formed using a resin film embrittled by the decrease in the cross-link density. Manufacturing method of bearing device. 3. A pair of bearing surfaces opposed to each other by a shaft member and a bearing member rotatably mounted on the shaft member, and a resin is formed on at least one of the pair of bearing surfaces. In the bearing device in which the coating is formed, the resin coating is formed from a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, and the density of the crosslinking is reduced again beyond the maximum crosslinking density. A bearing device, wherein the bearing surface is formed by a brittle resin film. 4. The bearing device according to claim 3, wherein the bearing surface is a dynamic pressure surface for a dynamic pressure bearing using air as a lubricating fluid. 5. The resin film is made of an electrodeposition coating film using an acrylic resin material, and the thermosetting resin for crosslinking is one containing urethane, melamine, or epoxy. The bearing device according to claim 1 or 3, wherein 6. The embrittled resin film may be reheated at a heating temperature higher than the heating temperature at which the maximum crosslink density is generated, or by X-ray irradiation, or ozone irradiation, or ultraviolet irradiation, 4. The bearing device according to claim 1, wherein the crosslinking density is lower than the maximum crosslinking density. 5. 7. A bearing member is mounted on the shaft member so as to be relatively rotatable, and a resin film is formed on at least one of a pair of bearing surfaces formed opposite to each other by the shaft member and the bearing member. In the method of manufacturing a bearing device, the resin film is formed by electrodeposition coating using a resin obtained by crosslinking a thermoplastic resin with a thermosetting resin, and after the resin film is thermally cured by a heat treatment, A method of manufacturing a bearing device, wherein the cross-linking density is reduced again beyond the maximum cross-linking density, and the bearing surface is formed using a resin film embrittled by the reduction in the cross-linking density. 8. An acrylic resin material is used as the resin film, and a resin containing one of urethane, melamine, and epoxy is used as the thermosetting resin for crosslinking. The method for manufacturing a bearing device according to claim 7.