JPH08219146A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE: To form a resin layer on a dynamical pressure surface simply, at a low cost, thickly and with high accuracy by forming a shaft body which consists of aluminum or aluminum alloy, and also attaching lubricative resin on the outer circumference of a shaft body. CONSTITUTION: A dynamic pressure generating groove 33 is formed in a closing condition in which the groove 33 is not communicated with the axial direction both end parts of the dynamical pressure surface of a shaft inserting body 32 side on which the groove 33 is formed. In such dynamical pressure bearing device, tightly sticking property of lubricative resin 34 is improved while utilizing rough surface of a bearing body 31 made of aluminum or aluminum alloy, the lubricative resin 34 is formed without pre-working, and also cut working is enabled. When cut working is carried on an outer circumference, a dynamical pressure generating groove is formed simultaneously, and size accuracy is improved by cut working to more extent. Since dynamical frictional coefficient of the lubricative resin 34 is set to 0.6 and less and a bending elastic coefficient is set to 5 GPa or more, generation of seize and the like is eliminated at the time of rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device for rotatably supporting a shaft body and a shaft fitting insert body by a dynamic pressure.

[0002]

2. Description of the Related Art Since a polygon mirror driving motor, a hard disk driving motor and the like are required to rotate with high precision and high speed, a dynamic pressure bearing device using a fluid such as air or oil is being used. An example of a device using this dynamic pressure bearing device is a polygon mirror drive motor as shown in FIG. 1, for example. The motor for driving the polygon mirror shown in FIG. 1 constitutes a laser scanner in a digital copy, a laser printer, etc. Since it rotates at a high speed of about 10,000 to 3000 RPM, it rotates without contacting the bearing. A supportable air dynamic pressure bearing or the like is used.

That is, in FIG. 1, a rotor 2 is inserted into a bearing 5 fixed to a base 8 with a screw with a gap of several μm to several tens of μm, and is formed on an outer peripheral surface 14 of the rotor 2. The rotor 2 is rotatably supported by the air dynamic pressure bearing 4 which is composed of the spiral groove 15 and the inner peripheral surface of the bearing 5. Further, a drive coil 9 is fitted and fixed on the outer periphery of the central columnar portion of the base 8, and the annular magnet 10 forms a magnetic circuit for drive so as to face the drive coil 9 in the circumferential direction.
Is arranged. The annular magnet 10 is arranged inside the rotor 2 via a yoke 19 made of iron, and constitutes a motor drive unit together with the drive coil 9.

The tip of the rotor 2 (the upper end in the figure)
Is provided with a convex portion 13, and the polygon mirror 1 is fitted into the convex portion 13. The balance plate 1 is provided on the polygon mirror 1 via a wave spring 17.
6 is mounted coaxially and its balance plate 16
The fixing screw 18 inserted from the side is the convex portion 13 of the rotor 2
The polygon mirror 1 is fixed by being screwed on.

Further, a pair of annular magnets 11 and 12 are attached to the outer periphery of the upper part of the central columnar portion of the base 8 and the inner periphery of the balance plate 16 so as to face each other. The respective annular magnets 11 and 12 are magnetized by reversing the polarities in the axial direction, thereby forming a magnetic thrust bearing.

In such a dynamic pressure bearing, a metal dynamic pressure surface such as an aluminum material is coated or integrally molded with a resin layer to prevent wear at the time of starting and stopping and to impair the function of the bearing even in the case of a contact accident due to a large disturbance. Conventionally, there has been conventionally proposed a dynamic pressure bearing which enables a longer life.

[0007]

However, when a resin coating is applied to the dynamic pressure surface as described above, in order to obtain a resin film having a required thickness, for example, the coating must be repeated many times and the productivity is improved. There is a problem that is bad. on the other hand,
If the thickness of the resin film is reduced, the underlying surface may be exposed during cutting. Therefore, conventionally, the dynamic pressure surface cannot be directly coated, and pre-processing is required. Further, since the slidable resin material is generally difficult to adhere, it is necessary to take measures to enhance the adhesive force.

It may be possible to integrally mold a resin on the metal dynamic pressure surface, but in that case, the adhesion with the metal dynamic pressure surface deteriorates due to the molding shrinkage of the resin material. In addition, when the resin is thickened by integral molding, the thermal expansion of the resin is larger than that of metal, which causes a problem that the gap for obtaining the dynamic pressure cannot be narrowed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dynamic pressure bearing device capable of molding a resin layer on a dynamic pressure surface with high precision with a simple, low cost and thick wall.

[0010]

Means for Solving the Problems In order to achieve the above object, the means according to the first aspect of the present invention rotatably supports a shaft body and a shaft fitting insert body by a dynamic pressure. In a dynamic pressure bearing device in which a groove for dynamic pressure generation is formed on at least one side of a dynamic pressure surface composed of an outer peripheral surface of a shaft body and an inner peripheral surface of a shaft fitting body, the shaft body is made of aluminum or aluminum alloy. At the same time, the outer peripheral surface of the shaft body is coated with a lubricating resin.

At this time, as the above-mentioned lubricating resin, a resin having a dynamic friction coefficient of 0.6 or less or a composite resin obtained by filling the resin with a modifier for improving wear resistance and lubricity is adopted.

Further, the means according to the second aspect of the present invention rotatably supports the shaft body and the shaft fitting insert body by a dynamic pressure, wherein the outer peripheral surface of the shaft body and the shaft fitting insert body are supported. In a dynamic pressure bearing device in which a groove for dynamic pressure generation is formed on at least one side of a dynamic pressure surface formed of an inner peripheral surface, the shaft body is made of high-rigidity resin, and a lubricating resin is provided on the outer peripheral surface of the shaft body. It is configured to be attached.

At this time, as the high-rigidity resin, each resin similar to the above-mentioned lubricating resin or a resin obtained by compounding a filler with these resins is used, and the rotating member during rotation collides with the shaft body to be deformed. A resin having a flexural modulus of 5 GPa (gigapascal) or more is used so as not to cause it.

[0014]

In the means according to the first aspect of the invention,
The rough surface of the shaft body made of aluminum or aluminum alloy is used to improve the adhesion to the lubrication resin, making it possible to form a thick and highly accurate lubrication resin without pre-processing, and it is also possible to cut Becomes At the time of cutting the outer peripheral portion, the dynamic pressure generating groove can be formed at the same time.

At this time, the dynamic friction coefficient of the lubricating resin is 0.6.
If it is set below, it is possible to further prevent the image sticking.

Further, the thicker the lubricating resin is, the better the seizure resistance is. However, if the lubricating resin is insert-formed, a thick lubricating resin film can be obtained at a low cost, and even if the surface precision of the inner metal is slightly poor, it may be painted. There is no need to perform pre-processing.

Further, if the dynamic pressure generating groove is formed in a closed state so as not to communicate with both axial end portions of the dynamic pressure surface, wear in the vicinity of the groove pattern at the time of starting / stopping is reduced and stable bearing performance is obtained. Can be maintained.

In the means according to the second aspect of the present invention, the high rigidity resin and the lubricating resin of the shaft body are melt-bonded to enhance the adhesion, and the thick and highly accurate lubricating resin can be molded without pre-processing. In addition, cutting processing is possible. At the time of cutting the outer peripheral portion, the dynamic pressure generating groove can be formed at the same time.

At this time, if the resin material serving as the base of the high-rigidity resin and the lubricating resin is common, the adhesion is further enhanced.

If the high-rigidity resin has a dynamic friction coefficient of 0.6 or less and a bending elastic modulus of 5 GPa or more, seizure and the like can be further prevented, and at the same time, the shaft body and the shaft fitting body can be prevented. It is possible to eliminate deformation due to collision during relative rotation.

Further, particularly when the film thickness of the high-rigidity resin is set to 3 μm or more, seizure or the like can be surely prevented.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings. As an application example of the present invention, there is a polygon mirror driving motor in FIG. 1. However, since the entire structure of the motor has already been described in the section of the prior art, it will be omitted. explain.

In the dynamic pressure bearing device shown in FIG. 2, the present invention is applied to an air dynamic pressure bearing device, and a rotating member (rotor) is used with respect to a shaft body 31 as a fixed member (stator). The shaft fitting insert 32 as is rotatably supported by pneumatic pressure. That is, the outer peripheral surface of the shaft body 31 and the inner peripheral surface of the shaft fitting insert 32 respectively form dynamic pressure surfaces, and the dynamic pressure surfaces on the inner peripheral surface side of the shaft fitting insert 32 are electroless nickel plated. In addition, the groove 33 for generating dynamic pressure is formed by cutting.

At this time, the shaft body 31 is made of aluminum or aluminum alloy, and the shaft body 31 is
Lubricating resin 34 is adhered to the outer peripheral surface of the. As the lubricating resin 34, a resin having a dynamic friction coefficient of 0.6 or less, or a composite resin filled with a modifier for improving abrasion resistance and lubricity is used.

In the case of thermosetting plastic, the lubricating resin 34 is, for example, phenol, unsaturated polyester,
Epoxy resin, polyimide, etc. are adopted, and in the case of thermoplastics, for example, polystyrene, ABS resin, polyether sulfone, polycarbonate, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide resin (polyamide 6, Polyamide 66, Polyamide 12), Polyacetal (Polyoxymethylene), Polyfluorinated ethylene (PT
EE), liquid crystal resin (econol, etc.), etc. are adopted.

Further, as the filler for modification, carbon fiber, carbon particles, amorphous carbon, graphite, molybdenum disulfide (Mo S ₂ ), polytetrafluoroethylene (PTFE), potassium titanate and the like are used.

Further, the dynamic pressure generating groove 33 in the present embodiment.
Is a shaft fitting insert 3 in which the dynamic pressure generating groove 33 is formed.
It is formed in a closed state where it does not communicate with both axial end portions of the dynamic pressure surface on the second side.

In the hydrodynamic bearing device according to the first embodiment as described above, the rough surface of the shaft body 31 made of aluminum or aluminum alloy is utilized to improve the adhesion with the lubricating resin 34, and the lubricating resin 34 can be formed without pre-processing, and can be cut. At the time of cutting the outer peripheral portion, the dynamic pressure generating groove can be formed at the same time, and the dimensional accuracy is further improved by the cutting.

If the dynamic friction coefficient of the lubricating resin 34 is set to 0.6 or less as in the first embodiment, the occurrence of seizure during rotation can be eliminated.

Further, since the dynamic pressure generating groove 33 in the first embodiment is formed in a closed state so as not to communicate with both axial end portions of the dynamic pressure surface, the groove pattern and the shaft fitting insertion at the time of starting / stopping. Sliding contact with the body 32 is prevented, wear of the shaft fitting body is reduced, and stable bearing performance is maintained.

On the other hand, the above-mentioned lubricating resin 34 is thickly formed with high precision by insert forming on the shaft body 31. That is, first, the shaft body 31 die-cast as shown in FIG. 3 (a) is inserted into a predetermined injection mold (not shown), and the above-mentioned lubricous resin 34 is placed in FIG.
Injection molding is performed as in (b). And the lubricating resin 3
The outer peripheral surface of No. 4 is cut to form a predetermined outer diameter as shown in FIG. At the time of the cutting process, a groove for generating a dynamic pressure is simultaneously formed.

On the other hand, in the second embodiment of the present invention, the shaft body 31 is made of high-rigidity resin and the shaft body 3 is
Lubricant resin 34 is adhered to the outer peripheral surface of No. 1 in the form of a film.
As the high-rigidity resin that constitutes the shaft body 31, the above-mentioned first resin is used.
The lubricating resin or the resin in which the filler is compounded is used in the examples, and the resin having the flexural modulus of 5 GPa or more is used.

As the filler at this time, an inorganic material such as carbon fiber, carbon particles, glass fiber or glass particles is used.

In the hydrodynamic bearing device according to the second embodiment as described above, the highly rigid resin of the shaft body 31 and the lubricating resin 34 are used.
The adhesion between the and is improved by melt adhesion, and the lubricating resin 34
It is thick and can be cut with high precision without any pre-processing. According to the cutting process, the dimensional accuracy is further improved, and the dynamic pressure generating groove 33 is simultaneously formed during the cutting process.

At this time, if the resin material serving as the base of the high-rigidity resin and the lubricating resin is common, the adhesion between the two is further enhanced.

The high-rigidity resin in the second embodiment has a dynamic friction coefficient of 0.6 or less and a flexural modulus of 5 G.
Since it is set to Pa or more, it is possible to prevent deformation due to a collision during relative rotation between the shaft body 31 and the shaft fitting body 32 while preventing seizure or the like.

For example, as shown in FIG. 4, an acceleration of 10 G, a shaft diameter of 10 to 30 mm, and a rotational speed of 60,000 /
When the relationship between the bending elastic modulus of the shaft material (horizontal axis) and the seizure probability (vertical axis) is taken under the driving condition of 5 minutes, 5 GP
When a or more, the seizure occurrence rate was 0.

Further, the lubricating resin in the second embodiment is integrally molded by two-color molding with a high rigidity resin. That is, as shown in FIG. 5, using a mold having a pair of injection nozzles A and B, first, the shaft core portion is injection-molded by the nozzle A for injecting the high-rigidity resin, and then the mold is opened. The core is rotated 180 °, the shaft core portion is moved to the nozzle B side and the mold is closed, and the lubrication resin is injection-molded by the nozzle B to mold the lubrication resin outside the shaft core portion. At this time, the injection molding of the shaft core portion by the nozzle A is simultaneously formed in parallel. According to such two-color molding, the shaft body described above is automatically molded at low cost.

FIG. 6 shows a PPS (trade name: Toray A31) in which glass fiber as a highly rigid resin is reinforced and mixed with a filler.
0, coefficient of thermal expansion 1.6 to 2.3 × 10 ⁻⁵ / ° C.),
Sliding PPS as a lubricating resin (trade name: Toray A51
5, a thermal expansion coefficient of 2.3 to 3.0 × 10 ⁻⁵ / ° C.) is used. As shown in this figure, it has been found that the production cost of the product according to the present embodiment is reduced to about half of the conventional product while maintaining various evaluations.

Further, when cutting the outer periphery, a hard composition such as an inorganic filler cannot be used as the lubricating resin component, but in that case, the thermal expansion of the material becomes larger than that of the metal, so If the mating sliding member is made of metal, it is impossible to form a stator and a rotor with high dimensional accuracy. However, in the present invention, the thickness of the outer resin layer is made thinner in accordance with the improvement in accuracy, and the insert molding or 2
By color molding, it is possible to mold what has the same thermal expansion as metal using an inorganic filler-filled resin on the inside,
High accuracy can be obtained.

FIG. 8 shows the thermal expansibility when the stator (shaft body) 11 and the rotor (shaft fitting body) 12 have the dimensional relationship as shown in FIG. 7, for example.
As is clear from this figure, in order to maintain the motor performance, the gap between the stator outer diameter and the rotor inner diameter is 0.003.
It is necessary to keep below (0.006 or less on both sides). Actually, even if the coefficient of thermal expansion at the average value level is calculated with the extreme value of the material, it is 0.0 at the operating temperature of the motor of 5 to 80 ° C.
It was 06 and it turned out that there was no problem at all.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, a device for rotationally driving various rotary plates such as a magnetic disk and an optical disk other than a polygon mirror, a device using fluid such as oil other than air, a shaft rotation type device, and a device other than a motor. The present invention can be similarly applied.

[0043]

As described above, the first invention of the present application according to claims 1 and 2 forms a shaft body from aluminum or an aluminum alloy, and uses a rough surface of the shaft body to adhere to a lubricating resin. It is possible to form a thick and highly accurate lubrication resin without pre-processing and to enable cutting, and it is also possible to form a groove for generating dynamic pressure at the same time when cutting the outer peripheral part. Therefore, the resin layer can be formed on the dynamic pressure surface in a simple and low cost and with high thickness and high precision, and the reliability and productivity of the dynamic pressure bearing device can be improved.

The invention according to claim 3 is, in addition to the structure of the first invention, that the lubricating resin can be obtained at a low cost and a thick film thickness by insert forming, even if the surface precision of the inner metal is slightly poor. Since it is not necessary to perform such pre-processing, the reliability and productivity of the dynamic pressure bearing device can be further improved in addition to the above effects.

Further, the second invention of the present application according to claim 4 is
The shaft body is made of high-rigidity resin, and the adhesion between the high-rigidity resin of the shaft body and the lubrication resin is improved by adhesion, making it possible to form a thick and highly accurate lubrication resin without pre-processing. Since cutting is possible and the groove for dynamic pressure generation can be formed at the same time when cutting the outer peripheral part, the resin layer can be easily and inexpensively formed on the dynamic pressure surface with high thickness and high precision. Therefore, the reliability and productivity of the dynamic pressure bearing device can be improved.

At this time, the invention according to claim 5 is, in addition to the structure of the second invention, a lubricating resin integrally molded with a high-rigidity resin by two-color molding. Therefore, the shaft body according to the second invention. In addition to the above effects, it is possible to further improve the productivity of the dynamic pressure bearing device.

The invention according to claim 6 is the above-mentioned second aspect.
In addition to the configuration of the invention, the resin material that serves as the base of the high-rigidity resin and the lubricative resin is commonly used to further enhance the adhesion. Therefore, in addition to the above effects, the reliability and production of the dynamic pressure bearing device are improved. The property can be further improved.

Further, the invention according to claim 7 is the above first aspect.
In addition to the configuration of the invention or the second invention, since the dynamic friction coefficient of the lubricating resin is set to 0.6 or less to prevent the occurrence of seizure, in addition to the above effects, the reliability of the dynamic pressure bearing device is improved. It can be further improved.

Further, in the invention according to claim 8, in addition to the structure of the above-mentioned second invention, seizure or the like is further generated by setting the dynamic friction coefficient of the high-rigidity resin to 0.6 or less and the bending elastic modulus to 5 GPa or more. In addition to the above effects, the reliability of the dynamic pressure bearing device can be further improved since the deformation is eliminated by the collision when the shaft body and the shaft fitting insert body are relatively rotated.

On the other hand, in the invention according to claim 9, in addition to the structure of the above-mentioned second invention, the film thickness of the high-rigidity resin is set to 3 μm or more so as to surely prevent the seizure or the like. In addition to the above effects, the reliability of the dynamic pressure bearing device can be further improved.

According to a tenth aspect of the invention, there is provided the first aspect of the invention.
In addition to the configuration of the invention or the second invention, the dynamic pressure generating groove is formed in a closed state that does not communicate with both axial end portions of the dynamic pressure surface,
Since the wear in the vicinity of the groove pattern is reduced at the time of starting / stopping and the stable bearing performance is maintained, the reliability of the dynamic pressure bearing device can be further improved in addition to the above effects.

[Brief description of drawings]

FIG. 1 is a half cross-sectional explanatory view showing an air dynamic bearing type motor to which the present invention is applied.

FIG. 2 is a semi-longitudinal section explanatory view showing an enlarged main part in one embodiment of the present invention.

FIG. 3 is a cross-sectional view showing an insert molding procedure of the dynamic pressure bearing shown in FIG.

FIG. 4 is a diagram showing a burn-in probability.

FIG. 5 is a cross-sectional view showing an example of a two-color molding die.

FIG. 6 is a list showing performance evaluations.

FIG. 7 is a cross-sectional explanatory view showing dimensional conditions for evaluation.

FIG. 8 is a list showing the effects of thermal expansion.

[Explanation of symbols]

 31 Shaft 32 Shaft Fitting 34 Lubricating Resin

Claims (10)

[Claims] 1. A bearing for rotatably supporting a shaft body and a shaft fitting insert body by a dynamic pressure, wherein a dynamic pressure surface comprising an outer peripheral surface of the shaft body and an inner peripheral surface of the shaft fitting insert body. In a dynamic pressure bearing device having a groove for generating dynamic pressure on at least one side, the shaft body is made of aluminum or an aluminum alloy, and a lubricating resin is adhered to the outer peripheral surface of the shaft body. Dynamic pressure bearing device. 2. A dynamic pressure bearing device, wherein the lubricating resin according to claim 1 is insert-molded. 3. The dynamic pressure bearing device according to claim 1, wherein the shaft body is formed so as to form a fixed member, and the shaft fitting body is formed so as to form a rotating member. Characteristic hydrodynamic bearing device. 4. A bearing for rotatably supporting a shaft body and a shaft fitting insert body by a dynamic pressure, wherein a dynamic pressure surface composed of an outer peripheral surface of the shaft body and an inner peripheral surface of the shaft fitting insert body. In a dynamic pressure bearing device in which a groove for generating dynamic pressure is formed on at least one side, the shaft body is made of high-rigidity resin, and a lubricating resin is adhered to the outer peripheral surface of the shaft body. Dynamic bearing device. 5. The hydrodynamic bearing device according to claim 4, wherein the lubricative resin is integrally formed with the high-rigidity resin by two-color formation. 6. A hydrodynamic bearing device, wherein the lubricating resin and the high-rigidity resin according to claim 4 contain a common base material. 7. A dynamic bearing device, wherein the lubricating resin according to claim 1 or 4 is formed of a resin material having a dynamic friction coefficient of 0.6 or less. 8. The dynamic bearing device according to claim 4, wherein the high-rigidity resin is formed of a resin material having a dynamic friction coefficient of 0.6 or less and a bending elastic modulus of 5 GPa or more. 9. The lubricating resin according to claim 4 has a film thickness of 3
A hydrodynamic bearing device characterized by being formed to a thickness of at least μm. 10. The dynamic pressure bearing device according to claim 1, wherein the dynamic pressure generating groove is formed in a closed state in which it does not communicate with both axial end portions of the dynamic pressure surface on which the dynamic pressure groove is formed. The hydrodynamic bearing device is characterized in that