JP2000179541A - Liquid dynamic pressure bearing and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid dynamic pressure bearing not polluting a storage medium or a reading device such as a hard disk, and to reduce the cost of the liquid dynamic pressure bearing having a resin coating. SOLUTION: In a liquid dynamic bearing having a columnar shaft member 1, a cylindrical receiving member 2 to which the columnar shaft member 1 is rotatably fitted, and a lid member 3, the columnar shaft member 1 comprises a metallic core N with a resin coating layer P thereon, and the resin coating layer P and a dynamic pressure generating groove provided in the resin coating layer P are integrated with each other by forming a liquid crystal polymer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical shaft member and a cylindrical receiving member. The outer peripheral surface of the cylindrical shaft member and / or the inner peripheral surface of the cylindrical receiving member are coated with a resin. The present invention relates to a liquid dynamic pressure bearing having a layer formed thereon and a spindle motor including the liquid dynamic pressure bearing.

[0002]

2. Description of the Related Art An ultra-small spindle motor having a thickness of about 10 mm or less is used as a drive source of a hard disk drive (HDD) of a small and lightweight portable computer or information terminal that can be used while a person is traveling. Has been adopted. Naturally, the liquid dynamic pressure bearing, which is the bearing, is smaller than the size of the micro spindle motor. Bearings are important components that determine the performance of ultra-small spindle motors, and there are even more stringent demands for high stability, small size, and low cost.

Accordingly, as disclosed in Japanese Patent Application Laid-Open No. 7-332353, a shaft member having a resin coating formed on the outer peripheral surface of a metal shaft, and a sleeve-shaped receiving member into which the shaft member is rotatably fitted. There has been proposed a liquid dynamic bearing having a member as a main component, that is, a liquid dynamic bearing manufactured by so-called resin processing. This liquid dynamic pressure bearing is a liquid dynamic pressure bearing provided with a sleeve cooperating with a shaft, and a synthetic resin insert-molded on the outer surface of the shaft is provided with a bearing surface having a groove for generating dynamic pressure. It is characterized by the following. With such a configuration, it is possible to use a thermoplastic resin having a relatively large shrinkage by utilizing the molding shrinkage of the synthetic resin, as well as being excellent in slidability and mass productivity of the bearing surface, and using the synthetic resin layer. The effect of the invention is that the dimensional accuracy is excellent and the dimensional change is small with time because the metal shaft is in close contact, and the squareness between the radial bearing surface and the thrust bearing surface is determined by the mold accuracy, and the product quality is stable. Is described.

However, the above-mentioned conventional liquid dynamic bearing has a problem of a coating material. That is, the resin that coats the metal shaft is a PPS (polyphenylene sulfide) resin, an epoxy resin, a polyamide resin, or a polyacetal resin, which is filled with an abrasion resistance improving substance such as carbon fiber, econol, graphite, molybdenum disulfide, or polyimide. However, these abrasion resistance improving substances contaminate a storage medium such as a hard disk or a reading device and Pb, Si, S
That is, elements such as n, P, and S are included. When this conventional liquid dynamic pressure bearing is used for a long period of time, the above-mentioned contaminant elements elute from the coating resin. If the eluted contaminant element adheres to a storage medium such as a hard disk, the quality of the storage medium itself deteriorates and the device malfunctions. Accordingly, a liquid dynamic bearing having a shaft member in which a metal shaft is coated with a resin filled with a wear resistance improving substance containing a contaminant element as described above is used for a spindle motor that rotates a storage medium such as a hard disk or a reading device. There is a problem that can not be adopted.

[0005] Another problem relates to the thickness of the coating resin. In the above-described conventional liquid dynamic pressure bearing, the thickness of the synthetic resin layer on the radial receiving surface, which is the bearing surface, is too small, the flow of the resin is poor, and if the thickness is too large, it is difficult to secure molding accuracy. ~ 1mm, but 10mm
For bearings used in small spindle motors of the order of magnitude or less, this thickness prevents a sufficient Young's modulus to withstand the rotational load and prevents cost savings of the resin material. .

Still another problem is common to the conventional liquid dynamic pressure bearings including the above-mentioned ones. However, in the case of a very small liquid dynamic pressure bearing, the size of the dynamic pressure generating groove is limited. This means that the generated dynamic pressure becomes smaller.

[0007]

A first object of the present invention is to provide a liquid dynamic bearing having a high load capacity. The second problem to be solved is
An object of the present invention is to provide a liquid dynamic bearing that does not contaminate a storage medium such as a hard disk or a reading device. A third problem to be solved is to reduce the cost of a liquid dynamic bearing having a resin coating. A fourth object to be solved is to improve the quality and operation stability of a small spindle motor having a liquid dynamic pressure bearing having a resin coating.

[0008]

In order to solve the above-mentioned first problem, there is provided a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted. In a liquid dynamic pressure bearing in which a dynamic pressure generating groove is formed on one of the outer peripheral surface of the member and the inner peripheral surface of the cylindrical receiving member, at least a wall surface on the rotation direction side of the dynamic pressure generating groove is a tapered wall surface.

[0009] Further, there is provided a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted. Either the outer peripheral surface of the cylindrical shaft member or the inner peripheral surface of the cylindrical receiving member. In the liquid dynamic pressure bearing in which the dynamic pressure generating groove is formed on one side, both the wall surface on the rotation direction side and the opposite wall surface of the dynamic pressure generating groove are tapered wall surfaces, and the latter taper angle is larger than the former taper angle. Was also smaller.

Further, the taper angle is set to about 20 to about 70 degrees with respect to a perpendicular line formed on the bearing surface.

In order to solve the above second problem, a liquid dynamic pressure bearing having a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted is provided. The resin coating layer provided on the metal core material and the dynamic pressure generating grooves provided on the resin coating layer were integrally formed by molding a liquid crystal polymer material.

Further, in a liquid dynamic pressure bearing having a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted, a resin coating layer applied to a metal core of the cylindrical receiving member is provided. And the dynamic pressure generating groove provided in the resin coating layer were integrally formed by molding a liquid crystal polymer material.

Further, the liquid crystal polymer material may be a polymer starting from a polymer of polyhydroxybenzoic acid, bisphenol and terephthalic acid, or a polymer starting from polyhydroxybenzoic acid and 6-hydroxynaphthoic acid. Alternatively, it was selected from polymers using polyethylene terephthalate and polyhydroxybenzoic acid as starting materials.

In order to solve the third problem, a liquid dynamic pressure bearing comprising a cylindrical shaft member with a flange and a stepped cylindrical receiving member into which the cylindrical shaft member with a flange is rotatably fitted. In the spindle motor in which the rotor is supported by the stator, the resin coating layer formed on the metal core of the cylindrical shaft member with the flange and the dynamic pressure generating groove provided in the resin coating layer are formed by molding a liquid crystal polymer material. It was formed integrally by processing.

Further, in the spindle motor, at least a wall surface on the rotation direction side of the dynamic pressure generating groove is a tapered wall surface. Further, both the wall surface on the rotation direction side and the wall surface on the opposite side of the dynamic pressure generating groove are tapered wall surfaces, and the taper angle of the latter is smaller than the taper angle of the former.

[0016]

FIG. 1 is a sectional view of one embodiment of a liquid dynamic pressure bearing according to the present invention, and FIG. 2 is a side view of only the cylindrical shaft member with a flange in the liquid dynamic pressure bearing of FIG. Things. 1 and 2, reference numeral 1 denotes a cylindrical shaft member with a flange, and reference numeral 2 denotes a stepped cylindrical receiving member into which the cylindrical shaft member 1 with a flange is rotatably fitted. Reference numeral 3 denotes a lid member which also functions as a thrust holding plate, and has a through hole at the center thereof for forming a capillary seal S with the upper outer peripheral surface of the cylindrical shaft member 1 with flange. R1 is a minute gap formed between the lower end surface of the shaft member 1 and the bottom surface of the receiving member 2, and R2 is the outer peripheral surface of the lower cylindrical portion of the shaft member 1 and the inner peripheral surface of the small-diameter cylindrical portion of the receiving member 2. Between the lower surface of the flange portion of the shaft member 1 and the receiving member 2.
A small gap formed between the bottom surface of the large-diameter cylindrical portion of
R5 is a minute gap formed between the outer peripheral surface of the flange portion of the shaft member 1 and the inner peripheral surface of the large-diameter cylindrical portion of the receiving member 2, and R5 is the upper surface of the flange portion of the shaft member 1 and the lower surface of the lid member 3. And R6 are the cylindrical shaft member 1 with flange.
Are small gaps formed between the outer peripheral surface of the upper cylindrical portion and the through hole of the lid member 3. These minute gaps are several μm to several tens μm, depending on the size of the liquid dynamic pressure bearing. F is a lubricating oil filled in these gaps.

As shown in the perspective view of FIG. 5, the cylindrical shaft member 1 with a flange is a cross-shaped cylindrical shaft member including a cylindrical portion 1a and a flange portion 1b. The cylindrical shaft member 1 with a flange is composed of a cylindrical metal core material having a cross-shaped cross section and a resin coating layer P of a liquid crystal polymer material applied to the outer peripheral surface thereof.
A radial dynamic pressure generating groove G1 is formed in the resin coating layer P below the cylindrical portion 1a, and a thrust dynamic pressure generating groove G2 is formed on the upper surface and the lower surface of the flange portion 1b.

FIGS. 3 and 4 show a cylindrical shaft member 1 with a flange.
3 is a cross-sectional view of a different embodiment. The cylindrical shaft member 1 with a flange is composed of a cylindrical metal core material having a cross-shaped cross section and a resin coating layer P of a liquid crystal polymer material applied to the outer peripheral surface thereof. Flanged cylindrical shaft member 1 shown in FIGS. 3 and 4
There are two differences. The first relates to the configuration of a cylindrical metal core having a cross-shaped cross section, and the second relates to the formation of a resin coating layer P of a liquid crystal polymer material and a dynamic pressure generating groove.

The columnar metal core material having a cross-shaped cross section has a cylindrical portion 1
The cylindrical member 1c is a metal core material of a and a disk member 1d is a metal core material of a flange portion 1b. The columnar metal core material having a cross-shaped cross section is formed by integrally forming the columnar member 1c and the disk member 1d in FIG. 3, whereas the columnar member 1c and the disk member with through-hole 1d are separately formed in FIG. And then press-fit the former into the latter. These metal cores are manufactured by casting or cutting.

The resin coating layer P of the liquid crystal polymer material includes a cylindrical member 1c, which is a metal core material of the cylindrical portion 1a, and a flange portion 1b.
And a disk member 1d, which is a metal core material, is a coating layer formed on a columnar metal core material having a cross-shaped cross section, and the dynamic pressure generating grooves G1 and G2 are formed of a resin coating layer P of a liquid crystal polymer material.
The micro-grooves formed in FIG. The resin coating layer P of the liquid crystal polymer material is formed on both the columnar member 1c and the disk member 1d in FIG. 3, but is formed only on the disk member 1d in FIG. In FIG. 3, the radial dynamic pressure generating groove G1 is formed in the resin coating layer P on the lower cylindrical portion of the cylindrical portion 1a, and the thrust dynamic pressure generating groove G2 is formed on the upper and lower resin coating layers of the flange portion 1b. P are formed respectively. On the other hand, in FIG. 4, the thrust dynamic pressure generating groove G2 is formed on the resin coating layer P on the upper side and the lower side of the flange portion 1b, respectively, but the radial dynamic pressure generating groove G1 is formed on the outer peripheral surface of the flange portion 1b. It is formed on the coating layer P.

As shown in the perspective view of FIG. 6, the stepped cylindrical receiving member 2 has a small-diameter cylindrical portion 2a at a lower level and a large-diameter cylindrical portion 2b.
Are formed in the upper stage. The small-diameter cylindrical portion 2a of the stepped cylindrical receiving member 2 has a cylindrical portion 1 of a cylindrical shaft member 1 with a flange.
The lower part of a, that is, the radial dynamic pressure column part is rotatably fitted, and the large diameter cylindrical part 2b is rotatably fitted with the flange part 1b of the flanged cylindrical shaft member 1, ie, the thrust dynamic pressure disk part. Fit.

The liquid dynamic bearing according to the present invention configured as described above is applied to, for example, a spindle motor shown in FIG. 7 to realize a microminiature spindle motor. That is, FIG.
Is a micro-spindle motor whose rotor is axially supported by a stator by a liquid dynamic pressure bearing whose basic components are a cylindrical shaft member 1 with a cross-shaped cross section and a cylindrical receiving member 2 with a step. It is. Although not shown, the cylindrical shaft member 1 with a cross-shaped cross-section has a liquid-crystal polymer resin coating layer formed on a column-shaped metal core material having a cross-shaped cross section, and the resin coating layer has a dynamic pressure. This is one in which a generation groove is formed. Reference numeral 3 denotes a lid member, which also functions as a thrust holding plate. The micro spindle motor includes a cup-shaped hub member 4 coaxially fixed to an end of a cylindrical shaft member 1 with a flange and holding a rotating body such as a hard disk, and an inner periphery of a sleeve portion of the cup-shaped hub member 4. The rotor magnet 5 attached to the surface, the stator coil 6 attached to the outer peripheral surface of the stepped cylindrical receiving member 2 to generate a rotational force in cooperation with the rotor magnet 5, and the stepped cylindrical receiving member 2 stand. The provided substrate 7 is also included.

A flanged columnar shaft member 1 having a cross-shaped cross-section and having a flange portion 1b formed at the center in the axial direction shown in FIG. 7 and a stepped cylindrical receiver for rotatably housing the flanged columnar shaft member 1 are shown. The liquid dynamic pressure bearing composed of the member 2 has a flanged cylindrical shaft member having a T-shaped cross section with a flange formed at one end of the shaft, and rotatably accommodates the flanged cylindrical shaft member. The problem inherent in the liquid dynamic pressure bearing composed of the cylindrical receiving member that is formed, that is, the rotation caused by the half-whirl phenomenon caused by the inconsistency between the direction of the axial displacement and the direction of the restoring force at the time of high speed rotation. Instability was eliminated and high stability at high speed rotation was realized.

According to the present invention, not only the shaft-rotating liquid dynamic pressure bearing shown in FIG. 7 but also a shaft-fixed liquid dynamic pressure bearing shown in FIG. 8, that is, a flange is formed at one end of the shaft. T
A liquid dynamic pressure bearing comprising a flanged cylindrical shaft member 1 having a U-shaped cross section and a cylindrical receiving member 2 rotatably accommodating the flanged cylindrical shaft member 1, wherein one end of the shaft is a substrate 7. The present invention can also be applied to a liquid dynamic pressure bearing fixed to a bearing. Furthermore,
The liquid dynamic pressure bearing according to the present invention is a liquid dynamic pressure bearing of a fixed type at both ends shown in FIG. 9, that is, a flanged cylindrical shaft member 1 having a T-shaped cross section and a flange formed at one end of the shaft. And a cylindrical receiving member 2 rotatably accommodating the columnar shaft member 1 with a flange, and is also applicable to a liquid dynamic bearing in which both ends of the shaft are fixed to a substrate 7. it can.

Next, the shape of the dynamic pressure generating groove according to the present invention will be described with reference to FIGS. FIG.
0 is a partial perspective view of one embodiment of the cylindrical shaft member 1 in which the radial dynamic pressure generating groove G1 is exaggerated. The radial dynamic pressure generating groove G1 is a herringbone groove formed in two steps in the upper and lower parts in FIG. 5, but is a V-shaped herringbone groove in FIG. The rotation directions of the cylindrical shaft members 1 are all counterclockwise. The radial dynamic pressure generating groove G1 is an elongated groove having a depth of several μm formed in the resin coating layer formed on the metal core, and has a wall surface Wa on the rotation direction side, a wall surface Wb on the opposite side to the rotation direction, a rotation direction. And two bottom walls Wc.

Conventionally, as shown in FIG. 12, the wall surface of the dynamic pressure generating groove is formed at right angles to the bearing surface. In the present invention, at least the wall surface Wa of the dynamic pressure generating groove on the rotation direction side is a tapered wall surface. That is, as shown in FIG.
The wall surface Wb on the side opposite to the rotation direction is perpendicular to the bearing surface as before, but the wall surface Wa on the rotation direction side is a tapered wall surface inclined by an angle α with respect to a perpendicular to the bearing surface. Further, as shown in FIG. 14, the wall surface Wb on the opposite side to the rotation direction is a tapered wall surface inclined by an angle β with respect to a perpendicular to the bearing surface, and the wall surface Wa on the rotation direction side is inclined by an angle α. Alternatively, a dynamic pressure generating groove may be formed in which the former taper angle β is smaller than the latter taper angle α. These taper angles range from about 20 degrees to about 7 degrees.
0 degrees.

FIG. 11 shows the characteristics of the dynamic pressure generating groove with the taper angle α on the horizontal axis, the load capacity on the vertical axis, and the angle difference between the taper angle α and the taper angle β, that is, the taper angle difference as a parameter. FIG. Note that the taper angle α is positive in the clockwise direction,
The taper angle β is positive in the counterclockwise direction. The four curves a, b, c, and d shown in FIG. 11 are characteristic curves for taper angle differences of 20 degrees, 10 degrees, 0 degrees, and minus 10 degrees. As is apparent from FIG. 11, when the taper angle α is increased, the taper angle minus 1 shown by the characteristic curve d is obtained.
The load capacity of the 0 degree hardly changes from about 20 degrees to about 50 degrees, and thereafter gradually decreases. The load capacity of the taper angle of 0 degree shown by the characteristic curve c, that is, the conventional one shown in FIG. 12, hardly changes until about 30 degrees, but then gradually increases and peaks at about 50 degrees,
Since then, it has been gradually declining.

On the other hand, in the case of the dynamic pressure generating groove having the shape shown in FIG. 13 or FIG. 14 according to the present invention, the load capacity is significantly increased when the taper angle α is between about 20 degrees and about 70 degrees. And it reaches a maximum especially at around 50 degrees. It is also recognized that the taper angle difference tends to increase as the angle difference increases from 20 degrees to 10 degrees as the angle difference increases. Incidentally, when the taper angle difference was 20 degrees, an increase in the load capacity of up to nearly 30% was recognized as compared with the case of the conventional right-angled wall surface.

The shape of the dynamic pressure generating groove shown in FIGS. 13 and 14 is applied not only to the radial dynamic pressure generating groove G1 but also to the thrust dynamic pressure generating groove G2. Therefore, in a spindle motor in which a rotor is supported by a stator by a liquid dynamic pressure bearing including a flanged cylindrical shaft member and a stepped cylindrical receiving member into which the flanged cylindrical shaft member is rotatably fitted. The resin coating layer P formed on the metal core material of the flanged cylindrical shaft member 1 and the dynamic pressure generating grooves G1 and G2 provided on the resin coating layer P are integrally formed by molding a liquid crystal polymer material. In addition, the load capacity of the ultra-small spindle motor of FIG. 7 in which at least the wall surface on the rotation direction side of the dynamic pressure generating groove is tapered is improved.

As described in detail above, the liquid dynamic pressure bearing according to the present invention has a cylindrical shaft member 1 which is a main component thereof.
Both the cylindrical member 2 and at least the cylindrical shaft member 1 are members in which a resin coating layer P is applied to a metal core material.
Applying the resin coating layer P to the metal core material and providing the resin coating layer P with the dynamic pressure generating groove are integrally formed by resin molding of a liquid crystal polymer material.
A coating layer P formed by resin molding of this liquid crystal polymer material
A method of integrally forming the dynamic pressure generating groove and the dynamic pressure generating groove will be described with reference to FIG. That is, in FIG. 15 which is a resin processing method by compression molding, first, the metal core material N is positioned on the lower mold 10 and the upper mold 11 is disposed thereon and loaded into the mold. The mold is filled from the filling port of the upper mold 11 (FIG. 15A). Next, the mold in this state is set on a press machine, and the resin of the liquid crystal polymer material M melted by heating and pressing is poured into the gap between the mold and the metal core N by the plunger 12 (FIG. 15). b). After the molten resin of the liquid crystal polymer material M has been poured, the upper mold is opened and the product is taken out of the mold (15).
Figure c). A groove for forming a dynamic pressure generating groove is formed on a predetermined surface of the upper die 11, and therefore, this product is a member in which the resin coating layer P and the dynamic pressure generating groove are integrally formed. is there. The resin molding of the main components of the liquid dynamic pressure bearing according to the present invention is not limited to the compression molding of FIG.
Any method of transfer molding, injection molding, and injection compression molding can be used.

The liquid crystal polymer material is a polymer starting from a polymer of polyhydroxybenzoic acid, bisphenol and terephthalic acid, or a polymer starting from polyhydroxybenzoic acid and 6-hydroxynaphthoic acid. Alternatively, it was selected from polymers using polyethylene terephthalate and polyhydroxybenzoic acid as starting materials. The use of such a resin material has made it possible to form a very thin resin coating layer having a particularly small thickness of 200 μm or less. Moreover, the formed ultra-thin resin coating layer is excellent in lubricity, impact resistance, heat resistance and chemical resistance. Materials that can be used besides these liquid crystal polymer materials include wholly aromatic polyimide resins, polyamideimide resins, polyphthalamide resins, polyetherimide resins, polyimide resins, and PEEs.
K resin, polyketone resin, fluorine resin and the like. In addition, liquid crystal polymer materials containing inorganic fillers such as carbon, graphite, and silicon dioxide, and reinforced fibers such as whiskers, carbon fibers, and glass fibers in the resin alone or the resin matrix can also be used.

[0032]

According to the present invention, a liquid dynamic bearing having a resin coating layer which does not contaminate a storage medium such as a hard disk or a reader can be provided. Both the cylindrical shaft member and the cylindrical receiving member, which are the main components of the liquid dynamic pressure bearing, or at least the cylindrical shaft member has a metal core material of 200 mm.
Since the resin coating layer of a liquid crystal polymer material with a very thin wall thickness of less than μm is applied, compared to the conventional liquid dynamic pressure bearing having a resin coating layer with a wall thickness of more than 200 μm, it has the same size. With such a structure, the size of the metal core can be increased, thereby improving the Young's modulus, that is, the strength, of the shaft member. In addition, the amount of the resin material used for the resin coating can be reduced, thereby reducing the material cost. Forming a resin coating layer of a liquid crystal polymer material on the main components of a liquid dynamic pressure bearing and forming a dynamic pressure generating groove in the resin coating layer can be performed simultaneously by a normal resin molding method, so that the manufacturing cost is also reduced. Could be reduced. The dynamic pressure generating groove formed in the resin coating layer is not a conventional groove with a right-angled wall, but a groove with a tapered wall, so that the product can be easily removed from the mold and damage during processing of the dynamic pressure generating groove Quality has improved. In short, according to the present invention, ultra-small size and cost reduction of the liquid dynamic bearing having the resin coating layer can be realized.

Further, by adopting the ultra-compact liquid dynamic pressure bearing having the above-mentioned features, the quality, operation stability and load capacity of the ultra-compact spindle motor can be improved. Furthermore, there is no need to take a large amount of industrial waste such as etching for the processing of the dynamic pressure generation groove. Even if defective resin coating occurs, the resin can be easily regenerated, minimizing environmental destruction. Could be held down.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of a liquid dynamic pressure bearing according to the present invention.

FIG. 2 is a sectional view of another embodiment of the liquid dynamic pressure bearing according to the present invention.

FIG. 3 is a sectional view of one embodiment of a cylindrical shaft member.

FIG. 4 is a sectional view of another embodiment of the cylindrical shaft member.

FIG. 5 is a perspective view of one embodiment of a cylindrical shaft member.

FIG. 6 is a perspective view of one embodiment of a cylindrical receiving member.

FIG. 7 is a cross-sectional view of one embodiment of a microminiature spindle motor using the liquid dynamic pressure bearing according to the present invention.

FIG. 8 is a sectional view of another embodiment of the liquid dynamic bearing to which the present invention can be applied.

FIG. 9 is a sectional view of still another embodiment of the liquid dynamic pressure bearing to which the present invention can be applied.

FIG. 10 is a partial perspective view of an example of a cylindrical shaft member in which a radial dynamic pressure generating groove is exaggerated.

FIG. 11 is a characteristic diagram showing an effect of the dynamic pressure generating groove according to the present invention.

FIG. 12 is a partially enlarged sectional view of a conventional dynamic pressure generating groove.

FIG. 13 is a partially enlarged sectional view of one embodiment of a dynamic pressure generating groove according to the present invention.

FIG. 14 is a partially enlarged sectional view of another embodiment of the dynamic pressure generating groove according to the present invention.

FIG. 15a is a view showing one example of a method for manufacturing a liquid dynamic bearing according to the present invention.

FIG. 15b is a diagram showing an example of the method for manufacturing a liquid dynamic bearing according to the present invention.

FIG. 15c is a view showing one example of a method for manufacturing a liquid dynamic bearing according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 cylindrical shaft member 1a cylindrical portion 1b flange portion 1c cylindrical member which is metal core material of cylindrical portion 1a disk member which is metal core material of cylindrical portion 1b 2 cylindrical receiving member 2a small diameter cylindrical portion 2b large diameter cylindrical portion 3 lid member 4 Cup-shaped hub 5 Rotor magnet 6 Stator coil 7 Substrate 10 Lower die 11 Upper die 12 Plunger F Lubricating oil G1 Radial dynamic pressure generating groove G2 Thrust dynamic pressure generating groove M Liquid crystal polymer material N Metal core material P Resin coating layer R1, R2, R3, R4, R5, R6 Minute gap S Capillary seal Wa Wall surface on rotating side of dynamic pressure generating groove Wb Wall surface on opposite side of rotating direction of dynamic pressure generating groove Wc Bottom surface of dynamic pressure generating groove

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yukien Hyobu 1-18-2 Nishiikebukuro, Toshima-ku, Tokyo F-term in Kakizaki Manufacturing Co., Ltd. (Reference) 3J011 AA04 BA02 BA04 BA09 CA03 QA05 SC01 SC12

Claims (9)

[Claims] 1. A cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted, wherein either an outer peripheral surface of the cylindrical shaft member or an inner peripheral surface of the cylindrical receiving member. A liquid dynamic pressure bearing in which a dynamic pressure generating groove is formed on one side, wherein at least a wall surface on the rotation direction side of the dynamic pressure generating groove is a tapered wall surface. 2. A cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted, wherein either the outer peripheral surface of the cylindrical shaft member or the inner peripheral surface of the cylindrical receiving member. In the liquid dynamic pressure bearing in which the dynamic pressure generating groove is formed on one side, both the wall surface on the rotation direction side and the opposite wall surface of the dynamic pressure generating groove are tapered wall surfaces, and the latter taper angle is larger than the former taper angle. Liquid dynamic pressure bearing characterized in that the size is also reduced. 3. A liquid dynamic pressure bearing according to claim 1, wherein said taper angle is set to about 20 to about 70 degrees with respect to a vertical line formed on the bearing surface. 4. A liquid dynamic pressure bearing having a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted, wherein the cylindrical shaft member has a resin coating layer formed on a metal core material. Wherein the resin coating layer and the dynamic pressure generation groove provided in the resin coating layer are integrally formed by molding a liquid crystal polymer material. 5. A liquid dynamic pressure bearing having a cylindrical shaft member and a cylindrical receiving member into which the cylindrical shaft member is rotatably fitted, wherein the cylindrical receiving member is formed by applying a resin coating layer to a metal core material. Wherein the resin coating layer and the dynamic pressure generation groove provided in the resin coating layer are integrally formed by molding a liquid crystal polymer material. 6. A polymer starting from a polymer of polyhydroxybenzoic acid, bisphenol and terephthalic acid, and a polymer starting from polyhydroxybenzoic acid and 6-hydroxynaphthoic acid. 6. The liquid dynamic pressure bearing according to claim 4, wherein the liquid dynamic pressure bearing is selected from a polymer starting from polyethylene terephthalate and polyhydroxybenzoic acid. 7. A rotor is supported by a stator by a liquid dynamic pressure bearing having a flanged cylindrical shaft member and a stepped cylindrical receiving member into which the flanged cylindrical shaft member is rotatably fitted. In the spindle motor, the flanged cylindrical shaft member is a metal core material provided with a resin coating layer, and the resin coating layer and the dynamic pressure generating groove provided in the resin coating layer are made of a liquid crystal polymer material. A spindle motor which is formed integrally by molding. 8. The spindle motor according to claim 7, wherein at least a wall surface on the rotation direction side of said dynamic pressure generating groove is a tapered wall surface. 9. The taper angle of the dynamic pressure generating groove according to claim 7, wherein both the wall surface on the rotation direction side and the wall surface on the opposite side are tapered, and the taper angle of the latter is smaller than the taper angle of the former. Spindle motor.