JP2001027225A - Hydrodynamic pressure bearing made of resin, and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage during manufacture of a dynamic pressure generating groove formed simultaneously with the manufacture of bearing constituent members by resin molding in a hydrodynamic pressure bearing made of resin with a disc-like thrust bearing and a cylindrical radial bearing formed adjacently. SOLUTION: This hydrodynamic pressure bearing made of resin is composed of a flanged shaft member 1 having a resin flange part 3 and a resin shaft part 2 with its outer peripheral surface inclined at a specified angle, formed by applying resin to a metal core material 1a, and a sleeve member 4 having a resin sleeve part 4b with its inner peripheral surface inclined at the same angle as the specified angle of inclination by applying resin to the inner surface of a metal sleeve part 4a. An angle defined by the specified angle of inclination and a rotation axis is set to 5 deg.-75 deg., and the flanged shaft member 1 and the sleeve member 4 are manufactured by molding liquid crystal polymeric material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin fluid dynamic pressure bearing in which a disk-shaped thrust bearing and a columnar radial bearing are formed adjacent to each other, and a spindle motor provided with the same. The present invention relates to a structure of a resin fluid dynamic pressure bearing formed at the same time as the production of a constituent member.

[0002]

2. Description of the Related Art Aiming at low price and mass production by molding, a resin fluid dynamic pressure bearing in which all bearing components are made of synthetic resin, or a resin fluid in which a resin layer is applied to a part of the bearing components Various types of dynamic pressure bearings have been proposed or developed. However, a high-quality and low-priced fluid dynamic pressure bearing made of resin applicable to a small spindle motor has not yet been provided.

Japanese Patent No. 2615998 discloses a sleeve member composed of a metal outer cylinder and a synthetic resin inner cylinder,
A metal shaft member rotatably fitted to the synthetic resin inner cylindrical body, wherein the synthetic resin inner cylindrical body and a radial dynamic pressure generating groove formed on an inner peripheral surface thereof are formed of a thermosetting resin. Discloses a resin dynamic pressure bearing formed simultaneously using a transfer molding machine.

In the production of this resin dynamic pressure bearing, a mold core pin provided with a groove forming projection on the outer peripheral surface is inserted coaxially into the metal outer cylinder, and the metal core pin is inserted into the metal outer cylinder. A thermosetting resin is injected into a gap between the inner peripheral surface and the outer peripheral surface of the mold core pin. The injected thermosetting resin is cured, and the synthetic resin inner cylinder and the radial dynamic pressure generating groove are simultaneously formed. In this case, since the volume of the thermosetting resin is reduced when it is cured, the mold core pin can be released from the inner peripheral surface of the synthetic resin inner cylinder.

However, in this manufacturing method, interference between the groove forming projection and the radial dynamic pressure generating groove is inevitable at the time of release from the mold, so that there is a problem that the radial dynamic pressure generating groove is easily damaged. Therefore, this problem is solved by filling the thermosetting resin with wax. However, this method is only effective when a specific thermosetting resin is filled with a specific component and a wax in a percentage by weight, and is hardly widely adopted.

Japanese Patent Application Laid-Open No. Hei 7-332353 discloses that
A dynamic pressure bearing having a structure that can be manufactured by resin molding, that is, a resin in which a disk-shaped thrust bearing and a column-shaped radial bearing are formed adjacently, with a shaft member with a cross-shaped flanged shaft member and a cylindrical sleeve member as basic constituent members. A fluid dynamic bearing is disclosed. The cross-shaped flanged shaft member disclosed herein has a metal cylindrical member formed with a synthetic resin thrust dynamic pressure flange at the center and a resin coating layer formed on the upper and lower outer peripheral surfaces thereof. Things.

The production of a flanged shaft member having a synthetic resin thrust dynamic pressure flange is performed by inserting a metal cylindrical member into a mold having a predetermined shape and insert-molding the synthetic resin. Since a groove forming projection is provided on the inner peripheral surface of the mold, both the thrust dynamic pressure generating groove and the radial dynamic pressure generating groove are formed at the same time during insert molding. Since the volume of the synthetic resin shrinks when cured, the mold can be released from the outer peripheral surface of the flanged shaft member having the synthetic resin thrust dynamic pressure flange. However, even in this manufacturing method, the interference between the groove forming projections and the radial dynamic pressure generating grooves is inevitable at the time of mold release, so that there is a problem that the radial dynamic pressure generating grooves are easily damaged.

Further, JP-A-7-110028 discloses that
Fluid dynamics composed of a synthetic resin ring-shaped member having a V-shaped radial dynamic pressure generating groove extending to an end surface on its inner peripheral surface and a thrust dynamic pressure generating groove provided on one surface thereof, and a rotating shaft. A pressure bearing is disclosed. The ring-shaped member is manufactured by forming a plurality of inclined ridges for forming grooves on the outer peripheral surface corresponding to half of the V-shape and extending to the end surface,
This is performed by resin molding using a pair of dies having a large number of inclined ridges for groove formation corresponding to the other half of the V-shape and extending to the end face on the outer peripheral surface. Since it is a ring-shaped member provided with a specially shaped radial dynamic pressure generating groove, it can be easily manufactured by molding a resin using a pair of specially shaped dies, and the groove-forming protrusions at the time of mold release. There is no interference between the groove and the radial dynamic pressure generating groove, and the radial dynamic pressure generating groove is not damaged. However, this method is not versatile, and cannot be applied to a fluid dynamic pressure bearing made of resin in which a disk-shaped thrust bearing and a cylindrical radial bearing are formed adjacent to each other.

[0009] In short, it has been conventional to manufacture a resin-made bearing component made of a metal portion and a resin portion by resin molding so that the radial dynamic pressure generating groove formed in the resin portion is not damaged at the time of mold release. It was impossible with technology.

Although not a fluid dynamic pressure bearing made of resin, a bearing gap forming surface of a shaft member and a bearing gap forming surface of a sleeve member having inclined surfaces of the same angle are disclosed in, for example, Japanese Patent Application Laid-Open No. 60-208629. It has been disclosed. this is,
As shown in FIG. 4, a conical shaft member 1 having a truncated conical cross section
1 and a sleeve member 13 which is rotatably fitted with the sleeve member 13 as a main component, and a dynamic pressure generating groove G such as a herringbone groove is formed on a tapered outer peripheral surface 11a of a conical shaft member 11 forming a bearing gap. And a conical fluid dynamic pressure bearing. Since this conical fluid dynamic bearing requires the use of a magnetic bearing for thrust, the size of the device is correspondingly large, the assembling work is difficult, and a reduction in manufacturing cost cannot be expected very much. Therefore, this conical fluid dynamic bearing cannot be used for a small spindle motor.

[0011]

A first object of the present invention is to provide a fluid dynamic pressure bearing made of resin in which a disk-shaped thrust bearing and a cylindrical radial bearing are formed adjacent to each other. The purpose of the present invention is to prevent the dynamic pressure generating grooves formed simultaneously with the production of the resin by resin molding from being damaged during the production. A second problem to be solved is to provide a resin-made fluid dynamic pressure bearing capable of increasing a bearing area. A third problem to be solved is to provide a fluid dynamic bearing that does not contaminate a storage medium such as a hard disk or a reading device. Further, a fourth problem to be solved is to provide a spindle motor capable of driving with low current consumption without reducing load capacity and shaft rigidity in a wider temperature range.

[0012]

In order to solve the above-mentioned first and second problems, a resin-made fluid dynamic bearing is prepared by applying a resin to a metal core so that a resin-made flange portion and an outer peripheral surface thereof have a predetermined inclination. A flanged shaft member formed with a resin shaft portion having an angle, and a sleeve formed by applying a resin to an inner surface of a metal sleeve to form a resin sleeve portion having an inner peripheral surface having the same inclination angle as the inclination angle. A thrust dynamic pressure generating groove is formed on a predetermined surface of the resin flange portion, and a radial dynamic pressure generating groove is formed between the inner peripheral surface of the resin shaft portion and the resin The sleeve was formed on one of the outer peripheral surfaces. The angle between the inclined surface and the rotation axis is set to 5 to 75 degrees.

In order to solve the third problem, the flanged shaft member and the sleeve member are manufactured by molding a liquid crystal polymer material.

Further, in order to solve the fourth problem, the resin material of the resin shaft portion and the resin material of the resin sleeve portion have substantially the same linear expansion coefficient, or the former is larger than the latter. Was selected in this way.

[0015]

FIG. 1 is a sectional view of a first embodiment of a spindle motor according to the present invention. In FIG. 1, a resin-made fluid dynamic pressure bearing has a flanged shaft member 1, and the flanged shaft member 1 is rotatable. Sleeve member 4 that fits
And an annular pressing member 5 arranged at the open end of the sleeve member 4. The annular pressing member 5 is a member that also functions as a thrust pressing plate. The spindle motor provided with the resin-made fluid dynamic bearing is provided with a cup-shaped hub 6 attached to the flanged shaft member 1, a rotor magnet 7 attached to the inner peripheral surface of the cup-shaped hub 6, and a rotor magnet 7 facing the same. A stator coil 8 attached to the outer peripheral surface of the sleeve member 4 and a motor substrate 9 on which the sleeve member 4 is erected.

In FIG. 2, which is a cross-sectional view of a first embodiment of a resin-made fluid dynamic pressure bearing according to the present invention, in which a minute gap and a dynamic pressure generating groove are exaggerated, a flanged shaft member 1 is cut or the like. A resin is applied to the manufactured substantially T-shaped metal core material 1a and molded to form a member having a resin shaft portion 2 and a resin flange portion 3. Further, the sleeve member 4 is manufactured as a member having a resin sleeve portion 4b by applying a resin to a stepped metal sleeve portion 4a manufactured by cutting or the like and molding the resin. The stepped metal sleeve portion 4a includes a small-diameter cylindrical portion having a bottom on the lower side and a large-diameter cylindrical portion having an open end on the upper side.

The outer peripheral surface of the resin shaft portion 2 is formed to have a predetermined inclination angle with respect to the rotation axis.
Similarly, the inner peripheral surface of the resin sleeve portion 4b is also formed to have the same predetermined inclination angle with respect to the rotation axis. Since the bearing component according to the present invention is manufactured by resin molding, the inclination angle is set to 5 degrees or more in order to release the radial dynamic pressure generating groove without damaging the groove, and functions as a radial dynamic pressure bearing. It is set to 75 degrees or less in order to make

A radial dynamic pressure generating groove G1 such as a herringbone groove is formed on the outer peripheral surface of the resin shaft portion 2. Thrust dynamic pressure generating grooves G2 such as herringbone grooves are formed on the upper and lower surfaces of the resin flange portion 3, respectively. These dynamic pressure generating grooves G1 and G2 are formed by the metal core 1a.
Are formed at the same time as a member having a resin shaft portion 2 and a resin flange portion 3 is formed by applying a resin to the resin.

Small gaps R 1 to R are provided between the flanged shaft member 1, the sleeve member 4 and the annular holding member 5.
5 are formed. That is, R1 is a minute gap between the upper surface of the resin flange portion 3 and the lower surface of the annular holding member 5,
Is a minute gap between the outer peripheral surface of the resin flange portion 3 and the inner peripheral surface of the large diameter portion of the sleeve member 4, and R3 is between the lower surface of the resin flange portion 3 and the bottom surface of the large diameter portion of the sleeve member 4. R4 is a resin sleeve portion 4 formed on the outer peripheral surface of the resin sleeve portion 2 and the inner peripheral surface of the small diameter portion of the sleeve member 4.
b, and R5 is a minute gap between the lower end surface of the flanged shaft member 1 and the bottom surface of the sleeve member 4.

These minute gaps are on the order of several μm to several hundred μm, depending on the size of the fluid dynamic pressure bearing, the number of rotations and the viscosity coefficient of the lubricating oil. F is the lubricating oil filled in these minute gaps. In addition, R
1, R3 and R4 function as bearing clearances, and R2 and R5
Functions as a lubricant reservoir. Further, the tapered minute gap S communicating between the minute gap R1 and the atmosphere prevents the lubricating oil F filled in the fluid dynamic pressure bearing from leaking to the outside by utilizing capillary action and surface tension. It functions as a capillary seal.

In a fluid dynamic pressure bearing filled with lubricating oil, the bearing stiffness decreases as the temperature increases. This is because when the temperature of the lubricating oil increases, its viscosity coefficient decreases. Therefore, in the present invention, the resin materials of the resin shaft portion 2 and the resin sleeve portion 4b are selected such that their linear expansion coefficients are substantially equal or the former is larger than the latter. As a result, in the high-temperature region, the manner of narrowing the interval of the bearing gap R4 became larger as compared with the bearing gap that did not employ such means.

As described above, the interval between the bearing gaps can be changed more greatly than in the conventional apparatus, and the liquid dynamic pressure bearing according to the present invention has a wider range that can be automatically adjusted depending on the temperature. Therefore, by utilizing the effect of the automatic adjustment of the interval of the bearing gap by this temperature, the bearing stiffness can be more dynamically and automatically adjusted. That is, in a high temperature range, the gap between the bearing gap formed between the shaft member and the sleeve member becomes narrow, and the bearing rigidity increases. This increase in bearing stiffness compensates for a decrease in bearing stiffness due to a decrease in the viscosity coefficient of the lubricating oil. Therefore, a predetermined bearing stiffness is maintained in a high temperature range. On the other hand, in a low temperature range, the gap between the bearing gap formed between the shaft member and the sleeve member is widened, and the bearing rigidity is reduced.
This decrease in bearing stiffness compensates for an increase in bearing stiffness due to an increase in the viscosity coefficient of the lubricating oil. Therefore, a predetermined bearing stiffness is maintained even in a low temperature range. That is, a change in bearing stiffness due to a viscosity coefficient of lubricating oil can be compensated for over a wide temperature range by a change in bearing stiffness due to a bearing gap.

The spindle motor according to the second embodiment of the present invention, as shown in the sectional view of FIG. 3, excludes the resin fluid dynamic pressure bearing (the resin fluid dynamic pressure bearing of the second embodiment) employed. For example, it has the same configuration as the spindle motor of the first embodiment.

The fluid dynamic bearing made of resin of the second embodiment is shown in FIG.
Has basically the same configuration as the resin fluid dynamic pressure bearing of the first embodiment shown in FIG. The difference between the two is in the shapes of the resin shaft portion 2 and the resin sleeve portion 4b. That is, the first
In the resin fluid dynamic bearing of the embodiment, the inclination angle of the outer peripheral surface of the resin shaft portion 2 and the inclination angle of the inner peripheral surface of the resin sleeve portion 4b are about 10 degrees, whereas the inclination angle of the second embodiment is about 10 degrees. The inclination angle of the resin fluid dynamic pressure bearing is as large as about 40 degrees. Therefore, the dynamic pressure generated by the radial dynamic pressure generation groove G1 is much larger in the former than the radial component in the former, whereas it is slightly larger in the latter. By increasing the inclination angle in this manner, a bearing area and a thrust dynamic pressure component are increased, thereby realizing a fluid dynamic pressure bearing applicable to a larger thrust load. Also, since the inclination angle is large, the first
The detachment from the metal mold during the resin molding process was further improved than in the case of the resin fluid dynamic pressure bearing of the embodiment. Therefore, a deep dynamic pressure generating groove can be formed.

The resin-made fluid dynamic pressure bearing of the first embodiment shown in FIGS. 1 and 2 and the second embodiment shown in FIG. 3 has a shaft member 1 having a cross-shaped flange and a shaft member 1 having a flange. And a ring-shaped pressing member 5 disposed at an open end of the sleeve member 4. Therefore, the resin-made fluid dynamic pressure bearing according to the present invention can eliminate rotational instability caused by the half-whirl phenomenon caused by the direction of the axial displacement and the direction of the restoring force for the displacement during high-speed rotation, The stability of the spindle motor equipped with this during high-speed rotation has also been improved. The angle formed between the outer peripheral surface of the resin shaft portion and the inner peripheral surface of the resin sleeve portion as the rotation axis is preferably in a range from about 5 degrees to about 75 degrees. If the angle is smaller than this range, the removability of the mold becomes worse. On the other hand, if the angle is larger than this range, the radial load capacity sharply decreases and the rotational stability deteriorates.

Next, a method of manufacturing the flanged shaft member 1 by resin molding will be described. The mold used for the production has a lower mold having a predetermined inner surface shape on which a ridge for forming a thrust dynamic pressure generating groove is formed and a lower mold having a predetermined inner surface on which a ridge for forming a radial dynamic pressure generating groove is formed. Type. First, the metal core material 1a is placed upside down, the upper mold is placed on the lower mold, and the upper mold is loaded on the mold, and then the measured liquid crystal polymer material is filled into the mold from the filling port of the upper mold. Then
The mold in this state is set on a press machine, and the resin of the liquid crystal polymer material melted by heating and pressing is poured into the gap between the mold and the metal core 1a by a plunger. After the molten resin of the liquid crystal polymer material has been poured, the upper mold is opened and the product is taken out of the mold. Since the ridges for forming the dynamic pressure generating grooves are formed in the upper mold, the product taken out of the mold has a resin portion of a predetermined shape formed in the metal core 1a, and is radially connected to the thrust dynamic pressure generating grooves G2. A member in which the dynamic pressure generating groove G1 is integrally formed at a predetermined location of the resin portion,
That is, it is a shaft member with a flange made of resin. The sleeve member 4 is similarly manufactured by resin molding. In addition,
The resin molding of the resin bearing member according to the present invention is not limited to compression molding, but may be transfer molding,
Either injection molding or 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, a polymer starting from polyhydroxybenzoic acid and 6-hydroxynaphthoic acid, or It was selected from polymers using polyethylene terephthalate and polyhydroxybenzoic acid as starting materials. Materials that can be used in addition to these liquid crystal polymer materials include wholly aromatic polyimide resins, polyamideimide resins, polyphthalamide resins, polyetherimide resins, polyimide resins, PEEK resins, polyketone resins, and fluorine-based resins. Also, these resins alone or resin matrix, carbon,
Liquid crystal polymer materials including inorganic fillers such as graphite and silicon dioxide, and reinforcing fibers such as whiskers, carbon fiber, and glass fiber can also be used.

[0028]

According to the present invention, the resin dynamic pressure bearing is manufactured by forming a resin flange portion and a resin shaft portion, forming a thrust dynamic pressure generating groove, and forming a radial dynamic pressure. The formation of the generated grooves can be performed simultaneously by the ordinary resin molding method. Therefore,
It has become possible to mass-produce resin dynamic pressure bearings at low cost. Further, since the outer peripheral surface of the resin shaft portion and the inner peripheral surface of the resin sleeve portion are formed to have an inclination angle of 5 to 75 degrees with respect to the rotation axis, the product does not come off from the mold. As a result, the quality of the dynamic pressure generating groove was improved without damage.

Since the flanged shaft member and the sleeve member are manufactured by molding a liquid crystal polymer material, a fluid dynamic bearing that does not contaminate a storage medium such as a hard disk or a reader can be provided. . In addition, the resin material of the resin shaft portion and the resin material of the resin sleeve portion are selected so that their linear expansion coefficients are substantially equal or the former is larger than the latter, so that the load capacity and the shaft rigidity are wider in a wider temperature range. It has become possible to provide a spindle motor capable of driving with low current consumption without lowering.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of a spindle motor according to the present invention.

FIG. 2 is a cross-sectional view of a first embodiment of a resin-made fluid dynamic pressure bearing according to the present invention, in which a gap and a dynamic pressure generating groove are exaggerated.

FIG. 3 is a sectional view of a second embodiment of the spindle motor according to the present invention.

FIG. 4 is a sectional view of a conventional conical fluid dynamic pressure bearing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft member 1a Metal core material 2 Resin shaft part 3 Resin flange part 4 Sleeve member 4a Metal sleeve part 4b Resin sleeve part 5 Annular holding member 6 Cup-shaped hub 7 Rotor magnet 8 Stator coil 11 Conical shaft member 11a Taper Outer peripheral surface 12 fixed shaft 13 sleeve 13a tapered inner peripheral surface 14, 15 permanent magnet 16 rotor magnet 17 stator coil 18 lower substrate 19 upper substrate G dynamic pressure generating groove G1 radial dynamic pressure generating groove G2 thrust dynamic pressure generating groove F Lubricating oil R1, R2, R3, R4, R5 Small gap S Capillary seal

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Naoki Kawawada 1-8-1, Nakase, Mihama-ku, Chiba City, Chiba Prefecture Inside Seiko Instruments Inc. -Instruments Inc. (72) Inventor Koji Nitori 1-8-1, Nakase, Mihama-ku, Chiba-shi 3K011 BA09 BA11 CA02 SC01 5H607 AA04 BB01 BB14 BB25 CC01 DD03 EE10 GG12 GG15 JJ01 KK04 KK07

Claims (5)

[Claims] 1. A flanged shaft member in which a resin is formed on a metal core to form a resin flange and a resin shaft having an outer peripheral surface having a predetermined inclination angle, and a resin is formed on an inner surface of a metal sleeve. And a sleeve member having a resin sleeve portion having an inner peripheral surface having the same inclination angle as the inclination angle with respect to the rotation axis, as a basic constituent member, and a thrust dynamic pressure generating groove formed in a predetermined position of the resin flange portion. And a radial dynamic pressure generating groove formed on one of the inner peripheral surface of the resin shaft portion and the outer peripheral surface of the resin sleeve portion. 2. The method according to claim 1, wherein the angle between the inclination angle and the rotation axis is 5 degrees
The resin-made fluid dynamic pressure bearing according to claim 1, wherein the bearing is at 75 degrees. 3. The resin-made fluid dynamic bearing according to claim 1, wherein the shaft member with flange and the sleeve member are manufactured by molding a liquid crystal polymer material. 4. The resin material of the resin shaft portion and the resin material of the resin sleeve portion has a linear expansion coefficient substantially equal to each other,
2. The resin-made fluid dynamic pressure bearing according to claim 1, wherein the former is larger than the latter. 5. A spindle motor comprising the resin fluid dynamic pressure bearing according to claim 1.