JP2006200666A - Dynamic-pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce manufacturing cost of a dynamic-pressure bearing device of this kind. <P>SOLUTION: A resin-made flange part 2b is provided above a lower end of a shaft member 2, and a lower end face 2b2 of the flange part 2b opposes to an upper end face 8b of a sleeve member 8 to form a thrust bearing clearance between both faces 8b and 2b2 when the shaft member 2 rotates relatively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing device that supports a rotating member in a non-contact manner by a hydrodynamic action of a fluid (lubricating fluid) generated in a bearing gap. This bearing device is a spindle of information equipment such as magnetic disk devices such as HDD and FDD, optical disk devices such as CD-ROM, CD-R / RW and DVD-ROM / RAM, and magneto-optical disk devices such as MD and MO. Suitable for motors.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, the use of a hydrodynamic bearing having characteristics excellent in the required performance has been studied or actually used. Yes.

For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD, a structure is known in which a bearing sleeve is fixed to the inner periphery of a housing and a shaft member is disposed on the inner periphery of the bearing sleeve (for example, , See Patent Document 1). In this bearing device, the rotation of the shaft member generates a pressure in the radial bearing gap between the inner periphery of the bearing sleeve and the outer periphery of the shaft member by the hydrodynamic action of the fluid, and this pressure causes the shaft member to move in the radial direction. Support in contact.
JP 2002-61636 A

  This type of hydrodynamic bearing device is composed of various parts including a housing, a bearing sleeve, and a shaft member, and in order to ensure the high bearing performance required as the performance of information equipment increases. Efforts are being made to increase the processing accuracy and assembly accuracy of each part. On the other hand, along with the trend of price reduction of information equipment, the demand for cost reduction for this type of hydrodynamic bearing device has become increasingly severe.

  An object of the present invention is to reduce the manufacturing cost of this type of hydrodynamic bearing device.

  In order to solve the above problems, a hydrodynamic bearing device according to the present invention includes a stationary member, a rotating member that is mounted with a driven body, and rotates relative to the stationary member, and a stationary member and a rotating member. Of the fluid generated in the thrust bearing gap between the radial bearing portion between the stationary side member and the rotating side member, and the radial bearing portion that supports the rotating side member in the radial direction without contact by the dynamic pressure action of the fluid generated in the radial bearing gap between A thrust bearing portion that supports the rotation side member in a thrust direction by pressure action in a non-contact manner, and the thrust bearing gap of the thrust bearing portion is on the driven body side, and the rotation side member and the fixed side member face each other. At least one of a portion facing the thrust bearing gap of the fixed member and a portion facing the thrust bearing gap of the rotating member is formed of resin.

  In this way, by forming the portion facing the thrust bearing gap with a resin material, it is not necessary to perform machining such as turning, so that the same portion is manufactured at a lower cost than when formed with a metal material. be able to. In addition, when forming the dynamic pressure groove in the resin-formed part, since the molding of the resin forming portion and the dynamic pressure groove can be performed at the same time, and when these molding are performed in separate steps In comparison, the number of processes can be reduced and the cost can be reduced.

  The fixed side member may include, for example, a sleeve member that faces the radial bearing gap and a housing that fixes the sleeve member therein. The rotation side member includes a shaft member, and the shaft member may include a flange portion.

  The said structure WHEREIN: A radial bearing part can be comprised with the multi-arc bearing which has a several wedge-shaped clearance gap in a radial bearing clearance.

  In the above configuration, when the thrust bearing gap is formed between the end surface of the flange portion and the end surface of the sleeve member facing the flange portion, as a member including a portion facing the thrust bearing gap of the rotation side member, for example, A part or the whole of the flange portion can be formed of resin.

  The part of the fixed side member that faces the thrust bearing gap and the part of the rotary side member that faces the thrust bearing gap may be formed of resin. It is necessary to consider wear due to contact sliding. Reinforcing fibers for improving the strength are usually blended in the resin-formed part, but depending on the fiber shape and blending amount, the reinforcing fiber blended in the resin part may damage or wear the other resin part. There is a risk that

  According to the verification by the present inventors, when the fiber diameter of the reinforcing fiber to be blended in the resin is too large, specifically, when the fiber diameter exceeds 12 μm, the rigidity of the reinforcing fiber increases, and the resin member on the other side at the time of sliding increases. Caused scratches and wear. Moreover, even if there were too many compounding quantities of a reinforced fiber, when it exceeded 20 vol%, for example, it turned out that the same problem arises because the contact frequency of a reinforced fiber and the other party resin part increases.

  From this point of view, it is preferable that a reinforcing fiber having a fiber diameter of 1 to 12 μm is blended as a filler in at least one of the resin portion of the stationary member and the resin portion of the rotating member.

  Thus, since the reinforcing fiber is softened by setting the fiber diameter of the reinforcing fiber to 12 μm or less, it is possible to prevent the counterpart resin member in contact with the fiber from being damaged, and to resist the thrust bearing portion. Abrasion can be improved.

  Furthermore, if the blending amount of the reinforcing fiber in the resin is set to 5 to 20 vol%, the frequency of contact of the reinforcing fiber with the counterpart resin member can be reduced, so that the wear resistance of the thrust bearing portion is further improved. be able to. The reason why the blending amount of the reinforcing fiber is set to 5 vol% or more is that if the amount is less than this, the reinforcing effect is reduced, so that the wear resistance is lowered.

  Since the portions of the fixed side member and the rotating side member that are opposed to each other through the thrust bearing gap are made of resin, the linear expansion coefficient in the axial direction of the both becomes substantially the same value, so that the temperature change In contrast, the thrust bearing gap can be maintained at a constant width, and the rotational accuracy can be further improved. Further, since the rotation side member includes the resin portion, the weight is reduced as compared with the case where the rotation portion is made of metal, so that the impact resistance is improved.

  In addition to the reinforcing fibers, the filler can further contain a conductive agent. Generally, since resin is an insulating material, when each member is made into a resin as described above, static electricity of the rotating side member generated by friction with air is charged to the rotating side member, and the potential difference between the magnetic disk and the magnetic head is reduced. There is a risk of damage or damage to peripheral equipment due to electrostatic discharge. On the other hand, if a conductive agent is included in the filler in the resin member, the inconvenience on the rotating side and the fixed side can be ensured and such a problem can be solved. The type of the conductive agent is not particularly limited, and for example, fibrous or powdery materials such as carbon fiber, carbon black, graphite, carbon nanomaterial, and metal powder can be used.

  Any one of the resin portion of the fixed side member and the resin portion of the rotation side member is desirably formed by LCP in consideration of oil resistance and moldability. Further, from the same viewpoint, either the resin portion of the fixed side member or the rotation side member can be formed of PPS.

  If the total amount of filler in the resin (the total amount of filler including the conductive agent is also included) exceeds 30 vol%, the welding strength when other members are ultrasonically welded to the resin member is remarkably high. descend. In order to prevent this, the total amount of filler in the resin is desirably 30 vol% or less.

  As the reinforcing fiber, a PAN-based carbon fiber having characteristics excellent in strength and elastic modulus can be used.

  If the resin portion of the fixed side member and the resin portion of the rotation side member are formed of resin materials having different base resins, adhesion during sliding between the fixed side member and the rotation side member can be prevented.

  The hydrodynamic bearing device described above can be used by being incorporated in a spindle motor of a disk device, for example. In this case, the driven member corresponds to a disk-shaped information recording medium (hereinafter simply referred to as a disk) such as a magnetic disk.

  According to the present invention, at least one of the fixed side member and the rotation side member is made of resin, thereby reducing the cost of the member, thereby reducing the manufacturing cost of this type of hydrodynamic bearing device. be able to.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to a first embodiment of the present invention. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a shaft member 2 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, and a radial direction, for example. The stator coil 4 and the rotor magnet 5 are opposed to each other with a gap therebetween. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The disk hub 3 holds one or more disks D on its outer periphery. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force generated between the stator coil 4 and the rotor magnet 5. The disk D held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a shaft member 2, a housing 7, a sleeve member 8 fixed to the housing 7, and a seal member 9 as main components. In this embodiment, among the above-described components, the shaft member 2 is a component of the rotation side member, and the housing 7, the sleeve member 8, and the seal member 9 are components of the fixed side member. For convenience of explanation, the following description will be made with the side of the opening 7a of the housing 7 as the upper side and the side opposite to the opening 7a as the lower side.

  The shaft member 2 includes a shaft portion 2a and a disk-shaped flange portion 2b. The shaft portion 2a is formed of a metal material such as stainless steel. On the other hand, the flange portion 2b is formed by injection molding a resin composition using a resin material such as a liquid crystal polymer (LCP) as a base resin, and is provided above the lower end of the shaft portion 2a.

  The flange portion 2b can be integrally injection-molded using the metal shaft portion 2a as an insert part. Or what was shape | molded separately from the axial part 2a can also be fixed to the axial part 2a by retrofit. In addition to this, in order to prevent the flange portion 2b from being removed, for example, although not shown, a groove may be provided over the entire circumference in the flange portion 2b formation portion of the shaft portion 2a. In addition, the flange portion 2b can be prevented from rotating by providing circumferential engagement portions such as concave portions or uneven portions at a plurality of locations in the circumferential direction. Further, although not shown in the drawing, the flange portion 2b of the shaft portion 2a is provided with a core bar protruding to the outer diameter side, and the flange portion 2b is covered with the resin composition around the core bar. It can also be formed. Thereby, the fixing strength of the flange part 2b can be raised. The metal core is preferably made of metal, and can be formed integrally with or separately from the shaft portion 2a.

  As the base resin of the resin composition forming the flange portion, in addition to the resins exemplified above, for example, polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide ( A noncrystalline resin such as PEI) or a crystalline resin such as polybutylene terephthalate (PBT), polyetheretherketone (PEEK), or polyphenylene sulfide (PPS) can be used.

  Examples of the resin composition include fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, carbon black, graphite, carbon nanomaterials, An appropriate amount of a fibrous or powdery conductive filler such as various metal powders can be blended depending on the purpose.

  The housing 7 has an opening 7a at one end and is formed in a bottomed cylindrical shape with the other end closed, and includes a cylindrical side portion 7b and a bottom portion 7c integrally connected to the other end side of the side portion 7b. I have. The housing 7 is formed by injection molding a resin composition in which the above-exemplified resins and fillers are appropriately combined. The side part 7b and the bottom part 7c may be formed separately, and both may be bonded to each other by means of adhesion and welding (such as ultrasonic welding). Note that the housing 7 does not necessarily need to be formed of resin, and can be formed by, for example, pressing a metal material.

  The sleeve member 8 is made of, for example, a soft metal material such as copper or aluminum (including an alloy) or a sintered metal material. In this embodiment, the sleeve member 8 is formed in a cylindrical shape with a porous body of sintered metal mainly composed of copper. Then, the lower end surface 8c of the sleeve member 8 is brought into contact with the bottom 7c of the housing 7, and the axial position of the sleeve member 8 with respect to the housing 7 is determined. Then, the sleeve member 8 is fixed to the housing by fixing means such as adhesion and welding. 7 is fixed.

  As shown in FIG. 3, a plurality of arcuate surfaces 8a1 serving as radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 are respectively provided in regions spaced apart from each other on the inner peripheral surface 8a of the sleeve member 8. It is formed. Each arcuate surface 8a1 is an eccentric arcuate surface centered at a point offset from the rotational axis O by an equal distance, and is formed at equal intervals in the circumferential direction. An axial separation groove 8a2 is formed between each eccentric arc surface 8a1.

  By inserting the shaft portion 2a of the shaft member 2 into the inner peripheral surface 8a of the sleeve member 8, the eccentric arc surface 8a1 and the separation groove 8a2 of the sleeve member 8 and the perfect circular outer peripheral surface 2a1 of the shaft portion 2a are interposed. The radial bearing gaps of the first and second radial bearing portions R1 and R2 are respectively formed. In the radial bearing gap, a region facing the eccentric arc surface 8a1 is a wedge-shaped gap 8a3 in which the gap width is gradually reduced in the circumferential direction. The reduction direction of the wedge-shaped gap 8a3 coincides with the rotation direction of the shaft member 2.

  For example, although not shown in the drawings, a spiral-shaped dynamic pressure groove is formed as a thrust dynamic pressure generating portion on the entire upper surface 8b of the sleeve member 8 or a part of the annular region. The dynamic pressure groove forming region of the upper end surface 8b faces the lower end surface 2b2 of the flange portion 2b, and when the shaft member 2 rotates, a thrust bearing gap of the thrust bearing portion T1 is formed between the both surfaces 8b and 2b2. (See FIG. 2).

  The seal member 9 is formed in an annular shape with, for example, a resin material or a metal material. The seal member 9 is disposed on the inner periphery of the opening 7a of the housing 7, and ultrasonic welding or the like is performed with the flange portion 2b accommodated between the lower end surface 9b of the seal member 9 and the upper end surface 8b of the sleeve member 8. It is fixed to the housing 7 by fixing means such as welding or adhesion. In this case, a predetermined seal space S is formed between the cylindrical inner peripheral surface 9a of the seal member 9 and the outer peripheral surface 2a1 of the opposed shaft portion 2a. The inner space of the housing 7 sealed with the seal member 9 is filled with lubricating oil as a lubricating fluid including the inner pores of the sleeve member 8, and the oil level of the lubricating oil is within the range of the sealing space S. Maintained.

  The lower end surface 9b of the seal member 9 is opposed to the upper end surface 2b1 of the flange portion 2b via a gap in the axial direction. When the shaft member 2 is displaced upward, the upper end surface 2b1 of the flange portion 2b is engaged with the lower end surface 9b of the seal member 9 in the axial direction, and the shaft member 2 is locked. Thus, the sealing member 9 in this embodiment has both a sealing function and a retaining function.

  In the dynamic pressure bearing device 1 configured as described above, when the shaft member 2 rotates, the region (two upper and lower regions) serving as the radial bearing surface of the inner peripheral surface 8a of the sleeve member 8 is radial with the outer peripheral surface 2a1 of the shaft portion 2a. The bearings are opposed to each other through a bearing gap to form multi-arc bearings (also referred to as taper bearings). As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed into the reduction side of the wedge-shaped gap 8a3, and the pressure rises. The first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft portion 2a in a non-contact manner are configured by the dynamic pressure action of the lubricating oil.

  At the same time, an oil film of lubricating oil is also formed in the thrust bearing gap between the lower end surface 2b2 of the flange portion 2b and the upper end surface 8b of the sleeve member 8 facing the flange portion 2b by the dynamic pressure action of the dynamic pressure groove. A thrust bearing portion T1 that supports the flange portion 2b in a non-contact manner so as to be rotatable in the thrust direction is configured by the pressure.

  In this manner, by forming the flange portion 2b from a resin material, it can be manufactured at a lower cost than the case of the metal flange portion 2b that requires machining such as turning. In this embodiment, the case where the dynamic pressure groove is formed on the upper end surface 8b of the sleeve member 8 facing the thrust bearing gap of the thrust bearing portion T1 has been described. A dynamic pressure groove can also be formed in the end face 2b2. In that case, the molding of the resin flange portion 2b and the molding of the dynamic pressure groove can be performed at the same time, and the number of processes can be reduced and the cost can be reduced compared to the case where these moldings are performed in separate processes. Can be planned.

  In the first embodiment, the case where the seal space S is formed between the cylindrical inner peripheral surface 9a of the seal member 9 and the outer peripheral surface 2a1 of the shaft portion 2a opposed thereto is exemplified. Other forms are also possible. For example, FIG. 4 illustrates a case where a tapered seal space S ′ is formed by gradually increasing the radial gap width toward the outside of the housing 7 (upper side in FIG. 4).

  Further, in FIG. 5, in order to reduce the axial dimension of the housing 7 and reduce the size of the hydrodynamic bearing device 1, the inner peripheral surface 9a of the seal member 9 and the outer peripheral surface 2b3 of the flange portion 2b are shown. An example is shown in which a tapered seal space S ′ is formed between the opposing surfaces.

  Furthermore, as an example of considering the retaining of the shaft member 2, a configuration as shown in FIG. 6 can be given, for example. The seal space S ′ in the figure includes an upper outer peripheral surface 2b3 and an inner peripheral surface 9a of the seal member 9 facing the upper outer peripheral surface 2b3 among the outer peripheral surfaces defined by the axial step provided in the flange portion 2b. Formed between. In addition, the end surface 2 b 4 on the outer diameter side of the upper end surface 2 b 1 defined by the steps is opposed to the lower end surface 9 b of the seal member 9.

  With such a configuration, the sealing space S ′ has a sealing action due to centrifugal force and intercapillary force, and leakage of lubricating oil to the outside is prevented. Further, when the shaft member 2 is relatively displaced upward, the outer diameter side end surface 2b4 of the flange portion 2b is engaged with the lower end surface 9b of the seal member 9 in the axial direction, whereby the shaft member 2 is prevented from being detached.

  In the illustrated example, the seal member 9 has a form in which a portion of the lower end surface 9b that does not face the outer diameter side end surface 2b4 is protruded downward. Therefore, when the downward projecting portion 9c of the seal member 9 is brought into contact with the upper end surface 8b of the sleeve member 8, the seal member 9 can be easily positioned in the axial direction.

  The second embodiment of the present invention will be described below with reference to FIGS. In addition, about a matter common with 1st Embodiment, description is abbreviate | omitted below.

  FIG. 7 shows a configuration example of a spindle motor for information equipment in which the hydrodynamic bearing device 11 according to the second embodiment is incorporated. This spindle motor is also used in a disk drive device such as an HDD, and a dynamic pressure bearing device 11 that rotatably supports a rotation-side member including a shaft member 12 and a disk hub 13 and a radial gap, for example. And a stator coil 14 and a rotor magnet 15 which are opposed to each other via a bearing, and a bracket 16 fixed to the outer periphery of the hydrodynamic bearing device 11.

  FIG. 8 shows the hydrodynamic bearing device 11. The hydrodynamic bearing device 11 includes a housing 17, a sleeve member 18 fixed to the inner periphery of the housing 17, a shaft member 12 inserted into the inner periphery of the sleeve member 18, and a disk fixed to the upper end of the shaft member 12. The hub 13 is configured as a main component. In this embodiment, among the above-described components, the shaft member 12 and the disk hub 13 are components of the rotation side member, and the housing 17 and the sleeve member 18 are components of the fixed side member.

  The shaft member 12 is formed in a shaft shape having the same diameter, for example, with a metal material such as stainless steel.

  The disk hub 13 is made of resin, and in this embodiment, the shaft member 12 is used as an insert part for injection molding. The disk hub 13 includes a disk-shaped main portion 13a covering the opening side of the housing 17, a cylindrical portion 13b extending downward in the axial direction from the outer peripheral portion of the main portion 13a, and a disk provided on the outer periphery of the cylindrical portion 13b. And a mounting surface 13c. In this embodiment, a disk (not shown) is fitted on the outer periphery of the main portion 13a and placed on the disk mounting surface 13c. Then, the disk is held on the disk hub 13 by appropriate holding means (not shown).

  The housing 17 is a bottomed cylindrical resin molded product. The housing of the illustrated example includes a cylindrical side portion 17b and a bottom portion 17c provided at the lower end of the side portion 17b, and the bottom portion 17c is integrally formed with the side portion 17b.

  For example, a spiral dynamic pressure groove is formed as a thrust dynamic pressure generating portion on the entire or partial annular region of the opening-side end surface (upper end surface) 17d of the housing 17 as a thrust dynamic pressure generating portion. The dynamic pressure groove forming region of the upper end surface 17d faces the lower end surface 13d of the main portion 13a of the disk hub 13, and a thrust bearing portion, which will be described later, is formed between the both surfaces 17d and 13d when the shaft member 2 (rotating body) rotates. A thrust bearing gap of T2 is formed.

  A tapered outer wall 17e that gradually increases in diameter upward is formed on the outer periphery of the upper portion of the housing side portion 17b. The tapered outer wall 17e and the inner wall 13b1 of the cylindrical portion 13b provided on the disk hub 13 A tapered seal space S ′ that gradually decreases upward is formed therebetween. The seal space S 'communicates with the outer diameter side of the thrust bearing gap of the thrust bearing portion T2 when the shaft member 12 and the disk hub 13 are rotated. Further, the inner periphery of the lower end of the cylindrical portion 13b of the disk hub 13 is engaged with the housing 17 in the axial direction to engage the shaft member 2 when the shaft member 2 (rotary member) is relatively displaced in the axial direction. A locking member 19 for stopping is attached.

  As described above, the housing 17 and the disk hub 13 are resin molded products. As the base resin, for example, the thermoplastic resins exemplified in the first embodiment can be used. Among them, LCP and PPS are particularly suitable as a material for the housing 17 because they have excellent properties such as oil resistance and dimensional stability.

  At this time, if the base resin used in the housing 17 and the disc hub 13 is different, adhesion between the housing 17 and the disc hub 13 during sliding can be prevented. As an example, for example, LCP is used as the base resin of the housing 17 and PPS is used as the base resin of the disk hub 13.

  For example, the filler exemplified in the first embodiment is blended with these base resins, and the housing 17 and the disc hub 13 are individually injection molded using the resin composition thus obtained. As an example, in the present embodiment, PAN-based carbon fibers having excellent characteristics such as strength and elastic modulus are used as reinforcing fibers, and high conductivity can be ensured with a small blending amount as a conductive agent. Carbon nanotubes are used.

  The sleeve member 18 is formed into a cylindrical shape, for example, a porous body made of sintered metal, particularly a sintered metal porous body mainly composed of copper, and is fixed to a predetermined position on the inner periphery of the housing 17 by, for example, ultrasonic welding. The

  In this embodiment, as described above, a thrust bearing gap is formed between the upper end surface 17d of the housing 17 and the lower end surface 13d of the disk hub 13 opposite to the upper end surface 17d, thereby causing a dynamic pressure action of fluid (lubricating oil). A dynamic pressure groove is formed on the upper end surface 17 d of the housing 17. Therefore, the sleeve member 18 in the second embodiment has a plurality of arc surfaces as shown in FIG. 3 on its inner peripheral surface 18a, while the upper end surface 18b is a smooth surface without a dynamic pressure groove.

  In the hydrodynamic bearing device 11 having the above-described configuration in which the internal space of the housing 17 including the seal space S ′ and the thrust bearing gap is filled with lubricating oil, the inner periphery of the sleeve member 18 is rotated when the shaft member 12 (rotation side member) rotates. A region (two upper and lower regions) serving as a radial bearing surface of the surface 18a faces the outer peripheral surface 12a of the shaft member 12 via a radial bearing gap, and constitutes a multi-arc bearing (also referred to as a taper bearing). . As the shaft member 12 rotates, the lubricating oil in the radial bearing gap is pushed into the reduction side of the wedge-shaped gap (see FIG. 3), and the pressure rises. The first radial bearing portion R11 and the second radial bearing portion R12 that support the shaft member 12 in a non-contact manner are configured by the dynamic pressure action of the lubricating oil.

  At the same time, an oil film of lubricating oil is also formed in the thrust bearing gap between the lower end surface 13d of the disk hub 13 and the upper end surface 17d of the housing 17 facing the disk hub 13 by the dynamic pressure action of the dynamic pressure groove. Thus, a thrust bearing portion T2 is configured to support the shaft member 12 (rotation side member) in a non-contact manner so as to be rotatable in the thrust direction.

  Thus, in 2nd Embodiment, the effect similar to 1st Embodiment is acquired by forming the housing 17 and the disk hub 13 including the part which faces a thrust bearing clearance gap with resin. Further, since both the housing 17 and the disk hub 13 that are opposed to each other through the thrust bearing gap are formed of resin, the linear expansion coefficient thereof is substantially the same level. Therefore, the axial expansion amount due to the temperature change can be made substantially the same between the fixed side and the rotation side, and the fluctuation of the width of the thrust bearing gap due to the temperature change can be suppressed to obtain stable bearing performance.

In the above configuration, the upper end surface 17d of the housing 17 and the lower end surface 13d of the disk hub 13 that are opposed to each other with the thrust bearing gap between them are the cause of the swinging of the rotating shaft member 12 or the like when the motor is started or stopped. Due to this, sliding contact is temporarily made. As a problem caused by the sliding contact between the two, sliding of the resin in the sliding portion P can be cited.

  According to the verification by the present inventors, it has been found that when the average fiber diameter of the carbon fiber blended as the reinforcing fiber exceeds 12 μm, the amount of wear at the sliding portion P of the disk hub 13 and the housing 17 is remarkably increased. This is because the carbon fiber, which has become rigid as the fiber diameter increases, damages the soft resin material on the other side at the sliding portion P, and the surface of the roughened resin material further slides on the other side resin material. This is thought to be due to the progress of wear. On the other hand, if the average fiber diameter of the carbon fibers is less than 1 μm, the reinforcing effect that is the original purpose of the carbon fibers becomes insufficient, which is not appropriate. Therefore, it is desirable that the carbon fiber as the filler is set within a range of an average fiber diameter of 1 to 12 μm (preferably 5 to 10 μm).

  If the reinforcing fiber is too long, the fiber is cut finely when the surplus resin material is reused, and thus recyclability is impaired. In addition, transferability when the dynamic pressure groove is molded is also impaired. From such a viewpoint, it is desirable that the average length of the reinforcing fibers is 500 μm or less (preferably 300 μm or less).

  Further, according to the verification by the present inventor, it was also found that the amount of wear at the sliding portion P between the resins increases remarkably even when the blending ratio of the carbon fibers exceeds 20 vol%. This is considered because the frequency of contact between the carbon fiber and the counterpart resin member increases as the blending amount of the carbon fiber increases. On the other hand, if the blending ratio of the carbon fibers is less than 5%, it is difficult to ensure the necessary mechanical strength and it is difficult to ensure the wear resistance of the resin member. Accordingly, the blending amount of the carbon fiber is desirably 5 to 20 vol%.

  On the other hand, even if the fiber diameter and blending ratio of the reinforcing fibers are within the above range, if the blending amount of other fillers such as a conductive agent is too large, the housing 17 may be separated from another member (for example, the sleeve member 18). The welding strength at the time of sonic welding decreases. As a result of verification by the present inventors, when the total amount of fillers including reinforcing fibers and conductive agents (total amount of metal fillers or inorganic fillers) exceeds 30 vol%, the decrease in welded portion strength increases, and in terms of strength. It turned out to be a bug. Therefore, the total amount of filler is desirably 30 vol% or less.

  FIG. 9 shows another embodiment of the multi-arc bearing constituting the radial bearing portions R1, R2 (R11, R12) in the first and second embodiments. In this embodiment, in the configuration shown in FIG. 3, the predetermined region θ on the minimum gap side of each eccentric arc surface 8a1 is configured by a concentric arc centered on the rotation axis O. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

  In FIG. 10, a region serving as a radial bearing surface of the inner peripheral surface 8 a of the sleeve member 8 is formed by three arc surfaces 8 a 1, and the centers of the three arc surfaces 8 a 1 are offset from the rotation axis O by the same distance. Yes. In each region defined by the three eccentric arc surfaces 8a1, the radial bearing gap has a shape that is gradually reduced with respect to both circumferential directions.

  The multi-arc bearings of the radial bearing portions R1 and R2 (R11, R12) described above are all so-called three-arc bearings. A multi-arc bearing composed of the number of arc surfaces may be adopted. In addition to the configuration in which the two radial bearing portions are provided apart in the axial direction as in the above embodiment, one radial bearing portion is provided over the upper and lower regions of the inner peripheral surface 8a of the sleeve member 8. It is good also as a structure.

  Further, in the above embodiment, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 (11) and causes the hydrodynamic action in the radial bearing gap or the thrust bearing gap. A fluid that can cause a dynamic pressure action in each bearing gap, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or a lubricating grease may be used.

1 is a cross-sectional view of a spindle motor for information equipment incorporating a fluid dynamic bearing device according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of a fluid dynamic bearing device. It is sectional drawing of a radial bearing part. It is an expanded sectional view showing other examples of composition of seal space. It is an expanded sectional view showing other examples of composition of seal space. It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of a fluid dynamic bearing device. It is sectional drawing which shows the other structural example of a radial bearing part. It is sectional drawing which shows the other structural example of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 Dynamic pressure bearing apparatus 2, 12 Shaft member 2a Shaft part 2b Flange part 3, 13 Disc hub 4 Stator coil 5 Rotor magnet 7, 17 Housing 8, 18 Sleeve member 9 Seal member 19 Locking member S, S 'Seal Space R1, R2 Radial bearing part T1, T2 Thrust bearing part

Claims (6)

Dynamic pressure action of fluid generated in a stationary side member, a rotating side member mounted with a driven body and rotating relative to the stationary side member, and a radial bearing gap between the stationary side member and the rotating side member And a radial bearing portion that supports the rotating side member in a radial direction in a non-contact manner, and a dynamic pressure action of fluid generated in a thrust bearing gap between the fixed side member and the rotating side member causes the rotating side member to move in the thrust direction. In the hydrodynamic bearing device provided with a thrust bearing portion that supports non-contact,
The thrust bearing gap of the thrust bearing portion is provided in a portion where the rotating side member and the fixed side member face each other on the driven body side,
At least one of the portion facing the thrust bearing gap of the fixed side member and the portion facing the thrust bearing gap of the rotating side member is formed of resin.   2. The hydrodynamic bearing device according to claim 1, wherein the fixed side member includes a sleeve member facing the radial bearing gap and a housing for fixing the sleeve member therein.   The rotation side member includes a shaft member, the shaft member includes a flange portion, and the thrust bearing gap is formed between an end surface of the flange portion and an end surface of the sleeve member facing the flange portion. The hydrodynamic bearing device according to claim 2, wherein:   The hydrodynamic bearing device according to claim 3, wherein the flange portion is formed of resin.   The hydrodynamic bearing device according to claim 1, wherein the radial bearing portion is a multi-arc bearing.   A spindle motor of a disk device having the hydrodynamic bearing device according to any one of claims 1 to 5.

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