JP2007002966A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device having a tilted bearing clearance of high precision at low cost. <P>SOLUTION: The fluid bearing device 1 comprises a shaft member 2, a bearing member 7 with the shaft member 2 inserted in an inner circumference, and a tilted bearing clearance C1 which is formed between an outer circumferential surface of the shaft member 2 and an inner circumferential surface of the bearing member 7, and tilted in the axial direction. The bearing member 7 has an electroforming unit 10 facing the tilted bearing clearance C1 and a mold part 14 which is injection-molded while inserting the electroforming unit 10 therein. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device. A hydrodynamic bearing device is a device that rotatably supports a shaft member with an oil film formed in a bearing gap. This bearing device is a magnetic disk device such as an information device such as an HDD or an FDD, a CD-ROM, a CD-R / For spindle motors mounted on optical disk devices such as RW and DVD-ROM / RAM, magneto-optical disk devices such as MD and MO, for polygon scanner motors mounted on laser beam printers (LBP), personal computers (PC), etc. It is suitable for a fan motor mounted on a motor or a small motor mounted on an electric device such as an axial fan.

  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 these required performances is a bearing that supports the spindle of the motor. In recent years, as this type of bearing, the use of a hydrodynamic bearing device having characteristics excellent in the required performance has been studied. Or actually used.

  This type of hydrodynamic bearing device includes a hydrodynamic bearing provided with a dynamic pressure generating portion for generating dynamic pressure in the lubricating oil in the bearing clearance, and a so-called perfect bearing (bearing cross section) provided with no dynamic pressure generating portion. Are roughly divided into bearings having a perfect circle shape.

  For example, an example of a hydrodynamic bearing device used for a disk device such as an HDD may be one having the structure shown in FIG. In this hydrodynamic bearing device, a radial bearing portion 400 for supporting the shaft member 100 in a non-contact manner is provided between the outer peripheral surface of the shaft member 100 and the inner peripheral surface of the bearing member 200 facing each other through a radial bearing gap. . Further, the shaft member is thrust between the both end surfaces of the flange portion 110 provided on the shaft member 100 and the end surfaces of the members (the bearing member 200 and the lid member 300) facing the both end surfaces through the thrust bearing gap. A thrust bearing portion 500 for non-contact support in the direction is provided.

  By the way, in recent years, in information equipment in which a disk device such as an HDD is incorporated, the performance has been improved rapidly, and the size and thickness (compact) have been reduced. The demand for is getting stricter. However, in the structure of the hydrodynamic bearing device described above, since the radial bearing portion and the two thrust bearing portions are stacked in the axial direction, the overall axial size of the bearing device is large and the hydrodynamic bearing device is compact. There is a limit to the conversion.

Thus, for example, a shaft gap is formed in a truncated cone shape, and a bearing gap (with a large diameter on one side in the axial direction and a small diameter on the other side in the axial direction between the bearing members made of sintered metal disposed on the outer periphery thereof ( An inclined bearing gap is formed, and a thrust bearing gap is formed between the end surface of the shaft member and the closing member facing the shaft member. With this configuration, since the flange portion 110 of the shaft member 100 shown in FIG. 16 is not required, the axial dimension of the bearing device can be made compact accordingly (for example, see Patent Document 1).
JP 2002-276649 A

  In general, the bearing performance including the rotational accuracy of the hydrodynamic bearing device is greatly influenced by the accuracy of the bearing clearance. In the hydrodynamic bearing device described in Patent Document 1, it is necessary to form the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing member in a conical shape in order to form an inclined bearing gap. Good and efficient processing is not easy. In particular, since machining of the inner peripheral surface is generally difficult as compared with the outer peripheral surface, it is difficult to accurately finish the conical inner peripheral surface of the bearing member at a low cost with the current processing technology. Therefore, a highly accurate inclined bearing gap cannot be obtained stably, and there is a possibility that sufficient bearing performance cannot be ensured depending on the design conditions.

  Then, an object of this invention is to provide the hydrodynamic bearing apparatus provided with the highly accurate inclination bearing clearance at low cost.

  In order to solve the above problems, a hydrodynamic bearing device according to the present invention is formed between a shaft member, a bearing member in which the shaft member is inserted into an inner periphery, and an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing member. An inclined bearing gap inclined in the axial direction, the shaft member is rotatably supported by an oil film formed in the inclined bearing gap, and the bearing member includes an electroformed portion facing the inclined bearing gap, And it is the injection molded product which inserted the electroformed part, It is characterized by the above-mentioned.

  The electroformed part is a metal structure formed by being deposited on the surface of the master member by electroforming, and the surface shape of the master member is accurately transferred on the order of microns on the contact surface with the master member. Therefore, if the outer peripheral surface of the master member is formed in a conical shape corresponding to the inner peripheral surface shape of the electroformed part, and the precision is sufficiently increased by carefully finishing this, the conventional processing method A conical inner peripheral surface that is difficult to process can be obtained with high accuracy. Compared to the inner peripheral surface, high-accuracy machining of the outer peripheral surface is generally easy, so it is not so difficult to finish the outer peripheral surface of the master member into a conical surface with high accuracy. Therefore, by forming the electroformed part so as to face the inclined bearing gap, an inclined bearing gap having a large diameter on one side in the axial direction and a small diameter on the other side in the axial direction can be obtained with high accuracy and low cost.

  The bearing member is formed by injection molding in which the above-described electroformed part is inserted. If it is injection molding, it can be molded at a low cost, and further, since the bearing member can be molded into an arbitrary shape, the bearing member composed of two or more members can be integrated. Therefore, further cost reduction can be achieved by reducing the number of parts.

  In the above configuration, the fluid dynamic pressure is generated in the inclined bearing gap by forming the dynamic pressure generating part on the outer peripheral surface of the shaft member or the electroformed part of the bearing member so as to face the inclined bearing gap. The bearing rigidity can be improved. When forming the dynamic pressure generating part in the electroformed part of the bearing member, if the master member is formed with a mold corresponding to the shape of the dynamic pressure generating part, the dynamic pressure can be generated with high accuracy from the above-mentioned electroforming characteristics. The part can be manufactured at low cost. When the dynamic pressure generating portion is formed on the outer peripheral surface of the shaft member, the outer peripheral surface of the master member is formed into a smooth surface without unevenness. By forming an electroformed part using this master member and separating the electroformed part from the master member, a shaft member in which a dynamic pressure generating part is previously formed on the outer peripheral surface is inserted into the inner peripheral surface of the electroformed part. The bearing device is assembled.

  The dynamic pressure generating portion is not particularly limited as long as fluid dynamic pressure can be generated in the inclined bearing gap, for example, a plurality of dynamic pressure grooves arranged in a herringbone shape or a spiral shape, and at equal intervals in the circumferential direction. Examples thereof include an axial groove provided, a plurality of circular arc surfaces provided in the circumferential direction, and harmonic wave surfaces.

  The hydrodynamic bearing device having the above-described configuration can be preferably used for a motor having a stator coil and a rotor magnet, for example, a spindle motor for information equipment.

  As described above, according to the present invention, a hydrodynamic bearing device having a highly accurate inclined bearing gap can be provided at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (dynamic pressure bearing device) 1 having the configuration of the present invention. This spindle motor for information equipment is used in a disk drive device such as an HDD. The hydrodynamic bearing device 1 that rotatably supports the shaft member 2 and the shaft member 2 are mounted on one or more disks D. The disk hub 9 to hold | maintain, the stator coil 4 and the rotor magnet 5 which oppose through a gap of radial direction, and the bracket 6 are provided. 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 9. When the stator coil 4 is energized, the rotor magnet 5 is rotated by electromagnetic force generated between the stator coil 4 and the rotor magnet 5, and the shaft member 2 and the disk hub 9 are moved together with the member (rotating member 3). And rotate together.

  When the hydrodynamic bearing device 1 is used in a spindle motor for other information equipment, for example, a spindle motor of an optical disk device or a magneto-optical disk device, a turntable (not shown) that supports the disk is a polygon of a laser beam printer (LBP). A polygon mirror (not shown) is fixed to the shaft member 2 when used for a scanner motor, and a fan (not shown) is used for a fan motor of a personal computer (PC).

  The hydrodynamic bearing device 1 includes a shaft member 2, a bearing member 7 disposed on the outer periphery of the shaft member 2, and a lid member 8 that seals one end opening of the bearing member 7 as main components. For convenience of explanation, the lid member 8 side is described as the lower side, and the side opposite to the axial direction is described as the upper side.

  The shaft member 2 is made of a metal material that satisfies the required rigidity and wear resistance, for example, stainless steel. The shaft member 2 is provided above the conical portion 2a and a truncated cone-shaped conical portion 2a having a small diameter on one side (upper side in the illustrated example) and a large diameter on the other side (lower side in the illustrated example). And a cylindrical base portion 2b formed integrally with the conical portion 2a. The outer peripheral surface 2a1 and the lower end surface 2a2 of the conical portion 2a are formed as smooth surfaces without unevenness.

  A disc hub 9 is fixed to the base portion 2b of the shaft member 2 by appropriate means such as press-fitting and press-fitting adhesion, and the shaft member 2 and the disc hub 9 integrated together constitute a rotating member 3. The rotating member 3 can also be configured by inserting the shaft member 2 and injection molding the disk hub 9.

  The bearing member 7 includes an electroformed part 10 having an inner peripheral surface having a conical surface shape and a mold part 14 that covers the outer periphery of the electroformed part 10. The mold part 14 is injection-molded with the electroformed part 10 inserted as will be described later.

  The inner peripheral surface 7 a of the bearing member 7 is formed in a tapered surface shape corresponding to the outer peripheral surface shape of the conical portion 2 a of the shaft member 2. The inner peripheral surface 7a of the bearing member 7 and the outer peripheral surface 2a1 of the conical portion 2a of the shaft member 2 are parallel to each other in the generatrix, so that both surfaces 7a and 2a1 can be in surface contact with each other. As will be described later, with the rotation of the shaft member 2, between the inner peripheral surface 7 a of the bearing member 7 and the outer peripheral surface 2 a 1 of the conical portion 2 a of the shaft member 2, the upper side in the axial direction has a smaller diameter and the lower side in the axial direction has Inclined bearing gaps C1 that are inclined so as to have a large diameter are formed at two locations in the vertical direction. In the illustrated example, the gap width of the inclined bearing gap C1 is exaggerated for easy understanding, but in actuality, it is about several μm to several tens of μm.

  As shown in FIG. 2, the inclined bearing surface A is formed at two upper and lower portions on the inner peripheral surface of the electroformed portion 10, and each of the inclined portions is inclined to a region facing the inclined bearing surface A when the shaft member 2 rotates. A bearing gap C1 is formed. In the inclined bearing surface A, a plurality of dynamic pressure grooves Aa arranged in a herringbone shape, for example, are formed as dynamic pressure generating portions that generate fluid dynamic pressure in the inclined bearing gap C1. In the illustrated example, the case where two inclined bearing surfaces A are formed on the inner peripheral surface of the common electroformed part 10 is illustrated, but each inclined bearing surface A is individually formed on two or more electroformed parts 10. May be. As the dynamic pressure groove shape, a spiral shape or the like can be adopted in addition to the herringbone shape shown in the figure.

  The lid member 8 is formed in a disc shape with a metal material such as stainless steel or brass, and is fixed to a step formed in the large-diameter side opening of the bearing member 7 by means such as adhesion. A thrust bearing surface B is formed on the upper end surface 8a of the lid member 8, and a thrust bearing gap C2 is formed in a region facing the thrust bearing surface B when the shaft member 2 rotates. For example, a plurality of dynamic pressure grooves Ba arranged in a spiral shape as shown in FIG. 3 are formed on the thrust bearing surface as thrust dynamic pressure generating portions for generating fluid dynamic pressure in the thrust bearing gap C2. As the dynamic pressure groove shape, a herringbone shape, a radial shape, or the like can be employed in addition to the spiral shape shown in the figure. The thrust bearing surface B having a dynamic pressure generating portion such as a dynamic pressure groove can also be formed on the lower end surface 2a2 of the shaft member 2.

  Although illustration is omitted, a seal space can be formed between the upper end of the inner peripheral surface of the bearing member 7 and the outer peripheral surface 2a1 of the shaft member 2 opposed to the upper end. For example, the seal space is formed in a tapered shape in which the inner side of the bearing device is narrowed. By forming the tapered shape in this way, the lubricating oil is drawn into the inside of the bearing device by the capillary force, so that it is possible to prevent the lubricating oil from leaking out of the bearing device. The seal space has a volume that can absorb the thermal expansion amount of the lubricating oil due to temperature changes, and therefore the oil level that is open to the outside air always exists in the seal space. The seal space is fixed to the inner peripheral surface of the upper end of the bearing member 7 and may be formed between the inner peripheral surface of the seal member separate from the bearing member and the outer peripheral surface of the shaft member facing the seal member. Good.

  In the above configuration, the lubricating oil is filled in the internal space of the bearing device. In this state, when the shaft member 2 and the bearing member 7 are relatively rotated (in this embodiment, the shaft member 2 is rotated), the inclined bearing surface A on the inner peripheral surface of the bearing member 7 is the outer periphery of the shaft member 2. It faces the surface 2a1 via two inclined bearing gaps C1. As the shaft member 2 rotates, a dynamic pressure of lubricating oil is generated in each inclined bearing gap C1, and as shown in FIG. 4, a horizontal component (radial direction) component force Fr and a vertically downward direction ( A component force Ft in the thrust direction) acts. Thereby, the 1st inclination bearing part K1 and the 2nd inclination bearing part K2 which support the shaft member 2 in a radial direction and one thrust direction so that rotation is possible are formed.

  As the shaft member 2 rotates, the thrust bearing surface B formed on the upper end surface 8a of the lid member 8 faces the lower end surface 2a2 of the shaft member 2 through the thrust bearing gap C2. As the shaft member 2 rotates, dynamic pressure of the lubricating oil is generated in the thrust bearing gap C2, and the shaft member 2 is supported in a non-contact manner so as to be rotatable upward in the thrust direction by the oil film of the lubricating oil formed in the thrust bearing gap C2. The Thereby, the thrust bearing part T which supports the shaft member 2 in a non-contact manner so as to be rotatable in the other thrust direction is formed.

  Next, the manufacturing process of the bearing member 7 will be described below.

  5-7 shows each manufacturing process of the bearing member 7 in the said bearing apparatus. More specifically, FIG. 5 (a) is a process of manufacturing the master member 12 (master member manufacturing process), FIG. 5 (b) is a process of masking a required portion of the master member 12 (masking process), and FIG. FIG. 7 shows a step (molding step) of molding the electroformed part 10 of the electroformed member 11 with resin or the like. After passing through these steps, the bearing member 7 is manufactured through a step of separating the electroformed part 10 and the master member 12.

  In the master member manufacturing process shown in FIG. 5A, the master member 12 is formed of a conductive material, for example, stainless steel, nickel chrome steel, other nickel alloy, chromium alloy or the like that has been subjected to quenching. In addition to these metal materials, the master member 12 can also be formed of a non-metallic material such as a ceramic subjected to a conductive treatment (for example, forming a conductive film on the surface). The master member 12 includes a truncated cone part 12a and a cylindrical part 12b that is formed integrally with the truncated cone part 12a and extends in the axial direction from the lower end of the truncated cone part 12a. The outer peripheral surface of the truncated cone part 12a is formed in a tapered surface shape corresponding to the inner peripheral surface shape of the bearing member 7 and having a small diameter on one side in the axial direction and a large diameter on the other side in the axial direction.

  A molding portion N1 for molding the electroformed portion 10 of the bearing member 7 is formed in a partial region in the axial direction on the outer peripheral surface of the truncated cone portion 12a constituting the master member 12. The forming part N1 has a shape in which the concave / convex pattern on the inner peripheral surface of the electroformed part 10 is reversed, and at two places in the axial direction, there are rows of concave parts Ka for forming the hills between the dynamic pressure grooves Aa in the circumferential direction. Is formed. Of course, the shape of the recess Ka can correspond to the dynamic pressure groove pattern and can be formed in a spiral shape or the like.

  In the masking step shown in FIG. 5 (b), masking 13 (dot pattern) is applied to the outer surface of the master member 12 except for the molding portion N1. As the covering material for the masking 13, an existing product having non-conductivity and corrosion resistance against the electrolyte solution is appropriately selected and used.

  In electroforming, after the master member 12 is immersed in an electrolyte solution containing metal ions such as Ni and Cu, the master member 12 is energized, and the masking 13 is applied to the outer surface of the master member 12. This is performed by depositing (electrodepositing) the target metal in a non-existing region (molded portion N1). If necessary, the electrolyte solution may contain a sliding material such as carbon or a stress relaxation material such as saccharin. The type of electrodeposited metal is appropriately selected according to physical properties such as hardness and fatigue strength required for the bearing surface of the hydrodynamic bearing, and chemical properties.

  Through the above steps, as shown in FIG. 6, the electroformed part 10 is formed on the molded part N <b> 1 of the master member 12, and the electroformed part 10 and the master member 12 are integrated. Is formed. At this time, the inner peripheral surface of the electroformed portion 10 is formed in a taper shape corresponding to the outer peripheral surface shape of the truncated cone portion 12a of the master member 12, and the uneven pattern of the molding portion N1 formed on the master member 12 is transferred. Is done. As a result, as shown in FIG. 2, two inclined bearing surfaces A having a plurality of dynamic pressure grooves Aa are formed on the inner peripheral surface of the electroformed portion 10 so as to be separated from each other in the vertical direction. In addition, if the thickness of the electroformed part 10 is too thick, the peelability from the master member 12 is lowered, and conversely, if it is too thin, the durability of the electroformed part 10 is reduced. Furthermore, the optimum thickness is set according to the application.

  Next, the electroformed member 11 formed through the above steps is transferred to a molding step for insert-molding the bearing member 7.

  FIG. 7 conceptually shows the molding process. In this molding process, the electroformed member 11 has its axial direction parallel to the mold clamping direction (vertical direction in the drawing), for example, an upper mold 15 and a lower mold. 16 is supplied into the mold. The lower mold 16 is formed with a positioning hole 18 adapted to the outer diameter of the cylindrical portion 12b constituting the master member 12, and the electroformed member 11 transferred from the previous process is inserted into the positioning hole 18 to form an electroformed member. 11 positioning is performed. The upper mold 15 is formed with a guide hole 20 that can be fitted to the upper end of the master member 12 coaxially with the positioning hole 18.

  In the above mold, when the movable mold (the upper mold 15 in the present embodiment) is brought close to the fixed mold (the lower mold 16 in the present embodiment), the master member 12 is guided to a predetermined position of the upper mold 15 by the guide holes 20. And then clamped. After completion of the mold clamping, a resin material is injected into the cavity 17 through the gate 19 and insert molding is performed. Any resin material can be used as long as it is an injection moldable material. For example, polysulfone (PSF), polyethersulfone (PES), polyphenylsulfone (PPSF), polyetherimide (PEI) can be used as an amorphous resin. As the crystalline resin, liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and the like can be used. The resin material is mixed with one or two or more kinds of fillers such as a reinforcing material (regardless of the form of fiber, powder, etc.), a lubricant, and a conductive material as necessary.

  A metal material can also be used as the material to be injected. As the metal material, for example, a low melting point metal material such as a magnesium alloy or an aluminum alloy can be used. In this case, strength, heat resistance, conductivity, etc. can be further improved as compared with the case of using a resin material. In addition, so-called MIM molding may be employed in which after the injection molding with a mixture of metal powder and binder, degreasing and sintering. In addition, ceramic can also be used as the material to be injected.

  When the mold is opened after the insert molding is completed, a molded product in which the electroformed member 11 including the master member 12 and the electroformed part 10 and the mold part 14 are integrated is obtained.

  The molded product is then transferred to a separation step, where it is separated into one in which the electroformed part 10 and the molded part 14 are integrated (bearing member 7) and the master member 12. In this separation step, the internal stress accumulated in the electroformed part 10 is released, so that the inner peripheral surface of the electroformed part 10 is expanded and peeled off from the outer peripheral surface of the master member 12. The internal stress is released, for example, by applying an impact to the electroformed member 11 or the bearing member 7 or applying an axial pressure between the inner peripheral surface of the electroformed portion 10 and the outer peripheral surface of the master member 12. Is done. By releasing the internal stress, the inner peripheral surface of the electroformed part 10 is radially expanded, and a gap (dynamic motion) of an appropriate size is formed between the inner peripheral surface of the electroformed part 10 and the outer peripheral surface of the master member 12. If a gap greater than the depth of the pressure groove is desirable), excessive interference between the dynamic pressure groove pattern formed on the inner peripheral surface of the electroformed portion 10 and the molding portion N1 formed on the outer peripheral surface of the master member 12 Thus, the master member 12 can be smoothly pulled out in the axial direction from the inner peripheral surface of the electroformed part 10, whereby the molded product is obtained as a bearing member 7 including the electroformed part 10 and the mold part 14, and the master member. 12 can be separated. The diameter expansion amount of the electroformed part 10 can be controlled, for example, by changing the thickness of the electroformed part 10.

  When the inner circumference of the electroformed part 10 cannot be sufficiently expanded only by applying an impact, the electroformed part 10 and the master member 12 are heated or cooled, and a difference in thermal expansion is generated between them. The master member 12 and the bearing member 7 can also be separated.

  On the other hand, the master member 12 separated from the electroformed part 10 can be repeatedly used for manufacturing the bearing member 7.

  In addition, since the outer peripheral surface of the electroformed part 10 is formed into a rough surface due to the characteristics of electroforming, the material constituting the mold part 14 enters minute irregularities on the outer surface of the electroformed part at the time of insert molding, and the anchor effect. A strong fixing force due to is exhibited. Further, since the electroformed part 10 is formed to be inclined with respect to the axial direction, it is prevented from coming off in at least one axial direction. Therefore, it is possible to provide a high-strength bearing member 7 that is rich in impact resistance.

  Then, the shaft member 2 separately manufactured is inserted into the inner periphery of the bearing member 7 formed through the above steps, and the large-diameter side opening of the bearing member 7 is sealed with the lid member 8. By filling the internal space with lubricating oil, the hydrodynamic bearing device 1 shown in FIG. 1 is obtained.

  As described above, in the present invention, the bearing member 7 is formed by the electroformed portion 10 facing the inclined bearing gap C1 and the mold portion 14 that is injection-molded by inserting the electroformed portion 10. From the characteristics of electroforming, the inner peripheral surface shape of the electroformed portion 10 follows the surface shape of the master member 12, and the inner peripheral surface accuracy of the electroformed portion 10 follows the surface accuracy of the master member 12. Therefore, if the master member 12 is formed in a predetermined shape and with a predetermined accuracy, the inner peripheral surface of the electroformed part 10 is formed with a high accuracy following that of the master member. It is possible to form a conical inner peripheral surface that is difficult to achieve with high accuracy and low cost. Thereby, the width | variety precision of the inclination bearing clearance C1 can be improved, and the bearing performance of the hydrodynamic bearing apparatus which has this kind of inclination bearing clearance can be improved. In addition, if the inclined bearing surface A having the dynamic pressure groove Aa is formed by electroforming as in the present embodiment, the dynamic pressure groove can be formed with high accuracy due to the characteristics of electroforming. The bearing performance of the hydrodynamic bearing device can be improved.

  As a method for forming the dynamic pressure groove Aa on the inner peripheral surface of the electroformed part 10, another method can be adopted. FIG. 8 shows an example, and a convex conductive film 22 corresponding to the shape of the dynamic pressure groove Aa is formed on the molding portion N1 on the surface of the master member 12 to perform electroforming, and then the conductive film 22 is formed to form the dynamic pressure groove Aa. Specifically, first, as shown in FIG. 8 (a), a molded part N1 is formed in a partial region of the outer peripheral surface of the master member 12, and the convex conductive material corresponding to the dynamic pressure groove pattern is formed in the molded part N1. The conductive film 22 is formed. For example, the conductive coating 22 can be formed with high accuracy by ink-jet printing a conductive resin on the surface of the master member 12. Next, as shown in FIG. 4B, electroforming is performed using the master member 12 to form the electroformed part 10 to which the shape of the molded part N1 is transferred. After the completion of the electroforming, the mold part 14 is injection-molded in the same manner as the above process, and the master member 12 is separated from the molded product as shown in FIG. At this time, the conductive coating 22 is peeled off from the surface of the master member 12 together with the electroformed part 10. Thereafter, as shown in FIG. 4D, the dynamic pressure groove Aa is formed on the inner peripheral surface of the electroformed portion 10 by removing the conductive coating 22 on the inner peripheral surface of the electroformed portion 10 using a solvent or the like. The formed bearing member 7 is obtained.

  In the above description, the case where the inclined bearing surface A having the dynamic pressure groove Aa is formed on the inner peripheral surface of the electroformed part 10 is illustrated. However, the inclined bearing surface A having the dynamic pressure groove Aa is the outer peripheral surface of the shaft member 2. It can also be formed. The hydrodynamic bearing device 1 of this embodiment performs an electroforming process using the master member 12 whose outer peripheral surface is a smooth surface having no irregularities, and further passes through a molding step and a separation step to obtain a bearing member 7 having a smooth inner peripheral surface. Apart from this, the inclined bearing surface A having the dynamic pressure groove Aa is formed on the outer peripheral surface of the shaft member 2, and the shaft member 2 can be assembled by inserting it into the inner periphery of the bearing member 7. In this case, the inclined bearing surface A on the outer peripheral surface of the shaft member 2 can be formed by means such as etching processing or ink jet printing in addition to plastic processing such as forging and rolling.

  In the above description, the inclined bearing gap C1 having a small diameter on the upper side and a large diameter on the lower side is illustrated. However, the inclination direction of the inclined bearing gap is the opposite direction, that is, the upper diameter is larger and the lower is smaller diameter. It can also be inclined.

  FIGS. 9A and 9B show another embodiment of the present invention, which corresponds to a configuration in which two hydrodynamic bearing devices 1 shown in FIG. 1 are installed side by side in the axial direction.

  In any hydrodynamic bearing device 1, the shaft member 2 is formed by integrating two conical portions 2a and 2a, and the bearing member 7 includes two electroformed portions 10a opposed to the outer peripheral surface of each conical portion 2a, 10b and a mold part 14 for integrally molding the electroformed parts 10a and 10b. At the time of rotation of the shaft member 2, two types of inclined bearing gaps C11 and C12 having the inclined directions reversed between the outer peripheral surfaces of the two conical portions 2a and the inner peripheral surfaces of the electroformed portions 10a and 10b opposed thereto. The shaft member 2 is supported in a non-contact manner in the radial direction and in both thrust directions by the dynamic pressure action of the lubricating oil generated in the inclined bearing gaps C11 and C12. FIG. 9 (a) is an example in which both of the two types of inclined bearing gaps C11 and C12 are arranged so that the diameter is closer to the side closer to the opposite inclined bearing gap in the inclination direction. In contrast to this, the example is arranged such that the closer to the counterpart inclined bearing gap, the larger the diameter.

  In any hydrodynamic bearing device 1, a seal space is formed between the outer peripheral surfaces of the upper and lower conical portions 2a and the inner peripheral surfaces of the upper and lower end portions of the bearing member 7 to prevent leakage of lubricating oil (bearing). The seal space may be formed by a separate seal member from the member 7). In this case, the lid member 8 is not necessary. Further, in any hydrodynamic bearing device 1, since thrust support force in both directions is generated in the inclined bearing gaps C11 and C12, other thrust bearing gaps (for example, in the embodiment shown in FIG. 1, in the embodiment shown in FIG. The thrust bearing gap C1) formed between the lower end surface 2a2 of the shaft member 2 facing this is not necessary.

  9 (a) and 9 (b), in the method according to FIG. 8, that is, after forming the molded part N1 with the conductive coating 22 on the outer peripheral surface of the master member 12, an electroforming process step, By passing through the molding step and the separation step, the dynamic pressure groove Aa can be formed on the inner peripheral surfaces of the electroformed portions 10a and 10b. In this case, the master member 12 is used as it is as the shaft member 2 after separation of the master member 12 and the electroformed portions 10a and 10b.

  In addition, the bearing member 7 and the shaft member 2 are each divided into two at the axially central portion, and the divided bodies are individually manufactured, and then the divided bodies are joined and integrated to each other as shown in FIGS. The hydrodynamic bearing device 1 shown in FIG. As a method for joining the divided members of the shaft member 2, for example, adhesion is conceivable. As a method for joining the divided members of the bearing member 7, in addition to adhesion, welding (ultrasonic welding or the like) is also conceivable.

  FIG. 10 shows the configuration shown in FIG. 9 (a), in order to eliminate the pumping amount imbalance that occurs in the two inclined bearing gaps C11 and C12, between the outer peripheral surface of the shaft member 2 and the inner peripheral surface of the bearing member 7. Among the annular gaps between them, the bent portion in the central portion in the axial direction is communicated with the outside of the bearing member 7 through the circulation path 23. Although illustration is omitted, the circulation path 23 can be similarly formed in the configuration shown in FIG.

  In the above description, as the inclined bearing portions K1 and K2 and the thrust bearing portion T, a configuration in which fluid dynamic pressure is generated by a dynamic pressure groove having a herringbone shape or a spiral shape is illustrated, but the present invention is not limited thereto. Is not to be done.

  For example, so-called multi-arc bearings, step bearings, or non-circular bearings may be employed as the inclined bearing portions K1, K2. In each of these bearings, a plurality of circular arc surfaces, axial grooves, and harmonic waveform surfaces serve as dynamic pressure generating portions for generating dynamic pressure in the inclined bearing gap. These dynamic pressure generating portions are formed in the electroformed portion of the bearing member 7 as in the above-described embodiment. However, the method for forming the dynamic pressure generating portions is the same as that in the case of forming the dynamic pressure grooves, and a description thereof will be omitted.

  FIG. 11 shows an example in which one or both of the inclined bearing portions K1 and K2 are constituted by multi-arc bearings. In this example, the area | region used as the inclined bearing surface of the internal peripheral surface of the bearing member 7 is comprised by the three circular arc surfaces 43 (what is called a 3-arc bearing). The centers of curvature of the three arcuate surfaces 43 are offset by an equal distance from the shaft center O of the bearing member 7 (shaft member 2). In each region defined by the three arcuate surfaces 43, the inclined bearing gap is a wedge-shaped gap 45 that gradually decreases in a wedge shape in both circumferential directions. Therefore, when the bearing member 7 and the shaft member 2 rotate relative to each other, the lubricating oil in the inclined bearing gap is pushed into the minimum gap side of the wedge-shaped gap 45 according to the direction of the relative rotation, and the pressure rises. . The bearing member 7 and the shaft member 2 are supported in a non-contact manner by the dynamic pressure action of the lubricating oil. In order to prevent the occurrence of negative pressure, a deeper axial groove called a separation groove may be formed at the boundary between the three arc surfaces 43.

  FIG. 12 shows another example in which one or both of the inclined bearing portions K1 and K2 are constituted by multi-arc bearings. Also in this example, although the area | region used as the inclined bearing surface A of the internal peripheral surface of the bearing member 7 is comprised by the three circular arc surfaces 43 (what is called three circular arc bearings), each divided by the three circular arc surfaces 43 In the region, the inclined bearing gap is a wedge-shaped gap 45 that gradually decreases in a wedge shape with respect to one direction in the circumferential direction. The multi-arc bearing having such a configuration may be referred to as a taper bearing. A separation groove 44 is formed at the boundary between the three arcuate surfaces 43. Therefore, when the bearing member 7 and the shaft member 2 are relatively rotated in a predetermined direction, the lubricating oil in the inclined bearing gap is pushed into the minimum gap side of the wedge-shaped gap 45 and the pressure rises. The bearing member 7 and the shaft member 2 are supported in a non-contact manner by the dynamic pressure action of the lubricating oil.

  FIG. 13 shows another example in which one or both of the inclined bearing portions K1 and K2 are constituted by multi-arc bearings. In this example, in the configuration shown in FIG. 12, the predetermined regions θ on the minimum gap side of the three circular arc surfaces 43 are each configured by concentric arcs with the axis center O of the bearing member 7 (the shaft member 2) as the center of curvature. Has been. 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.

  FIG. 14 shows an example in which one or both of the inclined bearing portions K1 and K2 are configured by step bearings. In this example, a plurality of axial groove-shaped dynamic pressure grooves 46 are provided at predetermined intervals in the circumferential direction in a region that becomes an inclined bearing surface on the inner peripheral surface of the bearing member 7.

  FIG. 15 shows an example in which one or both of the inclined bearing portions K1 and K2 are configured by non-round bearings. In this example, the region serving as the inclined bearing surface of the bearing member 7 is composed of three harmonic waveform surfaces 47. In each region defined by the three harmonic wave surfaces 47, the inclined bearing gap becomes a wedge-shaped gap 48 that gradually decreases in a wedge shape in both circumferential directions. Therefore, when the shaft member 2 and the bearing member 7 rotate relative to each other, the lubricating oil in the inclined bearing gap is pushed into the minimum gap side of the wedge-shaped gap 48 according to the direction of the relative rotation, and the pressure rises. . The shaft member 2 and the bearing member 7 are supported in a non-contact manner by the dynamic pressure action of the lubricating oil. The minimum width h of the wedge-shaped gap 48 is approximately expressed by the following equation when there is no eccentricity (axial center O).

h = c + aw · cos (Nw · θ)
In the above equation, c, aw, and Nw are constants, c is an average bearing radius gap, aw is the amplitude of the wave, θ is the phase in the circumferential direction, and Nw is the wave number (where Nw ≧ 2). In this embodiment, Nw = 3). In the illustrated example, the shaft center O of the shaft member 2 and the bearing member 7 is concentric. However, the shaft member 2 can be used by being eccentric to the shaft center O ′.

  The multi-arc bearings shown in FIGS. 11 to 13 described above are so-called three-arc bearings, but are not limited to this, and are constituted by so-called four-arc bearings, five-arc bearings, and more than six arc surfaces. A multi-arc bearing may also be employed. Further, the non-circular bearing shown in FIG. 15 is formed by three harmonic wave surfaces, but a non-circular bearing having four or more harmonic wave surfaces may be adopted as in the multi-arc bearing. it can. In the embodiment shown in FIG. 1, when the inclined bearing portion is constituted by a multi-arc bearing, a step bearing, or a non-circular bearing, the two inclined bearing portions are separated in the axial direction as in the inclined bearing portions K1 and K2. In addition to the above-described configuration, one inclined bearing portion may be provided across the upper and lower regions of the inner peripheral surface of the bearing member 7 or the outer peripheral surface of the shaft member 2.

  Furthermore, as an example of the configuration of the thrust bearing portion T, the configuration in which the dynamic pressure is generated in the lubricating oil by the spiral-shaped dynamic pressure groove is illustrated. A so-called step bearing provided at a predetermined interval in the circumferential direction, a so-called corrugated bearing (the corrugated step type), etc. (not shown) can also be used.

  Moreover, although the case where the inclined bearing portions K1 and K2 are configured by dynamic pressure bearings was illustrated in the above description, the tilted bearing portions K1 and K2 may be configured by other bearings. For example, although not shown, the inner peripheral surface of the bearing member 7 (electroformed part 10) is formed into a perfect circular inner peripheral surface that does not have a dynamic pressure groove or an arc surface, and is inclined with respect to the inner peripheral surface. By setting the outer peripheral surface 2a1 of the shaft member 2 opposed through the bearing gap as a perfect circular outer peripheral surface, a so-called perfect circular bearing can be configured.

It is sectional drawing which shows an example of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which has a structure of this invention. It is a principal part expanded sectional view of the hydrodynamic bearing apparatus concerning FIG. It is sectional drawing which shows the upper end surface of a cover member. It is the schematic explaining the dynamic pressure action in an inclination bearing clearance gap. (A) A figure is a perspective view of a master member, (b) A figure is a perspective view which shows the state which masked the master member. It is a perspective view of an electroformed member. It is a schematic diagram which shows the state which attached the electroformed member to the injection mold. It is sectional drawing which shows the process in the case of shape | molding a dynamic pressure groove with another method. (A) The figure is sectional drawing which shows 2nd Embodiment of the hydrodynamic bearing apparatus which has a structure of this invention, (b) Drawing is sectional drawing which shows 3rd Embodiment of the hydrodynamic bearing apparatus which has the structure of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus which formed the circulation path in the said embodiment. It is sectional drawing which shows the other form of an inclination bearing part. It is sectional drawing which shows the other form of an inclination bearing part. It is sectional drawing which shows the other form of an inclination bearing part. It is sectional drawing which shows the other form of an inclination bearing part. It is sectional drawing which shows the other form of an inclination bearing part. It is the schematic which shows the structure of the conventional hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 4 Stator coil 5 Rotor magnet 6 Bracket 7 Bearing member 8 Cover member 9 Disc hub 10 Electroformed part 11 Electroformed member 12 Master member 13 Masking 14 Mold part A Inclined bearing surface B Thrust bearing surface C1 Inclined Bearing clearance C2 Thrust bearing clearance Fr (Radial direction) component force Ft (Thrust direction) component force N1 Molding part K1, K2 Inclined bearing part T Thrust bearing part

Claims (3)

An inclined bearing gap comprising: a shaft member; a bearing member in which the shaft member is inserted into the inner periphery; and an inclined bearing gap formed between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing member and inclined in the axial direction. In the hydrodynamic bearing device that rotatably supports the shaft member with the oil film formed in
A hydrodynamic bearing device, wherein the bearing member is an injection-molded product having an electroformed part facing an inclined bearing gap and having the electroformed part inserted therein.   The hydrodynamic bearing device according to claim 1, wherein a dynamic pressure generating portion is formed on either the outer peripheral surface of the shaft member or the electroformed portion of the bearing member so as to face the inclined bearing gap.   A motor comprising the hydrodynamic bearing device according to claim 1, a stator coil, and a rotor magnet.

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