JP5133008B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device supports a rotating member among a pair of relatively rotating members in a non-contact manner with respect to a stationary member by a dynamic pressure action of lubricating oil generated in a bearing gap. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise, and in recent years, taking advantage of the characteristics, the bearing device for motors mounted on various electric devices including information equipment. More specifically, spindle motors such as magnetic disk devices such as HDD, optical disk devices such as CD-ROM, CD-R / RW, and DVD-ROM / RAM, polygon scanner motors of laser beam printers (LBP), It is suitably used as a bearing device for a motor such as a fan motor.

  For example, a dynamic pressure bearing device for a spindle motor incorporated in a disk drive device includes a shaft member. The hydrodynamic bearing device is roughly classified into a so-called shaft rotation type in which the shaft member is on the rotation side and a so-called shaft fixed type in which the shaft member is on the stationary side. Among these, as a fixed shaft type hydrodynamic bearing device, for example, one disclosed in JP-A-10-112955 (Patent Document 1) is known.

  Specifically, a rotating member is disposed on the outer diameter side of the shaft member provided on the stationary side via a radial bearing gap, and a dynamic pressure groove formed on the outer peripheral surface of the shaft member as the rotating member rotates. This is a bearing device in which a dynamic pressure action is generated in the lubricating oil that fills the radial bearing gap, and the rotating member is rotatably supported on the shaft member by the pressure. In this dynamic pressure bearing device, the rotating member has a sleeve portion on the inner diameter side formed of a porous material such as sintered metal that forms a radial bearing gap with the shaft member, while a sleeve portion on the outer diameter side ( The housing part) is formed of a non-porous solid material for the purpose of preventing leakage of lubricating oil to the outside of the bearing.

In this way, when the sleeve portion on the inner diameter side is formed of a porous material, the radial bearing gap is filled with abundant lubricating oil by the seepage of the lubricating oil held in the internal holes into the radial bearing gap. Therefore, compared with the case where the two members (two surfaces) forming the radial bearing gap are formed of a solid material, it is possible to effectively prevent a decrease in bearing performance such as a decrease in bearing rigidity due to the oil film running out.
JP-A-10-112955

  However, in the above-described conventional configuration, the centrifugal force acts on the lubricating oil held in the inner hole of the sleeve portion on the inner diameter side as the rotating member rotates, so that the radial bearing gap on the inner diameter side with respect to the sleeve portion. Lubricating oil is difficult to ooze out. In this case, the supply amount of the lubricating oil to the radial bearing gap is insufficient, and there is a possibility that the bearing performance is deteriorated.

  An object of the present invention is to effectively prevent a decrease in bearing performance due to a lack of lubricating oil in a radial bearing gap in a shaft-fixed type hydrodynamic bearing device.

In order to solve the above problems, in the present invention, a shaft member provided on the stationary side, a rotating member that accommodates the shaft member in the inner periphery, a radial bearing gap formed between the shaft member and the rotating member, and rotation In a hydrodynamic bearing device having a radial dynamic pressure generating section that generates a dynamic pressure action of lubricating oil in the radial bearing gap as the member rotates, the shaft member has a cylindrical surface outer periphery that does not protrude to the outer diameter side. a shaft portion having a surface, and a sleeve portion of the fixed porous the outer periphery of the shaft portion, the rotation member, one end of at least the axial direction is open, not covered with the outer periphery of the sleeve portion, and the inner diameter side A housing having a cylindrical inner peripheral surface without overhanging , and a hub portion extending in the outer diameter direction of the housing and integrally formed with the housing, and an inner peripheral surface of the housing and an outer peripheral surface of the sleeve portion A radial bearing gap is formed between Lubricating oil is filled in the internal space of the housing, including the holes in the sleeve, and the seal member facing the end surface of the sleeve is fixed to the inner periphery of the opening of the housing, and the inner peripheral surface of the seal member and the outer peripheral surface of the shaft portion A seal space having an oil level is formed between the end of the seal member and the end of the shaft in the axial direction protrudes outward from the end surface of the seal member in the axial direction. The protrusion is fixed to the stationary bracket. is the possible to provide a dynamic pressure bearing device according to claim. Here, the radial dynamic pressure generating portion may be any member that can generate the dynamic pressure action of the lubricating oil in the radial bearing gap. In addition to the dynamic pressure groove such as a herringbone shape, an arc surface or an axial groove may be used. A plurality provided in the circumferential direction is also included.

  In the above configuration, during rotation of the rotating member, due to the dynamic pressure action in the radial dynamic pressure generating portion, the lubricating oil filled in the radial bearing gap is collected in a partial region of the radial bearing gap to generate a positive pressure, At this positive pressure portion, the lubricating oil flows back into the porous sleeve portion. In parallel with this, lubricating oil oozes out from the outer peripheral surface of the sleeve part to the radial bearing gap one after another, but this oozing is caused by centrifugal force as in the conventional case because the sleeve part is provided on the stationary shaft member. It is performed smoothly without being affected by. Therefore, abundant lubricating oil can be supplied to the radial bearing gap, and deterioration of bearing performance due to insufficient supply of lubricating oil can be avoided.

  Further, in the present invention, since the radial bearing gap is formed on the outer peripheral surface of the sleeve portion, the radial bearing gap is located on the outer diameter side as compared with the conventional configuration in which the radial bearing gap is formed on the inner peripheral surface of the sleeve portion. It will be. Therefore, from this point, it is possible to increase bearing rigidity such as moment rigidity as compared with the conventional configuration.

  In the above configuration, the sleeve portion made of a porous body can be formed of, for example, a sintered metal or a porous resin. In particular, when the sleeve portion is made of porous resin, the sleeve portion can be injection-molded (insert molding) by inserting the shaft portion. In insert molding, not only can the accuracy of assembly of the shaft and sleeve be improved by simply increasing the mold accuracy, but also the molding of the sleeve and assembly of the sleeve to the shaft can be performed in one step. Therefore, the manufacturing cost can be reduced, which is desirable. In this case, the radial dynamic pressure generating portion is provided on the outer peripheral surface of the sleeve portion simultaneously with the injection molding of the sleeve portion by providing a mold portion corresponding to the shape of the radial dynamic pressure generating portion in the injection molding die of the sleeve portion. Can be molded. With this configuration, it is possible to save the trouble of providing the radial dynamic pressure generating portion in a separate process, and to further reduce the manufacturing cost of the dynamic pressure bearing device.

  When the sleeve portion is made of sintered metal and the radial dynamic pressure generating portion is formed on the outer peripheral surface thereof, the radial dynamic pressure generating portion is formed by plastic processing such as rolling in view of the good workability of the sintered metal. Can be easily formed.

  In the above configuration, the rotating member can be supported in the thrust direction. As an example of a mode in which the bearing member is supported in the thrust direction, it is conceivable to contact and support the rotating member at one end of the shaft member.

  Further, as another example of the configuration in which the rotating member is supported in the thrust direction, a thrust bearing pressure is generated by forming a thrust bearing gap on at least one end surface of the shaft member and generating a dynamic pressure action of the lubricating oil in the thrust bearing gap. It is conceivable that the rotating member is supported in a non-contact manner in the thrust direction by providing the portion.

  When the dynamic pressure bearing device is incorporated into the motor, the rotating member is provided with a hub portion. This hub portion may be provided separately from the housing (member disposed on the outer diameter side of the sleeve portion) that constitutes the rotating member, but if it is provided integrally, it eliminates the trouble of assembling the hub portion. In addition to reducing the manufacturing cost, a highly accurate integrated product can be obtained, which is desirable from the viewpoint of increasing the rotational accuracy. Examples of the hub portion include one for mounting a disc-shaped recording medium (disc) and one having blades (fans).

  As described above, since the hydrodynamic bearing device according to the present invention has high bearing rigidity, the motor including the hydrodynamic bearing device, the stator coil, and the rotor magnet has high rotational accuracy. It is.

  As described above, according to the present invention, in the fixed shaft type hydrodynamic bearing device, it is possible to eliminate the insufficient supply of lubricating oil from the porous body in the radial bearing gap. It can be effectively prevented.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor in which a dynamic pressure bearing device 1 is incorporated. The spindle motor is used in a disk drive device such as an HDD, and includes a dynamic pressure bearing device 1, a disk hub 3 as a hub portion provided on a rotating member 10 of the dynamic pressure bearing device 1, and a radial direction, for example. A stator coil 4 and a rotor magnet 5 which are opposed to each other via a gap, and a 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 hub portion 3. The shaft member 11 of the hydrodynamic bearing device 1 is fixed to the stationary bracket 6. One or a plurality of disks D such as magnetic disks (two in the illustrated example) are held on the disk hub 3. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the disk D held by the disk hub 3 rotates integrally with the rotating member 10. .

  FIG. 2 shows an example of the hydrodynamic bearing device 1 according to the embodiment of the present invention. The hydrodynamic bearing device 1 shown in FIG. 1 mainly includes a stationary shaft member 11, a rotating member 10 disposed on the outer diameter side of the shaft member 11, and a seal member 9 that seals one end opening of the rotating member 10. Prepare as a simple configuration. For convenience of explanation, the following explanation will be made with the seal member 9 side as the lower side and the opposite side in the axial direction as the upper side.

  The rotating member 10 includes a housing 7 and a disk hub 3 as a hub portion projecting from the upper end portion of the housing 7 to the outer diameter side. In this embodiment, the housing 7 and the disk hub 3 are integrally formed of a metal material. It is formed. As described above, various means can be adopted as a means for integrally forming the housing 7 and the disk hub 3 with a metal material. However, a means capable of reducing the manufacturing cost as much as possible is desirable. For example, forging, pressing, etc. Preferable is plastic processing, metal injection molding using a low melting point metal such as an aluminum alloy or magnesium alloy, or so-called MIM molding in which a mixed material of metal powder and binder is injected and then degreased and sintered.

  The housing 7 has a cup shape in which a cylindrical side portion 7a and a disc-shaped lid portion 7b that closes the upper end portion of the side portion 7a are integrated. The inner peripheral surface 7a1 of the side portion 7a is formed as a smooth cylindrical surface having a constant diameter, and the lower end surface 7b1 of the lid portion 7b is formed as a smooth flat surface.

  The disc hub 3 includes a disc portion 3a extending from the upper end portion of the housing 7 to the outer diameter side, a cylindrical portion 3b extending downward from the outer diameter end of the disc portion 3a, and a flange protruding from the lower end of the cylindrical portion 3b to the outer diameter side. A disk mounting surface 3d on which the disk D is placed. A rotor magnet 5 (see FIG. 1) is fixed to the inner periphery of the lower end of the cylindrical portion 3b by an appropriate means such as adhesion or welding.

  The rotating member 10 can be integrally formed of a resin material. Resin materials that can be used in this case include, for example, crystalline resins such as liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and the like. Examples thereof include amorphous resins such as (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI). These resin materials can be used alone or in combination of two or more. Moreover, if necessary, one or more kinds of various fillers for imparting various properties can be added.

  The shaft member 11 includes a shaft portion 2 having a lower end fixed to the stationary bracket 6 and a cylindrical sleeve portion 8 fixed to the outer peripheral surface 2 a of the shaft portion 2. Note that. In the present embodiment, the shaft portion 2 is provided separately from the bracket 6, but the shaft portion 2 may be provided integrally with the bracket 6.

  The shaft portion 2 is formed in a solid shaft with a metal material such as stainless steel, and the outer peripheral surface 2a is formed in a smooth cylindrical surface over the entire axial length. The upper end of the shaft portion 2 is formed in a convex spherical shape that is gradually reduced in diameter upward, and the top portion of the convex spherical surface 2 b makes point contact with the lid lower end surface 7 b 1 of the housing 7.

  The sleeve portion 8 is formed in a cylindrical shape with a porous body, here, a porous body of sintered metal mainly composed of copper, and is fixed to the outer peripheral surface 2 a of the shaft portion 2. As the fixing means, press-fitting, bonding (including press-fitting bonding), or the like can be employed. In addition, shrinkage fitting (under the presence of an adhesive) using the difference in the linear expansion coefficient between the shaft portion 2 and the sleeve portion 8 is possible. It is also possible to do this). On the inner peripheral surface 8a of the sleeve portion 8, one or a plurality of axial grooves 8a1 opened at both end surfaces are formed.

  As shown in FIG. 3, the outer peripheral surface 8b of the sleeve portion 8 is formed with a plurality of dynamic pressure grooves 8b1 and 8b2 arranged in a herringbone shape as a radial dynamic pressure generating portion, spaced apart at two upper and lower positions. The In the present embodiment, the lower dynamic pressure groove 8b2 is formed to be axially asymmetric with respect to the axial center (the axial center of the upper and lower inclined groove regions), and the axis of the lower region from the axial center. The directional dimension is larger than the axial dimension of the upper region. On the other hand, the upper dynamic pressure groove 8b1 is formed symmetrically in the axial direction, and the axial dimensions of the upper and lower regions thereof are respectively equal to the axial dimension of the upper region of the lower dynamic pressure groove 8b2. The shape of the dynamic pressure groove is not limited to the herringbone shape, and may be other known shapes such as a spiral shape. These dynamic pressure grooves 8b1 and 8b2 (radial dynamic pressure generating portions) can be easily and highly accurately formed by plastic working such as rolling in view of the characteristics of sintered metal having good workability.

  The seal member 9 is formed in a ring shape from, for example, a soft metal material such as brass, other metal materials, or a resin material, and is fixed to the lower end of the inner peripheral surface 7a of the housing 7 by an appropriate means such as adhesion or press fitting. The A predetermined seal space S is formed between the inner peripheral surface 9 a of the seal member 9 and the outer peripheral surface 2 a of the shaft portion 2. The seal space S has a buffer function for absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the housing 7 (the rotating member 10). The oil level is always in the seal space S. In the present embodiment, the inner peripheral surface 9a of the seal member 9 is formed as a tapered surface whose radial dimension gradually decreases upward, while the outer peripheral surface 2a of the shaft portion 2 is formed as a straight surface. Accordingly, the seal space S has a taper shape in which the radial dimension gradually decreases, and the lubricating oil in the seal space S is drawn upward by the pulling action by the capillary force, and as a result, the lower end opening of the housing 7 Is sealed. Further, by fixing the seal member 9 to the lower end of the housing 7 in this manner, the sleeve portion 8 of the shaft member 11 and the seal member 9 can be engaged in the axial direction, and the rotary member 10 can be removed from the shaft member 11. Prolapse is effectively prevented.

  The hydrodynamic bearing device 1 is mainly composed of the above-described constituent members, and the internal space of the housing 7 (the rotating member 10) sealed by the seal member 9 is filled with lubricating oil including the internal holes of the sleeve portion 8. . Various lubricating oils can be used. Considering temperature changes during use and transportation, low-evaporation and low-viscosity ester-based lubricating oils such as dioctyl sebacate (DOS) and dioctylase A rate (DOZ) or the like is preferable.

  In the dynamic pressure bearing device 1 having the above-described configuration, when the rotating member 10 rotates, the dynamic pressure grooves 8a1 and 8a2 (radial dynamic pressure generating portions) of the sleeve portion 8 form a radial bearing gap with the inner peripheral surface 7a1 of the housing 7. Through each other. As the rotating member 10 rotates, the oil film formed in the radial bearing gap is enhanced in its oil film rigidity by the dynamic pressure action of the dynamic pressure grooves 8b1 and 8b2, and the rotating member 10 is rotated in the radial direction by this pressure. It is supported non-contact freely. As a result, radial bearing portions R1 and R2 (black portions in the figure) for supporting the rotating member 10 in a non-contact manner so as to be rotatable in the radial direction are spaced apart at two locations in the axial direction.

  When the rotating member 10 rotates, the lid portion lower end surface 7b1 of the housing 7 is contacted and supported by the convex spherical surface 2b of the shaft portion 2. As a result, a thrust bearing portion T composed of a pivot bearing that rotatably supports the rotating member 10 in the thrust direction is formed.

  Further, as described above, the lower dynamic pressure groove 8b2 in the radial dynamic pressure generating portion is formed in an asymmetric shape in the axial direction, so that the pulling force of the lubricating oil by the dynamic pressure groove when the rotating member 10 rotates. (Pumping force) is relatively greater in the lower region than in the upper region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the outer peripheral surface 8b of the sleeve portion 8 and the inner peripheral surface 7a1 of the housing 7 flows upward, and the upper end surface 8d of the sleeve portion 8 A path between the lower end surface 7b1 of the housing 7 → a fluid passage formed by the axial groove 8a1 of the sleeve portion 8 → a path between the lower end surface 8c of the sleeve portion 8 and the upper end surface 9b of the seal member 9. It circulates and is drawn again into the radial bearing gap of the second radial bearing portion R2.

  As described above, the lubricating oil flows and circulates in the inner space of the housing 7, so that the pressure balance of the lubricating oil is maintained, and at the same time, the generation of bubbles due to the generation of local negative pressure and the generation of bubbles are caused. Problems such as leakage of lubricating oil and occurrence of vibration can be solved. Since the sealing space S communicates with the above circulation path, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, the lubricating oil in the sealing space S It is discharged from the oil surface (gas-liquid interface) to the outside air. Therefore, adverse effects due to air bubbles can be more effectively prevented.

  In addition, when the above pumping force is not required, both the dynamic pressure grooves 8b1 and 8b2 can be made symmetrical in the axial direction. Even when the dynamic pressure groove is applied, when a local negative pressure is generated, the lubricating oil circulates in the circulation path, so that problems such as lubricating oil leakage are effective. Can be resolved.

  As described above, during rotation of the rotating member 10, the lubricating oil filled in the radial bearing gap is caused by the dynamic pressure action of the dynamic pressure grooves 8 b 1 and 8 b 2 serving as the radial dynamic pressure generating portions, and a partial region of the radial bearing gap. In this positive pressure portion, the lubricating oil flows back into the porous sleeve portion 8. In parallel with this, lubricating oil oozes out one after another from the outer peripheral surface 8b of the sleeve portion 8 into the radial bearing gap. This oozing occurs because the sleeve portion 8 is provided on the shaft member 11 on the stationary side. So that it is performed smoothly without being affected by centrifugal force. Therefore, abundant lubricating oil can be supplied to the radial bearing gap, and a reduction in bearing performance due to insufficient supply of the lubricating oil, for example, a reduction in bearing rigidity due to oil film breakage can be effectively avoided.

  Further, as a result of the radial bearing gap being formed on the outer peripheral surface 8b of the sleeve portion 8, the radial bearing portions R1 and R2 that support the rotating member 10 in the radial direction are positioned on the outer diameter side as compared with the conventional configuration. Therefore, also from this point, bearing rigidity such as moment rigidity can be increased.

  Further, due to the configuration of the present invention, the accuracy of the radial bearing gap depends on the accuracy of the outer peripheral surface 8b of the sleeve portion 8, and the accuracy of the outer peripheral surface 2a of the shaft portion 2 does not affect the accuracy of the radial bearing gap. Therefore, it is not necessary to increase the accuracy of the outer peripheral surface 2a of the shaft portion 2 as in the conventional configuration in which a radial bearing gap is formed between the outer peripheral surface 2a of the shaft portion 2 and the inner peripheral surface 8a of the sleeve portion 8. As described above, since the shaft portion 2 is formed of a difficult-to-process material such as stainless steel, the processing cost is generally high, whereas the sintered metal forming the sleeve portion 8 is excellent in workability. Therefore, the cost reduction effect due to the fact that the finishing process of the shaft part 2 can be omitted exceeds the cost increase due to the finishing of the outer peripheral surface 8b of the sleeve part 8, so that the cost of the hydrodynamic bearing device 1 can be reduced.

  In the present embodiment, the rotating member 10 is constituted by the housing 7 and the disk hub 3 provided integrally therewith. Therefore, when both are manufactured individually and integrated by appropriate means, Compared with this, the manufacturing cost can be reduced.

  The hydrodynamic bearing device 1 according to the embodiment of the present invention has been described above, but the present invention is not limited to the hydrodynamic bearing device having the above configuration. Hereinafter, other embodiments of the hydrodynamic bearing device according to the present invention will be described with reference to the drawings, but only the parts different from those described above will be described, and common to the configurations according to the above-described ones. A reference number is attached and a duplicate description is omitted.

  FIG. 4 shows a hydrodynamic bearing device 1 according to the second embodiment of the present invention. The main difference between the hydrodynamic bearing device 1 shown in FIG. 2 and the hydrodynamic bearing device shown in FIG. 2 is that the thrust bearing portions T1 and T2 (both black portions in the figure) made of hydrodynamic bearings are provided at both ends of the sleeve portion 8. ). In this case, as shown in FIG. 5, the upper end surface 8d of the sleeve portion 8 is provided with an annular region in which a plurality of dynamic pressure grooves 8d1 are arranged in a spiral shape as a thrust dynamic pressure generating portion. Although not shown, the lower end surface 8c of the sleeve portion 8 is provided with an annular region in which a plurality of dynamic pressure grooves are arranged in a spiral shape as a thrust dynamic pressure generating portion. The upper thrust dynamic pressure generating portion can be formed on the upper end surface 2 c of the shaft portion 2, or can be formed on both the upper end surface 2 c of the shaft portion 2 and the upper end surface 8 d of the sleeve portion 8.

  FIG. 6 shows a hydrodynamic bearing device 1 according to a third embodiment of the present invention. The main differences between the hydrodynamic bearing device 1 shown in FIG. 2 and the hydrodynamic bearing device shown in FIG. 2 are that the housing 17 of the rotating member 10 is formed in a cylindrical shape with both ends open, and both end openings of the housing 17 are open. The ring-shaped seal members 19 and 20 are fixed to each other, and the taper-shaped seal spaces S1 and S2 are provided at the opening portions at both ends. Further, in the present embodiment, thrust bearing portions T1 and T2 made of dynamic pressure bearings are provided at both ends of the sleeve portion 8 as in the second embodiment shown in FIG. However, in the present embodiment, the upper thrust bearing portion T <b> 1 is formed between the lower end surface 19 b of the seal member 19 and the upper end surface 8 d of the sleeve portion 8.

  When the seal spaces S1 and S2 are provided in the opening portions at both ends of the housing 17 as in this embodiment, the function as an oil buffer is more axial than in the above embodiment in which the seal space S is provided only at the lower end opening portion. Since it is obtained in two places, the buffer function of the entire bearing device can be enhanced. Accordingly, the volumes of the individual seal spaces S1 and S2 can be further reduced, and the axial dimensions of the seal members 19 and 20 can be reduced to reduce the size (compactness) of the dynamic pressure bearing device 1.

  The case where the sleeve portion 8 of the shaft member 11 is formed of a sintered metal has been described above. However, the sleeve portion 8 can also be formed of another porous body, for example, a porous resin. As described above, when the sleeve portion 8 is formed of a porous resin, the shaft member 11 can be obtained by injection molding the sleeve portion 8 using the shaft portion 2 as an insert part. In the case of insert molding, it is possible not only to improve the assembly accuracy of the shaft portion 2 and the sleeve portion 8 by increasing the mold accuracy, but also to form the sleeve portion 8 and to assemble the sleeve portion 8 to the shaft portion 2. Since it can be performed in one step, it is effective in reducing the cost of the hydrodynamic bearing device 1.

  Further, in this case, the dynamic pressure grooves 8b1 and 8b2 as the radial dynamic pressure generating portions are formed by providing a mold portion corresponding to the dynamic pressure groove shape in the injection mold of the sleeve portion 8, so that the injection molding of the sleeve portion 8 is performed. At the same time, it can be molded. With this configuration, it is possible to save the trouble of providing the dynamic pressure grooves 8b1 and 8b2 in a separate process, and the manufacturing cost of the dynamic pressure bearing device 1 can be further reduced. Further, in the embodiment shown in FIGS. 4 and 6, the thrust dynamic pressure generating portion can be molded simultaneously with the injection molding of the sleeve portion 8.

  The base resin that can be used when the sleeve portion 8 is formed of a porous resin is a thermoplastic resin that can be injection-molded and satisfies the required heat resistance, oil resistance, mechanical strength, and the like. Any thermosetting resin can be used. For example, one or a plurality of materials selected from the material group exemplified below can be used. In addition, the base resin may contain one or more kinds of various fillers such as a reinforcing material, a lubricant, and a conductive material.

  Examples of resin materials that can be used as the base resin include polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide (PEI), and polyether sulfone. (PES), polyamideimide (PAI), thermoplastic polyimide (TPI), thermosetting polyimide, polyamide (PA), polyamide 6T, polyamide 9T, and other aromatic polyamides, tetrafluoroethylene / hexafluoropropylene copolymer (PFA) ), Fluorine-based copolymer resins such as ethylene / tetrafluoroethylene copolymer (ETFE), and the like.

  By mixing the above base resin with a pore-forming material and a filler by a kneading method generally used for resin mixing such as dry blending, melt kneading, etc., a resin composition used for molding the sleeve portion 8 is obtained. . As the pore forming material, in order to prevent melting at the time of molding, the sleeve portion 8 having a melting point higher than the melting temperature of the selected base resin and blended with the base resin is molded, and then the base resin is molded. Those which can be removed by using a solvent having insolubility can be used. Among these, in particular, weak alkaline substances that can be easily removed after molding (for example, water-soluble) and can be used as a rust preventive agent can be suitably used.

  As the pore-forming material, organic alkali metal salts represented by sodium benzoate, sodium acetate, sodium sebacate, sodium succinate, or sodium stearate, potassium carbonate, sodium molybdate, potassium molybdate, sodium tungstate, Inorganic alkali metal salts such as sodium triphosphate and sodium pyrophosphate can be used. Among these, sodium benzoate, sodium acetate, and sodium sebacate are particularly preferable because they have a high melting point, increase the degree of freedom in selecting a base resin, and exhibit excellent water solubility. These metal salts may be used alone or in combination of two or more.

  In the above description, the hydrodynamic bearing device 1 using the rotating member 10 in which the housing 7 (17) and the disk hub 3 are integrally formed has been described. For example, characteristics required for the housing 7 and the disk hub 3 are described. However, if it is difficult to integrally form the rotating member 10, the rotating member 10 in which the housing 7 and the disc hub 3 manufactured individually are integrated by an appropriate means can be used. Alternatively, it is also possible to use a rotating member 10 in which one of the housing 7 and the disk hub 3 is an insert part and the other is injection-molded.

  In the above description, the case where the radial dynamic pressure generating portion is provided on the outer peripheral surface 8b of the sleeve portion 8 and the thrust dynamic pressure generating portion is provided on the end surfaces 8c and 8d of the sleeve portion 8 has been described. May be formed on surfaces facing each other via a radial bearing gap and a thrust bearing gap.

  In the above description, the radial bearing portions R1 and R2 are exemplified by a configuration in which the dynamic pressure action of the lubricating oil is generated by a dynamic pressure groove having a herringbone shape or the like, but the radial bearing portions R1 and R2 are so-called step bearings. A multi-arc bearing or a non-circular bearing may be employed. In this case, each of the radial dynamic pressure generating portions is configured by a plurality of axial grooves, circular arc surfaces, and harmonic wave surfaces provided in the circumferential direction. Moreover, although the structure which provided the radial bearing part in the axial direction two places was illustrated above, a radial bearing part can also be provided in the axial direction one place or three places or more.

  Further, as in the embodiment shown in FIGS. 4 and 6, when the thrust bearing portions T1 and T2 are configured by dynamic pressure bearings, either one or both of the thrust bearing portions T1 and T2 are so-called step bearings or wave shapes. A bearing may be adopted.

  In the above, the case where the dynamic pressure bearing device 1 is incorporated in a spindle motor for a disk drive device has been described. However, since the dynamic pressure bearing device 1 of the present invention has high bearing performance, it has high rotational accuracy. Therefore, it can be suitably used for other motors that require the above, such as a fan motor and a polygon scanner motor. When the hydrodynamic bearing device 1 is used for a fan motor, the housing 7 is provided with a rotor having a fan instead of the disk hub 3, and when used for a polygon scanner motor, the housing 7 is replaced with a polygon instead of the disk hub 3. A mirror is provided (both are not shown).

It is sectional drawing which shows notionally the spindle motor for disk apparatuses. It is sectional drawing which shows 1st Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. FIG. 3 is a perspective view of a shaft member used in the fluid dynamic bearing device shown in FIG. 2. It is sectional drawing which shows 2nd Embodiment of the hydrodynamic bearing apparatus which concerns on this invention. It is a top view of the sleeve part used with the fluid dynamic bearing apparatus shown in FIG. It is sectional drawing which shows 3rd Embodiment of the hydrodynamic bearing apparatus which concerns on this invention.

Explanation of symbols

1 Hydrodynamic bearing device 2 Shaft 3 Hub (disc hub)
3d Disc mounting surface 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 8 Sleeve portion 8b1, 8b2 Dynamic pressure groove (radial dynamic pressure generating portion)
9 Seal member 10 Rotating member 11 Shaft member R1, R2 Radial bearing portion T, T1, T2 Thrust bearing portion S, S1, S2 Seal space

Claims (7)

The shaft member provided on the stationary side, the rotating member that accommodates the shaft member in the inner periphery, the radial bearing gap formed between the shaft member and the rotating member, and the radial bearing gap is lubricated as the rotating member rotates. In a hydrodynamic bearing device comprising a radial dynamic pressure generating section that generates a dynamic pressure action of oil,
The shaft member has a shaft portion having a cylindrical outer peripheral surface that does not protrude to the outer diameter side, and a porous sleeve portion fixed to the outer periphery of the shaft portion,
The rotating member, at least one axial end is open, a housing provided with a projecting free cylindrical surface shape of the inner peripheral surface of not covering the outer periphery of the sleeve portion, and the inner diameter side, extends in the outer diameter direction of the housing, and A hub portion formed integrally with the housing, and a radial bearing gap is formed between the inner peripheral surface of the housing and the outer peripheral surface of the sleeve portion,
The interior space of the housing is filled with lubricating oil, including the holes in the sleeve,
A seal member facing the end surface of the sleeve portion is fixed to the inner periphery of the opening of the housing, and a seal space having an oil surface is formed between the inner peripheral surface of the seal member and the outer peripheral surface of the shaft portion ,
A hydrodynamic bearing device , wherein one axial end of a shaft portion is protruded axially outward from an end surface on one axial end side of a seal member, and the protruding portion is fixed to a stationary bracket .   The hydrodynamic bearing device according to claim 1, wherein the sleeve portion is formed of a sintered metal.   The hydrodynamic bearing device according to claim 1, wherein the sleeve portion is formed of a porous resin.   The hydrodynamic bearing device according to claim 3, wherein the sleeve portion is injection-molded with the shaft portion as an insert part.   The hydrodynamic bearing device according to claim 4, wherein a radial dynamic pressure generating portion is molded on the outer peripheral surface of the sleeve portion.   The hydrodynamic bearing device according to claim 1, wherein the rotating member is contacted and supported in the thrust direction at one end of the shaft member. A thrust bearing gap formed on at least one end face of the sleeve portion;
The dynamic pressure bearing device according to claim 1, further comprising: a thrust dynamic pressure generating section that generates a dynamic pressure action of the lubricating oil in the thrust bearing gap.

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