JP2007263169A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device which can keep high rotation performance for a long period of time, at low cost. <P>SOLUTION: A bearing member 6 has an inner diameter part 8 having a radial bearing face, and an outer diameter part 7 having a mounting face for a bracket 5. The inner diameter part 8 and the outer diameter part 7 are made from resin, and they are formed by injection molding in which either the inner diameter part 8 or the outer diameter part 7 is inserted. Preferably, the inner diameter part 8 should be made from oleoresin, and more preferably, the inner diameter part should be made from porous resin. The outer diameter part 7 is made from non-porous resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  The hydrodynamic bearing device is a bearing device that rotatably supports a shaft member with an oil film formed in a bearing gap by relative rotation of the bearing member and the shaft member. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, by utilizing the characteristics, information devices such as magnetic disk devices such as HDD and FDD, CD-ROM, CD -For spindle motors mounted on optical disk devices such as R / RW and DVD-ROM / RAM, magneto-optical disk devices such as MD, MO, etc., for polygon scanner motors mounted on laser beam printers (LBP), etc., personal computers ( Widely used as a bearing for a fan motor mounted on a PC) or a small motor mounted on an electric device such as an axial fan.

  This type of hydrodynamic bearing includes a hydrodynamic bearing provided with a dynamic pressure generating section that generates dynamic pressure in a fluid (for example, lubricating oil) in a bearing gap, and a so-called circular bearing (not provided with a dynamic pressure generating section). The bearing surface is roughly divided into a bearing having a perfect circular shape.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor such as an HDD, a radial bearing portion that supports a shaft member in the radial direction and a thrust bearing portion that supports the shaft member in a thrust direction are provided. As a bearing for the radial bearing portion, a dynamic pressure bearing in which a groove for generating dynamic pressure is provided on two surfaces (an outer peripheral surface of the shaft member or an inner peripheral surface of the bearing member) facing each other through the radial bearing gap is used. There are many. On the other hand, as the thrust bearing portion, there are a case where a dynamic pressure bearing is used and a case where a bearing (so-called pivot bearing) having a structure in which one end of a shaft member is contacted and supported is used.

The bearing member incorporated in this type of hydrodynamic bearing device includes an inner diameter portion having a radial bearing surface (“bearing sleeve” in the patent document) and an outer diameter portion having an attachment surface with another member on the outer peripheral surface (in the patent document “ In recent years, a bearing device having an outer diameter portion made of resin has been proposed for the purpose of reducing costs (for example, see Patent Document 1).
JP 2005-114164 A

  With the rapid price reduction of information equipment in recent years, further cost reduction is desired for the hydrodynamic bearing device. In the bearing device described in Patent Document 1, the inner diameter portion and the outer diameter portion are separate structures, and the inner diameter portion is fixed to a predetermined portion of the outer diameter portion by an appropriate means such as adhesion. The accuracy depends on the width accuracy of the bearing gap (radial bearing gap and thrust bearing gap), in other words, the rotational performance of the bearing device. Therefore, special consideration is required for the assembly, and this consideration increases the cost. May invite.

  In addition, the inner diameter part is made of a sintered metal porous material that can retain lubricating oil inside to prevent poor lubrication and wear due to sliding contact with the shaft member and maintain high bearing performance over a long period of time. It is often formed of a solid material. However, many steps are required to form an inner diameter portion made of sintered metal with high accuracy, and its manufacturing cost is generally likely to increase. In particular, when a dynamic pressure generating portion such as a dynamic pressure groove is provided in the inner diameter portion, more steps are required.

  The subject of this invention is providing the low-cost hydrodynamic bearing apparatus which can maintain high bearing performance over a long period of time.

  In order to solve the above-mentioned problems, a hydrodynamic bearing device according to the present invention includes a bearing member having an inner diameter portion having a radial bearing surface and an outer diameter portion having a mounting surface with another member, and a radial surface facing the radial bearing surface. A radial bearing portion that supports a shaft to be supported by an oil film formed in the bearing gap in the radial direction, and the bearing member is made of resin, and the inner diameter portion or the outer diameter portion It is an injection-molded product in which either one is an insert part. Examples of the “other member” include a bracket and a stator coil that serve as a motor base.

  As described above, in the present invention, both the inner diameter portion and the outer diameter portion of the bearing member are made of resin. Therefore, compared with the conventional configuration in which the inner diameter portion is made of sintered metal, the manufacturing process is simplified and the material cost is reduced. By reducing the cost, manufacturing costs can be reduced. Further, this bearing member is injection-molded by inserting either the inner diameter portion or the outer diameter portion. In insert molding, it is possible not only to improve the assembly accuracy of the inner diameter part and the outer diameter part by increasing the mold accuracy, but also to form the inner diameter part or the outer diameter part and assemble them in one step. Therefore, the manufacturing cost can be further reduced.

  By the way, when injection molding (insert molding) a member in which a part of the insert part is exposed to the cavity, in order to avoid deterioration of accuracy due to heat during insert molding, the insert part should have a melting point higher than that of the injection material. However, since it is necessary to prepare an injection mold with high accuracy while forming insert parts with high accuracy, there is a possibility that the cost merit by insert molding cannot be fully enjoyed.

  Therefore, in the present invention, the inner diameter portion and the outer diameter portion are formed of different resins, and the lower melting point of the inner diameter portion and the outer diameter portion is used as the insert part. With such a configuration, the surface of the member to be the insert part can be deformed by heat or pressure applied during insert molding to follow the surface of the insert mold (for example, the surface of the inner mold). Therefore, if the insert mold is formed with high accuracy, the accuracy of the part can be roughened at the stage of forming the insert part, so that the manufacturing cost can be further reduced. The above-mentioned “different resin” includes not only “different base resins” but also “different resin compositions as a whole including fillers”. That is, the base resin constituting the inner diameter portion and the outer diameter portion may be the same. This is because the melting point can be varied depending on the type and blending ratio of the filler.

  For example, if the inner diameter part is molded with a resin composition having a lower melting point than the outer diameter part, and this is used as an insert part, a mold corresponding to the shape of the dynamic pressure generating part is formed in the inner mold in advance. By utilizing the above features, the dynamic pressure generating portion can be provided simultaneously with the insert molding on the radial bearing surface of the inner diameter portion. In this case, the number of steps can be reduced as compared with the case where this kind of dynamic pressure generating portion is provided in advance in the sintered metal.

  Further, at this time, the surface of the insert part is melted by heat applied at the time of insert molding to be in a melt-bonded state, or the bonding interface with the molding-side member becomes uneven, so that the inner diameter portion is formed by a so-called anchor effect. The bond strength of the outer diameter portion is strong.

  The inner diameter portion is preferably formed of an oil-containing resin capable of supplying lubricating oil to the bearing gap, and in particular, a porous body similar to a sintered metal and a resin porous body capable of holding a sufficient amount of lubricating oil It is more desirable to form with (porous resin). A porous resin body can be formed by, for example, injection molding using a resin containing a pore-forming material and then removing the pore-forming material, and its manufacturing process is simple compared to sintered metal. It becomes.

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

  As described above, according to the present invention, it is possible to provide a hydrodynamic bearing device capable of maintaining high bearing performance over a long period of time at a low cost.

  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 for information equipment incorporating a hydrodynamic bearing device 1 according to 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, a rotor (disk hub) 3 mounted on the shaft member 2, and a radial direction, for example. The stator coil 4a and the rotor magnet 4b are opposed to each other through the gap. The stator coil 4 a is attached to the outer periphery of the bracket 5, and the rotor magnet 4 b is attached to the inner periphery of the disk hub 3. The bearing member 6 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 5. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator coil 4a is energized, the rotor magnet 4b is rotated by the electromagnetic force between the stator coil 4a and the rotor magnet 4b, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows an example of the hydrodynamic bearing device 1 used in the spindle motor. The hydrodynamic bearing device 1 includes a rotation-side shaft member 2 and a fixed-side bearing member 6 as main components. For convenience of explanation, the description will be given with the side where the end of the shaft member 2 protrudes from the opening of the bearing member 6 being the upper side and the opposite side in the axial direction being the lower side.

  In the present embodiment, the first radial bearing portion R1 and the second radial bearing portion R2 are separated in the axial direction between the inner peripheral surface 8a of the inner diameter portion 8 constituting the bearing member 6 and the outer peripheral surface 2a of the shaft member 2. Provided. A first thrust bearing portion T1 is provided between the upper end surface 8b of the inner diameter portion 8 and the lower end surface 9b of the first flange portion 9, and the lower end surface 8c of the inner diameter portion 8 and the upper side of the second flange portion 10 are provided. A second thrust bearing portion T2 is provided between the end surface 10b.

  The shaft member 2 is formed of a metal material such as stainless steel. The shaft member 2 as a whole has a shaft shape with substantially the same diameter, and an intermediate portion is formed with a relief portion 2b having a slightly smaller diameter than other portions. In the outer peripheral surface 2a of the shaft member 2, a recessed portion, for example, a circumferential groove 2c is formed at a fixing position of the first and second flange portions 9 and 10.

  The bearing member 6 includes a cylindrical inner diameter portion 8 formed of a resin porous body (porous resin), and an outer diameter portion 7 that is inserted into the inner diameter portion 8 and injection-molded with resin. . The inner diameter portion 8 made of a porous resin is formed by, for example, injection molding using a resin composition containing a pore forming material, and then removing the pore forming material with a solvent such as water or alcohol. In addition to the above-described injection molding, the inner diameter portion 8 may be molded by methods such as compression molding, extrusion molding, blow molding, vacuum molding, transfer molding, etc. according to the shape of the inner diameter portion 8 and the resin material selected. It can also be used.

  The inner peripheral surface 8a of the inner diameter portion 8 is provided with two upper and lower regions which are radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2, and are provided in the axial direction apart from each other. For example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. In the illustrated example, the dynamic pressure grooves 8a1 and 8a2 are symmetrical with respect to the axial center. For example, in the upper dynamic pressure groove 8a1, the groove in the upper region with respect to the axial center is more than the groove in the lower region. By increasing the axial width, it is possible to apply a downward pushing force (pumping force) to the lubricating oil when the shaft member 2 rotates. The dynamic pressure grooves 8a1 and 8a2 can also be formed on the outer peripheral surface 2a of the shaft member 2 facing each other through a radial bearing gap. The dynamic pressure grooves can be formed not only in a herringbone shape but also in other shapes such as a spiral shape.

  Further, a thrust bearing surface of the first thrust bearing portion T1 is formed in a part or all of the annular region of the upper end surface 8b of the inner diameter portion 8, and a dynamic pressure generating portion is formed in the region that becomes the thrust bearing surface, for example, as shown in FIG. A spiral-shaped dynamic pressure groove 8b1 as shown in 3 (b) is formed. Similarly, a thrust bearing surface of the second thrust bearing portion T2 is formed in a part or all of the annular region of the lower end surface 8c of the inner diameter portion 8, and a dynamic pressure generating portion is formed in the region that becomes the thrust bearing surface. For example, a spiral-shaped dynamic pressure groove 8c1 as shown in FIG. 3C is formed. The dynamic pressure generating portion can also be formed on the surfaces facing through the thrust bearing gap, that is, the lower end surface 9 b of the first flange portion 9 and the upper end surface 10 b of the second flange portion 10. The dynamic pressure groove shape can be formed in an arbitrary shape such as a herringbone shape in addition to the spiral shape.

  The base resin used to form the inner diameter portion 8 can be used regardless of thermoplastic resin or thermosetting resin as long as it can be injection-molded and satisfies the required heat resistance, oil resistance, mechanical strength, and the like. For example, a mixture of one or a plurality of types selected from general-purpose plastics, general-purpose engineering plastics and super-engineering plastics exemplified below can be used, and it is desirable to mix at least one super-engineering plastic having the above required characteristics. One or more kinds of various fillers such as a reinforcing material, a lubricant, and a conductive material can be blended in the base resin.

  Usable general-purpose plastics include, for example, polyethylene (PE), polypropylene (PP), polystyrene (PS), epoxy (EP) and the like, and general-purpose engineering plastics include, for example, polyacetal (POM), polyethylene terephthalate. (PET), polybutylene terephthalate (PBT), polycarbonate (PC) and the like.

  Examples of usable super engineering plastics include polyphenylene sulfide (PPS), polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide (PEI), polyether sulfone (PES), and polyamide imide. (PAI), thermoplastic polyimide (TPI), thermosetting polyimide, polyamide (PA), polyamide 6T, polyamide 9T and other aromatic polyamides, tetrafluoroethylene / hexafluoropropylene copolymer (PFA), ethylene / tetrafluoro Examples thereof include fluorine copolymer resins such as ethylene copolymer (ETFE).

  A resin composition (injection material) is produced by mixing the pore-forming material and filler with the base resin by a kneading method generally used for resin mixing such as dry blending or melt kneading. As a pore forming material, in order to prevent melting at the time of molding, it has a melting point higher than the molding temperature of the selected base resin, and after blending with the base resin and molding the inner diameter portion 8, the base resin is dissolved. Those that can be removed using non-solvents can be used. Among these, in particular, a weakly alkaline substance that is water-soluble and can be used as a rust preventive can be preferably used because it can be easily removed after molding.

  As the pore forming material, organic alkali metal salts such as 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 are excellent in water solubility. These metal salts may be used alone or in combination of two or more. The average particle size of the pore-forming material used is preferably 0.1 to 500 μm. When the particle diameter of the pore forming material, that is, the hole diameter formed in the inner diameter portion 8 is 0.1 μm or less, the lubricating oil is not smoothly supplied to the bearing gap due to the surface tension of the lubricating oil, and the hole diameter is 500 μm or more. This is because the surface area becomes small and the desired bearing rigidity cannot be obtained.

  In addition, the mixing ratio of the pore forming material is preferably 10 vol% to 90 vol% with respect to the total amount including the base resin, the pore forming material, the filler, and the like. 10 vol% to 30 vol%, and when increasing the oil content, it is more preferably 40 vol% to 60 vol%. This is because a sufficient amount of pores cannot be ensured at 10 vol% or less, and an expected mechanical strength cannot be obtained at 90 vol% or more.

  The outer diameter portion 7 is a non-porous body of resin that is injection-molded by inserting the inner diameter portion 8 and is formed in a substantially cylindrical shape. A mounting surface of the bracket 5 shown in FIG. 1 is formed on the outer peripheral surface of the outer diameter portion 7, and this mounting surface is fixed to the inner peripheral surface of the bracket 5 by means such as press-fitting, bonding, and press-fitting adhesion.

  The base resin constituting the outer diameter portion 7 can be used regardless of thermoplastic resin or thermosetting resin as long as the inner diameter portion 8 can be injection-molded and satisfies the required heat resistance, oil resistance, mechanical strength, and the like. One or a plurality of types selected from the above-mentioned general-purpose plastics, general-purpose engineering plastics and super-engineering plastics can be used. Resin that forms the outer diameter portion 7 by mixing one or two or more kinds of fillers such as a reinforcing material (in any form such as fibrous or powder), a lubricant, and a conductive material in the base resin. A composition is produced. In this embodiment, the resin composition that forms the outer diameter portion 7 is generated so as to have a higher melting point than the resin composition that forms the inner diameter portion 8.

  If the outer diameter portion 7 is formed of a resin composition having a melting point higher than that of the inner diameter portion 8 as described above, the surface (outer periphery) of the inner diameter portion 8 disposed in the mold as an insert part when the outer diameter portion 7 is molded. The surface 8d) is melted to be in a melt-bonded state, or is an uneven surface as shown in the enlarged view of FIG. 2 (the enlarged view on the right side in the figure). Therefore, the injected resin composition enters the unevenness of the outer peripheral surface 8d, and the outer diameter portion 7 and the inner diameter portion 8 are firmly fixed to each other by a so-called anchor effect. Thereby, the bearing member 6 excellent in impact resistance is obtained.

  In order to further increase the bonding strength between the outer diameter portion 7 and the inner diameter portion 8, it is possible to inject resin so as to cover the upper and lower end surfaces 8b and 8c of the inner diameter portion 8 when the outer diameter portion 7 is molded. Further, in order to further increase the bonding strength, for example, the inner diameter portion 8 provided with an annular groove intermittently or continuously on the outer peripheral surface 8d can be used as an insert part (not shown).

  Although not shown, in the present embodiment, an injection mold in which mold parts corresponding to the dynamic pressure groove shapes of the inner peripheral surface 8a, the upper end surface 8b, and the lower end surface 8c of the inner diameter portion 8 are provided on the inner surface. Was used to injection-mold the outer diameter portion 7. Since the outer diameter portion 7 is formed of a resin composition having a higher melting point than the inner diameter portion 8 as described above, each surface of the inner diameter portion 8 is the same as the outer peripheral surface 8d when the inner diameter portion 8 is put into a mold. 8a-8c can be melted (softened) to follow the surface shape of the mold. In this manner, the dynamic pressure grooves 8a1, 8a2, 8b1, and 8c1 described above can be formed simultaneously with the formation of the outer diameter portion 7. As described above, in the present embodiment, all the required shapes of the bearing member 6 are ensured at the time of insert molding, so there is no problem even if the molding accuracy of the inner diameter portion 8 is rough at the molding stage. It can be formed at low cost.

  The first flange portion 9 and the second flange portion 10 are both formed of a soft metal material such as brass, other metal materials, or a resin material in a ring shape that is separate from the shaft member 2, and the shaft member 2 has a predetermined shape. Glued in place. At this time, the adhesive applied to the shaft member 2 is filled and solidified in the circumferential groove 2c as an adhesive reservoir, whereby the adhesive strength of the flange portions 9 and 10 to the shaft member 2 is improved.

  A first seal space S1 having a predetermined volume is formed between the outer peripheral surface 9a of the first flange portion 9 and the inner peripheral surface 7a of the upper end opening of the outer diameter portion 7, and the outer peripheral surface 10a of the second flange portion 10 is also formed. Forms a second seal space S2 having a predetermined volume between the inner peripheral surface 7a of the lower end opening of the outer diameter portion 7. In this embodiment, the outer peripheral surface 9a of the 1st flange part 9 and the outer peripheral surface 10a of the 2nd flange part 10 are each formed in the taper surface shape gradually diameter-reduced toward the outer side of the bearing apparatus. Therefore, both the seal spaces S1 and S2 have a tapered shape that is gradually reduced in diameter in a direction approaching each other (inner direction of the bearing member 6). When the shaft member 2 rotates, the lubricating oil in the seal spaces S1 and S2 is narrowed by the pulling action by capillary force and by the pulling action by the centrifugal force during rotation (inner direction of the bearing member 6). It is drawn toward. Thereby, the leakage of the lubricating oil from the inside of the apparatus is effectively prevented. In order to reliably prevent oil leakage, as shown in the enlarged view of FIG. 2 (the enlarged view on the left side in the figure), the upper end surface 7b and the lower end surface 7c of the outer diameter portion 7, and the upper end surface of the first flange portion 9 A film 11 made of an oil repellent agent can also be formed on the lower end surface 10c of the second flange portion 10 and 9c.

  The first and second seal spaces S <b> 1 and S <b> 2 have a buffer function that absorbs a volume change amount associated with a temperature change of the lubricating oil filled in the internal space of the bearing member 6. Within the assumed temperature change range, the oil level is always in both seal spaces S1, S2. In order to achieve this, the sum of the volumes of both the seal spaces S1, S2 is set to be larger than at least the volume change amount associated with the temperature change of the lubricating oil filled in the internal space.

  As described above, after the shaft member 2 is inserted into the inner periphery of the bearing member 6 (inner diameter portion 8), the first flange portion 9 and the second flange portion 10 are fixed to the shaft member 2 so as to sandwich the inner diameter portion 8. Adhere and fix to the location. When the assembly is completed in this manner, the internal space of the bearing member 6 sealed by the flange portions 9 and 10 is filled with, for example, lubricating oil as a lubricating fluid including the internal pores of the inner diameter portion 8.

  Lubricating oil in the hydrodynamic bearing device 1 is performed by, for example, immersing an unlubricated hydrodynamic bearing device in the lubricating oil in a vacuum chamber and then releasing it to atmospheric pressure. In the hydrodynamic bearing device 1 of the present embodiment, since both ends of the bearing member 6 are open, the air in the internal space is reliably replaced with lubricating oil as compared with a configuration in which one end is closed (see Patent Document 1). Thus, adverse effects caused by residual air, such as oil leakage at high temperatures, can be reliably avoided. In addition to such a lubrication method using reduced pressure, it is possible to lubricate under normal pressure (for example, pressurized lubrication of lubricating oil), simplifying the lubrication equipment and processes, and reducing manufacturing costs. Can do.

  In addition, when the bearing member 6 (outer diameter part 7) has a substantially symmetrical shape with respect to the axial center as in the present embodiment, there is a risk that assembly is performed upside down. Therefore, although not shown, it is desirable to form an identification symbol that can distinguish the upper and lower sides on the outer peripheral surface of the outer diameter portion 7 and the like. Such an identification symbol can be formed simultaneously with the molding of the outer diameter portion 7, for example.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, the regions provided separately at the two upper and lower positions serving as the radial bearing surface of the inner peripheral surface 8a of the inner diameter portion 8 are the outer peripheral surface 2a of the shaft member 2, respectively. And through a radial bearing gap. As the shaft member 2 rotates, the oil film formed in the radial bearing gap is increased in rigidity by the dynamic pressure action of the dynamic pressure groove, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction. The As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are formed.

  Further, when the shaft member 2 rotates, the region that becomes the thrust bearing surface of the upper end surface 8b of the inner diameter portion 8 faces the lower end surface 9b of the first flange portion 9 via a predetermined thrust bearing gap, and the inner diameter portion 8 A region serving as a thrust bearing surface of the lower end surface 8c faces the upper end surface 10b of the second flange portion 10 via a predetermined thrust bearing gap. As the shaft member 2 rotates, the oil film formed in the thrust bearing gap is increased in rigidity by the dynamic pressure action of the dynamic pressure groove, and the shaft member 2 is supported in a non-contact manner so as to be rotatable in the thrust direction. . Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 2 in a non-contact manner so as to be rotatable in the thrust direction are formed.

  As described above, in the present invention, since the inner diameter portion 8 and the outer diameter portion 7 are both made of resin, the manufacturing process can be simplified and the material cost can be reduced as compared with the conventional configuration in which the inner diameter portion 8 is made of sintered metal. Thus, the cost of the bearing member 6 can be reduced. The bearing member 6 is formed by inserting the inner diameter portion 8 and injection molding the outer diameter portion 7. In the case of insert molding, it is possible to increase the assembly accuracy of the inner diameter portion 8 and the outer diameter portion 7 only by increasing the mold accuracy, and further, the molding of the outer diameter portion 7 and the assembly of both can be performed in one step. Therefore, the cost of the hydrodynamic bearing device 1 can be reduced also from this point.

  In the present embodiment, the inner diameter portion 8 is formed of a resin porous body, and the resin porous body is injection-molded using a resin containing a pore forming material as described above, and thereafter It can be formed by removing the pore forming material, and can be manufactured by a simpler process than the sintered metal. Therefore, if the inner diameter portion 8 is formed of a resin porous body, the manufacturing cost can be reduced as compared with the conventional configuration in which the inner diameter portion 8 is formed of sintered metal. In addition, since the resin porous body can hold lubricating oil or the like in the internal pores as in the case of the sintered metal, the hydrodynamic bearing device 1 capable of maintaining high rotational performance for a long period can be provided at low cost. .

  In the above description, the case where the inner diameter portion 8 is formed of a porous resin has been described. However, the inner diameter portion 8 can also be formed of a nonporous resin. In this case, the inner diameter portion 8 is desirably formed of a so-called oil-containing resin that can supply lubricating oil to the bearing gap as in the case of the porous resin. As the oil-impregnated resin, for example, one obtained by solidifying (curing) a lubricating component (lubricating oil or lubricating grease) dispersed and held in the base resin can be used. The type is not particularly limited and can be adopted. Specific examples of the resin component of such an oil-containing resin include thermoplastic resins such as ultrahigh molecular weight polyolefin, polyphenylene sulfide (PPS), and liquid crystal polymer (LCP). Specific examples of the lubricating component include mineral oil and synthetic resin. Examples include lubricating oils such as hydrocarbon oils and ester oils. Further, when a thermoplastic resin is used as the resin and a lubricating grease is used as the lubricating component, it is preferable to employ a lubricating grease having a dropping point higher than the melting point of the thermoplastic resin. These resin materials are blended with one or a plurality of various fillers such as a reinforcing material (regardless of the form of fiber, powder, etc.), a lubricant, and a conductive material as necessary.

  In the above description, the inner diameter portion 8 is molded from a resin composition having a melting point lower than that of the outer diameter portion 7, and the outer diameter portion 7 is injection molded using this as an insert part. It is also possible to mold the resin composition having a melting point lower than that of the inner diameter portion 8 and to injection mold the inner diameter portion 8 using this as an insert part.

  Furthermore, although illustration is omitted, in order to further reduce the cost, the bracket 5 shown in FIG. 1 can be integrally formed when the outer diameter portion 7 is injection-molded.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limitedly applied to said hydrodynamic bearing apparatus 1, It can apply preferably also to the hydrodynamic bearing apparatus of another form. Hereinafter, other configuration examples of the hydrodynamic bearing device will be described, but the same reference numerals are assigned to the components and elements having the same functions and operations as those shown in FIG.

  FIG. 4 shows a second embodiment of the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 of this embodiment is different from the embodiment shown in FIG. 2 in that one of the first flange portion 9 and the second flange portion 10 (the second flange portion 10 in FIG. 4) is replaced with the shaft member 2. It is in the point formed integrally. Thereby, the dispersion | variation in the assembly | attachment precision (for example, squareness) between the shaft member 2 and the flange part 10 at the time of fixation of the flange part 10 can be suppressed, and it becomes possible to facilitate the accuracy management at the time of an assembly. . In this case, the shaft member 2 and the second flange portion 10 may be integrally formed of a metal material, or may be a hybrid structure in which the shaft member 2 is formed of a metal material and the second flange portion 10 is formed of a resin material.

  FIG. 5 shows a third embodiment of the hydrodynamic bearing device 1. The hydrodynamic bearing device is different from the first embodiment shown in FIG. 2 in that the inner diameter portion 8 is composed of an upper inner diameter portion 81 and a lower inner diameter portion 82, and both inner diameter portions 81, The spacer portion 83 is provided to fill the space between the two. In the present embodiment, the first radial bearing portion R1 is provided between the inner peripheral surface 81a of the upper inner diameter portion 81 and the outer peripheral surface 2a of the shaft member 2, and the inner peripheral surface 82a of the lower inner diameter portion 82 and the shaft portion 2a. The second radial bearing portion R2 is provided between the outer peripheral surface 2a of the second radial bearing portion. A first thrust bearing portion T1 is provided between the upper end surface 81b of the upper inner diameter portion 81 and the lower end surface 9b of the first seal member 9, and the lower end surface 82c of the lower inner diameter portion 82 and the second seal member. A second thrust bearing portion T <b> 2 is provided between the upper end surface 10 b of 10.

  FIG. 6 shows a fourth embodiment of the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 is different from the above embodiment mainly in that first and second thrust bearing portions T1 and T2 are provided at both ends of a flange portion 10 provided in the shaft member 2, and a seal. The space S is provided only between the outer peripheral surface 2a of the shaft member 2 and the inner peripheral surface 13a of the seal member 13 fixed to the upper end side inner peripheral surface 7a of the outer diameter portion 7, and the lower end side of the bearing member 6 is It is in the point sealed with the lid member 12. In this embodiment, the thrust bearing portion can also be constituted by a pivot bearing in which the lower end side of the shaft member 2 is formed in a convex spherical shape and the shaft end is in contact with and supported by the upper end surface of the lid member 12.

  FIG. 7 shows a fifth embodiment of the hydrodynamic bearing device 1. In the hydrodynamic bearing device 1 shown in the figure, the second thrust bearing portion T2 is mainly provided between the lower end surface 14a of the hub portion 14 fixed to the shaft member 2 and the upper end surface 7b of the outer diameter portion 7. The configuration and configuration described above are different from each other in that the seal space S is formed between the outer peripheral surface 7d of the outer diameter portion 7 and the inner peripheral surface 14b of the hub portion 14.

  In the above description, the configuration in which the dynamic pressure action of the lubricating oil is generated by the herringbone-shaped or spiral-shaped dynamic pressure grooves is exemplified as the radial bearing portions R1, R2, but the radial bearing portions R1, R2 are so-called A multi-arc bearing or a step bearing may be adopted. A multi-arc bearing or a step bearing is a bearing having a configuration in which a plurality of arc surfaces and axial grooves are provided in a region serving as a radial bearing surface (not shown).

  Further, in the above description, the radial bearing portions are provided at two locations in the axial direction as in the radial bearing portions R1 and R2, but one radial bearing portion or three or more radial bearing portions are provided. It is good also as a composition.

  Further, one or both of the thrust bearing portions T1 and T2 are, for example, so-called step bearings, so-called wave bearings, in which a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction in a region serving as a thrust bearing surface. It can also be constituted by a mold bearing (a step type having a wave shape) or the like (not shown).

  Moreover, although the form which comprises both radial bearing part R1, R2 by a dynamic pressure bearing was shown in the above description, either one or both of radial bearing part R1, R2 can also be comprised by a perfect circle bearing. (Not shown).

  In the above description, the inside of the hydrodynamic bearing device 1 is filled and a radial bearing gap between the inner diameter portion 8 and the shaft member 2 or between the inner diameter portion 8 and the shaft member 2 (both flange portions 9, 10) is filled. Although the lubricating oil is exemplified as the fluid filled in the thrust bearing gap, other than the lubricating oil, for example, a gas such as air, a magnetic fluid, or the like can be used.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which concerns on this invention. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on this invention. (A) A figure is sectional drawing of an internal diameter part, (b) A figure is a figure which shows the upper end surface of an internal diameter part, (c) A figure is a figure which shows the lower end surface of an internal diameter part. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of the hydrodynamic bearing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 4a Stator coil 4b Rotor magnet 5 Bracket 6 Bearing member 7 Outer diameter part 8 Inner diameter part 9 First flange part 10 Second flange part R1, R2 Radial bearing part T1, T2 Thrust bearing part S1, S2 Seal space

Claims (5)

A bearing member having an inner diameter portion having a radial bearing surface and an outer diameter portion having a mounting surface with another member, and a shaft to be supported by an oil film formed in a radial bearing gap facing the radial bearing surface in the radial direction In a hydrodynamic bearing device comprising a radial bearing portion to support,
The hydrodynamic bearing device is characterized in that the bearing member is an injection-molded product in which both the inner diameter portion and the outer diameter portion are made of resin and either the inner diameter portion or the outer diameter portion is an insert part.   The hydrodynamic bearing device according to claim 1, wherein the inner diameter portion and the outer diameter portion are formed of different resins, and the lower melting point of the inner diameter portion and the outer diameter portion is used as an insert part.   The hydrodynamic bearing device according to claim 2, wherein a dynamic pressure generating portion that generates a fluid dynamic pressure in the radial bearing gap is provided on the radial bearing surface of the inner diameter portion.   The hydrodynamic bearing device according to claim 1, wherein the inner diameter portion is formed of an oil-containing resin.   The hydrodynamic bearing device according to claim 1, wherein the inner diameter portion is a porous body.

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