JP2008008367A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device capable of easily and inexpensively forming a dynamic pressure generating part. <P>SOLUTION: A radial difference is formed on an inner peripheral surface 8a of a bearing member 7, by actively utilizing a difference in a molding contraction quantity of the bearing member 7, and the dynamic pressure generating part is formed by this radial difference. Thus, there is no need to process a recess-projection corresponding to a shape of the dynamic pressure generating part in an inner mood for molding the inner peripheral surface 8a of the bearing member 7, and since the inner mold is sufficient in a true circular shape, manufacturing cost of the inner mold is reduced. Since the inner mold is sufficient in the true circular shape, the inner mold and the bearing member 7 are not unreasonably drawn in mold separation, and damage of the dynamic pressure generating part can be avoided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member by the hydrodynamic action of a lubricating fluid generated in a bearing gap.

  The hydrodynamic bearing device is an information device, for example, a magnetic disk drive device such as HDD, an optical disk drive device such as CD-ROM, CD-R / RW, DVD-ROM / RAM, a magneto-optical disk drive device such as MD, MO, etc. It can be suitably used for a spindle motor of the present invention, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or an electric device such as a small motor such as a fan motor.

  For example, a hydrodynamic bearing device disclosed in Patent Document 1 includes a resin bearing member (bearing sleeve) and a shaft member, and an inner peripheral surface of the bearing member and a shaft member are provided on the inner peripheral surface of the bearing member. A dynamic pressure groove for generating a dynamic pressure action is formed in the lubricating fluid in the radial bearing gap formed between the outer peripheral surface and the outer peripheral surface. The dynamic pressure groove is formed by forming irregularities opposite to the dynamic pressure groove shape on the outer peripheral surface of the inner mold for forming the inner peripheral surface of the bearing member, and transferring the irregular shape. When the inner mold is released from the inner periphery of the bearing member, the inner mold is taken out by so-called forced removal by utilizing the slipperiness of the resin material.

JP 2004-316712 A

  However, in order to form irregularities having a complicated shape such as a herringbone shape on the outer peripheral surface of the inner mold, the inner mold needs to be processed with high precision, resulting in an increase in processing cost. In addition, if the inner mold and the bearing member are separated from each other by force, the dynamic pressure grooves may be damaged.

  An object of the present invention is to provide a hydrodynamic bearing device capable of forming a hydrodynamic pressure generating section easily and at low cost.

  In order to solve the above problems, the present invention provides a bearing member molded with resin, a shaft member inserted in the inner periphery of the bearing member, and an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. In the hydrodynamic bearing device having a hydrodynamic pressure generating portion that generates hydrodynamic action on the lubricating fluid in the formed radial bearing gap, the bearing member has a radial difference based on a difference in molding shrinkage on the inner peripheral surface. The dynamic pressure generating part was formed by the diameter difference.

  As described above, in the present invention, the difference in molding shrinkage of the bearing member is positively utilized to form a diameter difference on the inner peripheral surface of the bearing member, and the dynamic pressure generating portion is formed by this diameter difference. This difference in molding shrinkage can be provided, for example, by varying the circumferential thickness of the bearing member. As a result, it is not necessary to process the unevenness corresponding to the shape of the dynamic pressure generating portion in the inner mold for molding the inner peripheral surface of the bearing member, and for example, it can be made into a perfect circle shape. Is cheaper. Further, the cross-sectional shape of the inner mold can be made constant in the axial direction. According to this, the inner mold and the bearing member are not forcibly removed at the time of mold release, and damage to the dynamic pressure generating portion can be avoided.

  In this hydrodynamic bearing device, an axial through hole having an inner surface as a molding surface can be formed in the bearing member. This through hole is formed by disposing a forming pin having an outer peripheral surface corresponding to the inner surface shape of the through hole in a cavity for forming the bearing member. Of the bearing member, the region with the through hole is thinner than the region without the through hole by the thickness of the through hole. As described above, when the thickness of the bearing member is different in the circumferential direction, a difference occurs in the amount of molding shrinkage of the resin, and a diameter difference serving as a dynamic pressure generating portion is formed on the inner peripheral surface of the bearing member.

  Alternatively, in this dynamic pressure bearing device, a protruding portion protruding toward the outer diameter can be formed on the outer peripheral surface of the bearing member. Since the thickness of the bearing member differs in the circumferential direction due to the protrusion, a difference occurs in the amount of molding shrinkage of the resin, and a diameter difference serving as a dynamic pressure generating portion is formed on the inner peripheral surface of the bearing member.

  As described above, according to the present invention, it is possible to obtain a hydrodynamic bearing device in which the hydrodynamic pressure generating portion can be formed easily and at low cost.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 according to a first embodiment of the present invention. The spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that supports the shaft member 2 in a non-contact manner so as to be relatively rotatable, a disk hub 3 that is fixed to the shaft member 2, and a radius, for example. A stator coil 4 and a rotor magnet 5 and a bracket 6 are provided to face each other with a gap in the direction. The stator coil 4 is attached to the outer periphery of the bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The bearing member 7 of the fluid dynamic bearing device 1 is fixed to the inner periphery of the bracket 6. The disk hub 3 holds one or a plurality of disks D (two sheets in FIG. 1) as information recording media. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by an exciting force generated between the stator coil 4 and the rotor magnet 5, and accordingly, the disk hub 3 and the disk are rotated. The disk D held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 seals a bearing member 7, a shaft member 2 inserted into the inner periphery of the bearing member 7, a lid member 10 that closes one end of the bearing member 7, and the other end of the bearing member 7. The seal part 11 is mainly provided. For the sake of convenience of explanation, of the openings of the bearing member 7 formed at both ends in the axial direction, the side closed by the lid member 10 will be described as the lower side, and the side opposite to the closed side will be described as the upper side.

  The shaft member 2 includes a shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a, and is formed integrally or separately from a metal material such as SUS steel. Each part of the shaft member 2 can be made of the same kind of material or a different material. For example, the shaft portion 2a can be formed of a metal material, and a part or all of the flange portion 2b can be formed of a resin material. It is possible to make with.

  The bearing member 7 has a shape in which both ends in the axial direction are opened, and includes a substantially cylindrical sleeve portion 8 and a housing portion 9 positioned on the outer diameter side of the sleeve portion 8. In this embodiment, the bearing member 7 is made of, for example, a crystalline resin such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyphenyl sulfone (PPSU), polyether sulfone ( It is formed by injection molding a resin composition having an amorphous resin such as PES) or polyetherimide (PEI) as a base resin. The type of filler to be filled in the resin is not particularly limited. For example, as the filler, fibrous filler such as glass fiber, whisker-like filler such as potassium titanate, and scaly filler such as mica. A fibrous or powdery conductive filler such as carbon fiber, carbon black, graphite, carbon nanomaterial, or metal powder can be used. These fillers may be used alone or in combination of two or more.

  The inner peripheral surface of the bearing member 7, that is, the inner peripheral surface 8a of the sleeve portion 8, as exaggeratedly shown in FIG. 3, is a non-circular shape in which large diameter portions 8a1 and small diameter portions 8a2 are alternately provided in the circumferential direction. Presents a shape. When the shaft member 2 rotates, a radial bearing gap of the radial bearing portion R is formed between the inner peripheral surface 8a of the sleeve portion 8 and the outer peripheral surface 2a1 of the shaft portion 2a.

  A region where a plurality of dynamic pressure grooves are arranged is formed in the entire lower surface 8b of the sleeve portion 8 or in a partial annular surface region. In this embodiment, for example, as shown in FIG. 4, a region in which a plurality of dynamic pressure grooves 8b1 are arranged in a spiral shape is formed. During rotation of the shaft member 2, a thrust bearing gap of the first thrust bearing portion T1 is formed between the formation region of the dynamic pressure groove 8b1 and the upper end surface 2b1 of the flange portion 2b (see FIG. 2).

  The housing portion 9 positioned on the outer diameter side of the sleeve portion 8 is substantially cylindrical, and has a shape in which both ends in the axial direction protrude above and below the both end surfaces 8b and 8c of the sleeve portion 8 in the axial direction. A lid member 10 that closes the lower end side of the bearing member 7 is bonded, press-fitted, press-fitted with an adhesive (hereinafter referred to as press-fitting adhesion), welding, It is fixed by means such as welding. Under the present circumstances, between the fixed surfaces of the housing part 9 and the cover member 10, the sealing performance of the extent which the lubricating oil with which the inside of a bearing was filled at least is not leaked outside is ensured.

  An annular seal portion 11 is fixed to the inner periphery of the upper end protruding portion 9 b of the housing portion 9 with its lower end surface 11 b in contact with the upper end surface 8 c of the sleeve portion 8. Between the inner peripheral surface 11a of the seal portion 11 and the outer peripheral surface 2a1 of the shaft portion 2a facing this surface, a tapered seal space S1 is formed in which the radial dimension is gradually enlarged upward. The In a state where the bearing is filled with the lubricating oil, the oil level of the lubricating oil is always within the range of the seal space S1.

  As shown in FIG. 2, a plurality of through-holes 12 penetrating the bearing member 7 in the axial direction are formed in the radial intermediate portion of the bearing member 7. In this embodiment, the through-holes 12 are provided at a plurality of, for example, four locations at equal intervals in the circumferential direction. The through-hole 12 opens to the outer diameter side of the lower end surface 8b of the sleeve portion 8 at the lower end side than the region where the dynamic pressure groove 8b1 is formed (see FIG. 4), and at the upper end to the outer diameter side of the upper end surface 8c of the sleeve portion 8. Open.

  The size of the inner diameter of the through hole 12 is set to an appropriate value in consideration of the fluidity of the lubricating fluid inside the bearing, the moldability of the through hole 12, and the like. However, if the inner diameter of the through hole 12 is too large, the strength of the bearing member is reduced, or excessive fluid flows from the other fluid holding space into the fluid flow path, so that the pressure should be increased, that is, the radial bearing gap. In addition, fluid may escape from the thrust bearing gap, or a negative pressure state may be locally generated, and the pressure balance may be lost. For this reason, the inside diameter of the through-hole 12 is within a range in which the lubricating fluid can flow satisfactorily and a dynamic pressure generating portion described later is formed due to a molding shrinkage difference in the circumferential direction of the bearing member 7. It is desirable to set the diameter as small as possible.

  In this embodiment, the inside is formed by the through-hole 12, a plurality of radial grooves 10 c provided on the contact surface 10 b 1 of the lid member 10, and a plurality of radial grooves 11 b 1 provided on the lower end surface 11 b of the seal portion 11. A fluid flow path is formed through which fluid can flow.

  Such a bearing member 7 is formed as follows, for example. As shown in FIG. 5, molding for molding a through hole 12 in a cavity 16 formed by an outer mold 14 having a perfect circular inner peripheral surface and an inner mold 15 having a perfect circular outer peripheral surface. The pin 13 is disposed, and a resin material is injected into the cavity 16 through the sprue 17 and the gate 18. The inner peripheral surface 8a ′ of the bearing member 7 immediately after injection has a perfect circle shape (indicated by a dotted line in FIG. 3), but the inner peripheral surface 8a ′ recedes in the diameter increasing direction due to molding shrinkage at the time of subsequent solidification. To do. Of the resin filled in the cavity 16, the thickness of the region where the molding pin 13 is present is larger than the radial width of the cavity 16 (indicated by L in FIG. 5) than the diameter of the molding pin 13 (indicated by l in FIG. 5). Only thin). As described above, the difference in the thickness of the resin in the circumferential direction causes a difference in the amount of molding shrinkage in the radial direction, and the diameter expansion amount of the inner peripheral surface 8a 'varies in the circumferential direction.

  In the present invention, the difference in molding shrinkage is actively utilized to form a non-circular inner peripheral surface 8a (shown by a solid line in FIG. 3), and the non-circular inner peripheral surface 8a is large. The diameter difference between the diameter portion 8a1 and the small diameter portion 8a2 is caused to function as a dynamic pressure generating portion that generates a dynamic pressure action in the lubricating oil in the radial bearing gap. Thereby, it is not necessary to process the unevenness | corrugation corresponding to the shape of the dynamic-pressure generation | occurrence | production part in the inner type | mold 15 which shape | molds the internal peripheral surface 8a of the bearing member 7, For example, it is set as a perfect circle shape like FIG. Therefore, the manufacturing cost of the inner mold 15 is low. In addition, when the cross-sectional shape of the inner die 15 is formed to be constant in the axial direction, the inner die 15 and the bearing member 7 are not forcedly removed at the time of releasing, and damage to the dynamic pressure generating portion can be avoided.

  In order to make the molding shrinkage of the bearing member 7 by the molding pin 13 uniform in the axial direction, the radial sectional shape of the molding pin 13, that is, the radial sectional shape of the through hole 12 is shown in FIG. Thus, it is desirable to be constant in the axial direction. Of course, if there is no particular problem even if the cross-sectional shape of the forming pin 13 is not constant in the axial direction, a forming pin having a different cross-sectional shape in the axial direction may be used.

  Although not shown in the partial annular surface region of the upper end surface 10a of the lid member 10, for example, a plurality of dynamic pressure grooves are arranged so as to have a shape opposite to the spiral shape shown in FIG. A region is formed. When the shaft member 2 rotates, a thrust bearing gap of the second thrust bearing portion T2 is formed between the dynamic pressure groove forming region and the lower end surface 2b2 of the flange portion 2b (see FIG. 2).

  A protrusion 10b that protrudes upward is provided on the outer periphery of the upper end surface 10a of the lid member 10, and the contact surface 10b1 positioned at the upper end of the protrusion 10b is brought into contact with the lower end surface 8b of the sleeve portion 8. In this state, the lid member 10 is fixed to the inner periphery of the lower end protruding portion 9a. In this case, a value obtained by subtracting the axial width of the flange portion 2b from the axial dimension of the protruding portion 10b is equal to the sum of the thrust bearing gaps of the thrust bearing portions T1 and T2.

  Various types of lubricating oil can be used, but the lubricating oil provided to the hydrodynamic bearing device for a disk drive device such as an HDD, in consideration of temperature changes during use or transportation, An ester-based lubricating oil excellent in low evaporation rate and low viscosity, such as dioctyl sebacate (DOS), dioctyl azelate (DOZ) and the like can be suitably used.

  In the hydrodynamic bearing device 1 having the above-described configuration, when the shaft member 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the sleeve portion 8 and the outer peripheral surface 2a1 of the opposing shaft portion 2a. Since the inner peripheral surface 8a of the sleeve portion 8 has a non-circular shape having a large diameter portion 8a1 and a small diameter portion 8a2, the radial bearing gap has a different gap width in the circumferential direction. As the shaft member 2 rotates, the lubricating oil in the portion having a relatively large gap width facing the large diameter portion 8a1 in the radial bearing gap is pushed into the portion having the relatively small gap width facing the small diameter portion 8a2. As a result, the pressure of the lubricating oil film increases. Thus, the radial bearing portion R that supports the shaft member 2 in the radial direction in a non-contact manner is formed by the dynamic pressure action of the lubricating oil generated in the radial bearing gap.

  At the same time, the thrust bearing gap between the dynamic pressure groove 8b1 formation region of the lower end surface 8b of the sleeve portion 8 and the upper end surface 2b1 of the flange portion 2b opposed thereto, and the dynamic pressure groove of the upper end surface 10a of the lid member 10 The pressure of the lubricating oil film formed in the thrust bearing gap between the formation region and the lower end surface 2b2 of the flange portion 2b facing the formation region is increased by the dynamic pressure action of the dynamic pressure groove. The first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in the thrust direction in a non-contact manner are constituted by the pressure of these oil films.

  At this time, as described above, the through hole 12 formed in the bearing member 7, the radial groove 10c formed in the end surface of the protruding portion 10b of the lid member 10, and the lower end surface 11b of the seal portion 11 are formed. The outer diameter end of the thrust bearing gap of the first thrust bearing portion T1 and the upper end of the radial bearing gap are in communication with each other by the fluid flow path constituted by 11b1. According to this, avoiding a situation where the pressure of the fluid (lubricating oil) on the closing side of the housing 7 is excessively increased or decreased for some reason, the shaft member 2 is stably supported without contact in the thrust direction. Is possible.

  Although the first embodiment of the present invention has been described above, the present invention is not limited to this embodiment. Hereinafter, other embodiments of the present invention will be described. Note that, in the drawings shown below, parts and members that have the same configuration and function as those of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  For example, as shown in FIG. 6, by providing a protruding portion 7 a in the outer diameter direction on the outer peripheral surface of the bearing member 7, the difference in thickness of the bearing member 7 is increased, and the difference in molding shrinkage is positively increased. By doing so, the non-circular inner peripheral surface 8a can also be formed. Here, the case where three protrusion parts 7a are provided at equal intervals in the circumferential direction is shown. In this case, a large diameter portion 8a1 is formed at the circumferential position of the protruding portion 7a.

  The diameter difference between the large diameter portion 8a1 and the small diameter portion 8a2 at this time can be adjusted by the protruding amount of the protruding portion 7a. Or it can also adjust with the position which provides the through-hole 12. FIG. For example, as shown in FIG. 6, when the through hole 12 is formed at a circumferential position avoiding the protruding portion 7a, the thickness difference of the bearing member 7 can be increased, so that the large diameter portion 8a1 and the small diameter portion 8a2 are formed. And the diameter difference can be further increased.

  Below, the structural example of the hydrodynamic bearing apparatus which concerns on other embodiment to which this invention is applied is shown. The hydrodynamic bearing device 21 shown in FIG. 7 is mainly provided with a first seal portion 23 and a second seal portion 24 on the shaft member 22, respectively, and faces the outer peripheral surfaces 23a and 24a of the seal portions 23 and 24. Seal spaces S2 and S3 are formed between the inner peripheral surfaces 9a1 and 9b1 of the housing portion 9. A first thrust bearing portion T11 is formed between the upper end surface 23b of the first seal portion 23 (lower side) and the lower end surface 8b of the sleeve portion 8, and the lower end surface of the second seal portion 24 (upper side). A second thrust bearing portion T12 is formed between 24b and the upper end surface 8c of the sleeve portion 8 (in this embodiment, the upper end surface 8c is also provided with a dynamic pressure groove forming region). In this embodiment, the seal portions 23 and 24 are both separated from the shaft member 22, and the seal portions 23 and 24 are fixed to the shaft member 22 by means such as adhesion and press-fitting. However, the present invention is not limited thereto, and for example, one of the seal portions 23 and 24 can be formed integrally with the shaft member 22.

  In this embodiment, the fluid flow path penetrates the bearing member 27 in the axial direction, and one or a plurality of (for example, four) penetrating openings on both sides in the axial direction (both ends 8b and 8c side of the sleeve portion 8). Consists of holes 12. By this fluid flow path, the lubricating oil filled in the hydrodynamic bearing device 21 can flow between the outer diameter ends of the thrust bearing gaps of the first and second thrust bearing portions T11 and T12.

  8 includes a first thrust bearing portion T21 formed between the lower end surface 8b of the sleeve portion 8 and the upper end surface 32b1 of the flange portion 32b, and a disc portion constituting the disc hub 33. A second thrust bearing portion T22 is formed between the lower end surface 33a1 of 33a and the upper end surface 39a of the housing portion 39. Further, a taper seal surface 39b is provided at the outer peripheral upper end of the housing portion 39, and a seal space S4 is formed between the taper seal surface 39b and the inner peripheral surface 33b1 of the cylindrical portion 33b of the disk hub 33 facing this surface. .

  In this embodiment, the fluid flow path penetrates the bearing member 37 in the axial direction, and one or a plurality (for example, four) of penetrating openings on both sides in the axial direction (both ends 8b and 8c side of the sleeve portion 8). Consists of holes 12. By this fluid flow path, the lubricating oil filled in the hydrodynamic bearing device 31 is allowed to flow outside the outer diameter end of the thrust bearing gap of the first thrust bearing portion T11, below the upper end surface 8c of the sleeve portion 8 and the disk portion 33a. It becomes possible to circulate through the gap between the side end face 33a1.

  In the above embodiment, the case where the sleeve portion and the housing portion are integrally formed as the bearing member is illustrated. However, the present invention is not limited to this. For example, a sleeve-shaped bearing member having a through hole is separately formed in the housing. You may fix to an inner periphery.

  Moreover, although the above embodiment demonstrated the case where the through-hole 12 which comprises a fluid flow path was formed in the position opened to the both end surfaces 8b and 8c of the sleeve part 8, the through-hole 12 is in the position shown in figure. Not limited to this, the bearing members 7, 27, and 37 can be formed at any positions as long as they penetrate the axial direction. In addition, as shown in FIG. 2, when the fluid flow path is constituted by the radial grooves 10c and 11b1 provided in the lid member 10 and the seal portion 11 in addition to the through-hole 12, the radial grooves 10c and 11b1 are formed. It is also possible to provide on the side of the opposing member (for example, both end faces 8b, 8c of the sleeve portion 8).

  Moreover, in the said embodiment, although the through-hole 12 which has a cylindrical internal peripheral surface was illustrated, as long as the through-hole formed in the bearing member 7 can distribute | circulate the fluid between the both-ends opening, it is shaping | molding. As long as the pin can be formed at the same time as the injection molding of the bearing member, a through-hole having another shape such as a rectangular cross section can be adopted.

  In addition, the dynamic pressure generating portion of the thrust bearing portion is not limited to the spiral-shaped dynamic pressure generating portion as described above, and although not shown in the drawing, a herringbone-shaped dynamic pressure groove and a region where the dynamic pressure generating portion is formed (For example, a plurality of radial groove-shaped dynamic pressure grooves are provided at predetermined intervals in the circumferential direction on both end surfaces 8b and 8c of the sleeve portion 8, the upper end surface 10a of the lid member 10, and the upper end surface 39a of the housing portion 39). A so-called step bearing or a corrugated bearing (the corrugated step bearing) may be used.

  Moreover, although the above embodiment demonstrated the case where the thrust dynamic pressure generation part (dynamic pressure groove 8b1 etc.) was formed in the sleeve part 8, the lid member 10, and the housing part 39 side, the dynamic pressure generation part was formed. The region to be formed can be provided, for example, on both end surfaces 2b1 and 2b2 of the flange portion 2b opposed to these, or on the lower end surface 33a1 side of the disc hub 33.

  Further, in the above description, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing devices 1, 21, and 31 and causes the hydrodynamic action in the radial bearing gap and the thrust bearing gap. A fluid capable of generating a dynamic pressure action in each bearing gap, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

  Further, the hydrodynamic bearing device of the present invention is not limited to the spindle motor used in the disk drive device such as the HDD as described above, but is used for information used under high-speed rotation, such as a spindle motor for driving a magneto-optical disk of an optical disk. It can also be suitably used as a fan motor for rotating shaft support in a small motor for equipment, a polygon scanner motor of a laser beam printer, or a cooling fan for electrical equipment.

It is sectional drawing of the spindle motor incorporating the dynamic pressure bearing apparatus 1 which concerns on embodiment of this invention. 1 is a cross-sectional view of a fluid dynamic bearing device 1. FIG. 3 is a radial cross-sectional view of a bearing member 7. FIG. 4 is a bottom view of the bearing member 7. FIG. 5 is a cross-sectional view showing an injection molding process of the bearing member 7. It is sectional drawing which shows the bearing member 7 of other embodiment of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus 21 which concerns on other embodiment of this invention. It is sectional drawing which shows the hydrodynamic bearing apparatus 31 which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 7 Bearing member 8 Sleeve part 9 Housing part 10 Lid member 11 Seal part 12 Through-hole 13 Forming pin 14 Outer mold 15 Inner mold 16 Cavity R Radial bearing part T1, T2 Thrust bearing part

Claims (3)

The bearing member molded with resin, the shaft member inserted in the inner periphery of the bearing member, and the lubricating fluid in the radial bearing gap formed between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member In the hydrodynamic bearing device provided with a dynamic pressure generating unit that generates a pressure action,
A hydrodynamic bearing device in which a bearing member has a diameter difference based on a difference in molding shrinkage on an inner peripheral surface, and the dynamic pressure generating portion is formed by the diameter difference.   The hydrodynamic bearing device according to claim 1, wherein an axial through hole having an inner surface as a molding surface is formed in the bearing member.   The hydrodynamic bearing device according to claim 1, wherein a protruding portion protruding toward the outer diameter is formed on the outer peripheral surface of the bearing member.

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