JP2008008473A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dynamic pressure bearing device having a bearing member having a through-hole, and superior in moldability. <P>SOLUTION: Since the through-hole is molded by a molding pin 13 arranged in a cavity 16, the through-hole can be easily molded more than when molded by machining, and there is no risk of mixing-in of contamination. Risk of breaking an extra fine molding pin 13 can be reduced by arranging the molding pin 13 in a wide part A1' of relatively low pressure by an injected resin among the cavity 16. <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 bearing member (bearing sleeve) and a shaft member, and is a radial bearing formed between an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. The shaft member is rotatably supported by the dynamic pressure action of the lubricating fluid in the gap. In this dynamic pressure bearing device, the material cost is reduced by forming the bearing member with resin.

  In addition, such a bearing member may be formed with an axial through hole (bypass passage) through which the lubricating fluid can flow for the purpose of maintaining the pressure balance inside the bearing (see Patent Document 2). ).

JP 2004-316712 A JP 2004-11897 A

  However, since the inner diameter of the through hole is generally very small (several tens to several hundreds of μm), it is extremely difficult to form a through hole in the bearing member by machining or the like, and the processing powder or the like is inside the bearing. There is a risk of contamination.

  An object of the present invention is to provide a hydrodynamic bearing device having a through-hole and having a bearing member excellent in formability.

  In order to solve the above problems, the present invention includes a bearing member formed by resin molding and a shaft member inserted into 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 a hydrodynamic bearing device that generates a dynamic pressure action of a lubricating fluid in a radial bearing gap formed between the shaft and the bearing member, a thick-walled portion and a thin-walled portion are provided, and an inner surface is formed on the thick-walled portion. A through hole in the direction is provided.

  Thus, in the present invention, since the inner surface of the through hole is a molding surface, the through hole can be molded simultaneously with the molding of the bearing member using the molding pin disposed in the cavity. Therefore, the through hole can be easily formed and the problem of contamination can be avoided.

  Further, since the bearing member is provided with a thick part and a thin part, the cavity has a wide radial part (hereinafter referred to as a wide part) and a narrow radial part (hereinafter referred to as a narrow part). It is formed. For this reason, the pressure by the resin material injected into the cavity (hereinafter referred to as injection pressure) varies depending on the location. When a high injection pressure is applied to an extremely fine molding pin, the molding pin may be broken. In the present invention, since the axial through hole is provided in the thick part of the bearing member, the molding pin is arranged in the wide part of the cavity where the injection pressure is relatively small, and the risk of the molding pin being broken can be reduced. it can.

  The thick part and the thin part of the bearing member can be provided alternately in the circumferential direction of the bearing member, for example.

  One end of the through hole formed in this way is communicated with one end of the radial bearing gap, and the other end of the through hole is communicated with the other end of the radial bearing gap so that the radial bearing gap, the through hole, and the through hole and the radial bearing gap are communicated. By filling all the gaps with the lubricating fluid, the lubricating fluid can be circulated inside the bearing device. Thereby, it can prevent that a bubble and a local negative pressure arise in the lubricating fluid inside a bearing.

  As described above, according to the present invention, a hydrodynamic bearing device including a bearing member having a through hole and excellent in moldability can be obtained.

  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. In this case, the shaft member 2 is a resin injection molding using the shaft portion 2a as an insert part. 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 sleeve portion 8 is alternately provided with thick portions A1 and thin portions A2 in the circumferential direction, and an inner peripheral surface 8a thereof has a multi-arc shape including a plurality of arc surfaces (exaggerated in FIG. 3). . 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 the fluid flows excessively from another fluid holding space into the through hole 12, 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, it is desirable to set the inner diameter of the through hole 12 as small as possible within a range in which the lubricating fluid can flow satisfactorily.

  The upper end of the through hole 12 communicates with the upper end of the radial bearing gap via a plurality of radial grooves 11 b 1 provided on the lower end surface 11 b of the seal portion 11, and the lower end of the through hole 12 is the contact surface 10 b 1 of the lid member 10. Are communicated with the lower end of the radial bearing gap via a plurality of radial grooves 10c provided in the first thrust bearing portion and the thrust bearing gap of the first thrust bearing portion T1.

  The bearing member 7 is formed as follows. As shown in FIG. 5, the mold used in the injection molding of the bearing member 7 is a multi-circular arc corresponding to the shape of the outer mold 14 having a perfect circular inner peripheral surface and the inner peripheral surface 8 a of the bearing member 7. And an inner mold 15 having a shape outer peripheral surface. A molding pin 13 for molding the through hole 12 is disposed in the cavity 16 formed by the outer mold 14 and the inner mold 15, and a resin material is injected into the cavity 16 through the sprue 17 and the gate 18. In this way, since the inner surface of the through hole 12 is formed with the molding pin 13, the through hole 12 can be easily formed simultaneously with the molding of the bearing member 7, and no processing powder is generated, so that problems due to contamination are also eliminated. it can.

  Further, since the outer peripheral surface of the inner mold 15 has a multi-arc shape, the cavity 16 is formed with wide portions A1 'and narrow portions A2' alternately in the circumferential direction. The pressure of the resin material injected from the gate 18 becomes maximum at the narrow portion A2 '. In the present invention, as shown in FIG. 5, by arranging the molding pin 13 in the wide portion A1 ′ having a relatively low pressure in the cavity 16, it is possible to reduce the risk of the ultrafine molding pin 13 being broken. it can.

  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.

  The internal space of the hydrodynamic bearing device 1 having the above-described configuration, specifically, the radial bearing gap, the thrust bearing gap, the through hole 12, and the space between them are all filled with lubricating oil. 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, the radial bearing gap has a different gap width in the circumferential direction (see FIG. 3). Along with the rotation of the shaft member 2, the lubricating oil in the portion having a relatively large gap width in the radial bearing gap is pushed into the portion having a relatively small gap width, thereby increasing the pressure of the lubricating oil film. 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.

  In the hydrodynamic bearing device 1, as described above, the upper end of the through hole 12 formed in the bearing member 7 communicates with the upper end of the radial bearing gap, and the lower end of the through hole 12 is the lower end of the radial bearing gap. Communicate. For this reason, it is possible to avoid the situation where the fluid (lubricating oil) pressure on the closing side of the housing 7 is excessively increased or decreased for some reason, and to stably support the shaft member 2 in the thrust direction in a non-contact manner. Become.

  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, the shape of the inner peripheral surface 8a of the sleeve portion 8 is not limited to a multi-arc shape, and may be a step shape as shown in FIG. Specifically, the inner peripheral surface 8a of the sleeve portion 8 is composed of small-diameter portions 8a1 and large-diameter portions 8a2 that appear alternately in the circumferential direction, and the circumferential position of each large-diameter portion 8a2, that is, the bearing member 7 The through-hole 12 is formed in one or a plurality of places (three places in FIG. 6) in the thick part A1.

  Alternatively, the inner peripheral surface 8a of the sleeve portion 8 can be constituted by a so-called taper bearing. Specifically, as shown in FIG. 7, the inner peripheral surface 8a of the sleeve portion 8 is composed of three arcuate surfaces 8a3, 8a4, 8a5 having a center O ′ offset by an equal distance from the rotation axis O. . The radial bearing gaps facing each arc surface have a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. A deeper axial groove G called a separation groove is formed at the boundary between the three arcuate surfaces 8a3, 8a4, 8a5. At this time, the circumferential position where the clearance width of the radial bearing gap is the smallest is the thick portion A1 of the bearing member 7, and the circumferential position of the separation groove G is the thin portion A2 of the bearing member 7. The through hole 12 is formed in one or a plurality of locations (three locations in FIG. 7) in the thick portion A1 of the bearing member 7.

  Alternatively, the inner peripheral surface 8a of the sleeve portion 8 can be constituted by a so-called tapered flat bearing (see FIG. 8). In this case, in the configuration shown in FIG. 7, the predetermined regions θ on the minimum gap side of the three circular arc surfaces 8a3, 8a4, and 8a5 are each configured by concentric arcs with the rotation axis O as the center of curvature. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant.

  In the above embodiment, although the case where the outer peripheral surface 9c of the bearing member 7 was a perfect circle shape was shown, it is not restricted to this. For example, as shown in FIG. 9, you may form the protrusion part 7a which protruded toward the outer diameter in the multiple places (3 places in FIG. 9) of the outer peripheral surface 9c of the bearing member 7 in the circumferential direction. In this case, the region where the protruding portion 7a is formed is the thick portion A1, the region between the circumferential directions thereof is the thin portion A2, and the through hole 12 is formed in the thick portion A1. In the present embodiment, the thickness difference between the thick portion A1 and the thin portion A2 is positively increased by providing the protruding portion 7a as described above. The large diameter portion 8a1 and the small diameter portion 8a2 can be formed on the inner peripheral surface 8a using the difference in molding shrinkage due to the thickness difference between the thick portion A1 and the thin portion A2. The diameter difference between the large diameter portion 8a1 and the small diameter portion 8a2 becomes a dynamic pressure generating portion that generates a dynamic pressure action on the lubricating fluid in the radial bearing gap. For this reason, since the inner mold | die which shape | molds the inner peripheral surface of the bearing member 7 is sufficient for a perfect circle shape, the manufacturing cost of an inner mold | type is reduced.

  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. 10 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. Further, the 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 upper end of the through hole 12 communicates with the upper end of the radial bearing gap via the thrust bearing gap of the first thrust bearing portion T11, and the lower end of the through hole 12 is the thrust of the second thrust bearing portion T12. It communicates with the lower end of the radial bearing gap via the bearing gap.

  A hydrodynamic bearing device 31 shown in FIG. 11 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 disk 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 upper end of the through hole 12 communicates with the upper end of the radial bearing gap via a gap between the upper end surface 8c of the sleeve portion 8 and the lower end surface 33a1 of the disk portion 33a, and the through hole 12 The lower end communicates with the lower end of the radial bearing gap via the thrust bearing gap of the first thrust bearing portion T21.

  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 was formed in the position opened in the both end surfaces 8b and 8c of the sleeve part 8, it is not restricted to this, The bearing members 7, 27, and 37 are made into an axial direction. As long as it penetrates through and is located in the thick part A1, it can be formed at any position. Further, as shown in FIG. 2, when the radial grooves 10c and 11b1 are formed in the lid member 10 and the seal portion 11, the radial grooves 10c and 11b1 are opposed to the opposite member side (for example, both end surfaces 8b of the sleeve portion 8). 8c).

  Further, in the above embodiment, the through hole 12 having a cylindrical inner peripheral surface has been exemplified. However, the through hole formed in the bearing member 7 can also be used as long as fluid can flow between the openings at both ends. As long as the molding pin can be formed at the same time as the injection molding of the bearing member, a through hole having another shape 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 (where the step mold is a corrugated bearing) can also 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 bearing member 7 of other embodiment of this invention. It is sectional drawing which shows the bearing member 7 of other embodiment of this invention. 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 A1 Thick part A2 Thin part R Radial bearing part T1, T2 thrust bearing

Claims (3)

A bearing member formed by injection molding and a shaft member inserted in the inner periphery of the bearing member are lubricated in a radial bearing gap formed between the inner peripheral surface of the bearing member and the outer peripheral surface of the shaft member. In a hydrodynamic bearing device that generates fluid dynamic pressure action,
A hydrodynamic bearing device characterized in that a thick member and a thin member are provided in a bearing member, and an axial through hole having an inner surface as a molding surface is provided in the thick member.   2. The hydrodynamic bearing device according to claim 1, wherein the thick portions and the thin portions are alternately provided in a circumferential direction of the bearing member.   One end of the through hole is communicated with one end of the radial bearing gap, and the other end of the through hole is communicated with the other end of the radial bearing gap to lubricate the radial bearing gap, the through hole, and between the through hole and the radial bearing gap. The hydrodynamic bearing device according to claim 1 or 2 filled with a fluid.

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