JP2009243605A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a stress concentration occurring in a housing of a fluid bearing device so as to enhance the strength of the housing. <P>SOLUTION: A corner rounded portion 7e is formed at a boundary between an inner peripheral surface 7a1 and an inner bottom surface 7b1 of the housing 7. The corner rounded portion 7e is formed by smoothly connecting a first circular arc surface 7e1 and a second circular arc surface 7e2 having a radius of curvature smaller than that of the first circular arc surface 7e1. The first circular arc surface 7e1 having a larger radius of curvature is arranged at the part of the corner rounded portion 7e where the stress concentration is liable to occur. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member with a fluid film generated in a bearing gap.

  Due to its high rotational accuracy and quietness, the hydrodynamic bearing device is a magnetic disk drive device for information equipment (for example, HDD), an optical disk drive device such as a CD-ROM, CD-R / RW, DVD-ROM / RAM, or MD, For spindle motors of magneto-optical disk drive devices such as MO, for polygon scanner motors of laser beam printers (LBP), for color wheel motors of projectors, or for small motors such as fan motors used for cooling of electrical equipment, etc. It is used as

  For example, the hydrodynamic bearing device described in Patent Document 1 includes a shaft member, a bearing sleeve in which the shaft member is inserted in the inner periphery, and a housing in which the shaft member and the bearing sleeve are accommodated in the inner periphery. The housing has a side part and a bottom part integrally.

JP 2003-239974 A

  When an impact load is applied to the fluid dynamic bearing device as described above, the shaft member may collide with the bottom of the housing. At this time, stress concentrates on the boundary portion between the side portion and the bottom portion of the housing, specifically, the boundary portion between the inner peripheral surface and the inner bottom surface, and there is a possibility that the boundary portion is cracked or broken. In order to alleviate such stress concentration, a corner radius portion having a single radius of curvature may be provided at the boundary portion.

  In recent years, with the increase in capacity of HDDs, the number of disks stacked on a spindle motor tends to increase. Since this disc is attached to the shaft member of the hydrodynamic bearing device via the disc hub, the weight on the shaft member side of the hydrodynamic bearing device increases as the number of discs increases, and the load received by the housing due to the impact load as described above is increased. growing. Under such circumstances, a device for further relaxing the stress concentration generated in the housing is required.

  For example, if the radius of curvature of the corner rounded portion is increased, the stress concentration can be relaxed. However, if the radius of curvature of the corner rounded portion is increased, the corner rounded portion may invade the bearing inner side and interfere with the flange portion or the like of the shaft member (see 7e1 'in FIG. 5). On the other hand, if the radius of curvature of the corner rounded portion is increased by removing a part of the housing, the risk of interference between the corner rounded portion and the flange portion of the shaft member can be avoided (7e1 '' in FIG. 5). reference). However, the portion where the stress is concentrated in the housing is locally thinned, which causes a reduction in the strength of the housing.

  An object of the present invention is to alleviate stress concentration generated in a housing of a hydrodynamic bearing device and increase the strength of the housing.

  In order to solve the above-described problems, the present invention provides a shaft member, a housing that accommodates the shaft member on the inner periphery, and integrally includes a side portion and a bottom portion, and a fluid film in a radial bearing gap that faces the outer periphery of the shaft member. In the hydrodynamic bearing device having a radial bearing portion for supporting the shaft member in the radial direction, a corner radius portion having a plurality of arc surfaces having different curvature radii is provided at a boundary portion between the inner peripheral surface and the inner bottom surface of the housing. It is characterized by that.

  Thus, in the hydrodynamic bearing device of the present invention, the corner radius portion having a plurality of circular arc surfaces having different curvature radii is provided at the stress concentration portion of the housing, that is, the boundary portion between the inner peripheral surface and the inner bottom surface. By arranging an arc surface having a large curvature radius on the side where the stress is concentrated among the plurality of arc surfaces in the corner rounded portion, the stress concentration in this portion is alleviated and the strength of the housing can be increased. Further, by providing an arc surface having a small radius of curvature at the corner radius portion, the amount of the corner radius portion protruding into the bearing inner side or the amount of removing the housing can be reduced.

  If this housing is injection-molded, it can be easily and accurately formed including the corner rounded portion. When a fibrous filler (for example, carbon fiber) is blended in the injection material, the strength of the housing in the stress concentration portion can be increased by orienting the fibrous filler along the corner radius portion (see FIG. 6). .

  For example, a flange portion is provided on the shaft member, a thrust bearing portion that supports the shaft member in the thrust direction with a fluid film generated in a thrust bearing gap between the end surface of the flange portion and the inner bottom surface of the housing is provided, and the inner bottom surface of the housing is provided. A thrust dynamic pressure generating portion that generates a dynamic pressure action on the fluid film in the thrust bearing gap can be formed. At this time, if a flat surface is provided on the outer peripheral edge portion of the inner bottom surface of the housing, and one end of the corner rounded portion is smoothly connected to the flat surface and the other end is smoothly connected to the inner peripheral surface, stress concentration at these connecting portions can be reduced. Can do.

  In addition, if the thrust dynamic pressure generating part is provided with a hill and a recess, and a step surface having an obtuse angle with respect to the flat surface is formed between the hill and the flat surface, the stress at the boundary between the step surface and the flat surface Concentration can be eased. Furthermore, if the step surface and the flat surface are smoothly connected, the stress concentration at these boundary portions can be further alleviated.

  As described above, according to the present invention, stress concentration generated in the housing of the hydrodynamic bearing device can be alleviated and the strength of the housing can be increased.

  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 (dynamic pressure bearing device 1) according to an embodiment of 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 disk hub 3 fixed to the upper end portion of the shaft member 2, and a radial direction. The stator coil 4 and the rotor magnet 5 that are opposed to each other through the gap, and the motor bracket 6 are provided. The stator coil 4 is attached to the outer periphery of the motor bracket 6, and the rotor magnet 5 is attached to the inner periphery of the disk hub 3. The hydrodynamic bearing device 1 is fixed to the inner periphery of the motor bracket 6. The disc hub 3 holds one or a plurality of discs D (two in this embodiment) as information recording media, and is fixed by a clamping device (not shown). When the stator coil 4 is energized, the rotor magnet 5 rotates, and accordingly, the disk hub 3 and the disk D held by the disk hub 3 rotate integrally with the shaft member 2.

  The hydrodynamic bearing device 1 shown in FIG. 2 has a shaft member 2, a bearing sleeve 8 with the shaft member 2 inserted into the inner periphery, the shaft member 2 accommodated in the inner periphery, and the bearing sleeve 8 fixed to the inner peripheral surface. It has a bottomed cylindrical housing 7 and a seal portion 9 disposed in the opening of the housing 7. For convenience of explanation, the opening side of the housing 7 in the axial direction is referred to as the upper side, and the closing side of the housing 7 is referred to as the lower side.

  The shaft member 2 has a substantially cylindrical shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a. The shaft member 2 may be formed integrally with a metal material such as SUS, or the shaft portion 2a and the flange portion 2b may be formed separately. Or you may form a part of shaft member, for example, both end surfaces with a resin material.

  The bearing sleeve 8 is formed in a cylindrical shape with a porous body of sintered metal whose main component is copper, for example. In addition, the bearing sleeve 8 can be formed of other metals, resins, ceramics, or the like.

  As shown in FIG. 3A, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed on the inner peripheral surface 8a of the bearing sleeve 8 in two regions separated in the axial direction. Specifically, a hill portion 8a10, 8a20 having a belt-like portion and a plurality of inclined portions extending from the belt-like portion to both sides in the axial direction is provided (indicated by cross hatching in the figure), and a circle of the slope portion of the hill portion 8a10, 8a20 is provided. Dynamic pressure grooves 8a1 and 8a2 are formed between the circumferential directions, respectively. The upper dynamic pressure groove 8a1 is formed in an axially asymmetric shape. Specifically, the axial dimension X1 of the upper groove from the belt-like portion of the hill part 8a10 is larger than the axial dimension X2 of the lower groove. (X1> X2).

  As shown in FIG. 3B, a spiral-shaped dynamic pressure groove 8c1 is formed on the lower end surface 8c of the bearing sleeve 8. Specifically, a hill portion 8c10 having an annular portion and a plurality of inclined portions extending spirally from the annular portion to the outer diameter side is provided (indicated by cross hatching in the drawing), and the circumference of the inclined portion of the hill portion 8c10 A dynamic pressure groove 8c1 is formed between the directions.

  An arbitrary number of grooves 8d1 extending in the axial direction are formed on the outer peripheral surface 8d of the bearing sleeve 8 over the entire length in the axial direction. In this embodiment, three axial grooves 8d1 are formed at equal intervals in the circumferential direction. As shown in FIG. 3, a circumferential groove 8b1 having a V-shaped cross section is formed on the entire upper end surface 8b of the bearing sleeve portion, and an arbitrary number of radial grooves are formed on the inner diameter side of the circumferential groove 8b1. 8b2 is formed.

  The housing 7 integrally includes a substantially cylindrical side portion 7a and a bottom portion 7b that closes a lower end opening of the side portion 7a. In this embodiment, the housing 7 is injection-molded with a resin material. The resin material of the housing 7 is not particularly limited. For example, a crystalline resin such as liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyphenylsulfone (PPSU), polyethersulfone, or the like. Resin compositions based on amorphous resins such as (PES) and polyetherimide (PEI) can be used. In this resin material, various fillers can be blended in appropriate amounts according to the purpose. For example, fibrous fillers such as carbon fibers and glass fibers, whisker-like fillers such as potassium titanate, and scaly forms such as mica. Fibrous or powdery conductive fillers such as filler, carbon fiber, carbon black, graphite, carbon nanomaterial, and various metal powders can be blended.

  The material of the housing 7 is not limited to the above. For example, a low melting point metal material such as a magnesium alloy or an aluminum alloy may be used. Further, the housing 7 may be formed by so-called MIM molding in which degreasing and sintering are performed after injection molding with a mixture of metal powder and binder. Furthermore, the housing 7 can also be formed by press molding of a metal material, for example, a soft metal such as brass, or machining such as cutting.

  The inner peripheral surface 7a1 of the housing 7 is formed in a cylindrical surface shape. The bearing sleeve 8 is fixed to the inner peripheral surface 7a1 by appropriate means such as adhesion (including loose adhesion and press-fit adhesion), press-fit, and welding.

  On the upper end surface 7b1 (inner bottom surface 7b1) of the bottom 7b of the housing 7, as shown in FIG. 4, there is formed a thrust dynamic pressure generating portion including, for example, a hill portion 7b12 and a concave portion (for example, a spiral dynamic pressure groove 7b11). The Specifically, a hill portion 7b12 having an annular portion 7b13 and a plurality of inclined portions 7b14 extending spirally from the annular portion 7b13 to the outer diameter side is provided (indicated by cross-hatching in the figure), and the hill portion 7b12 is inclined. A dynamic pressure groove 7b11 is formed between the circumferential directions of the portion 7b14. As shown in FIGS. 4 and 5, an annular flat surface 7b10 is formed on the outer peripheral edge portion of the inner bottom surface 7b1 on the outer diameter side of the hill portion 7b12. The flat surface 7b10 is equal to the level of the dynamic pressure groove 7b11, and the hill portion 7b12 is located higher than the flat surface 7b10. A step surface 7b15 between the hill portion 7b12 and the flat surface 7b10 is formed in a tapered shape having an obtuse angle θ with respect to the flat surface 7b10 (θ> 90 °).

  The bottom portion 7b of the housing 7 is provided with an annular protruding portion 7c that protrudes downward in the axial direction from the outer diameter end of the lower end surface 7b2 of the bottom portion 7b. The inner peripheral surface 7c1 of the protruding portion 7c is formed with a smaller diameter than the inner peripheral surface 7a1 of the side portion 7a. That is, the radial thickness of the protruding portion 7c is formed to be larger than the thickness of the side portion 7a. A tapered surface 7d is formed between the inner peripheral surface 7c1 of the protruding portion 7c and the lower end surface 7b2 of the bottom portion 7b. By fixing not only the outer peripheral surface of the side portion 7a of the housing 7 but also the outer peripheral surface of the protruding portion 7c to the inner peripheral surface of the bracket 6, the fixing area is expanded and the fixing strength of both is increased.

A corner radius portion 7e is formed at the boundary between the inner peripheral surface 7a1 and the inner bottom surface 7b1 of the housing 7. As shown in FIG. 5, the corner rounded portion 7e is composed of a first arc surface 7e1 and a second arc surface 7e2. The radius of curvature _{r 1} of the first arcuate surface 7e1 is set larger than the radius of curvature _{r 2} of the second circular arc surface 7e2 _{(r 1> r} 2). In the illustrated example, the first arc surface 7e1 and the second arc surface 7e2 are each formed at 45 °. The first arc surface 7e1 having a large curvature radius is disposed on the side portion 7a side, and the second arc surface 7e2 having a small curvature radius is disposed on the bottom portion 7b side. The first arc surface 7e1 and the second arc surface 7e2 are smoothly connected to each other, and the first arc surface 7e1 is smoothly connected to the inner peripheral surface 7a1 and the second arc surface 7e2 is smooth to the flat surface 7b10 of the inner bottom surface 7b1. linked.

Thus, by providing the corner radius portion 7e at the boundary portion between the inner peripheral surface 7a1 and the inner bottom surface 7b1 of the housing 7, the stress concentration in this portion can be reduced. By configuring the corner rounded portion 7e with the first arc surface 7e1 and the second arc surface 7e2 having different radii of curvature, stress concentration can be reduced while avoiding a decrease in strength of the housing 7. That is, in the illustrated example, the protrusion 7c and the tapered surface 7d are provided so that the axial thickness of the housing 7 at the corner radius portion 7e is larger than the radial thickness. That is, the strength at the corner rounded portion 7e of the housing 7 is higher on the bottom 7b side than on the side 7a side. Therefore, by providing the first circular arc surface 7e1 having a large curvature radius on the side portion 7a having a relatively low strength, the stress concentration in this portion can be alleviated and the strength at the corner radius portion 7e can be increased. Incidentally, the radius of curvature r ₂ of the curvature radius r ₁ and a second arcuate surface 7e2 of the first arcuate surface 7e1 is not particularly limited as long as the above effect can be obtained, for example, an outer diameter of about 4mm of the shaft portion 2a for the hydrodynamic bearing, the range of the radius of curvature _{r 1} of the first arcuate surface 7e1 is 0.4 to 0.5 mm, the radius of curvature _{r 2} of the second arcuate surface 7e2 in the range of 0.15~0.25mm Set to

  By the way, when the corner radius portion 7e is formed only by the first arc surface, the corner radius portion may protrude into the bearing inner side and interfere with the flange portion 2b of the shaft member 2 (indicated by a dotted line 7e1 ′ in FIG. 5). ). When the diameter of the flange portion 2b is reduced in order to solve this problem, the radial dimension of the thrust bearing portion is also reduced, leading to a reduction in thrust load capacity. On the other hand, if a part of the housing 7 is removed to provide a first arc surface (indicated by a one-dot chain line 7e1 ″ in FIG. 5) in order to avoid buffering with the flange portion 2b, the strength of the housing 7 is reduced. Therefore, by providing the second arcuate surface 7e2 smoothly connected to the first arcuate surface 7e1 and having a smaller radius of curvature than the first arcuate surface 7e1, the corner radius portion 7e does not protrude toward the bearing inner side, and the housing The first circular arc surface 7e1 and the inner bottom surface 7b1 can be smoothly connected without partially removing.

For example, when a fibrous filler such as carbon fiber or glass fiber is blended in the injection material of the housing 7, as shown in FIG. 6, if the fibrous filler F is oriented along the corner radius portion 7e, The strength of the corner radius portion 7e where the stress is concentrated can be further increased. At this time, if the radius of curvature of the corner rounded portion is small, the injection material of the housing 7 becomes difficult to flow along the corner rounded portion, so it is difficult to orient the fibrous filler F as shown in FIG. Therefore, as described above, if the first arcuate surface 7e1 having a large radius of curvature is provided at the corner rounded portion 7e, the injection material can easily flow along the first arcuate surface 7e1, and the fibrous filler F is formed as shown in FIG. It becomes relatively easy to orient like. If the average fiber length of the fibrous filler is too short, sufficient strength cannot be imparted to the corner rounded portion 7e of the housing 7, and if too long, the fluidity of the injection material is significantly reduced. Since it becomes difficult to mold, it is desirable that the thickness be in the range of 30 to 360 μm, preferably 160 to 240 μm.

  When the thrust dynamic pressure generating portion is provided on the housing inner bottom surface 7b1 as in the present embodiment, stress concentration occurs on the step surface 15 between the hill portion 7b12 of the thrust dynamic pressure generating portion and the flat surface 7b10 of the housing inner bottom surface 7b1. May occur. Therefore, as described above, by making the angle θ between the step surface 7b15 and the flat surface 7b10 an obtuse angle, the stress concentration in this portion can be relaxed (see FIG. 5). In FIG. 5, a corner is formed between the stepped surface 7b15 and the flat surface 7b10. However, if the boundary is smoothly connected with a rounded surface, the stress concentration can be further relaxed.

  The seal portion 9 is formed in an annular shape with, for example, a resin material, and is fixed to the inner peripheral surface 7a1 of the housing 7 by appropriate means such as press fitting or adhesion. The inner peripheral surface 9a of the seal portion 9 is formed in a tapered surface shape whose diameter is gradually increased upward. Thus, a wedge-shaped seal space S is formed between the inner peripheral surface 9a of the seal portion 9 and the outer peripheral surface 2a1 of the shaft member 2 with the radial dimension gradually reduced downward. Lubricating oil is injected into the internal space of the housing 7 sealed by the seal portion 9, and the inside of the housing 7 is filled with the lubricating oil (a dotted area in FIG. 2). In the seal space S, an oil surface (gas-liquid interface) of the lubricating oil filled in the bearing is formed, and the oil surface is always held in the seal space S by the pulling action of the capillary force of the wedge-shaped seal space S. . The volume of the seal space S is set so that the oil level of the lubricant can always be kept within the range of the seal space S even when the lubricant filled in the bearing expands and contracts with a change in temperature.

  In the dynamic pressure bearing device 1 having the above configuration, when the shaft member 2 rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a. The pressure of the oil film in the radial bearing gap is increased by the dynamic pressure grooves 8a1 and 8a2, thereby forming the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner in the radial direction.

  At the same time, between the upper end surface 2b1 of the flange portion 2b of the shaft member 2 and the lower end surface 8c of the bearing sleeve 8, and the lower end surface 2b2 of the flange portion 2b of the shaft member 2 and the inner bottom surface 7b1 of the housing 7 A thrust bearing gap is formed between each of them. The pressure of the oil film in each thrust bearing gap is increased by the dynamic pressure grooves 8c1 and 7b11, thereby forming the first thrust bearing portion T1 and the second thrust bearing portion T2 that support the shaft member 2 in a non-contact manner in the thrust direction.

  Further, the outer diameter end of the thrust bearing gap of the first thrust bearing portion T1 and the seal space S provided in the opening of the housing 7 are the axial groove 8d1 of the bearing sleeve 8 and the upper end surface 8b of the bearing sleeve 8. And a gap between the lower end surface 9b of the seal portion 9 and a communication state. As a result, it is possible to avoid a situation in which the pressure of the oil film of the first thrust bearing portion T1 excessively increases or decreases for some reason, so that the shaft member 2 can be stably supported in the thrust direction. Become.

  In this embodiment, since the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed to be axially asymmetric (X1> X2) (see FIG. 3), the dynamic pressure groove 8a1 is rotated when the shaft member 2 is rotated. The pulling force (pumping force) of the lubricating oil by the upper groove is relatively larger than the pulling force of the lower groove. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the gap between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a flows downward, and the first thrust bearing portion T1 Thrust bearing clearance → Axial groove 8d1 → Circulates a path between the upper end surface 8b of the bearing sleeve 8 and the lower end surface 9b of the seal portion 9, and is drawn into the radial bearing clearance again. As described above, the lubricating oil is forced to flow and circulate in the inner space of the housing 7, whereby the pressure balance inside the bearing can be properly maintained. As a result, it is possible to reliably prevent the generation of bubbles due to the generation of the negative pressure of the lubricating oil, and to solve problems such as the leakage of the lubricating oil and the occurrence of vibrations.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described. In the following description, parts having the same configuration and function as those of the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the embodiment shown in FIG. 7, the bottom 7b of the housing 7 is formed thinner than the side 7a. In this case, at the corner rounded portion 7e of the housing 7, the axial thickness is thinner than the radial thickness. That is, the strength at the corner rounded portion 7e of the housing 7 is closer to the bottom 7b side than the side 7a side. Is lower. In this case, as shown in FIG. 8, by arranging the first circular arc surface 7e1 having a large curvature radius in the corner rounded portion 7e on the bottom 7b side, stress concentration on the bottom 7b side is alleviated, and the housing 7 Strength can be increased.

  In the above embodiment, the corner rounded portion 7e is composed of two arcuate surfaces 7e1 and 7e2, but is limited to this configuration as long as it has a plurality of arcuate surfaces with different radii of curvature and the above effects are obtained. I can't. For example, another arc surface or a straight line portion may be interposed between the two arc surfaces 7e1 and 7e2. In this case, it is preferable that all of these circular arc surfaces and straight line portions are smoothly connected. Alternatively, the corner radius portion 7e may be configured such that the radius of curvature gradually increases (or decreases) gradually from one end to the other end. In the above description, the flat surface 7b10 is provided on the inner bottom surface 7b1 of the housing 7. However, this flat surface may be omitted, and the inner diameter end of the corner radius portion 7e may be directly connected to the step surface 7b15.

  In the above embodiment, the radial bearing portions R1 and R2 and the dynamic pressure generating portions of the thrust bearing portions T1 and T2 are respectively formed on the inner peripheral surface 8a, the lower end surface 8c of the bearing sleeve 8, and the inner bottom surface 7b1 of the housing 7. Although formed, they may be formed on the surfaces facing these surfaces through a bearing gap, that is, the outer peripheral surface 2a1 of the shaft portion 2a, the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b.

  Further, in the above embodiment, the herringbone-shaped dynamic pressure grooves are exemplified as the radial dynamic pressure generating portions of the radial bearing portions R1 and R2. However, the present invention is not limited to this, and for example, so-called step bearings and wave bearings Alternatively, a multi-arc bearing can be employed. Further, both the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft member 2 may be cylindrical surfaces, and so-called circular bearings having no dynamic pressure generating portions may be employed as the radial bearing portions R1 and R2. it can.

  In the above embodiment, the spiral dynamic pressure grooves are exemplified as the thrust dynamic pressure generating portions of the thrust bearing portions T1 and T2. However, the present invention is not limited to this, and for example, step bearings or wave bearings are employed. You can also. Or the pivot bearing which contacts and supports the edge part of a shaft member is also employable as thrust bearing part T1, T2.

  Further, in the above embodiment, the radial bearing portions R1 and R2 are provided separately in the axial direction, but these may be provided continuously in the axial direction. Alternatively, only one of these may be provided.

  Further, in the above embodiment, lubricating oil is used as a lubricant that fills the internal space of the hydrodynamic bearing device. However, the present invention is not limited to this. For example, a gas such as air, lubricating grease, magnetic fluid, or the like is used. You can also

  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 supporting a rotating shaft in a small motor for equipment, a polygon scanner motor of a laser beam printer, or for cooling an electrical equipment.

It is sectional drawing of a spindle motor. It is sectional drawing of a hydrodynamic bearing apparatus. (A) is sectional drawing of a bearing sleeve, (b) is the bottom view. It is a top view of a housing. It is an enlarged view of the A section of FIG. It is sectional drawing which shows the mode of the orientation of the fibrous filler in the corner round part of a housing. It is sectional drawing of the hydrodynamic bearing apparatus which concerns on other embodiment. It is an enlarged view of the B section of FIG.

Explanation of symbols

1 Hydrodynamic bearing device (fluid bearing device)
2 Shaft member 7 Housing 7a1 Inner peripheral surface 7b1 Inner bottom surface 7b10 Flat surface 7b11 Dynamic pressure groove (concave portion)
7b12 Hill portion 7b15 Stepped surface 7e Corner radius portion 7e1 First arc surface 7e2 Second arc surface 8 Bearing sleeve 9 Seal portions R1, R2 Radial bearing portions T1, T2 Thrust bearing portion S Seal space

Claims (6)

A shaft member, a housing that accommodates the shaft member on the inner periphery, and integrally having a side portion and a bottom portion, and a radial bearing portion that supports the shaft member in the radial direction with a fluid film in a radial bearing gap that faces the outer peripheral surface of the shaft member In a hydrodynamic bearing device comprising:
A hydrodynamic bearing device comprising a corner radius portion having a plurality of circular arc surfaces having different curvature radii at a boundary portion between an inner peripheral surface and an inner bottom surface of a housing.   The hydrodynamic bearing device according to claim 1, wherein the housing is injection-molded with a resin material including a fibrous filler, and the fibrous filler is oriented along the corner rounded portion.   The shaft member is provided with a flange portion, and has a thrust bearing portion that supports the shaft member in the thrust direction with a fluid film generated in a thrust bearing gap between the end surface of the flange portion and the inner bottom surface of the housing. The hydrodynamic bearing device according to claim 1, wherein a thrust dynamic pressure generating portion for generating a dynamic pressure action on a fluid film in the thrust bearing gap is formed.   The hydrodynamic bearing device according to claim 1, wherein a flat surface is provided on the outer peripheral edge of the inner bottom surface of the housing, and one end of the corner rounded portion is smoothly connected to the flat surface and the other end is smoothly connected to the inner peripheral surface.   5. The hydrodynamic bearing device according to claim 4, wherein a hill portion and a groove portion are provided in the thrust dynamic pressure generating portion, and a step surface having an obtuse angle with respect to the flat surface is formed between the hill portion and the flat surface.   The hydrodynamic bearing device according to claim 5, wherein the step surface and the flat surface are smoothly connected.

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