JP2009079679A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid bearing device strongly fixing a bearing sleeve and a housing molded by injection using the bearing sleeve as an insert component. <P>SOLUTION: In the fluid bearing device, one area of an outer circumference face 8d of the bearing sleeve 8 is removed by laser beam machining to form a recessed part 8d1, and the housing 7 is molded by injection using the bearing sleeve 8 as an insert component. By this, the recessed part 8d1 of the bearing sleeve 8 and one part of the housing 7 fitting into the recessed part 8d1 are engaged in an axial direction, and fixing force between both members is enhanced. By forming the recessed part 8d1 by laser beam machining, generation of cutting powder is avoided, and a situation of an inner circumference face 8a or the like deforming due to fixing force during machining can be avoided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device.

  A hydrodynamic bearing device is a bearing device that rotatably supports a shaft member with a fluid film in a bearing gap formed between the shaft member and a bearing component. This hydrodynamic bearing device has characteristics such as high-speed rotation, high rotation accuracy, and low noise. In recent years, the hydrodynamic bearing device has been utilized as a motor bearing device for motors mounted on various electrical devices including information devices. More specifically, magnetic disk devices such as HDDs, optical disk devices such as CD-ROM, CD-R / RW, DVD-ROM / RAM, spindle motors such as magneto-optical disk devices such as MD and MO, laser beams, etc. It is preferably used as a bearing device for a motor such as a polygon scanner motor of a printer (LBP), a fan motor for cooling an electric device or the like.

  As such a hydrodynamic bearing device, for example, Patent Document 1 includes a shaft member, a sintered metal bearing sleeve in which the shaft member is inserted on the inner periphery, and a housing that is injection-molded using the bearing sleeve as an insert part. In this way, the housing is injection-molded using the bearing sleeve as an insert part, so that the assembly process of the bearing sleeve and the housing can be omitted, and the manufacturing can be simplified.

JP 2004-52999 A

  However, when the housing is injection-molded using a sintered metal bearing sleeve as an insert part, the fixing force between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve becomes a problem. That is, when the bearing sleeve is made of sintered metal, the outer peripheral surface of the bearing sleeve has a constant shape in the axial direction of a cylindrical surface or the like in order to enable compacting or sizing with a mold. There is a need. Therefore, since the outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing are fixed to each other between the cylindrical surfaces, there is a problem that the removal force with respect to the axial force is weak.

  An object of the present invention is to provide a hydrodynamic bearing device in which a bearing sleeve and a housing are firmly fixed.

  In order to solve the above-described problems, the present invention includes a shaft member, a bearing sleeve formed of sintered metal and having the shaft member inserted into an inner periphery thereof, and a housing that accommodates the bearing sleeve, and an outer peripheral surface of the shaft member; In a hydrodynamic bearing device in which a shaft member is rotatably supported by a fluid film generated in a radial bearing gap between the inner circumferential surface of the bearing sleeve, a recess is formed by removing a part of the outer circumferential surface of the bearing sleeve. Features.

  Thus, in the hydrodynamic bearing device of the present invention, a recess is formed by removing a partial region of the outer peripheral surface of the bearing sleeve. Thus, for example, when the housing is injection-molded using the bearing sleeve as an insert part, the injection material of the housing enters the concave portion of the bearing sleeve, and the concave portion and the material of the housing are engaged in the axial direction so that the fixing force between both members is fixed. Is increased. Alternatively, when the bearing sleeve and the housing are bonded and fixed, the concave portion on the outer peripheral surface of the bearing sleeve becomes an adhesive reservoir, and the fixing force between the two members is increased.

  If such a recess is formed by machining, it is necessary to completely remove such cutting powder and the like in order to avoid a situation in which cutting powder or the like by machining is mixed into the bearing as contamination. Invite. Further, according to machining, a relatively large load is applied to the bearing sleeve at the time of machining, and it is necessary to fix the bearing sleeve with a chuck device or the like with a force capable of withstanding this load. When such a load during processing or a load due to fixation reaches the inner peripheral surface of the bearing sleeve and this surface is deformed, the width accuracy of the radial bearing gap is lowered, and the bearing performance in the radial direction is lowered. On the other hand, if the recess is formed by laser processing as in the present invention, there is no generation of cutting powder and a step of removing this is unnecessary, so that the recess can be formed at a lower cost than machining. . Also, with laser processing, the load applied to the bearing sleeve during processing is relatively small, and the bearing sleeve can be fixed with a relatively small force. Can be avoided.

  By irradiating laser on the outer peripheral surface of the bearing sleeve from the tangential direction, it is possible to form a recess over a relatively wide range in the circumferential direction with the bearing sleeve fixed, so that the retaining effect by the recess is enhanced. Can do.

  By the way, during the operation of such a hydrodynamic bearing device, a partial region of the lubricating fluid that fills the internal space may become negative pressure due to various factors. The generation of such negative pressure causes the generation of bubbles, the leakage of lubricating oil, the generation of vibrations, etc., and contributes to the deterioration of bearing performance. In view of this point, if a through-hole is formed in the bearing sleeve, the lubricating fluid inside the bearing can be circulated through the through-hole, so that local negative pressure can be prevented from being generated. Further, when the bearing sleeve is formed of sintered metal, the through hole can be easily formed by laser processing as compared with machining or the like.

  If the concave portion and the through hole of the bearing sleeve are formed at the same position in the circumferential direction, the thickness at these forming positions becomes locally thin, and the strength of this portion may be insufficient. Therefore, it is desirable to form the recess and the through hole at different positions in the circumferential direction. Further, if a through hole is opened at the outer diameter end of the thrust bearing surface, the lubricating fluid can be circulated over the entire radial direction of the thrust bearing gap, so that the generation of negative pressure can be reliably prevented. .

  If the depth in the radial direction of the recess formed in the bearing sleeve is too shallow, a sufficient anchor effect cannot be obtained, and if it is too deep, the strength of the bearing sleeve may be insufficient. For this reason, for example, in the case of a bearing device having a shaft diameter of about 1 mm incorporated in a spindle motor for HDD, it is preferable that the radial depth of the recess is 0.1 mm or more and 0.5 mm or less.

  As described above, according to the present invention, it is possible to obtain a hydrodynamic bearing device in which a bearing sleeve and a housing in which this is used as an insert part are firmly fixed.

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

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device 1 (dynamic pressure bearing device 1) having bearing components according to the present invention. This spindle motor is used in a disk drive device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a shaft member 2, a disk hub 3 mounted on the shaft member 2, and a radial gap, for example. The stator coil 4a and the rotor magnet 4b are provided to face each other. The stator coil 4 a is attached to the outer periphery of the bracket 5, and the rotor magnet 4 b is attached to the inner periphery of the disk hub 3. The housing 7 of the hydrodynamic bearing device 1 is mounted on the inner periphery of the bracket 5. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator coil 4a is energized, the rotor magnet 4b is rotated by the electromagnetic force between the stator coil 4a and the rotor magnet 4b, whereby the disk hub 3 and the shaft member 2 are rotated together.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a shaft member 2, a bearing sleeve 8 as a bearing component according to the present invention in which the shaft member 2 is accommodated on the inner periphery, a housing 7 in which the bearing sleeve 8 is disposed on the inner periphery, and a housing 7 A seal member 9 that seals one end opening of the housing 7 and a lid member 10 that seals the other end opening of the housing 7 are provided as main components. In the following description, for convenience of description, the description will be made with the seal member 9 side as the upper side and the opposite side in the axial direction as the lower side.

  The shaft member 2 is formed of, for example, a metal material such as stainless steel, and includes a shaft portion 2a and a flange portion 2b provided integrally or separately at the lower end of the shaft portion 2a. The shaft member 2 may be entirely formed of a metal material, or may be a hybrid structure of metal and resin, for example, the entire flange portion 2b or a part thereof (for example, both end surfaces) made of resin.

  The bearing sleeve 8 is formed in a cylindrical shape by a porous body made of sintered metal, for example, a porous body of sintered metal mainly containing copper. On the inner peripheral surface 8a of the bearing sleeve 8, as a radial dynamic pressure generating portion, for example, a plurality of dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape as shown in FIG. It is formed in the area. The upper dynamic pressure grooves 8a1 and 8a2 are respectively hill portions 8a10 and 8a20 (shown by cross-hatching in FIG. 3A) extending in a herringbone shape on both sides in the axial direction from an annular (cylindrical surface) smooth portion. Formed between. The upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the annular smooth portion of the hill portion 8a10, and the axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region. (X1> X2). The axial region excluding the dynamic pressure grooves 8a1 and 8a2 and the hill portions 8a10 and 8a20 is formed to have the same outer diameter as the dynamic pressure grooves 8a1 and 8a2, and is continuous with the dynamic pressure grooves 8a1 and 8a2.

  A plurality of dynamic pressure grooves 8b1 arranged in a spiral shape as shown in FIG. 3B, for example, are formed on the lower end surface 8b of the bearing sleeve 8 as thrust dynamic pressure generating portions. The dynamic pressure groove 8b1 is formed between hill portions 8b10 (indicated by cross-hatching in FIG. 3B) extending in a spiral shape from an annular (hollow disk-shaped) smooth portion to the outer diameter side. The outer diameter end of the dynamic pressure groove 8b1 reaches the outer diameter end of the lower end face 8b.

  An annular groove 8c1 is formed at a substantially central portion in the radial direction of the upper end surface 8c of the bearing sleeve 8, and one or a plurality of radial grooves 8c2 are formed in a region on the inner diameter side of the annular groove 8c1. In the present embodiment, the radial grooves 8c2 are equally arranged at three locations in the circumferential direction.

  A concave portion 8d1 is formed in a partial region in the axial direction of the outer peripheral surface 8d of the bearing sleeve 8. When the material of the housing 7 enters the recess 8d1, it functions as a retainer. The shape, number, and formation location of the recess 8d1 are not limited as long as it functions as a retainer. For example, in the example shown in FIG. 3, three circumferentially equal intervals in the outer peripheral surface 8d are arranged in the tangential direction of the outer peripheral surface 8d. It is formed in a notch shape removed by laser processing (see FIG. 3B). In this case, since the recessed portion 8d1 formation region is melted by laser processing, the surface opening of the bearing sleeve 8 in this portion is sealed. When the shaft diameter is about 1 mm, the radial depth of the recess should be set to 0.1 mm or more and 0.5 mm or less in order to exert a sufficient anchor effect and maintain the strength of the bearing sleeve 8. Is preferred.

  In the bearing sleeve 8, axial through holes 11 are formed by, for example, laser processing. In this embodiment, as shown in FIG. 3B, the three through holes 11 are formed at equidistant positions in the circumferential direction. Yes. The through-holes 11 open to the outer diameter ends of the upper end surface 8c and the lower end surface 8b, respectively. In the present embodiment, the dynamic pressure groove 8b1 as the thrust dynamic pressure generating portion is formed to the outer diameter end of the lower end face 8b, and the through hole 11 opens at the outer diameter end of the dynamic pressure groove 8b1 forming portion. By forming the through-hole 11 by laser processing, the inner surface thereof is melted and the surface opening of the inner surface is sealed.

  The housing 7 is a substantially cylindrical shape and is a resin injection molded product using the bearing sleeve 8 as an insert part. As the base resin of the resin material used for the housing 7, either an amorphous resin or a crystalline resin can be used. Examples of the amorphous resin that can be used include polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), and polyetherimide (PEI). Examples of the crystalline resin that can be used include liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and the like. The above base resin can be added with a filler that imparts various properties thereto. The type of filler that can be used is not particularly limited. For example, fibrous fillers such as glass fibers, whisker-like fillers such as potassium titanate, scaly fillers such as mica, carbon fibers, and carbon black Fibrous or powdery conductive fillers such as graphite, carbon nanomaterial, and metal powder can be used. These fillers may be used alone or in combination of two or more. In addition to the resin, the housing 7 can be injection-molded with a low melting point metal such as an aluminum alloy. Alternatively, the housing 7 can also be formed by so-called MIM molding in which after the injection molding is performed with a mixture of a metal powder and a binder, degreasing and sintering are performed.

  The lid member 10 is formed in a disk shape with a metal material such as stainless steel or brass. On the upper end surface 10a of the lid member 10, although not shown, a plurality of dynamic pressure grooves arranged in a spiral shape are formed, for example.

  The seal member 9 is formed in a ring shape from a soft metal material such as brass, other metal materials, or a resin material, for example. The inner peripheral surface 9a of the seal member 9 faces the outer peripheral surface 2a1 of the shaft portion 2a via a predetermined seal space S. The outer diameter side region 9b1 of the lower end surface 9b of the seal member 9 is formed in a state of being slightly retreated upward in the axial direction from the inner diameter side region.

  The manufacturing process of the hydrodynamic bearing device 1 composed of the above-described components will be described below with a focus on the process of forming the bearing sleeve 8 and the housing 7.

  The bearing sleeve 8 is formed as follows. First, the metal sleeve is compacted into a predetermined shape and then sintered to form the bearing sleeve 8 with a rough dimensional accuracy. The bearing sleeve 8 is subjected to primary sizing to adjust its shape. As shown in FIG. 4, the primary sizing is performed by inserting the core rod 22 into the inner peripheral surface 8a of the bearing sleeve 8 and restraining the bearing sleeve 8 from above and below with the upper punch 23 and the lower punch 24. This is done by press-fitting the outer peripheral surface 8 d of the bearing sleeve 8 into the inner peripheral surface 21 a of the die 21. At this time, by pressing the outer peripheral surface 8 d of the bearing sleeve 8 in the inner diameter direction by the inner peripheral surface 21 a of the die 21, the inner peripheral surface 8 a of the bearing sleeve 8 is pressed against the perfect circular outer peripheral surface 22 a of the core rod 22 at the same time. The upper and lower end surfaces 8c and 8b of the bearing sleeve 8 are pressed against the end surface 23a of the upper punch 23 and the end surface 24a of the lower punch 24, whereby the bearing sleeve 8 is finished to a predetermined dimensional accuracy.

  Next, the through hole 11 is formed in the bearing sleeve 8 by laser processing. Specifically, as shown in FIG. 5A, the bearing sleeve 8 is extrapolated to a stepped fixing pin 32 and the lower end surface 8b of the bearing sleeve 8 is brought into contact with the shoulder surface 32a of the fixing pin 32. In this state, the through hole 11 is formed by irradiating the upper end surface 8 c of the bearing sleeve 8 with the laser L from the laser irradiation device 33. At this time, the irradiation position of the laser L is set so that the lower end opening of the through hole 11 opens at the outer diameter end of the lower end surface 8 b of the bearing sleeve 8. Although not shown, a beam diameter adjusting means having a convex lens or a concave lens can be disposed between the laser irradiation device 33 and the bearing sleeve 8. By providing such a beam diameter adjusting means, the beam diameter can be easily adjusted according to the hole diameter of the through-hole 11 to be formed.

  The laser irradiation device 33 includes an excitation source such as a discharge lamp or a semiconductor laser, and irradiates a laser beam L from its tip toward the bearing sleeve 8, and is arranged so as to be able to irradiate a laser beam L parallel to the axis. Established. As the laser, various known lasers such as a carbon dioxide laser, a YAG laser, and a fiber laser can be used. Further, the irradiation method of the laser beam L in the laser irradiation device 33 may be either a continuous type or a pulse type.

  When one through hole 11 is formed, a partial region of the outer peripheral surface 8d of the bearing sleeve 8 is removed by laser processing while the fixed state is maintained, thereby forming a recess 8d1. In the present embodiment, as shown in FIG. 5B, the outer peripheral surface 8d of the outer peripheral surface 8d of the bearing sleeve 8 is placed by the laser irradiation device 34 at a symmetrical position across the center axis and the place where the through hole 11 is formed. A notch-like recess 8d1 is formed by irradiating the laser L from the tangential direction to remove a part of the bearing sleeve 8. Thus, if the recessed part 8d1 is made into the notch shape of a tangential direction, the recessed part 8d1 can be formed in the comparatively wide range in the circumferential direction in the state which fixed the bearing sleeve 8. FIG.

  After forming the through hole 11 and the recess 8d1 one by one, the bearing sleeve 8 and the laser irradiation device 33 are rotated relative to each other by 120 ° in the circumferential direction, and the through hole is formed at another position of the bearing sleeve 8 in the same manner as described above. 11 and the recess 8d1 are formed. Thereafter, the bearing sleeve 8 and the laser irradiation device 33 are further rotated relative to each other by 120 ° in the circumferential direction to form the through hole 11 and the concave portion 8d1 at different locations. As a result, the through holes 11 are formed at three positions in the circumferential direction at equally spaced positions, and the recesses 8 d 1 are formed at the circumferential intermediate portion of each through hole 11. In this way, by making the circumferential positions of the through hole 11 and the recess 8d1 different, a situation in which the thickness of the bearing sleeve 8 is locally reduced can be avoided, and a decrease in the strength of the bearing sleeve 8 can be prevented. Note that the method of forming the plurality of through holes 11 and the recesses 8d1 is not limited to this, and for example, a laser irradiation apparatus that can irradiate a plurality of laser beams L by disposing the laser irradiation apparatus 33 at a plurality of locations in the circumferential direction. It is also possible to form a plurality of through holes 11 and recesses 8d1 at the same time.

  Next, groove sizing is performed on the bearing sleeve 8, and dynamic pressure grooves are formed on the inner peripheral surface 8a and the lower end surface 8b. This groove sizing is performed using a die 41, a core rod 42, and upper and lower punches 43 and 44 as shown in FIG. Forming dies 42a1 and 42a2 for forming dynamic pressure grooves 8a1 and 8a2 (see FIG. 3A) on the inner peripheral surface 8a of the bearing sleeve 8 are formed on the outer peripheral surface 42a of the core rod 42. The molds 42a1 and 42a2 are formed of recesses corresponding to the shapes of the hill portions 8a10 and 8a20 shown by cross hatching in FIG. Further, a molding die 44a1 (shown by a dotted line in FIG. 6) for forming a dynamic pressure groove 8b1 (see FIG. 3B) is formed on the lower end surface 8b of the bearing sleeve 8 on the end surface 44a of the lower punch 44. Is done. The molding die 44a1 is configured by a concave portion corresponding to the shape of the hill portion 8b10 shown by cross hatching in FIG.

  In the groove sizing, the core sleeve 42 is inserted into the inner periphery of the bearing sleeve 8 and the bearing sleeve 8 is restrained by the upper punch 43 and the lower punch 44 from above and below in the same manner as the primary sizing described above. It is done by press-fitting into. At this time, the inner peripheral surface 8a of the bearing sleeve 8 is pressed against the molding dies 42a1 and 42a2 of the outer peripheral surface 42a of the core rod 42 by the pressing force from the die 41, thereby forming the molding die 42a1 against the inner peripheral surface 8a of the bearing sleeve 8. , 42a2 is transferred, and dynamic pressure grooves 8a1 and 8a2 are formed. At the same time, the lower end surface 8b of the bearing sleeve 8 is pressed against a forming die 44a1 formed on the end surface 44a of the lower punch 44, whereby a dynamic pressure groove 8b1 is formed in the lower end surface 8b of the bearing sleeve 8.

  The bearing sleeve 8 shown in FIG. 3 is completed by forming the dynamic pressure grooves 8a1, 8a2, and 8b1 as described above and then washing them. In the above description, the annular groove 8c1 and the radial groove 8c2 formed in the upper end surface 8c of the bearing sleeve 8 are omitted, but these are, for example, the above-described dust forming process, primary sizing process, or In any one of the groove sizing steps, the mold can be formed by providing a molded part corresponding to the annular groove 8c1 and the radial groove 8c2 and pressing the molded part against the upper end surface 8c.

  As described above, by forming the through-hole 11 after the primary sizing process, the outer peripheral surface 32a of the fixing pin 32 is fitted to the inner peripheral surface 8a of the bearing sleeve 8 whose dimensional accuracy is improved in the primary sizing process. By doing so, the bearing sleeve 8 can be accurately positioned. By forming the through hole 11 in this state, the formation accuracy of the through hole 11 can be increased. The manufacturing process of the bearing sleeve 8 is not limited to the above. For example, if the formation accuracy of the through hole 11 can be sufficiently secured, the through hole 11 is formed before the primary sizing process or after the groove sizing process. May be.

  Next, a process of injection molding the housing 7 using the bearing sleeve 8 as an insert part will be described. For example, as shown in FIG. 7, the mold used in this step includes a fixed mold 51 and a movable mold 52, and both molds 51, 52 constitute a cavity 53 corresponding to the shape of the housing 7. The fixed mold 51 is provided with a gate 54 for injecting the molten resin P into the cavity 53. As the gate 54 shape, an arbitrary shape corresponding to the shape of the housing 7 to be molded can be selected. In addition, the gate 54 of this embodiment is provided in three places of the circumferential direction equal intervals. In this way, by providing the gates at a plurality of positions at equal intervals in the circumferential direction, the material can be injected evenly into the cavity, so that the bearing sleeve 8 is deformed unevenly due to injection pressure, resin molding shrinkage, or the like. The situation can be prevented. A fixed pin 55 is provided on the axis of the movable mold 52. The bearing sleeve 8 is fitted to the outer periphery 55 a of the fixed pin 55 with a fit that restricts movement in the radial direction, and is in contact with the end surface 55 b of the movable mold 52, thereby being positioned with respect to the movable mold 52. The In this state, the movable mold 52 is brought close to the fixed mold 51 and clamped.

  After completing the mold clamping, the molten resin P is injected and filled into the cavity 53 through the gate 54, and the housing 7 is molded integrally with the bearing sleeve 8. At this time, the injection material also enters the recess 8d1 formed in the outer peripheral surface 8d of the bearing sleeve 8. On the other hand, the openings of the through holes 11 opened on both end faces 8b and 8c of the bearing sleeve 8 are sealed by the end face 51a of the fixed mold 51 and the end face 52a of the movable mold 52 and separated from the cavity 53. 11 does not enter the molten resin. When mold opening is performed after completion of solidification of the molten resin P, an integrated product of the housing 7 and the bearing sleeve 8 is obtained.

  The shaft member 2 is inserted into the inner periphery of the integrated product of the housing 7 and the bearing sleeve 8 manufactured as described above, and the seal member 9 and the lid member 10 are bonded and press-fitted to the upper end opening and the lower end opening of the housing 7, respectively. Fix by appropriate means. Thereafter, the internal space of the bearing sealed by the seal member 9 is filled with lubricating oil including the internal holes of the bearing sleeve 8 and the through holes 11 to complete the hydrodynamic bearing device 1 shown in FIG.

  In the hydrodynamic 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. Then, the pressure of the oil film in the radial bearing gap is increased by the dynamic pressure action of the dynamic pressure grooves 8a1 and 8a2 formed on the inner peripheral surface 8a of the bearing sleeve 8, and the shaft member 2 can be rotated in the radial direction by this pressure. Non-contact supported. As a result, the first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft member 2 in a non-contact manner so as to be rotatable in the radial direction are formed.

  When the shaft member 2 rotates, a thrust bearing gap is formed between the lower end surface 8b of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b, and the upper end surface 10a of the lid member 10 and the flange portion 2b A thrust bearing gap is formed between the lower end surface 2b2. And the pressure of the oil film formed in each thrust bearing gap by the dynamic pressure action of the dynamic pressure groove 8b1 formed on the lower end surface 8b of the bearing sleeve 8 and the dynamic pressure groove formed on the upper end surface 10a of the lid member 10 The shaft member 2 is supported in a non-contact manner so as to be rotatable in both thrust directions by this pressure. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which support the shaft member 2 in a non-contact manner so as to be rotatable in both thrust directions are formed.

  In addition, when the shaft member 2 rotates, as described above, since the seal space S has a tapered shape that gradually decreases toward the inner side of the bearing, the lubricating oil in the seal space S is pulled by a capillary force. Then, the seal space is drawn toward the narrowing direction, that is, toward the inner side of the bearing. This effectively prevents leakage of the lubricating oil from the inside of the bearing. Further, the seal space S has a buffer function that absorbs a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the bearing, and the oil level of the lubricating oil is within a range of assumed condition changes. Always in the seal space S.

  Further, the upper dynamic pressure groove 8a1 is formed axially asymmetric with respect to the annular smooth portion formed in the central portion in the axial direction, and the axial dimension X1 of the upper region from the annular smooth portion is the axis of the lower region. It is larger than the directional dimension X2 (X1> X2). Therefore, when the shaft member 2 rotates, the lubricating oil pulling force (pumping force) by the dynamic pressure groove 8a1 is relatively larger in the upper region than in the lower region. Then, due to the differential pressure of the pulling force, the lubricating oil filled in the radial bearing gap is pushed downward, and the thrust bearing gap of the first thrust bearing portion T1 → the through hole 11 → the outside of the lower end surface 9b of the seal member 9 Circulating an annular gap between the radial region 9b1 and the upper end face 8c of the bearing sleeve 8 → an annular groove 8c1 on the upper end face 8c of the bearing sleeve 8 → a radial groove 8c2 on the upper end face 8c of the bearing sleeve 8; It is again drawn into the radial bearing gap of the first radial bearing portion R1.

  In this way, by configuring the lubricating oil to flow and circulate in the internal space of the bearing, the phenomenon that the pressure of the lubricating oil in the internal space becomes a negative pressure locally can be prevented, and bubbles accompanying the generation of negative pressure can be prevented. Problems such as leakage of lubricating oil, deterioration of bearing performance, generation of vibration, and the like due to generation of bubbles and generation of bubbles can be solved. In addition, even if bubbles are mixed in the lubricating oil for some reason, when the bubbles circulate with the lubricating oil, it is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal space S to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  In particular, as shown in FIG. 2, the through-hole 11 is opened at the outer diameter end portion of the lower end surface 8b (thrust dynamic pressure generating portion forming region) of the bearing sleeve 8 to thereby provide a thrust bearing for the first thrust bearing portion T1. Since the lubricating oil can be circulated in the entire area of the gap, the generation of negative pressure around the first thrust bearing portion T1 can be more reliably prevented.

  Further, when the thrust dynamic pressure generating portion is a pump-in type spiral dynamic pressure groove 8b1 as in the present embodiment, the pressure is at the inner diameter end of the dynamic pressure groove 8b1 formation region (annular smooth portion of the hill portion 8b10). Is the highest, and the pressure is lowest at the outer diameter end. Therefore, by forming the through hole 11 at the outer diameter end of the lower end surface 8b, it is possible to avoid a situation in which the lubricating oil whose pressure has been increased passes through the through hole 11 and deteriorates the bearing performance.

  In addition, a surface opening made of sintered metal is formed on the inner surface of the through hole 11. In the present invention, since the through hole 11 is formed by laser processing, the inner surface of the through hole 11 is melted by laser processing. The surface opening is sealed. For this reason, when the lubricating oil inside the bearing circulates due to the rotation of the shaft member 2, the lubricating oil flowing inside the through hole 11 is prevented from escaping from the surface opening of the inner surface of the through hole 11 into the bearing sleeve 8, and the efficiency. Lubricating oil can be circulated well.

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

  In the above embodiment, the recess formed in the outer peripheral surface 8d of the bearing sleeve 8 forms a notch shape in which the outer peripheral surface 8d is removed in the tangential direction, but the shape of the recess is not limited thereto. For example, as shown in FIG. 8, the outer peripheral surface 8d of the bearing sleeve 8 may be irradiated with a laser L obliquely from above to form a recess 8d1 inclined downward toward the inner diameter. By allowing the material of the housing 7 to enter the oblique recess 8d1, an excellent anchor effect can be exhibited. In addition, for example, a large number of concave portions may be formed in the dimple shape on the outer peripheral surface of the bearing sleeve, or an annular concave portion may be formed on the entire outer peripheral surface by irradiating the laser while rotating the bearing sleeve. (Not shown). Further, if there is no problem of mixing with cutting powder or deformation due to chuck fixing, the recess 8d1 can be formed by machining.

  Moreover, in the above embodiment, although the case where the housing 7 is injection-molded by using the bearing sleeve 8 as an insert part is shown, it is not limited to this. For example, although not shown, a housing having a cylindrical inner peripheral surface and a bearing sleeve may be separately formed, and these may be bonded and fixed. In this case, a recess formed in a partial region in the axial direction of the outer peripheral surface of the bearing sleeve serves as an adhesive reservoir, and the fixing force of both members is enhanced.

  Further, in the above embodiment, the through hole 11 opens at the outer diameter end portion of the lower end surface 8b of the bearing sleeve 8 and on the inner diameter side of the outer peripheral chamfer. A part of the opening 11 may be on the outer peripheral chamfer of the lower end face 8b. In this case, dross or the like due to the formation of the through hole 11 may adhere to the outer chamfer, but the dross or the like in this portion does not face the thrust bearing gap, so that the bearing performance in the thrust direction is not deteriorated.

  Further, in the above embodiment, the herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed as the radial dynamic pressure generating portion. However, the present invention is not limited to this, and for example, a spiral-shaped dynamic pressure groove, a step bearing, or a multi-arc A bearing may be adopted. Or you may comprise what is called a perfect-circle bearing which provided both the outer peripheral surface 2a1 of the shaft member 2, and the inner peripheral surface 8a of the bearing sleeve 8 as a cylindrical surface, without providing a dynamic pressure generation | occurrence | production part.

  In the above embodiment, the spiral dynamic pressure groove is formed as the thrust dynamic pressure generating portion. However, the present invention is not limited to this. For example, the herringbone-shaped dynamic pressure groove, the step bearing, or the wave bearing (step It is also possible to adopt a wave type).

  In the above embodiment, the dynamic pressure generating portion is formed on the inner peripheral surface 8a of the bearing sleeve 8 and the upper end surface 10a of the lid member 10, but the surfaces facing each other through the bearing gap, that is, the shaft You may provide a dynamic-pressure generation | occurrence | production part in the outer peripheral surface 2a1 of the part 2a, and the lower end surface 2b2 of the flange part 2b.

  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, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and causes the hydrodynamic action in the radial bearing gap or the thrust bearing gap. In addition, a fluid capable of generating a dynamic pressure action, for example, a gas such as air, a magnetic fluid, or lubricating grease can be used.

  Further, the hydrodynamic bearing device having bearing parts manufactured by the method 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 a spindle motor for driving the magneto-optical disk of the optical disk, etc. It can also be suitably used as a small motor for information equipment used under high-speed rotation, a rotating shaft support in a polygon scanner motor of a laser beam printer, or a fan motor for a cooling fan of electric equipment.

  As shown in FIG. 2, the housing is injection-molded with a bearing sleeve having a recessed portion formed in a partial region of the outer peripheral surface as an insert part, and the housing is injected with a bearing sleeve having a cylindrical outer peripheral surface as an insert part. Prepared comparative products were prepared, and the removal force between the bearing sleeve and the housing was measured for each. As a result, the removal force of the comparative product was 60 N, while the removal force of the implementation product was 270 N. Thereby, it was confirmed by this invention that the extraction force of a bearing sleeve and a housing improves.

It is sectional drawing which shows the motor incorporating a dynamic pressure bearing apparatus. It is sectional drawing of a hydrodynamic bearing apparatus. (A) is sectional drawing of a bearing sleeve, (b) is a bottom view of a bearing sleeve. It is sectional drawing which shows the primary sizing process of a sintered compact. (A) is a longitudinal cross-sectional view which shows a mode that a through-hole is formed by laser processing, (b) is a top view which shows a mode that a recessed part is formed by laser processing. It is sectional drawing which shows the groove | channel sizing process of a sintered compact. It is sectional drawing which shows the injection molding process of a housing. It is a longitudinal cross-sectional view which shows the other example of a mode that a recessed part is formed in the outer peripheral surface of a bearing sleeve by laser processing.

Explanation of symbols

1 Fluid bearing device (dynamic pressure bearing device)
2 Shaft member 7 Housing 8 Bearing sleeve 8d1 Recess 11 Through hole 9 Seal member 10 Cover member 13 Laser irradiation device 32 Fixing pin L Laser R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space

Claims (8)

A radial bearing gap between the outer peripheral surface of the shaft member and the inner peripheral surface of the bearing sleeve, comprising: a shaft member; a sintered metal bearing sleeve having the shaft member inserted into the inner periphery; and a housing that accommodates the bearing sleeve. In the hydrodynamic bearing device that rotatably supports the shaft member with the fluid film generated in
A hydrodynamic bearing device, wherein a concave portion is formed by removing a partial region in the axial direction of the outer peripheral surface of the bearing sleeve.   The hydrodynamic bearing device according to claim 1, wherein the housing is injection molded using the bearing sleeve as an insert part.   The hydrodynamic bearing device according to claim 1, wherein the recess is formed by laser processing.   The hydrodynamic bearing device according to claim 1, wherein the recess is formed along a tangential direction of an outer peripheral surface of the bearing sleeve.   The hydrodynamic bearing device according to claim 1, wherein a through hole is formed in the bearing sleeve by laser processing.   The hydrodynamic bearing device according to claim 5, wherein the through hole and the concave portion are provided at different circumferential positions.   The hydrodynamic bearing device according to claim 5, wherein a thrust bearing surface is formed on an end surface of the bearing sleeve, and the through hole is opened at an outer diameter end of the thrust bearing surface.   The hydrodynamic bearing device according to claim 1, wherein a radial depth of the recess is 0.1 mm or more and 0.5 mm or less.

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