JP2009281464A - Fluid bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance fixing strength of a bearing sleeve and a housing and improve slip-off resisting force of the bearing sleeve. <P>SOLUTION: A tapered face 7a13 having a diameter reduced on the housing opening side is provided on the inner peripheral face 7a1 of the housing 7, and the outer peripheral face 8d of the bearing sleeve 8 is formed to have a shape of a tapered face having a diameter reduced on the housing opening side. Tapered fitting of these faces is performed. When stripping force is applied to the bearing sleeve 8, since the tapered face 7a13 of the housing 7 applies downward resistance to the outer peripheral face 8d of the bearing sleeve 8, movement of the bearing sleeve 8 to the housing opening side is regulated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrodynamic bearing device that rotatably supports a shaft member with a lubricating film generated in a radial 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, a hydrodynamic bearing device described in Patent Document 1 includes a shaft member having a shaft portion and a flange portion, a bearing sleeve having the shaft member inserted into the inner periphery, a bearing sleeve fixed to the inner peripheral surface, and one end thereof A housing that is open and has the other end closed, and a seal member that is fixed to the opening of the housing. The outer peripheral surface of the bearing sleeve and the inner peripheral surface of the housing are fixed by press-fitting or bonding.

  In this fluid dynamic bearing device, when the flange portion of the shaft member and the bearing sleeve are engaged in the axial direction, a force toward the housing opening is applied to the bearing sleeve. At this time, the pull-out strength of the bearing sleeve depends on the fixing strength between the bearing sleeve and the housing and the fixing strength between the seal member and the housing.

JP 2003-239974 A JP 2005-155912 A

  For example, in a hydrodynamic bearing device incorporated in a spindle motor for an HDD, the number of mounted disks tends to increase as the capacity of the HDD increases. As a result, the load applied to the hydrodynamic bearing device is increased, and the impact load applied to the axial engagement portion between the shaft member and the bearing sleeve is increased, so that an improvement in the fixing strength between the bearing sleeve and the housing is required. ing. In particular, in a hydrodynamic bearing device in which the seal member and the housing are not fixed (for example, Patent Document 2), the seal member cannot handle the pull-out strength of the shaft member, so that it is necessary to improve the fixing strength between the bearing sleeve and the housing. Become.

  An object of the present invention is to increase the fixing strength between a bearing sleeve and a housing of a hydrodynamic bearing device.

  In order to solve the above-described problems, the present invention provides a shaft member, a bearing sleeve having a shaft member inserted into an inner periphery, a housing having a bearing sleeve fixed to an inner peripheral surface, having one end opened and the other end closed. A hydrodynamic bearing device including a radial bearing portion that supports a shaft member in a radial direction with a lubricating film generated in a radial bearing gap between an outer peripheral surface of the shaft member and an inner peripheral surface of the bearing sleeve. A taper surface having a diameter reduced toward the housing opening side is provided on at least a part of the housing.

  As described above, in the hydrodynamic bearing device of the present invention, a tapered surface having a diameter reduced toward the housing opening side is provided on at least a part of the inner peripheral surface of the housing. In this case, for example, when the taper surface is brought into close contact with the outer peripheral surface of the bearing sleeve at least at the end portion of the housing opening side of the taper surface, a force (extraction force) for pulling the bearing sleeve from the housing is applied. The taper surface provides axial resistance to the bearing sleeve. With this resistance, the relative movement of the bearing sleeve toward the housing opening side can be restricted to increase the bearing sleeve's pull-out resistance. This effect can be obtained even more effectively by bringing the tapered surface into close contact with the outer peripheral surface of the bearing sleeve with a tightening margin. The “tapered surface reduced in diameter toward the housing opening side” means that the end portion Tp1 of the tapered surface Tp (thick line portion) is the opening end of the housing 7, as shown in FIGS. 14 (a) and 14 (b). It is not intended to be limited to the portion that reaches the portion 7f, and includes those in which the end portion Tp1 of the tapered surface Tp does not reach the opening end portion 7f of the housing 7, as shown in FIGS. 14 (c) and 14 (d). (The same applies to a tapered surface formed on a sleeve described later).

  Further, depending on the outer peripheral surface shape of the bearing sleeve (for example, a cylindrical surface shape), a gap may be formed between the tapered surface on the inner periphery of the housing and the outer peripheral surface of the bearing sleeve. If this gap is used as an adhesive reservoir, it is possible to further improve the pull-out resistance of the bearing sleeve.

  On the other hand, you may form the taper surface diameter-reduced toward the housing opening side in at least one part of the outer peripheral surface of a bearing sleeve. In this case, if the taper surface is brought into close contact with the inner peripheral surface of the housing at the end of the taper surface at the housing opening side, an axial drag is applied from the housing to the bearing sleeve, thereby allowing the bearing sleeve to pull out. Can be improved. On the other hand, when a gap is formed between the inner peripheral surface of the housing and the taper surface of the outer periphery of the bearing sleeve, this gap can also be used as an adhesive reservoir. Yield can be improved.

  Further, if a tapered surface having a reduced diameter on the housing opening side is provided on the inner peripheral surface of the housing, and a tapered surface having a reduced diameter on the housing opening side is provided on the outer peripheral surface of the bearing sleeve, the bearing sleeve from the housing is provided. Since the taper surfaces are taper-fitted in a direction in which the slippage of the bearing sleeve is restricted, the slippage resistance of the bearing sleeve can be improved. If the taper surfaces are brought into close contact with each other with a tightening margin at least at the end portion on the housing opening side of the fitting portions of both the taper surfaces, it is possible to further increase the proof stress.

  By the way, as shown in FIG. 15A, the inner peripheral surface 107a of the housing 107 and the inner peripheral surface 108a of the bearing sleeve 108 are both formed into a cylindrical surface, and these are press-fitted and fixed with an adhesive interposed therebetween. The following problems may occur. That is, when the bearing sleeve 108 is press-fitted from the opening side of the inner peripheral surface 107 a of the housing 107 with the adhesive G applied to the inner peripheral surface 107 a of the housing 107 in advance, the housing 107 The adhesive G applied to the inner peripheral surface 107a is captured. As a result, when the bearing sleeve 108 is inserted to a predetermined position, the adhesive G may wrap around one end face 108b of the bearing sleeve 108 as shown in FIG. As described above, when the adhesive G wraps around the end surface 108b of the bearing sleeve 108, the adhesive G present on the fixing surface between the bearing sleeve 108 and the housing 107 decreases, and the fixing strength thereof decreases. Further, when the end surface 108b of the bearing sleeve 108 faces the flange portion of the shaft member, the wraparound adhesive G may come into contact with the flange portion, and support for the operation of the bearing may occur.

  Such wraparound of the adhesive G can be avoided by providing a tapered surface having a diameter reduced on the housing opening side on the inner peripheral surface of the housing. In this case, when the bearing sleeve is pushed to the inner periphery of the housing with the adhesive applied to the inner peripheral surface of the housing, the outer peripheral surface of the bearing sleeve at the end of the housing closing side when the bearing sleeve passes through the tapered surface. Since the gap between the taper and the taper surface on the inner periphery of the housing gradually increases, the adhesive can be captured by this gap and the wraparound of the adhesive to the end surface of the bearing sleeve can be avoided. Similarly, the adhesive G can also be formed by forming a tapered surface in which the diameter of the housing opening is reduced on the outer peripheral surface of the bearing sleeve and press-fitting the inner periphery of the housing with an adhesive applied to the outer peripheral surface of the bearing sleeve. Can be prevented.

  In this fluid dynamic bearing device, if an adhesive reservoir is interposed between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve, the fixing strength of both can be further increased. Further, if a plurality of axial grooves are formed on the inner peripheral surface of the housing in the axial direction, and a groove on the housing closing side is provided near the housing closing side end surface of the bearing sleeve, the bearing When the sleeve is inserted into the inner periphery of the housing, the adhesive trapped at the end face of the bearing sleeve can be held by the annular groove, so that it is possible to prevent the adhesive from wrapping around more reliably.

  When the bearing sleeve is formed in an asymmetric shape in the axial direction, it must be fixed to the housing in a predetermined direction. For example, when a tapered surface is formed on the bearing sleeve by reducing the diameter of the housing opening side, it is necessary to fix the tapered surface so that the small diameter side of the tapered surface is the housing opening side. However, the taper surface of the bearing sleeve is often formed with a slight diameter difference, and in this case, it is difficult to confirm the direction of diameter reduction of the taper surface with the naked eye. Therefore, if the dynamic pressure generating portion is formed on the end surface of the bearing sleeve, the assembly direction of the bearing sleeve to the housing can be easily confirmed using the dynamic pressure generating portion as a mark.

  As described above, according to the present invention, it is possible to increase the fixing strength between the bearing sleeve and the housing, and to improve the slip-off resistance of the bearing sleeve.

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

  FIG. 1 conceptually shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 1 according to an embodiment of the present invention. This spindle motor is used for a disk drive device such as an HDD, and has 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. And a stator magnet 4 and a rotor magnet 5 which are opposed to each other. 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 housing 7 of the hydrodynamic bearing device 1 is attached to the inner periphery of the bracket 6. The disk hub 3 holds one or more disks D such as magnetic disks. When the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force between the stator coil 4 and the rotor magnet 5, whereby the disk hub 3 and the shaft member 2 are rotated together.

  A hydrodynamic bearing device 1 shown in FIG. 2 seals a shaft member 2, a housing 7 having one end opened and the other end closed, a bearing sleeve 8 fixed to the inner periphery of the housing 7, and an opening of the housing 7. The sealing member 9 to be used is a main component. In the following description, for convenience of explanation, the description will proceed with the opening side of the housing 7 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 flange portion 2b faces the lower end surface 8b of the bearing sleeve 8 in the axial direction. The flange portion 2b and the bearing sleeve 8 engage in the axial direction, thereby preventing the shaft member 2 from coming off. 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 with a porous material, for example, a sintered metal mainly composed of copper (or copper and iron). In addition, it is also possible to form the bearing sleeve 8 with another metal material that is not a porous body, for example, a soft metal such as brass.

  The inner peripheral surface 8a of the bearing sleeve 8 is provided with two upper and lower regions (black portions in FIG. 2) which are radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2 and are separated in the axial direction. In these two regions, for example, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 as shown in FIG. 3 are formed. The upper dynamic pressure groove 8a1 is formed to be axially asymmetric with respect to the belt-like portion at the central portion in the axial direction of the hill (shown by cross-hatching in FIG. 3), and the axial dimension X1 of the upper region from the belt-like portion is It is larger than the axial dimension X2 of the lower region. The dynamic pressure groove can also be formed on the outer peripheral surface 2a1 of the shaft portion 2a.

  The lower end surface 8b of the bearing sleeve 8 is provided with a region (blacked portion in FIG. 2) that becomes the thrust bearing surface of the first thrust bearing portion T1, and this region is omitted in illustration, for example in a spiral shape. A plurality of arranged dynamic pressure grooves are formed. Thus, by forming the dynamic pressure groove in one of the bearing sleeves 8, it is possible to confirm the top and bottom of the bearing sleeve 8, so that the top and bottom of the bearing sleeve 8 may be erroneously inserted into the housing 7 during assembly. It can be avoided.

  The outer peripheral surface 8d of the bearing sleeve 8 is formed in a tapered surface shape whose diameter is reduced upward. The outer peripheral surface 8d is formed with one or a plurality of axial grooves 8d10 that allow the both end surfaces 8b and 8c to communicate with each other. In the present embodiment, the axial grooves 8d10 are equally distributed at three locations in the circumferential direction. In the drawings, the inclination angle of the outer peripheral surface 8d is exaggerated for easy understanding.

  The housing 7 includes a cylindrical small-diameter portion 7a, a cylindrical large-diameter portion 7b disposed above the small-diameter portion 7a, and a bottom portion 7c that seals the lower end opening of the small-diameter portion 7a. ˜7c are integrally formed. The inner peripheral surface 7a1 and the outer peripheral surface 7a4 of the small diameter portion 7a are formed with a smaller diameter than the inner peripheral surface 7b1 and the outer peripheral surface 7b2 of the large diameter portion 7b, respectively. The inner peripheral surface of the small-diameter portion 7a and the inner peripheral surface 7b1 of the large-diameter portion 7b are continuous with a step surface 7e formed in a flat surface shape in a direction orthogonal to the axial direction.

  As shown in FIG. 4, the inner peripheral surface 7a1 of the small-diameter portion 7a has an upper cylindrical surface 7a11, a tapered guide surface 7a12 that gradually increases in diameter upward, and upward (toward the opening side of the housing 7). A tapered surface 7a13 (indicated by a thick line) and a lower cylindrical surface 7a14 that are gradually reduced in diameter are provided. The upper cylindrical surface 7a11 and the lower cylindrical surface 7a14 are formed to have the same diameter. An adhesive reservoir is interposed between the inner peripheral surface 7a1 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8. In this embodiment, an annular groove 7a10 formed between the guide surface 7a12 and the tapered surface 7a13 in the axial direction. Functions as an adhesive reservoir. The annular groove 7a10 is provided slightly above the central portion in the axial direction on the inner peripheral surface 7a1 of the small diameter portion 7a. A bearing sleeve 8 is fixed to the inner peripheral surface 7a1 of the small diameter portion 7a. Specifically, an adhesive is interposed between the tapered surface 7a13 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 and in the annular groove 7a10. Thus, the taper surface 7a13 and the outer peripheral surface 8d of the bearing sleeve 8 are in close contact with each other with a tightening margin. 4 indicates the inner peripheral surface 7a1 'of the housing 7 before the bearing sleeve 8 is inserted, and the diameter difference between the dotted line 7a1' and the solid line 7a1 is a tightening margin. In the drawings, the inclination angles of the guide surface 7a12 and the tapered surface 7a13 are exaggerated for easy understanding.

  The inner bottom surface 7c1 of the bottom portion 7c of the housing 7 is provided with a region (blacked portion in FIG. 2) that becomes the thrust bearing surface of the second thrust bearing portion T2. A plurality of dynamic pressure grooves arranged in a shape are formed.

  The housing 7 having the above configuration is injection-molded with resin. In order to prevent deformation due to the difference in shrinkage during molding shrinkage, the portions 7a to 7c of the housing 7 are formed to have a substantially uniform thickness.

  The resin forming the housing 7 is mainly a thermoplastic resin. For example, as the amorphous resin, polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI) As the crystalline resin, liquid crystal polymer (LCP), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or the like can be used. In addition, as a filler, for example, fiber filler such as glass fiber, whisker filler such as potassium titanate, scaly filler such as mica, carbon fiber, carbon black, graphite, carbon nanomaterial A fibrous or powdery conductive filler such as metal powder can be used. These fillers may be used alone or in combination of two or more.

  The seal member 9 is made of, for example, a soft metal material such as brass, or other metal material, or a resin material used for molding the housing 7 described above, and the disc-shaped first seal portion 9a and the outside of the first seal portion 9a. The cylindrical second seal portion 9b projecting downward from the radial side is integrally formed with an inverted L-shaped cross section. A first seal space S1 having a predetermined volume is formed between the inner peripheral surface 9a2 of the first seal portion 9a and the outer peripheral surface 2a1 of the shaft portion 2a. Further, the outer peripheral surface 9 b 1 of the second seal portion 9 b forms a second seal space S 2 having a predetermined volume with the inner peripheral surface 7 b 1 of the large diameter portion 7 b constituting the housing 7. In the present embodiment, the inner peripheral surface 9a2 of the first seal portion 9a and the inner peripheral surface 7b1 of the large-diameter portion 7b of the housing 7 are both formed in a tapered surface shape whose diameter is enlarged upward, and therefore the first and first The two seal spaces S1, S2 have a tapered shape that gradually decreases downward.

  As shown in FIG. 5, one or a plurality of radial grooves 10 that cross the lower end surface 9a1 are formed in the lower end surface 9a1 of the first seal portion 9a. In this embodiment, the radial grooves 10 are equally distributed at three places in the circumferential direction as shown in FIG.

  In the hydrodynamic bearing device 1 composed of the above-described constituent members, the shaft member 2 is accommodated in the housing 7, the bearing sleeve 8 is fixed to the inner periphery of the housing 7, and the seal member 9 is fixed to the bearing sleeve 8. Can be assembled. Hereinafter, a method of fixing the housing 7 and the bearing sleeve 8 will be described with reference to FIGS. In these drawings, the shaft member 2 is omitted.

First, as shown in FIG. 7, the housing 7 and the bearing sleeve 8 are formed. Outer diameter d ₁ of the lower end surface 8b of the bearing sleeve 8, formed slightly smaller inner peripheral surface 7a1 upper cylindrical surface 7a11 and an internal diameter d ₂ whether same diameter of the lower cylindrical surface 7a14 of, or from which the housing 7 (D ₁ ≦ d ₂ ). For example, a thermosetting adhesive G is applied to the inner peripheral surface 7 a 1 of the housing 7. In the illustrated example, the adhesive G is applied to the annular groove 7a10 provided on the inner peripheral surface 7a1. In this state, the bearing sleeve 8 is inserted from the opening side of the housing 7.

  As shown in FIG. 8, the bearing sleeve 8 is inserted to the annular groove 7 a 10 while being guided by the guide surface 7 a 12 of the housing 7. When the insertion is further advanced, the bearing sleeve 8 is press-fitted into the tapered surface 7a13 while capturing a part of the adhesive G applied to the annular groove 7a10 at the lower end surface 8b of the bearing sleeve 8 (see FIG. 9). At this time, by pressing the bearing sleeve 8 while the adhesive G enters between the outer peripheral surface 8d of the bearing sleeve 8 and the tapered surface 7a13, the adhesive G functions as a lubricant, and press-fit is performed smoothly. be able to. In addition, since the adhesive G can be interposed between the outer peripheral surface 8d of the bearing sleeve 8 and the tapered surface 7a13 of the housing 7 as the bearing sleeve 8 is press-fitted, the fixing force between them can be increased. Of the guide surface 7a12 and the tapered surface 7a13, the region through which the lower end surface 8b of the bearing sleeve 8 passes is elastically restored following the shape of the outer peripheral surface of the bearing sleeve 8 and closely contacts the outer peripheral surface 8d with a margin.

  When the insertion is further advanced and the bearing sleeve 8 reaches a predetermined position, the insertion is stopped (see FIG. 10). At this time, the application amount of the adhesive G and the press-fitting allowance between the housing 7 and the bearing sleeve 8 may be set as appropriate so that the adhesive G does not enter the lower end surface 8 b of the bearing sleeve 8. Thereafter, the adhesive G interposed between the annular groove 7a10 and the tapered surface 7a13 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 is cured by heat treatment (baking), and both are fixed.

  After the bearing sleeve 8 is formed on the inner periphery of the housing 7 as described above, the seal member 9 is fixed to the upper end of the outer periphery of the bearing sleeve 8 by appropriate means such as adhesion, press-fitting, and press-fitting adhesion. When the assembly of the seal member 9 is completed, the lower end surface 9a1 of the first seal portion 9a constituting the seal member 9 comes into contact with the upper end surface 8c of the bearing sleeve 8, and the lower end surface of the second seal portion 9b is a predetermined axis. It faces the stepped surface 7e of the housing 7 through the directional gap 11. At the same time, a first seal space S1 is formed between the inner peripheral surface 9a2 of the first seal portion 9a and the outer peripheral surface 2a1 of the shaft portion 2a, and within the outer peripheral surface 9b1 of the second seal portion 9b and the large-diameter portion of the housing 7. A second seal space S2 is formed between the peripheral surface 7b1. Thereafter, the internal space of the housing 7 sealed with the seal member 9 is filled with lubricating oil including the internal pores of the bearing sleeve 8, whereby the hydrodynamic bearing device 1 shown in FIG. 2 is completed.

  When the shaft member 2 is rotated, the upper and lower two regions serving as the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 are opposed to the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gap. Further, the region that becomes the thrust bearing surface of the lower end surface 8b of the bearing sleeve 8 faces the upper end surface 2b1 of the flange portion 2b via the thrust bearing gap, and the region that becomes the thrust bearing surface of the inner bottom surface 7c1 of the housing 7 is It faces the lower end surface 2b2 of the flange portion 2b through a thrust bearing gap. As the shaft member 2 rotates, the dynamic pressure of the lubricating oil is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 is rotated in the radial direction by the lubricating oil film formed in the radial bearing gap. It is supported non-contact freely. Thus, 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 configured. At the same time, the dynamic pressure of the lubricating oil is generated in the thrust bearing gap, and the shaft member 2 is supported in a non-contact manner rotatably in the thrust direction by the lubricating oil film formed in the thrust bearing gap. Thereby, the 1st thrust bearing part T1 and 2nd thrust bearing part T2 which non-contact-support the shaft member 2 so that rotation in both thrust directions is possible are comprised.

  Further, when the shaft member 2 is rotated, as described above, the first and second seal spaces S1 and S2 have a tapered shape that is gradually reduced toward the inner side of the housing 7, and thus both the seal spaces S1. The lubricating oil in S2 is drawn toward the direction in which the seal space becomes narrow, that is, toward the inside of the housing 7, by the drawing action by the capillary force. Thereby, the leakage of the lubricating oil from the inside of the housing 7 is effectively prevented. Further, the seal spaces S1 and S2 have a buffer function of absorbing a volume change amount accompanying a temperature change of the lubricating oil filled in the internal space of the housing 7, and within the range of the assumed temperature change, The oil level is always in the seal space S1, S2.

  In addition, while the inner peripheral surface 9a2 of the first seal portion 9a is a cylindrical surface, the outer peripheral surface of the shaft portion 2a facing this may be a tapered surface. In this case, the first seal space S1 further includes Since the function as a centrifugal force seal can also be provided, the sealing effect is further enhanced.

  Further, as described above, the upper dynamic pressure groove 8a1 is formed to be axially asymmetric, and the axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region than the belt-like portion of the hill. (See FIG. 3). 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 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 The radial passage of the first radial bearing portion R1 is circulated through a path of thrust bearing clearance → fluid passage formed by the axial groove 8d10 of the bearing sleeve 8 → fluid passage formed by the radial groove 10 of the first seal portion 9a. It is pulled back into the bearing gap.

  In this way, by configuring the lubricating oil to flow and circulate in the internal space of the housing 7, the pressure balance of the lubricating oil is maintained, and at the same time, the generation of bubbles accompanying the generation of local negative pressure, Problems such as leakage of lubricating oil and generation of vibration due to generation can be solved. When the first seal space S1 communicates with the circulation path, and the second seal space S2 communicates with the axial clearance 11, the bubbles are mixed into the lubricating oil for some reason. However, when the bubbles circulate with the lubricating oil, the air is discharged from the oil surface (gas-liquid interface) of the lubricating oil in the seal spaces S1 and S2 to the outside air. Therefore, adverse effects due to air bubbles can be more effectively prevented.

  Although illustration is omitted, the axial fluid passage can be formed by providing an axial groove on the inner peripheral surface of the housing 7, and the radial fluid passage is radially formed on the upper end surface 8 c of the bearing sleeve 8. It can also be formed by providing a groove.

  When an upward load is applied to the shaft member 2 of the fluid dynamic bearing device 1 as described above, the upper end surface 2b1 of the flange portion 2b of the shaft member 2 and the lower end surface 8b of the bearing sleeve 8 are engaged with each other. Load (extraction force) toward the housing opening side is applied. At this time, as described above, the tapered surface 7a13 is provided on the inner peripheral surface 7a1 of the housing 7, and the outer peripheral surface 8d of the bearing sleeve 8 is formed into a tapered surface. Accordingly, a downward drag (housing closing side) is applied to the bearing sleeve 8 from the tapered surface 7a13 of the housing 7. As a result, the movement of the bearing sleeve 8 toward the housing opening is restricted, and the slip-off resistance of the bearing sleeve 8 is increased. Further, in the present embodiment, the adhesive force is further interposed between the annular groove 7a10 and the tapered surface 7a13 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8, whereby the fixing force between the two is further increased. In particular, as shown in FIG. 2, when the second seal space S2 is formed on the outer diameter side of the bearing sleeve 8, the fixed area between the bearing sleeve 8 and the housing 7 is reduced. It is desirable to increase the fixing strength with the sleeve 8.

If the difference in diameter between the upper end portion and the lower end portion of the tapered surface 7a13 of the housing 7 is too small, the above effect cannot be obtained. If it is too large, the inner peripheral surface 7a1 of the housing 7 may be plastically deformed. Therefore, it is preferable that the diameter difference is set in the range of 2 to 50 μm, preferably in the range of 5 to 30 μm.

  Further, in the hydrodynamic bearing device 1 of the present embodiment, a seal space is formed not only on the inner peripheral side of the seal member 9 but also on the outer peripheral side. The seal space has a volume capable of absorbing a volume change amount due to a temperature change of the lubricating oil filled in the internal space of the housing 7, and therefore the second seal space S2 has the configuration of this embodiment. The axial dimension of the first seal space S1 can be made smaller than that of the configuration shown in FIG. Therefore, for example, the axial length of the bearing sleeve 8 without increasing the axial dimension of the bearing device (housing 7), in other words, the bearing span between the radial bearing portions R1 and R2, than the configuration shown in FIG. The moment rigidity can be increased. Also from this point, it becomes possible to cope with the multi-stacking of disks.

  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 in the above embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the above embodiment, the tapered surface 7a13 is formed in advance on the inner peripheral surface 7a1 of the housing 7, and the reduced diameter portion (outer peripheral surface 8d) of the bearing sleeve 8 is press-fitted into the tapered surface 7a13. Absent. For example, as shown by a dotted line in FIG. 11, a cylindrical surface 7a13 ′ is provided on the inner peripheral surface 7a1 of the housing 7, and the tapered outer peripheral surface 8d of the bearing sleeve 8 is press-fitted into the cylindrical surface 7a13 ′. The inner peripheral surface can be made to follow the shape of the outer peripheral surface of the bearing sleeve 8, whereby the tapered surface 7 a 13 can be formed on the housing 7.

  In addition, as shown in FIG. 11, a plurality of annular grooves serving as adhesive reservoirs may be formed at a plurality of locations in the axial direction on the inner peripheral surface 7 a 1 of the housing 7. At this time, the lower annular groove 7a15 is preferably provided in the vicinity of the lower end surface 8b of the bearing sleeve 8. In the illustrated example, the lower end portion of the annular groove 7 a 15 is disposed at the same position as the lower end portion of the outer peripheral surface 8 d of the bearing sleeve 8. As a result, when the bearing sleeve 8 is press-fitted into the inner peripheral surface 7a1 of the housing 7, the adhesive G captured by the lower end surface 8b of the bearing sleeve 8 can be held by the lower annular groove 7a15. The situation where the adhesive G wraps around the lower end surface 8b of the bearing sleeve 8 serving as the bearing surface can be reliably prevented.

  Moreover, in said embodiment, although the adhesive reservoir is comprised by the annular groove provided in the internal peripheral surface 7a1 of the housing 7, it is not restricted to this. For example, an annular groove may be provided on the outer peripheral surface 8 d of the bearing sleeve 8. Alternatively, annular grooves may be provided on both the inner peripheral surface of the housing 7 and the outer peripheral surface 8 d of the bearing sleeve 8. Further, the adhesive reservoir is not limited to the annular groove, and may be constituted by, for example, an annular groove that is partially cut off in the circumferential direction or a plurality of concave portions that are separated in the circumferential direction.

  In the above embodiment, both the housing 7 and the bearing sleeve 8 are provided with tapered surfaces. However, the present invention is not limited to this, and either one may be provided with a tapered surface. For example, in the embodiment shown in FIG. 12, the outer peripheral surface 8d of the bearing sleeve 8 is provided in a cylindrical surface shape. In this case, a space P1 is formed between the tapered surface 7a13 of the housing 7 and the cylindrical outer peripheral surface 8d of the bearing sleeve 8 with the radial dimension gradually enlarged downward. Since the space P1 functions as an adhesive reservoir, the fixing strength between the housing 7 and the bearing sleeve 8 can be increased. Further, when the bearing sleeve 8 is inserted into the inner periphery of the housing 7, if the adhesive is applied to the taper surface 7a13 of the housing 7 in advance, the adhesive G can be captured in the space P1, so the bearing sleeve 8 can prevent the adhesive G from wrapping around the lower end surface 8b. Further, if a part of the taper surface 7a13 of the housing 7 is brought into close contact with the outer peripheral surface 8d of the bearing sleeve 8 with a tightening margin, the housing 7 can be slightly recessed toward the bearing sleeve 8 by this contact portion. Thereby, when an extraction force is applied to the bearing sleeve 8, the taper surface 7 a 13 gives a downward drag to the bearing sleeve 8 at the close contact portion, and it is possible to increase the pull-out resistance of the bearing sleeve 8. In addition, such a space P1 is formed by forming the inner peripheral surface 7a1 of the housing 7 into a cylindrical surface and forming the outer peripheral surface 8d of the bearing sleeve 8 into a tapered surface gradually increasing in diameter upward. It can also be configured (not shown).

  In the embodiment shown in FIG. 13, the inner peripheral surface 7a1 of the housing 7 is formed in a cylindrical shape, and the outer peripheral surface 8d of the bearing sleeve 8 is tapered toward the upper side (opening side of the housing 7). Is formed. In this case, a space P2 is formed between the cylindrical inner peripheral surface 7a1 of the housing 7 and the tapered outer peripheral surface 8d (shown by a thick line) of the bearing sleeve 8 with the radial dimension gradually reduced downward. Since the space P2 functions as an adhesive reservoir, the fixing strength between the housing 7 and the bearing sleeve 8 can be increased. Further, when the bearing sleeve 8 is inserted into the inner periphery of the housing 7, if the adhesive is applied to the outer peripheral surface 8d of the bearing sleeve 8 in advance, the adhesive G can be held in the space P2. It is possible to prevent the adhesive G from flowing into the lower end surface 8b of the sleeve 8. At this time, if the inner peripheral surface 7a1 of the housing 7 and the outer peripheral surface 8d of the bearing sleeve 8 are in close contact with each other with a tightening margin, the pull-out resistance of the bearing sleeve 8 can be increased as described above. In addition, such a space P2 is formed by forming the outer peripheral surface 8d of the bearing sleeve 8 into a cylindrical surface shape and forming the inner peripheral surface 7a1 of the housing 7 into a tapered surface shape whose diameter is gradually increased upward. It can also be configured (not shown).

  The wedge-shaped space P1 or P2 as described above may be formed by forming a reduced diameter portion on both the inner peripheral surface 7a1 of the housing and the outer peripheral surface 8d of the bearing sleeve 8 and making the inclination angles thereof different. it can.

  Further, in the above embodiment, the seal space is formed on the inner diameter side and the outer diameter side of the seal member 9, respectively, but not limited to this, for example, a seal member that forms the seal space only on the inner diameter side is fixed to the housing. May be.

  In the above embodiment, the dynamic pressure generating portions of the radial bearing portions R1 and R2 and the thrust bearing portions T1 and T2 are respectively formed on the inner peripheral surface 8a, the lower end surface 8b of the bearing sleeve 8, and the inner bottom surface 7c1 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. It is sectional drawing of a bearing sleeve. It is an expanded sectional view which shows the fixing | fixed part of a housing and a bearing sleeve. It is AA sectional drawing of the sealing member of FIG. It is a top view of the sealing member seen from the A direction of FIG. It is sectional drawing which shows the fixing method of a housing and a bearing sleeve. It is sectional drawing which shows the fixing method of a housing and a bearing sleeve. It is sectional drawing which shows the fixing method of a housing and a bearing sleeve. It is sectional drawing which shows the fixing method of a housing and a bearing sleeve. It is an expanded sectional view which shows the fixing | fixed part of the housing and bearing sleeve which concern on other embodiment. It is an expanded sectional view which shows the fixing | fixed part of the housing and bearing sleeve which concern on other embodiment. It is an expanded sectional view which shows the fixing | fixed part of the housing and bearing sleeve which concern on other embodiment. It is sectional drawing which shows the example of the housing in which the taper surface was formed in the internal peripheral surface. It is sectional drawing which shows the fixing method of both when the fixing surfaces of a housing and a bearing sleeve are both cylindrical.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing apparatus 2 Shaft member 7 Housing 7a Small diameter part 7a1 Inner peripheral surface 7a10 Annular groove 7a12 Guide surface 7a13 Tapered surface 7a15 Annular groove 8 Bearing sleeve 8d Outer peripheral surface (tapered surface)
9 Seal member G Adhesives R1, R2 Radial bearing part T1, T2 Thrust bearing part S1, S2 Seal space

Claims (7)

A shaft member, a bearing sleeve having a shaft member inserted into the inner periphery, a housing having a bearing sleeve fixed to the inner peripheral surface and having one end opened and the other end closed, an outer surface of the shaft member, and an inner periphery of the bearing sleeve In a hydrodynamic bearing device including a radial bearing portion that supports a shaft member in a radial direction with a lubricating film generated in a radial bearing gap between the surface and
A hydrodynamic bearing device, wherein a tapered surface having a diameter reduced toward a housing opening side is provided on at least a part of an inner peripheral surface of the housing. A shaft member, a bearing sleeve having a shaft member inserted into the inner periphery, a housing having a bearing sleeve fixed to the inner peripheral surface and having one end opened and the other end closed, an outer surface of the shaft member, and an inner periphery of the bearing sleeve In a hydrodynamic bearing device including a radial bearing portion that supports a shaft member in a radial direction with a lubricating film generated in a radial bearing gap between the surface and
A hydrodynamic bearing device, wherein a tapered surface having a diameter reduced toward a housing opening side is provided on at least a part of an outer peripheral surface of the bearing sleeve. A shaft member, a bearing sleeve having a shaft member inserted into the inner periphery, a housing having a bearing sleeve fixed to the inner peripheral surface and having one end opened and the other end closed, an outer surface of the shaft member, and an inner periphery of the bearing sleeve In a hydrodynamic bearing device including a radial bearing portion that supports a shaft member in a radial direction with a lubricating film generated in a radial bearing gap between the surface and
A tapered surface having a diameter reduced toward the housing opening side is provided on at least a part of the inner peripheral surface of the housing, and a tapered surface having a diameter reduced toward the housing opening side on at least a part of the outer peripheral surface of the bearing sleeve. A hydrodynamic bearing device comprising:   The hydrodynamic bearing device according to any one of claims 1 to 3, wherein an outer peripheral surface of the bearing sleeve and an inner peripheral surface of the housing are in close contact with each other at at least an end of the tapered surface on the housing opening side.   The hydrodynamic bearing device according to claim 1, wherein an adhesive reservoir is interposed between the inner peripheral surface of the housing and the outer peripheral surface of the bearing sleeve.   The fluid according to claim 5, wherein a plurality of grooves for forming an adhesive reservoir are formed at a plurality of axial positions on an inner peripheral surface of the housing, and a groove on the housing closing side is provided in the vicinity of the housing closing side end surface of the bearing sleeve. Bearing device.   The hydrodynamic bearing device according to claim 1, wherein a dynamic pressure generating portion is formed on an end surface of the bearing sleeve.

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