JP4498932B2 - Hydrodynamic bearing device - Google Patents

Description

  The present invention relates to a hydrodynamic bearing device that supports a rotating member in a non-contact manner with an oil film of a fluid (lubricating fluid) generated in a bearing gap. This bearing device is a spindle motor such as an information device, for example, a magnetic disk device such as an HDD, an optical disk device such as a CD-ROM, CD-R / RW, DVD-ROM / RAM, or a magneto-optical disk device such as MD or MO, It is suitable for polygon scanner motors of laser beam printers (LBP) and other small motors.

  In addition to high rotational accuracy, the various motors are required to have high speed, low cost, low noise, and the like. One of the components that determine the required performance is a bearing that supports the spindle of the motor. In recent years, the use of a fluid bearing having characteristics excellent in the required performance has been studied or actually used. .

  This type of hydrodynamic bearing includes a hydrodynamic bearing provided with dynamic pressure generating means for generating dynamic pressure in a fluid (for example, lubricating oil) in a bearing gap, and a so-called circular bearing (not provided with dynamic pressure generating means). The bearing surface is roughly divided into a bearing having a perfect circular shape.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk drive device such as an HDD, both a radial bearing portion that supports a shaft member in the radial direction and a thrust bearing portion that supports the shaft direction in a thrust direction may be configured by dynamic pressure bearings. is there. As a radial bearing part in this type of hydrodynamic bearing device, for example, a dynamic pressure groove as a dynamic pressure generating part is formed on either the inner peripheral surface of the bearing sleeve or the outer peripheral surface of the shaft member facing the bearing sleeve. In addition, there is known one that forms a radial bearing gap between both surfaces (see, for example, Patent Document 1).

Usually, the bearing sleeve is fixed at a predetermined position on the inner periphery of the housing, and a seal member is provided at the opening of the housing in order to prevent the lubricating oil injected into the inner space of the housing from leaking to the outside. There are many (patent document 1).
JP 2003-239951 A

  This type of hydrodynamic bearing device is composed of various parts including a housing, a bearing sleeve, and a shaft member. In order to ensure the high bearing performance required as the performance of information equipment increases, Efforts are being made to increase the processing accuracy and assembly accuracy of parts. On the other hand, along with the trend of lowering the price of information equipment, the demand for cost reduction for this type of hydrodynamic bearing device has become increasingly severe.

  As one of means for reducing this kind of cost, it can be considered that the housing is formed by plastic working of a metal material. However, a housing formed by plastic working (for example, press working) has a tendency that the roundness of the outer peripheral surface is worse (the value of roundness is larger) than a housing made by machining such as cutting. Such deterioration of the roundness of the outer peripheral surface of the housing may cause the following problems.

  That is, when this type of hydrodynamic bearing device is used for the rotation support part of the above-mentioned various motors, the outer peripheral surface of the housing is usually closely fixed to the inner peripheral surface of the bracket (holding member) via an adhesive. In consideration of the adhesive strength, the axial dimension of the adhesive part between them and the filling gap of the adhesive are determined. However, if the roundness of the outer peripheral surface of the housing is poor, the adhesive filling gap becomes non-uniform in the circumferential direction when mounted on the inner peripheral surface of the holding member, resulting in problems such as a decrease in adhesive strength and resonance. Concerned.

  In addition, a method of fixing the outer peripheral surface of the housing tightly to the inner peripheral surface of the bracket by press fitting is also conceivable. However, in this case, if the roundness of the outer peripheral surface of the housing is poor, the housing is pressed into the inner peripheral surface of the holding member. In addition, the press-fitting allowance becomes non-uniform in the circumferential direction, and there is a similar concern about a decrease in press-fitting strength and a problem of resonance.

  The subject of this invention is providing the hydrodynamic bearing apparatus which improved the roundness of the outer peripheral surface of the metal housing which is a plastic work product.

In order to solve the above problems, the present invention provides a housing, a bearing sleeve fixed inside the housing, a rotating member that rotates relative to the housing and the bearing sleeve, and a radial bearing between the rotating member and the bearing sleeve. The housing is fixed to the inner peripheral surface of the bracket by bonding or press fitting, and the housing is press-molded with a metal material. Shinadea is, the bearing sleeve is formed of sintered metal, the inner circumference of the roundness of the outer circumferential surface has dimensions sizing is performed such that less than 5 [mu] m, housing the outer circumferential surface of the bearing sleeve over the entire circumference By pressing into the surface, the outer peripheral surface of the housing is deformed following the outer peripheral surface of the bearing sleeve, so that the roundness of the outer peripheral surface of the housing is 5 μm or less. Provided is a hydrodynamic bearing device characterized in that it is as below. The roundness referred to here is 2 when the diameter of the circumscribed circle and the diameter of the inscribed circle in the circumferential shape measured by a roundness measuring device under a temperature condition of 20 ° C. It is a value of 1 / (radius roundness).

  A housing formed by plastic working (pressing or the like) of a metal material can be manufactured at a lower cost than a metal housing formed by machining such as turning. Further, the outer peripheral surface of the housing is configured so that the roundness of the outer peripheral surface of the housing is 5 μm or less with the outer peripheral surface of the metal bearing sleeve being press-fitted into the inner peripheral surface of the housing. When bonding and fixing to the peripheral surface, it is possible to avoid a situation in which the bonding gap between the two members is not uniform in the circumferential direction, and to suppress a decrease in bonding strength and resonance.

  Usually, a metal housing formed by plastic working such as press working is formed to be relatively thin in consideration of its formability. In this case, with the press-fitting of the metal bearing sleeve, the roundness of the outer peripheral surface of the bearing sleeve is transferred to the housing, and the roundness of the outer peripheral surface of the housing is improved within the above range. Such roundness of the outer peripheral surface of the bearing sleeve can be obtained, for example, by dimension sizing after sintering when the bearing sleeve is formed of a sintered metal porous body, and the value can be suppressed to less than 5 μm. . Even when the metal housing formed by plastic processing is relatively thick, the bearing sleeve press-fitting allowance, the rigidity of the sintered metal bearing sleeve (the difficulty of deformation during housing press-fitting), etc. It is possible to cope by adjusting.

  The hydrodynamic bearing device having the above-described configuration can be provided as a spindle motor of a disk device including the hydrodynamic bearing device, for example.

  Thus, according to the present invention, it is possible to provide a hydrodynamic bearing device in which the roundness of the outer peripheral surface of a metal housing that is a plastic work product is improved.

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

  FIG. 1 conceptually shows one configuration example of a spindle motor for information equipment incorporating a fluid dynamic bearing device (dynamic pressure bearing device) 1 according to a first 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 in a non-contact manner, a disk hub 3 mounted on the shaft member 2, and a radial direction, for example. A stator coil 4 and a rotor magnet 5 are provided to face each other through a gap. 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 outer peripheral surface of the housing 7 of the hydrodynamic bearing device 1 is fixed to the inner peripheral surface of the bracket 6 by means such as adhesion or press fitting. The disk hub 3 holds one or more disk-shaped information storage media (hereinafter simply referred to as disks) D such as magnetic disks on the outer periphery thereof. In the spindle motor configured as described above, when the stator coil 4 is energized, the rotor magnet 5 is rotated by the electromagnetic force generated between the stator coil 4 and the rotor magnet 5. The disk D held by the hub 3 rotates integrally with the shaft member 2.

  FIG. 2 shows the hydrodynamic bearing device 1. The hydrodynamic bearing device 1 includes a shaft member 2, a housing 7, a bearing sleeve 8 and a thrust member 10 fixed to the housing 7, and a seal member 9 as main components. For convenience of explanation, the following description will be made assuming that the fixed side of the thrust member 10 of the housing 7 is the lower side and the side opposite to the fixed side of the thrust member 10 is the upper side.

  The shaft member 2 is formed of a metal material such as stainless steel or a hybrid structure of a metal material and a resin material, and the shaft portion 2a and a flange provided integrally or separately at the lower end of the shaft portion 2a. Part 2b is provided. In addition, as the shaft member 2 having a hybrid structure, the core portion of the shaft portion 2a, the flange portion 2b, or both of them formed of a resin material can be used.

  The housing 7 is a thin metal press-formed product, and is formed in a cylindrical shape by pressing a pipe material made of a soft metal such as brass. The press-molded product here means all molded products processed by a press machine attached with a metal mold, and includes, for example, products molded by a sheet metal press or the like. Further, in order to remove burrs and the like at the time of press working, it is possible to perform processing such as barrel polishing after the press working.

  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. As will be described in detail later, the bearing sleeve 8 is press-fitted and fixed at a predetermined position on the inner peripheral surface 7a of the housing 7 in a state of being in contact with the contact portion 10b of the thrust member 10. The outer diameter of the bearing sleeve 8 is formed larger than the inner diameter of the housing 7 by a predetermined press-fitting allowance with respect to the inner peripheral surface 7a of the housing 7 of an outer peripheral surface 8d of the bearing sleeve 8 described later. .

  A dynamic pressure groove as a radial dynamic pressure generating portion is formed on the entire inner surface 8a of the bearing sleeve 8 or a partial cylindrical region. In this embodiment, for example, as shown in FIG. 3A, two regions having a plurality of dynamic pressure grooves 8a1 and 8a2 arranged in a herringbone shape are formed apart from each other in the axial direction. In the formation region of the upper dynamic pressure groove 8a1, the dynamic pressure groove 8a1 is formed to be axially asymmetric with respect to the axial center m (the axial center of the upper and lower inclined groove regions). The axial dimension X1 of the upper region is larger than the axial dimension X2 of the lower region.

  One or more axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8 over the entire axial length. In this illustrated example, as shown in FIG. 3C, for example, three axial grooves 8d1 are formed at equal intervals in the circumferential direction. The bearing sleeve 8 is dimensioned after sintering, and the roundness of the outer peripheral surface 8d is corrected to less than 5 μm.

  For example, as shown in FIG. 3B, a region where a plurality of dynamic pressure grooves 8c1 are arranged in a spiral shape is formed as a thrust dynamic pressure generating portion on the entire lower surface 8c of the bearing sleeve 8 or a partial annular region. Is done.

  As shown in FIG. 3C, the upper end surface 8b of the bearing sleeve 8 is partitioned into an inner diameter side region 8b2 and an outer diameter side region 8b3 by a circumferential groove 8b1 provided at a substantially central portion in the radial direction. One or a plurality of radial grooves 8b21 are formed in the side region 8b2. In the illustrated example, three radial grooves 8b21 are formed at equal intervals around the circumference.

  The seal member 9 is formed in an annular shape from, for example, a resin material or a soft metal material, and is disposed on the upper end of the inner peripheral surface 7 a of the housing 7. The inner peripheral surface 9a of the seal member 9 faces the tapered surface 2a2 provided on the outer periphery of the shaft portion 2a via a predetermined seal space S1. The tapered surface 2a2 of the shaft portion 2a is gradually reduced in diameter toward the upper side (outside of the housing 7), and functions as a capillary force seal and a centrifugal force seal when the shaft member 2 rotates. Further, the lower end surface 9b of the seal member 9 has a form in which the outer diameter side region 9b1 is retracted upward in the axial direction as compared with the inner diameter side region.

  The thrust member 10 is formed of, for example, a resin material or a metal material, and is disposed at the lower end of the inner peripheral surface 7 a of the housing 7. For example, a plurality of dynamic pressure grooves similar to the dynamic pressure grooves 8c1 shown in FIG. 3B are arranged in a spiral shape on the partial annular region or the entire surface of the end face 10a of the thrust member 10 as a thrust dynamic pressure generating portion (for example, spiral A region having a reverse rotation direction is formed. This dynamic pressure groove forming region faces the lower end surface 2b2 of the flange portion 2b, and when the shaft member 2 rotates, a thrust bearing gap of the second thrust bearing portion T2 is formed between the dynamic pressure groove forming region and the lower end surface 2b2. (See FIG. 2). Further, in this embodiment, the thrust member 10 is integrally provided with an annular contact portion 10b extending upward from the outer peripheral edge portion of the end surface 10a. The upper end surface of the contact portion 10b is in contact with the lower end surface 8c of the bearing sleeve 8, and the inner peripheral surface of the contact portion 10b is opposed to the outer peripheral surface of the flange portion 2b through a radial gap.

  The hydrodynamic bearing device 1 of this embodiment is assembled in the following process, for example.

  First, the thrust member 10 is fixed to the lower end portion of the inner peripheral surface 7a of the housing 7 by means such as press fitting, adhesion, welding, welding (including laser welding) or the like. Next, the bearing sleeve 8 with the shaft member 2 mounted on the inner periphery is accommodated in the inner periphery of the housing 7, and the outer peripheral surface 8d of the bearing sleeve 8 is press-fitted into the inner peripheral surface 7a of the housing 7 with a predetermined press-fitting allowance, The lower end surface 8 c is brought into contact with the upper end surface of the contact portion 10 b of the thrust member 10.

  In this way, by pressing a bearing sleeve having an outer peripheral surface 8d with a roundness of less than 5 μm into the inner peripheral surface 7a of the housing 7 with a predetermined press-fitting allowance, the roundness of the outer peripheral surface 8d of the bearing sleeve 8 is increased. 7 and the roundness of the outer peripheral surface of the housing 7 is suppressed to 5 μm or less. The bearing sleeve 8 may be fixed to the housing 7 only by the press-fitting described above, or in addition to the press-fitting, fixing means such as adhesion or ultrasonic welding may be used in combination.

  Simultaneously with the press-fitting, the lower end surface 8c of the bearing sleeve 8 is brought into contact with the contact portion 10b of the thrust member 10, whereby the axial positioning of the bearing sleeve 8 with respect to the thrust member 10 is accurately performed. Accordingly, by managing the axial dimensions of the contact portion 10b and the flange portion 2b, the thrust bearing gap between the first thrust bearing portion T1 and the second thrust bearing portion T2, which will be described later, can be set with high accuracy.

  After fixing the bearing sleeve 8, the seal member 9 is disposed on the upper end portion of the inner peripheral surface 7 a of the housing 7, and the inner diameter side region of the lower end surface 9 b is brought into contact with the inner diameter side region 8 b 2 of the upper end surface 8 b of the bearing sleeve 8. . In this state, the seal member 9 is fixed to the housing 7 by an appropriate means such as press-fitting, adhesion, welding or the like. When ultrasonic welding is used for fixing the seal member 9 and the housing 7, illustration is omitted, but by providing convex ribs on the outer peripheral surface of the seal member 9, the fixing force at the time of ultrasonic welding is increased. be able to.

  When the assembly is completed as described above, the shaft portion 2a of the shaft member 2 is inserted into the inner peripheral surface 8a of the bearing sleeve 8, and the flange portion 2b is formed between the lower end surface 8c of the bearing sleeve 8 and the end surface 10a of the thrust member 10. It will be in the state accommodated in the space part between. Thereafter, the internal space of the housing 7 sealed with the seal member 9 is filled with lubricating oil including the internal holes of the bearing sleeve 8. The oil level of the lubricating oil is maintained within the range of the seal space S1.

  When the shaft member 2 rotates, the region (two upper and lower regions) of the inner peripheral surface 8a of the bearing sleeve 8 is opposed to the outer peripheral surface 2a1 of the shaft portion 2a via the radial bearing gap. As the shaft member 2 rotates, the lubricating oil in the radial bearing gap is pushed toward the axial center m of the dynamic pressure groove 8a1 (8a2), and the pressure rises. The first radial bearing portion R1 and the second radial bearing portion R2 that support the shaft portion 2a in a non-contact manner are configured by the dynamic pressure action of the dynamic pressure groove.

  At the same time, the thrust bearing gap between the upper end surface 2b1 of the flange portion 2b and the lower end surface 8c (dynamic pressure groove 8c1 formation region) of the bearing sleeve 8 facing the flange portion 2b, and the lower end surface 2b2 of the flange portion 2b opposes this. An oil film of lubricating oil is formed in the thrust bearing gap between the thrust member 10 and the end surface 10a (dynamic pressure groove forming region) by the dynamic pressure action of the dynamic pressure groove. And the thrust bearing parts T1 and T2 which non-contact-support the flange part 2b rotatably in both thrust directions are comprised by the pressure of these oil films.

  Further, as described above, the dynamic pressure groove 8a1 of the first radial bearing portion R1 is formed axially asymmetric (X1> X2) with respect to the axial center m {see FIG. 3 (a)}, 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 Thrust bearing gap → axial groove 8d1 → annular gap between outer diameter side region 9b1 of lower end surface 9b of seal member 9 and outer diameter side region 8b3 of upper end surface 8b of bearing sleeve 8 → upper end surface 8b of bearing sleeve 8 Is circulated through the path of the circumferential groove 8b1 → the radial groove 8b21 of the upper end surface 8b of the bearing sleeve 8 and is drawn into the radial bearing gap of the first radial bearing portion R1 again. In this way, the structure in which the lubricating oil flows and circulates in the internal space of the housing 7 prevents a phenomenon in which the pressure of the lubricating oil in the internal space becomes a negative pressure locally, resulting in the generation of negative pressure. Problems such as generation of bubbles, leakage of lubricating oil and generation of vibration due to generation of bubbles can be solved. Further, 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 S1 to the outside air. The adverse effects due to the bubbles are more effectively prevented.

  In the illustrated example, the case where the thrust member 10, the bearing sleeve 8, and the seal member 9 are fixed to the housing 7 in this order has been described. However, the order is not particularly limited, and for example, the seal member 9, the bearing sleeve 8, the thrust member The members 10 may be fixed to the housing 7 in the order.

  In the illustrated example, the seal member 9 is formed separately from the housing 7. However, the seal member 9 can be formed integrally with the housing 7. In that case, although not shown in the drawings, the upper end portion of the press-formed thin cylindrical housing 7 is reduced in diameter by, for example, necking or the like, and the inner diameter protruding portion protruding from the upper end of the housing 7 toward the inner diameter side, and the inner diameter protruding portion It is preferable to provide an upwardly extending portion extending upward from the inner diameter edge. Thus, a seal space is formed between the inner peripheral surface of the upward extending portion and the outer peripheral surface 2a1 of the opposed shaft portion 2a. Further, the upper end surface 8b of the bearing sleeve 8 is brought into contact with the lower end surface of the inner diameter protruding portion, whereby the axial positioning of the bearing sleeve 8 with respect to the housing 7 is easily and accurately performed.

  In addition, the thrust member 10 can be press-molded integrally with the housing 7. In that case, the portion corresponding to the thrust member 10 in the housing can be formed thicker than the other portions, or the thickness can be made constant over the entire housing 7.

Further, the abutting portion 10b of the thrust member 10 does not need to be formed integrally with the thrust member. For example, although not shown in the drawing, the thrust member 10 is formed separately from the thrust member 10 as an annular member such as a spacer. You may make it interpose between the member 10 and the bearing sleeve 8. FIG. Or positioning members, such as contact part 10b and a spacer, can also be omitted by performing axial positioning of thrust member 10 with other positioning means. Similarly, the seal member 9 can be omitted. In this case, although not shown in the figure, the upper end of the inner peripheral surface 8a of the bearing sleeve 8 is a region where no radial bearing gap is formed, and the outer periphery of the shaft portion 2a facing this region. A seal space is formed between the surface 2a1.

  In addition, about the hydrodynamic bearing apparatus of the said example of illustration, a thrust bearing part can also be comprised with what is called a pivot bearing other than the bearing of the said form. Further, as the radial bearing portion, a so-called perfect circle bearing can be used to constitute the radial bearing portion.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. Note that the description of items common to the first embodiment will be omitted below.

  FIG. 4 conceptually shows a configuration example of a spindle motor for information equipment incorporating a hydrodynamic bearing device 31 according to the second embodiment of the present invention. This spindle motor is also used in a disk drive device such as an HDD, and is opposed to a hydrodynamic bearing device 31 that rotatably supports a shaft member 32 to which a disk hub 33 is fixed, for example, via a radial gap. The stator coil 34 and the rotor magnet 35, and the bracket 36 fixed to the outer periphery of the housing 37 of the hydrodynamic bearing device 31 are provided.

  FIG. 5 shows the hydrodynamic bearing device 31. The hydrodynamic bearing device 31 includes a shaft member 32, a housing 37, a bearing sleeve 38 fixed to the housing 37, and a seal member 39 as main components. Below, for convenience of explanation, the side of the opening 37a of the housing 37 will be described as the upper side, and the side opposite to the opening 37a will be described as the lower side.

  The shaft member 32 is formed of a metal material such as stainless steel, for example, and includes a shaft portion 32a and a disk-shaped flange portion 32b. The flange portion 32b is provided above the lower end of the shaft portion 32a, and is integral with or separate from the shaft portion 32a.

  The housing 37 is a thin metal press-formed product, and is formed into a bottomed cylindrical shape by drawing a metal plate made of a soft metal such as brass. In this embodiment, an opening 37a is formed on one end side of the side portion 37b of the housing 37, and a bottom portion 37c is formed integrally with the side portion 37b on the other end side.

  The bearing sleeve 38 is formed in a cylindrical shape with a porous body made of sintered metal, for example, a sintered metal porous body mainly composed of copper, and is fixed to a predetermined position on the inner peripheral surface 37 d of the housing 37.

  As shown in FIG. 6, a plurality of arcuate surfaces 38a1 serving as the radial bearing surfaces of the first radial bearing portion R11 and the second radial bearing portion R12 are respectively provided in regions spaced apart from each other on the inner peripheral surface 38a of the bearing sleeve 38. It is formed. Each arc surface 38a1 is an eccentric arc surface centered on a point offset from the rotation axis O by an equal distance, and is formed at equal intervals in the circumferential direction. An axial separation groove 38a2 is formed between each eccentric arc surface 38a1.

  By inserting the shaft portion 32a of the shaft member 32 into the inner peripheral surface 38a of the bearing sleeve 38, the eccentric arc surface 38a1 and the separation groove 38a2 of the bearing sleeve 38 and the perfect circular outer peripheral surface 32a1 of the shaft portion 32a are interposed. The radial bearing gaps of the first and second radial bearing portions R11 and R12 are formed, respectively. In the radial bearing gap, a region formed by the eccentric arc surface 38a1 and the perfect circular outer circumferential surface 32a1 is a wedge-shaped gap 38a3 in which the gap width is gradually reduced in the circumferential direction. The reduction direction of the wedge-shaped gap 38a3 coincides with the rotation direction of the shaft member 32.

  For example, a plurality of dynamic pressure grooves similar to the dynamic pressure grooves 8c1 shown in FIG. 3B are arranged in a spiral shape on the entire upper surface 38b or a partial annular region of the bearing sleeve 38 as a thrust dynamic pressure generating portion (spiral). The rotation direction is reversed). The dynamic pressure groove forming region of the upper end surface 38b faces the lower end surface 32b2 of the flange portion 32b, and when the shaft member 32 rotates, a thrust bearing gap of the thrust bearing portion T11 is formed between the both surfaces 38b and 32b2. (See FIG. 5). On the other hand, the lower end surface 38c of the bearing sleeve 38 is a smooth surface without a dynamic pressure groove. The roundness of the outer peripheral surface 38d of the bearing sleeve 38 is set to be less than 5 μm by a predetermined dimension sizing.

  The seal member 39 is formed in an annular shape with, for example, a resin material or a metal material, and is fixed to the inner periphery of the opening 37 a of the housing 37. When the cylindrical inner peripheral surface 39a of the seal member 39 is fixed to the inner periphery of the opening 37a of the housing 37 (see FIG. 5), a predetermined seal is formed between the cylindrical inner peripheral surface 39a and the outer peripheral surface 32a1 of the opposed shaft portion 32a. A space S2 is formed.

  The lower end surface 39b of the seal member 39 is opposed to the upper end surface 32b1 of the flange portion 32b via a predetermined axial gap. When the shaft member 32 is relatively displaced upward, the upper end surface 32b1 of the flange portion 32b is engaged with the lower end surface 39b of the seal member 39 in the axial direction, and the shaft member 32 is locked. Thus, the sealing member 39 has both a sealing function and a retaining function.

  The hydrodynamic bearing device 31 of this embodiment is assembled in the following process, for example.

  First, the shaft member 32 is attached to the bearing sleeve 38. Then, the outer peripheral surface 38d of the bearing sleeve 38 is press-fitted into the inner peripheral surface 37d of the housing 37 with a predetermined press-fitting allowance. Thus, the roundness of the outer peripheral surface 38d of the bearing sleeve 38 is increased by press-fitting the bearing sleeve 38 having a roundness of the outer peripheral surface 38d of less than 5 μm into the inner peripheral surface 37d of the housing 37 with a predetermined press-fitting allowance. Transferred to the housing 37, the roundness of the outer peripheral surface of the housing 37 is suppressed to 5 μm or less.

  Further, the bearing sleeve 38 is pressed into the inner periphery of the housing 37 until the lower end surface 38 c of the bearing sleeve abuts against the bottom 37 c of the housing 37, whereby the axial positioning of the bearing sleeve 38 with respect to the housing 37 is performed accurately.

  Next, the seal member 39 is disposed on the inner periphery of the opening 37a of the housing 37, and the flange portion 32b is accommodated between the lower end surface 39b of the seal member 39 and the upper end surface 38b of the bearing sleeve 38, for example, bonding, The housing 37 is fixed by means such as press fitting or welding. Thereby, the hydrodynamic bearing device 31 shown in FIG. 5 is completed. At this time, the internal space of the housing 37 sealed by the seal member 39 is filled with the lubricating oil including the internal pores of the bearing sleeve 38, and the oil level of the lubricating oil is maintained within the range of the sealing space S2. .

  In the hydrodynamic bearing device 31 configured as described above, when the shaft member 32 is rotated, a region (two upper and lower regions) serving as a radial bearing surface of the inner peripheral surface 38a of the bearing sleeve 38 corresponds to the outer peripheral surface 32a1 of the shaft portion 32a and the radial bearing. They are opposed to each other through a gap, and each form a multi-arc bearing (also referred to as a taper bearing). As the shaft member 32 rotates, the lubricating oil in the radial bearing gap is pushed into the reduction side of the wedge-shaped gap 38a3, and the pressure rises. By such a dynamic pressure action, a first radial bearing portion R11 and a second radial bearing portion R12 that support the shaft portion 32a in a non-contact manner are configured.

  At the same time, an oil film of lubricating oil is also formed in the thrust bearing gap between the lower end surface 32b2 of the flange portion 32b and the upper end surface 38b of the bearing sleeve 38 facing the flange portion 32b by the dynamic pressure action of the dynamic pressure groove. A thrust bearing portion T11 that supports the flange portion 32b in a non-contact manner so as to be rotatable in the thrust direction is configured by the pressure.

  In the illustrated example, the case where the seal member 39 is formed separately from the housing 37 and fixed to the housing 37 later is described. However, for example, the seal member 39 is formed integrally with the housing 37 from a resin material. It can also be done (not shown). In that case, the bottom 37c of the housing 37 may be formed separately from the housing 37.

  In the illustrated example, the case where the seal space S2 is formed between the cylindrical inner peripheral surface 39a of the seal member 39 and the outer peripheral surface 32a1 of the shaft portion 32a opposite to the cylindrical inner peripheral surface 39a has been described. It is also possible to apply to other forms. For example, FIG. 7 illustrates a case where a tapered seal space S3 is formed in which the radial gap width is gradually increased toward the outside of the housing 37 (the upper side in FIG. 7).

  Further, in FIG. 8, in order to reduce the axial dimension of the housing 37 and reduce the size of the hydrodynamic bearing device 31, the inner peripheral surface 39 a of the seal member 39 and the outer peripheral surface 32 b 3 of the flange portion 32 b are opposed to each other. In this example, a tapered seal space S4 is formed between the opposing surfaces.

  Furthermore, as an example of taking into consideration the retaining of the shaft member 32, a configuration as shown in FIG. The seal space S5 in the figure is formed by the upper outer peripheral surface 32b3 and the inner peripheral surface 39a of the seal member 39 facing the upper outer peripheral surface 32b3 among the outer peripheral surfaces defined by the axial step provided in the flange portion 32b. Formed between. Further, the end surface 32b4 on the outer diameter side of the upper end surface 32b1 defined by the steps is opposed to the lower end surface 39b of the seal member 39 in the axial direction.

  With such a configuration, the sealing space S5 has a sealing action due to centrifugal force and intercapillary force, and leakage of lubricating oil to the outside is prevented. Further, when the shaft member 32 is relatively displaced upward, the outer diameter side end surface 32b4 of the flange portion 32b is engaged with the lower end surface 39b of the seal member 39 in the axial direction, so that the shaft member 32 is prevented from being detached.

  In the illustrated example, the sealing member 39 has a form in which a portion of the lower end surface 39b that does not face the outer diameter side end surface 32b4 is protruded downward. Therefore, the lower protrusion 39c of the seal member 39 is brought into contact with the upper end surface 38b of the bearing sleeve 38, whereby the seal member 39 can be easily positioned in the axial direction.

  FIG. 10 shows another embodiment of the multi-arc bearing constituting the first and second radial bearing portions R11, R12. In this embodiment, in the configuration shown in FIG. 6, the predetermined region θ on the minimum gap side of each eccentric arc surface 38 a 1 is configured by a concentric arc centering around the rotation axis O. Therefore, in each predetermined area θ, the radial bearing gap (minimum gap) is constant. The multi-arc bearing having such a configuration may be referred to as a tapered flat bearing.

  In FIG. 11, a region that is a radial bearing surface of the inner peripheral surface 38 a of the bearing sleeve 38 is formed by three arc surfaces 38 a 1, and the centers of the three arc surfaces 38 a 1 are offset from the rotation axis O by an equal distance. Yes. In each region defined by the three eccentric arc surfaces 38a1, the radial bearing gap has a shape gradually reduced with respect to both directions in the circumferential direction.

  The multi-arc bearings of the first and second radial bearing portions R11 and R12 described above are all so-called three-arc bearings, but are not limited thereto, so-called four-arc bearings, five-arc bearings, and more than six arcs. You may employ | adopt the multi-arc bearing comprised by the several circular arc surface. Further, as in the radial bearing portions R11 and R12, two radial bearing portions are provided apart from each other in the axial direction, and one radial bearing portion extends over the upper and lower regions of the inner peripheral surface 38a of the bearing sleeve 38. It is good also as a structure which provided.

  Moreover, although the case where a multi-arc bearing is employ | adopted as radial bearing part R11, R12 is illustrated in the above description, it can also be comprised with bearings other than this. As bearings that can constitute the radial bearing portions R11 and R12, for example, although not shown, a plurality of shafts are provided in a region facing the radial bearing gap (region serving as a radial bearing surface) on the inner peripheral surface 38a of the bearing sleeve 38. An example is a step bearing in which a directional groove-shaped dynamic pressure groove is formed. Of course, the bearings such as the multi-arc bearing described above can also be employed in the radial bearing portions R1 and R2 of the first embodiment.

  In the first and second embodiments described above, the lubricating oil is exemplified as the fluid that fills the inside of the hydrodynamic bearing device 1 and generates a dynamic pressure action in the radial bearing gap and the thrust bearing gap. Alternatively, a fluid capable of causing a dynamic pressure action in each bearing gap, for example, a gas such as air, a fluid lubricant such as a magnetic fluid, or lubricating grease may be used.

It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view of a hydrodynamic bearing device. They are (a) a longitudinal sectional view of the bearing sleeve, (b) a lower end surface, and (c) an upper end surface. It is sectional drawing of the spindle motor for information devices incorporating the hydrodynamic bearing apparatus which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view of a hydrodynamic bearing device. It is a cross-sectional view which shows a radial bearing part. It is an expanded sectional view showing other examples of composition of seal space. It is an expanded sectional view showing other examples of composition of seal space. It is an expanded sectional view showing other examples of composition of seal space. It is a cross-sectional view which shows the other structural example of a radial bearing part. It is a cross-sectional view which shows the other structural example of a radial bearing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluid dynamic bearing device 2 Shaft member 3 Disc hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 8 Bearing sleeve 8a1, 8a2 Dynamic pressure groove 8c1 Dynamic pressure groove 9 Seal member 10 Thrust member 31 Fluid bearing device 32 Shaft member 37 Housing 37a Opening Portion 37b side portion 37c bottom portion 38 bearing sleeve 38a1 eccentric arc surface 38a3 wedge-shaped gap 38d outer peripheral surface 39 seal members S1, S2, S3, S4, S5 seal spaces R1, R2, R11, R12 radial bearing portions T1, T2, T11 thrust Bearing part

Claims (2)

A housing, a bearing sleeve fixed inside the housing, a rotating member rotating relative to the housing and the bearing sleeve, and an oil film of fluid generated in a radial bearing gap between the rotating member and the bearing sleeve In the hydrodynamic bearing device comprising a radial bearing portion for supporting the rotating member in a radial direction in a non-contact manner,
The housing is fixed to the inner peripheral surface of the bracket by adhesion or press fitting,
The housing Ri press forming Shinadea metallic material, wherein the bearing sleeve is formed of sintered metal, and the dimensions sizing is applied as roundness is less than 5μm of its outer peripheral surface,
The outer circumferential surface of the housing is press-fitted into the inner circumferential surface of the housing over the entire circumference, and the outer circumferential surface of the housing is deformed following the outer circumferential surface of the bearing sleeve. The hydrodynamic bearing device is characterized in that the thickness is 5 μm or less.   A spindle motor of a disk device having the hydrodynamic bearing device according to claim 1.