JP2006200583A - Dynamic pressure bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a superior thrust bearing function, by preventing plastic deformation of a thrust surface, when pressing a rotary member in a shaft member. <P>SOLUTION: A guide surface 2c forming a guide when pressing in a disk hub as the rotary member, is formed on the upper end of the shaft member. The guide surface 2c, an outer peripheral surface 2a3 of the shaft member 2 adjacent to the guide surface 2c, and a boundary part between the guide surface 2c and the outer peripheral surface 2a3 are simultaneously ground, and a blunting part 2d of a radius (r) is formed in the boundary part. Thus, the disk hub can be pressed in and fixed by press-in force less than yield stress of a member surface for constituting a thrust bearing part, by reducing press-in resistance when pressing the disk hub in the shaft end of the shaft member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrodynamic bearing device that supports a shaft member in a non-contact manner by a hydrodynamic action of a fluid (lubricating fluid) generated in a bearing gap. This bearing device is a spindle of information equipment such as magnetic disk devices such as HDD and FDD, optical disk devices such as CD-ROM, CD-R / RW and DVD-ROM / RAM, and magneto-optical disk devices such as MD and MO. It is suitable as a bearing device for a motor, a polygon scanner motor of a laser beam printer (LBP), a color wheel of a projector, or a small motor such as an electric device such as an axial fan.

  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, as this type of bearing, a hydrodynamic bearing (fluid hydrodynamic bearing) having characteristics excellent in the required performance. Is being considered or actually used.

  For example, in a hydrodynamic bearing device incorporated in a spindle motor of a disk device such as an HDD, a radial bearing portion that supports a shaft member in a non-contact manner in a radial direction and a shaft member is supported in a non-contact manner in a thrust direction. And a thrust bearing portion. The radial bearing portion is non-rotatable in the radial direction by the fluid dynamic pressure action caused by the relative rotation of the shaft member and the bearing sleeve in the radial bearing gap formed between the inner circumferential surface of the bearing sleeve and the outer circumferential surface of the shaft member. Support contact. The thrust bearing portion is a fluid dynamic pressure generated by relative rotation of the shaft member and the bearing sleeve, etc., in a thrust bearing gap formed between the end surface of the flange portion provided on the shaft member and the end surface of the bearing sleeve facing the flange portion. By the action, it is supported in a non-contact manner so as to be rotatable in the thrust direction.

In a spindle motor incorporating this type of fluid dynamic bearing device, a rotating member (disk hub) for placing a disk-shaped information recording medium (hereinafter referred to as a disk) such as a magnetic disk is a shaft member of the fluid dynamic bearing device. It is fixed to the upper part by, for example, press fitting (for example, Patent Documents 1 to 3).
JP 2000-235766 A JP 2001-54628 A Japanese Patent Laid-Open No. 2003-174748

  By the way, the rotating member is generally fixed to the shaft member after the completion of the hydrodynamic bearing device. However, when press-fitting is adopted as a fixing means, various parts of the hydrodynamic bearing device, particularly the thrust bearing portion, are applied by press-fitting at the time of press-fitting. A large load is applied to the surface of the component member (for example, the end surface of the flange portion provided on the shaft member, the end surface of the bearing sleeve, the end surface of the thrust member, the inner bottom surface of the housing, etc., hereinafter referred to as “thrust surface”). In some cases, this may cause plastic deformation of the thrust surface. In particular, when the rotary member is tilted and press-fitted, the press-fitting resistance is further increased, and this tendency becomes more remarkable. The thrust surface has high flatness so that the thrust bearing gap can be managed with high accuracy, and the dynamic pressure generating means is formed with high accuracy on one of the thrust surfaces facing each other through the thrust bearing gap. For example, a dynamic pressure groove is provided. When plastic deformation of the thrust surface occurs due to the load accompanying the press-fitting of the rotating member, there is a possibility that the thrust bearing function is lowered, that is, the rotational accuracy of the hydrodynamic bearing device is lowered.

  Accordingly, an object of the present invention is to provide a dynamic pressure shaft device that prevents plastic deformation of a thrust surface and secures a good thrust bearing function when a rotating member such as a disk hub is press-fitted into a shaft member.

  In order to achieve the above object, a hydrodynamic bearing device provided by the present invention includes a bearing sleeve, a shaft member inserted into the inner periphery of the bearing sleeve, a rotating member press-fitted into the outer periphery of the shaft member, and a radial bearing gap. A radial bearing that non-contact supports the shaft member in the radial direction by the dynamic pressure action of the fluid generated in the shaft, and a thrust bearing portion that supports the shaft member in the thrust direction by the dynamic pressure action of the fluid generated in the thrust bearing gap. The rotating member is press-fitted with a pressure input less than the yield stress on the surface of the member constituting the thrust bearing portion.

  Thus, the thrust surface is prevented from being plastically deformed by press-fitting the rotating member with the shaft member with a pressure input less than the yield stress of the member surface (thrust surface) constituting the thrust bearing portion. The surface accuracy and the shape accuracy of the dynamic pressure generating means provided on the thrust surface can be maintained. Thereby, a favorable thrust bearing function can be secured.

  Here, as the fluid (lubricating fluid), gases such as lubricating oil (or lubricating grease), magnetic fluid, and air can be used.

  As a means for press-fitting the rotating member with a pressure input less than the yield stress of the thrust surface, for example, a means for suppressing the inclination of the rotating member at the time of press-fitting can be employed. More specifically, means for forming a tapered guide surface at the shaft end of the shaft member (end portion on the insertion side of the rotating member) can be employed. Normally, the shaft member is finished with high accuracy by grinding. However, since this guide surface does not directly affect the rotation accuracy of the shaft member, it is not necessary to finish the guide surface with high accuracy. Therefore, in the grinding process of the shaft member, for example, as shown in FIG. 10, it is sufficient to grind only the outer peripheral surface 21 of the shaft member 20 with the grindstone 30 and leave the guide surface 22 in an unground turning surface state.

  However, when only the outer peripheral surface 21 is ground, a boundary 23 between the outer peripheral surface 21 and the guide surface 22 of the shaft member becomes an edge called a pin angle, and this edge becomes a resistance when the disk hub is press-fitted and fixed to the shaft end. In order to remove this edge, it may be possible to barrel the shaft member after grinding the outer peripheral surface. However, the barrel processing is preferable in terms of bearing performance because the ground surface is rough and there are concerns about the occurrence of scratches. Absent.

  Based on the above verification, the shape of the edge is blunted between the guide surface serving as a guide when the rotary member is press-fitted into the shaft end of the shaft member and the outer peripheral surface of the shaft member adjacent to the guide surface. It is preferable to provide a blunt part.

  The guide surface is formed in a shape that is smaller in diameter than the outer peripheral surface of the shaft member adjacent to the guide surface, for example, a tapered surface that is reduced in diameter toward the upper side. The position of the guide surface is not particularly limited, but is usually formed at the upper end of the shaft member. An example of the rotating member fixed to the shaft member is a disk hub on which a disk is placed.

  As described above, by providing a guide surface that serves as a guide when the rotary member is press-fitted into the shaft member, the rotary member is tapered and guided to the guide surface of the shaft member during press-fitting. The inclination of the rotating member is suppressed. Moreover, since the blunting part which has the shape which blunted the edge is provided between the guide surface and the outer peripheral surface of the shaft member adjacent to this, both surfaces can be smoothly continued without passing through the edge. . Therefore, the press-fitting resistance when the rotary member is press-fitted is suppressed, and the press-fitting and fixing can be smoothly performed without tilting the rotary member. As a result, it is possible to avoid a phenomenon in which an excessive load exceeding the yield stress is applied to the thrust surface when the rotating member is press-fitted.

  Further, the press-fitting resistance can be further reduced by finishing the guide surface, the outer peripheral surface of the shaft member adjacent to the guide surface, and the blunt portion by grinding. In consideration of machining efficiency, it is desirable to grind the guide surface, the outer peripheral surface of the shaft member adjacent to the guide surface, and the blunted portion simultaneously.

  Furthermore, in order to further reduce the press-fitting resistance, it is preferable that the guide surface, the outer peripheral surface of the shaft member adjacent to the guide surface, and the bus bar shape of the blunt portion be made as smoothly as possible. In order to easily realize such continuity, it is desirable to form the blunt portion in a curved surface shape.

  In the hydrodynamic bearing device configured as described above, the radial bearing portion includes a hydrodynamic bearing provided with a hydrodynamic groove having a shape inclined in the axial direction, such as a herringbone shape, and a plurality of axial groove-shaped hydrodynamic grooves in the circumferential direction. It can be constituted by a dynamic pressure bearing (step bearing) provided at a predetermined interval or a dynamic pressure bearing (multi-arc bearing) in which a radial bearing surface is constituted by a multi-arc surface.

  The hydrodynamic bearing device of the present invention is particularly suitable for a spindle motor of a disk device.

  According to the present invention, it is possible to prevent the plastic deformation of the thrust surface during press-fitting of the rotating member, and maintain the surface accuracy of the thrust surface and the shape accuracy of the dynamic pressure generating means provided on the thrust surface. A good thrust bearing function can be secured.

  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 (fluid fluid dynamic bearing device) 1 according to an embodiment of the present invention. This spindle motor for information equipment is used in a disk device such as an HDD, and includes a hydrodynamic bearing device 1 that rotatably supports a shaft member 2 in a non-contact manner, and a disk hub as a rotating member attached to the shaft member 2. 3, for example, a stator coil 4 and a rotor magnet 5 that are opposed to each other via a radial gap, and a bracket 6. 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 bracket 6 has the hydrodynamic bearing device 1 mounted on the inner periphery thereof. In addition, one or more disks D such as magnetic disks are mounted on the disk hub 3. In this information equipment spindle motor, 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, and accordingly, the shaft member 2 and the disk hub 3, The disk D held by the disk hub 3 rotates as a unit.

  FIG. 2 shows a first embodiment of a hydrodynamic bearing device used in the spindle motor. The hydrodynamic bearing device 1 according to this embodiment includes a housing 7 having a bottom 7c at one end, a bearing sleeve 8 fixed to the housing 7, a shaft member 2 inserted into the inner periphery of the bearing sleeve 8, and a seal member. 9 as main constituent members. For convenience of explanation, the description will proceed with the bottom 7c side of the housing 7 as the lower side and the side opposite to the axial direction as the upper side.

  Between the inner peripheral surface 8a of the bearing sleeve 8 and the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2, the first radial bearing portion R1 and the second radial bearing portion R2 are provided apart from each other in the axial direction. A first thrust bearing portion T1 is provided between the lower end surface 8c of the bearing sleeve 8 and the upper end surface 2b1 of the flange portion 2b of the shaft member 2, and the upper end surface 7c1 of the bottom portion 7c of the housing 7 and the flange portion 2b A second thrust bearing portion T2 is provided between the lower end surface 2b2.

  The housing 7 includes a substantially cylindrical side portion 7b and a substantially disc-shaped bottom portion 7c that seals one end opening of the side portion 7b. The side part 7b and the bottom part 7c are integrally or separately formed of, for example, a metal material such as stainless steel or brass, or a resin material. In this embodiment, the side portion 7b and the bottom portion 7c are formed separately from each other with a metal material, and the bottom portion 7c is fixed to the lower end portion of the side portion 7b by an appropriate means such as adhesion, press-fitting, or laser welding. A dynamic pressure generating means is provided in a partial region of the upper end surface 7c1 of the bottom 7c serving as a thrust bearing surface of the second thrust bearing portion T2. Although illustration is omitted, for example, dynamic pressure grooves arranged in a spiral shape Is formed. Note that the side portion 7b and the bottom portion 7c can be integrally molded with a metal material or a resin material. At that time, the dynamic pressure groove provided in the upper end surface 7c1 can be molded simultaneously with the molding of the housing 7 including the side portion 7b and the bottom portion 7c, thereby eliminating the trouble of separately forming the dynamic pressure groove in the bottom portion 7c. be able to. As the shape of the dynamic pressure groove, the above-described herringbone shape or the like may be adopted.

  The bearing sleeve 8 is formed in a cylindrical shape with, for example, a soft metal material such as brass or aluminum (aluminum alloy), or a sintered metal material. The inner circumferential surface 8a of the bearing sleeve 8 is provided with dynamic pressure generating means in two upper and lower regions which are the radial bearing surfaces of the first radial bearing portion R1 and the second radial bearing portion R2. For example, a herringbone-shaped dynamic pressure groove is formed. Specifically, for example, as shown in FIG. 3, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed in two upper and lower regions spaced apart in the axial direction, respectively. It is formed axially asymmetric with respect to the axial center (the axial center of the upper and lower inclined groove regions), and the axial dimension X1 in the upper region from the axial center m is larger than the axial dimension X2 in the lower region. It is getting bigger. Further, one or a plurality of axial grooves 8d1 are formed on the outer peripheral surface 8d of the bearing sleeve 8 over the entire axial length. In this embodiment, three axial grooves 8d1 are formed at equal intervals in the circumferential direction.

  Furthermore, although not shown in the partial region of the lower end surface 8c of the bearing sleeve 8 that becomes the thrust bearing surface of the first thrust bearing portion T1, a plurality of dynamic arrays arranged in a spiral shape, for example, as dynamic pressure generating means. A pressure groove is formed.

  The shaft member 2 is formed, for example, by subjecting a metal material such as stainless steel to rough forming by turning or forging and then performing grinding. The shaft member 2 of the example of illustration is comprised by the shaft part 2a and the flange part 2b integrally provided in the lower end of the shaft part 2a. In addition, the shaft part 2a and the flange part 2b can also be made into a different body. In that case, the shaft member 2 is comprised by press-fitting, welding, etc. to the shaft part 2a. As a form of the shaft member 2, in addition to the above, a hybrid structure including a metal portion and a resin portion (for example, the shaft portion 2a is formed of a metal material and the flange portion 2b is formed of a resin material) can be used. . The shaft portion 2 a is inserted into the inner periphery of the bearing sleeve 8, and the outer peripheral surface 2 a 1 of the shaft portion 2 a faces the inner peripheral surface 8 a of the bearing sleeve 8.

  As shown in an enlarged view in FIG. 4, a tapered guide surface 2c is formed at the upper end of the shaft portion 2a. The taper angle θ (inclination angle with respect to the axis) of the guide surface 2c is formed to be about 5 ° to 20 °. The edge disappears at the boundary between the guide surface 2c and the outer peripheral surface 2a3 of the shaft member 2 adjacent to the guide surface 2c (hereinafter referred to as “adjacent outer peripheral surface”), and the edge is not formed between both surfaces. A blunt portion 2d having a blunt shape is formed. In this embodiment, the blunt portion 2d has a curved surface shape with a radius r, and the guide surface 2c and the adjacent outer peripheral surface 2a3 are smoothly continuous.

  In the present embodiment, the blunt portion 2d is formed by simultaneously grinding the boundary portion described above with the guide surface 2c and the adjacent outer peripheral surface 2a3. As shown in FIG. 4, the simultaneous grinding is performed by a grindstone 11 having a straight portion 11a corresponding to the adjacent outer peripheral surface 2a3, a tapered portion 11b corresponding to the guide surface 2c, and a curved surface portion 11c corresponding to the blunt portion 2d. The curved surface portion 11c of the grindstone 11 is formed in a range of R0.1 to R0.5, and the straight portion 11a and the tapered portion 11b of the grindstone 11 are smoothly and continuously connected through the curved surface portion 11c. By grinding the outer periphery of the shaft member 2 using the grindstone 11, the guide surface 2c, the blunted portion 2d, and the adjacent outer peripheral surface 2a3 become continuous surfaces without edges.

  An annular seal member 9 formed of a metal material or a resin material is fixed to the inner periphery of the opening 7a of the housing 7 by means such as press-fitting or bonding. The inner peripheral surface 9a of the seal member 9 faces the tapered surface 2a2 of the shaft portion 2a via a seal space S having a predetermined volume. The tapered surface 2a2 gradually decreases in diameter toward the upper side, and functions as a centrifugal force seal by the rotation of the shaft member 2. Further, the lower end surface 9 b of the seal member 9 is in contact with the upper end surface 8 b of the bearing sleeve 8. After assembly of the hydrodynamic bearing device, the internal space of the hydrodynamic bearing device 1 sealed with the seal member 9 is filled with, for example, lubricating oil as a fluid. In this state, the oil level of the lubricating oil is within the range of the seal space S. Maintained within. Note that the seal member 9 can be formed integrally with the housing 7 in order to reduce the number of parts and the number of assembly steps. Alternatively, the upper end side region of the inner peripheral surface 8a of the bearing sleeve 8 is formed to have a slightly larger diameter than the region serving as the radial bearing surface, and a seal space having a predetermined volume is formed on the inner diameter side of the region formed to have the large diameter. You may be made to do.

  The hydrodynamic bearing device 1 is configured as described above, and when the shaft member 2 rotates, the upper and lower two regions that become the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 are respectively the radial surface and the outer peripheral surface 2a1 of the shaft portion 2a. Opposing through the bearing gap. As the shaft member 2 rotates, dynamic pressure of lubricating oil is generated in the radial bearing gap, and the shaft portion 2a of the shaft member 2 is supported in a non-contact manner so as to be rotatable in the radial direction. 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.

  Further, the region that becomes the thrust bearing surface of the lower end surface 8c of the bearing sleeve 8 is opposed to 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 upper end surface 7c1 of the bottom portion 7c is It faces the lower end surface 2b2 of the flange portion 2b through a thrust bearing gap. As the shaft member 2 rotates, dynamic pressure of lubricating oil is generated in the thrust bearing gap, and the shaft member 2 is supported in a non-contact manner in both thrust directions by the pressure. Thereby, the 1st thrust bearing part T1 and the 2nd thrust bearing part T2 which non-contact-support the shaft member 2 rotatably in both thrust directions are formed.

  After the assembly of the hydrodynamic bearing device 1 having the above configuration is completed, the disk hub 3 as a rotating member is press-fitted and fixed to the upper end of the shaft portion 2a of the shaft member 2 when the motor is assembled. At the time of the press-fitting, the guide surface 2c provided at the upper end of the shaft portion 2a serves as a guide for press-fitting the disc hub 3, so that the disc hub 3 is taper-guided by the guide surface 2c, and the inclination of the disc hub 3 due to press-fitting is inclined. It is suppressed. Further, since the R-shaped blunt portion 2d is provided between the adjacent outer peripheral surface 2a3 and the guide surface 2c, the press-fit resistance is also reduced. Therefore, it is possible to press-fit smoothly without tilting the disk hub 3. Thus, the pressure input when the disk hub 3 is press-fitted into the upper end of the shaft portion 2a of the shaft member 2 is the surface of the member constituting the thrust bearing portions T1, T2, that is, the upper end surface 2b1 and the lower end surface of the flange portion 2b. 2b2, the lower end surface 8c of the bearing sleeve 8, and the lower end stress of the upper end surface 7c1 of the bottom portion 7c can be restricted to less than the yield stress. Further, when the disk hub 3 is press-fitted, the press-fitting can be easily performed without requiring a special device or the like, so that the assembly cost of the motor can be reduced.

  The present invention can be similarly applied not only to the fluid dynamic bearing device 1 shown in FIG. 2 but also to other fluid dynamic bearing devices exemplified below. In the following description, members and elements having basically the same functions as those in the embodiment shown in FIG.

  FIG. 5 shows another embodiment of the hydrodynamic bearing device. The thrust bearing portion T of the hydrodynamic bearing device 1 is located on the opening side of the housing 7 and supports the shaft member 2 with respect to the bearing sleeve 8 in a non-contact manner in one thrust direction. A flange portion 2 b is provided above the lower end of the shaft member 2, and a thrust bearing gap of the thrust bearing portion T is formed between the lower end surface 2 b 2 of the flange portion 2 b and the upper end surface 8 b of the bearing sleeve 8. A seal member 9 is attached to the inner periphery of the opening of the housing 7, and a seal space S is formed between the inner peripheral surface 9 a of the seal member 9 and the outer peripheral surface 2 a 1 of the shaft portion 2 a of the shaft member 2. The lower end surface 9b of the seal member 9 is opposed to the upper end surface 2b1 of the flange portion 2b via an axial clearance, and when the shaft member 2 is displaced upward, the upper end surface 2b1 of the flange portion 2b is the seal member. 9 is engaged with the lower end surface 9b, and the shaft member 2 is prevented from coming off. Also in this embodiment, when the disk hub 3 is press-fitted, the pressure input is less than the yield stress of the surface of the member constituting the thrust bearing portion T, that is, the lower end surface 2b2 of the flange portion 2b and the upper end surface 8b of the bearing sleeve 8. As shown in FIG. 4, a guide surface 2c, an adjacent outer peripheral surface 2a3, and a blunt portion 2d similar to those shown in FIG. 4 are provided.

  In the above-described embodiment, the dynamic pressure grooves of the radial bearing portions (R1, R2) can be formed on the outer peripheral surface 2a1 of the shaft portion 2a of the shaft member 2. The dynamic pressure grooves of the thrust bearing portions (T, T1, T2) are formed on the upper end surface 2b1 and the lower end surface 2b2 of the flange portion 2b of the shaft member 2 (lower end surface 2b2 in the case of the embodiment shown in FIG. 5). It can also be formed.

  Furthermore, in the above description, the radial bearing portions R1 and R2 and the thrust bearing portions T, T1, and T2 are exemplified by a configuration in which a fluid dynamic pressure action is generated by a herringbone shape or spiral shape dynamic pressure groove. However, the present invention is not limited to this.

  For example, so-called step bearings or multi-arc bearings may be employed as the radial bearing portions R1 and R2.

  FIG. 6 shows an example in which one or both of the radial bearing portions R1 and R2 are configured by step bearings. In this example, a plurality of axial groove-shaped dynamic pressure grooves 8a3 are provided at predetermined intervals in the circumferential direction in a region that becomes a radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8.

  FIG. 7 shows an example of a case where one or both of the radial bearing portions R1 and R2 are constituted by multi-arc bearings. In this example, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a4, 8a5, and 8a6 (so-called three arc bearings). The centers of curvature of the three arcuate surfaces 8a4, 8a5, 8a6 are offset from the shaft center O of the bearing sleeve 8 (shaft portion 2a) by an equal distance. In each region defined by the three arcuate surfaces 8a4, 8a5, and 8a6, the radial bearing gap has a shape gradually reduced in a wedge shape in both circumferential directions. For this reason, when the bearing sleeve 8 and the shaft portion 2a rotate relative to each other, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape in accordance with the direction of the relative rotation, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid. Note that a deeper axial groove called a separation groove may be formed at the boundary between the three arcuate surfaces 8a4, 8a5, 8a6.

  FIG. 8 shows another example in the case where one or both of the radial bearing portions R1 and R2 are constituted by multi-arc bearings. In this example as well, the region that becomes the radial bearing surface of the inner peripheral surface 8a of the bearing sleeve 8 is configured by three arc surfaces 8a7, 8a8, and 8a9 (so-called three arc bearings), but the three arc surfaces 8a7, In each region partitioned by 8a8 and 8a9, the radial bearing gap has a shape gradually reduced in a wedge shape with respect to one direction in the circumferential direction. The multi-arc bearing having such a configuration may be referred to as a taper bearing. Further, deeper axial grooves 8a10, 8a11, and 8a12 called separation grooves are formed at boundaries between the three arcuate surfaces 8a7, 8a8, and 8a9. Therefore, when the bearing sleeve 8 and the shaft portion 2a are relatively rotated in a predetermined direction, the lubricating fluid in the radial bearing gap is pushed into the minimum gap side reduced in a wedge shape, and the pressure rises. The bearing sleeve 8 and the shaft portion 2a are supported in a non-contact manner by the dynamic pressure action of the lubricating fluid.

  FIG. 9 shows another example in the case where one or both of the radial bearing portions R1 and R2 are configured by multi-arc bearings. In this example, in the configuration shown in FIG. 8, the predetermined regions α on the minimum gap side of the three arcuate surfaces 8a7, 8a8, 8a9 are concentric with the axis O of the bearing sleeve 8 (shaft portion 2a) as the center of curvature. It is composed of arcs. Accordingly, in each predetermined region α, 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.

  The multi-arc bearings in the above examples are so-called three-arc bearings, but are not limited to this, and so-called four-arc bearings, five-arc bearings, and multi-arc bearings composed of more than six arc surfaces are adopted. You may do it. Further, when the radial bearing portion is constituted by a step bearing or a multi-arc bearing, in addition to the configuration in which the two radial bearing portions are separated from each other in the axial direction as in the radial bearing portions R1 and R2, the bearing sleeve 8 It is good also as a structure which provided the one radial bearing part over the up-and-down area | region of the internal peripheral surface 8a.

  Further, one or both of the thrust bearing portion T and the thrust bearing portions T1 and T2 are provided with a plurality of radial groove-shaped dynamic pressure grooves at predetermined intervals in the circumferential direction, for example, in a region serving as a thrust bearing surface. A so-called step bearing, a so-called corrugated bearing (the step mold is a corrugated bearing), or the like can also be used.

  Moreover, in the above embodiment, the inside of the hydrodynamic bearing device 1 is filled, and the radial bearing gap between the bearing sleeve 8 and the shaft member 2 and the thrust between the bearing sleeve 8 and the housing 7 and the shaft member 2 are filled. Lubricating oil is exemplified as the fluid that generates dynamic pressure in the bearing gap, but other fluids that can generate dynamic pressure in each bearing gap, for example, gas such as air, magnetic fluid, etc. You can also.

It is sectional drawing which shows the outline | summary of a spindle motor. It is sectional drawing which shows one structural example of the hydrodynamic bearing apparatus concerning this invention. It is a longitudinal cross-sectional view of a bearing sleeve. It is the schematic which shows the grinding process of a shaft member. It is sectional drawing which shows other embodiment of a hydrodynamic bearing apparatus. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is sectional drawing which shows other embodiment of a radial bearing part. It is the schematic which shows the grinding process of the conventional shaft member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2b Flange part 2a3 The outer peripheral surface (adjacent outer peripheral surface) adjacent to a guide surface
2c Guide surface 2d Blunt part 3 Disc hub (rotating member)
4 Stator coil 5 Rotor magnet 7 Housing 8 Bearing sleeve R1 First radial bearing portion R2 Second radial bearing portion T1 First thrust bearing portion T2 Second thrust bearing portion T Thrust bearing portion

Claims (8)

A bearing sleeve, a shaft member inserted into the inner periphery of the bearing sleeve, a rotating member press-fitted into the outer periphery of the shaft member, and the dynamic pressure action of the fluid generated in the radial bearing gap causes the shaft member to be non-radial. In a hydrodynamic bearing device comprising a radial bearing portion that supports contact and a thrust bearing portion that non-contactally supports the shaft member in a thrust direction by a hydrodynamic action of a fluid generated in a thrust bearing gap.
The dynamic pressure bearing device according to claim 1, wherein the rotating member is press-fitted into the shaft member with a pressure input less than a yield stress of a member surface constituting the thrust bearing portion.   The shaft member is provided with a guide surface that serves as a guide for press-fitting the rotating member, and a blunt portion having a blunt shape is provided between the guide surface and the outer peripheral surface of the shaft member adjacent thereto. The hydrodynamic bearing device according to claim 1.   The hydrodynamic bearing device according to claim 1, wherein the guide surface, the outer peripheral surface of the shaft member adjacent to the guide surface, and the blunt portion are ground.   The hydrodynamic bearing device according to claim 1, wherein the blunt portion is formed in a curved surface shape.   The hydrodynamic bearing device according to claim 1, wherein the rotating member is a disc hub on which a disc is placed.   The hydrodynamic bearing device according to claim 1, wherein the radial bearing portion includes a hydrodynamic groove as a hydrodynamic pressure generating unit.   The hydrodynamic bearing device according to any one of claims 1 to 5, wherein the radial bearing portion is a multi-arc bearing. A spindle motor of a disk device comprising the hydrodynamic bearing device according to claim 1.

Images