JP5762774B2 - Fluid dynamic bearing device - Google Patents

Description

  The present invention relates to a fluid dynamic bearing device.

  The fluid dynamic pressure bearing device supports a shaft member so as to be relatively rotatable by a dynamic pressure action of lubricating oil generated in a radial bearing gap between an inner peripheral surface of the bearing member and an outer peripheral surface of the shaft member. Since the fluid dynamic bearing device has excellent rotational accuracy and quietness, for example, for spindle motors of various disk drive devices (such as HDD magnetic disk drive devices and CD-ROM optical disk drive devices), laser beams, etc. It is suitably used for a polygon scanner motor of a printer (LBP) or a color wheel motor of a projector.

  As a bearing member incorporated in a fluid dynamic pressure bearing device, a sintered bearing made of sintered metal and having a dynamic pressure groove region formed on an inner peripheral surface may be used. For example, in the sintered bearing 100 shown in FIG. 12A, radial bearing surfaces 110 are provided at two locations separated in the axial direction on the inner peripheral surface, and a dynamic pressure groove region is formed on each radial bearing surface 110. Specifically, a plurality of inclined groove portions 101 that are inclined to one side and the other side with respect to the circumferential direction and arranged in a herringbone shape, and a plurality of inclined hills provided between the plurality of inclined groove portions 101 in the circumferential direction. The portion 102 and an annular back portion 103 that is provided at the axial center of the radial bearing surface 110 and that is flush with the inclined hill portion 102 are provided. Cylindrical surfaces 104 that are flush with the inclined groove portions 101 are provided on both axial sides of each radial bearing surface 110. Due to the dynamic pressure groove region of the radial bearing surface 110, the lubricating oil filled in the radial bearing gap facing the inner peripheral surface of the sintered bearing 100 flows to the axial center side of the radial bearing surface 110, and the pressure is applied to the back portion 103. Is increased.

  As a method for forming the dynamic pressure groove region on the inner peripheral surface of the sintered bearing, for example, Patent Document 1 discloses a molding die corresponding to the shape of the dynamic pressure groove region on the inner periphery of the sintered body (bearing sleeve material). After inserting a forming pin having a method, a method is shown in which the shape of the forming die is transferred to the inner peripheral surface of the sintered body by pressing the sintered body in the radial direction and pressing the inner peripheral surface against the forming die. Yes. As shown in FIG. 13, the forming die 120 formed on the forming pin (core rod) forms an inclined convex portion 121 for forming the inclined groove portion of the dynamic pressure groove region and an inclined hill portion of the dynamic pressure groove region. It consists of the inclined recessed part 122 and the cyclic | annular back part shaping | molding surface 123 which shape | molds the back part of a dynamic pressure groove area | region. On both sides in the axial direction of the mold 120, cylindrical surfaces 124 that are continuous with the inclined convex portions 121 are provided. By pressing the inner peripheral surface of the sintered body against the molding die 120, the inclined convex portion 121 bites into the inner peripheral surface of the sintered body to form the inclined groove portion, and at the same time, the inclined concave portion 122 contains the sintered body. The material enters and the sloped hill is formed.

Japanese Patent Laid-Open No. 11-190344 Japanese Patent Application Laid-Open No. 2005-264983

  However, when the material of the sintered body 130 enters the inside of the inclined concave portion 122 of the mold 120, the material of the sintered body 130 flows due to friction with the side wall 121a of the inclined convex portion 121, as shown in FIG. It is obstructed, and the inside of the inclined recess 122 may not be filled with the material of the sintered body 130. In particular, since the tip 122a of the inclined recess 122 is surrounded on three sides by the side wall 121a of the inclined protrusion 121 and the side wall 124a of the cylindrical surface 124 (see FIG. 13), the material of the sintered body 130 is the inclined recess. In particular, it is difficult to enter the interior of 122, and the tip 102a of the inclined hill portion 102 in the dynamic pressure groove region may not reach a desired height (see FIG. 15). In this case, as shown in FIG. 12 (b), there is a possibility that so-called “sagging” occurs in the dynamic pressure groove region of the radial bearing surface 110 in which the height of the inclined hill portion 102 gradually decreases toward the tip. .

  As described above, when sagging occurs in the hill portion of the dynamic pressure groove region, the groove depth gradually becomes shallower toward the tip, so that sufficient dynamic pressure action cannot be obtained, and the bearing rigidity may be reduced. . In order to avoid such a problem, for example, Patent Document 2 shows a configuration in which a smooth surface facing the dynamic pressure groove region is partitioned by a step so that the length thereof is shorter than the length of the dynamic pressure groove region. ing. According to this configuration, in the hydrodynamic groove region, the portion where the groove depth is shallow due to sagging does not function as a bearing surface, and only the portion having a sufficient groove depth functions as a bearing surface. Can be prevented.

  However, the method described in Patent Document 2 suppresses a decrease in bearing rigidity on the premise of occurrence of sagging, and does not prevent sagging itself. Further, in the configuration described in Patent Document 2, since a dynamic pressure groove region wider than the bearing surface is required, the size of the sintered bearing must be increased, leading to an increase in the size of the entire bearing unit. On the other hand, if the size of the sintered bearing is maintained, the area of the bearing surface must be reduced, resulting in a decrease in bearing rigidity.

  The problem to be solved by the present invention is to prevent sagging of the hill portion of the dynamic pressure groove region formed on the inner peripheral surface of the sintered bearing and increase the bearing rigidity.

The present invention made in order to solve the above problems includes a sintered bearing, a shaft member inserted into the inner periphery of the sintered bearing, an inner peripheral surface of the sintered bearing, and an outer peripheral surface of the shaft member. A hydrodynamic bearing device including a radial bearing portion that supports the shaft member so as to be relatively rotatable by a hydrodynamic action of a lubricating fluid in a radial bearing gap formed therebetween, the inner circumferential surface of the sintered bearing A plurality of inclined groove portions extending in a direction inclined with respect to the circumferential direction and arranged at a predetermined interval in the circumferential direction, and provided between the plurality of inclined groove portions in the circumferential direction, and having an inner diameter larger than the inclined groove portion. A dynamic pressure groove region having a plurality of inclined hill portions raised to the side is formed at two locations separated in the axial direction, and has a larger diameter than the inclined hill portion between the two dynamic pressure groove regions in the axial direction. a cylindrical surface is formed, along with the relative rotation of the shaft member, the inclined groove respective dynamic groove region Along fine the inclined lands to dynamic flow of lubricating fluid, the axial ends of the cylindrical surface of the inner peripheral surface of the sintered bearing, the inclined land portions adjacent to the cylindrical surface, along the inclined lands A first annular hill portion that connects the upstream end in the flow direction of the lubricating fluid over the entire circumference , and the inclined groove portion, the inclined hill portion, and the first annular hill portion are all molded. A large-diameter outer peripheral surface and a small-diameter outer peripheral surface are provided on the shaft member, and the radial bearing gap is formed between each dynamic pressure groove region of the sintered bearing and the large-diameter outer peripheral surface of the shaft member. The first annular hill portion of the sintered bearing is opposed to the small-diameter outer peripheral surface of the shaft member in the radial direction.

This sintered bearing can be manufactured by the following method. That is, the inner circumferential surface is provided between a plurality of inclined groove portions extending in a direction inclined with respect to the circumferential direction and arranged at a predetermined interval in the circumferential direction, and between the plurality of inclined groove portions in the circumferential direction, A dynamic pressure groove region having a plurality of inclined hills raised on the inner diameter side of the inclined groove portion is formed, and the lubricating fluid is axially moved along the inclined groove portion with relative rotation of the shaft member inserted in the inner periphery. A method of manufacturing a sintered bearing that flows to one side in a direction , wherein a molding pin is inserted into the inner periphery of the sintered body, and the inner peripheral surface of the sintered body is formed into a molding die provided on the outer peripheral surface of the molding pin. by pressing, molding and molding the dynamic pressure generating groove region on the inner peripheral surface of the sintered body, wherein the mold comprises a plurality of ramps forming said plurality of inclined grooves, a plurality of inclined lands over a plurality of inclined recesses for the ends of the other axial side of said plurality of inclined recesses all around It can be prepared by a method and an annular recess for coupling.

  Thus, by providing an annular recess that connects the ends of the plurality of inclined recesses over the entire circumference in the molding die for forming the dynamic pressure groove region, the end of the inclined recess is surrounded on three sides; Must not. Therefore, when the mold is pressed against the inner peripheral surface of the sintered body, the material of the sintered body easily enters the inside of the inclined recess, and the inside of the inclined recess is filled with the material of the sintered body. Accordingly, since the inclined hill portion can be formed at a desired height to the end portion, the groove depth of the dynamic pressure groove region is sufficiently ensured to the end portion, and the bearing rigidity can be increased.

  The plurality of inclined groove portions in the dynamic pressure groove region can be arranged in a herringbone shape or a spiral shape, for example.

  If the axial width of the annular recess of the mold is increased, the material of the sintered body can easily enter the inside of the annular recess, so that the material can more easily enter the end of the inclined recess that is continuous with the annular recess. The height of the hill portion of the pressure groove region can be reliably ensured up to the end. In order to obtain such an effect, the axial width of the annular hill portion may be made larger than, for example, the width in the direction orthogonal to the extending direction of the inclined hill portion.

  The above-mentioned sintered bearing, the shaft member inserted in the inner periphery of the sintered bearing, and the lubricating fluid in the radial bearing gap formed between the inner peripheral surface of the sintered bearing and the outer peripheral surface of the shaft member A fluid dynamic pressure bearing device including a radial bearing portion that supports a shaft member so as to be relatively rotatable by dynamic pressure action has high bearing rigidity because the dynamic pressure groove region is formed with high accuracy.

  In this fluid dynamic pressure bearing device, for example, a shaft member is provided with a large-diameter outer peripheral surface and a small-diameter outer peripheral surface, and a radial bearing gap is formed between the dynamic pressure groove region of the sintered bearing and the large-diameter outer peripheral surface of the shaft member. It can be configured. In this case, if the annular hill portion of the sintered bearing and the small-diameter outer peripheral surface of the shaft member are opposed to each other in the radial direction, an increase in torque due to a decrease in the gap between the annular hill portion and the outer peripheral surface of the shaft member is avoided. it can.

  As described above, according to the present invention, the formation of the annular hill portion on the inner peripheral surface of the sintered bearing can prevent the hill portion of the dynamic pressure groove region from sagging, and thus the bearing rigidity can be increased.

It is sectional drawing of a spindle motor. It is sectional drawing of the fluid dynamic pressure bearing apparatus integrated in the said spindle motor. It is sectional drawing of the bearing sleeve as a sintered bearing which concerns on one Embodiment of this invention integrated in the said fluid dynamic pressure bearing apparatus. FIG. 4 is an enlarged view of FIG. 3. It is a bottom view of the said bearing sleeve. It is sectional drawing which shows the radial bearing clearance periphery of the said fluid dynamic pressure bearing apparatus. It is a front view of the shaping | molding pin used for shaping | molding of a sintered bearing. It is sectional drawing in the ZZ line | wire of FIG. 7 which shows a mode that a dynamic pressure groove area | region is shape | molded in the internal peripheral surface of a sintered compact with the said shaping | molding pin. It is sectional drawing of the bearing sleeve which concerns on other embodiment. It is sectional drawing of the bearing sleeve which concerns on other embodiment. It is sectional drawing of the bearing sleeve which concerns on other embodiment. It is sectional drawing of the conventional bearing sleeve. FIG. 13 is a front view of a forming pin used for forming the bearing sleeve of FIG. 12. It is sectional drawing in the XX line of FIG. 13 which shows a mode that a dynamic pressure groove is shape | molded in the internal peripheral surface of a sintered compact with the said shaping | molding pin. It is sectional drawing in the YY line | wire of FIG. 13 which shows a mode that a dynamic pressure groove is shape | molded in the internal peripheral surface of a sintered compact with the said shaping | molding pin.

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

  FIG. 1 shows a spindle motor in which a fluid dynamic bearing device 1 having a sintered bearing (bearing sleeve 8) according to an embodiment of the present invention is incorporated. This spindle motor is used in, for example, a 2.5-inch HDD disk drive device, and includes a fluid dynamic pressure bearing device 1 that rotatably supports a shaft member 2, a bracket 6 to which the fluid dynamic pressure bearing device 1 is attached, A stator coil 4 and a rotor magnet 5 are provided to face each other through a gap in the radial direction. The stator coil 4 is attached to the bracket 6, and the rotor magnet 5 is attached to the disk hub 3. A predetermined number (1 in the illustrated example) of disks D are mounted on the disk hub 3. 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 shaft member 2, the disk hub 3, and the disk D are rotated together.

  As shown in FIG. 2, the fluid dynamic bearing device 1 includes a shaft member 2, a bearing sleeve 8 as a sintered bearing in which the shaft member 2 is inserted on the inner periphery, and the bearing sleeve 8 fixed to the inner peripheral surface. The bottomed cylindrical housing 7 and a seal member 9 provided in the opening of the housing 7 are configured. In the following, for convenience of explanation, the opening side of the housing 7 in the axial direction is the upper side and the closing side is the lower side.

  The shaft member 2 includes a shaft portion 2a and a flange portion 2b provided at the lower end of the shaft portion 2a, and is integrally formed of a molten material such as stainless steel. The shaft portion 2a has a cylindrical large-diameter outer peripheral surface 2a1 and a tapered surface 2a2 that is gradually reduced in diameter upward. In the illustrated example, the large-diameter outer peripheral surface 2a1 is provided at two locations separated in the axial direction, and a small-diameter outer peripheral surface 2a3 having a smaller diameter than the large-diameter outer peripheral surface 2a1 is provided between these axial directions. The large-diameter outer peripheral surface 2a1 and the small-diameter outer peripheral surface 2a3 of the shaft portion 2a are opposed to the inner peripheral surface 8a of the bearing sleeve 8 in the radial direction, and the tapered surface 2a2 is opposed to the inner peripheral surface 9a of the seal member 9 in the radial direction.

  The bearing sleeve 8 is a sintered metal mainly composed of copper, iron, or both, and is formed in a substantially cylindrical shape. A radial bearing surface facing the radial bearing gap is provided on the inner peripheral surface 8a of the bearing sleeve 8, and in this embodiment, as shown in FIG. 3, the radial bearing is provided at two locations separated in the axial direction of the inner peripheral surface 8a. Surfaces A1 and A2 are provided.

  The radial bearing surfaces A1 and A2 are each formed with a dynamic pressure groove region for generating a dynamic pressure action on the lubricating fluid (lubricating oil in the present embodiment) in the radial bearing gap. In the illustrated example, a plurality of inclined groove portions 8a1, 8a2 that extend in a direction inclined with respect to the circumferential direction, are arranged at equal intervals in the circumferential direction, and are arranged in a herringbone shape, and a plurality of inclined groove portions 8a1, 8a2. A plurality of inclined hill portions provided between the circumferential directions and provided between the plurality of inclined hill portions 8a3, 8a4 and the plurality of inclined groove portions 8a1, 8a2 in an axial direction. The dynamic pressure groove region is configured by 8a3 and 8a4 and the annular back portion 8a5 which is flush with the surface. When the shaft member 2 rotates, the lubricating oil flows downward by the upper inclined groove portion 8a1, and the lubricating oil flows upward by the lower inclined groove portion 8a2, so that the lubricating oil is collected on the back portion 8a5 and lubricated. The pressure of is increased. In the illustrated example, in the upper radial bearing surface A1, the dynamic pressure groove region is formed to be asymmetric in the axial direction. Specifically, the axial dimension of the upper inclined groove portion 8a1 is the same as that of the lower inclined groove portion 8a2. It is larger than the axial dimension. The dynamic pressure groove region of the lower radial bearing surface A2 is formed symmetrically in the axial direction.

  Annular hill portions 8a6 and 8a7 are provided on at least one axial end side of the dynamic pressure groove region of each radial bearing surface A1 and A2, in this embodiment, on both upper and lower sides of each radial bearing surface A1 and A2. The annular hill portion 8a6 connects the upper end portions of the inclined hill portions 8a3 on the upper side of each dynamic pressure groove region over the entire circumference. The annular hill portion 8a7 connects the lower end of the inclined hill portion 8a4 on the lower side of each dynamic pressure groove region over the entire circumference. In the illustrated example, inclined hill portions 8a3 and 8a4, a back portion 8a5, and annular hill portions 8a6 and 8a7 are continuously provided on the same cylindrical surface (these are indicated by cross-hatching). As shown in FIG. 4, the axial width W1 of the annular hill portion 8a6 provided on the upper side of each radial bearing surface A1, A2 is in a direction orthogonal to the extending direction of the upper inclined hill portion 8a3 continuous with the annular hill portion 8a6. It is larger than the width W2 (W1> W2). Similarly, the axial width of the annular hill portion 8a7 provided on the lower side of each radial bearing surface A1, A2 is larger than the width in the direction orthogonal to the extending direction of the lower inclined hill portion 8a4 that is continuous therewith. Large (not shown). Between the annular hill portion 8a7 on the lower side of the radial bearing surface A1 and the annular hill portion 8a6 on the upper side of the radial bearing surface A2, a cylindrical surface 8a8 having a larger diameter than the annular hill portions 8a6 and 8a7 is provided.

  A thrust bearing surface that faces the thrust bearing gap is formed on the lower end surface 8 c of the bearing sleeve 8. On this thrust bearing surface, a dynamic pressure groove region for generating a dynamic pressure action on the lubricating oil filled in the thrust bearing gap is formed. In this embodiment, as shown in FIG. 5, a pump-in type spiral shape is formed. A dynamic pressure groove 8c1 is formed (cross hatching is a hill). An axial groove 8 d 1 is formed on the outer peripheral surface 8 d of the bearing sleeve 8. The number of the axial grooves 8d1 is arbitrary, and in the present embodiment, for example, three axial grooves 8d1 are arranged at equal intervals in the circumferential direction.

  The housing 7 integrally has a cylindrical side portion 7a having a bearing sleeve 8 fixed to the inner peripheral surface and a bottom portion 7b that closes the lower end of the side portion 7a. A thrust bearing surface that faces the thrust bearing gap is formed on the upper end surface 7b1 of the bottom 7b of the housing 7. On the thrust bearing surface, for example, a spiral-shaped dynamic pressure groove (not shown) is formed as a dynamic pressure groove region for generating a dynamic pressure action on the lubricating oil filled in the thrust bearing gap.

  The seal member 9 is formed in an annular shape with, for example, a resin material or a metal material, and is disposed on the inner periphery of the upper end portion of the side portion 7 a of the housing 7. The inner peripheral surface 9a of the seal member 9 is opposed to the tapered surface 2a2 provided on the outer periphery of the shaft portion 2a in the radial direction, and a seal space S in which the radial dimension is gradually reduced downward is formed therebetween. The Due to the capillary force of the seal space S, the lubricating oil is drawn into the inside of the bearing, and oil leakage is prevented. In this embodiment, since the taper surface 2a2 is formed on the shaft portion 2a side, the seal space S also functions as a centrifugal force seal. The oil level of the lubricating oil filled in the internal space of the housing 7 sealed with the seal member 9 is maintained within the range of the seal space S. That is, the seal space S has a volume that can absorb the volume change of the lubricating oil.

  After assembling the above members, the fluid inside the housing 7 including the internal pores of the bearing sleeve 8 is filled with lubricating oil, whereby the fluid dynamic bearing device 1 shown in FIG. 2 is completed. At this time, the oil level is held inside the seal space S.

  When the shaft member 2 rotates, a radial bearing gap is formed between the radial bearing surfaces A1 and A2 of the inner peripheral surface 8a of the bearing sleeve 8 and the large-diameter outer peripheral surface 2a1 of the shaft portion 2a. Then, the pressure of the lubricating oil filled in the radial bearing gap is increased by the dynamic pressure groove regions formed on the radial bearing surfaces A1 and A2, and the shaft member 2 can be rotated in the radial direction by this pressure (dynamic pressure action). Radial bearing portions R1 and R2 that support non-contact are configured.

  At the same time, a thrust is formed between the upper end surface 2b1 of the flange portion 2b and the lower end surface 8c of the bearing sleeve 8, and between the lower end surface 2b2 of the flange portion 2b and the upper end surface 7b1 of the bottom portion 7b of the housing 7. A bearing gap is formed. The pressure of the lubricating oil filled in each thrust bearing gap is increased by the dynamic pressure groove 8c1 of the lower end surface 8c of the bearing sleeve 8 and the dynamic pressure groove of the upper end surface 7b1 of the bottom 7b of the housing 7, and this pressure (dynamic Thrust bearing portions T1 and T2 that support the shaft member 2 in a non-contact manner so as to be rotatable in both thrust directions are configured by the pressure action.

  At this time, as shown in FIG. 6, among the inner peripheral surface 8a of the bearing sleeve 8, the radial bearing surfaces A1 and A2 face the large-diameter outer peripheral surface 2a1 of the shaft portion 2a in the radial direction, and the radial bearing surfaces A1 and A2 The annular hill portions 8a6 and 8a7 between the axial directions are opposed to the small-diameter outer peripheral surface 2a3 of the shaft portion 2a (including a region having a smaller diameter than the large-diameter outer peripheral surface 2a1 and tapered surfaces at both axial ends) in the radial direction. As a result, a relatively large gap is formed between the annular hill portions 8a6 and 8a7 and the small-diameter outer peripheral surface 2a3 of the shaft portion 2a. Therefore, the annular hill portions 8a6 and 8a7 do not function as bearing surfaces. An increase in torque due to the provision of the portions 8a6 and 8a7 can be suppressed. 6 exaggerates the groove depth in the dynamic pressure groove region of the radial bearing surfaces A1 and A2, the diameter difference between the large diameter outer peripheral surface 2a1 and the small diameter outer peripheral surface 2a3 of the shaft member 2, or the radial bearing gap. ing. Actually, the groove depth of the radial bearing surfaces A1 and A2 is set to about 2 to 5 μm, the diameter difference of the shaft member 2 is set to about 50 to 100 μm, and the radial bearing gap is set to about 10 to 20 μm. In the illustrated example, the annular hill portion 8a6 provided on the upper side of the radial bearing surface A1 and the annular hill portion 8a7 provided on the lower side of the radial bearing surface A2 are formed in the radial direction with the large-diameter outer peripheral surface 2a1 of the shaft member 2. In the shaft member 2, a region (for example, a small-diameter cylindrical surface or a tapered surface) having a smaller diameter than the large-diameter outer peripheral surface 2a1 is provided in the region facing the annular hill portions 8a6 and 8a7. Also good.

  The axial groove 8d1 formed in the outer peripheral surface 8d of the bearing sleeve 8 forms a communication path through which lubricating oil can flow. This communication path can prevent a local negative pressure from being generated in the lubricating oil filled in the housing 7. In particular, in this embodiment, as shown in FIG. 3, the dynamic pressure groove region of the upper radial bearing surface A1 formed on the inner peripheral surface 8a of the bearing sleeve 8 is formed in an axially asymmetric shape. As the member 2 rotates, the lubricating oil in the radial bearing gap is pushed downward, and the lubricating oil circulates through the communication path, so that local negative pressure can be reliably prevented.

  The bearing sleeve 8 includes a compression molding process in which a metal powder is compression molded to form a cylindrical green compact, a sintering process in which the green compact is sintered at a predetermined temperature to obtain a sintered body, The sintered body is manufactured through a sizing process for sizing the sintered body with a predetermined dimensional accuracy and a groove forming process for forming a dynamic pressure groove region on the inner peripheral surface and the lower end surface of the sintered body in order. Hereinafter, the groove forming step will be described in detail.

  The groove forming step includes a step of inserting a forming pin 20 (see FIG. 7) into the inner periphery of the sintered body, a step of restraining both end surfaces in the axial direction of the sintered body with an upper punch and a lower punch, By press-fitting into the inner periphery of the die, the inner peripheral surface of the sintered body is pressed against the molding die on the outer peripheral surface of the molding pin 20, and a dynamic pressure groove region is formed on the inner peripheral surface of the sintered body. Done.

  As shown in FIG. 7, a forming die 20a for forming the radial bearing surface A1 and a forming die 20b for forming the radial bearing surface A2 are provided on the outer peripheral surface of the forming pin 20. The mold 20a includes inclined convex portions 20a1 and 20a2 for forming the inclined groove portions 8a1 and 8a2 in the dynamic pressure groove region, inclined concave portions 20a3 and 20a4 for forming the inclined hill portions 8a3 and 8a4 in the dynamic pressure groove region, and the dynamic pressure groove. It has a cylindrical back molding surface 20a5 that molds the back portion 8a5 of the region, and annular recesses 20a6 and 20a7 that mold the annular hill portions 8a6 and 8a7. The plurality of inclined convex portions 20a1 and 20a2 extend in a direction inclined with respect to the circumferential direction, are arranged at equal intervals in the circumferential direction, and are arranged in a herringbone shape. The plurality of inclined concave portions 20a3 and 20a4 are provided between the plurality of inclined convex portions 20a1 in the circumferential direction, and are recessed closer to the inner diameter side than the inclined convex portions 20a1. One end of each of the plurality of inclined recesses 20a3 and 20a4 is connected over the entire circumference with the back molding surface 20a5, and the other end is connected over the entire periphery with the annular recesses 20a6 and 20a7. That is, the inclined concave portions 20a3 and 20a4, the back molding surface 20a5, and the annular concave portions 20a6 and 20a7 are formed in the same continuous cylindrical surface shape, and a plurality of inclined convex portions 20a1 and 20a2 protrude from the cylindrical surface to the outer diameter side. ing.

  The molding die 20b for molding the radial bearing surface A2 has the same configuration as the molding die 20a except for the lengths of the upper inclined convex portion 20a1 and the inclined concave portion 20a3. Is omitted. A cylindrical molding surface 20a8 for molding the cylindrical surface 8a8 is provided between the molding die 20a and the molding die 20b in the axial direction. The cylindrical molding surface 20a8 has a larger diameter than the annular recesses 20a6 and 20a7.

  If the sintered body is pressed into the inner periphery of the die with the molding pin 20 as described above inserted into the inner periphery of the sintered body via a radial gap, the sintered body is pressed toward the inner diameter and sintered. The inner peripheral surface of the body is pressed against the outer peripheral surface of the forming pin 20. Thereby, the inclined convex portions 20a1 and 20a2 of the molds 20a and 20b are recessed into the inner peripheral surface of the sintered body to form the inclined groove portions 8a1 and 8a2, and the cylindrical formed surface 20a8 is formed on the inner peripheral surface of the sintered body. A cylindrical surface 8a8 is formed. At the same time, the sintered material enters the inclined recesses 20a3 and 20a4, the back molding surface 20a5, and the annular recesses 20a6 and 20a7 of the molds 20a and 20b, and the inclined hill portions 8a3 and 8a4, the back portion 8a5, and the annular hill portion 8a6. , 8a7 are formed.

  At this time, as shown in FIG. 8, the tips of the inclined recesses 20a3 and 20a4 of the mold 20a (20b) (particularly the tips on the upper and lower ends of the molds 20a and 20b) and the annular recesses 20a6 and 20a7 are flush with each other. Since it is continuous, it becomes easier for the material of the sintered body 10 to enter the ends of the inclined recesses 20a3 and 20a4 as compared with the conventional mold (see FIG. 13) in which the tip of the inclined recess is surrounded on three sides. Accordingly, the inclined hill portions 8a3 and 8a4 are accurately formed up to the end portions, and a decrease in bearing rigidity due to occurrence of sagging can be prevented. In addition, as shown in the figure, the end of the annular hills 8a6 and 8a7 of the sintered body 10 may be sag due to friction with the wall surfaces of the annular recesses 20a6 and 20a7, but the annular hills 8a6 and 8a7 are the bearing surfaces. Since it does not function as a bearing, the bearing rigidity is not affected. As described above, the dynamic pressure groove region of the radial bearing surface A1 and the dynamic pressure groove region of the radial bearing surface A2 are accurately formed on the inner peripheral surface of the sintered body 10. At the same time, a molding die provided on the lower punch (not shown) is pressed against the lower end surface of the sintered body to form a dynamic pressure groove region on this surface, and the bearing sleeve 8 is completed.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected to the location which has the same function as said embodiment, and duplication description is abbreviate | omitted.

  In the above embodiment, as shown in FIG. 3, the annular hill portion 8a7 provided below the upper radial bearing surface A1, and the annular hill portion 8a6 provided above the lower radial bearing surface A2. However, the present invention is not limited to this. For example, as shown in FIG. 9, the cylindrical surface 8a8 is omitted and the axial direction between the upper radial bearing surface A1 and the lower radial bearing surface A2 is omitted. A common annular hill portion 8a9 may be provided.

  Further, in the above embodiment, the annular hill portions 8a6 and 8a7 are provided on the both axial ends of the radial bearing surfaces A1 and A2, but the present invention is not limited to this. For example, as shown in FIG. You may provide an annular hill part only in one edge part of the axial direction of surface A1, A2. In the illustrated example, the annular hill portion 8a7 is provided below the upper radial bearing surface A1, the upper annular hill portion of the radial bearing surface A1 is omitted, and the inclined groove portion 8a1 and the inclined portion of the radial bearing surface A1 are further inclined. The hill part 8a3 is extended until it reaches the chamfer provided at the upper end of the inner peripheral surface 8a. Similarly, the annular hill portion 8a6 is provided on the upper side of the lower radial bearing surface A2, the lower annular hill portion is omitted from the radial bearing surface A2, and the inclined groove portion 8a2 of the radial bearing surface A2 and the inclined surface are inclined. The hill part 8a4 is extended until it reaches the chamfer provided at the lower end of the inner peripheral surface 8a. Thus, by extending the inclined hill portions 8a3, 8a4 to the end of the cylindrical inner peripheral surface 8a of the bearing sleeve, the end portions of the inclined concave portions (not shown) of the molding die for forming the inclined hill portions 8a3, 8a4 However, the inclined hill portions 8a3 and 8a4 can be accurately formed up to the end portions.

  Moreover, although the case where the back part 8a5 was provided between the axial directions of inclination groove part 8a1 and 8a2 was shown in said embodiment, not only this but a back part may be abbreviate | omitted as shown, for example in FIG. In this case, the upper and lower inclined groove portions 8a1 and 8a2 of the radial bearing surfaces A1 and A2 have a continuous V shape, and the upper and lower inclined hill portions 8a3 and 8a4 of the radial bearing surfaces A1 and A2 have a continuous V shape. It can be.

  In the above embodiment, the case where the plurality of inclined groove portions 8a1 and 8a2 formed on the radial bearing surfaces A1 and A2 are arranged in a herringbone shape is shown. 8a2 may be arranged in a spiral shape (not shown).

  In the above embodiment, the dynamic pressure groove region of the upper radial bearing surface A1 has an asymmetric shape in the axial direction, and the lubricating oil in the radial bearing gap is forcibly circulated. If smooth circulation is not necessary, the dynamic pressure groove region of the upper radial bearing surface A1 may be shaped symmetrical in the axial direction.

  In the above-described embodiment, the case where the dynamic pressure grooves on the thrust bearing surface are arranged in a spiral shape has been described. However, the present invention is not limited to this, and the dynamic pressure grooves may be arranged in a herringbone shape or a radial shape.

  In the above embodiment, the lubricating fluid is a lubricating oil. However, the present invention is not limited to this. For example, a fluid such as a magnetic fluid or air can be used.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft member 2a Shaft part 2a1 Large diameter outer peripheral surface 2a3 Small diameter outer peripheral surface 3 Disc hub 4 Stator coil 5 Rotor magnet 6 Bracket 7 Housing 8 Bearing sleeve (sintered bearing)
8a1, 8a2 Inclined groove portions 8a3, 8a4 Inclined hill portion 8a5 Back portion 8a6, 8a7 Annular hill portion 8a8 Cylindrical surface 9 Seal member 10 Sintered body 20 Molding pins 20a, 20b Molding die 20a1, 20a2 Inclined convex portion 20a3, 20a4 Inclined concave portion 20a5 Back portion Molding surface 20a6, 20a7 Annular recess 20a8 Cylindrical molding surface A1, A2 Radial bearing surface R1, R2 Radial bearing portion T1, T2 Thrust bearing portion S Seal space

Claims (6)

Lubrication fluid movement in a radial bearing gap formed between a sintered bearing, a shaft member inserted in the inner periphery of the sintered bearing, and an inner peripheral surface of the sintered bearing and an outer peripheral surface of the shaft member A fluid dynamic pressure bearing device including a radial bearing portion that supports the shaft member so as to be relatively rotatable by pressure,
Provided on the inner peripheral surface of the sintered bearing between a plurality of inclined groove portions extending in a direction inclined with respect to the circumferential direction and arranged at predetermined intervals in the circumferential direction, and between the plurality of inclined groove portions in the circumferential direction. The dynamic pressure groove region having a plurality of inclined hills raised to the inner diameter side than the inclined groove portion is formed at two locations separated in the axial direction, and between the axial directions of the two dynamic pressure groove regions, A cylindrical surface having a larger diameter than the inclined hill portion is formed,
With the relative rotation of said shaft member, to the dynamic flow of lubricating fluid along the inclined groove portion and the inclined lands of respective dynamic groove region,
At the both ends in the axial direction of the cylindrical surface of the inner peripheral surface of the sintered bearing, the end on the upstream side in the flow direction of the lubricating fluid along the inclined hill portion of the inclined hill portion adjacent to the cylindrical surface A first annular hill that connects over the
The inclined groove part, the inclined hill part, and the first annular hill part are all molded surfaces,
The shaft member is provided with a large-diameter outer peripheral surface and a small-diameter outer peripheral surface, and the radial bearing gap is formed between each dynamic pressure groove region of the sintered bearing and the large-diameter outer peripheral surface of the shaft member. A fluid dynamic bearing device in which a first annular hill portion of a bearing is opposed to a small-diameter outer peripheral surface of the shaft member in a radial direction. 2. The fluid according to claim 1 , wherein in each dynamic pressure groove region, the inclined groove portion and the inclined hill portion adjacent to the cylindrical surface and the inclined groove portion and the inclined hill portion on the side separated from the cylindrical surface are arranged in a herringbone shape. Hydrodynamic bearing device. The fluid dynamic pressure bearing device according to claim 2, further comprising a second annular hill portion that connects the end portion on the axially outer side of the inclined hill portion on the side separated from the cylindrical surface over the entire circumference. 3. The axially outer end portion of the inclined groove portion and the inclined hill portion on the side separated from the cylindrical surface reaches a chamfer provided at an axial end portion of the inner peripheral surface of the sintered bearing. Fluid dynamic bearing device. The fluid dynamic pressure bearing device according to claim 1 , wherein the plurality of inclined groove portions are arranged in a spiral shape in each dynamic pressure groove region . The fluid dynamic bearing device according to any one of claims 1 to 5 , wherein an axial width of the first annular hill portion is larger than a width in a direction orthogonal to an extending direction of the inclined hill portion.

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