JP2016180427A - Bearing member of fluid dynamic pressure bearing device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing member in which cylindrical bodies adjacent in an axial direction are properly connected, and concentricity between radial bearing surfaces provided at two places in the axial direction so as to separate from each other is properly secured.SOLUTION: In a bearing member 3 for a fluid dynamic pressure bearing device, by sizing first and second cylindrical bodies 31, 32 arranged consecutively in an axial direction and made of a sintered metal, the cylindrical bodies 31, 32 are connected; on the inner peripheral surfaces of the first and second cylindrical bodies 31, 32, radial bearing surfaces A1, A2 molded by the sizing are provided respectively; and an intermediate relief part B is provided between the radial bearing surfaces A1, A2. To a recess part 5 provided only at one (32c) of two end surfaces 31b, 32c opposite to each other in an axial direction, a convex projection part 6 occurring at the other (31b) with the sizing is closely contacted, thereby to form a fitting structure 7 having irregularities. The first and second cylindrical bodies 31, 32 are connected by the fitting structure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bearing member for a fluid dynamic bearing device and a method for manufacturing the same, and more particularly to a bearing member formed by connecting a plurality of cylindrical bodies arranged in an axial direction and a method for manufacturing the same.

  As is well known, a fluid dynamic bearing device has features such as high-speed rotation, high rotation accuracy, and low noise. Therefore, a spindle motor incorporated in a disk drive device such as an HDD, a fan motor incorporated in a PC, etc. It is suitably used as a bearing device for a motor such as a polygon scanner motor incorporated in a laser beam printer.

  The fluid dynamic bearing device includes a bearing member having a cylindrical radial bearing surface on the inner periphery, and a shaft to be supported by a lubricating film (for example, an oil film) of fluid generated in a radial bearing gap formed by the radial bearing surface. And a radial bearing portion that is rotatably supported in the radial direction. As the bearing member, a radial bearing surface is provided at two locations spaced apart in the axial direction on the inner peripheral surface, and a so-called cylindrical surface (medium escape portion) having a larger diameter than the radial bearing surface is provided between both radial bearing surfaces. In some cases, a middle relief structure is employed.

  The bearing member having the intermediate relief structure may be configured by a single cylindrical body or may be configured by combining and integrating a plurality of cylindrical bodies arranged in the axial direction. However, as the cylindrical body having the radial bearing surface, a cylindrical body made of a sintered metal excellent in workability (mass productivity) and oil film forming ability in the radial bearing gap is used.

  For example, the following Patent Document 1 (FIG. 1) discloses a bearing member in which a middle relief portion is formed by joining two cylindrical bodies arranged continuously in the axial direction. More specifically, referring to FIG. 6 of the present application, the bearing member 100 is a combination in which a sintered metal first and second cylindrical bodies 110 and 120 are arranged between the two, which are arranged continuously in the axial direction. The first radial bearing surface 101 is provided on the inner periphery of the first cylindrical body 110, and the second radial bearing surface 102 and both radial bearing surfaces are provided on the inner periphery of the second cylindrical body 120. A cylindrical surface (medium escape portion) 103 having a diameter larger than those of 101 and 102 is provided.

  The bearing member 100 is finished into a finished product shape using a sizing mold 130 shown in FIGS. Specifically, as shown in FIG. 7A, first, on the outer periphery of the sizing core 131, the second cylindrical body 120 (strictly, the cylindrical material that is finished to the second cylindrical body 120 shown in FIG. 6 by sizing). ) With respect to the cylindrical fitting portion (meat removal portion) 121 provided on the outer peripheral side of one end of the first cylindrical body 110 (strictly, the cylindrical material finished to the first cylindrical body 110 shown in FIG. 6 by sizing) ), The assembly formed by fitting the cylindrical fitting portion 111 provided on the outer peripheral side of the other end is disposed, and then the sizing core 131 and the upper punch 133 are lowered as shown in FIG. Thus, the assembly is press-fitted into the inner periphery of the die 132. Then, as shown in FIG. 7C, the sizing core 131 and the upper punch 133 are further lowered, and the assembly is compressed in the axial direction by the upper punch 133 and the lower punch 134. When the assembly is compressed in the axial direction, both cylindrical bodies 110 and 120 expand and deform in the radial direction, and the inner and outer peripheral surfaces of both cylindrical bodies 110 and 120 become the outer peripheral surface of the sizing core 131 and the inner peripheral surface of the die 132. Each is pressed. Along with this, the opposing two surfaces of both the cylindrical bodies 110 and 120 (for example, the large-diameter inner peripheral surface 112 of the first cylindrical body 110 and the small-diameter outer peripheral surface 122 of the second cylindrical body 120 shown in FIG. A coupling portion 104 that couples both the cylindrical bodies 110 and 120 is formed. In addition, radial bearing surfaces 101 and 102 are formed on a portion of the inner peripheral surfaces of both cylindrical bodies 110 and 120 pressed against the sizing core 131, and between the two cylindrical bodies 110 and 120 (particularly, both radial bearing surfaces 101, 102).

Japanese Patent No. 3475215

  As described above, according to the technical means disclosed in Patent Document 1, even when a plurality (two) of cylindrical bodies are coupled, they are required between two radial bearing surfaces spaced apart in the axial direction. It is also considered that the bearing member 100 that appropriately secures a coaxial degree of a micron order can be easily obtained. However, the cylindrical bodies constituting the bearing member 100 are not always formed in the same shape and dimensions because they are mass-produced parts. Actually, the first cylindrical bodies 110 and the second cylinder are not formed. There are variations in the shape and dimensions of each part between the bodies 120. Therefore, when obtaining the bearing member 100, for example, as shown in FIG. 8A, there may be a case where the first cylindrical body 110 having a different thickness in each circumferential portion due to uneven thickness may be used. For ease of understanding, the degree of uneven thickness is exaggerated in the illustrated example.

  At this time, as described with reference to FIGS. 7A to 7C, sizing is performed on both cylinders 110 and 120 in a state in which both cylinders 110 and 120 are fitted in advance (concave fitting). Since the movement of the first cylindrical body 110 inward in the radial direction is restricted by the presence of the second cylindrical body 120, the area to be molded of the radial bearing surface 101 in the inner peripheral surface of the first cylindrical body 110 is sized. There is a possibility that the radial bearing surface 101 having a predetermined shape and accuracy cannot be formed on the inner peripheral surface of the first cylindrical body 110 because the core 131 cannot be appropriately pressed against the outer peripheral surface of the core 131. In this case, the required coaxiality between the radial bearing surfaces 101 and 102 cannot be ensured [see FIG. 8B].

  In view of the above circumstances, an object of the present invention is a bearing member for a fluid dynamic bearing device formed by connecting a plurality of cylindrical bodies arranged in an axial direction, and is disposed on one end side in the axial direction. A radial bearing surface formed by sizing is provided on each of the inner peripheral surface of the cylindrical body and the inner peripheral surface of the cylindrical body disposed on the other end side in the axial direction, and an intermediate clearance portion is provided between the radial bearing surfaces. It is possible to appropriately secure the shape and dimensional accuracy of each radial bearing surface and the coaxiality between both radial bearing surfaces while appropriately coupling the cylindrical bodies to each other. It is to be possible to realize a fluid dynamic pressure bearing device having excellent bearing performance.

  In order to solve the above-described problem, in the present invention, by sizing a plurality of cylindrical bodies arranged in a row in the axial direction, cylinders adjacent in the axial direction are coupled to each other. In accordance with the sizing, each of the first cylindrical body made of sintered metal disposed on one end side in the direction and the second peripheral body made of sintered metal disposed on the other end side in the axial direction A bearing member for a fluid dynamic pressure bearing device in which a molded radial bearing surface is provided, and an intermediate clearance portion having a diameter larger than that of both radial bearing surfaces is provided between both radial bearing surfaces. Adjacent in the axial direction by the concave-convex fitting structure formed by bringing the convex ridges formed on the other end face in close contact with the concave part provided on only one of the two end faces Characterized by the combination of cylinders To provide a fluid dynamic pressure bearing bearing member.

  The “radial bearing surface” as used in the present invention means a surface that forms a radial bearing gap with the outer peripheral surface of the shaft to be supported, and a dynamic pressure generating portion such as a dynamic pressure groove is formed on this surface. It doesn't matter whether it is done or not.

  If cylindrical bodies adjacent to each other in the axial direction are joined by the concave-convex fitting structure, a convex ridge portion that closely contacts a concave portion provided on the one (end surface) is attached to the other (the As long as it can be generated on the end face), the other shape before the sizing can be arbitrarily set. Therefore, before the sizing is performed (initiation stage), the other can be formed into, for example, a plane (flat surface) in a direction orthogonal to the axis, that is, a shape that does not engage with the one in the radial direction. In this case, at least until the sizing progresses to some extent, the radial movement of one of the two cylinders adjacent in the axial direction is not restricted by the presence of the other, so that the inner circumference of the first and second cylinders The area of the surface radial bearing surface to be molded can be appropriately pressed against the outer peripheral surface of the sizing core (can be deformed following the outer peripheral surface of the sizing core). Accordingly, a bearing member in which cylindrical bodies adjacent in the axial direction are appropriately coupled is obtained in a state in which both radial bearing surfaces are molded with a predetermined accuracy and the coaxial alignment between both radial bearing surfaces is appropriately performed. Can do.

  As a specific example of a bearing member to which the present invention can be applied, a concave portion is provided on the end surface on the other axial side of the first cylindrical body, or on the end surface on one axial end side of the second cylindrical body, and the intermediate relief portion is provided. And an inner peripheral surface on the other axial end side of the first cylindrical body, or an inner peripheral surface on the one axial end side of the second cylindrical body. In this case, of the first and second cylindrical bodies, if the yield point of the cylindrical body provided with the concave portion is relatively large, the concave portion is deformed with sizing, and the first cylindrical body and the second cylindrical body are formed. Can be prevented as much as possible.

  Further, as another example of a bearing member to which the present invention can be applied, the bearing member further includes a third cylindrical body disposed between the first cylindrical body and the second cylindrical body and provided with a middle escape portion on the inner periphery thereof, There may be mentioned those in which the concave portions are provided on the end surfaces on the one end side and the other end side in the axial direction of the third cylindrical body, respectively. In this case, if the yield point of the third cylindrical body is made larger than the yield points of the first and second cylindrical bodies, the concave portion is deformed with sizing, and the first cylindrical body and the second cylindrical body It is possible to prevent as much as possible the situation in which the third cylindrical body is not properly coupled. The third cylinder having a yield point larger than that of the first and second cylinders can be obtained, for example, by forming the third cylinder with a melted material such as stainless steel or brass.

  In the above configuration, dynamic pressure generating portions such as dynamic pressure grooves can be provided on both radial bearing surfaces. The dynamic pressure generating portion can be molded at the same time as sizing is performed on a plurality of cylindrical bodies arranged in series in the axial direction. In general, a bearing member having a dynamic pressure generating portion such as a dynamic pressure groove on a radial bearing surface is generally a bearing member in which a dynamic pressure generating portion such as a dynamic pressure groove is not provided on the radial bearing surface (radial bearing surface). Is used in a region where the gap width of the radial bearing gap formed between the outer peripheral surface of the shaft to be supported is small compared to the bearing member formed on the smooth cylindrical surface), and between the two radial bearing surfaces The required coaxiality is relatively small. In this respect, in the bearing member according to the present invention, the coaxiality between the two radial bearing surfaces can be appropriately ensured as described above. For this reason, the present invention can achieve further effects in the bearing member in which the dynamic pressure generating portion is provided on the radial bearing surface.

  Further, in the bearing member according to the present invention, a thrust is provided between at least one of the end surface on the one axial end side of the first cylindrical body and the end surface on the other axial end side of the second cylindrical body with the end surface of the shaft to be supported. A thrust bearing surface that forms a bearing gap can also be provided. This thrust bearing surface can also be formed at the same time as sizing a plurality of cylindrical bodies arranged in the axial direction.

  As described above, in the bearing member according to the present invention, the cylindrical bodies adjacent in the axial direction are appropriately coupled to each other, and the coaxial member is provided between the radial bearing surfaces that are provided apart from each other in two axial directions. Since the degree is appropriately secured, the fluid dynamic pressure bearing device including the housing in which the bearing member is fixed to the inner periphery has low torque and excellent bearing rigidity (moment rigidity). Further, due to the structure of the bearing member according to the present invention, even if the shaft to be supported is long in the axial direction, it can be accurately supported. Therefore, the fluid dynamic pressure bearing device including the bearing member according to the present invention can be used as a bearing for a relatively large motor (for example, a fan motor for a server).

  Further, in order to solve the above-described problems, in the present invention, a fluid dynamic pressure bearing device in which cylindrical bodies adjacent in the axial direction are coupled to each other by sizing a plurality of cylindrical bodies arranged continuously in the axial direction. A first sintered body made of sintered metal disposed on one end side in the axial direction of the plurality of cylindrical bodies, and a first made of sintered metal disposed on the other end side in the axial direction. A radial bearing surface formed in accordance with the above sizing is provided on each of the inner peripheral surfaces of the two cylindrical bodies, and an intermediate relief portion having a larger diameter than both radial bearing surfaces is provided between the radial bearing surfaces. In the method for manufacturing, the plurality of cylindrical bodies formed on the flat surface in the direction perpendicular to the axial direction while the concave portion is provided only in one of the two end surfaces facing each other in the axial direction. Characterized by sizing Method of manufacturing a Karadado圧 bearing device for a bearing member, provides.

  As described above, according to the present invention, there is provided a bearing member for a fluid dynamic pressure bearing device including a plurality of cylindrical bodies arranged in an axial direction, and each radial bearing surface is appropriately coupled to each other while appropriately coupling the cylindrical bodies. It is possible to provide a bearing member in which shape / dimensional accuracy and coaxiality between both radial bearing surfaces are appropriately secured.

It is a schematic sectional drawing of the fluid dynamic pressure bearing apparatus provided with the bearing member which concerns on one Embodiment of this invention. It is sectional drawing of the bearing member shown in FIG. It is sectional drawing which shows typically the sizing process included in the manufacturing process of the bearing member shown in FIG. 1, Comprising: (a) A figure is a figure which shows the initial stage of the process, (b) A figure and (c) figure are the same It is a figure which shows the intermediate stage of a process. FIG. 5A is a partially enlarged view of a bearing member according to a modified example, and FIG. 5B and FIG. 5C are diagrams schematically showing modified examples of the recesses. It is a schematic sectional drawing of the fluid dynamic pressure bearing apparatus provided with the bearing member which concerns on other embodiment of this invention. It is a schematic sectional drawing of the conventional bearing member. It is sectional drawing which shows typically the sizing process included in the manufacturing process of the bearing member shown in FIG. 6, Comprising: (a) A figure is a figure which shows the initial stage of the process, (b) A figure and (c) figure are the same It is a figure which shows the intermediate stage of a process. (A) A figure and (b) figure are the schematic diagrams for demonstrating the problem of the conventional bearing member.

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

  FIG. 1 conceptually shows one configuration example of a fluid dynamic bearing device provided with a bearing member according to an embodiment of the present invention. The fluid dynamic pressure bearing device 1 shown in FIG. 1 includes a bearing member 3, a shaft member 2 inserted in the inner periphery of the bearing member 3, and an appropriate means such as adhesion or press-fit adhesion (adhesion in a press-fit state). The shaft member 2 is supported by radial bearing portions R1 and R2 formed at two positions spaced apart in the axial direction so as to be relatively rotatable in the radial direction. The bearing member 3 includes a plurality of cylindrical bodies (in the present embodiment, first and second cylindrical bodies 31 and 32) arranged in series in the axial direction. Although detailed illustration is omitted, the internal space of the housing 4 is filled with lubricating oil as a lubricating fluid. In the following, for the sake of convenience, the description will proceed with the side on which the first cylindrical body 31 is disposed as the upper side and the side on which the second cylindrical body 32 is disposed on the lower side. However, the fluid dynamic bearing device 1 (bearing member 3) However, there is no limitation on the use mode.

  The shaft member 2 is made of, for example, a metal material such as stainless steel, and a portion of the outer peripheral surface 2a that faces the inner peripheral surface of the bearing member 3 is formed into a smooth cylindrical surface without unevenness.

  Each of the first and second cylindrical bodies 31 constituting the bearing member 3 is a sintered metal porous body mainly composed of copper or iron and is formed in a substantially cylindrical shape. In the present embodiment, the yield point of the first cylindrical body 31 is relatively small, and the yield point of the second cylindrical body 32 is relatively large. In short, the second cylindrical body 32 is formed of a sintered metal having a higher strength than the first cylindrical body 31. As described above, the sintered metal cylinders 31 and 32 having different yield points are different from each other in, for example, the composition of the raw material powder, the forming pressure when obtaining the green compact of the raw material powder, or It can be obtained by adopting means such as different sintering conditions.

  A cylinder that forms a radial bearing gap of the radial bearing portion R1 on the inner peripheral surface 31a of the first cylindrical body 31 between the outer peripheral surface 2a of the opposing shaft member 2 when the shaft member 2 and the bearing member 3 are relatively rotated. A radial bearing surface A1 is provided. As shown in FIG. 2, the radial bearing surface A1 is formed with a dynamic pressure generating portion (radial dynamic pressure generating portion) 8 for generating a dynamic pressure action on the lubricating oil in the radial bearing gap of the radial bearing portion R1. ing. The illustrated dynamic pressure generator 8 includes a plurality of upper dynamic pressure grooves 8a1 inclined with respect to the axial direction, a plurality of lower dynamic pressure grooves 8a2 inclined in a direction opposite to the upper dynamic pressure grooves 8a1, and a dynamic pressure. The grooves 8a1 and 8a2 are divided into convex hills, and the dynamic pressure grooves 8a1 and 8a2 are arranged in a herringbone shape as a whole. The hill portion includes an inclined hill portion 8b provided between the dynamic pressure grooves adjacent in the circumferential direction, and an annular hill portion 8c provided between the upper and lower dynamic pressure grooves 8a1 and 8a2 and having substantially the same diameter as the inclined hill portion 8b. Consists of.

  The inner peripheral surface 32a of the second cylindrical body 32 is partitioned into a relatively small-diameter small-diameter internal peripheral surface 32a1 and a relatively large-diameter large-diameter internal peripheral surface 32a2. A cylindrical radial bearing surface that forms a radial bearing gap of the radial bearing portion R2 between the small-diameter inner peripheral surface 32a1 and the outer peripheral surface 2a of the opposing shaft member 2 when the shaft member 2 and the bearing member 3 rotate relative to each other. A2 is provided. As shown in FIG. 2, the radial bearing surface A2 is formed with a dynamic pressure generating portion (radial dynamic pressure generating portion) 8 for generating a dynamic pressure action on the lubricating oil in the radial bearing gap of the radial bearing portion R2. ing. The dynamic pressure generation unit 8 has the same configuration as the dynamic pressure generation unit 8 provided on the inner peripheral surface 31a (radial bearing surface A1) of the first cylindrical body 31. The large-diameter inner peripheral surface 32a2 is disposed between the two radial bearing surfaces A1 and A2 to form a middle escape portion B.

  The shape of the dynamic pressure generating portion 8 provided on both the radial bearing surfaces A1 and A2 is merely an example, and it is of course possible to adopt other known shapes of the dynamic pressure generating portion 8.

  The first and second cylindrical bodies 31 and 32 constituting the bearing member 3 are coupled and integrated by a concave / convex fitting structure 7 formed between the cylindrical bodies 31 and 32. The concave-convex fitting structure 7 has an upper end surface of the second cylindrical body 32 among two surfaces facing each other in the axial direction (here, the lower end surface 31b of the first cylindrical body 31 and the upper end surface 32c of the second cylindrical body 32). It is formed by closely contacting the convex raised portion 6 provided on the lower end surface 31b of the first cylindrical body 31 with the concave portion 5 (the inner wall surface) provided on the 32c. In the present embodiment, the concave portion 5 and the convex raised portion 6 in close contact with the concave portion 5 each have an annular shape. The annular region excluding the portion where the raised portion 6 is formed in the lower end surface 31b of the first cylindrical body 31 and the annular region excluding the portion where the recessed portion 5 is formed in the upper end surface 32c of the second cylindrical body 32 are These are all formed on a flat surface extending in a direction orthogonal to the axis (axial direction), and the two flat surfaces are in close contact with each other.

  As described above, the radial fitting surfaces A1 and A2 having the dynamic pressure generating portion 8 are provided on the inner peripheral surfaces of the cylindrical bodies 31 and 32, respectively, and the concave-convex fitting structure formed between the cylindrical bodies 31 and 32. 7, the bearing member 3 formed by connecting the two cylindrical bodies 31 and 32 to each other includes first and second cylindrical bodies 31 and 32 arranged in series in the axial direction (strictly, each of the first and second cylinders 31 and 32 has the above-described configuration by sizing. And the first and second cylindrical materials 31 ′ and 32 ′) finished to the second cylindrical bodies 31 and 32. Hereinafter, the sizing process will be described in detail with reference to FIGS.

  As shown in FIGS. 3A to 3C, the sizing process uses a sizing die 10 including a core 11, a cylindrical die 12, and a pair of upper and lower punches 13, 14 arranged coaxially. Executed. Although detailed illustration is omitted, on the outer peripheral surface of the core 11, concave and convex mold portions corresponding to the shapes of the dynamic pressure generating portions 8 and 8 (having the radial bearing surfaces A1 and A2) are separated vertically. It is provided in two places.

  Next, the first and second cylindrical materials 31 'and 32' used in the sizing process will be described. The first cylindrical material 31 'is finished to the first cylindrical body 31 having the above-described configuration by sizing, and the radial bearing surface A1 (dynamic pressure generating portion 8) is not provided on the inner peripheral surface thereof. Further, in the first cylindrical material 31 ′, the lower end surface 31 b ′ which becomes the lower end surface 31 b of the first cylindrical body 31 after sizing is formed as a flat surface in the direction orthogonal to the axis. The second cylindrical material 32 'is finished into a second cylindrical body 32 having the above-described configuration by sizing, and the inner peripheral surface thereof is a relatively small-diameter inner peripheral surface and a relatively large-diameter large-diameter inner surface. Although divided into a peripheral surface, the radial bearing surface A2 (dynamic pressure generating portion 8) is not provided on the small-diameter inner peripheral surface. However, in the second cylindrical material 32 ′, an annular recess 5 is provided on the upper end surface 32c ′ that becomes the upper end surface 32c of the second cylindrical body 32 after sizing [see FIGS. 3A and 3B. )]. The first and second cylindrical materials 31 ′ and 32 ′ having the above configuration are both sintered metal porous bodies obtained by sintering a green compact of raw material powder. Then, what has a yield point smaller than 2nd cylindrical raw material 32 'is used as 1st cylindrical raw material 31'.

  In the above configuration, first, as shown in FIG. 3A, both cylindrical materials 31 ′ and 32 ′ are arranged on the upper end surface 12 a of the die 12 so as to be connected in the axial direction (superimposed vertically). More specifically, the second cylindrical material 32 ′ is placed on the upper end surface 12 a of the die 12 in an upright posture with the upper end surface 32 c ′ provided with the recess 5 on the upper side, and the lower end surface 31 b ′ is placed on the lower side. The first cylindrical material 31 ′ is placed on the second cylindrical material 32 ′ in the standing posture. Then, the core 11 is inserted into the inner periphery of both cylindrical materials 31 'and 32'.

  Next, as shown in FIG. 3B, by lowering the core 11 and the upper punch 13, both cylindrical materials 31 ′ and 32 ′ are press-fitted into the inner periphery of the die 12, and both cylindrical materials 31 ′ and 32 ′ are pressed. Restrain the outer peripheral surface. Thereafter, as shown in FIG. 3C, when the core 11 and the upper punch 13 are further lowered and both the cylindrical materials 31 ′ and 32 ′ are compressed in the axial direction by the upper punch 13 and the lower punch 14, both the cylindrical materials 31 ′. , 32 ′ expand and deform in the radial direction, and the outer peripheral surface and inner peripheral surface of both cylindrical materials 31 ′, 32 ′ are pressed against the inner peripheral surface 12 a of the die 12 and the outer peripheral surface 11 a of the core 11, respectively. Thereby, the outer peripheral surface and inner peripheral surface of both cylindrical materials 31 'and 32' are deformed following the inner peripheral surface 12a of the die 12 and the outer peripheral surface 11a of the core 11, and the inner peripheral surface of the first cylindrical material 31 '. And radial bearing surface A1, A2 which has the dynamic pressure generation | occurrence | production part 8 is shape | molded on each of the internal peripheral surface (small diameter internal peripheral surface) of 2nd cylindrical raw material 32 '. Then, when the core 11 and the upper punch 13 are further lowered, the portion of the lower end surface 31b ′ of the first cylindrical material 31 ′ protrudes from the portion facing the concave portion 5 provided on the upper end surface 32c ′ of the second cylindrical material 32 ′. A raised portion 6 is formed, and this raised portion 6 is in close contact with the inner wall surface of the recess 5. As a result, the concave / convex fitting structure 7 is formed between the cylindrical materials 31 ′ and 32 ′.

  Although not shown in the figure, after forming the concave-convex fitting structure 7 as described above, for example, the core 11 and the upper and lower punches 13 and 14 are raised integrally to form both cylindrical materials 31 ′ and 32 ′. After the integrated product is discharged to the outside of the die 12, the upper punch 13 and the core 11 are further raised. As a result, the radial bearing surface A1 having the dynamic pressure generating portion 8 is formed on the inner peripheral surface 31a of the first cylindrical body 31, and is moved to the inner peripheral surface 32a (small-diameter inner peripheral surface 32a1) of the second cylindrical body 32. A bearing member 3 is obtained in which a radial bearing surface A2 having a pressure generating portion 8 is formed, and the two cylindrical bodies 31 and 32 are joined by the concave-convex fitting structure 7.

  In the fluid dynamic bearing device 1 having the above-described configuration, when the shaft member 2 and the bearing member 3 are relatively rotated, the radial bearing surfaces A1 and A2 that are spaced apart from each other at two locations on the inner periphery of the bearing member 3 and these Radial bearing gaps are respectively formed between the outer peripheral surface 2a of the shaft member 2 facing each other. As the shaft member 2 and the bearing member 3 rotate relative to each other, the pressure of the oil film formed in the radial bearing gaps is increased by the dynamic pressure action of the dynamic pressure generating portions 8 and 8, and as a result, the shaft member 2 is moved in the radial direction. Radial bearing portions R1 and R2 that are supported in a non-contact manner so as to be relatively rotatable are formed at two locations separated in the axial direction. At this time, a cylindrical lubricating oil reservoir is formed between the two radial bearing gaps by providing the cylindrical surface intermediate escape portion B on the inner periphery of the bearing member 3 (second cylindrical body 32). Therefore, it is possible to prevent as much as possible an oil film breakage between the radial bearing gaps, that is, a reduction in bearing performance of the radial bearing portions R1 and R2.

  Although not shown, the fluid dynamic bearing device 1 described above includes, for example, (1) a spindle motor for a disk device, (2) a polygon scanner motor for a laser beam printer, or (3) a fan for a PC. Used as a bearing device for a motor such as a motor. In the case of (1), for example, a disk hub having a disk mounting surface is integrally or separately provided on the shaft member 2, and in the case of (2), for example, a polygon mirror is integrally or separately provided on the shaft member 2. . In the case of (3), for example, a fan having blades on the shaft member 2 is provided integrally or separately.

  As described above, in the bearing member 3 according to the present invention, any one of the lower end surface 31b of the first cylindrical body 31 and the upper end surface 32c of the second cylindrical body 32 facing each other in the axial direction [ Here, with respect to the concave portion 5 provided only on the upper end surface 32c (32c ′)], the convex raised portion 6 generated on the other end surface [here, the lower end surface 31b (31b ′)] is brought into close contact with the sizing. The first and second cylindrical bodies 31 and 32 that are adjacent in the axial direction are joined together by the concave-convex fitting structure 7 formed in the above.

  If the cylindrical bodies 31 and 32 adjacent in the axial direction are coupled to each other by such an uneven fitting structure 7, a convex raised portion 6 that closely contacts the concave portion 5 is generated on the lower end surface 31 b ′ along with sizing. As long as it can be made, the shape of the lower end surface 31b ′ of the first cylindrical material 31 ′ before the sizing can be arbitrarily set. Therefore, before the sizing, the entire lower end surface 31b ′ of the first cylindrical material 31 ′ is flat with the direction perpendicular to the axis, that is, the upper end surface 32c ′ of the second cylindrical material 32 ′ (as described above). It can be formed into a shape that does not engage (in the radial direction). In this case, until the sizing progresses to some extent, the radial movement of one of the two cylindrical bodies adjacent in the axial direction is not restricted by the presence of the other, so the first cylindrical material 31 ′ and the second The forming area of the radial bearing surface on the inner peripheral surface of the cylindrical material 32 ′ can be appropriately pressed against the outer peripheral surface 11 c of the core 11. Therefore, the cylindrical bearings adjacent in the axial direction are formed in a state where the radial bearing surfaces A1 and A2 having the dynamic pressure generating portion 8 are formed with a predetermined accuracy and the coaxial bearings between the radial bearing surfaces A1 and A2 are also properly formed. The bearing member 3 in which 31 and 32 are appropriately coupled can be obtained.

  In particular, in the present embodiment, of the two cylindrical bodies 31 and 32 (cylindrical materials 31 ′ and 32 ′) to be coupled, the yield of the second cylindrical body 32 (second cylindrical material 32 ′) provided with the recess 5 is provided. Since the point is relatively large, the concave portion 5 of the second cylindrical body 32 is deformed with sizing, and the situation where the two cylindrical bodies 31 and 32 are not properly coupled is prevented as much as possible. Can do.

  The bearing member 3 according to the embodiment of the present invention and the fluid dynamic pressure bearing device 1 including the bearing member 3 have been described above. However, the bearing member 3 can be variously modified without departing from the gist of the present invention. Can be applied.

  For example, in the embodiment described above, the concave portion 5 for forming the concave-convex fitting structure 7 has two end surfaces (the lower end surface 31b of the first cylindrical body 31 and the second cylindrical body 32 of the first cylindrical body 32) facing each other in the axial direction. Of the upper end surface 32c), the upper end surface 32c is configured by an annular groove provided at a substantially central portion in the radial direction. However, the concave portions 5 formed by the annular groove are provided at a plurality of locations spaced in the radial direction of the upper end surface 32c. Also good. FIG. 4A specifically shows an example of this, and the concave portions 5 each formed of an annular groove are provided at two locations spaced in the radial direction of the upper end surface 32 c of the second cylindrical body 32. In this case, the convex raised portions 6 that are in close contact with the concave portion 5 are formed at two locations that are spaced apart in the radial direction of the lower end surface 31 b of the first cylindrical body 31.

  Moreover, the recessed part 5 for forming the uneven | corrugated fitting structure 7 is comprised by the groove | channel which is end | ended in the circumferential direction other than an annular groove, as shown, for example in FIG.4 (b) and FIG.4 (c). It is also possible. In this case, after the formation of the concave-convex fitting structure 7, the possibility that the cylindrical bodies 31 and 32 adjacent in the axial direction rotate relative to each other around the axis can be reduced. FIG. 4B is an example in which the concave portion 5 is formed by a radial groove whose groove width gradually decreases toward the outer diameter side, and FIG. 4C shows a radial groove having a constant groove width. It is an example at the time of comprising the recessed part 5 by. Of course, the shape of the recess 5 is not limited to that described above, and the recess 5 may be configured by, for example, a spiral groove or dimple (a recess having a semicircular cross section) (not shown).

  In addition, the concave-convex fitting structure 7 includes a first and a second that are arranged continuously in the axial direction with respect to the concave portion 5 provided on the lower end surface 31b of the first cylindrical body 31 (the lower end surface 31b ′ of the first cylindrical material 31 ′). As the two cylinders 31 and 32 (first and second cylindrical materials 31 ′ and 32 ′) are sized, the upper end surface 32c of the second cylindrical body 32 (the upper end surface 32c ′ of the second cylindrical material 32 ′). It is also possible to form it by closely contacting the raised ridges 6 produced in the above.

  Further, the middle escape portion 5 may be configured not by the second cylindrical body 32 but by the inner peripheral surface of the first cylindrical body 31, or by both the inner peripheral surfaces of the first and second cylindrical bodies 31 and 32. It may be configured.

  The bearing member 3 is connected in the axial direction as shown in FIG. 5 in addition to the configuration in which two cylindrical bodies (first and second cylindrical bodies 31 and 32) arranged in the axial direction are coupled. It is also possible to configure by connecting three cylindrical bodies arranged in the same manner. More specifically, in the embodiment shown in FIG. 5, the bearing member 3 is disposed at one end (upper end) in the axial direction, and the sintered metal first cylindrical body 31 having the radial bearing surface A1 on the inner peripheral surface 31a. And a third cylindrical body 33 disposed between the second cylindrical body 32 made of sintered metal and disposed on the other end (lower end) in the axial direction and having a radial bearing surface A2 on the inner peripheral surface 32a. The middle escape portion B is formed by the inner peripheral surface 33 a of the three cylindrical body 33. The first cylindrical body 31 and the third cylindrical body 33 that are adjacent in the axial direction are joined by the concave-convex fitting structure 7 formed therebetween, and the third cylindrical body 33 and the second cylindrical body that are adjacent in the axial direction. 32 is couple | bonded by the uneven | corrugated fitting structure 7 formed between both.

  In the embodiment shown in FIG. 5, the convex raised portion 6 formed on the lower end surface 31 b of the first cylindrical body 31 with respect to the concave portion 5 formed of an annular groove provided on the upper end surface 33 b of the third cylindrical body 33. To form the concave-convex fitting structure 7 for joining the first and third cylindrical bodies 31 and 33 to the concave portion 5 formed of an annular groove provided on the lower end surface 33c of the third cylindrical body 33. By bringing the raised ridge 6 formed on the upper end surface 32 b of the second cylindrical body 32 into close contact, the concave-convex fitting structure 7 that joins the second and third cylindrical bodies 32 and 33 is formed. Of course, either one or both of these two concave-convex fitting structures 7 are formed by a concave portion 5 as shown in FIGS. 4A to 4C and a convex raised portion 6 that is in close contact therewith. Is also possible.

  Although detailed illustration is omitted, the bearing member 3 shown in FIG. 5 is also obtained by sizing the three cylindrical bodies 31 to 33 arranged in the axial direction in the same manner as the bearing member 3 shown in FIG. . That is, both the radial bearing surfaces A1 and A2 are formed with the above sizing, and the concave-convex fitting structure 7 in which the cylindrical bodies adjacent in the axial direction are joined together is below the first cylindrical body 31 with the sizing. The convex ridge 6 generated on the end surface 31b and the convex ridge 6 generated on the upper end surface 32b of the second cylindrical body 32 are provided on the upper end surface 33b and the lower end surface 33c of the third cylindrical body 33, respectively. It is formed by being in close contact with the recesses 5 and 5.

  In this embodiment, the concave portion 5 is deformed with sizing, and the predetermined concave-convex fitting structure 7 cannot be obtained, and the possibility is reduced as much as possible. Therefore, the third cylindrical body 33 having the concave portion 5 is replaced with the first cylinder. The body 31 and the second cylindrical body 32 are made of a material having a higher yield point. The third cylindrical body 33 may be formed of a sintered metal porous body in the same manner as the first and second cylindrical bodies 31 and 32, but here, the third cylindrical body 33 is made of a molten material such as stainless steel or brass. A cylindrical body 33 is formed. In this case, since the amount of lubricating oil to be filled in the internal space of the fluid dynamic pressure bearing device 1 (housing 7) can be reduced as compared with the case where the third cylindrical body 33 is formed of sintered metal, the fluid dynamic pressure bearing This is advantageous in reducing the cost of the apparatus 1.

  Although not shown in the drawings, the bearing member 3 described above can be used not only for radial loads but also for supporting thrust loads. In this case, a thrust bearing surface is provided on one or both of the upper end surface 31c of the first cylindrical body 31 and the lower end surface 32b of the second cylindrical body 32 in accordance with the shape of the shaft (shaft member 2) to be supported. be able to. Like the radial bearing surface, the thrust bearing surface can be molded at the same time as sizing a plurality of cylindrical bodies arranged in a row in the axial direction, and the thrust bearing surface has a dynamic pressure such as a dynamic pressure groove. A generator (thrust dynamic pressure generator) may be provided. The thrust dynamic pressure generating portion can be molded simultaneously with sizing the plurality of cylindrical bodies.

  In the embodiment described above, in the sizing process for manufacturing the bearing member 3, the radial dynamic pressure generating portion 8 is molded on the inner peripheral surface of the bearing member 3. 8 may be provided on the outer peripheral surface 2 a of the shaft member 2 facing the inner peripheral surface of the bearing member 3.

  Further, as described above, the present invention is not limited to the case where the bearing member 3 is composed of two or three cylindrical bodies arranged in a row in the axial direction, but also four or more pieces arranged in a row in the axial direction. The present invention can also be applied when the bearing member 3 is formed of a cylindrical body.

1 Fluid dynamic bearing device 2 Shaft member (shaft to be supported)
DESCRIPTION OF SYMBOLS 3 Bearing member 4 Housing 5 Recessed part 6 Raised part 7 Concavity and convexity fitting structure 8 Dynamic pressure generating part 31 First cylindrical body 31a Inner peripheral surface 32 Second cylindrical body 32a Inner peripheral surface 33 Third cylindrical body 33a Inner peripheral surfaces A1, A2 Radial bearing surface B Center relief R1, R2 Radial bearing

Claims (10)

By sizing a plurality of cylindrical bodies arranged in a row in the axial direction, cylindrical bodies adjacent in the axial direction are joined together, and the sintered metal made of sintered metal disposed on one end side in the axial direction of the plurality of cylindrical bodies. A radial bearing surface formed by the sizing is provided on each of the inner peripheral surfaces of the first cylindrical body and the second cylindrical body made of sintered metal disposed on the other end side in the axial direction, and between the radial bearing surfaces. A bearing member for a fluid dynamic pressure bearing device in which a middle escape portion having a larger diameter than both radial bearing surfaces is provided,
The concave / convex fitting structure formed by bringing the convex ridges generated on the other side in accordance with the sizing into close contact with the concave portions provided only on either one of the two end faces that face each other in the axial direction. A bearing member for a fluid dynamic bearing device, wherein the adjacent cylindrical bodies are coupled together. The concave portion is provided on the end surface on the other axial end side of the first cylindrical body, or on the end surface on the one axial end side of the second cylindrical body,
2. The fluid dynamic bearing device according to claim 1, wherein the middle relief portion is provided on an inner peripheral surface on the other axial end side of the first cylindrical body or on an inner peripheral surface on one axial end side of the second cylindrical body. Bearing member.   The bearing member for a fluid dynamic bearing device according to claim 1 or 2, wherein a yield point of a cylindrical body provided with the concave portion is relatively large among the first and second cylindrical bodies.   A third cylinder disposed between the first cylinder and the second cylinder and provided with the intermediate relief portion on an inner periphery thereof, wherein the concave portion has one axial end side of the third cylinder and The bearing member for a fluid dynamic bearing device according to claim 1, wherein the bearing member is provided on an end surface on the other end side.   The bearing member for a fluid dynamic bearing device according to claim 4, wherein the yield point of the third cylindrical body is larger than the yield points of the first and second cylindrical bodies.   The bearing member for a fluid dynamic bearing device according to claim 5, wherein the third cylindrical body is formed of a molten material.   The fluid dynamic pressure bearing device bearing member according to any one of claims 1 to 6, wherein a dynamic pressure generating portion is provided on the radial bearing surface.   A fluid dynamic pressure bearing device comprising: the fluid dynamic pressure bearing device bearing member according to claim 1; and a housing in which the bearing member is fixed to an inner periphery. By sizing a plurality of cylindrical bodies arranged in a row in the axial direction, cylindrical bodies adjacent in the axial direction are coupled to each other, and a sintered metal made of one of the plurality of cylindrical bodies is disposed on one end side in the axial direction. A radial bearing surface formed in accordance with the sizing is provided on each of the inner peripheral surface of the first cylindrical body and the second cylindrical body made of sintered metal disposed on the other end side in the axial direction. A method for producing a bearing member for a fluid dynamic bearing device in which a middle clearance portion having a larger diameter than both radial bearing surfaces is provided between the bearing surfaces,
A sizing is performed on the plurality of cylindrical bodies formed on a flat surface in a direction perpendicular to the axial direction, with a recess provided only on one of two end faces facing each other in the axial direction. A method for manufacturing a bearing member for a fluid dynamic bearing device.   The method for manufacturing a bearing member for a fluid dynamic bearing device according to claim 9, wherein a yield point of the cylindrical body having the one is relatively increased, and a yield point of the cylindrical body having the other is relatively decreased.

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