WO2018037822A1

WO2018037822A1 - Dynamic pressure bearing and method for manufacturing same

Info

Publication number: WO2018037822A1
Application number: PCT/JP2017/027187
Authority: WO
Inventors: 隆生新井
Original assignee: Ntn株式会社
Priority date: 2016-08-26
Filing date: 2017-07-27
Publication date: 2018-03-01
Also published as: CN207526872U; CN107781293A; JP6858508B2; JP2018031460A; CN107781293B

Abstract

A dynamic pressure bearing 8 comprises dynamic pressure grooves 8b1 formed on an upper-side end surface 8b. The bottom groove surfaces of the dynamic pressure grooves 8b1 slope downward toward the outer diameter side.

Description

Hydrodynamic bearing and manufacturing method thereof

The present invention relates to a dynamic pressure bearing, and more particularly to a dynamic pressure bearing in which a dynamic pressure groove is formed on an end surface, and a method for manufacturing the same.

A dynamic pressure bearing is a fluid pressure generated in a bearing gap between a relatively rotating shaft member and supports the shaft member in a non-contact manner. A dynamic pressure groove that generates a dynamic pressure in a lubricating fluid (for example, lubricating oil) filled in the bearing gap may be formed on the inner peripheral surface and the end surface of the dynamic pressure bearing. The dynamic pressure groove extends along a direction intersecting the circumferential direction (the relative rotation direction of the shaft member), and the flow direction of the lubricating fluid in the bearing gap flowing in the circumferential direction with the relative rotation of the shaft member is determined by the dynamic pressure groove. By correcting, the lubricating fluid is collected and the fluid pressure is increased.

The dynamic pressure groove is often molded by pressing a mold against the bearing material. For example, Patent Document 1 discloses a method in which dynamic pressure grooves are molded on the inner peripheral surface and end surface of a cylindrical sintered body.

Japanese Patent No. 3607661

By the way, normally, the circumferential dimension ratio between the dynamic pressure groove and the hill formed between the circumferential directions is constant (for example, 1: 1). In the case of the dynamic pressure groove formed on the end surface (thrust bearing surface) of the dynamic pressure bearing, if the circumferential dimension ratio between the dynamic pressure groove and the hill portion is constant, the dynamic pressure groove and The circumferential width is increased (see FIG. 4). When such a dynamic pressure groove is molded on the end face of the bearing material, the amount of strain (plastic deformation) generated in the hill when the mold is pressed differs depending on the radial position. So-called “sag” is likely to occur, where the height of the portion 101 decreases as it goes to the outer diameter side. In this case, since the groove depth of the dynamic pressure groove 102 becomes shallower toward the outer diameter side, the vicinity of the outer diameter end of the dynamic pressure groove 102 has the ability to correct the flow direction of the lubricating fluid (that is, the ability to collect the lubricating fluid). ) Is reduced, and the effect of improving the pressure by the dynamic pressure groove 102 may not be sufficiently exhibited.

Therefore, an object of the present invention is to enhance the pressure improvement effect by the dynamic pressure grooves formed on the end face of the dynamic pressure bearing.

In order to solve the above-mentioned problem, the dynamic pressure bearing according to the present invention has a dynamic pressure groove formed on the end surface on one axial side, and the groove bottom surface of the dynamic pressure groove faces the outer diameter side in the other axial direction. Inclined to the side.

As described above, in the dynamic pressure bearing of the present invention, the groove bottom surface of the dynamic pressure groove molded on the end surface on one side in the axial direction is directed toward the outer diameter side on the other side in the axial direction (side where the groove depth is increased). Tilted. As a result, even when a so-called “sag” occurs in which the top surface of the hill portion is inclined toward the other side in the axial direction toward the outer diameter side, it is possible to ensure a groove depth of a predetermined value or more over the entire dynamic pressure groove. it can. In this case, the ability to collect the lubricating fluid over the entire region of the dynamic pressure groove is exhibited, so that the fluid pressure in the bearing gap can be sufficiently increased.

The above hydrodynamic bearing can be formed of, for example, a sintered body. When the dynamic pressure groove is molded in the sintered body, for example, the spring back amount is larger than that in the case where the dynamic pressure groove is molded in the molten material. Therefore, it is particularly effective to incline the bottom surface of the dynamic pressure groove as described above.

When the above-described dynamic pressure bearing further has another dynamic pressure groove formed on the end surface on the other side in the axial direction, the groove bottom surface of the other dynamic pressure groove is inclined toward one side in the axial direction toward the outer diameter side. It is preferable to make it. As a result, the ability to collect the lubricating fluid in the entire area of the other dynamic pressure grooves is exhibited, so that the lubricating fluid in the other bearing gap facing the other axial end surface of the dynamic pressure bearing can be sufficiently increased.

The above hydrodynamic bearing can be incorporated into a fluid dynamic bearing device. Specifically, the hydrodynamic bearing has a shaft portion inserted in an inner periphery of the hydrodynamic bearing, and a flange portion projecting to the outer diameter side from the shaft portion, and is relatively rotated with respect to the hydrodynamic bearing. A shaft member, a radial bearing portion that relatively supports the shaft member in a radial direction with a fluid pressure generated in a radial bearing gap between an inner peripheral surface of the dynamic pressure bearing and an outer peripheral surface of the shaft portion, and the dynamic pressure A fluid dynamic pressure bearing device including a thrust bearing portion that relatively supports the shaft member in a thrust direction with a fluid pressure generated in a thrust bearing gap between an end surface on one axial side of the bearing and an end surface of the flange portion, The fluid pressure in the thrust bearing gap is high, and the bearing rigidity in the thrust direction is high.

Further, in the method for manufacturing a hydrodynamic bearing according to the present invention, when the hydrodynamic groove is molded by pressing the mold from one side in the axial direction against the end surface of the bearing material, the hydrodynamic groove of the mold is A molding surface for molding the bottom surface of the groove is inclined toward the other side in the axial direction toward the outer diameter side. This manufacturing method is a forming die for forming a dynamic pressure groove by pressing against an end face of a bearing material from one side in the axial direction, and a forming surface for forming the groove bottom surface of the dynamic pressure groove is directed toward the outer diameter side. Thus, it can be performed by using a molding die characterized in that it is inclined to the other side in the axial direction.

Thus, by inclining the molding surface for shaping the groove bottom surface of the dynamic pressure groove toward the outer diameter side toward the other side in the axial direction, as described above, even when `` sagging '' occurs in the hill part, The groove depth of the dynamic pressure groove can be ensured.

At this time, it is preferable that the depth of the concave portion for molding the hill portion provided between the circumferential directions of the dynamic pressure grooves in the molding die is made deeper toward the outer diameter side. Specifically, the bottom surface of the recess is preferably a flat surface orthogonal to the axial direction. Since the hill portion formed by this concave portion becomes higher as it goes to the outer diameter side, even if a springback occurs during subsequent release, the groove depth of the dynamic pressure groove near the outer diameter end (that is, the height of the hill portion). Can be secured.

As described above, according to the present invention, since the groove depth of the dynamic pressure groove molded on the end face of the dynamic pressure bearing is ensured in the entire region, the effect of improving the pressure by the dynamic pressure groove can be enhanced.

It is sectional drawing of the spindle motor of the disk drive device of HDD. It is sectional drawing of the fluid dynamic pressure bearing apparatus integrated in the said spindle motor. It is sectional drawing of the dynamic pressure bearing which concerns on one Embodiment of this invention. It is a top view of the said dynamic pressure bearing. It is an expanded sectional view near the upper end face of the above-mentioned dynamic pressure bearing. It is a bottom view of the above-mentioned dynamic pressure bearing. It is a top view of the hydrodynamic bearing which concerns on other embodiment. It is sectional drawing which shows the state before dynamic pressure groove shaping | molding in the dynamic pressure groove formation process which molds a dynamic pressure groove on the end surface of a sintered compact. It is sectional drawing which expands and shows the end surface vicinity of the dynamic pressure bearing of FIG. It is sectional drawing which shows the state at the time of dynamic pressure groove shaping | molding in the said dynamic pressure groove formation process. It is sectional drawing which expands and shows the end surface vicinity of the dynamic pressure bearing of FIG. It is sectional drawing which shows a mode that a sintered compact is discharged | emitted from a metal mold | die in the said dynamic pressure groove formation process. It is sectional drawing which expands and shows the end surface vicinity of the dynamic pressure bearing of FIG. It is sectional drawing of the fluid dynamic pressure bearing apparatus which concerns on other embodiment. It is sectional drawing which expands and shows the end surface vicinity of the conventional dynamic pressure bearing.

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

FIG. 1 shows a spindle motor used in an HDD disk drive device. This spindle motor is opposed to a fluid dynamic pressure bearing device 1 having a dynamic pressure bearing 8 according to an embodiment of the present invention and a bracket 6 to which the fluid dynamic pressure bearing device 1 is attached via a radial gap. The stator coil 4 and the rotor magnet 5 are provided. The stator coil 4 is attached to the bracket 6, and the rotor magnet 5 is attached to the hub 3 of the fluid dynamic bearing device 1. A predetermined number of disks (not shown) are mounted on the 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 hub 3 and the disk are rotated together.

As shown in FIG. 2, the fluid dynamic pressure bearing device 1 is rotatably supported by a dynamic pressure bearing 8, a bottomed cylindrical housing 7 that holds the dynamic pressure bearing 8 on the inner periphery, and the dynamic pressure bearing 8. A shaft member. In the present embodiment, the shaft member includes a shaft portion 2 inserted in the inner periphery of the dynamic pressure bearing 8, a flange portion 9 provided at one end of the shaft portion 2, and the other provided at the other end of the shaft portion 2. And a hub 3 as a flange portion. 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 portion 2 is made of, for example, metal and has a straight cylindrical outer peripheral surface 2a having no irregularities. The flange portion 9 is made of metal, for example, and protrudes from the lower end of the shaft portion 2 to the outer diameter side. The end surfaces 9a and 9b on both sides in the axial direction of the flange portion 9 are flat surfaces without any unevenness.

The hub 3 is made of, for example, metal, and includes a disc portion 3a that protrudes from the upper end of the shaft portion 2 to the outer diameter side, a cylindrical portion 3b that extends downward in the axial direction from the outer diameter end of the disc portion 3a, and a cylindrical portion 3b. The flange portion 3c further extends from the lower end portion to the outer diameter, and the cylindrical annular projecting portion 3d extends downward from the substantially central portion in the radial direction of the disk portion 3a. A disc (not shown) is mounted on the upper end surface of the flange 3c. In the illustrated example, the hub 3 is integrally formed. However, the hub 3 may be formed of a plurality of members, for example, the annular protrusion 3d may be formed of another member.

The dynamic pressure bearing 8 is formed in a cylindrical shape with metal or resin. In the present embodiment, the hydrodynamic bearing 8 is a sintered metal, for example, a sintered metal containing a relatively large amount of copper (for example, 20% by mass or more), specifically, a copper-based sintered metal mainly composed of copper, or copper. And a copper-iron-based sintered metal containing iron as a main component.

A dynamic pressure groove is formed on the inner peripheral surface 8 a of the dynamic pressure bearing 8. In this embodiment, as shown in FIG. 3, herringbone-shaped dynamic pressure grooves 8a1 and 8a2 are formed in two regions separated in the axial direction of the inner peripheral surface 8a of the dynamic pressure bearing 8 (cross hatching). Haoka). In the illustrated example, the upper dynamic pressure groove 8a1 is formed asymmetrically in the axial direction. Specifically, the axial dimension of the region above the annular hill at the approximate center in the axial direction is lower than the annular hill. It is larger than the axial dimension of the side region. The lower dynamic pressure groove 8a2 is formed symmetrically in the axial direction.

As shown in FIG. 4, a dynamic pressure groove 8 b 1 is formed on the upper end surface 8 b of the dynamic pressure bearing 8. Specifically, dynamic pressure grooves 8b1 and hill portions 8b2 (indicated by cross-hatching) are alternately provided in the circumferential direction on the upper end surface 8b of the dynamic pressure bearing 8. The dynamic pressure groove 8b1 extends in a direction intersecting the circumferential direction and has, for example, a spiral shape. The dynamic pressure groove 8b1 is a pump-in type that pushes lubricating oil into the inner diameter side as the shaft member rotates. In the illustrated example, the dynamic pressure groove 8b1 has a pump-in type spiral shape inclined toward the inner diameter side toward the downstream side in the fluid flow direction (arrow direction in the figure) when the shaft member rotates. The dynamic pressure groove 8b1 and the hill portion 8b2 are both provided at the inner diameter end and outer diameter end of the upper end surface 8b of the dynamic pressure bearing 8 (specifically, at the boundary between the upper end surface 8b, the inner peripheral surface 8a, and the outer peripheral surface 8d). Chamfered part). The dynamic pressure groove 8b1 and the hill portion 8b2 have a constant dimensional ratio in the circumferential direction in the entire radial direction, and is 1: 1 in the illustrated example. For this reason, the circumferential width of the dynamic pressure groove 8b1 and the hill portion 8b2 gradually increases toward the outer diameter side.

As shown in FIG. 5, the upper surface of the hill part 8b2 is inclined downward toward the outer diameter side (right side in the figure). Further, the bottom surface of the dynamic pressure groove 8b1 is inclined downward toward the outer diameter side. As a result, the groove depth t (the axial distance between the upper surface of the hill portion 8b2 and the groove bottom surface of the dynamic pressure groove 8b1) of the dynamic pressure groove 8b1 is set to a predetermined value or more, for example, 10 μm or more. In FIG. 5, the inclination angles of the dynamic pressure groove 8b1 and the hill portion 8b2 are exaggerated. Actually, the axial distance d between the inner diameter end and the outer diameter end of the dynamic pressure groove 8b1 is 1 to It is about 5 μm.

The upper end surface 8b of the dynamic pressure bearing 8 is a surface in which the entire region including the dynamic pressure groove 8b1 and the hill portion 8b2 is molded. Further, the upper end surface 8b of the dynamic pressure bearing 8 is subjected not only to molding (forming) before sintering but also to molding (sizing) after sintering. On the other hand, the chamfered portion provided at the boundary between the upper end surface 8b of the dynamic pressure bearing 8 and the inner peripheral surface 8a and the outer peripheral surface 8d is subjected only to molding before sintering, and the molding after sintering is performed. It has not been. For this reason, the upper surface 8b (dynamic pressure groove 8b1 and hill portion 8b2) of the dynamic pressure bearing 8 has a smaller surface opening ratio than the chamfered portion.

As shown in FIG. 6, a dynamic pressure groove 8 c 1 as a thrust dynamic pressure generating portion is formed on the lower end surface 8 c of the dynamic pressure bearing 8. The specific shapes and the like of the dynamic pressure groove 8c1 and the hill portion 8c2 on the lower end surface 8c are the same as those of the dynamic pressure groove 8b1 and the hill portion 8b2 on the upper end surface 8b, and thus the description thereof is omitted.

The shape of the dynamic pressure grooves 8b1 and 8c1 is not limited to the above. For example, in the example shown in FIG. 7, the hill portion 8b2 of the upper end surface 8b of the dynamic pressure bearing 8 includes an inclined hill portion 8b21 provided between the circumferential directions of the spiral dynamic pressure groove 8b1, and an inner diameter of the inclined hill portion 8b21. And an annular land portion 8b22 connecting the ends. Thus, further improvement of fluid pressure can be expected by providing the land portion 8b22 at the inner diameter end of the hill portion 8b2.

The dynamic pressure grooves 8b1 and 8c1 are not limited to the pump-in type, and may be a pump-out type that pushes the lubricating fluid to the outer diameter side as the shaft member rotates. Further, the dynamic pressure grooves 8b1 and 8c1 are not limited to the spiral shape, but may be a herringbone shape or a step shape (radial shape).

An axial groove 8 d 1 is formed on the outer peripheral surface of the dynamic pressure bearing 8. The number of the axial grooves 8d1 is arbitrary, and in the illustrated example, three axial grooves 8d1 are arranged at equal intervals in the circumferential direction (see FIGS. 4 and 6).

As shown in FIG. 2, the housing 7 is formed in a bottomed cylindrical shape integrally having a side portion 7a and a bottom portion 7b. The inner peripheral surface 7a1 of the side portion 7a is formed in a straight cylindrical surface shape, and the outer peripheral surface 8d of the dynamic pressure bearing 8 is fixed by gap bonding, press-fitting, press-fitting with an adhesive interposed therebetween, or the like. At the upper end of the outer peripheral surface of the side portion 7a, as shown in FIG. 2, a tapered surface 7a3 that gradually increases in diameter upward is formed. Between this taper surface 7a3 and the cylindrical inner peripheral surface 3d1 of the annular protrusion 3d of the hub 3, an annular seal space S whose radial dimension is gradually reduced upward is formed. The capillary force of the seal space S prevents the lubricating oil filled in the housing 7 from leaking out.

After the above structure is assembled, the fluid dynamic pressure bearing device 1 shown in FIG. 2 is completed by filling the space inside the housing 7 including the internal pores of the dynamic pressure bearing 8 with lubricating oil. The oil level is always held inside the seal space S within the range of the assumed operating temperature of the fluid dynamic bearing device 1.

When the shaft member rotates, a radial bearing gap is formed between the inner peripheral surface 8a of the dynamic pressure bearing 8 and the outer peripheral surface 2a of the shaft portion 2, and an oil film generated in the radial bearing gap by the dynamic pressure grooves 8a1 and 8a2. The pressure of is increased. Due to the pressure of the oil film (dynamic pressure action), radial bearing portions R1 and R2 are configured to support the shaft portion 2 and the hub 3 in a non-contact manner so as to be rotatable in the radial direction.

At the same time, between the lower end surface 3a1 of the disk portion 3a of the hub 3 and the upper end surface 8b of the dynamic pressure bearing 8, and between the upper end surface 9a of the flange portion 9 and the lower end surface 8c of the dynamic pressure bearing 8. The thrust bearing gaps are formed respectively, and the pressure of the oil film generated in each thrust bearing gap is increased by the dynamic pressure grooves 8b1 and 8c1 on both end faces of the dynamic pressure bearing 8. The pressure (dynamic pressure action) of these oil films constitutes first and second thrust bearing portions T1 and T2 that support the shaft portion 2 and the hub 3 in a non-contact manner so as to be rotatable in both thrust directions.

At this time, the axial groove 8d1 formed in the outer peripheral surface 8d of the hydrodynamic bearing 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 the present embodiment, as shown in FIG. 3, the upper dynamic pressure groove 8a1 formed on the inner peripheral surface 8a of the dynamic pressure bearing 8 is formed in an axially asymmetric shape, so that the rotation of the shaft portion 2 is performed. Along with this, the lubricating oil in the radial bearing gap is pushed downward, and the lubricating oil circulates through the communication path, thereby reliably preventing the generation of local negative pressure.

Next, a method for manufacturing the hydrodynamic bearing 8 will be described. The hydrodynamic bearing 8 is performed through a mixing process, a compression molding (forming) process, a sintering process, a dimension correction (sizing) process, and a dynamic pressure groove forming (groove sizing) process.

In the soot mixing process, various metal powders are mixed to prepare raw material powder for the hydrodynamic bearing 8. As metal powder which comprises raw material powder, iron powder, copper powder, tin powder, etc. can be used, for example, and iron powder and copper powder are used in this embodiment. In addition, a solid lubricant such as graphite or a molding lubricant such as metal soap may be blended in the raw material powder.

In the compression molding step, after the above raw material powder is supplied to the forming mold, it is compressed to form a cylindrical green compact.

In the sintering step, the green compact is sintered at a predetermined sintering temperature to obtain a sintered body. The sintering temperature is set to less than the melting point of copper (1085 ° C.), for example, 850 to 900 ° C.

In the dimension correction process, the sintered body is re-compressed with a sizing mold to correct the dimensions of the sintered body (inner diameter, outer diameter, and axial dimension). In the dimension correction process, the chamfered portions provided between the both end faces of the sintered body and the outer peripheral face and the inner peripheral face are not molded (not in contact with the sizing mold).

In the dynamic pressure groove forming step, the dynamic pressure grooves 8a1 and 8a2 shown in FIG. 3 are molded on the inner peripheral surface of the sintered body by a groove sizing die, and the both ends of the sintered body are formed as shown in FIG. The dynamic pressure grooves 8b1 and 8c1 shown in FIG. 6 are molded. In the dynamic pressure groove forming step, the chamfered portion of the sintered body is not formed (not in contact with the groove sizing mold), as in the dimension correcting step.

Hereinafter, the dynamic pressure groove forming process will be described in detail. As shown in FIG. 8, the groove sizing mold includes a core rod 11, an upper punch 12, a lower punch 13, and a die 14 as molds for molding each surface of the sintered body 18.

Formed portions

11a and 11b having shapes corresponding to the dynamic pressure grooves 8a1 and 8a2 are provided on the outer peripheral surface of the core rod 11.

The forming surface (lower surface) of the upper punch 12 is provided with a forming portion 12a having a shape corresponding to the dynamic pressure groove 8b1. As shown in FIG. 9, the molding portion 12a includes a groove bottom molding surface 12a1 for molding the groove bottom surface of the dynamic pressure groove 8b1, and a recess 12a2 for molding the hill portion 8b2. The groove bottom molding surface 12a1 is inclined downward toward the outer diameter side. The bottom surface of the recess 12a2 (that is, the molding surface that molds the top surface of the hill portion 8b2) is substantially parallel to the surface orthogonal to the axial direction. As a result, the depth of the recess 12a2 (the axial distance between the groove bottom molding surface 12a1 and the bottom surface of the recess 12a2) becomes deeper toward the outer diameter side.

The molding surface (upper surface) of the lower punch 13 is provided with a molding portion 13a having a shape corresponding to the dynamic pressure groove 8c1. As shown in FIG. 9, the molding portion 13a includes a groove bottom molding surface 13a1 for molding the groove bottom surface of the dynamic pressure groove 8c1, and a recess 13a2 for molding the hill portion 8c2. The groove bottom molding surface 13a1 is inclined upward toward the outer diameter side. The bottom surface of the recess 13a2 (that is, the molding surface that molds the top surface of the hill portion 8c2) is substantially parallel to the surface orthogonal to the axial direction. As a result, the depth of the recess 13a2 (the axial distance between the groove bottom molding surface 13a1 and the bottom surface of the recess 13a2) becomes deeper toward the outer diameter side. In FIGS. 8 to 13, the depths of the

molding portions

11a, 11b, 12a, and 13a are exaggerated. 9, 11, and 13, the inclination angles of the groove bottom molding surfaces 12a1 and 13a1 are exaggerated.

In the dynamic pressure groove forming step, first, as shown in FIG. 8, the core rod 11 is inserted into the inner periphery of the sintered body 18 supported from below by the lower punch 13 to move the inner peripheral surface of the sintered body 18. The

molding parts

11a and 11b of the core rod 11 are opposed to the pressure groove formation scheduled region. In a state where the axial positional relationship between the sintered body 18 and the core rod 11 is maintained, the sintered body 18 is pressed into the inner periphery of the die 14 with the upper punch 12 as shown in FIG. The inner peripheral surface of the body 18 is pressed against the

molding parts

11 a and 11 b of the core rod 11. Thereby, the shape of the

molding parts

11a and 11b is transferred to the inner peripheral surface of the sintered body, and the dynamic pressure grooves 8a1 and 8a2 are molded.

At the same time, the sintered body 18 is pressed from both sides in the axial direction by the upper punch 12 and the lower punch 13, thereby pressing the molded

portions

12 a and 13 a of the

punches

12 and 13 against both end surfaces of the sintered body 18. As a result, the shapes of the

molding portions

12a and 13a are transferred to both end faces of the sintered body 18, and the dynamic pressure grooves 8b1 and 8c1 are molded. Specifically, as shown in FIG. 11, the end surfaces of the sintered body 18 are pressed by the groove bottom forming surfaces 12a1 and 13a1 of the forming

portions

12a and 13a of the

punches

12 and 13, and the dynamic pressure grooves 8b1 and 8c1 are formed. At the same time, the meat in the vicinity of the end face of the sintered body 18 plastically flows and enters the recesses 12a2 and 13a2 of the

molding portions

12a and 13a to form the hill portions 8b2 and 8c2. At this time, since the depth of the recesses 12a2 and 13a2 increases toward the outer diameter side, the height of the hill portions 8b2 and 8c2 filled in the recesses 12a2 and 13a2 increases toward the outer diameter side. It is high.

Thereafter, as shown in FIG. 12, the sintered body 18 is discharged from the inner periphery of the die 14. Accordingly, the sintered body 18 is spring-backed toward the outer diameter, the inner peripheral surface of the sintered body 18 is peeled off from the

molding portions

11a and 11b on the outer peripheral surface of the core rod 11, and the core rod is pulled out from the inner periphery of the sintered body. . Then, the upper and

lower punches

12 and 13 are separated from each other, and the

molding portions

12 a and 13 a of the

punches

12 and 13 are peeled from both end surfaces of the sintered body 18.

At this time, when the axial pressing force by the

punches

12 and 13 is released, an axial spring back is generated in the sintered body 18, so that the height of the hill portions 8b2 and 8c2 is the spring back as shown in FIG. It becomes lower than the previous state (see dotted line). Since the hill portions 8b2 and 8c2 become wider toward the outer diameter side, the strain amount (plastic deformation amount) when formed by the forming

portions

12a and 13a of the upper and

lower punches

12 and 13 goes to the outer diameter side. Small enough. For this reason, the amount of springback of the hill portions 8b2 and 8c2 (that is, the reduction width of the height of the hill portions 8b2 and 8c2) increases toward the outer diameter side.

On the other hand, the dynamic pressure grooves 8b1 and 8c1 formed on the end face of the sintered body 18 have a relatively large amount of compression by the

molding portions

12a and 13a of the upper and

lower punches

12 and 13, and therefore, the amount of distortion compared to the hill portions 8b2 and 8c2. (Plastic deformation amount) is large. For this reason, when the compression force by the upper and

lower punches

12 and 13 is released, the amount of spring back generated in the dynamic pressure grooves 8b1 and 8c1 is very small. Accordingly, the shapes of the groove bottom molding surfaces 12a1 and 13a1 of the

molding portions

12a and 13a of the upper and

lower punches

12 and 13 are transferred almost as they are to the groove bottom surfaces of the dynamic pressure grooves 8b1 and 8c1. In the present embodiment, since the groove bottom molding surfaces 12a1 and 13a1 are inclined inward in the axial direction (sintered body 18 side) toward the outer diameter side, the groove bottom surfaces of the dynamic pressure grooves 8b1 and 8c1 are outside. The surface is inclined toward the axially central side of the sintered body 18 toward the radial side.

As described above, even when the top surfaces of the hill portions 8b2 and 8c2 are inclined toward the outer diameter side toward the outer diameter side by the springback, the bottom surfaces of the dynamic pressure grooves 8b1 and 8c1 are axially directed toward the outer diameter side. By inclining toward the center in the direction, the height of the hill portions 8b2 and 8c2, that is, the groove depth of the dynamic pressure grooves 8b1 and 8c1 can be secured to a predetermined value or more. Thereby, when the shaft member rotates, the ability to collect oil is sufficiently exerted even near the outer diameter ends of the dynamic pressure grooves 8b1 and 8c1, and the oil film pressure in the thrust bearing gap can be increased to improve the bearing rigidity.

In addition, since the springback amounts of the hill portions 8b2 and 8c2 are not strictly constant for each product, the height of the hill portions 8b2 and 8c2 (particularly the height near the outer diameter end) varies somewhat for each product. At this time, if the height of the hill portions 8b2 and 8c2 is too high, this region may come into contact with the opposing members (flange portion 9 and hub 3) through the thrust bearing gap. In the present embodiment, as described above, the groove bottom surfaces of the dynamic pressure grooves 8b1 and 8c1 are inclined to ensure the groove depths of the dynamic pressure grooves 8b1 and 8c1 at a predetermined level or more, and the top surfaces of the hill portions 8b2 and 8c2 are secured. Since the vicinity of the outer diameter end can be retracted toward the center in the axial direction of the sintered body 18, contact between the hill portions 8b2 and 8c2 and the member facing the hill portions 8b2 and 8c2 can be reliably prevented.

Thereafter, by removing the sintered body 18 from the groove sizing mold, the hydrodynamic bearing 8 is completed.

The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described, but the description of the same points as the above-described embodiments will be omitted.

For example, in the above-described embodiment, the case where the molded dynamic pressure grooves are provided on the end surfaces on both sides in the axial direction of the dynamic pressure bearing 8 is shown, but not limited to this, one axial direction of the dynamic pressure bearing 8 is provided. A molded dynamic pressure groove may be provided only on the end surface. For example, in the fluid dynamic pressure bearing device 21 shown in FIG. 14, the dynamic pressure groove 8 c 1 shown in FIG. 6 is formed on the lower end face 8 c of the dynamic pressure bearing 8, and the dynamic pressure is shown on the upper end face 8 b of the dynamic pressure bearing 8. A groove is not formed, and an annular groove 8b3 and a radial groove 8b4 are formed. At the upper end of the housing 7, a seal portion 7c protruding toward the inner diameter is provided. A wedge-shaped seal space S is formed between the tapered inner peripheral surface 7 c 1 of the seal portion 7 c and the outer peripheral surface 2 a of the shaft portion 2. The side part 7a and the bottom part 7b of the housing 7 are formed separately. A dynamic pressure groove is formed on the upper end surface 7 b 1 of the bottom 7 b of the housing 7. A thrust bearing gap of the first thrust bearing portion T1 is formed between the lower end surface 9b of the flange portion 9 and the upper end surface 7b1 of the bottom portion 7b of the housing 7.

In the above-described embodiment, the case where the dynamic pressure grooves 8a1 and 8a2 are molded on the inner peripheral surface 8a of the dynamic pressure bearing 8 is shown. However, the inner peripheral surface 8a of the dynamic pressure bearing 8 may be a cylindrical surface. . Or it is good also considering the bottom part 7b of the housing 7 of FIG. 14 as a dynamic pressure bearing which concerns on this invention. In this case, a dynamic pressure groove is formed on the upper end surface 7b1 of the bottom 7b, and the groove bottom surface of the dynamic pressure groove is inclined downward toward the outer diameter side.

Further, in the above embodiment, the case where the dynamic pressure bearing 8 is fixed and the shaft member having the shaft portion 2 rotates is shown. On the contrary, the shaft member is fixed and the dynamic pressure bearing 8 side is fixed. It may be rotated.

In the above embodiment, the lubricating fluid is oil. However, grease, magnetic fluid, air, or the like may be used as the lubricating fluid.

The hydrodynamic bearing according to the present invention and the fluid hydrodynamic bearing device including the hydrodynamic bearing are not only a spindle motor for a disk drive device such as an HDD but also a fan motor for a cooling fan and a polygon scanner motor for a laser beam printer. It can also be incorporated and used.

DESCRIPTION OF SYMBOLS 1 Fluid dynamic pressure bearing apparatus 2 Shaft part 3 Hub 7 Housing 8 Dynamic pressure bearing 8a1, 8a2 (Radial) Dynamic pressure groove 8b1, 8c1 (Thrust) Dynamic pressure groove 8b2, 8c2 Hill part 9 Flange part 11

Core rod

12, 13

Punch

12a , 13a Molding parts 12a1, 13a1 Groove bottom molding surfaces 12a2, 13a2 Recess 14 Die 18 Sintered body R1, R2 Radial bearing part T1, T2 Thrust bearing part S Seal space

Claims

In a dynamic pressure bearing in which a dynamic pressure groove is molded on the end surface on one axial side,
A dynamic pressure bearing, wherein a bottom surface of the dynamic pressure groove is inclined toward the other side in the axial direction toward the outer diameter side.
The hydrodynamic bearing according to claim 1, comprising a sintered body.
Another dynamic pressure groove is molded on the other end face in the axial direction,
The dynamic pressure bearing according to claim 1 or 2, wherein a groove bottom surface of the other dynamic pressure groove is inclined to one side in the axial direction toward the outer diameter side.
A hydrodynamic bearing according to any one of claims 1 to 3, a shaft portion inserted into an inner periphery of the hydrodynamic bearing, and a flange portion projecting outward from the shaft portion, A shaft member that rotates relative to the pressure bearing, and a radial member that supports the shaft member in a radial direction relative to a radial pressure generated in a radial bearing gap between the inner peripheral surface of the dynamic pressure bearing and the outer peripheral surface of the shaft portion. A bearing portion; and a thrust bearing portion that relatively supports the shaft member in the thrust direction with a fluid pressure generated in a thrust bearing gap between an end surface on one axial side of the hydrodynamic bearing and an end surface of the flange portion. Fluid dynamic bearing device.
A motor having the fluid dynamic pressure bearing according to claim 4.
When molding the dynamic pressure groove by pressing the mold from one side in the axial direction against the end face of the bearing material,
A method of manufacturing a hydrodynamic bearing, wherein a molding surface for molding the bottom surface of the dynamic pressure groove in the molding die is inclined toward the other side in the axial direction toward the outer diameter side.
The hydrodynamic bearing according to claim 6, wherein a depth of a concave portion for molding a hill portion provided between circumferential directions of the dynamic pressure groove in the molding die becomes deeper toward an outer diameter side. Method.
The method for manufacturing a hydrodynamic bearing according to claim 7, wherein the bottom surface of the recess is a flat surface orthogonal to the axial direction.
In the molding die for molding the dynamic pressure groove by pressing against the end face of the bearing material from one side in the axial direction,
A molding die, wherein a molding surface for molding the bottom surface of the dynamic pressure groove is inclined toward the other side in the axial direction toward the outer diameter side.
The molding die according to claim 9, wherein the depth of the concave portion for molding the hill portion provided between the circumferential directions of the dynamic pressure grooves becomes deeper toward the outer diameter side.
The mold according to claim 10, wherein the bottom surface of the recess is a flat surface orthogonal to the axial direction.