JP2023184104A - Hydrodynamic bearing and fluid hydrodynamic bearing device - Google Patents

Abstract

To provide a hydrodynamic bearing that can support whirling even if the total length (axial length) of the bearing is short, and provide a fluid hydrodynamic bearing system that can support whirling of a rotor and prevent oil leakage without causing an increase in assembly cost.SOLUTION: A hydrodynamic bearing comprises a plurality of radial hydrodynamic grooves in an inside diameter surface, and a plurality of thrust hydrodynamic grooves in one end surface in an axial direction. The thrust hydrodynamic grooves are of a pump-in type for pushing lubricating oil from an outside diameter side to an inside diameter side. The groove depths of the thrust hydrodynamic grooves on the outside diameter side are shallower than those on the inside diameter side.SELECTED DRAWING: Figure 6

Description

The present invention relates to a hydrodynamic bearing and a fluid dynamic bearing device.

As a dynamic pressure bearing used to support a shaft member in a small motor such as a fan motor, as described in Patent Document 1, a pump pushes lubricating oil O from the outer diameter side to the inner diameter side on both axial end surfaces of the bearing. Some are equipped with in-type thrust dynamic pressure grooves. There are two types of thrust dynamic pressure grooves: a pump-in type shown in FIGS. 10 and 11, and a pump-out type shown in FIGS. 12 and 13.

The fan motor shown in FIGS. 11 and 13 includes a hydrodynamic bearing 51, a shaft member 52 inserted into the inner periphery of the hydrodynamic bearing, and a rotor 53 attached to one side of the shaft member 52 in the axial direction. It is something that The dynamic pressure bearing 51 in this case has a plurality of radial dynamic pressure grooves (not shown) on the inner diameter surface 51a and a plurality of thrust dynamic pressure grooves 55 (see FIG. 10) on one end surface in the axial direction. That is, a radial bearing portion 70 is formed that relatively supports the shaft member in the radial direction by the fluid pressure generated in the radial bearing gap provided between the inner peripheral surface 51a of the hydrodynamic bearing 51 and the outer peripheral surface 52a of the shaft member 52. . A thrust bearing portion 71 is formed that relatively supports the shaft member 52 in the thrust direction using fluid pressure generated in the thrust bearing gap between one end surface 51b of the hydrodynamic bearing 51 and the inner surface 53a of the rotor 53.

As shown in FIG. 10, the pump-in type thrust dynamic pressure groove 55 (55A) acts to push lubricating oil O from the outer diameter side to the inner diameter side as the shaft member rotates (rotation indicated by arrow A). It has a spiral shape in the direction of In FIG. 10, the cross-hatched area indicates the hill 56. Therefore, as shown by the arrow B1 in FIG. 11, the lubricating oil O is drawn from the outer diameter side to the inner diameter side.

As shown in FIG. 12, the pump-out type thrust dynamic pressure groove 55 (55B) pushes lubricating oil O from the inner diameter side to the outer diameter side as the shaft member 52 rotates (rotation indicated by arrow A). It has a spiral shape in the direction of action. In addition, in FIG. 12, the cross-hatched portion indicates the hill 56. As shown by arrow B2 in FIG. 13, lubricating oil is drawn from the inner diameter side to the outer diameter side.

In the conventional thrust dynamic pressure groove 55 of this type, the groove width in the radial direction widens toward the outer diameter side, as shown in FIG. 14, in order to increase the pressure on the inner diameter side. Further, FIG. 15 shows the principle of dynamic pressure generation, in which a dynamic pressure groove 62 is provided on the bearing facing surface 61 with respect to the shaft 60, and thereby, a hill 63 is provided on the facing surface 61 adjacent to this dynamic pressure groove 62. Therefore, a gap G1 is provided between the shaft outer circumferential surface 60a and the hill outer surface 63a, and a gap G2 is provided between the shaft outer circumferential surface 60a and the dynamic pressure groove bottom 62a. In this case, G1<G2.

Therefore, when the shaft 60 rotates in the direction of the arrow C, the lubricating oil O flows in the direction of the arrow D in the gap G2, and the flow of the lubricating oil O becomes dense at the step between the gap G2 and the gap G1. A wedge film effect is generated to generate dynamic pressure in the direction of arrow E.

Therefore, in order to increase the pressure, it is necessary to increase the number of hills 63 and grooves 62. However, as shown in FIG. There is no space to add 62.

By the way, cooling fan motors used in Ultrabooks (Intel Corporation: registered trademark) and the like are becoming thinner and thinner, and the overall length (axial length) of the bearings used therein needs to be thinner. However, as the axial length of the bearing becomes shorter, the dynamic pressure generated in the dynamic pressure grooves (radial dynamic pressure grooves) formed on the inner diameter surface of the bearing becomes smaller.

Furthermore, in order to maintain cooling performance, it is necessary to increase the radial size (rotor diameter) of the fan motor, and in such a case, the load acting on the bearing will increase. For this reason, the dynamic pressure generated on the inner diameter surface of the bearing becomes insufficient.

Therefore, as the axial length of the bearing becomes shorter and the generated dynamic pressure becomes smaller, the radial size (rotor diameter) increases, and in order to compensate for the lack of generated dynamic pressure, Patent Document 1 is proposed. As described, the thrust dynamic pressure groove was a pump-in type.

JP2018-31460A

By the way, in the case of the pump-in type, it is possible to increase the pressure on the center side, but the pressure on the outer diameter side is relatively low, making it difficult to support the whirling of the rotor. In addition, in the case of a pump-in type, lubricating oil is drawn from the outer diameter side to the inner diameter side, which tends to create negative pressure on the outer diameter side. In the case of the pump-out type, since the lubricating oil flows from the inner diameter side to the outer diameter side, the pressure on the outer diameter side increases, so the pump-out type is preferable in order to support the whirling of the rotor. However, in the pump-out type, lubricating oil flows from the inner diameter side to the outer diameter side, so there is a possibility that lubricating oil leakage (oil leakage) may occur.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a dynamic pressure bearing that can support swinging even if the bearing has a short overall length (axial length), and provides a hydrodynamic bearing that can support swinging of the rotor without increasing assembly costs. The present invention provides a fluid dynamic pressure bearing device that can support the surroundings and prevent oil leakage.

A first hydrodynamic bearing of the present invention is a hydrodynamic bearing having a plurality of radial hydrodynamic grooves on an inner diameter surface and a plurality of thrust hydrodynamic grooves on one axial end surface, wherein the thrust hydrodynamic grooves are It is a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the groove depth of the thrust dynamic pressure groove is set to be shallower on the outer diameter side than on the inner diameter side.

According to the first dynamic pressure bearing of the present invention, since the thrust dynamic pressure groove is of the pump-in type, the dynamic pressure generated on the inner diameter surface of the bearing can be increased. Moreover, since the groove depth of the thrust dynamic pressure groove is set to be shallower on the outer diameter side than on the inner diameter side, the pressure on the outer diameter side can be increased.

It is preferable that the depth of the outer diameter groove of the thrust dynamic pressure groove is less than half the depth of the inner diameter groove. With this setting, it is possible to stably increase the pressure on the outer diameter side.

When the inner diameter dimension of the thrust dynamic pressure groove on the outer diameter side with shallow groove depth is D1, the dynamic pressure bearing inner diameter dimension is Da, the dynamic pressure bearing outer diameter dimension is Db, and the bearing outer diameter chamfer dimension is a. , (Da+Db)/2<D1<(Db-2a). With this setting, the dynamic pressure generated on the outer diameter surface of the bearing can be stably increased.

A second hydrodynamic bearing of the present invention is a hydrodynamic bearing having a plurality of radial dynamic pressure grooves on an inner diameter surface and a plurality of thrust dynamic pressure grooves on one end surface in the axial direction, wherein the thrust dynamic pressure groove is It is a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the thrust dynamic pressure groove includes a thrust dynamic pressure groove group on the inner diameter side and a thrust dynamic pressure groove group on the outer diameter side. The number of grooves in the dynamic pressure groove group is set to be larger than the number of grooves in the thrust dynamic pressure groove group on the inner diameter side.

According to the second dynamic pressure bearing of the present invention, since the thrust dynamic pressure groove is of the pump-in type, the dynamic pressure generated on the inner diameter surface of the bearing can be increased. Moreover, since the number of grooves in the thrust dynamic pressure groove group on the outer diameter side is set to be larger than the number of grooves in the thrust dynamic pressure groove group on the inner diameter side, the groove width in the radial direction is constant, so the amount of oil drawn in is reduced. This decrease leads to prevention of negative pressure generation on the outer diameter side.

It is preferable that the number of grooves in the thrust dynamic pressure groove group on the outer diameter side is greater than the number of grooves in the thrust dynamic pressure groove group on the inner diameter side, but not more than twice. By setting in this way, it is possible to stably increase the dynamic pressure generated on the outer diameter surface of the bearing, and to effectively suppress the generation of negative pressure on the outer diameter side.

It is preferable that the radial groove width of each thrust dynamic pressure groove is constant. By setting in this way, the amount of lubricating oil (oil amount) drawn from the outer diameter side to the inner diameter side can be effectively reduced.

When the inner diameter end diameter of the thrust dynamic pressure groove on the outer diameter side is D2, the dynamic pressure bearing inner diameter dimension is Da, the dynamic pressure bearing outer diameter dimension is Db, and the bearing outer diameter chamfer dimension is a, (Da + Db )/2<D2<(Db-2a). This setting is effective in increasing the pressure on the outer diameter side.

A third hydrodynamic bearing of the present invention is a hydrodynamic bearing having a plurality of radial hydrodynamic grooves on an inner diameter surface and a plurality of thrust hydrodynamic grooves on one axial end surface, wherein the thrust hydrodynamic grooves are The first thrust dynamic pressure groove group is a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the groove depth of the thrust dynamic pressure groove is set to be shallower on the outer diameter side than on the inner diameter side; The second thrust dynamic pressure groove group is set to have more grooves on the outer diameter side than on the inner diameter side.

According to the third dynamic pressure bearing of the present invention, since the thrust dynamic pressure groove is of the pump-in type, it is possible to increase the dynamic pressure generated on the inner diameter surface of the bearing. Furthermore, in the first thrust dynamic pressure groove group, the groove depth of the thrust dynamic pressure grooves is set to be shallower on the outer diameter side than on the inner diameter side, so that the pressure on the outer diameter side can be increased.

The fluid dynamic pressure bearing device of the present invention includes the hydrodynamic bearing, a housing into which the hydrodynamic bearing is fitted, a shaft member inserted into the inner periphery of the hydrodynamic bearing, and one axial direction of the shaft member. A fluid dynamic pressure bearing device comprising: a rotor attached to a side of the shaft member; The shaft member is moved in the thrust direction by fluid pressure generated in the thrust bearing gap between the radial bearing portion that is relatively supported in the radial direction, the axial end surface of the dynamic pressure bearing on one axial side, and the bearing facing surface of the rotor. It is equipped with a thrust bearing part that provides relative support.

According to the fluid dynamic pressure bearing device of the present invention, since the thrust dynamic pressure groove is a pump-in type, it is possible to increase the dynamic pressure generated on the inner diameter surface of the bearing, and the pressure on the outer diameter side increases, causing the rotor to swing around. can be supported. Furthermore, the thrust dynamic pressure groove is only provided on one axial end face, and the assembly is excellent. That is, it can be assembled by inserting a hydrodynamic bearing into the housing and inserting a shaft member to which a rotor is attached to the hydrodynamic bearing.

The present invention provides a hydrodynamic bearing that can support whirling even if the bearing has a short overall length (axial length), can support whirling of the rotor without increasing assembly cost, and can leak oil. An object of the present invention is to provide a fluid dynamic pressure bearing device that can prevent this.

1 is a sectional view of a spindle motor incorporating a fluid dynamic bearing device according to the present invention. 1 is a sectional view of a main part of a spindle motor incorporating a hydrodynamic bearing according to the present invention. 1 is a sectional view of a main part of a spindle motor incorporating a hydrodynamic bearing according to the present invention. 1 is a sectional view of a hydrodynamic bearing according to the present invention. FIG. 1 is a plan view of a hydrodynamic bearing according to the present invention. A thrust dynamic pressure groove is shown, (a) is a simplified cross-sectional view of the dynamic pressure groove with a tapered groove bottom, and (b) is a diagram showing an inner diameter groove with a deep groove depth and an outer diameter groove with a shallow groove depth. FIG. 1 is a schematic diagram of an operating state of a spindle motor incorporating a hydrodynamic bearing according to the present invention. FIG. 6 is a simplified diagram of another embodiment of a thrust dynamic pressure groove. It is a pressure distribution image diagram. FIG. 3 is a simplified diagram of a pump-in type thrust dynamic pressure groove. FIG. 3 is a simplified diagram showing the flow of lubricating oil in a pump-in type thrust dynamic pressure groove. FIG. 2 is a simplified diagram of a pump-out type thrust dynamic pressure groove. FIG. 3 is a simplified diagram showing the flow of lubricating oil in a pump-out type thrust dynamic pressure groove. FIG. 2 is a simplified diagram of a conventional thrust dynamic pressure groove. FIG. 2 is an explanatory diagram of the principle of dynamic pressure generation.

Embodiments of the present invention will be described below based on FIGS. 1 to 9.

FIG. 1 shows a spindle motor used in an HDD disk drive device. This spindle motor has a fluid dynamic pressure bearing device 1 having a fluid 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, facing each other with a gap in the radial direction. A stator coil 4 and a 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 rotates due to the electromagnetic force between the stator coil 4 and the rotor magnet 5, thereby causing the hub 3 and the disk to rotate together. In this case, the hub 3, rotor magnet 5, etc. constitute the rotor 10.

As shown in FIG. 2, the fluid dynamic bearing device 1 is rotatably supported by a hydrodynamic bearing 8, a bottomed cylindrical housing 7 that holds the hydrodynamic bearing 8 on its inner periphery, and the hydrodynamic bearing 8. A shaft member 2 is provided. Further, the shaft member 2 is provided at the bottom of the housing 7 and is received by a thrust receiver 9. Note that FIG. 2 shows a case in which the thrust receiver 9 is provided, and FIG. 3 shows a case in which the thrust receiver 9 is not provided.

The shaft member 2 is made of metal, for example, and has a straight cylindrical outer peripheral surface 2a with no irregularities. Further, a rotor 10 is attached to one end of the shaft member 2 in the axial direction, and the other end of the shaft member 2 in the axial direction is a convex spherical portion 2b. The receiving surface 9a of the thrust receiver 9 is made of resin, for example, and is a flat surface without unevenness.

The hub 3 is made of metal, for example, and includes a disk portion 3a protruding outward from the upper end of the shaft member 2, a cylindrical portion 3b extending axially downward from the outer radial end of the disk portion 3a, and a cylindrical portion 3b. It is composed of a flange portion 3c extending further to the outer diameter from the lower end portion, and a cylindrical annular protrusion portion 3d extending downward from a substantially central portion in the radial direction of the disk portion 3a. A disk (not shown) is mounted on the upper end surface of the collar portion 3c. Although the hub 3 is integrally formed in the illustrated example, the hub 3 may be formed from a plurality of members. For example, the annular protrusion 3d may be formed from a separate member.

The dynamic pressure bearing 8 is made of metal or resin and has a cylindrical shape. In this embodiment, the hydrodynamic bearing 8 is made of 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 whose main component is copper, or a copper-based sintered metal containing copper as a main component. and copper-iron sintered metal whose main component is iron.

A dynamic pressure groove is formed in the inner circumferential surface 8a of the dynamic pressure bearing 8. In this embodiment, as shown in FIG. 4, herringbone-shaped dynamic pressure grooves (radial dynamic pressure grooves) 8a1 and 8a2 are provided in two regions spaced apart in the axial direction of the inner circumferential surface 8a of the hydrodynamic bearing 8, respectively. formed (cross-hatched are hills). In the illustrated example, the upper dynamic pressure groove 8a1 is formed asymmetrically in the axial direction, and specifically, the axial dimension of the region above the annular hill at approximately the center in the axial direction is smaller than the annular hill. is also larger than the axial dimension of the lower region. The lower dynamic pressure groove 8a2 is formed symmetrically in the axial direction. For this reason, a radial bearing portion 20 (see FIG. 2 and FIG. 3) are formed.

As shown in FIG. 5, a dynamic pressure groove (thrust dynamic pressure groove) 8b1 is formed in the end surface 8b of the dynamic pressure bearing 8 on one axial end side. Specifically, on one end surface 8b of the hydrodynamic bearing 8, dynamic pressure grooves 8b1 and hill portions 8b2 (indicated by cross hatching) are provided alternately in the circumferential direction. 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 of a pump-in type that pushes the lubricating oil O into the inner diameter side as the shaft member rotates. That is, as shown in FIG. 5, by rotating in the direction of the arrow A, the lubricating oil O is drawn from the outer diameter side to the inner diameter side, as shown by the arrow B1 shown in FIGS. 2 and 3. A thrust bearing portion 21 (see FIGS. 2 and 3) that relatively supports the shaft member 2 in the thrust direction by the fluid pressure generated in the thrust bearing gap between one end surface 8b of the hydrodynamic bearing 8 and the inner surface of the hub 3 of the rotor 10. ) is formed. Note that such a dynamic pressure groove is not formed on the other end surface 8c of the dynamic pressure bearing 8.

The dynamic pressure groove 8b1 and the hill portion 8b2 are both chamfers provided at the inner and outer diameter ends of the end surface 8b of the hydrodynamic bearing 8 (more specifically, at the boundaries between the end surface 8b, the inner circumferential surface 8a, and the outer circumferential surface 8d). 8e, 8f). Note that the circumferential width of the dynamic pressure groove 8b1 and the hill portion 8b2 gradually increases toward the outer diameter side.

The dynamic pressure groove 8b1 has a groove depth set to be shallower on the outer diameter side than on the inner diameter side. In this case, even if the groove bottom 8b11 is made gradually shallower from the inner diameter side to the outer diameter side as shown in FIG. 6(a) (cross-sectional view taken along line XX' in FIG. 5), As shown in the cross-sectional view taken along the line XX' in FIG. Good too.

If the groove depth on the outer diameter side is too shallow, the groove will disappear due to wear etc., so even if the groove bottom 8b11 is tapered as shown in Fig. 6(a), the groove depth as shown in Fig. 6(b) Thus, even if the groove has an inner groove 8b1a and an outer groove 8b1b, the depth of the shallow groove should be set to 1 μm or more (if it is shallower than this, the groove may disappear due to wear). It is preferable that the depth of the outer diameter groove is less than half the depth of the inner diameter groove. In this case, in FIG. 6(a), the groove depth on the outermost diameter side is set to be 1 μm or more, in FIG. 6(b), the groove depth of the outer diameter side groove 8b1b is set to be 1 μm or more, and in FIG. 6(a), The groove depth on the outermost diameter side is set to be less than half of the groove depth on the innermost diameter side, and in FIG. 6(b), the groove depth of the outer diameter side groove 8b1b is set to be less than half the groove depth of the inner diameter side groove 8b1a.

Further, as shown in FIG. 6(b), in the case of a bearing having an inner diameter groove 8b1a and an outer diameter groove 8b1b, the inner diameter dimension (diameter dimension) of the inner diameter groove 8b1a is set as D1, and the inner diameter dimension of the hydrodynamic bearing 8. (diameter dimension) is Da (see Fig. 4), the outer diameter dimension (diameter dimension) of the hydrodynamic bearing 8 is Db (see Fig. 4), and the bearing outer diameter chamfer dimension (outer diameter end chamfer 8b dimension) is a. Then, (Da+Db)/2<D1<(Db-2a).

By the way, FIG. 7 shows a schematic diagram of the operating state of the spindle motor, where the solid line indicates when the spindle motor is stopped, and the broken line indicates when it is running. In this case, even if the gap between the rotor 10 and the rotor-side end surface 8b of the hydrodynamic bearing 8 becomes small when the rotor 10 touches each other during this operation, the rotor-side end surface 8b of the hydrodynamic pressure bearing 8 If a thrust dynamic pressure groove is provided in which the groove depth on the outer diameter side is set to be shallower than the groove depth on the inner diameter side, the pressure on the outer diameter side can be increased and the whirling of the rotor 10 can be reduced. can be supported.

In this way, as shown in FIGS. 6(a) and 6(b), the dynamic pressure bearing having the thrust dynamic pressure groove 8b1 is of the pump-in type, so that the dynamic pressure generated on the inner diameter surface of the bearing can be reduced. can be increased. Moreover, since the groove depth of the thrust dynamic pressure groove 8b1 is set to be shallower on the outer diameter side than on the inner diameter side, the pressure on the outer diameter side can be increased. Therefore, even if the bearing has a short overall length (length in the axial direction), it is possible to provide a dynamic pressure bearing that can support whirling.

Next, FIG. 8 shows a second dynamic pressure bearing, in which a plurality of thrust dynamic pressure grooves provided on one end surface 8b in the axial direction of the hydrodynamic pressure bearing are formed of a thrust dynamic pressure groove group 11 on the inner diameter side and a thrust dynamic pressure groove group 11 on the outer diameter side. and a thrust dynamic pressure groove group 12 on the side. The number of grooves in the thrust dynamic pressure groove group 12 on the outer diameter side is made larger than the number of grooves in the thrust dynamic pressure groove group 11 on the inner diameter side.

In this case, a plurality of thrust dynamic pressure grooves 13 having the same groove width in the radial direction are provided from the inner diameter side to the outer diameter side, and between the thrust dynamic pressure grooves, the groove width in the radial direction widens toward the outer diameter side. A plurality of thrust dynamic pressure grooves 15 having the same radial groove width are provided from the radially intermediate portion of each hill 14 to the outer diameter side. As a result, the thrust dynamic pressure groove group 11 on the inner diameter side and the thrust dynamic pressure groove group 12 on the outer diameter side are formed. The number is greater than the number of grooves 11a in the pressure groove group 11 (in this case, twice as many). That is, the inner diameter side of the thrust dynamic pressure groove 13 becomes the groove (dynamic pressure groove) 11a of the thrust dynamic pressure groove group 11 on the inner diameter side, and the outer diameter side of the thrust dynamic pressure groove 13 and the thrust dynamic pressure groove 15 become the groove (dynamic pressure groove) 11a of the thrust dynamic pressure groove group 11 on the inner diameter side. This becomes the groove (dynamic pressure groove) 12a of the side thrust dynamic pressure groove group 12.

In this case, the inner diameter end diameter (diameter) of the thrust dynamic pressure groove group on the outer diameter side is D2, the hydrodynamic bearing inner diameter is Da, the hydrodynamic bearing outer diameter is Db, and the bearing outer diameter chamfer is When a, it is assumed that (Da+Db)/2<D2<(Db-2a).

In this way, the number of grooves in the thrust dynamic pressure groove group 12 on the outer diameter side is made larger than the number of grooves in the thrust dynamic pressure groove group 11 on the inner diameter side, that is, the number of hills 14 and grooves 12a are increased on the outer diameter side. As a result, the pressure on the outer diameter side can be increased during rotation, and the whirling of the rotor 10 can be supported.

By the way, in order to increase the number of hills 14 and grooves 12a, it is preferable to keep the groove width in the radial direction constant. Further, by simply increasing the number of hills 14 and grooves 12a on the outer diameter side, rather than simply increasing the number of hills and grooves in the entire area, only the pressure on the outer diameter side can be increased.

According to the dynamic pressure bearing having the thrust grooves shown in FIG. 8, the thrust dynamic pressure grooves 11a and 12a are of the pump-in type, so it is possible to increase the dynamic pressure generated on the inner diameter surface of the bearing. Moreover, since the number of grooves in the thrust dynamic pressure groove group 12 on the outer diameter side is set to be greater than the number of grooves in the thrust dynamic pressure groove group 11 on the inner diameter side, the groove width in the radial direction is constant, so that the oil drawn in A reduction in the amount leads to prevention of negative pressure generation on the outer diameter side.

In this case, it is preferable that the number of grooves in the thrust dynamic pressure groove group 12 on the outer diameter side is greater than the number of grooves in the thrust dynamic pressure groove group 11 on the inner diameter side, but not more than twice. By setting in this way, it is possible to stably increase the dynamic pressure generated on the outer diameter surface of the bearing, and to effectively suppress the generation of negative pressure on the outer diameter side.

It is preferable that the radial groove width of each thrust dynamic pressure groove 11a, 12a is constant. By setting in this way, the amount of lubricating oil (oil amount) drawn from the outer diameter side to the inner diameter side can be effectively reduced.

When the inner diameter end diameter of the thrust dynamic pressure groove 12a on the outer diameter side is D2, the dynamic pressure bearing inner diameter dimension is Da, the dynamic pressure bearing outer diameter dimension is Db, and the bearing outer diameter chamfer dimension is a, ( Da+Db)/2<D2<(Db-2a). This setting is effective in increasing the pressure on the outer diameter side.

By the way, FIG. 9 shows a pressure distribution image. The solid line shows the thrust dynamic pressure groove shown in FIG. 8 formed therein, and the imaginary line shows the thrust dynamic pressure groove shown in FIG. 14 formed therein. As can be seen from this figure, in the thrust dynamic pressure groove shown by the solid line, the groove width in the radial direction is constant; The amount of lubricating oil (oil amount) drawn from the outside diameter side to the inside diameter side is reduced compared to the setting (setting), and negative pressure generation on the outside diameter side can be prevented. On the other hand, in the conventional thrust dynamic pressure groove shown by the imaginary line, the amount of oil drawn from the outer diameter side to the inner diameter side does not decrease, and negative pressure is generated on the outer diameter side.

By the way, as another dynamic pressure bearing, one provided with (a combination of) the thrust dynamic pressure groove 8b1 shown in FIG. 5 and the thrust dynamic pressure grooves 11a and 12a shown in FIG. 8 may be used. That is, a thrust dynamic pressure groove (which may be of the type shown in FIG. 6(a) or the type shown in FIG. 6(b)) in which the groove depth is shallower on the outer diameter side than on the inner diameter side. , as thrust dynamic pressure grooves, a thrust dynamic pressure groove group 11 on the inner diameter side and a thrust dynamic pressure groove group 12 on the outer diameter side are provided, and the number of grooves in the thrust dynamic pressure groove group 12 on the outer diameter side is determined by the thrust dynamic pressure groove group 12 on the inner diameter side. The number of thrust dynamic pressure grooves is greater than the number of grooves in the pressure groove group 11. In this case, the thrust dynamic pressure groove whose groove depth is shallower on the outer diameter side than on the inner diameter side is called the first thrust dynamic pressure groove, and the thrust dynamic pressure groove group 11 on the inner diameter side and the thrust dynamic pressure groove on the outer diameter side are called the first thrust dynamic pressure grooves. The thrust dynamic pressure grooves having the group 12 can be called a second thrust dynamic pressure groove.

Even with such other hydrodynamic bearings, the same effect as the hydrodynamic bearing with the thrust dynamic pressure groove 8b1 shown in FIG. 5 or the hydrodynamic bearing with the thrust dynamic pressure grooves 11a and 12a shown in FIG. 8 is obtained. be effective. Note that the ratio of the thrust dynamic pressure groove 8b1 shown in FIG. 5 to the thrust dynamic pressure grooves 11a and 12a shown in FIG. 8 may be the same, or one of them may be larger.

Fluid using dynamic pressure bearings with thrust dynamic pressure grooves as shown in Figure 5, dynamic pressure bearings with thrust dynamic pressure grooves as shown in Figure 8, and dynamic pressure bearings with thrust dynamic pressure grooves that are a combination of these. In the dynamic pressure bearing device, the thrust dynamic pressure groove is of the pump-in type, so it is possible to increase the dynamic pressure generated on the inner diameter surface of the bearing, and the pressure on the outer diameter side increases to support the whirling of the rotor 10. can. Furthermore, the thrust dynamic pressure groove is only provided on one axial end face, and the assembly is excellent. That is, it can be assembled by inserting a hydrodynamic bearing into the housing and inserting a shaft member to which a rotor is attached to the hydrodynamic bearing.

Therefore, it is possible to provide a fluid dynamic bearing device that can support the whirling of the rotor and prevent oil leakage without increasing assembly costs.

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and can be modified in various ways, and the number of thrust dynamic pressure grooves can be increased or decreased as desired. The inclination angle of the groove bottom of the thrust dynamic pressure groove shown in ) and the depth of each groove of the thrust dynamic pressure groove shown in FIG. 6(b) can also be set arbitrarily. Alternatively, the groove bottom of the thrust dynamic pressure may be changed stepwise to make the groove depth shallower on the outer diameter side than on the inner diameter side.

Furthermore, the hydrodynamic bearing according to the present invention and the fluid dynamic pressure bearing device equipped with the same are applicable not only to spindle motors for disk drive devices such as HDDs, but also to fan motors for cooling fans and polygon scanner motors for laser beam printers. It can also be used by incorporating it into

2 Shaft member 2a Outer peripheral surface 8 Dynamic pressure bearing 8a Inner peripheral surface 8a1 Radial dynamic pressure groove 8a2 Radial dynamic pressure groove 8b End surface 8b1 Thrust dynamic pressure groove 8b1a Inner diameter groove 8b1b Outer diameter groove 10 Rotor 11 Thrust dynamic pressure groove group 12 Thrust dynamic pressure Groove group 13 Thrust dynamic pressure groove 15 Thrust dynamic pressure groove

Claims (9)

A hydrodynamic bearing having a plurality of radial dynamic pressure grooves on an inner diameter surface and a plurality of thrust dynamic pressure grooves on one axial end surface,
The thrust dynamic pressure groove is of a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the groove depth of the thrust dynamic pressure groove is set to be shallower on the outer diameter side than on the inner diameter side. Hydrodynamic bearing. 2. The dynamic pressure bearing according to claim 1, wherein the depth of the outer diameter groove of the thrust dynamic pressure groove is less than half the depth of the inner diameter groove. When the inner diameter dimension of the thrust dynamic pressure groove on the outer diameter side with shallow groove depth is D1, the dynamic pressure bearing inner diameter dimension is Da, the dynamic pressure bearing outer diameter dimension is Db, and the bearing outer diameter chamfer dimension is a. , (Da+Db)/2<D1<(Db-2a). A hydrodynamic bearing having a plurality of radial dynamic pressure grooves on an inner diameter surface and a plurality of thrust dynamic pressure grooves on one axial end surface,
The thrust dynamic pressure groove is a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the thrust dynamic pressure groove includes a thrust dynamic pressure groove group on the inner diameter side and a thrust dynamic pressure groove group on the outer diameter side. A dynamic pressure bearing, characterized in that the number of grooves in the thrust dynamic pressure groove group on the outer diameter side is set to be larger than the number of grooves in the thrust dynamic pressure groove group on the inner diameter side. 5. The dynamic pressure bearing according to claim 4, wherein the number of grooves in the thrust dynamic pressure groove group on the outer diameter side is not more than twice the number of grooves in the thrust dynamic pressure groove group on the inner diameter side. 6. The hydrodynamic bearing according to claim 4, wherein the radial groove width of each thrust hydrodynamic groove is constant. When the inner diameter end diameter of the thrust dynamic pressure groove on the outer diameter side is D2, the dynamic pressure bearing inner diameter dimension is Da, the dynamic pressure bearing outer diameter dimension is Db, and the bearing outer diameter chamfer dimension is a, (Da + Db )/2<D2<(Db-2a). 6. The hydrodynamic bearing according to claim 4, wherein: A hydrodynamic bearing having a plurality of radial dynamic pressure grooves on an inner diameter surface and a plurality of thrust dynamic pressure grooves on one axial end surface,
The thrust dynamic pressure groove is a pump-in type that pushes lubricating oil from the outer diameter side to the inner diameter side, and the groove depth of the thrust dynamic pressure groove is set to be shallower on the outer diameter side than on the inner diameter side. A dynamic pressure bearing comprising a pressure groove group and a second thrust dynamic pressure groove group in which the number of grooves is set to be larger on the outer diameter side than on the inner diameter side. A fluid dynamic pressure bearing comprising the dynamic pressure bearing according to claim 1 or claim 4, a shaft member inserted into the inner periphery of the dynamic pressure bearing, and a rotor attached to one side in the axial direction of the shaft member. A bearing device,
a radial bearing portion that relatively supports the shaft member in the radial direction by fluid pressure generated in a radial bearing gap between the inner circumferential surface of the hydrodynamic bearing and the outer circumferential surface of the shaft member; and one axial direction of the hydrodynamic bearing. A fluid dynamic pressure bearing comprising: a thrust bearing portion that relatively supports the shaft member in the thrust direction using fluid pressure generated in the thrust bearing gap between the side axial end surface and the bearing facing surface of the rotor. Device.

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