JP2003065323A - Hydrodynamic bearing apparatus and electric motor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly remove air bubbles entrained into lubricating fluid in a hydrodynamic bearing apparatus of which the minute clearance between a shaft member and a sleeve member is entirely filled with the lubricating fluid. SOLUTION: The hydrodynamic bearing apparatus is provided with a shaft member 11 having a shaft part 111 and a thrust plate part 112, a sleeve member 12 made of porous sintered compact, a sleeve supporting member 13, a thrust bush member 14 for sealing a lower aperture of the sleeve supporting member 13, and the lubricating fluid for entirely filling the minute clearance. The shaft member 11 is supported by providing two or more radial hydrodynamic pressure generating grooves 121a, 121b for supporting a radial load on the shaft part 111 and the inside peripheral surface of the sleeve member 12 facing the shaft part 111, and by providing a thrust hydrodynamic pressure generating grooves 141 for supporting a thrust load on the lower side surface of the thrust plate part 112 and the inside surface of the thrust bush member 14 facing the lower side surface of the thrust plate part 112.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrodynamic bearing device and a motor using the same, and more particularly to a structure in which a lubricating fluid is filled in the entire minute gap between a shaft member and a sleeve member (hereinafter referred to as "full fill structure"). ) ”And a motor using the same.

[0002]

2. Description of the Related Art Magnetic disk devices such as hard disk drives (HDD) and high-capacity floppy disk drives (FDD) have been significantly increased in capacity and miniaturized year by year. A ball bearing that has been mainly used until now as a bearing means for such spindle motors is required to have a rotating side member and a stationary side member that rotate relative to each other. It is becoming difficult to satisfy such a requirement because contact is made by a ball between the two. Therefore, a dynamic pressure bearing device has been used which supports in a non-contact manner by using a fluid dynamic pressure generated in a lubricating fluid interposed between a rotating side member and a stationary side member. The structure of the dynamic pressure bearing device is roughly comprised of a shaft member having a thrust plate portion, a sleeve member arranged to face the shaft member with a minute gap, and a lubricating fluid filled in the minute gap. It comprises a dynamic pressure generating groove for inducing a fluid dynamic pressure in the lubricating fluid when the motor rotates.
In such a dynamic bearing device having a basic structure, a full-fill dynamic bearing device has been developed in order to meet the market demand for further reliability and durability of the device and cost reduction by simplifying the structure. There is. An example of a conventional dynamic pressure bearing device using a full-fill structure is shown in FIG.

In the hydrodynamic bearing device of FIG. 8, a through hole 131 is formed in the axial direction at the center of the sleeve supporting member 13, and the lower end of the sleeve supporting member 13 is formed with a diameter larger than the inner diameter of the through hole 131. A fitting groove portion 132 is formed.
Two radial dynamic pressure generating grooves 121a and 121b are formed on the inner peripheral surface of the through hole 131 so as to be axially separated from each other, and the thrust dynamic pressure generating groove 12 is formed on the lower end surface.
1c is formed, and the length in the axial direction is the sleeve support member 13
A hollow cylindrical sleeve member 12 made of a shorter porous sintered body is fixed.

On the other hand, the shaft member 11 comprises a shaft portion 111 and a thrust plate portion 112 formed at the lower end of the shaft portion 111. Then, the shaft portion 111 of the shaft member 11 is inserted into the hollow portion of the sleeve member 12 with a constant gap until the upper surface of the thrust plate portion 112 comes into contact with the lower end surface of the sleeve member 12, and is formed on the sleeve support member 13. The thrust bush member 14 having the thrust dynamic pressure generating groove 141 formed on the upper surface is mounted in the fitting groove portion 132 so as to seal the lower opening of the through hole 131. On the other hand, in the upper opening of the through hole 131, an annular seal member 15 fitted in the shaft portion 111 is provided, and its upper surface and the sleeve support member 13
Is fixed to the inner peripheral surface of the through hole 131 so that the upper end surface thereof is flush with the upper surface. The inside of the through hole 131 surrounded by the sleeve support member 13, the thrust bush member 14, and the seal member 15 is filled with a lubricating fluid (not shown). That is, the minute gaps between the sleeve member 12 and the shaft portion 111 and between the thrust plate portion 112 and the thrust bush member 14 and the continuous holes formed inside the sleeve member 12 are filled with the lubricating fluid.

In the dynamic bearing device having the above structure, the radial load of the shaft member 111 is generated by the fluid dynamics generated by the two herringbone type radial dynamic pressure generating grooves 121a, 121b formed on the inner peripheral surface of the sleeve member 12. On the other hand, the pressure causes the thrust load to be supported by the fluid dynamic pressure generated in the spiral thrust dynamic pressure generating grooves 121c and 141 formed in the lower end surface of the sleeve member 12 and the surface of the thrust bush member 14.

[0006]

In such a dynamic pressure bearing device, if air bubbles are mixed in the lubricating fluid, the following problems occur. First, as the temperature rises, the bubbles expand in volume, the lubricating fluid leaks out of the device, and the amount of lubricating fluid decreases. On the other hand, the lubricating fluid leaked to the outside of the device adheres to and contaminates other devices, causing a malfunction. Further, when air bubbles are caught in the dynamic pressure generation groove, non-repetitive vibration occurs, and the bearing rigidity is reduced. In particular, the thrust bearing portion in FIG. 8 is a spiral type thrust dynamic pressure generating groove 141 formed on the surface of the thrust bush member 14 to allow the lubricating fluid to flow from the outer peripheral side to the inner peripheral side of the thrust plate portion 112. Since the maximum dynamic pressure is generated in the central portion of the thrust plate portion 112 to support the thrust load, the bubbles that have flowed to the lower surface of the thrust plate portion 112 move from the outer peripheral side to the inner peripheral side of the thrust plate portion 112. It is carried by the flowing lubricating fluid to the center of the lower surface of the thrust plate and stays there permanently.

For this reason, in conventional bearing devices using a full-fill structure, various improvements and contrivances have been made, for example, in the operation of injecting the lubricating fluid into the bearing portion and the lubricating fluid itself so that air bubbles are not mixed in the lubricating fluid. Was there.

However, it was difficult to completely prevent air bubbles from being mixed in the step of injecting the lubricating fluid into the minute gap. Even if air bubbles are not mixed in the lubricating fluid in the assembly process, the ends of the dynamic pressure generating grooves oscillate the interface of the lubricating fluid when the motor rotates, so that air may be taken into the lubricating fluid to form bubbles. there were.

As a technique for preventing the entrapment of this air in the lubricating fluid that occurs when the motor rotates, for example, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 00-173656, it is proposed to increase the volume and size of the taper seal portion where the interface of the lubricating fluid is located, and to sufficiently lengthen the distance between the dynamic pressure generating groove and the interface of the lubricating fluid. However, in order to expand the area of the taper seal portion and simultaneously meet the market demand for smaller and thinner motors, the degree of freedom in designing the bearing portion is extremely limited. Further, there is a possibility that sufficient bearing rigidity cannot be obtained.

The present invention has been made in view of such conventional problems, and an object thereof is to smoothly remove bubbles mixed in a lubricating fluid in a bearing device having a full-fill structure.

Another object of the present invention is to provide a motor in which lubricating fluid does not leak from the dynamic pressure bearing device, non-repetitive vibration does not occur, and the bearing rigidity does not decrease.

[0012]

[Means for Solving the Problems] First to achieve the above object
In the dynamic pressure bearing device according to the invention, a shaft member having a shaft portion and a thrust plate portion projecting outward in the radial direction from the shaft portion, and the shaft member are arranged to face each other with a minute gap,
A sleeve member made of a porous sintered body, a sleeve support member supporting the sleeve member, and a lower surface of the thrust plate portion are arranged to face each other with a minute gap, and a lower opening of the sleeve support member is sealed. A thrust bush member and a lubricating fluid filled in the entire minute gap, and a radial load for supporting a radial load on at least one of the shaft portion and the inner peripheral surface of the sleeve member facing the shaft portion. Two or more dynamic pressure generating grooves are provided, and a thrust dynamic pressure generating groove for supporting a thrust load is provided on at least one of the lower side surface of the thrust plate portion and the inner side surface of the thrust bush member facing the lower side surface. A hydrodynamic bearing device for rotatably supporting the sleeve member and the shaft member relative to each other, wherein A porous sintered body is inserted into the hole formed in the through hole, a through hole communicating with the outer peripheral surface of the shaft portion is formed in the upper end portion of the hole, and the opening on the outer peripheral surface side of the shaft portion of the through hole is in the lubricating fluid. It is located in.

From the viewpoint of more smoothly removing the air bubbles present in the lubricating fluid, the opening of the through hole on the outer peripheral surface of the shaft portion is located above the radial dynamic pressure generating groove formed on the uppermost side in the axial direction. Alternatively, it is preferably located between the radial dynamic pressure generating grooves, and more preferably located near the interface of the lubricating fluid.

A hydrodynamic bearing device according to a second aspect of the present invention has a shaft member having a shaft portion and a thrust plate portion protruding outward in the radial direction from the shaft portion, and a minute gap with respect to the shaft portion. A sleeve member made of a metal material and opposed to the lower surface of the thrust plate portion with a minute gap, and a thrust bush member sealing a lower opening of the sleeve member, and the minute gap. A lubricating fluid filled in the entirety, and two or more radial dynamic pressure generating grooves for supporting a radial load are provided on at least one of the shaft portion and the inner peripheral surface of the sleeve member facing the shaft portion. Further, a thrust dynamic pressure generating groove for supporting a thrust load is provided on at least one of the lower side surface of the thrust plate portion and the inner side surface of the thrust bush member, and the sleeve is provided. A hydrodynamic bearing device for rotatably supporting a material and the shaft member, wherein a porous sintered body is inserted into a hole formed in the axial direction from the bottom center of the shaft part, A through hole communicating with the shaft outer peripheral surface is formed at the upper end of the shaft, and the shaft outer peripheral surface side opening of the through hole is above the radial dynamic pressure generating groove formed on the axially uppermost side and the lubrication is performed. It is characterized in that it is located in the fluid.

Here, from the viewpoint of more reliably supporting the thrust load, in the hydrodynamic bearing device according to the first invention and the second invention, the porous sintered body is fitted into the entire through hole without any clearance. Is desirable. Further, it is preferable that the thrust dynamic pressure generating groove allows the lubricating fluid to flow from the outer peripheral side to the inner peripheral side of the thrust plate portion. Further, the radial dynamic pressure generating groove formed on the uppermost side in the axial direction of the sleeve member is
From the viewpoint of preventing leakage of the lubricating fluid, a herringbone-shaped groove formed in the axially unbalanced manner to allow the lubricating fluid to flow axially downward is preferable.

A motor according to the present invention that achieves the above object is characterized by including any one of the dynamic pressure bearing devices described above.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention are completely contrary to the conventional technical idea of not mixing bubbles in a lubricating fluid, and assume that the bubbles are mixed in the lubricating fluid on the assumption that the bubbles are mixed. As a result of intensive studies based on the technical idea of removing the mixed fluid, it was found that mixed bubbles can be smoothly removed by largely circulating the lubricating fluid throughout the area filled with the lubricating fluid, and the present invention has been accomplished.

That is, one of the major features of the hydrodynamic bearing device according to the present invention is that a hole is formed in the axial direction from the center of the bottom surface of the shaft portion, and the upper end portion of the hole penetrates the outer peripheral surface of the shaft portion. A hole is formed, and the opening of the through hole on the outer peripheral surface of the shaft portion is provided in the lubricating fluid. By forming the hole and the through hole in the shaft portion, the lubricating fluid flows from the thrust bearing portion to the radial bearing portion through the hole and the through hole,
Further, it flows through the continuous holes inside the sleeve member made of the porous sintered body and returns to the thrust bearing portion. Here, the opening is provided in the lubricating fluid because when the opening of the through hole on the outer peripheral surface of the shaft portion is provided above the interface of the lubricating fluid, the lubricating fluid is opened by the centrifugal force due to the rotation of the shaft member. It will be scattered from. In order to remove bubbles in the lubricating fluid more smoothly, it is preferable to provide the opening near the interface of the lubricating fluid, that is, in the taper seal portion. By forming such a circulation path of the lubricating fluid, the bubbles in the lubricating fluid sequentially escape from the interface of the lubricating fluid to the atmosphere during the circulation.

Another major feature of the dynamic pressure bearing device according to the present invention is that a porous sintered body is inserted into a hole formed in the shaft portion. The thrust dynamic pressure generation groove is a spiral groove that allows the lubricating fluid to flow from the outer peripheral side to the inner peripheral side of the thrust plate portion, and the maximum dynamic pressure is generated at the center of the lower surface of the thrust plate portion to support the thrust load. If
If there is a hole in the center of the lower surface of the thrust plate, the lubricating fluid that has flowed from the outer peripheral side to the inner peripheral side of the thrust plate due to the spiral groove will circulate through the hole as it is, so the lower surface of the thrust plate Maximum dynamic pressure does not occur in the central part and bearing action does not occur. Therefore, in order to ensure the circulation of the lubricating fluid and to generate the dynamic pressure at the central portion of the lower surface of the thrust plate, the porous sintered body is inserted into the hole.

The hydrodynamic bearing device of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical sectional view of a dynamic pressure bearing device according to the first invention. The same members and parts as those of the conventional dynamic pressure bearing device shown in FIG. 8 are designated by the same reference numerals. Descriptions of structures and functions common to the dynamic pressure bearing device of FIG. 8 will be omitted here, and only different structures and functions will be described.

A bottomed hole 113 is formed in the axial direction from the center of the bottom surface of the shaft portion 111, and a porous sintered body 114 is fitted in the hole 113 without a gap. The size (diameter) of the hole 113 is not particularly limited as long as the lubricating fluid can flow. On the contrary, if the hole is made larger than necessary, the strength of the shaft portion 111 is reduced. Specifically, from the viewpoint of drilling workability, the smallest diameter is usually 0.5 to
It is about 2.0 mm. The cross-sectional shape of the hole is not particularly limited and may be circular, oval or polygonal.

The porous sintered body fitted into the hole is not particularly limited in its material as long as it has continuous pores inside.
Various metal powders, metal compound powders, and non-metal powders that have been molded and sintered can be used. Fe as a raw material
-Cu, Cu-Sn, Cu-Sn-Pb, Fe-C etc. are mentioned.

A through hole 115 is formed so that the upper end of the hole 113 and the outer peripheral surface of the shaft portion communicate with each other. An opening on the outer peripheral surface side of the shaft portion of the through hole 115 is formed below the interface of the lubricating fluid of the taper seal portion formed by the annular seal member 15 and the shaft portion tapered surface 117 (shown in FIG. 2). An enlarged cross-sectional view of this taper seal portion is shown in FIG.

A tapered surface 117 is formed on the shaft portion 111 facing the annular seal member 15 with a minute gap by gradually reducing the outer diameter of the shaft portion upward in the axial direction. At the taper seal portion composed of the taper surface 117 and the seal member 15, the lubricating fluid L is prevented from leaking out of the device by utilizing the capillary phenomenon. Through hole 1
The shaft outer peripheral surface side opening 116 of 15 is preferably formed below the interface of the lubricating fluid L in the taper seal portion.
The radial dynamic pressure generating groove 121a is formed near the interface of the lubricating fluid L.
Since it is apart from (illustrated in FIG. 1) to some extent, the flow pressure in the bearing direction is relatively low, and the bubbles in the lubricating fluid flowing to the taper seal part do not flow in the bearing direction and easily escape from the interface to the outside. Because it will be. Since the lubricating fluid interface of the taper seal portion moves due to the temperature change, it is necessary to form the shaft portion outer peripheral surface side opening 116 of the through hole 115 so that it is always positioned in the lubricating fluid L. Further, two or more such through holes 115 may be provided in the circumferential direction.
Furthermore, two or more through holes 115 may be provided in the axial direction.

In FIG. 1, two radial dynamic pressure generating grooves 121a and 121b are formed in the inner peripheral surface of a hollow cylindrical sleeve member 12 made of a porous sintered body so as to be vertically separated from each other. A thrust dynamic pressure generating groove 121c is formed on the lower end surface of the sleeve member 12 (the surface that faces the upper side surface of the thrust plate portion 112 in the axial direction). Figure 3
A concrete example of the radial dynamic pressure generating groove is shown in FIG. FIG. 3 is a vertical sectional view of the sleeve member. Two radial dynamic pressure generating grooves 121a, 121b formed on the inner peripheral surface of the sleeve member 12.
Both are herringbone grooves, but the lower radial dynamic pressure generating groove 121b is a herringbone groove in which the groove portions are formed in equilibrium in the axial direction of the sleeve member 12, while the upper radial dynamic pressure generating groove 121b is generated. The groove 121a is a herringbone groove in which the groove portion on the upper side (opening end side of the sleeve member 12) is formed longer than the groove portion on the lower side. As a result, in the upper radial dynamic pressure generating groove 121a, in addition to the bearing action, an action of causing the lubricating fluid to flow downward in the axial direction occurs, and in combination with the action of the taper seal portion, the leakage of the lubricating fluid is effectively prevented. . The thrust dynamic pressure generating groove 1
The specific shape of 21c is substantially the same as the thrust dynamic pressure generating groove 141 formed in the thrust bush member 14, which will be described later with reference to FIG.

In order to form such a dynamic pressure generating groove in the sleeve member 12 made of a porous sintered body, a conventionally known method can be used. For example, irregularities opposite to the dynamic pressure generating groove are formed on the surface. It can be manufactured by filling a shaped mold with a sintering material, compression-molding, and then sintering. The surface aperture ratio of the sleeve member 12 is generally preferably 15% or less, and more preferably 5 to 10% in consideration of the flow of the lubricating fluid. Further, in the portion where the dynamic pressure generating groove is formed, it is necessary to flow the lubricating fluid to generate the dynamic pressure, so that the surface aperture ratio is preferably 5% or less. To partially reduce the surface aperture ratio, for example, a sealing treatment may be performed. The surface opening ratio here means the ratio of the opening area per unit area.

The porous sintered body forming the sleeve member is molded and sintered using various metal powders, metal compound powders and non-metal powders as raw materials, like the porous sintered body fitted in the hole. It is made. The same raw materials are also exemplified.

Further, in FIG. 1, a thrust generating groove 141 is formed on the upper surface of the thrust bush member 14. FIG. 4 shows an example of the thrust dynamic pressure generating groove. FIG. 4 is a plan view of the thrust bush member 14, in which a spiral groove 141 is formed in a band-shaped region surrounded by two concentric circles coaxial with the thrust bush member 14.

Next, the flow of the lubricating fluid and bubbles in the dynamic pressure bearing device having such a structure will be described. Spiral groove 1 formed on the surface of thrust bush member 14
41 causes the lubricating fluid to flow from the outer peripheral side of the thrust plate portion 112 toward the inner peripheral side. On the other hand, a hole 113 is formed in the central portion of the thrust plate portion 112, but since the porous sintered body 114 is fitted and inserted in this hole 113, it flows into the central portion of the thrust plate portion 112. The lubricating fluid is the same as in the conventional thrust plate portion 1.
A maximum dynamic pressure is generated at the central portion of 12, and the shaft member 11 is supported in a non-contact manner by this dynamic pressure.

Here, part of the lubricating fluid that has flowed to the central portion of the thrust plate portion 112 is part of the porous sintered body 11.
4 flows into the continuous pores inside and flows axially upward in the sintered body 114. When it reaches the upper end of the hole 113, it further flows through the through hole 115 to the outer peripheral surface of the shaft portion. Since the opening 116 on the outer peripheral surface of the shaft portion of the through hole 115 (shown in FIG. 2) is formed under the lubricating fluid interface as described above, the bubbles existing in the lubricating fluid escape to the outside from this interface. The lubricating fluid from which air bubbles have been removed flows axially downward through a minute gap between the shaft member 11 and the sleeve member 12 and a continuous hole inside the sleeve member 12, and moves in the two radial dynamic pressure generating grooves 121a and 121b on the way. A pressure is generated to support the shaft member 11 in a non-contact manner. Then, it reaches the outer peripheral portion of the thrust bush member 14. The lubricating fluid circulates in such a closed flow path.

Another embodiment of the dynamic pressure bearing device according to the first invention is shown in FIG. FIG. 5 shows the shaft hole 1 on the upper end surface of the shaft member 11.
FIG. 7 is a vertical cross-sectional view of the device in which 17 is formed, in which case the hole 113 can be drilled only up to the middle of the shaft portion 111. Further, here, the upper end portion of the hole 113 and the outer peripheral surface of the shaft portion are communicated with each other through a substantially horizontal through hole 115.

In such a dynamic pressure bearing device, the lubricating fluid flows from the outer peripheral side of the thrust plate portion 112 to the inner peripheral side by the thrust dynamic pressure generating groove 141, and a part of the lubricating fluid of the thrust plate portion 112. The upper and lower radial dynamic pressure generating grooves 12 pass through the inside of the porous sintered body 114 of the hole 113 formed in the central portion and further through the through hole 115.
It reaches the outer peripheral surface of the shaft portion between 1a and 121b. Here, the bubbles in the lubricating fluid move axially upward through the continuous holes inside the sleeve member 12 and escape to the outside from the lubricating fluid interface of the taper seal portion. On the other hand, the lubricating fluid passes through a minute gap between the sleeve member 12 and the shaft member 11 and an internal continuous hole of the sleeve member 12, and a part of the lubricating fluid generates dynamic pressure by the lower radial dynamic pressure generating groove 121b. The shaft member 11 is supported in a non-contact manner and reaches the outer peripheral portion of the thrust plate portion 112. The lubricating fluid circulates in such a closed flow path.

In the hydrodynamic bearing device of FIG. 5, a through hole 115 connecting the upper end of the hole 113 and the outer peripheral surface of the shaft portion is provided substantially horizontally. For example, the through hole 115 reaches the taper seal portion. It may be formed obliquely. Further, it is of course possible to provide two or more through holes 115 in the circumferential direction.

Next, the second invention will be described. Second
In the invention, the technical idea of circulating the lubricating fluid to remove bubbles in the lubricating fluid is common to the first invention. The difference from the first invention is that the sleeve member is made of a porous sintered body in the first invention, whereas it is made of a metal material in the second invention. Due to such a difference, in the dynamic pressure generating device according to the second invention, the sleeve supporting member, which is necessary in the first invention, becomes unnecessary, and the seal portion is provided by the sleeve member without using the seal member. It is also possible to configure. Further, it is necessary that the opening of the through hole on the outer peripheral surface side of the shaft portion is located above the radial dynamic pressure generating groove formed on the uppermost side in the axial direction and in the lubricating fluid.

The dynamic pressure generating device according to the second invention will be described below with reference to the drawings. The same members and parts as those of the dynamic pressure generator of FIG. 1 are designated by the same reference numerals. Descriptions of structures and functions common to the dynamic pressure bearing device of FIG. 1 will be omitted here, and only different structures and functions will be described. FIG. 6 is a longitudinal sectional view showing an example of the dynamic pressure generating device according to the second invention. Sleeve member 1
Reference numeral 2'is made of a metal material and has a hollow cylindrical shape. Two radial dynamic pressure generating grooves 1 are formed at axially spaced positions on the inner peripheral surface of the hollow portion.
21a and 121b are formed, and a thrust dynamic pressure generating groove 121c is formed. Grooves 122 and 123 having a diameter larger than the inner diameter of the hollow cylinder are formed at the upper end and the lower portion of the sleeve member 12 ', respectively, and a fitting groove 124 having a larger diameter than the groove 123 is further formed at the lower end. Has been done.

The shaft member 11 includes a shaft portion 111 and a shaft portion 111.
And a thrust plate portion 112 formed at the lower end of the shaft portion 111, and a bottomed hole 113 is formed in the axial direction from the center of the bottom surface of the shaft portion 111.
4 is inserted. The shaft portion 111 is inserted into the hollow portion of the sleeve member 12 ′ until the thrust plate portion 112 of the shaft member 11 is mounted in the groove portion 123 of the sleeve member 12 ′. Then, the thrust bush member 14 having the thrust dynamic pressure generating groove 141 formed on the upper surface is mounted in the fitting groove portion 124 of the sleeve member 12 ′, and the lower opening of the sleeve member 12 ′ is sealed. On the other hand, in the upper opening of the sleeve member 12 ', an annular seal member 15 fitted in the shaft portion 111 is attached and fixed to the groove portion 122 so that the upper surface thereof and the upper end surface of the sleeve member 12' are flush with each other. Has been done. The hollow portion of the sleeve member 12 ′ surrounded by the sleeve member 12 ′, the thrust bush member 14, and the seal member 15 is filled with a lubricating fluid (not shown).

In such a dynamic pressure bearing device, the shaft portion 1
The through hole 115, which communicates the upper end of the hole 113 formed in 11 with the shaft outer peripheral surface, has an opening on the shaft outer peripheral surface side that is above the radial dynamic pressure generating groove 121a that is the uppermost in the axial direction and is in the lubricating fluid. It is important to be located. In the dynamic pressure bearing device according to the second aspect of the present invention, since the sleeve member 12 'is made of metal, the lubricating fluid cannot flow inside thereof.
Therefore, if the opening of the through hole 115 is located below the uppermost radial dynamic pressure generating groove 121a in the axial direction, the bubbles existing in the lubricating fluid cannot move to the lubricating fluid interface. This is because bubbles cannot escape to the outside.

Therefore, the shaft portion 11 as shown in FIG.
In the case of a device in which the fixed shaft hole 117 is formed in the upper end surface of the shaft 1, when the through hole 115 is formed in the horizontal direction, the shaft outer peripheral surface side opening is located between the two radial dynamic pressure generating grooves 121a and 121b. Therefore, for example, the through hole 115
Need to be formed obliquely toward the lubricating fluid interface direction.

In order to more effectively escape the bubbles in the lubricating fluid to the outside, as shown in FIG.
It is desirable to form the outer peripheral surface side opening of the shaft portion 5 under the interface of the lubricating fluid of the taper seal portion.

Next, the motor according to the present invention will be described. A major feature of the motor of the present invention is that the dynamic pressure bearing device described above is mounted. Hereinafter, the motor of the present invention will be described in detail with reference to the drawings.

FIG. 7 is a vertical sectional view of an HDD spindle motor equipped with a full-fill dynamic bearing device. The bracket 2 includes a base portion 21 provided at the center and the base portion 2
1, a peripheral wall 22 provided in the outer peripheral direction and a flange portion 23 extending further outward from the peripheral wall 22, which are integrally and coaxially formed.

An annular protrusion 24 is formed at the center of the base 21, and the dynamic pressure bearing device 1 shown in FIG. 1 is fitted and fixed thereto. The upper end of the shaft member 11 of the hydrodynamic bearing device 1 is fitted and fixed in a hole portion 31 formed in the central portion of the upper surface of the substantially cylindrical rotor hub 3. On the inner peripheral surface of the rotor hub 3, a rotor magnet 32, which is magnetized in multiple poles in the circumferential direction, is arranged over the entire circumference. Also rotor magnet 3
The stator 4 is arranged radially inward of 2 so as to face the rotor magnet 32 and to be an annular projection 24 formed on the base 22 of the bracket 2. Stator 4 and annular protrusion 2
Fixing with 4 may be fixed by fitting instead of fitting by press fitting.

A flange portion 33 is formed on the lower side of the outer periphery of the rotor hub 3, and a hard disk (not shown) is mounted on the flange portion 33. Specifically, after positioning the outer peripheral portion 34 of the rotor hub 3 and mounting a plurality of hard disks on the collar portion 33, a hole 35 is formed by a clamp member (not shown) or the like.
The hard disk is held and fixed to the rotor hub 3 by screwing.

[0044]

In the hydrodynamic bearing device according to the first invention and the second invention, the porous sintered body is inserted into the hole formed in the axial direction from the center of the bottom surface of the shaft, and the upper end of this hole is inserted. Since a through hole communicating with the outer peripheral surface of the shaft portion is formed in the portion, and the opening on the outer peripheral surface side of the shaft portion of this through hole is located in the lubricating fluid, bubbles mixed in the lubricating fluid in a bearing device of a so-called full-fill structure are formed. Can be removed smoothly.

In the dynamic pressure bearing device according to the first invention,
The shaft portion outer peripheral surface side opening of the through hole is located above the radial dynamic pressure generating groove formed on the uppermost axial direction, or between the radial dynamic pressure generating grooves, and more preferably in the vicinity of the interface of the lubricating fluid. When positioned, air bubbles present in the lubricating fluid can be removed more smoothly.

In the hydrodynamic bearing device according to the first and second aspects of the present invention, the thrust load can be more reliably supported by inserting the porous sintered body into the entire through hole without any clearance. Further, even if the thrust dynamic pressure generating groove is made to flow the lubricating fluid from the outer peripheral side to the inner peripheral side of the thrust plate portion, similarly, the thrust load can be supported more reliably. Further, if the radial dynamic pressure generating groove formed on the uppermost side in the axial direction of the sleeve member is a herringbone-shaped groove formed in an axially unbalanced manner that allows the lubricating fluid to flow downward in the axial direction, leakage of the lubricating fluid will occur. It can be prevented further.

Since the motor according to the present invention includes any one of the above dynamic pressure bearing devices, there is no leakage of the lubricating fluid from the dynamic pressure bearing device, no non-repetitive vibration occurs, and the bearing rigidity is high. Never decreases.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a dynamic pressure bearing device according to a first invention.

FIG. 2 is an enlarged sectional view of a taper seal portion in the dynamic pressure bearing device of FIG.

3 is a view showing an example of a radial dynamic pressure generating groove formed on the inner peripheral surface of the sleeve member of the dynamic pressure bearing device of FIG.

4 is a plan view showing an example of a thrust dynamic pressure generating groove formed in a thrust bush member of the dynamic pressure bearing device of FIG.

FIG. 5 is a vertical cross-sectional view showing another example of the dynamic pressure bearing device according to the first invention.

FIG. 6 is a vertical sectional view showing an example of a dynamic pressure bearing device according to a second invention.

FIG. 7 is a vertical sectional view showing an example of a motor according to the present invention.

FIG. 8 is a vertical sectional view showing a conventional dynamic pressure bearing device.

[Explanation of symbols]

1 Dynamic bearing device 2 bracket 3 rotor hub 4 stator 11 Shaft member 12, 12 'sleeve member 13 Sleeve support member 14 Thrust bush member 15 Seal member 111 Shaft 112 Thrust plate part 113 holes 114 porous sintered body 115 through hole 116 Shaft outer peripheral surface side opening 121a, 121b Radial dynamic pressure generating groove 121c, 141 thrust dynamic pressure generating groove L Lubricating fluid

Continued front page    F-term (reference) 3J011 AA04 AA07 BA02 BA08 CA02                 5H605 AA02 AA03 AA04 BB05 BB19                       CC02 CC04 CC05 DD03 DD07                       DD16 EB03 EB13 EB21 EB28                 5H607 AA04 AA05 AA06 BB01 BB14                       BB17 CC01 DD01 DD02 DD03                       DD09 DD16 FF12 GG01 GG03                       GG10 GG12 GG15 GG25                 5H621 HH01 JK08 JK17 JK19

Claims (8)

[Claims] 1. A porous sintered body, comprising a shaft member having a shaft portion and a thrust plate portion projecting outward in the radial direction from the shaft portion, and facing the shaft portion with a minute gap therebetween. A sleeve member formed of, a sleeve supporting member supporting the sleeve member, a thrust bushing member facing the lower surface of the thrust plate portion with a minute gap therebetween, and sealing a lower opening of the sleeve supporting member. A lubricating fluid that fills the entire minute gap, and a radial dynamic pressure generating groove for supporting a radial load is provided on at least one of the shaft portion and the inner peripheral surface of the sleeve member facing the shaft portion. Two or more are provided, and at least one of the lower surface of the thrust plate portion and the inner surface of the thrust bush member facing the lower surface,
A dynamic pressure bearing device, which is provided with a thrust dynamic pressure generating groove for supporting a thrust load, and rotatably supports the sleeve member and the shaft member in a relative axial direction from a central portion of a bottom surface of the shaft portion. A porous sintered body is inserted into the hole formed in the through hole, a through hole communicating with the outer peripheral surface of the shaft portion is formed in the upper end portion of the hole, and the opening on the outer peripheral surface side of the shaft portion of the through hole is in the lubricating fluid. A hydrodynamic bearing device characterized by being located at. 2. The opening of the through hole on the outer peripheral surface side of the shaft portion is located above the radial dynamic pressure generating groove formed on the uppermost side in the axial direction, or between the radial dynamic pressure generating grooves. Dynamic bearing device. 3. The hydrodynamic bearing device according to claim 1, wherein an opening on the outer peripheral surface side of the shaft portion of the through hole is located near the interface of the lubricating fluid. 4. A shaft member having a shaft portion and a thrust plate portion projecting outward in the radial direction from the shaft portion, and a sleeve made of a metal material, which is arranged to face the shaft portion with a minute gap therebetween. A member, a thrust bush member that is arranged to face the lower surface of the thrust plate portion with a minute gap, and seals the lower opening of the sleeve member; and a lubricating fluid that fills the entire minute gap. At least one of the shaft portion and the inner peripheral surface of the sleeve member facing the shaft portion is provided with two or more radial dynamic pressure generating grooves for supporting a radial load, and the lower surface of the thrust plate portion and the A thrust dynamic pressure generating groove for supporting a thrust load is provided on at least one of the inner side surfaces of the thrust bush member so that the sleeve member and the shaft member can rotate relative to each other. In the hydrodynamic bearing device, a porous sintered body is inserted into a hole formed in the axial direction from the center of the bottom surface of the shaft portion, and the upper end of the hole communicates with the outer peripheral surface of the shaft portion. A through hole is formed, and an opening on the outer peripheral surface side of the shaft portion of the through hole is positioned above the radial dynamic pressure generating groove formed on the uppermost side in the axial direction and in the lubricating fluid. Dynamic bearing device. 5. The hydrodynamic bearing device according to claim 1, wherein the porous sintered body is fitted into the entire through hole without any gap. 6. The dynamic pressure bearing device according to claim 1, wherein the thrust dynamic pressure generating groove causes the lubricating fluid to flow from the outer peripheral side to the inner peripheral side of the thrust plate portion. 7. The radial dynamic pressure generating groove formed on the uppermost side in the axial direction of the sleeve member is a herringbone-shaped groove formed in an axially unbalanced manner for allowing a lubricating fluid to flow downward in the axial direction. The dynamic pressure bearing device according to any one of 1 to 6. 8. A motor comprising the dynamic pressure bearing device according to any one of claims 1 to 7.