JP2002372039A - Hydrodynamic bearing device and spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact hydrodynamic bearing device of large load capacity, to miniaturize a spindle motor, and to increase speed of the rotation and accuracy of the rotation of the spindle motor using the hydrodynamic bearing device, in particular, an air dynamic bearing device. SOLUTION: This spindle motor 10 is provided with the hydrodynamic bearing device composed of a shaft 26 having a flange part 26a, a sleeve (bearing member) 34 sliding along an outer peripheral face of the shaft 26 and a lower face of the flange part 26a, and an upper thrust 36 (bearing member) sliding along an upper face of the flange part 26a. The outer peripheral face of the shaft 26, and the upper face and a lower face (first sliding face) of the flange part 26a are respectively provided with first hydrodynamic generating grooves 50, 54, 58. An inner peripheral face and an upper end face of the sleeve 34, and a lower face (second sliding face) of the upper thrust 36 are respectively provided with second hydrodynamic generating grooves 52, 56, 60.

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 spindle motor, and more particularly, to a magnetic recording device such as a magnetic disk and an optical disk, a precision machine tool such as a grinding machine and a precision lathe, a rotary table, and a straight line. The present invention relates to a spindle motor used for rotating a rotating body provided in a high-precision measuring device such as a guide with high accuracy and high speed, and a hydrodynamic bearing device used for the spindle motor.

[0002]

2. Description of the Related Art A spindle motor generally includes a stator, a rotor rotating around the stator, a driving device for rotating the rotor, and a bearing device for rotatably supporting the rotor on the stator. As bearing devices used for spindle motors, those having various structures are known. In spindle motors used for precision machine tools, high-precision measuring instruments, etc., hydrodynamic bearing devices are frequently used. .

[0003] A hydrodynamic bearing device is a type of sliding bearing device in which a fluid is pushed into a wedge-shaped gap by relatively moving opposing sliding surfaces, and the shaft is levitated by the pressure generated in the gap. The hydrodynamic bearing device further includes a liquid (eg,
Lubricating oil, magnetic fluid, etc.)
It is classified as a dynamic pressure gas bearing device using gas (for example, air).

[0004] The hydrodynamic bearing device is capable of high-precision rotation and high-speed rotation because the shaft completely floats from the bearing and rotates in a non-contact state. Further, in particular, the dynamic pressure gas bearing has a feature that the coefficient of friction is much smaller than the dynamic pressure liquid bearing using lubricating oil, and the inside of the system is not contaminated with lubricating oil.

However, the hydrodynamic bearing device has a problem that when a load exceeding a specified level is applied to the shaft, the shaft comes into contact with the bearing and seizure occurs. In particular, hydrodynamic gas bearings
Since a compressive gas is used as a fluid that fills the gap between the shaft and the bearing, there is a problem that the bearing rigidity is low.

In order to solve this problem, various proposals have hitherto been made. For example, JP-A-8-1
Japanese Patent No. 30851 has a stator in which a plurality of armature coils are arranged on a plane, a field permanent magnet opposed in the axial direction of the armature coils, and is provided rotatably with respect to the stator. A rotor, a rotating shaft provided on the rotor, and a rotating body provided on the rotating shaft, and a dynamic pressure generation groove is provided on either a side surface of the rotating shaft or an inner surface of a bearing cylinder surrounding the rotating shaft. An axial gap type motor is disclosed in which a radial bearing is provided, and a dynamic pressure generating groove is provided on either side of a rotating body or a stationary surface facing the rotating body to form a thrust bearing.

Japanese Patent Application Laid-Open No. 9-166145 discloses a radial bearing in which a dynamic pressure generating groove pattern is provided on either an outer peripheral surface of a rotating shaft or an inner peripheral surface of a bearing, and a thrust plate is provided on the rotating shaft. A magnetic pressure generating groove pattern is provided on both front and rear surfaces of the thrust plate or a surface facing the thrust plate to form a thrust bearing, and a magnetic seal for sealing a magnetic fluid in a radial bearing gap and a thrust bearing gap on a front end face of the rotating shaft. And a hydrodynamic bearing device in which a concave groove is provided on the outer peripheral surface of the rotating shaft facing the magnetic seal.

[0008]

As described above, a conventional hydrodynamic bearing device generally has both a radial bearing and a thrust bearing in order to increase the bearing rigidity. Further, the dynamic pressure generating groove for increasing the load capacity is formed only on one of the sliding surface on the shaft side and the sliding surface on the bearing side. Therefore, in the conventional hydrodynamic bearing device, in order to further increase the load capacity, it is necessary to increase the area of the sliding surface and the shaft diameter, and there is a limit to the increase in the load capacity.

In particular, there is an increasing demand for a magnetic recording device such as a hard disk drive to have a small size, a high speed rotation, and a high capacity (high density). On the other hand, if the inside of the magnetic recording device is contaminated with impurities such as lubricating oil, it may cause malfunction or failure. Therefore, as a spindle motor used in a magnetic recording device, a dynamic pressure gas bearing device that is less likely to contaminate the inside of the device is often used.

However, in the conventional dynamic pressure gas bearing device, the load capacity is insufficient, and when the rotor is rotated at a high speed, the lateral deflection of the rotor increases. As a result, there is a problem that the capacity of the hard disk is hindered. On the other hand, if the area of the sliding surface or the shaft diameter is increased to increase the load capacity, the dynamic pressure gas bearing device becomes larger,
This will hinder downsizing of the hard disk.

An object of the present invention is to provide a hydrodynamic bearing device which is small in size and has a large load capacity. Another object of the present invention is to reduce the size, speed, and precision of a spindle motor using a hydrodynamic bearing device, particularly a hydrodynamic gas bearing device.

[0012]

In order to solve the above-mentioned problems, a hydrodynamic bearing device according to the present invention slides along a shaft having a first sliding surface and the first sliding surface. A bearing member having a second sliding surface; a first dynamic pressure generating groove formed on the first sliding surface; and a second dynamic pressure generating groove formed on the second sliding surface. The point is that

In the hydrodynamic bearing device according to the present invention, the first dynamic pressure generating groove and the second dynamic pressure generating groove are formed on both the first sliding surface on the shaft side and the second sliding surface on the bearing member side, respectively. Since the grooves are provided, the pressure generated in the bearing gap increases. Therefore, the load capacity is increased as compared with a conventional hydrodynamic bearing device in which a dynamic pressure generating groove is provided on one of the first sliding surface and the second sliding surface. In addition, by using such a hydrodynamic bearing device for a spindle motor, it is possible to reduce the size, speed, and precision of the spindle motor.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a sectional view of a spindle motor according to the present embodiment. In FIG. 1, a spindle motor 10 includes a stator 20
And a rotor 30.

The stator 20 includes a base 22, fixing bolts 24, a shaft 26, and a stator core 28. The fixing bolt 24 is provided upright at the center of the projection 22 a provided at the center of the base 22. The shaft 26 is fixed around the fixing bolt 24, and a disk-shaped flange 26 a is provided at the upper end of the shaft 26. Further, a plurality of stator cores 2 are provided on the side surface of the convex portion 22a at positions facing each other.
8, 28... Are provided. Stator core 28 is an electromagnet for generating a rotational force.

The rotor 30 includes a hub 32, a sleeve (bearing member) 34, an upper thrust 36 (bearing member), a ring-shaped magnet 42, and a back yoke 44.
The sleeve 34 and the upper thrust 36 provided on the rotor 30 and the shaft 26 provided on the stator 20 constitute a hydrodynamic bearing device according to the present invention.

The hub 32 is for holding a rotating body 46 (for example, a hard disk), and has a cylindrical shape. A cylindrical sleeve 34 is fixed in the inside, and a disk-shaped upper thrust 36 is fixed to an upper end thereof.

The sleeve 34 has an inner diameter such that a predetermined bearing clearance is formed between the outer peripheral surface (first sliding surface) of the shaft 26 and the inner peripheral surface (second sliding surface) of the sleeve 34. Is stipulated. The sleeve 34 has an upper end surface (second
The height is determined so that a predetermined bearing clearance is formed between the sliding surface) and the lower surface (first sliding surface) of the collar portion 26a. Further, the upper thrust 36 has a lower surface (second sliding surface) and an upper surface (first sliding surface) of the flange 26a.
So that a predetermined bearing clearance is formed between them.
2 is fixed to the upper end.

The lower end of the hub 32 is formed in a skirt shape, and a multipolar magnetized ring-shaped magnet 42 is provided on the inner peripheral surface thereof.
Has been fixed. The ring-shaped magnet 42 is for generating a rotational force in cooperation with the stator core 28,
It is provided on substantially the same horizontal plane as stator core 28 and close to stator core 28. The back yoke 44 is for increasing the coercive force of the ring-shaped magnet 42, and is fixed between the back surface of the ring-shaped magnet 42 and the inner peripheral surface at the lower end of the hub 32.

Further, in the spindle motor 10 shown in FIG. 1, the dynamic pressure generating grooves are provided on both the shaft 26 side and the bearing member side. That is, the first dynamic pressure generating groove (A) 50 is formed on the outer peripheral surface (first sliding surface) of the shaft 26, and is formed on the inner peripheral surface (second sliding surface) of the sleeve 34 opposed thereto. , A second dynamic pressure generating groove (A) 52 is formed.

Similarly, a first dynamic pressure generating groove (B) 54 is formed on the upper surface (first sliding surface) of the collar portion 26a, and the lower surface (second sliding surface) of the upper thrust 36 opposed thereto. ), A second dynamic pressure generating groove (B) 56 is formed. Further, a first dynamic pressure generation groove (C) 58 is formed on the lower surface (first sliding surface) of the collar portion 26a, and the upper end surface (second sliding surface) of the sleeve 34 facing the first dynamic pressure generating groove (C) 58 A second dynamic pressure generating groove (C) 60 is formed.

In this embodiment, the first dynamic pressure generating grooves (A, B, C) 50, 54, 58,
And a second dynamic pressure generating groove (A,
B, C) The shapes of 52, 56 and 60 are not particularly limited, and dynamic pressure generating grooves having various shapes can be used. As the shape of the dynamic pressure generating groove, specifically,
Herringbone groove, spiral IN, spiral OUT
Etc. are mentioned as a suitable example.

In order to generate a high dynamic pressure in the gap between the shaft 26 and the bearing member, the first dynamic pressure generating grooves (A, B, C)
50, 54 and 58, and the respective second dynamic pressure generating grooves (A, B and C) 52, 56 and 60 facing the same.
It is preferable that the shape is determined so that a high pressure is generated in a region overlapping with each other. 2 to 4 show an example of a groove shape for generating a high pressure in an overlapping area.

FIG. 2 shows a first shaft formed on the outer peripheral surface of the shaft 26.
FIG. 4 shows an example of a dynamic pressure generating groove (A) 50 and a second dynamic pressure generating groove (A) 52 formed on the inner peripheral surface of a sleeve 34 opposed thereto. In the example shown in FIG.
The dynamic pressure generating groove (A) 50 includes first herringbone grooves 50 a and 50 b arranged in two rows along the axial direction of the shaft 26. In addition, each first herringbone groove 50a, 50b is
Each has a V-shape in which linear grooves are associated at the association points 50c and 50d.

On the other hand, the second dynamic pressure generating groove (A) 52
The second herringbone grooves 52a and 52b are arranged in two rows along the axial direction of No. 6. In addition, each of the second herringbone grooves 52a and 52b has a linear
It has a V-shape associated with 2c and 52d.

Furthermore, the second herringbone grooves 52a, 52
The meeting points 52c and 52d of 2b are substantially on the same horizontal plane as the meeting points 50c and 50d of the first herringbone grooves 50a and 50b, respectively. In addition, the second herringbone groove 5
The orientation of the meeting points 52c, 52d in 2a, 52b,
Meeting point 5 in first herringbone groove 50a, 50b
The directions of 0c and 50d are opposite to each other on the surface facing the rotation direction.

Therefore, as the sleeve 34 (that is, the rotor 30) rotates in the direction of the arrow in FIG. 2, the highest pressure is generated in the first dynamic pressure generating groove (A) 50 at the meeting points 50c and 50d. At the same time, in the second dynamic pressure generating groove (A) 52, the highest pressure is generated at the meeting points 52c and 52d.

That is, in the example shown in FIG.
0 indicates that the two meeting points 50c and 50d (or the meeting point 52d)
In c and 52d), two points are supported in the radial direction. In the region near the meeting points 50c and 50d (or the meeting points 52c and 52d), two opposing dynamic pressure generating grooves (that is, the first dynamic pressure generating groove (A) 50 and the second dynamic pressure generating groove). (A) The pressure generated by 52) is superimposed.

FIG. 3 shows a first dynamic pressure generating groove (B) 54 formed on the upper surface of the collar portion 26a and a second dynamic pressure generating groove formed on the lower surface of the upper thrust 36 opposed thereto. (B) shows a first specific example of 56. In the example shown in FIG. 3, the first dynamic pressure generating groove (B) 54 is formed of a third herringbone groove formed near the outer periphery of the upper surface of the collar 26a. The third herringbone groove 54 has a V-shape in which arcuate grooves are associated at an association point 54c.

On the other hand, the second dynamic pressure generating groove (B) 56 comprises a fourth herringbone groove formed near the outer periphery of the lower surface of the upper thrust 36. In addition, the fourth herringbone groove 56
Has a V-shape in which arcuate grooves are associated at an association point 56c.

Further, the meeting point 56c of the fourth herringbone groove 56 is connected to the meeting point 54c of the third herringbone groove 54.
And on the same circumference. Further, the direction of the meeting point 56c in the fourth herringbone groove 56 and the direction of the meeting point 54c in the third herringbone groove 54 are opposite to each other on the surface facing the rotation direction.

Therefore, the upper thrust 36 (that is, the upper thrust 36)
As the rotor 30) rotates in the direction of the arrow in FIG.
In the herringbone groove 54, the highest pressure is generated at the meeting point 54c. At the same time, the highest pressure is generated in the fourth herringbone groove 56 at the meeting point 56c.

That is, in the example shown in FIG. 3, the rotor 30 is moved at the meeting point 54c (or the meeting point 56c).
It is designed to be supported in the thrust direction. In the region near the meeting point 54c (or the meeting point 56c), the pressures generated by the two opposing dynamic pressure generating grooves (the third herringbone groove 54 and the fourth herringbone groove 56) overlap. Has become.

FIG. 4 shows a first dynamic pressure generating groove (B) 74 formed on the upper surface of the flange 26a and a second dynamic pressure generating groove formed on the lower surface of the upper thrust 36 opposed thereto. (B) shows a second specific example of 76.

In the example shown in FIG. 4, the first dynamic pressure generating groove (B) 74 comprises a first spiral groove formed near the outer periphery of the upper surface of the flange 26a. On the other hand, the second dynamic pressure generating groove (B) 76 is formed of a second spiral groove formed near the outer periphery of the lower surface of the upper thrust 36. Further, in the first spiral groove 74 and the second spiral groove 76, the rotation directions of the spirally provided grooves are opposite to each other on the surface facing the rotation direction.

Therefore, the upper thrust 36 (ie, the upper thrust 36)
As the rotor 30) rotates in the direction of the arrow in FIG.
In the spiral groove 74, the highest pressure is generated at the outer peripheral end of the flange 26a. At the same time, the highest pressure is generated at the outer peripheral end of the upper thrust 36 in the second spiral groove 76. That is, in the example shown in FIG. 3, the pressure generated by the two opposing dynamic pressure generating grooves (the first spiral groove 74 and the second spiral groove 76) at the outer peripheral end of the collar portion 26a (or the upper thrust 36). Are superimposed.

The first dynamic pressure generating groove (C) 58 formed on the lower surface (first sliding surface) of the collar 26a, and the sleeve 34
Although not shown, the second dynamic pressure generating groove (C) 60 formed on the upper end surface (second sliding surface) of
Dynamic pressure generating grooves (B) 54 and 74 and second dynamic pressure generating grooves (B)
A groove having a configuration similar to that of the grooves 56 and 76 can be used. That is, the first dynamic pressure generating groove (C) 58 and the second dynamic pressure generating groove (C) 60 may be herringbone grooves formed in opposite directions, or formed in opposite directions. It may be a spiral groove.

In the spindle motor 10 shown in FIG. 1, the shaft 26, the sleeve 34 and the upper thrust 36
A fluid is interposed in the gap between the fluid and the fluid. The fluid may be a liquid such as lubricating oil or a magnetic fluid, or may be a gas such as air. However, when a liquid is used as the fluid, it is preferable to provide a sealing means for preventing leakage of the liquid from the bearing clearance. Further, in order to prevent contamination of the system by a liquid, it is preferable to use a gas as the fluid.

Next, the operation of the spindle motor 10 according to the present embodiment will be described. When the polarity of the current supplied to each stator core 28 is reversed at appropriate intervals, the stator core 28 fixed to the stator 20 and the rotor 3
Attraction and repulsion are repeated between the ring-shaped magnet 42 fixed to 0 and the rotor 30 starts rotating around the shaft 26.

When the rotor 30 rotates about the shaft 26, fluid flows into a radial bearing clearance formed by the outer peripheral surface of the shaft 26 and the inner peripheral surface of the sleeve 34. When the fluid flows into the radial bearing clearance, the fluid moves by the relative movement between the outer peripheral surface of the shaft 26 and the inner peripheral surface of the sleeve 34 to cause the fluid to flow through the first dynamic pressure generating groove (A) 50 and the second dynamic pressure generating groove (A). ) 52. Therefore, pressure is generated in the radial bearing clearance, and the outer peripheral surface of the shaft 26 floats from the inner peripheral surface of the sleeve 34.

A part of the fluid flowing into the radial bearing clearance flows into the thrust bearing clearance formed by the lower surface of the collar 26a and the upper end surface of the sleeve 34. When the fluid flows into the thrust bearing clearance, the relative movement between the lower surface of the collar 26a and the upper surface of the sleeve 34 causes
The fluid is pushed into the first dynamic pressure generating groove (C) 58 and the second dynamic pressure generating groove (C) 60. As a result, pressure is generated in the thrust bearing clearance, and the lower surface of the flange 26 a floats from the upper surface of the sleeve 34.

Similarly, another part of the fluid is provided at the collar 26a.
Into the thrust bearing gap formed by the upper surface of the upper thrust 36 and the lower surface of the upper thrust 36. When fluid flows into the thrust bearing clearance, the upper surface of the flange 26a and the upper thrust 36
The fluid is pushed into the first dynamic pressure generation groove (B) 54 and the second dynamic pressure generation groove (B) 56 by the relative movement with respect to the lower surface of the liquid crystal. As a result, pressure is generated in the thrust bearing clearance, and the upper surface of the flange 26 a floats from the lower surface of the upper thrust 36.

The spindle motor 10 according to the present embodiment
Since the outer peripheral surface of the shaft 26 and the upper and lower surfaces of the flange 26a function as a radial bearing and a thrust bearing, respectively, the load can be supported in both the radial direction and the thrust direction.

The first dynamic pressure generating grooves (A, B, and B) are respectively provided on both the first sliding surface on the shaft 26 side and the second sliding surface on the bearing member (sleeve 34 and upper thrust 36) side. C) 5
0, 54, 58 and second dynamic pressure generating grooves (A, B, C) 5
Since 2, 56 and 60 are formed, a higher pressure is generated in the bearing clearance as compared with a case where a dynamic pressure generating groove is formed on one of the first sliding surface and the second sliding surface. Can be.

Further, the first dynamic pressure generating grooves (A, B, C) 5
0, 54, 58, and second dynamic pressure generating grooves (A, B, C)
In the case where those generating high pressure in the mutually overlapping regions are used as 52, 56, 60, the first dynamic pressure generating grooves (A, B, C) 50, 54, 58, and the second dynamic pressure generating grooves (A, B, C) The pressures generated at 52, 56, and 60 are superimposed, and a higher pressure is generated at the bearing clearance.

Therefore, the spindle motor 10 which is small in size, has high bearing rigidity, and can rotate at high speed and with high precision can be obtained. Further, if such a spindle motor 10 is applied to, for example, a hard disk drive, it is possible to reduce the size, speed, and capacity of the hard disk, and improve vibration resistance and shock resistance.

Further, if a flange 26a is provided at the upper end of the shaft 26 and the upper and lower surfaces of the flange 26a are held between the upper surface of the sleeve 34 and the lower surface of the upper thrust 36, a single thrust plate can be realized. In addition, space can be saved. Therefore, the hydrodynamic bearing device and the spindle motor using the same can be downsized. Further, since the problem on the space is solved, the design change is facilitated.

Further, since the number of thrust plates can be reduced to one, the structures of the hydrodynamic bearing device and the spindle motor using the same can be simplified. Therefore, the shape of the component alone is simplified, and the component processing accuracy and the assembly accuracy are improved. Further, the number of parts can be reduced, and the cost performance is dramatically improved.

[0049]

(Embodiment 1) In a radial dynamic pressure gas bearing device in which dynamic pressure generating grooves are provided on both the first sliding surface on the shaft side and the second sliding surface on the bearing member side, the bearing clearance is generated. The magnitude of the dynamic pressure was determined by numerical analysis. The dynamic pressure generating groove is
Each was a herringbone groove. Each herringbone groove was formed such that the meeting points were on the same horizontal plane, and the directions of the meeting points were opposite to each other on the surface facing the rotation direction.

(Comparative Example 1) With respect to a radial dynamic pressure gas bearing device provided with a dynamic pressure generating groove only on the first sliding surface on the shaft side, the magnitude of the dynamic pressure generated in the bearing clearance was determined by numerical analysis. The dynamic pressure generating groove was a herringbone groove, and the groove shape was the same as in Example 1.

Table 1 shows the results obtained in Example 1 and Comparative Example 1. In the case of Comparative Example 1 in which the dynamic pressure generating groove was provided only on the first sliding surface, the generated dynamic pressure was 2.2N. On the other hand, in the case of the embodiment 1 in which the dynamic pressure generating grooves are provided on both the first sliding surface and the second sliding surface, the generated dynamic pressure is 3.8 N, which is about 1.73 of the comparative example 1. Improved by a factor of two.

[0052]

[Table 1]

(Embodiment 2) In a thrust dynamic pressure gas bearing device in which dynamic pressure generating grooves are provided on both the first sliding surface on the shaft side and the second sliding surface on the bearing member side, the dynamics generated in the bearing clearance The magnitude of the pressure was determined by numerical analysis. Each of the dynamic pressure generating grooves was a herringbone groove. Each herringbone groove was formed such that the meeting points were on the same circumference, and the directions of the meeting points were opposite to each other on the surface facing the rotation direction.

(Comparative Example 2) With respect to a thrust dynamic pressure gas bearing device in which a dynamic pressure generating groove is provided only on the first sliding surface on the shaft side, the magnitude of the dynamic pressure generated in the bearing clearance was determined by numerical analysis. Note that the dynamic pressure generating groove was a herringbone groove, and the groove shape was the same as in Example 2.

Table 2 shows the results obtained in Example 2 and Comparative Example 2. In the case of Comparative Example 2 in which the dynamic pressure generating groove was provided only on the first sliding surface, the generated dynamic pressure was 15N. On the other hand, in the case of the embodiment 2 in which the dynamic pressure generating grooves are provided on both the first sliding surface and the second sliding surface, the generated dynamic pressure is 25N, which is about 1.67 times that of the comparative example 2. Improved.

[0056]

[Table 2]

Example 3 A spindle motor 10 having the structure shown in FIG. 1 was manufactured, and asynchronous runout (NRRO) and synchronous runout (RRO) were measured. As shown in FIG. 2, the outer peripheral surface of the shaft 26 and the inner peripheral surface of the sleeve 34
Herringbone grooves were formed in two rows along the axial direction. Further, the upper and lower surfaces of the brim portion 26a and the sleeve 3
As shown in FIG. 3, herringbone grooves arranged in a line on the circumference were formed on the upper end surface of 4 and the lower surface of upper thrust 36. Further, each of the opposed herringbone grooves was formed such that the meeting points were on the same plane or the same circumference, and the directions of the meeting points were opposite to each other on the surface facing the rotation direction.

(Comparative Example 3) A spindle motor having the same configuration as in Example 3 except that a dynamic pressure generating groove was formed only on the first sliding surface on the shaft side was manufactured, and asynchronous runout (NRRO) was performed.
And synchronous runout (RRO) were measured.

Table 3 shows the results obtained in Example 3 and Comparative Example 3. In the case of Comparative Example 3 in which the dynamic pressure generating groove is provided only on the first sliding surface, the asynchronous runout (NRRO) is 0.04 μm.
Met. On the other hand, in the case of Example 3 in which the dynamic pressure generating grooves are provided on both the first sliding surface and the second sliding surface, the asynchronous runout (NRRO) is 0.035 μm, which is smaller than that of Comparative Example 3. It decreased by 12.5%. Note that the synchronous runout (RRO) is slightly larger in the third embodiment, but the synchronous runout (RRO) is due to the machining accuracy, and this increase does not pose a problem.

[0060]

[Table 3]

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. is there.

For example, in the above embodiment, the shaft 26
Herringbone grooves formed on the outer peripheral surface of the sleeve 34 and the inner peripheral surface of the sleeve 34 are linear grooves associated with each other in a V-shape, but arc-shaped grooves are associated with each other in a V-shape. It may be something.

In order to generate a high dynamic pressure in the bearing clearance, the region where the high pressure is generated by the first dynamic pressure generating groove and the region where the high pressure is generated by the second dynamic pressure generating groove overlap. It is desirable that the dynamic pressure generated in the first dynamic pressure generating groove and the dynamic pressure generated in the second dynamic pressure generating groove be generated in different regions as long as the dynamic pressure is not canceled out. Even when the regions where the high pressure is generated do not overlap, a higher dynamic pressure can be obtained as compared with the case where the dynamic pressure generating groove is formed only on one of the first sliding surface and the second sliding surface. Obtainable.

When the dynamic pressure generating grooves are formed on the upper and lower surfaces of the collar portion 26a and on the surface opposite thereto, the groove shape may be the same on the upper surface side and the lower surface side of the collar portion 26a. Alternatively, they may be different. That is, a pair of herringbone grooves or spiral grooves may be formed on both the upper surface side and the lower surface side of the collar portion 26a, or
A pair of herringbone grooves may be formed on one of the upper surface or the lower surface of the collar portion 26a and the second sliding surface opposed thereto, and a pair of spiral grooves may be formed on the other. Further, as shown in FIG. 4, the spiral groove can be changed to a method in which the fluid is pushed into the inner peripheral part in addition to a method in which the fluid is pushed out to the outer peripheral part.

In the above embodiment, two herringbone grooves 50a and 50b arranged in two rows in the axial direction are used on the outer peripheral surface of the shaft 26 as first dynamic pressure generating grooves. The first dynamic pressure generating groove 50 may be a single row of herringbone groove, or a herringbone groove arranged in three or more rows in the axial direction, or may be a dynamic pressure generating groove having another structure. . Similarly, when the herringbone grooves are formed on the upper and lower surfaces of the flange portion 26a, the herringbone grooves may be arranged in two or more rows on a concentric circle.

Further, the spindle motor according to the present invention and the hydrodynamic bearing device used therein are particularly suitable as a spindle motor used in a magnetic recording device and a bearing device used therefor. However, the present invention is not limited to this, and may be used as a precision machine tool such as a precision lathe, a spindle motor used for a high-precision measuring instrument such as a rotary table, and a bearing device used for other rotating devices. it can.

[0067]

According to the hydrodynamic bearing device of the present invention, a first dynamic pressure generating groove and a second dynamic pressure generating groove are provided on a first sliding surface on the shaft side and a second sliding surface on the bearing member side, respectively. Since the grooves are formed, the effect that the pressure generated in the bearing clearance increases as compared with the case where the dynamic pressure generating grooves are formed only on one of the first sliding surface and the second sliding surface. is there.

In particular, when the first dynamic pressure generating groove and the second dynamic pressure generating groove opposed thereto are used to generate a high pressure in the mutually overlapping region, the pressure generated by the first dynamic pressure generating groove and the second dynamic pressure generating groove are reduced. (2) The pressure generated by the dynamic pressure generating groove is superimposed, and there is an effect that a higher dynamic pressure is generated in the bearing clearance.

Also, the spindle motor according to the present invention
Since the hydrodynamic bearing device in which the first dynamic pressure generating groove and the second dynamic pressure generating groove are respectively formed on the first sliding surface on the shaft side and the second sliding surface on the bearing member side is used. In addition, there is an effect that the spindle motor can be reduced in size, rotated at high speed, and rotated with high accuracy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor according to a first embodiment of the present invention.

FIG. 2 is a front view showing an example of a dynamic pressure generating groove formed on an outer peripheral surface of a shaft and an inner peripheral surface of a sleeve.

FIG. 3 is a perspective view showing an example of a dynamic pressure generating groove formed on an upper surface of a collar portion and a lower surface of an upper thrust.

FIG. 4 is a plan view showing another example of the dynamic pressure generating groove formed on the upper surface of the collar portion and the lower surface of the upper thrust.

[Explanation of symbols]

Reference Signs List 10 spindle motor 26 shaft 26a flange 34 sleeve (bearing member) 36 upper thrust (bearing member) 50 first dynamic pressure generating groove (A) 50a, 50b first herringbone groove 52 second dynamic pressure generating groove (A) 52a , 52b second herringbone groove 54 first dynamic pressure generating groove (B) (third herringbone groove) 56 second dynamic pressure generating groove (B) (fourth herringbone groove) 58 first dynamic pressure generating groove ( C) 60 second dynamic pressure generating groove (C) 74 first dynamic pressure generating groove (B) (first spiral groove) 76 second dynamic pressure generating groove (B) (second spiral groove)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA20 BA04 CA03 JA02 JA03 KA02 KA03 LA05 5H607 AA04 BB09 BB14 BB17 CC01 GG03 GG12 GG14

Claims (9)

[Claims] A shaft provided with a first sliding surface; a bearing member provided with a second sliding surface sliding along the first sliding surface; and a shaft formed on the first sliding surface. A hydrodynamic bearing device comprising: a first dynamic pressure generating groove; and a second dynamic pressure generating groove formed on the second sliding surface. 2. The hydrodynamic bearing device according to claim 1, wherein the first dynamic pressure generating groove and the second dynamic pressure generating groove generate a high pressure in an area overlapping each other. 3. The hydrodynamic bearing device according to claim 1, wherein the first sliding surface is an outer peripheral surface of the shaft. 4. The first dynamic pressure generating groove is a first herringbone groove, and the second dynamic pressure generating groove is formed in a direction opposite to the first herringbone groove on a surface facing a rotation direction. The hydrodynamic bearing device according to claim 3, wherein the second herringbone groove is formed. 5. The hydrodynamic bearing device according to claim 1, wherein the shaft includes a flange, and the first sliding surface is an upper surface and / or a lower surface of the flange. 6. The first dynamic pressure generating groove is a third herringbone groove, and the second dynamic pressure generating groove is formed in a direction opposite to the third herringbone groove on a surface facing a rotation direction. 6. The hydrodynamic bearing device according to claim 5, wherein the fourth herringbone groove is formed. 7. The first dynamic pressure generating groove is a first spiral groove, and the second dynamic pressure generating groove is formed in a direction opposite to the first spiral groove on a surface facing a rotation direction. 6. The hydrodynamic bearing device according to claim 5, wherein the hydrodynamic bearing device has two spiral grooves. 8. The hydrodynamic bearing device according to claim 1, wherein the fluid interposed in the gap between the first sliding surface and the second sliding surface is a gas. 9. A spindle motor comprising the hydrodynamic bearing device according to claim 1. Description: