JPH11257347A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress vibration of non-rotation synchronous component and a starting torque, and prevent a lubricating fluid from leaking from a thrust plate side by fixing a thrust plate while being brought into contact with a fixing member at an inner circumferential side, and arranging an annulus relief part on its outside. SOLUTION: A cylindrical shaft member 25 is fixed to a hub 22, and it is rotatably supported by a sleeve 23 having a cylindrical opening. A thrust plate 24 is arranged downward the sleeve 23, and the sleeve 23 and the thrust plate 24 are fixed to a base 26. A dynamic pressure generating groove is arranged on the thrust plat 24, a thrust load is supported on a lower end surface of the shaft member 25 and an upper surface of the thrust plat 24, a dynamic pressure generating groove is arranged on an inner circumferential surface of the sleeve 23, and a radial load is supported on an inner circumferential surface of the sleeve 23 and the outer peripheral surface of the shaft member 25. An annular sealing member which is brought into contact with the thrust plate 24 is arranged, and a relief part 37 is arranged on an outer periphery of the annular sealing member 26b. A lubricating fluid oozed out from between the sealing member 26b and the plate member 24 is held in the relief part 37 by its surface tension. It is thus possible to suppress vibration of non-rotation synchronous component and a starting torque, and it is also possible to prevent leakage of the lubricating fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a bearing device for a spindle motor. The present invention relates to a spindle motor for information equipment and audio / video equipment, and more particularly to a bearing device for a spindle motor that is most suitable for a disk drive such as a magnetic disk drive or an optical disk drive.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional bearing device 1 for a disk spindle motor. In the conventional bearing device 1, a hub 2 on which a disk can be mounted is rotatably supported on a shaft member 5 via two ball bearings 3, 4. The shaft member 5 is fixed to a base 6 attached to a housing of the disk drive. In base 6,
The stator 7 is fixed. A rotor magnet 8 is fixed to the hub 2. Thus, a spindle motor is formed, and the hub 2 can be electrically driven to rotate around the shaft member 5.

[0003] In the field of magnetic disk drives, higher recording densities are advancing, and spindle motors used therefor are required to have small fluctuations in non-rotational synchronous components.

Ball bearings have been used in conventional bearing devices for spindle motors. The ball bearing is required to have a small non-rotation synchronous component runout. However, ball bearings have ball passing vibrations and vibrations caused by shape errors of bearing parts, and it is difficult to reduce the run-out of the non-rotational synchronous component to a value equal to or less than a predetermined value even if machining accuracy is improved. .

On the other hand, a spindle motor having a structure as shown in FIG. 8 in which a dynamic pressure bearing having a small runout of a non-rotational synchronous component is used in place of a ball bearing for both a radial bearing and a thrust bearing has been studied. In this dynamic pressure bearing 11, a cylindrical shaft member 15 is fixed to a hub 12 on which a disk can be mounted. The shaft member 15 is a sleeve 1 having a cylindrical opening.
3 rotatably supported. The inner peripheral surface of the sleeve 13 and the outer peripheral surface of the shaft member 15 constitute a radial dynamic pressure bearing that supports a radial load. A thrust plate 14 is arranged at the lower end of the sleeve 13 and is fixed by a caulking portion 13 a provided at the lower end of the sleeve 13.
The lower end surface of the shaft member 15 and the upper surface of the thrust plate 14 constitute a thrust bearing that supports a thrust load. The sleeve 13 is fixed to a base 16 attached to a housing 19 of the disk drive. A stator 17 is fixed to the base 16. A rotor magnet 18 is fixed to the hub 12. Thereby, a spindle motor is formed, and the hub 12 can be electrically driven to rotate. A protrusion 13 b extending radially outward is provided at the upper end of the sleeve 13, and the protrusion 13 b engages with the stopper member 20 attached to the hub 12, thereby causing the hub 12 to rotate. The shaft member 15 is prevented from falling off the sleeve 13.

[0006] When the bearing device of the spindle motor is a dynamic pressure bearing, it is possible to reduce the fluctuation of the non-rotational synchronous component of the spindle motor.

[0007]

However, the thrust plate 14 is only fixed by caulking, and it is difficult to completely seal the space between the upper surface of the thrust plate 14 and the lower end surface of the sleeve 13. Therefore, the lubricating fluid may flow out from between the upper surface of the thrust plate 14 and the lower end surface of the sleeve 13, and the lubricating fluid may leak to the lower side of the thrust plate 14, thereby contaminating the outside of the bearing device. Further, since the lubricating fluid leaks from the inside of the bearing, the amount of the lubricating fluid inside the bearing is reduced, and there is a problem that the life of the bearing is shortened.

In view of the above-described problems, the present invention has a small non-rotational synchronous component swing, a small starting torque, no leakage of the lubricating fluid from the thrust plate side, and an improvement in the durability of the bearing. It is an object to provide a bearing device which is excellent and does not pollute the outside of the bearing device.

[0009]

In order to solve the above-mentioned problems, the present invention provides a rotating body driven by a motor, and the rotating body is supported via a radial dynamic pressure bearing and a thrust bearing. In the bearing device composed of the end face of the shaft and the thrust plate, the thrust plate is fixed by contacting the fixing member at least on the inner peripheral side.

According to the present invention, since the thrust plate is fixed in contact with the fixing member only at the innermost peripheral portion, the lubricating fluid spreads only to the portion where the upper surface of the thrust plate and the fixing member contact each other due to surface tension. It does not spread beyond the gap. Therefore, the lubricating fluid does not leak out of the bearing device. As a result, the life of the bearing is extended and
Does not contaminate the outside of the bearing device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a bearing device according to the present invention, a shaft member 2 is provided.
5, a plate member 24 disposed at an end of the shaft member 25, and a seal provided around the shaft member 25 so that the lubricating fluid around the shaft member 25 does not leak to the outside by coming into contact with the plate member 24. An annular sealing member 26b for stopping the fuel cell, and a relief portion 37 provided on the outer periphery of the annular sealing member 26b.
The height h of the escape portion 37 in the axial direction is set so that the lubricating fluid is held by the escape portion 37 by the surface tension of the lubrication fluid itself so that the lubricant fluid oozed from between the plate member 6b and the plate member 24 does not flow outside. Is set to a height between the distance t between the shaft member 25 and the annular sealing member 26b and 0.5 mm. This can prevent the lubricating fluid from flowing out of the bearing device.

The shaft member 25 may be fixed to a hub 22 on which a disk can be mounted, and may rotate together with the hub 22. A groove for generating dynamic pressure may be formed in the plate member 24 to form a thrust bearing together with the shaft member 25. The relief portion 37 may be provided with a tapered portion 37a whose height increases in the axial direction from the annular sealing member 26b outward in the radial direction. The angle θ between the inclined surface of the tapered portion 37a and the plate member 24 is preferably in the range of 1 ° to 90 °, and more preferably in the range of 1 ° to 45 °.

[0013]

Embodiments will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a first embodiment of a bearing device for a spindle motor according to the present invention. In the bearing device 21 of the first embodiment, a cylindrical rotating shaft, that is, a shaft member 25 is fixed to a hub 22 on which a disk can be mounted.
If the shaft member 25 is made of stainless steel, it does not rust. The shaft member 25 is rotatably supported by a sleeve 23 having a cylindrical opening. A thrust plate 24 is arranged below the sleeve 23. Sleeve 23
Are fixed to a fixing member attached to the housing of the disk drive, that is, a base 26. The thrust plate 24 is provided with a through hole 24a for passing a retaining screw. The base 26 has a screw hole 26a that matches the through hole 24a. A thrust plate 24 is fixed to the base 26 by passing a retaining screw (not shown) through the through hole 24a and screwing into the screw hole 26a. A stator 27 is fixed to the base 26. A rotor magnet 28 is fixed to the hub 22 via a back yoke 29. Thus, a motor is formed so that the hub 22 can be electrically driven to rotate. In addition, since the sleeve 23 and the thrust plate 24 are configured to be directly fixed to the base 26, the assembly is easy and the reliability is excellent.

In this embodiment, a groove for generating dynamic pressure is provided in the thrust plate 24 so that the lower end surface of the shaft member 25 and the thrust plate 2
4 constitutes a thrust bearing for supporting a thrust load. The thrust plate 24 is made by injection molding of plastic, and the grooves for generating dynamic pressure are processed by molding, so that the cost is low. In particular, it is preferable to manufacture by injection molding a plastic to which carbon fiber and Teflon are added, based on PPS (polyphenylene sulfide resin) because of excellent slidability, strength and moldability. When the axial load is large, a press of a steel plate for reinforcing the plastic thrust plate 24 may be added to the lower side of the thrust plate 24. The groove for generating the dynamic pressure may be formed on the shaft end face. Further, a so-called pivot support bearing in which at least one of the end surfaces of the thrust plate 24 or the shaft member 25 is formed as a convex spherical surface and supported in point contact by omitting the groove for generating dynamic pressure may be used.

A groove for generating a dynamic pressure is provided on the inner peripheral surface of the sleeve 23 to constitute a radial dynamic pressure bearing for supporting a radial load between the inner peripheral surface of the sleeve 23 and the outer peripheral surface of the shaft member 25. The sleeve 23 is preferably made of a copper-based material. By forming the sleeve 23 from a copper-based material, the slidability between the sleeve 23 and the stainless steel shaft member 25 is improved, and the start / stop durability is improved.

The lower end of the shaft member 25 has a retaining member 3
0 is fixed by press fitting or bonding. The retaining member 30 prevents the shaft member 25 from falling off the sleeve 23. The retaining member 30 may be formed integrally with the shaft member 25 made of stainless steel. When the retaining member 30 is formed separately from the shaft member 25, the retaining member 30 may be made of any material such as an aluminum alloy, stainless steel, or plastic, but the material of the retaining member 30 is linearly expanded. It is preferable that the coefficient is the same as the coefficient of linear expansion of the material of the shaft member 25 because the looseness does not occur due to a temperature change. It is desirable that the retaining member 30 is made of the same stainless steel as the shaft member 25 because the sliding property with the sleeve 25 made of a copper-based member is good. Further, the retaining member may be formed in a disk shape and attached to the end surface of the shaft member 25 by screwing or the like. In this case, the lower surface of the disc-shaped retaining member serves as a thrust bearing.

A magnet for attraction 32 is provided on the upper portion of the base 26 via a yoke 31, and the iron piece for attraction 33 provided on the inner surface of the hub 22 is attracted. A suction force of 30 N or less (preferably 10 N or less) is applied. The yoke 31 has a shape whose outer peripheral portion protrudes in the axial direction of the shaft member 25.

A lubricating fluid capturing circumferential groove 34 is provided around the inner surface 22a of the hub 22 facing the end surface of the upper end of the sleeve 23. When the lubricating fluid such as oil is scattered from the outer periphery of the shaft member 25 by rotation, the lubricating fluid capturing circumferential groove 34 captures the lubricating fluid in the circumferential groove 34 by the surface tension of the lubricating fluid itself. It is possible to prevent the lubricating fluid from scattering to the surface of the disk mounted on the disk 22. An upper balance correcting circumferential groove 35 for correcting imbalance is formed on the upper surface 22b of the hub 22, and the upper balance correcting circumferential groove 35 corrects the imbalance to reduce vibration during high-speed rotation. I have. The lower balance corrector for unbalance correction on the lower side of the hub 22 uses a corner 36 between the rotor magnet 28 and the hub 22.

Between the base 26 and the thrust plate 24,
An escape portion 37 is provided. FIG. 2 is an enlarged view showing a portion surrounded by a circle A in FIG. 1 in detail. The lower surface of the base 26 that contacts the thrust plate 24 has an annular projecting portion 26 such that only the radially inner portion contacts the thrust plate 24.
b is formed. In the radially outer portion, a relief portion 37 is provided so that the lower surface of the base 26 does not contact the thrust plate 24. Escape part 37
The first is a relief portion 3 which is tapered outward in the radial direction.
After the height in the axial direction of No. 7 increases and reaches a predetermined height h, the relief portion 37 is machined so that the height in the axial direction of the escape portion 37 remains unchanged.

Note that, as in the present embodiment, the thrust plate 24
Is fixed to the base 26 with a fixing screw, as shown in the figure, a through hole 24a for passing the fixing screw and the screw hole 26 are formed.
It is better that a is aligned with the escape portion 37. The lubricating fluid is held by the tapered portion 37a of the escape portion 37 by the surface tension of the lubricating fluid itself and does not spread outward any more. Thus, by aligning the position of the screw hole 26a with the escape portion 37, the lubricating fluid is fastened. Lubricating fluid can be prevented from entering the gap between the screw and the through hole 24a. FIG.
Indicates the state of holding the lubricating fluid.

The inclined surface of the tapered portion 37a and the thrust plate 2
4 is preferably set to 1 degree or more and 90 degrees or less. Desirably, 1 degree or more and 45 degrees or less are advantageous from the oil retaining property.

The height h of the clearance in the axial direction of the escape portion 37 is
It is preferable to set the radius gap of the bearing larger than the distance t between the outer diameter of the shaft 25 and the inner diameter of the sleeve 23 in this embodiment. When the height h is set to be equal to or smaller than the radial gap t of the bearing, the surface tension at the relief portion 37 becomes smaller than the radial gap t of the bearing.
Inner surface tension, the radial clearance t of the bearing
The lubricating fluid inside is sucked out to the escape portion 37, causing a problem that the bearing becomes poorly lubricated. Conversely, if the height h of the gap in the axial direction is too large, the oil retaining property of the escape portion 37 becomes poor, and the lubricating fluid leaks out of the bearing. Therefore, the height h of the clearance in the axial direction of the relief portion 37 is desirably equal to or larger than the radial gap t of the bearing and equal to or smaller than 0.5 mm.

The outer peripheral surface of the thrust plate 24 and the base 2
It is preferable that the thrust plate 24 is loosely fitted in the base 26 so that the clearance between the thrust plate 24 and the inner peripheral surface of the thrust plate 6 is 0.5 mm or less. In this way, even if the lubricating fluid flows out of the escape portion 37, the lubricating fluid can be captured by the clearance.

FIG. 3 is a longitudinal sectional view of a second embodiment of a bearing device for a spindle motor according to the present invention. FIG. 4 shows FIG.
FIG. 3 is an enlarged view showing a portion surrounded by a circle B in detail. Second
In the embodiment, for the same configuration as the first embodiment,
The same reference numerals are given and the description is omitted.

In the bearing device 41 of the second embodiment, the yoke 51 of the attracting magnet 32 has a shape in which the inner peripheral portion protrudes in the axial direction of the shaft member 25. Thrust plate 44
Is made of iron, and is provided with a through hole 44a for passing a retaining screw. As in the first embodiment, an upper balance correcting circumferential groove 55 for correcting imbalance is formed on the upper surface 22b of the hub 22.

Between the base 26 and the thrust plate 44,
An escape portion 57 is provided. The lower surface of the base 26 that contacts the thrust plate 44 is formed with an annular projecting portion 26b such that only the radially inner portion contacts the thrust plate 44. And in the radially outer part,
An escape portion 57 is provided, and the lower surface of the base 26 is
No contact with 4 The escape portion 57 is formed so that the height in the axial direction of the escape portion 57 increases radially outward in a tapered shape over the entire surface. From the viewpoint of the lubricating fluid holding characteristics, the maximum value h of the clearance 57 in the axial direction is preferably 0.5 mm or less, which exceeds the radial gap t of the bearing. If the maximum height h is set to be equal to or less than the radial gap t of the bearing, the lubricating fluid in the bearing portion is sucked out by the escape portion 57, and the lubricating fluid in the bearing portion may be insufficient. FIG.
Indicates the state of holding the lubricating fluid.

The angle θ between the inclined surface 57a of the escape portion 57 and the upper surface of the thrust plate 44 is preferably set in the range of 1 to 90 degrees as needed. In consideration of the retention characteristics of the lubricating fluid, it is desirable that the angle be 1 degree or more and 45 degrees or less.

FIG. 5 is a longitudinal sectional view of a third embodiment of a bearing device for a spindle motor according to the present invention. FIG. 6 shows FIG.
FIG. 4 is an enlarged view showing a portion surrounded by a circle C in detail. Third
In the embodiment, the same components as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the bearing device 61 of the third embodiment, the back yoke 69 of the rotor magnet 28 constituting the motor has a lower end 69a extending outward in the radial direction.
The attraction magnet 32 is provided on the base 26 so as to oppose the lower end portion 69a to exert an attraction force. The back yoke 6
9, a lower balance correcting portion 76 is provided between the outermost peripheral portion of the lower end portion 69a and the inner diameter portion of the hub 22, and is used as a lower unbalance correcting portion. In this case, the number of parts can be reduced by one, and the cost is low. Further, since the back yoke 69 can be fixed to the hub 22 by the cylindrical portion 69b, the bonding strength is improved as compared with the suction iron piece 33 of the first or second embodiment which is fixed in a flat plane. In the third embodiment, no lubricating fluid capturing circumferential groove is provided around the inner surface 22a of the hub 22 facing the end surface of the upper end of the sleeve 23.

The motor including the stator 27 and the rotor magnet 28 is provided on the inner surface of the hub 22 and has an in-hub type motor structure.

In the third embodiment, an escape portion 77 is provided between the base 26 and the thrust plate 24. The escape portion 77 is formed in a step shape. This corresponds to the case where θ is 90 degrees in the first embodiment. Base 26
The lower surface contacting the thrust plate 24 has an annular projecting portion 26 such that the radially inner portion contacts the thrust plate 24.
b is formed. In the radially outer portion, a relief portion 77 is provided so that the lower surface of the base 26 does not contact the thrust plate 24. Escape part 77
Is formed in an annular shape, and an annular protruding portion 26c is provided further outward in the radial direction of the escape portion 77 so that the thrust plate 24 and the base 26 come into contact with each other. From the viewpoint of the holding characteristics of the lubricating fluid, the height h in the axial direction of the escape portion 77 is
0.5 mm or less is desirable beyond the radial gap t of the bearing.
If the height h is set to be equal to or less than the radial gap t of the bearing, the lubricating fluid in the bearing portion is sucked out by the escape portion 77, and the lubricating fluid in the bearing portion may be insufficient. Conversely, 0.5 mm
If it is larger, the holding performance of the lubricating fluid will decrease. FIG. 6 shows a holding state of the lubricating fluid.

In the third embodiment, a plastic thrust plate 24 is used, and a steel pressing plate 78 is added below the thrust plate 24 to reinforce the thrust plate 24. The holding plate 78 has a through hole 7 through which a fastening screw is inserted.
8 a is provided in alignment with the through hole 24 a of the thrust plate 24.

Although the present invention has been described based on the first to third embodiments, the present invention is not limited to these embodiments, and various modifications may be made without departing from the technical scope of the present invention. Improvements are possible. For example, although the present invention has been described in the embodiment of the shaft rotation in which the shaft member rotates, a structure in which the sleeve is rotated while the shaft member is fixed may be used. The motor may be a flat opposed motor instead of a circumferentially opposed motor. Thrust bearings are
A groove for generating dynamic pressure may be provided at the shaft end. Further, a contact type pivot bearing may be used. Further, the groove for generating the dynamic pressure of the radial bearing may be provided on the outer diameter of the shaft. The thrust plate may be fixed by caulking instead of screwing.
Further, as the lubricating fluid, a fluorine oil (fluorine oil having a high viscosity index) having excellent temperature viscosity characteristics, that is, having a small change in viscosity with respect to a temperature change is preferable. In particular, in order to improve the slidability and the retention property of the lubricating fluid, a fluoro oil to which a perfluoroalkyl polyether having a carboxylic acid at a terminal is added is preferable.

[0034]

The present invention is embodied in the form described above and has the following effects. According to the present invention, the swing of the non-rotational synchronous component is small, and the starting torque is small. Further, it is possible to obtain a bearing device free from leakage of the lubricating fluid. As a result, the outside of the bearing device is not contaminated, and the bearing has a long life.

[0035]

[Brief description of the drawings]

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

FIG. 2 is an enlarged view showing a portion surrounded by a circle A in FIG. 1 in detail.

FIG. 3 is a longitudinal sectional view of a second embodiment of a bearing device for a spindle motor according to the present invention.

FIG. 4 is an enlarged view showing a portion surrounded by a circle B in FIG. 3 in detail.

FIG. 5 is a longitudinal sectional view of a third embodiment of a bearing device for a spindle motor according to the present invention.

6 is an enlarged view showing a portion surrounded by a circle C in FIG. 5 in detail.

FIG. 7 is a sectional view of a conventional bearing device for a disk spindle motor.

FIG. 8 is a sectional view of a hydrodynamic bearing device for a disk spindle motor.

[Explanation of symbols]

21 ... Bearing device 22 ... Hub 23 ... Sleeve 24 ... Thrust plate 25 ... Shaft member 26 ... Base 27 ... ··················································································· Escape Axial height t of the radial gap of the bearing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02K 7/08 H02K 7/08 A

Claims (1)

[Claims] 1. A bearing device in which a rotating body is driven to rotate by a motor, the rotating body is supported via a radial dynamic pressure bearing and a thrust bearing, and the thrust bearing is constituted by an end face of a shaft and a thrust plate. A bearing device comprising: a thrust plate that is fixed at least on an inner peripheral side thereof by contact with a fixing member, and an annular relief portion provided outside the thrust plate.