JPH11132230A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing device, for reducing a part cost, simplifying an assembly process, reducing NRRO, and also suppressing the generation of out-gas due to adhesive. SOLUTION: An bearing device 10 is equipped with a hub 11 forming an insertion part 12, for coaxially inserting first and second bearings 61 and 62, and a shaft 13 supported by the rolling bearings 61 and 62; and only the inner ring 61B of the rolling bearing 61 can abut on the large-diameter part 13A of the shaft 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bearing device, and more particularly to a bearing device used for a hard disk drive, an optical disk drive, and the like.

[0002]

2. Description of the Related Art As shown in FIG. 5, a hard disk drive 50 used for various information devices and the like is driven to rotate by a spindle motor 51. The spindle motor 51 includes a substantially disk-shaped hub 53 to which a plurality of hard disks 52 (chain lines in the figure) are fixed, and an insertion portion formed through the hub 53 along an axis thereof.
54 and a first rolling bearing coaxially inserted in the insertion portion 54
61 and a second rolling bearing 62, a shaft 55 supported by the first rolling bearing 61 and the second rolling bearing 62, and a base 56 into which an end (lower end in the figure) of the shaft 55 is press-fitted. Have been. When a coil 57 provided on a base 56 is energized, the spindle motor 51 rotates a hub 53 provided with a magnet 58 about a shaft 55, thereby driving the respective hard disks 52 collectively. It has become.

In recent years, as the density of hard disks has increased, there has been a demand for a spindle motor having less fluctuation (hereinafter abbreviated as NRRO) of non-rotational synchronous components. To satisfy such demands, the spindle motor
Reference numeral 51 denotes a bearing device 70 in which the hub 53, the first rolling bearing 61, the second rolling bearing 62, and the shaft 55 are integrally and precisely assembled in advance, and the shaft 55 of the bearing device 70 is used as a base. It is manufactured by press-fitting and fixing to 56. In assembling the bearing device 70, the first rolling bearing 61 and the second rolling bearing 62 are arranged at predetermined positions in the insertion portion 54 by using a jig and a spacer 59 (not shown), and the outer rings 61A, 62A are connected to the insertion portion 54. The shaft 55 is inserted and fixed to the inner peripheral surfaces of the inner rings 61B and 62B.

At the time of assembling the bearing device 70, it is necessary to move in the axial direction with respect to the first rolling bearing 61 and the second rolling bearing 62 to perform positioning, and to perform the first rolling bearing 61 and the second rolling bearing 61. It is necessary to apply a pressure to the rolling bearing 62. For this reason, the outer peripheral surface of the shaft 55 and each inner ring 61B,
The gap between the inner peripheral surface of the base 62B and the inner peripheral surface of the base 62B is relatively large (for example, 5
μm to 8 μm). The spindle motor 51 is connected to the end face of the shaft 55 of the bearing device 70 (the lower end face in the figure).
The hub 53 and the base 56 are relatively positioned by arranging the base and the bottom surface of the base 56 (the lower surface in the figure) flush with each other.

[0005]

However, in the bearing device 70 described above, the end face of the shaft 55 must be machined in advance into a flat surface perpendicular to the axis line due to its structure. There is a problem that the cost is high. Also,
In this bearing device 70, in order to position the hub 53 and the base 56 relative to each other, it is necessary to arrange the end surface of the shaft 55 flush with the bottom surface of the base 55.
There is also a problem that the assembly work of 51 is complicated.

Further, in such a bearing device 70, since the gap between the outer peripheral surface of the shaft 55 and the inner peripheral surfaces of the inner rings 61B, 62B is set relatively large, the axis of the shaft 55 and each inner ring are formed.
The axes of 61B and 62B may be inclined or eccentric. Therefore, in this bearing device 70, each inner ring 61
There is also a problem that the trajectories of B and 62B are deformed and it is difficult to reduce NRRO. In recent years, as the density of hard disks has increased, the influence of outgas generated from the adhesive has been concerned, and the amount of the adhesive used for mutually fixing the shaft 55 and the inner rings 61B, 62B has been reduced. There is a need for a bearing device that can.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to reduce the cost of parts and to simplify the assembly process, to reduce NRRO, and to reduce outgassing caused by an adhesive. An object of the present invention is to provide a bearing device capable of suppressing the occurrence.

[0008]

According to the present invention, there is provided a hub provided with an insertion portion into which a first rolling bearing and a second rolling bearing can be coaxially inserted, and supported by the first rolling bearing and the second rolling bearing. A large diameter portion is provided between the first rolling bearing and the second rolling bearing, and only the inner ring of the first rolling bearing is provided with a large diameter portion. It is characterized in that it is in contact with the diameter part.

Here, the large diameter portion may be provided integrally with the shaft, or may be provided by fitting a ring member into a groove formed along the outer peripheral surface of the shaft. The diameter of such a large-diameter portion is set smaller than the outer diameter of the inner race of the first rolling bearing, and its axial thickness is set to be smaller than the separation between the first rolling bearing and the second rolling bearing. It should be set small.

[0010] In such a bearing device, the first rolling bearing is inserted and arranged at a predetermined position in the insertion portion using an appropriate jig or the like, and then the shaft is inserted into the inner ring of the first rolling bearing. Is brought into contact with the inner ring of the first rolling bearing, and finally the second rolling bearing is inserted into the insertion portion of the hub with the shaft inserted into the inner ring. The second rolling bearing in which the inner ring is separated from the large-diameter portion may be moved along the shaft to apply an appropriate preload.

In such a bearing device, the shape and position of the large-diameter portion are appropriately selected in advance so that the shaft and the first rolling bearing are at desired relative positions, and the first rolling bearing contacts the base or the like. If the shaft is pressed in until it touches, the positioning of the hub with respect to the base is automatically completed. At this time, the large-diameter portion of the first rolling bearing with which the inner ring abuts serves as a stopper, so that there is no danger of moving along the axis.

Therefore, in this bearing device, in order to be applied to, for example, a spindle motor, it is necessary to machine the shaft end face with high precision in advance, or the shaft end face and the bottom surface of the base are arranged flush. The necessity is eliminated, and the cost of parts can be reduced and the assembling process can be simplified as compared with the related art.

In this bearing device, the shaft can be positioned by bringing the large-diameter portion into contact with the inner ring of the first rolling bearing, so that the shaft can be lightly press-fitted into the inner ring of the first rolling bearing. Become. That is, in this bearing device, since the gap between the inner ring and the shaft of the first rolling bearing can be made smaller than before, the inner ring and the shaft of the first rolling bearing tilt or eccentric with each other. The risk can be reduced, thereby reducing NRRO.

In addition, in the bearing device, since the shaft is lightly press-fitted into the inner ring of the first rolling bearing, no adhesive is used or the amount of the adhesive used can be reduced as compared with the conventional one. As a result, the outgas generated from the adhesive can be reduced.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a sectional view showing a first embodiment according to the present invention, FIG. 2 is a sectional view showing a second embodiment according to the present invention, and FIG. 3 is a sectional view showing a third embodiment according to the present invention. FIG. 4 is a sectional view showing a fourth embodiment according to the present invention. In addition, in each embodiment described below, the members and the like already described in FIG. 5 are denoted by the same reference numerals or corresponding reference numerals in the drawings to simplify or omit the description.

FIG. 1 shows, as a first embodiment according to the present invention, an inner rotor type, circumferentially opposed type spindle motor for driving a plurality of hard disks 52 (dashed lines in the figure) to rotate.
10 is shown. The spindle motor 10 includes a substantially cylindrical hub 11 to which each hard disk 52 is fixed, an insertion portion 12 formed through the hub 11 along an axis thereof, and a first rolling bearing 61 coaxially inserted into the insertion portion 12. And the second rolling bearing 62
And the shaft 13 supported by the first rolling bearing 61 and the second rolling bearing 62, and the base 14 into which the end (the lower end in the figure) of the shaft 13 is press-fitted.

The spindle motor 10 has a hub 11, a first rolling bearing 61,
The second rolling bearing 62 and the shaft 13 are integrally assembled, and a bearing device 15 having an appropriate preload applied to the second rolling bearing 62 is separately manufactured, and the shaft 13 of the bearing device 15 is attached to the base 14.
It is assembled by press-fitting. Here, the hub 11 is made of an aluminum alloy and has an iron back yoke.
A magnet 58 is attached via 11A.

The insertion portion 12 of the hub 11 includes a projection 12A whose inner peripheral surface is partially reduced in diameter and a pair of press-fit holes 12B and 12C sandwiching the projection 12A along the axial direction. I have.
The protrusion 12 </ b> A has a ring shape that is continuous along the circumferential direction and is integrally formed with the hub 11. This protrusion
12A has an inner diameter smaller than the inner diameter of the outer ring 61A of the first rolling bearing 61 and the outer ring 62A of the second rolling bearing 62, and has a smaller distance between the first rolling bearing 61 and the second rolling bearing 62. It has a corresponding axial length.
On the other hand, each of the press-fitting holes 12B and 12C has an inner diameter dimension in which each of the outer races 61A and 62A can be press-fitted.
It is formed shorter than the axial length of 62A. Here, two protrusions 12A may be provided so as to individually contact the outer rings 61A and 62A.

In such an insertion portion 12, when the end surfaces of the outer races 61A, 62A come into contact with the projections 12A, the first rolling bearing 61 and the second rolling bearing 62 form one of the outer peripheral surfaces of the outer races 61A, 62A. The part is press-fitted into the press-fit holes 12B and 12C, and the other part is held in a state separated from the inner peripheral surface of the insertion part 12. Therefore, in this bearing device 15, the mounting error of each of the outer rings 61A, 62A with respect to the hub 11 can be reduced, and the deformation of the bearing ring that occurs when an adhesive is used together can be prevented.
Further, in this bearing device 15, since a part of each of the outer rings 61A, 62A is held in a state of being separated from the insertion portion 12, each of the outer rings 61A, 62A is held.
Vibration propagating from the wheels A, 62A to the hub 11 can be reduced, and the deformation of the outer rings 61A, 62A can be reduced to reduce NRRO. In this embodiment, each outer ring
Although 61A and 62A are press-fitted into the press-fit holes 12B and 12C without using an adhesive, an adhesive may be used together.
Alternatively, clearance fit using an adhesive may be used.

On the other hand, the shaft 13 has a large-diameter portion 13A provided at a predetermined position thereof, and a mounting portion 13B, having a diameter smaller than the large-diameter portion 13A and having a diameter that allows the inner rings 61B, 62B to be lightly press-fitted.
13C and shaft portions 13D and 13E having a smaller diameter than the mounting portions 13B and 13C. The mounting portions 13B and 13C are arranged so as to sandwich the large-diameter portion 13A along the axial direction.
D and 13E are arranged so as to sandwich the large diameter portion 13A and the mounting portions 13B and 13C along the axial direction.

The large diameter portion 13A is formed on the inner race 61 of the first rolling bearing 61.
B has a diameter capable of contacting the end face, and the axial length is set shorter than the axial length of the projection 12A. The mounting portions 13B and 13C are formed on the outer peripheral surface and the inner race 61B and the inner race.
Since the gap (interference) between the inner peripheral surface of 62B and the inner peripheral surface is set to 8 μm or less in diameter, particularly preferably 4 μm or less,
Each inner ring 61B and inner ring lightly press-fitted into the mounting portions 13B, 13C.
There is no risk of deforming 62B.

When the shaft 13 is made of austenitic stainless steel, the shaft 13 and the hub 11
Since the coefficient of thermal expansion of (made of aluminum) is similar, a change in pressurization of the second rolling bearing 62 due to a temperature change can be reduced. Here, the ratio of the thermal expansion coefficients of the shaft 13 and the hub 11 (the shaft 13
Is larger than 0.5), the effect becomes remarkable. Further, when the shaft 13 is formed of austenitic stainless steel, the heat treatment and the grinding process are omitted, and the predetermined shape can be obtained only by the lathe processing, so that the manufacturing process can be greatly simplified. In particular, the shaft 13 is formed by lathe processing into a large-diameter portion 13A and mounting portions 13B, 13B.
A desired shape in which the C and the shaft portions 13D and 13E are formed in a multi-stage shape can be easily obtained. Furthermore, since austenitic stainless steel has good corrosion resistance, there is little possibility that corrosion such as rust will occur on the shaft 13.

When the shaft 13 is made of an aluminum alloy, the thermal expansion coefficients of the shaft 13 and the hub 11 (made of aluminum) become equal, so that a change in preload due to a temperature change can be eliminated. When the shaft 13 is formed of an aluminum alloy or free-cutting brass, a surface treatment such as an alumite treatment or a plating treatment may be performed to increase the surface hardness and prevent scratches or the like. The surface treatment such as the plating treatment can be applied to the case where the shaft 13 is formed of austenitic or martensitic stainless steel.

In such a bearing device 15, first, the first rolling bearing 61 is inserted into the press-fit hole portion 12A until the outer ring 61A comes into contact with the projection 12A.
B and then press the shaft 13D against the inner ring 61B to project the projection 12A.
After inserting from the side, the mounting part 13
B is lightly press-fitted into the inner race 61B, and then the second rolling bearing 62 is moved along the shaft 13 while guiding the inner race 62B to the shaft portion 13E. Is lightly pressed into the inner ring 62B. The bearing device 15 may be provided with a labyrinth seal or a magnetic fluid seal at the opening of the insertion portion 12 as necessary.

In this case, for example, US Pat. No. 5,341,569
According to the method disclosed in U.S. Pat. No. 5,509,198, a proper preload is applied by moving the second rolling bearing 62 along the shaft 13 while measuring the natural frequency of the bearing device 15. The second rolling bearing 62 is an annular stopper fixed to the shaft portion 13E of the shaft 13 by bonding, welding, or the like.
The inner race 62B is held by the second rolling bearing 62 even when an impact or the like is applied from outside the bearing device 15.
Does not move in a direction away from the large-diameter portion 13A, that is, there is no risk of so-called preload loss. Then, the shaft portion 13D of the shaft 13 is press-fitted into the through hole 14A of the base 14 until the inner ring 61B of the first rolling bearing 61 comes into contact, whereby the spindle motor 10 is obtained.

According to the bearing device 10 of the first embodiment as described above, the large diameter portion 13A is brought into contact with the inner ring 61B to thereby reduce the shaft 13
And the shaft portion 13D of the shaft 13 is inserted into the through-hole 14 until the relative positioning of the first rolling bearing 61 is completed and the inner ring 61B abuts.
Since the relative positioning of the hub 11 and the base 14 is completed by press-fitting into the A, it is necessary to process the end face of the shaft 13 with high precision in advance, and the end face of the shaft 13 and the bottom face of the 14 base are flush with each other. The necessity of disposition is eliminated, and the cost of parts can be reduced as compared with the related art, and the assembling process can be simplified.

According to the bearing device 10, the inner race 61B
To lightly press the mounting portion 13B of the shaft 13
Since the gap between B and the mounting portion 13B is set smaller than before, the risk that the inner ring 61B and the shaft 13 are inclined or eccentric with respect to each other can be reduced, thereby reducing NRRO. it can. In addition, since the mounting portion 13B is lightly press-fitted into the inner ring 61B, no adhesive is used, or the amount of the adhesive used can be reduced as compared with the conventional case. Can be reduced.

According to the bearing device 10, the insertion portion 12
Since the outer ring 61A of the first rolling bearing 61 and the outer ring 62A of the second rolling bearing 62 abut on the projection 12A provided on the inner peripheral surface of the hub 11, the hub 11, the first rolling bearing 61, and the second rolling bearing 62.
In addition, the relative positioning of the shaft 13 can be reliably and easily performed, and the spacer used in the conventional bearing device can be omitted, whereby the assembly process of the bearing device 10 can be further simplified and the number of components can be reduced. .

FIG. 2 shows, as a second embodiment of the present invention, a spindle motor 20 of an inner rotor type and a circumferentially opposed type. In the second to fourth embodiments described below, the members and the like already described in FIG. 1 are denoted by the same reference numerals or corresponding reference numerals in the drawings to simplify or omit the description.

The bearing device 25 constituting the spindle motor 20 has an inner ring 62B loosely fitted to a mounting portion 23C of the shaft 23 and is adhesively fixed in a state where a preload is applied thereto. A lid 26 covering the opening on the second rolling bearing 62 side prevents dust and the like from entering the insertion portion 22. Here, the inner ring 62 is attached to the mounting portion 23C of the shaft 23.
In order to prevent the NRRO from deteriorating due to the mounting error of the bearing, the mounting portion 23C and the inner ring 62 are required.
It is preferable to set the gap between B to 4 μm or less in diameter. Therefore, according to this bearing device 25, the first
The stopper employed in the embodiment can be omitted, and the number of components can be further reduced.

In this bearing device 25, the hub 21 is formed of a magnetic iron alloy (eg, ferritic stainless steel), and the shaft 23 is formed of SUS420, SUS4.
If it is formed of martensitic stainless steel such as 40, the back yoke 21A can be omitted, the number of components can be further reduced, and the thermal expansion coefficients of the hub 21 and the shaft 23 become extremely close, so that the temperature change may occur. First rolling bearing 61
Further, a change in preload of the second rolling bearing 62 can be reduced.

FIG. 3 shows, as a third embodiment of the present invention, a spindle motor 30 of an inner rotor type and a circumferentially opposed type. The bearing device 35 of the spindle motor 30 includes outer rings 61A and 62A for the hub 31,
Shaft 33 for each inner ring 61B, 62B, and back yoke 31
A is fixed to the magnet 58 by press-fitting without using an adhesive, and the back yoke is
31A is fixed by caulking without using an adhesive.
In this bearing device 35, each hard disk 52 is pressed against a substantially stepped disk-shaped holding member 38, and the inner peripheral surface of the holding member 38 is fitted to the outer ring 62A.

According to this bearing device 35, since no adhesive is used for mutually fixing the members, the possibility of outgassing due to the use of the adhesive as in the conventional case can be completely eliminated.
Further, according to such a bearing device 35, since the holding member 38 is held on the outer peripheral surface of the outer race 62A, the axial dimension of the hub 31 can be reduced, thereby reducing the processing cost and the weight.

FIG. 4 shows, as a fourth embodiment of the present invention, a bearing device 45 applied to a swing arm 40 of a disk head constituting an HDD. In this bearing device 45, a shaft 43 is supported by a first rolling bearing 61 and a second rolling bearing 62 which are press-fitted into a substantially cylindrical sleeve 41. The sleeve 41 has a plurality of grooves 41B on its outer peripheral surface. These grooves 41B are arranged at predetermined intervals along the axial direction of the sleeve 41, and are each formed continuously along the circumferential direction of the outer peripheral surface.

In the bearing device 45, the sleeve 41 is press-fitted into a predetermined position of the swing arm 40. At this time, whether or not the adhesive is applied between the sleeve 41 and the swing arm 40 is optional, and the fixing may be performed by appropriately using a fixing bolt or the like. In this bearing device 45, if the sleeve 41 and the shaft 43 are formed of ferritic stainless steel, the thermal expansion coefficients of the sleeve 41 and the shaft 43 become equal. Since the change in preload of the second rolling bearing 62 can be reduced and the corrosion resistance and the machinability are excellent, the cost is reduced without fear of rust.

In such a bearing device 45, one end surface (upper surface in the drawing) of the shaft 43 is fixed to a frame 49B by bolts, and the other end surface (lower surface in the drawing) of the shaft 43 is provided via a contact member 49C. ) Is fixed to the frame 49A by bolts, so that the swing arm is pivoted about the shaft 43.
40 is rotatable.

It should be noted that the bearing device of the present invention is not limited to the embodiments described above, but can be appropriately modified and improved. For example, in each of the embodiments described above,
Although the inner rotor type and the circumferentially opposed spindle motor have been exemplified, the bearing device of the present invention is also applicable to the outer rotor type and the circumferentially opposed spindle motor or the planarly opposed spindle motor.

In addition, the materials, shapes, dimensions, shapes, and numbers of the first rolling bearing, the second rolling bearing, the insertion portion, the hub, the shaft, the bearing device, the large-diameter portion, the projection, and the like exemplified in the above-described embodiments. The location, location, and the like are arbitrary as long as the present invention can be achieved, and are not limited.

[0039]

As described above, according to the present invention, since only the inner ring of the first rolling bearing is in contact with the large-diameter portion of the shaft, the shape, size, and position of the shaft and the large-diameter portion are provided. If appropriate selection is made, it is possible to reduce the cost of parts and simplify the assembling process, reduce NRRO, and suppress the generation of outgas due to the adhesive.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment according to the present invention.

FIG. 2 is a cross-sectional view showing a second embodiment according to the present invention.

FIG. 3 is a sectional view showing a third embodiment according to the present invention.

FIG. 4 is a sectional view showing a fourth embodiment according to the present invention.

FIG. 5 is a sectional view showing a conventional bearing device.

[Explanation of symbols]

 10, 20, 30, 40 Bearing device 11, 21, 31, 41 Hub 12, 22, 32, 42 Insertion section 12A, 22A, 32A, 42A Projection 13, 23, 33, 34 Shaft 13A, 23A, 33A, 34A Large Diameter part 61 First rolling bearing 62 Second rolling bearing

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Etsuo Maeda 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd.

Claims (1)

[Claims] 1. A bearing device comprising: a hub having an insertion portion into which a first rolling bearing and a second rolling bearing can be coaxially inserted; and a shaft supported by the first rolling bearing and the second rolling bearing. The shaft is provided with a large diameter portion between the first rolling bearing and the second rolling bearing, and only the inner ring of the first rolling bearing is in contact with the large diameter portion. A bearing structure characterized in that: