JPH1116263A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor capable of effectively preventing the occurrence of noises or vibration by reducing a load applied on a contact portion between a ball and an outer race track surface and maintaining the holding strength of a ball bearing at a sufficiently high level without reducing a substantial joining area between an outer race and a hub inner peripheral side face. SOLUTION: In a spindle motor, ball bearings 5 and 6 are positioned by a step part 812 formed in the inner peripheral side face 811 of a bearing holding hole 84. In overlapped positions in the axial direction of contact positions 57 and 67 between balls 53 and 63 and outer race track surfaces 522 and 622, annular grooves 16 and 18 are formed as joined parts with the outer races 52 and 62 of the ball bearings 5 and 6. In the corner parts 830 and 840 of the step part 812, annular adhesive stay parts 810 and 820 are formed for receiving superfluous adhesive from between the annular grooves 16 and 18 and the outer races 52 and 62 of the ball bearings 5 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for rotating a rotating object such as a magnetic disk.

[0002]

2. Description of the Related Art A spindle motor is used to rotationally drive a rotating body such as a magnetic disk or an optical disk. This spindle motor is disclosed in, for example,
As disclosed in Japanese Patent Publication No. 317585, a fixed shaft spindle motor in which a hub on which a rotating body is mounted is rotatably supported on a fixed shaft via a ball bearing, or a hub via a ball bearing. In addition, a shaft rotation type spindle motor in which a rotation shaft is rotatably supported by a fixed member is known.

The outer ring of the ball bearing is fixed to a hub in a fixed shaft type spindle motor, and is fixed to a fixed member in a shaft rotating type spindle motor. The outer ring is fixed by applying an adhesive to an inner peripheral side surface of a bearing holding hole formed in the hub or the fixed side member, and pressing a ball bearing into the bearing holding hole.

However, when the pressure contact portion between the outer ring and the hub or the fixed side member and the contact portion between the outer ring raceway surface and the ball are in a positional relationship overlapping in the axial direction, the pressure contact portion with respect to the contact portion. Large loads may be applied. Depending on the degree of this load, the ball may not be able to roll smoothly, and NRRO (no
n repeatable run out), RRO (repeatable run ou)
t) is deteriorated, or the vibration characteristics of the motor are deteriorated, which causes noise. In particular, when the dimensional accuracy of the press-fitting portion provided on the inner peripheral side surface of the bearing holding hole is poor, the load applied to the contact portion becomes large, and the above-described tendency becomes remarkable.

In order to solve such a problem, as shown in Japanese Patent Application Laid-Open No. 3-285545, an annular recess is provided at a position corresponding to the outer raceway surface of the inner peripheral side surface of the hub into which the outer race of the bearing is press-fitted. It is known to form With this arrangement, the outer peripheral side surface of the outer race corresponding to the contact portion between the outer raceway surface and the ball does not substantially contact the hub. And vibration and the like can be effectively prevented.

[0006]

However, in such a configuration, the annular concave portion is formed on the inner peripheral side surface of the hub, so that the substantial joint area between the outer ring of the ball bearing and the inner peripheral side surface of the hub is extremely large. Therefore, there is a problem that the holding strength of the ball bearing is reduced and noise and vibration cannot be sufficiently prevented.

[0007] Even if an adhesive commonly used as a means for fixing parts is used in combination, there is a problem in that the depth of the annular concave portion is relatively large, so that sufficient bonding strength cannot be ensured. However, there are various problems that processing for ensuring the accuracy is extremely difficult even if it is formed shallow.

In view of the above, an object of the present invention is to provide a contact portion between a ball and an outer raceway surface via an outer race of a ball bearing without reducing a substantial joint area between the outer race and the inner peripheral side surface of the hub. A spindle motor that can smoothly roll the ball by reducing the load applied to the shaft, maintains the ball bearing holding strength at a sufficiently high level, and sufficiently prevents noise and vibration. To provide.

[0009]

In order to solve the above-mentioned problems, according to the present invention, a fixed member, a fixed shaft erecting from the fixed member, a ball bearing fitted into the fixed shaft, and A hub rotatably supported with respect to the fixed shaft via a ball bearing, wherein the hub is provided with a bearing holding hole for holding an outer ring of the ball bearing on an inner peripheral side surface; An inner peripheral side surface of the holding hole has a positioning step portion against which an outer ring end face of the ball bearing abuts when the ball bearing is inserted into the bearing holding hole, and at least an outer ring raceway surface of the ball bearing from a corner of the step portion. Ring formed to a position overlapping in the axial direction with respect to the contact position between the ball bearing and the outer ring of the ball bearing And an outer ring press-fit portion formed on the side opposite to the step portion with respect to the annular groove, and at a corner of the step portion, an excess portion from between the annular groove and the outer ring of the ball bearing is provided. It is characterized in that an annular adhesive reservoir for receiving the adhesive is formed.

The ball bearing is press-fitted from the opening of the bearing holding hole until it hits a step formed on the inner peripheral side surface, and is held by the outer ring press-fitting portion. An adhesive is applied between the ball bearing and the annular groove, and the ball bearing is bonded and fixed in the bearing holding hole. Here, if the annular groove is too deep, the adhesive strength is weakened,
The outer ring press-fitting portion is mainly joined, and the joining area is reduced.
On the other hand, if the annular groove is uniformly shallow, the adhesive leaks out although the adhesive strength increases. However, in the present invention, since the annular adhesive reservoir is formed at the corner of the step (the connecting portion between the step and the annular groove), excess adhesive leaks even if the annular groove is made shallow. Instead, it is stored in the adhesive pool.
For this reason, although the annular groove and the outer peripheral surface of the outer ring are not in contact with each other, they face each other via an extremely thin adhesive,
The bonding strength is increased, and the outer ring is fixed to the inner peripheral side surface of the hub with a substantially large joint area.
Therefore, the holding strength of the ball bearing can be maintained at a sufficiently high level. As a result, the rotation accuracy of the hub and the rotating body is increased, and the generation of noise and vibration can be reliably prevented. In addition, the annular groove is formed at a position axially overlapping the contact position between the outer ring raceway surface and the ball, and the outer ring press-fit portion is displaced in the axial direction from the contact position between the outer ring raceway surface and the ball. JP-A-3-28554
As in the case of the spindle motor disclosed in Japanese Patent Application Publication No. 5 (1993) -5, the effect of reducing the load applied to the contact portion between the ball and the outer raceway surface via the outer race of the ball bearing can be obtained as it is. Therefore, the ball can smoothly roll, and from this point, it is possible to sufficiently prevent noise and vibration.

In the present invention, the hub may include a cylindrical portion having an annular yoke on an inner peripheral side surface, both ends of which are crimped over the entire periphery of the hub. In this case, it is preferable that the annular groove is formed by cutting the inner peripheral side surface of the bearing holding hole using the inner peripheral surface of the annular yoke as a reference surface. If the inner portion of the annular yoke fixed to the inside of the cylindrical portion of the hub is chucked and subjected to cutting, the cutting process can be performed with the inner peripheral surface of the annular yoke as a reference surface, so that the inner peripheral side surface of the bearing holding hole,
The dimensional accuracy of the step portion, the outer ring press-fit portion, and the annular groove can be improved. In addition, it becomes easy to uniformly process the shallow annular groove, which is optimal for increasing the holding strength of the ball bearing.

The present invention can be applied not only to a fixed shaft type spindle motor but also to a shaft rotating type spindle motor.

That is, in another embodiment of the present invention, a hub, a rotating shaft extending downward from the hub, a ball bearing fitted into the rotating shaft, and a fixed member holding the ball bearing are provided. Wherein the fixed side member has a bearing holding hole for holding an outer ring of the ball bearing on an inner peripheral side surface, wherein the inner peripheral side surface of the bearing holding hole inserts the ball bearing into the bearing retaining hole. When the outer ring end face of the ball bearing abuts, a positioning step portion abuts, formed from a corner of the step portion to at least a position axially overlapping a contact position between the outer ring raceway surface of the ball bearing and the ball, An annular groove serving as a bonding portion with the outer ring of the ball bearing; and an annular groove formed on an opposite side of the annular groove to the stepped portion. A wheel press-fitting portion, wherein at a corner of the step portion, an annular adhesive reservoir for receiving excess adhesive from between the annular groove and the outer ring of the ball bearing is formed. I do.

[0014] In the spindle rotating type spindle motor of the present invention, like the fixed shaft type spindle motor, an annular adhesive reservoir is formed at the corner of the step (the connecting portion between the step and the annular groove). Therefore, even if the annular groove is made shallow, excess adhesive does not leak out and is stored in the adhesive reservoir. For this reason, although the annular groove and the outer peripheral surface of the outer ring are not in contact with each other, they face each other via an extremely thin adhesive, and the bonding strength is increased, and the outer ring is substantially in contact with the inner peripheral surface of the hub. It will be fixed with a large joint area. Therefore, the holding strength of the ball bearing can be maintained at a sufficiently high level. As a result, the rotation accuracy of the hub and the rotating body is increased, and the generation of noise and vibration can be reliably prevented. In addition, the annular groove is formed at a position axially overlapping the contact position between the outer ring raceway surface and the ball, and the outer ring press-fit portion is displaced in the axial direction from the contact position between the outer ring raceway surface and the ball. JP-A-3-28
As in the spindle motor disclosed in Japanese Patent No. 5545, the effect of reducing the load applied to the contact portion between the ball and the outer raceway surface via the outer race of the ball bearing can be directly obtained. Therefore, the ball can smoothly roll, and from this point, it is possible to sufficiently prevent noise and vibration.

Here, the annular groove is preferably set to a depth of 10 μm or less when viewed from the inner peripheral side surface of the outer ring press-fitting portion. By setting such a depth dimension, the adhesive fixing strength between the outer ring and the annular groove is increased, and the substantial joining area is increased, so that the fixing strength between the outer ring and the bearing holding hole can be sufficiently secured. It is. In consideration of the fixing strength between the outer ring and the bearing holding hole, the workability of the annular groove, and the like, the thickness is most preferably about 5 μm. On the other hand, the gap size between the bearing holding hole side and the outer ring of the ball bearing in the adhesive pool is desirably 100 μm or more. Can be reliably prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A spindle motor to which the present invention is applied will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a sectional view of a spindle motor for driving a disk according to this embodiment.

As shown in this figure, the spindle motor 1 of the present embodiment has a cup-shaped frame 2, and a fixed shaft 3 stands vertically on a disk-shaped bottom wall 21 of the frame 2. I have. A vertically protruding cylindrical projection 23 is provided on the bottom wall 21 of the frame 2 so as to concentrically surround the fixed shaft 3. The outer peripheral portion of the cylindrical projection 23 is a stator core mounting portion, where the stator core 4 is mounted. The inner peripheral edge portion of the lower end surface of the stator core 4 is held by a step formed on the outer peripheral side surface of the cylindrical projection 23, and is positioned at a predetermined height with respect to the bottom wall 21 of the frame 2. Salient poles 41 projecting outward in the radial direction are formed on the stator core 4 at regular angular intervals. A drive coil 42 is wound around these salient poles 41.

In the spindle motor 1 of the present embodiment, the frame 2, the fixed shaft 3, and the cylindrical protrusion 23 are integrally formed of an aluminum material such as an aluminum alloy. If these parts are formed as separate parts, there is an advantage that the fixed shaft 3 and the like do not interfere when the frame 2 is processed. In this example, the fixed shaft 3 and the cylindrical projection 23 are integrated with the frame 2. By reducing the number of motor parts,
The cost of the motor is reduced.

First and second ball bearings 5 and 6 are attached to the fixed shaft 3 on the distal and proximal ends thereof. Each of the ball bearings 5, 6 has an inner ring 51,
61, outer rings 52 and 62, and balls 53 and 63 rotatably inserted between them. Inner ring 51, 6
1 is fixed to the fixed shaft 3, and the outer rings 52 and 62 are
The rotor 7 is fixed to the inner peripheral side surface 811 of the bearing holding hole 84 formed in the base portion 81 of the hub 8 of the rotor 7.
Therefore, the rotor 7 is rotatably supported by the fixed shaft 3 via the first and second ball bearings 5 and 6.

In the first ball bearing 5, the outer race 52
The annular seal members 54 and 55 are attached to the upper and lower positions of the inner peripheral portion of the inner ring 51, and the gap between the inner ring 51 and the outer ring 52 is substantially closed by the seal members 54 and 55. Also in the second ball bearing 6, similarly to the first ball bearing 5, annular seal members 64 and 65 are attached to the upper and lower positions of the inner peripheral portion of the outer ring 62, respectively. The gap between the inner race 61 and the outer race 62 is substantially closed by 65. Inner ring 5 of each ball bearing 5, 6
The gap between the seal members 1 and 61 and the seal members 54, 55, 64 and 65 is narrow, and the pressure in the gap is increased to prevent the oil mist from flowing out.

The rotor 7 has a hub 8 on which a rotating object such as a magnetic recording disk or an optical recording disk is mounted. The hub 8 has a base 81 having a stepped bearing holding hole 84 at the center, A horizontal portion 82 extends radially outward from a lower portion of the base portion 81, and a cylindrical portion 83 extending downward from an edge portion of the horizontal portion 81. At the inner peripheral side surface 811 of the bearing holding hole 84, the first and the second
The outer races 52, 62 of the ball bearings 5, 6 are held. The horizontal portion 82 of the hub 8 is a mounting portion on which a rotating body such as a disc is mounted, and the annular upper surface of the horizontal portion 82 is a mounting surface of the rotating body. The cylindrical portion 83 of the hub 8 concentrically surrounds the stator core 4.
The annular back yoke 9 is fixed to the inner peripheral side surface 831 by a method such as caulking or bonding.

A ring-shaped magnet 10 is attached to the inner peripheral side surface 901 of the back yoke 9. The inner peripheral side surface of the drive magnet 10 is opposed to the stator core 4, and the drive magnet 41 is wound around each salient pole 41 of the stator core 4 to control the energization of the drive magnet 10.
The hub 8 is rotationally driven by the magnetic force generated between the and the salient poles 41. As a result, the rotating object placed on the horizontal portion 82 of the hub 8 can be rotated.

An annular seal member 12 is fixed to a portion of the inner peripheral side surface 811 of the bearing holding hole 84 that is axially outside the first ball bearing 5. The annular gap formed between the fixed shaft 3 and the bearing holding hole 84 is closed by the annular seal member 12. The annular seal member 12 is fixed in a state where its outer peripheral side surface is sealed to an inner peripheral side surface 811 of the bearing holding hole 84 of the hub 8, and is configured to rotate integrally with the hub 8. The peripheral side faces the outer peripheral side of the fixed shaft 3 with a minute gap 27 therebetween, and forms a labyrinth seal mechanism.

In this embodiment, an annular flange 24 extending radially outward is formed on the upper edge of the peripheral wall 22 of the cup-shaped frame 2, and this portion is attached to the main body side (not shown) of the disk drive. Can be

FIG. 2A shows each of the ball bearings 5 and 6.
Is enlarged and shown. The first and second ball bearings 5 and 6 are provided with bearing holding holes 8 in the hub 8.
4 is press-fitted from opposite directions to a stepped portion 812 formed on an inner peripheral side surface 811 thereof, and is positioned by the stepped portion 812. In the first ball bearing 5, the lower end surface of the outer ring 52 is in contact with the upper end surface of the step portion 812, and the upper end surface of the outer ring 52 is in contact with the lower end surface of the annular seal member 12. For this reason, a preload is applied to the first ball bearing 5 in the direction indicated by the dashed line in the figure, and the ball 53 partially contacts the upper part of the inner raceway surface 512 and the lower part of the outer raceway surface 522. It is in a state of having done. In the second ball bearing 6, the upper end surface of the outer ring 62 is in contact with the lower end surface of the step portion 812, and the lower end surface of the inner ring 61 is in contact with the bottom wall 21 of the frame 2. For this reason, a preload is applied in the direction shown by the dashed line in the figure, and the ball 53
The lower part of the inner raceway 612 and the upper part of the outer raceway 622 are in partial contact.

In the inner peripheral side surface 811 of the bearing holding hole 84, the upper corner 830 of the step portion 812 moves from the upper portion 830 to the contact portion 57 (contact position) between the outer raceway surface 522 of the first ball bearing 5 and the ball 53. The annular groove 16 is formed to a position overlapping in the axial direction, and an annular outer ring press-fitting portion 17 slightly protruding inward is formed on the opposite side of the annular groove 16 from the step portion 812. The outer ring 52 of the first ball bearing 5 is formed by the outer ring press-fit portion 17.
Is held.

The inner peripheral side surface 8 of the bearing holding hole 84
11, the annular groove 18 extends from the lower corner 840 of the step portion 812 to a position axially overlapping the contact portion 67 (contact position) between the outer raceway surface 622 of the second ball bearing 6 and the ball 63. A ring-shaped outer ring press-fitting portion 19 slightly protruding inward is formed on the opposite side of the annular groove 18 from the step portion 812. The outer ring 62 of the second ball bearing 6 is held by the outer ring press-fit portion 19.

An anaerobic adhesive is applied between each of the annular grooves 16, 18 and the outer rings 52, 62 of each of the ball bearings 5, 6, and at the portions where these annular grooves 16, 18 are formed, The outer races 52 and 62 and the bearing holding hole 84 are bonded and fixed. That is, the annular grooves 16 and 18 function as a bonding portion.

If the annular grooves 16 and 18 are too deep,
The bonding strength is reduced, and the joint between the outer rings 52, 62 and the bearing holding holes 84 is formed mainly by the outer ring press-fit portions 17, 19, so that the joint area is reduced. For this reason, in the spindle motor 1 of this embodiment, in order to increase the adhesive strength at the portion where the annular grooves 16 and 18 are formed, the shallow annular grooves 16 and
18 are formed. In this example, the annular groove 1
The depth of the outer ring press-fitting portions 17 and 19 when viewed from the inner peripheral side is set to about 3 μm to 10 μm, and the adhesive fixing strength at the portion where the outer rings 52 and 62 and the annular grooves 16 and 18 are formed. And the fixing strength between the outer rings 52, 62 and the bearing holding holes 84 is maintained at a sufficiently high level. In consideration of the fixing strength, the workability of the annular grooves 16 and 18, and the like, a thickness of about 5 μm is most preferable.

At the lower end surface of the outer ring 52 of the first ball bearing 5, the outer peripheral edge portion is chamfered more, and the annular groove 16 and the first ball bearing 5 are provided at the upper corner 830 of the step 812. An annular adhesive reservoir 810 that receives excess adhesive from between the outer ring 52 and the outer ring 52 is formed. Adhesion pool 8 shown enlarged in FIG.
The gap dimension t between the bearing holding hole side and the outer ring 52 of the first ball bearing 5 in 10 is set to be 100 μm or more. Also, at the upper end surface of the outer ring 62 of the second ball bearing 6, the outer peripheral edge portion has a large amount of chamfer similarly to the first ball bearing 5, and is provided at the lower corner 840 on the lower side of the step 812. An adhesive reservoir 820 that receives excess adhesive from between the annular groove 18 and the outer ring 62 of the second ball bearing 6 is formed. As in the case of the above-mentioned adhesive pool portion 810, the gap between the bearing holding hole side and the outer ring 62 of the second ball bearing 6 has a clearance dimension of 100 μm.
It is set so as to be as described above.

In the present embodiment, the adhesive pool 8 is formed by utilizing the rounded outer peripheral edge of each of the outer rings 52 and 62.
10 and 820, but instead of the step 8
Twelve corners 830 and 840 are cut deeper than the annular grooves 16 and 18 to form necking grooves, and the adhesive grooves 810 and 820 are formed by the necking grooves.
May be formed.

As described above, in the spindle motor 1 of the present embodiment, the corner portion (the connecting portion between the step portion and the annular groove) 83 of the step portion 812 formed on the inner peripheral side surface 811 of the bearing holding hole 84.
Since the annular adhesive reservoirs 810 and 820 are formed at 0 and 840, the excess adhesive does not leak even if the annular grooves 16 and 18 are made shallow, and the adhesive reservoirs 16 and 18 are not leaked.
It is stored in. Therefore, the annular grooves 16, 18 and the outer ring outer peripheral side surfaces 51 of the first and second ball bearings 5, 6 are provided.
Although they are not in contact with 2 and 612, they face each other via an extremely thin adhesive and have high adhesive strength. Therefore, the outer rings 52 and 62 of the ball bearings 5 and 6 are formed in the bearing holding holes 84. It is fixed to the peripheral side surface 811 with a substantially large bonding area. Therefore, the holding strength of each ball bearing 5, 6 can be maintained at a sufficiently high level. As a result, the rotation accuracy of the hub 8 and the rotating body is enhanced, and the generation of noise and vibration can be reliably prevented. Moreover, the annular grooves 16 and 18 are provided at the contact positions 5 between the outer ring raceway surfaces 522 and 622 and the balls 53 and 63.
The outer ring press-fit portions 17 and 19 are formed at positions overlapping in the axial direction with respect to the outer ring raceway surfaces 522 and 62.
2 and the balls 53, 63, which are axially displaced from the contact positions 57, 67.
The effect of reducing the load applied to the contact portions 57 and 67 with the contact portions 2 and 622 can be obtained as it is. Therefore, the ball 5
3, 63 can be rolled smoothly, so from this point,
It is possible to sufficiently prevent noise and vibration.

Next, the inner peripheral side surface 83 of the cylindrical portion 83 of the hub 8
The method of fixing the back yoke 9 to the first and the method of processing the inner peripheral side surface 811 of the bearing holding hole 84 will be described. Referring back to FIG. 1, in the spindle motor 1 of the present embodiment, an annular first end covering the upper end of the back yoke 9 is provided on the annular inner end surface that is continuous with the inner peripheral side surface 831 of the cylindrical portion 83 of the hub 8. A tightening portion 85 is formed, and a second annular portion that covers the lower end portion of the back yoke 9 is provided at the opening end side portion of the cylindrical portion 83 of the hub 8.
Is formed. In order to perform such crimping and fixing, for example, the present applicant has disclosed in Japanese Patent Application No. 8-1692.
No. 38, when the hub 8 is manufactured by forging, the first and second caulking portions 85 and 86 are used.
The back yoke 9 is press-fitted into the hub 8 before the hub 8 is finished to the final shape, and the first and second blanks are formed by a forging die. It is enough to crush the blank of No. 2.

When the back yoke 9 is crimped and fixed in this manner, both ends of the annular back yoke 9 can be crimped over the entire circumference inside the rotor 7 (hub 8) without trouble. In addition, since the gap between the hub 8 and the back yoke 9 is completely sealed, it is possible to prevent cutting oil, cleaning liquid, and the like from entering the gap. In addition, hub 8
When the back yoke 9 is caulked and fixed to the
Chuck the inner part of
4 can be subjected to cutting. That is, when the back yoke 9 is fixed to the inside of the hub 8, a die is pressed into the inner periphery of the back yoke 9 at the same time as the forging process for forming the approximate shape of the hub 8.
The inner peripheral surface is plastically deformed according to the mold, and the roundness of the inner diameter is improved. Further, the back yoke 9 is formed by the forging.
Are crimped over the entire circumference to firmly adhere to the hub 8. Back yoke 9 fixed in this way
The inner peripheral surface 811 of the bearing holding hole 84 is subjected to cutting using the inner peripheral surface of the bearing holding hole 84 as a reference surface, so that the step 812 formed in the bearing holding hole 84, the annular groove 16, and the annular groove 16 are formed.
8, and the finishing accuracy of the outer ring press-fitting portions 17, 19 can be improved. Moreover, as long as the inner diameter of the back yoke 9 is the same, even if other shapes and dimensions are different,
There is also an advantage that the hub 8 can be held by the same chuck. Further, the annular grooves 16 and 18 having a small depth dimension can be processed with high accuracy, and the bonding strength between the outer rings 52 and 62 and the bearing holding holes 84 can be further increased.

[Embodiment 2] FIG. 3 is a sectional view showing an example of a shaft rotation type spindle motor to which the present invention is applied. In the spindle motor according to the present embodiment, the same reference numerals are given to parts common to the spindle motor according to the first embodiment, and detailed description will be omitted.

As shown in FIG. 3, the spindle motor 1A of this embodiment has a frame 2A as a fixed member and a rotor 7A rotatably supported by the frame 2A. The frame 2A includes a disc-shaped bottom wall 21A,
A base 25A formed at the center of the bottom wall 21A and having a stepped bearing holding hole 26A at the center;
It comprises a peripheral wall portion 23A rising from the peripheral wall portion of 1A, and an annular flange portion 24A protruding radially outward from the upper edge of the peripheral wall portion 23A. Base 2
The outer peripheral portion of 5A is a stator core mounting portion, where the stator core 4 is fixed. In this example, a step is formed on the outer peripheral portion of the base portion 25A, and the inner peripheral edge portion of the lower end surface of the stator core 4 is held by the step, and the stator core 4 is positioned at a predetermined height with respect to the frame 2A. I have.

The rotor 7A has a rotating shaft 3A inserted into the bearing holding hole 25A, and a hub 8A rotatable with the rotating shaft 3A. The hub 8A includes a disc-shaped top plate portion 85, a first cylindrical portion 86 that falls down from a peripheral portion of the top plate portion 85, and a horizontal portion 87 that projects radially outward from a lower portion of the cylindrical portion 86. , This horizontal part 8
7 and a second cylindrical portion 88 that falls down from the peripheral portion. The rotating shaft 3A and the hub 8A are integrally formed so that the rotating shaft 3A protrudes vertically downward from the center of the top plate portion 85 of the hub 8A.

First and second ball bearings 5 and 6 are fitted on the distal end side and the proximal end side of the rotating shaft 3A, similarly to the spindle motor 1 described in the first embodiment. The inner rings 51, 61 of the ball bearings 5, 6 are fixed to the fixed shaft 3A, and the outer rings 52, 62 are fixed to the inner peripheral side surface 251A of the bearing holding hole 26A. The rotating shaft 3A and the hub 8A are rotatably supported by the frame 2A via the ball bearings 5 and 6.

The second cylindrical portion 88 of the hub 8A surrounds the stator core 4 concentrically, and the drive magnet 10 is fixed to the inner peripheral side surface thereof. The drive magnet 10 and the stator core 4 face each other.

Note that the horizontal portion 87 of the hub 8A is a mounting portion for a magnetic disk or the like, and the rotated object can be rotated by mounting the rotated object on this portion. Also, frame 2
The annular flange portion 24A of A is a mounting portion to the main body side (not shown) of the disk drive.

In the spindle motor 1A of the present embodiment, the first and second ball bearings 5 and 6 are formed with stepped portions 252A formed on the inner peripheral side surface 251A thereof from opposite directions with respect to the bearing holding holes 26A of the frame 2A. And is positioned by the stepped portion 252A. In the first ball bearing 5, the outer race 52
Is in contact with the lower end surface of the step portion 252A, and a preload is applied in the direction shown by the dashed line in the figure. Therefore, the first
In the ball bearing 5 of FIG.
12 and the upper part of the outer raceway surface 522 are in partial contact with each other. In the second ball bearing 6, the upper end surface of the inner ring 61 is attached to the top plate 8 of the hub 8A.
5, and the lower end surface of the outer ring 62 is in contact with the upper end surface of the step 252. Therefore, in the second ball bearing 6, the ball 63 is in a state of being in partial contact with an upper portion of the inner raceway surface 612 and a lower portion of the outer raceway surface 622.

In the spindle motor 1A of this embodiment, the stepped portion 25 of the inner peripheral side surface 251A of the bearing holding hole 26A is formed.
2A from the lower corner 840 to the first ball bearing 5
The annular groove 16 is formed up to a position overlapping in the axial direction with a contact portion 57 (contact position) between the outer raceway surface 522 and the ball 53.
An annular outer ring press-fitting portion 17 is formed on the side opposite to the above.

Further, of the inner peripheral side surface 251A of the bearing holding hole 26A, the outer raceway surface 622 of the second ball bearing 6 and the ball 6
An annular groove 18 is formed up to a position overlapping in the axial direction with respect to a contact portion 67 (contact position) with the annular groove 3, and an annular outer ring press-fit portion 19 is formed on the opposite side of the annular groove 18 from the step portion 252A. Is formed.

In the upper end surface of the outer ring 52 of the first ball bearing 5, the outer peripheral edge portion has a larger chamfer amount, and the lower corner 840 of the step 252A is provided with the annular groove 16.
An adhesive reservoir 810 for receiving an excess adhesive between the outer ring 52 and the outer race 52 of the first ball bearing 5 is formed. Further, at the lower end surface of the outer ring 62 of the second ball bearing 6, the outer peripheral edge portion has a large amount of chamfering like the first ball bearing 5, and the step 252A.
The upper corner 830 has an adhesive reservoir 820 that receives excess adhesive between the annular groove 17 and the outer ring 62 of the second ball bearing 5.

In the spindle motor 1A of this embodiment as well, the corners 830 and 840 of the stepped portion 252A (the connecting portion between the stepped portion and the annular groove) 830 and 840 formed on the inner peripheral side surface 251A of the bearing holding hole 26A. Adhesive reservoir 810, 8
Since the annular groove 20 is formed, the excess adhesive does not leak even if the annular grooves 16 and 18 are made shallow, and the adhesive pool 1
6 and 18. For this reason, although the annular grooves 16 and 18 are not in contact with the outer ring outer peripheral side surfaces 512 and 612 of the first and second ball bearings 5 and 6, they face each other via an extremely thin adhesive. The bonding strength is increased, and the outer rings 52, 62 of the ball bearings 5, 6 are fixed to the inner peripheral side surface 251A of the bearing holding hole 26A with a substantially large bonding area. Therefore, the holding strength of each ball bearing 5, 6 can be maintained at a sufficiently high level. As a result, the hub 8A
And the rotation accuracy of the rotating body is increased, and the generation of noise and vibration can be reliably prevented. Moreover, the annular grooves 16, 18
Are formed at positions overlapping in the axial direction with respect to contact positions 57 and 67 between the outer ring raceway surfaces 522 and 622 and the balls 53 and 63, and the outer ring press-fit portions 17 and 19 are
Contact positions 57, 67 between 2, 622 and balls 53, 63
From Japanese Patent Application Laid-Open No. 3-285545.
No. 5,075,045, the ball 5 is inserted through the outer rings 52, 62 of the ball bearings 5, 6, like the spindle motor disclosed in
Contact portions 5 between 3, 3 and outer raceway surfaces 522, 622
The effect of reducing the load applied to 7, 67 can be obtained as it is. For this reason, the balls 53 and 63 can smoothly roll, and from this point, it is possible to sufficiently prevent noise and vibration.

[0047]

As described above, in the spindle motor according to the present invention, the outer raceway surface of the ball bearing, the ball, and the ball are positioned from the corner of the positioning step of the ball bearing formed on the inner peripheral side surface of the bearing holding hole. An annular groove is formed up to a position overlapping in the axial direction with respect to the contact position, and an annular adhesive reservoir is formed at the corner of the step so that excess adhesive leaks even if the annular groove is made shallow. Instead, it can be accommodated in the adhesive reservoir. Therefore, although the annular groove and the outer peripheral surface of the outer ring are not in contact with each other, they face each other via an extremely thin adhesive, and the bonding strength is increased, and the outer ring is substantially wider than the inner peripheral surface of the hub. It will be fixed with the joint area. For this reason, the holding strength of the ball bearing can be maintained at a sufficiently high level, and as a result, the accuracy of the hub and the driven body can be increased, and the generation of noise and vibration can be reliably prevented.

Further, the annular groove is formed at a position axially overlapping the contact position between the outer raceway surface and the ball, and the outer race press-fit portion is displaced in the axial direction from the contact position between the outer raceway surface and the ball. Therefore, the load applied to the contact position can be reduced. For this reason, the ball can roll smoothly,
From this point, it is possible to sufficiently prevent noise and vibration.

Further, a cylindrical portion having an annular yoke whose both ends are crimped over the entire circumference is formed on the inner peripheral surface of the hub, and the inner peripheral surface of the bearing holding hole is defined with the inner peripheral surface of the annular yoke as a reference surface. When cutting is performed, the dimensional accuracy of the inner peripheral side surface of the bearing holding hole, the outer ring press-fit portion, and the annular groove can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixed shaft type spindle motor according to Embodiment 1 of the present invention.

FIG. 2A is a cross-sectional view showing a peripheral portion of first and second ball bearings in the spindle motor shown in FIG. 1, and FIG. 2B is an enlarged view showing an adhesive pool portion.

FIG. 3 is a cross-sectional view showing a rotary spindle motor according to a second embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1A Spindle motor 2, 2A Frame (fixed side member) 22, 22A Cylindrical protrusion 3 Fixed shaft 3A Rotating shaft 4 Stator core 5 First ball bearing 6 Second ball bearing 51, 61 Inner ring 512, 612 Inner ring track Surface 52, 62 Outer ring 521, 621 Outer side surface of outer ring 522, 622 Outer ring raceway surface 53, 63 Ball 57, 67 Contact portion between ball and outer ring 7, 7A Rotor 8, 8A Hub 84, 26A Bearing holding holes 85, 86 Part 810, 820 Adhesive accumulation part 811, 251A Inner peripheral side surface of bearing holding hole 812, 252A Step part 830, 840 Corner part of step part 9 Annular yoke 901 Inner peripheral surface of annular yoke 16, 18 Annular groove 17, 19 Outer ring Press-fit section

Claims (5)

[Claims] 1. A fixed-side member, a fixed shaft rising from the fixed-side member, a ball bearing fitted into the fixed shaft, and rotatably supported by the fixed shaft via the ball bearing. A spindle motor having a hub, wherein the hub has a bearing holding hole for holding an outer ring of the ball bearing on an inner circumferential surface, wherein the inner circumferential side surface of the bearing holding hole includes the ball bearing in the bearing holding hole. A positioning step portion against which the outer ring end face of the ball bearing abuts when inserted,
An annular groove formed from a corner of the step portion to at least a position axially overlapping a contact position between the outer ring raceway surface of the ball bearing and the ball in the axial direction, and serving as an adhesive portion with the outer ring of the ball bearing; An outer ring press-fit portion formed on the side opposite to the stepped portion with respect to the annular groove, and at a corner of the stepped portion, excess adhesive is provided from between the annular groove and the outer ring of the ball bearing. A spindle motor comprising a ring-shaped adhesive reservoir for receiving. 2. The hub according to claim 1, wherein the hub includes a cylindrical portion provided on an inner peripheral side surface with an annular yoke both ends of which are crimped to the hub over the entire circumference.
A spindle motor formed by cutting an inner peripheral side surface of the bearing holding portion using an inner peripheral surface of the annular yoke as a reference surface. 3. A vehicle comprising: a hub; a rotating shaft extending downward from the hub; a ball bearing fitted to the rotating shaft; and a fixed member holding the ball bearing. A spindle motor having a bearing holding hole for holding an outer ring of the ball bearing on an inner circumferential side surface, wherein the inner circumferential side surface of the bearing holding hole is an outer ring end surface of the ball bearing when the ball bearing is inserted into the bearing holding hole. And a positioning step against which
An annular groove formed from a corner of the step portion to at least a position axially overlapping a contact position between the outer ring raceway surface of the ball bearing and the ball in the axial direction, and serving as an adhesive portion with the outer ring of the ball bearing; An outer ring press-fit portion formed on the side opposite to the stepped portion with respect to the annular groove, and at a corner of the stepped portion, excess adhesive is provided from between the annular groove and the outer ring of the ball bearing. A spindle motor comprising a ring-shaped adhesive reservoir for receiving. 4. The method according to claim 1, wherein
When viewed from the inner peripheral side surface of the outer ring press-fit portion, the annular groove is
A spindle motor having a depth of not more than μm. 5. The method according to claim 1, wherein
A clearance dimension between the bearing holding hole side and the outer ring of the ball bearing in the adhesive reservoir is 100 μm.
m or more.