JP2000134881A - Spindle motor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain, with a simple configuration sufficient assembly accuracy and joint strength of a shaft body 21. SOLUTION: In a shaft-fixing hole 23d of a soft shaft-fitting body 23, a shaft body 21 is fitted and fixed via a hard annular coupling body 24. As a result, the position of the shaft body 21 is controlled, without generating drag or the like along the hard annular coupling body 24, even when a slight error is generated in the positional relationship of perpendicularly or the like when the shaft body 21 is inserted into the shaft fixing hole 23d of the shaft fitting body 23, a smooth and accurate fitting state is set for obtaining high assembling accuracy and joint strength, at the same time, the nearly identical tightening margin is maintained due to the fluctuation of temperature environment, after assembling the shaft body 21 and the annular coupling body 24 which are directly fitted to the shaft body 21 as an equivalent coefficient of linear expansion, and an original firm joined state is maintained satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor having a shaft fixed to a shaft fitting and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a spindle motor used in various devices, a rotating shaft or a fixed shaft is fitted and fixed to a shaft fitting body such as a rotating hub or a fixed frame by means such as press-fitting, shrink fitting or bonding. Have been. At that time, as a metal member constituting a shaft fitting body such as the rotating hub and the fixed frame, a soft and lightweight metal material having good machinability, such as aluminum, is often adopted due to recent demand for reduction in size and weight. You.

[0003]

However, in the case where the shaft fitting body is formed of such a soft metal material having good machinability, when the shaft body is inserted into the shaft fitting body, the two members must be connected to each other. If there is a mounting error in the positional relationship, etc., there may be damage such as galling on the soft shaft fitting body side, and even after assembly, an accuracy error occurs in the squareness between the shaft body and the shaft fitting body. In addition, there is a problem in that the joining strength between the two members is lower than originally intended. further,
A soft, lightweight metal material having good machinability, such as aluminum, generally has a large coefficient of linear expansion, so that it is in a large expanded state particularly in a high-temperature environment. There is also a possibility that a squeeze between the shaft fitting body and the shaft fitting body becomes small and the shaft body comes off.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spindle motor and a method for manufacturing the same, which can obtain sufficient assembly accuracy and joining strength with a simple structure.

[0005]

According to the first aspect of the present invention, there is provided a shaft fitting body made of a first metal member, a shaft fixing hole formed in the shaft fitting body, and A second metal member having a greater hardness than the first metal member is inserted into the shaft fixing hole and fixed to the shaft fitting body, and is relatively rotatable between the shaft body and the shaft body. And a bearing means forming a bearing relationship, wherein an annular connecting body made of a third metal member is fitted and fixed to a shaft fixing hole of the shaft fitting body.
The shaft is fitted and fixed in a center hole of the annular connector, and a third metal member forming the annular connector is a first metal member forming the shaft fitting. A second hardness having a greater hardness than that of the shaft body.
Has a linear expansion coefficient equivalent to that of the metal member.

Further, in the invention according to claim 2, the first metal member according to claim 1 is made of an aluminum-based metal material, and the second and third metal members are made of stainless steel or copper. Or iron-based metal material.

Further, in the invention according to claim 3, the shaft fitting body according to claim 1 comprises a bottomed cylindrical rotating hub that rotates integrally with the shaft body.

Further, in the invention according to claim 4, the shaft fitting body according to claim 1 comprises a fixing member on a fixed frame side, and the shaft body is erected and fixed to the fixed frame.

In the invention according to claim 5, the joining strength of the annular connecting member to the shaft fitting body is set to be larger than the joining strength of the shaft body to the annular connecting member. I have.

Further, in the invention according to claim 6, the bearing means according to claim 1 comprises a dynamic pressure bearing device utilizing a dynamic pressure of a fluid.

In the invention according to claim 7, a shaft fixing hole is formed in the shaft fitting body made of the first metal member, and the shaft body is inserted into the shaft fixing hole, so that the shaft fitting body is formed in the shaft fitting body. And a step of fitting and fixing the shaft fitting, wherein the bearing means constitutes a rotatable bearing relationship with the shaft body. A reinforcing step of fitting and fixing an annular connecting body made of a metal member, and after this reinforcing step, a reference surface processing step of cutting and dimensioning a reference surface of the shaft fitting body with predetermined accuracy, A shaft fitting step of fitting and fixing the shaft to the annular connector, and a first metal member constituting the shaft fitting as the third metal member constituting the annular connector. Has a greater hardness, and constitutes the shaft body And to use a metal material having a second metallic member and the equivalent coefficient of linear expansion.

In the invention according to claim 8, the joining strength of the annular connecting member to the shaft fitting body is set to be higher than the joining strength of the shaft body to the annular connecting member.

According to the first aspect of the present invention, when the shaft body is inserted into the shaft fixing hole of the shaft fitting body, even if there is a slight error in the positional relationship such as a right angle, the shaft body can be used. The position is regulated without generating galling or the like along the rigid annular connection body, and a smooth and high-precision fitting state is achieved, so that good assembly accuracy and joining strength can be obtained. In addition, the shaft and the annular connector directly fitted to the shaft,
Since they have the same linear expansion coefficients, even if the temperature environment after assembling fluctuates, almost the same shimeshiro will be maintained, and the initially strong joint state will be favorably maintained. Has become.

The operation according to the first aspect of the present invention can be remarkably obtained in the specific structure according to the second, third, fourth or sixth aspect of the present invention.

Further, when the annular connecting member is more firmly fixed to the soft shaft fitting body by mechanical joining means as in the invention according to claim 5, the above-mentioned claim 1 is provided. The effect of the invention of the invention is further enhanced.

Further, according to the seventh or eighth aspect of the present invention, the spindle motor according to the first to sixth aspects of the present invention can be easily obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a so-called double-ended shaft rotation type HDD (for driving a hard disk) spindle motor will be described in detail with reference to the drawings.

First, the overall structure of the HDD spindle motor shown in FIG. 1 will be described. The HDD spindle motor includes a stator set 1 as a fixing member and a rotating assembly mounted on the stator set 1 from above in the figure. And a rotor set 2 as a member. The stator set 1 has a frame 11 screwed to a fixed base (not shown), and protrudes in an axial direction (upward in the figure) at a substantially central portion of the frame 11. In this way, the bearing holder 12 made of a relatively large-diameter substantially hollow cylindrical body is integrally formed.

A stator core 13 radially provided with a plurality of salient pole portions is fitted on the outer peripheral wall surface of the bearing holder 12, and a winding 14 is wound around each salient pole portion of the stator core 13. Have been.

On the other hand, a bearing sleeve 15 made of a substantially hollow cylindrical member having a relatively small diameter, which constitutes a dynamic pressure bearing device, is fitted on the inner peripheral wall surface of the bearing holder 12. A rotatable shaft 21 that constitutes the shaft of the rotor set 2 is rotatably supported in the hollow hole portion provided in the above. That is, the inner peripheral wall surface of the center hole penetratingly formed in the central portion of the bearing sleeve 15 and the outer peripheral wall surface of the rotary shaft 21 are circumferentially formed through a narrow gap of several μm to several tens μm in the radial direction. The radial dynamic pressure bearing portions RB are formed by facing each other and forming these opposing wall surfaces on the radial dynamic pressure surface.

A predetermined lubricating fluid such as oil, magnetic fluid, air or the like is continuously injected and filled into the narrow gap forming the radial dynamic pressure bearing portion RB. The lubricating fluid is pressurized by the pumping action at the time of rotation of a spiral-shaped dynamic pressure generating groove (not shown) formed on at least one side of the opposed radial dynamic pressure surfaces, and a dynamic pressure is generated. The rotating shaft 21 floats in the radial direction and is supported by the generated dynamic pressure.

Further, a disc-shaped thrust plate 16 is in close contact with the opening at the lower end side in the figure of the bearing holder 12 so as to close the opening. On the other hand, an annular thrust ring 22 is provided on the lower end of the rotary shaft 21 in the drawing so as to face the thrust plate 16 in the axial direction.
The lower end surfaces of the rotating shaft 21 and the thrust ring 22 are axially inserted through a narrow gap of several μm to several tens μm with respect to the inner end surface (the upper end surface in the drawing) of the thrust plate 16. The arrangement is face-to-face. The thrust plate 16, the rotating shaft 21, and the thrust ring 22 have opposing surfaces formed on a thrust dynamic pressure surface, thereby forming a thrust dynamic pressure bearing portion SB.

A predetermined lubricating fluid made of oil, magnetic fluid, air, or the like is continuously connected to the radial dynamic pressure bearing portion RB in the narrow gap forming the thrust dynamic pressure bearing portion SB. The lubricating fluid is pressurized by a pumping action during rotation of a spiral-shaped dynamic pressure generating groove (not shown) formed on at least one of the opposed thrust dynamic pressure surfaces, which is filled and filled, and the lubricating fluid is increased in pressure and moved. Pressure is generated, and the rotating shaft 21 floats in the thrust direction and is supported by the dynamic pressure generated in the lubricating fluid.

On the other hand, a rotating hub 23 as a shaft fitting body for supporting a predetermined recording medium (not shown) is provided at the upper end in the drawing, which is the opposite end of the rotating shaft 21. 24, it is fitted and fixed. The rotating hub 23 has a substantially cylindrical body 23a on which a recording medium such as a magnetic disk is mounted on an outer peripheral portion.
A drive magnet 23c is annularly mounted on an inner peripheral wall surface of the lower end opening portion of the body portion 23a via a back yoke 23b. The driving magnet 23c is disposed close to the outer peripheral surface of the salient pole portion of the stator core 13 so as to circumferentially oppose the driving magnet 23c.

The rotary hub 23 as the shaft fitting body is made of aluminum or an alloy thereof as a first metal member, and a relatively large diameter shaft is provided at the center of the upper end surface of the body 23a in the figure. The fixing hole 23d is formed so as to penetrate in the axial direction. And this shaft fixing hole 2
3d, the above-described annular connector 24 is fitted and fixed by press-fitting, shrink fitting, bonding, or the like, and the upper end portion of the rotary shaft 21 shown in the figure is fitted in the center hole of the annular connector 24. It is fixed. At this time, on the outer peripheral wall surface of the annular connector 24, a mechanical joining means including a fitting uneven surface such as a knurl is formed.
4 is fixed to the rotary hub 23 side more firmly than the shaft side.

Further, the rotating shaft 21 and the annular connector 24
Are formed of a second metal member and a third metal member having the same quality, and specifically, a stainless steel (SUS) -based, copper-based, or other iron-based metal material is employed. That is, the metal member (third metal member) constituting the annular connector 24 has a higher hardness than aluminum or its alloy (first metal member) constituting the rotary hub 23. Further, a member having a linear expansion coefficient equivalent to that of the metal member (second metal member) constituting the rotating shaft 21 is employed.

Further, the annular connecting member 24 and the rotary hub 23
Between the rotating shaft 21 and the annular connecting body 24.
The joining strength between the annular connecting body 24 and the rotary hub 23 is also increased by the mechanical joining means using the shimeshiro between the rotating shaft 21 and the annular connecting body 24. The connection relationship is larger than the bonding strength.

Next, an embodiment of a manufacturing method for fitting and fixing the rotary hub 23 and the rotary shaft 21 of the spindle motor according to such an embodiment will be described. Rotating hub 23
When the rotating shaft 21 is fitted on the side, first, a reinforcing step of fitting and fixing the annular connecting body 24 into the shaft fixing hole 23d of the rotating hub 23 is performed, and the shaft fixing hole 2 of the soft rotating hub 23 is formed.
3d is reinforced by a rigid annular connector 24.

Next, after the reinforcing step, a reference surface processing step of cutting the outer peripheral surface of the trunk portion 23a of the rotary hub 23, that is, a reference surface on which a recording medium such as a magnetic disk is mounted, with a predetermined accuracy is performed. Then, predetermined dimensions are set.

Thereafter, a shaft fitting step of inserting the rotating shaft 21 into the hard annular connecting body 24 is performed. At this time, since the annular connecting body 24 is made of a hard material (third metal member), when the shaft fitting step is set, a right angle or the like between the rotating hub 23 and the rotating shaft 21 is set. Even if there is some error in the positional relationship, the rotating shaft 21 is not
4 is slid along the inner peripheral wall surface, and the position is regulated to a regular position without generating galling or the like. As a result, the rotating shaft 21 is smoothly and precisely fitted to the rotating hub 23 side, and good assembly accuracy and joining strength can be easily obtained.

For example, FIG. 2 shows the result of actually mounting a recording medium (magnetic disk) on the rotating hub 23 and measuring the amount of rotational vibration (vertical axis). First, this figure (b)
In the conventional product shown in (1), each sample (horizontal axis)
There was a relatively large variation between them, and there was a case where a large rotational runout of 10 μm or more occurred. On the other hand, in the case of the present invention in which the rotary shaft 21 is fitted and fixed to the rotary hub 23 using the annular connector (SUS430) 24, as shown in FIG. The amount was reduced to about 1/3 of the above-mentioned conventional product, and it was found that the variation among the sample products was extremely small.

FIG. 3 shows the relationship between the shimeshiro (horizontal axis) and the pull-out strength (vertical axis) of the shaft body at normal temperature (23 ° C.) for each of the A line and the B line. , A
The wire is connected to the rotary hub 23 with an annular connector (SUS43).
0) This is the case of the present invention in which the rotating shaft 21 is fitted and fixed by using 24, and the B line directly fits the rotating shaft 21 to the rotating hub 23 without using the annular connecting body 24. This is the case of the conventional product fixed. As is clear from this figure, even if the same shimeshiro is used, when the annular connector 24 according to the present invention is used, a shaft fitting strength approximately twice as large as that of the related art can be obtained.

The rotation shaft 21 and the rotation shaft 21
And the annular connecting body 24 that directly fits into the two members have substantially the same linear expansion coefficient, so that the two members are maintained in substantially the same shrinking state even when the temperature environment changes after assembly. As a result, the initial strong bonding state is favorably maintained.

At this time, a mechanical joining means, that is, a large squeeze is provided between the soft rotating hub 23 and the annular connector 24, and a fitting uneven surface such as a knurl is provided. The joined state between the two members 23 and 24 is also firmly maintained.

Next, an embodiment in which the present invention is applied to a so-called both-end shaft fixed type HDD spindle motor will be described in detail with reference to FIG. First, the HDD shown in FIG.
The overall structure of the spindle motor will be described.
The spindle motor has a stator set 3 as a fixing member.
And a rotor set 4 as a rotating member assembled to the stator set 3 from above in the figure. The stator set 3 has a fixed frame 31 made of substantially dish-shaped aluminum or an alloy thereof, which is screwed to a fixed base (not shown).

At a substantially central portion of the fixed frame 31,
A substantially hollow cylindrical support holder 32 made of a first metal member constituting the shaft fitting body is attached, and a stator core 33 having a plurality of salient poles in a radial shape is fitted on the outer periphery of the support holder 32. In addition, a winding 34 is wound around each salient pole portion of the stator core 33.

A cylindrical hollow portion on the center side of the support holder 32 as the shaft fitting body is formed in a shaft fixing hole 32a, and an inner peripheral wall surface of the shaft fixing hole 32a is formed by a third metal member. A fixed shaft (shaft) 36 made of a second metal member is erected via a ring-shaped annular connecting member 35 so as to extend upward in the drawing by press-fitting, shrink fitting, bonding, or the like. I have.

At this time, the support holder 32 as the shaft fitting body is made of the same aluminum or its alloy (first metal member) as the fixed frame 31, and
The metal member (second metal member) forming the fixed shaft 36 and the metal member (third metal member) forming the annular connector 35 are described.
Metal member) is a metal member of the same quality,
More specifically, it is formed from stainless steel (SUS430), but other copper-based metals or other iron-based metal materials can also be used. That is, the metal member (third metal member) forming the annular connector 35 has a higher hardness than aluminum or its alloy (first metal member) forming the support holder 32. At the same time, it has a linear expansion coefficient equivalent to that of the metal member (second metal member) constituting the fixed shaft 36.

At this time, on the outer peripheral wall surface of the annular connecting member 35, mechanical joining means such as a knurl is formed, and the annular connecting member 35 is pivoted with respect to the support holder 32 side. It is in a stronger fixed state than the side. In addition, the squeeze between the annular connector 35 and the support holder 32 is set to be larger than the shimeshiro between the fixed shaft 36 and the annular connector 35, and the annular connector 35 and the support holder 32, the joint strength is larger than the joint strength between the fixed shaft 36 and the annular connector 35.

On the other hand, in the rotor set 4, a rotary hub 41 for supporting a recording medium such as a magnetic disk (not shown) is fixed to the outer peripheral side of a bearing sleeve 42 constituting a bearing member. The rotary hub 41 has a substantially cylindrical body 41a for mounting a recording medium on the outer periphery, and a drive magnet 41c is formed annularly on the inner periphery of the body 41a via a back yoke 41b. It is installed. The drive magnet 41c is disposed in proximity to the outer peripheral end surface of each salient pole portion of the stator core 33 so as to annularly face the aforementioned drive magnet.

A radial dynamic pressure surface is formed on the inner peripheral surface of the center hole formed through the center of the bearing sleeve 42 and on the outer peripheral surface of the fixed shaft 36, and both radial dynamic pressure surfaces are formed. Several μm to several tens μm in the radial direction
The radial dynamic pressure bearing portion RB is formed by being circumferentially opposed to each other with the narrow gap therebetween. A predetermined lubricating fluid such as oil, magnetic fluid, or air is continuously injected and filled into the narrow gap forming the radial dynamic pressure bearing portion RB. The lubricating fluid is pressurized by the pumping action at the time of rotation of a spiral-shaped dynamic pressure generating groove (not shown) formed on at least one side of both radial dynamic pressure surfaces to generate a dynamic pressure, which is generated in the lubricating fluid. The bearing sleeve 42 and the rotary hub 41 float in the radial direction and are supported by the applied dynamic pressure.

A disk-shaped thrust plate (annular thrust plate) 37 is press-fitted or shrink-fitted and fixed to the distal end portion (upper end portion in the figure) of the fixed shaft 36. . This thrust plate 37
The thrust dynamic pressure surface is disposed so as to be accommodated in a cylindrical recess formed in the above-described center portion of the bearing sleeve 42 on the upper side in the drawing, and provided on the bottom wall surface of the recess of the bearing sleeve 42. Against the thrust plate 3
The lower thrust dynamic pressure bearing portion SBa is configured by the thrust dynamic pressure surface provided on the lower surface side of FIG.

Further, a disk-shaped counter plate (thrust plate) 43 constituting a thrust bearing member is provided so as to approach the upper surface of the thrust plate 37 in the figure.
Are mounted so as to cover the recessed portion of the bearing sleeve 42, and a thrust dynamic pressure surface provided on the lower surface side of the counter plate 43 in the drawing and a thrust dynamic pressure surface provided on the upper surface side of the thrust plate 37 in the drawing. The upper surface of the thrust dynamic pressure bearing portion SBb is constituted by the pressure surface.

That is, in each of a pair of thrust dynamic pressure bearing portions SBa, SBb arranged adjacent to both axial end portions of the thrust plate 37, each of the thrust dynamic pressure bearing portions SBa and SBb on the bearing sleeve 42 or the counter plate 43 side is used. The thrust dynamic pressure surface and the two thrust dynamic pressure surfaces on the thrust plate 37 side are arranged facing each other via a narrow gap of several μm to several tens μm in the axial direction. The narrow gaps between the two thrust dynamic pressure bearing portions SBa and SBb are communicated with each other through a passage provided on the outer peripheral side of the thrust plate 43, and the continuous bearing space contains oil, magnetic fluid, or the like. The predetermined lubricating fluid consisting of is continuously injected and filled.

Each of the thrust dynamic pressure surfaces provided on both axial end surfaces of the thrust plate 43 includes:
A number of herringbone shaped thrust dynamic pressure generating grooves (not shown) are annularly arranged in parallel so that the lubricating fluid is pressurized by the pumping action of both thrust dynamic pressure generating grooves during rotation to generate dynamic pressure. The bearing sleeve 42 and the rotary hub 41 are axially supported in the thrust direction by the dynamic pressure generated in the lubricating fluid.

In such a fixed shaft type spindle motor, the same operation and effects as those of the above-described embodiment can be obtained with respect to the fixed shaft 36, the annular connecting member 35 and the support holder 32.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the present invention can be similarly applied to a spindle motor used other than the HDD motor described above.

[0049]

As described above, according to the present invention, when a shaft is inserted by inserting and fixing the shaft into a shaft fixing hole of a soft shaft fitting through a hard annular connecting member. Even if there is some error in the positional relationship such as the perpendicularity, the position of the shaft body is regulated without generating galling or the like along the hard annular coupling body, and a good state of smooth and high-precision fitting is obtained. In addition to obtaining assembling accuracy and joining strength, the shaft body and the annular coupling body directly fitted to the shaft body have the same linear expansion coefficient, and the initial strong Since the configuration is such that the bonding state is maintained well, sufficient assembly accuracy and bonding strength can be easily obtained with a simple configuration, and the reliability and productivity of the spindle motor can be improved.

Further, if the annular coupling body is more firmly fixed to the soft shaft fitting body as in the present invention, the above-mentioned effects can be more reliably obtained.

[0051]

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing an outline of a spindle motor according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing the amount of rotation fluctuation of a recording medium (magnetic disk), wherein FIG. 2A shows a case of a spindle motor according to the present invention, and FIG. 2B shows a case of a conventional spindle motor. It is shown.

FIG. 3 is a diagram showing the removal strength of a shaft body.

FIG. 4 is a cross-sectional explanatory view showing an outline of a spindle motor according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Rotating shaft 23 Rotating hub (shaft fitting) 23d Shaft fixing hole 24 Annular connector 32 Support holder 32a Shaft fixing hole 35 Annular connector 36 Fixed shaft

Continued on the front page (72) Inventor Shinji Ota 5329 Shimosuwa-cho, Suwa-gun, Nagano Prefecture F-term in Sankyo Seiki Seisakusho Co., Ltd. (reference) 5H615 AA01 BB01 BB14 PP01 PP02 PP10 PP13 PP24 PP25 PP28 QQ02 QQ19 SS19 TT05 TT15 TT16 TT16 5H621 BB07 GA04 HH01 JK07 JK17 JK19

Claims (8)

[Claims] 1. A shaft fitting body made of a first metal member, a shaft fixing hole formed in the shaft fitting body, and a second metal member having a higher hardness than the first metal member. A spindle motor, comprising: a shaft fixed to the shaft fitting body by being inserted and fitted into a shaft fixing hole; and bearing means for forming a relative rotatable bearing relationship with the shaft. An annular connector made of a third metal member is fitted and fixed in a shaft fixing hole of the shaft fitting body, and the shaft is fitted and fixed in a center hole of the annular connector. The third metal member that forms the annular connection body has a higher hardness than the first metal member that forms the shaft fitting body, and the second metal member that forms the shaft body Characterized by having a linear expansion coefficient equivalent to that of Motor. 2. The method according to claim 1, wherein the first metal member is made of an aluminum-based metal material, and the second and third metal members are made of stainless steel, copper, or another iron-based metal material. The spindle motor according to claim 1, wherein 3. The spindle motor according to claim 1, wherein the shaft fitting body comprises a bottomed cylindrical rotating hub that rotates integrally with the shaft body. 4. The spindle motor according to claim 1, wherein the shaft fitting body is formed of a fixing member on a fixed frame side, and the shaft body is fixed to the fixed frame. 5. A mechanical joining means for providing a joining strength of the annular connecting member to the shaft fitting body larger than a joining strength of the shaft body to the annular connecting member. Spindle motor. 6. The spindle motor according to claim 1, wherein said bearing means comprises a dynamic pressure bearing device utilizing a dynamic pressure of a fluid. 7. A step of forming a shaft fixing hole in a shaft fitting body made of a first metal member and inserting the shaft body into the shaft fixing hole to fit and fix the shaft body to the shaft fitting body. ,
A method of manufacturing a spindle motor, wherein a bearing relationship is established between the shaft body and the shaft body so as to be rotatable relative to the shaft body. An annular connecting body made of a third metal member is provided in a shaft fixing hole of the shaft fitting body. A reinforcing step of fitting and fixing, after this reinforcing step, a reference surface processing step of cutting and dimensioning the reference surface of the shaft fitting body with predetermined accuracy, and a shaft body with respect to the annular connection body. A shaft fitting step of fitting and fixing, wherein the third metal member forming the annular coupling body has a higher hardness than the first metal member forming the shaft fitting body, and A method of manufacturing a spindle motor, wherein a metal material having a linear expansion coefficient equivalent to that of a second metal member constituting the shaft body is used. 8. A mechanical joining means for setting the joining strength of the annular connecting member to the shaft fitting body larger than the joining strength of the shaft body to the annular connecting member by mechanical joining means. A manufacturing method of the spindle motor described in the above.