JPH11206062A - Fluid dynamic pressure bearing electrical machine and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely make the rotary center of a hub coincide with the center of a shaft. SOLUTION: The electrical machine is constituted of a shaft 2, a stator core 3, a rotary cylindrical body surrounding the stator core 3 and the shaft 2 and a fluid dynamic pressure bearing 6 formed between the inner peripheral face of the rotary cylindrical body and the outer peripheral face of the shaft 2. The stator core 3 is provided in an almost center part in the center direction of the shaft 2. The inner peripheral face of the rotary cylindrical body is constituted of an upper sleeve 5a, facing opposite the outer peripheral face of the shaft 2 above the stator core 3, a lower sleeve 5b facing the outer peripheral face of the shaft 2 and the cylindrical hub 4 connecting the upper and lower sleeves 5a and 5b. The fluid dynamic pressure bearing 6 is formed between the inner peripheral face of the upper and lower sleeves 5a and 5b and the outer peripheral face of the shaft 2. The outer diameter size of the upper sleeve 5a or the lower sleeve 5b is set, so that the gap of a prescribed size is formed between the outer peripheral face and the inner peripheral face of the hub 4 and adhesive is inserted into the gap. Thus, the lower sleeve hub 5b is fixed to the hub 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid dynamic bearing motor suitable for use in a hard disk drive (HDD), which is a large-capacity external storage device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A motor 100 for a magnetic disk drive having a fluid dynamic bearing described in U.S. Pat. No. 5,283,491 as shown in FIG. 9 is conventionally known. The electric motor 100 includes a shaft 101 integrally fixed to a base B, a stator core 102 concentrically fixed to the shaft 101, and a stator core 10
A hub 103 concentrically fitted with a predetermined gap between the hub 103 and the outer peripheral surface of the shaft 101 and the outer peripheral surface of the shaft 101. Further, a radial bearing 200 utilizing dynamic pressure of fluid (air) is provided.

The above-mentioned stator core 102 has an electromagnetic coil 1
In the meantime, an annular yoke 105 is mounted on the inner peripheral surface at the center of the hub 103 in the circumferential direction, and a cylindrical magnet 106 is mounted on the inner peripheral surface of the yoke 105. Have been. And the electromagnetic coil 1
04 generates a magnetic field by passing a DC current through the hub 10.
3 rotates around the shaft 101.

[0004] The radial bearing 200 is provided with a hub 1.
03, and a pair of sleeves 201 press-fitted at both ends thereof, and an annular gap 2 formed between the inner peripheral surface of the sleeve 201 and the outer peripheral surface of the shaft 101 and having a small radial dimension.
02, the rotating hub 103 is introduced into the annular gap 202, and is supported by the fluid 300 pressurized by the rotation of the hub 103.

[0005]

In the above-described electric motor 100 for rotating the magnetic disk, the positional relationship between the track of the rotating magnetic disk and the magnetic head must be secured on the order of microns. , Hub 1
The center of rotation of the shaft 03 must coincide with the axis of the shaft 101 with high accuracy. The hub 103 is fitted on the shaft 101 via a pair of upper and lower sleeves 201, and the dimensional accuracy of the upper and lower hubs 103 and the sleeve 201 is directly reflected on the rotation center of the hub 103. In some cases, the center of rotation of the hub 103 cannot be aligned with the axis of the shaft 101 due to a dimensional error in manufacturing the shaft 201. If the center of rotation of the hub 103 and the axis of the shaft 101 do not coincide with each other, there occurs a problem that the disk cannot be normally accessed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to make the center of rotation of the hub surely coincide with the axis of the shaft. It is an object of the present invention to provide a fluid dynamic bearing motor that realizes highly accessible access and a method of manufacturing the same.

[0007]

According to the first aspect of the present invention,
A fixed shaft, a stator core fixed concentrically to the fixed shaft and wound with an electromagnetic coil, a cylindrical rotating body surrounding the stator core and the fixed shaft concentrically and apart from each other, and an inner peripheral surface of the cylindrical rotating body And a radial bearing utilizing a fluid dynamic pressure generated in a fluid filled in a minute space formed between the fixed shaft and the outer peripheral surface of the fixed shaft. The cylindrical rotating body is provided at a substantially central portion in the axial direction of the shaft, and the cylindrical rotating body has an upper sleeve whose inner circumferential surface faces the outer circumferential surface of the fixed shaft above the stator core, and a lower portion which faces the outer circumferential surface of the lower fixed shaft. A sleeve, and a cylindrical hub having the upper and lower sleeves, wherein the radial bearing is provided between an inner peripheral surface of the upper and lower sleeves and an outer peripheral surface of the fixed shaft. At least one of the upper sleeve and the lower sleeve is formed separately from the hub, and is formed so that a gap of a predetermined dimension is formed between the outer peripheral surface and the inner peripheral surface of the hub. It is characterized in that a diameter is set and the adhesive is fixed in a gap between the separate sleeve and the hub by interposing an adhesive.

According to the present invention, the hub is supported at two points by the radial bearings of the upper sleeve and the lower sleeve provided at the upper and lower ends of the hub with respect to the fixed shaft having the stator core at the center. As a result, the supported state of the hub with respect to the fixed shaft is stabilized, whereby the hub rotates in a state where it is unlikely to oscillate in the radial direction.

Since a gap is provided between the separate sleeve and the hub, and the adhesive is interposed in the gap, the separate sleeve and the hub are integrated with each other. It is possible to make the axis of the separate sleeve concentric with the axis of the other sleeve by radially pressing the hub and finely adjusting its position with respect to the fixed shaft before it solidifies. The hub is prevented from being inclined with respect to the fixed shaft.

Further, since the axis of the hub coincides with the axis of the fixed shaft due to the fine adjustment described above, the motor may be, for example, an HD.
In the case of D, the rotating disk mounted on the hub is concentric with the fixed axis and rotates about the fixed axis on the same plane, so that the correct positional relationship between the track of the disk and the magnetic head is ensured. Secured and erroneous access is prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, at least a portion of the fixed shaft above the stator core constitutes a thrust bearing utilizing fluid dynamic pressure, and a thrust plate concentric with the fixed shaft. Is provided.

According to the present invention, the axial movement of the hub with respect to the fixed shaft is regulated by the presence of the thrust bearing, and the rotation of the hub in the same space is reliably ensured. Since the thrust bearing uses fluid dynamic pressure, the hub rotates smoothly and no unpleasant noise is generated.

According to a third aspect of the present invention, there is provided a method of manufacturing the fluid dynamic bearing motor according to the first aspect, wherein a fixed shaft having the stator core is fitted to the upper or lower sleeve. A shaft fitting step, a sleeve fitting step of fitting a separate sleeve to the hub via an adhesive to adjust the sleeve coaxially, and an adhesive solidifying step of solidifying the adhesive; A dynamic pressure fluid filling step of filling the radial bearing with a fluid for generating dynamic pressure.

According to the present invention, the upper or lower sleeve is fitted to the fixed shaft in the fixed shaft fitting step, so that the hub is mounted on the fixed shaft in a cantilever state, and the hub is fixed in the next sleeve fitting step. The hub having a pair of sleeves is temporarily attached to the fixed shaft by fitting a separate sleeve provided with an adhesive to the shaft, and further, a separate sleeve is attached to the fixed shaft in the adhesive solidification step. After performing fine adjustment by pressing in the direction to match the axis of each sleeve, a predetermined gap was formed between the outer peripheral surface of each sleeve and the inner peripheral surface of the fixed shaft by solidifying the adhesive. In this state, the hub is mounted around the fixed shaft. Then, a predetermined fluid is injected into the gap in the last dynamic pressure fluid injection step to complete the electric motor.

In the above-mentioned adhesive solidifying step, the axis of one sleeve and the axis of the other sleeve are concentric by fine adjustment of pressing the hub in a radial direction before the adhesive is solidified. The hub is prevented from being inclined with respect to the fixed shaft. Therefore, when the electric motor is for HDD, for example, the disk mounted on the hub and rotating is concentric with the fixed axis and rotates about the fixed axis on the same plane. The positional relationship is ensured, and erroneous access is prevented.

According to a fourth aspect of the present invention, there is provided a method of manufacturing the fluid dynamic bearing motor according to the second aspect, wherein the fixed shaft having the stator core is fitted to the upper or lower sleeve. A fitting step, a thrust plate mounting step of mounting and fixing the thrust plate to a portion corresponding to the other sleeve of the fixed shaft, and a separate sleeve fitted to the hub via an adhesive with the other sleeve. It comprises a sleeve fitting step of adjusting coaxially, an adhesive solidification step of solidifying the adhesive, and a dynamic pressure fluid filling step of filling the radial bearing and the thrust bearing with a fluid for generating dynamic pressure. Things.

According to the present invention, in the thrust plate mounting step, the thrust plate is mounted on the fixed shaft, and the motor obtained thereby is in a state where the movement of the hub in the thrust direction is restricted. The rotation in the space is reliably ensured.

The invention according to claim 5 is the invention according to claim 3 or 4.
The method of manufacturing a fluid dynamic bearing motor according to claim 1, wherein the sleeve fitting step includes: fitting the separate sleeve into a hub; and abut a fixed shaft on an inner peripheral surface of the other sleeve. In this state, a separate sleeve is pressed against a fixed shaft to adjust it coaxially with the other sleeve.

According to the present invention, after each sleeve is fitted inside the hub in the fitting process, whether or not the hub is concentric with the fixed shaft is measured in the adjusting process by using a predetermined measuring means. Is not concentric with the fixed shaft, the sleeve and the hub are adjusted concentrically by pressing the hub in a direction perpendicular to the fixed shaft while measuring the concentricity.

[0020]

FIG. 1 is an exploded perspective view showing an embodiment of a fluid dynamic bearing motor according to the present invention, and FIG. 2 is an assembled perspective view thereof. FIG. 3 is a sectional view taken along the line AA in FIG.
It is a line sectional view. As shown in these figures, the motor 1
Is a shaft (fixed shaft) 2 erected on a base B made of a frame of a hard disk drive or the like, and a stator core 3 mounted concentrically at substantially the center of the shaft 2.
And a cylindrical hub 4 surrounding the stator core 3 and the upper and lower sides of the shaft 2, and the shaft 2 is fitted in the hub 4 vertically and concentrically with the shaft 2.
And a fluid formed on a pair of cylindrical sleeves 5 (upper sleeve (one sleeve) 5 a and lower sleeve (other sleeve) 5 b) supporting the inner and outer peripheral surfaces of the sleeve 5 and the shaft 2. It has a basic configuration including a dynamic pressure bearing 6. The sleeve 5 has an insertion hole 51 through which the shaft 2 is inserted.

The shaft 2 has a threaded portion 21 fixed to the base B by being screwed and fastened to a screw hole B1 threaded in the base B, and an upper portion of the threaded portion 21 and a lower portion. Lower loose fitting portion 2 loosely fitted into insertion hole 51 of sleeve 5b
2 and a stator core supporting portion 23 formed above the lower loose fitting portion 22 and to which the stator core 3 is fixed.
An upper loose fitting portion 24 formed above the stator core supporting portion 23 and loosely fitted into the through hole 51 of the upper sleeve 5a; and a head 25 formed above the upper loose fitting portion 24. It has. In the present embodiment, the diameter of the stator core supporting portion 23 is set to be larger than the diameter of the lower loose fitting portion 22, the upper loose fitting portion 24, and the head 25.

The inner diameter of the insertion hole 51 of each of the sleeves 5 is set slightly larger than the outer diameter of each of the loose fitting portions 22 and 24 of the shaft 2.
An annular space 52 having a gap of several μm is formed between the outer peripheral surface of the sleeve 24 and the inner peripheral surface of the sleeve 5. Lubricating oil, which is one element of the fluid dynamic pressure bearing 6, is loaded into the annular space 52.

The lower loose fitting portion 22 has a constricted portion 26 whose upper and lower ends are tapered.
6, a taper seal portion 53 is formed between the outer peripheral surface of the lower sleeve 5b and the inner peripheral surface of the lower sleeve 5b. ing. Similarly, a similar constricted portion 26 is formed at the lower end of the upper loose fitting portion 24, and a tapered seal portion 53 is also formed at this portion.

Further, the shaft 2 has a thrust plate 27 constituting a thrust bearing integrally mounted on the upper part of the upper loose fitting portion 24. The thrust plate 27 is formed in a disk shape concentric with the shaft 2, and is fixed to the shaft 2 by being pressed into the upper loose fitting portion 24 from the head 25 side.

In the present embodiment, the upper sleeve 5a is formed separately from the hub 4, and is fitted into the upper portion of the hub 4 by press-fitting so that the upper sleeve 5a is formed.
Are integrally attached to the hub 4. The upper sleeve 5a has a first wide-diameter portion 54 on which the thrust plate 27 is mounted above the insertion hole 51, and a second wide-diameter portion 55 provided above the first wide-diameter portion 54. Yes,
The first wide-diameter portion 54 accommodates the thrust plate 27, and the second wide-diameter portion 55 is provided with a thrust bush 56 that defines the upper end of the thrust bearing.

A through hole 56a having an inner diameter larger than the outer diameter of the shaft 2 is formed in the center of the thrust bush 56, whereby the thrust bush 56 is mounted on the second wide diameter portion 55. In this state, the head 25 of the shaft 2 projects slightly outside from the through hole 56a.

The first wide-diameter portion 54 is mounted on the thrust plate 27 with the thrust plate 27 fitted therein.
Between the upper surface of the thrust bush 56, the outer peripheral surface of the thrust plate 27 and the inner peripheral surface of the first wide-diameter portion 54, and the lower surface of the thrust plate 27 and the first wide-diameter portion 5
Gaps 5 each having a minute dimension (several μm) between the lower surface 4 and the lower surface 4
4a are formed so that these gaps 5 are formed.
4a is filled with lubricating oil to form a thrust bearing.

The thrust bush 56 has a through hole 56.
A tapered seal portion 53 is formed at the lower end of the tapered portion a so that the lubricating oil held in the gap 54a is prevented from leaking to the outside by the buffer function of the tapered seal portion 53.

The stator core 3 includes a stator coil 3
1, a cylindrical rotor magnet 41 is disposed on the inner peripheral surface of the hub 4, and a DC current is supplied to the stator coil 31 to form a magnetic field. Rotate around the shaft 2. The rotor magnet 41 and the hub 4
An annular yoke 42 serving as a magnetic flux path between the inner yoke 42 and the inner circumferential surface of the yoke 42
Is interposed.

The outer diameter of the lower sleeve 5b is set to be several tens of μm smaller than the inner diameter of the hub 4 so that the lower sleeve 5b is in contact with the inner peripheral surface of the hub 4 with the lower sleeve 5b fitted inside the hub 4. An annular adhesive filling space 57 is formed therebetween. Then, the lower sleeve 5b with the adhesive applied to the outer peripheral surface is fitted into the hub 4, so that the lower sleeve 5b is attached to the hub 4 via the adhesive.
It is set to be in a state of being attached to.

In the present invention, before the adhesive 7 is solidified, the axis of the lower sleeve 5b is adjusted to be concentric with the axis of the upper sleeve 5a, and then the adhesive 7 is subjected to a solidifying treatment. Thereby, the electric motor 1 is formed.

In the present embodiment, an epoxy resin adhesive is used as the adhesive 7. Epoxy resin-based adhesives are soluble prepolymers containing two or more epoxy groups. Solidification is completed in a few hours at room temperature when a polyamine or the like as a curing agent is added, and in a few minutes when heated. Also, there is almost no change in capacity, and it is excellent for joining the lower sleeve 5b and the hub 4.

The motor 1 includes, as the fluid dynamic bearing 6, an upper radial bearing 61 formed between the inner peripheral surface of the insertion hole 51 of the upper sleeve 5a and the outer peripheral surface of the upper loose fitting portion 24, and a lower sleeve. The lower radial bearing 62 formed in the insertion hole 51 of the upper sleeve 5a, the upper surface of the first wide diameter portion 54 of the upper sleeve 5a, the lower surface of the thrust plate 27, the lower surface of the thrust bush 56, and the thrust plate 27
And a thrust bearing 63 formed between the upper surface and the upper surface. Each of these fluid dynamic pressure bearings 6 relatively bears the shaft 2 using dynamic pressure caused by fluid (lubricating oil) moving in a predetermined direction induced by rotation of the hub 4. In addition, since there is no direct contact between metals, frictional resistance is extremely small as compared with a normal bearing, rotation is smooth, noise is unlikely to occur, and application to the HDD motor 1 is suitable. Things.

FIG. 4 is a partially cutaway perspective view showing one embodiment of the radial bearings 61 and 62 using a fluid dynamic pressure. As shown in this figure, the radial bearing 6
Reference numerals 1 and 62 denote a dynamic pressure generating groove 64 which is formed in the inner peripheral surface of the insertion hole 51 of the sleeve 5 (upper and lower sleeves 5a and 5b) and extends obliquely in the vertical direction, and the shaft 2 (the loose fitting portions 22 and 24).
And the lubricating oil O injected into the annular space 52 between the outer peripheral surface of the sleeve 5 and the inner peripheral surface of the sleeve 5.

The above-mentioned dynamic pressure generating groove 64 is shaped so as to have a “U” shape in which the central portion is bent leftward toward the inner peripheral surface of the insertion hole 51. A plurality of such “<”-shaped dynamic pressure generating grooves 64 are formed at equal pitches on the inner peripheral surface of the insertion hole 51.

Therefore, by rotating the sleeve 5 clockwise around the shaft 2 as shown by the arrow, the lubricating oil O is guided by the "-"-shaped dynamic pressure generating groove 64 and Is generated, and the dynamic pressure at this time causes the inner peripheral surface of the sleeve 5 to float from the outer peripheral surface of the shaft 2 via the lubricating oil O, and the lubricating oil O serves as a bearing. It has become.

FIG. 5 is a partially cutaway perspective view showing one embodiment of a thrust bearing 63 utilizing fluid dynamic pressure. As shown in this figure, in the case of the thrust bearing 63, a plurality of "-" shaped dynamic pressure generating grooves 65 are formed on the bottom surface of the first wide diameter portion 54 of the upper sleeve 5a (not shown in FIG. 5). ) And on the lower surface of the thrust bush 56 at equal pitches in the circumferential direction.

Therefore, by rotating the upper sleeve 5a clockwise around the shaft 2, the lubricating oil O existing in the gap between the back surface of the thrust bush 56 and the upper surface of the thrust plate 27, and the first The thrust plate 27 is pressed and sandwiched by the dynamic pressure generated in the lubricating oil O existing in the gap between the bottom surface side of the wide diameter portion 54 and the lower surface side of the thrust plate 27. The hub 4 floats between the lubricating oils O, and the hub 4 rotates smoothly while being prevented from moving in the axial direction.

Hereinafter, a method for manufacturing the fluid dynamic bearing motor according to this embodiment will be described. First, the stator core 3 is attached to the stator core support portion 23 of the shaft 2 by bonding, and the upper sleeve 5 a is pressed into the upper portion of the hub 4 and fixed. When the upper sleeve 5a is formed integrally with the hub 4 from the beginning by cutting or forging a metal round bar, the press-fitting operation is not necessary.
Then, an upper sleeve 5a integrally connected to the hub 4.
A fixed shaft fitting process is performed in which the shaft 2 is internally fitted from the head 25 into the through hole 51 of the stator core 3.
Is in a state of facing the inner peripheral surface of the rotor magnet 41 in the hub 4.

In this state, the thrust plate 27 is press-fitted into the upper free fitting portion 24 of the shaft 2 and the upper sleeve 5
A mounting process of the thrust plate to be accommodated in the first wide diameter portion 54 of a is executed. After completion of this step, the lower sleeve 5b is fitted into the hub 4 from the lower end opening while the insertion hole 51 of the lower sleeve 5b having the outer peripheral surface coated with an adhesive is loosely fitted into the threaded portion 21 of the shaft 2. A fitting process is performed.

Further, in this sleeve fitting step, the hub 4 is pressed in a direction perpendicular to the direction in which the shaft 2 extends, so that the center of the lower sleeve 5b and the axis of the shaft 2 are finely aligned. Adjusted. At the time of this fine adjustment, a measuring device (not shown), which is a precision instrument for measuring whether or not the axis of the shaft 2 is aligned with the center of the lower sleeve 5b, is used. The pressing point and the pressing amount on the outer peripheral surface are detected, and the centering process of the hub 4 is executed based on the detection results.

After the completion of the centering process, the centering state is locked by using a predetermined locking means, and the hub 4 and the shaft 2 in the locked state are loaded into a predetermined heating furnace to perform a heating process. This promotes the solidification of the adhesive.
Then, after the adhesive is solidified, the hub 4 is removed from the heating furnace and cooled to room temperature, and the radial bearing and the thrust bearing formed on the outer peripheral surfaces of the lower loose fitting portion 22, the upper loose fitting portion 24 and the thrust plate 27 of the shaft 2 A fluid dynamic pressure filling step of filling the fluid with a fluid for generating dynamic pressure is performed.

Finally, the thrust bush 56
Into the second wide-diameter portion 55 of the upper sleeve 5a so that the head 25 of the shaft 2
Thus, the electric motor 1 is completed in a state in which the threaded portion 21 of the shaft 2 projects outside from the insertion hole 51 of the lower sleeve 5b. This electric motor 1
Is mounted on the hard disk drive by screwing the threaded portion 21 to the base B.

As described in detail above, in the manufacturing method of the present invention, the lower sleeve 5 having an adhesive applied to the outer peripheral surface thereof is used.
b is fitted into the hub 4 from the lower opening, and then the hub 4 is pressed in a direction perpendicular to the shaft 2 to align the core shaft 2 and the lower sleeve 5b. The sleeve 5b and the shaft 2 can be precisely concentric. Therefore, even if the processing accuracy of the lower sleeve 5b is inferior to that of the upper sleeve 5a, the centering process can make the sleeve 5 and the shaft 2 concentric, and the lower sleeve 5b is not processed with high precision. It is possible to obtain a high-precision motor for a hard disk drive while reducing the processing cost.

The present invention is not limited to the above embodiment, but includes the following contents.

(1) In the above embodiment, the upper sleeve 5a is initially formed separately from the hub 4, and the upper sleeve 5a is pressed into the hub 4 to integrate the upper sleeve 5a and the hub 4. However, the present invention is not limited to press-fitting the separate upper sleeve 5a into the hub 4, but the upper sleeve 5a and the hub 4 are integrated from the beginning by casting, forging or cutting. May be manufactured.

(2) In the above embodiment, an epoxy resin-based adhesive is used for joining the lower sleeve 5b and the hub 4, but in the present invention, the adhesive is an epoxy resin-based adhesive. It is not particularly limited, and a so-called anaerobic adhesive or a polyurethane-based adhesive obtained by blending a small amount of cumene hydroperoxide and trihydroquinone in a polyethylene glycol / acrylate diester monomer may be used.

(3) In the above embodiment, the dynamic pressure generating grooves 64 of the radial bearings 61 and 62 are
It is provided on the inner peripheral surface of the insertion hole 51 of the upper and lower sleeves 5a and 5b.
2, 24) or on the inner peripheral surface of the sleeve 5 and the outer peripheral surface of the shaft 2 respectively. Similarly, thrust bearings 63 provided on the bottom surface of the first wide diameter portion 54 of the upper sleeve 5a and the bottom surface of the thrust bush 56.
The dynamic pressure generating grooves 65 may be provided on the upper and lower surfaces of the thrust plate 27, the bottom surface of the first wide diameter portion 54, the bottom surface of the thrust bush 56, and the upper and lower surfaces of the thrust plate 27, respectively.

(4) In the above embodiment, the constricted portion 26 is formed at the upper and lower ends of the lower loose fitting portion 22 of the shaft 2 and the lower end of the upper loose fitting portion 24. It may be formed at the end and the lower end of the upper sleeve 5a.

(5) In the above-described embodiment, the lower sleeve 5b and the hub 4 are connected to each other via an adhesive. The lower sleeve 5b is press-fitted or formed integrally with the hub 4, and the upper sleeve 5a and the hub 4 are connected to each other via an adhesive. At times, the upper sleeve 5a and the shaft 2 may be aligned so as to be concentric.

[0051]

According to the first aspect of the present invention, the stator core wound with the electromagnetic coil is provided at a substantially central portion in the axial direction of the fixed shaft, and the cylindrical rotating body is fixed on the inner peripheral surface of the upper portion of the stator core. An upper sleeve facing the outer peripheral surface of the shaft, a lower sleeve facing the outer peripheral surface of the lower fixed shaft, and a cylindrical hub connecting the upper and lower sleeves. It is formed between the inner peripheral surface of the lower sleeve and the outer peripheral surface of the fixed shaft, and a gap of a predetermined size is formed between the outer peripheral surface and the inner peripheral surface of the hub with one of the upper sleeve and the lower sleeve separately. Since the outer diameter dimension was set so as to be formed, and a separate sleeve was fixed to the hub by interposing an adhesive in the gap,
The hub is supported at two points by the radial bearings of a pair of sleeves provided at the upper end and the lower end of the hub with respect to the fixed shaft, so that the supported state with respect to the fixed shaft is stable in the radial direction. It is possible to rotate in a state in which run-out hardly occurs.

Since a gap is provided between the separate sleeve and the hub, and the adhesive is interposed in the gap, the other sleeve and the hub are integrated with each other. Before the solidification, the hub is radially pressed to finely adjust the position of the other sleeve with respect to the fixed axis, so that the axis of the separate sleeve and the axis of the other sleeve can be made concentric. This can prevent the hub from being inclined with respect to the fixed shaft.

Also, since the axis of the hub and the axis of the fixed shaft can be made to coincide with each other by fine adjustment, when the motor is, for example, for an HDD, the disk mounted on the hub and rotating is mounted on the hub. And a rotation about a fixed axis on the same plane, a correct positional relationship between the track of the disk and the magnetic head can be reliably ensured, and erroneous access can be reliably prevented.

According to the second aspect of the present invention, since the thrust bearing utilizing fluid dynamic pressure is formed at least on the upper portion of the stator core of the fixed shaft, a thrust plate concentric with the fixed shaft is provided. The movement of the hub in the axial direction with respect to the fixed shaft is restricted, and the rotation of the hub in the same space can be reliably ensured. Since the thrust bearing utilizes the fluid dynamic pressure, the hub can be smoothly rotated and unpleasant noise can be reliably prevented.

According to the third aspect of the present invention, the upper or lower sleeve is fitted to the fixed shaft in the fixed shaft fitting step, so that the hub is mounted on the fixed shaft in a cantilevered state, and the next sleeve is fitted. In the mounting step, a hub having a pair of sleeves is temporarily mounted on the fixed shaft by fitting a separate sleeve provided with an adhesive to the fixed shaft in the mounting shaft. Is pressed in the direction of the fixed shaft to make fine adjustments to match the axis of each sleeve, and then the adhesive is solidified so that a predetermined gap is formed between the outer peripheral surface of each sleeve and the inner peripheral surface of the fixed shaft. When the hub is formed, the hub can be attached to the fixed shaft. Then, a motor can be obtained by injecting a predetermined fluid into the gap in the last dynamic pressure fluid injecting step.

In the adhesive hardening step, the axis of one sleeve and the axis of the other sleeve can be made concentric by fine adjustment in which the hub before the adhesive is solidified is radially pressed. Thereby, it is possible to reliably prevent the hub from being inclined with respect to the fixed shaft. Therefore, when the electric motor is for HDD, for example, the disk mounted on the hub and rotating is concentric with the fixed axis and rotates about the fixed axis on the same plane. The positional relationship is reliably ensured, and erroneous access can be reliably prevented.

According to the fourth aspect of the present invention, in the thrust plate mounting step, the thrust plate is mounted on the fixed shaft, and the motor obtained thereby is in a state where the movement of the hub in the thrust direction is restricted. The rotation of the hub in the same space can be reliably ensured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing one embodiment of a fluid dynamic bearing motor according to the present invention.

FIG. 2 is an assembled perspective view of the fluid dynamic bearing motor of FIG. 1;

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a partially cutaway perspective view showing one embodiment of a radial bearing using fluid dynamic pressure.

FIG. 5 is a partially cutaway perspective view showing one embodiment of a thrust bearing using fluid dynamic pressure.

FIG. 6 is a cross-sectional view illustrating a conventional fluid dynamic bearing motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric motor 2 Shaft (fixed shaft) 21 Threaded part 22 Lower loose fitting part 23 Stator core supporting part 24 Upper loose fitting part 25 Head 26 Narrow part 27 Thrust plate 3 Stator core 31 Stator coil 4 Hub 41 Rotor magnet 42 Yoke 5 Sleeve 5a Upper sleeve (other sleeve) 5b Lower sleeve (one or separate sleeve) 51 Insertion hole 52 Annular space 53 Tapered seal portion 54 First wide diameter portion 54a Gap 55 Second wide diameter portion 56 Thrust bush 56a Through hole 57 Adhesion Filling space 6 Fluid dynamic pressure bearing structure 61 Upper radial bearing 62 Lower radial bearing 63 Thrust bearing 64, 65 Dynamic pressure generating groove B Base B1 Screw hole

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16C 35/02 F16C 35/02 Z H02K 7/08 H02K 7/08 A 15/14 15/14 A 21/22 21/22 M

Claims (5)

[Claims] A fixed shaft, a stator core fixed concentrically to the fixed shaft and wound with an electromagnetic coil, a cylindrical rotating body surrounding the stator core and the fixed shaft concentrically and spaced apart from each other; A fluid dynamic pressure bearing motor comprising: a radial bearing utilizing a fluid dynamic pressure generated in a fluid filled in a minute space formed between an inner peripheral surface of the body and an outer peripheral surface of the fixed shaft; The stator core is provided at a substantially central portion in the axial direction of the fixed shaft. The cylindrical rotating body includes an upper sleeve having an inner peripheral surface facing an outer peripheral surface of the fixed shaft above the stator core, and an outer peripheral surface of the lower fixed shaft. And a cylindrical hub having the upper and lower sleeves. The radial bearing includes an inner peripheral surface of the upper and lower sleeves and an outer peripheral surface of a fixed shaft. And at least one of the upper sleeve and the lower sleeve is formed separately from the hub, and a gap of a predetermined dimension is formed between the outer peripheral surface and the inner peripheral surface of the hub. A fluid dynamic pressure bearing motor wherein an outer diameter is set so as to be formed, and is fixed by providing an adhesive in a gap between the separate sleeve and the hub. . 2. The fixed shaft according to claim 1, wherein a thrust plate concentric with the fixed shaft is provided at least above the stator core, the thrust bearing constituting a thrust bearing utilizing fluid dynamic pressure. Fluid dynamic bearing motor. 3. A manufacturing method for manufacturing a fluid dynamic bearing motor according to claim 1, wherein the fixed shaft provided with the stator core is fitted to the upper or lower sleeve; A sleeve fitting step of fitting a separate sleeve to the hub via an adhesive to adjust the other sleeve coaxially, and an adhesive solidifying step of solidifying the adhesive,
A method of filling the radial bearing with a fluid for generating a dynamic pressure. 4. A manufacturing method for manufacturing a fluid dynamic bearing motor according to claim 2, wherein: a fixed shaft fitting step of fitting a fixed shaft provided with the stator core to the upper or lower sleeve; A thrust plate mounting step of mounting and fixing the thrust plate to a portion corresponding to the other sleeve of the shaft, and a sleeve fitting for fitting a separate sleeve to the hub via an adhesive and adjusting the hub coaxially with the other sleeve. Mounting step, an adhesive solidifying step of solidifying the adhesive,
A method for manufacturing a fluid dynamic bearing motor, comprising a dynamic pressure fluid filling step of filling the radial bearing and the thrust bearing with a fluid for generating dynamic pressure. 5. The method of manufacturing a fluid dynamic bearing electric motor according to claim 3, wherein the sleeve fitting step includes: fitting the separate sleeve into a hub; A step of pressing a separate sleeve against a fixed shaft in a state in which the sleeve is in contact with the inner peripheral surface of the other sleeve to adjust the sleeve coaxially with the other sleeve. Method.