JP2004056963A - Motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable motor wherein lubricant does not leak from radial dynamic pressure bearing portions even under gyro load testing, and the dynamic pressure does not drop and the NPRO performance is maintained for a long time. <P>SOLUTION: The radial dynamic pressure bearing portions 4A and 4B are formed of a shaft 9 and a sleeve 5. Annular projected portions 3A and 3B which are protruded in the inner face of a through hole 5D into which the shaft 9 is inserted are formed between the bearing portions 4A and 4B and the ends 9A and 9B of the shaft 9. Thus, plain bearing portions 30A and 30B consisting of the annular projected portions 3A and 3B and the shaft 9 are formed. A rotor 60 is rotatably supported in the radial direction by the plain bearing portions 30A and 30B and the radial dynamic pressure bearing portions 4A and 4B. The ratio d/D of the axial width (d) of the projected portions 3A and 3B to the axial width D of the radial dynamic pressure bearing portions 4A and 4B is controlled to a value not less than 0.03 and not more than 0.3. Further, the projected portions 3A and 3B are separated from each other, and their surface hardness is made higher than that of the sleeve 5. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor having a dynamic pressure bearing, and more particularly to a bearing structure of a motor for a hard disk drive.
[0002]
[Prior art]
2. Description of the Related Art In recent years, hard disk drives (hereinafter referred to as HDDs), which are frequently used in personal computers and the like, are required to have performances that can withstand various uses in addition to miniaturization and high capacity.
In response to these demands, studies are being made to improve track density and linear density, withstand external vibrations, and to further reduce non-repeatability (NRRO: Non Repeatable Run Out).
[0003]
A spindle motor (hereinafter referred to as a motor) mounted on such an HDD is strictly required to have low vibration and low noise in order to be a source of vibration and noise. There is a limit to using ball bearings and other rolling bearings that are unsuitable, have high vibration noise, and are difficult to obtain excellent NRRO characteristics. I have.
[0004]
A conventional motor employing this dynamic pressure bearing will be described with reference to FIG. FIG. 7 is a partial sectional view.
This motor includes a stator portion 100A and a rotor portion 200A. The stator portion 100A mainly includes a base 100, an annular stator core 200 fixed to the base 100, and a sleeve 105. A drive coil 111 is wound around the stator core 200.
The rotor portion 200A includes a rotor yoke 106 to which an annular magnet 107 is fixed, a magnetic disk 114, and a rotor hub 112 to which a shaft 109 is fixed. The shaft 109 is inserted into the through hole 105D of the sleeve 105, and is fitted to the stator portion 100A. It is rotatably supported.
[0005]
On the inner surface of the through hole 105D of the sleeve 105, a pair of herringbone-shaped dynamic pressure grooves 150A and 150B are formed at positions separated in the axial direction, and the dynamic pressure grooves 150A and 150B and the shaft 109 form a radial dynamic pressure bearing portion 104A, 104B is formed.
A ring-shaped flange 108 is provided at the lower end of the shaft 109 in the drawing.
A thrust plate 110 for sealing the open lower end of the sleeve 105, a flange 108 having a herringbone-shaped dynamic pressure groove (not shown) formed on the upper and lower surfaces, and a thrust dynamic pressure bearing portion comprising the sleeve 105. 120 are configured.
Further, a lubricating oil 121 is filled and sealed between the radial dynamic pressure bearing portion 104A and the thrust plate 110 in the upper part of FIG.
[0006]
In this configuration, when the shaft 109 rotates, dynamic pressure is generated in the thrust dynamic pressure bearing portion 120 and the radial dynamic pressure bearing portions 104A and 104B by the dynamic pressure grooves 150A and 150B and the lubricating oil 121, and the shaft 109 Supported rotatably.
[0007]
[Problems to be solved by the invention]
By the way, with respect to applicability to various uses typified by mounting on a portable terminal, the performance of a motor is evaluated by a gyro load test assuming an external load.
This gyro load test is a test in which the entire motor is reciprocally rotated at an angular velocity of about 8 rad / sec while rotating the motor at a rated speed of 7200 revolutions / minute.
[0008]
The gyro load applied in this test generates a load on the axial end of the dynamic pressure bearing, wears the convex portion of the dynamic pressure groove, and causes a decrease in dynamic pressure and leakage of the filled and sealed lubricating oil.
Therefore, it is important to provide a highly reliable motor that can withstand the gyro load test.
[0009]
However, in a conventional motor using a dynamic pressure bearing, when a gyro load is continuously applied 10,000 times in a gyro load test, the radial dynamic pressure bearing portion on the inner surface of the sleeve is unevenly worn.
Specifically, the shaft end side of the inner surface of the through hole of the sleeve in the dynamic pressure bearing portion wears unevenly by about 2 μm. As a result, the gap between the shaft and the shaft is widened, and the depth of the dynamic pressure groove at that portion, which was 6 μm in the initial stage, becomes 4 μm.
Therefore, there has been a problem that the lubricating oil leaks or the dynamic pressure decreases.
In addition, there has been a problem that NRRO is deteriorated and a time during which performance can be maintained (reliability maintaining time) is shortened.
[0010]
The problem to be solved by the present invention is to provide a highly reliable motor in which lubricating oil does not leak from the radial dynamic pressure bearing portion and NRRO performance is maintained for a long time without a decrease in dynamic pressure. Is to do.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration as means.
That is, claim 1 includes a rotor 60 to which the shaft 9 is fixed, and a stator 50 to which the sleeve 5 provided with the through-hole 5D is fixed. The shaft 9 is inserted into the through-hole 5D, and the rotor 60 is fixed. A radial dynamic pressure bearing portion 4A, 4B composed of the shaft 9 and the sleeve 5; a motor rotatably supported in the radial direction with respect to the stator 50 by the radial dynamic pressure bearing portions 4A, 4B; Ring-shaped convex portions 3A and 3B protruding from the inner surface of the through hole 5D are provided between at least one end 9A and the sliding bearing portions 30A and 30B composed of the convex portions 3A and 3B and the shaft 9. And the rotor 60 is rotatably supported in the radial direction by the slide bearings 30A, 30B and the radial dynamic pressure bearings 4A, 4B. ,
Claim 2 is a rotor 60A to which the sleeve 5 provided with the through hole 5D is fixed.
A stator 50A to which the shaft 9 is fixed,
The shaft 9 is inserted into the through hole 5D,
In a motor in which the rotor 60A is rotatably supported in a radial direction with respect to the stator 50A by radial dynamic pressure bearings 4A and 4B including the shaft 9 and the sleeve 5,
On the end side of the shaft 9 with respect to the radial dynamic pressure bearing portions 4A and 4B,
Ring projections 3A, 3B protruding from the inner surface of the through hole 5D are provided to form sliding bearings 30A, 30B including the projections 3A, 3B and the shaft 9.
A motor characterized in that the rotor 60A is rotatably supported in the radial direction by the slide bearings 30A, 30B and the radial dynamic pressure bearings 4A, 4B,
The ratio d / D of the axial width d of the projections 3A, 3B to the axial width D of the radial dynamic pressure bearing portions 4A, 4B is set to 0.03 or more and 0.3 or less. The motor according to claim 1 or 2, wherein:
A fourth aspect is that the projections 3A and 3B are formed as substantially ring-shaped members including the projections 3A and 3B in separate bodies 300A and 300B from the sleeve, and the surfaces of the projections 3A and 3B. 4. The motor according to claim 1, wherein the hardness is higher than a surface hardness of the sleeve. 5.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a partial sectional view showing a first embodiment of the motor of the present invention,
FIG. 2 is a sectional view of a main part of the first embodiment of the motor of the present invention,
FIG. 3 is an enlarged sectional view of the most important part in the first embodiment of the motor of the present invention,
FIG. 3A shows details of the M1 part in FIG.
FIG. 3B shows details of the M2 part in FIG.
FIG. 5 is a diagram illustrating characteristics of the motor according to the first embodiment of the present invention.
FIG. 6 is a partial sectional view of a motor according to a second embodiment of the present invention.
[0013]
The first embodiment will be described first with reference to FIG.
This motor includes a stator section 50 and a rotor section 60.
The stator section 50 is mainly composed of a base 1, a sleeve 5, and a stator core 2.
The base 1 is provided with a substantially cylindrical wall 1a, and a cylindrical sleeve 5 made of a copper-based material is fixed to the inner surface of the base 1 by press-fitting or the like. The sleeve 5 has a through hole 5D.
The stator core 2 is fixed to the outer peripheral surface of the wall 1a. The stator core 2 has a plurality of salient poles (not shown), and a driving coil 11 is wound around each salient pole.
[0014]
On the other hand, the rotor section 60 is composed of the rotor hub 12, the rotor yoke 6, and the magnet 7.
The rotor hub 12 has a substantially cylindrical shape made of a stainless steel material and has a cylindrical portion 12a for fixing the magnetic disk 14 and a flange portion 12b for fixing the rotor yoke 6 to which the magnet 7 is fixed.
[0015]
A shaft 9 made of a stainless steel material is press-fitted and fixed to the rotor hub 12, the shaft 9 is inserted into the through hole 5D of the sleeve 5, and the rotor portion 60 is connected to the radial dynamic pressure bearing portions 4A and 4B and the thrust dynamic pressure. The bearing portion 20 rotatably supports the stator portion 50.
An annular flange 8 is fixed near one end 9B of the shaft 9 (the lower side in FIG. 1).
The flange 8 may be formed integrally with the shaft 9.
The magnet 7 has an annular shape and is arranged to face a plurality of salient poles (not shown) of the stator core 2 with a certain gap.
In this configuration, the rotor unit 60 is rotated by switching the energization of the drive coil 11. Next, the thrust and radial bearings will be sequentially described in detail.
[0016]
(A) Thrust Dynamic Pressure Bearing The thrust dynamic pressure bearing 20 is provided at the lower end of the sleeve 5 (the lower side in FIG. 1).
As shown in detail in FIG. 2, the lower end of the sleeve 5 is opened substantially stepwise, and first, second, and third shelves 5A, 5B, and 5C are formed from the opening side.
The flange 8 is fitted into the shelf 5C, and the axial depth of the shelf 5C is formed larger than the thickness of the flange 8 by a predetermined dimension.
[0017]
Further, a disc-shaped thrust plate 10 is press-fitted into the second shelf 5B to close the lower opening of the sleeve 5.
A gap between the thrust plate 10, the flange 8, and the shelf 5C is filled with a lubricating oil 21 having a predetermined viscosity.
Herringbone (fish bone) -shaped dynamic pressure grooves (not shown) are formed on the upper surface 8a and the lower surface 8b of the flange 8.
[0018]
The thrust dynamic pressure bearing portion 20 includes the upper surface 8a of the flange 8, the third shelf surface 5Ca of the third shelf 5C, the lower surface 8b of the flange 8, and the thrust plate 10.
In this configuration, when the shaft 9 rotates, the flange 8 is pushed downward by the dynamic pressure grooves provided on the upper surface 8a and the lubricating oil 21 between the upper surface 8a of the flange 8 and the shelf surface 5Ca opposed thereto. Dynamic pressure is generated.
[0019]
On the other hand, between the lower surface 8b of the flange 8 and the thrust plate 10 facing the lower surface 8b, a dynamic pressure for pushing the flange 8 upward is generated by the dynamic pressure groove provided on the lower surface 8b and the lubricating oil 21.
[0020]
These dynamic pressures are forces of equal magnitudes in opposite directions and urge the flanges 8 evenly.
As a result, the shaft 9 that has been in contact with the thrust plate 10 when it is stationary is separated from the thrust plate 10 by rotation, and is rotatably supported in the thrust direction.
[0021]
(B) Radial Dynamic Pressure Bearings The radial dynamic pressure bearings 4A and 4B are herringbone (fish bone) -shaped dynamic pressures provided at two axially separated locations on the inner peripheral surface of the through hole 5D of the sleeve 5. The grooves are formed by the grooves 15A and 15B and the shaft 9.
These dynamic pressure grooves 15A and 15B are formed at a depth of about 6 μm. The dynamic pressure grooves 15A and 15B may be provided not on the sleeve 5 but on the outer peripheral surface of the shaft 9.
1 to 4 and 6, the dynamic pressure grooves 15A and 15B provided in the sleeve 5 are drawn on the shaft 9 for convenience.
[0022]
The gap between the inner peripheral surface of the through hole 5D of the sleeve 5 and the outer peripheral surface of the shaft 9 in the range between the radial dynamic pressure bearing portion 4A on the end 9A side of the shaft 9 and the thrust plate 10 has a predetermined viscosity. Is filled so as to be able to flow.
[0023]
In the radial dynamic pressure bearing portions 4A and 4B, the dynamic pressure grooves 15A and 15B of the sleeve 5 and the lubricating oil 21 generate a dynamic pressure in the radial direction when the shaft 9 rotates.
The radial dynamic pressure presses the entire outer peripheral surface of the shaft 9 in the axial direction with a uniform force. Thus, the shaft 9 can be smoothly rotated by being inserted into the through hole 5D of the sleeve 5.
The rotor unit 60 is rotatably supported by the stator unit 50 by the thrust and radial dynamic pressure bearings described above.
[0024]
Electric power applied to the drive coil 11 wound around the stator core 2 is supplied from an external drive circuit (not shown) via a printed board 17 (see FIG. 1) provided below the motor base 1.
A flexible printed board (FPC) is used as the printed board 17. The base of the FPC is made of polyimide resin (PI) and has flexibility, so that it can be bent and attached to the motor base. A wiring pattern is formed of copper foil on the base, and an insulating layer is formed by attaching a PI thin film or printing an insulating paint.
[0025]
The rotor hub 12 is formed by casting or cutting aluminum, barrel-polished the surface, and then subjected to electroless nickel plating (ED coating).
This ED coating can reduce the number of fine powders (LPCs) generated from the surface of the aluminum and damaging a disk or a head (neither is shown).
[0026]
Regarding the number of fine powders with a size per unit volume of 0.5 μm or more, the number is 100,000 without ED coating, 50,000 with electrolytic coating, and further reduced to 10,000 with ED coating. It has been known.
Therefore, applying electroless nickel plating to the rotor hub 12 is a preferable effect because it has a great effect on the reduction of LPC.
[0027]
In the first embodiment, a pair of sliding bearings 30A, 30B are provided outside the radial dynamic pressure bearings 4A, 4B in addition to the above-described radial dynamic bearings, which will be described in detail below.
[0028]
(C) About the sliding bearing (see FIGS. 2 and 3)
The sliding bearing portions 30A, 30B are composed of ring-shaped convex portions 3A, 3B provided on the inner peripheral surface of the through hole 5D of the sleeve 5 and having a width d in the axial direction and protruding in the axial direction, and the shaft 9. Is done.
Therefore, the gap between the ring-shaped convex portions 3A, 3B and the outer peripheral surface of the shaft 9 is larger than the gap between the inner peripheral surface of the through hole 5D other than the radial dynamic pressure bearing portions 4A, 4B and the outer peripheral surface of the shaft 9. The thickness is set to about 3 to 5 μm so as to be narrow.
The gap between the projections 3A and 3B and the shaft 9 is filled with a lubricant 22 having a viscosity optimal for sliding bearing applications.
[0029]
The sliding bearings 30A and 30B are provided in parallel with the radial dynamic pressure bearings 4A and 4B, and the rotor 60 is supported by both bearings. Thus, even when a gyro load is applied to the motor, the radial dynamic pressure bearings 4A and 4B are provided. 4B is not unevenly worn, and the wear itself is reduced, so that a highly reliable motor can be obtained without a decrease in dynamic pressure or leakage of the lubricating oil 21.
[0030]
(D) Ratio d / D (see FIG. 5)
Further, the present inventors have found that the axial width d of the ring-shaped convex portions 3A, 3B of the sliding bearing portions 30A, 30B provided side by side with respect to the axial width D (see FIG. 2) of the radial dynamic pressure bearing portions 4A, 4B. As a result of intensive studies on the optimization of the ratio, a range of the ratio d / D at which extremely high reliability and performance can be obtained was found.
This will be described in detail below.
[0031]
The motor of the first embodiment in which the width D of the radial dynamic pressure bearing portions 4A and 4B is 5 mm and the width d of the ring-shaped convex portions 3A and 3B is changed to several types is prepared and subjected to a gyro test, and the reliability maintenance time and the drive are performed. The current was measured.
About the result,
(1) FIG. 5A shows the relationship between the ratio d / D and the reliability maintenance time of the test motor.
(2) FIG. 5B shows the relationship between the ratio d / D and the current for driving the test motor.
Here, the reliability maintaining time is a time until the predetermined performance of the test motor of the first embodiment cannot be maintained.
The smaller the drive current, the smaller the shaft loss of the motor and the better the performance.
[0032]
From these results, by setting the ratio d / D to 0.03 or more, the reliability time is maintained extremely long (about 5000 hours or more), and by setting the ratio to 0.3 or less, the driving current is sufficiently low (about 400 mA). Below) It was found that it could be suppressed.
[0033]
When the width d of the ring-shaped projections 3A, 3B is reduced, the function as a slide bearing becomes insufficient, the load on the radial dynamic pressure bearings 4A, 4B increases, and the bearing cannot withstand the gyro load. Be shorter.
Conversely, when the width d is increased, the width D of the radial dynamic pressure bearings 4A, 4B is reduced due to size restrictions, the dynamic pressure is reduced, and the shaft loss is increased (current is increased).
As described above, it is the most preferable embodiment that the sliding bearing is provided together with the radial dynamic pressure bearing, and the ratio d / D is set to 0.03 or more and 0.3 or less.
[0034]
Further, in the motor including the pair of radial dynamic pressure bearing portions 4A and 4B as in the first embodiment, the width D on the rotor side to which a large load is applied may be widened.
In this case, the ratio between the width d of the adjacent ring-shaped convex portions 3A and 3B of the sliding bearing portion and the width D of the radial dynamic pressure bearing portions 4A and 4B may have the above-described relationship.
[0035]
The first embodiment described above is a motor having a structure in which the shaft 9 is fixed to the rotor unit 60 and rotates. As a second embodiment, a motor having a structure in which the shaft 9 is fixed to the base 1 to form a stator unit 50A. It may be a motor (see FIG. 6).
Hereinafter, a configuration of the second embodiment that is different from that of the first embodiment will be described.
[0036]
This second embodiment includes a stator section 50A and a rotor section 60A.
The stator portion 50A mainly includes a base 1, a shaft 9, and a stator core 2.
The base 1 is provided with a hole substantially at the center, and the shaft 9 is fixed upright by press fitting or the like.
[0037]
On the other hand, the rotor section 60A includes the rotor hub 12, the rotor yoke 6, and the magnet 7.
A cylindrical sleeve 5 made of a copper-based material is fixed to the rotor hub 12 by press fitting or the like.
The sleeve 5 is provided with a through hole 5D, and the shaft 9 is inserted into the through hole 5D so that the rotor portion 60A is fixed to the stator portion by the radial dynamic pressure bearing portions 4A and 4B and the thrust dynamic pressure bearing portion 20. It is rotatably supported with respect to 50A.
[0038]
Further, the thrust bearing portion 120 is constituted by a flange 8 and the like provided on the shaft 9 and arranged above the shaft 9.
The configuration including the radial dynamic pressure bearing portions 4A and 4B, the shaft 9, and the sleeve 5, and the effects obtained by the configuration are the same as those of the first embodiment.
[0039]
The embodiments of the present invention are not limited to the above-described configuration, and can be modified as follows, for example, without departing from the gist of the present invention.
The ring-shaped convex portions 3A and 3B may not be formed integrally with the sleeve 5 and may be separate bodies. FIG. 4 shows an example in which this is performed in the first embodiment.
By forming the ring-shaped projections 3A, 3B as separate substantially ring-shaped bodies 300A, 300B including the ring-shaped projections 3A, 3B, the material can be arbitrarily selected, and the hardness is higher than that of a sleeve formed of a copper-based material. For example, by forming the sliding bearing with a high wear resistance, wear can be further reduced, and a more reliable sliding bearing can be obtained.
In addition, the surface hardness may be increased by the surface treatment, as long as at least the surface hardness of the surface of the ring-shaped convex portions 3A and 3B facing the axis 9 is increased.
[0040]
Further, by forming the separate bodies 300A and 300B including the ring-shaped protrusions 3A and 3B from an oil-impregnated metal, it is possible to eliminate the lubricant and the application step thereof while maintaining the lubrication performance.
[0041]
The sliding bearing portions 30A and 30B provided side by side may be only one of them instead of a pair. However, in order to maintain the gyro load resistance performance, as in the first and second embodiments described above, the radial dynamic pressure bearing is used. Most preferably, a sliding bearing is provided between the shaft portion and each end 9A, 9B of the shaft 9.
[0042]
As described above, the present invention provides a long-term bearing capable of withstanding a gyro load by providing an additional bearing in addition to the pair of radial dynamic pressure bearing portions 4A and 4B and using the additional bearings as the sliding bearing portions 30A and 30B. It has been found that reliability maintenance time and a small axis loss can be obtained.
Therefore, for example, even if a rolling bearing is used in place of the sliding bearing, the rolling bearing is unsuitable for high-speed rotation and has large vibration noise as described above, and it is difficult to obtain the NRRO characteristic. This effect can be obtained for the first time by using a sliding bearing as the additional bearing.
[0043]
【The invention's effect】
As described in detail above, according to the present invention, the sliding bearing is provided in parallel with the radial dynamic pressure bearing, and the rotor is rotatably supported in the radial direction by both bearings. Since the radial dynamic pressure bearing part does not wear unevenly and wear itself is reduced, lubricating oil does not leak, dynamic pressure does not decrease, NRRO performance can be maintained for a long time, and high reliability can be obtained .
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing a first embodiment of a motor according to the present invention.
FIG. 2 is a sectional view of a main part of the first embodiment of the motor of the present invention.
FIG. 3 is an enlarged sectional view of a most important part in the first embodiment of the motor of the present invention.
FIG. 4 is a cross-sectional view of a main part of another first embodiment of the motor of the present invention.
FIG. 5 is a diagram illustrating characteristics of the motor according to the first embodiment of the present invention.
FIG. 6 is a partial sectional view showing a second embodiment of the motor of the present invention.
FIG. 7 is a partial sectional view showing an example of a conventional motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base 1a Wall part 2 Stator core 3A, 3B (ring-shaped) convex part 4A, 4B Radial dynamic pressure bearing part 5 Sleeve 5A, 5B, 5C First, second, third shelf 5Ca Third shelf 5D penetration Hole 6 Rotor yoke 7 Magnet 8 Flange 8a, 8b Upper and lower surfaces (of flange) 9 Shaft 9A, 9B End 10 Thrust plate 11 Drive coil 12 Rotor hub 12a Cylindrical portion 12b Flange portion 14 Magnetic disks 15A, 15B (for radial dynamic pressure bearings) ) Dynamic pressure groove 17 Printed circuit board 20 Thrust dynamic pressure bearing 21 Lubricating oil 22 Lubricant 30A, 30B Sliding bearing 50, 50A Stator (part)
60, 60A rotor (part)
300A, 300B member (separate projection)
d, D width d / D ratio

Claims (4)

A rotor with a fixed shaft,
And a stator to which a sleeve provided with a through hole is fixed,
The shaft is inserted into the through hole,
A motor in which the rotor is supported in a radial direction so as to be rotatable with respect to the stator by a radial dynamic pressure bearing portion including the shaft and the sleeve.
On the end side of the shaft than the radial dynamic pressure bearing portion,
Providing a ring-shaped convex portion protruding on the inner surface of the through hole to form a sliding bearing portion comprising the convex portion and the shaft,
A motor, wherein the rotor is rotatably supported in the radial direction by the sliding bearing portion and the radial dynamic pressure bearing portion. A rotor to which a sleeve having a through hole is fixed,
And a stator with a fixed shaft,
The shaft is inserted into the through hole,
A motor in which the rotor is supported in a radial direction so as to be rotatable with respect to the stator by a radial dynamic pressure bearing portion including the shaft and the sleeve.
On the end side of the shaft than the radial dynamic pressure bearing portion,
Providing a ring-shaped convex portion protruding on the inner surface of the through hole to form a sliding bearing portion comprising the convex portion and the shaft,
A motor, wherein the rotor is rotatably supported in the radial direction by the sliding bearing portion and the radial dynamic pressure bearing portion. 3. The motor according to claim 1, wherein a ratio of an axial width of the convex portion to an axial width of the radial dynamic pressure bearing portion is 0.03 or more and 0.3 or less. The convex portion is formed as a substantially ring-shaped member including the convex portion separately from the sleeve, and the surface hardness of the convex portion is higher than the surface hardness of the sleeve. The motor according to any one of claims 1 to 3, wherein:

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