JPH08273289A - Motor for driving disk - Google Patents

Abstract

PURPOSE: To provide motor for driving disks of a thin type and low cost which is capable of abolishing ball bearings and eliminates playing and axial run-out. CONSTITUTION: A shaft 28 has a columnar part 28b and a flange part 28a of the diameter larger than the diameter of this columnar part 28b. A hub table 28 consists of a sintered compact impregnated with a lubricating oil and has a cylindrical part 29b integral with a disk hub placing part 29a. At least a part of this disk hub placing part 29a is disposed in superposition on the flange part 28a of the shaft 28 in its axial direction and is held in sliding contact with the front surface of the flange part 28a. The cylindrical part 29b is held in sliding contact with the outer peripheral surface of the flange part 28a. Plural balls may be inserted between the base of the disk hub placing part of the hub table and the flange part of the shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk drive motor applicable to, for example, a 3.5-inch floppy disk drive device.

[0002]

2. Description of the Related Art For example, there is a disk drive motor as shown in FIG. 6 in which a 3.5-inch floppy disk or the like is placed and is rotationally driven. In FIG.
A hole 1a is formed in the central portion of the substrate 1.
A sintered oil-impregnated bearing 2 is attached to a. An inward flange-shaped protrusion 2a is formed at the lower end of the sintered oil-impregnated bearing 2, and the outer periphery of this protrusion 2a is inserted into the hole 1a of the substrate 1. A laterally extending flange portion 2b is formed on the outer peripheral portion of the sintered oil-impregnated bearing 2, and the lower end surface of the flange portion 2b is in contact with the edge portion of the hole 1a of the substrate 1. Further, a step portion is formed at the upper end of the sintered oil-impregnated bearing 2 by projecting the outer peripheral end thereof upward, whereby a cylindrical holder portion 2c is formed at the upper end of the sintered oil-impregnated bearing 2. Has been done.

On the substrate 1, a stator 3 is attached to the outer peripheral portion of the collar portion 2b of the sintered oil-impregnated bearing 2. The stator 3 has a stator core 4 formed by laminating a plurality of magnetic plates. A plurality of salient poles are formed on the outer peripheral portion of the stator 3, and the drive coil 5 is wound around the rib of each salient pole.

One of the magnetic plates constituting the stator core 4 has an extension 4a extending to the sintered oil-impregnated bearing 2. The inner edge of the extended portion 4a is bent and abuts on the upper surface of the flange portion 2b of the sintered oil-impregnated bearing 2. The stator core 4 is fixed on the substrate 1 by a screw 6 inserted from the bottom surface side of the substrate 1 in the extension portion 4a, and by tightening the screw 6, the sintering is performed via the extension portion 4a. The oil-impregnated bearing 2 is fixed so as to be pressed onto the substrate 1.

On the inner peripheral surface of the holder 2c of the sintered oil-impregnated bearing,
The outer ring of the ball bearing 7 is fitted and fixed. The lower end surface of the outer ring of the ball bearing 7 is in contact with the protrusion 2a of the sintered oil-impregnated bearing. On the other hand, the shaft 8 is attached to the inner ring of the ball bearing 7. The lower end of the shaft 8 is inserted into the center hole of the sintered oil-impregnated bearing 2, so that the shaft 8 is rotatable with respect to the substrate 1, the stator 3, and the like. The inner diameter of the central hole of the sintered oil-impregnated bearing 2 into which the shaft 8 is inserted is substantially the same as the outer diameter of the shaft 8, but the inner diameter of the central hole of the sintered oil-impregnated bearing 2 is slightly larger. Therefore, a slight clearance is formed between the sintered oil-impregnated bearing 2 and the shaft 8. Therefore, when the shaft 8 rotates, the lubricating oil impregnated in the sintered oil-impregnated bearing 2 oozes into the clearance, and the shaft 8 and the sintered oil-impregnated bearing 2 slide on each other.

A hub base 9 is fitted and fixed to the outer peripheral surface of the shaft 8 above the ball bearings, and the upper surface of the hub base 9 serves as a disk hub mounting portion. Further, on the lower surface of the hub base 9, a suitable number of jetty walls 9a protruding downward are formed. The jetty 9a engages with a central hole formed in the central portion of the rotor case 10. In this state, the jetty 9a is swaged outward and crushed to crush the hub base 9
And the rotor case 10 are integrally connected.

An arm-shaped chucking lever 11 is attached to the upper surface of the rotor case 10 on the outer peripheral side of the hub base 9. The chucking lever 11 is mounted on the rotor case 10 so as to be swingable by an appropriate supporting member. Further, at the other end of the chucking lever, a protrusion that engages with the pin hole of the disk hub and drives the floppy disk to rotate is integrally provided. Further, a chucking magnet 12 is attached to the upper surface of the rotor case 10 so as to surround the chucking lever 11 and the hub base 9, and the chucking magnet 12 attracts the disk hub onto the hub base 9. There is.

The rotor case 10 has a peripheral wall on its outer circumference, and a ring-shaped drive magnet 13 is provided on the inner peripheral surface of this peripheral wall.
Is attached. The inner peripheral surface of the drive magnet 13 faces the outer peripheral surface of the stator 3, that is, the outer peripheral surface of the salient poles of the stator 3 with a predetermined gap. The drive magnet 13 is magnetized for driving in which N poles and S poles are alternately formed in the circumferential direction. When the drive coil 5 wound around the salient poles of the stator 3 is energized and controlled, the drive magnet 13 is energized, and the rotor 14 including the rotor case 10, the hub base 9, and the shaft 8 is rotationally driven. . When the floppy disk is mounted on the hub base 9, the projection of the chucking lever 11 engages with the pin hole of the floppy disk by the rotation of the rotor 14, and the inner peripheral surface of the pin hole is the projection. When pressed, the floppy disk is rotationally driven.

[0009]

According to the disk drive motor having the above-mentioned structure, since the ball bearing 7 is used as the bearing, there is a problem that the cost thereof becomes high. In particular, in a disk drive motor that is required to be small and thin, the ball bearing 7 itself must be small and thin, but if the ball bearing is made smaller and thinner, the cost becomes higher. There was a problem that it would end up.

Further, in the case where the ball bearing 7 is used as the bearing as described above, rattling, runout, etc. are caused due to the clearance at the time of inserting the shaft 8 into the inner ring thereof, which causes the disc. There is a problem that the characteristics of the drive motor are deteriorated.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to eliminate the ball bearings, there is no rattling or center run-out, and a thin and low-cost disk drive. The purpose is to provide a motor.

[0012]

According to the first aspect of the present invention,
A disk provided with a substrate, a shaft fixed to the substrate, a stator, a drive magnet mounted to the rotor case facing the stator, and a hub base fixed to the rotor case for mounting a disk hub. A drive motor, wherein the shaft has a cylindrical portion and a flange portion having a diameter larger than that of the cylindrical portion, and the hub base includes a disk hub mounting portion and a cylindrical portion integral with the disk hub mounting portion. And a disc hub mounting portion of the hub base, at least a portion of which is axially overlapped with the flange portion of the shaft and is slidably contacted with the upper surface of the flange portion of the shaft, The inner peripheral surface of the cylindrical portion of the hub base is in sliding contact with the outer peripheral surface of the flange portion of the shaft. According to the second aspect of the invention, the hub base may be made of a sintered body impregnated with lubricating oil. Claim 3
As in the invention described above, the hub base may be made of a slidable resin.

According to a fourth aspect of the present invention, a substrate, a shaft fixed to the substrate, a stator, and a drive magnet mounted on the rotor case so as to face the stator,
A disk drive motor having a hub base fixed to a rotor case and having a disk hub mounted thereon, wherein the shaft has a cylindrical portion and a flange portion having a diameter larger than that of the cylindrical portion. A disc hub mounting portion and a cylindrical portion integral with the disc hub mounting portion, and a plurality of balls are sandwiched between the bottom surface of the disc hub mounting portion of the hub base and the flange portion of the shaft. The inner peripheral surface of the cylindrical portion of the hub base is in sliding contact with the outer peripheral surface of the flange portion of the shaft.

According to a fifth aspect of the present invention, the contact surface of the hub base with the disk hub may be covered with a coating agent having slidability. Further, as in the invention described in claim 6, the outer peripheral surface of the cylindrical portion of the shaft may be covered with a coating material having slidability.

[0015]

Since a part of the disk hub mounting portion of the hub base is axially overlapped and slidably contacts the flange portion of the shaft, the load in the thrust direction of the rotor is supported by the flange portion of the shaft. Further, since the inner peripheral surface of the cylindrical portion of the hub base is in sliding contact with the outer peripheral surface of the flange portion of the shaft, the radial load of the rotor is supported by the flange portion of the shaft. Therefore, since the load of the rotor in the thrust direction and the radial direction is supported by the flange portion of the shaft, the ball bearing can be eliminated, and
It is possible to obtain stable rotation without rattling or wobbling of the rotor, and to improve the characteristics of the disk drive motor.

Further, a plurality of spheres are sandwiched between the bottom surface of the disk hub mounting portion of the hub base and the flange portion of the shaft, and the inner peripheral surface of the cylindrical portion of the hub base is the outer peripheral surface of the flange portion of the shaft. Even in the case of sliding contact with the shaft, the load of the rotor in the thrust direction is supported by the flange of the shaft via the sphere, so the ball bearing can be eliminated, and the inner peripheral surface of the cylindrical portion of the hub base and the shaft can be eliminated. By the sliding contact with the outer peripheral surface of the flange portion, it is possible to obtain stable rotation without rattling or runout of the rotor, and it is possible to improve the characteristics of the disk drive motor.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a disk drive motor according to the present invention will be described below with reference to the drawings. In FIG. 1 and FIG. 2, the hole 2 is formed in the central portion of the substrate 21.
1a is formed, and the lower portion of the shaft 28 is press-fitted and fixed in this hole 21a. The shaft 28 has a cylindrical portion 28b at its upper end and a flange portion 28a at its lower end. The columnar portion 28b engages with the central hole of the disc hub when the disc hub is placed, and the sliding contact surface of the outer peripheral surface of the cylindrical portion 28b with the disc hub has slidability and resistance. In order to improve the wear resistance, the coating is performed by slidable plating or a coating agent having slidability. Flange portion 28a of the shaft 28
Has a larger diameter than the cylindrical portion 28b. A small diameter portion having a small diameter is formed at the lower end of the flange portion 28a, and the small diameter portion is press-fitted and fixed to the central hole 21a of the substrate 21 or fixed by an adhesive.

The substrate 21 on the outer peripheral side of the shaft 28
A stator 23 is provided on the top. The stator 23 has a stator core 24 formed by stacking a plurality of magnetic plates. A central hole is formed in the center of the stator core 24, and a plurality of salient poles are provided so as to project outward from the central hole. An appropriate number of screw holes are formed in the vicinity of the central hole of the stator core 24, and the screws 26 inserted through the holes formed in the substrate 1 are screwed into the screw holes, whereby the stator core 25 is placed on the substrate 1. It is fixed. A drive coil 25 is wound around each salient pole of the stator core 24 by a predetermined number of turns. Drive coil 25
Are electrically connected to the drive control circuit formed on the substrate 21, and the energization is controlled thereby.

A hub base 29 is slidably mounted on the upper surface of the flange portion 28a of the shaft 28. Hub stand 29
Is a sintered body formed by sintering copper powder, iron powder, or the like, has an infinite number of pores, and this pore is impregnated with lubricating oil. The hub base 29 has an upper end disk hub mounting portion 29a and a cylindrical portion 29b extending downward from the lower surface of the disk hub mounting portion 29a. The disc hub mounting portion 29a is for mounting the disc hub on the upper surface thereof, and a coating agent having a good slidability such as Teflon (trade name) or acrylic resin on the contact surface of the upper surface with the disc hub. It is coated with 35.

A hole is formed in the central portion of the disk hub mounting portion 29a, and the peripheral surface of the central hole and the shaft 2 are formed.
The cylindrical portion 29b of the hub base 29 is fitted to the flange portion 28a of the shaft 28 with a predetermined gap between the cylindrical portion 28b and the cylindrical portion 28b. As a result, the disc hub mounting portion 29a
Of the central hole and the flange portion 28a of the shaft 28
And are stacked in the axial direction. A slight clearance is formed between the lower surface near the peripheral edge of the central hole of the disk hub mounting portion 29a, which is provided in an overlapping manner, and the upper surface of the flange portion 28a of the shaft 28. The impregnated lubricating oils are capable of sliding relative to each other by oozing out.

The cylindrical portion 29b of the hub base 29 is the substrate 2
1 is provided at a predetermined interval between the lower end and the substrate 21 so as not to come into contact with 1. The inner peripheral surface of the cylindrical portion 29b is in sliding contact with the outer peripheral surface of the flange portion 28a of the shaft 28. The inner peripheral surface of the cylindrical portion 29b and the flange portion 28
A slight clearance is formed between the outer peripheral surface and the outer peripheral surface, and the lubricating oil impregnated in the hub base 29 bleeds into this clearance so that they can slide with respect to each other.

The disc mounting portion 29a is provided on the lower surface of the disc hub mounting portion 29a on the outer peripheral side of the cylindrical portion 29b.
Jettys 29c projecting downward from the lower surface are formed in several places. The edge of the central hole of the rotor case 30 is in contact with the outer peripheral surface of the jetty 29c and the lower peripheral surface of the disk hub mounting portion 29a. Then, the hub 29 and the rotor case 30 can be integrally rotated by crimping and crushing the jetty 29c toward the outside.

The rotor case 30 is formed in a substantially cup shape, and has a central hole that engages with the hub base 29 in its central portion and a peripheral wall on its outer peripheral portion. A chucking lever 37 (see FIG. 2) is attached to the upper surface of the rotor case 30 on the outer peripheral side of the hub base 29. One end of the chucking lever 37 is supported by a fulcrum 36 (see FIG. 2) formed on the upper surface of the rotor case 30, and can swing horizontally along the upper surface of the rotor case 30. Further, the other end of the chucking lever 37 has a protrusion 31 protruding upward.
Are formed. When the floppy disk is placed, the protrusion 31 engages with the pin hole of the disk hub and drives the disk hub to rotate.

The chucking lever 37 is located on the outer peripheral side of the rotor case 30 with respect to the chucking lever 37.
A chucking magnet 32, which is substantially ring-shaped and surrounds the hub base 29, is fixed to the upper surface of the rotor case 30. The chucking magnet 32 is for attracting a disk hub when a floppy disk is placed and for attracting and holding the disk hub on the hub base 29. The upper surface of the chucking magnet 32 is formed so as to be slightly lower than the upper surface of the hub base 29. When the disk hub is placed on the hub base 29, the lower surface of the disk hub and the upper surface of the chucking magnet 32. A slight gap is formed between the and.

A ring-shaped drive magnet 33 is fixed to the inner peripheral surface of the outer peripheral wall of the rotor case 30. The drive magnet 33 is magnetized for driving in which N poles and S poles are alternately formed in the circumferential direction, and the inner peripheral surface thereof is the outer peripheral surface of the stator 23, that is, the stator 2.
It faces the outer peripheral surface of the salient pole 3 at a predetermined distance.
The hub base 29, the rotor case 30, the drive magnet 3
A rotor 34 is formed by 3 and the like, and the rotor 34 is rotationally driven by controlling the energization of the drive coil 25. When the disc hub is placed on the hub base 29, the chucking lever 37
Of the rotor 3 by engaging the projection 31 of the rotor with the pin hole of the disk hub.
The disk hub is rotationally driven by the rotation of 4.

In the disk drive motor configured as in the above embodiment, the peripheral edge of the central hole of the disk hub mounting portion 29a of the hub base 29 is slidably provided on the flange portion 28a of the shaft 28. Therefore, the load in the thrust direction of the rotor 34 and the mounted floppy disk or the like can be received by the flange portion 28a of the shaft 28. Further, since the inner peripheral surface of the cylindrical portion 29b of the hub base 29 is in sliding contact with the outer peripheral surface of the flange portion 28a of the shaft 28, it is possible to receive the radial load of the rotor 34 and the like. Therefore, since the sliding contact between them can receive the load in the thrust direction and the radial direction of the rotor 34 and the like, the rotation of the rotor 34 is extremely stable, and the ball bearing can be eliminated to eliminate rattling. Therefore, the characteristics of the disk drive motor can be improved. Further, since the shaft 28 is a fixed shaft, there is no center deviation, and the characteristics of the disk drive motor can be improved also from this point.

Further, since the ball bearing is eliminated by adopting the above-mentioned structure, the motor can be easily miniaturized and thinned, and the cost thereof can be kept low.

Since the outer peripheral surface of the cylindrical portion 28b of the shaft 28 is coated with a coating material having slidability, when the disc is mounted and rotated, the central hole of the disc hub and the shaft 28 are smoothly brought into sliding contact with each other. Therefore, the characteristics of the disk drive motor are not affected. Further, by coating the outer peripheral surface of the cylindrical portion 28b of the shaft 28 with a coating agent having excellent wear resistance, it is possible to prevent the shaft 28 from being worn due to friction with the disk hub.

Since the sliding contact surface of the hub base 29 with the disk hub is coated with a coating material having slidability, when the disk hub is chucked and placed on the hub base 29, the disk hub is smoothly moved. Can be placed.

In the above embodiment, the coating is applied only to the upper surface of the disc hub mounting portion 29a which is in sliding contact with the disc hub.
You may make it apply a coating to the whole surface. As a result, the lubricating oil oozing from the hub base 29 made of a sintered body will not be scattered by the rotation of the rotor 34,
The inconvenience of soiling a floppy disk or the like can be eliminated.

In the above-described embodiment, the hub base 29 is made of a sintered body impregnated with lubricating oil.
9 may be made of a slidable resin instead of the sintered body impregnated with lubricating oil. In such a case, it is not necessary to coat the sliding contact surface of the disc hub mounting portion 29a with the disc hub with a coating agent. Even in such a case, the hub base and the disk hub can be slidable between the hub base and the shaft, and the same effect as that of the above embodiment can be obtained.

Although the embodiment shown in FIGS. 1 and 2 is a circumferentially opposed motor, the air-core coil 44 is fixed on the substrate 21 as shown in FIG. 44
The ring-shaped drive magnet 43 is appropriately spaced from the upper surface.
May be a face-to-face type motor fixed to the bottom surface side of the rotor case 30. Since the configuration of the shaft, hub base and the like is the same as that of the embodiment shown in FIGS. 1 and 2, the same reference numerals are given and the description thereof is omitted. As described above, also in the embodiment shown in FIG. 3, the configurations of the shaft 28, the hub base 29, etc. are the same as those in the embodiments shown in FIGS. 1 and 2, and therefore, the embodiment shown in FIGS. As in the case of the configuration, it is possible to eliminate core runout, reduce the size and thickness of the motor, and reduce the cost.

In each of the embodiments described so far,
The structure is such that the flange portion 28a of the shaft 28 and the hub base 29 slide directly. According to this structure, when the substrate 21 is an iron plate substrate, the magnetic attraction between the substrate 21 and the drive magnet is increased, the thrust load is increased, and the flange portion 28a of the shaft 28 and the hub base 29 slide. Dynamic loss may increase. Therefore, as in the embodiment shown in FIGS. 4 and 5, a plurality of balls 50 are sandwiched between the flange portion 28a of the shaft 28 and the hub base 29, and a load in the thrust direction is received via these balls 50. It is good to do so. With such a configuration, the hub base 29
Since the sphere 50 rotates when is rotated, sliding loss can be reduced.

A lubricant such as grease is applied around each of the balls 50. The disk hub mounting portion 2 of the hub base 29
A concave portion for rotatably holding each sphere 50 is formed on the bottom surface of 9a, and the upper half of the sphere 50 is fitted into this concave portion and positioned with respect to the hub base 29. Each ball 5
The upper surface of the flange portion 28a of the shaft 28 on which 0 rests may be a flat surface, or a raceway having a concave cross section may be provided in an annular shape at the portion where the sphere 50 rolls. In addition, the inner peripheral surface of the cylindrical portion 29b of the hub base 29 is in sliding contact with the outer peripheral surface of the flange portion 28a of the shaft 28, and the sliding contact surface of the hub base 29 with the disk hub has slidability. Other configurations including being covered with a coating agent and the outer peripheral surface of the cylindrical portion 28b of the shaft 28 being covered with a coating agent having slidability, etc. are the same as those of the embodiment shown in FIGS. Since it is the same as, the description will be omitted.

[0035]

According to the invention described in claim 1, since at least a part of the hub base is axially overlapped with the flange portion of the shaft to be in sliding contact with the flange portion of the shaft, It can receive a load in the thrust direction. Further, since the inner peripheral surface of the cylindrical portion integrated with the hub base is in sliding contact with the outer peripheral surface of the flange portion of the shaft, it is possible to receive a load in the radial direction. Therefore, since the sliding contact between them can receive the load in the thrust direction and the radial direction, the rotation of the rotor is extremely stable, and the ball bearing can be eliminated to eliminate the rattling of the motor. The characteristics of the drive motor can be improved. Further, since the shaft is fixed to the substrate, there is no center deviation, and the characteristics of the disk drive motor can be improved also from this point.

Further, since the ball bearing is eliminated by adopting the above-mentioned structure, it is possible to easily reduce the size and thickness of the motor and to keep the cost low.

According to the invention of claim 2, the hub base is
Since the sintered body is impregnated with lubricating oil, the hub base and the flange portion of the shaft are in smooth sliding contact with each other, and sliding loss can be reduced.

According to the invention of claim 3, the hub base is
Since it is made of the slidable resin, when the disk hub is chucked and mounted on the hub base, the disk hub can be smoothly mounted.

According to the invention as set forth in claim 4, since a plurality of balls are sandwiched between the bottom surface of the disk hub mounting portion of the hub base and the flange portion of the shaft, sliding between the hub base and the flange portion of the shaft is achieved. The contact loss can be further reduced.

According to the fifth aspect of the present invention, since the sliding contact surface of the hub base with the disk hub is coated with the coating material having the slidability, the disk hub is chucked and mounted on the hub base. When placing, the disc hub can be placed smoothly.

According to the invention described in claim 6, since the outer peripheral surface of the cylindrical portion of the shaft is covered with the coating material having slidability, when the disk is placed and rotationally driven,
The central hole of the disc hub and the shaft are brought into smooth sliding contact with each other, so that wear of the shaft can be prevented and the characteristics of the disc drive motor are not affected.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a disk drive motor according to the present invention.

FIG. 2 is a plan view of the above embodiment.

FIG. 3 is a sectional view showing another embodiment of the disk drive motor according to the present invention.

FIG. 4 is a sectional view showing still another embodiment of a disk drive motor according to the present invention.

FIG. 5 is a plan view of a portion of a hub base in the above embodiment.

FIG. 6 is a sectional view showing an example of a conventional disk drive motor.

[Explanation of symbols]

 21 substrate 23 stator 28 shaft 28a flange part 28b cylindrical part 29 hub stand 29a disk hub mounting part 29b cylindrical part 30 rotor case 33 drive magnet 35 coating agent 43 drive magnet 44 drive coil

Claims (6)

[Claims] 1. A substrate, a shaft fixed to the substrate, a stator, a drive magnet mounted to a rotor case facing the stator, and a hub base fixed to the rotor case for mounting a disk hub. A disk drive motor comprising: a shaft portion having a cylindrical portion and a flange portion having a diameter larger than that of the cylindrical portion; A disk hub mounting portion of the hub base, at least a part of which is axially overlapped with the flange portion of the shaft and is provided on the upper surface of the flange portion of the shaft. The disk drive motor is slidably contacted, and the inner peripheral surface of the cylindrical portion of the hub base is slidably contacted with the outer peripheral surface of the flange portion of the shaft. 2. The disk drive motor according to claim 1, wherein the hub base is made of a sintered body impregnated with lubricating oil. 3. The disk drive motor according to claim 1, wherein the hub base is made of a slidable resin. 4. A substrate, a shaft fixed to the substrate, a stator, a drive magnet mounted to a rotor case facing the stator, and a hub base fixed to the rotor case for mounting a disk hub. A disk drive motor comprising: a shaft portion having a cylindrical portion and a flange portion having a diameter larger than that of the cylindrical portion; A plurality of balls are sandwiched between the bottom surface of the disk hub mounting portion of the hub base and the flange portion of the shaft, and the cylindrical portion of the hub base is A disk drive motor, the inner peripheral surface of which is in sliding contact with the outer peripheral surface of the flange portion of the shaft. 5. The disk drive motor according to claim 1, wherein a sliding contact surface of the hub base with the disk hub is covered with a coating material having a sliding property. 6. The disk drive motor according to claim 1, wherein the outer peripheral surface of the cylindrical portion of the shaft is covered with a coating agent having slidability.