JPH07245902A - Micromotor - Google Patents

Abstract

PURPOSE:To increase the recording density of a recording medium by setting the outer diameter of one bearing, on the side of a load to be coupled with the shaft, larger than that of the other bearing thereby preventing vibration of a motor. CONSTITUTION:The micromotor comprises a tubular bearing bush 22 mounted on a board 21, a shaft 25 supported on the inside thereof through a pair of sleeve bearings 23, 24, a rotor 26 secured to the upper part of the shaft 25, an annular rotor magnet 28 fixed to the inner peripheral surface at the peripheral wall part of the rotor 26, and a stator 27 disposed oppositely to the outside of the bearing bush 22. The sleeve bearing 23 on the upper side of the shaft 25 subjected to a load has outer diameter being set larger than that of the other sleeve bearing 24. The sleeve 23 having larger diameter abuts on a step part 22a provided at the inner peripheral part of the bearing bush 22 and secures the shaft in place. This structure prevents radial vibration of the shaft thus realizing high density recording on a recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to optical disks,
The present invention relates to a micromotor suitable for OA equipment such as a CD-ROM, AV equipment, and vehicle-mounted electrical equipment.

[0002]

2. Description of the Related Art A conventional micromotor for rotationally driving an optical disk, a CD-ROM, etc. will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a conventional micromotor.

In FIG. 3, one sleeve bearing 3 is fitted in from the upper part of a substantially cylindrical bearing bush 2 fixed to the base plate 1, and the other sleeve bearing 4 is fitted in from the lower part thereof. The position is defined by a step on the inner circumference of the middle part of Sleeve bearing 3,4
The shaft 5 is rotatably supported via. A substantially bowl-shaped rotor 6 is fixed to the upper portion of the shaft 5 by press fitting so as to rotate together with the shaft 5. Between the rotor 6 and the upper sleeve bearing 3, in order to ensure smooth rotation of the rotor 6, a washer 9 made of a lubricous resin such as a polyslider is interposed.
A washer 12 and a retaining bush 10 are attached to the lower end of the shaft 5 to prevent the shaft 5 from coming off. A turntable (not shown) is attached to the upper end of the shaft 5 so that a recording medium such as an optical disk or a CD-ROM can be placed.

A step portion is provided on the outer peripheral portion of the bearing bush 2, and the stator 7 is fitted onto the outer periphery of the bearing bush 2 and positioned by the step portion so as to face the rotor magnet 8. A cap 11 is provided at the lower end of the bearing bush 2 in order to prevent the lubricating oil and the like impregnated in the sleeve bearings 3 and 4 from scattering outside the motor.

[0005]

Problems to be Solved by the Invention OA equipment, AV equipment,
In-vehicle electrical equipment and the like are increasingly required to be smaller and have higher performance. Above all, OA for optical disks, CD-ROMs, etc.
Equipment and the like can be downsized, and the storage capacity can be increased and the density can be increased. Higher performance is also required for the micromotors incorporated in them. Therefore, in order to meet the demand for a large storage capacity, it is necessary to prevent the vibration of the motor as much as possible and to realize a higher rotation accuracy to increase the recording density on the recording medium. .

However, in the above-mentioned conventional micromotor, the structure is focused only on supporting the rotation of the shaft 5, and when the micromotor is actually attached to the equipment, No measures have been taken to concentrate the load force on the upper end.
As a result, the load force is concentrated on the upper end portion of the shaft 5 to cause radial deflection of the shaft 5, which causes rattling and vibration.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a structure in which a load force is taken into consideration to prevent vibration of a motor as much as possible. It is to increase the recording density on the recording medium by realizing a higher rotation accuracy.

[0008]

In order to achieve the above object, a micromotor according to the present invention includes a cylindrical bearing bush provided on a substrate and a pair of bearings provided inside the bearing bush. A freely supported shaft, a rotor fixed to the shaft, an annular rotor magnet attached to the inner surface of the peripheral wall of the rotor,
In a micromotor including a stator arranged outside the bearing bush so as to face the rotor magnet, a micromotor having a substrate mounted on an outer circumference of the bearing bush, and the shaft among the both bearings being provided on the shaft. The outer diameter of one of the bearings on the load side to be connected is made larger than the outer diameter of the other bearing.

In this case, it is preferable that a step portion having a larger diameter on the load side than on the opposite side is provided on the inner peripheral portion of the bearing bush, and the one bearing is positioned by the step portion.

The bearing bush is integrally formed by pressing the substrate, and the bearing bush has a large cylindrical portion on the base side and a small cylindrical portion on the tip side.
The one bearing may be fitted inside the large cylindrical portion, and the other bearing may be fitted inside the small cylindrical portion.

In particular, an inward bent portion is formed at the tip of the bearing bush, the other bearing is positioned so as to abut against the bent portion, and the one bearing is positioned to the large cylindrical portion and the large cylindrical portion. The stator is abutted against a step portion at the boundary with the small cylindrical portion and positioned, or the stator is fitted on the outside of the small cylindrical portion of the bearing bush, and the step portion defines the position of the stator. Good.

[0012]

According to the micromotor of the present invention, of the pair of bearings for rotatably supporting the shaft, one of the bearings on the load side is made larger in diameter than the other bearing, so that the load force becomes larger. The acting load side of the shaft can be supported more firmly, radial runout can be reliably prevented, and high rotation accuracy can be realized. Further, the durability of the bearing is increased, so that the life of the motor is extended.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first micromotor according to the present invention.
It is sectional drawing which shows the Example of. In FIG. 1, the illustrated micromotor is a metal substrate 2 that also serves as a motor case.
1, the bearing bush 22 having a substantially cylindrical shape is fixed,
A pair of sleeve bearings 23, 24 are fitted inside the bearing bush 22 from above so that the sleeve bearings 23, 24
A shaft 25 is rotatably supported via 24. A turntable (not shown) is attached to the upper portion of the shaft 25 so that a recording medium such as an optical disc or a CD-ROM can be placed. The sleeve bearing 23 on the load-bearing side of the shaft 25, that is, on the upper side, has an outer diameter larger than that of the other sleeve bearing 24.
This large diameter sleeve bearing 23 is used for the bearing bush 22.
The position is defined by abutting the stepped portion 22a provided on the inner peripheral portion of the. Since the diameter of the sleeve bearing 23 on the load side is larger than the diameter of the other sleeve bearing 24, radial runout of the shaft 25 due to a load force can be prevented, and the life of the motor is extended.

An upper portion of the shaft 25 has a substantially bowl-shaped rotor 2.
6 is fixed and is designed to rotate together with the shaft 25. An annular rotor magnet 28 is mounted on the inner peripheral surface of the peripheral wall portion of the rotor 26 so as to face the stator 27 fitted outside the bearing bush 22. The rotor magnet 28 is positioned by a plurality of recesses 26b provided on the outer peripheral edge of the upper surface of the rotor 26. The shaft 2 is provided at the center of the rotor 26.
5, a small cylindrical portion 26a is provided by press working, and by caulking the small cylindrical portion 26a on the peripheral surface including the D-cut surface 25a formed on the upper outer peripheral surface of the shaft 25, the rotor 26 is attached to the shaft 25. Is fixed, and at the same time it is stopped. Rotor 26 and upper sleeve bearing 2
In order to ensure smooth rotation of the rotor 26, a washer 29 made of a lubricous resin such as a polyslider is interposed between the washer 29 and the rotor 3. A cap 31 is provided below the bearing bush 22 in order to prevent unclean air inside the motor from being scattered by the lubricating oil impregnated in the sleeve bearings 23 and 24 to the outside of the motor.

In the conventional micromotor, in order to improve the rotational accuracy of the motor, when the motor is imbalanced, several recesses are formed on the outer peripheral surface of the rotor by cutting or the like to balance the rotation of the motor. In such a method, the background at the position of the recess is exposed, so that rust is likely to occur, which requires time and effort for rust prevention processing and is not good in appearance. Further, in the conventional micromotor, a retaining bush or the like is used for the shaft in order to prevent the shaft from coming off, but with such a method, it takes a lot of time and labor for assembling, and the assembling workability is not good.

In view of such a problem, in the embodiment, when the motor is imbalanced, the rotor magnet positioning recess 26b provided on the outer peripheral edge of the upper surface of the rotor 26 is used.
In addition, by filling the putty, the motor can be balanced, shake and rattling can be prevented by a simple operation, and the rotation accuracy of the motor can be improved.

Further, in the embodiment, the shallow dish-shaped magnet 30 is disposed on the cap 31, and the circular concave portion 30 at the center thereof is provided.
Since the lower end portion of the shaft 25 is fitted in a, the shaft 25 is prevented from coming off due to the attractive force of the magnet 30. The lower end surface of the shaft 25 is in contact with the magnet 30, but has an arc-shaped cross section in order to reduce friction during rotation. The magnet 30 is formed of a lubricous resin such as a polyslider, and has a shaft 25.
It reduces friction during rotation.

FIG. 2 is a sectional view showing another embodiment of the micromotor according to the present invention. 2, in the illustrated micromotor, a substantially cylindrical bearing bush 42 is integrally formed by pressing a metal substrate 41. The bearing bush 42 has a large cylindrical portion 42a on the base side (upper side in the drawing) and a small cylindrical portion 42b on the tip side (lower side of the peripheral surface), and the tip of the small cylindrical portion 42b is inward. An annular bent portion 42c is formed by bending the. A shaft 45 is rotatably supported inside the bearing bush 42 via a pair of sleeve bearings 43 and 44. A turntable (not shown) is attached to the upper portion of the shaft 45, and an optical disc or a CD-ROM is attached.
A recording medium such as the above is placed.

Sleeve bearing 43 on the load side of shaft 45
Has an outer diameter larger than that of the other sleeve bearing 44. Then, the other sleeve bearing 44 is first fitted inside the small cylindrical portion 42b of the bearing bush 42, and is positioned by bringing the sleeve bearing 44 into contact with the annular bent portion 42c, and subsequently, the one sleeve bearing 43. Is fitted inside the large cylindrical portion 42a of the bearing bush 42, and the sleeve bearing 43 is inserted into the large cylindrical portion 42a.
Is positioned by contacting the upper surface of the stepped portion 42d at the boundary between the small cylindrical portion 42b and the small cylindrical portion 42b. Therefore, shaft 4
Since the diameter of the sleeve bearing 43 on the loaded side of No. 5 is larger than the diameter of the other sleeve bearing 44, radial runout of the shaft 45 can be prevented, and the life of the motor is extended.

Below the shaft 45, a substantially bowl-shaped rotor 4 is provided.
6 is fixed and is designed to rotate together with the shaft 45. An annular rotor magnet 48 is mounted on the inner peripheral surface of the peripheral wall portion of the rotor 46 so as to face the stator 47 externally fitted to the outside of the bearing bush 42, and is provided at several locations on the outer peripheral edge portion of the lower surface of the rotor 46. Recess 46
Positioned by b. When the motor is out of balance, the recess 46b is filled with putty to balance the motor, prevent runout and rattling, and improve the rotational accuracy of the motor.

The rotor 46 is fixed to the shaft 45 and is prevented from rotating by caulking a small cylindrical portion 46a provided at the center of the rotor 46 to the peripheral surface including the D-cut surface of the lower peripheral surface of the shaft 45. Rotor 46 and lower sleeve bearing 4
In order to ensure smooth rotation of the rotor 46, a washer 49 made of a lubricous resin such as a polyslider is interposed between the washer 49 and the rotor 4. A cap 50 is provided on the upper surface of the substrate 41. The stator 47
Is externally fitted to the outer periphery of the small cylindrical portion 42b of the bearing bush 42, and is positioned by contacting the lower surface of the stepped portion 42d at the boundary with the large cylindrical portion 42a.

Although the embodiment of the micromotor according to the present invention has been described above, the present invention is not limited to this embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the magnet 30 for preventing the shaft 25 from coming off may not be in contact with the shaft 25, may be opposed to the shaft 25 with a slight gap, and the magnet 30 may have a shallow dish shape and a concave shape. It may have another shape such as a flat shape.

The number of recesses 26b and 46b for positioning the rotor magnets 28 and 48 provided on the outer peripheral portions of the upper (lower) surfaces of the rotors 26 and 46 may be any.
The D-cut surface of the shaft 25 is not limited to one surface, and may be two or more surfaces.

Further, the bearing is not limited to the sleeve bearing, and may be any bearing such as a ball bearing.

[0026]

As described above, in the micromotor of the present invention, of the pair of bearings that rotatably support the shaft, the outer diameter of one of the bearings on the load bearing side of the shaft is larger than that of the other bearing. As a result, radial runout of the shaft can be reliably prevented, and high rotation accuracy can be realized. Therefore, by increasing the rotation accuracy of the motor, it is possible to increase the recording density of the recording medium and prevent a reading error of the recording medium when the recording medium is applied to, for example, a CD-ROM. Further, the durability of the bearing is increased, so that the life of the motor is extended.

Further, by providing the step portion on the inner peripheral portion of the bearing bush, one of the bearings can be surely positioned on this, and the one bearing having the large diameter on the shaft load side can be surely positioned and fixed. Therefore, more stable rotation can be obtained. Furthermore, if the bearing bush is integrally formed by pressing the substrate, the number of parts can be reduced and the cost can be reduced. By forming the bent portion, one bearing and the other bearing can be reliably positioned and fixed, so that the assembly work is very simple and the stator can be easily and reliably assembled.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a micromotor according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the micromotor according to the present invention.

FIG. 3 is a cross-sectional view showing a conventional micromotor.

[Explanation of symbols]

 21, 41 Substrate 22, 42 Bearing bush 22a, 42d Step portion 23, 43 Upper sleeve bearing 24, 44 Lower sleeve bearing 25, 45 Shaft 26, 46 Rotor 27, 47 Stator 28, 48 Rotor magnet 42a Large cylindrical portion 42b Small cylinder Part 42c Circular bending part

Claims (5)

[Claims] 1. A cylindrical bearing bush provided on a substrate, a shaft rotatably supported inside the bearing bush via a pair of bearings, a rotor fixed to the shaft, and a rotor of the rotor. A micromotor comprising: an annular rotor magnet attached to an inner surface of a peripheral wall portion; and a stator disposed outside the bearing bush so as to face the rotor magnet. A substrate mounted on an outer circumference of the bearing bush. The micromotor, wherein the outer diameter of one of the bearings on the load side connected to the shaft is larger than the outer diameter of the other bearing. 2. A step portion having a larger diameter on the load side than on the opposite side to the inner side portion of the bearing bush, and one of the bearings is positioned by the step portion. Micromotor described. 3. The bearing bush is integrally formed by pressing the substrate, and the bearing bush has a large cylindrical portion on the base side and a small cylindrical portion on the tip side, and the inside of the large cylindrical portion has the small cylindrical portion. 2. The micromotor according to claim 1, wherein one bearing is fitted inside, and the other bearing is fitted inside the small cylindrical portion. 4. An inwardly bent portion is formed at a tip of the bearing bush, the other bearing is positioned so as to abut against the bent portion, and the one bearing is provided with the large cylindrical portion and the large cylindrical portion. The micromotor according to claim 3, wherein the micromotor is positioned in contact with a step portion at a boundary with the small cylindrical portion. 5. The micromotor according to claim 3, wherein the stator is externally fitted to the outside of the small cylindrical portion of the bearing bush, and the position of the stator is defined by the step portion.