JP2000166171A - Small-sized motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized motor which materializes damping and silencing by contriving the structure so that the vibration from a stator core may be hard to be transmitted to a bearing holder. SOLUTION: This small-sized motor is equipped with a cylindrical bearing holder 3, a radial bearing 7 retained within the bearing holder 3, a rotary shaft 8 supported rotatably by the radial bearing 7, a rotor 10 including the rotor case 20 fixed to the tip side of the rotary shaft 8, a rotor magnet 21 attached integrally to the rotor case 20, and a stator core 5 fixed opposite to the rotor magnet 21. This motor has a core holder 25 which holds the stator core 5 by pinching it from both sides in axial direction, and the core holder 25 is fixed to the periphery of the bearing holder 3 by elasticity. The core holder 25 has a plurality of pressure contact parts 26 which pressure-contact with the bearing holder 3 by elasticity, and a coupling part 40 which connects each pressure- contact part 26 with the next.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a motor for rotationally driving various disks such as a D-ROM, a DVD, and the like, and a small motor for other various uses, and more particularly to a small motor with low vibration and low noise.

[0002]

2. Description of the Related Art Small motors may be required to have low vibration and low noise depending on the application. For example, in a motor for rotationally driving various disks such as a CD, a CD-ROM, and a DVD, when vibration is generated from the motor, the vibration is transmitted to the disk through a turntable, and the disk vibrates to normally write a signal. Since reading may not be performed, low vibration is strongly required. Therefore, various measures have been taken to reduce vibration even in a conventional small motor, but it is difficult to eliminate vibration of the motor itself. Hereinafter, an example of a conventional small motor will be described with reference to FIG.
The example shown in FIG. 3 has substantially the same configuration as that described in Japanese Patent Application Laid-Open No. 10-108405 filed by the present applicant, and is an example of a spindle motor for driving a disk rotation.

The small motor shown in FIG. 3 has a motor portion and a turntable 82 which is rotated by the motor and on which a disk is placed. And a rotor 80. The rotor 80 has a rotor case 83 with a cup face down.
And a cylindrical rotor magnet 88 fixed to the inner peripheral side of the peripheral wall of the rotor case 83. A boss formed integrally with the center of the turntable 82 is press-fitted into a hole formed at the center of a portion corresponding to the bottom of the cup of the rotor case 83, and the rotary shaft 8 penetrates the inner peripheral side of the boss.
1 is press-fitted. The rotating shaft 81 includes a bearing holder 95.
The rotor 80 is rotatably supported by a radial bearing 96 fitted on the inner periphery of the turntable 82. The turntable 82 and the rotor case 83 constituting the rotor 80 together with the rotating shaft 81 are rotatable. The bearing holder 95 is fixed to the substrate 98 by press fitting. The stator section 90 includes a stator core 91 having a plurality of salient poles, and a drive coil 92 wound around each salient pole of the stator core 91. The stator core 91 is press-fitted and fixed to the outer peripheral side of the bearing holder 95, and the front end surface of each salient pole faces the inner peripheral surface of the rotor magnet 88 with an appropriate gap.

The upper portion of the rotating shaft 81 protrudes from the upper surface of the turntable 82, and a center ring 84 is slidably fitted along the rotating shaft 81 at the upper end of the rotating shaft 81. , A center cap 85 is integrally attached. The lower part of the center ring 84 is located in a concave part formed on the upper surface side of the turntable 82. A coil spring 86 for urging the center ring 84 upward is disposed in the recess, and the upward movement of the turntable 82 caused by the urging force is applied to the center cap 8.
5 regulates at a predetermined position. The outer peripheral surface of the upper half portion of the center ring 84 has a moderately sloping conical surface, and the lower portion has a steeply inclined conical surface. The largest diameter portion following this is larger than the diameter of the center hole of the disk 45. It has a diameter.

When the disk 45 is placed on the turntable 82, the center of the disk 45 is
Is shifted from the center of rotation, the edge of the center hole of the disk 45 hits the conical surface of the center ring 84 and pushes the center ring 84 down along the rotation shaft 81 against the urging force of the spring 86. Thereby, the storing force of the spring 86 is increased. The position of the disk 45 is shifted while the edge of the center hole of the disk 45 slides along the conical surface of the center ring 84 by the upward biasing force of the center ring 84 due to the stored force of the spring 86, and the disk 45 is placed on the turntable 82. The center hole of the disk 45 fits on the outer periphery of the center ring 84, and the center of the disk 45 is aligned with the rotation center of the turntable 82.
5 is regulated. The disk 45 whose position is thus regulated is pressed against the turntable 82 from above by an appropriate clamper, and is rotationally driven integrally with the rotor 80 of the motor.

[0006]

The stator core vibrates when the motor is driven, not limited to the conventional small motor as shown in FIG. According to the example shown in FIG. 3, the vibration generated from the stator core 91 is transmitted to the disk 45 through the bearing holder 95, the radial bearing 96, the rotating shaft 81, and the turntable 82, and the vibration of the disk 45 is particularly large during high-speed rotation. As a result, normal writing and reading of signals cannot be performed, and the disk may vibrate and generate noise. Further, the vibration is transmitted to the substrate 98 through the bearing holder 95, and the substrate 98 may resonate and generate noise.

One of the causes of the generation of such vibration and noise is a deviation between the magnetic center of the rotor magnet 88 and the magnetic center of the stator core 91 in the direction of the rotation axis.
In FIG. 3, this shift amount is indicated by d. The reason that the magnetic center of the rotor magnet 88 and the magnetic center of the stator core 91 are shifted from each other in the rotation axis direction is that a magnetic attraction between the rotor magnet 88 and the stator core 91 generates a thrust force on the rotor 80. This is for stabilizing the position of the rotor 80 by receiving it with the thrust receiver. In the example of FIG. 3, the rotor 80 is sucked downward, and the lower end of the rotating shaft 81 is pressed against an appropriate thrust receiver to stabilize the position of the turntable 82 in the direction of the rotating shaft 81. However, turntable 8
If the displacement d of the magnetic center is increased to stabilize the position 2 and the force in the thrust direction is increased, the vibration of the stator core 91 during driving is easily transmitted to the disk 45 through the rotating shaft 81 and the turntable 82. Become.
Conversely, if the displacement d of the magnetic center is reduced to reduce the force in the thrust direction, the vibration is hardly transmitted to the disk 45, but the disk 45 moves up and down together with the turntable 82. is there.

The present invention has been made to solve the above-mentioned problems of the prior art. The structure is devised so that vibration generated from the stator core during driving is hardly transmitted to the bearing holder, and the structure is temporarily applied to the rotor. Even if the force in the thrust direction is increased, vibration is hardly transmitted to the outside,
An object of the present invention is to provide a small motor capable of reducing noise.

[0009]

According to the first aspect of the present invention, there is provided a cylindrical bearing holder, a radial bearing held in the bearing holder, and a rotary shaft rotatably supported by the radial bearing. In a small motor including a rotor including a rotor case fixed to the tip end side of the rotating shaft, a rotor magnet integrally attached to the rotor case, and a stator core fixed to face the rotor magnet, A core holder having an elastic force for holding the stator core sandwiched from both sides in the axial direction is provided, and the core holder is fixed to the outer periphery of the bearing holder.

The core holder may be formed of a resin as in the second aspect of the invention, or may be formed of a leaf spring material as in the third aspect of the invention. Further, as in the invention according to claim 4, the core holder has a plurality of core holding portions that are in pressure contact with the bearing holder, and a connecting portion that connects these core holding portions, and a stator core is formed by the core holding portion. It may be held.

According to the fifth aspect of the present invention,
In the invention described in 2, 3 or 4, the magnetic center of the rotor magnet and the magnetic center of the stator core in the rotation axis direction are deviated, and a thrust force is applied to the rotor by the magnetic attraction between the rotor magnet and the stator core. It may be given.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a small motor according to the present invention will be described below with reference to FIGS. In FIG. 1, a hole 1 into which a bearing holder 3 is press-fitted is formed in a substrate 1 made of a metal plate such as iron, and the periphery of the hole is drawn to form a burring portion 2 which rises cylindrically upward. . The bearing holder 3 is press-fitted into the burring portion 2, and a core holder 25 is fitted on the outer periphery of the bearing holder 3 in advance. The stator core 5 is fitted on the outer periphery of the core holder 25, and the stator core 5 is sandwiched and held by the core holder 25 from both sides in the axial direction. The core holder 25 will be described later in detail. The bearing holder 3 is formed into a bottomed cylindrical shape by drawing a metal plate, and the outer periphery of the lower end portion is pressed into the burring portion 2 of the substrate 1 and fixed. The stator core 5 is a laminated core composed of a plurality of core plates, has a plurality of salient poles radially, and a driving coil 6 is wound around each salient pole.

A thrust receiving plate 9 is disposed on the inner bottom of the bearing holder 3, and a radial bearing 7 is fitted on the inner periphery of the bearing holder 3, and the radial bearing 7 is held by the bearing holder 3. In this embodiment, the radial bearing 7 is a sintered oil-impregnated bearing. A rotary shaft 8 is inserted into the inner peripheral side of the radial bearing 7, and the rotary shaft 8 is supported by the radial bearing 7 so as to be rotatable around its central axis. The lower end of the rotating shaft 8 is in contact with the thrust receiving plate 9 so that the thrust load applied to the rotating shaft 8 in the thrust direction is supported by the thrust receiving plate 9. The radial bearing 7 is impregnated with a lubricating oil, and the space between the inner peripheral surface of the radial bearing 7 and the outer peripheral surface of the rotating shaft 8 is lubricated with the lubricating oil. Since the bearing holder 3 is formed in a cylindrical shape with a bottom and has a bag shape, the structure is such that lubricating oil can be prevented from flowing out of the bearing holder 3.

The upper end of the rotary shaft 8 extends upward from the upper ends of the radial bearing 7 and the bearing holder 3. A boss 17 is press-fitted into the upper end of the rotary shaft 8 and the turntable 11 is pressed from above. Is press-fitted. The turntable 11 is made of a press-formed product of a metal plate,
A burring portion 12 having a cylindrical shape and facing upward is provided around the center hole, and the burring portion 12 is press-fitted to the rotating shaft 8. The turntable 11 is raised along a circle centered on the rotation shaft 8 so that a ring-shaped groove 13 having an open upper side is formed outside the burring portion 12, and then gradually lowers outward. Conical portion 34, followed by a falling cylindrical portion 35, followed by a horizontal portion 36
Are formed. A portion of the turntable 11 including the burring portion 12, the conical portion 34, and the cylindrical portion 35 constitutes a center ring 50 into which a center hole of the disc 45 can be inserted. The pad 16 is attached to the upper surface of the horizontal portion 36.

The details of the core holder 25 are shown in FIG. As shown in FIGS. 2 (a), 2 (b), 2 (c) and 2 (d), the core holder 25 has an elastic force, and is formed from three places at equal intervals in the circumferential direction based on the ring-shaped connecting portion 40. Partially cylindrical core holding portion 26 integrally formed to extend in the axial direction
And a partially cylindrical second cylindrical portion extending in the same direction as the core holding portion 26 integrally with the core holding portion 26 at three circumferential positions based on the connection portion 40 between the core holding portions 26. It has a two-core holding portion 28. A gap 27 is formed between each core holding portion 26 and each second core holding portion 28 so as to divide them. The core holder 25 is made of resin in the illustrated example, but may be formed of a leaf spring material instead. In any case, the core holder 25 is made of an elastic body and has an elastic force.
The inner diameters of the connecting portion 40 and each core holding portion 26 are substantially the same as the outer diameter of the bearing holder 3, and their inner peripheral surfaces are fitted on the outer periphery of the bearing holder 3 and pressed against the bearing holder 3, and the core holder 25 is pressed. Are fixed to the bearing holder 3. Each of the second core holding portions 28 is provided with a core holder 25.
Is smaller than each core holding portion 26 in the circumferential direction,
The diameter of the inner peripheral surface is larger than the diameter of the inner peripheral surface of each core holding portion 26, and the diameter of the outer peripheral surface is substantially the same as the diameter of the outer peripheral surface of each core holding portion 26. The outer peripheral end (lower end in FIG. 1) of each second core holding portion 28 has an edge protruding outward to form a hook 29.

On the outer periphery of the core holder 25, more specifically, on the outer periphery of the core holder 26 and the second core holder 28 of the core holder 25, the core holder 25 is provided with the bearing holder 3.
Before being fitted, the stator core 5 is fitted.
The entire core holder 25 has an elastic force. In particular, each second core holding portion 28 has a smaller thickness in the radial direction than the core holding portion 26 and has more elasticity. With the diameter of the second core holding portion 28 reduced, the center hole of the stator core 5 is inserted from the hook 29 forming end side. With the center hole of the stator core 5 riding over the hook 29, each second
By releasing the diameter reduction of the core holding portion 28, each second
The core holding portion 28 is expanded by the elastic force, and the stator core 5
Is pressed against the peripheral surface of the center hole. At the same time, the stator core 5 is sandwiched from both sides in the axial direction between the hook 29 of the core holder 25 and the outer peripheral edge of the connecting portion 40, and the stator core 5 is fixed to the core holder 25. The core holder 25 to which the stator core 5 is fixed in this manner is fixed with the center hole thereof fitted to the outer periphery of the bearing holder 3. In the state where the core holder 25 is fixed in this manner, since the diameter of each second core holding portion 28 cannot be reduced, the stator core 5 does not fall off the core holder 25.

An upper end surface of a rotor case 20 forming a part of the rotor 10 is integrally fixed to the lower surface of the turntable 11 by welding or other appropriate means. The rotor case 20 has a shape such that the cup is turned upside down, and a portion corresponding to the bottom of the cup is overlapped and fixed to the lower surface of the turntable 11. A cylindrical rotor magnet 21 is attached to the inner surface of the cylindrical peripheral wall of the rotor case 20. The rotor magnet 21 also forms part of the rotor 10 and is rotatable integrally with the rotor case 20. The inner peripheral surface of the rotor magnet 21 is the stator core 5
Opposing the outer peripheral surface with an appropriate gap. By switching and controlling the energization of the drive coils of each phase in accordance with the rotational position of each magnetic pole of the rotor magnet 21, the rotor 1 is driven by magnetic attraction between the rotor magnet 21 and each salient pole.
0 is continuously driven to rotate.

A disk is mounted on the pad 16 in a state where the disk is centered by fitting a center hole of the disk into the cylindrical portion 35 of the turntable 11.
The groove 13 has a ring-shaped chucking magnet 14.
Is inserted and fixed. When a disc holder (not shown) descends with the disc resting on the pad 16, the magnetic material of the disc holder and the magnet 14
The disk holder is attracted toward the turntable 11 by the magnetic attraction between the disk and the disk, and the disk is pressed toward the turntable 11. The disc holder is
Rotor 1 of motor including turntable 11 and rotating shaft 8
0 and the disk are provided rotatably.

A circuit board 30 is mounted and fixed on the upper surface of the board 1. An appropriate circuit pattern is formed on the circuit board 30, and appropriate circuit components, for example, a magnetic detection element 31 including a Hall element for detecting an index or a rotation speed of the rotor 10 and the like are mounted thereon.

Depending on the use of the small motor, it may be required that the perpendicularity of the rotating shaft 8 to the surface of the substrate 1 be adjusted with high accuracy. In particular, a disk drive motor requires high accuracy. Therefore, the press-fitting of the bearing holder 3 with respect to the substrate 1 is set to light press-fitting, and at the time when one type of assembling is completed, the perpendicularity of the rotating shaft 8 to the surface of the substrate 1 is checked using an appropriate jig or the like. If the accuracy is not obtained, the relative attitude is corrected in the lightly press-fitted portion between the substrate 1 and the bearing holder 3 to obtain the above-described verticality. In this state, the substrate 1 and the bearing holder 3 are finally fixed by means such as bonding or welding the light press-fitted portion.

According to the above-described embodiment, since the core holder 25 having elasticity is interposed between the bearing holder 3 and the stator core 5, the core holder 25 functions as a damper, and the stator core 5 is driven during driving. Is generated by the core holder 25 and the vibration is hardly transmitted to the rotating shaft 8 through the bearing holder 3 and the radial bearing 7. Moreover, since the core holder 25 is fixed to the outer periphery of the bearing holder 3 and holds the stator core 5 by sandwiching the stator core 5 from both sides in the axial direction with the core holder 25 made of an elastic body, the vibration absorbing effect of the core holder 25 is enhanced, 5 can be effectively blocked from being transmitted to the rotating shaft 8. Therefore, for example, in a small motor for driving a disk rotation,
The vibration of the disk can be made extremely small, and signals can be written and read correctly even when the disk is driven at high speed.

Further, in the small-sized disk rotation driving motor, as in the conventional example described with reference to FIG. 3, in order to stabilize the position of the turntable 11 in the rotation axis direction,
The magnetic center of the rotor magnet 21 in the direction of the rotating shaft 8 is shifted from the magnetic center of the stator core 5, and a magnetic attraction between the rotor magnet 21 and the stator core 5 generates a thrust force on the rotor 10 to generate a rotating shaft 8. Is pressed against the thrust receiver 9. Turntable 11
In order to further stabilize the position in the direction of the rotation axis, the pressing force may be increased. However, in the conventional small motor, when the pressing force in the thrust direction is increased, the vibration of the stator core is transmitted to the rotation shaft. There was a drawback that it was easy to be done. In this regard, according to the embodiment of the present invention, since the vibration of the core holder 25 is hardly transmitted to the rotating shaft 8 by the damping effect of the core holder 25, the pressing force of the rotor 10 in the thrust direction is provided. , The transmission of vibration to the rotating shaft 8 can be greatly reduced.

Further, since the vibration of the stator core 5 is cut off by the core holder 25 and the vibration transmitted to the substrate 1 is greatly reduced, the noise caused by the co-promotion of the substrate 1 can also be greatly reduced.

Further, the core holder 25 has a plurality of core holding portions 26 that are in pressure contact with the bearing holder 3 and a connecting portion 40 that connects these core holding portions 26, and the stator core 5 is held by the core holding portions 26. Has been
Each core holding portion 26 functions as an independent damper, and can enhance the effect of absorbing vibration from the stator core 5. In addition to this, the second
Since the core holding portions 28 can also be elastically deformed independently of each other, the vibration of the stator core 5 is
Thus, the vibration can be effectively cut off, and the vibration and noise can be further reduced.

The small motor according to the present invention can be used not only as a disk rotation drive motor but also as a general-purpose motor, but is suitable as a disk rotation drive motor which extremely dislikes transmission of vibration to the disk. ing. In the illustrated embodiment, the core holder 25 is made of a resin integrally molded product. However, the core holder 25 may be a pressed product of a leaf spring material.

[0026]

According to the first aspect of the present invention, since the core holder is interposed between the bearing holder and the stator core, the core holder functions as a damper, and vibration generated in the stator core during driving is reduced. The vibration is hardly transmitted to the rotating shaft through the bearing holder and the radial bearing, so that a small motor can be reduced in vibration and noise. Moreover, the core holder is fixed to the outer periphery of the bearing holder, and the stator core is sandwiched and held from both sides in the axial direction by the core holder having elasticity, so that the vibration absorption effect of the core holder is enhanced,
Vibration generated in the stator core can be effectively blocked from being transmitted to the rotating shaft.

The core holder is made of a resin as in the second aspect of the invention, or is made of a leaf spring material as in the third aspect of the invention, so that the elasticity of the core holder is used to absorb vibration. The effect can be enhanced, and the transmission of vibration from the core holder to the rotating shaft can be effectively blocked.

According to the fourth aspect of the present invention, the core holder has a plurality of core holding portions that are in pressure contact with the bearing holder, and a connecting portion that connects these core holding portions. Since the core holding portions are held, the respective core holding portions can independently absorb the vibration from the stator core, and can enhance the vibration absorbing effect.

According to the invention described in claim 5, claims 1 to 5
In any of the inventions described in the fourth aspect, the magnetic center of the rotor magnet and the magnetic center of the stator core in the rotation axis direction are shifted, and a thrust force is applied to the rotor by the magnetic attraction between the rotor magnet and the stator core. Therefore, by receiving the force in the thrust direction by the thrust receiver, the position of the rotor in the rotation axis direction can be further stabilized. In the conventional small motor, the vibration of the stator core is easily transmitted to the rotating shaft by the above-mentioned thrust force acting. However, according to the present invention, the thrust direction force is applied as in the invention of claim 5. Even if it is, the vibration can be effectively absorbed by the interposition of the core holder between the stator core and the bearing holder.

[Brief description of the drawings]

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

FIG. 2 shows a core holder according to the first embodiment (a).
Is a side view, (b) is a plan view, (c) is a front sectional view,
(D) is a bottom view.

FIG. 3 is a longitudinal sectional view showing an example of a conventional small motor.

[Description of Signs] 1 Substrate 3 Bearing holder 5 Stator core 7 Radial bearing 8 Rotating shaft 10 Rotor 20 Rotor case 21 Rotor magnet 25 Core holder 26 Press-contact part 28 Core holding part 40 Connecting part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H019 AA06 BB05 CC04 DD07 EE13 FF03 5H605 AA04 AA05 BB05 BB15 BB19 CC02 CC03 CC10 EA02 EA09 GG04 GG18

Claims (5)

[Claims] 1. A cylindrical bearing holder, a radial bearing held in the bearing holder, a rotating shaft rotatably supported by the radial bearing, and a rotor case fixed to a distal end side of the rotating shaft. , A driving magnet integrally mounted on the rotor case, and a stator core fixed to face the driving magnet, wherein the stator core sandwiches and holds the stator core from both sides in the axial direction. A small motor having a core holder having a force, wherein the core holder is fixed to an outer periphery of the bearing holder. 2. The core holder according to claim 1, wherein the core holder is made of resin.
Small motor as described. 3. The small motor according to claim 1, wherein the core holder is made of a leaf spring material. 4. The core holder according to claim 1, wherein the core holder has a plurality of core holding portions that are in pressure contact with the bearing holder, and a connecting portion that connects the core holding portions, and the stator core is held by the core holding portions. Small motor. 5. The magnetic center of the rotor magnet and the magnetic center of the stator core in the direction of the rotation axis are shifted from each other, and a thrust force is applied to the rotor by the magnetic attraction between the rotor magnet and the stator core. Item 5. The small motor according to item 1, 2, 3 or 4.