JPH114558A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cancel unbalanced centrifugal force due to the shift of the center of gravity of a disk and to suppress the swing of, for example, a shaft when the disk rotates speedily by providing a movable balance member for retaining the rotary balance of the disk between a rotor case and a turntable. SOLUTION: A deflection member 12 as a movable balance member being loosely engaged to a shaft 6 is arranged between a rotor case 7 and a turntable 9. Therefore, a centrifugal force for canceling the unbalance of a centrifugal force being generated due to the deviation center gravity of a disk 10 is generated. Then, while the deflection member 12 maintains a direction for canceling the unbalance of the centrifugal force being generated due to the deviation center gravity of the disk 10, it rotates along with the rotor case 7, the turntable 9, and the disk 10. Therefore, even if the disk 10 is rotated and driven speedily, the swing of the shaft 6, the turntable 9, and the disk 10 can be suppressed, thus accurately reading or recording the information signal of the disk 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for rotating a CD, a DVD, or a CD-ROM, a DVD-ROM, and various other information recording disks (hereinafter simply referred to as "disks"). The present invention relates to a spindle motor capable of reducing shaft runout and vibration caused by the eccentricity of a disk during rotation.

[0002]

2. Description of the Related Art In general, a spindle motor for rotating a disk has a turntable fitted to one end of a shaft, and the disk is mounted on the turntable. At the center of the turntable is a truncated conical or hemispherical projection, and the center position is determined by fitting the center hole of the disc into this projection.

When the turntable is driven to rotate by the drive of the spindle motor, the disk rotates together with the turntable, and a signal recorded on a recording track of the disk is read by a reading unit such as an optical pickup. In a rewritable or writable disc, an information signal can be rewritten or written. As seen in recent CD-ROM drive devices and the like, there has been a tendency to increase the speed of disk rotation in order to increase the processing speed of disk reading and writing, and there is a demand for a spindle motor that can cope with the higher speed. Have been.

[0004]

However, when the rotation speed of the disk is increased, the unbalance of the centrifugal force generated during the rotation of the disk increases due to the slight eccentricity of the disk, and the unbalance of the centrifugal force causes the shaft to oscillate. There is a problem that it rotates while rotating. If the shaft rotates while swinging and the vibration increases, there is a problem in that the information signal recorded on the disk cannot be read or written accurately by the reading unit or the writing unit.

In general, the centrifugal force generated by the eccentricity of a disk is proportional to the square of the rotation speed, and the higher the rotation speed, the more the shaft sway and vibration become extremely large. Therefore, the runout and vibration of the shaft caused by the eccentricity of the disk have a great adverse effect on the high-speed rotation of the disk.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and cancels the imbalance of centrifugal force at the time of disk rotation caused by the eccentricity of the disk to rotate the disk at a high speed. It is therefore an object of the present invention to provide a spindle motor capable of suppressing the deflection of the shaft and reducing the vibration, and thus capable of reading and writing information signals to and from a disk at high speed and accurately.

[0007]

According to a first aspect of the present invention, there is provided a shaft rotatably supported, a rotor case rotating integrally with the shaft, and a disk fitted to one end of the shaft to form a disk. A turntable that rotates while being mounted, and is located between the rotor case and the turntable, and moves on a circumference centered on the shaft along with the rotation of the rotor case to rotate the disk. And a movable balance member for holding

According to a second aspect of the present invention, there is provided a shaft rotatably supported, a rotor case rotating integrally with the shaft, and a turntable fitted to one end of the shaft and rotating while mounting a disk. And an eccentric member that is loosely fitted to the shaft located between the rotor case and the turntable and that rotates with the rotation of the rotor case.

The eccentric member may be rotated while maintaining the direction that offsets the eccentricity of the disk, as in the invention of the third aspect. A hole having a diameter larger than the diameter of the shaft may be provided at a shifted position, and the hole may be loosely fitted to the shaft. Further, as in the invention described in claim 5, two or more eccentric members may be loosely fitted to the shaft. It is more preferable that a low coefficient of friction member is interposed between the eccentric member and the rotor case.

According to a seventh aspect of the present invention, there is provided a shaft rotatably supported, a rotor case rotating integrally with the shaft, and a turntable fitted to one end of the shaft and rotating while mounting a disk. A peripheral wall provided on the rotor case or the turntable to form an annular space inside, and a sphere disposed so as to freely roll in the space. .

As in the invention described in claim 8, it is preferable that the sphere revolves around the shaft while rotating the disk while maintaining a position where the eccentricity of the disk is offset. As in the ninth aspect, a plurality of spheres may be put in the space. Claim 1
As in the invention described in Item 0, it is more preferable that the sphere is made of a magnetic material so that the sphere is attracted to an annular magnet provided inside the peripheral wall when the turntable is stopped.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spindle motor according to the present invention will be described below with reference to the drawings. FIG. 1 shows a state where the disk 10 is mounted on the turntable 9. Reference numeral 1 denotes a motor board made of an iron plate or the like. A thrust receiver 18 is fitted in a hole formed in the center of the motor substrate 1, and one end of a cylindrical bearing 2 is placed around the thrust receiver 18, and the bearing 2 is screwed into the bearing 2. Is the motor board 1
It is fixed to. The bearing 2 is made of a sintered oil-impregnated metal.

A stator core 4 is fitted concentrically on the outer peripheral side of the bearing 2, and is integrally fixed to the bearing 2 and the motor substrate 1 by the screw 3. Stator core 4
Is formed by laminating a plurality of core elements, has a plurality of salient poles radially, and a driving coil 5 is wound around each salient pole.

A shaft 6 is fitted on the inner peripheral side of the bearing 2, and the shaft 6 is rotatably supported by the bearing 2. Further, a load in the thrust direction of the shaft 6 is supported by the thrust receiver 18. The center hole of a cup-shaped rotor case 7 is press-fitted to the outer periphery of the shaft 6 protruding from the upper end surface of the bearing 2, and the shaft 6 and the rotor case 7 are integrally connected. The rotor case 7 covers a stator of the motor including the stator core 4, and a driving magnet 8 is provided on an inner surface of an outer peripheral wall 7 a of the rotor case 7.
Is fixed. The inner peripheral surface of the drive magnet 8
It faces the distal end surface of each of the salient poles, which is the outer peripheral surface of the stator core 4, with an appropriate gap.

A central hole of a disk-shaped turntable 9 on which a disk 10 is mounted is press-fitted into the outer periphery of one end of the shaft 6 protruding from the upper surface of the rotor case 7.
And the turntable 9 are integrally connected. At the center of the upper surface of the turntable 9, a hemispherical projection 9a is formed. The diameter of the outer edge of the projection 9a is
Is approximately the same as the diameter of the center hole. Disk 10
Is mounted on the turntable 9 while the edge of the center hole is guided by the outer peripheral edge of the projection 9a, and is positioned so that the center of the turntable 9 and the center of the disk 10 coincide. It is also possible to provide an urging member that can be moved back and forth in the radial direction on the outer peripheral surface of the convex portion 9a, and to position the disk using this urging member. On the surface of the turntable 9 on which the disk 10 is mounted, rubber (not shown) for preventing the mounted disk 10 from slipping is attached.

Further, as a means for restraining the disk 10, the disk 10 may be restrained by setting the clamp member 11 at a position above the turntable 9 so as to face the disk mounting surface of the turntable 9. In this case, for example, a magnet is embedded in the clamp member or a part of the turntable 9, and the magnetic attraction between the turntable 9 and the clamp member 11 attracts the clamp member 11 to the turntable 9 side, so that the disk 10 Can be restrained.

The spindle motor configured as described above controls the energization of the drive coil 5 of each salient pole in accordance with the rotational position of the drive magnet 8 by switching control.
The drive magnet 8, the rotor case 7, the shaft 6, and the turntable 9 are driven to rotate,
The disk 10 mounted thereon can be driven to rotate.

As described above, when the rotation speed of the disk 10 is increased in order to increase the processing speed of reading or reading / writing the recording signal of the disk 10, the unbalance due to the slight eccentricity of the disk 10 with the increase of the centrifugal force. The amount becomes large, and the deflection of the disk 10 and the turntable 9 becomes large. If the vibration of the disk 10 increases, the information signal recorded on the disk 10 cannot be read accurately. In addition, it becomes difficult to accurately write the information signal on the disk 10.

In the embodiment shown in FIG. 1, an eccentric member 1 as a movable balance member loosely fitted to a shaft 6 is provided between the rotor case 7 and the turntable 9.
2 are arranged. More specifically, as shown in FIGS. 1 and 2A, the eccentric member 12 is a disk-shaped member made of metal, resin, or the like. Also, a large diameter hole 12a is formed. The eccentric member 12 is loosely fitted to the shaft 6 and is placed on the rotor case 7 because the hole 12a is penetrated by the shaft 6 with a sufficient space. In this embodiment, the unbalance of the centrifugal force generated when the disk rotates due to the eccentricity of the disk 10 is offset by the action of the eccentric member 12, thereby suppressing the vibration of the shaft 6 and suppressing the generation of vibration.

When the rotor case 7 is rotated by the drive of the spindle motor, the eccentric member 12
Rotate in the same direction as the rotor case 7 rotates. At the beginning of the rotation of the rotor case 7, the eccentric member 12 is in an unspecified direction. As the rotation speed of the spindle motor increases, the rotation speed of the disk 10 also increases. Even if the disk 10 has an eccentricity, and even if the eccentricity is slight, the unbalance of the centrifugal force is increased by the increase in the rotation speed of the disk 10, and if the eccentric member 12 is not provided, the turn is increased. The runout of the table and the disk increases. However, according to the above embodiment, as shown in FIG.
If the direction of the eccentricity of α is α, the eccentric member 12 has its hole 1
The wide-area arc portion 12b occupying a large area around the center 2a has a direction β opposite to the direction α of the eccentricity of the disk 10.
Turn to. That is, the centrifugal force that offsets the unbalance of the centrifugal force generated by the eccentricity of the disk 10
2 occurs. In this way, the eccentric member 12 rotates together with the rotor case 7, the turntable 9, and the disk 10 while maintaining the direction in which the centrifugal force imbalance due to the eccentricity of the disk 10 is offset.

As described above, the unbalanced centrifugal force generated by the rotation of the eccentric member 12 causes the disc 10 to rotate.
Can cancel the unbalanced centrifugal force generated in the shaft 6, even if the disk 10 is driven at a high speed.
Runout of the turntable 9 and the disk 10 is reduced. As a result, an information signal recorded on the disk 10 can be accurately read by a reading unit (not shown),
Also, an information signal can be accurately recorded on the disk 10.

In order to promptly exert the unbalanced centrifugal force canceling action of the eccentric member 12, a configuration as shown in FIG. 4 may be used. In FIG. 4, the eccentric member 12
On the outer periphery of the shaft 6 between the rotor case 7 and
Disc-shaped low friction coefficient member 1 with low friction coefficient and good slidability
3 is attached. As described above, the eccentric member 12
Exerts an unbalanced centrifugal force canceling action only when the rotation speed of the rotor case 7 reaches a certain rotation speed. However, as shown in FIG.
By attaching the low friction coefficient member 13 to the side on which the eccentric member 2 is placed, the frictional force between the eccentric member 12 and the rotor case 7 can be reduced, so that even if the rotation speed of the rotor case 7 is relatively low, It is possible to quickly exert an unbalanced centrifugal force canceling action.

In the example shown in FIG. 4, the low friction coefficient member 13 is provided between the eccentric member 12 and the rotor case 7.
As shown in FIG. 5, a ring-shaped member 14 having a low friction coefficient and good slidability may be attached to the inner periphery of the hole 12a of the eccentric member 12. With this configuration, the friction between the eccentric member 12 and the rotor case 7 can be reduced, and the unbalanced centrifugal force canceling action can be quickly exhibited. The ring-shaped member 14 may be fitted into the eccentric member 12, or may be formed integrally with the eccentric member 12.

If the centrifugal force of the eccentric member 12 that cancels out the unbalanced centrifugal force due to the eccentricity of the disk is equal to the unbalanced centrifugal force generated from the eccentricity of the disk 10, this unbalanced centrifugal force can be completely eliminated. And the deflection of the shaft 6 due to the unbalance of the centrifugal force can be completely prevented. If the force that offsets the unbalanced centrifugal force is smaller than the unbalanced centrifugal force, the unbalanced centrifugal force cannot be completely offset, but it is equivalent to the unbalanced centrifugal force generated by the biasing member 12. Since the unbalanced centrifugal force can be canceled out, the deflection of the shaft 6 can be largely suppressed.

On the other hand, when the unbalanced centrifugal force by the eccentric member 12 is larger than the unbalanced centrifugal force by the eccentricity of the disk, the centrifugal force by the eccentric member 12 is larger than the unbalanced centrifugal force of the disk. Although the centrifugal force is unbalanced by an amount, if the unbalance between the centrifugal force by the disk and the centrifugal force by the biasing member 12 is within a predetermined small range, the deflection of the shaft 6 is suppressed to a small range. be able to.

In each of the embodiments described above, the case where one eccentric member 12 is provided has been described.
2 may be provided in plurality. FIG. 2B shows an embodiment in which two eccentric members 12 are loosely fitted to the shaft 6. Hereinafter, the operation of the eccentric member 12 when two eccentric members 12 are provided will be described.

As shown in FIG. 6, when the rotational speed of the disk 10 is increased to increase the unbalance of the centrifugal force due to the eccentricity of the disk 10, the two eccentric members 12, 12
They rotate together with the rotor case while maintaining the opening angle θ. Assuming that the centrifugal force of one eccentric member 12 at this time is β ′ and the offset force of the other eccentric member 12 is β ″, the resultant force of the offset force β ′ and the centrifugal force β ″ is determined by the eccentricity of the disk 10. The force is generated in the direction exactly opposite to the direction α of the generated unbalanced centrifugal force, and is equal to the unbalanced centrifugal force generated in the disk 10.

Therefore, unlike the case where one eccentric member 12 is provided, the centrifugal force β ′ generated in the two eccentric members 12, 12.
The unbalanced centrifugal force due to the eccentricity of the disk 10 can be offset by the resultant force of + β ″, so that even when the disk 10 is rotated at high speed, the turntable 9 and the shaft 6 do not swing. As a result, the disk 10 The above signal can be accurately read by the reading unit and can be accurately written.

In the embodiment shown in FIG.
Assuming that the resultant centrifugal force generated by the eccentric members 12 and 12 is M, M 、 k / θ (K = constant).
Accordingly, as the angle θ becomes smaller, the resultant force M of the centrifugal force becomes smaller.
Becomes larger. When the disk 10 has no eccentricity and no centrifugal force imbalance occurs, the angle θ is 18
It becomes 0 degrees. In short, the two eccentric members 12, 12
Rotate together with the disk while maintaining the mutual open angle θ so that the unbalanced centrifugal force of the disk is canceled by the resultant force of the mutual centrifugal force.

In the example of FIGS. 2B and 6, the eccentric member 12
Are provided, but also when three or more are provided, the unbalance of the centrifugal force caused by the eccentricity of the disk 10 can be canceled by the resultant force of the centrifugal force generated in each eccentric member 12.

Next, still another embodiment of the present invention will be described. In FIG. 7, a turntable 9 configured in the same manner as the turntable in the embodiment described so far has a peripheral wall 9 forming an annular space S inside.
c is provided integrally. The annular space S is defined by an inner peripheral surface of the peripheral wall 9c, an upper surface of the rotor case 7, and a lower surface of the turntable 9, and a spherical member 15 as a movable balance member made of a steel ball or the like is provided in the space S. Are placed so that they can roll freely. The peripheral wall 9c
The sphere 15 is prevented from spilling out of the space S.
As the turntable 9 rotates, the sphere 15 can rotate or rotate around the shaft 6 while being in contact with the inner peripheral surface of the peripheral wall 9c.

When the disk 10 is rotated at a high speed and the centrifugal force is unbalanced due to the eccentricity of the disk 10,
The sphere 15 moves in a direction opposite to the direction of the unbalanced centrifugal force. The sphere 15 is
Revolving around the shaft 6 in contact with the inner peripheral surface of the peripheral wall 9c while maintaining the position where the unbalanced centrifugal force is canceled.

As in the case of the eccentric member 12 in the above-described embodiment, the sphere 15 revolves around the shaft 6 while maintaining a predetermined relative position in relation to the turntable 9 with the rotation of the turntable 9. Sphere 1
5 generates a centrifugal force, which can cancel the unbalanced centrifugal force generated by the eccentricity of the disk 10. Therefore, even when the disk 10 is rotated at a high speed, the turntable 9 and the shaft 6 do not shake, so that the information signal recorded on the disk 10 is accurately read by the reading unit, and the information signal is accurately read by the disk 10. Can be written to.

In the embodiment shown in FIG. 7, the peripheral wall 9c is provided on the turntable 9, but a peripheral wall 16 may be provided outside the outer peripheral wall 7a of the rotor case 7, as shown in FIG. As described above, the upper end of the peripheral wall 16 is extended to be positioned between the rotor case 7 and the turntable 9 to form a space S inside the peripheral wall 11, and the sphere 15 is put in the space S. By doing so, a similar effect can be achieved.

The unbalanced centrifugal force offset by the sphere 15 depends on the product of the mass of the sphere 15 and the distance from the shaft 6. If the mass of the sphere 15 is increased and the revolving position is further away from the shaft 6, the force that offsets the eccentricity increases. Also, when a plurality of spheres 15 are put in the space inside the peripheral wall 9c, the unbalanced centrifugal force generated in the disk 10 can be canceled by the resultant force of the canceling forces generated in the respective spheres 15. When a plurality of spheres 15 are rollably inserted into the space S in the peripheral wall 9c, the opening angles of the spheres 15 cancel each other according to the principle described with reference to FIGS. Depending on the balanced centrifugal force, the unbalanced centrifugal force can be completely canceled.

As described above, when the sphere 15 is used to correct the imbalance generated in the disk, when the rotor such as the rotor case 7 or the turntable 9 is rotating at a constant speed, the sphere 15 is centrifuged. It revolves around the shaft 6 together with the peripheral wall 9c while maintaining substantially the same position as if it were stuck inside the peripheral wall 9c by the force. However, when the rotor is stopped or rotating at a low speed, the sphere 15 is not fixed at a predetermined position. May occur as noise.

Therefore, in order to hold the sphere 15 at the time of stop or low-speed rotation, an annular magnet 25 is attached inside the peripheral wall 9c as shown in the embodiment shown in FIG. The sphere 15 made of a magnetic material may be put in the space S defined by the above. According to such a configuration, at the time of stop or low-speed rotation, the sphere 15 is magnetically attracted to the outer peripheral surface of the magnet 25, and at random movement is restricted. On the other hand, when the rotor starts rotating and exceeds a predetermined number of revolutions, the magnet 25
The sphere 15 that has been adsorbed on the peripheral wall 9c separates from the magnet 25 and strikes the peripheral wall 9c. Then, the sphere 15 immediately moves to a position where the unbalanced centrifugal force of the disk is canceled, and corrects the unbalance of the centrifugal force. According to such a configuration, it is possible to reduce the occurrence of noise at the time of stop or low-speed rotation. A magnet similar to the magnet 25 can be attached to the embodiment shown in FIG. Also, when a plurality of spheres are used, a magnet similar to the magnet 25 can be used.

The present invention can be applied to any type of motor using a brushed motor or a ball bearing as a bearing. The design of the bearing structure, the structure of the turntable, and the like can be arbitrarily changed. FIG. 9 shows an embodiment in which the bearing structure and the structure of the turntable are different from the above embodiments. FIG. 9A shows an example in which an eccentric member 12 is provided in FIG. ) Sphere 1
5 shows an example in which 5 is arranged.

In FIG. 9A, a bearing holder 20 is fixed to a center hole formed in the center of the motor board 1 by caulking or the like. On the inner peripheral surface of the bearing holder 20, cylindrical metal bearings 22, 22 are fixed to both upper and lower ends. The shaft 6 is rotatably supported by the bearings 22,22. In addition, a thrust load applied to the shaft 6 in the thrust direction is supported by a thrust receiver 18 fitted on the inner periphery of the lower end portion of the bearing holder 20.

A stator core 4 is concentrically fixed to the outer peripheral side of the bearing holder 20 by caulking or the like. A drive coil 5 is wound around each salient pole of the stator core 4. The center hole of the cup-shaped rotor case 7 is press-fitted to the outer periphery of the shaft 6 protruding from the upper end surface of the upper bearing 22, and the shaft 6 and the rotor case 7 are integrally connected. A drive magnet 8 is fixed to the inner surface of the outer peripheral wall 7a of the rotor case 7. The inner peripheral surface of the drive magnet 8 faces the distal end surface of each of the salient poles, which is the outer peripheral surface of the stator core 4, with an appropriate gap.

The center hole of a disk-shaped turntable 29 on which the disk 10 is mounted is press-fitted to the outer periphery of one end of the shaft 6 protruding from the upper end surface of the rotor case 7, and the shaft 6 and the turntable 29 are integrally connected. ing. At the center of the upper surface of the turntable 29, a conical convex portion 29a is provided.
Is formed, and the center hole is formed at a radial center position.

A ring-shaped concave fitting portion 29b is formed on the outer periphery of the center hole of the convex portion 29a.
The magnet 30 is embedded in b. On the surface of the turntable 29 on which the disk 10 is mounted, a rubber 21 for preventing the mounted disk 10 from slipping is attached.

At a position above the turntable 29,
A clamp member 11 made of a magnetic member is provided.
The clamp member 11 is for chucking the disk 10, and is used for chucking the turntable 29 during chucking.
The disc 10 mounted thereon is pressed against the mounting surface of the turntable 9. Chucking is performed by the magnet 2
The clamp member 11 can be attracted to the turntable 29 by the magnetic attraction force 9b. The chucking of the disk 10 is not limited to the magnetic attraction, but may be the chucking with an appropriate mechanical pressing force.

Further, between the rotor case 7 and the turntable 29, there are provided two eccentric members 12, 12 which are loosely fitted through the shaft 6. When two eccentric members 12, 12 are provided, it is preferable to form a thick portion 12a around the holes of the eccentric members 12, 12. Thick part 12a
The frictional force between the eccentric member 12 and the rotor case 7 can be reduced. In this embodiment, a hole penetrated by the shaft 6 is formed at a position deviated from the center of the disk-shaped member. Instead, a hole penetrated by the shaft 6 is formed at the center of the disk-shaped member. And the eccentric member can be formed by offsetting the weight distribution of the disk-shaped member.

Next, in the embodiment shown in FIG. 9B, the turntable 29 is provided with a peripheral wall 29c located between the rotor case 7 and the turntable 29, and the spherical body 15 is provided inside the peripheral wall 29c. Is inserted. Other configurations are the same as those in FIG. 9A, and the same configurations are denoted by the same reference numerals and description thereof will be omitted. Note that FIG.
In FIG. 2B, a peripheral wall 29c for preventing the sphere 15 from spilling out is provided on the turntable 29. Instead of the peripheral wall 29c, the outer peripheral wall 7a of the rotor case 7 is replaced with a peripheral wall 29c. A peripheral wall located between the rotor case 7 and the turntable 29 may be provided outside.

[0046]

According to the first aspect of the present invention, between the rotor case and the turntable, the rotor moves on the circumference around the shaft with rotation of the rotor case around the shaft. The movable balance member for maintaining the rotational balance of the disk is provided, so that the unbalanced centrifugal force generated by the eccentricity of the disk can be offset by the movable balance member. Sway is suppressed, and vibration can be reduced. As a result, the information signal recorded on the disc can be accurately read, and the information signal can be accurately recorded on the disc.

According to the second, third or fourth aspect of the present invention, by providing the eccentric member as the movable balance member, the unbalanced centrifugal force generated by the eccentricity of the disk can be canceled by the eccentric member. , Claim 1
The same effect as the described invention can be obtained. Claim 5
When two or more eccentric members are loosely fitted to the shaft as in the described invention, the unbalanced centrifugal force can be more effectively canceled by the two or more eccentric members. If a low friction coefficient member is interposed between the eccentric member and the rotor case as in the invention according to claim 6, the operation of the eccentric member becomes smooth, and the unbalanced centrifugal force is more effectively reduced. Can be offset.

According to the seventh aspect of the present invention, by providing a spherical body as a movable balance member, the unbalanced centrifugal force generated by the eccentricity of the disk can be canceled by the spherical body. The same effect as that of the invention can be obtained. According to the eighth aspect of the present invention, when the disk rotates, the sphere revolves around the shaft while maintaining a position that offsets the eccentricity of the disk, thereby achieving an unbalanced state. The centrifugal force can be canceled more effectively. When a plurality of spheres are put in the space as in the invention according to claim 9, the unbalanced centrifugal force can be more effectively canceled by the plurality of spheres. If the sphere is made of a magnetic material and the sphere is attracted to an annular magnet provided inside the peripheral wall when the turntable is stopped as in the invention according to claim 10, The sphere is prevented from moving sloppyly when the table is stopped, and it is possible to suppress the occurrence of noise when the table is stopped or when rotating at low speed.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing various examples of an eccentric member applicable to the present invention.

FIG. 3 is a simplified view showing the operation of an eccentric member applicable to the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of the spindle motor according to the present invention.

FIG. 5 is a cross-sectional view showing still another embodiment of the spindle motor according to the present invention.

FIG. 6 is a simplified diagram showing the operation of two eccentric members applicable to the present invention.

FIG. 7 is a sectional view showing still another embodiment of the spindle motor according to the present invention.

FIG. 8 is a sectional view showing still another embodiment of the spindle motor according to the present invention.

FIG. 9 is a sectional view showing still another embodiment of the spindle motor according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 bearing 4 stator coil 5 drive coil 6 shaft 7 rotor case 8 drive magnet 9 turntable 9c peripheral wall 10 disk 11 clamp member 12 eccentric member 15 spherical body 16 peripheral wall

Claims (10)

[Claims] A shaft rotatably supported; a rotor case rotating integrally with the shaft; a turntable fitted to one end of the shaft and rotating while mounting a disk; and the rotor case. A spindle motor comprising a movable balance member positioned between the turntable and a circumference of the shaft centered along with the rotation of the rotor case to maintain a rotational balance of the disk. . 2. A shaft rotatably supported, a rotor case rotating integrally with the shaft, a turntable fitted to one end of the shaft and rotating while mounting a disk, and the rotor case. An eccentric member which is loosely fitted to the shaft positioned between the turntable and the eccentric member and rotates as the rotor case rotates. 3. The spindle motor according to claim 2, wherein the eccentric member rotates while maintaining a direction that offsets the eccentricity of the disk. 4. The shaft according to claim 2, wherein the eccentric member has a hole larger in diameter than the shaft at a position shifted from the center of gravity, and the hole is loosely fitted to the shaft. Spindle motor. 5. The spindle motor according to claim 3, wherein two or more eccentric members are loosely fitted on said shaft. 6. The spindle motor according to claim 2, wherein a low friction coefficient member is interposed between said eccentric member and said rotor case. 7. A shaft rotatably supported, a rotor case rotating integrally with the shaft, a turntable fitted to one end of the shaft and rotating while mounting a disk, the rotor case or A spindle motor comprising: a peripheral wall provided on the turntable to form an annular space inside; and a sphere disposed so as to freely roll in the space. 8. The spindle motor according to claim 7, wherein the sphere revolves around the shaft while rotating the disk while maintaining a position that offsets the eccentricity of the disk. 9. The spindle motor according to claim 7, wherein a plurality of spheres are placed in the space. 10. The sphere is made of a magnetic material, and when the turntable is stopped, the sphere is adsorbed to an annular magnet provided inside the peripheral wall. Or a spindle motor according to 9.