JP3594284B2 - Spindle motor - Google Patents

Description

[0001]
TECHNICAL 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 generated shaft runout and vibration.
[0002]
[Prior art]
Generally, in a spindle motor for rotating a disk, a turntable is 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.
[0003]
When the turntable is driven to rotate by the drive of the spindle motor, the disc rotates together with the turntable, and signals recorded on recording tracks of the disc are read by a reading unit such as an optical pickup. In a rewritable or writable disc, an information signal can be rewritten or written. In addition, as seen in recent CD-ROM drive devices and the like, there is a tendency to increase the rotation speed of the disk in order to increase the processing speed of reading and writing the disk, and there is a demand for a spindle motor capable of coping with the higher speed. Have been.
[0004]
[Problems to be solved by the invention]
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 swing and rotate. . When the shaft rotates while swinging and the vibration increases, there is a problem that the information signal recorded on the disk cannot be read or written accurately by the reading unit or the writing unit.
[0005]
In general, the centrifugal force generated by the eccentricity of the disk is proportional to the square of the rotation speed, and the higher the rotation speed, the more the deflection and vibration of the shaft become. 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.
[0006]
The present invention has been made in order to solve the problems of the conventional technology as described above, and by canceling the imbalance of centrifugal force at the time of disk rotation caused by the eccentricity of the disk, even if the disk is rotated at high speed. It is an object of the present invention to provide a spindle motor capable of suppressing shaft runout and reducing vibration, and thus capable of reading and writing information signals to and from a disk at high speed and accurately.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present application includes a shaft rotatably supported, a rotor case that rotates integrally with the shaft, a turntable that is fitted to one end of the shaft and rotates while mounting a disk, A hole having a diameter larger than the diameter of the shaft is provided between the rotor case and the turntable at a position deviated from the center of gravity, and the hole is loosely fitted to the shaft and rotates with the rotation of the rotor case. And an eccentric member that rotates.
[0008]
According to a second aspect of the present invention, in the first aspect, two or more eccentric members are loosely fitted to the shaft.
[0009]
In the eccentric member, it is more preferable that a low friction coefficient member is interposed between the eccentric member and the rotor case.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a spindle motor according to the present invention will be described 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 board 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. Are fixed to the motor substrate 1. The bearing 2 is made of a sintered oil-impregnated metal.
[0011]
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. The stator core 4 is formed by laminating a plurality of core elements, has a plurality of salient poles in a radial shape, and a driving coil 5 is wound around each salient pole.
[0012]
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 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 bearing 2, and the shaft 6 and the rotor case 7 are integrally joined. The rotor case 7 covers a stator of the motor including the stator core 4, and a drive magnet 8 is fixed to an inner surface of an outer peripheral wall 7 a 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.
[0013]
The center hole of a disk-shaped turntable 9 on which a disk 10 is mounted is press-fitted to the outer periphery of one end side of the shaft 6 protruding from the upper surface of the rotor case 7, and the shaft 6 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 substantially the same as the diameter of the center hole of the disk 10. The 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 which can be moved back and forth in the radial direction on the outer peripheral surface of the projection 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.
[0014]
In some cases, as a means for restraining the disk 10, the disk 10 is 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 clamp member 11 is attracted toward the turntable 9 by a magnetic attraction force between the turntable 9 and the clamp member 11. Can be restrained.
[0015]
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, thereby controlling the drive magnet 8, the rotor case 7, the shaft 6, and The turntable 9 is driven to rotate, and the disk 10 mounted on the turntable 9 can be driven to rotate.
[0016]
As described above, when the rotation speed of the disk 10 is increased to increase the processing speed of reading or reading / writing the recording signal of the disk 10, the unbalance amount due to the slight eccentricity of the disk 10 increases with the increase of the centrifugal force. As a result, the deflection of the disk 10 and the turntable 9 increases. 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 an information signal on the disk 10.
[0017]
Therefore, in the embodiment shown in FIG. 1, an eccentric member 12 as a movable balance member loosely fitted to the shaft 6 is disposed between the rotor case 7 and the turntable 9. More specifically, as shown in FIGS. 1 and 2A, the eccentric member 12 is a disc-shaped member made of metal, resin, or the like. Also, a large diameter hole 12a is formed. Since the hole 12a is penetrated by the shaft 6 with a sufficient space, the eccentric member 12 is loosely fitted to the shaft 6 and is placed on the rotor case 7. 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, and the vibration of the shaft 6 is suppressed, and the generation of vibration is suppressed.
[0018]
When the rotor case 7 is rotated by the drive of the spindle motor, the eccentric member 12 placed thereon rotates 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 the eccentricity is slight, the unbalance of the centrifugal force is increased by increasing 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-described embodiment, as shown in FIG. 3, when the direction of the eccentricity of the disk 10 at a certain moment is α, the eccentric member 12 has a wide-area circular arc portion 12b occupying a large area centered on the hole 12a. Are directed to the direction β which is exactly opposite to the direction α of the eccentricity of the disk 10. That is, a centrifugal force is generated in the eccentric member 12 to cancel the imbalance of the centrifugal force generated by the eccentricity of the disk 10. 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.
[0019]
As described above, the unbalanced centrifugal force generated in the disk 10 can be offset by the unbalanced centrifugal force generated by the rotation of the eccentric member 12, so that the shaft 6 and the turntable can be rotated even when the disk 10 is driven at a high speed. 9 and the disk 10 are reduced. As a result, the information signal recorded on the disk 10 can be accurately read by a reading unit (not shown), and the information signal can be accurately recorded on the disk 10.
[0020]
In order to quickly 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, a disk-shaped low friction coefficient member 13 having a low friction coefficient and good slidability is attached to the outer periphery of the shaft 6 between the eccentric member 12 and the rotor case 7. 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 12 is mounted, the frictional force between the eccentric member 12 and the rotor case 7 can be reduced. Therefore, 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.
[0021]
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, but as shown in FIG. 5, a ring-shaped member 14 having a low friction coefficient and good slidability is provided. 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.
[0022]
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 is completely canceled. Thus, it is possible to completely prevent the shaft 6 from swaying due to the unbalance of the centrifugal force. If the force that offsets the unbalanced centrifugal force is smaller than the unbalanced centrifugal force, the unbalanced centrifugal force cannot be completely canceled, but is equivalent to the unbalanced centrifugal force generated by the eccentric member 12. Since the unbalanced centrifugal force can be canceled out, the deflection of the shaft 6 can be greatly suppressed.
[0023]
On the other hand, when the unbalanced centrifugal force due to the eccentric member 12 is larger than the unbalanced centrifugal force due to the eccentricity of the disk, the centrifugal force due to the eccentric member 12 is larger than the unbalanced centrifugal force of the disk. A force imbalance will occur, but if the unbalance between the centrifugal force by the disk and the centrifugal force by the eccentric member 12 is within a predetermined small range, the deflection of the shaft 6 can be suppressed to a small range. .
[0024]
In each of the embodiments described above, the case where one eccentric member 12 is provided has been described, but a plurality of eccentric members 12 may be provided. 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.
[0025]
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 move together with the rotor case while maintaining the open angle θ with each other. Rotate. 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.
[0026]
Therefore, unlike the case where one eccentric member 12 is provided, the unbalanced centrifugal force due to the eccentricity of the disk 10 can be offset by the resultant force of the centrifugal force β ′ + β ″ generated in the two eccentric members 12, 12. Therefore, even if the disk 10 is rotated at a high speed, the turntable 9 and the shaft 6 do not shake, so that the signal on the disk 10 can be accurately read by the reading unit and written accurately.
[0027]
In the embodiment shown in FIG. 2B, when the resultant force of the centrifugal force generated by the eccentricity of the two eccentric members 12 is M, M∝k / θ (K = constant). Therefore, as the angle θ decreases, the resultant force M of the centrifugal force increases. When the disk 10 has no eccentricity and no centrifugal force imbalance occurs, the angle θ is 180 degrees. In short, the two eccentric members 12 and 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 centrifugal force of each other.
[0028]
In the example of FIGS. 2B and 6, two eccentric members 12 are provided. However, when three or more eccentric members 12 are provided, the eccentricity of the disk 10 is also increased by the resultant force of the centrifugal force generated in each eccentric member 12. The centrifugal imbalance caused by the heart can be offset.
[0029]
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. 7 shows an embodiment in which a bearing structure, a turntable structure, and the like are different from the previous embodiments.
[0030]
In the embodiment shown in FIG. 7, a bearing holder 20 is fixed by caulking or the like to a center hole formed in the center of the motor substrate 1. 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 and 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 of the bearing holder 20.
[0031]
The 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.
[0032]
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. At the center of the upper surface of the turntable 29, a conical projection 29a is formed, and the center hole is formed at a radial center position.
[0033]
A ring-shaped concave fitting portion 29b is formed on the outer periphery of the center hole of the convex portion 29a, and a magnet 30 is embedded in the concave fitting portion 29b. 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.
[0034]
A clamp member 11 made of a magnetic member is arranged above the turntable 29. The clamp member 11 is for chucking the disk 10 and presses the disk 10 mounted on the turntable 29 against the mounting surface of the turntable 9 during chucking. The chucking can be performed by causing the turntable 29 to attract the clamp member 11 by the magnetic attraction force of the magnet 29b. The chucking of the disk 10 is not limited to the magnetic attraction, but may be the chucking with an appropriate mechanical pressing force.
[0035]
Further, between the rotor case 7 and the turntable 29, two eccentric members 12, 12 which are loosely fitted through the shaft 6 are provided. When two eccentric members 12, 12 are provided, a thick portion 12a may be formed around the holes of the eccentric members 12, 12. The frictional force between the eccentric member 12 and the rotor case 7 can be reduced by forming the thick portion 12a. 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.
[0036]
【The invention's effect】
According to the first aspect of the present invention, the rotational balance of the disk is moved between the rotor case and the turntable on the circumference around the shaft with rotation of the rotor case around the shaft. By providing an eccentric member as a movable balance member for holding the disk, the unbalanced centrifugal force generated by the eccentricity of the disk can be offset by the eccentric member, and the shaft and the turntable run out even when the disk is rotated at high speed. It is suppressed and vibration can be reduced. As a result, the information signal recorded on the disk can be accurately read, and the information signal can be accurately recorded on the disk.
[0037]
When two or more eccentric members are loosely fitted to the shaft as in the invention described in claim 2 of the present application, the unbalanced centrifugal force is more effectively canceled by the two or more eccentric members. be able to.
If a low friction coefficient member is interposed between the eccentric member and the rotor case as in the invention according to claim 3, the operation of the eccentric member becomes smooth, and the unbalanced centrifugal force is more effectively reduced. Can be offset.
[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 diagram showing an 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 sectional view showing still another embodiment of the spindle motor according to the present invention.
FIG. 6 is a simplified view 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.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Bearing 4 Stator coil 5 Drive coil 6 Shaft 7 Rotor case 8 Drive magnet 9 Turntable 10 Disk 11 Clamp member 12 Eccentric member 13 Low friction coefficient member

Claims (3)

A rotatably supported shaft,
A rotor case that rotates integrally with the shaft,
A turntable that is fitted to one end of the shaft and rotates while mounting a disk,
A hole having a diameter larger than the diameter of the shaft is provided between the rotor case and the turntable at a position deviated from the center of gravity, and the hole is loosely fitted to the shaft and rotates with the rotation of the rotor case. A spindle motor having an eccentric member that rotates. The spindle motor according to claim 1, wherein two or more eccentric members are loosely fitted to the shaft. 2. A spindle motor according to claim 1, wherein a low friction coefficient member is interposed between said eccentric member and said rotor case.

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