JP3635196B2 - Disk drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk drive device, and more particularly to a disk drive device having means for correcting dynamic balance.
[0002]
[Prior art]
In recent years, the rotational speed of a recording disk has been remarkably increased with the widening of the reproduction signal in the recording disk. In particular, in the CD-ROM device, the recording disk is rotated at a high speed of 7000 to 8000 rpm. At that time, in the case of a recording disk with a good weight balance, vibration does not occur even if it rotates at a high speed, but the recording disk with a poor weight balance or even if the balance is good, the recording disk is mounted eccentrically with respect to the center of rotation. In such a case, vibration occurs due to a deviation between the center of rotation and the center of gravity of the disk. Since the excitation force of this vibration is proportional to the square of the rotation speed, a large vibration is generated at high speed rotation, which causes noise.
[0003]
As a means for automatically correcting such a discrepancy between the center of rotation and the center of gravity of the disk (eccentric center of gravity), a plurality of metal balls rotating around the center of rotation of the disk are inserted into the disk drive device, while the rotation system is A so-called ball balancer device that uses the characteristic that the natural frequency including the rotation frequency is set lower than the rotation frequency and the balls gather in the eccentric direction during high-speed rotation is a “vibration control” JOHN N. MACDUFF JOHNR. CURRERI published by Kokorona Publishing Co., Ltd. 258-266. However, the conventional ball balancer device has the following problems.
[0004]
[Problems to be solved by the invention]
In other words, when the disk drive device is placed vertically (when the disk surface is vertical), the balls are gathered downward when stationary due to the influence of gravity, and the rotation speed is not higher than when the disk drive device is placed horizontally. And can't balance. Further, not only does the balance not only improve during high-speed rotation but also during low-speed rotation, at this time, a sliding sound of the ball due to the relative rotation of the ball and the rotating body is generated, resulting in noise.
[0005]
In order to correct the balance, it is necessary to rotate the ball smoothly with little friction of the ball. However, due to the reasons described below, the friction with the ball is increased and the correction ability is lowered. That is, the ball is pressed against the side wall of the ring groove when rotating. For this reason, the side wall of the ring groove is recessed by Hertz force, and friction increases. Since this pressing force is a centrifugal force, the friction further increases during high-speed rotation. In addition, since the ball is in contact with the ring at two points, that is, the side wall and the bottom surface during rotation, not only a pure rolling motion but also slipping occurs, resulting in increased friction.
[0006]
Further, when the friction caused by the rotation of the ball is small and the eccentricity of the recording disk is small, the ball causes a self-excited vibration, which causes a phenomenon that the relative rotation between the ball and the rotating body is difficult to stop.
[0007]
An object of the present invention is to eliminate such drawbacks of the prior art, and to provide a disk drive device that can significantly reduce vibration and noise even when a recording disk having a large deviation in the center of gravity is rotated at high speed. It is in.
[0008]
[Means for Solving the Problems]
The present invention provides a ring groove on the disk mounting surface side of the turntable that is centered on the rotation center of a shaft that is integrally rotated by press-fitting the turntable so that the dynamic balance correction ball can be moved in the ring groove. This is intended for the inserted disk drive.
[0009]
In order to achieve the above object, the present invention provides the dynamic balance correction ball that drops vertically in the ring groove with the rotation of the turntable, with the disk drive device placed vertically and the disk surface arranged vertically. Protrusions for hooking and lifting upward again by rotation of the turntable are provided on the inner peripheral side of the ring groove, and when the dynamic balance correction ball moves in the outer peripheral direction of the ring groove by rotation of the turntable, The protrusion is non-contact .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
As described above, in the present invention, by providing a protrusion on the inner peripheral side of the ring groove, the rotation of the ball is promoted even when the apparatus is placed vertically, and the balance is corrected even at a relatively low speed. Can do.
[0023]
Next, an example in which the embodiment of the present invention is applied to a CD-ROM disk drive will be described with reference to the drawings. 1 is a cross-sectional view of the disk drive device, FIG. 2 is a schematic configuration diagram showing a support structure of the disk drive device, and FIG. 3 is an enlarged cross-sectional view of a ring groove.
[0024]
In these drawings, reference numeral 1 denotes a turntable which is press-fitted into a shaft 2 and rotates integrally. The shaft 2 is rotatably supported by two bearings 3 provided in a case 4. A stator 5 is attached to the outer peripheral portion of the case 4, and a rotor magnet 6 bonded to a metal case 7 is attached to the outer peripheral portion of the turntable 1, and the motor constituted by the stator 5 and the rotor magnet 6 is used to turn. The table 1 rotates. The recording disk 12 is placed on the sheet 13, fitted into the central protrusion of the turntable 1, and pressed against the turntable 1 by the cap 14.
[0025]
A ring groove 8 centering on the rotation center is formed on the outer peripheral upper surface of the turntable 1, that is, the disk mounting surface side, and a plurality of metal balls 9 are rotatably inserted therein. A guide ring 10 is attached to the inner wall of the ring groove 8, and the upper part of the ring groove 8 is covered with a lid 11 to prevent the ball 9 from jumping out.
[0026]
Thus, the disk drive device 101 is configured, and as shown in FIG. 2, the disk drive device 101 is fixed to a chassis 103 provided with a pickup and its feed mechanism (both not shown). The chassis 103 is attached to the frame 104 via a damper rubber 105. Due to such a structure, when the recording disk 102 with the center of gravity shifted from the rotation center of the shaft 2 is mounted and rotated, the vibration force in the disk surface direction acts on the disk drive device 101 and the chassis 103, and the chassis 103 Since it is elastically supported on the frame 104 by the damper rubber 105, the disk drive device 101 vibrates together with the chassis 103 as well as oscillates around the disk surface at a rotational frequency.
[0027]
This vibration system has a resonance frequency determined by the spring constant of the damper rubber 105 and the masses of the disk drive device 101 and the chassis 103. Due to this vibration, when the rotational speed increases, a deviation occurs between the center of swinging and the rotational center of the turntable 1. This shift direction with respect to the center-of-gravity shift direction changes as the number of rotations increases, and shifts in the center-of-gravity direction at low-speed rotation and deviates from the direction of center-of-gravity shift at a rotation speed higher than the resonance frequency. For this reason, when the rotational frequency is lower than the resonance frequency, the ball 9 is subjected to a force toward the direction of the center of gravity, and when the rotational frequency exceeds the resonance frequency, a force toward the direction opposite to the direction of the center of gravity is exerted. By this force, the ball 9 acts in the direction for correcting the shift of the center of gravity, that is, the direction for correcting the balance. This is the principle of the ball balancer. Since the force acting on the ball is weak, it is necessary to minimize the friction against the ball.
[0028]
The cross-sectional shape of the ring groove 8 for reducing this friction is shown in FIG. During low-speed rotation, the ball 9 is in a position indicated by a broken line in the figure, that is, a position in contact with both the groove bottom surface and the outer peripheral surface due to gravity and centrifugal force. In this state, pure rolling motion does not occur at both contact points, and the friction coefficient does not decrease because of the intermediate motion state between rolling and sliding. Therefore, the lower part of the outer peripheral surface of the ring groove 8 and the vicinity of the part where the ball 9 is in contact with the broken line incline in the direction in which the groove width increases as it goes upward, and this part of the outer peripheral surface becomes a conical surface as a whole. ing.
[0029]
Since the ball 9 is pressed against the outer peripheral surface by centrifugal force, if it is inclined as described above, a force for pushing the ball 9 upward is generated. The ball 9 is in the position indicated by a broken line due to static friction during low-speed rotation, but the centrifugal force increases during high-speed rotation, and this push-up force overcomes the static friction and pushes the ball 9 up to the position indicated by the solid line in the figure. At the position of the solid line, the ball 9 rotates in contact with the outer peripheral surface without contacting the groove bottom surface.
[0030]
When the angle formed with the vertical direction of the oblique portion of the outer peripheral surface is small, the ball 9 comes into contact with two points that are in close proximity to the outer peripheral surface. This state is very close to the state where the ball 9 is in contact with one point of the wall, and therefore the ball 9 rotates in a state close to a pure rolling motion, so that the friction is extremely small, the ball 9 moves lightly, and the balance correction ability is Increase. If the angle between the inclined surface and the vertical direction is large, the point of contact with the ball 9 is separated and pure rolling friction is eliminated, so that the inclination angle cannot be increased too much. Therefore, the angle between the vertical direction of the oblique portion of the outer peripheral surface is suitably in the range of 1 to 20 degrees.
[0031]
The depth of the ring groove 8 (the distance from the lower surface of the lid 11 to the groove bottom surface) corresponds to a value obtained by adding the diameter of the ball 9 and the clearance. Since the ball 9 needs only to be slightly separated from the groove bottom surface, it is sufficient that the maximum height of the inclined surface is ½ of the depth of the ring groove 8 in consideration of the amount of deflection of the groove bottom surface. In this state, the clearance above and below the ball 9 is substantially equal.
[0032]
FIG. 4 is a cross-sectional view showing a second embodiment of the present invention. In this example, one or more annular grooves 16 such as V grooves or U grooves extending in the circumferential direction are formed on the outer peripheral surface of the ring groove 8. When the ball 9 is caught in the annular groove 16 as shown in FIG. 4 for some reason, it is in a stable state and continues to rotate in this state, close to pure rolling motion, and the friction coefficient becomes extremely small.
[0033]
As described above, the ball 9 rotates while being pressed against the wall of the ring groove 8 by the action of centrifugal force and gravity. Therefore, the wall is elastically recessed due to the Hertz force, and the larger the recess, the greater the friction. This dent becomes smaller as the surface hardness of the wall increases, and the coefficient of friction decreases. Therefore, by forming a hard layer on the wall surface of the ring groove 8 by, for example, metal plating such as chromium plating, vapor deposition or sputtering, the surface hardness can be increased and the friction coefficient can be reduced. Forming the hard layer not only reduces the coefficient of friction, but also has the effect of preventing surface corrosion and extending the life of the entire device.
[0034]
Next, the operation of the guide ring 10 will be described. FIG. 5 shows a state in which the ring groove 8 is viewed from the direction perpendicular to the disk surface in a state where the disk drive device is placed vertically, and FIG. 6 shows a perspective view of the guide ring 10. In FIG. 5, the downward direction is the direction of gravity. A plurality of small protrusions 15 are formed in the ring width direction on the outer peripheral portion of the guide ring 10 fitted to the inner wall portion of the ring groove 8.
[0035]
As shown in FIG. 5, when accelerating from a low-speed rotation, the balls 9 are gathered downward due to gravity. The balls 9 gathered below rotate together with the turntable 1 due to the frictional force with the wall of the ring groove 8 and try to be carried above the ring groove 8. Even if it is lifted, it often returns to its lower part due to gravity. The lifted ball 9 falls while contacting the inner peripheral wall of the ring groove 8. Therefore, when the guide ring 10 having the protrusion 15 is mounted on the inner peripheral wall of the ring groove 8, the falling ball 9 is caught by the protrusion 15 and is lifted upward again by the rotation of the turntable 1, and the ball 9 is easily carried upward. Become. When carried upward, the ball 9 falls in the rotational direction inside the groove, and the ball 9 starts to rotate in the same direction with respect to the ring groove 8.
[0036]
When further accelerated, a centrifugal force acts on the ball 9, and the ball 9 moves in the outer circumferential direction by this centrifugal force, and rotates in a stable state without contact with the protrusion 15. When the guide ring 10 having the protrusions 15 is mounted on the inner peripheral wall of the ring groove 8 as described above, the balls 9 do not continue to gather downward during low-speed rotation due to the action of the protrusions 15. But you can correct the balance.
[0037]
In the present embodiment, the guide ring 10 having the protrusions 15 is used. However, the friction coefficient is increased by adding innumerable irregularities to the outer peripheral surface of the guide ring 10, or the guide ring 10 has a large friction coefficient such as rubber. It is made of a material, a rubber ring is fitted to the outer peripheral portion of the guide ring 10, a protrusion is provided on the inner peripheral wall of the ring groove 8 without the guide ring 10, or the surface roughness of the inner peripheral wall of the ring groove 8 Even if the coefficient of friction is increased to increase the friction coefficient, the same effect as described above can be obtained.
[0038]
Since the lid 11 shown in FIG. 1 becomes a side wall when the disk drive device is placed vertically, the ball 9 also contacts the lid 11. Therefore, by increasing the coefficient of friction with respect to the ball 9 in this portion, the force for carrying the ball 9 from below to above can be increased. Therefore, as shown in FIG. 7, the protrusion 11 is formed on the surface of the lid 11 in contact with the ball 9, or innumerable irregularities are used to increase the friction coefficient, or the lid 11 has a large friction coefficient such as rubber. It is good to form with material.
[0039]
Further, as shown in FIG. 3, it is more effective to use the guide ring 10 at the inner peripheral portion and the inclined surface shape at the outer peripheral portion in combination. As described above, in order to reduce the friction coefficient in the inclined surface shape of the outer peripheral portion, the inclination angle cannot be increased so much, and therefore the force for pushing the ball 9 upward is not large. For this reason, there is a case where the ball 9 returns once it rises along the inclined surface. In this state, the coefficient of friction is large. However, when the ball 9 returns to the bottom surface, the ball 9 easily comes into contact with the guide ring 10. When the ball 9 comes into contact with the guide ring 10, the ball 9 moves in the rotation direction. The friction coefficient is lowered.
[0040]
As shown in FIG. 1, the ring groove 8 is formed by cutting directly on the disk mounting surface side of the turntable 1. Compared to the structure in which the ring groove 8 is formed on the side opposite to the disk mounting surface, the ring groove 8 can be formed by the same chucking or the same mold as the disk central hole guide portion of the turntable 1. Thus, the rotational vibration of the outer peripheral portion of the disk 8 can be reduced, and the dynamic balance of the disk drive device can be reduced, thereby reducing vibration and noise.
[0041]
When the chassis 103 (see FIG. 2) vibrates, a relative rotational force with respect to the turntable 1 acts on the ball 9 due to a shift between the rotation center and the center of the turntable 1. When the deviation of the center of gravity of the recording disk is small, the main cause of the deviation of the center of gravity of the entire system is the ball 9 itself, so that when the two or more balls 9 are used, a kind of oscillation phenomenon occurs in which the eccentric gravity centers are corrected. For this reason, the relative rotational movement of the ball 9 with respect to the turntable 1 does not stop even at high speed rotation, causing vibration and noise. This is a phenomenon that occurs because the frictional force and damper force with respect to the relative rotation of the ball 9 are too small.
[0042]
As a countermeasure, in the present embodiment, a lubricant such as graphite, molybdenum disulfide, fluororesin, or silicone oil is applied to the wall surface of the ring groove 8 or a liquid is injected to suppress the oscillation phenomenon and balance. Adjustment can be performed smoothly.
[0043]
In the above-described embodiment, the ring groove is provided in the turntable. However, the present invention is not limited to this, and the ring groove may be provided in another rotating member that rotates around the shaft.
[0044]
【The invention's effect】
As described above, in the present invention, by providing a protrusion on the inner peripheral side of the ring groove, the rotation of the ball is promoted even when the apparatus is placed vertically, and the balance is corrected even at a relatively low speed. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a disk drive device according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing a support structure of the disk drive device.
FIG. 3 is an enlarged sectional view of a ring groove of the disk drive device.
FIG. 4 is an enlarged cross-sectional view of a ring groove of a disk drive device according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a state where a guide ring is mounted in a ring groove according to the present invention.
FIG. 6 is a perspective view of a guide ring according to the present invention.
FIG. 7 is a perspective view of a lid according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Turntable 2 Shaft 3 Bearing 4 Case 5 Stator 6 Rotor magnet 7 Metal case 8 Ring groove 9 Metal ball 10 Guide ring 11 Cover 12 Recording disk 13 Sheet 14 Cap 15 Protrusion 16 Annular groove 17 Protrusion

Claims (1)

A disk drive in which a ring groove centered on the rotation center of a shaft that rotates integrally with a turntable is provided on the disk mounting surface side of the turntable , and a dynamic balance correction ball is movably inserted into the ring groove. In the device
The disk drive device is placed vertically, the disk surface is vertically arranged, and the dynamic balance correction ball that falls in the ring groove with the rotation of the turntable is caught and lifted upward again by the rotation of the turntable. Protrusions for providing on the inner peripheral side of the ring groove,
The disk drive apparatus according to claim 1, wherein when the dynamic balance correction ball moves in the outer circumferential direction of the ring groove by the rotation of the turntable, the protrusion is not in contact .

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