JP2001021004A - Spindle motor having automatic balance correcting means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To radially move and operate in a low position even with less centrifugal force in a member-constitution consisting of a minimum number of simple part items in order to maintain its position with no inpairment of a cost when the spindle motor is in balance, and compensate the difference in centrifugal force when the motor is in unbalanced state. SOLUTION: The upper face part 2b of a rotor case 2 is formed into a gentle ascent taper having grooves extending outward from a central, journalled part, and balance correcting members 1 are arranged on the upper face part. A cover member 3 is installed so that the balance correcting members do not run out, and a means 3a for preventing the balance correcting members 1 from radially running out, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD-ROM, a DV
The present invention relates to an improvement of a spindle motor for driving an optical medium such as a D-ROM, and more particularly to a spindle motor having an automatic balance correcting means for correcting vibration due to imbalance of a rotating body including a medium.

[0002]

2. Description of the Related Art In recent years, a spindle motor having an auto balancer below a turntable to correct these imbalances in order to prevent vibration during high-speed rotation due to imbalance of a rotating system including a medium of a motor has been known. It has become. The prototype of this technology was a Thearl's automatic balancer (Mechanical Mechanics p146, 147, published by Rigaku Corporation).
However, recently, various auto balancer systems using this technology have been proposed. For example,
As shown in FIG. 5, there is a case in which a plurality of small balls B1 are stored in a shallow cylindrical case K1 and the centrifugal force imbalance during rotation is corrected using the free movement of the balls B1.

However, in the above configuration, since the ball freely moves in the case, the effect as a balancer is unstable. That is, when the ball was stationary, the position of the ball was not constant, and the ball was unstable. Also,
When the position of the ball is outside in this stationary state, the inertia becomes large and the start-up time is delayed, or when the rotating system is balanced, adverse effects may occur, or the motor may become unnecessary. I had to raise my power.

[0004]

For this reason, as shown in FIG. 6, a magnet M is arranged around a rotation axis S, and when stationary or balanced, the ball B1 is attracted to the magnet M1. In addition, if there is an imbalance at the start of rotation, a configuration in which the ball B moves outward against the magnetic force of the magnet M and corrects the centrifugal imbalance may be considered. (See, for example,
However, in such a configuration, the cost of the magnet M1 becomes a problem this time. In any of the above structures, if the ball B1 is made of iron, and if the magnet m for the media chuck is arranged close to the turntable T arranged above the shallow cylindrical case K, the magnet m for the media chuck is used. The influence of the magnetic force cannot be ignored. Furthermore, in the above configuration, since the auto balancer portion is considerably thick, there is a dislike that the posture of the entire motor is increased.In order to lower the posture, the motor body is pressed down, and the performance of the motor is inevitably reduced. Getting worse.

In order not to sacrifice this posture,
A thin eccentric disk or eccentric ring may be used. Prior art using such an eccentric disk or eccentric ring is disclosed in JP-A-11-4558 and JP-A-10-257.
No. 710 and JP-A-11-69706. However, since these thin eccentric disks or eccentric rings do not always match the center of rotation and the center of gravity when the motor is stationary at the time of arrangement, when the rotating system including the medium is balanced at low speed, On the contrary, there is a problem that the eccentricity of the thin eccentric disk or the eccentric ring appears.

A first object of the present invention is to maintain the position when rotating while maintaining the position without sacrificing cost with a member configuration having a simple minimum number of parts, and to maintain the position when unbalanced. The object of the present invention is to make it possible to move in the radial direction with a small centrifugal force in order to correct a difference in centrifugal force. A second object of the present invention is to reduce the posture while having an automatic balance correction means.

[0007]

In order to solve the above-mentioned basic problem, there is provided an automatic balance correcting means for correcting the imbalance of the rotating system by the motor itself as in the first aspect of the present invention. In the spindle motor, the upper surface of the rotor case is formed with a gentle taper that rises outward from the center shaft support portion, a balance correction member is disposed on the upper surface, a cover member is attached so that the balance correction member does not jump, and This can be achieved by providing means for preventing the correction member from protruding in the radial direction. As a specific second means for solving the problem, as in the invention as set forth in claim 2, the balance correction member is a plurality of balls, the cover member is formed of a turntable, and the balls protrude in the radial direction. At least a part of the means for preventing the rotation can be achieved by a hakama portion hanging down from the outer periphery of the turntable. As a third specific means for solving the problem, a plurality of grooves having a smaller width than the balls are radially provided on the upper surface of the rotor case as in the invention as set forth in claim 3, and a part of the balls is stored in the grooves. Can be achieved with A fourth specific problem solving means can be achieved by disposing an elastic O-ring on an outer peripheral portion of the upper surface of the rotor case as in the invention as set forth in claim 4. A specific structure of the fourth problem solving means is that the upper surface of the rotor case and the cover member are hermetically sealed via the O-ring as in the invention shown in claim 5, and the density correction is made as a balance correction member in this sealed space.
What provided the above-mentioned flow members may be used. As a more specific means for solving the problem, it is preferable that the space in which the O-ring is disposed utilizes a step formed when the driving magnet is disposed, as in the invention described in claim 6.

According to the first aspect of the present invention, the balance correction member is concentrated at the center when stationary or at a low speed due to the taper and is balanced, and when the rotation system is eccentric during rotation, it is anti-eccentric. , The balance can be obtained. According to the second aspect of the present invention, the balls roll on the upper surface of the rotor case, move in the radial direction, and further rotate, so that the balls gather in the direction of the anti-center of gravity even if the amount of eccentricity of the rotating system is large. , Can correct imbalance. According to the means for achieving the object set forth in claim 3, since a part of the ball is in the groove, a ball having a large size can be used only at this part, and if the size of the ball is the same, the overall thickness can be reduced. . According to the object achieving means described in claim 4, when the balance correction member is a ball,
The impact sound when moving to the outer periphery by centrifugal force is received by the O-ring, so that it does not occur outside. According to the means for achieving the object set forth in claims 5 and 6, a high-density fluid member such as oil mixed with tungsten powder or the like can be sealed to prevent outflow. According to the means for achieving the object, the dead space is used, so that the attitude can be lowered and the O-ring can be easily arranged.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below based on embodiments shown in the drawings. FIG. 1 is a longitudinal sectional view showing a first embodiment of a spindle motor having an automatic balance correcting means according to the present invention, FIG. 2 is a longitudinal sectional view showing a main part of a second embodiment, and FIG. FIG. 4 is a plan view of an essential part for explaining the operation of the ball in a rotor case portion, and FIG. 4 is a longitudinal sectional view of the essential part showing a third embodiment of the motor.

In FIG. 1, reference numeral 1 denotes a steel ball (ball) having a diameter of about 3 mm as an unbalance correction member which is a feature of the present invention, and a rotor case having a gentle taper which rises outward from a central shaft support 2a. 2 are arranged on the upper surface 2b. A rotating shaft S protrudes from a central shaft supporting portion 2a of the rotor case 2, and a resin turntable 3 as a cover member is attached so that the steel ball 1 does not protrude. The turntable 3 is received on the outer periphery by a skirt portion 3a on the outer periphery of the rotor case upper surface 2b. For this reason, the disk portion 3b in the range where the steel ball rolls can be made thin.
With this configuration, the steel balls 1 are gathered at the center by their own weight when stationary, and if the rotating system including the motor, the turntable and the media disk is eccentric, centrifugal force vibration occurs at high speed. The sphere 1 reverses the loose taper due to the centrifugal force and gathers in the anti-eccentric direction, cancels out, and the center of gravity coincides with the center of the rotating shaft, and no vibration is generated outside. Further, the steel ball 1 rolls at the time of high-speed rotation and hits the skirt portion 3a of the turntable 3, but since the skirt portion 3a is formed of resin, the impact sound does not matter. This configuration is extremely advantageous in terms of cost since only a steel ball is required as the balance correction means. In the drawing, reference numeral B denotes a stator base that supports an armature coil 5 wound around the iron core 4 via a bearing housing H, and rotatably supports the rotating shaft S via a middle relief bearing J. M is a magnet driven by the armature coil 5.

FIGS. 2 and 3 aim at lowering the height of the rotor case 22. A slot 22c in which a part of the ball 11 enters the upper surface portion 22b of the rotor case 22 is formed in the shaft support portion 22a. As shown in the figure, the light source is provided radially in the normal direction or crescent-shaped radially in accordance with the rotation direction. Of course, in this case, there is no change in forming a taper similar to that in FIG. As means for preventing the ball from protruding in the radial direction, as shown in the right half of the body, the hakama portion 3a of the turntable 3 may be used, or as shown in the left half of FIGS. A tongue piece 22d cut and raised from an O-ring R may be used. In the case where the O-ring R is interposed, no impact sound is produced. In this way, the height of the ball can be reduced by the thickness of the rotor case, and if the low attitude is not required, the size of the ball can be increased as shown in the figure. Note that the rotor cases 2 and 22 and the groove 22c are preferably coated with a fluororesin to improve the slip. With this configuration, when the ball 11 is stationary, it gathers at the central portion due to its own weight, and if the rotating system including the motor, the turntable, and the media disk has eccentricity A, centrifugal force vibration occurs at high speed. The ball 11 rises up the loose taper by the centrifugal force and gathers in the anti-eccentric direction, cancels out, and the center of gravity coincides with the center of the rotating shaft, so that vibration does not occur outside.

FIG. 4 shows the use of a high-density fluid 12 having a density of about 5 in which a high specific gravity material such as tungsten powder or fine steel ball lead powder is mixed with a fluid such as oil in place of a ball as a balance correction member. That is, the upper surface portion 2b of the rotor case 2 is tapered, but the inclination is preferably slightly increased. Then, an O-ring RR is formed on the stepped portion 2e for receiving the driving magnet M having a built-in outer periphery.
Is mounted, the high-density fluid 12 is injected, and the O-ring RR is pressed down and sealed by the skirt portion 33a of the turntable 33 as described above. The high-density fluid 12
Although the larger the density, the larger the eccentricity can be accommodated, the eccentricity of the rotating system is not so large, so that a density of 3 or more that ensures fluidity is sufficient. In this way, the high-density fluid 12 gathers at the center due to its own weight when stationary, and if the rotary system including the motor, the turntable and the media disk is eccentric, centrifugal vibration occurs at high speed, As shown by the imaginary line, the high-density fluid 12 reverses the gentle taper due to the centrifugal force and gathers in the anti-eccentric direction, cancels out each other, and the center of gravity and the center of the rotation axis coincide with each other, so that vibration is not generated outside. The O-ring RR is desirably subjected to a liquid-repellent treatment to prevent outflow. In the figure, the same members as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The unbalance correcting member (the ball and the ball pop-out preventing means, the high-density fluid 12 and the O-ring, etc.) is provided within a range not departing from the technical idea and gist of the present invention, that is, within the scope of the claims. Various quantities, shapes and materials can be employed.

[0014]

As described above, the compact vibration motor according to the present invention has a simple structure with a minimum number of parts and does not sacrifice cost. Since the position can be maintained and the radial direction can be moved with a small centrifugal force, in the unbalanced state, the rotational system moves to the opposite side to the combined eccentric direction to correct the difference in the centrifugal force.

More specifically, the following effects can be obtained. According to the first aspect of the present invention, the balance correction member is gathered at the center when stationary or at a low speed due to the taper so as to be balanced, and when the rotation system is eccentric during rotation, the balance correction member moves in the anti-eccentric direction. According to the invention described in claim 2, the ball is rolled on the upper surface of the rotor case, moves in the radial direction, and further rotates, so that the rotation center and the center of gravity are balanced. Is large, they gather in the direction of the anti-center of gravity, and can correct imbalance.
According to the third aspect of the present invention, since a part of the ball enters the groove, a ball having a large size can be used only in this part. If the size of the ball is the same, the overall thickness can be reduced. According to the fourth aspect of the invention, if the balance correction member is a ball, the impact sound when moving to the outer periphery by the centrifugal force is received by the O-ring, so that it does not occur outside. According to the fifth aspect of the invention, a high-density member such as oil mixed with tungsten powder or the like can be sealed, and outflow can be prevented. According to the sixth aspect of the present invention, since the dead space is used, the attitude can be lowered, and the O-ring can be easily arranged.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of a spindle motor having an automatic balance correcting means of the present invention.

FIG. 2 is a vertical sectional view showing a main part of the second embodiment of the motor.

FIG. 3 is a perspective view of a main part for explaining the operation of the ball in the rotor case portion of FIG. 2;

FIG. 4 is a vertical sectional view showing a main part of the third embodiment of the motor.

FIG. 5 is a cross-sectional side view of a main part showing a first embodiment of the conventional motor.

FIG. 6 is a cross-sectional side view showing a main part of a second embodiment of the conventional motor.

[Explanation of symbols]

 Reference Signs List 1 steel ball (unbalance correction member) 11 ball (unbalance correction member) 12 high-density flow member (unbalance correction member) 2, 22 rotor case 2a, 22a shaft support 2b, 22b upper surface 2d tongue piece 2e step 22c Slot 3, 33 Turntable 3a, 33a Hakama section 4 Iron core 5 Armature coil S Rotating shaft B Stator base H Bearing housing J Bearing R, RRO ring

Claims (6)

[Claims] In a spindle motor having an automatic balance correcting means for correcting imbalance of a rotating system by a motor itself, a gentle taper is formed in which a top surface of a rotor case rises outward from a center shaft supporting portion. A spindle motor having an automatic balance correcting means provided with a balance correcting member on an upper surface, a cover member attached so that the balance correcting member does not jump, and a means for preventing the balance correcting member from jumping out in the radial direction. 2. The balance correction member is a plurality of balls, and the cover member is a turntable,
2. The spindle motor according to claim 1, wherein at least a part of the means for preventing the ball from jumping out in the radial direction is a skirt portion hanging down from the outer periphery of the turntable. 3. The automatic balance correcting means according to claim 1, wherein a plurality of grooves having a width smaller than that of said balls are radially provided on an upper surface of said rotor case, and a part of said balls is stored in said grooves. Having a spindle motor. 4. The spindle motor according to claim 1, wherein an elastic O-ring is provided on an outer peripheral portion of an upper surface of the rotor case. 5. The automatic balance correction according to claim 4, wherein the upper surface of the rotor case and the cover member are sealed via the O-ring, and a high-density flow member having a density of 3 or more is disposed as a balance correction member in the sealed space. Spindle motor with means. 6. The spindle motor according to claim 4, wherein the space in which the O-ring is disposed utilizes a step formed when a driving magnet is disposed.