JP2007333099A - Automatic balancing device, rotating device and disc driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic balancing device capable of surely keeping a balance even at a high rotational frequency, and to provide a rotating device and a disc driving device loading the same. <P>SOLUTION: This automatic balancing device 10 comprises a housing 5 composed of a case 2 and a cover 1 disposed on an opening formed at the top of the case 2. A magnetic fluid 9, a plurality of balancers 11 each composed of a magnet 17 and a yoke 13, a magnet 18 for attracting the balancers generating attraction to the balancers 11, and a pair of upper and lower yokes 19 disposed on the magnet 18 for attracting the balancers, are received in the housing 5. By mounting the magnet 18 for attracting the balancers, the attraction acts on the balancers 11 to an inner peripheral side even if centrifugal forces are applied to the balancers 11 after the housing 5 starts its rotation, and the balancers do not move to an outer peripheral side until the release rotational frequency is achieved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automatic balancing device for maintaining a balance of rotation, a rotating device equipped with the device, and a disk drive device.

  For example, in a disk device such as an optical disk device or a magnetic disk device that records / reproduces data, when the disk as a recording medium rotates on a turntable, the rotation becomes unbalanced due to the eccentricity of the disk, and recording / reproduction is performed. The stability of the may decrease.

  As a technique for improving the balance of disk rotation, a technique for causing a fluid to function as a balancer is disclosed (for example, see Patent Documents 1 and 2). In Patent Document 1, the fluid is a magnetic fluid, and a disk-shaped member having a space that can accommodate the fluid is provided so as to be rotatable integrally with the motor shaft. The disk-shaped member has a boss portion, and a ring magnet is attached to the side peripheral surface of the boss portion. Thereby, when the rotation speed of a rotating shaft is small, a magnetic fluid is attracted | sucked to a ring magnet so that balance may not be lost.

  Further, in Patent Document 2, when the automatic balancing apparatus is not in operation, the fluid balancer is held with surface tension by a holding member provided on the inner peripheral side of the housing member.

JP-A-4-31244 (paragraph [0006], FIG. 1) Japanese Patent Laying-Open No. 2005-331102 (paragraph [0037], FIG. 2)

  However, since a fluid balancer is lighter than a conventional balancer made of a metal sphere or the like, noise is ensured, but there is a problem that it is difficult to balance.

  In view of the circumstances as described above, an object of the present invention is to provide an automatic balancing device that can be surely balanced, a rotating device equipped with the same, and a disk drive device.

  Another object of the present invention is to provide a technique capable of achieving a balance even at a high rotational speed.

  In order to achieve the above object, an automatic balancing apparatus according to the present invention includes a magnetic fluid, a first magnet, a balancer having a yoke attached to the magnet, a rotatable balancer, and contains the magnetic fluid. And a housing that houses the balancer so that the yoke is positioned on the inner peripheral side of the rotation, and a second magnet that generates a force for attracting the balancer from the inner peripheral side.

  In the present invention, since the first magnet has a high specific gravity like a conventional metal ball or the like, a balance can be reliably obtained. Further, since the magnetic fluid adheres to the first magnet and the balancer moves smoothly, noise caused by the movement of the conventional metal sphere can be reduced.

  In addition, since the second magnet that generates a force for attracting the balancer from the inner peripheral side is provided, even if centrifugal force is applied to the balancer after the housing starts rotating, the second magnet The suction force works and does not move to the outer peripheral side until a predetermined rotational speed is reached. The predetermined rotational speed at this time is hereinafter referred to as “separation rotational speed”. Therefore, the rotation speed of the housing when the balancer moves to the outer peripheral side by centrifugal force can be increased, and a balance can be achieved even at a relatively high rotation speed.

  Specifically, since the magnetic fluid moves to the outer peripheral side due to the centrifugal force, if there is no second magnet, the balancer and the housing are in direct contact by the initial rotation of the housing, and the friction force is generated. The balancer may be difficult to move and may be difficult to balance. When the second magnet is provided, the balancer is attracted by the second magnet even if the magnetic fluid moves to the outer peripheral side due to the initial rotation of the housing (when the rotational speed is smaller than the separation rotational speed). . Therefore, it is possible to balance in a high rotational speed range.

  “To ensure that the yoke is located on the inner peripheral side” is to prevent the magnetic field from leaking to the inner peripheral side of the balancer, and to generate a field having a uniform magnetic flux density on the inner peripheral side of the balancer. The purpose. Thereby, an attractive force or a repulsive force is not partially generated between the balancer and the second magnet due to the polarity of the magnetic pole, and the balancer and the second magnet can move smoothly in the housing.

  In the present invention, the automatic balancing apparatus further includes a second yoke mounted on the second magnet. By optimally setting the magnetization direction of the second magnet, the mounting position of the second yoke, and the like, for example, a magnetic field can be generated on the outer peripheral side of the second magnet. Moreover, in this invention, the range of the magnetic field by a 2nd magnet which extends over the outer peripheral side of a 2nd magnet can be narrowed. Therefore, for example, when the balance is achieved, that is, when the balancer moves to the outermost periphery in the housing due to centrifugal force and the housing and the balancer rotate integrally, the magnetic field generated by the second magnet is substantially reduced. It is possible not to reach the balancer. As a result, when the housing is decelerated, the balancer can be prevented from returning to the inner peripheral side unless the initial low rotational speed is reached, and a balanced state can be maintained in a wide rotational speed range.

  In the present invention, the second magnet is accommodated in the housing. Alternatively, the second magnet may be mounted outside the housing. Thereby, even after the inside of the housing is sealed, the second magnet can be attached to the housing, and the automatic balancing device can be easily manufactured.

  In the present invention, the second magnet is magnetized in the axial direction of the rotation, and the second yoke is disposed in at least one of the axial directions of the second magnet. Alternatively, the second magnet is magnetized in the axial direction of the rotation, and the second yoke is provided so as to be positioned on the inner peripheral side of the second magnet.

  A rotating device according to the present invention includes a magnetic fluid, a first magnet, and a balancer having a yoke attached to the magnet, and is rotatably provided to contain the magnetic fluid, and the yoke includes the yoke A housing that houses the balancer so as to be positioned on the inner peripheral side of rotation; a second magnet that generates a force for attracting the balancer from the inner peripheral side; and a rotational drive mechanism that rotationally drives the housing. To do.

  A disk drive device according to the present invention includes a holding unit for holding a disk-shaped recording medium capable of recording a signal, a magnetic fluid, a first magnet, and a balancer having a yoke attached to the magnet, and a rotation A housing configured to accommodate the magnetic fluid, and to accommodate the balancer so that the yoke is positioned on the inner peripheral side of the rotation, and to generate a force for attracting the balancer from the inner peripheral side A second magnet; and a rotation driving mechanism that integrally rotates the holding portion and the housing.

  As described above, according to the present invention, a balance can be reliably obtained, and a balance can be immediately achieved even at a high rotational speed.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the principle of the automatic balancing apparatus will be described. This is illustrated by Theearl's self-balancing device. For details on the automatic balancing apparatus of Thear, refer to “Mechanical Mechanics” (March 1982) P146, 147 published by Rigaku Corporation.

  With reference to FIG. 1, Theear's automatic balancing apparatus 101 will be briefly described. The automatic balancing apparatus 101 of Thearl is a rotating disk 102 and two steel balls (balance members) 104, 104 arranged so as to be freely movable in a groove 103 of the rotating disk 102, and a rotation. When the rotational speed of the rotating disk 102 exceeds the natural circular frequency (critical speed) of the rotating shaft 105, Me = 2mR · cos α (M: rotating with the rotating disk 102). The steel ball 104 at a position that satisfies the rotor mass of the shaft 105, e: the amount of eccentricity of the rotor ball, m: the mass of the steel ball 104, r: the starting radius of the steel ball, α: angle formed by the eccentric direction and the steel ball 104), A device 104 is automatically positioned to eliminate the eccentricity of the rotating disk 102 and reduce the vibration of the rotor portion. Note that this equation is an equation when the steel ball 104 is regarded as a mass point. However, when the radius of the steel ball 4 is r, considering the rigid system, the above equation is Me = 2m (R−r) · cosα.

  Here, the reason why the Automatic automatic balancing apparatus 101 operates when the natural circular frequency of the rotating shaft 105 is exceeded will be briefly described. The motion of the center of gravity G of the rotating disc 102 and the motion of the steel balls 104 and 104 This is because the steel balls 104 and 104 are moved and positioned in the opposite direction to the eccentric direction.

  FIG. 2 is a cross-sectional view seen from the top of the automatic balancing apparatus according to the embodiment of the present invention. 3 is a cross-sectional view taken along line AA in FIG.

  The automatic balancing apparatus 10 includes a housing 5 including a case 2 and a cover 1 attached to an opening provided in the upper portion of the case 2. A plurality of balancers 11 including a magnetic fluid 9, a magnet 17 and a yoke 13, a balancer suction magnet 18 that generates a suction force with respect to the balancer 11, and the balancer suction magnet 18 are mounted in the housing 5. The paired upper and lower yokes 19 are accommodated. A boss 2b protruding upward is formed in the center of the inside of the housing 5. A moving space 14 in which the balancer 11 moves is formed in a space between the outer peripheral wall surface 2a in the housing 5 and a side surface 18a of a balancer attracting magnet 18 described later. The upper and lower spaces of the moving space 14 are limited by the lower road surface 2d and the upper road surface 1b (the back surface of the cover 1).

  A flange 2c is provided on the upper surface of the boss portion 2b, and a hole 1a (see FIG. 1) formed substantially at the center of the cover 1 is fitted in the flange 2c. The cover 1 and the case 2 are bonded by, for example, welding, pressure bonding, laser bonding, ultrasonic bonding, or the like, but are not limited to these bonding methods. The cover 1 and the case 2 are made of a material that is not affected by the magnetism of the balancer 11 described later. Examples of the material include plastics such as polycarbonate, aluminum alloys, bronze alloys, and ceramics. The rotary shaft member 16 is inserted and fixed in the through hole 2e formed in the boss portion 2b. As will be described later, the rotary shaft member 16 is, for example, a rotary shaft member of a spindle motor provided in a device on which the automatic balancing apparatus 10 is mounted, or a coaxial shaft member separate from the rotary shaft member.

  As shown in FIG. 3, the relationship between the radial width a of the balancer 11 and the axial width (height) b of the moving space 14 is set to a> b. According to such a configuration, it is possible to prevent the balancer 11 from moving in the movement space 14 and upside down and reversing the magnetization direction of the balancer 11. This is because when the magnetization direction is reversed, the balancers 11 are attracted to each other.

  As shown in FIG. 2, for example, four balancers 11 are provided, but in principle, any number of balancers 11 may be used as long as there are two or more. As a material of the magnet 17, for example, ferrite or neodymium is used, but is not limited thereto.

  4A and 4B are perspective views showing the balancer 11. 4A is a view seen from the inner peripheral side, and FIG. 4B is a view seen from the outer peripheral side. The balancer 11 has an arc block shape that forms a part of the ring. The magnets 17 of the balancer 11 are magnetized in the radial direction of rotation of the housing 5 and a plurality of pairs are magnetized in the circumferential direction. The magnets 17 are arranged with their magnetization directions determined so as to repel each other in the moving space 14. The number of magnetic poles of the magnet 17 and the magnetization direction can be changed as appropriate.

  A yoke 13 is joined to the magnet 17 so as to cover at least the inner peripheral surface 17e. In this example, the inner peripheral surface 17e and both side surfaces 17d are covered by the yoke 13. That is, the upper surface 17a, the lower surface 17b and the outer peripheral surface 17c of the magnet 17 are exposed. As a method for joining the magnet 17 and the yoke 13, there are welding, pressure bonding, laser joining, ultrasonic joining, and other joining methods. By providing such a yoke 13, more magnetic fluid 9 is adsorbed on the outer peripheral side than on the inner peripheral side of the balancer 11. Thereby, even when a centrifugal force is applied to the magnetic fluid 9 at the start of rotation of the housing 5, a magnetic fluid film is formed on the outer peripheral side of the balancer 11, and the balancer 11 moves smoothly while ensuring quietness. That is, problems such as the balancer 11 sticking directly to the outer peripheral wall surface 2a or the like of the moving space 14 before the equilibrium state is reached and the frictional force increases and cannot move can be solved. Further, since the magnetic field spreads on the outer peripheral side, the repulsive force between the magnets 17 is reduced, and each balancer 11 becomes easy to move. Since the magnetic fluid 9 is also attracted to the upper surface 17a and the lower surface 17b of the magnet 17, the balancer 11 is in a floating state in the moving space 14, as shown in FIG.

  Since the magnetic fluid 9 is also affected by the magnetic field generated by the balancer suction magnet 18, the magnetic fluid 9 is attracted to the outer peripheral side of the balancer 11 as much as possible in the stationary state of the automatic balancing device as shown in FIG. 3. Furthermore, it is desirable to set the magnetization strength of the magnet 17 and the balancer attracting magnet 18. Specifically, the magnetization intensity of the magnet 17 is set larger than that of the balancer attracting magnet 18.

  Instead of the magnetic fluid 9, a magnetoresistive fluid (MR fluid (Magneto-Rheological Fluid)) or the like may be used. As a solvent for the magnetic fluid 9, water, oil, sodium polytungstate, or the like is used, but is not limited thereto.

  The balancer attracting magnet 18 is formed in a ring shape and is provided so as to surround the outer peripheral portion of the boss portion 2b. Ring-shaped and plate-shaped yokes 19 are provided on the upper and lower surfaces of the balancer attracting magnet 18. The balancer attraction magnet 18 is, for example, two-pole magnetized in the axial direction of rotation, and the spread of the magnetic field is limited by the yoke 19. The balancer suction magnet 18 has a function of attracting the balancer 11 and pulling it toward the inner peripheral side until the housing 5 reaches a predetermined rotational speed. This predetermined rotational speed is hereinafter referred to as “separation rotational speed”. Further, since the yoke 13 is provided on the inner peripheral side of the balancer 11, a repulsive force or attractive force is partially generated between the balancer attracting magnet 18 and the balancer 11 depending on the polarity of the magnetic poles as will be described later. Can be prevented.

  Further, by providing the yoke 19 on the balancer attracting magnet 18, the magnetic flux is concentrated between the peripheral portions of the yokes 19, so that the magnetic field does not reach the outer peripheral side. The range covered by the substantial magnetic field can be adjusted by the diameter of the yoke 19.

  FIG. 5 is a perspective view showing a disk drive device on which the automatic balancing apparatus 10 is mounted. FIG. 6 is a cross-sectional view showing the main part of the disk drive device of FIG.

  The disk drive device 100 includes a mechanical chassis 63 on which the spindle motor 61 and the optical pickup 99 are mounted, and a plurality of dampers 62, 62,... That support the mechanical chassis 63 in a floating manner with respect to the base chassis 64. . The optical pickup 99 is supported by the mechanical chassis 63 through the guide shafts 98 and 98 so as to be movable in the radial direction of the optical disk D mounted on the disk table 65. The optical pickup 99 includes a moving base 94 and an actuator 93 that supports the objective lens 97 and is mounted on the moving base 94. The optical pickup 99 has a light source and a photodetector (not shown) such as a laser diode, irradiates the optical disk D with laser light emitted from the light source via the objective lens 97, and reflects the reflected light from the optical disk D of the laser light. Is detected by a photodetector.

  The spindle motor 61 includes, for example, a stator 61b provided with a coil 61d through which a drive current flows, a rotor 61c provided with a magnet 61e and rotatably provided via a bearing 61a, and the rotating shaft member 16. Yes. A disk table 65 that holds and mounts the disk D is provided at the upper end of the rotary shaft member 16. As described above, the automatic balancing device 10 is mounted on the rotary shaft member 16, and the automatic balancing device 10 and the disk table 65 are configured to be integrally rotatable. More specifically, the optical disk D, the disk table 65, the rotating shaft member 16, the automatic balancing apparatus 10, and the rotor 61c of the spindle motor 61 rotate integrally. Hereinafter, these members are collectively referred to as “synthetic rotating body”. That's it. In addition, hereinafter, the total center of gravity of each of these members, that is, the center of gravity of the combined rotating body is referred to as “combined center of gravity”.

  A vibration system 95 is constituted by the components above the damper 62 including the plurality of dampers 62 and the optical pickup 99 shown in FIG. The resonance frequency of the vibration system 95 is, for example, 75 Hz (4500 rpm) when the disk drive device 100 is a 12 × speed disk drive device, and the elastic coefficients of the dampers 62, 62,. Is set. This is because the operating speed range of the 12 × disk drive device is about 3000 to 6000 rpm, and in many disk drive devices at present, the signal on the innermost circumference side is read immediately after the start of the rotation drive. Generally, when the signal of the innermost circumference is read, the maximum number of revolutions (6000 rpm) is obtained. Therefore, it is only necessary to be balanced before reaching the maximum number of revolutions.

  An optical disc is a disc on which signals can be recorded or reproduced by optical methods such as CD (Compact Disc), DVD (Digital Versatile Disc), BD (Blu-ray Disc (registered trademark)), and other holograms. Is mentioned. The disk according to the present invention is not limited to an optical disk, and may be a magneto-optical disk such as MO (Magneto Optical disk) or MD (Mini-Disk), a magnetic disk such as a hard disk, or the like.

  Next, the operation of the automatic balancing apparatus 10 will be described. FIG. 7 is a diagram showing the operations in order.

  When the optical disk D is set on the disk table 65 and the spindle motor 61 starts to rotate, the vibration system 95 starts to vibrate. As shown in FIG. 7A, it is assumed that an unbalance 15 exists in the vibration system 95, for example. That is, it is assumed that the combined center of gravity 15 is displaced from the rotation center position of the combined rotating body (the position of the rotating shaft member 16).

  Here, FIG. 8 shows the acceleration (vertical axis) of the vibration system 95 generated in the radial direction (horizontal plane) of the optical disc D due to the rotational speed (horizontal axis) and the unbalance 15 at the time of acceleration of the spindle motor 61. It is a graph which shows an example of a relationship with). FIG. 9 is a graph showing an example of the relationship between the rotational speed of the spindle motor 61 and the acceleration generated in the vibration system 95 when the spindle motor 61 rotates and decelerates. 8 and 9, the optical disc D having an unbalance amount of 1 g · cm is used.

  In the initial rotation of the spindle motor 61 (for example, 0 to 4000 rpm), each balancer 11 and the magnetic fluid 9 rotate together. This is mainly because the attraction force of the balancer attraction magnet 18 works, and this attraction force is larger than the centrifugal force due to the rotation of the housing 5. In addition to the attraction force by the balancer attraction magnet 18, the force due to the viscosity of the magnetic fluid 9 and the frictional force that each balancer 11 acts on the upper road surface 1 b or the lower road surface 2 d via the magnetic fluid 9 are also affected.

  Here, in this embodiment, since the magnets 17 of the balancers 11 are magnetized so as to repel each other, the balancers 11 are arranged at equal intervals in the moving space 14. Therefore, there is no eccentric center of gravity due to the presence of the balancer 11, and there is no blurring caused by the balancer 11 in the rotation from the start of rotation to the separation of the balancer 11 at the separation rotational speed.

  When the rotation speed of the spindle motor 61 increases and reaches a separation rotation speed (for example, 4000 rpm), each balancer 11 starts to move to the outer peripheral side in the moving space 14 due to the centrifugal force together with the magnetic fluid 9. This separation rotational speed needs to be set slightly smaller than the resonance frequency (for example, 4500 rpm) of the vibration system 95. At the moment when each balancer 11 leaves in this way, the rotational speeds of each balancer 11 and housing 5 are substantially the same. However, due to the inertia of each balancer 11 itself, the acceleration of the housing 5 cannot be performed, and a difference in rotational speed appears for a moment. As a result, the acceleration due to the unbalance of the vibration system 95 decreases for a moment.

  Thereafter, the rotational force of the housing 5 is transmitted to the balancer 11 due to the frictional force acting on the housing 5 of each balancer 11, and the balance between the balancer 11 and the housing 5 in the circumferential direction immediately before the resonance frequency of the vibration system 95. The speed difference is zero. In this state, as shown in FIG. 7B, each balancer 11 is pressed against the outer peripheral wall surface 2a by centrifugal force. At this time, the magnetic fluid 9 spreads uniformly so as to form a film on the outer peripheral wall surface 2a. When the rotational speed is around 4500 rpm, resonance of the vibration system 95 occurs, and the balancer 11 pulls in. “Pull-in phenomenon” refers to a phenomenon in which each balancer 11 moves in a direction to cancel the unbalance 15 in a state where the balancer 11 is in contact with the outer peripheral wall surface 2 a via the magnetic fluid 9.

  Specifically, when the rotational speed is around 4500 rpm, the vibration of the housing 5 and the vibration of each balancer 11 are in opposite phases, and as shown in FIG. 7C, the total center of gravity position of the four balancers 11 is , Move in the direction A1 opposite to the direction of the unbalance 15. As a result, the vibration of the vibration system 95 is reduced, and the acceleration is about 0.5 G, which is small enough to cause no problem.

  Thereafter, even if the number of rotations of the spindle motor 61 increases, the vibration increases slightly, but does not increase greatly.

  When the optical disk D having no weight imbalance is used in the disk drive device 100, since the vibration of the vibration system 95 is originally small, each balancer 11 is moved within the moving space 14 when the separation rotational speed is exceeded. Somewhat rampage. However, since there is originally no unbalance amount, a pull-in phenomenon occurs early, and the balancers 11 are arranged at substantially equal angular intervals around the rotary shaft member 16 as shown in FIG. To position.

  FIG. 10 is a graph showing an experimental example of a disk drive device equipped with an automatic balancing device that does not have the balancer suction magnet 18. In this example, almost all of the magnetic fluid 9 is moved to the outer peripheral side by centrifugal force at about 3000 rpm, and each balancer 11 is in direct contact with the lower road surface 2d and cannot be moved by frictional force. Therefore, the vibration increases without causing a pull-in phenomenon. If the resonance frequency of the vibration system 95 is set to 40 Hz (2400 rpm), for example, the pulling phenomenon occurs without the magnetic fluid film disappearing, and the vibration can be suppressed small.

  However, in an actual disk drive device, it is necessary to suppress the deflection caused by the rotational drive, and it is necessary to avoid the secondary resonance frequency. Therefore, the elastic member of each component of the vibration system 95 must be set to a relatively hard material, that is, a material having a large spring constant, and the resonance frequency is increased to about 75 Hz. This is particularly noticeable in small and thin disk drive devices.

  Next, when the rotation speed of the spindle motor 61 is decreased from, for example, 6000 rpm, the vibration of the vibration system 95 is gradually decreased without largely changing. The reason for the low vibration during the deceleration is that once the balance is reached, the balancer 11 is removed from the balance state due to the influence of the magnet 18 for attracting the balancer and returns to the inner peripheral side (hereinafter referred to as return rotation). This is because the balance state is maintained until the number reaches. That is, hysteresis appears in the manner of vibration of the vibration system 95 at the time of acceleration and deceleration of rotation.

  When the rotational speed reaches the return rotational speed (for example, 1500 rpm), the attractive force of the balancer suction magnet 18 to each balancer 11 is superior to the centrifugal force acting on the balancer 11, and each balancer 11 is connected to the balancer suction magnet 18. It is attracted and attracted. In such a low rotation range, even if there is a slight eccentric gravity center, the vibration caused by this is small. Therefore, even if the signal of the optical disk D is read and written even in the rotational speed range within this range, there is no influence.

  As described above, in the present embodiment, the magnet 17 of the balancer 11 has a high specific gravity like a conventional metal ball or the like, so that a balance can be ensured. Further, since the magnetic fluid 9 adheres to the magnet 17 and the balancer 11 moves smoothly, noise caused by the movement of the conventional metal sphere can be reduced.

  Further, in the present embodiment, since the balancer suction magnet 18 is provided, even if a centrifugal force is applied to the balancer 11 after the housing 5 starts to rotate, the balancer 11 is attracted to the inner peripheral side. It does not move to the outer circumference until it reaches the separation rotational speed. Therefore, the rotation speed of the housing 5 when the balancer 11 moves to the outer peripheral side by centrifugal force can be increased, and a balance can be achieved even at a relatively high rotation speed.

  Further, the yoke 19 is attached to the balancer attracting magnet 18 to enhance the function of attracting the balancer 11. Thereby, the automatic balancing apparatus 10 can be used in a higher rotation speed range. Further, the presence of the yoke 19 can reduce the suction force applied to the balancer 11 that has moved to the outer peripheral side in the moving space 14, and until the centrifugal force applied to the balancer 11 becomes small, that is, at a low rotational speed. The balancer 11 can be positioned on the outer peripheral side in the moving space 14 until a certain rotational speed is reached. Therefore, a balanced state can be maintained in a wide rotational speed range.

  In the present embodiment, since the yoke 13 of the balancer 11 is provided at least on the inner peripheral side of the magnet 17, it is possible to prevent a magnetic field from leaking to the inner peripheral side of the balancer 11. A field with uniform magnetic flux density can be generated on the side. As a result, no attractive or repulsive force is generated between the balancer 11 and the balancer attracting magnet 18 due to the polarity of the magnetic poles, and the balancer 11 and the balancer attracting magnet 18 can move smoothly in the housing 5.

  The above-described use speed range (3000 to 6000 rpm) is a normal use speed range of the 12 × disk drive device 100. In such a high-speed disk drive device, the high-speed mode and the low-speed mode are used. There is a device that can set the mode. For example, there is a disk drive device having a high speed mode of 12 × speed and a low speed mode of 4 × speed, and the rotation speed range is 3000 to 6000 rpm in the high speed mode and 1000 to 2000 rpm in the low speed mode. Yes. Further, this type of disk drive device can be used even at 1 × speed, and in this case, the rotation speed range is about 200 to 500 rpm. In the disk drive device 100 described above, a balanced state can be maintained up to 1500 rpm, and even in such a low-speed rotation region, even if the balanced state is eliminated, there is little vibration. Therefore, vibrations that impede reading and writing of the recording disk do not occur in all rotation speed ranges of 0 to 6000 rpm as well as the above-mentioned rotation speed ranges of 4 × speed and 1 × speed.

  Furthermore, in recent years, a system for drawing characters and illustrations by irradiating a surface of the optical disc D that is not a recording surface with an optical pickup 99 or by an inkjet mechanism or the like has appeared. In this case, the rotational speed of the spindle motor is as low as about 1 Hz. Even in this case, since each balancer 11 is attracted by the balancer attracting magnet 18, the balancer 11 is not scattered and effective.

  Further, in the above embodiment, by setting the resonance frequency of the vibration system 95 within the use rotation speed range (3000 to 6000 rpm) of the disk drive device 100, a resonance frequency higher than this resonance frequency is used. It does not exist in the region. Therefore, vibration with a large amplitude that would occur if the rotation speed of the spindle motor 61 coincided with the higher order resonance frequency of the vibration system 95 does not occur, and a more stable rotation can be obtained.

  Thus, in order not to include the high-order resonance frequency of the vibration system 95 in the use rotation speed region of the spindle motor 61, the maximum use rotation speed is R and the primary resonance frequency of the vibration system 95 is fr. Then, the relationship R / 2 <fr <R may be satisfied. For example, in the case of the 12 × disk drive device 100 according to the above embodiment, the primary resonance frequency of the vibration system 95 is set in the range of 50 Hz (3000 rpm) to 100 Hz (6000 rpm). By doing in this way, the secondary resonance frequency of the vibration system 95 is in the range of 100 Hz to 200 Hz, the secondary rotation frequency is not included in the use rotation speed range, and the amplitude of the secondary resonance in the use rotation speed range is Large vibration does not occur.

  Furthermore, the resonance frequency of the vibration system 95 is set to be larger than the maximum use rotation speed, and once the spindle motor 61 is rotated to a rotation speed exceeding the resonance frequency to achieve a balance, the rotation speed is reduced. It is also possible to record or reproduce in the operating rotational speed range. That is, the resonance frequency of the vibration system 95 is set to 116 Hz (7000 rpm), the spindle motor 61 is rotated at a rotational speed of 7000 rpm or more to balance, and then the rotation is reduced and used at 3000 to 6000 rpm, which is the used rotational speed range. .

  Thus, once the balance state is maintained, the rotation of the combined rotating body can be stabilized by decelerating, and the balance state can be maintained in a wide rotational speed range. Therefore, further stable rotation of the composite rotating body can be realized in the operating rotational speed range.

  FIG. 12 is a cross-sectional view seen from above showing an automatic balancing apparatus according to another embodiment of the present invention. In the following description, the same members, functions, etc. of the automatic balancing apparatus 10 according to the above-described embodiment shown in FIG.

  In the automatic balancing device 20, the magnetization direction of the balancer attraction magnet 28 is different from the magnetization direction of the balancer attraction magnet 18 of the automatic balancing device 10. The balancer attracting magnet 28 is multipolarly magnetized in the circumferential direction. The number of poles is, for example, 12 poles, but is not limited thereto. A magnetic field generated between each pole is generated between poles adjacent in the circumferential direction. For this reason, the magnetic field generated here is narrower than that of the two magnets magnetized in the thickness direction (rotational axis direction) like the balancer attraction magnet 18, and thereby the magnetic field extending to the outer peripheral side. Less. Therefore, the balancer attracting magnet 28 itself includes the function of the yoke 19.

  Further, the influence of the balancer attracting magnet 28 on the outer peripheral side in the moving space 14 depends on the circumferential length of the outer peripheral surface of each multipolar magnetized pole. Therefore, the influence of the magnetic force on the outer peripheral portion can be reduced by increasing the number of magnetizations in the circumferential direction of the balancer attracting magnet 28 and shortening the circumferential length of the outer peripheral surface of each pole. Thereby, the function of the yoke 19 can be increased.

  FIG. 13 is a cross-sectional view showing a main part of a disk drive device according to another embodiment of the present invention. 14 is a cross-sectional view taken along line BB in FIG.

  The disk drive device 200 includes an automatic balancing device 30 and a spindle motor 71 provided below the automatic balancing device 30. In addition, the spindle motor 71 shows only a part of the rotor 7 and does not show other parts. The housing 85 of the automatic balancing apparatus 30 includes a case 82 having a ring-shaped moving space 74 inside, and a cover 81 attached to the opening thereof. The case 82 is integrated with the disk table, that is, is integrally molded, and is configured to hold the optical disk with a chucking portion 82a protruding upward. Thereby, the thickness in the rotation axis direction (direction of the rotation shaft member 16) can be reduced.

  In the moving space 74, four balancers 11 composed of the magnet 17 and the yoke 13 similar to the above are provided. A ring-shaped recess 82b is formed on the lower side of the case 82, and a ring-shaped balancer attracting magnet 38 is attached to a side wall surface 82c of the recess 82a. Further, a ring-shaped yoke 39 is mounted on the inner peripheral side of the balancer attracting magnet 38. That is, the balancer attracting magnet 38 and the yoke 39 are disposed outside the housing 85. The magnetizing direction of the balancer attracting magnet 38 is the rotation axis direction and is magnetized in two poles.

  Even with such a configuration, the same effect as that of the disk drive device 100 according to the above-described embodiment can be obtained. In addition, since the balancer attracting magnet 38 and the yoke 39 are disposed outside the housing 85, the members 38 and 39 can be mounted on the housing 85 even after the inside of the housing 85 is sealed. Thus, the automatic balancing device 30 and the disk drive device 200 can be easily manufactured.

  FIG. 15 shows a modification of the balancer attracting magnet 38. The balancer suction magnet 48 is made of, for example, rubber, and is manufactured by forming a ring shape and connecting both end portions 48a and 48b in the manufacturing process of the automatic balancing apparatus 30. The balancer attracting magnet 48 is magnetized in the vertical direction in the drawing, but may be multipolar magnetized in the horizontal direction. In the case of multipolar magnetization in the lateral direction, when the balancer attracting magnet is incorporated in the automatic balancing device, the balancer attracting magnet 28 as shown in FIG. 12 is obtained.

  The present invention is not limited to the embodiment described above, and various modifications are possible.

  The balancer attracting magnets 18 and 28 according to the above embodiments may not be mounted on the housing 5 and may not rotate.

  In each of the above embodiments, the balancer attracting magnets 18, 28, etc. are shown arranged on the inner peripheral side from the moving space 14. However, the balancer attracting magnet may be arranged on the outer peripheral side of the moving space 14. In that case, the balancer suction magnet may be disposed inside the housing 5 or may be disposed outside the housing 5.

  In each of the above-described embodiments, an example has been shown in which when the unbalanced optical disc D is mounted on the disc table 65, the balance operation is performed on the combined rotating body. However, the automatic balancing apparatus 10 and the like according to each of the above embodiments execute a balancing operation and suppress vibration during rotation even when a member other than the optical disk D of the combined rotating body has an unbalance. Can do.

  The yoke 19 for controlling the magnetic field of the balancer attracting magnet 18 shown in FIG. 3 is provided on both the upper and lower sides of the balancer attracting magnet 18 in FIG. 3, but may be provided on either the upper or lower side.

  Although the automatic balancing apparatuses 10 and 20 according to the above-described embodiment have been shown as examples applied to a disk drive device, they can also be applied to other industrial machines and other electrical appliances.

It is a figure for demonstrating the operation principle of The automatic balance apparatus of Theear. It is sectional drawing seen from the automatic balancing apparatus which concerns on one embodiment of this invention. It is the sectional view on the AA line in FIG. 4A is a view seen from the inner peripheral side, and FIG. 4B is a view seen from the outer peripheral side. It is a perspective view which shows the disk drive device in which an automatic balancing apparatus is mounted. It is sectional drawing which shows the principal part of the disk drive device shown in FIG. It is a figure which shows operation | movement of an automatic balancing apparatus in order. 6 is a graph showing an example of the relationship between the rotation speed of a spindle motor and the acceleration of a vibration system generated in the radial direction of the optical disc D due to the unbalance thereof during rotation acceleration of the spindle motor. It is a graph which similarly shows an example of the relationship between the rotation speed and the acceleration which generate | occur | produces in a vibration system at the time of rotation deceleration of a spindle motor. It is a graph which shows the experimental example of the disk drive device by which the automatic balancer which does not have a balancer attraction magnet is mounted. It is a figure which shows the automatic balance apparatus which rotates in the state without unbalance. It is sectional drawing seen from the top which shows the automatic balancing apparatus which concerns on other embodiment of this invention. It is sectional drawing which shows the principal part of the disk drive device which concerns on other embodiment of this invention. It is the BB sectional view taken on the line in FIG. 14 shows a modification of the balancer attracting magnet shown in FIG.

Explanation of symbols

D ... Optical disc 5, 85 ... Housing 9 ... Magnetic fluid 10, 20, 30 ... Automatic balancing device 11 ... Balancer 13, 19, 39 ... Yoke 14, 74 ... Moving space 15 ... Unbalanced 17 ... Magnet 18, 28, 38, 48 ... Balancer suction magnet 65 ... Disc table 61, 71 ... Spindle motor 100, 200 ... Disc drive device

Claims (8)

Magnetic fluid,
A balancer having a first magnet and a yoke attached to the magnet;
A housing that is rotatably provided, contains the magnetic fluid, and houses the balancer so that the yoke is positioned on the inner peripheral side of the rotation;
And a second magnet for generating a force for attracting the balancer from the inner peripheral side. The automatic balancing apparatus according to claim 1,
The automatic balancing apparatus further comprising a second yoke mounted on the second magnet. The automatic balancing apparatus according to claim 2, wherein
The automatic balancing apparatus, wherein the second magnet is accommodated in the housing. The automatic balancing apparatus according to claim 2, wherein
The automatic balancing apparatus, wherein the second magnet is mounted outside the housing. The automatic balancing apparatus according to claim 2, wherein
The second magnet is magnetized in the axial direction of the rotation,
The automatic balancing apparatus, wherein the second yoke is disposed on at least one of the second magnets in the axial direction. The automatic balancing apparatus according to claim 2, wherein
The second magnet is magnetized in the axial direction of the rotation,
The automatic balancing apparatus, wherein the second yoke is provided so as to be positioned on the inner peripheral side of the second magnet. Magnetic fluid,
A balancer having a first magnet and a yoke attached to the magnet;
A housing that is rotatably provided, contains the magnetic fluid, and houses the balancer so that the yoke is positioned on the inner peripheral side of the rotation;
A second magnet that generates a force for attracting the balancer from the inner peripheral side;
And a rotation drive mechanism for rotating the housing. A holding unit for holding a disc-shaped recording medium capable of recording a signal;
Magnetic fluid,
A balancer having a first magnet and a yoke attached to the magnet;
A housing that is rotatably provided, contains the magnetic fluid, and houses the balancer so that the yoke is positioned on the inner peripheral side of the rotation;
A second magnet that generates a force for attracting the balancer from the inner peripheral side;
A disk drive device comprising: a rotation drive mechanism that integrally rotates the holding portion and the housing.

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