Patent Abstract:
An auto balancing apparatus for a disk drive including a ball casing having a circular racing space installed concentrically with respect to a rotation member capable of rotating a disk. A plurality of balls roll along a racing face formed in the racing space for implementing a balancing operation. A guide member guides the movements of the balls. The proper guiding of the movements of the balls used for an auto balancing apparatus automatically corrects an unstable rotation of a disk and provides an accurate balancing operation.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an auto balancing apparatus for a disk drive, and in particular to an auto balancing apparatus for a disk drive which is capable of automatically balancing an up and down movement of a disk when a disk mounted on a turntable is rotated. 
     2. Description of the Background Art 
     As a disk drive is designed to rotate at a high speed, a disk rotation unbalance problem(an up and down movement of a disk) occurs when a disk is rotated at a high speed. 
     In the conventional art, it is impossible to implement an accurate signal recording and reproducing operation due to the above-described disk unbalance rotation problems. 
     The above-described disk unbalance rotation generally occurs due to a non-uniformly fabricated disk. As the disk is designed to rotate at a high speed, the disk unbalance problem is considered as an important problem. 
     In the case that a disk is not accurately mounted on a turntable and is rotated, the above-described disk unbalance problem may occur. 
     In order to overcome the above-described disk unbalance rotation problem which generally occurs when the disk is rotated at a high speed, an auto balancing apparatus is introduced by the conventional art. The construction of the auto balancing apparatus will be explained. 
     As shown in FIG. 1, a rotary shaft  6  is rotatably installed on an upper surface of a substrate  1  in a vertical direction. 
     A turntable  7  is tightly inserted onto an upper portion of the rotary shaft  6 , and a circular member having a certain thickness is formed on a lower surface of the turntable  7 , and a ball casing  9  having a space  9   a  for receiving a plurality of balls  10  therein which are made of a metallic material, is formed in the circular member. 
     The center portion of the ball casing  9  is tightly inserted onto the rotary shaft  6 . 
     A racing face  9   i  is formed on an inner wall in the space  8   a  formed in the ball casing  9 . The balls  10  roll on the racing face  9   i  based on a centrifugal force in order to correct a unbalance rotation which occurs when a disk is rotated at a high speed. 
     A magnet  11  is engaged at a portion neighboring with the rotary shaft  6  in the inner space  8   a  of the ball casing  9 , buffering portion(not shown) made of a rubber is formed on an outer surface of the magnet  11 . 
     When the apparatus is not driven, the magnet  11  prevents the balls from being freely moved in the space. 
     A spindle motor  3  is installed below the ball casing  9 . A rotor  5  which is one element forming the spindle motor  3  is integrally engaged to the rotary shaft  6 . A stator  4  which is one element forming the spindle motor  3  is installed on an upper surface of the substrate and is fixed on an outer surface of a bearing  2  inserted onto the rotary shaft  6 . 
     In the drawings, reference numeral 5M represents a magnet of the rotor  5 ,  8  represents a clamp for fixing the disk, and  16  represents a rubber which contacts with a lower surface of the disk and supports the disk. 
     The operation of the conventional auto balancing unit will be explained. 
     First, as the spindle motor  3  is driven, the rotor  5  is rotated, and the rotary shaft  6  is rotated. As the rotary shaft  6  is rotated, the turntable  2  is rotated, so that the disk mounted on the upper surface of the turntable  2  is rotated. 
     At this time, when the disk is rotated at a high speed, and an unbalance rotation problem occurs at the disk, the balls  10  inserted in the ball casing  9  are moved along the racing face  9   i  of the ball casing  9  and the unbalance rotation of the disk is corrected. 
     Namely, when the rotation of the disk exceeds a certain speed and an unbalance disk rotation problem occurs, the balls  10  are moved to a portion in which a certain resonance occurs. As a result, the unbalance rotation of the disk is corrected. 
     The above-described conventional auto balancing apparatus has the following problems. 
     First, the balls move freely in the interior of the ball casing in the radial direction, and the rotation cycle of the turntable and the rotation cycle of the balls are different. As a result, a self-excited vibration occurs, which makes it is impossible to implement a balancing operation. 
     In addition, magnets are serially installed on the portions around the rotary shaft. When the apparatus is not driven, the balls are pulled in one direction and then, are attached to the magnets. The attachment of the balls to the magnets results in an improper balancing operation. 
     When using the disk drive in a vertical direction, the balls are not rotated based on the centrifugal force. As a result, the balls do not properly race on the racing face of the ball casing, and it is impossible to implement a balancing operation. 
     The spindle motor, the ball casing and the turntable are sequentially installed below the rotary shaft installed on the upper surface of the substrate in the vertical direction. Thus, large space for installing the above-described elements is required, and the entire height of the disk drive apparatus is increased. 
     Namely, since the ball casing for implementing an auto balancing operation is positioned between the turntable and the spindle motor, the length of the rotary shaft is increased, and the entire height of the disk drive is increased. 
     Furthermore, when separately forming the spindle motor, the ball casing and the turntable, the total weight of the elements which are rotated by the spindle motor is increased, and the power consumption for driving the spindle motor is increased. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an auto balancing apparatus for a disk drive, which is capable of implementing an accurate balancing operation to automatically correct unstable rotation of a disk by properly guiding the movements of the balls used for an auto balancing apparatus. 
     It is another object of the present invention to provide an auto balancing apparatus for a disk drive, which makes it possible to decrease the occurrence of a self-excited vibration by preventing the balls from being slid during an auto balancing operation. 
     It is another object of the present invention to provide an auto balancing apparatus for a disk drive which is capable of preventing the balls used for an auto balancing operation from being moved in a certain direction when the apparatus is not driven. 
     It is another object of the present invention to provide an auto balancing apparatus for a disk drive, which is capable of decreasing the space needed for installing an auto balancing unit therein and the driving force required for rotating a disk. 
     To achieve the above objects, there is provided an auto balancing apparatus for a disk drive according to the present invention, which includes a ball casing having a circular racing space and installed concentrically with respect to a rotation member for rotating a disk. A plurality of balls which roll along a racing face formed in the racing space for implementing a balanced operation, and a guide member for guiding the movements of the balls. 
     Additional advantages, objects and features of the invention will become more apparent from the description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a cross-sectional view illustrating an auto balancing apparatus for a conventional disk drive; 
     FIG. 2 is a cross-sectional view illustrating the construction of an auto balancing apparatus for a disk drive according to a first embodiment of the present invention; 
     FIG. 3 is a plan view illustrating an inner construction of a ball casing according to a first embodiment of the present invention; 
     FIG. 4A is a cross-sectional view illustrating the position of balls before an auto balancing operation is performed according to a first embodiment of the present invention; 
     FIG. 4B is a cross-sectional view illustrating the position of balls during an auto balancing operation according to a first embodiment of the present invention; 
     FIG. 5 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive according to a second embodiment of the present invention; 
     FIG. 6 is a cross-sectional view illustrating the position of balls during an auto balancing operation according to a second embodiment of the present invention; 
     FIG. 7 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive according to a third embodiment of the present invention; 
     FIG. 8 is a cross-sectional view illustrating the position of balls during an auto balancing operation according to a third embodiment of the present invention; 
     FIG. 9 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive according to a fourth embodiment of the present invention; 
     FIG. 10 is a plan view illustrating the construction of a fourth embodiment of FIG. 9; 
     FIG. 11 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive according to a fifth embodiment of the present invention; 
     FIG. 12 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive according to a sixth embodiment of the present invention; and 
     FIG. 13 is a cross-sectional view illustrating the construction of a ball casing for an auto balancing apparatus for a disk drive based on another example of a sixth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will be explained with reference to the accompanying drawings. 
     As shown in FIGS. 2 through 4, in an auto balancing apparatus for a disk drive according to a first embodiment of the present invention, a rotary shaft  25  is rotatably installed on an upper surface of a substrate  20  in a vertical direction, and a bearing  22  is inserted onto a lower outer surface of the rotary shaft  25 . 
     A turntable  35  on which a disk is mounted is inserted onto an upper portion of the rotary shaft  25 . 
     Therefore, the rotary shaft  25  and the turntable  35  are integrally rotated. 
     A clamp  30  for fixing the disk is installed at an upper portion of the turntable  35 . In addition, a circular shape ball casing  50  is installed below the turntable  35 . The casing  50  is extended from an outer lower end portion of the turntable  35  and is bent towards center portion of the turntable  35 . Then the casing  50  is extended and bent towards the lower surface of the turntable  35  and is extended to the lower surface of the turntable  35 . 
     Namely, the upper surface of the ball casing  50  is formed of a lower surface of the turntable  35 , and the center portion of the ball casing  50  and  35  are concentrical. Also, to the turntable  35 , and a circular racing space  51  is formed in the interior of the ball casing  50 , and a plurality of balls  52  are received in the interior of the racing space  51 . 
     At this time, the racing space  51  is formed to have a width which does not exceed two times of the diameter of each ball  52 . The balls  52  are preferably made of a metallic material. 
     An inner wall of the racing space  51  becomes a racing face  51   i  along which the balls roll based on the centrifugal force during the balancing operation for correcting the unbalance rotation of the disk. The balls  52  roll along the racing face  51   i  in the circumferential direction for implementing a balancing operation. 
     As shown in FIGS. 3 through 4B, an inclined surface  55  is formed on an inner floor of the ball casing  50  and is upwardly inclined from the center portion toward the racing face  51   i.  Therefore, when the turntable  35  is rotated and a balancing operation is performed, the inclined surface  55  guides the balls  52  to roll on the racing face  51   i.    
     A plurality of ribs  56  are formed on the floor of the racing space  51  for implementing a proper balancing operation even when the disk drive is installed in the vertical direction (for example, when the disk mounted on the turntable  35  is vertical with respect to the surface of the ground). 
     Namely, when the disk drive is vertically installed with respect to the surface of the ground, the ribs  56  prevent the balls  52  from being moved by gravity to the lowest portion of the ball casing  50 . As a result, the balls  52  are not moved in a certain direction, and it is possible to implement a stable movement of the balls  52 . 
     In the first embodiment of the present invention, as shown in FIG. 3, the ribs  56  are preferably formed at an angle of 90°. The above-described angle is not limited thereto. More preferably, the range of the angle may be varied and determined based on the design conditions. 
     The spindle motor  40  is installed below the turntable  35  for rotating the turntable  35 . The spindle motor  40  includes a stator  45 , and a rotator  41  which is rotated based on an electromagnetic operation with the stator  45 . 
     The rotator  41  is engaged to the rotary shaft  25  and is rotated with the rotary shaft  25 . The stator  45  of the spindle motor  40  is installed on the upper surface of the substrate and is fixed to the outer surface of the bearing  22  inserted onto the rotary shaft  25 . 
     The rotator  41  includes a rotator yoke  42  installed on a lower surface of the turntable  35  and integrally rotated with the rotary shaft  25 . Also and a magnet  43  is attached on an inner surface of the rotator yoke  42 . 
     The stator  45  is installed opposite to the magnet  43  of the rotator yoke  42  in a state that the coils are wound onto the outer surface of the stator  45 . 
     In the drawings, reference numeral  36  represents a rubber which contacts with a portion of the lower surface of the disk for fixing the disk. 
     The operation of the auto balancing apparatus for a disk drive according to first embodiment of the present invention will be explained with reference to the accompanying drawings. 
     As shown in FIG. 4A, when the apparatus is not driven, the balls  52  are gathered at an inner portion of the ball casing  50 . In this state, when the disk is rotated at a certain speed, as shown in FIG. 4B, the balls  52  are moved along the racing face  51   i  via the inclined surface  55  based on the centrifugal force. 
     The balls  52  are moved along the racing face  51   i  in the circumferential direction for thereby performing a balancing operation of the disk. 
     At this time, the ribs  56  guide the movements of the balls  52  and prevent the balls  52  from being gathered at a certain portion. 
     In detail, when the disk is rotated at a lower speed, the ribs  56  collide with the balls  52  gathered at an inner portion in the racing space  51  for thereby preventing the balls  52  from being moved, and preventing the balls  52  from being gathered at a certain portion. In particular, when the disk drive is installed in a vertical direction, the balls  52  are prevented from being moved down toward the racing face  51   i  formed at the lowest portion of the ball casing  50 . During the balancing operation, the balls  52  collide with the upper portions of the ribs  56 , and the movements of the balls  52  are accelerated. 
     The auto balancing apparatus for a disk drive according to the second through seventh embodiments of the present invention will be explained. 
     The ball casings adapted in the second through seventh embodiments according to the present invention are circular and the same as the first embodiment except for the inner structures of the ball casings. Therefore, only the different inner structures of the ball casings will be explained. 
     In the second through seventh embodiments of the present invention, the lower surface of the turntable becomes an upper surface of the racing space, and the outer wall of the racing space formed in the interior of the ball casing becomes a racing face on which the balls roll for implementing a balancing operation in the racing space. 
     As shown in FIGS. 5 and 6, in the second embodiment of the present invention, a magnet  66  is installed in the interior of the ball casing  60  formed on the lower surface of the turntable  35 , namely, on the floor surface of the racing space  61  which receives the balls  62  therein, and an inclined step portion  65  is formed on an outer side portion in the racing space  61 . 
     The inclined step portion  65  is extended from an outer end portion of the magnet  66  toward the racing face  61   i  and includes a guide inclined surface  65 ′ formed at a portion neighboring with the magnet  66 , and a plane surface  65 ″ formed at a portion neighboring with the racing face  61   i.    
     The operation of the auto balancing apparatus for a disk drive according to a second embodiment of the present invention will be explained. 
     When the disk is rotated at a lower speed, the balls  62  collide with the magnet  66 , so that the balls  62  are not moved. 
     In this state, when the disk is rotated at a higher speed, the balls  62  roll along the racing face  61   i  based on the centrifugal force and are moved along the racing face  61   i  in the circumferential direction. 
     In detail, the balls  62  are moved off the magnet  66  and are guided along the inclined guide surface  65 ′ of the inclined step portion  65  and are positioned on the plane surface  65 ″. Thereafter, the balls  62  are moved along the racing face  61   i  on the plane surface  65 ″ in the circumferential direction for implementing a balancing operation. 
     As shown in FIG. 6, in the second embodiment of the present invention, the plane surface  65 ″ is formed in the interior of the ball casing  60 . So, when the balls  61  are moved along the racing face  61   i,  it is possible to implement a stable balancing operation in which the balls are not moved up and down. 
     At this time, the balls  62  slightly contact with the lower surface of the turntable  35  which is made of a metallic material and acts as an upper surface of the racing space  61 . Therefore, the sliding of the balls  62  during the balancing operation is prevented and it is possible to decrease the occurrence of the self-excited vibration. 
     The auto balancing apparatus for a disk drive according to a third embodiment of the present invention will be explained. 
     As shown in FIGS. 7 and 8, in the third embodiment of the present invention, a magnet  76  is installed in the interior of the ball casing  70  installed on the lower surface of the turntable  35  and on the upper surface of the racing space  71  which contacts with the lower surface of the turntable  35  and receives the balls  70  therein, and an inclined step portion  75  is formed on an outer side of the ceiling surface in the racing space  71 . 
     A lower plate  78  made of a metallic material is installed at a lower portion in the racing space  71 . 
     The lower plate  78  becomes a floor of the racing space  71 , and the balls  72  do not slide in the racing space  71  by the lower plate  78 . 
     The inclined step portion  75  is extended from an outer end portion of the magnet  76  to the racing face  71   i  and includes a guide inclined surface  75 ′ formed at a portion neighboring with the magnet  76 , and a plane surface  75 ″ formed at a portion neighboring with the racing face  71   i.    
     The operation of the auto balancing apparatus for a disk drive according to the third embodiment of the present invention will be explained. 
     As shown in FIG. 7, when the disk is rotated at a lower speed, the balls  72  contact with the magnet  76 , so that the balls  72  are not moved. 
     In this state, as shown in FIG. 8, when the disk is rotated at a higher speed, the balls  72  are moved to the racing face  71   i  by the centrifugal force and roll along the racing face  71   i  in the circumferential direction. 
     In detail, the balls  72  are moved from the magnet  76  and are guided along the inclined guide surface  75 ′ of the inclined step portion  75  and are gathered on the plane surface  75 ″. Thereafter, the balls  72  are moved along the racing face  71   i  on the plane surface  75 ″ in the circumferential direction for thereby implementing a balancing operation. 
     As shown in FIG. 8, in the third embodiment of the present invention, since the plane surface  75 ″ is formed in the interior of the ball casing  70 , when the balls  72  are moved along the racing face  71   i,  the balls  72  are not moved up and down during implementation of an accurate balancing operation. 
     The balls  72  slightly contact with the upper surface of the lower plate  78 , which is made of a metallic material and forms a lower surface of the racing space  71 . As a result, when the balls  72  do not slide during the balancing operation, and any self-excited vibration is decreased. 
     The auto balancing apparatus for a disk drive according to a fourth embodiment of the present invention will be explained. 
     As shown in FIGS. 9 and 10, in the fourth embodiment of the present invention, a plurality of magnets  86  are installed on an inner wall at a certain interval in the racing space  81  formed in the interior of the ball casing  80  installed on a lower surface of the turntable  35 , so that the balls  82  are not moved in the racing space  81  when the turntable is rotated at a lower speed. 
     As shown in FIGS. 9 and 10, according to the fourth embodiment of the present invention, the magnets may be installed on a certain surface, not on the racing face among the inner surface of the ball casing. 
     In the thusly constituted fourth embodiment of the present invention, when the turntable  35  is rotated at a lower speed, the balls  82  are spaced-apart from each other by the magnets  86  in the, racing space  81 , and the turntable  35  is not unbalanced. When the disk is rotated at a higher speed, the balls  82  are moved toward the racing face  81   i  by the centrifugal force and are moved along the racing face  81   i  in the circumferential direction. 
     The auto balancing apparatus for a disk drive according to a fifth embodiment of the present invention will now be explained. 
     As shown in FIG. 11, in the fifth embodiment of the present invention, a friction seat  95  is attached on a lower surface of the turntable  35  which is the upper surface of the ball casing  90 . 
     The friction seat  95  is preferably formed in a circular shape in such a manner that the friction seat  95  covers the entire upper surfaces of the racing space  91  in the ball casing  90 . 
     The friction seat  95  prevents the balls  92  from being slid when the balls  92  are moved along the facing face  91   i  during the balancing operation and thereby prevents a self-excited vibration. 
     In FIG. 11, reference numeral  96  represents an inclined surface. 
     The auto balancing apparatus for a disk drive according to a sixth embodiment of the present invention will be explained. 
     As shown in FIG. 12, in the sixth embodiment of the present invention, a friction rough surface  105  is formed on a floor surface in the racing space  101  formed in the interior of the ball casing  100 , which is installed on a lower surface of the turntable  35 . 
     The friction rough surface  105  is formed at an initial stage when fabricating the ball casing  100 . Namely, when fabricating the ball casing  100 , the friction rough surface  105  is formed by corroding a certain portion of the ball casing  100 . 
     In another example of the sixth embodiment of the present invention, as shown in FIG. 13, the racing face  111   i  on which the balls  112  roll during the balancing operation may be used as a friction rough surface by corroding the same when fabricating the ball casing  110  without using the corroded surface corresponding to a floor of the racing space  111  as the friction rough surface such as the rough surface  105  in FIG.  13 . 
     The above-described friction rough surfaces prevent a sliding of the balls  102  and  112  when the balls  102  and  112  roll along the racing faces  101   i  and  111   i  during the balancing operation. As a result, self-excited vibration is prevented. 
     As described above, in the auto balancing apparatus for a disk drive according to the present invention, the balls roll along the racing face during the auto balancing operation and any sliding in the racing space is prevented. As a result, it is possible to prevent a self-excited vibration and implement an accurate auto balancing operation. 
     In addition, since the ball casing is installed at an outer portion of the spindle motor, the distance between the substrate and the turntable is decreased. Thus, the size of the apparatus is significantly decreased. 
     The ball casing for the auto balancing operation and the rotor of the spindle motor are engaged at the same height as the turntable, and the turntable and the ball casing have the same installation structure. Therefore, the size of the ball casing can be decreased. The total weight of the elements needed to be rotated by the spindle motor is also decreased, making it possible to decrease the loads applied to the spindle motor, and prevent noise. In addition, the apparatus according to the present invention requires a small amount of power, so that it is well applicable to a portable apparatus. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as recited in the accompanying claims.

Technology Classification (CPC): 6