Abstract:
An auto-balancing disk drive apparatus is disclosed which makes it possible to decrease the installation space of an auto balancing unit thereof which is capable of automatically preventing an up and down movement of a disk when the disk is rotated at a high speed, reducing the driving force which is needed for the rotation of the disk and auto balancing unit, and reducing the noise and vibration which occur at the auto balancing unit. The disk drive apparatus includes a motor generating a rotational force with respect to a rotary shaft, and an auto balancing unit installed radially laterally and co-planar with respect to the rotary shaft for automatically correcting an unbalanced state of a rotation member when an unbalanced state occurs at the rotation member.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a disk drive apparatus, and in particular to a disk drive apparatus which includes an auto balancing unit capable of automatically balancing (an up and down) movement of a disk when a disk mounted on a turntable of the disk drive is rotated. 
     2. Description of the Background Art 
     As a disk drive is designed to operate at a high speed, a rotation unbalance condition (up and down movements) may occur when a disk is driven at a high speed. 
     The above-mentioned disk unbalance condition result in the problems that a signal recorded on a disk is not accurately reproduced, and a signal is not accurately recorded onto a disk. 
     The above-described disk unbalance problem may occur due to a nonuniformity of a disk when fabricating the disks. In addition, as the rotation speed of the disk is increased, the rotation unbalance problem of the disk is increased. Also, in the case that the disk is not accurately mounted on the turntable, the above-described unbalance problem may occur. 
     A conventional auto balancing unit which has been proposed to overcome the rotation unbalance problems of the disk will be explained. 
     As shown in FIG. 1, on the upper surface of a substrate  1 , a rotary shaft is vertically mounted. 
     A ball casing  9  is installed at a lower portion of a turntable  7  inserted onto an upper end portion of the rotary shaft  6  and is downwardly extended from an outer portion of the turntable  7  and is bent inwardly toward the center of the turntable and is extended to the outer surface of the rotary shaft and is bent upwardly toward the upper portion of the rotary shaft  6  and then is extended to the lower surface of the turntable  7 . 
     The ball casing  9  is formed in a circular plate shape like the turntable  7  and includes a space in which a plurality of metallic balls  10  are provided. 
     A lower portion of an outer side of the above-described space is rounded in order to implement a smooth movement of the balls  10 . 
     A racing face  9 i along which the balls  10  roll is formed at an outer portion of the inner wall of the space formed in the ball casing  9  so that a rotation unbalance which may occur when the disk is rotated is prevented. 
     A magnet  11  is engaged to an inner central portion of the ball casing  9 . 
     When the apparatus is operated at a low speed or is not operated, the magnet  11  serves to prevent the balls  10  from being freely moved. 
     A buffering member(not shown) which is made of a rubber is formed on an outer surface of the magnet  11 . 
     A spindle motor  3  is installed at a lower portion of the ball casing  9 , and a rotor  5  which is one of the elements of the spindle motor  3  is connected with the rotary shaft  6  for thereby implementing an integral rotation with the rotary shaft  6 , and a stator  4  which is another one of the elements of the spindle motor  3  is fixed to an outer portion of a bearing  2  inserted onto a lower outer portion of the rotary shaft  6 . 
     In the drawing, reference numeral  5 M designates a magnet forming the rotor  5 , and  8  designates a clamp for fixing a disk on the turntable. 
     The operation of the conventional auto balancing unit will be explained. 
     First, as the rotor  5  is rotated by the driving operation of the spindle motor  3 , the rotary shaft  6  is rotated. The turntable  2  is rotated by the rotation of the rotary shaft  6 , and a disk (not shown) mounted on the upper surface of the turntable  2  is rotated. 
     At this time, when the disk is rotated at a high speed, or if the disk is rotated in a rotation unbalance state, the balls  10  in the interior of the ball casing  9  are moved along the racing face  9 i of the ball casing  9  for thereby preventing an unbalanced state of the disk. 
     However, the above-described disk drive apparatus having an auto balancing unit has the following problems. 
     Since the spindle motor  3 , the ball casing  9  and the turntable  7  are sequentially installed from the lower portion of the rotary shaft  6  installed on the upper surface of the substrate  1 , the spaces therebetween are large, so that the entire height of the disk drive apparatus is increased. 
     Namely, as the spindle motor  3 , the ball casing  9  and the turntable  7  are independently formed, the weight of the elements which are driven by the spindle motor  3  is increased, so that a large/high amount of power is required for rotating the spindle motor  3 . 
     Generally, since the ball casing  9  is fabricated using a mold in order to decrease the fabrication cost, the ball casing  9  may be deformed during the operation of the apparatus or when the apparatus is not driven. 
     Since there is no element for fixing the outer portion of the ball casing  9  contacting with the lower surface of the turntable  7 , and the balls  10  which are moved in the interior of the ball casing  9  are made of a metallic material, the outer portion(in particular the portion contacting with the turntable  10 ) of the ball casing  9  may be deformed by the balls  10  during the operation of the apparatus or may be deformed by an externally applied force during the operation of the apparatus. 
     If the shape of the ball casing  9  is deformed, a smooth movement of the balls is not implemented. If the racing face  9 i which is preferably formed to have a roundness is deformed, it is impossible to implement the auto balancing operation. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an auto-balancing disk drive apparatus which is capable of decreasing a noise and vibration by obtaining a roundness of a racing face formed to guide balls for thereby implementing an effective auto-balancing operation. 
     It is another object of the present invention to provide an auto-balancing disk drive apparatus which is capable of significantly decreasing the space needed for installing an auto balancing unit for automatically balancing the rotation of a disk. 
     It is another object of the present invention to provide an auto-balancing disk drive apparatus which includes an auto balancing apparatus capable of decreasing the driving force needed for the rotation of a disk. 
     In order to achieve the above objects, there is provided a disk drive apparatus which includes a motor generating a rotational force with respect to a rotary shaft, and an auto balancing unit installed radially laterally with respect to the motor for automatically correcting an unbalanced state of a rotation member when an unbalanced state occurs at the rotation member. 
     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 the construction of a conventional disk drive apparatus; 
     FIGS. 2 a  and  2   b , hereinafter referred to as FIG. 2, are cross-sectional views illustrating a disk drive apparatus according to the present invention; 
     FIG. 3 is a partial cross-sectional view for explaining the structure in which a ball casing is installed at a turntable according to the present invention; and 
     FIG. 4 is a partial cross-sectional view illustrating another embodiment of the structure in which a ball casing is installed at a turntable according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The disk drive apparatus according to the present invention will be explained with reference to the accompanying drawings. 
     As shown in FIGS. 2 and 3, a rotary shaft  25  is vertically mounted on an upper surface of a substrate  20 , via a bearing  22  inserted onto a lower end of the rotary shaft  25 . 
     A turntable  35  having an upper surface on which a disk may be mounted is inserted onto an upper end of the rotary shaft  25 . 
     Therefore, the rotary shaft  25  and the turntable  35  are integrally rotatable. 
     A clamp  30  which fixes the disk is installed at an upper portion of the turntable  35 . 
     A ring shaped ball casing  50  is extended from a lower end portion of the turntable  35  on a lower surface of the turntable  35  and is bent and extended inwardly toward the center of the turntable  35  and is bent back upwardly toward the lower surface of the turntable  35  and is extended to the lower surface of the turntable  35  for implementing an auto balancing operation which is capable of automatically balancing the disk. 
     The ball casing  50  defines a space  51  into which a plurality of balls  52  which form an auto balancing unit together with the ball casing  50  are provided, and the space  51  formed in the interior of the ball casing  50  is rounded at its outer lateral portions, so that a smooth movement of the balls  52  is implemented. 
     The balls  52  are made of a metal, magnetic material, ceramic, etc. and are movable in the space  51 . The balls  52  are moved in a radial direction in the space  51  for thereby balancing the disk when an unbalanced state occurs during rotation of the disk. 
     The space  51  has a width which does not exceed two times the diameter of each of the balls  52 , and an outer side inner surfaces serves as a racing face  51 i which guides the flow of the balls  52  during the auto balancing operation. 
     A spindle motor  40  is installed at a lower center portion of the turntable  35  for rotating the turntable  35 . The spindle motor  40  is formed of a stator  45 , and a rotor  41  which is rotated based on an electromagnetic co-operation with the stator  45 . 
     The rotor  41  includes a yoke  42  which is formed to surround a region from a part of the lower portion of the ring shaped ball casing  50  to a part of the lower surface of the turntable  35  via an inner outer surface of the ball casing  50  and contacts with the above-described region, and a magnet  43  engaged to a portion which is parallel to an inner outer portion of the ball casing  50  at the inner surface of the yoke  42  and installed opposite the stator  45 . 
     As shown in FIG. 2, the yoke  42  is fixed to a lower surface of the turntable  35  by a caulking work. 
     The ball casing  50  is installed integrally with the yoke  42  which forms the rotor  41  of the spindle motor  40  and is rotated together with the rotor  41 , and the balls  52  are rotated together with the rotor  41 . 
     An outer upper end portion of the ball casing  50  is inserted into a shoulder  37  of the turntable  35 , so that the turntable  35  and the ball casing  50  are integrally rotated. 
     The stator  45  is installed at an outer surface of the bearing  22  and is opposite to the magnet  43 . 
     The magnet  43  is positioned laterally horizontal to the balls  52 , so that when the apparatus is driven at a low speed, or the apparatus is not driven, the balls  52  are prevented from freely moving in the interior of the space. 
     The engaging portion structure of the turntable  35  and the ball casing  50  will be further explained. 
     As shown in FIG. 3, as a roundness maintaining portion for maintaining a roundness of the ball casing  50 , there are provided a first shoulder portion  55  formed at an outer upper portion of the ball casing  50 , and a second shoulder portion  37  formed at an outer lower portion of the turntable  35  and engaged with the first shoulder portion  55 . 
     The second shoulder portion  37  of the turntable  35  which is formed by cutting a portion formed of a metallic material(for example, brass) supportedly contacts with the first shoulder portion  55  of the ball casing  50  fabricated by molding, so that the ball casing  50  which is fabricated by molding is not deformed. 
     FIG. 4 illustrates another engaging portion structure of the turntable and the ball casing according to the present invention. An engaging groove  137  is formed in a lower surface of the turntable  135 , and an outer upper portion of the ball casing  150  is inserted into the engaging groove  137 . 
     As shown in FIG. 4, the outer end portion of the ball casing  150  is tightly inserted into the engaging groove  137  of the turntable  135  for thereby preventing any deformation of the ball casing  150 , so that it is possible to maintain a roundness at an outer wall of the space  51  formed in the interior of the ball casing  150 . 
     In the thusly constituted disk drive apparatus according to the present invention, the balls  52  are directed to compensate for any unbalanced state of the disk which may occur during the high speed rotation of the turntable  35  for thereby implementing a balanced state of the disk drive. 
     In more detail, when the above-described disk unbalance state occurs at the disk, the balls  52  are moved in the space  51  to the portion opposite to the portion which is deflected in the upward direction for thereby balancing the disk. 
     In the present invention, the ball casing  50  is installed radially outwardly of the spindle motor  40  for thereby decreasing the distance between the substrate  20  and the turntable  35  compared to the conventional art in which the ball casing is provided between the spindle motor and the turntable. 
     In addition, since the ball casing  50  for the auto balancing operation and the rotor  41  of the spindle motor  40  are integrally formed, the installation structure is cooperatively used. Since the size of the ball casing  40  is small, the total weight of the elements which are driven by the spindle motor  40  is decreased. 
     As an example of the cooperative-use of the installation structure, the upper surface of the ball casing  50  is formed by the lower surface of the turntable  35 . 
     Therefore, the load applied to the spindle motor  40  is decreased, and the power consumption is decreased, so that the present invention is well applicable to a portable apparatus which uses a disk drive. 
     In addition, since an outer upper portion of the ball casing  50  is stably fixed by the shoulders  37  and  55  or the engaging groove  137 , the outer portion of the ball casing  50 , in particular the shape of the racing face  51 i is not easily deformed. 
     In other words, since the roundness of the racing face  51 i is maintained, it is possible to accurately control the movements of the balls  52  for thereby implementing an accurate auto balancing operation of the disk. 
     The ball casing  50  which is formed by molding is stably supported by the metallic turntable  35  formed by a cutting process for thereby preventing any deformation of the ball casing so. 
     In another embodiment of the present invention, the auto balancing unit may be installed radially inwardly of the spindle motor  40 . 
     In the disk drive apparatus according to the present invention, since the ball casing including the balls for implementing an auto balancing operation is installed at a lower portion of the turntable corresponding to an outer portion of the spindle motor, the space occupied by the turntable, ball casing and spindle motor is decreased. In addition, since the installation structure is cooperatively-used by the above-described elements, the load applied to the spindle motor is decreased. 
     Therefore, the disk drive apparatus may be fabricated to be light and compact, and the power consumption is decreased. 
     Since the outer upper portion of the ball casing which is formed by molding is supported by the turntable which is formed by the cutting process, it is possible to implement a roundness of the racing face of the ball casing which is capable of guiding the movements of the balls for the auto balancing operation, so that it is possible to effectively prevent any unbalance of the disk which is rotated at a high speed. 
     Although the preferred embodiment 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.