Abstract:
A disk apparatus has a head carriage and a head carriage drive mechanism. The head carriage drive mechanism has voice coil motors located on each side of the head carriage. The voice coil motors each have a drive coil, the two drive coils having different numbers of turns and being connected in parallel to a power source. The two voice coil motors generate identical propulsive forces despite having a different number of turns in the respective drive coils, making it possible to move the head carriage with precision. A head carriage position detecting mechanism is included in a space formed beneath the drive coil having the smaller number of turns, for added precision in positioning the head carriage.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a disk apparatus, and more particularly to a floppy disk apparatus for writing data to and reading data from a rotating floppy disk by movement of a head carriage. 
     2. Description of the Related Art 
     Conventionally, floppy disk apparatuses are widely used in personal computers as external memory devices. In recent years, in an effort to cope with the coming video age, floppy disk apparatuses have to be developed that greatly expand memory capacity from the current 1.44 MB to 200 MB or more. In order to expand memory capacity to such a large extent, it is necessary to increase the current 300 rpm rotation speed of the floppy disk by 10 times or more and at the same time increase the current track density of 135 tracks per inch (hereinafter tpi) by 10 times or more, to 2,000 to 3,000 tpi. In order to reliably write and read data under these high-speed, high-density conditions, a high degree of precision is required of the drive of the head carriage of the floppy disk apparatus so as to position the magnetic heads of the head carriage with a high degree of precision. Additionally, the floppy disk apparatus must be slim because it is included within the personal computer apparatus. 
     FIG.  8 (A) and FIG.  8 (B) show a head carriage drive mechanism  10  for a conventional high-density floppy disk device. The head carriage drive mechanism  10  has a head carriage  11 . The head carriage  11  has a head  12  and is moved and positioned longitudinally in the Y 1 -Y 2  direction along a radius of a rotating floppy disk  17  by a first voice coil motor  13  and a second voice coil motor  14  (hereinafter referred to collectively as first and second voice coil motors  13 ,  14 ) provided on either side of the head carriage  11  while being supported by guide rods  15  and  16 . The first voice coil motor  13  comprises a magnetic circuit structure  23  including a permanent magnet  20  and yokes  21  and  22 , and a drive coil  24  fitted to yoke  22  and fixedly mounted on the head carriage  11 . The second voice coil motor  14  comprises a magnetic circuit structure  33  including a permanent magnet  30  and yokes  31  and  32 , and a drive coil  34  fitted to yoke  32  and fixedly mounted on the head carriage  11 . 
     As shown in FIG.  8 (C), the drive coil  24  and drive coil  34  are connected in series to a power source  40 . The first and second voice coil motors  13 ,  14  generate identical propulsive forces and the head carriage  11  is moved in the Y 1 -Y 2  direction with precision. 
     When the first and second voice coil motors  13 ,  14  generate identical propulsive forces and the drive coil  24  and drive coil  34  are connected in series to the power source  40 , a number of turns in drive coil  24  and a number of turns in drive coil  34  are identical. As a result, it is difficult to create a space for including a head carriage position detecting mechanism that uses an encoder scale. 
     Moreover, it is difficult to independently set the propulsive forces of the first and second voice coil motors  13 ,  14  because drive coil  24  and drive coil  34  are connected in series to the power source  40 , thus limiting the freedom with which the head carriage drive mechanism can be designed. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a disk apparatus in which the problems described above are eliminated. 
     The above-described object of the present invention is achieved by a disk apparatus comprising: 
     a frame; 
     disk rotating means for supportably rotating a floppy disk; 
     a head for writing data to and reading data from a disk being rotated by said disk rotating means; 
     a head carriage for holding said head, said head carriage being movable in a direction of a radius of a disk supported by said disk rotating means; and 
     a first voice coil motor and a second voice coil motor for moving said head carriage provided on both sides of said head carriage, said first voice coil motor and second voice coil motor each respectively comprising: 
     a magnetic circuit structure mounted on said frame; and 
     drive coils mounted on said head carriage, 
     wherein said first voice coil motor and second voice coil motor are connected in parallel to an electric power source. 
     According to the above-described disk apparatus, it is possible to make the first voice coil motor and the second voice coil motor each generate an identical propulsive force even when the drive coil of the first voice coil motor and the drive coil of the second voice coil motor each have a different number of turns. Additionally, by connecting in series a resistor to one of either the first drive coil or the second drive coil it is also possible to make the first voice coil motor and the second voice coil motor each generate a slightly different propulsive force even when the drive coil of the first voice coil motor and the drive coil of the second voice coil motor have an identical number of turns. 
     As a result, it is possible to create a space for accommodating a head carriage position detecting mechanism that uses an encoder scale, thus expanding the freedom with which the head carriage drive mechanism can be designed. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a first embodiment of a disk apparatus according to the present invention; 
     FIGS.  2 (A),  2 (B) and  2 (C) are diagrams showing top, front and side views, respectively, of a first embodiment of a disk apparatus according to the present invention; 
     FIG. 3 is an exploded view of a head carriage and a voice coil motor of a first embodiment of the disk apparatus according to the present invention; 
     FIG. 4 is a top surface view of a head carriage and a voice coil motor of a first embodiment of the disk apparatus according to the present invention; 
     FIGS.  5 (A),  5 (B) are a cross-sectional view along the line V—V in FIG. 4 and a systems diagram, respectively: 
     FIG. 6 is a diagram showing a magnetic circuit structure; 
     FIG. 7 is a diagram showing a head carriage and voice coil motor portions of a second embodiment of the disk apparatus according to the present invention; and 
     FIGS.  8 (A),  8 (B) and  8 (C) are diagrams showing a conventional floppy disk device head carriage drive mechanism. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description will now be given of an embodiment of a disk apparatus according to the present invention, with reference to FIG.  1  and FIGS.  2 (A),  2 (B) and  2 (C). 
     FIG. 1 is an exploded view of an embodiment of a disk apparatus according to the present invention. FIGS.  2 (A),  2 (B) and  2 (C) are diagrams showing top, front and side views, respectively, of an embodiment of a disk apparatus according to the present invention. In the diagrams, X 1 -X 2  represents the horizontal dimension, Z 1 -Z 2  represents the vertical dimension and Y 1 -Y 2  represents the longitudinal front and rear depth dimension. 
     The floppy disk apparatus  50  is a high-density apparatus, and has a frame  51 , a turntable motor  52 , a turntable  53 , a head carriage  54 , a voice coil motor  55 , a holder  56 , a slider  57  that also functions as a cover, and a front bezel  58 . 
     A disk cartridge  60  is used with the floppy disk apparatus  50 . A cartridge body  61  of the disk cartridge  60  contains internally a floppy disk  62  having a diameter of 3.5 inches. Further, a shutter  63  is provided on an edge of the cartridge body  61 . The shutter  63  covers an upper opening  64  and a lower opening  65  in an upper and lower surface of the cartridge body  61 , respectively. A hub  66  of the floppy disk  62  is exposed at the lower surface of the cartridge body  61 . 
     When inserted from the front bezel  58  toward the rear, that is, in the Y 1  direction, the disk cartridge  60  fits inside the holder  56 , the shutter  62  slides horizontally in the X 2  direction and the openings  64  and  65  are opened. An upper magnetic head  70  opposes the upper opening  64  and a lower magnetic head  71  opposes the lower opening  65 . When a lock is released the slider  57  slides toward the front, that is, in the Y 2  direction, lowering the holder  56  together with the disk cartridge  60  in the Z 2  direction. The disk cartridge  60  is thus loaded into the floppy disk apparatus  50 , the hub  66  of the floppy disk  62  is set upon the turntable  53  and the lower opening  65  is placed over the lower magnetic head  71  so as to bring the lower magnetic head  71  into contact with a lower surface  62   b  of the floppy disk  62 . The floppy disk  62  is then rotated by the turntable motor  52  at a speed of approximately 3,600 rpm. Thereafter a head load mechanism (not shown) is activated by a solenoid  201  (see FIG.  2 (A)) being excited to lower a lift arm  202 . The upper magnetic head  70 , which is supported by the lift arm, then descends into the upper opening  64  to contact an upper surface  62   a  of the floppy disk  62 . 
     The head carriage  54  is moved longitudinally in the Y 1 -Y 2  direction by the voice coil motor  55  and data is written to or read from the surface of the floppy disk, which has been formed into tracks of 2,000-3,000 tpi, by the upper magnetic head  70  and lower magnetic head  71 . At this point, the upper magnetic head  70  and lower magnetic head  71  float slightly off the surface of the floppy disk due to the speed with which the floppy disk rotates. 
     By pressing the eject button  73  the disk cartridge  60  is ejected by moving first upward in the Z 1  direction and then forward in the Y 2  direction. 
     A detailed description will now be given of the head carriage  54  and the voice coil motor  55 , by reference to FIG.  3  through FIG.  7 . 
     As shown in FIG.  3  through FIG. 7, the head carriage  54  comprises a carriage body  80 , an upper head arm  81 , a lower magnetic head  71  provided on an upper front edge of the carriage body  80  and an upper magnetic head  70  provided on a lower front edge of the upper head arm  81 . Hollow drive coils  82 - 1  and  82 - 2  are fixedly mounted on an X 1  and an X 2  side of the carriage body  80 . As is explained below, the head carriage  54  is supported by parallel guide rods  84  and  85  affixed to the frame  51  so as to be movable longitudinally in the Y 1 -Y 2  direction. 
     The drive coils  82 - 1  and  82 - 2  are fitted into concave portions  80   a  and  80   b  provided on the carriage body  80  and fixedly positioned thereat. As shown in FIG. 3, guide rod  85  is engaged with a bearing portion  80   c  of the carriage body  80 . Guide rod  84  fits into a U-shaped holding portion  80   d  of the carriage body  80 . 
     As shown in FIG.  3  and FIG. 4, a strip of flexible cable  151  is connected to the lower magnetic head  71 . This strip of flexible cable  151  extends laterally away from the carriage body  80  in the horizontal X 2  direction and has an extended portion  151   a  having a length adequate to not restrict the movement of the head carriage  11 . 
     As shown in FIG.  3  and FIG. 4, the signal lead wire  150  attached to the upper magnetic head  70  is fixedly mounted on the upper head arm  81 , lead along the upper head arm  81  rearward in the Y 1  direction, further lead along the rear Y 1  edge of the head carriage  54  laterally in the horizontal X 2  direction and soldered to the extended flexible cable  151   a  at position  150 . 
     The voice coil motor  55  comprises voice coil motor  55 - 1  and voice coil motor  55 - 2  positioned parallel with respect to each other on the X 1  and X 2  sides, respectively, of a path along which the head carriage  54  moves. Voice coil motor  55 - 1  on the X 1  side comprises X 1 -side magnetic circuit structure  90 - 1  and X 1 -side drive coil  82 - 1 . Voice coil motor  55 - 2  on the X 2  side comprises X 2 -side magnetic circuit structure  90 - 2  and X 2 -side drive coil  82 - 2 . The X 1 -side magnetic circuit structure  90 - 1  and X- 2  side magnetic circuit structure  90 - 2  are substantially symmetrical to each other with respect to a center line  91  of the path along which the head carriage  54  moves. A magnetic circuit structure assembly  100  comprises the X 1 -side magnetic circuit structure  90 - 1  and X- 2  side magnetic circuit structure  90 - 2 . 
     As shown in FIG. 6, the magnetic circuit structure assembly  100  has a base comprising a yoke member  92  for mounting a permanent magnet. This yoke member  92  in turn comprises an X 1 -side yoke portion  92 - 1  for mounting a permanent magnet and an X 2 -side yoke portion  92 - 2  for mounting a permanent magnet, as well as a rear Y 2 -edge frame portion  92 - 3  and a front Y 1 -edge frame portion  92 - 4  that connect the X 1 -side yoke portion  92 - 1  and the X 2 -side yoke portion  92 - 2  in such a way as to form a substantially square shape when viewed from above. 
     The X 1 -side magnetic circuit structure  90 - 1  comprises the X 1 -side yoke portion  92 - 1  for mounting a permanent magnet, a permanent magnet  93 - 1  fixedly mounted on a lower surface of the X 1 -side yoke portion  92 - 1 , an X 1 -side drive coil yoke  94 - 1  and a magnetic gap  95 - 1 . The permanent magnet  93 - 1  is essentially a long, narrow strip, an upper surface of which is the S-pole and a lower surface of which is the N-pole. The drive coil yoke  94 - 1  axially passes through the drive coil  82 - 1  and ends of the drive coil yoke  94 - 1  are affixed to the Y 2 -edge frame portion  92 - 3  and Y 1 -edge frame portion  92 - 4 , respectively. The magnetic gap  95 - 1  is formed between the permanent magnet  93 - 1  and the X 1 -side drive coil yoke  94 - 1 . The drive coil  82 - 1  surrounds and is radially spaced from the drive coil yoke  93 - 1 . 
     The X 2 -side magnetic circuit structure  90 - 2  comprises the X 2 -side yoke portion  92 - 2  for mounting a permanent magnet, a permanent magnet  93 - 2  fixedly mounted on a lower surface of the X 1 -side yoke portion  92 - 2 , an X 2 -side drive coil yoke  94 - 2  and a magnetic gap  95 - 2 . The permanent magnet  93 - 2  is essentially a long, narrow strip, an upper surface of which is the N-pole and a lower surface of which is the S-pole. It will be observed that this pole configuration of permanent magnet  93 - 2  is the opposite of the pole configuration of permanent magnet  93 - 1 . The drive coil yoke  94 - 2  axially passes through the drive coil  82 - 2  and ends of the drive coil yoke  94 - 2  are affixed to the Y 2 -edge frame portion  92 - 3  and Y 1 -edge frame portion  92 - 4 , respectively. The magnetic gap  95 - 2  is formed between the permanent magnet  93 - 2  and the X 2 -side drive coil yoke  94 - 2 . The drive coil  82 - 2  surrounds and is radially spaced from the drive coil yoke  93 - 2 . 
     As shown in FIG.  5 (B), drive coil  82 - 1  and drive coil  82 - 2  are connected in parallel to a power source  40 . The drive coil  82 - 1  of the X 1 -side voice coil motor  55 - 1  has electrical wire having a diameter of 0.12 mm, a number of turns N 1  of said electrical wire being approximately  201 . The drive coil  82 - 2  of the X 2 -side voice coil motor  55 - 2  has electrical wire having a diameter of 0.12 mm, a number of turns N 2  of said electrical wire being  403 . Thus, the ratio of the number of turns N 1  to the number of turns N 2  is 1:2 and the resistance of the drive coil  82 - 1  is therefore less than the resistance of the drive coil  82 - 2 . 
     When a drive current is sent to the drive coils  82 - 1  and  82 - 2  by a control circuit, the ratio of a drive current i 1  sent to the drive coil  82 - 1  to a drive current i 2  sent to the drive coil  82 - 2  is 2:1 because the drive coils  82 - 1  and  82 - 1  are connected in parallel. 
     Accordingly, the X 1 -side voice coil motor  55 - 1  and the X 2 -side voice coil motor  55 - 2  each generate approximately equal propulsive forces and the head carriage  54  is moved with precision. As a result of this more precise positioning of the head carriage  54 , data can be accurately and reliably written to and read from even high-density disks having a track density in the range of 2,000 to 3,000 tpi. 
     It should be noted that the drive coil  82 - 1  having the lesser number of turns is smaller in size than the drive coil  82 - 2  having the greater number of turns. As a result, as shown in FIG.  5 (A) a space  160  is formed between the drive coil  82 - 1  and the frame  51 . By using this space  160  to mount an encoder scale  161  on the carriage body  80  and a photocoupler  162  on the frame  51 , a head carriage position detecting mechanism  163  can be provided for detecting a position of the head carriage. By providing a head carriage position detecting mechanism  163  in this space  160  formed between the drive coil  82 - 1  and the frame  51  the floppy disk apparatus  50  can be made slim. 
     As can be readily appreciated, the ratio of the number of turns N 1  to the number of turns N 2  is not limited to 1:2 but can be in any ratio. Nevertheless the X 1 -side voice coil motor  55 - 1  and the X 2 -side voice coil motor  55 - 2  will generate identical propulsive forces, respectively. 
     A detailed description will now be given of a second embodiment of a disk apparatus according to the present invention, with reference to FIG.  7 . 
     FIG. 7, like FIG.  5 (A) above, is a diagram showing a head carriage  54  and a voice coil motor  55 A. The voice coil motor  55 A is essentially identical to the voice coil motor  55  described above. Voice coil motor  55 A comprises voice coil motor  55 A- 1  and voice coil motor  55 A- 2  positioned parallel with respect to each other on the X 1  and X 2  sides, respectively, of the path along which the head carriage  54  moves. Except for the drive coils  82 A- 1  and  82 A- 2 , voice coil motors  55 A- 1  and  55 A- 2  are identical to voice coil motors  55 - 1  and  55 - 2  described above. 
     Drive coils  82 A- 1  and  82 A- 2  have electrical wires of an identical diameter and an identical number of turns. As shown in FIG. 7, drive coils  82 A- 1  and  82 A- 2  are connected in parallel. A resistor R is connected in series with drive coil  82 A- 2  on the drive coil  82 A- 2  side. The presence of this resistor R causes a current i 3  flowing to drive coil  82 A- 1  to be greater than a current i 4  flowing to drive coil  82 A- 2 , and as a result the propulsive force generated by the X 1 -side voice coil motor  55 A- 1  is slightly larger than the propulsive force generated by the X 2 -side voice coil motor  55 A- 2 . 
     The configuration described above, when used where the X 1 -side load is slightly greater than the X 2 -side load when moving the head carriage  54 , makes it possible to move the head carriage  54  with precision. 
     As can be readily appreciated from the above description, the present embodiment makes it possible to freely design voice coil motors to suit the loads arising on the X 1  side and X 2  side of the head carriage  54  when the head carriage  54  is moved. 
     The above description is provided to enable any person skilled in the art to make and use the invention and sets forth the best mode contemplated by the inventors of carrying out their invention. In addition, the present invention is not limited to the specifically disclosed embodiments and variations, and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No.10-61613 filed on Mar. 12, 1998, the entire contents of which are hereby incorporated by reference.