Abstract:
A flexible printed-wiring circuit board that connects a signal-processing circuit board and a pickup is prevented from coming into contact with the bottom (or the like) of a tray and thus becoming damaged. The flexible printed-wiring circuit board (FPC board) is disposed in a U-shaped folded state in a space sandwiched between a surface along which the tray moves, and a surface on which the signal-processing circuit board is mounted. An extension portion that restricts deformation of the FPC board toward the tray is provided at a connecting end of the pickup. Length D of the extension portion is set such that length S of the FPC board from a front end of the extension portion to a fold-back position of the FPC board is equal to or less than a required value.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese application serial no. JP 2006-149817, filed on May 30, 2006, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The present invention relates to optical disc drives for writing or reading out signals onto or from an optical disc. More particularly, the invention relates to a structure of a flexible printed-wiring circuit board that connects a pickup and a circuit board equipped with a signal-processing circuit. 
         [0004]    (2) Description of the Related Art 
         [0005]    Optical disc drives with an optical pickup adapted to enable emission of laser beams with three wavelengths including a blue laser beam are coming to be used in recent years. The dimension of the pickup tends to be increased. In the meantime, with a wide variety of use applications, there is a strong desire for the thinning-down and miniaturization of personal computers in which an optical disc drive is to be mounted regardless of whether the number of functions is increased. Optical disc drives are also requested to be thinned down and miniaturized. 
         [0006]    The main inhibiting factor in achieving the thinning-down and miniaturization of optical disc drives is the presence of drive mechanism sections for mounting an optical disc, driving a pickup, etc. In terms of a wiring structure for exchanging signals with the pickup, a flexible printed-wiring circuit board (hereinafter, abbreviated to FPC board) that has durability against repeated operation for optical disc data reading/writing and is excellent in the ease of handling has been generally used in recent years as a technique for thinning the driving section of the pickup. 
         [0007]    During connection of the FPC board and the pickup, the reliability of the connection may not be secured by using connectors. For this reason, the FPC board is connected to the pickup directly, instead of connectors. In the case where the FPC board is damaged, therefore, the pickup also requires replacement at the same time, and FPC board damage must be avoided. Also, the FPC board is structured such that it can be folded back in a U-shape state when moved, and a bend portion in the fold-back portion easily overhangs. During tray movement for mounting the optical disc or during pickup movement, FPC board damage will result if the overhanging portion of the FPC board comes into sliding contact with the tray member, the disc or other sections. There is a need, therefore, to avoid the sliding contact of the FPC board by suppressing the overhang of the FPC board toward the tray, and thus to prevent the occurrence of FPC board damage. 
         [0008]    Techniques in connection with this are disclosed in Japanese Patent Laid-Open No. 2005-346871, Japanese Patent Laid-Open No. 2005-203039, Japanese Patent Laid-Open No. 2004-355772 and Japanese Patent Laid-Open No. 2004-234803, for example, which propose techniques for preventing damage to the bend in a FPC board. 
       SUMMARY OF THE INVENTION 
       [0009]    The disc drive described in above Japanese Patent Laid-Open No. 2005-346871 has a structure in which a pickup that is connected with a FPC board is mounted on a disc tray that is extends from and retracted into an enclosure. Hence, the total vertical space of the disc drive is limited and the width of the FPC board connected to the pickup is increased with an increase in the number of electrical signal lines to read out/write data from/onto many types of discs. As a result, the U-shaped fold-back portion of the FPC board planarly overlaps on the pickup opening in the tray, and the resulting upward movement of the FPC board&#39;s fold-back portion from the opening damages the disc being used. In order to solve this problem, a top cover that constitutes the tray is used to prevent disc damage by holding down the overhang of the FPC board. However, since sliding the overhang inward or downward moves the FPC board itself, FPC board damage due to sliding contact with the top cover could result, and since the repulsion of the stress due to the hold-down of the overhang is applied to the pickup section, the pickup could be misaligned. 
         [0010]    The optical disc drive described in Japanese Patent Laid-Open No. 2005-203039 includes a mechanism for reading out and writing data from/onto a disc in a movable tray. The disc drive has an FPC board that connects a control circuit board disposed on the reverse side of the tray and a control circuit board placed on an enclosure, and the FPC board is bent to make the tray movable. Since the disc drive is small in thickness, there are the problems that if it is attempted to house the FPC board in the drive, the radius of curvature of the bend portion in the FPC board is reduced, thus making the FPC board prone to break, and resulting in wiring disconnections. In order to solve these problems, the bottom of the enclosure is notched and the radius of curvature of the bend is increased for the bend to jut out toward the notch portion, whereby the breakage of the FPC board is prevented. In this structure, it is assumed that the FPC board protrudes from the enclosure of the optical disc drive, so the particular relationship between the amount of protrusion and the position of the optical disc could lead to damage to the FPC board and the optical disc due to contact between them. 
         [0011]    The optical disc drive described in Japanese Patent Laid-Open No. 2004-355772 is characterized in that an FPC board is pulled out toward a spindle motor. However, since a pickup needs to move close to the spindle motor in order to perform data read/write operations on an optical disc, the FPC board and the spindle motor could come into contact with each other and become damaged. 
         [0012]    The recording and/or reproducing device described in Japanese Patent Laid-Open No. 2004-234803 uses an FPC board to establish electrical connection between a chassis and a pickup unit mounted on an extendible-retractable mobile body. In order to reduce the load on the FPC board due to movement of the mobile body, the bend region of the FPC board is formed more thinly than other regions of the FPC board. Varying the thickness of the FPC board from region to region, however, degrades the workability of the FPC board and is likely to result in a stress concentrated at the portions whose thicknesses change. 
         [0013]    The present invention was made in view of these problems of the above conventional techniques, and an object of the invention is to provide an optical disc drive with high reliability by reducing an overhang of a fold-back portion of a flexible printed-wiring circuit board which connects a circuit board and a pickup, and avoiding contact between the flexible printed-wiring circuit board and other members. 
         [0014]    An optical disc drive of the present invention includes: an enclosure; a tray on which to place an optical disc and which moves between a retracting position and an extending position with respect to the enclosure; a disc motor which rotationally drives the optical disc; a pickup which writes or reads out signals onto/from the optical disc; a pickup feeder which slides the pickup in a radial direction of the optical disc; a circuit board mounted on the enclosure and adapted for processing the signals that the pickup writes or reads out; and a flexible printed-wiring circuit board which electrically connects the pickup and the signal-processing circuit board and transmits the signals. The pickup has a connecting end member to connect the flexible printed-wiring circuit board, the flexible printed-wiring circuit board being disposed in a U-shaped folded state in a space sandwiched between a surface along which the tray moves and a surface on which the signal-processing circuit board is mounted, and the connecting end member having a restriction member to restrict deformation of the flexible printed-wiring circuit board toward the tray. 
         [0015]    The connecting end member of the pickup includes, as the restriction member, an extension portion protruding toward the flexible printed-wiring circuit board. 
         [0016]    Length D of the extension portion is set such that length S of the flexible printed-wiring circuit board from a front end of the extension portion to a fold-back position of the flexible printed-wiring circuit board is equal to or less than a required value. 
         [0017]    According to the present invention, it is possible to provide a highly reliable optical disc drive that avoids contact of a flexible printed-wiring circuit board with other members of the optical disc drive. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an exploded perspective view showing an embodiment of an optical disc drive according to the present invention. 
           [0019]      FIG. 2  is a sectional view showing the peripheral configuration of a pickup in the optical disc drive of  FIG. 1 . 
           [0020]      FIGS. 3A ,  3 B are diagrams schematically showing deformation of a flexible printed-wiring circuit board (FPC board). 
           [0021]      FIG. 4  is a diagram showing a relationship between an extension portion and the amount of an overhang of the FPC board. 
           [0022]      FIGS. 5A and 5B  are diagrams illustrating the deformation of the FPC board during movement of the pickup. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]      FIG. 1  is an exploded perspective view showing an embodiment of an optical disc drive according to the present invention. The optical disc drive  1  of the present embodiment includes an enclosure  2 . In a front panel of the enclosure  2 , an extending/retracting slot  21  for a tray  3  is provided. A concave portion  31  in which to place an optical disc  4 , and an opening  32  for rendering a pickup  5  accessible to the optical disc  4  are formed in the tray  3 . The tray  3  is constructed so as to be slidable with the optical disc  4  placed in the concave portion  31  between an extending position of the tray at which the tray is extended to an outside region of the enclosure  2  and a retracting position of the tray at which the tray is retracted into the enclosure. Upon completion of sliding to the retracting position, the tray  3  with the optical disc  4  placed on is positioned and held by a locking unit (not shown), and the optical disc  4  is engaged with a disc motor  6 . 
         [0024]    The optical disc  4  is rotationally driven by the disc motor  6 , and the pickup  5  facing the optical disc  4  uses an optical lens to focus laser beams emitted from a semiconductor laser which is a light source, and writes or reads out a signal onto/from the optical disc  4 . At this time, the pickup  5  is slidable in a radial direction of the optical disc  4  by a pickup feeder unit (not shown) at the opening  32  of the tray  3 , and thus slides between the innermost peripheral position on the disc and the outermost peripheral position thereon. 
         [0025]    Through a flexible printed-wiring circuit board (hereinafter, referred to as FPC board)  7 , the pickup  5  sends/receives the signal that the pickup writes or reads out to/from a circuit board  8  (shown in  FIG. 2 ) mounted in a main unit of the disc drive in order to process the signal. During exchange of the signal, the pickup  5  and the FPC board  7  are electrically connected on a connecting end member  71  of the pickup  5  directly, instead of via a connector. In order to enhance heat release during operation, the pickup  5  also has a heatsink plate  51  as required. 
         [0026]      FIG. 2  is a sectional view showing the peripheral configuration of the pickup in the optical disc drive of  FIG. 1 . During opening/closing of the tray  3 , the pickup  5  and the disc motor  6  are inclined at a required angle so as to move (i.e., downward in  FIG. 2 ) away from a sliding surface of the tray  3 , thus making it easy to mount the optical disc. The pickup  5  and the circuit board  8  are connected by folding back the flexible printed-wiring circuit board (FPC board)  7 . At this time, the pickup  5  and the FPC board  7  are connected on the connecting end member  71  of the pickup  5 . Deformation of the FPC board  7  during the connection thereof with the pickup  5 , however, is restricted by an extension portion  72  extending toward the FPC board  7 . The extension portion  72  is provided in the connecting end member  71 . The extension portion  72  is a restricting member that restricts the deformation of the FPC board  7  toward the tray  3  by protruding in a required distance from an edge of the pickup  5  or from an end of the heatsink plate  51 . With the extension portion  72 , the disc drive can prevent a fold-back portion of the FPC board  7  from coming into contact with a bottom portion  33  of the tray. In addition, propagation of heat which has been generated by the pickup  5 , to the FPC board  7 , is minimized since the heatsink plate  51  is receded from the extension portion  72 . 
         [0027]      FIGS. 3A ,  3 B are diagrams schematically showing the deformation of the flexible printed-wiring circuit board (FPC board)  7  in  FIG. 2 .  FIG. 3A  shows a comparative example in which the extension portion  72  is not provided so that the connecting end member  71  is as long as the pickup  5 , and  FIG. 3B  shows the present embodiment in which the connecting end member  71  includes the extension portion  72  of length D. Both  FIGS. 3A and 3B  show the case where the pickup  5  is positioned at which the deformation of the FPC board  7  becomes a minimum. 
         [0028]    As shown in  FIG. 3A , when the pickup  5  moves, a component force related to a radius R of curvature of the fold-back portion and the like deforms the FPC board  7  so that the FPC board  7  overhangs a distance “d” in a direction of the tray  3 . As a result, overhanging portion  73  of the FPC  7  slides while being brought into contact with the bottom portion  33  of the tray  3 , and could damage the FPC board  7 . 
         [0029]    In  FIG. 3B , in order to suppress the overhang of the FPC board  7 , the connecting end member  71  has the extension portion  72  of length D which serves as a restrictor to restrict the deformation of the FPC board  7 . As a result, the portion of the FPC board  7  which abuts on the extension portion  72  is not deformed toward the tray  3 , the radius of curvature of the fold-back portion of the FPC board  7  is reduced to R′, and the amount of the overhang is reduced to “d′”. This means that it is possible to prevent the overhanging portion  73  of the FPC  7  from coming into sliding contact with the bottom portion  33  of the tray  3 , and thus to avoid damaging the FPC board  7 . In other words, if the width of a space sandwiched between a bottom portion  33  of the tray  3  and an upper plane of the circuit board  8  is defined as H, it is possible to maintain a relationship of R′&lt;H/2. 
         [0030]    Next,  FIG. 4  is a diagram in which measurement results on a relationship between the extension portion  72  and the amount of the overhang of the FPC board  7  are shown to illustrate advantageous effects of the present embodiment. In  FIG. 4 , a relationship between length S of the FPC board to the fold-back portion thereof and height A of the FPC board during the deformation thereof is shown with varying length D of the extension portion  72 . Both dimensions S and A are shown in  FIG. 3B . In  FIG. 4 , the FPC board is formed of polyimide. The FPC board is 30.7 mm in width, 0.1 mm in thickness, and the extension portion  72  is 0.3 mm in thickness. The amount of the overhang of the FPC board  7  depends on length S from the front end of the extension portion  72  to the fold-back position of the FPC board  7 , not directly on length D of the extension portion  72 . In addition, as length S (i.e., increasing length D of the extension portion) is reduced, the deformation height A (the amount of the overhang) of the FPC board is reduced. If a maximum permissible value of deformation height A is 22 mm, for example, the extension portion  72  should be provided so that length S of the FPC board to the fold-back portion is equal to or less than 37.5 mm. Since a deformation level of the FPC board  7  depends on particular machine characteristics (rigidity), an appropriate value should be set to suit the type of a FPC board used. 
         [0031]      FIGS. 5A and 5B  are diagrams illustrating the deformation of the flexible printed-wiring circuit board (FPC board)  7  during the movement of the pickup in the present embodiment.  FIG. 5A  shows the state where the pickup  5  is present at the innermost peripheral position on the optical disc  4 , and  FIG. 5B  shows the state where the pickup  5  is present at the outermost peripheral position on the optical disc  4 . The pickup  5  returns to its original horizontal position and slides from an inner peripheral edge of the disc to an outer peripheral edge thereof while facing the opening  32  in the tray  3  horizontally. As the pickup  5  slides, the FPC board  7  also moves. The length of the FPC board  7  up to the fold-back portion thereof is L in  FIG. 5A , and L/2 in  FIG. 5B . 
         [0032]    In the present embodiment, the connecting end member  71  includes the extension portion  72 . The extension portion  72  restricts the deformation of the FPC board  7 . That is, the extension portion  72  is provided to suppress the length of the FPC board  7  up to the fold-back portion thereof to the required value or less. Although the maximum length of the FPC board  7  to the fold-back portion is L in  FIG. 5A , the length L should be, for example, the maximum permissible value of 37.5 mm or less as shown in  FIG. 4 . 
         [0033]    Thus, the amount of the overhang of the fold-back portion is reduced, the radius of curvature R can be decreased. When the pickup  5  moves, the FPC board  7  is placed into a space (width H) sandwiched between the bottom portion  33  of the tray  3  and the upper plane of the circuit board  8 . Therefore, the FPC board  7  moves without overhanging toward the opening  32  or coming into contact with the bottom portion  3  of the tray  3 . That is, the radii of curvature R 1  and R 2  of the fold-back portion in  FIGS. 5A and 5B  are always maintained in relationships of R 1 &lt;H/2 and R 2 &lt;H/2, respectively. This makes it possible to prevent the FPC board  7  from coming into sliding contact with the bottom portion  33  of the tray  3 , even during the movement of the pickup  5 , and hence to avoid damaging the FPC board  7 . 
         [0034]    In addition, in the present embodiment, since the moving distance L/2 of the fold-back portion of the FPC board  7  is ½ of the moving distance L of the pickup  5 , the fold-back portion suffers no damage due to being pressed against a rear wall and other portions of the disc drive. For these reasons, the FPC board in the present embodiment does not come into sliding contact with other members of the FPC board, and the FPC board thus improves in reliability. 
         [0035]    While the embodiment described above uses the structure using a flexible printed-wiring circuit board (FPC board), the present invention is also effective for cases using a flexible flat cable (FFC). In addition, while the connecting end member  71  and the extension portion  72  are integrally structured, the extension portion may be structured as an independent component. Furthermore, if the extension portion is formed to warp toward the circuit board  8  instead of forming the extension portion to be flat, the overhang of the FPC board can be reduced more significantly.