BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view showing an embodiment of an optical disc drive according to the present invention.
FIG. 2 is a sectional view showing the peripheral configuration of a pickup in the optical disc drive of FIG. 1.
FIGS. 3A, 3B are diagrams schematically showing deformation of a flexible printed-wiring circuit board (FPC board).
FIG. 4 is a diagram showing a relationship between an extension portion and the amount of an overhang of the FPC board.
FIGS. 5A and 5B are diagrams illustrating the deformation of the FPC board during movement of the pickup.
DESCRIPTION OF THE PREFERRED EMBODIMENT
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.
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.
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.
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.
FIGS. 3A, 3B 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.
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.
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′<H/2.
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.
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.
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.
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 R1 and R2 of the fold-back portion in FIGS. 5A and 5B are always maintained in relationships of R1<H/2 and R2<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.
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.
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.
Patent Application
20070283370
