Patent Publication Number: US-6983473-B2

Title: Optical pickup device and recording and/or reproducing device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of and claims priority under 35 U.S.C. § 120 to U.S. application Ser. No. 10/088,506, filed Aug. 6, 2002 now U.S. Pat. No. 6,880,163, which is the national stage of PCT/JP01/06606, filed Jul. 31, 2001 and is also based upon and claims priority under 35 U.S.C. § 119 from Japanese Patent Application No. P2000-232466, filed Jul. 31, 2000, the entire contents of which are incorporated herein by reference. 

   TECHNICAL FIELD 
   This invention relates to an optical pickup device for recording and/or reproducing information to and/or from a disc-shaped recording medium such as an optical disc or a magneto-optical disc, and a recording and/or reproducing device having this optical pickup device. 
   BACKGROUND ART 
   An optical pickup device which reproduces information from an optical disc such as a CD (compact disc) as an optical disc is known. The optical pickup device of this type has an optical pickup  111  for reproducing information from an optical disc, a moving mechanism  112  for moving the optical pickup  111  in the radial direction of the optical disc, and a chassis  113  for movably supporting the optical pickup  111  and also supporting the moving mechanism  112 , as shown in  FIG. 1 . 
   The optical pickup  111  is provided movably in the directions of arrows b 1  and b 2  in  FIG. 1 , in an aperture  116  for movement provided in the chassis  113 , as shown in  FIG. 1 . The optical pickup  111  has an optical system (not shown) having an objective lens  118 , a driving portion (not shown) for driving and displacing the objective lens  118  in the direction of the optical axis of the objective lens  118  and in the direction orthogonal to the optical axis, and a cover member  120  for covering the driving portion. 
   The optical pickup  111  has a light source such as a laser diode for emitting a laser beam, a group of lenses constituting the optical system, and a light receiving section for receiving a reflected light from the optical disc, though not shown in the drawing. The driving section provided in the optical pickup  111  has a lens holder for holding the objective lens  118 , a supporting mechanism for supporting the lens holder displaceably in the direction of the optical axis of the objective lens  118  and in the direction orthogonal to the optical axis, and an electromagnetic circuit section for driving the lens holder by an electromagnetic force. The cover member  120  is made of, for example, a resin material formed in a substantially box-like shape, and has a substantially elliptic aperture  121  provided therein for exposing the objective lens  118  to the optical disc, as shown in  FIG. 1 . 
   The moving mechanism  112  has a supporting base  123  for supporting the optical pickup  111 , a supporting shaft  124  for supporting the supporting base  123  movably in the radial direction of the optical disc, a guide portion  125  for movably guiding the supporting base  123 , a slide member  126  for moving the supporting base  123 , a compression coil spring  127  for energizing the slide member  126  in the axial direction of the supporting shaft  124  with respect to the supporting base  123 , a driving gear  128  for driving the slide member  126 , and a driving motor (not shown) for rotationally driving the driving gear  128 , as shown in  FIG. 1 . 
   The optical pickup  111  is arranged on the major surface of the supporting base  123 , and the supporting base  123  has bearing portions  131 ,  131  through which the supporting shaft  124  is movably inserted and a guide recess portion  132  which is movably engaged with the guide portion  125 , as shown in  FIGS. 1 and 2 . At one end of the supporting base  123 , a rack portion  133  which is meshed and moved with the driving gear  128  is integrally formed. 
   This rack portion  133  is formed parallel to the axial direction of the supporting shaft  124 , as shown in  FIG. 1 . The rack portion  133  has engagement pawls  135 ,  135  which are engaged with the slide member  126 , and a retaining piece  136  for retaining one end of the compression coil spring  127 . 
   As shown in  FIG. 1 , the axial direction of the supporting shaft  124  is arranged parallel to the radial direction of the optical disc, across the aperture  116  for movement of the chassis  113 , and both ends of the supporting shaft  124  are fixed on the chassis  113  by fixing portions, not shown. 
   The guide portion  125  is linearly formed by using a resin material and is formed parallel to the axial direction of the supporting shaft  124  along one lateral edge of the aperture  116  for movement of the chassis  113 , as shown in  FIG. 1 . With this guide portion  125 , the guide recess portion  132  of the supporting base  123  is movably engaged, as shown in  FIG. 2 . 
   The slide member  126  has a rack portion  138  formed parallel to the axial direction of the supporting shaft  124 , and this rack portion  138  is shifted by approximately a half cog thickness from he rack portion  133  of the supporting case  123 , as shown in  FIG. 3 . In the slide member  126 , engagement holes  140 ,  140  are formed which are engaged with the engagement pawls  135 ,  135  of the rack portion  133  of the supporting base  123 , as shown in  FIG. 1 . Moreover, an aperture  141  in which the compression coil spring  127  is arranged is provided substantially at the center of the major surface of the slide member  126 , and a retaining piece  142  for retaining the other end of the compression coil spring  127  is formed at one end of the aperture  141 . 
   As shown in  FIG. 1 , one end of the compression coil spring  127  is retained by the retaining piece  136  of the rack portion  133  of the supporting base  123 , and the other end of the compression coil spring  127  is retained by the retaining piece  142  of the slide member  126 . Therefore, the compression coil spring  127  energizes, by its elastic force, the slide member  126  in the direction of an arrow b 3  parallel to the axial direction of the supporting shaft  124  with respect to the rack portion  133  of the supporting base  123 . 
   In the optical pickup device, in order to prevent attachment of dust and particles to the facing surface of objective lens  118  of the optical pickup  111  which faces the optical disc due to an air current within the device in the reproduction standby state or the like, an opening/closing mechanism  145  is provided which has an opening/closing member  146  provided movably between a closing position for covering the facing surface of the objective lens  118  and an opening position for opening and exposing the facing surface of the objective lens  118  to the optical disc, as shown in  FIG. 1 . 
   The opening/closing mechanism  145  has the opening member  146  for opening/closing the facing surface of the objective lens  118 , a rotary shaft  147  for rotatably supporting the opening/closing member  146 , and a tension coil spring  148  for energizing the opening/closing member  146  to the closing position, as shown in  FIGS. 1 and 4 . 
   As shown in  FIG. 1 , the opening/closing member  146  has an opening/closing portion  151  for opening/closing the aperture  121  of the cover member  120  of the optical pickup  111 , a bearing portion  152  for rotatably supporting the rotary shaft  147 , a guide portion  153  slidably engaged with the cover member  120  for guiding the opening/closing portion  151 , and an operating portion  154  for rotating the opening/closing portion  151  in the directions of arrows c 1  and c 2  in  FIG. 1 . 
   The opening/closing portion  151  is formed in a substantially flat plate-like shape and slides on the upper surface of the cover member  120 , thus opening/closing the aperture  121  of the cover member  120 . The bearing portion  152  is integrally formed at one end of the opening/closing portion  151  and has a shaft hole in which the rotary shaft  147  is rotatably inserted. The guide portion  153  is formed to have a cross section of a substantially U-shape fallen sideways, and is slidably engaged with a substantially arc-shaped guide piece  155  which is integrally formed to protrude on the outer circumferential portion of the cover member  120 . The operating portion  154  is formed at a position where it is exposed to an operating protrusion  156  provided on the chassis  113 , on the outer circumferential portion of the bearing portion  152 , as shown in  FIG. 1 . When the optical pickup  111  is moved to the innermost part of the recording area of the optical disc, the operating portion  154  is abutted against the operating protrusion  156  and rotates the bearing portion  152  in the direction of rotation of the rotary shaft  147 . 
   The rotary shaft  147  is provided upright on the supporting base  123  and is rotatably inserted in the shaft hole of the bearing portion  152  of the opening/closing member  146 . The tension coil spring  148  has its one end retained by a retaining piece  158  provided on the supporting base  123  and has its other end retained by a retaining piece  159  situated near the bearing portion  152  of the opening/closing member  146 , as shown in  FIG. 1 . The tension coil spring  148  energizes the rack portion  133  of the supporting base  123  and the rack portion  138  of the slide member  126  in the direction for offsetting the backlash with respect to the driving gear  128 , and is precisely moved to the supporting base  123  and the slide member  126  by the driving gear  128 . That is, in the optical pickup device, since the rack portion  133  of the supporting base  123  and the rack portion  138  of the slide member  126  are energized by the compression coil spring  127  and thus meshed with the driving gear  128 , the optical pickup  111  can be moved with high precision. 
   On the chassis  113 , a disc rotational driving mechanism for rotationally driving the optical disc is provided. The disc rotational driving mechanism has a disc table  160  on which the optical disc is set, and a spindle motor (not shown) for rotationally driving the disc table  160 , as shown in  FIG. 4 . 
   In the optical pickup device constituted as described above, when reproducing information from the optical disc, the supporting base  123  is moved along the supporting shaft  124  and the guide portion  125  by the moving mechanism  112 , and the optical pickup  111  is moved in the radial direction of the optical disc. 
   In the optical pickup device, as shown in  FIG. 5 , when the optical pickup  111  is moved in the radial direction of the optical disc to the innermost part of the recording area of the optical disc, the operating portion  154  of the opening/closing member  146  is abutted against the operating portion  156  on the chassis  113  and the optical pickup  111  is moved further by a predetermined quantity, thus rotating the opening/closing member  146  in the direction of an arrow c 2  against the energizing force of the tension coil spring  148 . In the optical pickup device, when the optical pickup  111  is moved to the innermost circle of the optical disc, the opening/closing member  146  is rotated to the closing position to close the aperture  121  of the cover member  120 , thus preventing attachment of dust and particles to the facing surface of the objective lens  118 , as shown in  FIG. 5 . 
   In the optical pickup device, when the optical pickup  111  is moved into a TOC (table of contents) area on the inner side of the recording area, the opening/closing member  146  is rotated to the opening position and the facing surface of the objective lens  118  of the optical pickup  111  is exposed to the optical disc, thus enabling reproduction of information from the optical disc. The optical pickup  111  reproduces information from the optical disc while the opening/closing member  146  is situated to the opening position, as shown in  FIG. 4 . 
   Since the opening/closing mechanism  145  for causing the opening/closing member  146  to carry out the opening/closing operation has the rotary shaft  147  and the tension coil spring  148 , the above-described conventional optical pickup device has problems that the manufacturing cost is high, that the assembly work is troublesome, and that assembly failure tends to occur. 
   In the conventional optical pickup device, since the opening/closing member  146  is rotatably provided via the rotary shaft  147 , the lever ratio is related to the quantity of rotation near the bearing portion  152  and the quantity of rotation of the opening/closing portion  151 . 
   In the conventional optical pickup device, since the ratio of the quantity of movement of the optical pickup  111  moved when rotating the opening/closing member  146  to the quantity of rotation of the opening/closing member  146  is large, it is difficult to control the opening/closing operation of the opening/closing member  146  in accordance with the movement of the optical pickup  111  by a control circuit or the like. 
   Therefore, the conventional optical pickup device has a problem that the irregularity of the rotating position of the opening/closing member  146  prevents complete closure of the aperture  121  of the cover member  120 . To restrain the irregularity of the opening/closing operation of the opening/closing member  146 , the opening/closing mechanism  145  must increase the precision of each of its component parts and therefore the manufacturing cost must be increased. 
   In the conventional optical pickup device, the unevenness in the assembly precision or the like of the opening/closing mechanism  145  causes slight unevenness in the slide resistance between the guide portion  153  of the opening/closing member  146  and the guide piece  155  of the cover member  120 . Since the slide resistance is amplified by the lever ratio, the opening/closing member  146  cannot carry out the opening/closing operation. 
   DISCLOSURE OF THE INVENTION 
   Thus, it is an object of the present invention to provide an optical pickup device which enables improvement in the reliability of the opening/closing operation of the opening/closing member for preventing attachment of dust and particles to the objective lens of the optical pickup, realization of simplification of the overall structure and reduction in manufacturing cost, and recording and/or reproducing device having this optical pickup device. 
   A recording and/or reproducing device according to the present invention is a device using an optical disc as a recording medium. The device comprises: an optical pickup having an objective lens and provided to be movable in the radial direction of an optical disc; a first rack portion provided on the optical pickup; a slide member having an opening/closing portion for opening/closing a facing surface of the objective lens to the optical disc, and a second rack portion provided to be slidable on the first rack portion; and a driving mechanism having a driving gear which meshes with the first rack portion and the second rack portion. In this device, when the first and second rack portions are driven by the driving gear and the optical pickup is thus moved to a predetermined position, the meshing state of the first rack portion with the driving gear is canceled and the second rack portion is driven by the driving gear to move the slide member, thereby moving the opening/closing portion from a position for opening the facing surface side of the objective lens to a position for closing the facing surface side. 
   This device further comprises a detecting section for detecting that the optical pickup has reached a predetermined position on the inner circle side of the optical disc. The detecting section is operated by the optical pickup when the optical pickup reaches at least a position in a table-of-contents area of the optical disc. 
   The device according to the present invention further comprises a control section for driving a driving motor for a predetermined time period on the basis of a detection output from the detecting section. As the driving motor is driven for a predetermined time period, the optical pickup is moved further toward the inner circle side of the optical disc. 
   In the recording and/or reproducing device according to the present invention, when the first and second rack portions are driven by the driving gear and the optical pickup is thus moved to a predetermined position, the meshing state of the first rack portion with the driving gear is canceled and the second rack portion is driven by the driving gear to move the slide member, thereby moving the opening/closing portion from a position for opening the facing surface side of the objective lens to a position for closing the facing surface side and causing the opening/closing portion to close the facing surface side in a standby state. 
   An optical pickup device according to the present invention comprises: an optical pickup section having an objective lens and provided to be movable along a guide portion; a first rack portion provided on the optical pickup section; a slide member having an opening/closing portion for opening/closing a facing surface of the objective lens to an optical disc, and a second rack portion provided to be slidable on the first rack portion; and a driving mechanism having a driving gear which meshes with the first rack portion and the second rack portion. In this optical pickup device, when the first and second rack portions are driven by the driving gear and the optical pickup section is thus moved to a predetermined position, the meshing state of the first rack portion with the driving gear is canceled and the second rack portion is driven by the driving gear to move the slide member, thereby moving the opening/closing portion from a position for opening the facing surface side of the objective lens to a position for closing the facing surface side. 
   In this optical pickup device, at least one protrusion is provided on the slide member, and an abutment portion to be abutted against the protrusion is provided on the optical pickup section. As the second rack portion is moved in a direction such that the opening/closing portion opens the facing surface side so as to abut the protrusion against the abutment portion, the first rack portion is meshed with the driving gear. 
   The optical pickup device further comprises an elastic member tensioned between the first rack portion and the second rack portion. 
   The optical pickup section further has a cover which has an aperture formed therein at a position facing the objective lens and which is adapted for at least covering the objective lens. The opening/closing portion moves on the cover between the position for opening the facing surface and the position for closing the facing surface, thus opening/closing the aperture. 
   The optical pickup device further has a guide portion for guiding the movement of the optical pickup section in the radial direction of the optical disc. The guide portion has a supporting shaft for guiding the optical pickup section, a reference portion abutted at least at two positions of an outer circumferential portion of the supporting shaft for positioning the supporting shaft, an engagement portion engaged with the outer circumferential portion of the supporting shaft, and an elastic displacement portion formed integrally with the engagement portion for energizing the engagement portion in the radial direction of the supporting shaft. The elastic displacement portion is bent from a direction substantially parallel to the axial direction of the supporting shaft to a direction substantially orthogonal to the axial direction of the supporting shaft, thereby energizing the engagement portion in the radial direction of the supporting shaft. 
   The other objects and advantages of the present invention will be clarified further from the specific description of the embodiment with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view for explaining a conventional optical pickup device. 
       FIG. 2  is a perspective view for explaining a supporting base provided in the conventional optical pickup device. 
       FIG. 3  is a plan view for explaining a rack portion of the supporting base and a rack portion of a slide member provided in the conventional optical pickup device. 
       FIG. 4  is a plan view for explaining the state in which an opening/closing member of an opening/closing mechanism provided in the conventional optical pickup mechanism is opened. 
       FIG. 5  is a plan view for explaining the state in which the opening/closing member of the opening/closing mechanism is closed. 
       FIG. 6  is a plan view showing essential parts of a disc drive device in which an optical pickup device according to the present invention is provided. 
       FIG. 7  is an exploded perspective view showing an optical pickup device. 
       FIG. 8  is a plan view showing an optical pickup device using a shaft fixing mechanism according to the present invention. 
       FIG. 9  is a perspective view showing the shaft fixing mechanism. 
       FIG. 10  is a side view showing an engagement portion of a fixing piece of the shaft fixing mechanism. 
       FIG. 11  is a side view showing the state in which the engagement portion of the fixing piece is engaged with a supporting shaft. 
       FIG. 12  is a perspective view for explaining an optical pickup device. 
       FIG. 13  is a plan view for explaining a rack portion of a supporting base and a rack portion of a slide member provided in the optical pickup device. 
       FIG. 14  is a plan view for explaining one cog of the rack portion of the supporting base. 
       FIG. 15  is schematic view for explaining the state in which an opening/closing plate of the optical pickup device is moved to a closing position. 
       FIG. 16  is a schematic view for explaining the state in which the opening/closing plate is moved to an opening position. 
       FIG. 17  is a schematic view for explaining the state in which an objective lens of the optical pickup device is moved to a TOC area of an optical disc. 
       FIG. 18  is a schematic view for explaining the state in which the objective lens of the optical pickup device is moved to a recording area of the optical disc. 
       FIG. 19  is a flowchart for explaining the outline of the opening/closing operation of the opening/closing plate. 
       FIG. 20  is a view for explaining the operation timing of a detection switch provided in the optical pickup device. 
       FIG. 21  is a view for explaining the relation between the opening/closing operation of the opening/closing plate and the position of the optical pickup. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   An optical pickup device to which the present invention is applied and a disc drive device using this optical pickup device will now be described with reference to the drawings. 
   The disc drive device using the optical pickup device according to the present invention has an optical pickup device  1  for recording or reproducing information to or from an optical disc, and a disc driving mechanism  2  for rotationally driving an optical disc, as shown in  FIG. 6 . 
   An optical disc loaded on the disc drive device according to the present invention may be exemplified by a CD (compact disc) on which information is recorded. On the inner circle side and the outer circle side of the recording area of the optical disc in which information is recorded, a lead-in area and a lead-out area are provided, respectively. In the lead-in area, a TOC (table of contents) area is provided in which, for example, the index and physical address of the recorded information are recorded. 
   The optical pickup device  1  according to the present invention has an optical pickup section  11  having an objective lens  14 , a moving mechanism  12  for moving the optical pickup section  11  in the directions of arrows a 1  and a 2  parallel to the radial direction of the optical disc, and a chassis  13  for movably supporting the optical pickup section  11  and also supporting the moving mechanism  12 , as shown in  FIG. 6 . 
   The optical pickup section  11  is movably provided in an aperture  16  for movement provided in the chassis  13 , as shown in  FIGS. 6 and 7 . The optical pickup section  11  has an optical system having the objective lens  14 , an electromagnetic driving section (not shown) for driving and displacing the objective lens  14  in the focusing direction parallel to the optical axis of the objective lens and in the tracking direction orthogonal to the optical axis, and a cover member  18  for covering the electromagnetic driving section. 
   The electromagnetic driving section has a lens holder for holding the objective lens  14 , a supporting mechanism for supporting the lens holder displaceably in the focusing direction and the tracking direction, and an electromagnetic circuit section for driving and displacing the objective lens  14  by an electromagnetic force, though not shown. 
   In the optical pickup section  11 , the optical system has a laser diode as a light source for emitting a laser beam, a group of lenses constituting the optical system, and a light receiving section for receiving a reflected light from the optical disc, though not shown. The laser beam emitted from the laser diode is converged by the objective lens  14  and thus cast onto the recording layer of the optical disc. The laser beam is reflected by the recording layer of the optical disc, becomes incident on the optical pickup section  11  via the objective lens  14 , and is received by the light receiving section. 
   The cover member  18  is made of, for example, an ABS resin or the like, and is formed in a substantially box-like shape having an upper surface substantially parallel to the recording surface of the optical disc. As shown in  FIGS. 6 and 7 , an aperture  20  for exposing the objective lens  14  to the recording surface of the optical disc is provided substantially at the center of the upper surface of the cover member  18 . This aperture  20  is formed in a substantially elliptic shape having a longer side in the radial direction of the optical disc. 
   The moving mechanism  12  has a supporting base  21  for supporting the optical pickup device, a supporting shaft  22  for supporting the supporting base  21  movably in the radial direction of the optical disc, a guide portion  23  for movably guiding the supporting base  21 , a slide member  24  for moving the supporting base  21 , a tension coil spring  25  for energizing the slide member  24  in the axial direction of the supporting shaft  22  with respect to the supporting base  21 , a driving gear  26  for driving the slide member  24 , a group of gears (not shown) for rotationally driving the driving gear  26 , and a driving motor  28  for rotationally driving the driving gear  26  via the group of gears, as shown in  FIG. 7 . 
   The optical pickup device I according to the present invention has a shaft fixing mechanism  80  for positioning the supporting shaft  22  to the chassis  13 . 
   The shaft fixing mechanism  80  is provided on both ends of the supporting shaft  22 , and includes the supporting shaft  22 , the chassis  13 , a positioning piece  81  for positioning the supporting shaft  22  to the chassis  13 , and a fixing piece  82  for fixing the supporting shaft  22  to the chassis  13 , as shown in  FIGS. 8 and 9 . The supporting shaft  22  and the chassis  13  are made of a metal material. 
   The positioning piece  81  is formed integrally with the chassis  13  by cutting and raising a part of the chassis  13  to be substantially orthogonal to the major surface of the chassis, as shown in  FIG. 9 . The fixing piece  82  has an engagement portion  85  engaged with an outer circumferential portion of the supporting shaft  22 , an elastic displacement portion  86  for energizing the engagement portion  85  to press in the radial direction of the supporting shaft  22 , and a proximal end portion  87  integrally formed with the chassis  13 . 
   The engagement portion  85  is formed with a size which allows easy bending with respect to the proximal end portion  87 . The elastic displacement portion  86  is formed with a narrower width than those of the engagement portion  85  and the proximal end portion  87 , thus securing predetermined elasticity, as shown in  FIG. 9 . 
   On the major surface of the chassis  13 , regulating protrusions  89 ,  89  which are abutted against both ends of the supporting shaft  22  so as to regulate the displacement of the supporting shaft  22  in the axial direction are integrally provided at both ends of the supporting shaft  22 , as shown in  FIG. 8 . 
   In the fixing piece  82 , as the elastic displacement portion  86  is bent in advance by pressing, the engagement portion  85  is made orthogonal to the proximal end portion  87  and is thus made substantially parallel to the axial direction of the supporting shaft  22 , as shown in  FIGS. 8 and 9 . When the engagement portion  85  is made substantially parallel to the proximal end portion  87  by bending the elastic displacement portion  86  and is thus made substantially orthogonal to the axial direction of the supporting shaft  22 , a slope  88  is engaged with the outer circumferential portion of the supporting shaft  22 , as shown in  FIG. 11 . 
   A shaft fixing method for positioning and fixing the supporting shaft  22  to the chassis  13  by using the shaft fixing mechanism  80  constituted as described above will now be described with reference to the drawings. 
   The supporting shaft  22  has its outer circumferential portion abutted against a reference surface  83  of the positioning piece  81  and a reference surface  84  of the chassis  13 , and is thus positioned with respect to the chassis  13 . 
   The engagement portion  85  of the fixing piece  82 , bent in the direction substantially orthogonal to the proximal end portion  87 , rides over the outer circumferential portion of the supporting shaft  22 , and the slope  88  of the engagement portion  85  slides on the outer circumferential portion of the supporting shaft  22 . Thus, the engagement portion  85  is made substantially parallel to the proximal end portion  87  and the elastic displacement portion  86  is partly bent to make the engagement portion  85  substantially orthogonal to the axial direction of the supporting shaft  22 . 
   When the engagement portion  85  of the fixing piece  82  is bent to be substantially orthogonal to the axial direction of the supporting shaft  22 , the engagement portion  85  is engaged with the outer circumferential portion of the supporting shaft  22  and the engagement portion  85  is energized to be pressed in the radial direction of the supporting shaft  22  by the elastic force of the elastic displacement portion  86 . 
   Specifically, as shown in  FIG. 10 , since the engagement portion  85  has an area S which overlaps the cross section of the supporting shaft  22  when the engagement portion  85  is substantially parallel to the proximal end portion  87 , the elastic displacement portion  86  is elastically displaced with respect to the outer circumferential portion of the supporting shaft  22  in accordance with the area S. Therefore, the engagement portion  85  presses and securely fixes the supporting shaft  22  by a predetermined pressing force in the radial direction of the supporting shaft  22  due to the elastic force of the elastic displacement portion  86  which is elastically displaced. 
   In the shaft fixing mechanism  80  as described above, since the engagement portion  85  of the fixing piece  82  is formed integrally with the chassis  13 , no looseness due to any vibration or shock is generated in the engagement portion  85  for fixing the supporting shaft  22  and the supporting shaft  22  can be securely fixed. 
   In the shaft fixing mechanism  80 , since the fixing piece  82  is formed integrally with the chassis  13 , the number of components and the manufacturing cost can be reduced. 
   The supporting base  21  has the optical pickup section  11  arranged on its major surface, and has a bearing portion  31  in which the supporting shaft  22  is movably inserted, and a pair of guide pieces  32 ,  32  movably engaged with the guide portion  23 , as shown in  FIG. 12 . At one lateral edge of the supporting base  21 , a rack portion  33  is integrally formed which is meshed with and moved by the driving gear  26 , as shown in  FIG. 7 . 
   The rack portion  33  is formed parallel to the axial direction of the supporting shaft  22 , as shown in  FIG. 7 . On the rack portion  33 , engagement pawls  35 ,  36  movably engaged with the slide member  24  and a retaining piece  37  for retaining one end of the tension coil spring  25  are integrally formed. In the rack portion  33 , a cog  38  at the terminal end on the outer circumferential side of the optical disc is formed in a substantially triangular shape with a half thickness of the other cogs  39 , as shown in  FIGS. 13 and 14 , and therefore is easily detached from the driving gear  26  to cancel the meshing state of the rack portion  31  with the supporting base  21 . 
   On the supporting base  21 , at a position corresponding to the inner circle side of the optical disc, a inner-side stopper piece  41  for regulating the movement of the supporting base  21  in the direction of the arrow a 1  is integrally formed to protrude parallel to the direction of the movement of the supporting base  21 , as shown in  FIG. 12 . On the chassis  13 , at one lateral edge on the inner circle side of the aperture  16  for movement, a regulating recess portion  42  is cut out and formed to which the inner-side stopper piece  41  of the supporting base  21  is abutted. 
   On the supporting base  21 , at a position corresponding to the outer circle side of the optical disc, an outer-side stopper piece  43  for regulating the movement of the supporting base  21  in the direction of the arrow a 2  is integrally formed to protrude parallel to the direction of the movement of the supporting base  21 , as shown in  FIG. 12 . On chassis  13 , at one lateral edge on the outer circle side of the aperture  16  for movement, a regulating recess portion  44  is cut out and formed to which the outer-side stopper piece  43  of the supporting base  21  is abutted. 
   As shown in  FIGS. 6 and 7 , the supporting shaft  22  has its both ends fixed on the chassis  13  by fixing portions (not shown), with its axial direction arranged parallel to the radial direction of the optical disc over the movement aperture  16  of the chassis  13 . 
   The guide portion  23  is formed parallel to the axial direction of the supporting shaft  22  along one lateral edge of the movement aperture  16  of the chassis  13 , as shown in  FIGS. 7 and 12 . The guide pieces  32 ,  32  of the supporting base  21  stand face to face from above and below the guide portion  23  and the supporting base  21  movably engaged with guide portion  23 , thus regulating the movement of the supporting base  21  in the direction of axial rotation of the supporting shaft  22 . 
   The slide member  24  has a rack portion  46  formed parallel to the axial direction of the supporting shaft  22 , as shown in  FIG. 7 . The slide member  24  is mounted on the supporting base  21  so that the rack portion  46  is coincident with the rack portion  33  of the supporting base  21 . On the slide member  24 , engagement grooves  48 ,  49  are formed which are engaged with the engagement pawls  35 ,  36  of the rack portion  33  of the supporting base  21  in such a manner as to enable movement parallel to the axial direction of the supporting shaft  22 . 
   On the slide member  24 , regulating pins  50 ,  50  for regulating the relative position to the rack portion  33  are integrally formed to protrude, as shown in  FIGS. 7 and 13 . As the regulating pins  50 ,  50  are abutted against the one engagement pawl  36  of the engagement pawls  35 ,  36  provided on the rack portion  33  of the supporting base  21 , the relative position of the slide member  24  to the rack portion  33  is regulated. 
   On the slide member  24 , a guide piece  52  movably engaged with the driving gear  26  is integrally formed to protrude along the rack portion  46 . On the slide member  24 , a retaining piece  53  for retaining the tension coil spring  25  is integrally formed. 
   The tension coil spring  25  has its one end retained by the retaining piece  37  of the rack portion  33  of the supporting base  21 , and has its other end retained by the retaining piece  53  of the slide member  24 , as shown in  FIG. 7 . Therefore, the tension coil spring  25  energizes, by its elastic force, the slide member  24  in the direction of the arrow a 2  parallel to the axial direction of the supporting shaft  22  with respect to the rack portion  33  of the supporting base  21 . 
   The driving gear  26  has a gear portion  55  meshed with the rack portion  33  of the supporting base  21  and the rack portion  46  of the slide member  24 , as shown in  FIG. 7 . At the distal end of the driving gear  26 , a guide groove  56  is formed with which the guide piece  52  of the slide member  24  is movably engaged, as shown in  FIG. 7 . The driving gear  26 , and the group of gears, not shown, are provided on the chassis  13  so as to be rotatable via the supporting shaft  22 . The driving motor  28  is provided on the chassis  13 . The driving force from the driving motor  28  is transferred to the driving gear  26  via the group of gears, not shown. 
   The moving mechanism  12  has an opening/closing plate  58  which is enabled to move between a closing position for covering a facing surface, which faces the optical disc, of the objective lens  14  of the optical pickup section  11 , and an opening position for opening the facing surface of the objective lens  14  so as to expose it to the optical disc, as shown in  FIGS. 6 and 7 . 
   The opening/closing plate  58  is formed integrally with the slide member  24  by using a resin material such as POM (polyoxymethylene) or the like, as shown in  FIG. 7 . The opening/closing plate  58  is formed in a substantially rectangular shape having an area large enough to close the aperture  20  of the cover member  18 . The opening/closing plate  58  is formed to protrude from the slide member  24  via a pair of elastic linear connection pieces  59 ,  59 , and is energized toward the upper surface of the cover member  18  by the elastic force of the connection pieces  59 ,  59 , as shown in  FIG. 7 . 
   The moving mechanism  12  has a detection mechanism  60  for detecting that the optical pickup section  11  is moved into the TOC area of the optical disc or the inner circle side of the TOC area, as shown in  FIGS. 7 and 12 . The detection mechanism  60  is constituted by a detection piece  61  provided on the supporting base  21 , and a detection switch  62  operated by the detection piece  61 . 
   The detection piece  61  is formed integrally with the supporting base  21  by projecting a part of the supporting base  21  on the bottom side of the supporting base in the direction substantially orthogonal to the direction of the movement of the optical pickup section  11 . 
   The detection switch  62  is provided on a circuit board, not shown, mounted on the chassis  13 . More precisely, the detection switch  62  is arranged at a position such that it is abutted against the detection piece  61  when the objective lens  14  of the optical pickup section  11  on the circuit board, not shown, is moved substantially to the center in the radial direction of the TOC area of the optical disc. As will be described later, on the circuit board, not shown, there is provided a controller  71  having a timer circuit  72  for moving the optical pickup section  11  for a predetermined time period after the optical pickup section  11  is detected by the detection switch  62  as shown in  FIG. 19 . A driving circuit  73  for the driving motor  28  is also provided on the circuit board. 
   The driving motor  28  is driven for a predetermined time period by the timer circuit  72  of the controller  71 , and thus moves the slide member  24  by a predetermined quantity with respect to the rack portion  33  of the supporting base  21 , thereby moving the opening/closing plate  58  to the closing position for closing the aperture  20  of the cover member  18 . 
   The disc rotational driving mechanism  2  has a disc table  65  on which the optical disc is set, and a spindle motor (not shown) for rotationally driving the disc table  65 , as shown in  FIG. 6 . The spindle motor, not shown, is fixed to the chassis  13  and is drive-controlled by the driving circuit provided on the above-described circuit board, not shown, so that the optical disc rotates at a constant linear velocity. 
   The opening/closing operation of the opening/closing plate  58  accompanied by the movement of the optical pickup section  11 , in the optical pickup device  1  of the disc drive device constituted as described above, will now be described with reference to the drawings. 
   First, in the optical pickup device  1  in the standby state, the optical pickup section  11  is situated on the inner circle side of the TOC area of the optical disc. As shown in  FIG. 15 , the aperture  20  of the cover member  18  is closed by the opening/closing plate  58  and the facing surface of the objective lens  14  to the optical disc is thus covered by the opening/closing plate  58 . Therefore, in the optical pickup device  1  in the standby state, attachment of dust and particles to the facing surface of the objective lens  14  to the optical disc is prevented by the opening/closing plate  58 . In the optical pickup device  1  in this standby state, the meshing state between the rack portion  33  of the supporting base  21  and the driving gear  26  is canceled and the rack portion  46  of the slide member  24  having the opening/closing plate  58  provided thereon is meshed with the driving gear  26 , as shown in  FIG. 15 . Hereinafter, this state is called state S 4 . 
   Next, in the optical pickup device  1 , when reproduction of the optical disc is started, the motor  28  is driven on the basis of a driving signal from the driving circuit section  73  controlled by the controller  71  and the driving gear  26  is thus driven, as shown in  FIG. 16 . The slide member  24  having the rack portion  46  meshed with the driving gear  26  is moved in the direction of the arrow a 2  by the driving gear  26 . As a result, the opening/closing plate  58  is moved in the direction of the arrow a 2  to the opening position for opening the aperture  20  of the cover member  18  and for exposing the facing surface of the objective lens  14  to the optical disc. As shown in  FIG. 16 , in the optical pickup device  1 , as the slide member  24  is moved in the direction of the arrow a 2  by the driving gear  26 , the regulating pins  50 ,  50  of the slide member  24  are abutted against the engagement pawl  36  of the rack portion  33  of the supporting base  21 . Hereinafter, this state is called state S 3 . 
   In the optical pickup device  1 , as the regulating pins  50 ,  50  are abutted against the engagement pawl  36 , the energizing force of the tension coil spring  25  acts on the supporting base  21  and the supporting base  21  is moved in the direction of the arrow a 2 . Therefore, in the optical pickup device  1 , the rack portion  33  of the supporting base  21  is meshed with the driving gear  26 , and the cogs of the rack portion  33  of the supporting base  21  and the cogs of the rack portion  46  of the slide member  24  become coincident with each other and meshed with the driving gear  26 , as shown in  FIG. 17 . In this case, the supporting base  21  is displaced by a small distance d in the direction of the arrow a 2  because of the meshing of the rack portion  33  with the driving gear  26 . Therefore, in the moving mechanism  12 , the engagement pawl  36  is moved away by the small distance d from the regulating pins  50 ,  50 , along with the displacement of the supporting base  21  by the small distance d in the direction of the arrow a 2 , as shown in  FIG. 17 . In the moving mechanism  12 , since the regulating pins  50 ,  50  and the engagement pawl  36  are brought away from each other, the energizing force of the tension coil spring  25  acts to offset the backlash of the rack portion  33  of the supporting base  21  and the rack portion  46  of the slide member  24  with respect to the driving gear  26 , as shown in  FIG. 17 . Hereinafter, this state is called state S 2 . 
   In the optical pickup device  1 , as shown in  FIG. 18 , since the backlash is offset by the energizing force of the tension coil spring  25  in the reproducing state in which the optical pickup section  11  is reading out information from the recording area of the optical disc, the moving mechanism  12  can precisely move the optical pickup section  11  in the directions of the arrows a 1  and a 2  and information recorded on the optical disc can be satisfactorily read out by the optical pickup section  11 . Hereinafter, this state is called state S 1 . 
   When the stop of reproduction of the optical disc is set by operating a stop button, not shown, of the drive device, the optical pickup section  11  of the optical pickup device  1  is moved in the direction of the arrow a 1  toward the inner circle side of the optical disc under the control of the controller  71 , as shown in  FIG. 17 . If the optical pickup section  11  is moved into the TOC area of the optical disc or to a position on the inner side than the TOC area, the detection piece  61  of the supporting base  21  is abutted against the detection switch  62 , thus operating the detection switch  62 . The detection switch  62  is set in the ON-state and it is detected that the optical pickup section  11  is moved into the TOC area or to a position on the inner side than the TOC area. 
   When the detection switch  62  is set in the ON-state as shown in  FIG. 17 , a detection signal from the detection switch  62  is supplied to the controller  71 , as shown in  FIG. 19 . This controller  71  controls the driving circuit  73  so that the driving circuit  73  outputs a driving signal for rotationally driving the driving motor  28 , by a predetermined time period timed by the timer circuit  72 . That is, the moving mechanism  12  moves the optical pickup section  11  in the direction of the arrow al by using the driving motor  28 , by a time period preset by the timer circuit  72 , as shown in  FIG. 21 . 
   The detection switch  62  is operated and set in the ON-state by the detection piece  61  of the supporting base  21  when the optical pickup section  11  is situated substantially at the center of the TOC area of the optical disc, as shown in  FIGS. 20 and 21 . 
   As shown in  FIGS. 16 and 21 , when the optical pickup section  11  is moved further in the direction of the arrow a 1  and the optical pickup device  1  is in the state S 3  shown in  FIG. 16 , the inner-side stopper piece  41  of the supporting base  21  is abutted against the regulating recess portion  42  and the movement of the supporting base  21  is regulated, thus stopping the movement of the optical pickup section  11 . As shown in  FIGS. 16 and 19 , in the moving mechanism  12 , since the movement of the supporting base  21  is regulated, the cog  38  of the rack portion  33  of the supporting base  21  is detached from the driving gear  26  and the meshing state of the rack portion  33  with the driving gear  26  is canceled. 
   In the optical pickup device  1 , as shown in  FIGS. 15 and 21 , the driving motor  28  is driven by a predetermined time period preset by the timer circuit  72  after the movement of the supporting base  21  is regulated. As a result, only the slide member  24  is moved in the direction of the arrow a 1  by the driving gear  26  against the elastic force of the tension coil spring  25 . Therefore, in the moving mechanism  12 , as shown in  FIGS. 15 and 21 , the slide member  24  is moved in the direction of the arrow a 1  relatively to the supporting base  21 , and the opening/closing plate  58  provided on the slide member  24  is moved in the direction of the arrow a 1  to the closing position for closing the aperture  20  of the cover member  18  and for covering the facing surface of the objective lens  14  of the optical pickup section  11  to the optical disc. 
   As is described above, in the optical pickup device  1  according to the present invention, since the opening/closing plate  58  is securely situated at the opening position for opening the aperture  20  when the objective lens  14  of the optical pickup section  11  is situated in the TOC area of the optical disc, TOC data recorded in the TOC area of the optical disc can be read out satisfactorily. 
   As is described above, in the optical pickup device  1  provided in the disc drive device, since the opening/closing operation of the opening/closing plate  58  is not affected by the lever ratio as in the conventional opening/closing mechanism, it is possible to precisely control the operation for opening/closing the aperture  20  by the opening/closing plate  58 . Thus, it is possible to improve the reliability of the opening/closing operation and to precisely control the operation. 
   Therefore, with the optical pickup device  1  according to the present invention, since the aperture  20  of the cover member  18  can be securely closed by the opening/closing plate  58 , attachment of dust and particles to the objective lens  14  can be prevented satisfactorily. 
   In the optical pickup device  1  provided in the disc drive device, since the energizing force of the tension coil spring  25  is used for offsetting the backlash and for energizing the opening/closing plate  58  in the opening direction, the rotary shaft  147  and the tension coil spring  148  of the above-described conventional opening/closing mechanism  145  are not necessary. Therefore, the number of components is reduced and the structure is simplified, thus enabling reduction in manufacturing cost. 
   As the structure is simplified, the assembly work for the disc drive device and the optical pickup device can be simplified. Therefore, improvement in workability, reduction in assembly failure and improvement in yield can be realized. 
   Although the above-described disc drive device is constituted to reproduce information from an optical disc, the disc drive device may also be constituted to record information to a write-once type optical disc which enables additional writing of information or a rewritable optical disc to which information can be rewritten. As a matter of course, the disc drive device may also be constituted to record/reproduce information to/from other optical discs such as a magneto-optical disc or the like, by providing a magnetic head mechanism for recording information at a position facing the optical pickup device. 
   INDUSTRIAL APPLICABILITY 
   As is described above, with the optical pickup device according to the present invention and the recording and/or reproducing device using this optical pickup device, it is possible to improve the reliability of the opening/closing operation of the opening/closing member and to securely prevent attachment of dust and particles to the facing surface of the objective lens. Moreover, with the optical pickup device and the recording and/or reproducing device, simplification of the overall structure and reduction in manufacturing cost can be realized.