Abstract:
A disk drive including a turntable for holding and rotating a disk, a pickup for reading information carried by a signal and/or recording information carried by a signal to the disk by moving the pickup in a radial direction of the disk that is held and rotated by the turntable, and a feed motor for moving the pickup. A drive gear section, which engages a rack of the pickup, is integrally formed with a rotor of a sled motor. An axis of rotation of the sled motor is disposed parallel to an axis of rotation of the turntable. The disk drive makes it possible to perform seeking operations at a high speed, to reduce errors in movement of the pickup, and to achieve size reduction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a novel disk drive. More specifically, the present invention relates to a technique which allows high-speed seek operations, a reduction in pickup movement errors, and size reduction.  
           [0003]    2. Description of the Related Art  
           [0004]    There have been conventionally used two types of mechanisms for moving a pickup which performs reading of information from and/or recording of information to a disk. They are the rack-and-pinion mechanism in which a rack gear of a pickup is moved forwardly by means of a pinion gear, and the lead screw mechanism in which a nut member of a pickup is moved forwardly by means of a lead screw.  
           [0005]    In the rack-and-pinion mechanism, the rotation of the motor is slowed down and transmitted, through a plurality of reduction gears, to the pinion gear which engages the rack gear of the pickup.  
           [0006]    This, however, causes the seek time of the pickup to be lengthened.  
           [0007]    In addition, in the rack-and-pinion mechanism, a plurality of reduction gears are interposed between the motor and the pinion gear, so that the total backlash between the gears is increased, resulting in a larger error in movement of the pickup with respect to the number of rotations of the motor.  
           [0008]    When an attempt is made to eliminate backlash, which causes errors in the movement of the pickup, between the gears, a mechanism for eliminating the backlash is required, so that more parts are required, the number of manhours required for assembly is increased, costs are increased, and the disk drive becomes larger.  
           [0009]    In the lead screw mechanism, the amount of movement of the motor with respect to the number of rotations of the motor is small, so that, here again, the seek time is lengthened. In addition, the disk drive becomes thicker.  
           [0010]    In a disk drive used for writing information to or reading recorded information from a disk, information is written or read by moving a pickup in a radial direction of the disk. In order to write and read information to and from the disk, it is necessary to accurately irradiate, for example, laser beams, emitted from the pickup, perpendicular to or at a specified angle from an information recording surface of the disk.  
           [0011]    In such a disk drive, in order to allow the pickup to move freely from the inner periphery to the outer periphery of the disk, the pickup is guided using two guide shafts, and is moved as a result of transmitting driving power of a motor, or the like, to the pickup.  
           [0012]    In conventional disk drives, the two guide shafts, used for guiding the pickup, as well as the spindle motor, used for rotating the turntable that holds and allows rotation of the disk, are mounted to the chassis.  
           [0013]    For this reason, the degree of parallelism between the two guide shafts and the mounting portion of the stator base that supports the spindle motor is greatly affected by the degree of flatness and the dimensional precision of the chassis. When the degree of flatness or the dimensional precision of the chassis is reduced, the degree of parallelism between the guide shafts and the stator base is also reduced, causing, for example, laser beams from the pickup to strike the information recording surface of the disk obliquely rather than vertically (angle from the vertical will hereinafter be referred to as “skew angle”). When the skew angle becomes large, the performance of the disk drive is greatly reduced.  
           [0014]    In order to maintain the performance capabilities of the disk drive, it is necessary to keep the skew angle close to zero by making the chassis as flat as possible and its dimensions as precise as possible. Therefore, it becomes difficult to produce the chassis, chassis yield and thus disk drive yield are reduced, thus making it difficult to produce disk drives in large quantities, and increasing costs.  
         SUMMARY OF THE INVENTION  
         [0015]    Accordingly, it is an object of the present invention to make it possible to perform high-speed seeking operation, to reduce the amount of error in the movement of the pickup, and to achieve size reduction.  
           [0016]    It is another object of the present invention to make it possible to easily perform skew angle adjustment.  
           [0017]    To this end, according to the present invention, there is provided a disk drive in which a drive gear section which engages a rack of a pickup is formed integrally with a rotor of a sled motor, and a rotary shaft of the sled motor is provided parallel to a rotary shaft of a turntable that holds and rotates a disk that serves as a recording medium.  
           [0018]    Accordingly, in the disk drive of the present invention, the rotation of the sled motor is transmitted directly to the rack of the pickup.  
           [0019]    In addition, according to the present invention, there is provided a disk drive comprising a pickup for reading information carried by a signal from and/or recording information carried by a signal to a disk by moving the pickup in a radial direction of the disk that is held and rotated by a turntable; and two guide shafts for allowing the pickup to be guided; wherein one end of at least one of the two guide shafts is fixed and the other end serves as an adjustment end, with the position of the other end being adjustable in a direction which allows the other end to come into contact with and separate from the disk.  
           [0020]    Therefore, the disk drive of the present invention allows adjustment of the orientation of the pickup with respect to an information recording surface of the disk after manufacture, that is allows the disk drive of the present invention to perform skew adjustment.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a perspective view of an embodiment of an entire disk drive in accordance with the present invention, with the tray being in a housed state.  
         [0022]    [0022]FIG. 2 is a perspective view of the entire disk drive, with the tray being in a drawn-out state.  
         [0023]    [0023]FIG. 3 is an exploded perspective view of the entire disk drive.  
         [0024]    [0024]FIG. 4 is a perspective view of the left guide member.  
         [0025]    [0025]FIG. 5 is a perspective view of the left rail member.  
         [0026]    [0026]FIG. 6 is a perspective view of the left guide member and the left rail member combined together, when the tray is in the housed state.  
         [0027]    [0027]FIG. 7 is a perspective view of the left guide member and the left rail member combined together, when the tray is in the drawn-out state.  
         [0028]    [0028]FIG. 8 is a plan view of a drawer.  
         [0029]    [0029]FIG. 9 is a bottom view of the drawer.  
         [0030]    [0030]FIG. 10 is a perspective view of a lock mechanism and the members related thereto.  
         [0031]    [0031]FIG. 11 is an exploded perspective view of the lock mechanism and the members related thereto.  
         [0032]    [0032]FIG. 12 is a side view of the lock mechanism.  
         [0033]    [0033]FIG. 13 is a sectional view taken along line XIII-XIII of FIG. 12.  
         [0034]    [0034]FIG. 14 is a sectional view taken along line XIV-XIV of FIG. 12.  
         [0035]    [0035]FIG. 15 is a sectional view taken along line XV-XV of FIG. 12.  
         [0036]    [0036]FIG. 16 is a plan view of a base unit.  
         [0037]    [0037]FIG. 17 is a bottom view of the base unit.  
         [0038]    [0038]FIG. 18 is a sectional view taken along line XVIII-XVIII of FIG. 16.  
         [0039]    [0039]FIG. 19 is a perspective view of a guide shaft assembly.  
         [0040]    [0040]FIG. 20 is a sectional view taken along line XX-XX of FIG. 16.  
         [0041]    [0041]FIG. 21 is a perspective view of a movable base and a rack member.  
         [0042]    [0042]FIG. 22 is an exploded perspective view of the movable base and the rack member.  
         [0043]    [0043]FIG. 23 is a sectional view taken along line XXIII-XXIII of FIG. 16.  
         [0044]    [0044]FIG. 24 is a sectional view taken along line XXIV-XXIV of FIG. 16.  
         [0045]    [0045]FIG. 25, which along with FIGS. 26 and 27 is a plan view of the main portion of an optical pickup and a sled motor for illustrating the operations thereof, shows the optical pickup being positioned at the innermost periphery of an information recording area of a CD-ROM.  
         [0046]    [0046]FIG. 26 is a plan view showing the optical pickup being positioned at the outermost periphery of the information recording area of the CD-ROM.  
         [0047]    [0047]FIG. 27 is a plan view showing the optical pickup being positioned outside the outermost periphery of the information recording area of the CD-ROM.  
         [0048]    [0048]FIG. 28, which shows a second embodiment of a pickup guiding mechanism in a disk drive, is a plan view of a base unit.  
         [0049]    [0049]FIG. 29 is a sectional view taken along line XXIX-XXIX of FIG. 28.  
         [0050]    [0050]FIG. 30 is an enlarged sectional view of the main portion of a modification of the sub-guide shaft.  
         [0051]    [0051]FIG. 31 is an enlarged sectional view of the main portion of another modification of the sub-guide shaft.  
         [0052]    [0052]FIG. 32 is an enlarged sectional view of the main portion of still another modification of the sub-guide shaft.  
         [0053]    [0053]FIG. 33, which along with FIG. 34 shows a third embodiment of the disk drive in accordance with the present invention, is a plan view showing the optical pickup being positioned at the outermost periphery of the information recording area of the CD-ROM.  
         [0054]    [0054]FIG. 34 is a plan view showing the optical pickup being positioned outwardly of the outermost periphery of the information recording area of the CD-ROM.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0055]    A description will now be given of embodiments of a disk drive of the present invention, with reference to the attached drawings. It is to be noted that in the embodiments of the present invention a CD-ROM drive, which is mounted to a notebook personal computer, is taken as an example.  
         [0056]    As shown in FIGS.  1  to  3 , the CD-ROM drive  100  includes an outside housing  200  which is flat in the vertical direction and has an opening formed throughout the entire surface.  
         [0057]    The outside housing  200  includes a bottom chassis  210  and a cover member  200  affixed to the top surface of the bottom chassis  210 . The bottom chassis  210  is made of a sheet metal, and a protruding section  212  is integrally formed so as to protrude towards the right from a portion of a main face  211  not including the rear end of the right upper edge. The main face  211  has a recess which opens at the top and front sides. (In the specification, in FIG. 1, the left downward direction is defined as the forward direction, the right upward direction as the rearward direction, the left upward direction as the leftward direction, the right downward direction as the rightward direction, the upward direction as the upward direction, and the downward direction as the downward direction.) A right face section  213 , which protrudes slightly upward, is formed at the right end of the protruding section  212 , with the top edge of the right face section  213  and the top edge of a left face section  214  of the main face  211  being positioned at the same height. An engaging protrusion  216 , which protrudes upward, is formed towards the front side of the right edge of the bottom surface  215  of the main face  211 , with a front face  216   a  of the engaging protrusion  216  being an inclined face which inclines downward and towards the front, and a rear face  216   b  being an engaging face (see FIG. 12).  
         [0058]    The aforementioned cover member  220  is made of a sheet metal and formed into a substantially flat shape, and is affixed to the top surface of the bottom chassis  210  so as to cover it, whereby an opening is formed at the front side, so that a main space  230 , for accommodating a drawer section tg be described later, and a disk auxiliary space  231 , which extends towards the right and continuously from the upper end of the right edge of the main space  230 , are formed.  
         [0059]    A guide member  240 L (shown in FIG. 4) and a guide member  240 R are affixed at the left and right sides, respectively, of the main space  230 . The guide members  240 L and  240 R are symmetrically formed of synthetic resin on the left and right sides and are U-shaped in transverse cross section, and are affixed to the bottom chassis  210  so that their open sides face each other. Stoppers  242 , which protrude slightly upward, are formed at about the middle, in the forward-and-backward direction, of an edge of the opening at each of bottom sides  241  of the guide members  240 L and  240 R, respectively. (These guide members  240 L and  240 R are formed symmetrically on the left and right sides, so that only the left guide member  240 L is shown in detail.) In addition, dislodging preventing sections  243 , which protrude slightly upward, are formed towards the front side of the edge of the opening at their corresponding bottom sides  241 .  
         [0060]    A rail member  250 L (shown in FIG. 5) and a rail member  250 R are slidably supported, in the forward-and-backward direction, by the guide members  240 L and  240 R, respectively. The rail members  250 L and  250 R are symmetrically formed on the left and right sides by bending a sheet metal so that they are U-shaped in transverse section. These rail members  250 L and  250 R are slidably supported, in the forward-and-backward direction, by the guide members  240 L and  240 R, respectively, so that their open sides face each other. In other words, the rail member  250 L, as shown in FIGS. 6 and 7, is slidably supported by the guide member  240 L, whereas the rail member  250 R is slidably supported by the guide member  240 R. The stoppers  242  of the guide members  240 L and  240 R as well as the dislodging preventing sections  243  slidably contact an edge of the opening at the bottom sides  251  of the rail members  250 L and  250 R, whereby the rail members  250 L and  250 R are prevented from being dislodged from the guide members  240 L and  240 R, respectively.  
         [0061]    Stoppers  252 , which protrude towards each other, are formed at the rear end of their respective bottom sides  251  of the rail member  250 L (shown in FIG. 5) and the rail member  250 R. (These rail members  250 L and  250 R are symmetrically formed on the left and right sides, so that only the left rail member  250 L is shown in detail.) Engagement of the stoppers  252  with the stoppers  242  of the guide members  240 L and  240 R from behind their respective stoppers  242  prevents further forward movement of the stoppers  252 . In other words, dislodging from the guide members  240 L and  240 R in the forward direction is prevented.  
         [0062]    In addition, dislodging preventing edges  253  of small height, which protrude upward, are formed so as to extend along an edge of the opening at each of the bottom sides  251  of the rail members  250 L and  250 R, from a portion thereof located slightly towards the front from the center to the front end of the rail members  250 L and  250 R, in the forward-and-backward direction.  
         [0063]    The drawer section  300  is supported by the aforementioned outside housing  200  so that it can be housed in and drawn out from the outside housing  200 . The drawer section  300  is formed by making a tray  310 , made of synthetic resin, support a base unit to be described later.  
         [0064]    As shown in FIG. 8, the tray  310  has a planar shape and an external shape which is a long rectangle in the forward-and-backward direction. Its width is slightly smaller than the width of the main space  230  in the outside housing  200 .  
         [0065]    The tray  310  has a main face  311 , which has a planar shape and a long rectangular shape in the forward-and-backward direction, a front wall  312 , which is formed vertically at the front edge of the main face  311 , left and right walls  313  and  314 , which are formed vertically on the left and right edges of the main face  311 , and sliding sections  315 , which are formed outwardly of the left and right walls  313  and  314 . All of these parts are integrally formed of synthetic resin. A recess  316 , whose edge forms part of a circle for placing on the top surface thereof a CD-ROM, is formed in the main face, and an opening  316   a  is formed in the recess  316  to allow the base unit to be described later to face upward.  
         [0066]    The sliding sections  315 , which are square-shaped in transverse section and extend in the forward-and-backward direction, protrude from the outer surface of the left and right walls  313  and  314 , respectively, of the tray  310 . The top edges of the slide sections  315 , respectively, are located at a lower height than the top edges of the side walls  313  and  314  of the tray  310 . In addition, lower edges  315   a  protrude slightly downwardly from the side walls  313  and  314  of the tray  310 . As shown in FIG. 9, stopper protrusions  315   b,  which slightly protrude inwardly, are formed at the rear end of each of the sliding sections  315 . The sliding sections  315  are slidably supported by the rail members  250 L and  250 R. The dislodging preventing edges  253  of the rail members  250 L and  250 R slidably contact the inside side surface of the lower edges  315   a  of the sliding sections  315 , thereby preventing the sliding sections  315  from becoming dislodged from the rail members  250 L and  250 R, in the direction of the openings of their respective rail members  250 L and  250 R. When the tray  310  moves towards the front with respect to the rail members  250 L and  250 R, the stopper protrusions  315   b  of the sliding sections  315  come into contact with the back ends of the dislodging preventing edges  253  of the rail members  250 L and  250 R, thereby preventing further forward movement of the tray  310  with respect to the rail members  250 L and  250 R.  
         [0067]    Accordingly, with the tray  310  supported in such a manner that it can be accommodated in and drawn out from the outside housing  200 , the top side of the recess  316  is positioned at about the same height as the top surface of the protrusion  212  of the outside housing  200 .  
         [0068]    As shown in FIG. 9, an ejector  317 , which is supported so as to be movable in the forward-and-backward direction, is provided at the bottom surface, at the right side of the rear end of the main face  311  of the tray  310 . The ejector  317 , which is formed of a sheet metal, is a long plate extending in the forward-and-backward direction, and an extension coil spring  317   a,  which is stretched tightly between the ejector  317  and the main face  311 , produces a moving force that biases the ejector  317  in such a manner that the rear end thereof stops when it protrudes rearwardly from the rear edge of the main face  311  by a certain amount.  
         [0069]    A front panel  320  is mounted to the front face of the tray  310 . The front panel  320 , made of synthetic resin, is a horizontal long plate, whose length in the horizontal direction is about the same as the length, in the horizontal direction, of the outside housing  200 . The front panel  320  is affixed to the front face of the tray  310 , with its left end substantially aligned with the left end of the tray  310 . An indicator section  321 , for indicating the state of a CD-ROM drive  1 , and an eject button  322  are provided at the front panel  320 . Pressing the eject button  322  causes an eject operation to be described later to be performed. An emergency receiving hole  318  is formed at the right end of the front wall  312  of the tray  310 , and a receiving hole  323  is formed in a location of the front panel  320  corresponding to the location of the emergency receiving hole  318 .  
         [0070]    A lock mechanism  330 , which locks the drawer section  300  to keep it mounted in the outside housing  200 , is provided. A description will now be given of the lock mechanism  330  with reference to FIGS.  10  to  15 .  
         [0071]    A lock arm  331  is disposed at a portion of the lower surface of the main face  311  of the tray  310  located at the right side and towards the front end of the main face  311 . (Refer to FIG. 9.) The lock arm  331  is formed by bending a sheet metal, is substantially a long plate in the forward-and-backward direction, and has an engaging pawl  332  at the back end thereof. The engaging pawl  332  has an inclined edge  332   a  that inclines upward towards the back, and an engaging edge  332   b  that is formed continuously with the front end of the inclined edge  332   a  and extends directly upward therefrom. A push portion  333 , which bends to the right, is formed at a portion of the bottom edge of the lock arm  331  located slightly forwardly of the engaging pawl  332 . A spring contact portion  334 , which protrudes towards the left from the top edge of the front side of the lock arm  331 , is provided, and a protruding emergency pushing portion  335 , which inclines forwardly and downwardly from the front edge of the spring contact portion  334 , is provided. (Refer to FIG. 12.)  
         [0072]    A lock arm mounting plate  336  is affixed to a portion of the bottom surface of the main face  311  of the tray  310  located towards the front end of the right side of the main face  311 . As seen from the front, the lock arm mounting plate  336  looks like an inverted L shape, and the top edge of the front side portion of a supporting section  338 , which extends along the inside surface of the right wall  314 , is formed continuously with the right side edge of a mounting section  337  that is affixed to the lower surface of the main face  311  of the tray  310 . A spring supporting portion  339 , which protrudes towards the left, is formed at a portion of the bottom edge of the supporting section  338  located slightly rearwardly from the front end, and a spring externally fitting section  339   a  is formed so as to protrude upwardly from the left side edge of the spring supporting portion  339 . (Refer to FIGS. 12, 13, and  14 .)  
         [0073]    The portion of the lock arm  331  located slightly forwardly from the center, in the forward-and-backward direction thereof, is rotatably supported at about the center in the forward-and-backward direction of the supporting section  338 , with the spring contact portion  334  thereof being disposed so as to face the spring supporting portion  339  of the lock arm mounting plate  336 . A compressive coil spring  340  is interposed between the spring contact portion  334  and the spring supporting portion  339 , and produces a rotational force that biases the rear end of the lock arm  331  downward. It is to be noted that the compressive coil spring  340  is fitted to the spring externally fitting section  339   a  in order to prevent it from being dislodged therefrom.  
         [0074]    With the drawer section  300  being maximally drawn out from the outside housing  200 , the stoppers  252  of the rail members  250 L and  250 R, respectively, engage the back end of the stoppers  242  of the guide members  240 L and  240 R, and the stopper protrusions  315   b  of the drawer section  300  engage the rear ends of the dislodging preventing edges  253  of the rail members  250 L and  250 R. In this case, the rear end of the tray  310  is drawn out from the outside housing  200  (see FIGS. 2 and 7). The tray  310 , in this state, is said to be at a “drawn-out position.”  
         [0075]    As the drawer section  300 , in the drawn-out state, is pushed into the outside housing  200 , the sliding sections  315  slide backwards with respect to the rail members  250 L and  250 R, and, eventually, the back surface of the front panel  320  comes into contact with the front ends of the rail members  250 L and  250 R. As the drawer section  300  is further pushed into the outside housing  200 , the rail members  250 L and  250 R, along with the drawer section  300 , slide backward with respect to the guide members  240 L and  240 R and stop sliding, whereby the tray  310  is completely housed in the outside housing  200  (see FIGS. 1 and 6). The tray  310 , in this state, is said to be at a housed position.  
         [0076]    Just before the tray  310  reaches the housed position of FIG. 1, the inclined edge  332   a  of the engaging pawl  332  of the lock arm  331  slides along the inclined surface  216   a  of the engaging protrusion  216  of the outside housing  200 , and opposes the resilient force of the compressive coil spring  340 , so that the rear end of the lock arm  331  rotates upward to the location indicated by alternate long and two short dash lines, in FIG. 12, and the engaging pawl  332  moves to the back side of the engaging protrusion  216 . The rear end of the engaging pawl  332  rotates downward as a result of the resilient force of the compressive coil spring  340 , whereby the engaging edge  332   b  engages the engaging face  216   b  of the engaging protrusion  216  (see FIG. 12). This results in a locking operation that keeps the drawer section  300  completely housed in the outside housing  200 .  
         [0077]    A short time before the tray  310  reaches the housed position of FIG. 1, the back end of the ejector  317  shown in FIG. 9 is in contact with a rear face  217  of the bottom chassis  210  of the outside housing  200 . Pushing the drawer section  300  further rearward from the position in FIG. 1 causes the ejector  317  to oppose the tensile force of the extension coil spring  317   a  and to move forwardly relative to the drawer section  300 . This further stretches the extension coil spring  317   a,  so that force accumulates in the extension coil spring  317   a.    
         [0078]    Pressing the eject button  322  on the front panel  320  causes an unlocking mechanism described later to operate. When the unlocking mechanism operates, the back end of the lock arm  331  rotates upward, whereby the engaging pawl  332  and the engaging protrusion  216  of the outside housing  200  disengage from each other. The force, accumulated in the extension coil spring  317   a,  causes the ejector  317  to protrude from the back edge of the drawer section  300 , as a result of which the front edge of the drawer section  300  protrudes from the outside housing  200 . Here, when the front end of the drawer section  300 , which protrudes from the outside housing  200 , is pulled towards the front, the drawer section  300  as well as the rail members  250 L and  250 R slide forwardly with respect to the guide members  240 L and  240 R, respectively, until the stoppers  252  of the rail members  250 L and  250 R engage the stoppers  242  of the guide members  240 L and  240 R. When the stoppers  252  engage the stoppers  242 , the drawer section  300  slides forwardly with respect to the rail members  250 L and  250 R, until the stopper protrusions  315   b  come into contact with the back ends of the dislodging preventing edges  253  of the rail members  250 L and  250 R, and then move to the drawn-out position of FIG. 2.  
         [0079]    When an emergency, caused, for example, by the running down of a power supply, occurs, so that an eject operation is not performed even when the eject button  322  is pressed, a thin rod-like object may be inserted into the tray  310  through the receiving hole  323  in the front panel  320  and the emergency receiving hole  318  in the tray  310 . This causes an end of the rod-like object to push the emergency pushing portion  335  of the lock arm  331 , causing the back end of the lock arm  331  to rotate upward, whereby the engaging pawl  332  and the engaging protrusion  216  of the outside housing  200  disengage from each other. The force, accumulated in the extension coil spring  317   a,  causes the front end of the drawer section  300  to protrude from the outside housing  200 .  
         [0080]    [0080]FIGS. 16 and 17 show the base unit  40  being supported at the bottom surface of the main face  311  of the tray  310  of the drawer section  300 .  
         [0081]    A sub-chassis  410 , made of a sheet metal, is supported at the bottom surface of the tray  310  through rubber dampers  411 .  
         [0082]    The sub-chassis  410  has a large opening  412  that extends over almost the entire sub-chassis  410 . The opening  412  has a substantially rectangular shape which extends from the left front side to the right back side. The opening  412  includes continuously formed openings, that is, a pickup opening  412   a  that is inclined with respect to other portions such that its back edge extends substantially horizontally, a substantially semi-circular turntable opening  412   b  that is formed continuously with the rear edge of the pickup opening  412   a,  and a sled motor opening  412   c  whose shape is more than a semicircle and is formed continuously with the rear end portion of the side edge of the pickup opening  412   a  facing towards the right and forward direction.  
         [0083]    The turntable  420  is placed such that its top end protrudes upwardly of the sub-chassis  410  from the turntable opening  412   b.  In other words, as shown in FIG. 18, a stator base  422 , which supports a spindle motor  421 , is affixed to the bottom surface of the sub-chassis  410 , and the turntable  420  is integrally formed with the rotor of the spindle motor  421 , whereby the turntable  420  is disposed at the aforementioned position.  
         [0084]    An optical pickup  500  is disposed so as to be movable in a direction which allows it to separate from and come into contact with the turntable  420 , in the aforementioned pickup opening  412   a.    
         [0085]    The optical pickup  500  is formed by mounting on a movable base  510  an optical block (not shown) which includes, for example, a semiconductor laser; an objective lens  520  which gathers and concentrates laser beams on a CD-ROM on the turntable; and a biaxial actuator, or the like, which moves the objective lens  520  in a focusing direction and a tracking direction.  
         [0086]    The movable base  510  moves by being guided by a guide shaft  531  and a sub-guide shaft  532 . The guide shaft  531  is shaped like a round bar, and the sub-guide shaft  532  is formed by bending a sheet metal.  
         [0087]    As shown in FIG. 19, the sub-guide shaft  532  is integrally formed with a guide shaft supporting plate  533  which integrally supports the aforementioned two guide shafts  531  and  532 , with the guide shaft support plate  533  and the integrally supported guide shafts  531  and  532  together forming a guide shaft assembly  530 . The guide shaft supporting plate  533 , which is made of a springy metal sheet, is formed into the shape of a plate which is slightly longer than the width of an edge of the pickup opening  412   a,  with a guide shaft supporting section  534  formed at the right end thereof, a sub-guide shaft connecting section  535  formed at the left end thereof, and a mounting portion  536  formed at the center thereof in the horizontal direction of the front edge. Threaded holes  534   a  and  535   a  are formed in the guide shaft supporting section  534  and the sub-guide shaft connecting section  535 , respectively. The sub-guide shaft  532  has a guide section  532   a  formed by bending a side edge of a long plate-like sheet metal into a U shape, and a protruding mounting portion  532   b  formed continuously with the back end of the guide section  532   a.  The front end of the guide section  532   a  is integrally and continuously formed with the sub-guide shaft connecting section  535  of the guide shaft supporting plate  533 .  
         [0088]    The front end of the guide shaft  531  is affixed to the guide shaft supporting section  534  of the guide shaft supporting plate  533 . The guide shaft  531  is affixed to the guide shaft supporting section  534  by any suitable means, such as by bonding or screwing. In this way, the guide shaft  531  and the sub-guide shaft  532  are formed integrally with the guide shaft supporting plate  533 , whereby the guide shaft assembly  530  is formed.  
         [0089]    The mounting portion of the guide shaft supporting plate  533  is affixed, by any suitable means such as by screwing, to the bottom surface of an edge of the sub-chassis  410  in correspondence with the center of the front edge of the pickup opening  412   a.  Adjuster screws  537  and  537 , formed at locations corresponding to the locations of the threaded holes  534   a  and  535   a  in the sub-chassis, are inserted into the screw receiving holes  413  from above the screw receiving holes  413 , and are separately screwed into the threaded holes  534   a  and  535   a.  (Refer to FIG. 20.) Since the guide shaft supporting plate  533  is made of a springy sheet metal, when the adjuster screws  537  are screwed into the threaded holes  534   a  and  535   a,  the guide shaft supporting section  534  and the sub-guide shaft connecting section  535  move closer to the sub-chassis  410 , whereas when the adjuster screws  537  are screwed outward in the threaded holes  534   a  and  535   a,  the guide shaft supporting section  534  and the sub-guide shaft connecting section  535  move away from the sub-chassis  410 .  
         [0090]    The back ends of the guide shaft  531  and the sub-guide shaft  532  are affixed to the stator base  422 . More specifically, the back end of the guide shaft  531  is received by a receiver section  414 , formed into a U shape facing upward and formed on the top surface of the stator base  422 , from above the receiver section  414 , and a head  415   a  of a screw  415 , which has been screwed into a location adjacent to and behind the receiver section  414 , holds down the back end of the guide shaft  531  from above it, whereby the back end of the guide shaft  531  is affixed to the stator base  422  (see FIG. 19). The sub-guide shaft  532  is affixed by screwing the mounting portion  532   b  at the back end of the sub-guide shaft  532  into the stator base  422  (see FIG. 19).  
         [0091]    FIGS.  21  to  23  are views showing the assembled structure of the movable base  510  and a rack member  550  described later. Protruding guide sections  511  are formed at the right end of the movable base  510 , with a connecting section  512 , having a connecting hole  512   a  formed therein, being formed between these guide sections  511 . Guide holes  511   a  are formed coaxially in the guide sections  511 , respectively. (Refer to FIG. 23.) Guide portions  513 , which are spaced in the vertical direction and protrude parallel to each other, are formed at the left end of the movable base  510 .  
         [0092]    The guide shaft  531  is slidably inserted into the guide holes  511   a  in the movable base  510 , and the guide portions  513  of the movable base  510  are in slidably contact with the top and bottom faces of the aforementioned sub-guide shaft  532 , respectively, whereby the optical pickup  500  is supported by the sub-chassis  410  so as to be guidable and movable along the guide shaft  531  and the sub-guide shaft  532 .  
         [0093]    The degree of precision of signal reading by the optical pickup  500  with respect to a CD-ROM depends on the degree of verticalness of the laser beam, gathered and concentrated on the CD-ROM on the turntable  420 , with respect to the CD-ROM, that is on the degree of verticalness of the optical axis of the objective lens  520  with respect to the CD-ROM on the turntable  420 .  
         [0094]    Therefore, it is necessary to make adjustments or perform the so-called skew adjustment in order to make the optical axis of the objective lens  520  perpendicular to the CD-ROM on the turntable  420 .  
         [0095]    The aforementioned skew adjustment is performed with adjuster screws  537  in order to adjust the distance between the guide shaft supporting section  534  and/or the sub-guide shaft connecting section  535  and the sub-chassis  410 , that is the distance between the guide shaft  531  and/or the sub-guide shaft  532  and the sub-chassis  410 .  
         [0096]    As mentioned above, since the turntable  420  is integrally formed with the spindle motor  421  that is affixed to the stator base  422 , the disk-placing plane of the turntable  420  and the spindle motor  421  placing plane of the stator base  422  can be considered as being parallel to each other, so that a line connecting the back end of the guide shaft  531 , affixed to the stator base  422 , and the back end of the sub-guide shaft  532  can be considered as being parallel to the disk-placing plane of the turntable  420 .  
         [0097]    Adjusting the height of the front end of the guide shaft  531  and/or the sub-guide shaft  532  enables skew adjustment of the optical pickup  500  that is supported by the guide shaft  531  and the sub-guide shaft  532 . In other words, separately adjusting the height of the front end of the guide shaft  531  and the sub-guide shaft  532  enables skew adjustment in a tangential direction, and adjusting the height of the guide shaft  531  and the sub-guide shaft  532  at the same time by the same amount enables skew adjustment in a radial direction.  
         [0098]    A description will now be given of the mechanism for moving the optical pickup  500  in a radial direction of a CD-ROM on the turntable  420 .  
         [0099]    A motor-supporting plate  541 , which supports a sled motor  540 , is affixed to the bottom surface of the sub-chassis  410 , and the sled motor  540  is positioned at the sled motor opening  412   c.  A drive gear section  542  is formed at an outer periphery of a rotor  540   a  of the sled motor  540  so as to extend along substantially half the circumference of the sled motor  540 . A release cam section  543  is formed in contact with a side edge of the drive gear section  542  at a counterclockwise direction side, as seen from above the drive gear section  542 , and is substantially trapezoidal, as seen from thereabove. An outer end face  543   a  thereof is located on the same circumference as that of the addendum circle of the drive gear  542 , and the stem of the release cam section  543  is located on the same circumference as that of the deddendum circle of the drive gear section  542  (see FIGS. 10 and 11).  
         [0100]    As shown in FIGS.  21  to  23 , a rack member  550  is connected to the optical pickup  500 .  
         [0101]    The rack member  550  is made of synthetic resin, with rack teeth  551   a  formed, in a longitudinal direction, at one face of a rack section  551  having an elongated plate-like shape. A connecting portion  552  protrudes from a face of the rack section  551  which is opposite to the face of the rack section  551  where the rack teeth  551   a  are formed, with a connecting pin  552   a  being vertically provided at one end of the connecting portion  552 . Inverted L-shaped engaging portions  553  are formed on both sides of the connecting portion  552 , in a plane in which the connecting portion  552  is formed.  
         [0102]    The engaging portions  553 , formed on the rack member  550 , slidably engage the guide shaft  531 , and the connecting pin  552   a,  provided at the connecting portion  552 , engages a connecting hole  512   a  in the movable base  510  of the optical pickup  500 , whereby the movable base  510  and the rack member  550  are integrally moved so as to be guided by the guide shaft  531  and the sub-guide shaft  532 . The rack teeth  551   a  of the rack member  550  engage the drive gear section  542 . Accordingly, driving the sled motor  540  rotates the drive gear section  542 , causing the rack member  550  to move forward. Integrally therewith, the optical pickup  500  is guided by the guide shaft  531  and the sub-guide shaft  532  and moves in a radial direction of a CD-ROM on the turntable  420 .  
         [0103]    A description will now be given of the mechanism for unlocking the drawer section  300  that has been completely housed in the outside housing  200 .  
         [0104]    As shown in FIGS. 11 and 12, an unlocking arm  350 , formed into a substantially arcuate shape using synthetic resin, is provided at the sub-chassis  410 . As seen from above, the unlocking arm  350  has a substantially arcuate shape, with a support section  351  formed at the front end thereof. The support section  351  has a cylindrical shape that extends vertically.  
         [0105]    A push section  352  is formed so as to protrude inwardly from a portion, located slightly towards the support section  351  from the center of the unlocking arm  350 , of the top edge of the unlocking arm  350 . An inclined face  352   a,  which extends towards the back as it protrudes, is formed at the front face of the push section  352 .  
         [0106]    A pushing section  353  is formed at the outer side of the rear end of the unlocking arm  350 , that is, it formed in such a manner as to protrude downwardly from and outwardly of the lower edge, in an opposite direction from the center of the arcuate shape. A pushing face  353   a,  which is displaced downwards as it extends outwards, is formed at the upper face of the pushing section  353 .  
         [0107]    A support shaft  416 , which is vertically formed along an edge of a sled motor opening  412   c  in the sub-chassis  410 , is rotatably fitted into the support section  351  of the unlocking arm  350 , whereby the unlocking arm  350  is rotatably supported by the sub-chassis  410  and the motor supporting plate  541 . It is to be noted that the top edge of the unlocking arm  350  is located in the gap between an edge of the sled motor opening  412   c  of the sub-chassis  410  and the rotor  540   a  in the sled motor; that the push section  352  is located in a cutout  412   d  in the edge of the sled motor opening  412   c;  and that the pushing section  353  is located in a cutout  541   a  in the motor supporting plate  541 . When an end of the unlocking arm  350  is rotated towards the sled motor, the pushing section  353  comes into contact with the back edge of the cutout  541   b,  thereby limiting rotation in that direction, so that the unlocking arm  350  will not come into contact with the rotor  540   a  of the sled motor  540 . The pushing face  353   a  of the unlocking arm  350 , positioned in this manner, has one end disposed so as to come into contact with the push portion  333  of the lock arm  331  from therebelow or to be located in the vicinity of the push portion  333  of the lock arm  331 .  
         [0108]    A description will now be given of an unlocking operation by the above-described unlocking mechanism, with reference to FIGS.  25  to  27 .  
         [0109]    As shown in FIG. 25, when the optical pickup  500  is positioned at the innermost periphery of an information recording area of a CD-ROM  600  on the turntable  420 , the edge of the drive gear section  542  at the clockwise direction side is located near the push section  352  of the unlocking arm  350  at the counterclockwise direction side, whereas, as shown in FIG. 26, when the optical pickup  500  is at the outermost periphery of an information recording area of the CD-ROM  600 , the release cam section  543 , provided at the rotor  540   a  of the sled motor  540 , is located near the push section  352  of the unlocking arm  350 , as viewed from the clockwise direction side. Accordingly, during the time in which the optical pickup  500  is reading a signal from the CD-ROM  600 , movement of the rotor  540   a  of the sled motor  540  in no way affects the unlocking arm  350 .  
         [0110]    Pressing the elect button  322  on the front panel  320  causes the sled motor  540  to further rotate counterclockwise from its position shown in FIG. 26, so that the optical pickup  500  moves outward from the outermost periphery of an information recording area of the CD-ROM  600 . Meanwhile, as shown in FIG. 27, the release cam section  543  pushes the inclined face  352   a  of the push section  352  of the unlocking arm  350 , causing the unlocking arm  350  to be rotated slightly clockwise, as viewed from the top thereof.  
         [0111]    Rotating the unlocking arm  350  clockwise causes the portions that are higher than the pushing face  353   a  to oppose the push portion  333  of the lock arm  331  in order to cause the pushing face  353   a  to push the push portion  333  upward, whereby the back end of the lock arm  331  rotates upward (as indicated by the alternate long and two short dash lines in FIG. 12), as a result of which the engaging pawl  332  and the engaging protrusion  216  of the outside housing  200  disengage from each other. The action of the injector  317  and the extension coil spring  317   a  causes the front end of the drawer section  300  to protrude from the outside housing  200 .  
         [0112]    Immediately after the drawer section  300  protrudes from the outside housing  200  the sled motor  540  rotates clockwise, which causes the optical pickup  500  to move, for example, to a location in correspondence with the innermost periphery of an information recording area of the CD-ROM  600 , that is to a location where TOC of the CD-ROM can be read. This causes the release cam section  543  to move away from the push section  352  of the unlocking arm  350 , so that the resilient force of the compressive coil spring  340  causes the lock arm  331  to move back to its original position, that is the engaging pawl  332  to return back to the position where it can engage the engaging protrusion  216  of the outside housing  200 . The force of movement thereof acts on the pushing face  353   a  of the pushing section  353  through the push portion  333  of the lock arm  331 , causing the unlocking arm  350  to rotate to a location where it can contact the back edge of the cutout  541   b  in the motor supporting plate  541 . When this causes the drawer section  300  to be pushed again into the outside housing  200 , a locking operation is performed to keep the tray  310  completely housed in the main space  230  in the outside housing  200 , that is to lock it in the housed position. Since the horizontal width of the tray  310  is smaller than the diameter of the CD-ROM  600 , the right side of the CD-ROM  600 , placed on the turntable  420 , extends beyond the right side of the tray  310 . Therefore, when the tray  310  is housed in the outside housing  200 , the portion of the CD-ROM  600  extending beyond the right side of the tray  310  is placed within a disk auxiliary space  231  in the outside housing  200 .  
         [0113]    In the above-described CD-ROM drive  100 , the drive gear section  542 , which engages the rack section  551  of the optical pickup  500 , is provided integrally with the rotor  540   a  of the sled motor  540 , so that the rotation of the sled motor  540  is directly transmitted to the drive gear section  542 . The rack section  551  of the optical pickup  500  is moved forward by means of the drive gear section  542 , thereby shortening the seek time of the optical pickup  500  and allowing rapid seek operations.  
         [0114]    In addition, since nothing which causes backlash is provided in the area extending from the sled motor  540  to the drive gear section  542 , error in movement of the optical pickup  500  with respect to the amount of rotation of the sled motor  540  becomes very small, thereby allowing accurate seek operations. Further, a mechanism for eliminating backlash, required in conventional disk drives, does not have to be provided, thereby reducing the number of parts, costs, and disk drive size.  
         [0115]    Still further, according to the foregoing embodiments, when the drive gear section  542  is disposed in correspondence with about the center of the range of movement of the rack section  551  while the optical pickup  500  moves from the inner periphery to the outer periphery of an information recording area of the recording medium disk  600 , it is possible to reduce the length of the rack section  551  to the minimum required.  
         [0116]    Still further, when the direction of movement of the optical pickup  500  is set obliquely to the direction of movement of the drawer section  300 , that is, when the direction of extension of the guide shaft  531  and the sub-guide shaft  532  is set obliquely to the direction of movement of the drawer section  300 , so that the sled motor  540  is disposed in a triangular dead space produced at the sub-chassis  410 , it is possible to reduce the horizontal width of the tray  310 , that is the size of the drawer section  300  in a direction perpendicular to the direction of movement thereof.  
         [0117]    In the foregoing embodiments the drive gear section  542  was formed integrally with the rotor  540   a  of the sled motor  540 . All that is required is that the drive gear section be integrally formed with the rotor, so that, for example, with the rotary shaft of the rotor being formed so as to protrude towards or away from the rotor side, the drive gear section may be press-fitted and affixed to the rotary shaft.  
         [0118]    In the above-described disk drive  100 , skew adjustment of the optical pickup  500  can be performed by adjusting the space between the sub-chassis  410  and the adjustment end of the guide shaft  531  and/or the adjustment end of the sub-guide shaft  532  as a result of rotating the adjuster screw  537  and/or the adjuster screw  537 . Therefore, even if the sub-chassis  410  is not that flat or that precise as to dimension, the laser beams from the optical pickup  500  can be kept vertical with respect to the information recording surface of the CD-ROM  600  that it is irradiating. This results in increased yield of the sub-chassis  410 , making it possible to reduce costs and produce a greater number of disk drives.  
         [0119]    In the above-described embodiment, although the adjustment ends of the guide shaft  531  and the sub-guide shaft  532  were supported at the sub-chassis  410  through the guide shaft supporting plate  533 , they may be supported directly by the sub-chassis  410  in such a manner that the space therebetween is adjustable, without the use of guide shaft supporting plate  533 .  
         [0120]    In addition, in the above-described embodiment, although the locations of the adjustment ends of both the guide shaft  531  and the sub-guide shaft  532  were adjustable, in other embodiments either one of them may be made adjustable.  
         [0121]    [0121]FIGS. 28 and 29 are views showing a second embodiment of the present invention. The second embodiment primarily differs from the first embodiment in the form of the sub-guide shaft. The other parts are almost the same as those of the first embodiment. Therefore, only the aforementioned dissimilar part will be described in detail. Other parts corresponding to those of FIG. 1 are given the same reference numerals, and will not be described below.  
         [0122]    A guide shaft  710 , which is made of a metal and is cylindrical in shape, is disposed along one of the side edges of an opening  412  of the sub-chassis  410 , with both ends of the guide shaft  710  being affixed to the bottom surface of the sub-chassis  410 .  
         [0123]    A sub-guide shaft  720  is integrally formed with the other side edge of the opening  412  of the sub-chassis  410 . More specifically, an edge of the opening in the sub-chassis  410  is bent into an L shape in transverse cross section, and the outer edge of part  721  which extends horizontally from the bent edge is bent upward into the shape of an inverted U in transverse cross section from below, whereby the sub-guide shaft  720  is formed.  
         [0124]    The guide shaft  710  is slidably inserted into guide holes  511   a  and  511   a  of the optical pickup  500 , and guide portions  513  and  513  are in slidable contact with the upper and lower faces of the sub-guide shaft  720 , whereby the optical pickup  500  is movable in directions in which it comes into contact with and separates from the turntable  420 .  
         [0125]    FIGS.  30  to  32  are views showing different modifications of the sub-guide shaft.  
         [0126]    [0126]FIG. 30 is a view showing a sub-guide shaft  730  that is formed by bending a sheet metal into a U shape in transverse cross section.  
         [0127]    [0127]FIG. 31 is a view showing a sub-guide shaft  740  that is formed by folding a sheet metal upon itself.  
         [0128]    [0128]FIG. 32 is a view showing a sub-guide shaft  750  formed by bending a sheet metal into a substantially cylindrical shape.  
         [0129]    Obviously, the modified sub-guide shafts  730 ,  740 , and  750 , shown in FIGS.  30  to  32 , respectively, are applicable, not only to the second embodiment, but also to the first embodiment.  
         [0130]    As can be understood from the foregoing description, in the above-described optical pickup  500  guiding mechanism, the sub-guide shaft is formed by bending a sheet metal, so that when it is formed into a cylindrical shape it can be produced at a relatively low cost. In addition, since metal sheet is used as material, the sub-guide shaft has sufficient strength and has good temperature characteristics. As regards the way in which the optical pickup  500  can be made to occupy only a limited location, either the guide shaft  531  or the guide shaft  710  is formed into a cylindrical shape in order to limit the location occupiable by the optical pickup  500  in all directions perpendicular to a direction of movement thereof, so that no problems arise when the sub-guide shaft  532 ,  720 ,  730 ,  740 , or  750  is used to limit the location occupiable by the optical pickup  500  in all directions perpendicular to the direction in which the guide shaft  531  or the guide shaft  710  is disposed.  
         [0131]    A description will now be given of a third embodiment of the present invention with reference to FIGS. 33 and 34.  
         [0132]    The disk drive of the third embodiment differs from that of the first embodiment in the lock mechanism and the unlocking mechanism used for unlocking the lock mechanism which locks the tray at the housed position. The parts other than the lock mechanism and the unlocking mechanism are essentially the same. Therefore, only the lock and the unlocking mechanisms will be described in detail below. The parts corresponding to those of the first embodiment are given the same reference numerals as those given to the corresponding parts of the first embodiment, and will not be described below.  
         [0133]    The lock mechanism  800  of a CD-ROM drive  100 A comprises a lock arm  810  provided at a tray  300 , and an engaging section  820  provided at a bottom chassis  210 .  
         [0134]    The engaging section  820  is a plate-like section formed vertically from a location near the left side face  214  of a main section  211  of the bottom chassis  210 . It has a main section  821  and an inclined section  822  that is integrally formed with the main section  821 . The main section  821  extends in the forward-and-backward direction, and the inclined section  822  extends from a front edge of the main section  821  forwardly and slightly leftwards. The back edge  821 a of the main section  821  serves as an engaging edge.  
         [0135]    The lock arm  810  is long and extends substantially in the forward-and-backward direction, and is rotatably supported at a portion near the left edge of the lower surface of the tray  310 . A tension coil spring (not shown) is associated with the lock arm  810  which is biased thereby so as to be rotated counterclockwise as seen from above the lock arm  810 .  
         [0136]    An engaging pawl  811 , which engages the engaging edge  821   a  of the engaging section  820 , is formed at the left face of the rear end portion of the lock arm  810 , and a push section  812 , which protrudes obliquely towards the right and forwardly, is formed at the front end portion of the lock arm  810 . The engaging pawl  811  has an engaging face  811   a,  which extends virtually horizontally, and an inclined face  811   b,  which extends obliquely towards the left and rearwardly from the left end of the engaging face  811   a.    
         [0137]    Of the guide portions  513  of the optical pickup  500 , the lower guide portion  513  serves as unlocking means.  
         [0138]    As the drawer section  300  is pushed into the outside housing  200 , the inclined face  811   b  of the engaging pawl  811  of the lock arm  810  comes into contact with the right side face of the inclined portion  822  of the engaging section  820 , and is pushed towards the right by the right side face of the inclined section  822 . The lock arm  810 , along with the drawer section  300 , moves towards the back side of the outside housing  200 , while it rotates slightly clockwise. Thereafter, at the same time that the drawer section  300  reaches its housed position, the engaging face  811   a  of the lock arm  810  arrives at a location corresponding to the location of the engaging edge  821   a  of the engaging section  820 . Therefore, the lock arm  810 , as a result of being biased, rotates counterclockwise, as seen from above the lock arm  810 , whereby the engaging face  811   a  of the lock arm  810  engages the engaging edge  821   a  of the engaging section  820 . This causes the drawer section  300  to be locked at the housed position.  
         [0139]    A description will now be given of how the above-described locking mechanism  800  is unlocked.  
         [0140]    As shown in FIG. 33, when the optical pickup  500  is positioned at the outermost periphery of an information recording area of the CD-ROM on a turntable  420 , a guide portion  513 , at the lower side of the optical pickup  500 , is positioned near the back side of a push section  812  of the lock arm  810 . Therefore, when the optical pickup  500  is reading information carried by a signal from the CD-ROM, the movement of the optical pickup  500  in no way affects the locking operation of the locking mechanism  800  which locks the drawer section  300  at the housed position.  
         [0141]    Pressing an eject button  322  on a front panel  320  causes a sled motor  540  to rotate further in the counterclockwise direction from its location of FIG. 33, causing the optical pickup  500  to move outwardly of the outermost periphery of the information recording area of the CD-ROM  600 . During this time, when the guide portion  513 , at the lower side of the optical pickup  500 , pushes the push section  812  of the lock arm  810 , the lock arm  810  rotates clockwise, as seen from above the lock arm  810  (refer to FIG.  34 ).  
         [0142]    When the lock arm  810  rotates clockwise, the engaging face  811   a  thereof rotates towards the right and disengages from the engaging edge  821   a  of the engaging section  820 , so that the drawer section  300 , which has been locked at the housed position by the lock mechanism  811   a,  is unlocked. Unlocking the lock mechanism  800  causes the front end of the drawer section  300  to protrude from the outside housing as a result of the action of the extension coil spring  317   a.    
         [0143]    During this time, the clockwise rotation of the sled motor  540  causes the optical pickup  500  to move to, for example, a location corresponding to the innermost periphery of the information recording area of the CD-ROM  600 , that is to a location where TOC of the CD-ROM can be read. This causes the guide portion  513 , at the lower side of the optical pickup  500 , to separate from the back side of the push section  812  of the lock arm  810 , as a result of which the lock arm  810  that is biased by the tension coil spring rotates back to its original position, that is to the location where the engaging face  811   a  of the engaging pawl  811  can engage the engaging edge  821   a  of the engaging section  820  of the outside housing  200 . Therefore, when the drawer section  300  is pushed into the outside housing  200 , the locking mechanism locks the tray  310  completely accommodated in a main space  230  of the outside housing  200 .  
         [0144]    As can be understood from the foregoing description, according to the disk drive of the present invention, the unlocking means (the unlocking arm in the first embodiment, and the guide portion  513 , at the lower side of the optical pickup  500 , in the third embodiment) which operates as a result of driving power of the sled motor  540  unlocks the locking mechanism which has been locking the tray  310  completely housed in the outside housing  200 , thereby making it unnecessary to provide a drive source which is designed specifically for unlocking the locking mechanism.  
         [0145]    For this reason, it is not necessary to provide space for a drive source which is designed specifically for performing an unlocking operation, thereby reducing the size of the disk drive, and, particularly, making it easier to reduce the thickness of the disk drive and allowing use of fewer parts.  
         [0146]    In the case where a solenoid or the like is used, it is possible to prevent the locking mechanism to be unlocked unexpectedly due to shock, thereby ensuring locking of the tray at its housed position.  
         [0147]    Although in each of the above-described embodiments the locking mechanism is unlocked when the optical pickup  500  moves outwardly of the outermost periphery of the information recording area of the CD-ROM  600 , the present invention is not limited thereto. Therefore, in other embodiments the locking mechanism may be unlocked when the optical pickup moves inwardly of the innermost periphery of the information recording area of the CD-ROM.  
         [0148]    In addition, although in the foregoing description the present invention was applied to a CD-ROM drive, it may be applied to other types of disk drives in other embodiments.