Abstract:
An optical head apparatus comprises a head unit for irradiating an optical disk with a light beam for recording or reproducing data, a holder for fixing the head unit thereto, a support unit for movably supporting the holder in a radial direction of the optical disk, a support member fixed to the holder, a rack unit movably engageable with the support member within a predetermined range and having a rack along a moving direction of the holder, a gear meshing with the rack of the rack unit, so as to transmit rotating force of a drive source to the rack, and an urging unit for urging the rack unit against the support member in such a manner that the rack meshes with the gear by a predetermined resilient force.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-153078, filed May 29, 2003, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical head apparatus which records or reproduces data with respect to an optical disk and an optical head transferring method. Furthermore, the present invention relates to an optical disk apparatus which uses the above-described optical head apparatus. 
   2. Description of the Related Art 
   As is well known, there has been widely prevailed so-called multi disk drive equipment which not only can record and reproduce data with respect to a CD (i.e., a compact disk) but also can record and reproduce data with respect to an optical disk such as a DVD (i.e., a digital versatile disk). 
   The multi disk drive equipment of this type is used in equipment incorporated in a note book type personal computer or the like in addition to use as external equipment for a desk top type personal computer or the like, and therefore, its outside dimension is reduced in size and thickness as possible. 
   There is provided a feed mechanism in a general optical disk apparatus since an optical head for recording and reproducing data with respect to the optical disk must be moved in the radial direction of the optical disk. Such a feed mechanism is configured in such a manner as to convert the rotating force of a motor into a linear motion by means of a gear and a rack so as to transmit the force to the optical head. 
   Consequently, a play, that is, a backlash generated when the gear and the rack mesh with each other induces a drawback from the viewpoint of the accuracy of the transfer of the optical head. As a result, suppression of such a backlash without degrading miniaturization has been an important problem to enhance the accuracy of the transfer of the optical head. 
   Jpn. Pat. Appln. KOKAI Publication No. 2002-216442 discloses the configuration in which two racks are superimposed one on another to urge each other oppositely in a longitudinal direction by resilient force, so as to achieve favorable meshing with a pinion gear. Moreover, Jpn. Pat. Appln. KOKAI Publication No. 11-353824 discloses the configuration in which a pinion is pressed against a rack via a spring. 
   However, in the former configuration, the two racks need be superimposed one on another, thereby inducing a complicated configuration. In contrast, in the latter configuration, since the rotating pinion is pressed against the rack via the spring, a supporting mechanism for the pinion has a complicated and huge configuration, thereby arising a problem that a size cannot be reduced. 
   Additionally, Jpn. Pat. Appln. KOKAI Publication No. 7-93920 discloses the configuration in which a feed rack is moved in parallel to a rod, and further, the driving force of a gear is made constant by making a load applied on the gear uniform, thus eliminating a backlash. 
   In addition, Jpn. Pat. Appln. KOKAI Publication No. 7-122004 discloses the configuration in which an optical pickup can be moved with smaller acceleration so as to enhance track followability by alleviating an influence of slide friction. 
   Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 7-147018 discloses the configuration in which a rack and a gear are brought into smooth contact with each other by integrally forming a base provided with the rack of a plastic-based material, thus reading information with high accuracy. 
   However, the techniques disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 7-93920, 7-122004 and 7-147018 merely have had the complicated configuration and the large size, and therefore, they have not reached a practical and satisfactory level in current circumstances. 
   BRIEF SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, there is provided an optical head apparatus comprising: a head unit configured to irradiate an optical disk with a light beam for recording or reproducing data; a holder configured to fix the head unit thereto; a support unit configured to movably support the holder in a radial direction of the optical disk; a support member configured to be fixed to the holder; a rack unit configured to movably engage with the support member within a predetermined range and to have a rack along a moving direction of the holder; a gear configured to mesh with the rack of the rack unit, so as to transmit rotating force of a drive source to the rack; and an urging unit configured to urge the rack unit against the support member in such a manner that the rack meshes with the gear by a predetermined resilient force. 
   According to one aspect of the present invention, there is provided an optical head transferring method comprising: fixing a head unit which irradiates an optical disk with a light beam for recording or reproducing data, securing a support member to a holder movably supported in a radial direction of the optical disk, allowing a rack unit having a rack along a moving direction of the holder to movably engage with the support member within a predetermined range, and further, urging the rack unit against the support member in such a manner that the rack meshes with a gear by a predetermined resilient force; and rotating and driving the gear, so as to apply driving force to the rack, thus moving the head unit in the radial direction of the optical disk. 
   According to one aspect of the present invention, there is provided an optical disk apparatus comprising: a tray configured to allow an optical disk to be placed thereon; a loading unit configured to move the tray between a first position, at which the optical disk can be loaded or unloaded, and a second position, at which the optical disk is rotated to be driven; a head unit configured to irradiate the optical disk placed on the tray moved to the second position by the loading unit with a light beam for recording or reproducing data; a holder configured to fix the head unit thereto; a support unit configured to movably support the holder in a radial direction of the optical disk; a support member configured to be fixed to the holder; a rack unit configured to movably engage with the support member within a predetermined range and to have a rack along a moving direction of the holder; a gear configured to mesh with the rack of the rack unit, so as to transmit rotating force of a drive source to the rack; and an urging unit configured to urge the rack unit against the support member in such a manner that the rack meshes with the gear by a predetermined resilient force. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is an external view illustrating an optical disk apparatus in an embodiment according to the present invention; 
       FIG. 2  is a view illustrating the state of a disk loading unit in the optical disk apparatus, viewed from the top; 
       FIG. 3  is a view illustrating the state of the disk loading unit in the optical disk apparatus, as viewed from the bottom; 
       FIG. 4  is a view illustrating the state in which a tray is contained inside of a base member in the disk loading unit; 
       FIG. 5  is a view illustrating the state in which the tray is drawn from the base member in the disk loading unit; 
       FIG. 6  is a view illustrating the state of a chassis in the disk loading unit, viewed from the top; 
       FIG. 7  is a view illustrating the state of the chassis in the disk loading unit, viewed from the bottom; 
       FIG. 8  is a view illustrating the detail of a feed mechanism in the disk loading unit; 
       FIG. 9  is a view illustrating the detail of a support member in the feed mechanism; 
       FIG. 10  is a view illustrating the state in which a rack unit is fixed to the support member in the feed mechanism; 
       FIGS. 11A and 11B  are views illustrating the detailed structure of the support member and the rack unit in the feed mechanism, respectively; and 
       FIG. 12  is a view illustrating a modification of the feed mechanism. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment according to the present invention will be described below in reference to the accompanying drawings.  FIG. 1  is an external view of an optical disk apparatus  11  illustrated in this embodiment. That is, the optical disk apparatus  11  is provided with a cabinet  12  formed into a box of a substantially thin type. 
   At the center of a front panel  13  in the cabinet  12  is disposed a disk loading unit  14 , which is adapted to load or unload an optical disk such as a CD or a DVD by putting in or out a tray, described later, outward of the front panel  13  in the cabinet  12 . 
   Furthermore, a power source key  15  is disposed at one end of the front panel  13  in the cabinet  12 . Moreover, at the other end of the front panel  13  are provided a display unit  16  for displaying an operating state and a plurality of operating keys  17  for setting the optical disk apparatus  11  in a predetermined operative state or an inoperative state. 
     FIG. 2  illustrates the state in which the disk loading unit  14  is taken out, as viewed from the top. That is, a base member  18  serves as a fixing base for directly or indirectly supporting various component parts. 
   The base member  18  includes a top plate  18   a , side plates  18   b  and  18   b  formed at both ends facing to the top plate  18   a , a bottom plate  18   c , not illustrated in  FIG. 2 , extending from the side plates  18   b  and  18   b  and facing to the top plate  18   a , and a front plate  18   d , not illustrated in  FIG. 2 , for connecting the respective fore ends of the side plates  18   b  and  18   b  to each other and having a clearance formed thereat, into which a tray  22 , described later, is loosely inserted between the top plate  18   a  and the same. 
   Among these constituent parts, a connecting plate  19  is disposed across the side plates  18   b  and  18   b . At the center of the connecting plate  19  is fixed a clamp member  21  via a fixing piece  20  having resiliency. The clamp member  21  is urged by the fixing piece  20  inward of the base member  18  via an opening  21   a  formed at the top plate  18   a  of the base member  18 . 
   Additionally, the tray  22  is supported by the base member  18 . The tray  22  is supported in a freely slidable manner in a lateral direction in  FIG. 2  in the state in which a disk placing portion  22   a  faces to the top plate  18   a . In this case, the tray  22  is supported in a freely slidable manner while both side faces thereof are fixed via bosses disposed at the bottom plate  18   c  of the base member  18 . 
     FIG. 3  illustrates the state in which the disk loading unit  14  is viewed from the bottom. Namely, a chassis  23  is supported by the bottom plate  18   c  of the base member  18  in such a manner as to face to the bottom of the tray  22 . On the chassis  23  are mounted a turn table, an optical head and the like, described later. 
   In the chassis  23 , projections  23   a  an  23   a  formed at one end are rotatably supported by the bottom plate  18   c . Consequently, the chassis  23  can be supported to be moved in a tilting direction on the projections  23   a  and  23   a  as fulcrums at the other end thereof. 
   By the chassis  23  is supported a drive motor  24 . To the rotary shaft of the drive motor  24  is fitted a worm gear  25 . The worm gear  25  meshes with a worm wheel  26  rotatably supported by the chassis  23 , so that the rotating force of the drive motor  24  is transmitted to the worm wheel  26 . 
   In this manner, the worm wheel  26  is rotated by the rotating force of the drive motor  24 , and therefore, the tray  22 , the chassis  23 , the optical head and the like can be moved. 
     FIG. 4  illustrates the state of the tray  22  contained inside of the base member  18 , as viewed from the side. In this case, the chassis  23  is controlled at a position above the tray  22 . At this position, the optical disk is lifted up from the tray  22  by the turn table, so as to be held between the clamp member  21  and the turn table, and further, an optical head faces to a signal recording surface of the optical disk. 
     FIG. 5  illustrates the state in which the tray  22  is drawn from the base member  18 , as viewed from the side. In this case, the chassis  23  is controlled at a position under the tray  22 . At this position, the turn table is separated from the optical disk, which is placed on the tray  22 . 
     FIG. 6  illustrates the state of the chassis  23 , as viewed in the direction of  FIG. 2 .  FIG. 7  illustrates the state of the chassis  23 , as viewed from the bottom, that is, in the direction of  FIG. 3 .  FIG. 8  illustrates a part of a feed mechanism for transferring the optical head from the state illustrated in  FIG. 6 . 
   In other words, the turn table  27  is fitted to the rotary shaft of a disk motor (not illustrated) fixed to the chassis  23 , to be thus rotated and driven by the rotating force of the disk motor. 
   Furthermore, the above-described optical head  28  is fixed to the chassis  23 . This optical head  28  is constituted of a head unit  29  provided with a laser diode and a photo diode which are not illustrated, a printed circuit board  30  to which the head unit  29  is fixed, and a holder  31  to which the printed circuit board  30  is fixed. 
   The optical head  28  is movably supported in a direction in which the optical head  28  approaches the turn table  27 , and in a direction in which the optical head  28  is separated from the turn table  27 , by a pair of guide shafts  32  and  33  secured in parallel to the chassis  23 . 
   In this case, in the holder  31  are supported a holding member  34  slidably engageable with the guide shaft  32  and other holding members  35  slidably engageable with the guide shaft  33 . Moreover, the optical head  28  is slidably supported by the guide shafts  32  and  33  via the holding members  34  and  35 , respectively. 
   Here, as illustrated in  FIG. 8 , the holding member  34  engageable with the guide shaft  32  is constituted of a single member; in contrast, the two holding members  35  engageable with the guide shaft  33  are arranged at a predetermined interval along the axial direction of the guide shaft  33 . 
   These two holding members  35 ,  35  are contained inside of a support member  36  fixed to the holder  31 . With the support member  36 , a rack unit  38  having a rack  37  formed outward movably engages via urging means, described later. A pinion gear  39  meshes with the rack  37 . 
   The rotation of the pinion gear  39  enables the driving force in the axial direction of the guide shafts  32  and  33  to be transmitted to the rack  37 , so that the optical head  28  is transferred under the guide of the guide shafts  32  and  33 . The pinion gear  39  can be rotated and driven by the drive motor  24 . 
   That is, as illustrated in  FIG. 7 , the worm gear  25  is fitted to the rotary shaft of the drive motor  24 . The worm gear  25  meshes with the worm wheel  26  rotatably supported by the chassis  23 , so that the rotating force of the drive motor  24  is transmitted to the worm wheel  26 . 
   The pinion gear  39  is integrally formed coaxially with the worm wheel  26 . Consequently, the pinion gear  39  is driven by the drive motor  24  via the worm wheel  26 , and then, the optical head  28  is transferred. Incidentally, as the worm wheel  26  may be used, for example, a spur gear or a helical gear. 
   Here,  FIG. 6  illustrates the state in which the optical head  28  is positioned at the innermost circumference of the optical disk, in other words, the state in which the optical head  28  approaches most the turn table  27 . The optical head  28  is transferred from the position illustrated in  FIG. 6  in a direction separated from the turn table  27  by the rotation in one direction of the drive motor  24 . Additionally, the optical head  28  is transferred near the turn table  27  by the rotation of the drive motor  24  in the other direction. 
   Here, a connector  40  is disposed in the printed circuit board  30  having the head unit  29  fixed thereto. When a cable  41  is connected to the connector  40 , a signal is received from or transmitted to the head unit  29 . 
   In  FIG. 9 , the support member  36  illustrated in  FIG. 8  is shown in detail by a slash line. Furthermore,  FIG. 10  illustrates  FIG. 9 , as viewed from the bottom, in particular, in which the rack unit  38  is shown in detail. Incidentally, the guide shaft  33  is omitted in  FIGS. 9 and 10  for the sake of simplification. 
   In  FIG. 9 , the support member  36  indicated by the slash line is made of a resin, and is provided at the center thereof with containers  36   d  and  36   d  in a substantially box shape, for containing therein the holding members  35  and  35 , respectively. The support member  36  is formed into a substantially plate shape on both longitudinal sides of the containers  36   d  and  36   d  for the holding members  35  and  35 , respectively, and then, is fixed to the holder  31  via a screw  42 . 
   Moreover, bosses  36   a  and  36   b  are formed at both longitudinal ends of the support member  36 , and further, a projection  36   c  for allowing a tension spring  43 , described later, to be hooked thereon is formed near the containing positions of the holding members  35  and  35 . 
     FIG. 10  illustrates the rack unit  38  incorporated in the support member  36 , as viewed from the rack unit  38 , in which the support member  36  is indicated by a slash line. 
   The rack unit  38  is made of a resin, and the rack  37  is integrally formed at one edge in the longitudinal direction of the rack unit  38 . At both ends of the rack unit  38  are formed openings  381  and  382 , at the edges of which engaging portions  38   a  and  38   b  engageable with the respective tips of the bosses  36   a  and  36   b  of the support member  36  are formed. 
   One end of each of the openings  381  and  382  is widely formed so as to allow the bosses  36   a  and  36   b  of the support member  36  to be inserted; in contrast, at the respective other ends of the openings  381  and  382  are formed tapered portions  38   c  and  38   d.    
   Additionally, a hook  38   e  for allowing the tension spring  43  to be hooked between the projection  36   c  and itself is formed at the center of the rack unit  38  in the longitudinal direction. Moreover, a resilient piece  38   f , which can be displaced in a thickness direction, is formed at the rack unit  38 . The resilient piece  38   f  has the function of a stopper for preventing the rack unit  38  from being detached from the support member  36 . 
   In order to incorporate the rack unit  38  into the support member  36  such configured as described above, first, the resilient piece  38   f  of the rack unit  38  is displaced in the thickness direction, and then, the bosses  36   a  and  36   b  of the support member  36  are inserted through wide portions of the openings  381  and  382 , respectively, to engage at the tips thereof with the engaging portions  38   a  and  38   b . Thus, the rack unit  38  can be movably supported by the support member  36  within the range of the openings  381  and  382 . 
   When the wide portions of the openings  381  and  382  in the rack unit  38  move near the bosses  36   a  and  36   b  of the support member  36 , the tip of the projection  36   c  of the support member  36  abuts against the resilient piece  38   f  of the rack unit  38 , thereby restricting the movement. As a consequence, the bosses  36   a  and  36   b  can be inhibited from reaching the wide portions of the openings  381  and  382 . In other words, the rack unit  38  cannot be detached from the support member  36  in a normal operating state. 
   When the coil-like tension spring  43  is hooked between the projection  36   c  of the support member  36  and the hook  38   e  of the rack unit  38  in the state in which the rack unit  38  engages with the support member  36 , the rack unit  38  is urged by the resilient force in such a manner that the tapered portions  38   c  and  38   d  are press-fitted to the bosses  36   a  and  36   b.    
   At this time, with the tapered portions  38   c  and  38   d , the rack unit  38  receives force in such a manner as to be shifted in the direction of the rack  37 , and therefore, the rack  37  is press-fitted to the pinion gear  39  by force according to the resilient force of the tension spring  43 . Thus, it is possible to efficiently suppress a backlash between the rack  37  and the pinion gear  39 . 
     FIG. 11A  illustrates the support member  36 ; and  FIG. 11B  illustrates the rack unit  38 . In  FIG. 11A , a surface facing to the rack unit  38  is indicated by a slash line, and further, the containers  36   d  and  36   d , in which the holding members  35  and  35  are contained, respectively, are formed at the intermediate portion. 
   In the support member  36 , there are formed a pair of projections  36   e  at each of both ends in the longitudinal direction, projecting from the surface facing to the rack unit  38  in a vertical direction. The support member  36  is configured in such a manner as to be brought into contact with the rack unit  38  via the projections  36   e , such that the rack unit  38  can securely slide with ease. 
   In  FIG. 11B , the rack unit  38  is integrally made of a resin, and further, an opening  383  is formed also at a portion at which the tension spring  43  is disposed at the center, in addition to the two openings  381  and  382  formed at both ends. 
   In the above-described embodiment, the support member  36  is secured to the holder  31  having the head unit  29  fixed thereto, and the rack unit  38  having the rack  37  formed thereat is fixed to the support member  36  via the urging means in such a manner that the rack  37  meshes with the pinion gear  39  at a predetermined pressure. As a consequence, it is possible to securely suppress the backlash generated between the pinion gear  39  and the rack  37  by the simple structure, so as to stably transfer the optical head  28 . 
   Incidentally, although the support member  36  is secured to the holder  31  via the screw  42  in the above-described embodiment, it is possible to reduce the number of component parts and simplify the configuration if a support unit  44  having the same function as that of the support member  36  is formed integrally with the holder  31 , as illustrated in  FIG. 12 . 
   Furthermore, although the bosses  36   a  and  36   b  are formed at the support member  36  and the tapered portions  38   c  and  38   d  are formed at the rack unit  38  in the above-described embodiment, tapered portions may be formed at the support member  36  while bosses may be formed at the rack unit  38 . 
   It is to be understood that the present invention is not restricted to the embodiment, and that the constituent elements can be variously and specifically modified in embodiments without departing from the scope of the present invention. Moreover, the invention having various features can be devised by appropriately combining the plurality of constituent elements described in the above-described embodiment. For example, some constituent elements may be omitted from all of the constituent elements described in the embodiment. Additionally, constituent elements in another embodiment may be appropriately combined with each other.