Abstract:
A disc player includes an optical pickup for producing a laser beam onto an optical disc which is being rotated by virtue of a spindle motor. Two guide shafts are disposed on opposite sides of the optical pickup for guiding the movement of said optical pickup. An adjusting system adjusts the position of each guide shaft. The spindle motor is fixed on a motor base plate which forms part of the adjusting system.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a disc player, particularly to a compatible disc player capable of recording information on or reproducing information from DVD (digital video disc) and CD (compact disc). 
     A conventional compatible disc player comprises a driving system (using a spindle motor) for rotatably driving an optical disc, a servo mechanism mounting an optical pickup, both of which are arranged independently from each other on a base frame of the player. 
     The servo mechanism is movably connected with two mutually parallel guide shafts arranged on the base frame in a manner such that the center of the optical pickup may move along a trace coincident with a straight line passing through the center of an optical disc mounted on a turntable. 
     The optical pickup (two-focus optical pickup) is mounted on the servo mechanism. A driving motor is provided for reciprocatingly driving the servo mechanism through a group of driving force transmitting gears. 
     The optical pickup is fabricated so that when in use a laser beam emitted from a laser diode is allowed to pass through an objective lens and converged on to an optical disc so as to record information on the disc. Further, the optical pickup is also fabricated so that when in use a laser beam is allowed to irradiate an optical disc, a light beam reflected from the optical disc is permitted to pass through the objective lens to arrive at a photo-detector provided within the optical pickup, so as to reproduce information previously recorded on the optical disc. However, to ensure proper information recording and reproducing, it is extremely important to perform adjustments (tangential adjustment and radial adjustment) on the optical axis of the optical pickup, corresponding to a possible inclination of the optical disc mounted on the turntable. 
     For the above reason, an automatic optical axis adjusting device having a step motor is used to adjust the optical axis of an optical pickup. In detail, an upper chassis is mounted on the base frame. Between the upper chassis and the base frame is provided an optical axis adjusting device having adjustment screws capable of raising and lowering end portions of the guide shafts by virtue of the step motor. In this way, it is possible to adjust the optical axis of an optical pickup by raising or lowering the end portions of the guide shafts. 
     However, there are at least the following problems associated with the above-discussed conventional compatible disc player. Namely, since the driving system, the servo mechanism, and the base frame are arranged independently from one another, it is difficult to manufacture the disc player compact in size. Moreover, due to the above-discussed structure of the conventional compatible disc player, there are too many parts and elements forming the player, resulting in a high cost in manufacturing a compatible disc player. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a disc player having an improved optical axis adjusting system for adjusting the optical axis of an optical pickup, rendering the player to be manufactured with a reduced size using fewer parts and elements, thereby solving the above-mentioned problems peculiar to the above-discussed prior art. 
     According to the present invention, there is provided a disc player, comprising: an optical pickup for producing a laser beam onto an optical disc which is being rotated by virtue of a spindle motor; two guide shafts disposed on opposite sides of the optical pickup for guiding the movement of said optical pickup; and adjusting means for adjusting the position of each guide shaft. In particular, the spindle motor is fixed on a chassis which forms part of the adjusting means. 
     In one aspect of the present invention, the spindle motor is disposed on the inner side of the chassis, which is opposite to the outer side thereof where a turntable is provided for mounting an optical disc. 
     In another aspect of the present invention, the adjusting means includes a plurality of cylindrical holders and the same number of adjustment screws to be engaged into the cylindrical holders, further includes urging means provided in each cylindrical holder for urging end portion of each guide shaft in a predetermined direction. 
     In further aspect of the present invention, the chassis forms end walls for the cylindrical holders. 
     In a still further aspect of the present invention, the urging means includes a plurality of leaf springs each serving as one wall for each cylindrical holder. 
     In one more aspect of the present invention, the urging means includes a plurality of adjustment screws each having a sharp front end adapted to press against an outer periphery surface of a guide shaft. 
     The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a front view indicating an internal structure of a disc player made according to the present invention. 
     FIG. 2 is an end view seen in a direction shown by arrows A, A in FIG.  1 . 
     FIG. 3A is a side view seen in a direction shown by arrows B, B in FIG.  1 . 
     FIGS. 3B-3E are sectional views indicating adjusting means for adjusting attachment position of guide shaft. 
     FIGS. 4A and 4B are bottom views indicating the bottom structure of the disc player of FIG.  1 . 
     FIG. 5A is a front view indicating a gear assembly for use in the disc player of FIG.  1 . 
     FIG. 5B is an exploded cross sectional view indicating the gear assembly of FIG.  5 A. 
     FIG. 6A is a front view indicating a rack assembly for use in the disc player of FIG.  1 . 
     FIG. 6B is an exploded side view indicating the rack assembly of FIG.  6 A. 
     FIG. 7A is a front view indicating a flexible holder for use in the disc player of FIG.  1 . 
     FIG. 7B is a sectional view taken along a line C—C in FIG.  7 A. 
     FIGS. 7C and 7D are sectional views indicating how a flexible wire assembly is inserted through the flexible holder of FIG.  7 A. 
     FIG. 8 is an explanatory view indicating a condition where a rotation pulse detector has been attached to a motor base in the disc player of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a front view indicating an internal structure of a disc player made according to the present invention. 
     FIG. 2 is an end view seen in a direction shown by arrows A, A in FIG.  1 . FIG. 3A is a side view seen in a direction shown by arrows B, B in FIG.  1 . 
     Referring to FIG. 1, a disc player of the present invention includes a base frame  1  having a generally square configuration. Formed on the four corners of the base frame  1  are four installing holes  1   a  which are used for fixing (through vibration proof elements) the base frame  1  in position within the disc player. Further, cylindrical holders  2 A,  2 B,  2 C and  2 D forming important portions of optical axis adjusting means are formed on the base frame  1 . Moreover, as shown in FIGS. 2 and 3, a support member  3  supporting a base plate  15  is formed on the base frame  1 . 
     In practice, the cylindrical holders  2 A- 2 D may be formed by tightly attaching metal molds (for forming the holders  2 A- 2 D) on both the upper side and lower side of the base frame  1 , followed by injecting a liquid resin into the metal molds and hardening the resin. 
     In detail, the positions for forming the holders  2 A- 2 D on the base frame  1  are required to satisfy a relationship between a step motor rotating amount and a guide shaft length, in a manner such that the longitudinal directions of guide shafts  4  and  5  are parallel to a straight line passing through the rotating center of the spindle motor  6 . 
     FIG. 3B is used to illustrate the structure of each of the holders  2 A- 2 D. As shown in FIG. 3B, each of the holders  2 A- 2 D standing on the base frame structure  1  is formed into a cylindrical shape, with an opening  2   e  formed on the upper side thereof. The end portions of the guide shafts  4  and  5  are received through the openings  2   e  into the holders  2 A- 2 D and supported therein. Further, a guide portion  2   f  is formed in the opening  2   e  of each holder, in a manner such that an end portion of the guide shaft  4  or  5  is slidable along the guide portion  2   f.    
     Further, a screw spring  7  is disposed in the opening  2   e  of each of the holders  2 A- 2 D to press against an end of the guide shaft  4  or  5 . In detail, each screw spring  7  is so arranged that its smaller portion is located on the upper side within the opening  2   e . As shown in FIG. 3B, open portions of the holders  2 A and  2 C are covered up by a cover plate  8 , followed by fixing screws  9  through the holes formed on the plate  8 , thereby fixing the cover plate  8  on the holders  2 A and  2 C. In this way, one end of each of the guide shafts  4  and  5  is urged downwardly. On the other hand, open portions of the holders  2 B and  2 D are covered up by a motor base plate  10  having a projection  10   a , followed by fixing screws  9  through the holes formed on the motor base plate  10 , thereby fixing the motor base plate  10  on the holders  2 B and  2 D. In this way, the other end of each of the guide shafts  4  and  5  is urged downwardly (FIGS.  1 - 3 ). 
     Further, on the base frame  1  obturating the bottoms of the holders  2 A- 2 D, there are formed holes  1   b  which allow passing of adjustment screws  11  therethrough from below the base frame  1 , so that the adjustment screws  11  may be inserted into the holes  1   b . Here, each of the screws  11  is formed with a hexagonal recess portion  11   a  (FIG. 4) on the head thereof. Jigs of an automatic optical axis adjusting device (not shown) are allowed to engage into the hexagonal recess portions  11   a , so that the screws  11  may be screwed into the through holes  1   b  by virtue of a driving force from a step motor (not shown). In this way, the front end of each screw  11  will get in contact with the lower surface of an end portion (received in one of the holders  2 A- 2 D) of a guide shaft  4  or  5 . Thus, with the rotation of the step motor of the automatic optical axis adjusting device, the screws  11  may be rotated so as to move up or down, thereby adjusting the position of an end portion of (received in one of the holders  2 A- 2 D) of a guide shaft  4  or  5 . 
     Moreover, referring to FIGS. 2-4, each of the holders  2 A- 2 D is integrally formed with a retaining member  2   g  which is located on the underside of the base frame  1  for preventing a potential moving away of a holder from its installing position. 
     Referring to FIG. 2, the projection  10   a  of the motor base plate  10  is located on the center thereof and is protruding upwardly. On the other hand, the base frame  1  is formed with a recess portion  1   c  protruding downwardly, in a manner such that the recess portion  1   c  is facing the upwardly protruding portion  10   a . Therefore, a spindle motor  6  is allowed to be located in a space formed between the upwardly protruding portion  10   a  and the downwardly protruding portion  10   c . In detail, the spindle motor  6  is hung on the inner surface of the upwardly protruding port ion  10   a . In this way, the spindle shaft  6   a  of the spindle motor  6  is allowed to protrude from the upper surface of the upwardly protruding portion  10   a , a turntable  12  having a circular shape is mounted on the spindle shaft  6   a.    
     The guide shafts  4  and  5  are each formed into an elongated rod having a circular cross section, so that a servo mechanism  14  mounting the optical pickup  13  may be slidably mounted on the shafts  4 ,  5  to be slidable therealong. 
     In fact, the guide shaft  4  is longer than the guide shaft  5  and can serve as a bearing for slidingly moving the servo mechanism  14 . The guide shaft  5 , which is shorter than the guide shaft  4 , is used to guide the servo mechanism  14  as it slides. 
     As related in the above, the holders  2 A- 2 D are provided to serve as adjusting means for adjusting the optical axis of the optical pickup  13 . A relationship between a rotating amount of the step motor and an adjusting amount of the screws  11  is determined by some predetermined values (step motor: 3600 pulse/rev; screw pitch: 0.45 (M2.6); screw moving amount: 0.125 μm/pulse). In particular, when the shaft  4  and the shaft  5  have different lengths from each other, positions for disposing the holders  2 A- 2 D on the base frame  1  are required to satisfy the following relationship involving a step motor rotating amount and a guide shaft length. 
     At first, the tens center of the optical pickup  13  mounted on the servo mechanism  14  is assumed to be a reference point, a distance between the center of each of the holders  2 A- 2 D and each of X axis and Y axis (see FIG. 1) is indicated In FIG.  1 . For the sake of convenience, distances in the direction of X axis are defined as A0, B0, C0, D0, while the distances in the direction of Y axis are defined as E0 and F0. 
     In more detail, a distance A0 between the lens center O of the optical pickup  13  and the adjustment center of the holder  2 A in the direction of X axis is 36.0 mm. 
     A distance B0 between the lens center O of the optical pickup  13  and the adjustment center of the holder  2 B in the direction of X axis is 46.8 mm. 
     A distance C0 between the lens center O of the optical pickup  13  and the adjustment center of the holder  2 C in the direction of X axis is 24.0 mm. 
     A distance D0 between the lens center O of the optical pickup  13  and the adjustment center of the holder  2 D in the direction of X axis is 30.0 mm. 
     A distance between the lens center O of the optical pickup  13  and the adjustment centers of the holder  2 A,  2 B in the direction of Y axis is 18.5 mm. 
     A distance between the lens center O of the optical pickup  13  and the adjustment centers of the holder  2 C,  2 D in the direction of Y axis is 25.9 mm. 
     Referring to FIGS. 1-4, a driving system for slidably driving the servo mechanism  14  comprises: 1) a driving motor  16  mounted on a base plate  15  which is supported by a support member  3  positioned on the underside of the base frame  1 ; 2) a driving gear  17  attached at the front end of the driving shaft of the driving motor  16 , said driving gear  17  being provided on the base frame  1 ; 3) a reduction gear  18  engaged with the driving gear  17 , said reduction gear  18  being rotatably supported on the base frame  1 ; 4) a small gear  19  formed coaxially and integrally with the reduction gear  18 ; 5) a pair of gears  20 A and  20 B (overlapped one upon the other) both of which are rotatably supported on the base frame  1  and engaged with the small gear  19 ; 6) an intermediary gear  20 C formed coaxially and integrally with the gear  20 B on one side thereof; 7) racks  21 A and  21 B movably attached on the guide shaft  4 , both engaged with the intermediary gear  20 C. 
     As shown in FIGS. 5A and 5B, the pair of gears  20 A and  20 B have circumferential tooth portions  20 A 1  and  20 B 1 , and are coaxially overlapped one upon the other. The gear  20 A is formed with an opening  20 A 2  and is provided with a pin  20 A 3  protruding from one wall of the opening  20 A 2 . Similarly, the gear  20 B is formed with an opening  20 B 2  and is provided with a pin  20 B 3  protruding from one wall of the opening  20 B 2  in a direction opposite to the pin  20 A 3 . 
     The intermediary gear  20 C is disposed below the gear  20 B and is rotatably supported on the base frame  1 . The gear  20 A is disposed over the gear  20 B. A coil spring  22  is disposed between the mutually protruding pins  20 A 3  and  20 B 3 , thereby rendering the gears  20 A and  20 B to be urged in mutually opposite directions. In this way, both the gears  20 A and  20 B are allowed to be exactly engaged with the small gear  19 , preventing potential clatterring between the tooth portions  20 A 1 ,  20 B 1  of the gears  20 A and  20 B on one hand and the tooth portion of the small gear  19  on the other. 
     On the other hand, as shown in FIG. 6, the disc player has a pair of racks  21 A,  21 B including tooth portions  21 A 1 ,  21 B 1 . The rack  21 A is formed with a hole  21 A 2  having a pin  21 A 3  protruding from one wall thereof. Similarly, the rack  21 B is formed with a hole  21 B 2  having a pin  21 B 3  protruding from one wall thereof in a direction opposite to the pin  21 A 3 . A coil spring  23  is disposed between the mutually protruding pins  21 A 3  and  21 B 3 , thereby rendering the racks  21 A and  21 B to be urged in mutually opposite directions. In this way, even when the adjustment screws  11  are screw-drived to vertically displace the end portions of the guide shafts  4  and  5 , it is possible to prevent any potential clatterring between the tooth portions  21 A 1 ,  21 B 1  of the racks  21 A,  21 B on one hand and the intermediary gear  20 C on the other, thereby enabling the servo mechanism  14  to smoothly and stably move along the guide shafts  4 ,  5  in a correct manner. 
     In FIG. 6A, reference numeral  21 B 4  is used to represent a screw hole for installing the servo mechanism  14 . 
     Referring again to FIG. 4, a flexible holder  24  is attached on the underside of the servo mechanism  14  for connecting a flexible flat belt-like wire assembly  25  including a plurality of wires. 
     In detail, as shown in FIG. 7, the flexible holder  24  is made of a flexible resin material such as polypropylene resin, including a main body  24 A directly attached to the servo mechanism  14 , a comb-like wire insertion portion  24 B, and a connecting portion  24 C. Therefore, the flexible belt-like wire assembly  25  extending from the servo mechanism  14  to outside connector terminals is allowed to be pulled out in either direction in which the servo mechanism  14  moves. Accordingly, after the flexible belt-like wire assembly  25  has been inserted through the insertion portion  24 B in accordance with a course shown in FIG. 7C or FIG. 7D, the connecting portion  24 C shall be connected to the main body  24 A. 
     Referring to FIGS. 2 and 8, a detector holder  26  made of a synthetic resin is installed on the upper surface of the projection  10   a  of the motor base  10 . A detector  27  for detecting rotation pulse of the disc turntable  12  is attached on the detector holder  26 . The detector  27  is so formed that it can be used to attach front ends of flexible wires  28  directly onto the detector holder  26 , thereby making it sure to dispense with the use of a print substrate. 
     The operation for the optical axis adjustment for the disc player of the present invention will be described in the following, with reference to FIG.  1 . 
     Here, the optical axis of the objective lens of the optical pickup  13  mounted on the servo mechanism  14  will be adjusted in a direction of X axis in FIG.  1 . 
     At first, the servo mechanism  14  is set on an automatic optical axis adjusting device (not shown). Then, the step motor is operated to screw-drive the adjustment screw  11  engaged in the holder  2 C so as to raise the screw  11  by 20 pulses. At this moment, distances between the lens center O and the holders  2 C,  2 D in the direction of X axis may be indicated as follows. 
     
       
         C0:D0=24.0:30.0=1:1.25 
       
     
     In this way, in order not to change the height of the objective lens, the step motor is operated to screw-drive the adjustment screw  11  engaged in the holder  2 D so as to lower the screw  11  by 25 pulses. At this moment, distances between the lens center O and the holders  2 A,  2 B in the direction of X axis may be indicated as follows. 
     
       
         A0:B0=36.0:46.8=1.5:1.95 
       
     
     Therefore, in order to keep the guide shafts  5  and  4  in parallel to each other, the step motor is operated to screw-drive the adjustment screw  11  engaged in the holder  2 A so as to raise the screw  11  by 30 pulses. Meanwhile, the step motor is operated to screw-drive the adjustment screw  11  engaged in the holder  2 B so as to lower the screw  11  by 30 pulses. 
     In this way, with the use of the automatic optical axis adjusting device, the optical axis of the objective lens of the optical pickup  13  may be adjusted by being tilted in a direction of X axis in FIG. 1, while keeping the guide shafts  4 ,  5  parallel to each other all the time, thereby finishing the adjustment of the optical axis in the direction of X axis. 
     Further, the optical axis of the objective lens of the optical pickup  13  mounted on the servo mechanism  14  will be adjusted in a direction of Y axis in FIG.  1 . 
     At the first, the step motor is operated to screw-drive two adjustment screws  11  engaged in the holders  2 C and  2 D so as to lower the two screws  11  by 7 pulses. At this moment, distances between the lens center O and the holders  2 A,  2 B,  2 C,  2 D in the direction of Y axis may be indicated as follows. 
     
       
         E0:F0=18.5:25.9=1:1.4 
       
     
     In this way, in order not to change the height of the objective lens, the step motor is operated to screw-drive the other two adjustment screws  11  engaged in the holders  2 A and  2 B, so as to raise the two screws  11  by 5 pulses. 
     Thus, with the use of the automatic optical axis adjusting device, the optical axis of the objective lens of the optical pickup  13  may be adjusted by being tilted in a direction of Y axis in FIG. 1, while keeping the guide shafts  4 ,  5  parallel to each other all the time, thereby finishing the adjustment of the optical axis in the direction of Y axis. 
     An internal deformation within each of the holders  2 A- 2 D is shown in FIG.  3 D. Referring to FIG. 3D, one wall  2 ′ of each holder is formed into a leaf spring, so that an end portion of a guide shaft  4  or  5  may be urged toward an opposite wall in a direction shown by an arrow α in FIG. 3D, thereby preventing any potential clatterring within each of the holder  2 A- 2 D. 
     FIG. 3E is used to illustrate a further embodiment of the present invention using an adjustment screw  11  having a sharp front end. As shown in FIG. 3E, with the use of the adjustment screw  11  having a sharp front end, even if there is an unnecessary space formed between a guide shaft  4  or  5  and one wall  2 ″ of a holder, an end portion of a guide shaft  4  or  5  may be urged toward an opposite wall in a direction shown by an arrow β in FIG. 3E, thereby preventing any potential clatterring within each of the holder  2 A- 2 D. 
     With the use of the present invention, even if the guide shafts  4  and  5  have different lengths, it is still possible that the optical axis of the objective lens of the optical pickup  13  mounted on the servo mechanism  14  may be easily adjusted in both X direction and Y direction (shown in FIG. 1) with an improved precision, thereby greatly reducing a time period necessary for the adjustment of the optical axis of the objective lens. 
     While the presently preferred embodiments of the this invention have been shown and described above, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.