Patent Publication Number: US-2005128899-A1

Title: Disk player

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to disk players for reading signals from disk-shaped recording medium, such as optical disks, etc., to reproduce voice and/or image.  
      2. Description of the Related Art  
      A disk player comprises a turntable for rotatingly driving a disk, a pickup for reading signals from the rotating disk, and a pickup drive device for reciprocatingly driving the pickup radially of the disk by mesh between a rack and a pinion, to read optically the signals from a signal bearing surface of the disk.  
      With reference to  FIG. 14 , a disk D has a signal bearing surface provided thereon with a recording area A of audio signals and video signals, and provided in an inner periphery portion of the area A with a TOC (Table of Contents) area B for writing therein addresses of all trucks on the disk. A pickup reciprocatingly moves radially of the disk within these recording areas (content signal recording area) to read the signals.  
      A pickup drive device of the conventional disk player, as shown in  FIG. 13 , includes a pickup  4  to be guided so as to reciprocatingly move radially of the disk, a rack  5  attached to the pickup  4 , and a pinion  73  in mesh with the rack  5  and to be turnably driven by a motor (not shown). Further, the disk player includes a switch  74  to be turned on when the pickup  4  moves to an inner peripheral side of the disk through the content signal recording area, and a stopper  76  for receiving the rack  5  at a moving end on the inner peripheral side of the disk, whereby the pickup  4  is prevented from moving further inwardly of the disk beyond the TOC recording area.  
      In order to control positions of the pickup  4  with high accuracy, backlash between the rack  5  and the pinion  73  is required to be zero. Accordingly with the pickup drive device shown in  FIG. 13 , the rack  5  is attached to the pickup  4  by a spring piece  50 , whereby the rack  5  is pressed onto the pinion  73  at all times by biasing force of the spring piece  50  (JP-A-63213/1997).  
      With the disk player including the pickup drive device described, in the case where an excessive force acts on the rack  5  by an impact due to the disk player&#39;s falling, etc., the rack  5  is caused to be away from the pinion  73  against elastic force of the spring piece  50 , releasing mesh between the rack  5  and the pinion  73 , to thereby prevent damage to teeth.  
      In recent years, optical disks have a reference information recording area C termed BCA (Burst Cutting Area) or a barcode area arranged on a further inner periphery from the TOC area B on the signal bearing surface, as shown in  FIG. 14 . The pickup  4  reads reference information from the reference information recording area C to thereby make it possible to obtain various information services, for example. In order to correspond to such an optical disk as has the reference information recording area, the switch  74  and the stopper  76  provided with the disk player shown in  FIG. 13  are relocated to the inner peripheray of the disk to allow the pickup  4  to read information from the reference information recording area.  
      The content signal recording areas A and B are, however, different from the reference information recording area C in recording format of signals or information. Therefore, the control of movement of the pickup  4  in the content signal recording area, as it is, cannot be applied to the control of movement in the reference information recording area. Even if the pickup  4  is kept moving until the switch  74  is turned on, inertial force of the pickup  4  causes the rack  5  to bump the stopper  76 , to shift the position of mesh between the rack  5  and the pinion  73  due to the bump reaction, retreating the rack  5  by one to several pitches of tooth profile, whereby there is a likelihood that the pickup  4  is shifted from the reference information recording area C for reading signals. Furthermore, this also gives rise to the problem of noise involved in the repetition of tooth skip of the rack  5  and the pinion  73 .  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to provide a disk player which is adapted to read both content signals and reference information from a disk having a reference information recording area provided on an inner periphery of a content signal recording area of a signal bearing surface thereof.  
      Another object of the present invention is to provide a disk player free of likelihood of noise produced in reading the reference information.  
      A disk player embodying the present invention comprises a turntable  9  for rotatingly driving a disk, a pickup  4  for reading signals from the rotating disk, a pickup drive device  7  for reciprocatingly driving radially of the disk the pickup  4  between a content signal recording area and a reference information recording area by mesh between a rack  5  and a pinion  73 , a mesh release mechanism  3  for releasing the mesh between the rack  5  and the pinion  73  upon exertion of an excessive force on the rack  5 , detection means for detecting that the pickup  4  is positioned for reading signals as opposed to the middle position between the content signal recording area and the reference information recording area, drive control means for, upon a command given to read information from the reference information recording area, operating the pickup drive device  7  for a predetermined period of time from the time of detection by the detection means to move the pickup  4  toward an inner periphery of the disk, and a stopper  61  for restraining the pickup  4  from moving further upon the pickup  4  reaching a position for reading signals from the reference information recording area of the disk.  
      The disk player embodying the present invention further comprises a mesh release control mechanism  6  for controlling the operation of the mesh release mechanism  3  with the pickup  4  restrained from moving by the stopper  61 .  
      With the disk player of the present invention, when a command is given to read signals from the content signal recording area of the disk, the pickup  4  is caused to move toward the inner periphery of the disk by the operation of the pickup drive device  7 . Thereafter the detection means detects that the pickup  4  is positioned for reading signals as opposed to the middle position between the content signal recording area and the reference information recording area, whereupon the pickup drive device  7  ceases to operate, or is operated in a reverse direction for a predetermined period of time, followed by reading signals from the content signal recording area.  
      On the other hand, when a command is given to read information from the reference information recording area of the disk, the pickup  4  is caused to move toward the inner periphery of the disk by the operation of the pickup drive device  7 . Thereafter the detection means detects that the pickup  4  is positioned for reading signals as opposed to the middle position between the content signal recording area and the reference information recording area, whereupon the pickup drive device  7  is further operated in the same direction for a predetermined period of time from the time of the detection, moving the pickup  4  toward the inner periphery of the disk. In this case the predetermined period of time is set longer than a period of time required for moving the pickup  4  toward the inner periphery of the disk until the pickup  4  is restrained from moving by the stopper  61 .  
      As a result, the further movement of the pickup  4  is restrained by the stopper  61 , to hold the pickup  4  at the position for reading signals from the reference information recording area. On this occasion, even if a great impact acts on the pickup  4  to exert thereon a force in a direction for operating the mesh release mechanism  3 , the mesh release control mechanism  6  controls the operation of the mesh release mechanism  3 , obviating the likelihood of release of mesh between the rack  5  and the pinion  73  with ease. Accordingly, noise involved in the repetition of tooth skip of the rack  5  and pinion  73  is unlikely to be produced.  
      In the case where an excessive force is exerted on the rack  5  due to an impact caused by disk player&#39;s falling, etc. with the pickup  4  positioned for reading signals from the content signal recording area, the mesh release mechanism  3  is operated to release the mesh between the rack  5  and the pinion  73 , to thereby prevent the damage to the teeth.  
      Stated specifically, the mesh release mechanism  3  supports the rack  5  on a base  40  of the pickup  4  such that the rack  5  is allowed to be away from the pinion  73 , and elastically biases the rack  5  toward the pinion  73 . According to the specific construction, the mesh release mechanism  3  presses the rack  5  against the pinion  73 , and backlash is therefore zero. Furthermore, when an impact force is exerted on the pickup  4 , the rack  5  is away from the pinion  73  against elastic biasing force, to release the mesh therebetween, whereby the damage to the teeth is prevented.  
      Stated further specifically, the mesh release control mechanism  6  is in engagement with an end portion of the rack  5  adjacent to the inner periphery when the pickup  4  is restrained from moving by the stopper  61 , to prevent the end portion from being away from the pinion  73 . According to the specific construction, when a great impact force is exerted on the pickup  4 , the rack  5  is elastically deformed with the end portion adjacent the inner periphery of the disk serving as a fixed end, resulting in release of the mesh between the rack  5  and the pinion  73 , whereby damage to the teeth is precluded.  
      Stated still further specifically, the drive control means reduces a drive voltage in moving the pickup  4  to the reference information recording area of the disk, for a predetermined period of time from the detection by the detection means, which voltage is lower than a voltage in reciprocatingly moving the pickup  4  within the content signal recording area. According to the specific construction, the pickup  4  moves toward the reference information recording area of the disk with a decreased speed, to reduce the impact force when the movement of the pickup  4  is restrained by the stopper  61 , lowering stress applied on the teeth face of the rack  5 , whereby the pickup drive device  7  is given a prolonged life.  
      As described above, the disk player of the present invention is adapted to read both the content signals and the reference information from the disk having the reference information recording area provided on an inner periphery of the content signal recording area of the signal bearing surface thereof. Furthermore there is no likelihood of noise produced in reading the reference information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view showing a pickup drive system of a disk player embodying the present invention;  
       FIG. 2  is an exploded perspective view of a pickup and a rack;  
       FIG. 3  is a perspective view of the pickup and the rack in an assembled state;  
       FIG. 4  is a perspective view of a state wherein a spring member is assembled into the rack;  
       FIG. 5  is a perspective view of the spring member;  
       FIG. 6  is a bottom view of the pickup drive system;  
       FIG. 7  is a perspective view of the pickup drive system as seen from the bottom side;  
       FIG. 8  is a bottom view of the pickup drive system in a state wherein the pickup reaches a moving end on an inner periphery of the disk;  
       FIG. 9  is a perspective view of the pickup drive system as seen from the bottom side;  
       FIG. 10  is a flow chart illustrating a control procedure of a pickup drive device;  
       FIG. 11  is a time chart illustrating control of the pickup drive device in reading the content signals;  
       FIG. 12  is a time chart illustrating control of the pickup drive device in reading a barcode area;  
       FIG. 13  is a plan view of a pickup drive system of the conventional disk player;  
       FIG. 14  is a plan view showing a plurality of recording areas provided on a signal bearing surface of the disk. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      With reference to the drawings, modes for embodiment of the present invention will be described below. As shown in  FIG. 14 , a signal bearing surface of a disk D is provided thereon with a recording area A of audio and video signals (AV signals). An inner periphery of the area A is provided thereon with a TOC (Table of contents) area B for writing therein addresses of all trucks on the disk. Provided on further inner periphery of these recording areas (content signal recording area) is a barcode area C serving as a reference information recording area.  
      A disk player embodying the present invention comprises, as shown in  FIG. 1 , a turntable  9  for rotatingly driving a disk, a pickup  4  for reading signals from the rotating disk, a pickup drive device  7  for reciprocatingly driving the pickup  4  radially of the disk from the AV signal recording area to the barcode area through the TOC area, each of which are arranged on the chassis  1 .  
      The pickup  4  has an objective lens  44  mounted on a base  40 . The pickup  4  is reciprocatingly movably supported along a disk radial line by a guide member  2  including two parallel rails of a first rail  21  and a second rail  22  which are provided on the chassis  1 . As shown in  FIG. 6  and  FIG. 7 , the turntable  9  is coupled to a turntable drive motor  91  disposed on the rear surface of the chassis  1 .  
      With reference to  FIG. 2 , the base  40  of the pickup  4  has attaching portions  41 ,  45  for attaching thereto the rails  21 ,  22  which portions are provided at opposite ends in a direction orthogonal to a direction of movement (indicated by an X arrow). One attaching portion  41  has attaching pieces  42 ,  43  provided at opposite ends thereof. The first rail  21  extends through the attaching pieces  42 ,  43 . The other attaching portion  45  is slidably engaged with the second rail  22 .  
      The base  40  has a rack  5  extending in a direction of movement of the pickup  4  and provided at an end portion adjacent to the attaching portion  41  of the first rail  21 . As shown in  FIG. 2  and  FIG. 4 , the rack  5  has a rack face  52  formed on a side edge longitudinally of a spring attaching portion  51  for attaching thereto a spring member  8  to be described below. A pair of support pieces  53 ,  54  is provided in the vicinity of opposite end portions of the rack face  52 . The first rail  21  extends through the two support pieces  53 ,  54  of the rack  5 . The attaching portion  41  of the pickup  4  is fitted between the two support pieces  53 ,  54  of the rack  5  with a reserve in the direction of slide of the base  40 . The rack  5  is turnable about the first rail  21 .  
      As shown in  FIG. 1  and  FIG. 6 , the pickup drive device  7  comprises a motor  71 , deceleration gear train  72  coupled to the motor  71 , a pinion  73  positioned lowermost of the deceleration gear train  72  and to mesh with the rack face  52  of the rack  5 . The spring member  8  is attached to the spring attaching portion  51  of the rack  5 . As shown in  FIG. 4  and  FIG. 5 , the spring member  8  is formed by bending one metal spring material into an approximately V-shape. The spring member  8  has one end contacted with a latch portion  57  provided adjacent the support piece  53  on an inner peripheral side of the disk of the rack  5  while the member  8  has the other end contacted with the base  40  serving as the mating member as compressed.  
      The rack  5  is biased toward the pinion  73  by the reaction of the force of the spring member  8  for biasing the base  40 , i.e., the entire spring member  8  in the approximately V-shape serves as a first biasing portion  81  for biasing the rack  5  toward the pinion  73 . The rack  5  is turnably provided on the rail  21  to allow the rack  5  to be away from the pinion  73  while the rack  5  is biased toward the pinion  73  by the spring member  8 , whereby a mesh release mechanism  3  is provided for releasing mesh between the rack  5  and the pinion  73 . In the mechanism, when the excessive force is exerted on the rack  5 , the rack  5  is away from the pinion  73  to release the mesh between gears thereof.  
      Formed at an end portion adjacent to the latch portion  57  of the spring member  8  is a second biasing portion  82  for biasing the base  40  in one direction (a movement direction of the outer periphery of the disk in the present embodiment) so as to prevent jarring between the base  40  and the rack  5 . As shown in  FIG. 2 , spacing L 2  between the second biasing portion  82  and an inner surface of the support piece  54  adjacent to the outer periphery of the disk is slightly narrower than spacing L 1  between outer surfaces of the attaching pieces  42 ,  43  of the attaching portion  41  of the pickup  4 . The second biasing portion  82  is stretched outwardly to fit the attaching portion  41  of the base  40  between the second biasing portion  82  and the support piece  54  adjacent the outer peripheral of the disk, thereby biasing the attaching piece  43  of the base  40  toward the support piece  54  to cause the attaching piece  43  to contact with the support piece  54  at all times. Incidentally the biasing force of the second biasing portion  82  has an amplitude such that the rack  5  turns about the rail  21  free of trouble.  
      Referring to  FIG. 5 , the spring member  8  is formed by spring steel wire. The V-shaped bent portion comprises a ring-shaped attaching portion  83  formed by concentrically winding the spring steel wire a plurality of turns, and a cylindrical portion  84  formed by concentrically winding the wire a plurality of turns at a side end of the second biasing portion  82 . One end of the cylindrical portion  84  extends in an L-shape toward the ring-shaped attaching portion  83  to provide the second biasing portion  82 . The other end of the spring member  8  is bent so as to be folded outwardly in an approximately J-shape, thereby forming a contact portion  81   a  with the base  40 .  
      As shown in  FIG. 4 , the spring member  8  has the ring-shaped attaching portion  83  to be fitted around a circular boss  55  on the spring attaching portion  51  of the rack  5 , and the cylindrical portion  84  to be fitted into the latch portion  57  on the rack  5  to thereby be latched. The rack  5  has retainer pieces  56  provided at a plurality of positions for covering a linear part of the spring member  8 .  
      With reference to  FIG. 6 , the contact portion  81   a  of the spring member  8  is in contact with a receiving portion  46  formed on the base  40 . As shown in  FIG. 6  and  FIG. 7 , arranged on the chassis  1  are a switch  74  to be turned on when the pickup  4  is positioned for reading signals as opposed to the middle position between the TOC area and the barcode area of the disk, and a stopper  61  for restraining the further movement of the pickup  4  when the pickup  4  is positioned for reading information from the barcode area. A press piece  59  provided on the rack  5  presses an actuating piece  75 , turning on the switch  74 , to cutoff current supply to the motor  71  of the drive device  7 , thereby ceasing the movement of the pickup  4 .  
      When the pickup  4  is positioned for reading information from the barcode area, the stopper  61  serves also as a mechanism  6  for controlling mesh release to control the movement of the mesh release mechanism  3 , i.e., a notch  58  engageable with the stopper  61  is provided on an end surface of the rack  5  on the inner periphery of the disk which surface is opposed to the rack face  52 , causing an inner surface of the notch  58  facing the inner periphery of the disk to be in contact with the stopper  61 , whereby the movement of the rack  5  is restrained.  
      As shown in  FIG. 8  and  FIG. 9 , when the stopper  61  is engaged with the notch  58 , there merely exists a small clearance S between the face of the notch  58  opposed to the rack face  52  and the stopper  61  so as not to be in contact with the rack  5 . Thus even if a great force acts on the rack  5  upon the pickup  4  reaching the position for reading information from the barcode area of the disk, the stopper  61  interrupts the turn of the rack  5  in a direction away from the pinion  73 , to thereby prevent the release of mesh between the rack  5  and the pinion  73 . However, when the pickup  4  is positioned for reading signals from the content signal recording area, a great impact acts onto the rack  5  by the player&#39;s falling, etc., to turn the rack  5  about the rail  21  by the operation of the mesh release mechanism  3 , to release the mesh between the rack  5  and the pinion  73 . This precludes the damage to teeth of the rack  5  and the pinion  73 .  
       FIG. 11  shows control of the pickup drive device  7  when a command is given to read signals from the content signal recording area of the disk.  FIG. 12  shows control of the pickup drive device  7  when a command is given to read information from the barcode area of the disk. Incidentally, “SLED movement” indicated in the illustrations means the radial movement of the pickup while “SLED voltage” means voltage to be applied on the pickup drive device  7 .  
      When a command is given to read signals from the content signal recording area of the disk, first SLED voltage  1  is applied on the pickup drive device, as shown in  FIG. 11 , to move the pickup toward the inner periphery of the disk. The switch is thereafter turned on to detect that the pickup is positioned for reading signals as opposed to the middle position between the TOC area and the barcode area, whereupon SLED voltage  3  is applied on the pickup drive device for a predetermined period of time from the time of the detection (time  2 ), thereby moving the pickup in a reverse direction (in a direction of outer periphery of the disk), followed by reading the signals from the content signal recording area.  
      On the other hand, when a command is given to read information from the barcode area of the disk, first SLED voltage  1  is applied on the pickup drive device to move the pickup toward the inner periphery of the disk, as shown in  FIG. 12 . The switch is thereafter turned on to detect that the pickup is positioned for reading information as opposed to the middle position between the TOC area and the barcode area, whereupon drive voltage for the pickup drive device is reduced to SLED voltage  2 , holding the SLED voltage  2  for a given period of time (time  1 ), to move the pickup further in the same direction (in a direction of the inner periphery of the disk). Thus the pickup reaches a position opposed to the barcode area of the disk simultaneously when the pickup is restrained from further moving by the stopper. This causes the pickup to read a barcode from the barcode area. Incidentally the SLED voltage  2  can be set to the same voltage as the SLED voltage  1  depending on the conditions.  
       FIG. 10  illustrates the control procedure when a command is given to read information from the reference information recording area of the disk. First in step S 1  SLED voltage  1  is set to apply the voltage on the pickup drive device. Subsequently in step S 2  an inquiry is made as to whether the switch is turned on. When the answer to the inquiry of step S 2  is affirmative, step S 3  follows to set SLED voltage  2  to apply the voltage on the pickup drive device. In step S 4  a timer is started, and then step S 5  follows to inquire whether the time  1  has elapsed. When the answer to the inquiry of step S 5  is affirmative, step S 6  follows to complete the application of the SLED voltage.  
      By the execution of the control procedure described, the pickup moves from the position opposed to the content signal recording area of the disk toward the inner periphery of the disk at a relatively rapid speed, and is positioned as opposed to the middle position between the TOC area and the barcode area. The pickup thereafter moves further toward the inner periphery of the disk at a relatively slow speed, and reaches the position opposed to the barcode area. In this case, the rack  5  bumps the stopper  61 , but the reduced moving speed as described will not produce the great impact force to reduce stress applied on teeth face of the rack  5 . Consequently the pickup drive device  7  is given a prolonged life.  
      With the disk player embodying the present invention, as described above, when the pickup  4  is positioned as opposed to the barcode area of the disk, mesh between the rack  5  and the pinion  73  is not easily released owing to the operation of the mechanism  6  for controlling mesh release, so that unlike the conventional one, there is no likelihood of the problem of noise involved in teeth skip caused by releasing the mesh between the rack and the pinion due to the reaction when the pickup  4  bumps the stopper by inertia.  
      Furthermore, when the pickup is positioned as opposed to the barcode area of the disk, in the case where a great impact is produced by the player&#39;s falling, etc., free turn of the rack  5  is interrupted while the distance between a latch portion created by the stopper  61  of the rack  5  and the mesh portion thereof with the pinion  73  becomes great, so that the rack  5  is elastically deformed in a twisted direction with the latch portion created by the stopper  61  serving as a fixed end, resulting in release of the mesh between the rack  5  and the pinion  73 , whereby damage to the teeth is precluded.  
      Further, in the case where force of mesh between the rack  5  and the pinion  73  is set moderately high in the operation of the mesh release mechanism  3 , teeth skip of the rack  5  and the pinion  73  can be prevented even though drive voltage of the pickup drive device  7  is set to a high value to some extent in moving the pickup  4  to the position opposed to the barcode area. Thus the values of the drive voltage to be applied on the pickup drive device  7  can be in the broader range.  
      The device of the invention is not limited to the foregoing embodiment in construction but can be modified variously by one skilled in the art without departing from the spirit of the invention as set forth in the appended claims.