Chucking device and brushless motor and disc driving device in which the chucking device is installed

Abstract

A cone part in a chucking device capable of freely attaching and detaching a disc having a disc shape includes an abutting portion for abutting an inner peripheral surface of a central through hole of the disc with substantially equal forces along an entire circumference thereof and aligning the disc. The cone part is made of a resin material having a high slidability than that of a material used for the disc.

1 . A chucking device capable of attaching a disc having a central through hole rotating around a predetermined rotational axis in a detachable manner, the chucking device comprising:
 a turn table provided to be concentric to the rotational axis and having a placement surface on which the disc is placed;   a cone part axially movable including an abutting portion positioned on an upper-surface side of the turn table, the abutting portion having a tilting surface a diameter of which increases along axially downward direction and retains an inner peripheral surface of the central through hole of the disc with pressure approximately uniform in a circumferential direction;   a guiding portion which is a portion of the cone part, the upper-surface having a shape of a side face of a truncated cone with a diameter of which increases along axially downward direction, a radially outer edge of the upper-surface connected to the abutting portion at the upper-edge thereof from an axially upper direction;   a spring provided between the turn table and the cone part, the spring applying pressure to the cone part toward axially upward direction; and   an end part provided on an upper-surface side of the cone part, inhibiting the movement toward the upper direction beyond a predetermined position; wherein   at least a surface of the abutting portion of the cone part is made of a resin material which shows a smaller frictional coefficient against the inner peripheral surface of the central through hole of the disc than a frictional coefficient of a metal material thereagainst.   
     
     
         2 . The chucking device as claimed in  claim 1 , wherein the cone part is made of polyacetal or acetal resin. 
     
     
         3 . The chucking device as claimed in  claim 1 , wherein an angle φ formed by the tilting surface of the abutting portion in the cone part and the rotational axis satisfies the relationship of approximately 12 degrees≦φ≦approximately 15 degrees. 
     
     
         4 . The chucking device as claimed in  claim 1 , wherein a surface roughness Ry of the cone part satisfies the relationship of approximately 5 μm≦Ry≦approximately 20 μm. 
     
     
         5 . The chucking device as claimed in  claim 1 , wherein an axial surface roughness Rya of the abutting portion in the cone part satisfies the relationship of approximately 5 μm≦Rya≦approximately 20 μm. 
     
     
         6 . The chucking device as claimed in  claim 3 , wherein a spring force F of the spring satisfies the relationship of approximately 1.2N≦F≦approximately 2.0N. 
     
     
         7 . The chucking device as claimed in  claim 1 , wherein the disc is made of polycarbonate, and
 a coefficient of static friction μ between the central through hole of the disc and the abutting portion of the cone part satisfies the relationship of approximately 0.15 approximately 0.30.   
     
     
         8 . A brushless motor for rotating a disc having a central through hole comprising:
 a chucking device as claimed in  claim 1 ;   a rotational member to which the chucking device is secured, the rotational member integrally rotating around the rotational axis;   a fixed member having a bearing part for rotatably supporting the rotational member;   a rotor magnet rotating integrally with the rotational member; and   a stator facing the rotor magnet, the stator generating a driving force in a direction of the rotation around the rotational axis.   
     
     
         9 . A disc driving device in which a blushless motor for rotating a disc having a central through hole is equipped, comprising:
 a blushless motor as claimed in  claim 8 ;   a pickup mechanism for recording and reproduction information with respect to the disc;   a clamp member for retaining the disc by sandwiching the disc between itself and the placement surface;   a disc movement mechanism for moving the disc to the placement surface; and   a housing cabinet for housing the pickup mechanism, the clamp member and the disc movement mechanism.   
     
     
         10 . A chucking device capable of attaching a disc having a central through hole rotating around a predetermined rotational axis in a detachable manner, the chucking device comprising:
 a turn table provided to be concentric to the rotational axis and having a placement surface on which the disc is placed;   a cone part axially movable including an abutting portion positioned on an upper-surface side of the turn table, the abutting portion having a tilting surface a diameter of which increases along axially downward direction and retains an inner peripheral surface of the central through hole of the disc with pressure approximately uniform in a circumferential direction;   a guiding portion which is a portion of the cone part, the upper-surface having a shape of a side face of a truncated cone with a diameter of which increases along axially downward direction, a radially outer edge of the upper-surface connected to the abutting portion at the upper-edge thereof from an axially upper direction;   a spring provided between the turn table and the cone part, the spring applying pressure to the cone part toward axially upward direction; and   an end part provided on an upper-surface side of the cone part, inhibiting the movement toward the upper direction beyond a predetermined position; wherein   a surface roughness Ry of the cone part satisfies the relationship of approximately 5 μm≦Ry≦approximately 20 μm.   
     
     
         11 . The chucking device as claimed in  claim 10 , wherein an axial surface roughness Rya of the abutting portion in the cone part, the Rya being measured along the axial direction, satisfies the relationship of approximately 5 μm≦Ry≦20 μm. 
     
     
         12 . The chucking device as claimed in  claim 10 , wherein
 the disc is made of polycarbonate, and   a coefficient of static friction μ between the inner surface of the central through hole of the disc and that of the abutting portion of the cone part satisfies the relationship of approximately 0.15≦μ≦approximately 0.30.   
     
     
         13 . A brushless motor for rotating a disc having a central through hole comprising:
 a chucking device as claimed in  claim 10 ;   a rotational member to which the chucking device is secured, the rotational member integrally rotating around the rotational axis;   a fixed member having a bearing part for rotatably supporting the rotational member;   a rotor magnet rotating integrally with the rotational member; and   a stator facing the rotor magnet, the stator generating a driving force in a direction of the rotation around the rotational axis.   
     
     
         14 . A disc driving device in which a blushless motor for rotating a disc having a central through hole is equipped, comprising:
 a blushless motor as claimed in  claim 13 ;   a pickup mechanism for recording and reproducing information with respect to the disc;   a clamp member for retaining the disc by sandwiching the disc between itself and the placement surface;   a disc movement mechanism for moving the disc to the placement surface; and   a housing cabinet for housing the pickup mechanism, the clamp member and the disc movement mechanism.   
     
     
         15 . A chucking device capable of attaching a disc having a central through hole rotating around a predetermined rotational axis in a detachable manner, the chucking device comprising:
 a turn table provided to be concentric to the rotational axis and having a placement surface on which the disc is placed;   a cone part axially movable including an abutting portion positioned on an upper-surface side of the turn table, the abutting portion having a tilting surface a diameter of which increases along axially downward direction and retains an inner peripheral surface of the central through hole of the disc with pressure approximately uniform in a circumferential direction;   a guiding portion which is a portion of the cone part, the upper-surface having a shape of a side face of a truncated cone with a diameter of which increases along axially downward direction, a radially outer edge of the upper-surface connected to the abutting portion at the upper-edge thereof from an axially upper direction;   a spring provided between the turn table and the cone part, the spring applying pressure to the cone part toward axially upward direction; and   an end part provided on an upper-surface side of the cone part, inhibiting the movement toward the upper direction beyond a predetermined position; wherein   the disc is made of polycarbonate, and   a coefficient of static friction μ between the surface of the central through hole of the disc and that of the abutting portion of the cone part satisfies the relationship of approximately 0.15≦μ≦approximately 0.30.   
     
     
         16 . A brushless motor for rotating a disc having a central through hole comprising:
 a chucking device as claimed in  claim 15 ;   a rotational member to which the chucking device is secured, the rotational member integrally rotating around the rotational axis;   a fixed member having a bearing part for rotatably supporting the rotational member;   a rotor magnet rotating integrally with the rotational member; and   a stator facing the rotor magnet, the stator generating a driving force in a direction of the rotation around the rotational axis.   
     
     
         17 . A disc driving device in which a blushless motor for rotating a disc having a central through hole is equipped, comprising:
 a blushless motor as claimed in  claim 16 ;   a pickup mechanism for recording and reproduction information with respect to the disc;   a clamp member for retaining the disc by sandwiching the disc between itself and the placement surface;   a disc movement mechanism for moving the disc to the placement surface; and   a housing cabinet for housing the pickup mechanism, the clamp member and the disc movement mechanism.