Patent ID: 8095946

Claim:
An optical disk motor for rotating a disc having a central through hole, comprising: a shaft of a first single piece member having a rotational axis; a rotor holder of a second single piece member comprising an inner part extending axially downward to secure the shaft; a cap part having an upper surface; and a cylindrical part securing a rotor magnet, wherein there is a first vertical length from a lower end of the inner part to the upper surface; a third single piece member provided to be concentric to the rotational axis, the third single piece member having a placement face above which the disc is placed; a through hole having an innermost inner surface having a second vertical length; and a lower surface secured to an upper surface of the rotor holder; a cone part positioned on an upper-surface side of the third single piece member, the cone part comprising: an 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 sliding surface for sliding the cone part on the shaft, the sliding surface having a third vertical length; 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; and a spring provided between the third single piece member and the cone part, the spring applying pressure to the cone part toward axially upward direction; 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, wherein there is a gap between the cone part and the third single piece member when the cone part takes its uppermost position, wherein the third vertical length is longer than the second vertical length; wherein there is a fourth vertical length between the slidable surface and the innermost inner surface when the cone part takes its uppermost position, the fourth vertical length being shorter than the first vertical length, wherein the first vertical length, the second vertical length, the third vertical length and the fourth vertical length are along with the shaft.