Abstract: A motor, characterized in that a balance-correcting portion is provided within a range of ±L/3 in the axial direction from the center of the overall length in the axial direction of the rotor of the motor, where L denotes the overall length; a yarn winder provided with the motor; and a yarn package production method using the yarn winder. A long spindle capable of rotating at a high speed is used to allow yarns to be wound at a high speed in a large amount, thereby improving the productivity of yarn packages.

Abstract: In a bobbin holder 1 according to the present invention, flexible rings 3a to 3h each comprising a ring-like spring member 30, a pair of solid rings 38 fixed to both side surfaces of the paring member 30, a pair of solid rings 38 fixed to both side surfaces of the spring member 30 and rubber members 39 disposed on the inner and outer peripheries of the spring member between the solid rings, are loosely fitted between a cylindrical bobbin 23 and a rotary cylinder 2 to which the bobbin is inserted. The solid rings 38 are pressed from both side surfaces of the flexible ring, respectively, and the ring-like spring member 30 undergoes deformation in the direction of an outer diameter so as to increase its diameter. As the rubber members 39 come into close contact with the inner peripheral surface of the bobbin 23, the bobbin can be gripped. In this case, in the bobbin holder described above, the difference .delta.