Abstract
Camcorders would be more compact, lighter, and lower-priced, if their drive motors were built into their lens barrels. This paper proposes a new direct-drive motor built into a lens barrel. A unique rolling mechanism for bearing a rotor was incorporated into the motor to reduce the friction torque and power consumption of the armature windings. Balls are arrayed between a helical raceway made on the inner surface of a lens barrel shell and the raceway groove of a ring magnet. Three-dimensional algebraic formulas for the air-gap magnetic flux densities are presented, taking account of the effect of the raceway on the magnetic flux densities. The angular air-gap magnetic flux density distributions at the winding centers are sinusoidal and repeated for all poles. The calculated values agree well with the measured values, and the formulas have been verified.
