Abstract: A stator includes a core-back portion, teeth portions, insulators, and coils. The teeth portions extend radially from a circumferential surface of the core-back portion. The insulators are respectively mounted to the teeth portions. The coils are respectively mounted to the insulators. A tip end of the tooth portion has a circumferential width equal to or smaller than that of a base end of the tooth portion. The tip end has an axial width equal to or smaller than that of the base end. The insulator includes a tube portion accommodating the tooth portion. The tube portion includes a first opening existing at the tip end and a second opening existing at the base end. The first opening has an axial width smaller than an axial width of the second opening in a state that each of the insulators is removed from each of the teeth portions.

Abstract: A stator includes a core-back portion, teeth portions, insulators, and coils. The teeth portions extend radially from a circumferential surface of the core-back portion. The insulators are respectively mounted to the teeth portions. The coils are respectively mounted to the insulators. A tip end of the tooth portion has a circumferential width equal to or smaller than that of a base end of the tooth portion. The tip end has an axial width equal to or smaller than that of the base end. The insulator includes a tube portion accommodating the tooth portion. The tube portion includes a first opening existing at the tip end and a second opening existing at the base end. The first opening has an axial width smaller than an axial width of the second opening in a state that each of the insulators is removed from each of the teeth portions.

Abstract: A small, lightweight relative drive device is provided, which is capable of producing large torque. The relative drive device of a two-phase magnetic excitation type according to an aspect of the invention comprises first and second coil groups and a magnet group. The magnet group includes magnets disposed with alternating north and south poles facing the first and second coil groups. The first and second coil groups are disposed at positions that are out of phase with each other by an odd multiple of ?/2 in electrical angles. The coils in the first and second coil groups have substantially no magnetic material cores, and the relative drive device has substantially no magnetic material yoke for forming a magnetic circuit.