To obtain high torque at fully-open and fully-closed times, when a torque motor actually requires torque.
A rotatable rotor 5-1 and at least one magnetic force source are integrally built in with a magnetic path in-between. Magnets 6-3 and 6-4 having integral or separate north poles and south poles magnetized in opposite directions are placed on the rim of the rotor 5-1, and three magnetic pole pieces 9 to 11 are placed at the rim of an opening with the rotor 5-1 placed therein with the two adjacent magnetic pole pieces coupled with each other through coupling paths to form a torque motor. In this torque motor, both the ends of the magnets 6-3 and 6-4 are relatively thickened by thinning their central portions on the side in contact with the rotor 5-1. That is, a thickness l2 of both the ends of the magnets 6-3 and 6-4 is relatively increased by reducing a thickness l1 of their central portions on a side, where the magnets are in contact with the rotor 5-1, and thereby a magnet shape suitable for driving throttle valves is obtained.
UCHI HIROTO
MURAJI TETSURO
