To provide a torque motor which is easy to assemble and has smooth and flat torque characteristic.
A rotor core 41 is made elliptic in the cross section which is orthogonal to the rotation axis of the case 41. A permanent magnet 43 is formed integrally into an annular form being elliptic at the cross section orthogonal to the rotation axis of the rotor core 41, and it is magnetized in one direction parallel with the short diameter. An inside periphery 50a of the stator core 50 is made substantially right circular. A length a of the long diameter of the rotor core 41 and a length b of the short diameter are set, so that B1= B3=B2cosθ is, when defining the magnetic flux density in the radial direction at an intersecting point 44a of the short diameter of the permanent magnet 43 to be B1, the magnetic flux density in the direction of magnetization in the position in the circumferential direction of the outer periphery 44 which forms an angle θ with the intersecting point 44a of the short diameter, with a center 60 of the rotor core 41 as an apex, to be B2, and the magnetic flux density in the radial direction at a position in the circumferential direction of the outer periphery 44, which forms the angle θ with the intersecting point 44a of the short diameter to be B3.
KAJITA YUKINOBU
TANIMURA HIROSHI
