Patent ID: 8310228

Claim:
A resolver comprising: a disc-shaped rotor provided with a planar tertiary coil and a planar rotor-side rotary transformer coil; and a stator placed to concentrically face the disc-shaped rotor in an axial direction, the stator being formed in flat plate shape and provided with a planar primary coil, a planar secondary coil and a planar stator-side rotary transformer coil, wherein the planar secondary coil is placed at a position displaced by 90 degrees in electrical angle with respect to the planar primary coil, the planar primary coil and the planar secondary coil are placed to face the planar tertiary coil, the planar rotor-side rotary transformer coil is placed to face the planar stator-side rotary transformer coil, and the disc-shaped rotor is provided with a rotor back core made of a magnetic material and placed in a position corresponding to the planar tertiary coil and a rotary transformer back core placed in a position corresponding to the planar rotor-side rotary transformer coil, and the rotor back core and the rotary transformer back core are separated from each other in a radial direction of the disc-shaped rotor.