Kaimori Tomoaki,Nakayama Kenichi,Saito Yasuyuki,Ikeda Dai

A rotor is provided with a rotational axis in which at least one keyway is provided to the outer peripheral surface in the axial direction, and a rotor core having a key which is protruded to the inner peripheral side and fitted into the keyways, wherein, in the rotor core, recessed sections spread on the outside in the radial direction are formed on both sides of the key in the circumferential direction; wherein, in the bottom sections of the recessed sections, planar sections for relieving the stress on both sides of the key in the circumferential direction are formed; wherein the planar sections are linear sections extending with a predetermined length in a direction orthogonal to the direction in which the key is protruded, and at the opposite key side ends of the linear sections, connection side surfaces extending to the inner periphery of the rotor core are formed consecutively; wherein first corner sections in which the side surface of the key and the key side ends of the linear sections are connected