A structure of a rotor changeable of a magnetic force is provided, which includes a rotor core and a plurality of magnetic pole parts disposed therein. Each magnetic pole part includes a radially-magnetized fixed magnetic-force magnet and a circumferentially-magnetized variable magnetic-force magnet. A cavity part is disposed between the fixed magnetic-force magnet and the variable magnetic-force magnet. The cavity part has a cross-section extending from an end part of the fixed magnetic-force magnet toward an opposing surface. The cavity part is formed so that a distance between the variable magnetic-force magnet and the cavity part in the circumferential direction becomes larger as the cavity part approaches the opposing surface, and a width of the cavity part in the circumferential direction becomes smaller as the cavity part separates from the fixed magnetic-force magnet in the radial direction.

A rotor including a rotor core and magnetic pole parts provided therein is provided. Each magnetic pole part includes a fixed magnetic-force magnet of which a magnetizing direction is oriented in a radial direction, first variable magnetic-force magnets disposed radially outward of the fixed magnetic-force magnet on both sides thereof in a circumferential direction so that magnetizing directions are oriented in the circumferential direction, a first cavity part formed in the rotor core to extend between a position radially inward of the fixed magnetic-force magnet and a position radially inward of the first variable magnetic-force magnet, and a second cavity part formed in the rotor core to be separated radially outward from the first cavity part, and extend toward the first variable magnetic-force magnet in the circumferential direction from a position radially outward of a surface on a first variable magnetic-force magnet side of the fixed magnetic-force magnet side.

A rotor including a rotor core and magnetic pole parts provided therein is provided. The magnetic pole parts are lined up along an outer circumferential surface of the rotor core. Each magnetic pole part includes a fixed magnetic-force magnet with a radially-oriented magnetizing direction, first variable magnetic-force magnets with circumferentially-oriented magnetizing directions, a first cavity part formed in the rotor core to extend between a position radially inward of the fixed magnetic-force magnet and a position radially inward of the first variable magnetic-force magnet, and auxiliary fixed magnetic-force magnets disposed on both sides of the fixed magnetic-force magnet in a circumferential direction so that magnetizing directions thereof are oriented in the circumferential direction. A pole surface with the same polarity as a pole surface facing radially outward of the fixed magnetic-force magnet is located on a fixed magnetic-force magnet side of the auxiliary fixed magnetic-force magnets.

A rotor structure including a rotor, a stator, and magnetic pole parts is provided. Each magnetic pole part includes a radially-magnetized fixed magnetic-force magnet, first variable magnetic-force magnets which are disposed radially outward of, and at both circumferential end sides of, the fixed magnetic-force magnet, respectively, and have a magnetization state that is changeable in the circumferential direction by a magnetic flux, and a high magnetic-reluctance part formed between the fixed magnetic-force magnet and the first variable magnetic-force magnet in the circumferential direction and having a magnetic reluctance higher than the rotor core. The high magnetic-reluctance part includes a first vertically extending part radially extending at a position near the fixed magnetic-force magnet, a second vertically extending part radially extending at a position near one first variable magnetic-force magnet in the circumferential direction, and a laterally extending part connecting the first and second vertically extending parts in the circumferential direction.