Permanent magnet type motor

A permanent magnet motor comprising:

• a stator having a stator coil;
• and
• a rotor, having a plurality of axially bored magnet slots, provided in an amount for the number of poles in the rotor iron core, permanent magnets being fixed into the magnet slots so that neighboring magnetic poles are opposites;
• wherein
• in the rotor, the outer peripheral shape of rotor magnetic-pole portions, formed along each magnetic-pole face on the outer peripheral side of the permanent magnets, is formed so that, in a circumferentially central portion thereof, the distance from the center of the rotor iron core is longest, and, at the inter-polar space between a first of the permanent magnets and a second of the permanent magnets, the distance from the center of the rotor iron core is shortest, and so that the outermost surface of rotor magnetic-pole portions forms an arc, the radially outer side of each magnet slot substantially matching the arc, and being bored in an approximate bow shape;
• and
• given that sheath thickness tc formed by the outer-side surface of each permanent magnet and the outermost surface of each rotor magnetic-pole portion is substantially constant, and letting the thickness of each of the permanent magnets as a whole formed in an approximate bow shape be the magnet thickness tm, then the relation 0.143≦tc/tm≦0.174 is satisfied.