Patent ID: 6987341

Claim:
A motor having a rotor with built-in permanent magnets, the rotor comprising: a) a cylindrically shaped rotor core having: i) a central axial hole; and ii) a plurality of openings surrounding the central axial hole, each opening has at least four surfaces including a top flat surface and a bottom flat surface, the top flat surface is adjacent to the contour of rotor core and extends along the circumference of the contour to form two side surfaces respectively on two ends of the opening, and a distance is between the two side surfaces and the contour of rotor core; b) a plurality of permanent magnets, each of the plurality of permanent magnets having a cross-section that matches each of the plurality of openings, each magnet being inserted into one of the plurality of openings; and wherein the two side surfaces in each of the plurality of openings are each parallel with an outer contour of the cylindrically shaped rotor core, the distance is ΔR and ΔR=(R 0 −Rm)≦0.7 mm, wherein R 0 is the outer radius of the motor rotor and Rm is the distance from the center of the motor rotor to the side surface, each opening further includes two parallel channel side surfaces, and the permanent magnet for such kind of opening is in corresponding shape, wherein the angle formed by the two adjacent parallel channel side surfaces is ΔΘ, and ΔΘ≦[(0.7/Rm)*(360/π)](deg), and Θ 2 is the angle defined by p and ΔΘ, p is the number of the permanent magnets, and when p≧4,Θ 2 =[(360/p)−ΔΘ]](deg), and Θ 1 is the half angle formed by the line segment between two ends of the top flat surface and the center of the motor rotor, and the length of the top flat surface is 2[(Rm*sinΘ1)], and the length of the bottom flat surface is 2[(Rm*sinΘ2)].