Patent ID: 6972503

Claim:
A brushless motor comprising: a stator, and a permanent magnet used as a rotor, wherein the permanent magnet includes a plurality of magnetic poles having alternating polarity, wherein an intensity of magnetization increases from zero to a predetermined maximum over a magnetization-inclined range extending from respective boundaries of each pole to a circumferential position P situated a non-zero distance from the respective boundaries, and is constant over a remaining portion of each pole such that a graph of magnetic intensity versus distance from a boundary of a respective pole forms a trapezoidal shape, and wherein the magnetization-inclined range is set as α=β× r×θ T 0.375≦ r≦ 0.550 where α: magnetization-inclined range, θ T : 360 degree/(the least common multiple of the slot number and the magnet pole number); β: constant derived by dividing the least common multiple M of the magnet pole number n p and the slot number n s by two times the slot number n s (β:β=M/2n s ), and multiple thereof, and r: cogging torque relational number.