BRUSHLESS DC MOTOR AND ROTOR MAGNET THEREFOR

摘要

PURPOSE:To facilitate magnetization and to reduce uneven spatial density distribution by providing magnetic grooves of a rotor magnet to the surface facing a stator and by magnetizing the whole rotor magnet. CONSTITUTION:A rotor magnet 11 is of four-pole radial magnetization. Grooves 12a and 12b have widths of each theta deg. in the central angle symmetrically with 180 deg. from a pole cut-over point (or a neutral point) to N and S poles in total 2theta deg.. With respect to the surface flux density distribution of the rotor magnet 11 at grooves 12a and 12b the surface flux density interlinking with stator poles is extremely lowered compared with other parts and approaches the surface flux density distribution of a rotor main magnet in the conventional art. On the other hand, since the neutral point appears at the position of 90 deg. without fail in case of four-pole magnetization, the addition of a rotor position detection magnet is observed in the conventional art is dispensed with.