BRUSHLESS DC MOTOR CAPABLE OF PREVENTING A MAGNETIC FORCE LINE FROM BEING DISTRIBUTED IN THE ALTERNATING SECTION OF N-POLE AND S-POLE OF A ROTOR

摘要

PURPOSE: A brushless DC motor is provided to reduce back electromotive forces of the coil wound on a stator and operate the motor in a stable manner by preventing a magnetic force line from being distributed in the alternating section of N-pole and S-pole of a rotor. CONSTITUTION: A brushless DC motor comprises a stator(3) having phases wound with coils; a rotor(4) constituted by predetermined numbers of poles such that magnetic flux is concentrated on the selected phase of the stator; and a power switching unit for determining the direction of the current flowing along the coils of each phase in accordance with the input signal of a polarity detection encoder. The rotor includes a soft iron plate(12) including a silicon material; a permanent magnet(11) disposed on the soft iron plate; and a non-magnetic shaft(13) for fixing the soft iron plate where the permanent magnet is disposed. A magnetic field induction path(15) for inducing magnetic fields of the permanent magnet is arranged on the soft iron plate where the outer end of the permanent magnet is disposed.