Patent ID: 6982505

Claim:
A prestressing structure for rotationally balancing a motor, comprising: a motor stator having an axial tube at its center portion, the axial tube including a top end; a magnetically conductive member formed at the top end of the axial tube and including at least one upper surface; a motor rotor including a shaft seat and a rotary shaft mounted thereto at its center portion, the rotary shaft extending through the axial tube when assembled; and a balancing magnet mounted to the shaft seat of the motor rotor and including at least one lower surface attracting the upper surface of the magnetically conductive member such that a gap formed between said upper surface of the magnetically conductive member and said lower surface of the balancing magnet is minimized to prevent dust from entering an interior of the axial tube when the motor is turning; wherein said gap is approximately closed by magnetic attraction of said upper surface of said magnetically conductive member towards said lower surface of said balancing magnet when the motor is stopped.