Rotor of brushless direct-current motor

Abstract

A permanent magnet rotor of a brushless direct current (BLDC) motor, in which cogging torque ripple and electromagnetic vibration noise transferred to the permanent magnet rotor can be blocked and a motor's power-to-weight ratio can be improved. A conventional BLDC motor has to use an electric steel sheet core so as to maintain the maximum magnetic flux density of the permanent magnet rotor and to minimize a rotating electric field loss. As a result, cogging torque vibration is unavoidably transferred to a load side through the motor rotary shaft. However, the rotor can enable stable driving of the BLDC motor by innovatively blocking the cogging torque vibration and the electromagnetic vibration noise and can greatly reduce the motor's weight by using a plastic or non-magnetic material instead of an electric steel sheet core.

Description

BACKGROUND[0001]1. Field[0002]One or more aspects of the embodiments discussed herein relates to a rotor of a brushless direct-current (hereinafter, referred to as “BLDC”) motor, and more particularly, to a rotor of an BLDC motor, which can prevent electromagnetic vibration and noise generated between a rotor and an armature from being transferred to a rotary shaft of the rotor during the motor driving to thereby minimize motor noise and can reduce the weight of the rotor to thereby maximize a motor's power-to-weight ratio.[0003]2. Description of the Related Art[0004]Generally, a conventional rotor of a brushless direct-current (BLDC) motor uses a permanent magnet and a rotor core is necessarily combined with a rotor shaft using a ferromagnetic body or an electric steel sheet in order to form a magnetic circuit of the permanent magnet.[0005]However, when the permanent-magnet rotor generates a rotation torque due to its interaction with a rotating magnetic field of an armature, elect...

AI Technical Summary

Benefits of technology

[0016]Accordingly, an aspect of the embodiments discussed herein has been made in view of the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a rotor of a BLDC motor, in which a permanent magnet of the rotor is formed integrally in a ring shape as one piece and has a magnetic circuit therein, thereby removing a need for a ferromagnetic for a separate magnetic circuit through which the magnetic flux of the permanent magnet can pass.

[0017]It is another aspect of the embodiments discussed herein to provide a rotor of a BLDC motor, which can be made of a non-magnetic material or a plastic material, thereby blocking motor noise and vibration transferred through the rotor, reducing unnecessary weight and improving motor's power-to-weight ratio and operating efficiency.

[0018]It is yet another aspect of the embodiments discussed herein to provide a rotor of a BLDC motor, which can prevent a permanent magnet of the rotor from being damaged by the thermal expansion of a sound-absorbing material that is formed inside the cylindrical permanent magnet in order to block noise.

Problems solved by technology

However, when the permanent-magnet rotor generates a rotation torque due to its interaction with a rotating magnetic field of an armature, electromagnetic cogging generated in an air gap between the rotor and the armature, torque ripple, or vibration caused by the interaction of electromagnetism is directly transferred to the rotor shaft and may be then transferred to the load side or may be amplified, thereby causing severe mechanical noise such as resonance noise.

Such vibration is directly transferred up to a load side through the rotor shaft 14, thereby amplifying mechanical vibration noise or causing resonance noise during the motor driving and increasing stress in a bearing while aggravating bearing noise, thus reducing the expected life span of a motor.

As a result, cogging torque vibration due to interaction with an armature core and electromagnetic vibration noise of the rotating magnetic field are unavoidably transferred to a load side through the motor rotary shaft.

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