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A low noise brushless dc motor has a rotor with a permanent magnet and a stator with a bearing system mounting a shaft for rotating the rotor. The bearing system includes at least one axially extending bearing surface that terminates in axially spaced apart ends defining the outer axial limits of th

A low noise brushless dc motor has a rotor with a permanent magnet and a stator with a bearing system mounting a shaft for rotating the rotor. The bearing system includes at least one axially extending bearing surface that terminates in axially spaced apart ends defining the outer axial limits of the bearing surface. Magnetic components of the rotor and the stator define a magnetic circuit. the magnetic components have an eccentricity creating an asymmetry in the magnetic circuit that causes a resultant lateral magnetic force to be applied on the shaft at a point axially inside the outer axial limits of the bearing surface, whereby the shaft exerts a pressure along the bearing surface between both ends of the bearing surface in a direction perpendicular to the rotor axis.

대표청구항 ▼

A low noise brushless dc motor comprising a rotor having a permanent magnet with an inside diameter; a shaft made fast in the rotor to rotate therewith; a stator; bearing means contained in the stator mounting the shaft for rotating the rotor and defining an axis of the motor around which the rotor

A low noise brushless dc motor comprising a rotor having a permanent magnet with an inside diameter; a shaft made fast in the rotor to rotate therewith; a stator; bearing means contained in the stator mounting the shaft for rotating the rotor and defining an axis of the motor around which the rotor rotates, the bearing means including at least one axially extending bearing surface rotatably supporting the shaft and terminating in axially spaced apart ends defining outer axial limits of the bearing surface; an iron core mounted on the bearing means and forming part of the stator; an active winding on the iron core providing an electromagnet in the stator when the winding is energized, magnetic components of the rotor and the stator defining a magnetic circuit in the motor, the magnetic components of the rotor and the stator having an eccentric configuration creating an asymmetry in the magnetic circuit and causing a resultant lateral magnetic force to be applied on the shaft at a point axially inside the outer axial limits between bearing points of the bearing surface, the shaft consequently exerting a pressure along the bearing surface between both ends of the bearing surface in a direction perpendicular to the rotor axis, whereby noise is reduced and service life of the bearing surface is increased; and magnet means mounted on the stator creating a defined starting position of the permanent magnet of the rotor and generating reluctance torque in the motor.