Magnetic levitated motor

Details Magnetic levitated motor Magnetic levitated motor

2000-08-18

2001-11-20

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

Reexamination Certificate

active

06320290

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a magnetic levitated motor in which a rotor is magnetically supported in non-contact and rotatable manner.
A magnetic bearing has been used for supporting a rotary member in non-contact manner. A radial type magnetic levitated motor is proposed which functions as a magnetic bearing and a motor. The magnetic levitation motor is advantageous in that it is capable of simultaneously exercising the rotor torque generation and the position control, but it is disadvantageous in that the stator structure and the control circuit are complex.
A magnetic levitated motor disclosed in Japanese Patent Publication No. 6-269144A includes a stator having magnetic poles formed on the inner face thereof, each magnetic pole being wound by a single pole coil a rotor made of permanent magnet, the rotor having M number of magnetic poles, which are confronted with the inner wall of the stator with a gap therebetween, and a controller for feeding current for generating a revolving magnetic field having (M±2) number of poles along the inner face of the stator and current for rotating the rotor to the coils of the stator, wherein a magnetic levitational force is developed through the magnetic interaction between the revolving magnetic field having (M±2) number of poles along the inner face of the stator and the permanent magnet of the rotor. The current for rotating the rotor is superposed on the current for developing the levitational force and the resultant is fed to the stator. As a result, the rotor is magnetically levitated and rotated.
The related magnetic levitated motor requires a complicated magnetic flux distribution for the stator. Therefore, its structure is complex, and complicated levitational force control is required. Accordingly, there is a limit in increasing the motor speed. Further its face is covered with the permanent magnet, so that a levitational force is weak, and its efficiency is unsatisfactory.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to provide a magnetic levitated motor which is simple in structure, and is made, by simple control, free from the mutual influence between the levitational force control and the rotational torque control, and reduced in axial length, and is high in its efficiency.
In order to achieve the above object, according to the present invention, there is provided a magnetic levitated motor comprising:
at least one rotor provided with a rotor magnet magnetized so as to have eight magnetic poles;
at least one stator confronted with the rotor while rotatably supporting the rotor with magnetic force, the stator provided with rotor driving coils confronted with the rotor magnet to generate a rotational torque in the rotor to rotate the rotor, and six bearing coils for generating a bearing force in a direction perpendicular to the rotational axis of the rotor; and
a displacement sensor for detecting displacement of the rotor with respect to a plane which is perpendicular to the rotational axis of the rotor,
wherein currents flowing in the bearing coils are controlled in accordance with output of the displacement sensor to keep the rotational axis of the rotor at a predetermined position.
In this configuration, since the number of magnetic poles of the rotor magnet is eight, and the number of the coils of the bearing coil set is six, the rotation and bearing coil sets may be formed to have the same configuration, and disposed at the same location while being laid one on the other. Therefore, the stator is simplified in construction. The probability that the magnetic levitational force control mutually influences the rotational torque control can be reduced.
Since the rotation and bearing coil sets may be formed to have the same configuration, the rotor driving coil set and the bearing coil set are integrated into a single common coil set, and bearing force generating current and rotational torque generation current, while being superposed one on the other, are fed to the single common coil.
The stator and the rotor may be arranged so as to constitute a planar confronting type motor. Preferably, two stators are provided such that two planar rotor magnets are arranged along the rotational axis thereof in between. The thus constructed motor is capable of producing larger levitational force and rotational torque, and performing the space four axes control except the position control in the rotational axis direction.
Alternatively, the stator and rotor may be arranged so as to constitute a cylindrical confronting type motor. Preferably, a pair of cylindrical rotor-stator sets are arranged along a common rotational axis of the rotors. The thus constructed motor is also capable of producing larger levitational force and rotational torque, and performing the space four axes control except the position control in the rotational axis direction.


REFERENCES:
patent: 4245869 (1981-01-01), Scheffer et al.
patent: 5111102 (1992-05-01), Meeks
patent: 5160877 (1992-11-01), Fujiwara et al.
patent: 6130494 (2000-10-01), Schob
patent: 6147425 (2000-11-01), Ueyama et al.
patent: 6166469 (2000-12-01), Osama et al.
patent: 6194800 (2001-02-01), Maruyama et al.
patent: 6208051 (2001-03-01), Ando
patent: 6-269144 (1994-09-01), None

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