Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1985-07-30
1987-04-28
Duggan, Donovan F.
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, 310269, H02K 2112
Patent
active
046617361
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rotor for a synchronous motor.
BACKGROUND ART
Among synchronous motors, a salient-pole synchronous motor having a rotor including permanent magnets as salient poles and disposed rotatably inside a stator having excitation coils of a plurality of phases for producing a revolving magnetic field is well known. In such a salient-pole synchronous motor, it is necessary that the field magnetic flux distribution due to the salient poles of the rotor, which interacts with the stator having an armature flux distribution of a sinusoidal waveform, be a sinusoidal waveform. One of the measures taken to set up such a magnetic field distribution of sinusoidal waveforms requires that the form of the pole face of each magnetic pole be decided so that the pole face of each magnetic pole of the rotor, G.sub.min is the minimum gap length along the axis of the magnetic pole, and .theta. is an angle to the right or to the left from the axis of the magnetic pole.
As illustrated in FIG. 1A, when the magnetic poles of a salient-pole synchronous motor are constituted only by permanent magnets, a rotor 2 rotatably disposed inside a stator 1 needs only permanent magnets 6 attached in the form of salient poles to the outer circumference of a spider 5 attached to a motor shaft 4, and hence the rotor 2 can be easily assembled. However, forming the permanent magnet 6, in general, is difficult, and forming a salient pole having a pole face 3 of the shape capable of establishing a magnetic flux distribution of a sinusoidal waveform is very difficult.
Accordingly, as illustrated in FIG. 1B, a widely employed rotor has a construction in which the projecting end face of a permanent magnet 6a is formed in a flat plane or in a plane of a circular arc, which can be easily formed, and a yoke piece 7 having a surface of a form capable of establishing the above-mentioned magnetic flux distribution of a sinusoidal waveform is attached to the projecting end face of the permanent magnet 6a. Since the yoke piece can be easily formed, this construction is capable of establishing a magnetic flux distribution of a sinusoidal waveform. However, this construction is complicated when assembled, reduces the mechanical accuracy and strength of the rotor, and requires an increased manufacturing cost.
DISCLOSURE OF THE INVENTION
Accordingly it is an object of the present invention to provide a rotor for a synchronous motor, capable of simplifying the processes of manufacturing and assembling the same and of rotating smoothly.
The present invention provides a rotor for a synchronous motor, rotatably supported inside a cylindrical stator provided with armature coils having a plurality of phases, comprising: a motor shaft; yoke means fixed to the motor shaft; a plurality of first magnetic poles formed by a plurality of permanent magnets fixedly disposed on the circumference of the yoke means at practically equal circumferential intervals; a plurality of second magnetic poles each projecting radially from the yoke means and disposed between the adjacent first magnetic poles; and a magnetic pole configuration in which the shape of the pole face of the second magnetic pole is decided dependent on the fixed form of the pole face of the adjacent first magnetic pole so that the distribution of the field magnetic flux set up by a pair of the adjacent first magnetic pole and the second magnetic pole is practically equivalent to a sinusoidal magnetic flux distribution in respect of the sweeping effect by the armature coil of each phase.
As mentioned above, in a salient-pole synchronous motor, it is necessary that the field magnetic flux distribution is a sinusoidal distribution in order to ensure smooth movement of the rotor, which means that the magnetic flux swept by the armature coil of the stator as the rotor rotates varies sinusoidally. Accordingly, when it is intended to obtain such an effect by a pair of the magnetic poles, the magnetic flux distribution of each of the paired magnetic poles need not necessari
REFERENCES:
patent: 3696260 (1972-10-01), Lace
patent: 4406958 (1983-09-01), Palmero et al.
International Search Report.
Amemiya Yoichi
Iwamatsu Noboru
Kawada Shigeki
Sogabe Masatoyo
Duggan Donovan F.
Fanuc Ltd.
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