Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1992-01-14
1994-10-11
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, 310261, H02K 2100
Patent
active
053550447
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a rotor structure of an electric synchronous motor, which is capable of cancelling a plurality of torque ripple components.
BACKGROUND ART
A conventional electric synchronous motor in which permanent magnets are used to construct a rotor thereof employs methods of reducing ripples in an output torque therefrom such as using a particular shaping of each of the permanent magnets or axially separating the rotor into a plurality of rotor components and arranging these rotor components to occupy one of two positions angularly displaced from one another about an axis of the rotor.
Nevertheless, the method of using a particular shaping of the permanent magnets is unable to completely cancel torque ripples from the output torque of the motor. Further, the method of arranging a plurality of rotor components of a synchronous motor at two angularly displaced positions fails to cancel all different torque ripples having respective different cycles, except for some specific torque ripples.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to provide a rotor structure of an electric synchronous motor, which is capable of cancelling a plurality of cyclic torque ripple components from an output torque of the motor.
In view of the above object of the invention, the present invention provides a structure of a permanent-magnet-included rotor for an electric synchronous motor generating an output torque containing therein "n" kinds of cyclic torque ripple components, the rotor being divided into 2.sup.n rotor elements having an equal longitudinal length respectively, these rotor elements being grouped into first through 2.sup.n-1 th pairs of rotor elements, and each pair of rotor elements including two rotor elements circumferentially shifted by an angle corresponding to a half of a wavelength of a first of the "n" kinds of torque ripple components, the 2.sup.n-1 pairs of said rotor elements being grouped into first through 2.sup.-2 th rotor sections, each rotor section including two said rotor-element pairs arranged to be circumferentially shifted by an angle corresponding to a half of a wavelength of a second of the "n" kinds of torque ripple components, and in turn, said rotor elements being finally grouped into two groups of rotor elements, said two groups being arranged to be circumferentially shifted from one another by an angle corresponding to a half of a wavelength of "n"th of the "n" kinds of torque ripple components.
In accordance with the above rotor structure for an electric synchronous motor, the arrangement of the 2.sup.n-1 rotor-element pairs circumferentially shifted by an angle corresponding to the half of the first of the "n" kinds of torque ripple components contributes to a cancelling of said first of the "n" kinds of torque ripple components, and the arrangement of the first through 2.sup.n-2 th rotor sections further contributes to a cancelling of the second of the "n" kinds of torque ripple components, and in turn, the arrangement of the two groups of rotor elements finally contributes to a canceling of the "n"th of the "n" kinds of torque ripple components. Thus, the permanent magnet-included rotor for the synchronous motor initially must be manufactured to include 2.sup.n rotor elements.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a rotor structure of an electric synchronous motor according to the present invention;
FIG. 2 is a schematic graphical view explaining an operation of the rotor structure of FIG. 1; and
FIG. 3 is a schematic graphical view explaining an operation of a rotor structure according to another embodiment of the present invention.
FIG. 4 is a front view of the rotor structure embodiment explained in FIG. 3.
BEST MODE OF CARRYING OUT THE INVENTION
The present invention will become more apparent from the ensuing description of the embodiments of the present invention with reference to the accompanying drawings.
Referring to FIG. 1, a rotor 10 for an electric synchronous motor,
REFERENCES:
patent: 4642502 (1987-02-01), Carpenter et al.
patent: 4739201 (1988-04-01), Brigham
patent: 4868438 (1989-09-01), Okamoto
patent: 4871934 (1989-10-01), Okamoto
patent: 5039897 (1991-08-01), Iwamatsu
Okamoto Takashi
Uchida Hiroyuki
Yamamoto Tomonaga
Fanuc Limited
Skudy R.
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