Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-13
2003-07-22
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216006
Reexamination Certificate
active
06597079
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an interior permanent magnet synchronous motor wherein a rotor core has a plurality of permanent magnets incorporated or embedded therein and includes magnetic salient pole sections defined between each two adjacent permanent magnets, and more particularly to a permanent magnet-equipped synchronous motor utilizing both reluctance generated due to the salient pole sections of the rotor core and torque by the permanent magnets.
One of conventional synchronous motors wherein a core between magnetic poles of permanent magnets is provided with magnetic salient pole sections is disclosed in Japanese Patent Application Laid-Open Publication No. 205499/1996. The synchronous motor is constructed in such a manner that rotation of a rotor is limited to only one direction, to thereby displace the silent pole sections, resulting in restraining generation of torque pulsation.
Also in Japanese Patent Application Laid-Open Publication No. 256455/1996 a technology in which generation of torque pulsation is restrained by changing the width of magnetic poles of magnetic salient pole sections of reluctance synchronous motor or by displacing a part of pairs of magnetic salient pole sections thereof in a peripheral direction is disclosed.
Another conventional synchronous motor having permanent magnets incorporated therein is disclosed in Japanese Patent Application Laid-Open Publication No. 18328/1999. The conventional synchronous motor disclosed is so constructed that a width of a core between magnetic poles of permanent magnets is set so as to establish relationship represented by the following expression, to thereby restrain generation of cogging torque:
&thgr;min≦&thgr;≦&thgr;max
In the conventional interior permanent magnet synchronous motor, the open angle &thgr; of the rotor core between permanent magnet poles is defined to be within a range of &thgr;min≦&thgr;≦&thgr; max determined depending on the number of teeth, a configuration thereof and a size thereof. However, a timing at which torque is generated between the magnetic poles of the permanent magnets is varied depending on “the number of slots per pole and per phase” q of a stator, so that the synchronous motor fails to satisfactorily restrain cogging torque and torque pulsation.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a permanent magnet-equipped synchronous motor which is capable of sufficiently restraining both cogging torque and torque pulsation during feeding of electricity thereto.
In accordance with the present invention, a permanent magnet-equipped synchronous motor is provided. The permanent magnet-equipped synchronous motor includes a stator including a stator core provided with a plurality of magnetic pole sections having windings of at least one phase wound thereon, as well as a rotor having p pole pairs (p: a positive integer of 1 or more) The rotor includes a shaft and a rotor core fixed on the shaft. The rotor core has 2p (a plural number) permanent magnets incorporated therein in a manner to be spaced from each other at intervals in a peripheral direction thereof. The 2p permanent magnets each constitute a permanent magnet magnetic pole section formed on an outer periphery of the rotor core. The rotor is formed with 2p magnetic salient pole sections arranged so as to interpose the permanent magnet magnetic pole section therebetween. It is to be noted that herein “one permanent magnet” means not only one permanent magnet in physical sense, but also such “one permanent magnet” as comprises a plural permanent magnets and yet functions as one permanent magnet magnetically.
According to the present invention the 2p permanent magnet magnetic pole sections comprise two groups (a first and a second groups) of permanent magnet magnetic pole sections. Each permanent magnet magnetic pole section of the first group is arranged to be spaced at equal intervals in the peripheral direction interposing one permanent magnet magnetic pole section of the second group between each two adjacent permanent magnet magnetic pole sections. Similarly, each permanent magnet magnetic pole section of the second group is also arranged to be spaced at equal intervals in the peripheral direction interposing one permanent magnet magnetic pole section of the first group mentioned above between each two adjacent permanent magnet magnetic pole sections. In other words each permanent magnet magnetic pole section of the two groups is arranged to appear alternately in the peripheral direction.
Also the 2p (p: a positive integer of one or more) magnetic salient pole sections comprise two groups (a first and a second groups) of magnetic salient pole sections. Each magnetic salient pole section of the first group is arranged to be spaced at equal intervals in the peripheral direction interposing one magnetic salient section of the second group between each two adjacent magnetic salient pole sections. Similarly, each magnetic salient pole section of the second group is also arranged to be spaced at equal intervals in the peripheral direction interposing one magnetic salient pole section of the first group mentioned above between each two adjacent permanent magnet pole sections. In other words magnetic salient pole sections of the two groups are arranged to appear alternately in the peripheral direction of the rotor core. In this instance an open angle of each of the p magnetic salient pole sections of the first group, &agr;1, is set to be smaller than an open angle of each of the p magnetic salient pole sections of the second group, &agr;2. Further the open angles &agr;1 and &agr;2 are set to satisfy the following expression.
&agr;2−&agr;1≈2&bgr;−(2
n−
1)&tgr;
s
wherein n is a natural number, &bgr; is an angle defined between two salient pole section virtual center lines, CL
1
and CL
2
. &tgr;s is a slot pitch of the stator core (denominated in rad). The outer peripheral surface sections of the permanent magnet pole sections of the rotor core may have a contour formed into an arcuate or elliptic configuration.
When the open angle &agr;1 of the p magnetic salient pole sections of the first group and the open angle &agr;2 of the p magnetic salient pole sections of the second group are defined as mentioned above, torque pulsation can be restrained and torque ripple can be diminished greatly as compared with the case in which the open angle of the 2p magnetic salient pole sections (each magnetic salient pole section of both first and second group) is set at equal value.
In this instance the curvature radius R1 of the magnetic pole surface of the p magnetic salient pole sections of the first group is set to be smaller than the curvature radius R2 of the magnetic pole surface of the p magnetic salient pole sections of the second group. Such arrangement permits torque ripple to be diminished as compared with the case in which the curvature radii R1 and R2 are set at the same value. In order to increase torque, on the other hand, the curvature radii R1 and R2 each are preferably set at a larger value than the curvature radii of the end portions of the magnetic pole surfaces of adjacent permanent magnet magnetic pole sections, and yet to satisfy the condition, R1<R2. However, in order to diminish torque ripple further, at the sacrifice of the torque strength, the curvature radii R1 and R2 each may, of course, be set at a smaller value than the curvature radii of the end portions of the magnetic pole surfaces of adjacent permanent magnet magnetic pole sections.
In this instance the shapes of the 2p permanent magnet magnetic pole sections and the 2p magnetic salient pole sections may preferably be determined so that the contour of the outer peripheral surface sections of the rotor core formed with two adjacent permanent magnet magnetic pole sections and a magnetic salient pole section interposed therebetween may have symmetrical shapes about th
Matsushita Manabu
Miyashita Toshihito
Onodera Satoru
Nguyen Tran
Rankin, Hill Porter & Clark LLP
Sanyo Denki Co. Ltd.
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