Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1994-06-07
1996-03-12
Budd, Mark O.
Electrical generator or motor structure
Dynamoelectric
Rotary
310254, H02K 100
Patent
active
054989175
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a stator for a motor comprised of laminated iron cores.
BACKGROUND ART
Hitherto, there is known a stator for a motor, which is constituted with a ring-shaped yoke portion iron core, tooth portion iron cores arranged at an equal interval on the inner circumferential side of the yoke portion iron core, and stator coils fitted into slots formed between respective adjacent tooth portion iron cores, wherein a rotor is oppositely disposed through a gap on the inner circumferential side of the tooth portion iron cores. In this case, there is disclosed a stator core in which the inner circumferential sides of respective adjacent tooth portion iron cores are connected by portions serving as a bridge between magnetic poles (hereinafter simply referred to as bridging portions) having a small cross section in order not to take the stator assembly to pieces at the time of punching or assembling of tooth portion iron cores and yoke portion iron core, and to reduce leakage reactance (e.g., the Japanese Patent Application Laid Open No. 196034/1987 (Tokkaisho No., 82-196034), the,Japanese Patent Application Laid Open No. 174531/1988 (Tokkaisho No. 63-174531).
However, with the above-described configuration, there were the drawbacks that the cogging torque cannot be sufficiently small and/or unevenness of the cogging torque becomes greater in dependency upon the dimensions of tooth portion iron cores employed.
DISCLOSURE OF THE INVENTION
An object of this invention is to provide a stator for a motor, which has small cogging torque.
This invention is directed to a stator for a motor comprising a ring-shaped yoke portion iron core, tooth portion iron cores arranged at an equal interval on the inner circumferential side of the yoke portion iron core, stator coils fitted into slots formed between respective adjacent tooth portion iron cores, and bridging portions for connecting the inner circumferential sides of the respective adjacent tooth portion iron cores, a rotor being oppositely disposed through a gap on the inner circumferential side of the tooth portion iron cores, characterized in that the ratio of the length in a circumferential direction of the bridging portion to a pitch in the circumferential direction of the tooth portion iron core falls within a range of 0.01 to 0.20. Further, the ratio of the thickness in a radial direction of the bridging portion to the thickness of laminated steel plates of the tooth portion iron core falls within the range of 0.2 to 1.0.
According as the ratio .alpha. of the length s in a circumferential direction of the bridging portion connecting adjacent tooth portion iron cores to the pitch p in the circumferential direction of the tooth portion iron core becomes smaller, the amplitude of the cogging torque becomes smaller. When the ratio .alpha. exceeds 0.2, the amplitude of the cogging torque suddenly increases. Further, by change of the dimensions of the bridging portion, induced electromotive force (EMF) slightly becomes greater according as the ratio .alpha. becomes greater.
Further, according as the ratio .beta. of the thickness b in a radial direction of the bridging portion to the thickness t of the laminated steel plates of the tooth portion iron core becomes greater, the amplitude of the cogging torque becomes smaller and MF becomes smaller at the same time. Accordingly, in accordance with this invention, by selecting optimum ranges of the ratios .alpha. and .beta., it is possible to advantageously lower the cogging torque of motor without lowering EMF.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front cross sectional view showing an embodiment of this invention,
FIG. 2 is a perspective view showing tooth portion iron core and bridging portion,
FIG. 3 is an explanatory view showing the relationship between ratio .alpha. and cogging torque.
FIG. 4 is an explanatory view showing the relationship between ratio .beta. and cogging torque.
BEST MODE FOR CARRYING OUT THE INVENTION
This invention will now be described in connecti
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patent: 3869629 (1975-03-01), Ogawa et al.
patent: 4719382 (1988-01-01), Listing
patent: 4782260 (1988-11-01), Gandhi et al.
Ninomiya Yuji
Ueyama Kenji
Budd Mark O.
Catan Mark
Froebrich Alfred W.
Kabushiki Kaisha Yaskawa Denki
Morrison Thomas R.
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