| 摘要 |
An efficient permanent magnet rotor for a brushless motor has a yoke (2) formed by laminating many steel sheets (4) so as to provide an even number of magnetic poles projected externally, filed permanent magnets (3) inserted in the magnetic poles, bridges (10) provided at either end of the permanent magnets and having a width, among a first minimum width below which said bridges cannot be punched out without breaking, a maximum width at which an allowable maximum number of magnetic fluxes passes through said bridges, and a second minimum width below which said bridges cannot withstand a centrifugal force caused by rotation of said permanent magnet rotor, (1) equal to or larger than the greater one of the first and second minimum widths and smaller than the maximum width when the first and second minimum widths are equal to or smaller than the maximum width, or (2) equal to or larger than the greater one of the first and second minimum widths when said greater one of the first and second minimum widths is equal to or larger than the maximum width, and (3) equal to or larger than the thickness of each of said steel sheets.
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