| 摘要 |
PROBLEM TO BE SOLVED: To prevent lowering of characteristics at low cost without requiring any difficult machining by making through holes at substantially same positions on the axial extension of the permanent magnet of a balance weight. SOLUTION: A rotor core 11 is provided with a through hole 12 and a permanent magnet 13 is embedded therein. At the opposite ends of the rotor core 11, an end plate 14 and a balance weight 15 are provided and secured by means of a rivet pin 16, or the like. The balance weight 15 is provided with through holes 17a, 17b at substantially same positions on the axial extension of the permanent magnet 13. The through holes 17a, 17b extend not only to the permanent magnet 13 but also a nonmagnetic layer. Consequently, not only the flux short-circuiting from the pole face 13a of the permanent magnet 13 to the counter-pole face 13b thereof through the balance weight 15 but also the flux short-circuiting to an adjacent pole case 13c can be prevented.
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