| 摘要 |
A field system produced with a high productivity. A field system (1) has a field core (2) and a field magnet (5). The field magnet (5) is composed of, e.g., two permanent magnets (51, 52), and the width of the field magnet (5) monotonously increases from the center toward the ends. The field magnet (5) has at its ends projections (51a, 52a) projecting in directions opposed to the rotation axis (P). A through hole (4) through which the field magnet (5) is inserted is made in the field core (2). The through hole (4) has insertion surfaces (4a, 4b) covering the respective magnetic pole surfaces (5a, 5b) of the field magnet (5). Specifically, the insertion surface (4b) has recesses (41a, 41b) into which the projections (51a, 52a) are fitted. When the field magnet (5) is inserted, the insertion surfaces (4a, 4b) serve to guide the field magnet (5). Therefore the field magnet (5) can be easily inserted into the through hole (4).
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