| 摘要 |
PROBLEM TO BE SOLVED: To improve the d-c current superposition characteristic of a coil and take measures for the downsize and increase of the operating current by combining permanent magnets so that the magnetic path length of a dust core is reverse to that of the permanent magnet. SOLUTION: The material of a dust core uses a powder showing soft magnetic properties such as pure iron, sendust, permalloy, silicon steel, etc., and they can be made by pulverizing an ingot made by the high frequency melting or the atomizing method without troubles. The powder is heat treated, an necessary, mixed with a binder and press-formed into a desired shape using a die. The moldings are heat treated to remove strains, thereby obtaining dust cores 1, 2. Permanent magnets 3 are adhered with adhesives so that the magnetic path direction 5 of the dust core is reverse to the magnetic path direction 6 of the permanent magnet 3, and windings 4 are provided to manufacture a choke coil.
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