Method for manufacturing a wound magnetic core
[PROBLEM] To provide a wound magnetic core and a method for manufacturing a wound magnetic core permitting improvement of insulation between ribbon layers in a wound magnetic core at which soft magnetic metal ribbon has been wound to form an annular wound body. [SOLUTION MEANS] A nonmagnetic insulating metal oxide powder is made to adhere to a surface of a soft magnetic metal ribbon having an amorphous structure; this is wound in annular fashion and made into a wound body at which the metal oxide powder intervenes between ribbon layers; the wound body is made to undergo heat treatment in a nonoxidizing atmosphere; the wound body is thereafter subjected to treatment for formation of an oxide film in an oxidizing atmosphere adjusted to be at a temperature lower than that at the heat treatment to cause oxidation of the surface of the soft magnetic metal ribbon; and spaces between ribbon layers at the wound body are moreover impregnated with resin and curing is carried out to fuse the metal oxide powder thereto.
1. A method for manufacturing a wound magnetic core, comprising:
a first operation in which a nonmagnetic insulating metal oxide powder is made to adhere to a surface of a soft magnetic metal ribbon having an amorphous structure;
a second operation in which, following the first operation, the soft magnetic metal ribbon is wound in annular fashion to obtain a wound body at which the metal oxide powder intervenes between layers of the ribbon;
a third operation in which the wound body is made to undergo heat treatment in a nonoxidizing atmosphere;
a fourth operation in which, following the third operation, the wound body is subjected to treatment for formation of an oxide film in an oxidizing atmosphere at a temperature lower than a heat treatment temperature at the third operation to cause oxidation of the surface of the soft magnetic metal ribbon;
a fifth operation in which, following the fourth operation, spaces between the layers of the ribbon of the wound body are impregnated with resin and curing thereof is carried out;
wherein:
an amount of the metal oxide powder which is made to adhere thereto at the first operation is not less than 0.1% but not greater than 1.2% when expressed as a metal oxide powder wt % ratio as obtained using the following formula (1); and
metal oxide wt % ratio (%)=(weight of metal oxide adhering to soft magnetic metal ribbon/weight of soft magnetic metal ribbon)×100 (1).
2. The method for manufacturing the wound magnetic core according to claim 1 , wherein:
the third operation is heat treatment A that causes formation of nanocrystals at the soft magnetic metal ribbon having the amorphous structure.
3. The method for manufacturing the wound magnetic core according to claim 1 , wherein:
the third operation is heat treatment B that relieves stresses at the soft magnetic metal ribbon having the amorphous structure.
4. The method for manufacturing the wound magnetic core according to claim 2 , wherein:
a temperature at the heat treatment A of the third operation is not less than 450° C. but not greater than 620° C.
5. The method for manufacturing the wound magnetic core according to claim 3 , wherein:
a temperature at the heat treatment B of the third operation is not less than 250° C. but not greater than 400° C.
6. The method for manufacturing the wound magnetic core according to claim 1 , wherein:
the oxide film forming treatment at the fourth operation is carried out in the oxidizing atmosphere at a temperature that is not less than 240° C. but less than the heat treatment temperature at the third operation.
7. The method for manufacturing the wound magnetic core according to claim 1 , wherein:
the metal oxide is magnesium oxide (MgO), titanium oxide (TiO 2 ), or aluminum oxide (Al 2 O 3 ).