Inductor devices – Core forms casing
Reexamination Certificate
1998-10-13
2001-08-14
Donovan, Lincoln (Department: 2832)
Inductor devices
Core forms casing
C336S200000, C336S096000, C029S602100
Reexamination Certificate
active
06275132
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inductor, and more particularly, to a high-current inductor for removing noise that originates in electronic equipment or noise that enters electronic equipment, and a method of manufacturing such an inductor.
2. Description of the Related Art
With recent miniaturization and increases in the level of integration and in the frequency of circuits, there has been an increasing demand for miniature surface-mount inductors.
An example of this type of inductor is a multilayer inductor disclosed in Japanese Examined Patent Publication No. 57-39521. This multilayer inductor is manufactured by alternately stacking green sheets of ferrite and conductive patterns for forming a coil, baking them together, and making a multilayer unit that incorporates a coil composed of the coil conductive patterns electrically connected in series.
A conventional wire-wound inductor may also be manufactured by forming electrodes on a substrate for holding a magnetic core, winding a conductive wire on the magnetic core, and connecting terminals of the conductive wire to the electrodes on the substrate.
In the conventional methods of manufacturing the multilayer inductor, however, it is necessary to repeat a printing step many times, the manufacturing process is complicated and the manufacturing cost is high. Although the wire-wound inductor has a relatively simple structure, it is difficult to automate the operations of winding the conductive wire on the magnetic core, processing the terminals of the conductive wire, and soldering the processed terminals of the conductive wire to the electrodes on the substrate for holding the magnetic core. Therefore, these operations are manually performed which increases the manufacturing cost of the wire wound inductor.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide an inductor with a simple structure which provides high reliability, high mass productivity, and low manufacturing cost, and a method of manufacturing such an improved inductor.
According to a preferred embodiment of the present invention, an inductor includes an insulating molded member having magnetic powders mixed therein, a coiled metal wire embedded in the insulating molded member, and metal caps respectively fitted on both ends of the insulating molded member and electrically connected to both ends of the coiled metal wire, wherein spaces are formed between the end surfaces of the insulating molded member and the metal caps. Preferably, the insulating molded member is made of resin, rubber material or the like.
According to the structure of the preferred embodiment described above, the metal caps function as outer terminals, the magnetic powders mixed in the insulating molded member increase the permeance of the insulating molded member, and the insulating molded member functions as a magnetic path for a magnetic flux generated around the coiled metal wire. Since the spaces between the end surfaces of the insulating molded member and the metal caps absorb the difference in thermal expansion between the insulating molded member and the coiled metal wire, it is possible to reduce the thermal stress that is applied to the connecting portions between the metal caps and the coiled metal wire.
Another preferred embodiment of the present invention provides a method of manufacturing an inductor, the method including the steps of forming an insulating molded member by putting a coiled metal wire in a mold and pouring into the mold an insulating material having magnetic powders mixed therein, fitting metal caps on both ends of the insulating molded member and putting the metal caps into contact with both ends of the coiled metal wire and welding the metal caps to both ends of the coiled metal wire and forming spaces between both end surfaces of the insulating molded member and the surfaces of the metal caps by using heat generated during welding.
According to the preferred embodiment of the method described above, the metal caps are electrically connected to both ends of the coiled metal wire, respectively, and both ends of the insulating molded member are caused by the heat produced during welding to melt, to contract, and to retreat from the metal cap surfaces, whereby spaces are easily formed between the metal caps and the end surfaces of the insulating molded member, respectively.
Further, the inductor of preferred embodiments of the present invention has spaces which are provided between the metal caps and the insulating molded member such that the difference of thermal expansion between the insulating molded member and the metal caps is absorbed.
In another preferred embodiment of the present invention, the inductor has spaces which are formed between the metal caps and the insulating molded member such that heat generated during welding melts and contracts the insulating molded member and the end surfaces of the insulating molded member retreat from the metal caps.
In another preferred embodiment of the present invention, both ends of the coiled metal wire project from the end surfaces of the insulating molded member.
Further objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the attached drawings.
REFERENCES:
patent: 4490706 (1984-12-01), Stou et al.
patent: 4801912 (1989-01-01), McElheny et al.
patent: 5307557 (1994-05-01), Te-Hsueh
patent: 5690771 (1997-11-01), Kato et al.
patent: 6055721 (2000-05-01), Mamada et al.
patent: 57-92807 (1982-06-01), None
patent: 3-196605 (1991-08-01), None
patent: 8-306570 (1996-11-01), None
Oshima Hisato
Shikama Takashi
Sugitani Masami
Yamamoto Takahiro
Donovan Lincoln
Keating & Bennett LLP
Murata Manufacturing Co. Ltd
Nguyen Tuyen T.
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