1997-02-28
1998-09-29
Gellner, Michael L.
Inductor devices
Core
336178, 336234, 336172, 336212, H01F 1706, H01F 2724
Patent
active
058150625
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a magnetic core for use in transformers, choke coils, etc., and particularly to a magnetic core with reduced leakage flux and suitable for transformers used in power factor improving circuits, power supply transformers for CRT color monitors, etc.
BACKGROUND OF THE INVENTION
Magnetic cores used for power supply transformers, etc. are conventionally made of magnetic materials such as ferrite, silicon steel plates, etc. An E type ferrite magnetic core is shown as one example of the conventional magnetic cores in FIG. 20. This magnetic core is constituted by a pair of E type ferrite magnetic core pieces 200, 200 abutting each other, and each E type ferrite magnetic core piece 200 comprises an intermediate leg portion 251, outer leg portions 252, 252 positioning on both sides thereof, and a web portion 253 connecting the intermediate leg portion 251 and the outer leg portions 252, 252. FIG. 21 shows a pair of assembled E type ferrite magnetic core pieces with a wound wire 254. When current is applied to the wire 254, a magnetic flux 255 is generated and circulates through the web portion 253, the intermediate leg portion 251 and the outer leg portions 252, 252. This is true of magnetic cores made of other magnetic materials.
When a conventional magnetic core constituted by a pair of E type ferrite magnetic core pieces 200, 200 and a wire wound around an intermediate leg portion 251 of the magnetic core is operated, there is a leakage flux 256 emanating from the magnetic core along the extension of the intermediate leg portion 251 in addition to the above magnetic flux 255 as shown in FIG. 21. The leakage flux 256 goes outwardly from the intermediate leg portion 251 in the axial direction thereof. Since the leakage flux 256 serves as noises to other electronic circuits and electronic equipments, it is desired to have such a magnetic core structure generating as small leakage flux 256 as possible.
Also known is a magnetic core structure in which each of recesses 257 is located at an outer surface of the web portion at a position of the intermediate leg portion as shown in FIG. 22, but such a structure is not fully satisfactory in reducing the leakage flux.
In view of the above problems, an object of the present invention is to provide a magnetic core with as small leakage flux as possible.
DISCLOSURE OF THE INVENTION
The magnetic core of the present invention comprises at least one magnetic core piece comprising a first leg portion around which a wire is wound, a second leg portion for circulating a magnetic flux generated in the first leg portion, and a web portion connecting the first leg portion and the second leg portion, the web portion being provided with a magnetic gap in a rear area extending from the root of the first leg portion.
Preferably, the magnetic core of the present invention comprises (a) a pair of E type magnetic core pieces each comprising a first leg portion around which a wire is wound, second leg portions for circulating a magnetic flux generated in the first leg portion, and a web portion connecting the first leg portion and the second leg portions, and (b) at least one I type magnetic core piece, a pair of the E type magnetic core pieces being attached to each other such that their respective first leg portions and second leg portions abut each other, the I type magnetic core piece being attached to an outer surface of the web portion of at least one E type magnetic core piece, a recess being provided in at least one of the E type magnetic core pieces and the I type magnetic core piece on an interface of both magnetic core pieces, and the recess being located in a rear area extending from the root of the first leg portion of the E type magnetic core piece.
In the present invention, the magnetic gap may be provided by a through hole or a low-permeability member. In any case, the width or cross-sectional area of the magnetic gap is preferably half or more as large as that of the first leg portion (intermediate leg portion). Th
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Koyuhara Norikazu
Tanaka Toshihiko
Yamamoto Youichi
Gellner Michael L.
Hitachi Ferrite Electronics Ltd.
Hitachi Metal Ltd.
Mai Anh
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