Inductor devices – Core forms casing
Reexamination Certificate
1997-08-25
2002-04-23
Mai, Anh (Department: 2832)
Inductor devices
Core forms casing
C336S192000, C336S206000
Reexamination Certificate
active
06377151
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chip inductor which uses a sintered magnetic core and also relates to a method of manufacturing the same.
2. Description of Related Art
Conventionally, there is known a method of manufacturing a chip inductor, characterized in that: a kneaded material to be obtained by kneading a powdered magnetic material (or magnetic substance) and a binder is pressurized to form it into a rectangular parallelepiped or a cylindrical body and thereafter sinter it to manufacture a bar of the magnetic material; a conductor (or a conducting wire) is wound around the bar of the magnetic material to thereby mount a coil in a coiled manner; terminals of the coil are extended to end surfaces of the bar of the magnetic material to thereby connect them to external terminals which are formed on the end surfaces of the bar of the magnetic material; the coil is then covered or coated with the kneaded material of the powdered magnetic material and the binder to thereby form an external cover (or coating); and thereafter a semimanufactured product thus obtained is sintered.
In the above-described chip inductor, the coil is covered with the magnetic material. Therefore, a circular magnetic circuit is formed in a manner to enclose the coil, with the result that an inductance value is high and that there is little or no magnetic field to leak outside the magnetic material. It has consequently an advantage in that, even if the chip inductor is disposed in close proximity to other parts, there will be no influence on the characteristics as an inductor and therefore that a density of mounting parts on a wiring circuit board or the like can be made higher.
However, this kind of inductor has a disadvantage in that, when a large pulse electric current is caused to flow therethrough, there is likely to occur a breaking at the connecting portions between the external electrodes and the terminal ends of the coil.
SUMMARY OF THE INVENTION
The present invention has an object of providing a chip inductor which is free from the above-described disadvantages and which is suitable for mass production, as well as providing a method of manufacturing the same.
In order to attain the above and other objects, the present invention provides a chip inductor comprising: coiled conducting wire means; a magnetic core which is formed by sintering and in which the coiled conducting wire means is embedded; wherein both end portions of the coiled conducting wire means are exposed to both end surfaces of the magnetic core in an arcuate or similar shape; and external electrodes which are coated on both the end surfaces of the magnetic core and which are connected to both end portions of the coiled conducting wire means.
Preferably, the coiled conducting wire means is made up of one or a plurality of bundled conducting wires. The one or a plurality of bundled conducting wires have a flattened cross section or an overall flattened cross section in the case of the plurality of conducting wires. The flattened cross section is arranged to lie along an axial line of the coiled conducting wire means.
According to another aspect of the present invention, there is provided a method of manufacturing a chip inductor comprising the steps of: forming a winding core by extruding a kneaded material which is obtained by kneading a powdered magnetic material and a binder; winding conducting wire means around the winding core in a coiled manner, a distance between adjoining winds being smaller than about twice the diameter of the conducting wire means; forming an external cover element to enclose the winding core around which the conducting wire means has been wound, the external cover element being formed by extruding the kneaded material; sintering the winding core and the external cover element; cutting a semimanufactured product obtained by the preceding steps into a predetermined length to thereby obtain a plurality of chip inductor main bodies, each of the chip inductor main bodies having on each of end surfaces thereof an arcuate or similar shape of exposed end of the conducting wire means; and forming an external electrode on each of the end surfaces of the respective said chip inductor main bodies to connect the external electrode to each of the exposed ends of the conducting wire means.
Preferably, the conducting wire means is made up of one or a plurality of bundled conducting wires whose cross section or an overall cross section in the case of the plurality of bundled conducting wires is flattened, the one or a plurality of bundled conducting wires being wound such that the flattened cross section lie along an axial line of the coiled conducting wire means.
According to the above-described method of manufacturing a chip inductor, a plurality of chip inductor main bodies are manufactured at the same time by following the steps of: forming a winding core by extruding a kneaded material to be obtained by kneading a powdered magnetic material and a binder; winding conducting wire means around the winding core in a coiled manner, a distance between adjoining winds being smaller than about twice the diameter of the conducting wire means; forming the external cover element to enclose the winding core around which the conducting wire has been wound, the external cover element being formed by extruding the kneaded material; sintering the winding core and the external cover member; and cutting a semimanufactured product obtained by the preceding steps into a predetermined length to thereby obtain a plurality of chip inductor main bodies. On both end surfaces of the respective chip inductor main bodies, there are formed external electrodes.
The chip inductor according to another aspect of the present invention has both end portions of the arcuate or similar shape of conducting wire means which are exposed to both end surfaces of each of the chip inductor main bodies. Therefore, the external electrodes formed on both end surfaces of the inductor main bodies are connected to the arcuate or similar shape of the conducting wire means. According to this arrangement, since the areas of connection between the external electrodes and the end portions of the conducting wire means become large, there will be no possibility of the connecting portions' being broken, before the conducting wire means is broken, when a pulsed electric current is caused to flow through the inductor. According to a preferred embodiment as described above, if the coiled conducting wire means is made up of one or a plurality of bundled conducting wires whose cross section or an overall cross section in the case of the plurality of bundled conducting wires is flattened, and the one or a plurality of bundled conducting wires are wound such that the flattened cross section lies along an axial line of the coiled conducting wire means, the distance between the adjoining winds becomes smaller than the one with a single conducting wire of round or square cross section, provided the magnetic core and the number of winding remain the same. Therefore, both the end portions, of arcuate or similar shape, of the conducting wire means have larger lengths and, as a consequence, still larger areas of connection to the external electrodes can be secured. According to still another preferred embodiment of the present invention in which the coiled conducting wire means is formed by a plurality of conducting wires which are bundled together, even if there occurs breaking at the connection between the external electrode and one of the conducting wires when the pulse electric current is caused to flow through the coiled conducting wires, there will still remain other connections between the remaining end portions of the conducting wires and the external electrodes, thereby securing a high safety.
REFERENCES:
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patent: 4549042 (1985-10-01), Akiba et al.
patent: 4696100 (1987-09-01), Yamomoto et al.
patent: 4801912 (1989-01-01), McEleheny et al.
patent: 4842352 (1989-06-01), Sasaki e
Saito Makoto
Takayama Manabu
Armstrong Westerman Hattori McLeland & Naughton LLP
Mai Anh
Taiyo Yuden Kabushiki Kaisha
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