Electricity: electrical systems and devices – Electrolytic systems or devices – Liquid electrolytic capacitor
Patent
1999-01-22
2000-05-16
Kincaid, Kristine
Electricity: electrical systems and devices
Electrolytic systems or devices
Liquid electrolytic capacitor
361520, 361536, 361537, H01G 912, H01G 910
Patent
active
060645636
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electrolytic capacitor with an open circuit mode mechanism, in which at the time the electrolytic capacitor malfunctions, an upper lid is deformed due to rise of pressure in a metallic casing so as to break an electric circuit in the casing.
BACKGROUND ART
A conventional aluminum electrolytic capacitor has been arranged as shown in FIG. 8. Namely, in FIG. 8, a capacitor element 1 is impregnated with driving electrolyte and two lead-out lead plates 2a and 2b are drawn from the capacitor element 1. A mouth sealing member 3 for sealing a mouth of a cylindrical metallic casing 9 made of, for example, aluminum and having a bottom is formed by laminating a rubber plate 3a and a resinous plate 3b integrally, while a-pair of metallic rivets 4a made of, for example, aluminum and a pair of metallic rivets 4b made of, for example, aluminum are pierced through the mouth sealing member 3. An external connecting terminal 5a is connected to one end of one of the rivets 4a and the lead-out lead plate 2a is connected to the other end of the one of the rivets 4a by crimping through metallic washers 6a and 7a made of, for example, aluminum. Likewise, an external connecting terminal 5b is connected to one end of one of the rivets 4b and the lead-wire lead plate 2b is connected to the other end of the one of the rivets 4b by crimping through metallic washers 6b and 7b made of, for example, aluminum. The capacitor element 1 and the mouth sealing member 3 provided integrally in this way are accommodated in the metallic casing 9 containing fixing agent 8. The metallic casing 9 is subjected to transverse drawing in the vicinity of the mouth. A distal end of the mouth of the metallic casing 9 is subjected to curling so as to retain the mouth sealing member 3. Meanwhile, a weak spot (not shown) formed by a thin wall portion is provided on the bottom of the metallic casing 9.
In case a voltage higher than its rated voltage is applied to the conventional aluminum electrolytic capacitor, temperature in the metallic casing 9 rises, so that organic solvent forming the driving electrolyte impregnated in the capacitor element 1 is vaporized and hydrogen gas is generated by electrochemical reaction. As a result, internal pressure of the metallic casing 9 accommodating the capacitor element 1 rises. If the internal pressure of the metallic casing 9 rises excessively, the weak portion provided on the bottom of the metallic casing 9 is ruptured, so that the organic solvent gas flows out of the metallic casing 9 through the ruptured weak portion, thereby resulting in prevention of a tremendous explosion of the metallic casing 9.
However, in the above known aluminum electrolytic capacitor, since the driving electrolyte gas spouts out of the metallic casing 9 in misty state, such problems arise that this spouted misty driving electrolyte gas soils interior of an electronic appliance incorporating the known aluminum electrolytic capacitor and is mistaken for smoke due to a fire.
In order to solve these problems of the known aluminum electrolytic capacitor, an electrolytic capacitor with an open circuit mode mechanism as shown in FIGS. 9A and 9B is proposed in, for example, Japanese Utility Model Publication No. 6-39446 (1994). This prior art electrolytic capacitor with the open circuit mode mechanism is arranged as follows. Namely, in FIG. 9A, a capacitor element 12 is accommodated in a metallic casing 11 and a metallic upper lid 14 is hermetically mounted on an upper peripheral edge of a mouth of the metallic casing 11 through an annular elastic packing 13. A pair of first rivets 15 are pierced through the metallic upper lid 14 and each of the first rivets 15 is a composite rivet in which a metallic rivet 15b made of iron or metal other than aluminum is press fitted into an opening of an aluminum hollow rivet 15a so as to be welded to the aluminum hollow rivet 15a. Each of the first rivets 15 not only is hermetically mounted on the metallic upper lid 14 but is electrically insulated from the
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Kurimoto Hiroshi
Minami Masaharu
Yamada Morihiro
Kincaid Kristine
Matsushita Electric - Industrial Co., Ltd.
Thomas Eric W.
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