Electricity: electrical systems and devices – Electrolytic systems or devices – Double layer electrolytic capacitor
Reexamination Certificate
2002-08-06
2003-04-22
Nguyen, Chau N. (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Double layer electrolytic capacitor
C361S511000
Reexamination Certificate
active
06552894
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric double layer capacitor in which electric double layers are formed at interfaces between electrodes and an electrolyte and electricity is stored in the electric double layers.
2. Description of the Related Art
An electric double layer capacitor is an electricity charging and discharging element. An example of such an electric double layer capacitor is disclosed in, for example, Japanese Patent Laid-Open Publication No. HEI-10-294102 entitled “Electricity Storing Element”.
The disclosed electric double layer capacitor comprises an electrode rolled body formed by overlapping a positive electrode plate, a negative electrode plate and a separator interposed therebetween to wind the same in a rolled manner. A lower end of the negative electrode plate is connected electrically to a negative collecting plate, which serves as a negative electrode terminal. An upper end of the positive electrode plate is connected electrically to a positive collecting plate, which serves as a positive electrode terminal. After the electrode rolled body in such a state is contained in a bottomed, cylindrical-shaped outer packaging can and an electrolyte is poured into the outer packaging can, the outer packaging can is closed by a cover. The positive collecting plate is electrically connected to the cover. The negative collecting plate is electrically connected to the outer packaging can.
With the above-mentioned electric double layer capacitor, heat generated due to electric resistance generated from the electrode rolled body and the like at the time of, for example, charging heats the electrolyte. Accordingly, to maintain the service life of an electric double layer capacitor over a long term, it is necessary to discharge the generated heat to the atmosphere.
FIG. 15
hereof shows a schematic constitution, in which heat of the above-mentioned electric double layer capacitor is discharged.
In
FIG. 15
, an electric double layer capacitor
500
is constructed such that a negative collecting plate
505
is interposed between a negative electrode plate
502
of an electrode rolled body
501
and a bottom
504
of an outer packaging can
503
to electrically connect the negative electrode plate
502
and the negative collecting plate
505
to each other to connect the negative collecting plate
505
electrically to the bottom
504
of the outer packaging can
503
.
The electric double layer capacitor
500
comprises a first connection
506
, which electrically connects the negative electrode plate
502
and the negative collecting plate
505
to each other, and a second connection
507
, which electrically connects the negative collecting plate
505
and the bottom
504
of the outer packaging can
503
to each other. Therefore, heat generated in the electric double layer capacitor
500
is discharged to the atmosphere from the outer packaging can through the first connection
506
and the second connection
507
.
However, because the first connection
506
and the second connection
507
are small in area, heat quantity transferred through the first connection
506
and the second connection
507
becomes small. Therefore, heat transfer quantity generated in the electric double layer capacitor
500
is held down by the first connection
506
and the second connection
507
, which is responsible for temperature rise in the electric double layer capacitor
500
to affect the service life thereof.
Further, with the electric double layer capacitor disclosed in Japanese Patent Laid-Open Publication No. HEI-10-294102, the positive collecting plate covers an upper end of the positive electrode plate, and so it acts as an obstacle when an electrolyte is filled into the electrode rolled body. Therefore, it takes time to fill the electrolyte into the electrode rolled body.
Japanese Patent Laid-Open Publication No. HEI-10-294102 further discloses a positive collecting plate having slits formed on both sides of radially extending convex ridges. Such a positive collecting plate will be described with reference to
FIG. 16
hereof.
FIG. 16
shows, in an enlarged scale, a part of the positive collecting plate having the slits formed on both sides of the convex ridges. The convex ridges
601
of the positive collecting plate
600
are used to bend an upper end
604
of a positive electrode plate
603
in an electrode rolled body
602
, and the convex ridges
601
are welded to bent portions
605
of the upper end
604
.
Because the positive collecting plate
600
has slits
606
,
606
on both sides of the convex ridges
601
, it is possible to fill an electrolyte into the electrode rolled body
602
through the slits
606
,
606
.
Since both ends
605
a
of the bent portions
605
of the positive electrode plate
603
extend to the slits
606
,
606
, however, a part of the slits
606
,
606
is closed by the both ends
605
a
of the bent portions
605
. Therefore, when an electrolyte is filled into the electrode rolled body
602
from the slits
606
,
606
, the both ends
605
a
of the bent portions
605
act as an obstacle, and so it is difficult to efficiently fill the electrolyte from the slits
606
,
606
.
Further, with the electric double layer capacitor disclosed in the above-mentioned Japanese Patent Laid-Open Publication No. HEI-10-294102, a leaf-spring shaped pressing member is mounted on a side of the cover in order to electrically connect the cover to the positive collecting plate, and the pressing member is brought into electrical contact with a central projection of the positive collecting plate. However, the pressing member contacts locally with the projection, and so the contact area therebetween is small. Therefore, electric current flowing in local contact portions between the pressing member and the projection is restricted.
To flow large electric current at contact portions is important in improving the performance of an electric double layer capacitor.
Hereupon,
FIG. 17
shows a conventional electric double
4
. layer capacitor capable of flowing a relatively large electric current.
Referring to
FIG. 17
, an electric double layer capacitor
700
is constructed such that an outer packaging can
707
contains therein an electrode rolled body
701
in a state, in which a negative collecting plate
704
is electrically connected to a lower end of a negative electrode plate
702
of the electrode rolled body
701
and a positive collecting plate
705
is electrically connected to an upper end of a positive electrode plate
703
. The negative collecting plate
704
is connected electrically to a bottom
708
of an outer packaging can
707
. The positive collecting plate
705
is electrically connected to a cover
709
. The outer packaging can
707
is filled with an electrolyte.
The positive collecting plate
705
is formed centrally with an upwardly extending projection
706
. The projection
706
is inserted into a hole
709
a
formed in the cover
709
. The projection
706
is welded to the cover
709
. The projection
706
is formed to have a relatively large diameter to be large in cross sectional area. Therefore, a relatively large electric current can be made to flow to the projection
706
to improve the performance of the electric double layer capacitor
700
.
It is necessary to reduce the electrode rolled body
701
in manufacturing error because it is required that a reference dimension H1 from the bottom
708
of the outer packaging can
707
, which serves as a negative electrode, to a tip end
706
a
of the projection
706
, which serves as a positive electrode, to be uniform. Therefore, a height hl of the electrode rolled body must be kept uniform by decreasing the electrode rolled body
701
in manufacturing error.
However, the electrode rolled body
701
shown in
FIG. 17
is constructed by overlapping and winding the positive electrode plate, negative electrode plate and a separator in a rolled manner, and so displacement upon winding to generate manufacturing error is liable to occur.
Matsumoto Kenji
Matsuoka Toshiyuki
Shibuya Kentaro
Shohoji Tomokazu
Yamamoto Yoshio
Honda Giken Kogyo Kabushiki Kaisha
Merchant & Gould P.C.
Nguyen Chau N.
Thomas Eric
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