Electric double layer capacitor

Details Electric double layer capacitor Electric double layer capacitor

1998-12-21

2001-04-24

Picard, Leo P. (Department: 2835)

Electricity: electrical systems and devices

Electrostatic capacitors

Fixed capacitor

C361S301100, C361S301500, C361S303000, C361S306100, C361S313000

Reexamination Certificate

active

06222720

ABSTRACT:

The present invention relates to an electric double layer capacitor. In particular, it relates to an electric double layer capacitor having wound or rolled electrodes.
Recently, an electric double layer capacitor having a large capacity and a high output, which aims at being mounted on a vehicle and is applicable to a driving power source for driving the vehicle, has been noted and developed.
As a structure for a large-sized electric double layer capacitor suitable for discharging a heavy current, such one having a cylindrical structure as shown in
FIG. 12
has been used. Namely, a pair of belt-like electrodes, specifically, a belt-like positive electrode
2
and a belt-like negative electrode
3
each comprising a metallic current collecting material on both sides of which electrode layers composed mainly of an activated carbon are formed, are rolled by interposing therebetween belt-like separators
4
,
4
′ to thereby form a cylindrically wound element. The wound element is housed in a bottomed cylindrical metallic casing
5
. After an electrolyte is filled in the casing
5
, current collecting leads
6
,
6
′ are connected respectively to the positive electrode
2
and the negative electrode
3
, and the current collecting leads drawn from the electrodes
2
,
3
are respectively connected to electrode terminals
9
,
9
′ which are provided on an electrically insulating opening sealing cover
8
fitted to the metallic casing
5
.
The conventional electric double layer capacitor had disadvantages as follows. Processings for the current collecting leads were troublesome and time for manufacturing was elongated. Further, an additional space was necessary to house the current collecting leads in the casing, which inevitably caused a small-sized wound element and thus density of the capacity of the capacitor per volume of casing was lowered.
It is an object of the present invention to provide an electric double layer capacitor having an increased density of capacity per volume.
In order to accomplish the above-mentioned object, the present invention is to provide an electric double layer capacitor as shown mainly in FIGS.
1
and
8
(
a
) and (
b
). Namely, the electric double layer capacitor comprises a first electrode
31
comprising a belt-like electricity collecting material
31
a
having at least one surface on which an electrode layer
31
b
(
31
c
) is formed leaving a belt-like portion
31
ax
in a side of the belt-like electricity collecting material
31
a
along its longitudinal direction; a second electrode
32
comprising a belt-like electricity collecting material
32
a
having at least one surface on which an electrode layer
32
b
(
32
c
) is formed leaving a belt-like portion
32
ax
in a side of the belt-like electricity collecting material
32
a
along its longitudinal direction; belt-like separators
33
a,
33
b
interposed between the first electrode
31
and the second electrode
32
to electrically insulate them; a post-like winding core
40
having both ends, on which the first electrode
31
, the second electrode
32
and the separators
33
a,
33
b
are wound to thereby form a cylindrically wound element
50
; a first electricity collecting plate
72
in contact with the belt-like portion
31
ax
of the first electrode
31
to collect electricity, and a second electricity collecting plate
62
(
73
in
FIG. 5
) in contact with the belt-like portion
32
ax
of the second electrode
32
to collect electricity, wherein the belt-like portion
31
ax
of the first electrode
31
and the belt-like portion
32
ax
of the second electrode
32
are respectively at opposing positions in the cylindrically wound element
50
; the both ends of the winding core
40
are respectively in direct or indirect contact with the first electricity collecting plate
72
and the second electricity collecting plate
62
(
73
in FIGS.
5
(
a
) and (
b
)) to determine the relative positions in axial directions of the first electricity collecting plate
72
and the second electricity collecting plate
62
(
73
in FIGS.
5
(
a
) and (
b
)), and the first electricity collecting plate
72
and the second electricity collecting plate
62
(
73
in
FIG. 5
) are electrically insulated.
The second electricity collecting plate may be constituted by a bottom plate
62
in the casing (
FIG. 1
) or may be the electricity collecting plate
73
which is provided independently (FIGS.
5
(
a
) and (
b
)). With respect to the contact between the electricity collecting plate and the belt-like portion, it is not always necessary to crush the belt-like portion but an elastic contact may be employed. Further, when the electricity collecting plate is provided with needle-like projections the belt-like portion may be in contact with the projections. The terms “direct” or “indirect” mean that a spacer is interposed between the electricity collecting plate and the belt-like portion to effect an indirect contact. For insulation, the winding core may be provided with an electrically insulating member in its axial direction or a spacer having an insulating property may be interposed therebetween.
With such arrangement, the belt-like portions of the first and second electrodes are positioned in a wound form at opposing ends in the cylindrically wound element. Since the first and second electricity collecting plates are respectively in contact with the belt-like portions of the first and second electrodes to collect electricity, tab-like electricity collecting leads are not required and the belt-like portions themselves act as electricity collecting leads. This structure makes it easy to manufacture, and further, time for manufacturing can be shortened. Further, since a space for receiving such tab-like electricity collecting leads is not required, an electric double layer capacitor having a high capacity density per volume can be provided.
Use of the winding core determines the relative positions of the first and second electricity collecting plates in their axial directions and sets the distance of the two plates in a desired value. Further, the winding core eliminates a danger that the two electricity collecting plates come to close or separate from each other due to vibrations during the use of the capacitor or the generation of gas inside the capacitor. Further, it maintains good contact between the belt-like portion and the electricity collecting plate.
The first electricity collecting plate
72
and the second electricity collecting plate
62
may respectively be in forcible contact with the belt-like portion
31
ax
of the first electrode and the belt-like portion
32
ax
of the second electrode. Alternatively, the belt-like portion
31
ax
of the first electrode and the belt-like portion
32
ax
of the second electrode may be crushed toward an axial direction of the post-like winding core
40
so that they are bent inwardly.
The term “forcible contact” means that the contact between the belt-like portions and the electricity collecting plates is performed by pressing them with a predetermined pressure for example. There are several ways of crushing the belt-like portions
31
ax,
32
ax.
They may previously be crushed toward the axial direction, or the electricity collecting plates may be pressed to the belt-like portions as a result of which the belt-like portions are crushed, or slits may previously be formed in the belt-like portions so as to be easily crushed. The formation of slits is advantageous when the electricity collecting plates have a certain thickness so that it can not be expected to crush sufficiently the belt-like portions by only pressing the electricity collecting plates. With such construction, when the first and second electricity collecting plates are respectively brought to forcible contact with the belt-like portions of the first and second electrodes, a variation of pressure by the winding core is suppressed to thereby minimize a variation of electric resistance at the forcible contact portions.
In an aspect of the present invention, the electric double l

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