Electricity: electrical systems and devices – Electrolytic systems or devices – Solid electrolytic capacitor
Reexamination Certificate
2003-08-27
2004-07-27
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrolytic systems or devices
Solid electrolytic capacitor
C361S509000, C361S516000, C361S525000, C361S528000, C361S529000
Reexamination Certificate
active
06768632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aluminum electrolytic capacitor having external terminals for use in various kinds of electronic equipment and to a method of manufacturing the capacitor.
2. Background Art
FIG. 5
is a sectional view illustrating a structure of a conventional aluminum electrolytic capacitor.
FIG. 6
is a sectional view of an essential part of the conventional capacitor.
FIG. 7
is a sectional view of an essential part of the conventional capacitor before a rivet thereof is upset. Capacitor element
10
shown in
FIGS. 5 through 7
is structured so that a positive electrode foil (not shown) and a negative electrode foil (not shown) are rolled, sandwiching a separator (not shown) therebetween. The positive electrode foil has dielectric surface oxide layers formed by anodizing an aluminum foil having roughened surfaces. The negative electrode foil is made of an aluminum foil having roughened surfaces.
The method of assembling a conventional aluminum electrolytic capacitor is outlined hereinafter. A conventional aluminum electrolytic capacitor includes aluminum internal leads
11
, i.e. one connected to the positive electrode foil at one end and the other to the negative electrode foil at one end, terminal plate
12
, a pair of external terminals
13
provided on this terminal plate
12
, aluminum rivets
14
, and aluminum spacers
15
. In a manufacturing process, external terminals
13
are fixed to terminal plate
12
by corresponding aluminum rivets
14
. At the same time, the tip portion of each aluminum rivet
14
penetrating through this terminal plate
12
and projecting therefrom is threaded through through-hole
110
previously provided at the other end of each of internal leads
11
, via spacer
15
. After another spacer
15
is further fitted on the rivet, the tip portion of aluminum rivet
14
projecting from the other spacer
15
is upset. With these steps, internal leads
11
and corresponding external terminals
13
are electrically connected with each other. Through-hole
110
previously provided at the other end of each internal lead
11
is formed to have opening diameter &phgr;C slightly larger than outer diameter &phgr;D of aluminum rivet
14
, in consideration of workability.
Further, this capacitor element
10
and an electrolyte solution (not shown) are contained in cylindrical metal case
16
having a bottom. Attached to the outer peripheral surface of this metal case
16
is resin sleeve
161
made of vinyl chloride. At last, the periphery of the opening of this metal case
16
is drawn so as to surround this terminal plate
12
, to seal the metal case. Thus, an aluminum electrolytic capacitor having a pair of external terminals
13
is constructed.
In a conventional aluminum electrolytic capacitor, a pair of internal leads
11
drawn from capacitor element
10
are electrically connected to a pair of external terminals
13
provided on terminal plate
12
by threading corresponding through-holes
110
provided at the other ends of internal leads
11
with aluminum rivets
14
and then upsetting the tip portions of aluminum rivets
14
. At this time, each of through-holes
110
is formed to have opening diameter &phgr;C slightly larger then outer diameter &phgr;D of aluminum rivet
14
, in consideration of workability. For this reason, connection between internal lead
11
and external terminal
13
depends on the contact between aluminum rivet
14
and the flat portion of internal lead
11
or part of through-hole
110
where aluminum is exposed by punching.
However, internal lead
11
connected to the positive electrode foil has dielectric oxide layers formed on the surfaces thereof by anodic oxidation. This has posed an inherent drawback: even when the surfaces of internal lead
11
are in contact with aluminum spacers
15
, it is difficult to provide electrical connection therebetween. Additionally, as an aluminum electrolytic capacitor continues to be used, the electrolyte solution entering into through-holes
110
having exposed aluminum surfaces chemically reacts with the aluminum and the reaction produces oxide layers on the exposed aluminum surfaces. As a result, it becomes more difficult to provide electrical connection. This has posed a problem of malfunction caused by contact failure.
SUMMARY OF THE INVENTION
The present invention addresses these conventional problems and aims to provide a reliable aluminum electrolytic capacitor in which electrical connection between internal leads and external terminals are ensured.
In order to attain these objects, an aluminum electrolytic capacitor of the present invention includes: (a) a capacitor element structured so that a positive electrode foil and a negative electrode foil are rolled, sandwiching a separator therebetween, (b) internal leads, i.e. one connected to the positive electrode foil at one end and the other to the negative electrode foil at one end, (c) a cylindrical metal case having a bottom for containing this capacitor element together with a electrolyte solution, (d) a pair of external terminals each coupled to the other end of one of the internal leads, and (e) a terminal plate disposed in an opening of the metal case and sealing the metal case. The other end of each of the internal leads has a through-hole. Provided around the peripheral edge of this through-hole is a cylindrical portion formed integral with the internal lead by drawing. While this cylindrical portion is threaded with an aluminum rivet for fixation of the external terminal and the inner peripheral surface of the cylindrical portion is in contact with the outer peripheral surface of the aluminum rivet, the tip portion of the aluminum rivet is upset. Thus, the external terminals provided on the terminal plate are electrically connected to the corresponding internal leads.
In a method of manufacturing an aluminum electrolytic capacitor of the present invention, a punch having a smaller diameter part at its tip, and a dice having a hole for receiving the smaller diameter part therein are used. By lowering the punch, a prepared hole is drilled at one end of each of aluminum internal leads connected to the positive electrode foil or the negative electrode foil. By successively lowering the punch, the prepared hole is drawn to form a cylindrical portion integral with the prepared hole.
Additional objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof, which is best understood with reference to the accompanying drawings.
REFERENCES:
patent: 4876451 (1989-10-01), Ikeda et al.
patent: 5366515 (1994-11-01), Kunugihara et al.
patent: 6310756 (2001-10-01), Miura et al.
patent: 6452784 (2002-09-01), Nakada et al.
patent: 6711000 (2004-03-01), Takeishi et al.
Hata Toshiyuki
Niibo Nario
Oe Yoshinori
Uemura Makoto
Yoshino Tsuyoshi
Dinkins Anthony
Ha Nguyen T.
Wenderoth , Lind & Ponack, L.L.P.
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