Current path cut-off component of cell

Details Current path cut-off component of cell Current path cut-off component of cell

1999-04-15

2001-05-08

Maples, John S. (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With control means responsive to battery condition sensing...

C429S007000, C429S090000, C429S057000

Reexamination Certificate

active

06228523

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a current path cut-off component of a cell and more particularly to a current path cut-off device of a cell to be used for ensuring safety against an increase in internal pressure of a cell case.
2. Description of the Prior Art
For example, a rechargeable lithium ion secondary cell with an organic solvent type electrolyte poured and sealed into the interior of a cell case has heretofore been used widely as a power source of portable devices such as portable telephones and personal computers.
However, when such a cell is recharged, if the recharging is performed to an excessive degree or with an electric current larger than a predetermined current, a problem will occur in the cell, with evolution of gas, increase in internal pressure and temperature of the cell, swelling of the cell, and eventual cracking of the cell case, resulting in that the electrolyte present within the cell case oozes to the exterior and may exert adverse effect to the device in which the cell is incorporated. Even if such a problem in the cell does not lead to such a result, if the use of the cell is continued under the aforesaid occurrence of such a problem, the swelling of the cell will become more and more conspicuous, which may cause bursting of the cell. Therefore, it has been necessary to immediately stop the use of the cell upon occurrence of such a problem.
In a conventional current path cut-off component of a cell, as shown in
FIGS. 8 and 9
, a cell lid
3
and an upwardly displaceable actuator
4
are mounted through a gasket
2
to a case
1
of a cell which is, for example, a circular cell. The cell lid
3
is mounted by caulking for example so as to hermetically seal the interior of the cell case
1
, and the actuator
4
is disposed below the cell lid
3
.
Vent holes
3
a
are formed in the cell lid
3
so that upon displacement of the underlying actuator
4
the air present inside the cell lid can escape to the exterior through the vent holes
3
a.
The actuator
4
has a disk-like safety valve portion
4
a
formed, for example, by drawing with use of a press. The safety valve portion
4
a
has a central protuberance
4
b
which projects downward in the figure, with radial grooves
4
c
being formed around the protuberance
4
b.
An insulating board
5
is disposed on the underside of the actuator
4
. A hole
5
a
for insertion therethrough of the protuberance
4
a
of the safety valve portion
4
a
and a vent hole
5
b
are formed through the insulating board
5
.
Underlying the insulating board
5
is a lead fixing member
6
, in which are formed a hole
6
a
communicating with the hole
5
a
of the insulating board
5
and a vent hole
6
b
communicating with the vent hole
5
b
of the insulating board
5
.
The protuberance
4
b
of the safety valve portion
4
a
is inserted into the holes
5
a
and
6
a
of the insulating board
5
and the lead fixing member
6
, respectively, and a lead
7
formed by a thin metallic plate is bonded to the tip of the protuberance
4
b.
The lead
7
is bonded to the tip of the protuberance
4
b
, the actuator
4
and the lead
7
are in electric conduction with each other. The opposite end of the lead
7
is connected to a power generating element
8
located at a lower position in the figure, with a current path being formed between the power generating element
8
and the cell lid
3
.
In the event of an increase in internal pressure of the cell case
1
due to a problem in the interior of the cell, a gas of an increased pressure flows like arrow A in FIG.
9
through the vent holes
5
b
and
6
b
and exerts an upward force on the back side of the safety vale portion
4
a.
With this force, the safety valve portion
4
a
is raised up and the lead
7
is ruptured at its portion bonded to the protuberance
4
b
, whereby the current path of the cell is cut off.
As a result, the increase in internal pressure of the cell case
1
is suppressed to prevent bursting of the cell.
As portable devices become smaller in size, the recent cells using such a current path cut-off component are encountering a strong demand for the reduction of size. Such a demand is becoming more and more strong also for the conventional cells.
However, in such a conventional current path cut-off component as referred to above, unless the size of the safety valve portion
4
a
is made large, an increased internal pressure of the cell cannot be detected with a high accuracy. This point has been an obstacle to the reduction of size.
Moreover, in the conventional current path cut-off component of a cell, since the cell lid
3
and the actuator
4
are formed as separate members, the number of parts used becomes larger and the cell assembling operation becomes complicated.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems and provide a current path cut-off component of a cell capable of being reduced in both the size and the number of parts used.
According to the first embodiment adopted by the present invention for solving the above-mentioned problems, there is provided a current path cut-off component of a cell, comprising a cell case containing a power generating element, a cell lid for closing the cell case in a hermetically sealed state, a diaphragm portion formed by swelling a thin-walled portion of the cell lid inwards of the cell case, a lead connected to the power generating element and bonded to a substantially central part of the diaphragm portion, and a fixing member for fixing the lead in the interior of the cell case in the bonded state of the lead to the diaphragm portion, wherein a current path is formed between the cell lid and the power generating element through the diaphragm portion and the lead, the diaphragm portion displaces itself upon an increase in internal pressure of the cell case above a predetermined value, and this displacement of the diaphragm portion causes the diaphragm portion and the lead to be disconnected from each other to cut off the current path.
According to the second embodiment adopted by the invention for solving the foregoing problems, in combination with the above first means, the diaphragm portion is formed thick at its central part and thereabouts to which the lead is bonded and is formed thin at its surrounding portion adjacent thereto.
According to the third embodiment adopted by the invention for solving the foregoing problems, in combination with the above first means, the lead is formed thinner at its portion bonded to the diaphragm portion than at the other portion thereof.
According to the fourth embodiment adopted by the invention for solving the foregoing problems, in combination with any of the above first to third means, the diaphragm portion and the lead are bonded together by welding.


REFERENCES:
patent: 4943497 (1990-07-01), Oishi et al.
patent: 5609972 (1997-03-01), Kaschmitter et al.

Affiliated with

Also associated with

Rating

Current path cut-off component of cell does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Current path cut-off component of cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Current path cut-off component of cell will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2535577