Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed... – Blowout type
Reexamination Certificate
2001-08-10
2004-10-19
Tsang-Foster, Susy (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
Blowout type
Reexamination Certificate
active
06805992
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to a battery and a portable equipment, and more particularly, to a battery having a safety valve such as to reduce an internal pressure thereof when the internal pressure rises high and to a portable equipment using the battery.
BACKGROUND ART
Along with the widely spread use of portable equipments such as a portable telephone, a note book PC or the like in recent years, studies have been progressed on a battery for use in the equipments. A structure of a battery used in a portable equipment is described in, for example, Japanese Patent Laying-Open No. 7-296790(1995).
FIG. 23
is a perspective view of a battery described in the publication. Referring to
FIG. 23
, the battery is constructed of an electrode group
204
, a rectangular prismatic battery case
205
housing the electrode group
204
, an opening seal plate
212
sealing up the electrode group housed in the rectangular prismatic case
205
.
The electrode group
204
is formed by rolling up a composite of an anode plate
201
and a cathode plate
202
with a separator
203
interposing therebetween into a whirl-like bundle.
The rectangular prismatic battery case
205
has an opening face A. The electrode group
204
is inserted into the case
205
through the opening face A. The rectangular prismatic battery case
205
has a space in the interior thereof. The rectangular prismatic case
205
is fabricated from an iron plate of 0.3 mm in thickness. The rectangular prismatic battery case
205
is filled with an electrolyte.
The opening seal plate
212
is constructed of a lid plate
209
, a glass hermetic seal
211
and an anode terminal
210
. The glass hermitic seal
211
is present between the opening seal plate
212
and the anode terminal
210
.
The anode terminal
210
and an anode plate
201
are electrically connected to each other by an anode lead
208
. The anode lead
208
is connected to the anode terminal
210
by means of resistance welding. Furthermore, the lid plate
209
is fixed to the rectangular prismatic battery case
205
by means of laser welding.
A gas vent is provided to the rectangular prismatic battery case
205
. A rupture film
206
is provided so as to close the gas vent. An etched portion
207
small in thickness formed by etching is provided to the rupture film
206
.
Such a prior art battery has cases where a temperature rises high therein due to various causes: as examples, a case where the battery is exposed to a high temperature, a case where internal or external short-circuit arises and a case where an excessive current discharge occurs to a rapid temperature increase. Especially in a case of a secondary battery, when charge is effected under application of an excessively high voltage in excess of a prescribed value, the battery would be heated to a high temperature.
When a battery is in a high temperature condition, an electrolyte evaporates to generate gas. Furthermore, the electrolyte also decomposes to generate gas. Since this gas is confined within the rectangular prismatic battery case
205
, an internal pressure of the battery increases. A further increase in the internal pressure breaks the battery and in some cases, a human body would be exposed to a danger.
Such circumstances being considered, a rupture film
206
has been provided to the rectangular prismatic battery case
205
to cope with the breakage caused by a built-up internal pressure. The rupture film
206
works this way: When an internal pressure of a battery exceeds a prescribed value, the etched portion
207
of the rupture film
206
is first blown off to avoid the breakage of a battery body itself. Gas or an electrolyte is leaked out through the blown-off portion to prevent increase in the internal pressure of the battery. The battery shown in
FIG. 23
is designed such that when the internal pressure thereof reaches 8.8×10
5
Pa, the rupture film
206
is broken.
In a construction as shown in
FIG. 23
, however, a necessity arises that the rupture film
206
is provided as a separate member from the rectangular prismatic battery case
205
, which has produced a problem to cause increase in manufacture cost.
Therefore, the present invention has been made in order to solve the problem as described above.
It is accordingly an object of the present invention to provide a battery having a safety valve capable of suppressing an increase in manufacture cost while adopting a simple and easy construction and a portable equipment using the battery.
DISCLOSURE OF THE INVENTION
A battery according to the present invention has an exterior member and a safety valve. The exterior member is of a tube-like shape. The safety valve is provided to the exterior member to reduce an internal pressure of the battery. The exterior member includes a relatively thick portion and a relatively thin portion, wherein the relatively thin portion constitutes the safety valve.
In a battery of such a construction, since the safety valve can be formed with a difference in thickness of the exterior member, the safety valve can be provided without using a separate member. As a result, a construction thereof is simple and easy, thereby enabling suppression of increase in manufacture cost.
Furthermore, preferably, the safety valve is formed at a side face of the battery. In this case, the side face of the battery is generally larger in area than is each of a top face thereof and a bottom face thereof. For this reason, a large area safety valve can be formed at the side face, which causes the safety valve to operate at a low pressure, with the result that a level of safety is further increased.
Moreover, preferably, the relatively thin portion is formed so as to surround part of the relatively thick portion. In this case, the thin portion and the thick portion surrounded by the thin portion constitute the safety valve. Since an area of the portions is increased, the safety valve operates at a low pressure, thereby, enabling a level of safety to further increase.
Besides, preferably, at least one of a length, a thickness and a shape of the relatively thin portion and a total area of the relatively thin portion and a region surrounded by the relatively thin portion is adjusted to set an internal pressure of a battery at which the safety valve operates. In this case, the internal pressure of the battery at which the safety valve operates can be properly set, whereby there can be provided a battery with a higher reliability and a higher level of safety.
Furthermore, preferably, the battery further includes an electrode disposed in the region surrounded by the relatively thin portion. In this case, the safety valve can be formed when the electrode is formed; therefore, the safety valve can be formed without adding a new process step.
A portable equipment according to the present invention includes: a battery; and a body of the portable equipment to which the battery is mounted. The battery includes: an exterior member of a tube-like shape and a safety valve provided to said exterior member to reduce an internal pressure of the battery. The exterior member is constituted of a relatively thick portion and a relatively thin portion. The safety valve is located so as to face the body of the portable equipment.
In a portable equipment constructed in such a way, the safety valve is located so as to face the body of the portable equipment. Hence, even when the safety valve operates to eject high pressure gas or liquid, a pressure of the gas or the liquid is imposed only on the body of the portable equipment; so, no chance arises that the pressure acts on a man holding the portable equipment. As a result, a level of safety is improved compared with a portable equipment such as in which a safety valve has its aperture directed to a human body.
Still furthermore, preferably, the portable equipment further includes a shield member interposing between the battery and the body thereof. In this case, even when the safety valve operates to eject high pressure gas or liquid, the gas or liquid is blocked by
Hanafusa Kiyoshi
Ishida Hiroichi
Rothwell, Figg Ernst & Manbeck, PC
Tsang-Foster Susy
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