Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed... – Blowout type
Reexamination Certificate
1998-03-09
2001-11-27
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
Blowout type
C429S059000, C429S061000
Reexamination Certificate
active
06322921
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sealed-type secondary battery, for example a lithium-ion secondary battery, incorporating a safety device; more specifically, a secondary battery in which an electric circuit of the safety device is made compact for inclusion within a sealing plate of the battery, and a sealing plate assembly containing the safety device for a secondary battery.
BACKGROUND ART
Because of high energy density, the sealed type secondary batteries, lithium-ion secondary batteries among others, are being increasingly used as the power source for driving compact portable appliances such as video camera, portable telephone, personal computer, etc. It is essential for the lithium-ion secondary batteries to have a safety device containing an electric circuit in order to protect the battery against over-charging, over-discharging and excessive electric current. Therefore, such batteries are normally packed in a so-called battery package incorporating an electric circuit working as the safety circuit, designed for installation in an appliance.
FIG. 1
is a conceptual drawing of a battery package containing lithium-ion secondary batteries; where, numeral
1
denotes a case to house cylindrical lithium-ion secondary batteries
2
and
3
designed to have a shape suitable for installation in a certain specific appliance,
4
is a safety circuit disposed between the lithium-ion secondary batteries
2
,
3
and a terminal of the case
1
.
FIG. 17
is a block diagram of a conventional safety circuit
4
; where, the positive voltage supplied from a battery charger flows through a plus terminal
5
, a PTC element
6
, lithium-ion secondary batteries
3
,
2
, FETs
7
,
8
, a thermal fuse
9
and terminal
10
, ultimately to the negative end of battery charger. The lithium-ion secondary batteries
2
,
3
are charged in the above manner.
The lithium-ion batteries
2
,
3
discharge through PTC element
6
, plus terminal
5
, a plus and a minus terminals of an appliance, minus terminal
10
, thermal fuse
9
and FETs
8
,
7
. Voltage detectors
11
,
12
for watching battery voltage are coupled to a control circuit
13
; which circuit turns FET
8
OFF when the battery voltage goes beyond a specified value to prevent over-charging, and turns FET
7
OFF when the battery voltage goes lower than a specified value to cut the electric current for preventing over-discharging. A voltage detector
14
which detects the source-drain voltage of the FET
7
is coupled to the control circuit
13
; which circuit turns the FETs
7
and
8
OFF to cut the electric current when an excessive electric current goes between the plus terminal
5
and minus terminal
10
due to short-circuiting etc. in outside. A thermistor
15
is for monitoring battery temperature from a battery charger, or an appliance, through a terminal
16
.
As described in the above, a conventional battery package contains in its case
1
a safety circuit
4
comprised of preventive means against over-charging, over-discharging of battery, electric current cutting means against excessive electric current flow, battery temperature monitor, etc. mounted on a printed circuit board.
The conventional battery package, however, is accompanied with following drawbacks.
1) Most of the battery packages are packed in their case
1
of specific design dedicated to each of respective shapes of appliances they serve, for the ease of installation.
2) Dedicated battery charger is needed for each of the respective appliances, because case
1
has its own specific design dedicated to each of the respective appliances, and a battery charger has to comply with the shape of case
1
.
3) Safety circuit and structure of terminals adapted to the shape of an appliance occupy a substantially bulky space relative to the space for lithium-ion secondary batteries
2
,
3
.
4) Lithium-ion secondary batteries or other secondary batteries alone are not readily available for ordinary consumers. The conventional battery packages lack versatility.
DISCLOSURE OF THE INVENTION
The invented secondary battery contains an electric circuit working as the safety device inside the battery; by so doing, a secondary battery having a built-in safety device is made available, which secondary battery may be handled as an independent battery in a same way as ordinary batteries.
The electric circuit may be incorporated in a sealing plate of the battery.
The present invention also presents a sealing plate which can discharge the gas within battery outside breaking a vent when the inner gas pressure is raised unusually high by some reason, as well as a secondary battery having such sealing plate.
A first exemplary embodiment of the present application refers to a secondary battery with which a safety circuit containing a current cutting element is incorporated in a sealing member for capping a battery. The safety circuit may be formed compact taking advantage of a high-density integration technology of semiconductors, a miniaturizing technology for components, and a technology for mounting such components in high-density; and such a miniaturized safety circuit may be housed entirely in a small space such as that formed between a sealing cap disposed at the top part of a battery and a current cutting valve, which space never be exposed to the electrolyte under normal conditions. Each of the secondary batteries having such a built-in safety circuit may be handled independently in a same way as an ordinary battery to be installed in a battery chamber of an appliance.
Another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which the safety circuit is treated with a water-resistive, anti-electrolyte resin such as epoxy resin, polybutylene terephthalate resin. The safety circuit is protected against water coming from outside or electrolyte from within.
Another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which an opening or a break-down structure is provided in a circuit substrate board on which a safety circuit is formed. In case the electrolyte or gasified electrolyte sneak into the area of safety circuit, it may be discharged outside through an aperture of a cap, via the opening or the break-down structure provided in the circuit board substrate of safety circuit.
Yet another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which a thermal fuse is provided in a safety circuit. The thermal fuse melts down with heat generated from current cutting element like an FET or the battery itself to break the electrical connection between the positive electrode of battery and the plus terminal for supply outside.
Another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which a thermistor is provided in a safety circuit. The safety of a battery is secured by specifying temperature range for charging a battery.
Another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which the plus output of a battery is connected to a safety circuit via a PTC element. The PTC element may be tripped by heat generated from current cutting element like an FET.
Yet another aspect of the present application refers to a secondary battery according to the first exemplary embodiment, with which a PTC element is provided between the plus terminal for safety circuit and the plus terminal for inputting/outputting with outside. The PTC element may be tripped with an excessive current caused by e.g. short-circuiting of battery output, heat of a battery, or by heat of the safety circuit.
A second exemplary embodiment of the present application refers to a secondary battery according to the first exemplary embodiment, with which a sealing cap is comprised of two terminals, a minus terminal for safety circuit and a plus terminal for inputting/outputting with outside. With the above
Iwaizono Yoshinori
Masumoto Kenjin
Tsurutani Shinji
Brouillette Gabrielle
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
Tsang Susy
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