Electricity: electrothermally or thermally actuated switches – Thermally actuated switches – With fusible – combustible or explosive material
Reexamination Certificate
2001-07-20
2003-04-29
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Thermally actuated switches
With fusible, combustible or explosive material
C337S414000, C337S159000, C337S186000, C337S290000, C337S297000, C337S416000, C429S007000, C429S061000, C429S150000
Reexamination Certificate
active
06556122
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermal fuse used to prevent equipment from being damaged due to overheat, and a battery pack.
BACKGROUND OF THE INVENTION
Recently, the advance in technical development of secondary batteries is very remarkable. Particularly, as batteries used for equipment such as cellular phones, PHS, and notebook sized personal computers, secondary batteries which are compact and can be used for a long time per charge are developed and put to practical use. Specifically, batteries such as Ni—Cd cells, Ni—H cells, Li-ion cells, and Li-polymer cells are increasingly developed and put to practical use, enhancing the development of secondary batteries which are smaller in size and have a long service life.
However, with reduction in size of the batteries, heat is generated due to rapid discharge, for example, caused by short-circuiting between positive and negative electrodes. And it gives rise to a fear of damage or explosion of the batteries. In order to prevent such problem, a thermal fuse is used, which blows when heat is generated due to short-circuiting or the like, thereby assuring safety of the secondary batteries. As a thermal fuse like this, a thermal fuse using a fusible metal is commonly employed. Such fusible metal is attached via an insulating layer to a part which may heat in a battery or power source equipment. When a battery or power source equipment is heated, the fusible metal is melted to break the circuit before the temperature reaches a dangerous level. Thus, discharging or charging of the battery is discontinued to prevent overheating of the battery. Further, breakdown of the power source equipment due to heat can be prevented.
FIGS. 22
,
23
,
24
show a conventional thermal fuse. In
FIGS. 22
,
23
,
24
, the conventional thermal fuse used is a thin-type fuse, comprising lead conductors
40
,
41
, and an insulating plate
42
. The conventional thermal fuse has an insulating plate
42
having a width greater than that of the lead conductor
40
,
41
.
Inter-terminal distance “d” between the lead conductor
40
and lead conductor
41
is less than the width of fusible alloy welding position
46
. Therefore, the inter-terminal distance d is shorter than the fusing distance when the thermal fuse is normally fused.
FIG. 21
is a perspective view of a conventional battery pack. The battery pack is used as a square battery pack whose thickness is identical with the width of the insulating plate
42
.
The conventional battery pack ranges from 6 mm to 5 mm in thickness. However, with the recent reduction in size and thickness of cellular phones, there has been an increasing demand for pack batteries of smaller and thinner type ranging from 2.5 mm to 4 mm in thickness. However, in a conventional thin-type thermal fuse, there has been a problem such that the width of insulating plate
42
cannot be reduced without reducing the width of lead conductors
40
,
41
. Also, there has been a limit to size reduction with respect to the lengthwise direction of the insulating plate since the withstand voltage distance between terminals is the above inter-terminal distance “d” in an air atmosphere.
Also, in case the conventional thermal fuse is merely reduced in size, deterioration of various characteristics such as bonding strength of each member and thermal response will take place as a matter of course.
The present invention provides a thermal fuse and battery pack which ensure excellent reliability, high quality and low cost, with power less consumed by the wiring in the battery body, even after being reduced in size.
SUMMARY OF THE INVENTION
A thermal fuse of the present invention comprises:
(a) a fuse main body having a substrate, a fusible metal and a cover;
(b) a pair of terminals protruding from the fuse main body,
the pair of terminals including a first terminal and a second terminal,
one end of the first terminal protruding from one end of the fuse main body, and
one end of the second terminal protruding from the other end of the fuse main body,
wherein the other end of the first terminal includes a first fusible metal connection;
the other end of the second terminal includes a second fusible metal connection;
the fusible metal is disposed between the first terminal and the second terminal;
one end of the fusible metal is connected to the first fusible metal connection, and the other end of the fusible metal is connected to the second fusible metal connection;
the cover is disposed so as to cover the fusible metal, the first fusible metal connection, and the second fusible metal connection; and
length L
1
of the fuse main body positioned between the first terminal and the second terminal and thickness L
3
of the main body are in a relationship as follows:
2.0 mm<L
1
<8.5 mm
0.4 mm<L
3
<2.5 mm.
A battery pack of the present invention comprises:
(i) a battery;
(ii) a main boy to accommodate the battery;
(iii) a wire led out of the main body and electrically connected to the battery; and
(iv) a thermal fuse disposed between the wire so as to contact with the main body,
wherein the thermal fuse comprises the above mentioned structure.
Preferably, the width of the first fusible metal connection is less than the width of the first terminal, and the width of the second fusible metal connection is less than the width of the second terminal.
Preferably, the fuse main body further comprises an bonding film disposed between the substrate and the cover, and the bonding film has a third through-hole, while the fusible metal, the first fusible metal connection and the second fusible metal connection are located in the third through-hole.
Preferably, each terminal of the first terminal and the second terminal ranges from 3×10
10
Pa to 8×10
10
Pa in Young's modulus, and from 4×10
8
Pa to 6×10
8
Pa in tensile strength.
A method of manufacturing a thermal fuse of the present invention comprises the steps of:
(a) manufacturing at least one substrate of a strip substrate and a plate substrate;
(b) disposing a first terminal and a second terminal opposed to each other on the substrate,
where one end of the first terminal includes a first fusible metal connection, and one end of the second terminal includes a second fusible metal connection,
the first fusible metal connection and the second fusible metal connection are opposed to each other on the substrate, and
the other ends of the first terminal and the second terminal protrude in the respective directions of the substrate;
(c) placing an bonding film on the substrate with the first terminal and the second terminal disposed thereon, then heating under pressures the substrate and the bonding film thus laminated, thereby bonding the bonding film to the substrate by first weld deposit produced by heating,
where the bonding film has a third through-hole, and the first fusible metal connection and the second fusible metal connection are exposed inside the third through-hole;
(d) disposing a fusible metal between the first fusible metal connection and the second fusible metal connection;
(e) disposing a cover film to cover the fusible metal and the bonding film, then heating the cover film and the bonding film positioned around the fusible metal except the zone where the fusible metal is disposed, thereby bonding the bonding film to the cover film by second weld deposit produced by heating; and
(f) forming a fuse main body by cutting off weld deposit zones, so as to include a part of the weld deposit zone between the cover film and the bonding film bonded by the second weld deposit,
where the fuse main body includes a rise portion and the weld deposit zone, and the fusible metal is located in the rise portion.
By the above configuration, a thermal fuse reduced in size and thickness can be obtained. Further, it is possible to obtain a thermal fuse and battery pack which ensure excellent reliability, high quality and low cost, with power less consumed by the wiring in the battery body, even after being reduced in size.
REFERENCES:
patent: 44941
Isozaki Kenzo
Izaki Masatoshi
Mukai Takahiro
Ohtsuka Shin'ichi
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
Vortman Anatoly
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