JPH0472336B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to circuit breakers, and more specifically, to batteries used in electrical devices that instantaneously flow large currents, such as rechargeable power tools and radio-controlled cars. Concerning a small circuit breaker with built-in bimetallic elements that protects.

<Conventional technology> Conventionally, lead-acid batteries, nickel-cadmium batteries, etc., used in electrical equipment such as VTRs, etc.
A small circuit breaker for protecting a secondary battery operates when a current of several amperes or more flows, and has the function of breaking the circuit.

FIG. 3 is a sectional view showing a conventional example of such a small circuit breaker, in which the external lead wire 2
A long plate-shaped conductive frame 21 connected to the frame 21 is used as a base, and in parallel with the base, a similarly long movable contact plate 22 is provided in a state where it is cantilevered at the tip of the frame 21. It is being Movable contact plate 22
A hemispherical contact 23 is fixed to the free end of. A contact plate 24 is installed on the frame 21 to face the contact 23 . In addition, contact plate 2
An insulating plate 29 is interposed between 4 and the frame 21,
Insulation between the two is maintained. Contact plate 24 is connected to another external lead wire 26 . A bimetal support pin 28 is protruded from the center of the frame 21, and a bimetal 27 that can be reversely bent is attached to the tip of the pin 28. Then, wrap the resin 3 around the connecting portion of the external lead wires 25 and 26
Exterior box 30 molded with 1 and made entirely of metal
It is stored in.

In the circuit breaker described above, the circuit current flows through the external lead wire 25, the frame 21, the movable contact plate 22, the contacts 23, the contact plate 24, and the external lead wire 26. In this case, contact 23
Electrical contact between the contact plate 24 and the movable contact plate 22
It is maintained by urging the contact point 23 toward the contact plate 24 using its own elastic force. Then, Joule heat is generated by the current flowing through the frame 21,
When the temperature of the bimetal 27 rises, the bimetal 27 bends and moves the movable contact plate 2 against the elastic force.
2 to release the contact state between the contact point 23 and the contact plate 24, and the circuit breaker can be disconnected.

Since the frame 21 serves as a support for not only the bimetal 27 but also the entire circuit breaker, brass, which has excellent rigidity, is used as its material. In addition, by not providing a conductive plate for electrical connection between the lead wire 25 and the movable contact plate 22, and having the frame 21 itself serve as a conductive plate, the entire circuit breaker can be made smaller and lighter. It is characterized by its brightness.

<Problems to be Solved by the Invention> However, in the above circuit breaker, all of the current flows through the frame 21, and the frame 21 is a relatively small piece with a small heat capacity and a relatively large electrical resistance. Since it is made of brass, it operates with a current of several amps to several tens of amps.

By the way, when a secondary battery such as a nickel-cadmium battery is short-circuited, a current of several tens of amperes to over a hundred amperes flows through it, so recently this power has been used to power rechargeable power tools, radio-controlled cars, etc. It is used in electrical equipment where a current of several tens of amperes or more flows instantaneously.

Therefore, to protect batteries for these large current applications,
Even when trying to use the above circuit breaker, there was a problem that it could not be used because the current capacity was small.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a circuit breaker that can operate with a large current.

<Means for Solving the Problems> In order to achieve the above object, in the circuit breaker of the present invention, a bypass member is fixed to a bimetal support frame. The bypass member is formed of a material having lower electrical resistance and thermal resistance than the frame, and bypasses the current so that less current flows into the frame.

In another aspect of the invention, a portion of the bypass member is exposed to the outside.

<Function> If the circuit breaker has the above configuration,
Since most of the current that would otherwise flow into the bimetal support frame is bypassed to the bypass member, the amount of current flowing through the frame can be reduced, and heat generation in the frame can be suppressed to a low level. Therefore, the operating current can be increased compared to conventional circuit breakers.

Furthermore, by exposing a portion of the bypass member to the outside, it is possible to enhance the radiation effect of heat generated in the frame and the bypass member.

<Examples> Hereinafter, examples will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a sectional view showing the circuit breaker of the present invention, in which a circuit breaker connected to an external lead wire 5,
A brass frame 1 is fixed by spot welding or the like on a long and relatively thick copper heat sink 12 that also serves as a conductive plate, and a movable contact is attached to the tip of the copper heat sink 12 as a bypass member. The plate 2 is supported in a cantilevered manner. A hemispherical contact 3 is fixed to the free end of the movable contact plate 2. A contact plate 4 is installed on the frame 1 to face the contact 3. Note that an insulating plate 9 is interposed between the contact plate 4 and the frame 1 to maintain insulation between the two. Contact plate 4 is connected to another external lead wire 6. A pin 8 for bimetal support is provided in the center of the frame 1.
A bimetal 7 that can be reversely bent is supported at the tip of the pin 8. and,
The circuit breaker is housed in a metal exterior case 10 with the connecting portion of the external lead wire 6 molded with resin 11 and one end of the heat sink 12 exposed to the outside.

In the above configuration, since the heat sink 12 made of copper with low electrical resistance and thermal resistance is fixed to the frame 1, most of the current bypasses the heat sink 12, which has good conductivity. Therefore, frame 1, heat sink 1
The heat generated in the heat sink 2 is small, and the generated heat is efficiently radiated to the outside through the exposed portion of the heat sink 12.

Therefore, the operating temperature of the bimetal 7 becomes higher than that of the conventional one, and the operating current value of the circuit breaker can also be increased from the conventional 4A to, for example, 20A.

Note that it is also possible to carry out the process without exposing the heat sink 12 to the outside. However, in that case, heat will be radiated to the outside via the outer box 10, so the heat radiation effect will be slightly lowered, and the operating current value of the circuit breaker will also be lowered accordingly.

In this embodiment, the heat sink 12 is longer than the frame 1 by the exposed portion;
Since the width of the heat sink 12 is the same as or slightly wider than the width of the frame 1, the overall size is not so large compared to the conventional example. Therefore, for example, as shown in FIG.
Since the battery pack 15 can be easily installed within the valley of the battery pack 15, there is no need to increase the external dimensions of the battery pack 15 for installation.

Furthermore, since the circuit breaker of the present invention uses bimetal, it operates even when the battery temperature rises abnormally due to overcharging of the secondary battery, just like the conventional circuit breaker described above. It can also play the role of charging protection.

Note that the present invention is not limited to the above embodiments; for example, the heat sink may be made of aluminum, silver, etc. as long as it is made of a material with high electrical conductivity and high thermal conductivity; Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, the present invention bypasses most of the current flowing into the bimetal support frame by the bypass member fixed to the frame, so that the current flowing through the frame can be reduced. The heat generated by the frame can be reduced. Therefore, the operating current of the circuit breaker can be increased.

Further, according to the present invention, the heat generated in the frame and the bypass member is radiated through the bypass member, and especially when a part of the bypass member is exposed to the outside, the heat radiation effect can be enhanced. . Therefore, it has the unique effect of increasing the operating current and allowing use even with a large current.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a circuit breaker of the present invention, FIG. 2 is a perspective view showing the circuit breaker installed in a battery pack, and FIG. 3 is a sectional view showing a conventional circuit breaker. 1... Frame, 3... Contact, 7... Bimetal, 12... Heat sink.

Claims (1)

[Claims] 1. A circuit breaker in which a circuit current is passed through a bimetal support frame and the bimetal is deformed by the heat generated in the frame to open and close contacts, wherein a bypass member is fixed to the frame. A circuit characterized in that the bypass member is made of a material having lower electrical resistance and thermal resistance than the frame, and bypasses the current so that the current flowing into the frame is reduced. breaker. 2. The circuit breaker according to claim 1, wherein the bypass member is partially exposed to the outside.