Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
1999-03-02
2001-06-05
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
C361S093100, C361S115000
Reexamination Certificate
active
06243245
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a forced-fusion fuse which when an abnormality has occurred due to short-circuiting of a wire harness within an automobile, a collision of automobiles, etc. compulsively interrupts the current between a power source and a respective load, and a circuit breaker that uses the forced-fusion fuse.
A conventional electrical system of an automobile uses a blade fuse or a large capacity fuse within a fuse box, thereby protecting a within-automobile wire harness when some abnormality or other has occurred in such wire harness or load (e g., power windows). A blade fuse and a large current fuse are fused when a large current has flown therein, As a result, the current between the battery and the wire harness in which an abnormality has occurred is interrupted, with the result that the wire harness or load is protected.
A large current fuse comprises a casing, first and second fuse terminals protruding from a lower end of the casing, a first connection plate within the casing that has been connected to the first fuse terminal, a second connection plate within the casing that has been connected to the second fuse terminal, a tin alloy on the first connection plate, and a fusion portion (or earth portion) connecting the first and second connection plates. A wire harness is connected to each of the fuse terminals. When the wire harness has been short-circuited whereby a large current has been caused to flow in the connection plate and a heat has been generated therein, the fusion portion is fused to thereby interrupt the current between the battery and the short-circuited wire harness. The tin alloy which is a low-melting-point metal is provided in correspondence with a rare short-circuiting and, by diffusion thereof, plays the role of causing the formation of an alloy layer on the fusion portion and thereby enlarging the resistance.
SUMMARY OF THE INVENTION
However, in the above-described electrical system, when an excessively large current has flown in the wire harness due to a slight short-circuiting resulting from a rub thereof with a body or the like of the automobile, the slight short-circuiting intermittently occurs and so the large current fuse is not fused, with the result that there is the possibility that the wire harness will be largely damaged.
When no short-circuiting occurs in the wire harness at the collision time of the automobile, no large current flows in the large current fuse and so the large current fuse is not fused. For this reason, even after an automobile has given rise to a collision accident, there is the possibility that the electric power will continue to flow from the battery to the load. Accordingly, during a disposing of the automobile accident, there is the possibility that the wire harness will be short-circuited and as a result an excessively large current will flow.
As one method of solving such a problem, there is a method wherein the capacity of the large current fuse is made small so that even at a slight short-circuiting of the wire harness, the large current fuse will be fused. However, as illustrated in
FIG. 5
, when making the capacity of the large current fuse small, the fuse cutoff-by-fusion characteristic approaches to the waveform of the start-up rush current of a motor which is a load. For this reason, when the start-up rush current (e.g., the start-up rush current of a motor, etc.) has flown in the load, there is the possibility that the large current fuse will be cut off by fusion.
In view of the above, an object of the present invention is to provide a forced-fusion fuse which when there is the fear that an abnormality will occur in a wire harness or the like can compulsively interrupt the current between the battery and the wire harness to thereby zero the adverse effect thereof upon the automobile.
To attain the above object, a first aspect of the present invention provides a forced-fusion fuse which comprises a casing, a heat generating material within the casing, inducing means for inducing the heat generating material to make a heat generation reaction, and a fusion member that is fused by the generation of heat in the heat generating material.
According to the above-described construction, the heat generation reaction of the heat generating material is induced to occur by the operation of the inducing means, whereby the heat generating material generates heat. When the temperature of the heat generated from the heat generating material rises up to a prescribed, or higher than prescribed, temperature, the fusion member is fused with the result that the flow of a current through the fusion member is stopped.
The heat generating material may include a mixture of a powder of metal oxide and a powder of aluminium.
As a result of this, the heat generating material becomes instantaneously high in temperature due to the thermit reaction between the metal oxide and aluminium, with the result that the fusion member is instantaneously fused.
The inducing means may cause the occurrence of a heat generation reaction of the heat generating material by heating and, in this case, may include a heating wire.
The inducing means may cause the occurrence of the heat generating material by arc discharge and, in this case, the inducing means may include an electrode for causing arc discharge.
A second aspect of the present invention provides a circuit breaker which comprises a sensor, a forced-fusion fuse, and a controller.
The forced-fusion fuse includes a casing, a heat generating material within the casing, inducing means for inducing the heat generating material to make a heat generation reaction, and a fusion member that is fused by the generation of heat by the heat generating material. The fusion member makes a connection between a battery and the electric parts of an automobile. The sensor senses an abnormal state in which it is necessary to stop the supply of the power from the battery to the electric parts of the automobile to thereby output an abnormality detection signal. The controller causes the operation of the inducing means when an abnormality detection signal has been output from the sensor. The heat generation reaction of the heat generating material is induced to occur by the inducing means, and the fusion member is fused by the generation of heat from the heat generating material to thereby interrupt the current between the battery and the electric parts of the automobile.
According to the above-described construction, for example, in an abnormal state in which it is necessary to stop the supply of the power from the battery to the electric parts of the automobile, as when the wire harness has fallen in an abnormality or a collision of automobiles has occurred, the sensor senses this abnormality and outputs an abnormality detection signal to the controller, whereby the controller causes the operation of the inducing means. Through the operation of the inducing means, the heat generating member generates heat and this heat fuses the fusion member, whereby the supply of the power from the battery to the electric parts of the automobile is interrupted.
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European Search Report dated Sep. 17, 1999.
Nakamura Goro
Totsuka Mitsuhiko
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Jackson Stephen W.
Yazaki -Corporation
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