Information
-
Patent Grant
-
6483420
-
Patent Number
6,483,420
-
Date Filed
Wednesday, August 2, 200023 years ago
-
Date Issued
Tuesday, November 19, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
-
CPC
-
US Classifications
Field of Search
US
- 337 401
- 337 157
- 337 119
- 180 271
- 180 274
- 180 279
- 200 6108
- 361 115
-
International Classifications
-
Abstract
When an ignitor 29 is ignited by an abnormal signal sent from outside, a heating agent 27 charged into a thermite case 26 is heated, a retainer 45 is melted by the heat, a compression spring 39a is expanded to allow the thermite case 26 to move up. Therefore, electrical connection between the thermite case 26 and each of a first bus bar 11a and a second bus bar 19a is interrupted. Thus, it is possible to reliably interrupt a circuit within a short time. Further, a low-melting metal 28 mounted to an intermediate portion of the second bus bar 19a is blown out by heat caused by a current flowing through the second bus bar 19a to interrupt the circuit. Therefore, even if an abnormal signal is not sent to the ignitor 29 due to failure of a control circuit or the like, it is possible to reliably interrupt the circuit.
Description
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a circuit breaker for interrupting an electric circuit for a short time.
2. Description of The Related Art
In an electrical component system provided in a vehicle, when something is wrong with a load of a power window or the like, or when something is wrong with a wire harness or the like constituted by a plurality of electric wires connecting a battery and various loads to each other, a high-current fuse inserted between the battery and the wire harness is blown out to interrupt a connection between the battery and the wire harness, thereby preventing the loads, the wire harness and the like from being burnt and damaged.
However, in the case of the electric component system using such a high-current fuse, even if something is wrong with the load of the power window or the like, or something is wrong with the wire harness or the like connecting the battery and various loads, the fuse is not blown out unless a current equal to or greater than a tolerated value which is previously set for the high-current fuse. Therefore, various protecting apparatuses have been developed for detecting the current and interrupt the connection between the battery and the wire harness when a high current close to the tolerated value is continuously flowing.
FIG. 1
is a sectional view showing one example of the protecting apparatus using a bimetal (Japanese Utility Model Application Laid-open No. S64-29756). The protecting apparatus shown in
FIG. 1
is made of insulation resin, and comprises a housing
103
formed at its upper portion with a fuse accommodating portion
102
, a lid
113
for closing the fuse accommodating portion
102
such that the latter can be opened and closed, a power source terminal
105
disposed in a lower portion in the housing
103
such that an upper end of the power source terminal
105
projects into the fuse accommodating portion
102
and a lower end thereof is exposed outside, and the exposed portion of the power source terminal
105
being connected to a positive terminal of a battery
104
, a load terminal
109
disposed in a lower portion in the housing
103
such that an upper end of the load terminal
109
projects into the fuse accommodating portion
102
and a lower end thereof is exposed outside, and the exposed portion of the load terminal
109
being connected to a load
108
through an electric wire
107
constituting a wire harness
106
, a fusible member
110
made of low-melting metal disposed in the fuse accommodating portion
102
, and having one end connected to an upper end of the power, source terminal
105
and the other end connected to an upper end of the load terminal
109
, an intermediate terminal
111
disposed in a lower portion in the housing
103
such that the intermediate terminal
111
is located at an intermediate position between the power source terminal
105
and the load terminal
109
and a lower end of the intermediate terminal
111
is exposed outside, and the exposed portion being connected to a negative terminal of the battery
104
, and a bimetal
112
which is made of a long plate-like member comprising two kinds of metal bonded together and which is disposed such as to be opposed to the fusible member
110
such that a lower end of the bimetal
112
is connected to an upper end of the intermediate terminal
111
and an upper end thereof being bent into an L-shape.
When an ignitor switch and the like of the vehicle are operated, and a current is flowing through a path comprising the positive terminal of the battery
104
, the power source terminal
105
, the fusible member
110
, the load terminal
109
, the electric wire
107
of the wire harness
106
, the load
108
, and the negative terminal of the battery
104
, and when an abnormal condition occurs in the load
108
or in the wire harness
106
connecting the load
108
and a protecting apparatus
101
, and a current equal to or greater than the tolerated value flows through the fusible member
110
, the fusible member
110
is heated and blown out for protecting the load
108
, the wire harness
106
and the like.
Further, even if something is wrong with the load
108
or the wire harness
106
connecting the load
108
and the protecting apparatus
101
, and a large current flows through the fusible member
110
, if the current does not exceed the tolerated value, the fusible member
110
is heated by the current flowing through the latter, and the bimetal
112
starts deforming. When a predetermined time is elapsed from the instant when the large current starts flowing through the fusible member
110
, a tip end of the bimetal
112
comes into contact with the fusible member
110
, and a large short-circuit current flows through the fusible member
110
in a path comprising the positive terminal of the battery
104
, the power source terminal
105
, the fusible member
110
, the intermediate terminal
111
, and the negative terminal of the battery
104
, and the latter is blown out.
With the above structure, even when a current equal to or lower than the tolerated value flows for a preset time or longer, the circuit is interrupted to protect the wire harness
106
and the load
108
.
As another protecting apparatus rather than this protecting apparatus
101
, a protecting apparatus
121
shown in
FIG. 2
has also developed (Japanese Utility Model Application Laid-open No. S64-29756).
The protecting apparatus
121
shown in
FIG. 2
comprises a housing
122
made of insulation resin, a power source terminal
124
embedded in one side surface of the housing
122
and having a lower end connected to a positive terminal of a battery
123
, and a load terminal
128
embedded in the other side surface of the housing
122
and having a lower end connected to a load
127
through an electric wire
126
constituting a wire harness
125
. The protecting apparatus
121
further comprises an electric wire
131
including a fusible lead
129
which is made of low-melting metal and formed into U-shape and a heat-proof coating
130
formed such as to cover the fusible lead
129
. The protecting apparatus
121
further comprises a coil
132
. The coil
132
is made of shape-memory alloy which is formed into a shape wound around the electric wire
131
as shown in
FIG. 2
when it is in a martensite phase state, and which is returned to its original phase shape fastening the electric wire
131
when it is heated to 120° C. to 170° C. The protecting apparatus
121
further comprises an external terminal
133
whose upper end is connected to one end of the coil
132
and whose lower end is connected to a negative terminal of the battery
123
.
When an ignitor switch and the like of the vehicle are operated, and a current is flowing through a path comprising the positive terminal of the battery
123
, the power source terminal
124
, the fusible lead
129
of the electric wire
131
, the load terminal
128
, the electric wire
126
of the wire harness
125
, the load
127
and the negative terminal of the battery
123
, and when an abnormal condition occurs in the load
127
or in the wire harness
125
connecting the load
127
and a protecting apparatus
121
, and a current equal to or greater than the tolerated value flows through the fusible lead
129
, the fusible lead
129
is heated and blown out for protecting the load
127
, the wire harness
125
and the like.
Further, even if something is wrong with the load
127
or the wire harness
125
connecting the load
127
and the protecting apparatus
121
, and a large current flows through the fusible lead
129
, if the current does not exceed the tolerated value, the fusible lead
129
is heated by the current flowing through the latter, and a temperature of the coil
132
rises. When a predetermined time is elapsed from the instant when the large current starts flowing through the fusible lead
129
, and the temperature of the coil
132
rises to 120° C. to 170° C., the coil
132
changes from its martensite phase state to its original phase and bites into the heat-proof coating
130
which is softened by heat and comes into contact with the fusible lead
129
, and a large short-circuit current flows through the fusible lead
129
in a path comprising the positive terminal of the battery
123
, the power source terminal
124
, the fusible lead
129
, the coil
132
, the external terminal
133
, and the negative terminal of the battery
123
, and the latter is blown out.
With the above structure, even when a current equal to or lower than the tolerated value flows for a preset time or longer, the circuit is interrupted to protect the wire harness
125
and the load
127
.
FIG. 3
is a perspective view of a conventional fusible-link fusible conductor (Japanese Utility Model Application Laid-open No. S56-20254). This fusible-link fusible conductor
201
comprises a fusible conductor body
202
made of high-melting metal, and a fusible conductor piece
203
made of low-melting metal held on an intermediate portion of the fusible conductor body
202
through a pinching piece
202
a
, and a blowout characteristics are improved by dispersing low-melting metal and producing an alloy.
According to such a structure, if an excessive current flows through the fusible conductor body
202
, the fusible conductor piece
203
is melted by heat caused by the excessive current, thereby blowing out the fusible conductor
201
.
However, in the above-described conventional protecting apparatuses
101
and
121
, there are problems as follows.
First, in the case of the protecting apparatus shown in
FIG. 1
, it is detected whether a large current flows through the fusible member
110
using the bimetal
112
made of two kinds of metals having different thermal expansion coefficients and bonded to each other. Therefore, if the magnitude of the current flowing through the fusible member
110
, the bimetal
112
is deformed, and the time that elapsed before the circuit is interrupted is varied.
Thus, when a failure that a large current flows intermittently occurs, a temperature of the fusible member
110
does not rise more than a certain value, and there is an adverse possibility that the wire harness
106
or the load
108
may be burnt before the protecting apparatus
101
interrupts the circuit.
In the case of the protecting apparatus
121
shown in
FIG. 2
, it is detected whether a large current flows through the fusible lead
129
using the coil
132
made of shape-memory alloy. Therefore, if the magnitude of the current flowing through the fusible lead
129
, the coil
132
is deformed, and the time that elapsed before the circuit is interrupted is varied.
Thus, when a failure that a large current flows intermittently occurs, a temperature of the fusible lead
129
does not raise more than a certain value, and there is an adverse possibility that the wire harness
125
or the load
127
may be heated excessively before the protecting apparatus
121
interrupts the circuit.
Further, in the protecting apparatuses shown in
FIGS. 1 and 2
, the heat reaction time of the bimetal
112
or the coil
132
which is a thermal-deformable electrical conduction member is varied depending upon the current flowing therethrough. Further, the heat reaction of the thermal-deformable electrical conduction member is not operated timely in some cases when an abnormal condition occurs (when excessive current flows).
In the case of the fusible conductor
201
shown in
FIG. 3
, the dispersion time of the low-melting metal is varied low-melting metal, it takes a long time for dispersing the low-melting metal and thus, the low-melting metal is not operated timely in some cases when an abnormal condition occurs (when excessive current flows).
Thereupon, as a circuit breaker which operates timely when an abnormal condition occurs (when excessive current flows), Japanese Patent Application No. H11-64055 (filed on Mar. 10, 1999) (not prior art) shows a circuit breaker. According to this circuit breaker, a pair of connecting terminals comprise a connecting terminal (e.g., buss bar) for a battery and a connecting terminal for a load. A conductor member (e.g., thermite case) is in contact with the pair of connecting terminals. When an abnormal condition of a vehicle occurs, the conductive member is moved upward by a compression spring or the like in response to an abnormal signal input from a control circuit or the like, thereby cutting off the electrical connection between the one connecting terminal and the other connecting terminal to interrupt the circuit.
However, this circuit breaker has problems that if a wire of the control circuit or the like may be broken, or if a current sensor or the like is damaged and the abnormal signal is not sent to the circuit breaker, the circuit can not be interrupted.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a circuit breaker capable of reliably interrupting a circuit in a short time to protect an electrical part when an abnormal signal of a vehicle is input, and capable of reliably interrupting the circuit even if the control circuit is out of order and the abnormal signal is not sent.
To achieve the above object, according to a first aspect of the present invention, there is provided a circuit breaker comprising: a first breaker including a first connecting terminal connected to a power source, a second connecting terminal connected to a load, and a conductive member coming into electrical contact with both the first and second connecting terminals, the first breaker moves the conductor member when a vehicle is under an abnormal condition to cut the electrical connection between the first and second connecting terminals, thereby interrupting a current; and a second breaker including a notch which is a fusible conductor formed on an intermediate portion of at least one of the first and second connecting terminals, the notch is blown out by heat caused by a current flowing through the at least one of the first and second connecting terminals, thereby interrupting the current, wherein a current is supplied from the power source to the load, and a circuit from the power source to the load is interrupted when the vehicle is under the abnormal condition.
According to the first aspect, the first breaker supplies a current to the load through the pair of connecting terminals comprising the first and second connecting terminals and the conductive member under a normal condition, and moves the conductive member based on the interrupting signal input when the vehicle is under the abnormal condition, thereby cutting off the electrical connection between the one connecting terminal and the other connecting terminal to interrupt the current. Therefore, it is possible to reliably interrupt the circuit within a short time.
Further, the second breaker includes the notch which is the fusible conductor formed on the intermediate portion of at least one of the first and second connecting terminals, and the notch is blown out by heat caused by the current flowing through the at least one of the first and second connecting terminals, thereby interrupting the current. That is, since the two kinds of circuit protecting members are provided, even when the interrupting signal is not input to the first breaker due to failure of a control unit or the like and the circuit can not be interrupted by the first breaker, the circuit can be interrupted by the second breaker, and an electrical part can be protected.
According to a second aspect of the invention, in the circuit breaker of the first aspect, the first breaker comprises a heating portion having the conductive member into which a heating agent is charged, an ignitor for igniting the heating agent by an interrupting signal, an outer case for accommodating the ignitor and the heating portion, an extensible resilient member, and a removable member for mounting the resilient member in its compressed state, the removable member being capable of being attached to and detached from the outer case, and being disposed in the vicinity or in contact with the heating portion when the removable member is mounted to the outer case, and the removable member is melted by heat caused by the heating agent.
According to the second aspect, the removable member for mounting the resilient member in its compressed state is disposed in the vicinity or in contact with the heating portion when the removable member is mounted to the outer case. When the ignitor ignited by the abnormal signal sent from outside, the heating agent charged into the heating portion is heated, and the removable member is melted by the heat. Since the resilient member which had been compressed is expanded to allow the heating portion to jump up, the electrical connection between the first and second connecting terminals is cut. Therefore, it is possible to reliably interrupt the circuit within a short time to protect the electrical part.
Further, since the removable member can be attached to and detached from the outer case, the attaching and detaching operation of the removable member is simple. Since the resilient member is held by the removable member, no external force is applied to the connected portion between the first and second connecting terminals and the heating portion.
According to a third aspect of the invention, in the circuit breaker of the second aspect, the second breaker comprises a low-melting metal as the fusible conductor.
According to the third aspect, since the low-melting metal is added as the fusible conductor, the low-melting metal is dispersed by the heat caused by the current flowing through the connecting terminal, the resistance is increased, thereby blowing out the fusible conductor to interrupt the circuit.
According to a fourth aspect of the invention, in the circuit breaker of the circuit breaker of the third aspect, the fusible conductor is mounted to the intermediate portion of at least one of the first and second connecting terminals by heat welding or caulking.
According to the fourth aspect, since the fusible conductor is mounted to the intermediate portion of at least one of the first and second connecting terminals by heat welding or caulking, the low-melting metal is dispersed by the heat caused by the current flowing through the connecting terminal, the resistance is increased, thereby blowing out the fusible conductor to interrupt the circuit.
According to a fifth aspect of the invention, in the circuit breaker of the third aspect, the interrupting signal is input to the first breaker when a value of the current became equal to or greater than a threshold value, and the value of the current when the fusible conductor is blown out is set greater than the threshold value.
According to the fifth aspect, since the interrupting signal is input to the first breaker when a value of the current became equal to or greater than a threshold value, and the value of the current when the fusible conductor is blown out is set greater than the threshold value, when the circuit can not be interrupted by the first breaker, the circuit can be interrupted by the second breaker, and the second breaker is not operated before the first breaker is operated.
According to a sixth aspect, in the circuit breaker of the second aspect, the heating portion is formed at its end with a side wall, the side wall and tip ends of the first and second connecting terminals are connected to each other by low-melting members.
According to the sixth aspect, since the side wall and tip ends of the first and second connecting terminals are connected to each other by low-melting members, if the removable member and the low-melting metal are melted by the heat of the heating agent, the heating portion jumps up to interrupt the electrical connection between the first and second connecting terminals. Therefore, it is possible to reliably interrupt the circuit within a short time to protect the electrical part. Further, since no spring force is applied to the low-melting metal which is the connected portion between the first and second connecting terminals and the heating portion, it is possible to enhance the reliability of the connected portion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a sectional view showing one example of a conventional protecting apparatus using a bimetal;
FIG. 2
is a sectional view showing another example of the conventional protecting apparatus;
FIG. 3
is a perspective view of a conventional fusible-link fusible conductor;
FIGS. 4A and 4B
are sectional views of a circuit breaker of an embodiment before a circuit is interrupted;
FIG. 5
is an exploded perspective view of the circuit breaker of the embodiment;
FIG. 6
is a sectional view of the circuit breaker taken along the line VI—VI in
FIG. 4
;
FIG. 7
is a circuit diagram for sending an interrupting signal to an ignitor provided in the circuit breaker;
FIG. 8
is a view of a retainer of the circuit breaker of the embodiment before the circuit is interrupted;
FIG. 9
is a view of the retainer of the circuit breaker of the embodiment after the circuit is interrupted;
FIG. 10
is a perspective view of an essential portion of a circuit breaker of a first modification;
FIG. 11
is a sectional view of the circuit breaker of the first modification shown in
FIG. 10
taken along the line XI—XI in
FIG. 10
;
FIG. 12
is a perspective view of an essential portion of a circuit breaker of a second modification;
FIGS. 13A and 13B
are partial sectional views of the circuit breaker of the second modification shown in
FIG. 12
taken along the line XIII—XIII in
FIG. 12
; and
FIG. 14
is a perspective view of an essential portion of a circuit breaker of a third modification.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Embodiments of a circuit breaker of the present invention will be explained in detail with reference to the drawings.
First, a structure of a first breaker will be explained. In
FIG. 4A
, a plate-like long first buss bar
11
a
is made of copper or copper alloy for example, and is connected to a battery (not shown) or the like. A plate-like long second buss bar
19
a
is also made of copper or copper alloy for example, and is connected to a load (not shown) or the like.
In
FIG. 5
, a cap
14
a
is formed with an extended portion
50
having a rectangular groove
51
. A resin case
14
b
is formed with a wedge-like locking portion
55
. If the groove
51
is fitted to the locking portion
55
, the cap
14
a
is put on the resin case
14
b
. The cap
14
a
and the resin case
14
b
constitute an outer case, and comprise container made of insulation material such as resin (thermoplastic resin).
The resin case
14
b
is formed with an opening
53
into which a cylindrical thermite case
26
is accommodated. A heating agent
27
and an ignition
29
to which a lead wire
31
is connected are accommodated in the thermite case
26
. An upper lid
24
is put on an upper portion of the heating agent.
The thermite case
26
has excellent thermal conductivity, and is not melted by heat of the heating agent
27
. It is preferable to use brass, copper, copper alloy, stainless steel or the like as material of the thermite case
26
. The thermite case
26
is formed by restriction working or the like of metal, and is shaped into a cylindrical or rectangular parallelepiped shape.
The ignition
29
includes an igniting agent so that the igniting agent is ignited by heat generated by a current flowing through the lead wire
31
when an abnormal condition occurs in the vehicle such as collision accident of the vehicle, thereby allowing the heating agent
27
to generate the thermite reaction heat.
The first buss bar
11
a
having a circular hole
12
and the second buss bar
19
a
having a circular hole
20
are bent upward at right angles, the bent portions are inserted into the resin case
14
b
, and bus bar tip ends
13
a
and
16
a
are respectively in contact with left and right side walls of the thermite case
26
through low-melting metals
23
as low-melting material such as solder (melting point is 200° C. to 300° C.) or the like.
The left and right side walls of the thermite case
26
are bonded to the bus bar tip ends
13
a
and
16
a
by means of the low-melting metals
23
, and the first buss bar
11
a
and the second buss bar
19
a
can be electrically connected to each other through the low-melting metals
23
and the thermite case
26
.
The low-melting metal
23
is made of at least one metal selected from Sn, Pb, Zn, Al and Cu.
The heating agent
27
is made of metal-oxide powder such as ferric oxide (Fe
2
O
3
) and aluminum powder, and is thermite agent which thermite-reacts by heat of the lead wire
31
to generate high heat. The thermite agent is charged for moisture proofing into the thermite case
26
which is a metal container. Chromic oxide (Cr
2
O
3
), manganese oxide (MnO
2
) or the like may be used instead of ferric oxide (Fe
2
O
3
).
The heating agent
27
may be made of mixture comprising at least one metal powder selected from B, Sn, Fe, Si, Zr, Ti and Al; at least one metal selected from CuO, MnO
2
, Pb
3
O
4
, PbO
2
, Fe
3
O
4
and Fe
2
O
3
; and at least one additive comprising alumina, bentonite and talc. Such a heating agent is easily is ignited by the ignition
29
, and the low-melting metal
23
can be melted within a short time.
A retainer
45
made of resin is disposed in the opening
53
of the resin case
14
b
and in a lower portion of the thermite case
26
. A compression spring
39
a
is accommodated in the retainer
45
in a compressed manner. The retainer
45
can be attached to and detached from the resin case
14
b
. When the retainer
45
is attached to the resin case
14
b
, the retainer
45
is disposed in the vicinity or in contact with the thermite case
26
, and constitutes an attaching/detaching member which is melted by heat of the heating agent
27
.
As shown in
FIG. 8
, the retainer
45
comprises a base
61
, notches
63
formed in the base
61
, retainer bellies
65
embedded uprightly with respect to the notches
63
, and a pair of retainer locking portions
67
formed on tip ends of the retainer bellies
65
. The pair of retainer locking portions
67
are mounted to the resin case
14
b.
A compression spring
39
a
which is helically wound around the retainer locking portions
67
is disposed outside the retainer bellies
65
. A tip end of the compression spring
39
a
is locked by the retainer locking portions
67
. That is, the compression spring
39
a
is sandwiched in the retainer
45
in the compressed state. The first breaker has the above-described structure.
Next, a structure of a second breaker will be explained. In
FIG. 4B
, a low-melting metal
28
which is a fusible conductor as the second breaker is mounted to an intermediate portion of the second buss bar
19
a
. The low-melting metal
28
is dispersed by heat caused by a current flowing through the second buss bar
19
a
, and if the resistance is increased, the fusible conductor is blown out to interrupt the current. Here, the fusible conductor is a notch of the buss bar including the low-melting metal
28
. The low-melting metal
28
functions to blow out the fusible conductor more quickly.
The low-melting metal
28
is made of tin, cadmium, lead, bismuth, indium or alloy thereof.
As shown in
FIG. 6
, the low-melting metal
28
is mounted to the intermediate portion of the second buss bar
19
a
by heat welding. The low-melting metal
28
may be mounted to each of the first buss bar
11
a
and the second buss bar
19
a.
As shown in
FIG. 7
, the circuit breaker comprises a current sensor
71
for detecting current flowing through the first buss bar
11
a
and the second buss bar
19
a
, a collision sensor (G sensor)
73
for detecting a collision of the vehicle, a control circuit
75
for outputting a driving control signal to the driving circuit
77
when a current value detected by the current sensor
71
became equal to a threshold value, or for outputting the driving control signal to the driving circuit
77
when an acceleration value detected by the G sensor
73
became equal to or greater than a predetermined value, and the driving circuit
77
for applying an interrupting signal which interrupts the circuit to the heater
79
in the ignitor
29
.
The circuit breaker may include a voltage sensor for detecting an excessive voltage and a temperature sensor for detecting a temperature, and may output, to the control circuit
75
, an output from the voltage sensor and an output from the temperature sensor.
The interrupting signal is applied to the heater
79
when the detected current value became equal to or greater than the threshold value. The value of a current flowing through the second buss bar
19
a
when the low-melting metal
28
is blown out is set to a value exceeding the threshold value.
Next, the operation of the circuit breaker of the embodiment having the above-described structure will be explained with reference to the drawings.
First, under normal conditions, the first buss bar
11
a
and the second buss bar
19
a
are electrically connected to each other through the low-melting metal
23
and the thermite case
26
, and a current is supplied from the battery (not shown) to the load (not shown).
Next, the operation will the current sensor
71
, the G sensor
73
, the control circuit
75
and the like are under normal conditions and the interrupting signal is sent to the ignitor
29
when the vehicle is under abnormal conditions will be explained. If an abnormal condition occurred in the vehicle and the excessive current flowed through the first buss bar
11
a
and the second buss bar
19
a
, the current sensor
71
detects the current. If the current value detected by the current sensor
71
became equal to or greater than the threshold value, the control circuit
75
outputs the driving control signal to the driving circuit
77
, and the driving circuit
77
applies the interrupting signal to the heater
79
in the ignitor
29
in accordance with the driving control signal. Therefore, the current flows to the heater
79
of the ignitor
29
through the lead wire
31
.
Then, the ignitor
29
is ignited by heat generated by the current and therefore, the heating agent
27
which is a thermite agent generates a thermite reaction heat according to the following reaction expression:
Fe
2
O
3
+2Al→Al
2
O
3
+2Fe+386.2 Kcal
The thermite case
26
is heated by the thermite reaction heat, the low-melting metals
23
are heated and melted by the heat of the heating agent
27
and the heat of the thermite case
26
. Simultaneously, the resin retainer locking portions
67
which compress and fix the compression spring
39
to the retainer
45
are melted by the heat. As a result, the compression spring
39
a
is expanded, and the thermite case
26
jumps up toward the cap
14
a
as shown in FIG.
9
.
Therefore, the electrical connection between the thermite case
26
, the first buss bar
11
a
and the second buss bar
19
a
is cut off. That is, the electric circuit of the vehicle is interrupted.
Next, there will be explained the operation when the current sensor
71
, the G sensor
73
are damaged, disconnection of the control circuit
75
occurs, the interrupting signal (abnormal signal) is not sent to the ignitor
29
when the vehicle is under the abnormal conditions, and the first breaker is short-circuited.
In this case, the first breaker is not operated. If an excessive current exceeding the threshold value flowed through the second buss bar
19
a
, the low-melting metal
28
provided on the intermediate portion of the second buss bar
19
a
is heated by the excessive current, the low-melting metal
28
is dispersed to the copper alloy of the second buss bar
19
a
so that its resistance is increased. If the resistance is increased, a heating value is further increased, and the fusible conductor is blown out. This fusible conductor is a notch of the buss bar including the low-melting metal
28
, and the low-melting metal
28
functions to blow out the fusible conductor more quickly. Therefore, the first buss bar
11
a
and the second buss bar
19
a
are electrically disconnected from each other swiftly, and the electric circuit of the vehicle is swiftly interrupted.
In this manner, according to the circuit breaker of the present embodiment, the abnormal signal is input from the vehicle, the thermite reaction is caused by the heating agent
27
using the heat of the ignitor
29
, the low-melting metal
23
and the retainer locking portion
67
are melted by the thermite reaction heat and thus, the compression spring
39
a
instantaneously jumps up. Therefore, it is possible to reliably interrupt the electric circuit of the vehicle within a short time, and to protect the electric parts.
Further, since there are provided two kinds of circuit protecting members, i.e., the first and second breakers, even if the control circuit or the like is out of order and the interrupting signal is not input to the first breaker and the circuit can not be interrupted by the first breaker, the circuit can be interrupted by the second breaker to protect the electric parts.
Further, since the current value when the fusible conductor is blown out is set to be greater than the threshold value, the second breaker is not operated before the first breaker is operated. Moreover, since the two kinds of circuit protecting members can efficiently be disposed, space can be saved, and the costs can be reduced.
Further, since the retainer locking portion
67
is disposed at an inner side with respect to the compression spring
39
a
, the retainer locking portion
67
tends to be tilted inward by the reaction force of the compression spring
39
a
, the thermite case
26
and the retainer
45
come into strong contact with each other. Therefore, heat is excellently transmitted from the thermite case
26
to the retainer
45
and as a result, the retainer locking portion
67
can be melted efficiently.
Furthermore, the compression spring
39
a
can easily be assembled into the retainer
45
only by pushing the compression spring
39
a
into the retainer
45
, and the retainer
45
can easily be mounted to the resin case
14
b.
Since the compression spring
39
a
is held by the retainer
45
, no external force is applied to the connected portion between the first buss bar
11
a
, the second buss bar
19
b
and the thermite case
26
, i.e., to the low-melting metal
23
. Therefore, the reliability of the connected portion can be enhanced.
A sub-assembly between the compression spring
39
a
and the retainer
45
is inserted from a fuse lower surface, i.e., from the opening
53
of the resin case
14
b
. Therefore, the assembling operation of the entire circuit breaker is facilitated. Further, after the circuit is interrupted, if the retainer
45
and the thermite case
26
are replaced by new ones, the resin case
14
b
can be used again as it is as a fuse.
Further, since the cap
14
a
is put on the resin case
14
b
, the thermite case
26
will not jump out from the cap
14
a
when the circuit is interrupted, and this can prevent a burn caused by heat.
Next, three modifications of the circuit breaker of the embodiment will be explained.
FIG. 10
is a perspective view of an essential portion of a circuit breaker of a first modification.
FIG. 11
is a sectional view of the circuit breaker of the first modification shown in
FIG. 10
taken along the line XI—XI in FIG.
10
.
A circuit breaker of a first modification shown in
FIG. 10
is characterized in that a first low-melting metal
28
a
and a second low-melting metal
28
b
are mounted to an intermediate portion of a second buss bar
19
b
by heat welding as the second breaker.
By providing the first low-melting metal
28
a
and the second low-melting metal
28
b
in this manner, the first low-melting metal
28
a
and the second low-melting metal
28
b
are dispersed by heat caused by an excessive current and the resistance is further increased. Therefore, the fusible conductor is blown out and even if the first breaker is not operated, the circuit can be interrupted more quickly.
FIG. 12
is a perspective view of an essential portion of a circuit breaker of a second modification.
FIG. 13B
is partial sectional view of the circuit breaker of the second modification shown in
FIG. 12
taken along the line XIII—XIII in FIG.
12
. As shown in
FIG. 13B
, a low-melting metal
28
caulked by caulking pieces
93
a
and
93
b
is mounted to an intermediate portion of a second buss bar
19
c
as the second breaker.
First, as shown in
FIG. 13A
, a buss bar
91
which is the intermediate portion of the second buss bar
19
c
is formed with a pair buss bar pieces
92
a
and
92
b
. The low-melting metal
28
is disposed on the buss bar
91
between the pair of projecting buss bar pieces
92
a
and
92
b
. The pair of buss bar pieces
92
a
and
92
b
are inwardly bent (in the direction of the arrow in
FIG. 13A
) into inverted U-shape and caulked, thereby forming the pair of caulking pieces
93
a
and
93
b
as shown in FIG.
13
B.
That is, the low-melting metal
28
is caulked by the pair of caulking pieces
93
a
and
93
b
and mounted to the buss bar piece
91
. Therefore, according to the circuit breaker of the second modification also, the same effect as that of the circuit breaker of the embodiment can be obtained.
FIG. 14
is a perspective view of an essential portion of a circuit breaker of a third modification. As shown in
FIG. 14
, in the case of the circuit breaker of the third modification, the low-melting metal
28
is not provided on the intermediate portion of the second buss bar
19
a
, and only a buss bar notch
38
is formed by cutting the buss bar, thereby forming the second breaker. A resistance value of the buss bar notch
38
is higher than that of portion of buss bar other than the buss bar notch
38
. Here, the fusible conductor is only the buss bar notch
38
.
According to the circuit breaker of such a third modification, even if the low-melting metal
28
is not added, when the excessive current flows to the buss bar notch
38
, since the resistance value of the buss bar notch
38
is higher than that of other portion, the resistance is further increased. Therefore, the buss bar notch
38
which is the fusible conductor is blown out, and even if the first breaker is not operated, the circuit can be interrupted more quickly. Further, the circuit structure is simple and thus, the cost is reduced.
The present invention is not limited to the circuit breaker of the above-described embodiment. Although the compression spring
39
a
and the low-melting metal
23
are provided, and when the retainer
45
and the low-melting metal
23
are melted, the circuit is interrupted in the embodiment, only the retainer
45
may be provided without providing the low-melting metal
23
, and when the retainer
45
is melted, the circuit may be interrupted.
Further, although the resin member is used as the retainer
45
in the embodiment, the low-melting metal such as solder (melting point is 200° C. to 300° C.) which is melted by heat of the heating agent
27
may be used. It is of course possible to make various modifications without departing from the spirit and scope of the invention.
Claims
- 1. A circuit breaker comprising:a first breaker including: a first connecting terminal connected to a power source; a second connecting terminal connected to a load; a movable conductive member coming into electrical contact with both said first and second connecting terminals; wherein said movable conductive member is moved into a position to interrupt the electrical connection between said first and second connecting terminals by an interrupting signal which is input to said first breaker in an abnormal condition; and a second breaker including a notch which is filled with a fusible conductor formed on a portion of at least one of said first and second connecting terminals, wherein said fusible conductor in said notch is blown out due to heat caused by a current flowing through said at least one of said first and second connecting terminals, wherein said second breaker is activated to interrupt the electrical connection between said first and second connecting terminals in case of a failure of said first breaker during the abnormal condition.
- 2. A circuit breaker according to claim 1, wherein said first breaker comprises:a heating portion having said conductive member into which a heating is charged; an ignitor for igniting said heating agent by said interrupting signal; outer case for accommodating said ignitor and said heating portion; an extensible resilient member; and a removable member for mounting said resilient member in its compressed state, said removable member being capable of being attached to and detached from said outer case, and being disposed in the vicinity or in contact with said heating portion when said removable member is mounted to said outer case, and said removable member is melted by heat caused by said heating agent.
- 3. A circuit breaker according to claim 2, wherein said second breaker comprises a low-melting metal as said fusible conductor.
- 4. A circuit breaker according to claim 3, wherein said fusible conductor is mounted to the intermediate portion of at least one of said first and second connecting terminals by heat welding or caulking.
- 5. A circuit breaker according to claim 3, wherein said interrupting signal is input to said first breaker when a value of said current became equal to or greater than a threshold value, and said value of said current when said fusible conductor is blown out is set greater than said threshold value.
- 6. A circuit breaker according to claim 2, wherein said heating portion is formed at its end with a side wall, said side wall and tip ends of said first and second connecting terminals are connected to each other by low-melting members.
- 7. A circuit breaker comprising:a first connecting terminal; a second connecting terminal; a first breaker including a heating portion movably disposed in electrical contact with each of the first connecting terminal and the second connecting terminal, the heating portion being charged with a heat generation agent and configured to generate heat during an abnormal condition; and a second breaker comprising a fusible notch formed on a portion of at least one of the first and second connecting terminals, the notch configured to be blown out by heat generated from a current flowing through the connecting terminals to disconnect electrical connection between the first and second connecting terminals, wherein, during the abnormal condition, at least one of the first and second breakers is activated to disconnect the electrical connection between the first and second connecting terminals.
- 8. A circuit breaker according to claim 7, wherein the first breaker further comprises an ignitor for igniting the heat generation agent during the abnormal condition.
- 9. A circuit breaker according to claim 8, wherein the ignitor is configured to be activated when the magnitude of the current flowing through the terminals exceeds a predetermined threshold value.
- 10. A circuit breaker according to claim 7, wherein the first breaker further comprises:an extendable resilient member; a locking member for mounting the resilient member in a compressed state to a retainer, the locking member disposed near the heating portion, so that, during the abnormal condition, the locking member is melted by the heat generated in the heating portion to allow the resilient member to extend from the compressed state, thereby exerting force onto the heating portion to be displaced.
- 11. A circuit breaker according to claim 7, wherein the fusible notch is made of a low-melting material.
- 12. A circuit breaker according to claim 7, wherein the fusible notch is welded or caulked to the portion of at least one of said first and second connecting terminals.
- 13. A circuit breaker according to claim 7, wherein:the first breaker has a first threshold value of current for igniting the heat generation agent; and the second breaker has a second threshold value of current for blowing out the fusible notch, the second threshold value set greater than the first threshold value.
- 14. A circuit breaker according to claim 7, wherein tips of the first and second connecting terminals are connected to an end portion of the heating portion, and a low-melting material is disposed between the tips of the first and second connecting terminals and the end portion of the heating portion.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-220155 |
Aug 1999 |
JP |
|
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May 1989 |
JP |
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Feb 1998 |
JP |
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JP |
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Sep 1998 |
JP |
10-241524 |
Sep 1998 |
JP |
10-310004 |
Nov 1998 |
JP |
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Dec 1998 |
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