JP2001145251A - Circuit-protecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit-protecting device for coping with troubles being generated in many sites of an electrical circuit and also troubles other than those for generating an overcurrent. SOLUTION: The circuit-protecting device is provided with a PTC element 41 being connected in series with a coil 21 of a relay 20 that is provided between a battery 10 and a load L, while an electrical heating element 52 is arranged near the PTC element 41. Then, a control circuit 43 drives the electrical heating element 42 in response to a signal from the outside when a vehicle fails and trips the PTC element 41, thus breaking current flowing to the coil 21, releasing a contact 22 of the relay 20, and breaking current flowing to an electrical circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection device used for protecting an electric circuit of a motor vehicle, for example.

[0002]

2. Description of the Related Art Conventionally, an electric circuit of an automobile is, for example, shown in FIG.
As shown schematically in FIG.
It comprises a circuit protector 30 and a load L. As the circuit protector 30, a fuse is mainly used.

In this electric circuit, when an ignition switch (not shown) is turned on, the battery 10 supplies power to the relay 20. As a result, a current flows through the coil 21 built in the relay 20, and the contact 22 is closed. As a result, the current from the battery 10 is
It is supplied to the load L via the zero contact 22 and the circuit protector 30. Thereby, the electric circuit enters the operating state.

In this operating state, if a failure such as a short circuit of a circuit conductor or a failure of a component occurs in a circuit component constituting an electric circuit, an overcurrent flows through the circuit protector 30 and the fuse generates heat. The fuse element melts. Thereby, the current flowing from the battery 10 to the load L is cut off, and the electric circuit is protected.

[0005]

However, the conventional circuit protection device in which the circuit protector 30 composed of a fuse is incorporated functions only when the fault occurs downstream of the circuit protector 30, If a failure occurs upstream of the circuit protector 30, for example, between the relay 20 and the circuit protector 30, the function does not work.

For this reason, the circuit could not be cut off when a failure occurred on the upstream side of the circuit protector 30. Further, when a factor other than the overcurrent, for example, when the airbag is activated, the current flowing in the electric circuit cannot be cut off.

Further, in a conventional circuit protection device in which a current is interrupted by a fuse, when the fuse is blown, the electric circuit cannot be returned to the original state unless the fuse is replaced with a new one.

Therefore, such a problem has been solved by, for example, an automotive wiring protection device disclosed in Japanese Patent Application Laid-Open No. 6-335159. FIG. 3 shows a block diagram of a conventional automobile wiring protection device.

That is, in this automobile wiring protection device, as shown in FIG. 3, a PTC (Positive Temperature Coe) is connected in series with a circuit conductor 107 disposed on the body of the automobile.
fficient) The element 101 is inserted, and power from the battery is supplied to the load L via the PTC element 101. The PTC element 101 has a function of rapidly increasing the resistance value at a certain temperature (referred to as “trip phenomenon”).

Therefore, when an overcurrent flows through the circuit conductor 107, the PTC element 101 generates heat and the resistance value increases,
The current flowing through the circuit conductor 107 is substantially cut off. Thereby, the electric circuit is protected.

However, since the PTC element 101 in this automotive wiring protection device is only used as a substitute for the fuse in the above-described conventional circuit protection device, if a failure occurs upstream of the PTC element 101, However, there is a problem that the circuit protection device does not function.

An object of the present invention is to provide a circuit protection device that can cope with a fault that has occurred in many parts of an electric circuit and that can cope with a fault other than a fault that generates an overcurrent.

[0013]

The present invention has the following arrangement to solve the above-mentioned problems. The circuit protection device according to claim 1 includes a relay having a coil and a contact, wherein one end of the contact is connected to a power supply side and the other end of the contact is connected to a load side; A variable resistance element connected in series and having a resistance value that increases as the temperature increases, a heating element disposed in the vicinity of the variable resistance element, and the heating element in response to a signal supplied from outside when a vehicle malfunctions And a control circuit for driving the control circuit.

According to the first aspect of the present invention, the control circuit causes the heating element to generate heat in response to, for example, an abnormal signal supplied from the outside when the vehicle is abnormal. As a result, the resistance value of the variable resistance element arranged near the heating element increases, and the current flowing through the variable resistance element is cut off, so that the current flowing through the coil of the relay is also cut off. As a result, the contact of the relay is opened and the current supplied from the power supply to the load is cut off. Therefore, by appropriately selecting a signal supplied from the outside, it is possible to provide a circuit protection device capable of coping with a failure occurring in many parts of the electric circuit.

Further, the invention of claim 2 is characterized in that, in the invention of claim 1, the variable resistance element is a PTC element.

According to the second aspect of the present invention, since the variable resistance element is a PTC element, the resistance value of the PTC element is further increased, and the effect is enhanced.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a current sensor for detecting a current is further provided, and the control circuit responds to a current detection signal from the current sensor. And driving the heating element.

According to the third aspect of the present invention, the control circuit drives the heating element when the current detection signal from the current sensor indicates, for example, an overcurrent. Thereby, the contact of the relay is opened, and the current supplied from the power supply to the load is cut off. Therefore, for example, if a current sensor is arranged in the vicinity of the power supply, the current supplied to all loads can be cut off when a failure such as an overcurrent flows in any part of the electric circuit. It is possible to provide a circuit protection device that can cope with a failure of substantially the entire circuit.

According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, an airbag sensor for detecting that an airbag has been activated is further provided, and the control circuit comprises: The heating element is driven in response to an airbag operation detection signal from the airbag sensor.

According to the fourth aspect of the present invention, the control circuit drives the heating element when the airbag sensor detects that the airbag has been activated. Thereby, the contact of the relay is opened, and the current supplied from the power supply to the load is cut off. Accordingly, the present invention provides a circuit protection device that can cut off a current flowing in an electric circuit not only when an overcurrent flows due to a short circuit of a circuit conductor or a failure of a component, but also when an unexpected event such as activation of an airbag occurs. it can.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the circuit protection device of the present invention will be described in detail with reference to the drawings. In addition,
Hereinafter, the same or corresponding parts as those described in the section of the related art will be denoted by the same reference numerals.

An electric circuit to which the circuit protection device according to the embodiment of the present invention is applied includes a battery 1 as shown in FIG.
0, a relay 20, a circuit protector 40, a current sensor 50, an airbag sensor 60, and a load L.

The battery 10 supplies power to the entire electric circuit. The first terminal of the battery 10 is grounded, and the second terminal of the battery 10 is connected to the relay 2 via the current sensor 50.
Connected to 0. Although FIG. 1 shows an electric circuit having one relay 20 for simplification of description, the number of relays may be plural. In this case, the second terminal of the battery 10 is connected to each relay, and a circuit protector and a load are connected downstream of each relay.

The relay 20 comprises a coil 21 and a contact 22. The first terminal of the coil 21 is the battery 1
0 is connected to the second terminal, and the second terminal of the coil 21 is connected to the circuit protector 40.

The first terminal of the contact 22 is connected to the battery 10
, And the second terminal of the contact 22 is connected to the first terminal of the load L via the circuit protector 40. The contact 22 of the relay 20 is open when no current flows through the coil 21 and is closed by the flow of current.

The load L includes, for example, lamps such as a headlamp and a direction indicator, motors for driving a wiper and a power window, and the like. As described above, the first terminal of the load L is connected to the second terminal of the contact 22 of the relay 20 via the circuit protector 40, and the second terminal of the load L is grounded.

The current sensor 50 detects the magnitude of the current output from the battery 10 and supplies a current detection signal indicating the detection result to the circuit protector 40. As the current sensor 50, various types of well-known current sensors can be used.

The current sensor 50 is arranged near the second terminal of the battery 10. Thereby, the battery 10
Can monitor the total current output from the battery 10, even if a failure such as a short circuit of a circuit conductor or a failure of a component occurs in any part of the electric circuit, the battery 10 is supplied to the load L. Current can be interrupted.

The airbag sensor 60 detects whether an airbag (not shown) has been activated, and supplies an airbag activation detection signal indicating the detection result to the circuit protector 40.

The circuit protector 40 comprises a PTC element 41, a heating element 42 and a control circuit 43. As described above, the PCT element 41 has a function of rapidly increasing the resistance value at a certain temperature and substantially interrupting the current flowing through the PCT element 41. The first terminal of the PTC element 41 is connected to the second terminal of the coil 21 described above.
Are grounded.

The heating element 42 is arranged near the PTC element 41 and generates heat when a driving signal is supplied from the control circuit 43. The temperature of the PTC element 41 is controlled by the heat generated by the heating element 42. That is, P
The TC element 41 is turned on or off according to the heat generated by the heating element 42.

The control circuit 43 supplies a drive signal to the heating element 42 in response to a current detection signal from the current sensor 50 and an airbag operation detection signal from the airbag sensor 60. That is, the control circuit 43 supplies a drive signal to the heating element 42 when the current value based on the current detection signal from the current sensor 50 is equal to or greater than the predetermined current value.

Further, the control circuit 43 generates a detection value based on an air bag operation detection signal from the air bag sensor 60,
When the value is equal to or more than the predetermined value, a drive signal is supplied to the heating element 42. In FIG. 1, the supply path of the power supply to the control circuit 43 is not shown.

Next, the operation of the electric circuit to which the circuit protection device according to the embodiment of the present invention thus configured is applied will be described.

First, when an ignition switch (not shown) is turned on, the battery 10 supplies power to the relay 20. Thereby, the coil 2 built in the relay 20
Current flows through the PTC element 41 and the PTC element 41, and the contact 22 is closed. As a result, the current from the battery 10 is supplied to the load L via the relay 20 and the circuit protector 40.
Thereby, the electric circuit enters the operating state.

In this operating state, a current detection signal from the current sensor 50 and an airbag operation detection signal from the airbag sensor 60 are supplied to the control circuit 43 of the circuit protector 40.

Next, assuming that a short circuit fault has occurred in the load L, the current from the battery 10 flows directly to the ground via the relay 20 and the circuit protector 40. Accordingly, the current detection signal supplied from the current sensor 50 to the control circuit 43 changes so as to indicate that an overcurrent has flowed. When the control circuit 43 determines that the current detection signal indicates a current of a predetermined value or more, that is, that an overcurrent has flowed, the control circuit 43 supplies a drive signal to the heating element 42.

As a result, the heating element 42 generates heat and the PTC
The element 41 is heated. This heating causes the PTC element 41
Rises to a predetermined temperature, the PTC element 41 trips. As a result, the current flowing through the PTC element 41 is substantially cut off, so that the current flowing through the coil 21 of the relay 20 is also cut off, and the contact 22 is opened. Thus, the electric circuit is protected from burnout due to overcurrent.

Thereafter, the failure of the load L is repaired and the heating element 4
When the supply of the drive signal to 2 is stopped, the temperature of the heating element 42 decreases, and accordingly, the temperature of the PTC element 41 also decreases. Then, when the temperature of the PTC element 41 falls to a predetermined value, a current starts to flow through the PTC element 41 again.

As a result, a current also flows through the coil 21 of the relay 20, and the contact 22 is closed. As a result, the electric circuit returns to the original normal state. The supply of the drive signal to the heating element 42 is stopped, for example, by the control circuit 43 and the heating element 4.
2 by providing a manual open / close switch.

When the air bag operation detection signal from the air bag sensor 60 is supplied to the control circuit 43, the electric circuit is cut off and restored in the same manner as described above.

As described above, according to the circuit breaker according to the embodiment, not only when a failure occurs on the downstream side of the circuit protector 40, but also when a failure occurs on the upstream side of the circuit protector 40. Even so, the current flowing through the electric circuit can be cut off.

The PTC element 41 is disclosed in Japanese Unexamined Patent Publication No.
Unlike the automotive wiring protection device disclosed in Japanese Patent No. 5159, instead of being inserted in series with a circuit conductor through which a large current flows, it is connected in series with the coil 21 of the relay 20 and can withstand a large current. There is no need to have characteristics, and a low-current compatible product is sufficient.

Therefore, since a cheap and small PTC element can be used, the cost and size of the circuit protection device can be reduced. In addition, a PTC element having the same performance can constitute a circuit protection device that cuts off a current larger than that of the above-described automotive wiring protection device.

In the circuit breaker according to this embodiment, since the PTC element is used, circuit break and circuit return can be performed, and the circuit breaker can be used repeatedly, thereby reducing maintenance costs. And the maintenance work is simplified.

In the above-described embodiment, the case where an overcurrent flows in an electric circuit and the case where an airbag is activated are described as examples of factors that activate the circuit breaker. However, the present invention is not limited thereto. It is not limited. If a signal representing a factor for interrupting the electric circuit is supplied to the control circuit 43 in the circuit protector 40, the current flowing through the electric circuit in response to various factors may be interrupted. it can.

In the above-described embodiment, a PTC element is used as an element for interrupting a current flowing in an electric circuit. However, a circuit interrupting device is constructed using, for example, a field effect transistor (FET) instead of the PTC element. You can also. In this case, the drain of the FET is connected to the second terminal of the coil 21 and the source is grounded.
Is connected to the gate. If the FET is turned on / off by a drive signal from the control circuit 43, the same operation as in the above-described embodiment can be performed.

[0048]

According to the first aspect of the present invention, the control circuit comprises:
When the vehicle is abnormal, the heating element generates heat in response to, for example, an abnormal signal supplied from the outside. As a result, the resistance value of the variable resistance element arranged near the heating element increases, and the current flowing through the variable resistance element is cut off, so that the current flowing through the coil of the relay is also cut off. As a result, the contact of the relay is opened and the current supplied from the power supply to the load is cut off. Therefore, by appropriately selecting a signal supplied from the outside, it is possible to provide a circuit protection device capable of coping with a failure occurring in many parts of the electric circuit.

According to the second aspect of the present invention, since the variable resistance element is a PTC element, the resistance value of the PTC element is further increased, and the effect is enhanced.

According to the third aspect of the present invention, the control circuit drives the heating element when the current detection signal from the current sensor indicates, for example, an overcurrent. Thereby, the contact of the relay is opened, and the current supplied from the power supply to the load is cut off. Therefore, for example, if a current sensor is arranged in the vicinity of the power supply, the current supplied to all loads can be cut off when a failure such as an overcurrent flows in any part of the electric circuit. It is possible to provide a circuit protection device that can cope with a failure of substantially the entire circuit.

According to the fourth aspect of the invention, the control circuit drives the heating element when the airbag sensor detects that the airbag has been activated. Thereby, the contact of the relay is opened, and the current supplied from the power supply to the load is cut off. Accordingly, the present invention provides a circuit protection device that can cut off a current flowing in an electric circuit not only when an overcurrent flows due to a short circuit of a circuit conductor or a failure of a component, but also when an unexpected event such as activation of an airbag occurs. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electric circuit to which a circuit protection device according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram illustrating a configuration of an electric circuit to which a conventional circuit protection device is applied.

FIG. 3 is a block diagram showing a conventional automobile wiring protection device.

[Explanation of symbols]

 Reference Signs List 10 battery 20 relay 21 coil 22 contact 40 circuit protector 41 PTC element 42 heating element 43 control circuit 50 current sensor 60 airbag sensor L load

Claims (4)

[Claims] 1. A relay having a coil and a contact, one end of the contact being connected to a power supply side and the other end of the contact being connected to a load side, and a relay connected in series to the coil of the relay and having a high temperature. A variable resistance element that increases the resistance value as the resistance becomes larger; a heating element disposed in the vicinity of the variable resistance element; and a control circuit that drives the heating element in response to a signal externally supplied when the vehicle is abnormal. A circuit protection device comprising: 2. The circuit protection device according to claim 1, wherein said variable resistance element is a PTC element. 3. The apparatus according to claim 1, further comprising a current sensor for detecting a current, wherein the control circuit drives the heating element in response to a current detection signal from the current sensor. Circuit protection device as described. 4. An air bag sensor for detecting that an air bag has been activated, wherein the control circuit drives the heating element in response to an air bag activation detection signal from the air bag sensor. The circuit protection device according to any one of claims 1 to 3, wherein