JP3715155B2 - Circuit protection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit protection device used, for example, to protect an electric circuit of an automobile.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electric circuit of an automobile includes a battery 10, a relay 20, a circuit protector 30, and a load L as schematically shown in FIG. As the circuit protector 30, a fuse is mainly used.
[0003]
In this electric circuit, the battery 10 supplies power to the relay 20 when an ignition switch (not shown) is turned on. Thereby, an electric current flows into the coil 21 built in the relay 20, and the contact 22 is closed. As a result, the current from the battery 10 is supplied to the load L via the contact 22 of the relay 20 and the circuit protector 30. As a result, the electric circuit enters an operating state.
[0004]
In this operating state, when a failure occurs such as a circuit component constituting the electric circuit, for example, a short circuit of a circuit conductor or a failure of a component, an overcurrent flows through the circuit protector 30 and the fuse generates heat. The part melts. Thereby, the electric current which flows from the battery 10 to the load L is interrupted | blocked, and an electric circuit is protected.
[0005]
[Problems to be solved by the invention]
However, the conventional circuit protection device in which the circuit protector 30 composed of a fuse is incorporated functions only when the failure occurs downstream from the circuit protector 30, and the upstream side of the circuit protector 30, for example, It does not function when a failure occurs between the relay 20 and the circuit protector 30.
[0006]
For this reason, the circuit could not be interrupted at the time of failure on the upstream side of the circuit protector 30. Moreover, the current flowing through the electric circuit cannot be interrupted when a factor other than overcurrent, for example, when an airbag is activated.
[0007]
Further, in the conventional circuit protection device that cuts off the current by the fuse, when the fuse is blown, the electric circuit cannot be restored to the original state unless the fuse is replaced with a new one.
[0008]
Therefore, such a problem is solved by, for example, an automobile wiring protection device disclosed in JP-A-6-335159. FIG. 3 shows a block diagram of a conventional automobile wiring protection apparatus.
[0009]
That is, in this automobile wiring protection device, as shown in FIG. 3, a PTC (Positive Temperature Coefficient) element 101 is inserted in series with a circuit conductor 107 disposed on the body of the automobile, and the electric power from the battery is It is supplied to the load L via the PTC element 101. The PTC element 101 has a function of increasing the resistance value rapidly at a certain temperature (referred to as “trip phenomenon”).
[0010]
Therefore, when an overcurrent flows through the circuit conductor 107, the PTC element 101 generates heat and the resistance value increases, and the current flowing through the circuit conductor 107 is substantially cut off. As a result, the electric circuit is protected.
[0011]
However, since the PTC element 101 in this wiring protection device for automobiles is only used as a substitute for the fuse in the conventional circuit protection device described above, circuit protection is provided when a failure occurs upstream from the PTC element 101. There was a problem of not functioning as a device.
[0012]
An object of the present invention is to provide a circuit protection device that can cope with a failure that has occurred in many parts of an electric circuit and that can also deal with a failure other than a failure that generates an overcurrent.
[0013]
[Means for Solving the Problems]
The present invention has the following configuration in order to solve the above problems. According to a first aspect of the present invention, there is provided a circuit protection device including a coil and a contact, one end of the contact connected to a power supply side and the other end of the contact connected to a load side, and the coil included in the relay. A variable resistance element that is connected in series and increases the resistance value as the temperature rises, a heating element disposed in the vicinity of the variable resistance element, a current sensor that detects a current , And a control circuit for driving the heating element in response to a current detection signal.
[0014]
According to the first aspect of the present invention, the control circuit causes the heating element to generate heat when the current detection signal from the current sensor indicates, for example, an overcurrent . As a result, the resistance value of the variable resistance element disposed in the vicinity of the heating element becomes high, and the current flowing through the variable resistance element is cut off, so that the current flowing through the relay coil is also cut off. As a result, the relay contacts are opened and the current supplied from the power source to the load is interrupted. Therefore, for example, if a current sensor is arranged in the vicinity of the power supply, the current supplied to the entire load can be cut off in the event of a fault in which 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 almost the entire circuit.
[0015]
The invention of claim 2 includes a relay having a coil and a contact, one end of the contact being connected to the power supply side and the other end of the contact being connected to the load side, and the coil included in the relay in series. A variable resistance element that is connected and increases in resistance as the temperature rises, a heating element disposed near the variable resistance element, an airbag sensor that detects that the airbag has been activated, And a control circuit for driving the heating element in response to an airbag operation detection signal from an airbag sensor .
[0016]
According to the invention of claim 2 , the control circuit drives the heating element when the airbag sensor detects that the airbag is activated. Thereby, the contact of a relay is open | released and the electric current supplied to a load from a power supply is interrupted | blocked. Therefore, a circuit protection device capable of interrupting the current flowing in the electric circuit not only when an overcurrent flows due to a short circuit of a circuit conductor or a component failure but also when an unexpected situation such as the operation of an airbag occurs. it can.
[0017]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the variable resistance element is a PTC element .
[0018]
According to the invention of claim 3, since the variable resistance element is a PTC element, the resistance value of the PTC element becomes higher, and the effect becomes large.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a circuit protection device of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to the same or corresponding parts as those in the conventional technology.
[0022]
As shown in FIG. 1, an electric circuit to which a circuit protection device according to an embodiment of the present invention is applied includes a battery 10, a relay 20, a circuit protector 40, a current sensor 50, an airbag sensor 60, and a load L. Has been.
[0023]
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 20 via the current sensor 50. In FIG. 1, for simplicity of explanation, an electric circuit having one relay 20 is shown, but 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 to the downstream side of each relay.
[0024]
The relay 20 includes a coil 21 and a contact 22. The first terminal of the coil 21 is connected to the second terminal of the battery 10, and the second terminal of the coil 21 is connected to the circuit protector 40.
[0025]
The first terminal of the contact 22 is connected to the second terminal of 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 when the current flows.
[0026]
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.
[0027]
The current sensor 50 detects the magnitude of the current output from the battery 10 and supplies a current detection signal representing the detection result to the circuit protector 40. As the current sensor 50, various known types of current sensors can be used.
[0028]
The current sensor 50 is disposed in the vicinity of the second terminal of the battery 10. Thereby, since the total current output from the battery 10 can be monitored, even if a fault 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 The current supplied to the load L can be cut off.
[0029]
The airbag sensor 60 detects whether an airbag (not shown) has been activated and supplies an airbag activation detection signal representing the detection result to the circuit protector 40.
[0030]
The circuit protector 40 includes a PTC element 41, a heating element 42 and a control circuit 43. As described above, the PCT element 41 has a function of suddenly increasing the resistance value at a certain temperature and substantially blocking 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, and the second terminal of the PTC element 41 is grounded.
[0031]
The heating element 42 is disposed in the vicinity of the PTC element 41 and generates heat when supplied with a drive signal from the control circuit 43. The temperature of the PTC element 41 is controlled by the heat generated by the heat generating element 42. That is, the PTC element 41 is turned on or off according to the heat generated by the heating element 42.
[0032]
The control circuit 43 supplies a drive signal to the heating element 42 in response to the current detection signal from the current sensor 50 and the 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 a predetermined current value.
[0033]
The control circuit 43 supplies a drive signal to the heating element 42 when the detection value based on the airbag operation detection signal from the airbag sensor 60 is a predetermined value or more. In FIG. 1, the power supply path to the control circuit 43 is not shown.
[0034]
Next, the operation of the electric circuit to which the circuit protection device according to the embodiment of the present invention configured as described above is applied will be described.
[0035]
First, when an ignition switch (not shown) is turned on, the battery 10 supplies power to the relay 20. Thereby, a current flows through the coil 21 and the PTC element 41 built in the relay 20, 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. As a result, the electric circuit enters an operating state.
[0036]
In this operating state, the current detection signal from the current sensor 50 and the airbag operation detection signal from the airbag sensor 60 are supplied to the control circuit 43 of the circuit protector 40.
[0037]
Next, assuming that a short circuit failure 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. Thus, 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 that a current of a predetermined value or more, that is, an overcurrent has flowed, the control circuit 43 supplies a drive signal to the heating element 42.
[0038]
As a result, the heating element 42 generates heat and the PTC element 41 is heated. When the temperature of the PTC element 41 rises to a predetermined temperature due to this heating, the PTC element 41 trips. As a result, since the current flowing through the PTC element 41 is substantially cut off, the current flowing through the coil 21 of the relay 20 is also cut off and the contact 22 is opened. This protects the electrical circuit from burning and the like due to overcurrent.
[0039]
Thereafter, when the failure of the load L is repaired and the supply of the drive signal to the heating element 42 is stopped, the temperature of the heating element 42 decreases, and the temperature of the PTC element 41 also decreases accordingly. Then, when the temperature of the PTC element 41 falls to a predetermined value, current starts to flow again through the PTC element 41.
[0040]
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 can be stopped by providing a manual open / close switch between the control circuit 43 and the heating element 42, for example.
[0041]
Even when the airbag operation detection signal from the airbag sensor 60 is supplied to the control circuit 43, the electrical circuit is shut off and returned in the same manner as described above.
[0042]
Thus, 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, The current flowing through the electric circuit can be cut off.
[0043]
Further, the PTC element 41 is not inserted in series with a circuit conductor through which a large current flows, but in series with the coil 21 of the relay 20 as in the automobile wiring protection device disclosed in Japanese Patent Laid-Open No. 6-335159. Therefore, it is not necessary to have a characteristic that can withstand a large current, and a low-current compatible product is sufficient.
[0044]
Therefore, since an inexpensive and small PTC element can be used, the circuit protection device can be reduced in price and size. Further, if the PTC elements have the same performance, a circuit protection device that cuts off a larger current than the above-described automotive wiring protection device can be configured.
[0045]
Further, since the circuit breaker according to this embodiment uses the PTC element, the circuit breaker and the circuit return can be performed, the circuit can be used repeatedly, and the cost for maintenance can be reduced. At the same time, there is an advantage that the maintenance work is simplified.
[0046]
In the above-described embodiment, the case where an overcurrent flows in the electric circuit and the case where the airbag is activated are described as examples of factors for operating the circuit breaker, but the present invention is limited to these. It is not a thing. If a signal representing a factor that should cut off the electric circuit is supplied to the control circuit 43 in the circuit protector 40, the current flowing through the electric circuit can be cut off in response to various factors. it can.
[0047]
In the above-described embodiment, the PTC element is used as an element that cuts off the current flowing in the electric circuit. However, for example, a field effect transistor (FET) may be used instead of the PTC element to configure the circuit interruption device. it can. In this case, the drain of the FET is connected to the second terminal of the coil 21, the source is grounded, and the drive signal from the control circuit 43 is connected to the gate. If the FET is turned on / off by the drive signal from the control circuit 43, the same operation as that of the above-described embodiment can be performed.
[0048]
【The invention's effect】
According to the first aspect of the present invention, the control circuit causes the heating element to generate heat when the current detection signal from the current sensor indicates, for example, an overcurrent . As a result, the resistance value of the variable resistance element disposed in the vicinity of the heating element becomes high, and the current flowing through the variable resistance element is cut off, so that the current flowing through the relay coil is also cut off. As a result, the relay contacts are opened and the current supplied from the power source to the load is interrupted. Therefore, for example, if a current sensor is arranged in the vicinity of the power supply, the current supplied to the entire load can be cut off in the event of a fault in which 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 almost the entire circuit.
[0049]
According to the invention of claim 2 , the control circuit drives the heating element when the airbag sensor detects that the airbag is activated. Thereby, the contact of a relay is open | released and the electric current supplied to a load from a power supply is interrupted | blocked. Therefore, a circuit protection device capable of interrupting the current flowing in the 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 situation such as the operation of an airbag occurs. it can.
[0050]
According to the invention of claim 3, since the variable resistance element is a PTC element, the resistance value of the PTC element becomes higher, and the effect becomes large.
[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 showing a configuration of an electric circuit to which a conventional circuit protection device is applied.
FIG. 3 is a block diagram showing a conventional automotive wiring protection device.
[Explanation of symbols]
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 (3)

A relay having a coil and a contact and having one end of the contact connected to the power supply side and the other end connected to the load side;
A resistance variable element connected in series to the coil of the relay and increasing the resistance value as the temperature increases;
A heating element disposed in the vicinity of the variable resistance element;
A current sensor for detecting current;
A control circuit that drives the heating element in response to a current detection signal from the current sensor when a vehicle abnormality occurs;
A circuit protection device comprising: A relay having a coil and a contact and having one end of the contact connected to the power supply side and the other end connected to the load side;
  A resistance variable element connected in series to the coil of the relay and increasing the resistance value as the temperature increases;
  A heating element disposed in the vicinity of the variable resistance element;
  An airbag sensor that detects that the airbag has been activated;
  A control circuit that drives the heating element in response to an airbag operation detection signal from the airbag sensor when a vehicle abnormality occurs;
A circuit protection device comprising: Wherein the resistance variable element, the circuit protection device of claim 1 or claim 2, wherein it is a PTC element.

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