JP2001309546A - Protector for vehicle wiring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly and delicately decide a slight short circuit when a protector is provided in a wiring system for an electric load of a vehicle in order to cut off an abnormal current applied to the wiring system, before a damage occurs in the wiring system to surely cut off the abnormal current, particularly in a short circuit which generates intense sparks, and to improve safety and reliability of an apparatus while the practicality of the apparatus is improved. SOLUTION: An FET 4, an overcurrent breaker 5 and a current detection resistor 6 are provided in a wiring 3. It is decided whether a slight short circuit exists or not in accordance with the magnitude of the detected abnormal current, the number of occurence of the abnormal current, etc. In accordance with the decision result, the FET 4 is turned off by a CPU 15 at least before the overcurrent breaker 5 is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for protecting a wiring system of a vehicle by preventing an excessive current from flowing through the wiring system, and more particularly to a protection device for protecting a wiring system of a vehicle, for example, at a portion where the coating of the wiring is peeled off. The present invention relates to measures for effectively coping with short-time short-circuits that occur.

[0002]

2. Description of the Related Art Conventionally, a wiring system for supplying power to an electric load of a vehicle generally receives an abnormally large current due to a short circuit or a failure of the electric load.
A fuse is provided so that the fuse is cut off by itself and the current is cut off before the wiring system is damaged.

[0003] In recent years, the number of wirings in vehicles has increased drastically with the mounting of safety equipment and measures against engine exhaust pollution, and the number of fuses has also reached at least 40 or more.
For this reason, it takes time and effort to find and replace a blown fuse, and it is necessary to identify the abnormal part of the wiring system that caused the fuse. Has occurred.

Further, when a large current exceeding the rated value flows for a predetermined time or more (so-called dead short) due to a complete short circuit of a wiring system or a failure of an electric load, the fuse is reliably blown by Joule heat. However, for example, when the coating of the wiring is deteriorated and peels off, and the portion is short-circuited with a surrounding vehicle body component (body earth) for a very short time due to a running vibration of the vehicle (so-called short short). , It does not blow. On the other hand, if the frequency of occurrence of a short-circuit is extremely short, heat is accumulated in the vicinity of the separated portion of the wiring, and if there is a combustible material around the short-circuit, ignition may occur. It is known that there is.

For example, in the abnormal current interrupting device disclosed in Japanese Patent Application Laid-Open No. 11-136846, a current detecting resistor and a semiconductor switch are provided in the middle of wiring to an electric load of a vehicle, and an abnormal current caused by the current detecting resistor is provided. When the number of detections exceeds the set number, the current is cut off by the semiconductor switch. As a result, even if the short circuit is extremely short, if the short circuit is repeated, the current is interrupted, and the risk of the above-described ignition can be reduced.

[0006]

However, in general, the degree of aging of the wiring in a vehicle, the state of peeling of the coating or the state of the periphery of the peeled portion vary widely, and in the conventional example described above. It is impossible to uniformly judge a short-circuit like an abnormal current interrupter. That is, for example, even in a short-circuit state for an extremely short time,
Depending on the current, a strong spark may fly between the stripped portion of the wiring and the body ground, and this spark may ignite combustibles around the wiring. In the event that a short-time short-circuit condition is repeated intermittently, the current is only interrupted to prevent ignition due to heat accumulation, so that ignition due to such a strong spark is prevented. I can't get it.

On the other hand, in order to prevent the ignition caused by the strong spark as described above, if the set number of times for judging the short-circuit in the conventional example is set to once or twice, for example, the electric load to the electric load is reduced. A change in a current value such as an inrush current at the start of energization is erroneously determined to be due to a short-circuit, and the current is interrupted, which is not practical.

In the above conventional example, the function of the fuse is replaced by an abnormal current interrupting device. However, in general, there is an inherent possibility of a so-called short mode failure in which a semiconductor switch is always in a conductive state. In this case, even if a dead short circuit occurs in the wiring system, the current cannot be cut off, so that an excessive current may continue to flow and a fire of the vehicle may occur, which is a problem.

The present invention has been made in view of the above points, and a main object of the present invention is to devise a method of judging a short short based on a current value.
An object of the present invention is to make it possible to cut off a current when a short circuit that generates a strong spark occurs, thereby further improving the safety and reliability of the wiring system protection device while improving its practicality.

[0010]

In order to achieve the above object, according to the present invention, a semiconductor switch is provided in a wiring system, and a switch is provided based on both the frequency of occurrence of abnormal current and the current value at that time. In addition to making a short judgment,
In addition to the semiconductor switch, an overcurrent breaker capable of reliably shutting off excessive current is provided.

More specifically, according to the first aspect of the present invention, when an abnormal current flows, the current is cut off before the wiring system is damaged when the abnormal current flows. An overcurrent breaker that is provided in the middle of the wiring in the wiring system, and is in a cutoff state when a large current of a predetermined value or more flows for a predetermined time or more, with respect to the protection device of the vehicle wiring system, A semiconductor switch disposed in series with the overcurrent circuit breaker on the wiring, a detecting means for outputting a detection value corresponding to a current flowing through the wiring, and receiving an output from the detecting means to connect the wiring to a predetermined position. Determining means for determining whether to interrupt the current based on the frequency of the abnormal current that is larger than the reference value and the current value at that time, and determining that the current should be interrupted by the determining means, Wiring Control means for switching the semiconductor switch to an off state so that a current to be cut off is provided, and the control means switches the switching element to an off state at the latest before the overcurrent breaker enters a cutoff state. Configuration.

With the above arrangement, when an abnormal current flows in the wiring system, a detection value corresponding to the abnormal current is output from the detecting means, and the determining means receiving the output determines the frequency of the abnormal current and the current time. Based on the current value, it is determined whether the current should be interrupted. The state of the semiconductor switch is switched by the control means in accordance with the result of this determination. That is, for example, if the value of the abnormal current is large, if the current is cut off even if the frequency of occurrence is small, it is possible to reliably prevent ignition caused by a short-circuit and to enhance safety. . On the other hand, if the value of the abnormal current is small, the current is not interrupted while the frequency of occurrence is small, thereby preventing erroneous determination due to a change in the current value and ensuring sufficient practicality.

[0013] Even if a short-circuit failure occurs in which the semiconductor switch is always in a conductive state,
Since the overcurrent breaker is provided in series with the semiconductor switch, if a dead short circuit occurs in the wiring system at this time, the overcurrent breaker is turned on when a large current of a predetermined value or more flows for a predetermined time or more. The current will be interrupted, thereby further improving safety and reliability.

[0014] In the invention according to claim 2, the determination means includes a map in which a plurality of predetermined determination current values and a determination time and a number of determinations set for each of the determination current values are recorded.
Based on the output from the detecting means, referring to the map,
A determining unit that determines that the current should be cut off when a state in which the current value flowing through the wiring exceeds any of the determination current values occurs more than the number of determinations during the determination time corresponding to the determination current value; And a configuration having:

[0015] In this configuration, the judging means, which has received the output from the detecting means, refers to the map based on the output value and determines the number of times that the current value flowing through the wiring exceeds a certain judging current value. It is determined that the current should be cut off when the number of determinations is exceeded during the determination time set to correspond to the current value. Therefore, in the map, for a plurality of determination current values exceeding the rating of the wiring, if the value of the determination current value is larger, the determination time is set to be shorter, or the number of determinations is set to be smaller, Appropriate and detailed judgment can be made in accordance with the frequency and the degree of occurrence of the abnormal current, so that the operation and effect of the first aspect can be sufficiently obtained.

In addition, if the maximum value among the judgment current values is made larger than a predetermined value at which the overcurrent breaker is turned off and the number of judgments corresponding to the judgment current value is set to one, a short-circuit is caused. Accordingly, even in a state where a strong spark flies between the stripped portion of the wiring and the body ground, ignition caused by such a strong spark can be reliably prevented.

According to a third aspect of the present invention, the judging means compares the output value from the detecting means with a set value, and outputs a judgment signal when the output value is larger than the set value. An output circuit is provided, and the control means is provided with a cutoff circuit made of hardware that switches a semiconductor switch to an OFF state instantly when a determination signal is input from the determination signal output circuit.

That is, assuming in advance that a strong spark will fly between the stripped portion of the wiring and the body ground due to a short-circuit, the output value of the detecting means corresponding to an excessive current value corresponding to this state is determined. , Set value. Thereby, the current value flowing through the wiring becomes excessive, and when the output from the detection means exceeds the set value, a determination signal is output from the determination signal output circuit of the determination means that has received the output,
The semiconductor switch is instantaneously switched to the off state by the shutoff circuit of the control means that receives the determination signal. In other words, in a state where a strong spark flies due to a short circuit, the current is cut off by the dedicated hardware circuit before the second short circuit occurs, so that ignition by the spark can be reliably prevented.

According to a fourth aspect of the present invention, in the third aspect,
A microcomputer that receives a determination signal from a determination signal output circuit and outputs a control signal so that a semiconductor switch is turned off; and a signal hold that holds a signal input from the determination signal output circuit to the microcomputer for a set time. And a shutoff circuit that holds the semiconductor switch in an off state until the set time elapses after receiving the determination signal from the determination signal output circuit.

That is, if the judgment signal output circuit and the cutoff circuit are constituted by a dedicated hardware circuit as described in the third aspect of the present invention, as described above, the judgment signal output circuit corresponds to the abnormal current flowing through the wiring. Outputs a determination signal, and the shutoff circuit instantaneously switches the semiconductor switch to the off state. However, when the current is cut off, the judgment signal disappears as a result,
It is conceivable that the semiconductor switch immediately returns to the on state.

Therefore, in the present invention, the shut-off circuit is configured so that the semiconductor switch is kept off for a set time from the input of the determination signal, and the microcomputer turns off the semiconductor switch during that time. . Thus, the current can be instantaneously interrupted by the hardware circuit, and the current interruption state can be stably maintained by controlling the semiconductor switch by the microcomputer.

At this time, since the input signal to the microcomputer is maintained by the signal holding circuit for a set time, so-called interrupt processing is not required in the processing of the signal, and the load of signal processing by the microcomputer is reduced. You. As a result, even when a plurality of wiring systems are provided with protective devices, the microcomputer can be shared and the cost can be reduced.

According to a fifth aspect of the present invention, there is provided a structure comprising: a diagnosis means for diagnosing an abnormality of a wiring system or an electric load based on a determination result by the determination means; and a notifying means for notifying the diagnosis result by the diagnosis means. .

[0024] Thus, the abnormality of the wiring system or the electric load is diagnosed by the diagnosing means, and the diagnosis result is notified by the notifying means.
The time and labor for repair can be reduced. On the other hand, if the abnormality is not reported, the driver of the vehicle does not need to worry about a trouble due to a failure in the wiring system, so that a sense of security is enhanced, which can contribute to an improvement in vehicle safety.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(Configuration of Apparatus) FIG. 1 shows a protection device A for a vehicle wiring system according to an embodiment of the present invention. The protection device A is applied to an electric load 1, 1 such as a headlight of a vehicle. On the other hand, it is provided in a wiring system W for supplying electric power from the battery 2, and when an abnormal current flows through the wiring 3 in the wiring system W, the current is cut off before the core material or the covering material is damaged. It was made. In the middle of the wiring 3, a field effect transistor (hereinafter referred to as FET) 4 which is a semiconductor switch that can be switched between an ON state for conducting a current and an OFF state for interrupting a current, and a large current of a predetermined value or more for a predetermined time. An overcurrent circuit breaker 5 which is turned on and off by itself when the current flows as described above, and a current detecting resistor 6 for detecting a current flowing through the wiring 3 are arranged in series.

The FET 4 has a source terminal connected to the battery 2 and a drain terminal connected to the overcurrent breaker 5.
And a current detecting resistor 6 connected to the electric loads 1 and 1, and a gate terminal is connected to the battery 2 via a resistor 7.
And is normally in an on state in which current flows from the source terminal to the drain terminal (between the drain and the source). The gate terminal of the FET 4 is also connected via a transistor 8 to an OR circuit 9 to which a current cut-off signal or the like to be described later is input, and the transistor 8 is turned on in response to a signal from the OR circuit 9. FE
T4 is turned off to interrupt the current between the drain and the source.

The overcurrent breaker 5 is composed of, for example, an auto fuse having a rating of 10 amps. When a large current of 10 amps or more flows for a predetermined time (so-called dead short), the overcurrent breaker 5 is blown by Joule heat. As a result, the current is reliably cut off.

The current detecting resistor 6 has a very small resistance value in order to suppress unnecessary power consumption.
Both ends are connected to the differential voltage amplifier circuit 10 via voltage dividers (not shown). The differential voltage amplifying circuit 10 is composed of, for example, an operational amplifier, and receives a voltage between terminals of the current detection resistor 6 via the two voltage dividers.
A detection voltage obtained by differentially amplifying this voltage value is output. At this time, the amplification characteristic of the differential amplifier circuit 10 is such that the value of the current flowing through the current detection resistor 6 is an extremely large value (for example, 20 amperes) such as a strong spark even if the current is short-circuited for an extremely short time. In this case, a detection voltage that is substantially proportional to the voltage between the terminals of the current detection resistor 6 is output so as to be equal to the set value Vref (for example, 5 volts).

As described above, a state in which an extremely large current flows and a strong spark flies due to a short circuit for a short time is as follows.
Even in the case of short-time short-circuit (slight short-circuit), it is necessary to immediately switch the FET 4 to the OFF state. Therefore, in this embodiment, the following description deals with the case where the overcurrent breaker 5 enters the cut-off state. It is called short.

The detection voltage output from the differential amplifier circuit 10 is input to a comparison circuit 12 (determination signal output circuit) including a comparator 11. This comparator 11
Receives the detection voltage and receives a voltage corresponding to the set value Vref from the power supply of the digital circuit. When the detected voltage is higher than the set value Vref, the level becomes a high level and an abnormality detection signal (determination Signal), and if the detection voltage is lower than the set value Vref,
Low level.

A signal from the comparison circuit 12 is output to a cutoff signal output circuit 13 for outputting a current cutoff signal to the OR circuit 9.
And a detection signal output circuit 14 (signal holding circuit) for outputting a dead short detection signal to a microcomputer 15 (CPU) described later. The cutoff signal output circuit 13 includes, for example, a transistor, a resistor, a capacitor, and the like. When an abnormality detection signal is input from the comparison circuit 12, the cutoff signal output circuit 13 outputs a current cutoff signal instantaneously.
The ET4 is switched to the off state, and the output of the current cutoff signal is maintained until a set time (for example, 60 milliseconds) elapses, during which the FET 4 is kept in the off state.

Here, the fact that the cut-off signal output circuit 13 instantaneously outputs the current cut-off signal is determined according to the running vibration of the vehicle after the abnormality detection signal is input to the cut-off signal output circuit 13. That is, the current cutoff signal is output before the short time elapses. That is,
When the separated portion of the wiring 3 and the body ground are short-circuited due to the running vibration of the vehicle, the time interval at which the short-circuit occurs depends on the running vibration of the vehicle. In order to prevent the second short circuit, the minute time should be determined so as to correspond to the maximum value of the traveling frequency of the vehicle.

The transistor 8, the OR circuit 9, and the cutoff signal output circuit 13 constitute a cutoff circuit that switches the FET 4 to the OFF state instantaneously when the abnormality detection signal from the comparison circuit 12 is input.

The detection signal output circuit 14 is composed of a transistor, a resistor, a capacitor, and the like, like the shut-off signal output circuit 13. When an abnormality detection signal is input from the comparison circuit 12, the detection signal output circuit 14 operates in the same manner as described above. The output of the dead short detection signal is continued until the set time elapses. Then, the first determination unit 15a of the CPU 15 that has input the dead short detection signal,
It is determined that the current should be interrupted in accordance with a predetermined determination program, and the interruption control unit 15b that has received the determination result outputs a control signal so that the FET 4 is turned off.

As described above, the detection signal output circuit 14 outputs C
Since the input of the dead short detection signal to the PU 15 is continued for the set time, the CPU 15 does not need to perform the so-called interrupt processing for reading the dead short detection signal, and the load of the signal processing is reduced. Thus, even when a plurality of wiring systems are provided with protection devices, the CPU 15 can be shared, and the cost can be reduced.

On the other hand, the detection voltage output from the differential amplifier circuit 10 is converted into a digital signal of a predetermined number of bits by an A / D conversion circuit 17 and input to the CPU 15. Then, the second determination unit 15c of the CPU 15 determines whether or not to interrupt the current based on the digital signal, that is, based on the magnitude of the abnormal current flowing through the wiring 3 and the number of occurrences thereof, and determines whether the current should be interrupted. When it is determined that the cutoff should be performed, a control signal is output by the cutoff control unit 15b, and the FET 4 is switched to the off state. That is, as shown in Table 1 and FIG. A plurality of judgment current values i1 to i
4 and a determination condition map in which the determination times t5 to t2 and the number of determinations for each determination current value are set and recorded, are electronically stored, and a digital signal input from the A / D conversion circuit 17 is received. The second determination unit 15c of the CPU 15 refers to the determination condition map and determines that the abnormal state where the current value flowing through the wiring 3 exceeds any of the determination current values i1 to i4 is determined by the determination current values i1 to i4. Determination time t5 corresponding to i4
It is determined that the current should be interrupted when it occurs more than the number of times of determination between t and t2.

[0038]

[Table 1]

More specifically, in Table 1, the current value (slight current value) detected by the current detecting resistor 6 is equal to the reference value i1 (this wiring 3
Is smaller than 7 amps), there is no abnormality in the wiring system W (normal). In addition, as for the first determination current value i1 which is the smallest as the abnormal current, the current value is detected 1000 times during the longest time width t5 set so as to correspond thereto, and the detected value is 500 times. As described above, the first
If it is equal to or greater than the determination current value i1, it is determined that there is an abnormality, that is, a short-circuit.

Further, with respect to the second judgment current value i2 which is the second smallest abnormal current, the current value is detected 100 times during the second longest time width t4 corresponding to the second judgment current value i2.
If the detected value is 50 times or more and the second determination current value i2 or more, it is determined that a short-circuit has occurred. Furthermore, for the third and fourth determination current values i3, i4,
A current value is detected a predetermined number of times during each of the set time widths t3 and t2. If an abnormal current is detected more than the number of times of determination, it is determined that a short-circuit has occurred.

In short, a criterion for judging a short short,
In other words, the OFF operation characteristic of the FET 4 is as shown by the solid line in FIG. 2, and for a plurality of determination current values i1 to i4 exceeding the rating of the wiring system, the determination current values i1 to i4
The larger the value of 4, the shorter the corresponding determination time t5 to t2 and the smaller the number of determinations. As a result, the larger the value of the abnormal current, the higher the possibility of sparking due to a short circuit, and the greater the accumulation of heat, the smaller the number of occurrences, and it is determined that a short circuit has occurred, and the current is interrupted. On the other hand, in the case of a weak short-circuit state where the possibility of sparks is low and the heat accumulation is low, it is not determined that a short-circuit occurs until the number of occurrences of the short-circuit becomes large. Is minimized.

In this embodiment, as described above, the first determination unit 15a of the CPU 15 determines that the current should be cut off in response to the dead short detection signal from the detection signal output circuit 14. Sometimes, FET
4 is turned off. This means
In the OFF characteristic of the FET 4 shown in FIG. 2, when a current value exceeding the fifth determination current value i5 is detected even once, the current is cut off before the elapse of a minute time. Here, the fifth determination current value i5 is a rated value (10 amps) at which the overcurrent circuit breaker 5 is turned off.
In a short-circuit state where a strong spark is blown between the peeled portion of the wiring 3 and the body ground, even if the short-circuit time is extremely short and the overcurrent breaker 5 does not enter the cut-off state. However, it can cut off the current instantaneously and prevent ignition by a strong spark.

Further, as shown in FIG.
Is set on the safer side than the protection characteristic of the overcurrent circuit breaker 5 in the relation between the current and the conduction time thereof, so that the FET 4 is turned off at the latest before the overcurrent circuit breaker 5 enters the cutoff state. It can be switched off. The protection characteristic of the overcurrent breaker 5 is set on the safer side than the smoke generation characteristic of the wiring 3.

Thus, when any abnormality occurs in the wiring system W, the FET 4 is normally turned off first,
Since the current is interrupted, the overcurrent circuit breaker 5 does not enter the interrupted state. Even if the FET 4 causes a short mode failure and a dead short occurs at this time, in this case, the overcurrent circuit breaker 5 is cut off before the wiring 3 is damaged. W is reliably protected. In addition, the smoke generation characteristic indicates a relationship between an abnormal current and an energizing time corresponding to a state in which an organic substance contained in a wiring coating is vaporized by heat generated due to the abnormal current and smokes. This is an indication that the wiring system has been damaged.

In FIG. 1, reference numeral 18 denotes an FET failure detection circuit comprising a voltage conversion circuit branched and connected in parallel on the wiring 3 upstream of the electric loads 1 and 1. The FET failure detection circuit 18 converts this voltage to approximately 5 volts when a voltage of approximately 24 volts (or approximately 12 volts) is applied to the wiring 3, and sends a digital signal (high level) to the CPU 15. ) Is output. On the other hand, as described above, when the FET 4 is in the short mode failure and the dead short circuit occurs, and the overcurrent breaker 5 is in the cutoff state, the output from the FET failure detection circuit 18 becomes substantially 0 volt, and the CPU 15 The third determination unit 15d determines a short-mode failure of the FET4.

(Operation of Apparatus) Next, the operation of the wiring system protection apparatus A configured as described above will be specifically described with reference to the flowcharts shown in FIGS. In this flow, for example, steps S12 to S15
Such processing by the CPU 15 is executed at predetermined time intervals (for example, 10 milliseconds) in accordance with a control program stored electronically in the ROM.

First, when a short-circuit failure has occurred in the FET 4 disposed on the wiring 3, YES is obtained in step S1 after the start shown in FIG.
If the normal short mode failure has not occurred (NO), the process proceeds to step S2, where the detection voltage corresponding to the current value flowing through the wiring 3 is output by the differential amplifier circuit 10. Is done. This output is input to the comparison circuit 12 and the A / D conversion circuit 17, respectively.
One is provided for the dead short handling operation shown in steps S3 to S10, and the other is provided in step S11 in FIG.
S16 to S16.

That is, in step S3, the comparison circuit 1
In step 2, the detected voltage is compared with the set voltage Vref. If the detected voltage is equal to or lower than the set voltage Vref and the determination is NO, the process returns to the step S1. If the detected voltage exceeds the set voltage Vref, the process returns to the step S4. Proceed,
An abnormality detection signal is output from the comparison circuit 12, and this output is input to the cutoff signal output circuit 13 and the detection signal output circuit 14, respectively.

In response to the input of the abnormality detection signal, the cutoff signal output circuit 13 instantaneously outputs the FET cutoff signal and switches the FET 4 to the off state, as shown in step S5. In other words, by the hardware circuit,
The FETOFF process is performed before the second short circuit occurs. Further, the FET cutoff signal is continued for the set time, during which the FET 4 is kept in the off state. When the set time has elapsed, the FET OF by the hardware circuit described above is used.
The F process ends (step S6), and a series of dead short handling operations by the hardware circuit ends.

On the other hand, the detection signal output circuit 14 receiving the abnormality detection signal from the comparison circuit 12 outputs a dead short detection signal to the CPU 15 as shown in step S7. While this signal continues for the set time, the first determination unit 15a of the CPU 15 determines in step S8 that the current should be cut off (dead short).
A control signal is output by the cutoff control unit 15b of
An FET OFF process is performed by software in which T4 is kept off. And the following step S
At 10, a dead short flag is established, and the routine proceeds to step S17 of the flow of FIG.

That is, when an excessive current flows through the wiring 3, first, the FET 4 is instantaneously switched to the OFF state by the hardware circuit, and the current is cut off.
The FET 4 is kept off by the control signal from the CPU 15, so that the current cutoff state is stably maintained.

On the other hand, when the coating of the wiring 3 is peeled off, for example, and a short-circuit is generated intermittently and a relatively small abnormal current flows, as shown in the step S2, A detection voltage corresponding to the current value is input from the differential amplifier circuit 10 to the A / D conversion circuit 17. Then, as shown in step S11 of FIG. 4, the detection voltage is converted into a digital signal by the A / D conversion circuit 17 and output, and this digital signal is input to the CPU 15.
Subsequently, in step S12, the digital signal is read by the second determination unit 15c of the CPU 15, and the first to fourth determination current values i are determined based on the signal value.
For each of 1 to i4, the number of occurrences of abnormal current exceeding it is counted (calculation of current-time product).

Subsequently, in step S13, based on the detection result of the abnormal current, the number of occurrences of the abnormal current counted within the determination time for each of the determination current values i1 to i4 is determined by referring to the determination condition map. It is determined whether the number of determinations corresponding to the determination current value is less than the number of determinations (is the determination condition within a specified range?). If this determination is YES and the number of occurrences of the abnormal current is smaller than the number of determinations for any of the determination current values, the counter is cleared and the process proceeds to step S22, where it is determined that the wiring system W is normal. To return. On the other hand, if the number of occurrences of the abnormal current is equal to or more than the number of determinations for any of the determination current values, the process proceeds to step S14, and it is determined that the current should be cut off because of a short-circuit.

Subsequently, in step S15, the CPU
A control signal is output by the 15 cut-off control units 15b,
An FET OFF process is performed by software in which the FET 4 is turned off. Then, in a succeeding step S16, a light short flag is established, and the process proceeds to a step S17.

That is, for example, when a defect such as peeling has occurred in the coating of the wiring 3 and a short short has occurred,
The CPU 15 determines whether a short-circuit has occurred based on the magnitude of the abnormal current flowing through the wiring 3 and the number of occurrences, and the FET 4 is turned off according to the result of the determination to cut off the current.

Subsequent to step S10 or step S16, in step S17, the CPU 15 determines that a failure has occurred in the wiring system W. In step S18, whether or not a dead short has occurred is determined based on the state of the flag. A determination is made. If the determination is YES, the process proceeds to step S19, and a diag output is performed assuming that a dead short has occurred. If the determination is NO, the process proceeds to step S20, and a diag output is performed assuming that a short short has occurred, The process proceeds to step S21. In this step S21, it is determined whether or not the cause of the failure in the wiring system W has been removed by repair, and if the cause of the failure has been removed (YES), the process returns. That is, an abnormal state of the wiring system W is diagnosed by the protection device A, and when the result of the diagnosis is notified,
4 (YES in step S1), even if a dead short occurs in the wiring system W and the dead short is determined based on the current value as described above, Accordingly, the current cannot be cut off by FET4. However, in this case, as shown in step 23 of FIG. 4, the auto fuse is blown and the overcurrent breaker 5 is cut off, so that the wiring system W is reliably protected without being damaged.

Then, when the overcurrent breaker 5 is cut off, the voltage value of the wiring 3 downstream thereof becomes substantially zero, so that the output from the FET failure detection circuit 18 becomes low as shown in step S24. Level (abnormal signal), and the third determining unit 15d of the CPU 15 receiving this abnormal signal determines in step S25 that the short-circuit failure of the FET 4 has occurred. Then, in step S26,
A diagnostic output is performed as an FET short mode failure, and then the process proceeds to step S21.

That is, even if the FET 4 causes a short mode failure, the overcurrent breaker 5
Is provided, so if a dead short occurs,
The current is cut off by the overcurrent breaker 5. In addition, this is diagnosed, and the diagnosis result is notified.

In the flow of FIG. 4, step S1
In each of the procedures 2 to S16, based on the output voltage from the current detection resistor 6, the current value flowing through the wiring 3 is determined by referring to the determination condition map to one of the first to fourth determination current values i1 to i4. The state that exceeds the threshold value corresponds to the determination unit that determines that the current should be cut off when the number of times of occurrence has occurred more than the number of times of determination during the determination times t5 to t2 corresponding to the respective determination current values i1 to i4.

Each of the steps S17, S18 and S25 corresponds to a diagnosis means for diagnosing an abnormality of the wiring system W or the electric load 1 based on the result of the judgment by the judgment section. , S20, S26
Correspond to the notifying means for notifying the diagnosis result by the diagnosing means.

Therefore, according to the protection device A for a vehicle wiring system according to this embodiment, when the coating of the wiring 3 in the wiring system W is peeled off and short-circuited to the body ground, Based on the value of the current flowing through the wiring 3, the short-circuit short is appropriately and finely determined based on the magnitude of the abnormal current and the number of occurrences thereof, and the current is cut off by the FET 4 based on the determination result.
While minimizing the possibility of erroneous determinations due to fluctuations in the current value, etc., and ensuring sufficient practicality, it is possible to reliably prevent ignition due to a short-circuit short, thereby improving safety.

Further, a state in which a strong spark is likely to fly even in an extremely short-time short circuit is treated in the same manner as a so-called dead short circuit, and an extremely large abnormal current corresponding to this state is detected only once. Since the FET 4 is instantaneously turned off by a dedicated hardware circuit, the occurrence of the second short circuit can be reliably prevented, and safety can be further improved.

Further, since the overcurrent breaker 5 is provided in the wiring 3 in series with the FET 4, even if the FET 4 causes a short mode failure and a dead short circuit occurs in the wiring 3 at this time, the overcurrent breaker 5 does not occur. At times, the current is interrupted by the overcurrent breaker 5, so that safety and reliability are further improved.

Further, since the judgment condition (OFF characteristic of the FET 4) when the FET 4 is switched to the OFF state is set on the safer side than the protection characteristic of the overcurrent breaker 5, the short-circuit failure of the FET 4 usually occurs. Does not occur, when any abnormality occurs in the wiring system W, the FET 4 is first turned off to cut off the current, and the overcurrent breaker 5 is cut off, that is, It is extremely rare for an autofuse to blow.

Therefore, in the protection device A, the blown fuse is hardly found and replaced, and the time and effort for repair is greatly reduced. Further, since such fuse replacement is rarely performed, the necessity of providing the fuse box itself near the driver's seat as in the related art is eliminated, and the degree of freedom in layout of the wiring 3 is greatly improved. Thus, the wiring 3 can be reduced in length and length, and the installation space for the on-vehicle equipment around the driver's seat can be increased.

In addition, the abnormality of the wiring system W or the electric load 1 which has caused the short circuit is diagnosed based on the judgment result of the above-mentioned short short and the like, and the diagnosis is output, so that the abnormal portion can be easily specified. And the time and labor for repair can be greatly reduced. On the other hand, when the output of the abnormality is not performed, the driver of the vehicle can concentrate on the driving operation without worrying about the trouble due to the failure of the wiring system W, thereby improving the safety of the vehicle. Can also contribute.

It should be noted that the configuration of the present invention is not limited to the configuration of the above embodiment, but encompasses other various embodiments. For example, in the above-described embodiment, the overcurrent breaker 5 is made of an auto fuse, but is not limited to this. In addition, it goes without saying that, for example, a junction transistor may be used instead of the FET 4.

In the above embodiment, in response to the abnormality detection signal from the comparison circuit 12, first, the FE is
T4 is turned off, and subsequently, the FET4 is kept off by the control signal from the CPU 15. However, the invention is not limited to this, and the FET4 may be kept off only by a hardware circuit.

On the other hand, it is also possible to control the FET 4 only by the CPU 15 based on the detected current value without providing a hardware circuit as in the above embodiment.

Further, in the above-described embodiment, the short short is finely determined based on the determination reference map, that is, the plurality of abnormal current values i1 to i4, the corresponding determination times t5 to t2, and the number of determinations. However, the method of judging the short-circuit is not limited to this, and it can be performed in various forms based on the value of the abnormal current and its occurrence frequency.

[0071]

As described above, according to the protection device for a vehicle wiring system according to the first aspect of the present invention, a semiconductor switch is provided in the wiring system, and both the frequency of occurrence of abnormal current and the current value at that time are provided. Is determined based on the short-circuit, and the state of the semiconductor switch is switched in accordance with the result of the determination. Fire can be reliably prevented, and safety can be improved. Further, since an overcurrent circuit breaker capable of reliably shutting off excessive current is provided separately from the semiconductor switch, even if the semiconductor switch causes a short-mode failure, when a dead short circuit occurs in a wiring system, the overcurrent breaker is provided. The current can be reliably shut off by the overcurrent breaker,
Therefore, safety and reliability are further improved.

According to the second aspect of the present invention, a map in which a plurality of determination current values, the determination time and the number of determinations for each determination current value are recorded, and the short short determination is performed with reference to this map. Therefore, the short-circuit short can be appropriately and finely determined in accordance with the frequency and the degree of occurrence of the abnormal current, whereby the effect of the invention of claim 1 can be sufficiently obtained.

According to the third aspect of the present invention, in a state where a strong spark flies due to a short circuit, the current can be instantaneously interrupted by a dedicated hardware circuit in response to a single short circuit. It is possible to reliably prevent ignition by sparks.

According to the fourth aspect of the present invention, the current can be instantaneously interrupted by the hardware circuit in response to the excessive current, and the current interruption state is stably maintained by controlling the semiconductor switch by the microcomputer. be able to. In addition, since signal processing by the microcomputer does not need to perform so-called interrupt processing, the microcomputer can be used in common for a large number of protection devices, thereby reducing costs.

According to the fifth aspect of the present invention, there is provided the diagnosis means for diagnosing an abnormality in the wiring system or the electric load based on the judgment result by the judgment means, and the notifying means for notifying the diagnosis result by the diagnosis means. In addition, it is possible to easily identify an abnormal portion, and to reduce time and labor for repair. In addition, when there is no abnormality, the driver of the vehicle can concentrate on the driving operation with a sense of security, which can also contribute to improving the safety of the vehicle.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a wiring system protection device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating an example of an OFF characteristic of an FET with respect to a current value and a time width.

FIG. 3 is a flowchart illustrating a procedure of a dead short handling operation by the wiring system protection device.

FIG. 4 is a flowchart illustrating a procedure of a short-shooting response operation and a diagnosis operation performed by the wiring system protection device.

[Explanation of symbols]

 A Wiring system protection device W Wiring system 1 Electric load 3 Wiring 4 FET (semiconductor switch) 5 Overcurrent breaker 6 Current detection resistor (detection means) 8 Transistor (cutoff circuit) 9 OR circuit (cutoff circuit) 12 Comparison circuit ( Judgment signal output circuit) 13 Cut-off signal output circuit (cut-off circuit) 14 Detection signal output circuit (signal holding circuit) 15 CPU (microprocessor) 15b Control circuit 15c Second judgment unit (judgment unit)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02H 3/087 H02H 3/087

Claims (5)

[Claims] 1. A protection device for a vehicle wiring system, which is disposed in a wiring system to an electric load of a vehicle and cuts off the current before an abnormal current flows before the wiring system is damaged. An overcurrent breaker that is provided in the middle of the wiring in the wiring system and is turned off when a large current of a predetermined value or more flows for a predetermined time or more, and in series with the overcurrent breaker on the wiring A switch that outputs a detection value corresponding to a current flowing through the wiring; and receives an output from the detection means and causes an abnormal current larger than a predetermined reference value to flow through the wiring. Determining means for determining whether or not to cut off the current based on the frequency and the current value at that time; and when the determining means determines that the current should be cut off, the current flowing through the wiring is cut off. Control means for switching the semiconductor switch to an off state, wherein the control means is configured to switch the switching element to the off state at the latest before the overcurrent breaker is turned off. A protection device for a wiring system for a vehicle, comprising: 2. The method according to claim 1, wherein the determining means includes: a map in which a plurality of predetermined determination current values and a determination time and the number of determinations set for each of the determination current values are recorded; Based on the output, referring to the map,
When the state in which the current value flowing through the wiring exceeds one of the above-mentioned respective judgment current values occurs more than the number of times of judgment during the judgment time corresponding to each of the above judgment current values, it is judged that the current should be cut off. And a protection device for a vehicle wiring system. 3. The determination unit according to claim 1, wherein the determination unit compares an output value from the detection unit with a set value and outputs a determination signal when the output value is larger than the set value. A signal output circuit, wherein the control means includes a cutoff circuit including hardware for switching a semiconductor switch to an off state instantly when a determination signal is input from the determination signal output circuit. Wiring system protection device. 4. The microcomputer according to claim 3, wherein the microcomputer receives a determination signal from the determination signal output circuit and outputs a control signal so that the semiconductor switch is turned off. A signal holding circuit that holds a signal input for a set time; and a cutoff circuit holds the semiconductor switch in an off state until the set time has elapsed after receiving the input of the determination signal from the determination signal output circuit. A protection device for a vehicle wiring system, wherein 5. A diagnostic device according to claim 1, wherein the diagnostic device diagnoses an abnormality of a wiring system or an electric load based on a result of the determination by the determining device, and a notification that notifies the diagnostic result of the diagnostic device. Means for protecting a vehicle wiring system.