JP2001045651A - Interlayer short circuit decision device and interlayer short circuit deciding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a interlayer short circuit decision device, protecting an electric wire from the overcurrent of rare shorting. SOLUTION: A fuse element with interlayer short circuit decision function F is provided with a current sensor 2, IC7 and a microcomputer 8. When a detection current L flows in a load 5 via an FET 4, a potential difference is generated in both ends of the current sensor 2. When the potential difference is inputted, IC7 compares the potential difference with a prescribed voltage threshold. The microcomputer 8 compares the characteristic value of detection current L with a reference value, based on the comparison result of IC7. Namely, the microcomputer 8 conducts decision as to interlayer short circuit, based on at least one of four characteristic value: the abnormal current value while a current value related to an input detection signal exceed a prescribed current threshold, the time when the abnormal current value exceeding the prescribed threshold flows, the on-duty ratio, or the number of times passing which exceeds the prescribed current threshold. At the time of interlayer short circuit, the FET 4 is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare short judging device and a rare short judging method for mainly detecting an overcurrent flowing in an electric circuit for an automobile.

[0002]

2. Description of the Related Art A conventional fuse mounted in a fuse box for an automobile is disclosed in US Pat.
There is a blade type fuse of the type disclosed in Japanese Patent No. 023264. The conventional blade type fuse is used in a large number in the electric system of an automobile, but often has a slow blow characteristic (the fuse is not blown by an instantaneous overcurrent, and when the overcurrent continues for a certain period of time, That is, a function of preventing the danger by fusing when there is a danger such as a fire if the overcurrent continues is provided.

[0003]

For this reason, the fuse is blown at the time of a dead short in which a large current flows continuously, but the fuse may not be blown in a short intermittent rare short region.

In such a case, a current in a rare short-circuit region flows through a load or a circuit element, and the electric wire of an automobile circuit emits smoke,
It ignites, causing a vehicle fire. Therefore, the appearance of a rare short determination device that can reliably determine a rare short in the rare short region has been desired.

An object of the present invention is to provide a rare short judging device and a rare short judging method which can protect an electric wire from rare short overcurrent at the time of rare short.

[0006]

According to a first aspect of the present invention, an input detection signal corresponding to a current to be detected flowing through an electric circuit for a vehicle is input, and based on the input detection signal. A rare short judging device including a judging means for judging whether or not the electric current is abnormal such that the electric wire provided in the electric circuit for a vehicle does not emit smoke. Four characteristics of an abnormal current value in which the current related to the detection signal exceeds a predetermined current threshold, a time during which an abnormal current value exceeding the predetermined current threshold flows, an on-duty ratio, or the number of times of passage exceeding the predetermined current threshold The gist of the present invention is a rare short judging device that performs the judgment based on at least one of the characteristic values.

A second aspect of the present invention is directed to a rare short judging device according to the first aspect, wherein at least two of the four characteristic values become abnormal levels and perform an abnormality judgment. Things.

[0008] The invention of claim 3 is claim 1 or claim 2.
Output means for outputting a first mode signal for permitting energization to a load in which the current to be detected is consumed, or a second mode signal for interrupting energization to the load, based on a result of the abnormality determination The gist of the present invention is a rare short judgment device provided with:

[0009] The invention of claim 4 is the invention of claim 1 or claim 2.
In the above, the determination means, for each predetermined level region divided by a plurality of different current thresholds, the time during which an abnormal current value exceeding the predetermined current threshold is flowing, the on-duty ratio,
Or a storage unit for storing a reference value relating to at least one characteristic value of the number of times of passage exceeding a predetermined current threshold, wherein the determination unit determines that a current value related to the input detection signal is divided by the current threshold. When you belong to one of the level areas,
The gist of the invention is a rare short judging method characterized by judging, for each of the predetermined level regions, whether or not the value is larger than a reference value relating to a characteristic value set according to the predetermined level.

The invention according to claim 5 is based on an input detection signal relating to a current to be detected flowing through an electric circuit for a vehicle.
In the rare short judging method of judging whether or not the current is abnormal such that the electric wire provided in the automobile electric circuit does not smoke, the abnormal judgment is performed when the current related to the input detection signal exceeds a predetermined current threshold. In the determination relating to at least one of the four characteristic values of the current value, the time during which the abnormal current value exceeding the predetermined current threshold flows, the on-duty ratio, and the number of times of passage exceeding the predetermined current threshold value, The gist is a method of judging a rare short to be performed.

According to a sixth aspect of the present invention, in the fifth aspect, the abnormality determination is performed when at least two of the four characteristic values become abnormal. The gist is a method of determining a rare short.

The invention of claim 7 is the invention of claim 5 or claim 6.
In the abnormality determination, when the current value related to the input detection signal belongs to one of predetermined level ranges defined by the current threshold, the abnormality determination is set for each of the predetermined level ranges according to the predetermined level. The gist is to judge whether or not the value is larger than a reference value related to the characteristic value.

(Operation) According to the first aspect of the present invention, the judging means judges whether or not the inputted input detection signal is a rare short overcurrent. This rare short judgment,
The determining means is configured to detect an abnormal current value in which the current related to the input detection signal exceeds the predetermined current threshold, a time during which the abnormal current value exceeding the predetermined current threshold flows, an on-duty ratio, or a passage exceeding the predetermined current threshold. The determination is performed based on at least one of the four characteristic values of the number of times.

According to the second aspect of the present invention, the judging means makes a rare short judgment if at least two of the four characteristic values combined are at an abnormal level. .

According to the third aspect of the present invention, the determining means
If it is determined that the current is not a rare short overcurrent,
The output means outputs a first mode signal that allows current to the load. When the determining means determines that the current is a rare short overcurrent, the output means outputs a second mode signal for cutting off the current supply to the load.

According to the present invention, the judging means stores a different reference value for each of predetermined level ranges defined by a plurality of different current thresholds, and the current value related to the input detection signal is the current value. When belonging to any of the predetermined level ranges defined by the threshold value, it is determined whether or not the characteristic value of the current corresponding to the predetermined level range is different from the reference value corresponding to the predetermined level range. I do.

According to the fifth aspect of the present invention, the abnormality is determined by determining an abnormal current value in which the current relating to the input detection signal exceeds the threshold, a time during which the abnormal current value exceeding the threshold flows, an on-duty ratio, and a threshold value. Of the four characteristic values of the number of passes exceeding
The determination is made based on at least one characteristic value.

According to a sixth aspect of the present invention, the abnormality determination is performed when the combined characteristic values of the four characteristic values are both abnormal. According to the seventh aspect of the present invention, the abnormality determination is performed when the current value related to the input detection signal belongs to any one of predetermined level ranges defined by the current threshold.
The determination is performed for each of the predetermined level regions by determining whether or not the reference value is larger than a reference value related to a characteristic value set according to the predetermined level.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the rare short judging device of the present invention is embodied in a fuse element F having a rare short judging function will be described below with reference to FIGS.

FIG. 6A is a front sectional view of an example of a fuse element with a rare short function (hereinafter, referred to as a fuse element) F, and FIG. 6B is a side sectional view. As shown in the figure, the housing 100 of the fuse element F is composed of split housing cases 100a and 100b made of a heat-resistant and insulating synthetic resin or the like. A pair of conductive terminals 102a, 102b spaced apart from each other, thin male terminals 104, 105, 106, and a judging portion H described later are arranged on inner surfaces of the housing cases 100a, 100b facing each other. Case 10
It is pinched without rattling at 0a and 100b.

The conductive terminals 102a and 102b extend downward from the housing 100 in the same direction. The male terminals 104, 105, and 106 disposed between the conductive terminals 102a and 102b extend downward. Between the inner ends of the front conductive terminals 102a and 102b,
A thin-walled fusing portion 2 corresponding to the current carrying capacity of the fuse is integrally connected.

The pair of input terminals 6e and 6f of the judgment section H are electrically connected to connecting pieces 2a and 2b provided on the inner ends of the conductive terminals 102a and 102b. The power supply terminal 6a of the determination unit H is a branch electrode branched from the conductive terminal 102a, and the first output terminal 6b is a male terminal 104 for a shutoff signal.
And the second output terminal 6c is a male terminal 105 for the LED signal.
And the ground terminal 6d are connected to the male terminal 106 for ground.

The fuse element F is mounted on a terminal block (not shown) provided in an electric circuit for an automobile, and connects the connection pieces 2a and 2b and the input terminals 6e and 6f to a current flowing through the fuse element F. The signal (voltage) is passed through the determination unit H
Is always input (applied).

Here, the fusing section 2 comprises current detecting means,
The fusing portion 2 is referred to as a current sensor 2 hereinafter. The current sensor 2 has a predetermined impedance Z
have. In the fusing section constituting the current sensor 2, in the flowchart of the control program executed by the microcomputer 8 described later, the current (overcurrent) of A2 amperes or more in step S7 flows, and after the current flows, When the elapsed time is less than T2, the current supply capacity is provided so as not to blow. That is, at the time of the dead short determination when the microcomputer 8 is operating normally,
The current-carrying capacity is set so that the microcomputer 8 determines whether or not the microcomputer 8 is dead short before the fusing section is blown.

FIG. 1 is an electric circuit diagram in which a fuse element F having a rare short function is connected to an electric circuit for an automobile. An accessory switch (hereinafter simply referred to as a switch) 15 is connected between the battery power source B and the current sensor 2. When the switch 15 is in the off state,
A switch-off signal is input to each of the IC 7 and the microcomputer 8 of the determination unit H. When the switch 15 is turned on, a switch-on signal is input to each of the IC 7 and the microcomputer 8.

As shown in FIG. 1, a fuse element F and a power MOSFET (hereinafter simply referred to as F) as a relay are provided between a battery B constituting an electric circuit for an automobile and a ground line.
ET) 4 and a load 5 are provided. The load 5 includes, for example, a head lamp, a radio, and the like (not shown).

Next, the details of the judging section H constituting the fuse element F will be described. Judgment unit H is IC7
And a microcomputer 8. As shown in FIG. 2, the IC 7 includes a differential amplifier circuit 11, an operational amplifier, a first comparator circuit 12, and a second comparator circuit 13, respectively. Differential amplifier circuit 11 (operational amplifier)
Is connected to an input terminal 6e. And the current sensor 2
Is connected to the “+” terminal 1 of the differential amplifier 11
1a. Further, an inverting input terminal (hereinafter, referred to as a “-” terminal) 11b of the differential amplifier circuit 11
Is connected to the input terminal 6f. Then, the potential E2 on the other end side of the current sensor 2 is input to the “−” terminal 11b of the differential amplifier circuit 11.

The differential amplifier circuit 11 has a potential E1 and a potential E2.
Is input as an input detection signal, the potential difference (E
1−E2) is amplified by a predetermined number (N (> 0) times in the present embodiment), and the amplified voltage V (= N × (E1−E2)) is output from the output terminal 11c. Here, when a current (detection current L) having the current value LL flows through the load 5 and the current sensor 2, a potential difference having a value of “impedance Z × current value LL of the detection current L” is applied to both ends of the current sensor 2. E1-E
2) occurs. That is, the voltage V is expressed as “V = N × (E1-
E2) = N × Z × LL ”. Therefore, since the voltage V and the current value LL of the detection current L are in a proportional relationship, knowing the voltage V makes it possible to obtain the current value LL of the detection current L.
You can know. In the following description, the current value LL of the detection current L may be used instead of the voltage V for convenience of description.

Output terminal 11c of the differential amplifier circuit 11
Is connected to an inverting input terminal (hereinafter, referred to as “−” terminal) 12 a of the first comparator circuit 12 (operational amplifier). A non-inverting input terminal (hereinafter, referred to as a “+” terminal) 12b of the first comparator circuit 12 includes a resistor R2 and a resistor R3.
Connected to the middle point. That is, if the voltage value of the battery power supply B is VB, the resistance value of the resistor R1 is RA, the resistance value of the resistor R2 is RB, and the resistance value of the resistor R3 is RC, "+"
The terminal 12b has (VB × RC / (RA + RB + R
A voltage VF1 represented by the formula C)) is applied.

In the present embodiment, the value of the voltage VF1 (predetermined voltage threshold) is such that the detected current L of A1 amperes (current value constituting the current threshold value of the present invention and having no adverse effect on the electric wire) flows through the load 5. Voltage (= A1 ×
Z) is set to be equal to a value obtained by multiplying N by N.

The first comparator circuit 12 receives the amplified voltage V from the differential amplifier circuit 11 and receives the voltage V and the voltage V.
Compare with F1. That is, the first comparator circuit 12 determines whether or not the current value LL of the detection current L is larger than A1 ampere. When the current value LL (voltage V) of the detection current L is smaller than or equal to A1 ampere (voltage VF1), the first comparator circuit 12 outputs an H-level signal from the output terminal 12c. When the current value LL of the detection current L is larger than A1 ampere,
The first comparator circuit 12 outputs an L level signal from the output terminal 12c.

The output terminal 11 of the differential amplifier circuit 11
c is connected to an inverting input terminal (hereinafter, referred to as a "-" terminal) 13a of the second comparator circuit 13 (operational amplifier). A non-inverting input terminal (hereinafter, referred to as a “+” terminal) 13b of the second comparator circuit 13 is connected to an intermediate point between the resistors R1 and R2. That is, "+" terminal 1
3b includes (VB × (RB + RC) / (RA + RB + R)
A voltage VF2 represented by the formula C)) is applied.

In the present embodiment, the value of the voltage VF2 (predetermined voltage threshold) is determined by the current sensor when the detection current L of A2 (> A1) amps (constituting the current threshold of the present invention) flows through the load 5. 2 is set to be equal to a value obtained by multiplying the voltage between both ends (= A2 × Z) by N.

When the amplified voltage V is input from the differential amplifier circuit 11, the second comparator circuit 13 receives the voltage V and the voltage V.
Compare with F2. That is, the second comparator circuit 13 determines whether or not the current value LL of the detection current L is larger than A2 ampere. When the current value LL (voltage V) of the detection current L is smaller than or equal to A2 ampere (voltage VF2), the second comparator circuit 13 outputs an H level signal from the output terminal 13c. When the current value LL of the detection current L is larger than A2 ampere,
The second comparator circuit 13 outputs an L level signal from the output terminal 13c.

The output terminal 12c of the first comparator circuit 12 is connected to the microcomputer 8 via an output signal line OS1, and the output terminal 13c of the second comparator circuit 13 is connected to the microcomputer 8 via an output signal line OS2. It is connected to the. The IC 7 is connected to the microcomputer 8 via the input signal line IS1 and the input signal line IS2.

The microcomputer 8 outputs an H level or L level signal from the first comparator circuit 12 input via the output signal line OS1 and an H level signal from the second comparator circuit 13 input via the output signal line OS2. Alternatively, it is determined whether or not the characteristic value of the detection current L is larger than a reference value based on the L level signal. In the present embodiment, the characteristic value of the detection current L is the current value L of the detection current L.
L, the continuous time TA exceeding A1 ampere, the current value LL of the detection current L, the continuous time TB exceeding A2 ampere, and the ratio of the on-time per unit time of the detection current L (on-duty ratio, hereinafter, DUTY ratio) D) means the number of times K per unit time that the current value LL of the detection current L has exceeded A2 amperes on the rising side.

One output terminal of the IC 7 is connected to the judgment unit H
, And the first output terminal 6b is connected to the gate G of the FET4. The IC 7 receives the current-permit signal from the microcomputer 8 and charges the charge pump 1
4 (see FIG. 2), and FE is connected to the gate G of FET4.
A T-on signal is output. When the FET 4 receives the FET ON signal from the IC 7, the FET 4 is turned on between the drain D and the source S. As a result, the detection current L flows to the load 5.

Further, the IC 7 discharges the charge pump 14 when the power cutoff signal is inputted from the microcomputer 8, and the IC 4
To the gate G of the FET. FET4 is I
When the FET-OFF signal is input from C7, the state between the drain D and the source S is turned off, and as a result, the power supply to the load 5 is cut off.

The other output terminal of the IC 7 is connected to the second output terminal 6c of the judgment section H, and is provided with a light emitting diode (hereinafter, referred to as an LED) 9 provided in an electric circuit of the automobile.
Is connected via the LED signal male terminal 105. The IC 7 turns on the LED 9 when an LED lighting signal is input from the microcomputer 8. The IC 7 turns off the LED 9 when the LED turning off signal is input from the microcomputer 8. The LED 9 is provided, for example, on an unillustrated instrument panel of an automobile. Microcomputer 8
Has a central processing unit (not shown), a ROM for storing a rare short overcurrent protection control program described later, and a working memory (RAM).

In this embodiment, the judgment means and the output means are constituted by the IC 7 and the microcomputer 8. Also, FE
Switching means and a relay are constituted by T4. Further, the first mode signal is configured by the energization permission signal. Further, the second mode signal is constituted by the energization cutoff signal.

Now, the operation of the fuse element F configured as described above will be described. 3 to 5 are flowcharts showing processing operations based on the rare short overcurrent protection control program executed by the microcomputer 8. The rare short overcurrent protection control determines whether or not a rare short overcurrent is flowing in the circuit. If it is determined that the rare short overcurrent is not flowing, the power supply to the load 5 is allowed, and the rare short overcurrent is controlled. When it is determined that the current is flowing, the power supply to the load 5 is interrupted.

When the microcomputer 8 is supplied with the predetermined voltage VB from the battery power source B, first, in step (hereinafter, step is referred to as S) 1, the counters CTA, CTB,
Initial setting such as resetting C3 to C6 to “0” is performed, and the process proceeds to S2.

At S2, it is determined whether a switch-on signal has been input. When it is determined that the switch-on signal has not been input, the process proceeds to S16. On the other hand, if it is determined that the switch-on signal has been input, the process proceeds to S3.

Next, in S16, an energization cutoff signal and an LED extinguishing signal are output to the IC 7. The IC 7 discharges the charge pump 14 upon receiving the power cutoff signal, and
An FET-off signal is output to ET4 to turn off FET4. Also, when the LED 7 receives the LED extinguishing signal,
The LED 9 is turned off. Then, the microcomputer 8 returns to S2.

In S3, an energization permission signal is output to IC7. The IC 7 charges the charge pump 14 based on the input of the energization permission signal, and outputs an FET ON signal to the FET 4. Then, the FET 4 is turned on.

Next, at S4, the current value LL is fetched, and the routine goes to S5. Next, in S5, it is determined whether or not the current value LL is larger than A1 ampere. That is,
The determination is made based on the L level or H level signal from the output signal lines OS1 and OS2. When both the signal from the output signal line OS1 and the signal from the output signal line OS2 are L level signals, it is determined that the current value LL is smaller than or equal to A1 ampere. Also, the signal from the output signal line OS1 is an H level signal, and the output signal line O1
When the signal from S2 is an L level signal, the current value L
It is determined that L is greater than A1 amps. And
If it is determined that the current value LL is larger than A1 amp, the process proceeds to S6. On the other hand, if it is determined that the current value LL is smaller than or equal to A1 amp, the process proceeds to S17.

In S17, the energization permission signal and the LED extinguishing signal are output to the IC 7. The IC 7 charges the charge pump 14 upon input of the energization permission signal, and sets the FET 4
Outputs the ET ON signal. Then, the FET 4 is turned on, and energization of the load 5 is allowed. IC7 is LE
When the D extinguishing signal is input, the LED 9 is extinguished. Then, the microcomputer 8 returns to S2.

Next, at S6, the counter CTA is set to 1
And the process proceeds to S7. This counter CT
Continuous time T over A1 amp of current value LL due to A
A is integrated.

Next, in S7, it is determined whether or not the current value LL is larger than A2 ampere. That is, the determination is made based on the L level or H level signals from the output signal lines OS1 and OS2. When both the signal from the output signal line OS1 and the signal from the output signal line OS2 are L level signals, it is determined that the current value LL is smaller than or equal to A2 ampere. When the signal from the output signal line OS1 is an H level signal and the signal from the output signal line OS2 is an L level signal, the current value LL becomes A
It is determined to be less than or equal to 2 amps.

Further, when the signal from output signal line OS1 and the signal from output signal line OS2 are both H level signals, it is determined that current value LL is larger than A2 ampere. When it is determined that the current value LL is larger than A2 ampere, the process proceeds to S8. On the other hand, if the current value LL is A
If determined to be less than or equal to 2 amps,
Move to S18.

At S18, the continuous time TA is set to T2 sec.
It is determined whether it is greater than (constituting the reference value of the present invention). If it is determined that the continuous time TA is longer than T2 sec, the process proceeds to S19 assuming that there is a possibility of dead short. On the other hand, the continuous time TA is T2se
If it is determined that it is smaller than or equal to c, the process proceeds to S17.

Next, in step S19, an energization cutoff signal and an LED lighting signal are output to the IC 7. The IC 7 discharges the charge pump 14 upon receiving the power cutoff signal, and
An FET off signal is output to ET4. Then, FET4
Is turned off, and the power supply to the load 5 is cut off. As a result, dead short is prevented. IC7 is L
When an ED lighting signal is input, the LED 9 is turned on. Then, the microcomputer shifts to S20.

At S20, a DIAG signal is output, and a self-diagnosis is performed. Then, the microcomputer moves to S21.
Next, in S21, it is determined whether or not an IG (ignition) signal of the vehicle has been input. And I
If it is determined that the G signal has not been input, the process proceeds to S19. On the other hand, if it is determined that the IG signal has been input, S1
Move on to

On the other hand, when shifting from S7 to S8, in S8,
The counter CTB is incremented by one, and the routine goes to S9. The continuous time TB exceeding A2 ampere of the current value LL is integrated by the counter CTB.

In S9, the on-time counter C3 and the off-time counter C4 are each incremented by one.
Move to S10. The on-time counter C3 is for accumulating the on-time of the detection current L. The off-time counter C4 is for integrating the off-time of the detection current L.

Next, in S10, the number counter C5
, And the time counter C6 is incremented by one, and the process proceeds to S11. The number counter C5 is for accumulating the number of times the current value LL has exceeded A2 ampere.

In S11, the continuous time TB is T1 (<T
2) It is determined whether it is larger than sec (which constitutes the reference value of the present invention). And the continuous time TB is T1se
If it is determined to be larger than c, it is determined that there is a possibility of a rare short, and the routine goes to S19. Therefore, after shifting to S19, an energization cutoff signal is output, so that the FET 4 is turned off, and a rare short circuit is prevented. On the other hand, when it is determined that the continuous time TB is smaller than or equal to T1 sec, the process proceeds to S12.

Next, in S12, the ratio of the on-time per unit time of the detected current L (DUTY) is determined by the value of the on-time counter C3 and the value of the off-time counter C4.
Ratio) D is calculated.

Next, in S13, the duty ratio D becomes D
It is determined whether it is greater than 1% (constituting the reference value of the present invention). When it is determined that the duty ratio D is larger than D1%, the process proceeds to S19 as a possibility of a rare short. Therefore, after shifting to S19,
Since the conduction cutoff signal is output, the FET 4 is turned off, and rare short circuit is prevented. On the other hand, the duty ratio D
Is less than or equal to D1%, S
Move to 14.

In S14, the number K per unit time exceeding the current value LL of A2 ampere is calculated based on the value of the number counter C5 and the value of the time counter C6. S1
5, the number of times K per unit time is K1 times / sec.
It is determined whether it is greater than (constituting the reference value of the present invention). Then, the number of times K per unit time is K1 times /
If it is determined that it is longer than sec, it is determined that there is a possibility of a rare short, and the routine goes to S19. Therefore, after shifting to S19, an energization cutoff signal is output.
4 is turned off, and rare short circuit is prevented. On the other hand, if it is determined that the number of times K per unit time is smaller than or equal to K1 times / sec, the process proceeds to S17.

In this embodiment, S5, S7, S18, S
The determination means is constituted by 11, S13, and S15. The ROM has a continuous time as a reference value and a DUT.
It corresponds to storage means for storing the Y ratio and the number of times per unit time.

Therefore, according to the present embodiment, the following effects can be obtained. (1) In the present embodiment, it is determined in S5 that the current value LL is larger than A1 ampere, and the current value LL is determined in S7.
If it is determined that L is smaller than or equal to A2 amperes, and if it is determined in S18 that the continuous time TA of the current value LL exceeding A1 amperes is greater than T2 sec, the FET 4 is turned off, and the load is turned off. 5 is shut off. Therefore, in this case, the load 5 and the like of the automobile circuit can be protected from an overcurrent caused by a dead short.

(2) In this embodiment, the current value L is set at S7.
When it is determined that L is larger than A2 ampere (abnormal level), and that the continuous time TB of the current value LL exceeding A2 ampere is larger than T1 sec (abnormal level) in S11, the FET 4 is turned off. And the energization to the load 5 is cut off. Therefore, in this case, the electric wire can be protected from overcurrent at the time of rare short circuit.

(3) In this embodiment, the current value L is set at S7.
L is determined to be greater than A2 amperage (abnormal level), the continuous time TB is determined to be less than or equal to T1 sec in S11, and the duty ratio D of the detection current L is determined to be D1 in S13. When it is determined that the value is larger than the% (abnormal level), the FET 4 is turned off, and the power supply to the load 5 is cut off. Therefore, even in this case, the electric wire can be protected from overcurrent at the time of rare short circuit.

(4) In this embodiment, the current value L is set at S7.
L is determined to be greater than A2 amperage (abnormal level), and in S11 the continuous time TB is determined to be less than or equal to T1 sec, and in S13 the DUTY ratio D is greater than D1%. When it is determined that the current value LL is smaller or equal to each other and the number K of times that the current value LL exceeds A2 ampere per unit time is larger than K1 times / sec (abnormal level) in S15, the FET 4 is turned off. Then, the power supply to the load 5 is cut off. Therefore, even in this case, the electric wire can be protected from overcurrent at the time of rare short circuit.

(5) In this embodiment, the voltage V proportional to the current value LL can be detected by using the fuse as the current sensor 2. The embodiment of the present invention may be modified as follows.

(A) In the above-described embodiment, a fuse is used as the current sensor 2, but another resistor such as a resistor or a thermistor may be used instead of the fuse. In such a case, (1) to (5) in the above embodiment are used.
The effect described in (1) is obtained.

(B) In the above embodiment, whether or not the detected current L is a rare short overcurrent is determined based on the potential difference (E1-E2) between both ends of the current sensor 2 (fuse). Alternatively, the following may be performed using an ammeter.

That is, as the current sensor 2, the internal resistance RIN
And the detection current L is measured by the ammeter. Then, a resistance loss having a value of “internal resistance RIN × detection current L × detection current L” is calculated using the detection current L measured by the ammeter. Then, the microcomputer 8 determines whether or not the resistance loss generated in the ammeter is larger than a predetermined resistance loss. If the resistance loss generated in the ammeter is larger than the predetermined resistance loss, the detected current is detected. It may be determined that L is a rare short overcurrent. In such a case, (1) to (1) in the above embodiment are used.
The effect described in (5) is obtained.

When it is determined that the temperature rise value due to the resistance loss generated in the current sensor 2 is larger than a predetermined temperature rise value, it is determined that the detected current L is a rare short overcurrent. You may. In this case, the effects described in (1) to (5) in the embodiment can be obtained.

(C) Further, at S5, the current value LL becomes A1
If it is determined that the current value LL is greater than A1 ampere in S18, the continuous time TA exceeding A1 ampere for S2
It is determined whether it is greater than c. If it is determined in S18 that the continuous time TA is smaller than or equal to T2sec, the current value LL is determined in S7.
May be determined whether or not is larger than A2 ampere.

(D) Furthermore, in the above embodiment, the first
Although the IC 7 has two comparator circuits of the comparator circuit 12 and the second comparator circuit 13, the IC 7 may have one comparator circuit. or,
The IC 7 may include three or more comparator circuits. In this case, after comparing the current value LL of the detection current L with the current threshold value of each comparator circuit, the characteristic value of the detection current L is compared with a reference value corresponding to a predetermined level area defined by the current threshold value. It is determined whether or not the detection current L is a rare short overcurrent. The characteristic value and the reference value are
As in the previous embodiment, the continuous time exceeding the current threshold, D
UTY ratio means the number of times per unit time exceeding the current threshold.

(E) If it is determined in S5 that the current value LL is larger than A1 ampere, the process may proceed to S19. In this case, S6, S7, S18, S8 to S
15 is omitted.

(F) In the above embodiment, the LED 9 is provided on the instrument panel of the automobile. However, the LED 9 may be provided on the fuse element F itself. In this case, the male terminal 105 for the LED signal is omitted.

(G) In the above embodiment, the first mode signal is constituted by the conduction permission signal and the FET ON signal, and the second mode signal is constituted by the conduction interruption signal and the FET OFF signal. Instead, the first mode signal may be constituted only by the energization permission signal, and the second mode signal may be constituted only by the interruption signal.

(H) In the above embodiment, different current thresholds are set to A1 and A2 (> A1), and T1 is set to a time during which an abnormal current value exceeding A2 (predetermined current threshold) flows.
D1 was the on-duty ratio, and K1 was the number of passes exceeding A2 (predetermined current threshold). Therefore, in the present embodiment, when A2 is exceeded, a rare short is determined based on any one of the four characteristic values.

Instead of this configuration, a plurality of current thresholds different from each other are set, and reference values are provided for different characteristic values in a region between the current thresholds. May be performed. In this case, a plurality of comparators are used as in (D).

The following table shows a combination example in the case where a rare short is determined. Rare short determination may be made by a combination shown in Table 1, Table 2, or Table 3 below. The example of combination in each column indicates a case where each of them has an abnormal level.

Table 1 shows that the current values A1 to A5 (where A1 <A
The levels and duty ratios D1 to D5 (D1 <D2 <D3 <) defined by the respective current thresholds up to 2 <A3 <A4 <A5
D4 <D5). Note that each column in the table indicates the level up to the value of the adjacent lower column. For example, the column of “A1 ≦” indicates “level of A1 or more and less than A2”. Note that only the last column indicates a case where the value is equal to or more than that value. For example, “A5 ≦” indicates A5 or more.

Table 2 shows the levels divided by the current values A1 to A5 and the number of passes K1 to K5 (where K1 <K2 <K3 <K
4 <K5). Table 3 shows current values A1 to A5 and duty ratios D6 to D1.
0 (D5 <D6 <D7 <D8 <D9 <D10),
And a case where the levels divided by the number of passages K6 to K10 are combined.

The current values A1 to A5 are predetermined current threshold values, and D1 to D10 and K1 to K10 are reference values.

[0082]

[Table 1]

[0083]

[Table 2]

[0084]

[Table 3] Therefore, in the above combinations of Tables 1 to 3,
These current threshold values and reference values are stored in the ROM serving as a storage unit, and reference values corresponding to levels defined by these current threshold values are set. When the input current value belongs to one of the levels classified by the current thresholds, the microcomputer 8 determines which level the characteristic value corresponding to the level is, and determines each of the above Tables 1 to If any of the combinations shown in Table 3 applies, a rare short judgment is made.

Next, technical ideas other than those described in the claims that can be understood from the above-described embodiment and other examples will be described below together with their effects. (1) In Claim 3, the output means outputs a warning means ON signal when outputting the first mode signal, and outputs a warning means OFF signal when outputting the second mode signal. apparatus. In this case, the warning means can be turned on by the warning means on signal, and the warning means can be turned off by the warning means off signal, and it can be known whether or not there is a rare short by the warning means on / off operation. .

In the above embodiment, the LED 9 corresponds to a warning means, the LED lighting signal output in S19 corresponds to a warning means ON signal, and the LED extinguishing signal output in S16 and S17 corresponds to a warning means OFF signal. Equivalent to.

(2) In any one of claims 1 to 4, the determination means determines whether or not the current related to the input detection signal is larger than a predetermined first current value. A rare short judging device characterized by including a first comparing means. Therefore, according to the invention described in (2), the first comparing unit determines that the current value of the current related to the input input detection signal is smaller than or equal to the predetermined first current value. Then, it is determined that the current is not a rare short overcurrent. If the first comparing means determines that the current value of the current is larger than the first current value, it is determined that the current is a rare short overcurrent. The effects of the described invention can be obtained. In the above embodiment, the microcomputer 8 constitutes a first comparing unit. S5 constitutes first comparing means. Further, A1 amps constitute the first current value.

[0088]

As described in detail above, according to the first and fifth aspects of the present invention, the determining means determines whether or not the current relating to the input detection signal is a rare short overcurrent. Therefore, at the time of a rare short, the electric wire can be protected from the overcurrent of the rare short.

According to the second and sixth aspects of the present invention, the judging means judges whether or not the rare short is at least two of the four characteristic values combined with each other.
When both become abnormal levels, it is possible to make an abnormality determination, and it is possible to make a more accurate rare short determination.

According to the third aspect of the present invention, when the judging means judges that the current related to the input detection signal is a rare short overcurrent, the second mode signal for cutting off the current supply to the load is output. Claim 1 because the data is output from the output means.
The effects of the invention described in (1) can be realized.

According to the fourth and seventh aspects of the present invention, it is possible to cope with different patterns of the layer short.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an automobile including a fuse element with a rare short judgment function according to an embodiment.

FIG. 2 is an electric circuit diagram showing a schematic configuration of an IC.

FIG. 3 is a flowchart showing a processing operation based on a rare short overcurrent protection control program executed by a microcomputer.

FIG. 4 is a flowchart showing a processing operation based on a rare short overcurrent protection control program executed by a microcomputer.

FIG. 5 is a flowchart showing a processing operation based on a rare short overcurrent protection control program executed by a microcomputer.

FIG. 6A is a front sectional view of an example of a fuse element having a rare short function (hereinafter, referred to as a fuse element);
(B) is a side sectional view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rare short judgment apparatus, 2 ... Current detection means, Current sensor as a resistance element and a fuse element, 4 ... FET as a relay, 5 ... Load, 7 ... IC which constitutes judgment means and output means, 8 ... Judgment means And a microcomputer constituting an output means, L: detected current as current, LL: current value, T
A: a continuous time exceeding the current value A1 amperes, constituting a current characteristic value; TB: a continuous time exceeding the current value A2 amperes, constituting a current characteristic value; D: constituting a current characteristic value , The ratio of the ON time per unit time of the detected current (DUTY ratio), K... Constituting the characteristic value of the current, the number of times the current value exceeds A2 ampere per unit time, S5
... Step 5 constituting the judging means, S7. Step 7 constituting the judging means, S18. Step 18 constituting the judging means. S11. Steps S11 and S constituting the judging means.
13: Step 13 configuring the determination means, S15 ... Step 15 configuring the determination means.

Claims (7)

[Claims] An input detection signal corresponding to a current to be detected flowing through an electric circuit for a vehicle is input, and the electric current based on the input detection signal is such that the electric current does not cause an electric wire provided in the electric circuit for a vehicle to smoke. A rare short judging device provided with a judging means for judging whether or not there is an abnormality, wherein the judging means judges the abnormality as an abnormal current value when a current related to an input detection signal exceeds a predetermined current threshold, a predetermined current The rare operation is performed based on at least one of four characteristic values of a time during which an abnormal current value exceeding a threshold value flows, an on-duty ratio, or a number of times of passage exceeding a predetermined current threshold value. Short judgment device. 2. The rare short judging device according to claim 1, wherein when at least two of the four characteristic values are at an abnormal level, an abnormality is determined. 3. The first mode signal according to claim 1 or 2, wherein the first mode signal for permitting energization to the load in which the current to be detected is consumed, or the energization to the load is cut off based on a result of the abnormality determination. A short-circuit judging device provided with an output means for outputting a second mode signal for performing the operation. 4. The apparatus according to claim 1, wherein the determination unit determines that a time during which an abnormal current value exceeding the predetermined current threshold flows for each predetermined level range divided by a plurality of different current thresholds. A storage unit for storing a reference value related to at least one characteristic value of an on-duty ratio or a number of times of passage exceeding a predetermined current threshold, wherein the determination unit determines that a current value related to the input detection signal is the current threshold. When belonging to any of the predetermined level areas defined by the above, for each of the predetermined level areas, it is determined whether it is greater than a reference value related to a characteristic value set according to the predetermined level Rare short judgment device to do. 5. A rare short judgment for judging, based on an input detection signal relating to a current to be detected flowing through an electric circuit for a vehicle, whether or not the current is abnormal so as not to smoke an electric wire provided in the electric circuit for a vehicle. In the method, the abnormality determination may include determining an abnormal current value in which a current related to the input detection signal exceeds a predetermined current threshold, a time during which an abnormal current value exceeding the predetermined current threshold flows, an on-duty ratio, and a predetermined current threshold. A rare short judging method characterized in that the judgment is made based on at least one of the four characteristic values of the number of times of passage exceeding the characteristic value. 6. The method according to claim 5, wherein the abnormality is determined by determining
A rare short judging method characterized in that when at least two of the two characteristic values become abnormal, an abnormality judgment is made. 7. The abnormality determination according to claim 5, wherein the abnormality determination is performed when a current value of the input detection signal belongs to one of predetermined level ranges defined by the current threshold. A rare short determination method for determining, for each region, whether or not the value is greater than a reference value related to a characteristic value set according to the predetermined level.