JPH11136846A - Abnormal current cutting apparatus for wiring system in vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormal current cutting apparatus for a wiring system in a vehicle wherein the current flowing through the wiring system is out off independently of any fuse, even in the case of the hard intermittent short-circuit of the wiring system where the fuse is hard to melt. SOLUTION: A current sensor 20 senses the current flowing through a wiring system (L) for connecting a DC power supply 10 with an electric load 40 to generate the sensed output thereof. When the sensed output is an abnormal value corresponding to an instantaneous large abnormal current, a dead-short judging circuit (D) judges it as abnormal. Also, when the sensed output is an abnormal value corresponding to an intermittent small abnormal current, a layer-short judging circuit (R) judges it as abnormal. Then, a MOSFET 30 cuts the current flow of the wiring system L based on one of the judgements of both the abnormal values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular wiring system abnormal current interrupter for interrupting an abnormal current flowing in a vehicle wiring system.

[0002]

2. Description of the Related Art Conventionally, wiring systems 4, 5 and electric loads 2, 3 connected between a DC power supply 1 mounted on an automobile and electric loads 2, 3, such as electric components, are shown in FIG. As shown, for example, the fuses 6 interposed in the wiring systems 4 and 5,
7 is performed.

[0003]

By the way, in the above configuration, if a large abnormal current flows instantaneously when the wiring system 4 or the wiring system 5 is completely short-circuited, the fuses 6 and 7 are surely blown by the heat accumulation. . However, when the coating of the wiring of the wiring system is partially peeled due to its aging, the wiring is intermittently interposed between the peeled portion and a resistive load in the vicinity due to the vibration of the automobile. When a short circuit occurs, the fuse does not accumulate enough heat to blow due to the intermittent small abnormal current flowing through the fuse.

On the other hand, even if the intermittent short circuit as described above has a combustible material around it, there is a possibility that the combustible material may ignite due to intermittent heat generation in a portion after the wiring is peeled off. is expected. In view of the foregoing, the present invention has been made to solve the above-described problem, and it is possible to interrupt a current flowing through a wiring system without relying on a fuse even by an intermittent short-circuit of a wiring system in which a fuse is difficult to blow. It is intended to provide an abnormal current interrupting device for use.

[0005]

In order to solve the above-mentioned problems, according to the first and second aspects of the present invention, the detecting means is connected between a power supply mounted on the vehicle and an electric load. A current flowing through the wiring system is detected and a detection output is generated. When the detected output is the first abnormal value corresponding to the instantaneous large abnormal current, the first judging means judges that this is abnormal. The second determination means determines that the detected output is abnormal when the detected output is a second abnormal value corresponding to the intermittent small abnormal current.

[0006] Then, the current interrupting means interrupts the flow of current in the wiring system based on the first or second judging means judging the abnormality. Thus, in the case where a large abnormal current flows instantaneously in the wiring system or in the case where an intermittent small abnormal current flows in the wiring system, these currents are timed by the current interrupting means without depending on the fuse. Often shut off.

[0007] As a result, not only the large abnormal current but also the intermittent small abnormal current does not cause a fire to the wiring system and the electric load.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a first embodiment of an abnormal current interrupting device according to the present invention mounted on a vehicle.

[0009] The abnormal current interrupting device includes a current sensor 20.
The current sensor 20 is interposed in a wiring system L connected between the DC power supply 10 mounted on the vehicle and the electric load 40. The current sensor 20 includes a shunt resistor 21 and both voltage dividers 22 and 23. One end of the shunt resistor 21 is connected to the positive terminal of the DC power supply 10 through the wire harness L1 of the wiring system L, and the other end of the shunt resistor 21 is connected to the wiring system L.
, The MOSFET 30 and the wiring harness L3 of the wiring system L are connected to the electric load 40.

The shunt resistor 21 generates a terminal voltage according to the inflow current. This terminal voltage varies according to the current consumed when driving the electric load 40. Each of the voltage dividers 22 and 23 divides a voltage generated at each terminal of the shunt resistor 21 to generate a divided voltage.
The MOSFET 30 is an N-channel MOSFET that functions as a current interrupting element.
T30 is a wire terminal connected to the wire harness L2.
Is connected to the other end of the shunt resistor 21 via a wire harness L3.
And the vehicle is grounded to the vehicle through an electric load 40.

When the MOSFET 30 is turned on, the current from the DC power supply 10 is supplied to the wire harness L.
1. Flow to the electric load 40 through the shunt resistor 21, the wire harness L2, and the wire harness L3. Also, M
The OSFET 30 shuts off the flow of current from the DC power supply 10 to the electric load 40 when turned off. The abnormal current interrupting device includes a differential amplifier 50 connected to both voltage dividers 22 and 23, and a dead short determination circuit D and a rare short determination circuit R connected to the differential amplifier 50.

The differential amplifier 50 differentially amplifies each divided voltage from both voltage dividers 22 and 23 to generate a differential amplified voltage. The dead short determination circuit D includes a comparator 60. The comparator 60 includes a differential amplifier 50
Is received through a resistor 61, and this differential amplified voltage is compared with a threshold voltage TH from a threshold voltage generator 62. Here, this threshold voltage TH is determined by the MOSFET
The voltage is set to the smaller one of the rated current 30 and the rated current of the wiring system L, that is, the voltage corresponding to the instantaneous large abnormal current flowing through the wiring system L.

When the differential amplified voltage is higher than the threshold voltage TH, the comparator 60 generates a comparison output at a high level. This comparison output becomes low level when the differential amplified voltage is lower than the threshold voltage TH. The output terminal of the comparator 60 is connected to a resistor 63
Pulled up by The latch circuit 70 latches the high-level comparison output of the comparator 60 and outputs it from its output terminal Q.

The rare short determination circuit R includes a comparator 80. The comparator 80 receives the differential amplified voltage from the differential amplifier 50 through a resistor 81, and receives the differential amplified voltage from a threshold voltage generator 82. Is compared with the threshold voltage th. Here, when the coating of the wire harness of the wiring system L is partially peeled, the threshold voltage th is intermittent due to a resistive load in the vicinity of the wire harness after the peeling and the vibration of the vehicle in the vicinity thereof. The voltage is set to a voltage corresponding to an intermittent small abnormal current flowing by short-circuiting. The threshold voltage th is not limited to the voltage corresponding to the small abnormal current caused by the intermittent short circuit, but may be any voltage generally corresponding to the small abnormal current in the wire harness.

When the differential amplified voltage is higher than the threshold voltage th, the comparator 80 generates a comparison output at a high level. This comparison output becomes low level when the differential amplified voltage is lower than the threshold voltage th. The output terminal of the comparator 80 is a resistor 83
Pulled up by The n-ary counter 90 counts the number of times the comparison output of the comparator 80 changes to a high level, and generates a count output when the counted value reaches a value representing a predetermined number (for example, four times). The reset circuit 100 repeatedly resets the n-ary counter 90 at predetermined time intervals (for example, 0.2 seconds). The predetermined time interval is the same as the reset interval of the n-ary counter 90 shown in FIG.

The latch circuit 110 latches the count output of the n-ary counter 90 and outputs the latched output from its output terminal Q. Note that the reset circuit 120 includes both latch circuits 70 and 110
Initially reset Also, the abnormal current interrupter is
An OR gate 130 is provided.
Receives one of the latch outputs of both latch circuits 70 and 110 and outputs it to the base of transistor 140.

The transistor 140 is connected to both latch circuits 7
0, 110 and receives one of the latch outputs to turn on the MOSF
Turn off ET30. Transistor 140 turns on MOSFET 30 when turned off. Note that reference numeral 1 in FIG.
Reference numeral 50 denotes a charge pump circuit for the MOSFET 30. Since the MOSFET 30 is an N-channel type, when the MOS-FET is turned on (that is, when the transistor 140 is turned off), the gate voltage needs to be higher than the source voltage. Therefore, in order to generate a voltage twice as high as the voltage of the DC power supply 10, the charge pump circuit 15
0 has been adopted.

Therefore, when a P-channel type MOS-FET is used as the MOSFET 30, the charge pump circuit 150 is unnecessary. In the first embodiment configured as described above, if a complete short circuit (dead short circuit) occurs for some reason in the wiring system L in the on state of the MOSFET 30 under the off state of the transistor 140, a large abnormal current is supplied from the DC power supply 10. Flows through the shunt resistor 21 instantaneously.

Accordingly, the voltage generated at each terminal of the shunt resistor 21 is divided by the voltage dividers 22 and 23 and is differentially amplified by the differential amplifier 50. Then, the differential amplified voltage of the differential amplifier 50 is compared with the threshold voltage TH of the threshold voltage generator 62 by the comparator 60 and is also compared with the threshold voltage th of the threshold voltage generator 82 by the comparator 80.

Here, as described above, the shunt resistor 21
, A large abnormal current flows instantaneously, so that the differential amplified voltage is higher than the threshold voltage TH (see FIG. 2A). Therefore, the comparator 60 generates a comparison output (see FIG. 2B) at a high level, and the latch circuit 70 latches this comparison output and outputs it to the OR gate 130 as a latch output (see FIG. 2C). I do.

This means that the dead short determination circuit D outputs the latch output of the latch circuit 70 to the OR gate 130 based on the determination of dead short.
Accordingly, the transistor 140 is supplied with the latch output of the latch circuit 70 by the OR gate 130 and is turned on to lower the output voltage (see FIG. 2D) to a low level, thereby turning off the MOSFET 30.

As a result, the DC power supply 10
Large abnormal current flowing through the electric load 40 through the MOSFE
It is cut off with good timing by T30. As a result, the wiring system L and the electric load 40 do not cause ignition due to dead short. Note that the differential amplified voltage becomes higher than the threshold voltage th, and the comparator 80 generates a comparison output at a high level. However, since the comparison output of the comparator 80 changes to a high level only once, There is no output of the n-ary counter 90 and the latch circuit 1
There is no output of 10.

Further, when the coating of the wire harness of the wiring system L is partially peeled off, the wire harness is caused by the vibration of the vehicle (for example, the rotational vibration of the engine) at the portion after the peeling, and the vicinity of the wire harness. Intermittent short (rare short) with resistive load. This intermittent short circuit causes an intermittent small abnormal current to flow through the shunt resistor 21 at intervals of several tens (Hz) via the resistive load, even if the intermittent short circuit does not occur.

Therefore, when a differential amplified voltage is generated from the differential amplifier 50 based on the voltage generated at each terminal of the shunt resistor 21 in response to the intermittent small abnormal current, the differential amplified voltage is intermittently set to the threshold value. Exceeding the voltage th, the comparator 8
The comparison output of 0 becomes high level intermittently (see FIG. 3).
(See (a) and (b)). Accordingly, the number of intermittent changes of the comparison output to the high level is counted by the reset circuit 100 by the n-ary counter 90 during the predetermined time interval.

When the n-ary counter 90 generates a count output by counting the predetermined number of times, the count output is latched by the latch circuit 110 and latched (see FIG. 3).
(Refer to (d)) is applied to the base of the transistor 140 through the OR gate 130. This means that the rare short determination circuit R outputs the latch output of the latch circuit 110 to the transistor 140 through the OR gate 130 based on the determination of the rare short.

Therefore, the transistor 140 is turned on and its output voltage (see FIG. 3E) is lowered to a low level, thereby turning off the MOSFET 30. This allows
The intermittent small abnormal current flowing from the DC power supply 10 to the electric load 40 through the wiring system L is cut off by the MOSFET 30 with good timing. As a result, the wiring system L and the electric load 40 do not cause ignition due to rare short circuits.

When the comparison output of the comparator 80 is input to the n-ary counter 90 before and after the end of the predetermined time interval by the reset circuit 100, no count output is generated from the n-ary counter 90. This allows
The MOSFET 30 cannot be turned off due to a rare short. In this case, there is a possibility that a delay of the predetermined time interval may occur at the maximum, but the ignition does not occur in such a time.

Therefore, with regard to the intermittent short circuit of the predetermined number or less based on the input by the step, the MOSFET
The predetermined time interval is set appropriately so that 30 does not need to be turned off. As described above, even if a fuse is not employed unlike the related art, by using the dead short determination circuit D and the rare short determination circuit R, not only the case due to the dead short but also the case due to the rare short can be caused. The occurrence of a cause of ignition of the electric system of the vehicle can also be reliably prevented.

(Second Embodiment) FIGS. 4 and 5 show a second embodiment of the present invention. In the second embodiment,
A microcomputer 160 is connected between the differential amplifier 50 and the OR gate 130 instead of the dead short determination circuit D and the rare short determination circuit R described in the first embodiment.

The microcomputer 160 executes the computer program according to the flowchart shown in FIG. 5, and during this execution, performs substantially the same functions as the dead short judgment circuit D and the rare short judgment circuit R. Calculation processing is performed as follows. Other configurations are the same as those of the first embodiment. In the second embodiment configured as described above, when the microcomputer 160 starts executing the computer program according to the flowchart of FIG.
Is cleared to C = 0.

When a differential amplified voltage is generated from the differential amplifier 50 as in the first embodiment, step 2
At 10, the differential amplified voltage is input to the microcomputer 160 and is converted into a digital signal.
The voltage after this digital conversion is called a differential amplified voltage. Here, if the differential amplified voltage is higher than the threshold voltage TH described in the first embodiment, the determination in step 220 is YES, and in step 221,
It is determined that the dead short has occurred in the wiring system L.

Accordingly, in step 222, a current cutoff process by the MOSFET 30 based on the dead short is performed. Specifically, a first output signal for turning off MOSFET 30 is output to transistor 140 through OR gate 130. Therefore, the transistor 140 turns on and the MOSFET 30 turns off. Thus, as in the first embodiment, a large abnormal current flowing from the DC power supply 10 to the electric load 40 through the wiring system L is cut off by the MOSFET 30 with good timing.
As a result, the wiring system L and the electric load 40 do not cause ignition due to dead short.

If the determination in step 220 is NO
In this case, the differential amplified voltage is compared with the threshold voltage th. Here, if the differential amplified voltage is higher than the threshold voltage th, the determination in step 223 is YES. Then, in step 224, the count data C
Is C = C + 1 under C = 0 in step 200.
In step 24a, a timer built in the microcomputer 160 is reset and started. Thus, the timer starts measuring time.

At this stage, the elapsed time after the first determination of YES in step 223 is a predetermined time t (the first time t).
(Equal to the reset time interval by the reset circuit 100 described in the embodiment), so that the determination in step 230 is NO based on the time measured by the timer. Since the count data C has not reached the predetermined number n (equal to the predetermined number described in the first embodiment), the determination in step 240 is NO.

Thereafter, the determination at step 240 is Y
When the ES becomes ES, it is determined in step 241 that the rare short circuit is present, and in step 242, a current interruption process by the MOSFET 30 based on the rare short circuit is performed.
Specifically, a second output signal for turning off MOSFET 30 is output to transistor 140 through OR gate 130.

For this reason, the transistor 140 turns on and the MOSFET 30 turns off. Thus, as in the first embodiment, the intermittent small abnormal current flowing from the DC power supply 10 through the wiring system L to the electric load 40 is
It is cut off with good timing by T30. As a result, the wiring system L and the electric load 40 do not cause ignition due to rare short circuits.

If the determination in step 230 is YES based on the time counted by the timer before the determination in step 230 is NO, the timer is reset in step 231 and the computer The program returns to step 200. As described above, according to the second embodiment, even if a fuse is not employed as in the related art, the above-described arithmetic processing by the microcomputer 160 may cause a rare short, not to mention a dead short. Therefore, it is possible to reliably prevent the occurrence of a cause of ignition of the electric system of the vehicle due to the above.

In implementing the present invention, a MOS
Instead of the FET 30, a semiconductor switching element or a switching element including an electromagnetic relay may be employed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a timing chart showing output waveforms of main constituent elements in FIG. 1 in the case of a dead short.

FIG. 3 is a timing chart showing output waveforms of main constituent elements of FIG. 1 in the case of a rare short.

FIG. 4 is a main block diagram showing a second embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the microcomputer of FIG.

FIG. 6 is a circuit diagram in which a fuse is connected to a conventional wiring system.

[Explanation of symbols]

10 DC power supply 20 Current sensor 30 MOSFE
T, 40: electrical load, 50: differential amplifier, 60, 80
... Comparator, 62, 82 ... Threshold voltage generator, 70,
110 latch circuit, 90 n-counter, 100 reset circuit, 130 OR gate, D dead short judgment circuit, R rare short judgment circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ikuo Hayashi 14 Iwatani, Shimowakaku-cho, Nishio-shi, Aichi Pref. Japan Automobile Parts Research Institute (72) Inventor Susumu Akiyama 1-1-1 Showa-cho, Kariya-shi, Aichi Stock In Denso (72) Inventor Politics Kawai 1-1-1 Showa-cho, Kariya, Aichi

Claims (2)

[Claims] 1. A detecting means (20) for detecting a current flowing in a wiring system (L) connected between a power supply (10) mounted on a vehicle and an electric load (40) and generating a detection output.
When the detection output is the first abnormal value corresponding to the instantaneous large abnormal current, the first determining means (D, 2
20, 221), and when the detected output is a second abnormal value corresponding to the intermittent small abnormal current, the second determining means (R, 2
23, 224, 240, 241) and a current interrupting means (30) for interrupting the flow of current in the wiring system based on the first or second determining means determining an abnormality. Abnormal current interrupt device. 2. The method according to claim 1, wherein the detection unit outputs the detection output as a detection voltage, and the first determination unit generates a first threshold voltage corresponding to the first abnormal value.
A threshold voltage generating means (62); and a first comparing means (60, 220) for comparing the detected voltage with the first threshold voltage, wherein when the detected voltage exceeds the first threshold voltage, An abnormality is determined based on a comparison output generated from the first comparison unit, and the second determination unit generates a second threshold voltage corresponding to the second abnormal value.
Threshold voltage generating means (82); second comparing means (80, 223) for comparing the detected voltage with the second threshold voltage; and performing the second comparison when the detected voltage exceeds the second threshold voltage. Counting means (90, 224) for counting the number of comparison outputs generated by the means; when the count value of the counting means reaches a value representing a predetermined number of times, it is determined that there is an abnormality; 2. The vehicle wiring system abnormal current interrupt device according to claim 1, wherein the switching device is a switching element that interrupts the flow of current in the wiring system based on the determination by the first or second determining unit that the current is abnormal. 3.