JPH10336886A - Device for breaking overcurrent in wiring system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for breaking overcurrent in the wiring system of a vehicle, which promptly breaks conduction to the wiring system without depending on the integration of the overcurrent when the overcurrent flows to the wiring system for a shot time. SOLUTION: When an overcurrent flows to shunt resistor 20, each terminal voltage of the shunt resistor 20 corresponding to the overcurrent is differentially amplified by a differential amplifier 40 via voltage dividers 21 and 22. The differential amplification voltage of the differential amplifier 40 is higher than a reference voltage from a reference voltage generator 52, thus generating a comparison output at a high level by a comparator 50 and generating a break signal at a high level by a DFF 60. As a result, a transistor 80 receives a break signal from the DFF 60 through an OR gate 70 and is turned on for turning off a MOSFET 30.

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 overcurrent cutoff device that cuts off an overcurrent when the overcurrent flows in a wiring system of a vehicle.

[0002]

2. Description of the Related Art Conventionally, in a vehicle wiring system, for example, as shown in FIG. 9, a vehicle load 1 is connected to a battery via a wire harness 2, a fuse 3, a wire harness 4, a fusible link 5 and a wire harness 6. 7 is connected. Then, for example, when a short circuit fault occurs between a part of the wire harness 2 and the body ground of the vehicle, an overcurrent flows in a short circuit between the wire harness 2 and the body ground. For this reason, the fuse 3 and the fusible link 5 are prevented from being blown, thereby preventing abnormal heat generation in the wire harness 2. Thereby, ignition of the wire harness 2 is prevented.

[0003]

In the above-mentioned wiring system, if the short fault occurs due to repetition in a short time, an overcurrent that blows the fuse 3 or the fusible link 3 does not flow. As a result, there is a risk that the wire harness 2 may ignite due to an abnormal rise in its temperature.

On the other hand, for example, Japanese Patent Application Laid-Open No.
As shown in Japanese Patent No. 1925, an overcurrent flowing per unit time at the time of a short circuit fault of a wire harness is integrated, a driver is alerted, and a current cutoff element connected to the wire harness is turned off by a CPU to connect to the wire harness. There has been proposed a technique for shutting off the energization. However, in the technique of this publication, since the overcurrent is integrated, it takes time to detect the overcurrent and turn off the current cutoff element. Therefore, even if a current equal to or higher than the DC current rating of the current interrupting element repeatedly flows through the wire harness due to a short-circuit fault,
Until the CPU recognizes this, the overcurrent continues to flow through the wire harness and the current cutoff element.

[0005] Therefore, there is a risk that the current interrupting element may be broken while maintaining a current-carrying state, or may be ignited due to heat generated by the current interrupting element itself. In order to avoid this, it is necessary to use a current interrupting element having high current resistance to withstand a short-time repeated overcurrent even for a load requiring only a few amperes. Failure occurs.

[0006] In order to cope with the above problems, the present invention provides a vehicle in which when an overcurrent flows through a wiring system for a short time, the power supply to the wiring system is immediately cut off without depending on the integration of the overcurrent. It is an object to provide an overcurrent interruption device for a wiring system.

[0007]

In order to solve the above-mentioned problems, according to the first to third aspects of the present invention, when the flow judging means judges that the overcurrent flow in the wiring system is short, the current interrupting means is turned on. , To interrupt the current flow of the wiring. As a result, the power supply to the wiring system can be immediately cut off without depending on the integration of the overcurrent. Therefore, the wiring system does not fire. In order to achieve such an effect, it is not necessary for the current interrupting means to include a current interrupting element having high current resistance.

Here, according to the second aspect of the present invention,
The integrating means includes a current detecting element interposed in the wiring system to detect a current. In addition, the current interrupting means includes a current interrupting element interposed in the wiring system to maintain the current flowing through the wiring system when turned on and to shut off when turned off. Then, the control means controls the current cutoff element to be turned off when the detection current of the current detection element is an overcurrent.

Thus, the operation and effect of the invention described in claim 1 can be more reliably achieved. According to the third aspect of the present invention, the notifying unit notifies the abnormal point of the wiring system in different forms from each other based on the determination of the abnormality by the abnormality determining unit and the short time determination by the flow determining unit. I do. As a result, it is possible to know the abnormal location while checking whether or not the overcurrent is integrated.

According to the present invention, the current interrupting element is interposed in a wiring system in which a DC power supply, a power distribution control circuit, and an electric load are connected by wiring. The current flowing through is maintained by turning it on and cut off by turning it off. Further, a current detecting element is interposed in the wiring system to detect the current. Then, the control means controls the current cutoff element to be turned off when the detection current of the current detection element is an overcurrent.

Thus, the power supply to the wiring system can be immediately cut off without depending on the integrating means as described in the first aspect. Therefore, the wiring system does not fire.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals PS1 to PS5 indicate power supply control circuits mounted on the vehicle, respectively. Power supply distribution control circuits PS1 to PS
As shown in FIG. 1, reference numerals 5 are dispersedly arranged on the vehicle body of the vehicle, and these power distribution control circuits PS1 to PS5 are connected by wire harnesses C1 to C4, respectively.

Here, these wire harnesses C1 to C
Numeral 4 is a cable composed of two 12V load power supply lines S1, S2, 5V ECU power supply line S3, and GND line S, as shown in FIG.
The four and two communication lines S5 and S6 are shielded by a shield S7 in the form of an armor made of stainless steel, and the shield S7 is covered with a cover S8. Thereby, each of the cables has a structure that is difficult to fire.

Each of the power distribution control circuits PS1 to P1
As shown in FIG. 1, wire harnesses C5 to C9 are respectively connected between S5 and the respective modules M1 to M5 to be connected thereto, and these wire harnesses C5 to C9 are low-voltage wires for automobiles. (AV line) or a thin low-voltage piezoelectric line (AVS line) for automobiles.

The modules M1 to M5 are respectively
Actuators required for traveling of the vehicle and various functions,
Each of the modules M1 to M5 includes a sensor, an ECU, and an electric load, and these modules M1 to M5 distribute power and communication control of the battery B (see FIG. 3) by the corresponding power distribution control circuits PS1 to PS5. Is to be done. Note that the wire harnesses C5 to C9 are power lines,
It has a GND line and a communication line. Each of the wire harnesses C1 to C9 is connected to the battery B by a power supply line.

Here, the configuration of the wiring system 10 including the battery B, the power distribution control circuit PS1, and the module M1 will be described with reference to FIG. The power distribution control circuit PS1 includes a shunt resistor 20 and a MOSFET 30 as a current cutoff element. One end of the shunt resistor 20 is connected to the power supply line S of the wire harness C1.
1 and S2 are connected to the positive terminal of the battery B. The shunt resistor 20 generates a terminal voltage according to the inflow current. Note that this terminal voltage varies according to the current consumed when driving the module M1.

The MOSFET 30 has its drain terminal connected to the other end of the shunt resistor 20 via a power supply line in the form of an armor. The source terminal of the MOSFET 30 connects the power supply line of the wire harness C5 and the module M1. Through the body earth. And MOSFET3
0, when turned on, causes the current from the battery B to flow to the module M1 through the power line of the wire harness C1, the shunt resistor 20, and the power line of the wire harness C5.
When the MOSFET 30 is turned off, the current from the battery B to the module M1 is cut off.

The power distribution control circuit PS1 includes a differential amplifier 40. The differential amplifier 40 differentially amplifies each divided voltage from the two voltage dividers 21 and 22 to perform differential amplification. Generates voltage. Each of the voltage dividers 21 and 22 divides a voltage generated at each terminal of the shunt resistor 20 and generates a divided voltage. The comparator 50 receives the differential amplified voltage from the differential amplifier 40 through the resistor 51,
This differential amplified voltage is compared with the reference voltage from the reference voltage generator 52. Here, this reference voltage is MOSFET
The voltage is set to a voltage corresponding to 30 DC current rated values.

When the differential amplified voltage is higher than the reference voltage, the comparator 50 generates a comparison output at a high level. This comparison output becomes low level when the differential amplified voltage is lower than the reference voltage. The output terminal of the comparator 50 is pulled up by a resistor 53. The D-type flip-flop 60 (hereinafter, referred to as DFF 60) is reset by a microcomputer 100 described later. And this DFF
60 receives the comparison output of the comparator 50 as a clock at its rise, and generates a high-level cutoff signal from the output terminal Q. A positive voltage Vcc of a DC power supply is applied to a D input terminal of the DFF 60 through a resistor 61.

The OR gate 70 outputs one of a cutoff signal of the DFF 60 and a high level cutoff signal (described later) from the microcomputer 100 to the base of the transistor 80. The transistor 80 is turned on in response to the cutoff signal from the OR gate 70, thereby turning the MOSFET 30 on.
Turn off. The transistor 80 is connected to the OR gate 7
When the cutoff signal from 0 is at a low level, M
OSFET 30 is turned on. In FIG. 3, reference numeral 90 denotes a charge pump circuit.

The A / D converter 101 converts the differential amplified voltage from the differential amplifier 40 into a digital signal,
It is output to the microcomputer 100 as a terminal voltage of 0. The microcomputer 100 executes a computer program according to the flowcharts shown in FIGS. During this execution, the microcomputer 100 issues an operation command to the module M1, a DFF6
0, the output of the shut-off signal to the OR gate 70 based on the output from the AD converter 101, and the output of D
Calculation processing such as display alarm processing of the alarm 110 based on the output of the FF 60 is performed.

In the wiring system including each of the other power distribution control circuits PS2 to PS5, each power distribution control circuit PS2 to PS5 is connected to the power distribution control circuit P2.
It has a configuration substantially similar to S1. The operation of this embodiment configured as described above is performed by the power distribution control circuit PS.
1 will be described as an example.

The microcomputer 100 is assumed to be executing a computer program in accordance with the operation thereof in accordance with the flowcharts of FIGS. It is assumed that the module M1 is in an operating state in response to a command from the microcomputer 100. The MOSFET 30
Is in the ON state. In such a state, when a reset signal is output from the microcomputer 100 in step 200 of FIG. 4, the DFF 60 is reset.

Here, from the battery B to the MOSFET 30
When an overcurrent exceeding the DC current rated value flows for a short time in the ON state, the terminal voltage of the shunt resistor 20 increases for the short time in accordance with the overcurrent. Accordingly, the voltage generated at each terminal of the shunt resistor 20 is divided by the voltage dividers 21 and 22 and differentially amplified by the differential amplifier 40.

Then, the differential amplified voltage of the differential amplifier 40 is digitally converted by the A / D converter 101 and input to the microcomputer 100 as the terminal voltage of the shunt resistor 20 at step 210. Next, in step 220, the output voltage of the AD converter 101 is converted into a current value flowing through the shunt resistor 20. Here, since this current value is of a short time, the determination in step 230 is YES. Then, DFF
Until the interruption signal is generated from 60, the determination in step 240 is maintained as NO.

In this case, since the current value depending on the conversion cycle of the AD converter 101 is measured, the detection of the short-time overcurrent may be delayed, and the overcurrent may be continuously applied during the conversion cycle. . On the other hand, since the differential amplified voltage from the differential amplifier 40 is higher than the reference voltage from the reference voltage generator 52, the comparator 50 generates a comparison output at a high level, and in response, the DFF 60 Generates a cutoff signal.

Along with this, the transistor 80 receives the cutoff signal from the DFF 60 through the OR gate 70 and turns on to turn off the MOSFET 30. Thereby, the MOSFE
The flow of the overcurrent from the battery B to the module M1 via T30 is cut off. As described above, without waiting for the shut-off command from the microcomputer 100, the MOS transistor is immediately generated based on the short-time overcurrent of the shunt resistor 20.
The FET 30 is turned off. Therefore, until the microcomputer 100 outputs the cutoff signal based on the output of the AD converter 50 by the integration of the overcurrent described later, the MOSF
It is possible to prevent a situation in which a short-time overcurrent repeatedly flows through the ET 30.

Therefore, the MOSFET 30 may be destroyed by the heat generated while maintaining a short-time overcurrent conduction state,
The MOSFET 30 itself does not ignite due to heat generation, and the wiring such as the wire harness C5 does not ignite. In order to achieve such an effect, it is not necessary to employ an element having high current resistance as the MOSFET 30.

Further, as described above, when the cutoff signal is output from the DFF 60, the microcomputer 100 determines YES in step 240,
In step 241, a display and an alarm process are performed to indicate that a short-time overcurrent fault has occurred in the power distribution control circuit PS1. Thus, the alarm 110 alerts the user, and the short-time overcurrent failure of the power distribution control circuit PS1 is displayed in black (see FIG. 8).

As a result, a failure in the power distribution control circuit PS1 can be dealt with immediately. In step 230, if the current is not a short-time overcurrent, a determination of NO is made. Therefore, in Step 231, Step 2
The current value at 20 is compared with the previous current value. Here, if the current flowing through the shunt resistor 20 is rising,
The determination in step 250 is YES.

In step 260, it is determined whether or not the current value is equal to or greater than the allowable current value Ir of the conductor of the wire harness. If the current value is equal to or greater than the allowable current value Ir, the determination in step 260 is YES.
If this determination is YES for the first time, YES is determined in step 270 based on the determination that the current value has become equal to or greater than the allowable current value Ir for the first time.

Next, in step 271, the count data D is updated by adding D = D + 1 = 1. Then, in step 272, the heat value of the conductor of the wiring harness in the wiring system 10 is initialized. Note that the count data D has been cleared in step 200 by initial setting. The determination in step 270 is N
If it becomes O, in step 273, the count data D is updated by adding D = D + 1. Then, in step 274, the heat generation amount of the wire harness of the wiring system 10 is integrated. At this stage, the current value is increasing.

Specifically, the integration is performed based on the following equation (1).

[0034]

(Equation 1) However, in the equation (1), Cth represents a calorific value (J / ° C.) of the conductor of the wire harness. I represents a current value (A) flowing through the conductor of the wire harness. T ₁ represents the temperature (° C.) before the short-circuit fault of the wire of the wire harness. T represents the temperature (° C.) after the short-circuit fault of the wire of the wire harness.
a represents the resistance temperature coefficient (1 / ° C.) of the wire of the wire harness. r represents the resistance of the wire of the wire harness. “t” represents the energization time (second) of the wire harness.

Then, in step 280, if the integrated heat generation amount in step 273 does not exceed the allowable current value Ir, a determination of NO is made. The allowable current of the wire harness is determined by the type and diameter of the conductive wire. Thereafter, until the determination in step 280 becomes YES, the accumulation of the heat generation amount in step 274 is repeated based on the addition update of the count data D in step 273. In such a process, as can be easily understood from the rising portion (rightward rising portion) of the graph shown in FIG. 7, the current value I equal to or more than the allowable current value Ir and both count data D
Is repeated based on the time corresponding to the interval of.

When the integrated heat generation exceeds the allowable heat generation of the wire harness, a determination of YES is made in step 280. Then, in step 281, a high-level current cutoff signal is output from the microcomputer 100.
Is output to the transistor 80 through the OR gate 70. At this time, the transistor 80 is turned on and the MOSF
Turn off ET30.

In other words, even when an overcurrent is continuously flowing through the wiring harness of the wiring system 10, when the integrated heat generation exceeds the allowable heat generation, the MOSFET 3
By turning off 0, continuous inflow of overcurrent from the battery B to the module M1 is cut off. Thus, ignition due to abnormal heat generation of the wire harness of the wiring system 10 can be prevented.

When the count data D is cleared in step 282, in step 283, display / alarm processing of the position of the continuous overcurrent occurrence failure of the wiring harness of the wiring system 10 is performed. Thereby, the effect is displayed in black by the alarm 110 and an alarm is issued. As a result, it is possible to accurately repair the continuous overcurrent occurrence failure portion.

If a negative determination is made in step 250, the current value is falling. Therefore, in step 290, it is determined whether or not the current current value is equal to or greater than the allowable current value Ir. If the determination in step 290 is YES, in step 291,
The heating value of the wire harness of the wiring system 10 is integrated substantially in the same manner as in the case of step 274 (see the descending portion of the graph in FIG. 7).

Here, if the accumulated heat generation exceeds the allowable heat generation, a determination of YES is made in step 300, and in step 301, step 28 is executed.
1, as in the case of FIG.
And output to the transistor 80. Therefore, the transistor 80 turns off the MOSFET 30 when turned on.

Thus, as in the case where the current value is rising, the ignition of the wire harness of the wiring system 10 is prevented. In steps 302 and 303, the same processing as in steps 282 and 283 is performed. If the determination in step 290 is NO, it is determined in step 292 whether or not the current value has become less than the allowable current value Ir for the first time. If the determination in step 292 is YES, the processing after step 291 is performed.

On the other hand, if the determination in step 292 is NO
In step 293, the wiring system 10
Of the wire harness are integrated. This can be calculated by using the above equation (1) since the current value is falling (see FIG. 7). If the amount of heat radiation matches the amount of heat generated at this stage, the thermal energy of the wire harness is in a proper equilibrium state. Therefore, step 3
The determination at 10 is YES, and at step 311, the count data D is cleared.

This means that, when the current value decreases, the current is continuously monitored until the heat generation amount and the heat release amount are equal or the heat release amount becomes larger even if the current value becomes smaller than the allowable current value Ir.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view of the wire harnesses C1 to C4 in FIG.

FIG. 3 is a detailed circuit diagram of a power distribution control circuit PS1 of FIG. 1;

FIG. 4 is a part of a flowchart showing an operation of the microcomputer of FIG. 3;

FIG. 5 is a part of a flowchart showing an operation of the microcomputer of FIG. 3;

FIG. 6 is a part of a flowchart showing an operation of the microcomputer of FIG. 3;

FIG. 7 is a diagram showing an example of integrating heat generation values based on a graph showing a relationship between count data D and a current value I.

FIG. 8 is a block diagram of the alarm device of FIG. 3;

FIG. 9 is a diagram showing a conventional wiring system.

[Explanation of symbols]

C1 to C9: wire harness, M1 to M5: module, PS1 to PS5: power distribution control circuit, 10:
Wiring system, 20: shunt resistor, 30: MOSFET,
Reference numeral 40: differential amplifier, 52: reference voltage generator, 50: comparator, 60: DFF, 70: OR gate, 80: transistor, 100: microcomputer, 110:
Alarm.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Susumu Akiyama 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. Inside

Claims (4)

[Claims] 1. A wiring system (B1) mounted on a vehicle and connecting a DC power supply (B), a power distribution control circuit (PS1 to PS5) and an electric load (M1 to M5) by wirings (C1 to C9). 10) When an overcurrent flows from the DC power supply in the wiring system due to occurrence of an abnormal point,
Integrating means (20, 2, 2) for integrating the amount of heat based on this overcurrent
74, 291, 293) and abnormality determining means (280, 300, 3) for determining the presence or absence of an abnormality in the wiring system based on the integrated heat amount by the integrating means.
10), and current interrupting means (281, 301, 3) for interrupting the flow of current in the wiring in accordance with the determination of the abnormality by the abnormality determining means.
0, 50 to 80), comprising a flow determining means (230) for determining whether or not the overcurrent flow is for a short time, wherein the current interrupting means comprises: An overcurrent cutoff device for a vehicle wiring system configured to cut off a current flow in the wiring even when a short time is determined by a flow determination unit. 2. The system according to claim 1, wherein said integrating means includes a current detecting element (20) interposed in said wiring system to detect said current, and said current interrupting means is interposed in said wiring system and flows through said wiring system. A current interrupting element (30) for maintaining the current when turned on and interrupting the current when turned off, and control means (50 to 8) for controlling the current interrupting element to be turned off when the current detected by the current detecting element is an overcurrent.
0), the vehicle wiring system overcurrent cut-off device according to claim 1, comprising: 3. An informing means (110, 241, 283, 303) for informing each of the abnormal locations in a different form from each other based on the abnormality determination by the abnormality determining means and the short time determination by the flow determining means. The vehicle wiring system overcurrent interruption device according to claim 1 or 2, further comprising: 4. A wiring system provided in a vehicle and connecting a DC power supply (B), a power distribution control circuit (PS1 to PS5) and an electric load (M1 to M5) by wirings (C1 to C9). A current interrupting element (30) interposed in the wiring system 109 for maintaining the current flowing through the wiring system on and interrupting the current when it is off, and a current detecting element (20) interposed in the wiring system for detecting the current Control means (50 to 8) for controlling the current cutoff element to be turned off when the current detected by the current detection element is an overcurrent.
0) A vehicle wiring system overcurrent cutoff device comprising: