JP2001037068A - Leakage detection method and device in vehicle power supply circuit and leakage prevention method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a leak caused by intermittent grounding, etc., in the feeder circuit of a vehicle, and more preferably, quickly obstruct the leak. SOLUTION: A current in a feeder circuit from an automotive power supply 10 to a load 12 is detected at two positions of the feeder circuit by current sensors 21 and 22. A difference ΔI between the two detected current values is monitored. If the difference ΔI exceeds a certain value, it is decided that a leak exists. Furthermore, a breaker 18 is tripped by the leak detection signal to forcibly cut off the power feeding from the automotive power supply 10 to the load 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for accurately detecting and, more quickly, preventing a leakage in a power supply circuit mounted on a vehicle due to a short circuit between an electric wire or the like constituting the circuit and ground. And an apparatus.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional power supply circuit for a vehicle which has been conventionally known.

A power supply (battery) 10 is mounted on a vehicle, and its negative terminal is connected to the ground, while its positive terminal is connected to a load (such as on-vehicle electrical components) 12 via an electric wire 14 or the like. . A fuse 16 is provided at a position near the positive terminal of the power supply 10, and a short-circuit portion of the electric wire 14 is short-circuited to the ground (two-dot chain line L1 in the figure).
Is excessive, the fuse 16 is blown and the power supply from the power supply 10 to the load 12 is urgently cut off.

Japanese Patent Application Laid-Open No. H11-18279 discloses a power supply circuit in which an overcurrent is detected by a current sensor. The outline is shown in FIG.

In FIG. 1, a positive terminal of a power supply 10 and a load 1
2 is connected via an electric wire 14, the negative terminal of the power supply 10 and the other terminal of the load 12 are connected via an earth electric wire 15, and the negative terminal of the power supply 10 is connected to the ground. Between them, a normally closed switch 18 and a current sensor 20 are provided. If the detected current I of the current sensor 20 becomes excessive due to a short circuit in the middle of the electric wire 14 to the ground (two-dot chain line L1 in the figure), the sensor 2
When a command signal is output from 0 to the switch 18, the contact of the switch 18 is forcibly opened, the ground wire 15 is disconnected from the ground, and the overcurrent is prevented from continuing to flow.

[0006]

As a mode in which the circuit shown in FIG. 4 leaks, for example, when the conductor of the electric wire 14 is exposed and keeps in contact with the ground (so-called complete short circuit), vibrations during running of the vehicle, etc. There is a case where the conductor part intermittently and periodically contacts the ground (so-called chattering).

[0007] Of the above, in the former complete short circuit, a very large current is generated because the short circuit state continues, and the fuse 16 is blown by the overcurrent. Therefore, the amount of increase in the current I is very small (at most several amperes), and the current does not exceed the capacity of the fuse 16. Therefore, even if the chattering occurs, the fuse 16 is not blown and the electric leakage is left.

[0008] In recent years, studies have been made on electrification of vehicle-mounted actuators such as a steering device and a brake device, and in order to cope with such electrification,
Instead of or in addition to the conventional low-voltage power supply (generally 12V), a high-voltage power supply with a higher battery voltage (for example, 36V power supply) is mounted on the vehicle, and a low-voltage power supply circuit and a high-voltage power supply circuit are provided side by side. The concept is underway. When such a high-voltage power supply is used as the on-vehicle power supply 10 shown in FIG. 4, when chattering as described above occurs,
Even if the current rise value due to the chattering is slight, each time a short circuit occurs, there is a possibility that an arc is generated at the short-circuit location.

[0009] Since such an arc is an obstacle in securing high safety, it is required to prevent its continuous occurrence. However, as described above, the current rise value during chattering is small, and
4 does not melt, and the circuit shown in FIG. 4 cannot effectively detect chattering and prevent arcing caused by the chattering.

[0010] Further, a circuit shut-off system shown in FIG.
The purpose of the present invention is to prevent overcurrent, and the current sensor 20
Since the current threshold value for opening the switch 18 (that is, forcibly interrupting the circuit) by the output signal is set to a considerably high value, the circuit interruption does not work when the current rises only slightly as in chattering.

Moreover, the shut-off system shown in FIG. 5 can be applied to a circuit in which the negative terminal of the power supply 10 and the load 12 are connected by the ground wire 15, but does not have the ground wire 15 as shown in FIG. Not applicable to circuits.

The present invention has been made in view of the above circumstances, and provides a method and apparatus capable of accurately detecting an electric leakage including so-called chattering in a power supply circuit of a vehicle, and more preferably, quickly preventing the electric leakage. With the goal.

[0013]

According to the present invention, there is provided a power supply circuit for a vehicle in which a vehicle-mounted power supply and a load are electrically connected. Detect the current flowing in each of the two positions,
This is a leakage detection method for determining that leakage has occurred when the difference between the detected currents is equal to or greater than a certain value.

In this method, if chattering occurs where the conductor part intermittently comes into contact with the ground due to, for example, the conductor of the electric wire being exposed in the region between the two current detection points, the circuit is disconnected when the short circuit occurs. There is a difference between the detected currents at the two current detection points by the amount of the current leaking to the ground side. Therefore, when the current difference is equal to or more than a certain value, it can be determined that an electric leakage due to chattering or the like has occurred in a region between the two current detection points.

In this case, by forcibly interrupting the power supply, the electric leakage can be quickly stopped, and the occurrence of an arc due to the chattering or the like can be prevented. It is also effective to perform a warning operation in a vehicle interior or the like based on the leakage detection signal.

In addition, in the state where no electric leakage occurs, even if the level of the current flowing from the power supply to the load slightly fluctuates, the difference between the detected currents at the two current detection points does not change, so that erroneous detection is made due to the current fluctuation. There is no fear.

However, if the distance between the two current detection points is large, for example, the timing at which the current values rise at the two current detection points at the start of power supply is slightly shifted, so that a remarkable difference occurs instantaneously between the two detection currents. obtain. If this difference is sensed, the circuit may be erroneously detected as a leakage even though the circuit is normal. As a countermeasure, instead of simply monitoring the difference between the two detected currents, if it is determined that leakage occurs only when the state in which the detected current becomes a certain level or more occurs at a certain frequency or lower, it is possible to start power supply at Erroneous detection can be prevented more reliably.

According to the present invention, there is provided an apparatus for implementing the method for detecting an electric leakage, wherein first and second current detecting means for detecting current flowing at each of two positions between the on-board power supply and the load. And determining means for comparing the current values detected by these current detecting means and outputting a leakage detection signal when the difference is equal to or more than a predetermined value.

Further, in addition to this device, a circuit breaker provided in the power supply circuit and forcibly shutting off the power supply circuit in response to the leakage detection signal is provided, so that a circuit leakage can be quickly prevented. Will be possible. The circuit breaker is widely applicable as long as it performs a breaking operation by inputting a command signal, and may be a relay or other switch, or a device that forcibly breaks a conductor using explosive force of explosive.

Further, the determination means includes a filter for removing a high frequency component of a signal corresponding to a difference between current values detected by the first current detection means and the second current detection means. If a circuit configured to output a leakage detection signal to the circuit breaker when the signal from which the high-frequency component is removed is equal to or more than a predetermined value is used, detection is performed only temporarily and instantaneously, for example, at the start of power supply. It is possible to more reliably prevent erroneous detection of occurrence of electric leakage until a current difference occurs.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

The power supply circuit shown in FIG. 1 includes a vehicle-mounted power supply (battery) 10 having a negative terminal connected to the ground and a positive terminal connected to a load (vehicle) via an electric connection box, electric wires 14 and the like (not shown). 12), and the other terminal of the load 12 is connected to the ground. And
The power supply circuit is provided with a leakage detection device and a leakage prevention device according to the present invention.

Specifically, a circuit breaker 18 and a first current sensor (first current detecting means) 21 are provided between a positive terminal of the power supply 10 and a power supply side terminal of the electric wire 14.
A second current sensor (second current detecting means) 22 is provided between the load side terminal of the electric wire 14 and the load 12, and a control circuit including a comparator 24 and an amplifier 28 is provided.

Each of the current sensors 21 and 22 outputs a detection signal corresponding to the level of a current flowing through the location where the current sensor is provided. For example, a sensor that measures a voltage drop due to a constant resistance can be applied.

The comparator 24 generates a signal corresponding to the difference ΔI between the current levels detected by the two current sensors 21 and 22. The amplifier 28 amplifies the signal, and inputs a leakage detection signal to the circuit breaker 18 when the signal level after the amplification is equal to or higher than a certain level.

The circuit breaker 18 maintains the power supply circuit from the power supply 10 to the load 12 in the connected state in the normal state, and when the leakage detection signal is input from the amplifier 28,
In response to this, an operation of interrupting the circuit is performed.

As the circuit breaker 18, besides a remote control switch such as a relay (a switch for opening and closing a setting in response to an external signal), for example, JP-A-10-55742
As disclosed in Japanese Unexamined Patent Application Publication No. 2000-209, a method in which a conductor for circuit configuration is forcibly broken using the explosive force of an explosive is applicable.
In any case, the configuration may be such that a cutoff operation (an operation of opening a relay contact or an operation of igniting explosive) is performed when a specific leakage detection signal is input.

Next, the operation of this circuit will be described.

First, in a normal state where a short circuit does not occur in the circuit, all of the current output from the power supply 10 via the current sensor 21 flows into the load 12 through the current sensor 22, so that both the current sensors 21 and 22 detect the current. Current level I
1, I2 are equal, and their difference ΔI is zero. Therefore, the leakage detection signal is not output from the comparator 24 and the amplifier 28 to the circuit breaker 18, and the power supply state is maintained.

On the other hand, for example, the covering of the middle part of the electric wire 14 is broken and the conductor part is partially exposed, and the conductor part intermittently comes into contact with the ground part of the vehicle due to vibrations during running of the vehicle. When chattering occurs (two-dot chain line L1 in FIG. 1), the detected current value I1 of the first current sensor 21 and the detected current of the second current sensor due to the current Id leaking from the electric wire 14 to the ground side each time the intermittent short circuit occurs. A difference ΔI occurs between the value and the value I2, and a signal having a level corresponding to the difference ΔI is output from the comparator 24. This signal is amplified by an amplifier 28, and if its level is above a preset threshold,
A leakage detection signal is input from the amplifier 28 to the circuit breaker 18. The circuit breaker 18 receiving this performs a breaking operation (such as an operation of opening a relay contact or an operation of igniting an explosive and exploding a conductor) to forcibly cut off the power supply from the power supply 10 to the load 12.

Therefore, by setting the threshold value as a value corresponding to, for example, the minimum value of the current difference ΔI that can be caused by the chattering, the power supply can be automatically cut off when a leakage occurs due to the chattering. ,
It is possible to quickly prevent the occurrence of an arc due to the chattering.

In addition, even if the absolute value of the detected current fluctuates slightly in the normal state where the short circuit does not occur, there is no relative difference ΔI between the detected currents. Unlike a system that measures only the absolute value of, it is possible to avoid erroneous detection and erroneous operation (supply interruption) due to a slight change in the current value. That is, in the method and the apparatus according to the present invention, by monitoring not the absolute value of the current but the difference between the detected currents at two points sandwiching the area where leakage detection and leakage prevention are required, proper leakage detection and It has realized leakage prevention.

However, in the circuit of FIG. 1, if the length of the electric wire 14, that is, the distance between the two current sensors 21 and 22, is large, when the power supply is switched from off to on by a switch operation or the like, as shown in FIG. The rising timing of the current value I1 detected by the first current sensor 21;
A slight time difference (for example, several μs) occurs between the rising timing of the current value I2 detected by the current sensor 22 and the difference ΔI between the two current values rises instantaneously and temporarily only during that time. Since the occurrence of the current difference ΔI is not abnormal, it is necessary to exclude this from the leakage determination condition.

In order to solve this problem, in the circuit shown in FIG. 2, a filter 26 is provided between the comparator 24 and the amplifier 28 shown in FIG. This filter 26
Removes the high-frequency component of the output signal of the comparator 24, that is, the signal corresponding to the current difference ΔI, and passes only the frequency component equal to or lower than a certain frequency to the amplifier 28.

As shown in FIG. 3, the threshold value of the frequency is, as shown in FIG.
A pulse of a minute width (left side in the figure) generated due to the time difference of the rise of the current is removed, and a fluctuation of the current difference I caused by chattering (generally, a cycle having a period of several ms or more like a waveform shown on the right side in the figure). (Variation) may be set in a range that does not remove the fluctuation.

According to this configuration, the signal f output from the filter 26 has the pulse waveform at the time of the rise of the current already removed, and only the frequency components below a certain level remain. Appropriate leakage judgment and power supply cutoff control can be performed. That is, it is possible to accurately detect chattering and swiftly prevent leakage and arc generation due to the chattering without erroneously performing a power supply cutoff operation when the current rises.

Further, in addition to such chattering, even when a complete short circuit occurs in which the conductor portion of the electric wire 14 is in contact with the ground portion, the fluctuation frequency of the current difference ΔI is equal to or less than a certain value (= 0), a leakage detection signal is output in the same manner as in chattering, whereby power supply is cut off, and the electric wire 14 is protected from overcurrent.

As shown in this embodiment, instead of adding the filter 26, a timer or the like is provided to monitor the current difference ΔI from a point in time when a certain time has elapsed from the start of power supply to the load 12. However, it is possible to prevent the power supply circuit from being erroneously shut off due to the current difference ΔI caused by the time difference between the current rises. Further, instead of using the electric circuit as shown in the figure, a microcomputer may be used as the determination means.

In addition, the present invention can take the following embodiments, for example.

(1) In the apparatus shown in FIGS. 1 and 2, the signal amplified by the amplifier
May be output. In this case, the circuit breaker 18 may be operated only when the input signal is at a certain level or higher. That is, in this case,
Of the signals input to the circuit breaker 18, only a signal having a level equal to or higher than a certain level is a leakage detection signal.

(2) The location of the current detecting means such as the current sensors 21 and 22 can be appropriately set. Specifically, in the path from the power supply to the load, an area where an arc may occur due to chattering or the like (for example, an area where electric wires are routed) is set as a protection area,
At least two positions sandwiching the protection area may be set as the arrangement portions of the current detection means. For example, the first current sensor 21 on the vehicle power supply side may be incorporated in an electric junction box in the engine room, and the second current sensor 22 on the load side may be
This may be integrated with the load.

(3) The present invention can be applied to a power supply 10 and a load 12 connected by a ground wire 15 as shown in FIG. Also in this case, the power supply side path (the path from the positive terminal of the power supply 10 to the load 12 in FIG. 5).
The current detection locations may be set at two appropriate locations.

(4) In the above-described embodiment, the power supply is cut off by operating the circuit breaker 18 using the leakage detection signal. Even if a warning operation is performed, it can be a means for effectively preventing the leakage of the electric current from being left.

[0044]

As described above, according to the present invention, the current is detected at two positions in the power supply circuit of the vehicle, and if the difference between the detected current values is large, the leakage is determined (more preferably, the power supply is cut off). Therefore, the occurrence of electric leakage including chattering can be accurately detected without fail, and further, the detection result is used to quickly prevent the occurrence of the electric leakage and an arc resulting therefrom. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power supply circuit of a vehicle and an electric leakage detection device thereof according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a circuit obtained by adding a filter to the circuit shown in FIG. 1;

FIG. 3 is a time chart showing signals generated by the circuit shown in FIG. 2;

FIG. 4 is a diagram showing a power supply circuit of a conventional vehicle.

FIG. 5 is a diagram showing a power supply circuit of a conventional vehicle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 On-board power supply 12 Load 14 Electric wire 18 Circuit breaker 21 First current sensor 22 Second current sensor 24 Comparator 26 Filter 28 Amplifier ΔI Current difference

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Chen No. 1-7-10 Kikuzumi, Minami-ku, Nagoya-shi, Aichi F-term in Harness Research Institute, Inc. (reference) 2G014 AA03 AA16 AA27 AB24 AB35 AB61 5G004 AA04 AB02 BA01 DA02 DB03 DC04 EA04 FA01

Claims (6)

[Claims] In a power supply circuit of a vehicle in which a vehicle-mounted power supply and a load are electrically connected, currents flowing in two positions between the vehicle-mounted power supply and the load are detected, and a difference between the detected currents is constant. A method of detecting a leakage in a power supply circuit of a vehicle, wherein it is determined that a leakage has occurred at the time described above. 2. The method for detecting an electric leakage in a power supply circuit of a vehicle according to claim 1, wherein it is determined that an electric leakage has occurred only when the state in which the difference between the detected currents is equal to or more than a certain value occurs at a frequency equal to or less than a certain value. A method for detecting an electric leakage in a power supply circuit of a vehicle. 3. A power supply circuit for a vehicle, wherein the power supply from the on-vehicle power supply to the load is forcibly cut off when it is determined that a leakage has occurred by the method for detecting a leakage in the power supply circuit of the vehicle according to claim 1. Ground fault prevention method. 4. In a power supply circuit of a vehicle in which a vehicle-mounted power supply and a load are electrically connected, first current detection means for detecting a current flowing at each of two positions between the vehicle-mounted power supply and the load, and A second current detecting means, and a determining means for comparing current values detected by these current detecting means and outputting a leakage detection signal when the difference is equal to or greater than a predetermined value. Leakage detection device in power supply circuit. 5. The leakage detection device for a power supply circuit of a vehicle according to claim 4, wherein the determination unit corresponds to a difference between current values detected by the first current detection unit and the second current detection unit. A filter for removing a high-frequency component of a signal to be output, and outputting a leakage detection signal when the signal from which the high-frequency component has been removed by the filter becomes a certain level or more. Leakage detection device in circuit. 6. An electric leakage detection device in a power supply circuit of a vehicle according to claim 4, wherein the device is provided in the power supply circuit.
A circuit breaker for receiving a leakage detection signal output from the leakage detection device and forcibly shutting off the power supply circuit.