JP2000304800A - Device and method for detecting breaking of wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for detecting the breaking of wires to detect the breaking of wires in lamps, etc., accurately by a simple method. SOLUTION: The device for detecting the breaking of wires is provided with a right lamp 17 and a left lamp 18 supplied with current from a battery 11, a right current detecting part 19a and a left current detecting part 19b provided correspondingly to the right lamp 17 and the left lamp 18 to detect current flowing through each lamp, and a microcomputer 23 to compare a pair of current values with each other detected at the pair of current detecting parts and to determine the presence or absence of the breaking of a wire in each lamp on the basis of the result of the comparison. In other words, as a reference value fluctuates similarly according to fluctuations of temperature and a power source voltage, the effects of errors due to fluctuations of temperature and a power source voltage do not occur in theory at the time of detecting the breaking of a wire by comparing the right and left current values with each other. Therefore, it is possible to detect the breaking of wires in a lamp accurately by a simpler method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disconnection detecting device and a disconnection detecting method for detecting disconnection of lamps (hereinafter referred to as "lamps"), which are paired loads of an automobile, a vehicle, and the like. The present invention relates to a disconnection detection device and a disconnection detection method capable of improving the detection accuracy of disconnection of a lamp by a simple method.

[0002]

2. Description of the Related Art A conventional disconnection detecting device for detecting disconnection of a pair of lamps of an automobile, a vehicle, or the like performs disconnection detection of the lamp in accordance with, for example, a process shown in a flowchart of FIG.

First, the value of the current flowing from the power supply to the lamp is detected by some method (step S101), and it is determined whether the detected current value is larger than a predetermined threshold value (step S103).

If the detected current value is larger than the threshold value, it is determined that the lamp is not disconnected (step S105), and if the detected current value is smaller than the threshold value, , It is determined that the lamp is disconnected, and a process for detecting disconnection is performed (step S10).
7).

As a method of current detection generally performed, for example, there are a current sensor using a magnetic field, an ammeter, and a method using a voltage drop of a shunt resistor. For example, when detecting disconnection of a lamp of an automobile or the like, current detection using a shunt resistor is generally used from the viewpoint of cost, installation environment, and the like.

However, this current detection method has the following error factors and problems.

(1) Errors due to variations in the elements of the measurement system including the shunt resistance. (2) Variations in the amplifier circuit (amplifier) that amplifies the voltage drop across the shunt resistor.
(3) Variation of the lamp itself and variation due to aging. (4) Temperature variations due to changes in the temperature environment during measurement. (5) Variation due to fluctuations in battery voltage on the vehicle.
(6) Since a shunt resistor is inserted in series with the load and the voltage drop across the shunt resistor is measured, a large shunt resistor cannot be used.

For this reason, various corrections for errors are made to eliminate the effects of these errors, and the following methods are used for this correction.

(A) Adjustment by an external element. (B) Numerical correction in a processing system, which is performed at the time of calculation by a computer.

[0010] As an apparatus that has performed such error correction,
For example, a disconnection detecting device described in Japanese Patent Application Laid-Open No. 1-174216 is known. This disconnection detecting device 131
As shown in FIG. 4, disconnection of the lamps 132a and 132b is detected, and a driver or the like is warned to prevent an accident due to disconnection of the lamp 132.

This disconnection detecting device includes a lamp 132, a resistor R2, and a specific level generator 1 for generating a specific voltage level.
33, voltage level of terminal T6 and specific level generator 133
134, which compares the voltage level of
135 that performs switching control by the output of the capacitor 135, a capacitor 136 connected to the relay 135, and a terminal 135b
And a comparator 137 for comparing the voltage level with the reference level V _REF and outputting a disconnection detection signal to an alarm device (not shown).

According to the disconnection detecting device having such a configuration,
For example, when the lamp 132a is disconnected, a current flows through the resistor R2, and the voltage drop at the resistor R2 decreases. For this reason, the voltage level of the terminal T6 increases and exceeds the specific level generated by the specific level generator 133.
At this time, the signal A2 output from the comparator 134 becomes L level.

In the relay 135, when the signal A2 is at the L level, the terminals 135a and 135b are in a conductive state, and the electric current generated by the constant current source 138 causes electric charges to be accumulated in the capacitor 136.

When the capacitor 136 is charged, the terminal 1
The voltage level of 35 increases. The comparator 137 outputs a disconnection detection signal B2 which becomes L level when the voltage level exceeds the reference level. The alarm device warns the disconnection of the lamp 132 when the disconnection detection signal B2 is at the L level.

The specific level generator 133 corrects the voltage level according to the input voltage level to the lamp 132 and outputs the corrected voltage level to the comparator 134 because the relationship between the input voltage level of the lamp 132 and the current value is not linear. Error correction can be performed.

[0016]

However, in the disconnection detecting device described in Japanese Patent Application Laid-Open No. 1-174216, error correction is performed at the time of manufacturing and assembling the device. Correction.

That is, in the case of static correction, there are many limitations when dealing with dynamic fluctuations such as temperature changes and power supply voltage changes. For this reason, take a large margin for correction,
Or, at present, more accurate adjustment is required. This causes a malfunction or a cost increase.

Accordingly, the present invention provides a disconnection detecting device and a disconnection detecting device which can detect disconnection of a lamp or the like with a simpler method and with high accuracy without requiring special adjustment to cope with a dynamic change. It is an object to provide a detection method.

[0019]

Means for Solving the Problems To solve the above problems, the present invention has the following arrangement. The disconnection detecting device according to the first aspect of the present invention includes a pair of loads supplied with current from a power supply,
A pair of current detectors provided corresponding to the pair of loads, for detecting current flowing through each load, a comparator for comparing a pair of current values detected by the pair of current detectors, And a disconnection determination unit that determines the presence or absence of disconnection of each load based on the comparison result.

According to the first aspect of the present invention, when a current flows from a power supply to a pair of loads, a pair of current detectors provided corresponding to the pair of loads detect a current flowing through each load.
The comparing section compares a pair of current values detected by the pair of current detecting sections, and the disconnection determining section determines presence / absence of disconnection of each load based on a comparison result of the comparing section.

That is, the reference value fluctuates in the same manner in accordance with fluctuations in temperature, power supply voltage, and the like. Therefore, when a pair of current values are compared with each other, an error due to fluctuations in temperature, power supply voltage, or the like upon disconnection detection is detected. The effect does not occur in principle.
Therefore, disconnection of a load such as a lamp can be accurately detected by a simpler method.

The comparing section of the invention of claim 2 calculates a difference between the pair of current values detected by the pair of current detecting sections, and the disconnection determining section calculates the difference obtained by the comparing section. It is characterized in that the presence / absence of disconnection of each load is determined by comparing with a predetermined threshold value.

According to the second aspect of the present invention, the comparing section calculates a difference between the pair of current values detected by the pair of current detecting sections, and the disconnection determining section determines the difference obtained by the comparing section in advance. Since the presence or absence of disconnection of each load is determined by comparing with the obtained threshold value, disconnection of the load can be easily detected.

According to a third aspect of the present invention, the disconnection determination unit determines that there is a disconnection when the difference obtained by the comparison unit is equal to or greater than the threshold, and the difference is less than the threshold. In this case, it is determined that there is no disconnection.

According to the third aspect of the present invention, the disconnection determining section
If the difference obtained by the comparison unit is equal to or greater than the threshold value, it is determined that there is a disconnection, and if the difference is less than the threshold value, it is determined that there is no disconnection, so that disconnection of the load can be easily detected. .

A method for detecting a disconnection according to a fourth aspect of the present invention includes a current detection step of detecting a current flowing through each load by a pair of current detection units provided corresponding to a pair of loads to which a current is supplied from a power supply. A comparison step of comparing a pair of current values detected by the pair of current detection units, and a disconnection determination step of determining whether or not each of the loads is disconnected based on a comparison result of the pair of current values, I do.

According to the fourth aspect of the present invention, a current flowing through each load is detected by a pair of current detectors provided corresponding to a pair of loads to which current is supplied from a power supply. The pair of detected current values are compared, and the presence or absence of disconnection of each load is determined based on the comparison result of the pair of current values.

That is, since the reference value fluctuates in the same manner in accordance with fluctuations in temperature, power supply voltage, and the like, if a pair of current values are compared with each other, an error due to fluctuations in temperature, power supply voltage, or the like at the time of disconnection detection is detected. The effect does not occur in principle.
Therefore, disconnection of a load such as a lamp can be accurately detected by a simpler method.

The comparing step of the invention according to claim 5 calculates the difference between the pair of current values detected by the pair of current detectors, and the disconnection determining step calculates the difference obtained in the comparing step. It is characterized in that the presence / absence of disconnection of each load is determined by comparing with a predetermined threshold value.

According to the fifth aspect of the present invention, the difference between the pair of current values detected by the pair of current detectors is calculated, and the obtained difference is compared with a predetermined threshold value.
Since the presence or absence of disconnection of each load is determined, disconnection of the load can be easily detected.

In the disconnection determining step of the invention according to claim 6, when the difference obtained in the comparing step is equal to or larger than the threshold value, it is determined that there is a disconnection, and the difference is smaller than the threshold value. In this case, it is determined that there is no disconnection.

According to the invention of claim 6, when the obtained difference is equal to or more than the threshold value, it is determined that there is a disconnection, and when the difference is less than the threshold value, it is determined that there is no disconnection. Disconnection of the load can be detected.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a disconnection detecting apparatus and a disconnection detecting method according to the present invention will be described below in detail with reference to the drawings. An example in which the disconnection detecting device and the disconnection detecting method are applied to a device for supplying power from a battery to a load such as a lamp in an automobile will be described. Note that the disconnection detection device and the disconnection detection method according to the embodiment can of course be applied to a device other than an automobile.

FIG. 1 is a circuit diagram of a disconnection detecting device according to an embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the disconnection detecting device according to the embodiment.

The disconnection detecting device shown in FIG. 1 uses a pair of left and right lamps and compares the current values flowing through the pair of lamps, so that special adjustment is required to cope with a dynamic change. And detecting the disconnection of the lamp with high accuracy by a simpler method.

In this disconnection detecting device, the output voltage of the battery 11 as a power supply is controlled by the shunt resistor 13a and the first
And the output voltage of the battery 11 is supplied to the shunt resistor 13b,
The second relay 15 b is supplied to the left lamp 18.

Each of the right ramp 17 and the left ramp 18 is
For example, there are a tail lamp, a head lamp, and the like, and the right lamp 17 includes lamps 17a, 17b, and 17c,
Is turned on when the relay 15a is turned on, and the left lamp 18 is composed of lamps 18a, 18b and 18c.
Is turned on when the relay 15b is turned on.

The current detector 21 detects the current flowing through the right lamp 17 and the left lamp 18, and includes shunt resistors 13a and 13b, a right current detector 19a, and a left current detector 19b. .

The right current detector 19a is connected to both ends of a shunt resistor 13a inserted in series with the right lamp 17, and detects a current flowing through the right lamp 17 by detecting a voltage drop of the shunt resistor 13a. I do.

The left current detector 19b is connected to both ends of a shunt resistor 13b inserted in series with the left lamp 18, and detects a current flowing through the left lamp 18 by detecting a voltage drop of the shunt resistor 13b. I do.

The right current detector 19a has an amplifier 20a for amplifying the detected current and outputting the amplified current to the microcomputer 23. The left current detector 19b amplifies the detected current and outputs the amplified current to the microcomputer 23. , And an amplifier 20b that outputs the signal.

The control unit 27 performs disconnection detection of the right lamp 17 and the left lamp 18 and on / off control of the right lamp 17 and the left lamp 18.
It comprises a first relay 15a and a second relay 15b.

The microcomputer 23 outputs a control signal such as a current detection request to the right current detector 19a and the left current detector 19b. The microcomputer 23 inputs left and right current values from the right current detection unit 19a and the left current detection unit 19b, and converts the left and right current values into A.
/ D25 converts the current value into left and right digital current values.

The microcomputer 23 compares the left and right digital current values to calculate a difference between the left and right digital current values, determines whether the difference is greater than a predetermined threshold value, and determines whether the difference is greater than the threshold value. Is larger than the threshold, it is determined that the lamp is disconnected.
It is determined that there is no lamp disconnection. Microcomputer 23
Constitute a comparison unit and a disconnection determination unit.

The microcomputer 23 has a first
By outputting a switching signal to the first and second relays 15a and 15b to control on / off of the first and second relays 15a and 15b, on / off control of the lamps 17 and 18 is performed. ing.

The power supply voltage correction circuit 29 measures the battery voltage of the battery 11 and generates a correction signal of the power supply voltage necessary for detecting disconnection of the right lamp 17 and the left lamp 18 based on the measured battery voltage. Then, the correction signal is output to the microcomputer 23.

Next, the operation of the disconnection detecting device thus constructed according to the embodiment will be described with reference to the flowchart shown in FIG. First, the shunt resistor 1
3a, a current flows to the right lamp 17 via the first relay 15a, and a shunt resistor 13b from the battery 11
A current flows through the right lamp 18 via the second relay 15b.

The right current detector 19a detects the value of the current flowing through the right lamp 17, and the detected current is amplified by the amplifier 20a and output to the microcomputer 23 as the current value. Further, the left current detector 19b detects a current flowing through the left lamp 18, and the detected current is amplified by the amplifier 20b and output to the microcomputer 23 as a current value (step S11).

Further, A in the microcomputer 23
/ D25 is the right current detector 19a and the left current detector 19a.
The left and right current values are input from b, and the left and right current values are converted into left and right digital current values.

Then, the microcomputer 23 compares the left and right digital current values and calculates the difference (step S13), and determines whether the difference is smaller than a predetermined threshold value (step S15). ).

If the difference is smaller than the threshold value, it is determined that there is no lamp disconnection (step S17). If the difference is larger than the threshold value, it is determined that there is a lamp disconnection, and processing for detecting disconnection is performed (step S19).

For example, it is assumed that three left lamps 18 are on and two right lamps 17 are on. In this case, assuming that the current value per lamp is a, the total current value of the left lamp 18 is 3a. On the other hand, in the right lamp 17, the total current value is 2a.

Therefore, when the left and right current values are compared, the difference is a, and the disconnection of the lamps 17 and 18 can be detected by setting the threshold value of the disconnection detection to 3a / 4 or the like.

As described above, according to the disconnection detecting apparatus of the embodiment, the current values of the left and right currents flowing through the pair of left and right lamps are compared by utilizing the fact that the left and right lamps are provided.
In other words, since the reference value fluctuates in the same manner in response to fluctuations in temperature, power supply voltage, etc., comparing the current values on the left and right sides, the effect of errors due to fluctuations in temperature, power supply voltage, etc., upon disconnection detection, is the principle. No longer occurs.

Therefore, it is possible to improve the accuracy of lamp disconnection detection. Further, since the disconnection can be detected by a simple current value comparison, the load on the microcomputer 23 can be reduced.

Next, a comparative example of the disconnection detecting device of the embodiment and a conventional disconnection detecting device will be described. Here, in the characteristics of the amplifiers 20a and 20b, the offset value at 25 ° C. is 50, and the temperature characteristic of the offset value is 0.2 /
° C, and the current value at the time of three lamps is the offset value +11
8, the current value at the time of two lamps is the offset value +11
A comparison between the conventional example and the embodiment in the case where the threshold value is 114 and the threshold value which is a criterion for determining two lamps and three lamps is 114 will be described below.

Here, the offset value is the current value when the input is 0 (that is, the current flowing through the shunt resistors 13a and 13b is 0), and the current value is the output of the amplifiers 20a and 20b. Is a value obtained by A / D conversion. A /
D23 may be provided in the current detection unit 21 or in the microcomputer 25.

The current values in the conventional example and the embodiment described here are all digital quantities handled in the microcomputer 25. For example, if the current value of three lamps is actually 1.5 A, the shunt resistors 13a, 1
When a resistor of 20 mΩ is used for 3b, the shunt resistance is 1
The amount of voltage drop at 3a and 13b is 1.5 × 20 = 30 mv. Assuming that the gain (amplification degree) of the amplifiers 20a and 20b of the current detection unit 21 is 80, the output from the amplifiers 20a and 20b is 80 × 30 × 10 ⁻³ = 2.4V. When this output voltage is converted into a digital amount by the 8-bit A / D 23, it becomes 2.4 / 5 × 255 = 122.

Next, a comparison between the conventional example and the embodiment when the battery voltage is increased by a factor of 1 or 1.5 will be described. First, a comparison is made when the battery voltage is increased by a factor of one.

(Conventional Example 1) Offset value 5 at the time of assembly
When 0 is held, when the temperature of the current detection unit 21 reaches 40 ° C., the offset value becomes 50 + 0.2 × (40−25) = 53. The difference obtained by subtracting the offset value is 115. In this case, since the difference exceeds the threshold value 114, two lamps cannot be detected and an erroneous determination is made.

(Embodiment 1) The temperature of the current detector 21 is 40
When the temperature reaches ° C, the offset value becomes 53. For example,
When there are two lights on the right side and three lights on the left side, the outputs of the amplifier are 165 and 171 respectively, but the difference is maintained at 6 regardless of the fluctuation of the offset value. For this reason, if it is determined that the lamps 17 and 18 are disconnected when the difference is 5 or more, two lamps can be determined and no erroneous determination is made.

Next, a comparison is made when the battery voltage is increased by a factor of 1.5.

(Conventional Example 2) Offset value 5 at the time of assembly
0, the output of the two lamps is given by the offset value + 112 × when the battery voltage becomes 1.5 times 18V from 12V at the time of the offset setting and the current value becomes 1.1 times. At 1.1, it becomes 173, and this output greatly exceeds the threshold value 114. For this reason, disconnection detection of two lamps cannot be performed and an erroneous determination is made. For this reason, the power supply voltage correction circuit 29 is used. However, as a practical problem, the possibility of erroneous determination cannot be excluded due to an error in the power supply voltage correction circuit.

(Embodiment 2) When the battery voltage is increased from 1.5V to 18V from 12V at the time of offset setting and the current value is increased by 1.1 times, the output of the two lamps is as follows.
The offset value is + 112 × 1.1, which is 173. Similarly, the output of the three lamps is 180, so the difference is 8. For this reason, if it is determined that the lamps 17 and 18 are disconnected when the difference is 5 or more, two lamps can be determined and no erroneous determination is made.

The present invention is not limited to the disconnection detecting method and the disconnection detecting device according to the above-described embodiments. In the embodiment, the first relay 15a and the second relay 15b are mechanical relays. However, for example, a field effect transistor, for example, an N-channel type MOS-F
A thermal FET with built-in ET or temperature protection may be used.

Further, in the embodiment, the comparison of the left and right current values is performed by the microcomputer 23 using the A / D 25. However, the comparison of the left and right current values is physically performed using the comparator (comparator). It may be performed, and it is not limited to the method of comparison.

Although the A / D 25 is provided in the microcomputer 23 in the embodiment, for example, the A / D 2
5 may be provided in the current detection unit 21 instead of being provided in the microcomputer 23. In addition, it goes without saying that various modifications can be made without departing from the technical idea of the present invention.

[0068]

According to the first and fourth aspects of the present invention, a current flowing through each load is detected by a pair of current detectors provided corresponding to a pair of loads supplied with current from a power supply. Then, the pair of current values detected by the pair of current detection units are compared, and the presence or absence of disconnection of each load is determined based on the comparison result of the pair of current values.

That is, since the reference value fluctuates in the same manner in accordance with fluctuations in temperature, power supply voltage, and the like, if a pair of current values are compared, an error due to fluctuations in temperature, power supply voltage, or the like at the time of disconnection detection is detected. The effect does not occur in principle.
Therefore, disconnection of a load such as a lamp can be accurately detected by a simpler method.

According to the second and fifth aspects of the invention, the difference between the pair of current values detected by the pair of current detectors is calculated, and the obtained difference is compared with a predetermined threshold value. By making a comparison, the presence or absence of disconnection of each load is determined, so that disconnection of the load can be easily detected.

According to the third and sixth aspects of the present invention, if the obtained difference is equal to or larger than the threshold value, it is determined that there is a disconnection, and if the difference is less than the threshold value, it is determined that there is no disconnection. Since the determination is made, disconnection of the load can be easily detected.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a disconnection detection device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of the disconnection detecting device according to the embodiment;

FIG. 3 is a flowchart showing an operation of a conventional disconnection detecting device.

FIG. 4 is a circuit configuration diagram of another conventional disconnection detection device.

[Explanation of symbols]

 Reference Signs List 11 battery 13a, 13b shunt resistor 15a first relay 15b second relay 17 right lamp 17a, 17b, 17c lamp 18 left lamp 18a, 18b, 18c lamp 19a right current detector 19b left current detector 20a, 20b amplifier 21 Current detection unit 23 Microcomputer 25 A / D 27 Control unit 29 Power supply voltage correction circuit

Claims (6)

[Claims] 1. A pair of loads to which a current is supplied from a power supply, a pair of current detectors provided corresponding to the pair of loads, and detecting a current flowing through each load; and a pair of current detectors. A disconnection detection device, comprising: a comparison unit that compares a pair of detected current values; and a disconnection determination unit that determines presence or absence of disconnection of each of the loads based on a comparison result of the comparison unit. 2. The comparison unit calculates a difference between a pair of current values detected by the pair of current detection units, and the disconnection determination unit determines the difference obtained by the comparison unit in advance. 2. The disconnection detecting device according to claim 1, wherein the presence or absence of disconnection of each of the loads is determined by comparing with a threshold value. 3. The disconnection determination unit determines that there is a disconnection when the difference obtained by the comparison unit is equal to or greater than the threshold value, and determines that there is no disconnection when the difference is less than the threshold value. 3. The disconnection detecting device according to claim 2, wherein: 4. A current detection step of detecting a current flowing through each load by a pair of current detection units provided corresponding to a pair of loads to which a current is supplied from a power supply; A disconnection detecting step of comparing the pair of current values, and a disconnection determining step of determining the presence or absence of disconnection of each of the loads based on a comparison result of the pair of current values. 5. The comparison step calculates a difference between a pair of current values detected by the pair of current detection units, and the disconnection determination step determines the difference obtained in the comparison step in advance. 5. The disconnection detecting method according to claim 4, wherein the presence or absence of disconnection of each of the loads is determined by comparing with a threshold value. 6. The disconnection determining step determines that there is a disconnection when the difference obtained in the comparing step is equal to or more than the threshold value, and determines that there is no disconnection when the difference is less than the threshold value. 6. The method according to claim 5, wherein
The disconnection detection method described.