JP2009300400A - Insulation resistance detector and insulation resistance detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation resistance detector and insulation resistance detecting method which more accurately determine degradation of insulation resistance. <P>SOLUTION: In the insulation resistance detector 1 for detecting insulation resistance 13 between car body 40 and high-voltage circuit 2, its insulation determining means produced by ECU 7 includes false detection determining means which determines detection of potential between coupling capacitor 3 and detected resistance 4 as an incorrect detection if no amplitude of this detected potential exists within its predefined limit of coverage, and additionally includes effective range setting means for allowing variation of the predefined limit of coverage to be used by the false detection determining means based on the values up to preceding cycle of the detected potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an insulation resistance detection device and an insulation resistance detection method for detecting an insulation resistance between a high voltage circuit and a body of an electric / hybrid vehicle.

  Conventionally, an electric / hybrid vehicle is equipped with a high-voltage battery as a drive source. In order to eliminate the risk of an electric shock from an occupant or the like due to this high voltage, In addition, a structure for electrically insulating a high voltage circuit including a battery is employed.

  However, there is a risk that the insulation resistance between the vehicle body and the high-voltage circuit may decrease due to aging, such as adhesion of foreign matter, battery leakage, or motor insulation breakdown. There is a risk of electric shock.

  In view of this, an insulation resistance detection device is provided to detect a decrease in insulation resistance between the vehicle body and the high-voltage circuit before a risk of electric shock from an occupant or the like occurs in an electric / hybrid vehicle (for example, Patent Document 1). reference).

  Further, in the invention described in Patent Document 1, in order to improve the detection accuracy of the insulation resistance detection device, for example, a detection value protruding due to external noise is regarded as a false detection, and is excluded from the determination of a decrease in insulation resistance. The accuracy is improved.

Furthermore, in the invention described in Patent Document 1, the detection accuracy is improved by looking at the high-order peak and the low-order peak of the detection value that fluctuates at a predetermined frequency.
JP 2007-108074 A

  However, the invention described in Patent Document 1 has the following problems.

  The value detected by the insulation resistance detection device has a large amplitude when insulation is normal, and the amplitude decreases as insulation decreases. Therefore, a decrease in insulation is determined by a change in the amplitude.

  However, in the invention described in Patent Document 1, for example, if the voltage fluctuation of the high voltage circuit continues in a state where the insulation is normal and the amplitude is large, it is determined that the above-described erroneous detection occurs on either the high side peak or the low side peak. Will continue. In this case, the detected value deviates from the true value (the deviation of the detected value from the true value increases), and there is a problem that accurate determination cannot be performed.

  In this case, even if the high-order peak and the low-order peak of the detected value are viewed together, the deviation of the detected value from the true value remains large.

  The present invention has been made in view of the above problems, and an object thereof is to provide an insulation resistance detection device and an insulation resistance detection method capable of more accurately determining a decrease in insulation resistance.

  Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.

1. In the insulation resistance detection device that detects the insulation resistance between the vehicle body and the high voltage circuit,
An oscillation circuit for outputting a predetermined frequency signal; a coupling capacitor having one terminal connected to the high voltage circuit; and a detection resistor connected between the other terminal of the coupling capacitor and the oscillation circuit; A potential detecting means for detecting a potential between the coupling capacitor and the detection resistor; and when the amplitude of the potential detected by the potential detecting means is a predetermined value or less, between the vehicle body and the high voltage circuit. Insulation determination means for determining that the insulation is reduced.
The insulation determination means has a false detection determination means for determining that the detection is a false detection when the amplitude of the potential detected by the potential detection means is not within a predetermined effective range;
An insulation resistance detection apparatus, further comprising effective range setting means for changing a predetermined effective range used by the erroneous detection determination means based on a value of the potential detected by the potential detection means up to a previous period.

  According to the means 1, a decrease in insulation resistance can be determined more accurately.

  That is, the effective range setting means of the means 1 varies the effective range based on the value of the potential detected by the potential detection means up to the previous period, so that it can follow the voltage fluctuation of the high voltage circuit and can accurately Resistance reduction determination can be performed.

  2. 2. The insulation resistance detection apparatus according to claim 1, wherein the effective range setting unit varies the effective range based on a moving average value of the amplitude of the potential detected by the potential detection unit.

  According to the means 2, since the effective range is changed based on the moving average value of the amplitude of the potential detected by the potential detecting means, even if there is a large difference value up to the previous period, it is averaged and close to the true value. A value can be obtained, and an accurate insulation resistance reduction determination can be performed.

  3. The effective range setting unit varies the effective range based on a moving average value of values of the potential detected by the potential detection unit up to the previous period of the high-order peak and / or low-order peak. The insulation resistance detection device according to means 2.

  According to the means 3, it is possible to obtain a value close to the true value by using the frequency variation of the potential detected by the potential detecting means by the oscillation circuit, and to perform accurate insulation resistance reduction determination.

  4). When the erroneous detection determination means determines that it is a false detection, the insulation determination means uses a value within the effective range closest to the detection value as a detection value instead of the detection value. The insulation resistance detection apparatus according to any one of means 1 to 3 for performing the above.

  According to the means 4, when it is determined that there is a false detection, instead of simply excluding it, a value within the effective range closest to the detected value is used in the subsequent processing instead of the detected value. Therefore, even if the actual detection value is abnormally projected, a value close to the true value can be obtained by reflecting it with a value within the effective range, and an accurate insulation resistance reduction determination can be performed. it can.

5. In the insulation resistance detection method for detecting the insulation resistance between the vehicle body and the high voltage circuit,
An oscillation circuit for outputting a predetermined frequency signal; a coupling capacitor having one terminal connected to the high voltage circuit; and a detection resistor connected between the other terminal of the coupling capacitor and the oscillation circuit; Of circuit with
Detecting a potential between the coupling capacitor and the detection resistor;
If the amplitude of the detected potential is not within a predetermined effective range, it is determined that the detection is a false detection,
When the amplitude of the detected potential is a predetermined value or less, it is determined that the insulation is reduced between the vehicle body and the high voltage circuit,
An insulation resistance detection method, wherein the predetermined effective range is varied based on a value of the detected potential up to a previous period.

  According to the means 5, it is possible to more accurately determine the decrease in insulation resistance.

  That is, the means 5 changes the effective range based on the value of the detected potential up to the previous period, so that it can follow the voltage fluctuation of the high voltage circuit and can perform accurate insulation resistance reduction determination.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which an insulation resistance detection device of the present invention is embodied will be specifically described with reference to the drawings.

(Description of configuration)
FIG. 1 is a block diagram showing a configuration of an embodiment of an insulation resistance detection apparatus according to the present invention.

  As shown in FIG. 1, the high voltage circuit 2 includes a battery 8 that is a drive source of an electric / hybrid vehicle, and further boosts a voltage of about 200 to 300 V that is an output voltage of the battery 8 to about 650 V. 9, a smoothing capacitor 10, an inverter 11, and an MG (motor generator) 12 that drives an electric / hybrid vehicle.

  This high voltage circuit 2 ensures an insulation resistance 13 (floating capacitance between bodies) of, for example, several MΩ or more with the body (the body of an electric / hybrid vehicle) 40.

  One side of the coupling capacitor 3 is connected to the low voltage side (the negative side of the battery 8) of the booster circuit 9 of the high voltage circuit 2, and the detection resistor 4 is connected to the other side of the coupling capacitor 3. An oscillation circuit 5 is provided between the detection resistor 4 and the body 40, and an oscillation voltage generated by the oscillation circuit 5 is applied in series to the detection resistor 4, the coupling capacitor 3, and the insulation resistor 13.

  The potential detected between the coupling capacitor 3 and the detection resistor 4 is input to an ECU (Electronic Control Unit) 7 through a filter 6 that is a band-pass filter that passes the oscillation frequency of the oscillation circuit 5.

  In this embodiment, the configuration in which the coupling capacitor 3 and the detection resistor 4 are electrically connected and the potential at this point is input to the ECU 7 via the filter 6 is the potential detection of the present invention. It constitutes a means.

  The insulation resistance detection device 1 includes the coupling capacitor 3, the detection resistor 4, an oscillation circuit 5, a filter 6, and an ECU 7. The coupling capacitor 3 is, for example, one having a capacitance of 1 μF or more, the detection resistor 4 is, for example, about 100 kΩ to 150 kΩ, and the oscillation circuit 5 is, for example, one that outputs 2.5 Hz at 5V.

(Description of operation)
When the insulation resistance 13 between the high voltage circuit 2 and the body 40 decreases, the amplitude of the potential detected between the coupling capacitor 3 and the detection resistor 4, which fluctuates at the oscillation frequency of the oscillation circuit 5, that is, the filter 6 is changed. Thus, the amplitude of the detection value input to the ECU 7 is reduced. Therefore, the ECU 7 of the insulation resistance detection device 1 determines whether or not the amplitude has become smaller than a predetermined value and determines a decrease in the insulation resistance 13. This point will be described with reference to FIG. FIG. 2 is a diagram illustrating a waveform of the potential detected between the coupling capacitor 3 and the detection resistor 4 after passing through the filter 6.

  In FIG. 2, a waveform 14 shows an example of the detected potential after passing through the filter 6, and a waveform 15 shows another example of the detected potential after passing through the filter 6. In this example, the waveform 14 is a detection value when the insulation resistance 13 is normal, and the waveform 15 is a detection value when the insulation resistance 13 is lowered.

  In FIG. 2, point A is the amplitude value of the higher peak of the waveform 14, point B is the amplitude value of the higher peak of the waveform 15, and point C is the amplitude value of the lower peak of the waveform 14. Point D is the amplitude value of the lower peak of the waveform 15. Value 16 is the amplitude value of the higher peak of waveform 14, and value 17 is the amplitude value of the higher peak of waveform 15.

  Referring to FIG. 2, it can be seen that the amplitude value of the waveform 15 when the insulation resistance 13 is lowered is smaller than the waveform 14 when the insulation resistance 13 is normal. The ECU 7 of the insulation resistance detection apparatus 1 stores in advance a threshold value that can be distinguished from the normal value 16 and the insulation decrease value 17, and this and the detected value (moving average value of the detected value in this embodiment). Is compared to determine the insulation reduction.

  The ECU 7 of the insulation resistance detection apparatus 1 includes a CPU (not shown), a RAM that temporarily stores various data, and a ROM that continuously stores various data. The software program stored in the ROM is stored in the CPU. The processing of this embodiment is executed by executing the above.

  As described above, in the insulation resistance detection device 1 of the present embodiment, the fluctuation of the amplitude of the potential detected between the coupling capacitor 3 and the detection resistor 4, which fluctuates with the oscillation frequency of the oscillation circuit 5, is observed. Based on the above, the lowering of the insulation resistance 13 is determined. As a process in the preceding stage, in order to eliminate erroneous detection due to the influence of external noise or the like, when the detected amplitude value of the potential deviates from the effective range, it is Process.

  Further, the effective range is changed based on the past value of the detected potential. For example, a moving average process of the amplitude value is performed on past data within a predetermined period immediately after the detected amplitude of the potential, and a range having a predetermined variation limit width for the moving average value is defined as an effective range. To do. The moving average process may be a weighted moving average process such as increasing the weight of the latest data.

  If the amplitude value of the detected potential deviates from this effective range, that is, if it is determined that it is a false detection, a value within the effective range closest to this false detection value is detected instead of this false detection value. Use as a value. Therefore, in the subsequent processing, a value within this effective range is used as past data for obtaining a subsequent moving average value. This past data is stored in the RAM of the ECU 7.

  Hereinafter, the processing of this embodiment will be described with reference to flowcharts. FIG. 3 is a flowchart of processing executed by the ECU 7 shown in FIG.

  First, if a signal is input through the band pass filter 6 (S300), the amplitude value of the potential between the coupling capacitor 3 and the detection resistor 4 in the current detection is obtained, and before the calculation so far The moving average value up to the cycle is read out from the RAM (S301). If there is not enough past data and the moving average value has not been calculated yet, such as at the time of start-up, the preset initial value may be used as the moving average value. An average value of past data may be used as the moving average value.

  Subsequently, it is determined whether or not the current amplitude value obtained in step (S301) is larger than the effective range upper limit value, which is a value obtained by adding the variation restriction amount to the moving average value (S302). : Yes), it is determined that the current amplitude value is not within the effective range and is a false detection, and instead of the current detected amplitude value, the effective range upper limit value (moving average value + variation limit amount) is used as the current detection value. The process proceeds to (S303) and step (S307).

  On the other hand, in step (S302), when the current amplitude value is equal to or less than the effective range upper limit value which is a value obtained by adding the variation restriction amount to the moving average value (S302: no), the process proceeds to step (S304). .

  In step (S304), it is determined whether or not the current amplitude value obtained in step (S301) is smaller than the effective range lower limit value, which is a value obtained by subtracting the variation restriction amount from the moving average value. : Yes), it is determined that the current amplitude value is not within the effective range and is a false detection, and instead of the current detected amplitude value, the effective range lower limit value (moving average value−variation limit amount) is used as the current detection value. (S305), the process proceeds to step (S307).

  On the other hand, in step (S304), when the current amplitude value is equal to or greater than the effective range lower limit value that is a value obtained by subtracting the variation restriction amount from the moving average value (S304: no), the current amplitude value is within the effective range. Since it is equal to or lower than the upper limit and equal to or higher than the lower limit of the effective range, it is within the effective range, and the current amplitude value is set as the detected value as it is (S306), and the process proceeds to step (S307).

  In the present embodiment, the processing in steps (S302) and (S304) functions as an erroneous detection determination unit of the present invention.

  In step (S307), a new moving average value is calculated using the current detected value (value set in steps (S303), (S305), and (S306)) and past data within a predetermined period.

  In this embodiment, the processes of steps (S302: yes), (S303), (S304: yes), (S305), and (S307) function as effective range setting means of the present invention.

  Subsequently, an insulation decrease determination process is performed (S308). For example, if the moving average value calculated in step (S307) is equal to or greater than a predetermined threshold value (the threshold value shown in FIG. 2 that can distinguish between the normal value 16 and the insulation decrease value 17), the insulation resistance 13 is determined to be normal, and if it is smaller than the predetermined threshold, it is determined that the insulation resistance 13 has decreased.

  In this embodiment, the processing of steps S302, S303, S304, S305, S306, S307, and S308 functions as an insulation determination unit of the present invention. Is.

  As described above, in this embodiment, the effective range for determining whether or not the detected amplitude is valid is varied based on the moving average value of the detected potential (moving average value ± variation limit amount). However, a comparison with the case where the effective range is fixed will be described below. FIG. 4 is a diagram illustrating a case where the effective range is fixed, and FIG. 5 is a diagram illustrating a case where the effective range is changed based on the moving average value according to the present embodiment.

  4 and 5, a waveform 14 is an example of a detected potential after passing through the filter 6, a value 16 is an amplitude value of a high-side peak when insulation is normal, and a value 17 is a high-side peak when insulation is lowered. The range 18 is an effective range for determining whether or not the detected amplitude is valid, the value 18a is the upper limit value in the effective range 18, and the value 18b is the lower limit value in the effective range 18. , The value 19 is the amplitude value of the higher peak within the detected effective range 18, the value 20 is the amplitude value of the higher peak outside the detected effective range 18, and the value 25 is before the amplitude value of the higher peak. It is a moving average value up to a cycle.

  The waveform 14 in FIGS. 4 and 5 is for the case where the insulation resistance 13 is normal, and therefore the amplitude value of the high-order peak of the waveform 14 should reach the value 16. However, the actual waveform 14 fluctuates due to, for example, the influence of the operation of the booster circuit 9, and the amplitude values 19 and 20 of the high-order peak move up and down as shown in FIGS.

  FIG. 4 is a reference example. In this example, the effective range 18 is fixed, and the amplitude values at the points E and F deviate from the effective range 18, so that the detection values used for calculating the moving average are shown in FIG. The upper limit value 18a of the effective range 18 is used. On the other hand, since the amplitude value of the point G is within the effective range 18, the amplitude value is used as a detection value for calculating the moving average.

  On the other hand, FIG. 5 is an example in the case where the processing shown in FIG. 3 is performed, and a predetermined variation restriction amount is set above and below the moving average value 25 up to the previous cycle. Yes. Therefore, the effective range 18 also varies based on the variation of the moving average value 25.

  In FIG. 5, since the amplitude value at the point E deviates from the effective range 18, the upper limit value 18 a of the effective range 18 is used as the detection value used for calculating the moving average. In FIG. 4, the point F is also outside the effective range 18, but in FIG. 5, the amplitude value of the point F is within the effective range 18, and thus the amplitude value is used as a detection value for calculating the moving average. In FIG. 4, the point G is within the effective range 18, but in FIG. 5, the amplitude value of the point G deviates from the effective range 18, so that the detection value used for calculating the moving average is the effective range 18. The lower limit 18b is used.

  FIG. 4 and FIG. 5 compare the deviation of the moving average value 25 from the amplitude value 16 (true value) of the high-order peak when insulation is normal. In FIG. In FIG. 5, the moving average value 25 is located near the true value 16 and represents a value closer to the true value 16, whereas the moving average value 25 and the true value 16 are separated from each other. Is done.

  Next, the degree of deviation between the moving average value calculated in the process of FIG. 3 and the true value, and the degree of deviation between the value and the true value obtained by another method will be described by comparing these. FIG. 6 is a diagram showing the deviation from the true value of each calculated value in a detection waveform that fluctuates due to the influence of the operation of the booster circuit 9 when the insulation resistance 13 is normal. Is the amplitude value, that is, the true value of the higher peak, 22 is a moving average value when a value that deviates from the effective range is used as it is without changing into the effective range, and 23 is when the effective range is fixed (FIG. 4 is a moving average value in the case where the effective range is changed (this embodiment shown in FIGS. 3 and 5).

  Referring to FIG. 6, the value 22 fluctuates greatly, and the deviation from the true value 21 is large. Further, in the value 23 obtained by setting the effective range and excluding the case where the effective range is deviated, the variation can be reduced, but the value is lower than the true value 21 and far from the true value 21. On the other hand, it can be seen that the value 24 calculated by the present embodiment has little variation, fluctuates around the true value 21, and is close to the true value 21.

  In the first embodiment described above, the moving average value is calculated using the amplitude value of the higher peak of the potential detected between the coupling capacitor 3 and the detection resistor 4 shown in FIG. However, the present invention is not limited to this, and either the amplitude value of the higher peak or the amplitude value of the lower peak may be used, or the amplitude value of the higher peak and the lower peak may be used. Both amplitude values may be used. In the second embodiment, a case where both the amplitude value of the higher peak and the amplitude value of the lower peak are used will be described. The configuration of the second embodiment is the same as that of the first embodiment and will be described with reference to the configuration of FIG.

  Hereinafter, the processing of the second embodiment will be described with reference to a flowchart. FIG. 7 is a flowchart of processing executed by the ECU 7 shown in FIG.

  First, if a signal is input through the bandpass filter 6 (S700), a moving average value based on the amplitude value of the higher peak is calculated in step (S701), and the amplitude value of the lower peak is calculated in step (S702). Calculate the moving average value. Since the processing in this step (S701) and the processing in step (S702) do not matter in order of processing, they can be executed in parallel by multitask processing.

  Each of the process of step (S701) and the process of step (S702) corresponds to the process of step (S301) to step (S307) shown in FIG. That is, the process of step (S701) is the same as the process of step (S301) to step (S307) shown in FIG. 3, and in step (S702), step (S301) to step (S307) shown in FIG. Then, what is necessary is just to perform the process changed from using the high-order peak to using the low-order peak.

  In step (S703), an average value of the moving average value of the higher peak obtained in step (S701) and the moving average value of the lower peak obtained in step (S702) is calculated. The calculation using the amplitude value of the lower peak can be performed in the same manner as the calculation using the amplitude value of the higher peak by aligning the signs by using the absolute value of the amplitude value of the lower peak. .

  Subsequently, an insulation decrease determination process is performed (S704). For example, if the average value calculated in step (S703) is greater than or equal to a predetermined threshold value, it is determined that the insulation resistance 13 is normal, and if the average value is smaller than the predetermined threshold value, it is determined that the insulation resistance 13 has decreased. To do.

  In the present embodiment, the processing of steps (S701) and (S702) functions as an erroneous detection determination means of the present invention, and the processing of steps (S701), (S702), and (S703) It functions as an effective range setting unit of the present invention, and the processing of steps (S701), (S702), (S703), and (S704) functions as an insulation determination unit of the present invention.

  If the insulation lowering determination process is performed using the average value of the moving average value of the high-order peak and the moving average value of the low-order peak as in the second embodiment, the variation can be further reduced.

  The present invention can be applied to a high voltage circuit of an electric / hybrid vehicle and is effective in improving the safety of the electric / hybrid vehicle.

It is a block diagram which shows the structure of one Example of the insulation resistance detection apparatus by this invention. It is a figure which shows the waveform after the filter 6 has detected the electric potential detected between the coupling capacitor 3 and the detection resistance 4. FIG. It is a flowchart of the process performed by ECU7 shown in FIG. It is a figure which shows the case where an effective range is fixed. It is a figure which shows the case where an effective range is fluctuate | varied based on a moving average value of a present Example. It is a figure which shows the deviation from the true value of each calculated value in the detection waveform which fluctuates under the influence of the operation of the booster circuit 9 and the like when the insulation resistance 13 is normal. It is a flowchart of the process performed by ECU7 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation resistance detection apparatus 2 High voltage circuit 3 Coupling capacitor 4 Detection resistance 5 Oscillator 6 Filter circuit 7 ECU (electronic control unit)
8 Battery 9 Booster circuit 10 Smoothing capacitor 11 Inverter 12 MG (Motor generator)
13 Insulation resistance 40 Body

Claims (5)

In the insulation resistance detection device that detects the insulation resistance between the vehicle body and the high voltage circuit,
An oscillation circuit for outputting a predetermined frequency signal; a coupling capacitor having one terminal connected to the high voltage circuit; and a detection resistor connected between the other terminal of the coupling capacitor and the oscillation circuit; A potential detecting means for detecting a potential between the coupling capacitor and the detection resistor; and when the amplitude of the potential detected by the potential detecting means is a predetermined value or less, between the vehicle body and the high voltage circuit. Insulation determination means for determining that the insulation is reduced.
The insulation determination means has a false detection determination means for determining that the detection is a false detection when the amplitude of the potential detected by the potential detection means is not within a predetermined effective range;
An insulation resistance detection apparatus, further comprising effective range setting means for changing a predetermined effective range used by the erroneous detection determination means based on a value of the potential detected by the potential detection means up to a previous period.   2. The insulation resistance detection apparatus according to claim 1, wherein the effective range setting unit varies the effective range based on a moving average value of the amplitude of the potential detected by the potential detection unit.   The effective range setting unit varies the effective range based on a moving average value of values of the potential detected by the potential detection unit up to the previous period of the high-order peak and / or low-order peak. The insulation resistance detection apparatus according to claim 2.   When the erroneous detection determination means determines that it is a false detection, the insulation determination means uses a value within the effective range closest to the detection value as a detection value instead of the detection value. The insulation resistance detection device according to any one of claims 1 to 3. In the insulation resistance detection method for detecting the insulation resistance between the vehicle body and the high voltage circuit,
An oscillation circuit for outputting a predetermined frequency signal; a coupling capacitor having one terminal connected to the high voltage circuit; and a detection resistor connected between the other terminal of the coupling capacitor and the oscillation circuit; Using a circuit with
Detecting a potential between the coupling capacitor and the detection resistor;
If the amplitude of the detected potential is not within a predetermined effective range, it is determined that the detection is a false detection,
When the amplitude of the detected potential is a predetermined value or less, it is determined that the insulation is reduced between the vehicle body and the high voltage circuit,
An insulation resistance detection method, wherein the predetermined effective range is varied based on a value of the detected potential up to a previous period.

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