JP2004170103A - Insulation detector for non-grounded power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation detector for a non-grounded power supply with enhanced detection accuracy. <P>SOLUTION: A combination of first and second switches S1 and S2 as a first switching means for performing connection for a first set period, a combination of the first and fourth switches S1 and S4 as a second switching means for performing connection for a second set period, a combination of the second and third switches S2 and S3 as a third switching means for likewise performing connection for the second set period, and a combination of the third and fourth switches S3 and S4 as a fourth switching means for thereto connecting a microcomputer 11 for detecting the terminal voltage of a capacitor 9, are prepared for a series circuit comprising a DC power supply 3 and the capacitor 9. These switching means of four kinds are used successively to calculate insulation resistance by means of the microcomputer 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an insulation detection device for an ungrounded power supply, and more particularly to an insulation detection device suitable for an ungrounded DC power supply mounted on a vehicle that uses electric propulsion.
[0002]
[Prior art]
The insulation detection device of the ungrounded power supply is connected to the positive and negative terminals of the ungrounded DC power supply, and is insulated from the ground potential part by the insulation resistance to the ground potential part of the main circuit wiring on the positive and negative sides, that is, the ground fault resistance. Is detected to detect insulation with respect to the ground potential portion and a ground fault state (for example, see Patent Document 1). In such a conventional insulation detection device, switching means for connecting a capacitor in series between a positive terminal of an ungrounded DC power supply and a ground potential section for a set time, a negative terminal of an ungrounded power supply and a ground potential section A switching means for connecting a capacitor in series for a set time, a switching means for detection connecting a detection means for detecting a voltage between both terminals of the capacitor after each switching means is cut off, Calculation means for obtaining an insulation resistance to a ground potential portion of a power supply, that is, a ground fault resistance, based on a voltage between both terminals of the capacitor after the switching means is cut off and a power supply voltage previously calculated by fully charging the capacitor. And performs detection and determination of the insulation state from the ground fault resistance obtained by the calculation means.
[0003]
[Patent Document 1]
JP-A-8-226950 (page 4-7, FIG. 1)
[Problems to be solved by the invention]
In the insulation detection device as described above, when calculating the ground fault resistance, an expression including the capacitance of the capacitor as a constant is used, but the capacitance of the capacitor to be used as a constant depends on variations in capacitance between products and temperature changes. There may be variations in capacitance and the like, and there may be a change with time in the capacitance and the like. If the values used as constants vary or change in this way, the measurement error between the obtained ground fault resistance value and the actual ground fault resistance value increases, and the insulation state detection accuracy decreases. I will. Therefore, it is desirable to reduce the measurement error of the ground fault resistance as much as possible and to improve the detection accuracy of the insulation state, even if there are variations or changes in the values used as constants for obtaining the ground fault resistance such as the capacitance of the capacitor. ing.
[0004]
An object of the present invention is to improve the detection accuracy of an insulation state.
[0005]
[Means for Solving the Problems]
The insulation detection device of the present invention includes a capacitor connected in series to a DC power supply in which the wiring on the positive terminal side and the wiring on the negative terminal side are insulated from the ground potential, and a first set time shorter than the time required for the capacitor to be completely charged. A second switching means for connecting a capacitor in series between a positive terminal of the power supply and the ground potential section for a second set time; a first switching means connected between the ground potential section and the power supply. A third switching means for connecting a capacitor in series with the terminal for a second set time, and detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off. A power supply voltage is estimated based on a voltage detected by the fourth switching means for connecting the detection means and the detection means after the first switching means is cut off, and the estimated power supply voltage and the second and third switching means are estimated. The solution to the problem by calculating means for obtaining the insulation resistance to ground potential of the power on the basis of the respective detection voltage by the detection means after blocking the configuration with.
[0006]
With such a configuration, if the first set time is set to a time shorter than the time required to completely charge the capacitor, the DC power is supplied by the first switching means during the first set time. The capacitor is connected and charged between the power supply and the ground potential section by direct current, and the voltage between both terminals of the capacitor at this time is detected by the detecting means connected by the fourth switching means, thereby detecting the voltage. The calculation means can estimate the power supply voltage from the voltage. Then, an insulation resistance is obtained based on the estimated power supply voltage and a voltage detected by the detection unit after the second and third switching units are cut off, thereby reducing a measurement error of the insulation resistance and detecting the insulation state. Accuracy can be improved.
[0007]
Further, as the above insulation detection device, the first switching means includes a first switch unit connected to a positive terminal of the power supply, and a second switch unit connected to a negative terminal of the power supply, Switching means includes a second switch section and a third switch section connected in series to the first switch, and the second switching means includes a first switch section and a second switch section. And a fourth switch unit connected in series with the first switch unit and the third switch unit, and between the second switch unit and the fourth switch unit on the positive side. A first diode, a first resistor, and a capacitor rectifying in a direction from the first diode to the negative side are connected in series, and a first diode rectifying in a direction opposite to the first diode in parallel with the first diode and the first resistor. Two diodes and a second resistor are connected in series. And the detection means is connected between the third switch part and the fourth switch unit, between the detecting means and the fourth switching unit is a circuit configuration which is grounded to the ground potential portion.
[0008]
Further, when the bypass means including the fifth switch section that forms a path for bypassing the second resistor when the circuit is closed is provided, the fourth switching means may be closed while the fourth switching means is closed. When the switch unit 5 is closed, the discharging time of the capacitor can be reduced, and the time required for detecting the insulation state can be reduced, which is preferable.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an insulation detection device to which the present invention is applied will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an insulation detection device to which the present invention is applied. FIG. 2 is a flowchart showing the operation of calculating the insulation resistance of the insulation detection device according to the present invention. FIG. 3 is a time chart showing the charging / discharging state of the capacitor and the voltage reading timing with respect to the operation of each switch unit. FIG. 4 is a diagram illustrating a detection error of the value of the insulation resistance detected during the measurement time of each power supply voltage with respect to the value of the insulation resistance.
[0010]
As shown in FIG. 1, the insulation detection device 1 of the present embodiment is applied to a DC power supply 3 serving as a power source of, for example, an electric propulsion vehicle that obtains propulsion using electric power. The power supply 3 is a battery in which a plurality of storage batteries or the like are connected in series or a fuel cell. The positive main circuit wiring 5a on the positive terminal side and the negative main circuit wiring 5b on the negative terminal side of the power supply 3 are each connected to the ground potential. The power supply 3 is a non-grounded power supply. The insulation detecting device 1 includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a capacitor 9, a microcomputer 11 which also serves as detecting means and calculating means and determines an insulation state, and sets each switch. And a switching control circuit (not shown) that performs opening and closing control according to the set time.
[0011]
Note that the detection unit, the calculation unit, the switching control circuit, and the like can be formed separately or integrally as appropriate, for example, a switching control circuit (not shown) is integrally included in the microcomputer 11. Further, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 shown in FIG. 1 are typically formed by using, for example, a switch unit composed of components having various switch functions such as a relay and a semiconductor switch as a contact. This is shown in FIG.
[0012]
A first switch S1 and a third switch S3 are sequentially connected in series to the positive terminal of the power supply 3 from the positive terminal, and a second switch S2 and a second switch S2 are connected to the negative terminal of the power supply 3 from the negative terminal. The four switches S4 and the fourth resistor R4 are sequentially connected in series. A first diode D1, a first resistor R1, and a capacitor 9 are sequentially connected in series between the first switch S1 and the third switch S3 and between the second switch S2 and the fourth switch S4. A second diode D2 and a second resistor R2 are sequentially connected in series between the first resistor R1 and the capacitor 9 and between the first switch S1 and the third switch S3. That is, the first diode D1 and the first resistor R1, and the second diode D2 and the second resistor R2 are connected in parallel. A fifth switch S5 is connected between both terminals of the second resistor R2 in parallel with the second resistor R2. The first diode D1 rectifies in the direction from the positive side to the negative side, and the second diode D2 rectifies in the direction opposite to the first diode D1.
[0013]
A third resistor R3 is connected between the third switch S3 and the fourth resistor R4 in series with the third switch S3 and the fourth resistor R4, and is connected between the third switch S3 and the third resistor R3. Is connected to the microcomputer 11 via an analog / digital conversion port of the microcomputer 11, that is, an A / D port. Further, a portion between the third resistor R3 and the fourth resistor R4 is grounded to the ground potential section 7.
[0014]
Accordingly, the first switching means for connecting the capacitor 9 in series with the power supply 3 for the first set time is a first switch S1, a second switch S2, a switching control circuit (not shown), and the like. A second switching means for connecting a capacitor 9 in series between the terminal and the ground potential unit 7 for a second set time includes a first switch S1, a fourth switch S4, a switching control circuit (not shown), and the like. The third switching means for connecting a capacitor 9 in series between the ground potential unit 7 and the negative terminal of the power supply 3 for a second set time includes a second switch S2, a third switch S3, and not shown. In a switching control circuit or the like, the fourth switching means is formed by a third switch S3, a fourth switch S4, a switching control circuit (not shown), and the like. The capacitor 9 has a relatively high capacitance of, for example, several μF, and the first resistor R1 and the second resistor R2 have a relatively high resistance of, for example, several hundred kΩ. .
[0015]
The operation of the insulation detecting device having such a configuration and the features of the present invention will be described. When the insulation detection device 1 starts detecting the insulation state as shown in FIGS. 2 and 3, a switching control circuit (not shown) sets the first switch S1 and the second switch S2 to a first set time. The circuit is closed for one closing time T1 (step 101). That is, the first switching means forms a circuit for connecting the capacitor 9 in series to the power supply 3 without passing through the ground potential unit 7, and the capacitor 9 is charged during the first closed time T1, and the capacitor 9 is charged. 9, the voltage VC between both terminals increases. The first closing time T1 is set to a time shorter than the time required to completely charge the capacitor 9, and is, for example, 1/5 to 1 to 1 times the time required to completely charge the capacitor 9. / 10, and the first closing time T1 is selected according to the required measurement error range of the insulation resistance.
[0016]
In step 101, when the first closing time T1 elapses, the first switch S1 and the second switch S2 are opened or cut off, and after the lapse of a predetermined time tw1 shorter than the first closing time T1, the third switch S3 and the fourth switch S4. Is closed (step 103). That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. After a lapse of a predetermined time tw2 shorter than the first closing time T1 from the closing of the third switch S3 and the fourth switch S4, the microcomputer 11 outputs the A / D conversion data, that is, both ends of the capacitor 9, through the A / D port. The voltage VC between the slaves is read (step 105). From the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detected voltage V0, the estimated power supply voltage V0s is calculated from the following equation (1) (step 107).
V0 = V0s (1−EXP (−T1 / C · R1)) (1)
In the equation (1), T1 is the closing time of the first switch S1 and the second switch S2, C is the capacitance of the capacitor 9, and R1 is the resistance value of the first resistor R1.
[0017]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 105, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, and the time required for discharging from the capacitor 9 is reduced. After the fifth switch S5 is closed and a predetermined time td1 shorter than the first closed time T1 has elapsed, the fifth switch S5 is opened or shut off, and then the microcomputer 11 outputs the A / D converted data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 109).
[0018]
When it is confirmed in step 109 that the voltage VC is 0 V, a switching control circuit (not shown) opens the third switch S3 and closes the first switch S1 after a lapse of a predetermined time tw1. Then, the first switch S1 and the fourth switch S4 are closed for a second closing time T2, which is a second set time (step 111). That is, a circuit in which the capacitor 9 is connected in series between the positive terminal of the power supply 3 and the ground potential unit 7 by the second switching means, that is, as shown in FIG. The switch S1, the first diode D1, the first resistor R1, the capacitor 9, the fourth switch S4, the fourth resistor R4, the ground potential unit 7, and the ground on the negative terminal side assumed at a position shown by a dotted line in FIG. A circuit is formed in which the short-circuit resistance Rn and the negative-side main circuit wiring 5b are sequentially connected in series to the power supply 3. Thereby, the capacitor 9 is charged during the second closing time T2, and as shown in FIG. 3, the voltage VC between both terminals of the capacitor 9 increases according to the value of the ground fault resistance Rn. The second closing time T2, which is the second set time, is also shorter than the time required to completely charge the capacitor 9, similarly to the first closing time T1, and is shorter than the predetermined times tw1, tw2, and td1. Set for a long time.
[0019]
When the second closing time T2 elapses in step 111, as shown in FIGS. 2 and 3, the first switch S1 is opened or shut off, and after the elapse of a predetermined time tw1, the third switch S3 is closed and the third switch S3 is opened. And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a lapse of a predetermined time tw2 since the third switch S3 is closed, the microcomputer 11 reads the A / D conversion data via the A / D port, that is, the voltage VC between both terminals of the capacitor 9 (step 113). . Based on the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detection voltage VCN, the insulation resistance with respect to the vehicle body or the like which becomes the ground potential portion 7 on the negative terminal side of the power supply 3 from the following equation (2), that is, the ground on the negative terminal side The short-circuit resistance Rn is calculated (step 115).
Rn = -R1-T2 / C.ln (1-VCN / V0s) (2)
In the equation (2), T2 is the closing time of the first switch S1 and the fourth switch S4, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and V0s is the power supply voltage estimated in step 107. is there.
[0020]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 115, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, and the time required for discharging from the capacitor 9 is reduced. After the fifth switch S5 is closed and a predetermined time td2 shorter than the second closing time T2 has elapsed, the fifth switch S5 is opened or shut off, and then the microcomputer 11 outputs the A / D converted data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 117).
[0021]
When it is confirmed in step 117 that the voltage VC is 0 V, a switching control circuit (not shown) opens the fourth switch S4, and after a predetermined time tw1, closes the second switch S2. Then, the second switch S2 and the third switch S3 are closed for a second closing time T2, which is a second set time (step 119). That is, a circuit in which the capacitor 9 is connected in series between the ground potential section 7 and the negative terminal of the power supply 3 by the third switching means, that is, as shown in FIG. , A ground fault resistor Rp on the positive terminal side assumed at a position indicated by a dotted line, a ground potential portion 7, a third resistor R3, a third switch S3, a first diode D1, a first resistor R1, a capacitor 9, and a second A circuit is formed in which the switch S2 and the negative-side main circuit wiring 5b are sequentially connected in series to the power supply 3. Thereby, the capacitor 9 is charged during the second closing time T2, and as shown in FIG. 3, the voltage VC between both terminals of the capacitor 9 increases according to the value of the ground fault resistance Rp.
[0022]
When the second closing time T2 elapses in step 119, as shown in FIGS. 2 and 3, the second switch S2 is opened or cut off, and after the elapse of a predetermined time tw1, the fourth switch S4 is closed and the third switch S3 is opened. And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a predetermined time tw2 has elapsed since the fourth switch S4 was closed, the microcomputer 11 reads the A / D conversion data via the A / D port, that is, the voltage VC between both terminals of the capacitor 9 (step 121). . Based on the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detection voltage VCP, the insulation resistance to the vehicle body or the like which becomes the ground potential portion 7 on the positive terminal side of the power supply 3 from the following equation (3), that is, the ground on the positive terminal side The short-circuit resistance Rp is calculated (step 123).
Rp = -R1-T2 / C.ln (1-VCP / V0s) (3)
In the equation (3), T2 is the closing time of the second switch S2 and the third switch S3, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and V0s is the power supply voltage estimated in step 107. is there.
[0023]
On the other hand, the switching control circuit (not shown) closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed after detecting the voltage VC between both terminals of the capacitor 9 in step 123. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, and the time required for discharging from the capacitor 9 is reduced. After a lapse of a predetermined time td2 after closing the fifth switch S5, and after opening or shutting off the fifth switch S5, the microcomputer 11 outputs A / D conversion data, that is, between the two terminals of the capacitor 9 through the A / D port. The voltage VC is read (step 125). Then, when it is confirmed in step 125 that the voltage VC is 0 V, one insulation state detection cycle ends. In addition, while detecting the insulation state, the insulation state detection cycle from step 101 to step 125 is repeated.
[0024]
The microcomputer 11 determines the insulation state from the value of the ground fault resistance Rp on the positive terminal side of the power supply 3 and the value of the ground fault resistance Rn on the negative terminal side obtained in one insulation state detection cycle. For example, the ground fault resistance Rp on the positive terminal side of the power supply 3 is compared with a predetermined reference resistance value. If the ground fault resistance Rp is equal to or less than the reference resistance value, insulation failure has occurred. Is determined.
[0025]
By the way, as can be seen from the equations (2) and (3), if the capacitance C of the capacitor 9 and the resistance value R1 of the first resistor R1 vary due to a difference between products or a temperature change, the positive terminal side of the power supply 3 is changed. The measurement accuracy of the ground fault resistance Rp and the ground fault resistance Rn on the negative terminal side is affected, and the accuracy of the detected ground fault resistances Rp and Rn is reduced. Therefore, the detection accuracy of the insulation state is reduced. In particular, since the capacitor 9 needs to have a relatively large value of several μF in consideration of the stray capacitance, for example, if there is a variation of about ± 5% in the difference between products, it is ± 10% in consideration of a temperature change. % In some cases, and such variation in the capacitance of the capacitor 9 reduces the detection accuracy of the insulation state. In addition, variations caused by changes in component constants due to changes over time also lower the detection accuracy of the insulation state.
[0026]
On the other hand, in the insulation detection device 1 of the present embodiment, the first switch S1 and the second switch S2 in the first stage of the insulation detection cycle are set to the first switch S1 and the second switch S2, which are shorter than the time required to completely charge the capacitor 9. By closing the circuit for the closing time T1, the power supply voltage of the power supply 3 is estimated. When charging the capacitor 9 by closing the first switch S1 and the second switch S2 for a short time, when charging is performed with a time constant C · R1 determined by the actual capacitance of the capacitor 9 and the resistance value of the resistor R1. The estimated power supply voltage V0s is not an actual power supply voltage of the power supply 3 but a value including an error between the capacitance and resistance value of the capacitor 9 and the resistor R1, that is, a value including variation. . Then, the estimated power supply voltage V0s including the variation is used in the calculation of the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side performed in steps 115 and 123, so that the capacitance and the resistance of the capacitor 9 are obtained. Corrections are made for variations in the resistance value of R1, and the actual values of the positive terminal side ground fault resistance Rp and the negative terminal side ground fault resistance Rn, and the calculated positive terminal side ground fault resistance Rp and negative An error with the value of the terminal-side ground fault resistance Rn can be reduced. Therefore, the detection accuracy of the insulation state can be improved.
[0027]
The values of the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side measured by the insulation detection device 1 of the present embodiment and the actual ground fault resistance Rp on the positive terminal side and the actual ground fault resistance Rp on the negative terminal side are measured. FIG. 4 shows the result of calculating the error from the value of the ground fault resistance Rn on the assumption that the capacitor 9 having a certain predetermined standard capacity and the first resistor R1 having a certain predetermined standard resistance value are used. The capacitor 9 has a capacitance variation of about ± 10% in consideration of the difference between products and the temperature change, and the first resistor R1 has a capacitance variation of about ± 2% in consideration of the difference between products and the temperature change. It is assumed that there is. In FIG. 4, the V0 measurement time means the first closing time. Therefore, in FIG. 4, the measurement is performed when the first closing time T1 is t seconds, 2t seconds, and 3t seconds, where t <2t <3t. The error is shown. FIG. 4 is a graph in which the calculation results are plotted with the vertical axis representing the detection accuracy, that is, the detection error, and the horizontal axis representing the ground fault resistance value.
[0028]
As can be seen from FIG. 4, the case where detection is performed by the insulation detection device 1 of the present embodiment, that is, the case where correction is performed, is greater than the case where detection is performed by the conventional insulation detection device, that is, without correction. The measurement error is reduced with respect to the value. Further, the degree of reduction of the measurement error varies depending on the setting of the V0 measurement time, that is, the setting of the first closing time T1, and when the first closing time T1 is t seconds, the error increases as the ground fault resistance decreases. The error decreases as the resistance increases. When the first closing time T1 is 2t seconds, when the ground fault resistance is large, the error becomes larger than when the first closing time T1 is t seconds, but the error becomes smaller on average over the short-circuit resistance in each place. I have. Even when the first closing time T1 is 3 t seconds, the error is smaller on average across the short-circuit resistance, but the error is larger than when the first closing time T1 is 2 t seconds.
[0029]
Therefore, when the value of the ground fault resistance for determining the insulation failure is set to a relatively large value, the first closing time T1 is preferably set to t seconds. When the setting is a relatively small value, the first closing time T1 is preferably set to 2t seconds. As described above, it is preferable that the first closing time T1, that is, the first set time, is selected such that the measurement error becomes small around the value of the ground fault resistance for determining the insulation failure. For example, if the value of the ground fault resistance for judging insulation failure is set to RΩ in FIG. 4, it is preferable to select 2t seconds as the first closing time T1, and at this time, ± 10 %, Whereas the insulation detection device 1 of the present embodiment has a measurement error of ± 2% or less, and the insulation state detection accuracy can be improved.
[0030]
Furthermore, in the insulation detection device 1 of the present embodiment, it is possible to reduce the influence on the detection of the insulation state due to the variation in the capacitance of the capacitor 9 or the like. Therefore, an increase in cost for improving insulation detection accuracy can be suppressed.
[0031]
Furthermore, the insulation detecting device 1 of the present embodiment includes bypass means including the fifth switch S5 that forms a path that bypasses the second resistor R2 when the circuit is closed. By closing the fifth switch S5 after the detection of the voltage, the discharge time from the capacitor 9 can be shortened. Therefore, the time required for one cycle for insulation detection can be reduced, the number of insulation detections per unit time can be increased, and the accuracy of insulation detection can be further improved.
[0032]
Note that the bypass unit including the fifth switch S5 is not limited to the configuration of the present embodiment, and the bypass unit includes a ground potential unit 7 between the second diode D2 and the second resistor R2 as shown in FIG. Alternatively, a configuration may be adopted in which a fifth switch S5 and a fifth resistor R5 having a lower resistance than the second resistor R2 are connected in series. Further, when there is no need to shorten the time required for one cycle for insulation detection or the like, a configuration without the bypass unit including the fifth switch S5 can be adopted.
[0033]
Further, in the present embodiment, the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side are individually calculated, so that a portion having insulation failure can be detected. However, in the case where only the occurrence of insulation failure is determined without detecting the location of insulation failure, for example, the ground fault resistance Rp on the positive terminal side and the negative terminal on the basis of the estimated power supply voltage V0s and the detection voltages VCP, VCN, etc. Another formula for calculating a ground fault resistance value or the like representing the ground fault resistance Rn on the side can also be used.
[0034]
In addition, the present invention is not limited to the circuit configuration shown in the present embodiment, and a capacitor is connected in series to a DC power supply whose positive terminal side and negative terminal side wiring are insulated from the ground potential portion for a first set time. First switching means, second switching means for connecting the capacitor in series between the positive terminal of the power supply and the ground potential section for a second set time, and between the negative terminal of the power supply and the ground potential section A third switching means for connecting a capacitor in series for a second set time, and a detecting means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off. If it has the fourth switching means and the like, it can be applied to insulation detection devices having various circuit configurations.
[0035]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the detection precision of an insulation state can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an embodiment of an insulation detection device to which the present invention is applied.
FIG. 2 is a flowchart showing an operation of calculating an insulation resistance in one embodiment of an insulation detection device to which the present invention is applied.
FIG. 3 is a time chart showing a charge / discharge state of a capacitor and a voltage reading timing with respect to an operation of each switch unit.
FIG. 4 is a diagram illustrating a detection error of an insulation resistance value detected during a measurement time of each power supply voltage with respect to the insulation resistance value.
FIG. 5 is a diagram showing a modification of the insulation detection device to which the present invention is applied.
[Explanation of symbols]
1 Insulation detection device
3 power supply
5a Positive main circuit wiring
5b Negative main circuit wiring
7 Ground potential section
9 Capacitor
11 microcomputer
S1 First switch
S2 Second switch
S3 3rd switch
S4 4th switch
Rp Positive terminal side ground fault resistance
Rn Negative terminal side ground fault resistance

Claims (3)

First switching in which a capacitor is connected in series to a DC power supply whose wiring on the positive terminal side and the negative terminal side are insulated from the ground potential portion for a first set time shorter than the time when the capacitor is completely charged Means,
Second switching means for connecting the capacitor in series between a positive terminal of the power supply and the ground potential portion for a second set time;
Third switching means for connecting the capacitor in series between the ground potential section and the negative terminal of the power supply for a second set time;
Fourth switching means for connecting a detecting means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off;
Estimating a power supply voltage of the power supply based on a voltage detected by the detecting means after the first switching means is cut off, and detecting the estimated power supply voltage and the detecting means after the second and third switching means are cut off Calculating means for calculating an insulation resistance of the power supply with respect to the ground potential portion based on each of the detection voltages obtained in the step (a). The first switching unit includes a first switch unit connected to a positive terminal of the power supply, and a second switch unit connected to a negative terminal of the power supply, wherein the third switching unit includes: The second switch unit; and a third switch unit connected in series to the first switch, wherein the second switching unit includes the first switch unit and the second switch unit. A fourth switch unit connected in series with the first switch unit, wherein the fourth switching unit includes the third switch unit and the fourth switch unit, and wherein the first switch unit and the fourth switch unit are connected to each other. 3, a first diode, a first resistor, and a first resistor that rectify in a direction from the positive side to the negative side between the second switch unit and the fourth switch unit. A capacitor is connected in series and the first A second diode and a second resistor, which rectify in the opposite direction to the first diode, are connected in series with the diode and the first resistor in parallel, and the detecting means includes: The insulation detection device according to claim 1, wherein the insulation detection device is connected between the fourth switch unit and the detection unit and the fourth switch unit are grounded to the ground potential unit. . 3. The insulation detecting device according to claim 1, further comprising a bypass unit including a fifth switch unit that forms a path that bypasses the second resistor when the circuit is closed.

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