Insulation resistance detection device and fault detection method

Abstract

To provide an insulation resistance detector capable of detecting a failure of a measurement unit that measures the voltage applied to a detection resistor, and a fault detection method.SOLUTION: An insulation resistance detector in an embodiment includes a measurement unit and a control unit. The measurement unit includes: a first switch connected to the positive side of the battery; a second switch connected to the negative side of the battery; a detection resistor; and a measurement circuit that measures the voltage applied to the detection resistor. The control unit is configured to turn on one switch out of the first switch and the second switch and to turn off the other switch to form a series connection circuit of the battery and the insulation resistance of the battery and the detection resistor, and to calculate the insulation resistance based on the voltage measured by the measurement circuit. The control unit is configured to turn on the first switch and the second switch to form a series connection circuit with the battery and the detection resistor and to detect a failure of the measurement unit based on the voltage measured by the measurement circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosed embodiments relate to an insulation resistance detection device and a fault detection method. [Background technology]

[0002] There is an insulation resistance detection device that detects the insulation resistance of a battery, and that includes a measurement unit that includes a first switch connected to the positive electrode side of the battery, a second switch connected to the negative electrode side, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor (see, for example, Patent Document 1).

[0003] The insulation resistance detection device turns on one of the first and second switches and turns off the other switch to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and detects the battery's insulation resistance based on the voltage measured by the measurement circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-66090 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the measurement unit that measures the voltage applied to the detection resistor breaks down, the insulation resistance detection device will not be able to detect the insulation resistance of the battery.

[0006] One aspect of the embodiment has been made in consideration of the above, and aims to provide an insulation resistance detection device and a fault detection method that can detect a fault in a measurement unit that measures the voltage applied to a detection resistor. [Means for solving the problem]

[0007] An insulation resistance detection device according to one aspect of the embodiment includes a measurement unit and a control unit. The measurement unit includes a first switch connected to the positive terminal of a battery, a second switch connected to the negative terminal of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor. The control unit turns on one of the first and second switches and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit. The control unit turns on the first and second switches to form the series connection circuit of the battery and the detection resistor, and detects a failure of the measurement unit based on the voltage measured by the measurement circuit. [Effects of the Invention]

[0008] Advantageous Effects of Invention An insulation resistance detecting device and a fault detection method according to an aspect of the embodiment have the advantage of being able to detect a fault in a measuring unit that measures a voltage applied to a detection resistor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing an example of the configuration of an insulation resistance detecting device according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of the operation of the insulation resistance detecting device according to the embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing an example of the operation of the insulation resistance detecting device according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of the operation of the insulation resistance detecting device according to the embodiment. [Figure 5] FIG. 5 is an explanatory diagram illustrating an example of the configuration of a measurement unit according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of processing executed by the control unit according to the embodiment. [Figure 7] FIG. 7 is a flowchart illustrating an example of processing executed by the control unit according to the embodiment. [Figure 8]FIG. 8 is an explanatory diagram showing an example of the configuration of an insulation resistance detecting device according to a modified example of the embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of processing executed by a control unit according to a modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of an insulation resistance detection device and a fault detection method will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments. The insulation resistance detection device according to the embodiment is mounted on a vehicle that runs using the driving force of an electric motor, such as an electric vehicle or a hybrid vehicle.

[0011] The battery that supplies power to the vehicle's electric motor is a high-voltage secondary battery (e.g., lithium-ion battery) that outputs a high voltage of several hundred volts or more. Such batteries pose a risk of electric shock if they leak electricity.

[0012] For this reason, batteries are housed in an insulating case or the like to be electrically insulated from the outside. When new, a battery case has a resistance value of several MΩ, meaning it barely conducts electricity. However, the insulating performance of a battery case can deteriorate over time, for example. For this reason, an insulation resistance detector detects and monitors the insulation resistance of the case, which is the insulation resistance of the battery.

[0013] [1. Example of insulation detection device configuration] Fig. 1 is an explanatory diagram showing an example of the configuration of an insulation resistance detecting device 1 according to an embodiment. As shown in Fig. 1, the insulation resistance detecting device 1 is connected to a battery 10 via a high-voltage side insulation resistor 12 and a low-voltage side insulation resistor 13. The battery 10 includes a plurality of battery cells 11 connected in series.

[0014] The high-voltage side insulation resistor 12 and the low-voltage side insulation resistor 13 are not resistive elements but are part of the insulating case that houses the above-mentioned battery 10. Note that the high-voltage side insulation resistor 12 and the low-voltage side insulation resistor 13 may be resistive elements provided to electrically insulate the battery 10 from the outside of the battery 10.

[0015] The insulation resistance detecting device 1 includes a measuring unit 2 and a control unit 3. The measuring unit 2 includes a first switch 21 connected to the positive electrode side of the battery 10, a second switch 22 connected to the negative electrode side of the battery 10, detection resistors 23 and 24, and a measuring circuit 25 that measures the voltage applied to the detection resistors 23 and 24. The measuring unit 2 further includes limiting resistors 26 and 27.

[0016] The control unit 3 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and various circuits. The control unit 3 controls the first switch 21 and the second switch 22 by the CPU executing a program stored in the ROM using the RAM as a working area.

[0017] The control unit 3 turns on one of the first switch 21 and the second switch 22 and turns off the other switch to form a series connection circuit of the battery 10, the insulation resistances 12 and 13 of the battery 10, and the detection resistances 23 and 24, and calculates the insulation resistances 12 and 13 based on the voltage measured by the measurement circuit 25.

[0018] The control unit 3 may be partially or entirely configured with hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0019] [2. Example of insulation resistance detection device operation] Next, an example of the operation of the insulation resistance detecting device 1 will be described with reference to Figures 2 to 4. Figures 2 and 3 are explanatory diagrams showing an example of the operation of the insulation resistance detecting device 1 according to the embodiment.

[0020] [2.1. Operation when insulation resistance is detected] 2, when detecting the resistance value of low-voltage side insulation resistor 13, control unit 3 turns on first switch 21 and turns off second switch 22 to form a first series connection circuit R1 of battery 10, limiting resistor 26, detection resistor 23, and low-voltage side insulation resistor 13. Then, measurement circuit 25 measures the voltage applied to detection resistor 23 (voltage difference across detection resistor 23) and outputs the measurement result to control unit 3.

[0021] At this time, if the resistance value of the low-voltage side insulation resistor 13 is sufficiently high, almost no current flows through the first series-connected circuit R1. In this case, the voltage measured by the measurement circuit 25 will be close to 0 V. In contrast, if the resistance value of the low-voltage side insulation resistor 13 is low, current will flow through the first series-connected circuit R1. The lower the resistance of the low-voltage side insulation resistor 13, the higher the voltage measured by the measurement circuit 25 will be.

[0022] For this reason, the control unit 3 calculates the resistance value of the low-voltage side insulation resistor 13 based on the voltage measured by the measurement circuit 25, and determines that there is no leakage if the calculated resistance value is equal to or greater than a predetermined resistance value. Furthermore, the control unit 3 determines that there is leakage if the calculated resistance value is less than the predetermined resistance value. If the control unit 3 determines that there is leakage, it warns the user to that effect using a warning device such as a warning light.

[0023] 3, when detecting the resistance value of the high-voltage side insulation resistor 12, the control unit 3 turns off the first switch 21 and turns on the second switch 22 to form a second series connection circuit R2 of the battery 10, the high-voltage side insulation resistor 12, the detection resistor 24, and the limiting resistor 27. The measurement circuit 25 then measures the voltage applied to the detection resistor 24 (the voltage difference across the detection resistor 24) and outputs the measurement result to the control unit 3.

[0024] At this time, if the resistance value of the high-voltage side insulation resistor 12 is sufficiently high, almost no current flows through the second series-connected circuit R2. In this case, the voltage measured by the measurement circuit 25 will be close to 0 V. In contrast, if the resistance value of the high-voltage side insulation resistor 12 is low, current will flow through the second series-connected circuit R2. The lower the resistance of the high-voltage side insulation resistor 12, the higher the voltage measured by the measurement circuit 25 will be.

[0025] For this reason, the control unit 3 calculates the resistance value of the high-voltage side insulation resistor 12 based on the voltage measured by the measurement circuit 25, and determines that there is no leakage if the calculated resistance value is equal to or greater than a predetermined resistance value. Furthermore, the control unit 3 determines that there is leakage if the calculated resistance value is less than the predetermined resistance value. If the control unit 3 determines that there is leakage, it warns the user to that effect using a warning device such as a warning light.

[0026] In this way, the insulation resistance detecting device 1 calculates the resistance values ​​of the insulation resistors 12 and 13 based on the voltages applied to the detection resistors 23 and 24 measured by the measuring unit 2, and therefore, if the measuring unit 2 fails, it will be unable to calculate the resistance values ​​of the insulation resistors 12 and 13. Therefore, the control unit 3 of the insulation resistance detecting device 1 according to this embodiment checks whether the measuring unit 2 has failed before detecting the insulation resistors 12 and 13.

[0027] [2.2. Operation during fault detection of the measuring unit] When inspecting the measurement unit 2, as shown in Figure 4, the control unit 3 turns on the first switch 21 and the second switch 22 to form a series connection circuit of the battery 10 and the detection resistors 23 and 24, and detects a fault in the measurement unit 2 based on the voltage measured by the measurement circuit 25.

[0028] For example, when the first switch 21 and the second switch 22 are turned on when the measurement unit 2 is not malfunctioning, the measurement unit 2 outputs a voltage value corresponding to the voltage of the battery 10 to the control unit 3 as the measurement result.

[0029] Specifically, if the voltage of the battery 10 is V and the resistance values ​​of the detection resistors 23, 24 and the limiting resistors 26, 27 are R23, R24, R26, and R27, respectively, the measurement unit 2 outputs to the control unit 3 the voltage value obtained by dividing the voltage V of the battery 10 by the detection resistors 23 and 24, which is V × (R23 + R24) / (R23 + R24 + R26 + R27).

[0030] In contrast, when the measurement unit 2 is faulty and the first switch 21 and the second switch 22 are turned on, the measurement unit 2 outputs a voltage value different from the voltage value corresponding to the voltage of the battery 10 to the control unit 3 as the measurement result.

[0031] Therefore, when the control unit 3 turns on the first switch 21 and the second switch 22, if a voltage value corresponding to the voltage of the battery 10 is input from the measurement unit 2, the control unit 3 can determine that the measurement unit 2 is not malfunctioning.

[0032] Furthermore, when the control unit 3 turns on the first switch 21 and the second switch 22, if a voltage value different from the voltage value corresponding to the voltage of the battery 10 is input from the measurement unit 2, the control unit 3 can determine that the measurement unit 2 is faulty.

[0033] In this way, the control unit 3 can detect a fault in the measurement unit 2 simply by simultaneously turning on the first switch 21 and the second switch 22, which are alternately turned on and off to detect the insulation resistances 12 and 13, and detecting the measurement results input from the measurement unit 2 at that time.

[0034] [3. Measurement unit configuration example] Next, with reference to Fig. 5, a specific example of the configuration of the measurement unit 2 will be described, along with the operation of the control unit 3 and specific examples of parts of the measurement unit 2 that may malfunction. Fig. 5 is an explanatory diagram of a configuration example of the measurement unit 2 according to an embodiment. Note that, among the configuration example shown in Fig. 5, components that are the same as those shown in Fig. 1 are assigned the same reference numerals as those shown in Fig. 1, and redundant explanations will be omitted.

[0035] 5, the limiting resistors 26 and 27 of the measurement unit 2 are each composed of a plurality of resistor elements connected in series. The measurement unit 2 also includes capacitors 51 and 52 connected in parallel to the detection resistors 23 and 24, respectively. The capacitors 51 and 52 smooth out noise components contained in the voltages applied to the detection resistors 23 and 24, respectively.

[0036] Measurement circuit 25 also includes a differential amplifier 61, a resistor 53 between first switch 21 and differential amplifier 61, and a resistor 54 between second switch 22 and differential amplifier 61. Measurement circuit 25 also includes capacitors 55 connected between ground and a wiring that connects resistor 53 and differential amplifier 61, and between ground and a wiring that connects resistor 53 and differential amplifier 61. Capacitor 55 smoothes noise components contained in the voltage input to measurement circuit 25.

[0037] An offset voltage generator (offset 66) that applies an offset voltage via resistor 67 is connected to the positive input of differential amplifier 61. The output of differential amplifier 61 is fed back to the negative input of differential amplifier 61 via resistor 62. The output of differential amplifier 61 is also connected to control unit 3 via a CR filter formed by resistors 63 and 64 and capacitor 65.

[0038] The control unit 3 is connected to a battery monitoring device 4, which is an example of an external device. The battery monitoring device 4 is a device that monitors the state of the battery 10, including the voltage, SOC (State Of Charge), etc. When detecting a failure in the measurement unit 2, the control unit 3 receives and acquires the voltage of the battery 10 from the battery monitoring device 4.

[0039] Then, the control unit 3 turns on the first switch 21 and the second switch 22, and compares the measurement result of the voltage of the battery 10 input from the measurement unit 2 with the voltage of the battery 10 input from the battery monitoring device 4. If the measurement result of the measurement unit 2, that is, the voltage of the battery 10 calculated backward from the voltage applied to the detection resistors 23 and 24, and the voltage of the battery 10 obtained from the battery monitoring device 4 are approximately equal, the control unit 3 determines that the measurement unit 2 is not faulty. "Approximately equal" includes cases where they match perfectly, and cases where a slight difference can be judged to be normal.

[0040] In contrast, for example, if the actual voltage of the battery 10 is several hundred volts and the measurement result of the measurement unit 2 is 0 volts, there is a possibility that there is an open circuit failure in the limiting resistors 26, 27 and resistors 53, 54, 64, an open circuit failure in the first switch 21 and second switch 22, or a short circuit failure in the resistor 63 and capacitors 55, 65. Furthermore, for example, if there is a large difference between the voltage of the battery 10 and the measurement result of the measurement unit 2, there is a possibility that the gain of the differential amplifier 61 is abnormal.

[0041] Therefore, the control unit 3 determines that the measurement unit 2 is faulty when the difference between the measurement result of the measurement unit 2, i.e., the voltage of the battery 10 calculated from the voltage applied to the detection resistors 23 and 24, and the voltage of the battery 10 obtained from the battery monitoring device 4, exceeds a predetermined threshold value.

[0042] In this way, the control unit 3 can detect a failure of the measurement unit 2 by simultaneously turning on the first switch 21 and the second switch 22 and comparing the measurement result input from the measurement unit 2 at that time with the voltage of the battery 10 obtained from the battery monitoring device 4.

[0043] In the above example, a fault in the measurement unit 2 is determined by comparing the voltage of the battery 10 obtained from the measurement result of the measurement unit 2 with the voltage of the battery 10 obtained from the battery monitoring device 4. Alternatively, the voltage of the battery 10 obtained from the battery monitoring device 4 may be divided by the formula (R23+R24) / (R23+R24+R26+R27) to obtain the voltage applied to the detection resistors 23 and 24, and compared with the measurement result of the measurement unit 2. In this case, the control unit 3 determines that there is no fault in the measurement unit 2 if the voltage obtained by dividing the voltage of the battery 10 received from the battery monitoring device 4 by a predetermined voltage division ratio is approximately equal to the voltage measured by the measurement circuit 25.

[0044] [4. Processing performed by the control unit] Next, the processing executed by the control unit 3 of the insulation resistance detecting device 1 will be described with reference to Fig. 6 and Fig. 7. Fig. 6 and Fig. 7 are flowcharts showing an example of the processing executed by the control unit 3 according to the embodiment. The control unit 3 sequentially and repeatedly executes the processing shown in Fig. 6 and Fig. 7 while the vehicle power supply is on.

[0045] 6, the control unit 3 first turns on both the first switch 21 and the second switch 22 (step S101). Then, the control unit 3 determines whether the difference between the voltage measurement result by the measurement unit 2 and the voltage of the battery 10 acquired from the battery monitoring device 4 is equal to or less than a threshold value (step S102).

[0046] If the control unit 3 determines that the difference between the measurement result and the voltage of the battery 10 is equal to or less than the threshold value (step S102, Yes), it determines that there is no malfunction in the measurement unit 2 (step S103). If the control unit 3 determines that the difference between the measurement result by the measurement unit 2 and the voltage of the battery 10 is not equal to or less than the threshold value (step S102, No), it determines that there is a malfunction in the measurement unit 2 (step S104) and issues a warning to the user (step S105).

[0047] Thereafter, the control unit 3 starts the process shown in Fig. 7. Specifically, as shown in Fig. 7, the control unit 3 first turns on the first switch 21 and turns off the second switch 22 to form the first series connection circuit R1 (step S201). Then, the control unit 3 calculates the insulation resistance value of the insulation resistor 13 from the voltage measured by the measurement unit 2 (step S202), and determines whether the insulation resistance value is equal to or greater than a predetermined resistance value that does not pose a problem in the insulation of the battery 10 (step S203).

[0048] If the control unit 3 determines that the insulation resistance value is equal to or greater than a predetermined resistance value (Yes in step S203), it determines that there is no leakage (step S204). Thereafter, the control unit 3 turns off the first switch 21 and turns on the second switch 22 to form the second series connection circuit R2 (step S205).

[0049] Then, the control unit 3 calculates the insulation resistance value of the insulation resistor 12 from the voltage measured by the measurement unit 2 (step S206), and determines whether the insulation resistance value is equal to or greater than a predetermined resistance value that does not pose a problem in the insulation of the battery 10 (step S207).

[0050] If the control unit 3 determines that the insulation resistance value is equal to or greater than a predetermined resistance value (step S207, Yes), it determines that there is no leakage (step S208), terminates the processing, and starts the processing again from step S101 shown in FIG. 6.

[0051] Furthermore, if the control unit 3 determines in step S203 or step S207 that the insulation resistance value is not equal to or greater than the predetermined resistance value (step S203, No, or step S207, No), it determines that there is a leak (step S209). Thereafter, the control unit 3 warns the user that there is a leak (step S210), ends the process, and starts the process again from step S101 shown in FIG.

[0052] [5. Modified examples of insulation resistance detection device] Next, a modified example of the insulation resistance detecting device will be described with reference to Fig. 8. Fig. 8 is an explanatory diagram showing a configuration example of an insulation resistance detecting device 1a according to a modified example of the embodiment. Here, among the components shown in Fig. 8, the same components as those shown in Fig. 5 are assigned the same reference numerals as those shown in Fig. 5, and redundant description will be omitted.

[0053] 8, the insulation resistance detecting device 1a includes, in addition to the components included in the insulation resistance detecting device 1 shown in FIG. 5, a voltage generator 7 that can apply a known fixed voltage to the detection resistors 23 and 24. The voltage generator 7 includes a fixed voltage source 71 that outputs a fixed voltage, and a third switch 72.

[0054] When the control unit 3a of the insulation resistance detecting device 1a detects a fault in the measuring circuit 25, it turns off the first switch 21 and the second switch 22, forms a series connection circuit of the voltage generator 7 and the detecting resistors 23 and 24, and applies a fixed voltage to the detecting resistors 23 and 24. Then, the control unit 3a detects a fault in the measuring unit 2 based on the voltage measured by the measuring circuit 25.

[0055] Specifically, the control unit 3a turns off the first switch 21 and the second switch 22, turns on the third switch 72, and if the voltage measured by the measurement circuit 25 is a voltage corresponding to a known fixed voltage, i.e., approximately equal to the known fixed voltage, determines that there is no fault in the measurement circuit 25.

[0056] At this time, the control unit 3a estimates the voltage applied to the detection resistors 23 and 24 from the voltage measured by the measurement circuit 25, and if the difference between the estimated voltage and a known fixed voltage is less than a threshold value, it determines that there is no fault in the measurement circuit 25.

[0057] Furthermore, if the difference between the estimated voltage and the known fixed voltage is equal to or greater than a threshold, the control unit 3a determines that there is a fault in the measurement circuit 25. This allows the control unit 3a to determine whether or not there is a fault in the measurement circuit 25 in the measurement unit 2.

[0058] [6. Processing Executed by the Control Unit According to the Modification] Next, processing executed by the control unit 3a according to the modified example will be described with reference to Fig. 9. Fig. 9 is a flowchart showing processing executed by the control unit 3a according to the modified example of the embodiment.

[0059] Of the processes shown in Figures 6 and 7, the control unit 3a performs the process shown in Figure 9 instead of the process shown in Figure 6. That is, the control unit 3a repeatedly executes the process shown in Figure 9 and the process shown in Figure 7 in sequence.

[0060] 9, the control unit 3a first turns off both the first switch 21 and the second switch 22, and turns on the third switch 72 (step S301). After that, the control unit 3a executes the same processes as steps S102 to S105 shown in FIG.

[0061] By this process, the control unit 3a can determine in step S103 that there is no failure in the measurement circuit 25 of the measurement unit 2. Also, the control unit 3a can determine in step S104 that there is a failure in the measurement circuit 25 of the measurement unit 2.

[0062] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0063] 1. Insulation resistance detector 2. Measurement section 21 First Switch 22 Second Switch 23,24 Detect resistor 25 Measurement circuit 26,27 Limiting resistor 3. Control Unit 4 Battery monitoring device 51, 52, 55, 65 capacitors 53,54,62,63,64 Resistance 61 Differential Amplifier 66 offset 7. Voltage Generator 71 Fixed Voltage Source 72 The Third Switch 10 batteries 11 Battery Cells 12,13 Insulation resistance

Claims

1. a measurement unit including a first switch connected to the positive terminal side of the battery, a second switch connected to the negative terminal side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; Equipped with The control unit The first switch and the second switch are turned on to form a series connection circuit of the battery and the detection resistor, the voltage of the battery is calculated based on the voltage measured by the measurement circuit, and if the calculated battery voltage and the battery voltage received from the external device are approximately equal, it is determined that there is no failure in the measurement unit. Insulation resistance detection device.

2. A measurement unit including a first switch connected to the positive electrode side of a battery, a second switch connected to the negative electrode side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; Equipped with The control unit The first switch and the second switch are turned on to form a series circuit of the battery and the detection resistor, and when the voltage measured by the measurement circuit is approximately equal to the voltage obtained by dividing the battery voltage received from an external device at a predetermined voltage division ratio, it is determined that there is no failure in the measurement unit. Insulation resistance detection device.

3. a measurement unit including a first switch connected to the positive terminal side of the battery, a second switch connected to the negative terminal side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; a voltage generator capable of applying a fixed voltage to the sense resistor; Equipped with The control unit The first switch and the second switch are turned off, a series connection circuit of the voltage generator and the detection resistor is formed, the fixed voltage is applied to the detection resistor, and a failure of the measurement unit is detected based on the voltage measured by the measurement circuit. Insulation resistance detection device.

4. The control unit 4. The insulation resistance detecting device according to claim 3, wherein if the voltage measured by the measuring circuit is a voltage corresponding to the fixed voltage, it is determined that the measuring unit is not faulty.

5. a measurement unit including a first switch connected to the positive terminal side of the battery, a second switch connected to the negative terminal side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; The control unit of the insulation resistance detection device includes: The first switch and the second switch are turned on to form a series connection circuit of the battery and the detection resistor, the voltage of the battery is calculated based on the voltage measured by the measurement circuit, and if the calculated battery voltage and the battery voltage received from the external device are approximately equal, it is determined that there is no failure in the measurement unit. Fault detection methods.

6. A measurement unit including a first switch connected to the positive electrode side of a battery, a second switch connected to the negative electrode side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; The control unit of the insulation resistance detection device includes: The first switch and the second switch are turned on to form a series circuit of the battery and the detection resistor, and when the voltage measured by the measurement circuit is approximately equal to the voltage obtained by dividing the battery voltage received from an external device at a predetermined voltage division ratio, it is determined that there is no failure in the measurement unit. Fault detection methods.

7. a measurement unit including a first switch connected to the positive terminal side of the battery, a second switch connected to the negative terminal side of the battery, a detection resistor, and a measurement circuit that measures the voltage applied to the detection resistor; a control unit that turns on one of the first switch and the second switch and turns off the other to form a series connection circuit of the battery, the battery's insulation resistance, and the detection resistor, and calculates the insulation resistance based on the voltage measured by the measurement circuit; a voltage generator capable of applying a fixed voltage to the sense resistor; The control unit of the insulation resistance detection device includes: The first switch and the second switch are turned off, a series connection circuit of the voltage generator and the detection resistor is formed, the fixed voltage is applied to the detection resistor, and a failure of the measurement unit is detected based on the voltage measured by the measurement circuit. Fault detection methods.

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