Insulation resistance detection device and fault detection method

Abstract

This disclosure provides an insulation resistance detection device and a fault detection method, improving the detection accuracy of insulation resistance. The insulation resistance detection device according to the embodiment includes: a first switch connected to the positive terminal of a battery, a second switch connected to the negative terminal, a detection resistor, a capacitor connected in parallel with the detection resistor, a measuring unit for measuring the voltage of the detection resistor, and a control unit. The control unit performs a first measurement process to calculate the insulation resistance of the negative terminal of the battery based on a first voltage measured by turning on the first switch and turning off the second switch; a second measurement process to calculate the insulation resistance of the positive terminal of the battery based on a second voltage measured by turning off the first switch and turning on the second switch; a third measurement process to calculate an offset voltage based on a third voltage measured by turning off the first and second switches; and detects capacitor faults based on the change in the measured voltage after switching between the first and third measurement processes.

Description

Technical Field

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

[0002] There is an insulation resistance detection device for detecting the insulation resistance of a battery, which includes a measuring unit comprising: a first switch connected to the positive terminal of the battery, a second switch connected to the negative terminal, a detection resistor, and a measuring circuit for measuring the voltage applied to the detection resistor (see, for example, Patent Document 1).

[0003] An insulation resistance detection device turns on one of two switches (a first switch and a second switch) and turns off the other switch, thus forming a series circuit of a battery, the battery's insulation resistance, and a detection resistor. The battery's insulation resistance is detected based on the voltage measured by the measuring circuit. To stabilize the voltage applied to the detection resistor, it is desirable to connect a capacitor in parallel with the detection resistor.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-66090

[0007] -The problem the invention aims to solve-

[0008] However, if the insulation resistance testing device experiences an open-circuit fault in the capacitor, the voltage applied to the testing resistor becomes unstable, thus reducing the accuracy of the insulation resistance testing. Summary of the Invention

[0009] One embodiment is proposed in view of the above circumstances, and its purpose is to provide an insulation resistance detection device and a fault detection method that can improve the detection accuracy of insulation resistance.

[0010] -The problem the invention aims to solve-

[0011] One embodiment of the insulation resistance detection device includes: a measuring unit comprising 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, a capacitor connected in parallel with the detection resistor, and a measuring circuit for measuring the voltage applied to the detection resistor; and a control unit for controlling the first switch and the second switch. The control unit performs a first measurement process, in which the first switch is turned on and the second switch is turned off, forming a first series connection circuit of the battery, the detection resistor, and the insulation resistance of the negative terminal of the battery, and calculating the insulation resistance of the negative terminal based on a first voltage measured by the measuring circuit. The control unit performs a second measurement process, in which the first switch is turned off and the second switch is turned on, forming a second series connection circuit of the battery, the detection resistor, and the insulation resistance of the positive terminal of the battery, and calculating the insulation resistance of the positive terminal based on a second voltage measured by the measuring circuit. The control unit performs a third measurement process, in which the first switch and the second switch are turned off, and the offset voltage is calculated based on the third voltage measured by the measurement circuit.

[0012] The control unit detects the change in voltage measured by the measurement circuit after switching from one of the first measurement process, the second measurement process, and the third measurement process to another measurement process, and detects a fault in the capacitor based on the change in voltage.

[0013] -Invention Effects-

[0014] The insulation resistance detection device and fault detection method involved in one embodiment can achieve the effect of improving the detection accuracy of insulation resistance. Attached Figure Description

[0015] Figure 1 This is an explanatory diagram showing an example of the structure of the insulation resistance detection device according to the embodiment.

[0016] Figure 2 This is an explanatory diagram illustrating an example of the operation of the insulation resistance detection device according to the embodiment.

[0017] Figure 3 This is an explanatory diagram illustrating an example of the operation of the insulation resistance detection device according to the embodiment.

[0018] Figure 4 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0019] Figure 5 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0020] Figure 6 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0021] Figure 7 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0022] Figure 8 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0023] Figure 9 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0024] Figure 10 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0025] Figure 11 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0026] Figure 12 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0027] Figure 13 This is an explanatory diagram of the capacitor inspection method according to the embodiment.

[0028] Figure 14 This is a flowchart illustrating an example of the processing performed by the control unit involved in the implementation method.

[0029] Figure 15 This is a flowchart illustrating an example of the processing performed by the control unit involved in the implementation method.

[0030] Figure 16 This is a flowchart illustrating an example of the processing performed by the control unit involved in the implementation method.

[0031] Figure 17 This is a flowchart illustrating an example of the processing performed by the control unit involved in the implementation method.

[0032] Figure 18 This is an explanatory diagram of the measurement circuit involved in a variation of the implementation method.

[0033] Figure 19 This is an explanatory diagram of the measurement circuit involved in a variation of the implementation method.

[0034] Symbol Explanation

[0035] 1 Insulation resistance testing device

[0036] 2. Measurement Department

[0037] 21. Switch No. 1

[0038] 22. Switch No. 2

[0039] 23, 24 Detection resistors

[0040] 25, 25a Measurement Circuit

[0041] 251 Differential Amplifier

[0042] 252 First detector

[0043] 253 Second Detector

[0044] 26, 27 Limiting resistors

[0045] Capacitors 28 and 29

[0046] 30 Offset voltage application section

[0047] 3. Control Department

[0048] 10 batteries

[0049] 11 Battery cells

[0050] 12. Insulation resistance on the positive side

[0051] 13. Insulation resistance on the negative side. Detailed Implementation

[0052] Hereinafter, embodiments of the insulation resistance detection device and fault detection method will be described in detail with reference to the accompanying drawings. However, the invention is not limited to the embodiments shown below. The insulation resistance detection device according to the embodiments is mounted on vehicles that use the driving force of an electric motor, such as electric vehicles and hybrid vehicles.

[0053] The batteries that power the vehicle's motors use high-voltage secondary batteries (such as lithium-ion batteries) with an output voltage of several hundred volts or higher. If such batteries leak, there is a risk of electric shock.

[0054] Therefore, the battery is housed in an insulating casing to insulate it from external electricity. In a new product, the battery casing has a resistance of several MΩ, meaning it carries almost no current. However, the insulation performance of the battery casing deteriorates over time, for example, due to aging. Therefore, an insulation resistance detection device detects and monitors, for example, the insulation resistance of the casing, which serves as the insulation resistance of the battery.

[0055] [1. Example of the structure of an insulation testing device]

[0056] Figure 1 This is an explanatory diagram showing a structural example of the insulation resistance detection device 1 according to the embodiment. For example... Figure 1As shown, the insulation resistance detection device 1 is connected to the battery 10 via the insulation resistance 12 on the positive side and the insulation resistance 13 on the negative side. The battery 10 has a plurality of battery cells 11 connected in series.

[0057] The insulation resistance 12 on the positive electrode side and the insulation resistance 13 on the negative electrode side are not resistive elements, but are part of the insulating housing that houses the battery 10. Alternatively, the insulation resistance 12 on the positive electrode side and the insulation resistance 13 on the negative electrode side may be resistive elements provided to electrically insulate the battery 10 from the external environment of the battery 10.

[0058] The insulation resistance testing 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 terminal of the battery 10, a second switch 22 connected to the negative terminal of the battery 10, detection resistors 23 and 24, and a measuring circuit 25 for measuring the voltage applied to the detection resistors 23 and 24. Furthermore, the measuring unit 2 includes: limiting resistors 26 and 27, capacitors 28 and 29 connected in parallel with the detection resistors 23 and 24, and an offset voltage application unit 30. The offset voltage application unit 30 applies a predetermined offset voltage to the connection line connecting the first switch 21 and the measuring circuit 25.

[0059] The control unit 3 includes a microcomputer with a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various circuits. The control unit 3 uses the CPU to use the RAM as a working area and executes the program stored in the ROM to control the first switch 21 and the second switch 22.

[0060] Control unit 3 turns on one of the first switch 21 and the second switch 22 and turns off the other switch, thereby forming a series connection circuit between battery 10, the insulation resistances 12 and 13 of battery 10, and the detection resistors 23 and 24. The insulation resistances 12 and 13 are calculated based on the voltage measured by the measuring circuit 25. For a specific example of the operation of this control unit 3, see [reference needed]. Figure 2 as well as Figure 3 To be described later.

[0061] In addition, part or all of the control unit 3 may include hardware such as ASIC (Application Specific Integrated Circuit) and FPGA (Field Programmable Gate Array).

[0062] [2. Operation during insulation resistance testing]

[0063] Next, refer to Figure 2 as well as Figure 3 The operation of the insulation resistance testing device 1 during insulation resistance testing is explained. Figure 2 as well as Figure 3 This is an explanatory diagram showing an example of the operation of the insulation resistance detection device 1 according to the embodiment.

[0064] For example, when testing the resistance value of the insulation resistance 13 on the negative side, such as Figure 2 As shown, the control unit 3 performs the first measurement process, namely: turning on the first switch 21 and turning off the second switch 22, forming a first series connection circuit R1 of the battery 10, the detection resistor 23, and the insulation resistance 13 on the negative terminal side of the battery 10. Based on the first voltage V1 measured by the measurement circuit 25, the insulation resistance 13 on the negative terminal side is calculated. Furthermore, the measurement circuit 25 measures the first voltage (the voltage difference across the detection resistor 23) V1 applied to the detection resistor 23 and outputs the measurement result to the control unit 3.

[0065] At this point, if the resistance value of the insulation resistance 13 on the negative side is sufficiently high, almost no current flows through the first series connection circuit R1. In this case, the first voltage V1 measured by the measuring circuit 25 becomes a value close to 0V. Conversely, if the resistance value of the insulation resistance 13 on the negative side decreases, current flows through the first series connection circuit R1. Furthermore, the lower the resistance of the insulation resistance 13 on the negative side, the higher the first voltage V1 measured by the measuring circuit 25 becomes.

[0066] Therefore, the control unit 3 calculates the resistance value of the insulation resistance 13 on the negative side based on the first voltage V1 measured by the measuring circuit 25. If the calculated resistance value is above the specified resistance value, it is determined that there is no leakage. Conversely, if the calculated resistance value is below the specified resistance value, the control unit 3 determines that there is leakage. In the case of determining that there is leakage, the control unit 3 will, for example, warn the user of this via a warning device such as a warning light.

[0067] Furthermore, for example, when detecting the resistance value of the insulation resistance 12 on the positive side, such as Figure 3 As shown, the control unit 3 performs a second measurement process, namely: opening the first switch 21 and opening the second switch 22, forming a second series connection circuit R2 of the battery 10, the detection resistor 23, and the insulation resistance 12 on the positive terminal side of the battery 10. The insulation resistance 12 on the positive terminal side is calculated based on the second voltage V2 measured by the measurement circuit 25. Furthermore, the measurement circuit 25 measures the second voltage (the voltage difference across the detection resistor 24) V2 applied to the detection resistor 24 and outputs the measurement result to the control unit 3.

[0068] At this point, if the resistance value of the insulation resistance 12 on the positive side is sufficiently high, almost no current flows through the second series connection circuit R2. In this case, the second voltage V2 measured by the measuring circuit 25 becomes a value close to 0V. Conversely, if the resistance value of the insulation resistance 12 on the positive side decreases, current flows through the second series connection circuit R2. Furthermore, the lower the resistance of the insulation resistance 12 on the positive side, the higher the value of the second voltage V2 measured by the measuring circuit 25 becomes.

[0069] Therefore, the control unit 3 calculates the resistance value of the insulation resistance 12 on the positive side based on the second voltage V2 measured by the measuring circuit 25. If the calculated resistance value is above the specified resistance value, it is determined that there is no leakage. Furthermore, if the calculated resistance value is below the specified resistance value, the control unit 3 determines that there is leakage. In the case of determining that there is leakage, the control unit 3 warns the user, for example, through a warning device such as a warning light.

[0070] Here, capacitors 28 and 29 are configured to smooth out the noise component in the voltage applied to the detection resistors 23 and 24, thereby stabilizing the voltage applied to the detection resistors 23 and 24. Therefore, for the control unit 3, for example, if capacitors 28 and 29 are open-circuited, the measurement result of the voltage measured by the measurement unit 2 becomes unstable, and the detection accuracy of insulation resistances 12 and 13 decreases. For this reason, the control unit 3 of the insulation resistance detection device 1 according to the embodiment checks whether capacitors 28 and 29 are faulty.

[0071] [3. Methods for inspecting capacitors]

[0072] Next, refer to Figures 4 to 13 The inspection method for capacitors 28 and 29 involved in the implementation method will be described. Figures 4 to 13 This is an explanatory diagram of the capacitor inspection method according to the embodiment. Here, the case where the insulation resistance 12 on the positive side and the insulation resistance 13 on the negative side have the same insulation resistance value without deterioration will be described.

[0073] The control unit 3 performs the aforementioned insulation resistance detection and capacitor 28 and 29 inspection in a series of operations described later. Specifically, the control unit 3 repeatedly executes the first measurement process described above (see...). Figure 2 ), second measurement process (refer to) Figure 3 ), reference Figure 4 The third measurement process described herein is used to inspect capacitors 28 and 29.

[0074] like Figure 4As shown, the control unit 3 performs the third measurement process, namely: disconnecting the first switch 21 and the second switch 22, and calculating the offset voltage based on the third voltage V3 measured by the measurement circuit 25.

[0075] Furthermore, the control unit 3 monitors the voltage change measured by the measurement circuit 25 after switching from one of the measurement processes (first measurement process, second measurement process, and third measurement process) to another measurement process, and detects faults in capacitors 28 and 29 based on the voltage change.

[0076] Measurement circuit 25, for example, has Figure 5 The differential amplifier 251 is shown. (As shown...) Figure 5 As shown, the differential amplifier 251 outputs a voltage corresponding to the difference between the voltage of the wiring connected to the first switch 21 and the voltage of the wiring connected to the second switch 22 to the control unit 3. Thus, the measurement circuit 25 includes a differential amplifier 251 that differentially amplifies the first voltage V1 and the second voltage V2. Therefore, the insulation resistance detection device 1 can detect and measure the voltage using only a differential amplifier 251, thereby reducing the cost of the measurement circuit 25.

[0077] Furthermore, for example, control unit 3 presses Figure 6 The measurement sequence shown is used to check capacitors 28 and 29. (As shown) Figure 6 As shown, the control unit 3 performs a third measurement process during the period from time t1 to t2. In the third measurement process, the control unit 3 disconnects the first switch 21 and the second switch 22 to measure the voltage measured by the measurement circuit 25.

[0078] Control unit 3 performs a first measurement process during the period from time t2 to t3. In this first measurement process, control unit 3 turns on the first switch 21 and turns off the second switch 22 to measure the voltage measured by measurement circuit 25. Control unit 3 performs a second measurement process during the period from time t3 to t4. In this second measurement process, control unit 3 turns off the first switch 21 and turns on the second switch 22 to measure the voltage measured by measurement circuit 25. Thereafter, control unit 3 repeatedly performs measurement processes in the order of third measurement process, first measurement process, and second measurement process.

[0079] In measurement unit 2, under normal conditions where capacitors 28 and 29 are not disconnected, if the process switches from the third measurement process to the first measurement process at time t2, capacitor 28 is charged. Then, if the process switches from the first measurement process to the second measurement process at time t3, capacitor 28 is discharged and capacitor 29 is charged. Then, if the process switches from the second measurement process to the first measurement process at time t4, capacitor 29 is discharged.

[0080] Therefore, if capacitors 28 and 29 are in a normal state, then as follows Figure 7 As shown, the voltage measured by the measuring circuit 25 (hereinafter sometimes referred to as the "measuring voltage") rises smoothly from time t2 until the charging of capacitor 28 ends. Furthermore, the measuring voltage decreases smoothly from time t4 until the discharging of capacitor 29 ends.

[0081] Therefore, if the voltage measured from time t2 gradually increases, the control unit 3 determines that capacitor 28 is normal. Similarly, if the voltage measured from time t4 gradually decreases, the control unit 3 determines that capacitor 29 is normal.

[0082] In contrast, for example, in the case of capacitor 28 being disconnected, such as Figure 8 As shown, since capacitor 28 was not charged at time t2, the measured voltage rises sharply. Therefore, when the measured voltage rises sharply at time t2, the control unit 3 determines that capacitor 28 is disconnected.

[0083] Furthermore, for example, in the case of capacitor 29 being disconnected, such as Figure 9 As shown, since capacitor 28 did not discharge at time t4, the measured voltage dropped sharply. Therefore, when the measured voltage dropped sharply at time t4, the control unit 3 determined that capacitor 29 was disconnected.

[0084] In this way, the control unit 3 can check whether the voltage change measured by the measurement circuit 25 after switching from one of the measurement processes (first measurement process, second measurement process, and third measurement process) is gradual or rapid.

[0085] More specifically, if the control unit 3 switches from one of the measurement processes (first measurement process, second measurement process, and third measurement process) to another measurement process, and the time until the voltage measured by the measurement circuit 25 stabilizes is less than a predetermined time, it determines that capacitors 28 and 29 are faulty.

[0086] Furthermore, if the control unit 3 determines that capacitors 28 and 29 are not faulty if the time it takes for the voltage measured by the measurement circuit 25 to stabilize exceeds a predetermined time after switching from one of the measurement processes (first, second, and third) to another measurement process.

[0087] At this time, the control unit 3 detects the fault of capacitors 28 and 29 based on at least one of the time it takes for the voltage measured by the measurement circuit 25 to rise and stabilize, and the time it takes for the voltage measured by the measurement circuit 25 to fall and stabilize.

[0088] Therefore, the control unit 3 can accurately detect whether capacitors 28 and 29 are faulty. In addition, the control unit 3 can also detect whether capacitors 28 and 29 are faulty based on the rate of change of voltage measured by the measurement circuit 25 after switching from one of the measurement processes (first measurement process, second measurement process, and third measurement process) to another measurement process.

[0089] In this case, if the rate of change of voltage is above the specified rate, the control unit 3 determines that capacitors 28 and 29 are faulty; if the rate of change of voltage is below the specified rate, the control unit 3 determines that capacitors 28 and 29 are not faulty.

[0090] Furthermore, after switching from one measurement process to another among the first, second, and third measurement processes, the control unit 3 detects the voltage changes measured multiple times by the measurement circuit 25 at a period shorter than the normal measurement cycle.

[0091] Specifically, the measurement circuit 25 detects the voltage by switching from one of the first, second, and third measurement processes to another until the voltage change applied to the detection resistors 23 and 24 is reliably stabilized within a predetermined time period.

[0092] Furthermore, when checking for faults in capacitors 28 and 29, the measuring circuit 25 repeatedly measures the voltage during the aforementioned one cycle and outputs the results to the control unit 3. Therefore, the control unit 3 can accurately calculate the rate of change of the voltage applied to the sensing resistors 23 and 24 over a very short period of time. Thus, the control unit 3 can determine whether capacitors 28 and 29 are faulty before the voltage applied to the sensing resistors 23 and 24 stabilizes after it begins to change.

[0093] Furthermore, if the resistance values ​​of insulation resistors 12 and 13 are sufficiently high, then as Figure 10 As shown, there are cases where the voltage measured by the measurement circuit 25 hardly changes before and after switching from one of the measurement processes (first measurement process, second measurement process, and third measurement process) to another measurement process.

[0094] In this case, although capacitors 28 and 29 are not open-circuit faults, the time from when the voltage measured by the measuring circuit 25 starts to change until it stabilizes is less than the specified time. There is a concern that the control unit 3 may mistakenly judge that capacitors 28 and 29 are open-circuit faults.

[0095] Therefore, if the change in voltage measured by the measurement circuit 25 before and after switching from one of the measurement processes (first, second, and third) to another is less than a specified change, the control unit 3 sets the fault detection results of capacitors 28 and 29 to invalid.

[0096] The specified change amount is defined as the change in voltage measured by the measuring circuit 25 from the start of the change to stabilization within a specified time when switching from one of the first series connection circuit R1 to the other, where the difference between the measured voltage of the first series connection circuit R1 and the measured voltage of the second series connection circuit R2 is small. Furthermore, the phrase "setting the fault detection result invalid" includes the concept of "not performing fault detection."

[0097] Therefore, the control unit 3 can prevent capacitors 28 and 29, which have no open circuit fault, from being mistakenly identified as having an open circuit fault when the resistance values ​​of insulation resistances 12 and 13 are sufficiently high.

[0098] Furthermore, this explanation describes the case where the insulation resistance 12 on the positive side and the insulation resistance 13 on the negative side have the same value when the insulation resistance is not deteriorated; however, this is only one example. It is also possible for the insulation resistance 12 on the positive side and the insulation resistance 13 on the negative side to have different values ​​when the insulation resistance is not deteriorated.

[0099] In this case, a resistive element is connected in series with either the insulation resistance 12 on the positive side or the insulation resistance 13 on the negative side. As a result, the resistance value of the insulation resistance connected to the resistive element on the positive side is higher than the resistance value of the insulation resistance on the negative side.

[0100] Here, we will explain the case where the insulation resistance 13 on the negative side is connected to a resistive element, that is, the combined resistance of the insulation resistance 13 on the negative side and the resistive element connected in series is greater than the resistance of the insulation resistance 12 on the positive side.

[0101] In this case, in measurement unit 2, under normal conditions where capacitors 28 and 29 are not disconnected, if the process switches from the third measurement process to the first measurement process at time t2, capacitor 28 is charged. Then, if the process switches from the first measurement process to the second measurement process at time t3, capacitor 28 discharges and capacitor 29 is charged. Then, if the process switches from the second measurement process to the first measurement process at time t4, capacitor 29 discharges.

[0102] Therefore, if capacitors 28 and 29 are in a normal state, then as follows Figure 11As shown, the measured voltage rises smoothly from time t2 until the charging of capacitor 28 ends. Furthermore, the measured voltage decreases smoothly from time t3 onwards, but does not decrease to the offset voltage. Additionally, the measured voltage decreases smoothly from time t4 until the discharging of capacitor 29 ends.

[0103] Therefore, if the voltage measured from time t2 gradually increases, the control unit 3 determines that capacitor 28 is normal. Similarly, if the voltage measured from time t4 gradually decreases, the control unit 3 determines that capacitor 29 is normal.

[0104] In contrast, for example, in the case of capacitor 28 being disconnected, such as Figure 12 As shown, since capacitor 28 was not charged at time t2, the measured voltage rises sharply. Furthermore, the measured voltage drops sharply at time t3. Therefore, the control unit 3 determines that capacitor 28 is disconnected when the measured voltage rises sharply at time t2 and drops sharply at time t3.

[0105] Furthermore, for example, in the case of capacitor 29 being disconnected, such as Figure 13 As shown, since capacitor 28 did not discharge at time t4, the measured voltage dropped sharply. Therefore, when the measured voltage dropped sharply at time t4, the control unit 3 determined that capacitor 29 was disconnected.

[0106] [4. Processing executed by the control department]

[0107] Next, refer to Figures 14-17 The processing performed by the control unit 3 will be explained. Figures 14-17 This is a flowchart illustrating an example of the processing performed by the control unit 3 according to the embodiment. The control unit 3 repeatedly executes this process during the period when the vehicle's power is on. Figure 14 The processing is shown.

[0108] Specifically, such as Figure 14 As shown, 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 S101). Furthermore, the control unit 3 detects the first voltage V1 applied to the detection resistor 23 (step S102).

[0109] Next, the control unit 3 determines whether the time until the first voltage V1 stabilizes is less than or equal to a predetermined time (step S103). If the control unit 3 determines that the time until the first voltage V1 stabilizes is not less than or equal to a predetermined time (step S103, No), it determines that the capacitor 28 is normal and transfers the processing to step S107.

[0110] If the control unit 3 determines that the time until the first voltage V1 stabilizes is less than a predetermined time (step S103, yes), it detects an open circuit fault in the capacitor 28 (step S104) and determines whether the change in the first voltage V1 is less than a predetermined change (step S105).

[0111] If the control unit 3 determines that the change in the first voltage V1 is not below the specified change (step S105, No), the process is transferred to step S107. If the control unit 3 determines that the change in the first voltage V1 is below the specified change (step S105, Yes), the detection result of the open circuit fault of capacitor 28 is set to invalid (step S106).

[0112] Next, in step S107, the control unit 3 performs insulation resistance determination processing. For an example of insulation resistance determination processing, refer to... Figure 15 This will be described later. Afterwards, the control unit 3 opens the first switch 21 and turns on the second switch 22, forming the second series connection circuit R2 (step S108). Furthermore, the control unit 3 detects the second voltage V2 applied to the detection resistor 24 (step S109).

[0113] Next, the control unit 3 determines whether the time until the second voltage V2 stabilizes is less than or equal to a predetermined time (step S110). If the control unit 3 determines that the time until the second voltage V2 stabilizes is not less than or equal to a predetermined time (step S110, no), it determines that the capacitor 29 is normal and transfers the processing to step S114.

[0114] If the control unit 3 determines that the time until the second voltage V2 stabilizes is less than a predetermined time (step S110, yes), it detects an open circuit fault in the capacitor 29 (step S111) and determines whether the change in the second voltage V2 is less than a predetermined change (step S112).

[0115] If the control unit 3 determines that the change in the second voltage V2 is not below the specified change (step S112, No), the process is transferred to step S114. If the control unit 3 determines that the change in the second voltage V2 is below the specified change (step S112, Yes), the detection result of the open circuit fault of capacitor 29 is set to invalid (step S113), and the insulation resistance judgment process is executed (step S114).

[0116] Next, control unit 3 executes the third measurement process (step S115) and ends the process. For an example of the third measurement process, refer to... Figure 16 This will be described later. Next, refer to... Figure 15An example of the insulation resistance determination process performed by the control unit 3 in steps S107 and S114 will be described.

[0117] like Figure 15 As shown, the control unit 3 calculates the resistance value of the insulation resistance based on the voltage measured by the measurement unit 2 (step S201). At this time, during the insulation resistance determination process in step S107, the control unit 3 calculates the insulation resistance value of the insulation resistance 13 on the negative side based on the first voltage V1 detected in step S102.

[0118] Furthermore, during the insulation resistance determination process in step S114, control unit 3 calculates the insulation resistance value of the positive electrode side insulation resistance 12 based on the second voltage V2 detected in step S109. Then, control unit 3 determines whether the insulation resistance value is higher than or equal to a predetermined resistance value indicating that the battery 10 has no insulation problems (step S202).

[0119] If the control unit 3 determines that the insulation resistance value is above the specified resistance value (step S202, yes), it determines that there is no leakage current (step S203) and ends the insulation resistance judgment process.

[0120] Furthermore, if the control unit 3 determines in step S202 that the insulation resistance value is not above the specified resistance value (step S202, No), it determines that there is leakage (step S204). Afterwards, the control unit 3 warns the user of the existence of leakage (step S205) and ends the insulation resistance determination process.

[0121] Next, refer to Figure 16 The third measurement process will be explained. For example... Figure 16 As shown, if the control unit 3 starts the third measurement process, the control unit 3 first disconnects the first switch 21 and disconnects the second switch 22 (step S301), and then detects the third voltage V3 (step S302).

[0122] Next, the control unit 3 determines whether the time until the third voltage V3 stabilizes is less than or equal to a predetermined time (step S303). If the control unit 3 determines that the capacitor 29 is normal if the time until the third voltage V3 stabilizes is not less than or equal to a predetermined time (step S303, No), the process is transferred to step S307.

[0123] If the control unit 3 determines that the time until the third voltage V3 stabilizes is less than a predetermined time (step S303, Yes), it detects an open circuit fault in the capacitor 29 (step S304) and determines whether the change in the third voltage V3 is less than a predetermined change (step S305).

[0124] If the control unit 3 determines that the change in the third voltage V3 is not below the specified change (step S305, No), the process is transferred to step S307. If the control unit 3 determines that the change in the third voltage V3 is below the specified change (step S305, Yes), the detection result of the open circuit fault of capacitor 29 is set to invalid (step S306), the detected third voltage V3 is stored as an offset voltage (step S307), and the process ends.

[0125] The third voltage V3 stored in step S307 is used to calculate the insulation resistance 12 on the positive side and the insulation resistance 13 on the negative side. In the insulation resistance detection device 1, when the first voltage V1 is detected in the first measurement process, the first voltage V1 + the third voltage V3 is output from the operational amplifier provided in the measurement circuit 25. This is because: if it is a ground reference, the first voltage V1 (+0V) is output from the operational amplifier, but since the amount of the floating offset voltage is included, the first voltage V1 + the third voltage V3 is output. The control unit 3 detects this as the first voltage V1.

[0126] The second measurement process is similar. The second voltage V2 + the third voltage V3 are output from the operational amplifier, and the control unit 3 detects this as the second voltage V2. When calculating the insulation resistance, the control unit 3 subtracts the third voltage V3 from the first voltage V1 and the second voltage V2 respectively, thereby calculating the true first voltage V1 and second voltage V2 after removing the offset.

[0127] In addition, as Figure 14 In a modified example of the capacitor detection process in steps S104 to S106 shown, the control unit 3 may, for example, delete step S106, swap steps S104 and S105, and swap whether step S105 is yes or no to perform the detection process.

[0128] Figure 17 It means to replace Figure 14 The flowchart shows a modified example of the capacitor detection process performed by the control unit 3 in steps S104 to S106. Figure 17 As shown, when the control unit 3 performs the detection process involved in the modified example, if step S105 is yes, the process proceeds to step S107; if step S105 is no, the process proceeds to step S104. In this case, if the control unit 3 determines that the time until the first voltage V1 stabilizes is less than a predetermined time (step S103, yes), and determines that the change in the first voltage V1 is greater than or equal to a predetermined change (step S105, no), it detects an open-circuit fault in capacitor 28 (step S104).

[0129] Furthermore, if the control unit 3 determines that the time until the first voltage V1 stabilizes is less than a predetermined time (step S103, yes), or determines that the change in the first voltage V1 is less than a predetermined change (step S105, yes), it does not perform the processing in step S104 (does not detect the open-circuit fault of capacitor 28). Therefore, it is also possible to perform the same processing as setting the detection result of the open-circuit fault of capacitor 28 in step S106 to invalid.

[0130] Regarding the above Figure 14 The modification process shown in steps S104 to S106 is also applied to steps S111 to S113. That is, step S113 can be deleted, steps S111 and S112 can be swapped, and the "yes" and "no" options in step S112 can be changed. Furthermore, for... Figure 14 The steps S104 to S106 shown are modified for the following purposes. Figure 16 The same applies to steps S304 to S306 shown. That is, step S306 can be deleted, steps S304 and S30 can be swapped, and the yes / no of step S305 can be swapped.

[0131] [5. Variations]

[0132] Next, refer to Figure 18 as well as Figure 19 The measurement circuit 25a involved in the modified embodiment will be described. Figure 18 as well as Figure 19 This is an explanatory diagram of the measurement circuit 25a involved in a variation of the implementation.

[0133] like Figure 18 As shown, the measurement circuit 25a includes a first detector 252 and a second detector 253. The first detector 252 is a differential amplifier that outputs a voltage corresponding to the difference between the voltage of the wiring connected to the first switch 21 and the ground voltage to the control unit 3. The second detector 253 is a differential amplifier that outputs a voltage corresponding to the difference between the voltage of the wiring connected to the second switch 22 and the ground voltage to the control unit 3.

[0134] Thus, the measurement circuit 25a includes a first detector 252 for detecting a first voltage V1 and a second detector 253 for detecting a second voltage V2. The first detector 252 and the second detector 253 are pressed by the control unit 3. Figure 6 The measurement sequence shown controls the period during which the first switch 21 and the second switch 22 are used to detect and measure the voltage.

[0135] Therefore, the first detector 252 is able to Figure 19 The first voltage V1, represented by a thick solid line, is output to the control unit 3. On the other hand, the second detector 253 is capable of... Figure 19The second voltage V2, represented by a thick dashed line, is output to the control unit 3.

[0136] Therefore, the control unit 3 can detect the fault of capacitor 28 based on the change in the measured voltage from time t2, detect the fault of capacitor 29 based on the change in the measured voltage from time t4, and further detect the faults of capacitors 28 and 29 based on the measured voltage at time t3.

[0137] For example, if the first voltage V1 decreases gradually at time t3, the control unit 3 can determine that capacitor 28 is normal; if the first voltage V1 decreases sharply at time t3, the control unit 3 can determine that capacitor 28 is open-circuited. Furthermore, if the second voltage V2 increases gradually at time t3, the control unit 3 can determine that capacitor 28 is normal; if the second voltage V2 increases sharply at time t3, the control unit 3 can determine that capacitor 29 is open-circuited.

[0138] Thus, since the control unit 3 can detect the first voltage V1 and the second voltage V2 independently, even when there is no difference between the first voltage V1 and the second voltage V2, the faults of capacitors 28 and 29 can be detected correctly when switching between the first measurement process and the second measurement process.

[0139] Those skilled in the art can readily derive further effects and modifications. Therefore, the invention is not limited to the specific details and representative embodiments shown and described above. Thus, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the claims and their equivalents.

Claims

1. An insulation resistance testing device, comprising: The measuring unit includes a first switch connected to the positive terminal of the battery, a second switch connected to the negative terminal of the battery, a detection resistor, a capacitor connected in parallel with the detection resistor, and a measuring circuit for measuring the voltage applied to the detection resistor; and The control unit controls the first switch and the second switch. The control unit performs a first measurement process, in which the first switch is turned on and the second switch is turned off, forming a first series connection circuit of the battery, the detection resistor, and the insulation resistance of the negative terminal of the battery. The insulation resistance of the negative terminal is calculated based on the first voltage measured by the measurement circuit. The control unit performs a second measurement process, in which the first switch is turned off and the second switch is turned on, forming a second series connection circuit of the battery, the detection resistor, and the insulation resistance of the positive electrode side of the battery. The insulation resistance of the positive electrode side is calculated based on the second voltage measured by the measurement circuit. The control unit performs a third measurement process, in which the first switch and the second switch are disconnected, and the offset voltage is calculated based on the third voltage measured by the measurement circuit. The control unit detects the change in voltage measured by the measurement circuit after switching from one of the first measurement process, the second measurement process, and the third measurement process to another measurement process, and detects a fault in the capacitor based on the change in voltage.

2. The insulation resistance testing device according to claim 1, wherein, After switching from one measurement process to another, the control unit detects the change in voltage measured multiple times by the measurement circuit at a shorter period than the usual measurement cycle.

3. The insulation resistance detection device according to claim 1 or 2, wherein, If the change in voltage measured by the measurement circuit before and after switching from one measurement process to another is less than a predetermined change, the control unit will invalidate the fault detection result of the capacitor.

4. The insulation resistance testing device according to claim 1 or 2, wherein, If the time from switching from one measurement process to the other until the voltage measured by the measurement circuit stabilizes is less than a predetermined time, the control unit detects a fault in the capacitor.

5. The insulation resistance testing device according to claim 1 or 2, wherein, The measurement circuit includes a differential amplifier that differentially amplifies the first voltage and the second voltage.

6. The insulation resistance testing device according to claim 1 or 2, wherein, The measurement circuit includes: a first detector for detecting the first voltage and a second detector for detecting the second voltage.

7. A fault detection method, the insulation resistance detection device comprising: a measuring unit, including 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, a capacitor connected in parallel with the detection resistor, and a measuring circuit for measuring the voltage applied to the detection resistor; and a control unit for controlling the first switch and the second switch. The control unit performs a first measurement process, in which the first switch is turned on and the second switch is turned off, forming a first series connection circuit of the battery, the detection resistor, and the insulation resistance of the negative terminal of the battery. The insulation resistance of the negative terminal is calculated based on the first voltage measured by the measurement circuit. The control unit performs a second measurement process, in which the first switch is turned off and the second switch is turned on, forming a second series connection circuit of the battery, the detection resistor, and the insulation resistance of the positive electrode side of the battery. The insulation resistance of the positive electrode side is calculated based on the second voltage measured by the measurement circuit. The control unit performs a third measurement process, in which the first switch and the second switch are disconnected, and the offset voltage is calculated based on the third voltage measured by the measurement circuit. The control unit detects the change in voltage measured by the measurement circuit after switching from one of the first measurement process, the second measurement process, and the third measurement process to another measurement process, and detects a fault in the capacitor based on the change in voltage.

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