Insulation resistance detection device and insulation resistance detection method

Abstract

An insulation resistance detection device (1) comprises: a voltage measurement unit (10) that measures a voltage at a first node (N2) among a plurality of nodes between a plurality of voltage dividing resistors of an insulation detection circuit (100) for detecting insulation resistance (Riso1 and Rios2) on a path on which current from a battery (Bat) flows; a determination unit (control unit (20)) that determines whether the voltage at the first node (N2) measured by the voltage measurement unit (10) is less than or equal to a prescribed voltage; and a switching unit (control unit (20)) that, when it is determined that the voltage at the first node (N2) measured by the voltage measurement unit (10) is less than or equal to the prescribed voltage, switches a switch (SW1) connected to a second node (N1) among the plurality of nodes so that the voltage measured by the voltage measurement unit (10) exceeds the prescribed voltage.

Description

Insulation resistance detection device and insulation resistance detection method

[0001] The present disclosure relates to an insulation resistance detection device and an insulation resistance detection method for detecting insulation resistance in a path through which current flows from a battery.

[0002] Patent Document 1 describes a device that can detect insulation resistance in a path through which current flows from a battery.

[0003] JP 2018-128454 A

[0004] However, the device described in Patent Document 1 detects insulation resistance by measuring the voltage at one node, and if the voltage measured at that node drops due to a drop in battery voltage or during measurement control, the measurement error of the voltage at that node increases, reducing the accuracy of detecting insulation resistance.

[0005] Therefore, the present disclosure provides an insulation resistance detection device and the like that can suppress a decrease in the detection accuracy of insulation resistance even if the voltage of the node where the voltage is measured decreases.

[0006] An insulation resistance detection device according to one aspect of the present disclosure includes a voltage measurement unit that measures the voltage at a first node among a plurality of nodes between a plurality of voltage dividing resistors connected between the positive and negative terminals of a battery, the plurality of voltage dividing resistors being included in an insulation detection circuit for detecting insulation resistance in a path through which current flows from the battery; a determination unit that determines whether the voltage at the first node measured by the voltage measurement unit is equal to or lower than a predetermined voltage; and a switching unit that, when it is determined that the voltage at the first node measured by the voltage measurement unit is equal to or lower than the predetermined voltage, switches a switch connected to a second node among the plurality of nodes so that the voltage measured by the voltage measurement unit exceeds the predetermined voltage.

[0007] An insulation resistance detection method according to one aspect of the present disclosure includes a voltage measurement step of measuring a voltage at a first node among a plurality of nodes between a plurality of voltage divider resistors connected between the positive and negative terminals of a battery, the plurality of voltage divider resistors being included in an insulation detection circuit for detecting insulation resistance in a path through which current flows from the battery; a determination step of determining whether the voltage at the first node measured in the voltage measurement step is equal to or lower than a predetermined voltage; and a switching step of switching a switch connected to a second node among the plurality of nodes so that the voltage measured in the voltage measurement step exceeds the predetermined voltage when it is determined that the voltage at the first node measured in the voltage measurement step is equal to or lower than the predetermined voltage.

[0008] According to an insulation resistance detection device and the like according to an aspect of the present disclosure, it is possible to suppress a decrease in the detection accuracy of the insulation resistance even if the voltage at the node where the voltage is measured decreases.

[0009] Fig. 1 is a configuration diagram showing an example of an insulation resistance detection device according to embodiment 1. Fig. 2 is a diagram for explaining the effect of the insulation resistance detection device according to embodiment 1. Fig. 3 is a configuration diagram showing an example of an insulation resistance detection device according to a modified example of embodiment 1. Fig. 4 is a configuration diagram showing an example of an insulation resistance detection device according to embodiment 2. Fig. 5 is a flowchart showing an example of an insulation resistance detection method according to another embodiment.

[0010] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0011] The embodiments described below are all comprehensive or specific examples, and the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0012] First Embodiment An insulation resistance detecting device 1 according to a first embodiment will be described below with reference to FIG.

[0013] Fig. 1 is a configuration diagram showing an example of an insulation resistance detection device 1 according to embodiment 1. In addition to the insulation resistance detection device 1, Fig. 1 also shows a battery Bat, insulation resistances Riso1 and Riso2 in a path through which current flows from the battery Bat, and an insulation detection circuit 100. The battery Bat or the insulation detection circuit 100 may be components of the insulation resistance detection device 1.

[0014] The insulation resistance detecting device 1 is mounted on a vehicle such as an electric vehicle that uses electric power for propulsion. A high-voltage battery Bat is mounted on the vehicle, and power is supplied from the battery Bat to a drive load such as a motor, thereby propelling the vehicle. The battery Bat is a battery for an HV, PHEV, EV, or the like.

[0015] Insulation resistance refers to the insulation between a path through which a current flows and ground. A low insulation resistance can cause a current leak, which can lead to electric shock or a fire. Therefore, detecting insulation resistance can detect dangerous vehicle conditions in advance. Figure 1 shows an insulation resistance Riso1 between the path connected to the positive terminal t1 of the battery Bat and ground GND, and an insulation resistance Riso2 between the path connected to the negative terminal t2 of the battery Bat and ground GND. Ground GND is, for example, the potential of the vehicle chassis.

[0016] The insulation detection circuit 100 is a circuit for detecting insulation resistances Riso1 and Riso2 and includes a plurality of voltage-dividing resistors connected between the positive terminal t1 and the negative terminal t2 of the battery Bat. In the first embodiment, the plurality of voltage-dividing resistors are represented by resistors R1, R2, R3, R4, R5, and R6. Specifically, the resistors R1, R2, and R3 are connected in series between the positive terminal t1 and ground GND, and the resistors R4, R5, and R6 are connected in series between ground GND and the negative terminal t2. In this manner, the positive terminal t1 is connected to ground GND via at least one of the plurality of voltage-dividing resistors, and the negative terminal t2 is connected to ground GND via at least one other of the plurality of voltage-dividing resistors. In the first embodiment, at least one resistor is represented by resistors R1, R2, and R3, and at least one other resistor is represented by resistors R4, R5, and R6. By connecting the positive terminal t1 to ground GND and the ground GND to the negative terminal t2 via at least one resistor, respectively, the potential of ground GND can be stabilized.

[0017] Nodes N1, N2, N3, N4, and N5 are also shown as nodes between the voltage dividing resistors. Node N1 is a node between resistors R1 and R2, node N2 is a node between resistors R2 and R3, node N3 is a node between resistors R3 and R4, node N4 is a node between resistors R4 and R5, and node N5 is a node between resistors R5 and R6.

[0018] Although not shown here, the insulation detection circuit 100 may include one or more switches connected to one or more of the multiple voltage divider resistors. By controlling the one or more switches included in the insulation detection circuit 100, it is possible to change the voltage at any one of the multiple nodes. Then, the insulation resistance detection device 1 can accurately calculate the values ​​of the insulation resistances Ris01 and Ris02 from the voltages before and after the change.

[0019] 1, the insulation detection circuit 100 does not have to include one or more switches. Even in this case, it is possible to determine whether the insulation resistor Riso1 or Riso2 is abnormal (i.e., whether a leakage current has occurred) from the voltage at any one of the multiple nodes. This is because if the insulation resistor Riso1 or Riso2 is abnormal and its value is low, the voltage at any one of the multiple nodes will also be abnormal.

[0020] The insulation resistance detecting device 1 is a device for detecting insulation resistances Riso1 and Riso2, and includes a voltage measurement unit 10 and a control unit 20. The insulation resistance detecting device 1 is realized by, for example, a microcontroller unit (MCU). In the first embodiment, the insulation resistance detecting device 1 uses the potential of the ground GND (node ​​N3) as a reference potential.

[0021] The voltage measurement unit 10 is capable of measuring voltages at multiple nodes between multiple voltage-dividing resistors included in the insulation detection circuit 100. For example, the voltage measurement unit 10 has an A / D converter and measures the voltages at the multiple nodes using the A / D converter. For example, the voltage measurement unit 10 has A / D converters 11 and 12 and is capable of measuring the voltage at node N1 using A / D converter 11 and measuring the voltage at node N2 using A / D converter 12. Node N1 is an example of a second node, and node N2 is an example of a first node. In the first embodiment, the voltage measurement unit 10 measures the voltages at nodes N1 and N2 relative to the potential of ground GND.

[0022] The control unit 20 determines whether the voltage at the node N2 measured by the voltage measurement unit 10 is equal to or lower than a predetermined voltage. The control unit 20 is an example of a determination unit. The predetermined voltage is not particularly limited, but may be, for example, ½ or ⅕ of the absolute maximum rating of the voltage measurement unit 10 (A / D converters 11 and 12).

[0023] Furthermore, when the control unit 20 determines that the voltage at the node N2 measured by the voltage measurement unit 10 is equal to or lower than a predetermined voltage, the control unit 20 switches the switch SW1 connected to the node N1 among the plurality of nodes so that the voltage measured by the voltage measurement unit 10 exceeds the predetermined voltage. The control unit 20 is an example of a switching unit.

[0024] In the first embodiment, the node N1 is a node to which a higher voltage is applied than the node N2. Specifically, a voltage according to the two resistors R2 and R3 is applied to the node N1, and a voltage according to the single resistor R3 is applied to the node N2, so that a higher voltage is applied to the node N1 than to the node N2.

[0025] Furthermore, in the first embodiment, switch SW1 is connected between node N1 and voltage measurement unit 10, and when control unit 20 determines that the voltage at node N2 measured by voltage measurement unit 10 is equal to or lower than a predetermined voltage, control unit 20 switches switch SW1 to connect node N1 and voltage measurement unit 10. Specifically, in this case, control unit 20 switches switch SW1 from a non-conductive state to a conductive state. When switch SW1 is switched to the conductive state, A / D converter 11 of voltage measurement unit 10 can measure the voltage at node N1.

[0026] Furthermore, the control unit 20 detects the insulation resistances Riso1 and Riso2 based on the voltage measured by the voltage measurement unit 10. For example, when the voltage measured by the voltage measurement unit 10 is an abnormal value, the control unit 20 can determine that the insulation resistance Riso1 or Riso2 is abnormal. For example, when the control unit 20 controls the switch SW1 to be in the non-conductive state, the control unit 20 detects the insulation resistances Riso1 and Riso2 using the voltage at the node N2 measured by the A / D converter 12, and when the control unit 20 controls the switch SW1 to be in the conductive state, the control unit 20 detects the insulation resistances Riso1 and Riso2 using the voltage at the node N1 measured by the A / D converter 11.

[0027] When the insulation detection circuit 100 includes one or more switches, the control unit 20 can calculate the values ​​of the insulation resistances Riso1 and Riso2 using a predetermined algorithm from the voltage at node N1 or N2 measured before and after switching one or more switches.

[0028] Note that the voltage measurement unit 10 may include only one A / D converter, which may measure the voltages at nodes N1 and N2. In this case, a switch may be provided between the A / D converter and node N2, and the voltage at node N2 may be measured with the switch in a conductive state and switch SW1 in a non-conductive state. If it is determined that the voltage at node N2 is equal to or lower than a predetermined voltage, the switch in a non-conductive state and switch SW1 in a conductive state may be measured, and the voltage at node N1 may be measured.

[0029] The control unit 20 may also diagnose a fault in the insulation detection circuit 100 or the voltage measurement unit 10 by comparing the voltage at node N2 measured by the voltage measurement unit 10 with the voltage at node N1. The control unit 20 is an example of a fault diagnosis unit. For example, the ratio of the voltage at node N1 to the voltage at node N2 should be a constant ratio depending on the resistance values ​​of resistors R1, R2, and R3, but if the constant ratio is not achieved, it can be determined that at least one of resistors R1, R2, and R3 has failed, or that the voltage measurement unit 10 has failed.

[0030] Furthermore, four or more voltage-dividing resistors may be connected between the positive terminal t1 and ground GND, and for example, when the voltage at node N1 also falls below a predetermined voltage, a node to which a voltage higher than that of node N1 is applied may be connected by a switch to the voltage measurement unit 10, and the voltage at that node may be measured. Then, when the voltage at that node also falls below the predetermined voltage, the voltage at another node to which a higher voltage is applied may be measured.

[0031] Although not shown, the voltage measurement unit 10 may measure the voltage at node N4 or N5, and the control unit 20 may also use the voltage at node N4 or N5 to detect the insulation resistances Riso1 and Riso2. Alternatively, multiple voltage-dividing resistors may not be connected between ground GND and the negative terminal t2 as shown in FIG. 1 , and for example, only one resistor may be connected. In this case, the voltage measurement unit 10 does not need to measure the voltage at the node between ground GND and the negative terminal t2.

[0032] As described above, the insulation resistance detection device 1 includes a voltage measurement unit 10 that measures the voltage at node N2, which is one of a plurality of nodes between the plurality of voltage dividing resistors provided in the insulation detection circuit 100 for detecting insulation resistances Riso1 and Riso2 in a path through which a current flows from the battery Bat, a determination unit (control unit 20) that determines whether the voltage at node N2 measured by the voltage measurement unit 10 is equal to or lower than a predetermined voltage, and a switching unit (control unit 20) that, when it is determined that the voltage at node N2 measured by the voltage measurement unit 10 is equal to or lower than the predetermined voltage, switches the switch SW1 connected to node N1 of the plurality of nodes so that the voltage measured by the voltage measurement unit 10 exceeds the predetermined voltage.

[0033] According to this, when the voltage measured at node N2 drops below a predetermined voltage during a voltage drop of battery Bat or during measurement control, switch SW1 is switched so that the voltage measured by voltage measurement unit 10 exceeds the predetermined voltage. Therefore, voltage measurement unit 10 can measure a voltage higher than the predetermined voltage, thereby reducing the measurement error of voltage measurement unit 10. Therefore, even if the voltage at node N2 where the voltage is measured drops, a decrease in the detection accuracy of insulation resistances Riso1 and Riso2 can be suppressed. This will be described in detail using FIG. 2 .

[0034] FIG. 2 is a diagram for explaining the effects of the insulation resistance detecting device 1 according to the first embodiment.

[0035] As shown in (a) of FIG. 2 , when the voltage measured by the voltage measurement unit 10 (the voltage at node N2 in the first embodiment) exceeds a predetermined voltage, the switch SW1 is brought into a non-conductive state. Thereafter, the voltage of the battery Bat drops, and as shown in (b) of FIG. 2 , the voltage measured by the voltage measurement unit 10 (the voltage at node N2 in the first embodiment) falls below the predetermined voltage. In this case, the ratio of error to the input voltage to the voltage measurement unit 10 (A / D converter 11) increases, resulting in a larger measurement error by the voltage measurement unit 10. Therefore, the switch SW1 connected between node N1 and the voltage measurement unit 10 is switched from a non-conductive state to a conductive state, and the voltage measurement unit 10 measures the voltage at node N1. As shown in (c) of FIG. 2 , the voltage at node N1 is higher than the voltage at node N2, so the ratio of error to the input voltage to the voltage measurement unit 10 (A / D converter 12) can be reduced, thereby reducing the measurement error by the voltage measurement unit 10.

[0036] The reason why the voltage measurement unit 10 does not measure the voltage at node N1 before the voltage of the battery Bat drops, in other words, before the voltage at node N2 falls below a predetermined voltage, is because there is a risk that the voltage at node N1 will exceed the absolute maximum rating of the voltage measurement unit 10.

[0037] For example, node N1 is a node to which a higher voltage than node N2 is applied, switch SW1 is connected between node N1 and voltage measurement unit 10, and when the switching unit (control unit 20) determines that the voltage at node N2 measured by voltage measurement unit 10 is equal to or lower than a predetermined voltage, it switches switch SW1 to connect node N1 and voltage measurement unit 10, and voltage measurement unit 10 measures the voltage at node N1.

[0038] According to this, when the voltage measured at node N2 drops below a predetermined voltage due to a voltage drop of battery Bat or during measurement control, node N1, to which a voltage higher than that of node N2 is applied, is connected to voltage measurement unit 10 by switch SW1. Therefore, voltage measurement unit 10 can measure a voltage higher than the predetermined voltage at node N1, thereby reducing measurement error of voltage measurement unit 10. In this way, by switching the node at which voltage measurement unit 10 measures voltage to the node to which a higher voltage is applied when the voltage of battery Bat drops, for example, it is possible to suppress a decrease in the detection accuracy of insulation resistances Riso1 and Riso2.

[0039] For example, the voltage measurement section 10 may measure the voltages at the nodes N1 and N2 with respect to the potential of the ground GND.

[0040] For example, insulation resistance detection device 1 is realized by a microcomputer or the like, and in embodiment 1, if the reference potential of the microcomputer is set to the potential of ground GND, the voltages at nodes N1 and N2 can also be measured based on the potential of ground GND.

[0041] For example, the insulation resistance detection device 1 may further include a fault diagnosis unit (control unit 20) that diagnoses a fault in the insulation detection circuit 100 or the voltage measurement unit 10 by comparing the voltage at node N2 measured by the voltage measurement unit 10 with the voltage at node N1.

[0042] This makes it possible to diagnose a fault in the insulation detection circuit 100 or the voltage measurement unit 10 depending on whether the ratio between the voltage at the node N1 and the voltage at the node N2 is constant.

[0043] (Modification of Embodiment 1) Next, an insulation resistance detecting device 1a according to a modification of Embodiment 1 will be described with reference to Fig. 3. The following description will focus on differences from the insulation resistance detecting device 1 according to Embodiment 1, and a description of the same points will be omitted.

[0044] Fig. 3 is a configuration diagram showing an example of an insulation resistance detection device 1a according to a modification of embodiment 1. In addition to the insulation resistance detection device 1a, Fig. 3 also shows a battery Bat, insulation resistances Riso1 and Riso2 in a path through which current flows from the battery Bat, and an insulation detection circuit 100a. The battery Bat or the insulation detection circuit 100a may be components of the insulation resistance detection device 1a.

[0045] The insulation resistance detecting device 1a is mounted on a vehicle such as an electric vehicle that uses electric power for propulsion.

[0046] The insulation detection circuit 100a is a circuit for detecting insulation resistances Riso1 and Riso2 and includes multiple voltage-dividing resistors connected between the positive terminal t1 and the negative terminal t2 of the battery Bat. In a modification of the first embodiment, resistors R7, R8, R9, and R10 are shown as the multiple voltage-dividing resistors. Specifically, resistor R7 is connected between the positive terminal t1 and ground GND, and resistors R8, R9, and R10 are connected in series between ground GND and the negative terminal t2. In this manner, the positive terminal t1 is connected to ground GND via at least one of the multiple voltage-dividing resistors, and the negative terminal t2 is connected to ground GND via at least one other of the multiple voltage-dividing resistors. In the modification of the first embodiment, at least one resistor is resistor R7, and at least one other resistor is resistors R8, R9, and R10. By connecting the positive terminal t1 to ground GND and the ground GND to the negative terminal t2 via at least one resistor, respectively, the potential of ground GND can be stabilized.

[0047] Nodes N6, N7, and N8 are also shown as nodes between the voltage dividing resistors. Node N6 is a node between resistors R7 and R8, node N7 is a node between resistors R8 and R9, and node N8 is a node between resistors R9 and R10.

[0048] Although not shown here, the insulation detection circuit 100a may include one or more switches connected to one or more of the multiple voltage divider resistors. By controlling the one or more switches included in the insulation detection circuit 100a, the voltage at one of the multiple nodes can be changed. Then, the insulation resistance detection device 1a can accurately calculate the values ​​of the insulation resistances Riso1 and Riso2 from the voltages before and after the change.

[0049] The insulation detection circuit 100a does not have to include one or more switches as shown in FIG. 3. Even in this case, it is possible to determine whether or not the insulation resistance Riso1 or Riso2 is abnormal (i.e., whether or not a leakage current has occurred) from the voltage at any one of the multiple nodes.

[0050] The insulation resistance detecting device 1a is a device for detecting insulation resistances Riso1 and Riso2, and includes a voltage measuring unit 10a and a control unit 20a. The insulation resistance detecting device 1a is realized by, for example, a microcomputer. In a modification of the first embodiment, the insulation resistance detecting device 1a uses the potential of the negative terminal t2 as a reference potential.

[0051] The voltage measurement unit 10a is capable of measuring voltages at multiple nodes between multiple voltage-dividing resistors included in the insulation detection circuit 100a. For example, the voltage measurement unit 10a includes an A / D converter and measures the voltages at the multiple nodes using the A / D converter. For example, the voltage measurement unit 10a includes A / D converters 11a and 12a and is capable of measuring the voltage at node N7 using the A / D converter 11a and measuring the voltage at node N8 using the A / D converter 12a. Node N7 is an example of a second node, and node N8 is an example of a first node. In a modification of the first embodiment, the voltage measurement unit 10a measures the voltages at nodes N7 and N8 relative to the potential of the negative terminal t2.

[0052] The control unit 20a determines whether the voltage at the node N8 measured by the voltage measurement unit 10a is equal to or lower than a predetermined voltage. The control unit 20a is an example of a determination unit. The predetermined voltage is not particularly limited, but may be, for example, ½ or ⅕ of the absolute maximum rating of the voltage measurement unit 10a (A / D converters 11a and 12a).

[0053] Furthermore, when the control unit 20a determines that the voltage at the node N8 measured by the voltage measurement unit 10a is equal to or lower than a predetermined voltage, the control unit 20a switches the switch SW1a connected to the node N7 among the plurality of nodes so that the voltage measured by the voltage measurement unit 10a exceeds the predetermined voltage. The control unit 20a is an example of a switching unit. The node N7 is an example of a second node.

[0054] In the modification of the first embodiment, the node N7 is a node to which a higher voltage is applied than the node N8. Specifically, a voltage according to the two resistors R9 and R10 is applied to the node N7, and a voltage according to the single resistor R10 is applied to the node N8, so that a higher voltage is applied to the node N7 than to the node N8.

[0055] In the modification of the first embodiment, the switch SW1a is connected between the node N7 and the voltage measurement unit 10a, and when the control unit 20a determines that the voltage at the node N8 measured by the voltage measurement unit 10a is equal to or lower than a predetermined voltage, the control unit 20a switches the switch SW1a to connect the node N7 and the voltage measurement unit 10a. Specifically, the control unit 20a switches the switch SW1a from a non-conductive state to a conductive state in this case. When the switch SW1a is switched to the conductive state, the A / D converter 11a of the voltage measurement unit 10a can measure the voltage at the node N7.

[0056] The control unit 20a also detects the insulation resistances Riso1 and Riso2 based on the voltage measured by the voltage measurement unit 10a. For example, if the voltage measured by the voltage measurement unit 10a is an abnormal value, the control unit 20a can determine that the insulation resistance Riso1 or Riso2 is abnormal. For example, when the control unit 20a controls the switch SW1a to be in the non-conductive state, the control unit 20a detects the insulation resistances Riso1 and Riso2 using the voltage at node N8 measured by the A / D converter 12a, and when the control unit 20a controls the switch SW1a to be in the conductive state, the control unit 20a detects the insulation resistances Riso1 and Riso2 using the voltage at node N7 measured by the A / D converter 11a.

[0057] If the insulation detection circuit 100a has one or more switches, the control unit 20a can calculate the values ​​of the insulation resistances Riso1 and Riso2 using a predetermined algorithm from the voltage at node N7 or N8 measured before and after switching one or more switches.

[0058] Note that the voltage measurement unit 10a may include only one A / D converter, which may measure the voltages at nodes N7 and N8. In this case, a switch may be provided between the A / D converter and node N8, and the voltage at node N8 is measured with the switch in a conductive state and switch SW1a in a non-conductive state. If it is determined that the voltage at node N8 is equal to or lower than a predetermined voltage, the switch in a non-conductive state and switch SW1a in a conductive state are set, and the voltage at node N7 is measured.

[0059] The control unit 20a may also diagnose a fault in the insulation detection circuit 100a or the voltage measurement unit 10a by comparing the voltage at node N8 measured by the voltage measurement unit 10a with the voltage at node N7. The control unit 20a is an example of a fault diagnosis unit. For example, the ratio of the voltage at node N7 to the voltage at node N8 should be a constant ratio depending on the resistance values ​​of resistors R8, R9, and R10. If the constant ratio is not achieved, it can be determined that at least one of resistors R8, R9, and R10 is faulty, or that the voltage measurement unit 10a is faulty.

[0060] Furthermore, four or more voltage-dividing resistors may be connected between ground GND and the negative terminal t2, and for example, when the voltage at node N7 also falls below a predetermined voltage, a node to which a voltage higher than that of node N7 is applied may be connected by a switch to the voltage measurement unit 10a, and the voltage at that node may be measured. Then, when the voltage at that node also falls below the predetermined voltage, the voltage at another node to which a higher voltage is applied may be measured.

[0061] As described above, in the modification of the first embodiment, the voltage measurement unit 10a may measure the voltages at the nodes N7 and N8 with respect to the potential of the negative terminal t2.

[0062] For example, the insulation resistance detecting device 1a is realized by a microcomputer or the like. In a modified example of the first embodiment, if the reference potential of the microcomputer is set to the potential of the negative terminal t2, the voltages at the nodes N7 and N8 can also be measured based on the potential of the negative terminal t2.

[0063] In the modification of the first embodiment, as in the first embodiment, even if the voltage of the battery Bat drops or the voltage of the node N8 drops during the measurement control process, a decrease in the detection accuracy of the insulation resistances Riso1 and Riso2 can be suppressed.

[0064] Second Embodiment Next, an insulation resistance detecting device 1b according to a second embodiment will be described with reference to Fig. 4. The following description will focus on differences from the insulation resistance detecting device 1 according to the first embodiment, and a description of the same points will be omitted.

[0065] Fig. 4 is a configuration diagram showing an example of an insulation resistance detection device 1b according to embodiment 2. In addition to the insulation resistance detection device 1b, Fig. 4 also shows a battery Bat, insulation resistances Riso1 and Riso2 in a path through which current flows from the battery Bat, and an insulation detection circuit 100b. The battery Bat or the insulation detection circuit 100b may be components of the insulation resistance detection device 1b.

[0066] The insulation resistance detecting device 1b is mounted on a vehicle such as an electric vehicle that uses electric power for propulsion.

[0067] The insulation detection circuit 100b is a circuit for detecting insulation resistances Riso1 and Riso2 and includes multiple voltage-dividing resistors connected between the positive terminal t1 and the negative terminal t2 of the battery Bat. In the second embodiment, the multiple voltage-dividing resistors are resistors R11, R12, R13, R14, and R15. Specifically, the resistors R11 and R14 are connected in parallel between the positive terminal t1 and ground GND, and the resistor R13 is connected in series with a circuit in which the resistors R12 and R15 are connected in parallel between ground GND and the negative terminal t2. In this manner, the positive terminal t1 is connected to ground GND via at least one of the multiple voltage-dividing resistors, and the negative terminal t2 is connected to ground GND via at least one other of the multiple voltage-dividing resistors. In the second embodiment, at least one resistor is the resistors R11 and R14, and at least one other resistor is the resistors R12, R13, and R15. The potential of the ground GND can be stabilized by connecting the positive terminal t1 to the ground GND and the ground GND to the negative terminal t2 via one or more resistors, respectively.

[0068] Nodes N9 and N10 are also shown as nodes between the voltage-dividing resistors. Node N9 is a node between the parallel circuit of resistors R11 and R14 and the parallel circuit of resistors R12 and R15, and node N10 is a node between the parallel circuit of resistors R12 and R15 and resistor R13.

[0069] The insulation detection circuit 100b includes switches SW2 and SW3. The switches SW2 and SW3 are connected to a node N9 and one of a plurality of voltage-dividing resistors. Here, the switch SW2 is connected between the node N9 and a resistor R14, and the switch SW3 is connected between the node N9 and a resistor R15. The node N9 is an example of a second node. When the switch SW2 is conductive, the resistance value of the parallel circuit of the resistors R11 and R14 decreases. When the switch SW2 is non-conductive, the resistance value of the parallel circuit of the resistors R11 and R14 increases. When the switch SW3 is conductive, the resistance value of the parallel circuit of the resistors R12 and R15 decreases. When the switch SW3 is non-conductive, the resistance value of the parallel circuit of the resistors R12 and R15 increases.

[0070] Although not shown here, the insulation detection circuit 100b may further include one or more switches connected to one or more of the voltage-dividing resistors R11, R12, and R13 in addition to the switches SW2 and SW3. By controlling the one or more switches further included in the insulation detection circuit 100b, the voltage at node N10 can be changed. Then, the insulation resistance detection device 1b can accurately calculate the values ​​of the insulation resistances Riso1 and Riso2 from the voltages before and after the change.

[0071] As shown in FIG. 4, the insulation detection circuit 100b does not need to include any switches other than the switches SW2 and SW3. Even in this case, it is possible to determine from the voltage at the node N10 whether the insulation resistor Riso1 or Riso2 is abnormal (i.e., whether a leakage current has occurred).

[0072] The insulation resistance detecting device 1b is a device for detecting insulation resistances Riso1 and Riso2, and includes a voltage measuring unit 10b and a control unit 20b. The insulation resistance detecting device 1b is realized by, for example, a microcomputer. In the second embodiment, the insulation resistance detecting device 1b uses the potential of the negative terminal t2 as a reference potential.

[0073] The voltage measurement unit 10b measures the voltage at node N10, one of multiple nodes between multiple voltage-dividing resistors included in the insulation detection circuit 100b. For example, the voltage measurement unit 10b has an A / D converter 13, and measures the voltage at node N10 using the A / D converter 13. Node N10 is an example of a first node. In the second embodiment, the voltage measurement unit 10b measures the voltage at node N10 with respect to the potential of the negative terminal t2.

[0074] The control unit 20b determines whether the voltage at the node N10 measured by the voltage measurement unit 10b is equal to or lower than a predetermined voltage. The control unit 20b is an example of a determination unit. The predetermined voltage is not particularly limited, but may be, for example, ½ or ⅕ of the absolute maximum rating of the voltage measurement unit 10b (A / D converter 13).

[0075] Furthermore, when the control unit 20b determines that the voltage at node N10 measured by the voltage measurement unit 10b is equal to or lower than a predetermined voltage, the control unit 20b switches the switches SW2 and SW3 connected to node N9 so that the voltage at node N10 measured by the voltage measurement unit 10b exceeds the predetermined voltage. The control unit 20b is an example of a switching unit.

[0076] For example, when the switches SW2 and SW3 are in a non-conductive state and the voltage at the node N10 is equal to or lower than a predetermined voltage, the control unit 20b switches at least one of the switches SW2 and SW3 to a conductive state, thereby increasing the voltage at the node N10 and allowing the voltage at the node N10 to exceed the predetermined voltage.

[0077] In the first embodiment, an example was described in which the node at which the voltage measurement unit 10 measures the voltage is switched by controlling the switch SW1, but in the second embodiment, the voltage applied to the node at which the voltage measurement unit 10b measures the voltage is switched by controlling the switches SW2 and SW3.

[0078] The control unit 20b detects the insulation resistances Riso1 and Riso2 based on the voltage measured by the voltage measurement unit 10b. For example, if the voltage measured by the voltage measurement unit 10b is an abnormal value, the control unit 20b can determine that the insulation resistance Riso1 or Riso2 is abnormal.

[0079] In addition, if the insulation detection circuit 100b has one or more switches in addition to the switches SW2 and SW3, the control unit 20b can calculate the values ​​of the insulation resistances Riso1 and Riso2 using a predetermined algorithm from the voltage at the node N10 measured before and after the switching of one or more switches.

[0080] The control unit 20b may also diagnose a fault in the insulation detection circuit 100b or the voltage measurement unit 10b by comparing the voltage at the node N10 measured by the voltage measurement unit 10b before and after the switching of the switches SW2 and SW3. The control unit 20b is an example of a fault diagnosis unit. For example, the ratio of the voltages at the node N10 before and after the switching of the switches SW2 and SW3 should be a constant ratio corresponding to the resistance values ​​of the resistors R11, R12, R13, R14, and R15. However, if the constant ratio is not achieved, it can be determined that at least one of the resistors R11, R12, R13, R14, and R15 is faulty, or that the voltage measurement unit 10b is faulty.

[0081] In addition, in the second embodiment, the example in which the switches connected to the node N9 are the two switches SW2 and SW3 has been described, but this is not limiting. For example, the number of switches connected to the node N9 may be one, or three or more.

[0082] In addition, in embodiment 2, an example was described in which the voltage measurement unit 10b measures the voltage at node N10 based on the potential of the negative terminal t2, but it may also measure the voltage at node N10 based on the potential of ground GND.

[0083] The effects of the insulation resistance detecting device 1b according to the second embodiment can also be explained using FIG. 2 in the same manner as in the first embodiment.

[0084] As shown in (a) of FIG. 2, when the voltage measured by voltage measurement unit 10b (the voltage at node N10 in the second embodiment) exceeds a predetermined voltage, switches SW2 and SW3 are brought into a non-conductive state. Thereafter, the voltage of battery Bat drops, and as shown in (b) of FIG. 2, the voltage measured by voltage measurement unit 10b (the voltage at node N10 in the second embodiment) falls below the predetermined voltage. In this case, the proportion of error relative to the input voltage to voltage measurement unit 10b (A / D converter 13) increases, and the measurement error of voltage measurement unit 10b increases. Therefore, switches SW2 and SW3 are switched from a non-conductive state to a conductive state, and voltage measurement unit 10b measures the voltage at node N10. As shown in (c) of Figure 2, since the voltage at node N10 is higher than the voltage before the switches SW2 and SW3 are switched, the proportion of error relative to the input voltage to the voltage measurement unit 10b (A / D converter 13) can be reduced, and the measurement error of the voltage measurement unit 10b can be reduced.

[0085] In the second embodiment, as in the first embodiment, a switch may be connected between the voltage measurement unit 10b and a node to which a voltage higher than that of the node N10 is applied, and when it is determined that the voltage at the node N10 is equal to or lower than a predetermined voltage, the switch may be switched to measure the voltage at the node to which a voltage higher than that of the node N10 is applied. This improves the detection accuracy of the insulation resistances Riso1 and Riso2.

[0086] As described above, in embodiment 2, switches SW2 and SW3 are connected to node N9 and one of the multiple voltage dividing resistors, and when the switching unit (control unit 20b) determines that the voltage at node N10 measured by voltage measurement unit 10b is equal to or lower than a predetermined voltage, it switches switches SW2 and SW3 so that the voltage at node N10 measured by voltage measurement unit 10b exceeds the predetermined voltage.

[0087] According to this, when the voltage measured at node N10 drops below a predetermined voltage during a voltage drop of battery Bat or during measurement control, switches SW2 and SW3 are switched so that the voltage applied to node N10 becomes higher. Therefore, voltage measurement unit 10b can measure a voltage higher than the predetermined voltage at node N10, thereby reducing measurement errors of voltage measurement unit 10b. In this way, by switching the voltage applied to node N10, at which voltage measurement unit 10b measures voltage, for example, when the voltage of battery Bat drops, it is possible to suppress a decrease in the detection accuracy of insulation resistances Riso1 and Riso2.

[0088] For example, the voltage measurement unit 10b may measure the voltage at the node N10 with respect to the potential of the ground GND.

[0089] For example, the insulation resistance detecting device 1b is realized by a microcomputer or the like, but in the second embodiment, if the reference potential of the microcomputer is set to the potential of ground GND, the voltage at the node N10 can also be measured based on the potential of ground GND.

[0090] Alternatively, for example, the voltage measurement unit 10b may measure the voltage at the node N10 with the potential of the negative terminal t2 as the reference.

[0091] For example, the insulation resistance detection device 1b is realized by a microcomputer or the like. In the second embodiment, if the reference potential of the microcomputer is set to the potential of the negative terminal t2, the voltage at the node N10 can also be measured based on the potential of the negative terminal t2.

[0092] For example, the insulation resistance detection device 1b may further include a fault diagnosis unit (control unit 20b) that diagnoses a fault in the insulation detection circuit 100b or the voltage measurement unit 10b by comparing the voltage at node N10 measured by the voltage measurement unit 10b before and after switching of the switches SW2 and SW3.

[0093] This makes it possible to diagnose a fault in the insulation detection circuit 100b or the voltage measurement unit 10b depending on whether the ratio of the voltages at the node N10 before and after the switching of the switches SW2 and SW3 is constant.

[0094] (Other Embodiments) As described above, the embodiments have been described as examples of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. For example, the following modifications are also included in one embodiment of the present disclosure.

[0095] For example, the present disclosure can be realized not only as an insulation resistance detection device, but also as an insulation resistance detection method including steps (processing) performed by components that make up the insulation resistance detection device.

[0096] FIG. 5 is a flowchart showing an example of an insulation resistance detection method according to another embodiment.

[0097] As shown in FIG. 5 , the insulation resistance detection method includes a voltage measurement step (step S11) of measuring a voltage at a first node among a plurality of nodes between a plurality of voltage dividing resistors connected between the positive and negative terminals of a battery, the plurality of voltage dividing resistors being included in an insulation detection circuit for detecting insulation resistance in a path through which a current flows from the battery; a determination step (step S12) of determining whether the voltage at the first node measured in the voltage measurement step is equal to or lower than a predetermined voltage; and a switching step (step S13) of switching a switch connected to a second node among the plurality of nodes so that the voltage measured in the voltage measurement step exceeds the predetermined voltage if it is determined that the voltage at the first node measured in the voltage measurement step is equal to or lower than the predetermined voltage (Yes in step S12).

[0098] For example, the steps of the insulation resistance detection method may be executed by a computer (computer system), and the present disclosure may be realized as a program for causing a computer to execute the steps included in the insulation resistance detection method.

[0099] Furthermore, the present disclosure can be realized as a non-transitory computer-readable recording medium, such as a CD-ROM on which the program is recorded.

[0100] For example, when the present invention is realized as a program (software), each step is performed by running the program using hardware resources such as a computer's CPU, memory, input / output circuits, etc. In other words, each step is performed by the CPU acquiring data from memory or input / output circuits, etc., performing calculations, and outputting the calculation results to memory or input / output circuits, etc.

[0101] Furthermore, each of the components included in the insulation resistance detecting device of the above-described embodiment may be realized as a dedicated or general-purpose circuit.

[0102] Furthermore, each of the components included in the insulation resistance detecting device of the above-described embodiment may be realized as an LSI (Large Scale Integration) which is an integrated circuit (IC).

[0103] Furthermore, the integrated circuit is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor. A programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor in which the connections and settings of circuit cells within the LSI can be reconfigured may also be used.

[0104] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, that technology may naturally be used to integrate the components included in the insulation resistance detection device.

[0105] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope of the present disclosure.

[0106] The present disclosure can be applied to a device for detecting insulation resistance in a path through which current flows from a high-voltage battery mounted on a vehicle or the like.

[0107] 1, 1a, 1b Insulation resistance detection device 10, 10a, 10b Voltage measurement unit 11, 11a, 12, 12a, 13 A / D converter 20, 20a, 20b Control unit 100, 100a, 100b Insulation detection circuit Bat Battery GND Ground N1, N2, N3, N4, N5, N6, N7, N8, N9, N10 Nodes R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 Resistors Riso1, Riso2 Insulation resistance SW1, SW1a, SW2, SW3 Switches t1 Positive terminal t2 Negative terminal

Claims

1. a voltage measuring unit configured to measure a voltage at a first node among a plurality of nodes between the plurality of voltage dividing resistors included in an insulation detection circuit configured to detect insulation resistance in a path through which a current from the battery flows, the plurality of voltage dividing resistors being connected between a positive terminal and a negative terminal of the battery; a determination unit that determines whether or not the voltage at the first node measured by the voltage measurement unit is equal to or lower than a predetermined voltage; a switching unit that switches a switch connected to a second node among the plurality of nodes when it is determined that the voltage at the first node measured by the voltage measurement unit is equal to or lower than a predetermined voltage, so that the voltage measured by the voltage measurement unit exceeds the predetermined voltage. Insulation resistance detection device.

2. the second node is a node to which a voltage higher than that of the first node is applied, the switch is connected between the second node and the voltage measurement unit, the switching unit switches the switch to connect the second node and the voltage measurement unit when it is determined that the voltage at the first node measured by the voltage measurement unit is equal to or lower than the predetermined voltage; The voltage measurement unit measures a voltage at the second node.

2. An insulation resistance detection device according to claim 1.

3. the positive terminal is connected to ground via at least one of the plurality of voltage dividing resistors; the negative terminal is connected to the ground via at least one other resistor among the plurality of voltage dividing resistors; the voltage measurement unit measures voltages at the first node and the second node with respect to a potential of the ground; 3. An insulation resistance detection device according to claim 2.

4. the voltage measurement unit measures voltages at the first node and the second node with respect to a potential of the negative electrode terminal; 3. An insulation resistance detection device according to claim 2.

5. further comprising a fault diagnosis unit that diagnoses a fault in the insulation detection circuit or the voltage measurement unit by comparing a voltage at the first node and a voltage at the second node measured by the voltage measurement unit. The insulation resistance detection device according to any one of claims 2 to 4.

6. the switch is connected to the second node and any one of the plurality of voltage dividing resistors; when it is determined that the voltage at the first node measured by the voltage measurement unit is equal to or lower than the predetermined voltage, the switching unit switches the switch so that the voltage at the first node measured by the voltage measurement unit exceeds the predetermined voltage.

3. An insulation resistance detection device according to claim 1 or 2.

7. the positive terminal is connected to ground via at least one of the plurality of voltage dividing resistors; the negative terminal is connected to the ground via at least one other resistor among the plurality of voltage dividing resistors; the voltage measurement unit measures a voltage at the first node with respect to a potential of the ground; 7. An insulation resistance detection device according to claim 6.

8. The voltage measurement unit measures a voltage at the first node based on a potential of the negative electrode terminal.

7. An insulation resistance detection device according to claim 6.

9. and a fault diagnosis unit that diagnoses a fault in the insulation detection circuit or the voltage measurement unit by comparing a voltage at the first node measured by the voltage measurement unit before and after switching of the switch.

7. An insulation resistance detection device according to claim 6.

10. a voltage measuring step of measuring a voltage at a first node among a plurality of nodes between a plurality of voltage dividing resistors included in an insulation detection circuit for detecting insulation resistance in a path through which a current from the battery flows, the plurality of voltage dividing resistors being connected between a positive terminal and a negative terminal of the battery; a determination step of determining whether or not the voltage at the first node measured in the voltage measurement step is equal to or lower than a predetermined voltage; a switching step of switching a switch connected to a second node among the plurality of nodes so that the voltage measured in the voltage measuring step exceeds the predetermined voltage when it is determined that the voltage at the first node measured in the voltage measuring step is equal to or lower than a predetermined voltage. Insulation resistance detection method.