Insulation Abnormality Detection Device and Insulation Abnormality Detection Method

Abstract

The present invention provides an insulation abnormality detection device and method capable of highly accurately detecting insulation abnormalities in a vehicle. A control unit is connected to a second switch in a voltage detection circuit, closing the first switch connected to one terminal of a capacitor and the second switch connected to the other terminal of the capacitor, thereby forming an insulation measurement path. The voltage of the capacitor charged through the insulation measurement path is measured, and insulation abnormalities are detected based on this voltage. The control unit also forms the insulation measurement path and closes a third switch. After a first time has elapsed, the control unit detects insulation abnormalities based on the capacitor voltage measured a second time after the third switch is closed.

Description

Technical Field

[0001] The present invention relates to an insulation abnormality detection device and an insulation abnormality detection method. Background Art

[0002] In recent years, the number of ECUs (Electric Control Units) requiring power supply has continued to increase in vehicles as control becomes more complex. This increase in ECUs has also led to an increase in parasitic capacitance accumulated in the vehicle body, which functions as a ground. If an abnormality occurs, such as a drop in the insulation resistance of the vehicle body, the parasitic capacitance could be supplied to the load via the battery, potentially causing malfunction.

[0003] In contrast, conventionally known technology detects vehicle insulation abnormality based on the voltage of a flying capacitor charged while a battery, a flying capacitor, vehicle insulation resistance, and vehicle body ground are connected (see, for example, Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-133965

[0007] However, in the conventional technology, there is still room for further improvement in terms of detecting insulation abnormalities in vehicles with high accuracy. Summary of the Invention

[0008] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an insulation abnormality detection device and an insulation abnormality detection method capable of detecting an insulation abnormality of a vehicle with high accuracy.

[0009] To solve the above-mentioned problems and achieve the purpose, the present invention relates to an insulation abnormality detection device comprising a voltage detection circuit and a control unit. The voltage detection circuit comprises a battery, a capacitor connected in parallel with the battery, a plurality of first switches connected to the input sides of the two electrodes of the capacitor, a plurality of second switches connected to the output sides of the two electrodes of the capacitor, and a third switch connected in parallel with the capacitor. The control unit is connected to the second switch in the voltage detection circuit, turns on the first switch connected to one electrode of the capacitor and the second switch connected to the other electrode of the capacitor, thereby forming an insulation measurement path, measures the voltage of the capacitor charged through the insulation measurement path, and detects insulation abnormalities based on this voltage. The control unit forms the insulation measurement path and turns on the third switch. After a first time has passed, the control unit detects insulation abnormalities based on the capacitor voltage measured after a second time has passed since the third switch was turned off.

[0010] According to the present invention, insulation abnormality in a vehicle can be detected with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram showing an example of an in-vehicle system according to an embodiment.

[0012] Figure 2 This is a diagram showing an example of a voltage detection circuit according to an embodiment.

[0013] Figure 3 It is a graph showing the measured voltage values of VRp and VRn.

[0014] Figure 4 This is a flowchart showing the overall processing procedure executed by the battery ECU according to the embodiment.

[0015] Figure 5 This is a flowchart showing the processing procedure of VRp measurement processing executed by the battery ECU according to the embodiment.

[0016] Figure 6 This is a flowchart showing the processing procedure of VRn measurement processing executed by the battery ECU according to the embodiment.

[0017] -Explanation of symbols-

[0018] 1: Vehicle system;

[0019] 2: Battery;

[0020] 2A, 2B: battery stack;

[0021] 2a, 2b: battery cells;

[0022] 4: Motor;

[0023] 5: compressor;

[0024] 10: Battery ECU;

[0025] 12: Voltage detection circuit;

[0026] 13: AD conversion unit;

[0027] 14: Control Department;

[0028] 15: Power IC;

[0029] 21: DCDC converter;

[0030] 30: Air conditioning ECU;

[0031] 31: Inverter;

[0032] 40:MG_ECU;

[0033] 50: HV_ECU;

[0034] C1: capacitor;

[0035] C2: parasitic capacitance;

[0036] 11a, 11b: monitoring IC;

[0037] R: insulation resistance;

[0038] R1~R6: resistors;

[0039] Rp, Rn: insulation resistance;

[0040] SW1~SW5: switches. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the insulation abnormality detection device and insulation abnormality detection method disclosed in the present application will be described in detail with reference to the accompanying drawings.

[0042] Figure 1 This figure illustrates an example of an in-vehicle system according to an embodiment. In-vehicle system 1 is a system installed in a vehicle such as a hybrid electric vehicle (HEV), an electric vehicle (EV), or a fuel cell vehicle (FCV). In-vehicle system 1 controls the charging and discharging of a power supply, including the power supply to the motor that powers the vehicle.

[0043] The in-vehicle system 1 includes a battery 2, SMRs (System Main Relays) 3a and 3b, a motor 4, a compressor 5, a battery ECU (an example of an insulation failure detection device) 10, a PCU 20, an air conditioning ECU 30, a MG_ECU (Motor Generator ECU) 40, and an HV_ECU (Hybrid ECU) 50. Electrical components such as the motor 4, compressor 5, PCU 20, air conditioning ECU 30, and MG_ECU 40 are examples of load circuits. PCU stands for Power Control Unit, and ECU stands for Electronic Control Unit.

[0044] Battery 2 is a power source (battery) insulated from the vehicle body (not shown). It is composed of a plurality of, for example, two, battery stacks 2A and 2B connected in series. Each battery stack 2A and 2B is composed of a plurality of, for example, three, battery cells 2a and 2b connected in series. In other words, battery 2 is a high-voltage DC power source.

[0045] The number of battery stacks and the number of battery cells are not limited to the numbers described above or shown in the drawings. For example, lithium-ion secondary batteries, nickel-metal hydride secondary batteries, etc. can be used as battery cells, but the present invention is not limited thereto.

[0046] SMR 3a is turned on and off by the control of HV_ECU 50, and when turned on, connects the highest voltage side of battery 2 to PCU 20. SMR 3b is turned on and off by the control of HV_ECU 50, and when turned on, connects the lowest voltage side of battery 2 to PCU 20.

[0047] The battery ECU 10 is an electronic control unit that monitors and controls the status of the battery 2. The battery ECU 10 includes a monitoring IC (Integrated Circuit) 11a, a monitoring IC 11b, a voltage detection circuit 12, an A / D (Analog / Digital) converter 13, a control unit 14, and a power supply IC 15. The power supply IC 15 supplies power to the monitoring ICs 11a, 11b, the voltage detection circuit 12, the A / D converter 13, and the control unit 14.

[0048] The monitoring IC 11a is connected to each of the multiple battery cells 2a (connection wires omitted) to monitor the voltage of each battery cell 2a. Furthermore, the monitoring IC 11a is connected to the highest and lowest voltage sides of the battery stack 2A to monitor the voltage of the battery stack 2A. Furthermore, the monitoring IC 11b is connected to each of the multiple battery cells 2b (connection wires omitted) to monitor the voltage of each battery cell 2b. Furthermore, the monitoring IC 11b is connected to the highest and lowest voltage sides of the battery stack 2B to monitor the voltage of the battery stack 2B.

[0049] Alternatively, a monitoring IC may be provided for each battery cell, or a monitoring IC may be provided for each battery 2. When a monitoring IC is provided for each battery cell, the control unit 14 uses the sum of the voltages of each battery stack monitored by each monitoring IC as the total voltage of the battery 2. Furthermore, when a single monitoring IC is provided for each battery 2, the control unit 14 uses the total voltage of the battery 2 monitored by the monitoring IC. The monitoring ICs 11a and 11b are external devices to the control unit 14.

[0050] In addition, the configuration and operation of the voltage detection circuit 12, the A / D (Analog / Digital) converter 13, and the control unit 14 of the battery ECU 10 are as follows: Figure 2 To be discussed later.

[0051] The PCU 20 boosts the power supply voltage supplied to the motor 4, the vehicle's electrical equipment, etc., and converts it from DC to AC voltage. Figure 1 As shown, the PCU 20 is connected to the positive and negative sides of the battery 2. The PCU 20 includes a DC-DC converter 21, a three-phase inverter 22, a low-voltage side smoothing capacitor 23a, and a high-voltage side smoothing capacitor 23b.

[0052] The air-conditioning ECU 30 includes a control device (not shown) and an inverter 31 that converts a power supply voltage supplied to the compressor 5 from a direct current to an alternating current.

[0053] The MG_ECU 40 is an electronic control unit that monitors and controls the status of the PCU 20. Specifically, it monitors the operating states of the DC-DC converter 21 and the three-phase inverter 22, as well as the charge states of the low-voltage smoothing capacitor 23a and the high-voltage smoothing capacitor 23b. The MG_ECU 40 then obtains information regarding the presence or absence of voltage boosting in the PCU 20 and the boosted voltage, and notifies the HV_ECU 50, the higher-level device. Furthermore, the MG_ECU 40 controls the operation of the PCU 20 based on instructions from the HV_ECU 50.

[0054] Next, use Figure 2The voltage detection circuit 12 according to the embodiment will be described. Figure 2 1 is a diagram showing an example of the voltage detection circuit 12 according to the embodiment. Figure 2 In FIG. 1 , the structure of the voltage detection circuit 12 connected to the battery stack 2A in the battery 2 is shown, but the battery stack 2B is also configured with the voltage detection circuit 12 connected to the battery stack 2A. Figure 2 The same voltage detection circuit 12. In addition, Figure 2 In the description, the battery stack 2A is referred to as the battery 2 .

[0055] like Figure 2 As shown, the voltage detection circuit 12 includes switches SW1 to SW5, a capacitor C1, and resistors R1 to R6. Although solid-state relays (SSRs) can be used as the switches SW1 to SW5, for example, the present invention is not limited thereto.

[0056] Furthermore, among the switches SW1 to SW5 , the switches SW1 and SW2 are first switches, the switches SW4 and SW5 are second switches, and the switch SW3 is a third switch.

[0057] like Figure 2 As shown, on the positive side of battery 2 (battery stack 2A), switch SW1, resistor R1, switch SW4, and resistor R3 are connected in series in order of proximity to battery 2. Furthermore, on the negative side of battery 2 (battery stack 2A), switch SW2, resistor R2, switch SW5, and resistor R4 are connected in series in order of proximity to battery 2.

[0058] Capacitor C1 is connected in parallel with battery 2, functioning as a flying capacitor. Specifically, one electrode of capacitor C1 is connected between resistor R1 and switch SW4, and the other electrode is connected between resistor R2 and switch SW5. In other words, one electrode of capacitor C1 has switch SW1 connected to the input side and switch SW4 connected to the output side; the other electrode has switch SW2 connected to the input side and switch SW5 connected to the output side. Specifically, multiple first switches, namely switches SW1 and SW2, are connected to the input side of each of capacitor C1's two electrodes, respectively, while multiple second switches, namely switches SW4 and SW5, are connected to the output side of each of capacitor C1's two electrodes. Furthermore, switch SW3 is connected in parallel with capacitor C1.

[0059] One end of the resistor R5 is connected to the switch SW4 in parallel with the resistor R3 and the other end is grounded to the vehicle body, etc. One end of the resistor R6 is connected to the switch SW5 in parallel with the resistor R4 and the other end is grounded to the vehicle body, etc.

[0060] Insulation resistance Rn and parasitic capacitance C2 are connected in parallel between the negative side of battery 2 and one end of resistors R5 and R6. Insulation resistance Rp and parasitic capacitance C3 are connected in parallel between the positive side of battery 2 and one end of resistors R5 and R6. Parasitic capacitance C2 and parasitic capacitance C3 have approximately the same value. Parasitic capacitance is also referred to as common capacitance.

[0061] Resistor R3 is connected to the positive terminal of AD converter 13, which is configured as an amplifier, and resistor R4 is connected to the negative terminal of AD converter 13. AD converter 13 converts the analog voltage input from voltage detection circuit 12 into a digital voltage and outputs it to control unit 14.

[0062] The control unit 14 is a processing device such as a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory).

[0063] The control unit 14 detects insulation abnormalities of the insulation resistances Rp and Rn by executing the insulation abnormality detection method according to the embodiment.

[0064] Here, use Figure 2 The circuit operation of the voltage detection circuit 12 when the insulation abnormality detection method according to the embodiment is executed will be described. In the insulation abnormality detection method according to the embodiment, the following four processes (1) to (4) are performed.

[0065] (1) Battery voltage measurement and processing

[0066] (2) VRp measurement processing

[0067] (3) VRn measurement processing

[0068] (4) Insulation abnormality detection and processing

[0069] In the insulation abnormality detection method involved in the embodiment, by particularly improving the measurement methods of (2) VRp measurement and (3) VRn measurement, it becomes possible to measure the voltage of capacitor C1 without the influence of parasitic capacitances C2 and C3, thereby achieving high-precision insulation abnormality detection.

[0070] (1) Battery voltage measurement and processing

[0071] The battery voltage measurement process is a process for measuring the battery voltage of the battery 2. Specifically, the control unit 14 first turns on the switches SW1 and SW2, and turns off the switches SW3, SW4, and SW5.

[0072] As a result, a charging path is formed in the order of the battery 2 , the switch SW1 , the resistor R1 , the capacitor C1 , the resistor R2 , and the switch SW2 , whereby the capacitor C1 is charged by the battery 2 .

[0073] Next, after a predetermined time has elapsed, i.e., after the charging of capacitor C1 has completed, the control unit 14 opens switches SW1 and SW2 and closes switches SW4 and SW5. This establishes electrical continuity from capacitor C1 to the ground (the vehicle body), allowing the charge stored in capacitor C1 to be discharged via resistors R5 and R6. Furthermore, at this time, the analog voltage of capacitor C1 is output to the A / D converter 13 via resistors R3 and R4, where it is converted into a digital voltage. Based on the digital voltage output from the A / D converter 13, the control unit 14 then measures the voltage of capacitor C1, i.e., the battery voltage of battery 2.

[0074] Then, after measuring the battery voltage of the battery 2 , the control unit 14 turns on the switch SW3 to completely discharge the charge of the capacitor C1 , thereby terminating the battery voltage measurement process.

[0075] (2) VRp measurement processing

[0076] After the battery voltage measurement process, the VRp measurement process is performed. Alternatively, the VRn measurement process may be performed first. The VRp measurement process forms an insulation measurement path by closing switch SW2 connected to the input side of capacitor C1 and switch SW4 connected to the output side of capacitor C1. This forms the insulation measurement path, thereby measuring VRp, a voltage used to calculate the resistance value of insulation resistance Rp on the positive side of battery 2. Specifically, the insulation measurement path in the VRp measurement process includes the negative side of battery 2, switch SW2, resistor R2, capacitor C1, switch SW4, resistor R5, insulation resistance Rp, parasitic capacitance C3, and the positive side of battery 2. Forming this insulation measurement path charges capacitor C1 with a voltage (VRp) corresponding to the resistance value of insulation resistance Rp. In this embodiment, a removal operation is performed to remove the parasitic capacitance C3 flowing through capacitor C1 before the VRp measurement operation, thereby enabling VRp measurement without the influence of parasitic capacitance C3.

[0077] Specifically, the control unit 14 turns on the switches SW2, SW3, and SW4 as the removal operation. Since the switch SW3 is turned on during the discharge process performed at the end of the battery voltage measurement process, it remains turned on during the removal operation.

[0078] The control unit 14 maintains the state of switches SW2, SW3, and SW4 being turned on for a fixed time (a first time). In other words, the control unit 14 performs the following removal operation: the control unit 14 turns on switch SW2 (the first switch) and switch SW4 (the second switch) to form an insulation measurement path, and turns on switch SW3 (the third switch) for the first time.

[0079] As a result, the insulation measurement path passes through the switch SW3 instead of the capacitor C1 , so that the charge of the parasitic capacitance C3 is not charged to the capacitor C1 but is discharged (removed).

[0080] After the removal operation, VRp measurement is performed. Specifically, after the first time period, the control unit 14 closes switches SW4 and SW5, thereby converting the voltage of capacitor C1 through the A / D converter 13, and then opens switch SW3. Next, the control unit 14 closes switches SW2 and SW4 to form an insulation measurement path, and maintains the open state of switch SW3 for a fixed time period (a second time period). In this case, if the insulation resistance Rp is normal (sufficiently large), the insulation measurement path is not conductive, and thus capacitor C1 is not charged. However, if the insulation resistance Rp decreases due to an abnormality such as degradation, capacitor C1 will be charged.

[0081] After the second time has passed, the control unit 14 turns off the switch SW2 and turns on the switches SW4 and SW5, thereby converting the voltage of the capacitor C1 by the AD converter 13 and measuring it as VRp. The measured VRp is used in the subsequent insulation abnormality detection process.

[0082] That is, the control unit 14 detects an insulation abnormality based on the voltage VRp of the capacitor C1 measured after the second time has passed since the switch SW3 serving as the third switch was turned off.

[0083] After measuring VRp, the control unit 14 closes switch SW3, completely discharging the charge in capacitor C1 and terminating the VRp measurement process. In other words, switch SW3, as the third switch, serves both as a switch for removing the charge from parasitic capacitance C3 and as a discharge switch for discharging the charge from capacitor C1. This eliminates the need for separate switches, thereby reducing costs.

[0084] (3) VRn measurement

[0085] After the VRp measurement process, the VRn measurement process is performed. The VRn measurement process forms an insulation measurement path by closing switch SW1 connected to the input side of capacitor C1 and switch SW5 connected to the output side of capacitor C1. This process measures VRn, a voltage used to calculate the resistance value of insulation resistance Rn on the negative side of battery 2. Specifically, the insulation measurement path in the VRn measurement process includes the positive side of battery 2, switch SW1, resistor R1, capacitor C1, switch SW5, resistor R6, insulation resistance Rn, parasitic capacitance C2, and the negative side of battery 2. This insulation measurement path allows capacitor C1 to be charged with a voltage (VRn) corresponding to the resistance value of insulation resistance Rn. In this embodiment, similar to the VRp measurement process, a removal operation is performed before the VRn measurement operation to remove the parasitic capacitance C2 flowing through capacitor C1. This allows VRn measurement to be performed without the influence of parasitic capacitance C2.

[0086] Specifically, the control unit 14 turns on the switches SW1, SW3, and SW5 as the removal operation. Note that since the switch SW3 is turned on during the discharge process performed at the end of the VRp measurement process, it remains turned on during the removal operation.

[0087] The control unit 14 maintains the state of switches SW1, SW3, and SW5 being turned on for a fixed time (a first time). In other words, the control unit 14 performs the following removal operation: the control unit 14 turns on switch SW1 (the first switch) and switch SW5 (the second switch) to form an insulation measurement path, and turns on switch SW3 (the third switch) for the first time.

[0088] As a result, the insulation measurement path passes through the switch SW3 instead of the capacitor C1 , so that the charge of the parasitic capacitance C2 is not charged to the capacitor C1 but is discharged (removed).

[0089] After the removal operation, VRn is measured. Specifically, after a first time has elapsed, the control unit 14 closes switches SW4 and SW5, thereby converting the voltage of capacitor C1 via the A / D converter 13, and then opens switch SW3. Next, the control unit 14 closes switches SW1 and SW5 to form an insulation measurement path, and maintains the closed state of switch SW3 for a predetermined time (a second time). In this case, if the insulation resistance Rn is normal (sufficiently large), the insulation measurement path is not connected via the insulation resistance Rn, and thus capacitor C1 is not charged. However, if the insulation resistance Rn decreases due to an abnormality such as degradation, the insulation measurement path is connected via the insulation resistance Rn, and thus capacitor C1 is charged.

[0090] Then, after the second time has passed, the control unit 14 turns off the switch SW1 and turns on the switches SW4 and SW5, thereby converting the voltage of the capacitor C1 by the AD converter 13 and measuring it as VRn. The measured VRn is used in the subsequent insulation abnormality detection process.

[0091] That is, the control unit 14 detects an insulation abnormality based on the voltage VRn of the capacitor C1 measured after the second time has passed since the switch SW3 serving as the third switch was turned off.

[0092] After measuring VRn, the control unit 14 closes switch SW3, completely discharging the charge in capacitor C1 and terminating the VRn measurement process. In other words, switch SW3, as the third switch, serves both as a switch for removing the charge from parasitic capacitance C2 and as a discharge switch for discharging the charge from capacitor C1. This eliminates the need for separate switches, thereby reducing costs.

[0093] Here, use Figure 3 The voltage values of VRp and VRn measured by the VRp measurement process and the VRn measurement process will be described. Figure 3 Graph showing the measured voltage values of VRp and VRn. Figure 3 In FIG, the vertical axis shows the sum of VRp and VRn, and the horizontal axis shows the charging time of capacitor C1. Figure 3 , the sum of VRp and VRn is shown, but VRp and VRn may be shown separately.

[0094] also, Figure 3 The so-called "common removal period" shown is the first time, and the so-called "insulation resistance calculation period" is the second time. Figure 3 , as a reference example, shows the total of VRp and VRn detected in a voltage detection circuit that does not include the switch SW3 as the third switch.

[0095] like Figure 3 As shown, in the reference example, the charge of the parasitic capacitance is charged to the capacitor. Therefore, during the period from time t1 to time t2, i.e., the common removal period, the charge of the battery and the parasitic capacitance are accumulated in the capacitor. Therefore, for example, if the parasitic capacitance increases, the charge accumulated in the capacitor increases, and there is a concern that the battery voltage cannot be accurately measured based on the capacitance of the capacitor.

[0096] Therefore, in this embodiment, the control unit 14 forms an insulation measurement path and turns on the switch SW3 during the period from time t1 to time t2 when the charge of the parasitic capacitors C2 and C3 are mutually removed, thereby preventing the charge of the parasitic capacitor C2 from accumulating in the capacitor C1. Figure 3 As shown, during the common removal period, the switch SW3 is turned on, so that the capacitor C1 is not charged, and thus the voltage of the capacitor C1 is substantially zero.

[0097] Then, after the common elimination period has elapsed, that is, at time t2 after the charge in parasitic capacitors C2 and C3 has completely discharged, the control unit 14 performs A / D conversion on the voltage of capacitor C1 using the A / D converter 13, establishes an insulation measurement path, and opens switch SW3, thereby starting to charge capacitor C1. Specifically, the common elimination period, which is the first time, is the time required from the formation of the insulation measurement path to the completion of charging of parasitic capacitor C2, assuming the absence of switch SW3. This eliminates the influence of parasitic capacitors C2 and C3, allowing only the charge of battery 2 to be stored in capacitor C1.

[0098] Then, the control unit 14 continues to open the switch SW3 during the insulation resistance calculation period (the period from time t2 to time t3) as the second time, thereby charging the capacitor C1. In other words, the second time is the time required for the battery 2 to complete charging of the capacitor C1.

[0099] Then, at time t3 after the insulation resistance calculation period, the control unit 14 performs AD conversion on the voltage of the capacitor C1 through the AD conversion unit 13, and detects abnormalities in the insulation resistances Rp and Rn based on the AD-converted voltage of the capacitor C1 through the insulation abnormality detection process (4) described later.

[0100] Thus, in the insulation abnormality detection method according to the embodiment, by turning on switch SW3 during the common removal period, it is possible to measure the voltage of capacitor C1 without the influence of parasitic capacitances C2 and C3. In other words, the insulation abnormality detection method according to the embodiment can accurately detect abnormalities in insulation resistances Rp and Rn.

[0101] Furthermore, as described above, in the insulation abnormality detection method according to the embodiment, since the charge of parasitic capacitance C2 is not accumulated in capacitor C1, the capacitance of capacitor C1 can be reduced by the amount of parasitic capacitance C2. In other words, the capacitance of capacitor C1 is set to the capacitance minus the parasitic capacitance C2. This reduces the cost of capacitor C1.

[0102] (4) Insulation abnormality detection and processing

[0103] The insulation abnormality detection process is a process for detecting an abnormality in the insulation resistance RN based on the measured VRp and VRn. Specifically, the control unit 14 calculates Figure 3 The voltage (Vt2) of the capacitor C1 that has undergone AD conversion at time t2 and the voltage (Vt3) of the capacitor C1 that has undergone AD conversion at time t3 are shown as increasing rates (slopes). That is, the increasing rate is calculated as (Vt3-Vt2) / (t3-t2). Then, the control unit 14 determines that the insulation resistances Rp and Rn are normal when the increasing rate is less than a given threshold value, and determines that the insulation resistances Rp and Rn are abnormal when the increasing rate is greater than a given threshold value. In other words, the control unit 14 determines that the insulation resistances Rp and Rn are abnormal based on the increasing rate. Figure 3 The slopes of VRp and VRn during the insulation resistance calculation period (the period from time t2 to time t3) shown here detect insulation abnormality.

[0104] In addition, the control unit 14 may use the increase rate of the sum of VRp and VRn, or may calculate the increase rate for each of VRp and VRn to detect insulation abnormalities in each of them.

[0105] The control unit 14 is not limited to performing insulation abnormality determination based on the increase rate, and may determine insulation abnormality based on whether the sum of VRp and VRn (or the individual values of VRp and VRn) is equal to or greater than a given threshold.

[0106] Alternatively, the control unit 14 may detect an insulation abnormality without performing A / D conversion on the voltage of the capacitor C1 at time t2. In such a case, the control unit 14 may calculate the above-mentioned rate of increase by setting Vt2 = 0.

[0107] Furthermore, the control unit 14 can detect the abnormality of the switch SW3 being fixed open based on the voltage of the capacitor C1. Specifically, the control unit 14 measures the first time ( Figure 3 When the voltage of the capacitor C1 after the common removal period (shown as shown) has passed is equal to or greater than a predetermined value, an off-stuck abnormality of the switch SW3 serving as the third switch is detected.

[0108] Specifically, if the voltage, which should be substantially zero, is not zero after the common removal period, the control unit 14 assumes that the capacitor C1 is unintentionally charged due to an abnormality in which the switch SW3 is not closed, and detects the abnormality of the switch SW3 being stuck open. This allows for highly accurate detection of the abnormality of the switch SW3 being stuck open.

[0109] Furthermore, the control unit 14 may measure the parasitic capacitance C2 before the common removal period, which serves as the first time, and determine the length of the common removal period based on the parasitic capacitance C2. Specifically, in (2) or (3) above, the control unit 14 forms an isolated measurement path before turning on the third switch SW3 for the first time, and then turns off the switch SW3 for the first time to measure the voltage of the charged capacitor C1. This voltage is the voltage that charges the parasitic capacitance C2, so the first time is determined based on the parasitic capacitance C2 estimated based on this voltage.

[0110] This allows the length of the common removal period as the first time to be determined with high accuracy, thereby accurately preventing, for example, the first time from being excessively long or too short so that charge in the parasitic capacitance C2 remains during insulation resistance calculation.

[0111] Next, use Figures 4 to 6 The content of the processing executed by the battery ECU 10 , which is the insulation abnormality detection device according to the embodiment, will be described. Figure 4 1 is a flowchart showing the overall processing procedure executed by the battery ECU 10 according to the embodiment. Figure 5 : is a flowchart showing the processing procedure of the VRp measurement process executed by the battery ECU 10 according to the embodiment. Figure 6 This is a flowchart showing the processing procedure of the VRn measurement process executed by the battery ECU 10 according to the embodiment.

[0112] First, use Figure 4 The overall processing procedure is described.

[0113] like Figure 4 As shown, the control unit 14 of the battery ECU 10 controls the voltage detection circuit 12 to measure the battery voltage of the battery 2 (step S101). Next, after measuring the battery voltage, the control unit 14 performs a discharge process to discharge the charge of the capacitor C1 (step S102).

[0114] Next, the control unit 14 controls the voltage detection circuit 12 to perform a VRp measurement process (step S103 ). Next, after measuring VRp, the control unit 14 performs a discharge process to discharge the charge of the capacitor C1 (step S104 ).

[0115] Next, the control unit 14 controls the voltage detection circuit 12 to perform a VRn measurement process (step S105 ). Next, after measuring VRn, the control unit 14 performs a discharge process to discharge the charge of the capacitor C1 (step S106 ).

[0116] Next, the control unit 14 performs insulation abnormality detection processing for detecting insulation abnormality of the insulation resistance RN based on the measured VRp and VRn (step S107 ), and ends the processing.

[0117] Next, use Figure 5 The processing procedure of VRp measurement processing will be described.

[0118] like Figure 5 As shown, the control unit 14 turns on the switches SW2, SW3, and SW4 in the voltage detection circuit 12 (step S201). Figure 4 The step S102 shown is already connected, so in step S201, it will continue to be connected.

[0119] Next, the control unit 14 determines whether the first time has elapsed since the switches SW2 , SW3 , and SW4 were turned on (step S202 ). If the first time has not elapsed (step S202 : No), step S202 is repeatedly executed until the first time has elapsed.

[0120] When the first time has elapsed (step S202: YES), the control unit 14 performs AD conversion on the voltage of the capacitor C1 using the AD converter 13 and turns off the switch SW3 (step S203). This starts charging the capacitor C1 (step S204).

[0121] Next, the control unit 14 determines whether the second time has elapsed after the switch SW3 is turned off (step S205 ). If the second time has not elapsed (step S205 : No), step S205 is repeatedly executed until the second time has elapsed.

[0122] When the second time has elapsed (step S205 : Yes), the control unit 14 acquires VRp through AD sampling by the AD converter 13 (step S206 ), and ends the process.

[0123] Next, use Figure 6 The processing procedure of VRn measurement processing will be described.

[0124] like Figure 6 As shown, the control unit 14 turns on the switch SW1, the switch SW3 and the switch SW5 in the voltage detection circuit 12 (step S301). In addition, the switch SW3 is turned on due to the discharge process ( Figure 4 The step S104 shown is already connected, so in step S301, it will continue to be connected.

[0125] Next, the control unit 14 determines whether the first time has passed after the switches SW1 , SW3 , and SW5 are turned on (step S302 ). If the first time has not passed (step S302 : No), step S302 is repeatedly executed until the first time has passed.

[0126] When the first time has elapsed (step S302: YES), the control unit 14 performs AD conversion on the voltage of the capacitor C1 by the AD converter 13 and then turns off the switch SW3 (step S303). This starts charging the capacitor C1 (step S304).

[0127] Next, the control unit 14 determines whether the second time has elapsed after the switch SW3 is turned off (step S305 ). If the second time has not elapsed (step S305 : No), step S305 is repeatedly executed until the second time has elapsed.

[0128] When the second time has elapsed (step S305 : Yes), the control unit 14 acquires VRp through AD sampling by the AD converter 13 (step S306 ), and ends the process.

[0129] As described above, the insulation abnormality detection device (battery ECU 10) according to the embodiment includes a voltage detection circuit 12 and a control unit 14. The voltage detection circuit 12 includes a battery 2, a capacitor C1 connected in parallel with the battery 2, a plurality of first switches (switches SW1 and SW2) connected to the input side of each of the two electrodes of capacitor C1, a plurality of second switches (switches SW4 and SW5) connected to the output side of each of the two electrodes of capacitor C1, and a third switch (switch SW3) connected in parallel with capacitor C1. The control unit 14 is connected to the second switch in the voltage detection circuit 12. By closing the first switch connected to one electrode of capacitor C1 and the second switch connected to the other electrode of capacitor C1, an insulation measurement path is formed. The voltage of capacitor C1 charged through the insulation measurement path is measured, and insulation abnormalities are detected based on this voltage. The control unit 14 forms the insulation measurement path and closes the third switch. After a first time has passed, the control unit 14 detects insulation abnormalities based on the voltage of capacitor C1 measured after a second time has passed since the third switch was closed. This allows for highly accurate detection of insulation abnormalities in a vehicle.

[0130] Further effects and modifications can be readily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Therefore, various modifications can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

Claims

1. An insulation abnormality detection device, characterized in that: have: a voltage detection circuit comprising a battery, a capacitor connected in parallel with the battery, two first switches, two second switches, and a third switch also serving as a discharge switch for discharging the capacitor; as well as a control unit that controls the operation of the voltage detection circuit to detect insulation abnormality of the battery, wherein one of the two first switches connects the positive electrode of the battery to one end of the capacitor, and the other connects the negative electrode of the battery to the other end of the capacitor; One of the two second switches connects one end of the capacitor to the control unit, and the other connects the other end of the capacitor to the control unit. The third switch forms a current path that bypasses the capacitor when turned on, and the third switch is connected in parallel with the capacitor at a position closer to the battery than the two second switches. The control unit turns on the third switch in a state where one of the two first switches and the other of the two second switches are turned on, or the other of the two first switches and one of the two second switches are turned on to form an insulation measurement path including the insulation resistance between the positive electrode and the negative electrode, turns off the third switch after a first time has elapsed, and detects the insulation abnormality based on the voltage of the capacitor measured after a second time has elapsed.

2. The insulation abnormality detection device according to claim 1, characterized in that: The first time is the time required from forming the insulation measurement path to completing charging of the parasitic capacitance.

3. The insulation abnormality detection device according to claim 1 or 2, characterized in that: The control unit forms the insulation measurement path and opens the third switch before turning on the third switch for the first time, thereby measuring the voltage of the charged capacitor and determining the first time based on the parasitic capacitance estimated based on the voltage.

4. The insulation abnormality detection device according to claim 1 or 2, characterized in that: The capacitance of the capacitor is set to a capacitance obtained by removing parasitic capacitance.

5. The insulation abnormality detection device according to claim 1 or 2, characterized in that: The control unit measures the voltage of the capacitor after the first time has elapsed, and detects an off-stuck abnormality of the third switch when the voltage is equal to or greater than a predetermined value.

6. An insulation abnormality detection method, performed by an insulation abnormality detection device including a voltage detection circuit and a control unit, wherein the voltage detection circuit includes a battery, a capacitor connected in parallel with the battery, two first switches, two second switches, and a third switch also serving as a discharge switch for discharging the capacitor, wherein the control unit controls the operation of the voltage detection circuit to detect an insulation abnormality in the battery. The insulation abnormality detection method is characterized in that: One of the two first switches connects the positive electrode of the battery to one end of the capacitor, and the other connects the negative electrode of the battery to the other end of the capacitor. One of the two second switches connects one end of the capacitor to the control unit, and the other connects the other end of the capacitor to the control unit. The third switch forms a current path that bypasses the capacitor when turned on, and the third switch is connected in parallel with the capacitor at a position closer to the battery than the two second switches. The insulation abnormality detection method comprises: a control step of turning on one of the two first switches and the other of the two second switches, or turning on the other of the two first switches and one of the two second switches, thereby forming an insulation measurement path including insulation resistance between the positive electrode and the negative electrode, measuring a voltage of the capacitor charged through the insulation measurement path, and detecting insulation abnormality based on the voltage; The control step turns on the third switch in a state where the insulation measurement path is formed, turns off the third switch after a first time has elapsed, and detects the insulation abnormality based on the voltage of the capacitor measured after a second time has elapsed.

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