Determination device and determination program

Abstract

This determination device (20) comprises a first resistor (R1) connected to a positive electrode-side power supply path (L1) via a first switch (Sp), and a second resistor R2 connected to a negative electrode-side power supply path (L2) via a second switch (Sn). A voltage acquisition unit (23) of the determination device acquires a first inter-terminal voltage (Vpy) that is the voltage across the first resistor when a first detection time (ty) has elapsed since the timing when the first switch was turned on, and acquires a second inter-terminal voltage (Vny) that is the voltage across the second resistor when the first detection time has elapsed since the timing when the second switch was turned on. A computation unit (26) of the determination device calculates a first detected value (Ry) as an insulation resistance value based on the first inter-terminal voltage (Vpy) and the second inter-terminal voltage (Vny), and a determination unit (28) of the determination device compares the first detected value and a first threshold (Ry_th) to determine whether the ground capacitance is within a desired range.

Description

Determination Device and Determination Program , ,

[0007] , ,

[0006] ,

[0005] Cross - Reference to Related Applications

[0001] This application is based on Japanese Application No. 2025 - 006742 filed on January 17, 2025, the contents of which are incorporated herein by reference.

[0002] This disclosure relates to a device for determining capacitance to ground and a determination program.

[0003] Conventionally, a leakage determination device for determining leakage between a DC power source and a ground part in a vehicle or the like has been known. Such a leakage determination device is described in, for example, Patent Document 1.

[0004] Incidentally, it is known that there is also capacitance to ground such as stray capacitance between a DC power source and a ground part. Conventionally, the magnitude of this capacitance to ground itself has rarely been a detection target, but in an electric vehicle having a high - voltage power source and various electrical devices, the capacitance to ground has tended to increase. And when the capacitance to ground increases and charges are stored therein, there is a risk that these charges will discharge during inspection or the like, causing a large current to flow. For this reason, in recent years, it has been desired to detect the magnitude of the capacitance to ground. As a method for detecting this capacitance to ground, for example, as described in Patent Document 2, a method of changing the measurement frequency, specifying the impedance characteristics of a circuit, and specifying the capacitance to ground by matching or the like from the impedance characteristics is known.

[0005] Japanese Patent No. 7468287 Japanese Patent No. 7243494

[0006] However, in order to specify the impedance characteristics by the method described in Patent Document 2, it is necessary to sequentially change the measurement frequency and measure, and for this purpose, functions such as sine - wave current application means are required, resulting in a problem that the circuit becomes large - sized and the cost increases.

[0007] This disclosure has been made in view of the above problems, and an object thereof is to provide a determination device and a determination program capable of determining capacitance to ground with a smaller - sized circuit and at a lower cost.

[0008] A determination device for solving the above problem is a determination device for determining the capacitance to ground between a DC power supply and a grounding part, comprising: a first resistor provided in a first electrical path between the grounding part and the positive electrode side power supply path; a first switch for switching the energization and disconnection of the first electrical path; a second resistor provided in a second electrical path between the grounding part and the negative electrode side power supply path; a second switch for switching the energization and disconnection of the second electrical path; a switch control unit for controlling the on / off state of the first switch and the second switch; a first voltage sensor for detecting a first terminal voltage which is the voltage across the first resistor; a second voltage sensor for detecting a second terminal voltage which is the voltage across the second resistor; a voltage acquisition unit for acquiring the first terminal voltage from the first voltage sensor and the second terminal voltage from the second voltage sensor; a calculation unit for calculating the value of insulation resistance based on the first terminal voltage and the second terminal voltage acquired by the voltage acquisition unit; and a determination unit for determining whether the capacitance to ground is within a desired range. The voltage acquisition unit acquires a first voltage between the first terminals detected when a first detection time has elapsed from the moment the first switch is turned on and the second switch is turned off, and acquires a first voltage between the second terminals detected when a first detection time has elapsed from the moment the first switch is turned off and the second switch is turned on, the first detection time is set to be shorter than a predetermined time for the changes in the voltage between the first terminals and the voltage between the second terminals to converge from the time the first switch and the second switch are switched on, the calculation unit calculates a first detected value as the value of the insulation resistance based on the first voltage between the first terminals and the first voltage between the second terminals, and the determination unit compares the first detected value with a first threshold value to determine whether the capacitance to ground is within a desired range.

[0009] A determination program for solving the above problem is a determination device for determining the capacitance to ground between a DC power supply and a grounding part, the determination device having a first resistor provided in a first electrical path between the grounding part and a positive-side power supply path, a first switch for switching the energization and disconnection of the first electrical path, a second resistor provided in a second electrical path between the grounding part and a negative-side power supply path, a second switch for switching the energization and disconnection of the second electrical path, a first voltage sensor for detecting a first terminal voltage which is the voltage across the first resistor, and a second voltage sensor for detecting a second terminal voltage which is the voltage across the second resistor, the determination program performed by the determination device comprises: a switch control step for controlling the on / off state of the first switch and the second switch; a voltage acquisition step for acquiring the first terminal voltage from the first voltage sensor and the second terminal voltage from the second voltage sensor; a calculation step for calculating the value of insulation resistance based on the first terminal voltage and the second terminal voltage acquired in the voltage acquisition step; and a determination step for determining whether the capacitance to ground is within a desired range. In the voltage acquisition step, the first voltage between the first terminals is acquired when a first detection time has elapsed from the time the first switch is turned on and the second switch is turned off, and the first voltage between the second terminals is acquired when a first detection time has elapsed from the time the first switch is turned off and the second switch is turned on, the first detection time is set to be shorter than a predetermined time for the changes in the voltage between the first terminals and the voltage between the second terminals to converge from the time the first switch and the second switch are switched on, the calculation step calculates a first detected value as the value of the insulation resistance based on the first voltage between the first terminals and the first voltage between the second terminals, and the determination step compares the first detected value with a first threshold value to determine whether the capacitance to ground is within a desired range.

[0010] With the above configuration, the capacitance to ground can be determined using a circuit that can detect the state of the existing insulation resistance, thus enabling miniaturization and cost reduction of the circuit.

[0011] The above-mentioned and other purposes, features, and benefits of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. The diagrams are as follows: Figure 1 is a configuration diagram of the control system; Figure 2 is a block diagram showing the functions of the control device; Figure 3 is a map showing the relationship between Rz and ty; Figure 4 is a diagram showing the relationship between Cx and Rz; Figure 5 is a diagram showing a comparison with Rz in relation to Cx and Ry; Figure 6 is a diagram showing the characteristics due to the change in Rx in relation to Cx and Ry; Figure 7 is an enlarged view of Figure 6; Figure 8 is a diagram showing the relationship between Cx and Ry in a comparative example; Figure 9 is a flowchart showing the flow of the map creation process; Figure 10 is a flowchart showing the flow of the detection process; Figure 11 is a diagram showing the plot of (Rzi, tyi); Figure 12 is a flowchart showing the flow of the abnormality detection process; Figure 13 is a flowchart showing the flow of the first detection process; Figure 14 is a flowchart showing the flow of the second detection process; Figure 15 is a timing chart showing the voltage detection timing; Figure 16 is a diagram showing the determination device of a modified example; and Figure 17 is a diagram showing the determination device of a modified example.

[0012] Hereinafter, a first embodiment of the determination device relating to this disclosure will be described with reference to the drawings. Note that functionally and / or structurally corresponding parts and / or related parts may be assigned the same reference numeral, or reference numerals with a difference of hundreds or more digits, between embodiments and modifications. For corresponding parts and / or related parts, refer to the descriptions of other embodiments and modifications.

[0013] The determination device 20 of this embodiment is installed in the control system of an electrified vehicle such as a hybrid vehicle or an electric vehicle. As shown in Figures 1 and 2, the control system comprises a storage battery 10 as a "DC power source" and the determination device 20. The positive terminal of the storage battery 10 and the first external terminal P1 of the determination device 20 are connected by a positive-side path L1 (positive-side power supply path). The negative terminal of the storage battery 10 and the second external terminal P2 of the determination device 20 are connected by a negative-side path L2 (negative-side power supply path).

[0014] The battery 10 is a battery pack in which multiple battery cells are connected in series, and the terminal voltage Vc of the battery 10 is, for example, 100V or more. For example, lithium-ion batteries or nickel-metal hydride batteries can be used as battery cells. The terminal voltage Vc of the battery 10 is supplied to the rotating electric machine, which is the main engine of the vehicle, via an inverter. Note that the inverter and rotating electric machine that constitute the control system are not shown in Figure 1.

[0015] The positive electrode path L1 is electrically insulated from the ground point G1 of the vehicle body, etc. The insulation state between the positive electrode path L1 and the ground point G1 can be represented as the positive electrode ground fault resistance Rp. In addition, between the positive electrode path L1 and the ground point G1, there are passive elements such as capacitors and stray capacitances for noise suppression, and these are collectively represented as the positive electrode capacitance Cp.

[0016] The negative electrode path L2 is electrically insulated from the ground point G1 of the vehicle body, etc. The insulation state between the negative electrode path L2 and the ground point G1 can be represented as the negative electrode ground fault resistance Rn. In addition, between the negative electrode path L2 and the ground point G1, there are passive elements such as capacitors and stray capacitances for noise suppression, and these are collectively represented as the negative electrode capacitance Cn.

[0017] In this embodiment, the positive and negative electrode capacitances Cp and Cn include not only stray capacitance but also the capacitance of a capacitor as a passive element, but this is not limited to this. For example, in a control system where a capacitor as a passive element is not provided between the positive and negative electrode paths L1 and L2 and the ground G1, the positive and negative electrode capacitances Cp and Cn consist only of stray capacitance. In other words, the positive and negative electrode capacitances Cp and Cn are composed of at least stray capacitance.

[0018] In the following, the value of Cp + Cn will be referred to as the capacitance to ground Cx. Also, the value of Rp / / Rn (= 1 / ((1 / Rp) + (1 / Rn))) will be referred to as the insulation resistance Rx. The capacitance to ground Cx corresponds to the common capacitance.

[0019] As shown in Figure 2, the determination device 20 includes a first series connection consisting of a first switch Sp and a first resistor R1, and a second series connection consisting of a second switch Sn and a second resistor R2. The first series connection and the second series connection are connected in series to form a resistor circuit 30. When viewed from the positive terminal path L1, that is, from the first external terminal P1, the devices are connected in series in the order of first external terminal P1 → first switch Sp → first resistor R1 → second resistor R2 → second switch Sn → second external terminal P2. The midpoint M1 between the first resistor R1 and the second resistor R2 is connected to the ground G1.

[0020] Specifically, the first resistor R1 is provided in the first electrical path L11 between the ground G1 and the positive electrode path L1, and the first switch Sp is a switch that switches between energizing and disconnecting the first electrical path L11. Furthermore, the second resistor R2 is provided in the second electrical path L12 between the ground G1 and the negative electrode path L2, and the second switch Sn is a switch that switches between energizing and disconnecting the second electrical path L12.

[0021] The determination device 20 includes a first voltage sensor V1 that detects the voltage across the first terminals of the first resistor R1, and a second voltage sensor V2 that detects the voltage across the second terminals of the second resistor R2.

[0022] As shown in Figure 1, the determination device 20 includes a control device 21. The control device 21 includes a processor 21a as hardware, a storage unit 21b, and a communication bus 21c connecting the processor 21a and the storage unit 21b. The storage unit 21b includes memory and storage as hardware. The memory is a storage device for storing data used for processing by the control device 21. For example, the memory provides the processor 21a with a temporary workspace for use when the processor is performing processing. The memory includes, for example, ROM or RAM. The storage is a storage device that stores various programs and data for the processor 21a to read and execute, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or flash memory. The storage stores program information for various processes, etc.

[0023] For example, program information stored on a non-transitional physical recording medium is installed in the storage unit 21b. The recording medium is, for example, a USB memory stick, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as OTA (Over The Air), is installed in the storage unit 21b.

[0024] As shown in Figure 2, the control device 21 is equipped with various functions related to determination. For example, the control device 21 has the functions of a switch control unit 22, a voltage acquisition unit 23, a switch timing determination unit 24, an insulation resistance detection timing determination unit 25, an insulation resistance calculation unit 26, a capacitance detection timing determination unit 27, and an abnormality determination unit 28. These functions are realized by the processor 21a of the control device 21 executing a program (determination program) stored in the storage unit 21b.

[0025] The switch control unit 22 controls the on / off states of the first switch Sp and the second switch Sn. The switch control unit 22 switches the on / off states of the first switch Sp and the second switch Sn at the timing instructed by the switch timing determination unit 24.

[0026] The voltage acquisition unit 23 acquires the first terminal voltages Vpz and Vpy of the first resistor R1 detected by the first voltage sensor V1, and the second terminal voltages Vnz and Vny of the second resistor R2 detected by the second voltage sensor V2. Specifically, the voltage acquisition unit 23 acquires the first terminal voltage Vpz detected by the first voltage sensor V1 when the second detection time tz has elapsed from the timing when the first switch Sp is turned ON and the second switch Sn is turned OFF. The voltage acquisition unit 23 also acquires the second terminal voltage Vnz detected when the second detection time tz has elapsed from the timing when the first switch Sp is turned OFF and the second switch Sn is turned ON. The second detection time tz is determined by the insulation resistance detection timing determination unit 25 and instructed to the voltage acquisition unit 23.

[0027] Furthermore, the voltage acquisition unit 23 acquires the first terminal voltage Vpy detected by the first voltage sensor V1 when the first detection time ty has elapsed from the moment the first switch Sp is turned ON and the second switch Sn is turned OFF. Also, the voltage acquisition unit 23 acquires the second terminal voltage Vny detected when the first detection time ty has elapsed from the moment the first switch Sp is turned OFF and the second switch Sn is turned ON. The first detection time ty is determined by the capacitance detection timing determination unit 27 and instructed to the voltage acquisition unit 23.

[0028] Furthermore, the voltage between the first terminals Vpz corresponds to the voltage between the second terminals Vnz, and the voltage between the second terminals Vny corresponds to the voltage between the second terminals Vny. Also, the voltage between the first terminals Vpy corresponds to the voltage between the first terminals Vny, and the voltage between the second terminals Vny corresponds to the voltage between the second terminals Vny.

[0029] The switch timing determination unit 24 determines the on / off timing of the first switch Sp and the second switch Sn, and instructs the switch control unit 22, the insulation resistance detection timing determination unit 25, and the capacitance detection timing determination unit 27.

[0030] The insulation resistance detection timing determination unit 25 measures a second detection time tz from the moment the first switch Sp is turned on and the second switch Sn is turned off. When the second detection time tz has elapsed, it instructs the voltage acquisition unit 23 to do so, causing the voltage acquisition unit 23 to acquire the voltage Vpz across the first terminals. The insulation resistance detection timing determination unit 25 also measures a second detection time tz from the moment the first switch Sp is turned off and the second switch Sn is turned on. When the second detection time tz has elapsed, it instructs the voltage acquisition unit 23 to do so, causing the voltage acquisition unit 23 to acquire the voltage Vnz across the second terminals. The timing of when each switch Sp and Sn is turned on and off is notified by the switch timing determination unit 24.

[0031] In this embodiment, the insulation resistance detection timing determination unit 25 measures the second detection time tz and instructs the voltage acquisition unit 23 when the second detection time tz has elapsed. However, it is also possible to notify the voltage acquisition unit 23 of the second detection time tz and have it measure it.

[0032] The second detection time tz is predetermined and stored in the memory unit 21b. This second detection time tz corresponds to a sufficient amount of time from when the first switch Sp or the second switch Sn is turned on until the positive and negative electrode capacitances Cp and Cn are charged. For example, the second detection time tz is set to be longer than or equal to the time constant TC (predetermined time) of the circuit between the battery 10 and the ground unit G1 (see Figure 1). The time constant TC can be calculated from the resistance value of the insulation resistance Rx, the value of the capacitance to ground Cx, the resistance value of the first resistor R1, and the resistance value of the second resistor R2. The values ​​of the insulation resistance Rx and the capacitance to ground Cx are arbitrary values ​​from among appropriate values ​​(normal values), and may be determined, for example, by actual measurement.

[0033] The insulation resistance calculation unit 26 calculates the value of the insulation resistance Rx based on the first terminal voltage and the second terminal voltage acquired by the voltage acquisition unit 23. For example, the insulation resistance calculation unit 26 calculates a second detected value Rz as the value of the insulation resistance Rx from equation (1) based on the acquired first terminal voltage Vpz and second terminal voltage Vnz. The insulation resistance calculation unit 26 also calculates a first detected value Ry as the value of the insulation resistance Rx from equation (2) based on the acquired first terminal voltage Vpy and second terminal voltage Vny.

[0034] In equations (1) and (2), "Vc" is the terminal voltage of the battery 10, which is obtained, for example, from a voltage sensor (not shown). Also, in equations (1) and (2), "Rs" is a value correlated with the resistance values ​​of the first resistor R1 and the second resistor R2. In this embodiment, the resistance values ​​of the first resistor R1 and the second resistor R2 are the same, so "Rs" is equal to the resistance value of the first resistor R1 (= the resistance value of the second resistor R2).

[0035]

[0036] Furthermore, the second detected value Rz is calculated based on the terminal voltages Vpz and Vnz detected after the positive and negative electrode capacitances Cp and Cn have been sufficiently charged and discharged and no longer change, and is therefore unaffected by the positive and negative electrode capacitances Cp and Cn. In other words, the second detected value Rz is close to the insulation resistance Rx (true value).

[0037] On the other hand, the first detected value Ry is calculated based on the terminal voltages Vpy and Vny detected when the positive and negative electrode capacitances Cp and Cn change during charging and discharging. Therefore, if the positive and negative electrode capacitances Cp and Cn are large, the first detected value Ry will be affected by the charging of the positive and negative electrode capacitances Cp and Cn, resulting in an error with the insulation resistance Rx (true value), and is likely to be a smaller value compared to the insulation resistance Rx.

[0038] The capacitance detection timing determination unit 27 measures a first detection time ty from the moment the first switch Sp is turned on and the second switch Sn is turned off. When the first detection time ty has elapsed, it instructs the voltage acquisition unit 23 to do so, causing the voltage acquisition unit 23 to acquire the voltage Vpy across the first terminals. Similarly, the capacitance detection timing determination unit 27 measures a first detection time ty from the moment the first switch Sp is turned off and the second switch Sn is turned on. When the first detection time ty has elapsed, it instructs the voltage acquisition unit 23 to do so, causing the voltage acquisition unit 23 to acquire the voltage Vny across the second terminals.

[0039] In this embodiment, the capacitance detection timing determination unit 27 measures the first detection time ty and instructs the voltage acquisition unit 23 when the first detection time ty has elapsed. However, it is also possible to notify the voltage acquisition unit 23 of the first detection time ty and have it measure it.

[0040] The capacitance detection timing determination unit 27 sets a time shorter than the second detection time tz as the first detection time ty. That is, the first detection time ty corresponds to a time insufficient for charging and discharging the positive electrode side and negative electrode side capacitances Cp and Cn after the first switch Sp or the second switch Sn is turned on. More specifically, the first detection time ty is shorter than the time constant TC (predetermined time). Therefore, the capacitance detection timing determination unit 27 instructs the voltage acquisition unit 23 to acquire the inter-terminal voltages Vpy and Vny during the charging and discharging. In the present embodiment, the capacitance detection timing determination unit 27 determines the first detection time ty by referring to the Rz-ty map (see FIG. 3) stored in the storage unit 21b based on the second detection value Rz. The Rz-ty map shown in FIG. 3 is a map that correlates the second detection value Rz with the first detection time ty. The horizontal axis corresponds to the second detection value Rz, and the vertical axis corresponds to the first detection time ty.

[0041] When the calculated second detection value Rz is less than or equal to the second threshold value Rz_th, the abnormality determination unit 28 determines that the insulation resistance Rx is not within the desired range. That is, the abnormality determination unit 28 determines that the insulation resistance Rx has decreased below the second threshold value Rz_th and that the value of the insulation resistance Rx is abnormal.

[0042] When the calculated first detection value Ry is less than or equal to the first threshold value Ry_th, the abnormality determination unit 28 determines that the capacitance to ground Cx is not within the desired range. That is, the abnormality determination unit 28 determines that the capacitance to ground Cx has become greater than or equal to a predetermined magnitude and that the value of the capacitance to ground Cx is abnormal.

[0043] Here, the reason for being able to determine whether or not the capacitance to ground Cx is within the desired range based on the comparison between the first detection value Ry and the first threshold value Ry_th will be described. FIG. 4 is a diagram showing the relationship between the second detection value Rz calculated based on the inter-terminal voltages Vpz and Vnz detected at the second detection time tz and the capacitance to ground Cx. In FIG. 4, the relationship between the second detection value Rz and the capacitance to ground Cx in the case where the insulation resistance Rx (true value) is "Rx1" to "Rx7" is shown in order from the bottom.

[0044] The second detection value Rz is calculated based on the detected inter-terminal voltages Vpz and Vnz when a second detection time tz equal to or longer than the time constant TC has elapsed after the switches Sp and Sn are turned on and when the insulation resistance Rx and the capacitance to ground Cx are at appropriate values (see Fig. 15). Therefore, when the capacitance to ground Cx is within an appropriate range, for example, when the capacitance to ground Cx is "Cx1" as shown in Fig. 4, it is possible to determine whether the value of the insulation resistance Rx is appropriate based on the comparison between the calculated second detection value Rz and the second threshold value Rz_th.

[0045] Next, a case where the capacitance to ground Cx increases to "Cx2" and is outside the appropriate range (Cx2 ≥ Cz_th) will be described. In this case, when the insulation resistance Rx (true value) is relatively large (for example, in the cases of "Rx5" to "Rx7"), the second detection value Rz significantly decreases at the capacitance to ground "Cx2". Therefore, if the threshold value is set appropriately, it is possible to detect an increase in the capacitance to ground Cx. However, when the insulation resistance Rx (true value) is less than or equal to a predetermined value Th1 (for example, in the cases of "Rx1" to "Rx4"), the second detection value Rz hardly changes even at the capacitance to ground "Cx2". Therefore, when the insulation resistance Rx (true value) is less than or equal to the predetermined value Th1, it is impossible to determine whether the capacitance to ground Cx has increased.

[0046] In particular, when the insulation resistance Rx is greater than the second threshold value Rz_th and less than or equal to the predetermined value Th1 (for example, in cases such as "Rx3" to "Rx4"), although the insulation resistance Rx is normal, it is impossible to determine that the capacitance to ground Cx is abnormal, which poses a problem.

[0047] Here, Figure 5 shows the relationship between the first detected value Ry, calculated based on the terminal voltages Vpy and Vny acquired at a first detection time ty which is shorter than the second detection time tz, and the capacitance to ground Cx. As shown in Figure 5, even if the insulation resistance Rx (true value) is the same, the first detected value Ry, shown by the solid line, begins to decrease when the capacitance to ground Cx is smaller than the capacitance threshold Cz_th, compared to the second detected value Rz, shown by the dashed line. Furthermore, as shown in Figures 6 and 7, even if the insulation resistance Rx (true value) decreases, the first detected value Ry begins to decrease when the capacitance to ground Cx is smaller than the capacitance threshold Cz_th, compared to the second detected value Rz. Note that Figures 6 and 7 show, from bottom to top, the relationship between the first detected value Ry and the capacitance to ground Cx for insulation resistance Rx (true value) from "Rx1" to "Rx7". Figure 7 is a magnified view of a portion of Figure 6.

[0048] Therefore, in this embodiment, the first detection time ty is set to be shorter than the time constant TC (predetermined time) at which the changes in the voltages between the first and second terminals converge from the time of switching of the first switch Sp and the second switch Sn. This ensures that when the capacitance to ground Cx becomes greater than or equal to the capacitance threshold Cz_th, the first detected value Ry becomes less than or equal to the first threshold Ry_th corresponding to the capacitance threshold Cz_th. By comparing the first detected value Ry with the first threshold Ry_th, it is possible to determine whether or not the capacitance to ground Cx has become greater than the capacitance threshold Cz_th.

[0049] However, it was found that the following problems arise when the first detection time ty is kept constant. Figure 8 shows the first detection value Ry calculated when the first detection time ty is fixed to a constant value (for example, "ty_fix"). Figure 8 also shows the relationship between the first detection value Ry and the capacitance to ground Cx when the insulation resistance Rx (true value) is "Rx1" to "Rx7".

[0050] As shown in Figure 8, for example, when the insulation resistance Rx is "Rx7", the first detected value Ry takes a minimum value in the region where the capacitance to ground Cx is below the capacitance threshold Cz_th. After the minimum value, as the capacitance to ground Cx increases, the first detected value Ry also increases, and then converges to a steady state. Similar trends are observed for other values ​​such as "Rx5" to "Rx6".

[0051] Therefore, regardless of the value set for the first threshold Ry_th, there is a possibility of misjudgment, or even inability to judge. For example, if the first threshold Ry_th is set to "Ry_th1" as shown in Figure 8, then misjudgment will occur in the region Cx11 to Cz_th, indicated by the dashed line, where the capacitance to ground Cx is. "Ry_th1" shown in Figure 8 is the value corresponding to the capacitance threshold Cz_th when the insulation resistance Rx is "Rx7". Also, if the insulation resistance Rx is a value smaller than "Rx7", such as "Rx1" to "Rx4", then it will never fall below "Ry_th1", making judgment impossible. Similarly, even if the first threshold Ry_th is set to "Ry_th2" or "Ry_th3" as shown in Figure 8, misjudgment or inability to judge will occur.

[0052] Therefore, in this embodiment, as shown in Figure 7, the first detection time ty is shortened according to the value of the second detection value Rz (i.e., the insulation resistance Rx (true value)) by referring to the Rz-ty map in Figure 3, so that when the capacitance to ground Cx is at the capacitance threshold Cz_th, the first detection value Ry becomes a specific first threshold Ry_th and the first detection value Ry decreases monotonically.

[0053] Furthermore, by determining the first detection time ty using the Rz-ty map in Figure 3, as shown in Figure 7, it becomes possible to detect an anomaly where the capacitance to ground Cx becomes smaller than the capacitance threshold Cz_th for all insulation resistance values ​​Rx1 to Rx7, based on a single first threshold Ry_th. As shown in Figure 5, when the second detection time tz is reduced to the first detection time ty, the position where the first detection value Ry becomes smaller relative to the capacitance to ground Cx shifts to the left of the graph. This position can also be controlled by changing the first detection time ty. Therefore, the Rz-ty map in Figure 3 allows the Cx-Ry characteristics in Figure 7 to be adjusted so that the first threshold Ry_th is equal to the capacitance threshold Cz_th for all insulation resistances Rx. These effects enable highly accurate detection of anomalies in the capacitance to ground Cx, independent of the value of the insulation resistance Rx.

[0054] Here, an example of how to create the map shown in Figure 3 will be explained with reference to the flowchart in Figure 9. Note that the process shown in the flowchart in Figure 9 may be obtained experimentally using actual equipment, or through computer simulation. Furthermore, the process itself may be performed by a computer or by manual calculation.

[0055] As a prerequisite for carrying out the process shown in this flowchart, first, the desired capacitance threshold Cz_th is determined. Also, the number of i (number of plots) for determining the granularity when creating the Rz-ty map is determined. In this embodiment, i = 1 to 20. Next, the first threshold Ry_th corresponding to the capacitance threshold Cz_th is determined. This first threshold Ry_th is set to an appropriate value that is smaller than the second threshold Rz_th and can be detected as the first detected value Ry. This takes into account that while the second detected value Rz is a composite value of the positive-side ground fault resistance Rp and the negative-side ground fault resistance Rn in Figure 1, the first detected value Ry is further composited with the positive-side capacitance Cp and the negative-side capacitance Cn, so when the insulation resistance Rx is normal, the first detected value Ry will always be smaller than the second detected value Rz.

[0056] Then, after initiating the process shown in the flowchart of Figure 9, the desired capacitance threshold Cz_th is first determined as the capacitance to ground Cx (step S401). In other words, in the simulation or experiment, the capacitance to ground Cx in the control system circuit is set to the capacitance threshold Cz_th.

[0057] Next, the initial value "1" is set for "i" (step S402). Then, "Rzi" is set as the insulation resistance Rx (step S403). "i" is the value set in step S402 or S410. Also, Rzi (i = 1 to 20) is a value that can be detected as the second detection value Rz, and is set within a range of values ​​greater than the second threshold Rz_th. In step S403, the insulation resistance Rx in the control system circuit is set to "Rzi" in the simulation or experiment.

[0058] Furthermore, the second detection time tz is set as the initial value of the first detection time ty (step S404). The second detection time tz may be determined from the time constant TC calculated based on the capacitance to ground Cx determined in step S401 and the insulation resistance Rx set in step S403. The initial value of the first detection time ty does not have to be the second detection time tz, but it is desirable that it be a value close to the second detection time tz.

[0059] Next, the detection process for the first detected value Ry shown in Figure 10 is performed (step S405). Here, the detection process for the first detected value Ry will be explained with reference to Figure 10. In the detection process, first the first switch Sp is turned on and the second switch Sn is turned off (step S501). Next, the system waits until the first detection time ty set in step S404 or step S407 has elapsed (step S502). After the first detection time ty has elapsed, the first terminal voltage Vpy detected by the first voltage sensor V1 is obtained (step S503).

[0060] Subsequently, the first switch Sp is turned off and the second switch Sn is turned on (step S504). Next, the system waits until the first detection time ty set in step S404 or step S407 has elapsed (step S505). After the first detection time ty has elapsed, the voltage Vny between the second terminals detected by the second voltage sensor V2 is obtained (step S506). Then, the first detection value Ry is calculated from equation (2) (step S507), and the first detection value Ry is output to terminate the detection process in step S405.

[0061] Let's return to the explanation of the process shown in Figure 9. After the process in step S405, it is determined whether the calculated first detection value Ry matches the first threshold Ry_th determined in the premise (step S406). Since the first detection value Ry and the first threshold Ry_th rarely match perfectly, if the error between the first detection value Ry and the first threshold Ry_th is within a predetermined range, the result of the determination in step S406 is affirmed. Incidentally, the first detection time ty can also be calculated by linear interpolation or the like from the difference between the first detection value Ry and the first threshold Ry_th before and after the relationship between the first detection value Ry and the first threshold Ry_th is reversed, but a detailed explanation is omitted as this is an existing general method.

[0062] If the result of step S406 is negative, the first detection time ty is reduced by a predetermined number and reset (step S407), and the process of step S405 is performed again. When the process of step S405 is performed again, the first detection time ty reset in step S407 is adopted in steps S502 and S505. Thereafter, the processes of steps S405 to S407 are repeated until the result of step S405 is positive.

[0063] If the result of step S405 is positive, the first detection time ty at the time the result of step S405 was positive is set to "tyi" (where "i" is the value set in step S402 or S410). Then, the point on the Rz-ty coordinate system consisting of "Rzi" set in step S403 and "tyi" is plotted in the Rz-ty coordinate system (step S408). Next, it is determined whether "i" is the final value (in this embodiment, "20") (step S409). If this determination result is negative, 1 is added to "i" (step S410), and the processing from step S403 onwards is repeated. On the other hand, if the result of step S410 is positive, the process is terminated.

[0064] The points plotted on the Rz-ty coordinate system (Rzi, tyi (where i = 1 to 20)) will look like those shown in Figure 11, for example. From these plots, the relationship between the second detection value Rz and the first detection time ty can be determined using methods such as the least squares method. This allows for the creation of the Rz-ty map shown in Figure 3.

[0065] Note that the method in Figure 9 is just one example of the simplest algebraic method, and (Rzi, ty) in Figure 11 can also be obtained using any existing algebraic algorithm, such as the Newton method.

[0066] Next, the abnormality determination process in this embodiment will be explained with reference to Figures 12 to 14. The abnormality determination process is performed at predetermined intervals by the control device 21 of the determination device 20. As shown in Figure 12, first, the control device 21 determines whether the first detection time ty has already been set (step S101). In other words, it determines whether this is the first abnormality determination process after the determination device 20 has been started. If this determination result is negative, the control device 21 performs the first detection process to detect the second detection value Rz shown in Figure 13 (step S102).

[0067] The first detection process will now be explained with reference to Figure 13. The control device 21 first turns on the first switch Sp and turns off the second switch Sn (step S201). The timing for turning on the first switch Sp and turning off the second switch Sn is determined and instructed by the switch timing determination unit 24. Based on the instructions from the switch timing determination unit 24, the switch control unit 22 turns on the first switch Sp and turns off the second switch Sn.

[0068] Next, the control device 21 waits from the time the process in step S201 is performed until a predetermined second detection time tz has elapsed (step S202). The switch control unit 22 notifies the control device 21 of the time when the process in step S201 is performed. The insulation resistance detection timing determination unit 25 also notifies the voltage acquisition unit 23 when the second detection time tz has elapsed. After the second detection time tz has elapsed, the voltage acquisition unit 23 of the control device 21 acquires the first terminal voltage Vpz detected by the first voltage sensor V1 (step S203).

[0069] Subsequently, the control device 21 turns off the first switch Sp and turns on the second switch Sn (step S204). The timing for turning off the first switch Sp and turning on the second switch Sn is determined and instructed by the switch timing determination unit 24. Based on the instructions from the switch timing determination unit 24, the switch control unit 22 turns off the first switch Sp and turns on the second switch Sn.

[0070] Next, the control device 21 waits from the time the process in step S204 is performed until a predetermined second detection time tz has elapsed (step S205). The switch control unit 22 notifies the control device 21 of the time when the process in step S204 is performed. The insulation resistance detection timing determination unit 25 also notifies the voltage acquisition unit 23 when the second detection time tz has elapsed. After the second detection time tz has elapsed, the voltage acquisition unit 23 of the control device 21 acquires the second terminal voltage Vnz detected by the second voltage sensor V2 (step S206). Subsequently, the insulation resistance calculation unit 26 of the control device 21 calculates the second detection value Rz from equation (1) (step S207), outputs the second detection value Rz, and terminates the first detection process in step S102.

[0071] After identifying the second detected value Rz through the process in step S102, the abnormality determination unit 28 of the control device 21 determines whether the second detected value Rz is less than or equal to the second threshold Rz_th (step S103). If this determination result is positive, the control device 21 determines that the insulation resistance Rx is less than or equal to the second threshold Rz_th and has decreased in value, and performs error processing (step S104). For example, in error processing, the control device 21 notifies an external device (such as a higher-level ECU) that an abnormality has occurred in the insulation resistance Rx. Then, the abnormality determination process is terminated.

[0072] On the other hand, if the result of step S103 is negative, the capacity detection timing determination unit 27 of the control device 21 refers to the Rz-ty map in Figure 3 and determines the first detection time ty from the identified second detection value Rz (step S105). The control device 21 stores the identified first detection time ty in the storage unit 21b. From this point onward, the processing in step S101 will be judged positively. This first detection time ty is erased at a predetermined timing (for example, when the ignition switch is turned off). After the processing in step S105, the abnormality determination process is terminated.

[0073] On the other hand, if the result of step S101 is positive, the second detection process shown in Figure 14 is performed (step S106). Here, the second detection process shown in Figure 14 will be explained. The second detection process is a process for identifying the second detection value Rz and the first detection value Ry.

[0074] In the second detection process, first, the control device 21 turns on the first switch Sp and turns off the second switch Sn, similar to step S201 of the first detection process (step S301). Next, from the time the process in step S301 is performed, it waits until the first detection time ty has elapsed (step S302). The time when the process in step S301 is performed is notified by the switch control unit 22, and the time when the first detection time ty has elapsed is notified by the capacitance detection timing determination unit 27. After the first detection time ty has elapsed from the time the process in step S301 is performed, the voltage acquisition unit 23 of the control device 21 acquires the first terminal voltage Vpy detected by the first voltage sensor V1 (step S303).

[0075] Subsequently, the control device 21 waits until the time obtained by subtracting the first detection time ty from the second detection time tz has elapsed (step S304). In other words, similar to step S202 of the first detection process, it waits from the time the process of step S301 is performed until the second detection time tz has elapsed. After the second detection time tz has elapsed, the voltage acquisition unit 23 of the control device 21 acquires the first terminal voltage Vpz detected by the first voltage sensor V1 (step S305).

[0076] Then, the control device 21 turns off the first switch Sp and turns on the second switch Sn, similar to step S204 of the first detection process (step S306). Next, from the time the process in step S306 is performed, it waits until the first detection time ty has elapsed (step S307). The time when the process in step S306 is performed is notified by the switch control unit 22, and when the first detection time ty has elapsed, it is notified by the capacitance detection timing determination unit 27. From the time the process in step S306 is performed, after the first detection time ty has elapsed, the voltage acquisition unit 23 of the control device 21 acquires the second terminal voltage Vny detected by the second voltage sensor V2 (step S308).

[0077] Subsequently, the control device 21 waits until the time obtained by subtracting the first detection time ty from the second detection time tz has elapsed (step S309). In other words, similar to step S205 of the first detection process, it waits from the time the process in step S306 is performed until the second detection time tz has elapsed. After the second detection time tz has elapsed, the voltage acquisition unit 23 of the control device 21 acquires the second terminal voltage Vnz detected by the second voltage sensor V2 (step S310).

[0078] Then, the insulation resistance calculation unit 26 of the control device 21 calculates the first detected value Ry from equation (2) (step S311). The insulation resistance calculation unit 26 also calculates the second detected value Rz from equation (1) (step S312). Then, the second detection process is completed.

[0079] After the completion of the second detection process in step S106, the abnormality determination unit 28 of the control device 21 determines whether the second detection value Rz identified by the second detection process is less than or equal to the second threshold Rz_th (step S107). If this determination result is positive, the control device 21 performs error processing (step S104).

[0080] On the other hand, if the determination result in step S107 is negative, the abnormality determination unit 28 of the control device 21 determines whether the first detection value Ry identified by the second detection process is less than or equal to the first threshold Ry_th (step S108). If this determination result is positive, the control device 21 performs error processing (step S104). On the other hand, if the determination result in step S108 is negative, the capacity detection timing determination unit 27 of the control device 21, similar to step S105, refers to the map in Figure 3 and identifies the first detection time ty from the identified second detection value Rz (step S109). The control device 21 stores the identified first detection time ty in the storage unit 21b and updates the value of the first detection time ty. Then, the abnormality determination process ends.

[0081] Next, an example of the on / off timing of switches Sp and Sn, and the detection timing of terminal voltages Vpz, Vnz, Vpy, and Vny will be explained with reference to the timing chart in Figure 15. The explanation assumes that the process begins immediately after the ignition switch is turned on (immediately after startup) and before the first detection time ty is set.

[0082] After the ignition switch is turned on, the control device 21 starts the first detection process. Then, the control device 21 turns on the first switch Sp by the process of step S201 (time T1). The control device 21 waits from time T1 until a predetermined second detection time tz has elapsed, and after the second detection time tz has elapsed, it acquires the first terminal voltage Vpz (time T2). After that, the control device 21 turns off the first switch Sp and the second switch Sn (time T3), and after a predetermined dead time, it turns on the second switch Sn by the process of step S204 (time T4). The control device 21 waits from time T4 until a predetermined second detection time tz has elapsed, and after the second detection time tz has elapsed, it acquires the second terminal voltage Vnz (time T5).

[0083] The control device 21 then calculates a second detection value Rz based on the first terminal voltage Vpz and the second terminal voltage Vnz, and determines whether the insulation resistance Rx is abnormal based on a comparison between the second detection value Rz and the second threshold Rz_th. If the insulation resistance Rx is normal, the control device 21 identifies and sets the first detection time ty by referring to the map shown in Figure 3 from the second detection value Rz.

[0084] Subsequently, the control device 21 starts the second detection process. Then, from time T5, after a predetermined dead time, the control device 21 turns on the first switch Sp by the process of step S301 (time T6). From time T6, the control device 21 waits until the set first detection time ty has elapsed, and after the first detection time ty has elapsed, it acquires the first terminal voltage Vpy (time T7). Also, from time T6, after the second detection time tz has elapsed, the control device 21 acquires the first terminal voltage Vpz (time T8).

[0085] Subsequently, the control device 21 turns off the first switch Sp and the second switch Sn (time T9), and after a predetermined dead time, turns on the second switch Sn by the process in step S306 (time T10). The control device 21 waits from time T10 until the set first detection time ty has elapsed, and after the first detection time ty has elapsed, it acquires the second terminal voltage Vny (time T11). Also, the control device 21 acquires the second terminal voltage Vnz after the second detection time tz has elapsed from time T10 (time T12).

[0086] The control device 21 then calculates a first detected value Ry based on the first terminal voltage Vpy and the second terminal voltage Vny, calculates a second detected value Rz based on the first terminal voltage Vpz and the second terminal voltage Vnz, and determines if the insulation resistance Rx is abnormal based on a comparison between the second detected value Rz and the second threshold Rz_th. If the insulation resistance Rx is normal, the control device 21 calculates a first detected value Ry based on the first terminal voltage Vpy and the second terminal voltage Vny, and determines if the capacitance to ground Cx is abnormal based on a comparison between the first detected value Ry and the first threshold Ry_th. If normal, the control device 21 identifies the first detection time ty by referring to the map shown in Figure 3 from the second detected value Rz, and updates the value of the first detection time ty. Thereafter, the abnormality determination of the insulation resistance Rx and capacitance to ground Cx and the updating of the first detection time ty are repeated in the same manner.

[0087] According to the embodiment described in detail above, the following effects can be obtained.

[0088] The voltage acquisition unit 23 acquires the first terminal voltage Vpz detected when the second detection time tz has elapsed from the moment the first switch Sp is turned on, and also acquires the second terminal voltage Vnz detected when the second detection time tz has elapsed from the moment the second switch Sn is turned on. Then, the insulation resistance calculation unit 26 calculates the second detected value Rz as the value of the insulation resistance Rx from equation (1) based on the first terminal voltage Vpz and the second terminal voltage Vnz. Here, since the second detection time tz is set to a time that is equal to or greater than the time constant TC, the second detected value Rz can be calculated as the value of the insulation resistance Rx where charging and discharging to the capacitance to ground Cx is completed and there is almost no influence (error) due to the capacitance to ground Cx.Therefore, the abnormality determination unit 28 can determine whether the insulation resistance Rx has decreased and whether there is a possibility of leakage current, that is, whether there is an abnormality, by determining whether the second detected value Rz is less than or equal to the second threshold Rz_th.

[0089] The voltage acquisition unit 23 acquires the first terminal voltage Vpy detected when the first detection time ty has elapsed from the moment the first switch Sp is turned on, and also acquires the second terminal voltage Vny detected when the first detection time ty has elapsed from the moment the second switch Sn is turned on. Then, the insulation resistance calculation unit 26 calculates the first detected value Ry as the value of the insulation resistance Rx from equation (2) based on the first terminal voltage Vpy and the second terminal voltage Vny. Here, since the first detection time ty is set to a time shorter than the time constant TC, the charging and discharging of the capacitance to ground Cx is not completed, and the first detected value Ry can be calculated as the value of the insulation resistance Rx that is affected (error) by the capacitance to ground Cx. Generally, the effect of the capacitance to ground Cx becomes larger as the capacitance to ground Cx is larger, and the first detected value Ry is calculated to be smaller. Therefore, by comparing the first threshold Ry_th, which is smaller than the second threshold Rz_th, it is possible to determine if the capacitance Cx to ground is greater than the capacitance threshold Cz_th.

[0090] The capacitance detection timing determination unit 27 shortens the first detection time ty according to the value of the second detection value Rz (i.e., the insulation resistance Rx (true value)) by referring to the Rz-ty map in Figure 3, so that when the capacitance to ground Cx matches the capacitance threshold Cz_th, the first detection value Ry becomes a specific first threshold Ry_th, and the first detection value Ry decreases monotonically as the capacitance to ground Cx increases. Therefore, by determining whether the first detection value Ry is less than or equal to the first threshold Ry_th, it is possible to determine whether the capacitance to ground Cx is within a desired range.

[0091] The first detection value Ry can be detected by almost directly using the same circuit configuration as for detecting the second detection value Rz, which is used to determine an abnormality in the insulation resistance Rx. Therefore, no special circuit configuration is required to determine the capacitance to ground Cx, which suppresses an increase in the number of components and prevents the determination device 20 from becoming larger.

[0092] Furthermore, as shown in Figure 15, the capacitance to ground Cx can be determined at the same frequency as the determination frequency for the insulation resistance Rx. In other words, it is no longer necessary to specify the impedance characteristics of the circuit, and consequently, it is no longer necessary to sequentially change the measurement frequency during measurement. Therefore, the capacitance to ground Cx can be determined much faster compared to when impedance characteristics are specified. In addition, abnormalities in the capacitance to ground Cx can be accurately determined regardless of the value of the insulation resistance Rx.

[0093] (Modifications) The following describes modifications in which a part of the determination device 20 of the above embodiment is changed.

[0094] In the above embodiment, terminal voltages Vpy and Vny were detected by voltage sensors V1 and V2 when a first detection time ty had elapsed in order to calculate the first detected value Ry. However, current may be detected instead of voltage. That is, as shown in Figure 16, a first current sensor A1 may be provided to detect the current Ipy flowing through the first resistor R1, and a second current sensor A2 may be provided to detect the current Iny flowing through the second resistor R2. A current detection unit 29 may be provided that acquires the current Ipy when a first detection time ty has elapsed after the first switch Sp is turned on, and acquires the current Iny when a first detection time ty has elapsed after the second switch Sn is turned on. A voltage calculation unit 29a may be provided that calculates the first terminal voltage Vpy from the acquired current Ipy and the resistance value of the first resistor R1, and calculates the second terminal voltage Vny from the acquired current Iny and the resistance value of the second resistor R2. This eliminates the need to detect terminal voltages Vpy and Vny, which are higher than terminal voltages Vpz and Vnz, and allows the detection range of voltage sensors V1 and V2 to be suppressed.

[0095] In the above embodiment, the determination device 20 does not have to be connected to the total positive terminal and the total negative terminal of the battery pack, and as shown in Figure 17, it may be connected to any two of the battery cells 10a to 10e that constitute the battery pack 110 as a DC power source.

[0096] The following is an addition regarding the technical ideas that can be derived from the above embodiments and modifications. [Configuration 1] A determination device (20) for determining the capacitance to ground (Cx) between a DC power supply (10) and a grounding part (G1), comprising: a first resistor (R1) provided in a first electrical path (L11) between the grounding part and a positive-side power supply path (L1); a first switch (Sp) for switching the energization and disconnection of the first electrical path; a second resistor (R2) provided in a second electrical path (L12) between the grounding part and a negative-side power supply path (L2); a second switch (Sn) for switching the energization and disconnection of the second electrical path; a switch control unit (22) for controlling the on / off state of the first switch and the second switch; a first voltage sensor (V1) for detecting the first terminal voltage, which is the voltage across the first resistor; and a second voltage sensor (V2) for detecting the second terminal voltage, which is the voltage across the second resistor. The system includes: a voltage acquisition unit (23) that acquires the voltage between the first terminals from the first voltage sensor and the voltage between the second terminals from the second voltage sensor; a calculation unit (26) that calculates the value of the insulation resistance (Rx) based on the voltage between the first terminals and the voltage between the second terminals acquired by the voltage acquisition unit; and a determination unit (28) that determines whether the capacitance to ground is within a desired range, wherein the voltage acquisition unit acquires a first voltage between the first terminals (Vpy) detected when a first detection time (ty) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and acquires a first voltage between the second terminals (Vny) detected when a first detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, the first detection time is set to be shorter than a predetermined time in which the changes in the voltage between the first terminals and the voltage between the second terminals converge from the time of switching of the first switch and the second switch. The calculation unit calculates a first detected value (Ry) as the value of the insulation resistance based on a first voltage between the first terminals (Vpy) and a first voltage between the second terminals (Vny), and the determination unit compares the first detected value with a first threshold value (Ry_th) to determine whether the capacitance to ground is within a desired range.[Configuration 2] The determination device according to Configuration 1, wherein the predetermined time is calculated from the appropriate value as the insulation resistance, the appropriate value as the capacitance to ground, the resistance value of the first resistor, and the resistance value of the second resistor, and is the time constant (TC) of the circuit between the DC power supply and the grounding part, and the first detection time is a value smaller than the time constant. [Configuration 3] A determination device according to Configuration 1 or 2, further comprising a determination unit (25, 27) for determining the timing for detecting the first terminal voltage and the second terminal voltage, wherein the voltage acquisition unit acquires a second first terminal voltage (Vpz) detected when a predetermined second detection time (tz) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and acquires a second second terminal voltage (Vnz) detected when the second detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, the calculation unit calculates a second detected value (Rz) as the value of the insulation resistance based on the second first terminal voltage (Vpz) and the second second terminal voltage (Vnz), and the determination unit determines the first detection time (ty) based on the second detected value. [Configuration 4] The determination device according to Configuration 3, wherein the predetermined time is calculated from the appropriate value as the insulation resistance, the appropriate value as the capacitance to ground, the resistance value of the first resistor, and the resistance value of the second resistor, and is the time constant (TC) of the circuit between the DC power supply and the grounding part, and the second detection time is a value greater than or equal to the time constant. [Configuration 5] The determination device according to Configuration 3 or 4, wherein the determination unit shortens the first detection time when the calculated second detection value becomes small. [Configuration 6] The determination device according to any one of Configurations 3 to 5, wherein the determination unit shortens the first detection time according to the value of the second detection value such that the first detection value becomes the first threshold (Ry_th) when the capacitance to ground matches the capacitance threshold (Cz_th), and the first detection value monotonically decreases as the capacitance to ground increases.[Configuration 7] The determination device according to any one of Configurations 3 to 6, wherein the determination unit determines that the insulation resistance is abnormal when the second detected value is less than or equal to a second threshold (Rz_th), and determines that the capacitance to ground is abnormal when the first detected value is less than or equal to a first threshold (Ry_th) which is smaller than the second threshold.[Configuration 8] A determination device (20) for determining the capacitance to ground (Cx) between a DC power supply (10) and a grounding part (G1), comprising: a first resistor (R1) provided in a first electrical path (L11) between the grounding part and a positive-side power supply path (L1); a first switch (Sp) for switching the energization and disconnection of the first electrical path; a second resistor (R2) provided in a second electrical path (L12) between the grounding part and a negative-side power supply path (L2); a second switch (Sn) for switching the energization and disconnection of the second electrical path; a first voltage sensor (V1) for detecting a first terminal voltage which is the voltage across the first resistor; and a second voltage sensor (V2) for detecting a second terminal voltage which is the voltage across the second resistor, wherein the determination device implements a determination program comprising: a switch control step for controlling the on / off state of the first switch and the second switch; The system includes: a voltage acquisition step of acquiring the voltage between the first terminals from the first voltage sensor and the voltage between the second terminals from the second voltage sensor; a calculation step of calculating the value of the insulation resistance (Rx) based on the voltage between the first terminals and the voltage between the second terminals acquired in the voltage acquisition step; and a determination step of determining whether the capacitance to ground is within a desired range, wherein in the voltage acquisition step, a first voltage between the first terminals (Vpy) is acquired when a first detection time (ty) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and a first voltage between the second terminals (Vny) is acquired when a first detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, and the first detection time is set to be shorter than a predetermined time in which the changes in the voltage between the first terminals and the voltage between the second terminals converge from the time of switching of the first switch and the second switch. The calculation step calculates a first detected value (Ry) as the value of the insulation resistance based on a first voltage between the first terminals (Vpy) and a first voltage between the second terminals (Vny). The determination step compares the first detected value with a first threshold value (Ry_th) to determine whether the capacitance to ground is within a desired range.[Configuration 9] A determination device (20) for determining the capacitance to ground (Cx) between a DC power supply (10) and a grounding part (G1), comprising: a first resistor (R1) provided in a first electrical path (L11) between the grounding part and a positive-side power supply path (L1); a first switch (Sp) for switching the energization and disconnection of the first electrical path; a second resistor (R2) provided in a second electrical path (L12) between the grounding part and a negative-side power supply path (L2); a second switch (Sn) for switching the energization and disconnection of the second electrical path; a first voltage sensor (V1) for detecting a first terminal voltage which is the voltage across the first resistor; and a second voltage sensor (V2) for detecting a second terminal voltage which is the voltage across the second resistor, wherein the determination device performs a determination method comprising: a switch control step for controlling the on / off state of the first switch and the second switch; The system includes: a voltage acquisition step of acquiring the voltage between the first terminals from the first voltage sensor and the voltage between the second terminals from the second voltage sensor; a calculation step of calculating the value of the insulation resistance (Rx) based on the voltage between the first terminals and the voltage between the second terminals acquired in the voltage acquisition step; and a determination step of determining whether the capacitance to ground is within a desired range, wherein in the voltage acquisition step, a first voltage between the first terminals (Vpy) is acquired when a first detection time (ty) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and a first voltage between the second terminals (Vny) is acquired when a first detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, and the first detection time is set to be shorter than a predetermined time in which the changes in the voltage between the first terminals and the voltage between the second terminals converge from the time of switching of the first switch and the second switch. The calculation step involves calculating a first detected value (Ry) as the value of the insulation resistance based on a first voltage between the first terminals (Vpy) and a first voltage between the second terminals (Vny). The determination step involves comparing the first detected value with a first threshold value (Ry_th) to determine whether the capacitance to ground is within a desired range.

[0097] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A determination device (20) for determining the capacitance to ground (Cx) between a DC power supply (10) and a ground (G1), comprising: a first resistor (R1) provided in a first electrical path (L11) between the ground and a positive-side power supply path (L1); a first switch (Sp) for switching the energization and disconnection of the first electrical path; a second resistor (R2) provided in a second electrical path (L12) between the ground and a negative-side power supply path (L2); a second switch (Sn) for switching the energization and disconnection of the second electrical path; a switch control unit (22) for controlling the on / off states of the first and second switches; a first voltage sensor (V1) for detecting the first terminal voltage, which is the voltage across the first resistor; and a second voltage sensor (V2) for detecting the second terminal voltage, which is the voltage across the second resistor. The system includes: a voltage acquisition unit (23) that acquires the voltage between the first terminals from the first voltage sensor and the voltage between the second terminals from the second voltage sensor; a calculation unit (26) that calculates the value of the insulation resistance (Rx) based on the voltage between the first terminals and the voltage between the second terminals acquired by the voltage acquisition unit; and a determination unit (28) that determines whether the capacitance to ground is within a desired range, wherein the voltage acquisition unit acquires a first voltage between the first terminals (Vpy) detected when a first detection time (ty) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and acquires a first voltage between the second terminals (Vny) detected when a first detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, the first detection time is set to be shorter than a predetermined time in which the changes in the voltage between the first terminals and the voltage between the second terminals converge from the time of switching of the first switch and the second switch. The calculation unit calculates a first detected value (Ry) as the value of the insulation resistance based on a first voltage between the first terminals (Vpy) and a first voltage between the second terminals (Vny), and the determination unit compares the first detected value with a first threshold value (Ry_th) to determine whether the capacitance to ground is within a desired range.

2. The determination device according to claim 1, wherein the predetermined time is calculated from the appropriate value as the insulation resistance, the appropriate value as the capacitance to ground, the resistance value of the first resistor, and the resistance value of the second resistor, and is the time constant (TC) of the circuit between the DC power supply and the grounding part, and the first detection time is a value smaller than the time constant.

3. The determination device according to claim 1, further comprising determination units (25, 27) for determining the timing for detecting the first terminal voltage and the second terminal voltage, wherein the voltage acquisition unit acquires a second first terminal voltage (Vpz) detected when a predetermined second detection time (tz) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and acquires a second second terminal voltage (Vnz) detected when the second detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, the calculation unit calculates a second detected value (Rz) as the value of the insulation resistance based on the second first terminal voltage (Vpz) and the second second terminal voltage (Vnz), and the determination unit determines a first detection time (ty) based on the second detected value.

4. The determination device according to claim 3, wherein the predetermined time is calculated from the appropriate value as the insulation resistance, the appropriate value as the capacitance to ground, the resistance value of the first resistor, and the resistance value of the second resistor, and is the time constant (TC) of the circuit between the DC power supply and the grounding part, and the second detection time is a value greater than or equal to the time constant.

5. The determination device according to claim 3 or 4, wherein the determination unit shortens the first detection time when the calculated second detection value becomes smaller.

6. The determination device according to claim 5, wherein the determination unit shortens the first detection time according to the value of the second detection value such that the first detection value becomes the first threshold value (Ry_th) when the capacitance to ground matches the capacitance threshold value (Cz_th), and the first detection value monotonically decreases as the capacitance to ground increases.

7. The determination device according to claim 3 or 4, wherein the determination unit determines that the insulation resistance is abnormal if the second detected value is less than or equal to a second threshold (Rz_th), and determines that the capacitance to ground is abnormal if the first detected value is less than or equal to a first threshold (Ry_th) which is smaller than the second threshold.

8. A determination device (20) for determining the capacitance to ground (Cx) between a DC power supply (10) and a ground (G1), comprising: a first resistor (R1) provided in a first electrical path (L11) between the ground and a positive-side power supply path (L1); a first switch (Sp) for switching the energization and disconnection of the first electrical path; a second resistor (R2) provided in a second electrical path (L12) between the ground and a negative-side power supply path (L2); a second switch (Sn) for switching the energization and disconnection of the second electrical path; a first voltage sensor (V1) for detecting a first terminal voltage which is the voltage across the first resistor; and a second voltage sensor (V2) for detecting a second terminal voltage which is the voltage across the second resistor, wherein the determination device performs a determination program comprising: a switch control step for controlling the on / off state of the first switch and the second switch; The system includes: a voltage acquisition step of acquiring the voltage between the first terminals from the first voltage sensor and the voltage between the second terminals from the second voltage sensor; a calculation step of calculating the value of the insulation resistance (Rx) based on the voltage between the first terminals and the voltage between the second terminals acquired in the voltage acquisition step; and a determination step of determining whether the capacitance to ground is within a desired range, wherein in the voltage acquisition step, a first voltage between the first terminals (Vpy) is acquired when a first detection time (ty) has elapsed from the timing when the first switch is turned on and the second switch is turned off, and a first voltage between the second terminals (Vny) is acquired when a first detection time has elapsed from the timing when the first switch is turned off and the second switch is turned on, and the first detection time is set to be shorter than a predetermined time in which the changes in the voltage between the first terminals and the voltage between the second terminals converge from the time of switching of the first switch and the second switch. The calculation step calculates a first detected value (Ry) as the value of the insulation resistance based on a first voltage between the first terminals (Vpy) and a first voltage between the second terminals (Vny). The determination step compares the first detected value with a first threshold value (Ry_th) to determine whether the capacitance to ground is within a desired range.

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