JP5091973B2 - Ground fault detection device and notification device - Google Patents

Description

  The present invention relates to a ground fault detection device applied to a fuel cell vehicle and the like and a notification device including the same.

  Conventionally, in a power supply device for a vehicle, the power line provided in the engine room is subject to constant vibration during traveling, and the insulation of the power line may decrease while they are in contact with the vehicle body. there were.

  For example, the current detection means for detecting the current value flowing through the power supply line, the differential calculation means for differentiating the detected current value, and the power supply line when it fluctuates continuously over the chattering period by the relay provided on the power supply line Has been proposed (see Patent Document 1).

JP-A-10-66246 (Claim 1, FIG. 1)

  By the way, in a vehicle (fuel cell vehicle) equipped with a fuel cell that generates a reaction by chemically reacting a reaction gas, water generated by reacting the fuel gas and the oxidant gas is collected in a communication hole penetrating the cell. Metal that is temporarily placed adjacent to the fuel cell from the fuel cell due to changes in the flow of the fuel gas (hydrogen) or oxidant gas (air), etc. There was a problem that a ground fault occurred through the water flowing toward an auxiliary machine (such as a humidifier) made by the manufacturer.

  However, such a ground fault due to the behavior of the vehicle is due to temporary drainage of water unlike the decrease in insulation of the power line, and basically recovers. For this reason, if the ground fault is directly reflected in the detection result, a warning is generated constantly or frequently, and there is a problem that the user (user) is excessively worried.

In addition, a ground fault path is likely to be formed with the aging deterioration of the fuel cell, and there is a problem that the ground fault resistance value is lowered compared with that before the deterioration even under the same operating condition, and the insulation is deteriorated. For example, as the aging progresses, the conductivity of the drainage from the fuel cell increases, and a ground fault path is easily formed. Alternatively, as aging progresses, deposits accumulate on the surface of the component member, wettability deteriorates, and a ground fault path is easily formed.
Therefore, in order to suppress the decrease in ground fault insulation due to aging, it is necessary to quantitatively grasp the extent of the ground fault insulation decrease due to aging. It is difficult to grasp quantitatively.

As for the ground fault resistance value of the circuit formed by drainage, the form of the water flow is not stable. For this reason, for example, as shown in FIG. 10, the change in the resistance value is large, and a transient and unstable behavior is often exhibited. In contrast to such resistance value behavior, it is difficult to represent the behavior of the resistance value in a certain time interval as a single quantitative value and to quantitatively grasp the degree of ground fault insulation.
For example, when the average value of the time interval T is compared as a representative value of two intervals with respect to two ground fault resistance waveforms whose qualitatively clear differences in tendency are qualitatively shown in FIG. A very close average value may be calculated. In this case, it cannot be said that the difference in waveform between the two ground fault resistance values can be quantitatively compared, and it is not appropriate to simply compare the average value as a representative value.

  As described above, since it is difficult to quantify the degree of ground fault insulation, it is impossible to grasp the degree of reduction in ground fault insulation due to deterioration over time. Therefore, there is a problem that it is impossible to change the operating conditions based on the degree of the insulation deterioration and to suppress the insulation deterioration.

  The present invention solves the above-mentioned conventional problem, and unless a ground fault occurs regularly, it is prevented from being determined as a ground fault, and the degree of decrease in ground fault insulation is quantified. It is an object of the present invention to provide a ground fault detection device for determination and a notification device including the same.

  The invention according to claim 1 is a ground fault detection device for detecting a ground fault in a vehicle including a fuel cell that generates electric power by a chemical reaction of a reaction gas, wherein each of the positive and negative electrodes of the fuel cell and the resistance of the vehicle body are detected. A resistance detector that detects a value, and a ground fault determination unit that determines a ground fault from the resistance value, the ground fault determination unit, a threshold setting unit that sets a threshold value from a resistance value within a predetermined period; A counting unit that counts the number of times or time when the resistance value becomes smaller than the threshold value, and a determination unit that determines a ground fault when the threshold value is equal to or less than a predetermined resistance value, and the threshold setting unit includes the number of times When the number of times is less than a predetermined number of times, or when the time is less than a predetermined time, the threshold value is corrected, and the determination unit determines that the number of times reaches a predetermined number of times or the time reaches a predetermined time. Threshold and the predetermined resistance And comparing the values.

According to this, a threshold value calculated from the detected resistance value is set, the number of times or time when the value falls below the threshold value is measured, and the threshold value and the predetermined resistance value when the number of times reaches a predetermined number of times or a predetermined time are compared. Then, when the threshold value is equal to or less than the predetermined resistance value, it is determined that there is a ground fault. Further, the threshold value is corrected until the resistance value satisfies a predetermined number of times or a predetermined time with respect to the set threshold value. Thereby, it is possible to prevent an unstable ground fault (temporary ground fault), for example, a ground fault generated by the flow of water due to the behavior of the vehicle, from being determined as a ground fault.

  According to a second aspect of the present invention, the threshold setting unit includes an initial value of the threshold value based on the average value of the resistance value, the average value of the logarithm, the peak value of the histogram, or (maximum value + minimum value) / 2. Is set.

  According to this, by setting an initial value suitable for each ground fault detection device, an unstable ground fault (temporary ground fault), for example, a ground fault generated by water flow due to vehicle behavior, etc. Can be more efficiently prevented from being judged as a true ground fault.

  According to a third aspect of the present invention, when the ratio of the threshold before correction and the difference between the threshold after correction and the threshold before correction is equal to or less than a predetermined ratio, the determination unit The predetermined resistance value is compared.

  According to this, when the corrected threshold value and the uncorrected threshold value are approximated as a result of the correction, further correction is stopped, and the corrected threshold value is compared with the predetermined resistance value. As a result, useless calculations can be reduced, which speeds up processing. Further, since it is not necessary to mount a high-performance CPU, the cost can be reduced.

  The invention according to claim 4 is characterized in that, when the number of times the threshold is corrected satisfies a predetermined number of corrections, the determination unit compares the last corrected threshold value with the predetermined resistance value.

  According to this, when a specific number of corrections (predetermined number of corrections) is exceeded, by comparing the last corrected threshold value with the predetermined resistance value, useless calculation can be reduced, and processing is accelerated. Further, since it is not necessary to mount a high-performance CPU, the cost can be reduced.

  In the invention according to claim 5, when the ground fault determination device compares the threshold value with the predetermined resistance value and determines that the threshold value is equal to or less than the predetermined resistance value, the operating condition of the fuel cell is determined. It is characterized by changing to a condition for reducing the water forming the ground fault path.

  According to this, it is possible to actively avoid a temporary ground fault due to water generated in the fuel cell.

  In the invention according to claim 6, the ground fault determination device sets a threshold value from the resistance value detected again by the resistance detector after the change of the operating condition, and compares the threshold value with the predetermined resistance value. The ground fault is determined when the threshold value is equal to or less than the predetermined resistance value.

  According to this, it is possible to positively avoid a temporary ground fault due to water generated in the fuel cell, and to more reliably determine a true ground fault (steady ground fault).

  In the invention according to claim 7, the ground fault judgment device compares the threshold value with the predetermined resistance value, and when the threshold value exceeds the predetermined resistance value, another value greater than the predetermined resistance value is obtained. A predetermined resistance value is compared with the threshold value, and when the threshold value is equal to or less than the other predetermined resistance value, the change of the operating condition is adjusted to a condition for further reducing the water forming the ground fault path. Features.

  According to this, it is possible to set an operating condition capable of effectively discharging water with respect to a decrease in ground fault insulation accompanying aging deterioration, and to suppress the occurrence of a ground fault.

  The invention according to claim 8 is provided with a ground fault detection device and a notification device that notifies the user of ground fault information when the determination unit of the ground fault detection device determines that a ground fault has occurred. And

  According to this, it is possible to reliably notify the user of the ground fault.

  According to the present invention, as long as a ground fault does not occur steadily, it is possible to prevent the ground fault from being determined and to quantify and determine the degree of decrease in ground fault insulation.

It is a whole lineblock diagram showing the vehicles carrying the ground fault detection device of this embodiment. It is an example of the waveform of the resistance value detected with a ground fault detection apparatus. It is a flowchart which shows the flow of ground fault determination. It is a flowchart which shows the calculation method of the representative resistance value as a threshold value. It is a histogram which shows the magnitude frequency of the resistance value in a predetermined period. It is a chart which shows the threshold value setting method by integration time. It is an image figure which shows the calculation method of a representative resistance value. It is an image figure which shows the calculation method of a representative resistance value. It is an image figure which shows the calculation method of a representative resistance value. It is a chart which shows an example of the waveform of a ground fault resistance value. It is a chart which shows the ground fault resistance value of a different waveform with the same average value.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, a ground fault detection device 1 according to the present embodiment is applied to a vehicle V such as a fuel cell vehicle, and is connected between a fuel cell 10 and a vehicle load 20 and is connected to a ground fault sensor. 4, ECU5 etc. are provided. Moreover, the ground fault detection apparatus 1 is equipped with the warning light 6 (notification device), and comprises the alerting | reporting apparatus.

  The fuel cell 10 is, for example, a polymer electrolyte fuel cell, and is configured by electrically connecting a plurality of single cells 11 in series. The single cell 11 is composed of an MEA (Membrane Electrode Assembly) and a pair of conductive separators. The MEA is configured by sandwiching an electrolyte membrane between an anode and a cathode. The separator facing the anode is formed with an anode flow path through which hydrogen (reactive gas, fuel gas) flows, and the separator facing the cathode has a cathode flow path through which air (reactive gas, oxidant gas) flows. Is formed.

  The vehicle load 20 includes a travel motor, an air compressor that supplies air to the cathode of the fuel cell 10, and the like, and is connected to the positive terminal of the fuel cell 10 via the cable C1 and connected to the fuel cell 10 via the cable C2. It is connected to the negative terminal.

  When hydrogen is supplied to each anode via the anode flow path and air containing oxygen is supplied to each cathode via the cathode flow path, a potential difference is generated in each single cell 11. When the fuel cell 10 and the vehicle load 20 are electrically connected and a current is taken out, the fuel cell 10 generates power.

  The ground fault sensor 4 includes a resistance detector that detects a ground fault resistance on the positive terminal side and a ground fault resistance on the negative terminal side of the fuel cell 10 as indicated by a broken line in FIG. , A resistor, a capacitor, and a switching control circuit that controls opening and closing of various switches according to a set time (see Japanese Patent No. 3963990). The ground fault sensor 4 is connected between the positive terminal of the fuel cell 10 of the cable C1 and the vehicle load 20 via the wiring 4a. The ground fault sensor 4 is connected between the negative terminal of the fuel cell 10 of the cable C2 and the vehicle load 20 via the wiring 4b. The ground fault sensor 4 is grounded to the vehicle body V1 via the wiring 4c. Note that the ECU 5 described later determines the insulation state from the fuel cell 10 based on the values of the ground fault resistance on the positive terminal side and the ground fault resistance on the negative terminal side. For example, the ground fault resistance on the positive terminal side is compared with a predetermined reference resistance value, and when the ground fault resistance is equal to or lower than the reference resistance value, it is determined that an insulation failure has occurred.

  The ECU 5 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory) storing a program, and the like, and includes a ground fault determination device including a threshold setting unit, a count unit, and a determination unit. Yes.

  The threshold setting unit sets the threshold from the resistance value detected from the ground fault sensor 4 within a predetermined period (for example, 60 seconds). In addition, the threshold setting unit, for example, integrates the time that is less than the threshold, and corrects the threshold when the integrated time does not match the predetermined time.

  The counting unit counts the time when the resistance value is less than the threshold value. For example, measurement is performed using a timer provided in the CPU.

  The determination unit determines a ground fault based on the threshold set by the threshold setting unit. When the number of times by the count unit reaches a predetermined number, or when the time (integrated time) reaches a predetermined time The threshold value is compared with a predetermined resistance value set in advance to determine whether or not there is a ground fault.

  The determination unit compares the threshold value after correction and the predetermined resistance value when a ratio between the threshold value before correction and the difference between the threshold value after correction and the threshold value before correction is equal to or less than a predetermined ratio. To do. In addition, when the number of times the threshold is corrected satisfies the predetermined number of corrections, the determination unit compares the last corrected threshold with a predetermined resistance value to determine whether there is a ground fault.

  Further, the determination unit (ground fault determination device) includes means for changing the operating condition of the fuel cell 10 and discharging the water forming the ground fault path when the threshold value is equal to or lower than the predetermined resistance value.

  Note that the predetermined time (predetermined accumulated time) is set from the shortest time during which a ground fault can be detected during one run and a time (margin) in consideration of not being cleared accidentally when a true ground fault occurs. .

Further, a humidifier made of a metal material such as iron is disposed adjacent to the fuel cell 10 as an auxiliary machine. That is, the humidifier is fixed to the vehicle body V1 of the vehicle V using a bolt or the like via the bracket. Further, the humidifier is configured such that a pipe through which humidified air flows is connected to the inlet of the cathode flow path of the fuel cell 10 and a pipe through which the cathode off gas flows is connected to the outlet of the cathode flow path. Therefore, when the fuel cell 10 and the humidifier are connected via the generated water due to the behavior of the vehicle V such as the vehicle V tilting back and forth or left and right, a ground fault occurs between the fuel cell 10 and the humidifier. resistance value is detected by the ground fault sensor 4 through a humidifier that is fixed to the vehicle body V1.

  The warning lamp 6 is controlled by the ECU 5 so as to be lit when a steady ground fault occurs instead of a temporary ground fault. The warning light 6 can be notified to the driver (user) by being turned on and blinking with a light bulb or LED. Moreover, it is not limited to what is notified to a driver | operator visually, You may notify by sound, such as a speaker. Or you may display and display a character and a picture on thin display panels, such as a liquid crystal.

Next, ground fault determination in the ground fault detection device 1 of the present embodiment will be described with reference to FIGS.
FIG. 2 is an example of a waveform diagram of resistance values detected by the ground fault detection device 1. For example, when an IG (ignition switch, not shown) provided in the vehicle V is turned on (IGON), the determination is started. First, a resistance value within a predetermined period T (for example, 60 seconds) from IGON ( Read resistance value history. Basically, between t0 seconds, the representative resistance value (threshold value) is calculated and the ground fault is determined based on the resistance value history for the past T seconds from the current time (see FIGS. 3 and 4). That is, the processing shown in FIGS. 3 and 4 is performed every t0 seconds. In addition, when it becomes Yes in step S200 of FIG. 3 to be described later (representative resistance value Xa ≦ predetermined resistance value A), in order to confirm the effect of changing the operating condition, a predetermined time has elapsed after the operating condition change. The representative resistance value Xb (threshold value) is determined (S400).

  As for the resistance value until the predetermined period T elapses from IGON, the final resistance value (resistance value history) at the time of IGOFF (starting of the vehicle V) at the previous operation is recorded in a memory (such as EEPROM). When the next operation is IGON, the final resistance value (resistance value history) recorded in the memory may be read.

  Then, a representative resistance value set as a threshold value is calculated for the resistance value for a predetermined period T immediately after IGON, and it is determined based on the flowcharts of FIGS. 3 and 4 whether or not a ground fault has truly occurred.

  As shown in FIG. 3, the ECU 5 calculates a representative resistance value (threshold value) Xa in step S100. This representative resistance value Xa is calculated based on the sub-flowchart shown in FIG. That is, in step S101, the ECU 5 reads the resistance value (resistance value history) for the past T seconds (predetermined period T) into the RAM as shown in FIG.

  In step S102, the ECU 5 records the maximum value XU and the minimum value XL in the read resistance value history in the RAM.

  In step S103, the ECU 5 sets an initial value X0 as a temporary representative resistance value (threshold value) Xn from the resistance value history. In the present embodiment, the initial value X0 is set by the average value Xave of the resistance value history. The initial value X0 is not limited to the average value Xave, and can be selected from any one of logarithmic average value Xlogave, histogram peak value, and (XU + XL) / 2. As shown in FIG. 5, the peak value of the histogram is set based on the distribution of the resistance value in the predetermined period T.

  Returning to FIG. 4, in step S <b> 104, the ECU 5 integrates the time during which the resistance value is smaller than Xn in the read resistance value history. This is defined as an integration time tn.

  In step S105, the ECU 5 determines whether or not the accumulated time tn matches the predetermined time C. That is, in the present embodiment, in principle, a resistance value at which the integration time tn matches the predetermined time C is detected, and the resistance value at the time of matching is determined as a representative resistance value (threshold value). The predetermined time C is a determination value for determining the representative resistance value, and is set to 10 seconds, for example.

  For example, as shown in FIG. 6, when the temporary representative resistance value Xn is set, the time when the resistance value falls below the temporary representative resistance value Xn is measured. Note that n = 0, 1, 2, 3,. Thus, in the section a, since the resistance value is lower than the temporary representative resistance value Xn, the time (for example, 2 seconds) while it is lower is counted (added). In the section b, since the resistance value is not lower than the temporary representative resistance value Xn, it is not counted (added). In section c, since it is below the temporary representative resistance value Xn, it is counted (added). In section d, it is not below the temporary representative resistance value Xn, so it is not counted (added) and in section e. Since it is below the temporary representative resistance value Xn, it is counted (added).

  In this way, it is determined whether or not the temporary representative resistance value is to be corrected by integrating the time when the threshold value Xn is below. Although details will be described later, the accumulated time at this time is 4 s and does not coincide with a predetermined time (for example, 10 s). Therefore, the temporary representative resistance value Xn is not set as an official representative resistance value, and the temporary representative resistance The value Xn is corrected.

  Returning to FIG. 4, when the ECU 5 determines in step S105 that the accumulated time tn coincides with the predetermined time (predetermined accumulated time) C (Yes), the ECU 5 proceeds to step S112, and the temporary representative resistance value at that time Xn is determined as the representative resistance value (threshold value) Xa. For example, if Yes in the first determination from the start of determination in step S105, the average value X0 (initial value) is determined as the representative resistance value (threshold value) Xa.

  If the ECU 5 determines in step S105 that the accumulated time tn does not coincide with the predetermined time C (No), the ECU 5 proceeds to step S106 and determines whether or not the accumulated time Tn is less than the predetermined time C. . This step S106 is a process for determining whether the threshold value set as the representative resistance value exists above or below the temporary representative resistance value Xn.

  If the ECU 5 determines in step S106 that the accumulated time tn is less than the predetermined time C (Yes), the ECU 5 proceeds to step S107, and uses the minimum value XL set in step S102 as the current temporary representative resistance value. Replace with Xn.

  That is, the integrated time tn being less than (less than) the predetermined time C (S106, Yes) means that the representative resistance value does not exist in a region lower than the set temporary representative resistance value Xn. Yes. Therefore, the detection range is narrowed by raising the minimum value XL to the temporary representative resistance value Xn.

  In step S109, the ECU 5 corrects the temporary representative resistance value (threshold value before correction) Xn to obtain a temporary representative resistance value (threshold value after correction) Xn + 1. That is, the corrected temporary representative resistance value Xn + 1 is calculated based on the formula of (maximum value XU + minimum value XL) / 2. The maximum value XU at this time is the value set in step S102, and the minimum value XL is the value set in step S107 (temporary representative resistance value Xn).

  In step S110, the ECU 5 determines whether or not the absolute value of the ratio between the temporary representative resistance value Xn and (temporary representative resistance value Xn + 1−temporary representative resistance value Xn) is equal to or smaller than a predetermined value D. The temporary representative resistance value Xn is a threshold value before correction, and (temporary representative resistance value Xn + 1−temporary representative resistance value Xn) is a difference between the corrected threshold value and the threshold value before correction. The predetermined value D is a predetermined ratio, and is set to 1%, for example.

  If the ECU 5 determines in step S110 that the absolute value of (Xn + 1−Xn) / Xn is not less than or equal to the predetermined value D (No), the ECU 5 proceeds to step S111, counts n up to n + 1, and proceeds to step S104. Return to. If the ECU 5 determines in step S110 that the absolute value of (Xn + 1−Xn) / Xn is equal to or smaller than the predetermined value D (Yes), the ECU 5 proceeds to step S112, and sets the temporary representative resistance value Xn + 1 at that time. The representative resistance value Xa is determined.

  If the ECU 5 determines in step S106 that the accumulated time tn is not less than the predetermined time C (No), the ECU 5 proceeds to step S108, and uses the maximum value XU set in step S102 as the current temporary representative resistance value. Replace with Xn.

  That is, if the accumulated time tn is not less than the predetermined time C (is equal to or longer than the predetermined time C) (S106, No), the value that becomes the representative resistance value is in a region that is higher than the set temporary representative resistance value Xn. Means that it does not exist. Therefore, as described above, the maximum value XU is lowered to the temporary representative resistance value Xn to narrow the detection range.

When the representative resistance value Xa is determined in this way, the flow returns to the flow of FIG. 3 and the ECU 5 determines whether or not the representative resistance value Xa is equal to or less than the predetermined resistance value A in step S200. Predetermined resistance value A is a judgment value for determining the true ground fault is set to For example 1 M.OMEGA..

  If the ECU 5 determines in step S200 that the representative resistance value Xa is equal to or less than the predetermined resistance value A (Yes), the ECU 5 proceeds to step S300 and changes the operating condition of the fuel cell 10. As a means for changing the operating condition, for example, control for forcibly discharging water forming the ground fault path to suppress the ground fault, or reducing the amount of power generation current taken out from the fuel cell 10 is performed. This is control to reduce the amount of water produced. Specifically, in order to forcibly drain water, the amount of reaction gas or oxidant gas supplied to the fuel cell 10 is increased for a certain period of time. In order to reduce the amount of water generated, the fuel cell 10 can be reduced by reducing the amount of power supplied to the traveling motor, or by reducing the output of the air compressor (rotational speed of the motor) required for the air conditioner. Reduce the amount of power generated.

  Then, in step S400, the ECU 5 calculates a representative resistance value Xb. This representative resistance value Xb is calculated based on the flowchart of FIG. 4 in the same manner as described above.

  In step S500, the ECU 5 determines whether the representative resistance value Xb is equal to or less than the predetermined resistance value A.

  When the ECU 5 determines in step S500 that the representative resistance value Xb is equal to or less than the predetermined resistance value A (Yes), the ECU 5 proceeds to step S800 and determines that it is a true ground fault (steady ground fault). The warning lamp 6 is turned on to notify the driver (user) of the ground fault information.

  On the other hand, when the ECU 5 determines that the representative resistance value Xb is not equal to or less than the predetermined resistance value A (No), the ECU 5 proceeds to step S600 and the representative resistance value Xb is equal to or less than the predetermined resistance value B (another predetermined resistance value). Judge whether there is. The predetermined resistance value B is set to a value larger than the predetermined resistance value A, for example, 10 MΩ.

  When the ECU 5 determines in step S600 that the representative resistance value Xb is equal to or less than the predetermined resistance value B (Yes), the ECU 5 proceeds to step S700 and adjusts the contents when the operating condition of the fuel cell 10 is changed next time. To do.

  As described above, the fact that the representative resistance value Xb is equal to or less than the predetermined resistance value A and equal to or less than the predetermined resistance value B is not a true ground fault state but is likely to be a true ground fault (gray) The content of the change in the operating condition of the fuel cell 10 in the next step S300 is adjusted.

  In addition, adjusting the contents of the operating condition change means that the water that forms the ground fault path is forcibly discharged to suppress the ground fault, or the true ground fault is more reliably resolved. Further, the amount of generated current taken out from the fuel cell 10 is further reduced to reduce the amount of generated water. Specifically, in order to forcibly drain water, the amount of reaction gas or oxidant gas supplied to the fuel cell 10 is increased for a certain period of time. To reduce the amount of water produced, fuel can be reduced by further reducing the amount of power supplied to the drive motor, or by further reducing the output of the air compressor (motor rotation speed) required for the air conditioner. The amount of power generated by the battery 10 is further reduced.

  If the ECU 5 determines in step S600 that the representative resistance value Xb is not equal to or less than the predetermined resistance value B (No), the ECU 5 ends the series of processes. If the ECU 5 determines in step S200 that the representative resistance value Xa is not equal to or less than the predetermined resistance value A (No), the ECU 5 ends the process.

  In this way, in the first comparison between the representative resistance value Xb and the predetermined resistance value A in step S200, when the representative resistance value Xa becomes equal to or lower than the predetermined resistance value A, the ground fault is not suddenly determined. By executing the operation condition change of 10, it becomes possible to more reliably determine whether it is a temporary ground fault due to the behavior of the vehicle V or a steady ground fault.

  Furthermore, it demonstrates in full detail, referring the image figure of FIG. 7 thru | or FIG. Note that the numbers in parentheses described in the image diagrams of FIGS. 7 to 9 correspond to the numbers in parentheses described in each step of the flowchart of FIG.

  As shown in (1) in FIG. 7, the resistance value (resistance value history) for the past T seconds (predetermined period T) is read (S101), and as shown in (2), the maximum value XU in the resistance value history and The minimum value XL is recorded (S102). Then, as shown in (3), the average value Xave of the resistance value history is set as the initial value X0 of the temporary representative resistance value Xn (S103). Then, as shown in (4), the times less than the temporary representative resistance value X0 in the resistance value history are integrated, and this is set as the integrated time t0 (S104).

  Then, as shown in FIG. 7 (5), it is determined whether or not the accumulated time t0 matches the predetermined time C (S105). If the accumulated time t0 coincides with the predetermined time C (S105, Yes), the temporary representative resistance value X0 is determined as the representative resistance value Xa as shown in (10) (S112). If the accumulated time t0 does not coincide with the predetermined time C (S105, No), as shown in (6), it is determined whether the accumulated time t0 is shorter than the predetermined time C (S106).

  When the accumulated time t0 is shorter than the predetermined time C (S106, Yes), the minimum value XL is reduced to the temporary representative resistance value X0 (average value Xave) as shown in (7) in FIG. The temporary representative resistance value X0 is set to the minimum value XL. That is, the fact that the integration time t0 is shorter than the predetermined time C means that there is no threshold value as a representative resistance value in the area Q1 indicated by the dots in FIG. 8A, and therefore the process of narrowing the minimum value XL to X0. Do.

  Then, as shown in (8) in FIG. 8A, the temporary representative resistance value X0 is corrected based on the formula of (maximum value XU + minimum value XL) / 2 to set the temporary representative resistance value X1 ( S109). That is, an intermediate value between the maximum value XL and the minimum value XL (X0) is set as the temporary representative resistance value X1.

  Then, as shown in (9) in FIG. 8A, it is determined whether or not | (X1-X0) / X0 | is equal to or smaller than a predetermined value D (S110). That is, the absolute value of the ratio (difference) obtained by subtracting the temporary representative resistance value X0 (initial value, average value Xave) from the temporary representative resistance value X1 to the initial value X0 (average value Xave) is equal to or less than the predetermined value D. In the case (S111, Yes), that is, even if the processing of (7) and (8) in FIG. 8A is performed, the difference between X0 and X1 is small, and even if processing is continued as it is, the result of ground fault detection If there is little influence, the temporary representative resistance value X1 is determined as the representative resistance value Xa as shown in (10) in FIG.

  If | (X1-X0) / X0 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 8A, a time less than the temporary representative resistance value X1 is set. Integration is performed and this is set as an integration time t1 (S104).

  Then, in the subsequent stage of FIG. 8A, as shown in (5), it is determined whether or not the integration time t1 matches the predetermined time C (S105). Here, when the integration time t1 coincides with the predetermined time C (S105, Yes), X1 is determined as the representative resistance value Xa as shown in (10) in the latter stage of FIG. 8 (S112). If the accumulated time t1 does not yet coincide with the predetermined time C (S105, No), whether the accumulated time t1 is shorter than the predetermined time C as shown in (6) in the subsequent stage of FIG. Is determined (S106).

  If the accumulated time t1 is shorter than the predetermined time C (S106, Yes), the minimum value XL is further raised to the temporary representative resistance value X1 as shown in (7) in FIG. 8B. In other words, the fact that the integration time t1 is shorter than the predetermined time C means that there is no threshold value as a representative resistance value in the region Q2 indicated by a dot in FIG. 8B, so the minimum value XL is further reduced to X1. Process.

  Then, as shown in (8) in FIG. 8B, the temporary representative resistance value X1 is corrected based on the formula of (maximum value XU + minimum value XL) / 2, and the next temporary representative resistance value X2 is set. (S109). That is, an intermediate value between the maximum value XU and the minimum value XL (X1) is set as the temporary representative resistance value X2.

  Then, as shown in (9) in FIG. 8B, it is determined whether or not | (X2−X1) / X1 | is equal to or smaller than a predetermined value D (S110). That is, when the absolute value of the ratio (difference) obtained by subtracting the temporary representative resistance value X2 from the temporary representative resistance value X2 with respect to the temporary representative resistance value X1 is equal to or less than the predetermined value D (S111, Yes), that is, FIG. Even if the processing of (7) and (8) is performed in (b), the difference between X2 and X1 is small, and if the processing is continued as it is, the result of ground fault detection is hardly affected. In (b), as shown in (10), the temporary representative resistance value X2 is determined as the representative resistance value Xa, and the process ends.

  If | (X2-X1) / X1 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 8B, a time less than the temporary representative resistance value X2 is set. Integration is performed and this is set as an integration time t2 (S104).

  On the other hand, as shown in (6) in the latter part of FIG. 8A, when the integration time t1 is equal to or longer than the predetermined time C (S106, No), as shown in (7 ′) in FIG. 8C. The maximum value XU is lowered to the temporary representative resistance value X1. That is, the integration time t1 being equal to or longer than the predetermined time C means that there is no threshold value serving as a representative resistance value in the area Q3 indicated by the dots in FIG. 8C, and therefore the maximum value XL is reduced to X1. .

  Then, as shown in (8) in FIG. 8C, the temporary representative resistance value X1 is corrected based on the formula of (maximum value XU + minimum value XL) / 2, and the next temporary representative resistance value X2 is set. (S109). That is, an intermediate value between the maximum value XL (X1) and the minimum value XL (X0) is set as the temporary representative resistance value X2.

  Then, as shown in (9) in FIG. 8C, it is determined whether or not | (X2−X1) / X1 | is equal to or smaller than a predetermined value D (S110). That is, when the absolute value of the ratio (difference) obtained by subtracting the temporary representative resistance value X2 from the temporary representative resistance value X2 with respect to the temporary representative resistance value X1 is equal to or less than the predetermined value D (S111, Yes), that is, FIG. Even if the processing of (7 ′) and (8) is performed in (c), the difference between X2 and X1 is small, and if the processing is continued as it is, the result of ground fault detection is hardly affected. In 8 (c), as shown in (10), the temporary representative resistance value X2 is determined as the representative resistance value Xa, and the process ends.

  If | (X2-X1) / X1 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 8C, a time less than the temporary representative resistance value X2 is set. Integration is performed and this is set as an integration time t2 (S104).

  On the other hand, as shown in [6] in FIG. 7, when the accumulated time t0 is equal to or longer than the predetermined time C (S106, No), as shown in (7 ′) in FIG. Is reduced to the temporary representative resistance value X0 (initial value, average value Xave). That is, the accumulated time t0 is equal to or longer than the predetermined time C means that there is no threshold value as a representative resistance value in the area Q4 indicated by dots in FIG. 9A, and therefore the process of narrowing the maximum value XU to X0. Do.

  Then, as shown in (8) in FIG. 9A, the temporary representative resistance value X0 is corrected based on the formula of (maximum value XU + minimum value XL) / 2 to set the temporary representative resistance value X1 ( S109). That is, an intermediate value between the maximum value XL (X0) and the minimum value XL is set as the temporary representative resistance value X1.

  Then, as shown in (9) in FIG. 9A, it is determined whether or not | (X1-X0) / X0 | is equal to or smaller than a predetermined value D (S110). If | (X1−X0) / X0 | is equal to or smaller than the predetermined value D (S110, Yes), the temporary representative resistance value X1 is set to the representative resistance as shown in (10) in FIG. The value is determined as Xa, and the process ends. If | (X1-X0) / X0 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 9A, a time less than the temporary representative resistance value X1 is set. Integration is performed and this is set as an integration time t1 (S104).

  Then, in the latter part of FIG. 9A, as shown in (5), it is determined whether or not the integration time t1 coincides with the predetermined time C (S105). Here, when the integration time t1 coincides with the predetermined time C (S105, Yes), X1 is determined as a representative resistance value as shown in (10) in the latter stage of FIG. 9 (S112). Further, when the accumulated time t1 still does not coincide with the predetermined time C (S105, No), it is determined whether or not the accumulated time t1 is shorter than the predetermined time C as shown in (6) in the latter stage of FIG. (S106).

  If the accumulated time t1 is shorter than the predetermined time C (S106, Yes), the minimum value XL is raised to the temporary representative resistance value X1 as shown in (7) in FIG. 9B. That is, the integration time t1 is shorter than the predetermined time C means that there is no threshold value as a representative resistance value in the area Q5 indicated by dots in FIG. 9B, and therefore the process of narrowing the minimum value XL to X1. Do.

  9B, the temporary representative resistance value X1 is corrected based on the formula of (maximum value XU + minimum value XL) / 2 to set the temporary representative resistance value X2 (see (8) in FIG. 9B). S109). That is, an intermediate value between the maximum value XL (X0) and the minimum value XL (X1) is set as the temporary representative resistance value X2.

  Then, as shown in (9) in FIG. 9B, when | (X2-X1) / X1 | is equal to or less than a predetermined value D (S111, Yes), it is shown in (10) in FIG. 9B. As described above, the temporary representative resistance value X2 is determined as the representative resistance value Xa, and the process is terminated. If | (X2-X1) / X1 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 9B, the time less than the temporary representative resistance value X2 is set. Integration is performed and this is set as an integration time t2 (S104).

  On the other hand, when the accumulated time t1 is equal to or longer than the predetermined time C (S106, No), the maximum value XU is further lowered to the temporary representative resistance value X1 as shown in (7 ') in FIG. 9C. That is, the cumulative time t1 is equal to or longer than the predetermined time C means that there is no threshold value that is a representative resistance value in the area Q6 indicated by the dots in FIG. 9C, and therefore the process of further reducing the maximum value XL to X1. Do.

  Then, as shown in FIG. 9C, (8), the temporary representative resistance value X1 is corrected based on the formula of (maximum value XU + minimum value XL) / 2, and the temporary representative resistance value X2 is set ( S109). That is, an intermediate value between the maximum value XL (X1) and the minimum value XL is set as the temporary representative resistance value X2.

  9 (c), when | (X2-X1) / X1 | is equal to or smaller than a predetermined value D (S111, Yes), FIG. 9 (c) shows (10). As described above, the temporary representative resistance value X2 is determined as the representative resistance value Xa, and the process is terminated. If | (X2-X1) / X1 | is not less than or equal to the predetermined value D (S111, No), as shown in (4) in FIG. 9C, a time less than the temporary representative resistance value X2 is set. Integration is performed and this is set as an integration time t2 (S104).

  In this way, the process is repeated until the determination in (9) in FIG. 8 or (9) in FIG. 9 becomes Yes. Then, the determined representative resistance value Xa (Xb) is compared with a predetermined resistance value A to determine whether it is a true ground fault (steady ground fault). Informs the driver of the ground fault information.

  As described above, in the ground fault detection device 1 of the present embodiment, the temporary representative resistance value Xn calculated from the resistance value (resistance value history) detected by the ground fault sensor 4 is set, and is less than the temporary representative resistance value Xn. When the integrated time tn coincides with the predetermined time C, the temporary representative resistance value Xn at that time is set as a representative resistance value (threshold value). Then, the representative resistance value (threshold value) and the predetermined resistance value A are compared, and when the representative resistance value (threshold value) Xn becomes equal to or less than the predetermined resistance value A, it is determined that there is a ground fault. Thereby, it is possible to prevent detection of a temporary ground fault (unstable ground fault) caused by the flow of water due to the behavior of the vehicle V (front / back / left / right inclination) or the like.

  In addition, according to the ground fault detection device 1 of the present embodiment, the representative resistance value (threshold value) is obtained when the accumulated time obtained by integrating the time when the resistance value is less than the temporary representative resistance value (threshold value) exceeds the predetermined time C. When the ground fault determination is performed by comparing with the predetermined resistance value A, even when the number of times that the representative resistance value (threshold value) falls below the predetermined number of times is less than the predetermined number, It can be judged as a ground fault.

  Further, according to the ground fault detection device 1 of the present embodiment, when the difference between the detected representative resistance value (threshold value) before correction and the corrected representative resistance value (threshold value) is approximate, further correction is stopped. Since the ground fault determination is performed by comparing the corrected representative resistance value (threshold value) and the predetermined resistance value at that time, it is possible to reduce useless calculation, thereby increasing the processing speed. Further, since it is not necessary to mount a high-performance CPU, the cost can be reduced.

  Moreover, according to the ground fault detection apparatus 1 of this embodiment, since the alarm lamp 6 is provided as a notification device for notifying the ground fault information together with the ground fault detection apparatus 1, the ground fault is detected with respect to the driver (user). It is possible to make sure that there is.

  Further, according to the ground fault detection apparatus 1 of the present embodiment, when it is determined that the representative resistance value Xa (threshold value) is equal to or less than the predetermined resistance value A, the operating condition of the fuel cell 10 is changed (S300), By reducing the water that forms the entanglement path, it is possible to actively avoid a temporary ground fault caused by the water generated in the fuel cell 10.

  Further, according to the ground fault detection device 1 of the present embodiment, the representative resistance value Xb (threshold value) is set from the resistance value detected again after the change of the operating condition, and the representative resistance value Xb becomes equal to or less than the predetermined resistance value A. In the case of a ground fault, a temporary ground fault due to water generated in the fuel cell 10 is actively avoided, and a true ground fault (steady ground fault) is more reliably determined. It becomes possible.

  Moreover, according to the ground fault detection apparatus 1 of the present embodiment, it is possible to quantitatively grasp the degree of ground fault insulation in a certain time section by calculating the representative resistance value. Thereby, the operating condition of the fuel cell 10 can be adjusted based on the grasped degree of decrease in insulation, and the decrease in ground fault insulation can be suppressed.

  In the above-described embodiment, when the accumulated time tn exceeds the predetermined time C by integrating the time below the temporarily set representative resistance value (threshold value), the representative resistance value (threshold value) and the predetermined resistance value are It is not limited to what determines the ground fault by comparing the above, and the number of times the representative resistance value (threshold value) falls below is measured, and when the measured number exceeds the predetermined number of times, the representative resistance value (threshold value) and the predetermined resistance value May be determined by comparing the two.

  Further, when the number of corrections of the representative resistance value (threshold value) satisfies the predetermined correction number, the ground resistance determination may be made by comparing the last corrected representative resistance value (threshold value) with the predetermined resistance value.

1 Ground fault detector 4 Ground fault sensor (resistance detector)
5 ECU (ground fault judgment device, threshold setting unit, counting unit, judgment unit)
6 Warning lights (notification device)
10 Fuel Cell 20 Vehicle Load V Vehicle V1 Body

Claims (8)

A ground fault detection device for detecting a ground fault in a vehicle equipped with a fuel cell that generates electricity by a chemical reaction of a reactive gas,
A resistance detector for detecting a resistance value between the positive electrode and the negative electrode of the fuel cell and the vehicle body;
A ground fault judging device for judging a ground fault from the resistance value,
The ground fault determiner includes a threshold setting unit that sets a threshold value from a resistance value within a predetermined period, a count unit that counts the number of times or time when the resistance value is smaller than the threshold value, and the threshold value is equal to or less than a predetermined resistance value. A determination unit that sometimes determines a ground fault,
The threshold setting unit corrects the threshold when the number of times is less than a predetermined number, or when the time is less than a predetermined time,
The determination unit is configured to compare a threshold value when the number of times reaches a predetermined number of times or when the time reaches a predetermined time with the predetermined resistance value.   The threshold value setting unit sets an initial value of a threshold value from an average value of resistance values, an average value of logarithms, a peak value of a histogram, or (maximum value + minimum value) / 2 in the predetermined period. The ground fault detection apparatus according to claim 1.   The determination unit compares the threshold value after correction and the predetermined resistance value when a ratio between the threshold value before correction and the difference between the threshold value after correction and the threshold value before correction is equal to or less than a predetermined ratio. The ground fault detection apparatus according to claim 2.   4. The determination unit according to claim 1, wherein when the number of corrections of the threshold satisfies a predetermined correction number, the determination unit compares the last corrected threshold with the predetermined resistance value. The ground fault detection apparatus according to item.   The ground fault determination device compares the threshold value with the predetermined resistance value, and determines that the threshold value is equal to or less than the predetermined resistance value, the operating condition of the fuel cell is determined as the water forming the ground fault path. The ground fault detection device according to any one of claims 1 to 4, wherein the ground fault detection device is changed to a condition for reducing the ground fault.   The ground fault determination device sets a threshold value from the resistance value detected again by the resistance detector after the change of the operating condition, compares the threshold value with the predetermined resistance value, and the threshold value is the predetermined resistance value. 6. The ground fault detection apparatus according to claim 5, wherein a ground fault is determined when the following condition is met.   The ground fault judging device compares the threshold value with the predetermined resistance value, and if the threshold value exceeds the predetermined resistance value, another predetermined resistance value greater than the predetermined resistance value and the threshold value are obtained. The comparison is performed, and when the threshold value is equal to or less than the another predetermined resistance value, the change of the operation condition is adjusted to a condition for further reducing the water forming the ground fault path. Ground fault detection device. A ground fault detection device according to any one of claims 1 to 7,
A notification device, comprising: a notification device that notifies a user of ground fault information when the determination unit of the ground fault detection device determines a ground fault.

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