JP5455348B2 - Abnormality detection device, abnormality detection method, and fuel cell system - Google Patents

Description

  The present invention relates to an abnormality detection device, an abnormality detection method, and a fuel cell system including an oxygen sensor.

  The oxygen sensor is a sensor that detects the oxygen concentration in the atmosphere. If an abnormality occurs in this oxygen sensor, it becomes difficult to detect an accurate oxygen concentration. In view of this, there has been disclosed a technique for determining an abnormality of an oxygen sensor based on a sensor output when the oxygen sensor is exposed to the atmosphere (see, for example, Patent Document 1).

JP 2004-198075 A

  However, the technique of Patent Document 1 cannot determine whether an abnormality has occurred in the oxygen sensor or the output processing circuit of the oxygen sensor.

  An object of the present invention is to provide an abnormality detection device, an abnormality detection method, and a fuel cell system that can determine whether an abnormality has occurred in an oxygen sensor or an output processing circuit of the oxygen sensor.

An abnormality detection apparatus according to the present invention includes an output processing circuit for processing an output of a limiting current type oxygen sensor activated by heating by a heater, an oxygen sensor before being heated by the heater and before applying a voltage to the oxygen sensor. A determination unit that determines an abnormality of the ground potential of the output processing circuit based on the output, and the determination unit is based on a time change rate of the output of the oxygen sensor after the voltage application to the oxygen sensor and before the heating by the heater. The abnormality of the output processing circuit is determined . In the abnormality detection device according to the present invention, the output of the oxygen sensor before heating by the heater is used. In this case, fluctuations in the output of the oxygen sensor based on changes in oxygen concentration are avoided. As a result, it can be determined whether or not an abnormality has occurred in the oxygen sensor, or whether or not an abnormality has occurred in the output processing circuit of the oxygen sensor.

Determine tough after voltage application to the oxygen sensor and based on the maximum value of the time rate of change of the output of the oxygen sensor before heating by the heater, it may determine an abnormality of the output processing circuit.

The determination unit may determine abnormality of the oxygen sensor based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor after the voltage application to the oxygen sensor reaches the maximum value. In this case, it can be determined whether or not an abnormality has occurred in the oxygen sensor.

When it is not determined that an abnormality of the oxygen sensor has occurred based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor reaches the maximum value, the output of the oxygen sensor is changed to the oxygen concentration of 0%. You may further provide the memory | storage part memorize | stored as an output. In this case, it is possible to compensate for aging of the oxygen sensor.

The determination unit may determine the abnormality of the oxygen sensor based on the time change rate of the output of the oxygen sensor after the voltage is applied to the oxygen sensor and the power supply to the heater is started. In this case, it can be determined whether or not an abnormality has occurred in the oxygen sensor.

The determination unit is configured to determine at least one of the oxygen sensor and the heater based on the time until the time change rate of the output of the oxygen sensor reaches a predetermined value after the voltage is applied to the oxygen sensor and the power supply to the heater is started. One of the abnormalities may be determined. In this case, it can be determined whether or not an abnormality has occurred in the heat capacity of the oxygen sensor or the heater.

  A fuel cell system according to the present invention includes a fuel cell that generates electricity by a chemical reaction between oxygen and hydrogen, a first pipe that passes through the cathode of the fuel cell, a second pipe that passes through the anode of the fuel cell, and a first pipe. Or a limiting current type oxygen sensor which is arranged at any position of the second pipe and is activated by heating with a heater, and the abnormality detection device according to any one of claims 1 to 8. It is. In the fuel cell system according to the present invention, it is possible to determine whether an abnormality has occurred in the oxygen sensor or whether an abnormality has occurred in the output processing circuit of the oxygen sensor. In this case, the accuracy of oxygen concentration detection of the oxygen sensor is improved. Thereby, the necessity for installation of an air flow meter or the like in the piping is suppressed. As a result, the cost of the fuel cell system is suppressed.

  The reforming unit that generates hydrogen from the hydrocarbon fuel further includes a heating unit that heats the combustion unit by burning the fuel. At least one of the first pipe and the second pipe is connected to the heating unit. It may be arranged in the exhaust gas pipe. In this case, the oxygen sensor can be heated using the heat of the exhaust gas of the heating unit. Thereby, power consumption in the heater provided in the oxygen sensor can be suppressed.

The abnormality detection method according to the present invention is based on the output of the oxygen sensor based on the output of the oxygen sensor before the limit current type oxygen sensor activated by heating by the heater is heated by the heater and before the voltage is applied to the oxygen sensor. look including the determination step of determining an abnormality of the ground potential of the output processing circuit for processing, in the determination step, based on the time rate of change of the output of the oxygen sensor before heating by voltage application after and heater to the oxygen sensor, output processing It is characterized by determining a circuit abnormality . In the abnormality detection method according to the present invention, the output of the oxygen sensor before heating by the heater is used. In this case, output fluctuations based on oxygen concentration changes are avoided. As a result, it can be determined whether or not an abnormality has occurred in the oxygen sensor, or whether or not an abnormality has occurred in the output processing circuit of the oxygen sensor.

In determine the constant step, after the application of a voltage to the oxygen sensor and based on the maximum value of the time rate of change of the output of the oxygen sensor before heating by the heater, may determine an abnormality of the output processing circuit.

In the determination step, the abnormality of the oxygen sensor may be determined based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor after the voltage application to the oxygen sensor reaches the maximum value. In this case, it can be determined whether or not an abnormality has occurred in the oxygen sensor.

  When it is not determined that an abnormality of the oxygen sensor has occurred based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor reaches the maximum value, the output of the oxygen sensor is changed to the oxygen concentration of 0%. A storage step of storing as an output may be further included. In this case, it is possible to compensate for aging of the oxygen sensor.

In the determination step, the abnormality of the oxygen sensor may be determined based on the rate of change over time of the output of the oxygen sensor after the voltage is applied to the oxygen sensor and the supply of power to the heater is started. In this case, it can be determined whether or not an abnormality has occurred in the oxygen sensor.

In the determination step, at least one of the oxygen sensor and the heater is based on the time until the time change rate of the output of the oxygen sensor reaches a predetermined value after the voltage is applied to the oxygen sensor and the power supply to the heater is started. One of the abnormalities may be determined. In this case, it can be determined whether or not an abnormality has occurred in the heat capacity of the oxygen sensor or the heater.

  According to the present invention, it is possible to determine whether an abnormality has occurred in either the oxygen sensor or the output processing circuit of the oxygen sensor.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a block diagram for explaining the configuration of the abnormality detection device 30 according to the first embodiment. The abnormality detection device 30 is a device that detects whether an abnormality has occurred in the oxygen sensor 10 or the output processing circuit 20 of the oxygen sensor 10.

  The oxygen sensor 10 is a limiting current type oxygen sensor, and an anode 12 is provided on one surface of the electrolyte 11, a cathode 13 is provided on the other surface of the electrolyte 11, and a porous substrate 14 in which pores are formed is a cathode 13. It has a structure arrange | positioned on the electrolyte 11 so that it may cover. A heater 15 is disposed on the electrolyte 11.

  The electrolyte 11 is made of an oxygen ion conductive electrolyte, for example, zirconia. The anode 12 and the cathode 13 are made of platinum, for example. The porous substrate 14 is made of, for example, porous alumina. The heater 15 is made of, for example, a platinum thin film.

  The output processing circuit 20 includes an applied voltage control unit 21, a heater power control unit 22, a current-voltage conversion unit 23, and the like. The output processing circuit 20 includes wiring for connecting the anode 12 and the output processing circuit 20 and wiring for connecting the cathode 13 and the output processing circuit 20. The applied voltage control unit 21 is a control circuit that controls the voltage applied to the anode 12 and the cathode 13. The heater power control unit 22 is a control circuit that controls the power supplied to the heater 15. The current-voltage conversion unit 23 is a conversion circuit that converts the limiting current of the oxygen sensor 10 into a voltage signal.

  The abnormality detection device 30 includes a determination unit 31 and a storage unit 32. The determination unit 31 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The determination unit 31 determines whether an abnormality has occurred in the oxygen sensor 10 or the output processing circuit 20 based on the voltage signal given from the current-voltage conversion unit 23. The storage unit 32 is composed of a nonvolatile memory or the like, and stores the determination result of the determination unit 31.

  The output processing circuit 20 is grounded. A sensor shield 24 is provided on the wiring connecting the anode 12 and the applied voltage control unit 21. A sensor shield 25 is provided on the wiring connecting the cathode 13 and the applied voltage control unit 21. The sensor shields 24 and 25 are grounded.

Next, an outline of operations of the oxygen sensor 10 and the output processing circuit 20 will be described. The applied voltage control unit 21 applies a relatively positive voltage to the anode 12 as compared with the cathode 13. This applied voltage is variable. When a voltage is applied to the anode 12 by the applied voltage control unit 21, oxygen becomes oxygen ions at the cathode 13 and conducts through the electrolyte 11 according to the following formula (1). In the anode 12, oxygen ions become oxygen molecules according to the following formula (2).
O ₂ + 4e ⁻ = 2O ²⁻ (1)
2O ²⁻ = O ₂ + 4e ⁻ (2)

  An electric current is generated by the reaction of the formulas (1) and (2). For example, the current-voltage converter 23 converts this current into a voltage signal having a magnitude corresponding to the current value. The current generated in the oxygen sensor 10 is determined by the oxygen gas diffusion amount in the pores of the porous substrate 14. This oxygen gas diffusion amount is determined by the oxygen concentration outside the porous substrate 14. Therefore, based on the voltage signal generated by the current-voltage converter, the oxygen sensor 10 can detect the oxygen concentration in the atmosphere in which the oxygen sensor 10 is disposed.

  Next, the heater power control unit 22 starts supplying power to the heater 15. Thereby, the temperature of the heater 15 rises and the electrolyte 11 is heated. For example, the heater power control unit 22 controls the power supplied to the heater 15 so that the temperature of the electrolyte 11 is about 500 ° C. to 700 ° C. Thereby, oxygen ions can be conducted through the electrolyte 11.

  FIG. 2 is a diagram for explaining the relationship between the output of the current-voltage conversion unit 23 and the elapsed time when a voltage is applied to the oxygen sensor 10. Prior to voltage application to the oxygen sensor 10, no theoretical current is generated in the oxygen sensor 10. Therefore, the output voltage of the current-voltage conversion unit 23 is almost zero. In this case, the output voltage of the current-voltage converter 23 is hereinafter referred to as an output voltage Vs_A.

  When a voltage difference is generated between the anode 12 and the cathode 13 due to voltage application by the applied voltage control unit 21, a current is generated in the oxygen sensor 10. In this case, the output current value of the oxygen sensor 10 increases until reaching a predetermined value. Correspondingly, the output voltage value of the current-voltage conversion unit 23 increases until it reaches a predetermined value. The output voltage value is substantially constant until power is supplied to the heater 15. Hereinafter, the output voltage of the current-voltage conversion unit 23 after the voltage is applied to the oxygen sensor 10 by the applied voltage control unit 21 and before the power is supplied to the heater 15 is referred to as an output voltage Vs_B.

  When electric power is supplied to the heater 15, oxygen ions are conducted through the electrolyte 11, whereby the output current value of the oxygen sensor 10 gradually increases and becomes a substantially constant value. Corresponding to this, the output voltage value of the current-voltage conversion unit 23 gradually increases and becomes a substantially constant value. Hereinafter, the output voltage of the current-voltage conversion unit 23 after power is supplied to the heater 15 will be referred to as output voltage Vs_C.

  In the present embodiment, the determination unit 31 determines whether an abnormality has occurred in the oxygen sensor 10 or the output processing circuit 20 based on the output voltage value of the current-voltage conversion unit 23. FIG. 3 is a diagram for explaining the relationship between the output voltage value of the current-voltage conversion unit 23, the time change rate of the output voltage value, and the elapsed time when a voltage is applied to the oxygen sensor 10.

  Before the voltage application to the oxygen sensor 10, the output voltage Vs_A becomes almost zero if there is no abnormality in the ground potential of the output processing circuit 20. However, when an abnormality occurs in the ground potential of the output processing circuit 20, the current-voltage conversion unit 23 outputs a voltage having a predetermined magnitude. The determination unit 31 determines whether an abnormality has occurred in the ground potential of the output processing circuit 20 based on the output voltage Vs_A.

  For example, the determination unit 31 determines that there is no abnormality in the ground potential of the output processing circuit 20 when the output voltage Vs_A is within a first allowable range (for example, Vs_A_min1 = −10 mV to Vs_A_max1 = 10 mV). Good. When the output voltage Vs_A is outside the first allowable range and within the second allowable range (for example, Vs_A_min2 = −50 mV to Vs_A_max2 = 50 mV), the determination unit 31 may execute a warning process for warning the user. . Further, when the output voltage Vs_A is outside the second allowable range, the determination unit 31 determines that an abnormality has occurred in the ground potential of the output processing circuit 20 and stops the oxygen concentration detection using the oxygen sensor 10. A stop process may be executed.

  Here, the output current of the limiting current type oxygen sensor is a very weak current on the order of μA. Therefore, a ground potential failure is directly connected to an abnormality in the detected oxygen concentration. If an abnormality in the ground potential of the output processing circuit 20 is detected as in this embodiment, the oxygen concentration detection accuracy of the oxygen sensor 10 is improved.

  Next, if there is no abnormality in the output processing circuit 20, the output voltage Vs_B has a predetermined time change rate. However, for example, if the time constant of the output processing circuit 20 is abnormal, the maximum value dVs_B_max of the time change rate dVs_B of the output voltage Vs_B becomes small. Therefore, the determination unit 31 determines whether there is an abnormality in the output processing circuit 20 based on the maximum value dVs_B_max of the time change rate dVs_B.

  For example, the determination unit 31 determines that no abnormality has occurred in the output processing circuit 20 when the maximum value dVs_B_max is equal to or greater than a first threshold value dVs_B1 (for example, a value that is 0.7 times the standard value). Also good. When the maximum value dVs_B is less than the first threshold value dVs_B1 and greater than or equal to the second threshold value dVs_B2 (for example, a value that is 0.5 times the standard value), the determination unit 31 issues a warning process to warn the user May be executed. Further, when the maximum value dVs_B is less than the second threshold value, the determination unit 31 determines that an abnormality has occurred in the output processing circuit 20 and stops the oxygen concentration detection using the oxygen sensor 10. May be executed.

  As described above, it is possible to determine whether or not an abnormality has occurred in the oxygen sensor 10 or the output processing circuit 20 by using the output of the current-voltage converter 23 before being heated by the heater 15. As a result, it is possible to discriminate the abnormality of the oxygen sensor 10 and the output processing circuit 20, and it is possible to reduce the repair time and cost.

  Next, after the rate of change of the output voltage Vs_B reaches the maximum value dVs_B, the output voltage Vs_B falls within a predetermined range as a value with an oxygen concentration of 0%. However, if an abnormality occurs in the oxygen sensor 10 due to secular change or the like, the output voltage Vs_B deviates from the predetermined range. Therefore, the determination unit 31 determines whether an abnormality has occurred in the oxygen sensor 10 based on the output voltage Vs_B after the rate of change of the output voltage Vs_B reaches the maximum value dVs_B.

  For example, when the output voltage Vs_B is within a first allowable range (for example, Vs_B_min1 = applied voltage−10 mV to Vs_B_max1 = applied voltage + 10 mV), the determination unit 31 determines that the oxygen sensor 10 is not abnormal. Good. When the output voltage Vs_B is outside the first allowable range and within the second allowable range (for example, Vs_B_min2 = output voltage−50 mV to Vs_B_max2 = output voltage + 50 mV), the determination unit 31 executes a warning process for warning the user. May be. Furthermore, when the output voltage Vs_B is outside the second allowable range, the determination unit 31 determines that an abnormality has occurred in the oxygen sensor 10 and executes a stop process for stopping the oxygen concentration detection using the oxygen sensor 10. May be.

  When the output voltage Vs_B after the change rate of the output voltage Vs_B reaches the maximum value dVs_B is within the first allowable range, the storage unit 32 uses the output voltage Vs_B when the oxygen concentration detected by the oxygen sensor 10 is 0%. It is stored as a voltage value in a certain case. In this case, by correcting the output of the current-voltage conversion unit 23 using the value stored in the storage unit 32, the manufacturing variation or aging of the oxygen sensor is compensated, and the accuracy of oxygen concentration detection is improved. According to this correction, the influence of the temperature distribution and other disturbances is reduced as compared with the correction in the high temperature atmosphere. Thereby, correction can be performed easily and with high accuracy.

  Next, if there is no abnormality in the responsiveness of the oxygen sensor 10 to the oxygen concentration, the output voltage Vs_C has a predetermined time change rate. However, if the responsiveness of the oxygen sensor 10 is abnormal, the maximum value dVs_C_max of the time change rate dVs_C of the output voltage Vs_C becomes small. Therefore, the determination unit 31 determines whether there is an abnormality in the responsiveness of the oxygen sensor 10 based on the maximum value dVs_C_max.

  For example, the determination unit 31 determines that there is no abnormality in the responsiveness of the oxygen sensor 10 when the maximum value dVs_C_max is equal to or greater than the first threshold value dVs_C1 (eg, 0.7 times the standard value). May be. When the maximum value dVs_C_max is less than the first threshold value dVs_C1 and greater than or equal to the second threshold value dVs_C2 (for example, 0.5 times the standard value), the determination unit 31 performs a warning process for warning the user. May be. Furthermore, when the maximum value dVs_C_max is equal to or smaller than the second threshold value, the determination unit 31 determines that an abnormality has occurred in the responsiveness of the oxygen sensor 10 and stops oxygen concentration detection using the oxygen sensor 10. A stop process may be executed.

  In this case, for example, it is possible to easily detect the presence of deposits on the surface of the oxygen sensor 10 that inhibits oxygen from reaching the oxygen sensor 10. Further, the deterioration of the sensor responsiveness of the oxygen sensor 10 may lead to a decrease in performance of the negative feedback control device, but this decrease in performance can be prevented in advance.

  Next, if there is no abnormality in the heat capacity of the oxygen sensor 10 and the heater 15, the time T_Vs until the output voltage Vs_C reaches the maximum value dVs_C_max after the supply of power to the heater 15 is started is smaller than a predetermined value. Become. However, if the heat capacity of the oxygen sensor 10 and the heater 15 are abnormal, the time T_Vs becomes longer. Therefore, the determination unit 31 determines whether an abnormality has occurred in the heat capacity of the oxygen sensor 10 and the heater 15 based on the time T_Vs.

  For example, the determination unit 31 may determine that no abnormality has occurred in the heat capacity of the oxygen sensor 10 and the heater 15 when the time T_Vs is less than the first threshold value T_Vs1 (for example, the standard value +10 sec). When the time T_Vs is equal to or greater than the first threshold T_Vs1 and less than the second threshold T_Vs2 (for example, the standard value + 30 sec), the determination unit 31 may execute a warning process for warning the user. Furthermore, when the time T_Vs is equal to or greater than the second threshold value T_Vs2, the determination unit 31 determines that an abnormality has occurred in at least one of the heat capacity of the oxygen sensor 10 and the heater 15, and used the oxygen sensor 10. You may perform the stop process which stops oxygen concentration detection.

  In this case, it is possible to easily detect the deterioration of the heater 15 and the presence of deposits on the oxygen sensor 10 main body. This facilitates maintenance, inspection work and the like for maintaining the functions of the oxygen sensor 10 and the output processing circuit 20 in a desired state.

  4 to 6 are diagrams for explaining an example of a flowchart executed when the abnormality detection device 30 detects abnormality of the oxygen sensor. First, referring to FIG. 4, the determination unit 31 reads the output voltage Vs_A from the current-voltage conversion unit 23 (step S1). Next, the determination unit 31 determines whether or not the output voltage Vs_A is in the second allowable range (Vs_A_min2 or more and Vs_A_max2 or less) (step S2).

  When it is determined in step S2 that the output voltage Vs_A is within the second allowable range, the determination unit 31 determines whether the output voltage Vs_A is within the first allowable range (Vs_A_min1 or more and Vs_A_max1 or less) (step S2). S3). When it is determined in step S3 that the output voltage Vs_A is within the first allowable range, the determination unit 31 controls the applied voltage control unit 21 so that a voltage is applied to the oxygen sensor 10 (step S4). Next, the determination unit 31 calls the routine 1 (step S5). Thereafter, the execution of the flowchart ends.

  If it is not determined in step S2 that the output voltage Vs_A is within the second allowable range, the determination unit 31 calls a stop processing routine (step S6). Thereby, the stop process of oxygen concentration detection is performed. If it is not determined in step S3 that the output voltage Vs_A is within the first allowable range, the determination unit 31 calls a warning processing routine (step S7). Thereby, warning processing for the user is executed.

  When the routine 1 is called in the flowchart of FIG. 4, the flowchart of FIG. 5 is executed. Referring to FIG. 5, determination unit 31 reads output voltage Vs_B from current-voltage conversion unit 23 (step S11). Next, (output voltage Vs_B−output voltage Vs_B_old) is substituted into the time change rate dVs_B of the output voltage Vs_B (step S12). The output voltage Vs_B_old is a value given when the previous flowchart is executed. Next, the determination unit 31 substitutes the value of the output voltage Vs_B for the output voltage Vs_B_old (step S13).

  Next, the determination unit 31 determines whether dVs_B is equal to or less than dVs_B_old (step S14). Here, dVs_B_old is a value given during the previous flowchart execution. When it is determined in step S14 that dVs_B is equal to or less than dVs_B_old, the determination unit 31 determines whether dVs_B_old is equal to or greater than a second threshold value dVs_B2 (step S15). When it is determined in step S15 that dVs_B_old is equal to or greater than the second threshold value dVs_B2, the determination unit 31 determines whether dVs_B_old is equal to or greater than the first threshold value dVs_B1 (step S16).

  When it is determined in step S16 that dVs_B_old is equal to or greater than the first threshold value dVs_B1, the determination unit 31 determines whether or not the output voltage Vs_B_old is in the second allowable range (Vs_B_min2 or more and Vs_B_max2 or less) ( Step S17). When it is determined in step S17 that the output voltage Vs_B_old is within the second allowable range, the determination unit 31 determines whether the output voltage Vs_B_old is within the first allowable range (Vs_B_min1 or more and Vs_B_max1 or less) (step S17). S18).

  When it is determined in step S18 that the output voltage Vs_B_old is within the first allowable range, the heater power control unit 22 starts supplying power to the heater 15 (step S19). Next, the determination unit 31 calls the routine 2 (step S30). Thereafter, the execution of the flowchart ends.

  If it is not determined in step S15 that dVs_B_old is greater than or equal to the second threshold value dVs_B2, and if it is not determined in step S17 that the output voltage Vs_B_old is in the second allowable range, the determination unit 31 A stop processing routine is called (step S21). Thereby, the stop process of oxygen concentration detection is performed. Thereafter, the execution of the flowchart ends.

  If it is not determined in step S16 that dVs_B_old is greater than or equal to the first threshold value dVs_B1, and if it is not determined in step S18 that the output voltage Vs_B_old is in the first allowable range, the determination unit 31 A warning processing routine is called (step S21). Thereby, warning processing for the user is executed. Thereafter, the execution of the flowchart ends.

  If it is not determined in step S14 that dV_B is equal to or lower than dVs_B_old, the determination unit 31 substitutes dVs_B for the output voltage dVs_B_old (step S23). Next, the determination unit 31 calls the routine 1 after 512 ms (step S24). Thereafter, the execution of the flowchart ends. By executing the steps S14, S23 and S24, the routine 1 is called until dV_B shows the maximum value.

  When the routine 2 is called in the flowchart of FIG. 5, the flowchart of FIG. 6 is executed. With reference to FIG. 6, the determination part 31 reads the output voltage Vs_C from the current-voltage conversion part 23 (step S31). Next, (output voltage Vs_C−output voltage Vs_C_old) is substituted into the time change rate dVs_C of the output voltage Vs_C (step S32). The output voltage Vs_C_old is a value given when the previous flowchart is executed. Next, the determination unit 31 substitutes the output voltage Vs_C for the output voltage Vs_C_old (step S33).

  Next, the determination unit 31 determines whether dV_C is equal to or lower than dVs_C_old (step S34). dVs_C_old is a value given when the previous flowchart is executed. When it is determined in step S34 that dV_C is equal to or less than dVs_C_old, the determination unit 31 determines whether dVs_C_old is equal to or greater than a second threshold value dVs_C2 (step S35). When it is determined in step S35 that dVs_C_old is equal to or greater than the second threshold value dVs_C2, the determination unit 31 determines whether dVs_C_old is equal to or greater than the first threshold value dVs_C1 (step S36).

  When it is determined in step S36 that dVs_C_old is equal to or greater than the first threshold value dVs_C1, the determination unit 31 determines whether the time T_Vs is equal to or greater than the second threshold value T_Vs2 (step S37). When it is determined in step S37 that the time T_Vs is equal to or greater than the second threshold T_Vs2, the determination unit 31 determines whether or not the time T_Vs is equal to or greater than the first threshold T_Vs1 (step S38). . If it is determined in step S38 that the time T_Vs is equal to or greater than the first threshold value T_Vs1, the execution of the flowchart ends.

  If it is not determined in step S35 that dVs_C_old is greater than or equal to the second threshold value dVs_C2, and if it is not determined in step S37 that the time T_Vs is greater than or equal to the second threshold time T_Vs_2, the determination unit 31 calls a stop processing routine (step S39). Thereby, the stop process of oxygen concentration detection is performed. Thereafter, the execution of the flowchart ends.

  If it is not determined in step S36 that dVs_C_old is greater than or equal to the first threshold value dVs_C1, and if it is not determined in step S38 that the output voltage Vs_B_old is greater than or equal to the first threshold value T_Vs_1, 31 calls a warning processing routine (step S40). Thereby, warning processing for the user is executed. Thereafter, the execution of the flowchart ends.

  If it is not determined in step S34 that dV_C is equal to or less than dVs_C_old, the determination unit 31 substitutes dV_C for dVs_C_old (step S41). Next, the determination unit 31 substitutes time T_Vs + 1 for time T_Vs (step S42). Next, the determination unit 31 calls the routine 1 after 512 ms (step S43). Thereafter, the execution of the flowchart ends. By executing steps S34 and S41 to S43, routine 2 is called until dVs_C shows the maximum value.

  According to the flowcharts of FIGS. 4 to 6, it is possible to determine whether an abnormality has occurred in the ground potential of the output processing circuit 20 based on the output of the oxygen sensor 10 before voltage application to the oxygen sensor 10. . Further, based on the time change rate of the output of the oxygen sensor 10, it can be determined whether the oxygen sensor 10 or the output processing circuit 20 is abnormal. Further, the output value with an oxygen concentration of 0% can be corrected. Based on the time change rate of the output of the oxygen sensor 10 after the power supply to the heater 15 is started, it can be determined whether or not there is an abnormality in the responsiveness of the oxygen sensor 10. Further, whether or not an abnormality has occurred in the heat capacity of the oxygen sensor 10 and the heater 15 based on the time until the time change rate of the output of the oxygen sensor 10 reaches a predetermined value after the power supply to the heater 15 is started. Can be determined.

  FIG. 7 is a block diagram for explaining the overall configuration of the fuel cell system 100 according to the second embodiment. The fuel cell system 100 includes an oxygen sensor 10, a reformer 40, a fuel cell 50, a hydrocarbon fuel pump 71, an air pump 73, a condensed water pump 74, a control unit 80, and the like.

  The reformer 40 includes a reforming unit 41 and a heating unit 42. The fuel cell 50 has a structure in which an electrolyte is sandwiched between a cathode 51 and an anode 52. The hydrocarbon fuel pump 71 is a pump for supplying hydrocarbons to the reforming unit 41. The air pump 73 is a pump for supplying air to the cathode 51. The condensed water pump 74 is a pump for supplying condensed water stored in the condensed water tank 61 to the reforming unit 41. The hydrocarbon fuel pump 71 is provided with a flow meter 72.

  The oxygen sensor 10 has the same structure as that of the first embodiment. The control unit 80 includes a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), and the like, and includes the output processing circuit 20 and the abnormality detection device 30 according to the first embodiment.

  Next, an outline of the operation of the fuel cell system 100 will be described. First, the hydrocarbon fuel pump 71 supplies hydrocarbon fuel to the reforming unit 41 in accordance with an instruction from the control unit 80. In this case, the control unit 80 controls the rotational speed of the hydrocarbon fuel pump 71 according to the detection result of the flow meter 72. The condensed water pump 74 supplies condensed water to the reforming unit 41 in accordance with an instruction from the control unit 80.

  In the reforming unit 41, the steam reforming reaction of the hydrocarbon fuel proceeds by the hydrocarbon fuel and the condensed water. A reformed gas containing hydrogen is generated by the steam reforming reaction. This reformed gas is supplied to the anode 52 of the fuel cell 50.

  The air pump 73 supplies air to the cathode 51 in accordance with instructions from the control unit 80. In the fuel cell 50, the power generation reaction proceeds by the oxygen supplied to the cathode 51 and the hydrogen supplied to the anode 52. The cathode off gas discharged from the cathode 51 and the anode off gas discharged from the anode 52 are supplied to the heating unit 42.

  The cathode off gas contains oxygen. The anode off gas includes fuel such as hydrogen and carbon monoxide. Thereby, in the heating part 42, the fuel contained in the anode off gas burns using the oxygen contained in the cathode off gas. The combustion heat obtained by this combustion is given to the reforming unit 41. Thereby, the steam reforming reaction of endothermic reaction can be promoted.

  The off gas discharged from the heating unit 42 passes through the heat exchanger 62. A cooling medium such as tap water is supplied to the heat exchanger 62. Thereby, the water vapor in the off-gas from the heating unit 42 is condensed to become liquid water and flows into the condensed water tank 61.

  The oxygen sensor 10 detects the oxygen concentration in the off gas from the heating unit 42 and gives the detection result to the control unit 80. The control unit 80 controls the amount of oxygen supplied from the air pump 73 to the cathode 51 based on the detection result of the oxygen sensor 10. Since the oxygen concentration detection accuracy of the oxygen sensor 10 is improved by using the abnormality detection device 30 provided in the control unit 80, the necessity of installing a flow meter with respect to the air pump 73 is reduced. Thereby, cost reduction of the fuel cell system 100 can be achieved. In addition, since the oxygen sensor 10 is disposed between the heating unit 42 and the heat exchanger 62, the oxygen sensor 10 can be heated using the heat of off-gas from the heating unit 42. Thereby, the power consumption of the heater 15 can be suppressed.

  In this embodiment, the piping from the air pump 73 through the cathode 51 and the heating unit 42 corresponds to the first piping, and the piping from the hydrocarbon fuel pump 71 through the reforming unit 41, the anode 52 and the heating unit 42 is the first piping. It corresponds to 2 pipes.

It is a block diagram for demonstrating the structure of the abnormality detection apparatus which concerns on Example 1. FIG. It is a figure for demonstrating the relationship between the output of an electric current voltage conversion part, and elapsed time when applying a voltage to an oxygen sensor. It is a figure for demonstrating the relationship between the output voltage value of the current-voltage conversion part in the case of applying a voltage to an oxygen sensor, the time change rate of the output voltage value, and elapsed time. It is a figure for demonstrating an example of the flowchart performed in the case of abnormality detection of the oxygen sensor by a detection apparatus. It is a figure for demonstrating an example of the flowchart performed in the case of abnormality detection of the oxygen sensor by a detection apparatus. It is a figure for demonstrating an example of the flowchart performed in the case of abnormality detection of the oxygen sensor by a detection apparatus. 6 is a block diagram for explaining an overall configuration of a fuel cell system according to Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Oxygen sensor 11 Electrolyte 12 Anode 13 Cathode 14 Porous board | substrate 15 Heater 20 Detection apparatus 21 Applied voltage control part 22 Heater electric power control part 23 Current-voltage conversion part 24,25 Sensor shield determination part 31 Determination part 32 Memory | storage part 40 Reformer 41 reforming unit 42 heating unit 50 fuel cell 51 cathode 52 anode 80 control unit 100 fuel cell system

Claims (14)

An output processing circuit that processes the output of a limiting current type oxygen sensor that is activated by heating with a heater;
A determination unit for determining an abnormality in the ground potential of the output processing circuit based on an output of the oxygen sensor before being heated by the heater and before applying a voltage to the oxygen sensor ;
The determination unit determines an abnormality of the output processing circuit based on a time change rate of an output of the oxygen sensor after applying a voltage to the oxygen sensor and before heating by the heater. . The determination unit determines abnormality of the output processing circuit based on a maximum value of a time change rate of an output of the oxygen sensor after voltage application to the oxygen sensor and before heating by the heater. The abnormality detection device according to claim 1.   The determination unit determines an abnormality of the oxygen sensor based on an output of the oxygen sensor after a time change rate of the output of the oxygen sensor after applying a voltage to the oxygen sensor reaches a maximum value. The abnormality detection device according to claim 1, wherein When it is not determined that an abnormality of the oxygen sensor has occurred based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor reaches the maximum value, the output of the oxygen sensor is The abnormality detection device according to claim 3 , further comprising a storage unit that stores an output having a concentration of 0%. The determination unit determines abnormality of the oxygen sensor based on a time change rate of an output of the oxygen sensor after voltage application to the oxygen sensor and power supply to the heater is started. The abnormality detection device according to any one of claims 1 to 4 . The determination unit is configured to detect the oxygen sensor based on a time until a time change rate of the output of the oxygen sensor reaches a predetermined value after the voltage is applied to the oxygen sensor and the power supply to the heater is started. The abnormality detection device according to claim 1, wherein an abnormality of at least one of the heater and the heater is determined. A fuel cell that generates electricity by a chemical reaction between oxygen and hydrogen;
A first pipe passing through the cathode of the fuel cell;
A second pipe passing through the anode of the fuel cell;
A limiting current type oxygen sensor which is arranged at any position of the first pipe or the second pipe and is activated by heating by a heater;
A fuel cell system comprising the abnormality detection device according to claim 1 . A heating unit that heats the reforming unit that generates hydrogen from the hydrocarbon fuel by burning the fuel;
At least one of the first pipe and the second pipe is connected to the heating section;
The fuel cell system according to claim 7 , wherein the oxygen sensor is disposed in an exhaust gas pipe of the heating unit. Output processing for processing the output of the oxygen sensor based on the output of the oxygen sensor before the limiting current type oxygen sensor activated by heating by the heater is heated by the heater and before the voltage is applied to the oxygen sensor It looks including the determination step of determining an abnormality of the ground potential of the circuit,
In the determining step, an abnormality of the output processing circuit is determined based on a time change rate of an output of the oxygen sensor after applying a voltage to the oxygen sensor and before heating by the heater. . In the determination step, abnormality of the output processing circuit is determined based on a maximum value of a time change rate of the output of the oxygen sensor after voltage application to the oxygen sensor and before heating by the heater. The abnormality detection method according to claim 9 . In the determination step, the abnormality of the oxygen sensor is determined based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor after the voltage application to the oxygen sensor reaches a maximum value. The abnormality detection method according to claim 9, wherein: When it is not determined that an abnormality of the oxygen sensor has occurred based on the output of the oxygen sensor after the time change rate of the output of the oxygen sensor reaches the maximum value, the output of the oxygen sensor is The abnormality detection method according to claim 11 , further comprising a storage step of storing as an output having a concentration of 0%. In the determination step, the abnormality of the oxygen sensor is determined based on a time change rate of an output of the oxygen sensor after voltage application to the oxygen sensor and power supply to the heater is started. The abnormality detection method according to any one of claims 9 to 12 . In the determination step, based on the time until the time change rate of the output of the oxygen sensor reaches a predetermined value after the voltage is applied to the oxygen sensor and the power supply to the heater is started, the oxygen sensor The abnormality detection method according to claim 9, wherein an abnormality of at least one of the heater and the heater is determined.

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