JP2015018701A - Deterioration detecting device for vehicle fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine in detail the cause of deterioration so that, if a fuel battery mounted in a vehicle deteriorates, an operation for recovering from the deterioration is performed in appropriate conditions.SOLUTION: A target value for a current output from a fuel battery is changed in steps. The transient response of a voltage output from the fuel battery driven so as to follow this target value is measured. The transient response is decomposed into a quick response component and a late response component. The time constant Tof the quick response component and the time constant Tof the late response component are calculated. The difference ΔTbetween the time constant of the quick response component and the time constant Tin a normal time is calculated. The difference ΔTbetween the time constant of the late response component and the time constant Tin a normal time is calculated. The deterioration in which the reaction of the platinum catalyst of a fuel battery and the internal impedance of a cell change is determined based on the difference ΔT. The deterioration in which the supply of hydrogen and oxygen of the fuel battery changes is determined based on the difference ΔT.

Description

  The present invention relates to a deterioration detector for a fuel cell mounted on a vehicle.

  2. Description of the Related Art In recent years, in the field of vehicles such as motorcycles and automobiles, vehicles equipped with a polymer electrolyte fuel cell having a polymer film as a power source are known in consideration of the global environment. A polymer electrolyte fuel cell has a stack in which a plurality of cells as basic units are stacked and connected in series. In the cell, an anode electrode (fuel electrode) and a cathode electrode (air electrode) are bonded with a polymer membrane (proton exchange membrane) in between, and a support current collector made of carbon paper is disposed outside the cell. Furthermore, the separator which has the pipe line which flows cooling water on the outer side is arrange | positioned. The anode and cathode are composed of a catalyst having platinum fine particles supported on a carbon support and an electrolyte. When hydrogen is introduced into the anode electrode, the hydrogen ionizes and moves to the cathode electrode through the proton exchange membrane. At the same time, the electrons released when the ionization passes through the conducting wire without passing through the proton exchange membrane and escapes to the outside. It becomes. Oxygen introduced into the cathode electrode reacts with hydrogen ions that enter through the polymer film and electrons that enter through the external conducting wire to become water and is discharged.

  In an actual use situation of a vehicle equipped with such a fuel cell, the load during driving, the surrounding environment, and the surrounding environment during storage vary in various ways. For this reason, fuel cells have temporary or permanent performance degradation (deterioration) such as oxidation and elution of platinum catalyst surface, drying of proton exchange membrane, perforation, excessive moisture inside the cell, freezing of water, oxidation of separator surface, etc. ) Occurs. Among these deteriorations, oxidation of the surface of the platinum catalyst, drying of the proton exchange membrane, excessive moisture inside the cell, and water freezing are temporary deteriorations of the fuel cell. When such temporary deterioration occurs, it is necessary to operate the fuel cell under conditions for recovering from the deterioration (hereinafter referred to as recovery operation) to restore the performance of the fuel cell. That is, the degree of deterioration of the fuel cell is detected, the necessity of recovery operation is determined based on the detection result, the cause of deterioration of the fuel cell is identified, and recovery operation suitable for recovery from the deteriorated state is performed. Conditions must be selected based on the cause of degradation.

  As a technique for determining deterioration of the fuel cell, for example, in Patent Document 1, the output voltage of the fuel cell is controlled to a predetermined drop pattern, and the measured value of the output current of the fuel cell during this control is integrated and obtained. A system for determining deterioration of a fuel cell from the amount of electricity has been proposed. In this system, the output current measurement process is performed after the air blowing process for the cathode electrode to determine the deterioration of the carrier carrying the catalyst, and then the same measurement process is performed again to determine the catalyst change. Further, Patent Document 2 proposes a fuel cell system that discharges the fuel cell at an appropriate timing and detects deterioration of the proton exchange membrane by detecting the voltage change amount of the fuel cell after power generation is stopped. ing.

JP 2012-089448 A JP 2012-028221 A

  However, although the system of Patent Document 1 can detect the deterioration of the fuel cell caused by the catalyst and the carrier, other factors such as excessive moisture inside the cell, deterioration of the supply state of hydrogen and oxygen, and the like. Degradation cannot be detected. Therefore, when the cause of deterioration is other than the catalyst and the carrier, it is not possible to select an appropriate condition for the recovery operation of the fuel cell. Further, in the system of Patent Document 2, the degree of deterioration of the fuel cell cannot be detected, and the cause of actual deterioration cannot be identified from various causes of deterioration. Therefore, the recovery operation of the fuel cell cannot be appropriately performed as in the system of Patent Document 1.

  The present invention has been made in view of such a situation, and an object of the present invention is to appropriately set the conditions for the recovery operation of the deterioration when the deterioration of the fuel cell occurs in the actual use situation of the vehicle equipped with the fuel cell. It is to accurately determine the cause of the deterioration so that it can be selected.

  In order to solve the above-described problems of the prior art, the present invention is an apparatus for detecting deterioration of a fuel cell mounted on a vehicle, and increases the current output current value of the fuel cell in a stepped manner by a predetermined amount. Target value setting means for setting the target value to be set, and the output current of the fuel cell is controlled so that the output current value of the fuel cell follows the target value, and the transient response of the output voltage of the fuel cell at that time A transient response measuring means for measuring the output voltage, and a transient response decomposing means for decomposing a transient response of the output voltage of the fuel cell into a first component having a relatively fast response and a second component having a relatively slow response. A time constant calculating means for calculating a first time constant of the first component and a second time constant of the second component, and a time constant of the first component when the fuel cell is normal. The difference between a first reference time constant and the first time constant. A first difference is calculated, and a second difference that is a difference between a second reference time constant that is a time constant of the second component when the fuel cell is normal and the second time constant is calculated. When the difference calculation means and the first difference exceed the first component specified value, it is determined that the deterioration of the reaction state of the catalyst of the fuel cell and the impedance inside the cell has occurred, and Determining the degree of deterioration, and if the second difference exceeds the second specified component value, it is determined that deterioration has occurred that changes the supply state of hydrogen and oxygen in the fuel cell, and the deterioration Deterioration determining means for determining the degree of the above.

  Further, in the present invention, when the degree of deterioration determined based on the first difference exceeds a predetermined range, the first current in the first region where the current density is relatively small in the fuel cell. And a first voltage value is measured, and a second current value and a second voltage value in a second region where the current density in the fuel cell is greater than the first region are measured, and the normality of the fuel cell is measured. Sometimes, when the difference between the voltage value when driven with the first current value and the first voltage value exceeds a first current regulation value, the reduction reaction on the catalyst surface of the cell of the fuel cell is promoted. The difference between the first voltage value and the voltage value when the fuel cell is driven with the first current value when the fuel cell is operating normally is determined as the difference between the first voltage value and the first voltage value. And the fuel cell does not exceed the specified current value. When the difference between the voltage value when the second current value is always driven and the second voltage value exceeds the second specified current value, the polymer membrane of the fuel cell is humidified. It can be configured to perform an operation for recovering the deterioration of the fuel cell under conditions.

  Further, in the present invention, when the degree of deterioration determined based on the second difference exceeds a predetermined range, when the temperature of the fuel cell is higher than a specified temperature value, inside the cell of the fuel cell An operation for recovering the deterioration of the fuel cell under conditions for removing moisture is performed, and when the temperature of the fuel cell is lower than the temperature specified value, the condition is such that the frozen moisture inside the fuel cell is melted. It can be configured to perform an operation for recovering the deterioration of the fuel cell.

  Further, in the present invention, when the deterioration detection means determines the deterioration of the fuel cell based on the first difference, the recovery operation time of the fuel cell for recovering the deterioration is set to the first difference. If the deterioration of the fuel cell is detected based on the second difference by the deterioration detection means, the recovery operation time of the fuel cell for recovering the deterioration is based on the second difference. Can be configured.

  Further, in the present invention, when the deterioration of the fuel cell is not recovered despite executing the recovery operation for recovering the deterioration determined by the deterioration determining means, the output voltage value of the fuel cell at normal time When the decrease in the output voltage value of the fuel cell after the recovery operation is smaller than a predetermined allowable level, a new target value of the output current value of the fuel cell is set, and the output current value becomes the new target value. A transient response of the output voltage of the fuel cell when the fuel cell is controlled to follow is measured, and the transient response of the output voltage of the fuel cell is decomposed into the first component and the second component. , Calculating a third time constant of the first component and a fourth time constant of the second component, replacing the first reference time constant with the third time constant, Place the reference time constant in the fourth time constant Replace As can be configured.

  As described above, the vehicle fuel cell deterioration detection device according to the present invention sets a target value obtained by increasing the current output current value of the fuel cell in a stepped manner by a predetermined amount, and the output current value is the target value. The transient response of the output voltage of the fuel cell when the fuel cell is controlled to follow the first is measured, and the first component having a relatively fast response and the second component having a relatively slow response included in the transient response are measured. Based on the above, the cause and the degree of deterioration of the fuel cell are determined. Therefore, the necessity of the recovery operation of the fuel cell can be determined, and when the fuel cell has deteriorated, the recovery operation can be performed by selecting appropriate conditions for recovery from the deterioration.

  When the degree of degradation determined based on the first component having a relatively fast response included in the transient response described above exceeds a predetermined range, current values of a plurality of regions having different current densities in the fuel cell By measuring each voltage value, the cause of deterioration can be determined in more detail based on these current value and voltage value. Therefore, more appropriate conditions can be selected when performing the recovery operation for recovering the deterioration determined based on the first component having a relatively fast response.

  When the degree of deterioration determined based on the second component having a relatively slow response included in the transient response described above exceeds a predetermined range, the temperature of the fuel cell is measured to obtain the measured temperature. Based on this, the cause of deterioration can be determined in more detail. Therefore, more appropriate conditions can be selected when performing the recovery operation for recovering the deterioration determined based on the second component having a relatively slow response.

  When the occurrence of deterioration is determined based on the first component having a relatively fast response included in the transient response, the first time constant that is the difference between the first time constant and the first reference time constant described above is used. When the recovery operation time is calculated based on the difference and the occurrence of deterioration is determined based on the second component that is relatively slow in response included in the transient response, the second time constant and the second time constant described above are used. By calculating the recovery operation time based on the second difference that is the difference from the reference time constant, the recovery operation time can be optimized according to the cause of deterioration. Therefore, it is possible to suppress the influence on the traveling of the vehicle such as a decrease in the output of the fuel cell due to the recovery operation.

  In the case where the deterioration does not recover despite the execution of the recovery operation for recovering the deterioration, the decrease in the output voltage value of the fuel cell after the recovery operation with respect to the normal output voltage value of the fuel cell is lower than a predetermined allowable level. If it is small, the performance of the fuel cell is degraded, but it can continue to be used. In this case, by performing the above-described replacement process of the reference voltage value, it is possible to continue to determine the occurrence of temporary deterioration and perform an appropriate recovery operation.

1 is a block diagram of a deterioration detection device for a vehicle fuel cell according to an embodiment of the present invention. It is a block diagram of the 1st DC-DC converter of the deterioration detection apparatus of the fuel cell for vehicles which concerns on embodiment of this invention. It is a graph which shows the transient characteristic of a fuel cell. It is a flowchart which shows the procedure of the degradation detection process performed with a degradation detection apparatus. It is a graph which shows the loss characteristic of a fuel cell. It is a graph which shows a characteristic when the activation polarization of a fuel cell increases. It is a graph which shows a characteristic when the resistance polarization of a fuel cell increases. It is a flowchart which shows the procedure of the process which selects the conditions of recovery operation | movement of the deteriorated fuel cell. It is a flowchart which shows the procedure of the process which selects the conditions of recovery operation | movement of the deteriorated fuel cell. It is a flowchart which shows the procedure of the process performed after the recovery driving | operation of a deteriorated fuel cell. It is a timing chart which shows the voltage waveform of the fuel cell measured in the modification of a deterioration detection process. It is a timing chart which shows the voltage waveform of the fuel cell measured in the modification of a deterioration detection process.

  Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a block diagram of a vehicle fuel cell deterioration detection apparatus according to the present embodiment. The data processing device 10 is a system controller that controls the entire deterioration detection device. A fuel cell (FC) 20, a first DC-DC converter 30, an inverter 40, a second DC-DC converter 60, and a battery 70 are connected to the data processing device 10. A motor 50 is connected to the inverter 40, and a battery 70 is connected to the second DC-DC converter. The temperature data of the fuel cell 20 measured by the temperature sensor 21 of the fuel cell 20 and various data measured by the voltage sensor 31 and the current sensor 32 of the first DC-DC converter 30 are input to the data processing device 10. . The data processing device 10 performs arithmetic processing based on these various data, and generates a control signal. A control circuit (not shown) is mounted on each of the fuel cell 20, the first DC-DC converter 30, the inverter 40, the second DC-DC converter 60, and the battery 70. Thus, transmission and reception of control signals are performed.

  FIG. 2 is a diagram showing a configuration of the first DC-DC converter 30 of FIG. The first DC-DC converter is a step-up / step-down converter, and includes an inductance 33 and switches SW1, SW2, SW3, and SW4 in addition to the voltage sensor 31 and the current sensor 32 described above. The switches SW1 to SW4 are switching elements, and for example, power MOSFETs are used. When the step-up operation is performed in the first DC-DC converter 30, the switch SW1 is switched ON, the switch SW2 is switched OFF, and the switches SW3 and SW4 are switched at a duty ratio corresponding to the voltage difference between the input and output. Is done. Further, when the step-down operation is performed in the first DC-DC converter 30, the switch SW4 is switched ON, the switch SW3 is switched OFF, and the switches SW1 and SW2 are duty ratios according to the voltage difference between the input and output. It is switched at. Based on the detection results of the voltage sensor 31 and the current sensor 32, switching of the switches SW1 to SW4 is controlled so that the voltage and current follow a predetermined target value.

  The processing procedure of the recovery control of the fuel cell 20 executed by the data processing apparatus 10 is as follows. First, deterioration detection processing of the fuel cell 20 is performed, and it is determined whether or not the recovery operation of the fuel cell 20 should be executed based on the detection result. If it is determined that the recovery operation of the fuel cell 20 is necessary, the recovery operation condition is selected according to the state of deterioration, and then the recovery operation of the fuel cell 20 is executed under the selected condition. Then, after the recovery operation, it is confirmed whether or not the output of the fuel cell 20 has been recovered. If the output has not recovered, processing after the recovery operation described later is executed. Since these processes are executed while generating power from the fuel cell 20, electric power is output from the fuel cell 20 during the process. As described above, the output current of the fuel cell 20 is output to the motor 50 via the first DC-DC converter 30 and the inverter 40 to drive the motor 50, or the first DC-DC converter 30 and the first The battery 70 is charged by being output to the battery 70 via the second DC-DC converter 60. Motor driving and battery charging are performed according to the running state of the vehicle and the charged state of the battery 70.

[Fuel cell deterioration detection]
In the present embodiment, the degree of deterioration of the fuel cell 20 and the cause thereof are determined by paying attention to the transient characteristics of the fuel cell 20. FIG. 3 shows the transient response of the output voltage when the target value of the output current of the fuel cell is increased stepwise. When the target value of the output current of the fuel cell 20 is increased stepwise at the time t1, the output voltage of the fuel cell 20 shows a drop of about 50% at the time t1, as shown by the solid line L20, and then gradually decreases. To go. The transient response of the output voltage indicated by the solid line L20 can be approximated by the sum of a relatively fast response component (dashed line L21) and a relatively slow response component (dashed line L22). The component having a fast response shows a drop of about 50% at time t1, and then the voltage value is maintained. The slow-response component does not drop rapidly at time t1, but shows a gradual drop over time.

  The fast response component is related to the reaction of the platinum catalyst in the cell of the fuel cell 20 and the internal impedance of the cell. That is, in the fuel cell 20, when the deterioration due to the oxidation of the platinum catalyst surface of the cell or the deterioration due to the drying of the polymer film occurs, the supply state of hydrogen or oxygen deteriorates due to excessive moisture inside the cell. A delay occurs in a component having a quick response when deterioration occurs. In addition, the slow-response component is related to the supply of hydrogen and oxygen in the fuel cell 20. That is, when deterioration in which the supply state of hydrogen and oxygen in the fuel cell 20 changes (for example, a level of 80% or less in the normal state) occurs, a further delay occurs in the slow-response component. Since there is a large difference between the time constants of the fast response component and the slow response component, they can be detected individually.

ここで、ｔは時間、Ｖ_０は電圧初期値、Ｖは過渡応答電圧値、Ｖ_１は応答の速い成分の電圧値、Ｖ_２は応答の遅い成分の電圧値、Ｖ_１∞は応答の速い成分の電圧最終値、Ｖ_２∞は応答の遅い成分の電圧最終値、Ｔ_１は応答の速い成分の時定数、Ｔ_２は応答の遅い成分の時定数である。 In the present embodiment, the transient response of the output voltage when the output current value of the fuel cell 20 is increased stepwise is measured, and the time constant is calculated by decomposing the output voltage into a fast response component and a slow response component. Thus, the degree of deterioration of the fuel cell 20 and its cause are determined. The transient response of the output voltage of the fuel cell 20 is approximated by the sum of the step responses of the first-order lag transfer function, as shown by the equation (1).

Here, t is time, V ₀ is an initial voltage value, V is a transient response voltage value, V ₁ is a voltage value of a component with a fast response, V ₂ is a voltage value of a component with a slow response, and V _1∞ is a fast response. The final voltage value of the component, V _2∞ is the final voltage value of the slow response component, T ₁ is the time constant of the fast response component, and T ₂ is the time constant of the slow response component.

ここで、ΔＴ_１は応答の速い成分の正常状態における時定数と、検出された応答の速い成分の時定数との差分であり、Ｔ_１ｓｔｄは応答の速い成分の正常状態における時定数である。

ここで、ΔＴ_２は応答の遅い成分の正常状態における時定数と、検出された応答の遅い成分の時定数との差分であり、Ｔ_２ｓｔｄは応答の遅い成分の正常状態における時定数である。 Constant T ₁ time of the fast component voltage value V ₁ of the response, the constant T ₂ when the slow voltage components V ₂ response, Equation (2), the normal state as shown in (3) (the fuel cell 20 Compared with the time constant in a state where no deterioration has occurred.

Here, ΔT ₁ is the difference between the time constant of the fast response component in the normal state and the detected time constant of the fast response component, and T _1std is the time constant of the fast response component in the normal state.

Here, ΔT ₂ is the difference between the time constant of the slow response component in the normal state and the detected time constant of the slow response component, and T _2std is the time constant of the slow response component in the normal state.

In the present embodiment, the deterioration degree of the internal impedance of the reaction conditions and the cell of the catalyst in the fuel cell 20 is changed on the basis of the [Delta] T ₁ is determined, the supply state of the hydrogen and oxygen in the fuel cell 20 is changed on the basis of the [Delta] T ₂ The degree of deterioration is determined.

  FIG. 4 is a flowchart showing the procedure of the deterioration detection process of the fuel cell 20 executed by the data processing apparatus 10. In step S10, the switching control of the first DC-DC converter 30 is performed so that the current value of the current output from the fuel cell 20 and input to the first DC-DC converter 30 increases stepwise. The current value (target value) increased in a step shape is input to the data processing device 10. The data processing device 10 outputs a control signal to the fuel cell 20 so that the output current of the fuel cell 20 follows the target value. Next, in step S11, the transient response of the output voltage of the fuel cell 20 controlled so that the output current becomes the target value is measured by the voltage sensor 31 of the first DC-DC converter 30, and the transient measured by the voltage sensor 31 is measured. The response waveform is recorded in the data processing apparatus 10 as a time-series data array.

In step S12, the transient response waveform is approximated by the sum of the step response of the primary delay transfer function shown in equation (1) described above, at step S13, the constant T ₁ time of the fast component V ₁ response, response The time constant T ₂ of the slow component V ₂ is calculated. Then proceeds to step S14, the difference [Delta] T ₁ of the time constant, the constant T ₁ time of the fast component of the response calculated in step S13 is calculated in the normal state of the rapid component of the response, in a normal state of slow response component of A difference ΔT ₂ between the time constant and the time constant T ₂ of the slow response component calculated in step S13 is calculated.

In step S15, the difference ΔT ₁ is compared with a predetermined value, and if ΔT ₁ is equal to or larger than the predetermined value, the process proceeds to step S16. In step S16, based on the constants T ₁ time of the fast component of the response is changing the specified value or more compared to normal, the internal impedance of the reaction conditions and the cell of the cells of the platinum catalyst in the fuel cell 20 is changed deterioration It is determined that it has occurred. Further, the degree of deterioration is determined according to the value of ΔT ₁ . That is, it is determined that the greater the value of ΔT _1, the greater the degree of deterioration that changes the reaction state of the platinum catalyst and the internal impedance of the cell. Next, the process proceeds to step S17. When ΔT ₁ is lower than the specified value, the process of step S16 is skipped and the process proceeds to step S17.

Step S17 In difference [Delta] T ₂ is compared with a predetermined specified value, if [Delta] T ₂ is equal to or greater than the prescribed value, the process proceeds to step S18. At step S18, it determines that based on the fact that the constant T ₂ time a slow response component of has changed more than the specified value compared with the normal supply conditions of the hydrogen and oxygen are changed in the fuel cell 20 deteriorates occurs Is done. Further, according to the value of [Delta] T _2, the degree of deterioration is determined. That is, it is determined that the greater the value of ΔT ₂ is, the greater the degree of deterioration in which the supply state of hydrogen and oxygen changes. This completes the detection of the deterioration of the fuel cell 20. If [Delta] T ₂ is lower than the specified value, processing in step S18 is skipped, the degradation detection of the fuel cell 20 is completed.

[Selection of recovery operation conditions]
In the present embodiment, the conditions for the recovery operation of the fuel cell 20 are selected based on the cause and degree of deterioration determined in steps S16 and S18 of FIG. Based on the time constant difference ΔT ₁ of the fast-response component, when it is determined that the degree of deterioration in which the reaction state of the platinum catalyst of the fuel cell 20 or the internal impedance of the cell changes is large, the reduction reaction on the catalyst surface is promoted. The recovery operation of the fuel cell 20 is performed under conditions or conditions where the polymer membrane is humidified.

The loss of the fuel cell 20 includes activation polarization (V _act ) due to the activation energy of the electrode reaction, resistance polarization (V _ohm ) due to the electric resistance of the electrolyte and electrode, and the concentration phenomenon of the reactant on the electrode surface. There is a resulting diffusion polarization (V _trans ). FIG. 5 is a graph showing the characteristics of these losses. The deterioration of the reaction state of the platinum catalyst in the fuel cell 20 leads to an increase in the activation polarization _Vact , and the deterioration of the internal impedance of the cell of the fuel cell 20 leads to an increase in the resistance polarization _Vohm . Therefore, in the case where a decrease in the output voltage is observed from the region where the current density indicated by A11 is small in FIG. 5, it can be determined that the reaction state of the platinum catalyst of the fuel cell 20 has deteriorated. In addition, in FIG. 5, when the output voltage decreases in a region where the current density indicated by A12 is medium, it can be determined that the internal impedance of the cell has deteriorated.

Therefore, first, the voltage V ₁ and the current I ₁ of the region A 112 where the current density is low and the fuel cell 20 are measured, and compared with the voltage V _1std when the fuel cell 20 is normal and the current I ₁ is the same. Then, in the area A12 of moderate current density, similarly, the voltage _{V 2} and current _{I 2} of the fuel cell 20 is measured and compared with the voltage _{V 2Std} when the same current _{I 2} during normal fuel cell 20 . As shown in FIG. 6, in the case where the difference between the current density region A21 and the normal voltage V _1std is already large, the activation polarization is increased. Accordingly, it is determined that there is a problem in the reaction state of the platinum catalyst, and conditions for promoting the reduction reaction on the catalyst surface are selected in the recovery operation of the fuel cell 20. On the other hand, as shown in FIG. 7, in the region A11 where the current density is small, the difference from the normal voltage V _1std is small, and in the region A12 where the current density is medium, the difference from the normal voltage V _2std is large. Resistance polarization is increasing. Therefore, it is determined that there is a problem with the internal impedance of the cell, and the condition for humidifying the polymer membrane is selected in the recovery operation of the fuel cell 20. Further, since the degree of deterioration of the fuel cell 20 is determined based on the time constant difference ΔT ₁ of the component having a quick response, the recovery operation time is determined based on ΔT ₁ .

Based on the time constant difference ΔT ₂ of the slow-response component, when it is determined that the degree of deterioration in which the supply state of hydrogen and oxygen of the fuel cell 20 changes is large, the condition for removing moisture inside the cell, or the inside of the cell The recovery operation of the fuel cell 20 is performed under the condition of melting the frozen water. Which of these conditions is selected is determined based on the temperature of the fuel cell 20 detected by the temperature sensor 21 of the fuel cell 20.

Processing procedure for selecting conditions for the recovery operation of the fuel cell 20 when it is determined in steps S15 and S16 in FIG. 4 that the fuel cell 20 has deteriorated due to changes in the reaction state of the platinum catalyst and the internal impedance of the cell. Is shown in FIG. In step S20, the voltage _{V 1} and current _{I 1} of the fuel cell 20 in the area current density is small, are respectively measured by the voltage sensor 31 and current sensor 32 of the first DC-DC converter 30. Next, in step S21, the difference between the voltage V _1std and the voltage V ₁ when the current I ₁ is output at the normal time is calculated. In step S22, the voltage _{V 2} and current _{I 2} in the region of about current density medium, are respectively measured by the voltage sensor 31 and current sensor 32 of the first DC-DC converter 30. Then, in step S23, the difference between the voltage _{V 2Std} and the voltage _{V 2} when the current _{I 2} is output is calculated at the time of normal.

In step S24, it is determined whether or not the difference between the voltage V _1std and the voltage V ₁ is greater than a predetermined value. If the difference between the voltage V _1std and the voltage V ₁ is greater than the specified value, the process proceeds to step S25. In step S25, a condition for promoting a reduction reaction on the catalyst surface of the cell is selected as a condition for the recovery operation of the fuel cell 20. On the other hand, if the difference between the voltage V _1std and the voltage V ₁ is less than or equal to the specified value, the process proceeds to step S26.

In step S26, it is determined whether or not the difference between the voltage V _2std and the voltage V ₂ is greater than a predetermined value. When the difference between the voltage V _2std and the voltage V ₂ is larger than the specified value, the process proceeds to step S27. In step S27, a condition for humidifying the polymer membrane of the cell is selected as a condition for the recovery operation of the fuel cell 20.

After the conditions for the recovery operation of the fuel cell 20 are selected in step S25 or S27, the process proceeds to step S28. At step S28, the operation time of the recovery operation of the fuel cell 20 is determined based on the difference [Delta] T ₁ time constant of above calculated in step S14 in FIG. 4. The larger the difference ΔT ₁ is, the longer the operation time is set.

When the difference between the voltage V _1std and the voltage V ₁ is equal to or less than the specified value (NO in step S24) and the difference between the voltage V _2std and the voltage V ₂ is equal to or less than the specified value (NO in step S26), the fuel cell 20 is restored. It is determined that no deterioration has occurred. Therefore, the process for determining the recovery operation condition and time is not performed.

FIG. 9 shows a processing procedure for selecting the conditions for the recovery operation of the fuel cell 20 when it is determined in steps S17 and S18 in FIG. 4 that the fuel cell 20 is deteriorated in the supply state of hydrogen and oxygen. . Temperature _{T FC} of the fuel cell 20 is measured by the temperature sensor 21 in step S30, then, in step S31, the temperature _{T FC} is compared with a preset prescribed value. If the temperature T _FC is higher than the specified value, the process proceeds to step S32. In step S32, a condition for removing moisture inside the cell is selected as a condition for the recovery operation of the fuel cell 20. If the temperature T _FC is less than or equal to the specified value, the process proceeds to step S33. In step S33, a condition for melting the frozen water inside the cell is selected as a condition for the recovery operation of the fuel cell 20. If the conditions for the recovery operation of the fuel cell 20 are selected in step S32 or step S33, the process proceeds to step S34. In step S34, the operation time of the recovery operation of the fuel cell 20 is determined based on the difference [Delta] T ₂ time constant of above calculated in step S14 in FIG. 4. The larger the difference ΔT ₂ is, the longer the operation time is set.

  As described above, the recovery operation condition and time of the fuel cell 20 are selected based on the degree of deterioration of the fuel cell 20 and the cause determination result. Thereby, the performance of the fuel cell 20 can be maximized.

[Recovery operation and subsequent processing]
FIG. 10 is a flowchart showing the procedure of the recovery operation of the fuel cell 20 and the subsequent processing. In step S40, the recovery operation of the fuel cell 20 is performed. The recovery operation is executed based on the conditions and time determined by the above-described processing described with reference to the flowchart of FIG. 8 or FIG. Further, when step S40 is first executed, a variable indicating the number of recovery operations is set to “0”. When the recovery operation of the fuel cell 20 is completed, the variable indicating the number of recovery operations is incremented by “1”, and the process proceeds to step S41. In the processing after step S41, it is confirmed whether or not the current output of the fuel cell 20 has been recovered.

In step S41, the voltage V ₃ and the current I ₃ of the fuel cell 20 after the recovery operation are measured by the voltage sensor 31 and the current sensor 32, respectively. Then, in step S42, the voltage _{V 3} is compared with the reference voltage _{V std.} The reference voltage V _std is a voltage value when the current I ₃ is output when the fuel cell 20 is normal. If the difference between the reference voltage V _std a voltage V ₃ after recovery operation is less than a preset specified value, since the fuel cell 20 is judged to have recovered from the temporary deterioration, the processing after the recovery operation execution Not.

Meanwhile, since the difference between the reference voltage V _std a voltage V ₃ after recovery operation is larger than the prescribed value, the fuel cell 20 is determined not to have recovered from degraded, the flow proceeds to step S44. In step S44, the value of the variable indicating the number of recovery operations is checked to determine whether or not the number of recovery operations exceeds a preset specified value. If the number of recovery operations is less than or equal to the specified value, the process returns to step S40, and the recovery operation is executed again.

On the other hand, when the frequency | count of recovery driving | running exceeds the regulation value, it progresses to step S45. The case where the number of recovery operations exceeds the specified value is a state in which an output voltage close to the reference voltage V _std at normal time is not obtained from the fuel cell 20 even though the recovery operation is performed a predetermined number of times. . That is, the deterioration of the fuel cell 20 is not temporary but permanent. In other words, it can be understood that the basic performance itself of the fuel cell 20 is lower than before. Even if the basic performance of the fuel cell 20 is reduced, it is possible to continue using the fuel cell 20 if the degree of the reduction is small. Therefore, first, in step S45, whether the difference between the reference voltage V _std a voltage V ₃ after recovery operation is acceptable level, i.e. either decrease permanent output voltage of the fuel cell 20 is an acceptable level, determined Is done.

Although reduction in permanent output voltage to the fuel cell 20 has occurred, when the difference between the reference voltage V _std a voltage V ₃ after recovery operation is less than the allowable level, the process proceeds to step S46. Even if permanent deterioration occurs, if the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is smaller than the allowable level, the deterioration of the basic performance of the fuel cell 20 is not fatal. It is possible to continue using it. If the use of the fuel cell 20 is to be continued, the occurrence of temporary deterioration during use must be detected and an appropriate recovery operation must be performed. Therefore, in steps S46 to S50, processing for replacing the values of the time constant T _1std of the fast response component and the time constant T _2std of the slow response component in accordance with the current performance of the fuel cell 20 is performed.

_Calculation of new values of the time constants T _1std and T _2std is performed in the same manner as the processing of steps S10 to S13 in the deterioration detection processing of the fuel cell in FIG. In step S46, the first DC-DC converter 30 is subjected to switching control, and the target value of the output current of the fuel cell 20 is further changed stepwise from the target value determined in step S10, and the data processing device is set as a new target value. 10 is input. The data processing device 10 outputs a control signal to the fuel cell 20 so that the output current of the fuel cell 20 follows the new target value. In step S47, the transient response of the output voltage of the fuel cell 20 controlled so that the output current becomes a new target value is measured by the voltage sensor 31 of the first DC-DC converter 30, and the data processor 10 is time-series. Is recorded as a data array. Next, in step S48, the transient response waveform is approximated by the sum of the step responses of the first-order lag transfer function shown in the above equation (1), and in step S49, the time constant T _{1 of the} component V _{1 having} a fast response is obtained. The time constant of the time constant T ₂ of the component V _{2 having} a slow response is calculated. In step S50, the normal time constant T _1std is replaced with the time constant T ₁ of the fast response component V ₁ calculated in step S49, and the normal time constant T _2std is calculated in step S49. Is replaced by the time constant T ₂ of the slow component V ₂ . Thereafter, the condition selection for the recovery operation of the fuel cell 20 described with reference to FIGS. 8 and 9 is performed based on the replaced time constants T _1std and T _2std .

On the other hand, in step S45, when the difference between the reference voltage V _std a voltage V ₃ after recovery operation is the allowable level or higher, decrease in the permanent output voltage of the fuel cell 20 where it is determined at a level unacceptable, It is determined that the deterioration of the basic performance of the fuel cell 20 is fatal. In this case, the process proceeds to step S51, and the driver is notified that the fuel cell 20 is at the end of its life in order to prompt the replacement of the fuel cell 20.

  As described above, according to the embodiment of the present invention, the current value obtained by stepping up the output current value of the fuel cell 20 by a predetermined amount is determined as the target value, and the output current is driven so as to follow this target value. In this case, the transient response of the output voltage of the fuel cell 20 is decomposed into a component having a relatively fast response and a component having a slow response. And based on each component, generation | occurrence | production of the deterioration of the fuel cell 20 and its degree are determined. Therefore, the type of cause of deterioration can also be determined depending on from which component the occurrence of deterioration is detected. As a result, the recovery operation can be executed under appropriate conditions according to the cause of deterioration, in other words, to remove the cause of deterioration.

  Further, when the deterioration of the fuel cell 20 is detected based on a component having a fast response, the voltage value and the current value of the fuel cell 20 are measured in the low current density region and the medium current region, respectively. It is compared with the voltage value when the same current value is set during normal operation. Therefore, when the deterioration of the fuel cell 20 is detected based on the component having a quick response, the cause of the deterioration can be determined in more detail. Then, based on the difference between the voltage values, it can be determined whether the condition for the recovery operation is a condition for promoting the reduction reaction on the catalyst surface of the cell or a condition for humidifying the polymer film of the cell. Therefore, when the deterioration of the fuel cell 20 is detected based on a component having a quick response, the recovery operation can be executed under more appropriate conditions, and the fuel cell 20 can be recovered more reliably.

  When the deterioration of the fuel cell 20 is detected based on a slow response component, the temperature sensor 21 measures the temperature of the fuel cell 20. Based on the measurement result of the temperature sensor 21, the cause of deterioration of the fuel cell 20 detected based on the slow-response component can be determined in more detail. Then, based on the measurement result of the temperature sensor 21, it can be determined whether the condition for the recovery operation is a condition for removing the moisture inside the cell of the fuel cell 20 or a condition for melting the frozen moisture inside the cell. . Therefore, when the deterioration of the fuel cell 20 is detected based on the slow-response component, the recovery operation can be executed under more appropriate conditions, and the fuel cell 20 can be recovered more reliably.

[Modification]
In the present embodiment, in order to determine the degree of deterioration of the fuel cell 20 and the cause thereof, the transient response of the output voltage of the fuel cell 20 is measured and decomposed into a fast response component and a slow response component, and the respective time constants are determined. Although it is calculated, it is not limited to this. Here, a modification in which the time constant of the fast response component and the time constant of the slow component are calculated by the switching control of the first DC-DC converter 30 will be described.

In the modified example, calculation of the time constant of the component with quick response is performed in the following procedure. First, all the switches SW1 to SW4 of the first DC-DC converter 30 are turned off (initial state). Next, the switches SW1 and SW3 are turned on, the switches SW2 and SW4 are turned off, and the process waits until the output voltage of the fuel cell 20 drops to a predetermined value V _lower (first step-down operation). If the voltage sensor 31 confirms that the output voltage has reached the predetermined value V _lower , then the switches SW1 and SW3 are turned OFF, the switches SW2 and SW4 are turned ON, and the output voltage of the fuel cell 20 is set to the predetermined value V Wait until it rises to _upper (step-up operation). When it is confirmed by the voltage sensor 31 that the output voltage has increased to V _upper , SW1 and SW3 are turned on again, SW2 and SW4 are turned off, and the process waits until the output voltage falls to the value V _lower (second step-down). Operation). When the voltage sensor 31 confirms that the output voltage has reached the value V _lower , SW1 to SW4 are turned off.

The output voltage of the fuel cell 20 is measured by the voltage sensor 31 from the initial state until all the switches SW1 to SW4 are turned off again, and the measurement result is recorded in the data processing device 10. This measurement result is recorded as a time-series data array. FIG. 11 shows an example of the measurement result obtained by the voltage sensor 31. The first step-down operation is started at t11, the output voltage reaches V _lower at t12, the step-up operation is started, the output voltage reaches V _upper at t13, the second step-down operation is started, and output at t14. The voltage has reached V _lower . In the data processing apparatus 10, and time _{T 1a} to t12 to t13, the time _{T 1b} until t13~t14 is calculated. Then, based on the time T _1a and the time T _1b , the time constant T ₁ of the component V _{1 having} a quick response in the transient response is calculated. The calculation of the time constant T ₁ is performed by, for example, a method of defining a correlation between the average value of the time T _1a and the time T _1b and the actual time constant using a map or a function.

When definite constants T ₁ time steps fast component V ₁ response in the above, similar to the step S14 and subsequent steps in FIG. 4, the difference [Delta] T ₁ and the time constant T ₁ and the time constant in a normal state of the rapid component of the response Is calculated, and it is determined whether or not the difference ΔT ₁ is equal to or greater than a specified value. If the difference ΔT ₁ is equal to or greater than the specified value, it is determined that the reaction state of the platinum catalyst and the internal impedance of the cell have changed.

  Calculation of the time constant of the slow response component is performed in the following procedure. Each switch of the first DC-DC converter 30 is set to an initial state. The initial state of the step-down operation of the first DC-DC converter 30 is that the switch SW1 is ON, the switch SW2 is OFF, the switches SW3 and SW4 are specified duty ratios (a period during which the switch SW3 is ON and the switch SW4 is OFF) , The ratio of the period during which the switch SW3 is OFF and the switch SW4 is ON). The initial state of the step-up operation of the first DC-DC converter 30 is that the switch SW4 is ON, the switch SW3 is OFF, the switches SW1 and SW2 are specified duty ratios (a period during which the switch SW1 is ON and the switch SW2 is OFF) , The ratio of the period during which the switch SW1 is OFF and the switch SW2 is ON). In this modification, by controlling the step-down operation, that is, by controlling the duty ratio of the switches SW3 and SW4, the time constant of the component with a slow response is calculated.

First, the duty ratio of the switches SW3 and SW4 is set to the initial state of the step-down operation, that is, higher than the specified value, and the step-down operation is performed until the output voltage of the fuel cell 20 falls to a predetermined value V _lower (first step-down operation). I do. After that the output voltage of the first DC-DC converter 30 has reached a predetermined value _{V lower} confirmed by the voltage sensor 31, and returns the duty ratio of the switch SW3 and SW4 in the specified value. As a result, the output voltage rises from V _lower (step-up operation). When the voltage sensor 31 confirms that the output voltage has reached the predetermined value V _upper , the duty ratio of the switches SW3 and SW4 is set higher than the specified value again, and the voltage is stepped down until the output voltage falls to the predetermined value V _lower. The operation (second step-down operation) is performed. When the voltage sensor 31 confirms that the output voltage has reached the predetermined value V _upper , the duty ratio of the switches SW3 and SW4 is returned to the specified value. From the start of the first step-down operation to the end of the second step-down operation, the output voltage of the fuel cell 20 is measured by the voltage sensor 31 of the first DC-DC converter 30. This measurement result is recorded as a time-series data array. FIG. 12 shows an example of a measurement result obtained by the voltage sensor 31.

The first step-down operation is started at t21, the output voltage reaches V _lower at t22, the step-up operation is started, the output voltage reaches V _upper at t23, the second step-down operation is started, and the output is performed at t24. The voltage has reached V _lower . In the data processing apparatus 10, and time _{T 2a} to T22～t23, the time _{T 2b} until t23~t24 is calculated. Then, based on the time T _2a and the time T _2b , the time constant T ₂ of the slow response component V ₂ of the transient response is calculated. The time constant T ₂ is calculated by, for example, a method of defining a correlation between an average value of the time T _2a and the time T _2b and an actual time constant using a map or a function.

  In this modification, the step-up / step-down voltage of the output voltage of the fuel cell 20 is controlled by controlling the duty ratio of the switches SW3 and SW4, but the present invention is not limited to this. The step-up / step-down voltage of the output voltage of the fuel cell 20 may be controlled by turning on the switch SW4, turning off the switch SW3, and controlling the duty ratio of the switches SW1 and SW2.

  While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 10 Data processor 20 Fuel cell 21 Temperature sensor 30 1st DC-DC converter 31 Voltage sensor 32 Current sensor 40 Inverter 50 Motor 60 2nd DC-DC converter 70 Battery

Claims (5)

An apparatus for detecting deterioration of a fuel cell mounted on a vehicle,
Target value setting means for setting the current output current value of the fuel cell to a target value increased stepwise by a predetermined amount;
Transient response measuring means for controlling the output current of the fuel cell so that the output current value of the fuel cell follows the target value, and measuring the transient response of the output voltage of the fuel cell at that time;
Transient response decomposition means for decomposing a transient response of the output voltage of the fuel cell into a first component having a relatively fast response and a second component having a relatively slow response;
Time constant calculating means for calculating a first time constant of the first component and a second time constant of the second component;
Calculating a first difference that is a difference between a first reference time constant that is a time constant of the first component when the fuel cell is normal and the first time constant; Difference calculating means for calculating a second difference that is a difference between a second reference time constant that is a time constant of the second component and the second time constant;
If the first difference exceeds the first component specified value, it is determined that the deterioration of the reaction state of the catalyst of the fuel cell and the impedance inside the cell has occurred, and the degree of the deterioration is determined. If the second difference exceeds the second component specified value, it is determined that deterioration in which the supply state of hydrogen and oxygen in the fuel cell has changed and the degree of deterioration is determined. A vehicle fuel cell degradation detection device comprising degradation determination means. When the degree of deterioration determined based on the first difference exceeds a predetermined range,
Measuring a first current value and a first voltage value in a first region having a relatively low current density in the fuel cell;
Measuring a second current value and a second voltage value in a second region having a current density greater than the first region in the fuel cell;
When the difference between the voltage value when the fuel cell is driven with the first current value and the first voltage value exceeds the first current regulation value, the catalyst surface of the cell of the fuel cell Performing an operation for recovering the deterioration of the fuel cell under conditions that promote the reduction reaction of
The difference between the voltage value and the first voltage value when driven with the first current value when the fuel cell is normal does not exceed the first current regulation value, and when the fuel cell is normal When the difference between the voltage value when driven at the second current value and the second voltage value exceeds the second specified current value, the condition is such that the polymer membrane of the fuel cell is humidified. The vehicle fuel cell deterioration detection device according to claim 1, wherein an operation for recovering the deterioration of the fuel cell is performed. When the degree of deterioration determined based on the second difference exceeds a predetermined range,
When the temperature of the fuel cell is higher than a temperature regulation value, an operation for recovering the deterioration of the fuel cell under the condition of removing moisture inside the cell of the fuel cell,
2. The vehicle according to claim 1, wherein when the temperature of the fuel cell is lower than the temperature regulation value, an operation for recovering the deterioration of the fuel cell is performed under a condition of melting frozen water inside the cell of the fuel cell. Fuel cell deterioration detection device. When the deterioration detection means determines the deterioration of the fuel cell based on the first difference, the fuel cell recovery operation time for recovering the deterioration is determined based on the first difference,
When the deterioration of the fuel cell is detected based on the second difference by the deterioration detecting means, a recovery operation time of the fuel cell for recovering the deterioration is determined based on the second difference. Item 2. The fuel cell deterioration detection device according to Item 1. In the case where the deterioration of the fuel cell does not recover despite the execution of the recovery operation for recovering the deterioration determined by the deterioration determination means, the recovery operation after the recovery operation with respect to the output voltage value of the fuel cell at normal time If the drop in the output voltage value of the fuel cell is smaller than the predetermined allowable level,
Set a new target value of the output current value of the fuel cell,
Measure the transient response of the output voltage of the fuel cell when the fuel cell is controlled so that the output current value follows the new target value,
Decomposing the transient response of the output voltage of the fuel cell into the first component and the second component;
Calculating a third time constant of the first component and a fourth time constant of the second component;
The vehicle fuel cell deterioration detection device according to claim 1, wherein the first reference time constant is replaced with the third time constant, and the second reference time constant is replaced with the fourth time constant.

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