JP2015095305A - Fuel cell system and device for detecting progress of deterioration of fuel cell, method for detecting progress of deterioration of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for appropriately grasping the arrival time of performance degradation of a fuel cell associated with the operation history.SOLUTION: A control unit 20 of a fuel cell system 100 acquires the water balance information including the water increase amount WI, i.e., the moisture increment in a fuel cell 10, and the water decrease amount WD, i.e., the moisture decrement in the fuel cell 10 (step S30). The control unit 20 sequentially acquires the index value of dry ID, indicating the degree of drying trend in the fuel cell 10 while driving, based on the ratio of the water increase amount WI and water decrease amount WD, and acquires a drying history frequency D by integrating the product of the index value of dry ID by the measurement period (step S35). The control unit 20 detects arrival of an occurrence period of rapid performance degradation of the fuel cell, based on the drying history frequency D (step S40), and performs recovery operation arbitrarily (step S60).

Description

  The present invention relates to a fuel cell.

  Conventionally, various techniques for suppressing deterioration of a polymer electrolyte fuel cell (hereinafter also simply referred to as “fuel cell”) in a fuel cell system have been proposed. Patent Documents 1 and 2 disclose techniques for suppressing deterioration of a fuel cell caused by detection of a resistance value of an electrolyte membrane of the fuel cell. Patent Document 3 discloses a technique for suppressing deterioration of an electrolyte membrane due to hydroxy radicals.

JP2013-038086A JP 2009-048816 A JP 2012-040882 A

  Since the fuel cell has a polymer material such as an electrolyte membrane therein, when the operation in which the inside of the fuel cell is in a high temperature state (for example, 80 to 90 ° C.) or the operation in which it is in a dry state is repeated, There is a high possibility that deterioration due to operation is accumulated to cause performance degradation. In order to improve the reliability of the fuel cell system, it is desirable to be able to appropriately grasp the arrival time of the performance degradation of the fuel cell.

  As described above, Patent Documents 1 and 2 have a problem of suppressing deterioration of the fuel cell due to detection of the resistance value of the electrolyte film, and Patent Document 3 has a problem of suppressing deterioration of the electrolyte film due to hydroxy radicals. In any of Patent Documents 1-3, the purpose is to prevent the occurrence of a specific deterioration in advance, and it is particularly considered to appropriately grasp the time when the performance deterioration of the fuel cell accompanying the operation history comes. It has not been.

  As described above, in the fuel cell system, there is room for improvement in properly grasping the time when the performance degradation of the fuel cell accompanying the operation history comes. In addition, in the fuel cell system, improvement of system reliability and availability, simplification and miniaturization of maintenance means, improvement of mountability, cost reduction, resource saving, and improvement of convenience for users are desired. It was.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

[1] According to one aspect of the present invention, a fuel cell system is provided. The fuel cell system according to this aspect may include a fuel cell, a water balance information acquisition unit, an index value acquisition unit, and a deterioration reflected value acquisition unit. The water balance information acquisition unit may have a function of sequentially acquiring a drying index value indicating a degree of drying tendency inside the fuel cell during operation based on the water balance information. The index value acquisition unit reflects the degree of progress of deterioration of the fuel cell based on the drying index value and the time interval at which the drying index value is acquired when the drying index value is acquired. It is possible to have a function of accumulating and acquiring the deterioration reflection values that have been set. According to the fuel cell system of this embodiment, since the deterioration reflection value reflecting the operation history in which the inside of the fuel cell tends to dry has been acquired, the timing of the fuel cell performance deterioration due to such operation history is appropriately set. Can grasp.

[2] In the fuel cell system of the above aspect, the water balance information includes an increased amount of water that is an increased amount of water per unit time in the fuel cell and a decreased amount of water per unit time in the fuel cell. The index value acquisition unit may acquire the dry index value based on a ratio between a value representing the increased moisture content and a value representing the decreased moisture content. good. According to the fuel cell system of this embodiment, the degree of the drying tendency inside the fuel cell can be appropriately detected based on the water amount increase / decrease ratio in the operating fuel cell. Therefore, it is possible to appropriately grasp the time when the performance of the fuel cell is lowered due to the operation history in which the inside of the fuel cell tends to dry.

[3] In the fuel cell system of the above aspect, the deterioration reflected value acquisition unit starts from the time when the previous value of the dry index value is acquired every time the dry index value is acquired by the index value acquisition unit. The deterioration reflected value may be acquired by integrating the value obtained by multiplying the current value by the time until the time when the current value of the dry index value is acquired. In the fuel cell system of this embodiment, since the fluctuation history of the drying index value is reflected in detail in the deterioration reflection value, the time when the performance of the fuel cell is lowered due to the operation history in which the inside of the fuel cell tends to dry. It can be grasped more appropriately.

[4] The fuel cell system according to the above aspect includes a power generation amount detection unit that acquires a value representing the power generation amount of the fuel cell, and an exhaust gas information acquisition unit that acquires a flow rate of exhaust gas discharged from the fuel cell. May be. The water balance information acquisition unit acquires an increase in moisture in the fuel cell based on at least the amount of power generated by the fuel cell to acquire the water balance information, and reduces the moisture in the fuel cell. May be acquired based on at least the flow rate of the exhaust gas. According to the fuel cell system of this embodiment, it is possible to easily acquire the increase / decrease in the amount of water in the fuel cell during operation.

[5] The fuel cell system according to the above aspect may further include a deterioration timing detection unit that detects in advance the arrival of the time when the fuel cell reaches a predetermined degree of deterioration based on the deterioration reflection value. . According to the fuel cell system of this embodiment, since the occurrence time of the performance degradation of the fuel cell is detected in advance, the reliability of the system is improved.

[6] In the fuel cell system according to the above aspect, when the deterioration timing detector detects the arrival of the time when the fuel cell reaches a predetermined degree of deterioration, the recovery operation is performed to recover the deterioration of the fuel cell. An operation control unit that performs operation control for increasing the amount of water generated in the fuel cell may be provided. According to the fuel cell system of this embodiment, the performance deterioration of the fuel cell is prevented in advance.

[7] According to another aspect of the present invention, a fuel cell vehicle is provided. The fuel cell vehicle of this form may be mounted with the fuel cell system of the above form. According to the fuel cell vehicle of this aspect, it is possible to appropriately grasp the degree of progress of deterioration of the fuel cell due to the driving history in which the inside of the fuel cell tends to dry.

  The present invention can be realized in various forms other than the fuel cell system and the fuel cell vehicle. For example, an apparatus and method for detecting in advance the degree of progress of deterioration of a fuel cell, a fuel cell system and a fuel cell vehicle, a control method for the apparatus, a computer program for realizing the control method, and a temporary recording of the computer program It can be realized in the form of a non-recording medium or the like.

Schematic which shows the structure of a fuel cell system. Schematic which shows the principal part of the electrical structure of a fuel cell system. Explanatory drawing which shows the procedure of the operation control of the fuel cell system by a control part. Explanatory drawing for demonstrating the electric power generation control of the fuel cell by an operation control part. Explanatory drawing for demonstrating the relationship between moisture increase / decrease ratio (alpha) and deterioration of a fuel cell. Explanatory drawing which shows the graph obtained when making the fuel cell generate electric power by the 1st operation pattern. Explanatory drawing which shows the graph obtained when the fuel cell was made to generate electric power by the 2nd driving | running pattern. Explanatory drawing which shows the graph of the output change of the fuel cell obtained by the 1st and 2nd driving | operation pattern. Explanatory drawing which shows the performance recovery | restoration of the fuel cell in which the performance fell by catalyst poisoning. Explanatory drawing which shows the change of the resistance value of the fuel cell with respect to the performance fall of the fuel cell by dry operation.

A. First embodiment:
[Configuration of fuel cell system]
FIG. 1 is a schematic diagram showing a configuration of a fuel cell system 100 as a first embodiment of the present invention. The fuel cell system 100 is mounted on a fuel cell vehicle that is a moving body, and outputs electric power according to a load request from the fuel cell vehicle based on an operation of a driver (user) of the fuel cell vehicle. The fuel cell system 100 includes a fuel cell 10, a control unit 20, a cathode gas supply unit 30, a cathode gas discharge unit 40, an anode gas supply unit 50, an anode gas circulation discharge unit 60, and a refrigerant supply unit 70. .

  The fuel cell 10 is a polymer electrolyte fuel cell that generates power by receiving supply of hydrogen (fuel gas) and oxygen (oxidant gas) as reaction gases. The fuel cell 10 has a stack structure in which a plurality of power generators 11 called single cells are stacked. Each power generation body 11 has a membrane electrode assembly (not shown) which is a power generation body in which electrodes are arranged on both surfaces of an electrolyte membrane. The electrolyte membrane is composed of a solid polymer thin film that exhibits good proton conductivity in a wet state. The electrode is composed of conductive particles (for example, platinum-supported carbon) on which a catalyst for promoting a power generation reaction is supported, and an ionomer that is the same or similar to the electrolyte membrane.

  The control unit 20 is configured by a microcomputer including a central processing unit and a main storage device. In the control unit 20, various function units for controlling the fuel cell system 100 are realized by the central processing unit reading various programs into the main storage device and executing them (details will be described later). In addition, the control unit 20 executes a process of detecting in advance the arrival time of the performance degradation of the fuel cell 10 based on the amount of increase or decrease of the moisture in the fuel cell 10 (details will be described later).

  The cathode gas supply unit 30 supplies compressed air as a cathode gas to the cathode of the fuel cell 10. The cathode gas supply unit 30 includes a cathode gas pipe 31, an air compressor 32, an on-off valve 33, an air flow meter 34, and a pressure measurement unit 35. The cathode gas pipe 31 is a pipe connected to the inlet of the cathode side supply manifold (not shown) of the fuel cell 10.

  The air compressor 32 is connected to the fuel cell 10 via the cathode gas pipe 31, and supplies air compressed by taking in outside air to the fuel cell 10 as cathode gas. The on-off valve 34 is provided between the air compressor 32 and the fuel cell 10. The on-off valve 34 opens and closes according to the flow of supply air in the cathode gas pipe 31. Specifically, the on-off valve 34 is normally closed and opens when air having a predetermined pressure is supplied from the air compressor 32 to the cathode gas pipe 31.

  The air flow meter 34 measures the amount of outside air taken in by the air compressor 32 and transmits it to the control unit 20 on the upstream side of the air compressor 32. The pressure measurement unit 35 measures the pressure of air in the vicinity of the inlet of the cathode side supply manifold of the fuel cell 10 and outputs the measured pressure to the control unit 20. The control unit 20 controls the rotational speed of the air compressor 32 based on the output signals of the air flow meter 34 and the pressure measurement unit 35, and controls the amount of air supplied to the fuel cell 10.

  The cathode gas discharge unit 40 processes the cathode exhaust gas discharged from the cathode of the fuel cell 10. A cathode exhaust gas pipe 41, a pressure regulating valve 43, and an exhaust gas information acquisition unit 44 are provided. The cathode exhaust gas pipe 41 is a pipe connected to the outlet of the cathode side discharge manifold (not shown) of the fuel cell 10 and guides the cathode exhaust gas to the outside of the fuel cell system 100.

  The pressure of the cathode exhaust gas in the cathode exhaust gas pipe 41 (the back pressure on the cathode side of the fuel cell 10) is adjusted by the pressure regulating valve 43. The opening degree of the pressure regulating valve 43 is adjusted by the control unit 20. The exhaust gas information acquisition unit 44 is provided on the upstream side of the pressure regulating valve 43, and acquires exhaust gas information that is information relating to the state of the cathode exhaust gas. Specifically, in the present embodiment, the exhaust gas information acquisition unit 44 acquires the pressure, flow rate, and temperature of the cathode exhaust gas as exhaust gas information.

  The exhaust gas information acquisition unit 44 transmits the acquired exhaust gas information to the control unit 20. The control unit 20 adjusts the opening of the pressure regulating valve 43 based on the pressure of the cathode exhaust gas in the exhaust gas information. In addition, the control unit 20 uses the flow rate and temperature of the cathode exhaust gas included in the exhaust gas information to detect the amount of water decrease per unit time in the fuel cell 10 (details will be described later).

  The anode gas supply unit 50 supplies hydrogen as an anode gas to the anode of the fuel cell 10. The anode gas supply unit 50 includes an anode gas pipe 51, a hydrogen tank 52, an on-off valve 53, a regulator 54, a hydrogen supply device 55, and a pressure measurement unit 56. The hydrogen tank 52 is connected to the inlet of an anode side supply manifold (not shown) of the fuel cell 10 via the anode gas pipe 51, and supplies hydrogen filled in the tank to the fuel cell 10.

  The on-off valve 53, the regulator 54, the hydrogen supply device 55, and the pressure measuring unit 56 are provided in the anode gas pipe 51 in this order from the upstream side (hydrogen tank 52 side). The on-off valve 53 opens and closes according to a command from the control unit 20 and controls the inflow of hydrogen from the hydrogen tank 52 to the upstream side of the hydrogen supply device 55. The regulator 54 is a pressure reducing valve for adjusting the pressure of hydrogen on the upstream side of the hydrogen supply device 55. The opening degree of the regulator 54 is controlled by the control unit 20.

  The hydrogen supply device 55 is an electromagnetically driven on / off valve that adjusts the flow rate of hydrogen. The hydrogen supply device 55 is constituted by, for example, an injector. The control unit 20 controls the amount of hydrogen supplied to the fuel cell 10 by controlling the driving cycle of the hydrogen supply device 55. The pressure measurement unit 56 measures the pressure of hydrogen on the downstream side of the hydrogen supply device 55 and transmits it to the control unit 20.

  The anode gas circulation discharge unit 60 circulates and discharges the unreacted gas (hydrogen, nitrogen, etc.) discharged from the anode of the fuel cell 10 without being used for the power generation reaction and the anode exhaust gas including waste water. The anode gas circulation discharge unit 60 includes an anode exhaust gas pipe 61, a gas-liquid separation unit 62, an anode gas circulation pipe 63, a hydrogen circulation pump 64, an anode drain pipe 65, a drain valve 66, and a pressure measurement unit 67. And comprising.

  The anode exhaust gas pipe 61 is a pipe that connects the gas-liquid separator 62 and the outlet of the anode discharge manifold (not shown) of the fuel cell 10. The gas-liquid separator 62 is connected to the anode gas circulation pipe 63 and the anode drain pipe 65. The gas-liquid separator 62 separates the gas component and moisture contained in the anode exhaust gas, guides the gas component to the anode gas circulation pipe 63, and guides the moisture to the anode drain pipe 65.

  The anode gas circulation pipe 63 is connected downstream of the hydrogen supply device 55 of the anode gas pipe 51. The anode gas circulation pipe 63 is provided with a hydrogen circulation pump 64. Hydrogen contained in the gas component separated in the gas-liquid separation unit 62 is sent out to the anode gas pipe 51 by the hydrogen circulation pump 64.

  The anode drain pipe 65 is a pipe for discharging the water separated in the gas-liquid separator 62 to the outside of the fuel cell system 100. The anode drain pipe 65 is provided with a drain valve 66. The control unit 20 normally closes the drain valve 66 and opens the drain valve 66 at a predetermined drain timing set in advance or at a discharge timing of the inert gas in the anode exhaust gas.

  The pressure measuring unit 67 of the anode gas circulation discharge unit 60 is provided in the anode exhaust gas pipe 61. The pressure measuring unit 67 measures the pressure of the anode exhaust gas (the back pressure on the anode side of the fuel cell 10) in the vicinity of the outlet of the hydrogen manifold of the fuel cell 10 and transmits it to the control unit 20. The control unit 20 controls the supply of hydrogen to the fuel cell 10 based on the measurement value of the pressure measurement unit 56 of the anode gas circulation discharge unit 60 and the measurement value of the pressure measurement unit 56 of the anode gas supply unit 50 described above.

  The refrigerant supply unit 70 includes an upstream pipe 71a, a downstream pipe 71b, a radiator 72, a refrigerant circulation pump 75, and first and second refrigerant temperature measuring units 76a and 76b. The upstream pipe 71 a and the downstream pipe 71 b are refrigerant pipes that circulate a refrigerant for cooling the fuel cell 10.

  The upstream side pipe 71 a connects the inlet of the radiator 72 and the outlet of the refrigerant discharge manifold (not shown) of the fuel cell 10. The downstream pipe 71 b connects the outlet of the radiator 72 and the inlet of the refrigerant supply manifold (not shown) of the fuel cell 10. The radiator 72 cools the refrigerant by exchanging heat between the refrigerant flowing through the refrigerant pipe 71 and the outside air. The refrigerant circulation pump 75 is provided in the middle of the downstream pipe 71 b, and sends the refrigerant cooled in the radiator 72 to the fuel cell 10.

  The first and second refrigerant temperature measuring units 76 a and 76 b are provided in the upstream pipe 71 a and the downstream pipe 71 b, respectively, and transmit the measured values to the control unit 20. The control unit 20 detects the operating temperature of the fuel cell 10 from the difference between the measured values of the refrigerant temperature measuring units 76a and 76b. The control unit 20 adjusts the operating temperature of the fuel cell 10 by controlling the rotational speed of the refrigerant circulation pump 75 based on the detected operating temperature of the fuel cell 10.

  FIG. 2 is a schematic diagram showing the main part of the electrical configuration of the fuel cell system 100. The electric system of the fuel cell system 100 includes a fuel cell converter 81, a secondary battery 82, a secondary battery converter 83, and a DC / AC inverter 84. The fuel cell converter 81 is a step-up converter, and has an input side connected to the fuel cell 10 and an output side connected to a DC terminal of the DC / AC inverter 84. The fuel cell converter 81 boosts and outputs the output voltage of the fuel cell 10 in accordance with a command from the control unit 20.

  The secondary battery 82 is constituted by, for example, a lithium ion battery. The secondary battery 82 functions as a power storage unit that stores part of the output power of the fuel cell 10 and regenerative power, and also functions as a power supply unit that outputs power to the fuel cell vehicle together with the fuel cell 10. The secondary battery 82 is connected to the DC wiring between the fuel cell converter 81 and the DC / AC inverter 84 via the secondary battery converter 83. Secondary battery converter 83 controls charging / discharging of secondary battery 82 in accordance with a command from control unit 20. Further, the secondary battery converter 83 cooperates with the fuel cell converter 81 to variably adjust the input voltage to the DC / AC inverter 84.

  The DC / AC inverter 84 converts the DC power supplied from the fuel cell 10 and the secondary battery 82 into three-phase AC power in response to a command from the control unit 20, and the DC / AC inverter 84 is connected to the AC terminal of the DC / AC inverter 84. Output to the connected motor 200. The motor 200 is a three-phase AC motor and is a power source that drives the wheels of the fuel cell vehicle. Note that regenerative power may be generated in the motor 200 during operation of the fuel cell vehicle. This regenerative power is converted to DC power by the DC / AC inverter 84 and output to the secondary battery 82 for storage.

  The fuel cell system 100 includes a cell voltage measurement unit 91 and a current measurement unit 92 in addition to the above-described configuration. The cell voltage measurement unit 91 is connected to each power generator 11 of the fuel cell 10 and measures the voltage (cell voltage) of each power generator 11. The cell voltage measurement unit 91 transmits the measurement result to the control unit 20. The current measuring unit 92 is connected between the fuel cell 10 and the fuel cell converter 81, measures a current value output from the fuel cell 10, and transmits the current value to the control unit 20. The control unit 20 calculates the amount of increased water inside the fuel cell 10 using the measurement result of the current measurement unit 92 (details will be described later).

  Here, in the fuel cell system 100 of the present embodiment, the control unit 20 reads and executes various programs by the central processing unit, thereby causing the operation control unit 21, the drying history frequency acquisition unit 22, and the deterioration time. It functions as the detection unit 23. The operation control unit 21 controls power generation of the fuel cell 10 by controlling each component described with reference to FIGS. 1 and 2. In addition, the drying history frequency acquisition unit 22 and the deterioration timing detection unit 23 execute processing for detecting in advance the arrival of the performance deterioration of the fuel cell 10. Specifically, it is as follows.

[Operation control in fuel cell system]
FIG. 3 is a flowchart showing a procedure of operation control of the fuel cell system 100 by the control unit 20. This operation control is started with the start of operation of the fuel cell vehicle. In step S <b> 10, the drying history frequency acquisition unit 22 reads the drying history frequency D, which is a variable value stored in a nonvolatile manner at the end of the previous operation of the fuel cell system 100. The drying history frequency D will be described later.

  Steps S20 to S40 after step S10 are repeated at a predetermined control cycle until the operation of the fuel cell system 100 is completed (step S50). In step S <b> 20, the operation control unit 21 receives an output request from the fuel cell vehicle for the fuel cell system 100. In step S25, the operation control unit 21 controls the power generation of the fuel cell 10 based on the output request as follows.

FIG. 4 is an explanatory diagram for explaining the power generation control of the fuel cell 10 by the operation control unit 22. FIG. 4 shows a graph GIP showing the current-voltage characteristics ( _IP characteristics) of the fuel cell 10 and a graph GIV showing the current-voltage characteristics ( _IV characteristics), with the left and right vertical axes respectively. Voltage and power are shown, and the horizontal axis is shown as current.

The operation control unit 21 stores in advance information for each operating temperature of the fuel cell 10 representing the IP characteristic and the IV characteristic for the fuel cell 10 as control information, and based on the control information, The command value of the current / voltage of the battery 10 is acquired. The operation control unit 21 determines the target power Pt to be output by the fuel cell 10 based on the output request received in step S20. Then, based on the _IP characteristic (graph G _IP ) of the fuel cell 10, a target value (target current It) of the current that the fuel cell 10 should output with respect to the target power Pt is acquired.

The operation control unit 21 acquires a target value (target voltage Vt) of the cell voltage of the fuel cell 10 necessary for outputting the target current It based on the _IV characteristic (graph G _IV ) of the fuel cell 10. . The normal operation control unit 22 controls the fuel cell converter 81 and the secondary battery converter 83 to output the target voltage Vt to the fuel cell 10 and output the insufficient power to the secondary battery 82.

  In step S30 (FIG. 3), the drying history frequency acquisition unit 22 increases the amount of moisture in the fuel cell 10 during the period from the execution of step S30 in the previous control cycle to the execution of step S30 in the current control cycle. Get the reduction amount. Hereinafter, the period is referred to as a “measurement period”. Further, the amount of increase in water inside the fuel cell 10 during the measurement period is referred to as “increase water amount WI”, and the decrease amount is referred to as “decrease water amount WD”. The increased water amount WI corresponds to an increased amount of moisture per unit time inside the fuel cell 10. The reduced water amount WD corresponds to the reduced amount of water per unit time inside the fuel cell 10.

  The drying history frequency acquisition unit 22 increases the amount of generated water generated on the cathode side of the fuel cell 10 by the power generation reaction during the measurement period based on the output current of the fuel cell 10 measured by the current measurement unit 92. Obtain as WI. Further, the drying history frequency acquisition unit 22 acquires the reduced water amount WD based on the exhaust gas information acquired by the exhaust gas information acquisition unit 44 during the measurement period as follows.

  The drying history frequency acquisition unit 22 obtains the amount of cathode exhaust gas discharged from the fuel cell 10 during the measurement period from the flow rate of cathode exhaust gas. The drying history frequency acquisition unit 22 reduces the amount of water vapor contained in the cathode exhaust gas based on the temperature of the cathode exhaust gas and the saturated water vapor pressure, assuming that the cathode exhaust gas contains moisture of the saturated water vapor amount. Obtain as WD.

  In step S35, the drying history frequency acquisition unit 22 updates the drying history frequency D. The drying history frequency D is a deterioration reflection value that reflects the degree of progress of deterioration in the fuel cell 10, and, as will be described below, a drying index value ID and a time interval at which the drying index value ID is acquired. It is a value acquired by integration based on it.

The drying index value ID is sequentially acquired based on the water increase / decrease ratio α obtained as the ratio of the increased water amount WI and the decreased water amount WD (the following equation (1)).
Moisture increase / decrease ratio α = increasing water amount WI / decreasing water amount WD
Drying index value ID = 1−α (when 0 ≦ α <1) (1)
Drying index value ID = 0 (when α ≧ 1)

  The drying index value ID is closer to 1 as the decrease water amount WD is larger than the increase water amount WI, that is, as the water content in the fuel cell 10 tends to decrease and the drying tendency is stronger (0 ≦ α <1). ). On the other hand, it becomes 0 (α ≧ 1) when the moisture content in the fuel cell 10 tends to increase and the wetting tendency is strong. Thus, the drying index value ID corresponds to a drying index value indicating the degree of drying tendency inside the fuel cell 10.

The drying history frequency acquisition unit 22 calculates and updates the drying history frequency D by the following equation (2) using the drying index value ID.
Drying history frequency D = D _n = D _n-1 + ID × Δt (2)
n: Natural number greater than or equal to Δt: Measurement period (execution cycle of step S30)

“D _n ” in Equation (2) is the current value of the drying history frequency D. Further, “D _n-1 ” is the previous value of the drying history frequency D, and is the value acquired in step S40 of the previous control cycle. If the current control cycle is the first control cycle after the start of operation of the fuel cell system 100, the previous value D _n-1 is the drying history frequency D read in step S10. The drying history frequency D increases in accordance with the strength of the drying tendency and the operation time when the fuel cell 10 continues to operate in a drying tendency. Is maintained.

  By the way, if the operation of the fuel cell is continued in a dry tendency with low moisture inside the fuel cell, catalyst poisoning may occur in which a part of the material such as polymer resin adheres to the catalyst surface of the electrode. Are known. This catalyst poisoning accumulates unless the causative agent is removed from the catalyst surface. If the operation time in the dry tendency state is accumulated, there is an increased possibility that the performance of the fuel cell is suddenly deteriorated at a certain time due to the accumulation of the catalyst poisoning.

  As described above, the drying history frequency D is a variable reflecting the size of the drying index value ID and the cumulative operation time when the drying index value ID is less than 1. That is, the operation history in which the fuel cell 10 tends to dry is reflected in the drying history frequency D. Therefore, according to the drying history frequency D, it is possible to know in advance the degree of progress of catalyst poisoning in the fuel cell 10 that the performance degradation of the fuel cell 10 due to catalyst poisoning has arrived.

  Here, the water increase / decrease ratio α used for calculating the drying history frequency D in the present embodiment is a ratio of the increased water amount WI and the decreased water amount WD. If the moisture increase / decrease ratio α, the fluctuation due to the difference in operating conditions such as the flow rate of the reactant gas supplied to the fuel cell 10 and the power generation amount of the fuel cell 10 is small. Therefore, it can be said that the drying index value ID based on the moisture increase / decrease ratio α more appropriately reflects the degree of drying tendency inside the fuel cell 10 regardless of the difference in the operating conditions. Further, in the fuel cell system 100 of the present embodiment, since the drying history frequency D is obtained from the drying index value ID as described above, the operation history in which the fuel cell 10 is in a drying tendency is more appropriately reflected. It can be said that.

  In step S <b> 40, the deterioration time detection unit 23 determines the arrival of the deterioration time of the fuel cell 10 based on the drying history frequency D, and outputs the determination result to the operation control unit 21. When the drying history frequency D is equal to or less than a predetermined threshold value, the deterioration time detection unit 23 determines that there is a delay before the time when the rapid performance deterioration of the fuel cell 10 due to catalyst poisoning occurs. In this case, the operation control unit 21 repeats normal operation control until the operation of the fuel cell system 100 ends (steps S20 to S50). On the other hand, when the drying history frequency D is greater than a predetermined threshold, the deterioration time detection unit 23 determines that the time of occurrence of the performance deterioration of the fuel cell 10 due to catalyst poisoning is almost reached. In this case, the operation control unit 21 starts the recovery operation in step S60.

  The fuel cell performance degradation due to catalyst poisoning can be recovered by removing deposits on the catalyst surface. Therefore, in the recovery operation in step S60, the operation control unit 21 performs operation control to increase the amount of water inside the fuel cell 10 more than in normal operation control (steps S20 and S25), and removes deposits on the catalyst surface. Rinse away with increased moisture and remove. Specifically, the operation control unit 21 temporarily reduces the voltage of the fuel cell 10 regardless of an external load request. Thereby, since the current of the fuel cell 10 temporarily increases, the amount of water produced by the power generation reaction can be increased.

  The operation control unit 21 may execute a process for reducing the operation temperature of the fuel cell 10 as the recovery operation in step S60. Specifically, the operation control unit 21 performs a process of increasing the flow rate of the refrigerant supplied from the refrigerant supply unit 70 to the fuel cell 10 as compared with the normal operation control. If the operating temperature of the fuel cell 10 is lowered, the liquefaction of the water present inside the fuel cell 10 is promoted, so that the amount of water discharged as vapor from the fuel cell 10 is reduced. Accordingly, it is possible to increase the amount of moisture remaining inside the fuel cell 10.

  After completion of the recovery operation, the drying history frequency acquisition unit 22 sets the drying history frequency D to an initial value (step S65). Thereafter, the operation control unit 21 repeats normal operation control until the operation of the fuel cell system 100 is completed (steps S10 to S50). At the end of the operation of the fuel cell system 100, the drying history frequency acquisition unit 22 stores the drying history frequency D in the nonvolatile storage unit of the control unit 20 so that it can be read at the start of the next operation (step S55). ). As a result, the operation history in which the fuel cell 10 tends to dry is recorded in a nonvolatile manner.

  As described above, according to the fuel cell system 100 of the present embodiment, the rapid performance degradation that occurs due to the accumulation of the operation time during which the inside of the fuel cell 10 tends to dry is based on the drying history frequency D. Can be prevented appropriately. Therefore, the reliability of the fuel cell system 100 is improved.

[Dry history frequency D]
FIG. 5 is an explanatory diagram for explaining the relationship between the moisture increase / decrease ratio α used for calculating the drying history frequency D and the performance degradation of the fuel cell. FIG. 5 shows a graph in which the horizontal axis is the moisture increase / decrease ratio α and the vertical axis is the output change rate of the fuel cell. The output change rate on the vertical axis of the graph is a value expressed as a percentage when the output power of the fuel cell in the initial state is defined as 100%, based on the output power of the fuel cell in the initial state as a reference. is there.

  In this experiment, the fuel cell was intermittently generated at a constant current density in the medium load region, medium low load region, and low load region under various operating conditions determined so that the moisture increase / decrease ratio α was constant. Repeated. In any case, when the water increase / decrease ratio α is smaller than 1, the output power of the fuel cell gradually decreases from a certain time and converges to a certain value. On the other hand, when the moisture increase / decrease ratio α was 1 or more, no decrease in the output power of the fuel cell was observed.

  Here, as shown in the graph, when the moisture increase / decrease ratio α is smaller than 1, the decrease in the output power of the fuel cell is smaller as the moisture increase / decrease ratio α is smaller. In addition, in this experiment, the larger the moisture increase / decrease ratio α, the shorter the operation time until the decrease in the output of the fuel cell was converged. Further, when the cause of the decrease in the output of the fuel cell was examined by cyclic voltammetry measurement, it was found that it was caused by catalyst poisoning.

  Thus, the magnitude of the moisture increase / decrease ratio α when the moisture increase / decrease ratio α is smaller than 1 and the time during which the operation in which the moisture increase / decrease ratio α is smaller than 1 are continued are the performance of the fuel cell due to catalyst poisoning. Related to the progression of the decline. As described above, the drying index value ID is a value obtained by subtracting the moisture increase / decrease ratio α from 1, and the drying history frequency D is the value when the drying index value ID and the drying index value ID are smaller than 1. This is a value reflecting the cumulative operating time. Therefore, it can be seen from the above experimental results that if the drying history frequency is D, the arrival time of performance deterioration due to catalyst poisoning of the fuel cell can be grasped in advance.

FIGS. 6 to 8 are explanatory diagrams showing the difference in arrival of the fuel cell performance degradation time in the first and second operation patterns in which the change history of the moisture increase / decrease ratio α is different. FIG. 6 and FIG. 7 show graphs obtained when the fuel cell is generated with the predetermined first and second operation patterns, respectively. In the graphs of FIGS. 6 and 7, the horizontal axis indicates time, the vertical axis on the left side of the paper indicates the moisture increase / decrease ratio α, and the vertical axis on the right side of the paper indicates the current. A graph G _D of the solid line indicates the time variation of α moisture decrease ratio, the graph G _I of the dash-dotted line indicates the time variation of the current output by the fuel cell.

  Here, in the graphs of FIGS. 6 and 7, the area DA in which the moisture increase / decrease ratio α is smaller than 1 is indicated by hatching. Hereinafter, this area DA is referred to as “dry area DA”. The drying history frequency D is a value corresponding to the area of the dry area DA. In the graph of FIG. 6, the area of the dry area DA is larger than the graph of FIG. That is, in the first operation pattern in which the graph of FIG. 6 is obtained, the fuel cell tends to dry more than the second operation pattern in which the graph of FIG. 7 is obtained, and the drying history frequency D increases. This is a fast driving pattern.

  FIG. 8 is a graph showing changes in the output of the fuel cell when the first and second operation patterns obtained from the graphs of FIGS. 6 and 7 are each repeated as a plurality of times. In the graph of FIG. 8, the horizontal axis indicates the number of cycles, and the vertical axis indicates the output of the fuel cell. Further, the solid line graph Ga is a graph when the first operation pattern (FIG. 6) is repeated, and the broken line graph Gb is a graph when the second operation pattern (FIG. 7) is repeated. The two graphs Ga and Gb are obtained by measuring the voltages when a predetermined current is output to the fuel cell each time the first and second operation patterns are repeated a predetermined number of cycles. .

  As shown in the graph of FIG. 8, the time has come when the output of the fuel cell suddenly drops when either the first or second operation pattern is repeated. When the fuel cell after the output decreased was verified, it was confirmed that the cause of the decrease in the output of the fuel cell was due to catalyst poisoning. Further, when the first operation pattern is repeated (graph Ga), the output decrease of the fuel cell due to catalyst poisoning comes earlier than when the second operation pattern is repeated (graph Gb). did. That is, in the first operation pattern in which the drying history frequency D increases at a higher speed, the time when the performance deterioration due to catalyst poisoning occurs earlier. Also from this experimental result, it can be seen that when the drying history frequency D is used as an index, it is possible to grasp the time of occurrence of the performance deterioration of the fuel cell due to catalyst poisoning.

  FIG. 9 is an explanatory view showing the performance recovery of the fuel cell whose performance is degraded by catalyst poisoning. FIG. 9 is a bar graph showing changes in the output of the fuel cell before and after the recovery operation for performance recovery is performed on the fuel cell in which the performance deterioration due to catalyst poisoning is detected. In this experiment, as a recovery operation of the fuel cell, a wet operation was performed such that water having a water content of 2.0 g per single cell remained in the fuel cell after power generation. As described above, by performing the operation in which the moisture inside the fuel cell increases, the performance of the fuel cell can be recovered by catalyst poisoning.

[Reference example]
FIG. 10 is an explanatory diagram showing a change in the resistance value of the fuel cell as a reference example with respect to a decrease in performance due to the drying operation of the fuel cell. FIG. 10 is a graph in which the horizontal axis is current density, the vertical axis on the left side of the paper is voltage, and the vertical axis on the right side of the paper is area resistance. Graphs IVi, IVd, and IVw are graphs showing changes in voltage with respect to current density, and graphs IRi, IRd, and IRw are graphs showing changes in sheet resistance with respect to current density.

  Here, the solid line graphs IVi and IRi are graphs obtained in the fuel cell in the initial state. The broken line graphs IVd and IRd are graphs obtained in the fuel cell after the power generation performance is reduced by power generation after the inside of the fuel cell is dried. Dotted line graphs IVw and IRw are graphs obtained by performing power generation in a wet state in the fuel cell after the power generation performance is lowered.

  As shown in these graphs, the change in resistance with respect to the current density in the fuel cell varies depending on the wet state inside the fuel cell, but the effect of the decrease in fuel cell performance due to power generation in the dry state is I have not received it. Therefore, it is not easy to detect a decrease in the performance of the fuel cell due to power generation in a dry state depending on the measurement of the resistance of the fuel cell. On the other hand, as described above, since the drying history frequency D is acquired based on the information representing the water balance of the fuel cell, the history of power generation in the dry state of the fuel cell is appropriately reflected. In addition, it is possible to grasp in advance the time when the performance of the fuel cell deteriorates due to dry power generation.

B. Variation:
B1. Modification 1:
In the above embodiment, the drying history frequency acquisition unit 22 acquires the increased water amount WI based on the power generation amount of the fuel cell 10 and the decreased water amount WD based on the flow rate and temperature of the cathode exhaust gas. On the other hand, the drying history frequency acquisition unit 22 may acquire the increased water amount WI and the decreased water amount WD by other methods. For example, the drying history frequency acquisition unit 22 may add the increased water amount WI to the power generation amount of the fuel cell 10 and the humidity of the cathode gas supplied to the fuel cell 10. In addition, the drying history frequency acquisition unit 22 may acquire the reduced water amount WD by measuring the humidity of the cathode exhaust gas, or in addition to the amount of water discharged as vapor in the cathode exhaust gas, the cathode side or anode side The amount of waste water discharged as liquid water may be taken into account. Alternatively, the drying history frequency acquisition unit 22 may acquire the reduced water amount WD only from the flow rate of the cathode exhaust gas. In this case, assuming that the temperature of the cathode exhaust gas is about 80 ° C., for example, the saturated water vapor amount contained in the cathode exhaust gas may be acquired as the reduced water amount WD.

B2. Modification 2:
In the above-described embodiment, the drying history frequency acquisition unit 22 sequentially calculates the drying history frequency D based on the moisture increase / decrease ratio α, which is the ratio of the increased water amount WI and the decreased water amount WD. The drying history frequency acquisition unit 22 may not calculate the drying history frequency D based on the moisture increase / decrease ratio α. The drying history frequency acquisition unit 22 may calculate based on the water balance information of the fuel cell 10 including the increased water amount WI and the decreased water amount WD. For example, the drying history frequency acquisition unit 22 may calculate the drying history frequency D using the difference between the increased water amount WI and the decreased water amount WD. However, as described in the above embodiment, if the drying history frequency D is based on the upper water increase / decrease ratio α, there is little variation due to differences in operating conditions (for example, supply gas flow rate and power generation amount) in the fuel cell 10, The history of the drying tendency inside the fuel cell 10 is more appropriately reflected.

B3. Modification 3:
In the above embodiment, the drying history frequency acquisition unit 22 sequentially acquires the drying index value ID for each control cycle of the control unit 20, and updates the drying history frequency D each time. On the other hand, the drying history frequency acquisition unit 22 may sequentially acquire the drying index value ID at every predetermined timing regardless of the control cycle of the control unit 20. Further, the drying history frequency acquisition unit 22 may not update the drying history frequency D every time the drying index value ID is acquired. When it is detected that the drying index value ID has changed by a predetermined change amount, the drying history frequency acquisition unit 22 is a time interval from the update of the drying index value ID and the previous drying history frequency D to the present. Based on the above, the drying history frequency D may be updated. Alternatively, the drying history frequency acquisition unit 22 may update the drying history frequency D using the average value of the drying index value ID acquired a plurality of times and the time interval until the average value is acquired.

B4. Modification 4:
In the above embodiment, the deterioration time detection unit 23 determines the arrival of the occurrence time of the performance degradation of the fuel cell 10 based on the drying history frequency D, and the operation control unit 21 performs recovery operation based on the determination result (step S60). Was running. On the other hand, the determination process by the deterioration time detection unit 23 and the recovery operation by the operation control unit 21 may be omitted. The control unit 20 may execute a notification process of notifying the user of the value of the drying history frequency D by a meter or the like instead of the determination process by the deterioration time detection unit 23. Moreover, the control part 20 may alert | report to the user the determination result which the deterioration time detection part 23 outputs instead of the recovery driving | operation of step S60. In this case, the control unit 20 may start executing the recovery operation according to the user's instruction.

B5. Modification 5:
The fuel cell system of each of the above embodiments is not limited to a fuel cell vehicle, and may be mounted on a mobile body (for example, an aircraft or a ship) that uses the power of another fuel cell. In addition, the fuel cell system of each of the above embodiments may be introduced not to a moving body but to a facility or equipment whose position is fixed.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 11 ... Power generation body 20 ... Control part 21 ... Operation control part 22 ... Drying history frequency acquisition part 23 ... Degradation judgment part 30 ... Cathode gas supply part 31 ... Cathode gas piping 32 ... Air compressor 33 ... On-off valve 34 ... Air flow meter 35 ... Pressure measuring unit 40 ... Cathode gas discharge unit 41 ... Cathode exhaust gas pipe 43 ... Pressure regulating valve 44 ... Exhaust gas information acquisition unit 50 ... Anode gas supply unit 51 ... Anode gas pipe 52 ... Hydrogen tank 53 ... Open / close valve 54 ... Regulator 55 ... Hydrogen supply device 56 ... Pressure measuring part 60 ... Anode gas circulation discharge part 61 ... Anode exhaust gas pipe 62 ... Gas-liquid separation part 63 ... Anode gas circulation pipe 64 ... Hydrogen circulation pump 65 ... Anode drain pipe 66 ... Drain valve 67 ... pressure measuring section 70 ... refrigerant supply section 71a ... upstream pipe 71b ... downstream pipe 72 ... radiator 75 ... refrigerant circulation Pumps 76a, 76 b ... first and second refrigerant temperature measurement unit 81: fuel cell converter 82 ... secondary battery 83 ... secondary battery converter 84 ... DC / AC inverter 84
91 ... Cell voltage measurement unit 92 ... Current measurement unit

Claims (9)

A fuel cell system,
A fuel cell;
A water balance information acquisition unit for acquiring water balance information indicating an increase or decrease in the amount of water in the fuel cell;
An index value acquisition unit that sequentially acquires a drying index value indicating a degree of drying tendency inside the fuel cell during operation based on the water balance information;
When the drying index value is acquired, a deterioration reflecting value that reflects the degree of progress of deterioration of the fuel cell based on the drying index value and the time interval at which the drying index value is acquired. Deterioration reflected value acquisition unit that acquires and accumulates,
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
The water balance information includes an increased water amount that is an increased amount of moisture per unit time inside the fuel cell, and a decreased water amount that is a decreased amount of moisture per unit time inside the fuel cell,
The index value acquisition unit acquires the drying index value based on a ratio between the increased water content and the decreased water content. The fuel cell system according to claim 1 or 2, wherein
The deterioration reflected value acquisition unit acquires the current value of the dry index value from the time when the previous value of the dry index value is acquired each time the dry index value is acquired by the index value acquisition unit. A fuel cell system that obtains the deterioration reflection value by integrating a value obtained by multiplying a time between the current time and the current value. The fuel cell system according to any one of claims 1 to 3, further comprising:
A power generation amount detection unit for acquiring the power generation amount of the fuel cell;
An exhaust gas information acquisition unit for acquiring a flow rate of exhaust gas discharged from the fuel cell;
With
The water balance information acquisition unit acquires an increase in moisture in the fuel cell based on at least the amount of power generated by the fuel cell to acquire the water balance information, and reduces the moisture in the fuel cell. Is obtained based on at least the flow rate of the exhaust gas. The fuel cell system according to any one of claims 1 to 4, further comprising:
A fuel cell system comprising a deterioration timing detection unit that detects in advance the arrival of a time when the fuel cell reaches a predetermined degree of deterioration based on the deterioration reflection value. The fuel cell system according to claim 5, wherein
When the arrival of the time when the fuel cell reaches a predetermined degree of deterioration is detected by the deterioration time detection unit, the amount of moisture generated in the fuel cell is used as a recovery operation for recovering the deterioration of the fuel cell. A fuel cell system comprising an operation control unit that executes operation control to be increased. A fuel cell vehicle,
A fuel cell vehicle equipped with the fuel cell system according to any one of claims 1 to 6. An apparatus for detecting the progress of deterioration of a fuel cell,
A water balance information acquisition unit for acquiring water balance information indicating an increase or decrease in the amount of water in the fuel cell;
An index value acquisition unit that sequentially acquires a drying index value indicating a degree of drying tendency inside the fuel cell during operation based on the water balance information;
When the drying index value is acquired, a deterioration reflecting value that reflects the degree of progress of deterioration of the fuel cell based on the drying index value and the time interval at which the drying index value is acquired. Deterioration reflected value acquisition unit that acquires and accumulates,
An apparatus comprising: A method for detecting the progress of deterioration of a fuel cell,
A water balance information acquisition step for acquiring water balance information indicating an increase or decrease in the amount of water in the fuel cell;
An index value acquisition step of sequentially acquiring a drying index value indicating a degree of drying tendency inside the fuel cell during operation based on the water balance;
When the drying index value is acquired, a deterioration reflecting value that reflects the degree of progress of deterioration of the fuel cell based on the drying index value and the time interval at which the drying index value is acquired. Degradation reflected value acquisition process to be acquired by integrating,
A method comprising:

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