JP5601178B2 - Fuel cell system and control method thereof - Google Patents

Description

  The present invention relates to a catalyst deterioration determination for suppressing deterioration in catalyst performance due to aging deterioration of a catalyst electrode of a fuel cell in a fuel cell system.

  As a conventional technique, for example, in the fuel cell system described in Patent Literature 1, cyclic voltammetry (CV) is measured to determine the deterioration state of the catalyst electrode.

JP 2008-218097 A JP 2008-218051 A JP 2007-149595 A

  However, in the measurement of the CV, it is necessary to carry out a special operation for the measurement of the CV. In order to carry out this operation, a voltage / current control device which is an unnecessary function in normal power generation control is used. There is a problem in that the configuration of the fuel cell system becomes complicated because it is necessary to equip it and to provide time for this operation. Further, in the measurement of CV, the voltage of the fuel cell is forcibly changed, which may cause deterioration of the catalyst electrode, which causes a problem of reducing the durability of the fuel cell.

  Then, an object of this invention is to provide the technique which can determine the deterioration state of a catalyst electrode simply.

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 or application examples.
[Form 1]
A fuel cell system comprising a fuel cell having one or more fuel cells each having a catalyst electrode formed on both sides of an electrolyte membrane, and a gas supply unit for supplying fuel gas and oxidizing gas to the fuel cell as power generation gas A battery output control unit for controlling the output state of the fuel cell, and a control state of the fuel cell by the battery output control unit, wherein the voltage of the fuel cell measured by the output state measurement unit is a predetermined lower limit In the standby control state in which the supply of the gas by the gas supply unit is intermittently repeated so that the supply of power to the load of the fuel cell system is stopped so that the voltage is equal to or higher than the voltage and equal to or lower than the upper limit voltage. A time interval measuring unit that measures a time interval between intermittent execution of supply and stop, and a catalyst deterioration determining unit that determines a deterioration state of the catalyst electrode, The catalyst deterioration determination unit determines that the catalyst electrode is deteriorated when the time interval measured by the time interval measurement unit in the standby control state is larger than a preset allowable time interval. A fuel cell system.
According to the above configuration, it is possible to simplify the configuration of the fuel cell system as compared with the conventional CV measurement, and it is possible to easily determine the deterioration state of the catalyst electrode.
[Form 2]
The fuel cell system according to aspect 1, wherein the battery output control unit activates the output voltage of the fuel cell as a catalyst when the catalyst deterioration determination unit determines that the catalyst electrode is deteriorated. A fuel cell system that performs catalyst activation control to reduce the voltage.
According to the above configuration, it is possible to easily determine the deterioration state of the catalyst electrode, and it is possible to recover the deterioration state of the catalyst by executing the catalyst activation control in response to this determination.
[Form 3]
The fuel cell system according to Aspect 2, wherein the battery output control unit executes the catalyst activation control when shifting from the standby control state to a power supply control state for the load. Fuel cell system.
According to the above configuration, since the catalyst activation control can be executed when shifting from the standby control state to the power supply control state for the load, the deterioration state of the catalyst is recovered at an efficient catalyst activation timing. It is possible.

[Application Example 1]
A fuel cell system, a fuel cell having one or more fuel cells each having a catalyst electrode formed on both sides of an electrolyte membrane, a battery output control unit for controlling an output state of the fuel cell, and an output of the fuel cell An output state measuring unit for measuring a state, and a catalyst deterioration determining unit for determining a deterioration state of the catalyst electrode, wherein the catalyst deterioration determining unit is configured such that the control state of the fuel cell by the battery output control unit is the fuel In the standby control state in which the supply of power to the load of the battery system is stopped, when the output current value of the fuel cell measured by the output state measurement unit is lower than a preset allowable current value of the output current, A fuel cell system, wherein the catalyst electrode is determined to be deteriorated.
According to the above configuration, it is possible to simplify the configuration of the fuel cell system as compared with the conventional CV measurement, and it is possible to easily determine the deterioration state of the catalyst electrode.

[Application Example 2]
The fuel cell system according to Application Example 1, wherein the fuel cell system includes a gas supply unit that supplies fuel gas and oxidizing gas as power generation gas to the fuel cell, and the standby control state is measured by the output state measurement unit. The fuel cell is in a control state in which execution and stop of the supply of the gas by the gas supply unit are repeated intermittently so that the voltage of the fuel battery cell is not less than a predetermined lower limit voltage value and not more than an upper limit voltage value. Fuel cell system.
For example, in the case of starting the fuel cell system or stopping the supply of power to the drive target, that is, when there is no load, the standby control state is set so that the voltage of the fuel cell is equal to or higher than a predetermined lower limit voltage value. There may be a case where control is performed to intermittently repeat execution and stop of gas supply by the gas supply unit so as to be equal to or lower than the upper limit voltage value. According to the above configuration, it is possible to easily determine the deterioration state of the catalyst electrode using such a standby control state, and it is possible to simplify the configuration of the fuel cell system.

[Application Example 3]
The fuel cell system according to Application Example 1, wherein the fuel cell system includes a gas supply unit that supplies fuel gas and oxidizing gas as power generation gas to the fuel cell, and the standby control state is measured by the output state measurement unit. The fuel cell system is in a control state in which the supply of the gas by the gas supply unit is controlled so that the voltage of the fuel cell becomes a predetermined upper limit voltage value.
For example, in the case of starting the fuel cell system or stopping the supply of power to the drive target, that is, when there is no load, the standby control state is set such that the voltage of the fuel cell is a predetermined upper limit voltage value. In some cases, the gas supply by the gas supply unit may be controlled. According to the above configuration, it is possible to easily determine the deterioration state of the catalyst electrode using such a standby control state, and it is possible to simplify the configuration of the fuel cell system.

[Application Example 4]
A fuel cell system comprising a fuel cell having one or more fuel cells each having a catalyst electrode formed on both sides of an electrolyte membrane, and a gas supply unit for supplying fuel gas and oxidizing gas to the fuel cell as power generation gas A battery output control unit for controlling the output state of the fuel cell, and a control state of the fuel cell by the battery output control unit, wherein the voltage of the fuel cell measured by the output state measurement unit is a predetermined lower limit In the standby control state in which the supply of the gas by the gas supply unit is intermittently repeated so that the supply of power to the load of the fuel cell system is stopped so that the voltage is equal to or higher than the voltage and equal to or lower than the upper limit voltage. A time interval measuring unit that measures a time interval between intermittent execution of supply and stop, and a catalyst deterioration determining unit that determines a deterioration state of the catalyst electrode, The catalyst deterioration determination unit determines that the catalyst electrode is deteriorated when the time interval measured by the time interval measurement unit in the standby control state is larger than a preset allowable time interval. A fuel cell system.
According to the above configuration, it is possible to simplify the configuration of the fuel cell system as compared with the conventional CV measurement, and it is possible to easily determine the deterioration state of the catalyst electrode.

[Application Example 5]
The fuel cell system according to any one of Application Example 1 to Application Example 4, wherein the battery output control unit determines that the catalyst electrode is deteriorated by the catalyst deterioration determination unit. A fuel cell system that performs catalyst activation control for reducing the output voltage of the fuel cell to a catalyst activation voltage.
According to the above configuration, it is possible to easily determine the deterioration state of the catalyst electrode, and it is possible to recover the deterioration state of the catalyst by executing the catalyst activation control in response to this determination.

[Application Example 6]
The fuel cell system according to Application Example 5, wherein the battery output control unit executes the catalyst activation control when shifting from the standby control state to a power supply control state for the load. Fuel cell system.
According to the above configuration, since the catalyst activation control can be executed when shifting from the standby control state to the power supply control state for the load, the deterioration state of the catalyst is recovered at an efficient catalyst activation timing. It is possible.

  The present invention can be realized in various forms, for example, in various forms such as a fuel cell system and a control method of the fuel cell system.

It is explanatory drawing shown about the basic concept of deterioration determination of the catalyst electrode of the fuel cell of this invention. It is a block diagram which shows the structural example of the fuel cell system in 1st Example. It is a flowchart which shows the catalyst deterioration determination routine in 1st Example. It is explanatory drawing shown about the process in the catalyst deterioration determination routine of FIG. It is a block diagram which shows the structural example of the fuel cell system in 2nd Example. It is a flowchart which shows the catalyst deterioration determination routine in 2nd Example. It is explanatory drawing shown about the process in a 6th catalyst deterioration determination routine. It is a flowchart which shows a part of catalyst deterioration determination routine in 3rd Example.

Embodiments of the present invention will be described in the following order based on examples.
A. Basic concept of catalyst deterioration judgment:
B. First embodiment:
C. Second embodiment:
D. Third embodiment:
E. Variations:

A. Basic concept of catalyst deterioration judgment:
FIG. 1 is an explanatory view showing the basic concept of determination of deterioration of a catalyst electrode of a fuel cell according to the present invention, and FIG. 1 (B) shows the flow of determination of deterioration of the catalyst electrode.

  When the operation of the fuel cell system is stopped, the potential difference between the anode and cathode of the fuel cell constituting the fuel cell decreases from the operating state and finally becomes zero, so that the oxidation deterioration state of the catalyst electrode is recovered. . Therefore, immediately after the start of operation of the fuel cell system, the catalyst electrode shows a current-voltage characteristic in a state where the catalyst electrode is recovered from the oxidation deterioration state (see a solid line in FIG. 1A). Then, as the fuel electronic system is operated and the time elapses, the oxidation deterioration of the catalyst electrode progresses, and the current-voltage characteristic is shown in which the voltage is lowered accordingly (see dotted lines and broken lines in FIG. 1A). ).

A current value (hereinafter also referred to as “initial current value”) i _{t0 at} a predetermined voltage value E _t0 immediately after the start is expressed by the following formula (1) based on the Butler-Volumer formula.
i _t0 = k · θ _t0 · exp [− (α · n · F / RT) · E _t0 ] (1)
k: Reaction rate constant θ _t0 : Ratio of catalyst contributing to the reaction immediately after starting (catalyst ratio)
α: transfer coefficient n: number of redox reaction electrons F: Faraday constant R: gas constant T: temperature of fuel cell

Further, the current value i _{tr at} the predetermined voltage value E _t0 when a certain operating time has passed (after the operating time) is also expressed by the following formula (2) based on the Butler-former formula.
i _tr = k · θ _tr · exp [− (α · n · F / RT) · E _t0 ] (2)
θ _tr : Rate of catalyst contributing to the reaction after operation

The current value i _t0 ′ at the voltage value (E _t0 + Δη) when Δη is the allowable value of the voltage drop (allowable voltage drop) caused by oxidative degradation after the operation has elapsed is the initial current expressed by the equation (1) It is equal to the value _it0 and is expressed by the following formula (3) based on the Butler-former formula.
i _t0 ′ = i _t0 = k · θ _tr · exp [− (α · n · F / RT) · (E _t0 + Δη)] (3)
Therefore, θ _tr is expressed by the following expression (4) from the expressions (1) and (3).
θ _tr = θ _t0 · exp [(α · n · F / RT) · Δη] (4)

Then, the current value (allowable current _{value) i tr} at a predetermined voltage value _{E t0} in the case of a Δη the allowable voltage drop value after operation time (1), (2), (4) the following equation from the equation (5 ).
i _tr = k · θ _t0 · exp [− (α · n · F / RT) · E _t0 ] · exp [(α · n · F / RT) · Δη]
= I _t0 · exp [(α · n · F / RT) · Δη] (5)
That is, the allowable current value _{i tr} at a predetermined voltage _{E t0} can be set based on the initial current value _{i t0} and allowable voltage drop value Δη at a predetermined voltage _{E t0.}

Here, as shown in FIG. 1 (B), the current when the current value i _t at a predetermined voltage value E _t0 after certain operating time the above (5) smaller than the allowable current value i _tr indicated by formula The voltage-to-voltage characteristic is a state in which the voltage drop value ΔE is larger than the allowable voltage drop value Δη than the current-to-voltage characteristic in the case of the allowable voltage drop value Δη (see the dotted line in FIG. 1A) (FIG. 1). (See broken line in (A)). That is, in this case, it is considered that the oxidative deterioration of the catalyst exceeds the allowable range, so that it can be determined that the catalyst activation treatment is necessary.

  Therefore, in the following embodiment, the catalyst deterioration determination to which the basic concept of the catalyst electrode deterioration determination described above is applied will be described.

B. First embodiment:
B1. Configuration example of fuel cell system:
FIG. 2 is a block diagram showing a configuration example of the fuel cell system in the first embodiment. This fuel cell system 10 shows a fuel cell system mounted on a vehicle as an example.

  The fuel cell system 10 includes a fuel cell 100, an anode gas (fuel gas) supply unit 200 and a cathode gas (oxidizing gas) supply unit 300, a cooling device 400, a monitor unit 500, a power control unit 600, and a control unit. 700.

  The fuel cell 100 is formed by an electrochemical reaction between a fuel gas (hydrogen) as an anode gas supplied to an anode and an oxidizing gas (air, strictly speaking, oxygen contained in air) as a cathode gas supplied to a cathode. Generate power.

  The fuel cell 100 is a fuel cell composed of fuel cells using a solid polymer electrolyte membrane. The fuel cell 100 has a stack structure in which a plurality of fuel cells are stacked. Although not shown, the fuel cell basically has a configuration in which a membrane-electrode assembly (MEA) is sandwiched between separators. The MEA includes an electrolyte membrane made of an ion exchange membrane, a catalyst electrode (also referred to as “anode side catalyst electrode” or simply “anode”) formed on the anode side surface of the electrolyte membrane, and a cathode side surface of the electrolyte membrane. It is composed of the catalyst electrode formed above (also referred to as “cathode side catalyst electrode” or simply “cathode”). Between the MEA and the separator, gas diffusion layers (GDL) are respectively provided on the anode side and the cathode side. In addition, a groove-like gas flow path for flowing an anode gas or a cathode gas is formed on the surface in contact with the separator and the gas diffusion layer. However, a gas flow path portion may be separately provided between the separator and the gas diffusion layer. In addition, each component formed between the electrolyte membrane and the anode-side separator may be collectively referred to as an “anode”. In addition, each component formed between the electrolyte membrane and the cathode separator may be collectively referred to as a “cathode”.

  The anode gas supply unit 200 includes a hydrogen gas tank 210 that stores high-pressure hydrogen gas as an anode gas (fuel gas), an anode gas supply channel 220 for supplying the hydrogen gas in the hydrogen gas tank 210 to the fuel cell 100, And an anode gas circulation passage 230 for returning hydrogen offgas as anode offgas (fuel offgas) discharged from the fuel cell 100 to the anode gas supply passage 220. The anode gas supply channel 220 includes an open / close valve 222 that shuts off or allows the supply of hydrogen gas from the hydrogen gas tank 210, a regulator 224 that adjusts the pressure of the hydrogen gas, and a hydrogen supply unit 226 that adjusts the flow rate of the hydrogen gas. And are provided. The anode gas circulation channel 230 is provided with a hydrogen gas pump 232 that sends out hydrogen off-gas as the anode off-gas in the anode gas circulation channel 230 to the anode gas supply channel 220 side. Further, a discharge flow path 238 connected to the exhaust port 350 is connected to the anode gas circulation flow path 230 via a gas-liquid separation unit 234 and an exhaust drainage valve 236. The gas-liquid separator 234 collects moisture contained in the hydrogen off gas. The exhaust / drain valve 236 discharges the hydrogen off-gas containing moisture collected by the gas-liquid separator 234 and impurities in the anode gas circulation channel 230. The hydrogen off-gas discharged from the exhaust / drain valve 236 is exhausted from the exhaust port 350 to the atmosphere as exhaust gas. The open / close valve 222, the regulator 224, the hydrogen supply unit 226, the hydrogen gas pump 232, the gas-liquid separation unit 234, and the exhaust / drain valve 236 operate according to instructions from the control unit 700.

  The cathode gas supply unit 300 takes in air as cathode gas (oxidizing gas) through the intake port 310 and compresses and sends the air, and cathode gas supply for supplying air (air) to the fuel cell 100. A flow path 330 and a cathode off gas discharge flow path 340 for discharging the cathode off gas (oxidation off gas) discharged from the fuel cell 100 from the exhaust port 350 are provided. The cathode off gas discharge channel 340 is provided with a back pressure adjustment valve 342 for adjusting the pressure of the cathode gas (oxidizing gas) in the fuel cell 100. In the cathode gas supply channel 330 and the cathode offgas discharge channel 340, a humidification unit 360 that humidifies the cathode gas (oxidation gas) pumped from the compressor 320 using the cathode offgas (oxidation offgas) discharged from the fuel cell 100. Is provided. The cathode off-gas that has undergone moisture exchange or the like in the humidifying unit 360 is exhausted from the exhaust port 350 to the atmosphere as exhaust gas. The compressor 320, the back pressure adjustment valve 342, and the humidification unit 360 operate according to instructions from the control unit 700.

  The cooling device 400 includes a cooling unit 410, a refrigerant supply passage 420 that supplies the refrigerant to the fuel cell 100, and a refrigerant discharge passage 430 that returns the refrigerant discharged from the fuel cell to the fuel cell 100. The cooling unit 410 circulates the refrigerant by supplying the refrigerant to the fuel cell 100 via the refrigerant supply channel 420 and receiving the refrigerant after being provided for cooling of the fuel cell 100 via the refrigerant discharge channel 430. Then, the fuel cell 100 is cooled. As the refrigerant, water, antifreeze, or the like can be used.

  The monitor unit 500 includes a cell voltage monitor 510 that measures the cell voltage between the fuel cells, a voltage sensor 520 that measures the output voltage of the fuel cell 100, and a current sensor 530 that measures the output current. The monitor unit 500 includes a pressure sensor that measures the pressure of the anode gas and cathode gas supplied to the fuel cell 100, a humidity sensor that measures humidity, a flow rate sensor that measures the flow rate, the temperature of the fuel cell 100, and the refrigerant temperature. Various sensors (not shown) such as each temperature sensor for measuring temperature are provided. Each element such as a sensor is connected to the control unit 700, and the measurement result measured by each element is transferred to the control unit 700 in accordance with an instruction from the control unit 700.

  The power control unit 600 includes a secondary battery control unit 620, a motor control unit 640, various auxiliary machine control units (not shown), and the like. The secondary battery control unit 620 controls charging / discharging of the secondary battery 610. The motor control unit 640 controls the supply of electric power from the fuel cell 100 or the secondary battery 610 to the motor 630. For example, when the motor 630 is a three-phase AC motor, the motor control unit 640 includes a three-phase inverter that converts a direct current into a three-phase alternating current. The accessory control unit controls the supply of electric power for driving each device such as the hydrogen gas pump 232 and the compressor 320, for example. Motor 630 constitutes the main power source of the vehicle on which fuel cell system 10 is mounted.

  The control unit 700 is configured as a computer system mainly including a CPU 710, a memory 720, and an input / output unit 730. The input / output unit 730 connects various actuators, various sensors, various switches, and the like via control signal lines (not shown). Various actuators include the above-described on-off valve 222, regulator 224, hydrogen supply unit 226, hydrogen gas pump 232, compressor 320, back pressure adjustment valve 342, cooling pump (not shown) included in the cooling unit 410, cooling fan, and rotation of the motor 630. There is an accelerator 750 or the like for controlling the amount. Examples of the various sensors include the voltage sensor 520, the current sensor 530, a temperature sensor (not shown), a pressure sensor, a humidity sensor, and a flow rate sensor. Examples of the various switches include a start switch 740 that starts an electric vehicle on which the fuel cell system 10 is mounted.

  The memory 720 stores various computer programs (not shown) mainly for controlling the fuel cell system 10, and the CPU 710 operates as each functional block by executing these computer programs. For example, the CPU 710 functions as a battery output control unit 710a and a catalyst deterioration determination unit 710b by executing a computer program of a battery output control routine and a catalyst deterioration determination routine. The battery output control unit 710a controls the operation of the fuel cell 100 and the secondary battery 610. The catalyst deterioration determination routine executed by the catalyst deterioration determination unit 710b will be described in detail below.

  The anode gas supply unit 200 and the cathode gas supply unit 300 correspond to the gas supply unit of the present invention. The monitor unit 500 corresponds to the output state measuring unit of the present invention.

B2. Catalyst deterioration judgment routine:
FIG. 3 is a flowchart showing a catalyst deterioration determination routine in the first embodiment. FIG. 4 is an explanatory diagram showing processing in the catalyst deterioration determination routine of FIG. This catalyst deterioration determination routine is executed with dark current, specifically, with the electric power stored in the secondary battery 610 before the electric vehicle is started.

  As shown in the figure, when the process is started, the catalyst deterioration determination unit 710b of the CPU 710 determines whether or not the start switch 740 is in an ON state (step S100). Here, when it is determined that the start switch 740 is not in the on state, that is, in the off state, the catalyst deterioration determination unit 710b repeats the process of step S110, and the start switch 740 is operated by the operator to be in the on state. Wait for When the start switch 740 is turned on, the fuel cell 100 is separately activated by the battery output control unit 710a. Here, when the fuel cell 100 is started, the battery output control unit 710a first performs normal power generation control on the fuel cell 100 for driving the motor 630 that is the load of the fuel cell system 10 when the accelerator 750 is turned on. Is executed until normal power generation is started. When the accelerator 750 is turned on, normal power generation control for the fuel cell 100 is executed, and normal power generation according to the operation amount of the accelerator 750 is started.

Briefly describing the standby control, the supply of power from the fuel cell 100 to the motor 630 is stopped, and the cell voltage of the fuel cell 100 is set to a preset lower limit voltage value as shown in FIG. Control is performed to intermittently repeat the execution and stop of the gas supply by the anode gas supply unit 200 and the cathode gas supply unit 300 so as to keep between E _L and the upper limit voltage value E _H. Incidentally, the upper limit voltage E _H is set to a voltage lower than the open circuit voltage, the upper limit voltage E _L is set to a voltage higher than the normal operating voltage during power generation control. Therefore, in standby control, a current smaller than that during normal power generation is generated. For example, the current generated by the standby control is charged in the secondary battery 610 via the secondary battery control unit 620 or consumed by a load in the fuel cell system such as various auxiliary machines including various actuators. Cell voltage monitoring is performed via the cell voltage monitor 510. The cell voltage may be monitored with respect to the cell voltages of all the fuel cells, or the cell voltage of any one or more of the fuel cells may be selected and monitored. In consideration of the measurement time, it is common to select any one representative fuel cell and monitor the cell voltage.

If it is determined in step S100 that the start switch 740 is in the ON state, the catalyst deterioration determination unit 710b determines that the cell voltage during the standby control immediately after the start is the upper limit voltage value E _H as the initial standby current value _it0i. Is measured (step S110), and a determination reference current value i _tri is calculated (step S120). The output current is measured via the current sensor 530. The calculation of the determination reference current value i _tri is executed as follows. The determination reference current value i _tri corresponds to the allowable current value of the present invention.

The determination reference current value i _tri is expressed by the following formula (6) using the formula of the allowable current value i _tr shown in the formula (5).
i _tri = i _t0i · exp [(α · n · F / RT) · Δη] (6)
Therefore, if the initial standby current value i _t0i is measured, the determination reference current value i _tri can be calculated from the above equation (6).
For example, Δη = −5 mV, α = 0.5, n = 4, F = 9.64853 × 10 ⁴ Cmol ⁻¹ , R = 8.331447 JK ⁻¹ mol ⁻¹ , T = 353 K (= 80 ° C.) Then, the determination reference current value i _tri is expressed by the following equation (7) using the above equation (6).
i _tri ≒ 0.72 · i _t0i (7)
Therefore, if the initial standby current value i _t0i is measured, the determination reference current value i _tri can be calculated from the above equation (7).

  Then, the catalyst deterioration determination unit 710b determines whether or not the accelerator 750 is turned on and normal power generation for supplying electric power to the motor 630 is started by the battery output control unit 710a (step S130). Here, when it is determined that the accelerator 750 is not in the on state, that is, in the off state and in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S130, and the accelerator 750 is operated by the operator. Wait for it to turn on.

  When it is determined in step S130 that the accelerator 750 is in the on state, the catalyst deterioration determination unit 710b determines whether the standby control is started by the battery output control unit 710a when the accelerator 750 is changed from the on state to the off state. Determination is made (step S140). Here, when it is determined that the accelerator 750 is not in the off state, that is, remains in the on state and is not in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S140 so that the accelerator 750 Wait for the operator to turn it off.

In step S140, when it is determined that the accelerator 750 is changed from the on state to the off state and the standby control is started by the battery output control unit 710a, the catalyst deterioration determination unit 710b sets the standby current value i _ti as the standby state. cell voltage during the control measures the output current at the upper limit voltage value E _H (step S150).

Then, the catalyst deterioration determination unit 710b determines whether or not the measured standby current value i _ti is smaller than the determination reference current value i _tri (step S160). Here, FIG. 4 (A), the as shown in (B), when the standby current value _{i ti} is determined to determine the reference current value _{i tri} smaller than the voltage drop value ΔE corresponding to the current value _{i t0i} Since it is considered that the allowable voltage drop value Δη is greater and the medium deterioration state exceeds the allowable range, the catalyst deterioration determination unit 710b determines that the catalyst activation process is necessary and executes the catalyst activation process. (Step S170). This catalyst activation process is a so-called refresh process in which the cell voltage is reduced to the catalyst activation voltage (voltage with the catalyst electrode as the reduction region). For example, the cell voltage is reduced to about 0.7 V or less. It is realized by. In addition, as a method for reducing the cell voltage to the catalyst activation voltage, a method for reducing the cell voltage by changing the current output from the fuel cell 100, a method for reducing the cell voltage by stopping the supply of oxygen to the fuel cell 100, or the like. A well-known general method can be used.

After execution of the catalyst activation treatment, the catalyst degradation determination unit 710b, as the initial standby current value i _t0i, measuring the output current when the cell voltage during the standby control after the activation treatment is in the upper limit voltage value E _H Then, the determination reference current value i _tri is recalculated (step S190). Then, the catalyst deterioration determination unit 710b determines whether or not the start switch 740 has been changed from the on state to the off state (step S200). Here, when it is determined that the start switch 740 is in the state changed from the ON state to the OFF state, the catalyst deterioration determination unit 710b returns to the first step S100 and executes each process from the process of step S100. On the other hand, when the start switch 740 is not in the off state but remains in the on state, the process returns to step S130, and each process is executed from the process of step S130.

In step S160, as shown in FIG. 4 (B), standby current value _{i ti} is not determined reference current value _{i tri} less state, and that is, the standby current value _{i ti} the determination reference current value _{i tri} or determination In this case, since the voltage drop value ΔE corresponding to the current value _it0i is smaller than the allowable drop voltage value Δη and the catalyst deterioration state is considered to be within the allowable range, the catalyst deterioration determination unit 710b performs the catalyst activation. It is determined that the process is unnecessary, and the process of step S200 described above is executed.

As described above, in this embodiment, the supply of electric power from the fuel cell to the motor 630 is stopped, and the cell voltage of the fuel cell 100 is maintained between the lower limit voltage value E _L and the upper limit voltage value E _H. as described above, in the standby control repeating the execution and stop of the supply of gas by the anode gas supply unit 200 and the cathode gas supply unit 300 intermittently control is executed, the cell voltage is in the upper limit voltage value E _H Whether or not the output current value (standby current value) i _ti is smaller than the judgment reference current value i _tri obtained from the above equation (6) based on the preset allowable voltage drop Δη It can be determined whether the catalyst deterioration state is within the allowable range or exceeds the allowable range. As a result, the configuration of the fuel cell system can be simplified as compared with the conventional CV measurement, and the deterioration state of the catalyst electrode due to oxidation can be easily determined. When the catalyst deterioration state exceeds the allowable range, it is possible to recover the deterioration state of the catalyst electrode by executing the catalyst activation process.

C. Second embodiment:
C1. Configuration example of fuel cell system:
FIG. 5 is a block diagram showing a configuration example of the fuel cell system in the second embodiment. In this fuel cell system 10B, the CPU 710 of the control unit 700 functions as a time interval measurement unit 710c by executing a computer program of a time interval measurement routine in addition to the battery output control unit 710a and the catalyst deterioration determination unit 710b. Is the same as the configuration of the fuel cell system 10 of the first embodiment.

C2. Catalyst deterioration judgment routine:
FIG. 6 is a flowchart showing a catalyst deterioration determination routine in the second embodiment. FIG. 7 is an explanatory diagram showing processing in a sixth catalyst deterioration determination routine. This catalyst deterioration determination routine is also executed with a dark current before the electric vehicle is started. As shown in the figure, when the process is started, the catalyst deterioration determination unit 710b of the CPU 710 determines whether or not the start switch 740 is in the ON state, similarly to the catalyst deterioration determination routine (see FIG. 3) of the first embodiment. Determination is made (step S100). Here, when it is determined that the start switch 740 is not in the on state, that is, in the off state, the catalyst deterioration determination unit 710b repeats the process of step S110, and the start switch 740 is operated by the operator to be in the on state. Wait for When the start switch 740 is turned on, the fuel cell 100 is separately activated by the battery output control unit 710a as in the case of the first embodiment. As in the case of the first embodiment, the battery output control unit 710a first performs normal power generation control for driving the motor 630 of the fuel cell 100 by turning on the accelerator 750 to generate normal power generation. Perform standby control until it starts. When the accelerator 750 is turned on, normal power generation is started.

In step S100, when the start switch 740 is determined to be in the ON state, the catalyst deterioration determining unit 710b, as the initial standby control time interval _{t 0,} as shown in FIG. 4 (A), FIG. 7 (A) , repetition time interval of the on and off the gas supply (hereinafter, referred to as "standby control time interval") is measured (step S110b), and calculates the criterion standby control time interval _{t tr} (step S120b). Note that the standby control time interval can be measured by measuring the interval of the gas supply ON instruction timing executed by the battery output control unit 710a using, for example, a timer (not shown). The calculation of the determination reference standby control time interval t _tr is performed as follows. Note that the determination reference standby control time interval t _tr corresponds to the allowable time interval of the present invention.

When the gas amount in the fuel cell at the time of intermittent control in which the gas supply is repeatedly turned on and off as described above is Vc, an initial standby current value i _t0i is used as the initial standby control time interval t _t0 immediately after starting. Is expressed as the following equation (8).
t _t0 = Vc / i _t0i
= Vc · {k · θ _t0 · exp [− (α · n · F / RT) · E _H ]} ⁻¹ (8)
Similarly, the determination reference standby control time interval t _tr is expressed by the following equation (9) using the determination reference current value i _tri of the above equation (6) and the initial standby control time interval t _t0 of the above equation (8). expressed.
t _tr = Vc / i _tri
= Vc / { _it0i · exp [(α · n · F / RT) · Δη]}
= (Vc / i _tri ) · {1 / exp [(α · n · F / RT) · Δη]}
= T _t0 · exp [− (α · n · F / RT) · Δη] (9)
Therefore, if the initial standby control time interval t _t0 is measured, the determination reference standby control time interval t _tr can be calculated from the above equation (9).
For example, Δη = −5 mV, α = 0.5, n = 4, F = 9.64853 × 10 ⁴ Cmol ⁻¹ , R = 8.331447 JK ⁻¹ mol ⁻¹ , T = 353 K (= 80 ° C.) Then, the determination reference standby control time interval t _tr is expressed by the following equation (10) using the above equation (9).
t _tr ≈ 1.38 · t _t0 (10)
Therefore, if the initial standby control time interval t _t0 is measured, the determination reference standby control time interval t _tr can be calculated from the above equation (10).

  Then, the catalyst deterioration determination unit 710b determines whether or not the accelerator 750 is turned on to start power generation for supplying electric power to the motor 630 (step S130). Here, when it is determined that the accelerator 750 is not in the on state, that is, in the off state and in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S130, and the accelerator 750 is operated by the operator. Wait for it to turn on.

  When it is determined in step S130 that the accelerator 750 is in the on state, the catalyst deterioration determining unit 710b determines whether the standby control is started from the on state to the off state (step S140). . Here, when it is determined that the accelerator 750 is not in the off state, that is, remains in the on state and is not in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S140 so that the accelerator 750 Wait for the operator to turn it off.

In step S140, if it is determined that the standby control accelerator 750 is turned from the ON state and OFF state is started, the catalyst degradation determination unit 710b measures the standby control time interval t _t (step S150B).

Then, the catalyst deterioration determination unit 710b determines whether or not the measured standby control time interval t _t is larger than the determination reference standby control time interval t _tr (step S160b). Here, as shown in FIG. 7B, when it is determined that the standby control time interval t _t is larger than the determination reference standby control time interval t _tr , the state when the catalyst deteriorates exceeds the allowable range. Since it is considered, the catalyst deterioration determination unit 710b determines that the catalyst activation process is necessary and executes the catalyst activation process (step S170).

After performing the catalyst activation process, the catalyst deterioration determination unit 710b measures the initial standby control time interval t _t0 (step S180b), and recalculates the determination reference standby control time interval t _tr (step S190b). Then, the catalyst deterioration determination unit 710b determines whether or not the start switch 740 has been changed from the on state to the off state (step S200). Here, when it is determined that the start switch 740 is in the state changed from the ON state to the OFF state, the catalyst deterioration determination unit 710b returns to the first step S100 and executes each process from the process of step S100. On the other hand, when the start switch 740 is not in the off state but remains in the on state, the process returns to step S130, and each process is executed from the process of step S130.

In step S160b, as shown in FIG. 7B, the standby control time interval t _t is not larger than the determination reference standby control time interval t _tr , that is, the standby control time interval t _t is not the determination reference standby control time interval t. If it is determined that it is equal to or less than _tr , the catalyst deterioration state is considered to be within the allowable range, so the catalyst deterioration determination unit 710b determines that the catalyst activation process is unnecessary, and the process of step S200 described above is performed. Execute.

As described above, in this embodiment, the supply of electric power from the fuel cell to the motor 630 is stopped, and the cell voltage of the fuel cell 100 is maintained between the lower limit voltage value E _L and the upper limit voltage value E _H. As described above, in the standby control in which the control for intermittently repeating the execution and stop of the gas supply by the anode gas supply unit 200 and the cathode gas supply unit 300 is performed, the time interval between the execution and stop of the gas supply ( the wait control time interval) t _t, based on the allowable voltage drop value Δη set in advance, determines whether is greater than the determination reference standby control time interval t _tr obtained from the equation (9) Thus, it can be determined whether the catalyst deterioration state is within the allowable range or exceeds the allowable range. As a result, the configuration of the fuel cell system can be simplified as compared with the conventional CV measurement, and the deterioration state of the catalyst electrode due to oxidation can be easily determined. When the catalyst deterioration state exceeds the allowable range, it is possible to recover the deterioration state of the catalyst electrode by executing the catalyst activation process.

D. Third embodiment:
FIG. 8 is a flowchart showing a part of the catalyst deterioration determination routine in the third embodiment. In FIG. 8, the process of step S162c is added between step S160 and step S170 of the catalyst deterioration determination routine in the first embodiment shown in FIG. 3, and between step S160 and step S200, The process of step S164c is added.

In step S160, when it is determined that the standby current value i _ti is smaller than the determination reference current value i _tri , as described in the first embodiment, the voltage drop value ΔE corresponding to the current value _it0i is the allowable drop voltage. Since it becomes larger than the value Δη and the medium deterioration state is considered to exceed the allowable range, it is determined that the catalyst activation treatment is necessary. Then, the catalyst deterioration determination unit 710b determines whether or not the accelerator 750 is turned on and it is time to start normal power generation for supplying power to the motor 630 (step S162c). Here, when it is determined that the accelerator 750 is not in the on state, that is, in the off state and in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S162c, and the accelerator 750 is operated by the operator. Wait for it to turn on.

  In step S162c, when it is time to start normal power generation for supplying power to the motor 630 when the accelerator 750 changes from the off state to the on state, the catalyst deterioration determination unit 710b performs the catalyst activation process. Is executed (step S170). Note that normal power generation control for supplying electric power to the motor 630 by the battery output control unit 710a of the CPU 710 is started after the catalyst activation process.

After execution of the catalyst activation treatment, the catalyst degradation determination unit 710b, as the initial standby current value i _t0i, measuring the output current when the cell voltage during the standby control after the activation treatment is in the upper limit voltage value E _H Then, the determination reference current value i _tri is recalculated (step S190). Then, the catalyst deterioration determination unit 710b executes the process of step S200.

In step S160, the standby current value _{i ti} is not determined reference current value _{i tri} smaller state, i.e., when the standby current value _{i ti} is determined to be the determination reference current value _{i tri} or higher, in the first embodiment As described above, since the voltage drop value ΔE corresponding to the current value _it0i is smaller than the allowable drop voltage value Δη and the catalyst deterioration state is considered to be within the allowable range, it is determined that the catalyst activation process is unnecessary. Is done. Then, the catalyst deterioration determination unit 710b determines whether or not the accelerator 750 is turned on and it is time to start power generation for supplying power to the motor 630 (step S164c). Here, when it is determined that the accelerator 750 is not in the on state, that is, in the off state and in the standby control state, the catalyst deterioration determination unit 710b repeats the process of step S164c, and the accelerator 750 is operated by the operator. Wait for it to turn on.

  In step S164c, when it is time to start power generation for supplying power to the motor 630 when the accelerator 750 is switched from the off state to the on state, the catalyst deterioration determination unit 710b executes the process of step S200. To do. At this time, normal power generation control for supplying power to the motor 630 is started by the battery output control unit 710a of the CPU 710.

  In the first embodiment and the second embodiment, there is no limitation on the timing of the catalyst activation process, and the process is performed when it is determined that the catalyst activation process is necessary. During standby control, it is desirable that the power generation characteristics are poor from the viewpoint of fuel consumption and catalyst deterioration. During normal operation, that is, during power generation for supplying electric power to the motor 630, the power generation characteristics should be good. desirable. For this reason, if the catalyst activation process is executed immediately before the start of the standby control or during the standby control, the power generation characteristics are improved, and the consumption of fuel and the deterioration of the catalyst are promoted without sitting. On the other hand, in this embodiment, as described above, when the accelerator 750 is switched from the off state to the on state and the normal power generation for supplying power to the motor 630 is started, the power generation control is performed. The catalyst activation process is executed before the start. Therefore, the catalyst activation process can be executed at an efficient and optimal timing.

  In addition, although the present Example demonstrated the timing of the catalyst activation process based on the catalyst deterioration determination routine of 1st Example, it is applicable also to the catalyst deterioration determination routine of 2nd Example.

E. Variations:
In addition, this invention is not restricted to said Example and embodiment, In the range which does not deviate from the summary, it is possible to implement in various aspects.

E1. Modification 1:
In the first embodiment, the case where the deterioration of the catalyst is determined based on the standby current during the standby control in which the gas supply is intermittently executed and stopped is described as an example, but as shown in the basic concept of the invention, The catalyst deterioration may be determined based on a standby current during standby control in which gas supply is controlled such that the voltage of the fuel cell becomes a predetermined voltage value, for example, a predetermined upper limit voltage value.

E2. Modification 2:
In the above embodiment, the fuel cell system mounted on the vehicle is shown as an example, but the present invention can be applied not only to the vehicle but also to various moving bodies such as a motorcycle, a ship, an airplane, and a robot. Further, the present invention is not limited to a fuel cell system mounted on a moving body, but can be applied to a stationary fuel cell system and a portable fuel cell system.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 10B ... Fuel cell system 100 ... Fuel cell 200 ... Anode gas supply part 210 ... Hydrogen gas tank 220 ... Anode gas supply flow path 222 ... Opening / closing valve 224 ... Regulator 226 ... Hydrogen supply part 230 ... Anode gas circulation flow path 232 ... Hydrogen gas pump 234 ... Gas-liquid separation part 236 ... Exhaust drain valve 238 ... Discharge flow path 300 ... Cathode gas supply part 310 ... Intake port 320 ... Compressor 330 ... Cathode gas supply flow path 340 ... Cathode off-gas discharge flow path 342 ... Back Pressure adjusting valve 350 ... Exhaust port 360 ... Humidifying unit 400 ... Cooling device 410 ... Cooling unit 420 ... Refrigerant supply channel 430 ... Refrigerant discharge channel 500 ... Monitor unit 510 ... Cell voltage monitor 520 ... Voltage sensor 530 ... Current sensor 600 ... Power control unit 610 ... Secondary battery 620 ... Secondary battery control unit 630 ... Motor 640 ... Motor control unit 700 ... Control unit 710 ... CPU
710a ... Battery output control unit 710b ... Catalyst deterioration determination unit 710c ... Time interval measurement unit 720 ... Memory 730 ... Input / output unit 740 ... Start switch 750 ... Accelerator

Claims (4)

A fuel cell system,
A fuel cell having at least one fuel cell in which catalyst electrodes are formed on both sides of the electrolyte membrane;
A gas supply unit for supplying a fuel gas and an oxidizing gas as a power generation gas to the fuel cell;
A battery output control unit for controlling the output state of the fuel cell;
An output state measuring unit for measuring the output state of the fuel cell;
The control state of the fuel cell by the battery output control unit is such that the gas by the gas supply unit is such that the voltage of the fuel cell measured by the output state measurement unit is not less than a predetermined lower limit voltage and not more than an upper limit voltage. In a standby control state in which the supply and stop of the fuel are intermittently repeated and the supply of power to the load of the fuel cell system is stopped, the time for measuring the time interval between the intermittent and repeated execution of the gas supply and stop An interval measurement unit;
A catalyst deterioration determination unit for determining a deterioration state of the catalyst electrode;
With
The catalyst deterioration determining unit determines that the catalyst electrode is deteriorated when the time interval measured by the time interval measuring unit in the standby control state is larger than a preset allowable time interval. A fuel cell system. The fuel cell system according to claim 1 ,
The battery output control unit performs catalyst activation control for reducing the output voltage of the fuel cell to a catalyst activation voltage when the catalyst deterioration determination unit determines that the catalyst electrode is deteriorated. A fuel cell system. The fuel cell system according to claim 2 , wherein
The fuel cell system, wherein the battery output control unit executes the catalyst activation control when shifting from the standby control state to a power supply control state for the load. A control method for a fuel cell system, comprising:
The fuel cell system includes:
A fuel cell having at least one fuel cell in which catalyst electrodes are formed on both sides of the electrolyte membrane;
A gas supply unit for supplying a fuel gas and an oxidizing gas as a power generation gas to the fuel cell;
With
The control method of the fuel cell system includes:
The control state of the fuel cell is such that the gas supply unit intermittently repeats execution and stop of the gas supply so that the voltage of the fuel cell becomes equal to or higher than a predetermined lower limit voltage and lower than the upper limit voltage. A standby control state for stopping power supply to the system load; and
In the standby control state, measuring a time interval of intermittent repetition of execution and stop of the gas supply; and
Determining that the catalyst electrode has deteriorated when the measured time interval is greater than a preset allowable time interval; and
A control method for a fuel cell system, comprising:

Images