JP7120939B2 - FUEL CELL SYSTEM AND METHOD OF CONTROLLING FUEL CELL SYSTEM - Google Patents

Description

The present invention provides a fuel cell system including a fuel cell that generates electricity through an electrochemical reaction of reactant gases, and a scavenging gas supply section for circulating the scavenging gas in a reactant gas flow path in the fuel cell, and a fuel cell system. Regarding the control method.

As a fuel cell system of this type, for example, in Patent Document 1, a special power generation stop process (low temperature short time power generation stop process) is performed to stop power generation of the fuel cell in a short time after it starts at low temperatures such as below freezing. A technical idea is disclosed to carry out a scavenging process in which water remaining in the fuel cell is discharged by circulating the scavenging gas in the reactant gas flow path in the fuel cell.

Japanese Patent No. 5086584

By the way, when the above-described special power generation stop processing is performed, more water remains in the fuel cell than when the normal power generation stop processing is performed. Therefore, for example, if the scavenging degree of the scavenging process performed after the special power generation stop process is the same as that of the normal scavenging process performed after the normal power generation stop process, it is possible to effectively reduce the amount of water remaining in the fuel cell. It may not be possible.

The present invention has been made in consideration of such problems, and effectively reduces the amount of water remaining in the fuel cell even when the special power generation stop processing is performed, so that the next fuel cell can be recharged. An object of the present invention is to provide a fuel cell system and a method of controlling the fuel cell system that can ensure stable power generation.

One aspect of the present invention includes a fuel cell that generates electricity through an electrochemical reaction of reactant gases, a scavenging gas supply unit that distributes scavenging gas to a reactant gas flow path in the fuel cell, and a scavenging gas supply unit that causes the scavenging gas to flow through the reaction gas flow path in the fuel cell. When the temperature drops below the starting temperature, the scavenging process is performed to discharge stagnant water in the fuel cell by circulating the scavenging gas from the scavenging gas supply unit to the reaction gas flow path while the fuel cell is in a state where power generation is stopped. a scavenging control unit; and a power generation determination unit that determines that a special power generation stop process is performed when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during start-up operation of the fuel cell. Then, the scavenging control unit determines that the scavenging degree of the special scavenging process performed after the special scavenging process is determined to be the special scavenging process performed before the special scavenging process is determined to be the special scavenging process performed by the power generation determining unit. A fuel cell system that increases the degree of scavenging.

Another aspect of the present invention is a fuel cell system comprising: a fuel cell that generates electricity through an electrochemical reaction of reactant gases; wherein the power generation is determined to be a special power generation stop process when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during start-up operation of the fuel cell. a determining step, when it is determined by the power generation determining step that the special power generation stopping process is not performed, the scavenging gas is circulated from the scavenging gas supply unit to the reaction gas flow path in the state where the power generation of the fuel cell is stopped, and the fuel is a normal scavenging process step of performing a normal scavenging process for discharging stagnant water in the battery; and a scavenging gas supply unit in a state where power generation of the fuel cell is stopped when the power generation determining step determines that the special power generation stopping process is performed. a special scavenging process step of performing a special scavenging process for discharging stagnant water in the fuel cell by circulating the scavenging gas from the reaction gas flow path to the reaction gas flow path, and A control method for a fuel cell system, wherein the scavenging degree of the special scavenging process is made larger than the degree.

According to the present invention, the degree of scavenging in the special scavenging process is higher than that in the normal scavenging process. can be reduced to Therefore, it is possible to ensure stable power generation of the fuel cell next time.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention; FIG. FIG. 2 is a partially omitted longitudinal cross-sectional view of the fuel cell of FIG. 1; 2 is a flow chart for explaining a control method of the fuel cell system of FIG. 1; FIG. 2 is a timing chart for explaining a control method of the fuel cell system of FIG. 1; FIG. 7 is a graph showing the relationship between the number of consecutive times of special power generation stop processing and the flow rate of scavenging gas.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a fuel cell system and a control method for a fuel cell system according to the present invention will be described below with reference to the accompanying drawings.

A fuel cell system 10 shown in FIG. 1 is mounted in a fuel cell vehicle (not shown) such as a fuel cell electric vehicle. However, the fuel cell system 10 may be mounted on various moving bodies other than fuel cell vehicles, or may be used as a stationary type.

The fuel cell system 10 includes a fuel cell 12 , a fuel gas supply device 14 , an oxidant gas supply device 16 , a cooling medium supply device 18 , a battery 20 and a controller 22 .

In FIG. 2, the fuel cell 12 generates electricity through an electrochemical reaction between a fuel gas (eg, hydrogen gas) and an oxidant gas (eg, air). The fuel cell 12 is configured as a fuel cell stack including a plurality of power generation cells 24 stacked horizontally. The power generation cell 24 is configured by sandwiching an electrolyte membrane/electrode structure 26 between a first separator 28 and a second separator 30 . The first separator 28 and the second separator 30 are composed of metal separators or carbon separators.

The electrolyte membrane/electrode assembly 26 includes, for example, an electrolyte membrane 32 (solid polymer electrolyte membrane) which is a thin film of perfluorosulfonic acid containing water, and an anode electrode 34 and a cathode electrode 36 which sandwich the electrolyte membrane 32. Prepare. For the electrolyte membrane 32, an HC (hydrocarbon)-based electrolyte is used in addition to the fluorine-based electrolyte.

A fuel gas channel 38 is provided between the first separator 28 and the electrolyte membrane electrode assembly 26 to guide the fuel gas to the anode electrode 34 . An oxidizing gas flow path 40 for supplying an oxidizing gas to the cathode electrode 36 is provided between the second separator 30 and the electrolyte membrane electrode assembly 26 . Between the first separator 28 and the second separator 30, a cooling medium flow path 42 through which a cooling medium for cooling the power generation cells 24 flows is provided.

As shown in FIG. 1, the fuel cell 12 is provided with a fuel gas inlet 44a, a fuel gas outlet 44b, an oxidant gas inlet 46a, an oxidant gas outlet 46b, a coolant inlet 48a and a coolant outlet 48b.

1 and 2, the inner hole of the fuel gas inlet 44a communicates with the supply side of the fuel gas flow path 38 via a fuel gas inlet communication hole (not shown) penetrating each power generating cell 24 in the stacking direction. The fuel gas outlet 44b communicates with the discharge side of the fuel gas flow path 38 through a fuel gas outlet communication hole (not shown) penetrating each power generation cell 24 in the stacking direction. An anode channel 50 (see FIG. 1) is configured by the fuel gas channel 38, the fuel gas inlet communication hole, and the fuel gas outlet communication hole.

The inner hole of the oxidant gas inlet 46 a communicates with the supply side of the oxidant gas channel 40 via an oxidant gas inlet communication hole (not shown) that penetrates each power generation cell 24 in the stacking direction. The inner hole of the oxidizing gas outlet 46b communicates with the discharge side of the oxidizing gas flow path 40 via an oxidizing gas outlet communication hole (not shown) penetrating each power generating cell 24 in the stacking direction. A cathode flow path 52 (see FIG. 1) is configured by the oxidizing gas flow path 40, the oxidizing gas inlet communication hole, and the oxidizing gas outlet communication hole.

The inner hole of the cooling medium inlet 48a communicates with the supply side of the cooling medium flow path 42 via a cooling medium inlet communication hole (not shown) penetrating each power generating cell 24 in the stacking direction. The inner hole of the cooling medium outlet 48b communicates with the discharge side of the cooling medium flow path 42 via a cooling medium outlet communication hole (not shown) that penetrates the power generating cells 24 in the stacking direction.

As shown in FIG. 1, the fuel gas supply device 14 supplies fuel gas to the fuel cell 12 . The fuel gas supply device 14 includes a fuel gas supply section 54 and a fuel gas introduction path 56 that guides the fuel gas supplied from the fuel gas supply section 54 to the fuel gas inlet 44a. The fuel gas supply unit 54 includes a fuel gas tank (hydrogen gas tank) (not shown) that stores high-pressure fuel gas (high-pressure hydrogen), a pressure control valve for the fuel gas, and the like.

A fuel gas discharge path 58 is connected to the fuel gas outlet 44b of the fuel cell 12 . The fuel gas discharge path 58 leads from the fuel cell 12 the fuel exhaust gas, which is the fuel gas at least partially used in the anode electrode 34 .

The fuel exhaust gas guided to the fuel gas discharge path 58 may be introduced into the fuel gas supply unit 54 and circulated to the fuel cell 12, or may be diluted with the oxidant exhaust gas and discharged into the atmosphere.

The oxidant gas supply device 16 supplies oxidant gas to the fuel cell 12 . The oxidant gas supply device 16 includes an oxidant gas supply unit 60 and an oxidant gas introduction path 62 that guides the oxidant gas supplied from the oxidant gas supply unit 60 to the oxidant gas inlet 46a. As the oxidant gas supply unit 60, for example, an air pump that compresses and supplies air from the atmosphere is used.

An oxidant gas outlet 46 b of the fuel cell 12 is connected to an oxidant gas discharge path 66 . The oxidizing gas discharge path 66 discharges oxidizing exhaust gas, which is the oxidizing gas at least partially used in the cathode electrode 36, into the atmosphere.

The cooling medium supply device 18 includes a cooling medium supply path 68 , a cooling medium discharge path 70 , a pump 72 for circulating the cooling medium, and a radiator 74 . As the cooling medium, water or a liquid containing ethylene glycol as a main component is used. One end of the cooling medium supply path 68 is connected to the cooling medium inlet 48 a and the other end of the cooling medium supply path 68 is connected to the radiator 74 . One end of the cooling medium discharge path 70 is connected to the cooling medium outlet 48 b and the other end of the cooling medium discharge path 70 is connected to the radiator 74 . A pump 72 is provided in the cooling medium supply path 68 .

The fuel cell system 10 as described above includes a scavenging gas supply unit 76 that supplies scavenging gas for discharging water remaining in the fuel cell 12 . The scavenging gas supply unit 76 distributes the scavenging gas to the reaction gas flow path 78 inside the fuel cell 12 .

The reactant gas channel 78 consists of an anode channel 50 and a cathode channel 52 . In the present embodiment, the scavenging gas supply unit 76 is the oxidant gas supply unit 60 for circulating the oxidant gas as the scavenging gas to the cathode channel 52 . That is, in the fuel cell system 10, the accumulated water in the cathode channel 52 can be discharged by the scavenging gas (oxidant gas).

However, the scavenging gas supply unit 76 may allow the oxidant gas as the scavenging gas to flow through the anode channel 50 . In this case, it is also possible to discharge water remaining in the anode channel 50 by the scavenging gas.

The fuel gas supply unit 54 and the oxidant gas supply unit 60 constitute a reaction gas supply unit that supplies reaction gas (fuel gas and oxidant gas) to the fuel cell 12 .

Signals from various sensors are input to the control unit 22 . These sensors include, for example, a temperature sensor 82, a current/voltage sensor 84 and an ignition switch (hereinafter referred to as "IG switch 86"). A temperature sensor 82 acquires the temperature of the fuel cell 12 . Specifically, the temperature sensor 82 acquires the temperature of the cooling medium flowing through the inner hole of the cooling medium outlet 48b or its vicinity. Thereby, the temperature of the fuel cell 12 can be obtained with high accuracy.

The temperature sensor 82 may acquire the temperature of the fuel gas flowing through or near the inner hole of the fuel gas outlet 44b or the temperature of the oxidizing gas flowing through or near the inner hole of the oxidizing gas outlet 46b. You can get the temperature. A current/voltage sensor 84 detects the generated current and generated voltage of the fuel cell 12 . A signal from an impedance measurement unit 87 that measures the impedance value of the fuel cell 12 is also input to the control unit 22 .

The control unit 22 is a computer including a microcomputer, and has a CPU (Central Processing Unit) and memory such as ROM and RAM. It functions as an implementation unit (function implementation means). It should be noted that the various function realization units can also be configured by a function realization device as hardware.

The control unit 22 has a fuel cell control unit 88 , a warm-up control unit 90 , a temperature determination unit 92 , a scavenging control unit 94 , a power generation determination unit 96 , a special power generation stop processing frequency determination unit 98 , and a scavenging limit determination unit 100 .

The fuel cell control unit 88 controls the driving of each of the fuel gas supply unit 54 and the oxidant gas supply unit 60, and adjusts the flow rate, pressure, etc. of the reaction gas (fuel gas and oxidant gas) guided to the fuel cell 12. do. The warm-up control unit 90 restarts the fuel cell 12 immediately after power generation is stopped, and causes the fuel cell 12 to generate power for a predetermined warm-up time.

The temperature determination unit 92 determines whether the temperature of the fuel cell 12 has become equal to or lower than the scavenging start temperature. The scavenging start temperature is preset and stored in the memory of the controller 22 . The scavenging control unit 94 circulates the scavenging gas from the scavenging gas supply unit 76 to the cathode flow channel 52 (reactant gas flow channel 78) while the fuel cell 12 is in a state where power generation is stopped, thereby discharging water remaining in the fuel cell 12. process.

The power generation determination unit 96 determines whether or not special power generation stop processing of the fuel cell 12 has been performed. The special power generation stop process is a process of stopping power generation immediately after starting power generation of the fuel cell 12 when the temperature is low (when the temperature is below freezing). In other words, the special power generation stopping process is a process of starting the fuel cell 12 for a short time and then stopping it when the temperature is low.

The number-of-times determination unit 98 determines whether or not the special power generation stop processing has been performed a plurality of times (two or more times) in succession. The scavenging limit determination unit 100 determines whether or not the number of consecutive special power generation stop processes is less than the scavenging limit number of times. The scavenging limit number of times is preset and stored in the memory of the controller 22 .

A control method for the fuel cell system 10 configured in this manner will be described below.

As shown in FIG. 3, in step S1, the control unit 22 determines whether or not an OFF signal has been received from the IG switch 86 while the fuel cell 12 is in operation. Step S<b>1 is repeated until control unit 22 receives an off signal from IG switch 86 .

When the control unit 22 receives the OFF signal from the IG switch 86 (step S1: YES), the fuel cell control unit 88 stops the fuel cell 12 in step S2 (see time t1 in FIG. 4). At this time, the fuel cell vehicle is stopped (vehicle speed of the fuel cell vehicle is 0).

Subsequently, in step S3 (power generation determination step), the power generation determination unit 96 determines whether or not the current power generation stop processing was the special power generation stop processing. Specifically, the power generation determination unit 96 performs special power generation stop processing when the temperature of the fuel cell 12 at the start of power generation is lower than a predetermined temperature and power generation is stopped during startup operation of the fuel cell 12. I judge.

In other words, the power generation determination unit 96 determines that the special power generation stop processing is performed when the outside temperature is below freezing when the fuel cell 12 starts power generation and power generation is stopped during startup operation of the fuel cell 12. do. The predetermined temperature is set to 0° C., which is the freezing point at which water generated in the fuel cell 12 freezes. However, the predetermined temperature may be set higher than 0°C.

The power generation determination unit 96 determines whether or not special power generation stop processing is performed based on the temperature of the fuel cell 12 at the start of power generation, the vehicle speed of the fuel cell vehicle, and the current generated by the fuel cell 12 . Specifically, the power generation determination unit 96 determines that the temperature of the fuel cell 12 at the start of power generation is below a predetermined temperature (for example, 0° C.), the vehicle speed at the time of power generation stop is 0, and the power generation current is limited immediately before the power generation is stopped. If so, it is determined to be special power generation stop processing. In other words, the power generation determination unit 96 determines that power generation has been stopped during the startup operation of the fuel cell 12 when power generation is stopped in a state where the generated current is limited.

However, the power generation determining unit 96 may determine that the power generation has been stopped during the start-up operation of the fuel cell 12 when, for example, the integrated power generation amount of the fuel cell 12 is less than the predetermined power generation amount. The integrated power generation amount is the power amount calculated based on the generated current and generated voltage detected by the current/voltage sensor 84 and the elapsed time from the start of power generation to the stop of power generation. Alternatively, the power generation determination unit 96 may determine whether or not power generation has been stopped during startup operation of the fuel cell 12 based only on the elapsed time from the start of power generation of the fuel cell 12 to the stop of power generation.

When the power generation determining unit 96 determines that the special power generation stopping process is not performed (step S3: NO), in step S4, the temperature determining unit 92 determines whether the temperature T of the fuel cell 12 has become equal to or lower than the scavenging start temperature Ta. judge. The scavenging start temperature Ta is set to a temperature higher than 0° C., which is the freezing point at which water generated in the fuel cell 12 freezes. Specifically, the temperature of the fuel cell 12 when the outside air temperature is 0° C. is used as the scavenging start temperature Ta. The scavenging start temperature Ta is preferably set to a temperature higher than 0°C and lower than 5°C. In this case, the scavenging process can be started before the water remaining in the fuel cell 12 freezes.

When the temperature determination unit 92 determines that the temperature T of the fuel cell 12 has become equal to or lower than the scavenging start temperature Ta (step S4: YES), in step S5, the scavenging control unit 94 performs normal scavenging processing (see FIG. 4). See time t2). Specifically, the scavenging control unit 94 circulates the scavenging gas (oxidant gas) from the scavenging gas supply unit 76 (oxidant gas supply unit 60 ) into the cathode flow path 52 of the fuel cell 12 . As a result, the amount of water remaining in the fuel cell 12 is reduced by the scavenging gas, and the next subzero start-up can be carried out satisfactorily (see FIG. 4).

Thereafter, in step S6, control unit 22 determines whether or not an ON signal for IG switch 86 has been received. Step S<b>6 is repeated until control unit 22 receives an ON signal from IG switch 86 .

When the controller 22 receives the ON signal from the IG switch 86 (step S6: YES), the fuel cell controller 88 normally starts the fuel cell 12 in step S7 (see time t3 in FIG. 4). That is, the fuel cell control unit 88 supplies the fuel gas from the fuel gas supply unit 54 to the fuel cell 12 and the oxidant gas from the oxidant gas supply unit 60 to the fuel cell 12, thereby causing the fuel cell 12 to generate power. (activate). This completes a series of operation flows.

If the temperature determination unit 92 determines in step S4 that the temperature T of the fuel cell 12 is higher than the scavenging start temperature Ta (step S4: NO), in step S8, the control unit 22 turns on the IG switch 86. is received. If the controller 22 does not receive the ON signal of the IG switch 86 (step S8: NO), the process of step S4 is performed again. When the control unit 22 receives the ON signal of the IG switch 86 (step S8: YES), normal activation processing is performed in step S7.

In step S3, if the power generation determining unit 96 determines that the special power generation stopping process is performed (step S3: YES), in step S9 (warming step), the warm-up control unit 90 performs warm-up processing for the fuel cell 12. (see time t4 in FIG. 4).

Specifically, the warm-up control unit 90 supplies the fuel gas from the fuel gas supply unit 54 to the fuel cell 12 immediately after the power generation of the fuel cell 12 is stopped, and also supplies the fuel gas from the oxidant gas supply unit 60 to the fuel cell 12 . By supplying the oxidant gas, the fuel cell 12 continues power generation for a predetermined warm-up time. As a result, freezing of water remaining in the fuel cell 12 is suppressed.

In this step S9, the warm-up of the fuel cell 12 is continued until the temperature T of the fuel cell 12 reaches a predetermined warm-up temperature higher than 0.degree. The control unit 22 stops warming up the fuel cell 12 based on the temperature T of the fuel cell 12 acquired by the temperature sensor 82 and the residual water in the fuel cell 12 due to the impedance acquired by the impedance measurement unit 87 .

After that, in step S10 (number of times determination step), the number of times determination unit 98 determines whether or not the number N of consecutive times of special power generation stop processing is two or more. In other words, the number-of-times determining unit 98 determines whether or not the special power generation stopping process has been continuously performed a plurality of times (two times or more).

If the number-of-times determination unit 98 determines that the special power generation stop process is the first time (step S10: NO, see time t5 in FIG. 4), the temperature determination unit 92 determines in step S11 that the temperature T of the fuel cell 12 is It is determined whether or not the scavenging start temperature Ta is reached or not.

When the temperature determining unit 92 determines that the temperature T of the fuel cell 12 is higher than the scavenging start temperature Ta (step S11: NO), in step S12, whether the control unit 22 has received the ON signal of the IG switch 86. determine whether or not When the controller 22 does not receive the ON signal of the IG switch 86 (step S12: NO), the process of step S11 is performed again. When the controller 22 receives the ON signal of the IG switch 86 (step S12: YES), the process of step S7 is performed.

When the temperature determining unit 92 determines that the temperature T of the fuel cell 12 has become equal to or lower than the scavenging start temperature Ta (step S11: YES), scavenging control is performed in step S13 (first special scavenging process step, special scavenging process step). The unit 94 performs a first special scavenging process (special scavenging process) (see time t6 in FIG. 4). Specifically, the scavenging controller 94 increases the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the first special scavenging process more than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the normal scavenging process. The scavenging gas supply unit 76 is controlled as follows.

However, the scavenging controller 94 controls the scavenging gas so that at least one of the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the first special scavenging process is greater than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the normal scavenging process. The supply section 76 may be controlled. That is, the scavenging controller 94 may set any scavenging gas flow rate, scavenging gas pressure, and scavenging time as long as the scavenging degree of the first special scavenging process is higher than the scavenging degree of the normal scavenging process.

By the way, when the low-temperature short-time shutdown process is performed, the amount of water remaining in the fuel cell 12 (particularly, the power generating cell 24 located at the outermost position in the stacking direction) becomes relatively large. The stagnant water includes generated water generated by the power generation reaction of the fuel cell 12 and moisture generated from the atmosphere due to humidification or the like. However, since the scavenging degree of the first special scavenging process is higher than the scavenging degree of the normal scavenging process, the accumulated water in the fuel cell 12 is efficiently discharged by the scavenging gas.

The scavenging control unit 94 preferably controls the scavenging gas supply unit 76 so that the scavenging gas flow rate in the first special scavenging process is 1.2 to 1.5 times the scavenging gas flow rate in the normal scavenging process (Fig. 5). In this case, water remaining in the fuel cell 12 can be discharged more efficiently.

Thereafter, in step S14, control unit 22 determines whether or not an ON signal for IG switch 86 has been received. Step S<b>14 is repeated until control unit 22 receives an ON signal from IG switch 86 .

When the controller 22 receives the ON signal of the IG switch 86 (step S14: YES), in step S15, the fuel cell controller 88 performs the first activation process of the fuel cell 12 (see time t7 in FIG. 4). That is, the fuel cell control unit 88 controls the driving of the oxidant gas supply unit 60 so that the flow rate and pressure of the oxidant gas in the first start-up process are higher than the flow rate and pressure of the oxidant gas in the normal start-up process. . As a result, the pressure and stoichiometric ratio of the oxidant gas are increased, so that water remaining in the cathode channel 52 of the fuel cell 12 is quickly discharged.

In step S15, the fuel cell control unit 88 controls the oxidant gas so that the flow rate and pressure of the oxidant gas and fuel gas in the first start-up process are higher than the flow rate and pressure of the oxidant gas and fuel gas in normal start-up. The driving of the supply unit 60 and the fuel gas supply unit 54 may be controlled. In this case, water remaining in both the cathode channel 52 and the anode channel 50 of the fuel cell 12 is quickly discharged. After that, a series of operation flows ends.

In step S10, if the number-of-times determination unit 98 determines that the special power generation stop process has been performed a plurality of times (two or more times) in succession (step S10: YES, see time t8 in FIG. 4), in step S16, the temperature The determination unit 92 determines whether or not the temperature T of the fuel cell 12 has become equal to or lower than the scavenging start temperature Ta.

When the temperature determination unit 92 determines that the temperature T of the fuel cell 12 is higher than the scavenging start temperature Ta (step S16: NO), in step S17, whether the control unit 22 has received the ON signal of the IG switch 86? determine whether or not When the controller 22 does not receive the ON signal of the IG switch 86 (step S17: NO), the process of step S16 is performed again. When the controller 22 receives the ON signal of the IG switch 86 (step S17: YES), the process of step S7 is performed.

When the temperature determination unit 92 determines that the temperature T of the fuel cell 12 has become equal to or lower than the scavenging start temperature Ta (step S16: YES), in step S18 (scavenging limit determination step), the scavenging limit determination unit 100 performs special power generation. It is determined whether or not the consecutive number N of stop processes is greater than or equal to the scavenging limit number Na. In the present embodiment, the scavenging limit number of times Na is set to three. However, the scavenging limited number of times Na may be set to four times or more.

When the number N of consecutive special power generation stop processes is less than the scavenging limit number Na (step S18: NO), in step S19 (second special scavenging process step, special scavenging process step), the scavenging control unit 94 performs the second A special scavenging process (special scavenging process) is performed (see time t9 in FIG. 4). Specifically, the scavenging controller 94 increases the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the second special scavenging process more than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the first special scavenging process. Thus, the scavenging gas supply unit 76 is controlled. That is, the scavenging controller 94 makes the scavenging degree of the second special scavenging process larger than the scavenging degree of the first special scavenging process.

However, the scavenging control unit 94 is configured such that at least one of the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the second special scavenging process is greater than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the first special scavenging process. The scavenging gas supply section 76 may be controlled. That is, the scavenging controller 94 may set any scavenging gas flow rate, scavenging gas pressure, and scavenging time as long as the scavenging degree of the second special scavenging process is higher than the scavenging degree of the first special scavenging process. do not have.

By the way, when the low-temperature short-term shutdown process is continuously performed a plurality of times, the amount of water retained in the fuel cell 12 (particularly, the power generating cell 24 located at the outermost position in the stacking direction) is the same as the first low-temperature short-time shutdown process. more than time. However, since the scavenging degree of the second special scavenging process is set higher than the scavenging degree of the first special scavenging process, the accumulated water in the fuel cell 12 is efficiently discharged by the scavenging gas.

The scavenging control unit 94 preferably controls the scavenging gas supply unit 76 so that the scavenging gas flow rate in the second special scavenging process is 1.2 to 1.5 times the scavenging gas flow rate in the first special scavenging process. (See Figure 5). In this case, water remaining in the fuel cell 12 can be discharged more efficiently.

Further, for example, when the scavenging limit number of times Na is set to 4 or more and the number of consecutive times N of the special power generation stop processing is 3, the scavenging control unit 94 sets the current (third) second special scavenging The scavenging gas supply unit 76 is set so that the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the process are each greater than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the previous (second) second special scavenging process. to control.

The scavenging controller 94 determines that at least one of the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the second special scavenging process of this time is higher than the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the second special scavenging process of the previous time. The scavenging gas supply section 76 may be controlled to increase. That is, how the scavenging control unit 94 sets the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time when the scavenging degree of the current second special scavenging process is greater than the scavenging degree of the previous second special scavenging process. I don't mind.

By the way, when the low temperature short time shutdown process is performed three times in succession, the fuel cell 12 (especially the outermost power generation cell 24 in the stacking direction) at the time of the low temperature short time shutdown process this time (third time) ) may be larger than the previous (second time) low-temperature short-time shutdown process. Even in such a case, by making the scavenging degree of the current second special scavenging process higher than the scavenging degree of the previous second special scavenging process, the accumulated water in the fuel cell 12 can be efficiently removed by the scavenging gas. can be discharged to

Thereafter, in step S20, control unit 22 determines whether or not an ON signal for IG switch 86 has been received. Step S<b>20 is repeated until control unit 22 receives an ON signal from IG switch 86 .

When the controller 22 receives the ON signal of the IG switch 86 (step S20: YES), in step S21, the fuel cell controller 88 performs the second activation process of the fuel cell 12 (see time t10 in FIG. 4). That is, the fuel cell control unit 88 controls the driving of the oxidant gas supply unit 60 so that the flow rate and pressure of the oxidant gas in the second start-up process are higher than the flow rate and pressure of the oxidant gas in the first start-up process. do. As a result, the pressure and stoichiometric ratio of the oxidant gas are increased, so that water remaining in the cathode channel 52 of the fuel cell 12 is quickly discharged.

In step S21, the fuel cell control unit 88 controls the oxidizing agent so that the flow rate and pressure of the oxidizing gas and fuel gas in the first start-up process are higher than the flow rates and pressures of the oxidizing gas and fuel gas in the first start-up process. The gas supply section 60 and the fuel gas supply section 54 may be controlled. In this case, water remaining in both the cathode channel 52 and the anode channel 50 of the fuel cell 12 is quickly discharged. After that, a series of operation flows ends.

In step S18, if the number N of consecutive special power generation stop processes is greater than or equal to the scavenging limit number of times Na (step S18: YES), in step S22, the scavenging controller 94 performs the same process as the previous second special scavenging process. conduct. That is, as shown in FIG. 5, the scavenging control unit 94 controls the scavenging gas flow rate, the scavenging gas pressure, and the scavenging time in the current second special scavenging process. Make it approximately the same as the scavenging time. In this case, excessive drying of the electrolyte membrane 32 of the fuel cell 12 due to the scavenging gas is suppressed. After that, the processing of steps S20 and S21 is performed, and the series of operation flows ends.

In this case, the fuel cell system 10 according to this embodiment has the following effects.

In the fuel cell system 10, the scavenging controller 94 controls the scavenging degree of the normal scavenging process performed before the power generation determination unit 96 determines that the special power generation stop process is performed. Increase the scavenging degree of the processes (first special scavenging process and second special scavenging process).

In the control method of the fuel cell system 10, when the temperature of the fuel cell 12 at the start of power generation is lower than a predetermined temperature and power generation is stopped during the startup operation of the fuel cell 12, it is determined that special power generation stop processing is performed. and when it is determined in the power generation determination step that the special power generation stop processing is not performed, the scavenging gas is circulated from the scavenging gas supply unit 76 to the reaction gas flow path 78 in the power generation stop state of the fuel cell 12. In the normal scavenging process step of performing the normal scavenging process for discharging stagnant water in the fuel cell 12, and in the power generation determination step if the power generation determination step determines that the special power generation stop process is performed, the scavenging gas supply unit is operated while the power generation of the fuel cell 12 is stopped. a special scavenging process step (a first special scavenging process step and a second special scavenging process step) for discharging stagnant water in the fuel cell 12 by circulating the scavenging gas from 76 to the reaction gas flow path 78; ,I do. In the special scavenging process steps (the first special scavenging process step and the second special scavenging process step), the scavenging degree of the special scavenging process is made larger than the scavenging degree of the normal scavenging process.

In this way, since the scavenging degree of the special scavenging processing (the first special scavenging processing and the second special scavenging processing) is set higher than the scavenging degree of the normal scavenging processing, even if the special power generation stop processing is performed, Also, the amount of water retained in the fuel cell 12 can be effectively reduced. Therefore, it is possible to ensure stable power generation of the fuel cell 12 next time.

The fuel cell system 10 includes a frequency determination unit 98 that determines whether or not the special power generation stop processing determined by the power generation determination unit 96 has been performed a plurality of times in succession. The scavenging control unit 94 determines the scavenging degree of the first special scavenging process performed after the first special power generation stopping process when the number of times determining unit 98 determines that the special power generation stopping process has been performed a plurality of times in succession. The scavenging degree of the second special scavenging process that is performed after the second and later special power generation stop processes is made larger than the scavenging degree.

In the control method of the fuel cell system 10, a number of times determination step is performed to determine whether or not the special power generation stop processing determined by the power generation determination step has been performed a plurality of times in succession. is the first time, the accumulated water in the fuel cell 12 is removed by circulating the scavenging gas from the scavenging gas supply unit 76 to the reaction gas flow path 78 while the power generation of the fuel cell 12 is stopped. and a first special scavenging process step of performing a first special scavenging process to discharge the fuel cell 12, and when it is determined by the number of times determining step that the special power generation stopping process has been continuously performed a plurality of times, the scavenging process is performed while the fuel cell 12 is in a power generation stop state. and a second special scavenging process step of performing a second special scavenging process of discharging stagnant water in the fuel cell 12 by circulating the scavenging gas from the gas supply unit 76 to the reaction gas flow path 78 . In the second special scavenging process step, the scavenging degree of the second special scavenging process is made larger than the scavenging degree of the first special scavenging process.

By the way, when the special power generation stop processing is continuously performed a plurality of times, more water remains in the fuel cell 12 . However, since the scavenging degree of the second special scavenging process is set higher than the scavenging degree of the first special scavenging process, even if the special power generation stop process is continuously performed a plurality of times, can effectively reduce the amount of stagnant water. Therefore, it is possible to ensure stable power generation of the fuel cell 12 next time.

The scavenging controller 94 increases the flow rate of the scavenging gas in the special scavenging process (the first special scavenging process and the second special scavenging process) more than the flow rate of the scavenging gas in the normal scavenging process. According to such a configuration, the scavenging degree of the special scavenging process can be reliably made larger than the scavenging degree of the normal scavenging process.

The power generation determination unit 96 determines that special power generation stop processing is performed when the outside air temperature is below freezing when the fuel cell 12 starts power generation and power generation is stopped during startup operation of the fuel cell 12 .

In this case, a large amount of stagnant water accumulates in the fuel cell 12 when the fuel cell 12 is started at a subzero temperature, but the amount of stagnant water in the fuel cell 12 can be effectively reduced by performing the special scavenging process.

The fuel cell system 10 includes a warm-up control section 90 that restarts the fuel cell 12 to generate power for a predetermined warm-up time when the power generation determination section 96 determines that special power generation stop processing is being performed.

Further, in the control method of the fuel cell system 10, when the power generation determination step determines that special power generation stop processing is performed, the fuel cell 12 is restarted and a warm-up step is performed to generate power for a predetermined warm-up time.

As a result, it is possible to prevent the staying water generated in the fuel cell 12 from freezing.

A scavenging control part 94 does not make the scavenging degree of the current second special scavenging processing larger than the scavenging degree of the previous second special scavenging processing when the special power generation stop processing is continuously performed more than the scavenging limit number of times.

Further, in the control method of the fuel cell system 10, a scavenging limit determination step is performed to determine whether or not the number of times the special power generation stop processing has been continuously performed is equal to or greater than the scavenging limit number of times, and in the second special scavenging processing step , when it is determined in the scavenging limit determination step that the number of times the special power generation stop processing has been continuously performed is equal to or greater than the scavenging limit number of times, the scavenging degree of the current second special scavenging process is changed to that of the previous second special scavenging process. Do not increase the degree of scavenging.

As a result, excessive drying of the interior of the fuel cell 12 due to the scavenging gas can be suppressed.

The scavenging controller 94 increases the scavenging gas pressure and the scavenging time for the special scavenging process (the first special scavenging process and the second special scavenging process) more than the scavenging gas pressure and the scavenging time for the normal scavenging process. According to such a configuration, the scavenging degree of the special scavenging process can be more reliably increased than the scavenging degree of the normal scavenging process.

After the reaction gas supply unit (the fuel gas supply unit 54 and the oxidant gas supply unit 60) that supplies the reaction gas to the fuel cell 12 and the special scavenging process (the first special scavenging process and the second special scavenging process) are performed. The flow rate and pressure of the reaction gas when the fuel cell 12 is first started up are higher than the flow rate and pressure of the reaction gas when the fuel cell 12 is first started after the normal scavenging process. and a fuel cell control unit 88 for controlling the driving of the supply units (the fuel gas supply unit 54 and the oxidant gas supply unit 60). With such a configuration, the pressure and stoichiometric ratio of the reaction gas are increased, so that water remaining in the fuel cell 12 can be rapidly discharged.

The present invention is not limited to the configurations and methods described above. The scavenging gas supply unit 76 may be provided separately from the oxidant gas supply unit 60 .

The present invention is not limited to the above-described embodiments, and can of course adopt various configurations without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10... Fuel cell system 12... Fuel cell 50... Anode flow path 52... Cathode flow path 76... Scavenging gas supply part 78... Reaction gas flow path 90... Warm-up control part 94... Scavenging control part 96... Power generation determination part

Claims (13)

a fuel cell that generates electricity through an electrochemical reaction of reactant gases;
a scavenging gas supply unit for circulating the scavenging gas in the reactant gas flow path in the fuel cell;
When the temperature of the fuel cell is lower than the scavenging start temperature, the scavenging gas is caused to flow from the scavenging gas supply unit to the reaction gas flow path while the fuel cell is in a state of stopping power generation, thereby removing water remaining in the fuel cell. a scavenging control unit that performs a scavenging process for discharging the
a power generation determination unit that determines that special power generation stop processing is performed when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during start-up operation of the fuel cell;
with
The scavenging control unit adjusts the scavenging degree of the special scavenging process performed after the special scavenging process is determined to be performed before the special scavenging process is determined to be the special power generation stop process by the power generation determination part. fuel cell system. a fuel cell that generates electricity through an electrochemical reaction of reactant gases;
a scavenging gas supply unit for circulating the scavenging gas in the reactant gas flow path in the fuel cell;
When the temperature of the fuel cell is lower than the scavenging start temperature, the scavenging gas is caused to flow from the scavenging gas supply unit to the reaction gas flow path while the fuel cell is in a state of stopping power generation, thereby removing water remaining in the fuel cell. a scavenging control unit that performs a scavenging process for discharging the
a power generation determination unit that determines that special power generation stop processing is performed when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during start-up operation of the fuel cell;
a frequency determination unit that determines whether or not the special power generation stop processing determined by the power generation determination unit has been performed a plurality of times in succession ;
with
The scavenging control unit adjusts the scavenging degree of the special scavenging process performed after the special scavenging process is determined to be performed before the special scavenging process is determined to be the special power generation stop process by the power generation determination part. is increased, and the scavenging degree of the first special scavenging process performed after the first special power generation stop process is performed when the number of times determining unit determines that the special power generation stop process has been performed a plurality of times in succession. a second special scavenging process performed after the special power generation stop process for a second time or later than the second special scavenging process. 3. The fuel cell system according to claim 1 or 2,
The scavenging control unit increases the flow rate of the scavenging gas in the special scavenging process more than the flow rate of the scavenging gas in the normal scavenging process. The fuel cell system according to any one of claims 1 to 3,
The power generation determination unit determines that the special power generation stop processing is performed when an outside air temperature is below freezing when the fuel cell starts to generate power, and power generation is stopped during start-up operation of the fuel cell. battery system. The fuel cell system according to any one of claims 1 to 4,
A fuel cell system, comprising: a warm-up control unit that restarts the fuel cell to generate power for a predetermined warm-up time when the power generation determination unit determines that the special power generation stop processing is performed. 3. The fuel cell system according to claim 2,
The scavenging control unit sets the scavenging degree of the current second special scavenging process higher than the scavenging degree of the previous second special scavenging process when the special power generation stop processing is continuously performed more than the scavenging limit number of times. A fuel cell system that doesn't make it big. The fuel cell system according to any one of claims 1 to 5,
The scavenging controller increases the scavenging gas pressure and scavenging time in the special scavenging process more than the scavenging gas pressure and scavenging time in the normal scavenging process. The fuel cell system according to any one of claims 1 to 7,
a reactant gas supply unit that supplies a reactant gas to the fuel cell;
The flow rate and pressure of the reaction gas at the first start-up of the fuel cell after the special scavenging process is performed is the flow rate and pressure of the reaction gas at the first start-up of the fuel cell after the normal scavenging process. and a fuel cell control section that controls driving of the reaction gas supply section so that the pressure increases more than the pressure. A control method for a fuel cell system comprising: a fuel cell that generates electric power through an electrochemical reaction of reactant gases; and a scavenging gas supply section for circulating the scavenging gas in a reactant gas flow path in the fuel cell, the method comprising:
a power generation determination step of determining that special power generation stop processing is performed when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during startup operation of the fuel cell;
When it is determined by the power generation determination step that the special power generation stop processing is not performed, the scavenging gas is circulated from the scavenging gas supply unit to the reaction gas flow path while the power generation of the fuel cell is stopped, thereby causing the scavenging gas to remain in the fuel cell. a normal scavenging process step of performing normal scavenging process of discharging water;
When it is determined by the power generation determining step that the special power generation stopping process is performed, the scavenging gas is allowed to flow from the scavenging gas supply unit to the reaction gas flow path while the power generation of the fuel cell is stopped, thereby causing the scavenging gas to remain in the fuel cell. a special scavenging process step of performing a special scavenging process for discharging water;
In the special scavenging process step, the scavenging degree of the special scavenging process is made larger than the scavenging level of the normal scavenging process. A control method for a fuel cell system comprising: a fuel cell that generates electric power through an electrochemical reaction of reactant gases; and a scavenging gas supply section for circulating the scavenging gas in a reactant gas flow path in the fuel cell, the method comprising:
a power generation determination step of determining that special power generation stop processing is performed when the temperature of the fuel cell at the start of power generation is lower than a predetermined temperature and power generation is stopped during startup operation of the fuel cell;
When it is determined by the power generation determination step that the special power generation stop processing is not performed, the scavenging gas is circulated from the scavenging gas supply unit to the reaction gas flow path while the power generation of the fuel cell is stopped, thereby causing the scavenging gas to remain in the fuel cell. a normal scavenging process step of performing normal scavenging process of discharging water;
When it is determined by the power generation determining step that the special power generation stopping process is performed, the scavenging gas is allowed to flow from the scavenging gas supply unit to the reaction gas flow path while the power generation of the fuel cell is stopped, thereby causing the scavenging gas to remain in the fuel cell. a special scavenging process step of performing a special scavenging process for discharging water;
a number-of-times determination step of determining whether or not the special power generation stop processing determined by the power generation determination step has been continuously performed a plurality of times ;
and
In the special scavenging process step, the scavenging degree of the special scavenging process is made larger than the scavenging level of the normal scavenging process,
The special scavenging process step includes:
When it is determined by the number-of-time determination step that the special power generation stop processing is the first time, the scavenging gas is circulated from the scavenging gas supply unit to the reaction gas flow path in the power generation stop state of the fuel cell. a first special scavenging process step of performing a first special scavenging process for discharging stagnant water in the
By circulating the scavenging gas from the scavenging gas supply unit to the reaction gas flow path in the power generation stop state of the fuel cell when it is determined by the number of times determination step that the special power generation stop processing has been continuously performed a plurality of times a second special scavenging process step of performing a second special scavenging process for discharging stagnant water in the fuel cell;
In the second special scavenging process step, the scavenging degree of the second special scavenging process is made larger than the scavenging level of the first special scavenging process. A control method for a fuel cell system according to claim 9 or 10,
A control method for a fuel cell system, wherein when the power generation determination step determines that the special power generation stop processing is performed, a warm-up step is performed to restart the fuel cell and generate power for a predetermined warm-up time. A control method for a fuel cell system according to claim 10,
performing a scavenging limit determination step of determining whether or not the number of times the special power generation stop processing has been continuously performed is equal to or greater than the scavenging limit number of times;
In the second special scavenging process step, when it is determined in the scavenging limit determination step that the number of times the special power generation stop process has been continuously performed is equal to or greater than the scavenging limit number of times, the current second special scavenging process is performed. A method of controlling a fuel cell system, wherein the degree of scavenging is not made larger than the degree of scavenging of the previous second special scavenging process. A control method for a fuel cell system according to any one of claims 9 to 12,
The flow rate and pressure of the reaction gas at the first start-up of the fuel cell after the special scavenging process is performed, and A control method for a fuel cell system that increases pressure.

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