JP2012169039A - Fuel cell system - Google Patents

Abstract

A fuel cell system capable of scavenging in a short time is provided.
A fuel cell stack, a fuel gas supply flow path, a fuel off-gas discharge flow path, an oxidant gas supply flow path, an oxidant off-gas discharge flow path, a compressor 31 and a compressor 31 can be operated simultaneously. , The first scavenging gas passage through which the scavenging gas from the compressor 31 toward the anode passage 11 flows, and the second scavenging gas through which the scavenging gas from the cathode passage 12 toward the expander 35 flows. A check valve 39 provided upstream of the cathode channel 12 and opened when the cathode channel 12 is scavenged to introduce outside air as a scavenging gas; an ECU 70 that controls the compressor 31 and the expander 35; Is provided. When scavenging the fuel cell stack 10, the ECU 70 simultaneously operates the compressor 31 and the expander 35, the compressor 31 scavenges the anode channel 11, and the expander 35 scavenges the cathode channel 12.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system.

  In recent years, the development of fuel cells that generate electricity by supplying hydrogen (fuel gas) and oxygen-containing air (oxidant gas) has been promoted. For example, it is expected as a power source for fuel cell vehicles (moving bodies). Yes. Note that hydrogen is supplied from a hydrogen tank or the like to the anode of the fuel cell, and air is supplied from a compressor (compressor) to the cathode of the fuel cell (see, for example, Patent Document 1).

JP 7-14599 A

  By the way, the fuel cell generates water (water vapor) at its cathode as power is generated. Moreover, in order to make the electrolyte membrane (solid polymer membrane) of MEA (Membrane Electrode Assembly) constituting the fuel cell into a good wet state, for example, the air toward the cathode is humidified by a humidifier. Therefore, immediately after the power generation of the fuel cell is stopped, moisture (water vapor, condensed water) stays in the fuel cell. Therefore, there is a possibility that the fuel cell freezes when the fuel cell becomes low temperature (such as 0 ° C. or less) after power generation is stopped.

  Therefore, when it is determined that the fuel cell may freeze after power generation is stopped, a technique for scavenging the fuel cell, that is, a scavenging gas (air, nitrogen, etc.) is passed through the fuel cell, and the scavenging gas is used to drive the fuel cell. A technique for removing water from the water has been proposed. However, when the scavenging (anode scavenging) of the anode flow path (fuel gas flow path) of the fuel cell and the scavenging (cathodic scavenging) of the cathode flow path (oxidant gas flow path) of the fuel cell are executed separately, the fuel Battery scavenging takes a long time.

  Therefore, an object of the present invention is to provide a fuel cell system capable of scavenging the fuel cell in a short time.

  As means for solving the above problems, the present invention has a fuel gas flow path and an oxidant gas flow path, wherein the fuel gas flow path is fuel gas, and the oxidant gas flow path is oxidant gas. A fuel cell that generates electricity by being supplied; a fuel gas supply channel through which fuel gas flows toward the fuel gas channel; and a fuel off-gas exhaust stream through which fuel off-gas discharged from the fuel gas channel flows An oxidant gas supply channel through which an oxidant gas directed to the oxidant gas channel flows, and an oxidant offgas discharge channel through which oxidant offgas discharged from the oxidant gas channel flows. A compressor that is provided in the oxidant gas supply flow path and that supplies the oxidant gas toward the oxidant gas flow path; and is provided in the oxidant off-gas discharge flow path and is operable simultaneously with the compressor. And upstream by operating And a compressor connected to one of the fuel gas flow path and the oxidant gas flow path, and the scavenging gas flowing from the compressor to the one side flows during the scavenging of the one side. The first scavenging gas flow path, the other of the fuel gas flow path and the oxidant gas flow path, and the suction device are connected, and during the other scavenging, the scavenging gas from the other to the suction device passes. A second scavenging gas flow channel that flows, and an outdoor air introduction valve that is provided upstream of the other of the fuel gas flow channel and the oxidant gas flow channel, and that opens at the time of the other scavenging, thereby introducing outside air as a scavenging gas. Control means for controlling the compressor and the suction machine, and during the scavenging of the fuel cell, the control means simultaneously operates the compressor and the suction machine, and the compressor moves the fuel gas Scavenging one of the flow path and the oxidant gas flow path The suction device is a fuel cell system, characterized in that scavenging the other of said fuel gas passage and the oxidant gas flow passage.

  According to such a configuration, when scavenging the fuel cell, the control means simultaneously operates the compressor and the suction machine, the compressor scavenges one of the fuel gas flow path and the oxidant gas flow path, and the suction machine The other of the fuel gas channel and the oxidant gas channel is scavenged. That is, anode scavenging (scavenging of the fuel gas flow path) and cathode scavenging (scavenging of the oxidant gas flow path) are performed simultaneously. Thereby, the fuel cell can be scavenged in a short time.

  Further, in the fuel cell system, the suction device is an expander that expands an oxidant off-gas during power generation of the fuel cell, and is provided in the oxidant off-gas flow path downstream of the expander to supply water. It is preferable that the apparatus includes: a water recovery unit that recovers; and a water injection unit that injects the water recovered by the water recovery unit into the oxidant gas flowing through the oxidant gas supply channel.

According to such a configuration, the expander expands the oxidant offgas (adiabatic mechanical expansion) during power generation of the fuel cell, so that the temperature of the oxidant offgas decreases, the amount of saturated water vapor decreases, and the saturated water vapor pressure decreases. Decreases. Thereby, in the oxidant off-gas after expansion, water vapor contained therein is condensed and condensed water is generated. Next, the water recovery means recovers water (condensed water), and the water injection means injects the water recovered by the water recovery means into the oxidant gas flowing through the oxidant gas supply channel.
Therefore, the humidifier which humidifies the oxidant gas toward the oxidant gas flow path can be downsized or omitted. Therefore, the overall configuration of the fuel cell system is also reduced in size, and the degree of freedom in layout is ensured.

  In the fuel cell system, the outside air introduction valve is preferably a check valve.

  According to such a configuration, the outside air introduction valve can be easily configured with a low-cost and lightweight check valve.

  In the fuel cell system, the first scavenging gas flow path connects the fuel gas flow path and the compressor, and the second scavenging gas flow path includes the oxidant gas flow path and the suction machine. It is preferable that when the fuel cell is scavenged, the compressor scavenges the fuel gas passage, and the suction device scavenges the oxidant gas passage.

  According to such a configuration, the fuel gas channel can be scavenged by the compressor, and the oxidant gas channel can be scavenged by the suction device.

  Further, in the fuel cell system, the oxidant gas flow path is provided in the oxidant gas supply flow path between the oxidant gas flow path and the compressor, and from the compressor to the oxidant gas flow path when scavenging the fuel cell. It is preferable to provide a shutoff valve for shutting off the scavenging gas.

According to such a configuration, during the scavenging of the fuel cell, the scavenging gas from the compressor to the oxidant gas flow path can be shut off by the shutoff valve. That is, scavenging gas that should go from the compressor to the fuel gas flow path is not supplied to the oxidant gas flow path.
In addition, when the outside air introduction valve is a check valve, the shut-off valve is connected to the check valve at a position where the check valve is connected in the oxidant gas supply flow path so that the check valve is quickly opened by the operation of a suction machine. Is also preferably provided upstream (see FIG. 1).

  In the fuel cell system, the first scavenging gas flow path connects the oxidant gas flow path and the compressor, and the second scavenging gas flow path includes the fuel gas flow path and the suction device. It is preferable that when the fuel cell is scavenged, the compressor scavenges the oxidant gas flow path, and the suction device scavenges the fuel gas flow path.

  According to such a configuration, the oxidant gas flow path can be scavenged by the compressor, and the fuel gas flow path can be scavenged by the suction machine.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can scavenge a fuel cell in a short time can be provided.

1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 1st Embodiment. In the fuel cell system according to the first embodiment, the flow path of the scavenging gas during scavenging is indicated by a bold line. It is a block diagram of the fuel cell system which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on 2nd Embodiment. In the fuel cell system according to the second embodiment, the flow path of the scavenging gas during scavenging is indicated by a bold line.

<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to the first embodiment shown in FIG. 1 is mounted on a fuel cell vehicle (moving body) (not shown). The fuel cell system 1 includes a fuel cell stack 10 (fuel cell), an anode system that supplies and discharges hydrogen (fuel gas) to and from the anode of the fuel cell stack 10, and oxygen to the cathode of the fuel cell stack 10. A cathode system that supplies and discharges air (oxidant gas), a refrigerant system that circulates (circulates) the refrigerant so as to pass through the fuel cell stack 10, and an output terminal (not shown) of the fuel cell stack 10; A power consumption system that consumes the generated power of the fuel cell stack 10 and an ECU 70 (Electronic Control Unit) that is a control means for electronically controlling these are provided.
In addition, the specific kind of fuel gas and oxidant gas is not limited to this.

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (eg, 200 to 400) solid polymer type single cells, and the plurality of single cells are connected in series. The single cell includes an MEA (Membrane Electrode Assembly) and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane or the like, and an anode and a cathode (electrode) that sandwich the membrane.

  The anode and the cathode include a porous body having conductivity such as carbon paper, and a catalyst (Pt, Ru, etc.) supported on the anode and causing an electrode reaction in the anode and the cathode.

  Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA, and through holes for supplying and discharging hydrogen or air to all single cells. It functions as a channel 11 (fuel gas channel) and a cathode channel 12 (oxidant gas channel).

  When hydrogen is supplied to each anode via the anode flow path 11, the electrode reaction of Formula (1) occurs, and when air is supplied to each cathode via the cathode flow path 12, Formula (2) Thus, a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell. Next, the fuel cell stack 10 and an external load such as a motor 51 described later are electrically connected, and when the current is taken out, the fuel cell stack 10 generates power.

2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

  When the fuel cell stack 10 generates power in this way, moisture (water vapor) is generated at the cathode, and the cathode off-gas discharged from the cathode channel 12 becomes humid.

  Each separator is formed with grooves and through holes for allowing a refrigerant for cooling each single cell to flow therethrough, and these grooves and the through holes function as the refrigerant flow path 13.

<Anode system>
The anode system includes a hydrogen tank 21 (fuel gas supply means), a normally closed shut-off valve 22, an ejector 23, a normally closed purge valve 24, and a normally closed scavenging gas discharge valve 25. Yes.

The hydrogen tank 21 is connected to the inlet of the anode channel 11 through a pipe 21a, a shutoff valve 22, a pipe 22a, an ejector 23, and a pipe 23a. When the shutoff valve 22 is opened by the ECU 70, the hydrogen in the hydrogen tank 21 is supplied to the anode flow path 11 through the pipe 21a and the like.
The ejector 23 generates a negative pressure by injecting hydrogen from the hydrogen tank 21 with a nozzle, and sucks the anode off gas of the pipe 23b by this negative pressure. The piping 22a is provided with a pressure reducing valve (regulator, not shown) for reducing the hydrogen from the hydrogen tank 21 to a predetermined pressure.

  Therefore, the fuel gas supply channel through which hydrogen flows toward the anode channel 11 includes the pipe 21a, the pipe 22a, and the pipe 23a.

The outlet of the anode channel 11 is connected to the intake port of the ejector 23 via a pipe 23b (fuel off gas discharge channel). The anode off gas (fuel off gas) discharged from the anode flow path 11 passes through the pipe 23b toward the ejector 23, and the anode off gas (hydrogen) is circulated.
The anode off gas contains hydrogen that has not been consumed by the electrode reaction at the anode and water vapor. The pipe 23b is provided with a gas-liquid separator (not shown) that separates and collects moisture (condensed water (liquid) and water vapor (gas)) contained in the anode off gas.

The middle of the pipe 23b is connected to a diluter 36 which will be described later via a pipe 24a, a purge valve 24, and a pipe 24b. Then, when the purge valve 24 is opened by the ECU 70, the anode off gas containing moisture (water vapor) is discharged to the diluter 36 through the pipe 24a and the pipe 24b so that the power generation performance of the fuel cell stack 10 is restored. It has become.
The ECU 70 determines that the purge valve 24 needs to be opened, for example, when the lowest voltage (minimum cell voltage) among the voltages of the single cells constituting the fuel cell stack 10 is equal to or lower than a predetermined single cell voltage. It is set to be.

  The middle of the pipe 23b is connected to a pipe 35b described later via the pipe 25a, the scavenging gas discharge valve 25, and the pipe 25b. The scavenging gas discharge valve 25 is opened by the ECU 70 together with the scavenging gas introduction valve 38 described later when scavenging the anode flow path 11 (fuel cell stack 10).

<Cathode system>
The cathode system includes a compressor 31 (compressor), a humidifier 32, a normally closed first sealing valve 33 (shutoff valve), a normally closed second sealing valve 34, and an expander 35 (suction). Machine, expansion means), a diluter 36, a water recovery device 37 (water recovery means), a normally closed scavenging gas introduction valve 38, and a check valve 39.

The intake port of the compressor 31 communicates with the outside of the vehicle (external) via the pipe 31a. The discharge port of the compressor 31 is connected to the inlet of the cathode flow path 12 through the pipe 31b, the humidifier 32, the pipe 33a, the first sealing valve 33, and the pipe 33b.
When the impeller of the compressor 31 rotates, the compressor 31 sucks and compresses air outside the vehicle via the pipe 31a, and the compressed air is pumped to the cathode channel 12 through the pipe 31b and the like. It is like that.
Therefore, the oxidant gas supply channel through which the air supplied through the cathode channel 12 flows is configured to include the piping 31a, the piping 31b, the piping 33a, and the piping 33b.

  Further, the compressor functions as a scavenging gas supply means when scavenging the fuel cell stack 10 and discharges the intake air as scavenging gas. In the first embodiment, the scavenging gas is configured to go to the anode channel 11 (see FIG. 3). In the second embodiment to be described later, the scavenged gas is configured to go to the cathode channel 12. (See FIG. 6).

Furthermore, the impeller of the compressor 31 is connected to the impeller (rotary body) of the expander 35 via a transmission shaft 31c so that power can be transmitted to each other. Thereby, the compressor 31 and the expander 35 operate | move simultaneously.
Alternatively, the transmission shaft 31c may be provided with a clutch that is controlled by the ECU 70 to be ON (connected) / OFF (not connected). Further, the transmission shaft 31c may be provided with a speed reduction mechanism.

Furthermore, a motor 31d (drive device) that is a power source for the compressor 31 and the expander 35 and whose rotation speed is controlled by the ECU 70 is attached to the compressor 31. That is, when the motor 31d is operated, the compressor 31 and the expander 35 are operated simultaneously (in parallel). When the rotational speed of the motor 31d increases, the rotational speed of the impeller of the compressor 31 increases, and the air discharge pressure of the compressor 31 increases.
The motor 31d uses the fuel cell stack 10 and / or a high voltage battery (not shown) as a power source.

  An orifice 31e is provided in the pipe 31a. Thereby, the flow velocity of the air sucked into the compressor 31 is increased by the orifice 31e, and a negative pressure is generated in the pipe 31a downstream of the orifice 31e.

  The pipe 31a is connected to the water recovery unit 37 via the pipe 31f. Thereby, the water of the water recovery device 37 is sucked by the negative pressure, and is injected into the air toward the compressor 31 through the pipe 31a, so that the air is humidified. Since air containing water (mist) is sucked into the compressor 31 in this way, the clearance between the impeller constituting the compressor 31 and its housing is sealed by the water (mist), and air leakage in the compressor 31 is prevented. Has been reduced.

Therefore, the water injection means for injecting the water recovered by the water recovery device 37 into the air flowing through the pipe 31a (oxidant gas supply flow path) includes the orifice 31e and the pipe 31f.
However, the specific configuration of the water injection unit is not limited to this, and for example, a configuration in which an electric pump is provided in the pipe 31f and the water in the water recovery unit 37 is injected into the pipe 31a by appropriately operating the electric pump. It is good. Moreover, it is good also as a structure which attaches an injector to the piping 31a and controls the injection quantity of water with high precision.

  The humidifier 32 includes a plurality of hollow fiber membranes 32a having moisture permeability. Then, the humidifier 32 exchanges moisture between the air toward the cathode channel 12 and the humid cathode offgas discharged from the cathode channel 12 via the hollow fiber membrane 32a, and humidifies the air toward the cathode channel 12 It is supposed to be.

At the outlet of the cathode channel 12, a pipe 34a, a second sealing valve 34, a pipe 34b, a humidifier 32, a pipe 35a, an expander 35, a pipe 35b, a diluter 36, a pipe 36a, a water recovery unit 37, and a pipe 37a are provided. Is connected. The cathode off gas (oxidant off gas) discharged from the cathode channel 12 is discharged outside the vehicle through the pipe 34a and the like.
Therefore, the oxidant off-gas discharge flow path through which the cathode off-gas discharged from the cathode flow path 12 is configured includes the pipe 34a, the pipe 34b, the pipe 35a, the pipe 35b, the pipe 36a, and the pipe 37a.

  The first sealing valve 33 and the second sealing valve 34 are closed when the fuel cell system 1 is stopped, thereby shutting off the cathode flow path 12 and the outside of the vehicle (external) and sealing the cathode flow path 12. It is. Thereby, when the fuel cell system 1 is stopped, the air outside the vehicle does not enter the cathode flow path 12 anew, and the deterioration of the fuel cell stack 10 is prevented. In addition, when air newly enters, there is a possibility that the cathode electrode reaction proceeds and the cathode deteriorates.

  Further, the first sealing valve 33 is disposed upstream of the pipe 33 b to which the check valve 39 is connected, and is closed when the fuel cell stack 10 is scavenged. As a result, during scavenging of the fuel cell stack 10, the scavenging gas from the compressor 31 is blocked by the first sealing valve 33, and the pressure in the pipe 33 b downstream of the first sealing valve 33 is accompanied by the operation of the expander 35. The check valve 39 opens quickly.

  The expander 35 includes an impeller (rotary body, turbine blade) therein, and the impeller rotates with a cathode off gas from a pipe 35a. As a result, the fluid energy of the flowing cathode off-gas is converted and recovered into rotational energy in the expander 35, while the cathode off-gas expands in volume (adiabatic mechanical expansion), and the pressure decreases. The rotational energy recovered by the expander 35 is transmitted to the compressor 31 through the transmission shaft 31c.

  In addition, the cathode off-gas releases heat as the volume of the expander 35 expands, the temperature decreases, the saturated water vapor amount and dew point decrease, the water vapor contained in the cathode off-gas condenses, and condensed water is generated. ing.

  Here, when the pressure of the air flowing through the cathode channel 12 (target air pressure) increases, the rotational speed (regenerative energy) of the expander 35 increases and the differential pressure across the expander 35 increases. Condensed water (g / min) downstream of the expander 35 tends to increase. The condensed water generated in this way passes through the diluter 36 and is collected and stored by the water recovery unit 37. Note that the pressure downstream of the expander 35 is approximately atmospheric pressure.

  Further, the expander 35 operates simultaneously with the compressor 31 during scavenging of the fuel cell stack 10, and as described later, together with the scavenging gas introduced (sucked) through the check valve 39, the expander 35. It functions as an aspirator that sucks the moisture remaining in the water.

  Therefore, the second scavenging gas flow path, which connects the cathode flow path 12 and the expander 35 and through which the scavenging gas from the cathode flow path 12 toward the expander 35 flows when the cathode flow path 12 is scavenged, includes the pipe 34a, A pipe 34b and a pipe 35a are provided.

  The diluter 36 is a container that mixes the anode off-gas from the pipe 24b and the cathode off-gas (dilution gas) from the pipe 35b, and dilutes the hydrogen in the anode off-gas with the cathode off-gas. It has. Further, when the cathode off gas flows into the diluter 36, the temperature decrease due to the expansion and heat dissipation of the cathode off gas further proceeds, and the generation of condensed water proceeds.

  The water recovery unit 37 recovers water (condensed water) accompanying the cathode off gas and temporarily stores it. The recovered water is temporarily stored in a tank part that forms the bottom of the water recovery unit 37.

  The middle of the pipe 31b is connected to the pipe 23a via the pipe 38a, the scavenging gas introduction valve 38, and the pipe 38b. The scavenging gas introduction valve 38 is opened by the ECU 70 together with the scavenging gas discharge valve 25 described above when scavenging the anode flow path 11 (fuel cell stack 10).

  Therefore, the first scavenging gas flow path that connects the anode flow path 11 and the compressor 31 and through which the scavenging gas from the compressor 31 toward the anode flow path 11 flows during the scavenging of the anode flow path 11 is the piping 31b and the piping 38a. The pipe 38b and the pipe 23a are provided.

In the middle of the pipe 33b, a pipe 39b, a check valve 39, and a pipe 39a whose upstream end is open to the outside of the vehicle are connected. The check valve 39 is a one-way valve that allows an air flow only from the pipe 39a to the pipe 39b. When the expander 35 operates (rotates) in the closed state of the first sealing valve 33 and the open state of the second sealing valve 34 when scavenging the cathode flow path 12, a negative pressure is generated in the pipe 39b. That is, the pressure in the pipe 39b is lowered, whereby the check valve 39 is opened and air outside the vehicle is taken in as scavenging gas (see FIG. 3).
Note that when the fuel cell stack 10 generates power, air having a pressure higher than that of the outside air flows through the pipe 33b, so that the check valve 39 does not open.

That is, the check valve 39 is provided upstream of the cathode channel 12 and functions as an outside air introduction valve that introduces outside air as a scavenging gas by opening when the cathode channel 12 is scavenged.
Since such a check valve 39 has a simple structure and is lightweight and low in cost, the cost required for the system configuration is reduced, and the weight of the system is reduced.
However, the specific configuration of the outside air introduction valve is not limited to the check valve 39, and may be a normally closed electromagnetic valve that is opened when the cathode channel 12 is scavenged.

<Refrigerant system>
The refrigerant system includes a pump 41, a radiator 42 (heat radiator), and a temperature sensor 43 (temperature detection means).

  The discharge port of the pump 41 is connected to the suction port of the pump 41 through the pipe 41a, the refrigerant flow path 13, the pipe 42a, the radiator 42, and the pipe 42b in this order. Then, when the pump 41 is operated in accordance with a command from the ECU 70, the refrigerant circulates between the refrigerant flow path 13 and the radiator 42, the fuel cell stack 10 is appropriately cooled, does not overheat, and has a suitable power generation temperature (80 ~ 100 ° C).

The temperature sensor 43 is attached to the pipe 42 a, detects the temperature of the refrigerant immediately after being discharged from the refrigerant flow path 13 as the temperature of the fuel cell stack 10, and outputs it to the ECU 70.
However, the position of the temperature sensor 43 that detects the temperature of the fuel cell stack 10 is not limited to this. For example, the fuel cell stack 10 itself, the pipe 23a, the pipe 23b, the pipe 33b, and the pipe 34a may be attached. . Moreover, the structure provided with a some temperature sensor may be sufficient.

<Power consumption system>
The power consumption system includes a motor 51 (load) and a power controller 52. The motor 51 is connected to the output terminal of the fuel cell stack 10 via the power controller 52.

The motor 51 is a traveling electric motor that is a power source of the fuel cell vehicle.
The power controller 52 controls the generated power (output current, output voltage) of the fuel cell stack 10 in accordance with a command from the ECU 70, and incorporates electronic circuits such as a DC / DC chopper and a DC / DC converter. .

<Accelerator>
The IG 61 is a start switch of the fuel cell system 1 (fuel cell vehicle) and is arranged around the driver's seat. The IG 61 outputs the ON / OFF signal to the ECU 70.

<ECU>
The ECU 70 is a control device that electronically controls the fuel cell system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and exhibits various functions according to programs stored therein. In addition, various devices such as the compressor 31 are controlled. Specific control processing contents will be described later.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 1 will be described with reference to FIGS.
Note that hydrogen is supplied to the anode flow path 11 and air is supplied to the cathode flow path 12, and the ECU 70 controls the power controller 52 based on the accelerator opening (required power generation amount), and the fuel cell stack 10 Is generating electricity. When the IG 61 is turned off, the ECU 70 that has detected the OFF signal starts the processing of FIG.

  In step S101, the ECU 70 controls the power controller 52 to stop the power generation of the fuel cell stack 10. In addition, the ECU 70 closes the shut-off valve 22 to stop the supply of hydrogen, stops the compressor 31 and stops the supply of air. Further, the ECU 70 closes the first sealing valve 33 and the second sealing valve 34 to seal (block) the cathode flow path 12 so that air does not newly flow into the cathode flow path 12 from the outside of the vehicle.

  In step S102, the ECU 70 determines whether or not the fuel cell stack 10 needs to be scavenged. The scavenging of the fuel cell stack 10 is to push out water (water vapor, condensed water) in the fuel cell stack 10 with the scavenging gas.

  Specifically, for example, when the temperature of the fuel cell stack 10 detected via the temperature sensor 43 is equal to or lower than a predetermined temperature (for example, 0 to 5 ° C.) at which scavenging is to be performed, Therefore, it is determined that the fuel cell stack 10 needs to be scavenged. However, the specific determination method is not limited to this.

  When it is determined that the fuel cell stack 10 needs to be scavenged (S102 / Yes), the processing of the ECU 70 proceeds to step S106. On the other hand, when it is determined that it is not necessary to scavenge the fuel cell stack 10 (S102, No), the process of the ECU 70 proceeds to step S103.

In step S103, the ECU 70 determines whether or not a predetermined time (for example, 30 minutes to 1 hour) has elapsed since the determination of No in step S102.
When it is determined that the predetermined time has elapsed (S103 / Yes), the process of the ECU 70 proceeds to step S102. On the other hand, when it determines with predetermined time not having passed (S103 * No), the process of ECU70 progresses to step S104.

In step S104, the ECU 70 determines whether the IG 61 is turned on.
When it is determined that the IG 61 is turned on (S104 / Yes), the processing of the ECU 70 proceeds to step S105. On the other hand, when it is determined that the IG 61 is not turned on (S104, No), the processing of the ECU 70 proceeds to step S103.
Thus, since the determination process in step S102 is repeated every time the predetermined time elapses (S103 / No) while the IG 61 is OFF (S104 / No), the fuel cell stack 10 is prevented from freezing.

  In step S105, the ECU 70 activates the fuel cell system 1. Specifically, hydrogen and air are supplied to the fuel cell stack 10 and power generation of the fuel cell stack 10 is started.

  In step S106, the ECU 70 opens the second sealing valve 34, the scavenging gas introduction valve 38, and the scavenging gas discharge valve 25 in order to scavenge the fuel cell stack 10.

  In step S107, the ECU 70 drives the motor 31d to operate the compressor 31 and the expander 35 at the same time, and performs anode scavenging (scavenging of the anode channel 11) and cathode scavenging (scavenging of the cathode channel 12). Are executed at the same time.

  Specifically, as shown in FIG. 3, the compressor 31 sucks air outside the vehicle and discharges it as scavenging gas. Then, this scavenging gas is pushed into the anode channel 11 through the pipe 31b, the pipe 38a, the pipe 38b, and the pipe 23a, and pushes out moisture (water vapor, condensed water) that stays in the anode channel 11. The extruded moisture is discharged out of the vehicle together with the scavenging gas through the pipe 23b, the pipe 25a, the pipe 25b, the pipe 35b, the pipe 36a, and the pipe 37a.

  Further, when the expander 35 operates (rotates), the upstream pressure gradually decreases, and the gas pressure in the pipe 39b also gradually decreases. For example, “the force of air outside the vehicle (the gas in the pipe 39a) biasing the valve body of the check valve 39 in the opening direction> the force of the gas in the pipe 39b biasing the valve body in the closing direction + the valve When the return spring force urges the body in the closing direction, the check valve 39 opens.

  Then, air outside the vehicle flows into the pipe 39b as a scavenging gas, and the scavenging gas flows into the cathode flow path 12 through the pipe 33b and pushes out moisture (water vapor, condensed water) remaining in the cathode flow path 12. . The extruded moisture is discharged out of the vehicle together with the scavenging gas through the pipe 34a, the pipe 34b, the pipe 35a, the pipe 35b, the pipe 36a, and the pipe 37a.

In step S108, the ECU 70 determines whether scavenging of the fuel cell stack 10 has been completed.
Specifically, for example, after the start of scavenging in step S107, when a predetermined time has elapsed in which it is determined that scavenging has been completed, it is determined that scavenging of the fuel cell stack 10 has been completed. The predetermined time serving as a reference for completion of scavenging is obtained by a preliminary test or a simulation and is stored in the ECU 70 in advance. However, the specific determination method is not limited to this.

  When it is determined that scavenging of the fuel cell stack 10 has been completed (S108 / Yes), the processing of the ECU 70 proceeds to step S109. On the other hand, when it is determined that scavenging of the fuel cell stack 10 has not been completed (No at S108), the ECU 70 repeats the determination at Step S108.

  In step S109, the ECU 70 stops the motor 31d and stops the compressor 31 and the expander 35.

  In step S110, the ECU 70 closes the second sealing valve 34, the scavenging gas introduction valve 38, and the scavenging gas discharge valve 25.

  Thereafter, the process of the ECU 70 proceeds to the end, and the fuel cell system 1 is stopped.

≪Effect of fuel cell system≫
According to such a fuel cell system 1, the following effects are obtained.
Since the anode scavenging (scavenging of the anode channel 11) and the cathode scavenging (scavenging of the cathode channel 12) are performed simultaneously, the time required for scavenging can be shortened as a whole of the fuel cell system 1. As a result, the operating time of the motor 31d is shortened and the power consumption by the motor 31d is also reduced.

  In the cathode scavenging, since the low-pressure scavenging gas that opens the check valve 39 flows through the cathode channel 12, the water staying in the cathode channel 12 can be removed well. This is because as the scavenging gas pressure decreases, the amount of saturated water vapor increases and the amount of water vapor that can be contained in the scavenging gas increases.

≪Modification≫
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, For example, it can change as follows.

  In the above-described embodiment, the configuration in which the compressor 31 and the expander 35 share the motor 31d as a power source is illustrated. However, a motor (drive device) is provided independently for each of the compressor 31 and the expander 35. It may be configured to be provided and operable independently. In such a configuration, the ECU 70 may control the independent motor so that anode scavenging and cathode scavenging are executed simultaneously. Further, the compressor 31 and the expander 35 may not be connected to each other via the transmission shaft 31c, and may be configured to operate independently.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been illustrated, but a configuration in which the fuel cell system 1 is mounted on another mobile body such as a motorcycle, a train, or a ship may be used. Further, the present invention may be applied to a stationary fuel cell system for home use or a fuel cell system incorporated in a hot water supply system.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, a different part from 1st Embodiment is demonstrated.

≪Configuration of fuel cell system≫
As shown in FIG. 4, the fuel cell system 2 according to the second embodiment includes a check valve 71 (outside air introduction valve) and a three-way valve 72. The scavenging gas introduction valve 38 and the check valve 39 (see FIG. 1) according to the first embodiment are not provided.

The upstream side of the check valve 71 is opened outside the vehicle via a pipe 71a, and the downstream side of the check valve 71 is connected to the pipe 23a via a pipe 71b. The check valve 71 is a one-way valve that allows the flow of air only from the pipe 71a to the pipe 71b. When the expander 35 is activated (rotated) during the scavenging of the anode channel 11, the pressure in the pipe 71b decreases, thereby opening the check valve 71 and taking in air outside the vehicle as the scavenging gas. (See FIG. 6).
Note that when the fuel cell stack 10 generates power, hydrogen having a pressure higher than that of the outside air flows through the pipe 23a, so that the check valve 71 does not open.

  The downstream end of the pipe 25b is connected to a pipe 35c described later.

  The cathode off-gas outlet of the humidifier 32 is connected to the expander 35 via a pipe 35a, a three-way valve 72, and a pipe 35c. One port of the three-way valve 72 is opened to the diluter 36 through a pipe 72a.

The three-way valve 72 is controlled by the ECU 70 so that the pipe 35 a and the pipe 35 c communicate with each other so that the cathode off-gas flows toward the expander 35 when the fuel cell stack 10 generates power. On the other hand, when scavenging the cathode channel 12 (fuel cell stack 10), the piping 35a and the piping 72a are controlled to communicate with each other so that the scavenging gas is directed to the diluter 36.
In addition, it is good also as a structure which replaces with the three-way valve 72, provides an on-off valve in the piping 35c and the piping 72a, respectively, and controls these suitably.

≪Operation of fuel cell system≫
Next, the operation of the fuel cell system 2 will be described with reference to FIGS.

In the second embodiment, when the determination result of step S102 is Yes, the process proceeds to step S206.
In step S206, the ECU 70 opens the first sealing valve 33, the second sealing valve 34, and the scavenging gas discharge valve 25. Moreover, ECU70 controls the three-way valve 72 and makes the piping 35a and the piping 72a communicate.

  In step S107, the ECU 70 drives the motor 31d to operate the compressor 31 and the expander 35 at the same time, and simultaneously performs scavenging of the anode (scavenging of the anode channel 11) and scavenging of the cathode (scavenging of the cathode channel 12). Execute.

Then, in the second embodiment, as shown in FIG. 6, the scavenging gas from the compressor 31 passes through the pipe 31b, the pipe 33a, the pipe 33b, the cathode flow path 12, the pipe 34a, the pipe 34b, the pipe 35a, and the pipe 72a. Then, it is sent to the diluter 36, and then discharged out of the vehicle through the pipe 36a and the pipe 37a. In this way, the cathode channel 12 is scavenged by the scavenging gas from the compressor 31.
Therefore, the first scavenging gas passage through which the cathode passage 12 and the compressor 31 are connected and the scavenging gas from the compressor 31 toward the cathode passage 12 flows when the cathode passage 12 is scavenged is the piping 31b and the piping 33a. The pipe 33b is provided.

  When the expander 35 is operated (rotated), the upstream pressure gradually decreases and the gas pressure in the pipe 71b also gradually decreases. For example, “the force that the air outside the vehicle (gas in the pipe 71a) urges the valve body of the check valve 71 in the opening direction> the force that the gas in the pipe 71b urges the valve body in the closing direction + the valve When the return spring force biases the body in the closing direction, the check valve 71 opens.

Then, the air outside the vehicle flows into the pipe 71b as a scavenging gas, and the scavenging gas passes through the pipe 23a, the anode flow path 11, the pipe 23b, the pipe 25a, the pipe 25b, the pipe 35c, and the pipe 35b, and is cathoded by the diluter 36. After being diluted well with scavenging gas from the flow path 12 (scavenging gas from the compressor 31), it is discharged out of the vehicle through the piping 36a and the piping 37a. In this way, the anode flow path 11 is scavenged by the scavenging gas (air outside the vehicle) from the check valve 71.
Therefore, the second scavenging gas flow path that connects the anode flow path 11 and the expander 35 and through which the scavenging gas from the anode flow path 11 to the expander 35 flows when the anode flow path 11 is scavenged is the pipe 23b, A pipe 25a, a pipe 25b, and a pipe 35c are provided.

In the second embodiment, the process of the ECU 70 proceeds to step S210 after step S109.
In step S210, the ECU 70 closes the first sealing valve 33, the second sealing valve 34, and the scavenging gas discharge valve 25. Moreover, ECU70 controls the three-way valve 72 and makes the piping 35a and the piping 35c communicate.

≪Effect of fuel cell system≫
According to such a fuel cell system 2, since anode scavenging and cathode scavenging are simultaneously performed, the time required for scavenging as a whole of the fuel cell system 2 can be shortened, and power consumption by the motor 31d can be reduced.

1, 2 Fuel cell system 10 Fuel cell stack (fuel cell)
11 Anode channel (fuel gas channel)
12 Cathode channel (oxidant gas channel)
21a, 22a, 23a Piping (fuel gas supply flow path)
23b Piping (Fuel off-gas discharge flow path)
31 Compressor
31a, 31b, 33a, 33b Piping (oxidant gas supply flow path)
33 First sealing valve (shutoff valve)
34a, 34b, 35a, 35b, 36a, 37a Piping (oxidant off-gas discharge flow path)
34a, 34b, 35a Piping (second scavenging gas flow path)
35 Expander (suction machine)
38a, 38b piping (first scavenging gas flow path)
39 Check valve (outside air introduction valve)
70 ECU (control means)

Claims (6)

A fuel cell having a fuel gas channel and an oxidant gas channel, wherein fuel gas is generated by supplying fuel gas to the fuel gas channel and oxidant gas to the oxidant gas channel;
A fuel gas supply channel through which fuel gas flows toward the fuel gas channel;
A fuel off-gas discharge channel through which the fuel off-gas discharged from the fuel gas channel flows;
An oxidant gas supply channel through which an oxidant gas directed to the oxidant gas channel flows;
An oxidant off-gas discharge channel through which the oxidant off-gas discharged from the oxidant gas channel flows;
A compressor that is provided in the oxidant gas supply flow path and that supplies the oxidant gas toward the oxidant gas flow path;
A suction device provided in the oxidant off-gas discharge flow path, operable simultaneously with the compressor, and suctioning a gas upstream thereof by operating;
A first scavenging gas flow path for connecting one of the fuel gas flow path and the oxidant gas flow path to the compressor, and passing a scavenging gas from the compressor toward the one during the one scavenging; ,
A second scavenging gas flow path for connecting the other of the fuel gas flow path and the oxidant gas flow path to the suction device, and for passing a scavenging gas from the other to the suction device during the other scavenging; ,
An outside air introduction valve that is provided upstream of the other of the fuel gas flow path and the oxidant gas flow path and that opens when the other scavenging gas is introduced, thereby introducing outside air as a scavenging gas;
Control means for controlling the compressor and the suction machine;
With
When scavenging the fuel cell,
The control means simultaneously operates the compressor and the suction machine,
The compressor scavenges one of the fuel gas flow path and the oxidant gas flow path;
The fuel cell system, wherein the suction device scavenges the other of the fuel gas channel and the oxidant gas channel. The suction machine is an expander that expands an oxidant off-gas during power generation of the fuel cell,
A water recovery means provided in the oxidant off-gas flow path downstream of the expander for recovering water;
Water injection means for injecting the water recovered by the water recovery means into an oxidant gas flowing through the oxidant gas supply channel;
The fuel cell system according to claim 1, comprising: The fuel cell system according to claim 1 or 2, wherein the outside air introduction valve is a check valve. The first scavenging gas flow path connects the fuel gas flow path and the compressor;
The second scavenging gas flow path connects the oxidant gas flow path and the suction machine,
When scavenging the fuel cell,
The fuel cell system according to any one of claims 1 to 3, wherein the compressor scavenges the fuel gas flow path, and the suction device scavenges the oxidant gas flow path. Provided in the oxidant gas supply flow path between the oxidant gas flow path and the compressor, and shuts off the scavenging gas from the compressor to the oxidant gas flow path when scavenging the fuel cell The fuel cell system according to claim 4, further comprising a valve. The first scavenging gas flow path connects the oxidant gas flow path and the compressor,
The second scavenging gas flow path connects the fuel gas flow path and the suction machine,
When scavenging the fuel cell,
The fuel cell system according to any one of claims 1 to 3, wherein the compressor scavenges the oxidant gas flow path, and the suction device scavenges the fuel gas flow path.

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