JP2010192251A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system preventing a back pressure valve formed downstream of an oxidant gas flow passage from freezing. <P>SOLUTION: The fuel cell system 1 is equipped with a fuel cell stack 10 possessing an anode flow passage 11 and a cathode flow passage 12, an oxidant gas supply passage, an oxidant gas exhaust passage, the back pressure valve 36, a scavenging gas supply means, and an ECU 50 (Electronic Control Unit) controlling the scavenging gas supply means. While the fuel cell stack 10 stops power generation, the scavenging gas supply means supplies the scavenging gas to the cathode passage 12 and scavenges the cathode passage 12. The system is further equipped with a first bypass passage which connects the oxidant gas supply passage to the oxidant gas exhaust passage and bypasses the cathode passage 12, and a first control valve 37 which controls gas passage in the first bypass passage. In the case of scavenging the back pressure valve 36, the ECU 50 controls the first control valve 37 so that the scavenging gas from the scavenging gas supply means is supplied to the back pressure valve 36 through the first bypass passage bypassing the cathode passage 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

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). ing.

  However, when such a fuel cell generates power, moisture (water vapor) is generated at the cathode. Therefore, if the fuel cell is exposed to a low-temperature environment (for example, 0 ° C. or less) after power generation is stopped, the fuel cell may freeze.

  Therefore, a technique has been proposed in which scavenging gas is supplied to the fuel cell after power generation is stopped, and moisture (water vapor, condensed water, etc.) remaining inside the fuel cell is pushed out from the fuel cell by the scavenging gas to scavenge the fuel cell ( Patent Document 1).

JP 2002-208422 A

  By the way, it is necessary to control the pressure of air in the cathode flow path (oxidant gas flow path) of the fuel cell in accordance with the amount of power generation required from the outside (for example, the accelerator opening of the fuel cell vehicle). Therefore, a technique for controlling the air pressure in the cathode flow path by providing a back pressure valve downstream of the cathode flow path and controlling the opening of the back pressure valve based on the required power generation amount can be considered.

  However, although the fuel cell is scavenged by the scavenging of the fuel cell described above, the water pushed out from the fuel cell remains and adheres to the back pressure valve, and then the back pressure valve freezes when exposed to a low temperature environment. There is a fear. When the back pressure valve is frozen as described above, the air pressure in the cathode flow path cannot be appropriately controlled, and it is necessary to eliminate the freezing at the next system startup, which takes time for system startup.

  Accordingly, an object of the present invention is to provide a fuel cell system that prevents freezing of a back pressure valve provided downstream of an oxidant gas flow path.

  As means for solving the above problems, the present invention has a fuel gas flow path and an oxidant gas flow path, the fuel gas in the fuel gas flow path, the oxidant gas in the oxidant gas flow path, A fuel cell that generates electric power by being supplied, an oxidant gas supply channel through which an oxidant gas directed to the oxidant gas channel flows, and an oxidant gas discharged from the oxidant gas channel pass therethrough. An oxidant gas discharge channel that flows; a back pressure valve that is provided in the oxidant gas discharge channel and controls the pressure of the oxidant gas in the oxidant gas channel; and a scavenging gas supply unit that supplies scavenging gas; Control means for controlling the scavenging gas supply means, and when the power generation of the fuel cell is stopped (system stopped), the scavenging gas supply means passes the oxidant gas flow through the oxidant gas supply flow path. Supply scavenging gas to the road, and the oxidant gas A fuel cell system for scavenging a passage, wherein the oxidant gas supply flow path and the oxidant gas discharge flow path upstream of the back pressure valve are connected to bypass the oxidant gas flow path. And a first control valve that controls the flow of gas in the first bypass flow path, and when scavenging the back pressure valve, the control means is configured so that the scavenging gas from the scavenging gas supply means The fuel cell system is characterized in that the first control valve is controlled to bypass the oxidant gas flow path and to be supplied to the back pressure valve via the first bypass flow path.

  According to such a fuel cell system, when scavenging the back pressure valve, the scavenging gas from the scavenging gas supply means bypasses the oxidant gas flow path and is supplied to the back pressure valve via the first bypass flow path. The That is, the scavenging gas bypasses the humid oxidant gas flow path in the fuel cell and is supplied to the back pressure valve in a dry state. As a result, the back pressure valve can be quickly scavenged, and at the next system start-up, the start time does not become longer due to the freezing of the back pressure valve, and the back pressure valve can be started quickly.

  In addition, since the scavenging gas generally bypasses the oxidant gas channel having a small channel cross-sectional area and a large pressure loss (channel resistance), a large load acts on the scavenging gas supply means from the oxidant gas channel. Nor. Thus, the scavenging gas supply means can operate smoothly while suppressing energy consumption (electric power in the embodiment described later).

  In the fuel cell system, when the control means scavenges the back pressure valve after scavenging the oxidant gas flow path and scavenges the back pressure valve, the scavenging gas from the scavenging gas supply means The first control valve is controlled to bypass the oxidant gas flow path and to be supplied to the back pressure valve via the first bypass flow path.

According to such a fuel cell system, since the back pressure valve is scavenged after scavenging the oxidant gas flow path, even if the water pushed out from the oxidant gas flow path remains in the back pressure valve, Is pushed out of the back pressure valve and the back pressure valve is purged.
Also, when scavenging the back pressure valve after scavenging the oxidant gas flow path, the scavenging gas bypasses the oxidant gas flow path, so that the back pressure valve can be scavenged quickly.

  Further, in the fuel cell system, a cooling device provided in the oxidant gas supply channel, a second bypass channel that bypasses the cooling device, and a gas flow in the second bypass channel are controlled. A second control valve, and when scavenging the back pressure valve, the control means controls the second control valve so that the scavenging gas from the scavenging gas supply means bypasses the cooling device It is characterized by that.

  According to such a fuel cell system, when scavenging the back pressure valve, the scavenging gas passes through the second bypass flow path and is supplied to the back pressure valve without being cooled by the cooling device. That is, the back pressure valve can be quickly dried by scavenging the back pressure valve with uncooled scavenging gas.

  The fuel cell system further includes a humidifier that is provided in the oxidant gas supply flow path and humidifies the oxidant gas toward the oxidant gas flow path, and the first bypass flow path is provided by the humidifier. Further, the scavenging gas from the scavenging gas supply means bypasses the humidifier when scavenging the back pressure valve.

  According to such a fuel cell system, when scavenging the back pressure valve, the scavenging gas bypasses the humidifier. That is, the scavenging gas is not humidified by the humidifier and is supplied to the back pressure valve while being dried. The back pressure valve can be quickly dried by scavenging the back pressure valve with such dry scavenging gas.

  In the fuel cell system, when the system temperature is equal to or lower than a first temperature at which the back pressure valve is determined to be frozen, the control means scavenges only the back pressure valve, and the system temperature is frozen at the fuel cell. When the temperature is determined and is equal to or lower than a second temperature lower than the first temperature, scavenging the oxidant gas flow path, and scavenging the back pressure valve after scavenging the oxidant gas flow path It is characterized by.

Here, the back pressure valve has a smaller thermal mass than the fuel cell, and the temperature tends to decrease.
According to such a fuel cell system, when it is determined that the system temperature is equal to or lower than the first temperature and the back pressure valve is frozen, only the back pressure valve is scavenged and the oxidant gas flow path is not scavenged. Energy consumption (electric power in the embodiment described later) can be suppressed.
Further, since the back pressure valve is again scavenged after scavenging the oxidant gas flow path, the back pressure valve is not frozen by moisture pushed out from the oxidant gas flow path.

  Further, in the fuel cell system, a first blocking valve that is provided in the oxidant gas supply channel downstream from the connection position of the first bypass channel and is closed after power generation of the fuel cell is stopped, A second blocking valve that is provided in the oxidant gas discharge flow channel upstream of the connection position of the first bypass flow channel and is closed after power generation of the fuel cell is stopped, and the system temperature is the second temperature The back pressure valve is scavenged with the first blocking valve and the second blocking valve closed, the oxidant gas flow path is blocked, and the system temperature is equal to or lower than the second temperature. In this case, the first blocking valve and the second blocking valve are opened, and the oxidant gas flow path is scavenged.

According to such a fuel cell system, the first blocking valve and the second blocking valve are closed until the system temperature becomes equal to or lower than the second temperature, and the oxidant gas flow path is blocked, When the back pressure valve is scavenged and becomes the second temperature or lower, the first block valve and the second block valve are opened, and the oxidant gas flow path is scavenged.
In other words, since the oxidant gas flow path is kept sealed until the system temperature becomes the second temperature or lower, air or the like does not enter the oxidant gas flow path from the outside, and the fuel cell is deteriorated. It becomes difficult to do.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which prevents the freezing of the back pressure valve provided downstream of the oxidant gas flow path can be provided.

It is a figure which shows the structure of the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment. It is a figure which shows the opening degree of the back pressure valve at the time of scavenging in steps, (a) shows the initial stage of scavenging, (b) shows the middle stage of scavenging, and (c) shows the latter stage of scavenging. It is a time chart which shows the opening degree of the back pressure valve at the time of the scavenging which concerns on a modification.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to this 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, an anode system that supplies and discharges hydrogen (fuel gas and reaction gas) to and from the anode of the fuel cell stack 10, and air that contains oxygen with respect to the cathode of the fuel cell stack 10. A cathode system for supplying and discharging (oxidant gas and reaction gas) and an ECU 50 (Electronic Control Unit) for electronically controlling them are provided.

<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 conductive porous material such as carbon paper, and a catalyst (Pt, Ru, etc.) that is supported on the porous body and causes 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, when the fuel cell stack 10 and an external circuit such as a travel motor are electrically connected and a current is taken out, the fuel cell stack 10 generates power.
Since moisture (water vapor) is generated at the cathode in this way, the cathode off-gas discharged from the cathode becomes humid and contains moisture (water vapor, condensed water, etc.).
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

Each separator is formed with grooves for allowing the refrigerant to flow through the entire surface of each MEA. These grooves and through holes function as the refrigerant flow path 13.
A pipe 13 a through which a refrigerant cooled by a radiator (not shown) flows is connected to the inlet of the refrigerant flow path 13. The outlet of the refrigerant flow path 13 is discharged from the refrigerant flow path 13, and the radiator A pipe 13b through which the refrigerant directed to the flow passes is connected.

And the temperature sensor 14 is attached to the piping 13b, and the temperature sensor 14 detects the temperature of the refrigerant | coolant in the piping 13b as system temperature, and outputs it to ECU50.
However, the position of the temperature sensor 14 for detecting the system temperature is not limited to this. For example, the temperature sensor 14 may be attached to the fuel cell stack 10 or the back pressure valve 36, or a plurality of them may be used.

<Anode system>
The anode system includes a hydrogen tank 21 and a normally closed shut-off valve 22.
The hydrogen tank 21 is connected to the inlet of the anode flow path 11 via a pipe 21a, a shutoff valve 22, and a pipe 22a. When the shutoff valve 22 is opened by a command from the ECU 50 to generate power in the fuel cell stack 10, hydrogen is supplied from the hydrogen tank 21 to the anode flow path 11 through the shutoff valve 22 and the like. ing.

  A pipe 22 b is connected to the outlet of the anode channel 11. And the anode off gas discharged | emitted from the anode flow path 11 is discharged | emitted outside the vehicle through the piping 22b.

<Cathode system>
The cathode system includes a compressor 31 (oxidant gas supply means, scavenging gas supply means), an intercooler 32 (I / C, cooling device), a normally closed (or normally open) first block valve 33, A humidifier 34, a normally closed (or normally open) second sealing valve 35, and a normally open back pressure valve 36 are provided.

  The compressor 31 is connected to the inlet of the cathode channel 12 via a pipe 31a, an intercooler 32, a pipe 32a, a first blocking valve 33, a pipe 33a, a humidifier 34, and a pipe 34a. When the compressor 31 operates in accordance with a command from the ECU 50, the compressor 31 takes in air containing oxygen and supplies the air to the cathode flow path 12 through the piping 31a and the like.

  The compressor 31 functions as a scavenging gas supply means for supplying a scavenging gas when scavenging the fuel cell stack 10 and the back pressure valve 36. Further, the compressor 31, the first blocking valve 33, the second blocking valve 35, the shutoff valve 22, and other valves are powered by the fuel cell stack 10 and / or a battery (not shown) that stores this electric power.

  Therefore, the oxidant gas supply channel through which air (oxidant gas) toward the cathode channel 12 (oxidant gas channel) flows is configured to include the pipe 31a, the pipe 32a, the pipe 33a, and the pipe 34a. ing. The first blocking valve 33 is provided in the oxidant gas supply flow path downstream of the connection position of the pipe 37 a constituting the first bypass flow path described later and upstream of the humidifier 34. The intercooler 32 is provided in the oxidant supply channel upstream of the connection position of the pipe 37a.

  The intercooler 32 cools the air that has been heated to a high temperature by being compressed by the compressor 31. The pipe 31a upstream of the intercooler 32 is connected to the pipe 32a via a pipe 38a and a normally closed second control valve 38 and a pipe 38b that are appropriately opened by the ECU 50. When the second control valve 38 is opened during the scavenging of the back pressure valve 36, the scavenging gas from the compressor 31 bypasses the intercooler 32.

Therefore, the second bypass flow path in which the scavenging gas bypasses the intercooler 32 is configured to include the pipe 38a and the pipe 38b, and the second control valve 38 provided in the second bypass flow path has the second bypass flow. It controls the flow of gas in the road.
Instead of the second control valve 38, for example, a configuration in which a three-way valve (second control valve) is provided at a connection position between the pipe 38a and the pipe 31a may be employed.

  The first closing valve 33 is a normally closed solenoid valve controlled by the ECU 50, and is open during power generation (system operation) of the fuel cell stack 10, and after power generation is stopped, that is, power generation is stopped (system stop). Middle) is closed.

  A pipe 34b, a humidifier 34, a pipe 34c, a second blocking valve 35, a pipe 35a, a back pressure valve 36, and a pipe 36a are sequentially connected to the outlet of the cathode channel 12. And the cathode off gas (oxidant gas) discharged | emitted from the cathode flow path 12 is discharged | emitted outside the vehicle via piping 34b etc. As shown in FIG.

  Therefore, the oxidant gas discharge flow path through which the air (oxidant gas flow) discharged from the cathode flow path 12 (oxidant gas flow path) flows includes the pipe 34b, the pipe 34c, the pipe 35a, and the pipe 36a. It is configured. The second blocking valve 35 is provided in the oxidant gas discharge channel upstream of the connection position of the pipe 37b constituting the first bypass channel described later and downstream of the humidifier 34.

The humidifier 34 incorporates a plurality of hollow fiber membranes 34d having moisture permeability, and through this hollow fiber membrane 34d, air toward the cathode channel 12 and the humid cathode offgas discharged from the cathode channel 12 Moisture is exchanged between the two and the air toward the cathode channel 12 is humidified.
However, the humidification method is not limited to this, and for example, air that is directed to the cathode flow path 12 may be humidified by a bubbling method.

  The second closing valve 35 is a normally closed electromagnetic valve controlled by the ECU 50, and is open during power generation (system operation) of the fuel cell stack 10, and after power generation is stopped, that is, power generation is stopped (system stop). Middle) is closed.

The back pressure valve 36 controls the air pressure in the cathode flow path 12 corresponding to the power generation request amount (load request amount) from the accelerator or the like, and its opening degree is controlled by the ECU 50. Such a back pressure valve 36 is composed of, for example, a butterfly valve, and includes a valve body 36b that is rotated around a rotation axis by a driving device (stepping motor or the like) (see FIG. 3).
Since such a back pressure valve 36 has a small thermal mass with respect to the fuel cell stack 10 and the downstream thereof communicates with the outside of the vehicle, the temperature drops earlier than the fuel cell stack 10, and the valve body 36 b and its The condensed water W adhering to the flow path wall portion 36c has a characteristic that it is easily frozen (see FIG. 3).

  The opening of the back pressure valve 36 is indicated by an angle θ between the reference and the valve body 36b, with the direction orthogonal to the scavenging gas going downstream as a reference (opening: 0 degree). When the drive device is turned off, the valve body 36b is designed so that the opening degree is approximately 90 degrees, that is, fully opened by two return springs.

The pipe 32a downstream from the connection position of the pipe 38b is connected to the pipe 35a via the pipe 37a, the normally closed first control valve 37, and the pipe 37b.
Then, (1) when scavenging only the back pressure valve 36, (2) when scavenging the back pressure valve 36 after scavenging the cathode flow path 12, and when the first control valve 37 is opened by the ECU 50, the scavenging gas from the compressor 31 However, by flowing the pipe 37a and the pipe 37b, the cathode flow path 12 and the humidifier 34 are bypassed and supplied to the back pressure valve 36.

Therefore, the first bypass flow path that bypasses the cathode flow path 12 and the humidifier 34 includes the pipe 37a and the pipe 37b, and the first control valve 37 provided in the first bypass flow path includes the first control valve 37. The gas flow in the bypass channel is controlled.
Instead of the first control valve 37, for example, a configuration in which a three-way valve (first control valve) is provided at a connection position between the pipe 37a and the pipe 32a may be employed.

<IG>
The IG 41 is a start switch of the fuel cell system 1 (fuel cell vehicle), and is provided around the driver's seat. The IG 41 is connected to the ECU 50, and the ECU 50 detects an ON / OFF signal of the IG 41.

<ECU>
The ECU 50 (control means) 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 according to a program stored therein, Various functions are exhibited and various devices are controlled.

Specifically, the ECU 50 has a function of opening / closing the first blocking valve 33 and the second blocking valve 35 and blocking / opening the cathode flow path 12.
Further, the ECU 50 has a function of controlling the first blocking valve 33, the second blocking valve 35, the first control valve 37, and the second control valve 38, and switching and controlling the flow path of the scavenging gas from the compressor 31. I have.

<ECU-scavenging determination function>
Furthermore, when the system temperature input from the temperature sensor 14 is equal to or lower than the first temperature (for example, 10 ° C.) while the system is stopped after the IG 41 is turned off (after the power generation of the fuel cell stack 10 is stopped), the ECU 50 A function for determining that scavenging of the pressure valve 36 is necessary is provided. The first temperature is a temperature obtained by a preliminary test or the like, and is a temperature at which it is determined that the back pressure valve 36 is frozen thereafter.

  Further, the ECU 50 has a function of determining that scavenging of the cathode flow path 12 (fuel cell stack 10) is necessary when the system temperature is equal to or lower than a second temperature (for example, 5 ° C.) while the system is stopped. Yes. The second temperature is a temperature obtained by a preliminary test or the like, and is a temperature at which the fuel cell stack 10 is determined to be frozen thereafter. The fuel cell stack 10 has a larger thermal mass than the back pressure valve 36 and is unlikely to decrease in temperature, so the second temperature is set to a temperature lower than the first temperature.

≪Function and effect of fuel cell system≫
Next, the effect of the fuel cell system 1 will be described with reference to FIG.
When the IG 41 is turned off, each process shown in the flowchart of FIG. 2 is started.

In step S101, the ECU 50 stops the power generation of the fuel cell stack 10.
Specifically, the ECU 50 electrically shuts off the fuel cell stack 10 and an external load (traveling motor or the like), then closes the shut-off valve 22 and stops the compressor 31.

In step S102, the ECU 50 closes the first blocking valve 33 and the second blocking valve 35, and blocks the cathode flow path 12.
In this way, the cathode flow path 12 is blocked after the fuel cell stack 10 stops generating power (after the system is stopped) and when power generation is stopped (when the system is stopped). There is no new flow into the cathode channel 12 through the second blocking valve 35.
Thereby, an increase in potential of the cathode or anode constituting the MEA, generation of OH radicals, and the like are suppressed, and deterioration of the cathode or anode and decomposition of the electrolyte membrane are suppressed. As a result, deterioration of the fuel cell stack 10 is suppressed and its durability is enhanced.

In step S103, the ECU 50 determines whether or not the system temperature input from the temperature sensor 14 is equal to or lower than a first temperature (for example, 10 ° C.).
When it is determined that the system temperature is equal to or lower than the first temperature (S103 / Yes), it is determined that scavenging of the back pressure valve 36 is necessary, and the process of the ECU 50 proceeds to step S104. On the other hand, when it is determined that the system temperature is not equal to or lower than the first temperature (S103, No), it is determined that scavenging of the back pressure valve 36 is not necessary, and the process of the ECU 50 proceeds to step S105.

In step S104, the ECU 50 scavenges the back pressure valve 36.
Specifically, the ECU 50 operates the compressor 31 after opening the first control valve 37 and the second control valve 38 with the first block valve 33 and the second block valve 35 closed. Then, the scavenging gas from the compressor 31 passes through the second control valve 38 and the first control valve 37 in order, and is supplied to the back pressure valve 36, and the back pressure valve 36 is scavenged.

That is, by passing through the second control valve 38 and the pipes 38a and 38b (second bypass flow paths) and bypassing the intercooler 32, the scavenging gas that is hot due to compression by the compressor 31 is not cooled and is directly It is supplied to the pressure valve 36.
In addition, by bypassing the cathode flow path 12 and the humidifier 34 that pass through the first control valve 37 and the pipes 37a and 37b (first bypass flow paths) and have a small flow sectional area and a large pressure loss, The scavenging gas is supplied to the back pressure valve 36 in a dry state without the load acting.

  Since scavenging gas in a high temperature and dry state is supplied to the back pressure valve 36 in this way, moisture (water vapor, condensed water W) in the back pressure valve 36 is pushed downstream by the scavenging gas and is dried in the back pressure valve 36. Advances. Thereby, freezing of the back pressure valve 36 is suitably prevented.

When scavenging the back pressure valve 36 in this way, as shown in FIG. 3 (a), at the initial stage of scavenging, the opening (angle θ) is reduced and the condensed water W adhering to the flow path wall 36c. As shown in FIG. 3B, in the middle stage of scavenging, the opening degree is fully opened (θ = 90 degrees), and the condensed water W adhering to the valve body 36b is blown away, and FIG. As shown in FIG. 5, it is preferable to reduce the opening degree again in the latter stage of scavenging, and to blow away the condensed water W adhering to the flow path wall 36c downstream.
In addition, as shown in FIG. 4, the opening degree of the back pressure valve 36 may be continuously changed.

  After scavenging the back pressure valve 36 in this way, the ECU 50 stops the compressor 31 and closes the first control valve 37 and the second control valve 38. Thereafter, the processing of the ECU 50 proceeds to step S108.

In step S105, the ECU 50 determines whether a predetermined time (for example, 30 minutes to 1 hour) has elapsed after the determination in step S103.
When it is determined that the predetermined time has elapsed (S105, Yes), the process of the ECU 50 proceeds to step S103. As a result, the determination in step S103 is repeated every time a predetermined time elapses, and freezing of the back pressure valve 36 is prevented. On the other hand, when it determines with predetermined time not having passed (S105 * No), the process of ECU50 progresses to step S106.

In step S106, the ECU 50 determines whether or not the IG 41 is turned on.
When it is determined that the IG 41 is turned on (S106 / Yes), the process of the ECU 50 proceeds to step S107. On the other hand, when it is determined that the IG 41 is not turned on (No in S106), the process of the ECU 50 proceeds to Step S105.

In step S107, the ECU 50 determines that an activation request has been received from the driver due to the IG 41 being turned on, and activates the system.
Specifically, the ECU 50 opens the shutoff valve 22, supplies hydrogen to the anode flow path 11, opens the first blocking valve 33 and the second blocking valve 35, then operates the compressor 31, and the cathode flow path 12. To supply air. Thereafter, the ECU 50 electrically connects the fuel cell stack 10 and an external load, and causes the fuel cell stack 10 to generate power in response to a power generation request amount from an accelerator or the like.

In step S108, the ECU 50 determines whether or not the system temperature input from the temperature sensor 14 is equal to or lower than a second temperature (for example, 5 ° C.).
When it is determined that the system temperature is equal to or lower than the second temperature (S108 / Yes), it is determined that scavenging of the cathode flow path 12 is necessary, and the process of the ECU 50 proceeds to step S109. On the other hand, when it is determined that the system temperature is not equal to or lower than the second temperature (S108, No), it is determined that scavenging of the cathode flow path 12 is not necessary, and the process of the ECU 50 proceeds to step S110.

In step S109, the ECU 50 opens the first blocking valve 33 and the second blocking valve 35, and opens the cathode channel 12 outside the vehicle.
That is, until the system temperature becomes equal to or lower than the second temperature, the closed state of the cathode flow path 12 is maintained even during the scavenging of the back pressure valve 36 in step S104, so that air does not flow into the cathode flow path 12 from the outside of the vehicle, and the fuel cell Deterioration of the stack 10 is suppressed.

In step S110, the ECU 50 determines whether a predetermined time (for example, 30 minutes to 1 hour) has elapsed after the determination in step S108.
When it is determined that the predetermined time has elapsed (S110 / Yes), the process of the ECU 50 proceeds to step S108. As a result, the determination in step S108 is repeated every time the predetermined time elapses, and the fuel cell stack 10 is prevented from freezing. On the other hand, when it determines with predetermined time not having passed (S110 * No), the process of ECU50 progresses to step S111.

In step S111, the ECU 50 determines whether or not the IG 41 is turned on.
When it is determined that the IG 41 is turned on (S111 / Yes), the processing of the ECU 50 proceeds to step S107. On the other hand, when it is determined that the IG 41 is not turned on (S111, No), the process of the ECU 50 proceeds to step S110.

In step S112, the ECU 50 scavenges the cathode flow path 12 of the fuel cell stack 10.
Specifically, the ECU 50 operates the compressor 31 after fully opening the back pressure valve 36. Then, the scavenging gas from the compressor 31 is supplied to the cathode channel 12 through the intercooler 32, the first blocking valve 33, and the humidifier 34. Then, moisture (water vapor, condensed water) in the cathode channel 12 is pushed out of the cathode channel 12 by the scavenging gas and flows out toward the back pressure valve 36. Thereby, freezing of the cathode flow path 12 (fuel cell stack 10) is prevented.

In addition, when scavenging the cathode flow path 12 in this way, the scavenging gas is appropriately cooled as the scavenging gas passes through the intercooler 32. As a result, the MEA of the fuel cell stack 10 and the hollow fiber membrane 34d of the humidifier 34 do not overheat and are not damaged.
Further, when scavenging the cathode flow path 12 in this way, the scavenging gas is also supplied to the anode flow path 11 via a pipe (not shown) connecting the pipe 32a and the pipe 22a, and the anode flow path 11 is also scavenged. It is preferable to do.
After scavenging the cathode flow path 12 in this way, the process of the ECU 50 proceeds to step S113.

  In step S113, the ECU 50 closes the first blocking valve 33 and the second blocking valve 35, and blocks the cathode channel 12 again. Note that the cathode channel 12 may not be blocked.

In step S114, the ECU 50 scavenges the back pressure valve 36 as in step S104.
Specifically, the ECU 50 opens the first control valve 37 and the second control valve 38. Then, the scavenging gas from the compressor 31 bypasses the intercooler 32, the cathode flow path 12, and the humidifier 34 and is supplied to the back pressure valve 36. Thereby, even if the water pushed out from the cathode flow path 12 stays in the back pressure valve 36, the water is pushed downstream of the back pressure valve 36, and the back pressure valve 36 is prevented from freezing. Also in this case, it is preferable to change the opening degree of the back pressure valve 36 as shown in FIGS.

Thus, after scavenging the back pressure valve 36 again, the ECU 50 stops the compressor 31 and closes the first control valve 37 and the second control valve 38.
Thereafter, the processing of the ECU 50 proceeds to step S115 (END), and the system is stopped.

  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 range which does not deviate from the meaning of this invention.

  In the above-described embodiment, a configuration in which the scavenging gas passes through the humidifier 34 when scavenging the cathode flow path 12 is illustrated. For example, the piping 33a and the piping 34a are connected by a bypass piping (not shown), May be configured to bypass the humidifier 34.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been illustrated. However, for example, a fuel cell system mounted on a motorcycle, a train, or a ship may be used. In addition, 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.

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
11 Anode channel (fuel gas channel)
12 Cathode channel (oxidant gas channel)
31 Compressor (oxidant gas supply means, scavenging gas supply means)
31a, 32a, 33a, 34a Piping (oxidant gas supply flow path)
32 Intercooler (cooling device)
33 1st sealing valve 34 Humidifier 34b, 34c, 35a, 36a Piping (oxidant gas discharge flow path)
35 Second block valve 36 Back pressure valve 37 First control valve 37a, 37b Piping (first bypass flow path)
38 Second control valve 38a, 38b Piping (second bypass flow path)
50 ECU (control means)
W condensed water

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;
An oxidant gas supply channel through which an oxidant gas directed to the oxidant gas channel flows;
An oxidant gas discharge channel through which the oxidant gas discharged from the oxidant gas channel flows;
A back pressure valve that is provided in the oxidant gas discharge channel and controls the pressure of the oxidant gas in the oxidant gas channel;
Scavenging gas supply means for supplying scavenging gas;
Control means for controlling the scavenging gas supply means;
The scavenging gas supply means supplies a scavenging gas to the oxidant gas flow path through the oxidant gas supply flow path and stops scavenging the oxidant gas flow path when the fuel cell is stopped in power generation. A battery system,
A first bypass flow path connecting the oxidant gas supply flow path and the oxidant gas discharge flow path upstream of the back pressure valve to bypass the oxidant gas flow path;
A first control valve for controlling the gas flow in the first bypass flow path;
With
When scavenging the back pressure valve, the control means allows the scavenging gas from the scavenging gas supply means to bypass the oxidant gas flow path and be supplied to the back pressure valve via the first bypass flow path. The fuel cell system, wherein the first control valve is controlled as described above. The control means includes
After scavenging the oxidant gas flow path, scavenging the back pressure valve,
When scavenging the back pressure valve, the scavenging gas from the scavenging gas supply means bypasses the oxidant gas flow path and is supplied to the back pressure valve via the first bypass flow path. The fuel cell system according to claim 1, wherein the first control valve is controlled. A cooling device provided in the oxidant gas supply flow path;
A second bypass flow path that bypasses the cooling device;
A second control valve for controlling the gas flow in the second bypass flow path;
With
When scavenging the back pressure valve, the control means controls the second control valve such that the scavenging gas from the scavenging gas supply means bypasses the cooling device. The fuel cell system according to claim 2. A humidifier that is provided in the oxidant gas supply flow path and humidifies the oxidant gas toward the oxidant gas flow path;
The first bypass flow path is connected to the oxidant gas supply flow path upstream of the humidifier,
The fuel cell system according to any one of claims 1 to 3, wherein when scavenging the back pressure valve, the scavenging gas from the scavenging gas supply means bypasses the humidifier. The control means includes
If the system temperature is below a first temperature at which the back pressure valve is determined to freeze, only the back pressure valve is scavenged;
When the system temperature is a temperature at which the fuel cell is determined to be frozen and is equal to or lower than a second temperature lower than the first temperature, the oxidant gas passage is scavenged, and the oxidant gas passage is scavenged. Thereafter, the back pressure valve is scavenged. The fuel cell system according to any one of claims 1 to 4, wherein the back pressure valve is scavenged. A first blocking valve that is provided in the oxidant gas supply flow channel downstream from the connection position of the first bypass flow channel and is closed after power generation of the fuel cell is stopped;
A second blocking valve that is provided in the oxidant gas discharge flow channel upstream of the connection position of the first bypass flow channel and is closed after power generation of the fuel cell is stopped;
With
Until the system temperature becomes equal to or lower than the second temperature, the back-off valve is scavenged with the first and second blocking valves closed, and the oxidant gas flow path blocked.
When the system temperature becomes equal to or lower than the second temperature, the first blocking valve and the second blocking valve are opened, and the oxidant gas flow path is scavenged. Item 5. The fuel cell system according to Item 4.

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