JP2010108755A - Fuel cell system and scavenging method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of surely scavenging generated water adhered to a purge valve at the time of shut-down of a fuel cell and a scavenging method of the fuel cell system. <P>SOLUTION: The fuel cell system 10 is provided with a fuel cell 11, anode gas passages 23, 35 in which anode gas flows, a purge valve 52 which can open and close for discharging the gas in the anode gas passages to the outside of the passages, a scavenging gas supply means 33 which supplies scavenging gas into the anode passages, and a scavenging valve 51 which is constructed capable of opening and closing for discharging the scavenging gas supplied into the anode gas passages to the outside of the passages and has a discharge passage cross-sectional area larger than the purge valve, and after the fuel cell has stopped operation, the anode gas passages can be scavenged by the scavenging gas supply means. The system can discharge the scavenging gas from the purge valve to the outside of the passages for a prescribed time with the scavenging valve closed, when it determines that scavenging in the anode gas passages is completed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a scavenging method for the fuel cell system.

  Conventionally, for example, in a fuel cell mounted on a vehicle, a membrane electrode structure is formed by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode from both sides, and a pair of separators are provided on both sides of the membrane electrode structure. A flat unit fuel cell (hereinafter referred to as a unit cell) is arranged to form a fuel cell stack (hereinafter referred to as a fuel cell) by stacking a plurality of unit cells. In such a fuel cell, hydrogen gas is supplied as an anode gas (fuel gas) between the anode electrode and the separator, and air is supplied as a cathode gas (oxidant gas) between the cathode electrode and the separator. As a result, hydrogen ions generated by the catalytic reaction at the anode electrode pass through the solid polymer electrolyte membrane and move to the cathode electrode, causing an electrochemical reaction with oxygen in the air at the cathode electrode, thereby generating power. It should be noted that water is generated inside the fuel cell with this power generation.

In a fuel cell system including such a fuel cell, for example, when used in a sub-freezing environment, the generated water remaining inside the fuel cell system is frozen while the fuel cell system is stopped. A method for removing water droplets adhering to the fuel cell system has been proposed (see, for example, Patent Document 1).
In the fuel cell system disclosed in Patent Document 1, water droplets attached to the flow control valve are blown off using air dried by an air dryer when the fuel cell is stopped. Specifically, a configuration is disclosed in which the opening of the flow control valve is adjusted so that air with a high flow velocity flows (the opening is reduced), air is blown there, and water droplets are blown away.
JP 2003-203665 A

  By the way, generally, when scavenging the anode gas flow path (piping) of the fuel cell system, the scavenging gas is discharged from the purge valve and the scavenging valve that are used when the fuel cell system is started and during operation. . Here, if the purge valve and the scavenging valve are closed at the same time when scavenging of the anode gas flow path is completed, the fuel cell system may stop due to freezing with the generated water remaining in the purge valve. If the generated water remains in the purge valve and freezes, there is a problem that the OCV purge at the start-up is not executed without opening the purge valve when starting the fuel cell system next time. Further, the generated water freezes on the purge pipe and the filter, so that the purge flow rate is lowered, and there is a problem that gas replacement is not reliably performed at the start-up OCV purge and the system is stopped. Therefore, a technique capable of removing water droplets from the purge valve and preventing the purge valve from freezing is desired.

  Accordingly, the present invention has been made in view of the above circumstances, and provides a fuel cell system and a scavenging method for the fuel cell system that can surely scavenge the generated water adhering to the purge valve when the fuel cell is stopped. Is.

  In order to solve the above problems, the invention described in claim 1 is a fuel cell (for example, fuel cell 11 in the embodiment) that generates electricity by supplying an anode gas to an anode electrode and a cathode gas to a cathode electrode; An anode gas flow path (for example, the anode gas supply pipe 23 and the anode off-gas discharge pipe 35 in the embodiment) through which the anode gas flows, and can be opened and closed to discharge the gas in the anode gas flow path to the outside of the flow path. A purge valve (for example, purge valve 52 in the embodiment), a scavenging gas supply means (for example, an air compressor 33 in the embodiment) for supplying a scavenging gas into the anode gas flow path, and a supply in the anode gas flow path The scavenging gas is configured to be openable and closable so as to be discharged out of the flow path, and the discharge flow path cross-sectional area is larger than the purge valve. A large scavenging valve (for example, the anode air discharge valve 51 in the embodiment), and after the fuel cell is started and stopped, the scavenging gas supplied by the scavenging gas supply means is used in the anode gas flow path. , And the scavenging gas can be discharged from the purge valve and the scavenging valve (for example, the fuel cell system 10 in the embodiment), and the scavenging of the anode gas channel is completed. It is determined that the scavenging gas can be discharged from the purge valve to the outside of the flow path for a predetermined time with the scavenging valve closed.

  The invention described in claim 2 is characterized in that, when the scavenging gas is discharged from the purge valve with the scavenging valve closed, the scavenging gas supply amount of the scavenging gas supply means is increased. Yes.

  The invention described in claim 3 has pressure adjusting means (for example, the back pressure valve 34 in the embodiment) for adjusting the pressure of the scavenging gas, and the pressure in the anode gas flow path is adjusted by the pressure adjusting means. It is characterized by being configured to be lower than the pressure at the start of the scavenging gas discharge from the purge valve.

  The invention described in claim 4 is characterized in that the pressure adjusting means is configured to reduce the pressure in the anode gas flow path at a predetermined rate.

  According to a fifth aspect of the present invention, the scavenging gas supply means is a cathode gas supply means for supplying the cathode gas to the cathode electrode, and the pressure adjusting means is a cathode gas flow path through which the cathode gas flows. A back pressure valve that adjusts the pressure, and is configured to be able to supply the cathode gas into the anode gas flow path as the scavenging gas by closing the back pressure valve, and adjusting the opening of the back pressure valve Thus, the pressure in the anode gas flow path can be adjusted.

  According to a sixth aspect of the present invention, there is provided a fuel cell for generating electricity by supplying an anode gas to the anode electrode and a cathode gas to the cathode electrode, an anode gas flow path through which the anode gas flows, and an anode gas flow path in the anode gas flow path. A purge valve that can be opened and closed to discharge gas out of the flow path, a scavenging gas supply means for supplying a scavenging gas into the anode gas flow path, and a flow of the scavenging gas supplied into the anode gas flow path. A scavenging valve configured to be openable and closable for discharging to the outside of the road and having a discharge passage cross-sectional area larger than that of the purge valve, and supplied by the scavenging gas supply means after the fuel cell is started and stopped A scavenging method for a fuel cell system, wherein the scavenging gas is used to scavenge the anode gas flow path after the fuel cell is started and stopped. A scavenging determination step for determining whether or not, an anode scavenging step for scavenging the anode gas flow path, an anode scavenging completion determination step for determining whether or not scavenging in the anode gas flow path is completed, A scavenging valve closing step for closing the scavenging valve and a purge valve scavenging determination step for determining whether or not the scavenging gas has passed through the purge valve through a predetermined flow rate are provided.

  According to the first aspect of the present invention, after the scavenging of the anode gas flow path is determined to be completed, the purge valve is kept closed for a predetermined time with the scavenging valve closed first. A sufficient scavenging gas flow rate can be circulated through the valve and the purge pipe, and water droplets (generated water) adhering to the purge valve or the like can be reliably removed. Therefore, when the fuel cell system is started next time, it is possible to prevent the occurrence of an opening / closing failure due to the freezing of the purge valve, and the system can be reliably started.

  According to the second aspect of the invention, when removing water droplets from the purge valve, the scavenging gas flow rate supplied to the purge valve is increased, so that the water droplet removal efficiency can be improved. Therefore, the generated water adhering to the purge valve when the fuel cell is stopped can be scavenged more reliably.

  According to the third aspect of the present invention, the pressure in the anode gas flow path during the water droplet removal of the purge valve is made lower than the pressure at the start of water droplet removal of the purge valve. It is possible to prevent water such as generated water from being led to the purge valve. Therefore, water droplet removal from the purge valve can be performed efficiently.

  According to the fourth aspect of the present invention, since the pressure in the anode gas flow path can be gradually reduced instead of being reduced at once, the generation of noise due to pressure fluctuation can be prevented.

  According to the fifth aspect of the invention, it is possible to remove water droplets from the purge valve and remove water droplets from the back pressure valve provided in the cathode gas flow path.

  According to the invention described in claim 6, after it is determined that scavenging in the anode gas flow path is completed, the purge valve is kept closed for a predetermined time with the scavenging valve closed first. A sufficient scavenging gas flow rate can be circulated through the valve and the purge pipe, and water droplets (generated water) adhering to the purge valve or the like can be reliably removed. Therefore, when the fuel cell system is started next time, it is possible to prevent the occurrence of an opening / closing failure due to the freezing of the purge valve, and the system can be reliably started.

(First embodiment)
Next, a first embodiment of a fuel cell system according to the present invention will be described with reference to FIGS. In the present embodiment, a case where the fuel cell system is mounted on a vehicle will be described.
(Fuel cell system)
FIG. 1 is a schematic configuration diagram of a fuel cell system.
As shown in FIG. 1, the fuel cell 11 of the fuel cell system 10 is a solid polymer membrane fuel cell that generates electric power by an electrochemical reaction between an anode gas such as hydrogen gas and a cathode gas such as air. An anode gas supply pipe 23 is connected to the anode gas supply communication hole 13 (inlet side of the anode gas passage 21) formed in the fuel cell 11, and a hydrogen tank 30 is connected to the upstream end thereof. A cathode gas supply pipe 24 is connected to the cathode gas supply communication hole 15 (inlet side of the cathode gas flow path 22) formed in the fuel cell 11, and an air compressor 33 is connected to the upstream end thereof. Yes. An anode off-gas exhaust pipe 35 (cathode gas flow path 22) is connected to the anode off-gas discharge communication hole 14 (exit side of the anode gas flow path 21) formed in the fuel cell 11. Is connected to a cathode offgas discharge pipe 38.

  Further, the hydrogen gas supplied from the hydrogen tank 30 to the anode gas supply pipe 23 is decompressed by a regulator (not shown), then passes through the ejector 26 and is supplied to the anode gas flow path 21 of the fuel cell 11. An electromagnetically driven solenoid valve 25 is provided in the vicinity of the downstream side of the hydrogen tank 30 so that the supply of hydrogen gas from the hydrogen tank 30 can be shut off.

  The anode off-gas discharge pipe 35 is connected to the ejector 26 so that the anode off-gas that has passed through the fuel cell 11 can be reused as the anode gas of the fuel cell 11 again. Further, the anode off-gas discharge pipe 35 is provided with two pipes branched in the middle, one being an anode air discharge pipe 36 and the other being a purge gas discharge pipe 37. Both the anode air discharge pipe 36 and the purge gas discharge pipe 37 are connected to the dilution box 31. The anode air discharge pipe 36 is provided with an electromagnetically driven anode air discharge valve 51, and the purge gas discharge pipe 37 is provided with an electromagnetically driven purge valve 52. The anode air discharge pipe 36 has a pipe diameter larger than that of the purge gas discharge pipe 37.

  Next, air (cathode gas) is pressurized by the air compressor 33, passes through the cathode gas supply pipe 24, and is then supplied to the cathode gas flow path 22 of the fuel cell 11. After this oxygen in the air is used as an oxidizing agent for power generation, it is discharged from the fuel cell 11 to the cathode offgas discharge pipe 38 as cathode offgas. The cathode offgas discharge pipe 38 is connected to the dilution box 31 and then exhausted to the outside of the vehicle. A back pressure valve 34 is provided in the cathode off gas discharge pipe 38.

  Further, in the cathode gas supply pipe 24 connecting the air compressor 33 and the fuel cell 11, the pipe is branched and one end of the scavenging gas introduction pipe 53 is connected. The other end of the scavenging gas introduction pipe 53 is connected between the ejector 26 and the fuel cell 11 in the anode gas supply pipe 23. That is, the air pressurized by the air compressor 33 can be supplied to the anode gas passage 21 of the fuel cell 11. The scavenging gas introduction pipe 53 is provided with an electromagnetically driven solenoid valve 54 so that the supply of air from the air compressor 33 can be shut off.

  Here, a temperature sensor 41 is provided immediately after (on the downstream side of) the anode offgas discharge communication hole 14 in the anode offgas discharge pipe 35. The temperature sensor 41 can detect substantially the same temperature as the temperature inside the fuel cell 11. The detection result (sensor output) from the temperature sensor 41 is transmitted to a control unit (ECU) 45, and based on the detection result, whether or not to perform anode scavenging of the fuel cell 11 (which will be described in detail later). Is configured to determine.

  FIG. 2 is a schematic block diagram of the control device 45. As shown in FIG. 2, the control device 45 includes a stop time detection unit 46 that counts the time since the fuel cell system 10 is stopped, and a time counted by the stop time detection unit 46 for a predetermined time. An anode scavenging execution determination unit 47 that determines whether or not to perform anode scavenging when it has elapsed, an anode scavenging completion determination unit 48 that determines whether or not anode scavenging has been completed when anode scavenging is performed, A purge valve droplet removal completion determination unit 49 that determines whether or not purge valve droplet removal for removing droplets attached to the purge valve 52 after scavenging is completed is completed.

  Further, the control device 45 can supply a predetermined amount of hydrogen gas from the hydrogen tank 30 to the fuel cell 11 by controlling the electromagnetic valve 25 according to the output required for the fuel cell 11. . The control device 45 drives the air compressor 33 according to the output required for the fuel cell 11 to supply a predetermined amount of air to the fuel cell 11 and controls the back pressure valve 34 to control the cathode gas flow path. It is comprised so that the supply pressure of the air to 22 can be adjusted.

  Then, when scavenging the anode gas supply pipe 23 and the anode off-gas discharge pipe 35 in accordance with an instruction from the anode scavenging execution determination unit 47, the electromagnetic valve 54 of the scavenging gas introduction pipe 53 is controlled to supply a predetermined amount of air. It is configured to be able to.

(Fuel cell system scavenging method)
Next, the scavenging method of the fuel cell system 10 in the present embodiment will be described.
FIG. 3 is a flowchart of the scavenging method of the fuel cell system 10, and FIG. 4 is a time chart showing the flow of FIG.
As shown in FIGS. 3 and 4, in S11, after turning off an ignition switch (not shown), which is a start signal of the fuel cell system 10, (whether T10 in FIG. 4), it is determined whether or not anode scavenging is necessary. judge. In this determination, the anode scavenging execution determination unit 47 of the control device 45 determines whether or not the anode scavenging is executed according to the temperature detected by the temperature sensor 41. If it is determined that anode scavenging is necessary, the process proceeds to step S12. If it is determined that anode scavenging is not necessary, the process is terminated. When it is determined that the anode scavenging is not necessary, the temperature of the temperature sensor 41 is detected at predetermined time intervals according to an instruction from the stop time detection unit 46 without ending the process, and the detected temperature becomes equal to or lower than the predetermined temperature. In such a case, it may be determined that anode scavenging is necessary, and the process may proceed to step S12.

  In step S12, anode scavenging is executed (at time T11 in FIG. 4). Specifically, the solenoid valve 54 (scavenging IN valve) of the scavenging gas introduction pipe 53, the anode air discharge valve 51 (scavenging OUT valve) of the anode air discharge pipe 36, and the purge valve 52 of the purge gas discharge pipe 37 are opened, The back pressure valve 34 of the cathode offgas discharge pipe 38 is closed. Then, by driving the air compressor 33, the pressurized air is supplied to the anode side, thereby performing anode scavenging.

  In step S13, it is determined whether or not anode scavenging has been completed. Specifically, the anode scavenging completion determination unit 48 of the control device 45 measures, for example, the time from the start of the anode scavenging, and determines that the anode scavenging has been completed when a predetermined time has elapsed. At this time, most of the air (scavenging gas) introduced from the air compressor 33 is discharged from the anode air discharge pipe 36. This is because the anode air discharge pipe 36 has a larger pipe diameter than the purge gas discharge pipe 37, and therefore has a low resistance and a larger flow rate of air flows. Further, when determining whether or not the anode scavenging has been completed based on the elapsed time, a correction may be made based on the temperature detected by the temperature sensor 41, the amount of generated water, or the like. If it is determined that the anode scavenging has been completed, the process proceeds to step S14.

  In step S14, only the anode air discharge valve 51 of the anode air discharge pipe 36 is closed (at time T12 in FIG. 4). In this way, the air introduced from the air compressor 33 is discharged from the purge gas discharge pipe 37. That is, in step S12, a large amount of scavenging gas flows through the anode air discharge pipe 36 having a large pipe diameter, and droplets adhering to the anode air discharge valve 51 can be removed. In step S14, the purge gas having a small pipe diameter is removed. The scavenging gas can be reliably circulated through the discharge pipe 37, and the droplets adhering to the purge valve 52 can be reliably removed. At this time, the internal pressure of the anode system such as the anode air discharge pipe 36 increases.

  In step S15, it is determined whether or not the droplets adhering to the purge valve 52 have been removed. Specifically, the rotational speed and driving time of the air compressor 33 are detected, and when a predetermined flow rate of air (scavenging gas) flows through the purge valve 52, it is determined that the droplet removal of the purge valve 52 has been completed. In the purge valve droplet removal completion determination unit 49 of the control device 45, for example, the time after the anode air discharge valve 51 is closed in step S14 is measured, and when a predetermined time elapses, the droplet removal of the purge valve 52 is removed. It may be determined that is completed.

  In step S16, the purge valve 52 and the electromagnetic valve 54 are closed, and the back pressure valve 34 is opened. And the drive of the air compressor 33 is stopped and a process is complete | finished (at T13 of FIG. 4).

  The electric power necessary for the above-described anode scavenging is secured from, for example, a battery (not shown) that stores the electric power of the fuel cell.

  According to the present embodiment, after it is determined that scavenging in the anode gas supply pipe 23 and the anode off-gas discharge pipe 35 has been completed, the purge valve 52 is opened while the anode air discharge valve 51 is closed first. In order to maintain for a predetermined time, it is possible to circulate sufficient air (scavenging gas) through the purge valve 52 and the purge gas discharge pipe 37, and to reliably remove water droplets (generated water) adhering to the purge valve 52 and the like. Can do. Therefore, when the fuel cell system 10 is started next time, it is possible to prevent the occurrence of an opening / closing failure due to the freezing of the purge valve 52, and the system can be reliably started.

(Second embodiment)
Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. Note that this embodiment is different from the first embodiment only in the method of scavenging the anode, and the configuration of the fuel cell system is substantially the same as that of the first embodiment. Description is omitted.

(Fuel cell system scavenging method)
A scavenging method of the fuel cell system 10 in the present embodiment will be described.
FIG. 5 is a flowchart of the scavenging method of the fuel cell system 10, and FIG. 6 is a time chart showing the flow of FIG.
As shown in FIGS. 5 and 6, in S21, after turning off an ignition switch (not shown), which is a start signal of the fuel cell system 10, (T20 in FIG. 6), whether or not anode scavenging is necessary is determined. judge. This determination method is the same as step S11 of the first embodiment.

  In step S22, anode scavenging is executed (at time T21 in FIG. 6). Specifically, the solenoid valve 54 of the scavenging gas introduction pipe 53, the anode air discharge valve 51 of the anode air discharge pipe 36, and the purge valve 52 of the purge gas discharge pipe 37 are opened, and the back pressure valve 34 of the cathode offgas discharge pipe 38 is opened. Close the valve. Then, by driving the air compressor 33, the pressurized air is supplied to the piping on the anode side, whereby the anode scavenging is executed.

  In step S23, it is determined whether or not anode scavenging has been completed. Specifically, the anode scavenging completion determination unit 48 of the control device 45 measures, for example, the time from the start of the anode scavenging, and determines that the anode scavenging has been completed when a predetermined time has elapsed.

In step S24, only the anode air discharge valve 51 of the anode air discharge pipe 36 is closed.
In step S25, the rotational speed of the air compressor 33 is increased substantially simultaneously with step S24 (at time T22 in FIG. 6). By doing in this way, the air introduced from the air compressor 33 is discharged from the purge gas discharge pipe 37 at a high flow rate. That is, the droplets adhering to the purge valve 52 can be removed more powerfully.

  In step S26, it is determined whether or not the droplets adhering to the purge valve 52 have been removed. Specifically, the rotational speed and driving time of the air compressor 33 are detected, and when a predetermined flow rate of air (scavenging gas) flows through the purge valve 52, it is determined that the droplet removal of the purge valve 52 has been completed.

  In step S27, the purge valve 52 is closed and the back pressure valve 34 is opened. Then, the driving of the air compressor 33 is stopped and the process is terminated (at time T23 in FIG. 6).

  According to this embodiment, when removing water droplets from the purge valve 52, the scavenging gas flow rate supplied to the purge valve 52 is increased, so that water droplet removal efficiency can be improved. Therefore, the generated water adhering to the purge valve 52 when the fuel cell 11 is stopped can be scavenged more reliably.

(Third embodiment)
Next, a third embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. Note that this embodiment is different from the first embodiment only in the method of scavenging the anode, and the configuration of the fuel cell system is substantially the same as that of the first embodiment. Description is omitted.

(Fuel cell system scavenging method)
A scavenging method of the fuel cell system 10 in the present embodiment will be described.
FIG. 7 is a flowchart of the scavenging method of the fuel cell system 10, and FIG. 8 is a time chart showing the flow of FIG.
As shown in FIGS. 7 and 8, in S31, after turning off an ignition switch (not shown), which is a start signal of the fuel cell system 10, (T30 in FIG. 8), whether or not anode scavenging is necessary is determined. judge. This determination method is the same as step S11 of the first embodiment.

  In step S32, anode scavenging is executed (at time T31 in FIG. 8). Specifically, the solenoid valve 54 of the scavenging gas introduction pipe 53, the anode air discharge valve 51 of the anode air discharge pipe 36, and the purge valve 52 of the purge gas discharge pipe 37 are opened, and the back pressure valve 34 of the cathode offgas discharge pipe 38 is opened. Close the valve. Then, by driving the air compressor 33, the pressurized air is supplied to the piping on the anode side, whereby the anode scavenging is executed.

  In step S33, it is determined whether or not anode scavenging has been completed. Specifically, the anode scavenging completion determination unit 48 of the control device 45 measures, for example, the time from the start of the anode scavenging, and determines that the anode scavenging has been completed when a predetermined time has elapsed.

In step S34, only the anode air discharge valve 51 of the anode air discharge pipe 36 is closed (at time T32 in FIG. 8).
In step S35, after a predetermined time has elapsed from step S34, the opening of the back pressure valve 34 is set to a half-open state (opening: about 50%) (at time T33 in FIG. 8). In this way, the pressure in the anode system can be reduced, and the purge valve 52 can be prevented while preventing droplets remaining in the fuel cell 11 and the like from adhering to the purge valve 52 due to pressure fluctuations. It is possible to remove the droplets already attached to the surface. In addition, since air (scavenging gas) also flows through the cathode offgas discharge pipe 38 provided with the back pressure valve 34, it is possible to remove droplets attached to the back pressure valve 34. Note that the back pressure valve 34 may be in a half-open state substantially simultaneously with step S34.

  In step S36, it is determined whether or not the droplets adhering to the purge valve 52 have been removed. Specifically, the rotational speed and driving time of the air compressor 33 are detected, and when a predetermined flow rate of air (scavenging gas) flows through the purge valve 52, it is determined that the droplet removal of the purge valve 52 has been completed.

  In step S37, the purge valve 52 is closed and the back pressure valve 34 is opened. Then, the driving of the air compressor 33 is stopped and the process is terminated (at time T34 in FIG. 8).

  According to the present embodiment, since the pressure in the anode system during the water droplet removal of the purge valve 52 is made lower than the pressure at the start of water droplet removal of the purge valve 52, the generated water remaining in the fuel cell 11 or the like It is possible to prevent the water from being guided to the purge valve 52. Therefore, water droplet removal from the purge valve 52 can be executed efficiently.

(Fourth embodiment)
Next, a fourth embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. Note that this embodiment is different from the first embodiment only in the method of scavenging the anode, and the configuration of the fuel cell system is substantially the same as that of the first embodiment. Description is omitted.

(Fuel cell system scavenging method)
A scavenging method of the fuel cell system 10 in the present embodiment will be described.
FIG. 9 is a flowchart of the scavenging method of the fuel cell system 10, and FIG. 10 is a time chart showing the flow of FIG.
As shown in FIGS. 9 and 10, in S41, after turning off an ignition switch (not shown), which is a start signal of the fuel cell system 10, (whether T40 in FIG. 10), whether or not anode scavenging is necessary is determined. judge. This determination method is the same as step S11 of the first embodiment.

  In step S42, anode scavenging is executed (at time T41 in FIG. 10). Specifically, the solenoid valve 54 of the scavenging gas introduction pipe 53, the anode air discharge valve 51 of the anode air discharge pipe 36, and the purge valve 52 of the purge gas discharge pipe 37 are opened, and the back pressure valve 34 of the cathode offgas discharge pipe 38 is opened. Close the valve. Then, by driving the air compressor 33, the pressurized air is supplied to the piping on the anode side, whereby the anode scavenging is executed.

  In step S43, it is determined whether or not anode scavenging has been completed. Specifically, the anode scavenging completion determination unit 48 of the control device 45 measures, for example, the time from the start of the anode scavenging, and determines that the anode scavenging has been completed when a predetermined time has elapsed.

In step S44, only the anode air discharge valve 51 of the anode air discharge pipe 36 is closed (at time T42 in FIG. 10).
In step S45, after a predetermined time has elapsed from step S44, the opening of the back pressure valve 34 is set to a half-open state (opening: about 50%) (from time T43 to time T44 in FIG. 10). In the present embodiment, when the opening degree of the back pressure valve 34 is adjusted, the opening speed of the valve is slowed down. That is, the back pressure valve 34 is gradually opened at a predetermined rate. By doing so, the pressure fluctuation in the anode system can be moderated, and droplets remaining in the fuel cell 11 and the like adhere (inflow) to the purge valve 52 due to the sudden pressure fluctuation. The droplets already attached to the purge valve 52 can be removed while preventing the droplets discharged to the downstream side (dilution box 31 side) of the purge valve 52 from flowing back. it can. In addition, since air (scavenging gas) also flows through the cathode offgas discharge pipe 38 provided with the back pressure valve 34, it is possible to remove droplets attached to the back pressure valve 34. Further, noise generated from the back pressure valve 34 due to sudden pressure fluctuation can be prevented. Further, the half-open state of the back pressure valve 34 is held for a predetermined time (from T44 to T45 in FIG. 10). By doing in this way, the droplet adhering to the valve body of the back pressure valve 34 (mainly the droplet adhering to the edge part of a valve body) can be removed efficiently.

  In step S46, it is determined whether or not the droplets adhering to the purge valve 52 have been removed. Specifically, the rotational speed and driving time of the air compressor 33 are detected, and when a predetermined flow rate of air (scavenging gas) flows through the purge valve 52, it is determined that the droplet removal of the purge valve 52 has been completed.

  In step S47, the purge valve 52 is closed and the back pressure valve 34 is opened. And the drive of the air compressor 33 is stopped and a process is complete | finished (T45-T46 time of FIG. 10). In addition, when adjusting the opening degree of the back pressure valve 34, the opening speed of the valve is slowed as in step S45. By doing so, the pressure fluctuation in the anode system can be moderated, and droplets remaining in the fuel cell 11 and the like adhere (inflow) to the purge valve 52 due to the sudden pressure fluctuation. It is possible to prevent the liquid discharged to the downstream side (dilution box 31 side) of the purge valve 52 from flowing backward. Further, noise generated from the back pressure valve 34 due to sudden pressure fluctuation can be prevented.

  According to the present embodiment, after it is determined that scavenging in the anode gas supply pipe 23 and the anode off-gas discharge pipe 35 has been completed, the purge valve 52 is opened while the anode air discharge valve 51 is closed first. In order to maintain for a predetermined time, it is possible to circulate sufficient air (scavenging gas) through the purge valve 52 and the purge gas discharge pipe 37, and to reliably remove water droplets (generated water) adhering to the purge valve 52 and the like. Can do. Therefore, when the fuel cell system 10 is started next time, it is possible to prevent the occurrence of an opening / closing failure due to the freezing of the purge valve 52, and the system can be reliably started.

  In addition, since the pressure in the anode system can be gradually reduced after the anode scavenging is completed, noise caused by pressure fluctuation can be prevented. Further, the droplets attached to the purge valve 52 can be removed, and the droplets attached to the back pressure valve 34 provided in the cathode offgas discharge pipe 38 can be removed.

(Fifth embodiment)
Next, a fifth embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. Note that this embodiment is different from the first embodiment only in the method of scavenging the anode, and the configuration of the fuel cell system is substantially the same as that of the first embodiment. Description is omitted.

(Fuel cell system scavenging method)
A scavenging method of the fuel cell system 10 in the present embodiment will be described.
FIG. 11 is a flowchart of the scavenging method of the fuel cell system 10, and FIG. 12 is a time chart showing the flow of FIG.
As shown in FIGS. 11 and 12, in S51, after turning off an ignition switch (not shown), which is a start signal of the fuel cell system 10, (whether T50 in FIG. 12), whether or not anode scavenging is necessary is determined. judge. This determination method is the same as step S11 of the first embodiment.

  In step S52, anode scavenging is executed (at time T51 in FIG. 12). Specifically, the solenoid valve 54 of the scavenging gas introduction pipe 53, the anode air discharge valve 51 of the anode air discharge pipe 36, and the purge valve 52 of the purge gas discharge pipe 37 are opened, and the back pressure valve 34 of the cathode offgas discharge pipe 38 is opened. Close the valve. Then, by driving the air compressor 33, the pressurized air is supplied to the piping on the anode side, whereby the anode scavenging is executed.

  In step S53, it is determined whether or not anode scavenging has been completed. Specifically, the anode scavenging completion determination unit 48 of the control device 45 measures, for example, the time from the start of the anode scavenging, and determines that the anode scavenging has been completed when a predetermined time has elapsed.

In step S54, only the anode air discharge valve 51 of the anode air discharge pipe 36 is closed (at time T52 in FIG. 12).
In step S55, after a predetermined time has elapsed from step S54, the opening of the back pressure valve 34 is fully opened (from time T53 to time T54 in FIG. 12). In the present embodiment, when the opening degree of the back pressure valve 34 is adjusted, the opening speed of the valve is slowed down. That is, the back pressure valve 34 is gradually opened at a predetermined rate. By doing so, the pressure fluctuation in the anode system can be moderated, and droplets remaining in the fuel cell 11 and the like adhere (inflow) to the purge valve 52 due to the sudden pressure fluctuation. The droplets already attached to the purge valve 52 can be removed while preventing the droplets discharged to the downstream side (dilution box 31 side) of the purge valve 52 from flowing back. it can. In addition, since air (scavenging gas) also flows through the cathode offgas discharge pipe 38 provided with the back pressure valve 34, it is possible to remove droplets attached to the back pressure valve 34. Further, noise generated from the back pressure valve 34 due to sudden pressure fluctuation can be prevented.

  In step S56, it is determined whether or not the droplets adhering to the purge valve 52 have been removed. Specifically, the rotational speed and driving time of the air compressor 33 are detected, and when a predetermined flow rate of air (scavenging gas) flows through the purge valve 52, it is determined that the droplet removal of the purge valve 52 has been completed.

  In step S57, the purge valve 52 is closed and the driving of the air compressor 33 is stopped, and the process is terminated (at time T54 in FIG. 12).

  According to the present embodiment, after it is determined that scavenging in the anode gas supply pipe 23 and the anode off-gas discharge pipe 35 has been completed, the purge valve 52 is opened while the anode air discharge valve 51 is closed first. In order to maintain for a predetermined time, it is possible to circulate sufficient air (scavenging gas) through the purge valve 52 and the purge gas discharge pipe 37, and to reliably remove water droplets (generated water) adhering to the purge valve 52 and the like. Can do. Therefore, when the fuel cell system 10 is started next time, it is possible to prevent the occurrence of an opening / closing failure due to the freezing of the purge valve 52, and the system can be reliably started.

  In addition, since the pressure in the anode system can be gradually reduced after the anode scavenging is completed, noise caused by pressure fluctuation can be prevented. Further, the droplets attached to the purge valve 52 can be removed, and the droplets attached to the back pressure valve 34 provided in the cathode offgas discharge pipe 38 can be removed.

Note that the present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention. That is, the specific structure and configuration described in the embodiment are merely examples, and can be changed as appropriate.
For example, in the present embodiment, the temperature sensor for detecting the temperature of the fuel cell is attached to the anode offgas discharge pipe, but the temperature of the fuel cell may be directly detected, and the cathode offgas discharge pipe, refrigerant, gas, You may employ | adopt the temperature of a peripheral auxiliary machine as an alternative temperature. Further, the temperature sensor may be attached not only at one place but also at a plurality of places. In that case, any temperature may be detected, or an average value of each temperature sensor may be obtained.
In the present embodiment, the back pressure valve 34 is scavenged at the end of the scavenging of the purge valve 52. By maintaining a constant anode pressure at that time, the anode air discharge valve 51 or the electromagnetic valve 54 is broken down. You may make it the structure which detects simultaneously.
Further, in this embodiment, when the anode air discharge valve 51 is closed and the electromagnetic valve 54 and the purge valve 52 are opened for a predetermined time, the pressure in the anode (or the cathode) is continuously increased. Further, it may be configured to simultaneously detect the closing failure of the electromagnetic valve 54 by the pressure change at that time.

1 is a schematic configuration diagram of a fuel cell system in an embodiment of the present invention. It is a schematic block diagram of the control apparatus in embodiment of this invention. It is a flowchart which shows the scavenging method of the fuel cell system in 1st embodiment of this invention. It is a time chart which shows the scavenging method of the fuel cell system in 1st embodiment of this invention. It is a flowchart which shows the scavenging method of the fuel cell system in 2nd embodiment of this invention. It is a time chart which shows the scavenging method of the fuel cell system in 2nd embodiment of this invention. It is a flowchart which shows the scavenging method of the fuel cell system in 3rd embodiment of this invention. It is a time chart which shows the scavenging method of the fuel cell system in 3rd embodiment of this invention. It is a flowchart which shows the scavenging method of the fuel cell system in 4th embodiment of this invention. It is a time chart which shows the scavenging method of the fuel cell system in 4th embodiment of this invention. It is a flowchart which shows the scavenging method of the fuel cell system in 5th embodiment of this invention. It is a time chart which shows the scavenging method of the fuel cell system in 5th embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 11 ... Fuel cell 23 ... Anode gas supply piping (anode gas flow path) 33 ... Air compressor (scavenging gas supply means) 34 ... Back pressure valve 35 ... Anode off-gas discharge piping (anode gas flow path) 41 ... Temperature Sensor 51 ... Anode air discharge valve (scavenging valve) 52 ... Purge valve

Claims (6)

A fuel cell for generating electricity by supplying an anode gas to the anode electrode and a cathode gas to the cathode electrode; and
An anode gas flow path through which the anode gas flows;
A purge valve that can be opened and closed to discharge the gas in the anode gas channel out of the channel;
A scavenging gas supply means for supplying a scavenging gas into the anode gas flow path;
A scavenging valve configured to be openable and closable for discharging the scavenging gas supplied into the anode gas channel out of the channel, and having a discharge channel cross-sectional area larger than the purge valve,
After the fuel cell is started and stopped, the inside of the anode gas channel is scavenged using the scavenging gas supplied by the scavenging gas supply means, and the scavenging gas can be discharged from the purge valve and the scavenging valve. A fuel cell system,
It is judged that scavenging in the anode gas channel is completed, and the scavenging gas is configured to be discharged from the purge valve to the outside of the channel for a predetermined time with the scavenging valve closed. Fuel cell system.   2. The fuel cell according to claim 1, wherein when the scavenging gas is discharged from the purge valve in a state where the scavenging valve is closed, a scavenging gas supply amount of the scavenging gas supply unit is increased. system. Pressure adjusting means for adjusting the pressure of the scavenging gas;
The pressure in the anode gas flow path is configured to be lower than the pressure at the start of the scavenging gas discharge from the purge valve by the pressure adjusting means. Fuel cell system.   4. The fuel cell system according to claim 3, wherein the pressure adjusting means is configured to be able to reduce the pressure in the anode gas flow path at a predetermined rate. The scavenging gas supply means is a cathode gas supply means for supplying the cathode gas to the cathode electrode,
The pressure adjusting means is a back pressure valve that adjusts the pressure of the cathode gas passage through which the cathode gas flows,
The cathode gas is configured to be supplied into the anode gas flow path as the scavenging gas by closing the back pressure valve,
5. The fuel cell system according to claim 3, wherein the pressure in the anode gas flow path is adjustable by adjusting the opening of the back pressure valve. A fuel cell for generating electricity by supplying an anode gas to the anode electrode and a cathode gas to the cathode electrode; and
An anode gas flow path through which the anode gas flows;
A purge valve that can be opened and closed to discharge the gas in the anode gas channel out of the channel;
A scavenging gas supply means for supplying a scavenging gas into the anode gas flow path;
A scavenging valve configured to be openable and closable for discharging the scavenging gas supplied into the anode gas channel out of the channel, and having a discharge channel cross-sectional area larger than the purge valve,
A scavenging method for a fuel cell system, wherein the scavenging gas supplied by the scavenging gas supply means is used to scavenge the anode gas flow path after the fuel cell is started and stopped.
A scavenging determination step for determining whether scavenging in the anode gas flow path is necessary after the fuel cell is started and stopped;
An anode scavenging step for scavenging the anode gas flow path;
Anode scavenging completion determination step for determining whether scavenging in the anode gas flow path is completed,
A scavenging valve closing step for closing the scavenging valve;
And a purge valve scavenging determination step for determining whether or not the scavenging gas has passed through the purge valve.

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