JP2011044337A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing freezing of a reactant gas flow channel without wasting power. <P>SOLUTION: The fuel cell system 10 includes a fuel cell 11, reactant gas flow channels 23, 24, 35, 38, reactant gas-supplying parts 30, 33, upstream-side valves 25, 46 arranged at upstream-side reactant gas flow channels of the fuel cell, downstream-side valves 48, 51, 52, 47 arranged at downstream-side reactant gas flow channels of the fuel cell, and a control part 45 carrying out various control. The control part is provided with a freeze prediction part for predicting freeze of the system, and, with the upstream valves opened and downstream side valves closed, operates the reactant gas-supplying parts to supply reactant gas into the reactant gas flow channels until it reaches a first given pressure greater than the ambient pressure. Thereafter, the upstream-side valves are closed to seal the reactant gas inside the reactant gas flow channels. When freezing is predicted by the freezing prediction part, the downstream side valves are opened to drain the reactant gas. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a 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. The thing which employ | adopted the structure which discharges | emits produced | generated water outside at the time of a driving | operation stop is proposed (for example, refer patent document 1).

  In the fuel cell system of Patent Document 1, immediately after the operation is stopped, the rotational speed of the air compressor constituting the cathode gas supply unit is increased over a predetermined time, and the back pressure valve and the discharge valve are closed. It is determined whether or not the pressure of the reaction gas flowing through the fuel cell has risen to the specified pressure. If the determination result is YES, the back pressure valve and the discharge valve are fully opened and the generated water (residual water) is removed from the system. To be discharged.

JP 2002-305017 A

  By the way, in the fuel cell system of Patent Document 1, regardless of the surrounding environment, when the pressure of the anode gas flow path rises to a predetermined pressure, the back pressure valve and the discharge valve are fully opened to generate water (residual water). ) Is discharged out of the system. That is, since the back pressure valve and the discharge valve are driven even when the generated water is not likely to freeze, useless power is used, and there is a possibility that power for performing the scavenging process cannot be secured thereafter.

  Accordingly, the present invention has been made in view of the above circumstances, and provides a fuel cell system that can prevent freezing of a reaction gas channel without using wasteful power.

  In order to solve the above problems, the invention described in claim 1 is a reaction gas flow path through which a reaction gas flows (for example, an anode gas supply pipe 23, a cathode gas supply pipe 24, and an anode off-gas discharge pipe 35 in the embodiment). , A cathode offgas discharge pipe 38), a fuel cell (for example, the fuel cell 11 in the embodiment) that generates power when the reaction gas is supplied, and a reaction gas supply that supplies the reaction gas to the reaction gas channel. (For example, the hydrogen tank 30 and the air compressor 33 in the embodiment) and the upstream valve (for example, the solenoid valve 25 and the cathode gas upstream seal in the embodiment) disposed in the reaction gas flow path upstream of the fuel cell. A stop valve 46) and a downstream valve (for example, an air discharge valve 48 in the embodiment, a drain) disposed in the reaction gas flow path downstream of the fuel cell. Fuel cell system (for example, the fuel in the embodiment), and the control unit (for example, the control device 45 in the embodiment) that performs various controls. In the battery system 10), the control unit includes a freezing prediction unit (for example, the freezing prediction unit 62 in the embodiment) that predicts freezing of the system, and opens the upstream valve and the downstream valve. With the reaction gas closed, the reaction gas supply unit is operated to supply the reaction gas in the reaction gas channel until the reaction gas reaches a first predetermined pressure greater than atmospheric pressure, and then the upstream valve is closed. The reaction gas is contained in the reaction gas flow path, and when the freezing is predicted by the freezing preside, the downstream valve is opened to discharge the reaction gas. .

  According to a second aspect of the present invention, the reaction gas channel includes an anode gas channel that supplies an anode gas to the anode electrode of the fuel cell, and a cathode gas channel that supplies a cathode gas to the cathode electrode of the fuel cell. The control unit is characterized in that the anode gas or the cathode gas is contained in the anode gas flow path, and the cathode gas is contained in the cathode gas flow path.

  According to a third aspect of the present invention, there is provided a reaction gas flow path through which a reaction gas flows, a fuel cell that generates power by supplying the reaction gas, and a reaction gas that supplies the reaction gas to the reaction gas flow path. A supply unit, an upstream valve disposed in a reaction gas channel upstream of the fuel cell, a downstream valve disposed in a reaction gas channel downstream of the fuel cell, and a control unit that performs various controls The control unit has a freezing confirmation unit (for example, the freezing confirmation unit 65 in the embodiment) for confirming the freezing state of the system, and the freezing confirmation unit confirms freezing. In the case where the upstream side valve is opened and the downstream side valve is closed, the reactive gas supply unit is actuated so that the reactive gas is larger than atmospheric pressure in the reactive gas flow path. (2) After supplying until a predetermined pressure is reached By closing the upstream valve, it encapsulates the reaction gas to the reaction gas flow path, and characterized by discharging the reaction gas by opening the downstream valve.

  According to a fourth aspect of the present invention, the control unit further includes a freeze prediction unit that predicts freezing of the system, and the reaction is performed in a state where the upstream valve is opened and the downstream valve is closed. After operating the gas supply unit and supplying the reaction gas into the reaction gas channel until the reaction gas reaches a first predetermined pressure greater than atmospheric pressure, the upstream valve is closed and the reaction gas channel is closed. The reaction gas is contained, and when the freezing is predicted by the freezing preside, the downstream valve is opened to discharge the reaction gas, and the second predetermined pressure is It is characterized by being set higher than the first predetermined pressure.

  According to the invention described in claim 1, while the fuel cell is stopped, the reaction gas is introduced into the reaction gas passage so that the pressure in the reaction gas passage becomes a first predetermined pressure higher than the atmospheric pressure. If the containment and freeze prediction unit determines that the fuel cell system may freeze, the downstream valve of the reaction gas flow path is opened to discharge the reaction gas. That is, when there is no risk of the fuel cell system freezing, the operation of the downstream valve can be eliminated and wasteful power consumption can be prevented. If there is a risk of the fuel cell system freezing, the reaction gas passes through the downstream valve by opening the downstream valve provided in the reaction gas flow path maintained at a pressure higher than atmospheric pressure. It will be discharged out of the system at high speed. Therefore, the generated water that is likely to be frozen due to the flow rate of the reaction gas can be blown out of the system, and the reaction gas channel can be prevented from freezing.

  According to the invention described in claim 2, since the reaction gas is supplied to both the anode gas channel and the cathode gas channel so as to be maintained at a high pressure, it is possible to prevent a pressure drop in the anode gas channel. it can. That is, by maintaining the cathode gas flow path at a high pressure, it is possible to prevent the pressure difference between the electrodes from occurring, and the pressure in the anode gas flow path can be maintained at a high pressure for a long time. Further, by maintaining the anode gas flow path at a high pressure, the anode gas flow path becomes high temperature and the occurrence of condensation can be suppressed, so that the reaction gas flow path can be further prevented from freezing.

  According to the third aspect of the present invention, when freezing is confirmed in the fuel cell system while the fuel cell is stopped, the second predetermined pressure in which the pressure in the reaction gas flow path is greater than the atmospheric pressure. The reaction gas is sealed in the reaction gas channel so that At this time, when the pressure of the reaction gas becomes high, the temperature of the reaction gas rises, so that the temperature of the reaction gas channel can be raised. That is, the frozen part formed in the reaction gas flow path or its immediate vicinity can be thawed. After that, since the reaction gas flow path is configured to open the downstream valve of the reaction gas flow path, the reaction gas flow of the reaction gas flow path passes through the downstream side valve and is discharged out of the system at a high speed. It becomes. Therefore, the generated water thawed by the reaction gas flow rate can be blown out of the system.

According to the invention described in claim 4, while the fuel cell is stopped, the reaction gas is introduced into the reaction gas passage so that the pressure in the reaction gas passage becomes a first predetermined pressure higher than the atmospheric pressure. If the containment and freeze prediction unit determines that the fuel cell system may freeze, the downstream valve of the reaction gas flow path is opened to discharge the reaction gas. That is, when there is no risk of the fuel cell system freezing, the operation of the downstream valve can be eliminated and wasteful power consumption can be prevented. If there is a risk of the fuel cell system freezing, the reaction gas passes through the downstream valve by opening the downstream valve provided in the reaction gas flow path maintained at a pressure higher than atmospheric pressure. It will be discharged out of the system at high speed. Therefore, it is possible to blow off the generated water that is likely to be frozen due to the flow rate of the reaction gas to the outside of the system, and to prevent the reaction gas flow path from being frozen in advance.
If the fuel cell system is frozen while the fuel cell is stopped, the reaction gas flow path is set so that the pressure in the reaction gas flow path becomes a second predetermined pressure higher than the atmospheric pressure. To contain the reaction gas. At this time, when the pressure of the reaction gas becomes high, the temperature of the reaction gas rises, so that the temperature of the reaction gas channel can be raised. That is, the frozen part formed in the reaction gas flow path or its immediate vicinity can be thawed. After that, since the reaction gas flow path is configured to open the downstream valve of the reaction gas flow path, the reaction gas flow of the reaction gas flow path passes through the downstream side valve and is discharged out of the system at a high speed. It becomes. Therefore, the generated water thawed by the reaction gas flow rate can be blown out of the system.
In addition, since the second predetermined pressure is set to be higher than the first predetermined pressure, when freezing is confirmed, the reaction gas flow path and its immediate temperature may be made higher than when freezing is predicted. it can. Therefore, the reaction gas flow path and the frozen portion formed in the immediate vicinity thereof can be surely thawed, and then the reaction gas flow path is opened and the reaction gas is discharged to open the downstream side of the reaction gas flow path. The generated water can be reliably blown out of the system.

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 freezing prevention method of the fuel cell system in 1st embodiment of this invention. It is a time chart explaining the opening-and-closing timing of each valve at the time of the freeze prevention measure of the fuel cell system in a first embodiment of the present invention. It is a flowchart which shows the freezing prevention method of the fuel cell system in 2nd embodiment of this invention. It is a graph which shows the relationship between the pressure in piping and temperature in 2nd embodiment of this invention.

(First embodiment)
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. The anode off gas discharge communication hole 14 (the outlet side of the anode gas flow path 21) formed in the fuel cell 11 is connected to an anode off gas discharge pipe 35, and the cathode off gas discharge communication hole 16 (cathode gas flow path 22). 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 discharged 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 three pipes branched in the middle, and a drain discharge pipe 36 for discharging generated water (drain) generated by the fuel cell 11, and an anode pipe. A purge gas discharge pipe 37 for discharging the gas in the pipe to properly maintain the hydrogen concentration in the pipe, and a scavenging gas for discharging the scavenging gas (air) when the scavenging process is performed while the fuel cell 11 is stopped And a gas discharge pipe 32.

  The drain discharge pipe 36, the purge gas discharge pipe 37 and the scavenging gas discharge pipe 32 are all connected to the dilution box 31 downstream thereof. The drain discharge pipe 36 is provided with an electromagnetically driven drain valve 51, the purge gas discharge pipe 37 is provided with an electromagnetically driven purge valve 52, and the scavenging gas discharge pipe 32 is electromagnetically driven. The air discharge valve 48 is provided. The purge gas discharge pipe 37 is attached with a pipe diameter larger than that of the drain discharge pipe 36. The scavenging gas discharge pipe 32 is attached with a pipe diameter larger than that of the purge gas discharge pipe 37. Furthermore, a catch tank 53 is provided as a gas-liquid separator at a branch point between the anode off-gas discharge pipe 35 and the drain discharge pipe 36.

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 oxidant for power generation, it is discharged from the fuel cell 11 to the cathode offgas discharge pipe 38 as the cathode offgas. The cathode offgas discharge pipe 38 is connected to the dilution box 31 and then exhausted outside the vehicle. A back pressure valve 34 is provided in the cathode off gas discharge pipe 38. The cathode gas supply pipe 24 is provided with an electromagnetically driven cathode gas upstream side sealing valve 46, and the cathode offgas discharge pipe 38 is provided with an electromagnetically driven cathode gas downstream side sealing valve 47. Yes.
A humidifier (not shown) may be provided between the cathode gas supply pipe 24 and the cathode offgas discharge pipe 38 so that the cathode gas is humidified by movement of moisture contained in the cathode offgas. Good.

  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 54 is connected. The other end of the scavenging gas introduction pipe 54 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 54 is provided with an electromagnetically driven solenoid valve 55 so that the supply of air from the air compressor 33 can be shut off.

  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 dilution gas supply pipe 56 is connected. The other end of the dilution gas supply pipe 56 is connected to the dilution box 31. That is, the air pressurized by the air compressor 33 can be supplied to the dilution box 31. The dilution gas supply pipe 56 is provided with an electromagnetically driven electromagnetic valve 57 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 fuel cell 11 is also provided with a temperature sensor 42. For example, by averaging the detected temperatures of the temperature sensors 41 and 42, a temperature substantially the same as the temperature inside the fuel cell 11 can be detected. Detection results (sensor outputs) from the temperature sensors 41 and 42 are transmitted to a control unit (ECU) 45, and based on the detection results, it is determined whether or not to execute various controls (described in detail later). It is configured as follows.

  Further, the anode gas supply pipe 23 is provided with a pressure sensor 43 for detecting the gas pressure in the pipe. The pressure sensor 43 is provided between the joining point of the anode gas supply pipe 23 and the scavenging gas introduction pipe 54 and the anode gas supply communication hole 13 of the fuel cell 11. Similarly, the cathode gas supply pipe 24 is provided with a pressure sensor 44 for detecting the gas pressure in the pipe. The pressure sensor 44 is provided between the cathode gas upstream side sealing valve 46 and the cathode gas supply communication hole 15 of the fuel cell 11.

  FIG. 2 is a schematic block diagram of the control device 45. As shown in FIG. 2, the control device 45 may cause the fuel cell system 10 to freeze, and the gas pressure increase execution unit 61 that performs a process of increasing the gas pressure in the fuel cell 11 when the ignition switch is turned off. A freezing prediction unit 62 for determining whether or not there is, a pressure release processing execution unit 63 for executing pressure release in the fuel cell 11, a scavenging process execution unit 64 for executing a scavenging process while the fuel cell 11 is stopped, have.

  The control device 45 can control the electromagnetic valve 25 according to the output required for the fuel cell 11 to supply a predetermined amount of hydrogen gas from the hydrogen tank 30 to 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.

  Further, in order to suppress an increase in the hydrogen concentration in the dilution box 31, the electromagnetic valve 57 of the dilution gas supply pipe 56 is controlled so that a predetermined amount of air can be supplied.

(Fuel cell system freeze prevention method)
Next, a method for preventing freezing of the fuel cell system 10 in the present embodiment will be described.
FIG. 3 is a flowchart of the freeze prevention method of the fuel cell system 10.
As shown in FIG. 3, the flowchart starts from a state in which an ignition switch (not shown) that is a start signal of the fuel cell system 10 is turned off.

  In step S11, the gas pressure in the piping of the fuel cell system 10 and the fuel cell 11 is increased. At this time, the gas pressures of both the anode side and the cathode side of the fuel cell system 10 are increased. Specifically, the solenoid valve 25, the air discharge valve 48, the drain valve 51, and the purge valve 52 are closed and the solenoid valve 55 is opened according to an instruction from the gas pressure increase execution unit 61 of the control device 45. By driving the air compressor 33 in this state, air is supplied to the anode side. Since each valve is closed, the gas pressure on the anode side increases. On the other hand, the cathode side closes the cathode gas downstream side sealing valve 47 and the electromagnetic valve 57 and opens the cathode gas upstream side sealing valve 46. By supplying air to the cathode in this state, the gas pressure on the cathode increases.

  In step S12, when the detected value of the pressure sensor 43 becomes a predetermined value or more, the electromagnetic valve 55 is closed, and gas (air) is sealed on the anode side. Further, when the detected value of the pressure sensor 44 becomes a predetermined value or more, the cathode gas upstream side sealing valve 46 is closed to contain gas (air) on the cathode side. In addition, the predetermined pressure value at the time of containment is set to a value larger than the atmospheric pressure obtained by a prior experiment or the like.

  In step S13, it is determined whether or not the ignition switch is turned on. If the ignition switch is turned on, the process proceeds to step S14. If the ignition switch remains in the off state, the process proceeds to step S15.

  In step S14, since the ignition switch is turned on, the gas contained in the anode side and the cathode side is discharged and the depressurization process is performed. More specifically, the drain valve 51 or the purge valve 52 is opened in accordance with an instruction from the pressure release processing execution unit 63 of the control device 45, and the gas on the anode side is discharged to reduce the pressure. At substantially the same time, the cathode gas downstream side sealing valve 47 is opened to discharge the cathode side gas to reduce the pressure. At this time, the back pressure valve 34 is opened.

  In step S15, the freeze prediction unit 62 of the control device 45 determines whether or not the fuel cell system 10 is likely to freeze. If it is predicted that there is a risk of freezing, the process proceeds to step S16 and may freeze. If it is determined that there is no, the process returns to step S13. Specifically, the freezing prediction unit 62 is configured to detect the temperatures of the temperature sensors 41 and 42 and to determine that there is a risk of freezing when the temperature becomes lower than a preset threshold temperature.

  In step S16, since it is predicted that the fuel cell system 10 may be frozen, the gas contained in the anode side and the cathode side is discharged and the depressurization process is performed. More specifically, the drain valve 51 or the purge valve 52 is opened in accordance with an instruction from the pressure release processing execution unit 63 of the control device 45, and the gas on the anode side is discharged to reduce the pressure. At substantially the same time, the cathode gas downstream side sealing valve 47 is opened to discharge the cathode side gas to reduce the pressure. At this time, the back pressure valve 34 is opened. When the depressurization is executed as described above, the generated water remaining in the fuel cell system 10 can be discharged at the same time as the gas is discharged. By discharging the generated water when the freezing of the fuel cell system 10 is predicted, it is possible to prevent the generated water from freezing in the fuel cell system 10.

  In step S17, it is determined whether or not the ignition switch is turned on. If the ignition switch is turned on, the process ends. If the ignition switch remains off, the process proceeds to step S18.

  In step S18, it is determined whether or not the ambient temperature of the fuel cell system 10 is equal to or lower than a predetermined temperature. If the temperature is lower than the predetermined temperature, the process proceeds to step S19, and if higher than the predetermined temperature, the process returns to step S17. The predetermined temperature is obtained in advance from an actual experiment or the like, such as −10 ° C., a temperature at which moisture in the gas remaining in the pipe is condensed and frozen. At this time, the determination may be made using the temperature sensors 41 and 42, or a temperature sensor (not shown) is provided in the immediate vicinity of the fuel cell system 10, and the determination is made based on the detection value of the temperature sensor. It may be.

  In step S19, the scavenging process of the fuel cell system 10 is executed according to an instruction from the scavenging process execution unit 64 of the control device 45. Specifically, the solenoid valve 25, the drain valve 51, and the purge valve 52 are closed, and the air discharge valve 48 and the solenoid valve 55 are opened. In this state, the air compressor 33 is driven to supply air to the anode side. After supplying air to the anode side for a predetermined time, driving of the air compressor 33 is stopped, the scavenging process is ended, and the freeze prevention process of the fuel cell system 10 is ended. By performing the scavenging treatment, the inside of the anode side pipe can be replaced with low-humidity air capable of suppressing freezing.

  FIG. 4 is a time chart showing the flow of the above-described flowchart. As shown in FIG. 4, the anode pressure and the cathode pressure are maintained at substantially the same pressure higher than the atmospheric pressure after the pressure containment is performed in step S12, and the anode pressure and the cathode pressure are reduced by the depressurization process in step S16. At this time, since the purge valve 52 (or the drain valve 51) is opened, the generated water remaining in the piping is discharged out of the system together with the gas (air). . Further, when the pressure is released, dilution air is supplied to the dilution box 31 in order to prevent the hydrogen concentration in the dilution box 31 from becoming too high. Specifically, the inside of the dilution box 31 is diluted by opening the electromagnetic valve 57 and driving the air compressor 33 to supply air from the dilution gas supply pipe 56 to the dilution box 31.

  According to this embodiment, while the fuel cell system 10 is stopped, air is contained in each flow path so that the pressure in the flow path on the anode side and the cathode side becomes a predetermined pressure higher than the atmospheric pressure. When it is determined that the fuel cell system 10 may be frozen by the freezing prediction unit 62, the anode-side purge valve 51 and the cathode-side cathode gas downstream sealing valve 47 are opened to discharge air. Configured. That is, when the fuel cell system 10 is not likely to freeze, the operations of the anode-side purge valve 51 and the cathode-side cathode gas downstream side sealing valve 47 can be eliminated, thereby preventing wasteful power consumption. Can do. Further, when the fuel cell system 10 may freeze, the anode-side purge valve 51 and the cathode-side cathode gas downstream sealing valve 47 provided in each flow path maintained at a pressure higher than atmospheric pressure are opened. By performing the valve operation, the air passes through the purge valve 51 and the cathode gas downstream side sealing valve 47 and is discharged out of the fuel cell system 10 at a high speed. Therefore, the generated water (residual water) that is likely to be frozen due to the flow rate at the time of air discharge can be blown out of the fuel cell system 10, and the freezing of each flow path can be prevented.

  In addition, since air is supplied to both the anode gas flow channel 21 and the cathode gas flow channel 22 so as to be maintained at a high pressure, a pressure drop in the anode gas flow channel 21 can be prevented. That is, by maintaining the cathode gas flow path 22 at a high pressure, it is possible to prevent the pressure difference between the electrodes from occurring, and the pressure in the anode gas flow path 21 can be maintained at a high pressure for a long time. . In addition, since the anode gas flow channel 21 is kept at a high pressure by holding the anode gas flow channel 21 at a high pressure, it is possible to suppress the occurrence of condensation, so that the reaction gas flow channel (the anode gas flow channel 21 and the cathode gas). Freezing of the flow path 22) can be further prevented.

In the present embodiment, in step S16, the purge valve 52 is opened when the anode side pressure relief is executed, and the gas and generated water are discharged from the purge gas discharge pipe 37. May be opened, or both valves 51 and 52 may be opened to discharge gas and generated water.
Further, in this embodiment, the gas is contained by increasing the pressure on both the anode side and the cathode side. However, since the generated water basically remains on the anode side, the gas pressure is increased only on the anode side and frozen. The pressure relief may be executed at the time when the pressure is predicted.

(Second embodiment)
Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. This embodiment is different from the first embodiment only in the method for preventing freezing of the fuel cell system, and the configuration of the fuel cell system is substantially the same as that of the first embodiment. Detailed description will be omitted. The control device 45 of the present embodiment is provided with a freezing confirmation unit 65 that determines whether or not the fuel cell system 10 is frozen.

(Fuel cell system freeze prevention method)
A method for preventing freezing of the fuel cell system 10 in the present embodiment will be described.
FIG. 5 is a flowchart of a freeze prevention method for the fuel cell system 10.
As shown in FIG. 5, the flowchart starts from a state in which an ignition switch (not shown) that is a start signal of the fuel cell system 10 is turned off.

  In step S21, the gas pressure in the piping of the fuel cell system 10 and the fuel cell 11 is increased. At this time, the gas pressures of both the anode side and the cathode side of the fuel cell system 10 are increased. Specifically, the solenoid valve 25, the air discharge valve 48, the drain valve 51, and the purge valve 52 are closed and the solenoid valve 55 is opened according to an instruction from the gas pressure increase execution unit 61 of the control device 45. By driving the air compressor 33 in this state, air is supplied to the anode side. Since each valve is closed, the gas pressure on the anode side increases. On the other hand, the cathode side closes the cathode gas downstream side sealing valve 47 and the electromagnetic valve 57 and opens the cathode gas upstream side sealing valve 46. By supplying air to the cathode in this state, the gas pressure on the cathode increases.

  In step S22, when the detection value of the pressure sensor 43 becomes equal to or higher than the first predetermined pressure value, the electromagnetic valve 55 is closed to contain gas (air) on the anode side. Further, when the detected value of the pressure sensor 44 becomes equal to or higher than the first predetermined pressure value, the cathode gas upstream side sealing valve 46 is closed to contain gas (air) on the cathode side. Note that the first predetermined pressure value at the time of containment is set to a value larger than the atmospheric pressure obtained in a prior experiment or the like.

  In step S23, it is determined whether or not the ignition switch is turned on. If turned on, the process proceeds to step S24. If the ignition switch remains in the off state, the process proceeds to step S25.

  In step S24, since the ignition switch is turned on, the gas contained in the anode side and the cathode side is discharged and the depressurization process is performed. More specifically, the drain valve 51 or the purge valve 52 is opened in accordance with an instruction from the pressure release processing execution unit 63 of the control device 45, and the gas on the anode side is discharged to reduce the pressure. At substantially the same time, the cathode gas downstream side sealing valve 47 is opened to discharge the cathode side gas to reduce the pressure. At this time, the back pressure valve 34 is opened.

  In step S25, the freeze prediction unit 62 of the control device 45 determines whether or not the fuel cell system 10 is likely to freeze, and if it is predicted that there is a risk of freezing, the process proceeds to step S26 and may freeze. If it is determined that there is no, the process returns to step S23. Specifically, the freezing prediction unit 62 is configured to detect the temperature of the temperature sensors 41 and 42 and to determine that there is a possibility of freezing when the temperature becomes equal to or lower than a preset first threshold temperature. Yes.

  In step S26, since it is predicted that the fuel cell system 10 may be frozen, the gas contained in the anode side and the cathode side is discharged and the depressurization process is performed. More specifically, the drain valve 51 or the purge valve 52 is opened in accordance with an instruction from the pressure release processing execution unit 63 of the control device 45, and the gas on the anode side is discharged to reduce the pressure. At substantially the same time, the cathode gas downstream side sealing valve 47 is opened to discharge the cathode side gas to reduce the pressure. At this time, the back pressure valve 34 is opened. When the depressurization is executed as described above, the generated water remaining in the fuel cell system 10 can be discharged at the same time as the gas is discharged. By discharging the generated water when it is predicted that the fuel cell system 10 will freeze, the generated water is prevented from freezing in the fuel cell system 10.

  In step S27, it is determined whether or not the ignition switch is turned on. If the ignition switch is turned on, the process is terminated as it is, and if the ignition switch is kept off, the process proceeds to step S28.

  In step S28, it is determined whether or not the fuel cell system 10 has been confirmed to be frozen by the freeze confirmation unit 65 of the control device 45. If the freeze has been confirmed, the process proceeds to step S29, and if the freeze has not been confirmed. Return to step S27. Specifically, the temperature of the temperature sensors 41 and 42 is detected, and when the temperature is equal to or lower than a preset second threshold temperature, it is determined that freezing has been confirmed. Here, the second threshold temperature is a temperature lower than the first threshold temperature, and is set, for example, to a temperature at which the device in the system obtained in a prior low temperature experiment is frozen.

  In step S29, the gas pressure in the piping of the fuel cell system 10 and the fuel cell 11 is increased. Specifically, the gas pressure is increased by substantially the same method as in step S21.

In step S30, when the detected value of the pressure sensor 43 becomes equal to or higher than the second predetermined pressure value, the electromagnetic valve 55 is closed to contain gas (air) on the anode side. Further, when the detected value of the pressure sensor 44 becomes equal to or higher than the second predetermined pressure value, the cathode gas upstream side sealing valve 46 is closed to contain gas (air) on the cathode side. Note that the second predetermined pressure value at the time of containment is set to a predetermined value larger than the first predetermined pressure value.
Here, the pressure value and temperature in the piping have a relationship as shown in FIG. That is, the higher the pressure value in the pipe, the higher the temperature in the pipe. That is, the higher the second predetermined pressure value, the higher the temperature in the pipe. Therefore, the second predetermined pressure value is set to a temperature at which the generated water remaining in the pipe and frozen can be thawed.

  In step S31, the gas contained in the anode side and the cathode side is discharged, and the pressure release process is performed. Specifically, substantially the same operation as step S26 described above is performed. At this time, since the generated water has been thawed in step S30, when the depressurization is performed, the generated water remaining in the fuel cell system 10 can be discharged at the same time as the gas is discharged.

  In step S32, it is determined whether or not the ignition switch is turned on. If the ignition switch is turned on, the process is terminated as it is. If the ignition switch remains off, the process proceeds to step S33.

  In step S33, it is determined whether or not the ambient temperature of the fuel cell system 10 is equal to or lower than a predetermined temperature. If the temperature is lower than the predetermined temperature, the process proceeds to step S34, and if higher than the predetermined temperature, the process returns to step S32. The predetermined temperature is obtained in advance from an actual experiment or the like, for example, at −10 ° C. or the like, a temperature at which a component in the gas remaining in the pipe is condensed and frozen. At this time, the determination may be made using the temperature sensors 41 and 42, or a temperature sensor (not shown) is provided in the immediate vicinity of the fuel cell system 10, and the determination is made based on the detection value of the temperature sensor. It may be.

  In step S34, the scavenging process of the fuel cell system 10 is executed according to an instruction from the scavenging process execution unit 64 of the control device 45. Specifically, the solenoid valve 25, the drain valve 51, and the purge valve 52 are closed, and the air discharge valve 48 and the solenoid valve 55 are opened. In this state, the air compressor 33 is driven to supply air to the anode side. After supplying air to the anode side for a predetermined time, driving of the air compressor 33 is stopped, the scavenging process is ended, and the freeze prevention process of the fuel cell system 10 is ended. By performing the scavenging treatment, the inside of the anode side pipe can be replaced with low-humidity air capable of suppressing freezing.

  According to the present embodiment, in addition to the operational effects of the first embodiment, when freezing is confirmed in the fuel cell system 10 while the fuel cell system 10 is stopped, the anode side and the cathode side Air is sealed in each flow path so that the pressure in the flow path becomes a second predetermined pressure higher than the first predetermined pressure. At this time, when the gas pressure in the pipe becomes high, the temperature of the gas rises, so that each flow path can be heated. That is, it is possible to thaw a frozen portion formed in each flow path or in the vicinity thereof. Thereafter, the purge valve 51 on the anode side and the cathode gas downstream sealing valve 47 on the cathode side are opened to discharge the air, so that the air filled in each flow path is downstream of the purge valve 51 and the cathode gas. It will pass through the side sealing valve 47 and be discharged out of the fuel cell system 10 at a high speed. Therefore, the generated water thawed by the air flow rate can also be blown out of the fuel cell system 10.

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 case where the freeze prediction unit is provided in the control device has been described. However, only the freeze confirmation unit may be provided without providing the freeze prediction unit.
In the present embodiment, when the gas pressure is increased, air is supplied to the anode side. However, hydrogen gas may be supplied to increase the gas pressure on the anode side.

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 11 ... Fuel cell 23 ... Anode gas supply piping (reaction gas flow path) 24 ... Cathode gas supply piping (reaction gas flow path) 25 ... Electromagnetic valve (upstream valve) 30 ... Hydrogen tank (reaction gas supply) 33) Air compressor (reactive gas supply unit) 35 ... Anode off-gas discharge piping (reaction gas flow path) 38 ... Cathode off-gas discharge piping (reaction gas flow path) 45 ... Control device (control unit) 46 ... Upstream side of cathode gas Seal valve (upstream valve) 47 ... Cathode gas downstream seal valve (downstream valve) 48 ... Air exhaust valve (downstream valve) 51 ... Drain valve (downstream valve) 52 ... Purge valve (downstream valve) 62 ... Freezing prediction unit 65 ... Freezing confirmation unit

Claims (4)

A reaction gas flow path through which the reaction gas flows;
A fuel cell that generates power by being supplied with the reaction gas;
A reaction gas supply unit for supplying the reaction gas to the reaction gas channel;
An upstream valve disposed in a reaction gas flow path upstream of the fuel cell;
A downstream valve disposed in a reaction gas flow path downstream of the fuel cell;
A fuel cell system comprising a control unit for performing various controls,
The controller is
A freezing prediction unit for predicting freezing of the system;
With the upstream valve opened and the downstream valve closed, the reaction gas supply unit is operated to reach a first predetermined pressure greater than atmospheric pressure in the reaction gas flow path. After the supply until it closes, the upstream valve is closed to contain the reaction gas in the reaction gas flow path,
When freezing is predicted by the freezing side, the fuel cell system is characterized in that the downstream valve is opened to discharge the reaction gas. The reaction gas flow path is
An anode gas flow path for supplying an anode gas to the anode electrode of the fuel cell, and a cathode gas flow path for supplying a cathode gas to the cathode electrode of the fuel cell,
The controller is
2. The fuel cell system according to claim 1, wherein the anode gas or the cathode gas is confined in the anode gas flow path, and the cathode gas is confined in the cathode gas flow path. A reaction gas flow path through which the reaction gas flows;
A fuel cell that generates power by being supplied with the reaction gas;
A reaction gas supply unit for supplying the reaction gas to the reaction gas channel;
An upstream valve disposed in a reaction gas flow path upstream of the fuel cell;
A downstream valve disposed in a reaction gas flow path downstream of the fuel cell;
A fuel cell system comprising a control unit for performing various controls,
The controller is
It has a freezing confirmation unit that confirms the freezing state of the system,
When freezing is confirmed by the freezing confirmation unit, the reaction gas supply unit is operated in a state where the upstream valve is opened and the downstream valve is closed, and the reaction gas flow path is moved into the reaction gas channel. After supplying until the reaction gas reaches a second predetermined pressure greater than atmospheric pressure, the upstream valve is closed, and the reaction gas is contained in the reaction gas flow path,
A fuel cell system, wherein the downstream gas is opened to discharge the reaction gas. The controller is
A freeze prediction unit for predicting freezing of the system;
With the upstream side valve opened and the downstream side valve closed, the reactive gas supply unit is operated to reach the first predetermined pressure in the reactive gas flow path where the reactive gas is greater than atmospheric pressure. After the supply until it closes, the upstream valve is closed to contain the reaction gas in the reaction gas flow path,
When freezing is predicted by the freezing side, the downstream valve is opened and the reaction gas is discharged.
The fuel cell system according to claim 3, wherein the second predetermined pressure is set higher than the first predetermined pressure.

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