JP5485930B2 - Control method of fuel cell system - Google Patents

Description

  The present invention relates to a control method of a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas and a fuel gas, and more particularly, by consuming hydrogen in an anode and oxygen in a cathode when power generation is stopped. The present invention relates to a control method for a fuel cell system that performs a power generation process at the time of stopping to fill a cathode in a battery with a gas having a high nitrogen concentration.

  In a fuel cell, a fuel gas (a gas mainly containing hydrogen, for example, hydrogen gas) and an oxidant gas (a gas mainly containing oxygen, for example, air) are supplied to an anode electrode and a cathode electrode to be electrochemical. It is a system that obtains direct-current electric energy by reacting with. This system is incorporated in a fuel cell vehicle for in-vehicle use as well as stationary use.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched between a pair of separators. Yes. A fuel gas passage for supplying fuel gas to the anode electrode is formed between one separator and the electrolyte membrane / electrode assembly, and between the other separator and the electrolyte membrane / electrode structure. Is formed with an oxidant gas flow path for supplying an oxidant gas to the cathode electrode.

  When the fuel cell is stopped, the supply of fuel gas and oxidant gas is stopped. However, while the fuel gas remains in the fuel gas channel, the oxidant gas remains in the oxidant gas channel. Yes. Therefore, particularly when the fuel cell is stopped for a long time, the fuel gas and the oxidant gas may permeate the electrolyte membrane, and the fuel gas and the oxidant gas may be mixed and reacted to deteriorate the electrolyte membrane / electrode structure. There is.

  Thus, for example, in the fuel cell system disclosed in Patent Document 1, when the operation of the fuel cell is stopped, the supply of the reaction gas to the anode side is cut off and the supply of the reaction gas to the cathode side is cut off. In addition, the anode-side exhaust gas is circulated upstream via the anode-side circulation line, and the cathode-side exhaust gas is circulated upstream via the cathode circulation line to continue the electrochemical reaction in the fuel cell. And the power generation output is charged to the battery. In this way, hydrogen in the anode side exhaust gas is consumed, oxygen in the cathode side exhaust gas is consumed and nitrogen gas is accumulated in the tank. The nitrogen gas accumulated in the tank causes gas in the anode and cathode of the fuel cell. Has been replaced.

Japanese Patent Laying-Open No. 2004-22487 (FIG. 1, [0029])

  As in the technique described in Patent Document 1, when the operation of the fuel cell is stopped, nitrogen gas replaces the anode and cathode of the fuel cell with an inert gas. This is preferable from the viewpoint of preventing the deterioration of the fuel cell.

  However, in the technology related to the power generation processing at the time of stop described in Patent Document 1, for example, the supply of the reaction gas on the anode side is shut off and power generation (electrochemical reaction) is continued. However, there is a problem that the stack constituting the fuel cell system is broken or the valve is erroneously opened (erroneously opened).

  In addition, this power generation process at the time of stoppage is a process that generates a small amount of heat and does not take a large electric load (i.e. draws a large current) and takes a relatively long time. If implemented, the fuel cell may freeze, and similarly, the stack or the like constituting the fuel cell system may be destroyed.

  The present invention has been made in consideration of the above-described problems, and in carrying out the power generation processing at the time of stopping of the fuel cell system, problems such as stack destruction, next-time mobility deterioration, and valve misopening are raised. It is an object of the present invention to provide a control method of a fuel cell system that can be prevented.

  The present invention relates to a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side, and an oxidant gas supply device that supplies the oxidant gas to the fuel cell. A fuel gas supply device that supplies the fuel gas to the fuel cell, a cooling medium supply device that supplies a cooling medium to the fuel cell, and a fuel gas supply when an operation stop command for the fuel cell is detected. A control method of a fuel cell system that performs power generation processing at the time of stopping while generating power while supplying the oxidant gas to the fuel cell while stopping is provided with the following feature (1).

  (1) The pressure on the anode side is equal to or lower than the threshold pressure and the voltage of the fuel cell {eg, cell (cell pair) voltage} is the threshold value during the power generation process at the time of stoppage from when the operation stop command of the fuel cell system is detected When at least one of the following conditions is detected: a voltage lower than the voltage, a temperature of the fuel gas on the anode side equal to or lower than a threshold temperature, and a temperature of the cooling medium equal to or higher than the threshold temperature, Features.

  According to the present invention, it is possible to prevent the stack from being destroyed and the valve from being erroneously opened (erroneously opened) by interrupting the power generation process at the stop when the pressure on the anode side is equal to or lower than the threshold pressure. Moreover, it is possible to prevent the fuel cell (cell) from being broken by interrupting the power generation process at the stop when the voltage of the fuel cell is lower than the threshold voltage. Furthermore, by interrupting the stop-time power generation process when the cooling medium temperature is equal to or higher than the threshold temperature, it is possible to prevent the fuel cell from being damaged (the cell is burned out) due to insufficient cooling.

  The present invention also provides a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side, and an oxidant gas supply that supplies the oxidant gas to the fuel cell. A fuel gas supply device for supplying the fuel gas to the fuel cell, and the fuel gas supply is stopped while an oxidant gas is supplied to the fuel cell upon detecting an operation stop command of the fuel cell. However, the control method of the fuel cell system that performs the power generation process at the time of stopping to generate the power of the fuel cell includes the following feature (2).

  (2) When an operation stop command for the fuel cell system is detected and a power generation malfunction during normal power generation of the fuel cell system is stored, the fuel cell system is activated in a state of a predetermined temperature or less and the fuel When at least one of the conditions is detected when the battery system has not been warmed up and when the control valve for controlling the gas pressure of the fuel cell is likely to be frozen, The processing is not performed.

  According to the present invention, when an operation stop command of the fuel cell system is detected and a power generation failure during normal power generation of the fuel cell system is stored, the power generation failure state is prevented by not performing the power generation process at the time of stop. There is room for improvement (continuing the power generation malfunction state is not preferable because it is more likely to promote deterioration). Further, when the fuel cell system operation stop command is detected, if the fuel cell system is started in a state below a predetermined temperature and before the fuel cell system has been warmed up, the power generation process at the time of stop is not performed. Thus, it is possible to prevent the fuel cell from being in a power generation malfunction state. Furthermore, when a control valve for controlling the gas pressure of the fuel cell has a possibility of freezing when an operation stop command for the fuel cell system is detected, freezing can be prevented by not performing the power generation process at the time of stopping. .

  In the present invention, when a malfunction such as a malfunction of power generation occurs, the power generation process at the time of stoppage is not performed or interrupted, so that other trouble countermeasure processes other than the power generation process at the time of stoppage, for example, anode side with dry air or By carrying out the scavenging treatment on the cathode side, etc., it is useful in that it is possible to solve problems such as power generation malfunctions.

  According to the present invention, when a malfunction is detected during the stop-time power generation process, the process is interrupted if the stop-time power generation process is in progress and is not performed before the stop-time power generation process. Deterioration or continuation of problems due to continuation or implementation of power generation processing can be avoided.

1 is a schematic configuration diagram of a fuel cell system in which a control method according to an embodiment of the present invention is implemented. It is circuit explanatory drawing which comprises the said fuel cell system. It is a timing chart explaining the said control method. It is a flowchart explaining the said control method. It is explanatory drawing of the hydrogen gas type | system | group volume part and the air system volume part of the said fuel cell system. It is whole explanatory drawing of a power generation process at the time of a stop. It is explanatory drawing of the specific operation example of an implementation propriety judgment part and an interruption necessity judgment part. It is explanatory drawing of the judgment table memorize | stored in the implementation propriety / interruption necessity judgment part. It is explanatory drawing of the mode switching table memorize | stored in the mode switching judgment part. It is explanatory drawing of the idea of differential pressure protection.

  As shown in FIG. 1, a fuel cell system 10 in which a control method according to an embodiment of the present invention is implemented includes a fuel cell stack 12, an oxidant gas supply device 14 that supplies an oxidant gas to the fuel cell stack 12, and A fuel gas supply device 16 that supplies fuel gas to the fuel cell stack 12, a cooling medium supply device 21 that supplies a cooling medium to the fuel cell stack 12, a scavenging device 15 that introduces scavenging gas into the fuel cell stack 12, A battery (power storage device) 17 that can be freely connected to the fuel cell stack 12 and a controller (control device, control unit) 18 that controls the entire fuel cell system 10 are provided.

  The controller 18 is a computer including a microcomputer, a CPU (central processing unit), a ROM (including EEPROM) as a memory, a RAM (random access memory), other A / D converters, and D / A converters. The input / output device such as a clock, a timer 19 as a timekeeping unit, and the like, and when the CPU reads and executes a program recorded in the ROM, various function realization units (function realization means) such as a control unit, It functions as a calculation unit, a processing unit, and the like.

  The fuel cell system 10 is mounted on a fuel cell vehicle such as a fuel cell vehicle. The battery 17 can normally travel in a fuel cell vehicle, and has a voltage of about 20 A to about 500 V, for example, and a higher voltage and a higher power capacity than a 12 V power source 98 described later.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells (also referred to as cells or cell pairs) 20. Each fuel cell 20 includes, for example, an electrolyte membrane / electrode structure (MEA) 28 in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode electrode 24 and an anode electrode 26. .

  The cathode electrode 24 and the anode electrode 26 have a gas diffusion layer made of carbon paper or the like, and porous carbon particles carrying platinum alloy (or Ru or the like) on the surface are uniformly applied to the surface of the gas diffusion layer. And an electrode catalyst layer formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  The electrolyte membrane / electrode structure 28 is sandwiched between the cathode side separator 30 and the anode side separator 32. The cathode side separator 30 and the anode side separator 32 are comprised by a carbon separator or a metal separator, for example.

  An oxidant gas flow path 34 is provided between the cathode side separator 30 and the electrolyte membrane / electrode structure 28, and a fuel gas is provided between the anode side separator 32 and the electrolyte membrane / electrode structure 28. A flow path 36 is provided.

  The fuel cell stack 12 communicates with each other in the stacking direction of the fuel cells 20 to supply an oxidant gas, for example, an oxidant gas inlet communication hole 38a for supplying an oxygen-containing gas (hereinafter also referred to as air), a fuel gas. For example, a fuel gas inlet communication hole 40a for supplying a hydrogen-containing gas (hereinafter also referred to as hydrogen gas), a cooling medium inlet communication hole 41a for supplying a cooling medium, and an oxidant gas outlet communication hole 38b for discharging the oxidant gas. A fuel gas outlet communication hole 40b for discharging the fuel gas and a cooling medium outlet communication hole 41b for discharging the cooling medium are provided.

  The oxidant gas supply device 14 includes an air pump 50 that compresses and supplies air from the atmosphere, and the air pump 50 is disposed in the air supply flow path 52. The air supply channel 52 is provided with a humidifier 54 that exchanges moisture and heat between the supply gas and the exhaust gas. The air supply flow path 52 communicates with the oxidant gas inlet communication hole 38 a of the fuel cell stack 12.

  The oxidant gas supply device 14 includes an air discharge channel 56 that communicates with the oxidant gas outlet communication hole 38b. The air discharge channel 56 communicates with a humidifying medium passage (not shown) of the humidifier 54, and is supplied to the fuel cell stack 12 from the air pump 50 through the air supply channel 52. A back pressure control valve (also simply referred to as a back pressure valve) 58 with an adjustable opening is provided, such as a butterfly valve for adjusting the air pressure. The back pressure control valve 58 is preferably constituted by a normally closed type (closed when not energized) control valve. The air discharge channel 56 communicates with the dilution box 60.

  The scavenging device 15 shares the air pump 50, the air supply channel 52, and the air discharge channel 56 that compress and supply air from the atmosphere with the oxidant gas supply device 14, and further, on the downstream side of the ejector 66. An air introduction channel 53 disposed between the hydrogen supply channel 64 and the air supply channel 52 and an air introduction valve 55 provided in the air introduction channel 53 are provided.

  The air introduction valve 55 is a so-called anode-side air scavenging process for introducing compressed air from the air pump 50 to the fuel gas passage 36 through the air supply passage 52 and the air introduction passage 53 through the fuel gas inlet communication hole 40a. An on-off valve that is sometimes opened. The anode-side air scavenging process differs from the anode-side air replacement process in that the air volume is large enough to blow off water droplets, and is common to the anode-side air replacement process in that the anode-side fuel gas is replaced with air.

  The fuel gas supply device 16 includes a hydrogen tank 62 that integrally stores an in-tank electromagnetic valve 63 that stores high-pressure hydrogen and is an on-off valve. The hydrogen tank 62 is connected to a fuel cell via a hydrogen supply channel 64. The fuel gas inlet communication hole 40a of the stack 12 communicates.

  The hydrogen supply channel 64 is provided with a shutoff valve 65 and an ejector 66 that are on-off valves. The ejector 66 supplies the hydrogen gas supplied from the hydrogen tank 62 to the fuel cell stack 12 through the hydrogen supply flow path 64 and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell stack 12. Then, the gas is sucked from the hydrogen circulation path 68 and supplied again as fuel gas to the fuel cell stack 12.

  The off gas passage 70 communicates with the fuel gas outlet communication hole 40b. A hydrogen circulation path 68 communicates with the off gas flow path 70, and a dilution box 60 is connected to the off gas flow path 70 via a purge valve 72. A discharge flow path 74 is connected to the discharge port side of the dilution box 60. A storage buffer (not shown) is disposed in the discharge channel 74, and an exhaust channel communicating with the atmosphere is connected to the storage buffer.

  The cooling medium supply device 21 includes a cooling medium circulation path 78 that communicates with the cooling medium inlet communication hole 41 a and the cooling medium outlet communication hole 41 b provided in the fuel cell stack 12 and circulates the cooling medium to the fuel cell stack 12. The cooling medium circulation path 78 is provided with a radiator 122 and a cooling medium circulation pump 120. The radiator 122 is provided with a radiator fan (not shown).

  The controller 18 detects the anode pressure Pa provided in the hydrogen supply flow path 64 and the cathode pressure Pk provided in the vicinity of the oxidant gas inlet communication hole 38a in order to execute various control processes. Pressure sensor 103, temperature sensor 104 for detecting the hydrogen temperature Th provided in the vicinity of the fuel gas outlet communication hole 40b, an outside air temperature sensor 105 for detecting the outside air temperature Te of the vehicle, and a cooling medium outlet communication hole 41b. A temperature sensor 106 that detects the coolant temperature Tc, a voltage sensor 108 that detects the voltage (cell voltage or cell pair voltage) Vc of each fuel cell 20, and a current that detects the current value Io of the current flowing out of the fuel cell stack 12. Each signal of the sensor 110 is taken in, and an FC contactor 86, which will be described later, is turned on (closed) off (opened), the shut-off valve 65, etc. Closing and opening control valves, and the control of actuators such as adjustment of the flow rate of the air pump 50 (air volume) performed.

  As shown in FIG. 2, one end of the main power line 80 is connected to the fuel cell stack 12, and the other end of the main power line 80 is connected to the inverter 82. A drive motor 84 for three-phase vehicle travel is connected to the inverter 82. In addition, although the two main power lines 80 are used substantially, in order to simplify description, it describes with the said one main power line 80. The same applies to the other lines described below. The high voltage appearing at the output of the fuel cell stack 12 is also referred to as the primary side voltage Vfc1.

  The main power line 80 is provided with an FC contactor (main power switch, fuel cell stack switch) 86 and an air pump 50. One end of a power line 88 is connected to the main power line 80, and the battery 17 is connected to the power line 88 via a DC / DC converter 90 and a battery contactor (power storage device switch) 92. The power line 88 is provided with a branch power line 94, and a 12 V power source 98 is connected to the branch power line 94 via a downverter (DC / DC converter) 96. Note that the 12V power source 98 only needs to have a voltage lower than that of the battery 17, and is not limited to 12V.

  The operation of the fuel cell system 10 configured as described above will be described below.

  First, during normal operation of the fuel cell system 10 (also referred to as normal power generation or normal power generation processing), air is supplied to the air supply flow path 52 via the air pump 50 constituting the oxidant gas supply device 14. Sent. The air is humidified through the humidifier 54 and then supplied to the oxidant gas inlet communication hole 38 a of the fuel cell stack 12. This air is supplied to the cathode electrode 24 by moving along the oxidant gas flow path 34 provided in each fuel cell 20 in the fuel cell stack 12.

  The used air is exhausted from the oxidant gas outlet communication hole 38 b to the air exhaust flow path 56 and is sent to the humidifier 54 to humidify the newly supplied air, and then through the back pressure control valve 58. Introduced into the dilution box 60.

  On the other hand, in the fuel gas supply device 16, the in-tank solenoid valve 63 and the shut-off valve 65 are opened, so that the pressure is reduced from the hydrogen tank 62 by a pressure reduction control valve (not shown), and then hydrogen is supplied to the hydrogen supply passage 64. Gas is supplied. This hydrogen gas is supplied to the fuel gas inlet communication hole 40 a of the fuel cell stack 12 through the hydrogen supply channel 64. The hydrogen gas supplied into the fuel cell stack 12 is supplied to the anode electrode 26 by moving along the fuel gas flow path 36 of each fuel cell 20.

  The used hydrogen gas is sucked into the ejector 66 from the fuel gas outlet communication hole 40b through the hydrogen circulation path 68, and is supplied again to the fuel cell stack 12 as fuel gas. Accordingly, the air supplied to the cathode electrode 24 and the hydrogen gas supplied to the anode electrode 26 react electrochemically to generate power.

  On the other hand, the hydrogen gas circulating in the hydrogen circulation path 68 is likely to contain impurities. For this reason, the hydrogen gas mixed with impurities is introduced into the dilution box 60 when the purge valve 72 is opened. The hydrogen gas is mixed with air off-gas in the dilution box 60 to reduce (dilute) the hydrogen concentration, and is then discharged to a storage buffer (not shown).

  Further, in the cooling medium supply device 21, the cooling medium is introduced from the cooling medium circulation path 78 into the cooling medium inlet communication hole 41 a of the fuel cell stack 12 under the action of the pump 120. The cooling medium is supplied to a cooling medium flow path (not shown) in the fuel cell stack 12, and after cooling each fuel cell 20, the cooling medium is discharged from the cooling medium outlet communication hole 41 b to the cooling medium circulation path 78.

  During normal power generation, the scavenging device 15 is not operated, and the air introduction valve 55 is kept closed. The air introduction valve 55 is preferably a normally closed type (closed when not energized) on-off valve.

  Next, a control method when the operation of the fuel cell system 10 is stopped will be described below with reference to a timing chart shown in FIG. 3 and a flowchart shown in FIG.

  The fuel cell system 10 mounted on a fuel cell vehicle (not shown), as described above, when the ignition switch (operation switch) is turned on (step S1: YES), the above-described normal power generation operation (step S2: By performing the power generation control), a desired traveling is performed. When the ignition switch (operation switch) is turned off (step S3: YES), the controller 18 detects this as a stop command (time point t1), and when the fuel cell system 10 is stopped after the step-up process in step S4. Start shutdown processing including power generation processing.

  First, after the discharge process (also referred to as stop power generation process, low oxygen stoichiometric power generation process, O2 lean power generation process, or O2 lean power generation process) described later, the fuel gas pressure (anode pressure Pa) in the fuel cell stack 12 is set to the set pressure. Thus, the supply pressure of hydrogen gas (fuel gas) is set in advance.

  Specifically, as shown in FIG. 5, the hydrogen gas system volume portion 200 that is filled with hydrogen gas and closed is a fuel gas flow path 36, a fuel gas inlet communication hole 40 a, and a fuel gas outlet in the fuel cell stack 12. The communication hole 40b, a region downstream of the ejector 66 in the hydrogen supply channel 64, a hydrogen circulation channel 68, and a region upstream of the purge valve 72 in the off-gas channel 70 are configured. In FIG. 5, the cooling medium supply device 21 in FIG. 1 is omitted to avoid complexity.

  The air system volume 202 that is to replace the air atmosphere with a nitrogen atmosphere that is an inert gas includes an oxidant gas flow path 34, an oxidant gas inlet communication hole 38a, and an oxidant gas outlet communication hole 38b in the fuel cell stack 12. The air supply channel 52, the air discharge channel 56, the humidifier 54, the dilution box 60, and a storage buffer (not shown).

  During the discharge process, air supplies oxygen stoichiometry at a low oxygen stoichiometry lower than that during normal power generation. Specifically, the low oxygen stoichiometry is set to around the value 1. Note that the oxygen stoichiometry is preferably within a range of 1.2 to 3.0 during normal power generation. On the other hand, during the discharge process, the supply of hydrogen gas is stopped.

For this reason, the nitrogen atmosphere is generated by the number of moles of residual oxygen nO 2 (O 2 is correctly expressed as O ₂ ) to be made into a nitrogen atmosphere in the fuel cell stack 12 in the air volume 202 and the low oxygen stoichiometric gas supplied by the air pump 50. The number of moles n′O2 of oxygen in the humidifier 54, the dilution box 60 and the storage buffer desired to be adjusted, and the number of moles nH2 of residual hydrogen in the hydrogen gas system volume 200 (H2 is correctly expressed as H ₂ ). 2 (nO2 + n′O2) = nH2 is set. As described above, hydrogen H2 is a hydrogen H _2, oxygen O2 is meant oxygen O _2.

  Then, from the set number of moles of residual hydrogen nH2, the supply of hydrogen gas using the formula n (number of moles) = P (pressure) × V (volume) / R (gas constant) × T (absolute temperature) The pressure (anode pressure) Pa1 is calculated (see FIG. 3). However, the anode pressure Pa1 is set so as to be maintained at a certain pressure Pa2 or higher when the discharge is completed. The constant pressure Pa2 is a pressure at which hydrogen deficiency or excess does not occur.

  Here, when the relationship of the capacity of the air system volume part 202 >> the capacity of the hydrogen gas system volume part 200 is satisfied, the pressure is increased to the anode pressure Pa1 in order to increase the capacity of the hydrogen gas system volume part 200. A method or a method of supplying a shortage of hydrogen can be employed.

  On the other hand, when the relationship of the capacity of the hydrogen gas system volume part 200 >> the capacity of the air system volume part 202 is satisfied, there is a method of reducing the pressure to the anode pressure Pa1 in order to reduce the capacity of the hydrogen gas system volume part 200. Adopted.

  When the ignition switch (operation switch) is turned off (time point t1), as shown in FIG. 3, hydrogen gas is supplied to the fuel cell stack 12 under the opening action of the in-tank electromagnetic valve 63 and the shutoff valve 65, and the fuel The pressure in the battery stack 12 rises to the anode pressure Pa1 (time t1 to t2: pressure increase process). The anode pressure Pa1 is calculated from the above calculation formula.

  When the pressure increasing process in step S4 ends (time t2), the in-tank electromagnetic valve 63 is closed, and the process proceeds to a failure detection process for the in-tank electromagnetic valve 63 in step S5. In this failure detection process, failure detection is performed based on whether or not the anode pressure Pa = Pa1 is changed. If not changed, the in-tank electromagnetic valve 63 is set to normal.

  When the failure detection process of the in-tank solenoid valve 63 is completed (time t3), in step S6, it is determined whether or not a stop-time power generation process (step S8) described later can be performed.

  Whether or not the power generation process at the time of stoppage can be performed is determined by an execution availability determination unit 212 illustrated in FIG. 7 in the execution availability / interruption necessity (interruption required) determination unit 210 illustrated in FIG.

  As will be described later in step S6, in this embodiment, whether or not the stop power generation process is interrupted during the stop power generation process is determined by whether or not the stop / non-interruption necessity determination unit 210 determines whether or not to interrupt (interruption). Necessary) This is done by the determination unit 214.

  The implementation availability determination unit 212 and the interruption necessity determination unit 214 perform implementation availability determination and interruption necessity determination using various information, respectively.

  As shown in FIG. 6, the various information includes power generation malfunction information {power generation malfunction information during normal power generation of the fuel cell system 10, for example, a cell voltage that is normally 1.2 [V] is 0.6 [V ] History information such as (being) the following values is included. }, Low-temperature short-time activation history information (history information when the fuel cell system 10 is activated in a state below a predetermined temperature such as below freezing and is stopped before warming up), air pressure sensor failure information (pressure Sensor 103 failure information), hydrogen pressure sensor failure information (pressure sensor 102 failure information), hydrogen temperature (current hydrogen temperature Th by temperature sensor 104), hydrogen temperature sensor failure information (temperature sensor 104 failure information), air pump Failure information (failure information of the air pump 50), air pressure increase failure information (information generated when the air pressure above the threshold pressure is detected by the pressure sensor 103), anode scavenging request (temperature at which the outside temperature is below freezing point during normal power generation) Or when there is a possibility of a temperature below the freezing point at the time of soaking. This is a request to send a large volume of compressed air to the card side to blow off the liquid droplets and prevent icing, and to facilitate the next start-up, etc.) Back pressure valve scavenging request (back pressure control valve) The back pressure valve scavenging process is performed when the compressed air supplied from the air pump 50 passes through the humidifier 54 and the fuel cell stack 12 and is further reduced by the humidifier 54. And a relatively high temperature dry air is supplied to the back pressure control valve 58.) Hydrogen ventilation request (when a hydrogen concentration sensor is provided in a center tunnel or the like in the vehicle) The hydrogen concentration process is performed by rotating the air pump 50, a radiator fan (not shown), etc.) and the minimum cell voltage. During normal power generation and discharge processing, information on the voltage of the cell that has the lowest voltage in the cell), voltage sensor failure information (failure information on the voltage sensor 108), back pressure valve failure information (failure information on the back pressure control valve 58) The cooling medium temperature (information on the cooling medium temperature Tc by the temperature sensor 106) and the like are included.

  The implementation feasibility / interruption necessity determination unit 210 refers to the information and the determination table 205 shown in FIG. 8 stored (stored) in advance, and determines whether the implementation is possible or is necessary.

  As shown in the determination table 205, the hydrogen pressure is equal to or lower than the threshold pressure (when power generation processing at the time of stoppage is started and during power generation processing at the time of stoppage), the cell pair voltage is decreased, the hydrogen temperature Th is equal to or lower than the threshold temperature, or the cooling medium temperature Tc is the threshold value When the temperature is higher than the temperature, it is determined that the stop power generation process (discharge process) is not performed or needs to be interrupted, and a predetermined protection function is activated.

  Further, in the case of an air pressure sensor (pressure sensor 103) failure, a hydrogen pressure sensor (pressure sensor 102) failure, a voltage sensor 108 failure, or a hydrogen temperature sensor 104 failure, it is determined that the sensor used for the determination is at failure. Therefore, it is determined that the power generation process at the time of stoppage is not implemented or needs to be interrupted.

  Further, in the case of an air pump 50 failure, an abnormal air pressure increase, or a back pressure valve (back pressure control valve 58) failure, it is determined that a failure has occurred that prevents the power generation process from being executed or continued, and is not to be executed or interrupted. to decide.

  Further, when the above-described stop-time anode scavenging request, back-pressure valve freezing countermeasure scavenging request, or hydrogen ventilation request is generated, it is determined that there is another processing request that has priority over the stop-time power generation processing, and is not implemented or Judge that interruption is necessary.

  6 and 7, the mode switching determination unit 206 includes an air pressure (cathode pressure Pk), a primary side voltage Vfc1, a hydrogen pressure (anode pressure Pa), an urgent O2 lean process stop request (stop power generation process stop request). ), And whether or not execution is possible and whether or not it is necessary to interrupt is determined based on the availability information (possible / not acceptable in FIG. 7) and the necessity information on interruption (continue / suspended in FIG. 7).

  Specifically, the mode switching determination unit 206 refers to the mode switching table 208 shown in FIG. 9 to determine the end condition for mode switching and the transition destination (mode) at the time of interruption.

  As shown in FIG. 9, during the stop-time power generation process (discharge process, DCHG O2 lean process), the end condition is a lapse of a predetermined time or a decrease in hydrogen pressure (anode pressure Pa) (FIG. 3: Pa = Pa2). When the transition destination at the time of interruption is a high hydrogen pressure (anode pressure Pa), the process proceeds to an anode depressurization process using the dilution box 60, and is terminated when the hydrogen pressure (anode pressure Pa) is low. During the discharge process (D / V: downverter), the end condition is a drop in the primary voltage Vfc (fully discharged), a lapse of a predetermined time, or a decrease in hydrogen pressure (anode pressure Pa), which is interrupted. The transition destination of time is ended.

  In determining whether or not step S6 (time t6) can be performed, for example, when a power generation failure during normal power generation of the fuel cell system 10 is stored in the power generation failure information (power generation failure history information), or when the fuel cell system 10 is at a predetermined temperature Information when the operation was stopped in the following state (for example, a low temperature state such as below freezing) and the operation was stopped before the completion of warming up of the fuel cell system 10 was stored in the low temperature short time activation history information, or the fuel cell When at least one of the conditions is detected when the back pressure control valve 58 for controlling the gas pressure of 20 is likely to be frozen, the power generation process at the time of stop is not started (not implemented). Becomes negative.

  If the determination in step S6 is feasible, a dilution / cathode scavenging process is performed in step S7 (time points t3 to t6). In this dilution / cathode scavenging process, scavenging by air (by the oxidant gas supply device 14) is performed to blow off droplets including water droplets on the cathode side and to completely dilute hydrogen remaining in the dilution box 60. Processing is performed. At this time, electric power that is insufficient to drive the air pump 50 set at a high rotation speed [rpm] is supplemented.

  After the dilution / cathode scavenging process, the opening control of the back pressure control valve 58 is temporarily stopped and opened to communicate with the atmosphere, and the cathode pressure Pk is Pk = 0 [kPag: g means gauge pressure. ] Is created (time t6 to t7). Further, at the end of the cathode scavenging process (time point t6), the air pump 50 constituting the oxidant gas supply device 14 is considerably decelerated compared to the normal operation, and the oxygen stoichiometry in the oxidant gas is generated by the normal power generation. Supply with low oxygen stoichiometry lower than the current oxygen stoichiometry. Specifically, the low oxygen stoichiometry is set to around 1. Then, the learning process (zero point correction) of the pressure sensor 103 is performed.

  Thereafter, at time t7 to t8, the cathode pressure Pk detected by the pressure sensor 103 is adjusted to a predetermined low pressure Pk1 corresponding to the low oxygen stoichiometry by adjusting the opening of the back pressure control valve 58. The learning process of the back pressure control valve 58 at the low pressure Pk1 is performed (time t7 to t8). Thereafter, the low pressure Pk1 is maintained until the air pump 50 is turned off (time point t9).

  Stop power generation processing in step S8 after learning processing (time t7 to t8) of the back pressure control valve 58, in other words, low oxygen stoichiometric power generation processing (also referred to as O2 lean power generation processing, or simply O2 lean processing. Time points t8 to t9). ), The current (FC current) taken out from the fuel cell stack 12 is set to a value that prevents the hydrogen gas as the fuel gas from moving from the anode side to the cathode side through the solid polymer electrolyte membrane 22. The At that time, in FIG. 2, the FC contactor 86 and the battery contactor 92 are turned on, and the electric power obtained at the time of power generation of the fuel cell stack 12 is charged to the battery 17 after the voltage is lowered by the DC / DC converter 90. The It can be considered that the power generation process at the time of stop (low oxygen stoichiometric power generation process) in step S8 is continued for a long time between time points t6 and t10.

  As described above, in the fuel cell stack 12, while low oxygen stoichiometric air is supplied, power generation is performed in a state where the supply of hydrogen gas is stopped due to the shutoff of the shutoff valve 65 (time point t <b> 3). The purge valve 72 is also closed. The electric power generated by the fuel cell stack 12 is supplied to the battery 17 to be discharged {DCHG (O2 lean process in FIG. 3)}. Therefore, when the power generation voltage of the fuel cell stack 12 decreases to a predetermined voltage, that is, a voltage that cannot be supplied to the battery 17 (substantially the same voltage as the voltage of the battery 17), the generated power is supplied only to the air pump 50.

  Thereby, in the fuel cell stack 12, the hydrogen concentration on the anode side decreases during the O 2 lean process (time points t8 to t9), while the oxygen concentration on the cathode side decreases. Therefore, for example, when the hydrogen pressure on the anode side (anode pressure Pa) becomes equal to or lower than a predetermined pressure Pa2, the air pump 50 is turned off and the battery contactor 92 is turned off (time point t9).

  For this reason, the fuel cell stack 12 is generated by the hydrogen gas and air remaining inside (time points t9 to t10). The electric power generated by the power generation of the fuel cell stack 12 is stepped down via the downverter 96, and then charged to the 12V power source 98 (D / V DCHG in FIG. 3). Electric power is supplied to a fan or the like. Further, when the power generation voltage of the fuel cell stack 12 decreases to the vicinity of the operation limit voltage of the downverter 96, the FC contactor 86 is turned off in step S10 (time t10). As a result, the fuel cell system 10 enters an operation stop state, a so-called soak state.

  On the other hand, while the power generation process at the time of stop in step S8 is being performed, during the time t6 to t10 (interruption determination period), in step S9, it is necessary to interrupt whether or not the power generation process at the time of stop should be interrupted. When it is always (intermittently) performed by the refusal determination unit 214 and should not be interrupted but continued, the process returns to the stop-time power generation process in step S8.

  Specifically, in the interruption necessity determination unit 214, for example, during the power generation process at the time of stop, the anode side pressure (anode pressure Pa) is equal to or less than the threshold pressure {the air introduction valve 55 or the purge that is closed by the spring pressure in the normally closed state The negative pressure (differential pressure) applied to the valve of the electromagnetic valve such as the valve 72 is equal to or lower than the pressure that does not cause the valve to be erroneously opened (erroneously opened) against the spring pressure}, and the voltage (cell voltage) Vc of the fuel cell 20 is Below the threshold voltage, the anode side fuel gas temperature Th is below the threshold temperature (if it is below the threshold temperature, icing may occur), and the cooling medium temperature Tc is above the threshold temperature. , The fuel cell (cell) 20 may be damaged.), The power generation process at the time of stop is interrupted (step S9: YES).

  The possibility of erroneous opening due to the differential pressure of the air introduction valve 55 and the purge valve 72 will be described in more detail with reference to FIG. 10. During the power generation process at the time of stop (O2 lean DCHG process), the shutoff valve 65 is Since it is closed (the air introduction valve 55 and the purge valve 72 are also closed), the hydrogen on the anode side of the fuel cell stack 12 is consumed by power generation. The negative pressure increases with time, and the negative pressure further increases. On the other hand, a small amount of compressed air is supplied to the cathode side at a flow rate with a pressure slightly larger than atmospheric pressure under the action of the back pressure control valve 58 and the air pump 50. Accordingly, when the negative pressure increases, the differential pressure between the anode and the cathode, that is, the so-called differential pressure between the anodes increases, and the anode pressure Pa (in this case, the negative pressure) increases the valve bodies of the air introduction valve 55 and the purge valve 72 to the port side. When it becomes larger than the elastic force of the spring that is pressed to close the valve, the valve body opens away from the port (referred to as an erroneous opening or erroneous opening). If an erroneous valve opening occurs, problems such as poor mobility will occur next time.

  In the characteristic 154 of the anode pressure Pa in FIG. 10, since the pressure falls below the threshold pressure −Pamax between time points t6 and t7, an erroneous opening occurs. In the characteristic 152 of the anode pressure Pa, the valve is erroneously opened when the pressure falls below the threshold pressure −Pamax after the soak at the time t10. It should be noted that the anode pressure Pa rapidly decreases as indicated by the pressure characteristics 150 and 152 during the stop-time power generation process (time points t6 to t10). On the other hand, during the soak (after the soak start time t10), hydrogen is not consumed, and the anode pressure Pa gradually decreases as shown in the characteristics 150 and 152, but when the amount of hydrogen decreases (time point). tx), the amount of nitrogen gas permeating from the cathode side to the anode side increases, and the anode pressure Pa gradually increases (from time tx).

  By storing these characteristics 150, 152, and 154 in advance by simulation and / or experimentation or the like, the threshold pressure Path at the time of stoppage of power generation interruption can be determined. The characteristic 150 is the minimum characteristic having a normal pattern (not lower than the threshold pressure −Pamax).

[Summary of Embodiment]
As described above, in the above-described embodiment, the fuel cell 20 that generates electricity by the electrochemical reaction of the oxidant gas supplied to the cathode side and the fuel gas supplied to the anode side, and the oxidant gas to the fuel cell 20 are supplied. An oxidant gas supply device 14 to supply, a fuel gas supply device 16 to supply the fuel gas to the fuel cell 20, a cooling medium supply device 21 to supply a cooling medium to the fuel cell 20, and an operation stop command for the fuel cell 20. Control of the fuel cell system 10 that performs power generation processing at the time of stopping the fuel cell 20 while generating the fuel gas 20 while supplying the oxidant gas to the fuel cell 20 with low oxygen stoichiometry. It relates to a method and a device.

  In this control method and apparatus, the pressure Pa on the anode side is equal to or lower than the threshold pressure Path from the time when the operation stop command of the fuel cell system 10 is detected (time point t1) to the time when the power generation process at the stop time (time points t6 to t10). If at least one of the following conditions is detected: the voltage 20 is equal to or lower than the threshold voltage, the anode-side fuel gas temperature Tc is equal to or lower than the threshold temperature, and the coolant temperature Tc is equal to or higher than the threshold temperature, Since the operation is interrupted, it is possible to prevent the fuel cell stack 12 from being broken, the valve from being opened incorrectly, and the fuel cell 20 from being broken.

  Further, in the above-described embodiment, the fuel cell 20 that generates electric power by the electrochemical reaction of the oxidant gas supplied to the cathode side and the fuel gas supplied to the anode side, and the oxidizer that supplies the oxidant gas to the fuel cell 20 When the agent gas supply device 14, the fuel gas supply device 16 for supplying fuel gas to the fuel cell 20, and the operation stop command for the fuel cell 20 are detected (time t1), the supply of the fuel gas is stopped while the oxidant The present invention relates to a control method and apparatus for a fuel cell system 10 that performs a power generation process at the time of stopping to generate power while supplying gas to the fuel cell 20 with low oxygen stoichiometry.

  In this control method and apparatus, when an operation stop command for the fuel cell system 10 is detected (time point t1), when the power generation malfunction during normal power generation of the fuel cell system 10 is stored, the fuel cell system 10 is below freezing point, etc. At least 1 when the fuel cell system 10 is started up in a state below the predetermined temperature and before the warm-up of the fuel cell system 10 is completed, and when the back pressure control valve 58 that controls the gas pressure of the fuel cell 20 is likely to be frozen. When one of the conditions is detected, the power generation process at the time of stoppage is not performed, so that further deterioration from the power generation malfunction state and freezing can be prevented.

  This is useful in that the possibility of resolving the problem by implementing other countermeasures other than the stop power generation process, such as scavenging with dry air, can be obtained by not performing the power generation process during the stop. .

  Further, according to the above-described embodiment, while performing power generation processing at the time of stop effective for suppressing deterioration of the fuel cell 20, securing the next mobility, protecting the fuel cell stack 12, securing hydrogen-related safety, etc. Can be achieved at the same time.

  Note that the present invention is not limited to the above-described embodiment, and various configurations can be adopted based on the description in this specification.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 15 ... Scavenging device 16 ... Fuel gas supply device 17 ... Battery 18 ... Controller 19 ... Timer 20 ... Fuel cell 21 ... Cooling medium supply device 22 ... Solid high Molecular electrolyte membrane 24 ... Cathode electrode 26 ... Anode electrode 28 ... Electrolyte membrane / electrode structure 30, 32 ... Separator 34 ... Oxidant gas channel 36 ... Fuel gas channel 38a ... Oxidant gas inlet communication hole 38b ... Oxidant gas Outlet communication hole 40a ... Fuel gas inlet communication hole 40b ... Fuel gas outlet communication hole 41a ... Cooling medium inlet communication hole 41b ... Cooling medium outlet communication hole 50 ... Air pump 52 ... Air supply flow path 53 ... Air introduction flow path 54 ... Humidifier 55 ... Air introduction valve 56 ... Air discharge flow path 58 ... Back pressure control valve 60 ... Dilution box 62 ... Hydrogen tank 63 ... In-tank Magnetic valve 64 ... Hydrogen supply flow path 65 ... Shut-off valve 66 ... Ejector 68 ... Hydrogen circulation path 70 ... Off gas flow path 72 ... Purge valve 74 ... Discharge flow path 78 ... Cooling medium circulation path 86 ... FC contactor 90 ... DC / DC converter 92 ... Battery contactor 96 ... Downverter 98 ... 12V power supply 102, 103 ... Pressure sensor 104, 105, 106 ... Temperature sensor 108 ... Voltage sensor 110 ... Current sensor 120 ... Pump 122 ... Radiator 210 ... Implementation feasibility / interruption necessity judgment unit 212 ... Execution availability determination unit 214 ... Interruption necessity determination unit

Claims (2)

A fuel cell that generates electricity by an electrochemical reaction of an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side;
An oxidant gas supply device for supplying the oxidant gas to the fuel cell;
A fuel gas supply device for supplying the fuel gas to the fuel cell;
A cooling medium supply device for supplying a cooling medium to the fuel cell;
A fuel cell system that, when detecting a stop command for the fuel cell, stops the power supply of the fuel gas, and performs a power generation process at the time of stopping to generate the fuel cell while supplying the oxidant gas to the fuel cell. In the control method,
The stop-time power generation process is to be terminated after a predetermined time has elapsed since the operation stop command for the fuel cell system was detected.
During the stop-time power generation process from when the fuel cell system operation stop command is detected, and before the predetermined time elapses ,
There are at least one of the following conditions: the anode side pressure is less than or equal to a threshold pressure, the fuel cell voltage is less than or equal to a threshold voltage, the anode side fuel gas temperature is less than or equal to a threshold temperature, and the coolant temperature is greater than or equal to a threshold temperature. If detected,
The fuel cell system control method, wherein the power generation process at the time of stop is interrupted. A fuel cell that generates electricity by an electrochemical reaction of an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side;
An oxidant gas supply device for supplying the oxidant gas to the fuel cell;
A fuel gas supply device for supplying the fuel gas to the fuel cell;
A fuel cell system that, when detecting a stop command for the fuel cell, stops the power supply of the fuel gas, and performs a power generation process at the time of stopping to generate the fuel cell while supplying the oxidant gas to the fuel cell. In the control method,
The stop-time power generation process is to be terminated after a predetermined time has elapsed since the operation stop command for the fuel cell system was detected.
When detecting an operation stop command of the fuel cell system,
When a malfunction of power generation during normal power generation of the fuel cell system is stored, when the fuel cell system is activated at a predetermined temperature or lower and before the fuel cell system is completely warmed up, and If at least one of the conditions is detected when the control valve controlling the gas pressure is likely to freeze,
The fuel cell system control method is characterized in that the stop-time power generation process is not performed.

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