JP2017004913A - Fuel cell system, and control method of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress waste of hydrogen gas and suppress deterioration of a cathode electrode during power generation stop of a fuel cell stack.SOLUTION: A fuel cell system comprises: a fuel cell stack 10; a hydrogen gas supply valve 35 on a downstream side of a hydrogen gas supply passage 31; a hydrogen gas pressure regulating valve 34 on an upstream side of the supply passage which is a valve for maintaining the pressure of the hydrogen gas supply passage from the hydrogen gas supply valve to the hydrogen gas pressure regulating valve at a set pressure; an anode off-gas exhaust valve 37 of an anode off-gas passage 36; a compressor 44 connected to an air-supplying path 41; a cathode off-gas exhaust valve 47 of a cathode off-gas passage 46; and a controller 60 which performs control so as to close the hydrogen gas supply valve, the anode off-gas exhaust valve and the cathode off-gas exhaust valve in transmitting a power generation stop signal, stop the compressor to stop power generation, set the set pressure to a lower pressure than pressure during power generation, and when a potential difference of a cathode electrode to an anode electrode is larger than the upper limit value during power generation stop, temporary open the hydrogen gas supply valve to supply hydrogen gas to the anode electrode.SELECTED DRAWING: Figure 1

Description

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

  A hydrogen gas passage, an anode electrode provided in the hydrogen gas passage, an air passage, and a cathode electrode provided in the air passage, the hydrogen gas supplied to the anode electrode and the air supplied to the cathode electrode in the air A fuel cell stack that generates electric power through an electrochemical reaction with oxygen gas, a hydrogen gas source, a hydrogen gas supply path that connects the inlet of the hydrogen gas path and the hydrogen gas source, and a hydrogen gas supply path. A hydrogen gas supply valve for supplying hydrogen gas into the hydrogen gas passage, an anode offgas passage connected to the outlet of the hydrogen gas passage, an anode offgas discharge valve disposed in the anode offgas passage, and an anode offgas discharge A fuel storage unit that is disposed in an anode off-gas passage on the downstream side of the valve and pressurizes and stores a part of the anode off-gas, a fuel storage unit, a hydrogen gas passage, and an air passage An anode off-gas supply path that connects the two, and another hydrogen gas that is disposed in the anode off-gas supply path and that supplies the anode off-gas from the fuel storage unit to the hydrogen gas passage and the air passage when power generation is stopped in the fuel cell stack A supply valve, an air supply passage connected to the inlet of the air passage, an air supply valve arranged in the air supply passage, a cathode offgas passage connected to the outlet of the air passage, and a cathode offgas passage When the cathode offgas discharge valve and a signal to stop power generation in the fuel cell stack are issued, supply of hydrogen gas by the hydrogen gas supply valve is stopped, the anode offgas discharge valve is closed, and air is supplied The supply of air through the valve is stopped and the cathode off-gas discharge valve is closed, thereby stopping power generation in the fuel cell stack and another hydrogen gas. The supply valve is temporarily opened to supply hydrogen gas to the hydrogen gas passage and the air passage, and further, the amount of hydrogen gas in the hydrogen gas passage is lower than a preset lower limit during power generation stoppage in the fuel cell stack. A fuel cell system comprising a controller configured to temporarily open another hydrogen gas supply valve to supply anode off gas into the hydrogen gas passage and the air passage when (See, for example, Patent Document 1).

  When power generation of the fuel cell stack is stopped, a method of confining the hydrogen gas remaining in the hydrogen gas passage as it is in the hydrogen gas passage and confining the air remaining in the air passage as it is in the air passage is conceivable. In this case, during the power generation stop of the fuel cell stack, the oxygen gas at the cathode electrode reacts with the hydrogen gas that has permeated the electrolyte membrane from the anode electrode and diffused to the cathode electrode to generate water. As a result, oxygen gas and hydrogen gas are consumed and reduced. However, when air enters the cathode electrode from the outside in this state, oxygen gas in the air permeates the electrolyte membrane from the cathode electrode and diffuses to the anode electrode. As a result, oxygen gas exists in the cathode electrode, and oxygen gas and hydrogen gas exist in the anode electrode. In this state, an undesired electrochemical reaction occurs in the cathode electrode, the carbon of the cathode electrode is oxidized, and the cathode electrode may be deteriorated to reduce the power generation performance. Therefore, in the fuel cell system of Patent Document 1, when the power generation of the fuel cell stack is stopped, hydrogen gas is supplied and confined in the hydrogen gas passage and the air passage. As a result, even if air enters the air passage, the oxygen gas in the air reacts with the hydrogen gas in the air passage to generate water, so that the oxygen gas can be removed. Further, when air enters the air passage, hydrogen gas at the anode electrode permeates the electrolyte membrane and diffuses to the cathode electrode, and reacts with oxygen gas in the air to produce water, thereby removing oxygen gas. it can. However, at that time, the amount of hydrogen gas in the anode electrode, that is, the hydrogen gas passage decreases. Therefore, if air further enters the air passage, the amount of hydrogen gas in the hydrogen gas passage is small, so that oxygen gas in the air permeates the electrolyte membrane and diffuses to the anode electrode, which may cause oxidation of the cathode electrode. . Therefore, in Patent Document 1, when the power generation of the fuel cell stack is stopped, another hydrogen gas supply valve is temporarily opened to supply the anode off-gas into the hydrogen gas passage and the air passage. When the amount of hydrogen gas becomes smaller than a preset lower limit value, another hydrogen gas supply valve is temporarily opened to introduce hydrogen gas (anode off gas) into the hydrogen gas passage and the air passage. Hydrogen gas is reacted with oxygen gas at the anode and cathode to generate water, thereby removing oxygen gas and suppressing carbon oxidation.

JP 2006-073377 A

  The technology of the fuel cell system of Patent Document 1 described above is such that when power generation of the fuel cell stack is stopped, the hydrogen gas remaining in the hydrogen gas passage is confined in the hydrogen gas passage as it is, and the air remaining in the air passage is directly used as the air passage. It can also be applied when confined in That is, when the amount of hydrogen gas in the hydrogen gas passage decreases, another hydrogen gas supply valve is temporarily opened to introduce hydrogen gas into the anode electrode, and the hydrogen gas and oxygen gas react to cause water to flow. By generating it, it is considered that the oxygen gas at the anode electrode can be removed and the occurrence of an oxidation reaction of carbon at the cathode electrode can be prevented.

  Here, the amount of hydrogen gas supplied to the anode electrode from another hydrogen gas supply valve is determined by the valve opening time. Therefore, in order to control the amount of hydrogen gas supplied from another hydrogen gas supply valve to the anode electrode, the valve opening time may be shortened. However, there is a limit to shortening the valve opening time due to the structure of another hydrogen gas supply valve. As a result, when the hydrogen gas supply valve is temporarily opened while the fuel cell stack is not generating power and hydrogen gas is supplied to the anode electrode, the excess of hydrogen gas is larger than the amount of hydrogen gas required to remove oxygen gas. There is a risk of supplying a large amount of hydrogen gas to the anode electrode. In this case, a part of the hydrogen gas supplied to the anode electrode is used for removing oxygen gas, but the surplus portion passes through the electrolyte membrane from the anode electrode and moves to the cathode electrode, and then passes through the cathode offgas discharge valve or the like. It is not used effectively, such as being released to the outside, and may be wasted.

  According to one aspect of the present invention, a hydrogen gas passage, an anode electrode provided in the hydrogen gas passage, an air passage, and a cathode electrode provided in the air passage, the anode electrode A fuel cell stack for generating electric power by an electrochemical reaction between the supplied hydrogen gas and oxygen gas in the air supplied to the cathode, a hydrogen gas source, an inlet of the hydrogen gas passage, and the hydrogen gas source; Are connected to each other, a hydrogen gas supply valve disposed in the hydrogen gas supply path for supplying hydrogen gas into the hydrogen gas path, and the hydrogen upstream of the hydrogen gas supply valve. A hydrogen gas pressure regulating valve arranged in a gas supply path, wherein the hydrogen gas supply from the hydrogen gas supply valve to the hydrogen gas pressure regulating valve regardless of whether the fuel cell stack is generating power or not generating power On the road A hydrogen gas pressure regulating valve for maintaining the pressure in the intermediate pressure passage at a predetermined set pressure, an anode off gas passage connected to an outlet of the hydrogen gas passage, and an anode off gas disposed in the anode off gas passage A discharge valve, a compressor, an air supply passage that connects the inlet of the air passage and the outlet of the compressor, a cathode offgas passage connected to the outlet of the air passage, and a cathode offgas passage are disposed in the cathode offgas passage When a signal to stop power generation in the cathode offgas discharge valve and the fuel cell stack is issued, the supply of hydrogen gas by the hydrogen gas supply valve is stopped while closing the anode offgas discharge valve, And the supply of air by the compressor is stopped and the cathode offgas discharge valve is closed, thereby Power generation in the fuel cell stack is stopped, the set pressure is set to a stop time pressure lower than that during power generation in the fuel cell stack, and the cathode with respect to the anode electrode is stopped during power generation stop in the fuel cell stack A controller configured to temporarily open the hydrogen gas supply valve to supply hydrogen gas into the hydrogen gas passage when the potential difference between the poles exceeds a preset upper limit; A fuel cell system is provided.

  According to another aspect of the present invention, the anode electrode includes a hydrogen gas passage, an anode electrode provided in the hydrogen gas passage, an air passage, and a cathode electrode provided in the air passage. A fuel cell stack that generates electric power by an electrochemical reaction between hydrogen gas supplied to the cathode electrode and oxygen gas in the air supplied to the cathode electrode, a hydrogen gas source, an inlet of the hydrogen gas passage, and the hydrogen gas source A hydrogen gas supply path that is connected to each other, a hydrogen gas supply valve that is disposed in the hydrogen gas supply path, for supplying hydrogen gas into the hydrogen gas path, and the upstream side of the hydrogen gas supply valve A hydrogen gas pressure regulating valve arranged in a hydrogen gas supply path, wherein the hydrogen gas from the hydrogen gas supply valve to the hydrogen gas pressure regulating valve regardless of whether the fuel cell stack is generating power or not generating power In the supply channel A hydrogen gas pressure regulating valve for maintaining the pressure in the intermediate pressure passage at a predetermined set pressure, an anode off-gas passage connected to the outlet of the hydrogen gas passage, and an anode disposed in the anode off-gas passage An off-gas discharge valve, a compressor, an air supply passage that connects the inlet of the air passage and an outlet of the compressor, a cathode off-gas passage connected to the outlet of the air passage, and a cathode off-gas passage. And a cathode offgas discharge valve, wherein when the signal to stop power generation in the fuel cell stack is issued, the anode offgas discharge valve is closed while the anode offgas discharge valve is closed. Stop the supply of hydrogen gas by the hydrogen gas supply valve and stop the supply of air by the compressor and Closing the cathode offgas discharge valve, thereby stopping power generation in the fuel cell stack, and further setting the set pressure to a stop pressure lower than that during power generation in the fuel cell stack, When the potential difference between the cathode electrode and the cathode electrode becomes larger than a preset upper limit value during the power generation stop at the engine, the hydrogen gas supply valve is temporarily opened to allow hydrogen gas to flow into the hydrogen gas passage. A fuel cell system and a control method for the fuel cell system are provided.

  While power generation of the fuel cell stack is stopped, it is possible to suppress deterioration of the cathode electrode while suppressing waste of hydrogen gas.

1 is an overall view of a fuel cell system. It is a time chart which shows the change of a cell voltage. It is a time chart explaining cathode pole protection control. It is a partial expanded sectional view of an injector. It is a time chart explaining power generation stop sequence control and cathode pole protection control. It is a flowchart which shows the routine which performs electric power generation stop sequence control. It is a flowchart which shows the routine which performs cathode pole protection control. It is a general view of the fuel cell system of another Example.

  Referring to FIG. 1, the fuel cell system A includes a fuel cell stack 10. The fuel cell stack 10 includes a plurality of fuel cell single cells stacked in the stacking direction. Each single fuel cell includes a membrane electrode assembly 20. The membrane electrode assembly 20 includes a membrane-like electrolyte membrane, an anode electrode formed on one side of the electrolyte membrane, and a cathode electrode formed on the other side of the electrolyte membrane. The anode and cathode are formed of an electrode catalyst containing carbon particles carrying fine particles of platinum or a platinum alloy. Examples of the platinum alloy include PtCo and PtRu, and examples of the carbon particles include carbon black.

  The anode electrode of the fuel cell unit cell is electrically connected to the cathode electrode of another fuel cell unit cell adjacent to one side, and the cathode electrode is electrically connected to the anode electrode of another fuel cell unit cell adjacent to the other side via a separator. Connected. The anode electrode of the fuel cell single cell on one end side and the cathode electrode of the fuel cell single cell on the other end side in the stacked body in which a plurality of fuel cell single cells are stacked constitute an electrode of the fuel cell stack 10. The electrode of the fuel cell stack 10 is electrically connected to the inverter 12 via the DC / DC converter 11, and the inverter 12 is electrically connected to the motor generator 13. Further, the fuel cell system A includes a power storage device 14, and this power storage device 14 is electrically connected to the inverter 12 via a DC / DC converter 15. The DC / DC converter 11 controls the magnitude of the output current / output voltage output from the fuel cell stack 10 and converts the magnitude of the output current / output voltage to be supplied to the inverter 12. is there. The inverter 12 is for converting a direct current from the DC / DC converter 11 or the power storage device 14 into an alternating current. The DC / DC converter 15 is for reducing the voltage from the fuel cell stack 10 or the motor generator 13 to the power storage device 14 or increasing the voltage from the power storage device 14 to the motor generator 13. In the fuel cell system A shown in FIG. 1, the power storage device 14 is composed of a battery. A cell voltage sensor 16 that detects a cell voltage that is a potential difference between the cathode electrode and the anode electrode is electrically connected to the cathode electrode and the anode electrode of the fuel cell stack 10.

  Further, in the single fuel cell, a hydrogen gas flow passage for supplying hydrogen gas to the anode electrode, an air flow passage for supplying air to the cathode electrode, and cooling water is supplied to the single fuel cell. Cooling water flow passages are formed respectively. The hydrogen gas flow paths of the plurality of fuel cell single cells are connected in parallel, the air flow paths of the plurality of fuel cell single cells are connected in parallel, and the cooling water flow paths of the plurality of fuel cell single cells are connected in parallel. Thus, the hydrogen gas passage 30, the air passage 40, and the cooling water passage 50 are formed in the fuel cell stack 10, respectively.

  A hydrogen gas supply path 31 is connected to the inlet of the hydrogen gas passage 30, and the hydrogen gas supply path 31 is connected to a hydrogen tank 32 that is a hydrogen gas source. In the hydrogen gas supply path 31, a main stop valve 33, a regulator 34, and a hydrogen gas injector 35 are arranged in this order from the upstream side. Hereinafter, the hydrogen gas supply passage 31 between the main stop valve 33 and the regulator 34 is referred to as a high pressure passage 31a, and the hydrogen gas supply passage 31 between the regulator 34 and the hydrogen gas injector 35 is referred to as an intermediate pressure passage 31b. The hydrogen gas supply passage 31 between the hydrogen gas injector 35 and the inlet of the hydrogen gas passage 30 is referred to as a low pressure passage 31c. The main stop valve 33 is an electromagnetic shut-off valve for shutting off the outflow of hydrogen gas from the hydrogen tank 32 to the high-pressure passage 31a. The regulator 34 is an electromagnetic pressure reducing valve for reducing the pressure of the hydrogen gas in the high pressure passage 31a and supplying the reduced pressure to the intermediate pressure passage 31b. In the embodiment of FIG. 1, the regulator 34 is a diaphragm valve. Regardless of whether the fuel cell stack 10 is generating power or stopping power generation, the regulator 34 maintains the pressure of the hydrogen gas in the intermediate pressure passage 31b at a predetermined set pressure. The set pressure of the regulator 34 is variable, and is set to different values when the fuel cell stack 10 generates power and when power generation is stopped. Since the regulator 34 adjusts and supplies the pressure of hydrogen gas from the high pressure passage 31a to the intermediate pressure passage 31b, it can be called a hydrogen gas pressure regulating valve. The hydrogen gas injector 35 is a hydrogen gas supply valve that supplies the hydrogen gas in the intermediate pressure passage 31b to the hydrogen gas passage 30 through the low pressure passage 31c. The hydrogen gas injector 35 can adjust the amount of hydrogen gas supplied to the anode electrode of the fuel cell stack 10. In the embodiment of FIG. 1, the hydrogen gas injector 35 is an electromagnetic needle valve. The pressure P1 of the hydrogen gas in the high pressure passage 31a, the pressure P2 of the hydrogen gas in the intermediate pressure passage 31b, and the pressure P3 of the hydrogen gas in the low pressure passage 31c have a relationship of P1 ≧ P2 ≧ P3. In another embodiment (not shown), an electromagnetic needle valve is used as the regulator 34. The needle valve controls the valve opening time based on the pressure in the high pressure passage 31a and the pressure in the intermediate pressure passage 31b, thereby reducing the pressure of the hydrogen gas in the high pressure passage 31a and supplying it to the intermediate pressure passage 31b. Can thus be viewed as a pressure reducing valve. On the other hand, an anode off gas passage 36 is connected to the outlet of the hydrogen gas passage 30. When the main stop valve 33 is opened and the hydrogen gas injector 35 is opened, the hydrogen gas in the hydrogen tank 32 is supplied into the hydrogen gas passage 30 in the fuel cell stack 10 via the hydrogen gas supply passage 31. The At this time, the gas flowing out from the hydrogen gas passage 30, that is, the anode off gas, flows into the anode off gas passage 36. An electromagnetic anode offgas discharge valve 37 is disposed in the anode offgas passage 36. The anode off gas discharge valve 37 is normally closed during power generation of the fuel cell stack 10, is temporarily opened when the anode off gas is to be discharged, and is kept closed when power generation is stopped.

  An air supply path 41 is connected to the inlet of the air passage 40, and the air supply path 41 is connected to the atmosphere 42 as an air source. In the air supply path 41, in order from the upstream side, an air cleaner 43, an air supplier or compressor 44 that pumps air, and an intercooler 45 that cools the air sent from the compressor 44 to the fuel cell stack 10 are provided. Be placed. On the other hand, a cathode offgas passage 46 is connected to the outlet of the air passage 40. When the compressor 44 is driven, air is supplied into the air passage 40 in the fuel cell stack 10 via the air supply path 41. At this time, the gas flowing out from the air passage 40, that is, the cathode offgas, flows into the cathode offgas passage 46. An electromagnetic cathode offgas discharge valve 47 for controlling the amount of cathode offgas flowing in the cathode offgas passage 46 and a muffler 90 are disposed in the cathode offgas passage 46. The anode off gas passage 36 is connected to the cathode off gas passage 46 on the upstream side of the muffler 90. In the embodiment shown in FIG. 1, the downstream side of the cathode offgas discharge valve 47 in the cathode offgas passage 46 and the downstream side of the intercooler 45 in the air supply passage 41 are connected to each other by an air bypass passage 49. An air bypass control valve 48 is disposed at the inlet of the air bypass passage 49. The air bypass control valve 48 bypasses the fuel cell stack 10 and controls the amount of air flowing from the air supply path 41 to the cathode offgas path 46. In the fuel cell system A shown in FIG. 1, the air bypass control valve 48 is formed of an electromagnetic three-way valve.

  In the embodiment shown in FIG. 1, a slight amount of air can pass through the compressor 44 when the compressor 44 is stopped. In the air bypass control valve 48, the air supply path 41 between the compressor 44 and the air bypass control valve 48, that is, the compressor-side air supply path 41 is communicated with the air bypass path 49, and the air bypass control valve 48 When the air supply path 41 between the fuel cell stack 10 and the air supply path 41 on the fuel cell stack 10 side is not communicated, a slight amount of air passes the air bypass control valve 48 from the air supply path 41 on the compressor 44 side. It can pass through the air supply path 41 on the fuel cell stack 10 side. Further, when the cathode offgas discharge valve 47 is closed, that is, when the opening degree of the cathode offgas discharge valve 47 is minimized, a slight amount of air can pass through the cathode offgas discharge valve 47. In other words, when the compressor 44 is stopped, the air supply passage 41 on the compressor 44 side communicates with the air bypass passage 49 in the air bypass control valve 48, and does not communicate with the air supply passage 41 on the fuel cell stack 10 side, and Even when the cathode offgas discharge valve 47 is closed, the air passage 40 of the fuel cell stack 10 is not completely sealed, that is, air can enter the air passage 40 from the atmosphere 42. It has become. When such a compressor 44 and cathode offgas discharge valve 47 are used, an inexpensive valve can be adopted, and the cost of the fuel cell system A can be greatly reduced.

  In the cathode off-gas exhaust valve 47 and the air bypass control valve 48, which can significantly reduce the cost of the fuel cell system A and the gas leakage amount is relatively large, the gas leakage amount (valve per second) The volume of air leaking from one side to the other) is, for example, 30 L / min @ 60 kPa. g.

  In another embodiment (not shown), the air bypass passage 49 is not disposed, and an air shut-off valve that shuts off the supply of air flowing through the air supply passage 41 is disposed instead of the air bypass control valve 48. During the power generation of the fuel cell stack 10, the air shut-off valve is opened. At this time, the amount of air supplied to the air passage of the fuel cell stack 10 is controlled by the compressor 44, and when the power generation of the fuel cell stack 10 is stopped, the air shutoff valve is closed together with the cathode offgas discharge valve 47. As the air shutoff valve, a valve similar to the cathode offgas discharge valve 47 can be used. Therefore, when the air shut-off valve is closed, that is, when the opening of the air shut-off valve is minimized, a slight amount of air can pass through the air shut-off valve. Also in this case, the cost of the fuel cell system A can be significantly reduced.

  One end of the cooling water supply pipe 51 is connected to the inlet of the cooling water passage 50, and the other end of the cooling water supply pipe 51 is connected to the outlet of the cooling water supply pipe 51. A cooling water pump 52 that pumps cooling water and a radiator 53 are disposed in the cooling water supply pipe 51. The cooling water supply pipe 51 upstream of the radiator 53 and the cooling water supply pipe 51 between the radiator 53 and the cooling water pump 52 are connected to each other by a radiator bypass pipe 54. Further, a radiator bypass control valve 55 that controls the amount of cooling water flowing in the radiator bypass pipe 54 is provided. In the embodiment shown in FIG. 1, the radiator bypass control valve 55 is formed of an electromagnetic three-way valve and is disposed at the inlet of the radiator bypass pipe 54. When the cooling water pump 52 is driven, the cooling water discharged from the cooling water pump 52 flows into the cooling water passage 50 in the fuel cell stack 10 through the cooling water supply pipe 51, and then passes through the cooling water passage 50. Then, it flows into the cooling water supply pipe 51 and returns to the cooling water pump 52 via the radiator 53 or the radiator bypass pipe 54.

  The electronic control unit 60 is composed of a digital computer and includes a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, a CPU (Microprocessor) 64, an input port 65 and an output port 66 which are connected to each other by a bidirectional bus 61. It comprises. A pressure sensor 81, a pressure sensor 82, and a pressure sensor 83 for detecting the pressure in the passage are disposed in the high pressure passage 31a, the intermediate pressure passage 31b, and the low pressure passage 31c, respectively. The output signal of the cell voltage sensor 16 and the output signals of the pressure sensor 81, the pressure sensor 82, and the pressure sensor 83 are input to the input port 65 via the corresponding AD converter 67. On the other hand, the output port 66 is connected to the DC / DC converter 11, the inverter 12, the motor generator 13, the DC / DC converter 15, the main stop valve 33, the regulator 34, the hydrogen gas injector 35, and the anode off-gas discharge valve via the corresponding drive circuit 68. 37, a compressor 44, a cathode offgas discharge valve 47, an air bypass control valve 48, a cooling water pump 52, and a radiator bypass control valve 55 are electrically connected. In the fuel cell system A shown in FIG. 1, the electronic control unit 60 is connected to the power source 72 via the switch circuit 71 and activated when the switch circuit 71 is turned on. The ignition switch 70 operated by the vehicle operator is electrically connected to the input port 65 of the electronic control unit 60. On the one hand, the switch circuit 71 is controlled to be turned on / off by the ignition switch 70, and on the other hand, when the electronic control unit 60 is de-energized, the switch circuit 71 is temporarily turned on at regular time intervals to temporarily start the electronic control unit 60. When the ignition switch 70 is turned off by the vehicle operator, a signal for stopping power generation in the fuel cell stack 10 is output from the ignition switch 70 and input to the electronic control unit 60 via the input port 65. When this signal is input, the electronic control unit 60 executes power generation stop sequence control (to be described later) for stopping power generation. When the power generation stop sequence control is ended, the switch circuit 71 disconnects the connection between the electronic control unit 60 and the power source 72. On the other hand, when the ignition switch 70 is turned on by the vehicle operator, a signal for starting power generation in the fuel cell stack 10 is emitted from the ignition switch 70 and input to the switch circuit 71. When the signal is inputted, the electronic control unit 60 and the power source 72 are connected by the switch circuit 71, and the electronic control unit 60 is activated.

When the fuel cell stack 10 is to generate power, the set pressure of the regulator 34 is set to the set pressure at the time of power generation, and the main stop valve 33, the hydrogen gas injector 35, and the anode offgas discharge valve 37 are opened. Hydrogen gas is supplied to the fuel cell stack 10. Further, the compressor 44 is driven, the compressor 44 and the fuel cell stack 10 are communicated with each other by the air bypass control valve 48, the cathode offgas discharge valve 47 is opened, and thus air is supplied to the fuel cell stack 10. As a result, an electrochemical reaction (anode electrode: H ₂ → 2H ⁺ + 2e ⁻ , cathode electrode: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O) occurs in the single fuel cell, and electric energy is generated. The The generated electrical energy is sent to the motor generator 13. As a result, the motor generator 13 is operated as an electric motor for driving the vehicle, and the vehicle is driven. On the other hand, for example, when the vehicle is braked, the motor generator 13 operates as a regenerative device, and the electrical energy regenerated at this time is stored in the power storage device 14.

  On the other hand, when the power generation of the fuel cell stack 10 is to be stopped, the power generation stop sequence control is executed. That is, the main stop valve 33, the hydrogen gas injector 35, and the anode offgas discharge valve 37 are closed, so that the supply of hydrogen gas to the fuel cell stack 10 is stopped and the hydrogen gas is confined in the hydrogen gas passage 30. In addition, the compressor 44 is stopped, the cathode offgas discharge valve 47 is closed, and therefore the supply of oxygen gas to the fuel cell stack 10 is stopped, and the oxygen gas is confined in the air passage 40.

  FIG. 2 shows the cell voltage CV before and after the power generation of the fuel cell stack 10 is stopped in the fuel cell system A shown in FIG. In the fuel cell system A shown in FIG. 1, since the potential of the anode electrode is maintained at zero, the cell voltage CV indicates the potential of the cathode electrode.

  At the timing indicated by X1 in FIG. 2, the fuel cell stack 10 is generating power. In this case, hydrogen gas is supplied to the anode electrode on one side of the electrolyte membrane, and air is supplied to the cathode electrode on the other side of the electrolyte membrane. In the fuel cell stack 10, the above-described electrochemical reaction is performed. Has been done. As a result, the cell voltage CV is CV1 (example: 1.0 V per single fuel cell).

  Next, when a signal for stopping the power generation of the fuel cell stack 10 is issued as indicated by X2 in FIG. 2, the supply of hydrogen gas and air to the fuel cell stack 10 is stopped, and the oxygen gas remaining in the cathode electrode Reacts with protons passing through the electrolyte membrane from the anode electrode and gradually decreases, so that the cell voltage CV gradually decreases as indicated by X3 in FIG. Next, when almost all of the residual oxygen gas at the cathode electrode is consumed, the electrochemical reaction stops, so that the cell voltage becomes zero, as indicated by X4 in FIG. At this time, hydrogen gas remains in the anode electrode. Therefore, hydrogen gas permeates through the electrolyte membrane from the anode electrode and diffuses to the cathode electrode, and hydrogen gas is present at the cathode electrode.

If almost no oxygen gas remains in the cathode electrode of the fuel cell stack 10, the cell voltage CV is maintained at zero, as indicated by X5 in FIG. However, as described above, in the fuel cell stack 10 shown in FIG. 1, air can enter the air passage 40 of the fuel cell stack 10 when the power generation of the fuel cell stack 10 is stopped, and thus air can reach the cathode electrode. . At that time, when the amount of hydrogen gas (number of moles) existing in the cathode electrode is more than twice the amount of oxygen gas (number of moles) existing in the cathode electrode (hydrogen oxygen ratio: 2), water is generated at the cathode electrode. Thus, the invading oxygen gas can be consumed (2H ₂ + O ₂ → 2H ₂ O). At this time, the potential of the cathode does not rise, and therefore the cell voltage is maintained at zero.

  However, when the amount of hydrogen gas remaining in the anode electrode gradually decreases, the amount of hydrogen gas that permeates from the anode electrode to the cathode electrode decreases, and the hydrogen-oxygen ratio at the cathode electrode becomes smaller than 2, it exists in the cathode electrode. The amount of oxygen gas to be increased increases, and the oxygen gas passes through the electrolyte membrane and reaches the anode electrode. As a result, hydrogen gas and oxygen gas are present at the anode electrode, and oxygen gas is present at the cathode electrode. In such a state, carbon is undesirably oxidized in the cathode electrode catalyst, and therefore the cathode electrode catalyst may be deteriorated. On the other hand, as the amount of residual oxygen gas at the cathode electrode increases, the potential at the cathode electrode gradually increases, so that the cell voltage CV gradually increases as indicated by X6 in FIG.

  Thus, the cell voltage CV when power generation of the fuel cell stack 10 is stopped indicates the amount of residual oxygen gas at the cathode electrode. When the cell voltage CV increases, that is, when the residual oxygen gas amount at the cathode electrode increases, a part of the gas moves to the anode electrode, and hydrogen gas and oxygen gas exist at the anode electrode. There is a risk that the electrode catalyst will deteriorate. Therefore, in the fuel cell system A shown in FIG. 1, when the cell voltage CV becomes larger than a preset upper limit voltage while the power generation of the fuel cell stack 10 is stopped, it is regarded as a sign that the cathode electrode catalyst is deteriorated. Cathode electrode protection control for protecting the cathode electrode is performed. Next, the cathode electrode protection control will be described with reference to FIG.

  That is, when the cell voltage CV becomes larger than the upper limit voltage CVUL (example: 0.05 V per fuel cell single cell) at time t1 in FIG. 3, the hydrogen gas injector 35 opens the valve opening time Δt1 (from time t1 to t2). Thus, the valve is temporarily opened, and a certain amount necessary for lowering the cell voltage CV to the lower limit voltage CVLL, that is, a hydrogen gas having a voltage lowering hydrogen gas amount is supplied to the anode electrode. In this case, the anode off gas discharge valve 37 is kept closed. As a result, a part of the hydrogen gas supplied to the anode electrode passes through the electrolyte membrane and moves to the cathode electrode, and reacts with the oxygen gas present in the cathode electrode to produce water, thereby generating oxygen content in the cathode electrode. Since the pressure decreases, the cell voltage CV decreases. By reducing the oxygen partial pressure in the cathode electrode, it is possible to suppress oxygen gas in the cathode electrode from passing through the electrolyte membrane and moving to the anode electrode. Therefore, deterioration of the cathode electrode is suppressed. Further, as the oxygen partial pressure at the cathode electrode decreases, the cell voltage CV gradually decreases, and at time t3, the cell voltage CV becomes smaller than the lower limit voltage CVLL (example: 0.01 V per fuel cell single cell). . If the cell voltage CV does not become lower than the lower limit voltage CVLL after a lapse of a preset delay time Δt2 (from time t2 to t4) after the hydrogen gas injector 35 is closed, the hydrogen gas injector 35 is temporarily turned on again. Thus, the valve is opened and a hydrogen gas having a reduced voltage is supplied to the anode.

  At this time, if the amount of hydrogen gas supplied to the anode electrode by the hydrogen gas injector 35 is too large, a part of the hydrogen gas lowers the cell voltage CV below the lower limit voltage CVLL, but hydrogen that has not contributed to the decrease in the cell voltage CV. At least a part of the surplus gas portion moves to the cathode electrode and then diffuses to the outside through the cathode offgas discharge valve 47 and the like, so that it cannot be used effectively. Therefore, in order to eliminate the waste of hydrogen gas, it is necessary to finely control the amount of hydrogen gas supplied to the anode electrode by the hydrogen gas injector 35 in order to supply the hydrogen gas of the above-described reduced voltage hydrogen gas amount to the anode. There is.

  FIG. 4 shows an example of the hydrogen gas injector 35. The hydrogen gas injector 35 includes a casing 84. A plunger receiving hole 85 and a hydrogen gas outflow hole 86 are formed in the casing 84 so as to communicate with each other. The plunger housing hole 85 is connected to the intermediate pressure passage 31 b of the hydrogen gas supply passage 31, and the hydrogen gas outlet hole 86 is connected to the low pressure passage 31 c of the hydrogen gas supply passage 31. A valve seat 87 is formed on the inner wall surface of the plunger accommodation hole 85 around the opening of the hydrogen gas outflow hole 86. A plunger 88 is accommodated in the plunger accommodation hole 85 so as to be movable in the axial direction. Plunger 88 includes a rubber seal 89 at the bottom end. The seal 89 has an annular convex portion.

  The plunger 88 is moved in the axial direction by a solenoid (not shown). When the plunger 88 is moved away from the valve seat 87, the plunger receiving hole 85 and the hydrogen gas outflow hole 86 are communicated with each other, that is, the hydrogen gas injector 35 is opened. As a result, hydrogen gas is supplied from the hydrogen gas injector 35. On the other hand, when the plunger 88 is moved in the direction approaching the valve seat 87 and the seal 89 is seated on the valve seat 87, the communication between the plunger housing hole 85 and the hydrogen gas outflow hole 86 is interrupted, that is, the hydrogen gas injector 35 is The valve is closed. As a result, the supply of hydrogen gas from the hydrogen gas injector 35 is stopped. Such a hydrogen gas injector 35 can be regarded as a kind of needle valve.

  When the hydrogen gas injector 35 having the configuration shown in FIG. 4 is used, the amount of hydrogen gas supplied to the anode electrode is the difference between the pressure in the intermediate pressure passage 31b and the pressure in the low pressure passage 31c, and It depends on the valve opening time. However, since the shortest valve opening time that can be controlled by the hydrogen gas injector 35 is determined, the minimum amount of hydrogen gas that can be supplied by the hydrogen gas injector 35 is the pressure in the intermediate pressure passage 31b and the pressure in the low pressure passage 31c. It will be determined by the differential pressure. That is, when the differential pressure is small, the minimum amount of hydrogen gas that can be supplied to the anode electrode is reduced, and the amount of hydrogen gas can be finely controlled. However, when the differential pressure is large, the minimum amount of hydrogen gas that can be supplied to the anode electrode becomes large, and fine control of the hydrogen gas amount becomes difficult.

  However, the set pressure of the regulator 34 during power generation of the fuel cell stack 10 is determined by the hydrogen gas consumption at the time of maximum output during power generation and the like, and in the embodiment of FIG. The pressure is set within a pressure range of ˜1000 kPa. Therefore, the pressure in the intermediate pressure passage 31b is substantially the same as the set pressure. On the other hand, the pressure of the low pressure passage 31c is controlled in the pressure range of, for example, 110 to 250 kPa from the operating conditions of the fuel cell stack 10. Therefore, when the cathode electrode protection control shown in FIG. 3 is performed under these pressure conditions, the pressure difference between the pressure in the intermediate pressure passage 31b and the pressure in the low pressure passage 31c is large, and the hydrogen gas that can be supplied to the anode electrode The smallest amount is bigger. Therefore, the amount of hydrogen gas cannot be finely controlled, and excess hydrogen gas is supplied to the anode electrode, which may cause waste of hydrogen gas.

  Therefore, in this embodiment, when the cathode electrode protection control is performed while the power generation of the fuel cell stack 10 is stopped, in the power generation stop sequence control, the set pressure of the regulator 34 during the power generation stop of the fuel cell stack 10 is set to the above fuel cell. The pressure is set lower than the set pressure during power generation of the stack 10. The low pressure is, for example, a pressure within a pressure range of 150 to 200 kPa. Hereinafter, the power generation stop sequence control and the cathode electrode protection control will be described with reference to FIG.

  FIG. 5 is a time chart for explaining power generation stop sequence control and cathode electrode protection control. (A) shows opening and closing of the main stop valve 33, (b) shows the pressure P1 of the high pressure passage 31a, and (c). Indicates the set pressure PS of the regulator 34, (d) indicates the pressure P2 in the intermediate pressure passage 31b, (e) indicates the opening / closing of the hydrogen gas injector 35, and (f) indicates the opening / closing of the anode off-gas discharge valve 37. (G) shows ON / OFF of the compressor 44, (h) shows opening / closing of the cathode offgas discharge valve 47, and (i) shows the cell voltage CV of the fuel cell stack 10.

  When power generation is performed in the fuel cell stack 10 (before time t11), the main stop valve 33 is opened, and the pressure P1 of the high-pressure passage 31a is P1H (example: about 70 MPa). The set pressure PS of the regulator 34 is set to a power generation pressure PSH (eg, 700 kPa) during power generation in the fuel cell stack 10, and therefore the pressure P2 of the intermediate pressure passage 31b is PSH. The hydrogen gas injector 35 repeats intermittent valve opening to supply hydrogen gas to the low pressure passage 31c, the anode off-gas discharge valve 37 is normally closed, and hydrogen gas is supplied to the anode electrode. On the other hand, the compressor 44 operates, the cathode offgas discharge valve 47 is opened, and air is supplied to the cathode electrode. Thereby, power generation is performed in the fuel cell stack 10, and the cell voltage CV becomes CV1.

  When a signal to stop the power generation in the fuel cell stack 10 is issued (time t11), the power generation stop sequence control is executed. In the power generation stop sequence control, the main stop valve 33 is closed, and the set pressure PS of the regulator 34 is set to a stop time pressure PSL (example: 150 kPa) lower than the power generation time pressure PSH. However, since the pressure P2 in the intermediate pressure passage 31b does not immediately decrease to the stop-time pressure PSL, the hydrogen gas injector 35 causes the hydrogen gas to flow into the anode electrode so that the pressure P2 in the intermediate pressure passage 31b decreases to the stop-time pressure PSL. To be supplied. At this time, air is supplied to the cathode by the compressor 44 and power is generated by the fuel cell stack 10 so that hydrogen gas is not wasted, and the generated power is stored in the power storage device 14. In the embodiment of FIG. 5, the cell voltage CV is CV1 as before time t11.

  When the pressure P2 in the intermediate pressure passage 31b is reduced to the stop-time pressure PSL (time t12), the hydrogen gas injector 35 is closed while the anode off-gas discharge valve 37 is closed, and the hydrogen gas injector 35 supplies hydrogen gas. The supply is stopped, the supply of air by the compressor 44 is stopped, and the cathode offgas discharge valve 47 is closed. Thereby, supply of hydrogen gas and air to the fuel cell stack 10 is stopped, and power generation is stopped. That is, the fuel cell stack 10 is in a power generation stop state. Thus, the power generation stop sequence control ends.

  When the fuel cell stack 10 is in a power generation stop state, the cathode electrode protection control is executed. After the fuel cell stack 10 stops generating power and the cell voltage CV becomes zero (time t13), as time elapses, air enters the air passage 40 of the fuel cell stack 10, and the above-described mechanism causes the cell to enter the cell. The voltage CV starts to increase gradually. Therefore, when the cell voltage CV becomes larger than the upper limit voltage CVUL (time t14), the hydrogen gas injector 35 is temporarily opened for the valve opening time Δt1 (time t14 to t15), and the hydrogen with the reduced voltage hydrogen gas amount. Gas is supplied to the anode electrode. As a result, the hydrogen gas that has passed through the electrolyte membrane from the anode electrode and moved to the cathode electrode reacts with the oxygen gas in the cathode electrode, and the oxygen gas is consumed, so that the cell voltage CV decreases and falls below the lower limit voltage CVLL. (Time t16). Here, when hydrogen gas is supplied to the anode by the hydrogen gas injector 35, the pressure on the primary side of the hydrogen gas injector 35, that is, the pressure P2 in the intermediate pressure passage 31b is lowered to the stop-time pressure PSL. The hydrogen gas injector 35 can finely control the amount of hydrogen gas. For this reason, the voltage drop hydrogen gas amount of the hydrogen gas injector 35 can be set small, so that when the hydrogen gas injector 35 is opened, hydrogen gas with a slight voltage drop hydrogen gas amount can be supplied to the anode electrode. As a result, it is possible to suppress generation of waste of hydrogen gas by supplying an excessive amount of hydrogen gas to the anode electrode. After the fuel cell stack 10 is in a power generation stop state, hydrogen gas is reduced due to the diffusion of hydrogen gas to the cathode electrode or the water generation reaction of oxygen gas and hydrogen gas diffused to the anode electrode. The pressure in the passage 30 gradually decreases, and is approximately atmospheric pressure (about 101 kPa) until the cell voltage CV reaches the upper limit voltage CVUL. In this state, when the hydrogen gas is supplied to the anode electrode by the hydrogen gas injector 35 by the amount of the reduced voltage hydrogen gas (time t14), the pressure in the hydrogen passage 30 is increased to, for example, about 110 to 120 kPa. Regarding the pressure in the hydrogen passage 30 thereafter, a change that gradually decreases to about atmospheric pressure due to the decrease in the amount of hydrogen gas, and a change that increases to a pressure of about 110 to 120 kPa when hydrogen gas is supplied to the anode electrode. Is repeated.

  Here, when the hydrogen gas injector 35 supplies hydrogen gas to the anode electrode, the pressure P2 in the intermediate pressure passage 31b is lower than the pressure PSL when the regulator 34 is stopped, and therefore the regulator 34 is connected to the high pressure passage 31a on the primary side. By supplying hydrogen gas to the secondary-side intermediate pressure passage 31b, the pressure P2 in the intermediate pressure passage 31b is maintained at the stop-time pressure PSL. At this time, since the main stop valve 33 is closed, the pressure P1 in the high pressure passage 31a decreases. In the embodiment of FIG. 5, the pressure P1 in the high pressure passage 31a decreases from P1H by ΔP1 (time t14 to t15).

  Thereafter, when the air further enters the air passage 40 of the fuel cell stack 10 and the potential of the cathode electrode becomes larger than the upper limit voltage CVUL (time t17), the hydrogen gas injector 35 is again opened for the valve opening time Δt1 (hour The valve is temporarily closed for t17 to t18), hydrogen gas is supplied to the anode electrode, and the cell voltage CV is made lower than the lower limit voltage CVLL (time t19). Also in this case, when the hydrogen gas injector 35 supplies the hydrogen gas, the pressure P1 of the high pressure passage 31a further decreases by ΔP1 (time t17 to t18).

  Similarly, when the potential of the cathode electrode becomes larger than the upper limit voltage CVUL, the hydrogen gas injector 35 is temporarily opened again for the valve opening time Δt1, and hydrogen gas is supplied to the anode electrode. Cell voltage CV is set lower than lower limit voltage CVLL.

  On the other hand, before or after supplying hydrogen gas to the anode electrode with the hydrogen gas injector 35, it is determined whether or not the pressure P1 of the high-pressure passage 31a is lower than a preset threshold pressure P1L (≧ pressure PSL at stop). Determined. When it is determined that the pressure P1 in the high-pressure passage 31a has decreased below the threshold pressure P1L (P1 <P1L) (time t23), the main stop valve 33 is temporarily opened (time t23 to t24). Hydrogen gas is supplied into the high-pressure passage 31a, and the pressure P1 of the high-pressure passage 31a is increased to a pressure equal to or higher than P1L, for example, P1M smaller than P1H during power generation. Thereby, since the pressure of the hydrogen gas in the high-pressure passage 31a is relatively lower than P1H, safety during power generation stop including vehicle stop can be further increased. In another embodiment (not shown), the pressure P1 in the high-pressure passage 31a is increased to P1H, which is the same as during power generation. Thereby, since the frequency | count that the main stop valve 33 opens is reduced, the power consumption during power generation stop can be suppressed.

  In this embodiment, when the cathode electrode protection control (FIG. 3) is performed, that is, when the fuel cell stack 10 stops power generation, the set pressure of the regulator 34 is set during power generation of the fuel cell stack 10 by power generation stop sequence control. It is set lower than the pressure. As a result, the pressure P2 in the intermediate pressure passage 31b becomes lower than that during the power generation of the fuel cell stack 10, so that in the cathode electrode protection control, the hydrogen gas injector 35 can supply a minute amount of hydrogen gas to the low pressure passage 31c. Supply of excess hydrogen gas to the anode electrode can be suppressed.

  FIG. 6 shows a routine for executing the power generation stop sequence control described above. This routine is executed by the electronic control unit 60 when a signal for stopping the power generation in the fuel cell stack 10 is issued.

  Referring to FIG. 6, the main stop valve 33 is closed at step 100. In the subsequent step 101, the set pressure PS of the regulator 34 is changed to a stop pressure PSL lower than the power generation pressure PSH. In the subsequent step 102, the hydrogen gas injector 35 is opened so that the pressure P2 in the intermediate pressure passage 31b drops to the stop-time pressure PSL, and the hydrogen gas in the intermediate pressure passage 31b is supplied to the anode electrode. At this time, air is supplied to the cathode by the compressor 44 and power is generated by the fuel cell stack 10 so that hydrogen gas is not wasted, and the generated power is stored in the power storage device 14. In the subsequent step 103, it is determined whether or not the pressure P2 in the intermediate pressure passage 31b is equal to or lower than the stop-time pressure PSL. When P2> PSL, the process returns from step 103 to step 102. When P2 ≦ PSL, the routine proceeds from step 103 to step 104, where the hydrogen gas injector 35 and the anode offgas discharge valve 37 are closed, and the compressor 44 is stopped and the cathode offgas discharge valve 47 is closed. Thereby, supply of hydrogen gas and air to the fuel cell stack 10 is stopped, and power generation is stopped.

  FIG. 7 shows a routine for executing the cathode electrode protection control described above. This routine is executed only once by the electronic control unit 60 every time the electronic control unit 60 is activated. The electronic control unit 60 is activated once every predetermined time, for example, every 4 to 8 hours, even when power generation is stopped.

  Referring to FIG. 7, in step 200, it is determined whether or not the fuel cell stack 10 is stopping power generation. When the fuel cell stack 10 is generating power, the processing cycle is terminated. When the power generation of the fuel cell stack 10 is stopped, the routine proceeds from step 200 to step 201, where it is determined whether or not the pressure P1 in the high pressure passage 31a is less than the threshold pressure P1L. When P1 ≧ P1L, the process proceeds from step S201 to step 203. When P1 <P1L, the routine proceeds from step 201 to step 202, where the main stop valve 33 is temporarily opened, and the pressure P1 of the high pressure passage 31a is made equal to or higher than the threshold pressure P1L. In the following step 203, it is determined whether or not the cell voltage CV is higher than the upper limit voltage CVUL. When CV ≦ CVUL, the processing cycle is terminated. When CV> CVUL, the routine proceeds from step 203 to step 204 where hydrogen gas having a reduced voltage hydrogen gas amount is supplied to the anode electrode. In the following step 205, it is determined whether or not the cell voltage CV is lower than the lower limit voltage CVLL. When CV ≧ CVLL, the process returns to step 204. When CV <CVLL, the processing cycle is terminated.

  Thus, the electronic control unit 60 that executes the power generation stop sequence control and the cathode electrode protection control can be regarded as a controller of the fuel cell system A.

  In the embodiment shown in FIG. 5, after a signal to stop the power generation in the fuel cell stack 10 is issued, the hydrogen gas by the hydrogen gas injector 35 is maintained until the pressure P2 in the intermediate pressure passage 31b drops to the stop-time pressure PSL. Stopping the supply of gas is delayed, thereby stopping the stop of power generation in the fuel cell stack 10. In another embodiment (not shown), after a signal to stop power generation in the fuel cell stack 10 is issued, before the pressure P2 in the intermediate pressure passage 31b decreases to the stop-time pressure PSL, the hydrogen gas injector 35 The supply of hydrogen gas is stopped. That is, the stop of power generation of the fuel cell stack 10 is not delayed. In other words, the power generation of the fuel cell stack 10 is stopped as soon as the ignition switch 70 is turned off. Therefore, the operation of the fuel cell stack 10 matches the operation of the operator. In this case, since the initial pressure P2 in the intermediate pressure passage 31b is higher than the stop-time pressure PSL, the amount of hydrogen gas that passes through the electrolyte membrane from the anode electrode and moves to the cathode electrode increases, and the hydrogen gas that has moved to the cathode electrode A part of the gas may be exhausted wastefully through the cathode offgas exhaust valve 47 or the like. However, due to several times of cathode electrode protection control and permeation of hydrogen gas from the anode electrode to the cathode electrode, the pressure P2 in the intermediate pressure passage 31b gradually decreases and reaches the stop-time pressure PSL. Therefore, thereafter, the amount of hydrogen gas supplied from the hydrogen gas injector 35 in the cathode electrode protection control is reduced, and the waste of hydrogen gas is eliminated.

  Further, in the embodiment shown in FIG. 5, after the signal to stop the power generation in the fuel cell stack 10 is issued, the air by the compressor 44 is maintained until the pressure P2 in the intermediate pressure passage 31b decreases to the stop-time pressure PSL. Is stopped and the cathode offgas discharge valve 47 is closed, thereby delaying the stop of power generation in the fuel cell stack 10. That is, the hydrogen gas in the intermediate pressure passage 31b is supplied to the anode electrode by the hydrogen gas injector 35 and used for power generation. In yet another embodiment (not shown), after the signal to stop the power generation in the fuel cell stack 10 is issued, the air pressure by the compressor 44 is reduced before the pressure P2 in the intermediate pressure passage 31b decreases to the stop-time pressure PSL. Is stopped and the cathode offgas discharge valve 47 is closed, so that the stop of power generation in the fuel cell stack 10 is not delayed. In other words, the hydrogen gas in the intermediate pressure passage 31b is supplied to the anode electrode by the hydrogen gas injector 35, but is not used for power generation, and is used, for example, to supply air to remove moisture in the anode electrode. That is, hydrogen gas is used effectively, and the power consumption of the compressor 44 is suppressed.

  In the embodiment shown in FIG. 5, the electric power generated in the fuel cell stack 10 after the signal for stopping the power generation in the fuel cell stack 10 is issued is stored in the power storage device 14. In still another embodiment (not shown), the electric power generated in the fuel cell stack 10 after the signal to stop the power generation in the fuel cell stack 10 is generated is used as another device in the fuel cell system A, such as the compressor 44 or the like. The fuel cell system A is used for equipment in a vehicle, for example, a vehicle auxiliary machine. That is, hydrogen gas is used effectively.

  Next, another embodiment will be described with reference to FIG. In the fuel cell system A shown in FIG. 1, the anode off-gas passage 36 connected to the outlet of the hydrogen gas passage 30 and the hydrogen gas supply passage 31 are separated, and the anode off-gas containing hydrogen gas circulates to the hydrogen gas supply passage 31. System, i.e., a hydrogen gas non-circulating fuel cell system. On the other hand, in the fuel cell system A shown in FIG. 8, the outlet of the hydrogen gas passage 30 and the hydrogen gas supply passage 31 are connected by the anode off-gas passage 36 and the hydrogen gas circulation passage 38, and the anode off-gas containing hydrogen gas is hydrogen gas. This is a system that is circulated to the supply path 31, that is, a hydrogen gas circulation fuel cell system.

  In the anode off-gas passage 36, a gas-liquid separator 37a for gas-liquid separation of the anode off-gas and a discharge control valve 37b for controlling discharge of the liquid accumulated in the gas-liquid separator 37a are arranged in this order from the upstream side. An inlet of a hydrogen gas circulation path 38 is communicated with an upper portion of the gas-liquid separator 37 a, and an outlet of the hydrogen gas circulation path 38 is communicated with a low pressure passage 31 c in the hydrogen gas supply path 31. In the hydrogen gas circulation path 38, a hydrogen gas circulation pump 39 that pressure-feeds the gas in the gas-liquid separator 37 a, that is, the gas-liquid separated anode off gas, is disposed. When the hydrogen gas circulation pump 39 is driven, the anode off gas accumulated in the gas-liquid separator 37 a is circulated to the hydrogen gas supply path 31. The amount of hydrogen gas supplied to the anode electrode is controlled by a hydrogen gas injector 35 and a hydrogen gas circulation pump 39. When the nitrogen gas concentration at the anode electrode increases or the amount of liquid water increases, the hydrogen gas circulation pump 39 is temporarily stopped and the hydrogen gas injector 35 and the discharge control valve 37b are temporarily opened. Thereby, nitrogen gas in the anode electrode is scavenged.

  When the stop of power generation in the fuel cell stack 10 is delayed after the signal to stop power generation in the fuel cell stack 10 described above is issued, the hydrogen gas injector 35 is opened and the discharge control valve 37b is closed. Then, the supply of hydrogen gas to the anode electrode by driving the hydrogen gas circulation pump 39 is continued, and power generation is continued. Thereafter, when the power generation of the fuel cell stack 10 is stopped, the hydrogen gas injector 35 and the discharge control valve 37b are closed, and the hydrogen gas circulation pump 39 is stopped.

  Also in this case, the same effect as the fuel cell system A of the embodiment shown in FIG. 1 can be obtained.

DESCRIPTION OF SYMBOLS 10 Fuel cell stack 31 Hydrogen gas supply path 32 Hydrogen tank 33 Main stop valve 34 Regulator 35 Hydrogen gas injector 36 Anode off gas passage 37 Anode off gas discharge valve 41 Air supply passage 44 Compressor 46 Cathode off gas passage 47 Cathode off gas discharge valve 60 Electronic control unit

Claims (8)

A hydrogen gas passage; an anode electrode provided in the hydrogen gas passage; an air passage; and a cathode electrode provided in the air passage. The hydrogen gas supplied to the anode electrode and the cathode electrode A fuel cell stack that generates electric power by an electrochemical reaction with oxygen gas in the air supplied to
A hydrogen gas source;
A hydrogen gas supply path connecting the inlet of the hydrogen gas path and the hydrogen gas source to each other;
A hydrogen gas supply valve disposed in the hydrogen gas supply path for supplying hydrogen gas into the hydrogen gas path;
A hydrogen gas pressure regulating valve disposed in the hydrogen gas supply path upstream of the hydrogen gas supply valve, regardless of whether the fuel cell stack is generating power or not generating power. A hydrogen gas pressure regulating valve for maintaining the pressure in the intermediate pressure passage which is the hydrogen gas supply path to the hydrogen gas pressure regulating valve at a predetermined set pressure;
An anode off-gas passage connected to an outlet of the hydrogen gas passage;
An anode offgas discharge valve disposed in the anode offgas passage;
A compressor,
An air supply path connecting the inlet of the air passage and the outlet of the compressor to each other;
A cathode offgas passage connected to an outlet of the air passage;
A cathode offgas discharge valve disposed in the cathode offgas passage;
When a signal to stop power generation in the fuel cell stack is issued, the supply of hydrogen gas by the hydrogen gas supply valve is stopped while the anode offgas discharge valve is closed, and the air by the compressor And the cathode off-gas discharge valve are closed, thereby stopping the power generation in the fuel cell stack, and the set pressure is set to a stop-time pressure lower than that during power generation in the fuel cell stack. If the potential difference between the cathode electrode and the anode electrode becomes larger than a preset upper limit during power generation stoppage in the fuel cell stack, the hydrogen gas supply valve is temporarily opened to A controller configured to supply gas into the hydrogen gas passage;
A fuel cell system comprising: After the signal to stop power generation in the fuel cell stack is issued, the controller supplies hydrogen gas by the hydrogen gas supply valve until the pressure in the intermediate pressure passage decreases to the stop-time pressure. Configured to delay the suspension of the
The fuel cell system according to claim 1. After the signal to stop power generation in the fuel cell stack is generated, the controller stops the supply of air by the compressor until the pressure in the intermediate pressure passage decreases to the stop-time pressure and the controller Configured to delay the closing of the cathode offgas discharge valve, thereby delaying the stoppage of power generation in the fuel cell stack,
The fuel cell system according to claim 2. A power storage device electrically connected to the fuel cell stack;
The controller is configured to store the power generated in the fuel cell stack in the power storage device after a signal to stop power generation in the fuel cell stack is issued.
The fuel cell system according to claim 3. The controller is configured such that, when power generation is stopped in the fuel cell stack, the pressure in the high-pressure passage that is the hydrogen gas supply path from the hydrogen gas adjustment valve to the main stop valve of the hydrogen gas source is equal to or higher than the stop-time pressure. Configured to temporarily open the main stop valve when the threshold pressure is less than
The fuel cell system according to any one of claims 1 to 4. The cathode offgas discharge valve is a valve through which gas can flow even when closed.
The fuel cell system according to any one of claims 1 to 5. The hydrogen gas supply valve is a needle valve;
The fuel cell system according to any one of claims 1 to 6. A hydrogen gas passage; an anode electrode provided in the hydrogen gas passage; an air passage; and a cathode electrode provided in the air passage. The hydrogen gas supplied to the anode electrode and the cathode electrode A fuel cell stack that generates electric power by an electrochemical reaction with oxygen gas in the air supplied to
A hydrogen gas source;
A hydrogen gas supply path connecting the inlet of the hydrogen gas path and the hydrogen gas source to each other;
A hydrogen gas supply valve disposed in the hydrogen gas supply path for supplying hydrogen gas into the hydrogen gas path;
A hydrogen gas pressure regulating valve disposed in the hydrogen gas supply path upstream of the hydrogen gas supply valve, regardless of whether the fuel cell stack is generating power or not generating power. A hydrogen gas pressure regulating valve for maintaining the pressure in the intermediate pressure passage which is the hydrogen gas supply path to the hydrogen gas pressure regulating valve at a predetermined set pressure;
An anode off-gas passage connected to an outlet of the hydrogen gas passage;
An anode offgas discharge valve disposed in the anode offgas passage;
A compressor,
An air supply path connecting the inlet of the air passage and the outlet of the compressor to each other;
A cathode offgas passage connected to an outlet of the air passage;
A cathode offgas discharge valve disposed in the cathode offgas passage;
A control method for a fuel cell system comprising:
When a signal to stop power generation in the fuel cell stack is issued, the supply of hydrogen gas by the hydrogen gas supply valve is stopped while the anode offgas discharge valve is closed, and the air by the compressor And the cathode off-gas discharge valve are closed, thereby stopping the power generation in the fuel cell stack, and the set pressure is set to a stop-time pressure lower than that during power generation in the fuel cell stack. If the potential difference between the cathode electrode and the anode electrode becomes larger than a preset upper limit during power generation stoppage in the fuel cell stack, the hydrogen gas supply valve is temporarily opened to Supplying gas into the hydrogen gas passage;
Control method of fuel cell system.

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