fuel cell system

Abstract

The present invention relates to a fuel cell system. When the fuel cell stack (18) is in an idle state, a valve continuous opening and closing control process is performed to repeatedly open and close a discharge valve (70) at predetermined intervals, thereby reducing the concentration of fuel gas contained in the fuel exhaust. As a result, the concentration of the fuel gas when the fuel exhaust is discharged to the outside in the idle state can be suppressed.

Description

Technical Field

[0001] The present invention relates to a fuel cell system mounted on a mobile object or the like. Background Art

[0002] In recent years, fuel cell vehicles (FCVs) that use hydrogen as fuel have attracted attention as an environmentally friendly alternative to gasoline vehicles. Fuel cell vehicles feed air (containing oxygen) and hydrogen as fuel gas into a fuel cell. The electricity generated by the electrochemical reaction in the fuel cell drives an electric motor, enabling the vehicle to travel. Therefore, unlike gasoline vehicles, they emit only water, rather than CO2, NOx, or SOx, making them environmentally friendly.

[0003] For example, as described in Patent Document 1, in such fuel cell vehicles, when nitrogen (N2) that permeates from the cathode flow path to the anode flow path of the fuel cell accumulates in the anode flow path, the electrochemical reaction is inhibited. This inhibition of the electrochemical reaction is known to reduce the output power of the fuel cell unit.

[0004] To solve this problem, in the technology related to the fuel cell control device disclosed in Patent Document 1, an on-off valve is provided in the exhaust passage of the fuel gas of the fuel cell, and the on-off valve is intermittently opened, thereby intermittently releasing the fuel gas containing nitrogen from the fuel cell to the outside.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese JP2005-108805A Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In Patent Document 1, a chamber, a flow control valve, and a converter are arranged downstream of the on-off valve provided in the exhaust passage to maintain a constant flow rate of the fuel exhaust gas released to the outside. This complicates the structure and control of the fuel cell system.

[0010] Generally speaking, when the operating state of the fuel cell stack in the fuel cell system is an idle state with low power generation, the flow rate of the oxidant gas supplied from the compressor to the fuel cell stack is small, so the fuel gas concentration in the exhaust gas formed by mixing part of the oxidant gas with the fuel exhaust increases.

[0011] However, Patent Document 1 does not describe exhaust control for exhausting gas to the outside when the operating state of the fuel cell stack in the fuel cell system is the idle state.

[0012] The object of the present invention is to solve the above-mentioned problems.

[0013] Solutions for solving problems

[0014] In order to achieve the above-mentioned purpose, a fuel cell system in one aspect of the present invention comprises: a fuel cell stack, which generates electricity using an oxidant gas and a fuel gas; an oxidant gas supply flow path, which supplies the oxidant gas to the fuel cell stack; an oxidant exhaust flow path, which circulates the oxidant exhaust discharged from the fuel cell stack; a fuel gas supply flow path, which supplies the fuel gas to the fuel cell stack; a fuel exhaust flow path, which circulates the fuel exhaust discharged from the fuel cell stack; a connecting flow path, which connects the oxidant gas supply flow path with the fuel exhaust flow path; a first opening and closing valve, which opens and closes the connecting flow path; and a control device, which controls the opening and closing state of the first opening and closing valve, and when the operating state of the fuel cell stack is an idle state, the control device implements a valve continuous opening and closing control process to continuously repeat the opening and closing of the first opening and closing valve at a predetermined interval.

[0015] Effects of the Invention

[0016] According to the present invention, when the fuel cell stack is in an idle state, a continuous valve opening and closing control process is performed to repeatedly open and close the first on-off valve at predetermined intervals, thereby reducing the concentration of fuel gas contained in the exhaust fuel gas. This reduces the concentration of fuel gas when the exhaust fuel gas is discharged to the outside during the idle state.

[0017] The above-mentioned objects, features, and advantages will be easily understood from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a fuel cell vehicle incorporating a fuel cell system according to an embodiment of the present invention.

[0019] Figure 2 This is a flowchart for explaining the operation of the fuel cell system according to the embodiment.

[0020] Figure 3A 3 is a waveform diagram showing the continuous opening and closing control process of the relief valve.

[0021] Figure 3B This is a waveform diagram of the exhaust hydrogen concentration when the continuous opening and closing control process of the dump valve is performed. DETAILED DESCRIPTION

[0022] [structure]

[0023] Figure 1It is a schematic structural diagram of a fuel cell vehicle 12 incorporating a fuel cell system 10 according to an embodiment of the present invention.

[0024] The fuel cell system 10 can also be incorporated into other mobile objects besides the fuel cell vehicle 12 , such as ships, aircraft, and robots.

[0025] The fuel cell vehicle 12 includes a control device 15 that controls the entire fuel cell vehicle 12 , a fuel cell system 10 , and an output unit 16 electrically connected to the fuel cell system 10 .

[0026] For example, the control device 15 may not be one but may be divided into two or more control devices such as a control device for the fuel cell system 10 and a control device for the output unit 16 .

[0027] The fuel cell system 10 is composed of a fuel cell stack (also simply referred to as a fuel cell) 18 , a hydrogen tank 20 , an oxidant gas supply device 22 , a fuel gas supply device 24 , and a refrigerant supply device 26 .

[0028] The oxidizing gas supply device 22 includes a compressor (CP) 28 and a humidifier (HUM) 30 .

[0029] The fuel gas supply device 24 includes an injector (INJ) 32, an ejector 34, and a gas-liquid separator 36. The injector 32 may be replaced by a pressure reducing valve.

[0030] The refrigerant supply device 26 includes a refrigerant pump (WP) 38 and a radiator 40 .

[0031] The output unit 16 includes a drive unit 42, a high-voltage power storage device (battery) 44, and a motor (electric motor) 46. The load on the drive unit 42 includes not only the motor 46 as the main device but also the compressor 28, other air compressors, and other vehicle auxiliary equipment as auxiliary equipment. The fuel cell vehicle 12 travels using the driving force generated by the motor 46.

[0032] The fuel cell stack 18 is formed by stacking a plurality of power generation cells 50. The power generation cells 50 include a membrane electrode assembly 52 and separators 53 and 54 that sandwich the membrane electrode assembly 52.

[0033] The electrolyte membrane-electrode assembly 52 includes a solid polymer electrolyte membrane 55 , which is, for example, a thin film of perfluorosulfonic acid containing water, and a cathode electrode 56 and an anode electrode 57 that sandwich the solid polymer electrolyte membrane 55 .

[0034] The cathode electrode 56 and the anode electrode 57 have gas diffusion layers (not shown) made of carbon paper or the like. Porous carbon particles carrying a platinum alloy on their surfaces are evenly coated on the surface of the gas diffusion layer, thereby forming an electrode catalyst layer (not shown). The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 55.

[0035] A cathode flow path (oxidant gas flow path) 58 that connects the oxidant gas inlet communication port 101 and the oxidant gas outlet communication port 102 is formed on a surface of one separator 53 that faces the membrane electrode assembly 52 .

[0036] An anode flow path (fuel gas flow path) 59 that connects the fuel gas inlet communication port 103 and the fuel gas outlet communication port 104 is formed on the surface of the other separator 54 that faces the membrane electrode assembly 52 .

[0037] In the anode electrode 57 , when fuel gas (hydrogen) is supplied, hydrogen molecules generate hydrogen ions due to an electrode reaction caused by the catalyst. The hydrogen ions pass through the solid polymer electrolyte membrane 55 and move to the cathode electrode 56 , while the hydrogen molecules release electrons.

[0038] The electrons released from the hydrogen molecules move from the negative electrode terminal 106 through the loads such as the drive unit 42 and the motor 46 , and then through the positive electrode terminal 108 to the cathode electrode 56 .

[0039] In the cathode electrode 56 , the hydrogen ions and the electrons react with oxygen contained in the supplied oxidant gas due to the action of the catalyst, thereby generating water.

[0040] A voltage sensor 110 for detecting generated voltage Vfc is provided between the wiring connecting positive electrode terminal 108 and drive unit 42 and the wiring connecting negative electrode terminal 106 and drive unit 42. Furthermore, a current sensor 112 for detecting generated current Ifc is provided in the wiring connecting positive electrode terminal 108 and drive unit 42.

[0041] Compressor 28 is comprised of a mechanical supercharger or the like driven by a compressor motor (not shown). Electric power from a power storage device 44 is supplied to the compressor motor via a drive unit 42. Compressor 28 has the following functions: it draws in external air (atmosphere, air) from an external air intake 113, pressurizes it, and supplies it to fuel cell stack 18 via a humidifier 30.

[0042] The humidifier 30 includes a flow path 31A and a flow path 31B. Air (oxidant gas) compressed and heated by the compressor 28 and dried flows through the flow path 31A. Exhaust gas discharged from the oxidant gas outlet communication port 102 of the fuel cell stack 18 flows through the flow path 31B.

[0043] Here, when the dump valve 70, which serves as a first on-off valve (described later), is closed, the exhaust gas becomes a moistened oxidant exhaust (moistened cathode exhaust, moistened oxidant exhaust gas). When the dump valve 70 is open, the exhaust gas becomes a moistened exhaust gas (exhaust gas) obtained by mixing the moistened oxidant exhaust with the fuel exhaust (anode exhaust, fuel exhaust gas) supplied through the dump valve 70.

[0044] The humidifier 30 has the function of humidifying the oxidant gas supplied from the compressor 28. Specifically, the humidifier 30 humidifies the oxidant gas by transferring moisture contained in the exhaust gas (exhaust gas) from the flow path 31B via the porous membrane inside the humidifier 30 to the supply gas (oxidant gas) flowing through the flow path 31A, and then supplies the humidified oxidant gas to the fuel cell stack 18.

[0045] In the oxidant gas supply flow path 60 (including oxidant gas supply flow paths 60A and 60B) extending from the outside air inlet 113 to the oxidant gas inlet communication port 101, a shutoff valve 114, an air flow sensor (AFS: flow sensor) 116, a compressor 28, a supply-side sealing valve 118, and a humidifier 30 are provided in this order from the outside air inlet 113. Furthermore, the flow paths such as the oxidant gas supply flow path 60 depicted with double lines are formed by piping (the same applies hereinafter).

[0046] The shutoff valve 114 is opened and closed to open or shut off the introduction of air into the oxidizing gas supply flow path 60 .

[0047] The air flow sensor 116 measures the flow rate of the oxidant gas supplied to the fuel cell stack 18 by the compressor 28 .

[0048] The supply-side sealing valve 118 opens and closes the oxidizing gas supply flow path 60A.

[0049] The outside air inlet 113 is provided with a temperature sensor 73 for detecting (measuring) the outside air temperature Ta.

[0050] In the oxidant exhaust flow path 62 communicating with the oxidant gas outlet communication port 102 , a humidifier 30 and a discharge-side sealing valve 120 also functioning as a back pressure valve are provided in this order from the oxidant gas outlet communication port 102 .

[0051] A bypass flow path 64 is provided between the intake port of the supply-side sealing valve 118 and the discharge port of the discharge-side sealing valve 120, connecting the oxidant gas supply flow path 60 with the oxidant exhaust flow path 62. A bypass valve 122 is provided in the bypass flow path 64 to open and close the bypass flow path 64. The bypass valve 122 adjusts the flow rate of the oxidant gas bypassing the fuel cell stack 18.

[0052] The junction of the bypass flow path 64 and the oxidant exhaust flow path 62 communicates with the exhaust flow path 62A.

[0053] The hydrogen tank 20 includes an electromagnetically operated shutoff valve and is a container for storing high-purity hydrogen compressed at a high pressure.

[0054] The fuel gas ejected from the hydrogen tank 20 passes through the injector 32 and the ejector 34 provided in the fuel gas supply flow path 72 and is supplied to the inlet of the anode flow path 59 of the fuel cell stack 18 through the fuel gas inlet communication port 103 .

[0055] The outlet of the anode flow path 59 communicates with the inlet 151 of the gas-liquid separator 36 via the fuel gas outlet communication port 104 and the fuel gas exhaust flow path 74 . The fuel exhaust as hydrogen-containing gas is supplied from the anode flow path 59 to the gas-liquid separator 36 .

[0056] The gas-liquid separator 36 separates the exhaust fuel into a gas component and a liquid component (liquid water). The gas component of the exhaust fuel (fuel exhaust gas) is discharged from the gas discharge port 152 of the gas-liquid separator 36 and supplied to the suction port of the ejector 34 through the circulation flow path 77. Meanwhile, when the discharge valve 70 is open, the exhaust fuel is also supplied to the oxidant gas supply flow path 60B through the connecting flow path (communication flow path) 78 and the discharge valve 70.

[0057] The liquid component of the fuel exhaust gas is mixed with the exhaust gas discharged from the exhaust flow path 62A from the liquid discharge port 160 of the gas-liquid separator 36 through the exhaust flow path 162 provided with a discharge valve 164 serving as a second opening and closing valve, and is discharged to the outside air through the exhaust flow path 99 and the exhaust gas exhaust port 168.

[0058] In practice, part of the fuel exhaust (hydrogen-containing gas) is discharged together with the liquid component to the drain flow path 162. In order to dilute the hydrogen in the fuel exhaust and discharge it to the outside, part of the oxidant gas discharged from the compressor 28 is supplied to the discharge flow path 62A through the bypass flow path 64.

[0059] The dump valve 70 provided in the connecting flow path 78 connecting the fuel exhaust gas circulation flow path 77 and the oxidizing gas supply flow path 60B is opened and closed under control for either of the two reasons described below.

[0060] First, while the fuel cell vehicle 12 is driving, in order to prevent the nitrogen gas present in the cathode flow path 58 from penetrating the electrolyte membrane-electrode assembly 52, thereby reducing the hydrogen concentration in the anode flow path 59 and causing degradation of the anode electrode 57, the discharge valve 70 is opened (the first valve continuous opening and closing control process of the discharge valve 70 during driving).

[0061] Second, when the fuel cell stack 18 is in the idle state, the dump valve 70 is opened to reduce the hydrogen concentration in the exhaust gas discharged from the exhaust gas outlet 168 (second valve continuous opening and closing control process of the dump valve 70 in the idle state).

[0062] When the dump valve 70 is opened, the fuel exhaust gas ejected from the fuel cell stack 18 through the fuel exhaust gas flow path 74 and the gas-liquid separator 36 flows to the cathode flow path 58 via the connecting flow path 78 , the oxidant gas supply flow path 60B and the oxidant gas inlet communication port 101 .

[0063] The fuel gas in the fuel exhaust flowing through the cathode flow path 58 is converted into hydrogen ions by a catalytic reaction in the cathode electrode 56. These hydrogen ions react with the oxidant gas to produce water. The remaining unreacted fuel exhaust (including nitrogen and a small amount of unreacted hydrogen) is discharged from the fuel cell stack 18 as oxidant exhaust and flows through the oxidant exhaust flow path 62.

[0064] The oxidant exhaust (including the remaining unreacted fuel exhaust) flowing into the oxidant exhaust flow path 62 is mixed with the oxidant gas supplied through the oxidant gas bypass flow path 64, and the oxidant exhaust in which the concentration of the fuel exhaust (including the fuel gas) is diluted flows into the exhaust flow path 62A.

[0065] The discharge flow path 62A communicates with and merges with the drain flow path 162 and communicates with the discharge flow path 99 .

[0066] In the discharge flow path 99 , the fuel gas in the mixed fluid of liquid water and fuel exhaust ejected from the drain flow path 162 is diluted with the oxidant exhaust from the discharge flow path 62A and discharged to the outside (atmosphere) of the fuel cell vehicle 12 through the exhaust gas exhaust port 168 .

[0067] Furthermore, the opening diameter of the dump valve 70 is larger than that of the drain valve 164. Due to this opening diameter, even if the drain valve 164 remains open due to a valve failure such as freezing, the amount of fuel exhaust gas flowing into the connecting flow path 78 is greater than the amount of fuel exhaust gas flowing into the drain valve 164. As a result, the concentration of the fuel gas discharged from the exhaust gas exhaust port 168 can be reduced.

[0068] The refrigerant supply device 26 of the fuel cell system 10 includes a refrigerant flow path 138 through which refrigerant circulates. The refrigerant flow path 138 includes a refrigerant supply flow path 140 and a refrigerant discharge flow path 142. The refrigerant supply flow path 140 supplies refrigerant to the fuel cell stack 18, and the refrigerant discharge flow path 142 discharges refrigerant from the fuel cell stack 18. The refrigerant supply flow path 140 and the refrigerant discharge flow path 142 are connected to the radiator 40. The radiator 40 cools the refrigerant. A refrigerant pump 38 is provided in the refrigerant supply flow path 140. The refrigerant pump 38 circulates the refrigerant within the refrigerant circulation circuit. The refrigerant circulation circuit includes the refrigerant supply flow path 140, the refrigerant flow path within the fuel cell stack 18, the refrigerant discharge flow path 142, and the radiator 40. A temperature sensor 76 is provided in the refrigerant discharge flow path 142. The temperature of the cooling medium (refrigerant outlet temperature) Ts detected by the temperature sensor 76 is detected (measured) as the (internal) temperature of the fuel cell stack 18 .

[0069] The control device 15 comprehensively controls the components of the above-described fuel cell system 10 .

[0070] Moreover, in addition to the stop valve 114, which is an on-off valve whose opening and closing are controlled by the control device 15, the supply side sealing valve 118, the discharge side sealing valve 120, the unloading valve 70, and the drain valve 164 are speed regulating valves whose opening is controlled by the control device 15, but the on-off valves can also be used for duty control.

[0071] The control device 15 is composed of an ECU (Electronic Control Unit). The ECU is composed of a computer having one or more processors (CPUs), memory, input / output interfaces, and circuits. The one or more processors (CPUs) execute programs (not shown) stored in the memory.

[0072] The processor (CPU) of the control device 15 executes calculations according to the program, thereby controlling the operation of the fuel cell vehicle 12 and the fuel cell system 10 .

[0073] The control device 15 is connected to a power switch (power SW) 71 of the fuel cell vehicle 12. The power switch 71 starts, continues (ON), or ends (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10. The control device 15 is also connected to an accelerator position sensor, a vehicle speed sensor, and a SOC (state of charge) sensor of the power storage device 44 (not shown).

[0074] [action]

[0075] The fuel cell system 10 according to this embodiment is basically configured as described above. Figure 2The control device 15 repeatedly executes the Figure 2 Flowchart processing.

[0076] In step S1, the control device 15 determines whether the power switch 71 is in the ON state or the OFF state.

[0077] When the power switch 71 is in the OFF state (step S1 : NO), the control device 15 ends the process, and the fuel cell system 10 and the fuel cell vehicle 12 enter the stopped state.

[0078] If the power switch 71 is on (step S1: YES), in step S2, the control device 15 calculates the required generated power for the fuel cell stack 18 based on the accelerator opening, vehicle speed, road gradient, etc. Furthermore, in step S2, the control device 15 controls the oxidant gas supply device 22 including the compressor 28 and the fuel gas supply device 24 including the hydrogen tank 20 so that the generated power of the fuel cell stack 18 reaches the calculated required generated power, and controls the refrigerant supply device 26 including the refrigerant pump 38.

[0079] exist Figure 1 In FIG. 1 , arrows drawn along the pipes show an example of the flow of fluids (oxidant gas, fuel gas, oxidant exhaust gas, fuel exhaust gas, liquid water) when the power switch 71 is in the on state.

[0080] In step S3 , the control device 15 acquires the outside air temperature (outside temperature) Ta [° C.] detected by the temperature sensor 73 and the refrigerant outlet temperature Ts [° C.] indicating the stack temperature.

[0081] In addition, in step S3, the control device 15 determines whether the environment is a low-temperature environment in which the external gas temperature Ta is less than a predetermined low-temperature threshold value Tlow (for example, less than 0 [°C]) (below the freezing point), and when determining whether it is in heating control, the heating control is a control that causes the refrigerant outlet temperature Ts corresponding to the internal temperature of the fuel cell stack 18 to rise to a set temperature (the target temperature of the fuel cell stack 18 of the fuel cell vehicle 12).

[0082] If the control device 15 determines that the outside air temperature Ta is below the low temperature threshold Tlow or that the temperature has not reached the set temperature and heating control is in progress, the process proceeds to step S4. If neither of these situations occurs, that is, if the outside air temperature Ta is above the low temperature threshold Tlow or heating control is not in progress (the refrigerant outlet temperature Ts has reached the target temperature), the process returns to step S1.

[0083] In step S4 , the control device 15 determines whether the operating state of the fuel cell vehicle 12 is the idle state.

[0084] The idle state is a state in which the fuel cell vehicle 12 is stopped or is traveling at a slow speed, such as approximately 10 km / h or less, and refers to a state in which the fuel cell stack 18 generates low power.

[0085] If the state is not idle (step S4: No), the process returns to step S1, and if the state is idle (step S4: Yes), the process proceeds to step S5.

[0086] In step S5, the control device 15 determines whether the drain valve 164 is in a fixed open state (a state in which the valve is fixed in an open state). The control device 15 can determine whether the drain valve 164 is in a fixed open state based on, for example, the fact that the liquid water level measured by a liquid flow meter (not shown) provided inside the gas-liquid separator 36 remains below a predetermined value despite a valve closing signal being sent from the control device 15 to the drain valve 164.

[0087] When the control device 15 determines that the drain valve 164 is not in the open fixed state (step S5 : NO), in step S6 , the control device 15 performs valve continuous opening and closing control for repeatedly opening and closing the dump valve 70 at predetermined intervals.

[0088] Figure 3A FIG. 1 shows a command waveform issued by the control device 15 in the valve continuous opening and closing control for causing the opening and closing of the discharge valve 70 to be repeated continuously at predetermined intervals. Figure 3B The concentration waveform is shown in which the exhaust hydrogen concentration discharged to the outside from the exhaust gas exhaust port 168 is maintained below the threshold concentration (corresponding to the second valve continuous opening and closing control process of the dump valve 70 in the idle state described above).

[0089] according to Figure 3A 、 Figure 3B It can be understood that the increase in exhaust hydrogen concentration is suppressed by rapidly repeating the opening and closing operations of the dump valve 70 .

[0090] In step S5 , when the control device 15 determines that the drain valve 164 is in the valve-open fixed state (step S5 : Yes), the process proceeds to step S7 .

[0091] In step S7 , the control device 15 performs a process of increasing the rotation speed of the compressor 28 to a target rotation speed obtained by increasing the rotation speed by a fixed amount via the driving unit 42 , and then proceeds to step S6 .

[0092] Even if the drain valve 164 becomes an open fixed state (step S5: yes), since the flow rate of the oxidant gas supplied from the bypass flow path 64 to the discharge flow path 62A increases, in step S6, the control device 15 continues to perform the first valve continuous opening and closing control processing of the discharge valve 70, thereby maintaining the exhaust hydrogen concentration below the threshold concentration.

[0093] In this case, when the speed increase processing of the compressor 28 in step S7 is performed, even if it is assumed that the compressor 28 is abnormal and the speed of the compressor 28 does not reach the target speed, the first valve continuous opening and closing control processing of the unloading valve 70 in step S6 is implemented, thereby suppressing the increase in exhaust concentration.

[0094] Furthermore, in the power generation control of step S2 after step S3 is “No”, step S4 is “No”, or step S6 is processed, when the control device 15 detects that the hydrogen concentration in the anode flow path 59 is reduced, the control device 15 performs the same operation as the reference operation. Figure 3A The second valve continuous opening and closing control process of the dump valve 70 described above is similar to the first valve continuous opening and closing control process of the dump valve 70. For example, a hydrogen concentration sensor may be provided in the fuel exhaust flow path 74 to measure the hydrogen concentration.

[0095] The following describes the technical ideas and effects that can be understood according to the above embodiment. In addition, for easy understanding, some of the components are marked with the reference numerals used in the above embodiment, but the components are not limited to the components marked with the reference numerals.

[0096] The fuel cell system 10 involved in the present invention comprises: a fuel cell stack 18, which generates electricity using an oxidant gas and a fuel gas; an oxidant gas supply flow path 60 (60A, 60B), which supplies the oxidant gas to the fuel cell stack; an oxidant exhaust flow path 62, which circulates the oxidant exhaust discharged from the fuel cell stack; a fuel gas supply flow path 72, which supplies the fuel gas to the fuel cell stack; a fuel exhaust flow path 74, which circulates the fuel exhaust discharged from the fuel cell stack; a connecting flow path 78, which connects the oxidant gas supply flow path with the fuel exhaust flow path; a first opening and closing valve 70, which opens and closes the connecting flow path; and a control device 15, which controls the opening and closing state of the first opening and closing valve. When the operating state of the fuel cell stack is an idle state, the control device implements a valve continuous opening and closing control process that causes the opening and closing of the first opening and closing valve to be continuously repeated at a predetermined interval.

[0097] With this configuration, when the fuel cell stack is operating in the idle state, a continuous valve opening and closing control process is performed, in which the first on-off valve is repeatedly opened and closed at predetermined intervals. This causes the fuel gas contained in the exhaust fuel gas to be hydrogen ionized by a catalytic reaction at cathode electrode 56. These hydrogen ions react with the oxidant gas to produce water, thereby reducing the concentration of the fuel gas contained in the exhaust fuel gas. This reduces the concentration of the fuel gas discharged to the outside through the oxidant exhaust flow path 62 and the drain flow path 162 during the idle state.

[0098] In addition, in the fuel cell system, when the fuel cell stack is started in a low-temperature environment or when the fuel cell stack is heated, when the operating state of the fuel cell stack is idle, the control device implements the valve continuous opening and closing control processing to continuously repeat the opening and closing of the first opening and closing valve at a predetermined interval.

[0099] Thus, when the fuel cell stack is started in a low temperature environment or when the fuel cell stack is under heating control, the fuel gas concentration of the fuel exhaust gas discharged to the outside can be suppressed when the fuel cell stack is operating in an idle state to generate electricity.

[0100] Furthermore, in a fuel cell system, the fuel exhaust flow path of the fuel cell stack may be branched, and the branch flow path on one side may be connected to the connecting flow path. A second opening and closing valve 164 may be provided on the branch flow path 162 on the other side. The second opening and closing valve 164 may be capable of discharging liquid water and the fuel exhaust discharged from the fuel cell stack to the outside. When it is detected that the second opening and closing valve is still fixed in the open state even when it is driven in the closing direction, the control device implements continuous opening and closing control processing of the first opening and closing valve.

[0101] According to the present invention, even if the second on-off valve capable of discharging liquid water and fuel exhaust gas from the fuel cell stack to the outside is fixed in an open state, the increase in exhaust hydrogen concentration can be suppressed by implementing the valve continuous opening and closing control process on the first on-off valve.

[0102] In addition, the fuel cell system may include a compressor 28, which supplies oxidant gas to the fuel cell stack through the oxidant gas supply path. Compared with the case where the valve continuous opening and closing control processing of the first opening and closing valve is not performed, the control device increases the speed of the compressor when the valve continuous opening and closing control processing of the first opening and closing valve is performed, thereby increasing the flow rate of the oxidant gas supplied to the fuel cell stack.

[0103] By increasing the oxidizing gas flow rate, the oxidizing gas flow rate flowing through the bypass flow path 64 increases, and the exhaust gas concentration of the fuel gas can be easily reduced.

[0104] Furthermore, even in an abnormal situation where the rotation speed of the compressor has not increased to the target rotation speed, the control device may continue the valve continuous opening and closing control process on the first opening and closing valve.

[0105] According to this configuration, it is possible to suppress an increase in the exhaust concentration of the fuel gas.

[0106] Furthermore, the present invention is not limited to the above-mentioned disclosure, and various configurations can be adopted without departing from the spirit of the present invention.

Claims

1. A fuel cell system comprising: a fuel cell stack (18) that generates electricity using an oxidant gas and a fuel gas; an oxidant gas supply flow path (60) for supplying the oxidant gas to the fuel cell stack; an oxidant exhaust flow path (62) for circulating the oxidant exhaust gas exhausted from the fuel cell stack; a fuel gas supply flow path for supplying the fuel gas to the fuel cell stack; a fuel exhaust flow path (74) for circulating fuel exhaust discharged from the fuel cell stack; a connecting flow path (78) connecting the oxidant gas supply flow path and the fuel exhaust flow path; a first opening and closing valve (70) for opening and closing the connecting flow path; and a control device for controlling the opening and closing state of the first opening and closing valve, When the fuel cell stack is in an idle state, the control device performs a valve continuous opening and closing control process for repeatedly opening and closing the first opening and closing valve at predetermined intervals.

2. The fuel cell system according to claim 1, wherein: When the fuel cell stack is started in a low-temperature environment or when the fuel cell stack is heated, when the operating state of the fuel cell stack is idle, the control device implements the valve continuous opening and closing control processing to repeat the opening and closing of the first opening and closing valve at a predetermined interval.

3. The fuel cell system according to claim 1 or 2, characterized in that: The fuel exhaust flow path of the fuel cell stack is branched, one branch flow path is connected to the connecting flow path, and a second opening and closing valve (164) is provided on the other branch flow path, wherein the second opening and closing valve can discharge liquid water discharged from the fuel cell stack and the fuel exhaust gas to the outside. The control device performs the valve continuous opening and closing control process on the first opening and closing valve when detecting that the second opening and closing valve is fixed in the open state even though the second opening and closing valve is driven in the valve closing direction.

4. The fuel cell system according to claim 1 or 2, characterized in that: A compressor (28) is provided, wherein the compressor (28) supplies oxidant gas to the fuel cell stack through the oxidant gas supply flow path. Compared with the case where the valve continuous opening and closing control processing for the first opening and closing valve is not implemented, the control device increases the speed of the compressor when implementing the valve continuous opening and closing control processing for the first opening and closing valve, thereby increasing the flow rate of the oxidant gas supplied to the fuel cell stack.

5. The fuel cell system according to claim 1 or 2, characterized in that: The operating state of the fuel cell stack being an idle state refers to a power generation state in which a fuel cell vehicle (12) equipped with the fuel cell stack is stopped or running at a speed of less than 10 [km / h].

6. The fuel cell system according to claim 2, wherein: The low-temperature environment of the fuel cell system is below freezing point, and the heating control of the fuel cell stack is a control time for raising the internal temperature of the fuel cell stack to a target temperature.

7. The fuel cell system according to claim 3, characterized in that An opening diameter of the first opening and closing valve is larger than an opening diameter of the second opening and closing valve.

8. The fuel cell system according to claim 4, wherein: Even when the rotation speed of the compressor has not increased to the target rotation speed, the control device continues the valve continuous opening and closing control process on the first opening and closing valve.

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