CN116742047A

CN116742047A - Fuel cell system for vehicle and water drainage method thereof

Info

Publication number: CN116742047A
Application number: CN202310209078.3A
Authority: CN
Inventors: 井上一秀; 中川拓人; 古贺一纱
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2022-03-11
Filing date: 2023-02-27
Publication date: 2023-09-12
Also published as: JP2023132392A

Abstract

The present invention relates to a fuel cell system for a vehicle and a water drainage method thereof. A control unit (96) of a fuel cell system (10) for a vehicle makes a first determination for determining whether or not a vehicle is stopped, estimates the amount of water remaining in the lower portion of a fuel cell stack (12) based on the amount of power generation of the fuel cell stack, makes a second determination for determining whether the amount of water is greater than or less than a water amount threshold, and controls the opening and closing of a valve (58) based on the results of the first determination and the second determination.

Description

Fuel cell system for vehicle and water drainage method thereof

Technical Field

The present invention relates to a fuel cell system for a vehicle that discharges water remaining in a lower portion of a fuel cell stack to the outside of the fuel cell stack, and a water discharge method for the fuel cell system for a vehicle.

Background

In recent years, in order to ensure that more people can use an appropriate, reliable, sustainable and advanced energy source, research and development are being conducted on fuel cells that contribute to energy efficiency.

The fuel cell system has a fuel cell stack. The fuel cell stack generates power by a reaction between an anode gas (a fuel gas containing hydrogen) and a cathode gas (an oxidizing gas containing oxygen). Water is produced during power generation. The water is discharged to the outside of the fuel cell stack together with the exhaust gas (exhaust gas).

The anode off-gas is mainly discharged to the gas-liquid separator. The gas-liquid separator separates the anode exhaust gas into gas (hydrogen, etc.) and water. The gas separated by the gas-liquid separator is reused as the anode gas. The water separated by the gas-liquid separator is temporarily retained in the gas-liquid separator and then discharged to the outside of the gas-liquid separator.

In recent fuel cell systems, the interior of the fuel cell stack is maintained at a high humidity. Water remains inside such a fuel cell stack. Patent document 1 discloses a technique of discharging water remaining in the fuel cell stack to a gas-liquid separator. The fuel cell system of patent document 1 has the following configuration: even in the case where the fuel cell stack is inclined, the water of the fuel cell stack can be discharged to the gas-liquid separator.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2021-18850

Disclosure of Invention

Problems to be solved by the invention

When the inside of the fuel cell stack is maintained at a high humidity, the amount of water remaining in the gas-liquid separator increases. Then, the proportion of the water remaining in the gas-liquid separator due to the inclination of the vehicle or the like increases in the reverse flow direction to the fuel cell stack. When the water remaining in the fuel cell stack merges with the water flowing back from the gas-liquid separator, the water in the fuel cell stack becomes excessive. In particular, when the fuel cell stack is inclined, the amount of water that is soaked in the power generation cells located at the lower position increases. When the power generation unit cells are immersed in water for a long period of time, not only is power generation unstable, but also the fuel cell stack is aged.

The present invention aims to solve the above-mentioned technical problems.

Solution for solving the problem

A first aspect of the present invention relates to a fuel cell system for a vehicle including a fuel cell stack that generates power using an anode gas and a cathode gas, the fuel cell system comprising: a drain flow path connected to the fuel cell stack so as to drain water remaining in a lower portion of the fuel cell stack to an outside of the fuel cell stack; a throttle member that makes a pressure upstream of the drain flow path higher than a pressure downstream of the drain flow path; a valve for opening and closing the drain flow path; and a control unit that controls opening and closing of the valve, wherein the control unit makes a first determination for determining whether or not the vehicle is stopped, wherein the control unit estimates an amount of water remaining in a lower portion of the fuel cell stack based on an amount of power generation of the fuel cell stack, wherein the control unit makes a second determination for determining whether the amount of water is greater than or less than a water amount threshold, and wherein the control unit controls opening and closing of the valve based on a result of the first determination and a result of the second determination.

A second aspect of the present invention relates to a water discharge method of a fuel cell system for a vehicle including a fuel cell stack that generates electric power using an anode gas and a cathode gas, the water discharge method of the fuel cell system for a vehicle including: a drain flow path connected to the fuel cell stack so as to drain water remaining in a lower portion of the fuel cell stack to an outside of the fuel cell stack; a throttle member that makes a pressure upstream of the drain flow path higher than a pressure downstream of the drain flow path; a valve for opening and closing the drain flow path; and a computer that controls opening and closing of the valve, wherein the computer performs a first determination for determining whether or not the vehicle is stopped, wherein the computer estimates an amount of water remaining in a lower portion of the fuel cell stack based on an amount of power generation of the fuel cell stack, wherein the computer performs a second determination for determining whether the amount of water is greater than or less than a water amount threshold, and wherein the computer controls opening and closing of the valve based on a result of the first determination and a result of the second determination.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the degradation of the fuel cell stack can be suppressed, and the power generation of the fuel cell stack can be stabilized.

The above objects, features and advantages will be readily understood from the following description of the embodiments with reference to the accompanying drawings and description.

Drawings

Fig. 1 is a schematic configuration diagram of a fuel cell system according to the present invention.

Fig. 2 is a partial cross-sectional view of a fuel cell stack.

Fig. 3 is a flow chart of the drainage process.

Detailed Description

[1 Structure of Fuel cell System 10 ]

Fig. 1 is a schematic configuration diagram of a fuel cell system 10 according to the present invention. The fuel cell system 10 is mounted on a vehicle (fuel cell vehicle). The fuel cell system 10 has a fuel cell stack 12, a hydrogen tank 14, an anode system 16, a cathode system 18, a cooling system 20, and an output 21. In addition, the fuel cell system 10 has a control device 94.

The fuel cell stack 12 has a plurality of power generation unit cells 22 stacked in one direction. Each of the power generation cells 22 has an electrolyte membrane-electrode assembly 24 (also simply referred to as an electrode assembly 24) and a set of separators 26, 28. A set of separators 26, 28 sandwich the electrode structure 24.

The electrode structure 24 includes a solid polymer electrolyte membrane 30 (also referred to as an electrolyte membrane 30), an anode electrode 32, and a cathode electrode 34. The electrolyte membrane 30 is, for example, a membrane of perfluorosulfonic acid containing moisture. The anode electrode 32 and the cathode electrode 34 sandwich the electrolyte membrane 30. The anode electrode 32 and the cathode electrode 34 have a gas diffusion layer formed of carbon paper or the like. Porous carbon particles are uniformly coated on the surface of the gas diffusion layer, thereby forming an electrode catalyst layer. Platinum alloy is supported on the surface of the porous carbon particles. Electrode catalyst layers are formed on both sides of the electrolyte membrane 30.

An anode flow path 36 is formed in a surface of the separator 26 facing the electrode structure 24. The anode flow path 36 is connected to the anode supply flow path 40 via the anode inlet 17A. The anode flow path 36 is connected to the anode discharge flow path 42 via the first anode outlet 17B. The anode flow field 36 is connected to the second drain flow field 48 via the second anode outlet 17C. The second anode outlet 17C is located at a lower position than the first anode outlet 17B. A cathode flow path 38 is formed in a surface of the separator 28 facing the electrode structure 24. The cathode flow path 38 is connected to the cathode supply flow path 62 via the cathode inlet 19A. The cathode flow path 38 is connected to the cathode discharge flow path 64 via the cathode outlet 19B.

An anode gas (hydrogen) is supplied to the anode electrode 32. At the anode electrode 32, hydrogen ions and electrons are generated from the hydrogen molecules due to the electrode reaction generated by the catalyst. The hydrogen ions permeate the electrolyte membrane 30 and move toward the cathode electrode 34. The electrons move in sequence to the negative electrode terminal (not shown) of the fuel cell stack 12, the load 104 such as a motor, the positive electrode terminal (not shown) of the fuel cell stack 12, and the cathode electrode 34. In the cathode electrode 34, hydrogen ions and electrons react with oxygen contained in the supplied air by the action of a catalyst to generate water.

The anode system 16 has structures for supplying anode gas to the anode electrode 32 and structures for discharging anode off-gas from the anode electrode 32. The anode system 16 has an anode supply flow path 40, an anode exhaust flow path 42, a circulation flow path 44, a first drain flow path 46, and a second drain flow path 48. In addition, the anode system 16 has an ejector 50, an ejector 52, a gas-liquid separator 54, a first drain valve 56, a throttle 57, and a second drain valve 58.

The anode supply flow path 40 communicates the discharge port of the hydrogen tank 14 with the anode inlet 17A. An ejector 50 and an ejector 52 are provided in the anode supply passage 40. The ejector 52 is disposed closer to the anode inlet 17A than the ejector 50.

The anode discharge flow path 42 communicates the first anode outlet 17B with the gas inlet of the gas-liquid separator 54. The circulation flow path 44 communicates the exhaust port of the gas-liquid separator 54 with the ejector 52. The first drain flow path 46 communicates the drain port of the gas-liquid separator 54 with the inlet of the diluter 60. The first drain valve 56 is provided in the first drain flow path 46. The second drain flow path 48 communicates the second anode outlet 17C with a portion of the first drain flow path 46 downstream of the first drain valve 56. A throttle 57 and a second drain valve 58 are provided in the second drain flow path 48. The throttle 57 is disposed closer to the second anode outlet 17C than the second drain valve 58.

The cathode system 18 has structures for supplying cathode gas to the cathode electrode 34 and structures for discharging cathode exhaust gas from the cathode electrode 34. The cathode system 18 has a cathode supply flow path 62, a cathode exhaust flow path 64, and a bypass flow path 66. In addition, cathode system 18 has a compressor 68, a humidifier 70, a first sealing valve 74, a second sealing valve 76, and a bypass valve 78.

The cathode supply flow path 62 communicates an air inlet (not shown) of air with the cathode inlet 19A. The cathode supply flow path 62 is provided with a compressor 68, a first sealing valve 74, and a flow path 72A of the humidifier 70. The portion of the cathode supply flow path 62 upstream of the humidifier 70 is referred to as a cathode supply flow path 62A. The portion of the cathode supply flow path 62 downstream of the humidifier 70 is referred to as a cathode supply flow path 62B. The cathode supply passage 62A is provided with a compressor 68 and a first sealing valve 74. The first sealing valve 74 is disposed closer to the humidifier 70 than the compressor 68.

The cathode discharge flow path 64 communicates the cathode outlet 19B with the inlet of the diluter 60. The cathode discharge flow path 64 is provided with a flow path 72B of the humidifier 70 and a second seal valve 76. The portion of the cathode discharge flow path 64 upstream of the humidifier 70 is referred to as a cathode discharge flow path 64A. The portion of the cathode supply flow path 62 downstream of the humidifier 70 is referred to as a cathode discharge flow path 64B. The cathode discharge flow path 64B is provided with a second sealing valve 76.

The bypass passage 66 communicates the cathode supply passage 62A with the cathode discharge passage 64B. For example, the bypass flow path 66 communicates a portion between the compressor 68 and the first seal valve 74 in the cathode supply flow path 62A with a portion downstream of the second seal valve 76 in the cathode discharge flow path 64B. A bypass valve 78 is provided in the bypass flow path 66.

Anode system 16 and cathode system 18 are connected by a connecting flow path 80. The connection flow path 80 communicates the circulation flow path 44 of the anode system 16 with the cathode supply flow path 62B of the cathode system 18. A discharge valve 82 is provided in the connection flow path 80.

The cooling system 20 has structures for supplying the refrigerant to the fuel cell stack 12 and structures for discharging the refrigerant from the fuel cell stack 12. The cooling system 20 has a refrigerant supply flow path 84 and a refrigerant discharge flow path 86. In addition, the cooling system 20 has a refrigerant pump 88 and a radiator 90.

A refrigerant flow path (not shown) for cooling the fuel cell stack 12 is formed inside the fuel cell stack 12. The refrigerant supply flow path 84 communicates an outlet of the radiator 90 with an inlet of the refrigerant flow path. A refrigerant pump 88 is provided in the refrigerant supply passage 84. The refrigerant discharge flow path 86 communicates an outlet of the refrigerant flow path with an inlet of the radiator 90.

The output unit 21 has respective structures for supplying electric power to the load 104 provided in the vehicle. Output unit 21 includes a drive unit 100, an electric storage device 102, a load 104, a current sensor 106, and a voltage sensor 108.

The driving unit 100 can supply electric power from the fuel cell stack 12 to the load 104. Further, the driving unit 100 can supply electric power from the fuel cell stack 12 to the power storage device 102. Further, driving unit 100 can supply electric power from power storage device 102 to load 104. Further, driving unit 100 can supply electric power from load 104 to power storage device 102. The load 104 is, for example, a main machine (a running motor) and an auxiliary device (a vehicle auxiliary device). The current sensor 106 detects the output current of the fuel cell stack 12. The voltage sensor 108 detects the output voltage of the fuel cell stack 12.

The control device 94 is a computer (e.g., ECU (Electronic Control Unit, electronic control unit)). The control device 94 has a control unit 96 and a storage unit 98. The control unit 96 has a processing circuit. The processing circuit may be a processor such as a CPU. The processing circuitry may also be an integrated circuit such as an ASIC (Application Specific Integrat ed Circuit ), FPGA (Field Programmable Gate Array, field programmable gate array), or the like. The processor can execute various processes by executing the program stored in the storage unit 98. At least a portion of the various processes may also be performed using circuitry comprising discrete devices.

The control unit 96 controls the operation of the fuel cell system 10. For example, the control unit 96 receives detection signals from various sensors provided in the fuel cell system 10. The control unit 96 outputs control signals for controlling the valves, the ejector 50, the compressor 68, the refrigerant pump 88, and the like, based on the detection signals. The valves, the ejector 50, the compressor 68, the refrigerant pump 88, and the like operate in response to control signals.

The storage section 98 has a volatile memory and a nonvolatile memory. Examples of the volatile memory include RAM (Random Access Memory ). The volatile memory is used as a working memory of the processor. The volatile memory temporarily stores data and the like necessary for processing or operation. Examples of the nonvolatile Memory include a ROM (Read Only Memory) and a flash Memory. The nonvolatile memory is used as a memory for storage. The nonvolatile memory stores programs, forms, mapping tables, and the like. The processor, the integrated circuit, and the like described above may be provided with at least a part of the storage section 98.

The nonvolatile memory stores a first threshold value and a second threshold value. The first threshold is a threshold for determining whether the vehicle is stopped. For example, the first threshold value is any one of a maximum power generation amount when the vehicle is parked and a minimum power generation amount when the vehicle is driven. The first threshold value can be set in advance based on the power consumption of the auxiliary equipment of the vehicle. The second threshold value is a threshold value (water amount threshold value) of the water storage amount of the fuel cell stack 12 for determining whether or not to drain water from the fuel cell stack 12. The first threshold and the second threshold are preset by a user, respectively.

[ flow of fluid ]

[ flow of fluid in the 2-1 anode System 16 ]

The injector 50 injects the anode gas (hydrogen) of the hydrogen tank 14 toward the downstream of the anode supply flow path 40. The anode gas injected from the injector 50 flows in the anode supply flow path 40 and is supplied to the anode flow path 36. The anode gas flows through the anode flow path 36 and is discharged as anode off-gas from the first anode outlet 17B. The anode off-gas contains hydrogen that does not react with oxygen, nitrogen in the cathode gas that permeates the electrolyte membrane 30, and moisture that is generated by the reaction of oxygen with hydrogen.

The anode off-gas flows through the anode off-gas flow path 42 and is supplied to the gas-liquid separator 54. The gas-liquid separator 54 separates the anode off-gas into a gas component (anode off-gas) and a liquid component (water). The anode off-gas discharged from the gas-liquid separator 54 flows in the circulation flow path 44 and is supplied to the ejector 52. In the ejector 52, the anode off-gas merges with the anode gas injected from the ejector 50.

The water separated by the gas-liquid separator 54 is temporarily stored in the bottom of the gas-liquid separator 54. In a state where the first drain valve 56 is opened, the water stored in the gas-liquid separator 54 flows through the first drain flow path 46 and is discharged to the diluter 60. When the first drain valve 56 is opened in a state where the water of the gas-liquid separator 54 is not present, the anode off-gas of the gas-liquid separator 54 flows in the first drain flow path 46 and is discharged to the diluter 60.

In the case where the inside of the fuel cell stack 12 is highly humid, water is stored in the bottom of the anode flow path 36. In a state where the second drain valve 58 is opened, the water stored in the anode flow path 36 flows through the second drain flow path 48 and the first drain flow path 46, and is discharged to the diluter 60. When the second drain valve 58 is opened in a state where the water in the anode flow path 36 is not available, the anode off-gas in the anode flow path 36 flows through the second drain flow path 48 and the first drain flow path 46 and is discharged to the diluter 60.

[ flow of fluid in 2-2 cathode System 18 ]

The compressor 68 discharges the cathode gas (air) sucked from the outside of the vehicle toward the downstream of the cathode supply flow path 62. In a state where the first sealing valve 74 is opened, the cathode gas discharged from the compressor 68 flows through the cathode supply passage 62 and is supplied to the cathode passage 38. The cathode gas flows through the cathode flow path 38 and is discharged as a cathode exhaust gas from the cathode outlet 19B. The cathode off-gas contains components contained in the air and moisture generated by the reaction of oxygen and hydrogen.

In a state where the second sealing valve 76 is opened, the cathode off-gas flows through the cathode off-gas flow path 64 and is discharged to the diluter 60. The cathode exhaust gas contains moisture. In the humidifier 70, moisture of the cathode off-gas is used for humidifying the cathode gas.

In a state where the bypass valve 78 is opened, the cathode gas flows through the bypass flow path 66 and the cathode discharge flow path 64, and is discharged to the diluter 60. The bypass flow path 66 is used when the supply amount of the cathode gas to the fuel cell stack 12 is to be reduced.

[ flow of fluid in 2-3 connecting flow passage 80 ]

With the discharge valve 82 opened, a part of the anode off-gas flowing in the circulation flow path 44 flows in the connection flow path 80 and is supplied to the cathode supply flow path 62B. However, opening the purge valve 82 is limited to the case where the pressure of the anode flow path 36 is higher than the pressure of the cathode flow path 38.

The hydrogen in the anode exhaust gas flowing through the connection flow path 80 and supplied to the cathode supply flow path 62B reacts with oxygen at the catalyst of the cathode electrode 34 and is consumed. Accordingly, the hydrogen discharged from the anode system 16 to the outside is reduced, and the air required for diluting the hydrogen in the diluter 60 is also reduced. Thus, according to the connection flow path 80, the rotation speed of the compressor 68 that supplies air to the diluter 60 can be reduced, and the fuel consumption can be reduced. Thus, the fuel cell system 10 contributes to the energy efficiency.

[3 conditions for Water drainage treatment ]

Fig. 2 is a partial cross-sectional view of the fuel cell stack 12. As shown in fig. 2, in the present embodiment, the power generation cells 22 are arranged in parallel in the up-down direction and the front-rear direction. Further, a plurality of power generation cells 22 are stacked in the left-right direction to form a stacked body 22L. An insulator 110R and an end plate 112R are disposed at the right end of the laminated body 22L. An insulator 110L and an end plate 112L are disposed at the left end of the laminated body 22L. A flow path corresponding to the first anode outlet 17B and the second anode outlet 17C is arranged behind the laminated body 22L. The flow paths corresponding to the first anode outlet 17B and the second anode outlet 17C extend from right to left. An anode discharge flow path 42 is connected to the left side of the end plate 112L. The flow path corresponding to the first anode outlet 17B penetrates the end plate 112L and communicates with the anode discharge flow path 42. A second drain flow path 48 is connected to the left side of the end plate 112L. The flow path corresponding to the second anode outlet 17C penetrates the end plate 112L and communicates with the second drain flow path 48. Although not shown, a flow path corresponding to the anode inlet 17A is arranged in front of the laminated body 22L.

Water is retained in the lower portion of the fuel cell stack 12. In fig. 2, water is represented by dots. When the vehicle leans to the right, as shown in fig. 2, the fuel cell stack 12 also leans to the right. Then, the amount of water that the power generation cells 22 located at the right side position are immersed in increases. As this condition continues, the fuel cell stack 12 ages. In order to avoid degradation of the fuel cell stack 12, it is preferable to drain water remaining in the lower portion of the fuel cell stack 12 as much as possible. By opening the second drain valve 58, the water remaining in the lower portion of the fuel cell stack 12 is discharged to the outside of the fuel cell stack 12 via the second drain flow path 48.

A throttle 57 is provided in the second drain flow path 48. The pressure upstream of the throttle 57 (inside the fuel cell stack 12) is higher than the pressure downstream of the throttle 57 (outside the fuel cell stack 12). Therefore, when the second drain valve 58 is opened, water remaining inside the fuel cell stack 12 can flow in the second drain flow path 48 toward the first drain flow path 46.

On the other hand, in a state where water does not remain in the lower portion of the fuel cell stack 12, when the second drain valve 58 is opened, the anode gas of the anode flow path 36 is discharged to the outside of the fuel cell stack 12. Thus, fuel consumption increases.

In the present embodiment, in order to avoid degradation of the fuel cell stack 12 and an increase in fuel consumption, the condition for water discharge is set in advance, and the second drain valve 58 is opened only when the condition is satisfied.

In the state where the fuel cell stack 12 is inclined as shown in fig. 2, the possibility that the vehicle continues to run is low. That is, the possibility that the vehicle is inclined to continue running is low. For example, when the vehicle is traveling on a road inclined rightward, the vehicle is inclined rightward. However, the inclination of the estimated road exists locally. Therefore, it is assumed that the inclination of the vehicle returns to the horizontal state in a short time as the vehicle travels. When the fuel cell stack 12 is in the horizontal state, the amount of water that is soaked in the power generation cells 22 located at the right side position is small.

On the other hand, when the vehicle is on an inclined road or is parked in a parking lot, the vehicle continues to incline until the vehicle starts. When the vehicle is parked in a state of being tilted to the right, as shown in fig. 2, the state in which the fuel cell stack 12 is tilted continues. When a large amount of water remains in the lower portion of the fuel cell stack 12, as described above, the amount of water that is soaked in the power generation unit cells 22 located on the right side increases.

Thus, in the present embodiment, when the vehicle is stopped, water is discharged from the fuel cell stack 12. In the present embodiment, when the water remaining in the fuel cell stack 12 exceeds the threshold value, water is discharged from the fuel cell stack 12.

[4 Water drainage treatment ]

Fig. 3 is a flow chart of the drainage process. The control unit 96 repeats the water discharge process shown in fig. 3 during the operation of the fuel cell system 10.

In step S1, the control unit 96 calculates the power generation amount. In the present embodiment, the control unit 96 uses the power generation amount to determine whether the vehicle is stopped. The control unit 96 calculates the amount of power generation (for example, generated power) using, for example, the detection value of the current sensor 106 and the detection value of the voltage sensor 108. When step S1 ends, the process proceeds to step S2.

In step S2, the control unit 96 determines whether the vehicle is stopped. When the vehicle is stopped, the power generation amount of the fuel cell stack 12 is equal to or less than a fixed value. The control section 96 compares the power generation amount calculated in step S1 with a first threshold value (+.ltoreq.fixed value). However, the control unit 96 may determine whether the vehicle is stopped using other sensors provided in the vehicle. The other sensor includes a vehicle speed sensor and the like. In the case where the power generation amount is lower than the first threshold, that is, in the case where the vehicle is stopped (step S2: yes), the process proceeds to step S3. On the other hand, when the amount of power generation is equal to or greater than the first threshold, that is, when the vehicle is not stopped (no in step S2), the process proceeds to step S7.

At the transition from step S2 to step S3, the control unit 96 estimates the amount of water (water storage amount) remaining in the lower portion of the fuel cell stack 12 after the shutdown. The amount of electricity generated is related to the amount of water generated. Therefore, the control unit 96 obtains the amount of water corresponding to the amount of power generation at each timing, and integrates the amount of water, whereby the amount of water stored in the fuel cell stack 12 can be estimated. For example, the nonvolatile memory of the storage unit 98 stores a map, a calculation formula, and the like for acquiring the amount of water from the amount of generated power. The control unit 96 uses the power generation amount calculated in step S1, the map, and the like to estimate the amount of water that can be generated at the current time point. The control unit 96 adds the calculated water amount to the latest water storage amount. When step S3 ends, the process proceeds to step S4.

In step S4, the control unit 96 determines whether or not drainage from the fuel cell stack 12 is necessary. Specifically, the control unit 96 compares the water storage amount with the second threshold value. When the water storage amount exceeds the second threshold value, that is, when water discharge is required (yes in step S4), the process proceeds to step S5. On the other hand, when the water storage amount is equal to or less than the second threshold, that is, when no water discharge is necessary (no in step S4), the process proceeds to step S7.

Upon transition from step S4 to step S5, the control unit 96 opens the second drain valve 58 for a fixed time. The fixed time is a time period in which water having a water storage amount corresponding to the second threshold value can be discharged from the fuel cell stack 12 to the diluter 60 via the second drain flow path 48 and the first drain flow path 46. When step S5 ends, the process proceeds to step S6.

In step S6, the control unit 96 initializes the water storage amount. When step S6 ends, the process proceeds to step S7.

When the process goes from step S2, step S4, or step S6 to step S7, the control unit 96 closes the second drain valve 58. When the second drain valve 58 is already closed, the control unit 96 maintains the state of the second drain valve 58. On the other hand, when the second drain valve 58 is open, the control unit 96 closes the second drain valve 58.

[5 ] the invention according to the embodiment ]

The invention which can be grasped according to the above embodiment will be described below.

A first aspect of the present invention relates to a fuel cell system 10 for a vehicle, including a fuel cell stack 12 that generates power using an anode gas and a cathode gas, the fuel cell system 10 for a vehicle including: a drain flow path 48 connected to the fuel cell stack so as to drain water remaining in a lower portion of the fuel cell stack to an outside of the fuel cell stack; a throttle 57 that makes the pressure upstream of the drain flow path higher than the pressure downstream of the drain flow path; a valve 58 for opening and closing the drain flow path; and a control unit 96 for controlling the opening and closing of the valve. The control unit performs a first determination for determining whether or not the vehicle is stopped, estimates the amount of water remaining in the lower portion of the fuel cell stack based on the amount of power generation of the fuel cell stack, performs a second determination for determining whether the amount of water is greater than or less than a water amount threshold, and controls opening and closing of the valve based on the result of the first determination and the result of the second determination.

The first embodiment can determine an appropriate timing for opening and closing the valve (the second drain valve 58) by performing the first determination (step S2) and the second determination (step S4). Therefore, according to the first aspect, the water remaining in the fuel cell stack can be appropriately discharged. In addition, according to the first aspect, when the drain flow path is connected to the anode flow path, it is possible to suppress the discharge of the anode gas more than necessary. Thus, according to the first aspect, the degradation of the fuel cell stack can be suppressed, and the power generation of the fuel cell stack can be stabilized.

In the above aspect, the control unit may cause the valve to open when it is determined that the vehicle is stopped in the first determination and when it is determined that the water amount is greater than the water amount threshold in the second determination.

According to the above configuration, the valve (the second drain valve 58) can be opened at an appropriate timing.

In the above aspect, the fuel cell stack may include an anode flow path 36 through which the anode gas flows and a cathode flow path 38 through which the cathode gas flows, and the drain flow path may be connected to the anode flow path.

A second aspect of the present invention relates to a water discharge method of a fuel cell system for a vehicle including a fuel cell stack that generates electric power using an anode gas and a cathode gas. The fuel cell system is provided with: a drain flow path connected to the fuel cell stack so as to drain water remaining in a lower portion of the fuel cell stack to an outside of the fuel cell stack; a throttle member that makes a pressure upstream of the drain flow path higher than a pressure downstream of the drain flow path; a valve for opening and closing the drain flow path; and a computer 94 that controls the opening and closing of the valve. The computer performs a first determination for determining whether the vehicle is stopped, estimates an amount of water remaining in a lower portion of the fuel cell stack based on an amount of power generation of the fuel cell stack, performs a second determination for determining whether the amount of water is more or less than a water amount threshold, and controls opening and closing of the valve based on a result of the first determination and a result of the second determination.

The present invention is not limited to the above-described disclosure, and various configurations can be adopted without departing from the spirit of the present invention.

Claims

1. A fuel cell system for a vehicle, which is provided with a fuel cell stack (12) that generates electricity using an anode gas and a cathode gas, is provided with:

a drain flow path (48) connected to the fuel cell stack so as to drain water remaining in the lower portion of the fuel cell stack to the outside of the fuel cell stack;

a throttle (57) that makes the pressure upstream of the drain flow path higher than the pressure downstream of the drain flow path;

a valve (58) for opening and closing the drain flow path; and

a control unit (96) for controlling the opening and closing of the valve,

the control portion makes a first determination for determining whether the vehicle is stopped,

the control portion estimates the amount of water remaining in the lower portion of the fuel cell stack based on the power generation amount of the fuel cell stack,

the control unit performs a second determination for determining whether the water amount is more or less than a water amount threshold,

the control unit controls opening and closing of the valve based on the result of the first determination and the result of the second determination.

2. The fuel cell system for a vehicle according to claim 1, wherein,

the control unit opens the valve when the first determination determines that the vehicle is stopped and when the second determination determines that the water amount is greater than the water amount threshold.

3. The fuel cell system for a vehicle according to claim 1 or 2, wherein,

the fuel cell stack has an anode flow path (36) through which the anode gas flows and a cathode flow path (38) through which the cathode gas flows,

the drain flow path is connected to the anode flow path.

4. A method for draining a fuel cell system for a vehicle, the fuel cell system for a vehicle including a fuel cell stack that generates electric power using an anode gas and a cathode gas,

the fuel cell system is provided with:

a drain flow path connected to the fuel cell stack so as to drain water remaining in a lower portion of the fuel cell stack to an outside of the fuel cell stack;

a throttle member that makes a pressure upstream of the drain flow path higher than a pressure downstream of the drain flow path;

a valve for opening and closing the drain flow path; and

a computer (94) for controlling the opening and closing of the valve,

the computer makes a first determination for determining whether the vehicle is stopped,

the computer estimates the amount of water remaining in the lower portion of the fuel cell stack based on the power generation amount of the fuel cell stack,

the computer makes a second determination for determining whether the amount of water is greater than or less than a water amount threshold,

the computer controls opening and closing of the valve based on a result of the first determination and a result of the second determination.