Fuel cell system and method for reducing vibration noise of fuel cell system

Abstract

The present application relates to a fuel cell system and a method for reducing vibration noise of a fuel cell system. A control unit (96) of the fuel cell system (10) opens a second valve (58) at a timing at which a first valve (56) is closed, and maintains an operation state of a compressor (68) before the first valve is closed after the second valve is opened.

Description

Technical Field

[0001] This invention relates to a fuel cell system for reducing compressor vibration and noise, and a method for reducing vibration and noise in a fuel cell system. Background Technology

[0002] In recent years, in order to ensure that more people have access to appropriate, reliable, sustainable and advanced energy, research and development are underway on fuel cells that contribute to energy efficiency.

[0003] Patent Document 1 discloses a fuel cell system for a fuel cell vehicle. Hereinafter, this fuel cell system will also be referred to as the first system. In the first system, anode gas is supplied from the anode supply path to the anode flow path within the fuel cell stack. The main component of the anode gas is hydrogen. In the first system, cathode gas is supplied from the cathode supply path to the cathode flow path within the fuel cell stack. The cathode gas is air (oxygen, nitrogen, etc.). The fuel cell stack generates electricity through the reaction of hydrogen in the anode gas and oxygen in the cathode gas. Anode exhaust gas (hydrogen, nitrogen, moisture, etc.) is discharged from the anode flow path. The anode exhaust gas is supplied to a gas-liquid separator. The gas-liquid separator separates the anode exhaust gas into air components (hydrogen, nitrogen, etc.) and liquid components (water).

[0004] The anode exhaust gas separated by the gas-liquid separator can be supplied to the anode supply flow path via a circulation flow path. Alternatively, the anode exhaust gas separated by the gas-liquid separator can be discharged to the outside of the fuel cell system along with water via a drain flow path and a diluter.

[0005] A new fuel cell system has now been developed. Hereinafter, this newly developed fuel cell system will also be referred to as the second system. In the second system, high humidity is maintained within the fuel cell stack. Therefore, a large amount of water is generated within the fuel cell stack. In addition to a drain path (first drain path) connected to a gas-liquid separator, the second system also includes a drain path (second drain path) directly connected to the anode flow path. The water remaining in the fuel cell stack can be discharged to the outside of the fuel cell system along with the anode exhaust gas through the second drain path and the diluter.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-18850 Summary of the Invention

[0009] When water and anode exhaust are to be discharged to the outside, the diluter uses air to dilute the hydrogen. Therefore, when water and anode exhaust are started to be discharged, the fuel cell system control unit increases the compressor speed to increase the air supply. Conversely, when water and anode exhaust are stopped, the control unit decreases the compressor speed to reduce the air supply.

[0010] With multiple discharge paths configured as in the second system, the total number of discharges of water and anode exhaust increases. Therefore, the control unit frequently changes the compressor's rotational speed. As the compressor's rotational speed increases, vibration and noise change. In other words, compared to the first system, the second system exhibits increased variations in compressor vibration and noise. These increased variations in compressor vibration and noise can cause user annoyance.

[0011] The purpose of this invention is to solve the above-mentioned problems.

[0012] A first aspect of the present invention relates to a fuel cell system comprising: a fuel cell stack for generating electricity using anolyte gas in an anode path and cathode gas in a cathode path; a gas-liquid separator for separating an exhaust fluid discharged from the anode path into gas and water; a first exhaust path for discharging the water and gas from the gas-liquid separator to the outside; a second exhaust path for discharging the exhaust fluid from the anode path to the outside; a first valve for opening and closing the first exhaust path; a second valve for opening and closing the second exhaust path; a compressor for supplying air for diluting the exhaust fluid and gas to be discharged to the outside; and a control unit for controlling the opening and closing of the first valve and the second valve, wherein in the fuel cell system, the control unit opens the second valve at a time when the first valve is closed, and maintains the operation of the compressor as before the first valve was closed after the second valve is opened.

[0013] A second aspect of the present invention relates to a method for reducing vibration and noise in a fuel cell system, the fuel cell system comprising: a fuel cell stack that generates electricity using anolyte gas in an anode path and cathode gas in a cathode path; a gas-liquid separator that separates discharge fluid from the anode path into gas and water; a first discharge path that discharges the water and gas from the gas-liquid separator to the outside; a second discharge path that discharges the discharge fluid from the anode path to the outside; a first valve that opens and closes the first discharge path; a second valve that opens and closes the second discharge path; a compressor that supplies air for diluting the discharge fluid and gas to be discharged to the outside; and a computer that controls the opening and closing of the first valve and the second valve, wherein in the method for reducing vibration and noise in the fuel cell system, the computer opens the second valve at a timed interval when the first valve is closed, and maintains the operation of the compressor as before the first valve was closed after the second valve is opened.

[0014] According to the present invention, the number of large-scale vibration changes and the number of large-scale noise changes of the compressor can be reduced.

[0015] The above-described objectives, features, and advantages can be readily understood from the following description of the embodiments, which are illustrated with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the fuel cell system involved in the present invention.

[0017] Figure 2 This is a flowchart of the control process for the first drain valve.

[0018] Figure 3 This is a flowchart of the control process for the second drain valve.

[0019] Figure 4 This is a flowchart of the compressor control process.

[0020] Figure 5 It is a timing diagram showing the opening and closing status of each valve in the existing technology, the amount of dilute air injected by the compressor, and whether there is a requirement to open the second discharge valve.

[0021] Figure 6 This is a timing diagram showing the opening and closing status of each valve in this embodiment, the amount of diluted air ejected by the compressor, and whether there is a requirement to open the second drain valve. Detailed Implementation

[0022] [Structure of fuel cell system 10]

[0023] Figure 1This is a schematic structural diagram of the fuel cell system 10 according to the present invention. The fuel cell system 10 is installed in a vehicle (fuel cell vehicle). In addition, the fuel cell system 10 can also be installed in, for example, ships, aircraft, and robots. The fuel cell system 10 includes a fuel cell stack 12, a hydrogen tank 14, an anode system 16, a cathode system 18, and a cooling system 20. Furthermore, the fuel cell system 10 includes a control device 94. The output (electricity) of the fuel cell stack 12 is supplied to a load (not shown) such as a motor.

[0024] The fuel cell stack 12 has multiple power-generating cells 22 stacked along one direction. Each power-generating cell 22 has an electrolyte membrane. - Electrode structure 24 (also referred to as electrode structure 24) and a set of spacers 26 and 28. The set of spacers 26 and 28 clamps electrode structure 24.

[0025] The electrode structure 24 comprises a solid polymer electrolyte membrane 30 (also referred to as electrolyte membrane 30), an anode electrode 32, and a cathode electrode 34. The electrolyte membrane 30 is, for example, a thin film of perfluorosulfonic acid containing water. 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 to form an electrode catalyst layer. A platinum alloy is supported on the surface of the porous carbon particles. The electrode catalyst layer is formed on both sides of the electrolyte membrane 30.

[0026] An anode flow path 36 is formed on the surface of the electrode-facing structure 24 within the surface of the spacer 26. The anode flow path 36 is connected to the anode supply flow path 40 via an anode inlet 17A. The anode flow path 36 is connected to the anode discharge flow path 42 via a first anode outlet 17B. Furthermore, the anode flow path 36 is connected to the second drain flow path 48 via a 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 on the surface of the electrode-facing structure 24 within the surface of the spacer 28. The cathode flow path 38 is connected to the cathode supply flow path 62 via a cathode inlet 19A. The cathode flow path 38 is connected to the cathode discharge flow path 64 via a cathode outlet 19B.

[0027] Anode gas (hydrogen) is supplied to the anode electrode 32. In the anode electrode 32, hydrogen ions and electrons are generated from hydrogen molecules due to an electrode reaction produced by the catalyst. Hydrogen ions permeate through the electrolyte membrane 30 and move towards the cathode electrode 34. Electrons move sequentially towards the negative terminal (not shown) of the fuel cell stack 12, a load such as a motor, the positive 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 through the action of a catalyst to produce water.

[0028] The anode system 16 has structures for supplying anode gas to the anode electrode 32 and structures for discharging anode exhaust gas from the anode electrode 32. The anode system 16 includes an anode supply flow path 40, an anode discharge flow path 42, a circulation flow path 44, a first discharge flow path 46 (first discharge flow path), and a second discharge flow path 48 (second discharge flow path). Additionally, the anode system 16 includes an ejector 50, an ejector 52, a gas-liquid separator 54, a first discharge valve 56 (first valve), and a second discharge valve 58 (second valve).

[0029] The anode supply path 40 connects the outlet of the hydrogen tank 14 to the anode inlet 17A. An ejector 50 and an ejector 52 are provided in the anode supply path 40. The ejector 52 is positioned closer to the anode inlet 17A than the ejector 50.

[0030] Anode discharge path 42 connects the first anode outlet 17B to the inlet of the gas-liquid separator 54. Circulation path 44 connects the exhaust port of the gas-liquid separator 54 to the ejector 52. First drain path 46 connects the drain outlet of the gas-liquid separator 54 to the inlet of the diluter 60. A first drain valve 56 is provided in the first drain path 46. Second drain path 48 connects the second anode outlet 17C to the downstream portion of the first drain path 46, below the first drain valve 56. A second drain valve 58 is provided in the second drain path 48.

[0031] The cathode system 18 has structures for supplying cathode gas to the cathode electrode 34 and structures for discharging cathode gas from the cathode electrode 34. The cathode system 18 has a cathode supply flow path 62, a cathode discharge flow path 64, and a bypass flow path 66. Additionally, the cathode system 18 includes a compressor 68, a humidifier 70, a first sealing valve 74, a second sealing valve 76, and a bypass valve 78.

[0032] The cathode supply flow path 62 connects the air inlet (not shown) to the cathode inlet 19A. A flow path 72A containing the compressor 68, the first sealing valve 74, and the humidifier 70 is provided in the cathode supply flow path 62. The portion of the cathode supply flow path 62 upstream of the humidifier 70 is designated as cathode supply flow path 62A. The portion of the cathode supply flow path 62 downstream of the humidifier 70 is designated as cathode supply flow path 62B. The compressor 68 and the first sealing valve 74 are provided in the cathode supply flow path 62A. The first sealing valve 74 is positioned closer to the humidifier 70 than the compressor 68.

[0033] The cathode discharge path 64 connects the cathode outlet 19B to the inlet of the diluter 60. A flow path 72B for the humidifier 70 and a second sealing valve 76 are provided in the cathode discharge path 64. The portion of the cathode discharge path 64 upstream of the humidifier 70 is designated as cathode discharge path 64A. The portion of the cathode supply path 64 downstream of the humidifier 70 is designated as cathode discharge path 64B. The second sealing valve 76 is provided in cathode discharge path 64B.

[0034] The bypass flow path 66 connects the cathode supply flow path 62A and the cathode discharge flow path 64B. For example, the bypass flow path 66 connects the portion of the cathode supply flow path 62A between the compressor 68 and the first sealing valve 74 to the portion of the cathode discharge flow path 64B downstream of the second sealing valve 76. A bypass valve 78 is provided in the bypass flow path 66.

[0035] The anode system 16 and the cathode system 18 are connected by a connecting flow path 80. The connecting flow path 80 connects 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 connecting flow path 80.

[0036] The cooling system 20 has structures for supplying refrigerant to the fuel cell stack 12 and structures for discharging 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. Additionally, the cooling system 20 has a refrigerant pump 88 and a radiator 90.

[0037] A refrigerant flow path (not shown) for cooling the fuel cell stack 12 is formed inside the fuel cell stack 12. A refrigerant supply flow path 84 connects the outlet of the radiator 90 to the inlet of the refrigerant flow path. A refrigerant pump 88 is provided in the refrigerant supply flow path 84. A refrigerant discharge flow path 86 connects the outlet of the refrigerant flow path to the inlet of the radiator 90.

[0038] The control device 94 is a computer (e.g., an ECU (Electronic Control Unit) in a vehicle). The control device 94 has a control unit 96 and a storage unit 98. The control unit 96 has processing circuitry. The processing circuitry can also be a processor such as a CPU. The processing circuitry can also be an integrated circuit such as an ASIC (Application-Specific Integrated Circuit) or a FPGA (Field-Programmable Gate Array). The processor can perform various processes by executing a program stored in the storage unit 98. At least some of the various processes can also be performed using circuitry containing discrete components.

[0039] 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 installed in the fuel cell system 10. Based on each detection signal, the control unit 96 outputs control signals for controlling each valve, injector 50, compressor 68, and refrigerant pump 88, etc. Each valve, injector 50, compressor 68, and refrigerant pump 88 operates according to the control signals.

[0040] Storage unit 98 includes volatile memory and non-volatile memory. Examples of volatile memory include RAM (Random Access Memory). Volatile memory is used as the processor's working memory. It temporarily stores data required for processing or computation. Examples of non-volatile memory include ROM (Read Only Memory) and flash memory. Non-volatile memory is used as storage memory. It stores programs, forms, and mapping tables. At least a portion of storage unit 98 may be included in processors and integrated circuits as described above.

[0041] [2 Fluid Flow]

[0042] [2-1 Fluid Flow in Anode System 16]

[0043] The ejector 50 injects anode gas (hydrogen) from the hydrogen tank 14 downstream of the anode supply path 40. The anode gas injected from the ejector 50 flows in the anode supply path 40 and is supplied to the anode path 36. The anode gas flows in the anode path 36 and is discharged from the first anode outlet 17B as anode exhaust. The anode exhaust contains unreacted hydrogen, nitrogen from the cathode gas permeating the electrolyte membrane 30, and moisture generated by the reaction of oxygen and hydrogen.

[0044] The anode exhaust gas flows in the anode discharge path 42 and is supplied to the gas-liquid separator 54. The gas-liquid separator 54 separates the anode exhaust gas into a gaseous component (anode exhaust gas) and a liquid component (water). The anode exhaust gas discharged from the gas-liquid separator 54 flows in the circulation path 44 and is supplied to the ejector 52. In the ejector 52, the anode exhaust gas merges with the anode gas ejected from the ejector 50.

[0045] The water separated by the gas-liquid separator 54 is temporarily stored at the bottom of the gas-liquid separator 54. With the first drain valve 56 open, the water stored in the gas-liquid separator 54 flows in the first drain path 46 and is discharged to the diluent 60. When the first drain valve 56 is opened when there is no water in the gas-liquid separator 54, the anode exhaust gas of the gas-liquid separator 54 flows in the first drain path 46 and is discharged to the diluent 60.

[0046] In a high-humidity environment inside the fuel cell stack 12, water is stored at the bottom of the anode flow path 36. With the second drain valve 58 open, 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 into the diluter 60. When the second drain valve 58 is opened when there is no water in the anode flow path 36, the anode exhaust gas from the anode flow path 36 flows through the second drain flow path 48 and the first drain flow path 46 and is discharged into the diluter 60.

[0047] [2-2 Fluid Flow in Cathode System 18]

[0048] Compressor 68 draws in cathode gas (air) from outside the vehicle and ejects it downstream of cathode supply path 62. With the first sealing valve 74 open, the cathode gas ejected from compressor 68 flows in cathode supply path 62 and is supplied to cathode path 38. The cathode gas flows in cathode path 38 and is discharged from cathode outlet 19B as cathode exhaust. Cathode exhaust contains all components of the air and moisture generated by the reaction of oxygen and hydrogen.

[0049] With the second sealing valve 76 open, the cathode exhaust flows in the cathode discharge path 64 and is discharged to the diluter 60. The cathode exhaust contains moisture. In the humidifier 70, the moisture in the cathode exhaust is used to humidify the cathode gas.

[0050] With bypass valve 78 open, cathode gas flows through bypass path 66 and cathode discharge path 64 and is discharged to diluter 60. Bypass path 66 is used when it is necessary to reduce the supply of cathode gas to fuel cell stack 12.

[0051] [2-3 Fluid flow in connecting flow path 80]

[0052] With the discharge valve 82 open, a portion of the anode exhaust flowing in the circulation path 44 flows in the connecting path 80 and is supplied to the cathode supply path 62B. However, the discharge valve 82 is only opened when the pressure in the anode path 36 is higher than the pressure in the cathode path 38.

[0053] Hydrogen flowing in the connecting flow path 80 and supplied to the cathode supply flow path 62B from the anode exhaust is consumed by reacting with oxygen on the catalyst of the cathode electrode 34. Therefore, less hydrogen is discharged from the anode system 16 to the outside, and consequently, less air is needed in the diluter 60 to dilute the hydrogen. Thus, according to the connecting flow path 80, the rotational speed of the compressor 68 supplying air to the diluter 60 can be reduced, improving fuel efficiency. Therefore, the fuel cell system 10 contributes to improved energy efficiency.

[0054] [Relationship between the diameter of each valve and the rotational speed of compressor 68]

[0055] As a discharge path from the anode flow path 36 to the diluter 60, there is a first path (first discharge flow path 46) including the first discharge valve 56. As a discharge path from the anode flow path 36 to the diluter 60, there is a second path (second discharge flow path 48, first discharge flow path 46) including the second discharge valve 58. As a discharge path from the anode flow path 36 to the diluter 60, there is a third path (connecting flow path 80, cathode supply flow path 62B, cathode flow path 38, cathode discharge flow path 64) including the discharge valve 82.

[0056] The diameter of the internal flow path of the first discharge valve 56 is the same as the diameter of the internal flow path of the second discharge valve 58. Therefore, the amount of air required to dilute the hydrogen when the discharge path is the first path is approximately the same as the amount of air required to dilute the hydrogen when the discharge path is the second path. In other words, the rotational speed of the compressor 68 when the discharge path is the first path can be approximately the same as the rotational speed of the compressor 68 when the discharge path is the second path. Therefore, when the valve opening target is switched from the first discharge valve 56 to the second discharge valve 58, the rotational speed of the compressor 68 can be approximately fixed.

[0057] On the other hand, the diameter of the internal flow path of the discharge valve 82 is smaller than the diameter of the internal flow path of the first discharge valve 56 and smaller than the diameter of the internal flow path of the second discharge valve 58. Furthermore, a portion of the hydrogen in the anode exhaust flowing in the third path is consumed by the fuel cell stack 12. Therefore, when the discharge path is the third path, the amount of air required to dilute the hydrogen can be less than the amount of air required to dilute the hydrogen when the discharge path is the first or second path.

[0058] [4. Processes executed by the control unit 96]

[0059] While the fuel cell stack 12 is generating electricity, the control unit 96 performs parallel control processing on the first drain valve. Figure 2 ), and the second drain valve control process ( Figure 3 ) and compressor control processing ( Figure 4 ).

[0060] [4-1 First Drain Valve Control Process]

[0061] Figure 2 This is a flowchart of the first discharge valve control process. The control unit 96 repeats this process while the fuel cell stack 12 is generating electricity. Figure 2 The first drain valve shown is controlled by a process.

[0062] In step S1, the control unit 96 determines whether there is a request to open the first drain valve 56. The control unit 96 may, for example, periodically repeat the opening and closing of the first drain valve 56. In this case, the control unit 96 can monitor system time to determine the opening and closing periods of the first drain valve 56. Alternatively, the control unit 96 can estimate the water volume of the gas-liquid separator 54 based on power generation and determine the opening and closing periods based on whether the estimated value exceeds a predetermined amount. The control unit 96 determines that there is a request to open the first drain valve 56 during the period when it should be open. Conversely, the control unit 96 determines that there is no request to open the first drain valve 56 during the period when it should be closed. The opening request is maintained during the opening period. If it is determined that there is a request to open the valve (step S1: Yes), the process proceeds to step S2. On the other hand, if it is determined that there is no request to open the valve (step S1: No), the process proceeds to step S3.

[0063] When moving from step S1 to step S2, the control unit 96 opens the first drain valve 56. If the first drain valve 56 is already open, the control unit 96 maintains the state of the first drain valve 56. Conversely, if the first drain valve 56 is closed, the control unit 96 opens it. A portion of the water from the gas-liquid separator 54 and a portion of the anode exhaust gas flows in the first drain path 46 and is discharged to the diluent 60.

[0064] When moving from step S1 to step S3, the control unit 96 closes the first drain valve 56. If the first drain valve 56 is already closed, the control unit 96 maintains the state of the first drain valve 56. Conversely, if the first drain valve 56 is open, the control unit 96 closes the first drain valve 56.

[0065] [4-2 Second Drain Valve Control Process]

[0066] Figure 3 This is a flowchart of the second drain valve control process. The control unit 96 repeatedly performs this process during fuel cell stack 12 power generation. Figure 3 The second drain valve shown is used for control processing.

[0067] In step S11, the control unit 96 determines whether there is a request to open the second drain valve 58. For example, the control unit 96 opens the second drain valve 58 for a fixed time when the water generation is high. The water generation is related to the power generation of the fuel cell stack 12. The control unit 96 accumulates the time for the target power generation to exceed a predetermined power generation threshold. If the accumulated time value exceeds the predetermined time threshold, the control unit 96 determines that there is a request to open the valve. Moreover, if a fixed time has elapsed after the second drain valve 58 has been opened, it is determined that there is no request to open the valve. The request to open the valve will remain for a fixed time. If it is determined that there is a request to open the valve (step S11: yes), the process moves to step S12. On the other hand, if it is determined that there is no request to open the valve (step S11: no), the process moves to step S16.

[0068] When moving from step S11 to step S12, the control unit 96 determines whether the discharge valve 82 is currently in a closed state. If it is determined that the discharge valve 82 is in a closed state (step S12: Yes), the process moves to step S13. On the other hand, if it is determined that the discharge valve 82 is not in a closed state, that is, if the discharge valve 82 is in an open state (step S12: No), the process moves to step S16.

[0069] When moving from step S12 to step S13, the control unit 96 determines whether the first drain valve 56 was switched from an open state to a closed state in the most recent first drain valve control process. In other words, the control unit 96 determines whether the first drain valve 56 has changed from an open state to a closed state. If it is determined that the first drain valve 56 has changed from an open state to a closed state (step S13: Yes), the process moves to step S15. At this point, the control unit 96 identifies the closing timing of the first drain valve 56. On the other hand, if it is determined that the first drain valve 56 has not changed from an open state to a closed state (step S13: No), the process moves to step S14.

[0070] When moving from step S13 to step S14, the control unit 96 determines whether the second drain valve 58 is currently in the open state. Step S14 is performed to prevent the second drain valve 58 from changing from the open state to the closed state when an opening request is made. If it is determined that the second drain valve 58 is in the open state (step S14: Yes), the process moves to step S15. On the other hand, if it is determined that the second drain valve 58 is not in the open state, i.e., the second drain valve 58 is in the closed state (step S14: No), the process moves to step S16.

[0071] When moving from step S13 or S14 to step S15, the control unit 96 opens the second drain valve 58. If the second drain valve 58 is already open, the control unit 96 maintains the open state of the second drain valve 58. Conversely, if the second drain valve 58 is closed, the control unit 96 opens the second drain valve 58. A portion of the water in the anode flow path 36 and anode exhaust gas flows in the second drain flow path 48 and the first drain flow path 46 and is discharged to the diluter 60.

[0072] When moving from step S11, S12, or S14 to step S16, the control unit 96 closes the second drain valve 58. If the second drain valve 58 is already closed, the control unit 96 maintains the closed state of the second drain valve 58. Conversely, if the second drain valve 58 is open, the control unit 96 closes the second drain valve 58.

[0073] [4-3 Compressor Control Processing]

[0074] Figure 4 This is a flowchart of the compressor control process. The control unit 96 repeatedly performs this process during the operation of the fuel cell system 10. Figure 4 The compressor control process is shown.

[0075] In step S21, the control unit 96 determines whether there is a request to open the first drain valve 56 or the second drain valve 58. If it is determined that there is a request to open at least one valve (step S21: Yes), the process proceeds to step S22. On the other hand, if it is determined that there are no requests to open either valve (step S21: No), the process proceeds to step S23.

[0076] When moving from step S21 to step S22, the control unit 96 switches the rotational speed of the compressor 68 from a low-speed state (including the stop state) to a high-speed state. If the compressor 68 is already at a high-speed state, the control unit 96 maintains the rotational speed of the compressor 68. On the other hand, if the compressor 68 is at a low-speed state, the control unit 96 increases the rotational speed of the compressor 68. This increases the ejection flow rate of air from the compressor 68 to the cathode supply flow path 62A. Consequently, the amount of air supplied to the diluter 60 increases. Furthermore, the control unit 96 opens the bypass valve 78 as needed to prevent the interior of the fuel cell stack 12 from drying out due to the increased air volume.

[0077] When moving from step S21 to step S23, the control unit 96 switches the rotational speed of the compressor 68 from a high-speed state to a low-speed state (including a stop state). When the compressor 68 is already at a low speed, the control unit 96 maintains the rotational speed of the compressor 68. Conversely, when the compressor 68 is at a high speed, the control unit 96 reduces the rotational speed of the compressor 68.

[0078] [5. Changes in the opening and closing status of each valve and the amount of dilution air over time]

[0079] Figure 5 It is a timing diagram showing the opening and closing status of each valve in the prior art, the amount of diluted air injected by the compressor 68, and whether there is a requirement to open the second drain valve 58. Figure 6 This is a timing diagram showing the opening and closing states of each valve in this embodiment, the amount of dilution air ejected by the compressor 68, and whether there is a requirement to open the second drain valve 58.

[0080] like Figure 5 As shown, in the prior art, the opening period (t01-t02) of the first drain valve 56 is separated from the opening period (t03-t04) of the second drain valve 58. The diluent 60 requires a large amount of air during the opening timing of the first drain valve 56 (t01) and the opening timing of the second drain valve 58 (t03). Therefore, the control unit 96 switches the rotational speed of the compressor 68 from low speed to high speed during the opening timing of the first drain valve 56 (t01) and the opening timing of the second drain valve 58 (t03), respectively. Furthermore, the control unit 96 switches the rotational speed of the compressor 68 from high speed to low speed during the closing timing of the first drain valve 56 (t02) and the closing timing of the second drain valve 58 (t04), respectively.

[0081] like Figure 6 As shown, in this embodiment, the opening period (t11-t12) of the first discharge valve 56 and the opening period (t12-t13) of the second discharge valve 58 are continuous. Therefore, the control unit 96 switches the rotational speed of the compressor 68 from low speed to high speed during the opening timing (t11) of the first discharge valve 56. Furthermore, the control unit 96 switches the rotational speed of the compressor 68 from high speed to low speed during the closing timing (t13) of the second discharge valve 58. On the other hand, the control unit 96 maintains the rotational speed of the compressor 68 during the closing timing (t12) of the first discharge valve 56 and the opening timing (t12) of the second discharge valve 58. In other words, no vibration or noise changes occur in the compressor 68 during the closing timing (t12) of the first discharge valve 56 and the opening timing (t12) of the second discharge valve 58.

[0082] like Figure 6As shown, the control unit 96 will not open more than two of the following valves simultaneously: the first discharge valve 56, the second discharge valve 58, and the discharge valve 82. When more than two valves are open, a large amount of air is required to dilute the hydrogen. In this case, the compressor 68 needs to rotate at high speed. As a result, the vibration, noise, and power consumption of the compressor 68 increase. Therefore, there are concerns that this will annoy the user. Moreover, fuel efficiency deteriorates. Therefore, the control unit 96 will not open other valves while one valve is open.

[0083] [6. Invention obtained according to the embodiments]

[0084] The invention that can be mastered according to the above embodiments is described below.

[0085] A first aspect of the present invention relates to a fuel cell system 10, comprising: a fuel cell stack 12 that generates electricity using anode gas in an anode flow path 36 and cathode gas in a cathode flow path 38; a gas-liquid separator 54 that separates discharge fluid from the anode flow path into gas and water; a first discharge flow path 46 that discharges the water and gas from the gas-liquid separator to the outside; a second discharge flow path 48 that discharges the discharge fluid from the anode flow path to the outside; a first valve 56 that opens and closes the first discharge flow path; a second valve 58 that opens and closes the second discharge flow path; a compressor 68 that supplies air for diluting the discharge fluid and gas to be discharged to the outside; and a control unit 96 that controls the opening and closing of the first valve and the second valve, respectively. The control unit opens the second valve at a time when the first valve is closed, and maintains the operation of the compressor as it was before closing the first valve after the second valve is opened.

[0086] In the first embodiment, the second valve opens at the time when the first valve closes, and the compressor continues to operate during this period. Therefore, in the first embodiment, it is not necessary to significantly reduce the compressor's rotational speed when the first valve closes. Furthermore, in the first embodiment, it is not necessary to significantly increase the compressor's rotational speed when the second valve opens. Thus, according to the first embodiment, the number of significant changes in compressor vibration and noise can be reduced.

[0087] Alternatively, in the above-described manner, the diameter of the internal flow path of the first valve and the diameter of the internal flow path of the second valve may be the same.

[0088] Based on the above structure, the compressor's rotational speed can be kept approximately constant when the valve being opened is switched from the first valve to the second valve. Therefore, the compressor's vibration and noise will not change when the valve being opened is switched from the first valve to the second valve.

[0089] A second aspect of the present invention relates to a method for reducing vibration and noise in a fuel cell system, the fuel cell system comprising: a fuel cell stack that generates electricity using anolyte gas in an anode path and cathode gas in a cathode path; a gas-liquid separator that separates discharge fluid from the anode path into gas and water; a first discharge path that discharges the water and gas from the gas-liquid separator to the outside; a second discharge path that discharges the discharge fluid from the anode path to the outside; a first valve that opens and closes the first discharge path; a second valve that opens and closes the second discharge path; a compressor that supplies air for diluting the discharge fluid and gas to be discharged to the outside; and a computer 94 that controls the opening and closing of the first valve and the second valve, wherein in the method for reducing vibration and noise in the fuel cell system, the computer opens the second valve at a timed interval when the first valve is closed, and maintains the operation of the compressor as before the first valve was closed after the second valve is opened.

[0090] Furthermore, the present invention is not limited to the above disclosure and various structures can be adopted without departing from the spirit of the present invention.

Claims

1. A fuel cell system comprising: The fuel cell stack (12) generates electricity using the anode gas in the anode flow path (36) and the cathode gas in the cathode flow path (38); A gas-liquid separator (54) separates the discharge fluid from the anode flow path into gas and water; The first discharge path (46) discharges the water and gas from the gas-liquid separator to the outside; The second discharge flow path (48) discharges the discharge fluid in the anode flow path to the outside; The first valve (56) opens and closes the first discharge path; The second valve (58) opens and closes the second discharge path; Compressor (68) supplies air for diluting the discharge fluid and the gas to be discharged to the outside; as well as The control unit (96) controls the opening and closing of the first valve and the second valve respectively. In the fuel cell system (10), The control unit opens the second valve at a timed interval when the first valve is closed, and maintains the compressor's operating state before the first valve was closed even after the second valve is opened.

2. The fuel cell system according to claim 1, characterized in that, The diameter of the internal flow path of the first valve is the same as the diameter of the internal flow path of the second valve.

3. A method for reducing vibration and noise in a fuel cell system, the fuel cell system comprising: A fuel cell stack generates electricity using anolyte gas in the anode flow path and cathode gas in the cathode flow path. A gas-liquid separator that separates the discharge fluid from the anode flow path into gas and water; The first discharge path discharges the water and gas from the gas-liquid separator to the outside; The second discharge flow path discharges the discharge fluid from the anode flow path to the outside; The first valve opens and closes the first discharge path; The second valve opens and closes the second discharge path; A compressor that supplies air for diluting the discharge fluid and the gas to be discharged to the outside; as well as Computer (94), which controls the opening and closing of the first valve and the second valve respectively. In the method for reducing vibration and noise in the fuel cell system, The computer opens the second valve at the timed interval when it closes the first valve. Furthermore, the compressor maintains the same operating state as before the first valve was closed, even after the second valve is opened.

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