fuel cell system

Abstract

To enable an open / close valve to open and close promptly even when a fuel cell system is started up when the outside temperature is below freezing.SOLUTION: The fuel cell system includes a fuel cell stack and a humidifier (62). Piping (84) is provided at an outlet (62o) of the humidifier. Gas that has been distributed through the humidifier is distributed in a distribution channel (86) formed in the piping. An open / close valve (74) is provided at an outlet (86o) of the distribution channel. Furthermore, the fuel cell system includes a water storage part (92) that is connected to the distribution channel. The water storage part is disposed at a lower level than the distribution channel. The open / close valve is disposed at a higher level than the water storage part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system including a fuel cell stack and a humidifier. [Background technology]

[0002] In recent years, research and development into fuel cells, which contribute to energy efficiency, has been conducted to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. Furthermore, regulations on automobile exhaust gases have become more stringent to reduce the burden on the global environment. From this perspective, attempts have been made to install fuel cell systems in automobiles instead of internal combustion engines. Fuel cell systems emit less CO2, SO X and NO X This is because no waste products or the like are discharged.

[0003] A fuel cell system includes a fuel cell stack in which a plurality of unit cells are stacked. When the fuel cell stack is operated, fuel gas is supplied to the anode electrode of each unit cell, and oxidant gas is supplied to the cathode electrode of each unit cell. Water is produced at the cathode electrode through an electrode reaction. Therefore, excess oxidant gas and produced water are discharged from the cathode electrode together. Hereinafter, the excess oxidant gas that has passed through the cathode electrode will be referred to as cathode off-gas.

[0004] The cathode off-gas is sent to a humidifier. A porous membrane is provided inside the humidifier. The produced water in the cathode off-gas is separated from the oxidant gas by the porous membrane. Here, the oxidant gas newly supplied to the cathode electrode flows through the humidifier. The produced water separated from the cathode off-gas is supplied to the oxidant gas. The oxidant gas moistened by the produced water is supplied from the humidifier to the cathode electrode. In this way, both the oxidant gas supplied to the cathode electrode and the cathode off-gas that has passed through the cathode electrode contain moisture.

[0005] A pipe is provided between the humidifier and the fuel cell stack. Patent Document 1 proposes providing a water trap in the pipe that sends oxidant gas from the humidifier to the fuel cell stack. Patent Document 1 describes that condensed water is stored in the water trap, which makes it possible to prevent condensed water from accumulating in the fuel cell stack and the humidifier. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5157086 Summary of the Invention [Problem to be solved by the invention]

[0007] An on-off valve is installed in the piping around the humidifier. Moisture contained in the cathode off-gas or oxidant gas can adhere to this on-off valve, causing condensation. If the outside temperature is below freezing, the condensed water freezes during the fuel cell stack soak. Generally, the on-off valve is closed during the fuel cell stack soak. If freezing occurs in this state, it becomes difficult to open the on-off valve until the fuel cell system reaches a predetermined temperature.

[0008] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0009] According to one embodiment of the present invention, there is provided a fuel cell system including a fuel cell stack, the fuel cell system comprising: a humidifier into which oxidant gas supplied to a cathode electrode of the fuel cell stack and cathode off-gas discharged from the fuel cell stack are introduced; piping formed with a flow passage through which either the oxidant gas that has flowed through the humidifier or the cathode off-gas that has flowed through the humidifier flows; an on-off valve provided at an outlet of the flow passage, the on-off valve opening the flow passage while the fuel cell stack is operating and closing the flow passage while the fuel cell stack is soaking; and a water storage section connected to the flow passage, wherein when a relatively low position in the vertical direction is defined as a low position and a relatively high position in the vertical direction is defined as a high position, the water storage section is positioned lower than the flow passage and the on-off valve is positioned higher than the water storage section. [Effects of the Invention]

[0010] During the soaking of the fuel cell stack, water contained in the oxidant gas or cathode off-gas condenses, resulting in condensed water. Because the water reservoir is located lower than the flow passage, the condensed water flows into the water reservoir by gravity. Because the on-off valve is located higher than the water reservoir, it is difficult for the condensed water stored in the water reservoir to move to the on-off valve.

[0011] For the reasons described above, condensed water is prevented from coming into contact with the on-off valve. Therefore, even in an environment where freezing is possible, such as when the outside air temperature is below freezing, there is no risk of water adhering to the on-off valve freezing. Therefore, even when the fuel cell system is started up when the outside air temperature is below freezing, the on-off valve can quickly open and close. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic system diagram of a fuel cell system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view of a connection structure between a humidifier and an on-off valve via a pipe. [Figure 3]FIG. 3 is a schematic vertical cross-sectional view of the connection structure when the fuel cell stack is in operation. [Figure 4] FIG. 4 is a schematic vertical cross-sectional view of the connection structure immediately after the fuel cell stack has stopped operating. [Figure 5] FIG. 5 is a schematic vertical cross-sectional view of the connection structure when the fuel cell stack is soaking. [Figure 6] FIG. 6 is a schematic vertical cross-sectional view of the connection structure immediately after the fuel cell stack starts operating. [Figure 7] FIG. 7 is a schematic system diagram of a fuel cell system according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a schematic vertical cross-sectional view of the connection structure when the fuel cell stack is soaking. [Figure 9] FIG. 9 is a schematic vertical cross-sectional view of the connection structure immediately after the fuel cell stack starts operating. [Figure 10] FIG. 10 is a schematic vertical cross-sectional view of the connection structure when the fuel cell stack is in operation. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, anode off-gas refers to excess fuel gas discharged from the anode electrode 22 of the fuel cell stack 12 shown in FIGS. 1 and 7. Cathode off-gas refers to excess oxidant gas discharged from the cathode electrode 24 of the fuel cell stack 12. Furthermore, "upstream" and "downstream" refer to upstream and downstream in the flow direction of the oxidant gas and cathode off-gas, respectively. "High" refers to a relatively high position in the vertical direction, and "low" refers to a relatively low position in the vertical direction. "High" and "low" are not limited to being arranged vertically one above the other.

[0014] First, a fuel cell system 10 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is simplified to facilitate understanding of the flow processes of fuel gas and oxidant gas. Therefore, the directions shown in Fig. 1 do not necessarily match the directions in the actual fuel cell system 10. Also, valves other than the first on-off valve 72, the second on-off valve 74, and the bypass valve 78 are omitted from Fig. 1. The same applies to Fig. 7, which will be described later.

[0015] The fuel cell system 10 includes a fuel cell stack 12. The fuel cell stack 12 is formed by stacking a plurality of unit cells 14. The unit cell 14 is formed by sandwiching a membrane electrode assembly (MEA) 16 between a first separator 18 and a second separator 20. The MEA 16 is formed by sandwiching an electrolyte membrane 26 between an anode electrode 22 and a cathode electrode 24. The first separator 18 and the second separator 20 are made of a material such as a metal. The electrolyte membrane 26 is made of a material such as a water-containing solid polymer such as perfluorosulfonic acid.

[0016] A first gas flow path 30 is formed in the first separator 18. Hydrogen gas (fuel gas) supplied to the anode electrode 22 flows through the first gas flow path 30. A second gas flow path 32 is formed in the second separator 20. Compressed air (oxidizer gas) supplied to the cathode electrode 24 flows through the second gas flow path 32. In adjacent unit cells 14, a coolant flow path (not shown) is formed between the first separator 18 and the second separator 20. A coolant flows through the coolant flow path.

[0017] The fuel cell stack 12 is formed with a hydrogen inlet 34 and a hydrogen outlet 36. The hydrogen inlet 34 is connected to the inlet of the first gas flow path 30. The outlet of the first gas flow path 30 is connected to the hydrogen outlet 36. The fuel cell stack 12 is formed with an air inlet 38 and an air outlet 40. The air inlet 38 is connected to the inlet of the second gas flow path 32. The outlet of the second gas flow path 32 is connected to the air outlet 40.

[0018] The fuel cell system 10 includes a high-pressure tank 50 and an ejector 52. The high-pressure tank 50 is filled with hydrogen gas. A first supply line 54 is provided between the high-pressure tank 50 and the fuel cell stack 12. The ejector 52 is provided on the first supply line 54 and supplies hydrogen gas to the anode electrode 22. The hydrogen gas sent from the ejector 52 flows toward the hydrogen inlet 34.

[0019] A gas-liquid separator 58 is connected to the fuel cell stack 12 via a first exhaust line 56. The anode off-gas discharged from the hydrogen outlet 36 is sent to the gas-liquid separator 58 via the first exhaust line 56. The anode off-gas is separated into hydrogen gas and water (liquid water) in the gas-liquid separator 58. The hydrogen gas is returned to the ejector 52 and then resupplied to the anode electrode 22.

[0020] The fuel cell system 10 further includes an air pump 60, a humidifier 62, and a circulation pump 64. The air pump 60 generates compressed air by compressing atmospheric air, for example. The fuel cell stack 12 and the humidifier 62 are connected via a second supply line 68 and a second exhaust line 70. The compressed air obtained by the air pump 60 is supplied with water (generated water PW, described below) generated during power generation by the fuel cell stack 12 in the humidifier 62. This wets the compressed air. The wetted compressed air flows toward the air inlet 38 via the second supply line 68. In this way, the second supply line 68 is an oxidant gas supply line for supplying compressed air (oxidant gas). The circulation pump 64 may be omitted.

[0021] The cathode off-gas discharged from the air outlet 40 is sent to the humidifier 62 via the second exhaust line 70. Water in the cathode off-gas is separated from the compressed air in the humidifier 62. The compressed air is resupplied to the cathode electrode 24 by, for example, a circulation pump 64. Meanwhile, the water is supplied to new compressed air sent from the air pump 60, as described above.

[0022] A first on-off valve 72 is provided in the second supply line 68 upstream of the humidifier 62. A second on-off valve 74 is provided in the second exhaust line 70 downstream of the humidifier 62.

[0023] A bypass line 76 branches off from the second supply line 68. The bypass line 76 merges with the second supply line 68 downstream of the humidifier 62 in the second supply line 68. In other words, the bypass line 76 bypasses the humidifier 62. A bypass valve 78 is provided in the bypass line 76.

[0024] The fuel cell system 10 is controlled by a control device 80. The control device 80, for example, switches each of the first on-off valve 72, the second on-off valve 74, and the bypass valve 78 from an open state to a closed state. Alternatively, the control device 80 switches each of the first on-off valve 72, the second on-off valve 74, and the bypass valve 78 from a closed state to an open state. The control device 80 can also maintain each of the first on-off valve 72, the second on-off valve 74, and the bypass valve 78 in either an open state or a closed state.

[0025] The fuel cell system 10 configured in this manner is mounted on the body of an automobile, for example.

[0026] 2 is a schematic vertical cross-sectional view of a connecting structure 82 that connects the cathode off-gas outlet (exhaust port 62o) of the humidifier 62 to the second on-off valve 74. Note that Fig. 2 shows a case where the fuel cell stack 12 is soaking. The humidifier 62 and the second on-off valve 74 are connected via a connecting pipe 84. The connecting pipe 84 is part of the second exhaust line 70.

[0027] The up-down direction in Fig. 2 corresponds to the vertical direction. That is, the upside in Fig. 2 corresponds to the upside when the fuel cell system 10 is mounted on a vehicle body or the like. The downside in Fig. 2 corresponds to the downside when the fuel cell system 10 is mounted on a vehicle body or the like. As can be seen from Fig. 2, the outlet 62o of the humidifier 62 opens facing vertically downward.

[0028] An exhaust path 86, which is a circulation passage, is formed in the connecting pipe 84. An inlet 86i of the exhaust path 86 faces the exhaust outlet 62o of the humidifier 62 and opens to extend along the horizontal direction. The exhaust path 86 has a first flow path 88 and a second flow path 90. The first flow path 88 is slightly inclined with respect to the vertical direction. The second flow path 90 intersects with the first flow path 88 at a predetermined angle. As a result, the exhaust path 86 is bent in a substantially L-shape. Therefore, an outlet 86o of the exhaust path 86 (second flow path 90) opens to extend along the vertical direction. The lowest point of the outlet 86o of the exhaust path 86 is the lowest point P1.

[0029] Below the second flow path 90, a recessed space communicating with the second flow path 90 is formed. This recessed space is a water storage section 92 that stores water. The water storage section 92 is located lower than the lowest point P1. In FIG. 2, the boundary between the second flow path 90 and the water storage section 92 is indicated by a boundary line L1. As can be seen from the above, the water storage section 92 is located lower than the second flow path 90 of the exhaust path 86, and is connected to the second flow path 90.

[0030] A recess 94 is formed in the first flow path 88, recessed toward the second on-off valve 74. The cross section of the recess 94 as viewed from the direction along the extension of the first flow path 88 is substantially triangular. The peak on the lower side of the recess 94 is near the boundary between the first flow path 88 and the second flow path 90. Therefore, the cross-sectional area of ​​the first flow path 88 is large at the valley of the recess 94 and small near the boundary between the first flow path 88 and the second flow path 90. In other words, the cross-sectional area of ​​the first flow path 88 is large upstream away from the water storage portion 92 and small downstream close to the water storage portion 92. In this way, the exhaust path 86 has a portion (cross-sectional area change region 87) where the cross-sectional area decreases as it approaches the water storage portion 92.

[0031] The downstream end of the cross-sectional area change region 87 is a throttle portion 87a, which has the smallest cross-sectional area in the cross-sectional area change region 87. The throttle portion 87a is located above the water storage portion 92 and faces the water storage portion 92. The water storage portion 92 has an end portion 92e that is farther from the outlet 86o of the exhaust path 86. The throttle portion 87a faces the end portion 92e of the water storage portion 92. The water storage portion 92 has a bottom portion 92a, which is the lowest portion in the water storage portion 92, and an inclined portion 92b that slopes toward the bottom portion 92a. The bottom portion 92a is located closer to the outlet 86o than the inclined portion 92b. The inclined portion 92b faces the throttle portion 87a below the throttle portion 87a. A part of the inclined portion 92b is the end portion 92e. The cross-sectional area of ​​the first flow path 88 is the cross-sectional area in a direction perpendicular to the flow direction of the cathode off-gas.

[0032] A second on-off valve 74 is provided at the outlet 86o of the exhaust passage 86 (second flow path 90). The second on-off valve 74 is a so-called butterfly valve, and has a housing 100, a rotating shaft 102, and a valve element 104. The housing 100 is connected to the connecting pipe 84 via bolts or the like (not shown). The rotating shaft 102 is rotatably supported by the housing 100. The valve element 104 is provided on the rotating shaft 102, and rotates integrally with the rotating shaft 102.

[0033] The height position of the valve body 104 of the second on-off valve 74 is approximately equal to the height position of the outlet 86o of the exhaust path 86. In other words, the second on-off valve 74 is disposed at a higher position than the water storage portion 92.

[0034] The fuel cell system 10 according to the first embodiment is basically configured as described above. Next, the effects of the fuel cell system 10 will be described.

[0035] The fuel cell system 10 is mounted on, for example, the body of an automobile. The fuel cell system 10 is activated when the automobile is driven. At this time, hydrogen gas is supplied from the high-pressure tank 50 to the fuel cell stack 12 via the first supply line 54 based on a command signal from a control device 80 (see FIG. 1). In addition, the control device 80 opens the first on-off valve 72 and the second on-off valve 74 and closes the bypass valve 78 based on the command signal. In other words, the second supply line 68 and the second exhaust line 70 are opened.

[0036] The second on-off valve 74 in the open state is shown in Figure 3. At this time, the rotary shaft 102 and the valve element 104 rotate integrally, opening the outlet 86o of the exhaust path 86. Therefore, the cathode off-gas can flow from the humidifier 62 toward the circulation pump 64.

[0037] The hydrogen gas passes through the ejector 52 and flows into the first gas flow passage 30 from the hydrogen inlet 34. While flowing through the first gas flow passage 30, the hydrogen gas comes into contact with the anode electrode 22 and undergoes an oxidation reaction. The excess hydrogen gas (anode off-gas), which contains moisture, is discharged from the first gas flow passage 30 through the hydrogen outlet 36 to the first exhaust line 56.

[0038] Thereafter, the water in the anode off-gas is separated from the hydrogen gas in the gas-liquid separator 58. The hydrogen gas with reduced humidity flows into the ejector 52. In the ejector 52, new hydrogen gas supplied from the high-pressure tank 50 and the hydrogen gas discharged from the gas-liquid separator 58 are merged. The merged hydrogen gas flows into the first gas flow path 30 via the same route as above, and the above circulation is repeated thereafter.

[0039] Meanwhile, compressed air is supplied from the air pump 60 to the fuel cell stack 12 via the second supply line 68. The compressed air flows through the humidifier 62. At this time, moisture is added to the compressed air. That is, the humidity of the compressed air increases. The compressed air flows into the second gas flow path 32 from the air inlet 38. As the oxygen in the compressed air flows through the second gas flow path 32, it comes into contact with the cathode electrode 24 and a reduction reaction occurs. In this reduction reaction, water is produced. This water is the produced water PW shown in FIG. 3.

[0040] The produced water PW is discharged together with excess compressed air (cathode off-gas) from the second gas flow path 32 via the air outlet 40 to the second exhaust line 70. The cathode off-gas containing the produced water PW flows into the humidifier 62. In the humidifier 62, the compressed air and the produced water PW are separated when the cathode off-gas passes through a porous membrane (not shown). This means that the humidity of the compressed air decreases. All or part of the compressed air is returned to the humidifier 62 by the circulation pump 64 (see FIG. 1). Along the way, the compressed air and new compressed air sent from the air pump 60 merge. The merged compressed air flows into the humidifier 62. At this time, the produced water PW is supplied to the compressed air as moisture, as described above. The moisture-supplied compressed air flows into the second gas flow path 32 via the same path as described above. The above circulation is then repeated.

[0041] The cathode off-gas discharged from the outlet 62o of the humidifier 62 (see FIG. 3) flows through the exhaust path 86 of the connecting pipe 84. Here, the cathode off-gas contains the produced water PW as described above. The produced water PW condenses, for example, on the inner wall of the first flow path 88 or the second flow path 90, forming droplets that move to a lower level. Since the second flow path 90 is connected to the water storage section 92, the produced water PW is collected in the water storage section 92. As a result, the produced water PW is stored in the water storage section 92. If the amount of stored produced water PW exceeds the maximum capacity of the water storage section 92, the excess produced water PW is discharged from the second on-off valve 74, which remains open.

[0042] When the operation of the automobile is stopped, for example, by parking, the operation of the fuel cell system 10 is also stopped. At this time, the control device 80 closes the first on-off valve 72 and opens the bypass valve 78 (see FIG. 1). The control device 80 also continues to operate the air pump 60 and maintains the second on-off valve 74 in an open state. Therefore, the compressed air supplied from the air pump 60 passes through the bypass line 76 and the second gas flow path 32, and flows from the second exhaust line 70 into the humidifier 62. The compressed air is not moistened in the humidifier 62, and flows into the exhaust path 86 of the connecting pipe 84 through the outlet 62o, as shown in FIG. 4.

[0043] As described above, the cross-sectional area of ​​the first flow path 88 of the exhaust passage 86 decreases downstream (at the throttle portion 87a) near the water storage portion 92. The throttle portion 87a forms a nozzle-shaped inlet from the first flow path 88 to the second flow path 90. Therefore, the flow velocity of the compressed air flowing into the second flow path 90 is greater than the flow velocity of the compressed air flowing through the first flow path 88. Because the second flow path 90 is connected to the water storage portion 92, the compressed air, whose flow velocity increases and flows into the second flow path 90, is guided by the inclined portion 92b and flows through. As a result, as shown in FIG. 4 , the compressed air blows (purges) the produced water PW remaining in the water storage portion 92 toward the outlet 86o. Because the flow velocity of the compressed air flowing into the second flow path 90 is sufficiently increased, much of the produced water PW remaining in the water storage portion 92 is discharged from the water storage portion 92 via the second on-off valve 74. In this way, according to the first embodiment, the amount of generated water PW remaining in the water storage section 92 can be reduced.

[0044] The compressed air and the produced water PW are discharged from the second on-off valve 74, which remains open. The compressed air is returned to the bypass line 76 by, for example, the circulation pump 64 and resupplied to the second gas flow path 32. Alternatively, the compressed air is released into the atmosphere. The produced water PW is discharged, for example, into the atmosphere.

[0045] After a predetermined time has elapsed, the control device 80 closes the bypass valve 78 and the second on-off valve 74. This puts the fuel cell stack 12 into a soak state. During the soak, as shown in FIG. 5, water vapor that has accumulated inside the humidifier 62 condenses. Water vapor that has accumulated in the exhaust path 86 of the connecting pipe 84 also condenses. The liquid water (condensed water DW) produced by the condensation is stored in the water storage section 92 in the same manner as described above. As shown in FIG. 4, at this point, much of the generated water PW has already been discharged from the water storage section 92. Therefore, the water storage capacity of the water storage section 92 is sufficiently ensured. This prevents the amount of condensed water DW from exceeding the maximum capacity of the water storage section 92, and therefore prevents the liquid level of the condensed water DW from exceeding the lowest point P1.

[0046] That is, the condensed water DW is prevented from coming into contact with the valve body 104. Therefore, even if the outside air temperature drops below freezing and the condensed water DW freezes, the valve body 104 is prevented from adhering to the housing 100 or the like through the frozen condensed water DW.

[0047] When starting up the fuel cell system 10 under conditions where freezing is predicted, such as when the outside air temperature is below freezing, the control device 80 performs a warm-up operation. Specifically, the control device 80 controls the supply of hydrogen gas to the fuel cell stack 12 via the first supply line 54 and the supply of compressed air to the fuel cell stack 12 via the second supply line 68. At this time, the control device 80 causes the fuel cell stack 12 to generate power at a low current density. Therefore, the amounts of anode off-gas and cathode off-gas generated are relatively small.

[0048] As the fuel cell stack 12 generates electricity, the temperature of the cathode off-gas rises. The cathode off-gas flows into the exhaust path 86 of the connecting pipe 84 via the outlet 62o of the humidifier 62. The cathode off-gas comes into contact with the condensed water DW in the water storage portion 92. Therefore, if the condensed water DW in the water storage portion 92 is frozen, the condensed water DW melts. Cathode offgasThis is because heat is transferred from the valve body 104 to the condensed water DW. Similarly, if the valve body 104 is fixed to the housing 100 or the like through the frozen condensed water DW, the condensed water DW will melt. Therefore, at this point, the second on-off valve 74 is in the open state.

[0049] As shown in FIG. 6, the condensed water DW that has melted and become liquid is blown away by the cathode off-gas that has flowed into the second flow path 90. For the same reason as above, the flow rate of the cathode off-gas that has flowed into the second flow path 90 is sufficiently increased. Therefore, most of the condensed water DW is discharged from the water storage section 92 via the second on-off valve 74. As described above, according to the first embodiment, it is possible to prevent the second on-off valve 74 from becoming inoperable due to freezing. Furthermore, even if freezing occurs, it is possible to quickly make the second on-off valve 74 operable.

[0050] Next, a fuel cell system 110 according to a second embodiment will be described with reference to Figures 7 to 10. Note that the same components as those shown in Figures 1 to 6 are given the same reference numerals, and detailed description thereof will be omitted.

[0051] The fuel cell system 110 includes a purge gas supply line 112 shown in Fig. 7. The purge gas supply line 112 branches off from the second supply line 68 upstream of the first on-off valve 72. The purge gas supply line 112 extends toward a connecting pipe 116 that constitutes a connecting structure 114 shown in Fig. 8. Compressed air diverted from the second supply line 68 flows through the purge gas supply line 112.

[0052] As shown in Fig. 8, the humidifier 62 and the second on-off valve 74 are connected via a connecting pipe 116. The connecting pipe 116 is part of the second exhaust line 70. Note that Fig. 8 shows the case where the fuel cell stack 12 is soaking.

[0053] The up-down direction in Fig. 8 corresponds to the vertical direction. That is, the upside in Fig. 8 corresponds to the upside when the fuel cell system 110 is mounted on a vehicle body or the like. The downside in Fig. 8 corresponds to the downside when the fuel cell system 110 is mounted on a vehicle body or the like. As in Fig. 2, the outlet 62o of the humidifier 62 opens facing vertically downward.

[0054] An exhaust path 118, which is a flow passage, is formed in the connecting pipe 116. An inlet 118i of the exhaust path 118 faces the exhaust outlet 62o of the humidifier 62 and opens to extend horizontally. The exhaust path 118 is curved in a C-shape. Therefore, an outlet 118o of the exhaust path 118 opens to extend vertically. The lowest point of the exhaust path 118 is the lowest point P2.

[0055] A water reservoir 120 is formed below the exhaust path 118. That is, the water reservoir 120 is disposed at a lower position than the exhaust path 118. The uppermost point of the water reservoir 120 is disposed at a lower position than the lowermost point P2 of the exhaust path 118. The water reservoir 120 is formed in the connecting pipe 116 as a space branched off from the exhaust path 118. The water reservoir 120 communicates with the exhaust path 118 via a communication passage 122. Specifically, the communication passage 122 extends from the bottom of the water reservoir 120 to the vicinity of the outlet 118o of the exhaust path 118. The cross-sectional area of ​​the communication passage 122 is smaller than the cross-sectional area of ​​the exhaust path 118. Here, the cross-sectional areas of the exhaust path 118 and the communication passage 122 refer to the cross-sectional areas in a direction perpendicular to the flow direction of the cathode off-gas. The volume of the water reservoir 120 is larger than the volume of the communication passage 122.

[0056] A purge gas supply path 124 is formed in the connecting pipe 116. The purge gas supply path 124 extends, for example, from near the curved top of the exhaust path 118 toward the top of the water storage section 120. An outlet 124a (downstream end) of the purge gas supply path 124 is connected to the top of the water storage section 120. The purge gas supply line 112 is connected to the purge gas supply path 124 via a joint member (not shown). In this way, compressed air, which serves as a purge gas, can be supplied to the water storage section 120 via the purge gas supply line 112 and the purge gas supply path 124. The pressure of the compressed air flowing through the purge gas supply path 124 is higher than the pressure of the cathode off-gas flowing through the exhaust path 118.

[0057] A ring member 126 is positioned and fixed near the outlet 118o of the exhaust path 118. The ring member 126 is located downstream of the communicating path 122. The ring member 126 protrudes inward from the inner wall of the exhaust path 118. The surface of the ring member 126 facing the inside (upstream) of the connecting pipe 116 serves as a guide wall that guides the condensation water DW to the communicating path 122. The ring member 126 may be replaced by an arc-shaped member having a C-shape (snap ring shape). In this case, the opening of the C faces vertically downward.

[0058] A heater 128, which is a heating unit, is provided on the outside of the portion of the connecting pipe 116 where the water storage unit 120 is formed. The heater 128 heats the water storage unit 120 when in an ON state.

[0059] A second on-off valve 74 is provided at the outlet 118o of the exhaust path 118. That is, the humidifier 62 and the second on-off valve 74 are connected via a connecting pipe 116. The height position of the valve body 104 of the second on-off valve 74 is approximately the same as the height position of the outlet 118o of the exhaust path 118. That is, the valve body 104 is disposed at a higher position than the water storage section 120.

[0060] The fuel cell system 110 is started, for example, when the automobile is driven. When the outside air temperature at the time of start-up is, for example, below freezing to several degrees Celsius, the control device 80 (see FIG. 1) determines that "freezing of the condensed water DW in the connecting structure 114 is expected." In this case, the control device 80 switches the heater 128 to the ON state. If the condensed water DW is frozen, the condensed water DW will melt as it is heated by the heater 128. In contrast, when the outside air temperature is, for example, 10 degrees Celsius or higher, the control device 80 determines that "freezing of the condensed water DW in the connecting structure 114 is not expected." In this case, the control device 80 keeps the heater 128 in the OFF state.

[0061] Meanwhile, based on a command signal from the control device 80, hydrogen gas is supplied from the high-pressure tank 50 to the fuel cell stack 12 via the first supply line 54. The control device 80 also opens the first on-off valve 72 and the second on-off valve 74 in response to the command signal. Because the condensed water DW is in a liquid phase in the connecting structure 114, the second on-off valve 74 can easily be opened. This opens the second supply line 68, the second exhaust line 70, and the purge gas supply line 112. Accordingly, compressed air is supplied to the cathode electrode 24 via the second supply line 68. Furthermore, cathode off-gas is discharged from the cathode electrode 24 to the second exhaust line 70.

[0062] The second on-off valve 74 in the open state is shown in Figure 9. At this time, the rotary shaft 102 and the valve element 104 rotate integrally, opening the outlet 118o of the exhaust path 118. Therefore, the cathode off-gas can flow from the humidifier 62 toward the circulation pump 64.

[0063] Furthermore, a portion of the compressed air flowing through the second supply line 68 is diverted to the purge gas supply line 112. This compressed air flows through the purge gas supply line 112 and is supplied as purge gas to the purge gas supply path 124, as shown in FIG. 9. The purge gas flows into the water storage unit 120 from the outlet 124a of the purge gas supply path 124. The purge gas presses the condensed water DW stored in the water storage unit 120 from above. As a result, the condensed water DW pressed by the purge gas is blown out of the water storage unit 120 and discharged through the second on-off valve 74, which is in the open state. As a result, the amount of water stored in the water storage unit 120 becomes approximately zero.

[0064] Thereafter, the fuel cell stack 12 is operated in the same manner as in the first embodiment. During this operation, as shown in FIG. 10 , purge gas is supplied to the water storage unit 120 via the purge gas supply line 112 and the purge gas supply path 124. That is, purge gas is continuously supplied to the water storage unit 120 from the start-up. The purge gas flows from the water storage unit 120 through the communication path 122 into the exhaust path 118. The purge gas is then discharged from the exhaust path 118 via the outlet 118o of the exhaust path 118 and the second on-off valve 74.

[0065] The purge gas discharged from the communication passage 122 forms an air curtain in the communication passage 122. This prevents the produced water PW contained in the cathode off-gas from entering the water storage unit 120 from the communication passage 122. Therefore, the produced water PW is discharged together with the cathode off-gas from the exhaust path 118 via the second on-off valve 74. Therefore, the produced water PW is hardly stored in the water storage unit 120.

[0066] When the operation of the automobile is stopped, for example, by parking, the operation of the fuel cell system 110 is also stopped. At this time, the control device 80 closes the first on-off valve 72 and the second on-off valve 74. The control device 80 also stops the operation of the air pump 60 and the circulation pump 64. That is, in the second embodiment, after the operation of the fuel cell system 110 is stopped, the water storage section 120 is not purged.

[0067] When the fuel cell system 110 is stopped, the fuel cell stack 12 enters a soak state. During the soak, as shown in FIG. 8 , water vapor that has accumulated inside the humidifier 62 condenses. Water vapor that has accumulated in the exhaust path 118 of the connecting pipe 116 also condenses. Liquid water (condensed water DW) produced by the condensation travels along the inner wall of the exhaust path 118 or one end face of the ring member 126 to the opening of the communicating passage 122. The condensed water DW further flows into the water storage section 120 via the communicating passage 122. As a result of the above, the condensed water DW is collected in the water storage section 120.

[0068] As described above, during operation of the fuel cell system 110, much of the produced water PW is discharged from the second on-off valve 74 together with the cathode off-gas (see FIG. 10). That is, even in the second embodiment, a sufficient water storage capacity of the water storage section 120 is ensured. This prevents the amount of condensed water DW from exceeding the maximum capacity of the water storage section 120, thereby preventing the condensed water DW from overflowing from the communication passage 122 into the exhaust passage 118. The liquid level of the condensed water DW is prevented from exceeding the lowest point P2.

[0069] That is, also in the second embodiment, the condensed water DW is prevented from coming into contact with the valve body 104. Therefore, even if the outside air temperature falls below freezing and the condensed water DW freezes, the valve body 104 is prevented from adhering to the housing 100 or the like through the frozen condensed water DW.

[0070] In the above-described first and second embodiments, the cases where the connecting structure 82 and the connecting structure 114 are provided on the second on-off valve 74 are respectively illustrated. However, the connecting structure 82 or the connecting structure 114 may be provided on the first on-off valve 72. The connecting structure 82 or the connecting structure 114 may be provided on both the first on-off valve 72 and the second on-off valve 74. Furthermore, for example, the connecting structure 82 may be provided on the first on-off valve 72 and the connecting structure 114 may be provided on the second on-off valve 74, or conversely, the connecting structure 114 may be provided on the first on-off valve 72 and the connecting structure 82 may be provided on the second on-off valve 74.

[0071] As described above, this embodiment discloses a fuel cell system (10) including a fuel cell stack (12), the fuel cell system comprising: a humidifier (62) into which an oxidant gas supplied to a cathode electrode (24) of the fuel cell stack and a cathode off-gas discharged from the fuel cell stack are introduced; a pipe (84) having a flow passage (86) formed therein through which either the oxidant gas that has flowed through the humidifier or the cathode off-gas that has flowed through the humidifier flows; an on-off valve (74) provided at an outlet (86o) of the flow passage, the on-off valve (74) opening the flow passage during operation of the fuel cell stack and closing the flow passage during soaking of the fuel cell stack; and a water storage section (92) communicating with the flow passage, wherein when a relatively low position in the vertical direction is defined as a low position and a relatively high position in the vertical direction is defined as a high position, the water storage section is positioned lower than the flow passage and the on-off valve is positioned higher than the water storage section.

[0072] During the soak of the fuel cell stack, water contained in the oxidant gas or cathode off-gas condenses. Because the water reservoir is located lower than the flow passage, the condensed water flows into the water reservoir due to gravity. In other words, the condensed water is collected in the water reservoir. However, because the on-off valve is located higher than the water reservoir, it is difficult for the condensed water collected in the water reservoir to move to the on-off valve against gravity. Therefore, the condensed water is prevented from coming into contact with the on-off valve.

[0073] This eliminates the concern that moisture adhering to the on-off valve will freeze even in environments where there is a risk of freezing, such as when the outside air temperature is below freezing, and therefore the on-off valve can open and close quickly even when the fuel cell system is started up when the outside air temperature is below freezing.

[0074] This embodiment discloses a fuel cell system in which the water storage portion is formed in the piping as a recessed space connected to the flow passage, the water storage portion is lower than the lowest point at the outlet of the flow passage, and the flow passage has a portion (87) upstream of the water storage portion whose cross-sectional area decreases as it approaches the water storage portion.

[0075] In this case, for example, immediately after the fuel cell stack starts operating, the cathode off-gas can blow away (purge) the produced water stored in the water storage section. Furthermore, since the flow passage has a portion whose cross-sectional area decreases as it approaches the water storage section, the flow rate of the cathode off-gas increases. This allows a large amount of produced water to be easily discharged from the water storage section. This ensures the water storage capacity of the water storage section.

[0076] This embodiment discloses a fuel cell system in which the water storage section is formed by branching off from the flow passage, and the piping is formed with a communication passage (122) that connects the flow passage and the water storage section, and a purge gas supply path (124) for supplying purge gas to the water storage section.

[0077] In this case, an air curtain can be formed in the communication passage by the purge gas. Therefore, for example, during operation of the fuel cell stack, the generated water can be prevented from flowing from the communication passage into the water storage portion, and the generated water can be discharged from the flow passage via the on-off valve. This prevents the generated water from accumulating in the water storage portion during operation of the fuel cell stack. This ensures the water storage capacity of the water storage portion, allowing condensation water generated during soaking of the fuel cell stack to be sufficiently stored in the water storage portion.

[0078] This embodiment discloses a fuel cell system including an oxidant gas supply line (68) that supplies the oxidant gas to the cathode electrode, and a purge gas supply line (112) that branches off from the oxidant gas supply line and is connected to the purge gas supply path, and in which a portion of the oxidant gas flowing through the oxidant gas supply line is supplied to the water storage section as the purge gas via the purge gas supply line.

[0079] According to this configuration, a portion of the oxidant gas can be supplied to the water reservoir as a purge gas. Therefore, a common source can be used as both the purge gas supply source and the oxidant gas supply source. In other words, there is no need to provide a new purge gas supply source. Therefore, even when the purge gas is supplied to the water reservoir, the configuration of the fuel cell system does not become complicated.

[0080] This embodiment discloses a fuel cell system including a heating unit (128) that heats the water storage unit.

[0081] Even when the outside temperature is below freezing, the water in the water storage unit can be quickly melted by heating the water storage unit with the heater, making it easy to purge the water from the water storage unit.

[0082] This embodiment discloses a fuel cell system in which the cathode off-gas flows through the flow passage.

[0083] The cathode off-gas contains moisture that adds humidity to the oxidant gas and moisture generated during power generation in the fuel cell stack. Therefore, by providing a water reservoir in the pipe through which the cathode off-gas discharged from the humidifier flows, this moisture can be sufficiently collected.

[0084] The present invention is not limited to the above disclosure, and various configurations can be adopted without departing from the gist of the present invention. [Explanation of symbols]

[0085] 10, 110... fuel cell system 12... fuel cell stack 14...unit cell 16...electrolyte membrane-electrode assembly 22...Anode electrode 24...Cathode electrode 30...first gas flow path 32...second gas flow path 50...High pressure tank 54...First supply line 56...First exhaust line 60...Air pump 62...humidifier 62o...outlet 68…Second supply line 70…Second exhaust line 72…First on-off valve 74…Second on-off valve 76…Bypass line 78…Bypass valve 80…Control device 82, 114…Connection structure 84, 116…Connection pipe 86, 118…Exhaust passage 86i, 118i…Inlet 86o, 118o…Outlet 87…Cross-sectional area change region 87a…Throttle portion 88…First flow path 90…Second flow path 92, 120…Water storage portion 94…Recessed portion 100…Housing 102…Rotating shaft 104…Valve body 112…Purge gas supply line 124…Purge gas supply path 126…Ring member 128…Heater DW…Condensed water PW…Generated water

Claims

1. 1. A fuel cell system including a fuel cell stack, a humidifier into which an oxidant gas supplied to a cathode electrode of the fuel cell stack and a cathode off-gas discharged from the fuel cell stack are introduced; a pipe having a flow passage formed therein through which either the oxidant gas that has passed through the humidifier or the cathode off-gas that has passed through the humidifier passes; an on-off valve provided at an outlet of the flow passage, the on-off valve opening the flow passage during operation of the fuel cell stack and closing the flow passage during soaking of the fuel cell stack; a water reservoir communicating with the flow passage; Equipped with When a relatively low position in the vertical direction is defined as a low position and a relatively high position in the vertical direction is defined as a high position, the water storage section is disposed at a lower position than the flow passage, and the on-off valve is disposed at a higher position than the water storage section, A fuel cell system in which the water storage section is formed by branching off from the flow passage, and the piping is formed with a communication passage that connects the flow passage with the water storage section, and a purge gas supply path for supplying purge gas to the water storage section.

2. 2. The fuel cell system according to claim 1, wherein the water reservoir is formed in the piping as a recessed space connected to the flow passage, and the water reservoir is located lower than the lowest point at the outlet of the flow passage; The flow passage has a portion upstream of the water storage portion, the cross-sectional area of ​​which decreases as the flow passage approaches the water storage portion.

3. 2. The fuel cell system according to claim 1, further comprising: an oxidant gas supply line for supplying the oxidant gas to the cathode; a purge gas supply line branching from the oxidant gas supply line and connected to the purge gas supply path; Equipped with A fuel cell system in which a portion of the oxidant gas flowing through the oxidant gas supply line is supplied to the water reservoir as the purge gas via the purge gas supply line.

4. 4. The fuel cell system according to claim 1, further comprising a heating section for heating the water storage section.

5. 2. The fuel cell system according to claim 1, wherein the cathode off-gas flows through the flow passage.

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