JP2009140795A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce air scavenging time when operation of a fuel cell is stopped. <P>SOLUTION: A gas flow channel forming member 30 comprises through-holes 30H in multi-rows and multi-stages. The alignment of the through-holes is defined as gas flow channels, and is arranged between an MGEA 25 and a separator 40. A bonded part 30B and a strand part 30S in each of the through-holes 30H are slanted. During normal operation of the fuel cell, supplied air is flown downstream while being introduced to the side of the separator 40 in the slanted bonded part 30B and the strand part 30S, and supplied to a gas diffusion layer 23a. When the air is scavenging, the air is made to flow in the direction reversed to the direction when the normal operation is performed, so that the supplied air is flown downstream while being introduced to the side of the gas diffusion layer 23a in the slanted bonded part 30B and the strand part 30S and allowed to enter the gas diffusion layer 23a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell having a stack structure in which a plurality of membrane electrode assemblies in which gas diffusion electrodes are bonded to both surfaces of an electrolyte membrane are stacked with a separator interposed therebetween.

  In such a fuel cell, during normal operation for power generation, both gas diffusion electrodes in the membrane electrode assembly are supplied with a reaction gas, for example, hydrogen gas and oxygen-containing gas (air), and an electrochemical reaction between hydrogen and oxygen. To generate electricity. As the electrochemical reaction proceeds, water is generated at the cathode, and this generated water is discharged to the outside by the continuously supplied air during the normal operation of the fuel cell. Since the air supply is stopped, it may remain at the cathode. If the generated water remains in this way, in cold districts or the like, the remaining generated water freezes on the gas diffusion electrode side as the outside air temperature decreases, and the gas diffusion electrode pores may be blocked. Therefore, various scavenging techniques have been proposed in which the supply of air is continued and the remaining produced water is discharged outside even after the power generation operation is stopped (Patent Document 1, etc.).

Japanese Patent Laid-Open No. 2005-209609

  In the above patent document, it is proposed that air is supplied in the direction opposite to the air flow during the power generation operation during scavenging. However, since the air in the opposite direction is only flowing in the reverse direction in the flow path between the gas diffusion electrode joined to the membrane electrode assembly and the separator, the pores of the gas diffusion electrode are blocked by freezing. Therefore, it has been desired to shorten the scavenging to complete the process within a short time.

  In view of the above-described problems, an object of the present invention is to shorten the scavenging time when the fuel cell is stopped.

  In order to achieve at least a part of the above object, the present invention adopts the following configuration.

[Application: Fuel cell]
A fuel cell having a stack structure in which a plurality of membrane electrode assemblies in which gas diffusion electrodes are bonded to both surfaces of an electrolyte membrane are stacked with a separator interposed therebetween,
A flow path forming member which is incorporated between the membrane electrode assembly and the separator and forms a gas supply flow path for supplying gas over the electrode surface of the gas diffusion electrode;
During normal operation in which the fuel cell is operated for power generation, the gas is supplied in a first flow direction from one side of the electrode surface to the other side with respect to the flow path forming member. A gas introducing means for guiding the gas in a second flow direction opposite to the first flow direction with respect to the flow path forming member when the normal operation is stopped;
The flow path forming member on at least one side of the membrane electrode assembly includes a plurality of inclined portions inclined so that gas can flow downstream in the gas supply flow path,
The gist of the inclined portion is to cause the gas introduced in the second flow direction to flow downstream along the second flow direction while guiding the gas to the gas diffusion electrode side.

  In the fuel cell having the above configuration, in a normal operation situation, the gas supply channel in the channel forming member between the membrane electrode assembly and the separator is directed from one side of the electrode surface to the other side. Gas is directed in the first flow direction. This gas interferes with the inclined portions provided in multiple rows by the flow path forming member in the gas supply flow path, but since the inclined portions are inclined so as to flow downstream, the gas is supplied in the first flow direction. The gas is supplied without any trouble over the electrode surface of the gas diffusion electrode through the flow path. In addition, since the inclined portion guides the gas introduced in the second flow direction toward the gas diffusion electrode and flows downstream along the second flow direction, the inclined portion is opposite to the second flow direction. The gas introduced in one flow direction is caused to flow downstream along the first flow direction while guiding the gas toward the separator. Therefore, the moisture accumulated on the separator side is contained in the gas flowing in the first flow direction (hereinafter referred to as the first flow direction gas) and flows downstream. Since the first flow direction gas is supplied in the state, inadvertent drying of the gas diffusion electrode can be avoided with high effectiveness under the condition of normal operation.

  On the other hand, when the normal operation is stopped, the gas flow in the gas supply channel is in the second direction opposite to the first direction, and the gas flowing in the second direction (hereinafter referred to as the second flow direction). (Referred to as gas) also flows downstream while interfering with multiple rows of inclined portions of the gas supply channel. However, since the second flow direction gas flows downstream along the second flow direction while being guided to the gas diffusion electrode side by the inclined portion, the opportunity of contact between the gas diffusion electrode and the second flow direction gas. Increases by the amount guided to the gas diffusion electrode. Therefore, the second flow direction gas contains the water stored on the gas diffusion electrode side and flows out the water downstream to achieve scavenging. Therefore, when the normal operation is stopped, the second flow direction gas is The diffusion electrode can be dried more reliably and within a short time. As a result, according to the fuel cell having the above-described configuration, during normal operation, as described above, the gas diffusion electrode is not inadvertently dried to facilitate the progress of the electrochemical reaction, and thus the power generation performance. When the normal operation is stopped, the gas diffusion electrode can be quickly dried by the second flow direction gas by the inclined portion in the gas supply flow path, and the scavenging time can be shortened.

  The fuel cell described above can be configured as follows. For example, a first gas flow path is formed outside the electrode surface so that gas is distributed to each flow path forming member between the membrane electrode assembly having the stack structure and the separator. A second gas flow path is formed outside the electrode surface with the first gas flow path and the electrode surface sandwiched therebetween so that the gas that has passed through the flow path forming member is guided to the outside. Then, the gas is introduced from the first gas flow path in the first flow direction to the second gas flow path by the gas introduction means, and from the second gas flow path in the second flow direction. It guide | induces to the said 1st gas flow path. By so doing, it is possible to shorten the scavenging by the second flow direction gas in each of the membrane electrode assemblies having the stack structure.

  Then, after providing the gas supply source, the gas introduction means selects the supply source as one of the first gas flow path and the second gas flow path in order to supply the gas from the supply source. Can be connected. In this way, it is possible to easily maintain both the power generation performance during normal operation and the shortening of the scavenging time when stopping normal operation with a simple configuration of selecting a flow path to be connected.

  Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 is an explanatory diagram schematically showing the overall configuration of a fuel cell system 1000 as an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the schematic configuration of a fuel cell 100.

  As shown in FIG. 1, the fuel cell system 1000 includes a fuel cell 100, a hydrogen gas supply source 200 such as a high-pressure tank or a reformer, a blower 300 that supplies air as an oxidizing gas, and a cooling to the fuel cell 100. A radiator 400 that circulates water to perform cooling and a control device 500 that controls the system are provided. The fuel cell 100 is a solid polymer type fuel cell that has a stack structure and receives supply of a hydrogen-containing fuel gas and an oxygen-containing oxidizing gas, and generates power by an electrochemical reaction between the fuel gas and the oxidizing gas. is there. The detailed configuration of the fuel cell 100 will be described later.

  From the hydrogen gas supply source 200 to the fuel cell 100, an upstream supply pipe 212 and a downstream supply pipe 214 are connected via a valve unit 210, and the upstream exhaust pipe from the fuel cell 100. 216 and a downstream exhaust pipe 218 are piped with a valve unit 210 interposed therebetween. The valve unit 210 can selectively switch the connection pipeline of the upstream supply pipeline 212 to one of the downstream supply pipeline 214 and the upstream exhaust pipeline 216 by a built-in valve. Therefore, the hydrogen gas supply source 200 is selectively connected to one of the downstream supply pipe 214 and the upstream exhaust pipe 216 by the valve unit 210, and the hydrogen gas is supplied to the fuel cell 100 via any one of the pipes. Is supplied by the following route.

  In the initial state of the fuel cell system 1000 and the operation state of the fuel cell 100, the valve unit 210 takes a valve position (initial position / normal operation position) that allows the upstream supply line 212 and the downstream supply line 214 to communicate with each other. . When in this valve position, from the hydrogen gas supply source 200, the upstream supply pipe 212 → the valve unit 210 → the downstream supply pipe 214 → the fuel cell 100 → the upstream exhaust pipe 216 → the valve unit 210 → the downstream side. A hydrogen gas normal path NLH of the exhaust pipe 218 is formed. Therefore, hydrogen gas (fuel gas) from the hydrogen gas supply source 200 is supplied to the fuel cell 100 through the valve unit 210 and the downstream supply pipe 214 and is supplied to the anode of each fuel cell 10 in the fuel cell 100. Is consumed. The anode off gas is exhausted through the upstream exhaust pipe 216, the valve unit 210, and the downstream exhaust pipe 218.

  During the scavenging process described later, the valve unit 210 takes a valve position (scavenging position) that causes the upstream supply pipe 212 and the upstream exhaust pipe 216 to communicate with each other. When in this valve position, from the hydrogen gas supply source 200, the upstream supply line 212 → the valve unit 210 → the upstream exhaust line 216 → the fuel cell 100 → the downstream supply line 214 → the valve unit 210 → the downstream side. A hydrogen gas scavenging path SLH of the exhaust pipe 218 is formed. In other words, the hydrogen gas supply from the hydrogen gas supply source 200 to the fuel cell 100 during the scavenging process is performed in the opposite direction to the gas supply in the hydrogen gas normal path NLH during the normal operation described above. Become.

  The same applies to the supply of air to the fuel cell 100. When the air is blown from the blower 300 to the fuel cell 100, an upstream supply line 312 and a downstream supply line 314 are piped with a valve unit 310 interposed therebetween. From 100, an upstream exhaust pipe 316 and a downstream exhaust pipe 318 are piped with a valve unit 310 interposed therebetween. Even in the valve unit 310, similarly to the valve unit 210, the connection line of the upstream supply line 312 is selectively switched to one of the downstream supply line 314 and the upstream exhaust line 316 by a built-in valve. Therefore, the blower 300 is selectively connected to one of the downstream supply pipe 314 and the upstream exhaust pipe 316 by the valve unit 310, and air is supplied to the fuel cell 100 through either of the pipes as follows. Supply by a simple route.

  In the initial state of the fuel cell system 1000 and the operating state of the fuel cell 100, the valve unit 310 takes a valve position (initial position / normal operation position) that allows the upstream supply line 312 and the downstream supply line 314 to communicate with each other. . When in this valve position, from the blower 300, the upstream supply line 312 → the valve unit 310 → the downstream supply line 314 → the fuel cell 100 → the upstream exhaust line 316 → the valve unit 310 → the downstream exhaust line. 318 air normal path NLO is formed. Therefore, the air (oxidizing gas) from the blower 300 is supplied to the fuel cell 100 through the valve unit 310 and the downstream supply pipe 314 and consumed at the cathode of each fuel cell 10 in the fuel cell 100. The cathode off-gas is exhausted through the upstream exhaust pipe 316, the valve unit 310, and the downstream exhaust pipe 318.

  In the scavenging process, the valve unit 310 takes a valve position (scavenging position) that allows the upstream supply pipe 312 and the upstream exhaust pipe 316 to communicate with each other. When in this valve position, from the blower 300, the upstream side supply line 312 → the valve unit 310 → the upstream side exhaust line 316 → the fuel cell 100 → the downstream side supply line 314 → the valve unit 310 → the downstream side exhaust line. 318 air scavenging paths SLO are formed. That is, the air supply from the blower 300 to the fuel cell 100 during the scavenging process is performed in the opposite direction to the gas supply in the air normal path NLO during the normal operation described above.

  The control device 500 is configured by a computer including a CPU, a ROM, a RAM, and the like, receives signals from the ignition switch 510 and a sensor group 512 for detecting a required load, and controls operation of the fuel cell system 1000. . In brief, the control device 500 calculates a power generation amount necessary to cover a required load, that is, a supply amount of fuel gas / oxidized oxide (hydrogen gas / air), and gas supply with the calculated amount is performed. In order to achieve this, the flow rate regulating valves (not shown) of the upstream supply pipeline 212 and the upstream supply pipeline 312 are controlled. Further, the valve units 210 and 310 are driven and controlled based on a signal from the ignition switch 510, and the valve position is switched between the normal operation position and the scavenging position.

  Next, the fuel cell 100 will be described. As shown in FIG. 2, the fuel cell 100 has a stack structure in which a plurality of fuel cells 10 are stacked, and the fuel cells 10 having a stack structure are sandwiched between end plates 85 and 86 at both ends. In the embodiment 100, air and hydrogen are supplied from the end plate 85 to each fuel cell 10, while the surplus, anode off-gas and cathode off-gas are supplied to the fuel cell 10 on the other end plate 86 side. This is a so-called dead-end type fuel cell that is folded back to the end plate 85 side (in detail, by the cell's paralator). The cooling water is also supplied from the end plate 85 to each fuel cell 10 and is turned back to return to the end plate 85. Therefore, the end plate 85 includes a through hole 85a for supplying anode gas (hydrogen gas), a through hole 85b for supplying cathode gas (air), and a through hole 85c for discharging anode off gas. A through hole 85d for discharging the cathode off-gas, a through hole 85e for supplying cooling water, and a through hole 85f for discharging cooling water. The downstream supply pipe 214 described above has a through hole 85a, the upstream exhaust pipe 216 has a through hole 85c, the downstream supply pipe 314 has a through hole 85b, and the upstream exhaust pipe 316 has a through hole. The cooling pipe from the radiator 400 is connected to the through hole 85e and the through hole 85f. Therefore, the hydrogen gas from the hydrogen gas supply source 200 is supplied into the fuel cell 100 through the through hole 85a of the end plate 85, and the air from the blower 300 is supplied into the fuel cell 100 through the through hole 85b. Is done. The cooling water is cooled by the radiator 400 and supplied to the fuel cell 100 through the through hole 85e.

  The fuel cell 10 includes an MEA 24 (Membrane Electrode Assembly) as a membrane electrode assembly in which a gas diffusion electrode is bonded to both surfaces of an electrolyte membrane, and the MEA 24 has gas diffusion layers 23a and 23b bonded to both sides thereof. MEGA25. The fuel cell 10 is provided with the MGA 25 formed integrally with the seal gasket 26, and the gas flow path forming members 30, 31 are incorporated between the MEA 24 and the separator 40 so as to overlap the MGA 25. As will be described later, the gas flow path forming members 30, 31 form gas flow paths by inclining multiple rows of through-holes and formation walls thereof, extending the gas diffusion layers 23a, 23b of the MEGA 25 and the electrode surface of the MEA 24. Gas is supplied over

  The MEA 24 includes a cathode electrode catalyst layer 22a and an anode electrode catalyst layer 22b as gas diffusion electrodes on the surface of the electrolyte membrane 21. The electrolyte membrane 21 is a thin film of a solid polymer material that has proton conductivity and exhibits good electrical conductivity in a wet state, and is smaller than the outer shape of the separator 40 and larger than the outer shape of the gas flow path forming members 30 and 31. It is formed in a rectangle. The electrolyte membrane 21 is, for example, a Nafion membrane (Nafion is a registered trademark). The cathode electrode catalyst layer 22a and the anode electrode catalyst layer 22b formed on the surface of the electrolyte membrane 21 are catalyst layers that support an electrochemical reaction, for example, platinum.

  The gas diffusion layers 23a and 23b are carbon porous bodies having a porosity of about 20%, and are formed of, for example, carbon cloth or carbon paper. The gas diffusion layers 23a and 23b are integrated with the MEA 24 by a joining method such as hot pressing to form the MEGA 25. The gas diffusion layer 23a is disposed on the cathode side of the MEA 24, and the gas diffusion layer 23b is disposed on the anode side. The gas diffusion layer 23a diffuses the cathode gas in the thickness direction and supplies it to the entire surface of the cathode electrode catalyst layer 22a. The gas diffusion layer 23b diffuses the anode gas in the thickness direction and supplies it to the entire surface of the anode electrode catalyst layer 22b. The gas diffusion layers 23a and 23b have a relatively low porosity because the main purpose is gas diffusion in the thickness direction.

  The gas flow path forming members 30 and 31 are metal members called expanded metals, and are thin metal plates in which through holes having the same shape are regularly arranged in multiple rows. The gas flow path forming members 30 and 31 are formed of a conductive metal, for example, stainless steel, titanium, or a titanium alloy, as will be described later, and have an outer shape that is slightly smaller than the MEGA 25.

  The gas flow path forming member 30 is disposed between the cathode side of the MEGA 25 (cathode side of the MEA 24) and the separator 40, and the air (oxidizing gas) supplied via the separator 40 is indicated by arrows in FIG. The air is supplied to the cathode side of the MEGA 25 while flowing in a flow from one side of the electrode surface of the MEA 24 to the other side. The gas flow path forming member 31 is disposed between the anode side of the MEGA 25 (the anode side of the MEA 24) and the separator 40, and hydrogen gas (fuel gas) supplied via the separator 40 is indicated by an arrow in FIG. In this way, hydrogen gas is supplied to the anode side of the MEGA 25 while flowing in a flow from one side of the electrode surface of the MEA 24 toward the other side.

  The reaction gas flowing through the gas flow path forming members 30 and 31 is supplied to the MEGA 25 in the course of flow, and is diffused to the cathode electrode catalyst layer 22a and the anode electrode catalyst layer 22b by the gas diffusion layers 23a and 23b of the MEGA 25. Subject to reaction. This electrochemical reaction is an exothermic reaction, and cooling water is supplied into the fuel cell 100 in order to operate the fuel cell 100 in a predetermined temperature range.

  The seal gasket 26 is made of an insulating resin material made of rubber, such as silicon rubber, butyl rubber, or fluorine rubber. The gas flow path forming members 30 and 31 are stacked on both sides of the MEGA 25, and the resin is injected to the outer periphery thereof. It is formed integrally with the MEGA 25 and the gas flow path forming members 30 and 31 by molding.

  The seal gasket 26 is formed in a substantially rectangular shape having the same size as the separator 40. As shown in FIG. 2, communication holes 20 a to 20 f are provided along the four sides of the seal gasket 26. Each of the communication holes 20a to 20f communicates with the above-described through hole 85a of the end plate 85 and constitutes a part of a manifold of fluid (fuel gas, oxidizing gas, cooling water) inside the fuel cell 100. The communication hole 20a constitutes a part of the anode gas manifold, and the communication hole 20b constitutes a part of the cathode gas manifold. The communication hole 20c constitutes a part of the anode offgas manifold, the communication hole 20d constitutes a part of the cathode offgas manifold, the communication hole 20e constitutes a part of the cooling water supply manifold, and the communication hole 20f A part of the cooling water discharge manifold.

  The seal gasket 26 is formed with a convex portion 26a surrounding each communication hole in the thickness direction. The convex portion 26a is sandwiched between the upper and lower separators 40 of the seal gasket 26, receives a fastening force in the stacking direction, and is crushed and deformed in the stacking direction. As a result, the convex portion 26a functions as a seal that suppresses leakage of fluid (fuel gas, oxidizing gas, cooling water) from the inside of the manifold.

  The separator 40 is a three-layer laminated separator formed by laminating three metal thin plates. Specifically, the cathode plate 41 that contacts the gas flow path forming member 30 that is the flow path of the oxidizing gas, and the anode that contacts the gas flow path forming member 31 that is the flow path of the fuel gas in the adjacent fuel cell 10. The plate 43 and an intermediate plate 42 sandwiched between the two plates and mainly serving as a cooling water flow path.

  The three plates have a flat surface with no irregularities for the flow path in the thickness direction (that is, the contact surface with the gas flow path forming members 30, 31 is flat), stainless steel, titanium, It is made of a conductive metal material such as a titanium alloy.

  The three plates are provided with through holes that constitute the various manifolds described above. Specifically, as shown in FIG. 2, an oxidant gas supply through hole 41 a and an oxidant gas discharge through hole 41 b are provided on the long side of the substantially rectangular separator 40. Further, on the short side of the separator 40, a through hole 41c for supplying fuel gas and a through hole 41d for discharging fuel gas are provided. On the short side of the separator 40, a through hole 41e for supplying cooling water and a through hole 41f for discharging cooling water are respectively provided.

  In addition to the manifold through-holes, the cathode plate 41 is formed with a plurality of holes 45 and 46 serving as oxidizing gas inlets and outlets to the gas flow path forming member 30. Similarly, the anode plate 43 is formed with a plurality of holes (not shown) serving as fuel gas inlets and outlets to the gas flow path forming member 31 in addition to the manifold through holes.

  Of the plurality of manifold through holes provided in the intermediate plate 42, the manifold through hole 42 a through which the oxidizing gas flows is formed so as to communicate with the hole 45 of the cathode plate 41. The manifold through-hole 42b through which the fuel gas flows is formed so as to communicate with a hole (not shown) of the anode plate 43.

  A plurality of notches are formed in the intermediate plate 42 along the long side direction of a substantially rectangular outer shape, and both ends of the notches communicate with manifold through-holes through which cooling water flows.

  By using the separator 40 formed by laminating such flat plates in combination with the gas flow path forming members 30 and 31, it is necessary to form a flow path groove in the separator 40 by a complicated manufacturing method such as etching. There is no.

  Next, the gas flow path forming members 30 and 31 will be described. 3 is a schematic perspective view of the gas flow path forming member 30, FIG. 4 is an explanatory view showing a manufacturing method of the gas flow path forming member 30, and FIG. 5 is a schematic perspective view of the manufacturing process of the gas flow path forming member 30. FIG. 6 is an explanatory diagram showing a side view of the gas flow path forming member 30, a front view, and an arrow view from obliquely above, and FIG. 7 is a gas flow path between the MGEA 25 and the separator 40. It is explanatory drawing which shows a mode that the formation member 30 was integrated.

  As shown in this figure, the gas flow path forming members 30 and 31 are expanded metal having square through holes 30H in this embodiment, and the strand portions 30S which are the formation walls of the through holes 30H are bonded to the bond portions. By connecting at 30B, the through holes 30H are arranged in multiple rows vertically and horizontally to provide a staggered pattern. In forming the gas flow path forming member 30 in which the through holes 30H are arranged in multiple rows in this way, as shown in FIG. 4, a feed roller made of a thin plate of stainless steel or the like (for example, a thickness of about 0.1 mm) is used. Then, it is fed to the processing device M in FIG. 5 and subjected to shearing by the upper blade UB and the lower blade DB of the processing device M.

  The upper blade UB and the lower blade DB are provided with a triangular wave shaped press blade to form a square-shaped through hole 30H, and the upper blade UB descends to the lower blade DB each time the material is pitch fed. Due to the lowering of the upper blade UB, the material is sheared in a slit shape in the overlapping range of both the upper blade UB and the lower blade DB, and at the sheared location, a square-shaped penetration is made following the upper blade UB and the lower blade DB. A hole 30H is formed. In this case, the upper blade UB is displaced in the left-right direction by a half pitch of its own triangular wave-shaped press blade when the material is lowered at every pitch feed, so that the through hole 30H is in front view from the plate surface of the material. They are formed in a staggered pattern arranged in multiple rows vertically and horizontally, and in multiple rows in a staircase pattern when viewed from the side of the plate. In addition, the gas flow path forming member 30 and the gas flow path forming member 31 are formed by cutting the expanded metal having the through holes 30H in multiple rows in this way into predetermined dimensions. Alternatively, the gas flow path forming members 30 and 31 may be formed by forming the through holes 30H in multiple rows on the thin plate that has been cut to a predetermined size by the processing apparatus M described above. In addition, by changing the shapes of the press blades of the upper blade UB and the lower blade DB, a gas flow path forming member provided with multiple rows of circular through holes 30H and hexagonal through holes 30H can be obtained.

  The flow path and gas flow formed by the gas flow path forming members 30 and 31 thus obtained will be described. As shown in FIG. 6, in the gas flow path forming members 30, 31 having through holes 30H in multiple rows in a stepped manner, the respective through holes 30H are in an oblique state, that is, the strand part 30S and the bond part 30B are inclined. Used to be Specifically, the strand portion 30S and the bond portion 30B are inclined in the range indicated as the flow path formation region in the figure, and the separator 40 gasses at one boundary (lower end side boundary in the figure) of the flow path formation region. The gas diffusion layers 23 a and 23 B of the MGEA 25 come into contact with the gas flow path forming members 30 and 31 at the other boundary (upper end side boundary in the drawing).

  When gas flows into the gas flow path forming members 30 and 31 from the right side in FIG. 6, this gas is bounded at the lower boundary in the figure by the inclined bond portion 30B and strand portion 30S of the through hole 30H on the upstream side. It passes through the through-hole 30H while being guided to the side, and wraps around the strand portion 30S of the downstream-side through-hole 30H and passes through the downstream-side through-hole 30H as described above. That is, the gas flowing into the gas flow path forming members 30 and 31 from the right flows downstream along the path indicated by GF1 in the drawing while repeating the passage through the above-described through holes.

  On the other hand, when the gas flows into the gas flow path forming members 30 and 31 from the left in FIG. 6, this gas is bounded at the upper boundary in the drawing by the inclined bond portion 30B and the strand portion 30S of the through hole 30H on the upstream side. It passes through the through-hole 30H while being guided to the side, and wraps around the strand portion 30S of the downstream-side through-hole 30H and passes through the downstream-side through-hole 30H as described above. That is, the gas that has flowed into the gas flow path forming members 30 and 31 from the left flows downstream along the path indicated by GF2 in the drawing while repeating the passage of the through holes.

  The gas flow in FIG. 6 will be described with reference to the cathode-side gas flow path forming member 30 incorporated between the MGEA 25 and the separator 40 as shown in FIG. Assuming that the gas supply from the right side is the gas supply during the normal operation of the fuel cell 100 as indicated by the black arrow in the figure, the supplied gas (air) is the first flow direction gas of the present invention. The gas flow path forming member 30 flows through the through hole 30H while being guided to the separator 40 side by the inclined bond part 30B and the strand part 30S of each through hole 30H. On the other hand, when gas (air) is supplied from the left as indicated by the white arrow in the figure, the supplied gas (air) corresponds to the second flow direction gas of the present invention. The gas flow path forming member 30 is guided to the gas diffusion layer 23a side of the MGEA 25 by the inclined bond portions 30B and the strand portions 30S of the respective through holes 30H, and flows downstream through the through holes 30H.

  Next, operation control in the fuel cell system 1000 having the above-described configuration will be described. FIG. 8 is a flowchart showing operation control of the fuel cell 100 executed by the control device 500. This operation control is repeatedly executed after the ignition switch 510 is turned on. First, the control device 500 drives and controls the valve unit 210 and the valve unit 310 to initialize the valve position (step S100). As described above, the initial positions of these valve units are the normal values for supplying the hydrogen gas from the hydrogen gas supply source 200 to the fuel cell 100 along the hydrogen gas normal path NLH in FIG. The valve unit 310 is a normal operation position in which the air from the blower 300 is supplied to the fuel cell 100 along the normal air path NLO. The flow of hydrogen gas / air flowing along these paths is a positive flow, and the gas supply in this flow is the supply by the black arrow shown in FIG. 7 on the cathode side. The same applies to the anode side. The initialization of the valve position in step S100 only needs to be executed at the beginning of the operation control in FIG. 8, and can be omitted after the operation control is once started.

  Next, the control device 500 reads the required load based on the sensor signal from the sensor group 512 (step S110), calculates the supply amount of hydrogen gas and air to obtain the generated power corresponding to the required load, and calculates the fuel cell. 100 (step S120). Thereby, the fuel cell 100 continues the power generation and outputs the generated power to the outside.

  In the normal operation state for this power generation, as described above, air is supplied by the black arrows shown in FIG. 7 on the cathode side, and the air flows downstream of the gas flow path forming member 30 to the MGEA 23. It is supplied to the gas diffusion layer 23a. In other words, in this normal operation state, the supplied air is guided to the separator 40 side by the inclined bond portions 30B and strand portions 30S of the respective through holes 30H of the gas flow path forming member 30, and the through holes 30H. And flows downstream, and is supplied to the gas diffusion layer 23 a of the MGEA 23. In this case, although air interferes with the inclined bond part 30B and the strand part 30S, since these are inclined with the through-hole 30H and are multi-staged (see FIG. 6), the gas flow path forming member toward the downstream side 30 and supplied to the gas diffusion layer 23a of the MGEA 23 over its electrode surface without any trouble. Also on the anode side, hydrogen gas is supplied to the gas diffusion layer 23b of the MGEA 25 without any trouble. Therefore, the fuel cell 100 can exhibit its power generation capability.

  In addition, since the inclined bond part 30B and the strand part 30S guide the air introduced from the right side in FIG. 7 to the separator 40 side and flow to the downstream side, the moisture H accumulated on the separator 40 side, It can be included in the air flowing downstream and flow downstream. Therefore, since air is supplied to the gas diffusion layer 23a of the MGEA 23 in a moisture-containing state, the gas diffusion layer 23a of the MGEA 23 and, in turn, the electrolyte membrane 21 of the MEA 24 are inadvertently dried under normal operating conditions. It can be made not to be in a state. The same applies to the anode side. Avoiding the dry state in this way is beneficial for facilitating the progress of the electrochemical reaction in each fuel cell 10 and maintaining the power generation capability of the fuel cell 100.

  Following step S120, the control device 500 determines whether or not the ignition switch 510 is turned off (step S130). If a negative determination is made, the control device 500 temporarily terminates the process to continue normal operation control, and the steps described above. Repeat the process. On the other hand, if an affirmative determination is made in step S120, control device 500 drives and controls valve unit 210 and valve unit 310, and changes the valve position from the normal operation position to the scavenging position (step S140). As described above, the scavenging positions of these valve units are positions where the hydrogen gas from the hydrogen gas supply source 200 is supplied to the fuel cell 100 along the hydrogen gas scavenging path SLH in FIG. In the valve unit 310, the air is supplied from the blower 300 to the fuel cell 100 along the air scavenging path SLO. The flow of hydrogen gas / air along these paths is a reverse flow opposite to the flow in step S100. The same applies to the anode side.

  As described above, the gas supply in this scavenging position is the air supply in the white arrow shown in FIG. 7 on the cathode side, and the air flows downstream through the gas flow path forming member 30 to diffuse the gas in the MGEA 23. Supplied to layer 23a. That is, the air supplied by the scavenging position is guided to the gas diffusion layer 23a side of the MGEA 25 through the inclined bond part 30B and the strand part 30S of each through hole 30H of the gas flow path forming member 30. After passing through 30H, it flows downstream and enters the gas diffusion layer 23a of the MGEA 23. In this case, although air interferes with the inclined bond part 30B and the strand part 30S, since these are inclined with the through-hole 30H and are multi-staged (see FIG. 6), the gas flow path forming member 30 is directed toward the downstream side. Through the gas diffusion layer 23a of the MGEA 23 without any trouble. Then, the chance of contact between the gas diffusion layer 23a and the air supplied in the opposite direction to that during normal operation by the white arrow shown in FIG. 7 increases by the amount of guidance to the gas diffusion layer 23a. Therefore, when the air supplied at the scavenging position passes through the gas diffusion layer 23a while containing the moisture H stored on the side of the gas diffusion layer 23a and flowing out the moisture downstream for scavenging. Also take away moisture contained in the layer. For this reason, when the operation is stopped when the ignition switch 510 is turned off, the gas diffusion layer 23a can be dried more reliably and within a short time by air flowing in the direction opposite to that during normal operation. The same applies to the anode side.

  The control device 500 continues the valve position change in step S140 described above for a predetermined time (step S150), and then ends the process once and repeats the process in the above step.

  As described above, in the fuel cell system 1000 according to the present embodiment, when the normal operation for generating power according to the requested load is stopped when the operation control of the fuel cell 100 is performed, the normal operation state is maintained. Air / hydrogen gas is supplied to the cathode side and the anode side in the direction opposite to the flow of the supplied gas. In the gas supply in the opposite direction, the supplied air / hydrogen gas is guided to the gas diffusion layers 23a and 23b by the inclined bond portion 30B and the strand portion 30S to increase the chance of contact. For this reason, according to the present embodiment, as described above, the gas diffusion layers 23a, 23b can be dried more reliably and within a short time, so that the scavenging time can be shortened.

  In this embodiment, the positions of the valve unit 210 and the valve unit 310 are different when the direction of the hydrogen gas supply from the hydrogen gas supply source 200 and the air supply from the blower 300 is changed between normal operation and scavenging. The change only switches the connection state of the pipeline selectively. Therefore, with a simple configuration of changing the valve position, it is possible to easily achieve both power generation performance maintenance during normal operation and shortening of the scavenging time when normal operation is stopped.

  Next, a modified example of the gas flow path forming member will be described. FIG. 9 is an explanatory view showing a schematic configuration of the gas flow path forming member 30A of the modified example in a perspective view, and FIG. 10 is an equivalent view of FIG. 7, in which the gas flow path forming member 30A of the modified example is interposed between It is explanatory drawing which shows a mode that it built in.

  As shown in the drawing, the gas flow path forming member 30A of the modified example is formed using a thin plate such as stainless steel (for example, a thickness of about 0.1 mm) similarly to the gas flow path forming member 30, and is inclined by press molding. The protruding pieces 30AP are arranged in multiple rows. The inclined protruding piece 30AP can also be formed in a needle shape. This gas flow path forming member 30 </ b> A is incorporated between the MGEA 25 and the separator 40, and the gas flow path is formed by bringing the tip of the protruding piece 30 </ b> AP into contact with the gas diffusion layer 23 a of the MGEA 25. Even in the fuel cell 100 having the gas flow path forming member 30A, air is supplied by a black arrow in the drawing during normal operation, and the supplied air is supplied by the protruding pieces 30AP of the gas flow path forming member 30A. The gas flows downstream while being guided to the separator 40 side, and is supplied to the gas diffusion layer 23 a of the MGEA 23. In the scavenging, the direction of air supply is reversed, and the air supply is indicated by the white arrow in the figure. The supplied air is supplied to the MGEA 25 by the protruding pieces 30AP of the gas flow path forming member 30A. The gas flows downstream while being guided to the gas diffusion layer 23a, and enters the gas diffusion layer 23a. Therefore, even if it exists in the fuel cell 100 which has 30 A of gas flow path formation members of a modification, there can exist the effect mentioned above.

  As mentioned above, although the embodiment of the present invention has been described in the embodiments, the present invention is not limited to the above-described embodiments and modifications, and can be implemented in various modes without departing from the gist thereof. Is possible. For example, in the above-described embodiments, the dead-end type fuel cell 100 in which the gas and the cooling water are turned back has been described. .

  Further, in the fuel cell 100 having the gas flow path forming members 30 and 31, in the scavenging, the gas is supplied in the opposite direction to that in the normal operation, and the reverse gas supply is continued in the high load operation. Can also be performed. During a high load operation, since the electrochemical reaction proceeds actively, the amount of generated water increases and the MEA 24 tends to be excessively wet. Accordingly, when air is supplied in the opposite direction to that during normal operation as indicated by the white arrow in FIG. 7 during high load operation, the air is guided to the MGEA 25 side by the inclined bond portion 30B and the strand portion 30S. Therefore, moisture removal from the gas diffusion layer 23a in the MGEA 25 is active. For this reason, excessive wetting of the MEA 24 can be suppressed.

  In the above embodiment, the gas flow path forming members 30 and 31 having the inclined bond portion 30B and the strand portion 30S are disposed on both the anode side and the cathode side, but one of the anode and cathode electrodes is disposed. It is also possible to dispose the gas flow path forming member only on this side.

It is explanatory drawing which shows roughly the whole structure of the fuel cell system 1000 as an Example of this invention. 2 is an explanatory diagram showing a schematic configuration of a fuel cell 100. FIG. 3 is a schematic perspective view of a gas flow path forming member 30. FIG. 5 is an explanatory view showing a method for manufacturing the gas flow path forming member 30. FIG. It is explanatory drawing which shows schematically the mode of the manufacturing process of the gas flow path formation member 30 with a perspective view. FIG. 3 is an explanatory view illustrating a side view, a front view, and an arrow view from obliquely above the gas flow path forming member 30. It is explanatory drawing which shows a mode that the gas flow path formation member 30 was integrated between MGEA25 and the separator 40. As shown in FIG. 3 is a flowchart showing operation control of the fuel cell 100 executed by a control device 500. It is explanatory drawing which shows the schematic structure of 30 A of gas flow path formation members of a modification in a perspective view. FIG. 8 is an equivalent diagram of FIG. 7, and is an explanatory view schematically showing a state in which a modified gas flow path forming member 30 </ b> A is incorporated between the MGEA 25 and the separator 40.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 20a-20f ... Communication hole 21 ... Electrolyte membrane 22a ... Cathode electrode catalyst layer 22b ... Anode electrode catalyst layer 23a ... Gas diffusion layer 23b ... Gas diffusion layer 26 ... Seal gasket 26a ... Convex part 30, 31 ... Gas flow path forming member 30A ... Gas flow path forming member 30B ... Bond part 30H ... Through hole 30S ... Strand part 30AP ... Projection piece 40 ... Separator 41 ... Cathode plate 41a-41f ... Through hole 42 ... Intermediate plate 42a ... Through hole 42b ... through hole 43 ... anode plate 45 ... hole 85, 86 ... end plate 85a to 85f ... through hole 100 ... fuel cell 200 ... hydrogen gas supply source 210 ... valve unit 212 ... upstream supply line 214 ... downstream supply pipe Path 216 ... Upstream exhaust pipe 218 ... Downstream exhaust pipe 300 ... Bro DESCRIPTION OF SYMBOLS 310 ... Valve unit 312 ... Upstream supply pipe 314 ... Downstream supply pipe 316 ... Upstream exhaust pipe 318 ... Downstream exhaust pipe 400 ... Radiator 500 ... Control device 510 ... Ignition switch 512 ... Sensor group 1000 ... Fuel Battery system NLH ... Hydrogen gas normal path SLH ... Hydrogen gas scavenging path NLO ... Air normal path SLO ... Air scavenging path M ... Processing equipment UB ... Upper blade DB ... Lower blade

Claims (3)

A fuel cell having a stack structure in which a plurality of membrane electrode assemblies in which gas diffusion electrodes are bonded to both surfaces of an electrolyte membrane are stacked with a separator interposed therebetween,
A flow path forming member which is incorporated between the membrane electrode assembly and the separator and forms a gas supply flow path for supplying gas over the electrode surface of the gas diffusion electrode;
During normal operation in which the fuel cell is operated for power generation, the gas is supplied in a first flow direction from one side of the electrode surface to the other side with respect to the flow path forming member. A gas introducing means for guiding the gas in a second flow direction opposite to the first flow direction with respect to the flow path forming member when the normal operation is stopped;
The flow path forming member on at least one side of the membrane electrode assembly includes a plurality of inclined portions inclined so that gas can flow downstream in the gas supply flow path,
The inclined portion causes the gas introduced in the second flow direction to flow downstream along the second flow direction while guiding the gas introduced to the gas diffusion electrode side. The fuel cell according to claim 1,
A first gas flow path formed outside the electrode surface so that gas flows to each flow path forming member between the membrane electrode assembly having the stack structure and the separator;
The first gas channel and a second gas channel formed outside the electrode surface across the electrode surface so as to guide the gas that has passed through each of the channel forming members to the outside;
The gas introduction means guides the gas from the first gas flow path in the first flow direction to the second gas flow path, and transfers the gas from the second gas flow path in the second flow direction. A fuel cell leading to the first gas flow path. The fuel cell according to claim 1 or 2, wherein
With a gas supply,
The gas introduction means selectively connects the supply source to one of the first gas flow path and the second gas flow path.

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