JP2008282580A - Fuel cell and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and a fuel cell system, capable of improving a lower temperature starting performance of the fuel cell. <P>SOLUTION: The fuel cell has a laminated structure of a plurality of unit cells 10, and receives a reaction gas to perform the power generation. The unit cell 10 has an MEA 20 in which electrodes are arranged on both surfaces of an electrolyte film, a porous member flow passage 14 disposed such that an oxidization gas as the reaction gas flows along a surface of the MEA 20, and a plate 42 arranged between the MEA 20 and the porous member flow passage 14 at a cathode upstream region. The plate 42 is structured, as a flat plate, so as to spread in a laminated direction of the fuel cell when the fuel cell is at a low temperature. The plate 42 is preferably made of shape memory alloy so as to spread in the laminated direction of the fuel cell when the fuel cell is at a subfreezing temperatures. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell and a fuel cell system.

  The fuel cell is used as a fuel cell stack in which a plurality of fuel cell cells (hereinafter referred to as “unit cells”) are stacked. The unit cell itself is also a laminate of planar members, and has a membrane electrode assembly (MEA) composed of an electrolyte membrane sandwiched between an anode and a cathode, and the MEA is sandwiched between separators from both sides. It is composed of that.

  In such a fuel cell, since the power generation efficiency is greatly reduced when the fuel cell is started at a low temperature, it takes a considerable time to reach a desired power generation state. In view of this, for example, Japanese Patent Application Laid-Open No. 2004-103477 discloses a fuel cell that can quickly start a fuel cell at a low temperature. According to this fuel cell, the thermal conductivity in the central portion of the MEA is configured to be lower than in other portions. According to such a configuration, when starting at a low temperature, the amount of heat propagating from the MEA central portion to the outside is suppressed, so that a power generation reaction is actively performed in the MEA central portion. For this reason, MEA can be rapidly heated to desired temperature by propagating the reaction heat by the said electric power generation reaction to circumference | surroundings.

JP 2004-103477 A

  However, when a power generation reaction is performed in the fuel cell, water is generated on the cathode side of the MEA by the reaction between the supplied oxygen and the proton that has moved through the electrolyte membrane. That is, in the above-described conventional fuel cell, water is generated at the MEA central portion at low temperature startup. For this reason, when the generated water flows toward the downstream side of the cathode flow channel, the moisture may condense or freeze in a low temperature region where the power generation reaction has not yet been performed, and power generation efficiency may be reduced. As described above, the conventional fuel cell that does not consider the flow of moisture generated by power generation still leaves room for improvement in order to perform a low temperature start well.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a fuel cell and a fuel cell system that can improve low-temperature startability.

In order to achieve the above object, a first invention is a fuel cell,
In a fuel cell having a structure in which a plurality of unit cells are stacked and generating power by receiving supply of a reaction gas,
The unit cell is
A membrane electrode assembly in which electrodes are arranged on both surfaces of the electrolyte membrane;
An oxidizing gas flow path provided so that an oxidizing gas as the reaction gas flows along the surface of the membrane electrode assembly;
A plate disposed in a region corresponding to the upstream side of the oxidizing gas channel between the membrane electrode assembly and the oxidizing gas channel;
The plate is a flat plate configured to spread in the stacking direction of the fuel cells when the temperature of the fuel cells is low.

According to a second invention, in the first invention,
The plate is a shape memory alloy that is configured to spread in the stacking direction of the fuel cells when the fuel cells are below freezing.

According to a third invention, in the first or second invention,
The oxidizing gas flow path includes a gas diffusion layer disposed on a surface facing the membrane electrode assembly.

A fourth invention is any one of the first to third inventions,
The plate has a plurality of through holes.

A fifth invention is the fuel cell system according to the first invention,
A membrane electrode assembly in which electrodes are arranged on both surfaces of the electrolyte membrane; an oxidizing gas flow path in which an oxidizing gas as the reaction gas flows along the cathode surface of the membrane electrode assembly; and the reaction A fuel cell having a plurality of unit cells each having a fuel gas flow path provided so that a fuel gas as a gas flows along the anode surface of the membrane electrode assembly;
Contact resistance control means for controlling the contact resistance in the membrane electrode assembly for each predetermined region;
With
The contact resistance control means increases contact resistance in a region corresponding to the upstream side of the oxidizing gas flow path in the membrane electrode assembly when the fuel cell is started at a low temperature.

According to a sixth invention, in the fifth invention,
A temperature acquisition means for acquiring the temperature of the fuel cell;
The contact resistance control means increases contact resistance in a region corresponding to the upstream side of the oxidizing gas flow path in the membrane electrode assembly when the temperature of the fuel cell is below freezing point.

A seventh invention is the fifth or sixth invention, wherein
The terminal further disposed at the end of the fuel cell and divided into a plurality along the gas flow direction in the oxidizing gas flow path,
The contact resistance control means includes
Pressurizing means for pressurizing the fuel cell from the outer surface of each terminal;
When the fuel cell is started at a low temperature, the surface pressure in the region corresponding to the upstream side of the oxidizing gas flow channel in the fuel cell is smaller than the surface pressure in the region corresponding to the downstream side of the oxidizing gas flow channel. Thus, the pressurizing means is controlled.

  According to the first aspect of the present invention, the region corresponding to the upstream side of the oxidizing gas channel (hereinafter, “ The plate is arranged in the “cathode upstream region”. The plate is made of a material that spreads in the fuel cell stacking direction when the fuel cell is started at a low temperature. When the plate spreads in the fuel cell stacking direction, the contact resistance in the upstream region of the cathode in the membrane electrode assembly increases. Therefore, according to the present invention, the power generation reaction can be concentrated in the region corresponding to the downstream of the oxidizing gas flow path (hereinafter referred to as “cathode downstream region”) when the fuel cell is started at a low temperature. The generated moisture can be discharged outside without circulating through a low temperature region where power generation is not actively performed. As a result, a situation in which the power generation efficiency of the fuel cell decreases due to condensation or freezing of the generated water in the flow path can be effectively suppressed, and low-temperature startability can be effectively improved.

  According to the second aspect of the invention, the plate is made of a shape memory alloy that is deformed so as to spread in the stacking direction of the fuel cell below the freezing point and deforms into a flat plate shape when the freezing point is removed. Therefore, according to the present invention, when the temperature of the fuel cell is below freezing, the power generation reaction is effectively concentrated in the downstream region of the cathode, and when the temperature is below freezing, the power generation reaction is performed on the entire surface of the MEA. it can.

  According to the third invention, the plate is disposed between the MEA and the gas diffusion layer. Therefore, according to the present invention, when the fuel cell is started at a low temperature, the contact resistance between the MEA and the gas diffusion layer in the cathode upstream region can be increased, and the power generation reaction in the region can be efficiently suppressed.

  According to the fourth invention, the plate is formed with a plurality of through holes for the reaction gas and moisture to pass therethrough. For this reason, according to this invention, even if it is the area | region where the plate is arrange | positioned, supply of the gas to a membrane electrode assembly and discharge of generated water can be performed without a problem.

  According to the fifth invention, in the system that can control the contact resistance in the membrane electrode assembly for each region, it is possible to increase the contact resistance in the cathode upstream region when the fuel cell is started at a low temperature. For this reason, according to the present invention, the power generation reaction can be concentrated in the cathode downstream region at the time of low temperature startup of the fuel cell, so that the moisture generated by the power generation reaction can be removed from the low temperature region where power generation is not actively performed. It can be discharged outside without being distributed. As a result, a situation in which the power generation efficiency of the fuel cell decreases due to condensation or freezing of the generated water in the flow path can be effectively suppressed, and low-temperature startability can be effectively improved.

  According to the sixth invention, when the temperature of the fuel cell is below freezing point, the contact resistance in the cathode upstream region is increased. For this reason, according to the present invention, the power generation reaction can be concentrated in the cathode downstream region at the time of low temperature start-up of the fuel cell, and the situation where the generated water freezes before being discharged is effectively suppressed. Can do.

  According to the seventh invention, the terminal disposed at the end of the fuel cell is divided into a plurality along the oxidizing gas flow path, and the contact resistance in the membrane electrode assembly is increased by pressurizing each terminal from the outside. Are controlled for each region. Therefore, according to the present invention, at the time of low temperature startup of the fuel cell, by reducing the pressurization amount of the terminal corresponding to the cathode upstream region as compared with the pressurization amount of the terminal corresponding to the cathode downstream region, The contact resistance in the cathode upstream region can be effectively increased.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The fuel cell as an embodiment of the present invention is used in a power generation system (fuel cell system) as shown in FIG. FIG. 7 is a schematic configuration diagram showing an entire fuel cell system in which the fuel cell according to the present invention can be used. This fuel cell system is suitable as a vehicle fuel cell system mounted on a fuel cell vehicle. Of course, application to fuel cell systems for other purposes is also possible.

  In the fuel cell system shown in FIG. 7, hydrogen (hereinafter also referred to as “anode gas”) as a fuel gas is supplied to the fuel cell 100. Hydrogen supplied to the fuel cell 100 is stored in a high-pressure hydrogen tank 114. The hydrogen tank 114 and the anode of the fuel cell 100 are connected by a hydrogen supply pipe 110, and a shut valve 116 and a pressure regulating valve 118 are disposed in the middle of the hydrogen supply pipe 110. Further, an off-gas discharge pipe 112 for discharging anode off-gas is connected to the anode of the fuel cell 100. The off-gas discharge pipe 112 is connected to the downstream side of the pressure regulating valve 118 in the hydrogen supply pipe 110 and constitutes a hydrogen circulation system together with the hydrogen supply pipe 110. A circulation pump 120 for circulating hydrogen in the circulation system is disposed in the middle of the offgas discharge pipe 112.

  In this system, air as an oxidizing gas (hereinafter also referred to as “cathode gas”) is supplied to the fuel cell 100. Air supplied to the fuel cell 100 is taken in from the atmosphere by the compressor 134. The compressor 134 and the cathode of the fuel cell 100 are connected by an air supply pipe 130. Further, an off-gas discharge pipe 132 for discharging the cathode off-gas is connected to the cathode of the fuel cell 100. The off gas discharge pipe 132 is opened to the atmosphere, and a pressure regulating valve 136 for adjusting the air pressure is provided in the middle of the pipe line.

  Further, in this system, a coolant (water, antifreeze, air, or the like) for cooling the fuel cell 100 is supplied to the fuel cell 100 separately from the reaction gas (fuel gas and oxidizing gas). The fuel cell 100 is connected to a refrigerant supply pipe 140 for supplying a refrigerant and a refrigerant discharge pipe 142 for discharging the refrigerant. Both the refrigerant supply pipe 140 and the refrigerant discharge pipe 142 are connected to the radiator 146, and the refrigerant circulates from the refrigerant discharge pipe 142 to the refrigerant supply pipe 140 through the radiator 146. A circulation pump 148 for circulating the refrigerant in the circulation system is arranged in the middle of the refrigerant discharge pipe 142.

  The fuel cell 100 of the present embodiment has a configuration as shown in FIG. FIG. 1 is a cross-sectional view schematically showing the configuration of the fuel cell 100 of the present embodiment. As shown in FIG. 1, a fuel cell stack (hereinafter also referred to as “FC stack”) 100 has a stack structure in which a plurality of unit cells 10 are stacked. The unit cell 10 includes a power generation body 12, porous body channels 14 and 16 through which cathode gas and anode gas flow, and a separator 18 that isolates adjacent power generation bodies 12. The power generation body 12 is integrally formed outside a membrane electrode assembly (MEA) 20 in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween, and a gas diffusion layer (not shown) is surrounded by a seal gasket.

  The porous body channels 14 and 16 are formed of a foamed sintered metal such as stainless steel, titanium, or a titanium alloy, or a porous body having a large number of pores inside a metal mesh or the like. Since the porous body channels 14 and 16 are mainly intended to flow the reaction gas in a predetermined direction, a porous body having a relatively high porosity is formed so as to suppress the pressure loss of the flow of the reaction gas and to structure drainage. used. The reaction gas introduced into the porous channels 14 and 16 passes through the internal pores and is supplied to the anode and cathode of the MEA 50.

  As shown in FIG. 1, a space is formed in the fuel cell 10, and these extend in the stacking direction of the unit cells 10, thereby forming a cathode system inlet manifold 30 and a cathode system outlet manifold 32. Yes. The porous body flow path 14 described above is provided so as to be interposed between the cathode system inlet manifold 30 and the cathode system outlet manifold 32. Similarly, the FC stack 100 is formed with an anode inlet manifold and an anode outlet manifold (not shown). The porous body channel 16 described above is provided so as to be interposed between the anode inlet manifold and the anode outlet manifold.

  The separator 18 is a three-layer laminated separator formed by laminating thin conductive metal plates such as stainless steel and titanium. More specifically, the cathode plate 22 is in contact with the porous body flow path 14, the anode plate 24 is in contact with the porous body flow path 16, and an intermediate plate 26 sandwiched between these plates. . As shown in FIG. 1, the intermediate plate 26 has a plurality of grooves. Thereby, a plurality of refrigerant flow paths 28 are formed in the separator 18.

  FIG. 2 is a schematic diagram showing the internal structure of the unit cell 10 as viewed from the stacking direction of the FC stack 100 shown in FIG. As shown in FIG. 2, the unit cell 10 has the spaces as the inlet manifold 30 and the outlet manifold 32 described above. The cathode gas introduced into the inlet manifold 30 flows through the porous body flow path 14 toward the outlet manifold 32. Similarly, in the unit cell 10, spaces as an anode inlet manifold 34, an anode outlet manifold 36, a cooling inlet manifold 38, and a cooling outlet manifold 40 are formed.

  Here, a plate 42 is disposed in the cathode upstream region of the unit cell 10. FIG. 3 is a schematic diagram showing in detail a part of the III-III cross section in the unit cell 10 shown in FIG. As shown in this figure, diffusion layers 44 and 46 are provided between the MEA 20 and the porous flow paths 14 and 16, and the plate 42 is disposed between the MEA 20 and the diffusion layer 46. . The plate 42 is a shape memory alloy that spreads in the stacking direction below the freezing point. For example, a Ni—Ti alloy having a composition such that the transformation point is in the vicinity of 0 ° C. is used. Further, the plate 42 is provided with a plurality of holes through which reaction gas and moisture pass.

[Operation in Embodiment 1]
Next, the operation of the present embodiment will be described with reference to FIGS. In order to improve the startability from below freezing point in a fuel cell, it is important to concentrate the power generation reaction in a part of the region and break through the freezing point quickly. For this reason, in the conventional system described above in “Problem to be Solved by the Invention”, the thermal conductivity of the central portion is compared with other regions so that the power generation reaction is actively performed in the central portion of the unit cell. Therefore, heat radiation to the outer periphery is suppressed.

  FIG. 4 is a diagram for explaining a state inside the stack when sub-freezing power generation is locally started in the central portion of the MEA 20. As shown in this figure, when a power generation reaction is started in a fuel cell below freezing point, the temperature rises in the central portion of the MEA 20 having low thermal conductivity, and the freezing point is broken through locally. Thereby, the power generation reaction is actively performed in the central portion, and the generated reaction heat is propagated to the surroundings, so that the power generation range is efficiently expanded.

  Here, when the power generation reaction is performed, water is generated on the cathode side of the MEA 20. The generated water is used for humidifying the MEA 20, but excess water flows through the porous body flow path 14 together with the off gas after the reaction and is discharged from the outlet manifold 32. For this reason, if the produced | generated water | moisture content distribute | circulates in the range which has not exceeded the freezing point, there exists a possibility that the said produced | generated water may dew condensation or freeze in the porous body flow path 14. As shown in FIG. When such a situation occurs, the porous body flow path 14 is blocked, resulting in a decrease in power generation efficiency.

  Therefore, in the present embodiment, the unit cell 10 on which the plate 42 is arranged is used. FIG. 5 is a diagram for explaining a state in the stack when sub-freezing power generation is started in the unit cell 10 having the plate 42. As described above, the plate 42 is configured as a shape memory alloy that extends in the stacking direction below the freezing point and becomes a substantially planar shape when breaking below the freezing point. That is, below freezing, the contact resistance between the MEA 20 and the diffusion layer 44 can be increased in the region where the plate 42 is disposed, and the power generation reaction in the region can be suppressed.

  As shown in FIG. 5, when sub-freezing power generation is started in the fuel cell having the plate 42, a power generation reaction is locally started in a range where the contact resistance is small, that is, in the cathode downstream region where the plate 42 is not disposed. The water generated by the power generation reaction is discharged to the outlet manifold 32 without flowing through the range below the freezing point in the porous body flow path 14. For this reason, it is possible to effectively avoid a situation in which the gas flow path is blocked due to condensation or freezing of the generated water in the porous body flow path 14. Thereby, the fall of the power generation efficiency in a fuel cell can be suppressed, and low temperature starting property can be improved effectively.

  FIG. 6 is a diagram for explaining a state inside the stack when the unit cell 10 having the plate 42 is removed from below freezing point. As shown in FIG. 6, when the reaction heat generated by the power generation reaction in the cathode downstream region is propagated to the surroundings, the freezing point breakthrough range is expanded to the cathode upstream region. When the plate 42 breaks through the freezing point, the plate 42 is deformed into a substantially planar shape to reduce the contact resistance of the MEA 20. For this reason, the power generation range is gradually expanded from the range where the freezing point in the plate 42 is broken.

  As described above, according to the fuel cell of the present embodiment, the plate 42 arranged in the cathode upstream region is configured to spread in the stacking direction of the fuel cell below the freezing point. For this reason, the contact resistance in the cathode upstream region of the MEA 20 can be effectively increased at the time of starting below freezing point. As a result, the power generation reaction can be concentrated locally in the downstream region of the cathode, and the reaction heat generated by the power generation reaction is propagated to the surroundings, so that the low-temperature startability can be effectively improved.

  Further, when the power generation reaction is concentrated in the cathode downstream region, moisture generated by the power generation reaction can be discharged outside without passing through the low temperature region. For this reason, it is possible to effectively avoid a situation where the generated water is condensed or frozen in the flow path and the power generation efficiency is lowered.

  By the way, in Embodiment 1 mentioned above, it is supposed that the plate 42 is arrange | positioned between MEA20 and the diffusion layer 46 in the unit cell 10, However, The arrangement | positioning of the said plate 42 is not restricted to this. That is, as long as the contact resistance on the surface of the MEA 20 can be changed, it may be disposed between the diffusion layer 46 and the porous body flow path 14. Further, when the fuel cell does not have the diffusion layer 44 or the diffusion layer 44 is formed integrally with the MEA 20, it may be disposed between the MEA 20 and the porous body flow path 14.

  Moreover, in Embodiment 1 mentioned above, although the plate 42 shall use a shape memory alloy, the material to be used is not restricted to this. That is, as long as the material is deformed based on temperature in the vicinity of 0 ° C., for example, bimetal or the like may be used.

  In the first embodiment described above, the porous body channel 14 corresponds to the “oxidizing gas channel” in the first invention, and the diffusion layer 46 corresponds to the “gas diffusion layer” in the third invention. is doing.

Embodiment 2. FIG.
[Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a schematic configuration diagram showing the entire fuel cell system on which the FC stack 200 according to the second embodiment is mounted. In the fuel cell system shown in FIG. 8, elements common to the fuel cell system shown in FIG.

  In the fuel cell system shown in FIG. 8, the surface pressure variable mechanism 52 is arranged in the FC stack 200. As will be described later, the surface pressure variable mechanism 52 includes a mechanism capable of controlling the surface pressure of the FC stack 200 for each predetermined region. A temperature sensor 62 is disposed in the refrigerant discharge pipe 142. The temperature sensor 62 acquires the temperature of the refrigerant discharged from the FC stack 200.

  Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 60 as shown in FIG. The output of the temperature sensor 62 described above is supplied to the ECU 60. The ECU 60 performs processing such as control of the variable surface pressure mechanism 52 based on these sensor outputs.

  FIG. 9 is a diagram schematically showing the internal structure of the FC stack 200 and its peripheral devices. In the fuel cell shown in FIG. 9, elements common to the fuel cell shown in FIG.

  As shown in FIG. 9, at the end of the FC stack 200 in which the unit cells 50 are stacked, a terminal 54a is disposed in the cathode upstream region, and a terminal 54b is disposed in the cathode downstream region (hereinafter, these are not particularly distinguished). Sometimes referred to as “Terminal 54”). In addition, coil springs 56 a and 56 b (hereinafter referred to as “coil spring 56” unless otherwise specified) are arranged as the surface pressure variable mechanism 52 in the terminals 54 a and 54 b, respectively. A control device (not shown) for controlling the amount of displacement of the coil spring 56 is connected to the other end of the coil spring 56.

[Characteristic operation of the second embodiment]
Next, characteristic operations in the second embodiment will be described with reference to FIGS. FIG. 10 is a diagram for explaining a state inside the stack in the FC stack 200 when sub-freezing power generation is started. As shown in this figure, when the power generation reaction is started below freezing point, the amount of compression displacement of the coil spring 56a in the upstream region of the cathode is set smaller than the amount of compression variation of the coil spring 56b. When the amount of compressive displacement is set to a small value, the surface pressure inside the stack decreases, so that the contact resistance in the cathode upstream region becomes larger than that in the cathode downstream region. Thereby, since the power generation reaction at the time of starting below the freezing point can be concentrated on the cathode downstream region, the water generated by the power generating reaction can be effectively discharged to the outside, and the starting property from below the freezing point can be improved.

  When the temperature of the FC stack 200 gradually rises due to reaction heat, the power generation possible range is expanded. FIG. 11 is a diagram for explaining a state inside the stack when the FC stack 200 has escaped from the below freezing point state. As shown in this figure, when the reaction heat generated by the power generation reaction in the cathode downstream region is propagated to the surroundings and the cathode upstream region deviates below freezing point, the amount of compression displacement of the coil spring 56a in the cathode upstream region becomes the compression variation of the coil spring 56b. It is set equal to the amount. When the contact resistance in the cathode upstream region decreases, the power generation range is expanded over the entire surface of the MEA 20. Thus, by controlling the surface pressure variable mechanism 52 during sub-zero power generation, the range in which the power generation reaction is actively performed on the MEA 20 surface can be limited.

[Specific Processing of Embodiment 2]
Next, specific processing of the present embodiment will be described with reference to FIG. FIG. 12 is a flowchart of a routine that is executed by the ECU 60 in order to perform the below-freezing start of the FC stack 50 in the second embodiment of the present invention. In the routine shown in FIG. 12, first, the refrigerant temperature Tw is detected (step 100). Since the refrigerant absorbs heat in the FC stack 200, the refrigerant temperature Tw is used as the internal temperature of the FC stack 200. Here, specifically, the temperature of the refrigerant discharged from the FC stack 50 is acquired based on the output signal of the temperature sensor 62 provided in the refrigerant discharge pipe 142.

  Next, it is determined whether or not the refrigerant temperature Tw acquired in step 100 is lower than 0 ° C. (step 102). As a result, if it is confirmed that Tw <0 ° C. is established, it is determined that the stack is below freezing, and the process proceeds to the next step, where the surface pressure in the cathode upstream region is larger than that in the cathode downstream region. The surface pressure variable mechanism 52 is controlled so as to decrease (step 104). Specifically, the amount of compressive displacement of the coil spring 56a is controlled to be smaller than the amount of compressive displacement of the coil spring 56b.

  On the other hand, if the establishment of Tw <0 ° C. is recognized in step 102, it is determined that the stack has already left the freezing point state, and the process proceeds to the next step. The surface pressure in the region is controlled so as to be the normal operation surface pressure (step 106).

  As described above, according to the fuel cell system of the second embodiment, the stack surface pressure in the cathode upstream region is set lower than that in the cathode downstream region when starting below freezing. The contact resistance is increased in the region where the stack surface pressure is low. For this reason, the power generation region can be concentrated in the cathode downstream region, and the water generated by the power generation reaction can be effectively discharged from the outlet manifold 32. As a result, it is possible to effectively avoid a situation in which the generated water is condensed or frozen in the sub-freezing region to block the cathode path.

  By the way, in the second embodiment described above, the terminal 54 is divided into two and the stack surface pressure in the cathode upstream region and the cathode downstream region is individually controlled. I can't. That is, if it is divided along the flow direction of the cathode gas, the terminal 54 may be divided into three or more to control the stack surface pressure in more detail.

  In the second embodiment described above, the compression displacement amount of the spring 56 provided in each terminal 54 is controlled to control the stack surface pressure for each region, but the stack surface pressure for each region is controlled. The configuration to be performed is not limited to this. That is, as long as the amount of pressure applied to each terminal 54 can be controlled individually, another actuator may be used instead of the spring 56.

  In the second embodiment described above, the porous body flow path 14 is the “oxidizing gas flow path” in the fifth invention, and the variable surface pressure mechanism 52 is the “pressurizing means” in the seventh invention. Each corresponds.

  In the second embodiment described above, the ECU 60 executes the process of step 104, and the “contact resistance control means” in the fifth aspect of the invention executes the process of step 100. The “temperature acquisition means” according to the sixth aspect of the invention is executed.

2 is a cross-sectional view schematically showing a configuration of an FC stack 100 according to the first embodiment. FIG. It is a schematic diagram which shows the internal structure of the unit cell 10 seen from the lamination direction of the FC stack 100 shown in FIG. FIG. 3 is a schematic diagram showing in detail a part of the III-III cross section of the unit cell 10 shown in FIG. 2. It is a figure for demonstrating the state inside a stack | stack when sub-zero power generation is started locally in the center part of MEA20. FIG. 6 is a diagram for explaining a state inside the stack when sub-freezing power generation is started in the FC stack. It is a figure for demonstrating the state inside a stack | stuck when the FC stack | stuck 100 has left the freezing point state. 1 is a schematic configuration diagram showing an entire fuel cell system applicable to Embodiment 1. FIG. It is a schematic block diagram which shows the whole fuel cell system by which FC stack 200 in this Embodiment 2 is mounted. It is a figure which shows typically the internal structure of FC stack 200 and its peripheral device. 6 is a diagram for explaining a state inside a stack when sub-zero power generation is started in the FC stack 200. FIG. It is a figure for demonstrating the state inside a stack when FC stack 200 has escaped from the freezing point state. FIG. 6 is a flowchart of a routine that is executed by the ECU 60 in order to carry out the below-freezing start of the FC stack 200 in the second embodiment.

Explanation of symbols

10 unit cell 12 power generation body 14 porous body flow path 16 porous body flow path 18 separator 22 cathode plate 24 anode plate 26 intermediate plate 30 inlet manifold 32 outlet manifold 42 plate 44 diffusion layer 46 diffusion layer 50 unit cell 52 surface pressure variable mechanism 54 Terminal 56 Coil spring 60 ECU (Electronic Control Unit)
62 Temperature sensor 100, 200 Fuel cell (FC) stack 110 Hydrogen supply pipe 112 Off gas discharge pipe 114 Hydrogen tank 116 Shut valve 118 Pressure regulating valve 120 Circulation pump 130 Air supply pipe 132 Off gas discharge pipe 134 Compressor 136 Pressure regulating valve 140 Refrigerant supply Pipe 142 Refrigerant discharge pipe 146 Radiator 148 Circulation pump

Claims (7)

In a fuel cell having a structure in which a plurality of unit cells are stacked and generating power by receiving supply of a reaction gas,
The unit cell is
A membrane electrode assembly in which electrodes are arranged on both surfaces of the electrolyte membrane;
An oxidizing gas flow path provided so that an oxidizing gas as the reaction gas flows along the surface of the membrane electrode assembly;
A plate disposed in a region corresponding to the upstream side of the oxidizing gas channel between the membrane electrode assembly and the oxidizing gas channel;
The fuel cell according to claim 1, wherein the plate is a flat plate configured to spread in a stacking direction of the fuel cells when the temperature of the fuel cell is low.   2. The fuel cell according to claim 1, wherein the plate is a shape memory alloy configured to spread in a stacking direction of the fuel cells when the fuel cells are below freezing.   3. The fuel cell according to claim 1, wherein the oxidizing gas flow path includes a gas diffusion layer disposed on a surface facing the membrane electrode assembly.   The fuel cell according to claim 1, wherein the plate has a plurality of through holes. A membrane electrode assembly in which electrodes are arranged on both surfaces of the electrolyte membrane; an oxidizing gas flow path in which an oxidizing gas as the reaction gas flows along the cathode surface of the membrane electrode assembly; and the reaction A fuel cell having a plurality of unit cells each having a fuel gas flow path provided so that a fuel gas as a gas flows along the anode surface of the membrane electrode assembly;
Contact resistance control means for controlling the contact resistance in the membrane electrode assembly for each predetermined region;
With
The fuel cell system characterized in that the contact resistance control means increases a contact resistance in a region corresponding to an upstream side of the oxidizing gas flow path in the membrane electrode assembly when the fuel cell is started at a low temperature. A temperature acquisition means for acquiring the temperature of the fuel cell;
The contact resistance control means increases contact resistance in a region corresponding to the upstream side of the oxidizing gas flow path in the membrane electrode assembly when the temperature of the fuel cell is below freezing point. 5. The fuel cell system according to 5. The terminal further disposed at the end of the fuel cell and divided into a plurality along the gas flow direction in the oxidizing gas flow path,
The contact resistance control means includes
Pressurizing means for pressurizing the fuel cell from the outer surface of each terminal;
When the fuel cell is started at a low temperature, the surface pressure in the region corresponding to the upstream side of the oxidizing gas flow channel in the fuel cell is smaller than the surface pressure in the region corresponding to the downstream side of the oxidizing gas flow channel. The fuel cell system according to claim 5 or 6, wherein the pressurizing means is controlled as described above.

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