JP2010153174A - Assembly method for fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an assembly method for a fuel cell stack capable of preventing load slipping-off as much as possible at the time of an operation in consideration of load variation over a utilized environmental range of the fuel cell stack. <P>SOLUTION: The assembly method for a fuel cell stack has a fastening process of fastening the fuel cell stack 12 by giving the fastening load to one set of end plate 28, a first detection process of operating the fuel cell stack 12 at the maximum load and detecting the first fastening load of the fuel cell stack 12 at the time of the operation at the maximum load, a second detection process of stopping the operation of the fuel cell stack 12 and detecting a second fastening load of the fuel cell stack 12 while the fuel cell stack 12 is cooled at temperature under the freezing point, and an adding process of adding the fastening load periodically varied between the first fastening load and the second fastening load to the newly-assembled fuel cell stack 12. The adding process is continued until an amount of variations of the total length of the fuel cell stack 12 in the laminated direction is within a designated zone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a laminate in which a plurality of electrolyte / electrode assemblies each provided with an electrode on both sides of an electrolyte are stacked with separators interposed therebetween, and a pair of end plates are arranged at both ends in the stacking direction of the laminate. The present invention relates to a method for assembling an installed fuel cell stack.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (an electrolyte / electrode structure) in which an anode electrode and a cathode electrode are disposed on both sides of an electrolyte membrane (electrolyte) made of a polymer ion exchange membrane, respectively. ) (MEA) is sandwiched between separators. This type of fuel cell is used as a fuel cell stack in which a predetermined number of electrolyte membrane / electrode structures and separators are laminated.

  Normally, a desired tightening load is applied to the fuel cell stack in the stacking direction. However, when the tightening load is applied over a long period of time, for example, in the fuel cell stack, for example, an electrolyte membrane / electrode structure Is likely to occur. For this reason, there is a problem that the tightening load and electrode load of the fuel cell stack are reduced, the contact resistance is increased, the terminal voltage is lowered, and the rigidity is lowered.

  Therefore, in order to suppress fluctuations in the length of the fuel cell stack, a fuel cell disclosed in Patent Document 1 and a manufacturing method thereof are known. This manufacturing method is characterized by having an aging process in which at least a compressive load is applied to the cell module to advance the initial creep.

JP 2006-294492 A

  In general, the environmental temperature region of the fuel cell stack covers a wide range from below freezing to room temperature (several tens of degrees Celsius). In particular, under a low temperature environment of −20 ° C. or lower, it is known that the tightening load is significantly reduced by drying of the electrolyte membrane / electrode structure.

  However, in the above-mentioned Patent Document 1, starting at below freezing point is not taken into consideration, and an increase in contact resistance due to load loss of the fuel cell stack is caused, and a problem that a shear strength is reduced due to a decrease in rigidity occurs. is there.

  The present invention solves this type of problem, taking into account load fluctuations over the usage environment region of the fuel cell stack, and capable of preventing load loss during operation as much as possible with a simple process. An object is to provide a method for assembling a battery stack.

  The present invention includes a laminate in which a plurality of electrolyte / electrode assemblies each provided with an electrode on both sides of an electrolyte are stacked with separators interposed therebetween, and a pair of end plates are arranged at both ends in the stacking direction of the laminate. The present invention relates to a method for assembling a provided fuel cell stack.

  This assembly method includes a tightening step of tightening the fuel cell stack by applying a predetermined tightening load to a set of end plates in directions close to each other, operating the fuel cell stack at maximum load, and operating at maximum load. A first detection step of detecting a first tightening load of the fuel cell stack at a time, and stopping the operation of the fuel cell stack and cooling the fuel cell stack to a temperature below freezing point. 2 a second detection step of detecting a tightening load, and an additional step of adding to the newly assembled fuel cell stack a tightening load that periodically varies between the first tightening load and the second tightening load; The above-described additional process is continued until the amount of change in the total length of the fuel cell stack in the stacking direction is within a predetermined range.

  Moreover, it is preferable that a clamping process is performed at normal temperature.

  Furthermore, the temperature below the freezing point is preferably set within a range of -20 ° C to -30 ° C.

  According to the present invention, in the aging of the assembled fuel cell stack, the tightening load that periodically varies between the first tightening load at the maximum load operation and the second tightening load at the temperature below freezing point is the fuel. It is attached to the battery stack.

  Therefore, the fuel cell stack is pre-applied with pressure fluctuations that exceed the load fluctuations during power generation, including low-temperature start-up, so that load loss during operation due to electrolyte membrane / electrode structure sag is minimized. It becomes possible to do. As a result, the tightening load and electrode load of the fuel cell stack can be maintained satisfactorily, and an increase in contact resistance and a decrease in rigidity can be prevented over a long period of time, and a good fuel cell stack can be reliably assembled. Become.

  FIG. 1 is a schematic configuration diagram of an assembling apparatus 10 for carrying out a method for assembling a fuel cell stack according to an embodiment of the present invention.

  The assembling apparatus 10 includes a pressing mechanism (for example, a pressing mechanism) 14 that applies a tightening load in the stacking direction in a state where the fuel cell stack 12 is disposed so that the stacking direction (arrow A direction) is directed in the direction of gravity. A pressure detection mechanism (for example, a load cell) 16 that detects a tightening load applied to the fuel cell stack 12, a displacement sensor 17 that detects a change amount in the stacking direction of the fuel cell stack 12, and the pressing mechanism 14 are controlled. And a controller 18 to which the tightening load detected by the pressure detection mechanism 16 and the displacement detected by the displacement sensor 17 are sent.

  The fuel cell stack 12 includes a laminated body 26 in which an electrolyte membrane (electrolyte) / electrode structure (MEA) 20 is laminated in a plurality with first and second separators 22 and 24 interposed therebetween. A pair of end plates 28 are disposed at both ends in the stacking direction. The first and second separators 22 and 24 are constituted by, for example, a carbon separator or a metal separator.

  As shown in FIGS. 1 and 2, between the electrolyte membrane / electrode structure 20 and the first and second separators 22 and 24, the periphery of the communication hole and the outer periphery of the electrode surface (power generation surface) described later are covered. Thus, a sealing member 29 such as a gasket is interposed. Note that the seal member 29 may be integrally formed with the first and second separators 22 and 24.

  One end edge of the laminate 26 in the arrow B direction (horizontal direction in FIG. 2) communicates with each other in the arrow A direction, which is the laminate direction, to oxidize for supplying an oxidant gas, for example, an oxygen-containing gas An agent gas supply communication hole 30a, a cooling medium discharge communication hole 32b for discharging a cooling medium, and a fuel gas discharge communication hole 34b for discharging a fuel gas, for example, a hydrogen-containing gas, are provided in the arrow C direction (vertical direction). Are provided in an array.

  The other end edge of the laminated body 26 in the direction of arrow B communicates with each other in the direction of arrow A, a fuel gas supply communication hole 34a for supplying fuel gas, and a cooling medium supply communication hole for supplying a cooling medium. 32a and an oxidant gas discharge communication hole 30b for discharging the oxidant gas are arranged in the direction of arrow C.

  The electrolyte membrane / electrode structure 20 includes, for example, a solid polymer electrolyte membrane 36 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 38 and a cathode side electrode 40 that sandwich the solid polymer electrolyte membrane 36. With.

  The anode side electrode 38 and the cathode side electrode 40 are formed by uniformly coating the surface of the gas diffusion layer with a gas diffusion layer made of carbon paper or the like and porous carbon particles having a platinum alloy supported on the surface. An electrode catalyst layer. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 36.

  The surface 22a of the first separator 22 on the electrolyte membrane / electrode structure 20 side is provided with, for example, an oxidant gas flow path 46 extending in the direction of arrow B. The gas supply communication hole 30a communicates with the oxidant gas discharge communication hole 30b.

  A fuel gas channel 48 communicating with the fuel gas supply communication hole 34a and the fuel gas discharge communication hole 34b is formed on the surface 24a of the second separator 24 on the electrolyte membrane / electrode structure 20 side. Between the surface 24 b of the second separator 24 and the surface 22 b of the first separator 22, a cooling medium flow path 50 that communicates with the cooling medium supply communication hole 32 a and the cooling medium discharge communication hole 32 b is formed.

  The operation of the fuel cell stack 12 configured as described above will be described below with reference to the flowchart shown in FIG. 3 in relation to the assembling method according to the present embodiment.

  First, the relationship between the thickness of the electrolyte membrane / electrode structure 20 and the load variation (pressing width or maximum surface pressure) is shown in FIG. Thereby, when the fuel cell stack 12 is assembled, the thickness of the electrolyte membrane / electrode structure 20 becomes smaller as the variation of the load applied to the electrolyte membrane / electrode structure 20 becomes larger.

  As shown in FIG. 5, in the fuel cell stack 12 having the electrolyte membrane / electrode structure 20 with a large load fluctuation indicated by Tb, the durability time during which the tightening load decreases to the functional limit is indicated by Ta. It is longer than the fuel cell stack 12 incorporating the electrolyte membrane / electrode structure 20 with small load fluctuation.

  Accordingly, when the fuel cell stack 12 is assembled, a large load fluctuation is applied to the electrolyte membrane / electrode structure 20, so that the electrolyte membrane / electrode structure 20 is caused by the load fluctuation during power generation (startup) of the fuel cell stack 12. It becomes possible to suppress sagging.

  Therefore, in the present embodiment, first, a multilayer body 26 in which a plurality of electrolyte membrane / electrode structures 20 are stacked with the first and second separators 22 and 24 interposed therebetween is formed in a room temperature environment, and the multilayer body is formed. The fuel cell stack 12 is tightened by applying a desired tightening load between the pair of end plates 28 disposed at both ends in the stacking direction 26 (step S1 in FIG. 3).

  Next, the process proceeds to step S2, and the fuel cell stack 12 is operated at the maximum load (rated load). Specifically, as shown in FIG. 2, a fuel gas such as a hydrogen-containing gas is supplied to the fuel gas supply communication hole 34a, and an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas supply communication hole 30a. Is done. Further, a coolant such as pure water, ethylene glycol, or oil is supplied to the coolant supply passage 32a.

  The oxidant gas is introduced into the oxidant gas flow path 46 of the first separator 22 from the oxidant gas supply communication hole 30 a and moves along the cathode side electrode 40 constituting the electrolyte membrane / electrode structure 20. On the other hand, the fuel gas is introduced into the fuel gas channel 48 of the second separator 24 from the fuel gas supply communication hole 34 a and moves along the anode side electrode 38 constituting the electrolyte membrane / electrode structure 20.

  Accordingly, in each electrolyte membrane / electrode structure 20, the oxidant gas supplied to the cathode side electrode 40 and the fuel gas supplied to the anode side electrode 38 are consumed by an electrochemical reaction in the electrode catalyst layer, Power generation is performed.

  Next, the fuel gas consumed by being supplied to the anode side electrode 38 is discharged in the direction of arrow A along the fuel gas discharge communication hole 34b. Similarly, the oxidant gas consumed by being supplied to the cathode side electrode 40 is discharged in the direction of arrow A along the oxidant gas discharge communication hole 30b.

  In addition, the cooling medium supplied to the cooling medium supply communication hole 32 a is introduced into the cooling medium flow path 50 of the second separator 24 and then flows along the arrow B direction. The cooling medium is discharged from the cooling medium discharge communication hole 32b after the electrolyte membrane / electrode structure 20 is cooled.

  As described above, when the fuel cell stack 12 is operating at the maximum load, the first tightening load T1 acting on the fuel cell stack 12 is detected (step S3). Next, the process proceeds to step S4, and after the operation of the fuel cell stack 12 is stopped, the fuel cell stack 12 is cooled.

  When the fuel cell stack 12 is cooled below the freezing point, more specifically, within a range of −20 ° C. to −30 ° C. (YES in step S5), the process proceeds to step S6, and the fuel cell stack 12 The acting second tightening load T2 is detected.

  Here, the relationship between the stack temperature of the fuel cell stack 12 and the electrode load is shown in FIG. As a result, when the stack temperature of the fuel cell stack 12 increases, that is, in a normal power generation environment, the electrolyte membrane / electrode structure 20 swells and the electrode load (and stack load) increases. On the other hand, in a low-temperature environment, particularly at below freezing, the humidity decreases, the electrolyte membrane / electrode structure 20 dries, and the electrode load (stack load) decreases significantly.

  For this reason, as shown in FIG. 7, the load amplitude width increases as the stack temperature of the fuel cell stack 12 decreases. In the present embodiment, in aging of the newly assembled fuel cell stack 12, a wide load range is set from the freezing temperature range to the temperature range during maximum load operation.

  Specifically, as shown in FIG. 8, a tightening load (load width) that periodically varies between the first tightening load T1 at the maximum load operation and the second tightening load T2 at the freezing point is set. . In other words, the load width of the load aging is set in consideration of the second tightening load T2 at the time of low temperature startup, which is larger than the conventional stack load T3 at normal temperature startup.

  Next, it progresses to step S7 and the new fuel cell stack 12 is clamped. The new fuel cell stack 12 is added with a tightening load that periodically fluctuates between the first tightening load T1 at the maximum load operation and the second tightening load T2 at the temperature below freezing point. Is performed (step S8).

  Specifically, the newly assembled fuel cell stack 12 is arranged in the direction of gravity with one end plate 28 on the lower side with respect to the assembly apparatus 10 shown in FIG. Further, the pressing mechanism 14 is driven via the controller 18, and under the pressing action of the pressing mechanism 14, a tightening load is applied between the pair of end plates 28 in a direction approaching each other.

  When the controller 18 detects that the pressure detection mechanism 16 has reached the first tightening load T1, the controller 18 performs control to reduce the pressing force by the pressing mechanism 14. Next, when the pressure detection mechanism 16 detects the second tightening load T2, the controller 18 performs control to increase the pressing force by the pressing mechanism 14 again.

  On the other hand, the displacement sensor 17 detects the amount of change in the total length of the fuel cell stack 12 in the stacking direction. When it is detected that the amount of change in the total length is within the predetermined range (YES in step S9), the load aging of the fuel cell stack 12 ends (step S10).

  Although not shown, the fuel cell stack 12 after load aging is fastened by applying a desired fastening load between the pair of end plates 28 by fastening means such as a tie rod. In addition, a newly assembled fuel cell stack 12 is disposed in the assembling apparatus 10 and the load aging process is performed.

  In this case, in this embodiment, in the load aging of the newly assembled fuel cell stack 12, the first tightening load T1 at the maximum load operation and the second tightening load T2 at the temperature below freezing point are periodically changed. A varying tightening load is applied to the fuel cell stack 12.

  Therefore, the fuel cell stack 12 is preliminarily provided with pressure fluctuations exceeding the load fluctuations during power generation including low-temperature start-up, so that load loss due to the sag of the electrolyte membrane / electrode structure 20 during operation is as much as possible. Can be suppressed.

  Thereby, the tightening load and electrode load of the fuel cell stack 12 can be favorably maintained. For this reason, it is possible to prevent an increase in contact resistance and a decrease in rigidity over a long period of time, and to obtain an effect that a good fuel cell stack 12 can be reliably assembled.

  The first tightening load T1 and the second tightening load T2 do not need to be actually detected in all the fuel cell stacks 12, and the values detected in the first fuel cell stack 12 are the values of the subsequent fuel cell stacks 12. What is necessary is just to use as a setting value at the time of an assembly.

It is a schematic block diagram of the assembly apparatus for enforcing the assembly method of the fuel cell stack which concerns on embodiment of this invention. It is a principal part disassembled perspective view of the said fuel cell stack. It is a flowchart explaining the said assembly method. It is a related figure of load variation and thickness of MEA. It is a related figure of endurance time and tightening load. It is a relationship figure of stack temperature and electrode load. It is a relationship figure of the said stack temperature and a load amplitude range. It is explanatory drawing of the variable load in the said assembly method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Assembly apparatus 12 ... Fuel cell stack 14 ... Pressing mechanism 16 ... Pressure detection mechanism 17 ... Displacement sensor 18 ... Controller 20 ... Electrolyte membrane electrode assembly 22, 24 ... Separator 26 ... Laminate 28 ... End plate 30a ... Oxidizing agent Gas supply communication hole 30b ... Oxidant gas discharge communication hole 32a ... Cooling medium supply communication hole 32b ... Cooling medium discharge communication hole 34a ... Fuel gas supply communication hole 34b ... Fuel gas discharge communication hole 36 ... Solid polymer electrolyte membrane 38 ... Anode Side electrode 40 ... Cathode side electrode 46 ... Oxidant gas channel 48 ... Fuel gas channel 50 ... Coolant flow channel

Claims (3)

A fuel in which an electrolyte / electrode assembly provided with electrodes on both sides of an electrolyte is provided with a laminate in which a plurality of laminates are interposed via separators, and a pair of end plates are disposed at both ends in the stacking direction of the laminate. A battery stack assembly method comprising:
A tightening step of tightening the fuel cell stack by applying a predetermined tightening load to the set of end plates in a direction close to each other;
A first detection step of operating the fuel cell stack at a maximum load and detecting a first tightening load of the fuel cell stack during a maximum load operation;
A second detection step of detecting a second tightening load of the fuel cell stack in a state where the operation of the fuel cell stack is stopped and the fuel cell stack is cooled to a temperature below freezing point;
An additional step of adding to the newly assembled fuel cell stack a tightening load that periodically varies between the first tightening load and the second tightening load;
Have
The method of assembling the fuel cell stack, wherein the additional step is continued until the amount of change in the total length in the stacking direction of the fuel cell stack falls within a predetermined range.   2. The method of assembling a fuel cell stack according to claim 1, wherein the tightening step is performed at room temperature.   3. The method of assembling a fuel cell stack according to claim 1, wherein the temperature below freezing point is set in a range of −20 ° C. to −30 ° C.

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