JP4592940B2 - Polymer electrolyte fuel cell stack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid polymer fuel cell stack using a solid polymer electrolyte membrane, and more particularly to a technique effective for preventing deterioration in performance of a single cell located at the stacking direction end of the fuel cell stack.
[0002]
[Prior art]
For example, a polymer electrolyte fuel cell is constructed by arranging an anode side electrode and a cathode side electrode on both sides of a solid polymer electrolyte membrane (cation exchange membrane), and sandwiching the outside with a pair of separators. Has been.
A single cell of this polymer electrolyte fuel cell is usually used as a fuel cell stack by stacking a predetermined number of cells.
[0003]
In this fuel cell stack, a fuel gas, for example, hydrogen gas, supplied to the anode side electrode is hydrogen ionized on the catalyst electrode and moves to the cathode side electrode side through an appropriately humidified electrolyte membrane. Electrons generated during that time are taken out to an external circuit and used as direct current electric energy. Since the oxidant gas, such as oxygen gas or air, is supplied to the cathode side electrode, the hydrogen ions, the electrons and the oxygen gas react with each other to generate water at the cathode side electrode.
[0004]
When the fuel cell stack is used by being mounted on a vehicle, particularly a passenger car, the space in the height direction is greatly limited because the fuel cell stack is often disposed under the floor of the passenger compartment.
As a technology to reduce the height of the fuel cell stack, a plurality of single cells are stacked in the horizontal direction, and a supply passage for supplying fuel gas, oxidant gas, etc. is provided as a communication hole in the surface of each separator A manifold structure is known (see, for example, JP-A-8-171926).
[0005]
An example thereof will be described with reference to FIG. 7. In FIG. 7, reference numeral 1 denotes a fuel cell stack, and this fuel cell stack 1 sandwiches a solid polymer electrolyte membrane between an anode side electrode and a cathode side electrode, Further, a plurality of unit cells 2 each having the outside sandwiched by a pair of separators are stacked in the horizontal direction. Each of the anode side electrode and the cathode electrode is provided with respective communication holes (not shown) for supplying and discharging fuel gas, oxidant gas, and cooling liquid penetrating the respective surfaces, thereby constituting an internal manifold.
[0006]
Each single cell 2 is fastened by a stud bolt 4.
A fastening structure portion 5 made of a disc spring or the like is provided on one end side in the stacking direction of the fuel cell stack 1, and another fastening structure portion 6 made of a washer or the like is provided on the other end side. Necessary tightening force is applied to each single cell 2 which is a power generation portion.
[0007]
Copper terminal plates 7 are provided in close contact with the end surfaces of the single cells 2a and 2b located at both ends of the fuel cell stack 1 in the stacking direction. The fastening structures 5 and 6 are arranged outside the terminal plates 7. Is provided via an insulating plate 8.
On the upper part of the terminal plate 7, a terminal portion 9 for taking out electric power extends, and this terminal portion 9 is bent toward the end side of the fuel cell stack 1.
[0008]
[Problems to be solved by the invention]
In this fuel cell, in order for each single cell 2 to maintain a predetermined output voltage (hereinafter referred to as “cell voltage”), it is necessary to keep each single cell 2 at a constant temperature.
However, since the copper terminal plates 7 are in intimate contact with the single cells 2a and 2b located at both ends in the stacking direction, the heat radiation from the terminal plates 7 is large, so that the cell temperature T of the single cells 2a and 2b is increased. ₁ and T _N tend to be lower than the cell temperatures T _{2 to N−1} of the other single cells 2.
[0009]
Therefore, as shown in FIG. 8, the cell voltages V ₁ and V _N of the single cells 2a and 2b having relatively low cell temperatures T ₁ and T _N are equal to the cell voltages V _{2 to N−} of the other single cells 2, respectively. There was a problem of being lower than ₁ .
When the temperature of the single cells 2a and 2b is decreased, the dew condensation water generated by the temperature decrease covers the electrode reaction surface and the reaction gas supply to the electrode reaction surface is hindered, leading to a decrease in the cell voltage of the single cells 2a and 2b. .
[0010]
The present invention has been made in view of the above circumstances, and an object thereof is to suppress a temperature drop of a single cell located at an end portion in a stacking direction of a fuel cell stack and effectively prevent a performance drop of the single cell. There is.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following means.
A solid polymer electrolyte membrane (for example, the solid polymer electrolyte membrane 12 in the embodiment) is sandwiched between a pair of electrodes (for example, the anode side electrode 13 and the cathode side electrode 14 in the embodiment), and the outside thereof is further paired with a pair of electrodes. A polymer electrolyte fuel cell configured by horizontally stacking a plurality of unit cells (for example, the unit cell 15 in the embodiment) sandwiched between separators (for example, the separators 16 and 17 in the embodiment). In the stack (for example, the fuel cell stack 11 in the embodiment), the single cell (for example, the single cells 15a and 15b in the embodiment) located at at least one end in the stacking direction and the outer side thereof are disposed. Conductive heat insulating layer (for example, in the embodiment) between the terminal plate (for example, the terminal plate 21 in the embodiment) Kicking wherein the interposed air chamber 51).
[0012]
According to such a configuration, the heat transfer from the single cell located at the end in the stacking direction to the terminal plate is hindered by the heat insulating layer, and the amount of heat released from the terminal plate to the outside is reduced. Can be suppressed.
[0013]
Further , a concave groove (for example, the round groove 50 or the lattice groove 53 in the embodiment) or a through hole (for example, the through hole in the embodiment) is provided between the single cell positioned at the at least one end and the terminal plate. A conductive heat insulating plate (for example, the conductive plate 22 in the embodiment) having a hole 52) is interposed, and the heat insulating layer is formed by the air chamber (for example, the air chamber 51 in the embodiment) including the concave groove or the through hole. It is characterized by comprising.
[0014]
According to such a configuration, since the linear expansion coefficients of the separator and the heat insulating plate are both equal, no thermal stress is generated between the two even if the operating temperature of the fuel cell stack changes.
Further, since the separator and the heat insulating plate are made of the same material, the contact resistance can be reduced.
[0015]
In the first aspect of the invention, the solid polymer electrolyte membrane (for example, the solid polymer electrolyte membrane 12 in the embodiment) is formed by a pair of electrodes (for example, the anode side electrode 13 and the cathode side electrode 14 in the embodiment). A plurality of single cells (for example, cells 15 in the embodiment), which are sandwiched and further sandwiched outside by a pair of separators (for example, separators 16 and 17 in the embodiment), are stacked in the horizontal direction. In the polymer electrolyte fuel cell stack (for example, the fuel cell stack 11 in the embodiment), a single cell (for example, the single cells 15a and 15b in the embodiment) positioned at at least one end in the stacking direction. When the conductive play between the terminal plate (e.g., a terminal plate 21 in the embodiment) is further disposed on the outside of its The interposed, to the end surface of the side contacting to the conductive plate of the terminal plate, characterized in that the formation of the grooves or holes.
[0016]
In such a configuration, the air chamber composed of the concave groove or the through hole serves as a heat insulating layer, and heat transfer from the single cell located at the end in the stacking direction to the terminal plate is hindered by the heat insulating layer formed in the terminal plate. Therefore, the temperature drop of the single cell can be suppressed without adding new parts.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In FIG. 1, the code | symbol 11 has shown the fuel cell stack for vehicle mounting.
The fuel cell stack 11 includes a plurality of single cells 15 in a horizontal direction in which a solid polymer electrolyte membrane 12 is sandwiched between an anode-side electrode 13 and a cathode-side electrode 14 and the outside is sandwiched between a pair of separators 16 and 17. This is a so-called polymer electrolyte fuel cell stack constituted by stacking individual pieces.
[0018]
A supply path 18 for hydrogen gas (a fuel gas that is a reaction gas) is formed between the anode side electrode 13 and the adjacent separator 16, while air is provided between the cathode side electrode 14 and the adjacent separator 17. A supply path 19 for (oxidant gas which is a reaction gas) is formed.
A refrigerant such as ethylene glycol is supplied to the supply path 20 between the back surfaces of the separators 16 and 17 to cool the single cell 15.
For the sake of illustration, hatching indicating a cross section is omitted in FIG.
[0019]
And in order to supply the said hydrogen gas, air, and a refrigerant | coolant to each supply path 18,19,20, the anode side electrode 13 of each single cell 15, the cathode side electrode 14, the electrode plate 21, the conductive plate 22, and the insulation plate mentioned later 23 and a through hole (not shown) are formed through each surface of the end plate 24. That is, the fuel cell stack 11 has an internal manifold structure.
[0020]
The stacked single cells 15 are tightened by stud bolts 28. Out of these single cells 15, the single cells 15a and 15b positioned at both ends in the stacking direction are provided with conductive plates (heat insulating materials) for refrigerant isolation and heat insulation. Plate) 22 is disposed in contact with the end faces of the single cells 15a and 15b.
[0021]
This conductive plate 22 is made of the same carbon material as that of the separator 16 constituting the end surfaces of the single cells 15a and 15b. One end surface 22A is in contact with the end surface 22A as shown in FIGS. A large number of blind-hole-shaped round grooves 50 constituting an air chamber (heat insulating layer) 51 (see FIG. 1) are formed over substantially the entire surface by being closed by the terminal plate 21 arranged in this manner.
Reference numeral 25 denotes a communication hole through which hydrogen gas passes, and 26 denotes a communication hole through which air passes.
[0022]
An insulating plate 23 made of resin or the like is disposed outside the conductive plate 22 on one end side (left side in FIG. 1) of the fuel cell stack 11 via an electrode plate 21 described later. A clamping structure 31 is provided in which a disc spring 30 is interposed between the end plate 24 and the backup plate 29.
[0023]
An insulating plate 23 made of resin or the like is disposed outside the conductive plate 22 on the other end side (right side in FIG. 1) of the fuel cell stack 11 via an electrode plate 21 described later. A fastening structure portion 33 is provided in which a washer 32 is interposed between the end plate 24 and the backup plate 29.
[0024]
The terminal plate 21 is made of a conductive material (for example, copper), and a terminal portion 21a for extracting power is provided in a substantially vertical direction from the substantially central portion, that is, in the stacking direction of the single cells 15. It protrudes.
The outer periphery of the terminal portion 21a is covered with an insulating tube 36 made of an insulating material to prevent an electrical short circuit with the end plate 24, the backup plate 29, and the like.
[0025]
The fuel cell stack 11 configured as described above has an end face of the conductive plate 22 disposed between the single cells 15a and 15b located at both ends in the stacking direction and the terminal plate 21 disposed further outside. An air chamber 51 formed by forming round grooves 50 in 22A and closing these round grooves 50 with the terminal plate 21 is configured to effectively function as a heat insulating layer.
[0026]
Therefore, heat transfer from the single cells 15a, 15b to the terminal plate 21 is inhibited by the air chamber 51, and the amount of heat released from the terminal plate 21 to the outside is reduced, so that the temperature drop of the single cells 15a, 15b is suppressed.
Thereby, the performance fall resulting from the fall of the reaction temperature in the single cell 15a, 15b and the production | generation of condensed water can be prevented effectively.
[0027]
Further, since the conductive plate 22 is made of the same carbon material as that of the separator 16 constituting the end surfaces of the single cells 15a and 15b, the linear expansion coefficients of the separator 16 and the conductive plate 22 that are in contact with each other are equal.
Therefore, even if the operating temperature of the fuel cell stack 11 changes, no thermal stress is generated between the two, and damage caused by applying an excessive clamping force to the single cell 15 can be effectively prevented.
Furthermore, since the separator 16 and the conductive plate 22 are made of the same material, the contact resistance can be reduced.
[0028]
The present invention is not limited to the above embodiment.
For example, in the above embodiment, the concave groove formed in the conductive plate 22 is a blind hole-like round groove 50, but the through hole 52 as shown in the cross-sectional view of FIG. 4, the plan view of FIG. A lattice-like lattice groove 53 as shown in the sectional view of FIG.
4 to 6, the same components as those in the above-described embodiment are denoted by the same reference numerals.
[0029]
In the case of the conductive plate 61 having the through holes 52 shown in FIG. 4, the openings at both ends of these through holes 52 are closed by the separators 16 of the single cells 15 a and 15 b and the terminal plate 21, thereby serving as a heat insulating layer. An air chamber is formed.
Since the total volume of these air chambers becomes larger than the total volume of the air chamber 51 according to the above embodiment, the function as a heat insulating layer is improved.
[0030]
On the other hand, in the case of the conductive plate 71 having the lattice groove 53 shown in FIGS. 5 and 6, the upper end opening of the lattice groove 53 is closed by the terminal plate 21, thereby forming an air chamber as a heat insulating layer.
Since the lattice grooves 53 are formed so as to open on the side surfaces 71A and 71B on the long side portion side of the conductive plate 71, the air chamber is not completely sealed.
Therefore, even if condensed water is generated in the air chamber, it is discharged naturally, and the function as a heat insulating layer can be maintained well.
[0031]
Further, in each of the above embodiments, the concave grooves (round grooves 50, lattice grooves 53) or through holes 52 are formed in the conductive plates 22, 61, 71 disposed between the single cells 15a, 15b and the terminal plate 21. However, you may form a ditch | groove or a through-hole in the end surface of the side which contacts the conductive plate 22 of the terminal plate 21. FIG.
In this case, since the temperature drop of the single cells 15a and 15b can be suppressed without adding new parts, it is possible to effectively prevent such performance drop.
[0032]
Moreover, in the said embodiment, although it was set as the structure which interposed the heat insulation layer between the single cell 15a, 15b located in the lamination direction both ends, and the terminal plate 21, it is located in either one edge part of the lamination direction. A heat insulating layer may be interposed only between the single cell 15a (or the single cell 15b) and the terminal plate 21.
Similarly, in the case where a groove or a through hole is formed on the end surface of the terminal plate 21, the groove or the through hole is formed only in the terminal plate 21 located at one end in the stacking direction. Also good.
[0033]
【The invention's effect】
As is clear from the above description, according to the present invention, the following effects are obtained.
(1) According to the invention described in claim 1, heat transfer from the single cell located at the end in the stacking direction to the terminal plate is hindered by the heat insulating layer, and the amount of heat released from the terminal plate to the outside is reduced. The temperature drop of the single cell can be suppressed, and the performance drop can be effectively prevented.
[0034]
(2) According to the invention described in claim 2, since the linear expansion coefficients of the separator and the heat insulating plate are both equal, even if the operating temperature of the fuel cell stack changes, no thermal stress is generated between them. In addition to the above effects, it is possible to effectively prevent damage caused by applying an excessive tightening force to the cell.
Further, since the separator and the heat insulating plate are made of the same material, the contact resistance can be reduced.
[0035]
(3) According to the invention described in claim 3, the air chamber composed of the concave groove or the through hole serves as a heat insulating layer, and the heat insulating layer formed in the terminal plate allows the terminal from the single cell located at the end in the stacking direction. Since heat transfer to the plate is hindered, the temperature drop of the single cell can be suppressed without adding new parts, and the performance drop can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an embodiment of a fuel cell stack according to the present invention.
FIG. 2 is a plan view of the conductive plate shown in FIG.
3 is a cross-sectional view showing a part of a cross section taken along the line AA in FIG. 2;
FIG. 4 is a cross-sectional view showing a part of a cross section of a conductive plate according to another embodiment of the fuel cell stack according to the present invention.
FIG. 5 is a plan view of a conductive plate according to still another embodiment of the fuel cell stack according to the present invention.
6 is a cross-sectional view showing a part of a cross section taken along line BB in FIG. 5;
FIG. 7 is a front view showing a conventional example of a fuel cell stack.
FIG. 8 is a characteristic diagram showing a relationship between a cell temperature and a cell voltage of each cell constituting the fuel cell stack.
[Explanation of symbols]
11 Fuel Cell Stack 12 Solid Polymer Electrolyte Membrane 13 Anode Side Electrode 14 Cathode Side Electrode 15, 15a, 15b Single Cell 16, 17 Separator 21 Terminal Plate 22, 61, 71 Conductive Plate (Insulation Plate)
50 Round groove (concave groove)
51 Air chamber (heat insulation layer)
52 Through-hole 53 Lattice groove (concave groove)

Claims (1)

In a polymer electrolyte fuel cell stack configured by laminating a plurality of unit cells in a horizontal direction, sandwiching a solid polymer electrolyte membrane between a pair of electrodes and further sandwiching the outside with a pair of separators,
A single cell located at least one end of the stacking direction, by interposing a conductive plate between the terminal plate is further disposed on the outside of its end faces on the side in contact with the conductive plate of the terminal plate And a polymer electrolyte fuel cell stack in which a concave groove or a through hole is formed.

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