JP2006147495A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell suppressing temperature rise of cooling fluid inside an inlet side manifold, is superior in durability, and realizes stable output voltage. <P>SOLUTION: In the fuel cell having a passage of the cooling fluid communicating the inlet side manifold of the cooling fluid with an outlet-side manifold in the cathode-side separator plate and an anode-side separator plate, a heat conducting member is arranged between a heat generating part (that is, a region corresponding to a cathode and an anode) of a cell and the inlet side manifold of the cooling fluid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell used for a home cogeneration system, a motorcycle, an electric vehicle, a hybrid electric vehicle and the like, and more particularly to a polymer electrolyte fuel cell. More specifically, the present invention relates to a fuel cell that is less prone to flooding and has excellent durability by reducing the temperature variation of each single cell in the cell stack of the fuel cell.

  A fuel cell using a polymer electrolyte having positive ion (hydrogen ion) conductivity is obtained by electrochemically reacting a fuel gas containing hydrogen with an oxidant gas containing oxygen such as air. Are generated at the same time. This fuel cell basically comprises a polymer electrolyte membrane having hydrogen ion conductivity that selectively transports hydrogen ions, and a pair of electrodes disposed on both sides of the polymer electrolyte membrane. These electrodes have a catalyst layer mainly composed of conductive carbon powder carrying an electrode catalyst (for example, a metal catalyst such as platinum), and both air permeability and electronic conductivity formed outside the catalyst layer. The gas diffusion electrode is composed of a gas diffusion layer (for example, carbon paper subjected to water repellent treatment). This is called a membrane electrode assembly (MEA).

  In order to prevent the supplied fuel gas and oxidant gas (reactive gas) from leaking outside and mixing with each other, a gas seal material and a gasket are arranged around the electrode with a polymer electrolyte membrane interposed therebetween. The sealing material and gasket are assembled in advance by being integrated with the electrode and the polymer electrolyte membrane. On the outside of the MEA, a conductive separator plate for mechanically fixing the MEA and electrically connecting adjacent MEAs to each other in series is disposed. A gas flow path for supplying reaction gas to the electrode surface and carrying away generated gas and surplus gas is formed in a portion of the separator plate that contacts the MEA. Although the gas flow path can be provided separately from the separator plate, a method of providing a gas flow path by providing a groove on the surface of the separator plate is generally used.

  These MEAs and separator plates are stacked alternately, and after stacking 10 to 200 cells, this is sandwiched between end plates via current collector plates and insulating plates, and is generally fixed from both ends with fastening bolts. The structure of the battery. This is called a cell stack.

The polymer electrolyte membrane functions as an electrolyte having hydrogen ion conductivity by reducing the specific resistance of the membrane by containing water in a saturated state. Therefore, during operation of the fuel cell, the fuel gas and the oxidant gas are supplied with humidification in order to prevent moisture from evaporating from the polymer electrolyte membrane. Moreover, at the time of battery power generation, the following electrochemical reaction occurs, and water is generated as a reaction product on the cathode side.
Anode; H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode: 2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)

  The water in the humidified fuel gas, the water in the humidified oxidant gas, and the reaction product water are used to keep the water content of the polymer electrolyte membrane saturated, and the surplus fuel gas oxidant gas At the same time, it is discharged outside the fuel cell.

  Further, since the above reaction is an exothermic reaction, it is necessary to cool the cell stack during battery power generation. In order to cool the cell stack, a flow path of the cooling fluid is formed on the surface (second surface) opposite to the surface (first surface) that contacts the MEA of the separator plate, and the cooling fluid is allowed to flow there. In general, a method of exchanging heat between the separator plate and the cooling fluid whose temperature has been increased by an exothermic reaction is common. Although the cooling fluid flow path can be provided separately from the separator plate, a method of providing a flow path by providing a groove on the surface of the separator plate is generally used.

  When the cell stack is not sufficiently cooled, the temperature of the MEA rises and water is evaporated from the polymer electrolyte membrane. As a result, the deterioration of the polymer electrolyte membrane is promoted and the durability of the cell stack is shortened, or the specific resistance of the polymer electrolyte membrane is increased and the output of the cell stack is lowered. On the other hand, when the cell stack is cooled more than necessary, moisture in the reaction gas flowing through the gas flow path is condensed, and the amount of liquid water contained in the reaction gas increases. Liquid water adheres as droplets to the gas flow path of the separator plate due to surface tension. When the amount of the droplets is excessive, water adhering to the gas flow path blocks the gas flow path, obstructs the gas flow, and causes flooding. As a result, the reaction area of the electrode is reduced and the battery performance is lowered.

Therefore, for the purpose of further cooling the region having a low water content in the flow path of the oxidant gas, the region having a low water content in the flow path of the oxidant gas, that is, the inlet side of the flow path of the oxidant gas In the cooling fluid flow path, a region where the temperature of the cooling fluid is low, that is, the inlet side of the cooling fluid flow path is provided close to each other, thereby suppressing flooding and stabilizing the output voltage. A cooling method has been proposed (see, for example, Patent Document 1).
Japanese National Patent Publication No. 9-511356

However, in the separator plate adopting the method of Patent Document 1, the region having a low water content in the flow path of the oxidant gas, that is, the total amount of reaction product water according to the equation (1) is small, and the oxidant gas concentration is high. In addition, since the region where the amount of heat generated by the reaction of the formula (1) is further promoted coincides with the introduction portion of the cooling fluid, the following problems occur.
Here, FIG. 9 shows a top view of the cooling fluid flow path side of a conventional cathode side separator plate having the same structure as the separator plate in Patent Document 1. The conventional separator plate 101 is provided with a groove-like cooling fluid flow path 107 that connects the cooling fluid inlet manifold hole 102a and the outlet manifold hole 102b, and the rear surface is provided with an oxidizing gas inlet side. The manifold hole 103a and the outlet side manifold hole 103b are connected by a groove-like gas flow path (not shown) of oxidant gas. 104a and 104b are an inlet side manifold hole and an outlet side manifold hole for fuel gas, respectively, and holes 106 for fastening bolts are provided at four corners.

In a region 109 indicated by hatching of the conventional cathode-side separator plate 101, a cooling fluid introduction portion and a region having a low water content in the oxidant gas flow path in the vicinity of the oxidant gas inlet side manifold hole 103a Therefore, the cooling fluid in the inlet manifold of the cooling fluid is affected by the heat generation in the region corresponding to the cathode indicated by the alternate long and short dash line 105. For this reason, the temperature T ₀ of the cooling fluid before or immediately after introduction into the cell stack rises to T ₁ due to the heated cathode temperature T ₂ (where T ₀ <T ₁ <T ₂ ), and the temperature rises. ΔT (= T ₁ −T ₀ ) is relatively large. The same applies to the anode separator plate. Then, in the manifold on the inlet side of the cooling fluid in the cell stack in which the single cells are stacked, the inlet portion with the short residence time of the cooling fluid and the farthest part from the inlet portion with the longer residence time (that is, the cooling fluid) The temperature difference of the cooling fluid is generated between the inlet side manifold of the first and second manifolds on the most downstream side in the flow direction of the cooling fluid. Therefore, the cooling effect decreases as it goes downstream in the stacking direction in the cell stack, the cooling state of each single cell varies, and it becomes difficult to cool to the optimum state.

As a result, the temperature of each single cell becomes non-uniform in the stacking direction in the cell stack, and in a single cell having a high temperature, moisture is evaporated from the polymer electrolyte membrane and the deterioration of the polymer electrolyte membrane is promoted. As a result, the durability of the single cell is shortened, and the output of the single cell is lowered due to the increase in the specific resistance of the polymer electrolyte membrane.
On the other hand, in a single cell having a low temperature, moisture in the reaction gas flowing through the gas flow channel is condensed and the water in the liquid state increases, and the water adhering to the gas flow channel closes the gas flow channel and flows the gas. There is a problem that flooding that inhibits the occurrence of the problem occurs.

Since the above problems are caused by non-uniform cooling of each single cell in the stacking direction in the cell stack, the flow pattern of the separator plate cooling fluid in each single cell, optimization of the cooling fluid flow rate, etc. Depending on the situation, it was difficult to solve.
The present invention has been made in view of the above problems, and the inlet is caused by the temperature difference between the temperature of the heat generating part of the single cell and the cooling fluid in the inlet side manifold of the cooling fluid during power generation of the fuel cell. Mitigating temperature rise in the cooling fluid in the side manifold and reducing temperature variation of each single cell in the stacking direction of the fuel cell stack, suppressing flooding, providing excellent durability and stable output voltage It aims at providing the fuel cell which implement | achieves.

In order to solve the above-mentioned problems, the present invention
A cell stack in which two or more single cells having a polymer electrolyte membrane, a membrane electrode assembly including a cathode and an anode sandwiching the polymer electrolyte membrane, and a cathode separator plate and an anode separator plate sandwiching the membrane electrode assembly are stacked A fuel cell comprising:
The cell stack has an inlet manifold and outlet manifold for oxidant gas, an inlet manifold and outlet manifold for fuel gas, and an inlet manifold and outlet manifold for cooling fluid,
The cathode side separator plate has, on the first surface facing the cathode, an oxidant gas flow path connecting the oxidant gas inlet side manifold and the oxidant gas outlet side manifold,
The anode-side separator plate has a fuel gas flow path communicating with the fuel gas inlet manifold and the fuel gas outlet manifold on the first surface facing the anode,
In at least one of the cathode-side separator plate and the anode-side separator plate, cooling that connects the inlet-side manifold of the cooling fluid and the outlet-side manifold of the cooling fluid to a second surface that is located on the opposite side of the first surface. A fluid flow path;
The cooling fluid flow path constitutes a cooling section that cools the area corresponding to the cathode and the anode,
A fuel cell comprising a heat conducting member satisfying a condition represented by the following formula (1) between a cooling unit and a cooling fluid inlet side manifold.
_{{T c / T s}>} 1.7 ··· (1)
[In the formula (1), T _c represents the thermal conductivity (W / m · K) of the heat conducting member, and T _s represents the thermal conductivity (W / m of at least one of the cathode side separator plate and the anode side separator plate). -Indicates K). ]

  As described above, in at least one of the cathode-side separator plate and the anode-side separator plate, in addition to the conventional cooling unit configured by the cooling fluid flow path, the cooling unit and the cooling fluid inlet-side manifold, By providing the heat conducting member that satisfies the condition expressed by the above formula (1), the heat accompanying the temperature rise of the heat generating part (that is, the anode and the cathode) of the single cell during power generation of the fuel cell is provided. The heat can be radiated without moving to the cooling fluid side in the inlet side manifold of the cooling fluid. And the temperature rise which arises in the cooling fluid in the inlet side manifold resulting from the temperature difference of the temperature of the said heat generating part and the cooling fluid in the inlet side manifold of a cooling fluid can be relieved, thereby The temperature variation of each single cell in the stacking direction of the cell stack can be reduced, flooding can be suppressed, and a fuel cell excellent in durability can be obtained.

Here, when the value {T _m / T _s } of the formula (1) is less than 1.7, sufficient heat conduction effect cannot be obtained, and the temperature of the heat generating part (ie, anode or cathode) of the single cell is increased. Along with this, the heat becomes difficult to dissipate, and the heat stays in the separator, so that a sufficient cooling effect cannot be obtained. There is no particular upper limit to the value {T _m / T _s } in formula (1), but it is preferable that the value be as large as possible.
The thermal conductivity can be measured by a disk heat flow meter method, a laser flash method, or the like, and when determining the value {T _m / T _s } of equation (1), the values of T _m and T _s Uses values that are aligned so that each unit is the same.

According to the present invention, since the temperature of the cooling fluid in the inlet side manifold can be suppressed, the temperature gradually increases as the cooling fluid advances from the inlet to the back in the inlet side manifold of the cooling fluid in the cell stack. There is no increase in temperature, and the temperature difference between the inlet and the innermost portion does not increase. For this reason, there is almost no temperature difference of the cooling fluid introduced into each cell of the cell stack, and the entire cell stack is cooled almost uniformly.
Therefore, according to the present invention, since the temperature variation of each cell in the cell stack of the fuel cell is reduced, it is possible to provide a highly durable fuel cell that suppresses flooding and realizes a stable output voltage. it can.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted.
FIG. 1 is a schematic cross-sectional view showing the basic configuration of a preferred embodiment of the fuel cell of the present invention. The single cell 10 includes a polymer electrolyte membrane 1 having hydrogen ion conductivity, which is an example of a polymer electrolyte membrane, and a cathode 2 and an anode 3 sandwiching the polymer electrolyte membrane 1. For the polymer electrolyte membrane 1, a membrane made of perfluorosulfonic acid (Nafion (trade name) manufactured by DuPont) is used. The cathode and anode are composed of a catalyst layer in contact with the polymer electrolyte membrane and a gas diffusion layer disposed on the outside thereof. As the cathode and anode catalysts, carbon carrying an electrode catalyst (for example, platinum metal) is used.

The single cell 10 includes a cathode-side separator plate 30 and an anode-side separator plate 40 that sandwich a membrane electrode assembly (MEA) composed of the polymer electrolyte membrane 1, the cathode 2, and the anode 3. The cathode side separator plate 30 and the anode side separator plate 40 are provided with a heat conducting member 38, as will be described in detail later. The polymer electrolyte membrane 1 is sandwiched between gaskets 4 at the outer peripheral portions of the cathode 2 and the anode 3.
In the following description, it is assumed that the single cell 10 is installed such that the MEA is perpendicular to the horizontal direction as shown in FIG.

  Next, FIG. 2 shows a schematic perspective view of a cell stack obtained by stacking two or more (plural) single cells 10 described above. The cell stack 20 is provided in each of the MEA, the cathode side separator plate 30 and the anode side separator plate 40, and is connected to an oxidant gas inlet 22a and an outlet side manifold hole connected to an oxidant gas inlet side manifold hole communicating with each other. An oxidant gas outlet 22b, a fuel gas inlet 23a connected to the fuel gas inlet manifold hole, a fuel gas outlet 23b connected to the outlet manifold hole, and a cooling water inlet 24a connected to the cooling water inlet manifold hole And a cooling water outlet 24b connected to the outlet side manifold hole. Note that the separator plates positioned at both ends of the cell stack 20 do not have a cooling water flow path. The cell stack 20 includes a fuel cell by stacking end plates on both ends via current collector plates and insulating plates and fastening them with fastening bolts.

  In the fuel cell configured as described above, the oxidant gas introduced into the inlet side manifold of each cell from the oxidant gas inlet 22a passes through the flow path 36 of the cathode side separator plate 30 to the gas diffusion electrode of the cathode 2. It diffuses into and is used for the reaction. Excess oxidant gas and reaction products are discharged from the flow path 36 through the outlet side manifold and from the outlet 22b. Similarly, the fuel gas is supplied to the anode 3 via the inlet 23a, the inlet-side manifold, and the flow path 46 of the anode-side separator plate 40, and excess fuel gas and reaction products are supplied from the flow path 46 to the outlet-side manifold. Then, it is discharged from the outlet 23b.

  Here, in the conventional fuel cell, as described above, the cooling fluid in the manifold on the inlet side of the cooling fluid is affected by the heat generated by the electrodes, and therefore the temperature of each single cell is not uniform in the stacking direction in the cell stack. In a single cell having a high temperature, moisture evaporates from the polymer electrolyte membrane and the deterioration of the polymer electrolyte membrane is promoted to shorten the durability of the single cell, or the specific resistance of the polymer electrolyte membrane. There is a problem that the output of the single cell is lowered due to the increase in the number. In contrast, in the fuel cell of the present invention, a cathode side separator plate having a structure as shown in FIGS. 3, 4 and 5, and an anode side separator plate having a structure as shown in FIGS. Is used.

FIG. 3 is a front view of the oxidant gas flow path side of the cathode side separator plate of the fuel cell in the present embodiment. FIG. 4 is a rear view of the cathode separator plate shown in FIG. 3, that is, a front view on the cooling fluid flow path side. FIG. 5 is a cross-sectional view showing the configuration of the XX line portion in FIG.
As shown in FIGS. 3 and 4, the cathode-side separator plate 30 includes an oxidant gas inlet side manifold hole 32a and an outlet side manifold hole 32b, a fuel gas inlet side manifold hole 33a and an outlet side manifold hole 33b, and cooling water. Inlet side manifold hole 34a and outlet side manifold hole 34b, and four holes 31 for passing fastening bolts. The cathode-side separator plate 30 has an oxidant gas flow path 36 connecting the oxidant gas manifold holes 32a and 32b on the surface facing the cathode, and on the back side the cooling water manifold holes 34a and 34b. The cooling water flow path 37 is connected.

  3 and 4, a region surrounded by an alternate long and short dash line 35 corresponds to a region where the power generation unit (that is, the cathode) including the MEA catalyst layer is located. As shown in FIG. 3, the oxidant gas flow path 36 is constituted by two parallel grooves, and in the region surrounded by the alternate long and short dash line 35, each groove is a straight line extending in seven horizontal directions. It is comprised from six turn parts which connect the straight part which adjoins a part. The number of grooves and the number of turn portions are not limited to these, and can be appropriately set within a range not impairing the effects of the present invention.

On the other hand, the cooling water flow path 37 is composed of two parallel grooves, and is a cooling portion 37c located in a region surrounded by a one-dot chain line 35, and an inlet side portion 37a connecting the cooling portion 37c to the inlet side manifold hole 34a. And an outlet side portion 37b connecting the cooling portion 37c to the outlet side manifold hole 34b.
The cooling part 37c is composed of two parallel grooves, and each groove is composed of seven straight parts extending in the horizontal direction and six turn parts connecting the adjacent straight parts, and the part on the outlet side 37b is formed of a straight line portion that simply extends in the vertical direction.

The cathode side separator plate 30 in the present embodiment has a heat conducting member 38 between the cooling water inlet side manifold hole 34a and the cooling part 37c, and two in parallel on the upper surface of the heat conducting member 38. Grooves are provided, and these grooves constitute a portion 37 a on the inlet side of the flow path 37 of the cooling water.
That is, in the present embodiment, the inlet 37 of the cooling water flow path 37 is formed on the heat conducting member 38, and therefore heat from the heat generating portion (ie, cathode) is dissipated in the heat conducting member 38. However, it is different from the outlet side portion 37b in that it can be effectively prevented from being transmitted to the cooling water inlet side manifold hole 34a.

  Thereby, it is possible to suppress the amount of heat from moving to the cooling water in the inlet side manifold of the cooling water as the temperature of the heat generating part (ie, cathode) of the single cell rises during power generation of the fuel cell. And the temperature rise which arises in the cooling water in an inlet side manifold resulting from the temperature difference of the temperature of the said heat generating part and the cooling water in the inlet side manifold of a cooling water can be relieved, and, thereby, a fuel cell The temperature variation of each single cell in the stacking direction of the cell stack can be reduced, flooding can be suppressed, and a fuel cell excellent in durability can be obtained.

  4 and 5, the heat conducting member 38 has a shape that is partially exposed to the outside of the cathode side separator plate 30, and is more than the cathode side separator plate 30 as shown in FIGS. 1 and 5. It is thin and fixed in a state of being embedded in the cathode side separator plate 30. Two parallel grooves are provided on the upper surface of the heat conducting member 38, and these constitute a portion 37a on the inlet side of the flow path 37 of the cooling water.

  As described above, since the heat conducting member 38 is exposed to the outside of the cathode side separator plate 30, the heat from the heat generating portion (that is, the cathode) is transferred to the cathode side separator plate 30 via the heat conducting member 38. It is possible to reliably release to the outside, that is, the outside of the cell stack, and it is possible to effectively suppress the transfer of heat to the cooling water inlet side manifold hole 34a.

In the present embodiment, the cathode separator plate 30 is made of conductive carbon (thermal conductivity: 128 W / m · K), and the heat conductive member 38 is made of copper (thermal conductivity: 400 W / m · K). Yes. Therefore, the {T _m / T _s } value in the cathode side separator plate 30 of the present embodiment is 3.13 (= 400/128), which satisfies the condition expressed by the above formula (1).

Next, FIG. 6 is a front view of the fuel gas flow path side of the anode separator plate of the fuel cell in the present embodiment. FIG. 7 is a rear view of the anode separator plate shown in FIG. 6, that is, a front view on the cooling fluid flow path side.
As shown in FIGS. 6 and 7, the anode-side separator plate 40 includes an oxidant gas inlet side manifold hole 42a and an outlet side manifold hole 42b, a fuel gas inlet side manifold hole 43a and an outlet side manifold hole 43b, and cooling water. Inlet side manifold hole 44a and outlet side manifold hole 44b, and four holes 41 for passing fastening bolts. The anode-side separator plate 40 has a fuel gas flow path 46 that connects the fuel gas manifold holes 43a and 43b on the surface facing the anode, and the cooling water manifold holes 44a and 44b on the back surface. A cooling water channel 47 is provided.

  6 and 7, the region surrounded by the alternate long and short dash line 45 corresponds to the region where the power generation unit (that is, the anode) including the MEA catalyst layer is located, as in the case of the cathode separator plate. The fuel gas flow path 46 is constituted by two parallel grooves, and in the region surrounded by the alternate long and short dash line 45, each groove has six straight portions extending in the horizontal direction and six adjacent straight portions. It consists of the turn part. The number of grooves and the number of turn portions are not limited to these, and can be appropriately set within a range not impairing the effects of the present invention.

  When the anode-side separator plate 40 is joined to the back surface of the cathode-side separator plate 30, the cooling-water flow path 47 for forming one cooling water flow path together with the cooling water flow path 37 of the separator plate 30. Have Therefore, the channel 47 has a shape that is plane-symmetric with the channel 37. That is, the flow path 47 connects the cooling portion 47c located in the region surrounded by the alternate long and short dash line 45, the inlet-side portion 47a that connects the cooling portion 47c to the inlet-side manifold hole 44a, and the cooling portion 47c connects to the outlet-side manifold hole 44b. It consists of a portion 47b on the outlet side.

The anode side separator plate 40 in the present embodiment has a heat conducting member 48 between the cooling water inlet side manifold hole 44a and the cooling part 47c, and two parallel grooves are formed on the upper surface of the heat conducting member 48. And these grooves constitute a portion 47a on the inlet side of the flow path 47 of the cooling water.
In other words, in the present embodiment, the cooling water flow path 47 has its inlet side portion 47a formed on the heat conducting member 48, and therefore heat from the heat generating portion (ie, anode) is supplied to the cooling water inlet side manifold. It is different from the outlet-side portion 47b in that it can be effectively suppressed from being transmitted to the hole 44a.

  Thereby, it is possible to suppress the amount of heat from being transferred to the cooling water in the inlet side manifold of the cooling water as the temperature of the heat generating part (that is, the anode) of the single cell rises during power generation of the fuel cell. And the temperature rise which arises in the cooling water in an inlet side manifold resulting from the temperature difference of the temperature of the said heat generating part and the cooling water in the inlet side manifold of a cooling water can be relieved, and, thereby, a fuel cell The temperature variation of each single cell in the stacking direction of the cell stack can be reduced, flooding can be suppressed, and a fuel cell excellent in durability can be obtained.

  The heat conducting member 48 has the same form as the heat conducting member 38 in the cathode side separator plate 30 described above. Although the drawing corresponding to FIG. 5 is omitted here, as shown in FIG. 1, the heat conducting member 48 has a shape in which a part is exposed to the outside of the anode side separator plate 40 in the same manner as the heat conducting member 38 described above. And is thinner than the thickness of the anode side separator plate 40 and fixed in a state of being embedded in the anode side separator plate 40. In addition, two parallel grooves are provided on the upper surface of the heat conducting member 48, and these constitute a portion 47a on the inlet side of the flow path 47 of the cooling water.

  As described above, since the heat conducting member 48 is exposed to the outside of the anode side separator plate 40, heat from the heat generating portion (that is, the anode) is transferred to the anode side separator plate 40 via the heat conducting member 48. It is possible to reliably release to the outside, that is, the outside of the cell stack, and it is possible to effectively suppress the transfer of heat to the cooling water inlet side manifold hole 34a.

In the present embodiment, the anode separator plate 40 is made of conductive carbon (thermal conductivity: 128 W / m · K), and the heat conductive member 48 is made of copper (thermal conductivity: 400 W / m · K). Yes. Therefore, the {T _m / T _s } value in the anode side separator plate 40 of the present embodiment is 3.13 (= 400/128), which satisfies the condition represented by the above formula (1).

Here, a mechanism in which the separator plate in the fuel cell according to the present embodiment solves the above-described conventional problems will be described by using the cathode-side separator plate 30 shown in FIGS. 3, 4 and 5 as a representative. .
FIG. 8 is a diagram conceptually showing the temperature state (distribution) of the cooling fluid flowing in the cooling fluid flow path 37 of the cathode side separator plate 30 (FIG. 3) of the fuel cell shown in FIG.

In the cathode side separator plate 30 according to the present invention, in addition to the cooling part 37c indicated by the alternate long and short dash line 35 and existing in the area corresponding to the cathode, in the area between the cooling part 37c and the cooling water inlet side manifold 34a, A heat conducting member 38 is provided.
In the conventional separator plate, the cooling water in the cooling water inlet side manifold is affected by the heat generation of the cathode in the region corresponding to the cathode indicated by the alternate long and short dash line 35. However, in the separator 30 of the present invention, the heat is heated. Since the heat is dissipated by the conductive member 38, the temperature T ₀ of the cooling water before or just after the introduction into the cell stack 20 rises to T ₁ due to the generated cathode temperature T ₂ (however, T ₀ <T ₁ <T ₂ ), and the temperature rise ΔT (= T ₁ −T ₀ ) is drastically reduced as compared with the prior art.

  Then, in the cooling water inlet-side manifold in the cell stack 20 in which the single cells 10 are stacked, the cooling water staying time is short and the farthest part from the inlet portion where the cooling time is long (that is, the cooling water is long). The transmission of heat to the cooling water can be suppressed in any of the water inlet side manifold and the most downstream part in the cooling water flowing direction. Therefore, variation in the cooling state of each single cell 10 in the stacking direction in the cell stack 20 can be reduced, and cooling to an optimum state can be achieved.

  That is, in the fuel cell of the present invention, the cooling water in the inlet side manifold is heated due to the temperature difference between the temperature of the heat generating part of the single cell 10 and the cooling water in the cooling water inlet side manifold during power generation. As a temperature rise mitigating means for mitigating the rise, in the separator plate of each single cell 10, a cooling unit 37c that cools the region indicated by the alternate long and short dash line 35 corresponding to the heat generating unit of the single cell with cooling water, and cooling A heat conducting member 38 is provided between the water inlet side manifold hole 34a. The heat conducting member 38 is provided to suppress heat transfer between the cooling unit 37c and the cooling water inlet side manifold hole 34a. Thereby, variation in the cooling state of each single cell 10 in the stacking direction in the cell stack 20 can be reduced, and cooling to an optimum state can be achieved.

  In the cell stack 20 of the fuel cell of the present embodiment having the above-described configuration, cooling water is introduced from the inlet 24a, and the flow path 37 of the cathode side separator plate 30 and the anode side separator plate 40 from the inlet side manifold. It flows through the flow path formed by the flow path 47 and is discharged from the outlet 24b through the outlet side manifold. The discharged cooling water is cooled by exchanging heat with an appropriate heat exchanger, and then again introduced into the cell stack 20 from the inlet 24a. The cooling water flowing through the flow path formed by the separator plates 30 and 40 passes through the portions of the separator plates 30 and 40 corresponding to the anode and cathode catalyst layers that are the heat generating portions of the single cell 10 in the cooling portions 37c and 47c. Cooling. Further, the heat conducting members 38 and 48 in the separator plates 30 and 40 suppress heat transfer from the heat generating portion to the inlet side manifold. As a result, it is possible to suppress an increase in the temperature of the cooling water flowing through the inlet side manifold formed by the separator plates 30 and 40 due to the heat of the heat generating portion of the single cell 10.

As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment.
For example, in the above embodiment, the heat conducting members 38 and 48 are provided on both the cathode side separator plate 30 and the anode side separator plate 40. However, in the present invention, any of the cathode side separator plate 30 and the anode side separator plate 40 is provided. One of them may be provided with a heat conducting member.

  The shapes and dimensions of the heat conducting members 38, 48 cathode side separator plate 30 and anode side separator plate 40 can be appropriately designed as long as they do not impair the effects of the present invention. Conventionally, the following materials are used. It can be produced by a known method (for example, molding or cutting).

The thicknesses of the heat conducting members 38 and 48 are preferably thinner or the same as the thicknesses of the cathode side separator plate 30 and the anode side separator plate 40.
When the thickness of the heat conduction member is thinner than the thickness of the cathode side separator plate 30 and the anode side separator plate 40, the cathode side separator plate 30 and the anode side separator plate 40 are provided with a groove or opening, and the groove or opening It is only necessary to fit it in, or it may be adhered with an adhesive. On the other hand, when the thickness of the heat conducting member is the same as the thickness of the cathode side separator plate 30 and the anode side separator plate 40, openings (through holes) are provided in the cathode side separator plate 30 and the anode side separator plate 40, and the openings It only needs to be fitted in the part, and it may be adhered with an adhesive.

The material constituting the heat conducting members 38 and 48, the cathode side separator plate 30 and the anode side separator plate 40 is particularly a material that satisfies the conditions represented by the above formula (1) and does not impair the effects of the present invention. It can be used without limitation.
Especially, as a material which comprises the heat conductive members 38 and 48, a metal can be used, As a metal, it is from the group which consists of copper, silver, aluminum, nickel, a copper-zinc alloy, stainless steel, platinum, tungsten. At least one selected can be used.

  The thermal conductivity of typical materials that can be used as the material constituting the heat conducting members 38 and 48 is shown in Table 1 below. For comparison, the thermal conductivity (W / m · K) of conductive carbon that is a constituent material of the separator is also described.

  Moreover, in the above-mentioned embodiment, although the cooling part by the flow path of a cooling water was provided between each single cell, you may provide a cooling part in the ratio of 1 to 2-3 cells, for example. The flow path of the cooling water is provided with a groove on both the cathode side separator plate and the anode side separator plate to form a pair of flow paths, but only one of the separator plates is provided with a groove, thereby A cooling water flow path may be provided.

  Further, in the above-described embodiment, in the cell stack in which the single cells are stacked, the cooling water flow path is formed between the cathode side separator plate and the anode side separator plate. In the cathode-side separator plate or anode-side separator plate located in the outer portion, a current collector plate, an insulating plate, and an end plate are laminated, and a cooling water flow path is formed between the separator plate and the current collector plate. Good.

The cooling water flow path in the separator plate is connected to the cooling water inlet side manifold and the outlet side manifold. In the above embodiment, the cooling water flow path is constituted by two parallel grooves, but is constituted by a plurality of grooves. May be. When the cooling part is constituted by a plurality of grooves, it may be constituted by the same number of grooves on the heat shielding member.
In addition, there is no restriction | limiting in particular about components other than the structure of a separator board, It can select suitably in the range which does not impair the effect of this invention. Further, the cooling fluid is not limited to cooling water.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to these Examples at all.
Example 1
In this example, a fuel cell based on the above embodiment of the present invention was produced.
The gas diffusion layer uses a carbon woven fabric (GF-20-E) manufactured by Nippon Carbon Co., Ltd. having a diameter of 80% or more of pores of 20 to 70 μm as a substrate, and this substrate is used as a surfactant. It was immersed in a dispersion liquid in which polytetrafluoroethylene (PTFE) was dispersed in pure water. Thereafter, the substrate was passed through a far-infrared drying oven and baked at 300 ° C. for 60 minutes. The amount of water repellent resin (PTFE) in the substrate at this time was 1.0 mg / cm ² .

Next, a paint for a coat layer was prepared. Carbon black was added to a solution obtained by mixing pure water and a surfactant and dispersed with a planetary mixer for 3 hours. PTFE and water were added to the obtained dispersion, and the mixture was further kneaded for 3 hours. In addition, as surfactant, what was marketed with the brand name of Triton (Triton) X-100 was used.
This coat layer coating was applied to one side of the carbon woven fabric subjected to water repellent treatment as described above using an applicator. The carbon woven fabric on which the coating layer was formed was baked at 300 ° C. for 2 hours using a hot air dryer to produce a gas diffusion layer. The amount of water repellent resin (PTFE) contained in the obtained gas diffusion layer was 0.8 mg / cm ² .

Next, a catalyst layer was produced. Catalyst body (50 mass% is Pt) obtained by supporting platinum as an electrode catalyst on Ketjen black (Ketjen Black EC, manufactured by Ketjen Black International Co., Ltd., particle size 30 nm) which is carbon powder 66 mass Part was mixed with 33 parts by mass (polymer dry mass) of perfluorocarbon sulfonic acid ionomer (5% by mass Nafion dispersion manufactured by Aldrich, USA) which is a hydrogen ion conductive material and a binder. Was formed into a catalyst layer (10 to 20 μm).
The gas diffusion layer and the catalyst layer obtained as described above were bonded to both sides of a polymer electrolyte membrane (Nafion 112 membrane of DuPont, USA, ion exchange group capacity: 0.9 meq / g) by hot pressing, and the MEA was bonded. Produced.

Next, a rubber gasket plate was joined to the outer peripheral portion of the polymer electrolyte membrane of MEA produced as described above to form a manifold hole for circulating fuel gas and oxidant gas.
On the other hand, FIG. 3, FIG. 4 and FIG. 4 are made of a graphite plate having an outer dimension of 160 mm × 160 mm × 5 mm, a gas flow path having a width of 1.0 mm and a depth of 1.0 mm, and impregnated with a phenol resin. The cathode side separator plate having the structure shown in FIG. 5 (thermal conductivity Ts: 128 W / m · K) and the anode side separator plate having the structure shown in FIGS. 6 and 7 (thermal conductivity Ts: 128 W / m · K). ) Was prepared. However, the heat conducting member was prepared by providing two parallel grooves on a copper plate (thermal conductivity Ts: 400 W / m · K).

Using these separator plates, a cathode side separator plate formed with a gas flow path for oxidant gas is superimposed on one surface of the MEA, and an anode side formed with a gas flow passage for fuel gas on the other surface The separator plates were stacked to obtain a single cell.
Next, 100 single cells are stacked to form a cell stack, and a copper current collector plate and an insulating plate and an end plate made of an electrically insulating material are arranged at both ends of the cell stack, and the whole is formed with a fastening rod. By fixing, the fuel cell 1 of the present invention was produced. The fastening pressure at this time was 10 kgf / cm ² per separator area.

<< Comparative Example 1 >>
A comparative fuel cell was fabricated in the same manner as in Example 1 except that the heat conducting member was not provided on the cathode side separator plate and the anode side separator plate. That is, the cathode side separator plate having the structure shown in FIG. 9 was used, and the anode side separator plate having the same structure as the cathode side separator plate was used.

[Evaluation]
About each fuel cell of the above Example and the comparative example, the cooling water with a temperature of 70 degreeC was supplied to the inlet part of the inlet side manifold at 3.7 liter / min. Also, heated and humidified hydrogen gas and air are supplied to the anode side and the cathode side, respectively, so that the dew point is 70 ° C., the fuel gas utilization rate Uf is set to 70%, and the oxidizing gas utilization rate Uo is set to 40%. did.

After operating for 24 hours at a current density of 0.2 A / cm ² , the cooling water temperature was measured at the inlet of the cooling water inlet side manifold and at the farthest part from the inlet.
Next, Uo was raised to 70% and the operation was performed for 6 hours, and the voltage stability was compared based on the standard deviation when the voltage was sampled every 10 seconds.
Moreover, it returned to 40% of Uo and it drive | operated for 24 hours. The operation was continued for 1000 hours from this point. The durability of the batteries was compared based on the decrease in average voltage due to this continuous operation.
These results are shown in Table 2.

  As is apparent from Table 1, the fuel cell of the comparative example has a difference of 4 ° C. in the cooling water temperature in the cooling water inlet side manifold between the inlet part and the farthest part farthest from the inlet part. The voltage stability during operation at a rate of 70% and durability during continuous 1000 hours operation are inferior to those of the examples.

  In the comparative example, it can be seen that it is difficult to cool each cell in the cell stack to an optimum state due to the non-uniformity of the cooling water temperature in the manifold. That is, the single cell temperature becomes high due to insufficient cooling, the deterioration of the polymer electrolyte membrane due to the evaporation of water from the polymer electrolyte membrane is promoted, the durability of the single cell is shortened, and the specific resistance of the polymer electrolyte membrane It is considered that the output of the single cell is reduced due to the increase in the number of cells.

  On the other hand, in the fuel cell of the present invention, the temperature rise mitigating means for mitigating the temperature rise of the cooling fluid caused by the temperature difference between the temperature of the heat generating portion of the MEA during power generation and the cooling fluid in the cooling fluid inlet manifold. As a result, the above-described problems did not occur, and the effect of suppressing the durability deterioration of the fuel cell was confirmed.

The present invention is not limited to the shape and number of cooling water flow paths described in the embodiments, and various modifications can be made without departing from the spirit of the invention.
Further, the above examples relate to a polymer electrolyte fuel cell, but the present invention relates to a fuel cell that generates heat due to an electrochemical reaction during battery power generation, and requires water as a reaction product on the cathode side that requires cooling. When applied to the produced fuel cell, a great effect is obtained.

  In the fuel cell of the present invention, the temperature variation of each single cell in the cell stack is reduced, the durability is excellent, and flooding and output voltage fluctuation do not occur. Therefore, the fuel cell of the present invention is useful for use in home cogeneration systems, motorcycles, electric vehicles, hybrid electric vehicles and the like.

It is a schematic longitudinal cross-sectional view of the basic composition (unit cell) of suitable one Embodiment of the fuel cell of this invention. It is a perspective view of the cell stack formed by laminating | stacking two or more single cells shown in FIG. It is a front view of the cathode side separator plate of the fuel cell shown in FIG. It is a rear view of the cathode side separator plate shown in FIG. It is the schematic which shows the XX sectional view in FIG. It is a front view of the anode side separator plate of the fuel cell shown in FIG. It is a rear view of the anode side separator plate shown in FIG. It is a front view which shows notionally the temperature state (distribution) of the cooling water in the cathode side separator plate used for the fuel cell shown in FIG. It is a front view which shows notionally the temperature state (distribution) of the cooling water in the cathode side separator plate used for the conventional (comparative example) fuel cell.

Explanation of symbols

      DESCRIPTION OF SYMBOLS 1 ... Polymer electrolyte membrane, 2 ... Cathode, 3 ... Anode, 4 ... Gasket, 10 ... Single cell, 20 ... Cell stack, 21, 31, 41 ... Fastening Shaft hole, 22a ... oxidant gas inlet, 22b ... oxidant gas outlet, 23a ... fuel gas inlet, 23b ... fuel gas outlet, 24a ... cooling water inlet 24b ... Cooling water outlet, 30 ... Cathode side separator plate, 32a, 32b, 42a, 42b ... Oxidant gas manifold hole, 33a, 33b, 43a, 43b ... Fuel gas manifold Holes 34a, 44a, 102a ... Cooling water inlet side manifold holes, 34b, 44b, 102b ... Cooling water outlet side manifold holes, 36 ... Oxidant gas flow path, 37, 47 ... Cooling water flow path, 37 , 47a ... part, 37c, 47c ... cooling part, 38, 48 ... heat conducting member, 40 ... anode side separator plate, 46 ... fuel gas flow path, 35, 45 ... -The part corresponding to the power generation part in the MEA region, 37b, 47b ... the part on the outlet side connecting the first cooling part to the outlet side manifold hole

Claims (4)

Two or more unit cells each having a polymer electrolyte membrane, a membrane electrode assembly including a cathode and an anode sandwiching the polymer electrolyte membrane, and a cathode separator plate and an anode separator plate sandwiching the membrane electrode assembly are stacked. A fuel cell comprising a cell stack,
The cell stack has an inlet side manifold and an outlet side manifold for oxidant gas, an inlet side manifold and an outlet side manifold for fuel gas, and an inlet side manifold and an outlet side manifold for cooling fluid,
The cathode side separator plate has an oxidant gas flow path communicating with the inlet side manifold of the oxidant gas and the outlet side manifold of the oxidant gas on a first surface facing the cathode. ,
The anode side separator plate has, on a first surface facing the anode, a fuel gas flow path connecting the inlet side manifold of the fuel gas and the outlet side manifold of the fuel gas;
In at least one of the cathode side separator plate and the anode side separator plate, on the second surface located opposite to the first surface, the inlet side manifold of the cooling fluid and the outlet side manifold of the cooling fluid A cooling fluid flow path communicating with the
The cooling fluid flow path constitutes a cooling unit that cools a region corresponding to the cathode and the anode,
A fuel cell comprising a heat conducting member satisfying a condition expressed by the following formula (1) between the cooling unit and an inlet side manifold of the cooling fluid.
_{{T c / T s}>} 1.7 ··· (1)
[In Formula (1), T _c represents the thermal conductivity (W / m · K) of the heat conducting member, and T _s represents the thermal conductivity (W of at least one of the cathode side separator plate and the anode side separator plate). / M · K). ]   The fuel cell according to claim 1, wherein a part of the heat conducting member is exposed to the outside of the cell stack.   The fuel cell according to claim 1, wherein the heat conducting member is made of metal.   The fuel cell according to claim 3, wherein the metal is at least one selected from the group consisting of copper, silver, aluminum, nickel, copper-zinc alloy, stainless steel, platinum, and tungsten.

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