JP2014044815A - Fuel cell - Google Patents

Abstract

An impurity trap mechanism is prevented from being clogged with impurities.
A fuel cell in which a plurality of power generation modules are stacked, and each power generation module has an impurity trap mechanism. The impurity trap mechanism 10 is configured by the grooves 4 provided in the non-power generation region on the gas introduction side of the GDLs 42 and 43 or the flow path forming member 20. The impurity trapping mechanism 10 preferably further includes a guide member 5 that guides the gas into the groove 4, and is preferably formed at an introduction port through which the gas is introduced into the groove 4.
[Selection] Figure 5

Description

  The present invention relates to a fuel cell.

  In a fuel cell, if impurities such as a reaction gas (fuel gas, oxidizing gas) and a refrigerant supplied to each fuel cell serving as a power generation module contain impurities, the impurities cause deterioration of the fuel cell. There is a case. As such impurities, for example, piping iron rust, abrasion powder of fluorine resin of pumps, etc. become ions in moisture contained in the gas flow, or become foreign substances without becoming ions. And the like. As an example, if the ions adhere to the catalyst, the catalyst performance may be reduced, and when entering the electrolyte membrane, ions are attached to the molecules used for proton transfer, thereby inhibiting the movement of protons in the membrane. The fuel cell may be deteriorated.

  In order to avoid such a problem, conventionally, a fuel cell in which an impurity trap mechanism (for example, an ion exchange resin) for capturing impurities is provided separately from the power generation module has been proposed (see, for example, Patent Document 1).

JP 2008-135188 A

  However, for example, when impurities having a certain volume, such as air compressor wear powder, are mixed, the impurity trapping mechanism may be clogged. In such a case, pressure loss (the shape of the fluid flow path) occurs in the power generation module. , Due to the smoothness of the surface of the fluid flow path, the energy such as pressure of the fluid is consumed, or the differential pressure acting on the fluid) Impurities may also enter the power generation section of the power generation module that easily flows (low pressure loss), and power generation may be hindered.

  Therefore, an object of the present invention is to provide a fuel cell in which the impurity trapping mechanism is eliminated from being clogged with impurities.

  In order to solve this problem, the present inventor has made various studies. If an impurity trap mechanism is not provided, a large amount of gas flows through the power generation module (fuel cell) with a smaller pressure loss. Since it is known that the performance degradation of the power generation module is accelerated, it can be said that in a normal design, it is a general measure to make the pressure loss of each power generation module uniform.

  However, it is difficult to strictly align the pressure loss of each power generation module (fuel cell) for the following two reasons. That is, the first is that due to manufacturing tolerances, there are variations due to pressure loss for each fuel cell and each power generation module. The second is that, as the power generation time of the power generation module increases, an event occurs in which the diffusion layer bends into the flow path, resulting in a power generation module in which the pressure loss increases. For these reasons, it is highly possible that uniform pressure loss in each cell cannot be an effective solution.

  Here, the above problems are caused by the fact that the impurities themselves cause an increase in pressure loss, and it is considered that the solution can be achieved by making the structure in which the pressure loss does not increase or is difficult to increase due to impurity contamination. It was. The present inventor who has further studied from this point of view, focusing on the above points, has come to obtain new knowledge that leads to the solution of such problems.

  The present invention is based on such knowledge. In a fuel cell in which a plurality of power generation modules are stacked, each power generation module has an impurity trap mechanism, and the impurity trap mechanism is a non-power generation on the gas introduction side of the GDL or the flow path forming member. It is characterized by comprising a groove provided in the region.

  In order to achieve a structure in which pressure loss does not increase or hardly increases due to impurity contamination, it is possible to provide a mechanism for trapping impurities in each power generation module by providing a conventional impurity trap mechanism separately from the power generation module. Become. In the present invention further sublimated based on such an idea, the impurity trap mechanism and the power generation module are not separated by disposing the impurity trap mechanism from the viewpoint of each power generation module. According to the fuel cell of the present invention based on such an idea, impurities are preferentially trapped in the power generation module in which the pressure loss is relatively lowered in all the power generation modules, and the pressure loss due to this is repeatedly repeated. The point is that the pressure loss of the cell is increased by actively mixing impurities that cause an increase in pressure loss into parts that do not affect the power generation performance of the power generation module, and no further impurities are mixed. Even after impurities are mixed, variations in pressure loss among the power generation modules hardly occur.

  In the fuel cell according to the present invention, it is preferable that the impurity trapping mechanism further includes a guide member that guides gas to the groove.

  Moreover, it is preferable that the impurity trapping mechanism is formed at the inlet through which the gas is introduced into the groove.

  Further, the groove preferably has a structure in which gas flows in the direction toward the bottom of the groove and has a communication structure in which gas flows in a direction opposite to the direction toward the bottom of the groove.

  Moreover, it is preferable that the adhesive substance is provided in the groove bottom part in a communication structure.

  Furthermore, it is preferable that all of the plurality of power generation modules have an impurity trap mechanism.

  According to the present invention, the impurity trapping mechanism can be solved from being clogged with impurities.

It is a figure which shows the structural example of a fuel cell. It is the elements on larger scale which show an example of the internal structure of a fuel cell (power generation module). It is the elements on larger scale which show the structural example of MEGA (membrane-electrode-diffusion layer assembly). It is a figure which shows the impurity trap mechanism of the fuel cell which shows one Embodiment of this invention. It is a figure which shows the other form of an impurity trap mechanism. It is a figure which shows the further another form of an impurity trap mechanism.

  1 to 6 show an embodiment of the present invention. In the embodiment described below, first, a schematic configuration of a cell (power generation module) 2 and a cell stack 3 constituting the fuel cell 1 will be described, and thereafter, a configuration of an impurity trap mechanism (also referred to as an impurity trap module) 10. Will be described.

  1 to 3 show a schematic configuration of the fuel cell 1. The fuel cell 1 in this embodiment includes an electrolyte membrane 31, an anode electrode layer (referred to herein as an anode catalyst layer) 32 that is an electrode catalyst layer formed on both surfaces of the electrolyte membrane 31, and a cathode electrode layer (this specification). 33), gas diffusion layers (GDL: Gas Diffusion Layer) 42, 43 for diffusing the reaction gas supplied to each catalyst layer 32, 33, electrolyte membrane 31, anode catalyst layer 32, cathode The separator 20 (20a, 20b) that sandwiches the catalyst layer 33 and the gas diffusion layers 42, 43 and the frame member 40 are provided (see FIG. 3 and the like). 1 to 3 show a general configuration of the fuel cell 1, and a configuration related to the magnetic levitation system 10 is shown in FIGS. 4 to 6.

  The cell 2 constituting the fuel cell 1 functions as a power generation module, and constitutes the cell laminate 3 by being sequentially laminated. The cell stack 3 formed in this way is sandwiched between end plates 8, for example, and a load in the stacking direction is applied in a state where a tension plate 9 is arranged so as to connect the end plates 8 facing each other. It is hung and fastened (see FIG. 1).

  In such a cell stack 3, conventionally, an impurity trap mechanism may be provided at both ends in the cell stack direction separately from the cell 2 (or cell stack 3) (see reference numeral 10 'in FIG. 1). In this embodiment, as will be described later, the impurity trapping mechanism is not provided separately from the cell 2 (or the cell stack 3), but is provided as a mechanism associated with the cell 2.

  The fuel cell 1 constituted by the cell stack 3 in which the cells 2 are stacked as described above can be used as, for example, an in-vehicle power generation system of a fuel cell vehicle (FCHV), but is not limited thereto. It can be used as a power generation system mounted on various mobile objects (for example, ships, airplanes, etc.), self-propelled devices such as robots. In some cases, it can be used as a stationary fuel cell 1.

  As an electrolyte contained in the cell 2, a membrane-electrode assembly (MEA) or a membrane-electrode-diffusion layer assembly (MEGA) can be used. For example, in this embodiment, a membrane-electrode-diffusion layer assembly (hereinafter also referred to as MEGA) 30 is used (see FIG. 3 and the like). The cell 2 includes such a MEGA (membrane-electrode-diffusion layer assembly) 30 and a pair of separators 20 that sandwich the MEGA 30 (indicated by reference numerals 20a and 20b in FIGS. 2 and 3, respectively). (See FIGS. 2 and 3). The MEGA 30 and the separators 20a and 20b are formed in a substantially rectangular plate shape. The MEGA 30 is formed so that its outer shape is slightly smaller than the outer shape of each separator 20a, 20b. Further, the MEGA 30 and the separators 20a and 20b are molded with a molding resin together with the first seal member 13a and the second seal member 13b at the peripheral portion therebetween (see FIG. 2).

  The MEGA 30 includes a polymer electrolyte membrane (hereinafter also simply referred to as an electrolyte membrane) 31 made of an ion exchange membrane of a polymer material, and a pair of electrodes (an anode catalyst layer and a cathode catalyst layer) 32 sandwiching the electrolyte membrane 31 from both sides. 33 (see FIGS. 2 and 3). Among these, the electrolyte membrane 31 is formed to be slightly larger than the electrodes 32 and 33. The electrodes 32 and 33 constituting the MEGA 30 are made of, for example, a porous carbon material (diffusion layer) carrying a catalyst such as platinum attached to the surface thereof. One electrode (anode catalyst layer) 32 is supplied with hydrogen gas as a fuel gas (reactive gas), and the other electrode (cathode catalyst layer) 33 is supplied with an oxidizing gas (reactive gas) such as air or an oxidant. Electrochemical reaction occurs in the MEGA 30 by the two kinds of reaction gases, and the electromotive force of the cell 2 can be obtained.

  The frame member 40 is a member (resin frame) made of, for example, a resin that is sandwiched between the separators 20a and 20b together with the MEGA 30. For example, in this embodiment, a thin frame-shaped frame member 40 is interposed between the separators 20a and 20b, and the frame member 40 sandwiches at least a part of the MEGA 30 such as a portion along the peripheral edge from the front side and the back side. (See FIG. 2). The frame member 40 thus provided exhibits a function as a spacer between the separators 20a and 20b that supports the fastening force, a function as an insulating member, and a function as a reinforcing member that reinforces the rigidity of the separators 20a and 20b.

  Separator 20a, 20b is comprised with the gas-impermeable electroconductive material. Examples of the conductive material include carbon and a hard resin having conductivity, and metals such as aluminum and stainless steel. The base material of the separators 20a and 20b of this embodiment is formed of a plate-like metal (metal separator), and a film (for example, gold plating) having excellent corrosion resistance is provided on the surface of the base material on the electrodes 32 and 33 side. Is formed).

  The separators 20a and 20b function as flow path forming members, and groove-shaped flow paths constituted by a plurality of concave portions are formed on both surfaces of the separators 20a and 20b. These flow paths can be formed by press molding in the case of the separators 20a and 20b of the present embodiment in which the base material is formed of, for example, a plate-like metal. The groove-shaped flow path formed in this way constitutes an oxidizing gas flow path 34, a hydrogen gas flow path 35, or a cooling water flow path 36. More specifically, a plurality of gas passages 35 for hydrogen gas are formed on the inner surface on the electrode 32 side of the separator 20a, and a plurality of cooling water passages 36 are formed on the back surface (outer surface). (See FIG. 2). Similarly, a plurality of gas channels 34 for oxidizing gas are formed on the inner surface of the separator 20b on the electrode 32b side, and a plurality of cooling water channels 36 are formed on the back surface (outer surface) (FIG. 2). reference). For example, in the case of the present embodiment, the gas flow path 34 for oxidizing gas and the gas flow path 35 for hydrogen gas in the cell 2 are formed so as to be parallel to each other. Further, in the present embodiment, regarding the two adjacent cells 2 and 2, when the outer surface of the separator 20a of one cell 2 and the outer surface of the separator 20b of the cell 2 adjacent thereto are attached together, The water flow path 36 is integrated to form a flow path having a rectangular or honeycomb cross section (see FIG. 2). In addition, the separator 20a and the separator 20b of the adjacent cells 2 and 2 are configured such that a peripheral portion between them is molded with a molding resin.

  The cell stack 3 is provided with a cell monitor (not shown) for measuring the voltage of the cell 2 in order to monitor and control the operation state of the fuel cell 1. In the fuel cell 1, control of output and the like based on the voltage measurement result is performed.

  Next, the impurity trap mechanism 10 in the fuel cell 1 will be described (see FIGS. 4 to 6).

  The impurity trapping mechanism 10 is configured so that impurities (piping iron rust, pump fluororesin wear powder, etc.) contained in the fluid (fuel gas, oxidizing gas, or refrigerant) supplied to each cell 2 are in the gas flow. It is a mechanism for catching ions that are ions in the contained moisture, and those that are not ions but become foreign substances). In the present embodiment, such an impurity trapping mechanism 10 is not provided separately from the cell 2 (or cell stack 3) as in the prior art, but is provided as a mechanism associated with the cell 2 (FIG. 4 and the like). reference). Such an impurity trapping mechanism 10 is preferably provided in each of all the cells 2. Further, the impurity trapping mechanism 10 may be provided on either the anode side or the cathode side of the cell 2, but is preferably provided on both the anode side and the cathode side.

  The impurity trap mechanism 10 can be configured by the groove 4 provided so as to be dug into the gas diffusion layers (GDL) 42 and 43 described above (see FIGS. 4 and 5). Such an impurity trapping mechanism 10 has an effect of retaining impurities by entanglement with the gas diffusion layers 42 and 43 in the groove 4. The groove 4 is preferably provided near the gas inlet in the cell 2 (near the portion where the oxidizing gas or hydrogen gas is introduced into the cell 2), and impurities mixed in the cell 2 are introduced near the inlet. By catching, the performance degradation of the fuel cell 1 resulting from reaching the inside of the cell 2 can be further reduced.

  Further, the impurity trapping mechanism 10 preferably has a guiding member for guiding gas to the groove 4. In the present embodiment, the plate-like guide member 5 inclined so as to guide the gas containing impurities mixed in the cell 2 toward the groove 4 is flowed (the gas flow path 34 of oxidizing gas or the gas flow of hydrogen gas). It is provided in the path 35) (see FIG. 4). The guide member 5 may be configured by a curved surface (see FIG. 4) or may be a flat plate shape. Moreover, a part of inclined part in the lath cut metal (expanded metal) formed by what is called lath cut processing can also be utilized as the induction | guidance | derivation member 5 (refer FIG. 4). Or the convex part which comprises the groove-shaped flow path of the separators 20a and 20b can also be functioned as the guide member 5 (refer FIG. 5).

  The groove 4 described above has a structure or shape that allows gas to flow to the groove bottom 4 a of the groove 4. Also, a structure in which the gas that has flowed to the groove bottom 4a flows so as to communicate with the direction opposite to the direction of the groove bottom 4a of the groove 4 (that is, the direction toward the entrance / exit of the groove 4 or the opening) (communication structure). It is preferable to have (refer FIG. 4, FIG. 5).

  Moreover, in this embodiment, the adhesive substance 6 is provided in the groove bottom part 4a made into the communication structure as mentioned above (refer FIG. 4, FIG. 5). The adhesive substance 6 is a substance having adhesive strength, and improves the trapping function (trapping function) of impurities in the groove 4 by the adhesive function.

  According to the fuel cell 1 provided with the impurity trapping mechanism 10 as described so far, it becomes possible to trap impurities in each cell 2 provided with the impurity trapping mechanism 10. In addition, when a pressure drop is reduced in a certain cell 2, gas flows more easily into the cell 2 where the pressure drop is relatively lower than other cells 2, and as a result, impurities are trapped preferentially. The repetition that the pressure loss increase in the cell 2 occurs occurs. In short, in the fuel cell 1 of the present embodiment, the pressure loss of the cell 2 is increased by positively mixing impurities that cause an increase in pressure loss into a portion that does not affect the power generation performance of the cell 2 as a power generation module. Further, it is possible to adjust the cell 2 so that impurities are not mixed (self-pressure loss adjustment function). According to this, even after impurities are mixed, the pressure loss between the cells 2 can be reduced. It becomes a state in which variations do not easily occur. In other words, in the fuel cell 1 of the present embodiment, rather than making the pressure loss of each cell 2 uniform, the cells that do not affect the cell power generation performance are positively mixed with impurities that cause an increase in pressure loss. It is possible to increase the pressure loss and prevent further impurities from being mixed. In the conventional fuel cell, the power generation module provided separately from the cell (power generation module) may be clogged with impurities. However, according to the fuel cell 1 of the present embodiment, such a situation is solved. .

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the impurity trapping mechanism 10 constituted by the grooves 4 provided in the gas diffusion layers (GDL) 42 and 43 has been described (see FIGS. 4 and 5), but this is only a preferred example. Absent. In addition, for example, the impurity trapping mechanism 10 can be configured by a groove (indicated by reference numeral 21 in FIG. 6) provided in a non-power generation region on the gas introduction side of the separators (flow path forming members) 20a and 20b (FIG. 6). 6). In this case, it is preferable that the guiding member 5 for guiding the gas to the groove 21 is formed by protrusions formed on the gas diffusion layers (GDL) 42 and 43 of the MEGA 30 (see FIG. 6).

  The present invention is suitable for application to a fuel cell in which a plurality of power generation modules are stacked.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Cell (electric power generation module), 3 ... Cell laminated body, 4 ... Groove provided in gas diffusion layer (GDL), 4a ... Groove bottom part, 5 ... Induction member, 6 ... Adhesive substance, 10 (10 ') ... Impurity trapping mechanism, 11 ... groove, 12 ... induction member, 20 (20a, 20b) ... separator (channel forming member), 21 ... separator groove, 42, 43 ... gas diffusion layer (GDL)

Claims (6)

In a fuel cell in which a plurality of power generation modules are stacked,
Each power generation module has an impurity trap mechanism,
The impurity trap mechanism is constituted by a groove provided in a non-power generation region on the gas introduction side of the GDL or the flow path forming member.   The fuel cell according to claim 1, wherein the impurity trapping mechanism further includes a guide member that guides the gas into the groove.   The fuel cell according to claim 2, wherein the impurity trapping mechanism is formed at an inlet through which the gas is introduced into the groove.   The fuel cell according to claim 3, wherein the groove has a structure in which the gas flows in a direction toward the bottom of the groove, and further has a communication structure in which the gas flows in a direction opposite to the direction toward the bottom of the groove.   The fuel cell according to claim 4, wherein an adhesive substance is provided on the bottom of the groove in the communication structure.   6. The fuel cell according to claim 1, wherein all of the plurality of power generation modules have the impurity trap mechanism. 7.

Images