JP2005293878A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent moisture condensation of H<SB>2</SB>O generated at an anode side due to reverse diffusion or the like when power is generated by a fuel cell stack. <P>SOLUTION: A coolant flow channel 18 formed at a separator 8 between adjacent membrane electrode structures 7, 7 of the fuel cell stack 1 is so formed that a near terminal part 18x of at least a part of the flow channel from the first end to the dead end is to exist in the vicinity of a terminal of a reaction gas flow channel 13 adjacent to the first end of the coolant flow channel 18 at a terminal of the reaction gas (hydrogen gas) flow channel 13 at a front surface side of an anode electrode 10 of the membrane electrode structure 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell stack, and more particularly to a fuel cell stack having a structure aimed at improving power generation performance.

  The fuel cell stack includes a plurality of membrane electrode structures (so-called MEAs) each composed of a solid polymer electrolyte membrane and an anode electrode and a cathode electrode bonded to both surfaces thereof, and each electrode of each membrane electrode structure. The battery main body part comprised by laminating | stacking the separator provided facing the surface so that a separator may interpose between membrane electrode structures adjacent to each other is provided. The separator forms a flow path of the reaction gas between the separator and the electrode facing the separator, and distributes the reaction gas along the surface of the electrode. Usually, hydrogen gas and air are used as the reaction gas flowing through the flow path on the surface side of the anode electrode and the reaction gas flowing through the flow path on the surface side of the cathode electrode, respectively.

  This type of fuel cell stack generates power between both electrodes of each membrane electrode structure by a gas reaction (reaction between hydrogen and oxygen in the air) through the solid polymer electrolyte membrane. In order to prevent the temperature rise of the fuel cell stack due to the heat generated during the generation of electric power, the separator between the membrane electrode structures adjacent to each other and the flow path of the reaction gas ( It is generally performed to form an isolated refrigerant flow path and to flow the refrigerant through the refrigerant flow path.

By the way, in the fuel cell stack, water or water vapor (H ₂ O) is generated by the reaction of oxygen and hydrogen, and the generated H ₂ O is usually a reactive gas flow channel facing the cathode electrode surface. Enter (air flow path). And most of the H ₂ O generated on the surface of the cathode electrode is terminated (exited) from the start end (inlet) side of the air flow path by the air supplied to the air flow path facing the surface of the cathode electrode. And is discharged from the air flow path. However, particularly when the fuel cell stack is operated in a relatively low temperature environment, H ₂ O is condensed near the outlet of the air flow path and remains attached to the cathode electrode. Alternatively, there is a risk of remaining in the air flow path. When the condensation of H ₂ O and the residue thereof are generated in this way, the air flow is deteriorated and the power generation capacity of the fuel cell stack is reduced.

In order to prevent such a problem, for example, in US Pat. No. 5,547,776 (Patent Document 1), air as a reaction gas passes through a reaction gas flow path (air flow path) on the surface side of the anode electrode from a position on the start end side. As it moves to the end side location, the location of the coolant channel adjacent to each location in the path of the reaction gas channel (each location of the reaction gas channel as viewed in the normal direction of the membrane electrode structure) There has been proposed a configuration in which the air flow path and the refrigerant flow path are formed so that the refrigerant flow paths that substantially overlap) move from the start end side to the end end side of the refrigerant flow path. According to this, the location in the vicinity of the end of the air flow path is likely to be heated through the refrigerant heated by the heat generated by the membrane electrode structure in the course of flowing through the refrigerant flow path. As a result, it becomes possible to prevent condensation of H ₂ O near the end of the air flow path.
US Pat. No. 5,547,776

By the way, the solid polymer electrolyte membrane of the fuel cell stack has recently been manufactured with a thinner film thickness in order to reduce the size of the fuel cell stack and reduce the cost. In particular, in a fuel cell stack using a thin polymer electrolyte membrane having a thin film thickness (for example, a solid polymer electrolyte membrane having a thickness of 40 μm), so-called reverse diffusion of H ₂ O produced in the membrane electrode structure is performed. Is likely to occur. In such a fuel cell stack in which reverse diffusion is likely to occur, the amount of H ₂ O that is generated does not diffuse to the surface of the cathode electrode but diffuses to the surface of the anode electrode (back diffusion) increases. H ₂ O easily enters the reaction gas channel (hydrogen gas channel) on the electrode side. Even when a solid polymer electrolyte membrane having a normal thickness is used, some back diffusion of H ₂ O to the anode electrode side may occur. And the degree of the occurrence of the reverse diffusion becomes higher as the thickness of the solid polymer electrolyte membrane becomes thinner.

In this case, the amount of H ₂ O diffusing on the surface on the anode electrode side is generally smaller than the amount of H ₂ O diffusing on the surface of the cathode electrode. For this reason, conventionally, with respect to H ₂ O generated on the anode electrode side, the influence of the condensation is not taken into consideration, and no special measures are taken to prevent the condensation. .

However, the inventor of the present application has found from various studies and experiments that prevention of condensation of H ₂ O on the anode electrode side is an important issue in preventing a decrease in power generation performance of the fuel cell stack. . That is, the flow rate of hydrogen gas supplied to the reaction gas channel (hydrogen gas channel) on the anode electrode side is smaller than the flow rate of air supplied to the air channel on the cathode electrode side. In addition, the hydrogen gas supplied to the hydrogen gas channel is gradually consumed in the process of flowing along the surface of the anode electrode, and the flow rate thereof decreases. For this reason, H ₂ O generated particularly on the anode electrode side is likely to accumulate near the terminal end of the hydrogen gas flow path along the surface of the anode electrode and cause condensation.

In this case, as in the case of Patent Document 1, even when the air flow path on the cathode electrode side and the refrigerant flow path adjacent to the cathode electrode side are formed, Insufficient prevention of dew condensation of H ₂ O generated in the fuel cell will result in inconvenience that the power generation capacity of the fuel cell stack tends to decrease.

The present invention has been made in view of such a background, and can effectively prevent dew condensation of H ₂ O generated on the anode electrode side by reverse diffusion or the like when power generation of the fuel cell stack is performed. An object is to provide a battery stack.

  In order to achieve the above object, the fuel cell stack of the present invention includes a plurality of membrane electrode structures each composed of a solid polymer electrolyte membrane and an anode electrode and a cathode electrode respectively bonded to both surfaces thereof, and each membrane. Provided with a battery body portion that is provided facing the surface of each electrode of the electrode structure, and is formed by laminating a separator that forms a reaction gas flow path between the electrodes, and at least a pair of adjacent ones In the separator between the membrane electrode structures, the reaction gas flow path on the surface side of the anode electrode of one membrane electrode structure of the pair of membrane electrode structures and the cathode electrode of the other membrane electrode structure In the fuel cell stack formed by forming a refrigerant flow path defined from the reaction gas flow path on the surface side, the refrigerant flow path formed in the separator between the pair of membrane electrode structures is: From the beginning to the end Of at least some of the channels leading to the end of the reactive gas channel on the surface side of the anode electrode of the one membrane electrode structure of the set of membrane electrode structures. It is formed so as to be close to the end of the flow path of the refrigerant and closer to the end of the flow path of the reaction gas.

  In the present invention, the reaction gas supplied to the reaction gas channel on the anode electrode side (the channel facing the surface of the anode electrode) is hydrogen gas or a gas containing the same, and the reaction gas on the cathode electrode side. The reaction gas supplied to the channel (the channel facing the surface of the cathode electrode) is oxygen gas or a gas containing this (preferably air).

According to the fuel cell stack of the present invention, since the refrigerant flow path formed in the separator of the pair of membrane electrode structures is formed as described above, the fuel cell stack is in the process of flowing through the flow path. When at least part of the refrigerant warmed by the heat generated during power generation reaches the vicinity of the end of the flow path (location near the outlet of the flow path of the refrigerant), the heat causes the flow of the reaction gas on the anode electrode side. The vicinity of the end of the path (the position near the outlet of the reaction gas flow path) is heated. As a result, even when the generated H ₂ O diffuses toward the anode electrode and enters the reaction gas flow channel facing the surface of the anode electrode when the power generation operation of the fuel cell stack is performed, the H ₂ O Is effectively prevented from condensing near the end of the reaction gas flow path on the anode electrode side.

Therefore, according to the fuel cell stack of the present invention, it is possible to effectively prevent dew condensation of H ₂ O generated on the anode electrode side by reverse diffusion or the like when the fuel cell stack generates power. As a result, it is possible to prevent a decrease in the power generation performance of the fuel cell stack due to the condensation of the generated H ₂ O.

In the present invention, the reaction gas supplied to the reaction gas flow path on the anode electrode side may be hydrogen gas itself, but the reaction gas supplied to the reaction gas flow path on the cathode electrode side is Air as a gas containing oxygen is preferable. By using air as the reaction gas on the cathode electrode side, the flow rate of air to be supplied to the flow path (air flow path) on the cathode electrode side becomes relatively large. For this reason, most of the H ₂ O generated on the anode electrode side can be transported by air and discharged from the end (exit) of the air flow path. In this case, in the present invention, the relationship between the reaction gas flow path and the coolant flow path on the anode electrode side is formed in the separator between the pair of membrane electrode structures as in the cathode electrode side. The refrigerant flow path is such that at least a part of the flow path from the start end to the end of the flow path is in the vicinity of the end of the cathode electrode of the other membrane electrode structure of the set of the membrane electrode structures. It is preferable that the reaction gas is formed so as to be close to the end of the reaction gas flow path on the surface side of the reaction gas and closer to the end of the reaction gas flow path. However, it is not always necessary to form in this way.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing the configuration of a fuel cell stack. As shown in FIG. 1, the fuel cell stack 1 includes a battery body 2 and a header 3 attached to the outer periphery of the battery body 2. On one side 3a (left side in the figure) of the header 3, a hydrogen gas introduction side passage 4in, a refrigerant introduction side passage 5in, and an air outlet side passage 6out are respectively provided in the longitudinal direction of the fuel cell stack 1. It is provided penetrating in the direction. These hydrogen gas introduction side passages 4in (hereinafter referred to as introduction side hydrogen gas passages 4in), refrigerant introduction side passages 5in (hereinafter referred to as introduction side refrigerant passages 5in), and air outlet side passages 6out (hereinafter referred to as outlet sides). Air passages 6out) are arranged in this order in the vertical direction from the upper side of the side portion 3a of the header 3 toward the lower side.

  Further, a hydrogen gas outlet side passage 4out, a refrigerant outlet side passage 5out, and an air inlet side passage 6in penetrate the other side 3b of the header 3 in the longitudinal direction of the fuel cell stack 1, respectively. Is provided. These hydrogen gas outlet side passages 4out (hereinafter referred to as outlet side hydrogen gas passages 4out), refrigerant outlet side passages 5out (hereinafter referred to as outlet side refrigerant passages 5out), and air inlet side passages 6in (hereinafter referred to as inlet sides). The air passage 6in) is arranged in the vertical direction from the lower side of the side portion 3b of the header 3 toward the upper side in this order.

  Although detailed illustration is omitted, the introduction-side hydrogen gas passage 4in and the discharge-side hydrogen gas passage 4out are one end portions in the longitudinal direction of the fuel cell stack 1 (the end portion on the back side in FIG. 1, hereinafter referred to as the rear end portion). Are communicated through a pipe (not shown). Then, as shown by an arrow (1), the introduction-side hydrogen gas passage 4in is not shown from the other end in the longitudinal direction of the fuel cell stack 1 (the end on the near side in FIG. 1, hereinafter referred to as the front end). Hydrogen gas is supplied by the hydrogen gas supply device. Further, of the supplied hydrogen gas, the remaining hydrogen gas excluding the hydrogen gas consumed in the battery body 2 is on the front side of FIG. 1 as indicated by the arrow (1) ′ in the outlet-side hydrogen gas passage 4out. The fuel cell stack 1 is led out from the lead-out side hydrogen gas passage 4out and collected at the front end of the fuel cell stack 1.

  Similarly, the introduction side refrigerant passage 5in and the outlet side refrigerant passage 5out communicate with each other at the rear end portion of the fuel cell stack 1. Then, as shown by the arrow (2), the introduction side refrigerant passage 5in is supplied with refrigerant from the front end portion of the fuel cell stack 1 by a refrigerant supplier (not shown). Further, after the supplied refrigerant passes through a refrigerant flow path, which will be described later, of the battery body 1, the refrigerant flows through the outlet-side refrigerant path 5 out toward the front side of FIG. 1 as indicated by an arrow (2) ′. The battery stack 1 is led out from the lead-out side refrigerant passage 5out and collected at the front end portion. The refrigerant recovered from the outlet-side refrigerant passage 5out is radiated outside the fuel cell stack 1 via a radiator (not shown) and then supplied again to the introduction-side refrigerant passage 5in.

  Further, the introduction-side air passage 6in and the outlet-side air passage 6out communicate with each other at the rear end portion of the fuel cell stack 1 in the same manner as described above. Then, air (atmosphere) is supplied to the introduction-side air passage 6in from the front end portion of the fuel cell stack 1 by an air supply device (not shown) as indicated by an arrow (3). Further, of the supplied air, air excluding oxygen consumed in the battery main body 2 flows toward the front side of FIG. 1 in the outlet side air passage 6out as indicated by an arrow (3) ′, The fuel cell stack 1 is led out from the lead-out side air passage 6out at the front end portion.

  The battery body 2 includes a plurality of plate-like membrane electrode structures 7 and conductive separators 8 mounted on each surface of each membrane electrode structure 7 in the normal direction of each membrane electrode structure 7 ( The fuel cell stack 1 is laminated in the longitudinal direction). In other words, the battery body 2 is configured by laminating a plurality of membrane electrode structures 7 and a plurality of separators 8 in the normal direction of each membrane electrode structure 7 so that they are alternately arranged. ing. In other words, a unit cell (one power generation element) of the fuel cell stack 1 is configured by each membrane electrode structure 7 and the separators 8 and 8 on both sides thereof, and the unit cells are stacked in series. Thus, the battery main body 2 is configured.

  Below, with reference to FIG. 2, the basic structure of the membrane electrode structure 7 and the separator 8 is demonstrated. FIG. 2 shows a cross-sectional view of a part of the membrane electrode structure 7 and the separator 8 constituting the battery body 2.

  Each membrane electrode structure 7 is usually referred to as MEA (Membrane Electrode Assembly), and as shown in the figure, a solid polymer electrolyte membrane 9 (hereinafter, referred to as a thin polymer ion exchange membrane having a thin rectangular film shape). (Hereinafter simply referred to as “electrolyte membrane 9”), and plate-like anode electrode 10 and cathode electrode 11 respectively joined to both surfaces thereof. In the present embodiment, the electrolyte membrane 9 has a thickness of, for example, 40 μm. Since the structure of each membrane electrode structure 7 is known, further description in this specification is omitted.

  The separator 8 forms a flow path of a reaction gas (in this embodiment, hydrogen gas and air are used as a reaction gas) between the electrodes 10 and 11 of each membrane electrode structure 7. In this case, the separator 8 between the membrane electrode structures 7, 7 adjacent to each other is mounted in more detail on the surface of the anode electrode 10 of one of the membrane electrode structures 7, and hydrogen gas is provided between the anode electrode 10. And a separator 8c that is mounted on the surface of the cathode electrode 11 of the other membrane electrode structure 7 and forms an air flow path between the cathode electrode 11 and the separator 8a. (Hereinafter, these separators 8a and 8c may be referred to as anode side separator 8a and cathode side separator 8c, respectively). In the present embodiment, these separators 8a and 8c are made of, for example, carbon.

  A plurality of grooves 12 are formed on the surface of the anode separator 8 a facing the anode electrode 10, and a space formed between the grooves 12 and the surface of the anode electrode 10 is formed as the hydrogen gas flow path 13. Has been. Similarly, a space is formed as an air flow path 15 between the plurality of grooves 14 formed on the surface facing the cathode electrode 11 of the cathode side separator 8 c and the surface of the cathode electrode 11.

  In this embodiment, the anode-side separator 8a and the cathode-side separator 8c that are joined adjacent to each other, that is, the surface of the anode-side separator 8a that faces the cathode-side separator 8c, and the cathode-side separator 8c A plurality of grooves 16, 17 facing each other are formed on the surface facing the anode separator 8 a, and a space formed between the separators 8 a, 8 c by the grooves 16, 17 is a coolant channel 19. It is formed as. The refrigerant channel 19 and the hydrogen gas channel 13 are defined by the anode side separator 8a, and the refrigerant channel 19 and the air channel 15 are defined by the cathode side separator 8c.

  Here, the pattern of the hydrogen gas flow path 13 between the anode-side separator 8a and the anode electrode 10 on which the anode-side separator 8a is mounted in this embodiment, and the refrigerant between the anode-side separator 8a and the cathode-side separator 8c joined together. The pattern of the flow path 18 will be described with reference to FIGS. 3 and 4, respectively. 3 shows a pattern of the hydrogen gas flow path 13 seen in the direction of the arrow III shown in FIG. 2, and FIG. 4 shows a pattern of the refrigerant flow path 18 seen in the direction of the arrow IV shown in FIG. ing. 3 and 4 also show the header 3 together. In this case, since the directions of the arrows III and IV are opposite, the headers 3 in FIG. 3 and FIG. 4 are opposite to each other.

  As shown in FIG. 3, the hydrogen gas flow path 13 (which is composed of a plurality of flow paths for each groove 12 in the present embodiment) formed by the plurality of grooves 12 of the anode-side separator 8a is A start end (inlet) 13in communicates with the introduction-side hydrogen gas passage 4in existing at the upper part of the side portion 3a of the head 3 at the upper right portion in the figure, and the lower left end in the figure while meandering from side to side. (Exit) 13out. A terminal end 13out of the hydrogen gas flow path 13 is communicated with a lead-out side hydrogen gas passage 4out existing at a lower portion of the side portion 3b of the head 3.

  Further, as shown in FIG. 4, the refrigerant flow path 18 communicates with the introduction-side refrigerant passage 5in existing at the central portion of the side portion 3a of the head 3 with the start end (inlet) 18in at the central portion on the left side of the drawing. After branching from the starting end 18in into a plurality of flow paths 18a, 18b, 18c arranged in the up-down direction, it merges with a terminal (outlet) 18out at the central portion on the right side of the figure. The end 18out of the refrigerant flow path 18 communicates with the outlet-side refrigerant passage 5out existing at the center of the side 3b of the head 3. Note that the broken lines in FIG. 4 indicate the overall (typical) path of the hydrogen gas flow path 13 in order to show the positional relationship between the refrigerant flow path 18 and the hydrogen gas flow path 13.

  Here, in the present embodiment, as shown in FIG. 1, the introduction-side hydrogen gas passage 4in and the introduction-side refrigerant passage 5in are respectively provided at the upper part and the central part (the central part in the vertical direction) of the side part 3a of the head 3. Further, a lead-out side refrigerant passage 5out and a lead-out side hydrogen gas passage 4out are respectively arranged at the central portion (vertical center portion) and the lower portion of the side portion 3b of the head 3. Therefore, when the refrigerant channel 18 and the hydrogen gas channel 13 are viewed from the same direction in the normal direction of the membrane electrode structure 7, the lower channel of the refrigerant channel 18 is seen as shown in FIG. 18c, the end vicinity portion 18x (the portion near the end 18out of the flow path 18c) is positioned near the end of the hydrogen gas flow path 13 (when viewed in the normal direction of the membrane electrode structure 7). The positions of the portions near the end of the end are almost the same position). Further, the end vicinity portion 18 x of the flow path 18 c on the lower side of the refrigerant flow path 18 is closer to the end of the hydrogen gas flow path 13 than the start end 18 in of the refrigerant flow path 18.

  In the present embodiment, the pattern of the air flow path 15 formed between the cathode side separator 8c and the cathode electrode 11 on which the cathode side separator 8c is mounted is approximately as viewed in the normal direction of the membrane electrode structure 7. The pattern is substantially symmetrical with the pattern of the hydrogen gas flow path 13. More specifically, when viewed in the direction of the arrow V in FIG. 2 (the same direction as the arrow III), the air flow path 15 is meandering from the upper left starting end (inlet) 15in to the left and right as shown by the broken line in FIG. The lower right end (exit) 15out is reached. The start end 15in of the air flow path 15 communicates with the introduction-side air passage 6in existing above the side portion 3b of the head 3, and the terminal end 15out communicates with the lead-out side air passage 6out existing below the side portion 3a of the head 3. ing. Therefore, regarding the relationship between the air flow path 15 and the refrigerant flow path 18, a portion near the start end of the lower flow path 18c of the refrigerant flow path 18 shown by a solid line in FIG. 5 (the start end of the flow path 18c). 18 in the vicinity of the end of the air flow path 15, and the vicinity of the start end of the flow path 18 c is closer to the end of the air flow path 15 than the end 18 out of the refrigerant flow path 18. Yes.

  In the fuel cell stack 1 of the present embodiment configured as described above, when generating electricity, the refrigerant is supplied to the introduction side refrigerant passage 5in of the header 3 while the introduction side hydrogen gas passage 4in and the introduction side of the header 3 are supplied. Hydrogen gas and air as reaction gases are respectively supplied to the air passage 6in. As the refrigerant, for example, water, ethylene glycol, or the like is used.

  At this time, the hydrogen gas supplied to the introduction-side hydrogen gas passage 4in flows from the start end 13in into the hydrogen gas passage 13 facing the anode electrode 10 of each membrane electrode structure 7, and passes through the hydrogen gas passage 13 through the hydrogen gas passage 13. It flows along the surface of the anode electrode 10. Then, it flows out from the terminal end 13out of the hydrogen gas passage 13 to the outlet side hydrogen gas passage 4out. Further, the air supplied to the introduction-side air passage 6in flows into the air passage 15 facing the cathode electrode 11 of each membrane electrode structure 7 from the start end 15in thereof, and the air passage 15 passes through the air passage 15 of the cathode electrode 11. Flows along the surface. Then, the air flows out from the terminal end 15out of the air flow path 15 to the outlet side air passage 6out. The refrigerant supplied to the introduction-side refrigerant passage 5in flows into the refrigerant flow paths 18 between the membrane electrode structures 7 and 7 adjacent to each other from the start end 18in and flows through the refrigerant flow paths 18. Then, the refrigerant flows out from the end 18out of the refrigerant flow path 18 to the outlet side refrigerant passage 5out.

Furthermore, in each membrane electrode structure 7 in which hydrogen gas is supplied to the surface of the anode electrode 10 and air is supplied to the surface of the cathode electrode 11 as described above, the hydrogen gas supplied to the anode electrode 10 is ionized, Hydrogen ions pass through the electrolyte membrane 9 and move to the cathode electrode 11. Then, the hydrogen ions moved to the cathode electrode 11 react with oxygen in the air supplied to the cathode electrode 11, and at that time, an electromotive force is generated between the electrodes 10 and 11 to generate power, H ₂ O (water or water vapor) is produced. Further, the heat energy generated in each membrane electrode structure 7 during this power generation is absorbed by the refrigerant flowing through the refrigerant flow path 18 inside the separator 8 adjacent thereto, thereby causing excessive temperature rise of the fuel cell stack 1. Is prevented. The electromotive force (generated power) generated between the electrodes 10 and 11 of each membrane electrode structure 7 is taken out from the separators 8 and 8 on both sides of each membrane electrode structure 7 via a cable (not shown). Is synthesized in series for all the membrane electrode structures 7 and supplied to an appropriate electric load.

During such power generation, most of the H ₂ O generated in each membrane electrode structure 7 diffuses to the cathode electrode 11 side of both electrodes 10, 11 of the membrane electrode structure 7, and the cathode electrode 11 It enters the air flow path 15 facing the surface. However, part of the generated H ₂ O by so-called reverse diffusion or the like diffuses to the anode electrode side 10 and enters the hydrogen gas flow path 13 facing the surface of the anode electrode 10.

In this case, among the air supplied to the air flow path 15, the component consumed for power generation of each membrane electrode structure 11 is only oxygen having a composition ratio of about 1/5 of the air. The flow rate of air supplied to the air flow path 15 is sufficiently larger than the flow rate of hydrogen gas supplied to the hydrogen gas flow path 13. Even if oxygen, which is a part of the composition component of the air supplied to the air flow path 15, is consumed by the power generation of each membrane electrode structure 11 in the process of flowing through the air flow path 15, the air flow path The flow rate of 15 does not decrease so much. For this reason, most of the H ₂ O entering the air flow path 15 is basically transported by the air flowing through the air flow path 15 without dew condensation remaining on the surface of the cathode electrode 11. Then, the air flows out from the air flow path 15 to the outlet side air passage 5in of the header 3.

On the other hand, the flow rate of hydrogen gas supplied to the hydrogen gas flow path 13 is smaller than the flow rate of air supplied to the air flow path 15, and the membrane electrode structure is in the process of flowing through the hydrogen gas flow path 13. By being consumed by the power generation of the body 11, the flow rate of the hydrogen gas in the hydrogen gas flow path 13 decreases as it approaches the terminal end 13 out of the hydrogen gas flow path 13 (the degree of decrease is that of the air flow path 15. Bigger than the case). For this reason, condensation of H ₂ O and its residue are likely to occur particularly near the end of the hydrogen gas flow path 13.

However, in the fuel cell stack 1 of the present embodiment, as described above, the lower flow path 18c of the refrigerant flow path 18 has its end vicinity portion 18x positioned near the end of the hydrogen gas flow path 13. Further, the end vicinity portion 18x of the flow path 18c is closer to the end of the hydrogen gas flow path 13 than the start end 18in of the refrigerant flow path 18. Therefore, the vicinity of the end of the hydrogen gas flow path 13 is difficult to dissipate heat due to the heat of the refrigerant (refrigerant in the vicinity of the end 18x of the flow path 18c) heated in the process of flowing through the refrigerant flow path 18 from the start end 18in to the end end 18out. It has become. As a result, H ₂ O is prevented from condensing near the end of the hydrogen gas flow path 13. Therefore, to avoid such a situation that the condensed power generation capacity of the membrane electrode assembly 7 by H _{2 O} remaining in the H _{2 O} and the hydrogen gas channel 13 attached to the anode electrode 10 (power output) is impaired be able to.

  Here, with reference to FIG. 6, the verification result of the effect of the fuel cell stack 1 of this embodiment is demonstrated. A graph a in FIG. 6 shows a steady state after the start of the fuel cell stack 1 of the present embodiment (the supply amount of hydrogen gas, the supply amount of air, the supply amount of refrigerant, the environmental temperature, etc. to the fuel cell stack 1 are constant). FIG. 6 shows measured values of output voltage of each unit cell (battery composed of each membrane electrode structure 7 and separators 8 and 8 on both sides thereof) in a maintained state (Example). FIG. 6 represents the position of the membrane electrode structure 7 of each cell in the longitudinal direction of the fuel cell stack 1 (normal direction of the membrane electrode structure 7), and the vertical axis represents the output voltage of each cell. is there.

  Moreover, the graph b of FIG. 6 shows the measured value of the output voltage of each unit cell in the steady state after starting the fuel cell stack of the comparative example. The structure of the fuel cell stack of the comparative example is the same as that of the fuel cell stack of the present embodiment. However, contrary to the fuel cell stack of the present embodiment, hydrogen gas is supplied from the lead-out side hydrogen gas passage 4out of the header 3 and is led out. Air is supplied from the side air passage 6out. That is, in the comparative example, the direction of the hydrogen gas flow in each hydrogen gas flow path and the direction of the air flow in each air flow path are opposite to those in the above embodiment. The other measurement conditions are the same as in the example of graph a. In this case, in the fuel cell stack of the comparative example, since hydrogen gas and oxygen gas are supplied as described above, the end of the hydrogen gas flow path is close to the vicinity of the start end of the refrigerant flow path. In the air flow path, the end is close to the vicinity of the end of the refrigerant flow path.

As seen in FIG. 6, in the fuel cell stack of the comparative example, a relatively large drop in output voltage occurs in the unit cells at positions corresponding to A and B in the figure. Here, in the fuel cell stack of the comparative example, in the vicinity end of the air passage, since the end portion near a portion of the flow path of the coolant channel is present, H ₂ O at the end near the air channel Although it is more advantageous than the embodiment in terms of preventing condensation, the end of the hydrogen gas flow path is separated from the vicinity of the end of the refrigerant flow path. Condensation of H ₂ O and its residue are likely to occur in the vicinity. In the fuel cell stack of the comparative example, in the unit cells at the positions corresponding to A and B in the figure, H ₂ O dew condensation and its residue occur near the end of the hydrogen gas flow path. It is thought that the output voltage has dropped.

On the other hand, in the fuel cell stack 1 of the embodiment, the drop in the output voltage of the unit cell at the position corresponding to A and B in the figure is smaller than that of the comparative example, and the output voltage of each unit cell. Is generally higher than the comparative example. In this case, in the fuel cell stack 1 of the embodiment, the end of the air flow path 15 is separated from the vicinity of the end of the refrigerant flow path 18, thereby preventing H ₂ O condensation near the end of the air flow path 15. However, although it is more disadvantageous than the comparative example, as described above, the output characteristics of each unit cell are better than those of the comparative example. This is considered to be because, in the fuel cell stack 1 of the example, as described above, the effect of preventing condensation of H ₂ O in the vicinity of the end of the hydrogen gas flow path 13 is great.

  Next, another embodiment of the present invention will be described. In the embodiments described below, the same reference numerals as those in the first embodiment are used for the same configuration or the same function as those in the first embodiment, and detailed description thereof is omitted.

  In the present invention, the relationship between the refrigerant flow path pattern and the hydrogen gas flow path pattern is not limited to that of the first embodiment. For example, patterns as shown in FIGS. 7 to 11 may be used.

  The embodiment (second embodiment) shown in FIG. 7, the embodiment (third embodiment) shown in FIG. 8, and the embodiment (fourth embodiment) shown in FIG. Only the pattern is different from the first embodiment. In the second embodiment shown in FIG. 7, the hydrogen gas flow path 13 is provided along the flow paths 18 a, 18 b, and 18 c of the refrigerant flow path 18 from the start end communicating with the introduction-side hydrogen gas path 4 in of the header 3. The flow is branched into two flow paths, which are merged in the vicinity of the derivation-side hydrogen gas passage 4out, reach the end, and communicate with the derivation-side hydrogen gas passage 4out.

  Further, in the third embodiment shown in FIG. 8, the hydrogen gas flow path 13 moves to the right side while meandering up and down from the start end communicating with the introduction-side hydrogen gas path 4in of the header 3 and moves to the outlet-side hydrogen gas path 4out. , And communicates with the outlet-side hydrogen gas passage 4out at the end thereof.

  Moreover, in 4th Embodiment shown in FIG. 9, the hydrogen gas flow path 13 moves to a lower side, meandering right and left from the starting end connected to the introduction side hydrogen gas path 4in of the header 3, and is located in the location on the lower left side. Then, it moves to the right side while meandering up and down, approaches the derivation-side hydrogen gas passage 4out, and communicates with the derivation-side hydrogen gas passage 4out at the end thereof.

  In any of these second to fourth embodiments, as in the first embodiment, the end vicinity portion 18x of the flow path 18c of the refrigerant flow path 18 exists in the vicinity of the end of the hydrogen gas flow path 13. Further, the end vicinity portion 18x of the flow path 18c is closer to the end of the hydrogen gas flow path 13 than the start end 18in of the refrigerant flow path 18. Therefore, the same effect as that of the first embodiment can be obtained.

  Further, in the embodiment (fifth embodiment) shown in FIG. 10 and the embodiment (sixth embodiment) shown in FIG. 11, the pattern of the hydrogen gas flow path 13 is the same as that of the fourth embodiment, for example. In addition, the pattern of the refrigerant flow path 18 and the positions of the inlet side refrigerant passage 5in and the outlet side refrigerant passage 5out of the header 3 are different from those of the first embodiment. The rest is the same as in the first embodiment.

  In this case, in the fifth embodiment shown in FIG. 10, the inlet side refrigerant passage 5 in and the outlet side refrigerant passage 5 out of the header 3 are respectively an upper central portion (a central portion in the left-right direction) of the header 3 and a lower central portion ( (Central part in the left-right direction). The refrigerant flow path 18 is branched into three flow paths 18a, 18b, 18c extending downward from a start end 18in communicating with the introduction-side refrigerant passage 5in of the header 3. And after these flow paths 18a, 18b, and 18c merge in the vicinity of the derivation side refrigerant passage 5out, the terminal end 18out is connected with the derivation side refrigerant passage 5out. In the fifth embodiment, the end portion 18x of the right flow path 18c of the refrigerant flow path 18 is present near the end of the hydrogen gas flow path 13, and the end vicinity portion 18x of the flow path 18c is The hydrogen gas flow path 13 is closer to the end than the start end 18 in of the refrigerant flow path 18. Therefore, the same effect as that of the first embodiment can be obtained.

  Further, in the sixth embodiment shown in FIG. 11, the introduction side refrigerant passage 5 in and the outlet side refrigerant passage 5 out of the header 3 are provided at the upper left corner and the lower right corner of the header 3, respectively. The refrigerant flow path 18 is branched into three flow paths 18a, 18b and 18c extending obliquely downward from a start end 18in communicating with the introduction-side refrigerant passage 5in of the header 3. And after these flow paths 18a, 18b, and 18c merge in the vicinity of the derivation side refrigerant passage 5out, the terminal end 18out is connected with the derivation side refrigerant passage 5out. In the sixth embodiment, the end vicinity portion 18x of the refrigerant flow path 18 (all flow paths 18a to 18c) is present near the end of the hydrogen gas flow path 13, and the end vicinity portion of the refrigerant flow path 18 is present. 18 x is closer to the end of the hydrogen gas flow path 13 than the start end 18 in of the refrigerant flow path 18. Therefore, the same effect as that of the first embodiment can be obtained.

  In the first to sixth embodiments described above, the separator is made of carbon, but the separator may be made of a metal plate. In this case, when forming a coolant channel between adjacent membrane electrode structures, for example, by pressing the two metal plates, concave and convex grooves are formed on both surfaces of each metal plate, and each metal plate is By joining to the anode electrode of one membrane electrode structure, and the cathode electrode of the other membrane electrode structure, a hydrogen gas flow path and an air flow path are formed between each electrode. Furthermore, a refrigerant flow path can be formed between both metal plates by joining these two metal plates.

  In addition, the refrigerant flow path, the air flow path, and the hydrogen gas flow path may be formed by interposing a plurality of protrusions (embosses) on a separator made of carbon or a metal plate, thereby forming the flow path. .

  In the first to sixth embodiments, the coolant channel is provided between each pair of membrane electrode structures 7 and 7 adjacent to each other. However, all the pairs of membrane electrode structures 7 are not necessarily provided. , 7 need not be provided. For example, a coolant channel may be provided for every other set of membrane electrode structures 7 and 7. In this case, for a set of membrane electrode structures 7 and 7 that do not have a coolant channel between them, the separator between the membrane electrode structures 7 and 7 is made of a single structure (one-part structure) carbon or metal plate. It may be formed.

  In the first embodiment, the relationship between the air flow path 15 and the refrigerant flow path 18 is a portion near the start end (flow) of the lower flow path 18c of the refrigerant flow path 18 shown by a solid line in FIG. The portion of the passage 18c near the start end 18in) is located near the end of the air flow path 15, and the portion near the start end of the flow path 18c is closer to the air flow path 15 than the end 18out of the refrigerant flow path 18. Close to the end of the. However, similarly to the relationship between the hydrogen gas flow path 13 and the refrigerant flow path 18, at least a part of the refrigerant flow path near the end of the flow path (portion near the start end of the flow path) is an air flow path. Further, at least a part of the refrigerant flow path in the vicinity of the end of the refrigerant flow path may be closer to the end of the air flow path than the start end of the refrigerant flow path. In the embodiment in this case, for example, the introduction-side air passage 6in and the discharge-side air passage 6out in the first embodiment are respectively used as the lead-out side and the lead-in side, contrary to the first embodiment, and the air is led-out side air. What is necessary is just to make it supply from the channel | path 6out. In this way, the direction of the air flow in each air flow path 15 is opposite to that in the first embodiment, so that the above relationship between the refrigerant flow path 18 and the air flow path 15 can be realized. The same applies to the second to sixth embodiments.

1 is a perspective view schematically showing an overall configuration of a fuel cell stack according to a first embodiment of the present invention. Sectional drawing which shows the structure of the membrane electrode structure and separator of the battery main-body part of the fuel cell stack of FIG. The figure which shows the pattern of the hydrogen gas flow path seen in the direction of arrow III of FIG. The figure which shows the pattern of the refrigerant flow path seen in the direction of arrow IV of FIG. The figure which shows the pattern of the refrigerant | coolant flow path and air flow path seen in the direction of the arrow V of FIG. The graph which shows the verification result of the effect of the fuel cell stack of 1st Embodiment. The figure which shows the relationship of the pattern of the refrigerant | coolant flow path and hydrogen gas flow path of the fuel cell stack in 2nd Embodiment. The figure which shows the relationship of the pattern of the refrigerant | coolant flow path and hydrogen gas flow path of the fuel cell stack in 3rd Embodiment. The figure which shows the relationship of the pattern of the refrigerant | coolant flow path and hydrogen gas flow path of the fuel cell stack in 4th Embodiment. The figure which shows the relationship of the pattern of the refrigerant | coolant flow path and hydrogen gas flow path of the fuel cell stack in 5th Embodiment. The figure which shows the relationship of the pattern of the refrigerant | coolant flow path and hydrogen gas flow path of the fuel cell stack in 6th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack, 2 ... Battery main-body part, 7 ... Membrane electrode structure, 8, 8a, 8b ... Separator, 9 ... Solid polymer electrolyte membrane, 10 ... Anode electrode, 11 ... Cathode electrode, 13 ... Hydrogen gas flow Road, 15 ... air flow path, 18 ... refrigerant flow path.

Claims (1)

A plurality of membrane electrode structures each composed of a solid polymer electrolyte membrane and an anode electrode and a cathode electrode respectively bonded to both surfaces thereof, and provided on the surface of each electrode of each membrane electrode structure, And a separator that forms a flow path for the reaction gas, and a separator between at least one pair of adjacent membrane electrode structures. A refrigerant gas defined by a reaction gas flow path on the surface side of the anode electrode of one of the membrane electrode structures and a reaction gas flow path on the surface side of the cathode electrode of the other membrane electrode structure. In a fuel cell stack formed by forming a flow path,
The refrigerant flow path formed in the separator between the pair of membrane electrode structures is such that at least a part near the end of the flow path from the start end to the end of the flow path is the set of membranes. Near the end of the reaction gas flow path on the surface side of the anode electrode of the one membrane electrode structure of the electrode structures, closer to the end of the coolant flow path and near the end of the reaction gas flow path A fuel cell stack, wherein the fuel cell stack is formed so as to exist.

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