JP2009176435A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing drying of a unit cell constituting a fuel cell, and furthermore, capable of simplifying a structure of the fuel cell. <P>SOLUTION: In the fuel cell system 1, temperature sensors 11 are provided which measure the temperature of the unit cells 10 of the fuel cell 2, and these temperature sensors 11 are electrically connected to controllers 22, respectively. Moreover, on the unit cell 10, an upper side fuel supply passage 38A, an intermediate fuel supply passage 38B and a lower side fuel supply passage 38C which are separated into three passages are formed. Moreover, fuel supply pipes 20A to 20C for supplying fuel to these upper fuel supply passages 38A, intermediate fuel supply passages 38B and upper side supply passages 38C are interposed with supply valves 23A to 23C, respectively, and these supply valves 23A to 23C are electrically connected to the controllers 22. Then, in the controllers 22, the opening degree control of the supply valves 23A to 23C is carried out based on the temperature measured by the temperature sensors 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  Conventionally, various fuel cells such as an alkaline type (AFC), a solid polymer type (PEFC), a phosphoric acid type (PAFC), a molten carbonate type (MCFC), and a solid electrolyte type (SOFC) are known.

  For example, a polymer electrolyte fuel cell is formed in a stack structure in which a plurality of unit cells are stacked.

  Each cell is configured as an MEA (Membrane Electrode Assembly) formed by pressure-bonding an electrolyte membrane, and a fuel-side electrode and an oxygen-side electrode arranged to face each other with the electrolyte membrane interposed therebetween. A plurality of MEAs are stacked via separators to form a fuel cell stack structure.

  On one side of the separator (the side in contact with the fuel side electrode), a single fuel supply path is formed in a meandering manner so that hydrogen spreads over the entire surface of the fuel side electrode. On the other hand, on the other surface of the separator (the surface in contact with the oxygen side electrode), one oxygen supply path is formed in a meandering manner so that oxygen spreads over the entire surface of the oxygen side electrode.

  In a fuel cell, an electromotive force is generated by supplying hydrogen to a fuel supply path, supplying oxygen to an oxygen supply path, and causing an electrochemical reaction at each electrode.

However, in the fuel cell described above, the fuel supply path and the oxygen supply path are each formed in one meandering flow path. Therefore, for example, when the supply amount of hydrogen or oxygen is excessive with respect to the power generation amount, the moisture content of the cell in the vicinity of the upstream side of each supply path decreases (drys), and the internal resistance of the portion increases. is there.
Therefore, for example, a channel cross-sectional area reducing member is disposed upstream of each of the fuel gas channel provided on the surface of the fuel electrode side separator and the oxidant gas channel provided on the surface of the oxidant electrode side separator. Thus, it has been proposed to increase the gas pressure in the upstream portion of each gas flow path with this flow path cross-sectional area reducing member to suppress drying of the electrode near the upstream side of each gas flow path (for example, , See Patent Document 1).
JP 2004-31197 A

  However, the drying of each cell does not necessarily occur near the upstream side of the fuel supply path and the oxygen supply path. Therefore, as in the fuel cell described in Patent Document 1, it is not sufficient to suppress drying of the electrodes in the vicinity of the upstream side of each gas flow path.

  On the other hand, it is conceivable to reduce the temperature difference between the upstream side and the downstream side of each supply channel by reducing the area of the MEA and shortening the channel length of each supply channel. As a result, the humidified state of each cell is made uniform, and the overall drying is suppressed.

  However, if the area of the MEA is reduced, the output amount of each cell is reduced, so the number of stacked cells must be increased. As a result, the structure of the fuel cell becomes complicated.

  An object of the present invention is to provide a fuel cell system capable of suppressing the drying of unit cells constituting the fuel cell and further simplifying the structure of the fuel cell.

  In order to achieve the above object, a fuel cell system according to the present invention includes an electrolyte layer, a fuel side electrode and an oxygen side electrode arranged opposite to each other across the electrolyte layer, the fuel side electrode, and the fuel side electrode. A unit cell comprising a fuel-side separator in which a fuel supply path for supplying fuel is formed, and an oxygen-side separator disposed adjacent to the oxygen-side electrode and having an oxygen supply path for supplying oxygen to the oxygen-side electrode A plurality of at least one of the fuel supply path and the oxygen supply path, a detection means for detecting a dry portion of the unit cell, and based on detection of the detection means, The apparatus further comprises control means for controlling the flow rate of fuel and / or oxygen supplied to the fuel supply path and / or each of the oxygen supply paths.

  According to the fuel cell system of the present invention, the dry portion of the unit cell can be detected by the detecting means. And based on the detection, the further drying of a dry part can be suppressed by controlling appropriately the flow volume of the fuel and / or oxygen to each fuel supply path and / or each oxygen supply path. Therefore, the humidified state of the unit cell can be maintained in an appropriate state.

  Further, since at least one of the fuel supply path and the oxygen supply path is provided in plural, and the flow rate of each supply path is controlled, the humidified state of the unit cell can be made uniform. Therefore, it is not necessary to reduce the area of the unit cell and shorten the flow path length of each supply path. As a result, the number of stacked unit cells can be reduced, so that the structure of the fuel cell can be simplified.

  In the fuel cell system of the present invention, the fuel cell includes a cell stack in which a plurality of the unit cells are stacked, and the cell stack is formed with a cooling water channel for cooling each unit cell. It is preferable that a plurality of the cooling water channels are formed along at least one of the fuel supply channel and the oxygen supply channel formed in each unit cell.

  When the cooling water cools a unit cell heated by power generation, its temperature rises due to heat exchange with the unit cell. Therefore, in the cell stack, in the unit cell on the downstream side of the cooling water channel, the temperature of the cooling water is higher than that of the unit cell on the upstream side, and a dry portion is easily generated in the entire cell. However, since the fuel supply path and / or the oxygen supply path are formed along the cooling water path, the humidified state of the cell stack is controlled by controlling the flow rate of the fuel and / or oxygen according to the dry state of each unit cell. Can be kept in a proper state as a whole.

  According to the fuel cell system of the present invention, drying of the unit cells constituting the fuel cell can be suppressed, and further, the structure of the fuel cell can be simplified.

  FIG. 1 is a unidirectional perspective view for explaining the structure of a fuel cell system 1 according to an embodiment of the present invention. FIG. 2 is a perspective view in the other direction for explaining the structure of the fuel cell system 1 according to the embodiment of the present invention.

  1 and 2, the fuel cell system 1 includes a fuel cell 2, a fuel supply / discharge unit 3, an oxygen supply / discharge unit 4, and a water supply / drainage unit 5.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and in the cell stack 6 and the stacking direction of the cell stack 6 (hereinafter, this direction may be simply referred to as “stacking direction”). A pair of current collector plates 7, a pair of insulating plates 8, and a pair of end plates 9 that are opposed to each other across the stack 6 are provided. That is, the fuel cell 2 is formed in a stack structure as a whole by sequentially stacking the current collector plate 7, the insulating plate 8, and the end plate 9 on both sides (front side and back side) of the cell stack 6 in the stacking direction. ing.

  The cell stack 6 includes a plurality of unit cells 10 that generate power by an electrochemical reaction between hydrogen and oxygen.

  Each unit cell 10 is formed in a substantially rectangular shape when viewed from the front. The plurality of unit cells 10 are stacked (stacked), whereby the cell stack 6 is formed in a stack structure. Each unit cell 10 is provided with a temperature sensor 11 as detection means for measuring the temperature of the unit cell 10.

  Each temperature sensor 11 is a known temperature sensor such as a thermistor or a thermocouple, and is electrically connected to a controller 22 described later. The number and arrangement of the temperature sensors 11 in each unit cell 10 will be described later with reference to FIGS.

  The current collector plate 7 is made of, for example, a conductive material such as copper, and the current collector plate 7 stacked on one side in the stacking direction (hereinafter referred to as the front side) of the cell stack 6 and the cell stack 6. It consists of the other collector plate 7 laminated | stacked on the other side (henceforth a back side) of the lamination direction. Each current collecting plate 7 is formed in substantially the same shape as the cell stack 6 in front view. Terminals 12 are provided on the upper peripheral edge of each current collector plate 7.

  The terminal 12 is formed integrally with the current collector plate 7 and is formed in a substantially rectangular parallelepiped shape protruding upward from the upper peripheral edge of the current collector plate 7. In the fuel cell 2, the electromotive force generated in the cell stack 6 is taken out by the current collector plate 7.

  The insulating plate 8 is made of, for example, an insulating material such as rubber or resin, and is stacked on one insulating plate 8 stacked on the front side of one current collecting plate 7 and on the back side of the other current collecting plate 7. And the other insulating plate 8. Each insulating plate 8 is formed in substantially the same shape as the cell stack 6 in front view. The insulating plate 8 insulates the cell stack 6 from the casing (not shown) that houses the fuel cell 2 and the end plate 9.

  The end plate 9 is made of a material having high rigidity such as steel, for example, and one end plate 9 stacked on the front side of one insulating plate 8 and the other end plate 9 stacked on the back side of the other insulating plate 8. And an end plate 9. Each end plate 9 is formed in substantially the same shape as the cell stack 6 in front view.

  The one end plate 9, the one insulating plate 8, and the one current collector plate 7 may be described as a width direction orthogonal to the vertical direction when viewed from the front (hereinafter, this direction is simply referred to as “width direction”). ) Is formed with an oxygen discharge port 13 for discharging oxidizing gas from the cell stack 6. The oxygen discharge port 13 is formed in a substantially circular shape when viewed from the front.

  Further, the fuel gas is supplied to the cell stack 6 to the one end plate 9, the one insulating plate 8, and the one current collecting plate 7, inside the oxygen discharge port 13 at the one side end in the front view width direction. For this purpose, three fuel supply ports 14 are formed.

  The fuel supply port 14 is formed in a substantially circular shape when viewed from the front. Further, the fuel supply ports 14 are arranged at predetermined intervals in the vertical direction, and the upper fuel supply port 14A and the lower fuel supply port disposed below the upper fuel supply port 14A. 14C and an intermediate fuel supply port 14B disposed between the fuel supply port 14A and the fuel supply port 14C.

  The one end plate 9, the one insulating plate 8, and the one current collecting plate 7 have oxygen supply ports for supplying oxygen to the cell stack 6 at the upper corner portion at the other side end portion in the front view width direction. 15 is formed.

  The oxygen supply port 15 is formed in a substantially circular shape when viewed from the front.

  Further, the one end plate 9, the one insulating plate 8, and the one current collecting plate 7 are provided with a drain port 16 for discharging cooling water from the cell stack 6 at a lower corner portion at the other side end portion in the front view width direction. Is formed.

  The drain port 16 is formed in a substantially circular shape when viewed from the front.

  Further, one end plate 9, one insulating plate 8, and one current collecting plate 7 are provided with fuel from the cell stack 6 inside the oxygen supply port 15 and the drain port 16 at the other side end in the width direction of the front view. Three fuel discharge ports 17 for discharging the fuel are formed.

  The fuel discharge port 17 is formed in a substantially circular shape when viewed from the front. Further, the fuel discharge ports 17 are arranged at predetermined intervals in the vertical direction, and the upper fuel discharge port 17A and the lower fuel discharge port disposed below the upper fuel discharge port 17A. 17C and an intermediate fuel outlet 17B disposed between the fuel outlet 17A and the fuel outlet 17C.

  Further, the other end plate, the other insulating plate 8 and the other current collecting plate 7 have upper corners at one end portion in the rear view width direction (a portion facing the one end portion in front view in the stacking direction). Further, a water supply port 18 for supplying cooling water to the cell stack 6 is formed.

  The water supply port 18 is formed in a substantially circular shape when viewed from the back.

  The fuel supply / discharge unit 3 includes a fuel tank 19, a fuel supply pipe 20, a fuel discharge pipe 21, and a controller 22 as control means.

  Fuel is stored in the fuel tank 19. The fuel to be stored is a compound containing at least hydrogen, for example, hydrogen, for example, hydrocarbons such as methane, ethane, and propane, alcohols such as methanol and ethanol, hydrazine, hydrated hydrazine, hydrazine carbonate, hydrazine sulfate, Hydrazines such as monomethylhydrazine and dimethylhydrazine, for example, urea, for example, ammonia, for example, imidazole, 1,3,5-triazine, 3-amino-1,2,4-triazole and other heterocyclic rings, for example, hydroxyl Examples thereof include hydroxylamines such as amines and hydroxylamine sulfate. These may be used alone or in combination of two or more.

  One end of the fuel supply pipe 20 is connected to the fuel tank 19. The fuel supply pipe 20 has a fuel supply pipe 20A on the upper side in the vertical direction, a lower fuel supply pipe 20C disposed below the upper fuel supply pipe 20A, and a fuel supply downstream of the one end portion. It branches off to an intermediate fuel supply pipe 20B disposed between the pipe 20A and the fuel supply pipe 20C. The other end portions of the fuel supply pipes 20A to 20C are connected to the fuel supply ports 14A to 14C, respectively. A supply valve 23 is interposed in the fuel supply pipe 20.

  The supply valve 23 is interposed in each of the fuel supply pipes 20A to 20C, the supply valve 23A interposed in the fuel supply pipe 20A, the supply valve 23B interposed in the fuel supply pipe 20B, and the fuel supply pipe 20C. It is distinguished from the supply valve 23 </ b> C interposed between the two. These supply valves 23A to 23C are valves that can adjust the flow rate of the fuel gas flowing through the fuel supply pipes 20A to 20C, respectively. For example, a known flow control valve such as a throttle valve is used.

  The fuel discharge pipe 21 includes an upper fuel discharge pipe 21A in the vertical direction, a lower fuel discharge pipe 21C disposed below the upper fuel discharge pipe 21A, and the fuel discharge pipe 21A and the fuel discharge pipe 21C. It is distinguished from the intermediate fuel discharge pipe 21 </ b> B. One end of each of the fuel discharge pipes 21A to 21C is, for example, a buffer tank for processing unreacted fuel gas discharged from the cell stack 6, water generated by an electrochemical reaction between hydrogen and oxygen, and the like. (Not shown). On the other hand, the other end portions of the fuel discharge pipes 21A to 21C are connected to the fuel discharge ports 17A to 17C, respectively.

  The controller 22 is composed of, for example, a microcomputer including a CPU, a ROM, a RAM, and the like, and is electrically connected to the temperature sensor 11 and the supply valve 23. In the fuel cell system 1, the flow rate of the fuel gas flowing through the fuel supply pipe 20 is controlled by inputting a predetermined control signal from the controller 22 to the supply valve 23.

  The oxygen supply / exhaust unit 4 includes an oxygen supply pipe 24 and an oxygen discharge pipe 25.

  One end of the oxygen supply pipe 24 is connected to, for example, a compressor (not shown). On the other hand, the other end portion of the oxygen supply pipe 24 is connected to the oxygen supply port 15.

  One end of the oxygen exhaust pipe 25 is exhausted. On the other hand, the other end of the oxygen discharge pipe 25 is connected to the oxygen discharge port 13.

  The water supply / drainage unit 5 includes a water supply pipe 26 and a drainage pipe 27.

  One end of the water supply pipe 26 is connected to the water supply port 18. The other end of the water supply pipe 26 is connected to, for example, a water supply device (not shown).

  For example, when the drain pipe 27 is drained at one end thereof, or when drainage from the drain pipe 27 is supplied to the water supply pipe 26 again, for example, the drainage pipe 27 is used to send the drainage to the water supply pipe 26. Connected to a pump (not shown). On the other hand, the other end portion of the drain pipe 27 is connected to the drain port 16.

FIG. 3 is a cross-sectional view of the main part when the cell stack 6 shown in FIG. 1 is cut along a cutting line indicated by LL. FIG. 4 is an exploded view of the main part of the cell stack 6 shown in FIG. FIG. 5 is an exploded view of the main part in the other direction of the cell stack 6 shown in FIG.
First, the structure of the cell stack 6 will be described mainly with reference to FIG.

  As described above, the cell stack 6 is formed in a stack structure in which a plurality of unit cells 10 are stacked.

  Each unit cell 10 includes an electrolyte layer 31, a fuel-side electrode 32 and an oxygen-side electrode 33 that are disposed to face each other with the electrolyte layer 31 interposed therebetween, a fuel-side separator 34 that is disposed adjacent to the fuel-side electrode 32, and an oxygen-side electrode. 33 and an oxygen side separator 35 disposed adjacent to 33.

  The electrolyte layer 31 is formed in a substantially rectangular shape when viewed from the front (see FIGS. 4 and 5). The thickness of the electrolyte layer 31 in the stacking direction is, for example, 10 to 100 μm. Examples of the electrolyte layer 31 include solid polymer membranes such as proton exchange membranes and anion exchange membranes.

The proton exchange membrane is not particularly limited as long as protons can move inside the proton exchange membrane, and examples thereof include a perfluorosulfonic acid membrane.

On the other hand, an anion exchange membrane has an anion (particularly a hydroxide ion (O
The membrane is not particularly limited as long as H ⁻ )) can move, and examples thereof include a solid polymer membrane (anion exchange resin) having an anion exchange group such as a quaternary ammonium group and a pyridinium group.

  The fuel-side electrode 32 is formed in a substantially rectangular shape having a smaller area than the electrolyte layer 31 when viewed from the front (see FIGS. 4 and 5).

  The material of the fuel side electrode 32 is not particularly limited, and examples thereof include a porous carrier on which a catalyst is supported.

  The porous carrier is not particularly limited, and examples thereof include water repellent carriers such as carbon.

  The catalyst is not particularly limited, and examples thereof include groups 8 to 10 (VIII) of the periodic table such as platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) and iron group elements (Fe, Co, Ni). Examples of the element include, for example, Group 11 (IB) elements of the periodic table such as Cu, Ag, and Au, and combinations thereof. Further, when carbon monoxide (CO) is by-produced depending on the type of fuel, poisoning of the catalyst can be prevented by using ruthenium (Ru) together with the elements exemplified above.

  The oxygen side electrode 33 is formed in substantially the same shape as the fuel side electrode 32 in a front view (see FIGS. 4 and 5).

The material for the oxygen side electrode 33 is not particularly limited, and examples thereof include a porous carrier on which a catalyst is supported, which is exemplified as the material for the fuel side electrode 32.
The fuel side electrode 32 and the oxygen side electrode 33 are formed in contact with the surface of the electrolyte layer 31 so as to sandwich the electrolyte layer 31 from both sides in the stacking direction. Specifically, the fuel side electrode 32 is formed in the approximate center of one surface on the front side of the electrolyte layer 31, and one surface of the electrolyte layer 31 is exposed around the fuel side electrode 32. On the other hand, the oxygen side electrode 33 is formed in the approximate center of the other surface on the back side of the electrolyte layer 31, and the other surface of the electrolyte layer 31 is exposed around the oxygen side electrode 33.

  The fuel separator 34 is formed in substantially the same shape as the electrolyte layer 31 in front view (see FIGS. 4 and 5), and is formed using, for example, a gas-impermeable conductive member.

  The fuel-side separator 34 is formed with a substantially rectangular recess 36 for receiving the fuel-side electrode 32 on the other surface on the back side in contact with the fuel-side electrode 32.

  A fuel side groove 37 opened toward the fuel side electrode 32 is formed in the recess 36, and vaporized fuel (for example, hydrogen gas, methanol, etc.) is formed between the fuel side groove 37 and the fuel side electrode 32. A fuel supply path 38 for flowing a fuel gas composed of gas, hydrazine gas, ammonia gas, or the like is formed.

  Further, the fuel side separator 34 has a water flow groove 39 that opens toward the oxygen side separator 35 on one side of the front surface that contacts the oxygen side separator 35 of the adjacent unit cell 10. They are formed in parallel (along the fuel side groove 37). Between the water flow groove 39 and a water flow groove 44 described later, a water flow path 40 is formed as a cooling water path for flowing cooling water for humidification. That is, the water passage 40 is formed in parallel with the fuel supply passage 38 and faces the fuel supply passage 38 with the fuel separator 34 interposed therebetween.

  The oxygen-side separator 35 is formed in substantially the same shape as the electrolyte layer 31 in front view (see FIGS. 4 and 5), and is formed using, for example, a gas-impermeable conductive member.

  The oxygen-side separator 35 is formed with a substantially rectangular recess 41 for receiving the oxygen-side electrode 33 on one surface on the front side in contact with the oxygen-side electrode 33.

  An oxygen side groove 42 opened toward the oxygen side electrode 33 is formed in the recess 41, and an oxidizing gas (for example, oxygen such as air is included) between the oxygen side groove 42 and the oxygen side electrode 33. An oxygen supply path 43 for flowing gas or the like is formed.

  The oxygen-side separator 35 has a water flow groove 44 that opens toward the fuel-side separator 34 on the other surface on the back side that contacts the fuel-side separator 34 of the adjacent unit cell 10. They are formed in parallel (along the oxygen side groove 42). As described above, the water flow path 40 for flowing the cooling water for humidification is formed between the water flow groove 44 and the water flow groove 39. That is, the water passage 40 is formed in parallel with the oxygen supply passage 43 and faces the oxygen supply passage 43 with the oxygen-side separator 35 interposed therebetween.

  Next, the structure of the cell stack 6 will be described mainly with reference to FIGS. 4 and 5.

  In each unit cell 10 of the cell stack 6, the fuel-side separator 34, the electrolyte layer 31, and the oxygen-side separator 35 have a lower corner portion at one end portion in the front width direction and an upper corner portion at the other end portion in the front view width direction. Two substantially circular oxygen holes 45 are formed.

  The oxygen holes 45 at the one end and the other end form a flow path for oxidizing gas that penetrates the unit cells 10 in the stacking direction in the stacked state, and communicate with each other via the oxygen supply path 43. . Further, in the stacked state, the oxygen hole 45 at one end is in communication with the oxygen discharge port 13, and the oxygen hole 45 at the other end is in communication with the oxygen supply port 15.

  In each unit cell 10, the fuel-side separator 34, the electrolyte layer 31, and the oxygen-side separator 35 have six fuel holes 46 that are substantially circular in front view, inside the oxygen holes 45 at both ends in the front view width direction. Is formed.

  There are three fuel holes 46 at one end and the other end, respectively, and are arranged at predetermined intervals in the vertical direction. The fuel holes 46 at one end and the other end form a fuel gas flow path penetrating each unit cell 10 in the stacking direction in the stacked state, and a pair of fuel holes 46 facing in the width direction are The fuel supply passages 38 communicate with each other. Also, in the stacked state, the fuel hole 46 at one end is in communication with the fuel supply port 14, and the fuel hole 46 at the other end is in communication with the fuel discharge port 17. The fuel hole 46 is disposed below the upper fuel hole 46A communicating with the fuel supply port 14A and the fuel discharge port 17A and below the upper fuel hole 46A, and is connected to the fuel supply port 14C and the fuel discharge port 17C. A lower fuel hole 46C that communicates with the fuel hole 46A is disposed between the fuel hole 46A and the fuel hole 46C, and an intermediate fuel hole 46B that communicates with the fuel supply port 14B and the fuel discharge port 17B.

  Further, in each unit cell 10, the fuel separator 34, the electrolyte layer 31, and the oxygen separator 35 are substantially circular in front view at the upper corner portion at one end portion in the front view width direction and at the lower corner portion at the other end portion. These two water passage holes 47 are formed.

  The water holes 47 at the one side end and the other side end form a cooling water flow path that penetrates each unit cell 10 in the stacking direction in the stacked state, and communicate with each other via the water flow path 40. . Further, in the stacked state, the water passage hole 47 at one end portion communicates with the water supply port 18, and the water passage hole 47 at the other end portion communicates with the drain port 16.

  In each unit cell 10 of the cell stack 6, as described above, the fuel-side separator 34 is formed with the fuel-side groove 37 on the other surface on the back side, and the water passage groove 39 is formed on one surface on the front side. .

  The fuel side groove 37 communicates between the fuel hole 46 at one end and the fuel hole 46 at the other end facing each other in the width direction in the recess 36, and is spaced apart from each other in the vertical direction. Nine branch grooves 48 are provided.

  Each branch groove 48 extends in the width direction, and among the nine branch grooves 48, the upper three branch grooves 48 merge at both ends thereof, and one side end and one groove unit (upper groove unit) and It communicates with the fuel hole 46A at the other end. Of the nine branch grooves 48, the lower three branch grooves 48 merge at both ends thereof, and form one groove unit (lower groove unit) in the fuel hole 46C at one end and the other end. Communicate. Further, among the nine branch grooves 48, the three intermediate branch grooves 48 between the upper three branch grooves 48 and the lower three branch grooves 48 merge at both ends thereof to form one groove unit (intermediate groove). Unit) communicates with the fuel hole 46B at one end and the other end. Accordingly, the fuel side groove 37 is constituted by an upper groove unit 37A constituted by the upper three branch grooves 48, an intermediate groove unit 37B constituted by the middle three branch grooves 48, and the lower three branch grooves 48. And a lower groove unit 37C. That is, in each unit cell 10, in the stacked state, the upper groove unit 37 </ b> A, the intermediate groove unit 37 </ b> B, and the lower groove unit 37 </ b> C are three (a plurality of) fuel supply paths that are independent from each other between the fuel side electrode 32. As shown, an upper fuel supply path 38A, an intermediate fuel supply path 38B, and a lower fuel supply path 38C are formed.

  In the water flow groove 39, nine linear grooves 49 extending in the width direction and substantially U-shaped folding grooves 50, which communicate with each other between the water flow holes 47 that face each other diagonally of the unit cell 10, are alternately continuous. It is formed in a twisted shape.

  The nine straight grooves 49 are formed in parallel with the branch grooves 48 (along the branch grooves 48) with the fuel-side separator 34 interposed therebetween. Therefore, in the stacked state of each unit cell 10, the water passage 40 formed by the water passage groove 39 and the water passage groove 44 is the fuel formed by the fuel side groove 37 and the fuel side electrode 32 as described above. It is formed in parallel with the supply path 38.

  Further, in each unit cell 10 of the cell stack 6, the oxygen-side separator 35 is formed with the oxygen-side groove 42 on the one surface on the front side and the water flow groove 44 on the other surface on the back side, as described above. ing.

  The oxygen-side groove 42 is a twisted shape in which linear grooves 51 extending in the width direction and substantially U-shaped folding grooves 52 are alternately connected to each other to connect the oxygen holes 45 opposite to each other diagonally of the unit cell 10. Is formed. The linear grooves 51 are arranged at intervals in the vertical direction, and are formed so as to face linear grooves 53 described later with the oxygen-side separator 35 interposed therebetween. The oxygen side groove 42 forms an oxygen supply path 43 between the unit cell 10 and the oxygen side electrode 33 as described above.

  The water flow groove 44 is a knot in which linear grooves 53 extending in the width direction and substantially U-shaped turn-back grooves 54 are alternately connected to each other through the water flow holes 47 that face each other diagonally of the unit cell 10. It is formed in a folded shape. The linear groove 53 and the folding groove 54 are formed in parallel with the linear groove 51 and the folding groove 52 with the oxygen-side separator 35 interposed therebetween. The water flow groove 44 forms a water flow path 40 with the water flow groove 39 formed in the fuel side separator 34 of the adjacent unit cell 10 in the stacked state of the unit cells 10 as described above. To do.

  Each unit cell 10 is divided into three sections in the vertical direction. Specifically, for example, the upper section 55 that extends from the lower end of the upper groove unit 37A to the upper end of the unit cell 10 and the lower section 57 that extends from the upper end of the lower groove unit 37C to the lower end of the unit cell 10; The entire intermediate groove unit 37 </ b> B is included and divided into an intermediate section 56 sandwiched between the upper section 55 and the lower section 57.

  One temperature sensor 11 shown in FIG. 1 is provided in each of the upper section 55, the intermediate section 56, and the lower section 57 in each unit cell 10. That is, each unit cell 10 includes a total of three temperatures: a temperature sensor 11A that measures the temperature of the upper section 55, a temperature sensor 11B that measures the temperature of the middle section 56, and a temperature sensor 11C that measures the temperature of the lower section 57. A sensor is provided.

  These temperature sensors 11 </ b> A to 11 </ b> C have fuel holes 46 in each unit cell 10, specifically, at the interface between the fuel-side separator 34 and the electrolyte layer 31 and at one end portion in the width direction when viewed from the front. It is provided slightly outside. The temperature sensors 11A to 11C are not electrically shown in FIGS. 4 and 5, but are electrically connected to the controller 22 independently of each other.

  A plurality of such unit cells 10 are stacked (stacked) to form a cell stack 6, and a current collector plate 7, an insulating plate 8 and an end plate 9 are sequentially stacked on both sides of the cell stack 6 in the stacking direction. Thus, the fuel cell 2 is configured.

  The fuel cell 2 is housed in a casing (not shown), and each fuel supply / discharge portion, that is, the fuel supply / discharge portion 3, the oxygen supply / discharge portion 4, and the water supply / drainage portion 5 are attached, whereby the fuel cell system 1 shown in FIG. Is done.

  In the fuel cell system 1, the fuel gas from the fuel tank 19 is supplied to the fuel supply port 14, and the oxidizing gas from, for example, a compressor is supplied to the oxygen supply port 15. Moreover, the cooling water for humidification from the water supply apparatus is supplied to the water supply port 18, for example.

  The fuel gas is supplied from the fuel supply port 14 into the cell stack 6 having a stack structure, and sequentially passes through the fuel hole 46 and the fuel supply path 38 of each unit cell 10 and then discharged from the fuel discharge port 17. Is done. The oxidizing gas is supplied from the oxygen supply port 15 into the cell stack 6 having a stack structure, and sequentially passes through the oxygen hole 45 and the oxygen supply path 43 of each unit cell 10, and then is discharged from the oxygen discharge port 13. Is done. In addition, the cooling water is supplied from the water supply port 18 into the cell stack 6 having a stack structure, and sequentially passes through the water passage holes 47 and the water passages 40 of each unit cell 10 and then is discharged from the drain port 16.

When the electrolyte layer 31 is an anion exchange membrane, each unit cell 10 generates power as follows. That is, in the fuel-side electrode 32 fuel gas is supplied, and generates from the fuel gas is hydrogen _{(H 2),} the oxidation reaction of the hydrogen _{(H 2),} hydrogen _{(H 2)} from the electronic (e ^-) is released And protons (H ⁺ ) are generated.

Electrons (e ⁻ ) released from hydrogen (H ₂ ) reach the oxygen side electrode 33 via an external circuit (not shown). That is, electrons (e ⁻ ) passing through the external circuit become current.

On the other hand, in the oxygen side electrode 33, electrons (e ⁻ ), water (H ₂ O) generated by a reaction from the outside or unit cell 10, and oxygen (O ₂ ) in the air flowing through the oxygen supply path 43. React with each other to produce hydroxide ions (OH ⁻ ) (see the following reaction formula (2)).

The generated hydroxide ions (OH ⁻ ) pass through the electrolyte layer 31 and reach the fuel side electrode 32. When the hydroxide ions (OH ⁻ ) reach the fuel side electrode 32, the hydroxide ions (OH ⁻ ) react with hydrogen (H ₂ ) in the fuel at the fuel side electrode 32 to generate electrons (e ^- ) And water (H ₂ O) are produced (see the following reaction formula (1)). The generated electrons (e ⁻ ) are supplied to the oxygen side electrode 33 via an external circuit (not shown).

By continuously performing the electrochemical reaction in the fuel side electrode 32 and the oxygen side electrode 33, a closed circuit is formed in the unit cell 10, an electromotive force is generated, and electric power is generated.
(1) 2H ₂ + 4OH ⁻ → 4H ₂ O + 4e ⁻ (Reaction at the fuel side electrode 32)
(2) O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (reaction at the oxygen side electrode 33)
(3) 2H ₂ + O ₂ → 2H ₂ O (reaction as a unit cell 10 as a whole)
In the fuel cell system 1 described above, the controller 22 controls the flow rate of the fuel gas from the fuel tank 19.

  FIG. 6 is a flowchart showing a flow of control processing for the supply valve 23 executed in the controller 22.

In the fuel gas flow rate control, specifically, during the power generation, first, measurement processing of the average temperature T ₀ of the unit cell 10 is performed (S1). The measurement process of the average temperature T ₀ is performed by, for example, detecting the temperature measured by the temperature sensor 11 of each unit cell 10 by the controller 22 and calculating the average value of the detected temperatures. The calculated average temperature T ₀ is stored in the controller 22 as a reference for determining the dry state described later.

  Next, the temperature Ti of each part of each unit cell 10 is measured (S2). Here, i is a positive integer of 1 to n, and is the number of sections in which the temperature is measured in each unit cell 10. In this fuel cell system 1, each unit cell 10 is divided into three sections, that is, an upper section 55, an intermediate section 56, and a lower section 57, so that fuel is set as i = 1 to 3 (that is, n = 3). Gas flow control is performed.

First, the temperature T ₁ of the first section (i = 1) in each unit cell 10, for example, the upper section 55 is measured by the temperature sensor 11A.

Measurement temperatures _{T 1} and the cell average temperature difference between _{T 0} is, the upper limit temperature _{T upper} (e.g., 3 to 20 ° C.) the predetermined larger than (S3: YES), _i.e., at _T i -T _0> T _upper If there is, the controller 22 determines that the upper section 55 is a dry portion in a dry state. This dry state is a state in which a so-called dry-out may occur, for example, an increase in internal resistance of the upper section 55 due to a decrease in water content of the upper section 55.

  When it is determined that the upper section 55 is a dry portion, the opening degree of the supply valve 23A is reduced, down processing is performed (S4), and the upper fuel supply path 38A through the fuel hole 46 from the fuel supply pipe 20A. The flow rate of the fuel gas flowing into the fuel cell decreases.

On the other hand, the difference between the measured temperatures _{T 1} and the cell average temperature _{T 0} is, the upper limit temperature _{T upper} follows (S3: NO), and pre-determined lower limit temperature _{T lower} (e.g., -10 to-3 ° C.) is smaller than (S5: YES), that is, in T _i −T ₀ ≦ T _upper and T _i −T ₀ <T _low controller 22, it is determined that the upper section 55 is a wet portion in a wet state. This wet state is a state where there is a possibility that so-called flooding may occur, for example, an excessive water content in the upper section 55 prevents the fuel gas from diffusing into the fuel side electrode 32 in the upper section 55. That is.

  If it is determined that the upper section 55 is in a wet state, the opening degree of the supply valve 23A is increased, an up process is performed (S6), and the upper fuel supply path is passed from the fuel supply pipe 20A through the fuel hole 46. The flow rate of the fuel gas flowing into 38A increases.

Then, if the opening degree of the supply valve 23A is controlled (S4 and S6), or if it is determined that T _i −T ₀ ≦ T _upper (S3: NO) and T _i −T ₀ ≧ T _low ( (S5: NO), the temperature of the upper section 55 is again measured by the temperature sensor 11A (S7).

If the absolute value of the difference between the measured temperatures _{T 1} and the cell average temperature _{T 0} is greater than the allowable temperature _{T x} of predetermined (S8: NO), measured at a temperature the temperature sensor 11A of the upper section 55 again (S2) Similarly to the above, the comparison with the _upper limit temperature T _upper and / or the lower limit temperature T _lower (S3 and S5) and the opening degree control process (S4 and S6) of the supply valve 23 are performed.

When the absolute value of the difference between the measured temperature T ₁ and the cell average temperature T ₀ is equal to or lower than the allowable temperature T _x (ie, | T _i −T ₀ | ≦ T _x (S8: YES)), the controller 22 It is determined that the upper section 55 is in a proper humidified state.

It is then determined whether the number i of sections where the temperature has been measured is equal to the maximum value i _max of i. In this fuel cell system 1, since the middle section 56 and the lower section 57 are set as the sections where the temperature is measured in addition to the upper section 55, it is determined that i = i _max is not satisfied (S9: NO) For example, the intermediate section 56 is loaded as the second section (i = 1 + 1 = 2) in each unit cell 10 (S10).

When the same process as the fuel gas flow rate control process for the upper section 55 is performed on the intermediate section 56 and the lower section 57, i = i _max is determined (S9: YES), and The fuel gas flow rate control process for the unit cell 10 ends.

  Thereafter, for example, the control process described above is performed on the unit cell 10 adjacent to the unit cell 10 for which the fuel gas flow rate control process has been completed, and such a process is continued during power generation of the fuel cell 2. .

  As described above, in the fuel cell system 1 of the present invention, the temperature of each of the upper section 55, the middle section 56, and the lower section 57 in each unit cell 10 is measured by the temperature sensor 11A, the temperature sensor 11B, and the temperature sensor 11C. The

  Based on the measured temperature, the controller 22 determines whether the sections 55 to 57 are in a dry state, a wet state, or an appropriate humidified state, and appropriately controls the opening degree of the supply valves 23A to 23C. Is done.

  As a result, even when the sections 55 to 57 are in a dry state or a wet state, the sections 55 to 57 are appropriately humidified with respect to the upper fuel supply path 38A, the intermediate fuel supply path 38B, and the lower fuel supply path 38C. Since the fuel gas of an appropriate flow rate can be supplied to obtain the state, further drying and wetting of each section 55 to 57 can be suppressed. Therefore, the humidified state of each unit cell 10 can be maintained in an appropriate state.

  Each unit cell 10 is divided into an upper section 55, an intermediate section 56, and a lower section 57, and further includes three fuel supply paths 38 (an upper fuel supply path 38A, an intermediate fuel supply path 38B, and a lower fuel supply path). 38C) are provided for each of these sections. Therefore, the humidified state of each unit cell 10 can be made uniform. Therefore, for example, by reducing the length of the fuel separator 34 in the width direction, it is not necessary to reduce the area of each unit cell 10 and the flow path length of the fuel supply path 38.

  Therefore, the output amount of each unit cell 10 can be covered widely. As a result, the area of each unit cell 10 can be increased and the number of stacked cells can be reduced, so that the structure of the fuel cell 2 can be simplified.

  Further, by providing a plurality of fuel supply paths 38 (three in this embodiment), water generated by the fuel side electrode 32 can be partially purged in each unit cell 10. Therefore, energy required for purging can be reduced. As a result, the running cost can be reduced.

  Further, a water passage 40 is formed in parallel with the fuel supply passage 38 (along the fuel supply passage 38), and faces the fuel supply passage 38 with the fuel side separator 34 interposed therebetween.

  For example, when the cooling water flowing through the water passage 40 cools the unit cell 10 heated by power generation, the temperature rises due to heat exchange with the unit cell 10. Therefore, in the cell stack 6, in the unit cell 10 on the downstream side (side closer to the drain port 16) of the water passage 47, the temperature of the cooling water is higher than that of the unit cell 10 on the upstream side (side closer to the water supply port 18). The unit cell 10 as a whole tends to become dry.

  However, in this fuel cell system 1, the water passage 40 in the fuel cell 2 faces the fuel supply passage 38 with the fuel separator 34 interposed therebetween. Therefore, by controlling the flow rate of the fuel gas according to the dry state of each unit cell 10, the humidified state of the cell stack 6 can be maintained in an appropriate state as a whole.

As mentioned above, although embodiment of this invention was described, embodiment of this invention is not limited to this, A design can be suitably changed in the range which does not change the summary of this invention.
Applications of the fuel cell system 1 of the present invention include, for example, electric vehicles, railways, ships, and aircraft.

  Further, in the above-described embodiment, only the fuel side groove 37 is formed as a groove that is distinguished from the three upper groove units 37A, the intermediate groove unit 37B, and the lower groove unit 37C, thereby three (a plurality) independent from each other. The upper fuel supply passage 38A, the intermediate fuel supply passage 38B, and the lower fuel supply passage 38C are formed as the fuel supply passages of the fuel. However, for example, the oxygen side groove 42 is also formed as a groove that is distinguished by three groove units. Thus, three oxygen supply paths 43 that are independent of each other can be formed. In this case, a water flow groove 44 can be formed along the three oxygen supply paths 43.

In the above-described embodiment, each unit cell 10 is divided into three sections, that is, an upper section 55, an intermediate section 56, and a lower section 57. However, the section of each unit cell 10 can be further subdivided.
In the above-described embodiment, the water passage 40 is formed in parallel with the fuel supply passage 38 via the fuel separator 34. However, the water passage 40 and the fuel supply passage 38 are connected to the fuel separator 34. For example, they may be orthogonal.

  In the above-described embodiment, the dry state and the wet state of each unit cell 10 are detected using the temperature sensor 11. For example, a reference electrode is provided in each unit cell 10, and alternating current is applied from the reference electrode. It is also possible to detect by the impedance method. Further, a piezoelectric element may be provided in each unit cell 10 to detect a load change in the surface of the unit cell 10 accompanying a temperature change of each unit cell 10, thereby detecting the temperature of each unit cell. .

In the above-described embodiment, the cell average temperature T ₀ of the unit cell 10 is calculated based on the measured value of the temperature sensor 11. For example, the cooling water temperature near the water supply port 18 and the cooling water near the drain port 16 are used. It can also be calculated based on the temperature rise rate of the cooling water passing through the unit cell 10 from the difference from the temperature.

1 is a unidirectional perspective view for explaining the structure of a fuel cell system according to an embodiment of the present invention. It is a perspective view of the other direction for explaining the structure of the fuel cell system concerning one embodiment of the present invention. It is principal part sectional drawing when the cell stack shown in FIG. 1 is cut | disconnected by the cutting line shown by LL. FIG. 2 is an exploded view of a main part of the cell stack shown in FIG. 1 in one direction. FIG. 2 is an exploded view of the main part of the cell stack shown in FIG. 1 in the other direction. It is a flowchart which shows the flow of the control processing with respect to the supply valve performed in a controller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 6 Cell stack 10 Unit cell 11 Temperature sensor 22 Controller 23 Supply valve 31 Electrolyte layer 32 Fuel side electrode 33 Oxygen side electrode 34 Fuel side separator 35 Oxygen side separator 37 Fuel side groove 38 Fuel supply path 39 Water flow Groove 40 Water channel 42 Oxygen side groove 43 Oxygen supply channel 44 Water channel 55 Upper section 56 Middle section 57 Lower section

Claims (2)

An electrolyte layer, a fuel-side electrode and an oxygen-side electrode disposed opposite to each other with the electrolyte layer interposed therebetween, a fuel-side separator disposed adjacent to the fuel-side electrode, and formed with a fuel supply path for supplying fuel to the fuel-side electrode; And a fuel cell having a unit cell including an oxygen-side separator disposed adjacent to the oxygen-side electrode and having an oxygen supply path for supplying oxygen to the oxygen-side electrode,
A plurality of at least one of the fuel supply path and the oxygen supply path are formed,
Detecting means for detecting a dry portion of the unit cell;
The fuel cell system further comprising: a control means for controlling a flow rate of fuel and / or oxygen supplied to each of the fuel supply paths and / or each of the oxygen supply paths based on detection of the detection means. . The fuel cell includes a cell stack in which a plurality of the unit cells are stacked,
In the cell stack, a cooling water channel for cooling each unit cell is formed,
2. The fuel cell system according to claim 1, wherein a plurality of the cooling water passages are formed along at least one of the fuel supply passages and the oxygen supply passages formed in each of the unit cells. 3. .

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