JP2014003011A - Method for operating fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a water content of an electrolyte membrane in a proper range, thereby simply and economically controlling operation of a fuel cell in a good state.SOLUTION: A method for operating a fuel cell 10 includes the steps of: estimating a water content of an electrolyte membrane-electrode structure 24 from a preliminarily set relationship between a potential and a water content on the basis of an output value of a potential sensor 60 disposed at an outer peripheral end of the electrolyte membrane-electrode structure 24; and adjusting operating conditions of the fuel cell 10 so that the estimated water content is maintained in a predetermined water content range.

Description

  The present invention relates to a method of operating a fuel cell in which an electrolyte membrane / electrode structure sandwiching an electrolyte membrane between an anode electrode and a cathode electrode and a separator are laminated.

  For example, a solid polymer fuel cell employs a solid polymer electrolyte membrane made of a polymer ion exchange membrane. This fuel cell has an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode each having an electrode catalyst (electrode catalyst layer) and porous carbon (gas diffusion layer) are disposed on both sides of a solid polymer electrolyte membrane ( MEA). The electrolyte membrane / electrode structure constitutes a power generation cell by being sandwiched between separators (bipolar plates). Normally, in a fuel cell, a fuel cell stack in which a predetermined number of power generation cells are stacked is used as, for example, an in-vehicle fuel cell stack.

  In this type of fuel cell, it is necessary to maintain the solid polymer electrolyte membrane in a desired wet state in order to exhibit a good power generation reaction. This is because if the electrode water content is high, water clogging (flooding) is caused in the electrode catalyst and the porous carbon, whereas if the electrode water content is low, the performance of the solid polymer electrolyte membrane is reduced. Therefore, it is important to satisfactorily control the water content of the cathode and anode electrodes constituting the fuel cell.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. As shown in FIG. 21, the fuel cell system estimates the water content of the fuel cell based on the relationship between the impedance calculation means 1 for measuring the impedance of the fuel cell and the estimated water content of the fuel cell with respect to the impedance. And a water content estimation means 2. The measured impedance or the estimated water content is corrected by the impedance temperature correction means 3 based on the environmental temperature of the fuel cell.

  Thus, the moisture content of the fuel cell can be estimated after correcting the influence of the ambient conditions (for example, environmental temperature, gas pressure) of the fuel cell body on the measured impedance value.

JP 2008-84601 A

  However, in Patent Document 1 described above, operation control of the fuel cell is performed based on the correlation between impedance measurement and moisture content measurement. For this reason, there is a problem that the entire apparatus is considerably complicated and the cost is increased, which is not economical.

  The present invention solves this type of problem, can maintain the water content of the electrolyte membrane in an appropriate range and prevent flooding, and can operate the fuel cell in a good condition simply and economically. It is an object of the present invention to provide a method of operating a fuel cell that can be controlled.

  The present invention relates to a method of operating a fuel cell in which an electrolyte membrane / electrode structure sandwiching an electrolyte membrane between an anode electrode and a cathode electrode and a separator are laminated.

  This operation method is based on the output value of the potential sensor provided at the outer peripheral end of the electrolyte membrane / electrode structure, and the inclusion of the electrolyte membrane / electrode structure is determined from the relationship between the preset potential and the water content. A step of estimating the amount of water. Furthermore, it has the process of adjusting the driving | running condition of a fuel cell so that the estimated water content may be maintained in the predetermined water content range.

  In this operation method, it is preferable that a single or a plurality of potential sensors be arranged in the plane.

  Further, in this operation method, it is preferable that the adjustment of the operation condition includes at least one of a flow rate adjustment, a pressure adjustment, a humidity adjustment, a temperature adjustment, or a purge process of the fuel gas supplied to the anode electrode side.

  Furthermore, in this operation method, it is preferable that the adjustment of the operation condition includes at least one of flow rate adjustment, pressure adjustment, temperature adjustment, and humidity adjustment of the oxidant gas supplied to the cathode electrode side.

  Further, in this operation method, it is preferable that the adjustment of the operation condition includes at least either a temperature adjustment or a flow rate adjustment of the cooling medium.

  Further, in this operation method, it is preferable that a notch is provided at at least one of the four corners of the electrolyte membrane / electrode structure, and a potential sensor is installed corresponding to the notch.

  According to the present invention, the water content of the electrolyte membrane / electrode structure can be easily and reliably detected only by detecting the output (potential) from the potential sensor provided at the outer peripheral end of the electrolyte membrane / electrode structure. Can be detected. Thus, it is only necessary to adjust the operating conditions of the fuel cell based on the estimated water content, and the water content of the electrolyte membrane / electrode structure is maintained within a predetermined water content range simply and economically. Thus, the fuel cell can be operated and controlled in a good state.

1 is an explanatory diagram of a schematic configuration of a fuel cell system in which a method for operating a fuel cell according to a first embodiment of the present invention is implemented. It is a principal part disassembled perspective explanatory drawing of the said fuel cell. It is principal part sectional explanatory drawing of the electrolyte membrane and electrode structure which comprises the said fuel cell. It is a front view of the electric potential sensor integrated in the said electrolyte membrane and electrode structure. It is a cross-sectional side view of the potential sensor. It is explanatory drawing of the relationship between an electric potential and moisture content. It is a map which shows the electric power generation conditions of a fuel cell. It is explanatory drawing at the time of increasing the flow volume of oxidizing agent gas as adjustment of an operating condition. It is a front view of another electric potential sensor. It is explanatory drawing at the time of adjusting the flow volume of a cooling medium as adjustment of the driving | running condition in the driving | running method which concerns on the 2nd Embodiment of this invention. It is principal part cross-sectional explanatory drawing of the electrolyte membrane and electrode structure which comprises the fuel cell with which the operating method which concerns on the 3rd Embodiment of this invention is implemented. It is front explanatory drawing of the electrolyte membrane and electrode structure which comprises the fuel cell with which the operating method which concerns on the 4th Embodiment of this invention is implemented. FIG. 13 is a cross-sectional view of the electrolyte membrane / electrode structure taken along line XIII-XIII in FIG. 12. It is a perspective explanatory view of the potential sensor which constitutes the fuel cell. It is front explanatory drawing of the electrolyte membrane and electrode structure which comprises the fuel cell with which the operating method which concerns on the 5th Embodiment of this invention is implemented. FIG. 16 is a cross-sectional view of the electrolyte membrane / electrode structure taken along line XVI-XVI in FIG. 15. It is front explanatory drawing of the electrolyte membrane and electrode structure which comprises the fuel cell with which the operating method which concerns on the 6th Embodiment of this invention is implemented. FIG. 18 is a cross-sectional view of the electrolyte membrane / electrode structure taken along line XVIII-XVIII in FIG. 17. It is front explanatory drawing of the electrolyte membrane and electrode structure which comprises the fuel cell with which the operating method which concerns on the 7th Embodiment of this invention is implemented. FIG. 20 is a cross-sectional view of the electrolyte membrane / electrode structure taken along line XX-XX in FIG. 19. 2 is a configuration diagram of a control unit of a fuel cell system disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, a fuel cell system 12 in which a method for operating a fuel cell 10 according to the first embodiment of the present invention is implemented is, for example, mounted on a fuel cell vehicle such as a fuel cell electric vehicle. A fuel cell system is configured.

  The fuel cell system 12 includes a fuel cell stack 14 in which a plurality of fuel cells 10 are stacked, an oxidant gas supply device 16 that supplies an oxidant gas to the fuel cell stack 14, and fuel gas to the fuel cell stack 14. A fuel gas supply device 18 to be supplied, a cooling medium supply device 20 for supplying a cooling medium to the fuel cell stack 14, and a control device (ECU) 22 for controlling the entire fuel cell system 12 are provided.

  As shown in FIG. 2, the fuel cell 10 sandwiches the electrolyte membrane / electrode structure 24 between a first separator 26 and a second separator 28. The first separator 26 and the second separator 28 are, for example, a steel plate, a stainless steel plate, a titanium (Ti) plate, an aluminum plate, a plated steel plate, a metal plate whose surface is subjected to anticorrosion treatment, or a carbon member. Etc.

  As shown in FIGS. 2 and 3, the electrolyte membrane / electrode structure 24 includes, for example, a solid polymer electrolyte membrane 30 in which a perfluorosulfonic acid thin film is impregnated with water, and the solid polymer electrolyte membrane 30 interposed therebetween. An anode electrode 32 and a cathode electrode 34 are provided. As the solid polymer electrolyte membrane 30, an HC (hydrocarbon) electrolyte is used in addition to the fluorine electrolyte.

  As shown in FIG. 3, the outer peripheral end 34 end of the cathode electrode 34 projects outward from the outer peripheral end 32 end of the anode electrode 32, and the anode electrode 32 is formed on one surface of the solid polymer electrolyte membrane 30. Be placed. The anode electrode 32 exposes the outer periphery of the solid polymer electrolyte membrane 30 in a frame shape. The cathode electrode 34 is disposed on the other surface of the solid polymer electrolyte membrane 30, and the outer peripheral end portion of the solid polymer electrolyte membrane 30 protrudes outward from the outer peripheral end portion 34 end of the cathode electrode 34. The outer peripheral end of the solid polymer electrolyte membrane 30 may be disposed at the same position as the outer peripheral end 34end of the cathode electrode 34.

  The anode electrode 32 includes an electrode catalyst layer joined to one surface of the solid polymer electrolyte membrane 30 and a gas diffusion layer laminated on the electrode catalyst layer. The cathode electrode 34 includes an electrode catalyst layer joined to the other surface of the solid polymer electrolyte membrane 30 and a gas diffusion layer laminated on the electrode catalyst layer.

  In the present invention, the method for producing the electrolyte membrane / electrode structure 24 is not particularly limited. For example, the electrode catalyst layer forms catalyst particles or platinum black in which platinum or platinum alloy particles are supported on carbon black, and uses, for example, a polymer electrolyte as an ion conductive binder. The electrode catalyst layer is formed by printing, coating, spraying, sputtering, or transferring a catalyst paste prepared by uniformly mixing catalyst particles in the polymer electrolyte solution on both surfaces of the solid polymer electrolyte membrane 30. Composed. The electrode catalyst layer may be provided on the entire surface of the gas diffusion layer, or a frame-like region where the electrode catalyst layer is not provided may be provided on the outer periphery of the gas diffusion layer.

  The electrolyte membrane / electrode structure 24 includes a resin frame member 36 that goes around the outer periphery of the solid polymer electrolyte membrane 30. The resin frame member 36 is, for example, PPS (polyphenylene sulfide), PPA (polyphthalamide), LCP (liquid crystal polymer), PES (polyethersulfone), PEEK (polyetheretherketone), PFA (fluororesin), or the like. Consists of.

  As shown in FIG. 2, the fuel cell 10 has, for example, a horizontally long shape, and is stacked in a horizontal direction in a standing posture. One end edge of the fuel cell 10 in the direction of arrow B (horizontal direction in FIG. 2) communicates with each other in the direction of arrow A, which is the stacking direction, and supplies an oxidant gas, for example, an oxygen-containing gas. An inlet communication hole 38a and a fuel gas outlet communication hole 40b for discharging a fuel gas, for example, a hydrogen-containing gas, are arranged in the arrow C direction (vertical direction).

  The other end edge of the fuel cell 10 in the direction of arrow B communicates with each other in the direction of arrow A, and a fuel gas inlet communication hole 40a for supplying fuel gas, and an oxidant gas for discharging oxidant gas. Outlet communication holes 38b are arranged in the direction of arrow C.

  A pair of cooling medium inlet communication holes 42a for supplying a cooling medium is provided at the upper end edge in the arrow C direction of the fuel cell 10, and the lower end edge in the arrow C direction of the fuel cell 10 is A pair of cooling medium outlet communication holes 42b for discharging the cooling medium is provided. The cooling medium inlet communication hole 42a and the cooling medium outlet communication hole 42b may each be one.

  An oxidant gas flow path 46 communicating with the oxidant gas inlet communication hole 38a and the oxidant gas outlet communication hole 38b is provided on the surface 26a of the first separator 26 facing the electrolyte membrane / electrode structure 24. A fuel gas passage 48 communicating with the fuel gas inlet communication hole 40a and the fuel gas outlet communication hole 40b is formed on the surface 28a of the second separator 28 facing the electrolyte membrane / electrode structure 24. The oxidant gas passage 46 and the fuel gas passage 48 allow the oxidant gas and the fuel gas to flow in the horizontal direction.

  The cooling medium inlet communication hole 42a and the cooling medium outlet communication hole 42b communicate with the surface 26b opposite to the surface 26a of the first separator 26 and the surface 28b opposite to the surface 28a of the second separator 28. A cooling medium flow path 50 is formed. The cooling medium channel 50 circulates the cooling medium downward in the vertical direction.

  The first seal member 52 is integrated with the surfaces 26 a and 26 b of the first separator 26 around the outer peripheral end of the first separator 26. The second seal member 54 is integrated with the surfaces 28 a and 28 b of the second separator 28 around the outer peripheral end of the second separator 28.

  The first seal member 52 and the second seal member 54 are, for example, EPDM, NBR, fluororubber, silicone rubber, fluorosilicone rubber, butyl rubber, natural rubber, styrene rubber, chloroprene or acrylic rubber or the like, cushion material, Alternatively, an elastic seal member such as a packing material is used.

  The second separator 28 has a supply hole portion 56 that communicates the fuel gas inlet communication hole 40a with the fuel gas flow channel 48, and a discharge hole portion 58 that communicates the fuel gas flow channel 48 with the fuel gas outlet communication hole 40b. It is formed.

  As shown in FIG. 3, one or a plurality of potential sensors 60 are directly provided on the outer peripheral end of the electrolyte membrane / electrode structure 24 on at least one of the anode side and the cathode side. The potential sensor 60 is covered with the resin frame member 36, but may not be covered with the resin frame member 36. The potential sensor 60 is preferably provided, for example, at a position within several millimeters from the outer peripheral end portion 32end of the anode electrode 32, and may be inside the anode electrode 32 or outside the anode electrode 32.

  The potential sensor 60 is installed on the cathode electrode 34 side as necessary. On the cathode electrode 34 side, the potential sensor 60 is preferably provided at a position within several millimeters (or several millimeters outward) from the outer peripheral end 34end of the cathode electrode 34. One or a plurality of potential sensors 60 may be set, and an average value, a maximum value or a minimum value of the values of the potential sensors 60, or a potential gradient of the plurality of potential sensors 60 may be used. The potential sensor 60 may be provided on both the anode side and the cathode side.

  Although not shown, the electrolyte membrane / electrode structure 24 is provided with a reference electrode. As the reference electrode, the anode electrode 32 may be used as the reference electrode, or a separate electrode may be provided on the anode side of the solid polymer electrolyte membrane 30.

  The potential sensor 60 is disposed in a region where the moisture content of the electrolyte membrane / electrode structure 24 is the largest and the smallest. As shown in FIG. 2, the potential sensor 60 is disposed below the gravitational direction, which is the region with the largest amount of moisture, in the vicinity of the fuel gas outlet communication hole 40 b and in the vicinity of the oxidant gas outlet communication hole 38 b.

  On the other hand, the potential sensor 60 is disposed above the fuel gas inlet communication hole 40a and in the vicinity of the oxidant gas inlet communication hole 38a above the gravity direction, which is a region where the amount of moisture is the smallest. The potential sensor 60 may be disposed only in a region where the moisture content of the electrolyte membrane / electrode structure 24 is the highest or lowest. However, the arrangement position of the potential sensor 60 is not particularly limited.

  As shown in FIGS. 4 and 5, the potential sensor 60 detects a potential difference from the reference electrode (or the anode electrode 32, preferably the central portion of the anode electrode 32), and is bent or bent to one side. A sheet-like or linear conductive terminal (potential measurement electrode) 62 having a projecting measurement part 62a is provided. The conductive terminal 62 is fixed to the base material 64 via a sheet-like insulating member 66.

  The base material 64 has substantially the same length in the length direction of the conductive terminal 62, and is wider than the conductive terminal 62 in the width direction of the conductive terminal 62. The insulating member 66 is configured to be shorter than the length of the conductive terminal 62, and the measuring portion 62a of the conductive terminal 62 is exposed to the outside. The thickness direction of the measuring part 62a is set to a dimension larger than the thickness of the insulating member 66, and the measuring surface of the measuring part 62a protrudes outward (front side of the end face) from the outer surface of the insulating member 66.

  The conductive terminal 62 is formed of, for example, thin film or linear gold (Au), platinum (Pt), or the like having acid resistance and heat resistance. One end of a conductive line 68 is connected to the end of the conductive terminal 62. The other end of the conductive line 68 is connected to the potential measuring device 70 (see FIG. 1). Although not shown, the potential measuring device 70 is connected to a conductive line connected to the reference electrode.

  The base material 64 and the insulating member 66 have insulating properties, are excellent in hot water resistance, acid resistance, and heat resistance, and are formed of a flexible material. For example, polytetrafluoroethylene (PTFE), liquid crystal polymer (LCP), polyimide, and the like are suitable.

  As shown in FIG. 1, the oxidant gas supply device 16 includes an air compressor (pump) 71 that compresses and supplies air from the atmosphere, and the air compressor 71 is disposed in an air supply flow path 72. The air supply channel 72 is provided with a humidifier 74 and a bypass channel 78 that bypasses the humidifier 74 via a valve 76, and communicates with the oxidant gas inlet communication hole 38 a of the fuel cell stack 14. An air discharge passage 80 communicates with the oxidant gas outlet communication hole 38b. The air discharge channel 80 is connected to the diluter 84 via a back pressure control valve 82.

  The fuel gas supply device 18 includes a high-pressure hydrogen tank 86 that stores high-pressure hydrogen. The high-pressure hydrogen tank 86 communicates with the fuel gas inlet communication hole 40 a of the fuel cell stack 14 via a hydrogen supply flow path 88. The hydrogen supply flow path 88 is provided with a valve 90 and an ejector 92, and an injector 93 is provided in a bypass flow path 88 a that bypasses the ejector 92.

  The valve 90 is used for pressure adjustment, and the injector 93 is used for fuel gas flow rate adjustment, humidity adjustment, and temperature adjustment. For example, by supplying unhumidified hydrogen by the injector 93, the humidity can be lowered. Since exhaust fuel gas (hereinafter also referred to as fuel off-gas) circulated through a circulation path 102 described later is higher in temperature than unreacted fuel gas newly supplied by the injector 93, the fuel gas is supplied. Thus, the temperature of the supply gas (supplied fuel gas) can be lowered. Further, in place of the injector 93, the hydrogen supply flow path 88 may be provided with a heat exchanger as necessary.

  An off-gas flow path 94 communicates with the fuel gas outlet communication hole 40 b of the fuel cell stack 14. The off-gas channel 94 is connected to a gas-liquid separator 96, and the gas-liquid separator 96 is provided with a drain channel 98 for discharging a liquid component and a gas channel 100 for discharging a gas component. It is done. The gas flow path 100 is connected to the ejector 92 via the circulation path 102, and communicates with the diluter 84 while the purge valve 104 is opened. The drain flow path 98 communicates with the diluter 84 via the valve 106. The diluter 84 includes off gas (containing fuel gas) discharged from the fuel gas outlet communication hole 40b of the fuel cell stack 14 and off gas (oxidant) discharged from the oxidant gas outlet communication hole 38b of the fuel cell stack 14. Gas containing) and diluting the fuel gas concentration (hydrogen concentration) below a specified value.

  The cooling medium supply device 20 includes a cooling medium circulation path 108 that communicates with the cooling medium inlet communication hole 42 a and the cooling medium outlet communication hole 42 b of the fuel cell stack 14 and circulates and supplies the cooling medium. In the cooling medium circulation path 108, a cooling pump 110 is disposed in the vicinity of the cooling medium inlet communication hole 42a side, and a radiator 112 is disposed in the vicinity of the cooling medium outlet communication hole 42b.

  Pressure gauges 114a, 114b, 114c, and 114d are disposed in the air supply flow path 72, the air discharge flow path 80, the hydrogen supply flow path 88, and the off-gas flow path 94, respectively. Hygrometers 116 a and 116 b are disposed in the air supply channel 72 and the hydrogen supply channel 88. Thermometers 118a, 118b, and 118c are disposed in the air discharge channel 80, the gas channel 100, and the cooling medium circulation channel 108.

  The potential measured from the potential measuring device 70 is input to the control device 22. The control device 22 includes a potential correction unit 120 that corrects the measured potential based on the detected temperature, pressure, and humidity, and a water content estimation unit 122 that estimates the water content based on the corrected potential. And a device control unit 124 that controls each device and adjusts the operating condition of the fuel cell 10 so that the estimated water content is maintained within a predetermined water content range.

  The operation of the fuel cell system 12 configured as described above will be described below.

  As shown in FIG. 1, the oxidant gas (air) is sent to the air supply flow path 72 via the air compressor 71 constituting the oxidant gas supply device 16. This oxidant gas is supplied to the oxidant gas inlet communication hole 38a of the fuel cell stack 14 after being humidified through the humidifier 74 or after bypassing the humidifier 74 through the bypass passage 78. The

  On the other hand, in the fuel gas supply device 18, the fuel gas (hydrogen gas) is supplied from the high-pressure hydrogen tank 86 to the hydrogen supply flow path 88 while the valve 90 is opened. The fuel gas passes through the ejector 92 and is then supplied to the fuel gas inlet communication hole 40 a of the fuel cell stack 14.

  In the cooling medium supply device 20, a cooling medium such as pure water, ethylene glycol, or oil is supplied from the cooling medium circulation path 108 to the cooling medium inlet communication hole 42 a of the fuel cell stack 14 under the action of the cooling pump 110. .

  As shown in FIG. 2, the oxidant gas is introduced into the oxidant gas flow path 46 of the first separator 26 from the oxidant gas inlet communication hole 38 a, moves in the direction of arrow B, and moves to the electrolyte membrane / electrode structure 24. It is supplied to the cathode electrode 34. On the other hand, the fuel gas is introduced into the fuel gas flow path 48 of the second separator 28 from the fuel gas inlet communication hole 40 a through the supply hole portion 56. The fuel gas moves in the direction of arrow B along the fuel gas flow path 48 and is supplied to the anode electrode 32 of the electrolyte membrane / electrode structure 24.

  Therefore, in each electrolyte membrane / electrode structure 24, the oxidant gas supplied to the cathode electrode 34 and the fuel gas supplied to the anode electrode 32 are consumed by an electrochemical reaction in the electrode catalyst layer to generate power. Done.

  Next, the oxidant gas consumed by being supplied to the cathode electrode 34 is discharged in the direction of arrow A along the oxidant gas outlet communication hole 38b. Similarly, the fuel gas consumed by being supplied to the anode electrode 32 passes through the discharge hole 58 and is discharged in the direction of arrow A along the fuel gas outlet communication hole 40b.

  In addition, the cooling medium supplied to the cooling medium inlet communication hole 42 a is introduced into the cooling medium flow path 50 between the first separator 26 and the second separator 28, and then flows in the direction of arrow C. This cooling medium is discharged from the cooling medium outlet communication hole 42b after the electrolyte membrane / electrode structure 24 is cooled.

  As shown in FIG. 1, the oxidant gas discharged to the oxidant gas outlet communication hole 38 b flows through the air discharge passage 80 and is introduced into the diluter 84. On the other hand, off-gas (fuel gas that has been partially consumed) discharged to the fuel gas outlet communication hole 40 b is introduced into the gas-liquid separator 96 from the off-gas flow path 94. The off-gas is sucked into the ejector 92 from the gas flow path 100 through the circulation path 102 after the liquid moisture is removed.

  The cooling medium discharged to the cooling medium outlet communication hole 42 b is cooled by the radiator 112 through the cooling medium circulation path 108. Further, the cooling medium is circulated and supplied to the fuel cell stack 14 under the action of the cooling pump 110.

  Next, an operation method according to the first embodiment of the present invention will be described below.

  First, the correlation between the water content of the electrolyte membrane / electrode structure 24 and the output (potential) of the potential sensor 60 was acquired in advance. Specifically, when the relationship between the water content on the anode electrode 32 side and the potential was experimentally detected, the potential-water content curve shown in FIG. 6 was obtained, and the potential range corresponding to the effective range of the water content was obtained. Was set.

  At that time, the relationship between the potential range and the water content according to various power generation conditions was acquired. The operating conditions (I, II, III, IV, i, ii, iii, iv) of the obtained fuel cell 10 corresponded to the water content (Z, Y, X, W) as shown in FIG. It is stored in the memory of the control device 22 as a map of potential ranges (a, b, c, d).

  Here, as operating conditions (for example, 1 and 2), the flow rate, dew point and pressure of the oxidant gas supplied to the fuel cell stack 14, the dew point and pressure of the oxidant gas discharged from the fuel cell stack 14, Flow rate, dew point and pressure of fuel gas supplied to the fuel cell stack 14, dew point and pressure of off-gas (fuel gas) discharged from the fuel cell stack 14, temperature of cooling medium supplied to the fuel cell stack 14 , The flow rate, the temperature of the cooling medium discharged from the fuel cell stack 14, and the like.

  In the first embodiment, specific adjustment of operating conditions (operation control) includes purge processing on the anode electrode 32 side (processing for opening the purge valve 104 for a short time), and oxidant supplied to the cathode electrode 34. It has gas flow rate adjustment, pressure adjustment, temperature adjustment, or humidity adjustment. On the anode electrode 32 side, flow rate adjustment, pressure adjustment, humidity adjustment, or temperature adjustment of the fuel gas supplied to the anode electrode 32 may be performed in addition to the purge process.

  On the anode electrode 32 side, there are water contained in the supplied fuel gas and generated water that reversely diffuses the solid polymer electrolyte membrane 30 from the cathode electrode 34 side. Therefore, by performing the purge process on the anode electrode 32 side, diffusion from the cathode electrode 34 side to the anode electrode 32 side is promoted, and the water content on the cathode electrode 34 side can be reduced.

  Next, when the fuel cell system 12 is in a power generation operation, the control device 22 receives the potential detected by each potential sensor 60 via the potential measurement device 70, and the potential correction unit 120 includes Each temperature, each pressure, and each humidity are input. Therefore, the potential correcting unit 120 obtains a corrected potential obtained by correcting the detected potential by temperature correction, pressure correction, and humidity correction, and sends the corrected potential to the water content estimation unit 122. The potential correction unit 120 may use an average value, a maximum value or a minimum value of the values of the plurality of potential sensors 60, or a potential gradient of the plurality of potential sensors 60.

  As shown in FIG. 6, the water content estimation unit 122 performs calculation processing using the input correction potential based on the correlation between the preset potential and the water content of the solid polymer electrolyte membrane 30. The amount of water is estimated. Furthermore, the device control unit 124 adjusts the operating conditions of the fuel cell stack 14 so that the estimated water content is maintained within a predetermined water content range (see the effective range in FIG. 6).

  Therefore, for example, the device control unit 124 causes the gas flow path 100 to communicate with the diluter 84 under the action of opening the purge valve 104 constituting the fuel gas supply device 18. Therefore, the fuel gas humidified through the fuel gas channel 48 of each fuel cell 10 is discharged as an offgas to the offgas channel 94 and then introduced into the diluter 84.

  The off-gas contains water vapor although liquid water is removed when passing through the gas-liquid separator 96. For this reason, the off gas is purged while the purge valve 104 is opened, so that the off gas containing water vapor is discharged to the diluter 84. As a result, dry fuel gas is supplied from the high-pressure hydrogen tank 86 to the fuel gas passages 48 of each fuel cell 10, so that moisture remaining in the fuel gas passages 48 is contained in the fuel gas. Is surely removed.

  As described above, since moisture is removed from the anode electrode 32 side, the water content on the anode electrode 32 side is reduced. On the other hand, the stagnant water on the cathode electrode 34 side is promoted to diffuse to the anode electrode 32 side through the solid polymer electrolyte membrane 30. Therefore, the water content on the cathode electrode 34 side can be reduced.

  When the water content on the anode electrode 32 side decreases, as shown in FIG. 6, the detected potential decreases. In the control device 22, the water content is estimated by monitoring the potential detected by each potential sensor 60 and input from the potential measuring device 70, and when the water content falls within the effective range, the anode electrode 32 is detected. The side purge process is stopped.

  In this case, in the first embodiment, only by detecting the output (potential) from the potential sensor 60 provided at the outer peripheral end of the electrolyte membrane / electrode structure 24, the electrolyte membrane / electrode structure 24 The water content can be detected easily and reliably.

  Accordingly, it is only necessary to adjust the operating condition of the fuel cell 10 based on the estimated water content, and the water content of the electrolyte membrane / electrode structure 24 is maintained within a predetermined water content range simply and economically. It becomes possible to do. For this reason, the effect that driving | operation control of the fuel cell 10 can be carried out reliably in a favorable state is acquired.

  Moreover, in the first embodiment, the potential sensor 60 is disposed in the region where the amount of moisture of the electrolyte membrane / electrode structure 24 is the largest and the region where the moisture amount is the smallest. Specifically, as shown in FIG. 2, the potential sensor 60 is located below the gravitational direction, which is the region with the largest amount of moisture, in the vicinity of the fuel gas outlet communication hole 40 b and in the vicinity of the oxidant gas outlet communication hole 38 b. Is arranged. On the other hand, the potential sensor 60 is disposed above the fuel gas inlet communication hole 40a and in the vicinity of the oxidant gas inlet communication hole 38a in the gravity direction, which is the region where the amount of moisture is the smallest.

  Therefore, the electrolyte membrane / electrode structure 24 is partially prevented from being flooded due to partial water content, and the electrolyte membrane / electrode structure 24 is partially short of water content. It becomes possible to suppress drying as much as possible. Thereby, the solid polymer electrolyte membrane 30 can reliably maintain a good wet state, and can perform a desired power generation reaction reliably and continuously.

  By the way, in the fuel cell system 12, other operating conditions can be adjusted in place of the above-described purge process on the anode electrode 32 side or in combination with the purge process. For example, on the cathode electrode 34 side, a process of increasing the flow rate of the oxidant gas supplied to the oxidant gas flow path 46 of each fuel cell 10 is performed.

  Specifically, as shown in FIG. 8, the detected potential increases as the water content increases, and when it is determined that the potential exceeds a predetermined value (threshold value), it is supplied to the oxidant gas flow path 46. The flow rate of the oxidant gas (Air flow rate) is increased. For this reason, drainage from the oxidant gas flow path 46 is improved, the water content is reduced, and the potential is lowered. Therefore, the water content of the electrolyte membrane / electrode structure 24 can be easily and economically maintained within a predetermined water content range.

  In the first embodiment, the potential sensor 60 is used. However, the present invention is not limited to this. For example, the potential sensor 60a shown in FIG. 9 can be used.

  In the potential sensor 60a, the conductive terminal 62 is fixed via the base material 64 and the insulating member 66a. The insulating member 66a has the same length as the base material 64, and an opening 66b that exposes the measuring portion 62a of the conductive terminal 62 to the outside is formed at one end edge portion.

  Thus, the configured potential sensor 60 a has the same operational effects as the potential sensor 60 described above.

  FIG. 10 is an explanatory diagram when adjusting the flow rate of the cooling medium as the adjustment of the operation condition in the operation method according to the second embodiment of the present invention.

  In the second embodiment, the water content is reduced by reducing the flow rate of the cooling medium supplied to the fuel cell stack 14. Therefore, the potential can be lowered simply by reducing the flow rate of the cooling medium, and the water content of the electrolyte membrane / electrode structure 24 can be maintained within a predetermined water content range in a simple and economical manner. For example, the same effects as those of the first embodiment can be obtained.

  In addition to the method of decreasing the flow rate of the cooling medium, it is also possible to decrease the water content and decrease the potential by increasing the temperature of the cooling medium.

  FIG. 11 is a cross-sectional explanatory view of a main part of an electrolyte membrane / electrode structure 132 constituting a fuel cell 130 in which the operation method according to the third embodiment of the present invention is implemented. The same components as those of the electrolyte membrane / electrode structure 24 constituting the fuel cell 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Similarly, in the fourth and subsequent embodiments described below, detailed description thereof is omitted.

  The electrolyte membrane / electrode structure 132 holds the solid polymer electrolyte membrane 30 between the anode electrode 32a and the cathode electrode 34a. The outer peripheral end of the anode electrode 32a protrudes outward from the outer peripheral end of the cathode electrode 34a. That is, the dimensions of the anode electrode 32a and the cathode electrode 34a are set opposite to the dimensions of the anode electrode 32 and the cathode electrode 34 of the first embodiment (see FIG. 3). On the solid polymer electrolyte membrane 30, a potential sensor 60 is installed on the surface on the anode electrode 32a side and on the surface on the cathode electrode 34a side.

  Accordingly, in the third embodiment, the water content of the electrolyte membrane / electrode structure 132 can be easily and reliably detected via the potential sensor 60, and the same effect as that of the first embodiment can be obtained. can get.

  FIG. 12 is an explanatory front view of the electrolyte membrane / electrode structure 142 constituting the fuel cell 140 in which the operation method according to the fourth embodiment of the present invention is performed.

  As shown in FIGS. 12 and 13, the electrolyte membrane / electrode structure 142 sandwiches the solid polymer electrolyte membrane 30 between an anode electrode 144 and a cathode electrode 146. The anode electrode 144 is set to have the same planar dimension as the solid polymer electrolyte membrane 30 or a smaller planar dimension than the solid polymer electrolyte membrane 30, and the anode electrode 144 is larger than the cathode electrode 146. The dimensions are set (see FIG. 12).

  Cutouts 144 a are formed at the four corners of the anode electrode 144. In each notch portion 144a, the outer peripheral end position of the cathode electrode 146 protrudes outward from the outer peripheral end position of the anode electrode 144 in the stacking direction. In addition, the shape of the notch part 144a is not specifically limited.

  Corresponding to each notch 144a, on the cathode side, that is, in the vicinity of the fuel gas outlet communication hole 40b and in the vicinity of the oxidant gas outlet communication hole 38b, which are regions where the amount of water in the electrolyte membrane / electrode structure 142 is the largest. In addition, the potential sensor 148 is installed in the vicinity of the fuel gas inlet communication hole 40a and the vicinity of the oxidant gas inlet communication hole 38a, which are regions where the moisture amount is the smallest.

  As shown in FIGS. 13 and 14, the potential sensor 148 detects a potential difference from the reference electrode, and has a plurality of sheet-like shapes having measuring portions 150a, 152a, 154a, and 156a that bend or protrude on one side. Alternatively, linear conductive terminals (potential measurement electrodes) 150, 152, 154, and 156 are provided. The conductive terminals 150, 152, 154, and 156 are interposed between the sheet-like first insulating member 158 and the sheet-like second insulating member 160. Note that one or a plurality of conductive terminals may be provided, and the number can be variously changed.

  The conductive terminals 150, 152, 154, and 156 are formed of, for example, a thin film or linear gold (Au), and are configured to be sequentially short from the conductive terminal 150 toward the conductive terminal 156. Is done. Each measurement unit 150a, 152a, 154a and 156a protrudes from the openings 158a, 158b, 158c and 158d formed in the first insulating member 158 to the outside by a length L (several μm to several tens μm). The measuring parts 150a, 152a, 154a and 156a may be formed thick by plating on the other parts 150b, 152b, 154b and 156b, or the tips may be bent and thickened.

  The measuring units 150a, 152a, 154a, and 156a are sequentially arranged in steps so as to be lowered in the height direction (arrow C direction), and as shown in FIG. 13, the cathode electrode 146 of the solid polymer electrolyte membrane 30 is disposed. Are arranged at predetermined positions on the sides. As shown in FIG. 14, conductive lines 162a, 162b, 162c and 162d are connected to the lower ends of the other portions 150b, 152b, 154b and 156b to the conductive terminals 150, 152, 154 and 156, respectively. The conductive lines 162a, 162b, 162c and 162d are connected to a potential measuring device (not shown).

  As a result, in the fourth embodiment, the water content of the electrolyte membrane / electrode structure 142 can be easily and reliably detected via the potential sensor 148, and is the same as in the first to third embodiments. The effect is obtained. Furthermore, the moisture content distribution in the planar area can be detected by the plurality of measuring units 150a, 152a, 154a, and 156a.

  Although the potential sensor 148 is used in the fourth embodiment, the potential sensor 60 may be employed instead. Further, the potential sensor 148 or the potential sensor 60 may be provided also on the anode electrode 144 side. At that time, notches are formed at the four corners of the cathode electrode 146. It is preferable that the notched portion has a shape in which the positional relationship between the cathode electrode 146 and the anode electrode 144 is optimal for potential measurement with the solid polymer electrolyte membrane 30 interposed therebetween. The same applies to the fifth and subsequent embodiments described below.

  FIG. 15 is an explanatory front view of the electrolyte membrane / electrode structure 165 constituting the fuel cell 163 in which the operation method according to the fifth embodiment of the present invention is implemented.

  As shown in FIGS. 15 and 16, the electrolyte membrane / electrode structure 165 sandwiches the solid polymer electrolyte membrane 30 between the anode electrode 164 and the cathode electrode 166. The anode electrode 164 is set to have the same plane size as the solid polymer electrolyte membrane 30 or a plane size smaller than the solid polymer electrolyte membrane, and the anode electrode 164 is a plane larger than the cathode electrode 166. The dimensions are set (see FIG. 15).

  When the anode electrode 164 and the solid polymer electrolyte membrane 30 have the same dimensions, when measuring the potential at the end of the anode electrode 164, notches 164a are formed at the four corners of the anode electrode 164. The In addition, when the planar dimension of the anode electrode 164 is smaller than the planar dimension of the solid polymer electrolyte membrane 30, it is not necessary to provide the notch part 164a.

  On the other hand, as with the anode electrode 164, when measuring the potential at the end of the cathode electrode 166, notches 166a are formed in at least one of the four corners of the cathode electrode 166 (or all four corners are acceptable). The The dimension of the notch 166a is set to be the same as the dimension that is the difference in size between the anode electrode 164 and the cathode electrode 166. Alternatively, the difference in size between the anode electrode 164 and the cathode electrode 166 is set by an optimum shape for potential measurement. When measuring the potential of only the cathode electrode 166, the cathode electrode 166 may not be provided with a notch.

  Corresponding to each notch 164a, that is, in the vicinity of the fuel gas outlet communication hole 40b and the vicinity of the oxidant gas outlet communication hole 38b, which are regions where the amount of water in the electrolyte membrane / electrode structure 165 is the largest, The potential sensor 148 is installed on the anode side corresponding to the vicinity of the fuel gas inlet communication hole 40a and the vicinity of the oxidant gas inlet communication hole 38a, which are the regions with the least amount of gas. Further, the potential sensor 148 may be provided only on either the anode electrode 164 or the cathode electrode 166, or on both.

  Thereby, in the fifth embodiment, the water content of the electrolyte membrane / electrode structure 165 can be easily and reliably detected via the potential sensor 148, and is the same as in the first to fourth embodiments. The effect is obtained.

  FIG. 17 is an explanatory front view of an electrolyte membrane / electrode structure 172 constituting a fuel cell 170 in which the operating method according to the sixth embodiment of the present invention is implemented.

  As shown in FIGS. 17 and 18, the electrolyte membrane / electrode structure 172 sandwiches the solid polymer electrolyte membrane 30 between the anode electrode 174 and the cathode electrode 176. The cathode electrode 176 is set to have the same planar dimension as the solid polymer electrolyte membrane 30 or a smaller planar dimension than the solid polymer electrolyte membrane 30, and the cathode electrode 176 is larger than the anode electrode 174. The dimensions are set (see FIG. 17).

  At the four corners of the cathode electrode 176, notches 176a are formed. In each notch 176a, the outer peripheral end position of the anode electrode 174 protrudes outward from the outer peripheral end position of the cathode electrode 176 in the stacking direction.

  Corresponding to each notch 176a, on the anode side, that is, in the vicinity of the fuel gas outlet communication hole 40b and in the vicinity of the oxidant gas outlet communication hole 38b, which are regions where the amount of water in the electrolyte membrane / electrode structure 172 is the largest. In addition, the potential sensor 148 is installed in the vicinity of the fuel gas inlet communication hole 40a and the vicinity of the oxidant gas inlet communication hole 38a, which are regions where the moisture amount is the smallest. Further, the potential sensor 148 or the potential sensor 60 may be provided also on the cathode electrode 176 side.

  Accordingly, in the sixth embodiment, the water content of the electrolyte membrane / electrode structure 172 can be easily and reliably detected via the potential sensor 148, and is the same as in the first to fifth embodiments. The effect is obtained.

  FIG. 19 is an explanatory front view of an electrolyte membrane / electrode structure 182 constituting a fuel cell 180 in which the operating method according to the seventh embodiment of the present invention is implemented.

  As shown in FIGS. 19 and 20, the electrolyte membrane / electrode structure 182 sandwiches the solid polymer electrolyte membrane 30 between an anode electrode 184 and a cathode electrode 186. The cathode electrode 186 is set to have the same planar dimension as the solid polymer electrolyte membrane 30 or a smaller planar dimension than the solid polymer electrolyte membrane 30, and the cathode electrode 186 is larger than the anode electrode 184. The dimensions are set (see FIG. 19).

  When measuring the potential at the end of the anode electrode 184 and measuring the potential at the end of the cathode electrode 186, notches 184a are formed at the four corners of the anode electrode 184, while the four corners of the cathode electrode 186 are formed. Is formed with a notch 186a. Note that the shape of the notches 184a and 186a is set as necessary, and can be changed to an optimum shape for potential measurement. When measuring the potential of only the anode electrode 184, the notch 184a is not necessarily provided in the anode electrode 184.

  Corresponding to the notches 184a and 186a, on the anode side and the cathode side, that is, in the vicinity of the fuel gas outlet communication hole 40b, which is the region where the amount of water of the electrolyte membrane / electrode structure 182 is the largest, and the oxidant gas outlet A potential sensor 148 is installed in the vicinity of the communication hole 38b, in the vicinity of the fuel gas inlet communication hole 40a and in the vicinity of the oxidant gas inlet communication hole 38a, which are regions where the amount of moisture is the smallest. Further, the potential sensor 148 may be provided only on one of the anode electrode 164 and the cathode electrode 166.

  Accordingly, in the seventh embodiment, the water content of the electrolyte membrane / electrode structure 182 can be easily and reliably detected via the potential sensor 148, and is the same as in the first to sixth embodiments. The effect is obtained.

DESCRIPTION OF SYMBOLS 10, 130, 140, 163, 170, 180 ... Fuel cell 12 ... Fuel cell system 14 ... Fuel cell stack 16 ... Oxidant gas supply device 18 ... Fuel gas supply device 20 ... Cooling medium supply device 22 ... Control devices 24, 132 , 142, 165, 172, 182... Electrolyte membrane / electrode structure 26, 28... Separator 30... Solid polymer electrolyte membranes 32, 32 a, 144, 164, 174, 184. 186 ... Cathode electrode 38a ... Oxidant gas inlet communication hole 38b ... Oxidant gas outlet communication hole 40a ... Fuel gas inlet communication hole 40b ... Fuel gas outlet communication hole 42a ... Cooling medium inlet communication hole 42b ... Cooling medium outlet communication hole 46 ... Oxidant gas flow path 48 ... Fuel gas flow path 50 ... Cooling medium flow path 60, 60a, 148 ... Potential sensor 62 150, 152, 154, 156 ... conductive terminals 62a, 150a, 152a, 154a, 156a ... measurement unit 70 ... potential measuring device 120 ... potential correcting section 122 ... water content estimator 124 ... device control unit

Claims (6)

An operation method of a fuel cell in which an electrolyte membrane / electrode structure sandwiching an electrolyte membrane between an anode electrode and a cathode electrode and a separator are laminated,
The water content of the electrolyte membrane / electrode structure is estimated from the relationship between the preset potential and the water content based on the output value of the potential sensor provided at the outer peripheral end of the electrolyte membrane / electrode structure. Process,
Adjusting the operating conditions of the fuel cell so that the estimated water content is maintained within a predetermined water content range;
A method of operating a fuel cell, comprising:   2. The method of operating a fuel cell according to claim 1, wherein the potential sensor is single or plural in a plane.   3. The operation method according to claim 1, wherein the adjustment of the operation condition includes at least one of a flow rate adjustment, a pressure adjustment, a humidity adjustment, a temperature adjustment, and a purge process of a fuel gas supplied to the anode electrode side. A method of operating a fuel cell characterized by the above.   The operation method according to any one of claims 1 to 3, wherein the adjustment of the operation condition includes at least one of a flow rate adjustment, a pressure adjustment, a temperature adjustment, and a humidity adjustment of an oxidant gas supplied to the cathode electrode side. A method for operating a fuel cell, comprising:   5. The operation method of a fuel cell according to claim 1, wherein the adjustment of the operation condition includes at least one of temperature adjustment and flow rate adjustment of a cooling medium.   6. The operation method according to claim 1, wherein a notch is provided in at least one of the four corners of the electrolyte membrane / electrode structure, and the potential sensor corresponds to the notch. A method of operating a fuel cell, characterized in that is installed.

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