JP7076418B2 - Fuel cell system and its control method - Google Patents

Description

The present invention relates to a fuel cell system including a laminated body in which a plurality of power generation cells are stacked, and a control method thereof.

Generally, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure in which an anode electrode is arranged on one surface of an electrolyte membrane made of a polymer ion exchange membrane and a cathode electrode is arranged on the other surface. (MEA) is provided. A power generation cell is formed by sandwiching the electrolyte membrane / electrode structure with a separator, and a laminated body is formed by laminating a plurality of power generation cells. A fuel cell stack is configured by providing terminal plates for collecting electric power generated by each power generation cell, end plates for holding the power generation cells in a stacked state, and the like at both ends of the stack in the stacking direction. To.

In a fuel cell system equipped with this type of fuel cell stack, fuel gas such as hydrogen-containing gas is supplied to the anode electrode side of each power generation cell, and an oxidizing agent gas such as oxygen-containing gas is supplied to the cathode electrode side. , Fuel gas and oxidant gas are electrochemically reacted to generate power (operation). At this time, at the anode electrode, hydrogen is ionized to generate a proton, and the proton is conducted in the electrolyte membrane and moves to the cathode electrode.

The electrolyte membrane needs to be wet in order to produce good proton conduction. However, if the water content of the laminate becomes excessive and stagnant water is generated in the cathode electrode and the anode electrode, there is a concern that the stagnant water obstructs the flow of the fuel gas and the oxidant gas, and the power generation stability is lowered. Therefore, it is required to appropriately control the water content of the laminated body.

For example, Patent Document 1 proposes a fuel cell system for determining whether or not the cathode electrode is too wet based on the measured impedance value of the entire laminated body. The overall impedance of the laminate increases when the water content of the laminate (electrolyte film) decreases and tends to dry, and decreases when the water content of the laminate increases and tends to become wet. Therefore, the water content of the laminated body is controlled by, for example, adjusting the humidity of the oxidizing agent gas supplied to the cathode electrode based on the measured impedance value of the entire laminated body.

Japanese Unexamined Patent Publication No. 7-235324

By the way, since heat dissipation is promoted via a terminal plate or the like on the end side of the laminated body in the laminating direction, the temperature tends to be lower due to the influence of the outside air temperature or the like as compared with the central side of the laminated body in the laminating direction. .. That is, in the end power generation section having at least one electrolyte membrane / electrode structure disposed on the end side of the laminate, dew condensation is likely to occur and the water content is likely to be higher than that on the center side of the laminate. Therefore, as described above, if the water content is controlled based on the measured impedance value of the entire laminated body, there is a concern that the water content of the end power generation unit becomes excessive and stagnant water is generated. In this case, it becomes difficult to suppress the decrease in power generation stability after all.

Therefore, an object of the present invention is to provide a fuel cell system and a control method thereof that can suppress the generation of stagnant water in the power generation portion at the end of the laminated body and can maintain good power generation stability.

In one aspect of the present invention, a plurality of power generation cells having an electrolyte membrane / electrode structure in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode and separators arranged on both sides of the electrolyte membrane / electrode structure are laminated. It is a fuel cell system that generates power by supplying a fuel gas to the anode electrode and supplying an oxidant gas to the cathode electrode, and is an impedance measurement for obtaining an impedance measurement value of the laminate. At least one of the above, which is arranged at the end of the laminate in the stacking direction by using the unit, the temperature measurement unit for obtaining the temperature measurement value of the laminate, and the impedance measurement value and the temperature measurement value. It includes an end impedance estimation unit that obtains an estimated value of the impedance of the end power generation unit having an electrolyte film / electrode structure, and a water content control unit that controls the water content of the laminate based on the estimated value.

Another aspect of the present invention is a power generation cell having an electrolyte membrane / electrode structure in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode, and separators arranged on both sides of the electrolyte membrane / electrode structure. It is a control method of a fuel cell system in which a plurality of laminated bodies are provided, and fuel gas is supplied to the anode electrode and an oxidizing agent gas is supplied to the cathode electrode to generate power, and the impedance of the laminated body is measured. Using the impedance measuring step for obtaining a value, the temperature measuring step for obtaining the temperature measured value of the laminated body, and the impedance measured value and the temperature measured value, they are arranged at the end of the laminated body in the stacking direction. An end impedance estimation step for obtaining an estimated value of the impedance of an end power generation unit having at least one electrolyte film / electrode structure, and a water content control step for controlling the water content of the laminate based on the estimated value. And have.

In this fuel cell system and its control method, the impedance measured value and the temperature measured value of the laminated body are used to obtain an estimated value of the impedance of the end power generation unit, and the water content of the laminated body is controlled based on the estimated value. .. Therefore, even when the temperature of the end power generation unit is lower than that of the center side of the laminated body, for example, it is possible to prevent the water content of the end power generation unit from becoming excessive. As a result, it is possible to suppress the generation of stagnant water in the power generation portion at the end of the laminated body, and it is possible to maintain good power generation stability of the fuel cell system.

It is a schematic configuration explanatory view of the fuel cell system which concerns on embodiment of this invention. It is an exploded perspective view of a fuel cell stack. It is a map which showed the difference between the impedance of a laminated body and the impedance of an end power generation part according to the temperature of a laminated body for each impedance of a laminated body. It is a flowchart explaining the control method of the fuel cell system which concerns on embodiment of this invention.

A suitable embodiment of the fuel cell system and the control method thereof according to the present invention will be described in detail with reference to the accompanying drawings. In the following figures, components having the same or similar functions and effects may be designated by the same reference numerals, and repeated description may be omitted.

The fuel cell system 10 according to the present embodiment shown in FIG. 1 can be mounted on, for example, a fuel cell vehicle (not shown) such as a fuel cell electric vehicle. Further, the fuel cell system 10 includes a fuel cell stack 12, a fuel gas supply / discharge unit 14, an oxidant gas supply / discharge unit 16, a cooling medium supply / discharge unit 18, an impedance measurement unit 20, and a temperature measurement unit 22. , A control unit 24 (ECU) is provided. The fuel cell system 10 may further include a battery (not shown) which is an energy storage device.

As shown in FIG. 2, the fuel cell stack 12 includes a laminated body 28 in which a plurality of power generation cells 26 are laminated in the horizontal direction (arrows A1 and A2 directions) or in the gravity direction (arrows C1 and C2 directions). The terminal plate 30a, the insulator 32a, and the end plate 34a are laminated in this order on one end side (arrow A1 side) of the laminated body 28 in the stacking direction. The terminal plate 30b, the insulator 32b, and the end plate 34b are laminated in this order on the other end side (arrow A2 side) of the laminated body 28 in the stacking direction.

A connecting bar (not shown) is arranged between each side of the rectangular end plates 34a and 34b. Both ends of each connecting bar are fixed to the inner surfaces of the end plates 34a and 34b via bolts (not shown), and a tightening load in the stacking direction (arrows A1 and A2 directions) is applied to the plurality of stacked power generation cells 26. do. Although not shown, the fuel cell stack 12 may include a housing having end plates 34a and 34b as end plates, and may be configured to accommodate the laminated body 28 and the like in the housing.

As shown in FIG. 1, in the present embodiment, the power generation cell 26 includes a first separator 36, an electrolyte membrane / electrode structure 38, a second separator 40, an electrolyte membrane / electrode structure 38, and a third separator. 42 and 42 are laminated in this order. Each of the first separator 36, the second separator 40, and the third separator 42 (collectively referred to as "separator") is composed of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, or the like, and has a flat surface. In addition to being rectangular, it is formed into an uneven cross-sectional shape by press working or the like.

As shown in FIG. 2, the separators 36, 40, and 42 of FIG. 1 are individually communicated with the edges of one end side (arrow B1 side) in the long side direction in the arrow A1 and A2 directions (stacking direction), respectively. Then, the oxidant gas inlet communication hole 44a and the fuel gas outlet communication hole 46b are provided. An oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas inlet communication hole 44a. A fuel gas such as a hydrogen-containing gas is discharged to the fuel gas outlet communication hole 46b. These oxidant gas and fuel gas are also collectively referred to as "reaction gas".

As shown in FIG. 2, the separators 36, 40, and 42 of FIG. 1 are individually communicated with the edges of the other end side (arrow B2 side) in the long side direction in the directions of arrows A1 and A2, respectively. A fuel gas inlet communication hole 46a to which the fuel gas is supplied and an oxidant gas outlet communication hole 44b to which the oxidant gas is discharged are provided. The oxidant gas inlet communication hole 44a, the fuel gas outlet communication hole 46b, the fuel gas inlet communication hole 46a, and the oxidant gas outlet communication hole 44b are collectively referred to as "reaction gas communication hole".

As shown in FIG. 2, the separators 36, 40, and 42 of FIG. 1 are individually communicated with the arrow B1 side of both end edges in the short side direction (arrows C1 and C2 directions) in the arrow A1 and A2 directions. , A pair of cooling medium inlet communication holes 48a to which the cooling medium is supplied are provided respectively. As the cooling medium, pure water, ethylene glycol, oil or the like can be used. As shown in FIG. 2, the separators 36, 40, and 42 of FIG. 1 communicate with each other individually in the directions of arrows A1 and A2 on the arrow B2 side of both end edges in the short side direction, and the cooling medium is discharged. A pair of cooling medium outlet communication holes 48b are provided respectively.

FIG. 1 shows that the cooling medium inlet communication hole 48a and the cooling medium outlet communication hole 48b of FIG. 2 communicate with each other on the surface of the first separator 36 on the arrow A1 side and the surface of the third separator 42 on the arrow A2 side. The cooling medium flow path 50 is formed. On the surface of the first separator 36 on the arrow A2 side and the surface of the second separator 40 on the arrow A2 side, oxidation communicating with the oxidant gas inlet communication hole 44a and the oxidant gas outlet communication hole 44b of FIG. 2 is performed. The agent gas flow path 52 is formed. The oxidant gas flow path 52 is composed of a plurality of wavy flow path grooves (or linear flow path grooves) parallel to each other.

FIG. 1 shows that the surface of the second separator 40 on the arrow A1 side and the surface of the third separator 42 on the arrow A1 side communicate with the fuel gas inlet communication hole 46a and the fuel gas outlet communication hole 46b of FIG. The fuel gas flow path 54 is formed. The fuel gas flow path 54 is composed of a plurality of wavy flow path grooves (or linear flow path grooves) that are parallel to each other.

In the power generation cell 26 adjacent to each other in the laminated body 28, the cooling medium flow path 50 on the arrow A2 side surface of the third separator 42 and the cooling medium flow path 50 on the arrow A1 side surface of the first separator 36 face each other. Therefore, the cooling medium can be distributed inside. That is, in the laminated body 28, a cooling medium flow path 50 through which a cooling medium flows is provided between adjacent power generation cells 26. The number of separators 36, 40, 42 and the electrolyte membrane / electrode structure 38 constituting each power generation cell 26 is not particularly limited to the above. For example, two separators (not shown) and one electrolyte are not shown. The power generation cell 26 may be configured from the membrane / electrode structure 38.

As shown in FIG. 1, the electrolyte membrane / electrode structure 38 includes, for example, a solid polymer electrolyte membrane (hereinafter, also simply referred to as an electrolyte membrane) 56 which is a thin film of perfluorosulfonic acid containing water. As the electrolyte membrane 56, an HC (hydrocarbon) -based electrolyte may be used in addition to the fluorine-based electrolyte. The electrolyte membrane 56 is sandwiched between the cathode electrode 58 and the anode electrode 60. A resin frame member (not shown) may be bonded to the outer periphery of the electrolyte membrane / electrode structure 38.

Although not shown, the cathode electrode 58 has a cathode electrode catalyst layer bonded to a surface on one end side (arrow A1 side) of the electrolyte film 56, and a cathode gas diffusion layer laminated on the cathode electrode catalyst layer. .. Although not shown, the anode electrode 60 has an anode electrode catalyst layer bonded to the other end side (arrow A2 side) of the electrolyte film 56 and an anode gas diffusion layer laminated on the anode electrode catalyst layer. Have.

The cathode electrode catalyst layer is formed, for example, by uniformly applying porous carbon particles having a platinum alloy on the surface to the surface of the cathode gas diffusion layer together with an ion conductive polymer binder. The anode electrode catalyst layer is formed, for example, by uniformly coating the surface of the anode gas diffusion layer with porous carbon particles having a platinum alloy supported on the surface together with an ion conductive polymer binder. The cathode gas diffusion layer and the anode gas diffusion layer are formed of a conductive porous body such as carbon paper or carbon cloth.

As shown in FIG. 2, the terminal plates 30a and 30b are made of a conductive material, for example, a metal such as copper, aluminum or stainless steel. Terminal portions 62a and 62b extending outward in the stacking direction are provided at substantially the center of the terminal plates 30a and 30b, respectively.

The terminal portion 62a is inserted into the insulating tubular body 64a, penetrates the hole portion 66a of the insulator 32a and the hole portion 67a of the end plate 34a, and projects to the outside of the end plate 34a. The terminal portion 62b is inserted into the insulating tubular body 64b, penetrates the hole portion 66b of the insulator 32b and the hole portion 67b of the end plate 34b, and projects to the outside of the end plate 34b.

The insulators 32a and 32b are formed of an insulating material such as polycarbonate (PC) or a phenol resin. Recesses 68a and 68b opened toward the laminated body 28 are formed in the central portions of the insulators 32a and 32b, and the recesses 68a and 68b communicate with the holes 66a and 66b. The insulator 32a and the end plate 34a are provided with reaction gas communication holes. On the other hand, the insulator 32b and the end plate 34b are provided with a cooling medium inlet communication hole 48a and a cooling medium outlet communication hole 48b.

The terminal plate 30a and the heat insulating body 70 are housed in the recess 68a, and the terminal plate 30b and the heat insulating body 70 are housed in the recess 68b. The heat insulating body 70 is configured by sandwiching a conductive heat insulating member 74 between a pair of conductive heat insulating plates 72. The heat insulating plate 72 is made of, for example, a porous carbon plate having a flat shape, and the heat insulating member 74 is made of a metal plate having a corrugated cross section.

As shown in FIG. 2, the electrolyte membrane / electrode structure 38 (FIG. 1) of the power generation cell 26 arranged on the end side of the laminated body 28 in the stacking direction is a terminal plate 30a arranged in the vicinity thereof. Heat dissipation is likely to be promoted via 30b, end plates 34a, 34b and the like. Therefore, at least one electrolyte membrane / electrode structure 38 (FIG. 1) disposed at the end of the laminate 28 in the stacking direction is an electrolyte membrane / electrode structure on the center side in the stacking direction of the laminate 28. Compared to 38 (Fig. 1), the temperature tends to be lower due to the influence of the outside temperature and the like. By being arranged at the end of the laminated body 28 in the laminating direction in this way, at least one electrolyte membrane / electrode structure 38 (FIG. 1), which tends to have a lower temperature than the central side in the laminating direction, is end at the end. The power generation unit 76.

In the present embodiment, as shown in FIG. 2, the two electrolyte membrane / electrode structures 38 (FIG. 1) disposed on one end side of the laminated body 28 in the stacking direction, and the other in the stacking direction of the laminated body 28. It is assumed that the end power generation unit 76 is composed of a total of four pieces including the two electrolyte membranes / electrode structures 38 (FIG. 1) arranged on the end side. However, the end power generation unit 76 is not limited to being composed of the above-mentioned four electrolyte membrane / electrode structures 38. That is, the end power generation unit 76 may have one electrolyte membrane / electrode structure 38, or may have a plurality of electrolyte membranes / electrode structures 38 other than four. The upper limit of the number of electrolyte membranes / electrode structures 38 possessed by the end power generation unit 76 is about 1 to 5% of the total number of electrolyte membranes / electrode structures 38 constituting the laminate 28, or the laminate 28. It is preferably about 1 to 5% of the total number of power generation cells 26 constituting the above.

As shown in FIG. 1, the fuel cell stack 12 includes a fuel gas supply port 78a, a fuel exhaust gas discharge port 78b, an oxidant gas supply port 80a, an oxidant exhaust gas discharge port 80b, and a cooling medium supply port 82a. , A cooling medium discharge port 82b is provided. Fuel gas is supplied to the fuel gas inlet communication hole 46a (FIG. 2) via the fuel gas supply port 78a. The fuel gas supplied to the fuel gas inlet communication hole 46a is supplied to the anode electrode 60 (FIG. 1) of each power generation cell 26 of the laminated body 28 by moving along the fuel gas flow path 54.

Further, the oxidant gas is supplied to the oxidant gas inlet communication hole 44a of FIG. 2 through the oxidant gas supply port 80a of FIG. The oxidant gas supplied to the oxidant gas inlet communication hole 44a in FIG. 2 is supplied to the cathode electrode 58 (FIG. 1) of each power generation cell 26 of the laminated body 28 by moving along the oxidant gas flow path 52. Will be done. In the fuel cell stack 12, power is generated by consuming the fuel gas and the oxidizing agent gas supplied as described above in the electrochemical reaction (power generation reaction) at the anode electrode 60 and the cathode electrode 58.

As shown in FIG. 1, of the fuel gas supplied to the fuel cell stack 12, the remaining fuel gas not consumed in the above power generation reaction is used as fuel exhaust gas from the fuel gas outlet communication hole 46b (FIG. 2). It is discharged to the fuel exhaust gas discharge port 78b. Further, of the oxidizing agent gas supplied to the fuel cell stack 12, the remaining oxidizing agent gas not consumed in the above power generation reaction is oxidized as the oxidizing agent exhaust gas from the oxidizing agent gas outlet communication hole 44b (FIG. 2). It is discharged to the agent exhaust gas discharge port 80b.

The cooling medium is supplied to the cooling medium inlet communication hole 48a of FIG. 2 through the cooling medium supply port 82a of FIG. The cooling medium supplied to the cooling medium inlet communication hole 48a in FIG. 2 flows along the cooling medium flow path 50 of each power generation cell 26 of the laminated body 28. In this way, the cooling medium after heat exchange with each power generation cell 26 by flowing through the cooling medium flow path 50 is discharged from the cooling medium outlet communication hole 48b to the cooling medium discharge port 82b of FIG.

The fuel gas supply / discharge unit 14 includes a hydrogen tank 84, a fuel gas supply path 86, an injector 88, an ejector 90, a fuel exhaust gas discharge path 92, a gas / liquid separator 94, a drain path 96, and a drain valve 98. It has a gas side discharge path 100, a fuel gas circulation path 102, a hydrogen pump 104, a purge path 106, and a purge valve 108.

The hydrogen tank 84 stores the fuel gas and is provided so that the fuel gas can be supplied to the fuel gas supply path 86. The fuel gas supply path 86 is a fuel gas flow path that guides the fuel gas supplied from the hydrogen tank 84 to the fuel gas supply port 78a (stacked body 28) of the fuel cell stack 12. In the fuel gas supply path 86, an injector 88 and an ejector 90 are provided in this order from the upstream side thereof, and fuel gas is supplied to the ejector 90 via the injector 88. The fuel gas discharged from the ejector 90 is supplied to the fuel gas supply port 78a.

The fuel exhaust gas discharge path 92 guides the fuel exhaust gas discharged from the fuel exhaust gas discharge port 78b to the gas-liquid separator 94. The fuel exhaust gas includes unconsumed fuel gas that was not consumed by the fuel cell stack 12, water that has moved from the cathode electrode 58 to the anode electrode 60 via the electrolyte membrane 56, and the like. The gas-liquid separator 94 separates the fuel exhaust gas into an exhaust gas mainly containing an unconsumed portion of the fuel gas and an exhaust fluid mainly containing water (liquid water) and the like.

A gas-side discharge path 100 is connected to the gas-side discharge port 94a of the gas-liquid separator 94 that discharges the exhaust gas. Therefore, the exhaust gas is discharged from the gas side discharge port 94a to the gas side discharge path 100. The downstream side of the gas side discharge path 100 branches into a fuel gas circulation path 102 and a purge path 106. The downstream side of the fuel gas circulation path 102 is connected to the ejector 90, and a hydrogen pump 104 is provided in the middle of the fuel gas circulation path 102. The hydrogen pump 104 sends the exhaust gas from the fuel gas circulation path 102 to the ejector 90. Since the fuel gas is supplied to the ejector 90 via the injector 88 as described above, the exhaust gas is supplied to the fuel cell stack 12 together with the fuel gas via the fuel gas supply port 78a.

The downstream of the purge path 106 communicates with the oxidant exhaust gas discharge path 122, which will be described later, of the oxidant gas supply / discharge section 16. Further, a purge valve 108 is provided in the middle of the purge path 106. The exhaust gas is discharged to the outside of the fuel cell system 10 via the purge path 106 and the oxidant exhaust gas discharge path 122 under the opening action of the purge valve 108, if necessary.

A drain path 96 is connected to the liquid side discharge port 94b of the gas-liquid separator 94 that discharges the discharged fluid. Therefore, the discharged fluid is discharged from the liquid side discharge port 94b to the drain path 96. The downstream of the drain path 96 communicates with the oxidant exhaust gas discharge path 122. Further, a drain valve 98 is provided in the middle of the drain path 96. The discharged fluid is discharged to the outside of the fuel cell system 10 via the drain passage 96 and the oxidant exhaust gas discharge passage 122 under the opening action of the drain valve 98, if necessary.

The oxidant gas supply / discharge unit 16 includes an air pump 110, an oxidant gas supply path 112, a supply side on-off valve (inlet sealing valve) 114, a humidifier 116, a humidification bypass path 118, and a humidification bypass valve 120. , Oxidizing agent exhaust gas discharge passage 122, discharge side on-off valve (outlet sealing valve) 124, back pressure valve 126, discharge side bypass passage 128, discharge side bypass valve 130, oxidant gas circulation passage 132, and circulation. It has a pump 134 and.

The air pump 110 takes in air as an oxidant gas from the atmosphere into the oxidant gas supply path 112 and supplies it to the downstream side in a compressed state. The oxidant gas supply path 112 is a flow path for the oxidant gas that guides the oxidant gas taken in through the air pump 110 to the oxidant gas supply port 80a (layer 28) of the fuel cell stack 12. The oxidant gas supply path 112 is provided with a supply-side on-off valve 114 and a humidifier 116 in this order from the upstream side thereof.

Further, an upstream end of the humidification bypass path 118 is connected between the supply-side on-off valve 114 of the oxidant gas supply path 112 and the humidifier 116. The downstream end of the humidifying bypass path 118 is connected between the downstream side of the humidifier 116 of the humidifying bypass path 118 and the oxidant gas supply port 80a. The humidifying bypass path 118 is provided with a humidifying bypass valve 120 that adjusts the flow rate of air flowing through the humidifying bypass path 118. The humidifying bypass valve 120 may be an on-off valve that opens and closes the humidifying bypass path 118.

The oxidant exhaust gas discharge path 122 is a flow path of the oxidant exhaust gas through which the oxidant exhaust gas discharged from the oxidant exhaust gas discharge port 80b flows. In the oxidant exhaust gas discharge path 122, the humidifier 116, the discharge side on-off valve 124, and the back pressure valve 126 are arranged in this order toward the downstream side. The oxidant exhaust gas includes an unconsumed portion of the oxidant gas that was not consumed in the fuel cell stack 12, water generated by the power generation reaction, and the like. Further, the oxidant exhaust gas has a higher temperature than the oxidant gas before being supplied to the fuel cell stack 12 due to heat generated by the power generation reaction or the like. The humidifier 116 is discharged from the oxidant gas of the oxidant gas supply path 112 (oxidant gas before being supplied to the fuel cell stack 12) and the oxidant exhaust gas of the oxidant exhaust gas discharge path 122 (fuel cell stack 12). Moisture and heat are exchanged with the oxidant exhaust gas after the process.

Therefore, the oxidant gas that has passed through the humidifier 116 is supplied to the oxidant gas supply port 80a of the fuel cell stack 12 after being humidified by the oxidant exhaust gas and raised in temperature. Therefore, when the opening degree of the humidifying bypass valve 120 is increased (including setting the valve opening degree to 100%), the oxidant gas supply port 80a is circulated through the humidifying bypass path 118 without going through the humidifying device 116. The amount of oxidant gas supplied increases. That is, the proportion of the dried oxidant gas supplied to the oxidant gas supply port 80a increases as the humidification by the humidifier 116 is not performed.

On the other hand, when the opening degree of the humidifying bypass valve 120 is reduced (including setting the valve opening degree to 0%), the amount of the oxidizing agent gas supplied to the oxidizing agent gas supply port 80a via the humidifier 116 increases. .. That is, the proportion of the oxidant gas having a high humidity supplied to the oxidant gas supply port 80a increases as the humidification is performed by the humidifier 116.

The discharge side bypass path 128 communicates between the air pump 110 of the oxidant gas supply path 112 and the supply side on-off valve 114 to the downstream side of the back pressure valve 126 of the oxidant exhaust gas discharge path 122. The discharge-side bypass path 128 is provided with a discharge-side bypass valve 130 that regulates the flow rate of the oxidant gas flowing through the discharge-side bypass path 128. The oxidant gas taken into the oxidant gas supply path 112 by the air pump 110 is fueled through the oxidant exhaust gas discharge path 122 and the oxidant exhaust gas discharge path 122 by opening the discharge side bypass valve 130 as needed. It is discharged to the outside of the battery system 10.

The oxidant gas circulation path 132 communicates between the humidifier 116 of the oxidant exhaust gas discharge path 122 and the discharge side on-off valve 124 between the supply-side on-off valve 114 of the oxidant gas supply path 112 and the humidifier 116. .. A circulation pump 134 is provided in the oxidant gas circulation path 132. The oxidant exhaust gas that has passed through the humidifier 116 is sent to the oxidant gas supply path 112 by the circulation pump 134 as needed, so that the oxidant exhaust gas is supplied together with the oxidant gas through the humidifier gas 116. It is supplied to the mouth 80a.

Under the opening action of the discharge side on-off valve 124, the oxidant exhaust gas that has passed through the discharge side on-off valve 124 goes to the downstream side of the oxidant exhaust gas discharge passage 122 in a state of being adjusted to the set pressure of the back pressure valve 126. The purge path 106 and the drain path 96 of the fuel gas supply / discharge section 14 are connected to the downstream side of the oxidant exhaust gas discharge path 122 (the downstream side of the connection portion of the oxidant exhaust gas discharge path 122 with the discharge side bypass path 128). Has been done. Therefore, when the purge valve 108 is in the open state, the exhaust gas in the purge path 106 flows into the oxidant exhaust gas discharge path 122. Further, when the drain valve 98 is in the open state, the exhaust fluid in the drain passage 96 flows into the oxidant exhaust gas discharge passage 122. These exhaust gas and exhaust fluid are diluted by the oxidant exhaust gas flowing through the oxidant exhaust gas discharge passage 122 and then discharged to the outside of the fuel cell system 10.

The cooling medium supply / discharge unit 18 includes a cooling medium supply path 136 connected to the cooling medium supply port 82a of the fuel cell stack 12 and a cooling medium discharge path 138 connected to the cooling medium discharge port 82b. The radiator 140 is connected to the upstream end of the cooling medium supply path 136 and the downstream end of the cooling medium discharge path 138. A water pump 142 is provided in the middle of the cooling medium supply path 136. By driving the water pump 142, the cooling medium circulates between the fuel cell stack 12, the cooling medium discharge path 138, the radiator 140, and the cooling medium supply path 136.

The impedance measuring unit 20 measures the impedance of the entire laminated body 28 of the fuel cell stack 12 and outputs the impedance measurement value obtained to the control unit 24. The temperature measuring unit 22 outputs, for example, a temperature measured value obtained by measuring the temperature of the cooling medium discharge path 138 (cooling medium) near the cooling medium discharge port 82b to the control unit 24 as a temperature measured value of the laminated body 28. do.

Since the temperature measuring unit 22 may be provided so as to be able to detect the temperature measured value of the laminated body 28, for example, the temperature of the laminated body 28 itself may be directly detected. Further, the temperature measuring unit 22 may be provided in the fuel exhaust gas discharge path 92 or the oxidant exhaust gas discharge path 122 instead of the cooling medium discharge path 138. That is, the temperature measuring unit 22 detects the temperature measured value of the fuel exhaust gas near the fuel exhaust gas discharge port 78b and the temperature measured value of the oxidant exhaust gas near the oxidant exhaust gas exhaust port 80b as the temperature measured value of the laminated body 28. You may.

The control unit 24 is configured as a computer equipped with a CPU (not shown), a memory, or the like, and the CPU executes a predetermined calculation according to a control program, and performs various processes and controls related to the operation of the fuel cell system 10. Specifically, the control unit 24 has an end impedance estimation unit 144 and a water content control unit 146. The end impedance estimation unit 144 uses the overall impedance measurement value of the laminate 28 detected by the impedance measurement unit 20 and the temperature measurement value of the laminate 28 detected by the temperature measurement unit 22, and the laminate 28 is used. The estimated value of the impedance of the end power generation unit 76 (hereinafter, also simply referred to as an estimated value) is obtained.

As an example of the method of obtaining the estimated value, the end impedance estimation unit 144 has the total impedance of the laminated body 28, the temperature of the laminated body 28, and the total impedance of the laminated body 28 obtained in advance by experiments, simulations, and the like. And the impedance difference of the end power generation unit 76 (hereinafter, also simply referred to as “difference”) and the relationship are used. Based on this relationship, first, the difference corresponding to the impedance measurement value obtained by the impedance measurement unit 20 and the temperature measurement value obtained by the temperature measurement unit 22 is obtained.

In the present embodiment, as shown in FIG. 3, the above relationship is shown in the form of a map M in which the difference depending on the temperature of the laminated body 28 is shown, for example, for each impedance of the entire laminated body 28 of A to C. , It is stored in a storage unit (not shown) provided in the control unit 24. A, B, and C increase, for example, in this order at predetermined intervals, and are set within a range in which the impedance of the entire laminated body 28 can be taken during the operation of the fuel cell system 10. In addition, in FIG. 3, it was decided to show the difference according to the temperature of the laminated body 28 for each impedance of the whole of the three laminated bodies 28 of A to C, but the laminated body 28 having 3 or more or less than 3 is shown. It is also possible to show the difference according to the temperature of the laminated body 28 for each impedance of the whole.

In addition, instead of storing the above relationship in the form of the map M shown in FIG. 3, the storage unit may store the above relationship in the form of a function, for example. Further, the end impedance estimation unit 144 may acquire the above relationship from the outside of the fuel cell system 10, for example, instead of storing the above relationship in the storage unit.

Next, the end impedance estimation unit 144 has an electrolyte film / electrode structure in which the end power generation unit 76 has a value obtained by subtracting the difference obtained as described above from the impedance measurement value obtained by the impedance measurement unit 20. Divide by the number of 38 (4 in this embodiment). This makes it possible to obtain an estimated value of the impedance of the end power generation unit 76. That is, the estimated value here corresponds to, but is not limited to, the average impedance of the electrolyte membrane / electrode structure 38 possessed by the end power generation unit 76.

The water content control unit 146 controls the water content of the laminated body 28 based on the estimated value obtained by the end impedance estimation unit 144. The overall impedance of the laminated body 28 increases when the water content of the laminated body 28 (electrolyte film 56) decreases and tends to dry, and decreases when the water content of the laminated body 28 increases and tends to become wet. Therefore, the water-containing control unit 146 has an appropriate size based on the estimated value, for example, according to the temperature of the environment in which the fuel cell system 10 is placed, the operating condition of the fuel cell system 10, the temperature of the laminated body 28, and the like. The water content of the laminated body 28 is controlled so as to be. As a result, the electrolyte membrane 56 is maintained in a wet state capable of producing good proton conduction, the generation of stagnant water in the cathode electrode 58 and the anode electrode 60 is suppressed, and the outside temperature is below freezing point. It becomes possible to suppress the freezing of the water content in the laminated body 28 in the above.

In the present embodiment, the water content control unit 146 operates in the direction of opening the humidification bypass valve 120 (increasing the opening degree of the humidification bypass valve 120) when controlling to reduce the water content of the laminated body 28. When controlling to increase the water content of the laminated body 28, the humidifying bypass valve 120 is operated in the closing direction (the opening degree of the humidifying bypass valve 120 is reduced).

Basically, the control method of the fuel cell system 10 configured as described above will be described with reference to FIG.

For example, although not shown, when the ignition switch (IG) of the fuel cell vehicle equipped with the fuel cell system 10 is turned on, a warm-up operation for warming up the fuel cell system 10 to a predetermined operating temperature starts. Will be done. At the same time, the impedance measuring unit 20 performs an impedance measuring step of obtaining the overall impedance measured value of the laminated body 28, and the temperature measuring unit 22 performs a temperature measuring step of obtaining the temperature measured value of the laminated body 28 (FIG. 4). Step S1).

Next, as shown in step S2 of FIG. 4, an end impedance estimation step of obtaining an estimated value of the impedance of the end power generation unit 76 by the end impedance estimation unit 144 using the impedance measurement value and the temperature measurement value. I do.

For example, in the end impedance estimation step, the end impedance estimation unit 144 selects one from A to C of the map M in FIG. 3 corresponding to the impedance measurement value obtained by the impedance measurement unit 20. Then, from the relationship between the temperature and the difference of the laminated body 28 according to the overall impedance of the selected laminated body 28, the difference corresponding to the temperature measured value obtained by the temperature measuring unit 22 is detected. Next, the electrolyte film / electrode structure 38 of the end power generation unit 76 is obtained by subtracting the difference obtained as described above from the overall impedance measurement value of the laminated body 28 obtained by the impedance measurement unit 20. Divide by 4, which is the number of. As a result, an estimated value of the impedance of the end power generation unit 76 can be obtained.

Next, as shown in step S3 of FIG. 4, the water content in which the water content of the laminated body 28 is controlled by the water content control unit 146 based on the estimated value of the impedance of the end power generation unit 76 obtained in the end impedance estimation step. Perform the control process.

For example, in this water content control step, the water content control unit 146 compares the estimated value with a predetermined threshold value, and when the estimated value is larger than the threshold value, determines that the laminated body 28 tends to dry. , The opening degree of the humidification bypass valve 120 is reduced. As a result, the amount of the oxidant gas supplied to the oxidant gas supply port 80a after being humidified by the humidifier 116 increases, so that humidification control for increasing the water content of the laminate 28 is performed.

On the other hand, when the estimated value is equal to or less than the threshold value, it is determined that the laminated body 28 tends to be over-humidified, and the opening degree of the humidification bypass valve 120 is increased. As a result, the amount of the oxidant gas supplied to the oxidant gas supply port 80a without being humidified by the humidifier 116 increases, so that drying control is performed to reduce the water content of the laminate 28.

After repeating each of the above steps S1 to S3 until the fuel cell system 10 rises to a predetermined operating temperature by, for example, an electrochemical reaction in the fuel cell stack 12, the flowchart of FIG. 4 is shown. finish. The flowchart of FIG. 4 may be terminated after each step from step S1 to step S3 is repeated until the IG of the fuel cell vehicle is turned off.

From the above, in the fuel cell system 10 and the control method thereof according to the present embodiment, the estimated value of the impedance of the end power generation unit 76 is obtained by using the measured impedance value and the temperature measured value of the entire laminated body 28, and the estimated value is obtained. The water content of the laminate 28 is controlled based on the value. Therefore, even when the temperature of the end power generation unit 76 is lower than that of the central side of the laminated body 28, for example, it is possible to prevent the end power generation unit 76 from having an excessive water content.

That is, for example, even though the impedance of the end power generation unit 76 of the laminated body 28 is equal to or less than a predetermined threshold value, the impedance of the central portion of the laminated body 28 or the entire laminated body 28 is larger than the predetermined threshold value. , It is possible to avoid the situation where the drying control by the water content control unit 146 is terminated. As a result, it is possible to effectively suppress the generation of stagnant water in the end power generation unit 76 of the laminated body 28, so that deterioration of the electrolyte membrane 56 of the end power generation unit 76 can be suppressed, or the reaction in the end power generation unit 76 can be suppressed. It is possible to suppress the inhibition of gas diffusivity. That is, it is possible to appropriately control the water content of the laminated body 28 to maintain good power generation stability of the fuel cell system 10.

In the fuel cell system 10 according to the above embodiment, the end impedance estimation unit 144 determines the impedance of the laminate 28, the temperature of the laminate 28, the impedance of the laminate 28, and the difference between the impedances of the end power generation unit 76. Based on the above relationship, the difference corresponding to the impedance measurement value and the temperature measurement value is obtained, and the value obtained by subtracting the difference from the impedance measurement value is divided by the number of the electrolyte membrane / electrode structure 38 of the end power generation unit 76. We decided to obtain an estimated value.

Further, in the control method of the fuel cell system 10 according to the above embodiment, in the end impedance estimation step, the impedance of the laminate 28, the temperature of the laminate 28, the impedance of the laminate 28, and the end power generation unit 76 Based on the relationship with the impedance difference, the difference corresponding to the impedance measurement value and the temperature measurement value is obtained, and the value obtained by subtracting the difference from the impedance measurement value is the number of the electrolyte membrane / electrode structure 38 possessed by the end power generation unit 76. It was decided to obtain the estimated value by dividing.

In these cases, the impedance estimation value can be easily obtained by obtaining the above relationship in advance by experiments, simulations, etc., and the water content of the laminated body 28 can be accurately controlled based on the impedance estimation value. Can be done. As a result, the power generation stability of the fuel cell system 10 can be well maintained with a simple configuration. The method for obtaining the estimated value is not particularly limited.

In the fuel cell system 10 according to the above embodiment, the oxidant gas supply path 112 for supplying the oxidant gas to the laminate 28 and the humidifier 116 provided in the oxidant gas supply path 112 to humidify the oxidant gas. , A humidification bypass path 118 that is provided in the oxidant gas supply path 112 and supplies the oxidant gas before humidification to the downstream side of the humidifier 116 by bypassing the humidifier 116, and a humidification bypass path 118 that opens and closes the humidification bypass path 118. A bypass valve 120 is provided, and the water content control unit 146 operates in the direction of opening the humidification bypass valve 120 when the water content is decreased, and in the direction of closing the humidification bypass valve 120 when the water content is increased. I decided to operate it.

Further, in the control method of the fuel cell system 10 according to the above embodiment, the fuel cell system 10 is provided in the oxidant gas supply path 112 for supplying the oxidant gas to the laminate 28 and the oxidant gas supply path 112. , A humidifying bypass path provided in the oxidizing agent gas supply path 112 and a humidifying device 116 for humidifying the oxidizing agent gas, and supplying the oxidizing agent gas before humidification to the downstream side of the humidifying device 116 by bypassing the humidifying device 116. A humidifying bypass valve 120 that opens and closes the humidifying bypass path 118 is provided, and in the water content control step, when the water content is decreased, the humidifying bypass valve 120 is operated in the opening direction to increase the water content. It was decided to operate the humidification bypass valve 120 in the closing direction.

In these cases, the water content control unit 146 makes it possible to easily adjust the water content of the laminated body 28 by a simple configuration for opening and closing the humidification bypass valve 120.

In the fuel cell system 10 according to the above embodiment, the water content control unit 146 is estimated to be at least from the start of the start-up of the laminate 28 (fuel cell system 10) until the laminate 28 reaches a predetermined operating temperature. Based on the above, it was decided to control the water content of the laminated body 28.

Further, in the control method of the fuel cell system 10 according to the above embodiment, the water content control step is at least from the start of the start-up of the laminated body 28 (fuel cell system 10) to the time when the laminated body 28 reaches a predetermined operating temperature. It was decided to be done in the meantime.

In particular, during the period from the start of the start-up of the laminated body 28 until the laminated body 28 reaches a predetermined operating temperature, the difference in impedance between the end power generation unit 76 and the central portion of the laminated body 28 is large. It tends to be easy. Therefore, by performing the water content control step by the water content control unit 146 during the above period, it is possible to effectively suppress the generation of stagnant water in the end power generation unit 76. As a result, it becomes possible to maintain good power generation stability of the fuel cell system 10.

Further, for example, when the fuel cell system 10 is started in a low temperature environment such as below freezing point, the temperature of the end power generation unit 76 is affected by the outside temperature, and the temperature of the end power generation unit 76 is the electrolyte film / electrode structure in the central portion of the laminate 28. It tends to be lower than the temperature of 38. Therefore, in the end power generation unit 76, dew condensation tends to occur and the water content tends to be excessive. If the water content of the end power generation unit 76 becomes excessive, there is a concern that the water content in the end power generation unit 76 may freeze. Even in such a case, as described above, the water content of the end power generation unit 76 is appropriately maintained by controlling the water content of the laminated body 28 based on the estimated value of the impedance of the end power generation unit 76. can do. As a result, it is possible to suppress freezing of water and the like, so that the power generation stability and durability of the fuel cell system 10 can be maintained satisfactorily.

The present invention is not particularly limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof.

In the above embodiment, the water content control unit 146 operates in the direction of opening the humidification bypass valve 120 when controlling to reduce the water content of the laminated body 28, and controls to increase the water content of the laminated body 28. When doing so, it was decided to operate the humidification bypass valve 120 in the closing direction. However, the method of controlling the water content of the laminated body 28 by the water content control unit 146 is not particularly limited to this.

For example, as shown in FIG. 1, the water content of the laminated body 28 is adjusted by adjusting the rotation speed of the air pump 110 and the opening degree of the back pressure valve 126 to control the pressure of the oxidant gas in the fuel cell stack 12. You may control it. In this case, if the pressure of the oxidant gas in the fuel cell stack 12 is increased by, for example, increasing the rotation speed of the air pump 110 or reducing the opening degree of the back pressure valve 126, it is included in the oxidant gas. The water vapor is easily condensed, and the condensed water generated thereby can increase the water content of the laminate 28. On the contrary, the water content of the laminated body 28 can be reduced by lowering the rotation speed of the air pump 110 or increasing the opening degree of the back pressure valve 126.

Further, for example, the water content of the laminated body 28 may be controlled by adjusting the rotation speed of the water pump 142 to control the flow rate of the cooling medium flowing through the cooling medium flow path 50 of the fuel cell stack 12. .. For example, when the temperature of the laminated body 28 is lower than that of the cooling medium, the temperature of the laminated body 28 can be promoted by increasing the flow rate of the cooling medium flowing through the cooling medium flow path 50. As a result, the occurrence of dew condensation can be suppressed and the water content of the laminated body 28 can be reduced.

10 ... Fuel cell system 20 ... Impedance measuring unit 22 ... Temperature measuring unit 26 ... Power generation cell 28 ... Laminated body 36 ... First separator 38 ... Electrolyte film / electrode structure 40 ... Second separator 42 ... Third separator 56 ... Electrolyte film 58 ... Cathode electrode 60 ... Anode electrode 76 ... End power generation unit 112 ... Oxidizing agent gas supply path 116 ... Humidifier 118 ... Humidity bypass path 120 ... Humidity bypass valve 144 ... End impedance estimation unit 146 ... Water content control unit

Claims (8)

A laminate comprising a plurality of power generation cells having an electrolyte membrane / electrode structure in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode and separators arranged on both sides of the electrolyte membrane / electrode structure is provided. A fuel cell system that generates power by supplying fuel gas to the anode electrode and supplying oxidant gas to the cathode electrode.
An impedance measuring unit that obtains the impedance measured value of the laminated body, and
A temperature measuring unit that obtains the temperature measured value of the laminated body, and
Using the impedance measurement value and the temperature measurement value, an estimated value of the impedance of the end power generation unit having at least one electrolyte film / electrode structure disposed at the end portion of the laminate in the stacking direction. The end impedance estimation unit that obtains
A water content control unit that controls the water content of the laminate based on the estimated value,
A fuel cell system equipped with. In the fuel cell system according to claim 1,
The end impedance estimation unit has the impedance measurement value and the temperature based on the relationship between the impedance of the laminate, the temperature of the laminate, the impedance of the laminate, and the impedance of the end power generation unit. The fuel corresponding to the measured value is obtained, and the estimated value is obtained by dividing the value obtained by subtracting the difference from the impedance measured value by the number of the electrolyte membrane / electrode structure possessed by the end power generation unit. Battery system. In the fuel cell system according to claim 1 or 2.
An oxidant gas supply path for supplying the oxidant gas to the laminate,
A humidifier provided in the oxidant gas supply path to humidify the oxidant gas, and
A humidification bypass path provided in the oxidant gas supply path and bypassing the humidifier to supply the oxidant gas before humidification to the downstream side of the humidifier.
A humidifying bypass valve that opens and closes the humidifying bypass path,
Equipped with
The water content control unit operates in the direction of opening the humidification bypass valve when the water content is decreased, and operates in the direction of closing the humidification bypass valve when the water content is increased. system. In the fuel cell system according to any one of claims 1 to 3.
The water content control unit controls the water content of the laminate based on the estimated value, at least from the start of activation of the laminate until the laminate reaches a predetermined operating temperature. .. A laminate comprising a plurality of power generation cells having an electrolyte membrane / electrode structure in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode and separators arranged on both sides of the electrolyte membrane / electrode structure is provided. It is a control method of a fuel cell system that generates power by supplying fuel gas to the anode electrode and supplying oxidant gas to the cathode electrode.
An impedance measurement step for obtaining an impedance measurement value of the laminate, and
A temperature measurement step for obtaining a temperature measurement value of the laminate, and
Using the impedance measurement value and the temperature measurement value, an estimated value of the impedance of the end power generation unit having at least one electrolyte film / electrode structure disposed at the end portion of the laminate in the stacking direction. The end impedance estimation process to obtain
A water content control step for controlling the water content of the laminate based on the estimated value, and
How to control a fuel cell system. In the control method of the fuel cell system according to claim 5,
In the end impedance estimation step, the impedance measurement value and the temperature are based on the relationship between the impedance of the laminate, the temperature of the laminate, the impedance of the laminate, and the impedance of the end power generation unit. The fuel corresponding to the measured value is obtained, and the estimated value is obtained by dividing the value obtained by subtracting the difference from the impedance measured value by the number of the electrolyte membrane / electrode structure possessed by the end power generation unit. How to control the battery system. In the control method of the fuel cell system according to claim 5 or 6.
The fuel cell system is
An oxidant gas supply path for supplying the oxidant gas to the laminate,
A humidifier provided in the oxidant gas supply path to humidify the oxidant gas, and
A humidification bypass path provided in the oxidant gas supply path and bypassing the humidifier to supply the oxidant gas before humidification to the downstream side of the humidifier.
A humidifying bypass valve that opens and closes the humidifying bypass path,
Equipped with
In the water content control step, the fuel cell is operated in the direction of opening the humidification bypass valve when the water content is decreased, and is operated in the direction of closing the humidification bypass valve when the water content is increased. How to control the system. The method for controlling a fuel cell system according to any one of claims 5 to 7.
The water content control step is a method for controlling a fuel cell system, which is performed at least from the start of activation of the laminate to the time when the laminate reaches a predetermined operating temperature.

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