JP4729866B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly, to a fuel cell including a polymer electrolyte membrane such as a polymer electrolyte fuel cell (PEFC) or a direct methanol fuel cell.

  In recent years, fuel cells that generate electricity by electrochemical reaction between hydrogen and oxygen have attracted attention as an energy supply source. For example, in a fuel cell equipped with a polymer electrolyte membrane, generally, an ion exchange resin membrane, which is a polymer electrolyte, is sandwiched between both anode and cathode electrodes, and further fuel is inserted between the electrodes. A separator is provided to form a flow path (anode side) and an oxidant gas flow path (cathode side) through which the oxidant gas is inserted.

  When the fuel cell is operated for power generation, when fuel and oxidant gas humidified as necessary are supplied to the anode side and the cathode side, respectively, an electrochemical reaction (cell reaction) is caused and electricity is taken out. In the oxidant gas flow path on the cathode side, water is generated with power generation.

  However, in order to maintain power generation efficiency satisfactorily and stably, not only does the tightening pressure applied to the membrane electrode assembly equalize and lower the contact resistance, but also the internal humidity varies depending on the location of the membrane electrode assembly. In addition, it is important to keep the temperature, saturation, conditions for condensing after reaching saturation, and the like as a whole.

  However, as the scale of the fuel cell increases, it is difficult to maintain uniform conditions such as internal humidity, temperature, saturation, and condensation at all locations inside the cell. For example, when the power generation operation is performed at a low current density (for example, an open circuit (OC) state), the humidity condition of the polymer electrolyte membrane is lowered, so that the power generation efficiency is likely to deteriorate, and the power generation is performed at a high current density. When operated, water droplets are retained in the flow channel due to the large amount of water generated on the cathode side, so that gas supply to the polymer electrolyte membrane is hindered, so-called flooding is likely to occur. Will fall.

  In particular, control of humidity conditions is important in terms of improving and maintaining power generation efficiency, but as described above, changes in humidity conditions inside the battery can be caused by operating conditions (such as high and low current density and continuous operation) and environmental conditions. However, it varies depending on the location of the membrane electrode assembly due to the influence of the humidity distribution derived from the structure, and varies greatly depending on the site (region) within the battery. Therefore, if the battery reaction within the battery is non-uniform, the power generation performance of the entire fuel cell is degraded.

  In relation to the above, there is a polymer electrolyte fuel cell including a water retention layer formed of a conductive material and a water retention resin and having a plurality of through holes (for example, see Patent Document 1). However, the function of discharging the produced water generated on the cathode side is insufficient, and the possibility of flooding cannot be eliminated, and the power generation performance cannot be ensured.

A method of controlling the humidity condition inside the battery from the temperature condition is also conceivable, but it is impossible to perform optimum control corresponding to the output of the fuel cell.
JP 2003-68330 A

  Conventionally, although various proposals have been made regarding the technology for improving the power generation performance of a fuel cell, the humidity conditions that vary in the fuel cell and conditions for condensation upon reaching saturation are made uniform throughout the fuel cell. This is difficult, and the power generation operation is only optimized under a certain humidity condition, and the desired power generation performance cannot be maintained under a humidity condition deviating from that condition. Therefore, it has been a challenge to make the humidity conditions different for each operating condition, environmental condition, etc., or for different regions inside the fuel cell, particularly for each region of the membrane electrode assembly.

  The present invention has been made in view of the above, and corresponds to operating conditions (high current density, continuous operation, etc.), environmental conditions (temperature, etc.), etc., and partially in a predetermined region unit inside the fuel cell. The purpose of the present invention is to provide a fuel cell capable of controlling humidity conditions, conditions for condensation upon reaching saturation, and drainage of generated water, and capable of stable power generation operation with high power generation efficiency. The challenge is to achieve.

In order to achieve the above object, a fuel cell of the present invention has a membrane electrode assembly including a polymer electrolyte membrane and an electrode pair sandwiching the polymer electrolyte membrane, and a plurality of ribs. A separator that forms a flow path between the electrodes, and a rib that is provided between the ribs (recesses) along the electrode surface in the flow path , has an opening, and expands and contracts when the voltage is applied. It is a molecular membrane and is composed of a permeation variable member that varies the permeation of the substance between the flow path and the membrane electrode assembly.

  In the present specification, the rib is a convex portion protruding in a convex shape on an uneven surface (hereinafter also referred to as a rib surface) formed on at least one side of the separator, and the concave portion between the ribs is In general, a fuel flow path for supplying and discharging fuel in a state where a tip of a rib (convex portion) is in contact with a membrane electrode assembly (in particular, a surface of an electrode, that is, a diffusion layer of an electrode in which a catalyst layer and a diffusion layer are laminated) An oxidant gas flow path for supplying and discharging the oxidant gas is configured.

  Further, the membrane electrode assembly can be composed of a polymer electrolyte membrane and a pair of electrode pairs sandwiching the polymer electrolyte membrane, and each electrode of the electrode pair generally has a catalyst layer and a diffusion layer in order from the polymer electrolyte membrane side. And are constructed.

  In the present invention, in the concave portion between the ribs of the rib surface of the separator, the outer wall surface of the membrane electrode assembly that closes the opening surface of the concave portion when the fuel cell is configured, that is, the electrode surface (specifically, In this case, a permeation variable member is disposed on the surface of the diffusion layer along the recess so as to provide a partition (partition wall) between the flow channel and the membrane electrode assembly, thereby being exposed in the flow channel. Since the exposed area of the membrane electrode assembly can be changed over time or partly, the amount of mass transfer between the channel and the electrode of the membrane electrode assembly, that is, the fuel component in the atmosphere in the channel ( The supply amount of hydrogen gas or the like to the membrane electrode assembly (particularly the electrode) and the discharge amount of the generated water generated by the electrode of the membrane electrode assembly to the flow channel side can be controlled to a desired level. .

  The transmission variable member preferably has an opening that can be expanded and contracted. An exposed area of the membrane electrode assembly exposed in the channel by providing a variable transmission member having an expandable / contractible opening on the electrode surface of the channel (specifically, the surface of the diffusion layer) along the recess. Therefore, the amount of material permeation between the flow path and the electrode of the membrane electrode assembly, that is, the fuel in the atmosphere in the flow path, as described above, functions like a valve with a variable opening. Control the supply amount of components (hydrogen gas, etc.) and moisture to the membrane electrode assembly (especially electrodes) and the discharge amount of the generated water generated by the electrodes of the membrane electrode assembly to the flow channel side to a desired level. Can do.

  For this reason, for example, in the case where the humidity condition of the polymer electrolyte membrane is likely to be lowered, such as when the power generation operation is performed at a low current density during OC, or the like, the water retaining state is formed by reducing the opening of the permeation variable member. In the case where a large amount of generated water is generated on the cathode side, such as when the power generation operation is performed at a high current density, the opening of the permeation variable member is enlarged to improve drainage. be able to. In this way, the degree of material permeation between the flow path and the membrane electrode assembly can be appropriately controlled according to various conditions such as the location and region selected as desired, locally, or the output of the fuel cell, It is possible to suppress the decrease in power generation performance and flooding due to the low humidity of the polymer electrolyte membrane, and to stably improve the power generation efficiency under all operating conditions.

  The permeation variable member can be configured by being provided on at least a part of the exposed surface exposed in the flow path of the electrode constituting the membrane electrode assembly. By providing it on the electrode surface exposed in the flow path, the structure can be simplified, and the material permeation control between the membrane electrode assembly and the flow path is performed directly, and the humidity condition and water content inside the bonded body Etc. are easy to control.

The transmission variable member has an opening, that make up an enlarged or reduced little capable polymer film openings by voltage application. This is a so-called electroactive polymer (artificial muscle) and is described in detail in US Pat. No. 6,583,533. In the electroactive polymer, for example, when an opening is provided on the film surface and this film is disposed between the electrodes and a voltage is applied, the applied voltage is changed to expand or contract the opening according to the voltage. It is possible to selectively change the opening area of the opening at a desired position by arranging and configuring the electrodes so that the voltage can be changed for each film having the opening or for each single or plural openings. it can. Therefore, by providing a polymer film with an opening on the electrode surface exposed in the flow channel, the exposed area of the membrane electrode assembly exposed in the flow channel (surface area of the diffusion layer) is partially changed. Therefore, depending on conditions, such as the location and region selected as desired, or depending on various conditions such as the output of the fuel cell, the membrane electrode assembly (especially electrodes) ) And the discharge amount of the generated water generated at the electrode of the membrane electrode assembly to the flow channel side can be controlled.

  A polymer film that expands and contracts when a voltage is applied has a dielectric constant higher than the dielectric constant 1 of air (for example, 2.5 to 10), and is distorted by contraction or the like when a voltage is applied across the electrodes. A dielectric polymer material that produces a film, for example, a known polymer material such as an acrylic elastomer, silicone, fluorosilicone, polyurethane, etc., is formed into a film and an opening is formed at a desired position. it can.

  The transmission variable member has an opening and a structure including two transmission plates arranged substantially in parallel, and at least one of the two transmission plates is moved in parallel, and the transmission unit is configured by the opening. Can be configured to open and close. When two transmissive plates are placed at a predetermined position, and a closed state is formed when the opening on one side of the transmissive plate and the opening on the other do not overlap, and at least one or both are translated Since the openings provided in each transmission plate overlap each other to form an open state, the opening at a desired position between the flow path and the membrane electrode assembly can be controlled by controlling the amount of translation. , That is, the opening area can be selectively changed. This configuration is also effective in that it is possible to appropriately control the location and region selected as desired locally or according to various conditions such as the output of the fuel cell.

  According to the present invention, the humidity condition or saturation is partially reached in a predetermined region unit within the fuel cell in accordance with the operating conditions (high and low current density, continuous operation, etc.) and environmental conditions (temperature, etc.). It is possible to provide a fuel cell capable of controlling the conditions for condensation and the drainage of generated water and capable of stably performing power generation operation with high power generation efficiency.

  Hereinafter, embodiments of a fuel cell of the present invention will be described with reference to the drawings. In the following embodiment, a case where hydrogen gas and air (air) are used as fuel and oxidant gas in a fuel cell configured in a solid polymer type will be mainly described. However, the present invention is not limited to these embodiments.

(First embodiment)
1st Embodiment of the fuel cell of this invention is described with reference to FIGS. In the present embodiment, a permeable variable film having a plurality of openings is provided on the surface of the diffusion layer exposed in the cathode air flow path and in the anode hydrogen gas flow path so that the applied voltage can be changed for each permeable variable film. It is a thing.

  As shown in FIG. 1, a fuel cell (single cell) 10 includes an ion exchange resin film 11, which is a polymer electrolyte, sandwiched between both electrodes of an anode electrode 12 and a cathode electrode 13, and further between each electrode. A plurality of ribs are provided so as to form a hydrogen gas passage (anode side) 15 that passes hydrogen gas (fuel) and an air passage (cathode side) 17 that passes air (oxidant gas). A pair of separators 14 and 16 having a recessed channel are provided. In general, since the electromotive force generated by a single cell is relatively small, it is usually used in a stack structure in which a plurality of single cells are stacked and connected in series.

FIG. 2 shows a part of a schematic cross-sectional structure of the fuel cell 10 configured as described above. When the power generation operation is performed, hydrogen gas having a high hydrogen (H ₂ ) density is supplied to the hydrogen gas passage 15, and air (Air) containing oxygen (O ₂ ) is supplied to the air passage 17. The electromotive force is generated by the electrochemical reaction (battery reaction) represented by () to (3). Equations (1) and (2) represent reactions on the anode side and cathode side, respectively, and equation (3) represents the total reaction in the fuel cell.
H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  As shown in FIG. 3, the cathode electrode 13 has a structure in which a catalyst layer 20 and a diffusion layer 21 are laminated in order from the ion exchange resin film 11 side, and the anode electrode 12 is configured in the same manner as the cathode electrode 13. ing. FIG. 3 is a partially enlarged schematic view of the cross-sectional structure on the cathode side of the fuel cell 10.

  A plurality of diffusion layers 21 constituting the cathode electrode 13 are provided on the surface not exposed to the catalyst layer 20 on the surface exposed in the air channel 17 (not provided on the rib portion of the separator) along the air channel 17. The permeation variable membranes 25 are provided regularly arranged. The same applies to the anode side where the anode electrode 12 is provided. Hereinafter, the cathode side will be described as an example.

  As shown in FIG. 4, the transmission variable membrane 25 is formed into a rectangular piece having a predetermined size (for example, length B = 1 mm, width C = 1 mm, thickness D = 100 μm). , 27 ′, and regularly arranged in stripes at intervals of a length B on the surface of the diffusion layer 21 of the same width exposed to the air flow path 17 of the road width A, It can be driven by Coulomb force when a voltage is applied between the two gold electrodes. In the region where the permeation variable membrane 25 is not arranged, the surface of the diffusion layer 21 is exposed in the air flow path.

  The permeation variable film 25 is formed by coating a polymer solution prepared in a coating liquid form by dissolving and diluting to a desired viscosity on a desired substrate in advance by, for example, spin coating, and evaporating the solvent. After the film formation, it can be provided by forming it into a pattern of a predetermined size and arranging it in stripes at desired positions of the diffusion layer 21. The application of the polymer solution can be performed by appropriately selecting a known coating method such as a dip coating method, a casting method, and a spray method in addition to the spin coating method. In particular, the spin coating method is preferable in terms of uniforming the film and reducing the film thickness.

  The thickness of the permeation variable membrane can be selected within a range that does not impair the passage of gas, water, or the like in the flow path, and is preferably a thin film from the viewpoint of reducing driving voltage, and is preferably in the range of 10 to 100 μm.

  The shape of the permeation variable membrane can be appropriately selected in consideration of the area of the region where the permeation variable membrane is provided, etc., as shown in FIG. 4, except that it is formed into a rectangular piece of length B × width C. In addition, it may be formed into a long shape with the width C as the road width A in FIG. 4 or a larger rectangular shape such as length 3B × width 3C. Further, the permeation variable film may be arranged in a stripe shape, or may be arranged on the entire surface of the diffusion layer 21 exposed in the air flow path 17, or a rectangular piece of a predetermined size is randomly provided in a sea-island structure. Alternatively, it may be selectively provided in a region having a high moisture content, such as the vicinity of the outlet of the air flow path, or a region where low humidity conditions are likely to occur, such as the vicinity of the inlet of the hydrogen gas flow path on the anode side.

  As shown in FIG. 5A, a plurality of circular openings 26 penetrating the film are arranged on each film surface of the permeation variable film 25, and air flows through the openings 26. Mass transfer is possible between the path 17 and the diffusion layer 21, that is, the membrane electrode assembly 18. The shape of the opening can be any shape such as an ellipse or a rectangle other than a circle.

  Further, the permeation variable membrane 25 has its front and back membrane surfaces narrowly covered with gold electrodes 27, 27 ′, and the gold electrodes 27, 27 ′ slightly surround the opening 26 so that the opening 26 is not covered. It is provided over the entire surface so that a voltage can be applied between the gold electrodes. The gold electrodes 27 and 27 ′ are electrically connected to a control unit (ECU) 30 (see FIGS. 3 to 4), apply a desired voltage to each transmission variable film 25, and change each transmission variable film 25. The opening 26 is expanded and contracted as shown by a broken line P in FIG. 5- (a), so that the opening state shown in FIG. 5- (a) and the closed state shown in FIG. The size of the opening area, that is, the amount of material permeation can be controlled.

  Since the gold electrodes 27 and 27 'need to be provided on the permeation variable membrane, they are formed in a flexible form so as not to inhibit or peel the membrane from contracting or distorting. For example, a compliant gold electrode has a gold film structure (for example, a line shape or a zigzag line shape in addition to the surface shape as described above) formed by photolithography on the surface of the transmission variable film in a state where the opening is maximized. It can be formed by making. In addition to the gold electrode, a polymer material constituting the permeation variable membrane or other electroactive polymer mixed with conductive particles such as carbon particles and metal particles can be used as an electrode material. This is useful in terms of adhesion to the permeation variable membrane.

  As shown in FIGS. 2 and 3, a humidity sensor 22 for detecting the humidity condition in the flow path is attached in the flow path of the air flow path 17, and the diffusion layer 21 on the cathode side is attached. A temperature sensor 23 for detecting the cell temperature t of the fuel cell 10 is further attached in the vicinity. Similarly, a humidity sensor 24 for detecting the humidity condition in the flow path is attached in the flow path of the hydrogen gas flow path 15 on the anode side (see FIG. 2). The humidity sensors 22 and 24 and the temperature sensor 23 are each electrically connected to the control unit 30 so that the humidity condition and the cell temperature t in the flow path can be detected at a predetermined monitoring interval.

  The ion exchange resin membrane 11 can be composed of a polymer electrolyte having ionic conductivity, and a perfluorosulfonic acid membrane or the like is generally used. In this embodiment, a Nafion membrane (manufactured by DuPont) is used. This membrane is usually in a wet state from the viewpoint of improving ionic conductivity, and hydrogen ions on the anode side obtained by supplying hydrogen gas can conduct ions through the membrane well and move to the cathode side. This wet state can be held and controlled by the permeation variable membrane as described above. Further, depending on the case, it is possible to add water (humidification) to air containing hydrogen gas as a fuel or oxygen on the cathode side.

  The catalyst layer 20 constituting the anode electrode and the cathode electrode is responsible for the electrochemical reaction, and is formed by applying platinum as a catalyst or an alloy made of platinum and another metal to the surface of the ion exchange resin film 11. Is. For coating, carbon powder carrying platinum or an alloy composed of platinum and another metal is prepared, and the carbon powder is dispersed in an appropriate organic solvent, and an electrolyte solution (for example, Aldrich Chemical Co., Nafion Solution) is added thereto. An appropriate amount can be added to form a paste and screen printed on the polymer electrolyte membrane. Alternatively, the paste containing the carbon powder may be formed into a sheet to form a sheet, and the sheet may be pressed onto the polymer electrolyte membrane. Alternatively, platinum or an alloy made of platinum and another metal may be applied to the surface of the diffusion layer on the side facing the polymer electrolyte membrane instead of the polymer electrolyte membrane.

  Further, the diffusion layer 21 constituting the anode electrode and the cathode electrode functions as a current collector, and is formed of a carbon cloth woven with yarns made of carbon fibers. In addition to the carbon cloth, the diffusion layer is preferably formed of carbon paper or carbon felt made of carbon fiber.

  The separators 14 and 16 can be made of a gas-impermeable conductive member, for example, dense carbon that has been made to be gas-impermeable by compressing carbon. In the separator, when a plurality of single cells are stacked to form a stack structure, one separator is shared between the two membrane electrode assemblies 18, and generally a flow path is formed on both sides of the separator.

In normal power generation operation of the fuel cell 10, hydrogen gas is supplied to the hydrogen gas flow path 15, the air is supplied to the air passage 17, as shown in FIG. 2, the anode side, hydrogen (H ₂ ) Passes through the opening 26 (see FIGS. 3 to 5) of the permeation variable membrane 25, becomes hydrogen ions H ⁺ at the anode electrode 12, moves inside the ion exchange resin membrane 11 toward the cathode side, and is released. The electrons e ⁻ flow to the cathode side through an external circuit 19 that connects the anode and cathode. On the cathode side, oxygen O ₂ in the air passes through the opening 26 of the permeation variable membrane 25 provided on the cathode side, reaches the cathode electrode 13, and reacts with H ⁺ and electrons e ⁻ from the anode side. Thus, water (H ₂ O) is generated. This water is discharged to the outside through the air flow path 17.

  Next, a control routine performed by the control unit 30 during the normal power generation operation will be described with reference to FIGS. 6 and 7 focusing on a control routine for performing opening / closing control of the permeation variable membrane 25 during the power generation operation. As described above, the humidity sensor 22, the temperature sensor 23, and the gold electrodes 27 and 27 'provided on the transmission variable film are electrically connected to the control unit 30 so that the operation timing can be controlled. It has become. In addition to the opening / closing control of the permeation variable membrane 25, the control unit 30 adjusts the amount of hydrogen gas and air according to the size of the load connected to the fuel cell 10 to control the output of the normal fuel cell. It is also responsible for power generation operation control.

FIG. 6 shows a control routine for performing opening / closing control of the permeable variable membrane on the cathode side under voltage monitoring at regular intervals during power generation operation control. When this routine is executed, in step 100, the humidity h ^c in the flow path is taken by the humidity sensor 22 mounted in the flow path of the air flow path 17, in a next step 120, the cell by the temperature sensor 23 The temperature t is taken.

Next, in step 140, it is determined whether or not the dew point T is reached when the humidity condition of the taken-in humidity h ^c is the cell temperature t. If it is determined that the dew point T has been reached, the air flow path 17 is reached. Since there is a large amount of moisture in the interior and there is a risk of flooding, if it is determined in step 160 that the opening of the opening 26 of the permeation variable membrane 25 is 100% (fully open) and the dew point T is not reached, Therefore, in step 180, the opening of the opening 26 is controlled to be reduced to 80%. Thereafter, in step 200, it is determined whether or not there is a request for stopping the power generation operation. When it is determined that there is no stop request yet, the process returns to step 100 and the same control is repeated to determine that there is a stop request. If this is the case, this routine is terminated.

  Next, the control routine on the anode side will be described with reference to FIG. FIG. 7 shows a control routine for performing opening / closing control of the anode-side permeable variable membrane under voltage monitoring at regular intervals during power generation operation control.

When this routine is executed, in step 300, the humidity h ^a in the flow path is taken by the humidity sensor 24 mounted in the flow path of the hydrogen gas passage 15. Next, in step 320, whether incorporated humidity h ^a is equal to or less than a predetermined value H is determined, when the humidity h ^a is determined to be equal to or less than the predetermined value H, moisturizing state of the ion exchange resin membrane it is necessary to keep the degree of opening of the opening 26 of the transmission variable layer 25 was reduced to 80% in step 340, when the humidity h ^a is determined to exceed a predetermined value H, it becomes low humidity conditions Therefore, in step 360, the opening of the opening 26 is controlled to 100% (fully open). Thereafter, in step 380, it is determined whether or not there is a request for stopping the power generation operation. When it is determined that there is no stop request yet, the process returns to step 300 and the same control is repeated to determine that there is a stop request. Sometimes, this routine is finished as it is.

  The results of the control as described above will be described with reference to FIGS. FIG. 13 is a relationship diagram comparing the relationship between the current density and the voltage with no control. In any current density from the low density region to the high density region such as during OC, the broken line (2 ) And (3), the voltage drop was suppressed and a high power generation voltage was obtained. FIG. 14 is a relational diagram comparing the relationship between current density and resistance compared to the case without control, and an increase in resistance value means that the condition has shifted to drying conditions. Humidity conditions were maintained even in the density range, and power generation efficiency was good.

  In the above, the control is performed so that the opening degree of the permeation variable membrane on the cathode side and the anode side is reduced by one step to 80%, but may be controlled to be further reduced to 80% or less (for example, 50%). . Further, the opening from the 100% (fully open) state to the substantially closed state (for example, 20% opening) is controlled so as to be expanded and contracted in multiple steps based on the difference from the dew point T, humidity conditions, and the like. You can also

  As mentioned above, it is possible to control humidity conditions, conditions that partially reach condensation within the fuel cell, and the drainage of produced water, and stable power generation operation with high power generation efficiency. it can.

(Second Embodiment)
A second embodiment of the fuel cell of the present invention will be described with reference to FIG. In this embodiment, the shape of the opening provided in the permeation variable membrane of the first embodiment is configured to be rectangular. Note that the fuel and oxidant gas used in the first embodiment can be the same as those used in the first embodiment, and the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof will be given. Omitted.

  The diffusion layer 21 on the cathode side in the present embodiment includes a plurality of the diffusion layers 21 along the air flow path 17 on the surface exposed in the air flow path 17 (not provided on the rib portion of the separator) on the side not in contact with the catalyst layer 20. The permeation variable membranes 30 are regularly arranged as shown in FIGS. The same applies to the anode side.

  As shown in FIG. 8A, four rectangular openings 31 penetrating the membrane are provided on the individual membrane surfaces of the permeation variable membrane 30, and the air flow paths are provided via the openings 31. Mass transfer is possible between 17 and the diffusion layer 21, that is, the membrane electrode assembly 18.

  Similarly to the first embodiment, the transmission variable film 30 has a gold electrode 32 and a gold electrode 32 ′ (not shown) for applying voltage to the front and back of the film surface (transmission variable film 30 and diffusion layer). The gold electrode is provided across the entire surface of the opening 31 so that the opening 31 is not covered, and a voltage can be applied between the gold electrodes. It is like that. Both the gold electrodes 32 and 32 'are electrically connected to a control unit (ECU) 30, and by applying a desired voltage to each transmission variable membrane 30 to expand and contract in the direction of the arrow in the figure, The size of the opening area, that is, the amount of material permeation can be controlled between the open state shown in FIG. 8- (a) and the closed state shown in FIG. 8- (b).

  Also according to the present embodiment, it is possible to control the humidity condition or the condition that the fuel cell partially condenses by reaching saturation, the drainage of generated water, and stable power generation operation with high power generation efficiency. Can do.

( Reference form)
The reference embodiment of fuel cell with reference to FIGS. 9-10 is described. In this reference embodiment, the transmission variable film of the first embodiment is configured by replacing a transmission variable device having a shutter structure. Note that the fuel and oxidant gas used in the first embodiment can be the same as those used in the first embodiment, and the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof will be given. Omitted.

The diffusion layer 21 provided on the cathode side of the membrane electrode assembly 18 of the present reference embodiment, the side not in contact with the catalyst layer 20, the rib portion of the whole (separator surface exposed to the air flow path 17 is (Not provided) A single long transmission variable device 40 is provided along the air flow path 17. The anode side is similarly configured.

  As shown in FIG. 9, the transmission variable device 40 is fixedly arranged so as not to move the surface exposed in the air flow path 17 of the diffusion layer 21, and has a support base 41 having a window portion 46 opened in a rectangular shape. And two transmission variable plates 42 and 43 that are arranged so as to sandwich the support base material 41 and are movable in parallel to the surface of the support base material 41.

  Each of the transmission variable plates 42 and 43 is provided with a plurality of circular (diameter 10 to 1000 mm) openings 44 and 45 that regularly penetrate the plates, and the transmission variable plates 42 and 43 are arranged at predetermined positions. When arranged, the opening 44 and the opening 45 do not overlap with each other, and when at least one of the transmission variable plates 42 and 43 is translated from a predetermined position, the opening 44 and the opening 45 gradually move. A so-called shutter structure is formed in which a transmission port is formed so as to overlap and a substance can be transmitted through the window 46. In the state where the opening 44 and the opening 45 do not overlap with each other, the transmission port is not formed, and the substance permeation through the transmission variable device 40 becomes impossible.

  The transmission variable plates 42 and 43 can be configured using a corrosion-resistant metal material such as stainless steel, titanium, or glassy metal inside the battery. In addition, the openings 44 and 45 can be configured to have different shapes and opening areas in addition to the same shape and opening area.

  For example, the movement of the transmission variable plates 42 and 43 is controlled by the control unit 30 while controlling the driving force of the motor driven by the power supply from the fuel cell based on the difference from the dew point, the humidity condition, and the like. It can be transmitted.

  Further, when the transmission variable plates 42 and 43 are moved, as shown in FIG. 10, either one of the transmission variable plates 42 and 43 may be translated in the arrow direction E or F. It is also possible to adopt a mode in which both 43 are translated in opposite directions (one direction is an arrow direction E and the other is an arrow direction F).

Even in this reference mode, it is possible to control the humidity condition, the condition that the fuel cell is partially saturated and condensed, and the drainage of the generated water, and stable power generation operation with high power generation efficiency. Can do.

Next, another example of the transmission variable member will be described. Other examples can be applied to the above-described embodiments.
FIG. 11 shows another example of the permeation variable member according to the present invention. A porous sheet (permeation variable member) 50 is disposed on the side wall of the air flow path 17 and is attached to one end of the porous sheet 50. The other end is moved up and down with a wire (not shown) provided in a stretched manner, and is arranged on the exposed surface exposed in the flow path of the cathode electrode 13. By loosening the wire, it can be caused to fall on the side wall of the air flow path 17 by its own weight. As the porous sheet, metal, ceramic, plastic, or the like can be used, and the material permeation between the flow path and the membrane electrode assembly can be easily changed depending on the presence or absence of the sheet.

  FIG. 12 also shows another example of the transmission variable member according to the present invention. The porous sheet (transmission variable member) 60 is arranged in a gap 61 provided between the separator 16 and the diffusion layer 21. For example, the controller 30 controls the motor drive and the like based on the difference from the dew point, the humidity condition, and the like, and is reciprocated in the arrow direction. The material permeation between the flow path and the membrane electrode assembly can be easily changed depending on the presence or absence of the porous sheet.

  In the above embodiment, the solid polymer fuel cell has been mainly described as the fuel cell. However, the present invention can also be applied to a direct methanol fuel cell (DMFC) using methanol instead of hydrogen gas as a fuel cell. Then, methanol is supplied to the hydrogen gas passage (fuel passage).

  In addition, the fuel cell of the present invention can be suitably applied as a power supply source for vehicles such as electric vehicles, ships, airplanes, and the like.

1 is a schematic view showing a fuel cell according to a first embodiment of the present invention. It is a schematic sectional drawing of the fuel cell of FIG. 1 is an enlarged schematic cross-sectional view showing a part of a cathode side of a fuel cell according to a first embodiment of the present invention. It is the schematic which shows the arrangement | sequence structure of the permeation | transmission variable membrane which concerns on 1st Embodiment of this invention. (A) is a figure which shows the opening state at the time of the non-voltage application of the transmission variable film which concerns on 1st Embodiment, (b) is a figure which shows the closing state at the time of the voltage application of the transmission variable film of (a). . 3 is a flowchart showing a control routine of a permeation variable membrane on the cathode side of the fuel cell according to the first embodiment of the present invention. 3 is a flowchart showing a control routine of a permeation variable membrane on the anode side of the fuel cell according to the first embodiment of the present invention. (A) is a figure which shows the opening state at the time of the non-voltage application of the transmission variable film which concerns on 2nd Embodiment, (b) is a figure which shows the closing state at the time of the voltage application of the transmission variable film of (a). . It is a schematic block diagram which shows the transmission variable device which concerns on a reference form. It is a figure for demonstrating the operation | movement and positional relationship of the transmission variable board which comprises the transmission variable device of FIG. It is a schematic sectional view showing another example of transparently variable member. It is a schematic sectional view showing another example of transparently variable member. It is a relationship figure which shows the relationship between the current density at the time of the electric power generation driving | operation of 1st Embodiment, and a voltage. It is a relationship figure which shows the relationship between the current density at the time of the electric power generation driving | operation of 1st Embodiment, and resistance.

Explanation of symbols

11 ... ion exchange resin membrane (polymer electrolyte membrane)
DESCRIPTION OF SYMBOLS 12 ... Anode pole 13 ... Cathode poles 14, 16 ... Separator 15 ... Hydrogen gas flow path 17 ... Air flow path 18 ... Membrane electrode assembly 25, 30 ... Transmission variable membrane 26, 31 ... Opening / contracting opening 40 ... Transmission variable device 44, 45 ... opening

Claims (3)

A membrane electrode assembly comprising a polymer electrolyte membrane and an electrode pair sandwiching the polymer electrolyte membrane;
A separator having a plurality of ribs and forming a flow path between each electrode of the electrode pair;
A polymer film provided between the ribs along the electrode surface in the flow path , having an opening, and the opening is expanded and contracted by voltage application, the flow path and the membrane electrode assembly A permeation variable member that varies the material permeation between
A fuel cell. The fuel cell according to claim 1, wherein the permeation variable member is provided on at least a part of an exposed surface of the electrode exposed in the flow path. 3. The fuel according to claim 1, further comprising an electrode pair that has an opening and is disposed so as to sandwich the polymer film that is a transmission variable member so that the opening of the transmission variable member is not covered. battery.

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