JP5019719B2 - Separator unit - Google Patents

Description

  The present invention relates to a separator unit.

  Conventionally, since fuel cells have high power generation efficiency and do not emit harmful substances, they have been put to practical use as power generators for industrial and household use, or as power sources for artificial satellites and spacecrafts. Development is progressing as a power source for vehicles such as passenger cars, buses and trucks. The fuel cell may be of an alkaline aqueous solution type, a phosphoric acid type, a molten carbonate type, a solid oxide type, a direct type methanol or the like, but has a low reaction temperature and is advantageous for miniaturization. Molecular fuel cells are common.

  In this case, a MEA (Membrane Electrode Assembly) in which a solid polymer electrolyte membrane is sandwiched between two gas diffusion electrodes and joined together is used. When one of the gas diffusion electrodes is used as a fuel electrode (anode electrode) and hydrogen gas as a fuel is supplied to the surface of the gas diffusion electrode, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are converted into a solid polymer electrolyte. Permeates the membrane. Further, when the other of the gas diffusion electrodes is an oxygen electrode (cathode electrode) and air as an oxidant is supplied to the surface, oxygen in the air is combined with the hydrogen ions and electrons to generate water. The An electromotive force is generated by such an electrochemical reaction.

  The polymer electrolyte fuel cell has a laminated structure in which a separator that forms a supply passage for a reactive gas such as hydrogen gas as a fuel gas or an oxidant gas such as oxygen is disposed outside the MEA. The separator prevents current gas from passing through the MEAs adjacent to each other in the stacking direction, and collects current to extract the generated current to the outside. In this way, a fuel cell stack is configured by laminating a large number of unit cells composed of MEAs and separators.

By the way, in a fuel cell system, an amount of heat corresponding to the generated electric power is generated in each cell due to an electrochemical reaction. In particular, in a polymer type fuel cell operating at a low temperature, each cell heats up excessively. Cooling means for preventing this is provided (for example, see Patent Documents 1 and 2).
JP-A-8-306371 JP 10-340734 A

  However, in the conventional fuel cell system, a temperature distribution may occur in the stacking direction of the unit cells, and the electrode temperature may increase. In this case, the amount of moisture dissipated to the outside of the MEA through the electrode is excessively increased, and the humidity inside the MEA is lowered, so that the power generation efficiency in each cell is lowered.

  The present invention solves the above-mentioned conventional problems, and locally changes the aperture ratio of the current collector made of a porous body, thereby eliminating the temperature distribution in the fuel cell stack, and To provide a separator unit that can appropriately control the temperature, appropriately maintain the humidity in the fuel cell, have high power generation efficiency, high cooling capacity, and increase the output of the fuel cell. Objective.

Therefore, in the separator unit of the present invention, the fuel gas supplied to the fuel electrode and the oxidizing gas supplied to the oxygen electrode are inserted between the fuel cells in which the electrolyte layer is sandwiched between the fuel electrode and the oxygen electrode. A plate-shaped separator body that is in contact with the fuel electrode or the oxygen electrode, and is provided on one or both sides of the separator body, and has a mesh-shaped opening that serves as a flow path for the fuel gas or oxidizing gas A separator unit having a current collector formed therein, wherein the separator main body is formed with a refrigerant flow path through which a refrigerant flows, and the current collector forms the mesh-shaped opening It was a metal plate made of expanded metal or punched metal by applying a pressing process, contacting the electrode contact portion to the fuel electrode or oxygen electrode, in contact with the separator against the said separator body Parts, and the electrode and the side wall portion is formed between the contact portion and the separator contact portion, and the opening pre-Symbol conductive Gokuto contact opening ratio of the portion other than the electrode contact portion Greater than rate.

In another separator unit of the present invention, furthermore, the current collector, the electrode contact portion, before xenon separator abutting portion, and wherein front SL side wall portion of each of the opening ratio of the following (1 ) Is satisfied.
Opening ratio of electrode contact portion> opening ratio of side wall portion ≧ opening ratio of separator contact portion (1)

  According to the present invention, in the separator unit, the separator unit is sandwiched between the fuel cells in which the electrolyte layer is sandwiched between the fuel electrode and the oxygen electrode, and the coolant channel for cooling the fuel cell is formed inside. A fuel cell having a plate-like separator body that cuts off a gas supplied to the fuel electrode and a gas supplied to the oxygen electrode; and a mesh-like opening provided on one side or both sides of the separator body. A current collector that contacts the electrode or the oxygen electrode and dissipates heat generated in the fuel cell, and the current collector has an electrode with an aperture ratio at the electrode contact portion that contacts the fuel electrode or the oxygen electrode. It is larger than the aperture ratio of parts other than the contact part.

  In this case, the temperature distribution in the fuel cell stack can be eliminated and the temperature of the fuel cell can be controlled appropriately. Therefore, the humidity in the fuel cell can be properly maintained, and the power generation efficiency can be improved. Further, the cooling capacity can be improved and the output of the fuel cell can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention, FIG. 3 is a diagram showing the configuration of the control system for the fuel cell system according to the first embodiment of the present invention, and FIG. It is a figure which shows the structure of the fuel cell stack in the 1st Embodiment of this invention.

  2 and 4, reference numeral 20 denotes a fuel cell stack as a fuel cell (FC), which is used as a power source for vehicles such as passenger cars, buses, trucks, passenger carts, and luggage carts. Here, the vehicle includes a large number of auxiliary devices that consume electricity, such as a lighting device, a radio, and a power window, which are used even when the vehicle is stopped. Since the required output range is extremely wide, it is desirable to use a fuel cell stack 20 as a power source in combination with a secondary battery as a power storage means (not shown).

  The fuel cell stack 20 is of an alkaline aqueous solution type (AFC), phosphoric acid type (PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), direct methanol (DMFC), or the like. However, a polymer electrolyte fuel cell (PEMFC) is desirable.

  More preferably, it is called a PEMFC (Proton Exchange Membrane Fuel Cell) type fuel cell or PEM (Proton Exchange Membrane) type fuel cell using hydrogen gas as fuel and oxygen or air as oxidant. Here, the PEM type fuel cell is generally a stack in which a plurality of cells (Fuel Cell) in which a catalyst, an electrode and a separator are combined on both sides of a solid polymer electrolyte membrane that transmits ions such as protons are connected in series. (Stack).

  In the present embodiment, the fuel cell stack 20 includes a plurality of cell modules 10 as shown in FIG. Note that the arrows in FIG. 4 indicate the flow of refrigerant in a closed cooling system that is one of a plurality of cooling systems for cooling the fuel cell stack 20. The cell module 10 is a unit cell (MEA) 11 to be described later as a fuel cell, electrically connects the unit cells 11 to each other, and the flow path of hydrogen gas introduced into the unit cell 11 and air Thickness direction (diagonal direction connecting the lower left corner and the upper right corner in FIG. 4) as a set of a separator unit 12 to be described later for separating the flow path and a frame (not shown) that supports the unit cell 11 and the separator unit 12. It is configured by overlapping multiple sets.

  FIG. 2 shows an apparatus for supplying hydrogen gas as fuel gas and air as oxidant to the fuel cell stack 20. Although hydrogen gas, which is fuel taken out by reforming methanol, gasoline, or the like by a reformer (not shown), can be directly supplied to the fuel cell stack 20, it is stable and sufficient even during high-load operation of the vehicle. In order to be able to supply an amount of hydrogen gas, it is desirable to supply the hydrogen gas stored in the fuel storage means 73. Thereby, the hydrogen gas is always sufficiently supplied at a substantially constant pressure, so that the fuel cell stack 20 can follow the fluctuation of the load of the vehicle and supply a necessary current. . In this case, the output impedance of the fuel cell stack 20 is extremely low and can be approximated to zero.

  Hydrogen gas is stored in a container containing a hydrogen storage alloy, a container containing a hydrogen storage liquid such as decalin, a fuel storage means 73 such as a hydrogen gas cylinder, a first fuel supply line 21 as a fuel supply line, and The fuel is supplied to the fuel chamber of the fuel cell stack 20 through a second fuel supply line 33 as a fuel supply line connected to the first fuel supply line 21. The first fuel supply line 21 includes a fuel storage means on / off valve 24, hydrogen pressure sensors 27 and 28 as pressure sensors for detecting the pressure of hydrogen gas, and hydrogen for adjusting the pressure of the supplied hydrogen gas. Supply pressure regulating valves 25a and 25b and a fuel supply electromagnetic valve 26 are provided.

  Here, the fuel storage means 73 has a sufficiently large capacity and is capable of always supplying a sufficiently high pressure of hydrogen gas. In the example shown in FIG. 2, a plurality of, for example, three fuel storage means 73 are provided, and a plurality of first fuel supply pipes 21 are connected to each fuel storage means 73. It is branched and is merged on the way to become one. However, the number of the fuel storage means 73 may be singular, plural, or any number in the case of plural.

  The hydrogen gas discharged from the fuel chamber of the fuel cell stack 20 is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A water recovery drain tank 60 as a recovery container is disposed in the fuel discharge line 31. The water recovery drain tank 60 is connected to a fuel discharge line 30 for discharging water and separated hydrogen gas. The fuel discharge line 30 is provided with a suction circulation pump 36 as a fuel forced discharge device. It is installed. The end of the fuel discharge line 30 opposite to the water recovery drain tank 60 is connected to the second fuel supply line 33. Thereby, the hydrogen gas led out of the fuel cell stack 20 can be recovered, supplied to the fuel chamber of the fuel cell stack 20, and reused.

  Further, a fuel discharge line 56 is connected to the water recovery drain tank 60, and a hydrogen exhaust valve 62 is disposed in the fuel discharge line 56, and is discharged from the fuel chamber when the fuel cell stack 20 is started up. The hydrogen gas to be discharged can be discharged into the atmosphere. Note that a hydrogen combustor may be provided in the fuel discharge line 56 as necessary. The hydrogen gas discharged by the hydrogen combustor can be combusted to form water, and then discharged into the atmosphere.

  Here, the hydrogen supply pressure regulating valves 25a and 25b are butterfly valves, regulator valves, diaphragm type valves, mass flow controllers, sequence valves, etc., but hydrogen gas flowing out from the outlets of the hydrogen supply pressure regulating valves 25a and 25b. Any type may be used as long as the pressure can be adjusted to a preset pressure. The pressure adjustment may be performed manually, but is preferably performed by an actuator including an electric motor, a pulse motor, an electromagnet, or the like. The fuel supply electromagnetic valve 26 and the hydrogen exhaust valve 62 are so-called on-off types, and are actuated by actuators such as an electric motor, a pulse motor, and an electromagnet. The fuel storage means original opening / closing valve 24 is operated manually or automatically using an electromagnetic valve. Further, the suction circulation pump 36 may be of any kind as long as it is capable of forcibly discharging hydrogen gas and bringing the fuel chamber into a negative pressure state.

  On the other hand, air as an oxidant is supplied from an air supply fan 75 as an oxidant supply source through an oxidant supply pipe 76 to the oxygen chamber of the fuel cell stack 20. As the oxidant supply source, an air cylinder, an air tank, or the like can be used instead of the air supply fan 75. Further, oxygen can be used as the oxidant instead of air. The air discharged from the oxygen chamber is discharged into the atmosphere through the exhaust manifold 77.

  In addition, in order to maintain the unit cell 11 in a wet state from the air electrode side of the fuel cell stack 20, water can be sprayed into the air supplied to the oxygen chamber. In this case, for example, water supplied from a tank for storing water is sprayed into the air through a water supply nozzle disposed in the middle of the oxidant supply pipe 76 or at the inlet of the oxygen chamber of the fuel cell stack 20. It is desirable. Further, it is desirable to arrange a condenser in the middle of the exhaust manifold 77 to collect and reuse water contained in the air discharged from the oxygen chamber.

  Incidentally, the air supplied to the oxygen chamber of the fuel cell stack 20 may be in a normal pressure state where the pressure is about atmospheric pressure, or in a state where the pressure is increased so as to be higher than the atmospheric pressure. However, in the present embodiment, it is assumed that the atmospheric pressure is about atmospheric pressure. That is, the fuel cell system in the present embodiment is not a so-called pressurization system but an atmospheric pressure system.

  FIG. 2 shows a closed cooling system device that is one of a plurality of cooling systems for cooling the fuel cell stack 20. Connected to the fuel cell stack 20 are a refrigerant supply line 53 through which refrigerant supplied to the fuel cell stack 20 passes and a refrigerant discharge pipe 71 through which refrigerant discharged from the fuel cell stack 20 passes. Yes. A refrigerant storage container 52 is connected to the ends of the refrigerant supply pipe 53 and the refrigerant discharge pipe 71 opposite to the fuel cell stack 20. The refrigerant supply pipe 53 is provided with a refrigerant supply pump 54 as a refrigerant pump and a filter 55. Further, a radiator 72 as a cooling device for cooling the refrigerant and a refrigerant discharge pump 51 as a refrigerant pump are disposed in the refrigerant discharge pipe 71. Here, the refrigerant is, for example, water, but may be antifreeze or any kind of fluid. The refrigerant discharge pump 51 and the refrigerant supply pump 54 may be of any type as long as they can suck and discharge a refrigerant such as water. The filter 55 may be of any type as long as it removes dust, impurities, etc. contained in a coolant such as water.

  And the refrigerant | coolant supplied to the fuel cell stack 20 distribute | circulates in the refrigerant | coolant flow path 45 formed in the separator main body 41 mentioned later of the separator unit 12 in each cell module 10, and cools each cell module 10. FIG. . In this case, the refrigerant circulates in the substantially closed cooling system formed by connecting the refrigerant storage container 52, the refrigerant supply pipe 53, the fuel cell stack 20, and the refrigerant discharge pipe 71, and the unit cell 11. There is no contact. Therefore, since the refrigerant does not come into contact with members such as the solid polymer electrolyte membrane, catalyst, and electrode constituting the unit cell 11, there is a possibility of affecting the members constituting the unit cell 11 such as an antifreeze liquid. Even a refrigerant containing a certain component can be used.

  The hydrogen gas supplied to the fuel chamber of the fuel cell stack 20 and the air supplied to the oxygen chamber also have a function of cooling the fuel cell stack 20. Therefore, an apparatus for supplying hydrogen gas as a fuel gas and air as an oxidant to the fuel cell stack 20 functions as one of the cooling systems for cooling the fuel cell stack 20. And since hydrogen gas and air are consumed or discharged | emitted outside, it can be said that the apparatus which supplies hydrogen gas and air is an open cooling system. In this case, the hydrogen gas and air flow through the cell module 10 while being in contact with members such as a solid polymer electrolyte membrane, a catalyst, and an electrode constituting the unit cell 11, thereby cooling the cell module 10. As described above, when water is supplied into the air supplied to the oxygen chamber, the cooling capacity is improved.

  The fuel cell stack 20 includes a voltmeter 78 that measures a terminal voltage of an electric terminal (not shown), and an exhaust air temperature that detects the temperature of air flowing through the fuel cell stack 20 or air discharged from the fuel cell stack 20. A total of 74 is attached. Water level sensors 52 a and 60 a for detecting the water level are attached to the refrigerant storage container 52 and the water recovery drain tank 60.

  The secondary battery as the power storage means is a so-called battery (storage battery), and a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, a sodium sulfur battery, and the like are common. The power storage means does not necessarily have to be a battery, and electrically stores and discharges energy, such as a capacitor (capacitor) such as an electric double layer capacitor, a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used as long as it has a function. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The fuel cell stack 20 is connected to a load (not shown) and supplies the generated current to the load. Here, the load is generally an inverter device that is a drive control device, and converts a direct current from the fuel cell stack 20 or the power storage means into an alternating current to rotate a vehicle wheel. To supply. Here, the drive motor also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor is rotated by the wheel to generate electric power, the wheel is braked, that is, functions as a vehicle braking device (brake). Then, the regenerative current is supplied to the power storage means, and the power storage means is charged.

  In the present embodiment, the fuel cell system has a control system as shown in FIG. In FIG. 3, reference numeral 81 denotes a type of computer that includes an arithmetic means such as a CPU and MPU, an input / output interface, and the like, and is a control device that controls the operation of the fuel cell system. The control device 81 is connected to a memory 82 as storage means such as a magnetic disk or a semiconductor memory. The control device 81 includes the voltmeter 78, the water level sensors 52a and 60a, the hydrogen pressure sensors 27 and 28, the exhaust air thermometer 74, and the hydrogen gas concentration discharged from the fuel chamber of the fuel cell stack 20. A hydrogen concentration sensor 83 to be detected is connected, and outputs of these various sensors are input to the control device 81. Further, the control device 81 includes a failure in the hydrogen supply pressure regulating valves 25a and 25b, a hydrogen exhaust valve 62, an air supply fan 75, a refrigerant supply pump 54 and a refrigerant discharge pump 51 as a refrigerant pump, and a fuel cell system. An alarm 86 is connected as a device for outputting an alarm when an accident or the like occurs, and the operation of these devices is controlled by the control device 81.

  Next, the configuration of the separator unit 12 will be described in detail.

  FIG. 1 is a diagram showing a configuration of a separator unit of a fuel cell system according to a first embodiment of the present invention, and FIG. 5 is a sectional view showing a configuration of a cell module of the fuel cell system according to the first embodiment of the present invention. FIG. 6 is a diagram showing the power generation performance of the fuel cell system according to the first embodiment of the present invention.

  As shown in FIGS. 1 and 5, the cell module 10 includes a unit cell 11, a fuel chamber as a flow path for hydrogen gas introduced into the unit cell 11, while electrically connecting the unit cells 11 to each other. And a separator unit 12 that separates the oxygen chamber as an air flow path, and a plurality of them are stacked. 1 is an enlarged perspective view showing only a part of the stacked cell modules 10, and FIG. 5 is an enlarged sectional view showing only a part of the stacked cell modules 10. For convenience, the frame supporting the unit cell 11 and the separator unit 12 is omitted.

  As shown in FIG. 5, the unit cell 11 includes a solid polymer electrolyte membrane 11a as an electrolyte layer that is an ion exchange membrane, and an oxygen electrode provided on one side of the solid polymer electrolyte membrane 11a. It consists of an air electrode 11b (cathode electrode) and a fuel electrode 11c (anode electrode) provided on the other side. The air electrode 11b and the fuel electrode 11c are formed on the electrode diffusion layer made of a conductive material that permeates while diffusing the reaction gas, and are supported in contact with the solid polymer electrolyte membrane 11a. And a catalyst layer containing a catalyst material. In FIG. 1, the solid polymer electrolyte membrane 11a, the air electrode 11b, and the fuel electrode 11c are not shown.

  In addition, the separator unit 12 is provided on one side of the separator body 41 as a gas blocking member between the unit cells 11 and the electrode diffusion layer on the air electrode 11b side of the unit cell 11 and is collected. The air electrode side collector 14 as a mesh-like current collector in which a large number of openings that allow electricity and permeate the mixed flow of air and water are formed, and the fuel of the unit cell 11 provided on the other side of the separator body 41 A fuel electrode side collector 15 as a mesh current collector for contacting the electrode diffusion layer on the electrode 11c side and leading out current to the outside. In FIG. 1, the illustration of the fuel electrode side collector 15 is omitted for convenience of explanation.

  The air electrode side collector 14 and the fuel electrode side collector 15 are formed of a conductive plate material, for example, a metal thin plate having a plate thickness of about 0.2 mm. The separator body 41 is a plate-like member made of a thin metal plate having a thinner plate thickness. For example, the separator body 41 has a double structure including a first plate member 41a and a second plate member 41b and is shown inside. Such a refrigerant flow path 45 is formed. As the constituent metal of the air electrode side collector 14, the fuel electrode side collector 15 and the separator body 41, a metal having conductivity and corrosion resistance (for example, stainless steel, nickel alloy, titanium alloy, etc., such as gold plating). The thing which gave the corrosion-resistant electroconductive process is mentioned.

  Further, the air electrode side collector 14 has a generally horizontally long rectangular shape and is made of a porous body. The porous body is, for example, a metal plate material such as expanded metal or punching metal having a mesh-like opening having an opening ratio of 59% or more, and is a corrugated plate having fine ridges formed by pressing. . In addition, the said protruding item | line is provided with the side wall part 14b and the top part 14c. And the said protruding item | line is the arrangement | positioning which extends in the vertical direction of a board | plate material, ie, the up-down direction in FIG. The cross-sectional shape of the ridges is roughly a rectangular wave-shaped cross section, and the base side has a slightly flared shape due to the punching of the press work. The height of the ridges is substantially equal to the thickness of a frame (not shown), so that, in the stacked state, between the electrode diffusion layer on the air electrode 11b side of the unit cell 11 and the side surface of the separator body 41. An air flow path having a predetermined opening area penetrating in the vertical direction is secured. In FIG. 1, an arrow A indicates the flow of air introduced into the unit cell 11 and flowing through the oxygen chamber. Here, the flat surface of the top portion 14c of each protrusion is a contact portion that contacts the side surface of the separator body 41, and the flat surface of the valley portion 14a between the protrusions is on the air electrode 11b side of the unit cell 11. The contact portion is in contact with the electrode diffusion layer.

  The fuel electrode side collector 15 is a porous body having the same dimensions as the air electrode side collector 14, and is made of a metal plate material such as an expanded metal or a punching metal having a mesh-like opening, and is formed by pressing. The corrugated sheet has fine ridges. And the said protruding item | line is provided with the side wall part 15b and the top part 15c similarly to the case of the air electrode side collector 14, is extended in the up-down direction in FIG. 5, and cuts a plate | board surface completely at equal intervals in parallel. It is supposed to be arranged. The cross-sectional shape of the ridges is roughly a rectangular wave-shaped cross-section, and the base side has a slightly flared shape due to die cutting in press working. The height of the ridges is substantially equal to the thickness of a frame (not shown), so that, in the stacked state, the gap between the electrode diffusion layer on the fuel electrode 11c side of the unit cell 11 and the side surface of the separator body 41. A fuel gas flow path having a predetermined opening area penetrating in the vertical direction is secured. Further, the flat surface of the top 15 c of each protrusion is a contact portion that contacts the side surface of the separator body 41, and the flat surface of each trough 15 a is the electrode diffusion on the fuel electrode 11 c side of the unit cell 11. It is the contact part which contacts a layer.

  The air electrode side collector 14 and the fuel electrode side collector 15 are arranged with the separator body 41 interposed therebetween so that the valley portions 14a and 15a are both outside. At this time, the top portions 14c and 15c of the ridges of the air electrode side collector 14 and the fuel electrode side collector 15 are in contact with the separator main body 41, and can be energized with each other. Further, by superposing the air electrode side collector 14 and the fuel electrode side collector 15 on the separator body 41, an air flow path, that is, an oxygen chamber is formed on one side of the separator body 41, and a fuel gas flow path on the other side. That is, a fuel chamber is formed. Then, air is supplied from the oxygen chamber to the air electrode 11b of the unit cell 11, and similarly, hydrogen gas is supplied from the fuel chamber to the fuel electrode 11c of the unit cell 11.

  In the unit cell 11, water moves. That is, when hydrogen gas is supplied as a fuel gas into the fuel chamber in which the fuel electrode side collector 15 is disposed, hydrogen is decomposed into hydrogen ions (protons) and electrons, and the hydrogen ions are accompanied by proton-entrained water and become solid. It penetrates the polymer electrolyte membrane 11a. Further, when the air electrode 11b is used as a cathode electrode and air as an oxidant is supplied into the oxygen chamber, oxygen in the air is combined with the hydrogen ions and electrons to generate water. Furthermore, moisture permeates through the solid polymer electrolyte membrane 11a as reverse diffusion water and moves into the fuel chamber. Here, the reverse diffusion water means that water generated in the oxygen chamber diffuses into the solid polymer electrolyte membrane 11a and permeates through the solid polymer electrolyte membrane 11a in the direction opposite to the hydrogen ions to enter the fuel chamber. It has penetrated until.

  The separator main body 41 is connected to a refrigerant inflow pipe and a refrigerant outflow pipe (not shown), and the refrigerant flowing in from the refrigerant inflow pipe cools through the refrigerant flow path 45 formed inside the separator main body 41, so that the refrigerant outflow Flows out of the tube. The refrigerant is a refrigerant in a closed cooling system device, and is supplied to the fuel cell stack 20 through the refrigerant supply pipe 53 and passes through a flow path (not shown) formed in the fuel cell stack 20. It flows into the inflow pipe. Further, the refrigerant flowing out from the refrigerant outflow pipe flows into the refrigerant discharge pipe 71 through a flow path (not shown) formed in the fuel cell stack 20 and is discharged from the fuel cell stack 20. The shape of the refrigerant flow path 45 may be a straight line, or may be a shape such as a serpentine shape, a spiral shape, or the like in which the refrigerant flow path length is long.

  In the example shown in FIG. 1, the separator body 41 is formed by pasting together a first plate member 41 a and a second plate member 41 b. In this case, a concave groove having a desired shape is formed on the inner surface of the second plate member 41b as one plate material using, for example, a photolithography technique such as chemical etching. And the separator main body 41 provided with the refrigerant | coolant flow path 45 can be obtained by superimposing the 1st board member 41a as the other board | plate material on the surface in which this concave groove was formed. In this case, since the surfaces on both sides of the separator body 41 are joined at various places, the electrical conductivity between the surfaces on both sides can be improved. Further, it is desirable that both outer surfaces of the separator main body 41 are flat surfaces having no irregularities. Thereby, the contact between the outer surface of the separator body 41 and the top portions 14c and 15c of the air electrode side collector 14 and the fuel electrode side collector 15 is ensured, and the separator body 41, the air electrode side collector 14 and the fuel electrode are secured. The thermal conductivity and electrical conductivity with the side collector 15 can be improved.

In the present embodiment, the air electrode side collector 14 and the fuel electrode side collector 15 are formed so that the aperture ratio changes locally. For example, the valley portions 14a and 15a as MEA contact portions that are electrode contact portions that contact the unit cell 11 have the highest opening ratio, and the top portion 14c as a separator contact portion that is a separator contact portion that contacts the separator body 41. And 15c have the lowest opening ratio, and the opening ratios of the side wall parts 14b and 15b as ribs constituting the ribs are intermediate between the opening ratios of the valley parts 14a and 15a and the opening ratios of the top parts 14c and 15c. Has been. Note that the opening ratios of the side wall portions 14b and 15b may be equal to the opening ratios of the top portions 14c and 15c. That is, the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are inclined with respect to the stacking direction of the unit cells 11 (the vertical direction in FIG. 5), and are defined by the following equation (1). Change.
Opening ratio of MEA contact part> Opening ratio of rib part ≧ Opening ratio of separator contact part (1)
Here, since the air electrode side collector 14 and the fuel electrode side collector 15 have mesh openings, the flow of hydrogen gas in the fuel chamber and air in the oxygen chamber is hindered by the air electrode side collector 14 and the fuel electrode side collector 15. It will not be done. That is, the hydrogen gas in the fuel chamber and the air in the oxygen chamber are sufficiently in contact with the electrode diffusion layers of the fuel electrode 11c and the air electrode 11b of the unit cell 11 through the openings of the valleys 14a and 15a that are in contact with the unit cell 11. can do. Furthermore, since the hydrogen gas in the fuel chamber and the air in the oxygen chamber can also move through the openings of the side wall portions 14b and 15b, the flow of hydrogen gas in the fuel chamber and the flow of air in the oxygen chamber are smooth.

  In particular, when water droplets are generated in the oxygen chamber due to generated water or water supplied to the air, and the water droplets block the flow path between the adjacent valley portions 14a, the air passes through the side wall portion 14b. Since it can flow into the adjacent flow path through the opening, the air flow is not hindered. The same applies when water droplets are generated in the fuel chamber due to the reverse diffusion water.

  The unit cell 11 is cooled by a separator body 41 that functions as a cooler for a closed cooling system. That is, the heat generated in the unit cell 11 is transmitted to the separator body 41 through the air electrode side collector 14 and the fuel electrode side collector 15, and is transmitted to the refrigerant flowing through the separator body 41. Similarly, the electricity generated in the unit cell 11 is also well transmitted to the air electrode side collector 14 and the fuel electrode side collector 15.

  The heat generated in the unit cell 11 is transmitted to the valley portions 14a and 15a from the outer surfaces of the air electrode 11b and the fuel electrode 11c, and is transmitted from the top portions 14c and 15c to the separator body 41 through the side wall portions 14b and 15b. Is done. Therefore, if the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are constant in all parts, the thermal conductivity in the air electrode side collector 14 and the fuel electrode side collector 15 is It becomes constant at. In this case, since the areas of the valleys 14a and 15a are larger than the areas of the tops 14c and 15c, the amount of heat per unit area transferred in the tops 14c and 15c is larger than the amount of heat per unit area transferred in the valleys 14a and 15a. Becomes larger, and the thermal resistance at the tops 14c and 15c becomes larger than the thermal resistance at the valleys 14a and 15a. Moreover, also in the side wall parts 14b and 15b, when an aperture ratio is large, thermal conductivity will become low and thermal resistance will become large. In particular, when water is supplied into the air, the side walls 14b and 15b function as cooling fins as a kind of cooler. In this case, if the aperture ratio is large, the area functioning as the cooling fins decreases. In addition, the thermal resistance increases. Then, when the thermal resistance in the valley portions 14a and 15a and the side wall portions 14b and 15b increases, as described in the section “Problems to be solved by the invention”, a temperature distribution occurs in the stacking direction of the unit cells 11, The temperature of the air electrode 11b and the fuel electrode 11c will rise. Therefore, the amount of moisture dissipated to the outside of the unit cell 11 through the air electrode 11b and the fuel electrode 11c is excessively increased, and the humidity inside the unit cell 11 is lowered, so that the power generation efficiency in the unit cell 11 is lowered.

  However, in the present embodiment, the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are inclined with respect to the stacking direction of the unit cells 11 and change as defined by the above formula (1). To do. Therefore, since the top portions 14c and 15c have a low aperture ratio and a high surface density, the amount of heat that can be transmitted per unit area increases, and the thermal resistance decreases. Further, since the side wall portions 14b and 15b also have a low aperture ratio and a high surface density, the amount of heat that can be transferred per unit area increases, and the thermal resistance decreases. As a result, the temperature distribution in the stacking direction of the unit cells 11 is eliminated, and the temperature of the air electrode 11b and the fuel electrode 11c does not rise. Therefore, the unit cell 11 passes through the air electrode 11b as shown by the arrow C in FIG. And the amount of moisture dissipated to the outside of the unit cell 11 through the fuel electrode 11c as indicated by the arrow D in FIG. Therefore, the humidity inside the unit cell 11 can be properly maintained, and the power generation efficiency in the unit cell 11 can be improved.

  FIG. 6 shows a comparison of power generation performance depending on the aperture ratio of the air electrode side collector 14 and the fuel electrode side collector 15 in a low humidification condition, that is, in a state where the unit cell 11 is relatively dry. In FIG. 6, the vertical axis represents the voltage in the unit cell 11 and the horizontal axis represents the current density. A line 47 connecting the experimental results plotted with ▲ indicates a case where the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are constant in all parts, and a line connecting the experimental results plotted with ◆. Reference numeral 48 denotes a case where the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are inclined with respect to the stacking direction of the unit cells 11 and change as defined by the above formula (1). From FIG. 6, when the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 are inclined with respect to the stacking direction of the unit cells 11 and change as defined by the above formula (1), the unit cell 11 It can be seen that the power generation efficiency is improved.

  Further, since the air electrode side collector 14 and the fuel electrode side collector 15 have a mesh-like opening, the flow of hydrogen gas in the fuel chamber and air in the oxygen chamber is hindered by the air electrode side collector 14 and the fuel electrode side collector 15. There is nothing. That is, the hydrogen gas in the fuel chamber and the air in the oxygen chamber are sufficiently in contact with the electrode diffusion layers of the fuel electrode 11c and the air electrode 11b of the unit cell 11 through the openings of the valleys 14a and 15a that are in contact with the unit cell 11. can do. Further, since the hydrogen gas in the fuel chamber and the air in the oxygen chamber can also move through the openings in the side wall portions 14b and 15b, the flow of hydrogen gas in the fuel chamber and the flow of air in the oxygen chamber become smooth. In particular, when water droplets are generated in the oxygen chamber due to generated water or water supplied to the air, and the water droplets block the flow path between the adjacent valley portions 14a, the air is adjacent through the opening of the side wall portion 14b. Therefore, the air flow is not hindered. The same applies when water droplets are generated in the fuel chamber due to the reverse diffusion water.

  Next, the operation of the fuel cell system having the above configuration will be described.

  FIG. 7 is a flowchart showing the start-up operation of the fuel cell system according to the first embodiment of the present invention. FIG. 8 is a flowchart showing the air supply amount control operation of the fuel cell system according to the first embodiment of the present invention. is there.

  First, the operation at startup will be described. In order to start the fuel cell system, the operator turns on a start switch (not shown) (step S1). Then, the refrigerant supply pump 54 and the refrigerant discharge pump 51, that is, the refrigerant pump is turned on (step S2), the refrigerant circulation is started, and the refrigerant flows through the refrigerant channel 45 in the separator body 41. Subsequently, an apparatus for supplying air as an oxidant to the fuel cell stack 20, that is, an air supply system is turned on (step S3). In this case, in order to prevent an abnormal reaction from occurring in the unit cell 11 of the fuel cell stack 20, the amount of air supplied from the air supply fan 75 is controlled to be maximum. Subsequently, an apparatus for supplying hydrogen gas as fuel gas to the fuel cell stack 20, that is, a hydrogen supply system is turned on (step S4), and the start-up operation ends. As a result, the operation shifts to a steady operation, and the current generated by the fuel cell stack 20 is supplied to the load and the secondary battery.

  In the case where the fuel cell system has an apparatus for spraying and supplying water into the air supplied to the oxygen chamber, the air supplied to the oxygen chamber before the hydrogen supply system is turned on. It is desirable to start supplying water into it. This is because, at the time of start-up, air is present in the unit cell 11 regardless of whether the air supply system is on or not, so that hydrogen gas is supplied in a state where the solid polymer electrolyte membrane 11a is dry. This is because abnormal combustion may occur. Therefore, even when abnormal heat is generated due to abnormal combustion, water is supplied before supplying hydrogen gas so that the unit cell 11 is not damaged, and the air electrode 11b of the unit cell 11 is wetted in advance. (Nu) needs to be kept. Thereby, abnormal heat can be converted into the heat of water evaporation, and further, wetting of the solid polymer electrolyte membrane 11a can be promoted to prevent damage to the unit cell 11 beforehand.

In addition, after starting operation is complete | finished, hydrogen gas supply amount control, air supply amount control, and water supply amount control are performed in parallel. In the hydrogen gas supply amount control, the hydrogen supply pressure regulating valves 25a and 25b are adjusted so that hydrogen gas is supplied to the fuel electrode 11c at a predetermined concentration below the explosion limit. Then, the hydrogen exhaust valve 62 closed at the time of startup is opened based on a predetermined rule, the fuel gas whose hydrogen partial pressure is reduced is exhausted, and the atmosphere gas of the fuel electrode 11c is refreshed. The predetermined rule at this time is stored in the memory 82, and the control device 81 reads out the rule from the memory 82 for adjusting the hydrogen supply pressure regulating valves 25 a and 25 b and opening and closing the hydrogen exhaust valve 62. Executed by. The reason why the hydrogen exhaust valve 62 is appropriately opened during operation is that the operation of the fuel cell system is continued with the hydrogen exhaust valve 62 closed, due to the influence of N ₂ , O ₂ or the generated water that passes through the air electrode 11b. This is because the partial pressure of hydrogen consumed at the fuel electrode 11c gradually decreases, and the output voltage of the fuel cell stack 20 also decreases accordingly, and a stable voltage cannot be obtained.

  In the air supply amount control, first, the temperature of the discharged air immediately after being discharged from the fuel cell stack 20 is detected by the discharged air thermometer 74 (step S11). Then, the control device 81 determines whether or not the detected temperature of the exhaust air is 80 [° C.] or less (step S12). Here, if the temperature of the discharged air is not 80 [deg.] C. or lower, i.e., exceeds 80 [[deg.] C.], the unit cell 11 may be seized, so the control device 81 increases the air volume (step S13). . Specifically, the air supply amount is increased by increasing the rotation speed of the air supply fan 75, and the temperature of the air electrode 11b, which is a heat generation source, is decreased.

  On the other hand, when the temperature of the exhaust air is 80 [° C.] or less, the control device 81 detects the load of the fuel cell stack 20, that is, the FC main body (step S14). Then, the control device 81 determines whether or not the supply amount of air, that is, the air volume is optimal (step S15). In this case, the relationship between the load of the fuel cell stack 20 and the air volume required in that state is compared with the relationship stored in the table format in the memory 82 to determine whether the air volume is optimal. To do. If the air volume is not optimal, the control device 81 adjusts the air volume (step S16). Specifically, the air volume is adjusted by adjusting the rotation speed of the air supply fan 75. If the air volume is optimal, the process is terminated.

  In the hydrogen gas supply control, the hydrogen pressure sensors 27 and 28 detect the pressure of the hydrogen gas on the fuel storage means 73 side, and the control device 81 adjusts the hydrogen supply pressure regulating valves 25a and 25b to control the fuel. The pressure of the hydrogen gas supplied to the battery stack 20 is adjusted to a predetermined value. The control device 81 controls the supply of hydrogen gas to the fuel cell stack 20 by controlling the opening and closing of the fuel supply electromagnetic valve 26. Note that when the supply of hydrogen gas to the fuel cell stack 20 is shut off, the fuel supply electromagnetic valve 26 is closed.

  Thus, in the present embodiment, the air electrode side collector 14 and the fuel electrode side collector 15 are formed so that the aperture ratio changes locally, and are inclined with respect to the stacking direction of the unit cells 11. Therefore, the temperature distribution in the stacking direction of the unit cells 11 is eliminated, and the temperature of the air electrode 11b and the fuel electrode 11c does not increase. Therefore, the moisture dissipated to the outside of the unit cell 11 through the air electrode 11b and the fuel electrode 11c. The amount is suppressed. Thereby, the humidity inside the unit cell 11 can be properly maintained, and the power generation efficiency in the unit cell 11 can be improved.

  Further, since the air electrode side collector 14 and the fuel electrode side collector 15 have a mesh-like opening, the flow of hydrogen gas in the fuel chamber and air in the oxygen chamber is hindered by the air electrode side collector 14 and the fuel electrode side collector 15. There is nothing. That is, the hydrogen gas in the fuel chamber and the air in the oxygen chamber are sufficiently supplied to the electrode diffusion layers on the fuel electrode 11c side and the air electrode 11b side of the unit cell 11 through the openings of the valley portions 14a and 15a contacting the unit cell 11. Can contact. Further, since the hydrogen gas in the fuel chamber and the air in the oxygen chamber can also move through the openings in the side wall portions 14b and 15b, the flow of hydrogen gas in the fuel chamber and the flow of air in the oxygen chamber become smooth. In particular, when water droplets are generated in the oxygen chamber due to generated water or water supplied to the air, and the water droplets block the flow path between the adjacent valley portions 14a, the air is adjacent through the opening of the side wall portion 14b. Therefore, the air flow is not hindered. The same applies when water droplets are generated in the fuel chamber due to the reverse diffusion water.

In the present embodiment, the temperature distribution in the stacking direction of the unit cells 11 is eliminated by inclining the aperture ratios of the air electrode side collector 14 and the fuel electrode side collector 15 with respect to the stacking direction of the unit cells 11. However, the temperature distribution in the stacking direction of the unit cells 11 can also be eliminated by forming the air electrode side collector 14 and the fuel electrode side collector 15 from a combination of different materials. In this case, the material forming the air electrode side collector 14 and the fuel electrode side collector 15 is locally changed, and the thermal conductivity of the material forming the valley portions 14a and 15a as the MEA contact portions contacting the unit cell 11 is increased. The lowest thermal conductivity of the material forming the top portions 14c and 15c as the separator contact portions contacting the separator body 41 is the highest, and the thermal conductivity of the material forming the side walls 14b and 15b as the rib portions constituting the ribs. It is formed so that the rate is intermediate between the valley portions 14a and 15a and the top portions 14c and 15c. Note that the thermal conductivity of the material forming the side wall portions 14b and 15b may be equal to the thermal conductivity of the material forming the top portions 14c and 15c. Thereby, the thermal resistance of each part of the air electrode side collector 14 and the fuel electrode side collector 15 is inclined with respect to the stacking direction of the unit cells 11 and changes as defined by the following equation (2).
Thermal resistance of MEA contact portion> Rib portion thermal resistance ≧ Separator contact portion thermal resistance (2)
In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is a figure which shows the structure of the separator unit of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the structure of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the structure of the control system of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the structure of the fuel cell stack in the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the cell module of the fuel cell system in the 1st Embodiment of this invention. It is a figure which shows the electric power generation performance of the fuel cell system in the 1st Embodiment of this invention. It is a flowchart which shows the starting operation | movement of the fuel cell system in the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement of air supply amount control of the fuel cell system in the 1st Embodiment of this invention.

Explanation of symbols

11 Unit cell 11a Solid polymer electrolyte membrane 11b Air electrode 11c Fuel electrode 12 Separator unit 14 Air electrode side collector 14a, 15a Valley part 14b, 15b Side wall part 14c, 15c Top 15 Fuel electrode side collector 20 Fuel cell stack 41 Separator body

Claims (2)

A plate-shaped separator body inserted between the fuel cell sandwiching the electrolyte layer between the fuel electrode and the oxygen electrode, and blocking the fuel gas supplied to the fuel electrode and the oxidizing gas supplied to the oxygen electrode;
A separator provided on one side or both sides of the separator main body in contact with the fuel electrode or the oxygen electrode, and having a mesh-like opening serving as a flow path for the fuel gas or oxidizing gas. A unit,
The separator body, inside which is a refrigerant passage for flowing refrigerant formed, and the current collector is subjected to press working to the metal plate material made of expanded metal or punched metal to form the mesh-like openings An electrode contact portion that contacts the fuel electrode or oxygen electrode, a separator contact portion that contacts the separator body, and a side wall portion between the electrode contact portion and the separator contact portion. and a separator unit before Symbol conductive Gokuto contact opening rate of being larger than the aperture ratio of the portion other than the electrode contact portion. The current collector, the electrode contact portion, before xenon separator abutting portion, and, to claim 1, front SL side wall portion of each of the opening ratio of satisfies the relationship represented by the following formula (1) The separator unit described.
Opening ratio of electrode contact portion> opening ratio of side wall portion ≧ opening ratio of separator contact portion (1)

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