JP4934938B2 - Fuel cell separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a separator for a fuel cell, and more particularly to a separator provided with a flow area for circulating cooling water.
[0002]
[Prior art]
A unit cell of a PEM type fuel cell has a configuration in which a polymer solid electrolyte membrane is sandwiched between a fuel electrode and an air electrode (oxidant electrode). Both the fuel electrode and the air electrode are composed of a catalyst layer containing a catalyst material, and an electrode base material that supports the catalyst layer, supplies a reaction gas, and further functions as a current collector. On the further outside of the fuel electrode and the air electrode, a separator (connector plate) provided with a gas flow groove for uniformly supplying the reaction gas from the outside into the electrode and discharging excess gas to the outside is laminated. This separator collects current to prevent gas permeation and to take out the generated current to the outside.
[0003]
A unit cell is constituted by the fuel cell main body and the separator. In an actual fuel cell system, a stack is formed by stacking a large number of such single cells in series. In the fuel cell main body, heat having a heat amount substantially corresponding to the generated power is generally generated. Therefore, cooling means are provided to prevent the fuel cell body from excessively heating up.
As a cooling means, a nozzle for injecting water is provided in an air manifold for sending air to the air electrode, and cooling is performed using latent heat when water injected with the air sent to the air electrode evaporates. A configuration in which a cooling plate is built in the stack can be mentioned.
[0004]
[Problems to be solved by the invention]
However, in the configuration in which water is injected from the injection nozzle, the water supplied to the surface of the air electrode takes heat from the air electrode itself and cools it. It is difficult to change the cooling capacity by controlling it. In addition, the fuel cell stack is provided with a large number of air supply paths having a small cross-sectional area, and it is extremely difficult to supply water that is uniformly injected into each air supply path.
[0005]
In addition, in the fuel cell air electrode, a temporary excessive water condition may occur, resulting in a shortage of air supply, which may impair voltage stability. In addition, in the conventional direct water injection method, water is intermittently supplied, so the state of the fuel cell (temperature, air flow rate, etc.) may change significantly temporarily at the start of water supply, which may impair voltage stability. There is. Therefore, the operating temperature could not be set high.
Furthermore, in the configuration incorporating the cooling plate, the number of parts increases, and the size of the fuel cell stack itself increases.
An object of the present invention is to provide a fuel cell separator that enables temperature control of the fuel cell more precisely and that can reduce the size of the fuel cell stack.
[0006]
[Means for Solving the Problems]
The present invention that achieves the above object has the following configuration.
(1) A metal plate-like separator subjected to corrosion-resistant conductive treatment of a fuel cell that partitions unit cells of a fuel cell and electrically connects the unit cells in series,
An oxidant gas supply groove formed on one end surface of the separator, and formed by a convex portion in contact with the oxidant electrode of the unit cell;
A cooling channel that is formed in the convex portion of the separator in parallel with the oxidant gas supply groove and that circulates cooling water from one end to the other end of the side edge of the separator;
A through hole formed in a side wall surface of the oxidant gas supply groove, passing through the oxidant gas supply groove and the cooling channel, and supplying cooling water of the cooling channel to the oxidant gas supply groove; Equipped with a fuel cell separator.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, a preferred embodiment of the present invention will be described. FIG. 1 is a side sectional view showing the configuration of a unit unit of a fuel cell using the separator 6 of the fuel cell according to the first embodiment of the present invention, FIG. 2 is a sectional plan view of the separator 6, and the separator of FIG. 6 is an overall front view of FIG. The unit unit of the fuel cell includes a unit cell including a solid polymer electrolyte membrane 5, an air electrode 3 and a fuel electrode 4 that are oxidant electrodes stacked on both sides of the solid polymer electrolyte membrane 5, respectively. A separator 6 overlaid on the air electrode 3 of the unit cell and a separator 7 overlaid on the fuel electrode 4 are provided. That is, the unit cell is configured by sandwiching the solid polymer electrolyte membrane 5 between the air electrode 3 and the fuel electrode 4, and the unit is further sandwiched between the separators 6 and 7.
[0008]
The separators 6 and 7 are made of a material having conductivity and corrosion resistance. For example, a metal, graphite or the like having conductivity and corrosion resistance is used. Examples of the metal having conductivity and corrosion resistance include those obtained by subjecting stainless steel, nickel alloy, titanium alloy or the like to corrosion-resistant conductive treatment.
[0009]
In the separator 6, a plurality of oxidant gas supply grooves are formed in parallel at substantially equal intervals on the surface (one end surface) on the side in contact with the air electrode 3, and the air supply path is overlaid on the air electrode 3. 80 is formed. The air supply path 80 is formed from one long side to the other long side of the separator 6, and both ends are open at each long side part. A partition wall 81 is formed by a convex portion between the air supply paths 80, and an upper end portion 812 thereof is in contact with the air electrode 3.
[0010]
The separator 6 includes a plate-like main body 60 in which an air supply path 80 and a partition wall 81 are provided, and a cooling flow path formed along the air supply path 80 that is an oxidant gas supply groove in the main body 60. 82 is provided. Water circulates in the cooling channel 82 as a cooling medium for cooling the fuel cell. The cooling flow paths 82 are respectively formed along a plurality of air supply paths 80 formed in the separator 6, and one end of the cooling flow path 82 is connected to the supply path 84 as shown in FIG. 4. The other ends are connected to the discharge path 85, respectively. The supply path 84 is connected to the supply line 52 of the water supply system 50 provided outside the fuel cell stack 2, and the discharge path 85 is connected to the return line 54, and the water that has not been supplied to the air supply path 80. Is returned to the water tank 53, and the cooling water is circulated between the fuel cell stack 2 and the water tank 53. In this way, the cooling water flows from one end of the side edge portion of the separator 6 to the other end.
[0011]
A through-hole 83 communicates between the air supply path 80 and the cooling flow path 82 as a path that is a supply means for supplying water to the air supply path 80. A plurality of through holes 83 are provided at equal intervals, and cooling water flowing in the cooling flow path 82 flows into the air supply path 80 through the through holes 83.
The water supplied from the through-hole 83 to the air supply path 80 exhibits a cooling effect due to latent heat when evaporating, prevents the air electrode 3 from drying, and can always maintain a wet state.
[0012]
Here, the cooling water flowing in the cooling flow path 82 does not necessarily have to be filled in the cooling flow path 82 without a gap, and may have a flow rate that can flow along the inner wall of the cooling flow path 82. Therefore, for example, when flowing through the side surface 821 in which the through hole 83 is formed, water flows out from the through hole 83 to the air supply path 80. However, when flowing through the different side surface, the water flows into the air. In some cases, it does not flow out to the supply path 80. However, if water flows along the inner wall of the cooling flow path 82, the separator 6 is cooled and a sufficient cooling effect can be obtained.
[0013]
The separator 7 on the fuel electrode 4 side is formed with a gas supply path 9 through which fuel gas flows. The gas supply path 9 is formed in a direction orthogonal to the air supply path 80 in a state in which a unit unit is configured. A flow path similar to the cooling flow path 82 through which the cooling medium provided in the separator 6 flows can also be provided in the separator 7.
[0014]
In this embodiment, the air supply path 80 is configured to be positioned along the vertical direction in a state in which the fuel cell unit unit is set in a use state. With such a configuration, the cooling water supplied to the air supply path 80 can be dropped downward and easily discharged from the air supply path 80.
[0015]
As shown in FIG. 5, the fuel cell stack 2 is configured by stacking a plurality of fuel cell unit units configured as described above, that is, connecting them in series. In the configuration of the separator 6, the cooling water may flow in the direction opposite to the air flow direction in the air supply path 80. The configuration of the fuel cell separator 6 described above may be other configurations as described below. As a second reference embodiment, the discharge path 85 is not provided, and the cooling water supplied to the cooling flow path 82 may all flow out to the air supply path 80 through the through hole 83. In this case, for example, sea urchin by that shown in Figure 6, along the end side of parallel opposing separator 6 (upper side and lower side), the supply passage 84a, the 84b respectively, each supply passage 84a , 84b, every other cooling channel 82a, 82b may be connected alternately. In this configuration, the cooling water flows from the upper side to the lower side in the cooling channel 82a, and the cooling water flows from the lower side to the upper side in the cooling channel 82b. That is, the cooling water flows in the opposite direction.
[0016]
Since the cooling water flows in the flow path while exchanging heat, the temperature of the cooling water rises toward the downstream side, and the cooling effect decreases. However, as in this embodiment, the separator 6 can be cooled more uniformly by alternately reversing the flow direction of the cooling water.
Alternatively, the discharge passage 85 may not be provided, and the lower end of the cooling passage 82 may be opened at the lower end side of the separator 6 and the cooling water may be discharged from the lower end side of the separator 6 to the outside. In this case, the drainage can be collected in a water collection tray provided on the lower side of the fuel cell stack 2 and returned to the tank 53 described later.
[0017]
As a third reference embodiment, as shown in FIG. 7, the cooling flow path 82 c may be formed in a direction intersecting the air supply path 80.
As an embodiment of the present invention , as shown in FIG. 8, a cooling channel 82 may be formed in the partition wall 81. Since the partition wall 81 is in contact with the air electrode 3, if the cooling channel 82 is formed in the partition wall 81, the position of the refrigerant approaches the air electrode 3, and the cooling effect is improved. In this case, the through hole 83 communicating with the air supply path 80 is formed in the side wall surface 811 of the air supply path 80. By providing the through hole 83 in the side wall surface 811, the cooling water supplied to the air supply path 80 can easily come into contact with the air electrode 3, and the effect of maintaining the electrode in a wet state can be reliably exhibited.
[0018]
As a fourth reference embodiment, as shown in FIG. 9, a cooling channel 82 is formed in the partition wall 81, and a through hole 83 is formed in an upper end portion (contact surface) 812 of the partition wall 81 with the air electrode 3. May be configured. In this configuration, the cooling water is supplied directly from the through hole 83 to the air electrode 3, and drying of the air electrode 3 can be prevented. As a fifth reference embodiment, as shown in FIG. 10, the separator 6 includes an air supply path constituting member 62 formed so that a plane cross-section is corrugated, and a flat plate stacked on the back side thereof. It can also be set as the structure provided with the back member 61 of the shape. A planar cooling flow path 82 d is formed in the gap between the back member 61 and the air supply path constituting member 62, and a groove-shaped flow path 82 e is formed in the partition wall 81. By setting it as such a structure, the range with which cooling water is filled increases and the cooling effect improves. Further, the through hole 83 can be formed on both the bottom surface 801 in the air supply path 80 and the side wall surface 811 of the air supply path 80.
[0019]
Next, the configuration of the fuel cell system using the fuel cell stack 2 configured as described above will be described.
As shown in FIG. 11, the fuel cell system 1 is mainly composed of a fuel cell stack 2, a fuel supply system 10 including the hydrogen storage alloy 11, an air supply system 40, a water supply system 50, and a load system 70. .
In the fuel supply system 10, the hydrogen released from the hydrogen storage alloy 11 through the hydrogen supply path 20 is sent to the hydrogen gas flow path 9 of each unit unit of the fuel stack 2. A hydrogen pressure regulating valve 21 is provided in the hydrogen supply path 20 to regulate the hydrogen gas released from the hydrogen storage alloy 11. Reference numeral 23 denotes a hydrogen supply electromagnetic valve 23 that controls opening and closing of the hydrogen supply path 20. The hydrogen gas pressure immediately before being supplied to the fuel cell stack 2 is monitored by a hydrogen source pressure sensor 25.
[0020]
In the fuel supply system 10, the hydrogen gas discharged from the fuel cell stack 2 is released to the atmosphere via the hydrogen exhaust path 30. The hydrogen exhaust passage 30 is provided with a check valve 31 and an electromagnetic valve 33. The check valve 31 prevents air from entering the fuel electrode of the fuel cell stack 2 through the hydrogen exhaust path 30. The electromagnetic valve 33 is intermittently driven to achieve complete combustion of hydrogen.
[0021]
The air supply system 40 supplies air from the atmosphere to the air flow path 8 of the fuel cell stack 2, and exhausts the air discharged from the fuel cell stack 2 through the water condenser 51. The air supply path 41 is provided with a fan 43 and sends air from the atmosphere to the air manifold 45. Air flows from the manifold 45 into the air supply path 8 of the fuel cell stack 2 and supplies oxygen to the air electrode 3. The air discharged from the fuel cell stack 2 is condensed and recovered by the water condenser 51 and released to the atmosphere. The temperature discharged from the fuel cell stack 2 is monitored by an exhaust temperature sensor 47.
[0022]
Most of the cooling water sent from the cooling water cooling passage 82 to the air supply passage 80 reaches the water condenser 51 while maintaining the liquid state, and is sent to the tank 53 as it is to be collected. A part of the supplied water evaporates and is condensed in the water condenser 51 and collected. In addition, it is thought that some water vapor | steam contained in exhaust air originates in the reaction water accompanying the electric power generation reaction of the fuel cell stack 2. FIG.
[0023]
The water supply system 50 pumps the water in the tank 53 by a pump 64 to the cooling water supply passage 84 of each fuel cell unit unit via the pipe 52, and a part of the supplied cooling water is supplied to each fuel cell unit unit. From the discharge path 85 to the tank 53 via the pipe 54. In each fuel cell unit, water supplied from the through hole 83 to the air supply path 80 is collected by the water condenser 51 and returned to the tank 53. Of course, since it is impossible to completely close the water supply system 50, the water level in the tank 53 is monitored by the water level sensor 56, and when this water level exceeds a predetermined threshold, water is replenished from the outside. A heater 57 and an antifreezing electromagnetic valve 58 are attached to the tank 53 so that the water in the tank 53 does not freeze in winter. An electromagnetic valve 65 is attached to the pipe connecting the water condenser 51 and the tank 53 to prevent the water in the tank 53 from evaporating.
[0024]
The output of the pump 64 is controlled in accordance with the temperature of the exhaust air detected by the exhaust temperature sensor 47, the amount of circulating cooling water is adjusted, and the temperature of the fuel cell stack 2 can be maintained at a desired temperature.
The load system 70 takes out the output of the fuel cell stack 2 to drive the load such as the motor 77. The load system 70 is provided with a relay 71 for switching and a secondary battery 75 as an auxiliary output source, and a rectifying diode 73 is interposed between the secondary battery 75 and the relay 71. Note that the output of the fuel cell stack 2 itself is constantly monitored by the voltage sensor 75. Based on this monitoring result, opening and closing of the hydrogen exhaust solenoid valve 33 is controlled by a control circuit (not shown).
[0025]
【Effect of the invention】
According to the first aspect of the present invention, since the cooling flow path through which the cooling water flows is provided in the separator, the cooling efficiency can be increased without increasing the size of the fuel cell structure. Moreover, each part of a separator can be cooled more uniformly and temperature control can be made more precise.
By forming the cooling channel in parallel with the gas supply channel, the cooling water is circulated along the electrode where reaction heat is generated, and the cooling efficiency is further improved.
[0026]
By forming the flow path of the cooling water in the partition which is the convex part, the cooling water flows in a position closer to the electrode, and the cooling efficiency is improved.
Since the through hole is formed in the side wall surface of the oxidant gas supply groove, water can be more reliably brought into contact with the electrode, and the wet state of the electrode can be easily maintained.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a fuel cell unit unit constituting a fuel cell.
FIG. 2 is a partial sectional plan view of a separator of a fuel cell according to a reference embodiment .
FIG. 3 is an overall front view of a separator of a fuel cell according to a reference embodiment .
FIG. 4 is a partially enlarged front view of a separator of a fuel cell according to a reference embodiment .
FIG. 5 is a partially enlarged perspective view of a fuel cell stack.
FIG. 6 is an overall front view of a separator of a fuel cell in a reference embodiment.
FIG. 7 is a partial cross-sectional plan view of a separator of a fuel cell in a reference embodiment.
FIG. 8 is a partial cross-sectional plan view of a separator of a fuel cell in an embodiment of the present invention .
FIG. 9 is a partial cross-sectional plan view of a separator of a fuel cell in a reference embodiment.
FIG. 10 is a partial cross-sectional plan view of a fuel cell separator according to a reference embodiment.
FIG. 11 is a schematic diagram showing a configuration of a fuel cell system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell stack 3 Air electrode 4 Fuel electrode 5 Solid polymer electrolyte membrane 6 Separator 7 Separator 80 Air supply path (oxidant gas supply groove)
81 Bulkhead (convex)
82 Cooling channel 83 Through hole 10 Fuel supply system 40 Air supply system 50 Water supply system 70 Load system

Claims (1)

A metal plate-like separator subjected to a corrosion-resistant conductive treatment of a fuel cell that partitions unit cells of a fuel cell and electrically connects the unit cells in series,
An oxidant gas supply groove formed on one end surface of the separator, and formed by a convex portion in contact with the oxidant electrode of the unit cell;
A cooling channel that is formed in the convex portion of the separator in parallel with the oxidant gas supply groove and that circulates cooling water from one end to the other end of the side edge of the separator;
A through hole formed in a side wall surface of the oxidant gas supply groove, passing through the oxidant gas supply groove and the cooling channel, and supplying cooling water of the cooling channel to the oxidant gas supply groove; Equipped with a fuel cell separator.

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