JP2008041611A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a water from staying in a circulation pump. <P>SOLUTION: A fuel cell system has a circulation pump 25 in a circulation route composed of a fuel gas supply passage 201B and a gas discharge passage 202, where the fuel gas supply passage 201B supplies a fuel gas to a fuel cell stuck 100, and the gas discharge passage 202 sends a discharge gas from the fuel cell stack 100 back to the fuel gas supply passage 201B. A flow sensor S5 detects a discharge quantity of the circulation pump 25. When a flow rate becomes a predetermined value or less, the fuel cell system determines that a condensation water is left in the circulation pump 25, to supply a dry high pressure fuel gas from a suction inlet of the circulation pump 25 and to remove the left condensation water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system having a circuit for circulating fuel gas supplied to a fuel cell stack.

  Conventionally, in a fuel cell using a polymer electrolyte membrane, there are a fuel chamber and an oxygen chamber on both sides of the electrolyte membrane, and the fuel gas in the fuel chamber passes through the fuel electrode or the oxidizing gas (mainly air) in the oxygen chamber. Oxygen inside) is ionized through the oxygen electrode, and the ions are taken out through the electrolyte membrane to obtain electric power.

In the conventional fuel cell system, the purpose of reusing unreacted gas in the fuel gas discharged from the fuel cell stack connected in series by stacking a plurality of fuel cells, etc., and the fuel gas and the oxidizing gas For the purpose of preventing the water generated on the oxygen electrode side due to the reaction with the reverse diffusion to the fuel electrode side and staying in the fuel chamber to circulate by supplying the exhaust gas from the fuel electrode to the fuel gas flow path Has been adopted.
JP 2006-40846 A (reference numbers 30, 31, 33, 36 in FIG. 1)

  As described in Patent Document 1, the fuel gas is discharged to the outside of the fuel cell stack 20 through the fuel discharge pipe 31. A fuel discharge line 30 is connected to the fuel discharge line 31, and a suction circulation pump 36 as a pump is disposed in the fuel discharge line 30. Thereby, the hydrogen gas led out of the fuel cell stack 20 is recovered and supplied to the fuel gas flow path of the fuel cell stack 20 for reuse. On the other hand, in the fuel cell stack, produced water is generated by the reaction between oxygen and hydrogen, which is the fuel gas, and this produced water passes through the polymer electrolyte membrane and reversely osmosis to the fuel chamber side. The phenomenon of staying occurs.

  The water accumulated in the fuel chamber is discharged together with the gas into the discharge pipe by the flow of the fuel gas, and is collected by the drain tank 60 or the like. However, the discharged fuel gas is in a saturated state of water vapor, and it is not sufficient to recover only by the drain tank, and it can be easily condensed by changes in atmospheric pressure and temperature. In particular, in the circulation pump, the fuel gas is agitated, so that condensation occurs due to a change in pressure. There is a problem that the condensed water stays in the circulation pump and lowers the discharge capacity of the pump.

  The object of the present invention is to provide a fuel cell system that suppresses the retention of water in the circulation means.

The present invention for solving the above problems has the following configuration.
(1) A fuel chamber into which fuel gas is introduced and an oxidizing gas chamber having an inlet through which oxidizing gas is introduced and an outlet through which oxidized gas after reaction is discharged are disposed adjacent to each other via an electrolyte layer. A fuel cell that generates electricity by reacting with oxidant gas;
A fuel gas supply path for supplying fuel gas from a fuel gas supply source to the fuel chamber;
An exhaust circuit for returning exhaust gas from the fuel chamber to the fuel gas supply channel;
A circulation means provided in the exhaust circulation path for sending exhaust gas to the fuel gas supply path;
A dry gas supply source for supplying a dry gas having a humidity lower than the humidity of the fuel gas in the exhaust circuit;
Dry gas supply means for adjusting the supply of dry gas to the circulation means;
A fuel cell system comprising: dry gas supply control means for controlling supply of dry gas by the dry gas supply means.

(2) The dry gas supply source is the fuel gas supply source,
The dry gas supply means includes a dry gas supply path that connects the fuel gas supply path and an exhaust gas circulation path upstream of the circulation means;
The fuel cell system according to (1), further including an on-off valve provided in the dry gas supply path.

  (3) The fuel cell system according to (1) or (2), wherein the gas pressure of the dry gas supplied by the dry gas supply means is higher than the gas pressure in the exhaust circuit.

(4) having a gas flow rate detecting means in a gas circulation path constituted by the fuel gas supply source, the fuel chamber, and the exhaust circulation path;
The fuel cell system according to any one of (1) to (3), wherein the dry gas supply control unit controls the supply of dry gas based on the gas flow rate detected by the gas flow rate detection unit.

  (5) The fuel cell system according to any one of (1) to (4), wherein the dry gas supply control unit performs control to supply dry gas immediately before performing the operation stop operation.

  According to the first aspect of the present invention, when the water vapor contained in the fuel gas discharged from the fuel chamber is condensed in the circulation means and stays there, the dry gas having a low humidity is supplied from the dry gas supply source to the circulation means. By supplying, it is possible to dry the inside of the circulation means and remove the staying water, and it is possible to maintain the ability of the circulation means.

  According to the second aspect of the invention, by using the dry gas as the fuel gas supplied from the fuel gas supply source, the fuel gas can be supplied simultaneously with the removal of the water in the circulation means. Further, it is not necessary to provide a separate dry gas supply source, and the configuration can be simplified.

  According to the third aspect of the present invention, the gas pressure supplied by the dry gas supply means is higher than the gas pressure in the exhaust circulation path, so that the flow rate of the dry gas flowing in the circulation means is the normal circulation flow. The flow rate becomes higher than the flow rate, and the dry gas flow rate causes an action of blowing off the remaining water, thereby further improving the removal effect of the remaining water.

  According to the invention described in claim 4, since the discharge capacity of the circulation means decreases as the amount of water staying in the circulation means increases, the dry gas is supplied according to the gas flow rate in the circulation path. The water in the circulation means can be removed using the dry gas efficiently.

  According to the fifth aspect of the present invention, the capacity of the circulation means can be ensured by supplying the dry gas and removing the water in the circulation means immediately before starting the operation of stopping the operation. It becomes possible to make negative pressure. Thereby, the fuel gas in the fuel chamber can be reliably used as the replacement gas.

  Next, a preferred embodiment of the present invention will be described. This embodiment is a fuel cell system mounted on an electric vehicle. FIG. 1 is a block diagram showing a configuration of a fuel cell system 1 of the present invention. As shown in FIG. 1, the fuel cell system 1 is roughly configured by a fuel cell stack 100, a fuel supply system 10 including a hydrogen storage tank 11, an air supply system 12, a water supply system 50, and a load system 7. The

  The configuration of the fuel cell stack 100 will be described. The fuel cell stack 100 is configured by alternately stacking fuel cell unit cells 15 and fuel cell separators 13. 2 is an overall front view showing the fuel cell separator 13, FIG. 3 is a partial cross-sectional plan view of the fuel cell stack 100 composed of the fuel cell separator 13 (AA cross-sectional view in FIG. 2), and FIG. FIG. 5 is a partially enlarged perspective view showing the positional relationship between the current collecting members 3, 4 and the partition wall 7.

  The separator 13 is in contact with the electrode of the unit cell 15 and collects current collecting members 3 and 4 for taking out current to the outside, and frame bodies 8 and 9 that are externally mounted on the peripheral ends of the current collecting members 3 and 4. And a partition wall 7 interposed between the current collecting members 3 and 4. The partition wall 7 prevents direct contact (mixing) of the fuel gas and the oxidizing gas. The current collecting members 3 and 4 and the partition 7 which are current collecting plates are made of metal. The constituent metals of the current collecting members 3 and 4 and the partition walls 7 are metals having electrical conductivity and corrosion resistance, and examples thereof include those obtained by subjecting stainless steel, nickel alloy, titanium alloy or the like to corrosion-resistant conductive treatment. Examples of the corrosion-resistant conductive treatment include gold plating. The current collecting member 3 is in contact with the fuel electrode of the unit cell 15, and the current collecting member 4 is in contact with the oxygen electrode. The current collecting member 3 is formed with a plurality of projecting convex portions 32 by pressing.

  The convex portions 32 are arranged at equal intervals along the long side of the plate material in the short side direction. Hydrogen channels 301 are formed between the convex portions 32 by grooves formed between the convex portions 32 arranged along the long side (lateral direction in FIG. 2), as shown in FIG. As shown, the hydrogen flow path 302 is formed by the groove 33 formed on the back side of the convex portion 32. The surface of the apex portion of the convex portion 32 is a contact portion 321 with which the fuel electrode contacts. Since the current collecting member 3 is a net, the fuel electrode can supply the fuel gas through the hole 320 even in the portion where the contact portion 321 contacts. Further, as shown in FIG. 5, hydrogen gas can also flow between the hydrogen channel 301 and the hydrogen channel 302 via the holes 320. Both ends of the current collecting member 3 extend to a hydrogen supply path (17a or 17b) formed when the separators 13 are stacked.

  The current collecting member 4 has a plurality of convex portions 42 formed by pressing. The convex portions 42 are continuously formed linearly in parallel (vertical direction) to the short sides of the plate material, and are arranged at equal intervals. A groove is formed between the convex portions 42 to form an air flow path 40 through which air flows. The surface of the apex portion of the convex portion 42 is an abutting portion 421 with which the oxygen electrode contacts. Since the current collecting member 4 is a net, the oxidizing gas (oxygen in the air) can be supplied through the holes 420 even at the portion where the contact portion 421 contacts. The back side of the convex portion 42 is a groove-like hollow portion 41.

  The current collecting members 3 and 4 as described above are overlapped and fixed so that the convex portions 32 and the convex portions 42 are on the outside. At this time, the back side surface 34 of the current collecting member 3 and the back side surface 403 of the air flow path 40 are in contact with the front and back surfaces of the partition wall 7, respectively, and are in a state where they can be energized with each other. As shown in FIG. 3, the air flow path 40 is overlapped with the unit cell 15, and a tubular flow path is formed by closing the groove opening 400, and the inner wall of the air flow path 40 is formed. A part of is composed of oxygen electrodes. Oxygen and water are supplied from the air flow path 40 to the oxygen electrode of the unit cell 15. Further, oxygen and water are supplied from the hollow portion 41 to the oxygen electrode through the mesh of the current collecting member 4. The oxygen supplied to the oxygen electrode is oxygen contained in the air passing through the air flow path 40 and the hollow portion 41.

The opening on one end side of the air flow path 40 is an introduction port 43 through which air and water flow, and the opening at the other end is a discharge port 44 through which air and water flow out. Moreover, the opening part of the one end side of the hollow part 41 becomes the inflow opening port 45 into which air and water flow in, and the opening part of the other end becomes the outflow opening port 46 through which air and water flow out. In the above configuration, the air flow paths 40 and the hollow portions 41 are alternately arranged in parallel and are adjacent to each other with the side wall 47 interposed therebetween. The air flow path 40 from the inlet 43 to the outlet 44, the hollow portion 41 from the inflow opening 45 to the outflow opening 46, and an assembly of these, an oxygen chamber (oxidizing gas) for supplying oxygen to the solid electrolyte membrane Function as a room).
Vent holes 73 are formed at both ends of the partition wall 7, and the long sides of the vent holes 73 are formed to have the same length as the short sides of the current collecting member 3. (17a or 17b) is configured.

  Frame members 8 and 9 are overlaid on the current collecting members 3 and 4, respectively. As shown in FIG. 2, the frame 8 overlaid on the current collecting member 3 is configured to have the same size as the partition wall 7, and a window 81 for accommodating the current collecting member 3 is formed at the center. . Further, in the vicinity of both end portions, a hole 83 is formed at a position that matches the flow hole 73 of the partition wall 7. Between the holes 83 a and 83 b and the window 81, there is a recess for housing the current collecting member 3. The hydrogen flow path 84 is formed. In addition, a concave portion whose contour is formed along the window 81 is formed on the plane opposite to the surface that contacts the current collecting member 3, and a storage portion 82 for storing the unit cell 15 is provided. Yes. The fuel chamber 30 is defined by the surface of the fuel electrode of the unit cell 15 accommodated in the accommodating portion 82, a plurality of alternately arranged hydrogen flow paths 301 and 302, and the window 81. Thus, the fuel chamber is provided adjacent to the fuel electrode, and the oxygen chamber is provided adjacent to the oxygen electrode.

The frame body 9 overlaid on the current collecting member 4 is configured to have the same size as the frame body 8 and the partition wall 7, and a window 91 for accommodating the current collecting member 4 is formed at the center. In addition, holes 93 a and 93 b are formed in the vicinity of both ends at positions corresponding to the flow holes 73 of the partition wall 7.
Grooves 941 and 951 are respectively formed along a pair of opposing long sides of the frame body 9 on the surface of the frame body 9 on which the current collection member 4 is overlapped. The grooves 941 and 951 include the current collection member 4. Upper and lower ends are accommodated. A passage formed by the grooves 941 and 951 and the current collecting member 4 communicates with the oxygen chamber.

  In addition, a concave portion having a contour formed along the window 91 is formed on the plane opposite to the surface of the frame body 9 that contacts the current collecting member 4, and the storage unit in which the unit cell 15 is stored. 92 is provided. A rectangular opening 940 (introduction port covering region (cross section is rectangular)) is formed on the upper surface of the fuel cell stack 100 by the assembly of the openings at the upper end of the current collecting member 4 of the groove 941. Air flows from air manifold 54 to 940.

  FIG. 6 is an enlarged cross-sectional view of the unit cell 15. The unit cell 15 includes a solid polymer electrolyte membrane 15a, and an oxygen electrode 15b and a fuel electrode 15c that are oxidant electrodes stacked on both side surfaces of the solid polymer electrolyte membrane 15a, respectively. The membrane 15a is sandwiched between the oxygen electrode 15b and the fuel electrode 15c. The solid polymer electrolyte membrane 15 a is formed in a size that matches the storage portions 82 and 92, and the oxygen electrode 15 b and the fuel electrode 15 c are formed in a size that matches the windows 91 and 81. Since the thickness of the unit cell 15 is extremely thin compared to the thicknesses of the frame bodies 8 and 9 and the current collecting members 3 and 4, the unit cell 15 is shown as an integral member in the drawing. The inner wall of the air flow path 40 is subjected to hydrophilic treatment. The surface treatment may be performed so that the contact angle between the inner wall surface and water is 40 ° or less, preferably 30 ° or less. As the treatment method, a method of applying a hydrophilic treatment agent to the surface is taken. Examples of the treating agent to be applied include polyacrylamide, polyurethane resin, and titanium oxide (TiO2).

  The separators 13 are configured by holding the current collecting members 3 and 4 by the frames 8 and 9 configured as described above, and the fuel cell stack 100 is configured by alternately stacking the separators 13 and the unit cells 15. . FIG. 7 is a partial plan view of the fuel cell stack 100. A large number of inlets 43 are opened on the upper surface of the fuel cell stack 100, and air flows into the inlets 43 from the air manifold 54 and is injected from the nozzles 55 in the air manifold 54 as will be described later. Water flows in at the same time. The nozzle 55 supplies water to the fuel cell stack 100 in the form of droplets (mist). The air and liquid water flowing from the inlet 43 cool the current collecting members 3 and 4 by latent heat cooling. Further, on the bottom surface of the fuel cell stack 100, a large number of outlets 44 are opened at positions opposed to the inlets 43 shown in FIG. 7, from which air and water supplied by injection are supplied. leak. That is, many inlets 43 are opened vertically and horizontally on the upper surface of the fuel cell stack 100, and similarly, many outlets 44 are opened vertically and horizontally on the bottom surface of the fuel cell stack 100.

  Next, the configuration of the fuel cell system shown in FIG. 1 will be described. The configuration of the fuel supply system 10 will be described. A hydrogen storage tank 11 that is a fuel gas cylinder is connected to a gas intake port of the fuel cell stack 100 via fuel gas supply channels 201A and 201B. A hydrogen storage tank 11 is connected to one end of the fuel gas supply channel 201A, and a hydrogen source valve 18, a primary pressure sensor S0, a regulator 19, a pressure sensor S1, a source electromagnetic valve 20, a hydrogen pressure regulating valve 21, and a supply electromagnetic valve 22 are provided. One end of the fuel gas supply channel 201B is connected to the other end of the fuel gas supply channel 201A. The other end of the fuel gas supply channel 201B is connected to the IN of the gas inlet 201B of the fuel cell stack 100. In addition to the other end of the fuel gas supply path 201A, one end of a gas discharge path 202 described later is connected to one end of the fuel gas supply path 201B. In the fuel gas supply path 201B, a supply electromagnetic valve 22, a pressure sensor S2, a safety valve Vsf, and a flow rate sensor S5 are sequentially arranged in the flow direction of the gas fuel gas, and on the upstream side of the supply electromagnetic valve 22, One end of the outside air flow path 205 is connected. A filter is connected to the other end of the outside air flow path 205, and impurities are filtered from the outside air flowing in by this filter. The outside air flow path 205 is provided with an outside air electromagnetic valve 23.

  The gas discharge port OUT of the fuel cell stack 100 is connected to the other end of a gas discharge channel 202 that is an exhaust circuit. The fuel gas supply channel 201B and the gas discharge channel 202 constitute a circulation path that connects the gas inlet IN and the gas outlet OUT of the fuel cell stack 100. In the gas discharge channel 202, a trap 24, a circulation electromagnetic valve 26, and a circulation pump 25 as a circulation means are arranged in this order from the gas discharge port side of the fuel cell stack 100. A water level sensor S10 is attached to the trap 24, and one end of the gas outlet path 203 is connected to the trap 24. The other end of the gas outlet path 203 is connected to the air duct 124. An exhaust solenoid valve 27 is provided in the gas outlet passage 203.

  Both ends of the startup flow path 204 are connected to the upstream side of the hydrogen pressure regulating valve 21 and the suction port side of the circulation pump 25, and the startup solenoid valve 29 is provided in the startup flow path 204. The startup flow path 204 functions as a dry gas supply path, and the startup electromagnetic valve 29 functions as an on-off valve that controls the flow of the dry gas.

  Next, the air supply system 12 will be described. The air supply system 12 includes an air introduction path 123, an air manifold 54, and an air duct 124 that is an air discharge path. In the air introduction path 123, a filter 121, an air fan 122, and an air manifold 54 are provided in this order along the inflow direction.

On the downstream side of the air introduction path 123, nozzles 55 for injecting cooling water into the openings 940 in the form of mist are provided at positions immediately before the air manifold 54. The nozzle 55 may be provided in the air manifold 54. The air manifold 54 divides and flows the air into the inlet 43 of the fuel cell stack 100.
An exhaust manifold 53A1 is connected to the outlet 44 of the fuel cell stack 100, and the air discharged from the outlet 44 is merged by the exhaust manifold 53A1 and sent to the air duct 124.

  The air duct 124 guides the air flowing out from the outlet 44 to the outside via the condenser 51. A condenser 51 to which a fan is attached is provided at the end of the air duct 124, and a filter 125 is subsequently connected. The condenser 51 extracts moisture from the air. Further, the water evaporated in the fuel cell stack 100 in the water supplied from the nozzle 55 is also collected here. The air duct 124 is provided with an exhaust temperature sensor S9, and the temperature in the fuel cell stack 100 is indirectly detected.

  Next, the water supply system will be described. The water supply system 50 includes a water tank 531 as water storage means, a water conduit 57 that guides the water collected by the condenser 51 to the water tank 531, and a water supply passage 56 that guides the water in the water tank 531 to the nozzle 55. A collection pump 62 is provided in the water conduit 57. The recovery pump 62 sends the water extracted from the exhaust gas by the condenser 51 to the water tank 531. The water supply path 56 is provided with a filter 64 and a pump 61 for supplying water to the nozzle 55 as water supply means. The water tank 531 is provided with a tank water level sensor S7 which is a storage amount detection means.

  A load system 7 is connected to the fuel cell stack 100, and electric power output from the fuel cell stack 100 is supplied to the load system 7. The electrode of the fuel cell stack 100 is connected to an inverter 73 via a wiring 71, and electric power is supplied from the inverter 73 to a load such as a motor. An auxiliary power supply 76 is connected to the inverter 73 via an IGBT (Insulated Gate Bipolar Transistor) 75 which is a switch means. The auxiliary power source 76 can be constituted by, for example, a battery or a capacitor. The load system 7 is provided with a voltage sensor S4 for detecting the output voltage of the fuel cell stack 100 and a current sensor S3 for detecting the output current.

  The control system of the fuel cell system 1 includes a control device as dry gas supply control means for controlling the start electromagnetic valve 29 that is an on-off valve. The control device includes other sensors S0 to S5, S7, S9, and S10, the electromagnetic valves 20, 22, 23, 26, 27, and 29, the circulation pump 25, the pumps 61 and 62, and the air fan. 122, the fan of the condenser 51, the inverter 73, and IGBT75 are connected. Note that an ignition switch (not shown) is connected to this control device, and an instruction signal for driving or stopping a drive motor for driving the vehicle is input.

In the fuel cell system configured as described above, the content of the dry control for removing the water in the circulation pump 25 will be described based on the flowcharts shown in FIGS.
The operation during steady power generation will be described with reference to FIG. During steady power generation, the circulation pump 25 is driven, the solenoid valve 20, the supply solenoid valve 22, and the circulation solenoid valve 26 are opened, and the solenoid valve 29, the exhaust solenoid valve 27, and the outside air solenoid valve 23 are closed. The flow rate of hydrogen gas, which is the fuel gas in the fuel gas supply channel 201B, is measured by the flow rate sensor S5 (step S101). When the circulating pump 25 is controlled to be in a state of steady power generation, when the measured flow rate is less than a value (for example, 10 L / min) indicating a normal discharge amount of the circulating pump 25, the inside of the circulating pump 25 It is determined that a certain amount of water has accumulated in step S103. The fuel gas discharged from the fuel cell stack 100 is saturated with water vapor from the generated water, and when the fuel gas is compressed in the circulation pump 25, condensation easily occurs. For this reason, the dew condensation water in the circulation pump 25 is accumulated. When the condensed water is accumulated to some extent, the capacity of the pump is reduced, so that the retention of water can be determined by the reduction in the discharge amount.

  Accordingly, if it is greater than 10 L / min, it is determined that there is no stagnation of water, and the process returns to step S101. If it is 10 L / min or less, control for removing water from the circulation pump 25 is started. That is, the circulation solenoid valve 26 is closed, and the exhaust solenoid valve 27 and the start solenoid valve 29 are opened (step S105).

  By this operation, the hydrogen gas upstream of the hydrogen pressure regulating valve 21, that is, the hydrogen gas having a gas pressure higher than the gas pressure of the gas discharge flow path 202 where the circulation pump 25 is disposed, enters the suction port side of the circulation pump 25. Supplied. Since this hydrogen gas is a gas accumulated in the hydrogen storage tank 11, it is dry and has a lower humidity than at least the gas in the gas discharge passage 202 discharged from the fuel cell stack 100. ing. By supplying such dry gas to the circulation pump 25 at a flow rate faster than the flow rate in the gas discharge passage 202, the water in the circulation pump 25 is blown off by the fast gas flow, and the humidity is high. Since it is low, it vaporizes into the gas and is removed from the circulation pump 25.

  The supplied hydrogen gas flows into the fuel chamber 30 in the fuel cell stack 100 from the fuel gas supply channel 201B, and the gas in the fuel chamber 30 passes through the exhaust electromagnetic valve 27 and is discharged from the gas outlet passage 203. The Since the gas in the hydrogen storage tank 11 is used as the dry gas having the action of blowing off and drying the water in the circulation pump 25, water removal and fuel supply can be performed simultaneously. Thereby, the discharge of water in the trap 24 can be completed simultaneously. Furthermore, the nitrogen gas that has permeated from the oxygen chamber to the fuel chamber side during power generation can be simultaneously discharged from the gas outlet passage 203.

Thereafter, the circulation solenoid valve 26 is opened, and the start solenoid valve 29 and the exhaust solenoid valve 27 are closed (step S107). Thereby, the circuit of the fuel gas supply system returns to the state at the time of steady power generation. Then, again, the flow rate of the hydrogen gas is measured by the flow rate sensor S5 (step S109), and it is determined whether or not the flow rate has returned to a value indicating the normal discharge amount of the circulation pump 25 (step S111). If not, steps S105, S107, and S109 are executed again, and this is repeated until the flow rate returns.
When the flow rate returns to the normal value (Yes in step S111), the dry control ends, and the process returns to the flow during steady power generation.

  In steps S103 and S111, it is determined that water has accumulated in the circulation pump 25 by measuring the flow rate of hydrogen gas, but the water retention has reached a predetermined value using another determination method. You may judge that. For example, the output voltage for each unit cell of the fuel cell stack 100 may be detected by a voltage sensor, and it may be determined that the flow rate of the circulation pump 25 has decreased based on the detected value. When the flow rate of the hydrogen gas is reduced, the output voltage is lowered. Therefore, when the output voltage becomes a predetermined value or less, the dry control (steps S105 to S107) may be started.

Alternatively, the current consumption of the circulation pump 25 is detected by a current sensor, and when the current consumption reaches a predetermined value or more, it is determined that the discharge amount of the circulation pump 25 has decreased, and the dry control may be started. .
In addition, instead of directly or indirectly detecting the discharge amount of the circulation pump 25, it is possible to perform dry control periodically. Further, when the water level sensor S10 of the trap 24 reaches a predetermined value and water needs to be discharged, dry control may be performed.

  The operation of the fuel supply system 10 at start-up will be briefly described. The original solenoid valve 20, the start solenoid valve 29, the supply solenoid valve 22, and the exhaust solenoid valve 27 are closed, and the circulation solenoid valve 26 and the outside air solenoid valve 23 are opened. Then, the circulation pump 25 is driven to discharge the replacement gas in each fuel chamber 30 of the fuel cell stack 100 (the gas replaced in place of the fuel gas, for example, air in the stopped state), while discharging the fuel chamber 30. Make the inside negative pressure. When the pressure reaches a predetermined value, the circulation solenoid valve 26 and the outside air solenoid valve 23 are closed, and then the original solenoid valve 20, the start solenoid valve 29, and the supply solenoid valve 22 are opened. As a result, hydrogen gas is instantaneously filled into each fuel chamber 30 and a reaction is possible. At this time, since the supplied hydrogen gas is supplied from the starting flow path 204 through the circulation pump 25, the circulation pump 25 is reset to a clear state without water retention at the time of activation.

  Next, the operation at the time of stop will be described based on the flowcharts shown in FIGS. In the steady operation state, the original solenoid valve 20, the supply solenoid valve 22, and the circulation solenoid valve 26 are open, and the circulation pump 25 is driven. When an operation for turning off the ignition switch is detected (step S201), the circulation solenoid valve 26 is closed, and the exhaust solenoid valve 27 and the start solenoid valve 29 are opened (step S203). Thereby, the water in the circulation pump 25 is removed as described in step S105 described above.

Next, the original solenoid valve 20 is closed, the exhaust solenoid valve 27 is closed, and the start solenoid valve 29 is closed (step S205). Thereby, the supply of hydrogen gas to the fuel cell stack 100 is stopped.

  The supply solenoid valve 22 is closed, and the circulation solenoid valve 26 and the outside air solenoid valve 23 are opened (step S207). As a result, the fuel gas in the fuel chamber 30 of the fuel cell stack 100 is discharged to the outside through the fuel gas supply channel 201B and the outside air channel 205, and the upstream side of the fuel chamber 30 and the circulation pump 25 is pressurized. It goes down.

The pressure sensor S2 checks the pressure in the fuel chamber 30 (step S209), and determines whether or not the negative pressure value (for example, −70 kPa) is sufficient to replace the pressure with the replacement gas. (Step S211).
If the predetermined negative pressure value has been reached, the circulation pump 25 is stopped and the circulation electromagnetic valve 26 is closed (step S213). Thereby, each fuel chamber 30 and the trap 24 in the fuel cell stack 100 located downstream from the supply electromagnetic valve 22 are maintained in a negative pressure state.

Next, the supply electromagnetic valve 22 is opened (step S215). As a result, outside air flows into the trap 24 and each fuel chamber 30 which are in negative pressure at once, and the inside of the fuel chamber 30 is replaced with replacement gas (air).
The voltage of the fuel cell stack 100 is detected by the voltage sensor S4 (step S217), and it is determined whether or not the voltage drops to a predetermined value (for example, 5.0 V) or less (step S219). The decrease in the output voltage of the fuel cell stack 100 means that no power generation reaction has occurred, and suggests that the gas in the fuel chamber 30 has been replaced with air. In step S219, Yes), the outside air solenoid valve 23, the supply solenoid valve 22, and the exhaust solenoid valve 27 are closed (step S221), and the control operation is terminated.

1 is a block diagram showing a fuel cell system 1 of the present invention. It is a whole front view which shows the separator for fuel cells. It is a fragmentary sectional top view (AA sectional view) of the fuel cell stack comprised with the fuel cell separator. It is the whole fuel cell separator rear view. It is a partial expansion perspective view which shows the positional relationship of a current collection member and a partition. It is an expanded side sectional view which shows the structure of a unit cell. It is a fragmentary top view which shows the structure of the upper surface of a fuel cell stack. It is a control flowchart at the time of steady power generation. It is a control flowchart at the time of stop operation. It is a control flowchart at the time of stop operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 100 Fuel cell stack 3 Current collection member 4 Current collection member 48 Projection part 7 Bulkhead 11 Hydrogen storage tank 13 Separator 123 Air introduction path 22 Supply solenoid valve 23 Outside air solenoid valve 25 Circulation pump 26 Circulation solenoid valve 29 Start solenoid valve 531 Water tank 53A1 Exhaust manifold 54 Air manifold 55 Nozzle 61 Supply pump

Claims (5)

A fuel chamber into which the fuel gas is introduced and an oxidizing gas chamber having an inlet through which the oxidizing gas is introduced and an outlet through which the oxidized gas after the reaction is discharged are adjacent to each other via the electrolyte layer, and the fuel gas and the oxidizing gas A fuel cell that generates electricity by reacting with
A fuel gas supply path for supplying fuel gas from a fuel gas supply source to the fuel chamber;
An exhaust circuit for returning exhaust gas from the fuel chamber to the fuel gas supply channel;
A circulation means provided in the exhaust circulation path for sending exhaust gas to the fuel gas supply path;
A dry gas supply source for supplying a dry gas having a humidity lower than the humidity of the fuel gas in the exhaust circuit;
Dry gas supply means for adjusting the supply of dry gas to the circulation means;
A fuel cell system comprising: dry gas supply control means for controlling supply of dry gas by the dry gas supply means. The dry gas supply source is the fuel gas supply source;
The dry gas supply means includes a dry gas supply path that connects the fuel gas supply path and an exhaust gas circulation path upstream of the circulation means;
The fuel cell system according to claim 1, further comprising an on-off valve provided in the dry gas supply path.   The fuel cell system according to claim 1 or 2, wherein a gas pressure of the dry gas supplied by the dry gas supply means is higher than a gas pressure in the exhaust circuit. A gas flow rate detecting means in a gas circulation path constituted by the fuel gas supply source, the fuel chamber, and the exhaust circulation path;
The fuel cell system according to any one of claims 1 to 3, wherein the dry gas supply control means controls the supply of dry gas based on the gas flow rate detected by the gas flow rate detection means. The fuel cell system according to any one of claims 1 to 4, wherein the dry gas supply control means controls to supply a dry gas immediately before the operation stop operation is performed.

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