JP4815900B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system for controlling a load of a polymer electrolyte fuel cell.

  In general, in a fuel cell using a polymer electrolyte membrane, fuel gas or oxidizing gas is ionized on both sides of the electrolyte membrane, and the ions permeate the electrolyte membrane to cause an electrochemical reaction.

  The fuel cell stack is for obtaining electric power by reacting a fuel gas and an oxidizing gas through a polymer electrolyte membrane. This fuel cell stack is configured by alternately laminating unit cells each having a polymer electrolyte membrane sandwiched between a fuel electrode and an oxidation electrode, and a separator made of a conductive material. An electrochemical reaction is caused by passing a fuel gas between them and an oxidizing gas between the separator and the oxidizing electrode.

  In such a fuel cell system, when the fuel cell (fuel cell stack) generates electric power, the fuel (mainly hydrogen) changes to hydrogen ions on the anode side, moves through the electrolyte membrane, reaches the cathode side, and oxygen To produce water. At this time, if the amount of water in the electrolyte is insufficient (dry up), the movement of hydrogen ions is inhibited, making it difficult to exhibit the performance of the fuel cell (FIGS. 18 and 19).

In general, the higher the load of power generation, the greater the amount of heat generated in the fuel cell, and the higher the temperature and the saturated water vapor pressure tend to increase (FIG. 18). Therefore, dry-up tends to occur during continuous power generation at a high load (FIG. 19). ). In particular, in a fuel cell system mounted on a moving body (vehicle or the like), avoidance of dry-up is an important issue. As a technique for avoiding such dry-up, a fuel cell system that can perform optimum start-up control even when the solid polymer membrane fuel cell is in a dry state has been proposed.
JP 2001-332280 A.

  However, the conventional technique has a problem that a system for avoiding dry-up is increased in size and complexity. An object of the present invention is to provide a fuel cell system capable of avoiding dry-up without increasing the size and complexity of the system.

The above object is achieved by the present invention described below.
(1) a polymer electrolyte fuel cell;
Load control means connected to the polymer electrolyte fuel cell, and applying a load of a pattern that periodically repeats a low load and a high load to the polymer electrolyte fuel cell;
A power storage means connected to the polymer electrolyte fuel cell and storing electric power generated by the polymer electrolyte fuel cell;
A load device connected to the polymer electrolyte fuel cell and the power storage means, and operated by receiving power from the polymer electrolyte fuel cell or the power storage means;
Determining means for determining an operation timing of the load control means ;
The determination means includes detection means for detecting dry-up of the electrolyte membrane of the polymer electrolyte fuel cell,
The load control unit applies a load to the polymer electrolyte fuel cell at the operation timing determined by the determination unit when dry-up is detected by the detection unit .

(2) The fuel cell system according to (1), wherein the load having a pattern in which the low load and the high load are periodically repeated is a load represented by a triangular wave.

( 3 ) The above-mentioned apparatus comprising means for comparing the remaining amount of electricity stored in the electricity storage means with a predetermined remaining amount, and releasing vehicle output control or vehicle output control based on the comparison result. The fuel cell system according to (1) or 2 .

( 4 ) The polymer electrolyte fuel cell is
A plurality of separators having current collector plates that are in contact with the fuel electrode of the unit cell and form a fuel gas flow path are stacked alternately with the unit cell, and the inlets of the fuel gas flow paths are connected by an inlet manifold and the outlets are connected to each other. Are connected by outlet manifolds to form a plurality of modules, and the outlet manifold of one module and the inlet manifold of the other module are connected so that the flow direction of fuel gas is reversed between adjacent modules. connect the to include a fuel cell stack having a pair of electrode plates which are superposed so as to be energized at both ends in the stacking direction of the unit cells from (1) above, wherein according to any one of (3) Fuel cell system.

According to the first aspect of the present invention, the polymer electrolyte fuel cell (hereinafter referred to as fuel cell) is provided with a load that periodically repeats a low load and a high load (regardless of the required load of the load device) . If the load of this pattern is adopted, the temperature of the fuel cell rises by the operation in the high load region, but the temperature rise is suppressed by the operation in the low load (low load region), and the total The temperature will settle to a constant value. That is, since continuous power generation with a high load is eliminated, it is possible to reduce the loss of moisture in the electrolyte due to an increase in fuel cell temperature due to continuous power generation with a high load. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated. Further, by preventing dry-up, it is possible to prevent damage to the fuel cell electrode and improve durability, and furthermore, it becomes possible to perform a (high-speed) high-load operation that becomes impossible when dry-up is performed.

The load device (for example, a motor) is also connected to a power storage means (for example, a battery), and operates by receiving power from at least the solid polymer fuel cell or the power storage means. Therefore, even if the actual required load of the load device and the power generated by the fuel cell do not match, the load that periodically repeats the low load and the high load is adopted, so the actual required load of the load device and the fuel cell generate power. If the power does not match, insufficient power can be supplied from the power storage means , so that the load device can be operated appropriately.

Since it is a load with a pattern that periodically repeats low and high loads, continuous power generation at high loads is eliminated, and continuous power generation at high loads increases the fuel cell temperature and loses moisture in the electrolyte. Can be reduced. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated.
Further, the load control means applies a specific pattern load to the fuel cell at the determined operation timing (for example, every time a timer is counted for a certain time, that is, periodically), thus preventing dry-up in advance. be able to.
Further, when the dry-up is detected, the load control means gives the fuel cell a load having a pattern in which the low load and the high load are periodically repeated, so that the adverse effects due to the dry-up can be minimized.

According to the invention described in claim 2, since the load having a pattern in which the low load and the high load are periodically repeated is a load represented by a triangular wave, continuous power generation is not performed at the high load, and the load is continuously generated at the high load. By generating electricity, it is possible to reduce the loss of moisture in the electrolyte due to an increase in the temperature of the fuel cell. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated.

According to the third aspect of the present invention, the means for comparing the remaining amount of electricity stored in the electricity storage means with a predetermined remaining amount, and performing vehicle output control or canceling vehicle output control based on the comparison result. Therefore, even if the remaining amount of electricity stored in the electricity storage means falls below a predetermined remaining amount, it is possible to ensure the minimum required vehicle output by controlling the vehicle output. Furthermore, during the vehicle output control, the power storage means can be charged by applying a load having a pattern in which a low load and a high load are periodically repeated .

According to the fourth aspect of the present invention, a fuel cell having a specific structure can be adopted as the solid polymer fuel cell.

  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 fuel supply system 10 of a system 1 using a fuel cell stack 100.

  The configuration of the stack 100 included in the fuel cell system 1 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 partial sectional side view (BB sectional view in FIGS. 2 and 3), FIG. 5 is a partial sectional side view of the fuel cell separator 13 (CC sectional view in FIGS. 2 and 3), and FIG. FIG. 3 is an overall rear view of the fuel cell separator 13.

  The separator 13 includes current collecting members 3 and 4 for contacting the electrodes of the unit cell 15 and 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. I have. The current collecting members 3 and 4 that are current collecting plates are made of metal. The constituent metal is a metal having conductivity and corrosion resistance, and examples thereof include stainless steel, nickel alloy, titanium alloy and the like subjected to corrosion-resistant conductive treatment.

  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. As shown in FIG. 7, the current collecting member 3 in contact with the fuel electrode is made of a rectangular wire mesh material, and a large number of holes 320 are formed on the surface thereof. Further, the current collecting member 3 is formed with a plurality of projecting convex portions 32 formed by pressing. In the drawings other than FIG. 7, in order to make the contents of the drawing easy to understand, the current collecting member 3 is shown as a plate material, and the display of the holes 320 of the mesh material is omitted in the cross-sectional view and the like.

  The convex portions 32 are arranged at equal intervals along the long side of the plate material in the short side direction. A hydrogen channel 301 is formed between the convex portions 32 by grooves formed between the convex portions 32 arranged along the long side (lateral direction in FIG. 2). A hydrogen flow path 302 is formed by the groove 33 formed in. 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. In addition, hydrogen gas can flow between the hydrogen channel 301 and the hydrogen channel 302 via the holes 320.

Through holes 35 are formed at both ends of the current collecting member 3. When the separators 13 are stacked, the through holes 35 form a hydrogen supply path.
The current collecting member 4 is made of a rectangular plate material, and a plurality of convex portions 42 are formed by pressing. The convex portions 42 are continuously formed in a straight line parallel 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. Further, the back side of the convex portion 42 is a groove-like hollow portion 41, and both ends of the hollow portion 41 are closed. Holes 48 are formed at both ends of the current collecting member 4. When the separators 13 are stacked, the holes 48 form a hydrogen supply path.

  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 each other, so that they can be energized with each other. As shown in FIGS. 3 and 5, 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. A part of the inner wall of 40 is composed of an oxygen electrode. Oxygen and water are supplied from the air flow path 40 to the oxygen electrode of the unit cell 15.

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. The air flow path 40 and its aggregate from the inlet 43 to the outlet 44 function as an oxygen chamber (air chamber) for supplying oxygen to the solid electrolyte membrane.
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.

  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 current collecting member 3, and a window 81 for accommodating the convex portion 32 is formed at the center. ing. Further, in the vicinity of both ends, a hole 83 is formed at a position matching the flow hole 35 of the current collecting member 3, and between the hole 83 and the window 81, the side in contact with the current collecting member 3 is formed. A recess is formed in the plane, and a hydrogen flow path 84 is provided. 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 fuel electrode surface of the unit cell 15 housed in the housing portion 82, the 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 a window 91 for accommodating the convex portion 42 is formed at the center. Further, in the vicinity of both end portions, holes 93 are formed at positions corresponding to the holes 83 of the frame body 8. Grooves are formed along the pair of opposing long sides of the frame 8 on the surface of the frame 8 on which the current collecting member 4 is overlapped. By overlapping the current collecting members 3 and 4, the air flow passage 94 is formed. , 95 is configured. One end of the air flow passage 94 is connected to an opening 941 formed on the end surface on the long side of the frame body 8, and the other end is connected to the introduction port 43 of the air flow path 40.

The upstream air flow passage 94 has a tapered inner surface 942 so that the cross-sectional area gradually decreases from the opening 941 side to the air flow path 40 side. It is easy to incorporate. On the other hand, one end of the downstream air flow passage 95 is connected to the outlet 44 of the air flow path 40, and the other end is connected to an opening 951 formed on the long side end surface of the frame 8. The air flow passage 95 has an end inner wall as a tapered surface 952 so that the cross-sectional area gradually decreases from the opening 951 side toward the air flow path 40 side. Even when the fuel cell stack 100 is tilted, the tapered surface 952 maintains the discharge of water.
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.

  FIG. 8 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 (TiO 2).

  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. 9 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 from the air manifold flows into the inlets 43 and water injected from the nozzles in the air manifold simultaneously flows. The air and water flowing in from the introduction port 43 cool the current collecting members 3 and 4 by latent heat cooling.

  FIG. 10 is an overall plan view of the fuel cell stack 100. The fuel cell separator 13 configured as described above includes a plurality of modules 130-1 to n (unit bodies) stacked by a predetermined number, and the fuel cell stack 100 is configured by stacking a plurality of the modules 130. Composed. A separator 14 having a shielding plate 16 sandwiched between the current collecting member 3 and the current collecting member 4 is interposed between the adjacent modules 130-m and 130-m + 1. The shielding plate 16 includes a hole 161a or 161b having the same shape as the cross-sectional shape of the hydrogen passages 17a and 17b at a position corresponding to either the hydrogen passage 17a or the hydrogen passage 17b. The shielding plate 16 has conductivity and does not hinder the flow of electricity within the fuel cell stack 100.

  On the other hand, when the shielding plate 16 has the holes 161a, the flow of hydrogen gas in the hydrogen passage 17b is blocked by the shielding plate 16. When the shielding plate 16 has the hole 161b, the hydrogen gas flow in the hydrogen passage 17a is blocked by the shielding plate 16. The shielding plate 16 is, in order from the hydrogen gas inflow side to the outflow side, the shielding plate 16 provided with the holes 161b, the shielding plate 16 provided with the holes 161a, and so on. Alternatingly arranged. As described above, by alternately shielding one of the hydrogen passage 17a and the hydrogen passage 17b for each of the modules 130-1 to 130-n, the supplied hydrogen gas circulates in each fuel chamber 30 in units of modules 130. Specifically, in the first module 130, hydrogen gas flows in each fuel chamber 30 from the hydrogen passage 17a toward the hydrogen passage 17b, and in the next module 130, from the hydrogen passage 17b toward the hydrogen passage 17a, Hydrogen gas flows in each fuel chamber 30, and in the next module 130, hydrogen gas flows in each fuel chamber 30 from the hydrogen passage 17 a toward the hydrogen passage 17 b... The distribution direction changes.

  That is, the fuel cell stack 100 is formed in the module 130 in which the unit cells 15 and the separator 13 are stacked, and is formed in the stacking direction of the separator 13 in the module 130, and is located on both sides of the fuel chamber 30. Each of the fuel chambers 30 has a pair of hydrogen passages 17a and 17b, and is formed by stacking modules 130. One hydrogen of each module 130 is interposed between adjacent modules 130. A communicating part (hole 161a (or 161b)) communicating between the passages 17a, 17a (or 17b, 17b) and a blocking part (shielding) for blocking hydrogen flow between the other hydrogen passages 17b, 17b (or 17a, 17a) Plate 16), and the communication portion and the blocking portion are sequentially arranged in the direction of stacking of the stacked modules 130, one hydrogen passage 17a, 7a (or 17b, 17b) and the other hydrogen passages 17b, 17b (or 17a, 17a) are alternately provided, and hydrogen gas flows through the fuel chambers 30 between the pair of hydrogen flow paths (17a, 17b). The direction is alternately changed in the opposite direction for each module 130.

  FIG. 11 is a longitudinal sectional view of the hydrogen flow passage 17a and the hydrogen flow passage 17a. Each of the modules 130-1 to 130-n has a hydrogen flow path 17a, a hydrogen flow path 84a communicating with the hydrogen flow path 17a, and a hydrogen flow path 17b and a hydrogen flow path 84b communicating with the hydrogen flow path 17b. Manifold is configured. When the hydrogen passage 17a is a fuel inflow passage, a manifold constituted by the hydrogen passage 17a and the hydrogen circulation path 84a serves as an inlet manifold, and a manifold constituted by the hydrogen passage 17b and the hydrogen circulation path 84b serves as an outlet. It becomes a manifold. Conversely, when the hydrogen passage 17a is a fuel outflow passage, the manifold constituted by the hydrogen passage 17a and the hydrogen circulation path 84a serves as an outlet manifold, and the manifold constituted by the hydrogen passage 17b and the hydrogen circulation path 84b It becomes the inlet manifold.

Further, even in the unit modules 130-1 to 130-n, it is possible to suppress a difference in hydrogen gas flow rate between the fuel chambers 30 constituted by the stacked separators 13 and unit cells 15. Furthermore, since the hydrogen gas supplied to the fuel cell stack 100 repeatedly flows in the modules 130-1 to 130-n, the chance of contacting the fuel electrode of the fuel chamber 30 increases, and the reaction efficiency is improved.
Electrode plates are stacked at both ends in the stacking direction of the modules 130-1 to 130-n and connected to the electrodes of the fuel cell stack 100.

  FIG. 12 is a schematic diagram showing a configuration of the module 130-n through which the fuel gas finally passes. One electrode plate D is overlaid on one end face of the module 130-n. The fuel gas sent from the adjacent module 130- (n-1) is supplied from the hydrogen flow passage 17a to the fuel chamber 30 constituted by each separator. When fuel gas flows from the hydrogen flow path 17a into a flow path constituted by a large number of fuel chambers 30, the gas flow direction is suddenly changed to form a bent flow path. Usually, when the flow path is curved, there is a difference in flow rate between the outside and the inside of the curve, and the flow rate is fast on the outside and slow on the inside. Similarly, there is a difference in the gas flow rate between the inside and outside of the bent channel, and the outside is fast and the inside is slow.

  However, the reference voltage may be detected from the unit cells of other modules 130-1 to (n-1). In this case, it is possible to select the unit cell 15 of the fuel chamber 30 that is less susceptible to heat radiation by the electrode plate D and that can obtain a more sufficient gas flow. In this case, if an abnormality occurs in units of modules, the abnormality can be detected by comparing the output voltages.

  FIG. 13 is a front view of the fuel cell stack 100. An introduction guide path 18a as a rectifying means is provided in the hydrogen gas inflow portion of the hydrogen passage 17a. In the introduction guide path 18a, the gas introduction port 181a has the same cross-sectional shape as the fuel gas supply flow channel 201, and the gas outlet port 182a has the same cross-sectional shape as the hydrogen passage 17a. The flow path 183a from the gas inlet 181a to the gas outlet 182a guides the gas flow so that the width of the cross section gradually increases and the gas flow velocity distribution in the cross section of the hydrogen passage 17a becomes uniform. Furthermore, the flow path 183a is provided with a rectifying plate 184a, which is configured to guide hydrogen gas while suppressing pressure loss of the gas flow. The gas outlet 182a is connected to the fuel supply port 171a.

FIG. 14 is a rear view of the fuel cell stack 100. A lead-out guide path 18 b is provided in the hydrogen gas outflow portion of the fuel cell stack 100. In the lead-out guide path 18b, the gas introduction port 181b has the same cross-sectional shape as the hydrogen passage 17a, and the gas lead-out port 182b has the same cross-sectional shape as the hydrogen lead-out path 203. The flow path 183b from the gas inlet 181b to the gas outlet 182b gradually decreases in cross-sectional width, and the flow path 183a is provided with a rectifying plate 184a while suppressing pressure loss of the gas flow. The hydrogen gas is guided. The gas inlet 181b is connected to the fuel outlet 171b.
With the configuration of the fuel cell stack 100 as described above, the pressure loss of the hydrogen gas flowing into the fuel cell stack 100 is suppressed, and the hydrogen gas is uniformly supplied to the fuel chamber 30 of each fuel cell separator 13.

Next, the configuration of the fuel cell system 1 will be described with reference to FIG.
The fuel supply system 10 includes a high-pressure hydrogen tank 11 that is a fuel cylinder, a fuel gas supply channel 201, and a gas supply valve V <b> 1 provided in the fuel gas supply channel 201. One end of the fuel gas supply channel 201 is connected to the high-pressure hydrogen tank 11, and the other end is connected to the fuel supply port 171 a of the fuel cell stack 100 via the introduction guide path 18 a of the fuel cell stack 100.

  The fuel gas supply channel 201 sends hydrogen released from the high-pressure hydrogen tank 11 as a fuel cylinder to the fuel supply port 171a of the fuel cell stack 100. A hydrogen primary pressure regulating valve LV is provided downstream of the high-pressure hydrogen tank 11 in the fuel gas supply channel 201. A gas supply valve V1 is provided downstream of the hydrogen pressure regulating valve LV. The pressure (fuel gas flow path internal pressure) suitable for supplying to the fuel cell stack 100 is adjusted by the hydrogen pressure regulating valve LV.

An air introduction path 202 is connected to the fuel gas supply flow path 201 on the downstream side of the gas supply valve V1, an air supply valve V4 is provided on the air introduction path 202, and a filter is provided on the upstream side. 27 is provided.
In the fuel cell stack 100, as shown in FIG. 3, hydrogen gas flows from the hydrogen passage 17a into the hydrogen flow path 84a, and further flows from the hydrogen flow path 84a into the hydrogen flow paths 301 and 302. In the hydrogen passages 301 and 302, hydrogen is supplied to the fuel electrode, and the remaining hydrogen gas flows into the hydrogen passage 17b from the hydrogen circulation passage 84b.

A fuel gas circulation passage 203 is connected to the fuel discharge side of the fuel cell stack 100. One end of the fuel gas circulation passage 203 is connected to the fuel discharge port 171b of the fuel cell stack 100 via the lead-out guide passage 18b, and the other end is connected to the fuel gas supply passage 201, and the fuel gas circulation passage. A fuel gas circulation circuit is formed by 203 and a part of the fuel gas supply channel 201. In this circulation circuit, the fuel gas circulates and flows in the order of the fuel cell stack 100, the fuel gas circulation passage 203, the gas supply passage 201, and the fuel cell stack 100.
The fuel gas supply channel 201 is provided with a pressure reducing shut-off solenoid valve V <b> 5 between the connection portion of the air introduction passage 202 and the connection portion of the fuel gas circulation passage 203.

In addition, one end of a gas lead-out path 204 is connected to the fuel gas circulation path 203, and the other end of the gas lead-out path 204 is an outlet 26 that is open to the outside. An exhaust solenoid valve V6 is provided.
A water recovery tank 21 is connected to the fuel gas circulation passage 203, a circulation pump 25 is connected to the downstream side thereof, and one end of the decompression discharge passage 205 is connected to the downstream side (discharge port side) thereof. . The other end of the decompression discharge path 205 is connected to the fuel gas discharge path 204, and is configured to join the gas downstream of the exhaust electromagnetic valve V6. The decompression discharge path 205 is provided with a decompression solenoid valve V3.

In the fuel gas circulation passage 203, a circulation electromagnetic valve V <b> 2 is provided on the downstream side of the connection portion of the decompression discharge passage 205. When the fuel gas is circulated in the circulation circuit, the circulation electromagnetic valve V2 is opened and the circulation pump 25 is driven.
Further, by opening the exhaust solenoid valve V6, the water in the water recovery tank 21 is discharged together with the fuel gas through the gas outlet path 204.

The circulation pump 25 is also driven when the fuel gas is discharged from the fuel cell stack 100. In this case, the circulation electromagnetic valve V2 is closed and the pressure reducing electromagnetic valve V3 is opened.
Further, a pressure sensor S1 is connected to the fuel gas supply channel 201, and the gas pressure supplied to the fuel electrode of the fuel cell stack 100 is monitored. As described above, the fuel cell stack 100 is provided with sensors S1 to S3 that detect output voltages for each unit cell.
Each valve V1-V6 is comprised so that opening / closing control is electrically possible. The water recovery tank 21 functions as a storage tank that stores generated water discharged from the fuel cell stack 100 together with the fuel gas.

  Further, the fuel cell system 1 is provided with a start switch (not shown) for starting and stopping the fuel cell system by ignition. An ON / OFF switch may be used instead of the ignition key. Further, a period in which the fuel cell system is connected to an external load (not shown) is assumed to be during normal operation.

In the above configuration, in a normal operation state where power is output from the fuel cell system 1, air is supplied to the air flow path 40 of the fuel cell stack 100 by an air fan or the like, and at the same time, hydrogen is supplied from the fuel supply system 10. Gas is supplied to the fuel cell stack 100. In the fuel cell stack 100, the power generation reaction is continued, and electric power and generated water generated by the reaction are generated. Such a power generation reaction is maintained by supplying air to the oxygen electrode and hydrogen gas to the fuel electrode. In the present invention, the normal operation state (normal power generation state) refers to a state in which the fuel cell system 1 is connected to an external load and generates power according to the load.
When the fuel cell is started, a period from when the start switch of the fuel cell system is pressed (ignition key is turned on) until the fuel cell system 1 is connected to an external load is applied.

  Next, the circuit configuration of the fuel cell system 1 will be described. FIG. 15 is a schematic circuit diagram for explaining a circuit configuration of the fuel cell system 1. The stack 100 is connected to an inverter 50 as a load device, and supplies the generated current to the inverter 50. The inverter 50 converts a direct current from the fuel cell stack 100 or the power storage means 60 into an alternating current, and supplies the alternating current to a motor (for example, a drive motor that rotates a vehicle wheel) M as a load device. Here, the drive motor M also functions as a generator, and generates a so-called regenerative current when the vehicle is decelerated. In this case, since the drive motor M is rotated by the wheels to generate electric power, the wheels are braked, that is, function as a braking device (brake) for the vehicle. Then, the regenerative current and the generated current in the stack 100 are supplied to the power storage means 60 and the power storage means 60 is charged.

  The secondary battery as the power storage means 60 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 conceivable. The power storage means 60 does not necessarily have to be a battery, as long as it has a function of electrically storing and discharging energy, such as a capacitor (capacitor), a flywheel, a superconducting coil, and a pressure accumulator. Any form may be used. Furthermore, any of these may be used alone, or a plurality of them may be used in combination.

  The stack 100 is connected to a coil 70 as load control means and a semiconductor switch 80 that is controlled to be turned on and off by the control unit, and current from the stack 100 flows through the coil 70 by turning on and off the semiconductor switch 80. When the semiconductor switch 80 is turned on, the current flowing through the coil 70 increases with time as shown in FIG. When the semiconductor switch 80 is turned off, the current flowing through the coil 70 decreases with time. Therefore, data of on / off control of the semiconductor switch 80 is stored in the storage means, and the control unit controls on / off of the semiconductor switch 80 based on this data, whereby the low load and the high load are cycled as shown in FIG. Can be generated repeatedly (a load represented by a triangular wave).

  Since the stack 100 and the power storage means 60 are connected in parallel to the inverter 50, when the output from the stack 100 decreases due to the operation at a low load under the control of the load control means, the power storage means 60. Current flows back into the stack 100. A diode 90 is provided to prevent this backflow. For this reason, all the current from the power storage means 60 is supplied to the inverter 50.

  Next, a dry-up detection method will be described. Unit cell 15 located in a place with high probability of occurrence of dry-up in stack 100 (that is, unit cell 15 that is likely to cause dry-up), unit cell 15 located in place where occurrence probability of dry-up is low (ie, normal unit) A voltmeter (not shown) for measuring the electromotive force of the corresponding unit cell 15 is attached to the cell 15). When the difference in electromotive force between the unit cell 15 that easily causes dry-up and the normal unit cell 15 exceeds a predetermined value, it is determined that a dry-up is likely to occur, and a dry-up flag is set. Up countermeasure processing (see FIG. 16) is executed.

  The unit cell 15 that easily causes dry-up is identified as follows, for example. In the stack 100 having a structure in which the flow of hydrogen gas introduced into the cell module 130 is folded back (meandering) as shown in FIG. 10, the flow rate and pressure of hydrogen gas are higher in the module 130 on the hydrogen gas introduction path 18a side. The flow rate of hydrogen gas decreases as it approaches the lead-out guide path 18b. The higher the flow rate and pressure of the hydrogen gas, the more likely it is that moisture is taken away from the fuel electrode 15c. Therefore, the module 130 closer to the hydrogen gas introduction path 18a is more likely to dry up. Further, as described above, since the flow of hydrogen gas is folded (meandered) for each cell module 130, the unit cell located outside the meander is easy to dry up, and the module is configured in units of 10 cells. In the present embodiment, the first, twentieth, twenty-first, twenty-first, forty-first, forty-first, forty-first, sixty-first, etc. unit cells 15 are counted from the hydrogen gas introduction path 18a. However, it is thought that it is easy to cause dry-up.

  Therefore, the unit cell that easily causes dry-up is considered to be the unit cell 15 that is closest to the hydrogen gas introduction path 18a in the cell module 130-1 that easily causes dry-up. However, the flow of hydrogen gas in the stack 100 and the cell module 130 is not necessarily uniform, and the flow velocity and pressure vary locally depending on the structure and the like. Therefore, it cannot be said that the unit cell is most likely to dry up on the hydrogen gas introduction path side 18a side in the cell module 130-1. Therefore, it is conceivable to more accurately identify a unit cell that is prone to dry-up by measuring a change in voltage for each unit cell. Note that the normal unit cell is a unit cell 15 that hardly causes dry-up, and an appropriate unit cell 15 (for example, a cell other than the unit cell that easily causes dry-up) is selected.

  The fuel cell system 1 described above has an ECU (Electronic Control Unit) (not shown) as a control unit. The control unit includes a calculation unit such as a CPU and an MPU, a storage unit such as a magnetic disk and a semiconductor memory, an input / output interface, and the like, and controls each unit. The detection values of the voltmeters connected to the sensors S1 to S4 and the unit cell 15 that easily causes dry-up and the normal unit cell 15 are supplied to the control unit. The control unit controls the opening and closing of the electromagnetic valves V1 to 6 and the stop and start of driving of the pump 25. In addition, when the control unit determines that dry-up has occurred in the stack 100 based on the output of a voltmeter connected to the unit cell 15 or the normal unit cell 15 that is likely to cause dry-up, a dry-up countermeasure process is performed. Execute. Furthermore, the control unit creates a load (a load represented by a triangular wave) that periodically repeats a low load and a high load as shown in FIG. 17 by controlling on / off of the semiconductor switch.

  The fuel cell system 1 having the above configuration performs the following operation. FIG. 16 is a flowchart showing the control operation of the fuel cell system 1. The following control operations are executed as control operations in the control unit.

  When an operation to start activation, such as ignition ON, is confirmed, activation processing is executed. In the activation process, for example, the pump 25 is activated, the hydrogen circulation switching valve V2 is closed, the pressure reducing electromagnetic valve V3, the pressure reducing cutoff electromagnetic valve V5, and the exhaust electromagnetic valve V6 are opened. Thereby, the discharge path | route of substitution gas is ensured. Next, the gas supply valve V1 is opened. By opening the gas supply valve V1, the fuel gas flows into the fuel cell stack 100, and the replacement gas in the fuel cell stack 100 is pushed out by the supplied fuel gas and discharged from the discharge port 26.

  The above state is maintained until a predetermined time elapses so that the replacement gas is sufficiently replaced with the fuel gas, and after the predetermined time elapses, the pressure reducing electromagnetic valve V3 and the exhaust electromagnetic valve V6 are closed. As a result, the activation process ends. Acquisition of the voltage detection value of a unit cell is started via voltage sensor S1-3. The circulation solenoid valve V2 is opened to start the circulation of the fuel gas in the circulation circuit, and the control shifts to the steady operation. In the steady operation state, the fuel gas circulates in the circulation circuit, the gas supply valve V1 is opened, and the fuel gas is replenished.

  While the steady operation is being performed, it is determined whether or not the dry-up flag is set (step S101). The dry-up flag is set when it is determined that the difference in electromotive force between the unit cell 15 susceptible to dry-up and the normal unit cell 15 exceeds a predetermined value.

  If it is not determined that the dry-up flag is set (step S101: NO), the steady operation is continued (step S111). In this case, the processing after step S103 is not performed. On the other hand, if it is determined that the dry-up flag is set (step S101: YES), it is further determined whether or not the remaining battery level (remaining power storage amount) exceeds the specified remaining level (step S103). That the remaining battery level is lower than the specified remaining amount (predetermined remaining amount) (battery remaining amount <specified remaining amount) means that the current from the stack 100 that is operating in the low load region ) Means that the current from 60 cannot be supplemented, that is, the current from the stack 100 and the battery 60 does not match the actual required load of the load device such as the motor M (insufficient power).

  Therefore, when the remaining battery level is below a predetermined remaining level (step S103: NO), the current from the stack 100 and the battery 60 matches the actual required load of the load device such as the motor M. Next, vehicle output control is performed (step S105). As the vehicle output control, for example, it is conceivable to control the motor M so as not to accelerate even when the accelerator is depressed (as compared with the case where the vehicle output control is not performed).

  Further, if the air conditioner is a load device, it is conceivable to lower the set temperature of the air conditioner by a predetermined temperature. Note that the remaining battery level exceeds or matches a predetermined remaining amount (battery remaining amount> = specified remaining amount), which means that the current from the stack 100 at a low load can be supplemented by the current from the battery 60. That is, it means that the current from the stack 100 and the battery 60 matches or exceeds the actual required load of the load device such as a motor (no power shortage). Therefore, when the remaining battery amount exceeds or matches the predetermined remaining amount (step S103: YES), if the vehicle output control in step S105 is performed, the cancellation is performed (step S107). .

  Next, triangular waveform pattern control (step S109) is performed. That is, the on / off control of the semiconductor switch 80 is controlled based on the data of the on / off control of the semiconductor switch 80 stored in the storage means, whereby a load (triangular wave) that periodically repeats a low load and a high load as shown in FIG. Is created). The temperature of the stack (fuel cell) 100 rises due to the operation in the high load region (the mountain and the vicinity of the mountain in FIG. 17), but the temperature increase is suppressed by the operation in the low load region (the vicinity of the valley and the valley in the drawing). As a result, the temperature as a whole settles down to a constant value.

  That is, since continuous power generation with a high load is eliminated, it is possible to reduce the loss of moisture in the electrolyte due to an increase in the temperature of the stack (fuel cell) 100 by continuous power generation with a high load. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load region. Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated. In addition, the current (electric power) generated in the stack 100 during the triangular waveform pattern control is supplied to the load device such as the motor M and is also supplied to the battery 60 to charge the battery 60. It is assumed that the vehicle output control in step S105 is also performed in parallel with the triangular waveform pattern control in step S109.

  It returns while executing this triangular waveform pattern control. Then, it is determined again whether or not the dry-up flag is set (step S101). If it is determined that the dry-up flag is not set (step S101: NO), the vehicle output control in step S105 is canceled and the triangular waveform pattern control is also released, and the operation returns to the steady operation (step S111). Thereafter, similarly to the above, the processing after step S101 is performed.

Next, reference examples and modifications of the above embodiment will be described.

In the above-described embodiment, the dry-up countermeasure process (see FIG. 16) is executed when the dry-up flag is set. However , as a reference example , it is regularly or at the determined operation timing. The dry-up countermeasure process may be executed (for example, every time a certain time is counted by the timer, that is, periodically). In this way, it is possible to prevent dry-up.

  Moreover, in the said embodiment, the semiconductor switch 80 on / off-controlled by the coil 70 and a control part is illustrated as a load control means, and a control part controls on / off of the semiconductor switch 80 based on the data of the on / off control of the semiconductor switch 80. Thus, as shown in FIG. 17, it has been described that a load (a load represented by a triangular wave) that periodically repeats a low load and a high load is created, but the present invention is not limited to this. For example, instead of the coil 70 and the semiconductor switch 80, it is possible to create a load that periodically repeats a low load and a high load by using a variable resistor whose resistance value can be controlled by a control unit.

  Moreover, although the said embodiment demonstrated that the load which repeats a low load and a high load periodically is a load represented by a triangular wave, this invention is not limited to this. In short, any load that periodically repeats a low load and a high load may be used. For example, a load represented by a sine wave may be used.

The present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, said embodiment is only a mere illustration in all points. The present invention is not construed as being limited by these descriptions.
This specification discloses the following matters.
(1) a polymer electrolyte fuel cell;
A load control means connected to the polymer electrolyte fuel cell and applying a specific pattern load to the polymer electrolyte fuel cell;
A power storage means connected to the polymer electrolyte fuel cell and storing electric power generated by the polymer electrolyte fuel cell;
A load device connected to the polymer electrolyte fuel cell and the electricity storage means, and operated by receiving power from the polymer electrolyte fuel cell or the electricity storage means;
The load of the specific pattern is a load that periodically repeats a low load and a high load.
According to the configuration described in (1) above, a specific pattern load is applied to the polymer electrolyte fuel cell (hereinafter referred to as a fuel cell). As the load of this specific pattern, for example, by adopting a load that periodically repeats a low load and a high load (regardless of the load demanded by the load device), the temperature of the fuel cell is increased by the operation in the high load region. However, the temperature rise is suppressed by the operation at a low load (low load region), and the total temperature is settled to a constant value. That is, since continuous power generation with a high load is eliminated, it is possible to reduce the loss of moisture in the electrolyte due to an increase in fuel cell temperature due to continuous power generation with a high load. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated. Further, by preventing dry-up, it is possible to prevent damage to the fuel cell electrode and improve durability, and furthermore, it becomes possible to perform a (high-speed) high-load operation that becomes impossible when dry-up is performed.
The load device (for example, a motor) is also connected to a power storage means (for example, a battery), and operates by receiving power from at least the solid polymer fuel cell or the power storage means. Therefore, even if the actual required load of the load device does not match the power generated by the fuel cell (for example, when a load that periodically repeats a low load and a high load is adopted as the load of the specific pattern, The required load may not match the power generated by the fuel cell), and insufficient power can be supplied from the power storage means, so that the load device can be operated appropriately.
Since the load of a specific pattern is a load that periodically repeats a low load and a high load, continuous power generation at a high load is eliminated, and continuous power generation at a high load increases the temperature of the fuel cell and the moisture in the electrolyte Loss can be reduced. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated.
(2) The fuel cell system according to (1), wherein the load that periodically repeats the low load and the high load is a load represented by a triangular wave.
According to the configuration described in (2) above, a load that periodically repeats a low load and a high load is a load represented by a triangular wave. By doing so, it is possible to reduce the loss of water in the electrolyte due to an increase in the temperature of the fuel cell. Further, the electrolyte membrane can be humidified with water generated by operation (power generation) in a high load (high load region). Therefore, dry-up can be prevented. In order to prevent dry-up, it is not necessary to increase the amount of humidification from the outside. For this reason, the system is not enlarged and complicated.
(3) The fuel cell system according to (1) or (2), wherein the load control unit constantly applies a specific pattern load to the polymer electrolyte fuel cell.
According to the configuration described in (3) above, the load control means constantly applies a specific pattern load to the fuel cell, so that dry-up can be prevented in advance.
(4) Further comprising a determining means for determining an operation timing of the load control means,
The load control unit applies a specific pattern load to the polymer electrolyte fuel cell at the operation timing determined by the determination unit, according to any one of the above (1) to (3), Fuel cell system.
According to the configuration described in (4) above, the load control means applies a load of a specific pattern to the fuel cell at the determined operation timing (for example, every time measured by a timer, that is, periodically). Therefore, dry-up can be prevented.
(5) The determination means includes a detection means for detecting dry-up of the electrolyte membrane of the polymer electrolyte fuel cell,
The fuel cell system according to (4), wherein the load control unit applies a specific pattern load to the polymer electrolyte fuel cell when dry-up is detected by the detection unit.
According to the configuration described in (5) above, the load control means applies a specific pattern load to the fuel cell when dry-up is detected, so that the adverse effects of dry-up can be minimized.
(6) The above-mentioned apparatus comprising means for comparing the remaining amount of electricity stored in the electricity storage means with a predetermined specified amount, and performing vehicle output control or canceling vehicle output control based on the comparison result. The fuel cell system according to any one of (1) to (6).
According to the configuration described in (6) above, the remaining amount of electricity stored in the electricity storage means is compared with a predetermined remaining amount, and vehicle output control or vehicle output control is canceled based on the comparison result. Since the means is provided, even if the remaining amount of electricity stored in the electricity storage means falls below a predetermined remaining amount, the minimum required vehicle output can be ensured by controlling the vehicle output. Furthermore, the power storage means can be charged by applying a specific pattern load during the vehicle output control.
(7) The polymer electrolyte fuel cell is
A plurality of separators having current collector plates that are in contact with the fuel electrode of the unit cell and form a fuel gas flow path are stacked alternately with the unit cell, and the inlets of the fuel gas flow paths are connected by an inlet manifold and the outlets are connected to each other. Are connected by outlet manifolds to form a plurality of modules, and the outlet manifold of one module and the inlet manifold of the other module are connected so that the flow direction of fuel gas is reversed between adjacent modules. The fuel according to any one of (1) to (6) above, further comprising a fuel cell stack having a pair of electrode plates connected to each other so as to be energized at both ends in the stacking direction of the unit cells. Battery system.
According to the configuration described in (7) above, a fuel cell having a specific structure can be adopted as the solid polymer fuel cell.

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 a partial section side view (BB sectional view) of a fuel cell stack constituted with a fuel cell separator. It is a partial cross section side view (CC sectional view) of a fuel cell separator. 1 is an overall rear view of a fuel cell separator. It is a partial expansion perspective view of the current collection member by the side of a fuel electrode. It is sectional drawing of a unit cell. It is a partial top view of a fuel cell stack. 1 is an overall plan view of a fuel cell stack. It is a fragmentary sectional view (DD sectional view) of a fuel cell stack which shows a longitudinal section of a hydrogen passage. It is a schematic diagram which shows the structure of the module through which fuel gas passes last. 1 is an overall front view of a fuel cell stack. 1 is an overall rear view of a fuel cell stack. It is a schematic circuit diagram of a fuel cell system. It is a flowchart which shows the control action of a fuel cell system. It is a load pattern at the time of dry-up solution processing. It is a graph showing the relationship between temperature and the amount of saturated water vapor (showing that the higher the temperature, the easier the water evaporates from the electrolyte). It is a schematic diagram (in the case of constant load) of the relationship between the amount of generated current, the amount of generated water per unit time, and the fuel cell temperature (indicating that the moisture tends to be deprived when the load is high).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 100 Fuel cell stack 13 Fuel cell separator 130-1 to n Module 15 Unit cell 17a, 17b Hydrogen passage 3 Current collection member 30 Fuel chamber 32 Convex part 301 Hydrogen flow path 302 Hydrogen flow path 4 Current collection member 40 Air channel 42 Convex portion 43 Inlet port 44 Outlet port 50 Inverter 60 Power storage means 70 Coil 80 Semiconductor switch 90 Diode 8 Frame body 9 Frame body 171a Fuel supply port 171b Fuel discharge port 201 Fuel gas supply channel 203 Fuel gas discharge flow Path S4 Pressure sensor S1-3 Voltage sensor V1 Gas supply valve V2 Circulating solenoid valve V3 Pressure reducing solenoid valve V4 Air supply valve V5 Pressure reducing shut-off solenoid valve V6 Exhaust solenoid valve M Motor

Claims (4)

A polymer electrolyte fuel cell;
Load control means connected to the polymer electrolyte fuel cell, and applying a load of a pattern that periodically repeats a low load and a high load to the polymer electrolyte fuel cell;
A power storage means connected to the polymer electrolyte fuel cell and storing electric power generated by the polymer electrolyte fuel cell;
A load device connected to the polymer electrolyte fuel cell and the power storage means, and operated by receiving power from the polymer electrolyte fuel cell or the power storage means;
Determining means for determining an operation timing of the load control means ;
The determination means includes detection means for detecting dry-up of the electrolyte membrane of the polymer electrolyte fuel cell,
The load control unit applies a load to the polymer electrolyte fuel cell at the operation timing determined by the determination unit when dry-up is detected by the detection unit . The fuel cell system according to claim 1, wherein the load having a pattern in which the low load and the high load are periodically repeated is a load represented by a triangular wave. Comparing the predetermined specified residual quantity and the remaining power amount of the power storage unit, based on the comparison result, according to claim 1 or, characterized in that it comprises means to release the vehicle output control or the vehicle output control 3. The fuel cell system according to 2. The polymer electrolyte fuel cell is
A plurality of separators having current collector plates that are in contact with the fuel electrode of the unit cell and form a fuel gas flow path are stacked alternately with the unit cell, and the inlets of the fuel gas flow paths are connected by an inlet manifold and the outlets are connected to each other. Are connected by outlet manifolds to form a plurality of modules, and the outlet manifold of one module and the inlet manifold of the other module are connected so that the flow direction of fuel gas is reversed between adjacent modules. connect the fuel cell system according to any one of claims 1 to 3, characterized in that it comprises a fuel cell stack having a pair of electrode plates which are superposed so as to be energized at both ends in the stacking direction of the unit cell .

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