JP2018101594A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of determining a freezing state in a fuel cell stack with good accuracy.SOLUTION: A fuel cell system comprises: a water storing part 72 provided in a fuel cell stack and connected to an oxidant gas exhaust manifold 30 and arranged for storing generated water discharged from a plurality of single cells; an oxidant gas exhaust path 64 provided outside the fuel cell stack and connected to the oxidant gas exhaust manifold, and arranged for discharging an oxidant exhaust gas; a pressure-control valve 68 provided in the oxidant gas exhaust path; a bypass flow path 74 connected between the water storing part and the oxidant gas exhaust path downstream of the water storing part and the pressure-control valve; a bypass valve 76 provided in the bypass flow path; a pressure sensor 70 provided in the oxidant gas exhaust path upstream of the pressure-control valve; and a freezing determination part which uses a pressure value obtained from the pressure sensor with the pressure-control valve closed and the bypass valve opened at the time of fuel cell activation to determine a freezing state in the fuel cell stack.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel cell system.

  A polymer electrolyte fuel cell includes a membrane electrode assembly in which catalyst electrode layers are disposed on both sides of an electrolyte membrane. In the membrane electrode assembly, an electrochemical reaction proceeds and water is generated, so water exists in the fuel cell stack. For this reason, when the fuel cell is used in a cold region, the water in the fuel cell stack may freeze after the operation is stopped. When the water in the fuel cell stack freezes, the gas flow path is blocked, and the output at the start-up may decrease. Therefore, by providing a water storage part that collects and holds the water discharged from the fuel cell stack in the reaction gas discharge pipe that discharges the exhaust gas of fuel gas and oxidant gas, it is possible to start by high pressure operation at the time of freezing start The technique which performs is proposed (for example, patent document 1).

JP 2010-250947 A

  However, in Patent Document 1, since the water reservoir is outside the fuel cell stack, the frozen state of the water reservoir and the frozen state inside the fuel cell stack may be different. That is, with the technique of Patent Document 1, it is difficult to accurately grasp the frozen state inside the fuel cell stack.

  The present invention has been made in view of the above problems, and an object thereof is to accurately determine the frozen state inside the fuel cell stack.

  The present invention includes a fuel cell stack in which a plurality of single cells are stacked, an internal flow path provided inside the fuel cell stack, through which an oxidant exhaust gas discharged from the plurality of single cells flows, and the fuel cell Provided inside the stack connected to the internal flow path, a water storage section for storing generated water discharged from the plurality of single cells, and connected to the internal flow path outside the fuel cell stack. A connection between the external flow path for discharging the oxidant exhaust gas, the pressure regulating valve provided in the external flow path, the water storage section, and the external flow path downstream of the pressure regulating valve. A bypass flow path, a bypass valve provided in the bypass flow path, a pressure sensor provided in the external flow path on the upstream side of the pressure control valve, and the pressure regulating valve when the fuel cell is started Closed One the bypass valve with the pressure values obtained from the pressure sensor in a state of open, and a freezing judgment section for determining the frozen state of the interior of the fuel cell stack, a fuel cell system.

  According to the present invention, it is possible to accurately determine the frozen state inside the fuel cell stack.

FIG. 1 is a diagram illustrating the configuration of the fuel cell system according to the first embodiment. 2A is a perspective view of a fuel cell stack, and FIG. 2B is a cross-sectional view of a single cell. FIG. 3 is a view of the vicinity of the oxidant gas discharge manifold in the end plate of the fuel cell stack. FIG. 4 is a flowchart illustrating an example of freezing determination processing by the control device in the first embodiment. FIG. 5 is a diagram illustrating fluctuations in the pressure value detected by the pressure sensor after the bypass valve is opened. FIG. 6 is a flowchart illustrating an example of freezing determination processing by the control device in the second embodiment. FIG. 7 is a diagram illustrating a change in pressure detected by the pressure sensor after the inlet valve and the bypass valve are opened. FIG. 8 is a diagram illustrating the configuration of the fuel cell system according to the third embodiment. FIG. 9 is a flowchart illustrating an example of freezing determination processing by the control device in the third embodiment. FIG. 10 is a diagram showing the fluctuation of the pressure loss after the inlet valve and the bypass valve are opened. Fig.11 (a) is a figure which shows the other example of a water storage part, FIG.11 (b) is a figure at the time of seeing Fig.11 (a) from A direction.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating the configuration of the fuel cell system according to the first embodiment. The fuel cell system 100 is mounted on, for example, a fuel cell vehicle or an electric vehicle as a system for supplying driving power. As shown in FIG. 1, the fuel cell system 100 includes a fuel cell stack 10, an oxidant gas piping system 60, and a control device 80. The fuel cell system 100 also includes a fuel gas piping system and a refrigerant piping system, which are not shown in FIG.

  The oxidant gas piping system 60 supplies an oxidant gas (for example, air) to the fuel cell stack 10. A fuel gas piping system (not shown) supplies fuel gas (for example, hydrogen) to the fuel cell stack 10. The refrigerant piping system (not shown) supplies the refrigerant to the fuel cell stack 10. The fuel cell stack 10 is of a solid polymer electrolyte type and has a stack structure in which a plurality of single cells are stacked. The single cell generates power by receiving supply of oxidant gas and fuel gas, and generates electric power accompanying power generation.

  2A is a perspective view of a fuel cell stack, and FIG. 2B is a cross-sectional view of a single cell. As shown in FIG. 2A, the fuel cell stack 10 includes a single cell 12 that generates power by an electrochemical reaction of a reaction gas, a cell stack 14 formed by stacking a plurality of single cells 12, and a cell stack 14. A pair of terminals (not shown), a pair of insulators 16 and a pair of end plates 18, a tension plate 20 connecting the end plates 18 at both ends, an end plate 18 on one end side, and the insulator 16 And a pair of pressure plates 22 that sandwich the elastic body from the stacking direction of the single cells 12.

  The end plate 18 on the other end side includes a fuel gas supply manifold 24 and a fuel gas discharge manifold 26 for fuel gas, an oxidant gas supply manifold 28 and an oxidant gas discharge manifold 30 for oxidant gas, and a refrigerant gas supply manifold. A refrigerant supply manifold 32 and a refrigerant discharge manifold 34 are provided.

  As shown in FIG. 2B, the single cell 12 includes a membrane electrode assembly 40 in which an anode catalyst layer 44a is provided on one surface of an electrolyte membrane 42 and a cathode catalyst layer 44c is provided on the other surface. A pair of gas diffusion layers (anode gas diffusion layer 46a and cathode gas diffusion layer 46c) and a pair of separators (anode side separator 48a and cathode side separator 48c) are arranged on both sides of the membrane electrode assembly 40. Yes. The anode-side separator 48a and the cathode-side separator 48c have irregularities for forming a gas flow path through which gas flows on the surface. The anode side separator 48a forms an anode gas flow path 50a through which fuel gas flows, between the anode gas diffusion layer 46a. The cathode separator 48c forms a cathode gas flow path 50c through which the oxidant gas flows, between the cathode gas diffusion layer 46c.

  As shown in FIG. 1, the oxidant gas piping system 60 includes an oxidant gas supply path 62 and an oxidant gas discharge path 64. The oxidant gas supply path 62 supplies oxidant gas to the fuel cell stack 10 via a compressor (not shown). The oxidant gas supplied to the fuel cell stack 10 is guided to the cathode electrodes of the plurality of single cells 12 via the oxidant gas supply manifold 28 and the cathode gas flow path 50c. The oxidant gas supply path 62 is provided with an inlet valve 66 that supplies the oxidant gas to the fuel cell stack 10 or shuts off the supply. The inlet valve 66 is, for example, an electromagnetic valve.

  The oxidant gas discharge path 64 discharges the oxidant exhaust gas discharged from the cathode electrodes of the plurality of single cells 12 via the cathode gas flow path 50c and the oxidant gas discharge manifold 30 to the outside of the system. A pressure regulating valve 68 is provided in the oxidant gas discharge path 64. The pressure of the oxidant exhaust gas discharged from the fuel cell stack 10 is regulated by the pressure regulating valve 68. A pressure sensor 70 is provided between the fuel cell stack 10 and the pressure regulating valve 68 in the oxidant gas discharge path 64. That is, the pressure sensor 70 is provided in the oxidant gas discharge path 64 on the upstream side of the pressure regulating valve 68.

  FIG. 3 is a view of the vicinity of the oxidant gas discharge manifold in the end plate of the fuel cell stack. In FIG. 3, the insulator 16 is omitted. As shown in FIG. 3, a water reservoir 72 connected to the oxidant gas discharge manifold 30 is provided inside the fuel cell stack 10. The water reservoir 72 is provided in the end plate 18, for example. The water storage unit 72 is provided below the oxidant gas discharge manifold 30 in the direction of gravity, is generated by an electrochemical reaction of the reaction gas in the plurality of single cells 12, and is discharged to the oxidant gas discharge manifold 30. Water 94 is stored.

  The oxidant gas discharge manifold 30 is bent stepwise in the direction of gravity in the end plate 18, for example. The water reservoir 72 is connected to the oxidant gas discharge manifold 30 on the lower side of the stairs. In this way, the oxidant gas discharge manifold 30 is formed in a staircase shape, and by connecting the water storage section 72 at the lower side of the staircase, the water 94 accumulated in the water storage section 72 can be prevented from flowing back to the single cell 12 side, When the water reservoir 72 is full, the water can be drained to the oxidant gas discharge path 64 connected to the oxidant gas discharge manifold 30.

  Although the capacity | capacitance of the water storage part 72 can be set suitably, the case of 100 mL or less is preferable, for example. In addition, the upper surface of the water storage unit 72 is preferably located above the lower end of the single cell 12.

  As shown in FIGS. 1 and 3, a bypass flow path 74 is provided to connect between the water storage section 72 and the oxidant gas discharge path 64 on the downstream side of the pressure regulating valve 68. A bypass valve 76 is provided in the bypass flow path 74. The bypass valve 76 is, for example, an electromagnetic valve. The bypass valve 76 is closed while the single cell 12 is generating power. For this reason, water 94 generated by an electrochemical reaction is stored in the water storage section 72.

  The control device 80 includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control device 80 controls the operation of the system according to a program stored in the ROM. In addition to the above programs, the ROM stores a map and threshold values used for system control. The control device 80 controls the operation of the system including freezing determination processing described later. The control device 80 functions as a valve control unit 82, a pressure acquisition unit 84, and a freezing determination unit 86 in the freezing determination process. The valve control unit 82 controls the opening / closing of the inlet valve 66, the pressure regulating valve 68, and the bypass valve 76. The pressure acquisition unit 84 acquires a pressure value from the pressure sensor 70. The freezing determination unit 86 determines the freezing state inside the fuel cell stack 10 using the pressure value acquired by the pressure acquisition unit 84.

  FIG. 4 is a flowchart illustrating an example of freezing determination processing by the control device in the first embodiment. As shown in FIG. 4, the control device 80 detects the ignition off signal, and then closes the pressure regulating valve 68 and the inlet valve 66 to stop the operation of the fuel cell (step S10). Since the bypass valve 76 is closed during power generation, the flow path through which the oxidizing gas in the fuel cell stack 10 flows is sealed by closing the pressure regulating valve 68 and the inlet valve 66. Even after the pressure regulating valve 68 and the inlet valve 66 are closed, the electrochemical reaction proceeds by the fuel gas and the oxidant gas remaining in the fuel cell stack 10. As a result, the pressure in the fuel cell stack 10 decreases. In addition, the pressure in the fuel cell stack 10 also decreases due to a change in the volume of gas remaining in the fuel cell stack 10 due to a temperature decrease in the fuel cell stack 10. For these reasons, the fuel cell stack 10 has a negative pressure.

  Next, the control device 80 waits until it detects an ignition on signal that starts the fuel cell (step S12). After detecting the ignition on signal (step S12: Yes), the control device 80 acquires the pressure value detected by the pressure sensor 70 from the pressure sensor 70 (step S14).

  Next, the control device 80 opens the bypass valve 76 (step S16). Since the inside of the fuel cell stack 10 has a negative pressure, when the bypass valve 76 is opened, outside air tries to flow into the fuel cell stack 10 via the bypass flow path 74, but is accumulated in the water storage portion 72. Depending on the state of the water 94, the flow of outside air changes. That is, the pressure value detected by the pressure sensor 70 varies depending on the state of the water 94 accumulated in the water storage unit 72.

  FIG. 5 is a diagram illustrating fluctuations in the pressure value detected by the pressure sensor after the bypass valve is opened. The horizontal axis in FIG. 5 is time, and the vertical axis is pressure. As shown in FIG. 5, when all of the water 94 accumulated in the water storage unit 72 is frozen and present as ice, the outside air cannot flow into the fuel cell stack 10 and is detected by the pressure sensor 70. The pressure value hardly changes. When all of the water 94 accumulated in the water storage part 72 exists in the state of liquid water, the outside air passes through the liquid water as bubbles and flows into the fuel cell stack 10, so the pressure detected by the pressure sensor 70. The value rises in a short time to a pressure value below atmospheric pressure. When the water 94 accumulated in the water storage section 72 exists as both ice and liquid water, the outside air passes only as a bubble through the liquid water portion and flows into the fuel cell stack 10. The detected pressure value rises slowly.

  Therefore, by using the pressure value acquired from the pressure sensor 70 after a predetermined time has elapsed since the bypass valve 76 was opened, it can be determined whether or not the water 94 accumulated in the water storage section 72 is frozen. Here, since the water storage unit 72 is provided inside the fuel cell stack 10, the temperature of the water storage unit 72 and the temperature inside the fuel cell stack 10 are substantially the same. That is, the frozen state of the water storage unit 72 and the frozen state inside the fuel cell stack 10 are substantially the same. Therefore, by determining whether or not the water 94 accumulated in the water storage section 72 is frozen, it is possible to accurately determine the frozen state inside the fuel cell stack 10.

  Therefore, as shown in FIG. 4, the control device 80 acquires the pressure value detected by the pressure sensor 70 from the pressure sensor 70 after a predetermined time has elapsed since the bypass valve 76 was opened (step S18). Then, the control device 80 determines whether or not the water 94 accumulated in the water storage section 72 is frozen by using the pressure values acquired in Step S14 and Step S18, thereby determining the frozen state inside the fuel cell stack 10. Judgment is made (step S20). For example, the difference between the pressure value after a predetermined time has elapsed since opening the bypass valve 76 (pressure value acquired in step S18) and the pressure value before opening the bypass valve 76 (pressure value acquired in step S14) is predetermined. When the value is less than the value, it is determined that at least a part of the water 94 accumulated in the water storage section 72 is frozen, and the inside of the fuel cell stack 10 is determined to be frozen.

  When the inside of the fuel cell stack 10 is frozen, the output is reduced. Therefore, when it is determined that the fuel cell stack 10 is in a frozen state (step S20: Yes), the control device 80 starts the operation of the fuel cell in the sub-freezing start mode ( Step S22). The sub-freezing start mode is a mode in which, for example, the supply amount of the oxidant gas is made smaller than that in the normal mode, and the operation is performed so that the cell voltage of each single cell 12 becomes lower than that in the normal mode. As a result, the amount of power generation loss increases and a large amount of heat is generated, so that the temperature rise of the fuel cell stack 10 can be promoted.

  Next, the control device 80 determines whether or not the temperature of the refrigerant supplied to the fuel cell stack 10 has reached a predetermined value (step S24). When the temperature of the refrigerant is lower than the predetermined value (step S24: No), the control device 80 continues the below-freezing start mode (step S22). When the temperature of the refrigerant becomes equal to or higher than the predetermined value (step S24: Yes), the control device 80 stops the below-freezing start mode and starts the operation of the fuel cell in the normal mode (step S26).

  In step S20, when it is determined that the inside of the fuel cell stack 10 is not frozen (step S20: No), the control device 80 starts the operation of the fuel cell in the normal mode (step S26).

  According to the first embodiment, the fuel cell system 100 includes a water storage unit 72 provided inside the fuel cell stack 10 and an oxidant gas discharge path 64 on the downstream side of the water storage unit 72 and the pressure regulating valve 68. And a bypass valve 76 provided in the bypass channel 74. When the fuel cell is started up, the control device 80 receives pressure from the pressure sensor 70 disposed in the oxidant gas discharge path 64 upstream of the pressure regulating valve 68 with the pressure regulating valve 68 closed and the bypass valve 76 opened. A value is acquired (step S18), and the frozen state inside the fuel cell stack 10 is determined using the acquired pressure value (step S20). As a result, the frozen state inside the fuel cell stack 10 can be determined by the water 94 accumulated in the water storage portion 72 provided inside the fuel cell stack 10, so that the frozen state can be accurately determined.

  Further, according to the first embodiment, the water reservoir 72 is provided in the end plate 18. Freezing of the fuel cell stack 10 proceeds from the single cell 12 located at the end. Therefore, by providing the water reservoir 72 in the end plate 18 near the single cell 12 located at the end of the stack, it is possible to accurately determine the frozen state inside the fuel cell stack 10. Further, since the end plate 18 has a thickness, it is suitable for forming the water reservoir 72. The water reservoir 72 may be provided in the fuel cell stack 10 other than the end plate 18, for example, in the insulator 16.

  Further, according to the first embodiment, the frozen state inside the fuel cell stack 10 can be determined without using a temperature sensor or a cell monitor that measures the cell voltage, so that the number of parts and the cost can be reduced.

  In the first embodiment, the case where the frozen state is determined using the difference between the pressure value after a predetermined time has elapsed after the bypass valve 76 is opened and the pressure value before the bypass valve 76 is opened is shown as an example. This is not the only case. For example, the frozen state may be determined based on the pressure value itself after a predetermined time has elapsed since the bypass valve 76 was opened, or the pressure value after the predetermined time has elapsed since the bypass valve 76 was opened. The frozen state may be determined based on the rate of increase or the rate of increase in how much the pressure value has increased from the previous pressure value.

  In the first embodiment, it is determined that the inside of the fuel cell stack 10 is in a frozen state when at least a part of the water 94 accumulated in the water storage section 72 is frozen, but this is not a limitation. When only a part of the water 94 collected in the water storage part 72 is frozen, it is determined that the inside of the fuel cell stack 10 is not frozen, and when all the water 94 collected in the water storage part 72 is frozen. Only when it is determined that the inside of the fuel cell stack 10 is in a frozen state.

  The configuration of the fuel cell system according to the second embodiment is the same as that of FIG. 1 of the first embodiment, and the fact that the water storage section 72 is provided in the end plate 18 is the same as that of FIG. Description is omitted. FIG. 6 is a flowchart illustrating an example of freezing determination processing by the control device in the second embodiment. As shown in FIG. 6, the control device 80 first performs the same processes as steps S <b> 10 to S <b> 14 described in FIG. 4 of the first embodiment in steps S <b> 40 to S <b> 44.

  Next, the control device 80 opens the inlet valve 66 and the bypass valve 76, operates the compressor, and supplies the oxidant gas into the fuel cell stack 10 (step S46). At this time, the way in which the oxidant gas flows into the bypass flow path 74 changes depending on the state of the water 94 accumulated in the water storage section 72, and the pressure value detected by the pressure sensor 70 changes.

  FIG. 7 is a diagram illustrating fluctuations in the pressure value detected by the pressure sensor after the inlet valve and the bypass valve are opened. In FIG. 7, the horizontal axis represents time, and the vertical axis represents pressure. As shown in FIG. 7, when all the water 94 accumulated in the water reservoir 72 is frozen and present as ice, the oxidant gas cannot be flown into the bypass flow path 74 and is detected by the pressure sensor 70. The pressure value increases. When all the water 94 accumulated in the water reservoir 72 is liquid water, the oxidant gas flows into the bypass channel 74 after the liquid water is pushed out to the bypass channel 74 side by the oxidant gas. For this reason, the pressure value detected by the pressure sensor 70 increases during drainage of liquid water, but decreases after drainage. When the water 94 collected in the water storage part 72 exists as both ice and liquid water, the liquid water is generated by the oxidant gas in the same manner as when all the water 94 stored in the water storage part 72 exists as liquid water. After being pushed out to the bypass flow path 74 side, the oxidant gas flows into the bypass flow path 74. For this reason, the pressure value detected by the pressure sensor 70 increases during the drainage of the liquid water and decreases after the drainage, but since the flow path of the oxidant gas is narrowed by ice, the pressure drop does not occur. Compared to the case where all of the liquid water exists (in the case of a broken line), it becomes smaller.

  Therefore, by using the pressure value acquired from the pressure sensor 70 after a predetermined time has elapsed after opening the inlet valve 66 and the bypass valve 76, it can be determined whether or not the water 94 accumulated in the water reservoir 72 is frozen, As a result, it can be determined whether or not the inside of the fuel cell stack 10 is in a frozen state.

  Therefore, as shown in FIG. 6, the control device 80 acquires the pressure value detected by the pressure sensor 70 from the pressure sensor 70 after a predetermined time has elapsed since the inlet valve 66 and the bypass valve 76 were opened (step S48). . Then, the control device 80 determines whether or not the water 94 accumulated in the water storage unit 72 is frozen by using the pressure values acquired in Step S44 and Step S48, thereby determining the frozen state inside the fuel cell stack 10. Judgment is made (step S50). For example, the pressure value after a predetermined time has elapsed after opening the inlet valve 66 and the bypass valve 76 (the pressure value acquired in step S48) and the pressure value before opening the inlet valve 66 and the bypass valve 76 (obtained in step S44). When the difference in pressure value is equal to or greater than a predetermined value, it is determined that at least a part of the water 94 accumulated in the water storage section 72 is frozen, and the fuel cell stack 10 is determined to be frozen.

  If it is determined that it is in a frozen state (step S50: Yes), steps S52 to S56, which are the same processes as steps S22 to S26 described in FIG. When it is determined that it is not in a frozen state (step S50: No), step S56 is performed.

  In the first embodiment, after detecting the ignition on signal, only the bypass valve 76 is opened, and the freezing state inside the fuel cell stack 10 is determined using the pressure value acquired from the pressure sensor 70. As in the second embodiment, After detecting the ignition-on signal, the inlet valve 66 and the bypass valve 76 may be opened and the frozen state inside the fuel cell stack 10 may be determined using the pressure value acquired from the pressure sensor 70.

  In the second embodiment, the frozen state is determined by using the difference between the pressure value after a predetermined time has elapsed after opening the inlet valve 66 and the bypass valve 76 and the pressure value before opening the inlet valve 66 and the bypass valve 76. The case of determining is shown as an example, but is not limited to this case. For example, the frozen state may be determined based on the pressure value itself after a predetermined time has elapsed after opening the inlet valve 66 and the bypass valve 76, or after a predetermined time has elapsed since the inlet valve 66 and the bypass valve 76 were opened. The frozen state may be determined by the rate of increase in how much the pressure value has increased from the pressure value before opening the inlet valve 66 and the bypass valve 76.

  FIG. 8 is a diagram illustrating the configuration of the fuel cell system according to the third embodiment. As shown in FIG. 8, in the fuel cell system 300 according to the third embodiment, the pressure sensor 78 is provided in the bypass flow path 74 on the downstream side of the bypass valve 76. The control device 80 also functions as a pressure loss calculation unit 88 in addition to the valve control unit 82, the pressure acquisition unit 84, and the freezing determination unit 86 in the freezing determination process. The pressure loss calculation unit 88 calculates the pressure loss using the pressure values acquired by the pressure acquisition unit 84 from the pressure sensor 70 and the pressure sensor 78. Other configurations are the same as those in the first embodiment, and a description thereof will be omitted.

  FIG. 9 is a flowchart illustrating an example of freezing determination processing by the control device in the third embodiment. As shown in FIG. 9, the control device 80 first performs the same processes as steps S <b> 10 and S <b> 12 described in FIG. 4 of the first embodiment in steps S <b> 70 and S <b> 72.

  Next, after detecting the ignition on signal (step S72: Yes), the control device 80 opens the inlet valve 66 and the bypass valve 76, operates the compressor, and supplies the oxidant gas into the fuel cell stack 10. Supply (step S74). Next, the control device 80 acquires a pressure value from the pressure sensor 70 and the pressure sensor 78 after a predetermined time has elapsed since the inlet valve 66 and the bypass valve 76 were opened (step S76). Next, the control device 80 calculates a pressure loss using the acquired pressure value (step S78). For the pressure loss, for example, the difference (first pressure value−second pressure value) between the pressure value (first pressure value) acquired from the pressure sensor 70 and the pressure value (second pressure value) acquired from the pressure sensor 78 is calculated. To calculate.

  FIG. 10 is a diagram showing the fluctuation of the pressure loss after the inlet valve and the bypass valve are opened. In FIG. 10, the horizontal axis represents time, and the vertical axis represents pressure loss. As described with reference to FIG. 7 of the second embodiment, the way in which the oxidizing gas flows into the bypass flow path 74 varies depending on the state of the water 94 accumulated in the water storage section 72. For this reason, the fluctuation of the pressure loss after opening the inlet valve 66 and the bypass valve 76 is as shown in FIG. That is, when all of the water 94 accumulated in the water reservoir 72 is frozen and present as ice, the pressure loss increases. When all the water 94 accumulated in the water storage part 72 is present as liquid water, the pressure loss increases during drainage of the liquid water, but decreases after drainage. When the water 94 accumulated in the water storage part 72 exists in both ice and liquid water, the pressure loss increases during the drainage of the liquid water and decreases after the drainage. Since the flow path is narrowed, the decrease in pressure loss is smaller than when all liquid water is present.

  As described above, it is possible to determine whether or not the water 94 accumulated in the water storage section 72 is frozen by using the pressure loss after a predetermined time has passed since the inlet valve 66 and the bypass valve 76 are opened. It can be determined whether or not the inside of the battery stack 10 is frozen.

  Therefore, as shown in FIG. 9, the control device 80 determines whether or not the water 94 accumulated in the water storage section 72 is frozen by using the pressure loss calculated in step S <b> 78. The frozen state is determined (step S80). For example, when the pressure loss is equal to or greater than a predetermined value, it is determined that at least a part of the water 94 accumulated in the water storage section 72 is frozen, and the inside of the fuel cell stack 10 is determined to be frozen.

  If it is determined that it is in a frozen state (step S80: Yes), steps S82 to S86, which are the same processes as steps S22 to S26 described in FIG. 4 of the first embodiment, are performed. When it is determined that it is not in the frozen state (step S80: No), step S86 is performed.

  According to the third embodiment, the control device 80 calculates the pressure loss from the pressure values acquired from the pressure sensor 70 and the pressure sensor 78 after a predetermined time has elapsed after opening the inlet valve 66 and the bypass valve 76, and The frozen state inside the fuel cell stack 10 is determined. Thereby, compared with the case of Example 2, the frozen state inside the fuel cell stack 10 can be determined more accurately.

  In the first to third embodiments, the case where the water storage unit 72 has a rectangular parallelepiped shape has been described as an example, but may have another shape such as a cylinder or a triangular prism. Fig.11 (a) is a figure which shows the other example of a water storage part, FIG.11 (b) is a figure at the time of seeing Fig.11 (a) from A direction. As shown in FIGS. 11 (a) and 11 (b), the water storage portion 72a is separated from the large-diameter portion 90 where the cross-sectional area of the portion connected to the oxidant gas discharge manifold 30 is larger than the opposite side and the cross-sectional area is large. The small diameter part 92 with a small area may be connected by the downward inclined surface. The cross sections of the large diameter portion 90 and the small diameter portion 92 have a circular shape, for example, but may have other shapes such as an elliptical shape or a rectangular shape.

  The diameter of the small diameter portion 92 is preferably 3 mm or less, and more preferably 1 mm or less. For example, the cross-sectional area of the small-diameter portion 92 may be made equal to the cross-sectional area of one of the plurality of grooves constituting the cathode gas flow path 50c. By making the cross-sectional area of the small-diameter portion 92 equal to the cross-sectional area of the cathode gas flow channel 50c, the frozen state of the water 94 accumulated in the water storage portion 72a is brought closer to the frozen state of the water remaining in the cathode gas flow channel 50c. Can do.

  By increasing the cross-sectional area of the portion connected to the oxidant gas discharge manifold 30 as the large-diameter portion 90, water can easily flow from the oxidant gas discharge manifold 30 to the water storage portion 72a. Further, by forming a downward inclined surface between the large-diameter portion 90 and the small-diameter portion 92, water can be easily collected in the small-diameter portion 92.

  Although only one small diameter portion 92 may be provided, a plurality of small diameter portions 92 may be provided. By providing the plurality of small-diameter portions 92, for example, even when one small-diameter portion 92 is blocked for some reason other than freezing, it is possible to determine the frozen state.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Fuel cell stack 12 Single cell 16 Insulator 18 End plate 28 Oxidant gas supply manifold 30 Oxidant gas discharge manifold 60 Oxidant gas piping system 62 Oxidant gas supply path 64 Oxidant gas discharge path 66 Inlet valve 68 Pressure regulating valve 70 Pressure sensor 72, 72a Water storage part 74 Bypass flow path 76 Bypass valve 78 Pressure sensor 80 Control device 82 Valve control part 84 Pressure acquisition part 86 Freezing judgment part 88 Pressure loss calculation part 90 Large diameter part 92 Small diameter part 94 Water 100, 300 Fuel cell system

Claims (1)

A fuel cell stack in which a plurality of single cells are stacked;
An internal flow path provided inside the fuel cell stack and through which an oxidant exhaust gas discharged from the plurality of single cells flows;
A water storage section that is provided in the fuel cell stack and connected to the internal flow path, and stores the generated water discharged from the plurality of single cells;
An external flow path that is connected to the internal flow path outside the fuel cell stack and discharges the oxidant exhaust gas;
A pressure regulating valve provided in the external flow path;
A bypass flow path connected between the water storage section and the external flow path on the downstream side of the pressure regulating valve;
A bypass valve provided in the bypass flow path;
A pressure sensor provided in the external flow path upstream of the pressure regulating valve;
A freezing determination unit for determining a freezing state inside the fuel cell stack using a pressure value acquired from the pressure sensor in a state where the pressure regulating valve is closed and the bypass valve is opened at the time of starting the fuel cell; A fuel cell system comprising:

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