JP2006302707A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively replace all cells in a stack when starting a fuel cell system. <P>SOLUTION: The fuel cell system is equipped with two stacks connected in series made by laminating a plurality of unit cells, each stack includes a manifold for supply and a manifold for evacuation connected to an inlet and an outlet of each gas flow path of the unit cell, respectively. A first evacuation pipe is connected to an equipotential surface side outlet of the manifold for evacuation, an evacuation part switching means to open and close the pipe is provided. also, A through-hole for retention gas evacuation penetrating the stack is provided, the manifold for evacuation and the through-hole for retention gas evacuation are connected with a connecting tube on a facing surface side, and a connecting tube switching means to open and close the connecting tube is provided. A second evacuation pipe connecting to the through-hole for retention gas evacuation is provided on the equipotential surface side. The first evacuation pipe and the second pipe connecting to each of stacks are joined together outside the stacks, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system. More specifically, the present invention relates to a fuel cell including two stacks connected in series, each of which is formed by stacking unit cells.

  Conventionally, Japanese Unexamined Patent Application Publication No. 2001-76751 discloses a fuel cell in which two fuel cell stacks are arranged in parallel and connected in series. In this fuel cell, a fuel gas supply port and a discharge port, and an oxygen gas supply port and a discharge port of each stack are arranged on one surface of both end surfaces in the stacking direction of cells that are unit cells. Further, between the stacks, the fuel gas supply ports, the discharge ports, the oxygen gas supply ports, and the discharge ports are connected by gas pipes.

  According to the above-described conventional fuel cell, the gas pipes can be concentrated on one surface of the stack with such a configuration. Therefore, the gas pipe connection structure can be simplified, and the height direction of the fuel cell can be effectively shortened.

Japanese Patent Laid-Open No. 2001-76751 JP 2002-367664 A Japanese Patent Laid-Open No. 5-41240 JP 2002-313390 A JP 2004-193107 A

  When power generation of the fuel cell is stopped and left as it is, the fuel gas supplied to the anode side may be gradually discharged out of the system due to leakage from a valve or the like. In addition, the reaction between the fuel gas and oxygen gradually proceeds even when left unattended, and the anode side fuel gas may be lost. Therefore, when the fuel cell is started after being left, the fuel gas on the anode side may be lost and the anode side may be filled with oxygen or nitrogen. In addition, in order to prevent an unnecessary reaction from occurring when left unattended, the inside of the fuel gas channel may be replaced with an inert gas such as nitrogen while power generation is stopped. For this reason, at the time of starting the fuel cell, it is necessary to first replace oxygen or nitrogen filled on the anode side with the fuel gas.

  However, in the fuel cell, the fuel gas supply port and the discharge port are provided on the same surface. For this reason, the fuel gas supplied for replacement is supplied more to the cells near the fuel gas supply port and the discharge port. Therefore, there is a case where the fuel gas does not sufficiently reach the cell located on the back side with respect to the supply port. In particular, the density of hydrogen is smaller than that of nitrogen. For this reason, when hydrogen is used as the fuel gas, it takes a long time to expel a gas having a high density such as nitrogen gas staying in the cell on the back side with respect to the supply port and replace it with hydrogen.

  On the other hand, in order to quickly replace the staying gas with the fuel gas, a discharge port for the staying gas is separately provided on the surface opposite to the supply port so that the fuel gas can quickly reach the inner cell. It is also possible to do. However, in the above prior art structure, the stacks are connected in series. For this reason, the electric potential of the surface opposite to the supply port is greatly different between the stacks. Providing piping for staying gas discharge on such a surface having a large potential difference causes a potential difference between the piping for discharging staying gas. Since it is conceivable to use a combustible gas such as hydrogen as the fuel gas, it is not preferable that a potential difference is generated in the stay gas discharge pipe.

  The present invention has been made to solve the above-described problems, and is an improved fuel cell system that can efficiently replace the entire cells in the stack at the start-up while suppressing the complexity of the piping structure of the fuel cell. The purpose is to provide.

In order to achieve the above object, a first invention is a fuel cell system comprising two stacks connected in series, wherein a plurality of single cells are stacked.
Each stack is
Of the both end faces of the unit cell in the stacking direction, through the stack from the equipotential surface that is equipotential between the stacks, to the facing surface that is the end face opposite to the equipotential face, and A supply manifold connected to each gas flow path of the unit cell;
A discharge manifold that passes through the stack from the equipotential surface to the opposing surface and is connected to each gas flow path;
A first exhaust pipe connected to an outlet on the equipotential surface side of the exhaust manifold and exhausting the gas exhausted from the exhaust manifold out of the stack;
Discharge part opening and closing means for opening and closing the first discharge pipe;
A stagnant gas discharge through-hole penetrating the stack from the equipotential surface to the opposing surface;
A connecting pipe connecting the exhaust manifold and the staying gas discharge through-hole on the opposite surface side;
Connecting pipe opening and closing means for opening and closing the connecting pipe;
A second discharge pipe connected to an outlet on the equipotential surface side of the staying gas discharge through hole, and discharging the gas discharged from the staying gas discharge through hole to the outside of the stack;
With
The first discharge pipes of the stacks merge with each other outside the stack,
The second discharge pipes of the stacks may join each other outside the stack.

According to a second aspect of the present invention, in the first aspect of the present invention, supply means for supplying a gas from an inlet on the equipotential surface side of the supply manifold;
When the fuel cell system is started, the discharge part opening / closing means is closed and the connecting pipe opening / closing means is opened to be in a first open / close state, and when the fuel cell system generates power, the discharge part opening / closing means is opened, Control means for controlling the pipe opening / closing means to be in a second open / closed state,
It is characterized by providing.

Further, the third invention comprises a replacement completion detecting means for detecting in the second invention that the staying gas in the gas flow passage is replaced with the supply gas from the supply means,
The control means sets the second open / close state when the gas replacement completion is detected.

In a fourth aspect based on the third aspect, the replacement completion detecting means is
A supply time detecting means for detecting a supply time of a supply gas for replacing the gas flow path with the supply gas;
A comparison means for comparing whether or not the supply time is equal to or longer than a required replacement time sufficient to replace the gas flow path;
With
The control means sets the second open / close state when the supply time is equal to or longer than the replacement time.

In a fifth aspect based on the third aspect, the replacement completion detecting means is
A gas concentration sensor provided in the connecting pipe;
Comparison means for comparing the output of the gas concentration sensor with a judgment value output when the gas flow path is replaced with the supply gas;
With
The control means sets the second open / close state when it is determined from the result of the comparison that the inside of the gas flow path is replaced with the supply gas.

  In a sixth aspect based on any one of the first to fifth aspects, the second discharge pipe is located on the downstream side of the gas flow with respect to the gas flow with respect to the discharge portion opening / closing means. It connects with.

  The seventh invention is the sixth invention, wherein the second discharge pipe is more upstream of the gas flow than the connection portion between the first discharge pipe and the second discharge pipe. It is characterized by comprising a retention gas opening / closing means for opening / closing the second discharge pipe.

Further, in an eighth invention according to any one of the first to seventh inventions, the connecting pipe is provided outside the stack,
The opposing surface is connected to the staying gas discharge through hole and the discharge manifold.

  According to a ninth invention, in any one of the first to eighth inventions, the supply manifold and the discharge manifold are manifolds on an anode side of the fuel cell.

Further, a tenth aspect of the invention is the ninth aspect of the invention, further comprising oxidant supply means for supplying an oxidant gas or air from an inlet on the equipotential surface side of the supply manifold,
The gas flow path is replaced with the oxidant gas or the air while the fuel cell system is stopped.

An eleventh aspect of the invention is the inert gas supply means for supplying an inert gas from an inlet on the equipotential surface side of the supply manifold in any one of the first to ninth aspects of the invention. With
The gas flow path is replaced with the inert gas while the fuel cell system is stopped.

  According to the first invention, the discharge manifold is connected to the first discharge pipe on the equipotential surface, and is connected to the staying gas discharge through hole on the opposite surface side. Further, the staying gas discharge through-hole penetrates from the opposing surface to the equipotential surface and is connected to the second discharge pipe on the equipotential surface. Accordingly, the discharge manifold can be provided with an outlet on the equipotential surface side and an outlet on the opposite surface side, and the gas can be discharged by selecting the outlet according to the situation. Further, when the outlet on the opposite surface side is selected, the final outlet of the gas discharged from the discharge manifold is the second discharge pipe to which the staying gas discharge through-hole is connected, and this pipe has an equipotential Arranged on the surface. Therefore, it is possible to prevent the potential difference from being generated in the pipes for the second discharge pipe for discharging the staying gas while enabling the discharge of the gas from the opposed surface side of the discharge manifold.

  Further, according to the second aspect of the invention, when the fuel cell system is started, the discharge part opening / closing means can be closed and the accumulated gas can be discharged from the outlet on the opposite surface side of the discharge manifold. Therefore, at the time of start-up, each gas flow path can be efficiently replaced with the supply gas. On the other hand, at the time of power generation, the connecting pipe opening / closing means can be closed and gas can be discharged from the outlet on the equipotential surface side of the discharge manifold, so that high power generation of the fuel cell system can be ensured.

  According to the third to fifth inventions, when it is detected that the replacement of the gas flow path is completed, the connection pipe opening / closing means on the opposite surface side is closed, and the outlet from the equipotential surface of the discharge manifold So that the gas is discharged. Therefore, gas replacement can be completed with certainty, and excess consumption of the supply gas can be suppressed.

  According to the sixth invention, the second discharge pipe is connected to the first discharge pipe on the downstream side of the gas flow with respect to the discharge portion opening / closing means. Therefore, the piping structure can be simplified.

  According to the seventh aspect of the invention, the staying gas opening / closing means for opening / closing the second exhaust pipe is provided. Therefore, the staying gas opening / closing means can be opened only when necessary, and unnecessary gas release can be suppressed.

  According to the eighth invention, each connecting pipe is connected to the staying gas discharge through-hole and the discharge manifold on the opposing surface outside the stack. Thereby, even when the connecting pipe is arranged outside the stack, it is possible to prevent a potential difference from occurring in the connecting pipe.

  Further, according to the ninth aspect, the fuel gas flow path can be efficiently replaced when the fuel cell system is started.

  According to the tenth aspect, the fuel gas flow path can be efficiently replaced with the oxidant gas or air while the fuel cell system is stopped. Thereby, it is possible to suppress an unnecessary reaction from occurring in the fuel cell system while the fuel cell system is stopped. In addition, even when the oxidant gas or air is replaced in this way, the gas flow path can be replaced efficiently at the time of startup.

  According to the eleventh aspect, the gas flow path is replaced with an inert gas while the fuel cell system is stopped. Thereby, it is possible to suppress an unnecessary reaction from occurring in the fuel cell system during the stop. Further, even when the inert gas is replaced in this way, the gas flow path can be replaced efficiently at the time of startup.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
[Configuration of Fuel Cell System of Embodiment 1]
FIG. 1 is a conceptual diagram for explaining a fuel cell system according to Embodiment 1 of the present invention.
As shown in FIG. 1, the fuel cell system of Embodiment 1 includes two stacks 2a and 2b. The stacks 2a and 2b are connected in series and arranged in parallel. FIG. 1 shows a cross section of each of the stacks 2a and 2b, but the dotted line represents the supply and discharge passages of the fuel gas.

  A plurality of cells 4 are stacked in each stack 2a, 2b. In each cell 4, a cathode, an anode, and a solid polymer film sandwiched between both electrodes are disposed. Further, a fuel gas flow path is provided on the anode side, and for example, hydrogen is supplied as the fuel gas. In addition, an oxygen gas flow path is provided on the cathode side, and air is supplied.

  In each stack 2a, 2b, a first end plate 6 is provided on one end surface of the cells 4 in the stacking direction, and a second end plate 8 is provided on the opposite end surface. The stack 2a and the stack 2b are electrically connected in series on the second end plate 8 side. Therefore, the second end plate 8 side of each stack 2a, 2b is an equipotential surface. On the other hand, the potential on the first end plate 6 side differs between the stacks 2a and 2b. The first end plates 6 of the stacks 2a and 2b are provided with terminals 10a and 10b, respectively. The terminal 10a is a positive terminal in this fuel cell system, and the terminal 10b is a negative terminal.

  A supply pipe 12 for supplying fuel gas is disposed outside the second end plate 8 of the stacks 2a and 2b. The supply pipe 12 is connected to a fuel gas supply means (not shown) for supplying fuel gas. The supply pipe 12 branches into two supply pipes 14. Each supply pipe 14 includes a first valve 16 in the middle thereof. Each supply pipe 14 is connected to a supply manifold 18 in the second end plate 8 of each stack 2a, 2b. The supply manifold 18 is formed to penetrate the cells 4 in the stacking direction of the cells 4 and is connected to one end of the fuel gas flow path in each cell 4.

  The discharge manifold 20 is formed through the cell 4 in the stacking direction of the cells 4 and is connected to the other end of the fuel gas flow path of each cell. Each discharge manifold 20 is connected to a discharge pipe 22 in the second end plate 8. Each discharge pipe 22 has a second valve 24 in the middle thereof. Further, the two discharge pipes 22 connected to the stacks 2a and 2b are connected to the single discharge pipe 26 and joined together.

  In each of the stacks 2 a and 2 b, a stay gas discharge through hole 28 is arranged in parallel with the discharge manifold 20. The stay gas discharge through hole 28 is formed between the first end plate 6 and the second end plate 8 so as to penetrate the cell 4 in the stacking direction of the cells 4.

The relationship between the staying gas discharge through hole 28 and the aforementioned supply manifold 18 and discharge manifold 20 will be described with reference to FIG. FIG. 2 is a front view of the cell 4 of the fuel cell system.
In FIG. 2, an anode inlet 30 is provided at the upper left of the cell 4. Further, an anode outlet 32 is arranged in a diagonal direction of the anode inlet 30. The anode inlet 30 and the anode outlet 32 are connected by a fuel gas flow path in the cell 4. A plurality of cells 4 are stacked and the anode inlet 30 is connected to form a supply manifold 18. Further, the discharge outlet manifold 20 is configured by connecting the anode outlet 32.

  A staying gas discharge port 34 is provided below the anode outlet 32. A plurality of cells 4 are stacked and the staying gas discharge port 34 is connected to form a staying gas discharge through hole 28.

  A cathode inlet 36 is provided at the upper right of the cell 4. A cathode outlet 38 is disposed diagonally to the cathode inlet 36. The cathode inlet 36 and the cathode outlet 38 are connected by an oxygen gas flow path in the cell 4. By stacking a plurality of cells 4, the cathode inlet 36 and the cathode outlet 38 are connected to each other, and the supply manifold and the discharge manifold for oxygen gas are similarly configured. The cell 4 is provided with a cooling medium inlet 40 and a cooling medium outlet 42. By stacking a plurality of cells 4, the cooling medium inlet 40 and the cooling medium outlet 42 are connected to each other, and the cooling medium supply manifold and the discharge manifold are configured similarly. The supply and discharge manifolds for oxygen gas and the supply and discharge manifolds for the cooling medium are omitted in FIG. 1 for simplicity.

  Referring again to FIG. 1, one end of the staying gas discharge through hole 28 is connected to the discharge manifold 20 by a connecting pipe 44 on the first end plate 6 side. The connecting pipe 44 is disposed outside the stacks 2a and 2b. The connecting pipe 44 has a third valve 46 in the middle thereof. The third valve 46 can open and close the connecting pipe 44.

  On the other hand, the other end of the staying gas discharge through hole 28 is connected to a discharge pipe 48 on the second end plate 8 side. The discharge pipe 48 has a fourth valve 50 in the middle thereof. The discharge pipe 48 is connected to the discharge pipe 22 on the downstream side of the second valve 24 of the discharge pipe 22 to join the exhaust pipe 22, and finally joins the discharge pipe 26.

  As described above, since the stacks 2a and 2b are connected in series, the potential difference between the stack 2a and the stack 2b is zero on the second end plate 8 side. In addition, the supply pipe 14 and the discharge pipes 22 and 48 connected to the stacks 2a and 2b are arranged on the second end plate 8 side where the potential difference is zero. Therefore, even if these supply pipes or discharge pipes finally join the supply pipe 12 and the discharge pipe 26, respectively, a problem such as a short circuit does not occur.

  On the other hand, the first end plate 6 has a large potential difference between the stacks 2a and 2b. A connecting pipe 44 is provided on the first end plate 6 side. However, each of the connecting pipes 44 is disposed on the same first end plate 6 and is configured so as not to cause a problem such as a short circuit.

  The fuel cell system has a control device 52. The control device 52 controls the supply of the fuel gas to the supply pipe 12 and the opening and closing of the first to fourth valves 16, 24, 46 and 50. The control device 52 can detect the fuel gas supply time.

[Operation of the fuel cell system according to Embodiment 1 during power generation]
FIG. 3 is a schematic diagram for explaining the flow of fuel gas during normal power generation in the fuel cell system of the first embodiment.
As shown in FIG. 3, during the normal power generation of the fuel cell system, only the first valve 16 and the second valve 24 are opened, and the third valve 46 and the fourth valve 50 are closed. The control device 52 of the fuel cell system is in a state of the first to fourth valves during power generation, that is, a state in which the first valve 16 and the second valve 24 are opened, and the third valve 46 and the fourth valve 50 are closed. These are stored as opening / closing conditions during power generation, and during power generation, each valve is controlled to the opening / closing conditions during power generation.

  During power generation of the fuel cell system, hydrogen is supplied from the supply pipe 12 to the supply manifold 18 as a fuel gas through the supply pipe 14 under the open / close conditions during power generation. The hydrogen supplied to the supply manifold 18 is supplied to the fuel gas channel on the anode side of each cell 4. On the other hand, similarly, air is supplied from the oxygen supply manifold and supplied to the oxygen gas flow path on the cathode side of each cell 4.

  When hydrogen is supplied to the anode, electrons are separated by the catalyst of the anode, and the supplied hydrogen becomes hydrogen ions. Hydrogen ions move to the cathode side through the solid polymer membrane. The hydrogen ions that have moved to the cathode side react with oxygen supplied to the cathode side to become water vapor. Here, the electrons separated from the hydrogen ions travel to the cathode through another path. As a result, current flows from the cathode to the anode, and electric power is generated. Thus, the electric power generated in each cell 4 is recovered from the terminals 10a and 10b.

  The exhaust gas on the anode side is discharged from the fuel gas passage to the discharge manifold 20. Here, the third valve 46 is in a closed state, that is, the first plate 6 side of the discharge manifold 20 is closed. Accordingly, the gas discharged from the discharge manifold 20 is discharged through the discharge pipe 26 via the discharge pipe 22 on the first end plate 6 side.

[Operation of the fuel cell system according to Embodiment 1 at the time of startup]
When the fuel cell system is left standing after power generation is stopped, the fuel gas supplied to the anode side may be gradually released. Further, even when left unattended, the reaction between the fuel gas and oxygen gradually proceeds, and the fuel gas on the anode side may be lost. Therefore, when the fuel cell is started after being left standing, the fuel gas on the anode side may be lost and the anode side may be filled with a staying gas such as oxygen or nitrogen. Therefore, when starting the fuel cell system after being left, it is necessary to replace the fuel gas flow path of the cell 4 with the fuel gas.

FIG. 4 is a schematic diagram for explaining a gas flow during fuel gas flow path replacement in the fuel cell system of the first embodiment.
As shown in FIG. 4, when the fuel gas flow path is replaced, the second valve 24 is closed and the first valve 16, the third valve 46, and the fourth valve 50 are opened. The control device 52 is in the state of the first to fourth valves at the time of such replacement, that is, the state in which the first valve 16, the third valve 46, the fourth valve 50 are opened and the second valve 24 is closed. It is stored as the opening / closing condition at the time of replacement. Further, the control device 52 stores the time required for replacing the fuel gas flow path of each cell 4 with the fuel gas as the required replacement time.

  When replacing the fuel gas flow path, the fuel gas is supplied from the supply pipe 12 under the opening and closing conditions during the replacement. The supplied fuel gas flows from the supply manifold 18 into the fuel gas flow path of each cell 4 via the supply pipe 14. The inflowing gas discharges a staying gas such as nitrogen or oxygen in the fuel gas flow path to the discharge manifold 20.

  Here, the discharge pipe 22 of the discharge manifold 20 is closed by the second valve 24. Accordingly, the staying gas discharged to the discharge manifold 20 is pushed out to the connecting pipe 44 and flows into the staying gas discharge through hole 28 from the connecting pipe 44. The staying gas flowing into the staying gas discharge through hole 28 flows into the discharge pipes 48 and 26 and is discharged.

  Thus, when replacing the fuel gas flow path, the fuel gas is supplied to the flow path of each cell 4 from the inlet on the second end plate 8 side of the supply manifold 18. Then, after passing through the fuel gas flow path of the cell 4, the discharge manifold 20 is once discharged toward the outlet on the first end plate 6 side, that is, the side opposite to the inlet of the supply manifold 18. Therefore, the fuel gas can be efficiently distributed to the cell 4 at the back of the inlet of the supply manifold 18.

[Control of fuel cell system]
FIG. 5 is a schematic diagram for explaining a control routine executed by the control device 52 in the fuel cell system of the first embodiment. Each of the above operations is executed by executing this routine.
As shown in FIG. 5, in step S102, first, it is detected whether or not the fuel cell is activated. If it has not been started, this routine is once terminated.

  If activation of the fuel cell system is detected in step S102, the first to fourth valves are set to satisfy the opening / closing conditions at the time of replacement (step S104). That is, the control device 52 controls the first to fourth valves according to opening / closing conditions stored at the time of replacement. As a result, the second valve 24 is closed, and the first, third, and fourth valves 16, 46, and 50 are opened.

  Next, fuel gas is supplied (step S106). The supplied fuel gas pushes out the accumulated gas accumulated in the fuel gas flow path and flows out to the discharge manifold 20 together with the flow of the fuel gas. The stagnant gas that has flowed out passes through the connecting pipe 44, the stagnant gas discharge through hole 28, and the discharge pipe 48 and is discharged from the discharge pipe 26.

  Next, it is determined whether or not a required replacement time has been detected after the start of fuel gas supply (step S108). The control device 52 determines whether or not the elapsed time from the start of fuel gas supply is equal to or longer than the replacement required time stored in advance. Thereby, it is determined whether or not the replacement of the fuel gas flow path of each cell 4 is completed. If it is determined in step S108 that the required replacement time has not elapsed, the replacement of the fuel gas is continued (step S106).

  On the other hand, if it is determined in step S108 that the required replacement time has elapsed, the first to fourth valves are set to open / close conditions during power generation (step S110). That is, the control device 52 controls the first to fourth valves according to opening / closing conditions at the time of power generation stored in advance. As a result, the second valve 24 is opened while the first valve 16 is open, and the third and fourth valves 46 and 50 are closed.

  Next, power generation of the fuel cell system is started (step S112). At this time, the fuel gas is supplied from the supply manifold 18 to the fuel gas flow path of each cell 4 and discharged from the discharge manifold 20 via the discharge pipe 22. In addition, the supply of fuel gas causes a reaction between hydrogen ions and oxygen on the anode side and the cathode side, and electrons are separated to generate electric power. This electric power is recovered from the power extraction terminals 10a and 10b.

  As described above, in the fuel cell system according to Embodiment 1, the fuel gas is supplied from the second end plate 8 side and discharged to the first end plate 6 side at the time of replacement before startup. Gas passages can be set. Therefore, unnecessary staying gas accumulated in the fuel gas passage can be efficiently discharged. On the other hand, during power generation, the fuel gas passage can be changed so that the fuel gas is supplied and discharged from the second end plate 8 side. Therefore, at the time of power generation, the fuel gas can be efficiently supplied and the power generation efficiency of the fuel cell system can be kept high.

  In the first embodiment, the structure in which the discharge pipe 22 and the discharge pipe 48 are connected downstream of the second valve 24 and merge with the discharge pipe 26 has been described. However, the present invention is not limited to this. For example, the discharge pipes 48 of the respective stacks 2a and 2b may be aggregated by providing other discharge pipes independently of the discharge pipe 22. .

  In the first embodiment, the case where the discharge manifold 20 and the staying gas discharge through hole 28 are connected by the connecting pipe 44 provided outside the stacks 2a and 2b has been described. However, the present invention is not limited to this, and the discharge manifold 20 and the staying gas discharge through hole 28 are connected inside the stacks 2a and 2b, for example, in the first end plate 6. May be. In this case, however, means corresponding to the third valve 46 for opening and closing between the discharge manifold 20 and the staying gas discharge through hole 28 is necessary.

Embodiment 2.
[Fuel Cell System of Embodiment 2]
FIG. 6 is a schematic diagram showing a hydrogen concentration sensor according to Embodiment 2 of the present invention.
The fuel cell system in Embodiment 2 is the same as the fuel cell system shown in FIG. 1 except that the hydrogen concentration sensor shown in FIG. 6 is provided.

  The hydrogen concentration sensor shown in FIG. 6 is installed in the connecting pipe 44. The hydrogen concentration sensor includes the inside of a container 60 insulated by an insulator 62. The container 60 is disposed in a hole provided in a part of the connecting pipe 44 by being insulated by an insulator 62. Further, the connection surface of the container 60 with the connecting pipe 44 is closed by an electrolyte membrane 64. The space formed by the container 60 and the electrolyte membrane 64 is filled with pure hydrogen 66. A first catalyst 68 is disposed in the container 60. The first catalyst 68 is in contact with the pure hydrogen 66 on one surface, and is in contact with the electrolyte membrane 64 on the surface opposite to this surface. A second catalyst 70 is provided on the side of the connecting pipe 44 of the electrolyte membrane 64. The second catalyst 70 is exposed in the connecting pipe 44 and is exposed to the gas flowing in the connecting pipe 44. In addition, a voltmeter 72 is connected to the first catalyst 68 and the second catalyst 70, and the voltage between the first catalyst 68 and the second catalyst 70 can be measured. A control device 52 is connected to the voltmeter 72.

  This hydrogen concentration sensor generates an electromotive force generated between the first and second catalysts 68 and 70 in accordance with the concentration difference between pure hydrogen 66 in the container 60 and hydrogen in the gas flowing through the connecting pipe 44. Measured with a total of 72. The control device 52 can output the hydrogen concentration of the gas in the connection pipe 44 according to the measured voltage.

  The hydrogen concentration in the staying gas discharged to the connection pipe 44 increases as the replacement of the fuel gas flow path of the cell 4 with hydrogen proceeds. The control device 52 stores the hydrogen concentration output when the replacement of the fuel gas flow path is completed as the replacement completed hydrogen concentration.

[Control of Embodiment 2]
FIG. 7 is a flowchart for illustrating a control routine executed by control device 52 in the fuel cell system of the second embodiment.
The routine shown in FIG. 7 is the same as the routine shown in FIG. 5 except that step S202 is performed instead of step S108 of the routine shown in FIG.

  Specifically, after the supply of fuel gas is started in step S106, it is determined in step S202 whether or not the hydrogen concentration of the gas flowing through the connecting pipe 44 is greater than the replacement completion hydrogen concentration. That is, it is determined based on the hydrogen concentration whether or not the replacement of the fuel gas flow path with the hydrogen gas is completed.

  If it is determined that the hydrogen concentration is higher than the substitution completion hydrogen concentration, the process proceeds to step S110 as described in the first embodiment. On the other hand, when it is determined that the hydrogen concentration is lower than the replacement completion hydrogen concentration, the fuel gas is continuously supplied (step S106).

  As described above, in the second embodiment, in addition to the first embodiment, the completion of the replacement of the fuel gas can be determined by measuring the hydrogen concentration in the connecting pipe 44. Therefore, as compared with the case of the first embodiment in which replacement is performed for a certain period of time, replacement can be surely performed and wasteful consumption of fuel gas can be suppressed.

[Another example of the second embodiment]
FIG. 8 shows another example of the fuel cell system in the second embodiment.
FIG. 8 is the same as that described in the second embodiment except that an N ₂ sensor 74 is used for the connecting pipe 44 instead of the hydrogen concentration sensor.

At the start of the fuel cell system, N ₂ stays in the fuel gas flow path. Therefore, in a state where the replacement of the fuel gas channel is not completed, N ₂ is mixed in the exhausted gas, and when the replacement is completed, N ₂ is hardly mixed in the exhaust gas. Therefore, even when the N ₂ sensor 74 is used, the end of the replacement can be detected. In this case, the control unit 52, the N ₂ concentration to be replaced ends, and stored as substituted completed N ₂ concentration, in step S202, N ₂ concentration is determined whether or not reduced to complete N ₂ concentration substituted . As described above, the completion of the replacement can also be detected by providing the N ₂ sensor 74 in the connecting pipe 44 and measuring the N ₂ concentration.

In FIG. 8, the case where the N ₂ sensor 74 is used instead of the hydrogen concentration sensor has been described. However, the present invention is not limited to this. For example, instead of the hydrogen concentration sensor of the concentration cell method as described above, a catalyst type hydrogen concentration sensor may be used. Similarly, in the present invention, for example, a CO ₂ sensor can be used instead of the N ₂ sensor. During replacement of the gas flow path, CO ₂ is mixed into the staying gas, but when the replacement is completed, CO ₂ is hardly mixed. Therefore, the end of replacement can be detected even using a CO ₂ sensor.

  Further, for example, the present invention may use a cell monitor to determine the completion of gas replacement based on whether or not the cell voltage has risen. However, if the gas is replaced near the cell monitor, the detected potential may increase. As a result, an erroneous determination may be made even though replacement of the entire cell has not been completed. Therefore, considering the certainty and ease of replacement determination, the method using the gas concentration sensor is effective as described above.

  In addition to the control of the fuel cell system according to the first and second embodiments, the present invention is provided with an inert gas supply means connected to the supply pipe 12 so that the nitrogen can be supplied from the supply pipe 12 while the fuel cell system is stopped. For example, an inert gas such as an inert gas may be supplied to replace the fuel gas flow path with an inert gas. Thereby, it is possible to suppress an unnecessary reaction from occurring in the fuel gas flow channel during the stop. At this time, the inert gas may be supplied by controlling each valve to the opening and closing conditions at the time of replacement. Thereby, it can replace efficiently to the fuel gas flow path of the cell 4 near the 1st end plate 6 side. Further, even when the fuel gas flow path is filled with the inert gas during the stop as described above, according to the fuel cell system of the present invention, the fuel gas can be efficiently replaced by the fuel gas at the time of startup.

  Further, instead of the inert gas, the supply pipe 12 is provided with an oxidant supply means for supplying air or oxidant gas, and the air or oxidant gas is supplied in a similar manner while the fuel cell system is stopped. Then, the fuel gas flow path may be replaced. As described above, even when air or oxidant gas is used, unnecessary reaction in the fuel gas flow channel during stoppage can be suppressed.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the number referred to It is not limited. Further, the structures described in the embodiments, steps in the method, and the like are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

For example, in the first and second embodiments, the first end plate 6 and the second end plate 8 correspond to the “opposing surface” and “equipotential surface” of the present invention, respectively, and the discharge pipe 22 and the discharge pipe. 48 correspond to “first discharge pipe” and “second discharge pipe”, respectively, and the second valve 24, the third valve 46, and the fourth valve 50 are “discharge section opening / closing means” and “connecting pipe”, respectively. It corresponds to “opening / closing means” and “opening / closing means for staying gas”. Further, for example, in the first embodiment, the “supply time detecting means” of the present invention is realized by detecting the supply time by the control device 52. Further, for example, the nitrogen concentration sensor, the N ₂ sensor 74, and the CO ₂ sensor according to the _second embodiment correspond to the “gas concentration sensor” of the present invention.

  Further, for example, in the first and second embodiments, by executing steps S104 and S110, the “control means” of the present invention is realized, and by executing step S108 or step S202, the “replacement completion” of the present invention is achieved. "Detection means" and "comparison means" are realized.

It is a schematic diagram for demonstrating the fuel cell system in Embodiment 1 of this invention. It is a front view for demonstrating the cell of the fuel cell system in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the state at the time of the electric power generation of the fuel cell system in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the state at the time of replacement | exchange of the fuel cell system in Embodiment 1 of this invention. It is a flowchart for demonstrating the routine of control which the fuel cell system in Embodiment 1 of this invention performs. It is a schematic diagram for demonstrating the fuel cell system in Embodiment 2 of this invention. It is a flowchart for demonstrating the routine of control which the fuel cell system in Embodiment 2 of this invention performs. It is a schematic diagram for demonstrating the other example of the fuel cell system in Embodiment 2 of this invention.

Explanation of symbols

2a, 2b Stack 4 cell 6 1st end plate 8 2nd end plate 10a, 10b Terminals 12, 14 Supply piping 16 First valve 18 Supply manifold 20 Discharge manifold 22 Discharge piping 24 Second valve 26 Discharge piping 28 Residual gas Through hole 30 for discharge 30 Anode inlet 32 Anode outlet 34 Remaining gas discharge hole 36 Cathode inlet 38 Cathode outlet 40 Cooling medium inlet 42 Cooling medium outlet 44 Connecting pipe 46 Third valve 48 Discharge pipe 50 Fourth valve 52 Controller 60 Container 62 Insulation Body 64 Electrolyte membrane 66 Pure hydrogen 68 First catalyst 70 Second catalyst 72 Voltmeter 74 N ₂ sensor

Claims (11)

In a fuel cell system comprising two stacks connected in series, wherein a plurality of unit cells are stacked,
Each stack is
Of the both end faces of the unit cell in the stacking direction, through the stack from the equipotential surface that is equipotential between the stacks, to the facing surface that is the end face opposite to the equipotential face, and A supply manifold connected to each gas flow path of the unit cell;
A discharge manifold that passes through the stack from the equipotential surface to the opposing surface and is connected to each gas flow path;
A first exhaust pipe connected to an outlet on the equipotential surface side of the exhaust manifold and exhausting the gas exhausted from the exhaust manifold out of the stack;
Discharge part opening and closing means for opening and closing the first discharge pipe;
A stagnant gas discharge through-hole penetrating the stack from the equipotential surface to the opposing surface;
A connecting pipe connecting the exhaust manifold and the staying gas discharge through-hole on the opposite surface side;
Connecting pipe opening and closing means for opening and closing the connecting pipe;
On the equipotential surface side, connected to the through hole for staying gas discharge, and a second discharge pipe for discharging the gas discharged from the through hole for staying gas discharge out of the stack;
With
The first discharge pipes of the stacks merge with each other outside the stack,
The fuel cell system according to claim 1, wherein the second discharge pipes of the stacks merge with each other outside the stack. Supply means for supplying gas from an inlet on the equipotential surface side of the supply manifold;
When the fuel cell system is started, the discharge part opening / closing means is closed and the connecting pipe opening / closing means is opened to be in a first open / close state, and when the fuel cell system is generating power, the discharge part opening / closing means is opened, Control means for controlling the pipe opening / closing means to be in a second open / closed state,
The fuel cell system according to claim 1, comprising: A replacement completion detecting means for detecting that the staying gas in the gas flow path is replaced with the supply gas from the supply means;
3. The fuel cell system according to claim 2, wherein when the gas replacement completion is detected, the control unit sets the second open / close state. 4. The replacement completion detecting means is a supply time detecting means for detecting a supply time of a supply gas for replacing the gas flow path with the supply gas;
A comparison means for comparing whether or not the supply time is equal to or longer than a required replacement time sufficient to replace the gas flow path;
With
4. The fuel cell system according to claim 3, wherein the control unit sets the second open / close state when the supply time is equal to or longer than the time required for replacement. The replacement completion detection means includes a gas concentration sensor provided in the connection pipe,
Comparison means for comparing the output of the gas concentration sensor with a judgment value output when the gas flow path is replaced with the supply gas;
With
4. The fuel cell according to claim 3, wherein the control means sets the second open / close state when it is determined from the result of the comparison that the inside of the gas flow path is replaced with the supply gas. 5. system.   6. The fuel according to claim 1, wherein the second discharge pipe is connected to the first discharge pipe on a downstream side of the gas flow with respect to the discharge portion opening / closing means. Battery system.   Residual gas opening / closing means for opening and closing the second discharge pipe is provided upstream of the connection of the first discharge pipe and the second discharge pipe of the second discharge pipe with respect to the gas flow. The fuel cell system according to claim 6. The connecting pipe is provided outside the stack,
The fuel cell system according to any one of claims 1 to 7, wherein the opposed surface is connected to the staying gas discharge through hole and the discharge manifold.   9. The fuel cell system according to claim 1, wherein the supply manifold and the discharge manifold are manifolds on an anode side of the fuel cell. An oxidant supply means for supplying an oxidant gas or the air from an inlet on the equipotential surface side of the supply manifold;
The fuel cell system according to claim 9, wherein the gas flow path is replaced with the oxidant gas or the air while the fuel cell system is stopped. The fuel cell system includes an inert gas supply means for supplying an inert gas from an inlet on the equipotential surface side of the supply manifold,
The fuel cell system according to any one of claims 1 to 9, wherein the gas flow path is replaced with the inert gas while the fuel cell system is stopped.

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