JP2006294341A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an excessive increase of a fuel gas pressure supplied to a fuel cell without restricting a design in order to facilitate diffusion of hydrogen discharged to an external. <P>SOLUTION: This fuel cell system 10 comprises a first hydrogen passage 60 for supplying fuel gas containing the hydrogen to the fuel cell 22, a second hydrogen passage 66 connected to the first hydrogen passage 60, a first relief valve 69 provided on the second hydrogen passage 66, and opening when a pressure in the second hydrogen passage 66 exceeds a first reference value, and a hydrogen concentration reducing part connected on a downstream side of the second hydrogen passage 66 for reducing the concentration of the hydrogen discharged through the first relief valve 69 before discharge to the external. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell.

  When power generation is performed using a fuel cell, a fuel gas containing hydrogen is supplied to the anode, and various safety measures are generally taken in such a fuel gas supply unit. In particular, in a system in which fuel gas is supplied from a high-pressure hydrogen-containing gas supply source (for example, a hydrogen tank) and the fuel gas is supplied to the fuel cell after the pressure is appropriately reduced, a mechanism related to the pressure adjustment of the fuel gas It is important to take countermeasures when problems occur. This is because if fuel gas having an excessive pressure is supplied, piping or valves on the downstream side or the fuel cell may be damaged. As one of such measures, a relief valve that opens at a predetermined pressure is provided in a supply path for supplying hydrogen gas to the fuel cell. When the hydrogen gas pressure exceeds a predetermined value, hydrogen gas is allowed to flow from the relief valve. A configuration for discharging outside the road is known (for example, Japanese Patent Application Laid-Open No. 2002-216812).

JP 2002-216812 A JP 2004-55287 A

  However, when such a relief valve is provided to discharge the hydrogen-containing gas to the outside, the relief valve is included so that the concentration when hydrogen, which is a combustible gas, is discharged to the outside can be kept as low as possible. It was necessary to set the shape of the whole discharge part of hydrogen gas. That is, in order to facilitate diffusion of hydrogen discharged to the outside, the piping length of the flow path connected to the relief valve, the arrangement position of the flow path connected to the relief valve and the relief valve, or hydrogen gas to the outside It was necessary to set the overall shape such as the direction of the discharge port for discharging the hydrogen so as to promote the diffusion of the discharged hydrogen. In particular, when the fuel cell system is used as a power source for driving a moving body such as a vehicle, the mounting space of the fuel cell system is limited, and the shape of piping related to hydrogen discharge may be limited. It was.

  The present invention has been made to solve the above-described conventional problems, and in a fuel cell system, the fuel cell system is supplied to the fuel cell without imposing design restrictions to promote the diffusion of hydrogen discharged to the outside. The purpose is to prevent an excessive increase in the fuel gas pressure.

To achieve the above object, the present invention provides a fuel cell system including a fuel cell,
A first flow path for supplying a fuel gas containing hydrogen to the fuel cell;
A second flow path connected to the first flow path;
The valve is provided when the second flow path or a connection portion between the second flow path and the first flow path exceeds the first reference value. A first relief valve;
A hydrogen concentration reduction unit that is connected to the downstream side of the second flow path and reduces the concentration of hydrogen discharged from the first flow path via the first relief valve prior to discharge to the outside. The gist is to provide and.

  According to the fuel cell system of the present invention configured as described above, the first relief valve opens when the pressure in the first flow path exceeds the first reference value. In this flow path, the gas having a pressure exceeding the allowable range is not supplied to the downstream side of the connection portion with the second flow path. As described above, when hydrogen is discharged from the first flow path to the outside via the first relief valve, the hydrogen concentration is reduced by the hydrogen concentration reducing unit, so that the hydrogen concentration in the gas discharged to the outside is reduced. Can be suppressed. Further, by using the hydrogen concentration reducing unit in this way, it is not necessary to promote the diffusion of hydrogen when discharging the gas as in the case of discharging to the outside without reducing the hydrogen concentration in advance. Design limitations imposed to promote hydrogen diffusion can be reduced.

In the fuel cell system of the present invention,
A pressure adjusting unit that is provided in the first flow path and adjusts the pressure of the fuel gas supplied to the fuel cell;
The second flow path may be connected to the first flow path on the downstream side of the arrangement position of the pressure adjusting unit.

  With such a configuration, it is possible to prevent an excessive pressure from being applied to the downstream side of the first flow path due to a problem occurring in the pressure adjusting unit.

In the fuel cell system of the present invention,
A hydrogen storage section for storing hydrogen and connecting to the first flow path;
A shut valve that is provided in the first flow path and that is closed when the fuel cell system is stopped. The second flow path is downstream of the shut valve with respect to the first flow path. It is good also as connecting.

  With such a configuration, when the shut valve is closed when the fuel cell system is stopped, hydrogen leaks from the shut valve to the downstream side, and downstream of the shut valve in the first flow path. Even when the pressure on the side increases, it is possible to prevent a pressure increase exceeding the allowable range.

In the fuel cell system of the present invention,
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path that connects the oxidant gas supply unit and the cathode of the fuel cell and guides the oxidant gas to the cathode of the fuel cell;
The hydrogen concentration reducing unit is provided in a cathode exhaust gas flow path for guiding cathode exhaust gas discharged from the cathode to the outside, and has a cross-sectional area larger than the cross-sectional area of the cathode exhaust gas flow path. It may be a diluter connected to the downstream side of the path.

  With such a configuration, the concentration of hydrogen discharged through the first relief valve can be reduced by using the cathode exhaust gas in the diluter.

In such a fuel cell system of the present invention,
An oxidizing gas amount control unit for controlling an oxidizing gas supply amount from the oxidizing gas supply unit when generating power with the fuel cell, and when the first relief valve opens, the oxidizing gas supply unit It is good also as providing the oxidizing gas amount control part which increases the oxidizing gas supply amount from from the value set based on the electric power generation amount in the said fuel cell.

  With such a configuration, the amount of cathode exhaust gas increases when hydrogen flowing through the first relief valve flows into the diluter, so that the effect of reducing the concentration when discharging hydrogen can be enhanced. .

Alternatively, in the fuel cell system of the present invention,
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path connecting the oxidant gas supply unit and the cathode of the fuel cell, and leading the oxidant gas to the cathode of the fuel cell;
A diluter having a cross-sectional area larger than the cross-sectional area of the cathode exhaust gas flow path, provided in the cathode exhaust gas flow path for guiding the cathode exhaust gas discharged from the cathode to the outside;
A fuel cell temperature acquisition unit for acquiring the temperature of the fuel cell;
A first branch path branched from the second flow path and connected to the diluter;
A second branch path branched from the second flow path and connected to the oxidizing gas flow path;
A switching unit that exclusively switches between a state in which the second flow path communicates with the first branch path and a state in which the second flow path communicates with the second branch path;
When the temperature of the fuel cell acquired by the fuel cell temperature acquisition unit is equal to or higher than a reference value, the switching unit is driven to connect the second flow path and the second branch path, and the fuel cell A switching control unit that drives the switching unit to connect the second flow path and the first branch path when the temperature is lower than a reference value;
When the second flow path communicates with the first branch path, the diluter functions as the hydrogen concentration reducing unit, and when the second flow path communicates with the second branch path, the fuel A cathode catalyst provided in the battery may serve as the hydrogen concentration reduction unit.

  With such a configuration, when the temperature of the fuel cell is equal to or higher than the reference value, the concentration of hydrogen discharged via the first relief valve can be reduced by the cathode catalyst, and the temperature of the fuel cell is set to the reference value. When below the value, the concentration of the discharged hydrogen can be reduced using cathode exhaust gas in the diluter. As described above, when the temperature of the fuel cell is low, the hydrogen concentration reducing unit different from the cathode catalyst is used. Therefore, even if the temperature of the fuel cell changes, it is possible to suppress a decrease in the efficiency of hydrogen concentration reduction.

In such a fuel cell system of the present invention,
An oxidizing gas amount control unit for controlling an oxidizing gas supply amount from the oxidizing gas supply unit when generating power by the fuel cell, wherein the first relief valve is opened and the second flow path is opened. Is provided with an oxidant gas amount control unit that increases the oxidant gas supply amount from the oxidant gas supply unit to a value that is set based on the power generation amount in the fuel cell when communicating with the first branch passage. It's also good.

  With such a configuration, the amount of cathode exhaust gas increases when hydrogen flowing through the first relief valve flows into the diluter, so that the effect of reducing the concentration when discharging hydrogen can be enhanced. .

In the fuel cell system of the present invention,
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path for connecting the oxidant gas supply unit and the fuel cell and introducing the oxidant gas to the cathode of the fuel cell;
The second flow path is further connected to the oxidizing gas flow path,
The hydrogen concentration reduction unit may be a cathode catalyst provided in the fuel cell.

  With such a configuration, the hydrogen concentration can be reduced by oxidizing the hydrogen discharged via the first relief valve on the cathode catalyst.

In the fuel cell system of the present invention,
The first flow path is connected to the first flow path so as to communicate with the second flow path via the first flow path, and the pipe diameter of the flow path is formed larger than that of the second flow path. A third flow path,
The second flow path is provided at a connection portion between the third flow path or the third flow path and the first flow path, and the pressure in the third flow path is larger than the first reference value. And a second relief valve that opens when the reference value is exceeded.

  With such a configuration, even when the pressure in the first flow path continues to rise after the first relief valve opens, the second relief valve opens and the third flow path opens. Since more gas is discharged from, the pressure rise in the first flow path can be suppressed. In addition, since the second channel has a smaller pipe diameter than the third channel, and the second channel has a smaller amount of gas flowing than the third channel, the second channel is connected to the second channel. The pressure of the gas supplied to the hydrogen concentration reduction unit can be suppressed, and damage to the hydrogen concentration reduction unit due to excessive gas pressure can be prevented.

In the fuel cell system of the present invention,
A hydrogen storage section for storing hydrogen and connecting to the first flow path;
The first flow path is provided in the first flow path, is closed when the fuel cell system is stopped, and is provided on the downstream side of the connection portion of the first flow path with the second flow path. The shut valve and
The second channel is provided in the first channel, is closed when the fuel cell system is stopped, and is provided upstream of the connection portion of the first channel with the second channel. With a shut valve and
The second flow path is further connected to the downstream side of the position where the first shut valve is disposed in the first flow path,
When the first relief valve is opened when the fuel cell system is stopped, hydrogen flows in through the relief valve, and the introduced hydrogen flows from the anode side channel to the cathode side. The fuel cell may pass through the electrolyte layer to the flow path.

  With this configuration, when the first and second shut valves are closed when the fuel cell system is stopped, hydrogen leaks downstream from the second shut valve, and the second Even when the pressure on the downstream side of the shut valve increases, it is possible to prevent excessive pressure from being applied to the first shut valve or further downstream. At that time, hydrogen concentration discharged through the first relief valve is allowed to permeate from the anode-side channel to the cathode-side channel through the electrolyte layer in the fuel cell. Can be reduced.

In such a fuel cell system of the present invention,
The first flow path is connected between the first shut valve and the second shut valve, and communicates with the second flow path via the first flow path. A third channel having a pipe diameter larger than that of the second channel;
The second flow path is provided at a connection portion between the third flow path or the third flow path and the first flow path, and the pressure in the third flow path is larger than the first reference value. And a second relief valve that opens when the reference value is exceeded.

  With such a configuration, even when the pressure in the first flow path continues to rise after the first relief valve opens, the second relief valve opens and the third flow path opens. Since more gas is discharged from, the pressure rise in the first flow path can be suppressed.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of a moving body in which the fuel cell system of the present invention is mounted as a driving power source.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Overall system configuration:
B. Action to prevent excessive hydrogen gas pressure rise:
C. Second embodiment:
D. Third embodiment:
E. Fourth embodiment:
F. Variations:

A. Overall system configuration:
FIG. 1 is a block diagram showing an outline of a configuration of a portion related to power generation of a fuel cell in a fuel cell system 10 which is an embodiment of the present invention. The fuel cell system 10 of the present embodiment is mounted on a vehicle and used as a power source for driving the vehicle. The fuel cell system 10 includes a fuel cell 22 that is a main body of power generation, a hydrogen tank 23 that stores hydrogen to be supplied to the fuel cell 22, and an air compressor 24 for supplying compressed air to the fuel cell 22. Yes. Here, the hydrogen tank 23 is connected to the anode of the fuel cell 22 by the first flow path 60, and hydrogen stored in the hydrogen tank 23 is supplied to the anode of the fuel cell 22 as fuel gas. The air compressor 24 is connected to the cathode of the fuel cell 22 by an oxidizing gas supply path 67, and the air taken in by the air compressor 24 is supplied as an oxidizing gas to the cathode of the fuel cell 22. Although various types of fuel cells can be used as the fuel cell 22, in this embodiment, a polymer electrolyte fuel cell is used as the fuel cell 22. The fuel cell 22 has a stack structure in which a plurality of single cells are stacked. Below, the flow of the gas in each part which comprises the fuel cell system 10, and the fuel cell system 10 is further demonstrated.

  The hydrogen tank 23 is, for example, a hydrogen cylinder that stores high-pressure hydrogen. Or it is good also as a tank which stores hydrogen by providing a hydrogen storage alloy inside and making it store in a hydrogen storage alloy. The hydrogen gas stored in the hydrogen tank 23 is discharged to the first hydrogen flow path 60 connected to the hydrogen tank 23, and then adjusted (depressurized) to a predetermined pressure by the pressure adjustment valve 62 to obtain fuel gas. The fuel cell 22 is supplied to the anode of each unit cell. In the fuel cell system 10 of FIG. 1, only one pressure adjusting valve is provided in the first hydrogen flow path 60, but when supplying hydrogen to the hydrogen pressure in the hydrogen tank 23 or supplying hydrogen to the fuel cell 22. A plurality of pressure regulating valves may be provided as appropriate according to the desired pressure. In this case, the pressure adjustment valve 62 in FIG. 1 corresponds to the pressure adjustment valve disposed on the most downstream side, that is, the position closest to the fuel cell 22.

  The anode exhaust gas discharged from the anode of the fuel cell 22 is guided to the anode exhaust gas path 63 and flows into the first hydrogen channel 60 again. As described above, the remaining hydrogen in the anode exhaust gas is a flow path (hereinafter referred to as a circulation flow path) including a part of the first hydrogen flow path 60, the anode exhaust gas path 63, and the flow path in the fuel cell 22. It circulates in the interior and is used again for electrochemical reaction. The pressure in the circulation channel is adjusted by the pressure regulating valve 62 so that the electrochemical reaction according to the load request can proceed, and the hydrogen tank 23 is passed through the pressure regulating valve 62 as the electrochemical reaction proceeds. To the circulation channel. In order to circulate the anode exhaust gas in the circulation channel, a hydrogen pump 65 is provided in the anode exhaust gas channel 63. Note that a shut valve 61 is provided in the first hydrogen flow path 60 on the upstream side of the pressure adjustment valve 62. The shut valve 61 is closed when power generation in the fuel cell 22 is stopped, and shuts off the supply of hydrogen gas from the hydrogen tank 23 to the fuel cell 22.

  Furthermore, a second hydrogen flow channel 66 that is a flow channel communicating with the first hydrogen flow channel 60 is connected to the first hydrogen flow channel 60 on the downstream side of the pressure regulating valve 62. The second hydrogen flow channel 66 is provided with a first relief valve 69 that opens at a preset first pressure and closes at a preset second pressure. The second hydrogen channel 66 is further connected to an oxidizing gas supply channel 67 that supplies an oxidizing gas to the fuel cell 22. The operation of discharging the hydrogen gas from the first hydrogen flow path 60 via the first relief valve 69 will be described in detail later.

  The anode exhaust gas path 63 is provided with a gas-liquid separator 27. As the electrochemical reaction proceeds, water is generated at the cathode, and the generated water is also introduced into the fuel gas supplied to the anode side through the electrolyte membrane of the fuel cell 22. The gas-liquid separator 27 condenses the water vapor contained in the anode exhaust gas and removes it from the anode exhaust gas. The gas-liquid separator 27 is provided with a valve 27a. By opening the valve 27a, water condensed in the gas-liquid separator 27 passes through an exhaust gas discharge path 64 connected to the valve 27a. It is discharged to the outside. When the valve 27a is opened, a part of the anode exhaust gas flowing in the anode exhaust gas path 63 is also discharged to the outside together with the condensed water. During operation of the fuel cell 22, in the gas flowing on the anode side, water is introduced from the cathode side through the electrolyte membrane as described above, and nitrogen in the air supplied to the cathode is also introduced. . Therefore, if power generation by the fuel cell is continued, the concentration of impurities such as nitrogen increases in the hydrogen-containing gas circulating in the circulation channel, but the hydrogen-containing gas circulating with the valve 27a opened at a predetermined timing. By discharging a part of the gas to the outside, an increase in impurity concentration in the hydrogen-containing gas is suppressed. Here, the exhaust gas discharge path 64 is connected to the diluter 26 which is a container having a larger cross-sectional area than the exhaust gas discharge path 64. The diluter 26 is provided to dilute the hydrogen in the anode exhaust gas with a cathode exhaust gas to be described later before discharging the anode exhaust gas to the outside.

  The air compressor 24 supplies pressurized air as an oxidizing gas to the cathode of the fuel cell 22 via the oxidizing gas supply path 67. When the air compressor 24 compresses air, the air is taken in from the outside via the air cleaner 28. The cathode exhaust gas discharged from the cathode is guided to the cathode exhaust gas path 68 and discharged to the outside. Here, the second hydrogen flow channel 66 is connected to the oxidizing gas supply channel 67 as described above. Therefore, when hydrogen flows from the second hydrogen channel 66 into the oxidizing gas supply channel 67 through the first relief valve 69, the hydrogen that has flowed in is supplied to the cathode of the fuel cell 22 together with the air that is the oxidizing gas. Is done. In this embodiment, the oxidizing gas supply path 67 and the cathode exhaust gas path 68 are routed through the humidification module 25. In the humidification module 25, the oxidizing gas supply path 67 and the cathode exhaust gas path 68 are separated from each other by a water vapor permeable membrane, and the pressurized air supplied to the cathode is humidified using the cathode exhaust gas containing water vapor. Yes. Further, the cathode exhaust gas path 68 passes through the diluter 26 described above before leading the cathode exhaust gas to the outside. Therefore, the cathode exhaust gas is mixed with the anode exhaust gas flowing in through the exhaust gas discharge path 64 in the diluter 26 to dilute it, and then discharged to the outside.

  Furthermore, the fuel cell system 10 includes a control unit 70 that controls the movement of each unit of the fuel cell system 10. The control unit is configured as a logic circuit centered on a microcomputer, and more specifically, a CPU that executes predetermined calculations in accordance with a preset control program, and a control program necessary to execute various arithmetic processes by the CPU And a ROM in which control data and the like are stored in advance, a RAM in which various data necessary for performing various arithmetic processes by the CPU are temporarily read and written, an input / output port for inputting and outputting various signals, and the like. The control unit 70 acquires detection signals from various sensors included in the fuel cell system 10 and information related to a load request for the fuel cell 22. Further, the control unit 70 outputs a drive signal to each unit related to power generation of the fuel cell 22 such as the pressure regulating valve 62, the air compressor 24, the hydrogen pump 65, or the valves 61 and 27a provided in the fuel cell system 10.

B. Action to prevent excessive hydrogen gas pressure rise:
FIG. 2 is an explanatory diagram showing a pressure rise process, which is an operation performed in the fuel cell system 10 when the hydrogen pressure in the first hydrogen flow path 60 rises beyond the allowable range. The pressure increase process shown in FIG. 2 does not represent the control that is actively performed by the control unit 70 but describes the operation that proceeds in the fuel cell system 10.

  During the power generation of the fuel cell 22, for example, if a failure occurs in the pressure adjustment valve 62 in the first hydrogen flow path 60, the hydrogen gas released from the hydrogen tank 23 is not sufficiently reduced in pressure, and the pressure adjustment valve 62. And the hydrogen pressure in the first hydrogen channel 60 rises (step S100). In this way, the hydrogen pressure rises, and the pressure in the first hydrogen flow path 60 downstream from the pressure regulating valve 62 is the pressure (first pressure) set as the valve opening pressure of the first relief valve 69. ), The first relief valve 69 is opened (step S110). Here, the valve opening pressure of the first relief valve 69 is a pressure exceeding the range in which the pressure in the first hydrogen flow path 60 fluctuates during normal operation of the fuel cell system 10, A pressure corresponding to the occurrence of an abnormality in the pressure adjustment in the hydrogen flow path 60 is set. As such valve opening pressure, the hydrogen pressure that the fuel cell 22 can tolerate, and the piping through which hydrogen flows when the hydrogen pressure is in the normal range, the first hydrogen channel 60 and the second hydrogen channel. A pressure lower than the hydrogen pressure that can be tolerated by the piping downstream of the connection portion with 66 and the components provided in the piping is set.

  When the first relief valve 69 is opened, hydrogen in the first hydrogen flow path 60 flows into the oxidizing gas supply path 67 (step S120), and this hydrogen together with the oxidizing gas is the cathode of the fuel cell 22. To be supplied. The hydrogen supplied to the cathode is oxidized on the cathode catalyst using oxygen in the oxidizing gas (step S130). As described above, since the fuel cell 22 is generating electricity, an electrochemical reaction proceeds on the cathode catalyst. However, when hydrogen is supplied together with oxygen to the cathode, the electrochemical reaction is performed on the cathode catalyst. Then, a hydrogen oxidation reaction, that is, a reaction for generating water from hydrogen and oxygen proceeds. As described above, the gas containing water vapor generated by the electrochemical reaction and the oxidation reaction of hydrogen further passes through the cathode exhaust gas channel 68 and the diluter 26 from the cathode catalyst to the outside (in the atmosphere) of the fuel cell system 10. Discharged. Thus, since at least a part of the hydrogen flowing into the oxidizing gas supply path 67 from the first relief valve 69 is consumed by the oxidation reaction that proceeds on the cathode catalyst, the cathode catalyst functions as a hydrogen concentration reduction unit. To do.

  Note that when the opening of the first relief valve 69 is detected, the power generation of the fuel cell 22 may be stopped by the control unit 70. That is, the shut valve 61 is closed to stop the supply of hydrogen gas, and the air compressor 24 is stopped to stop the supply of oxidizing gas to prevent further outflow of hydrogen and to stop the power generation in the state of malfunction. That's fine. As described above, in this embodiment, the fuel cell system 10 is used as a power source for driving the vehicle. However, for example, by installing a secondary battery together with the fuel cell 22 as a power source for driving the vehicle, It is possible to perform necessary vehicle travel even when power generation is stopped.

  Here, the opening of the first relief valve 69 can be detected, for example, by providing a pressure sensor downstream of the pressure regulating valve 62 in the first hydrogen flow path 60 of the fuel cell system 10. . That is, when the pressure downstream of the pressure regulating valve 62 in the first hydrogen flow path 60 reaches the valve opening pressure set in the first relief valve 69, the first relief valve 69 is opened. It can be judged. The same determination can be made when a pressure sensor is provided upstream of the first relief valve 69 in the second hydrogen channel 66. Alternatively, in the second hydrogen channel 66, a pressure sensor is provided on the downstream side of the first relief valve 69, and when there is a sudden pressure increase exceeding a predetermined reference value, the first relief valve 69 is It may be determined that the valve has opened. It is also possible to provide a flow meter for detecting the gas flow rate in place of any of the above pressure sensors and make the same determination based on the gas flow rate. In the fuel cell system, a pressure sensor is usually provided downstream of the pressure regulating valve 62 to monitor the pressure in the first hydrogen flow path 60. Therefore, when the detection signal of this pressure sensor is used, the first In order to determine whether the relief valve 69 is open, it is not necessary to provide a separate sensor.

  According to the fuel cell system 10 of the present embodiment configured as described above, the first relief valve 69 opens when the pressure in the first hydrogen flow path 60 rises above a predetermined set pressure. Therefore, the gas having a pressure exceeding the allowable range is not supplied to the fuel cell 22. As described above, when hydrogen is discharged to the outside via the first relief valve 69, at least a part of the hydrogen is consumed on the cathode catalyst, so that an increase in the hydrogen concentration in the gas discharged to the outside is suppressed. can do. In addition, by using the cathode catalyst as the hydrogen concentration reducing unit in this way, it is not necessary to promote the diffusion of hydrogen when discharging the gas as in the case of discharging the hydrogen gas to the outside without being consumed in advance. The design limitations imposed to promote the diffusion of hydrogen discharged into the can be suppressed.

  The operation of discharging the hydrogen from the first hydrogen flow path 60 by opening the first relief valve 69 is not only during the power generation of the fuel cell 22 but also during the stop of the fuel cell system 10. It may be done. Even in such a case, the cathode catalyst can function as a hydrogen concentration reduction unit, as in power generation. The operation of reducing the hydrogen concentration by the cathode catalyst when the system is stopped will be described below.

  While the fuel cell system 10 is stopped, the shut valve 61 and the pressure regulating valve 62 are closed and the hydrogen supply from the hydrogen tank 23 is stopped. For example, a slight amount of hydrogen leaks from these valves due to deterioration over time. May occur. If the system shutdown time is long and such hydrogen leakage continues, high-pressure hydrogen is stored in the hydrogen tank 23, and therefore, the downstream side of the shut valve 61 and the pressure regulating valve 62 The pressure in one hydrogen flow path 60 gradually increases. In such a case, when the pressure in the first hydrogen flow path 60 exceeds the valve opening pressure of the first relief valve 69, the first relief valve 69 opens and the first hydrogen flow path 60 is opened. The hydrogen inside flows into the oxidizing gas supply path 67. However, at this time, if the amount of leakage of hydrogen is very small, the pressure in the first hydrogen flow path 60 rapidly decreases when the first relief valve 69 is opened. Closes.

  Here, since the air compressor 24 is also stopped while the fuel cell system 10 is stopped, the oxidizing gas is not actively sent into the oxidizing gas supply path 67, but the oxidizing gas supply path 67 is in the atmosphere. It is open and filled with atmospheric air. Therefore, the hydrogen that has flowed in through the first relief valve 69 diffuses while being mixed with air in the oxidizing gas supply path 67 and gradually reaches the cathode of the fuel cell 22. When the system is stopped, the temperature of the fuel cell 22 is lower than that at the time of power generation. Therefore, the temperature of the cathode catalyst is lower than that at the time of power generation, and the activity is low. However, even when the temperature is lowered, the oxidation reaction of hydrogen proceeds slowly. Therefore, on the cathode catalyst, the consumption of the inflowed hydrogen gradually proceeds, and the hydrogen concentration in the oxidizing gas supply path 67 and the oxidizing gas flow path in the fuel cell 22 communicating with the oxidizing gas supply path 67 gradually decreases. Here, at the next start-up, when the discharge of the cathode exhaust gas via the diluter 26 is started together with the driving of the air compressor 24, the hydrogen flowing into the oxidizing gas supply path 67 is consumed on the cathode catalyst. The hydrogen concentration in the gas discharged to the outside can be suppressed.

C. Second embodiment:
FIG. 3 is a block diagram showing a schematic configuration of the fuel cell system 110 of the second embodiment. Similar to the fuel cell system 10 of the first embodiment, the fuel cell system 110 is used as a power source for driving the vehicle and has a configuration similar to that of the fuel cell system 10. The same reference numerals are assigned and detailed description is omitted.

  The fuel cell system 110 includes a second hydrogen channel 166 instead of the second hydrogen channel 66 of the fuel cell system 10. Like the second hydrogen channel 66, the second hydrogen channel 166 is connected to the first hydrogen channel 60 that is a part of the circulation channel, but the other end is an oxidizing gas. It is connected not to the supply path 67 but to the diluter 26. The second hydrogen channel 166 is provided with a first relief valve 69 as in the case of the second hydrogen channel 66.

  FIG. 4 is an explanatory diagram showing a pressure rise process, which is an operation performed in the fuel cell system 110 when the hydrogen pressure in the first hydrogen flow path 60 rises beyond the allowable range. The pressure rise processing shown in FIG. 4 represents the operation that proceeds in the fuel cell system 10 with the control that is positively performed by the control unit 70.

  Also in the second embodiment, as in the first embodiment, when the pressure in the first hydrogen flow path 60 rises to a predetermined value or more due to, for example, occurrence of a malfunction in the pressure regulating valve 62 (step S200), The first relief valve 69 is opened (step S210). Then, when the first relief valve 69 is opened, the hydrogen in the first hydrogen channel 60 flows into the diluter 26 via the second hydrogen channel 166 (step S220).

  When the first relief valve 69 is opened in this manner, in this embodiment, the opening of the first relief valve 69 is detected by the control unit 70 (step S230). As described above, the first relief valve 69 is opened by connecting a pressure sensor or a flow meter downstream of the pressure regulating valve 62 in the first hydrogen passage 60 or in the second hydrogen passage 66. By providing, detection becomes possible. When detecting the opening of the first relief valve 69, the controller 70 increases the drive amount of the air compressor 24 (step S240). Here, during the power generation of the fuel cell 22, an amount sufficient to obtain a desired electric power according to a load request (for example, a load request for vehicle travel set based on the vehicle speed and the accelerator opening). The air compressor 24 is driven so that a predetermined amount of oxidizing gas set as is supplied to the cathode. In step S240, for example, the driving amount of the air compressor 24 is increased so that the supplied oxidizing gas amount is increased by a predetermined amount compared to the oxidizing gas supply amount set in response to such a load request. Just do it. The predetermined amount is a sufficiently low hydrogen concentration in the gas discharged from the diluter 26 when the first relief valve 69 is opened and hydrogen gas flows into the diluter 26. The amount that can be set. Alternatively, in step S240, the drive amount of the air compressor 24 may be increased so that the maximum value in the range set as the driveable amount of the air compressor 24 is obtained.

  When hydrogen flows into the diluter 26 via the second hydrogen flow path 166 by opening the first relief valve 69, this hydrogen is supplied from the air compressor 24 via the inside of the fuel cell 22. And is discharged to the outside (in the atmosphere) of the fuel cell system 110 (step S250). Thus, in the present embodiment, the diluter 26 having a flow passage cross-sectional area larger than that of the cathode exhaust gas passage 68 and through which the air flows functions as a hydrogen concentration reduction unit. Since the air is supplied from the air compressor 24 during power generation of the fuel cell 22, the diluter 26 can function as a hydrogen concentration reducing unit even when the driving amount of the air compressor 24 is not particularly increased. . However, by increasing the drive amount of the air compressor 24 as in the second embodiment, the effect of reducing the hydrogen concentration in the gas discharged to the outside can be enhanced. When performing control to stop the power generation of the fuel cell 22 in response to detection of opening of the first relief valve 69, the air compressor 24 dilutes hydrogen introduced into the diluter 26. The air compressor 24 may be stopped after securing a sufficient drive amount and drive time.

  According to the fuel cell system 110 of the second embodiment configured as described above, the first relief valve 69 is used when the pressure in the first hydrogen flow path 60 rises above a preset valve opening pressure. Therefore, the gas having a pressure exceeding the allowable range is not supplied to the fuel cell 22. As described above, when the hydrogen is discharged to the outside through the first relief valve 69, the hydrogen concentration is reduced in the diluter 26, so that an increase in the hydrogen concentration in the gas discharged to the outside is suppressed. Can do. In addition, by using the diluter 26 as a hydrogen concentration reducing unit in this way, hydrogen diffusion is promoted when the hydrogen gas is discharged into the atmosphere from the pipe, as in the case of discharging the hydrogen gas to the outside without being diluted in advance. Therefore, it is possible to suppress design restrictions imposed to promote the diffusion of hydrogen discharged to the outside.

  As in the first embodiment, the operation of discharging the hydrogen from the first hydrogen flow path 60 by opening the first relief valve 69 is not only during the power generation of the fuel cell 22, but also in the fuel cell system. This may be done even when 110 is stopped. Even in such a case, the diluter 26 can function as a hydrogen concentration reduction unit as in power generation. The operation of reducing the hydrogen concentration by the diluter 26 when the system is stopped will be described below.

  If hydrogen leaks from the shut valve 61 and the pressure regulating valve 62 while the fuel cell system 110 is stopped, the pressure in the first hydrogen flow path 60 gradually increases and the first relief valve 69 opens. . Thereby, the hydrogen in the first hydrogen channel 60 flows into the diluter 26 through the second hydrogen channel 166. Here, since the air compressor 24 is stopped while the fuel cell system 110 is stopped, the oxidizing gas is not actively sent into the diluter 26. However, the diluter 26 is a container in which the cross-sectional area of the channel is larger than that of the cathode exhaust gas channel 68 and the second hydrogen channel 166, and air is retained therein. Therefore, the inflowing hydrogen is diluted by the air staying in the diluter 26 in the space in the diluter 26. If the amount of hydrogen leakage is very small when the system is stopped, the first relief valve 69 closes when the first relief valve 69 opens and the pressure in the first hydrogen flow path 60 decreases. Therefore, the amount of hydrogen that flows in is limited. Therefore, the hydrogen that flows in by opening the first relief valve 69 is effectively diluted in the diluter 26. When the system is started next time, since the hydrogen concentration is reduced in the diluter 26, even if the cathode compressor exhaust gas that has passed through the diluter 26 is discharged to the outside because the air compressor 24 is driven, it is discharged to the outside. The hydrogen concentration in the gas can be suppressed.

D. Third embodiment:
FIG. 5 is a block diagram showing a schematic configuration of the fuel cell system 210 of the third embodiment. Since the fuel cell system 210 has a configuration similar to that of the fuel cell system 10 and the fuel cell system 110, common portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  Similar to the second hydrogen channel 66 of the fuel cell system 10, the fuel cell system 210 includes a gas channel that guides hydrogen from the first hydrogen channel 60 to the oxidizing gas supply channel 67, and a fuel cell system 110. Similar to the second hydrogen channel 166, a gas channel for introducing hydrogen from the first hydrogen channel 60 to the diluter 26 is provided. Specifically, the fuel cell system 210 includes a second hydrogen channel 266 that is connected to the first hydrogen channel 60 and is provided with a first relief valve 69. The second hydrogen flow path 266 branches into a first branch path 80 connected to the oxidizing gas supply path 67 and a second branch path 82 connected to the diluter 26. A flow path switching valve 84 is provided at a branch point where the second hydrogen flow path 266 branches into the first branch path 80 and the second branch path 82. The flow path switching valve 84 is driven by the control unit 70 to selectively communicate the downstream side of the second hydrogen flow path 266 with either the first branch path 80 or the second branch path 82. In the first hydrogen channel 60, a pressure sensor 86 that detects the pressure in the first hydrogen channel 60 is provided in the vicinity of the connection portion with the fuel cell 22. Further, in the fuel cell system 210, a temperature sensor 88 is provided in the cathode exhaust gas passage 68 in the vicinity of the connection portion with the fuel cell 22. Since the oxidizing gas that passes through the fuel cell 22 and is discharged from the fuel cell 22 has substantially the same temperature as the internal temperature of the fuel cell 22, the internal temperature of the fuel cell 22 can be increased by using the temperature sensor 88. You can know the temperature. Detection signals from the pressure sensor 86 and the temperature sensor 88 are input to the control unit 70.

  Here, the control unit 70 drives the flow path switching valve 84 in accordance with the temperature of the fuel cell detected by the temperature sensor 88, so that the second hydrogen flow path 266 passes through the second branch path 82 and the first branch path. It functions as a switching control unit that communicates with any one of 80. Hereinafter, in the fuel cell system 210, the control performed by the control unit 70 when the hydrogen pressure in the first hydrogen channel 60 rises beyond the allowable range will be described.

  FIG. 6 is a flowchart illustrating a pressure increase determination processing routine that is executed by the CPU of the control unit 70 during operation of the fuel cell system 210. When this routine is started, the control unit 70 acquires a detection signal from the pressure sensor 86 and determines whether or not the first relief valve 69 is opened (step S300). That is, it is determined whether or not the pressure detected by the pressure sensor 86 has reached the reference value. Here, the reference value used for the determination in step S300 is a value corresponding to the valve opening pressure of the first relief valve 69 and is stored in the controller 70 in advance. Similar to the first embodiment, for example, when the pressure in the first hydrogen flow path 60 rises to a predetermined value or more due to the occurrence of a malfunction in the pressure regulating valve 62 (step S100 in FIG. 2), the first relief The valve 69 is opened (step S110). At the time of such valve opening, the detection value of the pressure sensor 86 rapidly increases and reaches the reference value, and the control unit 70 determines that the first relief valve 69 is opened. Note that the control unit 70 repeatedly acquires the detection signal from the pressure sensor 86 until it is determined that the relief valve 69 is opened.

  When it is determined in step S300 that the relief valve 69 is opened, the control unit 70 obtains the internal temperature of the fuel cell by acquiring the detection signal of the temperature sensor 88 (step S310). When the fuel cell temperature is acquired, the control unit 70 determines whether or not the fuel cell temperature is equal to or higher than a reference value (step S320). The reference value used for the determination in step S320 is a value that is set in advance as a temperature at which it can be determined that the temperature of the cathode catalyst included in the fuel cell is sufficiently high and is stored in the control unit 70.

  If it is determined in step S320 that the fuel cell temperature is equal to or higher than the reference value, the control unit 70 outputs a drive signal to the flow path switching valve 84 so that the hydrogen flow path is on the first branch path 80 side, that is, the oxidizing gas supply Switching to the path 67 side (step S330), this routine is finished. As a result, the hydrogen that has passed through the first relief valve 69 is supplied to the cathode of the fuel cell 22 together with the oxidizing gas flowing through the oxidizing gas supply path 67 and is oxidized on the cathode catalyst.

  If it is determined in step S320 that the fuel cell temperature does not reach the reference value, the control unit 70 outputs a drive signal to the flow path switching valve 84 so that the hydrogen flow path is on the second branch path 82 side, that is, the diluter 26. Switching to the side (step S340). At this time, the control unit 70 increases the drive amount of the air compressor 24 (step S350) as in step S240 of the second embodiment, and ends this routine. As a result, the hydrogen that has passed through the first relief valve 69 flows into the diluter 26, is diluted by the cathode exhaust gas whose flow rate has been increased, and is discharged to the outside.

  According to the fuel cell system 210 of the third embodiment configured as described above, the same effects as those of the first and second embodiments can be obtained. Furthermore, in the third embodiment, since either the cathode catalyst or the diluter 26 is used as the hydrogen concentration reducing unit based on the internal temperature of the fuel cell, the hydrogen concentration is reduced when the fuel cell temperature is less than the reference value. The diluter 26 is preferentially used for concentration reduction. In the normal operating temperature range of the fuel cell, the cathode catalyst has a higher activity for promoting the oxidation reaction as the temperature rises. Therefore, by performing such control, when the activity in the cathode catalyst is relatively low, Without using, the diluter 26 can be used to reduce the hydrogen concentration more reliably. In addition, by using the cathode catalyst at a high catalyst temperature at which the effect of reducing the hydrogen concentration by the cathode catalyst can be sufficiently expected, an increase in power consumption in the air compressor 24 due to the use of the diluter 26 as the hydrogen concentration reducing unit is suppressed, and the system Overall energy efficiency can be improved.

  Note that the reference value for switching the flow path used in step S320 may be appropriately set according to the type of catalyst used. Such a reference value can be set, for example, as a temperature at which the effect of reducing the hydrogen concentration is higher when the cathode catalyst is used as the hydrogen concentration reducing unit than when the diluter 26 is used. Alternatively, even if the cathode catalyst has a lower hydrogen concentration reducing effect than the diluter 26, if the hydrogen concentration in the exhaust gas when the cathode catalyst is used as a hydrogen concentration reducing unit is within an allowable range, The reference temperature may be set lower, and the efficiency reduction due to the increase in the driving amount of the air compressor 24 may be suppressed.

  In the third embodiment, the control unit 70 outputs a drive signal to the flow path switching valve 84 in both step S330 and step S340. Normally, the control unit 70 may be switched to either one. Good. And when it should be in a different switching state by the judgment result in step S320, the flow path switching valve 84 may be driven to switch the flow path. Alternatively, instead of switching the flow path switching valve 84 after detecting the opening of the first relief valve 69, the temperature during the power generation of the fuel cell 22 is maintained even when the first relief valve 69 is closed. In response to this, the switching operation of the flow path switching valve 84 may be performed. In this case, when the first relief valve 69 is opened, it is not necessary to make a determination for switching the flow path switching valve 84.

  Alternatively, in the third embodiment, the temperature of the cathode exhaust gas is detected in order to determine the fuel cell temperature (cathode catalyst temperature), but the fuel cell temperature may be determined based on a different value. Any value other than the cathode exhaust gas temperature may be a value that reflects the temperature of the fuel cell 22 such as the outlet temperature of the cooling water that passes through the fuel cell 22 in order to adjust the operating temperature of the fuel cell 22. In addition, as information for the control unit 70 to determine the opening of the first relief valve 69 in step S300, information other than the detection signal of the pressure sensor 86, for example, pressures provided at different positions as described above A detection signal from a sensor or a detection signal from a flow meter may be used.

  As in the first and second embodiments, the operation of discharging the hydrogen from the first hydrogen flow path 60 by opening the first relief valve 69 is not only during power generation of the fuel cell 22, This may be performed even when the fuel cell system 110 is stopped. Even in such a case, the cathode catalyst or the diluter 26 can function as a hydrogen concentration reducing unit as in power generation. In this case, the flow path switching valve 84 may be switched to the oxidizing gas supply path 67 side or the diluter 26 side when the fuel cell system is stopped. When switching to the oxidizing gas supply path 67 side, as with the first embodiment, the hydrogen discharged by the cathode catalyst is slowly consumed and diluted, or when switching to the diluter 26 side. In the same manner as in the second embodiment, hydrogen is diluted by air staying inside the diluter 26.

E. Fourth embodiment:
FIG. 7 is a block diagram showing a schematic configuration of the fuel cell system 310 of the fourth embodiment. Since the fuel cell system 310 has a configuration similar to that of the fuel cell system 10, common portions are denoted by the same reference numerals, detailed description thereof is omitted, and different portions will be described below.

  In the fuel cell system 310, a shut valve 61 and a pressure regulating valve 62 are provided in the first hydrogen flow path 60 as in the first embodiment. A pressure adjusting valve 94 is provided upstream of the shut valve 61 and the pressure adjusting valve 62, and a shut valve 96 is provided further upstream. In this embodiment, by providing a plurality of pressure control valves in this manner, the high-pressure hydrogen gas stored in the hydrogen tank 23 is sequentially reduced before supplying hydrogen to the fuel cell 22. In addition, the shut valve 96 is closed when power generation in the fuel cell 22 is stopped, and shuts off the flow of hydrogen gas in the vicinity of the connection portion with the hydrogen tank 23 in the first hydrogen flow path 60.

  The fuel cell system 310 is provided with a second hydrogen passage 366 connected to the first hydrogen passage 60 between the pressure adjustment valve 62 and the pressure adjustment valve 94. The second hydrogen channel 366 includes a first relief valve 69 similar to that of the first embodiment, and the downstream side of the second hydrogen channel 366 is shut with respect to the first hydrogen channel 60. The valve 61 is connected downstream of the arrangement position. That is, when the first relief valve 69 is opened, the hydrogen that has passed through the first relief valve 69 flows into the circulation channel, and together with the hydrogen circulating in the circulation channel, the anode side in the fuel cell 22 Supplied to the flow path. Therefore, when the first relief valve 69 is opened, the pressure in the circulation channel increases. Therefore, in the present embodiment, even when the first relief valve 69 is opened when the load demand is maximum and the hydrogen pressure in the circulation passage is increased, the inside of the circulation passage or the fuel is increased. The pipe diameter of the second hydrogen flow path 366 is set to be sufficiently small so that the gas pressure in the fuel gas flow path inside the battery 22 falls within the permissible range.

  Further, in the first hydrogen channel 60, the third hydrogen channel 90 is located between the pressure regulating valve 62 and the pressure regulating valve 94 and upstream of the connection with the second hydrogen channel 366. Is connected. A second relief valve 92 is provided in the third hydrogen channel 90. Here, the second relief valve 92 is set to have a higher valve opening pressure than the first relief valve 69. In addition, the third hydrogen channel 90 is formed with a larger pipe diameter than the second hydrogen channel 366.

  When the first relief valve 69 is opened during the power generation of the fuel cell 22, the hydrogen passing through the first relief valve 69 flows into the circulating hydrogen in which the hydrogen circulates. However, in this case, a special hydrogen concentration reduction operation does not proceed. In the present embodiment, in particular, when the first relief valve 69 is opened while the fuel cell system 310 is stopped, the fuel cell 22 into which hydrogen flows through the first relief valve 69 serves as a hydrogen concentration reduction unit. Function as. This operation while the fuel cell system 310 is stopped will be described below.

  FIG. 8 shows a pressure rise process that is an operation performed in the fuel cell system 310 when the fuel cell system 310 is stopped and the hydrogen pressure in the first hydrogen flow path 60 rises beyond an allowable range. It is explanatory drawing showing. The pressure rise process shown in FIG. 8 does not represent the control that is actively performed by the control unit 70 as in FIG. 2, but describes the operation that proceeds in the fuel cell system 10. .

  Here, when the fuel cell system 310 is stopped, the air compressor 24 is stopped along with the stop of power generation of the fuel cell 22, so that the inside of the flow path of the oxidizing gas in the fuel cell 22 becomes substantially atmospheric pressure. . In the flow path through which hydrogen flows in the fuel cell system 310, the four flow path adjustment valves 62 and 94 and the shut valves 61 and 96 are closed, and the circulation flow path becomes a closed space. Hydrogen in a pressure corresponding to the amount of power generated before power generation is stopped stays in this circulation channel. When the fuel cell system 310 is stopped and enters such a state, in the fuel cell 22, the electrolyte layer moves from the anode side to the cathode side according to the hydrogen partial pressure difference between the flow path of the fuel gas and the flow path of the oxidizing gas. Hydrogen permeates through. As a result, the hydrogen concentration in the fuel gas flow path in the fuel cell 22 gradually decreases, and the hydrogen partial pressures in the anode side flow path and the cathode side flow path become substantially the same via the electrolyte layer.

  When the fuel cell system 310 is stopped and in the above-described state, hydrogen leakage from these valves occurs in the first hydrogen passage 60 due to, for example, deterioration of the pressure regulating valve 94 and the shut valve 96 over time. When this occurs, the pressure in the first hydrogen channel 60 gradually increases (step S400). Thus, when the hydrogen pressure rises and the pressure in the first hydrogen flow path 60 exceeds the pressure set as the valve opening pressure of the first relief valve 69, the first relief valve 69 opens. (Step S410). When the first relief valve 69 is opened, the hydrogen in the first hydrogen flow path 60 flows into the downstream side of the first hydrogen flow path 60, and this hydrogen is the fuel in the fuel cell 22. It further flows into the gas flow path (step S420). Here, when the amount of hydrogen leakage from the pressure regulating valve 94 and the shut valve 96 is very small, when the first relief valve 69 opens and the pressure in the first hydrogen flow path 60 decreases, The first relief valve 69 is closed.

  When hydrogen flows into the flow path of the fuel gas in the fuel cell 22 as described above when the fuel cell system 310 is stopped, this hydrogen gradually permeates from the anode side to the cathode side through the electrolyte layer (step). S430). The permeated hydrogen diffuses into the oxidizing gas flow path in the fuel cell 22 and the cathode exhaust gas flow path communicating therewith. Therefore, in the oxidizing gas flow path in the fuel cell 22 and the cathode exhaust gas flow path communicating with the oxidizing gas flow path, the concentration of hydrogen discharged from the first hydrogen flow path 60 via the first relief valve 69 is further increased. It becomes a reduced state. When the fuel cell system 310 is activated next time, the hydrogen diluted in the flow path of the oxidizing gas and the cathode exhaust gas is released into the atmosphere as the air compressor 24 is activated. As described above, the fuel cell 22 including the electrolyte layer through which hydrogen permeates and the flow path of the oxidizing gas through which the permeated hydrogen diffuses functions as a hydrogen concentration reduction unit.

  If the pressure increase rate in the first hydrogen flow path 60 is fast and the pressure in the first hydrogen flow path 60 continues to increase even after the first relief valve 69 is opened, 2 relief valve 92 opens. Further, during normal power generation, even when the pressure in the first hydrogen flow path 60 continues to rise after the first relief valve 69 is opened, the second relief valve 92 is subsequently opened. To do.

  According to the fuel cell system 310 of the fourth embodiment configured as described above, the second hydrogen flow channel 366 and the third hydrogen flow channel in the first hydrogen flow channel 60 during the stop of the fuel cell system. The gas supply at a pressure exceeding the permissible range can be prevented from the downstream side of the connecting portion with 90, and an increase in the concentration of hydrogen discharged to the outside can be suppressed. In addition, by using the fuel cell 22 as a hydrogen concentration reduction unit, it is possible to suppress design restrictions imposed to promote diffusion of hydrogen discharged to the outside.

  Here, the third hydrogen flow path 90 is different from the fuel cell 22 through which the hydrogen passed through the second hydrogen flow path 366 is guided, for example, any of the first to third embodiments. It can be connected to the same hydrogen concentration reduction unit. In this case, as another hydrogen concentration reducing unit to which the third hydrogen channel 90 is connected, the hydrogen concentration reduction having a higher allowable gas pressure than the fuel cell 22 to which the third hydrogen channel 90 is connected. It is desirable to use parts.

  Alternatively, the third hydrogen channel 90 may be opened to the atmosphere. In the fuel cell system 310 of this embodiment, only the first relief valve 69 opens when the degree of hydrogen pressure rise is relatively small, and both relief valves open when the degree of hydrogen pressure rise is larger. It will be. Therefore, when the system is stopped and the degree of increase in the hydrogen pressure in the first hydrogen flow path 60 is relatively small, the hydrogen is not affected regardless of whether or not the third hydrogen flow path 90 is opened to the atmosphere. The concentration of discharged hydrogen can be reduced by the fuel cell 22 which is a concentration reducing unit. When the third hydrogen channel 90 having a larger pipe diameter is opened to the atmosphere, hydrogen having a pressure exceeding the allowable pressure at each of the above-described parts that can be used as the hydrogen concentration reducing part is the second relief. Even when the gas is discharged via the valve 92, it is possible to cope with the increase in the hydrogen pressure without damaging the respective parts.

F. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

F1. Modification 1:
In the first to third embodiments, the second hydrogen flow path including the first relief valve 69 is connected to a region constituting a part of the circulation flow path in the first hydrogen flow path 60. A different configuration may be used. That is, it may be connected to another position in the first hydrogen flow path 60 that connects the hydrogen tank 23 that is a fuel gas supply unit that supplies fuel gas and the anode of the fuel cell 22. For example, in the same manner as in the fourth embodiment, when the first hydrogen flow path 60 has a plurality of flow rate adjustment valves, the second hydrogen flow is located anywhere between the plurality of flow rate adjustment valves. The roads may be connected. When the high-pressure hydrogen gas is depressurized and supplied to the fuel cell 22, a second hydrogen passage connected to the middle of the first hydrogen passage 60 is provided, thereby connecting the second hydrogen passage. It becomes possible to prevent the supply of an undesirable high-pressure gas to the downstream side.

  Further, as in the first to third embodiments, when the second hydrogen flow path and the first relief valve 69 are provided in order to prevent an excessive increase in the gas pressure supplied to the fuel cell 22. The second hydrogen channel may be connected to the downstream side of the fuel cell 22 in the circulation channel, that is, to the anode exhaust gas channel 63.

  Alternatively, the first relief valve 69 may be provided at the connection portion between the second hydrogen channel and the first hydrogen channel 60 instead of being provided in the second hydrogen channel. Similarly, the second relief valve 92 can be provided at the connection portion between the third hydrogen channel 90 and the first hydrogen channel 60 instead of being provided in the third hydrogen channel 90.

F2. Modification 2:
In the fourth embodiment, any one of the hydrogen concentration reduction sections of the first to third embodiments may be used instead of the fuel cell 22 as the hydrogen concentration reduction section to which the second hydrogen flow path 366 is connected. good. Also in this case, as in the fourth embodiment, the valve opening pressure of the second relief valve 92 is set higher than that of the first relief valve 69, and the pipe diameter of the second hydrogen flow path 366 is set to the third value. By making it smaller than the pipe diameter of the hydrogen flow path 90, it becomes possible to prevent the supply of gas having a pressure exceeding the allowable range for the hydrogen concentration reducing portion. At this time, the third hydrogen channel 90 is connected to another hydrogen concentration reducing unit having a higher allowable pressure than the hydrogen concentration reducing unit to which the second hydrogen channel 366 is connected, or is opened to the outside. That's fine.

F3. Modification 3:
Instead of the hydrogen concentration reduction unit used in the first to fourth embodiments, another hydrogen concentration reduction unit may be used. For example, the downstream of the hydrogen channel provided with the relief valve may be opened to the atmosphere, and a fan driven by the control unit 70 may be provided as a hydrogen concentration reducing unit in the vicinity of the downstream opening of the hydrogen channel. The opening of the relief valve is detected using the pressure sensor or flow meter described above, and the fan may be driven when the relief valve is opened. By taking in external air in this way, hydrogen discharged through the relief valve can be diluted when discharged to the outside. The fan used as the hydrogen concentration reduction unit preferably uses a power source (for example, a secondary battery) other than the fuel cell 22 as a power source, and can be used as a hydrogen concentration reduction unit even when the fuel cell system is stopped. Become.

F4. Modification 4:
In the first to fourth embodiments, a relief valve that automatically opens when a predetermined valve opening pressure is set in advance is used, but a different valve may be used. For example, instead of the relief valve, a valve that is opened and closed by the control unit 70 may be provided, and the opening or closing control of the valve may be performed by detecting the pressure or gas flow rate upstream of the valve.

F5. Modification 5:
Furthermore, the present invention may be applied to a fuel cell system having a configuration different from that of the embodiment. For example, in the fuel cell systems of the first to fourth embodiments, the hydrogen gas supplied to the fuel cell 22 circulates in the circulation channel, but the anode exhaust gas channel 63 is not provided, and the anode exhaust gas is supplied from the fuel cell. It is good also as a structure (what is called a dead end type) which is not discharged. In the above configuration, hydrogen is not circulated, but an amount of hydrogen corresponding to the amount of hydrogen consumed by power generation is newly supplied into the fuel cell. Therefore, the present invention can be applied when a malfunction occurs in the adjustment of the amount of hydrogen newly supplied to the fuel cell and the pressure is exceeded.

  Alternatively, instead of a configuration including a hydrogen tank for storing high-purity hydrogen, a reformer may be provided, and a reformed gas obtained by reforming a hydrocarbon-based fuel may be supplied to the fuel cell as a fuel gas. good. Also in this case, when the fuel gas pressure supplied to the fuel cell becomes excessive, the same effect as in the embodiment can be obtained by guiding the hydrogen discharged through the shut valve to the predetermined hydrogen concentration reduction unit. be able to.

  Further, the present invention can be applied even when the fuel cell system is used as a stationary power generation apparatus in addition to the power source for driving the moving body as in the embodiment.

It is a block diagram showing schematic structure of the fuel cell system of 1st Example. It is explanatory drawing showing the operation | movement performed at the time of the pressure rise in a 1st hydrogen flow path. It is a block diagram showing schematic structure of the fuel cell system of 2nd Example. It is explanatory drawing showing the operation | movement performed at the time of the pressure rise in a 1st hydrogen flow path. It is a block diagram showing schematic structure of the fuel cell system of 3rd Example. It is a flowchart showing a pressure rise judgment processing routine. It is a block diagram showing schematic structure of the fuel cell system of a 4th Example. It is explanatory drawing showing the operation | movement performed at the time of the pressure rise in a 1st hydrogen flow path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,110,210,310 ... Fuel cell system 22 ... Fuel cell 23 ... Hydrogen tank 24 ... Air compressor 25 ... Humidification module 26 ... Diluter 27 ... Gas-liquid separator 27a ... Valve 28 ... Air cleaner 60 ... First hydrogen flow Path 61, 96 ... Shut valve 62, 94 ... Flow path regulating valve 63 ... Anode exhaust gas path 64 ... Exhaust gas discharge path 65 ... Hydrogen pump 66, 166, 266, 366 ... Second hydrogen flow path 67 ... Oxidizing gas supply path 68 ... cathode exhaust gas passage 69 ... first relief valve 70 ... control unit 80 ... first branch passage 82 ... second branch passage 84 ... flow path switching valve 86 ... pressure sensor 88 ... temperature sensor 90 ... third hydrogen flow path 92 ... Second relief valve

Claims (11)

A fuel cell system comprising a fuel cell,
A first flow path for supplying a fuel gas containing hydrogen to the fuel cell;
A second flow path connected to the first flow path;
The valve is provided when the second flow path or a connection portion between the second flow path and the first flow path exceeds the first reference value. A first relief valve;
A hydrogen concentration reduction unit that is connected to the downstream side of the second flow path and reduces the concentration of hydrogen discharged from the first flow path via the first relief valve prior to discharge to the outside. And a fuel cell system. The fuel cell system according to claim 1, further comprising:
A pressure adjusting unit that is provided in the first flow path and adjusts the pressure of the fuel gas supplied to the fuel cell;
The fuel cell system, wherein the second flow path is connected to the first flow path on the downstream side of the arrangement position of the pressure adjusting unit. The fuel cell system according to claim 1, further comprising:
A hydrogen storage section for storing hydrogen and connecting to the first flow path;
A shut valve that is provided in the first flow path and that is closed when the fuel cell system is stopped. The second flow path is downstream of the shut valve with respect to the first flow path. Connect the fuel cell system. The fuel cell system according to any one of claims 1 to 3, further comprising:
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path that connects the oxidant gas supply unit and the cathode of the fuel cell and guides the oxidant gas to the cathode of the fuel cell;
The hydrogen concentration reducing unit is provided in a cathode exhaust gas flow path for guiding cathode exhaust gas discharged from the cathode to the outside, and has a cross-sectional area larger than the cross-sectional area of the cathode exhaust gas flow path. A fuel cell system, which is a diluter connected to the downstream side of the road. The fuel cell system according to claim 4, further comprising:
An oxidizing gas amount control unit for controlling an oxidizing gas supply amount from the oxidizing gas supply unit when generating power with the fuel cell, and when the first relief valve opens, the oxidizing gas supply unit A fuel cell system comprising: an oxidizing gas amount control unit that increases an oxidizing gas supply amount from a value set based on a power generation amount in the fuel cell. The fuel cell system according to any one of claims 1 to 3, further comprising:
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path connecting the oxidant gas supply unit and the cathode of the fuel cell, and leading the oxidant gas to the cathode of the fuel cell;
A diluter having a cross-sectional area larger than the cross-sectional area of the cathode exhaust gas flow path, provided in the cathode exhaust gas flow path for guiding the cathode exhaust gas discharged from the cathode to the outside;
A fuel cell temperature acquisition unit for acquiring the temperature of the fuel cell;
A first branch path branched from the second flow path and connected to the diluter;
A second branch path branched from the second flow path and connected to the oxidizing gas flow path;
A switching unit that selectively communicates the second flow path with either the first branch path or the second branch path;
When the temperature of the fuel cell acquired by the fuel cell temperature acquisition unit is equal to or higher than a reference value, the switching unit is driven to connect the second flow path and the second branch path, and the fuel cell A switching control unit that drives the switching unit to connect the second flow path and the first branch path when the temperature is lower than a reference value;
When the second flow path communicates with the first branch path, the diluter functions as the hydrogen concentration reducing unit, and when the second flow path communicates with the second branch path, the fuel A fuel cell system in which a cathode catalyst provided in a battery serves as the hydrogen concentration reduction unit. The fuel cell system according to claim 6, further comprising:
An oxidizing gas amount control unit for controlling an oxidizing gas supply amount from the oxidizing gas supply unit when generating power by the fuel cell, wherein the first relief valve is opened and the second flow path is opened. Is provided with an oxidant gas amount control unit that increases the oxidant gas supply amount from the oxidant gas supply unit to a value that is set based on the power generation amount in the fuel cell when communicating with the first branch passage. Fuel cell system. The fuel cell system according to any one of claims 1 to 3, further comprising:
An oxidizing gas supply unit for supplying oxidizing gas;
An oxidant gas flow path for connecting the oxidant gas supply unit and the fuel cell and introducing the oxidant gas to the cathode of the fuel cell;
The second flow path is further connected to the oxidizing gas flow path,
The hydrogen concentration reduction unit is a cathode catalyst provided in the fuel cell. 9. The fuel cell system according to claim 1, further comprising:
The first flow path is connected to the first flow path so as to communicate with the second flow path via the first flow path, and the pipe diameter of the flow path is formed larger than that of the second flow path. A third flow path,
The second flow path is provided at a connection portion between the third flow path or the third flow path and the first flow path, and the pressure in the third flow path is larger than the first reference value. A fuel cell system comprising: a second relief valve that opens when a reference value of The fuel cell system according to claim 1, further comprising:
A hydrogen storage section for storing hydrogen and connecting to the first flow path;
The first flow path is provided in the first flow path, is closed when the fuel cell system is stopped, and is provided on the downstream side of the connection portion of the first flow path with the second flow path. The shut valve and
The second channel is provided in the first channel, is closed when the fuel cell system is stopped, and is provided upstream of the connection portion of the first channel with the second channel. With a shut valve and
The second flow path is further connected to the downstream side of the position where the first shut valve is disposed in the first flow path,
When the first relief valve is opened when the fuel cell system is stopped, hydrogen flows in through the relief valve, and the introduced hydrogen flows from the anode side channel to the cathode side. A fuel cell system, wherein the fuel cell is permeable to a flow path through an electrolyte layer. The fuel cell system according to claim 10, further comprising:
The first flow path is connected between the first shut valve and the second shut valve, and communicates with the second flow path via the first flow path. A third channel having a pipe diameter larger than that of the second channel;
The second flow path is provided at a connection portion between the third flow path or the third flow path and the first flow path, and the pressure in the third flow path is larger than the first reference value. A fuel cell system comprising: a second relief valve that opens when a reference value of

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