Fuel cell system

Abstract

To reduce a hydrogen concentration in an exhaust gas without providing a sensor for detecting concentration on an oxidant gas exhaustion passage.SOLUTION: A fuel cell system 10 includes a fuel cell stack 12 and a control device 20. During low-efficiency power generation that the fuel cell stack 12 generates power at an efficiency lower than a power generation efficiency determined by a target power generation amount for the fuel cell stack 12, the control device 20 controls at least one of oxidant gas output equipment 14 and a flow rate adjustment valve 18 on the basis of a temperature detected by a temperature sensor 19, in order to vary a power generation state of the fuel cell stack 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel cell system mounted on a moving body or the like.

Background Art

[0002] In recent years, research and development have been conducted on fuel cell systems that contribute to energy efficiency in order to enable more people to access affordable, reliable, sustainable, and advanced energy. For example, there is a fuel cell vehicle equipped with a fuel cell system. A fuel cell vehicle is a vehicle that runs by driving an electric motor using the electric power generated by a fuel cell system. Since a fuel cell vehicle only discharges water, it is more environmentally friendly than gasoline vehicles that emit CO2, NOx, SOx, etc. In addition to automobiles, the fuel cell system can be mounted on other moving bodies such as ships, airplanes, and robots.

[0003] The fuel cell system has a fuel cell stack that generates electricity through an electrochemical reaction between an oxidant gas and a fuel gas. In the fuel cell stack, moisture generated during power generation may remain inside. In this case, it may freeze depending on the environment where the fuel cell stack is placed.

[0004] In Patent Document 1 below, a fuel cell system that warms up a fuel cell stack by performing a low-efficiency operation with a lower power generation efficiency than normal operation is disclosed. By warming up the fuel cell stack, the moisture remaining inside the fuel cell stack evaporates, and the moisture remaining inside the fuel cell stack can be suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when low-efficiency operation is performed, a reaction is likely to occur in the fuel cell stack 12 in which hydrogen ions that permeate the electrolyte membrane from the anode electrode to the cathode electrode recombine with electrons to produce hydrogen. In this case, a problem may arise in which the hydrogen concentration in the exhaust gas containing the oxidizer gas emitted from the fuel cell stack becomes high.

[0007] The present invention aims to solve the problems described above. [Means for solving the problem]

[0008] An aspect of the present invention is a fuel cell system having a fuel cell stack that generates electricity by an electrochemical reaction between a fuel gas and an oxidizer gas, comprising: an oxidizer gas output device that outputs the oxidizer gas supplied to the fuel cell stack; an oxidizer gas supply channel for supplying the oxidizer gas output from the oxidizer gas output device to the fuel cell stack; an oxidizer gas discharge channel for discharging a mixed gas containing the oxidizer gas discharged from the fuel cell stack to the outside; a bypass channel that branches off from the oxidizer gas supply channel between the oxidizer gas output device and the fuel cell stack and merges with the oxidizer gas discharge channel; a flow control valve provided in the bypass channel; a temperature sensor for detecting the temperature of the fuel cell stack; and a control device that controls at least one of the oxidizer gas output device and the flow control valve based on the temperature during low-efficiency power generation, in which the fuel cell stack generates electricity at an efficiency lower than the power generation efficiency determined by the target power generation amount of the fuel cell stack, thereby varying the power generation state of the fuel cell stack. [Effects of the Invention]

[0009] According to an aspect of the present invention, the hydrogen concentration in the exhaust gas can be reduced without installing a concentration-detecting sensor in the oxidant gas exhaust channel. That is, the temperature of the fuel cell stack correlates with the hydrogen produced at the cathode electrode by the recombination of hydrogen ions and electrons that have permeated the electrolyte membrane. Therefore, it becomes possible to capture the amount of hydrogen produced at the cathode electrode by recombination without newly installing a concentration-detecting sensor in the oxidant gas exhaust channel. Furthermore, it becomes possible to change the power generation state of the fuel cell stack according to the amount of hydrogen. As a result, the hydrogen concentration in the exhaust gas can be reduced without installing a hydrogen concentration-detecting sensor in the oxidant gas exhaust channel. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a fuel cell system according to an embodiment. [Figure 2] Figure 2 is a flowchart showing the warm-up procedure. [Modes for carrying out the invention]

[0011] Figure 1 is a schematic diagram showing the configuration of a fuel cell system 10 according to an embodiment. The fuel cell system 10 is mounted on a mobile body such as a vehicle, ship, aircraft, or robot. In this embodiment, the fuel cell system 10 is mounted on a vehicle. The fuel cell system 10 comprises a fuel cell stack 12, an oxidizer gas output device 14, a fuel gas output device 16, a flow control valve 18, a temperature sensor 19, and a control device 20.

[0012] The fuel cell stack 12 generates electricity through a chemical reaction between an oxidizer gas and a fuel gas. The oxidizer gas is an oxygen-containing gas. The fuel gas is a hydrogen-containing gas. The oxidizer gas may also be air. The current generated by the fuel cell stack 12 is used to charge a battery. The electricity obtained by charging the battery is used as driving power to drive a vehicle or fuel cell system 10.

[0013] The fuel cell stack 12 has a plurality of power generation cells 21. The plurality of power generation cells 21 are stacked. Each power generation cell 21 has a membrane electrode structure 22 and a pair of separators 23 that sandwich the membrane electrode structure 22. The membrane electrode structure 22 comprises an electrolyte membrane 24 and a cathode electrode 25 and an anode electrode 26 that sandwich the electrolyte membrane 24. The electrolyte membrane 24 is, for example, a thin film of perfluorosulfonic acid containing water.

[0014] The fuel cell stack 12 also has a cathode channel 27, an anode channel 28, and a refrigerant channel 29. The cathode channel 27 is formed between the separator 23 and the cathode electrode 25. The cathode channel 27 communicates with an oxidizer gas supply channel 31 and an oxidizer gas discharge channel 32 located outside the fuel cell stack 12. The anode channel 28 is formed between the separator 23 and the anode electrode 26. The anode channel 28 communicates with a fuel gas supply channel 33 and a fuel gas discharge channel 34 located outside the fuel cell stack 12. The refrigerant channel 29 is formed between adjacent power generation cells 21. The refrigerant channel 29 communicates with a heat exchange refrigerant channel 35 located outside the fuel cell stack 12. The heat exchange refrigerant channel 35 includes a forward path 35A and a return path 35B. A cooling medium flows through the refrigerant channel 29 to cool the fuel cell stack 12. The cooling medium may be water.

[0015] The oxidant gas output device 14 is a device that outputs oxidant gas supplied to the fuel cell stack 12. The oxidant gas output device 14 adjusts the output amount (flow rate of oxidant gas) according to the control of the control device 20. Examples of the oxidant gas output device 14 include a compressor. The oxidant gas output from the oxidant gas output device 14 is supplied to the cathode channel 27 of the fuel cell stack 12 via the oxidant gas supply channel 31. A portion of the oxidant gas flowing through the cathode channel 27 flows out of the fuel cell stack 12 as off-gas into the oxidant gas discharge channel 32. The off-gas is a mixed gas containing oxidant gas.

[0016] The fuel gas output device 16 is a device that outputs fuel gas supplied to the fuel cell stack 12. The fuel gas output device 16 adjusts the amount of fuel gas output (fuel gas flow rate) according to the control of the control device 20. Examples of fuel gas output devices 16 include injectors. The fuel gas output from the fuel gas output device 16 is supplied to the anode flow path 28 of the fuel cell stack 12 via the fuel gas supply flow path 33. A portion of the fuel gas flowing through the anode flow path 28 flows out of the fuel cell stack 12 as off-gas into the fuel gas discharge flow path 34.

[0017] The flow control valve 18 is located in the bypass channel 36. The bypass channel 36 is a channel for discharging oxidant gas without supplying it to the fuel cell stack 12. The bypass channel 36 branches off from the oxidant gas supply channel 31 between the oxidant gas output device 14 and the fuel cell stack 12 and merges with the oxidant gas discharge channel 32. The flow control valve 18 is configured to allow adjustment of its opening. The opening of the flow control valve 18 is adjusted by the control device 20. When the opening of the flow control valve 18 is "0", no oxidant gas flows from the oxidant gas supply channel 31 to the bypass channel 36. When the opening of the flow control valve 18 is greater than "0", oxidant gas flows from the oxidant gas supply channel 31 to the bypass channel 36. The larger the opening of the flow control valve 18, the greater the flow rate of oxidant gas flowing into the bypass channel 36.

[0018] The temperature sensor 19 is a sensor that detects the temperature of the fuel cell stack 12. The temperature sensor 19 is installed in the fuel cell stack 12. The detected temperature, which is the temperature detected by the temperature sensor 19, is stored in a storage medium such as the control device 20, along with the detection time, which is the time when the temperature was detected. The detected temperature may be the average of the temperatures at multiple locations in the fuel cell stack 12, or it may be a representative temperature. The representative temperature may be, for example, the temperature at the outlet of the refrigerant flow path 29.

[0019] The control device 20 has one or more processors and a storage medium. The control device 20 executes various processes by means of calculations performed by the processor. The control device 20 may be provided in the ECU of the vehicle. The storage medium includes a volatile memory such as a RAM, and a non-volatile memory such as a ROM, a flash memory, and a hard disk. At least a part of the storage medium may be provided in the processor.

[0020] The control device 20 controls the fuel cell system 10 based on the ignition switch. The ignition switch is a switch for starting (turning on) or stopping (turning off) the operation of the vehicle (mobile body). When the ignition switch is turned on, the electric motor mounted on the mobile body is driven. The electric motor is one of the destinations for supplying the generated power of the fuel cell stack 12.

[0021] The control device 20 operates the fuel cell system 10 during the vehicle operation period from when the ignition switch is turned on until it is turned off. During the operation of the fuel cell system 10, the control device 20 causes the fuel cell stack 12 to generate electricity. In this case, the control device 20 drives the oxidant gas output device 14 to supply oxidant gas to the fuel cell stack 12, and drives the fuel gas output device 16 to supply fuel gas to the fuel cell stack 12. Further, the control device 20 controls the oxidant gas output device 14 and the fuel gas output device 16 to adjust the flow rate of the oxidant gas and the flow rate of the fuel gas. In this case, the control device 20 adjusts the flow rate so that the ratio of the oxidant gas to the fuel gas becomes the reference ratio determined by the target power generation amount.

[0022] When the ignition switch is turned off, the control device 20 stops the operation of the fuel cell system 10. During the operation stop of the fuel cell system 10, the control device 20 stops the power generation by the fuel cell stack 12. In this case, the control device 20 stops driving the oxidant gas output device 14 and the fuel gas output device 16. Therefore, the oxidant gas and the fuel gas are not supplied to the fuel cell stack 12, and power generation does not occur in the fuel cell stack 12.

[0023] After the operation of the fuel cell system 10 is stopped, when the detected temperature, which is the temperature detected by the temperature sensor 19, becomes equal to or lower than the freezing warning temperature, warm machine processing is started. The warm machine processing is processing for warming the fuel cell stack 12. The freezing warning temperature is a temperature set to warn of the possibility that the moisture remaining inside the fuel cell stack 12 may freeze.

[0024] FIG. 2 is a flowchart showing the procedure of the warm machine processing according to the embodiment. The warm machine processing is executed between when the operation of the vehicle (mobile body) is stopped and when the next startup is completed. The warm machine processing shifts to step S1 when the detected temperature becomes equal to or lower than the freezing warning temperature.

[0025] In step S1, the control device 20 causes the fuel cell stack 12 to perform power generation for warming the fuel cell stack 12. In this case, even when the ignition switch is off, the control device 20 drives the oxidant gas output device 14 and the fuel gas output device 16 to supply the oxidant gas and the fuel gas to the fuel cell stack 12.

[0026] In this embodiment, the control device 20 causes the fuel cell stack 12 to perform low-stoichiometric power generation. In this case, the control device 20 reduces the amount of oxidizer gas supplied to the fuel cell stack 12 so that the ratio of oxidizer gas to fuel gas falls below a reference ratio determined by the target power generation amount. That is, the control device 20 supplies the same amount of fuel gas to the fuel cell stack 12 as the amount of fuel gas supplied during normal power generation. On the other hand, the control device 20 supplies a smaller amount of oxidizer gas to the fuel cell stack 12 than the amount of oxidizer gas supplied during normal power generation. Normal power generation is power generation performed using amounts of fuel gas and oxidizer gas determined by the target power generation amount. In low-stoichiometric power generation, the amount of oxidizer gas supplied to the fuel cell stack 12 is less than in normal power generation, so the power generation efficiency of the fuel cell stack 12 decreases. Therefore, the heating rate of the fuel cell stack 12 is faster than in normal power generation. When low-stoichiometric power generation is started, warm machine The process then proceeds to step S2.

[0027] In step S2, the control device 20 sets a temperature threshold. In this case, the control device 20 sets a temperature threshold. machine The temperature threshold is set to a value higher than the detected temperature at the start of processing. Once the temperature threshold is set, the control device 20 compares the detected temperature with the predetermined temperature threshold. If the detected temperature exceeds the temperature threshold, the warm machine The process proceeds to step S3, and then to step S4. On the other hand, if the detected temperature is below the temperature threshold, machine The process proceeds to step S4 without going through step S3.

[0028] In step S3, the control device 20 changes the first rate of rise threshold and the second rate of rise threshold. The first rate of rise threshold and the second rate of rise threshold are values ​​compared to the rate of rise of the temperature per unit time. The second rate of rise threshold is smaller than the first rate of rise threshold.

[0029] The first rate of increase threshold has a first set value and a second set value that is smaller than the first set value. For example, the first set value is set to 1°C / sec. For example, the second set value is set to 0.9°C / sec. If the detected temperature exceeds the temperature threshold, the first rate of increase threshold is changed from the first set value to the second set value. On the other hand, if the detected temperature is below the temperature threshold, the first rate of increase threshold is not changed from the first set value to the second set value. In other words, the first rate of increase threshold is maintained at the first set value.

[0030] The second rate of rise threshold has a third setting value and a fourth setting value that is smaller than the third setting value. For example, the third setting value is set to 0.7°C / sec. For example, the fourth setting value is set to 0.6°C / sec. If the detected temperature exceeds the temperature threshold, the second rate of rise threshold is changed from the third setting value to the fourth setting value. On the other hand, if the detected temperature is below the temperature threshold, the second rate of rise threshold is not changed from the third setting value to the fourth setting value. In other words, the second rate of rise threshold is maintained at the third setting value.

[0031] In step S4, the control device 20 compares the rate of increase of the detected temperature (the rate of change of the detected temperature per unit time) with a first rate of increase threshold. If the rate of increase of the detected temperature exceeds the first rate of increase threshold, machine The process proceeds to step S5. On the other hand, if the rate of increase of the detected temperature is less than or equal to the first rate of increase threshold, warm machine The process proceeds to step S6.

[0032] In step S5, the control device 20 compares the detected temperature with the target temperature. The target temperature is warm machine This is the target temperature set for raising the temperature of the fuel cell stack 12 through processing. If the detected temperature reaches the target temperature, warm machine The process will end. On the other hand, if the detected temperature has not reached the target temperature, the warm machine The process returns to step S2.

[0033] In step S6, the control device 20 compares the detected temperature rise rate with a second rise rate threshold. If the detected temperature rise rate exceeds the second rise rate threshold, machine The process proceeds to step S7. On the other hand, if the rate of increase of the detected temperature is less than or equal to the second rate of increase threshold, the warm machine The process proceeds to step S8.

[0034] In step S7, the control device 20 controls the oxidizer gas output device 14 to increase the output flow rate of the oxidizer gas output from the oxidizer gas output device 14 from the current output flow rate. Furthermore, the control device 20 increases the opening degree of the flow control valve 18 provided in the bypass flow path 36. When the fuel cell system 10 is stopped, the opening degree of the flow control valve 18 is "0", so the control device 20 increases the opening degree of the flow control valve 18 to more than "0". In this case, the control device 20 may set the opening degree of the flow control valve 18 so that the amount of oxidizer gas increased from the current output flow rate flows through the bypass flow path 36. When the output flow rate of the oxidizer gas is increased from the current output flow rate and the opening degree of the flow control valve 18 is increased, warm machine The process proceeds to step S5.

[0035] When power generation is performed in the fuel cell stack 12 at a lower efficiency than normal power generation, a hydrogen generation reaction may occur at the cathode electrode 25 of the fuel cell stack 12 through the recombination of hydrogen ions and electrons that permeate the electrolyte membrane 24. Consequently, the amount of hydrogen in the off-gas flowing out of the fuel cell stack 12 to the oxidant gas discharge channel 32 tends to increase.

[0036] In this regard, the control device 20 increases the amount of oxidant gas supplied from the oxidant gas supply channel 31 to the oxidant gas discharge channel 32 via the bypass channel 36 by increasing the opening of the flow control valve 18. On the other hand, the control device 20 also increases the amount of oxidant gas from the oxidant gas output device 14. Therefore, the control device 20 can dilute the hydrogen in the off-gas flowing out of the fuel cell stack 12 to the oxidant gas discharge channel 32 without significantly changing the amount of oxidant gas supplied to the fuel cell stack 12. As a result, the exhaust hydrogen concentration can be reduced while maintaining lower-efficiency power generation in the fuel cell stack 12 than in normal power generation.

[0037] In step S8, the control device 20 switches the power generation by the fuel cell stack 12 from low-stoichiometric power generation to normal power generation. In this case, the control device 20 outputs a larger amount of oxidant gas to the oxidant gas output device 14 than the amount of gas used during low-efficiency power generation. When the power generation by the fuel cell stack 12 is switched to normal power generation, warm machine The process proceeds to step S9.

[0038] In step S9, the control device 20 compares the detected temperature with the target temperature. If the detected temperature has not reached the target temperature, the device will not warm up. machine The process remains at step S9. On the other hand, if the detected temperature reaches the target temperature, machine Processing is complete.

[0039] The above embodiment may be modified as follows.

[0040] (Variation 1) In step S7, the control device 20 may increase the opening of the flow control valve 18 without increasing the output flow rate of the oxidizer gas output from the oxidizer gas output device 14 from the current output flow rate.

[0041] In this case, the amount of oxidizer gas supplied to the fuel cell stack 12 is reduced, making power generation in the fuel cell stack 12 even less efficient. As a result, the amount of hydrogen in the off-gas flowing out of the fuel cell stack 12 into the oxidizer gas discharge channel 32 increases even further, but the hydrogen in the off-gas flowing out of the fuel cell stack 12 into the oxidizer gas discharge channel 32 can be diluted. In other words, even if the output flow rate of the oxidizer gas output from the oxidizer gas output device 14 is not increased, the exhaust hydrogen concentration can be reduced while maintaining power generation in the fuel cell stack 12 at a lower efficiency than normal power generation.

[0042] (Modification 2) The control device 20 may increase the amount of oxidizer gas in steps at predetermined time intervals without switching the power generation by the fuel cell stack 12 from low-stoichiometric power generation to normal power generation.

[0043] (Variation 3) The fuel cell system 10 may supply the electricity obtained by having the fuel cell stack 12 perform low-stoichiometric power generation to at least one of the oxidizer gas output device 14 and the fuel gas output device 16 as driving power. This can improve energy efficiency.

[0044] The inventions that can be understood from the above embodiments and modifications are described below.

[0045] (1) The present invention relates to a fuel cell system (10) having a fuel cell stack (12) that generates electricity by an electrochemical reaction between a fuel gas and an oxidizer gas, comprising: an oxidizer gas output device (14) that outputs the oxidizer gas supplied to the fuel cell stack (12); an oxidizer gas supply channel (31) for supplying the oxidizer gas output from the oxidizer gas output device (14) to the fuel cell stack (12); an oxidizer gas discharge channel (32) for discharging a mixed gas containing the oxidizer gas discharged from the fuel cell stack (12) to the outside; and the oxidizer gas output device (14) and the fuel cell stack (12) The system includes a bypass channel (36) that branches off from the oxidant gas supply channel (31) and merges with the oxidant gas discharge channel (32), a flow control valve (18) provided in the bypass channel (36), a temperature sensor (19) for detecting the temperature of the fuel cell stack (12), and a control device (20) that, during low-efficiency power generation when the fuel cell stack (12) generates power at an efficiency lower than the power generation efficiency determined by the target power generation amount of the fuel cell stack (12), controls at least one of the oxidant gas output device (14) and the flow control valve (18) based on the temperature to vary the power generation state of the fuel cell stack (12).

[0046] This allows for a reduction in the hydrogen concentration in the exhaust gas without installing a concentration sensor in the oxidizer gas exhaust channel. In other words, the temperature of the fuel cell stack correlates with the hydrogen produced at the cathode electrode by the recombination of hydrogen ions and electrons that have permeated the electrolyte membrane. Therefore, it becomes possible to capture the amount of hydrogen produced at the cathode electrode by recombination without installing a new concentration sensor in the oxidizer gas exhaust channel. Furthermore, it becomes possible to change the power generation state of the fuel cell stack according to the amount of hydrogen. As a result, the hydrogen concentration in the exhaust gas can be reduced without installing a hydrogen concentration sensor in the oxidizer gas exhaust channel.

[0047] (2) The present invention relates to a fuel cell system (10), wherein the control device (20) may control at least one of the oxidizer gas output device (14) and the flow control valve (18) based on the rate of increase of the temperature per unit time. machine Depending on the conditions, the flow rate of oxidizer gas supplied to the fuel cell stack can be adjusted. As a result, the power generation efficiency of the fuel cell stack can be adjusted while reducing the hydrogen concentration in the exhaust gas.

[0048] (3) The present invention relates to a fuel cell system (10), wherein the control device (20) determines whether or not to vary the power generation state of the fuel cell stack (12) based on the rate of increase of the temperature per unit time, and may control the oxidant gas output device (14) or the flow rate control valve (18) according to the determination result. Hydrogen produced at the cathode electrode by the recombination of hydrogen ions and electrons that have permeated the electrolyte membrane is generated when the rate of increase of the temperature of the fuel cell stack small The amount increases accordingly. Therefore, based on the rate of temperature rise, the amount of hydrogen that is not needed in the exhaust can be accurately detected, and as a result, unnecessary adjustments to the flow rate of the oxidizer gas supplied to the fuel cell stack can be suppressed.

[0049] (4) The present invention relates to a fuel cell system (10), in which, when the rate of temperature increase is less than or equal to a predetermined first rate of temperature increase threshold and exceeds a second rate of temperature increase threshold that is smaller than the first rate of temperature increase threshold, the control device (20) may increase the opening of the flow rate control valve (18). This reduces the amount of oxidant gas supplied to the fuel cell stack and, at the same time, dilutes the hydrogen in the exhaust gas discharged from the fuel cell stack. As a result, it is possible to reduce the hydrogen concentration in the exhaust gas while lowering the power generation efficiency of the fuel cell stack and increasing the heating rate of the fuel cell stack.

[0050] (5) The present invention relates to a fuel cell system (10), wherein the control device (20) may increase the opening of the flow control valve (18) and increase the output flow rate of the oxidizer gas output from the oxidizer gas output device (14). This makes it possible to reduce the hydrogen concentration in the exhaust gas without generally changing the state of low-efficiency power generation carried out by the fuel cell stack.

[0051] (6) The present invention relates to a fuel cell system (10), and when the rate of temperature increase is less than or equal to the second rate of increase threshold, the control device (20) may output a larger amount of the oxidizer gas to the oxidizer gas output device (14) than the amount of gas during low-efficiency power generation. This makes it possible to suppress the unnecessary continuation of a state in which the power generation efficiency of the fuel cell stack is reduced.

[0052] (7) The present invention relates to a fuel cell system (10), wherein the control device (20) may switch the values ​​of the first rate of rise threshold and the second rate of rise threshold according to the temperature. machine Depending on the conditions, the power generation state of the fuel cell stack can be precisely adjusted.

[0053] (8) The present invention relates to a fuel cell system (10), wherein the control device (20) may cause the fuel cell stack (12) to perform the low-efficiency power generation between the time the operation of the mobile body on which the fuel cell system (10) is mounted is stopped and the next start-up. This makes it possible to suppress the freezing of moisture remaining inside the fuel cell stack before the start-up of the mobile body, even if the temperature drops due to a rapid change in the environment in which the fuel cell system is located while the mobile body is stopped.

[0054] Furthermore, the present invention is not limited to the disclosure described above, and can take various configurations without departing from the spirit of the invention. [Explanation of symbols]

[0055] 10…Fuel cell system 12…Fuel cell stack 14…Oxidizer gas output equipment 16…Fuel gas output equipment 18…Flow control valve 19…Temperature sensor 20...Control device 31...Oxidizer gas supply channel 32... Oxidizer gas discharge channel 36... Bypass channel

Claims

1. A fuel cell system having a fuel cell stack that generates electricity through an electrochemical reaction between a fuel gas and an oxidizer gas, An oxidizer gas output device that outputs the oxidizer gas supplied to the fuel cell stack, An oxidizer gas supply channel for supplying the oxidizer gas output from the oxidizer gas output device to the fuel cell stack, An oxidizer gas discharge channel for discharging the mixed gas containing the oxidizer gas discharged from the fuel cell stack to the outside, A bypass channel branches off from the oxidizer gas supply channel between the oxidizer gas output device and the fuel cell stack and merges with the oxidizer gas discharge channel, A flow control valve is provided in the bypass channel, A temperature sensor for detecting the temperature of the fuel cell stack, A control device capable of changing the power generation state of the fuel cell stack by controlling at least one of the oxidizer gas output device and the flow control valve based on the temperature during low-efficiency power generation, in which the fuel cell stack generates power at an efficiency lower than the power generation efficiency determined by the target power generation amount of the fuel cell stack. Equipped with, If the rate of increase in temperature per unit time is less than or equal to a predetermined first rate of increase threshold, and exceeds a second rate of increase threshold that is smaller than the first rate of increase threshold, the control device increases the opening of the flow control valve. A fuel cell system in which, when the rate of temperature increase is less than or equal to the second rate of increase threshold, the control device causes the oxidizer gas to be output to the oxidizer gas output device in an amount greater than the amount of gas during low-efficiency power generation.

2. A fuel cell system according to claim 1, A fuel cell system comprising a control device that determines whether or not to change the power generation state of the fuel cell stack based on the rate of increase of the temperature per unit time, and controls the oxidizer gas output device or the flow control valve according to the determination result.

3. A fuel cell system according to claim 1 or 2, A fuel cell system in which the control device increases the opening of the flow rate control valve and increases the output flow rate of the oxidizer gas output from the oxidizer gas output device when the rate of temperature increase is less than or equal to the first rate of temperature increase threshold and exceeds the second rate of temperature increase threshold.

4. A fuel cell system having a fuel cell stack that generates electricity through an electrochemical reaction between a fuel gas and an oxidizer gas, An oxidizer gas output device that outputs the oxidizer gas supplied to the fuel cell stack, An oxidizer gas supply channel for supplying the oxidizer gas output from the oxidizer gas output device to the fuel cell stack, An oxidizer gas discharge channel for discharging the mixed gas containing the oxidizer gas discharged from the fuel cell stack to the outside, A bypass channel branches off from the oxidizer gas supply channel between the oxidizer gas output device and the fuel cell stack and merges with the oxidizer gas discharge channel, A flow control valve is provided in the bypass channel, A temperature sensor for detecting the temperature of the fuel cell stack, A control device capable of changing the power generation state of the fuel cell stack by controlling at least one of the oxidizer gas output device and the flow control valve based on the temperature during low-efficiency power generation, in which the fuel cell stack generates power at an efficiency lower than the power generation efficiency determined by the target power generation amount of the fuel cell stack. Equipped with, If the rate of increase in temperature per unit time is less than or equal to a predetermined first rate of increase threshold, and exceeds a second rate of increase threshold that is smaller than the first rate of increase threshold, the control device increases the opening of the flow control valve. The control device switches the values ​​of the first rate of increase threshold and the second rate of increase threshold according to the temperature in the fuel cell system.

5. A fuel cell system according to any one of claims 1, 2, or 4, A fuel cell system in which, between the time the operation of the mobile body on which the fuel cell system is installed is stopped and the time until the next start-up, the control device causes the fuel cell stack to perform the low-efficiency power generation.

Images