Fuel cell system and control method thereof

Abstract

The purpose of the present invention is to provide a fuel cell system capable of maintaining a hydrogen partial pressure within the system within an appropriate range even when external environmental conditions change. A fuel cell system (1) is provided with: a fuel cell (2) that generates electricity by reacting hydrogen gas, which is a fuel gas, with an oxidant gas; a hydrogen gas supply device (4) that supplies hydrogen gas to the fuel cell (2); a supply control unit (61) that determines the supply amount and supply timing of hydrogen gas to be supplied to the fuel cell (2); and an atmospheric pressure acquisition unit (atmospheric pressure sensor (7)) that acquires atmospheric pressure, and the supply control unit (61) supplies hydrogen gas to the fuel cell (2) at a supply amount and a supply timing that are determined according to at least the atmospheric pressure while the fuel cell (2) is idle in which the operation is stopped.

Description

Technical Field

[0001] The present invention relates to a fuel cell system and a control method thereof, which can adjust the supply timing and supply amount of fuel gas during idling according to atmospheric pressure. Background Art

[0002] In recent years, in order to ensure that more people can obtain appropriate and reliable sustainable and advanced energy, research and development related to fuel cells that contribute to energy efficiency improvement have been carried out.

[0003] In a fuel cell system that generates electricity through a fuel cell, there are the following problems: Since oxygen remains in the system of the cathode electrode during idling when the operation of the fuel cell has stopped, electrode deterioration occurs, or oxygen permeates through the electrolyte membrane and reacts with hydrogen in the anode electrode system to generate hydrogen peroxide, and the resulting OH radicals cause electrolyte membrane deterioration. In addition, there is also the following problem: When the operation of the fuel cell starts again, if there is oxygen above a specified value in the anode electrode system, the potential rises excessively and the electrode deteriorates.

[0004] In order to suppress such problems caused by residual oxygen during idling, the following method has been proposed: Even during idling, hydrogen is continuously supplied regularly for a given period, and the hydrogen partial pressure in the anode electrode system is maintained above a specified value (lower limit value), so that hydrogen that has permeated through the electrolyte membrane reacts with oxygen in the cathode electrode system to consume the residual oxygen.

[0005] Most of the hydrogen supply during idling is fixed in a fixed amount each time at a fixed time interval, but there is also a technique for determining the hydrogen supply timing based on physical parameters in the fuel cell stack. For example, in Patent Document 1, a technique for changing the hydrogen supply timing based on the pressure and temperature in the fuel cell stack and a technique for supplying hydrogen based on the hydrogen concentration on the anode side are disclosed.

[0006] Prior Art Documents Patent Documents Patent Document 1: U.S. Patent No. 8722263 Summary of the Invention Problems to be Solved by the Invention In the above prior art, when determining the hydrogen supply timing and supply amount during fuel cell idling, the external environmental conditions of the fuel cell system are not considered. However, the behavior of the hydrogen partial pressure inside the fuel cell system may change according to the atmospheric pressure and external temperature outside the system. Therefore, it is sometimes difficult to maintain the hydrogen partial pressure inside the system during idling within an appropriate range without considering such external environmental conditions.

[0007] The present invention has been completed to solve such a problem, and an object thereof is to provide a fuel cell system capable of maintaining the hydrogen partial pressure within the system within an appropriate range even when external environmental conditions change. Moreover, it further contributes to energy efficiency improvement.

[0008] Technical solution for solving the problem To achieve this object, the fuel cell system 1 according to Technical Solution 1 of the present invention includes: a fuel cell that generates electricity through the reaction of hydrogen as a fuel gas and an oxidant gas; a hydrogen supply device that supplies hydrogen to the fuel cell; a supply control unit that determines the supply amount and supply timing of hydrogen supplied to the fuel cell; and an atmospheric pressure acquisition unit that acquires the atmospheric pressure. The supply control unit supplies hydrogen to the fuel cell at a supply amount and supply timing determined at least based on the atmospheric pressure during idling when the operation of the fuel cell has stopped.

[0009] In this fuel cell system, the supply control unit determines the supply amount and supply timing of hydrogen at least based on the atmospheric pressure during idling of the fuel cell. Here, refer to Figure 5 to illustrate the influence of the atmospheric pressure, which is one of the external environmental conditions, on the hydrogen partial pressure within the fuel cell system. Figure 5 It is a diagram for explaining the gas behavior within the system under environmental conditions of low altitude and high altitude, that is, high atmospheric pressure conditions and low atmospheric pressure conditions, respectively.

[0010] First, when observing the changes in the total pressure in the anode electrode system and the cathode electrode system (upper figure), after the start of idling, the hydrogen existing in the anode electrode system permeates through the electrolyte membrane and moves to the cathode side, so the total pressure in the anode electrode system slowly decreases. In addition, within the cathode electrode system, the permeated hydrogen reacts with the oxidant gas remaining in the cathode electrode system and is consumed, also causing the total pressure to slowly decrease.

[0011] If comparing low altitude and high altitude, under the high altitude conditions with low atmospheric pressure, both the anode electrode system and the cathode electrode system shift at a level where the total pressure is lower than that under low altitude conditions.

[0012] Next, when observing the change in the hydrogen concentration in the cathode electrode system (middle figure), the hydrogen concentration temporarily increases after the start of idling due to the hydrogen permeating from the anode side, and then gradually decreases as the reaction between hydrogen and the oxidant gas progresses.

[0013] The hydrogen concentration in the cathode electrode system has a great influence on the hydrogen concentration in the exhaust gas, so an upper limit value is set from the perspective of safety.

[0014] The tendency of the change in the hydrogen concentration in the cathode electrode system does not show a large difference between low altitude conditions and high altitude conditions. However, under high altitude conditions, the total pressure in the cathode electrode system decreases, so the absolute amount of the oxidant gas in the cathode electrode system also decreases. Therefore, if the same amount of hydrogen as in the low altitude conditions is supplied when supplying hydrogen, the increase in the hydrogen concentration in the cathode electrode system will also become larger and may exceed the upper limit value. Therefore, under high altitude conditions, it is necessary to reduce the amount of hydrogen supplied once compared with the low altitude conditions.

[0015] Finally, when observing the change in the hydrogen partial pressure in the anode electrode system (the figure below), after the start of idling, hydrogen permeates through the electrolyte membrane and moves to the cathode side and is consumed by reaction with the oxidant, whereby the hydrogen partial pressure in the anode electrode system slowly decreases.

[0016] Here, from the viewpoint of suppressing the deterioration of the electrodes and the electrolyte membrane by consuming the oxidant gas remaining in the cathode electrode system through reaction with hydrogen during idling, the hydrogen partial pressure in the anode electrode system needs to be maintained above a given lower limit value.

[0017] As described above, under high altitude conditions, the total pressure in the anode electrode system decreases, so the absolute amount of hydrogen in the anode electrode system also decreases. Therefore, under high altitude conditions, the time until the hydrogen partial pressure in the anode electrode system reaches the lower limit value is shorter than that under low altitude conditions. Therefore, under high altitude conditions, it is necessary to supply hydrogen at intervals shorter than those under low altitude conditions so that the hydrogen partial pressure in the anode electrode system is not lower than the lower limit value.

[0018] Based on the above insights, in the fuel cell system of the present invention, the supply amount and supply timing of hydrogen can be determined according to the atmospheric pressure during idling, so that even when the atmospheric pressure as an external environmental condition changes, the hydrogen partial pressure in the system can be maintained within an appropriate range.

[0019] The invention according to Technical Solution 2 of the present invention is characterized in that, in the fuel cell system described in Technical Solution 1, an external air temperature acquisition unit for acquiring the external air temperature is further provided, and during idling, the supply control unit supplies hydrogen to the fuel cell at a supply timing determined at least according to the atmospheric pressure and the external air temperature.

[0020] According to this structure, the supply control unit determines the supply timing of hydrogen at least according to the atmospheric pressure and the external air temperature during the idling of the fuel cell. Here, refer to Figure 6 to illustrate the influence of the external air temperature, which is one of the external environmental conditions, on the hydrogen partial pressure in the fuel cell system. Figure 6 is a diagram for explaining the gas behavior in the system under normal temperature and low temperature, that is, environmental conditions with a high external air temperature and environmental conditions with a low external air temperature.

[0021] First, when observing the changes in the total pressures in the anode electrode system and the cathode electrode system (upper figure), compared with Figure 5 Similarly, after the start of idling, hydrogen in the anode electrode system permeates to the cathode side, whereby the total pressure in the anode electrode system decreases, and in the cathode electrode system, hydrogen reacts with the oxidant gas and is consumed, whereby the total pressure in the cathode electrode system also decreases.

[0022] Here, under low-temperature conditions where the external air temperature is low, due to the influence of the external air temperature, the temperature of the gas in the system decreases faster than under normal-temperature conditions, whereby the gas in each system condenses, and thus the total pressure decreases more significantly.

[0023] Next, when observing the change in the hydrogen concentration in the cathode electrode system (middle figure), compared with Figure 5 Similarly, after the start of idling, the hydrogen concentration temporarily increases due to the hydrogen permeating from the anode side, and then gradually decreases as the reaction between hydrogen and the oxidant gas progresses.

[0024] The tendency of the change in the hydrogen concentration in the cathode electrode system does not show a large difference between low-altitude conditions and high-altitude conditions.

[0025] Finally, when observing the change in the hydrogen partial pressure in the anode electrode system (lower figure), compared with Figure 5 Similarly, after the start of idling, hydrogen permeates through the electrolyte membrane and moves to the cathode side, and is consumed by reacting with the oxidant, whereby the hydrogen partial pressure in the anode electrode system slowly decreases.

[0026] Here, as described above, under low-temperature conditions, the total pressure in the anode electrode system decreases more significantly, so the decrease in the hydrogen partial pressure in the anode electrode system is also greater. Therefore, under low-temperature conditions, it is necessary to supply hydrogen at intervals shorter than under normal-temperature conditions so that the hydrogen partial pressure in the anode electrode system does not fall below the lower limit value.

[0027] Based on the above-mentioned understanding, in the fuel cell system with the above structure, it is possible to determine the supply timing of hydrogen according to the atmospheric pressure and external air temperature during idling, and supply hydrogen. Therefore, even when the atmospheric pressure and external air temperature, which are external environmental conditions, change, the hydrogen partial pressure in the system can be maintained within an appropriate range.

[0028] The invention according to Technical Solution 3 of the present invention is characterized in that, in the fuel cell system described in Technical Solution 2, the supply control unit determines the supply amount and supply timing of the next hydrogen at least based on the atmospheric pressure and external air temperature at the time of the last hydrogen supply during idling.

[0029] According to this structure, during idling, the supply amount and supply timing of hydrogen for the next time are determined based on the atmospheric pressure and the external air temperature at the time of the last hydrogen supply. Therefore, it is possible to determine the supply amount and supply timing of hydrogen with high responsiveness based on the relatively recent atmospheric pressure and external air temperature. Accordingly, it is possible to maintain the hydrogen partial pressure within the system within an appropriate range according to changes in the atmospheric pressure and external air temperature.

[0030] The invention according to Technical Solution 4 of the present invention is characterized in that, in the fuel cell system according to any one of Technical Solutions 1 to 3, the supply control unit determines the supply timing of hydrogen during idling such that the lower the atmospheric pressure, the shorter the interval from the last hydrogen supply to the next hydrogen supply.

[0031] As described above, there is a tendency that the lower the atmospheric pressure, the smaller the absolute amount of hydrogen in the anode electrode system, and the shorter the time until the hydrogen partial pressure in the anode electrode system reaches the lower limit value. In the fuel cell system of this structure, control is performed such that the lower the atmospheric pressure, the shorter the time interval for supplying hydrogen, so that it is possible to appropriately respond to changes in the atmospheric pressure and maintain the hydrogen partial pressure within the system within an appropriate range.

[0032] The invention according to Technical Solution 5 of the present invention is characterized in that, in the fuel cell system according to Technical Solution 2 or 3, the supply control unit determines the supply timing of hydrogen during idling such that the lower the external air temperature, the shorter the interval from the last hydrogen supply to the next hydrogen supply.

[0033] As described above, the lower the external air temperature, the more significantly the hydrogen partial pressure in the anode electrode system decreases due to gas condensation, and the higher the possibility of falling below the lower limit value. In the fuel cell system of this structure, control is performed such that the lower the external air temperature, the shorter the time interval for supplying hydrogen, so that it is possible to appropriately respond to changes in the external air temperature and maintain the hydrogen partial pressure within the system within an appropriate range.

[0034] The invention according to Technical Solution 6 of the present invention is characterized in that, in the fuel cell system according to Technical Solution 1, the supply control unit determines the supply amount of hydrogen during idling such that the lower the atmospheric pressure, the smaller the supply amount of hydrogen per time.

[0035] According to this structure, the supply control unit determines the supply amount of hydrogen during idling such that the lower the atmospheric pressure, the smaller the supply amount of hydrogen per time. Here, refer to Figure 7 Describe the change in the hydrogen concentration in the cathode electrode system during hydrogen supply caused by different atmospheric pressures. Figure 7 It is a diagram for explaining the gas behavior within the system under environmental conditions of low altitude and high altitude, that is, high atmospheric pressure and low atmospheric pressure, respectively.

[0036] First, when observing the changes in the total pressure in the anode electrode system and the cathode electrode system after the supply of hydrogen at idle (upper figure), due to the supply of hydrogen, the total pressure in the anode electrode system temporarily rises significantly. In this example, the supply amount of hydrogen is determined based on the gauge pressure, that is, the pressure based on atmospheric pressure. Therefore, regardless of whether it is a low altitude condition or a high altitude condition, the rising amplitude of the total pressure in the anode electrode system during hydrogen supply is fixed.

[0037] Next, when observing the change in the hydrogen concentration in the cathode electrode system (middle figure), starting from just after the supply of hydrogen, hydrogen on the anode side permeates through the electrolyte membrane and enters the cathode side, thereby causing the hydrogen concentration in the cathode electrode system to temporarily rise significantly.

[0038] Here, under high altitude conditions, the total pressure in both the anode electrode system and the cathode electrode system is small, and the absolute amount of gas is also small. Therefore, when hydrogen is supplied based on the same gauge pressure amplitude as in the low altitude condition during hydrogen supply, the rising amplitude of the hydrogen concentration in the cathode electrode system becomes larger compared to the low altitude condition, thereby increasing the possibility of exceeding the upper limit value of the hydrogen concentration in the system.

[0039] Therefore, under high altitude conditions, it is necessary to reduce the hydrogen supply amount once compared to the low altitude condition.

[0040] Finally, when observing the change in the hydrogen partial pressure in the anode electrode system (lower figure), due to the supply of hydrogen, the hydrogen partial pressure in the anode electrode system temporarily rises significantly. After that, since hydrogen permeates to the cathode side, it gradually decreases and soon reaches an equilibrium state. Regardless of whether it is a low altitude condition or a high altitude condition, the rising amplitude of the hydrogen partial pressure in the anode electrode system during hydrogen supply is fixed.

[0041] Based on the above insights, in the fuel cell system with the above structure, the hydrogen supply amount during idle is determined so that the lower the atmospheric pressure, the smaller the hydrogen supply amount per time. Therefore, when the atmospheric pressure, which is an external environmental condition, changes, the hydrogen partial pressure in the system can be more effectively maintained within an appropriate range.

[0042] The control method of the fuel cell system according to Technical Solution 7 of the present invention has: a fuel cell that generates electricity through the reaction of hydrogen and an oxidant gas; a hydrogen supply unit that supplies hydrogen to the fuel cell; a supply control unit that determines the supply amount and supply timing of the hydrogen supplied to the fuel cell; and an atmospheric pressure acquisition unit that acquires the atmospheric pressure. The supply control unit performs the following control: during idle when the operation of the fuel cell has stopped, hydrogen is supplied to the fuel cell with a supply amount and supply timing determined at least based on the atmospheric pressure.

[0043] In the control method of the fuel cell system of the present invention, the supply amount and supply timing of hydrogen can be determined according to the atmospheric pressure during idling, and hydrogen is supplied. Therefore, even when the atmospheric pressure, which is an external environmental condition, changes, the hydrogen partial pressure in the system can be maintained within an appropriate range. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic structural diagram of a fuel cell vehicle equipped with a fuel cell system according to an embodiment of the present invention.

[0045] Figure 2 is a diagram showing Figure 1 an example of the control process of hydrogen supply during idling in a fuel cell system.

[0046] Figure 3 is a flowchart showing the control process of a supply interval / supply amount determination subroutine.

[0047] Figure 4 is an explanatory diagram showing the change in the hydrogen partial pressure in the anode system during hydrogen supply control during idling in the embodiment and the prior example.

[0048] Figure 5 is an explanatory diagram for explaining the gas behavior in the system under low altitude and high altitude conditions.

[0049] Figure 6 is an explanatory diagram for explaining the gas behavior in the system under normal temperature and low temperature conditions.

[0050] Figure 7 is an explanatory diagram for explaining the gas behavior in the system under low altitude and high altitude conditions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] Hereinafter, a preferred embodiment of the fuel cell system of the present invention will be described in detail with reference to the drawings. The fuel cell system 1 according to the illustrated embodiment is mounted on a fuel cell vehicle 100 and functions as one of the power sources of the fuel cell vehicle 100. It should be noted that the structures described below illustrate the present invention, but the present invention is not limited thereto.

[0052] <Structure of Fuel Cell System 1> Figure 1 is a schematic structural diagram of a fuel cell vehicle 100 equipped with a fuel cell system 1 according to an embodiment. The fuel cell vehicle 100 is, for example, a fuel cell electric vehicle. As shown in the figure, it includes a fuel cell system 1, a battery 200, a current controller 300, a motor 400, etc. The battery 200 may include a secondary battery, a capacitor, etc.

[0053] The fuel cell system 1 includes a fuel cell stack (fuel cell) 2, an oxidant gas supply device 3, a hydrogen supply device 4, a refrigerant supply device 5, and a control device 6.

[0054] The oxidant gas supply device 3 supplies oxidant gas to the fuel cell stack 2, and the hydrogen supply device 4 supplies hydrogen as fuel gas to the fuel cell stack 2.

[0055] The refrigerant supply device 5 cools the fuel cell stack 2 by circulating and supplying refrigerant to the fuel cell stack 2.

[0056] The control device 6 is composed of an ECU (Electronic Control Unit), and as will be described later, by the CPU executing a program stored in the memory, it operates as various control units, etc. The control device 6 controls the entirety (each component) of the fuel cell system 1 through control lines (not shown).

[0057] The fuel cell stack 2 is a structure formed by stacking a plurality of power generation units 21. An oxidant gas inlet 2a, an oxidant gas outlet 2b, a hydrogen inlet 2c, a hydrogen outlet 2d, an output electrode 2e, a refrigerant outlet 2f, and a refrigerant inlet 2g are respectively provided in the fuel cell stack 2.

[0058] Each power generation unit 21 of the fuel cell stack 2 has, for example, the following structure: a solid polymer electrolyte membrane (hereinafter, also simply referred to as the electrolyte membrane) 22 which is a film of perfluorosulfonic acid containing moisture is sandwiched between an anode electrode 23 and a cathode electrode 24. As the electrolyte membrane 22, in addition to fluorine-based electrolytes, hydrocarbon-based electrolytes, etc. can also be used.

[0059] A pressure sensor 23a capable of measuring the total pressure (gauge pressure) inside the anode electrode 23 is provided in the sealing system of the anode electrode 23.

[0060] The fuel cell stack 2 generates electricity through the electrochemical reaction of the oxidant gas (such as air) supplied from the oxidant gas supply device 3 through the oxidant gas inlet 2a and hydrogen supplied from the hydrogen supply device 4 through the hydrogen inlet 2c. The generated electricity of the fuel cell stack 2 can, through the control of the control device 6, be charged from the output electrode 2e to the battery 200 through the current controller 300, or supplied to the motor 400.

[0061] The oxidant gas supply device 3 includes an air pump 31 that compresses and supplies air from the atmosphere, and the air pump 31 is disposed in the air supply flow path 32.

[0062] A humidifier 33 and a bypass flow path 35 that bypasses the humidifier 33 via a valve 34 are provided in the air supply flow path 32. The air supply flow path 32 communicates with the oxidant gas inlet 2a of the fuel cell stack 2.

[0063] It should be noted that the structure of bypass flow path 35 and valve 34 can also be omitted.

[0064] The oxidant gas outlet 2b communicates with the air discharge flow path 36 passing through the humidifier 33. An EGR (Exhaust Gas Recirculation) pump 37 is provided between the air discharge flow path 36 and the air supply flow path 32.

[0065] The EGR pump 37 causes a part of the gas discharged from the oxidant gas outlet 2b to flow back to the oxidant gas inlet 2a side.

[0066] It should be noted that the structure of the EGR pump 37 can also be omitted.

[0067] A supply side seal valve 32a is provided on the downstream side of the air pump 31 in the air supply flow path 32, and the opening / closing of the supply side seal valve 32a is used to switch the opening / closing of the air supply to the fuel cell stack 2.

[0068] In addition, a discharge side seal valve 36a is provided in the air discharge flow path 36, and a diluter 38 described later is connected to the downstream side of the discharge side seal valve 36a through a back pressure control valve 36b.

[0069] It should be noted that the structure can also be such that the discharge side seal valve 36a and the back pressure control valve 36b are not provided separately, and only a single seal valve is provided.

[0070] The hydrogen supply device 4 has a hydrogen tank 41 that stores high-pressure hydrogen. The hydrogen tank 41 communicates with the hydrogen inlet 2c of the fuel cell stack 2 via a hydrogen supply flow path 42.

[0071] In the hydrogen supply flow path 42, a block valve 42a, an injector (Japanese: インジェクタ) 43, and an ejector (Japanese: エゼクタ) 44 are sequentially connected in series from the upstream side.

[0072] As described later, the injector 43 controls its opening degree by the control device 6, thereby regulating the supply amount and supply timing of the hydrogen supplied to the fuel cell stack 2. The ejector 44 sucks hydrogen from a circulation path 45 described later by making the inside thereof negative pressure.

[0073] The hydrogen outlet 2d of the fuel cell stack 2 communicates with the waste gas flow path 46. A gas-liquid separator 47 is connected to the waste gas flow path 46.

[0074] In the gas-liquid separator 47, a drain flow path 48 for discharging the liquid component, a circulation path 45 for allowing the gas component to flow into the ejector 44, and a purge flow path 49 for purging the gas component to the outside are provided.

[0075] The drain flow path 48 communicates with the diluter 38 via the valve 48a. Additionally, the purge flow path 49 is connected to the diluter 38, and its opening and closing are switched by the operation of the purge valve 49a.

[0076] The diluter 38 mixes the fuel exhaust gas discharged from the hydrogen outlet 2d of the fuel cell stack 2 and separated by the gas-liquid separator 47 with the oxidant exhaust gas discharged from the oxidant gas outlet 2b of the fuel cell stack 2, dilutes the hydrogen concentration to below a specified value, and then discharges it to the outside.

[0077] The refrigerant supply device 5 has a refrigerant flow path 51 that communicates with the refrigerant outlet 2f and the refrigerant inlet 2g of the fuel cell stack 2 and circulates and supplies refrigerants such as pure water and ethylene glycol. In the refrigerant flow path 51, a cooling water pump 52 is provided on the refrigerant inlet 2g side, and a radiator 53 is provided on the refrigerant outlet 2f side.

[0078] The control device 6 is an ECU composed of a microcomputer including a CPU, RAM, ROM, and an I / O interface (all not shown). The control device 6 performs control of opening and closing various valves in the fuel cell system 1, drive control of various auxiliary machines (such as the air pump 31 and the cooling water pump 52), power generation control of the fuel cell stack 2 via the current controller 300, etc. Additionally, the control device 6 controls the opening degree of the ejector 43 with reference to the value of the pressure sensor 23a provided on the anode electrode 23, thereby controlling the supply amount and supply timing of the hydrogen supplied to the fuel cell stack 2.

[0079] It should be noted that the control device 6 can also perform charge and discharge control of the battery 200 and power running / regenerative drive control of the motor 400.

[0080] Additionally, an atmospheric pressure sensor 7 that detects the atmospheric pressure near the fuel cell vehicle 100 and an outside air temperature sensor 8 that detects the temperature near the fuel cell vehicle 100, i.e., the outside air temperature, are connected to the control device 6, and their detection signals are sequentially input to the control device 6.

[0081] The control device 6 reads and executes the program stored in the ROM or RAM, thereby implementing the function of the supply control unit 61 described later. The supply control unit 61 uses the values of the obtained atmospheric pressure and outside air temperature to execute the idle hydrogen supply control described later.

[0082] <Power generation operation of the fuel cell system 1> The power generation operation (power generation operation in the fuel cell stack 2) of the fuel cell system 1 configured as described above will be described below.

[0083] The oxidant gas supply device 3 supplies air as the oxidant gas to the air supply passage 32 via the air pump 31. The air is humidified by passing through the humidifier 33, or bypasses the humidifier 33 through the bypass passage 35, and then is supplied to the fuel cell stack 2 from the oxidant gas inlet 2a.

[0084] On the other hand, the hydrogen supply device 4 supplies hydrogen from the hydrogen tank 41 to the hydrogen supply passage 42 based on the opening control of the ejector 43 performed by the control device 6. The hydrogen is supplied to the fuel cell stack 2 from the hydrogen inlet 2c after passing through the ejector 44.

[0085] The air supplied to the fuel cell stack 2 from the oxidant gas inlet 2a is supplied to the cathode electrodes 24 of the respective power generation units 21, and the hydrogen supplied to the fuel cell stack 2 from the hydrogen inlet 2c is supplied to the anode electrodes 23 of the respective power generation units 21. Thus, in each power generation unit 21, hydrogen and oxygen in the air are consumed through an electrochemical reaction to generate electricity.

[0086] The electricity generated by power generation is supplied to the battery 200 or the motor 400 through the current controller 300 based on the control of the control device 6.

[0087] The reacted air (including the reacted gas and the exhaust gas) in the cathode electrodes 24 of the respective power generation units 21 is discharged from the oxidant gas outlet 2b to the air discharge passage 36. The discharged air is recovered of moisture when passing through the humidifier 33 and then introduced into the diluter 38.

[0088] It should be noted that the moisture recovered by the humidifier 33 is used to humidify the air passing through the air supply passage 32. Thus, the electrolyte membranes 22 in the respective power generation units 21 of the fuel cell stack 2 can be maintained at a humidity suitable for power generation.

[0089] In addition, the reacted hydrogen at the anode electrodes 23 of the respective power generation units 21 is discharged as fuel exhaust gas (partially consumed fuel gas) from the hydrogen outlet 2d to the exhaust gas passage 46. The discharged fuel exhaust gas is introduced from the exhaust gas passage 46 into the gas-liquid separator 47 to separate the liquid moisture, and then is sucked by the ejector 44 via the circulation passage 45.

[0090] In addition, during the execution of the above series of power generation operations, the refrigerant supply device 5 drives the cooling water pump 52 based on the control of the control device 6. Thus, the refrigerant is supplied to the fuel cell stack 2 from the refrigerant inlet 2g, and each power generation unit 21 is cooled by the heat exchange between the refrigerant and each power generation unit 21. The refrigerant after cooling each power generation unit 21 is discharged from the refrigerant outlet 2f and then cooled by the radiator 53 and supplied to the fuel cell stack 2 again.

[0091] <Idle hydrogen supply control> Next, with reference to Figure 2 and Figure 3 the hydrogen supply control during idling in the fuel cell system 1 of the present embodiment and the supply interval / supply amount determination control as its subroutine will be described. Figure 2 is a flowchart showing the hydrogen supply control process during idling in the present embodiment. This process is repeatedly executed at given intervals during idling when the power generation operation (power generation operation in the fuel cell stack 2) in the fuel cell system 1 stops.

[0092] It should be noted that the idling in the fuel cell system 1 can start when the ignition switch of the fuel cell vehicle 100 is turned off, or can be automatically started according to the charge state of the battery 200 and the operation state of the fuel cell vehicle 100.

[0093] First, in step 1 (illustrated as "S1", the same applies hereinafter), the supply interval / supply amount determination control for determining the hydrogen supply timing and supply amount during idling is executed.

[0094] Figure 3 is a subroutine showing the supply interval / supply amount determination control. First, in step 11, the value of the atmospheric pressure detected by the atmospheric pressure sensor 7 at the time of the previous hydrogen supply is obtained as the atmospheric pressure Pprev at the previous supply.

[0095] Here, the time of the previous hydrogen supply refers to the time of the previous hydrogen supply after the start of the current idling, rather than the time of the hydrogen supply during the previous idling.

[0096] In addition, in the case where there is no time of the previous hydrogen supply, that is, when the execution of the current supply interval / supply amount determination control is the first execution since the start of the current idling, the value of the atmospheric pressure at the start of idling is exceptionally obtained as the atmospheric pressure Pprev at the previous supply.

[0097] In the next step 12, the value of the external air temperature detected by the external air temperature sensor 8 at the time of the previous hydrogen supply is obtained as the external air temperature Tprev at the previous supply.

[0098] Here, the time of the previous hydrogen supply also refers to the time of the previous hydrogen supply after the start of the current idling. In the case where there is no time of the previous hydrogen supply, the value of the external air temperature at the start of idling is exceptionally obtained as the external air temperature Tprev at the previous supply.

[0099] In the next step 13, based on the atmospheric pressure Pprev at the time of the last supply and the external air temperature Tprev at the time of the last supply obtained, the next hydrogen supply timing is determined. This determination can also be made by substituting the values of the atmospheric pressure Pprev at the time of the last supply and the external air temperature Tprev at the time of the last supply obtained into a pre-prepared function or the like and performing calculations to derive the next hydrogen supply timing. Alternatively, it can also be made by reading out a map or table that has been previously determined based on the atmospheric pressure Pprev at the time of the last supply, the external air temperature Tprev at the time of the last supply, and other parameters, and retrieving this map or table to obtain the next hydrogen supply timing.

[0100] Although not shown, maps or tables like the above can have a tendency to determine the hydrogen supply timing such that the lower the atmospheric pressure or the lower the external air temperature, the shorter the interval from the last hydrogen supply to the next hydrogen supply. In addition, it can also be configured to determine the hydrogen supply timing by considering, in addition to the atmospheric pressure and the external air temperature, the pressure and temperature inside the fuel cell stack 2, the hydrogen partial pressure and hydrogen concentration in each power generation unit 21 of the fuel cell stack 2, and the like.

[0101] In the next step 14, based on the next hydrogen supply timing determined in step 13, a timer is set and counting is started.

[0102] In the next step 15, based on the atmospheric pressure Pprev at the time of the last supply obtained, the target gauge pressure value, which is the reference for the hydrogen supply amount at the time of the next hydrogen supply, is determined, and this process ends. The target gauge pressure value refers to the value of the gauge pressure that is set to be the total pressure inside the anode electrode 23 system that should be reached due to the supply of hydrogen.

[0103] The determination of the target gauge pressure value can be configured, for example, to be made by the following method: reading out a map or table that has been previously determined based on the atmospheric pressure Pprev at the time of the last supply and other parameters, and retrieving this map or table to obtain the target gauge pressure value (or the correction coefficient for the reference gauge pressure).

[0104] Although not shown, maps or tables like the above can have a tendency to determine the target gauge pressure value such that the lower the atmospheric pressure, the smaller the next hydrogen supply amount. In addition, it can also be configured to determine the hydrogen supply amount by considering, in addition to the atmospheric pressure, the pressure and temperature inside the fuel cell stack 2, the hydrogen partial pressure and hydrogen concentration in each power generation unit 21 of the fuel cell stack 2, and the like.

[0105] Return Figure 2 , after determining the next hydrogen supply timing and supply amount (target gauge pressure value) in step 1, in the next step 2, refer to the Figure 3In step 14, set and start a counting timer, and determine whether the set time has elapsed.

[0106] When the determination result is "yes" and the time set by the timer has elapsed, proceed to the next step 3.

[0107] On the other hand, when the determination result is "no" and the time set by the timer has not elapsed, repeatedly execute the determination in step 2 until the set time has elapsed.

[0108] In the next step 3, based on the target gauge pressure value at the time of the next hydrogen supply determined in step 1, perform the hydrogen supply. At this time, referring to the detection value of the pressure sensor 23a provided on the anode electrode 23, perform the hydrogen supply until this detection value reaches the target gauge pressure value.

[0109] In the next steps 4 to 5, determine whether the end condition of the hydrogen supply control during idling is satisfied.

[0110] First, in step 4, referring to the elapsed time since the start of the current idling, determine whether a preset given time has elapsed. This given time is set to an elapsed time sufficient to determine that the hydrogen supply during idling is not required. For example, it can be set to a time that can determine that the oxidant gas remaining in the cathode electrode 24 has been sufficiently consumed due to the reaction with hydrogen by repeatedly performing the hydrogen supply during idling (steps 1 to step 3).

[0111] It should be noted that instead of the given time, it can also be configured to count the number of executions of the hydrogen supply during idling (steps 1 to step 3), and when the execution of the hydrogen supply a given number of times is confirmed, determine that the hydrogen supply control during idling ends.

[0112] When the determination result in step 4 is "yes" and it is determined that the hydrogen supply control during idling is no longer required because the given time has elapsed, proceed to step 6.

[0113] In step 6, after resetting the timer and the target gauge pressure value set in the supply timing / supply amount determination control in step 1 ( Figure 3 ), end this control process.

[0114] On the other hand, when the determination result in step 4 is "no" and it is determined that the given time has not elapsed since the start of idling, proceed to step 5.

[0115] In step 5, determine whether the idling of the fuel cell system 1 has ended. When the determination result is "yes" and the end of the idling of the fuel cell system 1 is confirmed, proceed to step 6, and after resetting the timer and the target gauge pressure value, end this control process.

[0116] On the other hand, when the determination result in step 5 is "No" and the fuel cell system 1 is still in the idle state, return to step 1 and repeatedly execute the processing starting from step 1 until the end conditions of step 4 or step 5 are satisfied.

[0117] As described above, in the hydrogen supply control during the idle state of the fuel cell system 1, based on the values of the atmospheric pressure and the external temperature obtained most recently, the supply timing (interval) and the supply amount (target gauge pressure value) of hydrogen during the idle state are changed.

[0118] Figure 4 It is an explanatory diagram for comparing the change in the hydrogen partial pressure in the anode electrode system during the hydrogen supply control in the idle state of the existing example with the change in the hydrogen partial pressure in the anode electrode system during the hydrogen supply control in the present embodiment.

[0119] It can be seen from this figure that in the existing example where a fixed amount of hydrogen is supplied at fixed time intervals (fixed hydrogen supply amount / interval), it is impossible to cope with changes in external environmental conditions. For example, in an environment where the atmospheric pressure is low and the external temperature is also low, there is a situation where the supply of hydrogen cannot catch up with the decrease in the hydrogen partial pressure and the hydrogen partial pressure is lower than the lower limit value.

[0120] In this case, it is impossible to consume the oxidant gas remaining in the cathode electrode system during the idle state through the reaction with hydrogen, and it is impossible to suppress the deterioration of the electrodes and the electrolyte membrane.

[0121] On the other hand, in the present embodiment where the supply timing and the supply amount of hydrogen can be changed according to external environmental conditions (atmospheric pressure and external temperature), even when the external environmental conditions change, hydrogen can be supplied at an appropriate timing and in an appropriate amount, so that the hydrogen partial pressure can be maintained within an appropriate range. Thereby, the deterioration of the electrodes and the electrolyte membrane can be effectively suppressed.

[0122] <Effect of the Present Embodiment> Hereinafter, the effect of the present embodiment will be described.

[0123] According to the present embodiment, in the hydrogen supply control during the idle state of the fuel cell system 1, hydrogen can be supplied by determining the supply timing and the supply amount of hydrogen based on the atmospheric pressure. Thereby, even when the atmospheric pressure, which is an external environment that may affect the gas behavior in the system of each power generation unit 21 of the fuel cell stack 2, changes, the hydrogen partial pressure in the fuel cell stack 2 can be maintained within an appropriate range.

[0124] In addition, in the hydrogen supply control during the idle state of the fuel cell system 1 in the present embodiment, hydrogen can be supplied at a supply timing determined based on the atmospheric pressure and the outside air temperature. Thus, even when the outside air temperature, which is an external environment that may affect the gas behavior within the system of each power generation unit 21 of the fuel cell stack 2, changes, the hydrogen partial pressure within the fuel cell stack 2 can be maintained within an appropriate range.

[0125] In addition, the atmospheric pressure and the outside air temperature referred to in the hydrogen supply control during the idle state are the atmospheric pressure and the outside air temperature at the time of the previous hydrogen supply (or the atmospheric pressure and the outside air temperature at the start of the idle state). Therefore, based on the relatively recent atmospheric pressure and outside air temperature, the hydrogen supply amount and the supply timing can be determined with high responsiveness.

[0126] In addition, in the hydrogen supply control (supply timing / supply amount determination control subroutine) during the idle state, the lower the atmospheric pressure or the lower the outside air temperature, the shorter the time interval for hydrogen supply. Therefore, the hydrogen partial pressure within the system can be maintained within a more appropriate range according to the changes in the atmospheric pressure and the outside air temperature.

[0127] In addition, in the hydrogen supply control (supply timing / supply amount determination control subroutine) during the idle state, the lower the atmospheric pressure, the smaller the supply amount in one hydrogen supply. Therefore, the hydrogen partial pressure within the system can be more effectively maintained within an appropriate range according to the change in the atmospheric pressure.

[0128] It should be noted that the present invention is not limited to the described embodiments and can be implemented in various ways. In addition, within the scope of the gist of the present invention, the structure of the detailed parts can be appropriately changed.

[0129] Symbol Explanation 1: Fuel cell system 2: Fuel cell stack (fuel cell) 21: Each power generation unit 22: Solid polymer electrolyte membrane 23: Anode electrode 24: Cathode electrode 3: Oxidant gas supply device 4: Hydrogen supply device (hydrogen supply unit) 5: Refrigerant supply device 6: Control device (ECU) 61: Supply control unit (supply control unit) 7: Atmospheric pressure sensor (atmospheric pressure acquisition unit, atmospheric pressure acquisition unit) 8: Outside air temperature sensor (outside air temperature acquisition unit, outside air temperature acquisition unit).

Claims

1. A fuel cell system, comprising: A fuel cell that generates electricity through the reaction of hydrogen as a fuel gas with an oxidant gas; A hydrogen supply device that supplies the hydrogen to the fuel cell; A supply control unit that determines the supply amount and supply timing of the hydrogen supplied to the fuel cell; and An atmospheric pressure acquisition unit that acquires the atmospheric pressure, During idling when the operation of the fuel cell has stopped, the supply control unit supplies the hydrogen to the fuel cell at the supply amount and supply timing determined at least based on the atmospheric pressure.

2. The fuel cell system according to claim 1, characterized in that The fuel cell system further comprises an external temperature acquisition unit that acquires the external temperature, During idling, the supply control unit supplies the hydrogen to the fuel cell at the supply timing determined at least based on the atmospheric pressure and the external temperature.

3. The fuel cell system according to claim 2, characterized in that During idling, the supply control unit determines the supply amount and supply timing of the next hydrogen at least based on the atmospheric pressure and the external temperature at the time of the last hydrogen supply.

4. The fuel cell system according to any one of claims 1 to 3, characterized in that The supply control unit determines the supply timing of the hydrogen during idling such that the lower the atmospheric pressure, the shorter the interval from the time of the last hydrogen supply to the time of the next hydrogen supply.

5. The fuel cell system according to claim 2 or 3, characterized in that The supply control unit determines the supply timing of the hydrogen during idling such that the lower the external temperature, the shorter the interval from the time of the last hydrogen supply to the time of the next hydrogen supply.

6. The fuel cell system according to any one of claims 1 to 3, characterized in that The supply control unit determines the supply amount of the hydrogen during idling such that the lower the atmospheric pressure, the smaller the supply amount of hydrogen per supply.

7. A control method for a fuel cell system, having: A fuel cell that generates electricity through the reaction of hydrogen with an oxidant gas; A hydrogen supply unit that supplies the hydrogen to the fuel cell; A supply control unit that determines the supply amount and supply timing of the hydrogen supplied to the fuel cell; and An atmospheric pressure acquisition unit that acquires the atmospheric pressure, The supply control unit performs the following control: During idling when the operation of the fuel cell has stopped, it supplies the hydrogen to the fuel cell at the supply amount and supply timing determined at least based on the atmospheric pressure.

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