JP2019029350A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system in which hydrogen of an amount appropriate for reducing the occurrence of an abnormal potential is supplied while a fuel cell stops power generation.SOLUTION: In a fuel cell system, after a controller performs stop process of stopping power generation by a fuel cell, the controller performs hydrogen supply process n times (n is a natural number of one or more) if a residual hydrogen estimated amount showing an estimated amount of hydrogen remaining in an anode side of the fuel cell is smaller than a threshold, the hydrogen supply process being to supply hydrogen of a first supply amount responsive to a difference between the threshold and the residual hydrogen estimated amount. If a cathode potential acquired in an n-th hydrogen supply process satisfies a correction condition, the controller corrects the residual hydrogen estimated amount by reducing the residual hydrogen estimated amount before supply of hydrogen in the n-th hydrogen supply process.SELECTED DRAWING: Figure 1

Description

  The technology disclosed in this specification relates to a fuel cell.

  In a vehicle equipped with a fuel cell, a technology is disclosed in which deterioration suppression processing including processing for consuming oxygen remaining in the fuel cell by power generation is performed when the ignition is off (see, for example, Patent Document 1). ). The ignition originally means ignition of the internal combustion engine, and is not necessarily an appropriate term in the fuel cell system. However, for those skilled in the art, since an ignition switch has been used for many years to mean a vehicle start switch, Patent Document 1 also discloses a vehicle start switch (and hence a fuel cell power generation start switch). It is thought that the word “ignition” is used as it is in the meaning of the operator.

JP-A-2006-139590

  In a fuel cell, electrode deterioration may occur due to the occurrence of an abnormal potential. The present specification provides a technique for supplying an appropriate amount of hydrogen to suppress the occurrence of an abnormal potential in a state where power generation of a fuel cell is stopped.

  The technology disclosed in the present specification has been made to solve the above-described problems, and can be realized as the following forms.

(1) According to one form of the technique disclosed in this specification, a fuel cell, an anode gas supply unit that supplies hydrogen as an anode gas to the fuel cell, and a cathode that supplies a cathode gas to the fuel cell A fuel cell system is provided that includes a gas supply unit, a control unit that controls the operation of the fuel cell, and a potential measurement unit that measures the cathode potential of the fuel cell. In this fuel cell system, the control unit performs a stop process for stopping the power generation of the fuel cell, and then an estimated residual hydrogen amount that is an estimated amount of hydrogen remaining on the anode side of the fuel cell is greater than a threshold value. When it is small, a hydrogen supply process for supplying the anode gas supply unit with the first supply amount of the hydrogen corresponding to the difference between the threshold value and the estimated residual hydrogen amount is performed n times (n is a natural number of 1 or more). When the cathode potential acquired in the n-th hydrogen supply process satisfies the correction condition, the control unit estimates the remaining hydrogen before supplying the hydrogen in the n-th hydrogen supply process. A correction is made to reduce the amount to the estimated remaining hydrogen amount. When the correction condition is n = 1, the cathode potential acquired in the nth hydrogen supply process is taken in the stop process. The cathode potential acquired in the n-th hydrogen supply process when n ≧ 2, the cathode potential acquired in the (n−1) -th hydrogen supply process. It is higher than the potential.

  In the fuel cell system of this embodiment, when the cathode potential acquired in the hydrogen supply process satisfies the correction condition, correction for reducing the estimated residual hydrogen amount is performed before supplying hydrogen. When hydrogen is supplied in the hydrogen supply process, in order to supply the first supply amount of hydrogen according to the difference between the threshold value and the estimated residual hydrogen amount, if the correction for reducing the estimated residual hydrogen amount is performed, the residual amount before correction is performed. More hydrogen is supplied than the supply using the estimated amount of hydrogen. If the cathode potential acquired in the hydrogen supply process satisfies the correction condition, an abnormal potential may occur. That is, hydrogen remaining in the fuel cell may be deficient. By the above correction, a deficiency of hydrogen is eliminated by supplying more hydrogen than without correction. As a result, generation of abnormal potential is suppressed. Further, oxygen remaining in the fuel cell is consumed, and electrode deterioration is suppressed. That is, according to the fuel cell system of this embodiment, an appropriate amount of hydrogen is supplied to suppress the occurrence of abnormal potential.

(2) In the fuel cell system of the above aspect, the control unit supplies hydrogen after supplying a second supply amount of hydrogen that is equal to or less than the threshold value after stopping the supply of the cathode gas in the stop process. May be stopped. In this way, it is possible to further suppress the occurrence of an abnormal potential due to the lack of hydrogen in the fuel cell as compared with the case where hydrogen is not supplied in the stop process. Moreover, since the 2nd supply amount is below a threshold value, the deterioration of the fuel consumption by excessive supply of hydrogen can be suppressed, consuming oxygen.

(3) In the fuel cell system of the above aspect, the fuel cell system further includes a pressure measuring unit that measures an anode total pressure that is a total pressure on the anode side of the fuel cell, and the control unit is configured to experimentally obtain the anode Anode pressure information indicating the relationship between the total pressure and the partial pressure of a gas other than hydrogen existing on the anode side is provided, and the anode total pressure acquired in the hydrogen supply process and the anode side pressure information are used. Then, the estimated residual hydrogen amount may be calculated. In this way, the estimated residual hydrogen amount can be easily calculated.

(4) In the fuel cell system of the above embodiment, the n residual hydrogen estimate VH _n is the residual hydrogen estimator estimated in the hydrogen supplying process of the n-th, depending when n = 1 formula (1) A fuel cell system that is calculated and is calculated by the equation (2) when n ≧ 2. _{VH n = ((P (n} ) -Pp) / P (n)) × V ... formula (1). _{VH n = VH n-1 -} (ΔP / Pav) × V ... formula (2). However, the n-th total anode pressure acquired in the n-th hydrogen supply process is defined as P (n), and the fraction of gas other than hydrogen corresponding to the first total anode pressure P (1) in the anode-side pressure information. The pressure is Pp, the anode side volume is V, the difference between the nth anode total pressure value P (n) and the (n−1) th anode total pressure value P (n−1) is ΔP, and the nth An average of the anode total pressure value P (n) and the (n−1) th anode total pressure value P (n−1) is defined as Pav.
In this way, the estimated amount of residual hydrogen can be estimated more accurately.

  The technology disclosed in this specification can be realized in various modes. For example, it can be realized in the form of a mobile body equipped with a fuel cell system, a control method of the fuel cell system, and the like.

It is explanatory drawing which shows typically the fuel cell system in 1st Embodiment of this invention. It is a flowchart which shows the flow of a hydrogen supply process. It is explanatory drawing which shows notionally the time-dependent change of a cathode potential. It is explanatory drawing which shows notionally the time-dependent change of the hydrogen partial pressure and cathode potential by the side of an anode.

A. First embodiment:
FIG. 1 is an explanatory diagram schematically showing a fuel cell system 700 according to the first embodiment of the present invention. The fuel cell system 700 includes a fuel cell 600, an FC cooling unit 500, an anode gas supply unit 200, a cathode gas supply unit 100, a load connection unit 800, and a control unit 400. The fuel cell system 700 may be mounted on a vehicle as a power source of the vehicle, or may be a stationary fuel cell system.

  The fuel cell 600 has a stack structure in which a plurality of single cells (not shown) as power generators are stacked. In this embodiment, the fuel cell 600 is a polymer electrolyte fuel cell, but other types of fuel cells may be used. A carbon material is used as a support for the electrode catalyst of the fuel cell 600. The output voltage of the fuel cell 600 is changed according to the performance of each single cell, the number of stacked single cells, and the operating conditions (temperature, humidity, etc.) of the fuel cell 600. In the present embodiment, the output voltage of the fuel cell 600 when the fuel cell 600 is generated at the operating point where the power generation efficiency is highest is about 280V.

  The fuel cell 600 is provided with a potential measuring unit 300 that measures the cathode potential of each single cell. The cathode potential measured by each potential measuring unit 300 is output to the control unit 400.

  The FC cooling unit 500 includes a refrigerant supply pipe 510, a refrigerant discharge pipe 520, a radiator 530, a bypass pipe 540, a three-way valve 545, and a refrigerant pump 570. As the refrigerant, for example, water, antifreeze water such as ethylene glycol, air, or the like is used. The refrigerant pump 570 is provided in the refrigerant supply pipe 510 and supplies the refrigerant to the fuel cell 600. The three-way valve 545 is a valve for adjusting the flow rate of the refrigerant to the radiator 530 and the bypass pipe 540. The radiator 530 is provided with a radiator fan 535.

  The anode gas supply unit 200 includes an anode gas tank 210, an anode gas supply pipe 220, an anode gas recirculation pipe 230, a main stop valve 250, a pressure regulating valve 260, a pressure measurement unit 270, an anode gas pump 280, a gas liquid A separator 290, an exhaust drain valve 295, and an exhaust drain pipe 240 are provided. In this embodiment, an example is shown in which hydrogen is used as the anode gas. The anode gas tank 210 stores high-pressure hydrogen gas, for example. The anode gas tank 210 is connected to the fuel cell 600 via the anode gas supply pipe 220. The anode gas supply pipe 220 is provided with a main stop valve 250, a pressure regulating valve 260, and a pressure measuring unit 270 in this order from the anode gas tank 210 side. The main stop valve 250 turns on and off the supply of the anode gas from the anode gas tank 210. The pressure regulating valve 260 adjusts the pressure of the anode gas supplied to the fuel cell 600. The pressure measurement unit 270 measures the pressure in the anode gas supply pipe 220. In the present embodiment, the detected value of the pressure measuring unit 270 is used as the total pressure on the anode side.

  The anode gas recirculation pipe 230 is connected to the fuel cell 600 and the anode gas supply pipe 220, and recirculates the anode exhaust gas discharged from the fuel cell 600 to the anode gas supply pipe 220. The anode gas reflux pipe 230 is provided with a gas-liquid separator 290 and an anode gas pump 280. The gas-liquid separator 290 separates liquid water from the anode exhaust gas mixed with liquid water discharged from the fuel cell 600. Impurity gas contained in the anode exhaust gas, such as nitrogen gas, is also separated together with the liquid water. The anode exhaust gas containing unused hydrogen gas is driven by the anode gas pump 280 and is returned to the anode gas supply pipe 220. The separated liquid water and nitrogen gas are discharged outside the system through the exhaust / drain valve 295 and the exhaust / drain pipe 240 connected to the gas / liquid separator 290.

  The cathode gas supply unit 100 includes a cathode gas supply pipe 101, a bypass pipe 103, a cathode gas discharge pipe 104, an air cleaner 110, an intercooler 120, a flow dividing valve 130, a pressure regulating valve 140, a silencer 150, an air compressor. 160. The cathode gas supply unit 100 takes air (cathode gas) into the system by the air compressor 160 and supplies it to the fuel cell 600, and then discharges unused air (cathode exhaust gas) to the outside of the system.

  The cathode gas supply pipe 101 takes in air from the outside and supplies it to the fuel cell 600 as cathode gas. The cathode gas supply pipe 101 includes an air cleaner 110, an atmospheric pressure sensor 350, an outside air temperature sensor 360, an air flow meter 370, an air compressor 160, an intercooler 120, a shunt valve 130, a supply gas temperature sensor 380, A supply gas pressure sensor 390 is provided. The air cleaner 110 takes in the cathode gas from the upstream side, removes dust from the cathode gas, and sends it out to the downstream side. The atmospheric pressure sensor 350 measures the atmospheric pressure. The outside air temperature sensor 360 measures the temperature of the cathode gas before being taken in. The air flow meter 370 measures the amount of cathode gas taken into the cathode gas supply pipe 101 from the outside. The air compressor 160 compresses the cathode gas supplied from the upstream side and sends it to the downstream side. The intercooler 120 is compressed by the air compressor 160 and cools the cathode gas whose temperature has increased. The cooled cathode gas is supplied to the fuel cell 600. The supply gas temperature sensor 380 measures the temperature of the cathode gas supplied to the fuel cell 600. Supply gas pressure sensor 390 measures the pressure of the cathode gas supplied to fuel cell 600. The diversion valve 130 is connected to the bypass pipe 103 and diverts the cathode gas to the fuel cell 600 and the bypass pipe 103.

  The cathode gas discharge pipe 104 receives the cathode exhaust gas from the fuel cell 600 and discharges it to the outside. A pressure regulating valve 140 is provided in the cathode gas discharge pipe 104. A downstream portion of the bypass pipe 103 is connected to the cathode gas discharge pipe 104 on the downstream side of the pressure regulating valve 140. The pressure regulating valve 140 adjusts the pressure of the cathode gas in the fuel cell 600. A downstream portion of the exhaust drainage pipe 240 of the anode gas supply unit 200 is connected to the downstream side of the cathode gas discharge pipe 104. A silencer 150 is provided in the vicinity of the outlet of the cathode gas discharge pipe 104. The silencer 150 reduces the exhaust noise of the cathode exhaust gas.

  The load connection unit 800 is a device that can switch the connection between the fuel cell 600 and the electrical load 2000 outside the fuel cell system 700. The load connection unit 800 connects the fuel cell 600 and the electrical load 2000 during power generation. The electrical load 2000 includes, for example, a secondary battery, a power consuming device (such as a motor), and the like.

  The control unit 400 is configured as a logic circuit centered on a microcomputer. Specifically, a CPU that executes predetermined calculations according to a preset control program, a ROM that stores control programs and control data necessary for executing various calculation processes by the CPU, and various types of CPUs. It includes a RAM in which various data necessary for arithmetic processing are temporarily read and written, an input / output port for inputting / outputting various signals, and the like. The control unit 400 acquires measurement signals from the pressure measurement unit 270 and the potential measurement unit 300, information related to a load request for the fuel cell 600, and the like. Further, the fuel cell system 700 is related to power generation of the fuel cell 600 such as the main stop valve 250, the pressure regulating valve 260, the exhaust / drain valve 295, the diversion valve 130, the pressure regulating valve 140, the air compressor 160, the anode gas pump 280, etc. A drive signal is output to each part. In addition, the control unit 400 performs a hydrogen supply process (described later) for suppressing the occurrence of an abnormal potential in the fuel cell 600.

  FIG. 2 is a flowchart showing the flow of the hydrogen supply process. Steps S104 to S122 shown in FIG. 2 are referred to as “hydrogen supply processing”. That is, FIG. 2 illustrates the stop process performed before the hydrogen supply process. In the present embodiment, for example, the fuel cell system 700 includes a power switch (not shown) as an operator for instructing the user to start and stop the fuel cell system 700. The fuel cell system 700 is configured such that when the power switch is pressed by the user during startup of the fuel cell system 700, the fuel cell system 700 stops. When the power switch is pressed during startup of the fuel cell system 700, the control unit 400 starts the processing shown in FIG.

In step S102, the control unit 400 (see FIG. 1) performs a stop process.
FIG. 3 is an explanatory diagram conceptually showing changes with time in the cathode potential. In the stop process in the present embodiment, the control unit 400 stops the air compressor 160 (see FIG. 1) and stops the supply of the cathode gas (see FIG. 3). Further, the control unit 400 connects the cathode gas supply pipe 101 and the bypass pipe 103 with the diversion valve 130, closes the pressure regulating valve 140 (see FIG. 1), and seals the cathode flow path of the fuel cell 600 (see FIG. 1). (See FIG. 3). Then, after supplying the second supply amount of hydrogen from the anode gas tank 210, the main stop valve 250, the pressure regulating valve 260, and the exhaust / drain valve 295 are closed (see FIG. 1) to seal the anode flow path. (See FIG. 3). In the present embodiment, the second supply amount is made the same as a threshold value TH described later. Thereafter, the control unit 400 controls the load connecting unit 800 to disconnect the electrical load 2000 (see FIG. 1) from the fuel cell 600 (see FIG. 3). In addition, the control unit 400 acquires the cathode potential E ₀ when the electrical load 2000 is disconnected in the stop process. The cathode potential is the sum of the output voltages of all potential measuring units 300. In the following description, the time when the electrical load 2000 is disconnected from the fuel cell 600 is also referred to as “when the stop process is completed”.

  As shown in FIG. 3, while the control unit 400 is performing a stop process (see step S102 in FIG. 2), the cathode potential gradually decreases and becomes 0 V when the electrical load 2000 is disconnected. As described above, when the stop process is started, the supply of the cathode gas is stopped and the cathode flow path is sealed. On the other hand, after the second supply amount of hydrogen is supplied, the anode flow path is sealed. Therefore, power generation by the fuel cell 600 is performed using oxygen in the sealed cathode gas flow path, supplied hydrogen, and the like. As a result, oxygen remaining on the cathode side of the fuel cell 600 is consumed.

In step S104 (see FIG. 2), the control unit 400 sets n = 1. In step S106, the control unit 400 estimates the remaining amount of hydrogen VH _n of the anode side of the fuel cell 600. The remaining amount of hydrogen VH _n of the present embodiment, also referred to as "residual hydrogen estimator". A method for calculating the residual hydrogen quantity VH _n, described later. After the time T has elapsed from the previous processing of S106 when the processing of S106 is executed after completion of the above-described stop processing (step S102) or through the processing of S118 described later, the control unit 400 Start the hydrogen supply process. For example, the time T may be set to 24 hours.

In step S108, the control unit 400 acquires the cathode potential _{E n.} When [Cathode Potential E _n ]> [Cathode Potential E _n−1 ] (Yes in Step S112), the control unit 400 performs correction so that the residual hydrogen amount VH _n = 0 (Step S114). When [cathode potential E _n ] ≦ [cathode potential E _n−1 ] (No in step S112), control unit 400 does not perform the correction in step S114. “Cathode potential E _n > cathode potential E _n−1 ” in the present embodiment is also referred to as “correction condition”. That is, the cathode potential E _n obtained in the hydrogen supplying process of n-th time, when the correction condition is satisfied, the control unit 400, before the supply of hydrogen in the n-th hydrogen supplying process, subtracting the remaining amount of hydrogen VH _n Is corrected to zero.

In step S116, when [residual hydrogen amount VH _n ] ≦ [threshold TH] (Yes in step S116), the control unit 400 controls the main stop valve 250 and the pressure regulating valve 260 (see FIG. 1), and the first A supply amount of hydrogen is supplied (step S118). In the present embodiment, the difference between the threshold TH and the residual hydrogen quantity VH _n, is set to the first supply amount. When [residual hydrogen amount VH _n ]> [threshold TH] (No in step S116), control unit 400 does not supply anode gas supply unit 200 with hydrogen.

  In the present embodiment, the amount of hydrogen that needs to remain in the fuel cell 600 is experimentally determined in advance in order not to generate an abnormal potential for three days after the fuel cell 600 stops generating power. Is set as the threshold value TH. Specifically, using the fuel cell 600, hydrogen is not supplied in the stop process (that is, the cathode gas supply stop and the hydrogen supply stop are simultaneously performed), and immediately after the stop process is completed, a predetermined supply amount of hydrogen is supplied. A long-term storage experiment was conducted in which the sample was left after being supplied. A long-term leaving experiment was performed by changing the supply amount, and the minimum supply amount among the supply amounts in which no abnormal potential occurred for 3 days was set as the threshold value TH. In the present embodiment, assuming a startup pattern in which the fuel cell system 700 is stopped on Friday night, the fuel cell system 700 is not started on Saturday and Sunday, and the fuel cell system 700 is started on Monday morning, three days are assumed. The supply amount of hydrogen is determined so that no abnormal potential is generated.

  “Abnormal potential” refers to an electrode potential that is increased to a level at which the cathode potential increases under normal power generation conditions and the deterioration of the cathode (that is, carbon corrosion) proceeds. One of the causes of the abnormal potential is considered to be local hydrogen deficiency at the anode of the fuel cell.

In step S114, when the control unit 400 corrects the residual hydrogen amount VH _n = 0, the residual hydrogen amount VH _n ≦ threshold TH, so in step S118, the control unit 400 controls the anode gas supply unit 200. Hydrogen is supplied. Since the first supply amount is the difference between the threshold value TH and the residual hydrogen amount VH _n , when the correction is made so that the residual hydrogen amount VH _n = 0, the first supply amount becomes equal to the threshold value TH, and the threshold value TH An amount of hydrogen equal to is supplied.

  When two weeks have passed since the above power switch was pressed (Yes in step S120), the control unit 400 ends the hydrogen supply process. If two weeks have not elapsed since the power switch was pressed (No in step S120), control unit 400 increments n and returns to the process in step S106. That is, the control unit 400 repeatedly performs steps S106 to S122 (that is, hydrogen supply processing) until two weeks elapse after the power switch is pressed. In the present embodiment, the hydrogen supply process is repeated at time T, that is, with an interval of 24 hours.

First hydrogen supply process (ie, n = 1) In the case the cathode potential _{E 0} greater than that obtained in the obtained cathode potential _{E 1} is stopped (step S102) In step S108, the remaining amount of hydrogen VH _n Is corrected. On the other hand, the second and subsequent hydrogen supplying process (i.e., n ≧ 2) In, the cathode potential E _n obtained in step S108, is obtained in the last of the hydrogen supply process (i.e., n-1-th hydrogen supply process) and when the cathode potential is greater than _{E n-1,} the correction of the residual hydrogen quantity VH _n is performed.

  When the start instruction of the fuel cell system 700 is input, the control unit 400 ends the hydrogen supply process (see S104 to S122 in FIG. 2). For example, when the fuel cell system 700 is mounted on a vehicle, a start instruction for the fuel cell system 700 is input when the user presses a power switch while depressing a brake pedal. That is, even before two weeks have elapsed, when an instruction to start the fuel cell system 700 is input, the control unit 400 ends the hydrogen supply process (see S104 to S122 in FIG. 2). Therefore, if one day has elapsed since the completion of the stop process and an activation instruction is input to the fuel cell system 700 before two days have elapsed, the hydrogen supply process is completed only once. Further, if a start instruction is input to the fuel cell system 700 before one day has elapsed since the completion of the stop process, the hydrogen supply process is not performed.

  FIG. 4 is an explanatory diagram conceptually showing temporal changes in the hydrogen partial pressure on the anode side and the cathode potential. The consumption of oxygen on the anode side of the fuel cell system 700 when the hydrogen supply process in the present embodiment is performed will be described with reference to FIG. FIG. 4 shows the change in the cathode potential with time in the lower stage, and shows the hydrogen partial pressure on the anode side in association with the lower time axis in the upper stage. In FIG. 4, the timing at which the n-th hydrogen supply process (n is a natural number of 1 or more) is performed is indicated as <n> on the lower time axis. Here, the anode side is the portion downstream of the pressure regulating valve 260 of the anode gas supply pipe 220 (see FIG. 1), the anode gas flow path in the fuel cell 600, the anode gas recirculation pipe 230, and the exhaust gas from the exhaust drain pipe 240. It consists of the upstream part of the drain valve 295. In FIG. 1, the anode side is shown with hatching. The cathode side includes a downstream portion from the diversion valve 130 of the cathode gas supply pipe 101, a cathode gas flow path in the fuel cell 600, and an upstream portion from the pressure regulating valve 140 of the cathode gas discharge pipe 104.

In the example shown in FIG. 4, when the stop process is completed, oxygen remains on the cathode side and hydrogen remains on the anode side. Since the electrical load 2000 is disconnected after the stop process is completed, oxygen is consumed by the movement of hydrogen and oxygen in the fuel cell 600 through the electrolyte membrane (so-called crossover). Possible causes of the decrease in hydrogen on the anode side include reaction with oxygen remaining on the cathode side and reaction with oxygen that has entered the fuel cell 600 from the outside. Since hydrogen on the anode side is used for oxygen consumption, the hydrogen partial pressure on the anode side decreases as shown in the upper part of FIG. After time T has elapsed from the completion of the stop process, the first hydrogen supply process is performed (see <1> in the lower left of FIG. 4). In the example shown in FIG. 4, in the first hydrogen supply process, the remaining hydrogen amount VH ₁ is larger than the threshold value TH (S116: No in FIG. 2), so hydrogen is not supplied. Thereafter, when the anode-side hydrogen is further used for oxygen consumption and the anode-side hydrogen is depleted, the cathode potential starts to rise (see the lower part of FIG. 4). In the second hydrogen supply process in <2> in the lower left of FIG. 4, since the cathode potential E ₂ is larger than the cathode potential E ₁ (Yes in S112 in FIG. 2), the residual hydrogen amount VH ₂ = 0 is corrected. (See S114 in FIG. 2), the same amount of hydrogen as the threshold TH is supplied (see (1) in the upper part of FIG. 4). Similarly, the hydrogen supply process is repeatedly performed until an instruction to stop the fuel cell system 700 is input by the user or until two weeks elapse after the power switch is pressed. For example, in the fifth of the hydrogen supply process in <5> in FIG. 4 the lower right, since cathode potential E ₅ is equal to the cathode potential E _4, correction of the residual hydrogen quantity VH ₅ is not performed, the remaining amount of hydrogen VH ₅ threshold Since it is larger than TH (No in step S116 in FIG. 2), hydrogen is not supplied. In the sixth hydrogen supply process at <6> in the lower right of FIG. 4, the cathode potential E ₆ is equal to the cathode potential E ₅ (see the lower part of FIG. 4, No in S112 of FIG. 2), so the remaining hydrogen amount VH ₆ is corrected. Is not performed, and the remaining hydrogen amount VH ₆ is smaller than the threshold value TH (see the upper part of FIG. 4; Yes in step S116 in FIG. 2), the first supply amount (threshold value TH−residual hydrogen amount VH ₆ ) of hydrogen is supplied. (See S118 in FIG. 2).

In the present embodiment, the control unit 400 calculates the residual hydrogen amount VH _n using the following equations (1) and (2) (see S106 in FIG. 2). Equation (1) it is used to estimate the residual hydrogen amount VH _n during the first hydrogen supply process. Equation (2) is used to estimate the residual hydrogen amount VH _n in the second and subsequent hydrogen supply process.
(1) First hydrogen supply process (n = 1):
Residual hydrogen amount VH _n = ((P (n) −Pp) / P (n)) × V (1)
However, the n-th anode total pressure acquired in the n-th hydrogen supply process is P (n), and the partial pressure of gas other than hydrogen on the anode side corresponding to the first anode total pressure P (1) is Pp. Let V be the volume on the anode side.
The first remaining hydrogen amount VH ₁ is estimated using the ratio of the anode total pressure to the hydrogen partial pressure. In the above formula (1), the hydrogen partial pressure is calculated using the partial pressure Pp of a gas other than hydrogen existing on the anode side. Gases other than hydrogen present on the anode side are nitrogen, water vapor, oxygen, and the like. This is because nitrogen and oxygen on the cathode side pass through the electrolyte membrane and move to the anode side.
(I) The volume V on the anode side is, as described above, the portion downstream of the pressure regulating valve 260 of the anode gas supply pipe 220 (see FIG. 1), the anode gas flow path in the fuel cell 600, the anode gas recirculation pipe 230, The volume of the exhaust drain pipe 240 and the upstream portion of the exhaust drain valve 295 is a fixed value.
(Ii) The first anode total pressure is a value measured by the pressure measuring unit 270 (see FIG. 1) acquired in the first hydrogen supply process.
(Iii) The partial pressure Pp of a gas other than hydrogen is a value uniquely determined with respect to the first anode total pressure. Specifically, when performing the above-mentioned experiment, the relationship between the total anode pressure and the partial pressure of a gas other than hydrogen is examined, and the result is stored in the control unit 400 as anode-side pressure information. The controller 400 derives the partial pressure Pp of the gas other than hydrogen corresponding to the first anode total pressure using the anode side pressure information. The gas in the anode gas supply pipe 220 is analyzed using a gas analyzer, and the partial pressure Pp of a gas other than hydrogen can be calculated from the volume ratio. The reason why the partial pressure Pp of a gas other than hydrogen is used is easier than using the hydrogen partial pressure.
(2) Second and subsequent hydrogen supply processes (n ≧ 2):
Residual hydrogen amount VH _n = VH _n−1 − (ΔP / Pav) × V (2)
However, the difference between the nth anode total pressure value P (n) and the (n−1) th anode total pressure value P (n−1) is ΔP, and the nth anode total pressure value P (n) and the (nth) -1) An average with the total anode pressure value P (n-1) is Pav.
When n ≧ 2, a value obtained by subtracting the consumed hydrogen amount from the previous remaining hydrogen amount VH _{n−1 is} set as the remaining hydrogen amount VH _n . The consumed hydrogen amount is expressed as the nth anode total pressure value P (n) with respect to the average Pav between the nth anode total pressure value P (n) and the (n-1) th anode total pressure value P (n-1). And the ratio of the difference ΔP between the (n−1) th anode total pressure value P (n−1).
The remaining hydrogen amount VH _n in the present embodiment is also referred to as an “nth hydrogen estimated amount VH _n ”.

As described above, in the fuel cell system 700 of the present embodiment, the estimated remaining amount of hydrogen VH _n of the anode side. Since the remaining amount of hydrogen VH _n is an estimate and may be larger amount calculated than the actual remaining amount of hydrogen. When the remaining amount of hydrogen VH _n is the actual larger amount of calculation than the remaining amount of hydrogen and no correction processing as in this embodiment, the hydrogen supply process, or if hydrogen is not supplied, hydrogen is supplied Even so, the supply amount may be insufficient. In this embodiment, the hydrogen supply process, with respect to the cathode potential which is acquired at the last of the hydrogen supplying process, when the cathode potential is rising in the current hydrogen supply process, the remaining amount of hydrogen VH _n 0 (See S114 in FIG. 2). Therefore, when an increase in the cathode potential is detected, the same amount of hydrogen as the threshold value TH is supplied (see S118 in FIG. 2). Since the increase in the cathode potential is highly likely due to the lack of hydrogen on the anode side, the increase in the cathode potential is eliminated by supplying hydrogen. As a result, it is possible to suppress the occurrence of an abnormal potential on the cathode and to suppress the deterioration of the cathode.

Further, in the fuel cell system 700 of the present embodiment, when the remaining hydrogen amount VH _n becomes smaller than the threshold value TH, the first supply amount of hydrogen is supplied (see S118 in FIG. 2). The first supply amount, which stipulates that a difference between the threshold TH and the residual hydrogen quantity VH _n, the threshold value TH, provide that the amount of hydrogen required for the abnormal potential 3 days is not generated. Therefore, hydrogen necessary to prevent an abnormal potential from being generated for 3 days is supplied at an appropriate timing. For example, in the stop process, in the case of a fuel cell system in which an amount of hydrogen necessary to prevent an abnormal potential from being generated for two weeks is supplied in advance and then no hydrogen is supplied, the following process can be performed. That is, when the fuel cell system 700 is started three days after the stop of the fuel cell system, which is significantly shorter than two weeks, a lot of hydrogen remains on the anode side, and the residual hydrogen is discharged. . Compared to such a fuel cell system, the fuel cell system of this embodiment can suppress excessive supply of hydrogen and contribute to an improvement in fuel consumption.

  In the present embodiment, the second supply amount of hydrogen is supplied in the stop process. Therefore, the generation of abnormal potential after the fuel cell system 700 is stopped can be delayed as compared with the case where hydrogen is not supplied in the stop process. Moreover, since the 2nd supply amount is below a threshold value, the deterioration of the fuel consumption by excessive supply of hydrogen can be suppressed, consuming oxygen.

B. Other embodiments:
(1) In the above embodiment, an example in which the second supply amount of hydrogen is supplied in the stop process has been described (see S102 in FIG. 2). However, it is not necessary to supply hydrogen in the stop process. The second supply amount may be a constant amount. Furthermore, the second supply amount is not limited to the same value as the threshold value TH illustrated in the above embodiment, but depends on the timing of performing the first hydrogen supply process, the total anode pressure during the stop process of the fuel cell system 700, and the like. Accordingly, it can be set as appropriate.

(2) The threshold value TH (see S116 in FIG. 2) and time T (see S106 in FIG. 2) are not limited to the above embodiment, and can be set as appropriate. The threshold value TH may be set to, for example, the amount of hydrogen necessary for preventing an abnormal potential from being generated every day. In this case, it is preferable to set the time T to be shorter than one day such as 12 hours or 6 hours.

  As the time T, which is the interval at which the hydrogen supply process (see S104 to S122 in FIG. 2) is performed, a time experimentally obtained in advance can be determined. The interval time T (see S106 in FIG. 2) during which the hydrogen supply process is performed does not affect the endurance requirements of the stack even if the cathode potential is increased during that time (more specifically, deterioration of the electrode) Is set to the time).

  For example, using the fuel cell 600, an experiment is performed in which hydrogen is not supplied in the stop process (that is, the cathode gas supply is stopped and the hydrogen supply is stopped simultaneously), and the fuel cell 600 is left for a plurality of different times. Then, the time T can be determined based on the maximum leaving time among the leaving times in which the electrode has not deteriorated due to the increase in the cathode potential. By determining the time T in this way, the amount of power consumed by the control unit for executing the hydrogen supply process can be reduced.

(3) The time until the first hydrogen supply process is performed in step S106 after the completion of the stop process in step S102 in FIG. 2, and the interval between the multiple hydrogen supply processes performed in step S106 after the process in step S118. And may be set at different times. For example, when hydrogen is not supplied in the stop process, the time from the completion of the stop process until the first hydrogen supply process may be set shorter than the interval between the multiple hydrogen supply processes.

(4) a method of estimating the remaining amount of hydrogen VH _n the formula exemplified in the above embodiment (1), but is not limited to the method by the equation (2). For example, when n ≧ 2, it may be calculated using the hydrogen partial pressure on the anode side as in n = 1. Further, the hydrogen partial pressure on the anode side may be obtained from the ratio of hydrogen obtained using a gas analyzer. Further, when n = 1, the (n−1) th hydrogen supply process in Equation (2) may be replaced with a stop process.
In the above embodiment, the correction condition for determining whether or not to perform the correction for reducing the estimated residual hydrogen amount is that the cathode potential is larger than the cathode potential acquired in the immediately preceding hydrogen supply process, or in the stop process. The cathode potential is greater than the acquired cathode potential (see S108 and S112 in FIG. 2). However, the correction condition for determining whether or not to perform correction to reduce the estimated residual hydrogen amount is not limited to this. For example, the correction condition may be that the acquired cathode potential is larger than the cathode potential before a certain time. In this case, the certain time is preferably shorter than the cycle time T of the hydrogen supply process.

(5) method for correcting residual hydrogen amount VH _n is not limited to the method of S114 of FIG. 2 illustrated in the above embodiment. For example, as the difference between the cathode potential in the current hydrogen supply process and the previous hydrogen feed processing (see S108 in FIG. 2) is large, it may be reduced more residual hydrogen amount VH _n. Further, it may be corrected from the remaining amount of hydrogen VH _n by subtracting a certain amount, it may be corrected by subtracting a constant rate with respect to the remaining amount of hydrogen VH _n. Even if it does in this way, generation | occurrence | production of abnormal potential can be suppressed rather than the case where it does not correct | amend.

(6) In the above embodiment, the first supply amount, an example of the difference between the threshold TH and the residual hydrogen quantity VH _n (see S118 in FIG. 2). However, the first supply amount is not limited to this. For example, the first supply amount can be a constant amount. However, the first supply amount is preferably determined according to the difference between the threshold TH and the residual hydrogen quantity VH _n. For example, the difference between the threshold TH and the residual hydrogen quantity VH _n, determined in advance the relationship between the first supply amount, also be a mode comprising a first feed amount information indicating the relationship controller 400. In such an aspect, the control unit 400 may determine the first supply amount using the first supply amount information. In this case, as the first supply amount, for example, the difference between the threshold TH and the residual hydrogen quantity VH _n, may be employed a value obtained by adding a certain amount, the difference between the threshold TH and the residual hydrogen quantity VH _n A value multiplied by a coefficient may be adopted. However, the first supply amount is preferably an amount equal to or less than a predetermined amount. The predetermined amount can be, for example, an amount of anode gas that does not generate an abnormal potential for 3 days with the anode and cathode sealed.

  The present disclosure technique is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 100 ... Cathode gas supply part 101 ... Cathode gas supply pipe 103 ... Bypass pipe 104 ... Cathode gas discharge pipe 110 ... Air cleaner 120 ... Intercooler 130 ... Shunt valve 140 ... Pressure regulating valve 150 ... Silencer 160 ... Air compressor 200 ... Anode gas supply part 210 DESCRIPTION OF SYMBOLS ... Anode gas tank 220 ... Anode gas supply pipe 230 ... Anode gas recirculation pipe 240 ... Exhaust drain pipe 250 ... Main stop valve 260 ... Pressure regulating valve 270 ... Pressure measuring part 280 ... Anode gas pump 290 ... Gas-liquid separator 295 ... Exhaust drain valve 300 DESCRIPTION OF SYMBOLS ... Potential measurement part 350 ... Atmospheric pressure sensor 360 ... Outside air temperature sensor 370 ... Air flow meter 380 ... Supply gas temperature sensor 390 ... Supply gas pressure sensor 400 ... Control part 500 ... FC cooling part 510 ... Refrigerant supply pipe 520 ... Refrigerant discharge pipe 5 DESCRIPTION OF SYMBOLS 30 ... Radiator 535 ... Radiator fan 540 ... Bypass pipe 545 ... Three-way valve 570 ... Refrigerant pump 600 ... Fuel cell 700 ... Fuel cell system 800 ... Load connection part 2000 ... Electric load

Claims (6)

A fuel cell; an anode gas supply unit that supplies hydrogen as an anode gas to the fuel cell; a cathode gas supply unit that supplies a cathode gas to the fuel cell; a control unit that controls the operation of the fuel cell; A potential measuring unit for measuring a cathode potential of the fuel cell, and a fuel cell system comprising:
The control unit, after performing a stop process to stop the power generation of the fuel cell,
A hydrogen supply process,
Determining an estimated amount of residual hydrogen that is an estimated amount of hydrogen remaining on the anode side of the fuel cell;
Performing a correction to reduce the residual hydrogen estimated amount when a correction condition indicating that the cathode potential has increased is satisfied;
When the estimated amount of residual hydrogen is smaller than a threshold, supplying a predetermined amount or less of hydrogen to the anode gas supply unit;
A fuel cell system that repeatedly executes a hydrogen supply process. The fuel cell system according to claim 1,
The fuel cell system, wherein the amount of hydrogen supplied when the estimated residual hydrogen amount is smaller than the threshold value is determined according to a difference between the threshold value and the estimated residual hydrogen amount. The fuel cell system according to claim 1 or 2,
The correction condition is as follows:
For the residual hydrogen estimated amount initially determined after the stop process, the cathode potential is higher than the cathode potential obtained in the stop process,
The fuel cell system in which the cathode potential is higher than the cathode potential acquired in the previous hydrogen supply process for the remaining hydrogen estimated amount determined for the second and subsequent times after the stop process. The fuel cell system according to any one of claims 1 to 3,
The controller is
In the stop process,
After the supply of the cathode gas is stopped, a second supply amount of hydrogen that is equal to or less than the threshold value is supplied, and then the supply of hydrogen is stopped. The fuel cell system according to any one of claims 1 to 4, wherein
Furthermore, a pressure measuring unit that measures the total anode pressure that is the total pressure on the anode side of the fuel cell is provided,
The controller is
Anode pressure information indicating the relationship between the total anode pressure obtained experimentally in advance and the partial pressure of a gas other than hydrogen existing on the anode side,
A fuel cell system that calculates the estimated amount of residual hydrogen using the total anode pressure acquired in the hydrogen supply process and the anode side pressure information. The fuel cell system according to claim 5, wherein
The n-th remaining hydrogen estimated amount VH _n that is the remaining hydrogen estimated amount estimated in the n-th (n is an integer equal to or larger than 1) hydrogen supply process is calculated by the equation (1) when n = 1, A fuel cell system which is calculated by the equation (2) when ≧ 2.
VH _n = ((P (n) −Pp) / P (n)) × V (1)
VH _n = VH _n−1 − (ΔP / Pav) × V (2)
However, the n-th total anode pressure acquired in the n-th hydrogen supply process is defined as P (n), and the fraction of gas other than hydrogen corresponding to the first total anode pressure P (1) in the anode-side pressure information. The pressure is Pp, the anode side volume is V, the difference between the nth anode total pressure value P (n) and the (n−1) th anode total pressure value P (n−1) is ΔP, and the nth An average of the anode total pressure value P (n) and the (n−1) th anode total pressure value P (n−1) is defined as Pav.

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