JP2012123914A - Fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system having a gas supply restriction part for restricting the supply of oxidation gas to a fuel battery at the time of stop, and arranged so that the abnormal condition of the gas supply restriction part can be detected readily.SOLUTION: A fuel battery system 10 includes: a fuel battery 100; a fuel gas supply system 200; an oxidation gas supply system 300; a gas supply restriction part for restricting the supply of oxidation gas to the fuel battery 100 at the time of stopping the fuel battery 100; a voltage detector for detecting a voltage developed in the fuel battery; and an abnormal condition detector 912 which determines that an abnormal condition arises in the gas supply restriction part in the case of detecting a change such that an increase per unit time of a voltage detected by the voltage detector becomes negative with fuel gas remaining supplied to the fuel battery 100 at the time of starting the fuel battery 100.

Description

  The present invention relates to a fuel cell system.

  2. Description of the Related Art Conventionally, in a fuel cell system including a fuel cell and a gas supply system that supplies gas to the fuel cell, a gas supply system is provided to prevent the oxidizing gas from flowing into the fuel cell after the operation is stopped. There is known a fuel cell system in which a gas supply suppressing unit such as a sealing valve is provided on the above path. A technique for detecting an abnormality in the gas supply suppressing unit is also known.

JP 2010-080166 A JP 2006-209996 A

  However, in the case of the prior art, there is a problem that the cell voltage must be continuously monitored even after the operation of the fuel cell is stopped in order to detect an abnormality in the gas supply suppression unit. Further, when the oxidizing gas flows into the fuel cell after the cell voltage monitoring is finished, there is a possibility that an abnormality cannot be detected. In addition, in another conventional technique, it is necessary to add a device such as a pressure sensor to the fuel cell system in order to detect an abnormality in the gas supply suppression unit. As described above, there is still room for improvement in the technology for detecting the abnormality of the gas supply suppressing unit.

  The present invention has been made in order to solve the above problems, and in a fuel cell system including a gas supply suppression unit for suppressing supply of oxidizing gas to the fuel cell when the fuel cell is stopped. It is an object to easily detect an abnormality in a gas supply suppression unit.

  In order to solve at least a part of the above problems, the present invention can be realized as the following aspects or application examples.

[Application Example 1]
A fuel cell system,
A fuel cell;
A fuel gas supply system for supplying hydrogen as a fuel gas to the fuel cell;
An oxidizing gas supply system for supplying oxygen as an oxidizing gas to the fuel cell;
A gas supply suppressing unit for suppressing the supply of oxidizing gas to the fuel cell when the fuel cell is stopped;
A voltage detector for detecting a voltage generated in the fuel cell;
When detecting the state in which the increase amount per unit time of the voltage detected by the voltage detection unit is negative when the fuel cell is started and fuel gas is supplied to the fuel cell, An abnormality detection unit that determines that an abnormality has occurred in the gas supply suppression unit.

  According to this configuration, when a fuel gas is supplied to the fuel cell at the time of starting the fuel cell, if a state in which the increase amount per unit time of the voltage generated in the fuel cell is negative is detected, Therefore, it is possible to easily detect the abnormality of the gas supply suppressing unit.

[Application Example 2]
In the fuel cell system according to Application Example 1,
When the fuel gas is supplied to the fuel cell, the abnormality detection unit is in a state where the increase amount becomes negative until the increase amount per unit time of the voltage becomes zero for a predetermined period. A fuel cell system that, when detected, determines that an abnormality has occurred in the gas supply suppression unit.

  According to this configuration, if a state in which the increase amount per unit time of the voltage generated in the fuel cell becomes zero during a predetermined period is detected, the gas supply is suppressed. Since it is determined that an abnormality has occurred in the part, an abnormality in the gas supply suppressing part can be easily detected.

[Application Example 3]
In the fuel cell system according to Application Example 2,
The fuel cell has a configuration in which a plurality of fuel cells are stacked,
The voltage detection unit detects a cell voltage generated between the anode side and the cathode side of each fuel cell,
When the abnormality detection unit detects a state in which the amount of increase per unit time is negative at the start of the fuel cell in the cell voltage of the fuel cell, an abnormality has occurred in the gas supply suppression unit A fuel cell system that determines that

  According to this configuration, in the cell voltage of the fuel cell, when detecting a state in which the increase amount per unit time is negative at the start of the fuel cell, it is determined that an abnormality has occurred in the gas supply suppression unit. Abnormalities in the gas supply suppression unit can be easily detected.

[Application Example 4]
In the fuel cell system according to any one of Application Examples 1 to 3,
The gas supply suppression unit is a fuel cell system, which is a sealing valve disposed in the oxidizing gas supply system.

  According to this configuration, when a fuel gas is supplied to the fuel cell at the time of starting the fuel cell, a state in which the increase amount per unit time of the voltage generated in the fuel cell is negative is detected. Therefore, it is possible to easily detect the abnormality of the sealing valve.

  The present invention can be realized in various modes. For example, in addition to an abnormality detection device and a fuel cell vehicle including a fuel cell system, an abnormality determination method, a control method of the fuel cell system, and the like Can be realized.

It is explanatory drawing which shows schematic structure of the fuel cell system as 1st Example. It is a flowchart which shows the flow of a sealing valve abnormality process. It is explanatory drawing which illustrated the time change of the cell voltage when the sealing valve is not out of order. It is explanatory drawing for demonstrating the state of a fuel cell when the sealing valve has failed. It is explanatory drawing which illustrated the time change of the cell voltage when the sealing valve has failed. It is explanatory drawing which shows schematic structure of the fuel cell system as 2nd Example. It is explanatory drawing which showed the inside of the fuel cell of an anode dead end typically. It is explanatory drawing for demonstrating the electric power generation characteristic of the fuel cell of an anode dead end. It is a flowchart which shows the flow of timing control. It is explanatory drawing which illustrated the time change of the cell voltage in case hydrogen depletion does not arise in an anode. It is explanatory drawing which illustrated the time change of the cell voltage in case hydrogen deficiency has arisen in the anode.

  Next, embodiments of the present invention will be described based on examples.

A. First embodiment:
A-1. Configuration of fuel cell system:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system as a first embodiment. The fuel cell system 10 is mounted on an electric vehicle and used as a system for supplying driving power. The fuel cell system 10 includes a fuel cell 100, a fuel gas supply system 200, an oxidizing gas supply system 300, a fuel cell cooling system 400, a load device 500, a power supply switch 600, a battery 700, and a cell monitor 800. And a system controller 900.

  The fuel cell 100 has a stack structure in which a plurality of fuel cells 110 are stacked. The fuel battery cell 110 is configured to generate electricity between a fuel gas (hydrogen) supplied to an anode-side catalyst electrode layer provided with an electrolyte membrane interposed therebetween and an oxidizing gas (oxygen contained in air) supplied to a cathode-side catalyst electrode layer. Electricity is generated by chemical reaction. The fuel cell 100 can be composed of fuel cells using various electrolyte membranes such as a solid polymer electrolyte membrane. In this example, a fuel cell using a solid polymer electrolyte membrane is used. The catalyst electrode layer includes a catalyst, for example, carbon particles supporting platinum (Pt) and an electrolyte. In the fuel cell 100, two terminal plates 111 serving as total electrodes are disposed at both ends of the stacked fuel cells 110.

  The fuel gas supply system 200 includes a hydrogen tank 210, a flow rate adjustment unit 220, a humidification adjustment unit 230, a circulation compressor 240, a gas-liquid separation unit 250, and a switching valve 260. The fuel gas supply system 200 includes an anode side catalyst electrode layer (hereinafter also simply referred to as “anode”) of each fuel cell 110 constituting the fuel cell 100, a fuel gas supply channel 271 a and a flow rate adjustment from the hydrogen tank 210. Hydrogen, which is a fuel gas, is supplied through the section 220, the fuel gas supply channel 271b, the humidification adjusting unit 230, and the fuel gas supply channel 271c. At this time, the flow rate adjusting unit 220 supplies hydrogen to the anode of the fuel cell 100 at a flow rate and pressure according to instructions from the system controller 900. Further, the humidification adjusting unit 230 adjusts the humidification temperature so that the humidity of the hydrogen supplied to the anode of the fuel cell 100 is in a state in accordance with an instruction from the system controller 900. The hydrogen tank 210 can be configured using, for example, a hydrogen tank in which high-pressure hydrogen is stored and a pressure adjustment valve.

  Further, the fuel gas supply system 200 opens the switching valve 260 so that hydrogen that has not been used at the anode of the fuel cell 100 passes through the fuel gas discharge channel 271d, the gas-liquid separation unit 250, and the switching valve 260. Then, it is discharged outside the fuel cell system 10. Further, the fuel gas supply system 200 closes the switching valve 260 to remove hydrogen that has not been used at the anode of the fuel cell 100, as a fuel gas discharge channel 271d, a gas-liquid separator 250, a circulation channel 271e, and a circulation compressor 240. And it returns to the fuel gas supply flow path 271c via the circulation flow path 271f and is used again as fuel gas. The circulation compressor 240 adjusts the circulation amount and pressure of hydrogen in accordance with instructions from the system controller 900.

  The oxidizing gas supply system 300 includes an intake port 310, a compressor 320, a humidification adjusting unit 330, a sealing valve 340, and an exhaust port 390. The oxidant gas supply system 300 includes an intake port 310 and an oxidant gas supply channel 351a in the cathode side catalyst electrode layer (hereinafter also referred to as “cathode of the fuel cell 100”) of each fuel cell 110 constituting the fuel cell 100. Then, air containing oxygen, which is an oxidizing gas, is supplied via the compressor 320, the oxidizing gas supply channel 351b, the humidification adjusting unit 330, and the oxidizing gas supply channel 351c. At this time, the compressor 320 sends out the air taken in from the intake port 310 toward the humidification adjusting unit 330 at a pressure according to an instruction from the system controller 900. Further, the humidification adjustment unit 330 adjusts the humidification temperature so that the humidity of the air supplied to the cathode of the fuel cell 100 is in a state in accordance with an instruction from the system controller 900.

  In addition, the oxidizing gas supply system 300 converts the exhaust gas having a reduced concentration by the oxygen content used for the electrochemical reaction discharged from the fuel cell 100 into the oxidizing gas discharge channel 351d, the sealing valve 340, and the oxidation gas. The gas is discharged from the exhaust port 390 through the gas discharge channel 351e. The sealing valve 340 is adjusted according to an instruction from the system controller 900 to adjust its open / closed state, so that when the fuel cell system 10 is stopped, the exhaust port 390, the oxidizing gas discharge channel 351e, the sealing valve 340, and The air is suppressed from being supplied to the cathode side catalyst electrode layer through the oxidizing gas discharge channel 351d.

  The fuel cell cooling system 400 includes a radiator 410, a refrigerant temperature sensor 420, and a refrigerant circulation pump 430. The radiator 410 is connected to the fuel cell 100 via a refrigerant supply channel 441a and a refrigerant discharge channel 441b, and supplies a cooling medium to the fuel cell 100 via the refrigerant supply channel 441a. By receiving the cooling medium after being supplied from the fuel cell 100 via the path 441b, the cooling medium is circulated to cool the fuel cell 100. Water, air, or the like can be used as the cooling medium. The refrigerant temperature sensor 420 measures the cooling medium temperature after cooling that flows out of the fuel cell 100. The output of the refrigerant temperature sensor 420 is connected to the system controller 900. The system controller 900 estimates the internal temperature of the fuel cell 100 from the cooling medium temperature after cooling.

  The load device 500 is connected to the terminal plate 111 on the positive electrode side and the negative electrode side of the fuel cell 100 via the power supply changeover switch 600. The current sensor 560 is connected in series with the fuel cell 100 and measures a current value flowing through the fuel cell 100. The inverter 550 is connected in parallel with the fuel cell 100 and the battery 700, converts a direct current supplied from the fuel cell 100 or the battery 700 into an alternating current, and supplies the alternating current to the load device 500 (for example, a vehicle driving motor). .

  The battery 700 is connected in parallel with the load device 500 and the fuel cell 100 via the DC-DC converter 750. The DC-DC converter 750 boosts the output voltage of the battery 700 and supplies the boosted voltage to the inverter 550. In addition, the DC-DC converter 750 reduces the output voltage and supplies it to the battery 700 in order to store the surplus power generated by the fuel cell 100. In the fuel cell system 10 according to the present embodiment, when the power switch 600 is off (open), the battery 700 is connected to the load device 500 via the DC-DC converter 750 and the inverter 550. On the other hand, when power switch 600 is on (closed), fuel cell 100 is connected to load device 500.

  The cell monitor 800 is connected to each fuel cell 110 and measures the cell voltage (potential difference between the cathode and anode electrodes) of each fuel cell 110. The output of the cell monitor 800 is connected to the system controller 900.

  The system controller 900 includes a CPU (Central Processing Unit) 910, a ROM (Read Only Memory) 920, and a RAM (Random Access Memory) 930. The system controller 900 is electrically connected to each component of the fuel cell system 10 and controls the operation of each component based on information received from each component. In the system controller 900, a control program (not shown) for controlling the fuel cell system 10 is stored in the ROM 920. The CPU 910 functions as the control unit 911 and the abnormality detection unit 912 by executing this control program while using the RAM 930.

  In the fuel cell system 10 having the above-described configuration, the sealing valve 340 of the oxidizing gas supply system 300 is detected from the change in the cell voltage detected by the cell monitor 800 when the fuel cell 100 is started by the functions of the control unit 911 and the abnormality detection unit 912. A sealing valve abnormality determination process for determining whether or not an abnormality has occurred is executed. Details of the sealing valve abnormality determination process will be described later.

A-2. Seal valve abnormality judgment processing:
FIG. 2 is a flowchart showing the flow of the sealing valve abnormality process. When the system controller 900 detects that the ignition is turned on by the user, the system controller 900 performs various initialization processes in order to activate the fuel cell system 10 (step S100). When the initialization process is executed, the control unit 911 of the system controller 900 controls the fuel gas supply system 200 in a state in which the power supply changeover switch 600 is turned off (opened) to supply hydrogen as the fuel gas of the fuel cell 100. Supply to the anode (step S110).

  When hydrogen is supplied to the anode of the fuel cell 100, the abnormality detection unit 912 of the system controller 900 continuously acquires the cell voltage Vocv that is the open circuit voltage of each fuel cell 110 from the cell monitor 800, The voltage change per unit time (dVocv / dt) of the cell voltage Vocv is calculated. In the present embodiment, the following determination processing is performed for each of the cell voltages Voc acquired from each fuel cell 110, but only the cell voltages Voc acquired from some of the fuel cells 110 are used as follows. A determination process may be performed.

  The abnormality detection unit 912 determines whether the voltage change of the cell voltage Vocv changes from positive (dVovv / dt> 0) to negative (dVocv / dt <0) in a predetermined period after hydrogen is supplied to the fuel cell 100. It is determined whether or not (step S120). Specifically, the abnormality detection unit 912 starts to increase the cell voltage Vocv when hydrogen is supplied to the fuel cell 100, and then stabilizes in the vicinity of 1 (V) (for example, 0.8 to 1 V). Until the cell voltage Vocv changes from positive to negative. Therefore, the predetermined period refers to an arbitrary period including a period from when hydrogen is supplied to the fuel cell 100 until the cell voltage Vocv becomes stable in the vicinity of 1 (V).

  As a method for determining whether or not the cell voltage Vocv is stable in the vicinity of 1 (V), various methods can be implemented. For example, the abnormality detection unit 912 continues for a predetermined time (for example, 3 seconds), and the cell voltage Vocv becomes stable when the voltage change of the cell voltage Vocv is 0 (dVovv / dt = 0). The cell voltage Vocv is stable when the cell voltage Vocv is continuously within a predetermined range (Th1 ≦ Vov ≦ Th2, Th1 ≦ 1 (V) ≦ Th2). It may be determined that the state has been reached. Further, if the period until the cell voltage Vocv is stabilized is included, the period after stabilization may be included. For example, until just before the power supply switch 600 is switched on (closed), It is good also as a structure which continues determination of whether the voltage change of the cell voltage Vocv changes from positive to negative.

  If the abnormality detection unit 912 does not detect a state in which the voltage change of the cell voltage Vocv changes from positive to negative during the predetermined period (step S120: NO), the sealing valve 340 has not failed. (Step S130). On the other hand, when the abnormality detection unit 912 detects a state in which the voltage change of the cell voltage Vocv changes from positive to negative during the predetermined period (step S120: YES), the sealing valve 340 has failed. (Step S140). The reason why it is possible to determine whether or not the sealing valve 340 has failed by detecting whether or not the state in which the voltage change of the cell voltage Vocv changes from positive to negative during a predetermined period will be described later. If failure determination of the sealing valve 340 is performed by the abnormality detection unit 912, the sealing valve abnormality determination processing ends. The fuel cell system 10 may be configured to perform control corresponding to the result of the sealing valve abnormality determination process after the sealing valve abnormality determination process ends. For example, when it is determined that the sealing valve 340 has failed, the fuel cell system 10 may display a failure message to the user.

  Here, the reason why it is possible to determine whether or not the sealing valve 340 has failed depending on whether or not a state in which the voltage change of the cell voltage Vocv changes from positive to negative is specifically described with reference to FIGS. Explained. FIG. 3 is an explanatory diagram illustrating the time change of the cell voltage when the sealing valve is not malfunctioning. FIG. 4 is an explanatory diagram for explaining the state of the fuel cell when the sealing valve is malfunctioning. FIG. 5 is an explanatory diagram illustrating the time change of the cell voltage when the sealing valve has failed. 3 and 5, the horizontal axis indicates time T (sec), and the vertical axis indicates the cell voltage Vocv (V).

When normal, the sealing valve 340 is closed when the fuel cell system 10 is stopped according to an instruction from the system controller 900. Therefore, when the fuel cell system 10 is stopped, the inflow of air to the cathode is suppressed through the exhaust port 390, the oxidizing gas discharge channel 351e, the sealing valve 340, and the oxidizing gas discharge channel 351d. Thereby, the movement of oxygen from the cathode side to the anode side through the electrolyte membrane is also suppressed. In this state, the sealing valve abnormality determination process is started, in step S110, the hydrogen to the anode is supplied, as shown in FIG. 3, increase in the cell voltage begins (time T ₀ through T _1), hydrogen When the potential difference between the anode and the cathode caused by the supply of (approximately 1V) is reached (time T ₁ ), the cell voltage is stabilized (time T _1- ). During this time, the voltage change (dVocv / dt) of the cell voltage gradually changes from positive (dVocv / dt> 0) to 0 (dVocv / dt = 0), but does not become negative (dVocv / dt <0).

  On the other hand, when the sealing valve 340 is out of order, when the fuel cell system 10 is stopped, the sealing valve 340 does not close in accordance with an instruction from the system controller 900, so that the valve is opened. Therefore, when the fuel cell system 10 is stopped, air flows into the cathode through the exhaust port 390, the oxidizing gas discharge channel 351e, the sealing valve 340, and the oxidizing gas discharge channel 351d. Since some of the oxygen in the air flowing into the cathode moves from the cathode side to the anode side through the electrolyte membrane, the fuel cell 100 is deficient in hydrogen on the anode side. At this time, as shown in FIG. 4, in the anode, the reaction of the following formula (1) occurs due to the hydrogen inside the anode, and the reaction of the formula (2) occurs due to the oxygen moved from the cathode side to the anode side. An internal circuit for transferring electrons is formed by the reaction of (1) and formula (2).

  On the other hand, in the cathode, in addition to the reaction of the formula (3) caused by oxygen inside the cathode, the reaction of the formula (4) is caused by the oxidation (degradation) of carbon in the catalyst layer, and an internal circuit is formed in the same manner. Further, the potential of the cathode rises to nearly 1.5 (V) by the reaction of the formula (4).

In this state, the sealing valve abnormality determination process is started, in step S110, the hydrogen to the anode is supplied, as shown in FIG. 5, the increase in the cell voltage begins (time T ₀ through T _1), the cell The voltage rises to a point exceeding 1 (V) (time T ₁ ). Thereafter, since the reactions of the above formulas (2) and (4) decrease, the cell voltage gradually decreases (time T _{1 to} T ₂ ) and settles to a normal value (about 1 V) (time T _2). ). The voltage change (dVocv / dt) of the cell voltage at this time is positive (dVocv / dt> 0) during the time T _{0 to} T ₁ and negative (dVocv / dt <0) during the time T _{1 to} T _2. ), and the time T ₂ after 0 (dVocv / dt = 0) . That is, the cell voltage at the time when the sealing valve 340 has failed is a predetermined period, that is, until the cell voltage becomes stable in the vicinity of 1 (V) (time T _{0 to} T ₂ ). The voltage change (dVocv / dt) becomes negative (dVocv / dt <0).

  Therefore, if the fuel cell system 10 does not detect a state in which the voltage change (dVocv / dt) of the cell voltage changes from positive to negative during a predetermined period after supplying hydrogen to the fuel cell 100, the fuel cell system 10 By determining that the stop valve 340 has not failed and detecting a state in which the cell voltage change (dVocv / dt) changes from positive to negative, by determining that the sealing valve 340 has failed The abnormality of the sealing valve 340 can be easily detected.

  According to the fuel cell system 10 of the present embodiment described above, when hydrogen is supplied to the fuel cell 100 when the fuel cell 100 is started, the voltage change (dVovv / dt) of the cell voltage is negative (dVocv). When a state where / dt <0) is detected, it is determined that an abnormality has occurred in the sealing valve 340, so that the abnormality of the sealing valve 340 can be easily detected.

  Specifically, when the sealing valve 340 is out of order, when the fuel cell system 10 is stopped, the sealing valve 340 does not close in accordance with an instruction from the system controller 900, so that the valve is opened. Therefore, when the fuel cell system 10 is stopped, air flows from the exhaust port 390 to the cathode. When oxygen in the air flowing into the cathode moves to the anode side, a hydrogen deficient state occurs on the anode side. At this time, the reaction of the above formulas (1) and (2) occurs at the anode. On the other hand, in the cathode, the reactions of the above formulas (3) and (4) occur, and the cathode potential rises to near 1.5V. In this state, when hydrogen is supplied to the anode, the cell voltage rises to a point exceeding 1 (V). Thereafter, the cell voltage gradually decreases and settles to a normal value (about 1 V). That is, the cell voltage when the sealing valve 340 is broken becomes negative (dVovv / dt <0) until the cell voltage becomes stable near 1 (V).

  On the other hand, when the sealing valve 340 is normal, the sealing valve 340 is closed when the fuel cell system 10 is stopped. Therefore, when the fuel cell system 10 is stopped, the inflow of air from the sealing valve 340 to the cathode is suppressed. Therefore, the movement of oxygen from the cathode side to the anode side is also suppressed. In this state, when hydrogen is supplied to the anode, the cell voltage rises to about 1 (V) and then stabilizes. That is, during this time, the voltage change of the cell voltage when the sealing valve 340 is normal does not become negative (dVocv / dt <0). Therefore, the failure of the sealing valve 340 can be easily detected by detecting the difference in voltage change of the cell voltage.

  Conventionally, various techniques for detecting an abnormality in a gas supply suppressing unit including the sealing valve 340 and the like are known. However, even if these techniques are used, for example, in order to detect an abnormality in the gas supply suppression unit, it is necessary to continue monitoring the cell voltage even after the operation of the fuel cell is stopped. There is a problem that it is necessary to continue to supply power from, for example, or that abnormality cannot be detected when air flows into the cathode after monitoring is finished. Further, when a pressure sensor or the like is added to the fuel cell system in order to detect an abnormality in the gas supply suppression unit, there is a problem that the cost increases. According to the fuel cell system 10 of this embodiment, since the abnormality of the sealing valve 340 is detected when the fuel cell 100 is started, even if the abnormality of the sealing valve 340 occurs after the previous stop of the fuel cell system, the sealing is performed. Abnormality of the stop valve 340 can be easily detected. In addition, since a device such as a pressure sensor is unnecessary, an abnormality of the sealing valve 340 can be detected with a simple configuration.

B. Second embodiment:
In the first embodiment, the sealing valve abnormality determination process for determining the abnormality of the sealing valve using the voltage change (dVocv / dt) of the cell voltage at the time of start has been described. However, the voltage change (dVocv / dt) of the cell voltage is described. The method for controlling the fuel cell system using the above is not limited to the above. In the second embodiment, in a fuel cell in which the anode is in a dead end, the change in cell voltage (dVocv / dt) is used to control the timing for opening and closing the valve for discharging water accumulated in the anode. A method will be described. In the following description, the functional units and components having the same reference numerals as those in the first embodiment have the same functions and configurations as those in the first embodiment.

B-1. Configuration of fuel cell system:
FIG. 6 is an explanatory diagram showing a schematic configuration of a fuel cell system as a second embodiment. Compared with the fuel cell system 10 of the first embodiment, the fuel cell system 11 of the second embodiment uses hydrogen that has not been used at the anode of the fuel cell 100 in the fuel gas supply system 201 as a fuel gas again. 1 (for example, the gas-liquid separator 250, the circulation channel 271e, the circulation compressor 240, and the circulation channel 271f in FIG. 1) are not provided. Instead, the fuel gas discharge channel 271g, the outlet valve 280, and the fuel And a gas discharge channel 271h. The fuel cell system 11 of the second embodiment is a so-called anode dead end system that does not have a hydrogen circulation path.

  The outlet valve 280 is a valve for discharging the water accumulated in the anode to the outside of the fuel cell 100, and is closed during the operation of the fuel cell, but at a predetermined timing according to an instruction from the system controller 900. Open the valve temporarily. Hereinafter, temporarily opening the outlet valve 280 to discharge water accumulated in the anode is also simply referred to as “temporary opening” (push-out).

  The system controller 900 is electrically connected to each component of the fuel cell system 10 including the outlet valve 280, and controls the operation of each component based on information received from each component. The control unit 911 of the system controller 900 performs timing control for controlling the interval at which the temporary valve opening is performed based on the change in the cell voltage detected by the cell monitor 800. Details of the timing control will be described later.

  The characteristics of the anode dead end fuel cell will be briefly described. FIG. 7 is an explanatory view schematically showing the inside of an anode dead end fuel cell. FIG. 8 is an explanatory diagram for explaining power generation characteristics of an anode dead-end fuel cell. The vertical axis in FIG. 8 indicates the cell voltage (V), and the horizontal axis indicates time (sec).

  Since the anode dead-end fuel cell does not have a circulation path for reusing hydrogen that has not been used at the anode as fuel gas, as shown in FIG. 7, during operation (during anode dead-end operation) The water inside the anode cannot be discharged outside the fuel cell. Therefore, in an anode dead end fuel cell, when water starts to accumulate near the outlet of the anode due to power generation, the anode is partially depleted of hydrogen as shown in FIG. 8, and the cell voltage gradually decreases.

  By periodically opening the fuel cell system 11 periodically, the fuel cell system 11 can discharge the water inside the anode to the outside of the fuel cell and eliminate the partial hydrogen deficiency of the anode. On the other hand, the fuel cell system 11 also discharges hydrogen, which is a fuel gas, together with water inside the anode by temporarily opening the valve. Therefore, it is desirable that the frequency of the temporary valve opening is such that the partial hydrogen deficiency of the anode does not occur. When the frequency is high, the power generation efficiency decreases due to the discharge of the fuel gas. The fuel cell system 11 according to the present embodiment determines whether or not the partial hydrogen deficiency of the anode has occurred from the change in the cell voltage detected by the cell monitor 800, and determines the frequency of temporary valve opening according to the determination result. The following timing control for controlling is performed.

B-2. Timing control:
FIG. 9 is a flowchart showing the flow of timing control. The timing control is performed in parallel with the anode dead end operation by the fuel cell 100. That is, the system controller 900 is in a state in which the power supply changeover switch 600 is on (closed) and supplies hydrogen and oxygen to the fuel cell 100 to perform power generation (anodic dead end operation) (step S200). Implement control.

  During the anode dead end operation, the control unit 911 of the system controller 900 continuously acquires the cell voltage Vcel from the cell monitor 800 and calculates a voltage change (dVcel / dt) per unit time of the cell voltage Vcel. When the voltage change of the cell voltage is calculated, the control unit 911 determines whether or not the voltage change of the cell voltage is negative (dVcel / dt <0). That is, the control unit 911 determines whether or not the cell voltage has dropped during the anode dead end operation. Further, the control unit 911 measures an elapsed time Tco (sec) from the previous temporary valve opening, and determines whether or not the elapsed time Tco has passed a predetermined period Tth (sec) (Tco> Tth). Perform (step S210). The predetermined period Tth is the length of time registered in advance in the ROM 920 (for example, 5 seconds). As will be described later, when the predetermined condition is satisfied in this timing control, the length of time is Be changed.

In addition, when the valve opening has not been performed once during the anode dead end operation, the control unit 911 does not use the elapsed time Tco from the temporary valve opening, but instead passes the elapsed time Tco from the predetermined operation at the start. ₂ may be configured to determine whether or not the predetermined time Tth ₂ has elapsed (Tco ₂ > Tth ₂ ), or to determine whether or not the elapsed time Tco ₂ has elapsed the predetermined time Tth _2. It is good also as a structure which determines only whether the voltage change of a cell voltage is negative (dVcel / dt <0), without performing.

  The control unit 911 continues the anode dead end operation until the voltage change of the cell voltage becomes negative (dVcel / dt <0) and the elapsed time Tco has passed the predetermined period Tth (Tco> Tth) (step s210). : NO).

  On the other hand, when the voltage change of the cell voltage becomes negative (dVcel / dt <0) and the elapsed time Tco has passed a predetermined period Tth (Tco> Tth) (step S210: YES), the control unit 911 outputs the outlet valve. 280 is temporarily opened (step S220). That is, the control unit 911 controls the outlet valve 280 to perform temporary opening.

  The controller 911 continuously acquires the cell voltage Vcel after the temporary valve opening when the valve is temporarily opened, and the cell voltage from the cell voltage Vcel immediately after the temporary valve opening to the peak of the subsequently increased cell voltage Vcel. The increase amount ΔVcel is acquired. In addition, the control unit 911 acquires the voltage change dVcel / dt of the cell voltage after the peak in order to detect the degree of the drop after the peak of the cell voltage Vcel.

  When the cell voltage increase amount ΔVcel and the voltage change dVcel / dt of the cell voltage after the peak are acquired, the control unit 911 acquires the cell voltage increase amount ΔVcel acquired after the cell voltage increase amount ΔVcel acquired this time is temporarily opened. It is determined whether or not it is greater than (previous cell voltage increase ΔVcelα). The control unit 911 also displays the voltage change dVcel / dt of the cell voltage after the peak that appears after the absolute value of the voltage change dVcel / dt of the cell voltage after the peak acquired this time is previously opened. It is determined whether or not it is larger than the absolute value of the voltage change (dVcel / dtα). That is, the control unit 911 determines whether or not the peak of the cell voltage Vcel after temporary opening is higher than the previous peak, and the amount of voltage drop per unit time of the cell voltage after the peak is per unit time of the previous time. It is determined whether or not the voltage drop amount is larger than (step S230).

  The control unit 911 determines that the current cell voltage increase amount ΔVcel is larger than the previous cell voltage increase amount ΔVcelα (ΔVcelα <ΔVcel), and the absolute value of the voltage change dVcel / dt of the current cell voltage is the voltage of the previous cell voltage. If the change dVcel / dtα is larger than the absolute value (| dVcel / dtα | <| dVcel / dt |) (step S230: NO), there is a possibility that the anode is deficient in hydrogen. The timing is advanced (step S240). That is, the control unit 911 shortens the length of the predetermined period Tth registered in the ROM 920 (for example, changes Tth = 5 seconds to Tth = 4 seconds). As a result, the frequency of temporary valve opening is increased, and the retention of water inside the anode is suppressed.

  On the other hand, the control unit 911 determines that the current cell voltage increase amount ΔVcel is less than or equal to the previous cell voltage increase amount ΔVcelα (ΔVcelα ≧ ΔVcel), or that the absolute value of the current cell voltage change dVcel / dt is equal to the previous cell voltage. When the voltage change is less than or equal to the absolute value of dVcel / dtα (| dVcel / dtα | ≧ | dVcel / dt |) (step S230: YES), there is little possibility that the anode is short of hydrogen. The valve opening timing is not changed (step S250). Thereby, the fall of the power generation efficiency by discharge | emission of fuel gas is suppressed.

  In this way, it is determined whether or not the peak of the cell voltage Vcel after the temporary opening is higher than the previous peak, and the voltage drop amount per unit time of the cell voltage after the peak is the voltage per unit time of the previous time. The reason why it is possible to estimate whether or not the anode is deficient by determining whether or not it is larger than the descending amount will be described later. The control unit 911 continues the control in steps S200 to S250 while the fuel cell 100 is in operation.

  In step S230, the control unit 911 determines that the previous cell voltage increase ΔVcelα or the previous cell voltage change dVcel / dtα has not been temporarily opened during the anode dead end operation. If not, the timing for opening the outlet valve 280 is not changed (step S250). The above is the description of the flow of timing control.

  Here, it is determined whether or not the peak of the cell voltage Vcel after the temporary opening is higher than the previous peak, and the voltage drop amount per unit time of the cell voltage after the peak is the voltage drop per unit time of the previous time. The reason why it is possible to estimate whether or not the anode is deficient by determining whether or not it is larger than the amount will be described with reference to FIGS. FIG. 10 is an explanatory diagram illustrating the time change of the cell voltage when no hydrogen deficiency occurs in the anode. FIG. 11 is an explanatory diagram illustrating the time change of the cell voltage when the anode is deficient in hydrogen. 10 and 11, the horizontal axis represents time T (sec), and the vertical axis represents the cell voltage Vocv (V).

As shown in FIG. 10, the cell voltage of the anode dead-end fuel cell 100 rises by draining water from the anode by temporary opening (time T ₁ ) as shown in FIG. (Time T _{1 to} T ₂ ). Thereafter, the cell voltage, the anode and cathode potential difference due to the normal power (generally, about 1V) when raised to (time T _2), again, gradually drop due to the effects of product water (time T ₂ ~).

On the other hand, when there is a lack of hydrogen at the anode, the cell voltage of the anode dead-end fuel cell 100 exceeds 1 (V) after the temporary opening (time T ₁ ) as shown in FIG. It rises to this point (time T ₂ ). This is because the reaction of the above formula (1) and the above formula (2) occurs at the anode due to the lack of hydrogen at the anode, and the reaction of the above formula (3) and the above formula (4) occur at the cathode. This is because the cathode potential is increased. After that, since hydrogen spreads to the anode, the reactions of the above formulas (2) and (4) are suppressed, and the cell voltage rapidly increases from the state exceeding 1 (V) with the influence of generated water and the like. Decrease (time T ₂ ~).

  As can be seen from the above, the cell voltage after the temporary opening of the cell voltage when the hydrogen deficiency occurs at the anode is higher than that when the hydrogen deficiency does not occur at the anode. The peak of is high, and the amount of voltage drop per unit time of the cell voltage after the peak is large. Therefore, during the anode dead-end operation, the fuel cell system 11 has a cell voltage increase ΔVcel larger than the previous cell voltage increase ΔVcelα (ΔVcelα <ΔVcel), and the cell voltage voltage change dVcel / dt after the peak When the absolute value is larger than the absolute value of the voltage change dVcel / dtα of the previous cell voltage (| dVcel / dtα | <| dVcel / dt |), it is determined that a shortage of hydrogen has occurred in the anode, and the valve is temporarily opened. By increasing the timing, the power generation efficiency of the fuel cell can be improved.

  According to the fuel cell system 11 of the present embodiment described above, during the anode dead end operation, the cell voltage increase amount ΔVcel after the temporary valve opening is larger than the cell voltage increase amount ΔVcelα after the previous temporary valve opening (ΔVcelα <ΔVcel) and the absolute value of the voltage change dVcel / dt of the cell voltage after the peak is larger than the absolute value of the voltage change dVcel / dtα of the cell voltage after the previous peak (| dVcel / dtα | <| dVcel / dt |), The timing of opening the outlet valve 280 is advanced, so that the power generation efficiency of the fuel cell can be improved.

  Specifically, the cell voltage after the temporary valve opening has a peak of the cell voltage Vcel after the temporary valve opening when the anode is depleted of hydrogen compared to when the anode is devoid of hydrogen. The voltage drop amount per unit time of the cell voltage after the peak is high. Therefore, the cell voltage increase amount ΔVcel is larger than the previous cell voltage increase amount ΔVcelα (ΔVcelα <ΔVcel), and the absolute value of the voltage change dVcel / dt of the cell voltage after the peak is the voltage change dVcel / dtα of the previous cell voltage. If it is larger than the absolute value (| dVcel / dtα | <| dVcel / dt |), there is a high possibility that hydrogen deficiency occurs due to water remaining in the anode. As a result, the power generation efficiency of the fuel cell can be improved.

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

C1. Modification 1:
In the first embodiment, the configuration for determining the abnormality of the sealing valve 340 using the cell voltage change (dVocv / dt) at the start of the fuel cell system 10 has been described. However, the cell voltage change at the start is described. The content that can be determined by using (dVocv / dt) is not limited to the failure of the sealing valve 340, and it can be determined whether or not various conditions that cause a lack of hydrogen in the anode have occurred. For example, the fuel cell system 10 can be realized as a system that determines whether or not the anode has run out of hydrogen by using the voltage change (dVocv / dt) of the cell voltage at the start, As long as the air does not flow from the oxidizing gas discharge channel 351d, it can also be realized as a system for determining whether air is flowing from the oxidizing gas supply channel 351c.

C2. Modification 2:
In the first embodiment, it is configured to determine whether or not the sealing valve 340 has failed using the voltage change per unit time (dVocv / dt) of the cell voltage Vocv, but the sealing valve 340 has failed. In this case, since the cathode potential is higher than 1 (V), for example, the abnormality detection unit 912 does not change the voltage (dVovv / dt) but the cell voltage Vocv has a threshold value (for example, 1 V). It is good also as a structure which determines whether the sealing valve 340 is out of order by whether it exceeds.

C3. Modification 3:
In the first embodiment, the fuel gas is supplied to the anode of the fuel cell 100 after the fuel cell is started, and then the oxidizing gas is supplied to the cathode. The timing at which the gas is supplied is not limited to the above. For example, the supply of the fuel gas to the anode of the fuel cell 100 and the supply of the oxidizing gas to the cathode may be performed simultaneously, or the oxidizing gas may be supplied to the cathode first. Even in this case, when oxygen is present inside the anode due to a failure of the sealing valve 340, an electrochemical reaction occurs with hydrogen supplied later, and an internal circuit is formed. Abnormality of the stop valve 340 can be easily detected.

C4. Modification 4:
The fuel cell system 11 of the second embodiment has been described as having the same configuration as that of the fuel cell system 10 of the first embodiment except that the fuel cell system 11 of the second embodiment is not provided with a hydrogen circulation path. If it is an anode dead end system, it is not necessary to have all of the configuration shown in FIG. 6, and it can be realized even if it does not have a part of the configuration shown in FIG. For example, the fuel cell system 11 can be realized without the sealing valve 340.

C5. Modification 5:
The present invention can be realized in various modes, for example, in the form of an abnormality detection device, a fuel cell vehicle including a fuel cell system, an abnormality determination method, a control method of the fuel cell system, and the like. can do.

DESCRIPTION OF SYMBOLS 10,11 ... Fuel cell system 100 ... Fuel cell 110 ... Fuel cell 111 ... Terminal plate 200, 201 ... Fuel gas supply system 210 ... Hydrogen tank 220 ... Flow rate adjustment part 230 ... Humidification adjustment part 240 ... Circulation compressor 250 ... Gas-liquid Separator 260 ... Switching valve 271 ... Fuel gas flow path 280 ... Outlet valve 300 ... Oxidation gas supply system 310 ... Intake port 320 ... Compressor 330 ... Humidification adjustment unit 340 ... Sealing valve 351 ... Oxidation gas flow path 390 ... Exhaust port 400 DESCRIPTION OF SYMBOLS ... Fuel cell cooling system 410 ... Radiator 420 ... Refrigerant temperature sensor 430 ... Refrigerant circulation pump 441 ... Refrigerant flow path 500 ... Load device 550 ... Inverter 560 ... Current sensor 600 ... Power supply changeover switch 700 ... Battery 800 ... Cell monitor 900 ... System controller 910 ... CPU
911 ... Control unit 912 ... Abnormality detection unit 920 ... ROM
930 ... RAM

Claims (5)

A fuel cell system,
A fuel cell;
A fuel gas supply system for supplying hydrogen as a fuel gas to the fuel cell;
An oxidizing gas supply system for supplying oxygen as an oxidizing gas to the fuel cell;
A gas supply suppressing unit for suppressing the supply of oxidizing gas to the fuel cell when the fuel cell is stopped;
A voltage detector for detecting a voltage generated in the fuel cell;
When detecting the state in which the increase amount per unit time of the voltage detected by the voltage detection unit is negative when the fuel cell is started and fuel gas is supplied to the fuel cell, An abnormality detection unit that determines that an abnormality has occurred in the gas supply suppression unit. The fuel cell system according to claim 1, wherein
When the fuel gas is supplied to the fuel cell, the abnormality detection unit is in a state where the increase amount becomes negative until the increase amount per unit time of the voltage becomes zero for a predetermined period. A fuel cell system that, when detected, determines that an abnormality has occurred in the gas supply suppression unit. The fuel cell system according to claim 2, wherein
The fuel cell has a configuration in which a plurality of fuel cells are stacked,
The voltage detection unit detects a cell voltage generated between the anode side and the cathode side of each fuel cell,
When the abnormality detection unit detects a state in which the amount of increase per unit time is negative at the start of the fuel cell in the cell voltage of the fuel cell, an abnormality has occurred in the gas supply suppression unit A fuel cell system that determines that The fuel cell system according to any one of claims 1 to 3,
The gas supply suppression unit is a fuel cell system, which is a sealing valve disposed in the oxidizing gas supply system. An abnormality determination method for a fuel cell system, comprising: a fuel cell; and a gas supply suppression unit for suppressing supply of oxidizing gas to the fuel cell when the fuel cell is stopped,
Supplying fuel gas to the fuel cell at the start of the fuel cell;
When a fuel gas is supplied to the fuel cell and a state in which the amount of increase in voltage generated in the fuel cell per unit time is negative is determined, it is determined that an abnormality has occurred in the gas supply suppression unit. And an abnormality determination method for a fuel cell system.

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