JP2003173807A - Controller for fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve draining efficiency of water trapped in a fuel cell. <P>SOLUTION: When a fuel cell stack is made to generate electricity by a control unit (a step S1), a cell voltage of the fuel cell stack is monitored by a cell voltage sensor (a step S2), and when the cell voltage is judged to be lower than a predetermined value (a step S3), a hydrogen gas supply regulator is controlled so as to raise fuel gas pressure (a step S4), and then, a purge open/close valve is controlled to switch from a closed state to an open state (a step S5). With this, a kinetic pressure of hydrogen gas pressure is generated to make an anode electrode side drain efficiently. Then, the cell voltage is estimated to be higher than the predetermined value (a step S6), the purge open/close valve 6 is controlled to switch from an open state to a closed state (a step S7). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, as a drive source for automobiles and the like, and is supplied with hydrogen gas as a fuel gas and air as an oxidant gas to generate electric power and perform a purge operation in a hydrogen circulation path. The present invention relates to a fuel cell system control device for controlling a fuel cell system having a purge valve.

[0002]

2. Description of the Related Art As a conventional fuel cell system, for example, one disclosed in Japanese Patent Application Laid-Open No. 7-235324 is known. When the fuel cell system detects that water has accumulated in the fuel cell stack by operating the fuel cell stack, the cathode-side gas flow rate of the fuel cell stack is increased, and the accumulated water is retained by the dynamic pressure of oxygen gas. It was working to blow it away.

[0003]

In the conventional fuel cell system, when adjusting the fuel gas pressure supplied from the fuel gas tank to the fuel cell stack, the fuel gas pressure is adjusted while supplying the fuel gas to the fuel cell stack. Therefore, the fuel economy is not good. In contrast,
BACKGROUND ART Conventionally, there has been proposed a fuel cell system having a fuel gas circulation flow path for circulating the residual fuel gas discharged from the fuel gas outlet of the fuel cell stack to the fuel gas inlet of the fuel cell stack.

In such a fuel cell system, it is possible to improve the discharge efficiency of accumulated water by applying the technique of discharging accumulated water in the fuel cell stack to the anode side as well. However, in the case where the fuel gas circulation passage does not have a circulation pump, it is impossible to increase the fuel gas supply amount even if the fuel gas pressure is increased unless the fuel gas consumption amount of the fuel cell stack changes. is there. That is, it is impossible to make the fuel gas supply amount more than the fuel gas amount consumed in the fuel cell stack while keeping the fuel gas pressure constant according to the operating condition of the fuel cell stack. When water clogging occurs, the fuel gas flow rate cannot be easily increased.

On the other hand, when the occurrence of water clogging is detected, the purge valve is opened and the fuel gas supply flow rate is the sum of the fuel gas amount consumed in the fuel cell stack and the exhaust gas amount from the purge valve. And As a result, in the fuel cell system, the fuel gas can be supplied to the fuel cell stack by increasing the amount of exhaust gas from the purge valve, and the fuel gas supply flow rate on the anode side is increased. However, the fuel economy is reduced by releasing the fuel gas to the outside.

As a method of removing accumulated water in the fuel cell stack, there is a method of lowering the power output of the fuel cell stack by lowering the fuel gas pressure to recover the cell voltage. There is a problem that a period during which no power output is obtained occurs. This problem is particularly important in a fuel cell system that does not include a secondary battery.

Therefore, the present invention has been proposed in view of the above situation, and provides a control device for a fuel cell system capable of improving the drainage efficiency of water accumulated in the fuel cell. .

[0008]

According to a first aspect of the present invention, there is provided a control device for a fuel cell system in which a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are laminated, Side is supplied with an oxidant gas, and is supplied with fuel gas to the fuel electrode side to generate electric power, gas supply means for supplying the oxidant gas and the fuel gas to the fuel cell, and the fuel cell A fuel circulation passage that passes through the fuel gas outlet and the fuel gas inlet, and provided in this fuel circulation passage,
A fuel cell system having a purge valve for releasing a part of the gas in the fuel circulation path to the outside is controlled.

When the fuel cell system control device determines that the cell voltage of the fuel cell is smaller than a predetermined value, the fuel cell system control device controls the gas supply means so as to increase the fuel gas pressure, and then turns on the purge valve. Control is performed from the closed state to the open state, and when it is determined that the cell voltage of the fuel cell is higher than a predetermined value, the purge valve is controlled from the open state to the closed state.

According to a second aspect of the present invention, there is provided a control device for a fuel cell system in which a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are laminated, and an oxidant gas is provided on the oxidant electrode side. A fuel cell that is supplied with fuel gas to the fuel electrode side to generate electricity, a gas supply unit that supplies an oxidant gas and a fuel gas to the fuel cell, a fuel gas outlet of the fuel cell, and a fuel gas. The present invention controls a fuel cell system having a fuel circulation passage that passes through an inlet and a purge valve that is provided in the fuel circulation passage and discharges a part of the gas in the fuel circulation passage to the outside.

When the cell voltage of the fuel cell is determined to be lower than a predetermined value, the control device of the fuel cell system periodically controls the opening / closing of the purge valve so that the cell voltage of the fuel cell is a predetermined value. When it is determined that the value is larger than the above value, the purge valve is controlled to be closed.

According to a third aspect of the present invention, there is provided a control device for a fuel cell system in which a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are laminated, and an oxidant gas is provided on the oxidant electrode side. A fuel cell that is supplied with fuel gas to the fuel electrode side to generate electricity, a gas supply unit that supplies an oxidant gas and a fuel gas to the fuel cell, a fuel gas outlet of the fuel cell, and a fuel gas. The present invention controls a fuel cell system having a fuel circulation passage that passes through an inlet and a purge valve that is provided in the fuel circulation passage and discharges a part of the gas in the fuel circulation passage to the outside.

When the cell voltage of the fuel cell is determined to be lower than a predetermined value, the control device of the fuel cell system controls the purge valve after controlling the gas supply means so as to increase the fuel gas pressure. Open and close control periodically,
When it is determined that the cell voltage of the fuel cell is higher than a predetermined value, the purge valve is controlled to be closed.

A fuel cell system controller according to a fourth aspect of the present invention is the fuel cell system controller according to any one of the first to third aspects, wherein the cell voltage of the fuel cell is higher than a predetermined value. If it is determined to be small, control is performed to open at least one purge valve, and it is determined that the cell voltage of the fuel cell is smaller than a predetermined value after a lapse of a predetermined period after opening the one purge valve. When the fuel cell cell voltage of the fuel cell is determined to be higher than a predetermined value, the purge valve that has been opened is controlled to be closed. And

A fuel cell system controller according to a fifth aspect of the present invention is the fuel cell system controller according to the first or third aspect, wherein the cell voltage of the fuel cell is determined to be smaller than a predetermined value. In this case, the gas supply means is controlled so as to increase the fuel gas pressure stepwise.

A fuel cell system controller according to a sixth aspect of the present invention is the fuel cell system controller according to the first, third or fifth aspect, wherein the cell voltage of the fuel cell is greater than a predetermined value. When it is determined that is also small, the fuel gas pressure is increased and the gas supply means is controlled so as to maintain the oxidant gas flow rate at the oxidant electrode.

[0017]

According to the controller of the fuel cell system of the first aspect, when the cell voltage of the fuel cell is smaller than a predetermined value, the purge is performed after controlling the gas supply means so as to increase the fuel gas pressure. Since the valve is controlled to change from the closed state to the open state, the dynamic pressure of the fuel gas pressure immediately after the purge valve is opened can be increased. Therefore, according to this control device of the fuel cell system, it is possible to shorten the period of time during which the purge valve is opened, reduce the amount of fuel gas discharged by opening the purge valve, and improve the drainage efficiency. Can be improved.

According to the second aspect of the fuel cell system control device, the purge valve is controlled to open and close periodically when the cell voltage of the fuel cell is smaller than a predetermined value. You can do a lot. Therefore, according to this control device of the fuel cell system, it is possible to increase the number of times the dynamic pressure of the fuel gas pressure is generated, and it is possible to further improve the drainage efficiency.

According to the third aspect of the control device for the fuel cell system, when the cell voltage of the fuel cell is smaller than a predetermined value, the purge valve is turned on after controlling the gas supply means so as to raise the fuel gas pressure. Since it controls opening and closing periodically,
It is possible to exert a synergistic effect of increasing the dynamic pressure by increasing the fuel gas pressure and increasing the number of times the dynamic pressure is generated by periodically controlling the opening and closing of the purge valve. Even if the amount is small, it is possible to drain water efficiently.

According to the fourth aspect of the control device for the fuel cell system, when the cell voltage of the fuel cell is smaller than the predetermined value, at least one purge valve is controlled to be in the open state, and the one purge valve is opened. When it is determined that the cell voltage of the fuel cell is smaller than the predetermined value after the lapse of a predetermined period from the open state, the other purge valves are controlled to be in the open state. The flow rate can be increased and the dynamic pressure can be further increased.

According to the fifth aspect of the control device for the fuel cell system, since the fuel gas pressure is increased stepwise when the cell voltage of the fuel cell is smaller than a predetermined value, the dynamic pressure can be further increased. Therefore, the drainage efficiency can be further improved.

According to the sixth aspect of the control device for the fuel cell system, when the cell voltage of the fuel cell is smaller than a predetermined value, the fuel gas pressure is increased and the oxidant gas flow rate at the oxidant electrode is maintained. Therefore, even when the oxidant gas flow rate is decreased by increasing the fuel gas pressure and the oxidant gas pressure, it is possible to prevent the oxidant gas flow rate from decreasing and the drainage efficiency to decrease. The drainage efficiency can be maintained.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The present invention is applied to, for example, the fuel cell system according to the first embodiment configured as shown in FIG. 1 and the fuel cell system according to the second embodiment configured as shown in FIG. .

[Configuration of Fuel Cell System According to First Embodiment] The fuel cell stack 1 included in the fuel cell system according to the first embodiment has a solid polymer electrolyte membrane and an oxidizer electrode (cathode electrode) and a fuel electrode. It has a stack structure in which a plurality of cell structures sandwiched by (anode electrode) are laminated with a separator interposed therebetween. In addition, in the fuel cell stack 1, an oxidant gas passage through which an oxidant gas passes, a fuel gas passage through which a fuel gas passes,
A cooling water passage is provided for passing cooling water. Then, in the fuel cell stack 1, air as an oxidant gas is supplied to the oxidant electrode side, and hydrogen gas as a fuel gas is supplied to the fuel electrode side. As a result, in the fuel cell stack 1, each ion moves and contacts in the membrane using water as a medium to generate electricity.

In this fuel cell system, a hydrogen tank 2, which stores hydrogen, a hydrogen gas supply pressure regulating valve 3, a hydrogen circulation device 4 and a humidifier 5 are inserted through a hydrogen gas supply passage L1 to form a fuel cell stack 1. Connected to the hydrogen gas inlet 1a, the hydrogen gas outlet 1b of the fuel cell stack 1, the hydrogen gas inlet 1
a, a purge on-off valve 6 is equipped with a hydrogen gas system which is inserted through the hydrogen gas circulation flow path L2.

The hydrogen gas supply pressure regulating valve 3 and the purge opening / closing valve 6 are connected to an actuator (not shown), and the opening / closing operation and the opening degree are controlled by driving the actuator according to a control signal from the control unit 17. The purging on-off valve 6 is controlled to be opened and closed according to a control signal from the control unit 17, and is opened to discharge the hydrogen gas in the fuel gas circulation flow path L2 and the fuel cell stack 1 to the outside.

In this fuel cell system, when operating the fuel cell stack 1, the control unit 17
The hydrogen stored in the hydrogen tank 2 in a high pressure state is regulated by the hydrogen gas supply regulating valve 3 by the hydrogen gas supply passage L1.
It is supplied to the hydrogen circulation device 4 via. This adjusts the hydrogen gas pressure on the anode side of the fuel cell stack 1. The hydrogen circulation device 4 supplies the humidifier 5 with the hydrogen gas supplied from the hydrogen gas supply pressure regulating valve 3 and the hydrogen gas supplied through the hydrogen gas circulation flow path L2. The humidifier 5 has a semipermeable membrane inside, and by allowing pure water and hydrogen gas to be adjacent to each other through the semipermeable membrane, water molecules are allowed to pass through the semipermeable membrane to humidify the hydrogen gas. Supply to the fuel cell stack 1.

Further, in this fuel cell system, the compressor 7 is inserted into the air supply passage L3 and connected to the air inlet 1c of the fuel cell stack 1, and the air outlet 1d of the fuel cell stack 1 and the air pressure regulating valve 8 discharge the air. An oxidant gas system that is inserted through the flow path L4 is provided. The compressor 7 is driven by controlling its rotation speed according to a control signal from the control unit 17, and adjusts and supplies the air flow rate to the fuel cell stack 1. Further, the air pressure regulating valve 8 operates according to a control signal from the control unit 17, and the opening thereof is adjusted.

In this fuel cell system, when operating the fuel cell stack 1, the control unit 17
The compressor 7 is driven to supply air to the humidifier 5. The humidifier 5 humidifies the air in the same manner as the hydrogen gas and supplies the humidified air to the fuel cell stack 1. At this time, in the fuel cell system, by adjusting the opening degree of the air pressure regulating valve 8 by the control unit 17, the inside of the fuel cell stack 1
The air pressure in the air supply passage L3 and the air discharge passage L4 is adjusted.

Further, this fuel cell system has a water circulation system in which the water tank 9, the water pump 10, the radiator 11, the fuel cell stack 1, and the humidifier 5 are inserted through the water circulation flow path L5. In addition, the water circulation system in this fuel cell system includes a radiator fan 12 that cools water passing through the radiator 11.

In such a fuel cell system, the water in the water tank 9 is supplied to the radiator 11 by the water pump 10 to control the drive amount of the radiator fan 12 to control the water temperature, thereby controlling the fuel cell stack 1 Is supplied to the fuel cell stack 1 to cool the fuel cell stack 1 and adjust the temperature.
The water that has cooled the fuel cell stack 1 is supplied to the humidifier 5
Is partially supplied to the humidifier 5 and is stored in the water tank 9 again.

Furthermore, in this fuel cell system, the hydrogen gas supply passage L between the humidifier 5 and the fuel cell stack 1 is provided.
Hydrogen gas pressure sensor 1 for detecting hydrogen gas pressure in 1
3, an air pressure sensor 14 that detects the air pressure in the air supply flow path L3 between the humidifier 5 and the fuel cell stack 1, and an air flow rate sensor 15 that detects the air flow rate taken into the compressor 7. These hydrogen gas pressure sensors 1
3, the air pressure sensor 14, and the air flow sensor 15 are shown in FIG.
The hydrogen gas pressure, the air pressure, and the air flow rate in the fuel cell stack 1 are detected by arranging as shown in FIG.
Furthermore, the fuel cell system includes a cell voltage sensor 1 that detects a cell voltage of each cell that constitutes the fuel cell stack 1.
6 is provided. These sensors output the detected values to the control unit 17 as sensor signals.

The control unit 17 controls each section configured as described above. When a command to start driving the fuel cell stack 1 is input from the outside, the control unit 17 controls the hydrogen gas supply pressure regulating valve 3 so as to supply hydrogen gas to the fuel cell stack 1, and also controls the fuel cell stack 1 The compressor 7 and the air pressure regulating valve 8 are controlled so that air is supplied to the compressor. Further, the control unit 17 outputs a control signal to the water pump 10 and the radiator fan 12 to circulate water in the fuel cell stack 1 and the humidifier 5. As a result, the control unit 17 causes the fuel cell stack 1 to start power generation.

Further, the control unit 17 recognizes the amount of electric power generated by the fuel cell stack 1 according to a signal indicating the accelerator opening degree or the like from the outside, and recognizes necessary operating conditions such as hydrogen gas pressure and air pressure. Then, the control unit 17 controls the hydrogen gas supply pressure adjusting valve 3 so as to adjust the hydrogen gas pressure so as to realize the operating condition, and controls the compressor 7 and the air pressure adjusting valve 8 so as to adjust the air pressure. The water pump 10 and the radiator fan 12 are controlled so as to control the temperature of the fuel cell stack 1. Here, the control unit 17 refers to the sensor signals from the hydrogen gas pressure sensor 13, the air pressure sensor 14, and the air flow rate sensor 15 to make the hydrogen gas pressure and the air pressure substantially the same pressure value.

Further, the control unit 17 inputs the sensor signal from the cell voltage sensor 16 while operating the fuel cell stack 1 to monitor the cell voltage of the fuel cell stack 1 to detect the fuel cell stack 1 A cell voltage drop due to water clogging of the anode and cathode is detected.

Specifically, the control unit 17
Compares the detected cell voltage with a preset allowable lower limit value. The control unit 17 determines whether or not the detected cell voltage is less than or equal to the allowable lower limit value, and when the detected cell voltage is less than the allowable lower limit value, each cell due to water accumulated in the fuel cell stack 1 It is judged that the power generation capacity of the plant has deteriorated and water discharge is necessary, and the purge on-off valve 6
Water discharge processing is performed to control the operation of.

Here, by operating the purge on-off valve 6 from the closed state to the open state or from the open state to the closed state while supplying hydrogen gas to the fuel cell stack 1,
As shown in FIG. 2, a dynamic pressure that changes the hydrogen gas pressure (hydrogen gas pressure in the fuel cell stack 1) detected by the hydrogen gas pressure sensor 13 is generated. This dynamic pressure is generated when the purge on-off valve 6 is opened and closed to change the hydrogen gas flow velocity in the hydrogen gas supply passage L1 and the anode electrode of the fuel cell stack 1.

That is, as shown in FIG. 2B, time t
When the purge on-off valve 6 is changed from the closed state to the open state in 1,
The hydrogen gas flow velocity in the hydrogen gas supply passage L1 temporarily increases, and the hydrogen gas pressure temporarily decreases as shown in FIG. 2 (a). During time t1 to time t2 (purge period), when the purge on-off valve 6 is opened, the hydrogen gas flow velocity gradually decreases, so that the hydrogen gas pressure gradually returns to the original pressure value. Further, when the purge on-off valve 6 is changed from the open state to the closed state at time t2, the hydrogen gas supply flow path L
The hydrogen gas flow rate in 1 temporarily decreases, and the hydrogen gas pressure temporarily increases.

The control unit 17 uses the dynamic pressure of the hydrogen gas pressure according to the operation of the purge opening / closing valve 6 to perform the water discharge process. The detailed processing contents of the control unit 17 when performing this water discharge processing will be described later.

Further, the control unit 17 is
When performing the water discharge process, before controlling the open / closed state of the purge on-off valve 6, the hydrogen gas pressure is increased to a predetermined pressure value set according to the operating conditions of the fuel cell stack 1, the cell voltage decrease, etc. Then, the hydrogen gas supply pressure regulating valve 3 is controlled.

[Operation of Fuel Cell System According to First Embodiment] Next, the operation of the fuel cell system according to the above-described first embodiment will be described with reference to the flowchart of FIG.

According to this flowchart, first, the control unit 17 inputs a signal indicating the amount of electric power generated by the fuel cell stack 1 to adjust the hydrogen gas pressure under the target operating conditions. ,
For example, the water discharge process after step S1 is performed every predetermined period. In this state, the purge opening / closing valve 6 is closed.

First, in step S1, the control unit 17 detects the current hydrogen gas supply pressure from the sensor signal from the hydrogen gas pressure sensor 13, sets the hydrogen gas pressure to the reference hydrogen gas pressure, and proceeds to step S2. .

In step S2, the control unit 17 detects the cell voltage in the state where the reference hydrogen gas pressure is set in step S1 by the sensor signal from the cell voltage sensor 16, and the process proceeds to step S3.

In step S3, the control unit 17 determines whether the cell voltage detected in step S2 is smaller than the allowable lower limit value. This allowable lower limit value is preset with a voltage value when the fuel cell stack 1 is clogged with water and the cell voltage is reduced. The allowable lower limit value may be changed according to the generated electric power required for the fuel cell stack 1.

When the control unit 17 determines that the cell voltage is lower than the allowable lower limit value, it is determined that the anode electrode is clogged with water, and the process proceeds to step S4. It is determined that the cell voltage drop due to water clogging has not occurred at the anode electrode, and the process returns to step S1.

In step S4, the control unit 17 controls the hydrogen gas supply pressure regulating valve 3 to raise the hydrogen gas pressure to a predetermined pressure value. That is, the control unit 17 causes the hydrogen gas pressure supplied to the fuel cell stack 1 to be the sum of the reference hydrogen gas pressure in step S1 and the purge correction pressure corresponding to the pressure to be increased to the predetermined pressure value. To control. Here, the predetermined pressure value is set based on the operating conditions of the fuel cell stack 1, the cell voltage drop margin according to the cell voltage detected in step S2, and the like.

When it is detected from the sensor signal from the hydrogen gas pressure sensor 13 that the hydrogen gas pressure has reached the predetermined pressure value by the operation of step S4, the process proceeds to step S5 and the control unit 17 causes the purge on-off valve 6 to operate. Is controlled from the closed state to the open state, and the process proceeds to step S6.

In step S6, the control unit 17 detects the cell voltage after the purge on-off valve 6 is opened, and determines whether the cell voltage is lower than the allowable lower limit value. Determine if the clog is cleared. When the control unit 17 determines that the cell voltage is smaller than the allowable lower limit value and the water clogging has not been resolved, the process proceeds to step S8.
On the other hand, when it is determined that the cell voltage is larger than the allowable lower limit value and the water clogging is eliminated, the process proceeds to step S7, the purge on-off valve 6 is closed, and the process returns to step S1.

In step S8, the control unit 17 compares the purge valve opening time, which is the elapsed time from the time when the purge on-off valve 6 is opened in step S5, with the set time to set the purge valve opening time. Determine if it is longer than time. This set time is a time set to suppress the functional deterioration of the fuel cell stack 1 due to water clogging.

When the control unit 17 determines that the purge valve opening time is longer than the set time, the process proceeds to step S9, and in order to suppress the functional deterioration of the fuel cell stack 1, the power generation of the fuel cell stack 1 is stopped. The hydrogen gas supply pressure regulating valve 3 is closed to stop the operation, and the operation of the compressor 7 is stopped. On the other hand, when it is determined that the purge valve opening time is not longer than the set time, the process is returned to step S6.

FIG. 4 shows changes in cell voltage, hydrogen gas supply flow rate, hydrogen gas pressure, and open / close state of the purge on-off valve 6 in the fuel cell system performing such an operation.

When the control unit 17 detects that the cell voltage has dropped and the cell voltage has become smaller than the allowable lower limit value at time A (FIG. 4A, step S3),
The hydrogen gas supply pressure regulating valve 3 is controlled so as to have a predetermined pressure value.

Then, at time B, the hydrogen gas pressure is increased to a predetermined pressure value (FIG. 4 (c), step S
4) open the purge on-off valve 6 (FIG. 4 (d),
Step S5). At this time, since the hydrogen gas pressure is raised above the reference hydrogen gas pressure in step S1,
Further, a dynamic pressure is generated in which the hydrogen gas pressure decreases from time B to time C (FIG. 4C), which increases the hydrogen gas supply flow rate from time B to time C (FIG. 4C).
(B)), the hydrogen gas flow velocity in the anode increases.
By operating in this way, it is easy to blow off the water accumulated in the anode. As a result, when the cell voltage is increased after time B and it is detected that the cell voltage becomes higher than the allowable lower limit value, the purge on-off valve 6 is closed at time D (FIG. 4 (d), Step S7).

In the example shown in FIG. 4, time B-
The amount of decrease in the hydrogen gas pressure at time C occurs because the supply amount of hydrogen gas becomes insufficient when the purge opening / closing valve 6 is opened. Further, the amount of increase in the hydrogen gas pressure after time D is delayed by the period required for the hydrogen gas supply pressure regulating valve 3 to return from the predetermined pressure value to the normal pressure value with respect to the period required for closing the purge on-off valve 6. Caused by.

In order to eliminate the condensation of water vapor in the humidified air on the cathode side and the water clogging due to the generated water, for example, the flow rate of the compressor 7 is increased to generate the dynamic pressure of the air.

[Effects of Fuel Cell System According to First Embodiment] As described above in detail, according to the fuel cell system according to the first embodiment, the amount of water vapor in the hydrogen gas humidified by the humidifier 5 is increased. Fuel cell stack 1 by condensation
The water clogging that occurs in the anode electrode of is eliminated.

Further, in the fuel cell system according to the first embodiment, in order to increase the dynamic pressure immediately after the purge on-off valve 6 is opened, the hydrogen gas pressure is raised to a predetermined pressure value and then the purge is performed. Since the open / close valve 6 for the
The dynamic pressure can be increased to increase the hydrogen gas flow rate, and the drainage at the anode can be efficiently performed.
That is, according to this fuel cell system, compared with the operation of adjusting the hydrogen gas pressure by the generated electric power required for the fuel cell stack 1 and simply opening the purge on-off valve 6, the purge on-off valve is opened. The dynamic pressure immediately after opening 6 can be increased.

Therefore, according to this fuel cell system, the period in which the purge on-off valve 6 is in the open state can be shortened, so that the amount of hydrogen gas discharged by opening the purge on-off valve 6 can be reduced. The amount can be reduced, and the drainage on the anode side can be efficiently performed. As described above, according to the fuel cell system, it is possible to improve the fuel efficiency of hydrogen gas by efficiently discharging water, and
Improve the drainage efficiency while maintaining the power generation output without affecting the power generation output without the need to reduce the air pressure and hydrogen gas pressure to reduce the drainage time, reduce the power generation output, and reduce the generated gas by power generation. be able to.

[Configuration of Fuel Cell System According to Second Embodiment] Next, the fuel cell system according to the second embodiment will be described with reference to FIG. The same parts as those of the fuel cell system according to the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

The fuel cell system according to the second embodiment shown in FIG. 5 is that the first purge on-off valve 18 and the second purge on-off valve 19 are provided in the hydrogen gas circulation passage L2. The fuel cell system according to the present invention is different.

In such a fuel cell system, the control unit 17 detects the cell voltage drop of the fuel cell stack 1 by the sensor signal from the cell voltage sensor 16 as in the first embodiment, and opens and closes for the first purge. Valve 1
8 and / or the water discharge process of opening the second purge on-off valve 19 is performed.

[Operation of Fuel Cell System According to Second Embodiment] Next, the operation of the fuel cell system according to the second embodiment described above will be described with reference to the flowchart of FIG.

According to FIG. 6, in step S11 subsequent to the process of step S4, the control unit 17 controls to open only the first purge on-off valve 18. Then, if it is determined in step S6 that the cell voltage becomes larger than the allowable lower limit value, step S6
At 12, the first purge on-off valve 18 is closed to end the process.

When it is determined in step S6 that the cell voltage is lower than the allowable lower limit value, the process proceeds to step S8, and the control unit 17 causes step S8 to proceed.
At 11, it is determined whether the purge opening time, which is the elapsed time from the time when the first purge on-off valve 18 is opened, is longer than the first setting time, and the purge opening time is longer than the first setting time. If it is determined that it has become longer, the process proceeds to step S13.

In step S13, the control unit 17 controls the second purge on-off valve 19 to open it. As a result, both the first purge on-off valve 18 and the second purge on-off valve 19 are opened,
The gas in the hydrogen gas circulation flow path L2 is discharged from the first purge on-off valve 18 and the second purge on-off valve 19.

In step S14, the control unit 17 determines whether the cell voltage has become smaller than the allowable lower limit value by opening the first purge on-off valve 18 and the second purge on-off valve 19. . When it is determined that the cell voltage is not lower than the allowable lower limit value, the process proceeds to step S15 and the control unit 1
The second purge on-off valve 19 is closed by step 7, and the first purge on-off valve 18 is closed by step S12.

On the other hand, when it is determined that the cell voltage is smaller than the allowable lower limit value, the process proceeds to step S16, and the purge opening time from the time when the second purge opening / closing valve 19 is opened in step S13 is the second purge opening time. It is determined whether it has become longer than the set time. When the purge open time is longer than the second set time, the process proceeds to step S9, and when it is not long, the process returns to step S14 to open both the first purge on-off valve 18 and the second purge on-off valve 19. Holds the state of being in the state.

The first set time and the second set time are
The sum may be set to be the set time in the first embodiment, or may be a time obtained by equally dividing the set time in the first embodiment.

[Effects of Fuel Cell System According to Second Embodiment] As described above in detail, according to the fuel cell system according to the second embodiment, the first operation is performed in step S11.
If the cell voltage does not exceed the allowable lower limit value even when the purge on-off valve 18 is opened, the second purge on-off valve 19 is also opened in step S13.
Compared with the embodiment, the total gas discharge flow rate in the hydrogen gas circulation flow path L2 can be further increased, and the dynamic pressure can be further increased. Therefore, according to this fuel cell system, water can be discharged in a short time when the cell voltage requires a certain period of time to recover to the allowable lower limit value, and water can be effectively discharged. .

In the fuel cell system described below, the case where the two first purge on-off valves 18 and the second purge on-off valves 19 are provided has been described, but the present invention is not limited to this. Needless to say, the same effect can be obtained even if a purge on-off valve is provided.

[Another Operation Example of Fuel Cell System] Next, as another operation example of the fuel cell system according to the first embodiment and the fuel cell system according to the second embodiment, the first operation example, The second operation example and the third operation example will be described. In the operation example described below, the reference numerals used in the first embodiment are attached to omit detailed description thereof, but the fuel cell system according to the second embodiment is also applicable. .

[First Operation Example] In the first operation example, when the cell voltage does not recover even when the purge opening / closing valve 6 is opened, the operation of gradually increasing the hydrogen gas pressure is performed.

That is, as shown in FIG. 7, step S
5, even if the purge on-off valve 6 is opened, the cell voltage is smaller than the predetermined lower limit value (step S6), and the elapsed time from the time when the purge on-off valve 6 is opened is less than the set time. When it is short (step S8), the process proceeds to step S21.

In step S21, the control unit 17 obtains the hydrogen gas pressure currently supplied to the fuel cell stack 1 from the sensor signal from the hydrogen gas pressure sensor 13, and determines the current hydrogen gas pressure and the preset tolerance. Compare with upper pressure limit. The allowable upper limit pressure is set to a pressure value at which the function of the fuel cell stack 1 does not deteriorate, for example, in relation to the air pressure in the fuel cell stack 1.

When it is determined that the current hydrogen gas pressure is not higher than the allowable upper limit pressure, the process proceeds to step S22, and the hydrogen gas pressure supplied to the fuel cell stack 1 is increased by a predetermined rising pressure (α). Thus, the hydrogen gas supply pressure regulating valve 3 is controlled to return the process to step S6. As a result, the hydrogen gas pressure supplied to the fuel cell stack 1 becomes the pressure sum of the reference hydrogen gas pressure in step S4, the purge correction pressure, and the predetermined rising pressure (α).

In this fuel cell system, after the purge on-off valve 6 is opened, the cell voltage is at the allowable lower limit value, the purge opening time is shorter than the set time, and the hydrogen gas pressure is lower than the allowable upper limit pressure. If smaller, step S6,
By repeating the processes of step S8, step S21, and step S22, the hydrogen gas pressure is increased stepwise. On the other hand, when the hydrogen gas pressure becomes higher than the allowable upper limit pressure in step S21, the control unit 17 advances the process to step S9 to control the power generation of the fuel cell stack 1.

According to the fuel cell system performing such an operation, the dynamic pressure can be further increased by gradually increasing the hydrogen gas pressure, and the drainage at the anode can be performed more efficiently. You can

[Second Operation Example] In the second operation example, after it is determined that the cell voltage is lower than the allowable lower limit value and the purge on-off valve 6 is changed from the closed state to the open state, the purge on-off valve is opened within the purge open time. The valve 6 is periodically opened and closed.

That is, as shown in FIG. 8B, during the purge opening time from the time t11 to the time t12, the control unit 17 controls the time t11 to the time t1.
3, time t14 to time t15, time t16 to time t12
In the period of time, the purge on-off valve 6 is opened, and the time t13 is reached.
During the period from time t14 to time t15 to time t16, the purge on-off valve 6 is closed to periodically switch the purge on-off valve 6 between the open and closed states. The cycle for controlling the opening and closing of the purge on-off valve 6 in this way is determined by the operating conditions, the degree of recovery of the cell voltage, etc., and is controlled by the control unit 17.

By performing such an operation, as shown in FIG.
As shown in (a), the number of times the hydrogen gas pressure fluctuates can be increased. Therefore, according to this fuel cell system, the number of times the dynamic pressure of the hydrogen gas pressure is generated can be increased, and the drainage at the anode can be performed more efficiently.

According to this fuel cell system, the purge on-off valve 6 is periodically opened and closed after the process of step S4 to increase the dynamic pressure and increase the number of times the dynamic pressure is generated. Even if the total amount of hydrogen gas discharged from the purge opening / closing valve 6 during the purge opening time is small, the drainage can be efficiently performed.

In this second operation example, step S4
In the above, the case where the hydrogen gas pressure is increased has been described. However, even when the opening / closing valve 6 for purge is controlled to open / close without increasing the hydrogen gas pressure, the number of times the dynamic pressure of the hydrogen gas pressure is generated is increased. Therefore, drainage at the anode can be efficiently performed.

[Third Operation Example] In the third operation example, the hydrogen gas pressure is increased and the air pressure is also increased in step S4 so that the differential pressure between the anode electrode and the cathode electrode is set to a specified value or less. Further, the air flow rate is increased so as to maintain the air flow rate before increasing the air pressure of the cathode electrode.

That is, as shown in FIG. 9, in response to the decrease in cell voltage (FIG. 9A), the hydrogen gas pressure and hydrogen gas flow rate are increased in step S4 (FIGS. 9C and 9C). b)), the air supply flow rate is increased by increasing the air pressure (FIG. 9E) (FIG. 9E).
(F)). After that, the purge on-off valve 6 is opened to generate the dynamic pressure of the hydrogen gas pressure (FIG. 9D). At this time, the control unit 17 controls the air pressure regulating valve 8 so as to raise the air pressure by referring to the sensor signal from the air pressure sensor 14, and the compressor 7 while referring to the sensor signal from the air flow rate sensor 15. The air flow rate is increased by controlling the value to obtain the target air flow rate.

By performing such an operation, if the air flow rate when the air pressure is increased without changing the power generation output from the fuel cell stack 1 is constant, the air flow rate is increased by the increase in the air pressure. It is possible to prevent the drainage efficiency from decreasing due to the decrease in the air velocity at the cathode. Therefore, according to this fuel cell system, it is possible to maintain the air flow velocity and maintain the drainage efficiency even when the air pressure is increased.

The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and other than this embodiment, as long as it does not deviate from the technical idea of the present invention, various types according to the design etc. Of course, it is possible to change.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a fuel cell system according to a first embodiment to which the present invention is applied.

FIG. 2 is a diagram for explaining a change in hydrogen gas pressure when a purge on-off valve is changed from a closed state to an open state and then closed after a purging period. FIG. 3B shows the change over time in the open / closed state of the purge on-off valve.

FIG. 3 is a flowchart showing an operation procedure of water discharge processing by the fuel cell system according to the first embodiment to which the present invention is applied.

FIG. 4 is a diagram showing a relationship among a cell voltage, a hydrogen gas flow rate, a hydrogen gas pressure, and an open / closed state of a purge on-off valve when a water discharge process is performed, and (a) shows a time change of the cell voltage, (B) shows the time change of the hydrogen gas flow rate, (c)
Shows a change in hydrogen gas pressure, and (d) shows a time change in the open / closed state of the purge on-off valve.

FIG. 5 is a block diagram showing a configuration of a fuel cell system according to a second embodiment to which the present invention is applied.

FIG. 6 is a flowchart showing an operation procedure of water discharge processing by the fuel cell system according to the second embodiment to which the present invention is applied.

FIG. 7 is a flowchart showing a processing procedure in a first operation example of the fuel cell system to which the present invention is applied.

FIG. 8 is a diagram for explaining a second operation example of the fuel cell system to which the present invention is applied, (a) shows a time change of hydrogen gas pressure, and (b) shows an open / closed state of a purge on-off valve. Shows the change over time.

9A and 9B are views for explaining a third operation example of the fuel cell system to which the present invention is applied, in which FIG. 9A shows a time change of the cell voltage, and FIG. 9B shows a time change of the hydrogen gas flow rate. ,
(C) shows the change of hydrogen gas pressure, (d) shows the time change of the opening and closing state of the purge on-off valve, (e) shows the time change of the air pressure, (f) shows the time change of the air flow rate. Show.

[Explanation of symbols]

1 Fuel cell stack 2 hydrogen tank 3 Hydrogen gas supply pressure regulating valve 4 Hydrogen circulation device 5 humidifier 6 Purge on-off valve 7 compressor 8 Air pressure regulator 9 water tank 10 water pump 11 radiator 12 radiator fan 13 Hydrogen gas pressure sensor 14 Air pressure sensor 15 Air flow rate sensor 16 cell voltage sensor 17 Control unit L1 hydrogen gas supply channel L2 hydrogen gas circulation channel L3 air supply channel L4 air exhaust flow path L5 water circulation channel

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H026 AA06 HH06 HH09                 5H027 AA06 BA13 BA19 DD00 KK05                       KK22 KK54 MM08                 5H115 PA12 PC06 PG04 PI18 PU01                       SE06 TI05

Claims (6)

[Claims] 1. A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side and a fuel is supplied to the fuel electrode side. A fuel cell that is supplied with gas to generate power; and a gas supply unit that supplies an oxidant gas and a fuel gas to the fuel cell,
A fuel cell having a fuel circulation passage that passes through a fuel gas outlet and a fuel gas inlet of the fuel cell, and a purge valve that is provided in the fuel circulation passage and discharges a part of the gas in the fuel circulation passage to the outside. In the control device of the fuel cell system for controlling the system, when it is determined that the cell voltage of the fuel cell is lower than a predetermined value, the purge valve is turned on after controlling the gas supply means so as to increase the fuel gas pressure. A fuel cell system characterized by performing control from a closed state to an open state, and performing control from the open state to the closed state when it is determined that the cell voltage of the fuel cell is higher than a predetermined value. Control device. 2. A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side and a fuel is supplied to the fuel electrode side. A fuel cell that is supplied with gas to generate power; and a gas supply unit that supplies an oxidant gas and a fuel gas to the fuel cell,
A fuel cell having a fuel circulation passage that passes through a fuel gas outlet and a fuel gas inlet of the fuel cell, and a purge valve that is provided in the fuel circulation passage and discharges a part of the gas in the fuel circulation passage to the outside. In the control device of the fuel cell system for controlling the system, when it is determined that the cell voltage of the fuel cell is smaller than a predetermined value, the purge valve is cyclically controlled to open and close, and the cell voltage of the fuel cell is a predetermined value. A control device for a fuel cell system, which controls to close the purge valve when it is determined to be larger than the above. 3. A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side and a fuel is supplied to the fuel electrode side. A fuel cell that is supplied with gas to generate power; and a gas supply unit that supplies an oxidant gas and a fuel gas to the fuel cell,
A fuel cell having a fuel circulation passage that passes through a fuel gas outlet and a fuel gas inlet of the fuel cell, and a purge valve that is provided in the fuel circulation passage and discharges a part of the gas in the fuel circulation passage to the outside. In the control device of the fuel cell system for controlling the system, when it is determined that the cell voltage of the fuel cell is lower than a predetermined value, the purge valve is turned on after controlling the gas supply means so as to increase the fuel gas pressure. A control device for a fuel cell system, characterized in that opening / closing control is periodically performed, and control is performed to close the purge valve when it is determined that the cell voltage of the fuel cell is higher than a predetermined value. 4. The fuel cell system has a plurality of purge valves in the fuel circulation path, and opens at least one purge valve when it is determined that the cell voltage of the fuel cell is lower than a predetermined value. If the cell voltage of the fuel cell is determined to be lower than a predetermined value after a lapse of a predetermined period after the one purge valve is opened, the other purge valve is controlled to be opened. The fuel according to any one of claims 1 to 3, wherein when the cell voltage of the fuel cell is determined to be higher than a predetermined value, the open purge valve is controlled to be closed. Battery system controller. 5. The gas supply means is controlled to increase the fuel gas pressure stepwise when it is determined that the cell voltage of the fuel cell is lower than a predetermined value. The control device for the fuel cell system according to claim 3. 6. When the cell voltage of the fuel cell is determined to be lower than a predetermined value, the fuel gas pressure is increased and the gas supply means is arranged to maintain the oxidant gas flow rate at the oxidant electrode. It controls, The control apparatus of the fuel cell system of Claim 1, Claim 3, or Claim 5 characterized by the above-mentioned.