JP2008078101A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which can control to reduce hydrogen gas exhaust and can exhaust impurities inside a fuel cell. <P>SOLUTION: The fuel cell system is provided with a fuel cell 10, a tube passage 18 to exhaust an anode gas of the fuel cell and a large flow volume valve 24 which is provided with the tube passage 18 and exhausts the anode gas at a first flow volume to raise a pressure change inside the fuel cell 10, a small flow volume valve 32 which is provided with the tube passage 18 and exhausts anode gas at a second flow volume smaller than the first flow volume and a switching means to switch between the large flow volume valve 24 and the small flow volume valve 32. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system suitable for mounting on a vehicle.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-243477, a fuel cell system of a type in which an anode gas is kept inside has been disclosed. The main component of the anode gas is hydrogen gas. During the operation of the fuel cell, cathode gas and anode gas are supplied, and water is generated on the cathode side as the battery generates power. A part of the water on the cathode side penetrates to the anode side. Furthermore, part of the gas such as nitrogen contained in the cathode gas penetrates into the anode side of the fuel cell. In the fuel cell system of the type in which the anode gas is kept inside, impurities such as water and nitrogen tend to accumulate on the anode side of the fuel cell as the operating time of the fuel cell elapses. When there are many impurities inside the fuel cell, the operation of the battery is hindered, and the performance of the battery is degraded. Therefore, in the above conventional technique, when the impurity concentration inside the fuel cell is increased, the anode gas containing impurities of the fuel cell is temporarily discharged.

JP 2005-243477 A

  However, since the anode gas contains hydrogen gas, the anode gas cannot be discharged in a large amount. Therefore, in the conventional fuel cell system, there is a possibility that impurities remain inside the fuel cell.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a fuel cell system that easily discharges impurities inside the fuel cell while suppressing the discharge of hydrogen gas to a small extent. .

  In order to achieve the above object, a first invention is a fuel cell system, comprising a fuel cell, a conduit for discharging anode gas of the fuel cell, the conduit, and a pressure inside the fuel cell. A first flow means for discharging the anode gas at a first flow rate causing fluctuations; a second flow means for discharging the anode gas at a second flow rate less than the first flow rate provided in the conduit; And switching means for switching between the first distribution means and the second distribution means.

  According to a second aspect of the present invention, in the first aspect of the present invention, the first valve includes a first valve that circulates gas at the first flow rate, and a second valve that circulates gas at the second flow rate. A second valve is included, and the second flow means includes a second valve.

  According to a third aspect of the present invention, in the first aspect of the invention, the first valve includes a first valve that circulates the gas at the first flow rate, and the first flow means is a means for continuously flowing the first valve and the first valve. The second circulation means includes means for intermittently circulating the first valve and the first valve.

  A fourth invention is the fuel cell system according to any one of the first to third inventions, wherein the first flow rate is a pressure that gives initial action to liquid impurities inside the fuel cell. It is characterized by a flow rate that causes fluctuations.

  A fifth invention is the fuel cell system according to any one of the first to fourth inventions, wherein the second flow rate causes mainly gaseous impurities inside the fuel cell to be discharged. It is a flow rate.

  6th invention is a fuel cell system as described in any one of 1-5, Comprising: The electric power generation detection means which detects the electric power generation of the said fuel cell is further provided, The said switching means is the electric power generation of the said fuel cell. Switching to the first distribution means when an increase is detected.

  A seventh invention is the fuel cell system according to any one of the first to sixth aspects, further comprising activation detection means for detecting activation of the fuel cell, wherein the switching means is activation of the fuel cell. Switching to the first distribution means when it is detected.

  According to the first aspect of the invention, pressure fluctuation is given to the inside of the fuel cell, and impurities are easily discharged. And even if it switches to discharge | emission by the 2nd flow rate smaller than a 1st flow rate, the impurity inside a fuel cell can fully be discharged | emitted. Furthermore, since the second flow rate is discharged at a flow rate lower than the first flow rate, the discharge of hydrogen gas can be suppressed. Therefore, according to the present invention, it is possible to appropriately discharge impurities inside the fuel cell while suppressing the discharge of hydrogen gas to a small amount.

  According to the second aspect of the invention, the first valve performs discharge that causes a pressure fluctuation. Then, the second valve discharges impurities while suppressing the outflow of the anode gas.

  According to the third invention, the first valve is continuously circulated to discharge at the first flow rate. Furthermore, by discharging the first valve intermittently, discharging at the second flow rate is performed. In the present invention, discharge at the first flow rate and the second flow rate can be performed using a single valve.

  According to the fourth aspect of the invention, the discharge at the first flow rate gives an initial action to the liquid impurities inside the fuel cell. Since liquid impurities are likely to stay inside the fuel cell, the cell performance of the fuel cell tends to be hindered. Therefore, according to the present invention, the liquid impurities can be easily discharged by discharging the liquid impurities at a flow rate that gives an initial motion to the liquid impurities. Furthermore, the liquid impurities given the initial motion can be sufficiently discharged even when discharged at the second flow rate. Therefore, according to the present invention, more impurities inside the fuel cell can be discharged.

  According to the fifth invention, the second flow rate is a flow rate for discharging mainly gaseous impurities inside the fuel cell. By discharging gaseous impurities at the second flow rate, impurities inside the fuel cell can be reduced.

  According to the sixth aspect of the invention, when the power generation amount of the fuel cell increases, the anode gas is discharged, pressure fluctuation is given to the inside of the fuel cell, and impurities are easily discharged. When the amount of power generated by the fuel cell increases, it is particularly required to improve the performance of the fuel cell. At this time, according to the present invention, when an increase in the power generation amount of the fuel cell is detected, impurities are effectively discharged, and the cell performance of the fuel cell can be improved.

  According to the seventh aspect of the invention, when starting the fuel cell, the anode gas is discharged, pressure fluctuation is given to the inside of the fuel cell, and impurities are easily discharged. When starting the fuel cell, impurities are likely to accumulate inside the fuel cell. According to the present invention, the cell performance of the fuel cell can be improved by discharging impurities when the fuel cell is started.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of a fuel cell system according to Embodiment 1 of the present invention. The fuel cell system of Embodiment 1 includes a fuel cell 10. The fuel cell 10 includes a conduit 12 that supplies a cathode gas and a conduit 14 that discharges the cathode gas. The fuel cell 10 includes a conduit 16 for supplying anode gas and a conduit 18 for discharging the anode gas from the fuel cell to the outside. The fuel cell 10 includes a current sensor 19. The current sensor 19 measures the current of the fuel cell 10. The current sensor 19 is connected to the ECU 22, and the current measured by the current sensor 19 is transmitted to the ECU 22.

  A pressure sensor 20 is provided in the pipe line 18 from the fuel cell 10 to the outside. The pressure sensor 20 measures the pressure of the gas in the pipe line 18. The pressure sensor 20 is connected to the ECU 22, and the pressure measured by the pressure sensor 20 is transmitted to the ECU 22. A pipeline 18 from the fuel cell to the outside is connected to a pipeline 28 to the outside of the fuel cell system via a large flow valve 24. The large flow rate valve 24 allows the gas to flow from the pipe line 18 for discharging the anode gas from the fuel cell to the outside to the pipe line 28 to the outside of the fuel cell system. The large flow rate valve 24 is connected to the ECU 22 and can be opened and closed in accordance with a signal from the ECU 22. Further, a conduit 30 is provided so as to connect the conduit 18 and the conduit 28 to the outside of the fuel cell system. The conduit 30 is provided with a small flow valve 32. The small flow rate valve 32 circulates gas in the pipe line 30. The small flow valve 32 is connected to the ECU 22 and can be opened and closed in accordance with a signal from the ECU.

[Operation of the first embodiment]
During the operation of the fuel cell 10, air is supplied as the cathode gas from the conduit 12, and hydrogen gas is supplied as the anode gas from the conduit 16 to the fuel cell 10. In the fuel cell 10, a power generation reaction is performed with the supply of the cathode gas and the anode gas. With this power generation reaction, water is generated on the cathode side of the fuel cell 10. A part of the water generated on the cathode side moves to the anode side and stays mainly as liquid impurities. Further, a part of the air as the cathode gas permeates from the cathode side to the anode side and stays as a gaseous impurity. Further, hydrogen gas that has not been used for the power generation reaction is present on the anode side of the fuel cell 10. Therefore, anode gas containing impurities such as water and nitrogen and hydrogen gas exists on the anode side of the fuel cell 10.

  Gaseous impurities present in the anode gas can be discharged outside the fuel cell 10 by discharging a small amount of the anode gas from the fuel cell 10, for example. However, liquid impurities remain inside the fuel cell 10 when the anode gas flow is small. Therefore, liquid impurities cannot be discharged well with a small amount of discharge. Therefore, the following operation is performed to appropriately remove impurities in the anode gas regardless of liquid or gas.

  FIG. 2 is a diagram for explaining characteristic operations performed in the first embodiment. FIG. 2A shows the change over time of the flow rate of hydrogen discharged from the fuel cell 10. FIG. 2 (B) shows the time change of the gas pressure measured by the pressure sensor 20. FIG. 2C shows the change over time in the flow rate of gas flowing through the large flow rate valve 24. FIG. 2D shows a change over time in the flow rate of the gas flowing through the small flow rate valve 32.

  From time t1 to time t2, the large flow valve 24 is opened and the small flow valve 32 is closed. When the large flow valve 24 is opened, the gas existing near the pipe 18 is discharged outside the fuel cell system. Here, the flow rate of the gas flowing through the large flow rate valve 24 per unit time at this time is defined as the first flow rate. At this time, as shown in FIG. 2 (B), the pressure of the gas in the pipe line 18 rapidly decreases. When the pressure in the pipe line 18 rapidly decreases, a large pressure fluctuation occurs in the fuel cell 10. At this time, since the fuel cell 10 continues to receive the supply of the anode gas, a rapid flow of the anode gas occurs inside the fuel cell 10. Due to the flow of the anode gas, liquid impurities staying in the fuel cell 10 cause an initial movement. The liquid impurities that cause the initial movement easily move inside the fuel cell 10. Therefore, liquid impurities are discharged to the outside of the fuel cell system with the flow of the discharged anode gas. At this time, gaseous impurities present in the fuel cell 10 are discharged to the outside of the fuel cell system along with the flow of the discharged anode gas.

  After time t2, the large flow valve 24 is closed and the small flow valve 32 is opened. When the small flow valve 32 is opened, the anode gas inside the fuel cell 10 is discharged outside the fuel cell system at a second flow rate per unit time. The second flow rate is a smaller flow rate than the first flow rate. The liquid impurities that have been initially moved by the discharge from the large flow valve 24 are discharged to the outside of the fuel cell 10 even when the small flow valve 32 is discharged. During the opening of the small flow rate valve 32, the gaseous impurities inside the fuel cell 10 are also sufficiently discharged. Further, since the discharge at the second flow rate is small, the amount of hydrogen gas discharged outside the fuel cell system can be reduced.

[Effect of Embodiment 1]
As described above, the liquid impurities inside the fuel cell 10 cause an initial movement when discharged by the large flow valve 24. The liquid impurities that cause the initial movement easily move inside the fuel cell 10. Therefore, even when switching from the large flow valve 24 to the small flow valve 32, the liquid impurities can be sufficiently discharged.

  As described above, the small flow rate valve 32 discharges at a sufficiently small flow rate. While the small flow valve 32 is opened, gaseous impurities continue to be discharged. At this time. Hydrogen gas discharged outside the fuel cell system is sufficiently small. Therefore, if the small flow rate valve 32 is kept open, impurities inside the fuel cell 10 can be reduced while suppressing the discharge of hydrogen gas.

  The first flow rate is a flow rate that gives a pressure fluctuation for causing an initial motion to liquid impurities inside the fuel cell 10. In the case of a general fuel cell, the first flow rate is about 200 L / min. The second flow rate is a flow rate that is sufficiently small and discharges mainly gaseous impurities remaining inside the fuel cell 10 to the outside of the fuel cell system. In the case of a general fuel cell, the second flow rate is about 1 / 100-1 / 10 of the first flow rate.

[Specific processing of the first embodiment]
FIG. 3 is a flowchart showing processing in ECU 22 of the first embodiment. The flowchart of FIG. 3 is executed when the operation of the fuel cell is started. First, the small flow valve 32 is closed (step 100). Here, the small flow rate valve 32 is closed to stop the gas discharge at the second flow rate. Subsequently, the large flow rate valve 24 is opened to discharge at the first flow rate (step 102). Here, the first flow rate is a flow rate that makes it easy to discharge liquid impurities by initial movement.

  Then, the pressure P measured by the pressure sensor 20 is read (step 104). The pressure sensor 20 measures the pressure of the gas in the pipe line 18 from the fuel cell 10 to the outside. Here, the ECU 22 acquires the pressure P in the pipe line 18 measured by the pressure sensor 20. Then, the pressure P is compared with a preset reference value (step 106). If sufficient pressure fluctuation is given to the inside of the fuel cell 10, the liquid impurity can be easily discharged by giving the initial action to the liquid impurity. Here, if the pressure at the pressure sensor 20 provided on the downstream side of the fuel cell 10 fluctuates, it is considered that the pressure variation has occurred in the fuel cell 10. When the pressure P is equal to or higher than the reference value, the large flow rate valve 24 is kept open because sufficient pressure fluctuation is not given to the inside of the fuel cell 10. When the pressure P becomes smaller than the reference value, it is considered that sufficient pressure fluctuation has been given inside the fuel cell 10, and the large flow valve 24 is closed (step 108). Here, the large flow rate valve 24 is closed immediately after the pressure decreases, but processing may be performed so that the large flow rate valve 24 is opened for a certain period of time after the pressure becomes smaller than the reference value. .

  Next, the small flow rate valve 32 is opened, and discharge at the second flow rate is started (step 110). At this time, since the liquid impurities are initially given, the gaseous impurities are discharged together with the liquid impurities. Furthermore, hydrogen gas emissions are kept low enough. It is compared whether or not the opening time T at the small flow rate valve 32 becomes time T2 (step 112). If the opening time T at the small flow valve 32 is shorter than the time T2, the small flow valve 32 is kept open. When the open time T at the small flow rate valve 32 becomes equal to or longer than the time T2, it is determined whether or not the operation of the fuel cell 10 is finished (step 113). If the operation of the fuel cell 10 is not finished, the process returns to step 100 and the subsequent processing is executed in order to discharge impurities with the operation of the fuel cell 10. As a result, liquid impurities that could not be discharged at the flow rate of the small flow rate valve 32 are given initial action by the discharge at the large flow rate valve 24 and are easily discharged. When the operation of the fuel cell 10 is finished, this routine is finished.

  By periodically performing the above specific processing, the measured value of the pressure sensor 20 is compared with a reference value, and the large flow valve 24 is closed based on the comparison result, so that the time during which the large flow valve 24 is open is set appropriately. Can be adjusted to. Therefore, the large flow rate valve 24 can be discharged in an amount that is not excessive and insufficient, and unnecessary hydrogen gas discharge at the large flow rate valve 24 can be suppressed.

  In the case of a general fuel cell, the time T2 during which the small flow rate valve 32 is open may be in the range of 10 minutes to 1 hour, more preferably about 30 minutes.

  The reference value used in step 106 is a preset reference value, but is not limited to this. As an example, a reference value may be set from a change in past pressure measured by the pressure sensor 20.

[Modified Example 1 of Specific Processing in Embodiment 1]
FIG. 4 is a flowchart showing a modification of the specific process of the first embodiment. The flowchart of FIG. 4 is the same as the flowchart of FIG. 3 except that step 104 and step 106 are replaced by step 114. 4, the same parts as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the routine shown in FIG. 4, following step 102, it is compared whether or not the opening time T ′ of the large flow rate valve 24 is equal to time T1 (step 114). The time T1 is a preset time, and is a time for performing a discharge that gives a sufficient initial motion to liquid impurities while suppressing the discharge of hydrogen gas. In step 114, when the opening time T ′ is less than the time T1, it is determined that sufficient initial movement is not given to the liquid impurities, and the large flow rate valve 24 is kept open. When the opening time T ′ is equal to or longer than the time T1, it is determined that sufficient initial movement is given to the liquid impurities, and the large flow rate valve 24 is closed. Therefore, when the routine shown in FIG. 4 is performed, the impurities in the fuel cell 10 can be sufficiently discharged and the discharge of hydrogen gas can be suppressed without providing the pressure sensor 20 in the configuration of the first embodiment. The open time T1 of the large flow rate valve is preferably about 1 second in the case of a general fuel cell.

[Modification Example 2 of Specific Processing of Embodiment 1]
FIG. 5 is a flowchart showing a modification of the specific process of the first embodiment. The flowchart in FIG. 5 is the same as the flowchart in FIG. 3 except that step 112 is replaced with step 116. 5, the same parts as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the routine shown in FIG. 5, following step 110, it is determined whether or not there are many impurities inside the fuel cell 10 (step 116). Here, the impurity is measured by measuring the output current I from the current sensor 19. When there are many impurities inside the fuel cell 10, the power generation performance of the fuel cell is hindered. At this time, the power generation amount is constant depending on the load, the voltage is small, and the output current I is large. From the change in the output current I, it is possible to estimate the amount of impurities. In step 116, more specifically, it is determined whether or not the output current I is larger than a preset reference value. In step 116, if the output current I is not larger than the reference value, it can be determined that there are not many impurities. At this time, the small flow rate valve 32 is kept open. In step 116, if the output current I is larger than the reference value, it is determined that there are many impurities. At this time, returning to step 100, the small flow valve 32 is closed and the large flow valve 24 is opened to discharge more impurities. With the above processing, the discharge start timing of the large flow rate valve 24 can be appropriately adjusted.

  In step 116, the determination of whether or not there is a large amount of impurities inside the fuel cell 10 is performed using the measurement of the output current I, but is not limited to this. For example, the amount of impurities may be determined by measuring the electromotive force or impedance of the fuel cell 10. When the fuel cell has a cell stack structure, the amount of impurities may be determined from the electromotive force, output current I, and impedance distribution for each cell. Furthermore, it may be performed by using the electromotive force for each cell, the output current I, and the distribution of changes in impedance over time. Alternatively, the measurement may be performed by measuring the concentration of the impurity itself.

  The fuel cell system according to Embodiment 1 is a fuel cell system that continuously discharges the anode gas little by little. However, the system targeted by the present invention is not limited to this as long as the fuel cell does not circulate the anode gas. For example, it may be used for a fuel cell system in which anode gas is kept inside. The specific operation of the present invention at this time is performed by switching between discharge at the first flow rate, discharge at the second flow rate, and no discharge. More specifically, after the discharge at the second flow rate is stopped and no discharge is performed for a certain period, the discharge at the first flow rate is performed. When the anode gas is not discharged, the pressure inside the fuel cell 10 is higher than when the anode gas is discharged. By providing the non-discharge period, the pressure inside the fuel cell 10 can be increased. Therefore, many pressure fluctuations can be given to the inside of the fuel cell 10 by discharging at the first flow rate after the non-discharge period.

  In the first embodiment, a fuel cell using hydrogen gas and air gas as fuel is used as the fuel cell, but the present invention is not limited to this. For example, a direct methanol fuel cell can be used as the fuel cell. At this time, a methanol solution is used as the anode gas, and air (oxygen gas) is used as the cathode gas.

  In the present embodiment, hydrogen gas corresponds to the fuel component of the anode gas. For example, when a methanol direct fuel cell is used as the fuel cell, methanol is a fuel component of the anode gas.

Embodiment 2. FIG.
FIG. 6 is a diagram for explaining the configuration of the fuel cell system according to the second embodiment. The configuration of the fuel cell system according to Embodiment 2 in FIG. 6 is the same as that in FIG. 1 except for the downstream side of the pipe 18. In FIG. 6, the same parts as those in FIG.

  The pipe line 18 from the fuel cell 10 to the outside includes a large flow rate valve 24. The large flow rate valve 24 is connected to a variable flow rate adjustment valve 34 via a pipe line 33. The variable flow rate control valve 34 is connected to a pipe line 28 to the outside of the fuel cell system. The variable flow rate adjusting valve 34 adjusts the flow rate of the gas flowing between the pipe line 33 and the pipe line 28 to the outside of the fuel cell system to a predetermined flow rate. The variable flow rate adjustment valve 34 is connected to the ECU 22. The variable flow rate adjustment valve 34 can change the gas flow rate in accordance with a signal from the ECU 22.

  FIG. 7 is a diagram showing a flow for explaining the specific processing of the second embodiment. The specific processing of the second embodiment is the same as that in FIG. 3 except that steps 100 and 102 are replaced with step 118 and steps 108 and 110 are replaced with step 120. In step 118, the large flow rate valve 24 is opened, the gas flow rate at the variable flow rate adjustment valve 34 is set to the first flow rate, and the discharge is performed at the first flow rate. At this time, the initial movement is given to the liquid impurities in the fuel cell 10 by the discharge at the first flow rate. In step 120, the large flow rate valve 24 is opened, the gas flow rate at the variable flow rate adjustment valve 34 is set as the second flow rate, and the discharge is performed at the second flow rate. At this time, from the discharge at the second flow rate, the gaseous impurities are discharged together with the liquid impurities given the initial movement. By adjusting the gas flow rate at the variable flow rate adjustment valve 34 by the above specific processing, impurities inside the fuel cell 10 can be effectively discharged.

  FIG. 8 is a diagram for explaining characteristic operations performed in the second embodiment. FIG. 8A shows the change over time in the flow rate of hydrogen discharged from the fuel cell 10. FIG. 8B shows the time change of the gas pressure measured by the pressure sensor 20. FIG. 8C shows the change over time in the flow rate of the gas flowing through the variable flow rate adjustment valve 34. First, from time t1 to time t2, the gas flow rate flowing through the variable flow rate control valve 34 is the first flow rate, and the anode gas is discharged at the first flow rate. At this time, the pressure inside the fuel cell 10 rapidly decreases and a pressure fluctuation occurs inside the fuel cell 10. From time 0 to time t1 and after time t2, the gas flow rate at the variable flow rate adjustment valve 34 is the second flow rate. At this time, the fuel cell 10 is discharged at the second flow rate. At this time, the gaseous impurities are discharged together with the liquid impurities given the initial action.

  In the system of the second embodiment, when the large flow rate valve 24 provided in the pipe line 18 from the fuel cell to the outside is closed, the anode gas is not discharged from the fuel cell 10 to the outside. However, the configuration of the present invention is not limited to this, and the large flow valve 24 may not be provided when the anode gas does not need to be discharged.

Embodiment 3 FIG.
A fuel cell system according to Embodiment 3 will be described. The fuel cell system of the third embodiment is the same as the fuel cell system of the first embodiment except that the small flow valve 32 and the pipe line 30 are not provided. In the third embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the third embodiment, when the large flow rate valve 24 is continuously opened, the discharge at the first flow rate is performed. Then, when the large flow rate valve 24 is opened intermittently, the discharge at the second flow rate is performed, and the discharge with reduced hydrogen gas discharge is realized. From these, it is possible to discharge at the first and second flow rates using a single valve to discharge impurities.

  FIG. 9 is a diagram illustrating a flow for explaining specific processing of the third embodiment. The specific processing of the third embodiment is the same as that of FIG. 3 except that steps 100 and 102 are replaced with step 122 and steps 108 and 110 are replaced with step 124. In the present embodiment, the large flow rate valve 24 is continuously opened to discharge at the first flow rate (step 122). At this time, the liquid impurities inside the fuel cell 10 are subjected to pressure fluctuations to cause initial movement. When occurrence of pressure fluctuation is recognized in step 106, the large flow rate valve 24 is intermittently opened to discharge at the second flow rate per unit time (step 124). Here, the large flow valve 24 is repeatedly opened and closed for a short time. When the large flow valve 24 is open, the discharge at the first flow rate is performed. Therefore, when the large flow rate valve 24 is repeatedly opened and closed at a predetermined rate, the discharge at the second flow rate is realized on an average per unit time.

  FIG. 10 is a diagram for explaining the characteristic operation of the third embodiment. When the large flow rate valve 24 is continuously opened from the time t1 to the time t2, the fuel cell 10 is discharged at the first flow rate per unit time. From time 0 to time t1 and after time t2, the large flow valve 24 is intermittently opened to discharge the anode gas at the second flow rate.

Embodiment 4 FIG.
A fuel cell system according to Embodiment 4 will be described. The configuration of the fourth embodiment is the same as that of FIG. FIG. 11 is a flowchart for explaining specific processing of the fourth embodiment. In the flowchart of FIG. 11, the same parts as those in FIGS. The flowchart shown in FIG. 11 can be used simultaneously with the flowcharts shown in the first to third embodiments. First, the output current I is read (step 126). Here, the output current I measured by the current sensor 19 is acquired. Next, it is compared whether or not the differential value of the output current I is larger than a reference value (step 128). Here, a predetermined value set in advance is used as the reference value. During the operation of the fuel cell system, the power generation amount may increase rapidly. At this time, in order to cope with an increase in the amount of power generation, it is necessary to improve the battery performance. When the impurities inside the fuel cell 10 are reduced, the cell performance is increased accordingly. Therefore, if the differential value of the output current I is larger than the reference value, it is determined that the amount of power generation has increased abruptly, the large flow rate valve 24 is opened, and discharge is performed at the first flow rate for the time T1 (step). 102, 114). If the differential value of the output current I is smaller than the reference value, it is determined that the amount of power generation has not increased so much and normal operation is continued (step 130). Here, the normal operation is a flowchart (FIG. 3) of the first embodiment that is performed periodically. By periodically performing the above steps at predetermined intervals, impurities can be effectively discharged when the amount of power generation is rapidly increased, and battery performance can be improved.

  In step 114, the time during which the large flow rate valve 24 is open is time T1, but is not limited thereto. For example, the opening time of the large flow valve 24 may be a predetermined time longer than the opening time T1 in normal operation. At this time, if the large flow rate valve 24 is open for a long time, the amount of impurities to be discharged increases. If more impurities are discharged, the cell performance of the fuel cell 10 can be further improved. For example, the time during which the large flow valve 24 is open may be until the pressure measured by the pressure sensor 20 becomes sufficiently small. Further, the time during which the large flow rate valve 24 is open may be set to a certain time after a sufficient pressure fluctuation is applied.

  In step 130, the normal operation uses the specific process of the first embodiment, but the present invention is not limited to this. For example, the specific processing described in Embodiment 1-3 may be used. Regardless of this, any discharge that switches between the large flow valve 24 and the small flow valve 32 may be used.

  In the present embodiment, the determination of the increase in the amount of power generation is performed using the measurement of the output current I, but is not limited to this. Any device that can detect a change in the amount of power generation is acceptable. For example, an increase in the amount of power generation may be determined using measurement of electromotive force or measurement of the amount of power generation itself.

Embodiment 5. FIG.
A fuel cell system according to Embodiment 5 will be described. The configuration of the fifth embodiment is the same as that of FIG. FIG. 12 is a flowchart for explaining specific processing of the fifth embodiment. The flowchart of FIG. 12 is the same as the flowchart of FIG. 11 except that step 126 and step 127 are replaced with step 132. In the flowchart of FIG. 12, the same parts as those in FIG. 11 are denoted by the same reference numerals, and detailed description thereof is omitted. The flowchart shown in FIG. 12 can be used simultaneously with the flowcharts shown in the first to fourth embodiments. In the flowchart shown in FIG. 12, first, it is determined whether or not the fuel cell 10 is being started (step 132). Here, the temperature inside the battery at the time of startup of the fuel cell 10 is lower than that during the operation of the fuel cell 10. At this time, the water in the fuel cell 10 exists mainly as a liquid. Liquid water tends to stay inside the fuel cell 10. When there is much liquid water, battery performance will fall. More specifically, at step 132, the output current I from the current sensor 19 is acquired, and it is determined whether or not the output current I is rising. When it is determined that the output current is rising from the output 0, it is considered that the fuel cell 10 is activated. At this time, the large flow rate valve 24 is opened to discharge the gas at the first flow rate (step 102). If it is determined that the output current I is not rising, it is considered not when the fuel cell 10 is started, and normal operation is performed (step 130). Here, the normal operation is a flowchart (FIG. 3) of the first embodiment that is performed periodically. By periodically performing the above specific processing, impurities can be effectively discharged when the fuel cell 10 is started.

  In the present embodiment, detection at the time of startup of the fuel cell 10 is performed using measurement of the output current I. It is not restricted to this, What is necessary is just to be able to detect the start of the fuel cell 10. For example, the activation of the fuel cell 10 may be detected using measurement of the amount of power generation. In the case of an on-vehicle fuel cell, the start of the fuel cell may be detected using an ignition switch.

FIG. 1 is a diagram for explaining the configuration of a fuel cell system according to Embodiment 1 of the present invention. FIG. 2 is a diagram for explaining characteristic operations performed in the first embodiment. FIG. 3 is a flowchart showing processing in ECU 22 of the first embodiment. FIG. 4 is a flowchart showing a modification of the specific process of the first embodiment. FIG. 5 is a flowchart showing a modification of the specific process of the first embodiment. FIG. 6 is a diagram for explaining the configuration of the fuel cell system according to the second embodiment. FIG. 7 is a diagram showing a flow for explaining the specific processing of the second embodiment. FIG. 8 is a diagram for explaining characteristic operations performed in the second embodiment. FIG. 9 is a diagram illustrating a flow for explaining specific processing of the third embodiment. FIG. 10 is a diagram for explaining the characteristic operation of the third embodiment. FIG. 11 is a flowchart for explaining specific processing of the fourth embodiment. FIG. 12 is a flowchart for explaining specific processing of the fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 18 Pipe line 19 which discharges anode gas from a fuel cell to the outside 19 Current sensor 20 Pressure sensor 24 Large flow valve 32 Small flow valve

Claims (7)

A fuel cell;
A conduit for discharging the anode gas of the fuel cell;
First flow means provided in the pipe line and discharging anode gas at a first flow rate causing pressure fluctuation inside the fuel cell;
A second flow means provided in the conduit for discharging the anode gas at a second flow rate less than the first flow rate;
Switching means for switching between the first distribution means and the second distribution means;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
A first valve for flowing gas at the first flow rate;
A second valve for circulating gas at the second flow rate,
The first flow means includes a first valve;
The fuel cell system, wherein the second circulation means includes a second valve. The fuel cell system according to claim 1, wherein
Comprising a first valve for circulating gas at the first flow rate;
The first flow means includes means for continuously flowing the first valve and the first valve;
The fuel cell system, wherein the second circulation means includes means for intermittently circulating the first valve and the first valve. A fuel cell system according to any one of claims 1-3,
The fuel cell system according to claim 1, wherein the first flow rate is a flow rate causing a pressure fluctuation that causes an initial motion to liquid impurities inside the fuel cell. A fuel cell system according to any one of claims 1-4,
The fuel cell system characterized in that the second flow rate is a flow rate for discharging mainly gaseous impurities inside the fuel cell. The fuel cell system according to any one of claims 1 to 5, wherein
Further comprising power generation detection means for detecting power generation of the fuel cell,
The switching means includes switching to the first distribution means when an increase in power generation of the fuel cell is detected. The fuel cell system according to any one of claims 1 to 6, wherein
Further comprising activation detection means for detecting activation of the fuel cell;
The switching means includes switching to the first distribution means when detecting activation of the fuel cell.

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