JP5061464B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system that generates water during power generation.

  Solid polymer fuel cell (hereinafter also referred to as fuel cell) system has a problem that when water is more than necessary in the fuel cell or path when the system is stopped, the water freezes when exposed to freezing for a long time. . Therefore, in order to stably operate the fuel cell system even at a temperature below freezing point, it is necessary to discharge the water in the path of the fuel cell system when the fuel cell system is stopped. For this reason, in a fuel cell including a gas path in the circulation system, gas is circulated through a path including a gas-liquid separator (this is called scavenging) to reduce the amount of remaining water. However, if the scavenging time in the path of the fuel cell system becomes longer, the time required for stopping the fuel cell system becomes longer and the usability becomes worse. That is, since supply of scavenging and dilution air is relied on the pump, a long amount of scavenging consumes a large amount of power, and noise during driving of the pump becomes a problem. Furthermore, there is a problem in that the merchantability is impaired if it takes time to stop the fuel cell system after the ignition switch is turned off.

  In addition, protons (hydrogen ions) in the electrolyte membrane in the fuel cell move by water molecules. In the operation of the fuel cell, it is necessary to wet the electrolyte membrane of the fuel cell and the vicinity thereof in order to ensure proton mobility. Therefore, in order to smoothly start the fuel cell system and achieve a stable operation state even at a temperature below freezing point, a certain amount of moisture is required inside the fuel cell.

Patent Document 1 below discloses a technique for scavenging with a scavenging time corresponding to the operating state of the fuel cell. Patent Document 2 below discloses a technique for predicting a transition of the outside air temperature and performing a freeze prevention process when freezing is predicted. Patent Document 3 below discloses a technique for discharging water generated inside the fuel cell after power generation is stopped, and measures a specific state quantity that has a correlation with the amount of water inside the fuel cell. The technique which drains according to the state quantity is disclosed.
JP 2003-297399 A Japanese Patent Laid-Open No. 2004-22198 JP 2005-141943 A

  However, the above-mentioned conventional technology has a requirement that water remaining in the fuel cell system path and auxiliary machinery must be discharged as much as possible to prevent freezing, and a requirement to leave a certain amount of moisture inside the fuel cell. Are not compatible. An object of the present invention is to provide a technique for controlling the residual water in the fuel cell system to an appropriate amount with an appropriate scavenging time.

The present invention employs the following means in order to solve the above-described problems. That is, the present invention relates to a fuel cell main body, a gas supply passage for supplying gas to the fuel cell main body, a gas discharge passage for discharging gas from the fuel cell main body, and the gas discharge passage connected to the gas supply passage. A gas circulation passage, gas driving means for circulating the gas in the gas discharge passage through the gas circulation passage to the gas supply passage, a gas-liquid separator for separating moisture from the circulated gas, and a fuel cell body Means for calculating a residual water amount in the fuel cell system including the fuel cell main body, a gas supply passage, a gas discharge passage, and a gas circulation passage based on an operating state and an environmental state in which the fuel cell main body is operated; The gas driving means is operated to reduce the residual water amount to a predetermined value according to the separation performance of the gas-liquid separator and the state quantity of the gas when circulating. Calculation means for calculating the operating time is a fuel cell system and a control device for activating the gas sending apparatus until the end of the operation time.

  In the present invention, the remaining water amount in the fuel cell system is calculated from the operating state of the fuel cell main body and the environment in which the fuel cell main body is operated, and the separation performance of the gas-liquid separator and the state quantity of gas when circulating are calculated. Therefore, the operating time for operating the gas driving means is calculated. Then, the gas driving means is operated until the calculated operation time is finished. Thus, according to the present invention, the remaining water in the fuel cell system can be controlled to an appropriate amount by the appropriate scavenging time corresponding to the remaining water amount in the fuel cell system. That is, the remaining water in the passage of the fuel cell system can be scavenged, and an appropriate amount of moisture can be left inside the fuel cell body.

  In the fuel cell system, the state quantity of the gas to be circulated may include a gas circulation rate and a ratio of a moisture circulation rate to a gas circulation rate. In the present invention, based on the gas state quantity including the gas circulation rate and the ratio of the moisture circulation rate to the gas circulation rate, the remaining amount in the fuel cell system is determined by the appropriate scavenging time according to the remaining water amount in the fuel cell system. Water can be controlled to an appropriate amount.

  In the fuel cell system, when the operation time is equal to or greater than a predetermined threshold, the calculation unit operates the gas driving unit after the gas driving amount of the gas driving unit is increased by a predetermined value. The operation time may be newly calculated, and the control unit may increase the gas drive amount of the gas drive unit by a predetermined value and operate the gas drive unit until the end of the second operation time. In the present invention, when the operating time for operating the gas driving means is equal to or greater than a predetermined threshold, the operating time of the gas driving means can be shortened by increasing the gas driving amount of the gas driving means. Further, after shortening the operation time of the gas driving means, the remaining water in the fuel cell system can be controlled to an appropriate amount by an appropriate scavenging time corresponding to the remaining water amount in the fuel cell system.

  In the fuel cell system, when the operation time is equal to or greater than a predetermined threshold, the calculation unit newly sets a second operation time for operating the gas drive unit after pulsating the drive of the gas drive unit. And the control means may cause the gas driving means to pulsate and operate the gas driving means until the end of the second operating time. In the present invention, when the operating time for operating the gas driving means is equal to or greater than a predetermined threshold, the operating time of the gas driving means can be shortened by pulsating the gas driving means. Further, after shortening the operation time of the gas driving means, the remaining water in the fuel cell system can be controlled to an appropriate amount by an appropriate scavenging time corresponding to the remaining water amount in the fuel cell system.

  In the fuel cell system, when the gas driving unit is a pump and the operation time is equal to or greater than a predetermined threshold, the calculation unit increases the rotation speed of the pump by a predetermined value. A second operation time to be operated may be newly calculated, and the control unit may increase the rotation speed of the pump by a predetermined value and operate the pump until the end of the second operation time. In the present invention, when the operating time for operating the pump is equal to or greater than a predetermined threshold, the operating time of the pump can be shortened by increasing the rotational speed of the pump. Further, after shortening the pump operation time, the remaining water in the fuel cell system can be controlled to an appropriate amount by the appropriate scavenging time corresponding to the remaining water amount in the fuel cell system.

Further, the fuel cell system operates the pump after the calculation means increases the rotation speed of the pump by a predetermined value and pulsates the driving of the pump when the operation time is equal to or greater than a predetermined threshold. A second operating time is newly calculated, and the control means increases the rotational speed of the pump by a predetermined value and pulsates the driving of the pump to operate the pump until the end of the second operating time. May be. In the present invention, when the operating time for operating the pump is equal to or greater than a predetermined threshold, the pump operating time can be shortened by increasing the number of rotations of the pump and causing the pump to pulsate. Further, after shortening the pump operation time, the remaining water in the fuel cell system can be controlled to an appropriate amount by the appropriate scavenging time corresponding to the remaining water amount in the fuel cell system.

  According to the present invention, the remaining water in the fuel cell system can be scavenged with an appropriate scavenging time.

Hereinafter, a design apparatus according to the best mode (hereinafter referred to as an embodiment) for carrying out the present invention will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.
<First Embodiment>
A fuel cell system according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing a configuration example of a fuel cell system according to the first embodiment of the present invention. 1, the fuel cell system includes a fuel cell stack 1, an anode gas passage 2, an anode off gas passage 3, an anode off gas circulation passage 4, a cathode gas passage 5, a cathode off gas passage 6, a hydrogen tank 7, a hydrogen pump 8, and a pump 9. , Pressure control valves 10 and 11, filter 12, humidifier 13, gas-liquid separator 14, drain tank 15, drain valve 16, control unit 17, residual water amount calculation unit 18, and purge valve 19.

  The fuel cell stack 1 is configured by stacking a plurality of cells. Each cell includes an electrolyte membrane, an anode (fuel electrode), a cathode (air electrode), and a separator. Between the anode and the cathode, a flow path for hydrogen and air is formed.

  The anode gas passage 2 is a passage for supplying an anode gas containing hydrogen to the anode of the fuel cell stack 1. The cathode gas passage 5 is a passage for supplying cathode gas containing air to the cathode of the fuel cell stack 1.

  The hydrogen tank 7 supplies anode gas to the anode gas passage 2. The anode gas supplied from the hydrogen tank 7 is adjusted to a predetermined pressure by the pressure regulating valve 10. The anode gas is supplied from the anode gas passage 2 to the anode of the fuel cell stack 1.

  When the pump 9 (also referred to as an air compressor) is driven, the cathode gas supplied from outside the fuel cell system is supplied to the cathode of the fuel cell stack 1.

  In the anode of the fuel cell stack 1, when anode gas is supplied, hydrogen ions are generated from hydrogen contained in the anode gas. Further, oxygen contained in the air is supplied to the cathode of the fuel cell stack 1. In the fuel cell stack 1, an electrochemical reaction between hydrogen and oxygen occurs to generate electric energy. Further, at the cathode of the fuel cell stack 1, water is generated by combining hydrogen ions generated from hydrogen and oxygen.

  The humidifier 13 humidifies the air supplied to the fuel cell stack 1. In order for an electrochemical reaction to be appropriately performed in the fuel cell stack 1, the electrolyte membrane in the fuel cell stack 1 needs to be in a wet state containing moisture, and thus humidifies the air. In addition, the water in the electrolyte membrane is separated into fine clusters and is combined with sulfonic acid groups in the electrolyte membrane, so that the water in the electrolyte membrane hardly freezes.

  Of the anode gas supplied to the anode, a gas containing unreacted hydrogen and nitrogen permeating from the cathode (hereinafter referred to as anode off gas) is sent from the fuel cell stack 1 to the anode off gas passage 3.

  Further, unreacted gas (hereinafter referred to as cathode offgas) among the cathode gas supplied to the cathode is discharged from the fuel cell stack 1 to the cathode offgas passage 6. The cathode off gas discharged from the cathode passes through the cathode off gas passage 6 and is discharged out of the fuel cell system.

  The anode off gas discharged from the anode of the fuel cell stack 1 passes through the anode off gas passage 3 and the anode off gas circulation passage 4 and is supplied again to the anode of the fuel cell stack 1 together with the anode gas from the hydrogen tank 7. Therefore, the anode off gas passage 3 supplies the anode off gas discharged from the anode of the fuel cell stack 1 to the gas-liquid separator 14.

  The gas-liquid separator 14 separates water and hydrogen contained in the anode offgas discharged from the anode of the fuel cell stack 1. The hydrogen from which the water has been separated by the gas-liquid separator 14 is supplied to the anode gas passage 2 through the anode off-gas circulation passage 4 as the anode gas by the hydrogen pump 8. The anode off-gas circulation passage 4 is a passage for supplying the anode gas sent from the hydrogen pump 8 to the anode gas passage 2. The anode off gas circulation passage 4 constitutes a circulation path on the anode side.

  The drain tank 15 stores the water separated by the gas-liquid separator 14. By opening and closing the drain valve 16, the water stored in the drain tank 15 is discharged out of the circulation path. Further, the drain valve 16 is appropriately opened and closed so that the water stored in the drain tank 15 does not overflow.

  The control unit 17 is electrically connected to the hydrogen pump 8 and the drain valve 16 and controls the driving of the hydrogen pump 8 and the drain valve 16. The remaining water amount calculation unit 18 estimates the remaining water amount in the fuel cell system. The amount of remaining water in the fuel cell system is the amount of water present in the fuel cell stack 1, the anode gas passage 2, the anode offgas passage 3, the anode offgas circulation passage 4, the hydrogen pump 8, the gas-liquid separator 14, and the drain tank 15. The amount of water that affects freezing and dry-up of residual water in the fuel cell system.

  When impurities such as nitrogen increase in the anode off gas discharged from the anode, the purge valve 19 passes the anode off gas (and the anode gas circulated by the hydrogen pump 8) through a diluter (not shown) outside the circulation path. To discharge.

  FIG. 2 is a flowchart for explaining the operation of the fuel cell system according to the first embodiment of the present invention. The fuel cell system according to the first embodiment of the present invention executes the process of FIG. 2 when a power generation stop process is performed on the fuel cell system. For example, when the ignition switch is turned off, it is determined that there has been a command to stop the fuel cell system, and the process of FIG. 2 is performed.

  First, power generation stop processing of the fuel cell stack 1 is performed (S01). Specifically, a shut valve (not shown) provided in the hydrogen tank 7 is closed, and the supply of anode gas from the hydrogen tank 7 is shut off to stop power generation. In the fuel cell system according to the first embodiment of the present invention, anode gas and anode off gas are circulated in the fuel cell system in order to scavenge residual water in the fuel cell system. Even after the power generation stop processing of the fuel cell stack 1 is performed, the remaining water in the fuel cell system is scavenged by driving the hydrogen pump 8.

  Specifically, the control unit 17 controls driving of the hydrogen pump 8 to supply anode gas into the anode gas path 2 and the fuel cell stack 1. Then, water and hydrogen contained in the anode off-gas discharged from the anode of the fuel cell stack 1 are separated by the gas-liquid separator 14. And the control part 17 controls the drive of the drain valve 16, and discharges the isolate | separated water out of a circulation path. In the present embodiment, scavenging of the remaining water in the fuel cell system after the power generation stop of the fuel cell stack 1 is referred to as scavenging / circulation processing.

  Next, the remaining water amount calculation unit 18 estimates the remaining water amount in the fuel cell system when power generation is stopped from the state amount immediately before the power generation stop processing is performed (S02). For example, the remaining water amount calculation unit 18 calculates Qini as a process for estimating the remaining water amount in the fuel cell system when power generation is stopped. Qini is an estimated value of the remaining water amount in the fuel cell system at the time of power generation stop, which is obtained from the state quantity immediately before the power generation stop processing is performed.

  The state quantity includes impedance between the electrodes of the fuel cell stack 1 (membrane resistance), load integrated value (current integrated value), operation time, refrigerant temperature or amount of change in refrigerant temperature, outside air temperature, humidity, and the like.

  By measuring the impedance between the electrodes of the fuel cell stack 1, the wet state of the electrolyte membrane in the fuel cell stack 1 can be known. Impedance can be measured from the response when an alternating current of a certain frequency is applied from the high voltage electrical system between the electrodes of the fuel cell stack 1. As the impedance, the value immediately before the power generation stop processing is used. By always measuring the impedance until immediately before the power generation stop process, the impedance value immediately before the power generation stop process can be used.

  The load integrated value (current integrated value) is the total power generation amount, and the total amount of generated water in the fuel cell can be known by measuring the load integrated value.

  The operation time is the power generation time of the fuel cell system. In the case where the power generation of the fuel cell system is a short time and the case where the power generation of the fuel cell system is a long time, the temperature in the path is lower when the power generation of the fuel cell system is short even if the power generation amount is about the same. For this reason, in the case of short-time power generation, the amount of water that is liquid is larger than in the case of long-time power generation.

The amount of change in the coolant temperature or coolant temperature, relative change amount of how warmed much than the absolute value is important. When the temperature in the fuel cell stack 1 is high, the water in the fuel cell stack 1 becomes vapor and tends to go out of the fuel cell system. On the other hand, when the temperature in the fuel cell stack 1 is low, the water in the fuel cell stack 1 does not become vapor but tends to stay in the fuel cell system.

  Since the heat radiation from the fuel cell stack 1 varies depending on the outside air temperature, the outside air temperature affects the refrigerant temperature or the amount of change in the refrigerant temperature. Humidity also affects the refrigerant temperature or the amount of change in refrigerant temperature.

  As the state quantity, a state quantity within a predetermined time immediately after stopping power generation can be used. In addition, the remaining amount of water in the fuel cell system when power generation is stopped can be estimated by combining a plurality of the state quantities.

3 and 4 are diagrams showing examples of the relationship between the state quantity and the remaining water amount in the fuel cell system. In FIG. 3, when the load integrated value is small, the remaining water amount in the fuel cell system shows a small value, and when the load integrated value is large, the remaining water amount in the fuel cell system shows a large value. In FIG. 4, when the refrigerant temperature is high, the remaining water amount in the fuel cell system shows a small value, and when the refrigerant temperature is low, the remaining water amount in the fuel cell system shows a large value.

  Such an impedance (membrane resistance) between electrodes of the fuel cell stack 1, load integrated value (current integrated value), operation time, refrigerant temperature or refrigerant temperature change amount, outside air temperature, humidity and the like in the fuel cell system The relationship with the remaining water amount can be obtained as an empirical formula. Further, the impedance (membrane resistance) between the electrodes of the fuel cell stack 1, the load integrated value (current integrated value), the operation time, the refrigerant temperature or the change amount of the refrigerant temperature, the outside air temperature, the humidity, etc., and the remaining water amount in the fuel cell system It is also possible to obtain the relationship by mapping it and referencing the map (table). The remaining water amount calculation unit 18 calculates Qini according to this empirical formula or map. For example, among the state quantities, the impedance between the electrodes of the fuel cell stack 1 (membrane resistance), the load integrated value (current integrated value), the operation time, the refrigerant temperature or the amount of change in the refrigerant temperature, etc. are also called the operation history or the operation state. . In addition, among the state quantities, the outside air temperature, humidity, and the like are also referred to as a use environment or an operating environment.

  Further, the control unit 17 calculates a target remaining water amount Qreq (S03). The target remaining water amount Qreq is the remaining water amount in the fuel cell system that is necessary for the electrolyte membrane in the fuel cell stack 1 to be in a moderately wet state in operating the fuel cell system. This is the amount of residual water that can avoid water freezing. Accordingly, the target residual water amount Qreq is required to be an appropriate value in order to avoid freezing and dry-up of residual water in the fuel cell system.

  In addition, the target residual water amount Qreq depends on MEA (Mebrane Electrode Assembly) and components. Furthermore, the value of the target remaining water amount Qreq is a value at which the operating environment of the fuel cell system according to the present embodiment varies depending on the destination such as a cold region or a warm region.

  Next, the control unit 17 determines the following from the remaining water amount Q (0) in the fuel cell system when power generation is stopped, the gas-liquid separation performance α, the gas circulation rate β, and the ratio γ of the water circulation rate and the gas circulation rate. The required scavenging time T is calculated based on the conditional expression (S04).

Q (t) = Q (0) × (1-α) ^β · ^γ · ^t
The necessary scavenging time T is a value obtained by estimating a time for performing the scavenging / circulation processing necessary for reducing the remaining water amount in the fuel cell system to the target remaining water amount Qreq. That is, this is the estimated time for the scavenging / circulation processing necessary for the remaining water amount Q (t) in the fuel cell system to reach the target remaining water amount Qreq. This estimated time may be obtained in seconds.

  The gas-liquid separation performance α refers to the performance of separating water and hydrogen contained in the anode gas discharged from the anode of the fuel cell stack 1. For example, a value obtained by dividing the amount of recovered water (the amount of water stored in the drain tank 15) of the gas-liquid separator 14 by the amount of introduced water (the amount of water entering the inlet portion of the gas-liquid separator 14) can be used.

  The gas circulation speed β is the speed of the anode gas circulating in the fuel cell system. The gas circulation speed β depends on the rotation speed of the hydrogen pump 8, and when the rotation speed of the hydrogen pump 8 is increased, the gas circulation speed β also increases.

  Q (t) is the amount of remaining water in the fuel cell system t seconds after power generation is stopped. Further, Qini is used as the amount of remaining water in the fuel cell system when power generation is stopped. Therefore, the control unit 17 calculates the necessary scavenging time T by substituting the value of Qini for Q (0) in the above conditional expression.

That is, the control unit 17 substitutes the values of Qini, gas-liquid separation performance α, gas circulation rate β, water circulation rate and gas circulation rate ratio γ into the conditional expression, and Q (t) T is calculated such that becomes the same value as Qreq. Then, the control unit 17 determines the calculated t value as the required scavenging time T.

  The control unit 17 obtains in advance the values of the gas-liquid separation performance α, the gas circulation rate β, the ratio of the water circulation rate and the gas circulation rate γ by experiments or simulations from the current state of the fuel cell system. deep. Further, the control unit 17 acquires the value of Qini from the remaining water amount calculation unit 18 in advance.

  In the above conditional expression, the necessary scavenging time is calculated by using the gas circulation rate β and the ratio of the water circulation rate and the gas circulation rate γ without using the circulation rate of the water moving in the fuel cell system. T is calculated. Measure the circulation rate of water moving through the fuel cell system, and substitute for the above equation using the water circulation rate instead of the gas circulation rate β and the ratio of the water circulation rate and the gas circulation rate γ. May be.

  FIG. 5 is a diagram showing a correspondence relationship between the scavenging (circulation) time of the scavenging / circulation process and the remaining water amount. The horizontal axis in FIG. 5 is the processing time for scavenging the remaining water in the fuel cell system. The vertical axis in FIG. 5 is the amount of remaining water in the fuel cell system. In FIG. 5, Qini indicates the amount of remaining water in the fuel cell system immediately after the power generation is stopped. In FIG. 5, the scavenging / circulation processing time with respect to the value of the remaining water amount Qini in the fuel cell system indicates t = 0.

  In FIG. 5, the scavenging / circulation processing time with respect to the value of the remaining water amount Q (t) in the fuel cell system indicates t. Further, in FIG. 5, the scavenging / circulation processing time with respect to the value of the remaining water amount Qreq of the fuel cell system indicates T.

  In FIG. 5, the value of Qini indicates that when scavenging / circulation processing is performed for t seconds after the power generation is stopped, the value decreases to Q (t). In FIG. 5, the necessary scavenging time T during which the value of Qini decreases to Qreq is displayed as T.

  Then, the control unit 17 determines whether or not the scavenging / circulation processing time has reached the necessary scavenging time T (S05). Specifically, the control unit 17 acquires the elapsed time of the scavenging / circulation process from a timer that counts the time of the scavenging / circulation process, and compares it with the required scavenging time T. Then, the control unit 17 determines whether the acquired elapsed time of the scavenging / circulation process is the same value as the necessary scavenging time T or a value greater than that.

  When it is determined that the scavenging / circulation processing time has not reached the required scavenging time T, the control unit 17 continues the scavenging / circulation processing. On the other hand, when it is determined that the scavenging / circulation processing time has reached the required scavenging time T, the control unit 17 controls the hydrogen pump 8 to stop driving (S06).

  And when the control part 17 controls to stop the drive of the hydrogen pump 8, operation | movement of a fuel cell system is stopped.

According to the present embodiment, the values of Qini, gas-liquid separation performance α, gas circulation rate β, ratio of water circulation rate and gas circulation rate γ are added to the conditional expression based on the physical model of the fuel cell. Substituting and determining the calculated value of t as the required scavenging time T. Then, based on the required scavenging time T, scavenging / circulation processing in the fuel cell system is executed. Therefore, the remaining water in the fuel cell system can be scavenged with an appropriate scavenging time in order to avoid freezing and dry-up of the remaining water in the fuel cell system. Further, since an appropriate scavenging time can be calculated, it is possible to suppress water remaining due to insufficient scavenging and an increase in power consumption due to excessive scavenging. Second Embodiment
A fuel cell system according to a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a process for determining the required scavenging time T and a drive control process for the hydrogen pump 8 will be described.

  FIG. 6 is a flowchart for explaining the operation of the fuel cell system according to the second embodiment of the present invention. In the process of FIG. 6, the processes other than S04A and S04B are the same as those in FIG. Therefore, the same processes are denoted by the same reference numerals as those in FIG.

  The process for determining the required scavenging time T and the drive control process for the hydrogen pump 8 in the present embodiment are executed after performing the processes from S01 to S04 in FIG. After performing the process of S04 in FIG. 6, the control unit 17 determines whether the required scavenging time T is greater than a predetermined threshold A (S04A). The predetermined threshold A is a value obtained from the stop time required for the fuel cell system. The predetermined threshold A may be obtained in seconds.

  When the necessary scavenging time T is greater than the predetermined threshold A, the control unit 17 performs drive control of the hydrogen pump 8 (S04B). Specifically, the control unit 17 controls the drive of the hydrogen pump 8 so as to increase the rotation speed of the hydrogen pump 8.

  Further, the control unit 17 may control the driving of the rotation of the hydrogen pump 8 to be switched to pulsation instead of controlling the driving of the hydrogen pump 8 so as to increase the rotation speed of the hydrogen pump 8. In addition to controlling the drive of the hydrogen pump 8 so as to increase the rotational speed of the hydrogen pump 8, the control unit 17 may control the drive of the rotation of the hydrogen pump 8 to be switched to pulsation.

  In this case, the rotation speed of the hydrogen pump 8 (and hence the increase in the rotation speed) is determined so that the required scavenging time T is smaller than the predetermined threshold A. When the rotation speed of the hydrogen pump 8 is increased, the value of the gas circulation speed β increases and the value of the required scavenging time T decreases. In this case, the gas circulation rate β after increasing the rotational speed of the hydrogen pump 8 may be obtained by experiment (or simulation).

  When the driving of the rotation of the hydrogen pump 8 is switched to pulsation, the ratio γ of the water circulation speed and the gas circulation speed increases, and the required scavenging time T decreases. In this case, the ratio γ of the water circulation rate and the gas circulation rate after switching to pulsation may be obtained by experiment (or simulation).

  When the control of the hydrogen pump 8 is controlled so as to increase the rotational speed of the hydrogen pump 8, the control unit 17 newly obtains the gas circulation speed β (refer to a predetermined map (a table on the memory)). Good). Next, the control unit 17 calculates the required scavenging time T again using the newly obtained gas circulation rate β. And the control part 17 performs the process of S05 of FIG. 6 based on the required scavenging time T calculated again.

  When the control unit 17 controls to switch the driving of the rotation of the hydrogen pump 8 to pulsation instead of controlling the driving of the hydrogen pump 8 so as to increase the number of rotations of the hydrogen pump 8, A ratio γ between the velocity and the gas circulation velocity is newly obtained (refer to a predetermined map (a table on the memory)).

  Next, the control unit 17 calculates the necessary scavenging time T again using the newly obtained ratio γ of the water circulation rate and the gas circulation rate. And the control part 17 performs the process of S05 of FIG. 6 based on the required scavenging time T calculated again.

In addition to controlling the drive of the hydrogen pump 8 so as to increase the rotation speed of the hydrogen pump 8, the control unit 17 controls the switching of the rotation drive of the hydrogen pump 8 to pulsation. β, and the ratio γ of the water circulation rate and the gas circulation rate is newly obtained (refer to a predetermined map (a table on the memory)). Next, the control unit 17 calculates the necessary scavenging time T again using the newly obtained gas circulation rate β and the ratio γ of the water circulation rate and the gas circulation rate. And the control part 17 performs the process of S05 of FIG. 6 based on the required scavenging time T calculated again.

  On the other hand, when the required scavenging time T is smaller than the predetermined threshold A, the control unit 17 performs the process of S05 in FIG. Then, after performing the process of S05, the operation of the fuel cell system is stopped.

  FIG. 7 is a diagram showing a correspondence relationship between the scavenging (circulation) time of the scavenging / circulation process and the remaining water amount. A curve X in FIG. 7 is an example showing a correspondence relationship between the scavenging (circulation) time of the scavenging / circulation process and the remaining water amount of the fuel cell system according to the first embodiment. A curve Y in FIG. 7 is an example showing a correspondence relationship between the scavenging (circulation) time of the scavenging / circulation process and the remaining water amount of the fuel cell system according to the second embodiment. The curve Y in FIG. 7 is less than the curve X in the amount of remaining water in the fuel cell stack 1 with respect to the scavenging (circulation) time.

As described above, according to the scavenging / circulation process of the fuel cell system according to the second embodiment, the remaining water amount in the fuel cell stack 1 with respect to the scavenging (circulation) time decreases faster than the fuel cell system according to the first embodiment. To do. Therefore, the required scavenging time for reaching the target residual water amount Qreq is shorter than that of the fuel cell system according to the first embodiment, and the time taken until the end of the fuel cell system according to the second embodiment is shortened.
<Modification>
In the first embodiment and the second embodiment, the fuel cell system includes the hydrogen pump 8 and the gas-liquid separator 14. For example, the cathode-side pump 9 may be used to scavenge residual water in the fuel cell system, like the hydrogen pump 8. Further, the gas-liquid separator 14 of the anode off gas passage 3 may be provided in the cathode off gas passage 6. Further, a drain tank 15 and a drain valve 16 may be provided in the gas-liquid separator 14 in that case.

  Also, a cathode offgas circulation passage is provided so that air discharged to the cathode offgas passage 6 passes through the cathode offgas circulation passage and is supplied again to the cathode of the fuel cell stack 1 together with the cathode gas supplied from outside the fuel cell system. May be. The cathode off-gas circulation path constitutes a cathode-side circulation path. By controlling the driving of the pump 9 and the gas-liquid separator 14, the remaining water in the fuel cell system can be discharged out of the circulation path.

  Further, for example, in a state where the hydrogen pump 8 and the gas-liquid separator 14 are provided in the anode gas passage 2, the pump 9 is used for scavenging the remaining water in the fuel cell system, and the cathode off-gas passage 6 is provided with the cathode gas. A liquid separator may be provided. Further, a drain tank 15 and a drain valve 16 may be provided in the cathode gas-liquid separator in that case.

  Also, a cathode offgas circulation passage is provided so that air discharged to the cathode offgas passage 6 passes through the cathode offgas circulation passage and is supplied again to the cathode of the fuel cell stack 1 together with the cathode gas supplied from outside the fuel cell system. May be. The cathode off-gas circulation path constitutes a cathode-side circulation path. By controlling any or all of the hydrogen pump 8, the pump 9, the gas / liquid separator 14, and the cathode gas / liquid separator, the remaining water in the fuel cell system can be discharged out of the circulation path.

It is a figure which shows the structural example of the fuel cell system which concerns on 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the fuel cell system which concerns on 1st Embodiment of this invention. It is the figure which showed the example of the relationship between a state quantity and the amount of residual water in a fuel cell system. It is the figure which showed the example of the relationship between a state quantity and the amount of residual water in a fuel cell system. It is the figure which showed the correspondence of the scavenging (circulation) time of a scavenging / circulation process, and the amount of residual water. It is a flowchart explaining operation | movement of the fuel cell system which concerns on 2nd Embodiment of this invention. It is the figure which showed the correspondence of the scavenging (circulation) time of a scavenging / circulation process, and the amount of residual water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Anode gas passage 3 Anode off-gas passage 4 Anode off-gas circulation passage 5 Cathode gas passage 6 Cathode off-gas passage 7 Hydrogen tank 8 Hydrogen pump 9 Pump 10, 11 Pressure regulating valve 12 Filter 13 Humidifier 14 Gas-liquid separator 15 Drain Tank 16 Drain valve 17 Control unit 18 Remaining water amount calculation unit 19 Purge valve

Claims (5)

A fuel cell body;
A gas supply passage for supplying gas to the fuel cell body;
A gas discharge passage for discharging gas from the fuel cell body;
A gas circulation passage connecting the gas discharge passage to the gas supply passage;
Gas driving means for circulating the gas in the gas discharge passage through the gas circulation passage to the gas supply passage;
A gas-liquid separator for separating moisture from the circulating gas;
Based on the operating state of the fuel cell main body and the environment in which the fuel cell main body is operated, the amount of remaining water in the fuel cell system including the fuel cell main body, the gas supply passage, the gas discharge passage, and the gas circulation passage is calculated. Means to
Calculating means for calculating an operating time for operating the gas driving means to reduce the residual water amount to a predetermined value according to the separation performance of the gas-liquid separator and the state quantity of the gas when circulating;
Control means for operating the gas driving means until the end of the operating time ,
The state quantity of the gas to be circulated includes the gas circulation rate and the ratio of the moisture circulation rate to the gas circulation rate.
Fuel cell system. When the operation time is equal to or greater than a predetermined threshold, the calculation means newly calculates a second operation time for operating the gas drive means after increasing the gas drive amount of the gas drive means by a predetermined value, 2. The fuel cell system according to claim 1, wherein the control unit increases a gas drive amount of the gas drive unit by a predetermined value and operates the gas drive unit until the end of the second operation time. When the operation time is equal to or greater than a predetermined threshold, the calculation means newly calculates a second operation time for operating the gas drive means after pulsating the drive of the gas drive means, and the control means The fuel cell system according to claim 1, wherein the gas driving means is pulsated to operate the gas driving means until the end of the second operation time. The gas driving means is a pump;
When the operation time is equal to or greater than a predetermined threshold, the calculation means newly calculates a second operation time for operating the pump after increasing the rotation speed of the pump by a predetermined value, and the control means 2. The fuel cell system according to claim 1 , wherein the number of rotations of the pump is increased by a predetermined value and the pump is operated until the end of the second operation time. The gas driving means is a pump;
When the operation time is equal to or greater than a predetermined threshold, the calculation means newly sets a second operation time for operating the pump after increasing the rotation speed of the pump by a predetermined value and pulsing the pump. 2. The fuel cell according to claim 1 , wherein the control means increases the rotational speed of the pump by a predetermined value and pulsates the drive of the pump to operate the pump until the end of the second operation time. system.

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