JP5239201B2 - Fuel cell system and impurity discharge method in fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a solid polymer fuel cell.

In a fuel cell that generates electricity by an electrochemical reaction between hydrogen and oxygen, it is considered that the cell performance is degraded due to various state changes in the fuel cell during operation of the fuel cell.
For example, in a fuel cell, a circulation passage for circulating the exhaust gas of the hydrogen electrode (hereinafter referred to as anode exhaust gas) and supplying it again to the hydrogen electrode is provided to effectively utilize the residual hydrogen contained in the anode exhaust gas. There is something to do. In the case of such a fuel cell, since the anode exhaust gas includes, for example, water vapor, nitrogen, etc., if the anode exhaust gas is continuously circulated for a long period of time, the concentration of these components increases, The concentration may be reduced, and the battery performance may be reduced. For this reason, conventionally, a purge valve for discharging a part of the anode exhaust gas to the outside air is provided in the circulation flow path, and the purge valve is opened periodically to reduce the concentration of nitrogen and water vapor, thereby reducing the hydrogen concentration. There has been proposed a technique for avoiding the deterioration in battery performance caused by the phenomenon (see, for example, Patent Document 1).

  In the polymer electrolyte fuel cell, when the water content of the electrolyte membrane decreases, proton conductivity in the electrolyte membrane decreases and membrane resistance increases. As a result, the output voltage decreases and the cell performance decreases. In order to suppress such inconvenience, as a countermeasure against a decrease in the water content of the electrolyte membrane, a configuration has been proposed in which the gas pressure on the cathode side is further increased (see, for example, Patent Document 2).

JP 2003-151592 A JP 2002-175821 A

  When the gas pressure on the cathode side is increased, the gas pressure on the cathode side becomes relatively higher than that on the anode side, so that water generated on the cathode side moves to the anode side. Therefore, the water content of the electrolyte membrane can be increased. However, since the gas supply to the cathode side is normally performed by pressurizing and supplying air using a pump or the like, if the gas pressure on the cathode side is increased, the power consumption of the pump or the like, that is, the loss of auxiliary equipment is reduced. Will increase. When the auxiliary machine loss increases in this way, the energy efficiency of the entire system decreases.

  Therefore, the present invention suppresses fuel cell performance degradation due to a decrease in the water content of the electrolyte membrane without causing a decrease in energy efficiency due to an increase in auxiliary machinery loss or the like, and also results from a decrease in hydrogen concentration. It aims at suppressing the performance fall of the fuel cell which carries out.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A fuel cell system including a fuel cell having a solid polymer electrolyte membrane,
An impurity discharge part for discharging impurities in the anode gas;
An anode gas pressure adjusting unit for adjusting a gas pressure on the anode side of the fuel cell;
A control unit for controlling the impurity discharge unit and the anode gas pressure adjusting unit;
Further,
The controller is
When the gas pressure on the anode side of the fuel cell is set to a negative pressure, and when the impurity discharge unit is controlled to discharge the impurities in the anode gas to the outside of the fuel cell system, The gist of the invention is to control the anode gas pressure adjusting unit to increase the gas pressure on the anode side to a positive pressure before the discharge.

  For example, when the gas pressure on the anode side (hereinafter also referred to as anode internal pressure) is negative, the impurities in the anode gas may be discharged into the atmosphere due to the pressure difference even if the impurities in the anode gas are discharged into the atmosphere. Can not. According to the fuel cell system of the present invention, when the anode internal pressure is a negative pressure, the anode internal pressure is controlled to a positive pressure before discharging the impurities in the anode gas. Can be discharged. Therefore, it is possible to suppress a decrease in battery performance by discharging impurities in the anode gas to the atmosphere and increasing the hydrogen concentration in the anode gas.

  The timing for discharging the impurities in the anode gas may be, for example, periodically discharged at predetermined time intervals after the start of the fuel cell operation, or may be discharged based on the impurity concentration in the anode gas. You may make it make it. Further, it may be discharged when there is an instruction to discharge from the outside. In addition, the timing for discharging the impurities in the anode gas can be determined based on various criteria.

  By the way, in the fuel cell system of the present invention, the anode internal pressure is set to a negative pressure. Usually, since the cathode internal pressure is maintained at a positive pressure, when the anode internal pressure is set to a negative pressure, the movement of water from the cathode to the anode is promoted, and a decrease in the water content of the electrolyte membrane can be suppressed. Therefore, an increase in membrane resistance due to a decrease in the water content of the electrolyte membrane can be suppressed, a decrease in output voltage can be suppressed, and a decrease in battery performance can be suppressed.

  In addition, when the anode internal pressure is set to a negative pressure, the anode gas flow rate becomes larger than when the anode internal pressure is positive, and the liquid water remaining on the anode side in the fuel cell is fueled by the flow of the anode gas. Since it becomes easy to discharge out of the battery, flooding on the anode side can be suppressed. Accordingly, since the circulation of the anode gas is improved, it is possible to suppress the performance deterioration of the fuel cell. That is, according to the fuel cell system of the present invention, it is possible to comprehensively suppress a decrease in battery performance. Furthermore, since it is not necessary to increase energy consumption when controlling the anode internal pressure to a negative pressure, it is possible to suppress a decrease in battery performance without reducing energy efficiency.

[Application Example 2] In the fuel cell system according to Application Example 1,
The controller is
It is determined whether or not the impurity concentration in the anode gas in the fuel cell is in an increased state. When it is determined that the impurity concentration is in an increased state, the impurity in the anode gas is determined as the fuel cell system. You may make it discharge | emit outside.

  When the impurities in the anode gas are discharged, hydrogen in the anode gas may be discharged together. For example, when the impurities in the anode gas are periodically discharged at a predetermined time interval, the impurities may be discharged even when the impurity concentration in the anode gas is small. In such a case, the anode gas The hydrogen inside is wasted. If it is determined that the concentration of impurities in the anode gas in the fuel cell is in an increased state, the impurities in the anode gas are unnecessarily discharged if the control is performed so that the impurities in the anode gas are discharged out of the fuel cell system. Since this is not performed, it is possible to suppress wasteful discharge of hydrogen in the anode gas.

Application Example 3 In the fuel cell system according to Application Example 1 or Application Example 2, the control unit is a case where the gas pressure on the anode side of the fuel cell is set to a negative pressure, and the fuel cell When the load required for the above is larger than a predetermined load request value, impurities in the anode gas may not be discharged.

  FIG. 7 shows an example of a current-voltage curve of the fuel cell. A case where the anode internal pressure is a predetermined positive pressure value is indicated by a one-dot chain line, and a case where the anode internal pressure is a predetermined negative pressure value is indicated by a solid line. As shown in FIG. 7, when the anode internal pressure is positive and the negative pressure is compared, when the current is constant, the voltage tends to be lower when the anode internal pressure is positive. In either case, when the current is large, the voltage tends to decrease rapidly. Therefore, when the load demand on the fuel cell is large and the required current is large, if the anode internal pressure is increased from the negative pressure to the positive pressure, the voltage may drop rapidly and the fuel cell may not be operated.

  Therefore, when the load demand on the fuel cell is larger than a predetermined value, impurities in the anode gas are not discharged. That is, since the anode gas pressure is increased only when the load demand on the fuel cell is small, it is possible to avoid that the operation of the fuel cell cannot be continued due to the voltage drop.

Application Example 4 In the fuel cell system according to Application Example 1 or Application Example 2, the control unit is a case where the gas pressure on the anode side of the fuel cell is set to a negative pressure, and the fuel cell When the internal temperature of the anode is equal to or higher than a predetermined temperature, impurities in the anode gas may not be discharged.

  When impurities in the anode gas are discharged when the anode internal pressure is set to a negative pressure, the anode internal pressure must be set to a positive pressure as described above. However, when the internal temperature of the fuel cell is equal to or higher than a predetermined temperature, setting the anode internal pressure to a positive pressure makes it difficult for the water on the cathode side to move to the anode side, so the water content of the electrolyte membrane decreases. As a result, fuel cell performance may be reduced.

  Therefore, when the internal temperature of the fuel cell is equal to or higher than the predetermined temperature, if the impurities in the anode gas are not discharged, the internal pressure of the anode is increased only when the internal temperature of the fuel cell is equal to or lower than the predetermined temperature. become. For this reason, it is possible to suppress a decrease in fuel cell performance accompanying a decrease in the water content of the electrolyte membrane when impurities in the anode gas are discharged.

Application Example 5 In the fuel cell system according to any one of Application Examples 1 to 4,
An output adjusting unit for adjusting the output of the fuel cell;
In addition,
The controller is
Before the gas pressure on the anode side is increased to a positive pressure, the output adjusting unit may be controlled to limit the output of the fuel cell to a predetermined output value.

  As described above, when the load demand on the fuel cell is large, if the anode internal pressure is increased from a negative pressure to a positive pressure, the output voltage may decrease and the fuel cell operation may not be continued. According to the fuel cell system of Application Example 5, even when the load demand is large, by limiting the output of the fuel cell to an output value sufficient for the fuel cell to continue operation, Impurities in the anode gas can be discharged by setting the anode internal pressure to a positive pressure, and the operation of the fuel cell can be continued.

[Application Example 6] In the fuel cell system according to any one of Application Examples 1 to 5,
An internal temperature adjusting unit for adjusting the internal temperature of the fuel cell;
In addition,
The controller is
Before the gas pressure on the anode side is increased to a positive pressure, the internal temperature adjustment unit may be controlled to reduce the internal temperature of the fuel cell to a predetermined temperature.

  As described above, when the internal pressure of the fuel cell is high and the anode internal pressure is increased from a negative pressure to a positive pressure, the water content of the electrolyte membrane is decreased and the fuel cell performance may be decreased. According to the fuel cell system of Application Example 6, even if the internal temperature of the fuel cell is equal to or higher than a predetermined temperature, the internal temperature of the fuel cell is reduced to a temperature that allows the degradation of the performance of the fuel cell. Thus, the anode internal pressure can be set to a positive pressure, impurities in the anode gas can be discharged, and the performance degradation of the fuel cell can be suppressed. Note that the internal temperature of the fuel cell can be lowered by increasing the flow rate of the cooling water flowing through the fuel cell or by limiting the load demand on the fuel cell to be small.

Application Example 7 In the fuel cell system according to any one of Application Examples 1 to 6,
A hydrogen gas supply path for supplying hydrogen gas to the anode of the fuel cell;
An anode exhaust gas path that guides the gas discharged from the anode of the fuel cell to the hydrogen gas supply path,
A part of the hydrogen gas supply path and the anode exhaust gas path form a circulation path for circulating hydrogen between the inside of the fuel cell,
The anode gas pressure adjusting unit may adjust the pressure in the circulation channel as the gas pressure on the anode side.

  With such a configuration, in the fuel cell system that uses hydrogen gas as the fuel gas, it is possible to suppress the deterioration of the fuel cell performance while efficiently using the hydrogen gas.

Application Example 7 In the fuel cell system according to Application Example 6,
The anode gas pressure adjusting unit is
An injector provided upstream of the circulation flow path in the hydrogen gas supply path and having a discharge port for discharging the hydrogen gas to the circulation flow path side and a valve for opening and closing the discharge port;
The controller is
The anode gas adjusting unit may be controlled so as to reduce the gas pressure on the anode side from a positive pressure to a negative pressure by adjusting the opening / closing state of the discharge port by the valve of the injector.

  With such a configuration, the gas pressure on the anode side can be easily adjusted to a desired pressure by adjusting the opening / closing state of the discharge port by the valve.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in the form of an impurity discharge method for discharging impurities in the anode gas of the fuel cell in the fuel cell system to the outside of the fuel cell system. Is possible.

A. First embodiment:
A1. Overall configuration of the device:
FIG. 1 is an explanatory diagram showing the configuration of a fuel cell system 10 as a preferred embodiment of the present invention. As shown in FIG. 1, the fuel cell system 10 supplies a fuel cell stack 22 and hydrogen as a fuel gas to the fuel cell stack 22, and exhaust gas discharged from the fuel cell stack 22 (hereinafter also referred to as anode exhaust gas). .) Is discharged to the atmosphere, and air as an oxidant gas is supplied to the fuel cell stack 22, and the exhaust gas discharged from the fuel cell stack 22 is discharged to the atmosphere. And a control unit 70 that controls the movement of each unit of the fuel cell system 10.

  The fuel cell stack 22 is a polymer electrolyte fuel cell that is relatively small and excellent in power generation efficiency. Pure hydrogen as a fuel gas and oxygen in the air as an oxidant gas cause an electrochemical reaction at each electrode. Thus, an electromotive force is obtained.

  The hydrogen supply system mainly includes a hydrogen tank 23, a hydrogen supply path 60, an anode exhaust gas path 63, and an exhaust gas discharge path 64.

  The hydrogen tank 23 is, for example, a hydrogen cylinder that stores high-pressure hydrogen. Alternatively, a tank that stores hydrogen by storing a hydrogen storage alloy inside and storing the hydrogen storage alloy in the hydrogen storage alloy may be used.

  The hydrogen supply path 60 is provided with a pressure regulating valve 61 and an injector 62. The hydrogen gas stored in the hydrogen tank 23 is discharged to the hydrogen supply path 60 connected to the hydrogen tank 23, and then adjusted (depressurized) to a predetermined pressure by the pressure adjustment valve 61, and the fuel cell is supplied via the injector 62. The fuel gas is supplied to the anode of each single cell constituting the stack 22. Although the pressure regulating valve 61 is shown as a single valve in FIG. 1, it is sufficient if the high-pressure hydrogen gas supplied from the hydrogen tank 23 can be reduced to a desired pressure and supplied to the injector 62. A valve provided with any number of pressure regulating valves may be used.

  The injector 62 is a device that includes a discharge port and a valve that is an electromagnetic valve that opens and closes the discharge port, and injects hydrogen gas from the discharge port according to the differential pressure applied before and after the injector 62 when the valve is opened. Therefore, the amount of hydrogen gas supplied to the anode side can be adjusted by the valve opening time of the valve provided in the injector 62. Specifically, a drive signal (pulse signal) is sent from the control unit 70 to be described later to the injector 62. When the drive signal input to the injector 62 is ON, the valve of the injector 62 is opened and turned OFF. Sometimes the valve is closed. By adjusting the pulse width (that is, duty ratio) of this drive signal, the amount of hydrogen gas injected from the injector 62 is adjusted, and the amount of hydrogen gas supplied to the anode is adjusted.

  Further, the anode internal pressure can be controlled by controlling the open / close state of the valve of the injector 62. FIG. 2 is an explanatory diagram showing the relationship between the anode internal pressure and the operation of the injector 62. The valve opening / closing control in the injector 62 can be performed, for example, by changing the pulse width at a constant frequency f in the drive signal input to the injector 62. As shown in FIG. 2, the anode internal pressure increases while the discharge port is opened by the valve, and the anode internal pressure is consumed by the consumption of hydrogen in the circulation flow path for power generation while the discharge port is closed. Will decline. Therefore, by opening and closing the valve, the anode internal pressure pulsates within the range of the pressure difference ΔP shown in FIG. Therefore, by controlling the duty ratio in the injector 62, the anode internal pressure is maintained at a desired pressure as a whole while finely pulsating. In addition, the injector 62 in a present Example is equivalent to the anode gas pressure adjustment part in a claim.

  A hydrogen pump 65 is provided in the anode exhaust gas path 63, and the anode exhaust gas discharged from the anode of the fuel cell stack 22 is caused to flow again downstream of the position where the injector 62 is disposed in the hydrogen supply path 60. Therefore, the remaining hydrogen in the anode exhaust gas is contained in a flow path (hereinafter referred to as a circulation flow path) composed of the anode exhaust gas path 63, a part of the hydrogen supply path 60, and the flow path in the fuel cell stack 22. It is used again for the electrochemical reaction. At this time, the duty ratio in the injector 62 is adjusted in accordance with the amount of hydrogen consumed by the electrode reaction (determined based on the amount of power generation and load demand), and the hydrogen corresponding to the amount of hydrogen consumed passes through the injector 62 to the hydrogen tank. 23 is replenished to the circulation channel. Further, the duty ratio in the injector 62 is feedback controlled based on the anode internal pressure, and the anode internal pressure is kept at a predetermined substantially constant value. In addition, the anode internal pressure sensor 50 for measuring the anode internal pressure is provided in the hydrogen supply path 60 constituting the circulation channel.

  The exhaust gas discharge path 64 is branched from the anode exhaust gas path 63. A purge valve 27 is provided in the exhaust gas discharge path 64, and when the purge valve 27 is opened, part of the anode exhaust gas flowing in the anode exhaust gas path 63 is discharged to the outside through the exhaust gas discharge path 64. As a result, a part of the circulating hydrogen-containing gas is discharged to the outside, and the impurity concentration in the hydrogen-containing gas (the concentration of nitrogen in the air, which is the oxidizing gas that has moved to the anode side through the electrolyte membrane) The rise can be suppressed. In addition, the purge valve 27 and the exhaust gas discharge path 64 in the present embodiment correspond to the impurity discharge portion in the claims.

  The opening and closing of the purge valve 27 is controlled based on the nitrogen concentration in the anode exhaust gas in the anode exhaust gas path 63. The nitrogen concentration in the anode exhaust gas is determined as follows, for example. The temperature of cooling water (described later) flowing through the fuel cell stack 22 and the nitrogen concentration corresponding to the output of the fuel cell stack 22 are measured in advance, and the relationship is stored as a map in the control unit 70 (described later). Keep it. And the nitrogen concentration at that time can be calculated | required by measuring the said water temperature and output during the driving | operation of the fuel cell stack 22, and referring the said map. The nitrogen concentration can be obtained by various methods such as direct measurement using a nitrogen concentration sensor.

  The exhaust gas discharge path 64 is connected to the diluter 26. The diluter 26 is provided to dilute the hydrogen in the anode exhaust gas with the cathode exhaust gas before discharging the anode exhaust gas to the outside.

  The air supply / exhaust system mainly includes an air compressor 24, an oxidizing gas supply path 67, and a cathode exhaust gas path 68.

  The air compressor 24 pressurizes air taken from the outside via the air cleaner 28, and supplies this pressurized air as an oxidizing gas to the cathode of the fuel cell stack 22 via the oxidizing gas supply path 67.

  The cathode exhaust gas path 68 discharges the cathode exhaust gas discharged from the cathode to the outside. The cathode exhaust gas path 68 and the oxidizing gas supply path 67 pass through the humidification module 25. In the humidification module 25, the oxidizing gas supply path 67 and the cathode exhaust gas path 68 are separated from each other by a water vapor permeable film, and the pressurized air supplied to the cathode is humidified using the cathode exhaust gas containing water vapor. ing. Further, the cathode exhaust gas path 68 is connected to the diluter 26 described above. Therefore, in the diluter 26, the anode exhaust gas and the cathode exhaust gas are mixed, and the anode exhaust gas is diluted and discharged to the outside.

  The control unit 70 is configured as a logic circuit centered on a microcomputer. Specifically, a CPU 74 that executes predetermined calculations in accordance with a preset control program, a ROM 75 that stores in advance control programs and control data necessary for executing various calculation processes by the CPU 74, and various types of CPUs 74. A RAM 76 for temporarily reading and writing various data necessary for arithmetic processing, an input / output port 78 for inputting and outputting various signals, and the like are provided. The control unit 70 acquires measurement signals from various sensors (for example, the anode internal pressure sensor 50, the temperature sensor 52, and the voltage sensor 54) provided in the fuel cell system 10, information related to a load request for the fuel cell stack 22, and the like. In addition, a drive signal is output to each part related to power generation of the fuel cell stack 22, such as the injector 62, the air compressor 24, the hydrogen pump 65, or the purge valve 27 provided in the fuel cell system 10. In addition, CPU74 in a present Example functions as a control part in a claim.

  Further, the fuel cell stack 22 includes a cooling water flow path (not shown) through which cooling water circulates. By circulating the cooling water between the cooling water flow path formed inside the fuel cell stack 22 and a radiator (not shown), the internal temperature of the fuel cell stack 22 is maintained within a predetermined temperature range. Here, a temperature sensor 52 for measuring the outlet temperature of the cooling water is provided as a temperature sensor for measuring the internal temperature of the fuel cell stack 22 in the vicinity of the outlet from the fuel cell stack 22 in the cooling water flow path. ing. As a temperature sensor for measuring the internal temperature of the fuel cell stack 22, a sensor other than a sensor for measuring the outlet temperature of the cooling water may be provided. For example, as a thermocouple for directly measuring the temperature of the fuel cell stack 22. Also good. Further, the fuel cell system 10 is provided with a voltage sensor 54 for measuring the output voltage from the fuel cell stack 22.

  The anode internal pressure in the fuel cell system 10 of the present embodiment is sufficient when the fuel cell stack 22 is in steady operation, even when the load demand on the fuel cell stack 22 fluctuates and the hydrogen consumption is maximized. It is a value that can ensure the amount, and is set as a positive pressure value considering the balance with the gas pressure on the cathode side. Here, when the fuel cell stack 22 is in steady operation, the temperature of the fuel cell stack 22 is sufficiently raised, the water content of the electrolyte membrane is sufficient, and it is necessary according to the load demand. A state in which a large amount of electric power can be generated by the fuel cell stack 22 without hindrance.

A2. Control when membrane water content is reduced:
In the fuel cell system 10 of the present embodiment, when the water content in the solid polymer electrolyte membrane is reduced, the anode internal pressure is different from that during steady operation in order to suppress the reduction in battery performance due to the reduction in water content. Control to set a value lower than atmospheric pressure (negative pressure) is performed. FIG. 3 is a flowchart showing a membrane water content lowering processing routine executed by CPU 74 of control unit 70 provided in fuel cell system 10. This routine is repeatedly executed at predetermined intervals during the power generation of the fuel cell stack 22.

  When the membrane moisture content lowering processing routine is started, the CPU 74 first determines whether or not the fuel cell stack 22 satisfies a predetermined high temperature condition (step S110). In this embodiment, the temperature measured by the temperature sensor 52 is used as the internal temperature of the fuel cell stack 22, and when the internal temperature is 90 ° C. or higher, it is determined that the fuel cell stack 22 meets a predetermined high temperature condition. It is considered that when the internal temperature of the fuel cell stack 22 increases, the water vapor content of the electrolyte membrane decreases due to an increase in the saturated vapor pressure. Usually, when the internal temperature is operated at less than 90 ° C., the fuel cell performance is hardly deteriorated, and thus the water content of the electrolyte membrane is considered to be within the allowable range. Therefore, the criterion for the high temperature condition is 90 ° C. That is, in step S110, the reduced state of the water content of the electrolyte membrane is determined based on the internal temperature of the fuel cell stack 22.

  When it is determined in step S110 that the predetermined high temperature condition is satisfied, the CPU 74 performs control to reduce the set value of the anode internal pressure to a negative pressure (step S120). As described above, the anode internal pressure is a constant positive value considering the balance with the gas pressure on the cathode side when the fuel cell stack 22 is in steady operation (that is, until the process of step S120 is executed). It is set as a pressure value. Specifically, the control for setting the anode internal pressure to a negative pressure is performed by outputting a drive signal from the control unit 70 to the injector 62, whereby the measured value in the anode internal pressure sensor 50 becomes a predetermined value lower than the atmospheric pressure. In this manner, the duty ratio in the injector 62 is adjusted.

  As will be described in detail later, when the water content of the electrolyte membrane is reduced, the water content of the electrolyte membrane can be increased by reducing the anode internal pressure, resulting in a decrease in fuel cell performance. Can be suppressed. Therefore, in step S110, when it is determined that the predetermined high temperature condition is satisfied (that is, the water content of the electrolyte membrane is reduced), control for reducing the anode internal pressure is performed (step S120).

  Thereafter, the CPU 74 determines whether or not the impurity concentration in the anode gas has increased (step S130). In this embodiment, the nitrogen concentration in the circulation channel is used as the impurity concentration in the anode gas. As described above, as the nitrogen concentration, the value obtained by measuring the coolant temperature and the output of the fuel cell stack 22 during the operation of the fuel cell stack 22 and referring to the map is used. If the nitrogen concentration exceeds a predetermined high concentration criterion value, it is determined in step S130 that the impurity concentration has increased.

  If it is determined in step S130 that the impurity concentration has increased, the CPU 74 determines whether or not the anode internal pressure is negative (step S140). In the present embodiment, whether or not the anode internal pressure is a negative pressure is determined based on a measured value by the anode internal pressure sensor 50. If it is determined in step S140 that the anode internal pressure is negative, the CPU 74 further determines whether or not the load request for the fuel cell stack 22 is small (step S150). In the present embodiment, whether or not the load request is small is determined based on the output voltage of the fuel cell stack 22. Specifically, when the output voltage per fuel cell calculated based on the output voltage measured by the voltage sensor 54 is 0.7 V or more, for example, it is determined that the load requirement is small. The output voltage value that is the determination criterion of the load request is not limited to 0.7 V, and can be set to a different value depending on, for example, the type of fuel cell. In the present embodiment, when the output voltage becomes 0.6V or less, there is a possibility that the operation of the fuel cell stack 22 may not be continued. Yes.

  If it is determined in step S150 that the load is small, the CPU 74 performs control to set the anode internal pressure to a positive pressure value similar to that during steady operation (step S160). Specifically, by outputting a drive signal from the control unit 70 to the injector 62, the duty ratio in the injector 62 is adjusted so that the measured value in the anode internal pressure sensor 50 becomes the same value as in the steady operation. To do.

  Further, after setting the anode internal pressure to a positive pressure, the CPU 74 controls to discharge impurities in the anode exhaust gas (step S170). Specifically, by outputting a drive signal from the CPU 74 to the purge valve 27, the purge valve 27 is opened, a part of the anode exhaust gas is discharged, and after a predetermined time has elapsed, the purge valve 27 is closed.

  By the way, when it is determined in step S150 that the load requirement is large (that is, when the output voltage is less than 0.7 V), the anode exhaust gas is not exhausted and the process returns to step S110. In step S130, since it is determined that the impurity concentration in the anode gas has increased, it is preferable to exhaust the exhaust gas of the anode (step S170). However, when the load demand is large, the anode internal pressure is set to a positive pressure. If it is raised, as shown by the arrow in FIG. 7, the voltage drops suddenly and the fuel cell stack 22 may not be operated, so the anode exhaust gas is not exhausted.

  In Step S130, if it is not determined that the impurity concentration in the anode gas is increased, Steps S140 to 250 are not performed (that is, the anode exhaust gas is not exhausted), and the process returns to Step S110. When the impurity concentration does not exceed the predetermined high concentration criterion value, the decrease in battery performance based on the decrease in the hydrogen concentration in the anode gas is within the allowable range, so there is no need to exhaust the anode exhaust gas. Because it is considered.

  The control flow when it is determined in step S110 that the predetermined high temperature condition is satisfied has been described. On the other hand, when it is determined in step S110 that the predetermined high temperature condition is not satisfied (that is, when the internal temperature of the fuel cell stack 22 is less than 90 ° C.), the anode internal pressure is set to a predetermined positive pressure value during steady operation. Set (step S180), the process proceeds to step S130.

  If it is determined in step S130 that the impurity concentration in the anode gas has increased, the CPU 74 determines whether or not the anode pressure is negative (step S140). In step S180, since the anode internal pressure is set to a positive pressure value during steady operation, the CPU 74 exhausts the anode exhaust gas without performing steps S150 and 160 (step S170), and returns to step S110. This is because when the anode internal pressure is positive, the anode exhaust gas can be exhausted without adjusting the anode internal pressure.

  As described above, in the membrane water content lowering processing routine in the present embodiment, the reduced state of the water content of the electrolyte membrane is determined based on the internal temperature of the fuel cell stack 22, and the water content is reduced. By decreasing the anode internal pressure to a negative pressure, a decrease in the membrane water content is suppressed.

  Further, the rising state of the impurity concentration in the anode gas is determined based on the nitrogen concentration in the anode gas, and the impurity concentration in the anode gas is increased, and the anode internal pressure is controlled to a negative pressure. If so, the anode internal pressure is raised to a positive pressure, and then the anode exhaust gas is discharged. By discharging a part of the anode exhaust gas and newly supplying pure hydrogen, the impurity concentration in the anode gas is reduced, and the hydrogen concentration in the anode gas is increased. The anode internal pressure is increased to a positive pressure because the pressure in the circulation path is lower than the outside air pressure even if the purge valve 27 is opened while the anode inside pressure remains in the negative pressure state. This is because it flows into the road and the anode exhaust gas cannot be exhausted.

  Furthermore, in this embodiment, the magnitude of the load request for the fuel cell stack 22 is determined based on the output voltage, and only when the load request is determined to be small, as described above, the anode internal pressure is set to a positive pressure. While controlling, the anode exhaust gas is discharged. Therefore, by controlling the anode internal pressure from a negative pressure to a positive pressure, it is possible to avoid the fuel cell stack 22 from being stopped even if a voltage drop occurs.

  As described above, by performing the membrane moisture content lowering processing routine in the present embodiment, it is possible to suppress the degradation of the fuel cell performance accompanying the decrease in the moisture content of the electrolyte membrane and the decrease in the hydrogen concentration in the anode gas. .

A3. Relationship between anode internal pressure and membrane resistance:
In the fuel cell system 10 of the present embodiment, when the water content in the solid polymer electrolyte membrane is reduced, the anode internal pressure is different from that during steady operation in order to suppress the reduction in battery performance due to the reduction in water content. Control to set a value lower than atmospheric pressure (negative pressure) is performed. Therefore, the relationship between the internal resistance (cell resistance) and the anode internal pressure in the fuel cell will be described below.

  FIG. 5 is a graph showing the results of examining the relationship between anode internal pressure, cell resistance, and cell voltage. Here, a single cell (a pair of separators sandwiching an MEA (membrane electrode assembly)) is used as a fuel cell, and hydrogen gas as a fuel gas is not circulated. Then, while connecting the single cell to a constant load, that is, while maintaining the output current value at a constant value, the pressure of the hydrogen gas supplied to the anode side (anode internal pressure) is gradually changed, and the cell resistance and the cell voltage are changed. It was measured. Further, air is used as the oxidizing gas supplied to the cathode, and the pressure of the air flowing through the oxidizing gas flow path in the single cell, that is, the cathode internal pressure is constant. Moreover, the cooling water flow path through which cooling water flows was provided in the single cell, and the temperature in the single cell was maintained substantially constant by adjusting the outlet temperature of the cooling water. In addition, the humidification conditions of the fuel gas and the oxidizing gas were set such that the water content of the electrolyte membrane was lowered when the anode internal pressure was set to a pressure balanced with the cathode internal pressure.

  Here, the internal resistance in the fuel cell includes a resistance caused by contact resistance between the constituent members of the fuel cell and a resistance possessed by each constituent member of the fuel cell itself. Although it is difficult to measure these individual resistances, the value of these resistances can vary greatly depending on the power generation conditions of the fuel cell during power generation of the fuel cell. Fluctuating electrolyte membrane resistance, ie membrane resistance. This membrane resistance increases as the water content of the electrolyte membrane decreases and the proton conductivity in the electrolyte membrane decreases. Therefore, in the result shown in FIG. 5, an increase in membrane resistance due to a decrease in the water content of the electrolyte membrane is measured as an increase in the internal resistance of the fuel cell stack 22.

  The cell resistance, which is the internal resistance of the fuel cell, was determined by the AC impedance method. That is, a weak AC constant current having a relatively high frequency (for example, 10 kHz) is applied to a single cell, and an AC component caused by the AC current is separated from the output voltage using a filter (capacitor). The AC impedance, which is the voltage value of the AC component, was determined as the cell resistance.

  As shown in FIG. 5, the lower the internal pressure of the anode, the lower the cell resistance in the single cell and the higher the cell voltage.

  As described above, the cell resistance decreases as the anode internal pressure decreases. By reducing the anode internal pressure, the anode internal pressure becomes relatively lower than the cathode internal pressure, and the differential pressure between the two increases. This is probably because of this. When the pressure difference between the anode internal pressure and the cathode internal pressure increases, the movement of water in the electrolyte membrane from the cathode side to the anode side is promoted, resulting in an increase in the water content of the electrolyte membrane and a decrease in membrane resistance. This is probably because of this.

  As described above, from the results shown in FIG. 5, when the water content of the electrolyte membrane is reduced, if the anode internal pressure is lowered, the cell resistance can be lowered as the anode pressure is lowered. As a result, the cell voltage is increased. The knowledge that it can be made was obtained. Therefore, in the fuel cell system 10 of the present embodiment, by utilizing the above knowledge, when the water content of the electrolyte membrane is reduced, control is performed to reduce the anode internal pressure to a negative pressure, thereby maintaining the battery performance. Yes.

  In general, when operating a fuel cell using hydrogen gas as the fuel gas and air having a relatively low oxygen concentration as the oxidizing gas, the anode internal pressure is set in consideration of the balance with the cathode internal pressure. Therefore, it is excessive as compared with a value necessary for obtaining a desired power. Therefore, by reducing the anode internal pressure to a negative pressure within a sufficient range to generate power according to the load demand, it is possible to reduce cell resistance and increase cell voltage while obtaining desired power.

A4. Effects of the first embodiment:
FIG. 4 is a graph showing the influence of control by the processing routine when the membrane water content is reduced. 4A shows the nitrogen concentration in the anode gas, FIG. 4B shows the output voltage, FIG. 4C shows the anode pressure, and FIG. 4D shows the open / close state of the purge valve. In FIG. 4, all the graphs (a) to (d) are shown on the same time axis by taking time on the horizontal axis. FIG. 4 shows a case where the load demand on the fuel cell stack 22 is changed after the anode internal pressure is set to a negative pressure in step S120 described above.

  When the nitrogen concentration in the anode gas of the fuel cell stack 22 exceeds the high concentration determination reference value (that is, when it is determined in step S130 that the impurity concentration is increasing: FIG. 4A) time t1 4) When the load request is determined to be small because the output voltage exceeds the low load determination reference value shown in FIG. 4B, the anode internal pressure is set to a predetermined positive pressure value during steady operation. Together with (FIG. 4C), the purge valve 27 is opened (FIG. 4D). When the purge valve 27 is opened, a part of the anode exhaust gas is released into the atmosphere, and pure hydrogen is supplied accordingly, so that the nitrogen concentration in the anode gas decreases (FIG. 4A).

  In this embodiment, when the anode internal pressure is increased from the negative pressure to the positive pressure, the purge valve 27 is opened at the same time to discharge the anode exhaust gas. The purge valve 27 may be controlled to open after a predetermined time has elapsed after the anode internal pressure is set to a positive pressure. Further, when the anode internal pressure is gradually increased from the negative pressure to the positive pressure, the purge valve 27 needs to be opened after the anode internal pressure is set to the positive pressure.

  When the purge valve 27 is closed (FIG. 4D), the anode internal pressure is again set to a negative pressure (FIG. 4C). Note that after the exhaust processing of the anode exhaust gas is completed, if it is determined in step S110 described above that the predetermined high temperature condition is not met, the anode internal pressure is maintained at a predetermined positive pressure value during steady operation, In FIG. 4, it is determined in step S110 that the predetermined high temperature condition is met.

  When the purge valve 27 is closed, the nitrogen concentration in the anode gas rises again and exceeds the high concentration criterion value (time t2 in FIG. 4 (a)). However, at this time (time t2), the output voltage does not exceed the low load determination reference value (FIG. 4B). That is, since the load demand on the fuel cell stack 22 is large, the anode exhaust gas is not discharged (FIG. 4D). Therefore, the anode internal pressure is also maintained at a negative pressure (FIG. 4C). Since the purge valve 27 is closed, the nitrogen concentration in the anode gas continues to rise thereafter (FIG. 4 (a)). Thereafter, when the output voltage exceeds the low load determination reference value (FIG. 4B, time t3), the CPU 74 sets the anode internal pressure to a positive pressure value during steady operation (FIG. 4C), and the purge valve 27 is turned on. The valve is opened (FIG. 4 (d)). By opening the purge valve 27, the nitrogen concentration in the anode gas decreases as described above (FIG. 4A).

  In general, as shown in FIG. 7, when the load demand becomes large (that is, when the demand current becomes large), the output current tends to drop rapidly. Therefore, if the anode internal pressure is increased from a negative pressure to a positive pressure when the load demand is large, the output voltage may decrease to the extent that the fuel cell stack 22 cannot continue operation.

  In the processing routine when the membrane water content is lowered in this embodiment, the decrease in fuel cell performance is suppressed by the increase in the nitrogen concentration in the anode gas (that is, the decrease in the hydrogen concentration in the anode gas). In order to achieve this, control is performed to exhaust a part of the anode exhaust gas, but before that, the magnitude of the load request is determined based on the output voltage, and the exhaust control of the anode exhaust gas is performed only when the load request is small. Is doing.

  Therefore, when the anode exhaust gas is exhausted, it is possible to suppress the output voltage from greatly decreasing by setting the anode internal pressure to a predetermined positive pressure value. Therefore, it can be avoided that the fuel cell stack 22 cannot be operated.

  Furthermore, since the anode internal pressure is reduced by adjusting the opening / closing time of the valve of the injector 62, there is no need to increase energy consumption. Therefore, it is possible to suppress a decrease in battery performance due to a decrease in water content of the electrolyte membrane without reducing energy efficiency.

  In this embodiment, the anode internal pressure can be easily controlled to a desired value by a simple operation of opening / closing control of the valve of the injector 62. The anode internal pressure may be adjusted by a method other than the method of adjusting the opening / closing time of the valve of the injector 62. For example, the anode internal pressure may be adjusted by adjusting the opening of the valve.

B. Second embodiment:
The fuel cell system according to the second embodiment of the present invention has the same configuration as that of the fuel cell system 10 according to the first embodiment shown in FIG. A part of the routine is different from the processing routine for when the membrane water content is reduced in the first embodiment. FIG. 6 is a flowchart showing a part of the processing routine when the membrane water content is lowered in the second embodiment. In the present embodiment, step S250 shown in FIG. 6 is performed instead of step S150 in the membrane water content lowering processing routine shown in FIG.

  The membrane moisture content reduction processing routine of this embodiment differs from the membrane moisture content reduction processing routine of the first embodiment in the control when it is determined that the load demand on the fuel cell stack 22 is large. In the first embodiment, as shown in FIG. 3, when the CPU 74 determines in step S150 that the load demand on the fuel cell stack 22 is large, the process returns to step S110 without exhausting the anode exhaust gas. Yes. On the other hand, in this embodiment, as shown in FIG. 6, when the CPU 74 determines in step S250 that the load demand on the fuel cell stack 22 is large, it further determines whether or not emergency exhaust is necessary, Based on the necessity of emergency exhaust, exhaust control of anode exhaust gas is performed.

  Specifically, as shown in FIG. 6, in step S250, as in the first embodiment, it is determined whether or not the load demand on the fuel cell stack 22 is small, and if it is determined that the load is large ( That is, when the output voltage is less than 0.7 V), the CPU 74 further determines whether or not emergency exhaust of the anode exhaust gas is necessary (step S260). In step S130, when the nitrogen concentration in the anode gas exceeds a predetermined reference value, it is determined that the impurity concentration is increasing. This determination criterion is based on the increase in the nitrogen concentration. Since the power generation efficiency of the engine 22 is reduced, it is preferable to execute the exhaust process, but there is a certain margin that the operation of the fuel cell stack 22 will not be stopped even if it is not executed immediately. Is set to a value. On the other hand, in step S260, the reference value determined to require emergency exhaust is higher than the determination reference value in U210 that the fuel cell stack 22 may not be able to generate power unless the exhaust treatment of the anode exhaust gas is performed. A high reference value is set.

  If it is determined in step S260 that emergency exhaust is necessary, the CPU 74 limits the output of the fuel cell stack 22 to a predetermined limit value (step S270). The predetermined limit value is an output that does not stop the fuel cell stack 22 even if the anode internal pressure is controlled to a positive pressure. When it is determined in U260 that emergency exhaust is necessary, the CPU 74 controls the electrode reaction of the fuel cell stack 22 using the limit value instead of the actually required load request value. For example, the air compressor 24 and the injector 62 are controlled so that the output voltage becomes 0.7V. By doing in this way, although the fuel cell stack 22 is smaller than the required load, it can maintain a predetermined output and can continue the operation. Thus, when performing the process of step S270, the air compressor 24 and the injector 62 function as an output adjustment part in a claim.

  Subsequently, the CPU 74 performs control to set the anode internal pressure to the same positive pressure value as that in the steady operation (step S160 in FIG. 3), and controls to discharge impurities in the anode exhaust gas (step in FIG. 3). S170).

  As described above, according to the fuel cell system of the present embodiment, the effects of the first embodiment can be obtained, and further, even when the load demand on the fuel cell stack 22 is large, the output is limited so that the anode By setting the internal pressure to a positive pressure, impurities in the anode gas can be released into the atmosphere. Therefore, it is possible to suppress a decrease in fuel cell performance due to an increase in the impurity concentration in the anode gas while avoiding the operation of the fuel cell stack 22 from being stopped.

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

  (1) In the first embodiment described above, even if the nitrogen concentration in the anode gas is increased, the control for discharging the anode exhaust gas is not performed when the load requirement is large. When the internal temperature of the stack 22 is high, the control for discharging the anode exhaust gas may not be performed.

  For example, if the internal temperature of the fuel cell stack 22 is lower than 93 ° C., it is assumed that the performance degradation of the fuel cell stack 22 is within an allowable range even if the anode internal pressure is increased from a negative pressure to a positive pressure. The temperature is higher than the temperature used in step S110 of the example (for example, 90 ° C.). Therefore, if the control for discharging the anode exhaust gas is not performed when the internal temperature is 93 ° C. or higher, the anode internal pressure is changed from a negative pressure to a positive pressure when the internal temperature of the fuel cell stack 22 is 90 to 93 ° C. As a result, the anode exhaust gas is exhausted. By doing so, it is possible to reduce the impurity concentration in the anode gas while keeping the performance deterioration of the fuel cell stack 22 within the allowable range when performing the process of discharging the anode exhaust gas.

  (2) In the above-described second embodiment, even when the load demand is large, when emergency exhaust is necessary, after the output is limited to a predetermined value, the anode exhaust gas is exhausted. However, when the internal temperature of the fuel cell stack 22 is high and emergency exhaust is required, the internal temperature of the fuel cell stack 22 is lowered to a predetermined temperature and then the anode exhaust gas is discharged. May be. That is, it is determined whether or not the internal temperature is low in step S250, and if it is determined that the internal temperature is high, processing for reducing the internal temperature of the fuel cell stack 22 is performed in step S270. For example, the internal temperature of the fuel cell can be lowered by increasing the flow rate of the cooling water flowing through the fuel cell stack 22. Even in this case, it is possible to reduce the impurity concentration in the anode gas while keeping the performance degradation of the fuel cell stack 22 within the allowable range when performing the process of discharging the anode exhaust gas.

  (3) In the above-described embodiment, it is determined whether or not the load request to the fuel cell stack 22 is small based on the output voltage of the fuel cell stack 22, but the magnitude of the load request is determined by other methods. May be. For example, it may be determined based on the output current, or may be determined based on the internal temperature of the fuel cell. This is because if the load requirement is reduced, the internal temperature of the fuel cell is considered to decrease.

  (4) In the above-described embodiment, when the water content of the electrolyte membrane is reduced based on the internal temperature of the fuel cell stack 22, it is determined that the water content of the electrolyte membrane is reduced. However, in other cases, the anode internal pressure may be reduced to a negative pressure.

  For example, when it is considered that flooding occurs on the anode side, control may be performed to reduce the anode internal pressure to a negative pressure. Specifically, in step S110, it is determined whether or not a low temperature condition (for example, 80 ° C. or less) that may be in a flooding state. If the low temperature condition is satisfied, a decrease state of the output voltage is determined, If it is lower than a predetermined rate, it is determined that a flooding state has occurred.

  As a method for determining the output voltage drop state, for example, it can be determined as follows. The output voltage value of the fuel cell stack 22 measured by the voltage sensor 54 is acquired, and the output current value of the fuel cell stack 22 measured by a current sensor (not shown) is acquired. In general, a fuel cell performing steady operation has a property that an output voltage value is uniquely determined according to an output current value, and there is a certain relationship between the output current value and the output voltage value. (Current-voltage characteristics) Based on the acquired output current value and the current-voltage characteristics of the fuel cell stack 22 stored in advance in the control unit 70, the CPU 74 determines a reference voltage value that is a reference value of the output voltage value during steady operation. Ask. Then, the obtained reference voltage value is compared with the measured value of the output voltage value acquired from the voltage sensor 54 to determine the output voltage drop state.

  If it is determined in step S110 that the flooding state has occurred, control is performed to make the anode internal pressure negative (step S120).

  When the anode internal pressure is reduced to a negative pressure, the flow rate of the anode gas is increased, so that water staying in the fuel cell stack 22 can be easily discharged, and flooding can be suppressed.

  (5) In the above-described embodiment, the reduced water content of the electrolyte membrane is determined based on the internal temperature of the fuel cell stack 22 in step S110 of FIG. 3, but may be performed based on different criteria.

  For example, it may be determined based on the output voltage of the fuel cell stack 22 whether or not the water content of the electrolyte membrane is reduced. As described in (4), the reference voltage value is compared with the measured value of the output voltage value acquired from the voltage sensor 54, and the actual measured value is reduced by a predetermined percentage or more compared to the reference voltage value. If it is, the water content of the electrolyte membrane may be determined to be in a reduced state.

  Alternatively, the reduced water content of the electrolyte membrane may be determined based on the membrane resistance of the electrolyte membrane. As described above, when the water content of the electrolyte membrane decreases, the membrane resistance of the electrolyte membrane increases. Therefore, when the membrane resistance increases to a predetermined value or more, it can be determined that the water content is in a reduced state.

  Moreover, it is good also as determining the moisture content fall state of an electrolyte membrane based on the pressure loss (cathode pressure loss) in the oxidizing gas supplied to a cathode. When the water content of the membrane is low, the amount of water is also low in the oxidizing gas flow path, and the pressure loss is reduced by reducing the obstruction of the oxidizing gas flow by the liquid water. The state can be determined. Similarly, the water content reduction state of the electrolyte membrane may be determined based on the pressure loss (anode pressure loss) in the fuel gas supplied to the anode.

  Further, the moisture content reduction state of the electrolyte membrane may be determined based on the humidity of the exhaust gas (cathode exhaust gas or anode exhaust gas). In a fuel cell, when the temperature is relatively low, the water vapor pressure in the exhaust gas is a saturated vapor pressure. However, when the temperature of the fuel cell rises and the electrolyte membrane can be in a reduced water content state, the water vapor pressure in the exhaust gas falls below the saturated vapor pressure. Therefore, an exhaust gas humidity serving as a reference for determining a moisture content lowering state is determined in advance, and when the exhaust gas humidity determined based on the measured value is lower than the exhaust gas humidity serving as the reference, the electrolyte membrane has a reduced moisture content. It can be determined that it is in a state.

  (6) In the above-described embodiment, the injector 62 is used to replenish the circulation channel with hydrogen gas, but a different configuration may be used. For example, a pressure reducing valve may be provided in place of the injector 62, and the pressure inside the anode may be controlled by adjusting the fuel gas pressure supplied to the fuel cell stack 22 with the pressure reducing valve.

  (7) In the above-described embodiment, the hydrogen supply / exhaust system has a configuration in which the circulation flow path is configured to return the anode exhaust gas to the hydrogen supply path 60, but the anode exhaust gas may not be circulated. For example, the anode exhaust gas path 63 may not be provided, and the exhaust gas exhaust path 64 may be directly connected to the fuel cell stack 22. Even in such a configuration, the impurities in the anode gas in the fuel cell stack 22 can be discharged by opening the purge valve 27. Such a configuration is suitable, for example, when all of the supplied hydrogen is used for the electrode reaction.

  (8) In the above-described embodiment, the hydrogen gas stored in the hydrogen tank 23 is used as the fuel gas containing hydrogen. However, a different configuration may be used. For example, a hydrogen-rich reformed gas obtained by using a reforming reaction such as a steam reforming reaction from a fuel such as alcohol or hydrocarbon may be used as the fuel gas. Also in this case, when the water content of the electrolyte membrane is reduced, the same effect can be obtained by controlling the reduction of the anode internal pressure to suppress an increase in resistance in the electrolyte membrane and securing the output voltage.

It is explanatory drawing which shows the structure of the fuel cell system 10 as one suitable Example of this invention. FIG. 6 is an explanatory diagram showing a relationship between anode internal pressure and operation of an injector 62. 3 is a flowchart showing a membrane water content reduction processing routine executed in the fuel cell system 10. It is a graph which shows the influence of control by the processing routine at the time of membrane water content fall. It is a figure which shows the result of having investigated the relationship between anode internal pressure, cell resistance, and cell voltage. It is a flowchart which shows a part of process routine at the time of the film | membrane water content fall in a 2nd Example. It is explanatory drawing which shows an example of the current-voltage characteristic of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 22 ... Fuel cell stack 23 ... Hydrogen tank 24 ... Air compressor 25 ... Humidification module 26 ... Diluter 27 ... Purge valve 28 ... Air cleaner 50 ... Anode internal pressure sensor 52 ... Temperature sensor 54 ... Voltage sensor 60 ... Hydrogen supply path DESCRIPTION OF SYMBOLS 61 ... Pressure regulating valve 62 ... Injector 63 ... Anode exhaust gas path 64 ... Exhaust gas exhaust path 65 ... Hydrogen pump 67 ... Oxidation gas supply path 68 ... Cathode exhaust gas path 70 ... Control part 74 ... CPU
78 ... I / O port

Claims (9)

A fuel cell system comprising a fuel cell having a solid polymer electrolyte membrane,
An impurity discharge part for discharging impurities in the anode gas;
An anode gas pressure adjusting unit for adjusting a gas pressure on the anode side of the fuel cell;
A control unit for controlling the impurity discharge unit and the anode gas pressure adjusting unit;
Further,
The controller is
The gas pressure on the anode side of the fuel cell is normally controlled to a positive pressure,
When the water content of the solid polymer electrolyte membrane is less than the predetermined amount, the gas pressure on the anode side of the fuel cell is changed from positive pressure to negative pressure to increase the differential pressure from the gas pressure on the cathode side. Execute the control to
The control unit further includes:
When the gas pressure on the anode side of the fuel cell is set to a negative pressure, and when the impurity discharge unit is controlled to discharge the impurities in the anode gas to the outside of the fuel cell system, Before the discharge, the anode gas pressure adjusting unit is controlled to increase the gas pressure on the anode side to a positive pressure. The fuel cell system according to claim 1,
The controller is
It is determined whether or not the impurity concentration in the anode gas in the fuel cell is in an increased state. When it is determined that the impurity concentration is in an increased state, the impurity in the anode gas is determined as the fuel cell system. A fuel cell system characterized by being discharged to the outside. The fuel cell system according to claim 1 or 2, wherein
The controller is
When the gas pressure on the anode side of the fuel cell is set to a negative pressure and the load required for the fuel cell is larger than a predetermined load requirement value, impurities in the anode gas Cell system characterized by not discharging the fuel. The fuel cell system according to claim 1 or 2, wherein
The controller is
When the gas pressure on the anode side of the fuel cell is set to a negative pressure, and the internal temperature of the fuel cell is equal to or higher than a predetermined temperature, impurities in the anode gas are not discharged. A fuel cell system. A fuel cell system according to any one of claims 1 to 4,
An output adjusting unit for adjusting the output of the fuel cell;
In addition,
The controller is
Before increasing the gas pressure on the anode side to a positive pressure, the output adjustment unit is controlled to limit the output of the fuel cell to a predetermined output value. A fuel cell system according to any one of claims 1 to 5,
An internal temperature adjusting unit for adjusting the internal temperature of the fuel cell;
In addition,
The controller is
Before increasing the gas pressure on the anode side to a positive pressure, the internal temperature adjusting unit is controlled to reduce the internal temperature of the fuel cell to a predetermined temperature. The fuel cell system according to any one of claims 1 to 6, further comprising:
A hydrogen gas supply path for supplying hydrogen gas to the anode of the fuel cell;
An anode exhaust gas path that guides the gas discharged from the anode of the fuel cell to the hydrogen gas supply path,
A part of the hydrogen gas supply path and the anode exhaust gas path form a circulation path for circulating hydrogen between the inside of the fuel cell,
The anode gas pressure adjusting unit adjusts the pressure in the circulation channel as a gas pressure on the anode side. The fuel cell system according to claim 7, wherein
The anode gas pressure adjusting unit is
An injector provided upstream of the circulation flow path in the hydrogen gas supply path and having a discharge port for discharging the hydrogen gas to the circulation flow path side and a valve for opening and closing the discharge port;
The controller is
A fuel cell comprising: controlling the anode gas adjusting unit so as to reduce the gas pressure on the anode side from a positive pressure to a negative pressure by adjusting an opening / closing state of the discharge port by the valve of the injector. system. An impurity discharging method for discharging impurities in an anode gas of the fuel cell in a fuel cell system including a fuel cell having a solid polymer electrolyte membrane, to the outside of the fuel cell system,
The gas pressure on the anode side of the fuel cell is normally controlled to a positive pressure, and when the water content of the solid polymer electrolyte membrane is less than the predetermined amount, the gas pressure on the anode side of the fuel cell is set to a positive pressure. A first step of executing control to increase the pressure difference from the gas pressure on the cathode side by changing from negative pressure to negative pressure;
A second step of determining whether or not an impurity concentration in the anode gas in the fuel cell is increased;
When the gas pressure on the anode side of the fuel cell is set to a negative pressure in the first step, and when the impurity concentration is determined to be increased in the second step A third step of increasing the gas pressure on the anode side to a positive pressure;
The third keep step, after the gas pressure in the anode is raised to a positive pressure, a fourth step of discharging the impurities in the anode gas to the outside of the fuel cell system,
An impurity discharging method comprising:

Images