JP2006093028A - Fuel cell system and film drying state estimation method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately judge a drying state of a polymer film of a fuel cell in a simple system. <P>SOLUTION: A temperature sensor 15 is arranged in the vicinity of a ventilating outlet 14 of a stack case 12 housing the fuel cell 11. A ventilating device 13 for ventilating inside the stack case 12 is activated before starting the fuel cell 11, and a drying state of the polymer film 1 of the fuel cell 11 is estimated by a detected value of the temperature sensor 15 at that time, or more concretely, by the inclination of the time change of the detected value up to the time when the detected value of the temperature sensor 15 reaches an initial peak. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system in which a fuel cell is housed in a case, and in particular, a novel fuel cell system and fuel for estimating the dry state of a polymer film constituting the fuel cell by humidity detection means installed in the case The present invention relates to a method for estimating a film dry state of a battery.

  The fuel cell system supplies hydrogen gas to the fuel electrode (hydrogen electrode) of the fuel cell and air to the oxidant electrode (air electrode), respectively, and causes hydrogen and oxygen to react electrochemically in the fuel cell to generate generated power. To get. Such a fuel cell system is highly expected to be put into practical use, for example, as a driving energy source for automobiles. Currently, research and development for practical use is actively performed.

  As a fuel cell used in the fuel cell system, for example, a solid polymer type fuel cell is known as being suitable for in-vehicle use. In this solid polymer type fuel cell, a polymer membrane is provided between a fuel electrode and an air electrode, and this polymer membrane functions as a hydrogen ion conductor (electrolyte membrane). Yes. In this solid polymer type fuel cell, a reaction in which hydrogen gas is separated into hydrogen ions and electrons occurs in the fuel electrode, and a reaction in which water is generated from oxygen gas, hydrogen ions and electrons in the air electrode. At this time, the polymer film functions as an ion conductor, and hydrogen ions move in the polymer film toward the air electrode.

  By the way, in order for the polymer membrane to function as an ion conductor, it is necessary to include a certain amount of moisture in the polymer membrane. For this reason, in a fuel cell system using such a polymer electrolyte fuel cell, a supply gas such as hydrogen gas or air is supplied to the fuel cell while being humidified by a humidifier, or water is directly supplied to the fuel cell. In general, the polymer membrane of the fuel cell is humidified by supplying it. In this case, it is particularly important to appropriately perform moisture management, and it is necessary to control the moisture in the system so that the polymer membrane of the fuel cell is always in an optimum humidified state.

From this point of view, for example, in the following Patent Document 1, various patterns of cell voltage change over time for each single cell or each block are stored, and the actual voltage change is compared with the pattern. Has proposed a driving method of selecting an optimal driving pattern, such as determining the water-containing state of the water and promoting the wetting of the membrane in accordance with the state.
Japanese Patent Laid-Open No. 9-245826

  However, when storing and comparing cell voltage aging patterns as in the technique described in Patent Document 1, there are many parameters having sensitivity to cell voltage, and these parameters affect each other. It is very difficult to specify the moisture content of the membrane only from the change of the cell voltage because it is likely to match. In particular, when a fuel cell is used as a driving energy source for an automobile, there is a problem that required change in output is severe and it is difficult to set a change pattern of cell voltage that can be compared.

  Therefore, an object of the present invention is to provide a fuel cell system and a fuel cell membrane dry state estimation method capable of accurately determining the dry state of a polymer membrane of a fuel cell by a simple method.

  In order to achieve the above-mentioned object, a fuel cell system according to the present invention includes a fuel cell having a polymer membrane as an electrolyte membrane, a case for housing the fuel cell, and a gas in the case from the ventilation outlet of the case to the outside. Ventilation means for discharging to the outside, humidity detection means installed near the ventilation outlet of the case, and membrane dry state estimation means for estimating the dry state of the polymer film based on the detection result of the humidity detection means when the ventilation means is activated It is set as the structure provided with.

  The method for estimating the membrane dry state of a fuel cell according to the present invention is a method for estimating the membrane dry state of a fuel cell that is provided with a polymer membrane as an electrolyte membrane and is housed inside a case that is ventilated by a ventilation means. Thus, humidity detection means is installed near the ventilation outlet of the case, and the dry state of the polymer film is estimated based on the detection result of the humidity detection means.

  For example, considering a case where a fuel cell having a structure in which the outer peripheral end face of the polymer membrane is exposed is housed in the case, the humidity inside the case increases due to moisture evaporated from the outer peripheral end face of the polymer membrane. Thus, the humidity of the gas discharged from the ventilation outlet of the case when the ventilation means is operated reflects the amount of water evaporated from the polymer film. Therefore, the moisture amount evaporated from the polymer membrane of the fuel cell can be grasped by detecting the humidity of the gas discharged from the ventilation outlet of the case when the ventilation means is operated by the humidity detection means. The membrane dry state estimating means can accurately determine the dry state of the polymer membrane of the fuel cell by a simple method by estimating the dry state of the polymer membrane based on the detection result of the humidity detecting means. It becomes possible.

  In general, according to the present invention, the humidity at the ventilation outlet of the case used in most cases from various requirements (for example, protection of the fuel cell stack itself, prevention of electric shock-short circuit, mounting of brackets, container for peripheral equipment, etc.) It is possible to accurately determine the dry state of the polymer film by an extremely simple method of installing a detection means and estimating the dry state of the polymer film based on the detection result.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, the structure of a single cell that is one power generation unit of a solid polymer type fuel cell provided in the fuel cell system of the present embodiment will be briefly described with reference to FIG. A single cell constituting a solid polymer type fuel cell includes a polymer membrane 1 as an electrolyte membrane, and a carbon layer or a gas diffusion layer supporting a catalyst such as platinum is formed on both surfaces of the polymer membrane 1. Each is formed as a fuel electrode 2 serving as an anode electrode and an oxidizer electrode 3 serving as a cathode electrode. In general, the polymer film 1 and the electrodes 2 and 3 are collectively referred to as a membrane electrode assembly (MEA).

  The single cell of the fuel cell has a structure in which this MEA is sandwiched between a pair of bipolar plates 4 and 5. That is, an anode bipolar plate 4 made of a porous conductive material having a fuel gas passage is disposed on the surface of the fuel electrode 2 opposite to the surface on which the polymer film 1 contacts. A cathode bipolar plate 5 made of a porous conductive material having an oxidant gas passage is disposed on the surface of the oxidant electrode 3 opposite to the surface on which the polymer film 1 contacts.

  Here, the anode bipolar plate 4 and the cathode bipolar plate 5 are overlapped with the polymer film 1 of the MEA through the seal 6 at the outer peripheral end portion. In the single cell in which the MEA is sandwiched via the seal 6, the outer peripheral end surface of the polymer film 1 of the MEA is not covered with the seal 6 or the like and is exposed to the outside (in FIG. 1). (See Part A of). Therefore, in such a single cell, the moisture retained by the polymer membrane 1 evaporates little by little from the membrane end surface during operation of the fuel cell.

  A solid polymer type fuel cell has a stack structure in which a large number of single cells having the above structure are stacked. When a fuel cell having such a stack structure is incorporated into a system, generally, as shown in FIG. 2, a stack case 12 is used as an electric shock prevention or installation bracket, and the fuel cell 11 is disposed inside the stack case 12. It is stored in. In this case, the stack case 12 is always provided with a ventilator 13 for ventilating the inside of the case. This is because it is difficult to completely seal the hydrogen used as the fuel gas, and a small amount of leakage occurs from the fuel cell 11, and it is necessary to prevent the leakage of hydrogen from staying in the stack case 12 and dilute the concentration. Because there is. In addition, a hydrogen concentration sensor and a temperature sensor (not shown) are usually installed at the ventilation outlet 14 of the stack case 12, and the detection values of these sensors are used to monitor the deterioration and breakage of the sealing performance. Accordingly, the ventilation device 13 is operated to ventilate the stack case 12.

  Here, in the fuel cell system of the present embodiment, in addition to the hydrogen concentration sensor and the temperature sensor, a humidity sensor 15 that is a humidity detecting means is installed in the vicinity of the ventilation outlet 14 of the stack case 12, and the exhaust gas is exhausted from the ventilation outlet 14. By detecting the humidity of the air in the stack case 12, the dry state of the polymer membrane 1 of the fuel cell 11 is estimated. That is, in the solid polymer type fuel cell 11 having the above-described structure, the moisture held in the polymer membrane 1 evaporates little by little from the end surface of the membrane during operation. Therefore, the humidity of the gas discharged from the ventilation outlet 14 of the stack case 12 when the ventilator 13 is operated reflects the amount of water evaporated from the polymer film 1. Therefore, by detecting the humidity of the gas discharged from the ventilation outlet 14 of the stack case 12 by the humidity sensor 15 when the ventilation device 13 is operated, the amount of water evaporated from the polymer film 1 of the fuel cell 11 is grasped. Can do.

  In addition, when using the fuel cell 11 in which single cells are stacked as shown in FIG. 1 as in the present embodiment, the inside of the stack case 12 is in a high humidity state due to water vapor evaporated from the film end face during operation. . Therefore, when the ambient temperature outside the stack case 12 is low, condensation may occur on the wall surface of the stack case 12 or the surface of the fuel cell 11, and the ventilator 13 is also used for the purpose of preventing such condensation. Is done.

  FIG. 3 is a diagram showing a schematic configuration of the fuel cell system of the present embodiment. Fuel gas (hydrogen) and oxidant gas (air) are supplied to the fuel cell 11 housed in the stack case 12 via a humidifier 16 by a fuel gas supply device or an oxidant gas supply device (not shown). After the reaction is consumed in the battery 11, the remaining gas is discharged. The fuel cell 11 is cooled by the coolant pumped by the coolant pump 17 and is exhausted by a heat exchanger such as a radiator (not shown). The generated electric power is taken out by the load device 18 and used.

  The stack case 12 is provided with a ventilation inlet 19 and a ventilation outlet 14, and air is pumped into the stack case 12 by a ventilator 13 installed on the ventilation inlet 19 side, and the stack case 12 has an outside of the stack case 12. To be discharged. As described above, the humidity sensor 15 for detecting the humidity of the exhausted air is installed in the vicinity of the ventilation outlet 14. Then, the controller (membrane dry state estimating means) 20 reads the detected value of the humidity sensor 15, estimates the dry state of the polymer membrane 1 based on the detection result, and accordingly the fuel cell system of this embodiment. By outputting an operation command to each actuator in the above, the operation state of the fuel cell 1 is controlled to be in an optimum state according to the dry state of the polymer film 11.

  FIG. 4 is a diagram illustrating an example of a change in air humidity in the vicinity of the ventilation outlet 12 of the stack case 12 when the fuel cell 1 is started. In the drawing, the change in humidity with time is shown on the upper side, and the amount of output output from the fuel cell 11 is shown on the lower side.

  Usually, when the operation of the fuel cell 11 is resumed without a large interval, the ventilation device 13 is stopped after the operation of the fuel cell 11 is stopped, and then the water vapor evaporated during the operation of the fuel cell 11 is used. The humidity in the stack case 12 increases as the temperature in the stacker 12 decreases. On the other hand, at the ventilation outlet 14 where the humidity sensor 15 is installed, the humidity is substantially equal to the outside air. At the next start-up, if only the ventilator 13 is operated before the fuel cell 11 is started (before the fuel gas or oxidant gas is supplied and the coolant is stopped), the high humidity in the stack case 12 is increased. Since air is discharged outside from the ventilation outlet 14 and then approaches the outside air introduced from the ventilation inlet 19, the humidity in the vicinity of the ventilation outlet 14 changes so as to draw a mountain as shown in the figure. Thereafter, when the operation of the fuel cell 11 is started, the humidity increases again due to the evaporation of water vapor, and reaches an equilibrium with a balance between the ventilation flow rate and the humidity of the outside air.

  However, if the previous operation is operated under an operating condition that promotes drying of the polymer film 1 or has not been operated for a long period of time, a peak of the humidity change at the start of the ventilation device 13 may occur. Even if it is lower than normal or equivalent, the humidity after starting power generation does not increase, and there is almost no difference from the start of ventilation.

  Therefore, in the fuel cell system of this embodiment, the dry state of the polymer membrane 1 of the fuel cell 11 is estimated using the change in humidity in the vicinity of the ventilation outlet 14 of the stack case 12 as described above, and the estimation result Depending on the situation, the subsequent operating conditions are optimized. Thereby, for example, even when the polymer film 1 is completely dried and cannot withstand the operation, such as when the operation is resumed after being left for a long time, the state can be determined before the operation is started. Response can be made promptly. Alternatively, when the output can be reduced even if the operation is possible, it can be seen that the cause is the drying of the polymer film 1, so that the operation for searching for the cause of the output reduction is not required, and after some output restriction, If the molecular film 1 is sufficiently wetted, it is possible to return to normal operation.

  Further, in the fuel cell system of this embodiment, the dry state of the polymer membrane 1 of the fuel cell 11 is estimated based on the detection result of the humidity sensor 15 installed in the vicinity of the ventilation outlet 14 of the stack case 12. The following effects can also be obtained. That is, it is certain to directly monitor the humidity of the oxidant gas (air) at the oxidant electrode outlet of the fuel cell 11 only for grasping the dry state of the polymer membrane 1, and such a method is also possible. Although it is conceivable, the condition of constant exposure to high temperature and high humidity off-gas is a very severe environment for the sensor, and it is necessary to take measures such as preventing condensation at the sensor part and keeping the mounting pipe part warm. There is a problem that the degree is low. On the other hand, in the fuel cell system of the present embodiment, the high level of the fuel cell 1 can be achieved simply by attaching the humidity sensor 15 to a part where the environmental conditions such as the vicinity of the ventilation outlet 14 of the stack case 12 are moderate and the degree of freedom of installation is high. Since the dry state of the molecular film 1 can be estimated, it can contribute to cost reduction and downsizing of the entire system.

  FIG. 5 is a diagram showing a control flow in the fuel cell system of the present embodiment. In the fuel cell system of the present embodiment, when the system is activated, first, the humidity sensor 15 is activated to start monitoring the air humidity at the ventilation outlet 14 of the stack case 12 (step S1). At this time, the humidity at the start of monitoring is stored as H_ini.

  Next, the ventilation device 13 is operated to start ventilation in the stack case 12 (step S2). Then, the time change of the humidity at the ventilation outlet 14 of the stack case 12, particularly the slope until the humidity first rises and reaches the peak, is calculated, and it is confirmed whether the slope is positive (step S 3). ). Here, if the inclination is negative, it means that the inside of the stack case 12 is drier than the outside air. Therefore, the polymer membrane 1 of the fuel cell 11 is in a very dry state and cannot withstand operation. It is determined that there is (step S4), and the operation is stopped (step S5).

  On the other hand, as a result of the confirmation in step S3, if the slope of the humidity change over time is positive, it is next confirmed whether or not the slope is equal to or less than the first reference value DH_L1 (step S6). Here, when the inclination is equal to or smaller than the first reference value DH_L1, it is determined that the polymer membrane 1 of the fuel cell 11 is quite dry, but can be operated under specific restrictions (step S7). The output that can be taken out of the fuel cell 11 is limited to a predetermined value or less, and the humidifier 16 is instructed to supply gas in a highly humidified state (step S8).

  Then, after performing the output limitation and the high humidification operation command as described above, the cell voltage of the fuel cell 11 is monitored and compared with the voltage level in the normal state stored in the controller 20 in advance. It is determined whether or not has returned to the normal voltage level (step S9). Then, when the cell voltage level of the fuel cell 11 returns to the normal voltage level, the operation shifts to normal operation (step S10).

  On the other hand, as a result of the confirmation in step S6, if the slope of the humidity change over time exceeds the first reference value DH_L1, then the slope is equal to or less than the second reference value DH_L2 (DH_L2> DH_L1). It is confirmed whether or not there is (step S11). Here, when the inclination is equal to or less than the second reference value DH_L2, that is, between the first reference value DH_L1 and the second reference value DH_L2, the polymer film 1 of the fuel cell 11 is in a gently dry state. Therefore, it is determined that the operation is possible with some output restriction (step S12), and some restriction is applied to the output that can be taken out of the fuel cell 11 (step S13). The output limit here is a limit that is looser than the output limit in step S8, and the load device 18 is commanded to a value larger than that in step S8 as the power that can be taken out of the fuel cell 11.

  Then, after performing the output restriction as described above, the cell voltage of the fuel cell 11 is monitored and compared with the voltage level in the normal state stored in the controller 20 in advance, and the cell voltage level is the voltage in the normal state. It is determined whether or not the level has been restored (step S14). Then, when the cell voltage level of the fuel cell 11 returns to the normal voltage level, the operation shifts to normal operation (step S10).

  On the other hand, as a result of the confirmation in step S11, if the slope of the change in humidity over time exceeds the second reference value DH_L2, then the detection of the humidity sensor 15 after starting the operation of the fuel cell 11 is performed. The difference between the value and the initial value H_ini stored at the start of monitoring is calculated, and it is confirmed whether or not the difference is equal to or less than a predetermined reference value HD (step S15). When the difference is equal to or less than the reference value HD, the polymer membrane 1 of the fuel cell 11 is similar to the case where the slope of the time change of the detection value of the humidity sensor 15 is equal to or less than the second reference value DH_L2. Judging that the fuel cell 11 is in a moderately dry state (step S12), the output of the fuel cell 11 can be slightly limited (step S13), and the cell voltage level of the fuel cell 11 returns to the normal voltage level. At this stage, the operation shifts to normal operation (step S10).

  On the other hand, if the result of the confirmation in step S15 is that the difference between the detected value of the humidity sensor 15 after starting the operation of the fuel cell 11 and the initial value H_ini stored at the start of monitoring exceeds a predetermined reference value HD First, it is determined that the polymer membrane 1 of the fuel cell 11 is in a normal wet state (step S16), and the routine proceeds to normal operation (step S10).

  As described above, in the fuel cell system according to the present embodiment, in general, in most cases due to various requirements (for example, protection of the fuel cell 11 itself, electric shock-short circuit prevention, bracket attachment, peripheral container, etc.). By using a very simple method of installing humidity detecting means (humidity sensor 15) at the ventilation outlet 14 of the stack case 12 to be used and estimating the dry state of the polymer membrane 1 of the fuel cell 11 based on the detection result. The dry state of the polymer film 1 can be accurately determined. Further, for example, as compared with the case where the humidity of the oxidant gas at the oxidant electrode outlet of the fuel cell 11 is directly monitored, the environmental conditions for the humidity sensor 15 are loose, and there is a degree of freedom of installation, so the cost and size can be reduced. It is.

  Furthermore, in the fuel cell system of the present embodiment, the ventilation device 13 is operated before the operation of the fuel cell 11 is started and the detected value of the humidity sensor 15 is monitored, so that the polymer in advance before the fuel cell 11 is operated. The dry state of the membrane 1 can be determined, and the operating state of the fuel cell 11 can be optimized accordingly. In addition, when the output is reduced due to other factors after the operation of the fuel cell 11 is started, it is possible to identify the cause more quickly.

(Second Embodiment)
Next, a fuel cell system according to a second embodiment to which the present invention is applied will be described with reference to FIG. FIG. 6 is a diagram showing a schematic configuration of the fuel cell system of the present embodiment. The fuel cell system of the present embodiment has the same basic configuration as that of the fuel cell system of the first embodiment shown in FIG. 3, and the temperature detection for detecting the outside air temperature in the configuration of the fuel cell system of the first embodiment. A temperature sensor 21 as a means is added. The temperature sensor 21 is installed in the vicinity of the exhaust outlet 14 of the stack case 12, for example, similarly to the humidity sensor 15.

  Here, a flow of control in the fuel cell system of the present embodiment will be briefly described. Also in the fuel cell system of this embodiment, the outline of basic control is the same as that of the first embodiment described above, and control is performed according to the control flow shown in FIG. In the battery system, the monitoring of the outside air temperature by the temperature sensor 21 is started simultaneously with the start of the humidity monitoring by the humidity sensor 15 in step S1, and the initial temperature value T_ini is stored together with the initial humidity value H_ini.

  Then, when determining the slope of the time change of humidity in step S6, a coefficient corresponding to the initial temperature T_ini is applied to the first reference value DH_L1 with reference to the temperature table stored in advance in the controller 20. To correct. For example, when the outside air temperature is high, the humidity change width becomes small. Therefore, the first reference value DH_L1 is corrected by a coefficient smaller than 1, and when the outside air temperature is low, the humidity change width becomes large. Correction is performed by multiplying the reference value DH_L1 of 1 by a coefficient larger than 1. Similarly, in step S11, the second reference value DH_L2 is corrected by applying a coefficient corresponding to the initial temperature T_ini. Further, also in step S15, the predetermined reference value HD is similarly corrected by applying a coefficient corresponding to the initial temperature T_ini. Then, the dry state of the polymer membrane 1 of the fuel cell 11 is determined using each corrected reference value.

  As described above, in the fuel cell system of the present embodiment, not only the humidity change of the air discharged from the exhaust outlet 14 of the stack case 12 but also the state of the outside air temperature (temperature environment) is taken into consideration. Since the dry state of the polymer film 1 is estimated, the dry state of the polymer film 1 can be determined with higher accuracy.

(Third embodiment)
Next, a fuel cell system according to a third embodiment to which the present invention is applied will be described with reference to FIG. FIG. 7 is a diagram showing a schematic configuration of the fuel cell system of the present embodiment. The basic configuration of the fuel cell system of the present embodiment is the same as that of the fuel cell system of the second embodiment shown in FIG. 6, and the operating state transmission device as a notification means is added to the configuration of the fuel cell system of the second embodiment. 22 is added. In such a fuel cell system of the present embodiment, the fuel cell 11 that performs power generation is used as a driving power source of the vehicle, for example, and the operation state transmission device 22 provides information on the dry state of the polymer film 1 of the fuel cell 11. In addition, it is used for the purpose of informing the driver of the vehicle, for example, information such as an image, text, sound, warning sound, etc., about information on operation restrictions of the fuel cell 11 when the polymer membrane 1 is dry. Of course, when the controller 20 described above incorporates a similar notification function, it is not necessary to separately provide the operation state transmission device 22 as a separate configuration.

  Here, a flow of control in the fuel cell system of the present embodiment will be briefly described. Also in the fuel cell system of this embodiment, the outline of basic control is the same as that of the first and second embodiments described above, and control is performed according to the control flow shown in FIG. In the fuel cell system according to the embodiment, when it is determined in step S4, step S7, or step S12 that the polymer membrane 1 of the fuel cell 11 is in a dry state, a command is sent to the driving state transmission device 22 to indicate the state. Let the driver know. Further, depending on the dry state of the polymer membrane 1, for example, when the operation is stopped in step S5, when the output restriction and high humidification operation are performed in step S8, when the output restriction is performed in step S13, etc. A command may be sent to the transmission device 22 to inform the vehicle driver of the information. Furthermore, when returning to normal driving after performing output restriction, a command may be sent to the driving state transmission device 22 to inform the vehicle driver of the information.

  As described above, in the fuel cell system according to the present embodiment, the information on the dry state of the polymer film 1 of the fuel cell 11 and the fuel when the polymer film 1 is dried using the operation state transmission device 22. Since the driver of the vehicle on which the fuel cell system is mounted is informed of information on the operation restriction of the battery 11, the vehicle driver can predict the reduction in output in advance, It is possible to eliminate the inconvenience that the driver takes time to deal with the cause of the decrease in output.

  In the fuel cell systems of the second and third embodiments described above, the temperature value is monitored together with the humidity. However, when the ventilator 13 is started in step S2 in the flowchart of FIG. If the temperature change is very small or not at all, there is a high possibility that the ventilation device 13 itself has failed and is not operating, or the piping is clogged and the air flow is hindered. Therefore, by determining whether or not the change range of the detection value of the humidity sensor 15 and the change range of the detection value of the temperature sensor 21 are within a predetermined range when the ventilation device 13 is operated, failure of the ventilation device 13 or piping It is possible to determine whether or not clogging of the polymer film 1 has occurred, and diagnosis can be performed with a sensor for estimating the dry state of the polymer film 1 without incorporating a sensor or control logic for fault diagnosis in the ventilator 13 itself. I can also serve. By performing failure diagnosis of the ventilation device 13 by such a method, simple and appropriate failure diagnosis can be performed while reducing the number of parts.

  In the fuel cell system of each embodiment described above, the humidity (and temperature) when the humidity sensor 15 (and the temperature sensor 21) is installed near the exhaust outlet 14 of the stack case 12 and the ventilator 13 is started is detected. Therefore, it is possible to determine whether or not the inside of the stack case 12 is saturated and dew condensation occurs based on these detection values. Therefore, when it is determined from the detection value of the humidity sensor 15 (and the temperature sensor 21) that the stack case 12 is in a dew condensation state, a ventilator is provided so that the water vapor in the stack case 12 is quickly discharged. It is desirable to command the 13 air flow to increase. As a result, the condensed liquid water accumulates in the stack case 12 and becomes dirty, thereby preventing problems such as short-circuiting a single cell constituting the fuel cell 11 or causing electric leakage from the fuel cell 11 to the stack case 12. It becomes possible to do.

It is principal part sectional drawing which shows the structure of the single cell which comprises a solid polymer type fuel cell. It is a schematic diagram which shows the structure of the stack case which accommodated the fuel cell. It is a figure which shows the structure of the fuel cell system of 1st Embodiment. It is a figure which shows the mode of the time change of the air humidity in the ventilation outlet of a stack case. It is a flowchart which shows the flow of control in the fuel cell system of this invention. It is a figure which shows the structure of the fuel cell system of 2nd Embodiment. It is a figure which shows the structure of the fuel cell system of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polymer membrane 11 Fuel cell 12 Stack case 13 Ventilation apparatus 14 Ventilation exit 15 Humidity sensor 20 Controller 21 Temperature sensor 22 Operation state transmission apparatus

Claims (12)

A fuel cell having a polymer membrane as an electrolyte membrane;
A case for storing the fuel cell;
A ventilation means for discharging the gas in the case to the outside from the ventilation outlet of the case;
Humidity detecting means installed near the ventilation outlet of the case;
A fuel cell system comprising: a membrane dry state estimating unit that estimates a dry state of the polymer membrane based on a detection result of the humidity detecting unit when the ventilation unit is operated. An electrode is formed on the surface of the polymer membrane to form a membrane electrode assembly, and the membrane electrode assembly is sandwiched between electrode plates to constitute a fuel cell.
2. The fuel cell system according to claim 1, wherein in the fuel cell, an outer peripheral end face of the polymer film is exposed to the outside.   The fuel cell system according to claim 1 or 2, wherein the ventilation means is operated before the fuel cell is started.   The membrane dry state estimating means estimates the dry state of the polymer membrane before starting the fuel cell from the slope of the time variation of the detected value until the detected value of the humidity detecting means reaches the first peak. The fuel cell system according to claim 3.   The fuel cell system according to claim 3 or 4, wherein an operation state of the fuel cell is optimized according to an estimation result of the membrane dry state estimation means. A temperature detecting means for detecting the outside air temperature;
The fuel cell according to any one of claims 1 to 5, wherein the membrane dry state estimation unit corrects the estimation result of the dry state of the polymer membrane according to the detection result of the temperature detection unit. system.   7. The fuel cell system according to claim 6, wherein the presence or absence of a gas flow at the ventilation outlet of the case is determined based on detection results of the humidity detection unit and the temperature detection unit.   It is determined that a failure has occurred in the ventilation means when the change width of the detection value of the humidity detection means and the change width of the detection value of the temperature detection means are within a predetermined range during the operation of the ventilation means. 8. The fuel cell system according to claim 7, wherein   9. The fuel cell system according to claim 6, wherein it is determined whether or not the inside of the case is in a dew condensation state based on detection results of the humidity detection unit and the temperature detection unit. .   The fuel cell system according to claim 9, wherein when it is determined that the inside of the case is in a dew condensation state, a ventilation flow rate by the ventilation unit is increased. The fuel cell is a fuel cell used as a driving power source for a vehicle,
11. The fuel cell system according to claim 1, further comprising notification means for notifying a driver of the vehicle of information on an estimation result of the film dry state estimation means. A method of estimating a membrane dry state of a fuel cell that is provided with a polymer membrane as an electrolyte membrane and is housed inside a case that is ventilated by a ventilation means,
A method for estimating a membrane dry state of a fuel cell, comprising: installing a humidity detection means near a ventilation outlet of the case, and estimating a dry state of the polymer membrane based on a detection result of the humidity detection means.

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