JP5396325B2 - FUEL CELL SYSTEM AND CONTROL METHOD FOR FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system used in a fuel cell vehicle or the like and a control method for the fuel cell system.

  In a fuel cell mounted on a fuel cell vehicle or the like, a membrane electrode structure (MEA) is formed by sandwiching a solid polymer electrolyte membrane (hereinafter referred to as an electrolyte membrane) between an anode and a cathode from both sides. It is known that a pair of separators are arranged on both sides of a body to constitute a flat unit fuel cell (hereinafter referred to as a unit cell), and a plurality of unit cells are stacked to form a fuel cell stack. In a fuel cell, hydrogen is supplied as an anode gas (reactive gas) to the anode and air is supplied as a cathode gas (reactive gas) to the cathode, so that hydrogen ions generated by the catalytic reaction at the anode pass through the electrolyte membrane. It moves to the cathode and generates electricity by causing an electrochemical reaction with oxygen in the air at the cathode.

In the fuel cell described above, it is necessary to maintain the electrolyte membrane in a wet state in order to exhibit desired power generation performance. Therefore, the following patent document discloses a technique for grasping a humidified state (water content or the like) in a fuel cell using a dew point meter.
Specifically, in Patent Document 1, a dew point meter is installed in a cathode off gas discharge passage through which a cathode off gas supplied for power generation by a fuel cell flows, and the fuel cell is based on the dew point of the cathode off gas measured by the dew point meter. A configuration for measuring the amount of water discharged from the water is known.
In Patent Document 2, a dew point meter is installed between a humidifier and a fuel cell in an anode gas supply path for supplying anode gas to the fuel cell, and the anode gas is determined based on the measurement result of the dew point meter. A configuration is known in which the dew point (humidified state) of the anode gas is controlled by heating or cooling.

JP 2008-311081 A JP 2005-166309 A

However, in Patent Document 1 described above, the cathode offgas flowing through the cathode offgas discharge path is always highly humid. Therefore, when the temperature of the cathode offgas is relatively low, such as when the fuel cell system is started up or during a transition, water vapor in the cathode offgas is likely to condense in the cathode offgas discharge path. And since the condensed water adheres to the dew point meter, there is a problem that a measurement error occurs in the dew point meter or the responsiveness is lowered, so that the dew point of the cathode off gas cannot be measured accurately.
Moreover, in the structure of patent document 2, the anode gas which distribute | circulates the downstream rather than a humidifier is comparatively humid because it is humidified with a humidifier. For this reason, there is a problem that, as in the above-mentioned Patent Document 1, water adheres to the dew point meter due to condensation or the like, and accurate measurement cannot be performed.

  Therefore, the present invention provides a fuel cell system and a control method for the fuel cell system that can improve the measurement accuracy by the absolute humidity measuring means and accurately grasp the state quantity in the fuel cell based on the measurement result of the absolute humidity measuring means. It is to provide.

In order to solve the above problems, the invention described in claim 1 is directed to a fuel cell (for example, the fuel cell stack 2 in the embodiment) that is supplied with a reaction gas and generates electric power, and an electrode in the fuel cell. A reaction gas channel (for example, the anode gas channel 21 and the cathode gas channel 22 in the embodiment) and a reaction gas supply channel through which the reaction gas supplied to the reaction gas channel flows. (For example, the anode gas supply channel 23 and the cathode gas supply channel 24 in the embodiment) and the off gas discharge channel (for example, the anode gas discharge channel in the embodiment) through which the off gas discharged from the reaction gas channel flows. 35 and the cathode gas discharge flow path 38), and branch from a branch portion on at least one of the reaction gas supply flow path and the off-gas discharge flow path. A branch channel (for example, branch channels 41 to 44 in the embodiment) and an absolute humidity measuring means (for example, dew point meters 51 to 54 in the embodiment) disposed on the branch channel. A heating means (for example, heaters 45 to 48 in the embodiment) is provided in the branch flow path from the section to the absolute humidity measuring means , and a pressure loss forming means is provided downstream of the heating means on the branch flow path. (For example, the narrow tube portions 55 to 58 in the embodiment) are provided, and the downstream end of the branch flow path is a cathode off gas discharge flow path through which the cathode off gas discharged from the fuel cell flows out of the off gas discharge flow path. (For example, it is connected to the cathode offgas discharge channel 38 in the embodiment) .

The invention described in claim 2 is characterized in that the heating means heats the fluid flowing through the branch channel to an operating temperature of the fuel cell or higher.

The invention described in claim 3 is characterized in that the branch flow path is provided with an open / close valve capable of opening and closing the inside of the branch flow path.
In the invention described in claim 4, an anode reaction gas channel (for example, the anode gas channel 21 in the embodiment) that circulates the anode reaction gas along the anode in the fuel cell is provided as the reaction gas channel. The reaction gas supply channel includes an anode reaction gas supply channel (for example, the anode gas supply channel 23 in the embodiment) through which the anode reaction gas supplied to the anode reaction gas channel flows, and the off gas As an exhaust passage, an anode off-gas exhaust passage (for example, the anode gas exhaust passage 35 in the embodiment) through which the anode off-gas exhausted from the anode reaction gas passage circulates is provided, and the branch passage includes the anode reaction Branch from a branch portion on at least one of the gas supply channel and the anode off-gas discharge channel. The branch flow path is provided with an open / close valve (for example, the open / close valves 59 and 60 in the embodiment) that can open and close the branch flow path, and the fuel cell system measures the pressure of the anode reaction gas. An anode reaction gas measurement means; and a pressure control unit (for example, an anode gas pressure determination means 61 in the embodiment) that controls opening and closing of the on-off valve based on a measurement result of the anode reaction gas measurement means, and the pressure The control unit opens the on-off valve when the pressure of the anode reaction gas is equal to or higher than a predetermined value when the fuel cell is started, and closes the on-off valve when the fuel cell is stopped. And

  The invention described in claim 5 is the method of controlling a fuel cell system according to any one of claims 1 to 4, wherein the humidity measuring means is the reaction gas flowing through the branch flow path. A dew point meter for measuring the dew point of the fuel cell system, wherein the fuel cell system is measured by a cooling means (for example, the cooling means 13 in the embodiment) for cooling the fuel cell by circulating a refrigerant through the fuel cell, and the dew point meter. A control unit (for example, a humidified state determination unit 64) that controls the fuel cell using the reactive gas dew point, and the control unit uses the measured reactive gas dew point to A step of obtaining at least one state quantity among a first relative humidity of the reaction gas with respect to a temperature of the reaction gas, a second relative humidity of the reaction gas with respect to a temperature of the refrigerant, and a moisture retention amount of the fuel cell. By using the up, the state quantity calculated, and performing, and controlling the fuel cell.

By the way, in the main flow path (reactive gas supply flow path and reactive gas discharge flow path) of the fuel cell system, there is a lot of generated water discharged from the fuel cell. For this reason, in the configuration in which the humidity measuring means is directly arranged in the main flow path, there is a possibility that measurement error and responsiveness decrease due to the adhesion of water to the absolute humidity measuring means as described above.
Therefore, according to the first aspect of the present invention, by forming the branch channel branched from the main channel, the inflow of generated water into the branch channel can be suppressed. Thereby, at the time of measurement of an absolute humidity measuring means, the influence by produced | generated water can be excluded as much as possible, and the measurement precision by an absolute humidity measuring means can be improved.
In addition, by arranging the absolute humidity measurement means on the branch flow path via the heating means, the temperature of the reaction gas flowing through the branch flow path can be increased, and the relative humidity of the reaction gas in the branch flow path can be reduced. it can. Thereby, since dew condensation of water vapor contained in the reaction gas can be suppressed, the absolute humidity of the reaction gas flowing through the branch flow path can be accurately measured. Therefore, even when the reaction gas temperature is relatively low, such as when the fuel cell system is started up or during a transition, condensation of water vapor can be suppressed and measurement accuracy by the absolute humidity measuring means can be improved. As described above, since the relative humidity of the reaction gas is reduced by the heating means in the branch channel, water vapor in the reaction gas (moisture whose absolute humidity is to be measured) is condensed in the branch channel. Even if it does, this dew condensation water can be evaporated quickly. Therefore, the absolute humidity measuring means can be measured more accurately and the reliability can be improved.

Further , by obtaining the pressure loss in the branch flow path by the pressure loss forming means, the flow rate of the reaction gas flowing in the branch flow path can be adjusted, and the measurement accuracy by the absolute humidity measuring means can be further improved.

According to the second aspect of the present invention, the reaction gas in the branch channel is heated to a temperature higher than the operating temperature of the fuel cell, which is the maximum temperature in the fuel cell system. It is possible to reliably suppress, and more accurate measurement with the absolute humidity measuring means can be performed.

By the way, in the fuel cell system, when the anode side branch channel is open when the system is stopped, the atmosphere flows backward from the outside into the branch channel, and dust contained in the atmosphere undergoes an anode reaction. There is a risk of entering a gas flow path or the like.
Therefore, according to the fourth aspect of the present invention, the backflow of the atmosphere while the fuel cell is stopped can be prevented by closing the on-off valve when the fuel cell is stopped. As a result, it is possible to prevent dust from entering the reaction gas channel on the anode side. Further, when the pressure of the anode reaction gas is equal to or higher than a predetermined value, by opening the on-off valve, it is possible to prevent backflow of the atmosphere at the time when the on-off valve is opened and to distribute the reaction gas in a desired flow direction. . Therefore, the absolute humidity measuring means can be measured more accurately and the reliability can be improved.

According to the invention described in claim 5, the fuel cell is always controlled by controlling the fuel cell using the first relative humidity, the second relative humidity, and the water retention amount obtained based on the measurement result by the dew point meter. Can be kept moist. Thereby, desired power generation performance can be maintained.
In particular, according to the configuration of the present invention, since the fuel cell system of the present invention is used, the dew point of the reaction gas can be accurately measured by the dew point meter of the absolute humidity measuring means. As a result, the first relative humidity, the second relative humidity, and the moisture retention amount can be calculated with higher accuracy, so that the state quantity in the fuel cell can be accurately grasped and the reliability of control of the fuel cell can be improved. It can be improved.

1 is a schematic configuration diagram of a fuel cell system in an embodiment of the present invention. It is a system block diagram of ECU. It is a flowchart for demonstrating the control method of a fuel cell system. It is explanatory drawing for demonstrating the water balance in a fuel cell system (cathode side). It is a graph for judging a humidification state based on 1st relative humidity (phi) g (%) and 2nd relative humidity (phi) w (%). It is a graph for judging a humidification state based on the amount Q of humidification water. It is a graph which shows the relationship between the amount of humidification water Q (g / sec) and voltage (V) with respect to time (min).

Next, embodiments of the present invention will be described with reference to the drawings.
(Fuel cell system)
FIG. 1 is a schematic configuration diagram of a fuel cell system.
As shown in FIG. 1, a fuel cell system 1 is mounted on a fuel cell vehicle (not shown), for example, and includes a fuel cell stack 2 (hereinafter referred to as a fuel cell 2) and a cathode gas (reactive gas) in the fuel cell 2. ) Cathode gas supply means 11 for supplying air, anode gas supply means 12 for supplying hydrogen as the anode gas (reactive gas), and ECU (Electric) for overall control of these components. Control Unit) 6 (see FIG. 2).

The fuel cell 2 generates electricity by an electrochemical reaction between an anode gas and a cathode gas, and includes an electrolyte membrane. A membrane electrode structure is formed by sandwiching the electrolyte membrane between the anode and the cathode from both sides, and a cell is formed by arranging a pair of separators on both sides of the membrane electrode structure, and a plurality of the cells are stacked. Thus, the fuel cell 2 is configured. Then, hydrogen gas as an anode gas is supplied to the anode of the fuel cell 2 and air as a cathode gas is supplied to the cathode, so that hydrogen ions generated by a catalytic reaction (H ₂ → 2H ⁺ + 2e ⁻ ) at the anode are generated. Go to the cathode through the electrolyte, and electrochemically react with oxygen at the cathode _{(H 2 + O 2/2} → H 2 O) to is adapted to power generation.

  The cathode gas supply means 11 includes an air pump 33 that sends the cathode gas toward the fuel cell 2. A cathode gas supply channel (reactive gas supply channel) 24 for supplying cathode gas to the fuel cell 2 is connected to the air pump 33. The cathode gas supply channel 24 is connected to a cathode gas channel (reactive gas channel) 22 facing the cathode on the inlet side of the fuel cell 2 via a humidifier 29. On the other hand, on the outlet side of the cathode gas flow path 22, a cathode off gas discharge flow path (reactive gas discharge flow) through which the cathode off gas supplied for power generation by the fuel cell 2 and the generated water generated by the fuel cell 2 during power generation circulates. Road) 38 is connected.

  The above-described air pump 33 is connected to a flow rate sensor (not shown) for measuring the flow rate of the cathode gas sent from the air pump 33 (hereinafter also referred to as air amount), and the air supplied to the cathode of the fuel cell 2. The amount can be measured. Further, near the inlet side and the outlet side of the cathode gas flow path 22 are a temperature sensor (not shown) for measuring the temperature of the cathode gas (cathode inlet gas temperature and cathode outlet gas temperature), and the cathode gas. Is connected to a pressure sensor (not shown) for measuring the pressure (cathode inlet gas pressure and cathode outlet gas pressure).

  The cathode off gas discharge flow path 38 is connected to the dilution box 31 via the humidifier 29. The humidifier 29 is configured to be accommodated in a housing (not shown) in a state where a number of hollow fiber-like water permeable membranes (hollow fiber membranes) are bundled inside. When gases having different moisture contents flow through the hollow fiber membrane, the moisture in the gas having a high moisture content permeates the hollow fiber membrane and moves to a gas having a low moisture content. That is, in the present embodiment, the cathode gas delivered from the air pump 33 circulates inside the hollow fiber membrane, and the cathode offgas containing generated water circulates outside, so that the fuel cell 2 is used for power generation and is moistened. Moisture is transferred from the cathode off-gas thus formed to the cathode gas. As a result, the cathode gas can be humidified in advance before the fuel cell 2 is supplied.

  The cathode gas delivered by the air pump 33 passes through the cathode gas supply channel 24 and is then supplied to the cathode gas channel 22 of the fuel cell 2. In the cathode gas channel 22, oxygen in the cathode gas is supplied to the power generation as an oxidant, and then discharged from the fuel cell 2 to the cathode offgas discharge channel 38 as the cathode offgas. The cathode offgas discharge passage 38 is connected to the dilution box 31, and then the cathode offgas is exhausted outside the vehicle. The cathode offgas discharge channel 38 is provided with a back pressure valve 34 for adjusting the cathode gas pressure in the cathode gas channel 22 of the fuel cell 2.

  On the other hand, the anode gas supply means 12 includes a hydrogen tank 30 filled with anode gas. The hydrogen tank 30 is connected to an anode gas channel (reactive gas channel) 21 facing the anode on the inlet side of the fuel cell 2 through an anode gas supply channel (reactive gas supply channel) 23. On the other hand, an anode off gas discharge channel (reactive gas supply channel) 35 through which the anode off gas supplied for power generation in the fuel cell 2 flows is connected to the outlet side of the anode gas channel 21. A temperature sensor (not shown) for measuring the temperature of the anode gas (anode inlet gas temperature and anode outlet gas temperature) at each of the inlet side and the outlet side of the anode gas channel 21, and the anode gas Are connected to a pressure sensor (not shown) for measuring the pressure (the anode inlet gas pressure Pa1 and the anode outlet gas pressure Pa2).

A shutoff valve 25, a regulator 28, and an ejector 26 are connected to the anode gas supply channel 23 in order from the upstream side.
The shutoff valve 25 is of an electromagnetic drive type, and is configured to be able to shut off the supply of anode gas from the hydrogen tank 30.

  The regulator 28 uses the pressure of the cathode gas supplied to the fuel cell 2 (cathode inlet gas pressure) as a signal pressure, and the high-pressure anode gas supplied from the hydrogen tank 30 has a pressure within a predetermined range corresponding to the signal pressure. Thus, the pressure is adjusted (reduced pressure). Thereby, the pressure difference between the cathode and the anode of the fuel cell 2 is maintained at a predetermined pressure. The anode gas adjusted by the regulator 28 passes through the ejector 26 and is supplied to the fuel cell 2. Although not shown, the anode gas supply channel 23 is provided with a heat exchanger that exchanges heat with the anode gas supplied from the hydrogen tank 30. Thereby, the anode gas can be supplied to the fuel cell 2 in a state where the anode gas is heated to near the operating temperature of the fuel cell 2.

  The anode off gas discharge channel 35 is connected to the ejector 26 and is configured to circulate the anode off gas discharged from the fuel cell 2 so that it can be reused as the anode gas of the fuel cell 2. Further, the anode off-gas discharge channel 35 has a purge gas discharge channel 37 configured such that the channel branches in the middle. The purge gas discharge channel 37 is connected to the dilution box 31. The purge gas discharge passage 37 is provided with an electromagnetically driven purge valve 27.

  The dilution box 31 is provided with a retention chamber in which the anode off gas introduced from the purge gas discharge channel 37 is retained, and a cathode off gas discharge channel 38 is connected to the retention chamber. That is, the anode off-gas is diluted with the cathode off-gas in the staying chamber, and then discharged from the discharge passage 36 to the outside of the vehicle. The dilution box 31 is supplied with a cathode off gas based on the concentration of the anode off gas introduced from the purge gas discharge channel 37.

  The fuel cell system 1 also includes a cooling unit 13 that cools the fuel cell 2 by circulating a refrigerant in the fuel cell 2. The cooling means 13 includes a refrigerant passage 15 through which the refrigerant flows in the fuel cell 2, a radiator 10 that cools the refrigerant, a refrigerant supply passage 14 through which the refrigerant discharged from the radiator 10 flows toward the refrigerant passage 15, and a refrigerant A refrigerant discharge passage 17 is provided for allowing the refrigerant discharged from the passage 15 to flow toward the radiator 10. The refrigerant supply passage 14 is provided with a water pump (W / P) 18 for circulating the refrigerant between the fuel cell 2 and the radiator 10. Further, a refrigerant temperature sensor 19 for detecting the temperature of the refrigerant supplied into the fuel cell 2 (inlet refrigerant temperature Twin) is connected to the refrigerant supply passage 14. Further, a generator ammeter (not shown) for measuring the current value taken out from the fuel cell 2 is provided in the fuel cell 2.

Here, the cathode gas supply flow path 24 and the cathode off gas discharge flow path 38, and the anode gas supply flow path 23 and the anode off gas discharge flow path 35 branch from the branch portions of the flow paths 24, 38, 23, and 35. The branch flow paths 41 to 44 are connected.
Specifically, first, the branch channel 41 (hereinafter also referred to as the cathode gas branch channel 41) is located between the humidifier 29 and the fuel cell 2 in the cathode gas supply channel 24 and near the inlet of the fuel cell 2. Branches as a branching part. The branch flow path 42 (hereinafter also referred to as the cathode offgas branch flow path 42) is between the fuel cell 2 and the humidifier 29 in the cathode offgas discharge flow path 38 and branches near the outlet of the fuel cell 2 as a branch portion. doing.
The branch channel 43 (hereinafter also referred to as the anode gas branch channel 43) is between the ejector 26 and the fuel cell 2 in the anode gas supply channel 23, and the vicinity of the inlet of the fuel cell 2 serves as a branch part. Branched. The branch flow path 44 (hereinafter also referred to as the anode off gas branch flow path 44) branches near the outlet of the fuel cell 2 in the anode off gas discharge flow path 35.

  Dew point meters (absolute humidity measuring means) 51 to 54 are connected to the branch channels 41 to 44, respectively, so that the dew points of the reaction gas flowing through the branch channels 41 to 44 can be measured. Yes. And in each branch flow path 41-44, between an upstream end (branch part of each flow path 24, 38, 23, 35 and branch flow paths 41-44) and dew point meters 51-54, respectively, a heater (heating) Means) 45 to 48 are installed, and the reaction gas (cathode gas, cathode off gas, anode gas, and anode off gas) flowing through the branch channels 41 to 44 can be heated. That is, in the flow direction of each branch flow path 41-44, the area | region (area | region from a branch part to dew point meters 51-54) in which the heaters 45-48 were installed is a heating area | region.

  Further, the downstream sides of the dew point meters 51 to 54 in the branch channels 41 to 44 constitute narrow tube portions (pressure loss forming means) 55 to 58 in which the inner diameter of the channel is formed smaller than that of the upstream side. Yes. In addition, it may replace with the thin tube parts 55-58, and you may make it the structure which provides an orifice in a flow path.

Further, among the branch channels 41 to 44, on-off valves 59 and 60 are provided on the downstream side of the dew point meters 53 and 54 in the anode gas branch channel 43 and the anode off-gas branch channel 44, respectively. 43 and 44 can be opened and closed.
The branch flow paths 41 to 44 are connected between the back pressure valve 34 and the dilution box 31 in the cathode offgas discharge flow path 38 on the downstream side thereof. That is, the fluid branched from the respective flow paths 24, 38, 23, 35 to the branch flow paths 41 to 44 flows through the branch flow paths 41 to 44 to the cathode offgas discharge flow path 38. .

(ECU)
FIG. 2 is a block diagram of the ECU.
As shown in FIG. 2, the ECU 6 comprehensively controls each component of the fuel cell system 1, and includes an anode gas pressure determination unit (pressure control unit) 61, a humidity calculation unit 62, and a water balance calculation. Means 63 and humidified state determination means (control unit) 64 are provided.

  The anode gas pressure determination means 61 performs opening / closing control of the opening / closing valves 59, 60 provided in the branch flow paths 43, 44 described above. Specifically, the anode gas pressure determination means 61 stores an anode inlet gas pressure threshold value Pal1 and an anode outlet gas pressure threshold value Pal2 for determining opening / closing of the opening / closing valves 59, 60, and the pressure sensor of the fuel cell 2 is stored. When the anode gas pressure Pa (the anode inlet gas pressure Pa1 and the anode outlet gas pressure Pa2) detected by the above is higher than the anode gas pressure threshold value Pal, the on-off valves 59 and 60 are opened.

The humidity calculating means 62 calculates the first relative humidity φg with respect to the temperature of the reaction gas flowing through the branch flow paths 41 to 44 using the dew point of the reaction gas measured by the dew point meters 51 to 54, and the inlet refrigerant temperature. The second relative humidity φw with respect to Twin is calculated. These calculation methods will be described later.
The water balance calculation means 63 calculates the humidified water amount Q (water retention amount in the fuel cell 2) with respect to the generated current in the fuel cell 2 using the dew point of the reaction gas measured by the dew point meters 51 to 54.

The humidified state determination unit 64 is for determining the humidified state of the fuel cell 2 and includes a first relative humidity determination unit 65, a second relative humidity determination unit 66, and a humidification amount determination unit 67.
The first relative humidity determination unit 65 stores a first relative humidity threshold φgl, and compares the first relative humidity threshold φgl with the first relative humidity φg calculated by the humidity calculation unit 62 to determine the fuel. The humidified state of the battery 2 is determined.

The second relative humidity determination means 66 stores a second relative humidity threshold φwl, and the second relative humidity threshold φwl is compared with the second relative humidity φw calculated by the humidity calculation means 62 to thereby determine the fuel. The humidified state of the battery 2 is determined.
The humidification amount determination means 67 stores a humidification water amount threshold value Ql and compares the humidification water amount threshold value Ql with the humidification water amount Q calculated by the water balance calculation means 63 to determine the humidification state of the fuel cell 2. To do.

  Then, the humidification state determination unit 64 finally determines the humidification state of the fuel cell 2 based on the determination results of the determination units 65 to 67 described above. Specifically, when each of the determination units 65 to 67 determines that the calculated first relative humidity φg, second relative humidity φw, and humidified water amount Q are all equal to or greater than a predetermined threshold, the fuel cell 2 is wet. It is determined that efficient power generation is performed.

(Function)
Next, the operation of the fuel cell system 1 described above will be described. In the following description, of the branch channels 41 to 44, the operation mainly on the cathode side branch channels (the cathode gas branch channel 41 and the cathode offgas branch channel 42) will be described. The operations of the branch channels 43 to 44 are substantially the same as those of the cathode gas branch channel 41 and the cathode off-gas branch channel 42.
First, the cathode gas sent from the air pump 33 toward the cathode gas supply channel 24 is humidified by the cathode off gas in the humidifier 29 and then flows toward the anode of the fuel cell 2. Note that the cathode off-gas flowing through the humidifier 29 is subjected to power generation by the fuel cell 2 and thus has a relatively high temperature. Therefore, in the humidifier 29, heat exchange is also performed between the cathode gas and the cathode off gas, so that the cathode gas is heated.

Thereafter, a part of the cathode gas flows into the cathode gas branch channel 41 immediately before the entrance of the fuel cell 2. At this time, the flow rate of the cathode gas branched into the cathode gas branch channel 41 is determined in advance in consideration of the power generation efficiency in the fuel cell 2 and the flow rate range measurable by the dew point meter 51. That is, if the flow rate of the cathode gas to be bypassed is relatively large, the response of the dew point meter 51 is improved, but the flow rate of the cathode gas supplied to the fuel cell 2 is reduced and the power generation efficiency in the fuel cell 2 is reduced. Therefore, it is not preferable. On the other hand, if the flow rate of the cathode gas branched into the cathode gas branch channel 41 is relatively small, the power generation efficiency in the fuel cell 2 is maintained, but the responsiveness in the dew point meter 51 is deteriorated, which is not preferable.
Therefore, in the present embodiment, the flow rate of the cathode gas branched into the cathode gas branch flow path 41 is, for example, a preferable ratio with respect to the flow rate of the cathode gas sent out by the air pump 33 regardless of the power generation output of the fuel cell 2. As 0.8 to 1.5%. Thereby, while maintaining the power generation efficiency in the fuel cell 2, the responsiveness by the dew point meter 51 is also securable.

The cathode gas branched into the cathode gas branch channel 41 is heated by the heater 45 in the heating region, and then the dew point is measured by the dew point meter 51. At this time, in the heating region, the heater 45 heats the cathode gas to a temperature higher than the operating temperature of the fuel cell 2 (for example, about 85 ° C.). As described above, the cathode gas in the cathode gas branch channel 41 is heated to a temperature higher than the operating temperature of the fuel cell 2 which is the maximum temperature in the fuel cell system 1, thereby condensing water vapor in the cathode gas branch channel 41. Can be reliably suppressed.
In the heating region, the cathode gas flowing through the cathode gas branch channel 41 may be heated by 10 ° C. or more as compared with the cathode gas supplied to the cathode gas channel 22. Also by this, the dew condensation of water vapor in the cathode gas branch channel 41 can be reliably suppressed. However, if the heating temperature is too high, the power consumption of the heater 45 increases, which is not preferable.

  Further, the cathode gas branched into the cathode gas branch channel 41 flows into the cathode off-gas discharge channel 38 after passing through the narrow tube portion 55 on the downstream side of the dew point meter 51. In this case, by setting the narrow tube portion 55 so as to obtain a predetermined exhaust pressure loss, the flow rate of the cathode gas flowing through the cathode gas branch flow channel 41 can be adjusted, and the inside of the cathode gas branch flow channel 41 can be adjusted. The cathode gas can always be supplied at a constant flow rate. Thereby, real-time measurement without response delay can be realized. Thereafter, the cathode gas that has flowed into the cathode off-gas discharge flow path 38 is discharged from the discharge passage 36 through the dilution box 31.

  On the other hand, the cathode gas that flows through the cathode gas supply channel 24 toward the fuel cell 2 without branching to the cathode gas branch channel 41 is supplied to the cathode gas channel 22 on the inlet side of the fuel cell 2. The cathode gas is supplied for power generation in the cathode gas flow path 22 and then discharged to the cathode off gas discharge flow path 38 as a cathode off gas. Of the cathode offgas discharged to the cathode offgas discharge channel 38, a part of the cathode offgas branches into the cathode offgas branch channel 42 near the outlet of the fuel cell 2. The cathode gas branched into the cathode off-gas branching channel 42 is heated by the heater 46 in the heating region, and then the dew point is measured by the dew point meter 52. Thereafter, the cathode offgas branched into the cathode offgas branching channel 42 passes through the narrow tube portion 56 on the downstream side of the dew point meter 52 and then merges again into the cathode offgas discharge channel 38.

  By the way, in the fuel cell system 1, if the anode gas branch flow path 43 and the anode off gas branch flow path 44 are in an open state when the system is stopped, the atmosphere enters the anode gas branch flow path 43 and the anode off gas branch flow path 44 from the outside. May flow backward, and dust or the like contained in the atmosphere may enter the anode gas supply means 12 or the fuel cell 2.

  Therefore, in the present embodiment, the on / off valves 59 and 60 are provided in the anode gas branch channel 43 and the anode off gas branch channel 44, and the on / off valves 59 and 60 are closed when the fuel cell system 1 is stopped. It is possible to prevent backflow of the atmosphere while the fuel cell system 1 is stopped. Thereby, it is possible to prevent dust from entering the anode gas supply means 12, the fuel cell 2, and the like. In step S1, which will be described later, after the fuel cell system 1 is started, the anode gas pressure determination means 61 determines that the anode gas pressures Pa1 and Pa2 in the fuel cell 2 are equal to or higher than the anode gas pressure thresholds Pal1 and Pal2. In this case, by opening the on-off valves 59, 60, the backflow of the atmosphere at the time when the on-off valves 59, 60 are opened is prevented, and the reaction gas (anode gas and anode off-gas) is circulated in a desired flow direction. Can be made.

  In addition, the main flow path (the anode gas supply flow path 23, the cathode gas supply flow path 24, the anode gas discharge flow path 35, and the cathode gas discharge flow path 38) has a large amount of generated water discharged from the fuel cell 2. doing. Therefore, in the configuration in which the dew point meters 51 to 54 are directly arranged in the main flow path, there is a possibility that measurement errors and responsiveness may be reduced due to water adhering to the dew point meters 51 to 54.

Therefore, in the present embodiment, the branch flow paths 41 to 44 branched from the branch portion of the main flow path are formed.
According to this configuration, by forming the branch channels 41 to 44, the inflow of generated water from the main channel into the branch channels 41 to 44 can be suppressed. Thereby, the dew point of the reaction gas which distribute | circulates the inside of the branch flow paths 41-44 can be measured correctly, eliminating the influence by generated water as much as possible at the time of the measurement of the dew point meters 51-54.

  Moreover, the reaction gas temperature which distribute | circulates the inside of the branch flow paths 41-44 is raised by arrange | positioning the dew point meters 51-54 on the branch flow paths 41-44 via the heaters 45-48, and the branch flow paths 41-44 are increased. Since the relative humidity φg and φw of the reaction gas in the reaction gas 44 can be reduced, it is possible to suppress the dew condensation of water vapor contained in the reaction gas. Humidity) can be measured accurately. Therefore, even when the fluid temperature is relatively low, such as when the fuel cell system 1 is started up or in a transition, the dew point of the reaction gas can be accurately measured by suppressing the dew condensation of water vapor. As described above, since the relative humidity φg and φw of the reaction gas is reduced by the heaters 45 to 48 in the branch flow paths 41 to 44, the reaction gas flowing in the branch flow paths 41 to 44 is temporarily in the reaction gas. Even if water vapor (water whose dew point is to be measured) is condensed, the condensed water can be quickly evaporated. Therefore, the dew point can be measured more accurately by the dew point meters 51-54. Further, by raising the temperature above the operating temperature of the fuel cell 2 on the upstream side of the dew point meters 51 to 54, for example, compared to a configuration in which the dew point meters 51 to 54 are directly heated, an error caused by the heat of the dew point meters 51 to 54 is caused. The dew point of the reaction gas can be accurately measured by preventing operation and the like.

Further, since the anode off-gas circulated by the ejector 26 described above contains a large amount of water vapor, there is a problem that condensation is likely to occur in the anode gas supply channel 23. Further, when the fuel cell system 1 is started, the heat exchanger for heating the anode gas is not warmed, and the anode inlet gas temperature supplied to the fuel cell 2 is relatively low. Therefore, there is a problem that dew condensation is likely to occur in the anode gas supply channel 23.
In order to cope with these problems, in the present embodiment, the dew point meter 53 is disposed on the anode gas branch flow path 43 via the heater 47, thereby increasing the temperature of the anode gas flowing through the anode gas branch flow path 43. Thus, the relative humidity φg and φw in the branch channel 43 can be reduced. Thereby, the dew point of the water vapor contained in the anode gas can be suppressed, and the dew point of the anode gas can be accurately measured by the dew point meter 53.

(Control method of fuel cell system)
Next, the control method of the fuel cell system 1 described above will be described. Specifically, the humidification state control of the fuel cell 2 will be described. FIG. 3 is a flowchart for explaining a control method of the fuel cell system.
First, in step S1, the anode gas pressure Pa (anode inlet gas pressure Pa1 and anode outlet gas pressure Pa2) detected by the pressure sensor after the start of the fuel cell system 1 is stored in the anode gas pressure determination means 61. It is determined whether or not the gas pressure threshold is higher than the anode inlet gas pressure threshold Pa1l and the anode outlet gas pressure threshold Pa2l.

When the determination result in step S1 is “NO” (when Pa1 ≦ Pal and Pa2 ≦ Pal), the determination in step S1 is periodically repeated without opening the on-off valves 59 and 60.
On the other hand, when the determination result in step S2 is “YES” (when Pa1> Pal and Pa2> Pal), the process proceeds to step S2. In step S 2, when the on-off valves 59 and 60 are opened, the anode gas and the anode off gas flow through the anode gas branch channel 43 and the anode off gas branch channel 44.

  Next, in step S3, the dew point meters 51 to 54 connected to the branch channels 41 to 44 are used to determine the dew point temperature of the reaction gas in the branch channels 41 to 44 (the dew point temperature of the anode gas on the anode inlet side Than). And the dew point temperature Thaout of the anode off gas at the outlet side, the dew point temperature Thcin of the cathode gas at the cathode inlet side, and the dew point temperature Thcout of the cathode off gas at the outlet side.

  Subsequently, in step S4, based on the dew point temperature measured in step S3, the first relative humidity φg, the second relative humidity φw with respect to the inlet refrigerant temperature Twin, and the amount of humidified water Q are calculated.

(Humidity calculation method)
Here, a method of calculating the first relative humidity φg and the second relative humidity φw in step S4 will be described. In the following description, the calculation method of the first relative humidity φg and the second relative humidity φw on the cathode inlet side will be described as an example, but other portions can be measured by the same method.
The humidity calculating means 62 first substitutes the dew point temperature Thcin of the cathode gas at the cathode inlet side measured by the dew point meter 51 (hereinafter referred to as gas dew point temperature Thcin) into the approximate expression shown in Equation 1, and The saturated water vapor pressure Pcthin (kPa) at the gas dew point temperature Thcin is calculated.

  Next, the cathode inlet gas temperature Tcin of the fuel cell 2 measured by the temperature sensor is substituted into the approximate expression shown in Equation 2, and the saturated water vapor pressure Pct (kPa) at the cathode inlet gas temperature Tcin of the fuel cell 2 is calculated. .

  Based on Equation 3, the first relative humidity of the cathode gas with respect to the cathode inlet gas temperature Tcin is calculated from the ratio of the saturated water vapor pressure Pcth at the gas dew point temperature Thcin at the cathode inlet side to the saturated water vapor pressure Pct at the cathode inlet gas temperature Tcin. Calculate φg.

  On the other hand, in order to calculate the second relative humidity φw at the inlet side of the fuel cell 2, first, the saturated water vapor pressure Pcw (kPa) at the inlet refrigerant temperature Twin in the fuel cell 2 is calculated. More specifically, the saturated refrigerant pressure Pcw (kPa) at the inlet refrigerant temperature Twin is calculated by substituting the inlet refrigerant temperature Twin measured by the refrigerant temperature sensor 19 into the approximate expression shown in Equation 4.

  Then, based on Formula 5, the second relative humidity φw of the cathode gas with respect to the inlet refrigerant temperature Twin is calculated from the ratio of the saturated water vapor pressure Pcw at the cathode inlet gas dew point temperature Thcin to the saturated water vapor pressure Pct at the inlet refrigerant temperature Twin.

The reason for obtaining the second relative humidity φw is that, in the fuel cell system 1, the relationship between the refrigerant temperature (for example, the inlet refrigerant temperature Twin) and the dew point temperature (for example, the gas dew point temperature Thcin at the cathode inlet side), that is, This is because the amount of generated water QW (the amount of water used for humidification of the fuel cell 2) generated in the fuel cell 2 varies depending on the second relative humidity φw of the cathode gas with respect to the inlet refrigerant temperature Twin. For example, if the cathode inlet gas temperature Tcin is 50 ° C., the gas dew point temperature Thcin at the cathode inlet side is 30 ° C., and the inlet refrigerant temperature Twin is 25 ° C., the heat of the cathode gas and refrigerant in the fuel cell 2 By the exchange, the heat of the cathode gas is radiated toward the refrigerant. In this case, when the cathode gas temperature in the fuel cell 2 reaches the cathode inlet gas dew point temperature Thcin, water vapor in the cathode gas is condensed in the fuel cell 2, so that it becomes easy to supply moisture to the fuel cell 2.
Thus, by obtaining the second relative humidity φw of the cathode gas with respect to the inlet refrigerant temperature Twin, it is possible to grasp the dew condensation state of the cathode gas in the fuel cell 2 and to grasp the ease of humidification of the fuel cell 2.

(Method for calculating the amount of humidified water)
Next, the amount of humidified water Q in the fuel cell 2 (the amount of water used for humidifying the fuel cell 2) is calculated. FIG. 4 is an explanatory diagram for explaining a water balance in the fuel cell system (cathode side).
As shown in FIG. 4, the amount of water contained in the cathode gas supplied to the fuel cell 2 is the amount of input water Qin (g / sec), and the amount of generated water generated by the fuel cell 2 by power generation, condensation, etc. When the amount of generated water QW (g / sec) and the amount of water contained in the cathode off-gas discharged from the fuel cell 2 is the amount of water Qout (g / sec), the amount of humidified water Q (g / sec) in the fuel cell 2 ) Can be expressed by Equation 6.

Therefore, in the present embodiment, the water balance calculating means 63 first calculates the input water amount Qin, the generated water amount QW, and the discharged water amount Qout, respectively.
In order to calculate the input water amount Qin (g / sec), first, the amount of air supplied to the cathode detected by the flow sensor of the air pump 33 is Gin (NL / sec), standard state (1 atm. 0 ° C.) The ratio of the number of moles of water to the number of moles of air is expressed by Equation 7 where the volume of air per mole at that time is 22.4 (NL) and the molecular weight of water is 18.

  On the other hand, the saturated water vapor pressure at the gas dew point temperature Thcin on the cathode inlet side calculated by Equation 1 above is Pcthin, the cathode inlet gas pressure detected by the pressure sensor is Pcin, and the water vapor partial pressure relative to the air partial pressure is obtained by Equation 8. The ratio is calculated.

  Since the molar ratio of Equation 7 is equal to the partial pressure ratio of Equation 8, Equation 9 is established.

  When Equation 9 is solved for Qin, Equation 10 can be obtained. Then, by substituting the values into Equation 10, the input water amount Qin (g / sec) is calculated.

Next, in order to calculate the generated water amount QW (kPa) in the fuel cell 2, the current value I (C / sec) in the fuel cell 2 is first measured using a power generation ammeter, and the measured current value I ( C / sec) is used to calculate the hydrogen usage L (mol / sec). Specifically, the amount of hydrogen (anode gas) used in the fuel cell 2 is L (mol / sec), and the number of electrons extracted from one hydrogen molecule during the power generation reaction (H ₂ → 2H ⁺ + 2e ⁻ ) is 2 When the Faraday constant is 96500 (C / mol), the current value I (C / sec) in each cell can be expressed by Equation 11.

  Then, while solving Equation 11 for L (mol / sec) and multiplying by the number n of stacked cells of the fuel cell 2, the hydrogen consumption Lz (mol / sec) in the entire fuel cell 2 is calculated by Equation 12.

In this case, the consumption of hydrogen Lz (mol / sec), since water by the same number of moles is generated _{(H 2 + O 2/2} → H 2 O), water quantity QW (g / sec) is water The molecular weight of 18 can be used to express by Equation 13.
Thus, the generated water amount QW (g / sec) is calculated.

Next, in order to calculate the discharged water amount Qout (g / sec), the air amount (cathode off-gas amount) Gout (NL / sec) at the cathode outlet in the fuel cell 2 is calculated. The cathode off-gas amount Gout (NL / sec) can be expressed by Equation 14 when the oxygen consumption (22.4 × Lz / 2) in the fuel cell 2 is Go ₂ .

  Subsequently, the gas dew point temperature Thcout on the cathode outlet side measured by the dew point meter 52 is substituted into the approximate expression shown in Formula 15, and the saturated water vapor pressure Pcthout (kPa) at the gas dew point temperature Thcout is calculated.

  When the saturated water vapor pressure at the gas dew point temperature Thcout calculated by Equation 15 described above is Pcthout, the cathode outlet gas pressure detected by the pressure sensor is Pcout, and calculation is performed in the same manner as Equations 7 to 9, the amount of discharged water Qout (g / sec) can be calculated as in Expression 16. Then, by substituting the values into Equation 16, the discharged water amount Qout (g / sec) can be calculated.

  Then, the water balance calculation means 63 substitutes the input water amount Qin (g / sec), the generated water amount QW (g / sec), and the discharged water amount Qout (g / sec) into the above-described equation (6), respectively. The amount of humidified water Q (g / sec) is calculated.

  Next, returning to FIG. 3, in step S5, the humidification state of the fuel cell 2 is determined based on the first relative humidity φg, the second relative humidity φw, and the humidified water amount Q calculated in step S4. Specifically, the values calculated in step S4 by the determination means 65 to 67 of the humidification state determination means 64 are the predetermined threshold values (first relative humidity threshold value φgl, second relative humidity threshold value φwl, and humidified water amount threshold value Ql). Judgment is made based on whether or not this is the case. And the humidification state determination means 64 determines that a humidification state is favorable, when all the values calculated by step S4 are more than a predetermined threshold value.

5 and 6 are graphs for explaining the humidification state determination, and FIG. 5 is a graph for determining the humidification state based on the first relative humidity φg (%) and the second relative humidity φw (%). FIG. 6 is a graph for determining the humidified state based on the humidified water amount Q.
In the present embodiment, as shown in FIG. 5, the first relative humidity determination means 65 and the second relative humidity determination means 66 cause both the first relative humidity φg and the second relative humidity φw to be equal to or greater than a predetermined threshold (φg ≧ φgl). And φw ≧ φwl) (region A in FIG. 5), and as shown in FIG. 6, the humidification amount determination means 67 causes the humidification amount Q to be equal to or higher than the humidification amount threshold Ql (Q ≧). Q1) is determined (region Y in FIG. 6), it is determined that the humidified state is good. That is, it is determined that the fuel cell 2 is kept wet and efficient power generation is being performed. In this case, the flow of FIG. 3 ends.

On the other hand, as shown in FIGS. 5 and 6, if any of the first relative humidity φg, the second relative humidity φw, and the amount of humidified water Q with respect to the generated current is less than a predetermined threshold, it is determined that the humidification is defective. Then, the process proceeds to step S6.
In step S6, humidification increase control is performed to recover the humidified state. Although the first relative humidity φg is high as in the region B in FIG. 5, when the second relative humidity φw is less than a predetermined value (φg ≧ φgl and φw <φwl), the inlet refrigerant temperature Twin may be high. Therefore, control is performed to lower the inlet refrigerant temperature Twin. Specifically, the refrigerant flow rate supplied to the fuel cell 2 is increased to lower the inlet refrigerant temperature Twin, the saturated water vapor pressure Pcw at the inlet refrigerant temperature Twin is lowered, and the second relative humidity of the cathode gas with respect to the inlet refrigerant temperature Twin. Increase φw.
When the second relative humidity φw is less than a predetermined value and the cathode inlet gas temperature Tcin is likely to be low, the cathode flow rate (air amount) supplied to the fuel cell 2 in order to increase the cathode inlet gas temperature Tcin. ) (Lowering the stoichiometry) can promote a temperature increase due to heat exchange with the cathode off-gas in the humidifier 29. As a result, the cathode inlet gas temperature Twin is increased, and the second relative humidity φw of the cathode gas with respect to the inlet refrigerant temperature Twin is increased. Note that the stoichiometry is an input amount with respect to a necessary consumption amount of the cathode gas in the fuel cell 2.

  On the other hand, when the second relative humidity φw is high but the first relative humidity φg is less than a predetermined value (φw ≧ φwl and φg <φgl) as in the region C in FIG. 5, the second relative humidity φw is set to It is necessary to increase the first relative humidity φg while maintaining it. In this case, the cathode inlet gas temperature Tcin is lowered while maintaining the inlet refrigerant temperature Twin. In order to lower the cathode inlet gas temperature Tcin, for example, a measure such as increasing the cathode flow rate (air amount) (increasing stoichiometry) or the like can be considered. Thereby, the temperature rise by the heat exchange with the cathode off gas in the humidifier 29 is suppressed, and the cathode inlet gas temperature Tcin is lowered. As a result, the saturated water vapor pressure Pct at the cathode inlet gas temperature Tcin can be reduced, and the first relative humidity φg of the cathode gas with respect to the cathode inlet gas temperature Tcin can be increased.

  Further, when both the first relative humidity φg and the second relative humidity φw are less than a predetermined value (φg <φgl and φw <φwl) as in the region D in FIG. The first relative humidity φg and the second relative humidity φw are controlled to be equal to or higher than a predetermined value (area A in FIG. 5). It is also possible to increase the cathode inlet gas temperature Tcin by increasing the cathode gas pressure (decreasing the cathode gas flow rate).

  Further, as shown in the region X in FIG. 6, when the humidified water amount Q is less than the humidified water amount threshold Ql (Q <Ql), it is necessary to increase the humidified water amount Q. In this case, for example, measures such as increasing the efficiency of moisture exchange in the humidifier 29 can be considered.

Here, FIG. 7 is a graph showing the relationship between the humidified water amount Q (g / sec) and the voltage (V) with respect to time (min).
As shown in FIG. 7, when the humidified water amount Q is 3 (g / sec) or more, it can be seen that the power generation voltage in the fuel cell 2 maintains a high power generation performance of about 240 to 250 (V). . On the other hand, when the amount of humidified water Q is less than 3 (g / sec), it can be seen that the power generation voltage decreases as the amount of humidified water Q decreases. Therefore, in this embodiment, it is preferable to set the humidified water amount threshold Ql to, for example, about 3 (g / sec), and the humidified water amount Q is set so that the calculated humidified water amount Q is 3 (g / sec) or more. Control. Note that the state in which the humidified water amount Q is a negative value is a state in which the discharged water amount (g / sec) is smaller than the input water amount Qin (g / sec), that is, a state in which moisture is carried away in the fuel cell 2. Show.

By the way, if the first relative humidity φg, the second relative humidity φw, and the amount of humidified water Q are too high, a flooding phenomenon in the fuel cell 2 (a phenomenon in which the generated water locally stays in the fuel cell 2 and inhibits gas supply). ) May occur. Therefore, as shown in FIG. 3, upper limit values are set for the above-described predetermined threshold values (first relative humidity threshold value φgl, relative humidity threshold value φw and humidified water amount threshold value Ql), and in step S4, the first relative humidity φg and the second relative humidity value are set. When it is determined that the humidity φw and the humidified water amount Q are higher than the upper limit values, it is preferable to perform a humidification reduction control in step S7. The humidification reduction control can be realized by performing a method opposite to the humidification increase control described above.
The humidified state control flow is thus completed.

In the above-described embodiment, as a method for determining the first relative humidity φg, the second relative humidity φw, and the amount of humidified water Q, an upper limit value is provided for the predetermined threshold in addition to the method for determining whether or not the predetermined relative threshold is exceeded. Although the method has been described, the target values of the first relative humidity φg, the second relative humidity φw, and the amount of humidified water Q are set separately, and the humidification increase control or the humidification decrease control is performed so as to approach the target values. It doesn't matter.
In the present embodiment, the case where the humidification reduction control is performed in step S7 when the humidification is excessive has been described. However, the humidification reduction control is not necessarily performed.
Furthermore, in the humidification state determination of step S5, a fixed time is set, and the humidification state is determined based on the first relative humidity φg, the second relative humidity φw, and the humidified water amount Q that are continuously calculated within the fixed time. It is preferable to do. Thereby, the influence of a transient response delay can be eliminated and more accurate control can be performed, so that the reliability of the fuel cell system 1 can be improved.

Thus, in the present embodiment, the calculation result is obtained by calculating the state quantities such as the second relative humidity φw, the first relative humidity φg, and the humidified water amount Q based on the measurement results by the dew point meters 51 to 54. Based on the above, the humidified state of the fuel cell 2 can be controlled. Thereby, since the fuel cell 2 can be always kept wet, desired power generation performance can be maintained.
In particular, in this embodiment, since the dew point of the reaction gas can be accurately measured by the dew point meters 51 to 54 as described above, the second relative humidity φw, the first relative humidity φg, and the humidified water amount Q are calculated with higher accuracy. Therefore, the reliability of the humidified state control of the fuel cell 2 can be improved.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
For example, in the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been described as an example. However, the present invention is not limited thereto, and is applicable to, for example, motorcycles, robots, stationary and portable fuel cell systems. can do.

Further, in the above-described embodiment, each of the anode side and cathode side channels (the anode gas supply channel 23, the cathode gas supply channel 24, the anode gas discharge channel 35, and the cathode gas discharge channel 38) is branched. Although the configuration in which the flow paths 41 to 44 are provided has been described, the present invention is not limited thereto, and the flow path on the anode side (the anode gas supply flow path 23 and the anode gas discharge flow path 35) or the flow path on the cathode side (cathode gas supply) You may provide only in the flow path 24 and the cathode gas discharge flow path 38). Moreover, the structure provided only in any one among each flow path of an anode side and a cathode side may be sufficient.
Furthermore, in the above-described embodiment, the configuration in which the fuel cell 2 is controlled using all the state quantities of the second relative humidity φw, the first relative humidity φg, and the amount of humidified water Q has been described. It suffices to use at least one of the above-described state quantities.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell stack (fuel cell) 13 ... Cooling means 21 ... Anode gas flow path (reaction gas flow path, anode reaction gas flow path) 22 ... Cathode gas flow path (reaction gas flow path) 23 ... Anode gas supply flow path (reaction gas supply flow path, anode reaction gas supply flow path) 24... Cathode gas supply flow path (reaction gas supply flow path) 35... Anode gas discharge flow path (reaction gas discharge flow path, anode reaction gas) Exhaust flow path) 38 ... Cathode gas discharge flow path (reactive gas discharge flow path) 41-44 ... Branch flow path 45-48 ... Heater (heating means) 51-54 ... Dew point meter (absolute humidity measurement means) 55-58 ... Narrow tube section (pressure loss forming means) 59, 60 ... Open / close valve 61 ... Anode gas pressure determining means (pressure control section) 64 ... Humidity state determining means (control section)

Claims (5)

A fuel cell that is supplied with reactive gas and generates power;
A reaction gas flow path for allowing a reaction gas to flow along the electrodes in the fuel cell;
A reaction gas supply channel through which the reaction gas supplied to the reaction gas channel flows;
An off-gas discharge channel through which the off-gas discharged from the reaction gas channel flows;
A branching channel branched from a branching portion on at least one of the reaction gas supply channel and the off-gas discharge channel;
An absolute humidity measuring means disposed on the branch flow path,
A heating means is provided in the branch flow path from the branch portion to the absolute humidity measuring means ,
On the downstream side of the heating means on the branch flow path, pressure loss forming means is provided,
The downstream end of the branch channel is connected to a cathode offgas discharge channel through which the cathode offgas discharged from the fuel cell circulates in the offgas discharge channel . It said heating means, according to claim 1 Symbol mounting the fuel cell system of the fluid flowing through the branch flow path, wherein the heating above the operating temperature of the fuel cell.   The fuel cell system according to claim 1 or 2, wherein the branch flow path is provided with an open / close valve capable of opening and closing the inside of the branch flow path. As the reactive gas flow path, an anode reactive gas flow path for flowing an anode reactive gas along the anode in the fuel cell,
The reaction gas supply channel includes an anode reaction gas supply channel through which the anode reaction gas supplied to the anode reaction gas channel flows.
As the off gas discharge channel, an anode off gas discharge channel through which the anode off gas discharged from the anode reaction gas channel flows,
The branch channel branches from a branch part on at least one of the anode reaction gas supply channel and the anode offgas discharge channel,
The branch flow path is provided with an open / close valve capable of opening and closing the inside of the branch flow path,
The fuel cell system includes anode reaction gas measurement means for measuring the pressure of the anode reaction gas,
A pressure control unit that performs opening / closing control of the on-off valve based on the measurement result of the anode reaction gas measuring means,
The pressure controller is
When the pressure of the anode reaction gas is greater than or equal to a predetermined value when the fuel cell is started, the on-off valve is opened.
The fuel cell system according to any one of claims 1 to 3, wherein when the fuel cell is stopped, the on-off valve is closed. A method for controlling a fuel cell system according to any one of claims 1 to 4,
The humidity measuring means is a dew point meter that measures a dew point of the reaction gas flowing through the branch flow path.
The fuel cell system includes a cooling means for cooling the fuel cell by circulating a refrigerant through the fuel cell;
A controller that controls the fuel cell using a dew point of the reaction gas measured by the dew point meter;
The controller is
Using the measured dew point of the reaction gas, the first relative humidity of the reaction gas with respect to the temperature of the reaction gas, the second relative humidity of the reaction gas with respect to the temperature of the refrigerant, and the water retention amount of the fuel cell A step of obtaining at least one state quantity;
And a step of controlling the fuel cell using the obtained state quantity.

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