JPH07288136A - Fuel cell system - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize humidification of fuel gas while making the device compact and improving energy efficiency. [Configuration] The fuel cell system 1 includes a fuel cell main body 10
A fuel gas supply passage 20 for sending a fuel gas to the fuel cell body 10, an oxidizing gas supply passage 30 for sending an oxidizing gas to the fuel cell body 10, and an exhaust gas containing the fuel gas discharged from the fuel cell body 10. A fuel gas discharge passage 40,
An oxidizing gas exhaust passage 50 for sending exhaust gas containing the oxidizing gas exhausted from the fuel cell main body 10 is provided, and a circulation passage 60 for connecting the oxidizing gas exhaust passage 50 and the fuel gas supply passage 20 is provided. The exhaust gas from the oxidizing gas discharge passage 50 contains the oxidizing gas and the produced water, and when the exhaust gas is sent to the fuel gas side, the oxygen in the exhaust gas reacts with hydrogen, which is the fuel gas, to produce water, and the produced water. The fuel gas is humidified by water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system provided with a cell body for supplying gas to electrodes to obtain electromotive force from a chemical reaction of the gas.

[0002]

2. Description of the Related Art For example, in a polymer electrolyte fuel cell which is one of fuel cells,
As shown in the following equation, a reaction of hydrogen gas into hydrogen ions and electrons is performed at the anode, and a reaction of producing water from oxygen gas and hydrogen ions and electrons is performed at the cathode. Anode reaction: H ₂ → 2H ⁺ + 2e ⁻ Cathode reaction: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O

The hydrogen ions generated at the anode become hydrated (H ⁺ · xH ₂ O) and move to the cathode in the electrolyte membrane. For this reason, water becomes insufficient in the vicinity of the surface of the electrolyte membrane on the anode side, and in order to continuously carry out the above-mentioned reaction, it is necessary to replenish this insufficient water. The electrolyte membrane used in the polymer electrolyte fuel cell has good electric conductivity in a wet state, but when the water content decreases, the electric resistance of the electrolyte membrane increases and the electrolyte membrane does not sufficiently function as an electrolyte. Will stop the electrode reaction.

Replenishment of this water is generally performed by humidifying the fuel gas. As a device for humidifying the fuel gas, for example, there is a device for bubbling the fuel gas to humidify it (for example, Japanese Patent Laid-Open No. 5-94832), and the fuel gas humidified by this device is used in a solid polymer fuel cell. Supply inside the body.

However, in such a technique, since the humidifying device is provided as a separate member outside the stack accommodating the polymer electrolyte fuel cell main body, there is a problem that the device becomes large.

On the other hand, by supplying oxygen to the fuel gas,
A technique for generating water vapor in the catalyst layer of the electrode has been proposed (JP-A-62-216174). According to this technique, the oxygen-containing gas (oxidizing gas) to be supplied to the cathode may be supplied also to the fuel gas side without using a large-sized device such as a humidifying device, and the device can be made compact. did it. However, this technique has a problem that the consumption of the oxidizing gas is large and the energy efficiency is low.

The fuel cell system of the present invention has been made in view of these problems, and an object thereof is to realize humidification of fuel gas while achieving compactness of the apparatus and improvement of energy efficiency.

[0008]

In order to achieve such an object, the following constitution is adopted as a means for solving the above problems.

That is, the first fuel cell system of the present invention is a fuel cell system including a cell body in which an electrolyte is sandwiched between two electrodes, and one of the two electrodes contains hydrogen. A fuel gas supply passage for supplying a fuel gas, an oxidizing gas supply passage for supplying an oxidizing gas to the other electrode, a fuel gas discharge passage for discharging the supplied fuel gas from the cell body, and a fuel cell for discharging the fuel gas from the cell body. A configuration including an oxidizing gas discharge passage for discharging the supplied oxidizing gas, and a circulation passage for circulating the exhaust gas to the cell body by supplying the exhaust gas from the oxidizing gas discharge passage to the fuel gas supply passage I took it.

In such a fuel cell system, an operating state detecting means for detecting an operating state of the cell body and a circulating amount controlling means for controlling the circulating amount of the exhaust gas in the circulating passage according to the detected operating state are provided. It may have a configuration provided.

Alternatively, in the fuel cell system, the communication passage extending from the oxidizing gas supply passage to the fuel gas supply passage, the flow rate of gas flowing through the communication passage, and the flow rate of gas flowing through the circulation passage are respectively adjusted. A control valve for controlling the ratio of the both to an arbitrary ratio, an operating state detecting means for detecting the operating state of the battery body, and a control means for controlling the control valve according to the detected operating state. It may have a configuration provided.

In these fuel cell systems, the operating condition detecting means may be means for detecting the degree of water content of the electrolyte provided in the cell body. Further, the operating state detecting means may be provided in the circulation passage and may be a means for detecting the oxygen concentration in the exhaust gas flowing through the circulation passage. Further, the operating state detecting means may be a means provided in the circulation passage and detecting the humidity in the exhaust gas flowing through the circulation passage.

Further, in the above fuel cell system,
The battery main body is provided with a channel groove for the fuel gas on a surface of the electrode for supplying the fuel gas opposite to the electrolyte, and the electrode is a first catalyst formed on the electrolyte side. A layer and a second catalyst layer formed on the channel groove side may be provided.

The second fuel cell system of the present invention is a fuel cell system having a cell body in which an electrolyte is sandwiched between two electrodes, wherein one of the two electrodes contains hydrogen. A fuel gas supply passage for supplying a fuel gas, an oxidizing gas supply passage for supplying an oxidizing gas to the other electrode, a fuel gas discharge passage for discharging the supplied fuel gas from the cell body, and a fuel cell for discharging the fuel gas from the cell body. A configuration including an oxidizing gas discharge passage for discharging the supplied oxidizing gas, and a circulation passage for circulating the exhaust gas to the battery main body by supplying the exhaust gas from the fuel gas discharge passage to the oxidizing gas supply passage I took it.

[0015]

According to the first fuel cell system of the present invention configured as described above (according to claim 1), the exhaust gas discharged from the oxidizing gas discharge passage is circulated from the fuel gas supply passage to the cell body. To be done. The exhaust gas contains water generated in the battery main body and residual oxygen, and when this exhaust gas is supplied to the fuel gas supply passage, the water, the oxygen and hydrogen in the fuel gas are supplied. The fuel gas is humidified by the new water generated by the reaction between and.

According to the fuel cell system of the second aspect, the circulation amount control means controls the circulation amount of the circulation passage in accordance with the operation state of the battery main body detected by the operation state detection means. Since the humidification amount of the fuel gas changes when the circulation amount is controlled, the humidification amount of the fuel gas can be adjusted according to the operating state of the cell body.

According to the third aspect of the fuel cell system, the control means controls the control valve in accordance with the operating state of the cell body detected by the operating state detecting means, whereby the fuel is supplied from the oxidizing gas supply passage. The ratio between the flow rate of the gas flowing through the communication passage leading to the gas supply passage and the flow rate of the gas flowing through the circulation passage is controlled to an arbitrary ratio. Since the gas flowing through the communication passage is an oxidizing gas with a higher concentration than the gas flowing through the circulation passage, increasing the ratio of the flow rate of the gas in the communication passage allows the gas to be supplied compared to the case where gas is supplied only from the circulation passage. The oxidizing gas used can be highly concentrated. As a result, by controlling the control valve according to the operating state of the battery main body, it becomes possible to adjust the supply amount of the oxidizing gas and hence the humidifying amount of the fuel gas according to the operating state.

According to the fuel cell system of the fourth aspect, it is possible to adjust the humidification amount of the fuel gas according to the water content of the electrolyte provided in the cell body. According to the fuel cell system of the fifth aspect, it is possible to adjust the humidification amount of the fuel gas according to the oxygen concentration in the exhaust gas flowing through the circulation passage. According to the fuel cell system of the sixth aspect, it is possible to adjust the humidification amount of the fuel gas according to the humidity in the exhaust gas flowing through the circulation passage.

In general, the reaction between hydrogen in the fuel gas and the supplied oxygen is carried out in the catalyst layer (first catalyst layer on the electrolyte side) provided on the electrode. According to the fuel cell of (1), the second catalyst layer on the flow channel side is mostly used. When oxygen and hydrogen react with each other in the first catalyst layer provided in the electrode, the reaction heat may damage the electrolyte.
That is, it is possible to reduce the influence of reaction heat on the electrolyte by causing the reaction of oxygen and hydrogen in the second catalyst layer provided farther from the electrolyte.

According to the second fuel cell system of the present invention (claim 8), the exhaust gas discharged from the fuel gas discharge passage is circulated from the oxidizing gas supply passage to the cell body. There is a residual fuel gas (hydrogen) in the exhaust gas, and when this exhaust gas is supplied to the oxidizing gas supply passage, the hydrogen and oxygen in the oxidizing gas supply passage react with each other to generate a new gas. The water humidifies the oxidizing gas.

[0021]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above.

FIG. 1 is an overall configuration diagram of a fuel cell system 1 to which the first embodiment of the present invention is applied. As shown in FIG. 1, the fuel cell system 1 includes a polymer electrolyte fuel cell body 10, a fuel gas supply passage 20 for feeding a fuel gas (hydrogen gas) to the fuel cell body 10, and a fuel cell body 10.
Oxidizing gas supply passage 3 for sending the oxidizing gas (oxygen-containing gas)
0, a fuel gas discharge passage 40 for sending the exhaust gas containing the fuel gas discharged from the fuel cell body 10, and an oxidizing gas discharge passage 50 for sending the exhaust gas containing the oxidizing gas discharged from the fuel cell body 10. . Further, the fuel cell system 1 includes a circulation passage 60 that connects the oxidizing gas discharge passage 50 and the fuel gas supply passage 20. In addition, in the circulation passage 60, the exhaust gas in the passage is mixed with the oxidizing gas discharge passage 5
A circulation pump 62 is provided that pressure-feeds from the 0 side to the fuel gas supply passage 20 side.

The structure of the fuel cell body 10 will be described below. FIG. 2 is a schematic diagram of a cell structure of the fuel cell main body 10,
FIG. 3 is an exploded perspective view of the cell structure. As shown in these drawings, the cell includes an electrolyte membrane 110, and an anode 120 and a cathode 130 as gas diffusion electrodes having a sandwich structure in which the electrolyte membrane 110 is sandwiched from both sides.
While sandwiching this sandwich structure from both sides, a channel groove for fuel gas and oxidizing gas is formed and the anode 12
0 and the collector 130 for exchanging electrons with the cathode 130
40 and 150, and a separator 160 arranged outside the collector electrodes 140 and 150 to partition each cell. The separator 160 may be omitted if the electrode 150 is gas impermeable.

The electrolyte membrane 110 is an ion exchange membrane formed of a polymer material such as a fluorine resin, and exhibits good electric conductivity in a wet state. The anode 120 has a gas diffusion layer 121 formed by applying a mixture of Teflon and carbon to a carbon cloth woven with a yarn made of carbon fibers and sintering the mixture at a temperature equal to or higher than the melting point of Teflon to impart water repellency. A first catalyst layer 122 and a second catalyst layer 123 as catalysts are provided on the surface of the gas diffusion layer 121 on the electrolyte membrane 110 side and the surface of the gas diffusion layer 121 on the collector electrode 140 side, respectively. Both catalyst layers 122 and 123 are formed by applying a paste prepared by mixing carbon powder supporting platinum or an alloy of platinum and another metal with an electrolyte solution onto the surface of the gas diffusion layer 121. . The platinum-based metal may be replaced with nickel-cobalt-based metal or the like. Second catalyst layer 123
May be formed so as to support the catalyst near the surface by sputtering, or may be formed by supporting the catalyst on carbon used in the process of imparting water repellency to the gas diffusion layer 121.

The cathode 130 is a gas diffusion layer 131 made of carbon cloth as in the case of the anode 120 side.
And the electrolyte membrane 110 of the gas diffusion layer 131.
The same catalyst layer 132 as the catalyst layer 122 is provided on each side surface. Incidentally, there is no one corresponding to the second catalyst layer 123 on the cathode side.

The collecting electrodes 140, 150 are made of porous carbon having gas permeability.
The porosity is 40 to 80%. Further, a plurality of ribs 142 are formed on the collecting electrode 140,
The ribs 142 and the surface of the anode 120 form a channel groove 145 for a mixed gas of fuel gas and water vapor. The flow channel groove 145 is connected to the fuel gas supply passage 20 at one end and is connected to the fuel gas discharge passage 40 at the other end. On the other hand, a plurality of ribs 152 are also formed on the collector electrode 150.
A flow channel groove 155 for collecting water generated at the cathode 130 is formed while forming a flow channel for the oxidizing gas. The channel groove 155 is connected to the oxidizing gas supply passage 30 at one end thereof and is connected to the oxidizing gas discharge passage 50 at the other end thereof.

The separator 160 is made of gas-impermeable carbon that is made gas-impermeable by compressing carbon, and has an electrolyte membrane 110, an anode 120, and a cathode 13.
0, a partition wall for stacking cells constituted by the collecting electrodes 140, 150 in the thickness direction thereof. The members formed in this way are used as a separator 160, a collector electrode 140, an anode 120, an electrolyte membrane 110, a cathode 130, and a collector electrode 15.
A plurality of 0 and a separator 160 are laminated in this order to form a polymer electrolyte fuel cell.

The flow of gas in the fuel cell system 1 thus constructed will be described below. Fuel gas source 7
The fuel gas stored in 0 flows through the fuel gas supply passage 20 and flows into the flow path groove 145 on the anode 120 side of the fuel cell body 10.
Sent to. The fuel gas is introduced into the anode 120 through the flow channel 145, and the remainder is sent from the fuel gas discharge passage 40 to the outside. On the other hand, the oxidizing gas source 8
The oxidant gas stored in 0 flows through the oxidant gas supply passage 30 and flows into the channel groove 155 on the cathode 130 side of the fuel cell body 10.
Sent to. The oxidizing gas is taken into the cathode 130 through the channel groove 155, and the remainder is sent to the oxidizing gas discharge passage 50. Although water is generated at the cathode 130 by receiving the oxidizing gas, this water is also discharged from the oxidizing gas discharge passage 50 together with the residual oxidizing gas.

The oxidizing gas containing water as exhaust gas discharged from the oxidizing gas discharge passage 50 flows through the circulation passage 60, is sent to the fuel gas supply passage 20, and is circulated in the fuel cell body 10. When the exhaust gas is sent to the fuel gas, oxygen in the exhaust gas reacts with hydrogen, which is the fuel gas, to generate water, and the generated water humidifies the fuel gas.

Therefore, in the fuel cell system 1, since a large device such as a bubbler is unnecessary, it is possible to humidify the fuel gas while making the entire system compact. Further, the fuel gas supply passage 2
Since the oxidizing gas supplied to 0 is recycled exhaust gas from the oxidizing gas discharge passage 50, the oxidizing gas source 8
It is possible to save the consumption amount of the oxidizing gas of 0, and it is excellent in energy efficiency.

Further, in the first embodiment, the anode 12
Since the second catalyst layer 123 is formed on the surface of the No. 0 collector electrode 140 side, the reaction between hydrogen and oxygen (circulated in the circulation passage 60) supplied from the fuel gas supply passage 20 Most can be done with the second catalyst layer 123. Therefore, the first catalyst layer 122 hardly reacts with hydrogen and oxygen, and the electrolyte membrane 110
Is less affected by the reaction heat, and the electrolyte membrane 1
It is possible to prevent 10 from being damaged.

The second embodiment of the present invention will be described below. FIG. 4 is an overall configuration diagram of a fuel cell system 200 to which the second embodiment of the present invention is applied. As shown in FIG.
This fuel cell system 200 has the same fuel cell body 210, fuel gas supply passage 220, oxidizing gas supply passage 230, fuel gas discharge passage 240, oxidizing gas discharge passage 250, circulation passage 260 and circulation pump 262 as in the first embodiment.
Further, a 3-port electromagnetic switching valve 265 and a check valve 267 are provided in the circulation passage 260. The other end 265a of the 3-port electromagnetic switching valve 265 is connected to the oxidizing gas supply passage 23.
0, the control signal from the control system 290 is received, and either the circulation passage 260 or the oxidizing gas supply passage 230 is selectively connected to the fuel gas supply passage 220.

The control system 290 serves as a sensor for detecting the operating state of the fuel cell main body 210, and an impedance sensor 29 for detecting the impedance Z of the fuel cell main body 210.
2 and a temperature sensor 294 for detecting the temperature of the fuel cell main body 210, and further, an impedance sensor 292.
And an electronic control unit 296 connected to the temperature sensor 294.

The temperature sensor 294 is an ordinary thermometer. The impedance sensor 292 is the fuel cell main body 21.
It is an AC interelectrode resistance meter so as not to affect the electrochemical reaction of 0. The AC measurement frequency of the impedance sensor 292 is an optimum frequency, for example, 10 [kHz].

The electronic control unit 296 is configured as a logic circuit centered on a microcomputer. More specifically, the CPU 296a and the CPU 296a, which execute predetermined arithmetic operations according to a preset control program, perform various arithmetic operations. A ROM 296b in which necessary control programs, control data, etc. are stored in advance, and also the CPU 2
Inputting output signals from the RAM 296c, the impedance sensor 292, and the temperature sensor 294 at which various data necessary for executing various arithmetic processing in the 96a is temporarily read and written, and 3-port electromagnetic switching is performed according to the arithmetic result in the CPU 296a. An input / output circuit 296d for outputting a control signal to the valve 265 is provided.

The impedance sensor 292 is controlled by the CPU 296a of the electronic control unit 296 thus constructed.
And the wet state of the electrolyte membrane 110 of the fuel cell main body 210 is determined from the output signal from the temperature sensor 294, the 3-port electromagnetic switching valve 265 is drive-controlled according to the determination result, and the connection passage to the fuel gas supply passage 20 is obtained. Is the circulation passage 6
0 or the oxidizing gas supply passage 30 is selectively switched.

Next, the switching valve control process executed by the CPU 296a will be described with reference to the flowchart of FIG. When the CPU 296a starts processing,
First, the impedance Z detected by the impedance sensor 292 and the temperature T detected by the temperature sensor 294 are read (steps S300 and S310).

Next, a process for determining whether or not the electrolyte membrane 110 of the fuel cell main body 210 is in a dry state is performed from the impedance Z and the temperature T (step S).
330). This determination is made in steps S300 and S31.
The impedance Z and the temperature T detected at 0 are compared with the map stored in the ROM 296b in advance. As shown in FIG. 6, this map shows a plurality of equal moisture content curves W defined by the impedance Z and the temperature T. The equal moisture content curves W are such that the larger the impedance Z is, the larger the temperature T is. The lower the value. CPU2
By comparing the impedance Z and the temperature T with the map of FIG. 6, 96a selects the equal moisture content curve W determined from the impedance Z and the temperature T, and the moisture content indicated by the equal moisture content curve W is predetermined. It is determined whether or not the electrolyte membrane 110 is in a dry state by determining whether or not the value is smaller than the above value.

In step S330, the fuel cell main body 210
When it is determined that the electrolyte membrane 110 of is in a dry state,
Next, a process of determining whether or not the flag f (initial value = 0) prepared in advance has a value of 0 is performed (step S340). Here, when the flag f is determined to be 0, the 3-port electromagnetic switching valve 265 is switched to the position where the fuel gas supply passage 220 and the oxidizing gas supply passage 230 are connected (step S350), and the flag f is set. The value is set to 1 (step S360). On the other hand, if it is determined at step S340 that the flag f is not 0, then at step S350.
Assuming that the switching of the 3-port solenoid operated directional control valve 265 has been completed, the processing of steps S350 and S360 is skipped, the process returns to "return", and the processing of this routine is once completed.

On the other hand, if the negative determination is made in step S330, that is, if the electrolyte membrane 110 of the fuel cell main body 210 is not in the dry state, the process proceeds to step S370 to determine whether the flag f is 1 or not. Perform determination processing. Here, when the flag f is determined to be the value 1, the 3-port electromagnetic switching valve 265 is connected to the fuel gas supply passage 220 and the circulation passage 26.
Switch to the position where 0 is connected (step S38
Along with 0, the flag f is set to the value 0 (step S3).
90). On the other hand, when it is determined that the flag f is not 1 in step S370, it is assumed that the switching of the 3-port electromagnetic switching valve 265 has already been completed in step S380, the processes of steps S380 and S390 are skipped, and the process returns to “return”. Then, the processing of this routine is once finished.

That is, according to this switching valve control processing routine, when it is determined that the electrolyte membrane 110 of the fuel cell main body 210 is in a dry state, the 3-port electromagnetic switching valve 26.
5 is a fuel gas supply passage 220 and an oxidizing gas supply passage 23
0 is connected to the position where the fuel cell main body 2
When it is determined that the electrolyte membrane 110 of 10 is not in a dry state, the 3-port electromagnetic switching valve 265 is switched to a position where the fuel gas supply passage 220 and the circulation passage 260 are connected.

In the fuel cell system 200 of the second embodiment described in detail above, the exhaust gas from the oxidizing gas exhaust passage 250 is circulated to the fuel gas supply passage 220 during steady operation in which the electrolyte membrane 110 is in a good wet state. On the other hand, the oxidizing gas discharged from the oxidizing gas supply passage 230 is directly supplied to the fuel gas supply passage 220 at the initial stage of operation when the wet state of the electrolyte membrane 110 is poor or at the time of high output.
Generally, when the load suddenly increases or at the beginning of startup, the electrolyte membrane 110 has a low water content and tends to be dry, and a large amount of humidification to the fuel gas is required. As a result, the amount of residual oxygen in the circulating exhaust gas decreases, or the amount of water discharged becomes unstable, resulting in instability.
It is not possible to sufficiently increase the degree of humidification of the fuel gas without lowering the partial pressure ratio of hydrogen in the fuel gas only by circulating the exhaust gas of No. 2 in the fuel gas supply passage 220. On the other hand, by configuring as described above, the oxidizing gas supply passage 2
The oxidizing gas can be sufficiently supplied from 30 to the fuel gas supply passage 220.

Therefore, in the fuel cell system 200 of the second embodiment, similar to the first embodiment, the effect of improving the compactness of the entire system and the improvement of energy efficiency are achieved, and the following effects are also exhibited. . That is, in this fuel cell system 200, the amount of oxidizing gas supplied to the fuel gas supply passage 220, and hence the amount of humidification of fuel gas, can be adjusted appropriately according to the operating state of the fuel cell body 210. Play.

In the fuel cell system 200 of the second embodiment, by using the 3-port electromagnetic switching valve 265, either the circulation passage 260 or the oxidizing gas supply passage 230 is selectively selected. Connected to
Instead, the middle of the communication passage that connects the oxidizing gas supply passage 230 and the fuel gas supply passage 220 and the circulation passage 26
Two MFCs (Mass Flow Controller) in the middle of 0
And the flow rate A of the gas flowing through the communication passage and the flow rate B of the gas flowing through the circulation passage 260 are respectively adjusted by both MFCs to control the ratio of the two flow rates A and B to an arbitrary ratio. Good.

With this configuration, the ratio of the flow rates A and B is not switched to either 100: 0 or 0: 100 as in the second embodiment, but is controlled to an arbitrary ratio such as 50:50. can do. It should be noted that this ratio is determined so that the amount of oxygen supplied to the fuel gas supply passage 220 is a desired amount necessary for achieving a target humidification state of the fuel gas. Therefore, the humidification amount of the fuel gas can be adjusted more appropriately according to the operating state of the fuel cell body.

The third embodiment of the present invention will be described below. FIG. 7 is an overall configuration diagram of a fuel cell system 400 to which the third embodiment of the present invention is applied. As shown in FIG.
The fuel cell system 400 includes a fuel cell body 410, a fuel gas supply passage 420, an oxidizing gas supply passage 430, a fuel gas discharge passage 440, an oxidizing gas discharge passage 450, a circulation passage 460 and a circulation pump 462, which are similar to those of the first embodiment.
Further, a motor-operated valve 465 is provided on the downstream side of the circulation pump 462 in the circulation passage 460. The motor-operated valve 465 arbitrarily controls the flow rate according to the opening control signal provided from the control system 490.

The control system 490 is the electronic control unit 4 connected to the impedance sensor 492, the temperature sensor 494 and both the sensors 492 and 494, as in the second embodiment.
Equipped with 96. The electronic control unit 496 includes a CPU 496a, a ROM 496b, and a RAM 49 which are the same as those in the second embodiment.
6c and an input / output circuit 496d. With the CPU 496a of the electronic control unit 496 having such a configuration,
The wet state of the electrolyte membrane of the fuel cell body 410 is determined from the output signals from the impedance sensor 492 and the temperature sensor 494, the opening degree θ of the electric valve 465 is controlled according to the determination result, and the flow rate of the circulation passage 460 is changed. Controlled.

Next, the electric valve control processing executed by the CPU 396a will be described. This motor-operated valve control process is the same as that of the second embodiment except that the processing contents of steps S350 and S380 are different, and the other steps are exactly the same. In this embodiment, in step S350, the opening degree θ of the motor-operated valve 395.
Is controlled to be fully opened, and in step S380, a process of controlling the opening degree θ of the electric valve 395 to a predetermined opening degree θc on the closing side from the fully opened state is performed.

According to the motor-operated valve control process having such a configuration,
When it is determined that the electrolyte membrane of the fuel cell body 410 is in a dry state, the opening degree θ of the motor-operated valve 495 is controlled to be fully open, and when it is determined that the electrolyte membrane of the fuel cell body 410 is not in a dry state, The opening degree θ of the electric valve 495 is controlled to a predetermined opening degree θc on the closing side from the fully opened state.

Therefore, in the fuel cell system 400 of the third embodiment, a small amount of exhaust gas is circulated from the circulation passage 460 to the fuel gas supply passage 420 during the steady operation in which the electrolyte membrane 110 is in a good wet state, and A large amount of exhaust gas is circulated from the circulation passage 460 to the fuel gas supply passage 420 at the initial stage of operation when the electrolyte membrane 110 is in a poor wet state or at the time of high output. Therefore, in this fuel cell system 400, the amount of exhaust gas from the oxidizing gas discharge passage 450 supplied to the fuel gas supply passage 220 can be adjusted according to the operating state of the fuel cell main body 410, and as a result, the fuel The amount of humidification of gas can be adjusted appropriately. It should be noted that this fuel cell system 400 also has the effect of enhancing the compactness of the entire system and the improvement of energy efficiency, as in the first and second embodiments.

The fourth embodiment of the present invention will be described below. FIG. 8 is an overall configuration diagram of a fuel cell system 600 to which the fourth embodiment of the present invention is applied. As shown in FIG.
The fuel cell system 600 includes a fuel cell main body 610, a fuel gas supply passage 620, an oxidizing gas supply passage 630, a fuel gas discharge passage 640, an oxidizing gas discharge passage 650, a circulation passage 660 and a circulation pump 662, which are similar to those of the first embodiment.
And a MFC (Mass Flow Controller) 665 downstream of the circulation pump 662 in the circulation passage 660.
The oxygen concentration sensor 66 on the upstream side of the circulation pump 662.
7 are provided respectively. The MFC 665 detects the mass flow rate of gas and arbitrarily controls the mass flow rate of gas according to the opening control signal given from the electronic control unit 696. The oxygen concentration sensor 667 outputs a voltage signal E that changes stepwise before and after a predetermined oxygen concentration. The predetermined oxygen concentration is such that the wet state of the electrolyte membrane of the fuel cell body 610 is suitable.

The electronic control unit 696 includes a CPU 696a, a ROM 696b, and a RAM 696 similar to those of the second embodiment.
c and an input / output circuit 696d. The CPU 696a of the electronic control unit 696 having the above configuration responds to the voltage signal E from the oxygen concentration sensor 667 according to the voltage signal E.
The opening degree of 65 is controlled to control the flow rate of the circulation passage 660.

Next, the M executed by the CPU 396a
The FC control process will be described based on the flowchart of FIG. When the CPU 696a starts processing,
First, the voltage signal E from the oxygen concentration sensor 667 is read (step S700). Next, based on the voltage signal E, a process of determining whether the oxygen concentration is in the lean state or the rich state is performed (step S710). The rich state and the lean state indicate the required humidification amount, that is, the excess or deficiency of oxygen with respect to the oxygen amount. When it is determined in step S710 that the oxygen concentration is in the lean state, it is sent to the MFC 665. A process of incrementing the opening degree V that defines the flow rate setting signal by the minute opening degree ΔV is performed (step S720). On the other hand, if it is determined that the oxygen concentration is in the rich state, the opening degree V is changed to the minute opening degree ΔV. A decrementing process is performed (step S730).
After that, a flow rate setting signal corresponding to the opening degree V obtained in step S720 or step S730 is output to the MFC 665 (step S740). When the process of step S740 ends, the process returns to "return" and the process of this routine ends once.

According to the MFC control processing routine having such a configuration, when it is determined that the oxygen concentration determined by the voltage signal E from the oxygen concentration sensor 667 is in the lean state, the opening degree of the MFC 665 is gradually increased stepwise. Further, when it is determined that the oxygen concentration is in the rich state, the opening degree of the MFC 665 is gradually reduced in a stepwise manner. The lean oxygen concentration means that the amount of oxygen circulated in the fuel gas supply passage 620 is small.
Although the amount of water generated in 20 decreases, by increasing the opening degree of MFC 665 as described above, the circulation passage 6
The flow rate of 0 can be increased, and as a result, the circulation amount of oxygen is increased and the amount of produced water is increased.

On the other hand, the fact that the oxygen concentration detected by the oxygen concentration sensor 667 is in a rich state means that the amount of oxygen circulated in the fuel gas supply passage 620 is large. Although the amount of water generated in 620 increases, it is possible to reduce the flow rate in the circulation passage 60 and decrease the generated water by reducing the opening degree of the MFC 665 as described above.

Therefore, in the fuel cell system 600 of the fourth embodiment, the oxygen concentration in the gas supplied from the oxidizing gas exhaust passage 650 to the fuel gas supply passage 620 can always be optimally adjusted. Therefore, the amount of humidification of the fuel gas can be appropriately adjusted so that the electrolyte membrane of the fuel cell body 610 can always be kept in a good wet state regardless of the operating state. In addition, even in this fuel cell system 600,
Similar to the first to third embodiments, the effects of increasing the compactness of the entire system and the efficiency of energy can be obtained.

The fifth embodiment of the present invention will be described below. In the fifth embodiment, a humidity sensor for detecting the humidity in exhaust gas is provided in place of the oxygen concentration sensor 667 in the configuration of the fourth embodiment. The electronic control unit with such a configuration receives the detection signal from the humidity sensor and reduces the opening of the MFC when the humidity in the exhaust gas is high, and increases the opening of the MFC when the humidity in the exhaust gas is low. To execute the control.

As a result, when the electrolyte membrane is in a good wet condition and a large amount of water is discharged from the exhaust gas, the circulation amount of the exhaust gas can be reduced, while the wet condition of the electrolyte membrane is poor and the exhaust gas is exhausted. When the amount of water contained in is small, the circulation amount of exhaust gas can be increased. Therefore, the amount of humidification of the fuel gas can be appropriately adjusted to keep the wet state of the electrolyte membrane of the fuel cell main body always good regardless of the operating state. In this fuel cell system, the first
As in the case of the fourth embodiment, the effects of increasing the compactness of the entire system and the efficiency of energy can be achieved. Instead of the fifth embodiment, a configuration in which both an oxygen concentration sensor 667 (fourth embodiment) and a humidity sensor may be provided,
The circulating gas can be controlled from the viewpoint of more appropriately humidifying the fuel gas.

The sixth embodiment of the present invention will be described below. FIG. 10 is an overall configuration diagram of a fuel cell system 800 to which the sixth embodiment of the present invention is applied. This fuel cell system 800 has both the configuration of the second embodiment and the configuration of the fourth embodiment. That is, as shown in FIG.
The fuel cell system 800 has the same configuration as that of the second embodiment (in the figure, the same parts as those of the second embodiment are denoted by the same reference numerals), and further, the MFC 86 is provided in the circulation passage 260 thereof.
5 and an oxygen concentration sensor 667.

According to this structure, by driving and controlling the three-port electromagnetic switching valve 265 to switch the connection passage to the fuel gas supply passage 20 to the oxidizing gas supply passage 230 side,
The amount of oxygen supplied to the fuel gas supply passage 20 can be increased, and by controlling the opening of the MFC 865 to control the circulation amount of the exhaust gas from the circulation passage 260, the amount of oxygen supplied to the fuel gas supply passage 20 can be increased. The supply amount of oxygen can be precisely controlled. For this reason, the humidification amount of the fuel gas can be adjusted more appropriately according to the operating state, and further, the effect of making the entire system compact and making the energy efficient are both provided.

In the sixth embodiment, further,
A second oxygen concentration sensor is provided in the oxidizing gas supply passage 230, and in addition to the detection signals of the impedance sensor 292, the temperature sensor 294, and the first oxygen concentration sensor 867, three ports are provided according to the detection signals of the second oxygen concentration sensor. The electromagnetic switching valve 265 and the MFC 865 may be driven and controlled. According to this configuration, it is possible to control the humidification amount of the fuel gas according to the oxygen concentration supplied from the oxidizing gas supply passage 230, so that the oxygen content rate in the oxidizing gas supplied from the oxidizing gas source 280 can be controlled. Even when it fluctuates, it is possible to properly control the humidification amount of the fuel gas.

In the first to sixth embodiments described above,
Although the exhaust gas from the oxidizing gas discharge passage is circulated to the fuel gas supply passage as the circulation passage, the exhaust gas from the fuel gas discharge passage may be circulated to the oxidizing gas supply passage instead. With such a configuration, water is newly generated and the oxidizing gas is humidified by the water. As a result, the humidification can be performed while the system is made compact as in the embodiments. As an example corresponding to the second embodiment having such a configuration, the fuel gas discharge passage 240 and the oxidizing gas supply passage 23 are provided.
A circulation passage 260 communicating with 0 is provided, and a 3-port electromagnetic switching valve is provided in the middle of the circulation passage 260.
The other end of the port electromagnetic switching valve is connected to the fuel gas supply passage 230, and the other control system and the like have the same configuration as in the second embodiment. With this configuration, as in the second embodiment, the humidification amount of the oxidizing gas can be properly adjusted according to the operating state of the fuel cell.

The embodiments of the present invention have been described above.
The present invention is not limited to such an embodiment. For example, in place of the structure in which the first catalyst layer 122 is provided on the anode 120, a metal as a catalyst is added to the carbon cloth forming the gas diffusion layer 121. Needless to say, the present invention can be carried out in various modes without departing from the scope of the present invention, such as a configuration in which the carried carbon powder is kneaded into the gap of the cloth to form the anode 120.

[0064]

As described above, according to claims 1 and 8
The fuel cell system described in (1) has an effect that the fuel gas can be humidified while the overall system is made compact and the energy efficiency is improved by saving the consumption of the oxidizing gas. The fuel cell system according to the second to sixth aspects has an effect that the humidification amount of the fuel gas can be appropriately adjusted according to the operating state of the cell body. In the fuel cell system according to the seventh aspect, it is possible to reduce the effect of heat due to the reaction of oxygen and hydrogen on the electrolyte.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a fuel cell system 1 to which a first embodiment of the present invention is applied.

FIG. 2 is a schematic diagram of a cell structure of the fuel cell body 10.

FIG. 3 is an exploded perspective view of the cell structure.

FIG. 4 is an overall configuration diagram of a fuel cell system 200 to which a second embodiment of the present invention is applied.

5 is a flow chart showing a switching valve control process executed by a CPU 296a of an electronic control unit 296. FIG.

FIG. 6 is a graph showing a plurality of equal moisture content curves W determined from impedance Z and temperature T.

FIG. 7 is an overall configuration diagram of a fuel cell system 400 to which a third embodiment of the present invention is applied.

FIG. 8 is an overall configuration diagram of a fuel cell system 600 to which a fourth embodiment of the present invention is applied.

FIG. 9 is a flowchart showing MFC control processing executed by a CPU 396a of an electronic control unit 396.

FIG. 10 is an overall configuration diagram of a fuel cell system 800 to which a sixth embodiment of the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 10 ... Fuel cell main body 20 ... Fuel gas supply passage 30 ... Oxidation gas supply passage 40 ... Fuel gas discharge passage 50 ... Oxidation gas discharge passage 60 ... Circulation passage 62 ... Circulation pump 70 ... Fuel gas source 80 ... Oxidation Gas source 110 ... Electrolyte membrane 120 ... Anode 121 ... Gas diffusion layer 122 ... First catalyst layer 123 ... Second catalyst layer 130 ... Cathode 131 ... Gas diffusion layer 132 ... Catalyst layer 140 ... Collection electrode 142 ... Rib 145 ... Flow Channel groove 150 ... Collection electrode 152 ... Rib 155 ... Channel groove 160 ... Separator 200 ... Fuel cell system 210 ... Fuel cell main body 220 ... Fuel gas supply passage 230 ... Oxidation gas supply passage 240 ... Fuel gas discharge passage 250 ... Oxidation gas discharge Passage 260 ... Circulation passage 262 ... Circulation pump 267 ... Check valve 280 ... Oxidizing gas source 290 ... Control System 292 ... Impedance sensor 294 ... Temperature sensor 296 ... Electronic control unit 296a ... CPU 395 ... Motorized valve 396 ... Electronic control unit 396a ... CPU 400 ... Fuel cell system 410 ... Fuel cell main body 420 ... Fuel gas supply passage 430 ... Oxidizing gas supply Passage 440 ... Fuel gas discharge passage 450 ... Oxidation gas discharge passage 460 ... Circulation passage 462 ... Circulation pump 465 ... Motor valve 490 ... Control system 492 ... Impedance sensor 494 ... Temperature sensor 495 ... Motor valve 496 ... Electronic control unit 496a ... CPU 600 Fuel cell system 610 Fuel cell main body 620 Fuel gas supply passage 630 Oxidizing gas supply passage 640 Fuel gas exhaust passage 650 Oxidizing gas exhaust passage 660 Circulation passage 662 Circulation pump 665 MFC 667 Oxygen Degree sensor 696 ... electronic control unit 696a ... CPU

Claims (8)

[Claims] 1. A fuel cell system comprising a battery body in which an electrolyte is sandwiched between two electrodes, wherein a fuel gas supply passage for supplying a fuel gas containing hydrogen to one of the two electrodes, An oxidizing gas supply passage for supplying an oxidizing gas to the other electrode, a fuel gas discharge passage for discharging the supplied fuel gas from the cell body, and an oxidizing gas discharge for discharging the supplied oxidizing gas from the cell body A fuel cell system comprising: a passage; and a circulation passage that circulates the exhaust gas into the cell body by supplying the exhaust gas from the oxidizing gas discharge passage to the fuel gas supply passage. 2. The fuel cell system according to claim 1, wherein an operating state detecting means for detecting an operating state of the cell body, and a circulation amount of exhaust gas in the circulation passage according to the detected operating state. A fuel cell system comprising: a circulation amount control means for controlling. 3. The fuel cell system according to claim 1, wherein a communication passage extending from the oxidizing gas supply passage to the fuel gas supply passage, a flow rate of the gas flowing through the communication passage, and a gas flowing through the circulation passage. A control valve that adjusts the flow rate and controls the ratio of the two to an arbitrary ratio, an operating state detection unit that detects the operating state of the battery body, and the control valve that controls the operating state according to the detected operating state. A fuel cell system including a control unit for controlling. 4. The fuel cell system according to claim 2, wherein the operating state detecting means is a means for detecting a degree of water content of an electrolyte provided in the cell body. 5. The fuel cell system according to claim 2 or 3, wherein the operating state detecting means is provided in the circulation passage and detects oxygen concentration in exhaust gas flowing through the circulation passage. 6. The fuel cell system according to claim 2, wherein the operating state detecting means is provided in the circulation passage and detects humidity in exhaust gas flowing through the circulation passage. 7. The fuel cell system according to any one of claims 1 to 6, wherein the battery main body is provided with the fuel on a surface of the electrode for supplying the fuel gas opposite to the electrolyte. A fuel cell system comprising a gas flow channel groove, and the electrode including a first catalyst layer formed on the electrolyte side and a second catalyst layer formed on the flow channel side. 8. A fuel cell system comprising a cell body for sandwiching an electrolyte between two electrodes, wherein a fuel gas supply passage for supplying a fuel gas containing hydrogen to one of the two electrodes, An oxidizing gas supply passage for supplying an oxidizing gas to the other electrode, a fuel gas discharge passage for discharging the supplied fuel gas from the cell body, and an oxidizing gas discharge for discharging the supplied oxidizing gas from the cell body A fuel cell system comprising: a passage; and a circulation passage that circulates the exhaust gas in the cell body by supplying the exhaust gas from the fuel gas discharge passage to the oxidizing gas supply passage.