JP2002313379A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regulate the pressure different between the water and gas supplied to a humidifying means to a proper range while the increase in the driving force of a humidifying water pump is suppressed to a necessary minimum. SOLUTION: The fuel gas or oxidizer gas supplied through a gas supply pipe 3 is humidified by a humidifier 1. A passage 4 to supply water to the humidifier 1 is furnished with a pump 5 which sends the humidifying water while pressurizing it, and a place near the suction port of the pump 5 is communicated with the gas supply pipe 3 through a pressure tank 6. The pressure tank 6 keeps the humidifying water in its lower part at all times. Using a tank internal pressure regulating valve 7, a control unit 8 regulates at least either of the inflow and outflow of the gas to/from the tank 6 so that its internal pressure heightens as the system operating condition becomes with a higher load.

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 using a solid polymer electrolyte, and more particularly to a fuel cell system with improved energy efficiency in water pressure control for a humidifier for humidifying fuel gas or air.

[0002]

2. Description of the Related Art A fuel cell is a device for directly converting chemical energy of fuel into electric energy by electrochemically reacting a fuel such as hydrogen and an oxidant such as air. Applications for power generation systems and power sources for mobile objects such as automobiles are expanding. Among them, a solid polymer electrolyte fuel cell using a polymer ion exchange membrane as an electrolyte has many preferable features such as a high output density, a simple structure, and a relatively low operating temperature. Expectations for technology development are increasing.

FIG. 1 shows the configuration of a unit cell battery in such a conventional solid polymer electrolyte fuel cell (PEFC).
2 will be described. That is, an anode electrode 29 and a cathode electrode 30 are arranged with a solid polymer film 28 having ion conductivity interposed therebetween, and a fuel gas supply groove 31 for supplying a fuel gas to the anode electrode 29 and a cathode electrode 30.
Gas supply groove 32 for supplying an oxidant gas to the
Outside the supply grooves, a gas-impermeable anode separator 33 and a cathode separator 3 having conductivity are provided.
4. Further outside the anode separator 33, a conductive gas and water-impermeable water separator 35, a stack for removing excess heat generated by power generation to maintain a proper battery stack temperature. A cooling water supply groove 36 for flowing cooling water is provided, and a unit cell battery 37 is constituted by 28 to 36.

In the above-mentioned solid polymer electrolyte fuel cell, when a fuel gas is supplied to the anode electrode 29 and an oxidizing gas is supplied to the cathode electrode 30, the electrochemical reaction simply occurs between the pair of electrodes of the cell battery. , An electromotive force is generated as follows.

[0005]

[Number 1] anode ^{_{reaction: H 2 → 2H + + 2e}} - cathodic _{^{reaction: 2H + + 1 / 2O 2}} + 2e - → 2H 2 O In other words, usually, as the fuel gas of hydrogen is used, use air as an oxidant gas First, when hydrogen is supplied to the anode electrode 29 and air is supplied to the cathode electrode 30, the supplied hydrogen is dissociated into hydrogen ions and electrons at the anode electrode 29. Then, the hydrogen ions pass through the solid polymer membrane 28, and the electrons pass through the external circuit to the cathode electrode 30, respectively.

On the other hand, in the cathode electrode 30, the oxygen in the supplied air, the hydrogen ions, and the electrons react to generate water. At this time, the electrons passing through the external circuit become current and can supply power. That is, the reaction represented by the above-described chemical reaction proceeds between the anode electrode 29 and the cathode electrode 30. The generated water is discharged out of the battery together with the unreacted gas.

Incidentally, the electromotive force of the unit cell battery 37 is 1
V or less, the usual practical fuel cell system is
It has a battery stack in which several tens to hundreds of unit cells 37 are stacked, and power is generated by this battery stack.

[0008] As the solid polymer film 28 having the above-mentioned solid polymer electrolyte fuel ion conductivity for use in batteries, for example, a proton exchange membrane perfluorosulfonic b carbon sulfonic acid (Nafion ^R: DuPont Is known. This membrane has a hydrogen ion exchange group in the molecule and functions as an ion conductive electrolyte by containing saturated water, and also has a function of separating the fuel and the oxidant. Conversely, when the water content of the membrane decreases, the ionic resistance increases, and a crossover in which the fuel and the oxidant mix occurs,
Power generation with batteries becomes impossible. For this reason, it is desirable that the solid polymer membrane be saturated with water.

On the other hand, when hydrogen ions separated at the anode electrode by power generation move through the solid polymer membrane to the cathode electrode, water also moves together, and the solid polymer membrane tends to dry on the anode electrode side. is there. Also, if the amount of water vapor contained in the supplied fuel or air is small, the solid polymer membrane tends to dry near the respective reaction gas inlets. For the above reasons, it is common practice to supply a pre-humidified fuel and an oxidizing agent to a polymer electrolyte fuel cell.

As a prior art of the solid polymer electrolyte fuel cell system as described above, JP-A-2000-3
Japanese Patent Application Laid-Open Nos. 48751 and 2000-188119 are known. These are provided with humidifying means in one or both of a fuel supply pipe and an oxidant supply pipe, and by supplying water stored in a tank to the humidifier, the fuel gas and the oxidant gas are humidified in advance. From the supply to the fuel cell stack.

[0011]

However, in the conventional solid polymer electrolyte fuel cell system as described above,
There were the following problems.

As a means for humidifying the combustion gas and the oxidizing gas, a method is generally employed in which the gas is brought into contact with water via a polymer film. In this method, the pressure difference between gas and water must be adjusted to a predetermined range in order to prevent deterioration of the film due to the pressure difference between both surfaces of the film. Generally, the gas pressure increases as the load on the system increases, but if the amount of water is sufficient to maintain humidification performance, the slope of the water-side pressure rise may be less gradual than that of gas. Many. For this reason, in order to keep the pressure difference between water and gas within a predetermined range, a humidifying water pump sends out an amount of water equal to or more than the required amount of water for humidification, or a throttle valve is provided downstream of the humidifier in the humidification water circulation path. Closing this will increase the pressure on the water side. Therefore, as a result, more energy is consumed than necessary for driving the humidifying water pump, and there is a problem that the energy efficiency of the entire fuel cell system is not improved.

In view of the above problems, the present invention minimizes the increase in the driving force of the humidifying water pump even when the operating load of the system increases and the pressure on the gas side supplied to the humidifying means increases. It is an object of the present invention to provide a fuel cell system capable of adjusting the pressure difference between gas and water supplied to a humidifying unit to an appropriate range while suppressing the energy consumption, thereby increasing the energy efficiency of the entire system.

[0014]

According to the first aspect of the present invention, at least one unit cell in which an electrolyte membrane made of a solid polymer is disposed between a fuel electrode and an oxidant electrode is provided. A fuel cell stack, a fuel supply pipe for supplying a fuel gas to the fuel electrode, an oxidant supply pipe for supplying an oxidant gas to the oxidant electrode, and / or one of the fuel gas and the oxidant gas A humidifying unit for humidifying one of the humidifying units, a humidifying water supply pipe for supplying water to the humidifying unit, and a humidifying water pressurizing unit for supplying water to the humidifying unit while pressurizing the water; A tank that connects the vicinity of the suction port of the humidifying water pressurizing means of the water supply pipe with a fuel gas or oxidizing gas pipe and that always holds the humidifying water at a lower portion thereof, and the amount of gas flowing into or out of the tank Less of And a control means for adjusting the opening of the control valve so that the internal pressure of the tank increases as the operating state of the system increases. Is the gist.

According to a second aspect of the present invention, there is provided a fuel cell system according to the first aspect, wherein the tank is provided with a pressure relief valve for releasing internal pressure to the outside air. I do.

According to a third aspect of the present invention, there is provided a fuel cell system according to the first or second aspect, wherein a pipe branches from the fuel supply pipe or the oxidant supply pipe to the tank. Is arranged near the outlet of the high-pressure fuel gas cylinder or near the outlet of the air compressor that compresses air as an oxidant.

According to a fourth aspect of the present invention, in order to achieve the above object, the fuel cell system according to any one of the first to third aspects further comprises a pressure detecting means for detecting an internal pressure of the tank, The gist is that the control means controls the regulating valve based on the pressure detected by the pressure detection means.

According to a fifth aspect of the present invention, there is provided a fuel cell system according to any one of the first to fourth aspects, wherein a recovered water tank for storing water recovered from the fuel cell system is provided. And the tank are communicated with each other by a recovered water passage, and a recovered water adjusting valve whose opening can be adjusted under the control of the control means is provided in the recovered water passage, and the recovered water is discharged directly from the recovered water tank to the outside of the system. The point is that a water discharge valve is provided.

[0019]

According to the first aspect of the present invention, there is provided a fuel cell stack having at least one unit cell in which an electrolyte membrane made of a solid polymer is disposed between a fuel electrode and an oxidant electrode; A fuel supply pipe for supplying a fuel gas to an electrode, an oxidant supply pipe for supplying an oxidant gas to the oxidant electrode, and humidifying means for humidifying both or one of the fuel gas and the oxidant gas, In a fuel cell system comprising: a humidification water supply pipe for supplying water to the humidification means; and a humidification water pressurization means for supplying water to the humidification means while pressurizing the water. A tank that connects the vicinity of the suction port of the pressure means to the fuel gas or oxidizing gas pipe and always holds the humidified water in the lower part, and at least one of the inflow and outflow of the gas into and from the tank can be controlled. Key tone A valve, and control means for adjusting the opening of the regulating valve so that the internal pressure of the tank increases as the operating state of the system increases. When the required value is increased and the pressure on the gas side supplied to the humidifying unit is increased, the reference pressure in the humidifying water circulation path can be increased by increasing the internal pressure of the tank with the adjusting valve,
As a result, an increase in the head by the humidifying water pressurizing means corresponding to an increase in load is sufficient only by an amount corresponding to the amount of water that satisfies the humidifying performance of the humidifying means to the gas to be humidified.
That is, the pressure difference between gas and water supplied to the humidifying unit can be adjusted to an appropriate range while suppressing the increase in the driving force of the humidifying water pressurizing unit to a minimum, and as a result, the entire system can be adjusted. There is an effect that energy efficiency can be improved.

Further, when the operating load shifts from a high load to a medium to low load, under conditions where it is necessary to lower the tank internal pressure, the tank internal pressure is gradually leaked to the gas supply pipe side to be reduced. The same purpose can be achieved without leaking fuel gas or the like to the (atmosphere) and deteriorating fuel efficiency and the like.

According to the second aspect of the present invention, in addition to the effects of the first aspect of the present invention, since the tank is provided with a pressure relief valve for releasing the internal pressure to the outside air, the operating state of the system is improved. Or when the state at the time of supply of the humidified gas changes, and when the internal pressure of the pressurized tank is to be reduced, by adjusting the opening of the pressure relief valve to quickly reduce the internal pressure of the tank to the target. Therefore, there is an effect that the operability of the system is further improved.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, the location where the pipe branches from the fuel supply pipe or the oxidant supply pipe to the tank is provided with a high pressure. By arranging it near the outlet of the fuel gas cylinder or near the outlet of the air compressor that compresses air as an oxidant, the vicinity of the branch is the highest pressure point in the gas flow path. The adjustable width of the tank internal pressure at the time of introduction can be maximized, whereby the head in the humidifying water pressurizing means, that is, the supply pressure of the humidifying water to the humidifying means can be controlled independently of the humidifying water amount Can be widened, and as a result, there is an effect that it can be adapted to a wide range of system operating conditions.

According to a fourth aspect of the present invention, in addition to the effects of the first to third aspects, a pressure detecting means for detecting the internal pressure of the tank is provided, and the pressure detected by the pressure detecting means is provided. By controlling the regulating valve based on the, the tank internal pressure can be directly detected, it is possible to send a more accurate valve opening control signal to the regulating valve, the tank internal pressure, that is, The accuracy of adjustment of the reference pressure in the humidification water circulation path can be improved.
As a result, there is an effect that further improvement in operability and energy efficiency of the system can be expected.

According to the fifth aspect of the present invention, in addition to the effects of the first to fourth aspects, a recovered water tank for storing water recovered from the fuel cell system and a recovered water passage are provided. The collected water passage is provided with a collected water adjusting valve whose opening can be adjusted by the control of the control means in the collected water passage, and a water discharge valve for discharging collected water directly from the collected water tank to the outside of the system is provided. When the remaining amount of water in the tank storing the humidification water is reduced,
Since water condensed and recovered from the exhaust of the system or the like can be poured into the tank, the water balance of the entire system is improved, and the necessity of supplying water from outside the system is eliminated. There is an effect that the number of operation steps when operating the system can be significantly reduced.

Further, if more than necessary collected water accumulates in the collected water tank, it can be discarded outside the system. Therefore, when the fuel cell system is mounted on a vehicle or the like, the total weight is kept to a minimum. Therefore, it is possible to improve the drivability of the vehicle and reduce the fuel consumption.

[0026]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of a fuel cell system according to the present invention, and corresponds to the first aspect of the present invention.

In FIG. 1, a fuel cell stack 2 is a fuel cell stack in which at least one unit cell in which a solid polymer electrolyte membrane is disposed between a fuel electrode and an oxidant electrode is stacked in order to obtain a desired output voltage. It is. The humidifier 1 has a humidifying water flow path 4
And a gas supply pipe 3 serving as a passage for a fuel gas or an oxidizing gas, and a gas humidified by the humidifier 1 is supplied to the fuel cell stack 2.

A humidifying water pump 5 serving as a humidifying water pressurizing means is provided in a circulating system of the humidifying water flow path 4 to supply humidifying water to the humidifier 1. Pressurized tank 6 to replenish
The water stored therein is supplied to the vicinity of the suction portion of the humidifying water pump 5.

The gas supply pipe 3 and the upper part of the pressurized tank 6 communicate with each other via a tank internal pressure adjusting valve 7, and the tank internal pressure adjusting valve 7 is a control means according to the load during system operation. Opening / closing or opening is controlled by a control signal from the control unit 8. Thereby, the pressure of the gas supply pipe 3 is adjusted by the tank internal pressure adjusting valve 7 and applied to the pressurized tank 6.

FIG. 2 is a diagram illustrating the relationship between the internal pressure of the pressurized tank and the operating load in the first embodiment of the present invention.

FIG. 2A shows that the flow rate of the reactant gas Qgas supplied to the fuel cell stack is substantially proportional to the load, and that the flow rate of the reactant gas Qgas is substantially proportional to the gas supply pressure Pgas to the fuel cell stack. It is. From this, as a result, it is general that the load and the reaction gas pressure Pgas are also substantially proportional to each other.

From FIG. 2B, it can be seen that the humidifying water flow rate Qwater required to humidify the gas with respect to the load is substantially proportional to the humidifying water flow rate Qwater and the humidifying water pump head (or discharge pressure) ΔPhead. It is almost proportional. As a result, the relationship between the load and the humidification water pump head ΔPhead is almost proportional, but the slope is often smaller than that of gas.

FIG. 2 (c) shows the relationship between the gas supply pressure and the humidification water supply pressure by superimposing both of FIGS. 2 (a) and 2 (b). The pressure of the humidifying water supplied to the humidifier 1 needs to fall within a certain allowable differential pressure range based on the gas supply pressure in order to properly maintain the differential pressure with the gas. However, when only the amount of water necessary for humidification is sent out by the humidification water pump 5, as shown in the figure, as the load increases, the differential pressure falls below the allowable range, and the humidification water pressure increases the gas supply pressure. Therefore, the humidifier 1 may be deteriorated.

Therefore, according to the present invention, as the load increases, the pressure tank 6 as shown by the broken line in FIG.
The pressure difference between the gas supply pressure and the humidification water pressure is within an allowable range by adjusting the opening of the tank internal pressure adjusting valve 7 so as to increase the internal pressure of the tank and sending gas from the gas supply pipe 3 to the pressurized tank 6. In.

FIG. 3 is a view for explaining a method for simultaneously adjusting the humidifying water amount and the humidifying water pressure in the first embodiment of the present invention.

As shown in FIG. 3A, the humidification water flow rate Qwater is substantially proportional to the humidification water pump head ΔPhead.
It is adjusted by changing Phead, and basically, the load and ΔPhead are in a proportional relationship as shown in FIG. 2B. However, depending on the wet state of the solid polymer electrolyte membrane inside the stack, it may be necessary to increase or decrease the humidification water flow rate Qwater. Even in this case, according to the present invention, the supply pressure Pwater of the humidifying water to the humidifier 1 is kept constant within the allowable differential pressure range as shown in FIG. The distribution of ΔPhead can be changed.

The operation of this embodiment as described above is as follows. That is, the adjustment of the humidifying water amount when the load on the system is increased is limited to the amount that can maintain the humidifying performance of the humidifier 1, and the humidifying water pump 5 is operated at the humidifying water pump lift corresponding to the humidifying water amount. The internal pressure of the pressurized tank is adjusted by adjusting the opening of the tank internal pressure adjusting valve 7 so that the humidified water supply pressure falls within the allowable differential pressure range based on the humidified gas pressure. Further, in accordance with the wet state of the electrolyte membrane of the fuel cell stack 2, the pump head is changed to change the humidification water supply amount, and the pressure in the pressurized tank is adjusted to keep the humidification water supply pressure substantially constant.

Conversely, the adjustment of the amount of humidification water when the operating load is reduced is contrary to the above case, and the pressure of the pressurized tank is adjusted by adjusting the opening of the tank internal pressure adjusting valve 7 so as to gradually reduce the increased tank internal pressure. Pressure is leaked from the 6 side to the gas supply pipe 3 side, and as a result, the supply amount of humidification water is reduced. That is, the supply of desired humidification water is controlled without applying a relief valve, discharging fuel or air out of the system, and without deteriorating fuel efficiency and efficiency.

According to this embodiment as described above, even if the load on the system or the wet state of the film inside the stack changes, the driving force of the humidifying water pump 5 for pressurizing the humidifying water should be increased to the minimum necessary. The pressure difference between the gas and the water supplied to the humidifier 1 can be adjusted to an appropriate range while keeping it to a minimum, and as a result, the energy efficiency of the entire system can be improved.

FIG. 4 corresponds to the second aspect of the present invention.
FIG. 2 is a schematic configuration diagram showing a second embodiment of the fuel cell system according to the present invention, and shows only parts different from the configuration of the first embodiment in FIG. 1.

This embodiment is different from the first embodiment in that the pressurized tank 6 has an atmosphere opening passage 10 for releasing the pressure inside the tank to the outside air, and a pressure relief opening and closing the atmosphere opening passage 10. A relief valve 9 as a valve is added. Thereby, when the target value of the tank internal pressure corresponding to the load during the system operation and the intake state (the state at the time of supplying the humidified gas) becomes lower than the current value, the opening degree of the relief valve 9 is adjusted to thereby achieve the target. To the tank internal pressure can be quickly reduced with a sudden decrease in load.

FIG. 5 is a view for explaining the operation of the relief valve and the method of adjusting the humidification water pressure in the second embodiment of the present invention.

In particular, in the case of a general fuel cell system in which air as an oxidant gas is taken in from outside air, if the humidity during intake becomes low during operation of the system, even if the system load is the same, The required amount of humidifying water for humidifying the air in the humidifier 1 increases.

According to FIG. 5A, the supply amount of humidification water is Qwa
In order to make ter1 → Qwater2, the head of the humidification water pump 5 must be changed from ΔPhead1 to ΔPhead2. At this time, if the internal pressure of the pressurized tank 6 is the same, the humidification water pressure Pwater supplied to the humidifier 1 may become too high and exceed the allowable differential pressure range based on the gas pressure. For this reason, in the present embodiment, as shown in FIG. 5B, by adjusting the opening of the relief valve 9, a part of the internal pressure of the pressurized tank 6 is released, and the pressure is reduced from Ptank1 to Ptank2.
The humidification water pressure Pwater, which is the sum of tank2 and ΔPhead2, can be kept substantially constant.

FIG. 6 is a flowchart for controlling the tank internal pressure and the humidification water supply amount in the second embodiment of the present invention. The algorithm will be described below.

First, in step S11, the required humidifying water amount and the humidifying water pressure corresponding to the operating state and the intake state of the system are calculated and determined by the control unit 8, and in step S1.
Moving to 2, it is determined whether it is necessary to increase the current humidification water supply amount Qwater. If there is no need to increase the amount, the process returns to step S11. If there is, the process proceeds to the next step S13. In step S13, when the humidification water pump head ΔPhead is increased to increase the humidification water supply amount Qwater, the humidification water supply pressure P
It is determined whether or not water falls within the allowable differential pressure range.

If it falls within the allowable range, in the next step S14, ΔPhead is increased by a necessary amount to increase Qwater. If it is determined in step S13 that the pressure is out of the allowable differential pressure range, the tank internal pressure adjusting valve 7 connected to the air line is fully closed and shut off in step S24, and the relief valve 9 is opened in step S25. While adjusting the degree, the pump head ΔPhead is increased so that Pwater is kept almost constant. Next, in step S26, it is determined whether or not the target ΔPhead has been reached. Only when the target ΔPhead has been reached, the process proceeds to step S27 to fully close the relief valve 9 and stop increasing the pump head ΔPhead.

The operation of this embodiment differs from that of the first embodiment in the following. According to the control flow of FIG. 6 described above, the humidifier 1 is kept at a constant gas supply pressure.
Need to increase the supply of humidified water to
The opening degree of the relief valve 9 and the pump head of the humidification water pump 5 are changed at the same time to cope with this.

According to the present embodiment as described above, the same effects as those of the above-described first embodiment can be obtained. In addition, even when the required humidification water amount increases due to the relationship between the system load and the intake state, Since it is possible to quickly reduce the pressure to the target tank internal pressure and to improve the ability to follow an external input, the operability of the system is further improved.

FIG. 7 corresponds to the third aspect of the present invention.
It is a schematic structure figure showing a third embodiment of the present invention.

The present embodiment is different from the first and second embodiments described above in that the location where the piping is branched from the humidified gas supply pipe 3 to the pressurized tank 6 is different from that of the first embodiment.
Is supplied near the outlet of the high-pressure cylinder in the case of the type supplied from the compressor, and is disposed near the outlet of the gas compressor in the case of the type supplied with the humidified gas compressed by the compressor 11 under pressure. Is the same as in the above-described embodiments.

FIG. 8 is a diagram for explaining the effect of the configuration of the third embodiment of the present invention.

Considering the entire supply and discharge line of the gas to be humidified, the highest gas pressure is at the outlet of the high-pressure cylinder or the compressor 11 and the maximum value of the gas pressure that can be introduced into the pressurized tank 6. The higher the value, the wider the adjustable range of the internal pressure of the pressurized tank.

The operation of this embodiment differs from the first and second embodiments in that the pressurized tank by adjusting the opening of the tank internal pressure adjusting valve 7 as described in FIG. 6, the adjustable range of the internal pressure can be maximized.

According to this embodiment as described above, the same effects as those of the first and second embodiments can be obtained, and in addition, the head of the pressurizing pump 5, that is, the amount of humidified water is independent. The width of the supply pressure of the humidifying water to the humidifier 1 that can be controlled at a high speed can be widened, and as a result, it is possible to adapt to a wide range of system operating conditions.

FIG. 9 corresponds to the fourth aspect of the present invention.
It is a schematic structure figure showing a 4th embodiment of the present invention.

In the present embodiment, the pressure tank 6 is provided with a pressure sensor 12 for constantly detecting the tank internal pressure, and a signal from the pressure sensor 12 is sent to the control unit 8 in contrast to the second embodiment. It is configured to be. The configuration other than the above is the same as that of the second embodiment.

The operation of this embodiment differs from that of the second embodiment in that the internal pressure of the pressurized tank 6 can be directly detected. The valve opening control signal given to the relief valve 9 is more accurately and promptly supplied to the control unit 8.
It can be calculated and determined within.

According to the present embodiment as described above, in addition to the same effects as those of the first and second embodiments described above, in addition to the internal pressure of the pressurized tank 6, that is, the reference pressure in the humidification water circulation path, Accuracy of pressure adjustment can be improved, and as a result, further improvement in operability and energy efficiency of the system can be expected.

FIG. 10 is a schematic diagram showing a fifth embodiment of the present invention, corresponding to the fifth aspect of the present invention.

This embodiment is different from the fourth embodiment in the following points. A collected water tank 15 is provided for storing water collected by condensation from exhaust gas from the fuel cell system or the like. A collected water tank level sensor 16 for detecting the amount of stored water is provided in the collected water tank 15. The above-mentioned pressurized tank 6 is also provided with a pressurized tank water level sensor 17 for detecting the amount of stored water, and the water level signals from the two water level sensors are sent to the control unit 8. The recovered water tank 15 and the pressurized tank 6 are connected by a recovered water passage 14, and the recovered water passage 14 is provided with a recovered water regulating valve 13, and is directly recovered from the recovered water tank 15 to the outside of the system. A passage for discharging water is provided, and the discharge passage is provided with a recovered water discharge valve 18. The above-mentioned recovered water adjustment valve 13 and recovered water discharge valve 1
8, the opening is adjusted by a valve control signal from the control unit 8. The configuration other than the above is the same as in the first to fourth embodiments.

FIG. 11 is a flowchart for controlling the tank internal pressure, the humidified water supply amount, and the recovered water amount in the fifth embodiment of the present invention. The algorithm will be described below.

First, it is determined in step S31 whether or not the storage amount in the pressurized tank 6 is equal to or less than a predetermined lower limit. If it is determined that the storage amount is equal to or less than the lower limit, the process proceeds to step S32 and the tank internal pressure adjusting valve 7 is fully turned off. It is closed, and the head ΔPhead by the humidifying water pressurizing pump is increased within the allowable differential pressure range. In the next step S33, it is determined whether or not the internal pressure Ptank of the pressurized tank 6 is lower than the atmospheric pressure. If the internal pressure Ptank is lower than the atmospheric pressure, the recovered water adjusting valve 13 is opened in step S34. The injection of the water stored in the recovered water tank 15 into the pressurized tank 6 via the recovered water passage 14 is started.

Next, in step S35, the pressure tank 6
It is determined whether or not the amount of water inside is equal to or greater than a reference value. When it is determined that the reference value has not been reached in step S35, the process proceeds to step S36, and it is continuously checked whether or not the amount of water in the recovered water tank 15 is empty. If the recovered water tank 15 is not empty, the process returns to step S35 while the injection of the recovered water is continued. Step S36
If it is determined in step S3 that the collected water tank 15 is empty, the process proceeds to step S3 regardless of the water level in the pressurized tank 6.
At 7, the recovered water regulating valve 13 is closed. Then step S3
8, the opening degree of the tank internal pressure adjusting valve 7 and the head ΔPhead of the humidifying water pump 5 are adjusted to values suitable for the operating state and the intake state of the system.

When it is determined in step S33 that Ptank is higher than the atmospheric pressure, the recovered water cannot be poured into the pressurized tank due to the relationship between the internal pressure of the pressurized tank and the pressure difference between the recovered water tank. By such a procedure, Pta
nk will be reduced to below atmospheric pressure. In step S40, the relief valve 9 of the pressurized tank 6 is opened, and in step S41
It is checked whether or not Ptank has reached the atmospheric pressure, and if it has reached, the process proceeds to the next step S42, closes the relief valve 9, and returns to step S33.

If it is determined in the first step S31 that the amount of water in the pressurized tank is still sufficient, it is checked in the next step S43 whether the recovered water tank 15 is not full. If it is not full, the normal operation state can be maintained, but if it is determined that it is full, the recovered water discharge valve 18 is fully opened in step S44,
Start discharging the recovered water out of the system. While discharging the recovered water, it is checked in step S45 whether the water level in the recovered water tank 15 has returned to or below the reference value. If not yet, the discharge is continued. The collection water discharge valve 18 is fully closed to stop the collection water discharge.

The operation of this embodiment is characterized in that the humidifier 1 humidifies the gas in the pressurized tank 6 and the humidified water flow path 4 by humidifying the gas in the humidifier 1. As water gradually decreases, the amount of water can be maintained by adding water recovered from the exhaust of the system or the like.

According to this embodiment as described above, there is no need to supply water from outside the system, and the water balance of the entire system is improved, thereby greatly reducing the number of working steps when operating the system. Reduced. Also, the recovered water tank 15
Is provided with a collected water discharge valve 18 capable of discharging water directly out of the system, so that if more collected water is collected in the collected water tank 15, it can be discarded outside the system. For this reason,
When the fuel cell system is mounted on a vehicle or the like, the vehicle can be driven while keeping the total weight at a minimum, so that the drivability of the vehicle is improved and the fuel efficiency can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a fuel cell system according to the present invention.

FIG. 2 is a diagram illustrating a relationship between an internal pressure of a pressurized tank and an operation load according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a method for simultaneously adjusting a humidifying water amount and a humidifying water pressure in the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the fuel cell system according to the present invention.

FIG. 5 is a diagram illustrating an operation of a tank internal pressure relief valve and a method of adjusting humidification water pressure according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating control of a tank internal pressure and a humidification water supply amount according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a third embodiment of the fuel cell system according to the present invention.

FIG. 8 is a diagram illustrating the effect of the configuration of the third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram showing a fourth embodiment of the fuel cell system according to the present invention.

FIG. 10 is a schematic configuration diagram showing a fifth embodiment of the fuel cell system according to the present invention.

FIG. 11 shows a tank internal pressure according to a fifth embodiment of the present invention;
It is a flowchart for controlling the supply amount of humidification water and the amount of recovery water.

FIG. 12 shows a conventional solid polymer electrolyte fuel cell (PEF).
It is a schematic cross section which shows the structure of the unit cell battery in C).

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 humidifier 2 fuel cell stack 3 gas supply pipe 4 humidification water channel 5 humidification water pump 6 pressurized tank 7 tank internal pressure regulating valve 8 control unit 9 relief valve 10 atmosphere open passage

Claims (5)

[Claims] 1. A fuel cell stack having at least one unit cell in which an electrolyte membrane made of a solid polymer is disposed between a fuel electrode and an oxidant electrode, and a fuel supply pipe for supplying a fuel gas to the fuel electrode An oxidant supply pipe for supplying an oxidant gas to the oxidant electrode, a humidifier for humidifying both or one of the fuel gas and the oxidant gas, and a humidifier for supplying water to the humidifier. A fuel cell system comprising: a supply pipe; and a humidifying water pressurizing unit that pressurizes and sends out water to be supplied to the humidifying unit. Alternatively, a tank that communicates with the oxidizing gas pipe and always holds the humidifying water in the lower part, an adjustment valve that can control at least one of the gas inflow and outflow to the tank, and an operating state of the system. Control means for adjusting the opening of the regulating valve so that the internal pressure of the tank increases as the load increases. 2. The fuel cell system according to claim 1, wherein the tank is provided with a pressure relief valve for releasing internal pressure to outside air. 3. A location where a pipe branches from the fuel supply pipe or the oxidant supply pipe to the tank is disposed near a high-pressure fuel gas cylinder outlet or near an air compressor outlet for compressing air as an oxidant. The fuel cell system according to claim 1 or 2, wherein: 4. The apparatus according to claim 1, further comprising pressure detection means for detecting an internal pressure of the tank, wherein the control means controls the regulating valve based on the pressure detected by the pressure detection means. Item 4. The fuel cell system according to any one of items 3. 5. A recovered water tank for storing water recovered from the fuel cell system and said tank communicating with each other through a recovered water passage, and the recovered water whose opening degree can be adjusted by controlling said control means in said recovered water passage. The fuel cell system according to any one of claims 1 to 4, further comprising a regulating valve, and a water discharge valve for discharging the recovered water directly from the recovered water tank to the outside of the system.