JP3627716B2 - Fuel cell system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a fuel cell system for a vehicle.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 2001-155750 discloses a vehicle fuel cell system.
[0003]
Currently, fuel cells that are being considered for installation in vehicles are mainly of the polymer electrolyte membrane type. In this type of fuel cell, since the power generation efficiency deteriorates unless the solid polymer membrane is in a wet state, it is necessary to humidify at least one of air and fuel gas supplied to the fuel cell.
[0004]
As a humidifying method, there is a method in which a humidifier is provided upstream of the fuel cell to humidify at least one of air or fuel gas supplied to the fuel cell, and a method in which water is circulated inside the fuel cell and humidified with the water.
[0005]
[Problems to be solved by the invention]
By the way, when the electrical conductivity of the water for the said humidification is high, the phenomenon in which a short circuit current flows through water will generate | occur | produce and a part of generated electric power is consumed wastefully. Even when air or fuel gas supplied to the fuel cell is humidified, if the vapor condenses inside the fuel cell, a short-circuit current may flow in the same manner. Such a short-circuit current is the same as a non-controlling current flowing, and causes an increase in power consumption.
[0006]
The present invention has been made in view of such technical problems, and an object of the present invention is to reduce the conductivity of the humidifying water while operating the fuel cell when the conductivity of the humidifying water is high.
[0007]
[Means for solving problems]
In the fuel cell system, humidification means for humidifying at least one of fuel gas and air supplied to the fuel cell, conductivity reduction means for reducing the conductivity of the water for humidification, and conductivity of the water for humidification Detecting means, and when the detected conductivity of the water for humidification is higher than a predetermined value, the humidification by the humidifying means is prohibited and the fuel cell is operated without humidification. To increase.
[0008]
[Action and effect]
According to the present invention, when the conductivity of the humidifying water is high, the fuel cell is operated in a non-humidified state, and during that time, the conductivity of the humidifying water can be lowered over time, Even when the conductivity of the water for humidification is high after long-term storage, the fuel cell can be started early.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0010]
FIG. 1 shows a schematic configuration of a fuel cell system according to the present invention. The illustrated system is a system using a direct hydrogen fuel cell that supplies hydrogen directly to the anode from the hydrogen tank 17, but a reformed fuel cell that supplies a hydrogen-rich gas obtained by reforming liquid fuel. It may be.
[0011]
In the fuel cell 1, for example, a cathode electrode that circulates air with a solid polymer electrolyte membrane sandwiched therein and an anode electrode that supplies hydrogen are formed. The fuel cell 1 is also formed with a passage 9 through which a low melting point heat medium (hereinafter abbreviated as LLC) for controlling the temperature of the fuel cell body. Further, a pure water passage 3 (humidifying means) having a structure capable of exchanging pure water with the cathode and the anode through a porous material for humidifying the solid polymer electrolyte membrane and collecting condensed water is also provided. However, the humidification may be a type in which supplied air or hydrogen is humidified by an external humidifier.
[0012]
A temperature sensor 2 is provided as means for detecting the temperature of the fuel cell 1, and the temperature sensor 2 monitors the temperature of the fuel cell body. The pipe 3 is a pipe that circulates the pure water for humidification to the fuel cell 1, and the energy of the circulation is given by the water pump 4. In the present embodiment, the configuration is provided with a buffer tank 5 for humidifying water.
[0013]
A conductivity sensor 6 is provided as means for detecting the conductivity of the humidifying water, and the valve 7 is a three-way valve that switches between supplying the humidifying water to the fuel cell 1 or the ion exchange resin 8. is there. If the water for humidification is supplied to the ion exchange resin 8 (conductivity reduction means) by switching the three-way valve 7, the conductivity of the water for humidification can be lowered. The three-way valve 7 is configured so that even when humidifying water is supplied to the fuel cell 1, a part of the humidifying water is also supplied to the ion exchange resin 8, and the conductivity of the humidifying water is constantly reduced. You may do it.
[0014]
The pipe 9 is an antifreeze liquid (LLC) pipe and is shown by a double line so that it can be distinguished from a pipe for water for humidification. The LLC flows through the pipe 9 by the LLC pump 10 and is supplied to the fuel cell 1. The LLC that has flowed out of the fuel cell 1 is guided to a humidifying water buffer tank 5 so that it can be heated by a heater (not shown) together with the humidifying water at low temperatures such as below freezing. The LLC that has left the buffer tank 5 for humidifying water is guided to the three-way valve 11, and the flow path is switched between the line 13 that passes through the radiator 12 and the line 14 that does not pass through, depending on the temperature of the LLC and the required control temperature. If the three-way valve 11 is switched to supply LLC to the radiator 12, the temperature of the LLC can be lowered and the temperature of the fuel cell 1 can be lowered. The radiator 12 (and the three-way valve 11) constitutes temperature control means of the fuel cell 1.
[0015]
Hydrogen is supplied to the fuel cell 1 by adjusting the flow rate and pressure of the hydrogen in the hydrogen tank 17 using the control valve 18. Air is supplied to the fuel cell 1 from an air supply machine 20 such as a blower or a compressor after the temperature and humidity are detected by the air temperature sensor 22 and the air humidity sensor 23.
[0016]
In addition, a control unit 21 (control means) configured to include one or more microprocessors, a memory, an input / output interface, and the like is provided to control each valve, pump, and the like. In the control unit 21, the conductivity of water for humidification is from the conductivity sensor 6, the temperature of the fuel cell 1 is from the fuel cell body temperature sensor 2, the temperature of the intake air is an air thermometer 22 as an air temperature detecting means, Air humidity is sent from an air hygrometer 23 as air humidity detecting means. The control unit 21 controls the water pump 4, the three-way valve 7, the LLC pump 10, the three-way valve 11, and the adjustment valve 18 based on such information.
[0017]
Hereinafter, the control content of the control unit 21 will be described.
[0018]
FIG. 2 shows a control block diagram of the control unit 21. According to this, first, in block B1, it is determined whether the conductivity of the humidifying water is a level at which the supply of the humidifying water to the fuel cell 1 can be permitted or prohibited. If it is a prohibited level, next, in block B2, control for urgently reducing the conductivity of the humidifying water is executed. Further, in block B3, it is determined whether or not the environment is capable of non-humidifying operation, and whether or not non-humidifying operation is possible is determined. Further, if it is possible to change the operating conditions even if the non-humidified operation is difficult at present, the operating conditions are adjusted in the block B4 so that the operating conditions are satisfied. Thereafter, when it is determined that a non-humidifying operation is possible, the fuel cell 1 is operated in a non-humidified state in block B5.
[0019]
Next, detailed control contents in each means will be described. FIG. 3 is a flowchart showing the content of the humidifying water conductivity determination process performed by the control unit 21, and corresponds to the process in block B1 of FIG.
[0020]
According to this, first, in step S1, the conductivity C of the humidifying water corresponding to the output of the conductivity sensor 6 is read, and the read conductivity C and the predetermined value SLC are compared in step S2. Here, the predetermined value SLC is a value that causes a problem such as damage to the fuel cell 1 if the operation is continued at a higher conductivity. Of course, it is not necessary to define the marginal value at which a problem occurs as the predetermined value SLC, and it may be defined as a value having a sufficient margin including the influence of manufacturing variations.
[0021]
If the conductivity C of the humidifying water is less than the predetermined value SLC as a result of the comparison in step S2, it is determined that the fuel cell 1 can be operated as it is, and the conductivity deterioration flag FC is set to “0” in step S3. Declare that the rate has not deteriorated and end this flow. If the conductivity C of the humidifying water is greater than or equal to the predetermined value SLC, the conductivity deterioration flag FC is set to “1” in step S4, and the fact that the conductivity has deteriorated declares that it should not be operated as it is. Exit.
[0022]
FIG. 4 is a flowchart showing the content of the humidifying water conductivity reduction operation process performed by the control unit 21, and corresponds to the process in block B2 of FIG.
[0023]
According to this, first, in step S11, it is determined whether the flag FC set in the humidification water conductivity determination process is “1”, that is, whether the conductivity of the humidification water shows an abnormal value. If it is not abnormal, this flow is terminated without doing anything, but if it is abnormal (FC = 1), the processing of steps S12 and S13 is performed in order to quickly reduce the conductivity of the humidifying water.
[0024]
In step S <b> 12, the three-way valve 7 is switched so that substantially all of the humidifying water flowing out from the water pump 4 passes through the ion exchange resin 8. Next, in step S13, the flow rate of the humidifying water fed by the water pump 4 is increased, preferably the highest flow rate. By performing the above control, the conductivity of the humidifying water in the buffer tank 5 is rapidly reduced.
[0025]
FIG. 5 is a flowchart showing the content of the non-humidifying operation permission process performed by the control unit 21, and corresponds to the process in block B3 of FIG.
[0026]
In step S21, it is determined whether the flag FC set in the humidifying water conductivity determination process is 1, that is, whether the humidifying water conductivity shows an abnormal value. If not abnormal, the non-humidified operation is not permitted (FUH = O) and the operation of the fuel cell 1 is permitted in step S28, the normal operation state is kept, and this flow is terminated.
[0027]
If abnormal, the temperature TSTK of the fuel cell 1 is read from the temperature sensor 2, the intake air temperature TAIR is read from the air temperature sensor 22, and the intake air humidity HAIR is read from the air humidity sensor 23 in step S22. In step S23, the non-humidifying operation possible determination temperature TSLUH is set by referring to the map M1 according to the read intake air temperature TAIR and humidity HAIR. The non-humidified operation possible determination temperature TSLUH is set to a higher temperature as the intake air temperature TAIR becomes higher and as the humidity HAIR becomes higher. The higher the humidity of the intake air, the more moisture in the intake air. The higher the temperature of the intake air, the more moisture can be contained in the intake air. Therefore, the higher the humidity and temperature of the intake air, the higher the fuel cell. This is because the temperature at which 1 can be operated without humidification also increases.
[0028]
The non-humidifying operation possible determination temperature TSLUH is a temperature that means that the non-humidifying operation is impossible if the temperature of the fuel cell 1 exceeds this temperature. That is, if the temperature of the fuel cell 1 is equal to or higher than the determination temperature TSLUH that can be operated without humidification, the moisture is reduced by the balance between the moisture flowing in by the intake air, the water generated inside the fuel cell 1 and the moisture discharged by the off-gas. This means that the environment is such that the battery 1 cannot be operated.
[0029]
Accordingly, if the temperature TSTK of the fuel cell 1 is equal to or lower than the determination temperature TSLUH that allows the non-humidifying operation in step S24, the non-humidifying operation is permitted (FUH = 1) and the operation of the fuel cell 1 is permitted in step S27, and this flow is finished. . If the temperature TSTK of the fuel cell 1 exceeds the non-humidifying operation enable determination temperature TSLUH in step S24, the non-humidifying operation is not permitted (FUH = O) and the operation of the fuel cell 1 is also prohibited in step S25. However, when the temperature of the fuel cell 1 can be lowered to the non-humidified operation determination temperature TSLUH or less by the fuel cell cooling capacity of the temperature adjustment means (radiator 12) of the fuel cell 1 in the subsequent step S26, it will be described below. Control (operation environment adjustment processing) for lowering the temperature of the fuel cell 1 is performed.
[0030]
FIG. 6 is a flowchart showing the contents of the operating environment adjustment process performed by the control unit 21, and corresponds to the process in block B4 of FIG.
[0031]
According to this, first, in step S31, the temperature TAIR of the intake air is read from the air temperature sensor 22 and the humidity HAIR of the intake air is read from the air humidity sensor 23. Based on the read intake air temperature TAIR and humidity HAIR, the fuel cell 1 Whether the temperature of the fuel cell 1 can be lowered to a temperature at which the non-humidifying operation can be performed by cooling the fuel cell 1 with this temperature control means is determined by referring to the map M2 in step S32.
[0032]
A high intake air humidity means that there is a lot of moisture in the intake air, and therefore, a non-humidified operation is easy to realize. Accordingly, when the intake air humidity HAIR is higher, the non-humidified operation possible region (FCONT = 1) becomes wider. On the other hand, when the intake air temperature TAIR is high, the amount of water that can be contained in the intake air increases, but the temperature difference between the temperature of the LLC and the air becomes small and it becomes difficult to cool the fuel cell 1, so no humidification is performed. The operable range is narrowed. The non-humidified operation region changes depending on these balances. From the above, it is desirable that the non-humidifying operation possible region in the map M2 in step S32 is determined by experiment including manufacturing variations of parts.
[0033]
Next, in step S33, it is determined whether the non-humidified operation is possible by cooling the fuel cell 1 (FCONT = 1) or impossible (FCONT = 0). If so, in step S34, the three-way valve 11 is switched to the radiator 12 side to control the LLC to be cooled by the radiator 12, and the flow rate of the LLC is increased so as not to create a high temperature portion in the fuel cell 1. Then, the fuel cell 1 is cooled to a temperature at which the humidification operation can be performed.
[0034]
FIG. 7 is a flowchart showing the content of the non-humidifying operation process performed by the control unit 21, and corresponds to the process in block B5 of FIG.
[0035]
According to this, it is determined whether or not non-humidified operation is permitted in step S41 (FUH = 1), and if not permitted, the flow is terminated as it is, but if permitted, the output of the fuel cell is predetermined in step S42. Limit to the value PUH. This is because when the fuel cell 1 is operated at a high load, the temperature of the fuel cell 1 rises, and it becomes difficult to perform the humidification operation.
[0036]
Next, in step S43, the temperature TSTK of the fuel cell 1 is read from the temperature sensor 2, the intake air temperature TAIR is read from the air temperature sensor 22, and the intake air humidity HAIR is read from the air humidity sensor 23. In step S44, the unhumidified operation upper limit temperature is read. The TUH is set by referring to the map M3 based on the air temperature TAIR and the air humidity HAIR read in. This non-humidifying operation upper limit temperature TUH is a value sufficiently lower than the non-humidifying operation enabling determination temperature TSLUH referred to in step S23 of the non-humidifying operation permission process. That is, if the fuel cell 1 is controlled to this temperature, the non-humidifying operation possible determination temperature TSLUH is not exceeded, the non-humidifying operation is not permitted, and the operation can be performed at the highest possible temperature, so that the deterioration in efficiency is small. Become.
[0037]
Therefore, in step S45, it is determined whether the temperature TSTK of the fuel cell 1 exceeds the non-humidifying operation upper limit temperature TUH. If it exceeds, the three-way valve 11 is switched to the radiator 12 side to cool the fuel cell 1, and LLC The flow rate is increased to control the fuel cell 1 so as not to form a high temperature portion, and if it does not exceed, the three-way valve 11 is switched to the bypass side that does not pass through the radiator 12 until the fuel cell reaches a temperature at which operation can be performed as efficiently as possible. Warm 1
[0038]
By performing the above processing, the fuel cell can be operated in a non-humidified manner even when the conductivity of the humidifying water is deteriorated and the fuel cell cannot be humidified even during operation or startup after long-term storage. Operation can be continued while maintaining the state. Since the conductivity of the humidifying water can be sufficiently lowered while the operation is continued, the normal operation state can be shifted without interrupting the operation.
[0039]
As described above, in this embodiment, in the fuel cell system, the humidification means for humidifying at least one of the fuel gas and air supplied to the fuel cell, and the conductivity decrease for decreasing the conductivity of the water for humidification. A means for detecting the conductivity of the humidifying water, and when the detected conductivity of the humidifying water is higher than a predetermined value, prohibiting humidification by the humidifying means and causing the fuel cell to operate without humidification, The control means for increasing the conductivity lowering ability of the conductivity lowering means is provided, so that the fuel cell is operated without humidification when the conductivity of the humidifying water is high, and the conductivity of the humidifying water is compared during that time. The fuel cell can be started early without waiting for a decrease in the conductivity even when the conductivity of the water for humidification is high after long-term storage.
[0040]
Further, the conductivity lowering means is used as a means for lowering the conductivity of the humidifying water through the ion exchange resin, and the control means is used to increase the flow rate of the humidifying water passed through the ion exchange resin. By increasing the conductivity lowering ability of the lowering means, the present invention can be realized with a simple configuration, and cost reduction, mountability on a vehicle, and layout can be improved.
[0041]
Further, since the fuel cell can be operated without humidification when the temperature of the fuel cell is low, the fuel cell is further provided with a means for detecting the temperature of the fuel cell, and the control means can be operated without the humidification of the detected temperature of the fuel cell. If it is determined that non-humidified operation is possible when the temperature is lower than the judgment temperature and the non-humidified operation is performed, it is possible to determine whether or not non-humidified operation is possible with high accuracy, and humidification is not performed in situations where humidification is required. Can be avoided.
[0042]
In addition, the higher the humidity of the intake air, the more moisture in the intake air, and the higher the temperature of the intake air, the more moisture can be contained in the intake air. Therefore, the higher the humidity and temperature of the intake air, the higher the fuel cell. However, the temperature that can be operated without humidification also increases. In this embodiment, it further comprises means for detecting the humidity or temperature of the air supplied to the fuel cell, and the control means sets the non-humidified operation determination temperature based on the detected humidity or temperature of the supplied air, specifically, Since the higher the humidity or temperature of the detected supply air, the higher the determination temperature for non-humidifying operation is set, it can be determined with higher accuracy whether or not the non-humidifying operation is possible.
[0043]
The temperature control means further controls the temperature of the fuel cell, and the control means has a detected conductivity of the humidifying water higher than a predetermined value, and the detected temperature of the fuel cell is a non-humidified operation determination temperature. When the temperature is higher, it is determined whether the temperature of the fuel cell can be lowered below the determination temperature at which the non-humidifying operation is possible by the temperature adjustment means. Reduce the temperature of the fuel cell. As a result, even when the temperature of the fuel cell is high and non-humidified operation is impossible, when the temperature of the fuel cell can be lowered to a temperature at which non-humidified operation can be performed, the fuel cell is cooled by the temperature control means. As a result, it is possible to ensure as much as possible the opportunity for the fuel cell to perform a non-humidifying operation.
[0044]
In addition, when the fuel cell performs a non-humidifying operation, the control means is configured to lower the upper limit of the operating load of the fuel cell, so that the temperature rise due to the fuel cell operating at a high load is suppressed, and the temperature of the fuel cell It is possible to prevent the non-humidifying operation from becoming impossible due to the rise.
[0045]
In the configuration of the above embodiment, since the LLC is not extracted, there is a possibility that the gas cannot be supplied to the fuel cell when the LLC conductivity is high. However, in such a case, only the LLC is circulated, the LLC conductivity is lowered with an ion exchange resin (not shown), and the gas supply to the fuel cell is not performed until the LLC conductivity falls below a predetermined value. And it is sufficient. In the meantime, it is thought that the structure which drive | works with the electric power from the storage battery which is not shown in figure is effective.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel cell system according to the present invention.
FIG. 2 is a control block diagram of a control unit.
FIG. 3 is a flowchart showing the content of a humidifying water conductivity determination process.
FIG. 4 is a flowchart showing the contents of a humidifying water conductivity reduction operation process.
FIG. 5 is a flowchart showing the content of a non-humidifying operation permission process.
FIG. 6 is a flowchart showing the contents of an operation environment adjustment process.
FIG. 7 is a flowchart showing the contents of a non-humidifying operation process.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Temperature sensor 4 Water pump 6 Conductivity sensor 7 Three-way valve 8 Ion exchange resin 10 LLC pump 11 Three-way valve 12 Radiator 21 Control unit 22 Air temperature sensor 23 Air humidity sensor

Claims (8)

A fuel cell;
Humidifying means for humidifying at least one of fuel gas and air supplied to the fuel cell;
A conductivity lowering means for lowering the conductivity of water for humidification;
Means for detecting the conductivity of the water for humidification;
Control for prohibiting humidification by the humidifying means when the detected conductivity of the humidifying water is higher than a predetermined value, causing the fuel cell to perform a non-humidifying operation, and increasing the conductivity reducing ability of the conductivity reducing means Means,
A fuel cell system comprising: The conductivity lowering means is a means for lowering the conductivity of the water for humidification by allowing it to flow through an ion exchange resin.
2. The fuel cell system according to claim 1, wherein the control unit increases a conductivity decreasing capability of the conductivity decreasing unit by increasing a flow rate of the humidifying water flowing through the ion exchange resin. 3. Means for detecting the temperature of the fuel cell;
The control means determines that the non-humidifying operation is possible when the detected temperature of the fuel cell is lower than a predetermined non-humidifying operation determination temperature, and causes the fuel cell to perform a non-humidifying operation. 2. The fuel cell system according to 1. Means for detecting the humidity of the air supplied to the fuel cell;
The fuel cell system according to claim 3, wherein the control means sets the non-humidified operation determination temperature based on the detected humidity of the supplied air. 5. The fuel cell system according to claim 4, wherein the control unit sets the non-humidified operation determination temperature higher as the detected humidity of the supplied air is higher. Means for detecting the temperature of air supplied to the fuel cell;
The fuel cell system according to claim 3, wherein the control unit sets the non-humidified operation possible determination temperature based on the detected temperature of the supply air.   Further comprising temperature control means for controlling the temperature of the fuel cell;
  When the detected electric conductivity of the humidifying water is higher than a predetermined value and the detected temperature of the fuel cell is higher than the determination temperature for enabling the non-humidifying operation, the temperature adjusting means It is determined whether the temperature can be lowered below the non-humidified operation determination temperature, and when it is determined that the temperature can be decreased below the non-humidified operation determination temperature, the temperature of the fuel cell is decreased by the temperature adjusting means. The fuel cell system according to claim 3.   2. The fuel cell system according to claim 1, wherein when the fuel cell performs a non-humidifying operation, the control unit reduces an upper limit of an operation load of the fuel cell.

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