JP2007179749A - Control method of fuel cell and its control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of a catalyst during operation of a fuel cell. <P>SOLUTION: This control method of a fuel cell using a catalyst metal as an electrode catalyst includes: a step S1 for detecting load fluctuation of the fuel cell; a step S2 for detecting a cell voltage between an anode and a cathode of the fuel cell when the load fluctuation is detected; and steps S4-S6 for regulating, to a predetermined value, humidity of at least either of a fuel gas supplied to the anode and an oxidizer gas supplied to the cathode when the detected cell voltage is in a predetermined voltage range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell control method and a control apparatus therefor.

  In recent years, fuel cells have attracted attention in response to social demands and trends against the background of environmental problems. In particular, a polymer electrolyte fuel cell (hereinafter referred to as “PEFC”) using an ion conductive polymer electrolyte membrane can be operated at a low temperature of 100 ° C. or lower. It is expected as a power source and is being developed for practical use. In order for the PEFC to be put into practical use as a vehicle drive source or a stationary power source, it is necessary to have durability over a long period of time.

  The PEFC generally has a structure in which a membrane-electrode assembly (hereinafter referred to as “MEA”) is sandwiched between separators. The MEA generally has a structure in which a gas diffusion layer, a cathode catalyst layer, a solid polymer electrolyte membrane, and an anode catalyst layer are sequentially laminated. The cell reaction proceeds at least in a catalyst layer comprising a catalyst, a carrier supporting the catalyst, and an ion conductive polymer. For this reason, suppressing deterioration of the catalyst layer is an important issue in enhancing the durability of PEFC.

As a conventional technique for suppressing catalyst deterioration, as described in Patent Document 1 below, when the fuel cell is stopped, the fuel cell that limits the time during which the operating voltage is 0.9 V or more to 10 minutes or less. A system has been proposed.
JP 2004-172106 A

  According to this technique, it is possible to suppress the deterioration of the catalyst when the PEFC is stopped, but it is not possible to suppress the deterioration of the catalyst during the operation of the PEFC.

  During the operation of the PEFC, a phenomenon (hereinafter referred to as “load cycle”) in which the output voltage of the PEFC fluctuates periodically or aperiodically occurs in accordance with fluctuations in the power supplied to the load by the PFEC. Since the generation of the duty cycle is accompanied by a large potential change of the cathode electrode, the oxidation and reduction reactions of the catalyst constituting the catalyst layer are frequently repeated.

  If the catalyst (for example, platinum) is kept at a constant potential even at a high potential, the catalyst surface is stable, and the elution of the catalyst to the solid polymer electrolyte membrane is slight. However, when a duty cycle involving oxidation / reduction of the catalyst occurs, the potential of the catalyst fluctuates greatly, so that the elution of the catalyst becomes significant, and the corrosion of the carrier carbon and the solid polymer electrolyte membrane of the catalyst Elution is likely to occur, the catalyst is deteriorated, and the power generation performance of PEFC is lowered and the durability of PEFC is lowered.

  The present invention has been made in order to be able to suppress deterioration of a catalyst during operation of a PEFC, which has not been paid attention to in the past, and detects a cell voltage during operation to detect a fuel gas or an oxidant. It is an object of the present invention to provide a fuel cell control method and a control device for the fuel cell which can adjust the humidity of gas and the temperature of the fuel cell.

  In order to achieve the above object, a control method for a fuel cell according to the present invention is a control method for a fuel cell in which a catalyst metal is used as an electrode catalyst. Detecting a cell voltage between the anode and cathode of the fuel cell when a change is detected, and supplying the fuel gas supplied to the anode or the cathode when the detected cell voltage is within a predetermined voltage range Adjusting the humidity of at least one of the oxidizing gas to a predetermined humidity.

  Further, another fuel cell control method according to the present invention for achieving the above object is a fuel cell control method using a catalytic metal as an electrode catalyst, and detects a load fluctuation of the fuel cell. Detecting a cell voltage between the anode and cathode of the fuel cell when a load change is detected, and setting the temperature of the fuel cell to a predetermined temperature when the detected cell voltage is in a predetermined voltage range. Adjusting to the above.

  In order to achieve the above object, a fuel cell control device according to the present invention is a fuel cell control device in which a catalytic metal is used as an electrode catalyst, and detects a load fluctuation of the fuel cell. Detection means; cell voltage detection means for detecting a cell voltage between the anode and cathode of the fuel cell; and at least one of a fuel gas supplied to the anode and an oxidant gas supplied to the cathode. Humidity detection means for detecting humidity, and when the detected cell voltage is in a predetermined voltage range, based on the humidity of the gas detected by the humidity detection means, the fuel gas supplied to the anode or the oxidation supplied to the cathode And humidity adjusting means for adjusting the humidity of at least one of the agent gases to a predetermined humidity.

  In order to achieve the above object, another fuel cell control device according to the present invention is a fuel cell control device using a catalytic metal as an electrode catalyst, and detects a load fluctuation of the fuel cell. A load fluctuation detecting means; a cell voltage detecting means for detecting a cell voltage between the anode and cathode of the fuel cell; a temperature detecting means for detecting the temperature of the fuel cell; and the detected cell voltage is within a predetermined voltage range. The temperature adjusting means adjusts the temperature of the fuel cell to a predetermined temperature based on the temperature of the fuel cell detected by the temperature detecting means.

  According to the control method of the fuel cell according to the present invention configured as described above, it is possible to suppress deterioration of the catalyst accompanying the duty cycle even during operation of the fuel cell, so that the initial power generation performance of the fuel cell is prolonged. It can be maintained over a period of time, and the durability of the fuel cell can be improved.

  Further, according to the fuel cell control device according to the present invention configured as described above, it is possible to suppress deterioration of the catalyst accompanying the duty cycle even during operation of the fuel cell, so that the initial power generation performance of the fuel cell Can be maintained over a long period of time, and the durability of the fuel cell can be improved.

Hereinafter, a control method and a control device for a fuel cell according to the present invention will be described in detail with reference to the drawings, divided into first to sixth embodiments.

Before describing these embodiments, the overall configuration of the fuel cell stack will be briefly described in order to facilitate understanding of the present invention. FIG. 1 is a perspective view showing the overall configuration of the fuel cell stack, and FIG. 2 is an enlarged cross-sectional view of the main part showing the cell structure of the fuel cell stack.

  As shown in FIG. 1, the fuel cell stack 1 includes a predetermined number of cells 2 as unit cells that generate an electromotive force due to a reaction between a fuel gas (in this specification, hydrogen) and an oxidant gas (in this specification, oxygen). A laminated body 3 is formed, and a current collector plate 4, an insulating plate 5, and an end plate 6 are arranged at both ends of the laminated body 3, and through holes (not shown) penetrating through the laminated body 3 are provided. The tie rod 7 is penetrated, and a nut (not shown) is screwed onto the end of the tie rod 7.

  In this fuel cell stack 1, fuel gas, oxidant gas, and liquid medium (specifically, cooling water or hot water) are circulated through flow channel grooves formed in separators (not shown) of each cell 2. A fuel gas supply port 8, a fuel gas discharge port 9, an oxidant gas supply port 10, an oxidant gas discharge port 11, a medium supply port 12 and a medium discharge port 13 are formed in one end plate 6.

  The fuel gas is supplied from the fuel gas supply port 8, flows through the fuel gas supply channel groove formed in the separator, and is discharged from the fuel gas discharge port 9. The oxidant gas is supplied from the oxidant gas supply port 10, flows through the oxidant gas supply channel groove formed in the separator, and is discharged from the oxidant gas discharge port 11. The liquid medium is supplied from the medium supply port 12, flows through a medium supply channel groove formed in the separator, and is discharged from the medium discharge port 13.

  As shown in FIG. 2, the cell 2 is composed of a membrane electrode assembly (hereinafter also referred to as MEA (membrane electrode assembly)) 14 and separators 15 disposed on both surfaces of the MEA 14. Hereinafter, the separator 15 disposed on the anode side of the MEA 14 is referred to as an anode separator 15A, and the separator 15 disposed on the cathode side is referred to as a cathode separator 15B.

  The MEA 14 includes, for example, a solid polymer electrolyte membrane 141 that is a polymer electrolyte membrane that allows hydrogen ions to pass through, an anode electrode 144A that is an anode composed of an anode catalyst layer 142A and a gas diffusion layer 143A, and a cathode that is a catalyst metal that is an electrode catalyst. It consists of a cathode electrode 144B as a cathode comprising a catalyst layer 142B and a gas diffusion layer 143B. The MEA 14 has a laminated structure in which a solid polymer electrolyte membrane 141 is sandwiched from both sides by an anode electrode 144A and a cathode electrode 144B.

  The separator 15 is formed by forming a thin conductive metal plate into a predetermined shape using a mold. As shown in the figure, the separator 15 has an uneven shape (so-called corrugated shape) in which convex portions 16 and concave portions 17 are alternately formed in an active region that contributes to power generation (region of the central portion in contact with the MEA 14). is doing.

The convex portion 16A and the concave portion 17A of the anode separator 15A disposed in contact with the anode electrode 144A side of the MEA 14 serve as a flow channel for flowing fuel gas (hydrogen; H ₂ ) between the MEA 14 and a fuel gas flow channel (anode ) 18) is formed. On the other hand, the convex portion 16B and the concave portion 17B of the cathode separator 15B disposed in contact with the cathode electrode 144B side of the MEA 14 serve as a channel groove for flowing an oxidant gas (oxygen; O ₂ ) between the MEA 14 and the oxidant gas. A flow path (cathode flow path) 19 is formed. When hydrogen is passed through the fuel gas flow path 18 and oxygen is passed through the oxidant gas flow path 19, the hydrogen is converted into hydrogen ions by the catalytic action of the anode catalyst layer 142A and discharges electrons. The hydrogen ions that have released the electrons pass through the solid polymer electrolyte membrane 141. In the cathode catalyst layer 142B, hydrogen that has passed through the solid polymer electrolyte membrane 141 and electrons that have passed through an external circuit (not shown) react with oxygen to generate water. By this action, the anode electrode 144A becomes negative and the cathode electrode 144B becomes positive, and a DC voltage is generated between the anode electrode 144A and the cathode electrode 144B as shown in FIG.

  In this specification, a voltage appearing between the anode electrode 144A and the cathode electrode 144B is referred to as a cell voltage, and the cell voltage is detected by the cell voltmeter 20 functioning as a cell voltage detection means. The cell voltage may be detected from all cells constituting the fuel cell stack 1 or may be detected only from a plurality of representative cells among the cells constituting the fuel cell stack 1. Also good.

  Further, in this specification, the resistance between the anode electrode 144A and the cathode electrode 144B is referred to as a cell resistance value, and the cell resistance value is detected by the cell resistance value detecting means. The cell resistance value detection means is an AC interelectrode resistance meter that does not affect the electrochemical reaction of the fuel cell, and the measurement frequency is an optimum frequency, for example, 1 [kHz].

  In the present invention, in order to suppress the dissolution of platinum associated with the load variation cycle of the fuel cell, the humidity of the fuel gas or the oxidant gas is adjusted or the temperature of the fuel cell is adjusted during the load variation in which the cell voltage exhibits a predetermined range. By adjusting it, it is possible to suppress elution of platinum from the electrode catalyst layer (particularly, the cathode catalyst layer 142B of the cathode electrode 144B) when the load fluctuates.

  In the following embodiment in which platinum elution is suppressed from the electrode catalyst layer by adjusting the humidity of the gas, platinum elution from the electrode catalyst layer is suppressed by adjusting the humidity of oxygen as the oxidant gas. However, the present invention is not limited to this embodiment, and platinum elution may be suppressed by adjusting the humidity of hydrogen, which is a fuel gas. Platinum elution may be suppressed by adjusting the humidity of both gases.

Hereinafter, the fuel cell control method and the control device according to the present invention will be described in detail by dividing the first embodiment to the sixth embodiment.
[First Embodiment]
FIGS. 3 and 4 are diagrams for explaining the control method and the control device of the fuel cell according to the first embodiment of the present invention.

  FIG. 3 is a block diagram schematically illustrating the configuration of the fuel cell system and its control system according to the present embodiment. FIG. 4 is a flowchart illustrating the operation of the control unit illustrated in FIG. 3, which is a control method for the fuel cell according to the present embodiment. It is also equivalent to this procedure.

  As shown in FIG. 3, the fuel cell system according to the present embodiment includes a fuel cell stack 1 that generates power by supplying fuel gas (hydrogen) and an oxidant gas (oxygen), and all the cells constituting the fuel cell stack 1. A cell voltmeter 20 that detects a cell voltage, an ammeter 21 that detects a current supplied from the fuel cell stack 1 to a vehicle load such as a drive motor, a humidity adjuster 22 that adjusts the humidity of oxygen that is an oxidant gas, an oxygen The cell voltage is measured by the cell voltmeter 20 when the current detected by the humidity sensor 23 for detecting the relative humidity of the gas, the flow rate adjuster 24 for adjusting the flow rate of hydrogen as the fuel gas, and the ammeter 21 (load fluctuation) is increased. The relative humidity of oxygen is adjusted to the predetermined humidity while referring to the humidity detected by the humidity sensor 23 so that the cell voltage can be maintained within a predetermined voltage range (for example, 0.6 to 0.9 V). The control part 25 which adjusts is provided.

  The fuel cell stack 1 uses a catalytic metal as an electrode catalyst. Specifically, platinum is used for the cathode catalyst layer 142B (see FIG. 2) of the cathode electrode 144B.

  The cell voltmeter 20 functions as a cell voltage detection unit that detects cell voltages between the anode electrode 144A and the cathode electrode 144B of all the cells constituting the fuel cell stack 1.

  The ammeter 21 detects the amount of current supplied from the fuel cell stack 1 to a device mounted on the vehicle such as a drive motor, and detects load fluctuation from the increase / decrease state of the current amount. Functions as a means. Note that the load fluctuation in this embodiment includes not only the fluctuation of the fuel cell load while the vehicle is running, but also the load fluctuation from the start of the fuel cell to the operating state, from the operating state of the fuel cell to the stop. Load fluctuations are also included.

  The humidity adjuster 22 includes a humidifier (not shown) and functions as a humidity adjusting means for adjusting the relative humidity of oxygen. The humidity adjuster 22 has a passage that bypasses the humidifier, and oxygen is supplied to the fuel cell stack 1 through the bypass passage when there is no need to adjust the relative humidity of oxygen. Yes.

  The humidity sensor 23 is attached in an oxygen supply path connected to the cathode of the fuel cell stack 1 and constitutes a humidity detection means. The humidity of oxygen is adjusted based on the detection signal from the humidity sensor 23.

  The flow rate regulator 24 has a function of supplying hydrogen to the anode of the fuel cell stack 1, and has a function of measuring the supply amount of hydrogen at the same time.

  The control unit 25 constitutes humidity adjusting means together with the humidity adjuster 22, and when the voltage detected by the cell voltmeter 20 is within a predetermined voltage range (for example, 0.6 to 0.9V), the humidifier It has a function of adjusting the humidity of oxygen supplied to the fuel cell stack 1 to a predetermined humidity by controlling the amount of humidification of oxygen by or bypassing oxygen through a bypass passage.

  In FIG. 3, hydrogen supplied to the fuel cell stack 1 is filled in a gas cylinder 26 at a high pressure, and the supply amount thereof is adjusted by a flow rate regulator 24. The hydrogen that has passed through the fuel cell stack 1 is forcibly returned to the system by the compressor 27. Oxygen supplied to the fuel cell stack 1 is pumped by the compressor 28. Oxygen that has passed through the fuel cell stack 1 is directly discharged to the atmosphere.

  In the present embodiment, the humidity adjustment is performed only when the cell voltage is 0.6 to 0.9 volts for the following reason.

During operation of the fuel cell with a load fluctuation cycle, the potential of the cathode electrode 144B changes greatly. According to the researches of the inventors, when the cell voltage is in the range of 0.6 to 0.9 volts, platinum oxidation reaction and platinum oxide reduction reaction occur, which is the driving force for platinum dissolution / elution. There was found. If the humidity of the oxygen is adjusted so that the platinum oxidation current and the platinum oxide reduction current with a cell voltage of 0.6 to 0.9 volts are less likely to flow when the load fluctuates, platinum dissolution / elution is unlikely to occur. This is because the durability of the fuel cell is improved.

The procedure of the fuel cell control method of this embodiment will be described in detail with reference to FIG. First, the control unit 25 inputs the current value detected by the ammeter 21, recognizes the load fluctuation of the fuel cell from the change (increase / decrease state), and detects the load shift (S1). When the load shift is detected, the control unit 25 detects the current cell voltage with the cell voltmeter 20. The detection of the cell voltage may be performed for all the cells constituting the fuel cell stack 1 or may be performed for one or several representative cells (S2). The control unit 25 determines whether or not the detected cell voltage is within a predetermined voltage range, that is, whether or not the detected cell voltage is within a range of 0.6 volts to 0.9 volts (S3). If the cell voltage is not within the predetermined voltage range (S3: NO), it is not necessary to reduce the humidification of oxygen, and the process is terminated as it is.

  On the other hand, if the cell voltage is within the predetermined voltage range (S3: YES), the next process is performed following the step of S2.

  The control unit 25 detects the humidification amount of oxygen at the present time based on the detection signal output from the humidity sensor 23, that is, detects the relative humidity of oxygen (S4). The controller 25 controls the humidifier while feeding back the detected relative humidity, that is, controls the amount of humidification by the humidifier, and sets the humidity of oxygen to a predetermined humidity. In this case, the oxygen is in a low humidified state so that the humidity of the oxygen after adjusting the humidity is lower than the humidity of the oxygen before adjusting the humidity. More specifically, the humidity range is defined as follows when the humidity of oxygen before adjusting the humidity is X% and the humidity of oxygen after adjusting the humidity (first humidity) is Y%. The humidity is controlled to be within the range of 1 <X / Y <20. The oxygen humidity is controlled within this range because when the X / Y value is smaller than 1, the platinum oxidation current and platinum oxide reduction current of the electrode catalyst increase, so that platinum dissolves and elutes from the electrode catalyst. In addition, when the value of X / Y is larger than 20, the electrode catalyst layer becomes low in water content, so that the solid polymer electrolyte polymer (ionomer) or the electrolyte membrane in the electrode catalyst layer is It is because it becomes a dry state and favorable battery performance cannot be obtained (S5).

  The control unit 25 determines whether the humidification amount of oxygen is a predetermined value, that is, whether the relative humidity of oxygen has reached a predetermined humidity (S6). If the relative humidity of oxygen is not the predetermined humidity (S6: NO), Steps S4 and S5 are repeated until the humidity of oxygen reaches a predetermined humidity. On the other hand, when the relative humidity of oxygen reaches a predetermined humidity (S6: YES), the oxygen whose humidity has been adjusted is supplied to the fuel cell stack 1 (S7), and a current necessary for the load is supplied to continue the load shift. (S8).

  As described above, when the cell voltage is in the range of 0.6 volts to 0.9 volts at the time of load transition, the platinum oxidation reaction is performed by performing the process of reducing the humidity of oxygen supplied to the fuel cell stack 1. Thus, the degree of the platinum oxide reduction reaction can be suppressed, and platinum can be prevented from dissolving or eluting from the electrode catalyst.

In the above embodiment, the case where only the humidity of oxygen that is the oxidant gas is adjusted is illustrated, but the humidity of hydrogen that is the fuel gas or the humidity of both oxygen and hydrogen may be adjusted. good.
[Second Embodiment]
FIG. 5 is an operation flowchart showing a fuel cell control method according to the second embodiment of the present invention. Note that the control system of this embodiment and the configuration of the control system are the same as those shown in FIG. This operation flowchart shows a procedure processed by the control unit 25 shown in FIG.

  In the present embodiment, a process of increasing the humidity of oxygen once lowered along with the load shift is performed again after the load shift.

  The procedure of the fuel cell control method of this embodiment will be described in detail with reference to FIG. In this operation flowchart, the processing of steps S11 to S18 is exactly the same as the processing of the first embodiment, and the description thereof is omitted. However, in the process of steps S11 to S18, only the point in which the humidity of oxygen is adjusted to Y% (first humidity) in the process of S14 to S16 (first humidity adjustment stage) is the same as that of the first embodiment. It differs from the embodiment.

  After the load shift (S18) is performed, the control unit 25 inputs the current value detected by the ammeter 21, and detects the cancellation of the load fluctuation on the condition that the detected current value does not fluctuate. When the load change is detected and the shift to the load is completed (S19), the control unit 25 detects the humidification amount of oxygen at the present time based on the detection signal output from the humidity sensor 23, that is, detects the relative humidity of oxygen. (S20).

  The controller 25 controls the humidifier while feeding back the detected relative humidity, that is, controls the humidification amount by the humidifier, and sets the humidity of oxygen to Z% of the predetermined humidity. In this case, the oxygen is humidified so that the humidity Z% of the oxygen after adjusting the humidity is higher than the humidity Y% of the oxygen before adjusting the humidity. More specifically, the humidity range is such that the humidity of oxygen before adjusting the humidity (first humidity) is Y%, and the humidity of oxygen after adjusting the humidity (second humidity) is Z%. In this case, control is performed so that the relationship between the first humidity and the second humidity satisfies the relationship of 0.1 <Y / Z <1.

  In this way, once the oxygen humidity once lowered is increased again, the solid polymer electrolyte polymer (ionomer) or electrolyte in the electrode catalyst layer remains in a state of low water content after the end of load transfer. This is because the film continues to be in a dry state, and good battery performance cannot be obtained. In addition, controlling the humidity of oxygen in such a range requires a large humidifier, although the low moisture content of the electrode catalyst layer is eliminated when the value of Y / Z is less than 0.1. Therefore, there is a possibility that the fuel cell becomes unsuitable for a vehicle having a limited mounting space, and when the value of Y / Z is larger than 1, the electrode catalyst layer is in a low water content state. This is because the solid polymer electrolyte polymer (ionomer) or the electrolyte membrane in the catalyst layer is in a dry state and good battery performance cannot be obtained (S21).

  The control unit 25 determines whether the humidification amount of oxygen is a predetermined value, that is, whether the relative humidity of oxygen is Z% of the predetermined humidity (S22), and if the relative humidity of oxygen is not the predetermined humidity (S22: NO), the steps of S20 and S21 are repeated until the humidity of oxygen reaches a predetermined humidity. On the other hand, when the relative humidity of oxygen reaches a predetermined humidity (S22: YES), the oxygen whose humidity has been adjusted is supplied to the fuel cell stack 1 (S23).

  As described above, in the present embodiment, in the first humidity adjustment stage, which is the process from S14 to S16, the first humidity that is the humidity of oxygen after adjusting the humidity is higher than the humidity of oxygen before adjusting the humidity. The oxygen humidity is adjusted so that (Y%) is lower, and in the second humidity adjustment stage, which is the process from S20 to S22, the second humidity (Z%) is more than the first humidity (Y%). %) Is adjusted so that the humidity of oxygen is higher.

  By performing such treatment, the degree of platinum oxidation reaction and platinum oxide reduction reaction can be suppressed, and it is possible to prevent platinum from being dissolved or eluted from the electrode catalyst. It becomes possible to avoid a decrease in battery performance due to the solid polymer electrolyte polymer (ionomer) or the electrolyte membrane in the layer being kept dry.

In the above embodiment, the case where only the humidity of oxygen that is the oxidant gas is adjusted is illustrated, but the humidity of hydrogen that is the fuel gas or the humidity of both oxygen and hydrogen may be adjusted. good.
[Third Embodiment]
FIG. 6 is a schematic block diagram of a fuel cell control system and its control system according to the third embodiment of the present invention. In this figure, the only difference from the system shown in FIG. 3 is that a battery (secondary battery) 30 is connected in parallel with the fuel cell stack 1.

  The battery 30 compensates for insufficient power generation of the fuel cell stack 1 when the process of adjusting the humidity of oxygen to a predetermined humidity as described in the first and second embodiments is performed. is there. The amount of power generated by the fuel cell stack 1 varies greatly depending on the temperature and the like, not only when the humidity is adjusted, but if the battery 30 is connected in parallel to the fuel cell stack 1, Even if the amount of power generation is insufficient with respect to the required load, stable power supply to the load is possible.

Further, when the battery 30 is present, it is possible to prevent the fuel cell stack 1 from being overloaded, so that it is possible to prevent the electrode catalyst layer and the separator 15 constituting the cell 2 from being deteriorated.
[Fourth Embodiment]
FIGS. 7 and 8 are diagrams for explaining a control method and a control device for a fuel cell according to a fourth embodiment of the present invention.

  FIG. 7 is a schematic block diagram of the fuel cell system and its control system according to the present embodiment, and FIG. 8 is an operation flowchart of the control unit shown in FIG. 7. This flowchart is a control method for the fuel cell of the present embodiment. It is also equivalent to this procedure.

  In the present embodiment, a process of selecting whether to continue the load shift or stop the humidification control depending on the cell resistance value is added to the process described in the first embodiment.

  In the fuel cell control system shown in FIG. 6 and the schematic configuration block diagram of the control system, a cell resistor 32 for detecting the resistance value of the cell 2 is added to the system shown in FIG. The cell resistor 32 functions as cell resistance value detection means. The value of the cell resistance may be detected from all the cells constituting the fuel cell stack 1 or may be detected only from a plurality of representative cells among the cells constituting the fuel cell stack 1. Anyway.

  The procedure of the fuel cell control method of this embodiment will be described in detail with reference to FIG. In this operation flowchart, the processing of steps S31 to S38 is exactly the same as the processing of the first embodiment, and the description thereof is omitted.

  After the load shift (S38) is performed, the control unit 25 detects the value of the cell resistance detected by the cell resistor 32, and determines whether or not the value of the cell resistance is a predetermined value (S39). ). If the value of the cell resistance is a predetermined value (S39: YES), the load transfer process is continued as it is, and the electric power required by the vehicle load is provided from the fuel cell stack 1 and the battery 30 (S40). On the other hand, if the value of the cell resistance is not the predetermined value, the humidification control performed in steps S34 to S36 is stopped (S41).

By performing such treatment, the degree of platinum oxidation reaction and platinum oxide reduction reaction can be suppressed, and it is possible to prevent platinum from being dissolved or eluted from the electrode catalyst. It becomes possible to avoid a decrease in battery performance due to the solid polymer electrolyte polymer (ionomer) or the electrolyte membrane in the layer being kept dry.
[Fifth Embodiment]
FIGS. 9 and 10 are diagrams for explaining a control method and a control device for a fuel cell according to a fifth embodiment of the present invention.

  FIG. 9 is a schematic block diagram of the fuel cell system and its control system according to the present embodiment. FIG. 10 is an operation flowchart of the control unit shown in FIG. 9. This flowchart is a control method for the fuel cell of the present embodiment. It is also equivalent to this procedure.

  This embodiment adjusts the temperature at the time of operation of the fuel cell, unlike preventing the platinum from eluting from the electrode catalyst by adjusting the oxygen humidity in the first to fourth embodiments. Thus, platinum is prevented from eluting from the electrode catalyst.

  Accordingly, as shown in FIG. 6 and FIG. 9, the configuration of the fuel cell system includes a temperature sensor 34 that detects the temperature of the fuel cell stack 1 instead of the humidity sensor 23, and a fuel cell. A temperature regulator 36 for regulating the temperature of the stack 1 is provided.

  The temperature sensor 34 is attached to a place where the average temperature of the fuel cell stack 1 can be detected, and functions as a temperature detection means. The temperature sensors 34 may be attached to a plurality of locations of the fuel cell stack 1 and the average temperature may be obtained from the temperatures detected from all the temperature sensors 34.

The operation of the temperature adjuster 36 is controlled by the control unit 25, and adjusts the temperature of the cooling water (see the explanation of FIG. 1) flowing through the fuel cell stack 1. The temperature regulator 36 has a configuration for heating and cooling the cooling water therein, and the temperature of the cooling water is adjusted based on a command from the control unit 25.

The procedure of the fuel cell control method of this embodiment will be described in detail with reference to FIG. First, the control unit 25 inputs the current value detected by the ammeter 21, recognizes the load fluctuation of the fuel cell from the change (increase / decrease state), and detects the load shift (S51). When the load shift is detected, the control unit 25 detects the current cell voltage with the cell voltmeter 20. The detection of the cell voltage may be performed for all the cells constituting the fuel cell stack 1, or may be performed for one or several representative cells (S52). The control unit 25 determines whether or not the detected cell voltage is within a predetermined voltage range, that is, whether or not the detected cell voltage is within a range of 0.6 volts to 0.9 volts. Also in this embodiment, the temperature adjustment is performed only when the cell voltage is 0.6 to 0.9 volts for the same reason as in the first embodiment (S53). If the cell voltage is not within the predetermined voltage range (S53: NO), it is not necessary to control the temperature of the fuel cell stack 1, and the process is terminated as it is.

  On the other hand, if the cell voltage is within the predetermined voltage range (S53: YES), the next process is performed following the step of S52.

  The control unit 25 detects the current cell temperature of the fuel cell stack 1 based on the detection signal output from the temperature sensor 34 (S54). The control unit 25 performs cell temperature control while feeding back the detected cell temperature, that is, controls the temperature of the fuel cell stack 1, and sets the temperature of the fuel cell stack 1 to a predetermined temperature. The temperature of the fuel cell stack 1 is adjusted by a temperature regulator 36 whose operation is controlled by the control unit 25. In this case, the temperature of the fuel cell stack 1 is adjusted so that the temperature of the fuel cell stack 1 after adjusting the temperature becomes higher than the temperature of the fuel cell stack 1 before adjusting the temperature.

  The reason why the temperature of the fuel cell stack 1 is increased when the cell voltage is in the predetermined voltage range is as follows. Increasing the temperature of the fuel cell stack 1 decreases the relative humidity of oxygen supplied to the fuel cell stack 1, which is equivalent to decreasing the humidity of oxygen in the first embodiment. Therefore, when the temperature of the fuel cell stack 1 is increased, the degree of platinum oxidation reaction and platinum oxide reduction reaction can be suppressed, and platinum can be prevented from dissolving or eluting from the electrode catalyst. is there. In addition, when operating at a temperature of 50 ° C. or lower, the efficiency of the system is better when priority is given to adjusting the temperature of the fuel cell stack 1 than to adjusting the humidity of oxygen at the time of load transition. It is.

  More specifically, the range for adjusting the temperature of the fuel cell stack 1 includes the temperature T1 ° C. of the fuel cell before adjusting the temperature and the first temperature T2 ° C. that is the temperature of the fuel cell after adjusting the temperature. Satisfy the relationship of 0.03 <T1 / T2 <1. The temperature of the fuel cell stack 1 is controlled within this range because the platinum oxidation current and the platinum oxide reduction current of the electrode catalyst increase when the value of T1 / T2 is greater than 1, so that platinum dissolves from the electrode catalyst. In addition, when the value of T1 / T2 is smaller than 0.03, the electrode catalyst layer becomes low in water content, so that the solid polymer electrolyte polymer (ionomer) in the electrode catalyst layer This is because the electrolyte membrane is in a dry state and good battery performance cannot be obtained (S55).

  The control unit 25 determines whether or not the cell temperature is a predetermined value, that is, whether or not the temperature of the fuel cell stack 1 has reached a predetermined temperature (S56), and if the temperature of the fuel cell stack 1 has not reached the predetermined temperature (S56: NO), steps S54 and S55 are repeated until the temperature of the fuel cell stack 1 reaches a predetermined temperature. On the other hand, when the temperature of the fuel cell stack 1 reaches a predetermined temperature (S56: YES), the current required for the load is supplied to continue the load shift (S57).

  As described above, when the cell voltage is in the range of 0.6 volts to 0.9 volts at the time of load transition, the platinum oxidation reaction and the platinum oxide reduction reaction are performed by increasing the temperature of the fuel cell stack 1. It is possible to prevent the platinum from being dissolved or eluted from the electrode catalyst.

  Also in this embodiment, since the battery (secondary battery) 30 is connected in parallel with the fuel cell stack 1 as in the third embodiment, the power generation amount of the fuel cell stack 1 is insufficient with respect to the required load. However, since stable power supply to the load is possible and the fuel cell stack 1 can be prevented from being overloaded, the electrode catalyst layer and the separator 15 constituting the cell 2 are deteriorated. Can be prevented.

In this embodiment, a cell resistance meter is provided as in the fourth embodiment, and a process for selecting whether to continue the load transition or stop the temperature control of the cell depending on the magnitude of the cell resistance value is added. Also good.
[Sixth Embodiment]
FIG. 11 is an operation flowchart showing a control method of a fuel cell according to the sixth embodiment of the present invention. The control system of this embodiment and the configuration of the control system are the same as those shown in FIG. This operation flowchart shows the procedure processed by the control unit 25 shown in FIG.

  In the present embodiment, the process of lowering the temperature of the fuel cell stack 1 once raised along with the load shift is performed again after the load shift.

  The procedure of the fuel cell control method of this embodiment will be described in detail according to FIG. In this operation flowchart, the processing of steps S61 to S67 is exactly the same as the processing of the fifth embodiment, so that the description thereof is omitted. However, in the process of steps S61 to S67, only the point that the temperature of the fuel cell stack 1 is adjusted to T2 (first temperature) in the process of S64 to S66 (first temperature adjustment stage) is different from the present embodiment. This is different from the fifth embodiment.

  After the load shift (S67) is performed, the control unit 25 inputs the current value detected by the ammeter 21 and detects the cancellation of the load fluctuation on the condition that the detected current value does not fluctuate. When the load change is detected and the shift to the load is completed (S68), the control unit 25 detects the current temperature of the fuel cell stack 1 based on the detection signal output from the temperature sensor 34, that is, detects the cell temperature. (S69).

  The control unit 25 performs cell cooling control while feeding back the detected cell temperature, that is, performs control to lower the temperature of the fuel cell stack 1 by operating the temperature regulator 36, and sets the temperature of the fuel cell stack 1 to T3 (second Temperature). That is, the cell temperature is adjusted so that the second temperature T3 ° C. is lower than the first temperature T2 ° C.

  Thus, once the temperature of the fuel cell stack 1 raised is lowered, the solid polymer electrolyte polymer (ionomer) in the electrode catalyst layer can be reduced if the electrode catalyst layer remains in a low water content state after the end of load transfer. ) Or the electrolyte membrane will continue to be in a dry state, and good battery performance will not be obtained (S70).

  The control unit 25 determines whether or not the cell temperature has reached a predetermined value, that is, T3 (S71). If the cell temperature has not reached the predetermined value (S71: NO), the steps S69 and S70 are performed with the predetermined cell temperature. Repeat until the value is reached. On the other hand, when the cell temperature reaches a predetermined value (S71: YES), the process is terminated.

  Thus, in the first temperature adjustment stage, the first temperature T2 ° C., which is the temperature of the fuel cell after adjusting the temperature, is higher than the temperature T1 ° C. of the fuel cell before adjusting the temperature. By adjusting the cell temperature and adjusting the temperature so that the second temperature T3 ° C. is lower than the first temperature T2 ° C. in the second temperature adjustment stage, platinum oxidation reaction, platinum oxide reduction reaction It is possible to prevent the platinum from dissolving or eluting from the electrode catalyst, and the solid polymer electrolyte polymer (ionomer) or the electrolyte membrane in the electrode catalyst layer is in a dry state. It becomes possible to avoid a decrease in battery performance due to continuing.

  Since the present invention is useful for improving the life of a fuel cell, it can be used in the field related to control of a fuel cell.

It is a perspective view which shows the whole structure of a fuel cell stack. It is a principal part expanded sectional view which shows the cell structure of a fuel cell stack. 1 is a block diagram of a schematic configuration of a fuel cell system and a control system thereof according to a first embodiment. 4 is an operation flowchart according to the first embodiment of the control unit shown in FIG. 3. 4 is an operation flowchart according to a second embodiment of the control unit shown in FIG. 3. It is a schematic block diagram of a fuel cell control system and its control system according to a third embodiment of the present invention. It is a schematic block diagram of the fuel cell system which concerns on 4th Embodiment, and its control system. 8 is an operation flowchart according to a fourth embodiment of the control unit illustrated in FIG. 7. It is a schematic block diagram of the fuel cell system which concerns on 5th Embodiment of this invention, and its control system. It is an operation | movement flowchart which concerns on 5th Embodiment of the control part shown in FIG. It is an operation | movement flowchart which concerns on 6th Embodiment of the control part shown in FIG.

Explanation of symbols

1 Fuel cell stack,

2 cells,
3 laminates,
4 current collector,
5 Insulating plate,
6 End plate,
7 Tie rods
8 Fuel gas supply port,
9 Fuel gas outlet,
10 Oxidant gas supply port,
11 Oxidant gas outlet,
12 Cooling water supply port,
13 Cooling water outlet,
15A anode separator,
15B cathode separator,
15 separator,
16 ridges,
16A convex part,
16B convex part,
17 Concave part,
17A recess,
17B recess, 18 fuel gas flow path,
19 Oxidant gas flow path,
20 cell voltmeter,
21 Ammeter,
22 Humidity adjuster,
23 Humidity sensor
24 Flow regulator
25 control unit,
26 Gas cylinder,
27 Compressor,
28 Compressor,
30 battery,
32 cell resistance meter 34 temperature sensor,
36 Temperature controller,
141 solid polymer electrolyte membrane,
142A anode catalyst layer,
142B cathode catalyst layer,

143A gas diffusion layer,
143B gas diffusion layer, 144A anode electrode,
144B Cathode electrode.

Claims (24)

A method for controlling a fuel cell in which a catalytic metal is used as an electrode catalyst,
Detecting a load variation of the fuel cell;
Detecting a cell voltage between the anode and cathode of the fuel cell when a load change is detected;
Adjusting the humidity of at least one of the fuel gas supplied to the anode and the oxidant gas supplied to the cathode to a predetermined humidity when the detected cell voltage is in a predetermined voltage range;
A control method for a fuel cell comprising: The step of adjusting the humidity of the gas to a predetermined humidity is as follows:
A first humidity adjustment step of adjusting the humidity of at least one of the fuel gas supplied to the anode and the oxidant gas supplied to the cathode to a first humidity;
Detecting the elimination of the load fluctuation;
A second humidity adjustment step of further adjusting the humidity of the gas adjusted in the first humidity adjustment step to the second humidity after the cancellation of the load fluctuation is detected;
The fuel cell control method according to claim 1, comprising: further,
Detecting a value of cell resistance between the anode and cathode of the fuel cell;
When the detected cell resistance value is within the predetermined range, the process of adjusting the humidity of the gas to the predetermined humidity is continued. On the other hand, when the detected cell resistance value is not within the predetermined range, the humidity of the gas is continued. Ending the process of adjusting to a predetermined humidity;
The fuel cell control method according to claim 1, comprising: A method for controlling a fuel cell in which a catalytic metal is used as an electrode catalyst,
Detecting a load variation of the fuel cell;
Detecting a cell voltage between the anode and cathode of the fuel cell when a load change is detected;
Adjusting the temperature of the fuel cell to a predetermined temperature when the detected cell voltage is in a predetermined voltage range;
A control method for a fuel cell comprising: The step of adjusting the temperature of the fuel cell to a predetermined temperature includes:
A first temperature adjustment step of adjusting the temperature of the fuel cell to a first temperature;
Detecting the elimination of the load fluctuation;
A second temperature adjustment step of further adjusting the temperature of the fuel cell adjusted in the first temperature adjustment step to the second temperature after the cancellation of the load fluctuation is detected;
The fuel cell control method according to claim 4, further comprising: further,
Detecting a value of cell resistance between the anode and cathode of the fuel cell;
When the detected cell resistance value is within a predetermined range, the process of adjusting the temperature of the fuel cell to a predetermined temperature is continued. On the other hand, when the detected cell resistance value is not within the predetermined range, the fuel cell is continued. Ending the process of adjusting the temperature to a predetermined temperature;
The fuel cell control method according to claim 4, further comprising:   6. The fuel cell control method according to claim 1, wherein the load variation of the fuel cell is detected by a change in an amount of current supplied from the fuel cell to the load.   5. The fuel cell control method according to claim 1, wherein the predetermined voltage range is 0.6 to 0.9 volts.   2. The method of controlling a fuel cell according to claim 1, wherein the humidity of the gas is such that the humidity of the gas after adjusting the humidity is lower than the humidity of the gas before adjusting the humidity. . In the first humidity adjustment stage, the humidity of the gas is adjusted such that the first humidity which is the humidity of the gas after adjusting the humidity is lower than the humidity of the gas before adjusting the humidity;
3. The fuel cell control method according to claim 2, wherein in the second humidity adjustment step, the humidity of the gas is adjusted so that the second humidity is higher than the first humidity. 4. .   When the humidity of the gas before adjusting the humidity is X% and the first humidity which is the humidity of the gas after adjusting the humidity is Y%, the predetermined humidity is in the range of 1 <X / Y <20. The fuel cell control method according to any one of claims 1 to 3, wherein the control method is a fuel cell.   When the first humidity is Y% and the second humidity is Z%, the relationship between the first humidity and the second humidity is 0.1 <Y / Z <1. The fuel cell control method according to claim 2, wherein the fuel cell control method is satisfied.   5. The fuel cell according to claim 4, wherein the temperature of the fuel cell is such that the humidity of the fuel cell after adjusting the temperature is higher than the temperature of the fuel cell before adjusting the temperature. Control method. In the first temperature adjustment step, the first temperature T2 ° C., which is the temperature of the fuel cell after adjusting the temperature, is higher than the temperature T1 ° C. of the fuel cell before adjusting the temperature. Adjust the temperature of
The temperature of the fuel cell is adjusted in the second temperature adjustment step so that the second temperature T3 ° C is lower than the first temperature T2 ° C. Fuel cell control method.   The relationship between the temperature T1 ° C. of the fuel cell before adjusting the temperature and the first temperature T2 ° C. that is the temperature of the fuel cell after adjusting the temperature satisfies the relationship 0.03 <T1 / T2 <1. The fuel cell control method according to claim 5. A fuel cell control device in which a catalytic metal is used as an electrode catalyst,
Load fluctuation detecting means for detecting a load fluctuation of the fuel cell;
Cell voltage detecting means for detecting a cell voltage between the anode and cathode of the fuel cell;
Humidity detecting means for detecting the humidity of at least one of the fuel gas supplied to the anode and the oxidant gas supplied to the cathode;
When the detected cell voltage is in a predetermined voltage range, at least one of a fuel gas supplied to the anode and an oxidant gas supplied to the cathode based on the humidity of the gas detected by the humidity detecting means Humidity adjusting means for adjusting the humidity of the liquid to a predetermined humidity;
A fuel cell control device comprising: The humidity adjusting means is
The humidity of at least one of the fuel gas supplied to the anode and the oxidant gas supplied to the cathode was adjusted to the first humidity, and adjusted to the first humidity after the load fluctuation was eliminated. 17. The fuel cell control device according to claim 16, further comprising a function of adjusting the humidity of the gas to the second humidity.   The fuel according to claim 16, wherein the humidity adjusting unit includes a humidifier for humidifying at least one of a fuel gas supplied to the anode and an oxidant gas supplied to the cathode. Battery control device. Furthermore, it has cell resistance value detection means for detecting the value of cell resistance between the anode and cathode of the fuel cell,
The humidity adjusting unit further continues the process of adjusting the humidity of the gas to a predetermined humidity when the detected cell resistance value is within a predetermined range, while the detected cell resistance value is within the predetermined range. The fuel cell control device according to claim 16, further comprising a function of ending the process of adjusting the humidity of the gas to a predetermined humidity if it is not within the range. A fuel cell control device in which a catalytic metal is used as an electrode catalyst,
Load fluctuation detecting means for detecting a load fluctuation of the fuel cell;
Cell voltage detecting means for detecting a cell voltage between the anode and cathode of the fuel cell;
Temperature detecting means for detecting the temperature of the fuel cell;
A temperature adjusting means for adjusting the temperature of the fuel cell to a predetermined temperature based on the temperature of the fuel cell detected by the temperature detecting means when the detected cell voltage is in a predetermined voltage range;
A fuel cell control device comprising: The temperature adjusting means is
The fuel cell has a function of adjusting the temperature of the fuel cell to the first temperature, and further adjusting the temperature of the fuel cell adjusted to the first temperature after the load fluctuation is eliminated to the second temperature. 21. The fuel cell control device according to claim 20, wherein: Furthermore, it has cell resistance value detection means for detecting the value of cell resistance between the anode and cathode of the fuel cell,
The temperature adjusting means further continues the process of adjusting the temperature of the fuel cell to a predetermined temperature when the detected cell resistance value is within a predetermined range, while the detected cell resistance value is a predetermined value. 21. The fuel cell control device according to claim 20, further comprising a function of ending the process of adjusting the temperature of the fuel cell to a predetermined temperature if it is not within the range.   Furthermore, a secondary battery is connected in parallel to the fuel cell, and when the process of adjusting the humidity of the gas to a predetermined humidity is being performed, the secondary battery reduces the power generation insufficient power of the fuel cell. The fuel cell control device according to claim 16, wherein the control device is configured to compensate.   Furthermore, a secondary battery is connected in parallel to the fuel cell, and when the process of adjusting the temperature of the fuel cell to a predetermined temperature is being performed, the secondary battery generates insufficient power for the fuel cell. 21. The fuel cell control device according to claim 20, wherein the control device is configured to compensate for the fuel cell.

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