JP2010067434A - Operation control device and operation control method for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation control device and an operation control method for a fuel cell wherein it is possible to prevent deterioration of a catalyst metal such as platinum and platinum alloy without promoting deterioration of a storage battery. <P>SOLUTION: In the device to control operation of a fuel cell in which voltages are fluctuated according to required system power, a determining means (S2) of estimating a target voltage (Vt) after fluctuations based on the required system power, and determining whether or not the target voltage (Vt) is a voltage or more having possibility that a catalyst of an electrode catalyst layer is dissolved, and an operation control means (S4) to control operation of the fuel cell so that in the case the target voltage (Vt) is higher than the voltage (Vc) before the fluctuations and the dissolving start voltage or more, it is elevated up to a first stage elevated voltage (Vs1) which is the voltage or more of starting film formation in which the catalyst is covered by a protective film, and so that it becomes the target voltage (Vt) after a prescribed time (ts) passes from that time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and method for controlling the operation of a fuel cell.

In conventional fuel cell systems, even when the system power requirement increases gradually, the output voltage of the fuel cell is limited once by the oxidation-reduction potential, and control is performed to supplement the power corresponding to the limited voltage with the battery. Was. Thereafter, even if the fuel cell power generation is no longer necessary due to a decrease in the accelerator opening, the power generation was continued while maintaining the output voltage of the fuel cell below the oxidation-reduction potential. The surplus power generated in this way is continuously charged into the battery, and power generation is continued until the capacity of the battery exceeds a predetermined value.
JP 2007-5038 A

  However, in order to suppress the potential fluctuation in this way, it is necessary to vary the output of the storage battery in accordance with the fluctuation of the system required power. If it does in this way, the charge / discharge frequency of a storage battery will increase, As a result, deterioration of a storage battery was accelerated | stimulated and there existed a problem that the electric power generation efficiency of the whole system fell.

  The present invention has been made paying attention to such conventional problems, and suppresses the deterioration of the power generation efficiency of the entire system, suppresses the promotion of deterioration of the storage battery, and catalytic metals such as platinum and platinum alloys. An object of the present invention is to provide a fuel cell operation control apparatus and operation control method capable of preventing deterioration of the fuel cell.

  In the present invention, when the target voltage is higher than the voltage before the fluctuation and is equal to or higher than the melting start voltage, the catalyst is raised to the first stage rising voltage that is equal to or higher than the film starting voltage on which the catalyst is coated with the protective film. Further, the operation of the fuel cell is controlled so that the target voltage is reached after a predetermined time has elapsed since that time.

  According to the present invention, when the required power for the fuel cell fluctuates and there is a possibility that the catalyst of the electrode catalyst layer is dissolved, the target voltage is reached after waiting for the formation of the protective film on the catalyst. Thus, since the operation of the fuel cell is controlled, the deterioration of the power generation efficiency of the entire system can be suppressed, the acceleration of the deterioration of the storage battery can be suppressed, and the deterioration of the catalyst metal such as platinum or platinum alloy can be suppressed. is there.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
(First embodiment)
First, an example of a fuel cell system to which a fuel cell operation control device according to the present invention is applied will be described with reference to FIG.

  The fuel cell system includes a fuel cell stack 1, an air supply compressor 2, a hydrogen tank 3, a cooling water pump 4, a radiator 5, a temperature sensor 6, a temperature recording unit 7, and a load controller 8. .

  The fuel cell stack 1 is supplied with cathode gas and anode gas to generate electric power. The air supply compressor 2 supplies cathode gas (air) to the fuel cell stack 1. The hydrogen tank 3 is a sealed container that stores anode gas (hydrogen), and supplies the anode gas (hydrogen) to the fuel cell stack 1. The cooling water pump 4 circulates the cooling water supplied to the fuel cell stack 1. The radiator 5 releases the heat of the cooling water circulated by the cooling water pump 4 and prevents the cooling water from overheating. The temperature sensor 6 detects the cooling water temperature. The temperature recording unit 7 records the cooling water temperature detected by the temperature sensor 6. The load controller 8 sets the output load of the fuel cell based on the system required power and controls the operation of the fuel cell.

  FIG. 2 is an enlarged view of a single cell constituting the fuel cell. 2A is an exploded perspective view showing the configuration, and FIG. 2B is a side sectional view.

  The fuel cell has a configuration in which a cathode separator 13a and an anode separator 13b are arranged on both front and back surfaces of a membrane electrode assembly (hereinafter referred to as “MEA”) 10.

  The MEA 10 includes an electrolyte membrane 11, a cathode 12a, and an anode 12b.

  The electrolyte membrane 11 is a proton conductive ion exchange membrane formed of a fluorine resin. The electrolyte membrane 11 exhibits good electrical conductivity in a wet state. Therefore, in order to extract the performance of the electrolyte membrane 11 and improve the power generation efficiency, it is necessary to keep the moisture state of the electrolyte membrane 11 optimal. Therefore, the reaction gas (cathode gas and anode gas) introduced into the fuel cell is humidified. Note that pure water may be used as water for optimally maintaining the moisture state of the electrolyte membrane 11. This is because when water mixed with impurities is supplied to the fuel cell, impurities accumulate in the electrolyte membrane 11 and power generation efficiency decreases.

  The cathode 12a is provided on one side (left side of FIG. 2B) of the electrolyte membrane 11, and the anode 12b is provided on the opposite side (right side of FIG. 2B). The cathode 12 a and the anode 12 b include a catalyst layer 121 and a gas diffusion layer (GDL) 122. The catalyst layer 121 is formed of, for example, carbon black particles on which platinum is supported. The gas diffusion layer 122 is formed of a member having sufficient gas diffusibility and conductivity, such as carbon fiber.

  The cathode separator 13a overlaps the outside of the cathode 12a. On one side of the cathode separator 13 a (the surface facing the cathode 12 a), ribs 131 are provided so as to form a reaction gas channel 132 between the ribs 131. In FIG. 2, four rows of reaction gas flow paths 132 are formed. The cathode separator 13a is made of, for example, carbon or metal.

  The anode separator 13b overlaps the outside of the anode 12b. On one side of the anode separator 13 b (the surface facing the anode 12 b), a rib 131 is provided so as to form a reaction gas channel 132 between the ribs 131. In FIG. 2, four rows of reaction gas flow paths 132 are formed. The anode separator 13b is made of, for example, carbon or metal.

  A fuel cell stack 1 is formed by stacking several hundred fuel cells having the above-described configuration and maintaining a predetermined surface pressure.

  Next, in order to facilitate understanding of the present invention, the knowledge of the present inventors will be described.

  In the fuel cell system, when the required power for the system fluctuates, the generated power of the fuel cell fluctuates, and as a result, the voltage of the fuel cell fluctuates. Such voltage fluctuation is particularly noticeable when the fuel cell system is used as a power source for various mobile objects including automobiles. Generally, a unit cell constituting a fuel cell has a voltage fluctuation of about +0.6 volts to +1.0 volts. Since the hydrogen oxidation reaction at the anode is extremely fast, the anode potential hardly changes even when the voltage of the unit cell fluctuates, and is always approximately 0 volts, and the cathode potential varies between +0.6 volts and +1.0 volts.

  By the way, a catalytic metal is applied to the electrode in order to promote an electrochemical reaction. The catalyst metal is platinum or a platinum alloy, and is supported on the high specific surface area carbon in a fine particle state. Catalytic metals such as platinum and platinum alloys are usually chemically stable, but it has been confirmed that they deteriorate when the potential varies within the above range. When the catalyst metal deteriorates, the output of the fuel cell decreases.

  Conventionally, it has been considered that catalytic metal deterioration is caused by repetition of platinum oxidation reaction (formation of platinum oxide) and platinum oxide reduction reaction as shown in the following formula (1).

  It was thought that the catalyst deteriorates when the potential fluctuates so as to straddle the potential at which the oxidation-reduction reaction as shown in Formula (1) occurs. However, according to the view of the present inventors, the above mechanism cannot sufficiently explain the deterioration mechanism. As a result of intensive studies, the present inventors have thought that the catalyst is deteriorated by the following mechanism. The idea will be described below.

  FIG. 3 is a graph showing the relationship between the current density of the fuel cell and the cathode potential. FIG. 4A is a graph showing the relationship between the cathode potential and the dissolution rate of the catalytic metal. FIG. 4B is a graph showing the relationship between the cathode potential and the steady coverage of the oxide film formed on the surface of the catalyst metal.

  In the fuel cell, the current density of the fuel cell changes according to the fluctuation of the system power requirement, and the cathode potential (voltage) fluctuates as shown in FIG. In general, this potential varies in the range of approximately +0.6 to +1.0 volts. In general, metals tend to dissolve more easily as the exposed potential is higher. Considering platinum used for the cathode catalyst, the higher the potential, the more the reaction shown in the following formula (2) is promoted, and the platinum is easily dissolved and becomes platinum ions.

  The standard potential (theoretical value) at this time is +1.188 volts (25 ° C.). However, this potential varies depending on the temperature, platinum ion concentration, and the particle size of the platinum fine particles. According to the inventors of the present invention, as shown in FIG. 4A, platinum used for an actual cathode dissolves (platinum ionization) when the potential is higher than about +0.8 volts, and the higher the potential, the higher the potential. It was confirmed that the dissolution rate was increased. Hereinafter, a potential at which the catalytic metal (platinum) starts to dissolve is referred to as a dissolution start potential. The specific potential varies depending on the operating state / environment of the fuel cell and the material used, and is not a constant value.

  However, even if platinum is exposed to a potential higher than the dissolution start potential, if the oxide film is formed on the surface by the reaction shown in the following formula (3) and the coverage increases, this acts as a protective film, and FIG. ), The dissolution rate was confirmed to be extremely low, as indicated by the alternate long and short dash line.

  As shown in FIG. 4B, this reaction proceeds at a potential higher than about +0.7 volts (film formation start potential), and the coverage increases as the potential increases. In addition, this coverage changes with the log | history of an electric potential fluctuation | variation so that it may mention later. The film is formed with a delay in potential fluctuation. When the potential fluctuates, the film reaches the maximum value that can be taken at that potential, and that value becomes a steady value. FIG. 4B shows the coating rate in that state, that is, the steady coating rate. As will be described later, the steady coverage when the potential is increased is lower than the steady coverage when the potential is lowered. FIG. 4B shows the steady coverage when the potential is increased.

  When the system power requirement is very low or no load continues for a long time, platinum is exposed to a potential exceeding +0.8 volts (melting start potential) for a long time, and melting proceeds. If the oxide film is formed by the reaction of), the dissolution rate is extremely low as shown by the one-dot chain line in FIG.

  However, when the cathode potential changes from a potential lower than +0.7 volts (film formation start potential) to a potential exceeding +0.8 volts (dissolution start potential) in a short time according to fluctuations in system power requirements. Since almost no oxide film is formed on the platinum surface, the higher the potential, the higher the dissolution rate as shown by the solid line in FIG. 4A, and the platinum is dissolved by the reaction of formula (2).

  After that, an oxide film is formed by the reaction of the formula (3). The coverage of the oxide film reaches the maximum value that can be taken at the potential, and the value is a steady value. When the oxide film is formed, the dissolution rate of platinum becomes slow.

  However, when the system power requirement rises again and the cathode potential falls below the film formation start potential (+0.7 volts), the oxide film is reduced by the reverse reaction of equation (3). When the potential is increased, platinum is dissolved by the reaction of the formula (2).

  If the system power requirement is high and the potential to which platinum is exposed is lower than the film formation start potential (about +0.7 volts), an oxide film according to equation (3) is not formed, but in this case, platinum according to equation (2) is not formed. Since the dissolution does not proceed, the platinum catalyst does not deteriorate.

  The present inventors thought that the above is the mechanism of catalyst deterioration. Therefore, the present inventors have controlled the cathode potential to be the coating formation start potential when the required power for the fuel cell is reduced, and then a sufficient amount of protective coating is formed after that time. It was thought that the dissolution of the catalyst (platinum) can be suppressed by controlling so as to reach the dissolution start potential after waiting for the dissolution.

  It was also found that the platinum dissolution reaction strongly depends on the temperature and water content in the fuel cell. That is, even if the potential fluctuation waveform is the same, if the temperature and water content in the fuel cell are different, the degree of deterioration will be significantly different.

  In a chemical reaction, temperature is an important factor that determines the reaction rate, and the reaction rate increases exponentially as the temperature increases according to the Arrhenius rule. There is no difference in the dissolution reaction of platinum. Accordingly, even when the same potential fluctuation occurs during operation of the fuel cell, the platinum dissolution reaction proceeds as the temperature in the fuel cell increases.

  As for the influence of the water content, the platinum dissolution reaction is suppressed as the water content in the fuel cell becomes lower when the temperature in the fuel cell is constant. This is considered as follows. That is, in a low water content state, the ion conductivity in the polymer of the electrolyte membrane and the catalyst layer is lowered, and the movement of dissolved platinum ions is suppressed. As a result, the platinum ion concentration in the vicinity of the platinum particles in which the dissolution reaction is occurring becomes higher than when the water content is high, and platinum dissolution is less likely to occur in equilibrium. Furthermore, since platinum ions remain in the vicinity of the platinum particles, reprecipitation of platinum ions onto the platinum particles easily occurs, and movement and precipitation into the electrolyte membrane are also suppressed.

  Based on the above knowledge, there is a correlation between the state of the fuel cell and the ease of progress of platinum dissolution degradation, and the platinum dissolution reaction proceeds based on the temperature and water content in the fuel cell during operation. When it can be estimated that the state is difficult, it is possible to increase the voltage in a rectangular wave shape without performing the platinum dissolution suppression control at the time of voltage increase as described above, and to further improve the efficiency.

  Hereinafter, a specific invention for realizing such a technical idea will be described.

  FIG. 5 is a main flowchart of the control logic of the fuel cell operation control apparatus according to the present invention.

  When receiving a command to change the system power requirement, the controller repeatedly executes the following processing every minute time (for example, 10 milliseconds).

  In step S1, the controller determines whether or not the necessity for film formation control has been determined. If not yet determined, the process proceeds to step S2, and if already determined, the process proceeds to step S3.

  In step S2, the controller determines the necessity of film formation control. Specific contents will be described later.

  In step S3, the controller determines whether film formation control is necessary. If necessary, the process proceeds to step S4, and if not necessary, the process proceeds to step S5.

  In step S4, the controller executes film formation control. Specific contents will be described later.

  In step S5, the controller executes normal control without controlling film formation.

  FIG. 6 is a flowchart showing a film formation control necessity determination routine.

  In step S21, the controller detects the current voltage (cathode potential) Vc.

  In step S22, the controller estimates the target voltage Vt based on the required power Pd for the system determined from the accelerator opening, the vehicle speed, the auxiliary machine power consumption, and the like. Specifically, the target voltage Vt is estimated by applying the system required power Pd to the characteristic map shown in FIG. 8 stored in advance in the ROM.

  In step S23, the controller determines whether or not the target voltage Vt is higher than the current voltage Vc. If so, the process proceeds to step S24, and if low, the process proceeds to step S29.

  In step S24, the controller estimates the oxide film coverage θ based on the current voltage Vc. Here, the oxide film coverage θ tends to increase as the electric potential increases. However, it is not uniquely determined only by the potential, but has a certain width, so the fuel cell power generation history (for example, the time of exposure to a certain potential and the potential before or after exposure to that potential is high or low). , Etc. can be used to estimate the oxide coating rate θ more accurately. Specifically, the oxide film coverage θ is estimated by applying the current voltage Vc and the history to the characteristic map shown in FIG. 9 stored in advance in the ROM. For example, when the potential E1 is changed from the potential E1 having the coverage of 0 to the potential E2 in a very short time, the coverage is 0 immediately after the change, but thereafter the coverage increases with the passage of time and reaches the coverage θ1. On the other hand, when the potential E1 is changed from the potential E1, which is 0, to the potential E3 in a very short time, the coverage is 0 immediately after the change, but thereafter the coverage increases with time and reaches the coverage θ3. After that, when the potential E3 is decreased to the potential E2, the coverage rate θ3 is immediately after the decrease, but the coverage rate subsequently decreases with time and reaches the coverage rate θ2. That is, even with the same potential E2, the coverage varies depending on the change history of the potential. It is desirable that the time until the coverage reaches the steady coverage is measured separately, but if the measurement is difficult, there is no practical problem even if it is about 1 second, for example. Note that the method of changing the potential shown here is simply described. This is different from the method of change of the present invention. In any case, by setting a map showing the relationship as shown in FIG. 9 in advance, it is possible to estimate the coverage based on the power generation history. Since the cathode potential and the voltage are approximate, the cathode potential and the voltage can be replaced in this embodiment.

  In step S25, the controller estimates the first stage rising voltage Vs1 based on the oxide film coverage θ. Specifically, the first-stage rising voltage Vs1 is estimated by applying the coverage θ to the characteristic map shown in FIG. 10 stored in advance in the ROM. The first stage rising voltage Vs1 is a voltage that is equal to or higher than the film start voltage and lower than the melting start voltage.

  In step S26, the controller determines whether or not the first stage rising voltage Vs1 is lower than the target voltage Vt. If it is low, the process proceeds to step S27, and if it is high, the process proceeds to step S29.

  In step S27, the controller determines that film formation control is necessary.

  In step S <b> 28, the controller sets the second stage rising speed R. Specifically, for example, the second stage rising speed R is set by applying the degree of catalyst deterioration progress to the characteristic map shown in FIG. The degree of progress of catalyst deterioration may be determined simply by assuming that the longer the operating time of the fuel cell is, the more advanced it is. Alternatively, the second stage rising speed R may be set by applying the chargeable capacity of the storage battery to the characteristic map shown in FIG. 11B stored in advance in the ROM.

  FIG. 7 is a flowchart showing a film formation control routine.

  In step S41, the controller detects the current voltage (cathode potential) Vc.

  In step S42, the controller determines whether or not the current voltage (cathode potential) Vc is lower than the first stage rising voltage Vs1. If it is low, the process proceeds to step S43, and if it is high, the process proceeds to step S44.

  In step S43, the controller increases the voltage (cathode potential) V1 at once. The voltage V1 is equal to or higher than the first stage rising voltage Vs1 and lower than the melting start voltage Vs2.

  In step S44, the controller increases the voltage (cathode potential) at the second stage increase rate R.

  In step S45, the controller determines whether or not the current voltage (cathode potential) Vc is lower than the target voltage Vt. If it is low, the process is temporarily exited. If it is high, the process proceeds to step S46.

  In step S46, the controller completes the film formation control.

  FIG. 12 is a time chart showing the operation of the fuel cell operation control apparatus according to the present invention. In the following description, the step numbers of the flowcharts are shown with S to make it easy to understand the correspondence with the flowcharts.

  When the controller receives an instruction to change the system required power at time t11, the controller determines whether the necessity of film formation control has been determined (S1), detects the current voltage (cathode potential) Vc (S21), A target voltage Vt is estimated based on the required power Pd for the system (S22). Since the target voltage Vt is higher than the current voltage Vc (Yes in S23), the oxide film coverage θ is estimated based on the current voltage Vc (S24), and the first-stage rising voltage is determined based on the oxide film coverage θ. Vs1 is estimated (S25). Since the first stage rising voltage Vs1 is lower than the target voltage Vt (Yes in S26), it is determined that film formation control is necessary (S27), and the second stage rising speed R is set (S28).

  In the next cycle, the process proceeds from S1 to S3 to S4, and the current voltage (cathode potential) Vc is lower than the first-stage rising voltage Vs1 (Yes in S42), so that the voltage is increased to V1 at a stretch.

  After time t11, the process proceeds in the order of S1, S3, S4, S41, S42, S44, and S45, and the voltage increases at the second-stage increase rate R until the current voltage (cathode potential) Vc becomes higher than the target voltage Vt. In this way (S44), the process is repeated.

  At time t12, when the current voltage (cathode potential) Vc becomes higher than the target voltage Vt (Yes in S45), the film formation control is completed (S46).

  According to the present embodiment, when the required power for the fuel cell is reduced, the cathode potential is controlled to be the coating formation start potential, and then the protective coating is sufficiently formed after the predetermined time has elapsed. Since the control is performed so that the dissolution start potential is reached after waiting, the dissolution of the catalyst (platinum) can be suppressed, and the deterioration of the catalyst (platinum) can be prevented. Further, it is possible to suppress the deterioration of the storage battery while suppressing a decrease in the power generation efficiency of the entire system.

(Second Embodiment)
FIG. 13 is a flowchart showing a film formation control necessity determination routine of the second embodiment.

  In the following description, parts having the same functions as those described above are denoted by the same reference numerals, and redundant description is omitted as appropriate.

  In the present embodiment, in step S282, the controller sets the second stage holding time tk. Specifically, for example, the second stage holding time tk is set by applying the degree of catalyst deterioration progress to the characteristic map shown in FIG. Further, the second stage holding time tk may be set by applying the chargeable capacity of the storage battery to the characteristic map shown in FIG. 15B stored in advance in the ROM.

  FIG. 14 is a flowchart showing a film formation control routine of the second embodiment.

  In the present embodiment, in step S442, the controller holds the voltage V1.

  In step S452, the controller determines whether time tk has elapsed since the start of voltage holding. Until the time elapses, the process once exits, and when time elapses, the process proceeds to step S46.

  FIG. 16 is a time chart showing the operation of the fuel cell operation control apparatus according to the present invention.

  When the controller receives a command to change the system power requirement at time t21, the controller determines whether the necessity for film formation control has been determined (S1), detects the current voltage (cathode potential) Vc (S21), A target voltage Vt is estimated based on the required power Pd for the system (S22). Since the target voltage Vt is higher than the current voltage Vc (Yes in S23), the oxide film coverage θ is estimated based on the current voltage Vc (S24), and the first-stage rising voltage is determined based on the oxide film coverage θ. Vs1 is estimated (S25). Since the first stage rising voltage Vs1 is lower than the target voltage Vt (Yes in S26), it is determined that the film formation control is necessary (S27), and the second stage holding time tk is set (S282).

  In the next cycle, the process proceeds from S1 to S3 to S4, and the current voltage (cathode potential) Vc is lower than the first-stage rising voltage Vs1 (Yes in S42), so that the voltage is increased to V1 at a stretch.

  After time t21, the process proceeds from S1, S3, S4, S41, S42, S442, and S452, the voltage V1 is held until the second stage holding time tk elapses (S442), and the process is repeated.

  At time t22, when the second stage holding time tk has elapsed (Yes in S452), the film formation control is completed (S46).

  Also according to the present embodiment, when the required power for the fuel cell is reduced, the cathode potential is controlled to be the film formation start potential, and after that, a predetermined time has elapsed and a sufficient protective film is formed. Therefore, the dissolution potential of the catalyst (platinum) can be suppressed, and the deterioration of the catalyst (platinum) can be prevented. And it can implement simply compared with 1st Embodiment.

(Third embodiment)
FIG. 17 is a flowchart showing a film formation control necessity determination routine of the third embodiment.

  In the present embodiment, in step S201, the controller detects the temperature ts in the fuel cell stack.

  In step S202, the controller detects the water content ws in the fuel cell stack.

  In step S203, the controller determines whether film formation control is necessary in the current operation. Specifically, it is determined whether or not film formation control is necessary by applying the temperature ts and the water content ws in the fuel cell stack to the characteristic map shown in FIG. 18 (A) stored in advance in the ROM. The map of FIG. 18 (A) can be created from the experimental results obtained by experimenting the progress of the platinum dissolution reaction with respect to the temperature in the fuel cell for each water content as shown in FIG. 18 (B).

  According to this embodiment, when it can be estimated that the platinum dissolution reaction is unlikely to proceed, the platinum dissolution suppression control at the time of voltage increase as in the first embodiment and the second embodiment is not performed, and the voltage is rectangular. Therefore, the fuel cell can be controlled efficiently.

(Fourth embodiment)
FIG. 19 is a flowchart showing a film formation control necessity determination routine of the fourth embodiment.

  In the present embodiment, in step S2031, the controller determines whether or not the in-stack temperature ts is higher than the reference temperature ts0. If larger, the process proceeds to step S202, and if smaller, the process proceeds to step S29.

  In step S2032, the controller determines whether or not the moisture content in the stack ws is greater than the reference moisture content ws0. If larger, the process proceeds to step S21, and if smaller, the process proceeds to step S29.

  Here, the reference temperature ts0 and the reference water content ws0 will be described with reference to FIG. That is, the reference temperature ts0 and the reference water content ws0 are values for simply determining the film formation control necessary operation region of the third embodiment.

  Therefore, according to the present embodiment, it can be easily implemented without having the map as shown in FIG. 18A of the third embodiment.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the above description, platinum is exemplified as the catalyst metal, but a platinum alloy or the like may be used.

It is a figure explaining an example of the fuel cell system to which the operation control apparatus of the fuel cell by this invention is applied. It is an enlarged view of the single cell which comprises a fuel cell. It is a figure which shows the relationship between the current density of a fuel cell, and a cathode potential. It is a figure which shows the relationship between a cathode potential, the dissolution rate of a catalyst metal, and the steady coverage of the oxide film formed on the surface of a catalyst metal. It is an example of the main flowchart of the control logic of the operation control apparatus of the fuel cell by this invention. It is a flowchart which shows the film formation control necessity determination routine. It is a flowchart which shows a film formation control routine. It is a characteristic map for estimating target voltage Vt from system demand electric power Pd. It is a characteristic map for estimating the oxide film coverage θ from the current voltage Vc. It is a characteristic map for estimating the first stage rising voltage Vs1 from the coverage θ. 6 is a characteristic map for setting a second stage rising speed R. It is an example of the time chart which shows operation | movement of the operation control apparatus of the fuel cell by this invention. It is a flowchart which shows the film formation control necessity determination routine of 2nd Embodiment. It is a flowchart which shows the film formation control routine of 2nd Embodiment. It is a characteristic map for setting the second stage holding time tk. It is an example of the time chart which shows operation | movement of the operation control apparatus of the fuel cell by this invention. It is a flowchart which shows the film formation control necessity determination routine of 3rd Embodiment. It is a characteristic map for determining whether film formation control is required from the temperature ts and the water content ws in the fuel cell stack. It is a flowchart which shows the film formation control necessity determination routine of 4th Embodiment. It is a figure explaining standard temperature ts0 and standard moisture content ws0.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 8 Load controller S22 Voltage estimation means / voltage estimation process S23, S26 Determination means / determination process S4 Operation control means / operation control process

Claims (13)

An apparatus for controlling the operation of a fuel cell whose voltage varies according to the system power requirement,
Voltage estimation means for estimating a target voltage, which is a voltage after fluctuating based on system power requirement;
Determining means for determining whether or not the target voltage is equal to or higher than a melting start voltage at which the catalyst of the electrode catalyst layer may be dissolved;
When the target voltage is higher than the voltage before the fluctuation and is equal to or higher than the melting start voltage, the catalyst is increased to the first stage rising voltage that is equal to or higher than the film formation starting voltage to be coated with the protective film, and then the predetermined time Operation control means for controlling the operation of the fuel cell so that the target voltage is reached after elapse of time,
A fuel cell operation control apparatus comprising: The operation control means controls the operation of the fuel cell so as to gradually increase and reach the target voltage after elapse of the predetermined time after reaching the first step increase voltage.
The operation control apparatus for a fuel cell according to claim 1. The operation control means holds the voltage after reaching the first step increase voltage, and controls the operation of the fuel cell so as to become the target voltage after the predetermined time has elapsed.
The operation control apparatus for a fuel cell according to claim 1. The operation control means controls the operation of the fuel cell so that the predetermined time becomes shorter as the deterioration of the catalyst proceeds.
The operation control device for a fuel cell according to any one of claims 1 to 3, wherein the operation control device is a fuel cell. The operation control means controls the operation of the fuel cell so that the predetermined time is shorter as the chargeable capacity of the storage battery is smaller,
The fuel cell operation control device according to any one of claims 1 to 4, wherein the operation control device is a fuel cell. The operation control means controls the operation of the fuel cell so that the predetermined time becomes longer as the internal temperature of the fuel cell stack is higher.
The operation control apparatus for a fuel cell according to any one of claims 1 to 5, characterized in that: The operation control means controls the operation of the fuel cell so that the predetermined time becomes longer as the internal humidity of the fuel cell stack is lower.
The operation control apparatus for a fuel cell according to any one of claims 1 to 6, wherein the operation control apparatus is a fuel cell. The first step increase voltage is set higher as the current catalyst surface coverage is larger,
The fuel cell operation control apparatus according to any one of claims 1 to 7, wherein the operation control apparatus is a fuel cell. The coverage is greater at the time of voltage drop than at the time of voltage rise even at the same voltage,
The fuel cell operation control device according to claim 8. The coverage is determined by the power generation history of the fuel cell.
The fuel cell operation control device according to claim 8. Further provided is an operation state determination means for determining whether or not the operation state in which the catalyst of the electrode catalyst layer may be dissolved based on the temperature and humidity inside the fuel cell stack.
The operation control apparatus for a fuel cell according to any one of claims 1 to 10, wherein the operation control apparatus is a fuel cell. The operating state determining means includes
First, based on the temperature inside the fuel cell stack, it is determined whether or not the operation state is likely to dissolve the catalyst of the electrode catalyst layer,
Next, based on the humidity inside the fuel cell stack, it is determined whether or not there is a possibility that the catalyst of the electrode catalyst layer is dissolved,
The operation control apparatus for a fuel cell according to claim 11. A method for controlling the operation of a fuel cell whose voltage varies according to system power requirements,
A voltage estimation step for estimating a target voltage, which is a voltage after fluctuating based on system power requirement;
A determination step of determining whether or not the target voltage is equal to or higher than a dissolution start voltage at which the catalyst of the electrode catalyst layer may be dissolved;
When the target voltage is higher than the voltage before the fluctuation and is equal to or higher than the melting start voltage, the first stage rising voltage is equal to or higher than the film formation starting voltage on which the catalyst is coated with a protective film and lower than the melting start voltage. An operation control step for controlling the operation of the fuel cell so as to reach the target voltage after a predetermined time has elapsed since then,
A fuel cell operation control method comprising:

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