Fuel cell performance determination method, and fuel cell vehicle with fuel cell performance determination method

Abstract

To provide a performance determination method of a fuel cell that uses ceramics having n-type semiconductor properties as the electrode support, and a fuel cell vehicle equipped with this determination method.SOLUTION: A method for evaluating the performance of a fuel cell that uses ceramics having n-type semiconductor properties as an electrode support includes: a first step of changing the output of the fuel cell; a second step of acquiring the electrical resistance of the fuel cell when the output changes in the first step; and a third step of determining the performance of the fuel cell according to the change in electrical resistance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a fuel cell performance determination method and a fuel cell vehicle equipped with this performance determination method. [Background technology]

[0002] 2. Description of the Related Art Fuel cell vehicles having fuel cells are known in the art. Such fuel cells have electrodes. The electrodes have a precious metal supported on a support such as carbon. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-158020 Summary of the Invention [Problem to be solved by the invention]

[0004] Carbon-based supports are prone to corrosion. In recent years, electrodes in which precious metals are supported on ceramics that are not susceptible to corrosion have been developed. The loss or melting of precious metals supported on ceramics can cause a decrease in the performance of fuel cells.

[0005] An object of the present disclosure is to provide a method for determining the performance of a fuel cell that uses ceramics having n-type semiconductor properties as an electrode carrier, and a fuel cell vehicle equipped with this determination method. [Means for solving the problem]

[0006] The fuel cell performance evaluation method according to the present disclosure is a method for evaluating the performance of a fuel cell that uses ceramics having n-type semiconductor properties as an electrode support, and includes a first step of changing the output of the fuel cell, a second step of obtaining the electrical resistance of the fuel cell when the output is changed in the first step, and a third step of evaluating the performance of the fuel cell in accordance with the change in the electrical resistance.

[0007] According to this method for determining the performance of a fuel cell, the performance of a fuel cell that uses ceramics having n-type semiconductor properties as electrodes can be determined, for example, without disassembling the fuel cell.

[0008] Furthermore, a fuel cell vehicle according to the present disclosure is equipped with a control device that includes such a method for determining fuel cell performance.

[0009] In this fuel cell vehicle, the performance of the fuel cell can be determined while the fuel cell unit is mounted on the vehicle. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a method for determining the performance of a fuel cell that uses ceramics having n-type semiconductor properties as an electrode carrier, and a fuel cell vehicle equipped with this determination method. [Brief description of the drawings]

[0011] [Figure 1] 1 is a system diagram of a fuel cell vehicle according to one embodiment of the present disclosure. [Diagram 2] 4 is a graph showing the relationship between precious metal loading density, load current, and electrical resistance according to one embodiment of the present disclosure. [Diagram 3] 1 is a map showing a correlation between the amount of change and the precious metal loading density according to one embodiment of the present disclosure. [Figure 4] 4 is a flowchart of a control procedure executed by a control device according to an embodiment of the present disclosure. [Diagram 5]5 is a graph showing the relationship between the number of starts and stops, resistance, and load current of a fuel cell system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. As shown in Fig. 1, a fuel cell vehicle 1 includes a fuel cell system 2 as a power generation device, a control device 4, a motor generator (M) 8, and a driving battery (BT) 10.

[0013] As shown in Fig. 1, the fuel cell vehicle 1 of this embodiment is a range extender type plug-in fuel cell vehicle (PFCV) that can be externally charged or externally powered. The fuel cell system 2 is activated mainly when it is necessary to charge the driving battery 10. The fuel cell vehicle 1 supplies the electric power generated by the fuel cell system 2 to the driving battery 10 after voltage conversion using a DC-DC converter (not shown). Furthermore, when there is a shortage of output from the driving battery 10 to the motor generator 8, the fuel cell vehicle 1 temporarily supplies the electric power generated by the fuel cell system 2 to the motor generator 8.

[0014] The motor generator 8 drives the drive wheels 8b via a reduction gear (not shown) and a drive shaft 8a. The motor generator 8 is connected to the drive battery 10 via an inverter 8c. The inverter 8c is also electrically connected to the control device 4. In this embodiment, the motor generator 8 is a three-phase AC motor, and is controlled to power running or regeneration via the inverter 8c based on instructions from the control device 4. When the control device 4 instructs the inverter 8c to power, the inverter 8c receives power from the drive battery 10 and supplies power to the motor generator 8 to power it. On the other hand, when the control device 4 instructs the inverter 8c to regenerate, the inverter 8c receives power generated by the motor generator 8 and supplies power to the drive battery 10.

[0015] The driving battery 10 supplies power to the motor generator 8. In this embodiment, the driving battery 10 is composed of a secondary battery such as a lithium ion battery, and has a battery module (not shown) configured by combining multiple battery cells. The driving battery 10 functions as a power source for the motor generator 8. The driving battery 10 is also connected to a battery control device 10a which calculates the state of charge (hereinafter referred to as SOC) from the voltage of the battery module and other factors. The driving battery 10 is electrically connected to the control device 4 via the battery control device 10a.

[0016] The fuel cell system 2 has a fuel cell stack made up of fuel cell units 12, an air supply path 14, a turbocharger 16, a fuel gas circulation path 18, a fuel gas supply path 20, a fuel gas discharge path 24, an air discharge path 26, a cathode outlet valve 26a, a pressure sensor 28, a current sensor 30, and a voltage sensor 32. Note that Fig. 1 shows a simplified view of one fuel cell unit 12 in the fuel cell stack.

[0017] The fuel cell 12 is supplied with fuel gas and air, and generates electricity by a chemical reaction between the supplied fuel gas and air. In this embodiment, the fuel gas is hydrogen (H2). The fuel cell 12 supplies the generated electricity to the driving battery 10.

[0018] The fuel cell 12 includes an anode 12a and a cathode 12b. The anode 12a includes an anode-side electrode catalyst layer (not shown). In this embodiment, the anode-side electrode catalyst layer is composed of an electrode catalyst in which an electrode carrier supports a catalyst containing a precious metal such as a platinum (Pt)-based material. The electrode carrier is not particularly limited, and examples thereof include a carrier mainly composed of carbon and a carrier mainly composed of conductive ceramics.

[0019] A fuel gas supply path 20 is connected upstream of the anode 12a, and hydrogen is supplied from a hydrogen tank (not shown) through the fuel gas supply path 20. The hydrogen supplied to the anode 12a is decomposed into hydrogen ions and electrons by the electrode catalyst of the anode-side electrode catalyst layer. The hydrogen ions move to the cathode-side electrode catalyst layer. The electrons become a current and move to the cathode 12b. A fuel gas discharge path 24 for discharging fuel gas is connected downstream of the anode 12a, and hydrogen not decomposed at the anode 12a is discharged via the fuel gas discharge path 24.

[0020] The fuel gas circulation path 18 connects the fuel gas discharge path 24 and the fuel gas supply path 20, circulates a portion of the fuel gas supplied to the anode 12a, and supplies it again to the anode 12a. The fuel gas circulation path 18 is connected to the fuel gas supply path 20.

[0021] The cathode 12b is provided on the opposite side of the anode 12a with the electrolyte membrane 12c interposed therebetween. The cathode 12b includes a cathode-side electrode catalyst layer (not shown). In this embodiment, the cathode-side electrode catalyst layer is composed of an electrode catalyst in which a catalyst containing a precious metal such as a platinum (Pt)-based material is supported on an electrode carrier containing a ceramic material having properties as an n-type semiconductor, such as tin oxide or tantalum oxide.

[0022] An air supply path 14 is connected upstream of the cathode 12b. The air supply path 14 is connected to the atmosphere upstream of the cathode 12b, and supplies air in the atmosphere to the cathode 12b via a filter 14b. An air intake valve 14a, a supercharger 16, and an intercooler 14c are provided on the air supply path 14. When air is drawn into the air supply path 14, the air intake valve 14a opens the valve to communicate the upstream and downstream, and to communicate the atmosphere with the cathode 12b. The supercharger 16 draws air from the atmosphere and pumps it to the cathode 12b. The intercooler 14c cools the pumped air. In this embodiment, the supercharger 16 is an electric pump, and is electrically connected to the control device 4.

[0023] An air exhaust path 26 is connected downstream of the cathode 12b. The air exhaust path 26 is connected to the atmosphere downstream of the cathode 12b, and air that has not reacted at the cathode 12b is exhausted into the atmosphere.

[0024] A pressure sensor 28 senses the pressure in the anode 12a and the cathode 12b. A current sensor 30 senses the current in the cathode 12b. A voltage sensor 32 senses the voltage in the cathode. These sensors are electrically connected to the control device 4.

[0025] The control device 4 changes the output of the fuel cell 12, and acquires the electrical resistance Ω of the fuel cell system 2 when the output of the fuel cell 12 changes. In this embodiment, the fuel cell system 2 acquires the current A and the voltage V from the current sensor 30 and the voltage sensor 32. The control device 4 acquires the electrical resistance Ω of the fuel cell 12 from the acquired values ​​of current A and voltage V.

[0026] In addition, the control device 4 controls the fuel cell system 2 so that the fuel cell vehicle 1 is in a desired operating state based on signals from each sensor and various devices, and maps and programs stored in memory. The control device 4 also acquires the state of charge (SOC) of the driving battery 10, and calculates the target state of charge Bt according to the vehicle's running state, etc. The control device 4 starts up the fuel cell system 2 to generate power according to the calculated target state of charge Bt and state of charge (SOC). The control device 4 controls a DC-DC converter (not shown) to charge the driving battery 10 up to the target state of charge Bt. Furthermore, the control device 4 calculates the output required for the vehicle, and controls the motor generator 8 via the inverter 8c.

[0027] The control device 4 is actually an ECU (Electronic Control Unit) configured by a microcomputer including a calculation device, a memory, an input / output buffer, etc. Note that various controls are not limited to processing by software, and can also be processed by dedicated hardware (electronic circuits).

[0028] When oxygen is adsorbed onto the surface of an electrode support made of a ceramic material that has n-type semiconductor properties, the oxygen attracts electrons from the surface layer, creating a type of insulating layer called an electron depletion layer. When an electron depletion layer is created, electron movement is hindered and the electrical resistance Ω increases.

[0029] The electron depletion layer is reduced by the supply of electrons to the electrode support. The higher the density of the precious metal supported on the electrode support, the more electrons are supplied to the electrode support. Therefore, as shown in Figure 3, when the output (load current) of the fuel cell 12 is increased from zero to a predetermined output, the lower the density of the precious metal, the greater the decrease in electrical resistance Ω.

[0030] More specifically, as shown in the graph of high precious metal supporting density in FIG. 2, when the supporting density of the precious metal supported on the electrode support is high, the change amount ΔΩ in the electrical resistance Ω of the fuel cell 12 becomes small when the output (load current) of the fuel cell 12 is increased from zero (unloaded state) to a predetermined output. Here, the predetermined output may be the output when the decrease in the electrical resistance Ω has converged. In this embodiment, the change amount ΔΩ is almost zero in the graph of high metal supporting density. On the other hand, as shown in the graph of low precious metal supporting density in FIG. 2, when the supporting density of the precious metal supported on the electrode support is low, the change amount ΔΩ becomes large when the output (load current) of the fuel cell 12 is increased from zero to a predetermined output (see ΔΩa in FIG. 2). Furthermore, as shown in the graph of precious metal loading density in Figure 2, when the loading density of the precious metal loaded on the electrode carrier is between high and low, the change ΔΩ when the output (load current) of the fuel cell 12 is increased from zero to a predetermined output will be ΔΩb, which is a value between zero and ΔΩa.

[0031] The control device 4 can determine the performance of the fuel cell system 2 by utilizing the above characteristics. In this embodiment, the control device 4 stores a map in which the relationship between the change amount ΔΩ of the electrical resistance Ω and the precious metal support density as shown in FIG. 3 is recorded, or a correlation equation between the change amount ΔΩ and the metal support density that can be obtained from these maps. As shown in FIG. 3, the map or correlation equation may be a map or correlation equation in which the change amount ΔΩ increases as the support density of the precious metal supported by the electrode support decreases. Such a map or correlation equation may be obtained in advance by experiments or the like. For example, the map shown in FIG. 3 is an example in which the change amount ΔΩ from low to high precious metal support density of the fuel cell 12 in FIG. 2 is obtained in advance by experiments, and ΔΩa, which is the change amount ΔΩ at low precious metal support density, ΔΩb, which is the change amount ΔΩ in the precious metal support density, and the change amount ΔΩ at high precious metal support density are recorded in the map. The correlation equation may be determined in advance from such a map.

[0032] The control device 4 obtains the change amount ΔΩ of the electric resistance of the fuel cell 12 when the output of the fuel cell 12 is changed from zero to a predetermined output, and estimates the precious metal support density by comparing it with a stored map or correlation formula. More specifically, the control device 4 increases the output of the fuel cell 12 from an unloaded state to a predetermined output, and obtains a first resistance value which is the electric resistance Ω in the unloaded state and a second resistance value which is the electric resistance Ω in a state where the output is increased to the predetermined output. The control device 4 calculates the difference between the first resistance value and the second resistance value, and obtains the change amount ΔΩ of the electric resistance. The control device 4 applies the change amount ΔΩ to the map or correlation formula shown in FIG. 3 to estimate the precious metal support density. The control device 4 estimates that the larger the change amount ΔΩ, the lower the precious metal support density supported on the electrode carrier. The control device 4 determines that the lower the estimated precious metal support density, the lower the performance of the fuel cell system 2.

[0033] Next, the control procedure executed by the control device 4 will be described with reference to the flowchart of FIG.

[0034] In step S1, the control device 4 determines whether or not the number of starts / stops (one example of the number of starts), which is the number of times the fuel cell system 2 has been repeatedly started and stopped, has reached a predetermined number or more. If the number of starts / stops is equal to or greater than the predetermined number (YES in step S1), the control device 4 proceeds to step S2.

[0035] In step S2, the control device 4 starts performance determination control, and proceeds to step S3.

[0036] In step S3, the control device 4 increases the output of the fuel cell 12 to a predetermined output. The predetermined output may be the output when the decrease in the electrical resistance Ω has converged, as described above. After increasing the output of the fuel cell system 2 to the predetermined output, the control device 4 proceeds to step S4.

[0037] In step S4, the control device 4 executes a performance determination of the fuel cell system 2. In this embodiment, the control device 4 estimates the precious metal loading density from the amount of change ΔΩ as described above. After executing the performance determination of the fuel cell system 2, the control device 4 advances the process to step S5.

[0038] In step S5, the control device 4 determines whether the performance is below the allowable value. In this embodiment, if the control device 4 determines that the estimated precious metal loading density is equal to or lower than a predetermined value, the control device 4 determines that the performance is below the allowable value. If the control device 4 determines that the performance is below the allowable value (YES in step S5), the process proceeds to step S6.

[0039] In step S6, the control device 4 displays a warning. The warning may be displayed, for example, on a display provided on the instrument panel or the like of the fuel cell vehicle 1. After displaying the warning, the control device 4 ends the process.

[0040] When the control device 4 determines in step S1 that the number of starts / stops is less than the predetermined number (NO in step S1), the control device 4 repeats the process in step S1 until the number of starts / stops becomes equal to or greater than the predetermined number.

[0041] If the control device 4 determines in step S5 that the performance is equal to or greater than the allowable value (NO in step S5), the control device 4 advances the process to step S7.

[0042] In step S7, the control device 4 determines the number of starts and stops for the next judgment. When determining the number of starts and stops, the control device 4 may also determine the specified output for the next judgment. As shown in FIG. 5, the control device 4 may increase the specified output as the number of starts and stops increases. When the number of starts and stops increases, for example, the precious metal melts and the precious metal loading density decreases. In other words, deterioration of the fuel cell 12 progresses. As a result, the electrical resistance Ω due to the electron depletion layer in a no-load state increases.

[0043] When the electrical resistance Ω in a no-load state is large, the amount of change ΔΩ becomes large, and the output until the decrease in electrical resistance Ω converges becomes larger. In other words, a larger specified output is required. For this reason, the control device 4 can obtain the amount of change ΔΩ more quickly by increasing the specified output as the number of starts and stops increases. This shortens the time required for performance determination control.

[0044] As described above, the present disclosure can provide a method for determining the performance of a fuel cell that uses ceramics having n-type semiconductor properties as an electrode carrier, and a fuel cell vehicle 1 equipped with this determination method.

[0045] <Other embodiments> Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0046] For example, in the above embodiment, an example has been described in which the control device 4 of the series type fuel cell vehicle 1 executes the performance determination, but the present disclosure is not limited to this. For example, the performance determination method of the present disclosure may be used during the manufacture of the fuel cell system 2. The performance of the fuel cell system 2 decreases not only due to repeated start-up and stoppage, but also due to, for example, the falling off of a precious metal during the process of supporting the carrier. The performance determination method of the present disclosure can also determine such a decrease in performance. This improves the quality of the fuel cell system 2 during manufacture.

[0047] In the above embodiment, the change amount ΔΩ is calculated using the difference between the electric resistance Ω at no load and at a predetermined output, but the present disclosure is not limited to this. The change amount ΔΩ may be, for example, the ratio between the electric resistance Ω at zero (no load state) and the electric resistance Ω at a predetermined output. In this case, the control device 4 may calculate the ratio between the first resistance value, which is the electric resistance Ω at no load state, and the second resistance value, which is the electric resistance Ω in a state where the output is increased to a predetermined output, and estimate the precious metal support density by assuming that the smaller the ratio is, the larger the difference between the first resistance value and the second resistance value, i.e., the larger the change amount ΔΩ is. [Explanation of symbols]

[0048] 1: Fuel cell vehicle 2: Fuel cell system 4: Control device 10: Drive battery 12: Fuel cell

Claims

1. A method for evaluating the performance of a fuel cell that uses a ceramic having n-type semiconductor properties as an electrode carrier, comprising the steps of: A first step of varying an output of the fuel cell; a second step of acquiring an electrical resistance of the fuel cell when the output is changed in the first step; a third step of determining the performance of the fuel cell in accordance with the change in electrical resistance; A method for determining the performance of a fuel cell comprising:

2. In the first step, the output of the fuel cell is increased from a no-load state to a predetermined output, In the second step, a first resistance value in the no-load state and a second resistance value in the state where the output is increased to the predetermined output are obtained; In the third step, a difference between the first resistance value and the second resistance value is calculated; It is estimated that the larger the difference is, the lower the precious metal loading density on the electrode support is. The lower the estimated precious metal loading density, the lower the performance of the fuel cell is determined to be. The method for determining the performance of a fuel cell according to claim 1 .

3. The more the performance of the fuel cell deteriorates, the more the predetermined output is increased. The method for determining fuel cell performance according to claim 2 .

4. The first step to the third step are executed every time the number of startups of the fuel cell increases by a predetermined number. The method for determining the performance of a fuel cell according to claim 1 .

5. A control device including the fuel cell performance determination method according to any one of claims 1 to 4, Fuel cell vehicle.

6. a driving battery capable of storing the electric power generated by the fuel cell; a motor that drives wheels using power supplied from the drive battery; Further comprising: The fuel cell vehicle according to claim 5.

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