Fuel cell deterioration determination device and fuel cell vehicle

Abstract

Provided are a fuel cell deterioration determination device (10) capable of determining whether deterioration is progressing in catalyst metal or a catalyst carrier of a fuel cell, and a fuel cell vehicle (FCV).　The fuel cell deterioration determination device (10) comprises: an impedance measurement unit (10C) that applies an AC signal to a fuel cell stack (FC) and measures the AC impedance of the fuel cell stack; and a deterioration determination unit (10D) that estimates, on the basis of the characteristics of the measured AC impedance, the degree of activation overvoltage in the fuel cell stack as the deterioration of the catalyst metal, and estimates the degree of diffusion overvoltage as the deterioration of the catalyst carrier, and determines the degree of deterioration of the catalyst metal and catalyst carrier on the basis of pre-maintained reference values of activation overvoltage and diffusion overvoltage for vehicle mileage.

Description

[Technical field]

[0001] The present disclosure relates to a deterioration determination device for, for example, a fuel cell, and a fuel cell vehicle equipped with this deterioration determination device. [Background technology]

[0002] In modern society, transportation is essential, and various vehicles such as automobiles travel on the roads in our daily lives. Among these, fuel cells, which have a relatively small environmental impact, are attracting attention as a new power source to supply driving force to vehicles.

[0003] In such fuel cells, fuel gas (hydrogen) is supplied to one electrode (fuel electrode) and oxidant gas (oxygen) is supplied to the other electrode (air electrode), and electrical energy is obtained by a chemical reaction between them. Therefore, in order to continuously obtain an appropriate amount of electrical energy (generated power) from the fuel cell, it is necessary to appropriately determine whether the fuel cell installed in the vehicle has deteriorated.

[0004] One of the components that make up a fuel cell is an electrode catalyst (hereinafter, simply referred to as "catalyst"). Such a catalyst is in the form of a catalyst metal such as platinum bonded to a catalyst carrier such as carbon. For example, in Patent Document 1 below, an activation overvoltage is calculated based on the amount of electricity generated during reduction of the catalyst in each cell that makes up the fuel cell, and the FC voltage is estimated from the activation overvoltage that is calculated. In this case, Patent Document 1 proposes comparing the estimated FC voltage with the actual FC voltage detected by a voltage sensor, and judging the deterioration of the fuel cell based on the comparison result.

[0005] Furthermore, Patent Document 2 focuses on the water content in a fuel cell as a criterion for determining deterioration, and proposes estimating the water content by determining proton transfer resistance and gas reaction resistance using a Cole-Cole plot, which is a characteristic diagram showing the relationship between frequency and impedance on a complex plane. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-043645 A [Patent Document 2] JP 2020-87764 A Summary of the Invention [Problem to be solved by the invention]

[0007] Not limited to the above-mentioned patent documents, current technologies still do not meet market needs, and the following problems remain. In other words, it was found that in the electrodes of fuel cells, the repeated application of voltage to redox cycles causes dissolution of small catalytic metal particles. Some of the dissolved metal can then be redeposited on larger metal particles. The occurrence of such phenomena is largely due to the influence of the upper voltage limit when driving a vehicle. On the other hand, it has been found that when voltage repetition occurs, such as when a vehicle is normally accelerated or decelerated, if the voltage scanning speed is fast, corrosion of the catalyst support progresses even at a relatively low voltage.

[0008] When focusing on the catalyst in relation to fuel cell deterioration, it was concluded that two types of deterioration occur depending on driving habits and daily traffic environments: deterioration of the catalytic metal and deterioration of the catalyst support. Both of these types of deterioration affect the performance of the fuel cell, but properly determining which type of deterioration is progressing can be a very important factor in continuously obtaining appropriate electrical energy from the fuel cell.

[0009] The present disclosure has been made in consideration of the above-mentioned problems as an example, and aims to provide a fuel cell deterioration determination device and a fuel cell vehicle that are capable of determining whether deterioration is progressing in the fuel cell's catalytic metal or catalyst support. [Means for solving the problem]

[0010] In order to solve the above problems, according to one aspect of the present disclosure, there is provided a fuel cell deterioration determination device that determines deterioration of a catalyst including a catalytic metal in a fuel cell stack and a catalyst carrier supporting the catalytic metal, the deterioration determination device including: an impedance measurement unit that applies an AC signal to the fuel cell stack to measure the AC impedance of the fuel cell stack; and a deterioration determination unit that estimates the degree of activation overvoltage in the fuel cell stack as deterioration of the catalytic metal and estimates the degree of diffusion overvoltage as deterioration of the catalyst carrier based on characteristics of the measured AC impedance, and determines the progress of deterioration of the catalytic metal and the catalyst carrier based on previously stored reference values ​​of activation overvoltage and diffusion overvoltage for a vehicle traveling distance. Effect of the Invention

[0011] According to the present disclosure, it is possible to clearly distinguish between deterioration of the catalytic metal and the catalyst support, and if, for example, corrosion of either of them progresses at a rate faster than expected, it is possible to suppress the progression of deterioration by modifying the operating parameters of the fuel cell. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a fuel cell vehicle equipped with a fuel cell deterioration determination device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating the configurations and functions of the fuel cell vehicle according to the first embodiment. [Diagram 3] 2 is a schematic diagram showing an example of the configuration of a control device that also functions as a deterioration determination device according to the first embodiment and its surroundings; FIG. [Figure 4] 3 is a flowchart showing a method for determining catalyst deterioration of a fuel cell according to the first embodiment. [Diagram 5] FIG. 2 is a schematic diagram showing an example of a Cole-Cole plot diagram of the fuel cell stack according to the first embodiment. [Figure 6] FIG. 6 is a schematic diagram showing an example in which the high-frequency side semicircle is changed in the Cole-Cole plot shown in FIG. 5. [Figure 7]FIG. 6 is a schematic diagram showing an example in which the low-frequency side semicircle is changed in the Cole-Cole plot shown in FIG. 5. [Figure 8] 11 is an example of table data showing a correspondence relationship between a travel distance and a high-frequency side semicircle and a low-frequency side semicircle. [Figure 9] 4 is an example showing the time transition of cell voltage during acceleration and deceleration in a fuel cell vehicle. [Figure 10] 13 is an example showing the time transition of the cell voltage in a case where a catalyst support deterioration suppression mode (part 1) after deterioration determination is applied. [Figure 11] 13 is an example showing the time transition of the cell voltage in a case where a catalyst support deterioration suppression mode (part 2) after deterioration determination is applied. [Figure 12] 13 is an example showing the time transition of the cell voltage in a case where a catalytic metal deterioration suppression mode is applied after deterioration is determined. [Figure 13] FIG. 11 is a schematic diagram showing an example of a catalyst deterioration determination diagram for a fuel cell stack according to a second embodiment. [Figure 14] FIG. 14 is a schematic diagram showing an example of a case where the high frequency side plot changes in the catalyst deterioration determination diagram shown in FIG. 13. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, preferred embodiments of the present disclosure will be described. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and duplicated explanations will be omitted. In addition, configurations other than those described in detail below may be appropriately supplemented with elemental technologies and configurations related to known fuel cell systems and fuel cell vehicles, including those described in the above-mentioned patent documents.

[0014] [First embodiment] <Fuel cell vehicle FCV> 1 and 2 are schematic diagrams showing a configuration example and functional blocks of a fuel cell vehicle FCV equipped with a fuel cell stack FC according to this embodiment. As shown in Fig. 2, this fuel cell vehicle FCV is configured as a four-wheel drive vehicle in which a driving torque output from a driving force source 21 that generates a driving torque for the vehicle is transmitted to a left front wheel 3LF, a right front wheel 3RF, a left rear wheel 3LR, and a right rear wheel 3RR (hereinafter collectively referred to as "wheels 3" unless a distinction is required). In this embodiment, the driving force source 21 can be, for example, a known electric motor arranged on the front wheel side.

[0015] In this embodiment, the electric motors serving as the driving force source 21 may be arranged one each on the front wheel side and the rear wheel side, or one electric motor may be arranged for each wheel 3. In addition to the electric motor described above, the driving force source 21 may further include an internal combustion engine such as a gasoline engine, a diesel engine, or a gas turbine engine.

[0016] A power supply system that supplies desired power to such a driving force source 21 includes a fuel cell stack FC configured by stacking a plurality of known fuel cells such as PEFC (polymer electrolyte fuel cells), a hydrogen gas supply unit including a known hydrogen tank 23 and piping, an air supply unit including a known compressor 31 and piping, a known secondary battery 50 such as a lithium ion secondary battery or a lead storage battery, a known converter 22, and a control device 100 that controls these. Note that the control device 100 in this embodiment also functions as a deterioration determination device 10 that determines deterioration of the fuel cell stack FC. In this power supply system, each of the fuel cell stack FC and the secondary battery 50 is capable of supplying power to a load including the electric motor described above.

[0017] As shown in Fig. 2, the fuel cell stack FC is connected to a load including a driving force source 21 (electric motor) via the above-mentioned converter 22 and wiring. Also as shown in Fig. 2, the current and voltage in the fuel cell stack FC are detected by a well-known current sensor SR1 and voltage sensor SR2, respectively.

[0018] Converter 22 includes a known AC / DC converter that converts DC current to AC current, and a known DC / DC converter that adjusts the voltage of DC current to a desired voltage. As an example, converter 22 in this embodiment has a function of receiving a control signal from control device 100 to set the output voltage generated and output by fuel cell stack FC, and a function of boosting the power generated by fuel cell stack FC to a desired voltage when supplying the power to a load.

[0019] In addition, the fuel cell vehicle FCV of this embodiment is equipped with the above-mentioned driving force source 21, electric steering device 8, and brake devices 4LF, 4RF, 4LR, and 4RR (hereinafter collectively referred to as "brake device 4" unless a distinction is required) as equipment used for driving control.

[0020] The driving force source 21 outputs a driving torque that is transmitted to the front drive shaft 2F and the rear drive shaft 2R via a transmission, a front wheel differential mechanism 5F, and a rear wheel differential mechanism 5R (not shown). The driving force source 21 and the transmission are controlled by one or more electronic control units (ECUs). The control is performed by a known control device including:

[0021] The front-wheel drive shaft 2F is provided with an electric steering device 8. The electric steering device 8 includes an electric motor and a gear mechanism (not shown), and is controlled by a vehicle drive control device 20 to adjust the steering angles of the left front wheel 3LF and the right front wheel 3RF.

[0022] The vehicle drive control device 20 includes one or more known electronic control devices (ECUs) that control the drive of a drive force source 21 that outputs drive torque for the fuel cell vehicle FCV, an electric steering device 8 that controls the steering wheel 9 or the steering angle of the steering wheels, and a brake device 4 that controls the braking force of the fuel cell vehicle FCV. The vehicle drive control device 20 may also have a function of controlling the drive of a transmission that changes the speed of the output output from the drive force source 21 and transmits it to the wheels 3.

[0023] Also, as shown in FIG. 2, in a hydrogen gas supply section for supplying fuel (hydrogen) gas to the fuel cell stack FC, hydrogen gas stored in a hydrogen tank 23 is supplied to the anode side flow path of the above-mentioned fuel cell stack FC via a hydrogen intake valve 32a having a known structure installed in the hydrogen supply flow path.

[0024] A portion of the hydrogen gas discharged from the fuel cell stack FC may be returned to the hydrogen supply flow path by a circulation flow path and a known circulation pump 45. The remainder of the hydrogen gas discharged from the fuel cell stack FC is diluted by a diluter 41 at a predetermined timing via the opening and closing operation of a known hydrogen exhaust valve 32b under the control of the control device 100, and then released (exhausted) into the atmosphere.

[0025] 2, the air supply unit for supplying oxygen gas (air) to the fuel cell stack FC is configured to include, in addition to the above-mentioned compressor 31, a known oxygen intake valve 32c and an air exhaust valve (back pressure valve) 32d that adjust the amount of oxygen (air) supplied to the fuel cell 1. In addition, this air supply unit may further include a known flow rate sensor (not shown) that can measure the flow rate of air supplied to the fuel cell stack FC.

[0026] The air taken in by the compressor 31 is supplied to the cathode-side flow path in the fuel cell stack FC via the oxygen intake valve 32c and a known humidifier (not shown). The air supplied to the fuel cell 1 is supplied to the diluter 41 as cathode off-gas under the control of the oxygen exhaust valve (back pressure valve) 32d by the control device 100.

[0027] The control device 100 includes one or more processors (CPUs (Central Processing Units) ) and one or more memories communicatively connected to the one or more processors. The control device 100 may be configured to be connectable to a known external network NET such as the Internet via various known communication devices CD, such as a form that uses a smartphone, for example.

[0028] Such a control device 100 may be connected directly or through a CAN (Controller Area Network) or The compressor 31 and each valve 32 are connected to each other via a communication means such as LIN (Local Inter Net). (hydrogen intake valve 32a, hydrogen exhaust valve 32b, oxygen intake valve 32c, and oxygen exhaust valve 32d), well-known sensors SR such as a current sensor SR1 and a voltage sensor SR2 are electrically connected.

[0029] The fuel cell stack FC of this embodiment has a stack structure in which a plurality of known fuel cell cells, each having an electromotive force of, for example, about 1 V, are connected in series and stacked on top of each other. As an example, the fuel cell stack FC of this embodiment can be a polymer electrolyte fuel cell (PEFC) having a structure in which fuel cell cells are connected in series within a pair of known end plates that hold the fuel cells under pressure at both ends to provide the system voltage required by the fuel cell vehicle FCV.

[0030] Each fuel cell constituting the fuel cell stack FC has a structure in which a known MEA (membrane electrode assembly) is interposed between a pair of known separators installed on the fuel electrode side and the air electrode side. This MEA is configured to include at least a known cathode catalyst layer, a known anode catalyst layer arranged opposite to the cathode catalyst layer, and a known polymer electrolyte membrane arranged between the cathode catalyst layer and the anode catalyst layer. The membrane electrode assembly may further include a known air electrode side gas diffusion layer and a known fuel electrode side gas diffusion layer. Among them, the cathode catalyst layer in this embodiment is in a form in which a known catalytic metal, such as precious metal fine particles such as platinum (Pt) nanoparticles and platinum-cobalt (Pt-Co) particles, is bonded to a catalyst support exemplified by a metal material such as stainless steel or titanium, or a carbon material.

[0031] <Deterioration determination device 10> Next, a deterioration determination device 10 capable of determining deterioration of a catalyst in the fuel cell stack FC in this embodiment will be described with reference to Fig. 3. That is, the deterioration determination device 10 in this embodiment is configured to have a function of determining deterioration of a catalyst in the fuel cell stack FC, including a catalyst metal and a catalyst carrier that supports the catalyst metal.

[0032] The deterioration determination device 10 includes a current measurement unit 10A, a voltage measurement unit 10B, an impedance measurement unit 10C, and a deterioration determination unit 10D. As described above, the deterioration determination device 10 is configured as one function executed by the control device 100 of the present embodiment. As shown in FIG. 3, the control device 100 includes a drive control unit 30 and a presentation control unit 40.

[0033] The current measurement unit 10A is configured to have the function of measuring the current value of the fuel cell stack FC described above. More specifically, the current measurement unit 10A of this embodiment can measure the value of the current flowing through the fuel cell stack FC via the current sensor SR1 described above.

[0034] The voltage measurement unit 10B is configured to have the function of measuring the voltage value of the fuel cell stack FC described above. More specifically, the voltage measurement unit 10B of this embodiment can measure the voltage value applied to the fuel cell stack FC via the voltage sensor SR2 described above.

[0035] The impedance measuring unit 10C is configured to have a function of applying a measurement AC signal to the fuel cell stack FC to measure the AC impedance of the fuel cell stack FC. The impedance measuring unit 10C can measure the impedance of the fuel cell stack FC by, for example, a known AC impedance method based on the current and voltage values ​​of the fuel cell.

[0036] The deterioration determination unit 10D is configured to have a function of determining whether the catalyst of the fuel cell constituting the fuel cell stack FC has deteriorated based on the characteristics of the measured AC impedance. More specifically, the deterioration determination unit 10D of this embodiment can determine whether the catalyst metal or the catalyst support of the fuel cell has deteriorated by the following procedure.

[0037] First, the deterioration determining unit 10D calculates a Nyquist diagram based on the AC impedance measured as described above, as shown in FIG. Next, the deterioration determination unit 10D defines the arc radius Rh on the high frequency side in the calculated Nyquist diagram as the degree of activation overvoltage, and the arc radius Rl on the low frequency side in the Nyquist diagram as the degree of diffusion overvoltage. In other words, the deterioration determination unit 10D of this embodiment estimates the degree of activation overvoltage in the fuel cell stack FC as the degree of deterioration of the catalyst metal, and estimates the degree of diffusion overvoltage as the degree of deterioration of the catalyst support.

[0038] In the fuel cell vehicle FCV of this embodiment, as shown in FIG. 8, reference values ​​of activation overvoltage and diffusion overvoltage with respect to vehicle mileage are stored in advance in the memory device MR. Such reference values ​​indicate the standard degree of deterioration of the catalyst metal and catalyst carrier when the mileage is accumulated. The deterioration determination unit 10D is capable of reading out the reference values ​​of activation overvoltage and diffusion overvoltage with respect to vehicle mileage by referring to the memory device MR. The reference values ​​of activation overvoltage and diffusion overvoltage with respect to vehicle mileage described above can be calculated in advance by experiments or simulations using a vehicle.

[0039] Therefore, the deterioration judgment unit 10D judges the degree of deterioration (which can also be said to be the progress of deterioration) of the catalyst metal and catalyst support based on the arc radius (degree of activation overvoltage) on the high frequency side and the arc radius (degree of diffusion overvoltage) on the low frequency side in the calculated Nyquist diagram, and the reference values ​​of the activation overvoltage and diffusion overvoltage for the vehicle traveling distance stored in advance.

[0040] Specifically, when the arc radius (degree of activation overvoltage) on the high frequency side in the Nyquist diagram increases over a certain travel distance as shown in Fig. 6, the deterioration determination unit 10D calculates the increased arc radius on the high frequency side. Note that a known approximation method can be applied to the calculation of the arc radius described above, and for example, the arc radius can be obtained using a known approximation method such as the least squares method based on a plurality of measurement points on the high frequency side in the calculated Nyquist diagram.

[0041] Then, the deterioration determination unit 10D compares the calculated high-frequency side arc radius with the reference value of the activation overvoltage (high-frequency semicircle diameter) for the vehicle travel distance illustrated in Fig. 8, and calculates the degree of difference between the calculated high-frequency side arc radius and the reference value. For example, when the deterioration determination is performed when the fuel cell vehicle FCV has traveled 700 km, the high-frequency side arc radius is compared with the reference value a2.

[0042] The deterioration determination unit 10D can determine that the deterioration of the catalyst metal is progressing when the calculated high-frequency side arc radius exceeds a reference value a2, for example. Note that in this embodiment, it is determined that the deterioration is progressing when the calculated high-frequency side arc radius exceeds a reference value, but it may also be determined that the deterioration is progressing when the calculated high-frequency side arc radius exceeds a reference value, for example, by setting an appropriate range to around several to 10% of the reference value.

[0043] In addition, when the arc radius (degree of diffusion overvoltage) on the low-frequency side in the Nyquist diagram increases at a certain travel distance as shown in FIG. 7, the deterioration determination unit 10D calculates the increased arc radius on the low-frequency side in the same manner as described above. Then, the deterioration determination unit 10D compares the calculated low-frequency side arc radius with the reference value of the diffusion overvoltage (low-frequency semicircle diameter) for the vehicle travel distance illustrated in Fig. 8, and calculates the degree of difference between the calculated low-frequency side arc radius and the reference value. For example, when the deterioration determination is performed when the fuel cell vehicle FCV has traveled 1700 km, the low-frequency side arc radius is compared with the reference value b4.

[0044] The deterioration determination unit 10D can determine that the deterioration of the catalyst carrier is progressing when the calculated arc radius on the low frequency side exceeds a reference value b4, for example. Note that in this embodiment, it is determined that the deterioration is progressing when the calculated arc radius on the low frequency side exceeds a reference value, but it may also be determined that the deterioration is progressing when the calculated arc radius on the low frequency side exceeds the reference value, for example, by setting an appropriate range to around several to 10% of the reference value.

[0045] The drive control unit 30 is configured to have a function of controlling the drive of the fuel cell stack FC. More specifically, when the deterioration determination unit 10D determines that the deterioration of the catalyst carrier is progressing (i.e., the deterioration progresses quickly on the diffusion overvoltage side), the drive control unit 30 may reduce the rate of change of voltage per unit time during acceleration / deceleration operation of the fuel cell vehicle FCV. More specifically, when the rate of change of voltage per unit time as shown in FIG. 9 is set as a standard state, the drive control unit 30 may perform control to reduce the rate of change of voltage per unit time during acceleration / deceleration operation of the fuel cell vehicle FCV, as shown in FIG. 10.

[0046] Furthermore, when the deterioration determination unit 10D determines that the deterioration of the catalyst carrier is advanced, the drive control unit 30 may execute control to delay the timing of introducing air into the cathode electrode at the start of the fuel cell stack FC from the normal time, as illustrated in Fig. 11. More specifically, in a state where the deterioration progresses to a normal level, when the system of the fuel cell vehicle FCV is turned ON and a start request for the fuel cell stack FC is generated at time t1, as shown in Fig. 11, normally, the supply of hydrogen gas to the anode side flow passage via the hydrogen intake valve 32a is started at time t2, and then the supply of air to the cathode side flow passage via the oxygen intake valve 32c, etc. is started at time t3. In contrast, when the deterioration determination unit 10D determines that the deterioration of the catalyst carrier is advanced, the drive control unit 30 can execute control to delay the supply of air to the cathode side flow passage until time t4, which is later than time t3.

[0047] The degree of delay from time t3 to time t4 may be set according to the degree of deterioration of the catalyst carrier, for example. That is, the drive control unit 30 can set time t4 with a larger degree of delay as the degree of deterioration of the catalyst carrier increases.

[0048] On the other hand, when the deterioration determination unit 10D determines that the deterioration of the catalyst metal is progressing (i.e., the rate of deterioration is fast on the activation overvoltage side), the drive control unit 30 can execute control to suppress the upper limit voltage value of the fuel cell stack FC used in the fuel cell vehicle FCV, as exemplified in Fig. 12. More specifically, when the upper limit voltage value of the fuel cell stack FC is set to V0 when the rate of deterioration is standard, the drive control unit 30 can set the upper limit voltage value to V1, lowering it from V0 by Vd. The above-mentioned degree of voltage drop Vd may be set appropriately depending on the vehicle model, the specifications of the electric motor, etc.

[0049] At this time, the drive control unit 30 may suppress the upper limit voltage value of the fuel cell stack FC used in the fuel cell vehicle FCV in accordance with the deterioration on the activation voltage side. More specifically, when comparing the arc radius on the high frequency side with a reference value corresponding to the travel distance at that time, the greater the degree of exceedance from the reference value, the greater the suppression of the upper limit voltage value.

[0050] The presentation control unit 40 executes a process of presenting various information such as the deterioration state of the fuel cell stack FC via a presentation device DD including a known in-vehicle speaker SP and display DP. The presentation control unit 40 may present the above-mentioned various information to the occupant via the presentation device DD mounted in the vehicle, or may perform control to access and present the information on an external terminal such as a smartphone carried by the occupant.

[0051] <Method for preventing deterioration of catalytic metal and catalyst carrier> Next, a method for suppressing deterioration of a catalyst metal and a catalyst support that can be executed by a control device 100 including the deterioration determination device 10 in this embodiment will be described with reference to Fig. 4. The deterioration suppression method may be used as an algorithm of a computer-readable program. A program having such an algorithm may be distributed so as to be downloadable to a fuel cell vehicle FCV via a known network, for example, or may be distributed in the form of being stored on a recording medium. In the following, an example will be described in which the user activates the system of a fuel cell vehicle FCV and starts driving.

[0052] First, in step 1, the control device 100 determines whether a deterioration determination condition for the fuel cell stack FC is satisfied. More specifically, the control device 100 may determine whether the fuel cell stack FC has reached an appropriate temperature based on a known temperature sensor (not shown) to determine whether the fuel cell stack FC is in a state where it can be stably driven. Furthermore, the control device 100 may determine whether the moisture content state of the fuel cell stack FC has reached an appropriate state based on a known moisture content measurement method as exemplified in, for example, Patent Document 2.

[0053] If the deterioration judgment condition is satisfied in step 1, the control device 100 judges whether or not the carrier deterioration suppression condition is satisfied in the following step 2. More specifically, in step 2A, the deterioration judgment unit 10D calculates a Nyquist diagram based on the measured AC impedance. Next, the deterioration judgment unit 10D uses the calculated Nyquist diagram and a reference value stored in the memory device MR to obtain the difference between the low-frequency side arc radius (degree of diffusion overvoltage) and the reference value, and judges the deterioration progress of the catalyst carrier.

[0054] If it is determined in step 2A that the deterioration of the catalyst carrier is more advanced than the reference value (Yes in step 2A), the process proceeds to step 2B, where a carrier deterioration suppression process is executed. That is, in step 2B, the control device 100 (drive control unit 30) can execute at least one of the following: (α) control to reduce the rate of change of voltage per unit time during acceleration / deceleration operation of the fuel cell vehicle FCV as exemplified in Fig. 10, and (β) control to delay the timing of introducing air into the cathode electrode at the start of the fuel cell stack FC from the normal time as exemplified in Fig. 11.

[0055] On the other hand, if it is determined in step 2A that the deterioration of the catalyst carrier is within the reference value range (deterioration is not as advanced as expected) (No in step 2A), the process proceeds to step 3A, where it is determined whether the catalyst deterioration suppression condition is satisfied. That is, in step 3A, the deterioration determination unit 10D calculates a Nyquist diagram based on the measured AC impedance. Next, using the calculated Nyquist diagram and the reference value stored in the memory device MR, the deterioration determination unit 10D determines the deterioration progress of the catalyst metal by finding the difference between the high frequency side arc radius (degree of activation overvoltage) and the reference value.

[0056] If it is determined in step 3A that the deterioration of the catalytic metal is more advanced than the reference value (Yes in step 3A), the process proceeds to step 3B, where a catalytic metal deterioration suppression process is executed. That is, in step 3B, the control device 100 (drive control unit 30) may execute control to suppress the upper limit voltage value of the fuel cell stack FC used in the fuel cell vehicle FCV, as exemplified in FIG.

[0057] Next, in step 4, the control device 100 determines whether the system of the fuel cell vehicle FCV has been turned off, and if it has not yet been turned off (No in step 4), the control device 100 returns to step 1 and repeats the above-mentioned processing. On the other hand, if the system of the fuel cell vehicle FCV has been turned off in step 4 (Yes in step 4), the above-mentioned method for suppressing deterioration of the catalyst metal and catalyst support is terminated.

[0058] According to the above-described method for suppressing deterioration of the catalyst metal and catalyst support, deterioration of the catalyst metal and catalyst support can be clearly distinguished using the high-frequency side arc radius (degree of activation overvoltage) and the low-frequency side arc radius (degree of diffusion overvoltage) derived from the Nyquist diagram. Furthermore, according to the control device 100 of this embodiment, when corrosion progresses at a rate faster than expected in either of these, it is possible to suppress the progress of deterioration in the catalyst by correcting the operating parameters of the fuel cell described above.

[0059] <Computer programs and recording media> The computer program that realizes each of the functions of the deterioration determination device 10 described above is a computer program applied to a fuel cell deterioration determination device that determines the deterioration of a catalyst including a catalytic metal in a fuel cell stack and a catalyst carrier supporting the catalytic metal, and can cause one or more processors to execute processes including applying an AC signal to the fuel cell stack to measure the AC impedance of the fuel cell stack, estimating the degree of activation overvoltage in the fuel cell stack as deterioration of the catalytic metal based on the characteristics of the measured AC impedance, and estimating the degree of diffusion overvoltage as deterioration of the catalyst carrier, and determining the progress of deterioration of the catalytic metal and the catalyst carrier based on previously stored reference values ​​of activation overvoltage and diffusion overvoltage for the vehicle mileage.

[0060] Furthermore, the computer program realizing each function of the control device 100 including the deterioration determination device 10 may execute, in addition to the above-mentioned algorithm, suppressing the upper limit voltage value of the fuel cell vehicle in accordance with the deterioration on the activation voltage side when it is determined that the deterioration progress is rapid on the activation overvoltage side. Also, in addition to the above-mentioned algorithm, the computer program realizing each function of the control device 100 including the deterioration determination device 10 may execute, in addition to the above-mentioned algorithm, at least one of (α) decreasing the rate of change of voltage per unit time during acceleration / deceleration operation of the fuel cell vehicle and (β) delaying the timing of introducing air into the cathode electrode at the start of the fuel cell compared to normal times when it is determined that the deterioration progress is rapid on the diffusion overvoltage side.

[0061] Furthermore, such a computer program may be in a form stored in a known recording medium as described above, or in a form downloaded to the fuel cell vehicle FCV from a known server such as the cloud.

[0062] [Second embodiment] Hereinafter, the deterioration determination device for a fuel cell according to the second embodiment will be described with reference to Figures 13 and 14. In the above-mentioned first embodiment, a Nyquist diagram was generated from the measured AC impedance to determine the deterioration progress of the catalyst metal and catalyst support, respectively. In contrast, the deterioration determination device of the second embodiment is mainly characterized in that it does not require the generation of a Nyquist diagram, and determines the deterioration progress of the catalyst metal and catalyst support, respectively, based on a plurality of measurement points obtained from the AC impedance.

[0063] Therefore, in the following description of the second embodiment, the above-mentioned features will be mainly described, and components having the same functions as those in the first embodiment described above will be given the same reference numbers, and descriptions of such components will be omitted as appropriate.

[0064] That is, in this embodiment, after the deterioration determination condition is satisfied in step 1, the control device 100 extracts a plurality of measurement points based on the measured AC impedance in step 2A. More specifically, as shown in Fig. 13, the deterioration determination unit 10D extracts a plurality of measurement points in each of the high frequency side region and the low frequency side region based on the measured AC impedance. The boundary between the high frequency side region and the low frequency side region can be set, for example, at the central inflection point K (the inflection point sandwiched between the inflection point of the high frequency side region and the inflection point of the low frequency side region; see Fig. 13) when the Nyquist diagram is generated.

[0065] In FIG. 13, in this embodiment, three and two measurement points are extracted in the high frequency side region and the low frequency side region, respectively. However, the present invention is not limited to this form, and any number of measurement points may be extracted in the high frequency side region and the low frequency side region as long as it does not require the generation of a Nyquist diagram. As shown in FIG. 13, in this embodiment, a diagram in which measurement points are extracted to the extent that a Nyquist diagram cannot be generated based on the measured AC impedance is referred to as a "catalyst deterioration determination diagram."

[0066] Next, in step 2A, the control device 100 determines the degree of deterioration of the catalytic metal and the catalytic support based on the reference values ​​of activation overvoltage and diffusion overvoltage for the vehicle mileage previously stored in steps 2A and 3A, respectively, based on a method similar to that of the first embodiment described above.

[0067] For example, when the high frequency side plot (measurement point) changes in the catalyst deterioration determination diagram as shown in Fig. 14, the control device 100 calculates the arc radius by applying the above-mentioned known approximation method based on the position of this increased high frequency side plot. Thereafter, as in the first embodiment, the control device 100 compares the calculated high frequency side arc radius with the reference value of the activation overvoltage (high frequency semicircle diameter) for the vehicle travel distance, and calculates the degree of difference between the calculated high frequency side arc radius and the reference value.

[0068] 14 shows an example in which the high frequency side plot (measurement point) has changed in the catalyst deterioration judgment diagram, but the degree of deterioration of the catalyst carrier can be found in the same way when the low frequency side plot has changed. That is, the control device 100 compares the calculated low frequency side arc radius with a reference value of the diffusion overvoltage (low frequency semicircle diameter) for the vehicle travel distance, and calculates the degree of difference between the calculated low frequency side arc radius and the reference value.

[0069] In this way, in the catalyst deterioration judgment diagram of the second embodiment, the central inflection point K is used as the boundary, and the displacement of the measurement points belonging to the region on the higher frequency side of the central inflection point K is used to estimate the degree of deterioration of the catalyst metal, while the displacement of the measurement points belonging to the region on the lower frequency side of the central inflection point K is used to estimate the degree of deterioration of the catalyst support.

[0070] As a result, with the control device 100 and fuel cell vehicle FCV including the deterioration determination device 10 of the second embodiment, although the approximation accuracy of the arc radius is slightly reduced, it is possible to clearly distinguish between deterioration of the catalyst metal and the catalyst support in the same manner as in the first embodiment described above while reducing the computational load on the control device.

[0071] Although the preferred embodiment of the present disclosure has been described in detail above with reference to the attached drawings, the technology of the present disclosure is not limited to such examples. It is clear that a person having ordinary knowledge in the technical field to which the present disclosure belongs can conceive of various modified or amended examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. [Explanation of symbols]

[0072] 10 Deterioration determination device 20 Vehicle drive control device 30 Drive control unit 40 Presentation control unit FC Fuel Cell Stack FCV fuel cell vehicle

Claims

1. A deterioration determination device for a fuel cell that determines deterioration of a catalyst in a fuel cell stack, the catalyst including a catalyst metal and a catalyst carrier that supports the catalyst metal, comprising: an impedance measurement unit that applies an AC signal to the fuel cell stack to measure the AC impedance of the fuel cell stack; a deterioration determination unit that estimates the degree of activation overvoltage in the fuel cell stack as deterioration of a catalytic metal based on the measured characteristics of the AC impedance, and estimates the degree of diffusion overvoltage as deterioration of a catalyst support, and determines the degree of deterioration of the catalytic metal and the catalyst support based on previously stored reference values ​​of activation overvoltage and diffusion overvoltage for a vehicle mileage; A deterioration determination device for a fuel cell comprising:

2. The deterioration determination unit is Calculating a Nyquist diagram based on the AC impedance; The calculated arc radius on the high frequency side in the Nyquist diagram is defined as the degree of activation overvoltage, and the calculated arc radius on the low frequency side in the Nyquist diagram is defined as the degree of diffusion overvoltage, determining the degree of deterioration of the catalytic metal and the catalytic support; The fuel cell deterioration determination device according to claim 1 .

3. The deterioration determination device according to claim 1 or 2, a fuel cell electrically connected to the deterioration determination device; A fuel cell vehicle comprising: a control device that controls the operation of the fuel cell, The control device includes: when it is determined that the deterioration progresses faster on the activation overvoltage side, an upper limit voltage value of the fuel cell vehicle is suppressed in accordance with the deterioration on the activation voltage side. Fuel cell car.

4. The control device includes: When it is determined that the deterioration rate is fast on the diffusion overvoltage side, (α) reducing the rate of change in voltage per unit time during acceleration and deceleration of the fuel cell vehicle; and (β) delaying the timing of introducing air into the cathode electrode at the start-up of the fuel cell compared to normal. The fuel cell vehicle according to claim 3.

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