JP2012104355A - Fuel cell system and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy consumption while measuring a change in the form of an electrode catalyst.SOLUTION: A fuel cell system equipped with fuel cells measures a form change index value which reflects the degree of a change in the form of a fuel cell electrode catalyst and, when the measured value of a form change index converges on a given value (YES in step S230), stops measuring the form change index value. Then, after the measurement has stopped, the fuel cell system determines whether a signal indicating that a change has occurred in any component in it has been received and, if it is found that the signal was received (YES in step S260), restarts measuring the form change index value.

Description

  The present invention relates to a fuel cell system including a fuel cell and a control method for the fuel cell system.

  In a fuel cell, the cathode catalyst may change its shape during its lifetime, resulting in a voltage drop. Therefore, a configuration has been proposed in which the degree of change in the shape of the cathode catalyst is measured and the measurement result is used as an index for replacement of the fuel cell (Patent Document 1). The measurement is performed based on, for example, cyclic voltammetry (CV) characteristics.

JP 2008-218097 A

  However, in the conventional technique, it is necessary to forcibly create a state for measurement when measuring the degree of change in the shape of the cathode catalyst. This caused a problem of consuming excess energy. Such a problem is not limited to the cathode catalyst but is common to the anode catalyst.

  An object of this invention is to aim at reduction of energy consumption, measuring the form change of an electrode catalyst.

  The present invention can be realized as the following forms or application examples in order to solve at least a part of the above-described problems.

Application Example 1 A fuel cell system including a fuel cell having an electrolyte layer and an electrode catalyst formed on the electrolyte layer,
An index value measurement unit that measures a shape change index value that reflects the degree of shape change of the electrode catalyst;
A measurement stop unit that stops measurement by the index value measurement unit when a change in the measured form change index value satisfies a predetermined condition;
A fuel cell system comprising: a measurement resumption unit that resumes measurement by the index value measurement unit when a change is made to a component included in the fuel cell system after the measurement is stopped.

  According to the fuel cell system described in the application example 1, the change in the form change index value satisfies a predetermined condition and the measurement of the form change index value is stopped until the components included in the fuel cell system are changed. The measurement of the period and form change index value can be stopped. For this reason, the period of measurement of a form change index value can be shortened, and consumption of energy required for measurement can be reduced.

[Application Example 2] The fuel cell system according to Application Example 1, wherein the predetermined condition is a condition indicating that the measured form change index value has converged to a constant value, or a time point at which the measured condition change index value converges to a certain value. A fuel cell system, which is a condition indicating that is predicted.

  According to the fuel cell system described in Application Example 1, when the measured form change index value converges to a constant value or when the time point at which the form change index value converges to a constant value is predicted, the measurement of the form change index value is stopped. It can be performed. Since it is already known that the shape change index value converges to a constant value when the shape change index value converges to a constant value, it is already known that the shape change index value converges to a constant value. There is no need for measurement, and there is no problem even if the measurement is stopped. Therefore, since the measurement by the index value measurement unit can be stopped early, the consumption of energy necessary for measurement can be further reduced.

Application Example 3 In the fuel cell system according to Application Example 1 or 2, the form change index value measured by the index value measurement unit for a predetermined period after the measurement is restarted by the measurement restart unit. When the post-resumption determination unit that determines whether or not the value is close to the constant value and the post-resumption determination unit determine that the form change index value is close to the constant value, the indicator A fuel cell system comprising: a measurement re-stop unit that stops measurement by the value measurement unit.

  According to the fuel cell system described in Application Example 1, by changing the components included in the fuel cell system, it is possible to cope with a decrease in the shape change index value, and the measurement by the measurement restarting unit is restarted. However, depending on the type of component to be changed, the shape change index value may not change. On the other hand, according to the fuel cell system described in the application example 3, the post-resumption determining unit determines whether or not the shape change index value is a value close to the constant value. Can be determined when the value is not different from the value before the component change. When the form change index value does not change from the value before the component change, the measurement is stopped and energy loss due to useless measurement is eliminated.

Application Example 4 In the fuel cell system according to Application Example 3, when the post-resumption determination unit determines that the form change index value is not a value close to the constant value, the index value measurement unit A fuel cell system comprising a measurement continuation unit that continues measurement by the measurement stop unit and determines whether the predetermined condition is satisfied by the measurement stop unit.

  According to the fuel cell system of Application Example 4, when it is determined that the form change index value is not close to the constant value, the measurement by the index value measurement unit is continued, and the measurement stop unit performs the measurement. It is determined whether a predetermined condition is satisfied. For this reason, even after the change of the components included in the fuel cell system, the measurement of the form change index value is continued, and when the change of the form change index value satisfies a predetermined condition, the measurement is stopped by the measurement stop unit. Therefore, the consumption of energy required for measurement can be further reduced.

Application Example 5 In the fuel cell system according to Application Examples 1 to 4, the index value measurement unit outputs the output of the fuel cell in a state where the supply amount of the reaction gas supplied to the fuel cell is constant. A fuel cell system configured to measure the form change index value based on a cyclic voltammetry characteristic of an output current of the fuel cell detected with a change in voltage.

  According to the fuel cell described in Application Example 5, the degree of change in the shape of the electrode catalyst can be measured with high accuracy.

Application Example 6 A control method of a fuel cell system including a fuel cell having an electrolyte layer and an electrode catalyst formed on the electrolyte layer,
Measure the morphological change index value reflecting the degree of morphological change of the electrode catalyst,
When the change in the measured form change index value satisfies a predetermined condition, the measurement of the form change index value is stopped,
A control method for a fuel cell system, wherein, after the measurement is stopped, measurement of the form change index value is resumed when a part included in the fuel cell system is changed.

  According to the control method of the fuel cell system described in Application Example 6, as in the fuel cell system described in Application Example 1, it is possible to reduce the consumption of energy necessary for measuring the form change index value.

  Furthermore, the present invention can be realized in various forms other than the above application examples 1 to 6, and for example, can be realized in the form of a vehicle equipped with the fuel cell system of the present invention.

It is explanatory drawing which shows the structure of the fuel cell system 1 as 1st Example of this invention. It is a current-potential curve diagram (voltamogram) showing the relationship between oxidation current and voltage and the relationship between reduction current and voltage by cyclic voltammetry. It is a flowchart which shows an index value measurement routine. It is a flowchart which shows a form change monitoring routine. It is a graph which shows how charge amount Q changes with progress of time. It is a graph which shows the stop time of the measurement in 2nd Example.

  Hereinafter, embodiments of the present invention will be described based on examples with reference to the drawings.

A. First embodiment:
FIG. 1 is an explanatory diagram showing a configuration of a fuel cell system 1 as a first embodiment of the present invention. In this embodiment, the present invention is applied to an in-vehicle power generation system for a fuel cell vehicle. As shown in FIG. 1, a fuel cell 2 that generates power by receiving reaction gas (oxidizing gas and fuel gas) and generates electric power accompanying the power generation, and an oxidizing gas that supplies air as oxidizing gas to the fuel cell 2. A piping system 3, a fuel gas piping system 4 for supplying hydrogen gas as fuel gas to the fuel cell 2, a power system 5 for charging / discharging system power, a control device 6 for controlling the entire system, and the like are provided.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells (cells) are stacked. The unit cell of the fuel cell 2 has a cathode electrode (air electrode) on one surface of an electrolyte made of an ion exchange membrane, an anode electrode (fuel electrode) on the other surface, and includes a cathode electrode and an anode electrode. For the electrode, for example, platinum Pt is used as a catalyst (electrode catalyst) based on a porous carbon material. Further, a pair of separators are provided so as to sandwich the cathode electrode and the anode electrode from both sides. Then, the fuel gas is supplied to the fuel gas channel of one separator, and the oxidizing gas is supplied to the oxidizing gas channel of the other separator, and the fuel cell 2 generates electric power by this gas supply. In addition to the solid molecular electrolyte type, various types such as a phosphoric acid type and a molten carbonate type can be adopted as the fuel cell 2.

  The fuel cell 2 includes a current sensor (current detection means) 2a for detecting current (output current) during power generation, a voltage sensor (voltage detection means) 2b for detecting voltage (output voltage), and the temperature of the fuel cell 2. A temperature sensor (temperature detection means) 2c for detection is attached.

  The oxidizing gas piping system 3 includes an air compressor 31, an oxidizing gas supply path 32, a humidification module 33, a cathode offgas flow path 34, a diluter 35, a motor M <b> 1 that drives the air compressor 31, and the like.

  The air compressor 31 is driven by the driving force of the motor M <b> 1 that operates according to the control command of the control device 6, and oxygen (oxidizing gas) taken from outside air through an air filter (not shown) is supplied to the cathode electrode of the fuel cell 2. Supply. A rotation speed detection sensor 3a for detecting the rotation speed of the motor M1 is attached to the motor M1. The oxidizing gas supply path 32 is a gas flow path for guiding oxygen supplied from the air compressor 31 to the cathode electrode of the fuel cell 2. Cathode off-gas is discharged from the cathode electrode of the fuel cell 2 through the cathode off-gas channel 34. The cathode off gas includes oxygen off gas after being subjected to the cell reaction of the fuel cell 2, and pumping hydrogen generated on the cathode side. This cathode off gas is in a highly moist state because it contains moisture generated by the cell reaction of the fuel cell 2.

  The humidification module 33 exchanges moisture between the low wet state oxidizing gas flowing through the oxidizing gas supply path 32 and the high wet state cathode off gas flowing through the cathode off gas flow path 34, and is supplied to the fuel cell 2. Humidify the gas moderately. The cathode off-gas channel 34 is a gas channel for exhausting the cathode off-gas outside the system, and an air pressure regulating valve A1 is disposed in the vicinity of the cathode electrode outlet of the gas channel. The back pressure of the oxidizing gas supplied to the fuel cell 2 is regulated by the air pressure regulating valve A1. The diluter 35 dilutes the hydrogen gas discharge concentration so that it falls within a preset concentration range (such as a range determined based on environmental standards). The diluter 35 communicates with the downstream of the cathode offgas channel 34 and the downstream of the anode offgas channel 44 described later. The hydrogen offgas and the oxygen offgas are mixed and diluted by the diluter 35 and exhausted outside the system.

  The fuel gas piping system 4 drives a fuel gas supply source 41, a fuel gas supply path 42, a fuel gas circulation path 43, an anode off-gas flow path 44, a hydrogen circulation pump 45, a check valve 46, and a hydrogen circulation pump 45. A motor M2 and the like are included.

  The fuel gas supply source 41 is a fuel gas supply means for supplying a fuel gas such as hydrogen gas to the fuel cell 2, and is constituted by, for example, a high-pressure hydrogen tank or a hydrogen storage tank. The fuel gas supply path 42 is a gas flow path for guiding the fuel gas discharged from the fuel gas supply source 41 to the anode electrode of the fuel cell 2, and the gas flow path includes a tank valve H1, hydrogen gas from upstream to downstream. Valves such as a supply valve H2 and an FC inlet valve H3 are provided. The tank valve H1, the hydrogen supply valve H2, and the FC inlet valve H3 are shut valves for supplying (or shutting off) the fuel gas to the fuel cell 2, and are constituted by, for example, electromagnetic valves.

  The fuel gas circulation path 43 is a return gas flow path for recirculating unreacted fuel gas to the fuel cell 2, and the gas flow path includes an FC outlet valve H4, a hydrogen circulation pump 45, and a check valve from upstream to downstream. 46 are arranged respectively. The low-pressure unreacted fuel gas discharged from the fuel cell 2 is moderately pressurized by the hydrogen circulation pump 45 driven by the driving force of the motor M <b> 2 that operates according to the control command of the control device 6, and is supplied to the fuel gas supply path 42. Led. The backflow of the fuel gas from the fuel gas supply path 42 to the fuel gas circulation path 43 is suppressed by the check valve 46. The anode off gas passage 44 is a gas passage for exhausting the anode off gas containing the hydrogen off gas discharged from the fuel cell 2 to the outside of the system, and a purge valve H5 is disposed in the gas passage.

  The power system 5 includes a high-voltage DC / DC converter 51, a battery 52, a traction inverter 53, an auxiliary inverter 54, a traction motor M3, an auxiliary motor M4, and the like.

  The high-voltage DC / DC converter (voltage conversion means) 51 is a direct-current voltage converter, and has a function of adjusting the direct-current voltage input from the battery 52 and outputting it to the traction inverter 53 side, and the fuel cell 2 or the traction motor M3. The voltage conversion means has a function of adjusting the DC voltage input from the battery and outputting it to the battery 52. The charge / discharge of the battery 52 is realized by these functions of the high-voltage DC / DC converter 51. Further, the output voltage of the fuel cell 2 is controlled by the high voltage DC / DC converter 51.

  The battery 52 is a chargeable / dischargeable secondary battery, and is composed of various types of secondary batteries, such as a nickel metal hydride battery. The battery 52 can be charged with surplus power or supplementarily supplied with power by control of a battery computer (not shown). Part of the direct-current power generated by the fuel cell 2 is stepped up and down by the high-voltage DC / DC converter 51 and charged in the battery 52. The battery 52 is attached with an SOC sensor 5a that detects a state of charge (SOC) of the battery 52. Instead of the battery 52, a chargeable / dischargeable battery other than the secondary battery, for example, a capacitor, may be employed.

  The traction inverter 53 and the auxiliary inverter 54 are pulse width modulation type PWM inverters, and convert DC power output from the fuel cell 2 or the battery 52 into three-phase AC power in accordance with a given control command, thereby obtaining a traction motor. Supplied to M3 and auxiliary motor M4. The traction motor M3 is a motor (vehicle drive motor) for driving the wheels 7L and 7R, and is an embodiment of a load power source. The traction motor M3 is provided with a rotation speed detection sensor 5b for detecting the rotation speed. The auxiliary motor M4 is a motor for driving various auxiliary machines, and is a generic term for M1 that drives the air compressor 31, a motor M2 that drives the hydrogen circulation pump 45, and the like.

  The control device 6 is constituted by a CPU, a ROM, a RAM, and the like, and integrally controls each part of the system based on each input sensor signal. Specifically, the control device 6 outputs the output of the fuel cell 2 based on each sensor signal sent from the accelerator pedal sensor 9, the SOC sensor 5a, the rotation speed detection sensors 3a, 5b, and the like that detect the rotation of the accelerator pedal. Calculate the required power. At this time, the control device 6 uses a shift lever or the like for selecting an operation mode (P: parking mode, R: reverse mode, N: neutral mode, D: drive mode, B: regenerative brake mode) of the traction motor M3. On the basis of a signal sent from the operation unit 8, whether or not there is an output request from the traction motor M <b> 3 is determined.

  Then, the control device 6 controls the output voltage and output current of the fuel cell 2 so as to generate output power corresponding to the output required power. Control device 6 controls output pulses of traction inverter 53 and auxiliary inverter 54, and controls traction motor M3 and auxiliary motor M4.

  Here, when oxygen is adsorbed on the catalyst layer of the fuel cell 2, the output voltage of the fuel cell 2 decreases. For this reason, the control device 6 temporarily stops the supply of oxygen to the fuel cell 2 and lowers the power generation voltage of the fuel cell 2 to the reduction region of the catalyst layer to perform a reduction process or a refresh process for activating the catalyst layer. To do.

  Further, when the form of each electrode catalyst of the fuel cell 2 changes and the activity of the catalyst decreases with time, predetermined power cannot be obtained from the fuel cell 2, so the control device 6 The degree of change in the shape of the electrode catalyst of the fuel cell 2 is measured. This measurement relates to the present invention, and the control device 6 realizes a function as the index value measurement unit 6a. The control device 6 further realizes functions as a measurement stop unit 6b, a reception determination unit 6c, and a measurement restart unit 6d that perform control related to the index value measured by the index value measurement unit 6a. Details of the respective parts 6a to 6d will be described later.

  When the electrode catalyst of the fuel cell 2 is in an activated state, the output voltage of the fuel cell 2 is cycled from a low voltage → a high voltage → a low voltage by the high voltage DC / DC converter (current conversion means) 51. When voltammetry (CV) is measured, a voltammogram as shown in FIG. 2 is obtained. In this voltammogram, several characteristic parts appear due to the difference in the reaction that occurs depending on the voltage to be swept. By using this characteristic part, a morphological change index value that reflects the degree of morphological change of the electrode catalyst is measured.

That is, when the voltage is increased from a low voltage, an oxidation current flows through the fuel cell 2, and the voltammogram in FIG. 2 shows changes such as the characteristics I1 and I2. The case where the oxidation current flows means that the electrode catalyst of the fuel cell 2 is in the oxidation region. For example, in a predetermined voltage range (voltage sweep range), as shown by the characteristic I1 (oxidation current I1) in FIG. If H ⁺ + e ⁻ is generated and the voltage sweep range is further increased, as shown by the characteristic I2 (oxidation current I2), Pt + H ₂ O → Pt · OH + 2H + 2e ⁻ is generated as a reaction by electrolysis of water.

When the voltage is lowered from this state, a reduction current flows through the fuel cell 2, and the voltammogram in FIG. 2 shows changes such as the characteristics I3 and I4. The case where the reduction current flows means that the electrode catalyst of the fuel cell 2 is in the reduction region. For example, when the voltage is changed over a predetermined range under the condition that the output current of the fuel cell 2 indicates a reduction current, as shown by the characteristic I3 (reduction current I3), as a reaction of desorption of water, Pt OH + 2H ⁺ + 2e ⁻ → Pt + H ₂ O is generated, and when the voltage is further lowered, as shown by characteristic I4 (reduction current I4), as a reaction in which hydrogen ions are adsorbed to Pt, Pt + H ⁺ + e ⁻ → Pt · H is Arise.

  Cyclic voltammetry (CV) is measured and a voltammogram is obtained. For example, when the oxidation current I1 is integrated, the charge amount Q [C] associated with the desorption of hydrogen is calculated from the time per unit area and the current value. Can be sought. On the other hand, when the reduction current I3 is integrated, the charge amount Q [C] accompanying water desorption can be obtained from the time per unit area and the current value. These charge amounts Q correspond to the effective area of the electrode catalyst, and the effective area of the electrode catalyst becomes smaller as the degree of change in the shape of the electrode catalyst becomes larger. Can do.

  That is, by measuring cyclic voltammetry (CV) that measures current while repeatedly scanning the applied voltage of the fuel cell 2 within a certain range under the condition that the electrode catalyst is activated, the effectiveness of the electrode catalyst is improved. The area can be detected with high accuracy, and as a result, the morphological change index value reflecting the degree of morphological change of the electrode catalyst can be measured with high accuracy.

  In this case, the control device 6 monitors the detected voltage of the voltage sensor 2b on the condition that the activation process for the electrode catalyst of the fuel cell 2 is performed, and accompanies the change in the output voltage of the fuel cell 2. The effective area of the electrode catalyst is calculated based on the current detected by the current sensor 2a, and functions as an index value measuring unit that measures this effective area as a form change index value.

  Measurement of the shape change index value of the electrode catalyst is performed when the fuel cell 2 is intermittently operated. The intermittent operation of the fuel cell means that the power supply from the fuel cell is temporarily requested from the system when the vehicle equipped with the fuel cell is stable and the vehicle can be driven only by the power supply from the battery. An operation mode that suppresses the noise. During the intermittent operation, the supply of the oxidizing gas or the fuel gas to the fuel cell 2 can be stopped or changed. The refresh process for activating the electrode catalyst uses this intermittent operation, and is a process for temporarily stopping the supply of the oxidizing gas and operating the fuel cell 2 in the reduction region to activate the electrode catalyst. .

  Here, when the supply of the oxidizing gas is stopped for the refresh process, the output voltage of the fuel cell decreases. The fuel cell 2 is operated by passing through the region of the characteristic I3 or characteristic I4 of the voltammogram of FIG. If the output current at this time is detected, the voltammetric characteristics are measured. Therefore, by monitoring the characteristic features corresponding to the characteristics I3 and I4, the electrode catalyst, more precisely, the cathodic electrode catalyst (hereinafter, “ The shape change index value of “cathode catalyst”) can be measured.

  FIG. 3 is a flowchart showing an index value measurement routine for measuring the shape change index value of the cathode catalyst. This index value measurement routine is started when it is determined that intermittent operation is necessary from the request of the system. When the process is started, the control device 6 first determines whether or not the index value measurement prohibition flag F is 1 (step S110). The index value measurement prohibition flag F is a flag for storing the prohibition of index value measurement. If it is determined in step S110 that the index value measurement prohibition flag F is 1, the process returns to “RETURN” and the index value measurement routine ends. On the other hand, if it is determined in step S110 that the index value measurement prohibition flag F is not a value 1, that is, a value 0, the processing from step S120 is executed.

  In step S120, the intermittent operation is started as the refresh operation with the refresh process (reduction process) as in the case where there is no output request. For example, the control device 6 stops the driving of the air compressor 31 with respect to the motor M1, stops the supply of oxidizing gas (air) supplied from the air compressor 31 to the fuel cell 2 via the humidification module 33, and the voltage sensor. While monitoring the output voltage of 2b, the conversion output of the high-voltage DC / DC converter 51 is controlled, and the output voltage (total voltage) of the fuel cell 2 is reduced to a voltage for activating the cathode catalyst of the fuel cell 2. .

  Since the secondary side of the high-voltage DC / DC converter 51 is connected in parallel with the output terminal of the fuel cell 2, power conversion processing is performed on the high-voltage DC / DC converter 51 to reduce the voltage on the secondary side. If it does, even if the power generation voltage is higher than the secondary side voltage of the converter 51, the fuel cell 2 is forcibly regulated by the secondary side voltage of the converter 51, and the current value increases according to the IV characteristic. . That is, since the upper limit value of the power generation voltage of the fuel cell 2 is defined by the secondary side voltage of the converter 51, the output voltage (total voltage) of the fuel cell 2 is controlled by controlling the conversion output of the high-voltage DC / DC converter 51. Can be reduced to a voltage for activating the cathode catalyst of the fuel cell 2.

  Next, the control device 6 keeps the output voltage (total voltage) of the fuel cell 2 within a certain range under the condition of dV / dt = constant when the activation treatment for the cathode catalyst of the fuel cell 2 is performed. Control for scanning (voltage sweep) is performed on the high-voltage DC / DC converter 51 (step S130). For example, the control device 6 sequentially controls the conversion output to the high-voltage DC / DC converter 51 so that the characteristic I3 (reduction current I3) of FIG. 2 is obtained as a measurement of cyclic voltammetry (CV). When the output voltage (total voltage) of the fuel cell 2 changes over a certain range, the output current changes as the output voltage of the fuel cell 2 changes. At this time, the current detected by the current sensor 2a is a reduction current I3.

  Subsequently, the control device 6 integrates the reduction current I3, and calculates a charge amount Q accompanying water desorption from the time per unit area and the current value (step S140). The calculated charge amount Q serves as a form change index value that reflects the degree of form change of the cathode catalyst, and is stored in the RAM. After execution of step S140, the process returns to “return”, and the index value measurement routine is temporarily terminated. A function realized by the control device 6 executing this index value measurement routine corresponds to the index value measurement unit 6a (FIG. 1).

  A form change monitoring routine for monitoring the form change of the electrode catalyst using the form change index value measured in the index value measurement routine will be described next. FIG. 4 is a flowchart of the form change monitoring routine. This form change monitoring routine is executed by the control device 6, and after the ignition switch of the vehicle is first operated, it is continuously executed with interruption every predetermined time even if the ignition switch is turned off. . When the process is started, the control device 6 first sets the index value measurement prohibition flag F to 0 as an initial setting (step 210).

  Next, the control device 6 extracts the charge amount Q stored in the RAM in step S140 of the index value measurement routine (step S220), and determines whether or not the charge amount Q has converged to a constant value (step S230). If it is determined that the charge amount Q has not converged to a certain value, the process returns to step S220, and steps S220 and S230 are repeatedly executed. In step S230, it is determined that the charge amount Q has converged to a constant value when the change in the charge amount Q for the past multiple times extracted from step S220 is within a predetermined value.

  FIG. 5 is a graph showing how the charge amount Q changes with time. FIG. 5A is a graph of the entire lifetime, and FIG. 5B is a graph in which a part of FIG. 5A is enlarged. The horizontal axis indicates the time (elapsed time) from when the ignition switch of the vehicle is first operated, and the vertical axis indicates the charge amount Q [C]. As shown in FIG. 5 (a), the charge amount Q gradually decreases with time, gradually decreases, and converges to a constant value Q0. In step S230, it is determined whether it is time to converge to the constant value Q0.

  Returning to FIG. 3, when it is determined in step S230 that the charge amount Q has converged to a certain value, the control device 6 proceeds to step S240. In step S240, the control device 6 sets the index value measurement prohibition flag F to the value 1. That is, when it is determined in step S230 that the charge amount Q has converged to a certain value, the value 1 is set in the index value measurement prohibition flag F to stop the measurement by the index value measurement routine. In FIG. 5 (a), time t1 is the time point when this measurement is stopped.

  When the charge amount Q has converged to a certain value, it can be determined that the degree of change in the shape of the cathode catalyst is large. Therefore, in the subsequent step S250, a message indicating that the degree of change in the shape of the cathode catalyst is large, or prompting replacement of parts Is displayed on the display 55 in the meter, instrument panel or multi-information device (MID). As a result, it is possible to notify the user and the worker that it is time to replace the fuel cell 2 or its peripheral components.

  The worker who has received the notification performs an operation of changing the parts included in the fuel cell system as a countermeasure against the increase in the degree of change in the shape of the cathode catalyst. Here, “change” includes replacement and repair. Specifically, the worker performs an appropriate operation such as replacing the fuel cell 2 or changing a control program executed by the control device 6. Here, it is assumed that a change in software such as a control program is also a kind of change in parts. After the work is completed, the worker transmits a signal indicating that the change is completed (hereinafter referred to as “changed signal”) to the control device 6 using a dedicated device (not shown). That is, the fuel cell system 1 is provided with an external terminal 11 connected to the control device 6, and the operator can connect the dedicated device to the external terminal 11 and operate the dedicated device to change the changed signal. Is transmitted to the control device 6.

  The change of the control program is as follows. Normally, in the fuel cell system 1, high potential avoidance control is performed in order to suppress the progress of the shape change of the electrode catalyst. When the above message is received, the degree of change in the shape of the electrode catalyst has already increased, so this high potential avoidance control becomes unnecessary. The control program is changed to a logic program that does not perform the high potential avoidance control. When the control program is changed, the charge amount Q reflecting the degree of change in the shape of the electrode catalyst is not yet sufficiently reduced. In other words, the degree of change in the shape of the electrode catalyst is not too large.

  In the present embodiment, the changed signal is transmitted to the control device 6 in the above-described configuration using a dedicated device. Instead, a button for transmitting a changed signal is provided in advance in the fuel cell system 1. It is good also as a structure which transmits and the changed signal is transmitted to the control apparatus 6 when an operator operates this button. In short, any configuration can be used as long as it is a configuration that is operated by an operator and transmits a changed signal to the control device 6. Furthermore, the operator does not necessarily intend to transmit the changed signal. For example, the fuel cell system 1 automatically receives the completion of the operation of changing the parts included in the fuel cell system described above. Alternatively, the changed signal may be transmitted to the control device 6.

  In step S260 following step S250, the control device 6 determines whether or not a changed signal is received from the worker. If it is determined in step S260 that the changed signal has not been received, step S260 is repeatedly executed to wait for the changed signal to be sent from the operator.

  On the other hand, when it is determined in step S260 that the changed signal has been received, the index value measurement prohibition flag F is set to 0 (step S270). That is, when it is determined that the changed signal has been received, the index value measurement prohibition flag F is set to 0 to resume measurement by the index value measurement routine. In FIG. 5 (a), time t2 is the time when this measurement is resumed. As a result, during the period from time t1 to time t2, the measurement of the charge amount Q as the form change index value is stopped.

  After execution of step S270, the control device 6 starts a built-in timer (step S280). Next, the control device 6 takes out the charge amount Q stored in the RAM in step S140 of the index value measurement routine (step S290), and the absolute value | Q0-Q | of the difference between the charge amount Q and the above-described constant value Q0 is predetermined. It is determined whether or not the value is equal to or less than the value Qa (step S292). The predetermined value Qa is a minute value, and step S292 determines whether or not the charge amount Q is almost unchanged from the fixed value Q0, that is, whether or not the charge amount Q is a value close to the fixed value Q0. Judgment is performed.

  When it is determined in step S292 that the absolute value | Q0−Q | is equal to or less than the predetermined value Qa, the control device 6 determines whether or not the timer time activated in step S280 is equal to or greater than the predetermined time T0 ( Step S294). If it is determined that the timer time is less than the predetermined time T0, the process returns to step S290. On the other hand, when the timer time becomes equal to or longer than the predetermined time T0 in step S294, the process returns to step S240. That is, according to the processing of steps S290 to S294, when the absolute value | Q0−Q | of the difference with respect to the constant value Q0 of the charge amount Q continues for a predetermined time T0 during the predetermined time T0, the processing is performed. It returns to step S240. When the process returns to step S240, the control device 6 stops measuring the index value, displays a message to the operator again, and waits for reception of the changed signal.

  Note that when it is determined in step S292 that the absolute value | Q0−Q | exceeds the predetermined value Qa, that is, between the restart of the index value measurement and the elapse of the predetermined time T0, the absolute value | Q0 When it is determined that −Q | exceeds the predetermined value Qa, the process returns to step S220, and the index value measurement resumed in step S270 is continued.

  FIG. 5B is after time T2 when the measurement is resumed. As shown by the solid line in the figure, the charge amount Q decreases with a large decrease rate, and at time t3, becomes a difference of a predetermined value Qa or more with respect to the constant value Q0 that has converged when the measurement was stopped previously. . At this time, it is determined to continue the index value measurement. On the other hand, as shown by the one-dot chain line in the figure, when the state in which the charge amount Q hardly changes from the constant value Q0 continues for a predetermined time T0, the index value is obtained at time t4 after the predetermined time T0. Measurement will be stopped again.

  In the configuration change monitoring routine configured as described above, the processes of steps S220 to S240 correspond to the measurement stop unit 6b (FIG. 1), the process of step S260 corresponds to the reception determination unit 6c (FIG. 1), and step The process of S270 corresponds to the measurement restarting unit 6d (FIG. 1).

  According to the fuel cell system 1 of the embodiment configured as described above, as described above, the period from the time when the charge amount Q decreases to the constant value Q0 to the reception of the changed signal (time t1) To t2), the measurement of the charge amount Q is stopped. During the period, since the charge amount Q has already converged to a constant value, there is no need to measure the charge amount Q, and there is no problem even if the measurement is stopped. For this reason, according to the fuel cell system 1, the period of measurement of the charge amount Q as the form change index value can be shortened, and consumption of energy necessary for measurement can be reduced.

  Usually, when the degree of change in the shape of the cathode catalyst becomes large, the worker changes the parts included in the fuel cell system. However, if the changed parts are unrelated to the change in the form of the catalyst. There is no change in the charge amount Q. According to the fuel cell stem 1, after changing the part, the state in which the charge amount Q hardly changes from the value before the part change (= constant value Q0) continues for a predetermined time T0 (time t4). ), The measurement of the charge amount Q is stopped again. Therefore, energy loss due to useless measurement is eliminated.

  On the other hand, when the charge amount Q has changed to some extent from the value before the component change within a predetermined time T0 after the component change, the measurement of the charge amount Q is continued, and the charge amount Q again becomes a constant value (described above). Wait for convergence to a value one step lower than Q0). During the period from when the charge amount Q converges to the constant value until the changed signal is received, the measurement of the charge amount Q is stopped as in the times t1 to t2. Therefore, the measurement period of the charge amount Q as the form change index value can be shortened, and the consumption of energy required for the measurement can be further reduced.

  Note that the measurement of the charge amount Q as the shape change index value requires an operation for lowering the voltage, so that it becomes an environment where hydrogen peroxide is likely to be generated, which may damage the electrolyte membrane and the like. On the other hand, according to the fuel cell system 1 of this embodiment, the period of measurement of the charge amount Q can be shortened, so that it is possible to prevent the loss of function.

B. Second embodiment:
A second embodiment of the present invention will be described. The fuel cell system of the second embodiment is different from the fuel cell system 1 of the first embodiment only in the contents of the form change monitoring routine executed by the control device 6, and the other configurations are the same. is there. In the form change monitoring routine (FIG. 4) of the first embodiment, it is determined in step S230 whether or not the charge amount Q has converged to a constant value. Instead, in this second embodiment, The time when the charge amount Q converges to a constant value is predicted before the convergence, and it is determined whether or not the prediction is possible. In the prediction, for example, a point in time when the rate of decrease of the charge amount Q becomes 0 is predicted from a change in the rate of decrease of the charge amount Q.

  FIG. 6 is a graph showing a measurement stop time in the second embodiment. The rate of decrease of the charge amount Q corresponds to the slope of the tangent line K in contact with the curve indicating the change in the charge amount Q. A time point at which the inclination becomes 0 is predicted from the change in the inclination. In the figure, it is assumed that at the time t1x, a time point when the slope becomes 0 (that is, a time point when the charge amount Q becomes a constant value) is predicted, and measurement is stopped at this predicted time point. In the second embodiment, since only the configuration of step S230 is different from that of the first embodiment as described above, a point in time when the charge amount Q is predicted to be a constant value (hereinafter, referred to as “step S230”). A message is displayed (step S250) along with the stop of measurement.

  The fuel cell system of the second embodiment configured as described above can shorten the period of measurement of the charge amount Q as the form change index value, as in the fuel cell system 1 of the first embodiment. It is possible to reduce the consumption of energy required.

  In the fuel cell system of the second embodiment, the message is displayed at the predicted time point. Instead, the message is displayed until the predicted charge amount Q reaches a constant value. It can also be set as the structure which displays. In the second embodiment, it is notified that the charge amount Q becomes a constant value before the time point when the charge amount Q becomes a constant value, but in this modified example, the measurement stops at the predicted time point, The notification to the worker is made when the predicted charge amount Q becomes a constant value.

  Further, in the second embodiment, the method for predicting the time point at which the charge amount Q becomes a constant value is not necessarily limited to that obtained from the change in the decrease rate of the charge amount Q described above, and any method can be used. Good.

C: Modification:
The present invention is not limited to the first and second embodiments and modifications thereof, and can be carried out in various modes without departing from the gist thereof. For example, the following modifications are possible. Is also possible.

・ Modification 1:
In the first and second embodiments, the charge of the catalyst adsorbed material is adopted as the form change index value reflecting the degree of form change of the electrode catalyst. It is good also as composition adopted as a change index value. When the load applied to the fuel cell is small, the cell voltage of the fuel cell corresponds to the effective area of the cathode catalyst. For this reason, the cell voltage in the low load region can be used as the form change index value. Therefore, the same effect as that of the first embodiment can be obtained in the modified example.

Modification 2
In the first and second examples, in the embodiment, when the cyclic voltammetry (CV) is measured, the output voltage (total voltage) of the fuel cell 2 is reduced, and the total voltage is kept within a certain range. The method of detecting the current associated with the change in the total voltage was described, but instead of the voltage sensor 2b, the voltage of each cell was set corresponding to the cell group constituting the fuel cell 2, respectively. It is also possible to employ a configuration in which a voltage cell monitor for detection is provided, and the output current of the fuel cell accompanying the change in the voltage of each cell is detected by the current sensor 2a or the like while monitoring the voltage of each cell.

  Further, when the supply of the oxidizing gas is temporarily stopped and the output voltage is controlled, there is a cell that cannot be sufficiently lowered due to variations between the cells. Therefore, for example, a cell in which the voltage is likely to decrease, such as a cell farthest from the gas distribution pipe, may be specified in advance, and measurement may be performed using the cell.

・ Modification 3:
In the first and second embodiments, the change in the shape of the cathode catalyst is measured. Alternatively, the change in the shape of the anode catalyst may be measured, or the cathode catalyst and the anode catalyst may be measured. It is good also as a structure which measures both form changes.

-Modification 4:
In the first embodiment, when the charge amount Q as the form change index value measured in the index value measurement routine converges to a constant value, the measurement of the charge amount Q is stopped. In the second embodiment, the charge amount Q is When the time point at which the charge amount Q converges to a certain value is predicted, the measurement of the charge amount Q is stopped. Instead, the measurement of the charge amount Q is stopped by satisfying other conditions. Sometimes it can be. For example, the measurement of the charge amount Q may be stopped after a predetermined time has elapsed since the time when the charge amount Q as the form change index value measured by the index value measurement routine converges to a constant value is predicted. In short, any condition can be used as long as it is a predetermined condition that determines a time point related to the time when the charge amount Q converges to a constant value. Furthermore, any condition can be used as long as it can be a request for stopping the measurement.

-Modification 5:
In the first embodiment, immediately after the measurement of the charge amount Q as the form change index value measured in the index value measurement routine, the component is changed by displaying a message to the worker. Instead, the component may be changed at any timing as long as the measurement of the charge Q is stopped. For example, after the measurement of the charge amount Q is stopped, a part may be changed during a periodic inspection. In response to the change of the part, the measurement by the index value measurement routine is resumed.
Also with this configuration, as in the first embodiment, the measurement period of the charge amount Q as the form change index value can be shortened, and the consumption of energy required for measurement can be reduced.

Modification 6:
Further, the present invention may be applied to a fuel cell of a different type from the above embodiments and modifications. For example, it can be applied to a direct methanol fuel cell. Or the fuel cell which has electrolyte layers other than a solid polymer may be sufficient, and the same effect is acquired by applying this invention.

  It should be noted that elements other than those described in the independent claims among the constituent elements in the above-described embodiments and modifications are additional elements and can be omitted as appropriate. The present invention is not limited to these examples and modifications, and can be implemented in various modes without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell 2a ... Current sensor 2b ... Voltage sensor 3 ... Oxidation gas piping system 3a ... Rotation speed detection sensor 4 ... Fuel gas piping system 5 ... Electric power system 5a ... SOC sensor 5b ... Rotation speed detection sensor 6 DESCRIPTION OF SYMBOLS ... Control apparatus 7L ... Wheel 8 ... Operation part 9 ... Accelerator pedal sensor 11 ... External terminal 31 ... Air compressor 32 ... Oxidation gas supply path 33 ... Humidification module 34 ... Cathode off-gas flow path 35 ... Diluter 41 ... Fuel gas supply source 42 ... Fuel gas supply path 43 ... Fuel gas circulation path 44 ... Anode off gas flow path 45 ... Hydrogen circulation pump 46 ... Check valve 51 ... High-pressure DC / DC converter 52 ... Battery 53 ... Traction inverter 54 ... Auxiliary inverter 55 ... Indicator F ... Index value measurement prohibition flag A1 ... Air pressure regulating valve H1 ... Tank valve H2 ... Hydrogen supply valve 3 ... FC inlet valve H4 ... FC outlet valve H5 ... purge M1 ... motor M2 ... motor M3 ... traction motor M4 ... accessory motor I1 ... oxidation current I2 ... oxidation current I3 ... reduction current I4 ... reduction current Q ... charge amount

Claims (6)

A fuel cell system comprising a fuel cell having an electrolyte layer and an electrode catalyst formed on the electrolyte layer,
An index value measurement unit that measures a shape change index value that reflects the degree of shape change of the electrode catalyst;
A measurement stop unit that stops measurement by the index value measurement unit when a change in the measured form change index value satisfies a predetermined condition;
A fuel cell system comprising: a measurement resumption unit that resumes measurement by the index value measurement unit when a change is made to a component included in the fuel cell system after the measurement is stopped. The fuel cell system according to claim 1,
The predetermined condition is:
A fuel cell system, which is a condition indicating that the measured form change index value has converged to a constant value, or a condition indicating that a time point at which the measured form change index value has converged to a constant value has been predicted. The fuel cell system according to claim 1 or 2,
After restarting the measurement by the measurement restarting unit, a determination unit after restarting that determines whether the form change index value measured by the index value measuring unit is a value close to the constant value for a predetermined period;
A fuel cell system comprising: a measurement restarting unit that stops measurement by the index value measuring unit when the post-resumption determining unit determines that the form change index value is a value close to the constant value. The fuel cell system according to claim 3,
When the post-resumption determination unit determines that the form change index value is not a value close to the constant value, continues measurement by the index value measurement unit and satisfies the predetermined condition by the measurement stop unit. A fuel cell system including a measurement continuation unit that performs the determination. The fuel cell system according to any one of claims 1 to 4,
The index value measurement unit
Based on the cyclic voltammetry characteristics of the output current of the fuel cell detected as the output voltage of the fuel cell is changed while the supply amount of the reaction gas supplied to the fuel cell is constant. A fuel cell system configured to measure the form change index value. A control method of a fuel cell system comprising a fuel cell having an electrolyte layer and an electrode catalyst formed on the electrolyte layer,
Measure the morphological change index value reflecting the degree of morphological change of the electrode catalyst,
When the change in the measured form change index value satisfies a predetermined condition, the measurement of the form change index value is stopped,
A control method for a fuel cell system, wherein, after the measurement is stopped, measurement of the form change index value is resumed when a part included in the fuel cell system is changed.

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