DE102014107848B4 - Deterioration detection device for vehicle fuel cell unit - Google Patents

Abstract

Deterioration detection apparatus for a vehicular fuel cell unit that detects deterioration in a vehicle-mounted fuel cell unit (20), the apparatus comprising:target value setting means for setting a by increasing an actual output current value of the fuel cell unit (20) in a step pattern by a predetermined amount obtained target value;transient response measuring means for performing an output current control of the fuel cell unit (20) such that the output current value of the fuel cell unit (20) follows the target value, and measuring a transient response of the output voltage of the fuel cell unit (20) under the output current control;a transient response - decomposition means for decomposing the transient response in the output voltage of the fuel cell unit (20) into a first component representing a relatively fast response and a second component representing a relatively fast response slow response;a time constant calculating means for calculating a first time constant of the first component and a second time constant of the second component;a difference calculating means for calculating a first difference, which is a difference between a first reference time constant and the first time constant, and for calculating a second difference which is a difference between a second reference time constant and the second time constant, the first reference time constant being a time constant of the first component in the fuel cell unit (20) in a normal state, the second reference time constant being a time constant of the second component in the fuel cell unit (20 ) is in the normal state; anda deterioration determining means for determining that deterioration associated with changes in a reactive state of a catalyst of the fuel cell unit (20) and the resistance within a cell is occurring, and for determining the degree of deterioration if the first difference is greater than or equal to a prescribed one is value of the first component, and for determining that deterioration associated with a change in a supply state of hydrogen and oxygen in the fuel cell unit (20) is occurring, and for determining the degree of deterioration if the second difference is greater than or equal to one prescribed value of the second component, wherein if the degree of deterioration determined based on the second difference is above a predetermined range: an operation for recovering the fuel cell unit (20) from the deterioration under conditions are performed that allow the removal of in-cell moisture from the fuel cell unit (20) if the temperature of the fuel cell unit (20) is higher than a prescribed temperature value, and an operation for recovering the fuel cell unit (20) from deterioration is performed under a condition which allows ice in the cell of the fuel cell unit (20) to melt if the temperature of the fuel cell unit (20) is equal to or lower than the prescribed temperature value;wherein the duration of a recovery operation of the fuel cell unit (20) for recovery from deterioration is determined based on the first difference if the deterioration determining means determines based on the first difference that the quality of the fuel cell unit (20) is deteriorated, and wherein the duration of a recovery operation of the fuel cell unit (20) for the replay recovery from the deterioration is determined based on the second difference if the deterioration determining means determines based on the second difference that the quality of the fuel cell unit (20) is reduced.

Description

[Technical Field]

The present invention relates to a deterioration detection device for a vehicle-mounted fuel cell unit.

[Technological Background]

In recent years, in the field of vehicles such as two-wheeled vehicles and four-wheeled vehicles, a vehicle has been known. B. is equipped with a polymer electrolyte fuel cell (polymer electrolyte membrane fuel cell unit) containing polymer membranes as its power source in view of the global environment. In a polymer electrolyte fuel cell, a plurality of cells, each of which is a basic unit component, are stacked and connected in series to form a stack. In each cell, an anode (fuel electrode) and a cathode (air electrode) are connected to each other with a polymer membrane (proton exchange membrane) therebetween, with supporting collectors made of carbon black paper being placed on the outsides. In addition, separators with flow paths through which cooling water flows are arranged on the outer sides. The anode and the cathode are each formed of an electrolyte and a catalyst in which platinum fine particles are carried on a carbon carrier. When hydrogen is introduced to the anode, it becomes ionized, with the hydrogen ions passing through the proton exchange membrane to the cathode. At the same time, the electrons emitted in the ionization do not run through the proton exchange membrane, but through a conductive line to the outside, thereby generating a current. Oxygen introduced to the cathode reacts with the hydrogen ions coming in through the polymer membrane and with the electrons coming in through the outer conductive line to form water and is then vented.

When a vehicle equipped with such a fuel cell is actually used, the load and environment during running and the environment during storage change in various ways. As a result, in the fuel cell unit, temporary or permanent performance reduction (deterioration) such as oxidation of the surface of the platinum catalyst, its dissolution, drying and puncture of the proton exchange membranes, excessive moisture and ice in the cells, oxidation of the surfaces of the separators, and the like occurs. Among these types of deterioration, oxidation of the surface of the platinum catalyst, drying of the proton exchange membrane, and excessive moisture and ice in the cells are temporary deterioration of the fuel cell unit. When such deterioration occurs, it is necessary to operate the fuel cell unit under conditions that allow it to be recovered from the deterioration (hereinafter, recovery operation) in order to recover the performance of the fuel cell unit. More specifically, it is necessary to: detect the degree of deterioration of the fuel cell unit; determine the need for a recovery operation based on the detection result; further to identify the cause of the deterioration of the fuel cell unit; and select a recovery operation condition suitable for recovery from the degraded state based on the cause of the quality degradation.

As a technique for determining deterioration in a fuel cell unit, e.g. For example, Patent Document 1 proposes a system that controls the output voltage of the fuel cell unit to a predetermined drop pattern and determines deterioration of the fuel unit based on an amount of electricity obtained by integrating the measured values of the output current of the fuel cell unit during this control . After an air blowing process on the cathodes, this system performs the output current measurement process to determine deterioration in the carrier that supports the catalyst, and then performs the same measurement process again to determine a change in the catalyst. In addition, Patent Document 2 proposes a fuel cell system that discharges the fuel cell unit at an appropriate timing to prevent the proton exchange membranes from degrading by detecting the charge amount in the voltage of the fuel cell unit after its power generation is stopped.

document DE 10 2004 005 530 A1 discloses an operating state determination apparatus and method for determining the operating state of a fuel cell battery.

document U.S. 2009/0 061 263 A1 discloses a fuel cell system including a detection unit, an internal resistance estimation unit, a flow rate measurement unit, a pressure measurement unit, a determination unit, an adjustment unit, an output current measurement unit, an output voltage unit, and a calculation unit.

document U.S. 2013/0 059 215 A1 discloses a technique for suppressing performance degradation and degradation of a fuel cell due to negative voltage.

[State of the art]

[patent documents]

• [Patent Document 1] Japanese Laid-Open Patent Application JP 2012- 89 448 A
• [Patent Document 2] Japanese Laid-Open Patent Application JP 2012-28 221 A
• [Patent Document 3] DE 10 2004 005 530 A1
• [Patent Document 4] U.S. 2009/0 061 263 A1
• [Patent Document 5] US 2013/0059215 A1

[Summary of the Invention]

[Problems to be Solved by the Invention]

Although the system of Patent Document 1 can detect deterioration in the fuel cell unit attributable to the catalyst and its carrier, the system cannot detect deterioration in the fuel cell unit, the other factors such as excessive humidity in the cells and a reduction in the supply state of the hydrogen and the oxygen. Thus, it is impossible to select an appropriate condition for the recovery operation of the fuel cell unit if the cause of deterioration is other than the catalyst and its carrier. On the other hand, the system of Patent Document 2 cannot detect the degree of deterioration of the fuel cell unit and identify the actual cause of deterioration among various causes of deterioration. Thus, as in the system of Patent Document 1, it is impossible to properly perform the recovery operation of the fuel cell unit.

The present invention has been made in view of the above circumstances, an object of which is to accurately determine the cause of deterioration occurring as a result of actual use of a vehicle equipped with the fuel cell unit, so that the condition for a recovery operation for the deterioration is suitably selected will.

[Means for solving the problems]

The present invention is defined in independent claim 1. The dependent claims define embodiments of the invention.

• ein Sollwerteinstellmittel zum Einstellen eines durch Erhöhen eines Ist-Ausgangsstromwerts der Brennstoffzelleneinheit in einem Stufenmuster um einen vorgegebenen Betrag erhaltenen Sollwerts;
• ein Übergangsantwort-Messmittel zum Ausführen einer Ausgangsstromsteuerung der Brennstoffzelleneinheit in der Weise, dass der Ausgangsstromwert der Brennstoffzelleneinheit dem Sollwert folgt, und zum Messen einer Übergangsantwort der Ausgangsspannung der Brennstoffzelleneinheit unter der Ausgangsstromsteuerung;
• ein Übergangsantwort-Zerlegungsmittel zum Zerlegen der Übergangsantwort in der Ausgangsspannung der Brennstoffzelleneinheit in eine erste Komponente, die eine verhältnismäßig schnelle Antwort repräsentiert, und in eine zweite Komponente, die eine verhältnismäßig langsame Antwort repräsentiert; ein Zeitkonstanten-Berechnungsmittel zum Berechnen einer ersten Zeitkonstante der ersten Komponente und einer zweiten Zeitkonstante der zweiten Komponente;
• ein Differenzberechnungsmittel zum Berechnen einer ersten Differenz, die eine Differenz zwischen einer ersten Referenzzeitkonstante und der ersten Zeitkonstante ist, und zum Berechnen einer zweiten Differenz, die eine Differenz zwischen einer zweiten Referenzzeitkonstante und der zweiten Zeitkonstante ist, wobei die erste Referenzzeitkonstante eine Zeitkonstante der ersten Komponente in der Brennstoffzelleneinheit in einem Normalzustand ist, wobei die zweite Referenzzeitkonstante eine Zeitkonstante der zweiten Komponente in der Brennstoffzelleneinheit in dem Normalzustand ist; und
• ein Qualitätsminderungs-Bestimmungsmittel zum Bestimmen, dass eine Qualitätsminderung auftritt, die Änderungen eines reaktionsfähigen Zustands eines Katalysators der Brennstoffzelleneinheit und des Widerstands innerhalb einer Zelle zugeordnet ist, und zum Bestimmen des Grads der Qualitätsminderung, falls die erste Differenz größer als ein vorgeschriebener Wert der ersten Komponente ist, und zum Bestimmen, dass eine Qualitätsminderung auftritt, die einer Änderung eines Zuführungszustands von Wasserstoff und von Sauerstoff in der Brennstoffzelleneinheit zugeordnet ist, und zum Bestimmen des Grads der Qualitätsminderung, falls die zweite Differenz größer als ein vorgeschriebener Wert der zweiten Komponente ist.

In order to solve the problems in the conventional techniques, the present invention provides an apparatus for detecting deterioration in a fuel cell unit mounted on a vehicle, the apparatus comprising:

• a target value setting means for setting a target value obtained by increasing an actual output current value of the fuel cell unit in a step pattern by a predetermined amount;
• transient response measuring means for performing output current control of the fuel cell unit such that the output current value of the fuel cell unit follows the target value and measuring a transient response of the output voltage of the fuel cell unit under the output current control;
• transient response decomposition means for decomposing the transient response in the output voltage of the fuel cell unit into a first component representing a relatively fast response and a second component representing a relatively slow response; a time constant calculation means for calculating a first time constant of the first component and a second time constant of the second component;
• a difference calculation means for calculating a first difference which is a difference between a first reference time constant and the first time constant and for calculating a second difference which is a difference between a second reference time constant and the second time constant, the first reference time constant being a time constant of the first component in the fuel cell unit is in a normal state, wherein the second reference time constant is a time constant of the second component in the fuel cell unit in the normal state; and
• deterioration determining means for determining that deterioration associated with changes in a reactive state of a catalyst of the fuel cell unit and resistance within a cell is occurring, and for determining the degree of deterioration if the first difference is greater than a prescribed value of the first component is, and for determining that a deterioration associated with a change in a supply state of hydrogen and oxygen in the fuel cell unit occurs, and to determining the degree of degradation if the second difference is greater than a prescribed value of the second component.

• falls der auf der Grundlage der ersten Differenz bestimmte Grad der Qualitätsminderung über einem vorgegebenen Bereich liegt: ein erster Stromwert und ein erster Spannungswert der Brennstoffzelleneinheit in einem ersten Gebiet, in dem die Stromdichte verhältnismäßig niedrig ist, gemessen werden und ein zweiter Stromwert und ein zweiter Spannungswert der Brennstoffzelleneinheit in einem zweiten Gebiet, in dem die Stromdichte höher als in dem ersten Gebiet ist, gemessen werden;
• eine Operation zum Wiederherstellen der Brennstoffzelleneinheit von der Qualitätsminderung unter Bedingungen ausgeführt wird, die eine Reduktionsreaktion einer Katalysatoroberfläche der Zelle der Brennstoffzelleneinheit fördern, falls eine Differenz zwischen einem Spannungswert der durch den ersten Stromwert angesteuerten Brennstoffzelleneinheit in dem Normalzustand und dem ersten Spannungswert größer als ein erster vorgeschriebener Spannungswert bei dem ersten Stromwert ist; und
• eine Operation zum Wiederherstellen der Brennstoffzelleneinheit von der Qualitätsminderung unter Verwendung einer Bedingung ausgeführt wird, die eine Befeuchtung einer Polymermembran der Zelle der Brennstoffzelleneinheit zulässt, falls die Differenz zwischen dem Spannungswert der durch den ersten Stromwert angesteuerten Brennstoffzelleneinheit in dem Normalzustand und dem ersten Spannungswert kleiner oder gleich dem ersten vorgeschriebenen Spannungswert bei dem ersten Stromwert ist und eine Differenz zwischen einem Spannungswert der durch den zweiten Stromwert angesteuerten Brennstoffzelleneinheit in dem Normalzustand und dem zweiten Spannungswert größer als ein zweiter vorgeschriebener Spannungswert bei dem zweiten Stromwert ist.

In addition, the present invention may be such that:

• if the degree of deterioration determined based on the first difference is above a predetermined range: measuring a first current value and a first voltage value of the fuel cell unit in a first area where the current density is relatively low, and a second current value and a second voltage value of the fuel cell unit are measured in a second area in which the current density is higher than in the first area;
• an operation for recovering the fuel cell unit from deterioration is performed under conditions promoting a reduction reaction of a catalyst surface of the cell of the fuel cell unit if a difference between a voltage value of the fuel cell unit driven by the first current value in the normal state and the first voltage value is larger than a first prescribed one voltage value at the first current value; and
• an operation for recovering the fuel cell unit from deterioration is performed using a condition that allows humidification of a polymer membrane of the cell of the fuel cell unit if the difference between the voltage value of the fuel cell unit driven by the first current value in the normal state and the first voltage value is less than or equal to the first prescribed voltage value at the first current value and a difference between a voltage value of the fuel cell unit driven by the second current value in the normal state and the second voltage value is larger than a second prescribed voltage value at the second current value.

• eine Operation zum Wiederherstellen der Brennstoffzelleneinheit von der Qualitätsminderung unter Bedingungen ausgeführt wird, die die Entfernung von Feuchtigkeit in der Zelle aus der Brennstoffzelleneinheit zulassen, falls die Temperatur der Brennstoffzelleneinheit höher als ein vorgeschriebener Temperaturwert ist, und
• eine Operation zum Wiederherstellen der Brennstoffzelleneinheit von der Qualitätsminderung unter Bedingungen ausgeführt wird, die das Schmelzen gefrorener Feuchtigkeit in der Zelle der Brennstoffzelleneinheit zulassen, falls die Temperatur der Brennstoffzelleneinheit niedriger als der vorgeschriebene Temperaturwert ist.

Furthermore, the present invention may be such that,
if the level of degradation determined based on the second difference is above a specified range:

• an operation for recovering the fuel cell unit from deterioration is performed under conditions that allow removal of in-cell moisture from the fuel cell unit if the temperature of the fuel cell unit is higher than a prescribed temperature value, and
• an operation for recovering the fuel cell unit from deterioration is performed under conditions that allow melting of frozen moisture in the cell of the fuel cell unit if the temperature of the fuel cell unit is lower than the prescribed temperature value.

Moreover, the present invention may be such that the duration of a recovery operation of the fuel cell unit for recovery from the deterioration is determined based on the first difference if the deterioration determination means determines based on the first difference that the fuel cell unit is deteriorating and that the duration of a recovery operation of the fuel cell unit for recovery from the deterioration is determined based on the second difference if the deterioration determination means determines based on the second difference that the fuel cell unit is degraded.

• ein neuer Sollwert für den Ausgangsstromwert der Brennstoffzelleneinheit eingestellt wird;
• eine Übergangsantwort der Ausgangsspannung der Brennstoffzelleneinheit unter einer solchen Steuerung, dass ihr Ausgangsstromwert dem neuen Sollwert folgt, gemessen wird;
• die Übergangsantwort der Ausgangsspannung der Brennstoffzelleneinheit in die erste Komponente und in die zweite Komponente zerlegt wird;
• eine dritte Zeitkonstante der ersten Komponente und eine vierte Zeitkonstante der zweiten Komponente berechnet werden und die erste Referenzzeitkonstante durch die dritte Zeitkonstante ersetzt wird und die zweite Referenzzeitkonstante durch die vierte Zeitkonstante ersetzt wird.

In addition, the present invention may be such that if a recovery operation for recovery from the deterioration determined by the deterioration determination means is performed, but the fuel cell unit is not recovered from the deterioration, and if a decrease in an output voltage value of the fuel cell unit after the recovery operation from the output voltage value of the fuel cell unit to the normal state is less than a predetermined allowable level:

• a new target value for the output current value of the fuel cell unit is set;
• a transient response of the output voltage of the fuel cell unit is measured under control such that its output current value follows the new target value;
• the transient response of the output voltage of the fuel cell unit is decomposed into the first component and the second component;
• a third time constant of the first component and a fourth time constant of the second component are calculated and the first reference time constant is replaced by the third time constant and the second reference time constant is replaced by the fourth time constant.

[Advantageous Effects of the Invention]

As described above, the deterioration detection apparatus for a vehicle fuel cell unit according to the present invention: sets a target value obtained by increasing the actual output current value of the fuel cell unit in a step pattern by a predetermined amount; measuring the transient response of the output voltage of the fuel cell unit under a control where the output current value follows the target value; and determining the cause and degree of degradation of the fuel cell assembly based on the first component in the transient response representing a relatively fast response and the second component in the transient response representing a relatively slow response. In this way, the need for a recovery operation for the fuel cell unit can be determined. Furthermore, a recovery operation can be performed by selecting an appropriate condition for recovery from deterioration if deterioration occurs in the fuel cell unit.

If the degree of deterioration determined based on the first component in the transient response described above, which represents a relatively fast response, is above a predetermined range, the current values and the voltage values of the fuel cell unit are measured in several different current density regions. In this way, the cause of the deterioration can be determined more specifically based on these current values and voltage values. Accordingly, based on the first component representing a relatively fast response, a more appropriate condition for recovery from the determined degradation can be chosen when a recovery operation is to be performed.

If the degree of deterioration determined based on the second component in the aforementioned transient response, which represents a relatively slow response, is above a predetermined range, the temperature of the fuel cell assembly is measured. In this way, the cause of the deterioration can be determined more specifically based on the measured temperature. Accordingly, based on the second component representing a relatively slow response, a more appropriate condition can be chosen when a recovery operation is to be performed from the determined degradation.

If it is determined that degradation is occurring based on the first component in the transient response representing a relatively fast response, the duration of the recovery operation is calculated based on the first difference between the aforementioned first time constant and the first reference time constant. If it is determined that degradation is occurring based on the second component in the transient response representing a relatively slow response, the duration of the recovery operation is calculated based on the second difference between the aforementioned second time constant and the second reference time constant. In this way, the duration of the recovery operation can be optimized in accordance with the cause of the degradation. Accordingly, it is possible to reduce the effect of the recovery operation on the running of the vehicle, such as a decrease in the output of the fuel cell unit.

If a recovery operation for recovery from deterioration is performed but recovery from deterioration is not achieved, and a decrease in the output voltage value of the fuel cell unit after the recovery operation from the output voltage value of the fuel cell unit in the normal state is lower than a predetermined allowable level, it is still possible to continue using the fuel cell unit even though its performance has decreased. In this case, the determination of the occurrence of a temporary deterioration can be continued and an appropriate recovery operation can be performed by performing the process of replacing the reference voltage values mentioned above.

character list

• 1 12 is a block diagram of a deterioration detection device for a vehicle fuel cell unit in accordance with an embodiment of the present invention.
• 2 14 is a configuration diagram of a first DC/DC converter of the deterioration detection device for a vehicle fuel cell unit in accordance with the embodiment of the present invention.
• 3 Fig. 12 is a set of graphs showing transient characteristics of the fuel cell unit.
• 4 Fig. 12 is a flowchart showing the procedure of a deterioration detection process executed in the deterioration detection apparatus.
• 5 FIG. 14 is a graph showing a loss characteristic of the fuel cell unit.
• 6 14 is a graph showing characteristics of the fuel cell unit when activation polarization is increased.
• 7 14 is a graph showing the characteristics of the fuel cell unit when a polarization resistance is increased.
• 8th 14 is a flowchart showing the procedure of a process for selecting the condition for a recovery operation of the fuel cell unit in a degraded state.
• 9 14 is a flowchart showing the procedure of a process for selecting the condition for the recovery operation of the fuel cell unit in a degraded state.
• 10 14 is a flowchart showing the procedure of a process performed after the degraded fuel cell unit recovery operation.
• 11 14 is a timing chart showing the measured voltage waveform of the fuel cell unit in a change of the deterioration detection process.
• 12 14 is a timing chart showing the measured voltage waveform of the fuel cell unit in the change of the deterioration detection process.

[Modes for Carrying Out the Invention]

The present invention is described in detail below using an illustrated embodiment. 1 14 is a block diagram of a deterioration detection device for a vehicle fuel cell unit in accordance with this embodiment. A data processing device 10 is a system controller configured to control the entire deterioration detection device. A fuel cell unit (FC) 20, a first DC/DC converter 30, an inverter 40, a second DC/DC converter 60 and a battery 70 are connected to the data processing device 10 . A motor 50 is connected to the inverter 40 and the battery 70 is connected to the second DC/DC converter 60 . The data processing device 10 receives temperature data of the fuel cell unit 20 measured by a temperature sensor 21 of the fuel cell unit 20 and various kinds of data measured by a voltage sensor 31 and a current sensor 32 of the first DC/DC converter 30 . In the data processing device 10, arithmetic processing is performed based on these various kinds of data to generate control signals. The fuel cell unit 20, the first DC/DC converter 30, the inverter 40, the second DC/DC converter 60 and the battery 70 are each equipped with a control circuit (not shown) through which control signals are exchanged with the data processing device 10.

2 is a diagram showing the configuration of the first DC/DC converter 30 in 1 indicates. The first DC/DC converter 30 is a buck-boost converter and includes, in addition to the voltage sensor 31 and current sensor 32 mentioned above, an inductor 33 and switches SW1, SW2, SW3 and SW4.

The switches SW1 to SW4 are switching elements, e.g. B. power MOSFETs are used. If a boosting operation is performed in the first DC/DC converter 30, the switch SW1 is on, the switch SW2 is off, and the switches SW3 and SW4 are switched with a duty corresponding to the difference between the input and output voltages. In addition, if a voltage drop operation is performed in the first DC/DC converter 30, the first switch SW4 is on, the second switch SW3 is off, and the switches SW1 and SW2 are switched with a duty corresponding to the difference of the input and output voltages , switched. The switching of the switches SW1 to SW4 is controlled based on the results of detection by the voltage sensor 31 and by the current sensor 32 so that the voltage and the current follow their predetermined target values.

The procedure of a process for controlling the regeneration of the fuel cell unit 20 executed in the data processing device 10 is as follows. Initially, a deterioration detection process is performed for the fuel cell unit 20, and based on the detection result, it is determined whether a recovery operation of the fuel cell unit 20 should be performed. If it is determined that a recovery operation of the fuel cell unit 20 is necessary, the condition for the recovery operation is selected based on the state of deterioration. Then, using the selected condition, the recovery operation of the fuel cell unit 20 running. After the recovery operation, it is checked whether the output of the fuel cell unit 20 has been recovered. If the output has not yet been recovered, a recovery process post-processing to be described later is performed. These processes are performed while causing the fuel cell unit 20 to generate power. Thus, power is output from the fuel cell unit 20 during the processes. As mentioned above, the output current of the fuel cell unit 20 is output to the motor 50 via the first DC/DC converter 30 and the inverter 40, thereby driving the motor 50, or via the first DC/DC converter 30 and via the second DC/DC converter 60 is output to the battery 70, whereby the battery 70 is charged. Motor driving and battery charging are performed in accordance with the running state of the vehicle and the state of charge of the battery 70 .

[Detection of deterioration of fuel cell unit]

In this embodiment, the degree and cause of deterioration of the fuel cell unit 20 are determined by focusing on transient characteristics of the fuel cell unit 20 . 3 FIG. 12 shows a transient response of the output voltage of the fuel cell unit 20 when the target value of the output current of the fuel cell unit 20 is increased in step form. When the target value of the output voltage of the fuel cell unit 20 is stepped up at time t1, the output voltage of the fuel cell unit 20 falls to approximately 50% at time t1 and then gradually falls as shown by a solid line L20. The output voltage transient response shown by solid line L20 can be approximated using a relatively fast-response component (dashed line L21) and a relatively slow-response component (dashed line L22). The fast responding component shows a reduction of approximately 50% at time t1, with the voltage level remaining constant thereafter. The slow-response component does not abruptly decrease at time t1 but gradually decreases with the lapse of time.

The fast-acting component is related to the reaction of the platinum catalyst in the cells of the fuel cell assembly 20 and to the internal resistance of the cells. More specifically, the fast-response component z. B. delayed if degradation occurs in the fuel cell unit 20 attributable to oxidation of the platinum catalyst surfaces of the cells, degradation occurs in the fuel cell unit 20 attributable to drying of the polymer membranes, or degradation occurs in the fuel cell unit 20 that is results from a decrease in the supply state of hydrogen and oxygen due to excessive humidity inside the cells. In addition, the slow-response component is related to the supply of hydrogen and oxygen in the fuel cell unit 20 . More specifically, the slow-response component is further delayed if degradation associated with changing the supply status of the hydrogen and oxygen in the fuel cell unit 20 (e.g., down to a level of 80% or less of normal) occurs.

Since the time constants of the fast-response component and the slow-response component are very different, they can be detected individually.

wobei t die Zeit ist, V₀ der Anfangsspannungswert ist, V der Übergangsantwortspannungswert ist, V₁ der Spannungswert der schnell ansprechenden Komponente ist, V₂ der Spannungswert der langsam ansprechenden Komponente ist, V_1∞ der Endspannungswert der schnell ansprechenden Komponente ist, V_2∞ der Endspannungswert der langsam ansprechenden Komponente ist, T₁ die Zeitkonstante der schnell ansprechenden Komponente ist und T₂ die Zeitkonstante der langsam ansprechenden Komponente ist.In this embodiment, the transient response of the output voltage of the fuel cell unit 20 to a step increase in its output current value is measured and broken down into the above-mentioned fast-response component and slow-response component, and their time constants are calculated to determine the degree and cause of the deterioration of the fuel cell unit 20. As shown in formula (1), the transient response of the output voltage of the fuel cell unit 20 is approximated using the sum of step responses of first-order lag system transfer functions.
[Formula 1] $$\begin{array}{l}{V}_0+V=V_0+{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="DE102014107848B4\_0007.png,DE102014107848B4\_0008.png"\; state="\{\{state\}\}">V</figure-callout>}}_1+V_2\\ =V_0+\left({\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="DE102014107848B4\_0007.png,DE102014107848B4\_0008.png"\; state="\{\{state\}\}">V</figure-callout>}}_{1\infty }-V_0\right)\left(1-e^{-{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="DE102014107848B4\_0007.png,DE102014107848B4\_0008.png"\; state="\{\{state\}\}">T</figure-callout>}}_1\text{/}t}\right)+\left(V_{2\infty }-V_0\right)\left(1-e^{-T_2\text{/}t}\right)\end{array}$$

where t is time, V ₀ is the initial voltage value, V is the transient response voltage value, V ₁ is the voltage value of the fast-response component, V ₂ is the voltage value of the slow-response component, V _1∞ is the final voltage value of the fast-response component, V _{2 ∞} is the final voltage value of the slow-response component, T ₁ is the time constant of the fast-response component, and T ₂ is the time constant of the slow-response component.

wobei ΔT₁ die Differenz zwischen der Zeitkonstante der schnell ansprechenden Komponente in dem Normalzustand und der Zeitkonstante der detektierten schnell ansprechenden Komponente ist und T_1std die Zeitkonstante der schnell ansprechenden Komponente in dem Normalzustand ist.
[Formel 3] $$\mathrm{\Delta }{T}_2=T_2-T_{2std}$$

wobei ΔT₂ die Differenz zwischen der Zeitkonstante der langsam ansprechenden Komponente in dem Normalzustand und der Zeitkonstante der detektierten langsam ansprechenden Komponente ist und T_2std die Zeitkonstante der langsam ansprechenden Komponente in dem Normalzustand ist.As shown in formulas (2) and (3), the time constant T ₁ of the voltage value V ₁ of the fast-response component and the time constant T ₂ of the voltage value V ₂ of the slow-response component increase with time, respectively constants in the normal state (in which the quality of the fuel cell unit 20 is not yet degraded).
[Formula 2] $$\mathrm{<figure-callout\; id="1"\; label="\Delta \; T"\; filenames="DE102014107848B4\_0007.png,DE102014107848B4\_0008.png"\; state="\{\{state\}\}">\Delta </figure-callout>}{T}_{}{}_1={\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="DE102014107848B4\_0007.png,DE102014107848B4\_0008.png"\; state="\{\{state\}\}">T</figure-callout>}}_1-T_{1st\mathrm{i.e}}$$

where ΔT ₁ is the difference between the time constant of the fast responding component in the normal state and the time constant of the detected fast responding component, and T _1std is the time constant of the fast responding component in the normal state.
[Formula 3] $$\mathrm{\Delta }{T}_2=T_2-T_{2st\mathrm{i.e}}$$

where ΔT ₂ is the difference between the time constant of the slow-response component in the normal state and the time constant of the detected slow-response component, and T _2std is the time constant of the slow-response component in the normal state.

In this embodiment, the degree of deterioration associated with changes in the reactive state of the catalyst in the fuel cell unit 20 and the internal resistance of the cells is determined based on ΔT ₁ and the degree of deterioration associated with a change in the supply state of hydrogen and oxygen in the fuel cell unit 20 is determined based on ΔT ₂ .

4 14 is a flowchart showing the procedure for the deterioration detection process for the fuel cell unit 20 executed in the data processing apparatus 10. FIG. In step S10, the switching of the first DC/DC converter 30 is controlled such that the current value of the power output from the fuel cell unit 20 and the input to the first DC/DC converter 30 are increased in a step pattern. The current value (target value) increased in the step pattern is input to the data processing device 10 . The data processing device 10 outputs a control signal to the fuel cell unit 20 in such a way that the output current of the fuel cell unit 20 follows the target value. Then, the transient response of the output voltage of the fuel cell unit 20 whose output current is controlled to the target value is measured by the voltage sensor 31 of the first DC/DC converter 30 in step S11. The transient response waveform measured by the voltage sensor 31 is recorded in the data processing apparatus 10 in the form of a time-series array.

In step S12, the transient response waveform is approximated using the sum of step responses of first-order lag system transfer functions shown in the above-mentioned formula (1). In step S13, the time constant T ₁ of the voltage value V ₁ of the fast-response component and the time constant T ₂ of the voltage value V ₂ of the slow-response component are calculated. Then, the process proceeds to step S14, in which the difference ΔT ₁ between the time constant of the fast-response component in the normal state and the time constant T ₁ of the fast-response component calculated in step S13 is calculated, and the difference ΔT ₂ between the time constant of the slow responsive component in the normal state and the time constant T ₂ of the slow responsive component calculated in step S13.

In step S15, the difference ΔT ₁ is compared with a prescribed value determined in advance. If ΔT ₁ is greater than or equal to the prescribed value, the process goes to step S16. In step S16, based on the fact that the time constant T ₁ of the fast-response component has changed from that in the normal state by an amount greater than or equal to the prescribed value, it is determined that deterioration in the fuel cell 20 occurs, the changes in the responsive State of the platinum catalyst of the cells and the internal resistance of the cells is assigned. In addition, the degree of deterioration is determined in accordance with the value of ΔT ₁ . More specifically, it is determined that the degree of deterioration associated with changes in the reactive state of the platinum catalyst and the internal resistance of the cells is larger as the value of ΔT ₁ becomes larger. Then the process goes to step S17. If ΔT ₁ is smaller than the prescribed value, the operation in step S16 is skipped and the process goes to step S17.

In step S17, the difference ΔT ₂ is compared with a prescribed value determined in advance. If ΔT ₂ is greater than or equal to the prescribed value, the process goes to step S18. In step S18, it is determined that deterioration is occurring in the fuel cell unit 20 based on the fact that the time constant T ₂ of the slow-response component has changed from that in the normal state by an amount greater than or equal to the prescribed value. associated with a change in the supply state of hydrogen and oxygen. In addition, the degree of this deterioration is determined in accordance with the value of ΔT ₂ . More precisely, it is determined that the degree of deterioration associated with a change in the supply state of hydrogen and oxygen is larger as the value ΔT ₂ becomes larger. After the above step, the detection of deterioration in the fuel cell unit 20 ends. If ΔT ₂ is smaller than the prescribed value, the operation in step S18 is skipped and the detection of deterioration in the fuel cell unit 20 ends.

[Selection of the condition for the recovery operation]

In this embodiment, the condition for a recovery operation of the fuel cell unit 20 is determined based on the cause and the degree of deterioration determined in the above-described steps S16 and S18 in FIG 4 have been determined. It is believed that based on the difference ΔT ₁ between the time constants of the fast-response component, it has been determined that the degree of deterioration associated with changes in the reactive state of the platinum catalyst in the fuel cell unit 20 and the internal resistance of the cells is large . In this case, the recovery operation of the fuel cell unit 20 is performed under a condition that promotes the reduction reaction of the catalyst surfaces or under a condition that allows the polymer membranes to be humidified.

The losses of the fuel cell unit 20 include: the activation polarization (V _act ) attributable to the activation energy of the electrode reaction; polarization resistance (V _ohm ) attributable to the electrical resistances of the electrolytes and electrodes; and diffusion polarization (V _trans ) attributable to a phenomenon related to the density of the reactant at the electrode surfaces. 5 Figure 12 is a graph showing the characteristics of these losses. The degradation of the reactive state of the platinum catalyst in the fuel cell assembly 20 increases the activation polarization Vact, and the degradation of the internal resistance of the cells of the fuel cell assembly 20 increases the polarization resistance V _ohms . Thus, it can be determined that there is deterioration in the reactive state of the platinum catalyst in the fuel cell unit 20 if there is an in 5 area indicated by A11 where the current density is low, there is a decrease in the output voltage. In addition, it can be determined that there is deterioration in the internal resistance of the cells if it occurs in an in 5 area indicated by A12, in which the current density has an intermediate value, there is a decrease in the output voltage.

Thus, first, the voltage V ₁ and the current I ₁ of the fuel cell unit 20 are measured in the low current density area A11, and the voltage V ₁ is compared with the voltage V _1std of the fuel cell unit 20 with the same current I ₁ but in the normal state. Then, the voltage V ₂ and the current I ₂ of the fuel cell unit 20 are measured in the medium current density area A12, and the voltage V ₂ is compared with the voltage V _2std of the fuel cell unit 20 with the same current I ₂ but in the normal state. If the difference from the voltage V _1std in the normal state in the low current density region A11 as in FIG 6 shown is already large, the activation polarization has increased. Thus, it is determined that there is a problem in the reactive state of the platinum catalyst. Accordingly, in order to restore the operation of the fuel cell unit 20, the condition that promotes the reduction reaction of the catalyst surfaces is selected. If, on the other hand, as in 7 As shown, the difference from the voltage V _1std in the normal state is small in the low current density region A11 and the difference from the voltage V _2std in the normal state is large in the medium current density region A12, the polarization resistance has increased. Thus, it is determined that there is a problem with the internal resistance of the cells. Accordingly, the condition that allows the polymer membranes to be humidified is selected for the recovery operation of the fuel cell unit 20 . In addition, since the degree of deterioration of the fuel cell unit 20 is determined based on the difference ΔT ₁ between the time constants of the fast-response component, the duration of the recovery operation is determined based on ΔT ₁ .

It is assumed that based on the difference ΔT ₂ between the time constants of the slow-response component, it is determined that the degree of deterioration associated with a change in the supply state of the hydrogen and the oxygen in the fuel cell unit 20 is large. In this case, the recovery operation of the fuel cell unit 20 is performed under a condition allowing removal of moisture in the cells or under a condition allowing melted moisture in the cells to melt. Which of these conditions is selected is determined based on the temperature of the fuel cell unit 20 detected by the temperature sensor 21 of the fuel cell unit 20 .

8th 12 shows the procedure of a process for selecting the condition for the recovery operation of the fuel cell unit 20 if in steps S15 and S16 in FIG 4 it is determined that the fuel cell assembly 20 is experiencing the deterioration associated with changes in the reactive state of the platinum catalyst and the internal resistance of the cells. In step S20, the voltage V ₁ and the current I ₁ of the fuel cell unit 20 in an area of low current density are measured by the voltage sensor 31 and the current sensor 32 of the first DC/DC converter 30, respectively. Then, in step S21, the difference between the voltage V _1std in a setting where the current I ₁ is output in the normal state and the voltage V ₁ is calculated. In step S22, the voltage V ₂ and the current I ₂ are measured by the voltage sensor 31 and by the current sensor 32 of the first DC/DC converter 30 in an area of medium current density. Then, in step S23, the difference between the voltage V _2std in a setting where the current I ₂ is output in the normal state and the voltage V ₂ is calculated.

In step S24, it is determined whether the difference between the above-mentioned voltage V _1std and the voltage V ₁ is larger than a prescribed value determined in advance. If the difference between the voltage V _1std and the voltage V ₁ is larger than the prescribed value, the process goes to step S25. In step S25, the condition that promotes the reduction reaction of the catalyst surfaces of the cells is selected as the condition for the recovery operation of the fuel cell unit 20. On the other hand, if the difference between the voltage V _1std and the voltage V ₁ is less than or equal to the prescribed value, the process proceeds to step S26.

In step S26, it is determined whether the difference between the above-mentioned voltage V _2std and the voltage V ₂ is larger than a prescribed value determined in advance. If the difference between the voltage V _2std and the voltage V ₂ is larger than the prescribed value, the process goes to step S27. In step S27, the condition that allows the polymer membranes of the cells to be humidified is selected as the condition for the recovery operation of the fuel cell unit 20. FIG.

If the condition for the recovery operation of the fuel cell unit 20 is selected in step S25 or S27, the process proceeds to step S28. In step S28, based on the above-mentioned difference ΔT ₁ between the values in step S14 in 4 calculated time constants, the operating time of the recovery operation of the fuel cell unit 20 is determined. The greater the difference ΔT ₁ , the longer the operating time is set.

If the difference between the voltage V _1std and the voltage V ₁ is less than or equal to its prescribed value (No in step S24) and also if the difference between the voltage V _2std and the voltage V ₂ is less than or equal to its prescribed value (No in step S26), it is determined that no deterioration requiring restoration has occurred in the fuel cell unit 20 . Thus, the process of determining the condition and duration of the recovery operation is not performed.

9 12 shows the procedure of a process for selecting the condition for the recovery operation of the fuel cell unit 20 if in steps S17 and S18 in FIG 4 it is determined that the deterioration associated with a change in the supply state of hydrogen and oxygen occurs in the fuel cell unit 20 . The temperature T _FC of the fuel cell unit 20 is measured by the temperature sensor 21 in step S30. Then, in step S31, the temperature T _FC is compared with a prescribed value set in advance. If the temperature T _FC is higher than the prescribed value, the process goes to step S32. In step S32, the condition that allows the removal of moisture in the cells is selected as the condition for the recovery operation of the fuel cell unit 20. If the temperature T _FC is less than or equal to the prescribed value, the process goes to step S33. In step S33, the condition that allows the frozen moisture in the cells to melt is selected as the condition for the recovery operation of the fuel cell unit 20. FIG. If the condition for the recovery operation of the fuel cell unit 20 is selected in step S32 or S33, the process proceeds to step S34. In step S34, based on the above-mentioned in step S14 in 4 calculated difference ΔT ₂ between the time constants determines the service life of the recovery operation of the fuel cell unit 20. The greater the difference .DELTA.T ₂ , the longer the service life is set.

The condition and duration of the recovery operation of the fuel cell unit 20 are selected based on the results of the determination of the degree and cause of the deterioration of the fuel cell unit 20 as described above. In this way, the performance of the fuel cell unit 20 can be maximized.

recovery operation and subsequent process]

10 12 is a flowchart showing the procedures of the recovery operation of the fuel cell unit 20 and a subsequent process. In step S40, the recovery operation of the fuel cell unit 20 is performed. The restore operation will be performed based on the condition and duration determined by the using the schedule in 8th or 9 described above process are performed. In addition, when step S40 is executed for the first time, “0” is set for a variable indicative of the number of times the recovery operation is executed. When the recovery operation of the fuel cell unit 20 is completed, the variable indicating the number of execution times of the recovery operation is incremented by “1”, and the process proceeds to step S41. In a process in and after step S41, it is checked whether the actual output of the fuel cell unit 20 has been retrieved.

In step S41, the voltage V ₃ and the current I ₃ of the fuel cell unit 20 after the recovery operation are measured by the voltage sensor 31 and the current sensor 32, respectively. The voltage V ₃ is then compared with the voltage V _std in step S42. The reference voltage V _std is a voltage value required for the fuel cell unit 20 in the normal state to output the current I ₃ . If the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is less than or equal to a prescribed value set in advance, it is determined that the fuel cell unit 20 has recovered from the temporary deterioration. Thus, the recovery process post-processing is not executed.

On the other hand, if the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is larger than the prescribed value, it is determined that the fuel cell unit 20 has not recovered from the deterioration, and the process proceeds to step S44. In step S44, the value of the variable indicative of the number of execution times of the recovery operation is checked to determine whether the number of execution times of the recovery operation is greater than a prescribed value set in advance. If the number of execution times of the recovery operation is less than or equal to the prescribed value, the process returns to step S40 where the recovery operation has been executed again.

On the other hand, if the number of times of execution of the recovery operation is larger than the prescribed value, the process proceeds to step S45. The situation where the number of times of execution of the recovery operation is greater than the prescribed value represents a state where the fuel cell unit 20 in the normal state, even after a given number of recovery operations have been executed, has no output voltage close to the reference voltage V _hrs . More specifically, the deterioration of the fuel cell unit 20 is not temporary but permanent. In other words, the basic performance of the fuel cell unit 20 can be considered reduced compared to the initial state. Even if the basic performance of the fuel cell unit 20 has decreased, it can still be used if the degree of the decrease is small. Thus, first in step S45, it is determined whether the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is within an allowable level, that is, whether the permanent decrease in the output voltage of the fuel cell unit 20 is within an allowable level.

If a permanent reduction in output voltage has occurred in the fuel cell unit 20, but the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is smaller than the allowable level, the process proceeds to step S46. In a state where there is permanent deterioration, but the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is smaller than the allowable level, the reduction in the basic performance of the fuel cell unit 20 is not fatal and its use can continue will. If the use of the fuel cell unit 20 is to be continued, it is necessary to detect the occurrence of the temporary deterioration during use and perform an appropriate recovery operation. Thus, in steps S46 to S50, a process of substituting the values of the time constant T _1std of the fast-response component and the time constant T _2std of the slow-response component in accordance with the actual performance of the fuel cell unit 20 is performed.

The new values of the time constants T _1std and T _2std are set in a manner similar to the operations in steps S10 to S13 in the deterioration detection process for the fuel cell unit in FIG 4 calculated. In step S46, the switching of the first DC/DC converter 30 in is controlled such that the target value of the output current of the fuel cell unit 20 is further changed in a step pattern from the target value determined in step S10, with the result being input to the data processing device 10 as a new target value. The data processing device 10 outputs a control signal to the fuel cell unit 20 in such a way that the output current of the fuel cell unit 20 follows the new target value. In step S47, the transient response of the output voltage of the fuel cell unit 20 whose output current is controlled at the new target value is measured by the voltage sensor 31 of the first DC/DC converter 30 and recorded in the data processing device 10 in the form of a time-series array. Then, in step S48, the transient response waveform is approximated using the sum of step responses of first-order lag system transfer functions shown in the above-mentioned formula (1). In step S49, the time constant T ₁ of the voltage value V ₁ of the fast-response component and the time constant T ₂ of the voltage value V ₂ of the slow-response component are calculated. Then, in step S50, the time constant T _1std in the normal state is replaced by the time constant T ₁ of the voltage value V ₁ of the fast-response component calculated in step S49, and the time constant T _2std in the normal state is replaced by the time constant T ₂ of the voltage value V calculated in step S49 ₂ of the slow-response component replaced.

Subsequently, on the basis of the time constants T _1std and T _2std thus replaced, the choice of the condition for the as shown in FIG 8th and 9 described recovery operation of the fuel cell unit 20 is performed.

On the other hand, if it is determined in step S45 that the difference between the reference voltage V _std and the voltage V ₃ after the recovery operation is greater than or equal to the allowable level and that the permanent reduction of the output voltage of the fuel cell unit 20 is not within the allowable level. In this case, the process proceeds to step S51, where the operator is notified that the fuel cell unit 20 has reached the end of its life, so that the operator is prompted to replace the fuel cell unit 20.

As described above, according to the embodiment of the present invention, a current value obtained by increasing the output current value of the fuel cell unit 20 in a step pattern by a predetermined amount is determined as the target value, and the transient response of the output voltage of the fuel cell unit 20 to being in the manner is controlled so that the output current follows the target value, broken down into a component that responds relatively quickly and into a component that responds relatively slowly. Then, based on each component, occurrence and degree of deterioration of the fuel cell unit 20 are determined. In this way, by examining from which component the occurrence of the deterioration is detected, it is possible to determine the nature of the cause of the deterioration. As a result, under a condition suitable for the cause of the deterioration, in other words, in a manner that the cause of the deterioration is eliminated, a recovery operation can be performed.

In addition, if degradation is detected in the fuel cell unit 20 based on the fast-response component, the voltage value and current value of the fuel cell unit 20 are measured in both a low current density area and a medium current density area, and comparison with the voltage value of the Fuel cell unit 20 is made in the normal operating state with its current value set to the same value. In this way, if deterioration is detected in the fuel cell unit 20 based on the fast-response component, the cause of this deterioration can be determined more specifically. In addition, based on the difference between the voltage values, it can be determined whether to use the condition that promotes the reduction reaction of the catalyst surfaces of the cells or the condition that allows the polymer membranes of the cells to be humidified as the condition for the recovery operation shall be. In this way, the recovery operation can be performed under a more appropriate condition if deterioration is detected in the fuel cell unit 20 based on the quick-response component. Accordingly, the fuel cell unit 20 can be restored more reliably.

In addition, the temperature of the fuel cell unit 20 is measured by the temperature sensor 21 if deterioration is detected in the fuel cell unit 20 based on the slow-response component. Based on the result of the measurement by the temperature sensor 21, the cause of the slow responsive component detected degradation of the fuel cell unit 20 can be determined more specifically. Moreover, based on the result of the measurement by the temperature sensor 21, it can be determined whether the condition allowing the removal of moisture in the cells of the fuel cell unit 20 or the condition allowing the melting of ice in the cells as the condition to be used for the restore operation. In this way, if deterioration is detected in the fuel cell unit 20 based on the slow-response component, the recovery operation can be performed using a more appropriate condition. Accordingly, the fuel cell unit 20 can be restored more reliably.

[variations]

In the embodiment, the transient response of the output voltage of the fuel cell unit 20 is measured and decomposed into a fast-response component and a slow-response component, and their time constants are calculated to determine the degree and cause of deterioration of the fuel cell unit 20 . However, the present invention is not limited to this case. A description will now be given of a change in which the time constants of the fast-response component and the slow-response component are calculated by switching control of the first DC/DC converter 30 .

In this amendment, the time constant of the fast-response component is calculated by following the structure given below. First, the switches SW1 to SW4 of the first DC/DC converter 30 are all turned off (initial state). Then, the switches SW1 and SW3 are turned on and the switches SW2 and SW4 are turned off, and the process waits until the output voltage of the fuel cell unit 20 falls to a predetermined value _Vlower (first voltage lowering operation). After confirming by the voltage sensor 31 that the output voltage has reached the predetermined value V _lower , the switches SW1 and SW3 are turned off and the switches SW2 and SW4 are turned on and the process waits until the output voltage of the fuel cell unit 20 reaches a predetermined value V _upper has increased (voltage boost operation). When it is confirmed by the voltage sensor 31 that the output voltage has risen to V _upper , SW1 and SW3 are turned on and SW2 and SW4 are turned off again, and the process waits until the output voltage falls to the predetermined value V _lower (second voltage lowering operation). Then, when it is confirmed by the voltage sensor 31 that the output voltage has reached V _lower , SW1 to SW4 are turned off.

The output voltage of the fuel cell unit 20 from the above-mentioned initial state until all the switches SW1 to SW4 are turned off again is measured by the voltage sensor 31 and the result of this measurement is recorded in the data processing device 10. The result of the measurement is recorded in the form of a time series data array. 11 shows an example of the result of the measurement by the voltage sensor 31. At t11, the first voltage reduction operation starts, at t12 the output voltage reaches V _lower and starts the voltage increase operation, at t13 the output voltage reaches V _upper and starts the second voltage reduction operation, and at t14 the output voltage reaches V _lower . In the data processing device 10, a time period T _1a from t12 to t13 and a time period T _1b from t13 to t14 are calculated. Then, based on the time period T _1a and the time period T _1b , the time constant T ₁ of the voltage V ₁ of the fast-response component in the transient response is calculated. The time constant T ₁ is calculated e.g. B. using a method in which the correlation between the average value of the period T _1a and the period T _1b and the actual time constant is defined with a map or a function or using a similar method.

When the time constant T ₁ of the fast-response component voltage V ₁ has been determined through the above procedure, operations similar to those in and after step S14 in FIG 4 executed. The difference ΔT ₁ between the time constant of the fast-response component in the normal state and the time constant T ₁ is calculated, and it is determined whether the difference ΔT ₁ is greater than or equal to the prescribed value. If larger than the prescribed value, it is determined that this deterioration is associated with changes in the reactive state of the platinum catalyst and the internal resistance of the cells.

The time constant of the slow-response component is calculated by following the procedure given below. Each switch of the first DC/DC converter 30 is switched to an initial state. The initial state of the first DC/DC converter 30 for a voltage drop operation refers to a state where the switch SW1 is on, the switch SW2 is off, and the switches SW3 and SW4 are switched with a predetermined duty cycle (a ratio between a time period in which the switch SW3 is on and the switch SW4 is off and a time period in which the switch SW3 is off and the switch SW4 is on). The initial state of the first DC/DC converter 30 for the boosting operation refers to a state in which the switch SW4 is turned on, the switch SW3 is turned off, and the switches SW1 and SW2 are at a prescribed duty cycle (a ratio between a length of time in the switch SW1 is on and the switch SW2 is off, and a period in which the switch SW1 is off and the switch SW2 is on). In this modification, the time constant of the slow-response component is calculated by controlling the voltage reducing operations, that is, by controlling the duty of the switches SW3 and SW4.

First, the duty of the switches SW3 and SW4 is set larger than the initial state for voltage lowering operations, ie, to the prescribed value, and a voltage lowering operation (a first voltage lowering operation) is performed until the output voltage of the fuel cell unit 20 falls to the predetermined value V _lower . When it is confirmed by the voltage sensor 31 that the output voltage of the first DC/DC converter 30 has reached the predetermined value V _lower , the duty of the switches SW3 and SW4 is returned to the predetermined value so that the output voltage increases from V _lower ( voltage step-up operation). When it is confirmed by the voltage sensor 31 that the output voltage has reached the predetermined value V _upper , the duty of the switches SW3 and SW4 is again set higher than the prescribed value and a voltage lowering operation (second voltage lowering operation) is performed until the output voltage reaches the predetermined value V _lower has fallen. When it is confirmed by the voltage sensor 31 that the output voltage has reached the predetermined value V _lower , the duty of the switches SW3 and SW4 is reset to the prescribed value. The output voltage of the fuel cell unit 20 from the start of the first voltage drop operation to the end of the second voltage drop operation is measured by the voltage sensor 31 of the first DC/DC converter 30 . The result of this measurement is recorded in the form of a time series data array. 12 shows an example of the result of the measurement by the strain sensor 31.

The first voltage lowering operation begins at t21, at t22 the output voltage reaches V _lower and begins the voltage boosting operation, at t23 the output voltage reaches V _upper and begins the second voltage lowering operation, and at t24 the output voltage reaches V _lower . In the data processing device 10, a time period T _2a from t22 to t23 and a time period T _2b from t23 to t24 are calculated. Then, based on the time period T _2a and the time period T _2b , the time constant T ₂ of the voltage V ₂ of the slow-response component in the transient response is calculated. The time constant T ₂ is calculated e.g. B. using a method in which the correlation between the average of the period T _2a and the period T _2b and the actual time constant is defined with a map or a function or using a similar method.

Although the increase and decrease in the output voltage of the fuel cell unit 20 is controlled by controlling the duty of the switches SW3 and SW4 in this embodiment, it is noted that the present invention is not limited to this case. The increase and decrease in the output voltage of the fuel cell unit 20 can be controlled by turning on the switch SW4, turning off the switch SW3, and controlling the duty of the switches SW1 and SW2.

Although embodiments of the present invention have been discussed above, the present invention is not limited to the above embodiments and various changes and modifications can be made based on the technical idea of the present invention.

In summary, an embodiment can be described as follows: A target value of the output current of a fuel cell unit is changed in a step pattern. A transient response of the output voltage of the fuel cell unit driven so that the output current follows this target value is measured, and the transient response is separated into a fast-response component and a slow-response component. A time constant T ₁ of the fast-response component and a time constant T ₂ of the slow-response component are calculated. A difference ΔT ₁ between the time constant of the fast responding component in the normal state and the time constant T ₁ is calculated, and a difference ΔT ₂ between the time constant of the slow responding component in the normal state and the time constant T ₂ is calculated. Based on the difference ΔT ₁ , a quali Deterioration associated with changes in the reactive state of the platinum catalyst of the fuel cell unit and the internal resistance of the cells is determined, and based on the difference ΔT ₂ , a deterioration associated with a change in the supply state of the hydrogen and the oxygen in the fuel cell unit is determined.

Reference List

10

data processing device

20

fuel cell unit

21

temperature sensor

30

first DC/DC converter

31

voltage sensor

32

current sensor

40

inverter

50

engine

60

second DC/DC converter

70

battery

Claims (3)

Deterioration detection apparatus for a vehicle fuel cell unit which detects deterioration in an on-vehicle fuel cell unit (20), the apparatus comprising: a target value setting means for setting a target value obtained by increasing an actual output current value of the fuel cell unit (20) in a step pattern by a predetermined amount; a transient response measuring means for performing an output current control of the fuel cell unit (20) such that the output current value of the fuel cell unit (20) follows the target value and measuring a transient response of the output voltage of the fuel cell unit (20) under the output current control; a transient response decomposition means for decomposing the transient response in the output voltage of the fuel cell unit (20) into a first component representing a relatively fast response and a second component representing a relatively slow response; a time constant calculation means for calculating a first time constant of the first component and a second time constant of the second component; a difference calculation means for calculating a first difference which is a difference between a first reference time constant and the first time constant and for calculating a second difference which is a difference between a second reference time constant and the second time constant, the first reference time constant being a time constant of the first component in the fuel cell unit (20) is in a normal state, wherein the second reference time constant is a time constant of the second component in the fuel cell unit (20) in the normal state; and deterioration determining means for determining that deterioration associated with changes in a reactive state of a catalyst of the fuel cell unit (20) and the resistance within a cell is occurring, and for determining the degree of deterioration if the first difference is greater than or equal to a prescribed one is value of the first component, and for determining that deterioration associated with a change in a supply state of hydrogen and oxygen in the fuel cell unit (20) is occurring, and for determining the degree of deterioration if the second difference is greater than or equal to one prescribed value of the second component, wherein if the level of degradation determined based on the second difference is above a predetermined range: an operation for recovering the fuel cell unit (20) from deterioration is carried out under conditions that allow the removal of moisture in the cell from the fuel cell unit (20) if the temperature of the fuel cell unit (20) is higher than a prescribed temperature value, and an operation for recovering the fuel cell unit (20) from deterioration is performed under a condition that allows melting of ice in the cell of the fuel cell unit (20) if the temperature of the fuel cell unit (20) is equal to or lower than the prescribed temperature value; wherein the duration of a recovery operation of the fuel cell unit (20) for recovery from the deterioration is determined based on the first difference if the deterioration determination means determines based on the first difference that the quality of the fuel cell unit (20) is degraded, and wherein the duration of a recovery operation of the fuel cell unit (20) for recovering from the deterioration is determined based on the second difference if the deterioration determination means determines based on the second difference that the fuel cell unit (20) is degraded. Deterioration detection device for a vehicle fuel cell unit claim 1 , wherein if the degree of deterioration determined based on the first difference is above a predetermined range: a first current value and a first voltage value of the fuel cell unit (20) are measured in a first area where the current density is relatively low, and a second current value and a second voltage value of the fuel cell unit (20) are measured in a second area in which the current density is higher than in the first area; an operation for recovering the fuel cell unit (20) from deterioration is performed under conditions promoting a reduction reaction of a catalyst surface of the cell of the fuel cell unit (20) if a difference between a voltage value of the fuel cell unit (20) driven by the first current value in the normal state and the first voltage value is greater than a first prescribed voltage value at the first current value; and an operation for recovering the fuel cell unit (20) from the deterioration is performed using a condition that allows humidification of a polymer membrane of the cell of the fuel cell unit (20) if the difference between the voltage value of the fuel cell unit (20) driven by the first current value in the normal state and the first voltage value is less than or equal to the first prescribed voltage value at the first current value and a difference between a voltage value of the fuel cell unit (20) driven by the second current value in the normal state and the second voltage value is greater than a second prescribed voltage value at the second current value is. Deterioration detection apparatus for a vehicle fuel cell in accordance with any one of the preceding claims, wherein if a recovery operation for recovery from the deterioration determined by the deterioration determining means is performed but the fuel cell unit (20) is not recovered from the deterioration, and a decrease in an output voltage value of the fuel cell unit (20) after the recovery operation from the output voltage value of the fuel cell unit ( 20) to the normal state is less than a predetermined allowable level: a new target value for the output current value of the fuel cell unit (20) is set; a transient response of the output voltage of the fuel cell unit (20) is measured under control such that its output current value follows the new target value; the transient response of the output voltage of the fuel cell unit (20) is decomposed into the first component and the second component; calculating a third time constant of the first component and a fourth time constant of the second component; and replacing the first reference time constant with the third time constant and replacing the second reference time constant with the fourth time constant.

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