JP2012199010A - Fuel cell status diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell status diagnostic device which can diagnose the status of a fuel cell without causing an increase in the number of components.SOLUTION: The fuel cell status diagnostic device comprises an AC current application unit 51 which applies an AC current having a predetermined waveform to a fuel cell 1, a local current detection unit 4 which detects a local current flowing to a local part of a unit cell 10 to be diagnosed, an operation unit 521 which extracts the AC component from a local current and calculates the frequency characteristics in the AC component, and status diagnosis means 62 which diagnoses the status of the fuel cell based on the correspondence of the frequency characteristics in the AC component and the frequency characteristics in the local current. Since cell voltage detection means for detecting the cell voltage of the unit cell 10 is not required, the status of the fuel cell 1 can be diagnosed without causing an increase in the number of components.

Description

  The present invention relates to a fuel cell state diagnosis device that diagnoses the state of a fuel cell.

  Conventionally, a configuration has been proposed in which the impedance (internal resistance) of a fuel cell is measured by an AC impedance method, and the state of the fuel cell is diagnosed based on the measured impedance (see, for example, Patent Document 1).

  In Patent Document 1, a local voltage of a unit cell is detected based on a detection value of a cell voltage sensor that detects a voltage (cell voltage) of a unit cell of a fuel cell and a local current sensor that detects a current flowing through a local portion of the unit cell. The impedance at the site is measured.

JP 2009-252706 A

  However, in the configuration in which the AC impedance is measured using the AC impedance method as in Patent Document 1, a local current sensor and a cell voltage sensor (cell voltage detection means) are required, so the number of parts in the fuel cell state diagnosis device is small. There is a problem that the cost increases. In particular, the cell voltage sensor needs to take special insulation measures and the like, which is a main factor for cost increase.

  An object of the present invention is to provide a fuel cell state diagnosis device capable of diagnosing the state of a fuel cell without causing an increase in the number of parts.

  In order to achieve the above object, the present inventors have made extensive studies. As a result, it is noted that the current fluctuation (response characteristics) when a predetermined alternating current is applied to the fuel cell differs depending on the state of the fuel cell, and the fuel is caused by the current fluctuation when the alternating current is applied to the fuel cell. A configuration for diagnosing the state of the battery has been devised. That is, the state of the fuel cell (1) in which a plurality of unit cells (10) for generating electric energy by electrochemical reaction of an oxidant gas mainly containing oxygen and a fuel gas mainly containing hydrogen are stacked. An apparatus for diagnosing a fuel cell state, comprising: an alternating current applying means (51) for applying an alternating current having a predetermined waveform to the fuel cell (1); and a local part of a unit cell (10) to be diagnosed Local current detecting means (4) for detecting a local current flowing through the current, frequency characteristic calculating means (521) for calculating the frequency characteristics of the alternating current component by extracting the alternating current component from the local current, frequency characteristics and local current in the alternating current And a state diagnosing means (62) for diagnosing the state of the fuel cell on the basis of the correspondence relationship with the frequency characteristic.

  According to this, since it is not necessary to provide a cell voltage detecting means for detecting the cell voltage of the unit cell (10), it is possible to diagnose the state of the fuel cell (1) without increasing the number of parts.

  Further, in the invention according to claim 2, in the fuel cell state diagnosis apparatus according to claim 1, the local transfer for calculating the local transfer function having the frequency characteristic in the alternating current as an input and the frequency characteristic in the local current as an output is calculated. A function calculation means (522) and a storage means (61) for storing a plurality of reference transfer functions set in advance according to the state of the fuel cell (1). The state diagnosis means (62) A reference transfer function corresponding to the local transfer function calculated by the transfer function calculating means (522) is selected from the reference transfer function, and the state of the fuel cell (1) is specified based on the selected reference transfer function. And

  Thus, the state of the fuel cell (1) can be diagnosed by calculating the local transfer function indicating the fluctuation of the local current when a predetermined alternating current is applied to the fuel cell (1).

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a schematic configuration diagram of a fuel cell system according to a first embodiment. 1 is a schematic diagram of a signal processing device according to a first embodiment. It is a Nyquist diagram which shows an example of the frequency characteristic of a local transfer function. It is a Nyquist diagram which shows the frequency characteristic of the local transfer function according to the state of a fuel cell. It is a Bode diagram which shows the frequency characteristic of a local transfer function at the time of changing the frequency of an alternating current. It is a flowchart which shows the control processing performed with the signal processing apparatus and control apparatus of this embodiment. It is a schematic diagram of the signal processing apparatus which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
1st Embodiment of this invention is described based on FIGS. FIG. 1 is a schematic configuration diagram of a fuel cell system according to the present embodiment, and FIG. 2 is a schematic diagram of a signal processing device 5 according to the present embodiment. This fuel cell system is applied to a so-called fuel cell vehicle, which is a kind of electric vehicle, and supplies electric power to an electric load such as an electric motor for vehicle travel.

  First, as shown in FIG. 1, the fuel cell system includes a fuel cell 1 that generates electric power using an electrochemical reaction between hydrogen and oxygen. The fuel cell 1 outputs electric energy supplied to various electric loads such as a vehicle driving electric motor and a secondary battery (not shown). In this embodiment, a solid polymer electrolyte fuel cell is employed. More specifically, the fuel cell 1 is configured by stacking a plurality of unit cells 10 as basic units and electrically connecting each unit cell 10 in series.

  As shown in FIG. 2, each unit cell 10 includes a membrane electrode assembly (MEA) 100 in which a pair of electrodes 100b and 100c are disposed on both side surfaces of an electrolyte membrane 100a made of a solid polymer, It consists of a pair of separators 101 and 102 that sandwich the membrane electrode assembly 100.

  The pair of separators 101 and 102 is made of a plate plate made of a carbon material or a conductive metal, and a hydrogen flow path (not shown) through which hydrogen flows is formed on a surface facing the anode electrode 100b, and faces the cathode electrode 100c. An air flow path (not shown) through which air flows is formed on the surface.

  In the unit cell 10, as shown below, hydrogen and oxygen are electrochemically reacted to output electric energy.

(Negative electrode side: anode electrode) H ₂ → 2H ⁺ + 2e ⁻
(Positive electrode side: cathode electrode) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
Returning to FIG. 1, the fuel cell 1 and the electrical load 2 are electrically connected via a DC-DC converter (not shown) capable of transmitting power in both directions. The DC-DC converter controls the flow of electric power from the fuel cell 1 to the electric load or from the electric load to the fuel cell 1.

  Between the plurality of unit cells 10 stacked in the fuel cell 1, a current (local current) flowing in a local portion of a specific unit cell 10 (hereinafter referred to as a diagnostic target cell 10) to be diagnosed is detected. A local current detection unit 4 (local current detection means) is provided. The local current detection unit 4 can be provided at any part between the stacked unit cells 10.

  The local current detection unit 4 includes a plurality of current sensors (5 in the present embodiment) in order to detect local currents flowing in a plurality of parts including the vicinity of the hydrogen outlet and the vicinity of the air outlet in the diagnosis target cell 10. Configured. As the current sensor constituting the local current detection unit 4, a known sensor using a shunt resistance, magnetism, or the like can be used. The output signal output from the local current detection unit 4 is arithmetically processed by the arithmetic processing unit 52 of the signal processing device 5 described later. The signal processing device 5 will be described later.

  On the cathode electrode 100 c side of the fuel cell 1, the air supply pipe 20 for supplying an oxidant gas (air) containing oxygen as a main component to the fuel cell 1 and the electrochemical reaction in the fuel cell 1 are finished. An air discharge pipe 21 for discharging surplus air and generated water generated by the air electrode from the fuel cell 1 to the outside air is connected.

  An air pump 22 for pumping air sucked from the atmosphere to the fuel cell 1 is provided at the most upstream portion of the air supply pipe 20, and an air pressure in the fuel cell 1 is adjusted in the air discharge pipe 21. An air pressure regulating valve 23 is provided. In the present embodiment, the air pump 22 and the air pressure regulating valve 23 constitute air supply means for supplying air of a predetermined flow rate and pressure to the fuel cell 1.

  On the anode electrode 100b side of the fuel cell 1, a hydrogen supply pipe 30 for supplying a fuel gas containing hydrogen as a main component to the fuel cell 1, and the generated water collected on the anode electrode 100b side together with a trace amount of hydrogen, the fuel cell 1 A hydrogen discharge pipe 31 for discharging from the outside to the outside is connected.

  A high-pressure hydrogen tank 32 filled with high-pressure hydrogen is provided at the uppermost stream portion of the hydrogen supply pipe 30, and is supplied to the fuel cell 1 between the high-pressure hydrogen tank 32 and the fuel cell 1 in the hydrogen supply pipe 30. A hydrogen pressure regulating valve 33 for adjusting the hydrogen pressure is provided. In the present embodiment, the hydrogen pressure regulating valve 33 constitutes a fuel gas side gas supply means for supplying hydrogen at a desired pressure to the fuel cell 1.

  The hydrogen discharge pipe 31 is provided with an electromagnetic valve 34 that opens and closes at predetermined time intervals in order to discharge the produced water together with a small amount of hydrogen to the outside air. In the above-described electrochemical reaction, generated water is not generated on the anode electrode 100b side, but generated water that has permeated the electrolyte membrane 100a of each cell 10 from the cathode electrode 100c side may accumulate on the anode electrode 100b side. . For this reason, in this embodiment, the hydrogen discharge piping 31 and the solenoid valve 34 are provided.

  The fuel cell system is provided with a control device (ECU) 6 as power generation control means for performing various controls. The control device 6 controls the operation of various electric actuators constituting the fuel cell system based on an input signal. The control device 6 includes a well-known microcomputer comprising a CPU, a storage means 61 such as a ROM, a RAM, and the like. It consists of a circuit.

  Specifically, the input side of the control device 6 is connected to a signal processing device 5 and a vehicle activation switch 6a provided in the vehicle interior, and output signals from the signal processing device 5 and the vehicle activation switch 6a are received. Entered. The vehicle start switch 6a also functions as a start signal output unit that outputs operation start signals for the air pump 22, the air pressure regulating valve 23, the hydrogen pressure regulating valve 33, the electromagnetic valve 34, and the like. Note that the electric pump 22, the air pressure regulating valve 23, the hydrogen pressure regulating valve 33, the various electromagnetic actuators such as the electromagnetic valve 34, and the signal processing device 5 are connected to the output side of the control device 6.

  The control device 6 of the present embodiment is configured to be capable of bidirectional communication with the signal processing device 5 and diagnoses the state of the fuel cell 1 based on the output from the signal processing device 5. In the present embodiment, a part of the control device 6 and the signal processing device 5 function as a fuel cell state diagnosis device that diagnoses the state of the fuel cell 1.

  Next, the signal processing device 5 of the present embodiment will be described. The signal processing device 5 includes an alternating current application unit 51 that applies an alternating current of an arbitrary frequency to the output current of the diagnosis target cell 10, and an arithmetic processing unit 52 that performs arithmetic processing on the local current detected by the local current detection unit 4. The output current sensor 53 detects the output current of the diagnosis target cell 10 and the like.

  The alternating current application unit 51 constitutes alternating current application means for applying an alternating current such as a sine wave at an arbitrary frequency to the output current of the diagnosis target cell 10. The AC application unit 51 of the present embodiment is configured to be able to apply an AC signal obtained by synthesizing a plurality of different frequencies to the output signal of the fuel cell 1. The alternating current applied by the alternating current application unit 51 is preferably 10% or less of the generated current in the fuel cell 1 so as not to affect the power generation state of the fuel cell 1.

  The arithmetic processing unit 52 extracts an alternating current component having the same frequency as the alternating current applied by the alternating current applying unit 51, and calculates a frequency characteristic of the extracted alternating current component, based on a calculation result in the calculating unit 521. The local transfer function calculation unit 522 that calculates the local transfer function Fn in each local region of the diagnosis target cell is configured. In the present embodiment, the calculation unit 521 constitutes a frequency characteristic calculation unit, and the local transfer function calculation unit 522 constitutes a local transfer function calculation unit.

  When the alternating current application unit 51 applies an alternating current to the diagnosis target cell 10, the calculation unit 521 uses the alternating current applied by the alternating current application unit 51 from each of the output current sensor 53 and the local current detection unit 4. AC components with the same frequency are extracted, and frequency characteristics (gain, phase difference, etc.) for each AC component are calculated. The frequency characteristic of the AC component of the output current sensor 53 obtained by the calculation unit 521 is substantially the same as the frequency characteristic of the AC current applied by the AC application unit 51.

  The local transfer function calculation unit 522 receives the frequency characteristic (overall current fluctuation) ΔI of the AC component of the output current sensor 53 obtained by the calculation unit 521 as an input, and the frequency of the AC component of each current sensor of the local current detection unit 4. A local transfer function Fn with the characteristic (local current fluctuation) Δin as an output is calculated. The frequency characteristic of the local transfer function Fn calculated by the local transfer function calculation unit 522 becomes a locus as shown in FIG. FIG. 3 is a Nyquist diagram showing an example of the frequency characteristic of the local transfer function Fn, where Re (F) is a real part, Im (F) is an imaginary part, Abs (F) is a gain, and θ (F ) Indicates the phase difference.

  The local transfer function Fn indicates a current fluctuation (response characteristic) when an alternating current is applied to the diagnosis target cell 10, and the frequency characteristic changes according to the state of the fuel cell 1. For this reason, in this embodiment, the control device 6 performs a diagnosis process for diagnosing the state of the fuel cell 1 based on the local transfer function Fn calculated by the local transfer function calculation unit 522. In this embodiment, a configuration (including software and hardware) for diagnosing the state of the fuel cell 1 in the control device 6 is referred to as a state diagnosis unit 62.

  Next, a method for diagnosing the state of the fuel cell 1 in the present embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a Nyquist diagram showing the frequency characteristics of the local transfer function Fn according to the state of the fuel cell 1. FIG. 5 is a Bode diagram showing the frequency characteristics of the local transfer function Fn when the frequency of the alternating current is changed. FIG. 5A shows the change in gain when the frequency is changed. (B) shows the change in phase difference when the frequency is changed.

  As shown in FIG. 4, it can be seen that the fuel cell 1 exhibits different frequency characteristics in a normal state (normal), an oxygen-deficient state (oxygen-deficient), and a hydrogen-deficient state (hydrogen-deficient). .

  For this reason, the storage means of the control device 6 is preliminarily stored with the transfer function in the normal state (normal) of the fuel cell 1, the oxygen-deficient state (oxygen-deficient), and the hydrogen-deficient state (hydrogen-deficient) as the reference transfer function. It is possible to estimate the state of the fuel cell 1 by comparing each reference transfer function stored in 61 and the local transfer function Fn calculated by the local transfer function calculation unit 522. Become.

  Further, as shown in FIG. 5, when the fuel cell 1 is in a normal state (normal), in an oxygen-deficient state (oxygen-deficient), and in a hydrogen-deficient state (hydrogen-deficient), in a frequency band of 10 Hz or less, It can be seen that the gain and phase difference are significantly different.

  Therefore, the frequency of the alternating current applied by the alternating current application unit 51 is set to 10 Hz or less, and when the alternating current is applied, the local transfer function Fn calculated by the local transfer function calculation unit 522 and each of the storage means 61 stored in the storage unit 61. By comparing and collating the correspondence with the reference transfer function, the state of the fuel cell 1 can be accurately estimated.

  In the unit cell 10, hydrogen deficiency is likely to occur on the outlet side of the hydrogen flow path. Therefore, by using the local transfer function Fn calculated using the local current near the outlet side of the hydrogen flow path, Hydrogen deficiency can be accurately estimated. In the unit cell 10, oxygen deficiency is likely to occur on the outlet side of the air flow path. Therefore, by using the local transfer function Fn calculated using the local current near the outlet side of the air flow path, Oxygen deficiency can be accurately estimated.

  Next, the flow of the state diagnosis process for diagnosing three types of states of the normal state, the hydrogen deficient state, and the oxygen deficient state in the fuel cell system according to the above configuration will be described with reference to the flowchart shown in FIG. The control flow shown in FIG. 6 starts when the vehicle start switch 6a is turned on (ON) and the fuel cell 1 enters the power generation state. In FIG. 6, processing performed by the signal processing device 5 and the control device 6 is shown in one flowchart.

  When the vehicle starts, first, an alternating current having a single frequency sine wave is applied from the alternating current application unit 51 of the signal processing device 5 to the diagnosis target cell 10 (S10). The frequency of the alternating current applied by the alternating current application unit 51 is set to 10 Hz or less, and is stored in the storage unit 61 in advance.

  Next, output signals from the output current sensor 53 and each current sensor of the local current detector 4 are read (S20). And the alternating current component of the same frequency as the alternating current applied in the alternating current application part 51 is extracted from the output signal of the output current sensor 53 and the local current detection part 4 in the calculating part 521 of the arithmetic processing part 52, and each alternating current component is extracted. The frequency characteristic at is calculated (S30).

  Next, the frequency characteristic (total current fluctuation) ΔI of the AC component of the output current sensor 53 calculated in step S30 is input, and the frequency characteristic (local current fluctuation) of the AC component of each current sensor of the local current detector 4 is input. ) A local transfer function Fn with Δin as an output is calculated (S40).

  Next, the local transfer function Fn calculated in step S40 is collated with the reference transfer functions in the normal state, the hydrogen-deficient state, and the oxygen-deficient state stored in advance in the storage unit 61 (S50). Specifically, the reference transfer function that selects the gain and phase difference closest to the gain and phase difference of the local transfer function Fn at the same frequency as the alternating current applied by the AC application unit 51 is selected.

  Next, it is determined whether or not the state of the fuel cell 1 corresponding to the reference transfer function selected in step S50 is a hydrogen deficiency (S60). As a result, when it is determined that there is a hydrogen deficiency, the current state of the fuel cell 1 is diagnosed as a hydrogen deficiency (S70). If it is determined that the amount of hydrogen is deficient, it is considered that the supply amount of hydrogen to the fuel cell 1 is insufficient. For example, the opening of the hydrogen pressure regulating valve 33 is increased and By increasing the amount of hydrogen supplied, hydrogen deficiency can be eliminated.

  On the other hand, as a result of the determination process in step S60, when it is determined that there is no hydrogen deficiency, it is determined whether the state of the fuel cell 1 corresponding to the reference transfer function selected in step S50 is oxygen deficient ( S80). As a result, when it is determined that there is an oxygen deficiency, the current state of the fuel cell 1 is diagnosed as being oxygen deficient (S90), and when it is determined that there is no oxygen deficiency, the current state of the fuel cell 1 is normal. Is diagnosed (S100). If it is determined that there is an oxygen deficiency, it is considered that the generated water is accumulated on the cathode electrode 100c side. Therefore, the generated water accumulated on the cathode side is increased by increasing the opening of the air pressure regulating valve 23. By exhausting from inside 1, it becomes possible to eliminate oxygen deficiency.

  According to the configuration of the present embodiment described above, the fuel cell is calculated by calculating the local transfer function Fn indicating the fluctuation of the local current when a predetermined alternating current is applied to the diagnosis target cell 10 in the fuel cell 1. One state can be diagnosed. In such a configuration, since it is not necessary to provide a cell voltage detecting means for detecting the cell voltage of the unit cell 10, it is possible to diagnose the state of the fuel cell 1 without increasing the number of parts. Therefore, it is possible to avoid an increase in the cost of the fuel electric system due to the configuration for diagnosing the state of the fuel cell 1.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram of the signal processing device 5 according to the present embodiment. In the present embodiment, description of the same or equivalent parts as in the first embodiment will be omitted or simplified.

  In the first embodiment described above, an alternating current having a single frequency is applied by the alternating current application unit 51. However, in this embodiment, an alternating current having a combined wave obtained by combining different frequencies by the alternating current application unit 51. An electric current is applied. Note that the alternating current is preferably a combined wave obtained by synthesizing frequencies that tend to have frequency characteristics that are significantly different depending on the state of the fuel cell 1.

  Specifically, an FFT processing unit 523 is provided in the arithmetic processing unit 52 of the signal processing device 5 of the present embodiment. The FFT processing unit 523 extracts an AC component for each different frequency from output signals from the output current sensor 53 and the current sensors of the local current detection unit 4 by FFT (Fast Fourier Transform).

  In the arithmetic processing unit 52 of the present embodiment, the FFT processing unit 523 extracts an AC component for each different frequency from the output signals from the current sensors of the output current sensor 53 and the local current detection unit 4, and outputs the AC component to the arithmetic unit 521. The frequency characteristic of each AC component extracted by the FFT processing unit 523 is calculated.

  According to the configuration of the present embodiment, it is possible to calculate the local transfer function Fn having different frequency characteristics at a time by the local transfer function calculation unit 522 by applying an alternating current having a combined waveform obtained by combining different frequencies. Become. Furthermore, when an alternating current of a combined wave obtained by synthesizing frequencies whose frequency characteristics tend to be significantly different depending on the state of the fuel cell 1 is applied to the diagnosis target cell 10, the local transfer function calculation unit 522 It becomes possible to calculate the local transfer function Fn having a strong correlation with the frequency characteristic. As a result, it is possible to improve the diagnostic accuracy when diagnosing the state of the fuel cell 1.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, this invention is not limited to this, Unless it deviates from the range described in each claim, it is not limited to the wording of each claim, and those skilled in the art Improvements based on the knowledge that a person skilled in the art normally has can be added as appropriate to the extent that they can be easily replaced. For example, various modifications are possible as follows.

  (1) In the first embodiment described above, the calculation unit 521 calculates the frequency characteristic of the AC component of the output current sensor 53, and uses the calculated frequency characteristic of the AC component of the output current sensor 53 as the input of the local transfer function Fn. However, it is not limited to this. Since the frequency characteristic of the AC component of the output current sensor 53 obtained by the calculation unit 521 is substantially the same as the frequency characteristic of the AC current applied by the AC application unit 51, the AC applied by the AC application unit 51 The frequency characteristic of the current may be used as the input of the local transfer function Fn. According to this, since the output current sensor 53 can be omitted, the number of parts having a configuration for diagnosing the state of the fuel cell 1 can be reduced.

  (2) In each of the above-described embodiments, the example in which the local transfer function Fn and the reference transfer function are collated based on the correlation between the gain and the phase difference of each transfer function has been described. You may make it collate by the combination of the gain and phase difference in a transfer function, and the electric current value detected in the local electric current detection part 4. FIG.

  (3) As in the above-described embodiments, the frequency of the alternating current applied by the alternating current application unit 51 is preferably 10 Hz or less, but is not limited to this, for example, from 0.1 Hz to several hundred kHz. It is good also as arbitrary frequency between.

  (4) In the above-described embodiments, the frequency of the alternating current applied by the alternating current application unit 51 is constant. However, the present invention is not limited to this. For example, the frequency of the alternating current applied by the alternating current application unit 51 is variable. The state of the fuel cell 1 may be diagnosed for each changed frequency.

  (5) In each of the above-described embodiments, the example in which the local current detection unit 4 is configured with a plurality of current sensors in the local part (plural places) of the unit cell 10 is described. However, the present invention is not limited to this. You may comprise with the single electric current sensor arrange | positioned corresponding to ten local site | parts (one place).

  (6) In each of the above-described embodiments, the alternating current application unit 51 is configured to apply an alternating current having a single frequency sine wave or a synthesized wave obtained by synthesizing the sine wave to the diagnosis target cell 10. However, the present invention is not limited to this. For example, a configuration may be adopted in which an alternating current having a single-frequency rectangular wave or impulse wave, or a synthesized wave thereof is applied.

  (7) In each above-mentioned embodiment, although it is set as the structure which applies an alternating current with respect to the diagnostic object cell 10 in the alternating current application part 51, it is not limited to this, For example, it is a diagnostic object using a DC-DC converter. It is good also as a structure which applies an alternating current with respect to the cell 10. FIG. Thereby, reduction of the number of parts of the structure which diagnoses the state of the fuel cell 1 can be aimed at.

  (8) In each of the above-described embodiments, the signal processing device 5 and the control device 6 have been described as examples of performing the state diagnosis processing for diagnosing three types of states such as a normal state, a hydrogen deficient state, and an oxygen deficient state. It is not limited to this. For example, a dry-up in which a local part of the unit cell 10 of the fuel cell 1 is dried, an excessive hydrogen supply in which hydrogen is excessively supplied to the unit cell 10 of the fuel cell 1, and an excessive amount of oxygen (air) to the unit cell 10 of the fuel cell 1 ), The frequency characteristics of the local transfer function Fn are different. Therefore, a local transfer function Fn in a state such as dry-up, excessive hydrogen supply, excessive oxygen supply, or the like may be calculated to diagnose a state such as dry-up, excessive hydrogen supply, excessive oxygen supply, or the like.

  (9) In each of the above-described embodiments, the example in which the output signals from the local current detection unit 4 and the output current sensor 53 are calculated by the calculation processing unit 52 of the signal processing device 5 has been described. For example, the processing performed by the arithmetic processing unit 52 may be performed by the control device 6.

  (10) In each of the above-described embodiments, the example of diagnosing the state of the fuel cell 1 mounted on the fuel cell vehicle has been described. However, the present invention is not limited to this, and it is not limited to this. The state of the fuel cell 1 may be diagnosed.

DESCRIPTION OF SYMBOLS 1 Fuel cell 10 Unit cell 4 Local current detection part (local current detection means)
51 AC application section (AC current application means)
521 Calculation unit (frequency characteristic calculation means)
522 Local transfer function calculation unit (local transfer function calculation means)
61 Storage means 62 State diagnosis means

Claims (2)

Diagnosing the state of the fuel cell (1) in which a plurality of unit cells (10) for generating electric energy by electrochemical reaction of an oxidant gas mainly containing oxygen and a fuel gas mainly containing hydrogen are stacked. A fuel cell condition diagnosis device,
AC current application means (51) for applying an AC current having a predetermined waveform to the fuel cell (1);
Local current detection means (4) for detecting a local current flowing in a local part of the unit cell (10) to be diagnosed;
Frequency characteristic calculating means (521) for extracting an alternating current component from the local current and calculating a frequency characteristic in the alternating current component;
A state diagnosing means (62) for diagnosing the state of the fuel cell based on the correspondence relationship between the frequency characteristic in the alternating current and the frequency characteristic in the local current;
A fuel cell state diagnosis apparatus comprising: A local transfer function calculating means (522) for calculating a local transfer function having the frequency characteristic in the alternating current as an input and the frequency characteristic in the local current as an output;
Storage means (61) for storing a plurality of reference transfer functions set in advance according to the state of the fuel cell (1),
The state diagnosis means (62) selects a reference transfer function corresponding to the local transfer function calculated by the transfer function calculation means (522) from the plurality of reference transfer functions, and based on the selected reference transfer function The fuel cell state diagnosis apparatus according to claim 1, wherein the state of the fuel cell (1) is specified.

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