JP2008130308A - Fuel cell system - Google Patents

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JP2008130308A
JP2008130308A JP2006312640A JP2006312640A JP2008130308A JP 2008130308 A JP2008130308 A JP 2008130308A JP 2006312640 A JP2006312640 A JP 2006312640A JP 2006312640 A JP2006312640 A JP 2006312640A JP 2008130308 A JP2008130308 A JP 2008130308A
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fuel cell
exhaust gas
amount
partial pressure
cathode
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JP5103877B2 (en
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Hidetsugu Izuhara
英嗣 伊豆原
Yuichi Sakagami
祐一 坂上
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Denso Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of diagnosing precisely moisture status inside the fuel cell. <P>SOLUTION: The fuel cell system includes a fuel cell 10, a current sensor 12 to detect output current of the fuel cell 10, an air flow sensor 24 to detect air flow-rate supplied to the fuel cell 10, an oxygen sensor 25 to detect oxygen concentration in the cathode exhaust gas, and a pressure sensor 26 to detect the total pressure of the cathode exhaust gas. Oxygen partial pressure in the cathode exhaust gas is obtained by the oxygen concentration and the total pressure of the cathode exhaust gas, the steam partial pressure in the cathode exhaust gas is obtained by subtracting the oxygen partial pressure and nitrogen partial pressure from the total pressure of the cathode exhaust gas, and the moisture volume included in the cathode exhaust gas is obtained as a discharge water quantity by the steam partial pressure and the air flow-rate. The generated water quantity generated by the electrochemical reaction is obtained based on the output current of the fuel cell 10, and by subtracting the discharged water quantity from the generated water quantity, remaining water quantity is obtained, and the moisture status inside the fuel cell 10 is diagnosed based on the remaining water quantity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、水素と酸素との電気化学反応により電気エネルギを発生させる燃料電池を備える燃料電池システムに関するもので、車両、船舶及びポータブル発電機等の移動体用発電機に適用して有効である。   The present invention relates to a fuel cell system including a fuel cell that generates electrical energy by an electrochemical reaction between hydrogen and oxygen, and is effective when applied to a mobile generator such as a vehicle, a ship, and a portable generator. .

固体高分子型燃料電池は、燃料電池内部の電解質膜の導電率を維持するために加湿する必要がある。燃料電池の内部水分量が少なく電解質膜が乾燥している場合には、内部抵抗が大きくなり燃料電池の出力電圧が低下する。一方、燃料電池の内部水分量が過剰である場合には、燃料電池の電極が水分で覆われてしまうため、反応物質である酸素、水素の拡散が阻害され、出力電圧が低下する。   The polymer electrolyte fuel cell needs to be humidified in order to maintain the conductivity of the electrolyte membrane inside the fuel cell. When the amount of moisture in the fuel cell is small and the electrolyte membrane is dry, the internal resistance increases and the output voltage of the fuel cell decreases. On the other hand, when the internal water content of the fuel cell is excessive, the electrode of the fuel cell is covered with water, so that the diffusion of oxygen and hydrogen as reactants is hindered, and the output voltage decreases.

このため、燃料電池の内部水分量を診断する方法として、ガス循環系の静圧、全圧、温度から水蒸気分圧を算出する方法（特許文献１参照）や、燃料電池カソード側に供給される空気流量、燃料電池温度、燃料電池の発電量から燃料電池からの排水量を算出し、燃料電池内部における生成水量と排水量からセル内部の水分を推定する方法（特許文献２参照）が提案されている。
特開２００４−３９３９８号公報 特開２００４−３４２４７３号公報 For this reason, as a method for diagnosing the internal water content of the fuel cell, a method for calculating the partial pressure of water vapor from the static pressure, total pressure, and temperature of the gas circulation system (see Patent Document 1), or the fuel cell cathode side is supplied. A method has been proposed in which the amount of water discharged from the fuel cell is calculated from the air flow rate, the fuel cell temperature, and the amount of power generated by the fuel cell, and the moisture inside the cell is estimated from the amount of generated water and the amount of water discharged inside the fuel cell (see Patent Document 2). .
JP 2004-39398 A JP 2004-342473 A

しかしながら、ガス圧力を検出する特許文献１の構成では、燃料電池のカソード側では、発電量により酸素消費量が変化してガス流量が変化して圧損等の影響を受けるため、圧力検知による水蒸気検出は精度に欠けるという問題がある。また、排水量の算出に温度を用いる特許文献２の構成では、温度によって水分蒸発量が一定でないため、精度に欠けるという問題がある。   However, in the configuration of Patent Document 1 that detects the gas pressure, on the cathode side of the fuel cell, the oxygen consumption changes due to the amount of power generation, and the gas flow rate changes to affect the pressure loss. Has a problem of lack of accuracy. Moreover, in the structure of patent document 2 which uses temperature for calculation of a waste_water | drain amount, since the amount of water evaporation is not constant with temperature, there exists a problem that accuracy is missing.

本発明は上記点に鑑み、燃料電池の内部水分状態を正確に診断することができる燃料電池システムを提供することを目的とする。   In view of the above points, an object of the present invention is to provide a fuel cell system that can accurately diagnose the internal moisture state of a fuel cell.

上記目的を達成するため、本発明の第１の特徴は、酸素と水素を電気化学反応させて電気エネルギーを発生させる燃料電池（１０）と、燃料電池（１０）の出力電流を検出する電流検出手段（１２）と、燃料電池（１０）のカソード側に供給される空気であるカソード供給ガスの流量を検出する流量検出手段（２４）と、燃料電池（１０）のカソード側から排出されるカソード排ガス中の酸素濃度を検出する排ガス酸素濃度検出手段（２５）と、カソード排ガスの全圧を検出する排ガス圧力検出手段（２６）とを備える燃料電池システムであって、
カソード排ガス中の酸素濃度とカソード排ガスの全圧とから、カソード排ガス中の酸素分圧を取得する排ガス酸素分圧取得手段と、カソード排ガスにおける窒素分圧を取得する排ガス窒素分圧取得手段と、カソード排ガスの全圧から酸素分圧と窒素分圧とを減算して、カソード排ガス中の水蒸気分圧を取得する排ガス水蒸気分圧取得手段と、水蒸気分圧と流量検出手段（２４）により検出された空気流量とからカソード排ガスに含まれる水分量を排水量として取得する排水量取得手段と、燃料電池（１０）の出力電流に基づいて電気化学反応で生成する生成水量を取得し、生成水量から排水量を減算して燃料電池（１０）内部における残留水量を取得する残留水量取得手段と、残留水量取得手段により取得された残留水量に基づいて燃料電池（１０）内部における水分状態を診断する水分状態診断手段とを備えることである。 In order to achieve the above object, a first feature of the present invention is that a fuel cell (10) that generates electric energy by electrochemical reaction of oxygen and hydrogen, and current detection that detects an output current of the fuel cell (10). Means (12), flow rate detecting means (24) for detecting the flow rate of cathode supply gas which is air supplied to the cathode side of the fuel cell (10), and cathode discharged from the cathode side of the fuel cell (10) A fuel cell system comprising exhaust gas oxygen concentration detection means (25) for detecting oxygen concentration in exhaust gas and exhaust gas pressure detection means (26) for detecting total pressure of cathode exhaust gas,
From the oxygen concentration in the cathode exhaust gas and the total pressure of the cathode exhaust gas, exhaust gas oxygen partial pressure acquisition means for acquiring the oxygen partial pressure in the cathode exhaust gas, exhaust gas nitrogen partial pressure acquisition means for acquiring the nitrogen partial pressure in the cathode exhaust gas, Detected by the exhaust gas water vapor partial pressure acquisition means for subtracting the oxygen partial pressure and the nitrogen partial pressure from the total pressure of the cathode exhaust gas to acquire the water vapor partial pressure in the cathode exhaust gas, and the water vapor partial pressure and flow rate detection means (24). The amount of water contained in the cathode exhaust gas from the air flow rate is obtained as the amount of waste water, and the amount of water produced by the electrochemical reaction is obtained based on the output current of the fuel cell (10), and the amount of waste water is obtained from the amount of water produced. A residual water amount acquisition means for subtracting and acquiring a residual water amount inside the fuel cell (10), and a fuel cell based on the residual water amount acquired by the residual water amount acquisition means 10) it is to comprise a moisture condition diagnosis means for diagnosing a water state in the interior.

このように、カソード供給ガスの流量を測定し、カソード排ガスの酸素濃度と圧力を測定することで、燃料電池（１０）内部の水分状態を精度よく診断することができる。   Thus, the moisture state inside the fuel cell (10) can be accurately diagnosed by measuring the flow rate of the cathode supply gas and measuring the oxygen concentration and pressure of the cathode exhaust gas.

また、燃料電池（１０）の出力電流に基づいて電気化学反応による消費酸素量を取得し、空気中の酸素量から消費酸素量を減算してカソード排ガス中の酸素濃度を取得する排ガス酸素濃度取得手段を設けることで、カソード排ガス中の酸素濃度を検出する排ガス酸素濃度検出手段（２５）を省略することができる。   Further, the exhaust gas oxygen concentration acquisition is obtained by acquiring the oxygen consumption amount by the electrochemical reaction based on the output current of the fuel cell (10) and subtracting the oxygen consumption amount from the oxygen amount in the air to obtain the oxygen concentration in the cathode exhaust gas. By providing the means, the exhaust gas oxygen concentration detection means (25) for detecting the oxygen concentration in the cathode exhaust gas can be omitted.

また、本発明の第２の特徴は、カソード供給ガスを加湿する加湿手段（２２）と、加湿手段（２２）で加湿されたカソード供給ガスの酸素濃度を検出する供給ガス酸素濃度検出手段（２７）と、加湿手段（２２）で加湿されたカソード供給ガスの全圧を検出する供給ガス圧力検出手段（２８）と、供給ガス酸素濃度検出手段（２７）により検出したカソード供給ガス中の酸素濃度と供給ガス圧力検出手段（２８）により検出したカソード供給ガスの全圧とから、カソード供給ガス中の酸素分圧を取得する供給ガス酸素分圧取得手段と、カソード供給ガスの窒素分圧を取得する供給ガス窒素分圧取得手段と、カソード供給ガスの全圧から酸素分圧と窒素分圧とを減算して、カソード供給ガス中の水蒸気分圧を取得する供給ガス水蒸気分圧取得手段と、カソード供給ガス中の水蒸気分圧と流量検出手段（２４）により検出された空気流量とからカソード供給ガスに含まれる水分量を加湿量として取得する加湿量取得手段とを備え、残留水量取得手段は、生成水量に加湿量を加算した値から排水量を減算して燃料電池（１０）内部における残留水量を取得することである。   The second feature of the present invention is that the humidifying means (22) for humidifying the cathode supply gas and the supply gas oxygen concentration detecting means (27) for detecting the oxygen concentration of the cathode supply gas humidified by the humidifying means (22). ), Supply gas pressure detection means (28) for detecting the total pressure of the cathode supply gas humidified by the humidification means (22), and oxygen concentration in the cathode supply gas detected by the supply gas oxygen concentration detection means (27) Supply gas oxygen partial pressure acquisition means for acquiring the oxygen partial pressure in the cathode supply gas, and nitrogen partial pressure of the cathode supply gas is acquired from the total pressure of the cathode supply gas detected by the supply gas pressure detection means (28). Supply gas nitrogen partial pressure acquisition means for subtracting the oxygen partial pressure and nitrogen partial pressure from the total pressure of the cathode supply gas to obtain the water vapor partial pressure in the cathode supply gas And a humidification amount acquisition means for acquiring a moisture amount contained in the cathode supply gas as a humidification amount from the partial pressure of water vapor in the cathode supply gas and the air flow rate detected by the flow rate detection means (24). The means is to obtain the residual water amount in the fuel cell (10) by subtracting the drainage amount from the value obtained by adding the humidification amount to the generated water amount.

これにより、カソード供給ガスの加湿量を考慮して燃料電池（１０）の残留水量を算出することができ、燃料電池（１０）内部の水分状態を精度よく診断することができる。   Thereby, the residual water amount of the fuel cell (10) can be calculated in consideration of the humidification amount of the cathode supply gas, and the moisture state inside the fuel cell (10) can be diagnosed with high accuracy.

また、本発明の第３の特徴は、燃料電池（１０）の運転を停止させる際に、燃料電池（１０）の空気極の乾燥処理を行うパージ手段を備え、パージ手段は、排ガス酸素濃度取得手段により取得したアノード排ガス中の酸素濃度が所定値を下回っている場合に、乾燥処理を行うことである。これにより、燃料電池（１０）内部の水分量状態に基づいて乾燥処理を効率よく行うことができる。   Further, the third feature of the present invention is provided with a purge means for drying the air electrode of the fuel cell (10) when the operation of the fuel cell (10) is stopped, and the purge means acquires the exhaust gas oxygen concentration. When the oxygen concentration in the anode exhaust gas obtained by the means is below a predetermined value, the drying process is performed. Thereby, a drying process can be performed efficiently based on the moisture content state inside the fuel cell (10).

なお、上記各手段の括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示すものである。   In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

（第１実施形態）
本発明の第１実施形態に係る燃料電池システムについて説明する。図１は本実施形態に係る燃料電池システムを示す模式図で、この燃料電池システムは例えば電気自動車に適用される。 (First embodiment)
A fuel cell system according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a fuel cell system according to this embodiment, and this fuel cell system is applied to, for example, an electric vehicle.

図１に示すように、本実施形態の燃料電池システムは、水素と酸素との電気化学反応を利用して電力を発生する燃料電池１０を備えている。この燃料電池１０は、電力機器１１や２次電池（図示せず）等に電力を供給するように構成されている。電気自動車の場合、車両走行駆動源としての電動モータが電力機器１１に相当する。   As shown in FIG. 1, the fuel cell system of this embodiment includes a fuel cell 10 that generates electric power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell 10 is configured to supply power to the power device 11 and a secondary battery (not shown). In the case of an electric vehicle, an electric motor as a vehicle driving source corresponds to the electric power device 11.

本実施形態では燃料電池１０として固体高分子電解質型燃料電池を用いており、基本単位となるセルが複数個積層され、且つ電気的に直列接続されている。セルの構成については後述する。燃料電池１０では、以下の水素と酸素の電気化学反応が起こり電気エネルギが発生する。   In the present embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of cells serving as basic units are stacked and electrically connected in series. The configuration of the cell will be described later. In the fuel cell 10, the following electrochemical reaction between hydrogen and oxygen occurs to generate electric energy.

（水素極：アノード）Ｈ2→２Ｈ+＋２ｅ-
（空気極：カソード）２Ｈ+＋１／２Ｏ2＋２ｅ-→Ｈ2Ｏ
燃料電池システムには、燃料電池１０の出力電流を検出する電流検出手段としての電流センサ１２が設けられている。電流センサ１２で検出した電流信号は、後述する制御部４０に入力されるようになっている。 (Hydrogen electrode: anode) H 2 → 2H + + 2e −
(Air electrode: cathode) 2H + + 1 / 2O 2 + 2e − → H 2 O
The fuel cell system is provided with a current sensor 12 as current detection means for detecting the output current of the fuel cell 10. The current signal detected by the current sensor 12 is input to the control unit 40 described later.

燃料電池システムには、燃料電池１０の空気極（正極）側に空気（酸素）を供給するための空気流路２０と、燃料電池１０の水素極（負極）側に水素を供給するための水素流路３０が設けられている。   The fuel cell system includes an air flow path 20 for supplying air (oxygen) to the air electrode (positive electrode) side of the fuel cell 10 and hydrogen for supplying hydrogen to the hydrogen electrode (negative electrode) side of the fuel cell 10. A flow path 30 is provided.

空気流路２０の最上流部には、大気中から吸入した空気を燃料電池１０に圧送するための空気供給装置２１が設けられている。空気供給装置２１としては、例えばコンプレッサを用いることができる。空気流路２０における空気供給装置２１と燃料電池１０との間には、空気への加湿を行う加湿手段としての加湿器２２が設けられ、空気流路２０における燃料電池１０の下流側には、燃料電池１０に供給される空気の圧力を調整するための空気調圧弁２３が設けられている。   An air supply device 21 for pumping air sucked from the atmosphere to the fuel cell 10 is provided at the most upstream portion of the air flow path 20. For example, a compressor can be used as the air supply device 21. Between the air supply device 21 and the fuel cell 10 in the air flow path 20, a humidifier 22 is provided as a humidifying means for humidifying the air, and on the downstream side of the fuel cell 10 in the air flow path 20, An air pressure regulating valve 23 for adjusting the pressure of the air supplied to the fuel cell 10 is provided.

空気流路２０における空気供給装置２１の上流側には、燃料電池１０の空気極に供給されるカソード供給ガス（大気）の流量を検出するためのエアフロセンサ２４が設けられている。空気流路２０における燃料電池１０の下流側で、かつ、空気調圧弁２３の上流側には、燃料電池１０の空気極から排出されるカソード排ガスの酸素濃度を検出する酸素センサ２５と、カソード排ガスの圧力を検出する圧力センサ２６が設けられている。酸素センサ２５で検出した酸素濃度信号と圧力センサ２６で検出した圧力信号は、後述する制御部４０に入力されるようになっている。なお、エアフロセンサ２４が本発明の流量検出手段に相当し、酸素センサ２５が本発明の排ガス酸素濃度検出手段に相当し、圧力センサ２６が本発明の排ガス圧力検出手段に相当している。   An airflow sensor 24 for detecting the flow rate of the cathode supply gas (atmosphere) supplied to the air electrode of the fuel cell 10 is provided upstream of the air supply device 21 in the air flow path 20. An oxygen sensor 25 for detecting the oxygen concentration of the cathode exhaust gas discharged from the air electrode of the fuel cell 10 and a cathode exhaust gas are disposed downstream of the fuel cell 10 in the air flow path 20 and upstream of the air pressure regulating valve 23. A pressure sensor 26 is provided for detecting the pressure. The oxygen concentration signal detected by the oxygen sensor 25 and the pressure signal detected by the pressure sensor 26 are input to the control unit 40 described later. The airflow sensor 24 corresponds to the flow rate detection means of the present invention, the oxygen sensor 25 corresponds to the exhaust gas oxygen concentration detection means of the present invention, and the pressure sensor 26 corresponds to the exhaust gas pressure detection means of the present invention.

水素流路３０の最上流部には、水素供給装置３１が設けられている。本実施形態では、水素供給装置３１として、水素が充填された高圧水素タンクを用いている。水素供給装置３１からの燃料電池１０への水素供給量の調整は、後述の制御部４０により行われる。水素流路３０における燃料電池１０の下流側は、燃料電池１０の上流側に接続されて水素流路３０が閉ループに構成されている。これにより、水素流路３０内で水素を循環させて、燃料電池１０での未使用水素を燃料電池１０に再供給するようにしている。そして、水素流路３０における燃料電池１０の下流側には、水素流路３０内で水素を循環させるための水素ポンプ３２が設けられている。   A hydrogen supply device 31 is provided at the most upstream part of the hydrogen flow path 30. In the present embodiment, a high-pressure hydrogen tank filled with hydrogen is used as the hydrogen supply device 31. Adjustment of the hydrogen supply amount from the hydrogen supply device 31 to the fuel cell 10 is performed by the control unit 40 described later. The downstream side of the fuel cell 10 in the hydrogen channel 30 is connected to the upstream side of the fuel cell 10 so that the hydrogen channel 30 is configured in a closed loop. Thus, hydrogen is circulated in the hydrogen flow path 30 so that unused hydrogen in the fuel cell 10 is resupplied to the fuel cell 10. A hydrogen pump 32 for circulating hydrogen in the hydrogen flow path 30 is provided on the downstream side of the fuel cell 10 in the hydrogen flow path 30.

制御部（ＥＣＵ）４０は、ＣＰＵ、ＲＯＭ、ＲＡＭ等からなる周知のマイクロコンピュータとその周辺回路にて構成されている。そして、制御部４０には、電流センサ１２からの電流信号、酸素センサ２５からの酸素濃度信号、圧力センサ２６からの圧力信号等が入力される。また、燃料電池制御部４０は、演算結果に基づいて、空気供給装置２１、加湿器２２、空気調圧弁２３、水素ポンプ３２等に制御信号を出力する。   The control unit (ECU) 40 is composed of a well-known microcomputer comprising a CPU, ROM, RAM, etc. and its peripheral circuits. The controller 40 receives a current signal from the current sensor 12, an oxygen concentration signal from the oxygen sensor 25, a pressure signal from the pressure sensor 26, and the like. Further, the fuel cell control unit 40 outputs a control signal to the air supply device 21, the humidifier 22, the air pressure regulating valve 23, the hydrogen pump 32, and the like based on the calculation result.

次に、本実施形態の燃料電池システムの水分量診断制御について説明する。図２は、制御部４０のＣＰＵがＲＯＭ等に格納された制御プログラムにしたがって行う水分量診断制御の流れを示すフローチャートである。図２に示す水分量診断制御は、所定の制御間隔で繰り返し行われる。   Next, the moisture amount diagnosis control of the fuel cell system of the present embodiment will be described. FIG. 2 is a flowchart showing a flow of moisture amount diagnosis control performed by the CPU of the control unit 40 in accordance with a control program stored in a ROM or the like. The moisture amount diagnosis control shown in FIG. 2 is repeatedly performed at predetermined control intervals.

図２に示すように、まず、燃料電池システムの運転を終了させるか否かを判定する（Ｓ１００）。この結果、燃料電池システムの運転を終了させないと判定された場合には（Ｓ１００：ＮＯ）、エアフロセンサ２４によりカソード供給ガスの流量を測定し（Ｓ１１０）、酸素センサ２５によりカソード排ガスの酸素濃度を測定し（Ｓ１２０）、圧力センサ２６によりカソード排ガスの圧力を測定し（Ｓ１３０）、電流センサ１２により燃料電池１０の出力電流を測定する（Ｓ１４０）。   As shown in FIG. 2, it is first determined whether or not the operation of the fuel cell system is to be terminated (S100). As a result, when it is determined not to end the operation of the fuel cell system (S100: NO), the flow rate of the cathode supply gas is measured by the airflow sensor 24 (S110), and the oxygen concentration of the cathode exhaust gas is determined by the oxygen sensor 25. The pressure sensor 26 measures the pressure of the cathode exhaust gas (S130), and the current sensor 12 measures the output current of the fuel cell 10 (S140).

次に、燃料電池１０の空気極からの排水量を算出する（Ｓ１５０）。ここで、排水量の算出方法について説明する。   Next, the amount of drainage from the air electrode of the fuel cell 10 is calculated (S150). Here, a method for calculating the amount of drainage will be described.

図３は、エアフロセンサ２４を通過するカソード供給ガスの組成と、酸素センサ２５および圧力センサ２６を通過するカソード排ガスの組成を示している。カソード供給ガス（大気）は、酸素と窒素を約２：８の割合で含んでおり、圧力は大気圧となっている。カソード供給ガス中の酸素が電気化学反応で消費され、電気化学反応により発生する生成水の一部が水蒸気として排出される。このためカソード排ガスは、大気に対して、酸素が減少し、水蒸気が新規に加わっている。カソード排ガスの圧力は、燃料電池１０出口の背圧であり、エアフロセンサ２４を通過するカソード供給ガスより高圧となっている。   FIG. 3 shows the composition of the cathode supply gas passing through the airflow sensor 24 and the composition of the cathode exhaust gas passing through the oxygen sensor 25 and the pressure sensor 26. The cathode supply gas (atmosphere) contains oxygen and nitrogen at a ratio of about 2: 8, and the pressure is atmospheric pressure. Oxygen in the cathode supply gas is consumed by the electrochemical reaction, and a part of the generated water generated by the electrochemical reaction is discharged as water vapor. For this reason, oxygen is reduced in the cathode exhaust gas, and water vapor is newly added to the atmosphere. The pressure of the cathode exhaust gas is the back pressure at the outlet of the fuel cell 10 and is higher than the cathode supply gas passing through the airflow sensor 24.

窒素は電気化学反応に関与しないため、ガス中の窒素の組成は変化せず、カソード供給ガスとカソード排ガスにおける窒素モル分率は同一となっている。このため、圧力センサ２６で測定したカソード排ガスの全圧に既知の窒素モル分率を乗算することで、カソード排ガス中の窒素分圧を取得することができる。そして、カソード排ガスの全圧に酸素センサ２５で測定した酸素濃度を乗算することで、カソード排ガス中の酸素分圧を取得することができる。   Since nitrogen does not participate in the electrochemical reaction, the composition of nitrogen in the gas does not change, and the nitrogen mole fraction in the cathode supply gas and the cathode exhaust gas is the same. Therefore, the partial pressure of nitrogen in the cathode exhaust gas can be obtained by multiplying the total pressure of the cathode exhaust gas measured by the pressure sensor 26 by a known nitrogen mole fraction. Then, the partial pressure of oxygen in the cathode exhaust gas can be obtained by multiplying the total pressure of the cathode exhaust gas by the oxygen concentration measured by the oxygen sensor 25.

図３に示すように、カソード排ガスは、主に窒素と酸素と水蒸気から構成されているので、カソード排ガスの全圧から窒素分圧と酸素分圧を減算することで、水蒸気分圧を取得することができる。そして、エアフロセンサ２４で測定した空気流量に水蒸気分圧を乗算することで、カソード排ガスに含まれる水蒸気流量を取得することができ、気体の状態方程式を用いて単位時間あたりの燃料電池１０の空気極からの排水量を算出することができる。   As shown in FIG. 3, since the cathode exhaust gas is mainly composed of nitrogen, oxygen, and water vapor, the water vapor partial pressure is obtained by subtracting the nitrogen partial pressure and the oxygen partial pressure from the total pressure of the cathode exhaust gas. be able to. Then, by multiplying the air flow rate measured by the airflow sensor 24 by the water vapor partial pressure, the water vapor flow rate contained in the cathode exhaust gas can be obtained, and the air of the fuel cell 10 per unit time can be obtained using the gas state equation. The amount of drainage from the pole can be calculated.

図２に戻り、Ｓ１４０で測定した出力電流から電気化学反応で発生する生成水量を算出する（Ｓ１６０）。電気化学反応による生成水量〔ｍｏｌ／ｓ〕は、出力電流Ｉ／（２×Ｆ）で求めることができる。ただし、Ｆはファラデー定数である。   Returning to FIG. 2, the amount of water produced by the electrochemical reaction is calculated from the output current measured in S140 (S160). The amount of water produced by the electrochemical reaction [mol / s] can be determined by the output current I / (2 × F). However, F is a Faraday constant.

次に、生成水量から排水量を減算することで、燃料電池１０の空気極における残留水量を算出し（Ｓ１７０）、残留水量に基づいて燃料電池１０の水分量を診断する（Ｓ１８０）。   Next, the residual water amount at the air electrode of the fuel cell 10 is calculated by subtracting the drainage amount from the generated water amount (S170), and the water content of the fuel cell 10 is diagnosed based on the residual water amount (S180).

図４は、燃料電池１０の出力と残留水量の関係を示している。図４に示すように、燃料電池１０の出力は、残留水量の増加にともなって増加し、所定の残留水量でピークに達した後、残留水量の増加に伴って減少する。このため、燃料電池１０の出力がピーク付近となる残留水量の範囲の上限値と下限値を予め設定しておき、Ｓ１７０で取得した残留水量が上限値を上回っている場合に水分過剰と診断し、下限値を下回っている場合に水分不足と診断することができる。   FIG. 4 shows the relationship between the output of the fuel cell 10 and the amount of residual water. As shown in FIG. 4, the output of the fuel cell 10 increases as the residual water amount increases, reaches a peak at a predetermined residual water amount, and then decreases as the residual water amount increases. For this reason, the upper limit value and the lower limit value of the residual water amount range in which the output of the fuel cell 10 is in the vicinity of the peak are set in advance, and when the residual water amount acquired in S170 exceeds the upper limit value, it is diagnosed that there is excess water. If it is below the lower limit, it can be diagnosed that water is insufficient.

図２に戻り、Ｓ１８０の診断結果に基づいて燃料電池１０の内部水分量の制御を行う（Ｓ１９０）。燃料電池１０の内部水分量の制御は、例えば加湿器２２による燃料電池１０へのカソード供給ガスの加湿量の調整により行うことができる。さらに、空気供給装置２１による燃料電池１０への空気供給量の調整や空気調圧弁２３による燃料電池１０への空気供給圧力の調整を行うことで、燃料電池１０内での水分蒸発量を調整して内部水分量を制御することができる。   Returning to FIG. 2, the internal moisture content of the fuel cell 10 is controlled based on the diagnosis result of S180 (S190). The internal moisture content of the fuel cell 10 can be controlled by adjusting the humidification amount of the cathode supply gas to the fuel cell 10 by the humidifier 22, for example. Furthermore, the amount of water evaporation in the fuel cell 10 is adjusted by adjusting the air supply amount to the fuel cell 10 by the air supply device 21 and adjusting the air supply pressure to the fuel cell 10 by the air pressure regulating valve 23. The internal moisture content can be controlled.

次に、燃料電池１０を運転終了させる際の水分除去処理について説明する。燃料電池１０内部に多量の水分を残留させたまま燃料電池１０を停止させた場合には、低温環境下で残留水が凍結して、燃料電池１０が始動できなくなる。このため、燃料電池１０を停止させる際に、燃料電池１０内部の残留水量を運転時における適正水分量より少ない低温時始動可能範囲（図４参照）にする必要がある。   Next, a description will be given of a moisture removal process when the fuel cell 10 is terminated. When the fuel cell 10 is stopped while a large amount of water remains inside the fuel cell 10, the remaining water freezes in a low temperature environment, and the fuel cell 10 cannot be started. For this reason, when the fuel cell 10 is stopped, the residual water amount in the fuel cell 10 needs to be within a startable range at low temperature (see FIG. 4) that is smaller than the appropriate water amount during operation.

そこで、Ｓ１００の判定処理で、燃料電池システムの運転を終了させると判定された場合には（Ｓ１００：ＹＥＳ）、以下のように燃料電池１０の水分除去処理を行う。まず、酸素センサ２５によりカソード排ガスの酸素濃度を測定し（Ｓ２００）、カソード排ガスの酸素濃度が所定値を上回っているか否かを判定する（Ｓ２１０）。この判定処理では、カソード排ガス中の酸素濃度から燃料電池１０の残留水量を推定しており、「所定値」は低温時始動可能範囲の上限水分量に対応する酸素濃度である。   Therefore, if it is determined in S100 that the operation of the fuel cell system is to be terminated (S100: YES), the water removal process of the fuel cell 10 is performed as follows. First, the oxygen concentration of the cathode exhaust gas is measured by the oxygen sensor 25 (S200), and it is determined whether or not the oxygen concentration of the cathode exhaust gas exceeds a predetermined value (S210). In this determination processing, the residual water amount of the fuel cell 10 is estimated from the oxygen concentration in the cathode exhaust gas, and the “predetermined value” is the oxygen concentration corresponding to the upper limit water amount in the low temperature startable range.

Ｓ２１０の判定処理の結果、カソード排ガスの酸素濃度が所定値を上回っていないと判定された場合には（Ｓ２１０：ＮＯ）、カソード排ガス中に水蒸気が多く含まれており、燃料電池１０の残留水量が低温時始動可能範囲を上回っていると推定できるので、パージ処理を行い（Ｓ２２０）、Ｓ２００に戻る。パージ処理は、燃料電池１０の空気極に乾燥空気を供給することが行うことができる。   As a result of the determination processing in S210, when it is determined that the oxygen concentration of the cathode exhaust gas does not exceed the predetermined value (S210: NO), the cathode exhaust gas contains a large amount of water vapor, and the residual water amount of the fuel cell 10 Can be estimated to exceed the startable range at low temperature, purge processing is performed (S220), and the process returns to S200. The purge process can be performed by supplying dry air to the air electrode of the fuel cell 10.

一方、カソード排ガスの酸素濃度が所定値を上回っていると判定された場合には（Ｓ２１０：ＹＥＳ）、カソード排ガス中の水蒸気が少なくなり、燃料電池１０の残留水量が低温時始動可能範囲内であると推定できるので、燃料電池システムの運転を終了させる。   On the other hand, when it is determined that the oxygen concentration of the cathode exhaust gas exceeds the predetermined value (S210: YES), the water vapor in the cathode exhaust gas decreases, and the residual water amount of the fuel cell 10 is within the startable range at low temperature. Since it can be estimated that there is, the operation of the fuel cell system is terminated.

以上説明したように、カソード供給ガスの流量を測定し、カソード排ガスの酸素濃度と圧力を測定することで、燃料電池１０内部の水分状態、特に空気極における水分状態を精度よく診断することができる。さらに、燃料電池１０の運転終了時にカソード排ガスの酸素濃度を測定することで、燃料電池１０の内部水分量を診断することができ、燃料電池運転停止時における水分除去処理を効率よく行うことができる。   As described above, by measuring the flow rate of the cathode supply gas and measuring the oxygen concentration and pressure of the cathode exhaust gas, it is possible to accurately diagnose the moisture state inside the fuel cell 10, particularly the moisture state at the air electrode. . Furthermore, by measuring the oxygen concentration of the cathode exhaust gas at the end of the operation of the fuel cell 10, it is possible to diagnose the internal water content of the fuel cell 10 and to efficiently perform the water removal process when the fuel cell operation is stopped. .

なお、本発明の排ガス酸素分圧取得手段、排ガス窒素分圧取得手段、排ガス水蒸気分圧取得手段、排水量取得手段、残留水量取得手段、水分状態診断手段は、それぞれ制御部４０の処理によって構成されるものであり、排ガス酸素分圧取得手段、排ガス窒素分圧取得手段、排ガス水蒸気分圧取得手段、排水量取得手段はＳ１５０の処理に対応し、残留水量取得手段はＳ１７０の処理に対応し、水分状態診断手段はＳ１８０の処理に対応している。   The exhaust gas oxygen partial pressure acquisition means, exhaust gas nitrogen partial pressure acquisition means, exhaust gas water vapor partial pressure acquisition means, drainage amount acquisition means, residual water amount acquisition means, and moisture state diagnosis means of the present invention are each configured by processing of the control unit 40. Exhaust gas oxygen partial pressure acquisition means, exhaust gas nitrogen partial pressure acquisition means, exhaust gas water vapor partial pressure acquisition means, drainage amount acquisition means correspond to the processing of S150, residual water amount acquisition means corresponds to the processing of S170, moisture The state diagnosis means corresponds to the process of S180.

（第２実施形態）
次に、本発明の第２実施形態について説明する。本第２実施形態では、酸素センサ２５を用いることなく、燃料電池１０の出力電流に基づいてカソード排ガスの酸素濃度を取得している。 (Second Embodiment)
Next, a second embodiment of the present invention will be described. In the second embodiment, the oxygen concentration of the cathode exhaust gas is acquired based on the output current of the fuel cell 10 without using the oxygen sensor 25.

図５は、本第２実施形態の制御部４０のＣＰＵがＲＯＭ等に格納された制御プログラムにしたがって行う水分量診断制御の流れを示すフローチャートである。   FIG. 5 is a flowchart showing a flow of moisture amount diagnosis control performed by the CPU of the control unit 40 according to the second embodiment in accordance with a control program stored in a ROM or the like.

図５に示すように、本第２実施形態では、酸素センサ２５により酸素濃度測定Ｓ１２０に代えて、燃料電池１０の出力電流に基づいて電気化学反応で消費された酸素量を算出している（Ｓ１４１）。電気化学反応による消費酸素量〔ｍｏｌ／ｓ〕は、出力電流Ｉ／（４×Ｆ）で求めることができる。ただし、Ｆはファラデー定数である。   As shown in FIG. 5, in the second embodiment, the oxygen amount consumed in the electrochemical reaction is calculated based on the output current of the fuel cell 10 instead of the oxygen concentration measurement S120 by the oxygen sensor 25 ( S141). The amount of oxygen consumed [mol / s] due to the electrochemical reaction can be determined by the output current I / (4 × F). However, F is a Faraday constant.

そして、排水量算出処理Ｓ１５０において、大気中の酸素量からＳ１４１で算出した消費酸素量を減算してカソード排ガス中の残存酸素量を算出し、カソード排ガス中の酸素分圧を算出することができる。このように、燃料電池１０の出力電流から酸素消費量を算出することで、酸素センサ２５を用いることなく、カソード排ガス中の酸素分圧を間接的に取得することができる。   Then, in the drainage amount calculation process S150, the residual oxygen amount in the cathode exhaust gas can be calculated by subtracting the consumed oxygen amount calculated in S141 from the oxygen amount in the atmosphere, and the oxygen partial pressure in the cathode exhaust gas can be calculated. Thus, by calculating the oxygen consumption from the output current of the fuel cell 10, the oxygen partial pressure in the cathode exhaust gas can be indirectly acquired without using the oxygen sensor 25.

なお、本発明の酸素濃度取得手段は制御部４０の処理によって構成されるものであり、Ｓ１４１の処理に対応している。   The oxygen concentration acquisition means of the present invention is configured by the processing of the control unit 40 and corresponds to the processing of S141.

（第３実施形態）
次に、本発明の第３実施形態について説明する。本第３実施形態では、カソード供給ガスの加湿量を考慮して燃料電池１０の残留水量を算出している。 (Third embodiment)
Next, a third embodiment of the present invention will be described. In the third embodiment, the residual water amount of the fuel cell 10 is calculated in consideration of the humidification amount of the cathode supply gas.

図６は、本第３実施形態の燃料電池システムを示す模式図である。図６に示すように、本第３実施形態の燃料電池システムには、空気流路２０における加湿器２２の下流側で、かつ、燃料電池１０の上流側にカソード供給ガスの酸素濃度を検出する酸素センサ２７とカソード供給ガスの圧力を検出する圧力センサ２８が設けられている。これらのセンサ２７、２８の出力信号は制御部４０に入力される。なお、酸素センサ２７が本発明の供給ガス酸素濃度検出手段に相当し、圧力センサ２８が本発明の供給ガス圧力検出手段に相当している。   FIG. 6 is a schematic diagram showing a fuel cell system according to the third embodiment. As shown in FIG. 6, in the fuel cell system of the third embodiment, the oxygen concentration of the cathode supply gas is detected downstream of the humidifier 22 in the air flow path 20 and upstream of the fuel cell 10. An oxygen sensor 27 and a pressure sensor 28 for detecting the pressure of the cathode supply gas are provided. Output signals of these sensors 27 and 28 are input to the control unit 40. The oxygen sensor 27 corresponds to the supply gas oxygen concentration detection means of the present invention, and the pressure sensor 28 corresponds to the supply gas pressure detection means of the present invention.

図７は、本第３実施形態の制御部４０のＣＰＵがＲＯＭ等に格納された制御プログラムにしたがって行う水分量診断制御の流れを示すフローチャートである。図７に示すように、本第３実施形態では、Ｓ１３０でアノード排ガスの圧力を測定した後で、酸素センサ２７でカソード供給ガスの酸素濃度を測定し（Ｓ１３１）、圧力センサ２８でカソード供給ガスの圧力を測定している（Ｓ１３２）。   FIG. 7 is a flowchart showing a flow of moisture amount diagnosis control performed by the CPU of the control unit 40 according to the third embodiment in accordance with a control program stored in a ROM or the like. As shown in FIG. 7, in the third embodiment, after measuring the pressure of the anode exhaust gas in S130, the oxygen concentration of the cathode supply gas is measured by the oxygen sensor 27 (S131), and the cathode supply gas is measured by the pressure sensor 28. Is measured (S132).

排水量算出処理Ｓ１５０では、カソード供給ガスの酸素濃度と圧力と用い、第１実施形態で説明したカソード排ガス中の水分量を算出する手順と同様の手順によりカソード供給ガス中の水分量を算出する。さらに、燃料電池１０の残留水量を算出する際には、カソード供給ガス中の水分量と燃料電池１０の出力電流から算出される生成水量とを加算した値から、排水量を減算する。   In the drainage amount calculation process S150, the amount of moisture in the cathode supply gas is calculated by the same procedure as the procedure for calculating the amount of moisture in the cathode exhaust gas described in the first embodiment, using the oxygen concentration and pressure of the cathode supply gas. Furthermore, when calculating the amount of residual water in the fuel cell 10, the amount of drainage is subtracted from the value obtained by adding the amount of water in the cathode supply gas and the amount of generated water calculated from the output current of the fuel cell 10.

以上のように、カソード供給ガスの酸素濃度と圧力を測定し、カソード供給ガスに含まれる水分量を取得することで、カソード供給ガスの加湿量を考慮して燃料電池１０の残留水量を算出することができ、燃料電池１０の空気極における水分状態を精度よく診断することができる。なお、本発明の供給ガス酸素分圧取得手段、供給ガス窒素分圧取得手段、供給ガス水蒸気分圧取得手段、加湿量取得手段は制御部４０の処理によって構成されるものであり、供給ガス酸素分圧取得手段、供給ガス窒素分圧取得手段、供給ガス水蒸気分圧取得手段、加湿量取得手段はＳ１５０の処理に対応している。   As described above, the oxygen concentration and pressure of the cathode supply gas are measured, and the amount of water contained in the cathode supply gas is obtained, whereby the residual water amount of the fuel cell 10 is calculated in consideration of the humidification amount of the cathode supply gas. Therefore, the moisture state in the air electrode of the fuel cell 10 can be diagnosed with high accuracy. The supply gas oxygen partial pressure acquisition means, supply gas nitrogen partial pressure acquisition means, supply gas water vapor partial pressure acquisition means, and humidification amount acquisition means of the present invention are constituted by the processing of the control unit 40, and supply gas oxygen The partial pressure acquisition means, the supply gas nitrogen partial pressure acquisition means, the supply gas water vapor partial pressure acquisition means, and the humidification amount acquisition means correspond to the process of S150.

第１実施形態の燃料電池システムの模式図である。It is a schematic diagram of the fuel cell system of 1st Embodiment. 第１実施形態の水分量診断制御の流れを示すフローチャートであるIt is a flowchart which shows the flow of the moisture content diagnostic control of 1st Embodiment. カソード供給ガス（大気）の組成とカソード排ガスの組成を示す図である。It is a figure which shows the composition of cathode supply gas (atmosphere), and the composition of cathode exhaust gas. 燃料電池の出力と残留水量の関係を示す特性図である。It is a characteristic view which shows the relationship between the output of a fuel cell, and the amount of residual water. 第２実施形態の水分量診断制御の流れを示すフローチャートであるIt is a flowchart which shows the flow of the moisture content diagnostic control of 2nd Embodiment. 第３実施形態の燃料電池システムの模式図である。It is a schematic diagram of the fuel cell system of 3rd Embodiment. 第３実施形態の水分量診断制御の流れを示すフローチャートであるIt is a flowchart which shows the flow of the moisture content diagnostic control of 3rd Embodiment.

符号の説明Explanation of symbols

１０…燃料電池、１２…電流センサ、２０…空気経路、２１…空気供給装置、２２…加湿器、２３…空気調圧弁、２４…エアフロセンサ、２５…酸素センサ、２６…圧力センサ、２７…酸素センサ、２８…圧力センサ、３０…水素経路、３１…水素供給装置、４０…制御部。   DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 12 ... Current sensor, 20 ... Air path, 21 ... Air supply device, 22 ... Humidifier, 23 ... Air pressure regulating valve, 24 ... Air flow sensor, 25 ... Oxygen sensor, 26 ... Pressure sensor, 27 ... Oxygen Sensor, 28 ... Pressure sensor, 30 ... Hydrogen path, 31 ... Hydrogen supply device, 40 ... Control part.

Claims (4)

酸素と水素を電気化学反応させて電気エネルギーを発生させる燃料電池（１０）と、
前記燃料電池（１０）の出力電流を検出する電流検出手段（１２）と、
前記燃料電池（１０）のカソード側に供給される空気であるカソード供給ガスの流量を検出する流量検出手段（２４）と、
前記燃料電池（１０）のカソード側から排出されるカソード排ガス中の酸素濃度を検出する排ガス酸素濃度検出手段（２５）と、
前記カソード排ガスの全圧を検出する排ガス圧力検出手段（２６）とを備える燃料電池システムであって、
前記排ガス酸素濃度検出手段（２５）により検出した前記カソード排ガス中の酸素濃度と前記排ガス圧力検出手段（２６）により検出した前記カソード排ガスの全圧とから、前記カソード排ガス中の酸素分圧を取得する排ガス酸素分圧取得手段と、
前記カソード排ガスにおける窒素分圧を取得する排ガス窒素分圧取得手段と、
前記カソード排ガスの全圧から前記酸素分圧と前記窒素分圧とを減算して、前記カソード排ガス中の水蒸気分圧を取得する排ガス水蒸気分圧取得手段と、
前記水蒸気分圧と前記流量検出手段（２４）により検出された空気流量とから前記カソード排ガスに含まれる水分量を排水量として取得する排水量取得手段と、
前記燃料電池（１０）の出力電流に基づいて前記電気化学反応で生成する生成水量を取得し、前記生成水量から前記排水量を減算して前記燃料電池（１０）内部における残留水量を取得する残留水量取得手段と、
前記残留水量取得手段により取得された前記残留水量に基づいて前記燃料電池（１０）内部における水分状態を診断する水分状態診断手段とを備えることを特徴とする燃料電池システム。 A fuel cell (10) for generating electric energy by electrochemical reaction of oxygen and hydrogen;
Current detection means (12) for detecting an output current of the fuel cell (10);
Flow rate detection means (24) for detecting a flow rate of cathode supply gas which is air supplied to the cathode side of the fuel cell (10);
Exhaust gas oxygen concentration detection means (25) for detecting the oxygen concentration in the cathode exhaust gas discharged from the cathode side of the fuel cell (10);
An exhaust gas pressure detecting means (26) for detecting the total pressure of the cathode exhaust gas,
The oxygen partial pressure in the cathode exhaust gas is obtained from the oxygen concentration in the cathode exhaust gas detected by the exhaust gas oxygen concentration detection means (25) and the total pressure of the cathode exhaust gas detected by the exhaust gas pressure detection means (26). Exhaust gas oxygen partial pressure acquisition means,
Exhaust gas nitrogen partial pressure acquisition means for acquiring the nitrogen partial pressure in the cathode exhaust gas;
An exhaust gas water vapor partial pressure acquisition means for subtracting the oxygen partial pressure and the nitrogen partial pressure from the total pressure of the cathode exhaust gas to acquire a water vapor partial pressure in the cathode exhaust gas;
Waste water amount acquisition means for acquiring, as the drainage amount, the amount of water contained in the cathode exhaust gas from the water vapor partial pressure and the air flow rate detected by the flow rate detection means (24);
Based on the output current of the fuel cell (10), the amount of generated water generated by the electrochemical reaction is acquired, and the amount of residual water is acquired by subtracting the amount of drainage from the amount of generated water to obtain the amount of residual water in the fuel cell (10). Acquisition means;
A fuel cell system comprising: a water state diagnosis unit that diagnoses a water state inside the fuel cell (10) based on the residual water amount acquired by the residual water amount acquisition unit. 酸素と水素を電気化学反応させて電気エネルギーを発生させる燃料電池（１０）と、
前記燃料電池（１０）の出力電流を検出する電流検出手段（１２）と、
前記燃料電池（１０）のカソード側に供給される空気の流量を検出する流量検出手段（２４）と、
前記カソード排ガスの全圧を検出する圧力検出手段（２６）とを備える燃料電池システムであって、
前記燃料電池（１０）の出力電流に基づいて前記電気化学反応による消費酸素量を取得し、空気中の酸素量から前記消費酸素量を減算して前記カソード排ガス中の酸素濃度を取得する排ガス酸素濃度取得手段と、
前記酸素濃度取得手段により取得した前記カソード排ガス中の酸素濃度と前記圧力検出手段（２６）により検出した前記カソード排ガスの全圧とから、前記カソード排ガス中の酸素分圧を取得する排ガス酸素分圧取得手段と、
前記カソード排ガスにおける窒素分圧を取得する排ガス窒素分圧取得手段と、
前記カソード排ガスの全圧から前記酸素分圧と前記窒素分圧を減算して水蒸気分圧を取得する排ガス水蒸気分圧取得手段と、
前記水蒸気分圧と前記流量検出手段（２４）により検出された空気流量とから前記カソード排ガスに水蒸気として含まれる排水量を取得する排水量取得手段と、
前記燃料電池（１０）の出力電流に基づいて前記電気化学反応で生成する生成水量を取得し、前記生成水量から前記排水量を減算して前記燃料電池（１０）内部における残留水量を取得する残留水量取得手段と、
前記残留水量取得手段により取得された前記残留水量に基づいて前記燃料電池（１０）内部における水分状態を診断する水分状態診断手段とを備えることを特徴とする燃料電池システム。 A fuel cell (10) for generating electric energy by electrochemical reaction of oxygen and hydrogen;
Current detection means (12) for detecting an output current of the fuel cell (10);
Flow rate detection means (24) for detecting the flow rate of air supplied to the cathode side of the fuel cell (10);
A fuel cell system comprising pressure detecting means (26) for detecting the total pressure of the cathode exhaust gas,
Exhaust gas oxygen that obtains the amount of oxygen consumed by the electrochemical reaction based on the output current of the fuel cell (10) and subtracts the consumed oxygen amount from the amount of oxygen in the air to obtain the oxygen concentration in the cathode exhaust gas Concentration acquisition means;
The exhaust gas oxygen partial pressure for obtaining the oxygen partial pressure in the cathode exhaust gas from the oxygen concentration in the cathode exhaust gas acquired by the oxygen concentration acquisition means and the total pressure of the cathode exhaust gas detected by the pressure detection means (26). Acquisition means;
Exhaust gas nitrogen partial pressure acquisition means for acquiring the nitrogen partial pressure in the cathode exhaust gas;
Exhaust gas water vapor partial pressure obtaining means for obtaining a water vapor partial pressure by subtracting the oxygen partial pressure and the nitrogen partial pressure from the total pressure of the cathode exhaust gas;
Waste water amount acquisition means for acquiring the amount of waste water contained in the cathode exhaust gas as water vapor from the water vapor partial pressure and the air flow rate detected by the flow rate detection means (24);
Based on the output current of the fuel cell (10), the amount of generated water generated by the electrochemical reaction is acquired, and the amount of residual water is acquired by subtracting the amount of drainage from the amount of generated water to obtain the amount of residual water in the fuel cell (10). Acquisition means;
A fuel cell system comprising: a water state diagnosis unit that diagnoses a water state inside the fuel cell (10) based on the residual water amount acquired by the residual water amount acquisition unit. 前記カソード供給ガスを加湿する加湿手段（２２）と、
前記加湿手段（２２）で加湿された前記カソード供給ガスの酸素濃度を検出する供給ガス酸素濃度検出手段（２７）と、
前記加湿手段（２２）で加湿された前記カソード供給ガスの全圧を検出する供給ガス圧力検出手段（２８）と、
前記供給ガス酸素濃度検出手段（２７）により検出した前記カソード供給ガス中の酸素濃度と前記供給ガス圧力検出手段（２８）により検出した前記カソード供給ガスの全圧とから、前記カソード供給ガス中の酸素分圧を取得する供給ガス酸素分圧取得手段と、
前記カソード供給ガスにおける窒素分圧を取得する供給ガス窒素分圧取得手段と、
前記カソード供給ガスの全圧から前記酸素分圧と前記窒素分圧とを減算して、前記カソード供給ガス中の水蒸気分圧を取得する供給ガス水蒸気分圧取得手段と、
前記カソード供給ガス中の水蒸気分圧と前記流量検出手段（２４）により検出された空気流量とから前記カソード供給ガスに含まれる水分量を加湿量として取得する加湿量取得手段とを備え、
前記残留水量取得手段は、前記生成水量に前記加湿量を加算した値から前記排水量を減算して前記燃料電池（１０）内部における残留水量を取得することを特徴とする請求項１または２に記載の燃料電池システム。 Humidifying means (22) for humidifying the cathode supply gas;
Supply gas oxygen concentration detection means (27) for detecting the oxygen concentration of the cathode supply gas humidified by the humidification means (22);
Supply gas pressure detection means (28) for detecting the total pressure of the cathode supply gas humidified by the humidification means (22);
From the oxygen concentration in the cathode supply gas detected by the supply gas oxygen concentration detection means (27) and the total pressure of the cathode supply gas detected by the supply gas pressure detection means (28), Supply gas oxygen partial pressure acquisition means for acquiring oxygen partial pressure;
Supply gas nitrogen partial pressure acquisition means for acquiring a nitrogen partial pressure in the cathode supply gas;
A supply gas water vapor partial pressure acquisition means for subtracting the oxygen partial pressure and the nitrogen partial pressure from the total pressure of the cathode supply gas to acquire a water vapor partial pressure in the cathode supply gas;
Humidification amount acquisition means for acquiring the moisture amount contained in the cathode supply gas as a humidification amount from the partial pressure of water vapor in the cathode supply gas and the air flow rate detected by the flow rate detection means (24),
The said residual water amount acquisition means subtracts the said waste water amount from the value which added the said humidification amount to the said produced | generated water amount, and acquires the residual water amount in the said fuel cell (10), It is characterized by the above-mentioned. Fuel cell system. 前記燃料電池（１０）の運転を停止させる際に、前記燃料電池（１０）の空気極の乾燥処理を行うパージ手段を備え、
前記パージ手段は、前記排ガス酸素濃度取得手段により取得したアノード排ガス中の酸素濃度が所定値を下回っている場合に、前記乾燥処理を行うことを特徴とする請求項１ないし３のいずれか１つに記載の燃料電池システム。 When stopping the operation of the fuel cell (10), provided with a purge means for performing a drying process of the air electrode of the fuel cell (10),
The purge unit performs the drying process when the oxygen concentration in the anode exhaust gas acquired by the exhaust gas oxygen concentration acquisition unit is below a predetermined value. The fuel cell system described in 1.
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