JP4678132B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system that generates power by an electrochemical reaction between hydrogen and oxygen.

  An example of a fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen is a polymer electrolyte fuel cell. This polymer electrolyte fuel cell includes a stack constituted by stacking a plurality of cells. The cell constituting the stack includes an anode (fuel electrode) and a cathode (air electrode), and a solid polymer electrolyte membrane having a sulfonic acid group as an ion exchange group is interposed between the anode and the cathode. Intervene.

  A fuel gas containing a fuel gas (hydrogen gas or reformed hydrogen made by reforming hydrocarbons to be hydrogen rich) is supplied to the anode, and a gas containing oxygen as an oxidant, for example, air is supplied to the cathode. . By supplying the fuel gas to the anode, hydrogen contained in the fuel gas reacts with the catalyst of the catalyst layer constituting the anode, thereby generating hydrogen ions. The generated hydrogen ions pass through the solid polymer electrolyte membrane and cause an electrochemical reaction with oxygen at the cathode. It has a configuration in which power is generated by this electrochemical reaction.

  By the way, the function of the solid polymer electrolyte membrane is to pass hydrogen ions well. Therefore, it is desirable that the conductivity is as high as possible. As described above, in order to improve the electrical conductivity of the solid polymer electrolyte membrane, the supplied gas is humidified to include moisture in the solid polymer electrolyte membrane, thereby preventing the solid polymer electrolyte membrane from drying.

  On the other hand, electrodes such as an anode and a cathode are composed of a catalyst layer and a gas diffusion layer. Furthermore, the catalyst layer is a matrix in which a catalyst-carrying carbon carrying a catalyst such as platinum (platinum: Pt) and an electrolyte are appropriately mixed, and an electric current is generated between the catalyst supported on the carbon and the electrolyte interface. A chemical reaction takes place.

  Therefore, a supply path for supplying a reaction gas, that is, a gas channel, must be secured between the catalyst and the electrolyte interface. By the way, since the fuel cell has a structure that generates electricity by an electrochemical reaction between hydrogen and oxygen, water is generated by this electrochemical reaction. Here, if the amount of produced water generated in this way due to electrochemical reaction (that is, power generation) is excessive, voids in the catalyst layer, which is a gas channel, are filled with the produced water, and the reaction gas flows. There is a problem that is disturbed.

  As described above, humidification must be performed in order to allow the solid polymer electrolyte membrane to contain water. On the other hand, in order to secure a gas channel, generated water must be drained. For this reason, the amount of water in the stack of the fuel cell system must be detected with high accuracy.

  In order to detect the moisture content in the stack of such a fuel cell system, for example, in Patent Document 1 below, the moisture content of air supplied to the stack, the moisture content of air discharged from the stack, and power generation in the stack It is calculated from the amount of produced water based on the amount.

  Here, in the technique disclosed in Patent Document 1, the moisture content of the air supplied into the stack is calculated based on the detection result of the humidity of the air by the humidity sensor. When moisture is coagulated in the humidity sensor, the moisture sensor cannot detect the coagulated moisture.

  For this reason, the calculation result of the moisture change amount based on the detection result of the humidity sensor has low reliability, and the moisture change amount in the stack cannot be accurately calculated.

  On the other hand, in the following Patent Document 2, the saturated vapor pressure of the air discharged from the stack is calculated from the temperature, pressure, and flow rate of the air discharged from the stack, and the generated moisture amount calculated based on the power generation amount in the stack The ratio between the saturated vapor pressure and the water vapor control ratio is calculated. Furthermore, Patent Document 2 states that air humidification can be eliminated by operating the fuel cell system so that the water amount control ratio calculated as described above falls within a predetermined range.

That is, the water amount control ratio indicates how much water vapor is discharged with respect to the amount of water produced by the electrochemical reaction. However, in Patent Document 2, the calculated water vapor amount is a saturated water vapor amount to the last. For this reason, if the amount of water vapor is not saturated, a large error occurs between the calculated amount of water vapor and the actual amount of water vapor. For this reason, the moisture change amount in the stack calculated based on the technique disclosed in Patent Document 2 has low reliability, and the moisture change amount in the stack cannot be accurately calculated.
JP 2003-17104 A Japanese Patent Laid-Open No. 2001-256888

  In view of the above facts, an object of the present invention is to obtain a fuel cell system capable of accurately and accurately obtaining the water content in the fuel cell stack.

In the fuel cell system according to the first aspect of the present invention, an anode and a cathode are arranged to face each other through an electrolyte membrane including a solid polymer, and a fuel gas containing hydrogen is supplied to the anode from an anode side stack inlet. A fuel cell system including a fuel cell stack configured to supply power to the cathode side and generate an electric power by an electrochemical reaction by supplying an oxidizing gas containing oxygen from the cathode side stack inlet to the cathode side, The amount of produced water generated by the electrochemical reaction of hydrogen ions, electrons and oxygen in the battery is proportional to the amount of electric current generated by the fuel cell stack. Of the oxygen consumed in the electrochemical reaction out of the oxidizing gas supplied to the fuel cell stack. Therefore, the consumed oxygen amount is estimated based on the current amount, together with the oxidizing gas in the generated water. The amount of water vapor on the cathode side discharged as water vapor from the fuel cell stack is added to the value obtained by adding the amount of oxygen gas discharged from the fuel cell stack and the amount of oxygen consumed and supplied to the fuel cell stack. Estimated from the difference between the supply amount of the oxidizing gas and the difference between the amount of generated water and the amount of water vapor discharged on the cathode side as the amount of water remaining in the fuel cell stack, the change in moisture in the fuel cell stack It is characterized by comprising a moisture change amount estimating means for estimating the amount.

  According to the fuel cell system of the present invention, the fuel gas containing hydrogen is supplied to the anode side of the fuel cell stack, and the oxidizing gas (oxidant) containing oxygen is supplied to the cathode side of the fuel cell stack. Supplied. On the anode side, hydrogen molecules are decomposed into hydrogen ions and electrons by electrochemical reaction, and the hydrogen ions permeate the electrolyte membrane and move to the cathode side. On the other hand, the electrons go to the load via an external circuit.

  On the cathode side, water is produced by an electrochemical reaction between oxygen molecules in the oxidizing gas supplied to the cathode, hydrogen ions that have passed through the electrolyte membrane, and electrons from the load (hereinafter, this water is referred to as “ Product water "). In this way, an electric current is generated by electrons traveling to the load by an electrochemical reaction that occurs on the anode side and the cathode side, thereby generating electric power.

By the way, water (product water) is generated by the electrochemical reaction between hydrogen ions, electrons and oxygen in the oxidizing gas as described above, so the amount of produced water is basically proportional to the power generation amount (current value). Therefore, the amount of generated water can be calculated based on the power generation amount (current value) .

Further, the amount of water vapor contained in the oxidizing gas discharged from the fuel cell stack is equal to the amount of oxidizing gas discharged from the fuel cell stack, that is, oxygen consumed in the fuel cell stack (that is, the above electrochemical reaction). It can be calculated as the difference between the value obtained by adding the amount of oxygen provided) and the amount of oxidizing gas supplied to the fuel cell stack .

  If all the generated water is converted into water vapor and discharged from the fuel cell stack together with the oxidizing gas, the amount of generated water and the amount of discharged water vapor should match. Therefore, the difference between the discharged water vapor amount and the generated water amount can be considered as the water amount remaining in the fuel cell stack.

Here, the fuel cell system according to the present invention includes a moisture change amount estimating means, and the moisture change amount estimating means calculates the generated water amount based on the power generation amount in the fuel cell stack. Furthermore, since the amount of oxygen consumed in the fuel cell stack is the amount of oxygen supplied to the electrochemical reaction, the moisture change estimation means is proportional to the amount of power generated in the fuel cell stack, and thus the amount of power generated ( The amount of oxygen consumed is calculated based on the current value . Based on the amount of generated water and the amount of oxygen consumed thus calculated, and the amount of oxidizing gas supplied to the fuel cell stack and the amount of oxidizing gas discharged from the fuel cell stack, A change in the amount of water in the fuel cell stack is estimated.

  Since the moisture change amount obtained in this way is not affected by the humidity of the outside air or moisture coagulation, the accuracy is higher than the moisture change amount based on the detection result of the humidity sensor that detects the humidity in the oxidizing gas. For this reason, by controlling the fuel cell system based on the estimated value of the amount of moisture change, the gas channels of the catalyst layer and the gas diffusion layer constituting the anode and the cathode are filled with moisture, and the electrolyte membrane Generation | occurrence | production of the malfunction called drying can be prevented or suppressed effectively, and the electric power generation efficiency and reliability of this fuel cell system can be improved.

Fuel cell system according to the present invention described in claim 2 is the invention according to claim 1, wherein the moisture variation estimating means, a pre-Symbol water quantity Wp, said consumption acid quantal Oe, the Assuming that the amount of oxidizing gas supplied to the fuel cell stack is As and the amount of oxidizing gas discharged from the fuel cell stack is Gs, the amount of change in water Wc in the fuel cell stack is Wc = As−Gs + Wp−. The calculation is based on the equation of Oe.

  According to the fuel cell system of the present invention as set forth in claim 2, the amount of water produced in the electrochemical reaction based on the amount of electricity generated by the fuel cell stack in the moisture change amount estimation means, and the electrochemical reaction Thus, the amount of oxygen in the oxidizing gas consumed (hereinafter, this amount of oxygen is referred to as “the amount of consumed oxygen” for convenience) is calculated.

Further, in the moisture change amount estimation means, when the generated water amount is Wp, the consumed oxygen amount is Oe, the oxidizing gas amount supplied to the fuel cell stack is As, and the oxidizing gas amount discharged from the fuel cell stack is Gs, The amount of water change Wc in the battery stack is
Wc = As−Gs + Wp−Oe
It is calculated based on the following formula.

  As described above, in the fuel cell system according to the present invention, the amount of water change in the fuel cell stack is supplied to the fuel cell stack with the current value generated by power generation without being affected by the humidity of the outside air or moisture coagulation. Based on the amount of oxidizing gas and the amount of oxidizing gas discharged from the fuel cell stack, the amount of moisture change in the fuel cell stack can be determined.

A fuel cell system according to a third aspect of the present invention is the fuel cell system according to the first aspect of the present invention , wherein the amount of hydrogen consumed in the electrochemical reaction in the fuel gas supplied to the fuel cell stack. Since a certain amount of consumed hydrogen is proportional to the amount of electric current generated by the fuel cell stack, the amount of consumed hydrogen is estimated based on the amount of current, and the fuel gas and the fuel gas are included in the generated water. The amount of water vapor discharged on the anode side discharged as water vapor from the fuel cell stack, the value obtained by adding the amount of the fuel gas discharged from the fuel cell stack and the amount of hydrogen consumption, and the fuel cell stack supplied to the fuel cell stack estimated from the difference between the supply amount of the fuel gas, the amount and the anode side the water variation estimating means from the amount of exhaust steam of the exhaust steam of the cathode side and the amount of produced water Estimating an amount of change water in a serial fuel cell stack is characterized in that.

In the fuel cell system according to the third aspect of the present invention, since hydrogen in the fuel gas is consumed by the electrochemical reaction between hydrogen ions, electrons and oxygen in the oxidizing gas as described above, basically, The amount of hydrogen consumed is proportional to the amount of power generation (current value), and therefore the amount of hydrogen consumption can be calculated based on the amount of power generation (current value).

  On the other hand, if the fuel gas discharged from the fuel cell stack contains water vapor of the generated water, the amount of water vapor contained in the fuel gas is equal to the amount of fuel gas discharged from the fuel cell stack. It can be calculated by subtracting the difference in the amount of fuel gas supplied to the fuel cell stack from the value obtained by adding the amount of hydrogen consumed in the cell stack (that is, hydrogen supplied to the electrochemical reaction).

  Here, in the moisture change amount estimation means of the fuel cell system according to the present invention, the amount of hydrogen consumed is calculated in addition to the amount of generated water and the amount of oxygen consumed. Further, the moisture change amount estimation means calculates the amount of generated water, the amount of oxygen consumed, the amount of hydrogen consumed, the amount of oxidizing gas and fuel gas supplied to the fuel cell stack, and the oxidizing gas and fuel discharged from the fuel cell stack. A change in the amount of water in the fuel cell stack is estimated based on the amount of gas.

  Thus, in the fuel cell system according to the present invention, the consumption of hydrogen and the supply and discharge of fuel gas are taken into account not only on the cathode side of the fuel cell stack to which the oxidizing gas is supplied but also on the anode side of the fuel cell stack. Thus, the amount of moisture change is estimated. For this reason, even if all the generated water becomes water vapor, even if the conditions are such that all of the generated water is not discharged from the fuel cell stack together with the oxidizing gas, and a part is discharged together with the fuel gas, the estimated fuel The reliability of the change in the amount of moisture in the battery stack can be increased.

A fuel cell system according to a fourth aspect of the present invention is the fuel cell system according to any one of the first to third aspects, wherein the supply channel is a flow path of an oxidizing gas supplied to the fuel cell stack. And an exhaust path that is a flow path of the oxidizing gas discharged from the fuel cell stack, the oxidizing gas discharged from the fuel cell stack can be supplied to the supply path, and the exhaust of the supply path An oxidizing gas supply means for supplying the oxidizing gas in the supply path to the fuel cell stack on the fuel cell stack side of the connection portion with the path, and further, the moisture from the magnitude of the driving force of the oxidizing gas supply means The change amount estimating means calculates the supply amount of the oxidizing gas to the fuel cell stack.

  In the fuel cell system according to the fourth aspect of the present invention, a supply path that is a flow path for supplying oxidizing gas to the fuel cell stack, and an exhaust path that is a flow path for passing the oxidizing gas discharged from the fuel cell stack. And are connected. Therefore, when the oxidizing gas discharged from the fuel cell stack flows into the supply path, a mixture of the newly sucked oxidizing gas and the oxidizing gas discharged from the fuel cell stack passes through the supply path. Is supplied to the fuel cell stack.

  The oxidizing gas discharged from the fuel cell stack contains the water produced by the electrochemical reaction in the fuel cell stack, so the moisture content is higher than the oxidizing gas newly sucked in the supply channel. . For this reason, the air-fuel mixture has a higher humidity than the newly sucked oxidant gas. By supplying this air-fuel mixture to the fuel cell stack, the electrolyte membrane can be removed without using a humidifier or the like that requires special control. Drying is effectively prevented or suppressed.

  On the other hand, in the fuel cell system according to the present invention, an oxidizing gas supply means is provided, and the oxidizing gas is supplied to the fuel cell stack by operating the oxidizing gas supply means. Further, in the fuel cell system according to the present invention, the oxidizing gas supply means is provided on the fuel cell stack side of the supply path with respect to the connection portion of the supply path with the exhaust path. Therefore, the oxidizing gas supply means supplies not only newly sucked oxidizing gas but also oxidizing gas discharged from the fuel cell stack and flowing into the supply path to the fuel cell stack.

Here, the fuel cell system according to the present invention, oxidation gas supply means is supplied to the fuel cell stack based on the magnitude of the driving force as long as is operated by the driving force of the driving means such as a motor oxide The amount of gas is calculated. As described above, the oxidizing gas supplied to the fuel cell stack by the oxidizing gas supply means is a mixture of the newly sucked oxidizing gas and the oxidizing gas discharged from the fuel cell stack and flowing into the supply path. For this reason, the moisture content in the fuel cell stack can be accurately calculated without being influenced by the moisture content contained in the oxidizing gas discharged from the fuel cell stack and flowing into the supply path.

  As described above, in the fuel cell system according to the present invention, the amount of change in moisture in the fuel cell stack can be obtained accurately and accurately.

<Configuration of First Embodiment>
FIG. 1 is a block diagram schematically showing the overall configuration of a fuel cell system 10 according to a first embodiment of the present invention.

  As shown in this figure, the fuel cell system 10 includes a fuel cell stack or a stack 12 as a fuel cell body. As shown in FIG. 4, the stack 12 includes a cell 14. The cell 14 includes an electrolyte membrane 16.

  The electrolyte membrane 16 is formed in a thin film shape from, for example, a solid polymer having a sulfonic acid group as an ion exchange group. An anode 18 is provided on one side in the thickness direction of the electrolyte membrane 16.

  The anode 18 includes a substantially plate-like separator 20. The separator 20 is formed with a gas flow groove 22 opened toward the electrolyte membrane 16 side. One end of the gas flow groove 22 is connected to the anode side inlet 24 of the stack 12.

  As shown in FIG. 1, the anode side inlet 24 is connected to a fuel gas tank 28 via a fuel gas supply path 26, and fuel gas containing hydrogen is supplied into the stack 12 from the anode side inlet 24. . Further, a flow meter 30 is provided in the fuel gas supply path 26, and the flow rate of the fuel gas flowing through the fuel gas supply path 26 per unit time and supplied to the anode side inlet 24 is measured.

  As shown in FIG. 2, the flow meter 30 is connected to the input port of the control unit 32 as the moisture change amount estimation means of the fuel cell system 10, and corresponds to the current value output from the flow meter 30. An electric signal (hereinafter referred to as “fuel gas flow rate signal” for the sake of convenience in order to distinguish this electric signal from other electric signals) is input to the control unit 32 directly or via an A / D converter or the like. It has become.

  The fuel gas supplied from the anode side inlet 24 passes through the gas circulation groove 22. As shown in FIG. 2, a gas diffusion layer 34 is provided between the separator 20 and the electrolyte membrane 16.

  The gas diffusion layer 34 is made of water-repellent carbon paper or carbon cloth and has good conductivity and air permeability. A catalyst layer 36 is provided between the gas diffusion layer 34 and the electrolyte membrane 16. The catalyst layer 36 is a matrix in which platinum as a catalyst or carbon carrying a platinum-based alloy and an electrolyte are appropriately mixed, and the fuel gas supplied from the gas flow groove 22 and passing through the gas diffusion layer 34 is supplied. The structure is sent to the catalyst layer 36.

  On the other hand, the other end of the gas flow groove 22 is connected to the anode side outlet 38 of the stack 12. As shown in FIG. 1, a fuel gas exhaust path 40 is connected to the anode side outlet 38, and is connected to a gas-liquid separator 42 via the fuel gas exhaust path 40. The gas-liquid separator 42 is supplied with exhaust gas of fuel gas discharged from the anode side outlet 38 (hereinafter referred to as “anode exhaust gas” in order to distinguish this exhaust gas from fuel gas and cathode exhaust gas described later). Then, moisture contained in the anode exhaust gas is separated.

  Further, an exhaust passage 44 is connected to one of the pair of outlets of the gas-liquid separator 42, and the gas component of the anode exhaust gas that is connected to the exhaust portion 46 through the exhaust passage 44 and passes through the exhaust passage 44 is obtained. The exhaust section 46 exhausts the air. The exhaust passage 44 is provided with a flow meter 48, and the flow rate of the gas component of the anode exhaust gas flowing through the exhaust passage 44 and exhausted from the exhaust portion 46 per unit time is measured.

  As shown in FIG. 2, the flow meter 48 is connected to the input port of the control unit 32 of the fuel cell system 10, and an electric signal corresponding to the current value output from the flow meter 48 (hereinafter referred to as the electric meter). In order to distinguish the signal from other electrical signals, for the sake of convenience, the “anode exhaust gas flow rate signal” is input to the control unit 32 directly or via an A / D converter or the like.

  On the other hand, as shown in FIG. 1, a drainage channel 50 is connected to the other of the pair of outlets of the gas-liquid separator 42, and is connected to the drainage unit 52 via the drainage channel 50. The moisture contained in the anode exhaust gas that has passed through 50 is drained from the drainage channel 50. The drainage channel 50 is provided with a flow meter 54, and the flow rate of moisture exhausted from the drainage unit 52 through the drainage channel 50 per unit time is measured.

  As shown in FIG. 2, the flow meter 54 is connected to the input port of the control unit 32 of the fuel cell system 10, and an electric signal corresponding to the current value output from the flow meter 54 (hereinafter referred to as the electric meter). In order to distinguish the signal from other electrical signals, for the sake of convenience, it will be referred to as an “anode moisture flow signal”) or input to the control unit 32 directly or via an A / D converter or the like.

  On the other hand, as shown in FIG. 4, a cathode 56 is provided on the opposite side of the anode 18 via the electrolyte membrane 16. The cathode 56 also includes the separator 20, the gas diffusion layer 34, and the catalyst layer 36. However, unlike the anode 18, one end of the gas flow groove 22 formed in the separator 20 of the cathode 56 is connected to the cathode side inlet 58 of the stack 12, and the other end is connected to the cathode side outlet 60 of the stack 12. ing.

  From the cathode side inlet 58, an oxidizing gas containing oxygen or air as an oxidant is supplied into the stack 12, and the air supplied from the cathode side inlet 58 passes through the gas flow groove 22 of the separator 20 constituting the cathode 56. . A plurality of the cells 14 having the above configuration are stacked in the thickness direction, that is, the facing direction of the anode 18 and the cathode 56, and thus the stack 12 is configured by stacking a plurality of cells 14. .

  Further, as shown in FIG. 1, terminals 62 are attached to the anode side and the cathode side of the stack 12, respectively. The terminal 62 is connected to a load 64 via an electrical connection member such as a cord, and supplies electricity generated by the stack 12 to the load 64.

  Further, an ammeter 66 is provided on a connecting member such as a cord connected to the terminal on the anode 18 side, and the current value of electricity supplied to the load 64 is measured.

  As shown in FIG. 2, the ammeter 66 is connected to the input port of the control unit 32 as the moisture change amount estimation means of the fuel cell system 10, and corresponds to the current value output from the ammeter 66. An electric signal (hereinafter referred to as a “current value signal” for the sake of convenience in order to distinguish this electric signal from other electric signals) is input to the control unit 32 directly or via an A / D converter or the like. ing.

  On the other hand, as shown in FIG. 1, the cathode side inlet 58 of the stack 12 is connected to an air suction portion 70 via an air supply path 68 as a supply path. An air filter 72 is provided closer to the cathode side inlet 58 than the air suction part 70. Further, an air compressor 74 as an oxidant gas supply means (or oxidant supply means) is provided on the cathode side inlet 58 side of the air filter 72.

  The air compressor 74 includes a motor 76, and a negative pressure is generated on the air suction portion 70 side by the driving force of the motor 76, and an amount of air corresponding to the rotational speed of the motor 76 is sucked from the outside. The air sucked from the air suction part 70 by the air compressor 74 passes through the air filter 72 so that minute dusts sucked together with the air are removed.

  Further, as shown in FIG. 3, the motor 76 which is a driving means of the air compressor 74 is directly or indirectly through an output port of the air stoichiometric ratio controller 78 provided in the control unit 32 or via a motor driver or the like. The motor 76 is driven on the basis of an electric signal output from the air stoichiometric ratio controller 78 (hereinafter referred to as “compressor control signal” for the sake of convenience in order to distinguish this electric signal from other electric signals). It becomes the composition which is done. In addition, as shown in FIG. 1, a flow meter 80 is provided between the air filter 72 and the air compressor 74, and the flow rate of air flowing between the air filter 72 and the air compressor 74 per unit time. Is measured.

  As shown in FIG. 2, the flow meter 80 is connected to an input port of the control unit 32, and an electric signal corresponding to the flow rate of air output from the flow meter 80 (hereinafter, this electric signal is referred to as another electric signal). In order to distinguish them from each other, for the sake of convenience, this is referred to as a “supply flow rate signal”) or input to the control unit 32 directly or via an A / D converter or the like.

  On the other hand, as shown in FIG. 1, the cathode side outlet 60 of the stack 12 is connected to an air exhaust path 82 as an exhaust path, and is connected to a gas-liquid separator 84 via the air exhaust path 82. . The gas-liquid separator 84 is supplied with the exhaust gas of the fuel gas discharged from the cathode side outlet 60 (hereinafter referred to as “cathode exhaust gas” in order to distinguish this exhaust gas from the fuel gas and the anode exhaust gas). Then, moisture contained in the cathode exhaust gas is separated.

  Further, an exhaust path 86 is connected to one of the pair of outlets of the gas-liquid separator 84, and the gas component of the cathode exhaust gas passing through the exhaust path 86 is connected to the exhaust section 88 via the exhaust path 86. The exhaust section 88 exhausts the air. Further, a flow meter 90 is provided in the exhaust path 86, and the flow rate of the gas component of the cathode exhaust gas that flows through the exhaust path 86 and is exhausted from the exhaust unit 88 per unit time is measured.

  As shown in FIG. 2, the flow meter 90 is connected to an input port of the control unit 32, and an electric signal corresponding to the current value output from the flow meter 90 (hereinafter, this electric signal is referred to as another electric signal). For the sake of distinction, for the sake of convenience, a “cathode exhaust gas flow rate signal” is input to the control unit 32 directly or via an A / D converter or the like.

  On the other hand, as shown in FIG. 1, a drainage channel 92 is connected to the other of the pair of outlets of the gas-liquid separator 84, and is connected to the drainage part 94 via the drainage channel 92. The moisture contained in the cathode exhaust gas that has passed through 92 is drained from the drainage channel 92. The drainage channel 92 is provided with a flow meter 96, and the flow rate of moisture exhausted from the drainage part 94 through the drainage channel 92 per unit time is measured.

  As shown in FIG. 2, the flow meter 96 is connected to an input port of the control unit 32, and an electric signal corresponding to the current value output from the flow meter 96 (hereinafter, this electric signal is referred to as another electric signal). In order to make a distinction, for the sake of convenience, the “cathode moisture flow rate signal” is input to the control unit 32 directly or via an A / D converter or the like.

  Although not shown in FIGS. 1 and 4, the fuel cell system 10 includes a temperature sensor 98 (see FIG. 2), and the temperature in the stack 12 is detected by the temperature sensor 98. . The temperature sensor 98 is connected to the input port of the control unit 32, and an electric signal corresponding to the voltage value output from the temperature sensor 98 (hereinafter, for the sake of convenience, in order to distinguish this electric signal from other electric signals, “temperature The detection signal ”is input to the control unit 32 directly or via an A / D converter or the like.

  Further, as shown in FIG. 3, the control unit 32 is provided with a cooling water temperature controller 100, and a driving source (for example, a motor) of the cooling water pump 102 is provided at an output port of the cooling water temperature controller 100. ) Is connected. Although not shown in FIG. 1, the cooling water pump 102 is connected to a cooling water pipe passing through the inside or outside of the stack 12, and an electric signal output from the cooling water temperature controller 100 (hereinafter referred to as this electric power). When the cooling water pump 102 is operated based on a “pump control signal” for convenience in order to distinguish the signal from other electrical signals, the state of the cooling water pump 102 (for example, the driving source of the cooling water pump 102 is a motor). If so, the cooling water flows through the cooling water pipe at a speed corresponding to the number of rotations of the motor, absorbs heat inside and outside the stack 12, and cools the inside and outside of the stack 12.

<Operation and Effect of First Embodiment>
Next, the operation and effect of the present embodiment will be described.

  In the fuel cell system 10, the fuel gas supplied from the fuel gas tank 28 to the stack 12 passes through the gas flow groove 22 of the separator 20 on the anode 18 side of the cell 14. The fuel gas flowing through the gas flow groove 22 passes through the gas diffusion layer 34 having air permeability and reaches the catalyst layer 36.

  On the other hand, the air supplied to the stack 12 by the operation of the air compressor 74 passes through the gas flow groove 22 of the separator 20 on the cathode 56 side of the cell 14. The air flowing through the gas flow groove 22 passes through the gas diffusion layer 34 having air permeability and reaches the catalyst layer 36.

As described above, when the fuel gas containing hydrogen is supplied to the catalyst layer 36 on the anode 18 side and the air containing oxygen is supplied to the catalyst layer 36 on the cathode 56 side, an electrochemical reaction occurs in both catalyst layers 36. . In the catalyst layer 36 on the anode 18 side, hydrogen ions (H ⁺ ) and electrons (e ⁻ ) are generated from hydrogen molecules (H ₂ ). Hydrogen ions permeate the electrolyte membrane 16 and reach the catalyst layer 36 on the cathode 56 side.

On the other hand, the electrons become a current that flows to the load 64 via an external circuit, and are used as power for the load 64. In the catalyst layer 36 on the cathode 56 side, hydrogen ions that have permeated through the electrolyte membrane 16, oxygen molecules (O ₂ ) in the air, and electrons that have reached the catalyst layer 36 on the cathode 56 side through an external circuit from the load 64 are used. An electrochemical reaction occurs, and as a result, water is generated (the water thus generated is hereinafter referred to as “product water”). The produced water is discharged from the cathode side outlet 60 together with the cathode exhaust gas which is air after the completion of the electrochemical reaction.

  By the way, in the fuel cell system 10, electrons generated by an electrochemical reaction and directed to the load 64, that is, an electric current value generated by the fuel cell system 10 is detected by an ammeter 66. The ammeter 66 outputs an electrical signal corresponding to the detected current value, that is, a current value signal. This current value signal is converted by, for example, an A / D converter and is input to the control unit 32.

  Here, between the current value I of electricity generated by the fuel cell system 10 and the amount of water generated by the electrochemical reaction, that is, the generated water amount Wp, the following equation (1) is satisfied. There is a relationship shown.

Wp [mol / s] = I [A] × S [number of sheets] ÷ 2e [e] ÷ F [C / mol] (1)
Further, there is a relationship represented by the following formula (2) between the current value I and the amount of oxygen consumed in the electrochemical reaction, that is, the consumed oxygen amount Oe.

Oe [mol / s] = I [A] x S [number of sheets] ÷ 4e [e] ÷ F [C / mol] (2)
Further, there is a relationship represented by the following formula (3) between the current value I and the amount of hydrogen consumed in the electrochemical reaction, that is, the consumed hydrogen amount He.

He [mol / s] = I [A] x S [number of sheets] ÷ 2e [e] ÷ F [C / mol] (3)
In the above formulas (1) to (3), I is the current value measured by the ammeter 66 based on the current value signal, S is the number of cells 14 in the stack 12, e is the charge, and F is the Faraday constant. There are basically known values other than I. The control unit 32 calculates the generated water amount Wp, the consumed oxygen amount Oe, and the consumed hydrogen amount He based on the input current value signal and these equations (1) to (3).

  On the other hand, as described above, the flow meters 30 to 96 are connected to the input ports of the control unit 32, and each electric signal based on the measurement value of these flow meters 30 to 96, that is, the fuel gas flow signal. , An anode exhaust gas flow signal, an anode moisture flow signal, a supply flow signal, a cathode exhaust gas flow signal, and a cathode moisture flow signal are input. In the control unit 32, the discharge water vapor amount AVe on the anode 18 side and the discharge water vapor amount CVe on the cathode 56 side are calculated based on the following equations (4) and (5) from these flow rate signals. .

AVe [mol / s] = AGe [mol / s] − (AGs [mol / s] −He [mol / s]) (4)
CVe [mol / s] = CGe [mol / s] - (CGs [mol / s] - O e [mol / s]) ··· (5)
In the above equations (4) and (5), AGe is a measured value of the flow meter 48 based on the anode exhaust gas flow signal, AGs is a measured value of the flow meter 30 based on the fuel gas flow signal, and CGe is cathode exhaust. The measured value of the flow meter 90 based on the gas flow signal, CGs is the measured value of the flow meter 80 based on the supply flow signal.

  Furthermore, the water vapor balance Wc, which is the amount of change in water in the present fuel cell system 10, is calculated from the exhaust water vapor amounts AVe and CVe, the produced water amount Wp, and the anode water flow rate signal and the cathode water flow rate signal calculated as described above. It is calculated based on the equation (6).

Wc [mol / s] = Wp [mol / s] −Ve [mol / s] −We [mol / s] (6)
However,
Ve [mol / s] = CVe [mol / s] + AVe [mol / s] (7)
We [mol / s] = CWe [mol / s] + AWe [mol / s] (8)
In the above equation (8), CWe is a measured value of the flow meter 96 based on the cathode moisture flow signal, and AWe is a measured value of the flow meter 54 based on the anode moisture flow signal. That is, We is the total amount of water separated in the gas-liquid separators 42 and 84 on both the anode 18 side and the cathode 56 side.

  On the other hand, a moisture amount map is preset in the control unit 32, and the discharge water vapor amount CVe on the cathode 56 side, a current value signal from the ammeter 66, a temperature detection signal from the temperature sensor 98, and a flow meter. From each of the supply flow rate signals based on the measurement value at 80, a moisture content measurement value on the cathode 56 side is derived.

  The water content measurement value and the water content balance Wc thus determined are input to the water content estimation observer 104. In the moisture amount estimation observer 104, the retained moisture change amount Wd [mol], which is a time integral value of the moisture amount balance Wc, is calculated. Further, the sum of the retained water change amount Wd [mol] and the measured moisture content at a certain time is calculated as an estimated value of retained moisture (hereinafter referred to as “moisture estimated value”).

  Next, as shown in FIG. 3, the control unit 32 is provided with a ROM 106, and an appropriate water content is stored in advance in a state of a map or the like in the ROM 106. In the control unit 32, the proper retained water amount is read from the ROM 106, and the difference between the estimated moisture amount calculated by the moisture amount estimation observer 104 and the proper retained water amount is calculated as the retained moisture amount deviation.

  The retained water amount deviation calculated in this way is input to the cooling water temperature controller 100 and the air stoichiometric ratio controller 78.

  The cooling water temperature controller 100 generates and outputs a pump control signal based on the inputted retained water content deviation. The pump control signal output from the cooling water temperature controller 100 is input to a driver or the like of a driving source (for example, a motor) of the cooling water pump 102, thereby increasing or decreasing the driving force output from the driving source of the cooling water pump 102. Is done.

  For example, in a state where it is estimated that the retained water amount deviation is negative and the water is lost, the operating speed of the cooling water pump 102 is increased to decrease the temperature of the cooling water. Thereby, the discharge | emission of the water | moisture content in the stack 12 is suppressed, and the drying of the electrolyte membrane 16 is prevented.

  In the state where the retained water amount deviation is positive and it can be estimated that the water is excessive, the operating speed of the cooling water pump 102 is decreased to increase the temperature of the cooling water. Thereby, the evaporation of moisture in the stack 12 is promoted, and the moisture that has become water vapor is effectively discharged to the outside of the stack 12 together with the cathode exhaust gas and the anode exhaust gas. Thereby, it is possible to prevent excessive moisture from filling gas distribution portions (gas channels) in the gas diffusion layer 34 and the catalyst layer 36.

  On the other hand, the air stoichiometric ratio controller 78 generates and outputs a compressor control signal based on the input retained moisture content deviation. The compressor control signal output from the air stoichiometric ratio controller 78 is input to a driver or the like that drives and controls the motor 76 of the air compressor 74, whereby the rotational speed of the motor 76 is increased or decreased. Thus, the amount of air supplied to the stack 12 is increased or decreased by increasing or decreasing the rotation speed of the motor 76. As the amount of air supplied to the stack 12 is increased or decreased, the ratio of fuel gas to air, that is, the air stoichiometric ratio is increased or decreased.

  For example, when the retained water content deviation is negative, the motor 76 is driven so that the air stoichiometric ratio becomes small. Thereby, the discharge | emission of the water | moisture content in the stack 12 is suppressed, and the drying of the electrolyte membrane 16 is prevented.

  Further, when the moisture content deviation is positive, the motor 76 is driven so that the air stoichiometric ratio becomes large. Thereby, moisture is effectively discharged out of the stack 12 together with the cathode exhaust gas. Thereby, it is possible to prevent excessive moisture from filling gas distribution portions (gas channels) in the gas diffusion layer 34 and the catalyst layer 36.

  As described above, in the present fuel cell system 10, the moisture content in the stack 12 is adjusted based on the retained moisture content deviation. Therefore, the electrolyte membrane 16 is dried as described above, and excess moisture fills the gas channel. It is possible to prevent the occurrence of the problem of being extremely effective. Thereby, the reliability and efficiency of this fuel cell system 10 can be improved effectively.

  In the fuel cell system 10, the moisture amount deviation is basically estimated based on the power generation amount in the stack 12 (measurement result in the ammeter 66) and the measurement results in the flow meters 30 to 96. For this reason, the error resulting from moisture coagulation or the like is extremely small as compared with the case of using a detection means that directly detects the amount of moisture such as a humidity sensor.

  Thereby, the reliability of the obtained water content deviation (or water content balance) is extremely high, and the water content in the stack 12 can be adjusted appropriately as described above. In this sense as well, the present fuel cell system 10 reliability and efficiency can be improved effectively.

  On the other hand, the water vapor discharged from the cathode 56 side varies depending on the temperature in the stack 12, the amount of power generation, and the flow rate of air, but even in these same states, if the water content in the stack 12 is different, Therefore, the amount of water vapor discharged from the cathode 56 side changes.

  Here, in the present embodiment, the measured moisture value is derived from the moisture content map set in the control unit 32 using the measured values of the ammeter 66, the temperature sensor 98, and the flow meter 80 as parameters. For this reason, the accuracy of the moisture content measurement value is high, and accordingly, the moisture content in the stack 12 can be adjusted appropriately. In this sense, the reliability and efficiency of the fuel cell system 10 are effectively improved. Can be made.

  In addition, by using the moisture amount map, it is possible to obtain a measured amount of moisture as long as air is flowed. For this reason, it is possible to obtain a moisture content measurement value even when the fuel cell system 10 is basically not generating electric power, including when the fuel cell system 10 starts operation and when it ends.

  Therefore, in such a state where the fuel cell system 10 does not generate power, the moisture in the stack 12 can be detected based on the measured moisture content. Thereby, for example, the moisture content in the stack 12 can be adjusted before the fuel cell system 10 starts operating or after the operation ends. For this reason, it is possible to prevent freezing of moisture in the stack 12 at a low temperature, and it is possible to prevent unnecessary drying or humidification immediately after the start of operation of the fuel cell system 10.

  In the present embodiment, the cooling water circulation speed and the temperature and the air stoichiometric ratio are adjusted based on the retained water content deviation as described above. However, based on the retained water content deviation, The present invention is not limited to a configuration that adjusts all of the circulation speed, temperature, and air stoichiometric ratio, and may be configured to adjust any one of them.

  Further, in the present embodiment, the circulation speed, temperature, and air stoichiometric ratio of the cooling water are adjusted based on the retained water amount deviation, but other than these, for example, the power generation amount in the stack 12 based on the retained water amount deviation, It is good also as a structure which adjusts the flow velocity of air. That is, for example, when the retained water content deviation falls below a threshold value, the flow rates of both fuel gas and air are reduced to suppress the power generation amount in the stack 12. Thereby, so-called “dry-up” can be prevented. Further, when the retained water content deviation exceeds the threshold, the air flow rate is increased. Thereby, so-called “flooding” can be prevented.

<Configuration of Second Embodiment>
Next, other embodiments of the present invention will be described. In the following description of each embodiment, the configuration is basically the same as that of the previous embodiment, including the first embodiment, with the same configuration. Reference numerals are assigned and description thereof is omitted.

  FIG. 5 is a block diagram schematically showing the overall configuration of the fuel cell system 120 according to the second embodiment of the present invention.

  As shown in this figure, the fuel cell system 120 does not include the gas-liquid separator 42 and the flow meters 30 to 54. Therefore, basically, the anode side inlet 24 is directly connected to the fuel gas tank 28 via the fuel gas supply path 26, and the anode side outlet 38 is connected to the exhaust part 122 via the fuel gas exhaust path 40.

  The fuel cell system 120 does not include the gas-liquid separator 84 and the flow meters 90 and 96. Instead, the air exhaust path 82 is provided with a muffler (silencer) 124, and the cathode side outlet is provided. 60 is connected to the exhaust part 126 via the muffler 124.

  Further, a pressure adjustment valve 128 is provided between the muffler 124 and the cathode side outlet 60, and a drive source for opening and closing the pressure adjustment valve 128, that is, for opening and closing the valve body of the pressure adjustment valve 128. By driving the motor, the pressure of the cathode exhaust gas coming out from the cathode side outlet 60 can be adjusted.

  As shown in FIG. 6, the pressure adjusting valve 128 is provided with a rotation angle sensor 130 for detecting the opening degree of the valve body. The rotation angle sensor 130 is directly or indirectly connected to the input port of the control unit 132, and an electrical signal corresponding to the opening degree of the pressure regulating valve 128 (hereinafter, this electrical signal is used as another electrical signal). In order to distinguish it from the signal, for the sake of convenience, it will be referred to as a “valve opening / closing signal”).

  Further, the pressure regulating valve 128 is also connected directly or indirectly to the output port of the cathode gas pressure controller 134 provided in the control unit 132, and an electric signal (hereinafter referred to as the following) output from the cathode gas pressure controller 134. In order to distinguish this electrical signal from other electrical signals, the valve body of the pressure regulating valve 128 is opened and closed based on the “valve control signal” for convenience.

  Further, as shown in FIG. 5, a pressure sensor 136 is provided between the pressure adjustment valve 128 and the cathode side outlet 60, and the pressure of the cathode exhaust gas flowing from the cathode side outlet 60 to the pressure adjustment valve 128. Has been detected. Further, a temperature sensor 138 is provided between the pressure sensor 136 and the cathode side outlet 60, and the temperature of the cathode exhaust gas flowing from the cathode side outlet 60 to the pressure adjustment valve 128 is detected.

  As shown in FIG. 6, the pressure sensor 136 and the temperature sensor 138 are directly or indirectly connected to the input port of the control unit 132. The pressure sensor 136 outputs an electrical signal corresponding to the pressure of the cathode exhaust gas detected by the pressure sensor 136 (hereinafter referred to as “pressure signal” for the sake of convenience in order to distinguish this electrical signal from other electrical signals). The pressure signal is input to the control unit 132. Further, the temperature sensor 138 receives an electrical signal corresponding to the temperature of the cathode exhaust gas detected by the temperature sensor 138 (hereinafter referred to as “gas temperature signal” for the sake of convenience in order to distinguish this electrical signal from other electrical signals). Is output, and this gas temperature signal is input to the controller 132.

<Operation and Effect of Second Embodiment>
Next, the operation and effect of the present embodiment will be described.

  In the fuel cell system 120, the current value of electricity generated by the fuel cell system 120 is detected by the ammeter 66, as in the first embodiment. The ammeter 66 outputs an electrical signal corresponding to the detected current value, that is, a current value signal. This current value signal is converted by, for example, an A / D converter or the like and input to the control unit 132.

  Here, in the first embodiment, the generated water amount Wp is calculated based on the formula (1). However, under certain conditions, the generated water anode determined on the right side of the formula (1) is determined by the properties of the electrolyte membrane 16 and the like. The non-permeability coefficient Rc (0 <Rc <1) is multiplied, that is, the generated water amount Wp is obtained by the following equation (9).

Wp [mol / s] = I [A] × S [number of sheets] ÷ 2e [e] ÷ F [C / mol] × Rc (9)
Further, the cathode exhaust gas flow rate CGs which is the flow rate of the cathode exhaust gas from the cathode side outlet 60 based on the gas temperature signal from the temperature sensor 138, the pressure signal from the pressure sensor 136, and the valve opening / closing signal from the rotation angle sensor 130. Is calculated. Further, the control unit 132 calculates a supply air flow rate AGs that is a flow rate of air toward the cathode side inlet 58 based on a supply flow rate signal from the flow meter 80.

  Here, in the fuel cell system 120, when gas components other than oxygen and water vapor do not change in the stack 12, the amount of water vapor contained in the cathode exhaust gas and water vapor contained in the air supplied into the stack 12 The difference, that is, the amount of water vapor CVe exhausted on the cathode 56 side, which is the amount of water vapor generated when air passes through the stack 12 and becomes cathode exhaust gas, the amount of oxygen consumed Oe, the amount of supplied air AGs, and the cathode exhaust gas flow rate. There is a relationship represented by the following equation (10) with CGs.

CVe [mol / s] = CGs [mol / s] − (AGs [mol / s] −Oe [mol / s]) (10)
In the control unit 132, the discharged water vapor amount CVe is calculated based on the above equation (3), and the water amount balance Wc (that is, Wc = Wp−), which is the difference between the generated water amount Wp and the discharged water vapor amount CVe. CVe) is calculated.

  When the moisture balance Wc is calculated in this way, the retained moisture change amount Wd [mol], which is a time integral value of the moisture balance Wc, is further calculated. Further, as in the first embodiment, the sum of the retained water change amount Wd [mol] and the measured amount of water at a certain time is calculated as the estimated amount of water, and the estimated amount of water The difference from the proper retained water amount read from the ROM 106 is calculated as the retained moisture amount deviation.

  The retained water amount deviation calculated in this way is input to the cooling water temperature controller 100 and the air stoichiometric ratio controller 78 as in the first embodiment, and is further shown in FIG. In addition, in the present embodiment, the retained water amount deviation is input to the cathode gas pressure controller 134.

  The cathode gas pressure controller 134 generates and outputs a valve control signal based on the retained water content deviation. The valve control signal output from the cathode gas pressure controller 134 is input to a driver or the like that drives and controls a drive source (for example, a motor) that drives the valve body of the pressure regulating valve 128, thereby increasing or decreasing the opening degree of the valve body. Is done. Thus, the flow rate of the cathode exhaust gas is increased or decreased by increasing or decreasing the opening degree of the valve body. As a result, the pressure of the cathode exhaust gas is increased or decreased.

  For example, in the state where the retained water content deviation is negative, the opening of the pressure adjusting valve 128 is adjusted so as to increase, thereby increasing the pressure of the cathode exhaust gas. As the pressure of the cathode exhaust gas increases in this way, the discharge of moisture in the stack 12 is suppressed, and drying of the electrolyte membrane 16 is prevented.

  Further, in the state where the retained water content deviation is positive, the opening of the pressure adjusting valve 128 is adjusted to be small, thereby reducing the pressure of the cathode exhaust gas. As the pressure of the cathode exhaust gas decreases in this way, moisture is effectively discharged to the outside of the stack 12 together with the cathode exhaust gas. Thereby, it is possible to prevent excessive moisture from filling gas distribution portions (gas channels) in the gas diffusion layer 34 and the catalyst layer 36.

  As described above, in the fuel cell system 120, the moisture content in the stack 12 is adjusted based on the retained moisture content deviation. Therefore, the electrolyte membrane 16 is dried as described above, and excess moisture fills the gas channel. It is possible to prevent the occurrence of the problem of being extremely effective. Thereby, the reliability and efficiency of the fuel cell system 120 can be effectively improved.

  Further, in the fuel cell system 120, the power generation amount in the stack 12 (measurement result in the ammeter 66), the air flow rate into the stack 12 (measurement result in the flow meter 80), and the cathode exhaust gas flow rate (temperature). Based on the sensor 138, the pressure sensor 136, and the opening degree of the valve body of the pressure adjustment valve 128, the retained water amount deviation is estimated. For this reason, the error resulting from moisture coagulation or the like is extremely small as compared with the case of using a detection means that directly detects the amount of moisture such as a humidity sensor.

  As a result, the reliability of the retained water content deviation obtained is extremely high, and the water content in the stack 12 can be adjusted appropriately as described above. In this sense, the reliability and efficiency of the fuel cell system 120 can be adjusted. Can be improved effectively.

<Third Embodiment>
Next, a third embodiment of the present invention will be described.

  FIG. 8 and FIG. 9 show the calculation process (various calculation procedures) in the control unit 152 as the moisture change amount estimation means of the fuel cell system 150 according to the present embodiment, explaining the second embodiment. And a block diagram corresponding to FIG.

  The configuration of the fuel cell system 150 is basically the same as that of the fuel cell system 120 according to the second embodiment. However, unlike the fuel cell system 120, the present fuel cell system 150 includes an internal resistance detector 154 that detects the internal resistance in the stack 12. The internal resistance detector 154 is connected to the input port of the control unit 152, and an electric signal corresponding to the internal resistance in the stack 12 (hereinafter, for the sake of convenience, in order to distinguish this electric signal from other electric signals, “internal resistance signal ").

  The control unit 152 of the fuel cell system 150 measures the amount of water retained in the stack 12 based on the internal resistance signal from the internal resistance detector 154, and this measured amount of retained water is the so-called “plant observation signal”. Is input to the moisture measurement observer 156. Further, the moisture balance Wc calculated in the same manner as in the second embodiment is input to the moisture measurement observer 156 as a so-called “plant input signal”.

  In the moisture content measurement observer 156, the estimated moisture content is calculated based on the measured retained moisture content and the moisture balance Wc, and the difference from the proper retained moisture read from the ROM 106 is calculated as the retained moisture content deviation. Calculated.

  Here, instead of the estimated amount of moisture, the difference between the measured amount of retained water and the appropriate amount of retained moisture read from the ROM 106 may be calculated as the retained moisture amount deviation. However, the retained water content deviation calculated in this way is greatly affected by noise and measurement errors.

  On the other hand, in obtaining the moisture balance Wc, there is naturally an influence of noise and measurement errors. However, by incorporating a so-called “plant dynamic characteristic” as a configuration for obtaining an estimated amount of moisture from the moisture balance Wc and the measured amount of retained water, higher reliability than when using only the measured amount of retained water is used. Can be obtained.

  Thus, in the present embodiment, unlike the second embodiment, the moisture content balance Wc is not integrated over time, and the retained moisture content is determined from the measured retained moisture amount, the moisture content balance Wc, and the appropriate retained moisture amount. A quantity deviation is calculated. However, as described above, since the reliability of the retained water amount deviation is high, the water amount in the stack 12 can be appropriately adjusted as described above. In this sense as well, the reliability of the fuel cell system 150 is improved. And efficiency can be improved effectively.

  In addition, the error due to moisture coagulation and the like is extremely small as compared with the case of using a detection means that directly detects the amount of moisture such as a humidity sensor. Therefore, the reliability of the obtained moisture content deviation (or moisture content balance) is extremely high, and the moisture content in the stack 12 can be adjusted appropriately as described above. In this sense, the fuel cell system 150 The reliability and efficiency can be effectively improved.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described.

  FIG. 10 shows an outline of the entire configuration of the fuel cell system 170 according to the present embodiment, and FIG. 11 shows a calculation process (in a control unit 172 as a moisture change amount estimation means of the fuel cell system 170 ( Various calculation procedures) are shown in a block diagram corresponding to FIG. 2 for explaining the first embodiment.

  As shown in FIG. 10, unlike the fuel cell system 120 according to the second embodiment, the present fuel cell system 170 does not include the temperature sensor 138 and the pressure sensor 136. Instead, the pressure adjustment valve A flow meter 174 is provided between 128 and the muffler 124. The flow meter 174 has basically the same configuration as the flow meter 80, and measures the flow rate of the cathode exhaust gas that passes through the pressure adjustment valve 128 and travels toward the muffler 124.

  As shown in FIG. 11, the flow meter 174 is connected to the control unit 172, and an electric signal corresponding to the flow rate of the cathode exhaust gas output from the flow meter 174 (hereinafter, this electric signal is referred to as another electric signal). In order to make a distinction, for the sake of convenience, the “exhaust flow rate signal” is input to the control unit 172 directly or via an A / D converter or the like.

  Further, in the fuel cell system 170, a humidifier 176 as a humidifying means is provided between the pressure adjustment valve 128 and the flow meter 174, and the cathode exhaust gas from the pressure adjustment valve 128 toward the flow meter 174 passes. .

  The humidifier 176 passes air from the air compressor 74 toward the cathode side inlet 58, and part or all of the moisture contained in the cathode exhaust gas is absorbed by the humidifier 176. Further, moisture absorbed from the cathode exhaust gas or water stored in advance in a water storage unit (not shown) provided in the humidifier 176 is given to the air from the air compressor 74 toward the cathode side inlet 58 as moisture.

  In the control unit 172 of the fuel cell system 170, the flow rate of the cathode exhaust gas is measured by the flow meter 174, and based on the exhaust flow rate signal from the flow meter 174, the control unit 172 calculates the cathode exhaust gas outlet flow rate. This cathode exhaust gas outlet flow rate calculation result is used for the calculation of the moisture balance Wc, as in the second embodiment.

  Further, in the present fuel cell system 170, the difference between the calculation result of the cathode exhaust gas outlet flow rate based on the exhaust flow rate signal from the flow meter 174 and the calculation result of the air inflow amount based on the supply flow rate signal from the flow meter 80 is calculated. Is done. That is, the measurement result of the flow meter 174 is the flow rate of the cathode exhaust gas containing moisture generated in the stack 12, whereas the measurement result of the flow meter 80 is the state before the air is supplied to the stack 12. Flow rate. Therefore, the difference is nothing but the amount of moisture generated in the stack 12 included in the cathode exhaust gas, that is, the amount of retained moisture calculated based on the internal resistance of the stack 12 in the second embodiment.

  As described above, in the present fuel cell system 170, although the means for detecting the fuel cell system 170 are different, the current moisture content and the proper moisture content and the moisture balance Wc are closer to the stack 12 than the air compressor 74 and the flow meter 174. The retained water content deviation will be calculated.

  Therefore, by controlling the cooling water temperature controller 100, the air stoichiometric ratio controller 78, the cathode gas pressure controller 134, and the like based on this retained water amount deviation, the electrolyte can be controlled without specially controlling the humidifier 176. Generation | occurrence | production of the malfunction that drying of the film | membrane 16 and an excess water fills a gas channel can be prevented very effectively. Thereby, the reliability and efficiency of the fuel cell system 170 can be effectively improved.

<Fifth embodiment>
Next, a fifth embodiment of the present invention will be described.

  FIG. 12 shows an outline of the overall configuration of the fuel cell system 190 according to the present embodiment.

  As shown in this figure, the fuel cell system 190 has basically the same configuration as the fuel cell system 120 according to the second embodiment. However, as shown in FIG. 12, in the fuel cell system 190, the flow meter 80 and the air compressor 74 are connected, and the pressure adjustment valve 128 and the muffler 124 are connected. For this reason, the present fuel cell system 190 is configured such that a part or all of the cathode exhaust gas exhausted from the cathode side outlet 60 and passed through the pressure adjustment valve can be supplied between the flow meter 80 and the air compressor 74. ing.

  Further, the fuel cell system 190 includes a circulation valve 192, and the cathode exhaust gas that has passed through the pressure adjustment valve 128 according to the opening degree of the valve body of the circulation valve 192 includes the flow meter 80 and the air compressor 74. It is configured to be able to adjust the amount of supply to the space.

  On the other hand, as shown in FIG. 13, the control unit 194 as the moisture change amount estimating means of the fuel cell system 190 is basically the same as the control unit 132 of the fuel cell system 120 according to the second embodiment. It is. However, unlike the control unit 132, in the control unit 194, the flow meter 80 is not connected to the control unit 194.

  Instead, a speed detector 196 is connected to the control unit 194 at an input port of the control unit 194 of the fuel cell system 190. The speed detector 196 detects the rotation speed of the motor 76 of the air compressor 74, and an electric signal corresponding to the rotation speed of the motor 76 (hereinafter, this electric signal is distinguished from other electric signals. Output speed detection signal). Based on the speed detection signal output from the speed detector 196, the amount of air supplied to the cathode side inlet 58 is calculated.

  In the present fuel cell system 190, the cathode exhaust gas containing moisture generated in the stack 12 as described above is supplied to the air toward the cathode side inlet 58, so that it is generated in the stack 12 and discharged together with the cathode exhaust gas. The moisture thus applied is imparted to the air toward the cathode side inlet 58, thereby increasing the humidity of the air. As described above, in the fuel cell system 190, since moisture can be imparted to the air toward the cathode side inlet 58 without providing the humidifying device 176, the device configuration can be simplified.

  Further, since the retained water amount deviation is calculated as in the second embodiment, the cooling water temperature controller 100, the air stoichiometric ratio controller 78, and the cathode gas pressure controller 134 are based on the retained water amount deviation. Etc., the amount of water contained in the cathode exhaust gas that has passed through the pressure adjustment valve 128 can be adjusted appropriately. As a result, the amount of water contained in the air from the air compressor 74 toward the cathode side inlet 58 can be appropriately adjusted. Can be adjusted.

  Accordingly, it is possible to extremely effectively prevent the problem that the electrolyte membrane 16 is dried and excessive moisture fills the gas channel, and the reliability and efficiency of the fuel cell system 190 can be effectively improved. it can.

1 is a diagram showing an outline of the overall configuration of a fuel cell system according to a first embodiment of the present invention. It is a figure which shows the outline by the side of the input port of the control part of the fuel cell system which concerns on the 1st Embodiment of this invention. It is a figure which shows the outline by the side of the output port of the control part of the fuel cell system which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the outline of a structure of a cell. It is a figure which shows the outline of the whole structure of the fuel cell system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the outline by the side of the input port of the control part of the fuel cell system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the outline by the side of the output port of the control part of the fuel cell system which concerns on the 2nd Embodiment of this invention. It is a figure which shows the outline by the side of the input port of the control part of the fuel cell system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the outline by the side of the output port of the control part of the fuel cell system which concerns on the 3rd Embodiment of this invention. It is a figure which shows the outline of the whole structure of the fuel cell system which concerns on the 4th Embodiment of this invention. It is a figure which shows the outline by the side of the input port of the control part of the fuel cell system which concerns on the 4th Embodiment of this invention. It is a figure which shows the outline of the whole structure of the fuel cell system which concerns on the 5th Embodiment of this invention. It is a figure which shows the outline by the side of the input port of the control part of the fuel cell system which concerns on the 5th Embodiment of this invention.

Explanation of symbols

10 Fuel cell system 12 Stack (fuel cell)
16 Electrolyte membrane 18 Anode 32 Control unit (moisture change amount estimation means)
56 Cathode 68 Air supply path (supply path)
82 Air exhaust passage (exhaust passage)
120 Fuel Cell System 132 Control Unit (Moisture Change Estimation Unit)
150 Fuel Cell System 152 Control Unit (Moisture Change Estimation Unit)
170 Fuel Cell System 172 Control Unit (Moisture Change Estimation Unit)
190 Fuel Cell System 194 Control Unit (Moisture Change Estimation Unit)

Claims (4)

An anode and a cathode are arranged opposite to each other through an electrolyte membrane configured to include a solid polymer, and a fuel gas containing hydrogen is supplied to the anode side from the anode side stack inlet, and an oxygen containing oxygen is supplied from the cathode side stack inlet. A fuel cell system configured to include a fuel cell stack that generates electricity by an electrochemical reaction by supplying gas to the cathode side,
Since the amount of generated water generated by the electrochemical reaction of hydrogen ions, electrons and oxygen in the fuel cell stack is proportional to the amount of electric current generated by the fuel cell stack, the amount of generated water is Based on the amount of current, the amount of oxygen consumed, which is the amount of oxygen consumed by the electrochemical reaction in the oxidizing gas supplied to the fuel cell stack, is the electric current generated by the fuel cell stack. Since the relationship is proportional to the amount, the amount of oxygen consumed is estimated based on the amount of current,
A value obtained by adding the discharge amount of the oxidizing gas from the fuel cell stack and the oxygen consumption amount to the amount of the discharge water vapor on the cathode side discharged as water vapor from the fuel cell stack together with the oxidizing gas in the generated water. And the difference between the supply amount of the oxidizing gas supplied to the fuel cell stack,
A moisture change amount estimating means for estimating a change amount of moisture in the fuel cell stack by using a difference between the amount of generated water and the amount of water vapor discharged on the cathode side as a moisture amount remaining in the fuel cell stack;
A fuel cell system. The moisture change amount estimation means includes:
The pre-Symbol water quantity Wp, said consumption acid quantal Oe, when the aforementioned fuel cell stack supplied oxidation gas amount As, and an oxidizing gas amount discharged from the fuel cell stack and Gs, the fuel The amount of water change Wc in the battery stack is
Wc = As−Gs + Wp−Oe
Calculate based on the formula of
The fuel cell system according to claim 1. From the fuel gas supplied to the fuel cell stack, the amount of hydrogen consumed, which is the amount of hydrogen consumed in the electrochemical reaction, is proportional to the amount of electricity generated by the fuel cell stack. , Estimating the amount of hydrogen consumed based on the amount of current,
A value obtained by adding the amount of water vapor discharged from the fuel cell stack together with the fuel gas and the amount of water consumed in the generated water to the amount of hydrogen gas consumed from the fuel cell stack. And the difference between the supply amount of the fuel gas supplied to the fuel cell stack,
The moisture change amount estimating means estimates the amount of change of moisture in the fuel cell stack from the amount of generated water, the amount of discharged steam on the cathode side, and the amount of discharged steam on the anode side ;
The fuel cell system according to claim 1. A supply path, which is a flow path for oxidizing gas supplied to the fuel cell stack, and an exhaust path, which is a flow path for oxidizing gas discharged from the fuel cell stack, are connected, and the oxidizing gas discharged from the fuel cell stack is An oxidant gas supply means for supplying the oxidant gas in the supply path to the fuel cell stack on the fuel cell stack side than the connection part of the supply path with the exhaust path is provided.
Further, the moisture change amount estimating means calculates the supply amount of the oxidizing gas to the fuel cell stack from the magnitude of the driving force of the oxidizing gas supply means.
The fuel cell system according to any one of claims 1 to 3, wherein

Images