JP2008198431A - Cell voltage calculation method in fuel cell, and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to calculate a cell voltage precisely in a cell laminate in which a heat insulation layer is formed. <P>SOLUTION: When a heat insulation layer 4 is formed in a cell laminate, the cell voltage of a cell C of a calculation subject is calculated by correcting a deterioration portion by contact resistance of the heat insulation layer. This can be applied to cell voltage calculation in the case the heat insulation layer 4 is formed at the center side by one cell portion from the end cell C<SB>N</SB>of the cell laminate. In this case, it is preferable that the deterioration portion by contact resistance is forecast taking the running time and running distance of the vehicle on which the fuel cell is mounted and the temperature or the like of the fuel cell as a parameter, and the forecast deterioration portion is corrected to calculate the cell voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cell voltage calculation method and apparatus for a fuel cell. More specifically, the present invention relates to an improvement in means for monitoring the power generation status in a fuel cell.

  In general, a fuel cell (for example, a polymer electrolyte fuel cell) is configured by stacking a plurality of cells each having an electrolyte sandwiched between separators. Since the end of the cell stack (cell stack) configured by stacking cells in this way generally tends to have a low temperature due to heat exchange with the atmosphere, a heat insulating layer is provided at or near the end. The configuration is known.

In addition, when such a fuel cell (fuel cell system) is mounted on an electric vehicle or the like and used as a power source (power generation source), the power generation status of each cell constituting the fuel cell stack is abnormal during operation. It is important that no occurs. Conventionally, as a monitor device for calculating the voltage of each cell and monitoring whether the power is normally generated, for example, a device that is equipped with a voltage sensor for each cell and sequentially detects each cell voltage has been proposed. (For example, refer to Patent Documents 1 to 3).
JP 2006-179338 A JP 2006-236803 A JP 2005-19223 A

  However, depending on the conventional cell voltage detection device or the cell voltage detection method used there, the cell voltage in the cell stack in which the heat insulating layer is formed as described above may not be obtained accurately.

  Then, an object of this invention is to provide the cell voltage calculation method and its apparatus in a fuel cell which can calculate the cell voltage in the cell laminated body in which the heat insulation layer is formed correctly.

  The heat insulating layer provided to suppress the temperature drop at the end of the cell stack is configured by, for example, sandwiching a conductive plate instead of a membrane-electrode assembly between a pair of separators of a cell (heat insulating cell) corresponding to the power generation cell. Is done. In this case, the conductive plate is preferably excellent in heat insulation, and a conductive porous sheet or the like is used as an example. Furthermore, an air layer may be formed by sealing a portion of the manifold through which the reaction gas and the refrigerant flow. However, the voltage of the cell where such a heat insulating layer is interposed is different from cells in other parts and includes the heat insulating layer (heat insulating cell), so that it is difficult to calculate accurately. ing.

  The present inventor, who has made further studies focusing on such points, has come to obtain new knowledge that leads to the solution of such problems. The present invention is based on such knowledge, and in the cell voltage calculation method for calculating the voltage of each cell in the cell stack constituting the fuel cell, the calculation is performed when a heat insulating layer is formed in the cell stack. The cell voltage of the target cell is calculated by correcting the decrease due to the contact resistance of the heat insulating layer.

  As described above, it is important to provide a heat insulating layer from the viewpoint of suppressing the temperature drop at the end of the cell stack. In the present invention, on the premise of such a structure, in the cell in which the heat insulating layer is formed, the cell voltage is calculated by appropriately correcting in consideration of the influence of the heat insulating layer. Therefore, according to this cell voltage calculation method, it is possible to calculate the cell voltage more accurately even for the cell in which the heat insulation layer is formed.

  Such a cell voltage calculation method is suitable for application to cell voltage calculation when the heat insulation layer is formed closer to the center of one cell from the end cell of the cell stack. In a general fuel cell, for example, the total minus is used for the purpose of reducing the water content of an end cell (also referred to as a total minus cell) on the negative electrode (also referred to as a total minus electrode in this specification) side of the cell stack. A heat insulating layer may be formed near the positive electrode (air electrode) of the cell. In such a case, the cell voltage decreases due to the effect of IR drop (voltage drop due to resistance) generated in the heat insulation layer, making it difficult to accurately detect the cell voltage. However, according to the present invention, the influence in this case is considered. It is possible to accurately calculate the cell voltage with necessary corrections.

  In the cell voltage calculation method according to the present invention, a decrease due to the contact resistance is predicted using a travel time of a vehicle on which the fuel cell is mounted as a parameter, the predicted decrease is corrected, and the cell voltage is calculated. Can be calculated.

  Alternatively, the cell voltage can be calculated by predicting a decrease due to the contact resistance using a travel distance of a vehicle on which the fuel cell is mounted as a parameter, and correcting the predicted decrease.

  Alternatively, a decrease due to the contact resistance may be predicted using the temperature of the fuel cell as a parameter, and the cell voltage may be calculated by correcting the predicted decrease.

  Furthermore, the present invention provides a cell voltage calculation device for calculating a voltage of each cell in a cell stack constituting a fuel cell, a voltage sensor that detects the voltage of each cell, and the voltage sensor that is detected by the voltage sensor. A memory for storing a correction value corresponding to the voltage value of each cell; and a correction means for referring to the correction value stored in the memory and performing a required correction on the voltage value detected by the voltage sensor. The correction means calculates a cell voltage of a cell to be calculated by correcting a decrease due to contact resistance of the heat insulation layer when a heat insulation layer is formed in the cell stack. .

  According to the present invention, it is possible to accurately calculate a cell voltage in a cell stack in which a heat insulating layer is formed.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  1 to 4 show an embodiment of the present invention. The cell voltage calculation device according to the present invention is a device for calculating the voltage of each cell C in the cell stack 3 constituting the fuel cell 1, and includes a voltage sensor S for detecting the voltage of each cell C, and a voltage value. 2 is provided with an EEPROM (memory) 24 for storing correction values corresponding to 1 and a CPU 21 as correction means for performing a required correction on the voltage values (see FIG. 2). Below, the structure of the cell laminated body 3 etc. which comprise the fuel cell 1 is demonstrated first, Then, the content of this cell voltage calculation apparatus and the cell voltage calculation method by the said apparatus is demonstrated.

  FIG. 1 shows a schematic configuration of a fuel cell 1 in the present embodiment. Such a fuel cell 1 can be used in, for example, an in-vehicle power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle), but is not limited to this, and various mobile objects (for example, ships and airplanes). Etc.) and power generation systems mounted on self-propelled devices such as robots, and even stationary power generation systems.

  The fuel cell 1 includes a cell stack (cell stack) 3 in which a plurality of cells (hereinafter also referred to as power generation cells) 2 are stacked, and an end cell C positioned at both ends of the cell stack 3. Further, a terminal plate 5 with an output terminal 5a, an insulator (insulating plate) 6, and an end plate 7 are further provided on the outer side in the stacking direction. A predetermined compressive force in the stacking direction is applied to the cell stack 3 by a tension plate 8 that is bridged so as to connect both end plates 7. Furthermore, a pressure plate 9 and a spring mechanism 9a are provided between the end plate 7 on one end side of the cell stack 3 and the insulator 6 so that the fluctuation of the load acting on the power generation cell C is absorbed. It has become.

  The power generation cell C includes an electrolyte membrane composed of an ion exchange membrane and a membrane-electrode assembly (MEA) composed of a pair of electrodes sandwiching the electrolyte membrane from both sides, and a pair of separators sandwiching the membrane-electrode assembly from the outside. (Indicated by reference numeral 2 in FIG. 3). The separator 2 is, for example, a conductor based on metal, and has a fluid flow path for supplying an oxidant gas such as air and a fuel gas such as hydrogen gas to each electrode, and is supplied to power generation cells C adjacent to each other. It serves to block the mixing of different types of fluids. With this configuration, an electrochemical reaction occurs in the membrane-electrode assembly of the power generation cell C, and an electromotive force is obtained. Since this electrochemical reaction is an exothermic reaction, the separator 2 is provided with a fluid flow path for flowing a coolant (for example, cooling water) for cooling the fuel cell.

  Furthermore, manifolds (oxidizing gas manifold, fuel gas manifold, refrigerant manifold) for flowing each of oxidizing gas, fuel gas, and refrigerant in the cell stacking direction are formed at both ends of the separator 2 (not shown). ). In the fuel cell 1 of the present embodiment, each fluid (oxidizing gas, fuel gas, refrigerant) is supplied from the fluid supply pipe (not shown) provided on the end plate 7 at one end of the fuel cell 1 to the inlet side. Are supplied to the respective manifolds and flow through the respective fluid flow paths provided in the separators 2 of the respective cells C. Further, each fluid is discharged from each manifold on the outlet side to each fluid discharge pipe (not shown) provided on the end plate 7 at the other end of the fuel cell 1.

  The heat insulation cell 4 has a heat insulation layer formed of, for example, two separators 2 and a seal member, and plays a role of suppressing heat generated by power generation to be radiated to the atmosphere or the like. That is, in general, since the temperature of the end of the cell stack 3 is likely to be lowered by heat exchange with the atmosphere, heat exchange (heat dissipation) is suppressed by forming a heat insulating layer on the end of the cell stack 3. Has been done. An example of such a heat insulating layer is a structure in which a heat insulating member 10 such as a conductive plate is sandwiched between a pair of separators 2 similar to those in the power generation cell C instead of a membrane-electrode assembly (see FIG. 1). ). The heat insulating member 10 used in this case is more suitable as it has better heat insulating properties. Specifically, for example, a conductive porous sheet or the like is used.

  Here, in the present embodiment, the heat insulating cell 4 is provided closer to the center by one cell from the end cell C of the cell stack 3 (see FIG. 1). In this case, the heat insulating cell 4 (or the heat insulating member 10 inside the cell) can function as a heat insulating layer that reduces the water content of the end cell C. In addition, in the case of the fuel cell 1 of the present embodiment in which a plurality of cells C are stacked in series, the end cell C corresponds to the cell C at both ends in contact with the terminal plate 5.

  Note that the sealing member includes an elastic body (gasket) that seals fluid by physical contact with an adjacent member (for example, the separator 2), an adhesive that is bonded by chemical bonding with the adjacent member, and the like. Can be used. For example, in this embodiment, a member that is physically sealed by elasticity is employed as the sealing member, but instead, a member that is sealed by chemical bonding such as the above-described adhesive may be employed. However, the specific example is not particularly limited to this, and other than this, for example, a sealing member called a sealant, a gel-like sealing material, a liquid packing, and the like can be used.

  The terminal plate 5 is a member that functions as a current collecting plate, and is formed in a plate shape from a metal such as iron, stainless steel, copper, or aluminum. The surface of the terminal plate 5 on the heat insulating cell 4 side is subjected to a surface treatment such as a plating treatment, and the contact resistance with the heat insulating cell 4 is ensured by the surface treatment. Examples of the plating include gold, silver, aluminum, nickel, zinc, tin, and the like. For example, in this embodiment, tin plating is performed in consideration of conductivity, workability, and low cost.

  The insulator 6 is a member that performs a function of electrically insulating the terminal plate 5 and the end plate 7. In order to fulfill such a function, the insulator 6 is formed in a plate shape from a resin material such as polycarbonate. In addition, when an engineering plastic excellent in heat resistance is adopted as the material of the insulator 6, it is advantageous in terms of robustness and is suitable for reducing the weight of the fuel cell 1.

  The end plate 7 is formed in a plate shape with various metals (iron, stainless steel, copper, aluminum, etc.) like the terminal plate 5. For example, in the present embodiment, the end plate 7 is formed using copper, but this is merely an example, and the end plate 7 may be formed of another metal.

  Next, a system (hereinafter referred to as a fuel cell system) 11 including a cell voltage calculation device according to the present invention will be described. FIG. 2 shows an overall system diagram of the fuel cell system 11. As shown in FIG. 2, the fuel cell system 11 includes a monitoring device 12, a fuel cell control unit 13, and a gas supply system 14 in addition to the fuel cell 1 described above, and further includes a voltage sensor S, an EEPROM (memory) 24. The CPU (correction means) 21 is provided.

The cell stack 3 of the fuel cell 1 is configured by stacking cells C _{1 to} C _N (N is an arbitrary natural number) each generating electric power with a predetermined electromotive force (in FIG. The insulation cell 4 is not shown). Each of the cells C _n (1 ≦ n ≦ N) is configured by sandwiching the membrane-electrode assembly between a pair of separators 2 provided with flow paths for hydrogen gas, air, and a refrigerant (for example, cooling water). The membrane-electrode assembly is a structure in which a polymer electrolyte membrane or the like is narrowed by two electrodes, an anode and a cathode. The anode is provided with an anode catalyst layer on the porous support layer, and the cathode is provided with a cathode catalyst layer on the porous support layer.

During operation the fuel cell 1, the electrochemical reaction in each cell C _n, constant cell voltage anode - occurs between the cathode. The voltage Vn (1 ≦ n ≦ N) generated in each cell C _n is detected by the voltage sensor S and supplied to the monitor device 12 as a detection signal Sv. For example, the plurality of cells C _n in this embodiment are connected in series, and a predetermined high voltage is generated at the output terminal 5 a of the terminal plate 5.

The gas supply system 14 is configured to supply a hydrogen gas as a fuel gas to the anode (fuel electrode) side of each cell C _n of the fuel cell 1 to cause a chemical reaction, and to discharge a hydrogen off-gas. Yes. Further, air, which is an oxidizing gas, is supplied to the cathode (air electrode) side of each cell C _n of the fuel cell 1 to cause a chemical reaction, and the oxidizing off gas is discharged. More specifically, the gas supply system 14 includes, on the fuel gas supply side, a hydrogen tank as a fuel gas source, various shutoff valves, a regulating valve, a gas-liquid separator, a hydrogen pump, a purge shutoff valve, and the like. Yes. In addition, the supply side of the oxidizing gas is provided with a compressor, a humidifier and the like. The fuel off-gas is diluted by the oxidation off-gas so that the hydrogen gas concentration falls below the oxidation level and is discharged to the outside.

  The fuel cell control unit (FC control unit) 13 is a computer device that operates independently of the monitor device 12 described above, and the correction value according to the input of the cell voltage correction value Dc corrected by the monitor device 2. Various controls necessary for the system are performed corresponding to Dc. The fuel cell control unit 3 of the present embodiment controls the operation of auxiliary equipment 41 such as a compressor and a motor of the gas supply system 14 and opens / closes control valves 42 for controlling the gas flow of the fuel gas system and the oxidizing gas system. For example, the auxiliary machinery 41 and the control valves 42 corresponding to the cell voltage indicated by the cell voltage correction value Dc are controlled, and the operation of the appropriate fuel cell 1 is continued.

  Although not specifically shown, the fuel cell system 11 has a cooling system for circulating the refrigerant to cool the fuel cell 1, and the power generated by the fuel cell 1 is charged or supplied to a load. A power system is provided.

  The monitor device 12 is a device for monitoring the state of the fuel cell 1. For example, in the case of this embodiment, the monitor device 12 is configured as a computer device, and has an internal bus 20, CPU 21, RAM 22, ROM 23, EEPROM 24, interface (I / F). ) Circuits 25 and 26 are provided (see FIG. 2). Among these, the CPU 21 is a central processing unit, and sequentially reads out and executes the control programs stored in the ROM 23, thereby causing the device to function as the monitor device 12. The RAM 22 is used as a storage area when the CPU 21 executes processing, and the ROM 23 provides a control program storage area. When the interface circuits 25 and 26 function as outputs, the data supplied from the CPU 21 is latched and power amplified and supplied to the outside. When the interface circuits 25 and 26 function as inputs, the data received from the outside is latched. The data is output to the internal bus 20 at an appropriate timing. An EEPROM (Electrically Erasable Programmable Read-Only Memory) 24 stores a desired correction value for the cell voltage value. The EEPROM 24 is a ROM capable of electrically erasing (rewriting) data, and the data is not erased only by turning off the power. A voltage higher than the read voltage is required for erasing data. However, since the power supply voltage is boosted inside the EEPROM, the data can be erased and rewritten while being mounted on the substrate.

Further, the CPU (correction means) 21 refers to the correction value stored in the above-described EEPROM 24 and performs a required correction on the voltage value detected by the voltage sensor S. CPU21 of the present embodiment, in the cell laminate 3 heat insulation cell (insulation layer) 4 is formed, the cell voltage of the cell C _n is the calculation target, and correcting the degradation caused by the contact resistance of the heat insulation cell 4 I am trying to calculate.

Here, the “correction value” is a value for correcting and calculating a decrease due to the contact resistance of the heat insulating cell 4 with respect to a voltage value detected in a certain cell C _n . That is, in the present embodiment, as described above, a cell that is detected at a location sandwiching the heat insulation cell 4 is provided because the heat insulation cell 4 is provided closer to the center by one cell from the end cell C (see FIG. 1). Since the voltage value is affected by this, a correction value is set in advance in consideration of the influence. More specifically, since an IR drop (voltage drop due to the resistance of the heat insulation cell 4) occurs at a location where the heat insulation cell 4 is interposed, it is generally difficult to calculate an accurate value due to the influence of the cell voltage. It is. In this regard, in the present embodiment, it is possible to accurately calculate the cell voltage by performing appropriate correction. For example, the negative electrode (i.e. a fuel electrode) If only one cell from the side of the end cell (total minus cells) C _N positive heat insulation cell 4 (air electrode) close is provided, the total negative cell C _N and the next The cell voltage detected by the voltage sensor S between the cell C _N-1 can be calculated more accurately by correcting the decrease due to the contact resistance (see FIG. 3). Such a correction value is mapped in comparison with the cell C _n with respect to a cell voltage value at least at a location affected by the heat insulating cell 4.

In setting the above-described correction value, it is preferable to predict a decrease in the cell voltage due to contact resistance using various parameters as appropriate. For example, a characteristic of the heat insulating cell 4 is that the contact resistance increases as the creep time (the time during which a load that can cause a creep phenomenon is applied) elapses (see FIG. 4). Therefore, if the fuel cell 1 is mounted on, for example, a vehicle (fuel cell vehicle), a decrease due to contact resistance is predicted using the travel time of the vehicle as a parameter, and the cell voltage is calculated by correcting the predicted decrease. Can be calculated. Alternatively, a decrease due to contact resistance can be predicted using the travel distance of the vehicle on which the fuel cell 1 is mounted as a parameter. Furthermore, regardless of whether or not it is mounted on a vehicle, a decrease due to contact resistance can be predicted using the temperature of the fuel cell 1 as a parameter, and the cell voltage can be calculated by correcting the predicted decrease. Good. That is, if the cell voltage value detected by the voltage sensor S is E, the time (including the time obtained according to the travel distance) is t, and the temperature is T, the corrected cell voltage value E ′ is E ′ = E + IR (T, T)
(Where I and R are current and resistance values used for calculation of the voltage drop in the adiabatic cell 3).

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in FIGS. 1 and 3, the fuel cell 1 is shown in which the heat insulating cell 4 is provided in the center of the end cell C by one cell. However, this is only one form of the heat insulating layer, and other portions. Even when the heat insulating cell 4 is provided, the cell voltage value can be accurately calculated by applying the present invention.

It is a side view which shows the structural example of the fuel cell in this embodiment. It is a block diagram which shows the structural example of a fuel cell system (cell voltage calculation apparatus). It is a figure which shows roughly a part of cell laminated body provided with the heat insulation layer (heat insulation cell). It is a characteristic view of the heat insulation cell which shows the schematic example of the change of the contact resistance corresponding to creep time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 3 ... Cell laminated body, 4 ... Thermal insulation cell (thermal insulation layer), 10 ... Thermal insulation member (thermal insulation layer), 11 ... Fuel cell system (cell voltage calculation apparatus), 21 ... CPU (correction means), 24 ... EEPROM (memory), C ... power generation cell (cell), S ... voltage sensor

Claims (6)

In the cell voltage calculation method for calculating the voltage of each cell in the cell stack constituting the fuel cell,
When a heat insulation layer is formed in the cell stack, the cell voltage of a cell to be calculated is calculated by correcting a decrease due to the contact resistance of the heat insulation layer. Calculation method.   2. The cell voltage calculation method for a fuel cell according to claim 1, wherein the cell voltage calculation method is applied to cell voltage calculation in a case where the heat insulation layer is formed closer to the center by one cell from an end cell of the cell stack.   3. The cell voltage is calculated by predicting a decrease due to the contact resistance using a travel time of a vehicle on which the fuel cell is mounted as a parameter, and correcting the predicted decrease. The cell voltage calculation method in the described fuel cell.   3. The cell voltage is calculated by predicting a decrease due to the contact resistance using a travel distance of a vehicle on which the fuel cell is mounted as a parameter, and correcting the predicted decrease. The cell voltage calculation method in the described fuel cell.   3. The cell in the fuel cell according to claim 1, wherein a decrease due to the contact resistance is predicted using the temperature of the fuel cell as a parameter, and the cell voltage is calculated by correcting the predicted decrease. Voltage calculation method. In the cell voltage calculation device for calculating the voltage of each cell in the cell stack constituting the fuel cell,
A voltage sensor for detecting the voltage of each cell;
A memory for storing a correction value corresponding to the voltage value of each cell detected by the voltage sensor;
Correction means for referring to the correction value stored in the memory and performing a required correction on the voltage value detected by the voltage sensor;
With
The correction means calculates a cell voltage of a cell to be calculated by correcting a decrease due to contact resistance of the heat insulation layer when a heat insulation layer is formed in the cell stack. A cell voltage calculation apparatus in a fuel cell, characterized in that

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