JP2005141972A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a moisture state appropriate in a short time when an excess state of moisture in a cell is detected in a fuel cell system. <P>SOLUTION: This fuel cell system is provided with: two conductive wires 50 arranged oppositely to an air passage 131 in a separator 130; a switch 60 for connecting and separating the conductive wires 50 to/from each other; a control part 40 for controlling operation of the switch 60; a detection circuit 70 for detecting capacitance between the conductive wires 50 when the two conductive wires 50 are separated from each other; and a heating control circuit 80 for feeding power to the conductive wires 50 to generate heat when the two conductive wires 50 are short-circuited to each other; and the two conductive wires 50 are so structured as to function as capacitance sensors and to function as heaters as well. When the excess state of moisture in the cell is detected, the inside of the cell can quickly be dried by generating heat by the conductive wires 50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric energy by an electrochemical reaction between hydrogen and oxygen. The present invention relates to a generator for a mobile body such as a vehicle, a ship, and a portable generator, or a household generator. It is effective to apply.

  In a fuel cell system including a fuel cell configured by stacking a large number of cells, the output of the fuel cell is reduced due to the retention of liquid droplets in the gas flow path in the cell through which hydrogen and oxygen flow and the decrease in conductivity due to drying of the electrolyte membrane. Will fall. Therefore, it is necessary to detect the moisture state inside the cell and appropriately control the moisture state inside the cell based on the detection result. As a method for detecting the moisture state inside the cell, a method of indirectly estimating from the cell voltage, a method of directly detecting by a capacitance sensor, and the like have been proposed.

  However, in the conventional apparatus, when an excessive moisture state in the cell is detected, the amount of humidification by the humidifier is reduced so as to optimize the moisture state. There was a problem that it took a long time.

  In view of the above points, an object of the present invention is to make it possible to optimize a moisture state in a short time when an excessive moisture state in a cell is detected.

  In order to achieve the above object, according to the first aspect of the present invention, a fuel cell (10) having a cell (100) for generating electric energy by a chemical reaction, and two conductors arranged opposite to each other in the cell. (50), switching control means (40, 60) for switching and controlling the short circuit / opening between the two conductors, and a detecting means for detecting the capacitance between the conductors when the two conductors are open. (70) and a heating control means (80) for supplying heat to the conductor to generate heat when the two conductors are in a short-circuit state.

  According to this, since the electrostatic capacity increases with an increase in the amount of water, the moisture state in the cell can be detected based on the electrostatic capacity using two conductive wires. When an excessive moisture state in the cell is detected, the inside of the cell can be quickly dried by generating heat from the two conductive wires arranged in the cell.

  For example, when starting the fuel cell at a low temperature, it is possible to easily start the fuel cell at a low temperature by heating the two fuel wires to raise the temperature of the fuel cell.

  In addition, since the two conductive wires function as a capacitance sensor and also as a heater, they can be implemented with a small mounting space and at a low cost.

  As in the invention described in claim 2, the switching control means (40, 60) includes a switch (60) that opens and closes between the two conductors (50), and a control unit (40) that controls the operation of the switch. Can be provided.

  In the invention according to claim 3, the cell (100) includes a separator (130) in which a gas flow path (131) is formed, and a conductive wire (50) is disposed in the gas flow path in the separator. It is characterized by that.

  According to this, since the conducting wire is arranged in the gas flow path in the separator, the gas can be directly heated when the conducting wire functions as a heater, and therefore, the inside of the cell can be dried more quickly. it can.

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

  FIG. 1 is a diagram showing an overall configuration of a fuel cell system according to an embodiment of the present invention, and this fuel cell system is applied to, for example, an electric vehicle that runs using a fuel cell as a power source.

  As shown in FIG. 1, the fuel cell system of this embodiment includes a fuel cell 10 that generates electric power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell 10 supplies electric power to electric devices such as an electric load 11 and a secondary battery (not shown). Incidentally, in the case of an electric vehicle, an electric motor for running the vehicle corresponds to the electric load 11.

  In the present embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of cells (detailed later) are stacked and electrically connected in series. In the fuel cell 10, when hydrogen and air (oxygen) are supplied, the following electrochemical reaction between hydrogen and oxygen occurs and electric energy is generated.

(Fuel electrode side) H ₂ → 2H ⁺ + 2e ⁻
(Air electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The fuel cell system includes an air flow path 20 for supplying air (oxygen) to the air electrode (positive electrode) side of the fuel cell 10 and a fuel for supplying hydrogen to the fuel electrode (negative electrode) side of the fuel cell 10. A flow path 30 is provided. Air corresponds to the oxidizing gas of the present invention, and hydrogen corresponds to the fuel gas of the present invention.

  An air pump 21 is provided at the most upstream portion of the air flow path 20 to pump air sucked from the atmosphere to the fuel cell 10. Between the air pump 21 and the fuel cell 10 in the air flow path 20. A humidifier 22 that humidifies the air is provided. An air pressure regulating valve 23 for adjusting the pressure of the air supplied to the fuel cell 10 is provided on the downstream side of the fuel cell 10 in the air flow path 20.

  A hydrogen cylinder 31 filled with hydrogen gas is provided at the most upstream portion of the fuel flow path 30, and hydrogen supplied to the fuel cell 10 is interposed between the hydrogen cylinder 31 and the fuel cell 10 in the fuel flow path 30. A hydrogen pressure regulating valve 32 for regulating the amount of hydrogen supplied to the fuel cell 10 by adjusting the pressure of the fuel cell 10 is provided, and a humidifier 33 for humidifying hydrogen is provided between the hydrogen pressure regulating valve 32 and the fuel cell 10. It has been. A hydrogen outlet flow rate adjustment valve 34 that adjusts the flow rate of hydrogen supplied from the hydrogen cylinder 31 to the fuel cell 10 is provided on the downstream side of the fuel cell 10 in the fuel flow path 30.

  2 is a diagram showing the configuration of the main part of the cell 100 constituting the fuel cell 10, FIG. 3 is a diagram showing the configuration of the separator 130 and the electric circuit unit in the cell 100, and FIG. 4 is along the line AA in FIG. FIG. 5 is a sectional view of the conducting wire 50 of FIG.

  As shown in FIG. 2, the cell 100 includes an electrolyte membrane 110, a diffusion layer 120, a separator 130, and the like. The separator 130 is formed of a conductive member (for example, carbon material) that does not allow gas to pass therethrough, and serves to separate the flow paths of hydrogen and air between adjacent cells and to ensure electrical connection between the cells. Have.

  As shown in FIGS. 3 and 4, an in-cell air flow path 131 through which air passes, an air inlet 132, and an air outlet 133 are formed on the surface of the separator 130 that faces the diffusion layer 120. The in-cell air flow path 131 corresponds to the gas flow path of the present invention.

  In the in-cell air flow path 131, two conductive wires 50 are arranged to face each other. As shown in FIG. 5, the conductor 50 has a conductor 51 covered with an electrically insulating film 52. The cross-sectional shape of the conductor 51 may be round or square. The conducting wire 50 has a function of a capacitance sensor that outputs an electric signal corresponding to the capacitance between the conducting wires 50 as a parallel plate capacitor, and also functions as a heater that generates heat when an electric current flows. . Incidentally, as shown in FIG. 6, the capacitance increases as the amount of moisture increases, so that the amount of moisture can be detected by detecting the capacitance.

  Returning to FIG. 3 and FIG. 4, both ends of the two conductive wires 50 are led out of the separator 130. A switch 60 that opens and closes between the two conductors 50 is connected to one end of the two conductors 50, and the operation of the switch 60 is controlled by a control unit 40 described later. The switch 60 and the control unit 40 constitute the switching control means of the present invention.

  A detection circuit 70 and a heating control circuit 80 are connected to the other end side of the two conductive wires 50. The detection circuit 70 detects the moisture state in the cell 100 based on an electrical signal corresponding to the capacitance between the conductors 50 when the two conductors 50 are opened by the switch 60. And corresponds to the detection means of the present invention.

  The heating control circuit 80 opens and closes a power supply circuit that supplies power to the conductor 50 from a power source (not shown). When the two conductors 50 are short-circuited by the switch 60, the power supply circuit is turned on. By closing and supplying power to the conductor 50, the conductor 50 is heated. The heating control circuit 80 corresponds to the heating control means of the present invention.

  The control unit (ECU) 40 is composed of a well-known microcomputer comprising a CPU, ROM, RAM, etc. and its peripheral circuits. The control unit 40 receives a moisture amount signal from the detection circuit 70 and a fuel cell temperature signal from a temperature sensor (not shown) that detects the temperature of the fuel cell 10. Further, the control unit 40 controls the air pump 21, the humidifier 22, the air pressure regulating valve 23, the hydrogen pressure regulating valve 32, the humidifier 33, the hydrogen outlet flow rate regulating valve 34, the switch 60, and the heating control circuit 80 based on the calculation result. Output a control signal.

  Next, the operation of the fuel cell system configured as described above will be described with reference to FIG. FIG. 7 is a flowchart of a part of the control process executed by the control unit 40 for controlling the moisture content inside the fuel cell 10 and the temperature of the fuel cell 10 based on the moisture content signal and the fuel cell temperature signal. It is.

  In FIG. 7, first, the moisture amount signal from the detection circuit 70 and the fuel cell temperature signal from the temperature sensor are input (S101). Then, when the temperature of the fuel cell 10 is lower than a threshold value (for example, 10 ° C.) as when the fuel cell 10 is started at a low temperature (S102 is NO), the conductor 50 is functioned as a heater (S103). Specifically, the switch 60 short-circuits between the two conductors 50 and the heating control circuit 80 closes the power supply circuit to supply power to the conductor 50, thereby causing the conductor 50 to generate heat. The temperature of the fuel cell 10 is raised, and the fuel cell 10 is easily started at a low temperature.

  On the other hand, when the temperature of the fuel cell 10 is equal to or higher than the threshold (YES in S102), the switch 60 opens the two conductors 50 and opens the power supply circuit in the heating control circuit 80, thereby conducting the conductor 50. Is stopped (S104), thereby stopping the function of the conductor 50 as a heater.

  Next, when the amount of moisture in the cell is equal to or greater than the threshold value, that is, when the amount of moisture in the cell is excessive (YES in S105), an operation for drying the inside of the cell is performed (S106). Specifically, the conductive wire 50 is caused to function as a heater to evaporate the moisture in the cell and discharge the moisture to the outside of the fuel cell 10. Moreover, while the humidification amount to the air by the humidifier 22 is reduced, the humidification amount to hydrogen by the humidifier 33 is reduced. On the other hand, when the moisture content in the cell is less than the threshold value, that is, when the moisture content in the cell is not excessive (S105 is NO), the operation for drying the cell is stopped (S107).

  In the present embodiment, since the moisture content in the cell is controlled based on the detection result of the moisture content in the cell, it is possible to prevent a decrease in the output of the fuel cell 10 due to excessive moisture in the cell.

  Further, when the fuel cell 10 is started at a low temperature, the fuel cell 10 is heated to raise the temperature of the fuel cell 10, so that the fuel cell 10 can be easily started at a low temperature.

  Moreover, since the conducting wire 50 functions as a capacitance sensor and also as a heater, it can be implemented with a small mounting space and cost.

  Moreover, since the conducting wire 50 is disposed in the in-cell air flow path 131, when the conducting wire 50 functions as a heater, the air can be directly heated, and the inside of the cell can be dried quickly.

  In addition, when estimating the amount of water in the cell from the cell voltage, the situation has already deteriorated (the occurrence of a decrease in the output of the fuel cell 10 or the like) when the amount of moisture in the cell can be estimated to be excessive or too small. On the other hand, in the case of a capacitive sensor, it is possible to detect excessive or low moisture content in the cell before the situation worsens. The water content in the cell can be controlled to an appropriate value before deterioration.

  Further, in the case of a capacitive sensor, the withstand voltage of the detection circuit 70 can be lowered by AC coupling between the lead wire 50 serving as a sensor and the detection circuit 70.

  In addition, the conducting wire 50 may be disposed only in some cells, or may be disposed in all cells to detect the moisture state of all cells. The conducting wire 50 may be arranged in any way as long as it does not protrude from the space of the in-cell air flow path 131. The conducting wire 50 may be embedded in the separator 130. The two conductive wires 50 may be divided in the middle, and the moisture state may be detected by dividing the cell upper side and the lower side, for example.

1 is a schematic diagram illustrating an overall configuration of a fuel cell system according to a first embodiment. It is a figure which shows the structure of the principal part of the cell 100 which comprises the fuel cell 10 of FIG. It is a figure which shows the structure of the separator 130 and the electric circuit part in the cell 100 of FIG. It is sectional drawing which follows the AA line of FIG. It is sectional drawing of the conducting wire 50 of FIG. It is a figure which shows the relationship between an electrostatic capacitance and a moisture content. It is a flowchart of the moisture content control process and temperature control process of 1st Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 40 ... Control part (switching control means), 50 ... Conductor, 60 ... Switch (switching control means), 70 ... Detection circuit (detection means), 80 ... Heating control circuit (heating control means), 100 ... cell.

Claims (3)

A fuel cell (10) having a cell (100) for generating electric energy by an electrochemical reaction between a fuel gas mainly containing hydrogen and an oxidizing gas mainly containing oxygen;
Two conductors (50) arranged opposite to each other in the cell;
Switching control means (40, 60) for switching and controlling a short circuit / opening between the two conductors;
Detection means (70) for detecting a capacitance between the two conductors when the two conductors are in an open state;
A fuel cell system comprising heating control means (80) for supplying electric power to the conducting wire to generate heat when the two conducting wires are short-circuited. The said switching control means (40, 60) is provided with the switch (60) which opens and closes between the said two conducting wires (50), and the control part (40) which controls the action | operation of the said switch. Item 4. The fuel cell system according to Item 1. The cell (100) includes a separator (130) in which the gas flow path (131) is formed, and the conductive wire (50) is disposed in the gas flow path in the separator. The fuel cell system according to claim 1 or 2.

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