JP2009170388A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing deterioration of a cathode without using inert gas, and capable of removing hydrogen permeating into an oxidant gas passage while the fuel cell system is stopped. <P>SOLUTION: The fuel cell system includesa fuel cell 1 having an electrolyte layer, an anode electrode and a cathode electrode respectively arranged on both primary surfaces of the electrolyte layer, and a pair of conductive separators arranged by sandwiching the electrolyte layer and having a fuel gas passage wherein one of the separators supplies a fuel gas including hydrogen in the anode electrode and having an oxidizer gas passage wherein the other of the separators supplies an oxidizer gas to the cathode electrode, a DC voltage applying device 5 for applying DC voltage, wherein the cathode electrode becomes positive polarity to the anode electrode, between the pair of separators, and controller 6. The controller 6 executes application of the DC voltage by the DC voltage applying device 5 before starting supply of the oxidizer gas to the oxidizer gas passage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system including a mechanism for removing hydrogen that has permeated into an oxidant gas flow channel during a stop of the fuel cell.

  A conventional fuel cell generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. There are various types depending on the material used. Among these, solid polymer electrolyte fuel cells are known as typical fuel cells for home use and in-vehicle use. This solid polymer electrolyte fuel cell is provided with a polymer electrolyte membrane made of a cation exchange resin that selectively transports hydrogen ions as an electrolyte. The catalyst layer which has as a main component the carbon powder which carry | supported the metal which has is formed. A gas diffusion layer having both air permeability and electron conductivity for allowing a reaction gas made of a fuel gas or an oxidant gas to pass therethrough is formed outside the catalyst layer. A combination of the polymer electrolyte membrane and the gas diffusion layer and the catalyst layer present on both sides thereof is referred to as MEA (electrode-degradation membrane assembly).

  A pair of gas sealing materials are arranged around the MEA with a polymer electrolyte membrane interposed so that the supplied fuel gas and oxidant gas do not leak out or mix with each other. ing. Further, a pair of conductive separators for electrically connecting adjacent MEAs in series with each other are disposed on the outer surfaces of the pair of gas seal materials. A gas flow path for supplying fuel gas or oxidant gas to the catalyst layer is provided on the inner surfaces of the pair of separators. Further, a heat absorption structure for removing heat generated when power generation occurs in the MEA is provided on the outer surfaces of the pair of separators. This heat absorption structure generally absorbs heat by passing a liquid cooling medium such as water or antifreeze through a flow path provided on the separator surface. However, a cooling fin or heat conduction tube is used. A cooling structure has also been proposed.

  The unit battery composed of the MEA, the gas seal material, and the separator is laminated in two to 200 stages according to the required output, and a pair of current collector plates and a pair of insulating plates are disposed outside the unit cell. These are sandwiched between a pair of end plates and fastened with fastening bolts to form a cell stack. This cell stack constitutes the main part of the fuel cell.

  Such a fuel cell is incorporated in a fuel cell system composed of devices that maintain and control power generation. The power source of a cogeneration system that supplies electricity and hot water, the power source of transportation means such as automobiles and motorcycles, Used as a power source for portable devices.

  In such an application, the fuel cell system is repeatedly activated, operated, and stopped in response to a load request. Further, the operation time and the stop time vary greatly according to the load demand. Therefore, even if the cycle of start-up, operation, and stop is repeated irregularly, the fuel cell is required to have durability that can maintain power generation performance for thousands to tens of thousands of hours.

  However, if oxygen is present in the gas flow path of the fuel cell during stoppage, a metal catalyst such as Pt or a structural material such as carbon is worn out due to an oxidation reaction. In a fuel cell using a polymer electrolyte membrane, Decomposition reaction (degradation reaction) of the polymer electrolyte membrane occurs due to oxygen radicals generated from oxygen by catalytic action. In these deterioration reactions, the reaction rate increases in proportion to the height of the oxygen concentration. However, since oxygen is consumed during power generation, the deterioration reaction rate is small and is maximum during stoppage.

  Therefore, in order to improve the durability performance, it is necessary to remove oxygen from the inside of the stopped fuel cell.

  In order to solve this problem, for example, in Patent Document 1, an inert gas such as nitrogen, argon, or city gas is caused to flow through the oxidant gas flow channel during the stop operation, and the oxidant gas in the flow channel is pushed out. It has been proposed to keep the oxygen concentration in the fuel cell at a low level by sealing the fuel cell and confining the inert gas in the flow path during the stop.

By the way, in Patent Document 2, even if the inert gas is held in the oxidant gas flow path during the stop as described above, if the fuel gas containing hydrogen is held in the fuel gas flow path, the hydrogen is removed from the electrolyte membrane during the stop. When the oxidant gas is supplied to the oxidant gas channel at the next start-up, a direct combustion reaction between hydrogen and oxygen occurs on the cathode catalyst surface, and the combustion energy causes It has been pointed out that problems such as wear of fuel cell components such as electrolyte membranes and carbon, and deterioration of particle size due to sintering of Pt occur. Patent Document 2 describes that by flowing an inert gas through the oxidant gas flow channel immediately before the start-up operation, direct contact between hydrogen and oxygen can be prevented and deterioration can be suppressed.
JP 2005-259663 A JP-A-2005-93115

  However, in the conventional techniques described in Patent Document 1 and Patent Document 2, facilities for supplying inert gas such as city gas piping and gas storage means such as a cylinder are indispensable. For fuel cell systems used as power sources for mobile devices, mobile device power supplies, and land-based cogeneration systems that are supplied with fuel gas with hydrogen as one of its main components It was difficult.

  The present invention has been made to solve such a problem, and without using an inert gas, prevents deterioration of the cathode and removes hydrogen that has permeated into the oxidant gas flow path during stoppage. An object of the present invention is to provide a fuel cell system capable of satisfying the requirements.

  In order to solve the above-described problems, a fuel cell system of the present invention includes an electrolyte layer, an anode electrode and a cathode electrode respectively provided on both main surfaces of the electrolyte layer, and one of which is sandwiched between the electrolyte layers. A pair of conductive separators having a fuel gas flow path for supplying a fuel gas containing hydrogen to the anode electrode and the other having an oxidant gas flow path for supplying an oxidant gas to the cathode electrode; A fuel cell, a DC voltage applicator for applying a DC voltage having a positive polarity to the cathode electrode with respect to the anode electrode, and a controller between the pair of separators, the controller including the oxidant The application of the DC voltage is executed by the voltage applicator until the supply of the oxidant gas to the gas flow path is started. With such a configuration, when a DC voltage is applied, protons are generated by the hydrogen oxidation reaction at the cathode electrode, and hydrogen is generated by the proton reduction reaction at the anode electrode. That is, hydrogen in the oxidant gas flow path moves to the fuel gas flow path, and hydrogen in the oxidant gas flow path can be removed. As a result, it is possible to prevent the cathode electrode from deteriorating when the supply of the oxidizing gas is started.

The controller waits until the supply of the oxidant gas is started after the application of the DC voltage is finished, and the cathode electrode does not deteriorate even when the supply of the oxidant gas is started. Thus, the application of the DC voltage may be executed. With such a configuration, the standby time from the hydrogen removal treatment to the supply of the oxidant gas is limited to a time during which the cathode electrode does not deteriorate, so that the deterioration of the cathode electrode when the supply of the oxidant gas is started is prevented. can do.
The controller may execute the application of the DC voltage between the start of the start-up process of the fuel cell system and the start of the supply of the oxidant gas. With such a configuration, the amount of hydrogen gas that permeates and accumulates in the oxidant gas flow path after application of a DC voltage can be minimized, so that deterioration of the cathode electrode when the supply of oxidant gas is started Can be further reduced.

The controller, after executing the application of the DC voltage in a period from the completion of the stop process of the fuel cell system to the start of the next start process, when the start condition is not satisfied within a predetermined time, The application of the DC voltage may be executed again. With such a configuration, the hydrogen removal process can be performed during the stop period of the fuel cell, so that power generation can be started quickly, and the hydrogen removal process is performed after a predetermined time has elapsed after waiting for the activation command. Therefore, even when waiting for a long time, it is possible to prevent deterioration of the cathode electrode when the supply of the oxidant gas is started.
The predetermined time is preferably an upper limit time during which the cathode electrode does not deteriorate even when the supply of the oxidizing gas is started.

  The controller starts supplying the oxidant gas when the start condition is satisfied within the predetermined time after the stop process is completed, and within the predetermined time after the stop process is completed. If the start condition is not satisfied, the application of the DC voltage may be executed.

  The fuel cell includes a cell stack in which two or more unit cells each having the electrolyte layer, the anode electrode and the cathode electrode, and the pair of separators are stacked, and the controller includes one or more unit cells. The DC voltage may be sequentially applied to each unit battery unit. It is possible to prevent deterioration of the cathode electrode due to hydrogen deficiency and insufficient treatment, and hydrogen remaining in the oxidant gas flow path.

  The controller sets the upper limit of the DC voltage to be applied to a potential obtained by adding a diffusion overvoltage to a redox potential of a material having the lowest potential obtained by adding a diffusion overvoltage to a redox potential among materials constituting the cathode electrode. It is preferable to control to be a smaller value. With such a configuration, it is possible to suppress wear of the material due to an oxidation reaction that occurs at or above the redox potential of the material constituting the cathode electrode.

  It is preferable that the controller controls the upper limit value of the DC voltage to be applied so as to be a value smaller than the oxidation-reduction potential of the material having the lowest oxidation-reduction potential among the materials constituting the cathode electrode. With such a configuration, it is possible to suitably suppress wear of the material due to an oxidation reaction that occurs at or above the redox potential of the material constituting the cathode electrode.

  The present invention has a configuration as described above, and can prevent the deterioration of the cathode without using an inert gas, and can remove the hydrogen that has permeated into the oxidant gas passage during the stoppage. The system can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout all the drawings, and redundant description thereof is omitted.
(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel cell system 101 of this embodiment includes a fuel cell 1. The fuel cell system 101 is, for example, a power source for a moving or transportation means such as an automobile (for in-vehicle use), a power source for a mobile device, or a land-use coordinator that is supplied with fuel gas having hydrogen as a main component. It consists of a fuel cell system for a generation system. The fuel cell 1 is composed of, for example, a solid polymer electrolyte fuel cell.

  The fuel cell 1 has an internal fuel gas path 17 and an internal oxidant gas path 18. As will be described later, the internal fuel gas path 17 includes a fuel gas supply manifold, a fuel gas flow path, and a fuel gas discharge manifold that are connected in order. As will be described later, the internal oxidant gas passage 18 includes an oxidant gas supply manifold, an oxidant gas flow path, and an oxidant gas discharge manifold that are connected in order. The downstream end of the fuel gas supply path 7 is connected to the inlet 17 a of the internal fuel gas path 17. A fuel gas supply device 2 is connected to the upstream end of the fuel gas supply path 7. Here, hydrogen-containing gas or pure hydrogen gas is used as the fuel gas. The fuel gas supply device 2 adjusts the flow rate of hydrogen supplied from an external storage tank of alcohol fuel such as methanol, a reformer that reforms alcohol fuel into a hydrogen-containing gas, a high-pressure hydrogen tank, a hydrogen cylinder, and the like. It consists of a flow controller and the like.

The upstream end of the fuel gas discharge path 10 is connected to the outlet 17 b of the internal fuel gas path 17. The fuel gas discharge passage 10 is provided with a combustor or the like (not shown) for burning the discharged unreacted fuel gas as necessary, and the downstream end of the fuel gas discharge passage 10 is opened to the atmosphere. Yes.
A downstream end of the oxidant gas supply path 8 is connected to the inlet 18 a of the internal oxidant gas path 18. An oxidant gas supply device 3 is connected to the upstream end of the oxidant gas supply path 8. Here, air is used as the oxidant gas. The oxidant gas supply device 3 includes a compressor that sucks and compresses air (atmosphere), and a blower that sucks and sends air (atmosphere). The oxidant gas supply path 8 is provided with a humidifier (not shown) as necessary.

  The upstream end of the oxidant gas discharge path 13 is connected to the outlet 18 b of the internal oxidant gas path 18. The downstream end of the oxidant gas discharge path 18 is open to the atmosphere.

  A fuel gas supply path 7, a fuel gas discharge path 9, an oxidant gas supply path 11, and an oxidant gas discharge path 13 are respectively provided with a first sealing valve 8, a second sealing valve 10, and a third sealing valve. 12 and a fourth sealing valve 14 are provided. Each of the first to fourth sealing valves 8, 10, 12, and 14 is an on-off valve. By closing the first sealing valve 8 and the second sealing valve 10, the internal fuel gas path 17 (more precisely, the portion downstream of the first sealing valve 8 in the fuel gas supply path 7, the internal fuel gas The fuel gas can be sealed in the path 17 and the portion upstream of the second sealing valve 10 in the fuel gas discharge channel 9. Further, by closing the third sealing valve 12 and the fourth sealing valve 13, a portion of the oxidant gas supply path 11 downstream from the third sealing valve 12, the internal oxidant gas path 18, and the oxidant Oxidant gas can be sealed in a portion upstream of the fourth sealing valve 14 of the gas discharge channel 13 (hereinafter referred to as “oxidant gas sealing space 19”). That is, the oxidant gas can be sealed in the internal oxidant gas path 18.

  Further, the fuel cell system 101 includes a cooling system having a cooling water circulation path formed so as to pass through the fuel cell 1, and a cooling water circulation pump and a radiator disposed in the cooling water circulation path. In this cooling system, during power generation, the cooling water circulated through the cooling water circulation path by the cooling water circulation pump exchanges heat with the fuel cell 1, and the heat obtained by the heat exchange is released by the radiator. Thereby, the fuel cell 1 is maintained at a predetermined temperature. However, since this cooling system is not directly related to the present invention, further explanation and illustration thereof are omitted.

  An input terminal (not shown) of the output controller 4 is connected to the pair of electrical output terminals 16 </ b> A and 16 </ b> B of the fuel cell 1. The output controller 4 includes, for example, a DC-DC converter (not shown) and an inverter (not shown). In addition, an inverter is abbreviate | omitted when the load 21 is a direct current load like the vehicle-mounted fuel cell system.

  A load 21 is connected to an output terminal (not shown) of the output controller 4. A load detector 15 that detects power consumed by the load 21 (load power) is disposed on the electrical wiring that connects the output terminal of the output controller 4 and the load 21. The load detector 15 is composed of a power meter, for example. The load power detected by the load detector 15 is input to the controller 6 described later.

  The fuel cell system 101 further includes a voltage applicator 5 and a controller 6. The voltage applicator 5 is for applying a voltage to the fuel cell 1 and will be described in detail later.

  The controller 6 includes a calculation unit (not shown) and a storage unit (not shown). The controller 6 is composed of an arithmetic unit such as a microcomputer, the arithmetic unit is composed of a processor such as a CPU, and the storage unit is composed of an internal memory. In the present invention, the controller means not only a single controller but also a group of controllers. Therefore, the controller 6 does not necessarily need to be composed of a single controller, and a plurality of controllers may be arranged in a distributed manner so as to perform predetermined control in cooperation with each other.

  A load power detected by the load detector 15, a current (described later) detected by the voltage applicator 5, and an applied voltage are input to the calculation unit of the controller 6 (hereinafter simply referred to as a calculation unit). In addition, required information is input from required components of the fuel cell system 101. On the other hand, a predetermined control program is stored in the storage unit of the controller 6 (hereinafter sometimes simply referred to as a storage unit). The calculation unit reads out and executes these control programs from the storage unit, performs necessary processing based on the above-described input, outputs a control signal to the controlled element of the fuel cell system 101, and performs the entire fuel cell system 101. To control the operation.

  Next, the configuration of the fuel cell 1 will be described in detail. FIG. 2 is a partially exploded view showing the configuration of the fuel cell 1 of FIG.

  As shown in FIG. 2, the fuel cell 1 includes an MEA 34. The MEA 34 is formed on the polymer electrolyte membrane 31, the anode catalyst layer 32 </ b> A formed on a portion (central portion) excluding the peripheral portion of one main surface of the polymer electrolyte membrane 31, and the anode catalyst layer 32 </ b> A. A gas diffusion layer 33, a cathode catalyst layer 32B formed in a portion (central portion) excluding the peripheral edge of the other main surface of the polymer electrolyte membrane 31, and a gas diffusion layer 33 formed on the cathode catalyst layer 32B And. The anode catalyst layer 32A and the gas diffusion layer 33 constitute an anode electrode 71, and the cathode catalyst layer 32B and the gas diffusion layer 33 constitute a cathode electrode 72.

  The polymer electrolyte membrane 3 is made of a cation exchange resin that selectively transports hydrogen ions. Specifically, for example, the polymer electrolyte membrane 3 is made of a perfluorosulfonic acid material. The anode catalyst layer 32A and the cathode catalyst layer 32B are composed of, for example, a platinum-based catalyst and a carrier made of carbon powder that supports the catalyst. The gas diffusion layer 33 is made of a material having air permeability and conductivity. Specifically, for example, the gas diffusion layer 33 is made of a nonwoven fabric made of carbon, paper, or the like.

  A pair of gaskets 35 are disposed on the peripheral portions of both main surfaces of the MEA 34 so as to surround the anode electrode 71 and the cathode electrode 72, respectively. As shown in FIG. 2, the gasket 35 is formed in a shape that seals the flow path of the fuel gas and the flow path of the oxidant gas to each other and to the outside. An anode separator 36A and a cathode separator 36B are disposed so as to sandwich the pair of gaskets 35 and the MEA 34. The anode separator 36A is disposed such that one main surface (hereinafter referred to as an inner surface) is in contact with the anode electrode 71 of the MEA 34, and the cathode separator 36B has one main surface (hereinafter referred to as an inner surface) as the cathode electrode of the MEA 34. 72 so as to be in contact with 72. The anode separator 36A and the cathode separator 36B are made of a conductive material such as metal or carbon, and are formed in a plate shape. At the peripheral edge of the anode separator 36A, a fuel gas supply manifold hole 21A, a fuel gas discharge manifold hole 22A, an oxidant gas supply manifold hole 23A, an oxidant gas discharge manifold hole 24A, a cooling water supply manifold hole 25A, and a cooling water discharge A manifold hole 26A is formed. Fuel gas supply manifold hole 21B, fuel gas discharge manifold hole 22B, oxidant gas supply manifold hole 23B, and oxidant gas are located at positions corresponding to manifold holes 21A to 26A of anode separator 36A on the peripheral edge of cathode separator 36B. A discharge manifold hole 24B, a cooling water supply manifold hole 25B, and a cooling water discharge manifold hole 26B are formed.

  A groove-like fuel gas flow path 37A is formed on the inner surface of the anode separator 36A so as to connect the fuel gas supply manifold hole 21A and the fuel gas discharge manifold hole 22A. On the other main surface (hereinafter referred to as an outer surface) of the anode separator 36A, a grooved cooling water flow path 38A is formed so as to connect the cooling water supply manifold hole 25A and the cooling water discharge manifold hole 26A. A groove-like oxidant gas flow path 37B is formed on the inner surface of the cathode separator 36B so as to connect the oxidant gas supply manifold hole 21B and the oxidant gas discharge manifold hole 22B. On the other main surface (hereinafter referred to as an outer surface) of the cathode separator 36B, a grooved cooling water flow path 38B is formed so as to connect the cooling water supply manifold hole 25B and the cooling water discharge manifold hole 26B.

  These MEAs 34, a pair of gaskets 35, an anode separator 36A, and a cathode separator 36B constitute a unit cell 39. A predetermined number of unit batteries 39 are stacked to form a cell stack. A pair of current collecting plates 40A and 40B, a pair of insulating plates 41 and 41, and a pair of end plates 42 and 42 are sequentially disposed on both sides of the cell stack. Through holes 43 are provided at the four corners of the pair of end plates 42, and fastening bolts (not shown) are inserted into the through holes 43, and a pair of nuts (not shown) and the fastening bolts are used to form a pair. A fuel cell (cell stack) 1 is formed by fastening the end plates 42 and 42. The current collecting plates 40A and 40B are made of a metal material, and the insulating plate 41 and the end plate 42 are made of a resin material.

  In this fuel cell 1, fuel gas supply manifold holes 21A, 21B, fuel gas discharge manifold holes 22A, 22B, oxidant gas supply manifold holes 23A, 23B, and oxidant gas discharge manifold holes 24A of the anode separator 36A and cathode separator 36B. , 24B, cooling water supply manifold holes 25A, 25B, and cooling water discharge manifold holes 26A, 26B are connected to each other, and a fuel gas supply manifold, a fuel gas discharge manifold, an oxidant gas supply manifold, an oxidant gas discharge manifold, and a cooling respectively. A water supply manifold and a cooling water discharge manifold are formed. Further, at the boundary between adjacent unit cells, the cooling water channel 38A and the cooling water channel 38B are joined to form one cooling water channel. Further, an inlet 17a (see FIG. 1 and not shown in FIG. 2) of the internal fuel gas passage 17 is provided at one end of the fuel cell 1, and an inlet 18a of the internal oxidant gas passage 18 (see FIG. 1 and not shown in FIG. 2). And an inlet (not shown) for cooling water are formed, a fuel gas outlet 17b (see FIG. 1 and not shown) in the other end of the fuel cell 1, and an oxidant gas outlet 18b (see FIG. 1). , And an outlet (not shown) for cooling water are formed. The inlet 17a of the internal fuel gas path 17 and the inlet 18a of the internal oxidant gas path 18 so as to penetrate the current collector plate 40A, the insulating plate 41, and the end plate 42 disposed on one end side of the fuel cell 1. In addition, a communication hole (not shown) is formed to communicate the inlet of the cooling water, the fuel gas supply manifold, the oxidant gas supply manifold, and the end of the cooling water supply manifold on one end side of the fuel cell 1. . In addition, the outlet 17b of the internal fuel gas path 17 and the outlet 18b of the internal oxidant gas path 18 pass through the current collector plate 40B, the insulating plate 41, and the end plate 42 disposed on the other end side of the fuel cell 1. , And a cooling water outlet, and a communication hole (not shown) for communicating the fuel gas supply manifold, the oxidant gas supply manifold, and the cooling water supply manifold on the other end of the fuel cell 1 are formed. ing. The internal fuel gas path 17 is configured by the communication holes formed at both ends of the fuel cell 1, the fuel gas supply manifold, the fuel gas flow path 37A of each unit cell, and the fuel gas discharge manifold. Yes. Further, the internal oxidant gas path 18 is formed by the communication holes formed at both ends of the fuel cell 1, the oxidant gas supply manifold, the oxidant gas flow path 37B of each unit cell, and the fuel gas discharge manifold. It is configured. The above-described communication holes formed at both ends of the fuel cell 1, the cooling water supply manifold, the cooling water flow paths 38A and 38B between the unit cells, and the cooling water discharge manifold pass through the fuel cell in the cooling water circulation path. The part is composed.

  Next, the configuration of the voltage applicator 5 that characterizes the present invention will be described in detail. FIG. 3 is a schematic diagram showing the configuration of the voltage applicator 5 of FIG.

  In FIG. 3, the fuel cell 1 includes n unit cells 39. That is, the fuel cell 1 includes a first unit cell 39-1 to an nth unit cell 39-n. In FIG. 3, the configuration of the unit batteries 39-1 to 39-n is schematically simplified. For example, the MEA 34 is drawn to the same size as the separators 36A and 37B, and the gasket is omitted.

  The voltage applicator 5 includes a DC power source 51, a connection switch 52, a current detector 61, and a voltage detector 62. In the present embodiment, the DC power supply 51 is constituted by a voltage source capable of changing and outputting a DC voltage. Here, the DC power source 51 is constituted by a switching power source, for example. The controller 6 controls ON / OFF of the DC power supply 51 and the output voltage. Between the output terminals of the DC power supply 51, a voltage detector 62 for detecting a voltage applied by the DC power supply 51 (hereinafter sometimes referred to as an applied voltage or an output voltage) is disposed. The voltage detector 50 is composed of a voltmeter, for example. The applied voltage detected by the voltage detector 50 is input to the calculation unit of the controller 6. The connection switching device 52 includes the same number of switching units 57 as the number of unit cells 39 of the fuel cell 1. The switching unit 57 includes a first terminal 53, a second terminal 54 and a third terminal 55 that are disposed so as to face the first terminal 53 and are aligned with each other, and a contact 55. The contact 55 includes a first connection state in which the first terminal 53 is connected to the second terminal 54, a second connection state in which the first terminal 53 is connected to the third terminal 55, and the first terminal 53 as the second terminal 54 and It is positioned so as to be in any one of the third connection states in which it is not connected to any of the third terminals 55. Here, in order to facilitate understanding, the connection switch 52 configured to mechanically switch the connection is used. However, the same connection switching function is electrically and non-contacted using a semiconductor device. Needless to say, the connection switch 52 realized in the above may be used. A switching device with one input and multiple outputs such as a rotary switch and a demultiplexer may be used.

  The first terminal 53 is connected to a separator of the unit batteries 39-1 to 39-n corresponding to the switching unit 57 to which the first terminal 53 belongs. The separator to which the first terminal 53 is connected may be either the anode separator 36A or the cathode separator 36B, but it is unified to either the anode separator 36A or the cathode separator 36B through all the unit batteries 39-1 to 39-n. Must be. In the present embodiment, the first terminal 53 is connected to the cathode separator 36B.

  The second terminal 54 and the third terminal 55 are respectively connected to the minus (−) terminal and the plus (+) terminal of the DC power supply 51. In the present embodiment, the current collector plate 40 </ b> A that contacts the anode separator of the first unit cell 39-1 of the fuel cell 1 is connected to the negative terminal of the DC power source 51. The connection switching operation of the contact 55 is controlled by the controller 6. A current detector 61 is disposed on the wiring between the connection switch 52 and the output terminal of the DC power supply 51. The current detector 61 is composed of an ammeter, for example. The current detected by the current detector 61 is input to the calculation unit of the controller 6. As a result, the output voltage of the DC power supply 51 can be applied to any unit cell 39-1 to 39-n of the fuel cell 1.

  Next, the operation of the fuel cell system 101 configured as described above will be described by dividing it into a general operation and a characteristic operation. These operations are performed under the control of the controller 6.

  First, a general operation will be briefly described. 1 and 2, the fuel cell system 101 operates under the control of the controller 6, and includes a standby operation, a startup process, a power generation operation, and a stop process as the operations. The standby operation means a so-called “stop state”, in which the controller 6 is operating (activated) and the main part of the fuel cell system 101 (part directly related to power generation) is stopped. The state that is. The startup process refers to an operation for smoothly starting the fuel cell system from a standby operation and shifting to a power generation operation. The power generation operation refers to an operation for generating power. The stop process refers to an operation of smoothly shutting down the fuel cell system from the power generation operation and shifting to the standby operation.

  In the startup process, in the fuel cell system 101, the first to fourth sealing valves 8, 10, 12, and 14 are opened. Then, supply of fuel gas by the fuel gas supply device 2 and supply of oxidant gas by the oxidant gas supply device 3 are started. When the fuel cell system 101 is activated, if the controller 6 determines that a predetermined activation condition is satisfied, the controller 6 outputs an activation signal to a required component of the fuel cell system 101. More specifically, when the activation condition is satisfied, more specifically, when the load power is equal to or higher than a predetermined threshold, or when a user inputs an activation request through a predetermined input device (not shown), For example, when the activation time set by the input through the user input device is reached, or when the activation time preset by the learning operation control is reached. In the present invention, starting the activation process means that a predetermined activation condition is satisfied and the controller 6 outputs the activation signal.

  In the power generation operation, in the fuel cell system 101, the fuel gas is supplied from the fuel gas supply device 2 to the internal fuel gas path 17 of the fuel cell 1, and the oxidant gas is supplied from the oxidant gas supply device 3 to the internal oxidant of the fuel cell 1. It is supplied to the gas path 18. The fuel gas supplied to the internal fuel gas path 17 reaches the anode electrode 71, and electrons and protons are generated in the anode electrode 71 by an oxidation reaction of hydrogen in the fuel gas. Electrons move to the cathode electrode 72 through an electric circuit including the load 21, and protons are transported by the polymer electrolyte membrane 31 and move to the cathode electrode 72. Then, hydrogen is generated by a reduction reaction of protons at the cathode electrode 72. On the other hand, the oxidant gas supplied to the internal oxidant gas path 18 reaches the cathode electrode 72, and oxygen in the oxidant gas reacts with the aforementioned hydrogen at the cathode electrode 72 to generate water. In this series of reactions, electricity and heat are generated. The generated electricity is supplied to the load 21 through the output control device 4 and consumed there. The generated heat is carried by the cooling water and released from the radiator. In the power generation operation, the controller 6 sets a power generation target based on the load power detected by the load detector 15 and generates power while appropriately controlling the fuel cell system 101 based on the power generation target. At that time, the controller 6 appropriately stops and starts the fuel cell system 101 according to the load power.

  The unreacted fuel gas that has not been consumed by the anode electrode 71 is discharged to the fuel gas discharge passage 9, where it is burned and finally discharged into the atmosphere. Unreacted oxidant gas that has not been consumed by the cathode electrode 72 is discharged into the atmosphere through the oxidant gas discharge passage 13.

  In the stop process, in the fuel cell system 101, the supply of the fuel gas by the fuel gas supply device 2 and the supply of the oxidant gas by the oxidant gas supply device 3 are stopped. Then, the first to fourth sealing valves 8, 10, 12, and 14 are closed. As a result, the fuel gas is sealed in the internal fuel gas path 17 of the fuel cell 1, and the oxidant gas is sealed in the internal oxidant gas path 18 of the fuel cell 1. And it transfers to standby operation.

  In the standby operation, as time passes, hydrogen in the fuel gas sealed in the internal fuel gas path 17 passes through the polymer electrolyte membrane 31 and moves to the internal oxidant gas path 18. This transferred hydrogen reacts with oxygen in the oxidant gas and is consumed. Eventually, the oxygen in the internal oxidant gas path 18 (more precisely, in the oxidant gas sealing space 19) is consumed up. Thereby, the deterioration of the cathode electrode 72 due to oxidation is prevented. Then, after the oxygen has been consumed, hydrogen moving from the anode electrode 71 side accumulates in the internal oxidant gas path 18.

  Next, the characteristic operation of the present invention will be described.

  FIG. 4 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101. 5 and 6 are schematic diagrams showing the operation of the voltage applicator.

  As shown in FIG. 4, when the fuel cell system 101 completes its stop processing and shifts to a standby operation (step S <b> 1), the controller 6 (more precisely, its calculation unit) satisfies a predetermined activation condition. (Step S2).

  When the activation condition is satisfied, the controller 6 outputs an activation signal (step S3) and performs the hydrogen removal step S100.

  In this hydrogen removal step S100, first, the controller 6 connects the first unit battery 39-1 to the DC power source 51 (step S4). Specifically, as shown in FIG. 5, the controller 6 controls the connection switch 52 to connect the first terminal 53 by the contact 56 in the connection switching unit 57 corresponding to the first unit battery 39-1. Connect to the third terminal 55. In the connection switching unit 57 corresponding to the unit batteries 39-2 to 39-n other than the first unit battery 39-1, the contact 56, the first terminal 53, the second terminal 54, and the third terminal 55 Position it in a neutral position that does not connect to the

  Next, the controller 6 turns on the DC power supply 51 (step S5). As a result, a DC voltage is applied to the first unit battery 39-1 by the DC power source 51. Here, in the present embodiment, the upper limit value (hereinafter referred to as the upper limit voltage) of the applied voltage is stored (set) in the storage unit of the controller 6. This upper limit voltage is determined to be 90% of the redox potential of the material having the lowest redox potential among the materials constituting the cathode electrode 72. The reason why the upper limit voltage is determined based on the material having the lowest oxidation-reduction potential is to prevent deterioration (corrosion) due to oxidation of the material constituting the cathode electrode 72. The numerical value of 90% takes into account the delay in voltage application control by the DC power supply 51. Therefore, the numerical value of 90% needs to be changed according to the response speed of the voltage applicator 5. In the present embodiment, as described above, the cathode electrode 72 is composed of the cathode catalyst layer 32B composed of a platinum-based catalyst and a catalyst carrier made of carbon powder, and the gas made of non-woven fabric made of carbon, paper, or the like. Since it is composed of the diffusion layer 33, the material having the lowest redox potential among these is carbon. The redox potential of carbon is 0.23V. Therefore, in the present embodiment, 0.21V, which is 90% of 0.23V, is determined as the upper limit voltage. Here, in order to determine an ideal upper limit voltage, the upper limit voltage is determined based on the oxidation-reduction potential of the material having the lowest oxidation-reduction potential among the materials constituting the cathode electrode 72. The upper limit voltage may be determined based on the substantial oxidation potential of the material having the lowest voltage (hereinafter referred to as the substantial oxidation potential for convenience) obtained by adding an overvoltage to the oxidation-reduction potential among the materials to be processed. This is because the material constituting the cathode electrode 72 is not actually oxidized unless a voltage exceeding the substantial oxidation potential is applied. Thus, when the upper limit voltage is determined based on the substantial oxidation potential, it is determined based on the substantial oxidation potential of carbon. For example, in a state where nitrogen gas is supplied to the cathode electrode 72 of the unit battery and hydrogen gas is supplied to the anode electrode 71, the positive electrode and the cathode electrode 72 of the external DC power source are connected to the negative electrode of the external power source and the anode electrode 71, respectively. In the test, when the voltage of the external power supply is increased, the current value of 0.3 V to 0.5 V is stabilized at a low value. From this, it can be considered that current due to corrosion of carbon does not flow due to overvoltage in this voltage range. Therefore, in this case, the upper limit voltage is set to 0.4V. Since this value varies depending on the material and structure, it is necessary to determine the value by a similar test. The method for measuring the substantial oxidation potential is not limited to this, and other measurement methods may be used.

  Under this upper limit voltage, the controller 6 outputs the output voltage (applied voltage) of the DC power source 51 so that the value of the current (hereinafter referred to as the hydrogen removal current) becomes a predetermined constant value (hereinafter referred to as the predetermined current value). To control. The predetermined current value is not limited except for the condition that the voltage applied by the DC power source 51 does not exceed the upper limit voltage. The predetermined current value is determined in advance by experiments, calculations, etc., and is stored in the storage unit of the controller 6. The controller 6 controls the output voltage of the DC power supply 51 so that the current detected by the current detector 61 becomes the stored predetermined current value. As a result, an oxidation reaction of hydrogen existing in the internal oxidant gas path 18 (more precisely, in the oxidant gas sealing space 19) is started. As the time elapses, the hydrogen concentration in the oxidant gas path 18 becomes thinner (lower), and the diffusion overvoltage increases accordingly. On the other hand, since the controller 6 controls the applied voltage (output voltage) of the DC power supply 51 so as to maintain the hydrogen removal current at a predetermined current value, the applied voltage increases. The controller 6 monitors whether or not the applied voltage exceeds the upper limit voltage by the voltage detector 62 (step S6). Eventually, when the applied voltage exceeds the upper limit voltage, the controller 6 turns off the DC power supply 51. Thereby, the application of the DC voltage is completed (step S7). As a result, the hydrogen accumulated in the internal oxidant gas path 18 (more precisely, the oxidant gas sealing space 19) of the first unit battery 39-1 is removed. This hydrogen removal process (steps S5 to S7) usually ends in a few seconds.

  Next, the controller 6 determines whether or not the unit cell subjected to the hydrogen removal process is the last unit cell (step S8). Here, since it is not the last unit battery, it progresses to step S12.

  In step S <b> 12, the controller 6 connects the next unit battery, that is, the second unit battery 39-2 to the DC power source 51. Specifically, as shown in FIG. 6, the controller 6 controls the connection switching unit 52 to connect the first terminal 53 by the contact 56 in the connection switching unit 57 corresponding to the first unit battery 39-1. Connect to the second terminal 54. In the connection switching unit 57 corresponding to the second unit battery 39-2, the first terminal 53 is connected to the third terminal 55 by the contact 56. In the connection switching unit 57 corresponding to the unit batteries 33-3 to 39-n other than the first unit battery 39-1 and the second unit battery 39-2, the contact 56 is connected to the first terminal 53 and the second terminal is connected to the second terminal. 54 and the third terminal 55 are positioned in a neutral position where they are not connected.

  Next, the controller 6 performs a hydrogen removal process by applying a DC voltage to the second unit battery 39-2 in the same manner as described above (steps S5 to S7).

  Then, the controller 6 repeats steps S12, S5 to S8 for the remaining unit cells, and performs hydrogen removal processing (steps S5 to S5) for the last unit cell, that is, the nth unit cell 39-n. When S7) is performed, the process proceeds to step S9 (YES in step S8). Thereby, hydrogen removal process S100 is completed.

  In step S8, the controller 6 opens the sealing valves 8, 10, 12, and 14. Thereby, the fuel gas supply path 7, the fuel gas discharge path 9, the oxidant gas supply path 11, and the oxidant gas discharge path 13 are opened.

  Next, the controller 6 controls the fuel gas supply device 2 and the oxidant gas supply device 3 to start supplying fuel gas and oxidant gas (step S11). At this time, since the hydrogen in the internal oxidant gas path 18 (precisely, the oxidant gas sealing space 19) is removed, the fuel cell by the direct combustion reaction of oxygen and hydrogen in the supplied oxidant gas. It is possible to prevent the constituent members from being worn.

  Next, the controller 6 controls the entire fuel cell system 101 to start power generation (step S11).

  As described above, in the present embodiment, the fuel cell system 101 uses the sealing valves 8, 10, 12, and 14 to stop the internal fuel gas path 17 and the internal oxidant gas of the fuel cell 1 during the stop process. The fuel gas and the oxidant gas are sealed in the passage 18, respectively. As a result, oxygen in the oxidant gas in the internal oxidant gas path 18 is consumed by the hydrogen that permeates the polymer electrolyte membrane 31, so that deterioration due to oxidation of the cathode electrode 72 is prevented without using an inert gas. can do. Further, after the consumption of oxygen, hydrogen accumulated in the internal oxidant gas path 18 is removed by applying a voltage to each unit cell by the voltage applicator 5, so that the oxygen and hydrogen at the start of power generation are removed. It is possible to prevent the wear of the fuel cell constituent member due to the direct combustion reaction.

In the present embodiment, all unit batteries 39-1 to 39-n are subjected to hydrogen removal treatment by sequentially applying a DC voltage one by one. In addition, it is possible to prevent hydrogen that is not removed from some unit cells from remaining.
That is, when the number of unit cells constituting the fuel cell 1 is large, the DC voltage applied to the entire fuel cell 1 is (DC voltage necessary for one unit cell) × (number of unit cells stacked). . However, all unit cells need only be in a uniform state. However, variation in physical property values such as the amount of hydrogen contained in each unit cell (existing in its internal oxidant gas flow path 18) and component resistance of each unit cell, etc. As a result, the DC voltage required for the hydrogen removal process varies. In such a state, if a current is supplied to many unit cells in a lump, the unit cell with a small amount of hydrogen contained therein will finish the hydrogen removal process first. In the battery, untreated hydrogen remains. On the other hand, when the hydrogen removal process is completed at the time when the hydrogen removal process of the unit battery with the largest amount of hydrogen is completed, it is necessary to pass an electric current by a reaction other than the oxidation of hydrogen in the unit battery that has already lost hydrogen. Therefore, a deterioration reaction of the material constituting the cathode electrode is caused. Therefore, as in this embodiment, all unit batteries 39-1 to 39-n are subjected to hydrogen removal treatment by sequentially applying a DC voltage one by one to prevent such a problem. it can.

(Embodiment 2)
FIG. 7 is a schematic diagram showing the configuration of the voltage applicator of the fuel cell system according to Embodiment 2 of the present invention. FIG. 8 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101 of the present embodiment.

  In the present embodiment, the hydrogen removal step is different from that in the first embodiment, and the other steps are the same as those in the first embodiment. Hereinafter, this difference will be described.

  As shown in FIG. 7, in the present embodiment, first, the voltage detector 62 (FIG. 3) of the first embodiment is omitted from the voltage applicator 5. In the present embodiment, since it is not always necessary to change the applied voltage, in addition to the switching power supply, as the DC power supply 51, a physical battery such as a chemical battery such as a primary battery, a secondary battery, or a fuel cell, a solar battery, or a temperature difference battery. A battery, a capacitor, or the like can be used. Secondly, as shown in FIG. 8, in the hydrogen removal step S101, instead of step S6 (FIG. 4) for monitoring the applied voltage in the first embodiment, step S13 for monitoring the hydrogen removal current is performed.

  Specifically, in step S5, the controller 6 controls the DC power source 51 to output a predetermined constant voltage lower than the upper limit voltage. On the other hand, as the hydrogen concentration in the oxidant gas path 18 decreases with time, the hydrogen removal current decreases accordingly. Eventually, the hydrogen removal current converges to a certain value (current I described below).

  The process of changing the hydrogen removal current will be described in detail. The direct current (hydrogen removal current) after the oxygen in the internal oxidant gas path 18 is completely consumed is that hydrogen passing through the polymer electrolyte membrane 31 from the internal fuel gas path 17 is oxidized during the hydrogen removal process. Will be covered. That is, the hydrogen in the internal oxidant gas path 17 (more precisely, the oxidant gas sealing space 19) is determined by the partial pressure of hydrogen in the internal fuel gas path 17 and the hydrogen gas permeability coefficient in the electrolyte (polymer electrolyte membrane 31). The direct current value I per electrode area after the removal is obtained from the equation (1).

I = 2DFAΔP / δRT (1)
In the equation (1), I is a permeated hydrogen oxidation current (DC current) (A) necessary to oxidize hydrogen permeated from the internal fuel gas path 17, and D is a hydrogen diffusion coefficient (cm ² / sec) of the electrolyte. ), F is the Faraday constant (C / mol), A is the area (cm ² ) of the electrolyte that permeates hydrogen, and ΔP is the hydrogen partial pressure in the internal fuel gas path 17 and the hydrogen partial pressure in the internal oxidant gas path 18. Differential pressure (Pa), δ is the thickness (cm) of the electrolyte (polymer electrolyte membrane 31), R is a gas constant (mol · K / Pa / cm ³ ), and T is the temperature at which the hydrogen removal step is performed. (K).

  Therefore, when the applied voltage is controlled to be constant, the value of the direct current (hydrogen removal current) flowing through the unit cell decreases in proportion to the decrease in the hydrogen concentration in the internal oxidant gas path 18 (1 It becomes constant at the direct current I obtained by the equation (1). Therefore, the time point at which the value of the current flowing through the unit battery reaches I (decreases) is the time point at which the hydrogen removal process ends.

  In the present embodiment, the direct current value I is set in advance in a state where hydrogen is passed through the fuel gas passages 7, 17, 9 and nitrogen is passed through the oxidant gas passages 11, 18, 13. A current range ((I−δI) to (I + δI)), which is measured for each unit battery 39-1 to 39-n and allows a predetermined tolerance (error) δI to the measured DC current value I, is a hydrogen removal current. Is stored in the storage unit of the controller 6 for each unit battery 39-1 to 39-n. Then, the controller 6 monitors whether or not the current detected by the current detector 61 is within the permissible range of the hydrogen removal current of the corresponding unit battery (step S13). When the current detected by the current detector 61 falls within the permissible range of this hydrogen removal current (YES in step S13), the DC power supply 51 is turned off and the application of the DC voltage is stopped (step S7). The other steps are the same as in the first embodiment.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained.

  Note that the direct current value I, which is the basis of the allowable current range stored in the storage unit, is the previously measured physical properties of the electrolyte (here, the polymer electrolyte membrane 31), the structure of the fuel cell 1, and when the fuel cell system 101 is stopped. You may obtain | require by calculation from the state of.

  Further, instead of storing the current allowable range in the storage unit, the hydrogen removal current is acquired at a predetermined sampling interval, the change rate thereof is calculated, and whether or not the calculated change rate becomes substantially zero, You may make it determine whether the application of a voltage is complete | finished. In this case, the physical property value of the electrolyte changes due to deterioration due to the operation of the fuel cell 1, the moisture content of the electrolyte, disturbances such as the outside air temperature, the outside air pressure, and the like, thereby preventing erroneous determination due to the change. it can.

(Embodiment 3)
FIG. 9 is a schematic diagram showing the configuration of the voltage applicator of the fuel cell system according to Embodiment 3 of the present invention. FIG. 10 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101 of the present embodiment.

  In the present embodiment, the hydrogen removal step is different from that in the first embodiment, and the other steps are the same as those in the first embodiment. Hereinafter, this difference will be described.

  In the present embodiment, first, as shown in FIG. 9, in the voltage applicator 5, instead of the current detector 16 and the voltage detector 62 (FIG. 3) of the first embodiment, an integrated charge amount measuring device 64. Is arranged. In the present embodiment, since it is not always necessary to change the applied voltage, in addition to the switching power supply, the direct-current power supply 51 is a physical battery such as a chemical battery such as a primary battery, a secondary battery, or a fuel cell, a solar battery, or a temperature difference battery. A battery, a capacitor, or the like can be used.

  The integrated charge amount measuring device 64 measures the integrated value of the amount of charge moving from the DC power source 51 to the unit batteries 39-1 to 39-n. The integrated charge amount measuring device 64 includes, for example, an ammeter and a microcomputer, measures the hydrogen removal current at a predetermined sampling interval by the ammeter, and integrates the measured hydrogen removal current every sampling period by the microcomputer. The integrated charge amount is measured by sequentially integrating the integrated values.

  The accumulated charge amount measured by the accumulated charge amount measuring device 64 is input to the calculation unit of the controller 6.

  Second, as shown in FIG. 10, in the hydrogen removal step S102, instead of step S6 (FIG. 4) for monitoring the applied voltage in the first embodiment, step S14 for monitoring the accumulated charge amount is performed.

  Specifically, in step S4, the controller 6 controls the DC power source 51 to output a predetermined constant voltage lower than the upper limit voltage. On the other hand, as described above, when the hydrogen concentration in the oxidant gas path 18 becomes thinner with the passage of time, the hydrogen removal current decreases accordingly. Eventually, the hydrogen removal current converges to the current I as described above. This current I is a minute current compared to the initial hydrogen removal current. Accordingly, the accumulated charge amount substantially converges with a certain value (hereinafter referred to as a converged accumulated charge amount Q) as the hydrogen removal current converges to the current I. Therefore, the time at which the accumulated charge amount reaches the converged accumulated charge amount Q is the time point at which the hydrogen removal process ends.

  In the present embodiment, this converged accumulated charge amount Q is preliminarily flowed through the fuel gas flow paths 7, 17, 9 and nitrogen is flowed through the oxidant gas flow paths 11, 18, 13; An accumulated charge amount range ((Q−δQ) to (Q + δQ)) that is measured for each unit battery 39-1 to 39-n and allows a predetermined tolerance (error) δQ to the measured converged accumulated charge amount Q. Is stored in the storage unit of the controller 6 for each unit battery 39-1 to 39-n as an allowable range of the accumulated charge amount. Then, the controller 6 monitors whether or not the accumulated charge amount measured by the accumulated charge amount measuring device 64 is within an allowable range of the accumulated charge amount of the corresponding unit battery (step S14). When the integrated charge amount measured by the integrated charge amount measuring device 64 falls within the allowable range of this integrated charge amount (YES in step S14), the DC power supply 51 is turned off and the application of the DC voltage is stopped (step). S7). The other steps are the same as in the first embodiment.

  According to the third embodiment, the same effect as that of the first embodiment can be obtained.

  Note that the converged accumulated charge amount Q, which is the basis of the accumulated charge amount allowable range stored in the storage unit, is a previously measured physical property of the electrolyte (here, the polymer electrolyte membrane 31), the structure of the fuel cell 1, and the fuel cell system 101. You may obtain | require by calculation from the state at the time of a stop.

  Also, instead of storing the allowable accumulated charge amount range in the storage unit, the rate of change of the accumulated charge amount is calculated, and whether or not the voltage application is terminated depending on whether or not the calculated change rate becomes almost zero. You may make it determine. In this case, the physical property value of the electrolyte changes due to deterioration due to the operation of the fuel cell 1, the moisture content of the electrolyte, disturbances such as the outside air temperature, the outside air pressure, and the like, thereby preventing erroneous determination due to the change. it can.

(Embodiment 4)
FIG. 11 is a schematic diagram showing the configuration of the voltage applicator of the fuel cell system according to Embodiment 4 of the present invention. FIG. 12 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101 of the present embodiment.

  In the present embodiment, the hydrogen removal step is different from that in the first embodiment, and the other steps are the same as those in the first embodiment. Hereinafter, this difference will be described.

  As shown in FIG. 11, in the present embodiment, first, in the voltage applicator 5, the current detector 16 and the voltage detector 62 (FIG. 3) of the first embodiment are omitted. The fuel cell system 101 includes a timer 63. In the present embodiment, since it is not always necessary to change the applied voltage, in addition to the switching power supply, the direct-current power supply 51 is a physical battery such as a chemical battery such as a primary battery, a secondary battery, or a fuel cell, a solar battery, or a temperature difference battery. A battery, a capacitor, or the like can be used. Here, the timer 63 is constituted by a clock built in an arithmetic unit such as a microcomputer constituting the controller 6. The controller 6 is configured to appropriately acquire time information of the timer 63.

  Second, as shown in FIG. 12, in the hydrogen removal step S103, instead of step S6 (FIG. 4) for monitoring the applied voltage in the first embodiment, step S15 for measuring a predetermined time by the timer 63 is performed. The

  Specifically, in step S5, the controller 6 controls the DC power source 51 to output a predetermined constant voltage lower than the upper limit voltage. On the other hand, as described above, when the hydrogen concentration in the oxidant gas path 18 becomes thinner with the passage of time, the hydrogen removal current decreases accordingly. Eventually, the hydrogen removal current converges to the current I as described above. In other words, the hydrogen removal current converges on the current I within a certain time after the application of the DC voltage is started. Therefore, by appropriately selecting a period during which this voltage is applied (hereinafter referred to as a predetermined voltage application period), the end point of the predetermined voltage application period can be set as the end point of the hydrogen removal process.

  In the present embodiment, the predetermined voltage application period is obtained in advance by experiments, and the obtained predetermined voltage application period is stored in the storage unit of the controller 6. Note that the predetermined voltage application period may be obtained by calculation instead of experiment. Then, the controller 6 starts measuring the predetermined voltage application period by the timer 63 when the application of the DC voltage is started (step S5), and turns off the DC power source 51 when the predetermined voltage application period ends (step S15). Then, the application of the DC voltage is stopped (step S7). The other steps are the same as in the first embodiment.

  According to the fourth embodiment, the same effect as that of the first embodiment can be obtained.

(Embodiment 5)
In the first to fourth embodiments described above, the hydrogen removal step is performed during the start-up process, that is, after the start-up signal is output. In the fifth embodiment of the present invention, during the stop period (standby operation) Hydrogen removal step is performed.

  In this embodiment, the hardware configuration is exactly the same as in the first embodiment, and the control program related to the hydrogen removal step is different from that in the first embodiment. Hereinafter, this difference will be described.

  FIG. 13 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101 of the present embodiment.

  As shown in FIG. 13, in the present embodiment, when the stop process of the fuel cell system 101 is completed (step S1), the controller 6 determines whether the activation condition is satisfied (step S2).

  If the activation condition is satisfied (YES in step S2), an activation signal is output (step S3). Next, the sealing valves 8, 10, 12, and 14 are opened (step S9), and then supply of fuel gas and oxidant gas is started (step S10), and the fuel cell system 101 is shifted to a power generation operation (step S10). Steps S9-11).

  If the activation condition is not satisfied (NO in step S2), it is determined whether or not a hydrogen removal process is necessary (step S21). Here, criteria for determining whether or not this hydrogen removal treatment is necessary will be described.

  In the present embodiment, the hydrogen accumulation time period τ is calculated in advance based on the following equation (2), and it is determined whether or not a hydrogen removal process is necessary based on whether or not the hydrogen accumulation period τ has elapsed.

More specifically, after the oxygen in the internal oxidant gas path 18 (precisely, the oxidant gas sealing space 19) is consumed, the electrolyte (polymer electrolyte membrane 31) passes through the internal fuel gas path 17 and passes therethrough. The amount of hydrogen (in moles) present in the internal oxidant gas path 18 is
M = 2DAtΔP / δRT (2)
It becomes. Here, M is the number of moles (mol) of hydrogen present in the oxidant gas flow path, and t is the elapsed time (sec) from the point in time when oxygen is exhausted (when hydrogen accumulation starts). D, A, ΔP, δ, R, and T are as described for the expression (1).

  On the other hand, the amount of hydrogen that is allowed to be present in the internal oxidant gas path 18 from the viewpoint of safety (hereinafter sometimes referred to as the allowable hydrogen amount) is the material that constitutes the cathode electrode 72 when the hydrogen burns. This is an amount that generates an upper limit of heat that can be absorbed by the heat capacity. Therefore, the amount of hydrogen that generates the upper limit heat amount is substituted as M in equation (2), and this is solved for t until the allowable upper limit amount of hydrogen is accumulated in the internal oxidant gas path 18. Time tmax is calculated. Then, the hydrogen accumulation time τ is determined by multiplying the time tmax by a predetermined safety factor (a value not less than 0 and less than 1). The smaller the value of the safety factor, the better the safety, but the greater the number of hydrogen removal processes. The hydrogen accumulation time τ may be obtained by experiments or simulations. This hydrogen accumulation time τ actually varies and varies depending on the season, but is about 150 hours.

  The hydrogen accumulation time τ is stored in advance in the storage unit of the controller 6.

  When the elapsed time from the end of the previous hydrogen removal process (end of step S7 in FIG. 4) or the stop process of the fuel cell system 101 to the present time does not exceed the hydrogen accumulation product time τ, the controller 6 It is determined that the hydrogen removal process is not necessary (NO in step S21), and the process returns to step S2. The elapsed time from the completion of the stop process of the fuel cell system 101 to the present time includes the time during which oxygen in the internal oxidant gas path 18 is consumed, so the stop process of the fuel cell system 101 is completed. Determining whether or not a hydrogen removal process is necessary as a starting point is a safer determination than determining whether or not a hydrogen removing process is necessary starting from the end of the previous hydrogen removal process, and there is no problem.

  On the other hand, when the elapsed time from the end of the previous hydrogen removal process or the stop process of the fuel cell system 101 to the present time exceeds the hydrogen accumulation product time τ, the controller 6 determines that the hydrogen removal process is necessary. The determination is made (NO in step S21), the hydrogen removal step (step S100) of the first embodiment (FIG. 4) is performed, and then the process returns to step S2.

  According to the above control, the fuel cell system 101 is activated when the activation condition is satisfied (YES in step S2) at any timing after the fuel cell system 101 is stopped (steps S3 and S9). . Accordingly, if the activation condition is satisfied before it is determined that the hydrogen removal process is necessary, the activation is performed without performing the hydrogen removal step. However, when the fuel cell system 101 is stopped, hydrogen is not accumulated in the internal oxidant gas path 18, and after the stop, accumulation of hydrogen starts. Rather, it is preferable from the viewpoint of quickly starting the fuel cell system 101.

  On the other hand, if the activation condition is not satisfied and it is determined that the hydrogen removal process is necessary (NO in step S2, YES in step 21), a hydrogen removal process is performed (step S100). Furthermore, once the hydrogen removal process is performed and the start-up conditions are not satisfied, if it is determined that the hydrogen removal process is necessary (NO in step S2, YES in step 21), the hydrogen removal is performed again. A process is performed (step S100). Thereafter, this operation is repeated.

  According to this embodiment, the hydrogen removal process is performed using the stop time (standby operation) of the fuel cell system 101, and the start condition is satisfied whenever the fuel cell system 101 is stopped. Since it is activated, it can be activated quickly. In addition, after the hydrogen removal process is performed, if the hydrogen removal process becomes necessary again while waiting, this can be performed.

  Further, the upper limit amount of heat that can be absorbed by the heat capacity of the material constituting the cathode electrode 72 when the amount of hydrogen combusts the allowable amount of hydrogen accumulated in the internal oxidant gas path 18 during standby. Therefore, when the oxidant gas is supplied after the fuel cell system 101 is started, damage to the constituent material of the cathode electrode 72 caused by the accumulated hydrogen can be suppressed.

In the above description, the hydrogen removal step S100 of the first embodiment is performed. Alternatively, the hydrogen removal steps S101 to S103 of the second to fourth embodiments may be performed.
In the above description, whether or not the hydrogen removal process is necessary is determined based on whether or not a predetermined hydrogen accumulation time τ has elapsed. However, the amount of hydrogen accumulated in the internal oxidant gas path 18 is sensed or predicted. You may determine the necessity of a hydrogen removal process.

  For example, a hydrogen concentration sensor is provided in the oxidant gas path 18 and the hydrogen accumulation amount is calculated from the hydrogen concentration detected by the hydrogen concentration sensor. Depending on whether or not the hydrogen accumulation amount exceeds the allowable hydrogen amount described above. You may comprise so that the necessity of a hydrogen removal process may be determined.

  In addition, an analyzer such as gas chromatography is provided, a part of the gas in the internal oxidant gas path 18 is sampled, and quantitative analysis is performed by the analyzer to calculate the hydrogen accumulation amount. You may comprise so that the necessity of a hydrogen removal process may be determined by whether it exceeds the allowable hydrogen amount.

Further, the above equation (2) is stored in the storage unit of the controller 6, and the elapsed time from the end of the previous hydrogen removal step or the stop processing of the fuel cell system 101 to the present time is expressed as t in equation (2). It may be configured to calculate the hydrogen accumulation amount M by substituting and determine whether or not the hydrogen removal process is necessary based on whether or not the hydrogen accumulation amount M exceeds the above-described allowable hydrogen amount.
(Embodiment 6)
In the first to fourth embodiments described above, the hydrogen removal process is performed during the startup process, and in the fifth embodiment, the hydrogen removal process may not be performed. However, in the sixth embodiment of the present invention, the hydrogen removal process is stopped. During the period (during standby operation), the hydrogen removal process is always performed. The rest is the same as in the first embodiment.
In the fuel cell system 101 of the present embodiment, the standby time from the completion of the hydrogen removal process to the start of the supply of the oxidant gas to the internal oxidant gas flow path 18 of the fuel cell 1 is If the cathode electrode is not deteriorated even after the supply is started, the hydrogen removal process is executed during the standby operation even if it is not during the startup process.
Specifically, in the present embodiment, for example, when the activation time set by the input through the user input device is reached, or when the activation time preset by the learning operation control is reached, etc. In addition, the activation condition is that the time (activation time) to be activated is fixed and the current time is the activation time. Then, when the controller 6 detects that the current time is within a predetermined time until the activation time, the hydrogen removal step is performed.

This predetermined time is defined as an upper limit time during which the cathode electrode does not deteriorate even when the supply of the oxidizing gas is started. More specifically, the predetermined time is equal to the hydrogen accumulation time τ of the fifth embodiment. .
That is, as described in the fifth embodiment, the amount of hydrogen allowed to be present in the internal oxidant gas path 18 from the safety aspect is the same as that of the material constituting the cathode electrode 72 when the hydrogen burns. It is an amount that generates an upper limit heat quantity that can be absorbed by the heat capacity. Using the amount of hydrogen that generates the upper limit heat amount and the equation (2), the time tmax until an allowable upper limit amount of hydrogen is accumulated in the internal oxidant gas path 18 is calculated. The time tmax is then multiplied by a predetermined safety factor to determine the hydrogen accumulation time τ. The predetermined time, which is a time equal to the hydrogen accumulation time τ, is stored in advance in the storage unit of the controller 6.
FIG. 14 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system 101 of the present embodiment. As shown in FIG. 14, in the present embodiment, when the fuel cell system 101 is stopped (step S1), the controller 6 waits for the time from the current time to the activation time to be within the predetermined time. (Step S31). When the time from the current time to the activation time is within the predetermined time (YES in step S31), a hydrogen removal step is performed (step S100).
Next, it waits for the current time to become the activation time (step S32). This step S32 corresponds to step S2 for determining whether or not the activation condition is satisfied in the first to fifth embodiments. When the current time becomes the start time, the controller 6 outputs a start signal (step S3), and proceeds to the power generation operation through the start process (steps S9 to S11).
In this embodiment, the predetermined time (upper limit time) is usually longer than the startup time of the fuel cell system 101. Therefore, even if the hydrogen removal process is executed during the standby operation, the first to thirteenth embodiments are performed. The same effect as 4 can be obtained.

(Embodiment 7)
The present embodiment is a modification of the sixth embodiment. That is, in the fuel cell system 101 of the present embodiment, the activation condition is that the current time is the activation time, and the first operation mode in which the timing at which the activation condition is satisfied can be predicted in advance and the load power is predetermined. The activation condition is that the threshold is exceeded or the activation request is input by the user, and the second operation mode in which the timing when the activation condition is satisfied cannot be predicted in advance. The hydrogen removal process in the first operation mode is the same as in the sixth embodiment, and the hydrogen removal process in the second operation mode is the same as in the fifth embodiment. Therefore, here, a case will be described in which the operation mode is changed to the second operation mode after the hydrogen removal process is executed in the first operation mode.
FIG. 15 is a flowchart showing a control operation in the case where the operation mode is changed before and after the hydrogen removal step in the fuel cell system 101 of the present embodiment. As shown in FIG. 15, in the present embodiment, when the fuel cell system 101 is stopped (step S1), the controller 6 determines that the time from the current time to the activation time is within the first predetermined time. Waiting (step S31), and when the time from the current time to the activation time is within the first predetermined time (YES in step S31), a hydrogen removal step is performed (step S100). The first predetermined time is a time equal to the hydrogen accumulation time τ of the fifth embodiment.
Here, after that, the operation mode is changed from the first operation mode to the second operation mode (step S33).

  Next, the controller 6 determines whether or not the start condition in the second operation mode is satisfied within the predetermined time after the completion of the hydrogen removal step S100 (step S34). This step S34 corresponds to step S2 for determining whether or not the activation condition is satisfied in the first to fifth embodiments. If the activation condition is not satisfied within the second predetermined time (NO in step S34), the hydrogen removal step S100 'is performed. This hydrogen removal process step S100 'has exactly the same contents as the hydrogen removal process step S100. That is, the hydrogen removal process is performed again. Thereafter, the process returns to step S34. Then, this operation is repeated unless the activation condition is satisfied within the second predetermined time. The second predetermined time is a time equal to the hydrogen accumulation time τ of the fifth embodiment.

  On the other hand, in step S34, when the start condition is satisfied within the second predetermined time (YES in step S34), the controller 6 outputs a start signal (step S3), and starts the power generation operation through the start process. (Steps S9 to S11).

  According to the present embodiment, in the fuel cell system 101, even when the operation mode is changed to an operation mode in which the timing at which the start condition is satisfied cannot be predicted in advance after the hydrogen removal process is performed, the hydrogen is appropriately A removal process can be performed.

(Embodiment 8)
FIG. 16 is a schematic diagram showing the configuration of the voltage applicator of the fuel cell system according to Embodiment 8 of the present invention.

  As shown in FIG. 16, in the present embodiment, in the connection switch 52, a switching unit 57 is provided for each unit battery unit composed of a plurality (here, 2) unit batteries. The first terminal 63 of the switching unit 57 is connected to the cathode separator 36B of the even-numbered unit cells 39-2, 39-4,. Then, all the unit battery units are sequentially connected to the DC power source 51 by the connection switcher 52, and the hydrogen removal step (here, the hydrogen removal step S103 of the fourth embodiment) is performed. The other points are the same as in the fourth embodiment.

  The number of unit batteries belonging to the unit battery unit is not limited to 2, and may be 3 or 4. As the number of unit batteries belonging to the unit battery unit increases, the configuration for performing the hydrogen removal process is simplified, and the time required for the hydrogen removal process is shortened. However, when the number of unit batteries belonging to the unit battery unit is increased, there is a high risk of causing deterioration due to the hydrogen removal process as described in the first embodiment. Therefore, it is necessary to control the applied voltage with high accuracy.

  In the eighth embodiment, a DC voltage may be applied collectively to all the unit batteries of the cell stack. However, there is a higher risk of causing deterioration due to the hydrogen removal treatment as described in the first embodiment.

  In the present invention, the “separator” includes a “field plate” used in an in-vehicle fuel cell or the like. Therefore, in the first to sixth embodiments described above, the anode separator 36A and the cathode separator 36B may be configured by “field plates”.

  In Embodiments 6 and 7, the hydrogen removal step S100 of Embodiment 1 is performed, but it goes without saying that the hydrogen removal steps S101 to S103 of Embodiments 2 to 4 may be performed instead. Yes.

  In the first to eighth embodiments described above, an example in which the present invention is applied to a fuel cell that uses a gas containing hydrogen as a fuel gas has been described. For example, a direct methanol fuel cell that uses methanol as a direct fuel ( The present invention can also be applied to a fuel cell using a fuel that does not contain hydrogen, such as DMFC.

  In the first to eighth embodiments described above, the sealing valves 8, 10, 12, and 14 are provided in the fuel gas supply path 7, the fuel gas discharge path 9, the oxidant gas supply path 11, and the oxidant gas discharge path 13, respectively. Was provided. These sealing valves are preferably in consideration of safety. However, in the essence of the present invention, only the region in which the hydrogen permeated from the fuel gas flow path diffuses in the oxidant gas flow path is the range in which the present invention operates. It is not always necessary.

  The fuel cell system of the present invention is useful as a power source mounted on a moving and transportation machine such as an automobile or a motorcycle, a stationary cogeneration system, or the like. It can also be applied as a power supply system for mobile devices.

1 is a block diagram showing a schematic configuration of a fuel cell system according to Embodiment 1 of the present invention. FIG. FIG. 2 is a partially exploded view showing the configuration of the fuel cell 1 of FIG. 1. It is a schematic diagram which shows the structure of the voltage applicator 5 of FIG. 2 is a flowchart showing a control operation before and after a hydrogen removal step of the fuel cell system of FIG. 1. It is a schematic diagram which shows operation | movement of the voltage applicator of FIG. It is a schematic diagram which shows operation | movement of the voltage applicator of FIG. It is a schematic diagram which shows the structure of the voltage applicator of the fuel cell system which concerns on Embodiment 2 of this invention. It is a flowchart which shows the control operation before and behind the hydrogen removal process of the fuel cell system of Embodiment 2 of this invention. It is a schematic diagram which shows the structure of the voltage applicator of the fuel cell system which concerns on Embodiment 3 of this invention. FIG. 10 is a flowchart showing the control operation before and after the hydrogen removal step of the fuel cell system of the present embodiment. It is a flowchart which shows the control operation before and behind the hydrogen removal process of the fuel cell system of Embodiment 3 of this invention. It is a schematic diagram which shows the structure of the voltage applicator of the fuel cell system which concerns on Embodiment 4 of this invention. It is a flowchart which shows the control operation before and behind the hydrogen removal process of the fuel cell system of Embodiment 4 of this invention. It is a flowchart which shows the control operation before and behind the hydrogen removal process of the fuel cell system of Embodiment 5 of this invention. It is a flowchart which shows the control operation before and behind the hydrogen removal process of the fuel cell system of Embodiment 6 of this invention. It is a flowchart which shows the control action when the operation mode is changed before and after the hydrogen removal step in the fuel cell system according to the seventh embodiment of the present invention. These are the schematic diagrams which show the structure of the voltage applicator of the fuel cell system which concerns on Embodiment 8 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Fuel gas supply device 3 Oxidant gas supply device 4 Output controller 5 Voltage applicator 6 Controller 7 Fuel gas supply channel 8 First sealing valve 9 Fuel gas discharge channel 10 Second sealing valve 11 Oxidant Gas supply path 12 Third sealing valve 14 Fourth sealing valve 15 Load detector 17 Internal fuel gas path 18 Internal oxidant gas path 19 Oxidant gas sealing space 21 Load 31 Polymer electrolyte membrane 32A Anode catalyst layer 32B Cathode Catalyst layer 33 Gas diffusion layer 34 MEA
35 Gasket 36A Anode separator 36B Cathode separator 37A Fuel gas flow path 37B Oxidant gas flow path 38A, 38B Cooling water flow path 39 Unit battery 40A, 40B Current collecting plate 41 Insulating plate 42 End plate 43 Through hole 51 DC power supply 52 Connection switcher 53 1st terminal 54 2nd terminal 55 3rd terminal 56 Contact 57 Switching unit 61 Current detector 62 Voltage detector 63 Timer 64 Integrated charge measuring device 71 Anode electrode 72 Cathode electrode 101 Fuel cell system

Claims (9)

An electrolyte layer, an anode electrode and a cathode electrode respectively provided on both main surfaces of the electrolyte layer, and a fuel gas flow for supplying a fuel gas containing hydrogen to the anode electrode, one of which is disposed across the electrolyte layer A fuel cell comprising a pair of conductive separators having a channel and an oxidant gas flow path for supplying the oxidant gas to the cathode electrode on the other side;
A DC voltage applicator for applying a DC voltage having a polarity such that the cathode electrode is positive with respect to the anode electrode between the pair of separators;
With controller,
The said controller performs the application of the said DC voltage by the said voltage applicator by the time it starts supply of oxidant gas to the said oxidant gas flow path.   The controller waits until the supply of the oxidant gas is started after the application of the DC voltage is finished, and the cathode electrode does not deteriorate even when the supply of the oxidant gas is started. The fuel cell system according to claim 1, wherein the application of the DC voltage is performed as described above. The controller starts supplying the oxidant gas for applying the DC voltage between the start of the start-up process of the fuel cell system and the start of the supply of the oxidant gas. The fuel cell system described. The controller, after executing the application of the DC voltage in a period from the completion of the stop process of the fuel cell system to the start of the next start process, when the start condition is not satisfied within a predetermined time, The fuel cell system according to claim 2, wherein the fuel cell system is configured to execute the application of the DC voltage again. The fuel cell system according to claim 4, wherein the predetermined time is an upper limit time during which the cathode electrode does not deteriorate even if the supply of the oxidizing gas is started.   The controller starts supplying the oxidant gas when the start condition is satisfied within the predetermined time after the stop process is completed, and within the predetermined time after the stop process is completed. The fuel cell system according to claim 4, wherein the direct current voltage is applied when the activation condition is not satisfied. The fuel cell comprises a cell stack in which two or more unit cells having the electrolyte layer, the anode electrode and the cathode electrode, and the pair of separators are laminated,
2. The fuel cell system according to claim 1, wherein the controller is configured to sequentially apply the DC voltage for each unit cell unit including one or more unit cells.   The controller sets the upper limit of the DC voltage to be applied to a potential obtained by adding a diffusion overvoltage to a redox potential of a material having the lowest potential obtained by adding a diffusion overvoltage to a redox potential among materials constituting the cathode electrode. The fuel cell system according to claim 1, wherein the fuel cell system is controlled to be a smaller value.   2. The controller according to claim 1, wherein the controller controls an upper limit value of the DC voltage to be applied to be a value smaller than a redox potential of a material having a lowest redox potential among materials constituting the cathode electrode. The fuel cell system described.

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