JP2008130403A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a load of a pump or the like in the case an outside air temperature exceeds a given temperature, in a fuel cell system. <P>SOLUTION: The fuel cell system 10, provided with an air compressor 54 or the like sending pressurized gas to a fuel cell 12, and a gas exhaust piping 50 connected to the fuel cell 12 for conveying the pressurized gas exhausted by the air compressor or the like to given components, and preventing the given components from freezing by heating them with the exhausted gas, includes an outside air temperature sensor 60 for measuring an outside air temperature. The gas exhaust piping 50 has between the fuel cell 12 and the given components a switching valve 62 or the like for releasing the exhaust gas into open air, so that, if the outside air temperature exceeds the given temperature, the exhausted gas is released into open air with the switching valve 62 or the like to suppress a load of the air compressor 54 or the like. The gas is preferred to be oxidant gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and in particular, a pumping means for pumping a gas to the fuel cell, and a gas transport path connected to the fuel cell and transporting a gas pumped and exhausted by the pumping means to a predetermined part. The present invention relates to a fuel cell system that is provided and heats predetermined parts with exhausted gas to prevent freezing.

  In recent years, fuel cells have attracted attention as batteries having high efficiency and excellent environmental characteristics. 2. Description of the Related Art In general, a fuel cell generates electric energy by electrochemically reacting hydrogen, which is a fuel gas, with oxygen in the air, which is an oxidant gas. As a result of the electrochemical reaction between hydrogen and oxygen, water is generated.

  Types of fuel cells include phosphoric acid type, molten carbonate type, solid electrolyte type, alkali type, and solid polymer type. Among these, a fuel cell system using a polymer electrolyte fuel cell that has advantages such as startup at normal temperature and fast startup time has attracted attention. Such a fuel cell system is used, for example, as a power source for vehicles, particularly electric vehicles.

  A polymer electrolyte fuel cell generally operates at 60 to 100 ° C. Therefore, effective use of the heat of fuel gas and oxidant gas exhausted from the fuel cell is performed. For example, Patent Document 1 includes a double-pipe air preheater and a fuel gas preheater in a fuel cell stack, and low-temperature air before power generation is placed on one side of the double pipe of the air preheater. , One of the high-temperature air and fuel gas that has been generated is supplied to the other side, the fuel gas before power generation is supplied to one side of the double pipe of the fuel gas preheater, and the other of the generated air and fuel gas is supplied to the other side. It is shown that the heat of the air and fuel gas already generated in the stack can be effectively used.

Japanese Patent Laid-Open No. 6-163067

  By the way, when the fuel cell system is operated in a low temperature environment such as outdoors in a cold region, there is a possibility that predetermined parts such as valves and pipes in the fuel cell system are frozen. Therefore, freezing is prevented by heating predetermined parts such as valves and pipes with fuel gas or oxidant gas exhausted from the fuel cell. Therefore, the exhausted fuel gas and oxidant gas are conveyed to predetermined parts by piping or the like.

  However, even when the valve or piping in the fuel cell system is not likely to be clogged in a low-temperature environment, the exhausted oxidant gas or fuel gas is transported to the specified parts through the piping. As a result, the load on the pressure feeding means such as the pressure increases, and the efficiency of the fuel cell system may decrease.

  Therefore, an object of the present invention is to provide a fuel cell system that suppresses the load of the pressure feeding means when the outside air temperature is equal to or higher than a predetermined temperature.

  A fuel cell system according to the present invention includes: a pressure feeding unit that pumps a gas to the fuel cell; and a gas transport path that is connected to the fuel cell and transports a gas pumped and exhausted by the pressure feeding unit to a predetermined part. A fuel cell system that heats parts with exhausted gas to prevent freezing, and includes temperature measuring means for measuring the outside air temperature, and the gas transport path is exhausted between the fuel cell and a predetermined part. And switching means for releasing the gas to the atmosphere. When the outside air temperature is equal to or higher than a predetermined temperature, the switching means opens the exhausted gas to the atmosphere.

  In the fuel cell system according to the present invention, the gas is an oxidant gas.

  As described above, according to the fuel cell system of the present invention, when the outside air temperature is equal to or higher than the predetermined temperature, the gas exhausted from the fuel cell can be released to the atmosphere without being transported to the predetermined parts. The load of the pressure feeding means can be suppressed.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of the fuel cell system 10. The fuel cell system 10 includes a fuel cell 12, a fuel gas supply device 14, an oxidant gas supply device 16, and a control unit 18.

  The fuel cell 12 has a function of generating electric power by an electrochemical reaction between hydrogen as a fuel gas and oxygen as an oxidant gas. The fuel cell 12, for example, a polymer electrolyte fuel cell 12 includes a stack in which a plurality of single cells are stacked and assembled. Here, the single cell is assembled by laminating a separator on a membrane electrode assembly in which a catalyst layer is laminated on each side of an electrolyte membrane, and a gas diffusion layer is laminated on each catalyst layer. And an electric current can be taken out from a current collecting plate by providing a current collecting plate on both sides of such a stack.

  The electrolyte membrane has a function of moving hydrogen ions generated on the anode side to the cathode side. As the material of the electrolyte membrane, a chemically stable fluorine-based resin, for example, an ion exchange membrane of perfluorocarbon sulfonic acid is used. As an ion exchange membrane of perfluorocarbon sulfonic acid, a Nafion membrane (registered trademark of DuPont) or the like can be used.

  The catalyst layer has a function of promoting the oxidation reaction of hydrogen on the anode side and the reduction reaction of oxygen on the cathode side. The catalyst layer includes a catalyst and a catalyst carrier. In order to increase the electrode area to be reacted, the catalyst is generally used in the form of particles and attached to the catalyst support. As the catalyst, platinum, which is a platinum group element having a small activation overvoltage, is used for the oxidation reaction of hydrogen and the reduction reaction of oxygen. As the catalyst carrier, a carbon material such as carbon black is used.

  The gas diffusion layer has a function of diffusing hydrogen as a fuel or oxygen as an oxidant into the catalyst layer, a function of moving electrons, and the like. For the gas diffusion layer, carbon fiber woven fabric, carbon paper, or the like, which is a conductive material, can be used. And a membrane electrode assembly can be manufactured by laminating | stacking an electrolyte membrane, a catalyst layer, and a gas diffusion layer, and heat-pressing.

  The separator is laminated on the gas diffusion layer of the membrane electrode assembly, and has a function of separating hydrogen, which is a fuel gas, and air, which is an oxidant, in an adjacent single cell. The separator has a function of electrically connecting one unit cell and the other unit cell. The separator can be formed, for example, by pressing a titanium sheet, a stainless steel sheet, or the like.

  The cooling system of the fuel cell system 10 includes a cooling pipe 20 that circulates the cooling water, a temperature sensor (not shown) that detects the temperature of the cooling water discharged from the fuel cell 12, and radiates the heat of the cooling water to the outside. A radiator 22, a cooling water amount adjusting valve (not shown) that adjusts the amount of cooling water flowing into the radiator 22, a cooling water pump 24 that pressurizes and circulates the cooling water, and the like are provided.

  When cooling the fuel cell 12, the cooling water amount adjusting valve (not shown) increases the amount of cooling water flowing into the radiator 22 based on the control of the control unit 18, and uses the cooling water cooled by the radiator 22 as fuel. The battery 12 is supplied. On the other hand, when the fuel cell 12 is warmed up, the cooling water amount adjusting valve (not shown) reduces the amount of cooling water flowing into the radiator 22 based on the control of the control unit 18 and suppresses cooling by the radiator 22. The cooled cooling water is supplied to the fuel cell 12.

  The fuel gas supply system of the fuel cell system 10 circulates the fuel gas supply pipe 26 for supplying fuel gas to the anode of the fuel cell 12 and the fuel gas exhausted from the anode of the fuel cell 12 to the fuel gas supply pipe 26. And a fuel gas circulation pipe 28 for the purpose.

  The fuel gas supply pipe 26 includes a shutoff valve 30 that controls supply / stop of the fuel gas from the fuel gas supply device 14, a pressure sensor 32 that detects the pressure of the fuel gas, and a fuel gas pressure that adjusts the pressure of the fuel gas. An adjustment valve 34, a shutoff valve (not shown) for opening and closing the fuel gas supply port of the fuel cell 12, and the like are installed. The fuel gas supply device 14 includes, for example, a high-pressure hydrogen tank, a hydrogen storage alloy, a reformer, and the like.

  The fuel gas circulation pipe 28 includes a shutoff valve (not shown) for discharging the fuel gas, a pressure sensor 35 for detecting the pressure of the fuel gas, a circulation pump 36 driven by a motor, and a fuel gas in the fuel gas supply pipe 26. A check valve 38 and the like for preventing backflow to the fuel gas circulation pipe 28 side are installed. Based on the control of the control unit 18, the circulation pump 36 compresses the fuel gas that has received a pressure loss when passing through the anode of the fuel cell 12 to increase the pressure to an appropriate gas pressure, and returns the fuel gas to the fuel gas supply pipe 26. Let The fuel gas merges with the fuel gas supplied from the fuel gas supply device 14 through the fuel gas supply pipe 26 and is supplied to the fuel cell 12 for reuse.

  The fuel gas circulation pipe 28 is branched from a fuel gas exhaust pipe 40 for exhausting the fuel gas exhausted from the fuel gas circulation system to the outside of the vehicle via a diluter (for example, a hydrogen concentration reducing device) (not shown). An exhaust valve 41 is installed in the fuel gas exhaust pipe 40. By opening and closing the exhaust valve 41, the fuel gas with increased impurity concentration is exhausted to the outside by repeating the circulation in the fuel cell 12, and a new fuel is produced. Gas can be introduced to prevent the voltage of the fuel cell 12 from decreasing.

  The fuel gas exhaust pipe 40 can be formed into a double pipe 42 at a portion that is easily frozen in a low temperature environment. The double pipe 42 includes an inner pipe 44 and an outer pipe 46, and an oxidant gas exhaust pipe 50 to be described later is connected to the outer pipe 46 of the double pipe 42. By flowing the exhausted fuel gas through the inner tube 44 and flowing the oxidant gas exhausted from the fuel cell 12 between the inner tube 44 and the outer tube 46, the inner tube 44 is exhausted with the exhausted oxidant gas. Can be heated. Thereby, freezing of the fuel gas exhaust pipe 40 can be suppressed. Of course, depending on other conditions, the structure for heating the fuel gas exhaust pipe 40 with exhausted oxidant gas is not limited to a double pipe.

  The oxidant gas supply system of the fuel cell system 10 includes an oxidant gas supply pipe 48 having a function of supplying an oxidant gas to the cathode of the fuel cell 12 and an oxidant gas exhausted from the cathode of the fuel cell 12. An oxidant gas exhaust pipe 50 having a function of conveying to the fuel gas exhaust pipe 40 and an oxidant gas supply device 16 for supplying compressed air as an oxidant gas to the oxidant gas supply pipe 48 are provided.

  The oxidant gas supply device 16 includes an air filter 52 that removes dust and the like contained in the air taken in from the atmosphere, a pump or air compressor 54 that is driven by a motor and functions as a pressure feeding unit that pumps the oxidant gas. It is comprised including. The oxidant gas supply pipe 48 or the oxidant gas exhaust pipe 50 is provided with a pressure sensor 45 for detecting the pressure of the oxidant gas.

  The humidifier 56 is disposed between the oxidant gas supply device 16 and the fuel cell 12 and takes in from the atmosphere the oxidant gas that has become highly moistened by the generated water generated by the electrochemical reaction of the fuel cell 12. It has a function of exchanging moisture with a low-humidity oxidant gas. The humidifier 56 can humidify the low-humidity oxidant gas taken from the atmosphere.

  The oxidant gas pressure regulating valve 58 is disposed in the oxidant gas supply pipe 48 or the oxidant gas exhaust pipe 50 and has a function of adjusting the oxidant gas pressure at the cathode. As the oxidant gas pressure regulating valve 58, an electromagnetic valve or the like that is generally used for regulating a gas such as air can be used.

  The oxidant gas exhaust pipe 50 is connected to the outer pipe 46 of the double pipe 42 in the fuel gas exhaust pipe 40. The oxidant gas exhausted from the fuel cell 12 flows between the outer tube 46 and the inner tube 44 of the double tube 42, heats the inner tube 44, and then is exhausted outside the vehicle.

  The outside air temperature sensor 60 has a function as temperature measuring means for measuring the outside air temperature, and is provided in the fuel cell system 10. Outside air temperature data measured by the outside air temperature sensor 60 is sent to the control unit 18. A general thermometer, a thermocouple, etc. can be used for the outside temperature sensor 60.

  The switching valve 62 is provided in the oxidant gas exhaust pipe 50 and has a function as switching means for releasing the exhausted oxidant gas to the atmosphere. The switching valve 62 is provided between the fuel cell 12 and the fuel gas exhaust pipe 40. When the outside air temperature is equal to or higher than the predetermined temperature, the fuel gas exhaust pipe 40 is less likely to freeze. Therefore, the exhaust gas is not transported to the fuel gas exhaust pipe 40 and the fuel cell 12 and the fuel gas exhaust are not transported. It switches with piping 40 with the switching valve 62, and air-releases. As a result, the route for transporting the exhausted oxidant gas is shortened, so that the load on the pump or the air compressor 54 or the like can be suppressed. As the switching valve 62, generally used three-way valve or the like can be used.

  The control unit 18 is configured as a microcomputer including a CPU, a RAM, and a ROM therein, and controls the operation of each unit of the fuel cell system 10 according to a program stored in the ROM. The control unit 18 receives sensor signals from the temperature sensor and pressure sensor arranged in each pipe, and drives each motor in accordance with the battery operation state (for example, power load) to circulate the pump 36, the air compressor 54, and the like. And the opening / closing control of various valves or the adjustment of the valve opening. The control unit 18 is connected to each pump, each sensor such as the outside air temperature sensor 60, and each valve such as the switching valve 62 by an electric cable (not shown).

  Next, the operation of the fuel cell system 10 having the above configuration will be described. FIG. 2 is a diagram illustrating the operation of the fuel cell system 10, FIG. 2 (a) is a diagram illustrating a case where the outside air temperature is lower than a predetermined temperature, and FIG. 2 (b) is a diagram illustrating the outside air temperature being equal to or higher than the predetermined temperature. It is a figure which shows the case of. In addition, the flow of the oxidant gas exhausted is indicated by an arrow X, and the flow of the exhausted fuel gas is indicated by an arrow Y.

  First, the outside temperature data measured by the outside temperature sensor 60 is sent to the control unit 18. The control unit 18 compares the outside air temperature with the set predetermined temperature. When the outside air temperature is lower than the predetermined temperature, the control unit 18 causes the oxidant gas exhausted from the fuel cell 12 to reach the fuel gas exhaust pipe 40 through the oxidant gas exhaust pipe 50 as shown in FIG. The switching valve 62 is operated so as to be conveyed. The exhausted oxidant gas flows between the outer tube 46 and the inner tube 44 of the double tube 42 and heats the inner tube 44 through which the exhausted fuel gas flows by heat exchange. And the freezing of the fuel gas exhaust pipe 40 can be suppressed by heating the inner pipe 44 of the fuel gas exhaust pipe 40.

  When the outside air temperature measured by the outside air temperature sensor 60 is equal to or higher than a predetermined temperature, the control unit 18 switches the switching valve 62 and oxidizer exhausted from the fuel cell 12 as shown in FIG. Release gas to atmosphere. As a result, the distance for transporting the exhausted oxidant gas is shortened, so that the load on the pump, the air compressor 54 and the like can be reduced.

  According to the above configuration, when the outside air temperature is equal to or higher than the predetermined temperature, the oxidant gas exhausted from the fuel cell is switched to the atmosphere by the switching valve provided between the fuel cell 12 and the fuel gas exhaust pipe. By opening, the path for transporting the exhausted oxidant gas is shortened, and the load on the pump, the air compressor, etc. can be reduced. And since the path | route which conveys the exhausted oxidant gas is shortened, pressure loss can reduce and the efficiency of a fuel cell system can be improved.

  Next, another embodiment according to the present invention will be described in detail with reference to the drawings. FIG. 3 is a diagram showing the configuration of the fuel cell system 70. In addition, the same code | symbol is attached | subjected to the same element and detailed description is abbreviate | omitted. The fuel cell system 70 includes a fuel cell 12, a fuel gas supply device 14, an oxidant gas supply device 16, and a control unit 18.

  The oxidant gas exhaust pipes 72 a and 72 b are provided from the fuel cell 12 to the fuel gas pressure adjustment valve 34, and the oxidant gas exhausted from the fuel cell 12 is conveyed to the fuel gas pressure adjustment valve 34. The fuel gas pressure regulating valve 34 is heated by the conveyed oxidant gas, thereby suppressing freezing.

  The damper 74 is provided in the oxidant gas exhaust pipes 72a and 72b, and has a function as switching means for releasing the exhausted oxidant gas to the atmosphere. The damper 74 is provided between the fuel cell 12 and the fuel gas pressure regulating valve 34. The damper 74 has a rotation shaft 78 at a substantially central portion of the blade 76, and the oxidant gas exhausted can be released to the atmosphere by rotating the blade 76 with the rotation shaft 78. When the outside air temperature is equal to or higher than the predetermined temperature, the fuel gas pressure adjustment valve 34 is less likely to freeze, so the exhausted oxidant gas is not transported to the fuel gas pressure adjustment valve 34, and the fuel cell 12. And the fuel gas pressure regulating valve 34 are opened to the atmosphere. As a result, the route for transporting the exhausted oxidant gas is shortened, so that the load on the pump or the air compressor 54 or the like can be suppressed. In general, the damper 74 that is used when adjusting the amount of gas conveyed by a duct or the like can be used as the damper 74. The opening / closing of the damper 74 is controlled by the control unit 18.

  Next, the operation of the fuel cell system 70 having the above configuration will be described. FIG. 4 is a diagram showing the operation of the fuel cell system 70, FIG. 4 (a) is a diagram showing a case where the outside air temperature is lower than a predetermined temperature, and FIG. 4 (b) is a diagram where the outside air temperature is equal to or higher than the predetermined temperature. It is a figure which shows the case of. The flow of the exhausted oxidant gas is indicated by an arrow Z.

  First, the outside temperature data measured by the outside temperature sensor 60 is sent to the control unit 18. The control unit 18 compares the outside air temperature with the set predetermined temperature. When the outside air temperature is lower than the predetermined temperature, the control unit 18 causes the oxidant gas exhausted from the fuel cell 12 to flow through the oxidant gas exhaust pipes 72a and 72b as shown in FIG. 4A. The damper 74 is closed so as to be conveyed to the regulating valve 34. Then, the conveyed oxidant gas is sprayed on, for example, the fuel gas pressure adjustment valve 34, and the fuel gas pressure adjustment valve 34 is heated. Accordingly, freezing of the fuel gas pressure regulating valve 34 is suppressed.

  When the outside air temperature measured by the outside air temperature sensor 60 is equal to or higher than a predetermined temperature, the control unit 18 converts the oxidant gas exhausted from the fuel cell 12 into the fuel gas pressure as shown in FIG. The damper 74 is opened to release it to the atmosphere before being conveyed to the regulating valve 34. As a result, the distance over which the exhausted oxidant gas is conveyed is shortened, so that the load on the pump, the air compressor 54, and the like can be reduced.

  According to the above configuration, when the outside air temperature is equal to or higher than the predetermined temperature, the oxidant gas exhausted from the fuel cell is switched to the atmosphere by the damper provided between the fuel cell and the fuel gas pressure regulating valve. By opening, the path for transporting the exhausted oxidant gas is shortened, and the load on the pump, the air compressor, etc. can be reduced. And since the path | route which conveys the exhausted oxidant gas is shortened, pressure loss can reduce and the efficiency of a fuel cell system can be improved.

In embodiment of this invention, it is a figure which shows the structure of a fuel cell system. In embodiment of this invention, it is a figure which shows operation | movement of a fuel cell system. In other embodiment of this invention, it is a figure which shows the structure of a fuel cell system. In other embodiment of this invention, it is a figure which shows operation | movement of a fuel cell system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 70 Fuel cell system, 12 Fuel cell, 14 Fuel gas supply apparatus, 16 Oxidant gas supply apparatus, 18 Control part, 20 Cooling piping, 22 Radiator, 24 Cooling water pump, 26 Fuel gas supply piping, 28 Fuel gas circulation Pipe, 30 Shutoff valve, 32, 35, 45 Pressure sensor, 34 Fuel gas pressure regulating valve, 36 Circulation pump, 38 Check valve, 40 Fuel gas exhaust pipe, 41 Exhaust valve, 42 Double pipe, 44 Inner pipe, 46 Outer pipe, 48 Oxidant gas supply pipe, 50, 72a, 72b Oxidant gas exhaust pipe, 52 Air filter, 54 Air compressor, 56 Humidifier, 58 Oxidant gas pressure regulating valve, 60 Outside air temperature sensor, 62 switching Valve, 74 damper, 76 blades, 78 axis of rotation.

Claims (2)

A pumping means for pumping gas to the fuel cell;
A gas transport path connected to the fuel cell and transporting the gas pumped and exhausted by the pumping means to a predetermined part;
With
A fuel cell system that heats predetermined parts with exhausted gas to prevent freezing,
Including temperature measuring means for measuring the outside air temperature,
The gas conveyance path has a switching means for releasing the exhausted gas to the atmosphere between the fuel cell and the predetermined part,
A fuel cell system characterized in that when the outside air temperature is equal to or higher than a predetermined temperature, the switching means opens the exhausted gas to the atmosphere. The fuel cell system according to claim 1,
The fuel cell system, wherein the gas is an oxidant gas.

Images