JP4698965B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system, and more particularly to a system in which moisture remaining in a fuel cell is purged when the operation of the fuel cell is stopped.

A fuel cell including one or more membrane electrode structures (so-called MEAs) formed by joining electrodes on both surfaces of a solid polymer electrolyte membrane is provided with each electrode (anode electrode) of each membrane electrode structure in order to perform its power generation operation. Anode gas and cathode gas as reaction gases are supplied to the surfaces of the cathode electrode and the cathode electrode, respectively. Usually, hydrogen gas and air (specifically, air containing oxygen) are used as the anode gas and the cathode gas, respectively. The fuel cell generates power while generating H ₂ O (water or water vapor) by reacting the supplied hydrogen and air oxygen with each membrane electrode structure. Further, since the fuel cell generates heat during its power generation operation, a cooling device (heat radiator) such as a radiator and a fuel cell (specifically, a fuel cell) are used to prevent the fuel cell from becoming excessively hot due to its self-heating. The refrigerant is supplied to the fuel cell while the refrigerant is circulated through the refrigerant circulation passage provided so as to circulate via the refrigerant passage formed in the inside.

In this type of fuel cell, a part of H ₂ O generated during the operation of the fuel cell is condensed while remaining in the fuel cell after the operation of the fuel cell is stopped. In particular, when the amount of H ₂ O (hereinafter referred to as residual moisture) remaining in the fuel cell and dew condensation is relatively large, when the fuel cell is restarted, the residual moisture is contained in the fuel cell. Thus, the smooth flow of the reaction gas in the reaction gas flow path is hindered, or the diffusion of hydrogen and oxygen in the membrane electrode structure is hindered, so that the power generation capability at the start of the fuel cell is easily impaired. In particular, when the residual moisture freezes in a low temperature environment, the above-described disadvantage becomes remarkable, and the frozen residual moisture may damage the membrane electrode structure and the like.

  For this reason, for example, Japanese Patent Publication No. 2003-510786 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2002-246053 (Patent Document 2) disclose techniques for scavenging (purging) the fuel cell when the fuel cell is stopped. Proposed. In Patent Document 1, by supplying a purge fluid such as dry nitrogen gas or a reaction gas to a reaction gas channel in the fuel cell, the residual moisture in the membrane electrode structure and the reaction gas channel in the fuel cell is disclosed. Is forcibly discharged.

Moreover, in the thing of patent document 2, the dry reaction gas is supplied to a fuel cell, and the output current of this fuel cell is controlled while generating the power of the fuel cell. Accordingly, the residual moisture and newly generated water are evaporated by self-heating of the fuel cell and are discharged from the fuel cell together with the reaction gas. Further, in Patent Document 2, in order to prevent the temperature of the fuel cell from excessively high or the temperature of the fuel cell from being excessively lowered to reduce the amount of water evaporation, a refrigerant circulation passage for circulating the refrigerant is used. Is switched between a flow path passing through the radiator and a flow path bypassing the radiator according to the temperature of the fuel cell, so that the temperature of the refrigerant supplied to the fuel cell falls within a required temperature range.
Special table 2003-510786 gazette JP 2002-246053 A

  However, those in Patent Document 1 and Patent Document 2 have the following disadvantages. That is, since the thing of patent document 1 simply supplies the purge fluid or reaction gas, such as nitrogen gas, to the reaction gas flow path of a fuel cell and forcibly discharges the residual moisture in the fuel cell, The internal heat is discharged together with the purge fluid or reaction gas supplied to the outside of the fuel cell, and the temperature of the fuel cell tends to decrease. For this reason, condensation of residual moisture in the fuel cell tends to occur. As a result, in order to sufficiently discharge the residual moisture in the fuel voltage, the supply pressure of the purge fluid or the reaction gas is considerably high (for example, higher than the supply pressure of the reaction gas during operation of the fuel cell). Stuff). In order to supply the high-pressure purge fluid or reaction gas to the fuel cell, the pressure resistance of the supply means (compressor and flow path) and the fuel cell must be increased. In particular, when a purge gas different from the reaction gas is used to discharge residual moisture, a purge gas supply means is required in addition to the reaction gas supply means. There is an inconvenience that the configuration becomes larger and the operation of the fuel cell cannot be resumed until the purge fluid in the fuel cell is discharged.

Further, the intended in patent document 2, while the power generation of the fuel cell, in other words, since the to perform the discharge of the residual water with newly generate H 2 _O, to sufficiently remove residual moisture Therefore, complicated current control of the fuel cell is required. Furthermore, it takes time to reduce the residual moisture amount to a desired amount, and it is difficult to efficiently discharge the residual moisture in a short time. Further, in Patent Document 2, when a fuel cell is mounted on an electric vehicle and the fuel cell is generated to discharge residual moisture, the output current is provided separately from the fuel cell via a DC / DC converter. In addition, it is supplied to a secondary battery (a power source of a traveling motor). However, in this case, when the secondary battery is fully charged, the output current of the fuel cell cannot be controlled to a desired current value, and the residual water is effectively discharged from the fuel cell. It becomes difficult. In order to avoid this, it is necessary to separately provide a load capable of supplying a desired current from the fuel cell when the automobile is stopped.

  The present invention has been made in view of such a background, and provides a fuel cell system capable of efficiently discharging residual moisture in a fuel cell with a relatively simple configuration when the operation of the fuel cell is stopped. For the purpose.

In order to achieve the above object, the fuel cell system of the present invention includes a fuel cell, reaction gas supply means for supplying anode gas and cathode gas, which are reaction gases, to the fuel cell, and a refrigerant connected to the fuel cell. Refrigerant circulation means for supplying refrigerant to the fuel cell while circulating the refrigerant in the circulation flow path, refrigerant cooling means interposed in the refrigerant circulation flow path outside the fuel cell, and bypassing the refrigerant cooling means As described above, the refrigerant bypass passage branched from the upstream side of the refrigerant cooling means of the refrigerant circulation passage and joined to the downstream side of the refrigerant cooling means, and the refrigerant flow in the refrigerant circulation passage is changed to the refrigerant cooling means and the refrigerant In the fuel cell system comprising the refrigerant flow path switching means for selectively switching to the bypass flow path, when stopping the operation of the fuel cell, in the state where the output current of the fuel cell is cut off, While the reaction gas supply means and the refrigerant circulation means are operated so that the reaction gas and the refrigerant are supplied to the fuel cell until a certain condition is satisfied, the refrigerant flow in the refrigerant circulation passage is changed to the refrigerant cooling means side. Control means for operating the refrigerant flow path switching means to switch from the refrigerant bypass flow path side to the refrigerant bypass flow path side, and the reaction gas supply means adds at least one kind of reaction gas of the anode gas and the cathode gas. Pressurizing means for pressurizing, and a reaction gas supply path for supplying the pressurized reaction gas to the fuel cell via the heat exchange means interposed in the refrigerant bypass flow path, the heat exchange means The refrigerant bypass passage is configured to perform heat exchange between the refrigerant flowing through the refrigerant bypass passage and the pressurized reaction gas, and the refrigerant bypass passage is in operation of the fuel cell. A flow path constituting a part of a refrigerant flow path for equipment for flowing a refrigerant for cooling equipment other than the fuel cell, wherein the refrigerant flow path switching means is configured to operate the refrigerant bypass flow path during operation of the fuel cell. When the refrigerant flow in the refrigerant circulation channel is switched from the refrigerant cooling means side to the refrigerant bypass channel side. The flow path is configured to be cut off from the equipment coolant flow path and to communicate with the coolant circulation flow path .

According to the present invention, when the operation of the fuel cell is stopped, the flow of the refrigerant in the refrigerant circulation passage is switched from the refrigerant cooling means side to the refrigerant bypass passage side while supplying the reaction gas and the refrigerant to the fuel cell. Therefore, the refrigerant is supplied to the fuel cell while being circulated in the refrigerant circulation passage via the refrigerant bypass passage without being cooled by the refrigerant cooling means. For this reason, the temperature of the refrigerant flowing in the refrigerant circulation channel is unlikely to decrease, and the decrease from the temperature of the refrigerant during operation of the fuel cell (during power generation) becomes moderate. Therefore, the period during which the temperature of the fuel cell is maintained at a relatively high temperature close to the temperature during operation of the fuel cell is also relatively long. In such a state, since the reaction gas is supplied to the fuel cell, the residual moisture in the fuel cell is smoothly evaporated (vaporized) and discharged from the fuel cell together with the reaction gas. At this time, since the output current of the fuel cell is cut off, the fuel cell does not perform a substantial power generation operation, and H ₂ O newly generated by the reaction of the reaction gas remains in a very small amount. No special current control of the battery is required. Therefore, residual moisture in the fuel cell can be quickly discharged. Since the residual moisture in the fuel cell can be efficiently discharged with a relatively simple configuration, according to the present invention, the residual moisture in the fuel cell can be efficiently discharged with a relatively simple configuration.

  In the fuel cell system of the present invention, hydrogen gas and air (air containing oxygen) or oxygen gas are preferably used as the reaction gas. Further, it is preferable that the reaction gas supplied to the fuel cell when the operation of the fuel cell is stopped is at least dried (having less water content) than during the operation of the fuel cell. For example, when the reaction gas is supplied through the humidifier during the operation of the fuel cell, the reaction gas is bypassed to bypass the humidifier when the operation of the fuel cell is stopped. May be supplied to the fuel cell.

  In such a fuel cell system of the present invention, it is preferable that a heat accumulator having a refrigerant heat retaining function is interposed in the refrigerant circulation passage passing through the refrigerant bypass passage.

  According to this, it is possible to further suppress the temperature decrease of the refrigerant flowing through the refrigerant circulation flow path, and consequently, it is possible to accelerate the evaporation of the residual moisture in the fuel cell and to discharge the residual moisture more quickly. . In addition, as a heat storage device, the refrigerant | coolant tank etc. which were comprised, for example with the heat insulating material are mentioned.

  In the present invention, the predetermined condition that defines the timing for stopping the operation of the reaction gas supply means and the refrigerant circulation means can be defined by, for example, an elapsed time after the operation of the fuel cell is stopped. A residual moisture amount grasping means for grasping a residual moisture amount in the fuel cell; and the predetermined condition is a condition that the residual moisture amount grasped by the residual moisture amount grasping means is a predetermined value or less. preferable.

  According to this, the residual moisture can be discharged so as to reliably reduce the residual moisture content in the fuel cell to a predetermined value or less.

In the present invention, as described above, the reactive gas supply means includes a pressurizing means for pressurizing at least one of the anode gas and the cathode gas, and the pressurized reactive gas. And a reaction gas supply path for supplying the fuel cell with a heat exchange means interposed in the refrigerant bypass flow path, and the heat exchange means pressurizes the refrigerant flowing through the refrigerant bypass flow path and configurations to occupy perform heat exchange with the reaction gas.

  According to this, the reaction gas is heated by pressurizing the one kind of reaction gas. For this reason, when the refrigerant flowing through the refrigerant bypass passage passes through the heat exchange means of the refrigerant bypass passage, the temperature drop is further suppressed by heat exchange with the heated reaction gas. For this reason, the heat retention of the refrigerant supplied to the fuel cell, and hence the heat retention of the fuel cell, is further enhanced. As a result, the evaporation (vaporization) of the refrigerant in the fuel cell is further promoted, and as a result, the discharge of residual moisture in the fuel cell can be accelerated. In addition, it is possible to prevent the reaction gas supplied to the fuel cell stack from being excessively heated due to heat exchange between the reaction gas whose temperature has been increased and the refrigerant.

  In addition, the pressurization of the one kind of reaction gas is performed such that the pressurized reaction gas has a temperature substantially equal to the temperature of the refrigerant during operation of the fuel cell (a temperature in the vicinity of the temperature of the refrigerant), Alternatively, it is preferable that the temperature is raised to a slightly higher temperature. Further, when hydrogen gas and air are used as the anode gas and the cathode gas, which are reaction gases supplied to the fuel cell, respectively, it is preferable that the reaction gas to be pressurized is air.

  In the present invention in which heat is exchanged between the pressurized reaction gas and the refrigerant flowing through the refrigerant bypass flow path as described above, the refrigerant bypass flow path absorbs heat generation energy during operation of the pressurizing means. More preferably, it is provided via the pressurizing means.

  According to this, since the refrigerant flowing through the refrigerant bypass passage when the operation of the fuel cell is stopped can absorb the heat generation energy of the pressurizing means, the heat retention effect of the refrigerant is further enhanced, and the residual moisture in the fuel cell is increased. Can evaporate the gas and increase its discharge effect. At the same time, it is possible to prevent the pressurizing means (for example, a compressor or a supercharger) from becoming too hot.

Further, in the present invention in which heat is exchanged between the pressurized reaction gas and the refrigerant flowing through the refrigerant bypass passage, or the refrigerant bypass passage is passed through the pressurizing means , as described above, the refrigerant bypass passage is A flow path constituting a part of a refrigerant flow path for equipment for flowing a refrigerant for cooling equipment other than the fuel cell during operation of the fuel cell, and the refrigerant flow path switching means is configured to operate the fuel cell. The refrigerant bypass flow path is blocked from the refrigerant circulation flow path and communicated with the equipment refrigerant flow path, and the refrigerant flow in the refrigerant circulation flow path is changed from the refrigerant cooling means side to the refrigerant bypass flow path side. when switching, that is configured the refrigerant bypass flow path so as to communicate with the coolant circulation flow path while blocking the refrigerant flow path for the device.

  According to this, during the operation of the fuel cell, the refrigerant flows through the equipment refrigerant flow path including the refrigerant bypass flow path, and the reaction gas pressurized by the pressurizing means and the refrigerant flowing through the equipment refrigerant flow path. It is possible to prevent the reaction gas from becoming excessively hot by performing heat exchange with the heat exchange means. In particular, when the refrigerant bypass passage passes through the pressurizing means (in this case, the equipment other than the fuel cell includes equipment constituting the pressurizing means), the excessive temperature rise of the pressurizing means Can be prevented. At this time, since the refrigerant bypass flow path is blocked from the refrigerant circulation flow path, the flow of the refrigerant in the equipment refrigerant flow path does not affect the refrigerant circulation flow path, and the fuel cell is excessive. Therefore, it is possible to reliably prevent temperature rise without hindrance.

  When the operation of the fuel cell is stopped, the refrigerant bypass flow path is blocked from the equipment refrigerant flow path, but the refrigerant flowing in the refrigerant circulation flow path flows as described above. Residual moisture in the fuel cell can be efficiently discharged while maintaining the temperature, preventing excessive temperature increase of the pressurized reaction gas, or preventing excessive temperature increase of the pressurizing means. Further, by sharing the refrigerant bypass flow path for the apparatus refrigerant flow path and the refrigerant circulation flow path, the flow path configuration of the refrigerant combined with the flow paths can be made small and simple.

A first embodiment as a reference example related to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an overall configuration of the fuel cell system according to the first embodiment. As shown in FIG. 1, the fuel cell system of the present embodiment supplies a fuel cell stack 1 corresponding to the fuel cell of the present invention, and hydrogen gas (anode gas) and air (cathode gas) as reaction gases, respectively. Hydrogen gas supply means 2 and air supply means 3 as reactive gas supply means, refrigerant circulation means 4 for supplying the fuel cell stack 1 while circulating the refrigerant, fuel cell stack 1, hydrogen gas supply means 2, A controller 5 is provided as control means for controlling operation of the air supply means 3 and the refrigerant circulation supply means 4.

  The basic structure of the fuel cell stack 1 will be described with reference to FIG. FIG. 2 is a view schematically showing a cross section of a main part of the fuel cell stack 1.

  As shown in FIG. 2, the fuel cell stack 1 includes a membrane electrode structure (so-called MEA) 9 in which an anode electrode 7 and a cathode electrode 8 are bonded to both surfaces of a solid polymer electrolyte membrane 6, and this membrane electrode structure. By laminating a plurality of unit cells (minimum unit fuel cells) in the normal direction of the membrane electrode structure 9, each of which is composed of a conductive separator 10 mounted on the surface of each electrode 7, 8. The main body (power generation function unit) is configured. Of the separators 10 and 10 on both sides of each membrane electrode structure 9, the separator 10 facing the anode electrode 7 forms a hydrogen gas flow path 11 between the separator 10 and the surface of the anode electrode 7, and faces the cathode electrode 8. 10 forms an air flow path 12 between the surface of the cathode electrode 8. Moreover, in this embodiment, the separators 10 and 10 interposed between the adjacent membrane electrode structures 9 and 9 form a refrigerant flow path 13 between them. The flow paths 11, 12, and 13 as described above are usually formed by forming a groove in a separator made of a carbon material, or by forming a separator made of a metal plate into a corrugated plate by pressing. 2 exemplifies a separator 10 formed by pressing a metal plate to form the flow paths 11, 12, and 13, for example.

  Although not shown, the battery main body of the fuel cell stack 1 is accommodated in a housing, and the housing is provided with a hydrogen gas main passage through which the hydrogen gas flow paths 11 communicate with each flow of air. An air main passage that communicates with the passage 12 and a refrigerant main passage that communicates with each refrigerant flow passage 13 are provided. And inflow / outflow of hydrogen gas, air, and a refrigerant to each channel 11, 12, and 13 is performed through these main passages, respectively.

  Returning to FIG. 1, the fuel cell stack 1 is electrically connected to an electric load 14 that supplies an output current during the power generation operation via a switch 15 that is controlled to open and close by the controller 5. The fuel cell system of the present embodiment is mounted on, for example, an automobile (fuel cell automobile), and the electric load 14 includes, for example, a traveling motor, a capacitor as its main power source, or various auxiliary electrical components ( And a power source battery (secondary battery) of the controller 5 and the like.

  Furthermore, the fuel cell stack 1 has a built-in humidity sensor 16 that detects the relative humidity of the reaction gas flowing through the fuel cell stack 1. The humidity sensor 16 is provided, for example, in the vicinity of the air outlet of the fuel cell stack 1. The humidity sensor 16 corresponds to the residual moisture amount grasping means in the present invention, and a signal corresponding to the relative humidity in the vicinity of the air outlet of the fuel cell stack 1 represents the residual moisture amount in the fuel cell stack 1. Output as stuff. The humidity sensor 16 may be provided in the vicinity of the hydrogen gas discharge port of the fuel cell stack 1, or may be provided near both the air discharge port and the hydrogen discharge port, or each of the plurality of unit cells. It may be provided in the vicinity of the outlet of the air channel 12 or in the vicinity of the outlet of the hydrogen channel 11. When a plurality of humidity sensors are provided, for example, an average value or a maximum value of outputs from the humidity sensors may be used as an indication of the residual moisture content in the fuel cell stack 1.

  The hydrogen gas supply means 2 is led out from the hydrogen gas supplier 17 for sending out hydrogen gas and the hydrogen gas supplier 17, and is connected to the hydrogen gas inlet 1 a of the fuel cell stack 1 via the humidifier 18. A hydrogen gas supply path 19 and a hydrogen gas bypass flow path 20 branched from the upstream side of the humidifier 18 so as to bypass the humidifier 18 and joined to the downstream side of the humidifier 18. I have. The hydrogen gas flow sent from the hydrogen gas supply unit 17 is connected to the branching point of the hydrogen gas bypass channel 20 on the upstream side of the humidifier 18 with the path on the humidifier 18 side and the hydrogen gas bypass path 20 side. An electric switching valve 21 that selectively switches to a route is interposed.

  The humidifier 18 is for adding moisture to the hydrogen gas delivered from the hydrogen gas supplier 17 during the power generation operation of the fuel cell stack 1. This is because, in a state where each membrane electrode structure 9 of the fuel cell stack 1 is moistened to some extent, the reaction between the hydrogen gas and the oxygen gas in the air in each membrane electrode structure 9 and the power generation by the reaction are performed satisfactorily. Because it is.

  The operation of the hydrogen gas supplier 17 and the electric switching valve 21 of the hydrogen gas supply means 2 is controlled by the controller 5.

  The air supply means 3 sucks and pressurizes the atmosphere, supercharges 22 as a pressurizing means for sending out the pressurized air, and is derived from the supercharger 22, and sequentially passes through an intercooler 23 and a humidifier 24. The air supply flow path 25 connected to the air inlet 1b of the fuel cell stack 1 and the branch from the upstream side of the humidifier 24 (the downstream side of the intercooler 23) so as to bypass the humidifier 24. And the air bypass flow path 26 joined to the location of the downstream of this humidifier 24 is provided. At the branching point of the air bypass channel 26 on the upstream side of the humidifier 24, the air flow sent from the supercharger 22 is routed downstream of the intercooler 23 on the humidifier 24 side and the air bypass channel 26. An electric switching valve 27 that selectively switches to the side path is interposed.

  The humidifier 24 is for adding moisture to the air delivered from the supercharger 22 during the power generation operation of the fuel cell stack 1 for the same reason as in the case of hydrogen gas. The intercooler 23 has a heat dissipation function and prevents excessively high temperature air from being supplied to the fuel cell stack 1. In other words, the air pressurized by the supercharger 22 rises in temperature due to the pressurization, but after the heated air is radiated to some extent by the intercooler 23 and supplied to the fuel cell stack 1, Hot air is prevented from being supplied to the fuel cell stack 1.

  The operation of the supercharger 22 and the electric switching valve 27 of the air supply means 3 is controlled by the controller 5.

  The refrigerant circulation means 4 includes a refrigerant circulation passage 28 having both ends connected to the refrigerant inlet 1d and the refrigerant outlet 1c of the fuel cell stack 1 so as to circulate the refrigerant via the fuel cell stack 1. Yes. In this refrigerant circulation passage 28, in order from the upstream side (the refrigerant outlet 1 c side of the fuel cell stack 1), a refrigerant tank 29 that stores refrigerant, an electric pump 30, and a radiator 31 ( And a radiator). Further, the refrigerant circulation flow path 28 branches from a location on the upstream side of the radiator 31 (a location on the downstream side of the electric pump 30) so as to bypass the radiator 31, and is joined to a location on the downstream side of the radiator 31. A refrigerant bypass flow path 32 is provided. Electric switching valves 33 and 34 as refrigerant flow switching means are respectively provided at a branching point of the refrigerant bypass flow channel 32 on the upstream side of the radiator 31 and a joining point of the refrigerant bypass flow channel 32 on the downstream side of the radiator 31. Has been. For example, ethylene glycol is used as the refrigerant.

  Here, the refrigerant tank 29 is made of a highly heat-insulating material, and functions as a heat accumulator having a refrigerant heat-retaining function.

  The electric switching valve 33 selectively switches the flow of the refrigerant from the electric pump 30 between a path on the radiator 31 side and a path on the refrigerant bypass flow path 32 side, and the electric switching valve 34 includes this. The position where the merged portion is blocked from the refrigerant bypass flow path 32 and at the same time communicated with the radiator 31 side (hereinafter referred to as the radiator side communication position), and the position where the merge point is communicated with the refrigerant bypass flow path 32 is simultaneously blocked from the radiator 31 side. It moves to the position (refrigerant bypass channel side communication position). In this case, the electric switching valve 33 is operated to the refrigerant bypass flow path 32 side (the branch portion provided with the electric switching valve 33 is communicated only to the refrigerant bypass flow path 32 side), and the electric switching valve 34 is connected to the refrigerant. By operating to the bypass flow path side communication position, the refrigerant flows through the refrigerant bypass flow path 32 and is supplied to the fuel cell stack 1 without passing through the radiator 31. Further, the electric switching valve 33 is operated to the radiator 31 side (the branch portion provided with the electric switching valve 33 is communicated only to the radiator 31 side), and the electric switching valve 34 is operated to the radiator side communication position. Thus, the refrigerant flows through the radiator 31 and is supplied to the fuel cell stack 1 without passing through the refrigerant bypass passage 32.

  The operation of the electric pump 30 and the electric switching valves 33 and 34 of the refrigerant circulation means 4 is controlled by the controller 5. In the present embodiment, the electric switching valves 33 and 34 are provided at both the upstream branching point and the downstream joining point of the radiator 31, but either one may be omitted.

  The controller 5 is composed of an electronic circuit including a microcomputer. The detection signal of the humidity sensor 16, the operation request signal of the fuel cell system when the ignition switch (not shown) is turned ON / OFF, the operation stop signal, etc. Is entered. And the controller 5 is based on those input signals, data stored in advance, programs, etc., the hydrogen gas supplier 17, supercharger 22, electric switching valves 21, 27, 33, 34, electric pump 30, switch 15. Is controlled via an actuator or a drive circuit (not shown).

  Next, the operation of the fuel cell system of this embodiment will be described.

  In a state where the operation request signal is given to the controller 5 and the fuel cell system is operated (power generation operation of the fuel cell stack 1), the controller 5 closes the switch 15 and the electric power of the hydrogen gas supply means 2 The switching valve 21 is operated to the humidifier 18 side, and the electric switching valve 27 of the air supply means 3 is operated to the humidifier 24 side. Further, the controller 5 operates the electric switching valve 33 of the refrigerant circulation means 4 to the radiator 31 side and operates the electric switching valve 34 to the radiator side communication position. In such a state, the controller 5 operates the hydrogen gas supplier 17, the supercharger 22 and the electric pump 30.

At this time, hydrogen gas containing moisture is supplied to the fuel cell stack 1 from the hydrogen gas supply device 17 via the humidifier 18 (see the solid line arrow Y1 in FIG. 1), and from the supercharger 22 Air containing moisture is supplied to the fuel cell stack 1 via the cooler 23 and the humidifier 24 (see the solid line arrow Y3 in FIG. 1). The hydrogen gas supplied to the fuel cell stack 1 and the oxygen gas in the air react with each membrane electrode structure 9. Thereby, an electromotive force is generated between the electrodes 7 and 8 of each membrane electrode structure 9 while H ₂ O (water or water vapor) is generated in each membrane electrode structure 9, and this is generated for all the membrane electrode structures. An output current due to the electromotive force synthesized in series with respect to the body 9 is supplied to the electric load 14 via the switch 15. Thereby, the power generation operation of the fuel cell stack 1 is performed.

  Further, by the operation of the electric pump 30 of the refrigerant circulation means 4, the refrigerant is circulated from the refrigerant tank 29 through the electric pump 30, the radiator 31 and the fuel cell stack 1 in this order, and is supplied to the fuel cell stack 1 ( (See solid arrows Y5 and Y7 in FIG. 1). At this time, the refrigerant absorbs the heat generation energy of the membrane electrode structure 9 in the refrigerant flow path 13 in the fuel cell stack 1 and releases the absorbed heat energy by the radiator 31. This prevents the fuel cell stack 1 from becoming excessively hot.

  The above is the operation during the power generation operation of the fuel cell stack 1. Next, the operation when the power generation operation of the fuel cell stack 1 is stopped (the supply of the output current to the electric load 14 is stopped) will be described.

  When an operation stop signal is given to the controller 5 by turning off an ignition switch (not shown), the controller 5 executes a process described below. That is, the controller 5 opens the switch 15 to cut off the output current of the fuel cell stack 1 (after stopping the power generation of the fuel cell stack 1), and then the hydrogen gas supplier 17, the supercharger 22, and the electric pump 30, while switching the electric switching valve 21 of the hydrogen gas supply means 2 from the humidifier 18 side to the hydrogen gas bypass flow path 20, the electric switching valve 27 of the air supply means 2 is switched from the humidifier 24 side to the air bypass flow. Switch to the road 26 side. Further, the controller 5 switches the electric switching valve 33 of the refrigerant circulation means 4 from the radiator 31 side to the refrigerant bypass flow path 32 side, and switches the electric switching valve 33 from the radiator side communication position to the refrigerant bypass flow path side communication position.

At this time, the hydrogen gas delivered from the hydrogen gas supplier 17 and the air delivered from the supercharger 22 do not pass through the humidifiers 18 and 24, respectively, and the hydrogen gas bypass channel 20 and the air bypass channel. 26 (see arrows Y2 and Y4 of the two-dot chain line in FIG. 1), and supplied to the fuel cell stack 1. Therefore, relatively dry hydrogen gas and air are supplied to the fuel cell stack 1 as purge gas. In this case, since the output current of the fuel cell stack 1 is interrupted, the reaction between the supplied hydrogen gas and oxygen in the air does not occur so much, so that a small amount of H ₂ O is newly generated. .

  In the refrigerant circulation means 4, the refrigerant circulates from the refrigerant tank 29 via the electric pump 30, the refrigerant bypass flow path 32, and the fuel cell stack 1 (see the two-dot chain arrows Y 6 and Y 8 in FIG. 1). reference). In this case, the refrigerant does not pass through the radiator 31, and the refrigerant tank 29 has a heat retaining function. Furthermore, since the upstream side and the downstream side of the radiator 31 are closed by the electric switching valves 33 and 34, the refrigerant that has radiated and cooled the heat in the radiator 31 passes through the refrigerant bypass passage 32 in the refrigerant circulation passage 28. It is not mixed with the refrigerant flowing through. For this reason, the heat dissipation amount per unit time of the refrigerant in the refrigerant circulation means 4 is relatively small. As a result, the temperature of the refrigerant circulating through the inside of the fuel cell stack 1, and thus the temperature of the fuel cell stack 1, does not cause a rapid temperature decrease, and the temperature during the power generation operation of the fuel cell stack 1 (for example, 70 to From 75 ° C).

Accordingly, the residual moisture in the fuel cell stack 1 (specifically, inside the membrane electrode structure 9 and the flow paths 11 and 12) is purged gas that is supplied while being smoothly vaporized by the internal heat of the fuel cell stack 1. The hydrogen gas and the air are conveyed and discharged together with the hydrogen gas and air to the outside of the fuel cell stack 1. In this case, since H ₂ O generated during the power generation operation of the fuel cell stack 1 is likely to be generated in the air flow path 12, residual moisture tends to accumulate in the flow path 12. However, since the air supplied to the fuel cell stack 1 is pressurized and has a relatively high dynamic pressure, residual moisture in the flow path 12 is also smoothly discharged.

  The controller 5 monitors the output signal of the humidity sensor 16 while operating the fuel cell system as described above. Then, when the relative humidity indicated by the output signal of the humidity sensor 16 is equal to or lower than a predetermined value, it is assumed that the residual water content in the fuel cell stack 1 is equal to or lower than the predetermined amount. The operation of the supercharger 22 and the electric pump 30 is stopped.

  The above is the operation for discharging residual moisture in the fuel cell stack 1 when the operation of the fuel cell stack 1 is stopped. In this case, as described above, the residual moisture in the fuel cell stack 1 is discharged to the outside of the fuel cell stack 1 together with the supplied hydrogen gas and air while being smoothly vaporized. Can be done. At this time, the output current of the fuel cell stack 1 is cut off, the power generation of the fuel cell stack 1 is not performed, and the electromagnetic switching valve 21, the hydrogen gas supplier 17, the supercharger 22, and the electric pump 30 are operated. Residual moisture in the fuel cell stack 1 can be discharged in a short time only by performing the switching operation of 27, 33, and 34. That is, the residual moisture in the fuel cell stack 1 can be efficiently discharged with a simple configuration without requiring complicated operation control of the fuel cell system.

Next, a second embodiment as an embodiment of the present invention will be described with reference to FIG. Since the present embodiment is different from the first embodiment only in part of the configuration and operation, the same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment. Description is omitted using.

Referring to FIG. 3, the differences of the present embodiment from the first embodiment will be described. In the present embodiment, a travel motor, a motor drive circuit, and a device for cooling the supercharger 22 are not shown. A part of the refrigerant flow path 35 also serves as the refrigerant bypass flow path 32 of the refrigerant circulation means 4 for cooling the fuel cell stack 1. More specifically, in the present embodiment, the equipment refrigerant flow path 35 is provided so as to pass through the supercharger 22 and the intercooler 23, and the intercooler 23 extends from a location 36 on the upstream side of the supercharger 22. The portion up to the point 37 on the downstream side also serves as the refrigerant bypass passage 32 of the refrigerant circulation means 4, and the refrigerant circulation passage 28 via the electromagnetic switching valves 33 and 34 on the upstream side and the downstream side of the radiator 31. It is connected to the. Further, a location on the upstream side of the equipment refrigerant flow path 35 relative to the location 36 on the upstream side of the supercharger 22 and a location downstream of the equipment coolant flow path 35 relative to the location 37 on the downstream side of the intercooler 23. Are provided with solenoid valves 38 and 39 that are controlled to be opened and closed by the controller 5, respectively, and by closing these solenoid valves 38 and 39, the refrigerant bypass flow path 32 is cut off from the equipment refrigerant flow path 35. It has become so that is. The electromagnetic valves 38 and 39 together with the electromagnetic switching valves 33 and 34 constitute a refrigerant flow path switching unit.

  With the above configuration, the electromagnetic switching valve 33 on the upstream side of the radiator 31 is operated to the radiator 31 side, the electromagnetic switching valve 34 on the downstream side of the radiator 31 is operated to the radiator side communication position, and the electromagnetic valves 38, By opening the valve 39, the refrigerant bypass channel 32 communicates with the device refrigerant channel 35 and is incorporated into the device refrigerant channel 35, and the refrigerant circulation channel 28 and the device refrigerant channel 35 are provided. Is substantially interrupted, no refrigerant moves between the flow paths 28 and 35, and heat transfer between the flow paths 28 and 35 does not occur. In this state, the refrigerant flow in the equipment refrigerant flow path 35 (which passes through the supercharger 22 and the intercooler 23) and the refrigerant flow in the refrigerant circulation means 4 (which passes through the radiator 31) Are performed independently of each other.

  Further, the electromagnetic switching valve 33 on the upstream side of the radiator 31 is operated to the refrigerant bypass flow path 32 side, the electromagnetic switching valve 34 on the downstream side of the radiator 31 is operated to the communication position on the refrigerant bypass flow path side, and the electromagnetic valve By closing the valves 38 and 39, the refrigerant bypass flow path 32 communicates with the refrigerant circulation flow path 28 and is incorporated into the refrigerant circulation means 4, and is also cut off from the apparatus refrigerant flow path 35. The refrigerant does not move between the passage 35 and the refrigerant bypass flow path 32 and the refrigerant circulation flow path 28, and the heat transfer between them is substantially interrupted. In this state, the refrigerant flow in the refrigerant circulation means 4 is performed not via the radiator 31 but via the refrigerant bypass flow path 32 passing through the supercharger 22 and the intercooler 23.

  In the present embodiment, the intercooler 23 has a function of performing heat exchange between the refrigerant flowing through the refrigerant bypass passage 32 passing through the intercooler 23 and the pressurized air supplied from the supercharger 22. Therefore, in this embodiment, the intercooler 23 has a function as a heat exchange means in the present invention.

  Configurations other than those described above are the same as those in the first embodiment.

  Next, the operation of the fuel cell system of this embodiment will be described. During the power generation operation of the fuel cell stack 1, the controller 5 closes the switch 15, operates the electric switching valve 21 of the hydrogen gas supply means 2 to the humidifier 18 side, and electrically switches the air supply means 3. The valve 27 is operated to the humidifier 24 side. Further, the controller 5 operates the electric switching valve 33 of the refrigerant circulation means 4 to the radiator 31 side and operates the electric switching valve 34 to the radiator side communication position. Further, the controller 5 operates the solenoid valves 38 and 39 of the equipment refrigerant flow path 35 in the valve open state. In such a state, the controller 5 operates the hydrogen gas supplier 17, the supercharger 22 and the electric pump 30.

  At this time, as in the first embodiment, hydrogen gas and air are supplied to the fuel cell stack 1 (see solid arrows Y1 and Y2 in FIG. 3), and power generation of the fuel cell stack 1 is performed. The circulation means 4 circulates the refrigerant through the radiator 31 and is supplied to the fuel cell stack 1 (see solid arrows Y5 and Y7 in FIG. 3) to prevent the fuel cell stack 1 from being excessively heated. Is done. At this time, the pump (not shown) of the equipment refrigerant flow path 35 is operated, and the refrigerant flows through the refrigerant bypass flow path 32 of the equipment refrigerant flow path 35, so that the supercharger 22 and the intercooler 23 become excessive. High temperature is also prevented. If it supplements, the temperature of the refrigerant | coolant which flows through the refrigerant | coolant flow path 35 for apparatuses will be about 60 degreeC in a steady state, for example.

On the other hand, when the power generation operation of the fuel cell stack 1 is stopped by turning off an ignition switch (not shown), the controller 5 opens the switch 15 and cuts off the output current of the fuel cell stack 1 (the fuel cell stack 1 After the power generation is stopped), the electric switching valve 21 of the hydrogen gas supply means 2 is moved from the humidifier 18 side to the hydrogen gas bypass flow path 20 while the hydrogen gas supplier 17, the supercharger 22, and the electric pump 30 are operated. While switching, the electric switching valve 27 of the air supply means 2 is switched from the humidifier 24 side to the air bypass channel 26 side. Further, the controller 5 switches the electric switching valve 33 of the refrigerant circulation means 4 from the radiator 31 side to the refrigerant bypass flow path 32 side, and switches the electric switching valve 33 from the radiator side communication position to the refrigerant bypass flow path side communication position. Furthermore, the controller 5 operates the solenoid valves 38 and 39 in the closed state.

  At this time, as in the first embodiment, relatively dry hydrogen gas and air (pressurized air) are supplied to the fuel cell stack 1 as a purge gas. Further, in the refrigerant circulation means 4, the refrigerant passes through the refrigerant bypass passage 32 without passing through the radiator 31, as indicated by the two-dot chain arrows Y6, Y12, Y13, Y14 in FIG. Circulate through the circulation channel 28. In this circulation process, when the refrigerant passes through the intercooler 23 of the refrigerant bypass passage 32, heat exchange between the refrigerant and the pressurized air supplied to the intercooler 23 from the supercharger 22 is performed. In this case, in this embodiment, the air pressurized by the supercharger 22 causes the steady temperature (for example, 70 to 70) of the refrigerant flowing through the refrigerant circulation passage 28 during the power generation operation of the fuel cell stack 1 due to the pressurization. 75 ° C.) or slightly higher (for example, 80 ° C.). When the refrigerant flowing through the refrigerant circulation passage 28 passes through the intercooler 23 in the refrigerant bypass passage 32, the refrigerant is hardly radiated by heat exchange with the pressurized and heated air sent from the supercharger 22. To keep warm. Furthermore, in the present embodiment, the refrigerant bypass passage 32 passes through the supercharger 22, so that the refrigerant flowing through the refrigerant bypass passage 32 can absorb part of the heat generation energy of the supercharger 22. For this reason, the heat retaining property of the refrigerant flowing through the refrigerant circulation flow path 28 is higher than that of the first embodiment, and the temperature of the refrigerant decreases from the temperature at the end of the power generation operation of the fuel cell stack 1. Is more effectively suppressed. As a result, the state where the temperature of the fuel cell stack 1 is maintained at a temperature close to the temperature at the end of the power generation operation stably continues.

  As a result, in the present embodiment, vaporization of residual moisture in the fuel cell stack 1 (vaporization due to internal heat of the fuel cell stack 1) is promoted more smoothly than in the first embodiment, and the purge supplied to the fuel cell stack 1 The fuel cell stack 1 is more quickly discharged from the inside of the fuel cell stack 1 by hydrogen gas and air, which are working gases. The refrigerant flowing through the refrigerant bypass passage 32 absorbs the heat generation energy of the supercharger 22, so that the supercharger 22 can be prevented from becoming too hot, and the refrigerant and the superfluid flowing through the refrigerant bypass passage 32 can be prevented. Heat exchange with the air pressurized by the charger 22 prevents the air from becoming too hot.

  Then, as in the first embodiment, the controller 5 determines the amount of residual water in the fuel cell stack 1 when the relative humidity indicated by the output signal of the humidity sensor 16 is below a predetermined value. The operation of the hydrogen gas supplier 17, the supercharger 22, and the electric pump 30 is stopped as being below the fixed amount. Thereby, the operation | movement for discharging | emitting residual moisture in the fuel cell stack 1 is complete | finished.

  In this case, as described above, the residual moisture in the fuel cell stack 1 is discharged to the outside of the fuel cell stack 1 together with the supplied hydrogen gas and air while vaporizing more rapidly and smoothly than in the first embodiment. Therefore, the residual moisture can be discharged in a shorter time. In addition, the temperature of the refrigerant circulated in the refrigerant circulation passage 28 is maintained by using the intercooler 23 of the air supply means 3, and a part of the device refrigerant passage 35 is used as the refrigerant bypass passage 32. The refrigerant flow path configuration for efficiently discharging the residual moisture of the battery stack 1 can be made small and simple.

  In the embodiment described above, the humidity sensor 16 is used as the residual moisture amount grasping means. For example, the resistance value of one or a plurality of cells of the fuel cell stack 1 is measured, and the measured value of the resistance value is used. Based on this, it is possible to grasp the amount of residual water in the fuel cell stack 1. In this case, while the switch 15 is opened, for example, a pulse voltage is periodically applied to one or a plurality of cells of the fuel cell stack 1 from an auxiliary battery, and a current is applied. What is necessary is just to measure the electric current at the time of electricity supply, and to measure the resistance value of a cell based on the measured electric current value. In this case, since the resistance value of the cell decreases as the residual moisture amount increases, when the measured resistance value of the cell becomes equal to or higher than a predetermined value, it is determined that the residual moisture amount becomes equal to or lower than the predetermined amount. What should I do?

The figure which shows the whole structure of 1st Embodiment of the fuel cell system of this invention. The figure which shows the cross-section of the fuel cell stack with which the fuel cell system of FIG. 1 was equipped. The whole structure of 2nd Embodiment of the fuel cell system of this invention is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack, 2 ... Hydrogen gas supply means (reaction gas supply means), 3 ... Air supply means (reaction gas supply means), 4 ... Refrigerant circulation means, 5 ... Controller (control means), 16 ... Humidity sensor ( Residual moisture amount grasping means), 22 ... supercharger (pressurizing means), 23 ... intercooler (heat exchange means), 28 ... refrigerant circulation channel, 29 ... refrigerant tank (heat accumulator), 31 ... radiator (refrigerant cooling means) ), 32... Refrigerant bypass flow path, 33, 34, 38, 39... Refrigerant flow path switching means, 35.

Claims (4)

A fuel cell, a reaction gas supply means for supplying anode gas and cathode gas, which are reaction gases to the fuel cell, and a coolant supplied to the fuel cell while circulating the coolant through a coolant circulation channel connected to the fuel cell Branching from the upstream side of the refrigerant cooling means of the refrigerant circulation passage so as to bypass the refrigerant cooling means, and the refrigerant cooling means interposed in the refrigerant circulation passage outside the fuel cell A refrigerant bypass passage joined to the downstream side of the refrigerant cooling means, and a refrigerant passage switching means for selectively switching the refrigerant flow in the refrigerant circulation passage between the refrigerant cooling means and the refrigerant bypass passage. In the provided fuel cell system,
When stopping the operation of the fuel cell, in a state where the output current of the fuel cell is interrupted, the reaction gas supply means and the refrigerant are supplied to the fuel cell so that the reaction gas and the refrigerant are supplied until a predetermined condition is satisfied. Control means for operating the refrigerant flow switching means to switch the refrigerant flow in the refrigerant circulation flow path from the refrigerant cooling means side to the refrigerant bypass flow path side while operating the circulation means ;
The reactive gas supply means includes a pressurizing means for pressurizing at least one kind of the reactive gas of the anode gas and the cathode gas, and the pressurized reactive gas is interposed in the refrigerant bypass flow path. And a reaction gas supply path for supplying the fuel cell via the heat exchange means, and heat exchange between the refrigerant flowing through the refrigerant bypass flow path and the pressurized reaction gas is performed by the heat exchange means. Configured to squeeze,
The refrigerant bypass flow path is a flow path that constitutes a part of a refrigerant flow path for equipment for flowing a refrigerant for cooling equipment other than the fuel cell during operation of the fuel cell, and the refrigerant flow path switching means Shuts off the refrigerant bypass channel from the refrigerant circulation channel and communicates with the device refrigerant channel during operation of the fuel cell, and causes the refrigerant cooling means to flow the refrigerant in the refrigerant circulation channel A fuel cell system configured to block the refrigerant bypass channel from the device refrigerant channel and to communicate with the refrigerant circulation channel when switching from the refrigerant side to the refrigerant bypass channel side .   2. The fuel cell system according to claim 1, wherein a regenerator having a refrigerant heat retention function is interposed in the refrigerant circulation flow path passing through the refrigerant bypass flow path.   A residual moisture amount grasping means for grasping a residual moisture amount in the fuel cell, wherein the predetermined condition is a condition that the residual moisture amount grasped by the residual moisture amount grasping means is a predetermined value or less; The fuel cell system according to claim 1 or 2, characterized in that The said refrigerant | coolant bypass flow path is provided through this pressurization means so that the heat_generation | fever at the time of the action | operation of the said pressurization means may be absorbed , The any one of Claims 1-3 characterized by the above-mentioned. Fuel cell system.

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