JP4608250B2 - Fuel cell system and starting method thereof - Google Patents

Description

  The present invention relates to a fuel cell system and a startup method thereof.

  In general, a fuel cell is configured such that a cathode electrode is defined on one side with a proton conductive polymer electrolyte membrane (PEM membrane) interposed therebetween, and an anode electrode is defined on the other side, and is supplied to the cathode electrode. Electricity is generated by an electrochemical reaction between oxygen in the air and hydrogen supplied to the anode electrode. As such a fuel cell, a fuel cell in which a plurality of cells (single cells) in which a polymer electrolyte membrane is sandwiched between a cathode electrode and an anode electrode and sandwiched between separators having good conductivity is laminated. It is known that in this fuel cell, it is possible to perform good power generation by allowing hydrogen and oxygen to react well in each cell.

  By the way, although a fuel cell generates a voltage if there is fuel and oxygen, the activity of the catalyst of the fuel cell is lowered when left at a high voltage (for example, 0.8 V / unit cell or more) for a long time (Patent Document). 1 paragraph 0003). Also, in the case of stacked fuel cells, if the current is extracted from the fuel cell before the reaction gas reaches each unit cell of the fuel cell, the unit cell does not reach the reaction gas because the cells are stacked. As a result, a current flows, and the carbon which is the structure of the unit cell may corrode (paragraph 0004 of Patent Document 1).

  By the way, for this problem (the unit cell is in a high voltage state at the start-up, and a large current flows through the fuel-deficient unit cell due to connection to an external load before the reaction gas is supplied at the start-up) Conventionally, (1) “Check that the open circuit voltage of the unit cell has reached a predetermined voltage and then connect an external load” or (2) “Between the two poles of the fuel cell Is provided with an external connection circuit having a resistor and a switch, and a small amount of current is passed through the external connection circuit until the external load is connected, and the external load is connected after a predetermined time while lowering the voltage of the unit cell. (Patent Document 1, paragraph 0005).

However, in the above (1), the voltage of the single cell is still a high voltage, and in the above (2), a minute current is flowing in the external connection circuit, and it is not easy to detect the open circuit of the stack. There was a problem that the timing of external load connection was difficult to take (paragraph 0006 of Patent Document 1). For this reason, in the technology of Patent Document 1, at the time of starting the fuel cell, an auxiliary circuit consisting of at least a resistor is connected to prevent the cell voltage from increasing and a large current from flowing, The current and voltage flowing through the auxiliary circuit are detected, and when a predetermined current value or voltage value is reached, the external load is connected and the fuel cell is started to determine the timing of the external load connection (patent) (Claims 1 and 2 and paragraphs 0006 and 0007 of Document 1).
JP-A-10-284104 (Claims 1, 2, paragraphs 0004 to 0007)

  However, in the technique of Patent Document 1 described above, the fuel gas supplied to the anode electrode reacts with oxygen (oxidant) in the air supplied to the cathode electrode, so the fuel gas is consumed and the anode electrode It takes time to fill the gas with fuel gas. Further, the fuel gas supplied to the anode electrode reacts with oxygen in the air supplied to the cathode electrode together, so that a large current flows through the auxiliary circuit. In addition, when fuel is supplied to the anode electrode scavenged by air at the start-up, the fuel and air coexist on the same electrode (one electrode), and a so-called homopolar power generation phenomenon occurs, and the constituent material of the fuel cell May be deteriorated (a separator, a membrane electrode structure or the like is corroded).

  Therefore, the main object of the present invention is to solve this problem and to provide a fuel cell system and a method for starting the fuel cell that can favorably start the fuel cell.

In view of the above problems, the present inventors have found that the fuel cell can be favorably started by supplying the fuel gas to the anode electrode and then supplying the oxidant gas to the cathode electrode. It came to complete.
That is, the invention according to claim 1 of the present invention that solves the above-mentioned problems includes a fuel gas supplied from the fuel gas supply means to the anode electrode and an oxidant gas supplied from the oxidant gas supply means to the cathode electrode. As a result of the reaction, a fuel cell in which single cells that generate power to be supplied to the load are stacked, a second load that is electrically connected to the fuel cell and consumes less power than the load, and the second Load connecting / disconnecting means for connecting / disconnecting the load, and before starting the fuel cell, before supplying electric power from the fuel cell to the load, the load connecting / disconnecting means electrically connects the second load to the fuel cell. Control means for supplying the fuel gas to the anode electrode by the fuel gas supply means after the connection, and then supplying the oxidant gas to the cathode electrode by the oxidant gas supply means; A purge valve provided in a fuel discharge path connected to an outlet of the anode side of the fuel cell and controlled to be opened and closed by the control means, and a fuel gas discharged from the fuel discharge path are internally diluted to the outside A diluting means for discharging, and when the fuel gas is supplied to the anode electrode by the fuel gas supply means, the control means opens the purge valve to oxidant gas in the anode electrode of the fuel cell. After the dilution means is purged and discharged, it is determined whether or not the amount of the fuel gas in the anode electrode exceeds a predetermined value while the purge valve remains open. After the determination, the purge valve is closed, and then the second load is disconnected by the load connecting / disconnecting means before the oxidant gas is supplied to the cathode electrode .

According to the first aspect of the present invention, the control means connects the second load to the fuel cell by the load connecting / disconnecting means when starting the fuel cell, and then the fuel gas is supplied to the anode electrode by the fuel gas supply means. To supply. When the fuel gas is supplied to the anode electrode by the fuel gas supply means, the purge valve is opened, and the oxidant gas already present in the anode electrode of the fuel cell is purged to the dilution means and discharged. Therefore, in the present invention, the oxidant gas filled in the anode electrode before the system is started is purged from the anode electrode and discharged to the diluting means. Therefore, the oxidant gas and the fuel gas coexist in the anode electrode. Deterioration of the constituent materials of the fuel cell due to polar power generation is prevented. In this case, the fuel gas supplied to the anode electrode reacts with the oxidant gas already present at the cathode electrode. Since the electric power generated as a result is supplied to the second load, the high voltage of the single cell of the fuel cell is prevented. Further, by connecting the second load, deterioration of the constituent material of the fuel cell due to homopolar power generation is prevented.

By the way, when the second load consumes electric power in a state where the oxidant gas is not supplied, the cathode oxidant gas to be reacted with the fuel gas supplied to the anode electrode is deficient. Thus the reaction is suppressed, suppression Erareru the consumption of fuel gas in the anode electrode. As a result, it is possible to shorten the time for filling the anode electrode with the fuel gas. Moreover, it is suppressed that a big electric current flows into a single cell by suppressing reaction. Therefore, the problem of corrosion of the constituent material of the fuel cell due to a large current flowing through the single cell (fuel cell that is insufficient as a whole / single cell that is partially insufficient) that is short of fuel gas is suppressed. be able to. Moreover, the increase in voltage is also suppressed.
Then, the control means determines whether or not the amount of the fuel gas in the anode electrode has become a predetermined value or more with the purge valve kept open , and after determining that the amount has exceeded the predetermined value, The valve is closed, and then the second load is disconnected by the load connecting / disconnecting means, and the oxidizing gas is supplied to the cathode electrode by the oxidizing gas supply means.

Further, the invention according to claim 2 of the present invention for solving the above-mentioned problems is that the fuel gas supplied from the fuel gas supply means to the anode electrode, and the oxidant gas supplied from the oxidant gas supply means to the cathode electrode, A fuel cell in which unit cells for generating electric power to be supplied to a load are stacked by the reaction, an extraction power limiting means that is electrically connected to the fuel cell and limits the electric power extracted from the fuel cell, and the fuel cell At the time of start-up, the fuel gas is supplied to the anode electrode by the fuel gas supply means while the power taken out from the fuel cell toward the load is restricted to be small by the take-out power restriction means, and then the oxidant gas and control means for supplying the oxidant gas to the cathode electrode by the supply means, the fuel is connected to the anode side of the outlet of the fuel cell exhaust Provided the road, a purge valve which is opened and closed controlled by the control means, and a dilution means for discharging to the outside by diluting a fuel gas discharged from the fuel discharge passage inside, wherein, the When the fuel gas is supplied to the anode electrode by the fuel gas supply means, the purge valve is opened, the oxidant gas in the anode electrode of the fuel cell is purged and discharged to the dilution means, and then the purge valve In a state where the fuel gas amount in the anode electrode is kept at a predetermined value or more with the valve kept open, the purge valve is closed after the judgment is made that the fuel gas amount in the anode electrode has become a predetermined value or more. The restriction by the power restriction means is released or relaxed .

  In the second aspect of the present invention, what is performed by the second load in the first aspect is performed by the extraction power limiting means. The take-out power limiting means is controlled so that the power taken out from the fuel cell and applied to the load is reduced at the time of startup.

According to a third aspect of the present invention, in the control means, whether or not the amount of the fuel gas in the anode electrode exceeds a predetermined value is determined by determining the fuel gas concentration in the anode electrode and the fuel measured by a timer. It performed based on a map of the supply time of the gas, characterized in Rukoto.

According to the third aspect of the present invention, whether or not the amount (concentration / pressure) of the fuel gas in the anode electrode has exceeded a predetermined value is determined by the fuel gas concentration in the anode electrode and a timer. since determined based on a map of the supply time of the fuel gas, it is possible to know whether the anode is filled with the fuel gas accurately. In addition, since the second load is disconnected before supplying the oxidant gas to the fuel cell, a large current is generated by the reaction between the oxidant gas supplied into the cathode electrode and the fuel gas supplied into the anode electrode. Can be prevented from flowing to the second load. Therefore, the resistance provided in the second load can be reduced. As described above, when supplying the fuel gas to the fuel cell, only a small current flows through the second load. Therefore, it is sufficient to provide a resistor having a magnitude corresponding to the small current. The cost can be reduced accordingly. In addition, since it is possible to accurately know whether the anode electrode is filled with fuel gas, when the fuel cell can supply power to the load without restrictions, or when the power can be supplied to the loads with relaxed restrictions Can be determined objectively and with good reproducibility.

According to a fourth aspect of the present invention, the power supplied to the load is generated by the reaction between the fuel gas supplied from the fuel gas supply means to the anode electrode and the oxidant gas supplied from the oxidant gas supply means to the cathode electrode. A fuel cell in which single cells are stacked, a second load that is electrically connected to the fuel cell and that consumes less power than the load, and a load connection / disconnection means for connecting / disconnecting the second load A purge valve that is provided in a fuel discharge path connected to an outlet on the anode side of the fuel cell, opens and closes the fuel discharge path, and internally dilutes fuel gas discharged from the fuel discharge path. And a diluting means for discharging the fuel cell system, wherein the control means for controlling the start of the fuel cell system supplies power from the fuel cell to the load when the fuel cell is activated. Do To the load and connecting step of connecting the second load to the fuel cell by disengaging means, together with supplying the fuel gas to the anode from the fuel gas supply means, said fuel opening the purge valve Purging and discharging the oxidant gas in the anode electrode of the battery to the diluting means, and whether the amount of the fuel gas in the anode electrode has reached a predetermined value or more with the purge valve open Determining whether or not, and after determining that the amount of the fuel gas in the anode electrode has reached a predetermined value or more, the purge valve is closed, and then the second load is connected by the load connecting / disconnecting means. and cutting prior to supply to the cathode of the oxidant gas, to run and a oxidant gas supply step of supplying the oxygen-containing gas to the cathode from the oxidant gas supply means And butterflies.

According to the fourth aspect of the present invention, when the fuel cell is started, the second load is connected to the fuel cell in the connection step, and then the fuel gas is supplied to the anode electrode and the purge valve is opened. The oxidant gas in the anode electrode is purged and discharged, and it is determined whether or not the amount of the fuel gas in the anode electrode exceeds a predetermined value with the purge valve kept open. At this time, the fuel gas supplied to the anode electrode reacts with the oxidant gas already present at the cathode electrode. However, this reaction is limited because no oxidant gas is supplied to the cathode electrode, and high voltage and fuel gas consumption are suppressed. When it is determined that the amount of fuel gas supplied into the anode electrode has reached a predetermined value or more, the purge valve is closed and the second load is disconnected by the load connecting / disconnecting means, and then the oxidant gas is supplied to the cathode electrode. To supply.

According to the first, second, and fourth aspects of the invention, the fuel cell can be favorably started.

  According to the third aspect of the present invention, the second load is disconnected before the large electromotive force is generated from the fuel cell by supplying the oxidant gas to the fuel cell. Can be reduced in size, and the cost can be reduced accordingly.

  According to the fourth aspect of the present invention, the timing for canceling or relaxing the power limit (power generation timing) can be appropriately determined by the fuel detection means.

[System configuration]
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a configuration diagram showing a fuel cell system according to the present embodiment.

  As shown in FIG. 1, the fuel cell system 1 includes a high-pressure hydrogen tank (fuel gas supply means) 11, a compressor (oxidant gas supply means) 12, a fuel cell 13, a shutoff valve 14, a switching valve 15, a purge valve 16, and A control unit (control means) 17 is mainly provided. Further, the fuel cell system 1 includes a main circuit 30 for supplying electric power generated by the fuel cell 13 to a load 31 such as a motor, an auxiliary external circuit 40 used when the fuel cell 13 is started, a fuel A dilution box 50 is provided for diluting and discharging the hydrogen gas that has not contributed to the reaction in the battery 13 to the outside. In the present embodiment, the high-pressure hydrogen tank 11 and the compressor 12 will be described as being included in the constituent elements of the fuel cell system 1.

In the high-pressure hydrogen tank 11, high-pressure hydrogen gas (fuel gas) of several tens of MPa is stored, and this hydrogen gas is supplied to the anode electrode (fuel electrode) of the fuel cell 13 by opening the shut-off valve 14. It has come to be. A tubular fuel gas supply path 21 that serves as a passage for hydrogen gas is provided between the high-pressure hydrogen tank 11 and the fuel cell 13, and the fuel gas supply path 21 is connected to the high-pressure hydrogen tank 11 side. In order from the fuel cell 13 to the fuel cell 13 side, a shut-off valve 14, an ejector 21A, and a pressure sensor 21B are provided. The pressure sensor 21 B is upstream of the fuel cell 13 (the inlet of the anode electrode), but may be provided on the downstream side (the outlet of the anode).

  The ejector 21A returns the hydrogen gas sent from the high-pressure hydrogen tank 11 and the hydrogen returned from the discharge port on the anode electrode side of the fuel cell 13 via the circulation flow path RP (including a circulation pump not shown). Gas is mixed and re-supplied to the fuel cell 13 to circulate hydrogen gas. Further, the pressure sensor 21B constantly detects the pressure in the fuel gas supply path 21 (pressure in the anode electrode of the fuel cell 13), and outputs a signal indicating the pressure value to the control unit 17. Here, the pressure sensor 21B detects the pressure in the anode (inlet of the anode), but since the pressure and the amount of hydrogen gas are in a proportional relationship, the amount of hydrogen gas is indirectly detected. Will contribute.

  The compressor 12 compresses air (oxidant gas) and supplies it to the cathode electrode (air electrode) of the fuel cell 13. And between the compressor 12 and the fuel cell 13, the tubular air supply path 22 used as the passage of air is provided.

  The fuel cell 13 is configured by laminating a plurality of single cells 13 a (for example, hundreds of layers) composed of a polymer electrolyte membrane, a cathode electrode, an anode electrode, and a separator (not shown). Electric power is generated by an electrochemical reaction between the supplied hydrogen gas and oxygen in the air supplied from the compressor 12 in each single cell 13a. Specifically, in the fuel cell 13, hydrogen gas or air sent from the high-pressure hydrogen tank 11 or the compressor 12 is a single cell located on the outlet side from the single cell 13 a located on the inlet side of the fuel cell 13. It is sent to 13a in order.

  Further, a load 31 is connected to the fuel cell 13 via the main circuit 30, and the fuel cell 13 is operated / stopped by turning the load 31 ON / OFF (driving / stopping) by the control unit 17. The current is taken out from the fuel cell 13 and the take-out is stopped. Incidentally, when the fuel cell system 1 has a large amount of air corresponding to the power consumption, that is, when the power consumption is large so that the power corresponding to the power consumption consumed by the load 31 can be extracted from the fuel cell 13 (so that it can generate power). It is assumed that a large amount of air is supplied from the compressor 12 to the fuel cell 13 when the power consumption is low. Further, it is assumed that a large amount of hydrogen is supplied along with an increase in the amount of hydrogen consumed by the fuel cell 13. Note that due to the nature of the fuel cell 13, even if abundant air and hydrogen are supplied to the fuel cell 13, the fuel cell 13 does not generate power unless the load 31 consumes power (neither oxygen nor hydrogen is consumed).

  Next, in this embodiment, in addition to the main circuit 30 described above, an auxiliary external circuit 40 is connected to the fuel cell 13. Here, the auxiliary external circuit 40 is a circuit that mainly includes a resistor (second load) 41 and a switch (load connecting / disconnecting means) 42 that consume less power than the load 31. The fuel cell 13 and the auxiliary external circuit 40 are electrically connected / disconnected (connected / disconnected) by turning on / off the switch 42 by the control unit 17.

  The shut-off valve 14 is appropriately opened and closed by the control unit 17 to switch supply / stop of hydrogen gas from the high-pressure hydrogen tank 11 to the fuel cell 13.

  The switching valve 15 is a valve that is appropriately opened and closed by the control unit 17, and is provided in the scavenging flow path 23 connected so as to straddle the downstream portion of the cutoff valve 14 in the fuel gas supply path 21 and the air supply path 22. It has been. When the switching valve 15 is closed, the air from the compressor 12 is supplied only to the cathode electrode side of the fuel cell 13 via the air supply path 22. When the switching valve 15 is opened, the compressor 12 is supplied. In addition to being supplied to the cathode electrode side of the fuel cell 13, the air from is also supplied to the anode electrode side of the fuel cell 13 via the scavenging flow path 23 and the fuel gas supply path 21.

  The purge valve 16 is a valve that is appropriately opened and closed by the control unit 17, and is provided in the fuel gas discharge path 24 connected to the anode electrode side outlet of the fuel cell 13. Then, by opening both the purge valve 16 and the switching valve 15, the scavenging of the anode electrode side is performed.

The dilution box (dilution means) 50 combines the hydrogen gas discharged from the fuel gas discharge path 24 and the air discharged from the air discharge path 25 connected to the cathode electrode side outlet of the fuel cell 13. This is a device for diluting and discharging hydrogen gas to the outside by mixing inside.

  The control unit 17 includes a CPU, a memory (ROM / RAM), an input / output interface, various electronic circuits, and the like, and has a function of driving / stopping the compressor 12 or changing the rotation speed thereof, a shutoff valve 14, and switching. It mainly has a function of opening and closing the valve 15 and the purge valve 16 and a function of turning on and off the switch 42 and the load 31 and appropriately controls these devices when the fuel cell system 1 is started or stopped. is doing. The function of the control unit 17 at the time of starting the system will be briefly described. The control unit 17 prepares the various functions described above by turning on an ignition switch (IG-ON) (not shown). After the preparation, first, the switch 42 is turned ON and the shut-off valve 14 is opened to supply hydrogen to the anode electrode. When the hydrogen concentration exceeds a predetermined value, the switch 42 is turned OFF, and then the compressor 12 is driven. It has a function of supplying air to the cathode electrode. Specifically, at the time of system startup, the control unit 17 operates based on the flowchart shown in FIG.

[Startup behavior]
The operation of the control unit 17 at the time of starting the system will be described below with reference to the flowchart shown in FIG. 2 and FIG. In the drawings to be referred to, FIG. 2 is a flowchart showing the operation of the control unit at the time of starting the system, and FIG. 3 is a map used for deriving the hydrogen concentration from the purge time.

  The control unit 17 prepares various functions, for example, when a driver turns on an ignition switch (not shown) (step S1). Specifically, a program, a map, and the like written in the ROM of the control unit 17 are read into the CPU to prepare each function described above. At this stage, the main circuit 30 is not electrically connected to the fuel cell 13. If each function is prepared by step S1, next, the control part 17 will turn ON the switch 42, and will electrically connect the auxiliary | assistant external circuit 40 to the fuel cell 13 (step S2). After step S2, the control unit 17 opens the shut-off valve 14, thereby supplying hydrogen gas from the high-pressure hydrogen tank 11 to the anode electrode of the fuel cell 13 (step S3). At the same time, the control unit 17 opens the purge valve 16 to purge and discharge the air in the anode electrode of the fuel cell 13 to the dilution box 50 (step S4). As a result, the air (or inert gas) filled in the anode electrode before starting is discharged from the anode electrode, and the hydrogen concentration increases (hydrogen is spread and filled in the anode electrode).

  While purging in step 4, the control unit 17 measures the supply time of hydrogen with a timer (not shown). Based on this supply time and the map shown in FIG. It is determined whether or not the gas amount (concentration) has reached a predetermined value or more (step S5). That is, in step S5, it is determined whether each single cell 13a is filled with hydrogen. Note that the predetermined value, which is a determination value as to whether or not the fuel cell 13 is filled with hydrogen, is determined in advance by experiments or the like from the viewpoint of not shortening the life of the fuel cell 13. In this step S5, if the control part 17 judges that the density | concentration of hydrogen gas is less than predetermined value (No), it will repeat the process of step S5 again. When it is determined that the hydrogen gas concentration has become equal to or higher than the predetermined value (Yes), the control unit 17 closes the purge valve 16. The map in FIG. 3 for determining the amount of hydrogen in the anode electrode from the supply time is created in advance based on the results of experiments and the like, and is stored in advance in a memory (not shown) in the control unit 17. . Here, the timer and the map of FIG. 3 correspond to fuel detection means for detecting the amount of fuel gas. Incidentally, the order of steps S3 and S4 in the flowchart of FIG. 2 may be reversed. Further, step S4 to step S6 may be "open the purge valve only for a predetermined time when the hydrogen concentration is equal to or higher than a predetermined value". The predetermined time in this case can be calculated based on the volume of the gas flow path inside the fuel cell 13, the flow rate of the supplied gas, or the like, or can be determined in advance by experiments.

  By the way, when hydrogen is supplied to the anode electrode in step S3, this hydrogen causes an electrochemical reaction with the air already existing in the cathode electrode, thereby generating a voltage. However, since the auxiliary external circuit 40 is electrically connected to the fuel cell 13 in step S2, it is suppressed that a current flows through the auxiliary external circuit 40 and the voltage of the single cell 13a increases. In addition, when hydrogen is supplied to the anode electrode in step S3, both the hydrogen and oxygen are present in the anode electrode in a concentrated state, and there is a concern about deterioration of the constituent material of the fuel cell 13 due to the homopolar power generation. However, since the auxiliary external circuit 40 is electrically connected to the fuel cell 13 in step S2, deterioration of the anode electrode due to homopolar power generation is prevented. That is, the auxiliary external circuit 40 prevents corrosion of the separator and the membrane electrode structure.

  Incidentally, although the fuel cell 13 continues to generate power when the auxiliary external circuit 40 is connected, air is not supplied from the compressor 12 to the cathode electrode at the stage where Step S4 and Step S5 are executed. For this reason, the cathode electrode immediately becomes deficient in oxygen, and the electrochemical reaction is suppressed (converged). As a result, the consumption of hydrogen is suppressed, and the time taken to fill the anode electrode with hydrogen can be shortened. Further, since the reaction is suppressed, an increase in voltage is also suppressed, and further, a current flowing through the auxiliary external circuit 40 is also suppressed.

  The voltage of the fuel cell 13 and the current flowing through the auxiliary external circuit 40 will be described. When the anode electrode is filled with hydrogen, the voltage of the fuel cell 13 increases and the current flowing through the auxiliary external circuit 40 is increased. Also going in the direction of rising. On the other hand, as oxygen in the cathode electrode is consumed, the voltage of the fuel cell 13 tends to decrease, and the current flowing through the auxiliary external circuit 40 also decreases. For this reason, in step S3-step S5 of this embodiment, the rise in both voltage and current is suppressed as a whole.

  As a result, when the catalyst is left at a high voltage for a long time, the activity of the catalyst is reduced, or a large current is forced to flow in a situation where hydrogen is insufficient in the fuel cell 13, whereby the structure of the fuel cell 13 is Problems such as corrosion can be suppressed. In addition, consumption of the supplied hydrogen is suppressed, so that hydrogen can be quickly supplied to the anode electrode.

  In step S5, when the hydrogen concentration becomes a predetermined value or more, the control unit 17 closes the purge valve 16 (step S6), and then turns off the switch 42 to electrically disconnect the auxiliary external circuit 40 from the fuel cell 13. (Step S7).

  After step S7, the control unit 17 drives the compressor 12 to supply air to the fuel cell 13 (step S8). Then, it is determined whether or not the open cell voltage (OCV) of the fuel cell 13 in a state where the two circuits 30 and 40 are not connected to each other is equal to or higher than a predetermined value (step S9). That is, in step S9, it is determined whether or not air has spread to each single cell 13a (whether or not it is filled with air). In step S9, when the control unit 17 determines that the open cell voltage is less than the predetermined value (No), the control unit 17 repeats the process of step S9 again and determines that the open cell voltage is equal to or higher than the predetermined value (Yes). ), Power generation is started by turning on the load 31. The open cell voltage is detected by a voltmeter (not shown) or the like. According to this, the power generation timing of the fuel cell 13 can be appropriately determined.

  By the way, as described above, when a large current flows through the fuel cell 13 with the anode electrode short of fuel, problems such as carbon corrosion occur. However, even if a large current flows in a state where the cathode electrode is deficient in oxidant gas (oxygen deficiency), the constituent members of the fuel cell 13 have no oxidant instead of oxygen, so that the cathode electrode is deficient in oxygen. The corrosion reaction (reduction reaction) of the constituent members of the fuel cell 13 does not occur. Therefore, in this embodiment, a large current flows before each single cell 13a is filled with fresh air (air supplied by the compressor 12) or before the single cell 13a is filled with fresh air. Even so, in the state where the anode electrode is filled with hydrogen, it is considered that corrosion of carbon and other components of the fuel cell 13 are unlikely to occur. Considering this point, when each single cell 13a is filled with hydrogen, supply of air to the cathode electrode is started, and the main circuit 30 is electrically connected to the fuel cell 13 to supply power to the load 31. You may make it do.

[Operation when stopped]
Next, the operation of the control unit 17 when the system is stopped will be described with reference to the flowchart shown in FIG. 4 and FIG. Note that the operation of the control unit 17 at the time of the stop is only indirectly related to the present invention, and will be described simply as an example. In the drawings to be referred to, FIG. 4 is a flowchart showing the operation of the control unit when the fuel cell system is stopped.

  When the control unit 17 inputs a system stop request (step S11: Yes), the control unit 17 closes the shutoff valve 14 (shutoff valve OFF, step S12), and determines whether or not scavenging in the anode electrode of the fuel cell 13 is performed. (Step S13). Whether or not scavenging is performed is determined by, for example, whether or not the outside air temperature detected by a temperature sensor (not shown) is equal to or lower than a predetermined value (the water remaining in the flow path of the fuel cell system 1 may be frozen). Or not). It is also possible to acquire weather forecast data from the outside through a network and determine whether or not to perform scavenging based on this data.

  If the control unit 17 determines that the anode scavenging is not performed in step S13 (No), the fuel cell 13 until the pressure PH in the anode electrode (the pressure sensor (not shown) detects the pressure at the outlet of the anode electrode) reaches a predetermined value P1. (Step S14) When hydrogen is consumed and the pressure reaches the predetermined value P1, the load 31 is turned off (step S15) to stop the power generation by the fuel cell 13. In addition, the electric power generated during this time is not consumed by the load 31, but can be stored in a power storage means (not shown). After step S15, when the control unit 17 determines that the predetermined time T1 has elapsed (step S16: Yes), it determines that scavenging of the cathode side by the compressor 12 has been completed, and opens the purge valve 16 (purge valve 16). ON, step S17). Thereby, the gas in the anode electrode is discharged to the dilution box 50 by the residual pressure (predetermined value P1) of the hydrogen gas in the anode electrode.

  On the other hand, when the control unit 17 determines in step S13 that scavenging in the anode electrode is performed due to low temperature or the like (Yes), the pressure PH in the anode electrode becomes a pressure lower than the predetermined value P1. The power generation by the fuel cell 13 is continued until the predetermined value P2 is reached (step S18). When the predetermined value P2 is reached, the load 31 is turned off (step S19) to stop the power generation by the fuel cell 13. After step S19, the control unit 17 opens both the switching valve 15 and the purge valve 16 (switching valve / purge valve ON, step S20), and supplies air from the compressor 12 to both the anode electrode and the cathode electrode. Let As a result, both of these systems are scavenged.

  After step S20, when the control unit 17 determines that the predetermined time T2 has elapsed (step S21: Yes), the control unit 17 determines that scavenging of the anode electrode and the cathode electrode is completed, and closes the switching valve 15 (switching valve). OFF, step S22). As a result, the supply of air from the compressor 12 to the anode electrode is stopped.

  After step S22 or after step S17, the controller 17 determines whether or not the pressure PH of the anode electrode is equal to or less than a predetermined value P3 that is lower than the predetermined values P1 and P2 and higher than the atmospheric pressure. Is determined (step S23). If it is determined in step S23 that the pressure PH is equal to or lower than the predetermined value P3 (Yes), the control unit 17 closes the purge valve 16 (purge valve OFF, step S24), and then stops supplying air by the compressor 12. (Air supply OFF, step S25), and the operation according to this flowchart is terminated.

According to the above, in the present embodiment, the fuel cell system 1 (fuel cell 13) can be favorably started as follows.
When the fuel cell 13 is started up, the auxiliary external circuit 40 is connected to the fuel cell 13 and then hydrogen gas is supplied to the fuel cell 13 to suppress the reaction between hydrogen gas and oxygen in the air on the cathode electrode side. As a result, the time required to fill the anode electrode with hydrogen gas can be shortened.
When air is supplied to the fuel cell 13 after supplying hydrogen, a large electromotive force is generated from the fuel cell 13. In this embodiment, the auxiliary external circuit 40 is connected to the fuel cell 13 before supplying air to the fuel cell 13. Therefore, the resistor 41 provided in the auxiliary external circuit 40 can be reduced in size, and the cost can be reduced accordingly.
Further, by detecting the hydrogen concentration, it is possible to more appropriately determine the power generation timing of the fuel cell 13 at the time of start-up (timing for disconnecting the auxiliary external circuit 40 or timing for releasing or relaxing the restriction on the current described later). .

In addition, by disconnecting the auxiliary external circuit 40 before starting the power generation by the fuel cell 13, it becomes possible to check the open cell voltage, so that the power generation timing of the fuel cell 13 (the power to the load 31) Supply timing) can be appropriately determined. In addition, by checking the open cell voltage, it is possible to prevent leakage due to degradation of the polymer electrolyte membrane or other reasons, such as the occurrence of cross leaks (hydrogen and air permeate through the thin polymer electrolyte membrane). Can be confirmed.
Further, in the present invention, since hydrogen is supplied to the fuel cell 13 in advance without supplying air, it can be said that it is essentially difficult to run out of fuel and essentially difficult to attain high voltage. . For this reason, the fuel cell 13 can be favorably started. In addition, since it is essentially difficult to run out of fuel and essentially difficult to attain a high voltage, the timing of disconnecting the auxiliary external circuit 40 can be advanced.

The present invention is not limited to the above-described embodiment, and can be implemented in various forms.
For example, in the above-described embodiment, in order to know the hydrogen concentration in the anode electrode, in other words, to know whether the anode electrode is filled with hydrogen (in order to know the start timing of step S7 / step S8), Although the timer and the map of FIG. 3 are used, the hydrogen concentration (amount of hydrogen) may be detected by the pressure sensor 21B and the map. The reason why the hydrogen concentration can be detected by the pressure is that the pressure at the anode electrode of the fuel cell 13 is related to the amount of hydrogen. Further, in step S4 of FIG. 2, the purge valve 14 is opened for a predetermined time to perform the purge, and after the purge valve 14 is closed and the purge is completed, the pressure sensor 21B detects an increase in the pressure of the anode electrode to detect the hydrogen concentration. You may make it do. Further, instead of indirectly detecting the amount (concentration) of hydrogen, the amount (concentration) of hydrogen may be directly detected by a hydrogen concentration sensor. Maps can also be replaced with functions and tables.

  Further, in the present embodiment, it has been described that the fuel cell 13 is started from a state where the anode electrode is scavenged and the anode electrode is filled with air. However, the present invention is applied when the anode electrode is not scavenged. May be applied. That is, the present invention may be applied to the case where anode scavenging is not performed in step S13 in the flowchart of FIG. Even in this case, since no air is supplied until the anode electrode rises to a predetermined pressure, consumption of hydrogen can be suppressed, and the anode electrode pressure can be quickly increased.

  Further, the resistor 41 as the second load is not a simple resistor but may be one that generates something other than heat (light, vibration, rotational force), such as an illumination lamp. Further, the second load may be a power storage means for storing electric power generated by the fuel cell 13 at the time of startup.

Further, in place of (or in combination with) the configuration including the auxiliary external circuit 40 as shown in FIG. 1, as shown in FIG. 5, an extraction for limiting the power (current) extracted from the fuel cell 13 to the main circuit 30. The current limiting unit (extraction power limiting unit) 32 may be provided, and the current supplied to the load 31 by the extraction current limiting unit 32 may be limited to a small amount at the time of startup. In this case, “auxiliary external circuit connection” in step S2 of FIG. 2 may be read as “restriction of the electric power extracted from the fuel cell by the extraction current limiting means”. Also, “auxiliary external circuit disconnection” in step S7 may be read as “removal (relaxation) of restriction by extraction current restriction means”. By the way, the current taken out in a limited manner is configured to be stored in a power storage means such as a capacitor or a secondary battery, or is configured to be consumed by a device with low power consumption among various power consuming devices constituting the load 31. It can be done. Here, the limit amount of the extraction current (electric power) is set in consideration of the prevention of the high voltage of the single cell 13a at the time of start-up and the low consumption of hydrogen when filling the anode with hydrogen. .
FIG. 5 shows a configuration in which current is always taken out from the fuel cell 13 via the extraction current limiting means 32 and supplied to the load 31. However, the extraction current limiting means 32 is changed only at start-up by switching by a switch or the like. It may be interposed between the load 31 and the fuel cell 13.

  Further, in the flowchart of FIG. 4, when anode scavenging is performed, the auxiliary external circuit 40 is electrically connected to the fuel cell 13 after step S <b> 19 to prevent problems due to homopolar power generation during anode scavenging. You may do it. The connected auxiliary external circuit 40 may be disconnected after the anode electrode is replaced with air (for example, after step S21). Of course, in the case of the configuration including the extraction current limiting means 32 shown in FIG. 5 as well as the configuration of the auxiliary external circuit 40, the extraction current limiting means 32 causes a problem due to homopolar power generation during anode scavenging. Can be prevented.

It is a block diagram which shows the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the control part at the time of starting of a fuel cell system. It is a map utilized in order to derive | require hydrogen concentration from purge time. It is a flowchart which shows operation | movement of the control part at the time of a stop of a fuel cell system. FIG. 2 is a block diagram showing a configuration including an extraction current limiting unit instead of the auxiliary external circuit of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 11 High pressure hydrogen tank 12 Compressor 13 Fuel cell 13a Cell 14 Shut-off valve 15 Switching valve 16 Purge valve 17 Control part 21B Pressure sensor 30 Main circuit 31 Load 32 Extraction current limiting means (extraction electric power limitation means)
40 Auxiliary external circuit 41 Resistance (second load)
42 switch 50 dilution box

Claims (4)

A fuel cell in which single cells for generating electric power to be supplied to a load are stacked by a reaction between a fuel gas supplied from the fuel gas supply means to the anode electrode and an oxidant gas supplied from the oxidant gas supply means to the cathode electrode When,
A second load electrically connected to the fuel cell and consuming less power than the load;
Load connecting / disconnecting means for connecting / disconnecting the second load;
When starting the fuel cell, before supplying electric power from the fuel cell to the load, the fuel cell supplying unit connects the second load electrically to the fuel cell by the load connecting / disconnecting unit. Control means for supplying the fuel gas to the anode electrode and then supplying the oxidant gas to the cathode electrode by the oxidant gas supply means;
A purge valve provided in a fuel discharge path connected to an outlet on the anode electrode side of the fuel cell and controlled to be opened and closed by the control means;
Dilution means for diluting the fuel gas discharged from the fuel discharge passage inside and discharging it outside,
Equipped with a,
The control means includes
When supplying the fuel gas to the anode electrode by the fuel gas supply means, the purge valve is opened, and the oxidant gas in the anode electrode of the fuel cell is purged and discharged to the dilution means, and then the purge is performed. It is determined whether or not the amount of the fuel gas in the anode electrode has reached a predetermined value or more with the valve kept open.After determining that the amount has exceeded the predetermined value, the purge valve is closed, and then the The fuel cell system , wherein the second load is disconnected by a load connecting / disconnecting means before the oxidant gas is supplied to the cathode electrode . A fuel cell in which single cells for generating electric power to be supplied to a load are stacked by a reaction between a fuel gas supplied from the fuel gas supply means to the anode electrode and an oxidant gas supplied from the oxidant gas supply means to the cathode electrode When,
Extracted power limiting means that is electrically connected to the fuel cell and limits the power extracted from the fuel cell;
When the fuel cell is started, the fuel gas is supplied to the anode electrode by the fuel gas supply unit while the power extracted from the fuel cell toward the load is limited to be small by the extraction power limiting unit, and then the fuel cell is supplied. Control means for supplying the oxidant gas to the cathode electrode by an oxidant gas supply means ;
A purge valve provided in a fuel discharge path connected to an outlet on the anode electrode side of the fuel cell and controlled to be opened and closed by the control means;
Dilution means for diluting the fuel gas discharged from the fuel discharge passage inside and discharging it outside,
Equipped with a,
The control means includes
When supplying the fuel gas to the anode electrode by the fuel gas supply means, the purge valve is opened, and the oxidant gas in the anode electrode of the fuel cell is purged and discharged to the dilution means, and then the purge is performed. It is determined whether or not the amount of the fuel gas in the anode electrode has reached a predetermined value or more with the valve kept open.After determining that the amount has exceeded the predetermined value, the purge valve is closed, and then the A fuel cell system, wherein the restriction by the extracted power restriction means is released or relaxed . According to claim 1 or 2 fuel cell system according,
The control means determines whether or not the amount of fuel gas in the anode electrode exceeds a predetermined value based on a map of the fuel gas concentration in the anode electrode and the fuel gas supply time measured by a timer. the fuel cell system according to claim Rukoto performed Te. A fuel cell in which single cells for generating electric power to be supplied to a load are stacked by a reaction between a fuel gas supplied from the fuel gas supply means to the anode electrode and an oxidant gas supplied from the oxidant gas supply means to the cathode electrode When,
A second load electrically connected to the fuel cell and consuming less power than the load;
Load connecting / disconnecting means for connecting / disconnecting the second load;
A purge valve that is provided in a fuel discharge path connected to an outlet of the fuel cell on the anode electrode side and opens and closes the fuel discharge path;
A dilution means for diluting the fuel gas discharged from the fuel discharge path and discharging it to the outside, and a starting method of the fuel cell system comprising:
The control means for controlling the start of the fuel cell system, before supplying power from the fuel cell to the load at the start of the fuel cell,
A connecting step of connecting the second load to the fuel cell by the load connecting / disconnecting means;
Supplying the fuel gas from the fuel gas supply means to the anode electrode, and opening the purge valve to purge and dilute the oxidant gas in the anode electrode of the fuel cell to the dilution means;
Determining whether the amount of the fuel gas in the anode electrode is equal to or greater than a predetermined value while the purge valve remains open;
After determining that the amount of the fuel gas in the anode electrode has reached a predetermined value or more, the purge valve is closed, and then the second load is applied by the load connecting / disconnecting means to the cathode electrode of the oxidant gas. Cutting before supplying to
An oxidant gas supply step of supplying the oxidant gas from the oxidant gas supply means to the cathode electrode.

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