JP5007287B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system that performs scavenging when the system is stopped.

In the fuel cell system, various scavenging techniques for removing residual water when the system is stopped have been proposed in order to prevent freezing of water remaining in the system when used in a low temperature environment. For example, Patent Document 1 proposes a technique for performing a scavenging of a device such as a humidifier in addition to scavenging of the inside of the fuel cell to prevent a decrease in below-freezing startability due to moisture freezing.
Japanese Patent Laid-Open No. 2002-313395 (paragraphs 0035 and 0039, FIG. 2)

  By the way, since the power generation of the fuel cell is stopped during the scavenging, the energy used in the scavenging uses the electric power stored in the battery or the like. However, since power is limited in a battery or the like, there is a problem that energy consumption increases when scavenging is performed while preventing the device from freezing as described in Patent Document 1.

  The present invention solves the above-described conventional problems, and provides a fuel cell system capable of suppressing energy consumption during scavenging in a system that performs scavenging by supplying scavenging gas to a fuel cell and a humidifier. For the purpose.

The invention according to claim 1, the anode gas to the anode gas passage, and a fuel cell for generating electric power by supplying the cathode gas to the cathode gas passage, provided in the cathode gas passage, said one of said cathode gas A humidifier for humidifying the supply gas supplied to the fuel cell by exchanging moisture between an exhaust gas discharged from the fuel cell and a supply gas supplied to the fuel cell of the cathode gas ; A scavenging gas supply means for supplying a scavenging gas to the inside of the fuel cell and the humidifier, wherein the integrated power generation amount during operation of the fuel cell and the amount of water in the humidifier Humidifier internal water content acquisition means for acquiring the internal moisture content of the humidifier using the accumulated power generation based on a predetermined map of the relationship with the internal moisture content of the humidifier, and the humidifier internal water Based on the humidifier internal water content obtained by the obtaining means, and the scavenging gas flow rate determining means for determining the flow rate of the scavenging gas supplied to the humidifier, and bypassing the flow path of the feed gas side of the humidifier A first humidifier bypass flow path for circulating the scavenging gas, and a second humidifier bypass flow path for circulating the scavenging gas by bypassing the exhaust gas side flow path of the humidifier, During the scavenging of the cathode gas flow path, the scavenging gas bypasses the exhaust gas-side flow path when scavenging the supply gas-side flow path of the humidifier, and the second humidifier bypass flow After passing through the passage, when scavenging the exhaust gas side passage of the humidifier, the scavenging gas is passed through the first humidifier bypass passage while bypassing the supply gas side passage. It is characterized by.

According to this, since the flow rate of the scavenging gas is determined based on the moisture content inside the humidifier, it is possible to prevent the scavenging gas from being supplied unnecessarily and to suppress energy consumption. In addition, since the humidifier is not excessively dried, it is possible to maintain a predetermined amount of water inside the humidifier at the next start-up of the fuel cell, and to maintain the humidification performance at the next start-up. It becomes possible. It is also possible to prevent water from freezing inside the humidifier due to insufficient drying.
Furthermore, when scavenging the flow path on the supply gas side of the humidifier, the scavenging off gas is circulated through the second humidifier bypass flow path, so that moisture contained in the scavenging gas scavenged in the flow path on the supply gas side is discharged. It is possible to prevent the supply gas side channel from becoming wet again by exchanging moisture from the gas side channel to the supply gas side channel. Further, when scavenging the flow path on the exhaust gas side of the humidifier, the scavenging gas is circulated through the first humidifier bypass flow path, so that moisture contained in the scavenging off-gas scavenged through the flow path on the exhaust gas side is supplied. It is possible to prevent moisture from being exchanged between the gas side flow path and the exhaust gas side flow path. Therefore, it becomes possible to scavenge the humidifier efficiently.

In the invention according to claim 2, the humidifier humidifies the supply gas supplied from the scavenging gas supply means to the fuel cell by the exhaust gas discharged from the fuel cell, and the map is When the accumulated power generation amount is small, the moisture content inside the humidifier is small. As the cumulative power generation amount increases, the moisture content inside the humidifier increases, and when the cumulative power generation amount increases, the moisture content inside the humidifier converges. It is set as follows.

The invention according to claim 3 is characterized in that scavenging of the humidifier is executed before the cathode scavenging is performed.

  When scavenging the humidifier after scavenging the cathode, the scavenging gas that scavenged the humidifier again flows into the fuel cell even though the inside of the fuel cell is dried by the cathode scavenging. End up. According to the invention of claim 4, since the cathode scavenging is performed after scavenging the humidifier, it is possible to prevent the inside of the fuel cell from becoming wet again with the moisture of the humidifier.

The invention according to claim 4 has a fuel cell bypass channel that bypasses the fuel cell, and when scavenging the humidifier, the scavenging gas is circulated through the fuel cell bypass channel, and the fuel cell When scavenging gas, the scavenging gas is circulated bypassing the humidifier.

  According to this, since the fuel cell is bypassed when scavenging the humidifier, introduction of wet scavenging gas into the fuel cell can be suppressed, and energy consumption used for scavenging the fuel cell can be reduced. In addition, since the fuel cell is not subjected to pressure loss during scavenging of the humidifier, energy consumption when scavenging the humidifier can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the energy consumption at the time of scavenging can be suppressed in the system which scavenges by supplying scavenging gas to a fuel cell and a humidifier.

( Reference example )
Figure 1 is a whole configuration diagram showing a fuel cell system, Figure 2 is a flow chart for determining the moisture content of the humidifier, FIG. 3 is a map showing the relationship between the cumulative generated current amount and a humidifier internal water content, Figure 4 is scavenging control FIG. 5 is a sub-flowchart showing the scavenging execution determination unit of FIG. 4, FIG. 6 is a map showing the relationship between the moisture content inside the humidifier and the flow rate during scavenging of the humidifier, and FIG. It is a time chart which shows operation | movement. In the embodiment described later , a case where it is mounted on a fuel cell vehicle will be described as an example. However, the present invention is not limited to a vehicle, and is not limited to a vehicle. It can be applied to everything from stationary ones.

As shown in FIG. 1, the fuel cell system 1A, the fuel cell 10, the cathode system 20, the anode system 30, the scavenging system 40 is constituted by a control system 50.

  The fuel cell 10 has, for example, a structure in which a solid polymer electrolyte membrane is sandwiched between a cathode including a catalyst and an anode, and a plurality of single cells are sandwiched between a pair of conductive separators in the thickness direction. Yes. In addition, an anode channel 10a through which hydrogen (anode gas) flows is formed in the separator facing the anode, and a cathode channel 10c through which air (cathode gas) flows is formed in the separator facing the cathode. Yes. At the anode, when hydrogen is supplied, hydrogen ions permeate the solid polymer electrolyte membrane through the action of the catalyst and move to the cathode, and the electrons are externally loaded 60 (running motor (not shown), air pump 21 and the like). Through to the cathode. At the cathode, hydrogen ions and electrons react with oxygen contained in the supplied air to generate water by the action of the catalyst.

  The cathode system 20 includes an air pump 21, a humidifier 22, a back pressure valve 23, pipes 24a to 24d, and the like.

  The air pump 21 is composed of a mechanical supercharger or the like driven by a motor, and has a function of taking outside air (air) and pressurizing it.

  The humidifier 22 has a flow path 22a through which supply gas (cathode gas, dry air) flows, and a flow path 22b through which exhaust gas (cathode off-gas, wet air) from the cathode of the fuel cell 10 flows. And has a function of humidifying the supply gas supplied from the air pump 21. The degree of humidification at this time is set to a humidification amount in which the solid polymer electrolyte membrane is humidified so that the power generation performance is satisfactorily exhibited in the fuel cell 10. For example, the humidifier 22 is configured by bundling a plurality of water-permeable hollow fiber membranes, and the supply gas flows through one of the outer and inner sides of each hollow fiber membrane, and the exhaust gas flows through the other. The supply gas is humidified by the exhaust gas.

  Further, the humidifier 22 has a pipe 24 a extending from the air pump 21 connected to the supply gas inlet 22 a 1 and a pipe 24 b extending from the cathode side inlet 10 c 1 of the fuel cell 10 connected to the supply gas outlet 22 a 2. Further, in the humidifier 22, a pipe 24c extending from the cathode side outlet 10c2 of the fuel cell 10 is connected to an exhaust gas inlet 22b1, and a pipe 24d extending from a back pressure valve 23 described later is connected to an exhaust gas outlet 22b2. .

  The back pressure valve 23 is composed of, for example, a butterfly valve whose opening degree can be adjusted, and has a function of appropriately adjusting the pressure of air supplied to the cathode of the fuel cell 10.

Incidentally, the cathode gas channel is formed by the flow path of the mosquito cathode passage 10c and the pipe 24 a to 24 d.

  The anode system 30 includes a hydrogen tank 31, an ejector 32, a gas-liquid separator 33, a drain valve 34, a purge valve 35, an air discharge valve 36, pipes 37a to 37g, and the like.

  The hydrogen tank 31 includes an electromagnetically operated shut-off valve, and is a container in which high-purity hydrogen is compressed at a high pressure. The piping 37a connected to the hydrogen tank 31 is provided with a pressure reducing valve, etc., so that the high-pressure hydrogen supplied from the hydrogen tank 31 is reduced to a predetermined value and supplied to an ejector 32 described later. Has been.

  The ejector 32 is a vacuum pump that recirculates unreacted hydrogen discharged from the anode-side outlet 10a2 of the fuel cell 10 back to the anode-side inlet 10a1 of the fuel cell 10 via the pipes 37c, 37d, and 37b. It is a kind.

  The gas-liquid separator 33 is provided between the pipe 37 c and the pipe 37 d and has a function of storing water discharged from the outlet 10 a 2 on the anode side of the fuel cell 10. This water is generated water that has permeated from the cathode to the anode through the solid polymer electrolyte membrane.

  The drain valve 34 is provided in a pipe 37e connected to the bottom of the reservoir of the gas-liquid separator 33, and has a function of discharging water accumulated in the gas-liquid separator 33 by opening the valve.

  The purge valve 35 is provided in a pipe 37f that is branched and connected to the pipe 37d. For example, the purge valve 35 periodically removes impurities accumulated in the circulation flow path (the anode flow path 10a and the pipes 37b to 37d) during operation. Has the function of discharging outside the vehicle. Impurities include nitrogen and generated water contained in air that has permeated from the cathode to the anode through the solid polymer electrolyte membrane.

  The air discharge valve 36 is provided in a pipe 37g branched and connected to the pipe 37d, and has a function of discharging water remaining in the circulation flow path (the anode flow path 10a, the pipes 37b to 37d) by opening the valve. Have.

The pipe 37f is formed with a diameter larger than the diameter of the pipe 37e, the pipe 37g is formed with a diameter larger than the diameter of the pipe 37f, the pipe 37e has a small flow rate, the pipe 37f has a medium flow rate, and the pipe 37g. Is configured so that a large amount of fluid flows. In the pipe 37d, the pipe 37g is connected on the downstream side of the gas-liquid separator 33, and the pipe 37f is connected on the downstream side of the pipe 37g. The anode gas channel is formed by the flow path of the A node passage 10a and the pipe 37B～37d.

Further, the fuel cell system 1A, the diluter 25 is provided through the pipe 24e to the downstream of the back pressure valve 23. The diluter 25 has a space for retaining hydrogen, and has a function of diluting and discharging the hydrogen discharged from the anode system 30 to a predetermined hydrogen concentration or less with the cathode off-gas discharged from the cathode system 20.

  The scavenging system 40 includes air introducing means 41 for introducing air (air) as a scavenging gas to the anode side, and a humidifier bypass means 42 for circulating the air (air) as the scavenging gas by bypassing the humidifier 22. ing.

  The air introduction means 41 includes an air introduction pipe 41a and an air introduction valve 41b. One end of the air introduction pipe 41 a is connected to a pipe 24 a between the air pump 21 and the humidifier 22, and the other end is connected to a pipe 37 b between the ejector 32 and the inlet 10 a 1 of the fuel cell 10. The air introduction valve 41b is provided in the air introduction pipe 41a and has a function of blocking the flow path of the air introduction pipe 41a by being closed.

  The humidifier bypass means 42 includes a humidifier bypass pipe 42a and a humidifier bypass valve 42b. One end of the humidifier bypass pipe 42a is connected to a pipe 24a between one end of the air introduction pipe 41a and the humidifier 22, and the other end is connected to a pipe 24b between the humidifier 22 and the inlet 10c1 of the fuel cell 10. It is connected. The humidifier bypass valve 42b is provided in the humidifier bypass pipe 42a and has a function of blocking the flow path of the humidifier bypass pipe 42a when the valve is closed. Note that, by opening the humidifier bypass valve 42b, almost the entire amount of the scavenging gas flows through the humidifier bypass pipe 42a.

In addition, the structure of the humidifier bypass means 42 is not limited to this , For example, the piping 24a between the inlet 22a1 of the humidifier 22 and one end of the humidifier bypass piping 42a, the outlet 22a2 of the humidifier 22 And a configuration in which a shutoff valve is provided in each pipe 24b between the other end of the humidifier bypass pipe 42a.

  The control system 50 includes a control unit 51, an ammeter 52, a thermometer 53, a timer 54, and the like.

  The control unit 51 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory) in which a program is recorded, various circuits, an input / output interface, and the like, and acquires the moisture content inside the humidifier 22. A humidifier internal water content acquisition means, and a scavenging gas flow rate determination means for determining the flow rate of the scavenging gas (air) supplied to the humidifier 22.

  The ammeter 52 has a function of detecting a current value taken from the fuel cell 10 to the external load 60. The current value detected by the ammeter 52 is integrated to estimate the amount of water generated in the reaction in the fuel cell 10. Since the moisture generated in the fuel cell 10 is discharged to the humidifier 22, the amount of moisture remaining in the humidifier 22 can be estimated by integrating the generated current values.

The thermometer 53 has a function of detecting the temperature (system temperature) of the fuel cell system 1A, and is provided, for example, in a pipe 24c between the outlet 10c2 on the cathode side of the fuel cell 10 and the humidifier 22. The position of the thermometer 53 is not limited to this position as long as the system temperature can be detected, and may be the temperature on the anode side, the refrigerant temperature for cooling the fuel cell 10, or the outside air temperature. May be.

  The timer 54 has a function of measuring the scavenging time such as cathode scavenging for scavenging the cathode gas flow path and anode scavenging for scavenging the anode gas flow path. Note that the timer 54 may be provided outside the control unit 51, or a timer built in the control unit 51 may be used.

Then, 2 to 7 (as appropriate, Figure 1) the operation of the fuel cell system will be described with reference to. As shown in FIG. 2, when the ignition switch of the vehicle is turned on by the driver (IGSW ON), the drain valve 34, the purge valve 35, the air discharge valve 36, the air introduction valve 41b and the humidifier bypass valve 42b are closed. In this state, the control unit 51 starts driving the air pump 21, so that pressurized air is supplied to the cathode of the fuel cell 10 through the flow path 22 a of the humidifier 22. Further, the control unit 51 opens a shut-off valve (not shown) provided in the hydrogen tank 31 so that hydrogen is reduced to a predetermined pressure by a pressure-reducing valve (not shown) and then supplied to the anode of the fuel cell 10. At the time of IGSW-ON, the purge valve 35 is appropriately opened to increase the concentration of hydrogen supplied to the anode, and when the open-circuit voltage of the fuel cell 10 exceeds a predetermined value, the contactor (not shown) is turned on ( Connected), the fuel cell 10 and the external load 60 are connected, and power generation is started.

  When power generation of the fuel cell 10 is started, in step S10, the control unit 51 obtains a generated current value taken from the fuel cell 10 to the external load 60 from the ammeter 52 and integrates the generated current amount. Do. When power generation is performed, water is generated by the reaction between hydrogen and oxygen. Therefore, the amount of generated water generated inside the fuel cell 10 can be estimated by integrating the amount of generated current.

  In step S20, the control unit 51 determines whether or not the ignition switch is turned off (IGSW OFF). If the ignition switch is not turned off (No), the control unit 51 returns to step S10 to generate the generated current. If the amount accumulation is continued and the ignition switch is turned off (Yes), the process proceeds to step S30.

In step S <b> 30, the control unit 51 estimates the moisture content inside the humidifier 22 based on the accumulated generated current amount. The amount of moisture inside the humidifier 22 can be estimated based on the map of FIG. FIG. 3 shows the relationship between the integrated power generation amount (integrated power generation amount) and the amount of moisture in the humidifier 22, and the amount of moisture discharged from the fuel cell 10 is small immediately after the IGSW-ON. As the accumulated power generation amount increases, the amount of water discharged from the fuel cell 10 increases and the amount of water inside the humidifier 22 increases. When the accumulated power generation amount exceeds a predetermined value, the moisture content inside the humidifier 22 becomes saturated and transitions while maintaining the prescribed moisture content. Note that step S30 corresponds to the process performed by the humidification unit's internal water content acquisition means, the interior of the water content of the estimated humidifier 22 is stored in a storage device such as RAM.

Although estimated based on the integrated power generation current amount the amount of water inside the humidification unit 22, the invention is not limited thereto, may be estimated based on the integrated power generation (accumulated power generation amount), the In this case, the voltmeter that measures the voltage of the fuel cell 10 together with the ammeter 52 can be used to estimate based on a map showing the relationship between the accumulated power generation amount and the moisture content in the humidifier. Alternatively, it may be estimated based on the temperature of the fuel cell 10, and in this case, it can be estimated based on a map in which the amount of water increases as the temperature increases.

  As shown in FIG. 4, when the ignition switch is turned off by the driver, the air pump 21 is stopped by the control unit 51, and the supply of air to the cathode of the fuel cell 10 is stopped. Further, a shut-off valve (not shown) provided in the hydrogen tank 31 is closed by the control unit 51, and supply of hydrogen to the anode of the fuel cell 10 is stopped. Then, the contactor (not shown) is turned off, and the connection between the fuel cell 10 and the external load 60 is cut off.

  In step S100, the control unit 51 detects the system temperature every predetermined time. The system temperature is the temperature of the fuel cell system 1A and is detected by the thermometer 53.

  In step S200, the control unit 51 determines whether the system temperature is equal to or lower than a predetermined value. The predetermined value is a threshold value for determining whether or not water remaining in the fuel cell 10 and the humidifier 22 is frozen, and is set to, for example, 5 ° C. or 10 ° C. In step S200, when the control unit 51 determines that the system temperature is not equal to or lower than the predetermined value (No), the control unit 51 returns to step S100 and detects the system temperature. In step S200, when it is determined that the system temperature is equal to or lower than the predetermined value (Yes), the control unit 51 proceeds to step S300 and proceeds to the scavenging execution determination unit.

  As shown in FIG. 5, in the scavenging execution determination unit, in step S <b> 301, the control unit 51 performs anode droplet removal scavenging. The anode droplet removal scavenging is a process for removing moisture remaining in the anode gas flow path (anode flow path 10a, pipes 37b to 37d), the back pressure valve 23 is closed, the drain valve 34, the purge valve 35, and the air discharge. In a state where the valve 36, the air introduction valve 41b, and the humidifier bypass valve 42b are opened, a high flow rate of air is supplied by increasing the rotational speed of the motor of the air pump 21 (see FIG. 7). Thereby, a large flow of air from the air pump 21 is supplied to the anode gas flow path through the air introduction pipe 41a, and moisture (droplets) remaining in the anode gas flow path is discharged to the drain valve 34, the purge valve 35 and the air discharge. It is discharged to the outside (external) through the valve 36.

  In step S302, the control unit 51 performs drain line scavenging. The drain line scavenging is a process for removing moisture remaining in the drain valve 34 and the pipe 37e, and in a state where the purge valve 35 and the air discharge valve 36 are closed, air having a lower flow rate than that during anode droplet removal scavenging is used. Supply (see FIG. 7). Thereby, the air introduced into the anode gas flow path from the air pump 21 via the air introduction pipe 41a is discharged out of the vehicle through the drain valve 34, so that the generated water remaining in the drain valve 34 and the pipe 37e is reduced. Removed.

  In step S303, the control unit 51 performs scavenging line scavenging. The scavenging line scavenging is a process for removing moisture remaining in the air discharge valve 36 and the pipe 37g, and supplies air having a slightly lower flow rate than that during the drain line scavenging with the drain valve 34 and the purge valve 35 closed. (See FIG. 7). Thereby, the air introduced into the anode gas flow path from the air pump 21 through the air introduction pipe 41a is discharged outside the vehicle through the air discharge valve 36, thereby remaining in the air discharge valve 36 and the pipe 37g. Water is removed.

  In step S304, the control unit 51 performs purge line scavenging. The purge line scavenging is a process for removing moisture remaining in the purge valve 35 and the pipe 37f, and with the drain valve 34 and the air discharge valve 36 closed, air having a slightly higher flow rate than that during the drain line scavenging is supplied. (See FIG. 7). As a result, the air introduced into the anode gas flow path from the air pump 21 via the air introduction pipe 41a is discharged to the outside via the purge valve 35, whereby the generated water remaining in the purge valve 35 and the pipe 37f is removed. Removed.

And in step S305, the control part 51 implements humidifier scavenging. Humidifier scavenging is a process of removing moisture remaining in the humidifier 22, and the back pressure valve 23 is opened, a drain valve 34, a purge valve 35, an air discharge valve 36, an air introduction valve 41b, and a humidifier bypass valve. In a state in which 42b is closed, air having a flow rate equivalent to that during drain line scavenging is supplied (see FIG. 7). Thereby, the air from the air pump 21 flows through the flow path 22 a in the humidifier 22, the inside of the fuel cell 10 on the cathode side, and the flow path 22 b in the humidifier 22. At this time, water remaining in the flow path 22a of the humidifier 22 is pushed out, and the pushed water passes through the inside of the fuel cell 10 through the flow path 22b of the humidifier 22 and then through the back pressure valve 23 and the diluter 25. It is discharged outside the car.

  In step S305, the flow rate of air as the scavenging gas when scavenging the humidifier 22 is determined based on the map of FIG. FIG. 6 shows the relationship between the amount of moisture in the humidifier 22 and the flow rate of air necessary for scavenging the humidifier 22, and the air flow rate is determined based on the amount of moisture estimated in step S30 in FIG. Scavenging gas flow rate determining means). That is, at the beginning of power generation, the air flow rate increases as the moisture content inside the humidifier 22 increases, and the air flow rate becomes constant even if the moisture content inside the humidifier 22 increases thereafter. The air flow rate can be set based on time.

  In step S306, the controller 51 performs cathode droplet removal scavenging. The cathode droplet removal scavenging is a process for removing moisture remaining in the cathode gas flow path, and air with a slightly higher flow rate than the purge line scavenging is supplied with the humidifier bypass valve 42b opened (FIG. 7). reference). Thereby, the air from the air pump 21 is supplied to the cathode of the fuel cell 10 through the humidifier bypass pipe 42a. At this time, the generated water remaining inside the cathode of the fuel cell 10 is discharged outside the vehicle through the flow path 22b of the humidifier 22.

  It should be noted that each of the scavenging of the anode droplet removal scavenging (S301), the drain line scavenging (S302), the scavenging line scavenging (S303), the purge line scavenging (S304), and the cathode droplet removing scavenging (S306) is performed in advance by an experiment or the like. It implements based on the predetermined time calculated | required by. In each scavenging of steps S301 to S306, the air pump 21 is driven using electric power stored in a high voltage battery (not shown) provided in the fuel cell system 1A. The switching of the various valves is driven using electric power stored in a low voltage battery (for example, 12 volts) charged by a high voltage battery.

  In step S307, the control unit 51 stops the air pump 21, closes the humidifier bypass valve 42b, and ends scavenging. Then, returning to the flow of FIG. 4, the monitoring (detection) of the system temperature is stopped, and the process is terminated.

As described above, since the determined flow rate of the scavenging gas (air) on the basis of the internal water content of the pressurized humidifier 22, for supplying the scavenging gas to the humidifier 22 at the scavenging air pump 21 wasting Driving can be prevented, and energy consumption can be suppressed. In addition, since it is possible to prevent the inside of the humidifier 22 from being dried too much, it becomes possible to retain a predetermined amount of moisture in the humidifier 22 when the fuel cell 10 is started next time. It becomes possible to maintain the humidification performance of the. In addition, since the humidifier 22 is not deficient in drying, it is possible to prevent water from freezing inside the humidifier 22.

Further, since based on the integrated power generation amount of current is correlated with the volume of water generated in the fuel cells 10 and estimates the amount of water in the humidifier 22, can be appropriately set the flow rate of the air (scavenging gas) become. Therefore, since the air flow rate required for scavenging of the humidifier 22 can be set more appropriately, it is possible to more effectively prevent the air pump 21 from being driven wastefully.

Further, since the pressure Shimeki bypass means 42 is provided, as water contained in the discharged scavenging offgas (air) from the fuel cell 10 is introduced into the flow path 22b of the humidifier 22, the supply from the air pump 21 Since the moisture exchange between the scavenging gas and the scavenging off gas can be prevented, the humidity of the scavenging gas supplied into the fuel cell 10 is not increased. Therefore, it is possible to reduce the scavenging time when scavenging the cathode gas channel.

Further, the scavenging of the pressurized humidifier 22 because it is performed before performing the cathode scavenging (cathode droplet removal scavenge), the fuel cell 10 can be prevented from becoming water in a wet state again humidifier 22. Therefore, it is possible to reliably prevent the cathode gas passage from freezing.

( This embodiment)
FIG. 8 is an overall configuration diagram showing the fuel cell system of the present embodiment, and FIG. 9 is a time chart showing opening / closing operations of various devices during scavenging. The fuel cell system 1B of the present embodiment, in place of the humidifier bypass means 42 of the fuel cell system 1A as a humidifier bypass means 43 is configured by adding the fuel cell bypass means 44.

  The humidifier bypass means 43 includes a first humidifier bypass pipe 43a and a first humidifier bypass valve 43b, and a second humidifier bypass pipe 43c and a second humidifier bypass valve 43d. One end of the first humidifier bypass pipe 43 a is connected to a pipe 24 a between one end of the air introduction pipe 41 a and the humidifier 22, and the other end is a pipe between the humidifier 22 and the inlet 10 c 1 of the fuel cell 10. The flow path is connected to 24 b and bypasses the flow path 22 a on the supply gas side of the humidifier 22. The 1st humidifier bypass valve 43b is provided in the 1st humidifier bypass piping 43a, and has the function which interrupts | blocks the flow path of the 1st humidifier bypass piping 43a by closing. The second humidifier bypass pipe 43c has one end connected to the pipe 24c between the humidifier 22 and the outlet 10c2 of the fuel cell 10, and the other end connected to the pipe 24d between the humidifier 22 and the back pressure valve 23. And a flow path that bypasses the flow path 22b on the exhaust gas side of the humidifier 22 is configured. The second humidifier bypass valve 43d is provided in the second humidifier bypass pipe 43c and has a function of blocking the flow path of the second humidifier bypass pipe 43c by closing the valve.

  The fuel cell bypass means 44 includes a fuel cell bypass pipe 44a and a fuel cell bypass valve 44b. One end of the fuel cell bypass pipe 44a is connected to the pipe 24b between the other end of the first humidifier bypass pipe 43a and the inlet 10c1 of the fuel cell 10, and the other end is connected to one end of the second humidifier bypass pipe 43c. It is connected to a pipe 24c between the outlet 10c2 of the fuel cell 10 and constitutes a flow path that bypasses the fuel cell 10. The fuel cell bypass valve 44b is provided in the fuel cell bypass pipe 44a and has a function of closing the fuel cell bypass pipe 44a by closing the valve.

Next, the operation of the fuel cell system 1B of the present embodiment will be described with reference to FIG. The scavenging control of the fuel cell system 1B is performed based on the same flowchart as that in FIG. Since the anode droplet removal scavenging (S301) to the purge line scavenging (S304) are the same as those in the reference example , the description thereof is omitted, and only the processing of the humidifier scavenging (S305) and the cathode droplet removing scavenging (S306) is performed. explain.

  In the humidifier scavenging (S305), the first humidifier bypass valve 43b is closed, the second humidifier bypass valve 43d is opened, and the fuel cell bypass valve 44b is opened. Also, a slightly lower flow rate of air is supplied (see FIG. 9). Thereby, the air from the air pump 21 remains in the flow path 22a on the supply gas side of the humidifier 22 by passing through the flow path 22a of the humidifier 22, the fuel cell bypass pipe 44a, and the second humidifier bypass pipe 43c. Moisture is removed.

  Further, in the humidifier scavenging (S305), air of the same flow rate is supplied from the air pump 21 with the first humidifier bypass valve 43b opened and the second humidifier bypass valve 43d closed (FIG. 9). reference). Thereby, the air from the air pump 21 passes through the first humidifier bypass pipe 43a, the fuel cell bypass pipe 44a, and the flow path 22b of the humidifier 22, and thus remains in the flow path 22b on the exhaust gas side of the humidifier 22. Moisture is removed.

  In the cathode droplet removal scavenging (S306), air is supplied from the air pump 21 in a state where the second humidifier bypass valve 43d is opened and the fuel cell bypass valve 44b is closed (see FIG. 9). As a result, air remaining from the air pump 21 passes through the first humidifier bypass pipe 43a, the cathode flow path 10c inside the fuel cell 10 and the second humidifier bypass pipe 43c, so that moisture remaining in the cathode gas flow path is reduced. Removed.

As described above, according to the present embodiment, since the flow rate of the scavenging gas (air) is determined based on the moisture content inside the humidifier 22, the air is supplied to the humidifier 22 during the scavenging. In addition, it is possible to prevent the air pump 21 from being driven wastefully and to reduce energy consumption. Further, since the inside of the humidifier 22 is not dried too much, it becomes possible to keep a predetermined amount of water in the humidifier 22 when the fuel cell 10 is started next time. It becomes possible to maintain humidification performance. In addition, since the humidifier 22 is not deficient in drying, it is possible to prevent water from freezing inside the humidifier 22.

In addition, according to the present embodiment, the amount of water in the humidifier 22 is estimated based on the amount of accumulated power generation current that is correlated with the amount of water generated by the fuel cell 10, so that the flow rate of air (scavenging gas) is appropriately It becomes possible to set to.

Moreover, according to this embodiment, since the humidifier bypass means 43 which bypasses the humidifier 22 is provided, when scavenging the flow path 22a on the supply gas side of the humidifier 22, the second humidifier bypass pipe Since the scavenging off gas is circulated through 43c, moisture contained in the scavenging gas scavenged through the supply gas side flow path 22a is not exchanged from the exhaust gas side flow path 22b to the supply gas side flow path 22a. The supply gas side flow path 22a can be prevented from becoming wet again. Further, when scavenging the flow path 22b on the exhaust gas side of the humidifier 22, in order to circulate the scavenging gas through the first humidifier bypass pipe 43a, a scavenging off gas in a wet state flowing through the flow path 22b on the exhaust gas side, It is possible to prevent moisture from being exchanged with the scavenging gas flowing through the flow path 22a on the supply gas side. Therefore, it becomes possible to scavenge the humidifier 22 efficiently.

Further, according to the present embodiment, since the fuel cell bypass means 44 is provided, when scavenging the humidifier 22, the wet scavenging gas is introduced into the fuel cell 10 in order to bypass the fuel cell 10. The energy consumption used for scavenging the fuel cell 10 can be reduced. In addition, since the pressure loss due to the fuel cell 10 is not received when the humidifier 22 is scavenged, it is not necessary to drive the air pump 21 at a higher rotational speed, and energy consumption during scavenging of the humidifier 22 is reduced. Can do.

It is not intended to be limited to this embodiment shaped condition, for example, anode scavenging (anode droplet removal scavenge depending on the hydrogen concentration in the circulation flow path of the anode side during IG-OFF, the drain line scavenging, the scavenging Line scavenging, purge line scavenging) and cathode side scavenging (humidifier scavenging, cathode droplet removal scavenging) may be selected. That is, when the hydrogen concentration in the circulation channel is high, the cathode side scavenging may be performed while diluting the hydrogen in the circulation channel first, and then the anode side scavenging may be performed. By the way, switching between scavenging on the anode side and scavenging on the cathode side can be determined based on the elapsed time from IG-OFF to the start of scavenging, and if the elapsed time is short, it is determined that the hydrogen concentration in the circulation channel is high. If the elapsed time is long, it can be determined that the hydrogen concentration in the circulation channel is low.

It is a whole block diagram which shows the fuel cell system as a reference example . It is a flowchart which calculates | requires the moisture content of a humidifier. It is a map which shows the relationship between an integrated electric power generation amount and the moisture content in a humidifier. It is a flowchart which shows scavenging control. It is a subflowchart which shows the scavenging execution judgment part of FIG. It is a map which shows the relationship between the moisture content inside a humidifier, and the flow volume at the time of humidifier scavenging. It is a time chart which shows the opening / closing operation | movement of various devices at the time of scavenging. It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is a time chart which shows the opening / closing operation | movement of various devices at the time of scavenging.

Explanation of symbols

1A, 1B Fuel cell system 10 Fuel cell 10a Anode flow path (anode gas flow path)
10c Cathode channel (cathode gas channel)
21 Air pump (scavenging gas supply means)
22 Humidifier 22a Flow path (flow path on the supply gas side)
22b Flow path (Exhaust gas side flow path)
24a-24d piping (cathode gas flow path)
37a-37g Piping (Anode gas flow path)
42a Humidifier bypass piping (humidifier bypass flow path)
42b Humidifier bypass valve 43a 1st humidifier bypass piping (1st humidifier bypass flow path)
43b 1st humidifier bypass valve 43c 2nd humidifier bypass piping (2nd humidifier bypass flow path)
43d 2nd humidifier bypass valve 44a Fuel cell bypass piping (fuel cell bypass flow path)
44b Fuel cell bypass valve 51 Control unit (humidifier internal moisture content acquisition means, scavenging gas flow rate determination means)
52 Ammeter

Claims (4)

A fuel cell for generating electricity by supplying an anode gas to the anode gas channel and a cathode gas to the cathode gas channel;
By exchanging moisture between an exhaust gas discharged from the fuel cell of the cathode gas and a supply gas supplied to the fuel cell of the cathode gas , provided in the cathode gas flow path , A humidifier for humidifying the supply gas supplied to the fuel cell;
A scavenging gas supply means for supplying scavenging gas to the inside of the fuel cell and the humidifier,
The humidifier internal moisture amount is acquired using the cumulative power generation amount based on a predetermined map of the relationship between the cumulative power generation amount during operation of the fuel cell and the humidifier internal moisture amount, which is the moisture amount inside the humidifier. A means for obtaining moisture content inside the humidifier;
Scavenging gas flow rate determining means for determining the flow rate of the scavenging gas supplied to the humidifier based on the humidifier internal moisture content obtained by the humidifier internal moisture content acquiring means;
A first humidifier bypass flow path that bypasses the flow path on the supply gas side of the humidifier and distributes the scavenging gas;
A second humidifier bypass flow path that bypasses the flow path on the exhaust gas side of the humidifier and distributes the scavenging gas;
During the scavenging of the cathode gas flow path, the scavenging gas bypasses the exhaust gas-side flow path when scavenging the supply gas-side flow path of the humidifier, and the second humidifier bypass flow After passing through the passage, when scavenging the exhaust gas side passage of the humidifier, the scavenging gas is passed through the first humidifier bypass passage while bypassing the supply gas side passage. A fuel cell system. The humidifier humidifies the supply gas supplied from the scavenging gas supply means to the fuel cell by exhaust gas discharged from the fuel cell,
The map shows that the moisture content inside the humidifier is small when the cumulative power generation amount is small, the moisture content inside the humidifier increases as the cumulative power generation amount increases, and the moisture content inside the humidifier increases when the cumulative power generation amount further increases. 2. The fuel cell system according to claim 1, wherein the amount is set so as to converge. The scavenging of humidifier, a fuel cell system according to claim 1 or claim 2, characterized in that it is performed before performing the cathode scavenging. A fuel cell bypass passage for bypassing the fuel cell;
When scavenging the humidifier, the scavenging gas is circulated through the fuel cell bypass flow path, and when scavenging the fuel cell, the scavenging gas is circulated bypassing the humidifier. The fuel cell system according to any one of claims 1 to 3 .

Images