JP2006080027A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which efficient scavenging treatment is carried out. <P>SOLUTION: The fuel cell system supplies an oxidizer gas to the oxygen electrode side of the fuel cell via a supplying passage of the oxidizer gas, and discharges an exhaust gas containing steam formed at the oxygen electrode side by operation of the fuel cell using the oxidizer gas. This fuel cell system is provided with: a circulation control means in which, via a passage for circulation connecting the supplying passage to the exhaust gas passage, the exhaust gas is circulated from the exhaust gas passage side to the circulating direction to the supplying passage side; a direction reversing means in which flow of a gas in the passage for circulation is reversed from the supplying passage side to the exhaust gas passage side direction; and a scavenging control means in which the flow of the gas is reversed at the prescribed operating timing of the fuel cell by using the direction reversing means, and in which the scavenging of the passage for the circulation is carried out. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that circulates and uses exhaust gas discharged from the oxygen electrode side, and more particularly, to a scavenging process for removing moisture from a path through which an oxidant gas flows.

  In a fuel cell system that generates electricity using an electrochemical reaction between an oxidant gas (for example, air) and a fuel gas (for example, hydrogen), the oxidant gas supplied to the fuel cell in order to ensure a predetermined power generation efficiency Need to be humidified. Conventionally, in a fuel cell system, a system including a circulation path that circulates exhaust gas containing water vapor generated on the oxygen electrode side by an electrochemical reaction to the supply side of the oxidant gas has been employed (for example, patents). Reference 1).

  Conventionally, a scavenging treatment technique for removing moisture remaining in a fuel cell system, particularly in a fuel cell or in an exhaust pipe for an oxidant gas when the system is stopped has been disclosed (for example, Patent Document 2). reference). According to such a technique, it is said that moisture remaining in the system can be removed.

Japanese National Patent Publication No. 8-500931 JP-A-8-124588 JP 2001-185181 A JP 2003-115317 A JP-A-9-266002 JP 2003-157875 A

  In a fuel cell system equipped with an oxidant gas circulation path, there is a problem that moisture accumulates in the circulation path along with the exhaust pipe of the oxidant gas inside the fuel cell and the oxidant gas due to the operation of the system. It was. For example, moisture in the circulation path may be frozen due to a decrease in the outside air temperature, and the circulation path may be blocked. There is no disclosure of an efficient scavenging method for the inside of the circulation path, and it is difficult to efficiently perform scavenging processing for the entire system including the circulation path.

  In view of these problems, an object of the present invention is to provide a fuel cell system that performs efficient scavenging processing of the entire system, particularly a circulation path.

  In view of the above problems, the fuel cell system of the present invention employs the following method. That is, an exhaust gas containing water vapor generated on the oxygen electrode side by supplying the oxidant gas to the oxygen electrode side of the fuel cell through the supply path of the oxidant gas and operating the fuel cell using the oxidant gas A fuel cell system that exhausts the exhaust gas in a circulation direction from the exhaust path side to the supply path side via a circulation path that connects the supply path and the exhaust path. Circulating circulation control means, direction reversing means for reversing the gas flow in the circulation path from the supply path side to the exhaust path side, and the direction reversal at a predetermined operation timing of the fuel cell And a scavenging control means for reversing the gas flow using the means and scavenging the circulation path.

  According to the fuel cell system of the present invention, the flow of the gas in the circulation path is reversed from the circulation direction, and the moisture in the circulation path is discharged to the exhaust path side together with the gas. Therefore, for example, compared with the case where moisture is removed by flowing the fluid in the order of the supply path, the fuel cell, and the exhaust path, and removing the moisture by guiding the fluid flowing through the exhaust path to the circulation path and flowing it in the circulation direction, Can remove moisture. As a result, an efficient scavenging process for the entire system can be executed in the fuel cell system having the circulation path.

  The direction reversing means of the fuel cell system configured as described above is provided on the exhaust path downstream from the connection point between the exhaust path and the circulation path, and sucks the gas flowing through the circulation path It may be a means.

  According to such a fuel cell system, the scavenging process is performed by sucking the gas in the circulation path from the exhaust path downstream from the connection location, reversing the flow in the circulation direction in the circulation path, and removing moisture together with the gas. To do. As such suction means, for example, fluid devices such as a pump, a blower, and a fan can be assumed. Since a device dedicated to the scavenging process is arranged, a device suitable for the scavenging process can be selected, and the entire system can perform an efficient scavenging process.

  The circulation control means of the fuel cell system having the above configuration includes a flow rate adjustment valve that adjusts the flow rate of the exhaust gas flowing in the circulation direction on the circulation path, and the scavenging control means includes the flow rate adjustment valve. The amount of valve opening may be reduced, the gas may be sucked by controlling the suction means, and scavenging in the circulation path may be performed.

  According to such a fuel cell system, when the fuel cell generates power, the valve opening amount of the flow rate adjustment valve is adjusted to adjust the flow rate of the exhaust gas flowing in the circulation direction. When performing the scavenging process, the opening amount of the flow rate adjustment valve is reduced or the valve is closed, and the gas is sucked from the exhaust path downstream from the connection location. By this suction, the inside of the circulation path and the inside of the exhaust path become negative pressure, and in particular, the inside of the exhaust path becomes negative pressure, thereby facilitating the suction of moisture in the fuel cell. From the viewpoint of scavenging the circulation path, the flow rate adjustment valve is preferably provided in the vicinity of the supply path side on the circulation path, but even in the vicinity of the exhaust path side, The flow path can be scavenged.

  The direction reversing means of the fuel cell system having the above-described configuration may be a pressure feeding means that is provided on the circulation path and pumps the gas in the circulation direction or the reversing direction.

  According to such a fuel cell system, scavenging is performed by pumping the gas in the circulation path in the reverse direction and removing moisture together with the pumped gas. Therefore, the scavenging process for the circulation path can be executed promptly.

  The fuel cell system having the above configuration further includes a supply unit that sucks oxidant gas from the outside and supplies the oxidant gas to the fuel cell through the supply path, and the scavenging control means uses the pressure feeding means. In addition to scavenging of the circulation path, scavenging of the path through which the oxidant gas flows may be performed by flowing the oxidant gas from the supply unit to the exhaust path through the fuel cell.

  According to such a fuel cell system, the circulation path is quickly purged by flowing a fluid in the reverse direction, and the oxidant gas flow path is scavenged using the oxidant gas from the system supply unit. Do. That is, scavenging of the circulation path is performed by the pressure feeding means, and scavenging of the oxidant gas path, for example, the supply path and the exhaust path, is performed by the supply unit. Therefore, the scavenging process for the entire system can be performed efficiently.

  In the fuel cell system having the above-described configuration, the fuel cell system further includes a supply unit that sucks oxidant gas from the outside and supplies the oxidant gas to the fuel cell through the supply path. A flow rate adjusting valve for adjusting the flow rate of the exhaust gas flowing in the circulation direction, wherein the direction reversing means is disposed on the circulation path, which is closer to the exhaust path than the flow rate adjusting valve, from the supply unit to the fuel. A scavenging path that forms a path for sending part or all of the oxidant gas toward the battery, and a scavenging valve that opens and closes the scavenging path, wherein the scavenging control means controls the valve opening amount of the flow regulating valve. And the scavenging valve is opened to feed the oxidant gas into the circulation path, thereby scavenging the circulation path.

  According to such a fuel cell system, by opening the scavenging valve, part or all of the oxidant gas from the supply part of the system is sent to the circulation path. That is, using the supply unit, the fluid is flowed in the reverse direction to scavenge the circulation path. For example, in a system equipped with an air compressor or the like as an oxidant gas supply unit, scavenging processing can be performed with a relatively simple system configuration using existing equipment.

  The predetermined operation timing of the fuel cell system having the above-described configuration is at least one of the predetermined timings during the stop of the intermittent operation of the fuel cell before the start of power generation of the fuel cell, after the power generation is stopped. be able to.

  According to such a fuel cell system, the scavenging process is executed at any timing before the start of power generation of the fuel cell, after the stop of power generation, and during the stop of the intermittent operation of the fuel cell. Even if the scavenging process is executed at any timing, the generated water and the accumulated water generated in the fuel cell, each path, and the like can be excluded. The scavenging process may be executed by combining these timings.

Embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
A-1. System configuration:
A-2. Scavenging treatment:
B. Second embodiment:
B-1. System configuration:
B-2. Scavenging treatment:
B-3. Dilution process:
C. Third embodiment:
C-1. System configuration:
C-2. Scavenging treatment:
D. Variations:

A. First embodiment:
A-1. System configuration:
FIG. 1 is a schematic configuration diagram of a fuel cell system as a first embodiment of the present invention. This system is a fuel cell system 10 including a fuel cell stack 20 that generates electric power through an electrochemical reaction between hydrogen and oxygen, and is mounted on a vehicle powered by the power generated by the fuel cell stack 20.

  As shown in the figure, the fuel cell system 10 mainly includes a fuel cell stack 20, a hydrogen system 30 that supplies hydrogen gas as hydrogen used in the reaction, and an air compressor 48 that compresses and supplies air as oxygen used in the reaction. The air system 40, the cooling system 70 for supplying the cooling water for cooling the fuel cell stack 20, the exhaust system 80 for discharging the exhaust gas after the reaction, the output system 90, the control unit 100, and the like.

  The fuel cell stack 20 includes a plurality of unit cells 21 each including a hydrogen electrode, an electrolyte membrane, an oxygen electrode, a separator, and the like. The plurality of unit cells 21 are stacked and sandwiched between end plates 28 and 29 from both ends. Is formed. The end plate 28 includes a plurality of inlet ports for supplying a reaction gas such as hydrogen gas or air and cooling water into the fuel cell stack 20 and a plurality of outlet ports for discharging them to the outside. Each unit cell 21 is connected inside the battery stack 20. That is, the reaction gas and cooling water supplied from the outside are appropriately supplied to each single cell 21 via the plurality of inlet ports of the end plate 28.

  The separator of the single cell 21 is provided with a reaction gas flow path and a cooling water flow path, and the reaction gas and cooling water supplied via the end plate 28 pass through the flow path through the single cell. It reaches within 21. Each single cell 21 generates power by an electrochemical reaction of the supplied reaction gas. The fuel cell stack 20 obtains a high voltage by connecting a plurality of such single cells 21 in series. In this embodiment, Nafion (registered trademark), which is a solid polymer film, is used for the electrolyte membrane. Such an electrolyte membrane works well in a wet state.

  The hydrogen system 30 mainly includes a hydrogen tank 31, a hydrogen supply path 32, a hydrogen circulation path 33, a hydrogen discharge path 35, and the like. The hydrogen supply path 32 includes a pipe that connects the hydrogen tank 31 that stores high-pressure hydrogen gas and the inlet port of the end plate 28, a valve (not shown) provided on the pipe, and the like. The high-pressure hydrogen gas from the hydrogen tank 31 is depressurized by a valve (not shown) on the pipe, supplied to the inlet port (that is, the fuel cell stack 20), and used for the electrochemical reaction.

  The hydrogen circulation path 33 includes a pipe connecting the outlet port of the end plate 28 and the pipe of the hydrogen supply path 32, a circulation pump 34 provided on the pipe, and the like. The exhaust gas after being used for the reaction in the fuel cell stack 20 flows into the piping of the hydrogen circulation path 33 from the fuel cell stack 20 and is supplied to the hydrogen supply path 32 by the circulation pump 34. By performing such circulation, hydrogen gas discharged without being used in the electrochemical reaction is effectively used.

  The hydrogen discharge path 35 includes a pipe connecting the pipe of the hydrogen circulation path 33 and the diluter 82 of the exhaust system 80, an opening / closing valve 36 for opening and closing the path formed by the pipe. Part of the exhaust gas pushed out to the hydrogen supply path 32 by the circulation pump 34 (that is, part of the hydrogen gas in the circulation process) flows to the diluter 82 at the opening timing of the opening / closing valve 36 and is discharged after dilution. . Note that the hydrogen gas to the fuel cell stack 20 may be generated by reforming methane, methanol, or the like to supply hydrogen instead of supplying from the hydrogen tank 31.

  The air system 40 is mainly composed of three paths: an air supply path 45, an air discharge path 50, and an air circulation path 60.

  The air supply path 45 has an opening at one end and a pipe connecting the other end to the inlet port of the end plate 28, an air cleaner 46, an air flow meter 47, an air compressor 48, an intercooler 49, etc. provided on the pipe. It has.

  The air taken in from the outside by driving the air compressor 48 is purified by the air cleaner 46, passes through the air flow meter 47, is compressed by the air compressor 48, is cooled by the intercooler 49, and is supplied to the fuel cell stack 20. The air flow meter 47 detects the flow rate of air sucked from the outside. This air flow rate is output to the control unit 100 that controls the operation of the fuel cell stack 20 and is used to control the air compressor 48.

  The air compressor 48 uses a motor as a drive source, and sucks air corresponding to the number of rotations of the motor. Due to this intake air, the pressure in the piping of the air supply path 45 upstream of the air compressor 48 becomes negative.

  The air discharge path 50 includes a pipe connecting the outlet port of the end plate 28 and the diluter 82 of the exhaust system 80, and a temperature sensor 56, a pressure sensor 57, a pressure regulating valve 51, a pressure sensor 58, a pressure sensor 58 provided on the pipe. And a blower 55 and the like.

  The exhaust gas discharged from the fuel cell stack 20 is supplied to the diluter 82 through the pressure regulating valve 51 and the blower 55, and is discharged to the outside through the muffler 81 of the exhaust system 80. The pressure regulating valve 51 can adjust the valve opening degree by the advance / retreat operation of the internal valve, and adjusts the pressure of the air supplied to the fuel cell stack 20 by adjusting the valve opening degree by the control unit 100. Such valve opening degree control is performed by controlling the rotation angle of a valve driving motor.

  The blower 55 uses a motor as a driving source, and can mainly suck exhaust gas in the air discharge path 50 according to the number of rotations of the motor. The blower 55 is used for a scavenging process for removing moisture generated in the oxygen electrode side by an electrochemical reaction in the fuel cell stack 20 and staying in various pipes of the air system 40. This scavenging process will be described in detail later.

  The temperature sensor 56 and the pressure sensors 57 and 58 detect the temperature and pressure of the air as the exhaust gas flowing through the air discharge path 50, and output detection values to the control unit 100. Such detection values are used for controlling various valves.

  The air circulation path 60 is a pipe that connects a pipe of the air discharge path 50 between the pressure regulating valve 51 and the blower 55 and a pipe of the air supply path 45 between the air flow meter 47 and the air compressor 48, and this pipe. And a circulation valve 65 provided on the top. The exhaust gas discharged from the fuel cell stack 20 flows into the exhaust system 80 through the pressure regulating valve 51 in the air discharge path 50, and part or all of it flows into the air circulation path 60.

  The circulation valve 65 supplies air at a predetermined flow rate to the air supply path 45 by adjusting the valve opening degree by the control unit 100. The air having the predetermined flow rate is air that is in a wet state including water vapor caused by an electrochemical reaction (in other words, humidified air). Therefore, in the fuel cell system 10, a humidification amount necessary for the electrolyte membrane is ensured without providing a humidification module for humidifying the air. That is, the humidification amount of the air supplied to the fuel cell stack 20 is controlled by directly controlling the circulation valve 65 and adjusting the circulation flow rate of the air.

  The cooling system 70 includes a radiator 71, a pump 72, piping that connects them, and the like. Since the electrochemical reaction inside the fuel cell stack 20 is an exothermic reaction, the internal temperature rises. In order to suppress this temperature increase, the cooling water flowing into the fuel cell stack 20 is cooled by the radiator 71 and circulated by the pump 72.

  The exhaust system 80 includes a diluter 82, a muffler 81, piping connecting them, a hydrogen concentration sensor 83, and the like, and exhausts exhaust gas discharged from the fuel cell stack 20 to the outside of the fuel cell system 10. The exhaust gas from the hydrogen system 30 and the air system 40 described above is guided to the diluter 82. In the diluter 82, the hydrogen gas contained in the exhaust gas from the hydrogen system 30 is sufficiently diluted with air and discharged to the outside through the muffler 81. Such dilution of hydrogen gas is performed by controlling the flow rate of air taken into the diluter 82 using the blower 55.

  The output system 90 includes an inverter 91, a vehicle travel motor 92, a DC / DC converter 93, a secondary battery 94, and the like. The electric power generated by the electrochemical reaction between the hydrogen gas and the air supplied to the fuel cell stack 20 is used to drive the vehicle travel motor 92 via the inverter 91. For example, surplus generated during steady travel or deceleration. The amount is stored in the secondary battery 94 via the DC / DC converter 93.

  The control unit 100 controls actuators such as various valves, motors, and pumps of the fuel cell system 10 composed of such devices. Specifically, pressures P1, P2, temperature T, air flow rate q from various sensors such as pressure sensors 57, 58, temperature sensor 56, air flow meter 47, hydrogen concentration sensor 83, accelerator position sensor, vehicle speed sensor not shown. , Hydrogen concentration S, accelerator opening θ, vehicle speed V, etc. are input, and the required output (electric power) is calculated, air compressor 48, pressure regulating valve 51, circulation valve 65, blower 55, circulation pump 34, pump 72, etc. Is controlled to operate the fuel cell system 10.

  In particular, in the present fuel cell system 10 in which no humidification module is provided as described above, the control unit 100 controls the required humidification amount. Specifically, the output of the current and voltage values of the fuel cell stack 20 (not shown), the temperature T from the temperature sensor 56, the flow rate q from the air flow meter 47, the intake amount from the motor speed of the air compressor 48, etc. The humidification amount is calculated from the detected value and the predetermined moisture amount map, and the circulation flow rate of the exhaust gas corresponding to the required humidification amount is determined based on the calculated moisture amount, and the valve of the circulation valve 65 is opened. The degree is determined. For example, when it is determined that the humidification amount is small with respect to the required amount, the valve opening degree of the circulation valve 65 is increased, and when it is determined that the humidification amount is large, the valve opening degree of the circulation valve 65 is decreased. Yes.

  In the configuration described above, the piping of the air supply path 45 is the “supply path” in the claims, the piping of the air discharge path 50 is the “exhaust path”, and the piping of the air circulation path 60 is the “circulation path”. Respectively. In this embodiment, a configuration in which various devices are connected by piping will be described, but the devices may be connected by a duct or the like.

  In such a fuel cell system 10, generated water is generated by the operation of the system, and moisture adheres to the inside of the fuel cell stack 20 and various pipes of the air system 40, in particular, the pipes of the air discharge path 50 and the air circulation path 60. And stay. Hereinafter, the scavenging process for removing the staying water will be described.

A-2. Scavenging treatment:
FIG. 2 is a flowchart of the scavenging process in the fuel cell system 10 of the first embodiment. This process is executed by the control unit 100 at a timing after the power generation of the fuel cell stack 20 is stopped.

  When the process is started, the control unit 100 instructs the pressure regulating valve 51 to open and the circulation valve 65 to close (step S200). In response to such a command, the pressure regulating valve 51 is fully opened and the circulation valve 65 is fully closed. Note that the air compressor 48 is in a stopped state because it is the timing after the power generation is stopped.

  The control unit 100 outputs a start command to the motor of the blower 55 together with a command to the valve (step S210). The blower 55 that has received the command rotates the motor and starts sucking air. Since the blower 55 is disposed downstream of the joining point of the air discharge path 50 and the air circulation path 60, the blower 55 sucks not only the air in the air discharge path 50 but also the air in the air circulation path 60. By this suction operation, air flows in the air circulation path 60 in the direction opposite to the circulation direction, and moisture remaining in the air circulation path 60 is removed.

  In the course of the suction operation by the blower 55, the circulation valve 65 is closed, so that no new air flows from the outside via the air cleaner 46 and the air flow meter 47. When a predetermined amount of air and moisture is sucked from the air circulation path 60 and the air discharge path 50, the blower 55 sucks the air and moisture inside the fuel cell stack 20 through the opened pressure regulating valve 51, and finally The air and moisture in the air supply path 45 are sucked.

  Subsequently, the control unit 100 determines whether or not a predetermined time for executing the suction operation by the blower 55 has elapsed (step S220). Specifically, with the start of the blower 55, the elapsed time is counted and compared with a preset time.

  If it is determined in step S220 that the set time has not elapsed (No), this determination process is repeated at a predetermined timing. In addition, it is good also as what performs the process which changes the drive amount of the blower 55 for every predetermined timing.

  On the other hand, if it is determined in step S220 that the set time has elapsed (Yes), a stop command is output to the motor of the blower 55 (step S230), and the scavenging process is terminated. Upon receiving this command, the blower 55 stops the suction operation.

  As described above, according to the scavenging process in the fuel cell system 10 of the first embodiment, the suction operation of the blower 55 provided on the downstream side of the confluence of the air discharge path 50 and the air circulation path 60 causes the inside of the air circulation path 60. Air and moisture flow in the opposite direction in the path. The air and moisture that flow in the reverse direction are discharged from the air discharge path 50 to the outside without passing through the fuel cell stack 20. By executing such a scavenging process, for example, scavenging in the air circulation path 60 can be performed more quickly than in the case where air is circulated by driving the air compressor 48 to scavenge the air circulation path 60. As a result, moisture remaining in the air circulation path 60, the circulation valve 65, and the like can be removed, and freezing due to a decrease in the outside air temperature while the system is stopped can be prevented.

  Moreover, scavenging in the air discharge path 50 can also be performed by performing suction from the downstream side of the junction. Furthermore, since the circulation valve 65 is closed during the suction operation by the blower 55, the air discharge path 50 is likely to have a negative pressure, and the water in the fuel cell stack 20 can be easily discharged.

  In a general fuel cell system that does not include such a blower 55, it can be considered that the function of the air compressor 48 is also used for scavenging processing. In this case, it is necessary to drive the air compressor 48 in a low efficiency region, and the power consumption of the system increases. In contrast, in the fuel cell system 10 of the first embodiment, since the blower 55 dedicated to scavenging is newly provided, it is not necessary to drive the air compressor 48 in an inefficient area, and the power consumption is reduced as a whole. A system can be constructed.

  Such scavenging processing may be executed when the fuel cell system 10 is started (before power generation is started). FIG. 3 is a timing chart showing the operation timing of each actuator in the scavenging process at startup. As shown in the figure, during the stop period of the fuel cell system 10, the blower 55 and the air compressor 48 are stopped, and the pressure regulating valve 51 and the circulation valve 65 are in an open state.

  The control unit 100 closes the circulation valve 65 and drives the blower 55 for a predetermined time at the timing of starting the fuel cell system 10 to perform a scavenging process. In this case, the pressure regulating valve 51 remains fully open. While the scavenging process is finished, the blower 55 is stopped and the power generation by the fuel cell stack 20 is started. The control unit 100 drives the air compressor 48 and opens the pressure regulating valve 51 and the circulation valve 65 by a predetermined amount. Thus, the fuel cell system 10 outputs electric power according to the operating conditions.

  By controlling the operation of each actuator at such timing, the scavenging process can be executed before the start of power generation, and the performance degradation of the fuel cell system 10 can be suppressed. Of course, the scavenging process may be executed not only when the fuel cell system 10 is started, but also when power generation from the fuel cell stack 20 is intermittent.

B. Second embodiment:
B-1. System configuration:
FIG. 4 is a schematic configuration diagram of a fuel cell system as a second embodiment of the present invention. As shown in the figure, the fuel cell system 12 mainly includes a fuel cell stack 20, a hydrogen system 30, an air system 41, a cooling system 70, an exhaust system 80, an output system 90, a control unit 100, and the like. This fuel cell system 12 differs from the fuel cell system 10 of the first embodiment only in the configuration of the devices of the air system 41. Therefore, parts other than the air system 41 are the same as those in the first embodiment, and a description thereof is omitted.

  The air system 41 in the fuel cell system 12 includes three paths, that is, an air supply path 45, an air discharge path 50, and an air circulation path 60, as in the first embodiment. Among them, a blower 110 is disposed on the air circulation path 60 in place of the circulation valve 65 of the first embodiment. The blower 110 can flow the air in the air circulation path 60 in the circulation direction from the air discharge path 50 side to the air supply path 45 side or in the opposite direction (that is, bidirectional). That is, the blower 110 operates in the circulation direction when the humidified air is circulated and in the reverse direction when the scavenging is performed, and performs the two functions of the circulation valve 65 and the blower 55 of the first embodiment. be able to. Therefore, the suction blower 55 shown in the first embodiment is not provided on the air discharge path 50.

  In the fuel cell system 12 having the above configuration, when generating power from the fuel cell stack 20, the control unit 100 activates actuators such as the air compressor 48 and the pressure regulating valve 51 to supply air to the fuel cell stack 20. At the same time, the circulation amount with respect to the required humidification amount is calculated, and the blower 110 is driven at the number of rotations corresponding to the circulation amount. In this way, air flows in the circulation direction in the air circulation path 60, and the humidified air is supplied to the fuel cell stack 20, so that the electrochemical reaction is favorably performed.

  On the other hand, when the scavenging process is performed, the control unit 100 controls the operation of the blower 110 according to the flowchart shown below.

B-2. Scavenging treatment:
FIG. 5 is a flowchart of the scavenging process in the fuel cell system 12 of the second embodiment. This process is executed by the control unit 100 when the fuel cell system 12 is started, stopped, or intermittent.

  When the process is started, the control unit 100 outputs a valve opening command to the pressure regulating valve 51 (step S500). In response to this command, the pressure regulating valve 51 is fully opened.

  Subsequently, the control unit 100 outputs a start command to the air compressor 48 (step S510). In response to this command, the air compressor 48 rotates, sucks air from the outside, and sends the air into the fuel cell stack 20. The fed air flows through the fuel cell stack 20 and the air discharge path 50 and is discharged from the exhaust system 80. In the course of this air flow, moisture inside the air supply path 45, the fuel cell stack 20, and the air discharge path 50 is pushed away and removed.

  The control unit 100 determines whether or not a predetermined time for executing scavenging by the air compressor 48 has elapsed (step S520). Specifically, the elapsed time is counted as the air compressor 48 is started.

  If it is determined in step S520 that the set time has not elapsed (No), this determination process is repeated at a predetermined timing. On the other hand, if it is determined in step S520 that the set time has elapsed (Yes), a stop command is output to the air compressor 48 (step S530). In response to this command, the air compressor 48 stops. In the steps so far, the blower 110 remains stopped.

  Subsequently, the control unit 100 outputs a start command to the blower 110 (step S540). Here, unlike the normal operation of the fuel cell system 12, the blower 110 is commanded to flow air in the direction opposite to the circulation direction. Specifically, a command for performing a reverse rotation to the rotation at the time of circulation is output to the motor of the blower 110.

  In response to the command, the blower 110 pushes the air in the air circulation path 60 in the reverse direction, that is, the air supply path 45 side to the air discharge path 50 side, and scavenges the air circulation path 60.

  The control unit 100 determines whether or not a predetermined time for executing scavenging by the blower 110 has elapsed (step S550). Specifically, the elapsed time is counted as the blower 110 is started.

  If it is determined in step S550 that the set time has not elapsed (No), this determination process is repeated at a predetermined timing. On the other hand, if it is determined in step S550 that the set time has elapsed (Yes), a stop command is output to the blower 110 (step S560), and the series of scavenging processes is terminated. Upon receiving this command, the blower 110 stops rotating.

  As described above, according to the scavenging process in the fuel cell system 12 of the second embodiment, the operation of the blower 110 capable of adjusting the air flow in both directions causes the air and moisture in the air circulation path 60 to flow through the pipe. Flows in the opposite direction. Therefore, as in the first embodiment, the air circulation path 60 can be quickly scavenged. In addition, since the bidirectional blower 110 can perform the two functions of the circulation valve 65 and the blower 55 of the first embodiment, the number of parts of the entire system can be reduced.

  In the fuel cell system 12 of the second embodiment, the air sucked from the outside can be sent out to the air discharge path 50 and the diluter 82 of the exhaust system 80 via the air circulation path 60 by the operation of the blower 110. This air flow, that is, the air flow that does not pass through the fuel cell stack 20, can be used for the scavenging process as described above, and can also be used for the dilution process for diluting the hydrogen gas with a large amount of air. That is, by supplying a large amount of air from the outside to the diluter 82 by the blower 110 at a predetermined timing, the hydrogen gas can be sufficiently diluted and discharged without using the air compressor 48. Below, this dilution process is demonstrated.

B-3. Dilution process:
FIG. 6 is a flowchart of the dilution process in the fuel cell system 12 of the second embodiment. The on-off valve 36 in the hydrogen system 30 is normally closed, but is opened at a predetermined timing for a predetermined time in order to release pressure in the circuit and discharge a nitrogen component. Simultaneously with the opening of the valve, high-concentration hydrogen gas flows into the diluter 82 through the hydrogen discharge path 35. This dilution process is executed by the control unit 100 at the opening timing of the opening / closing valve 36.

  When the process is started, the control unit 100 outputs a start command to the blower 110 (step S600). Specifically, a command for performing a reverse rotation to the rotation at the time of circulation is output to the motor of the blower 110. In response to the command, the blower 110 starts rotating at a predetermined rotational speed, and sends a predetermined amount of air sucked from the outside to the diluter 82 via the air circulation path 60 and the air exhaust path 50.

  Subsequently, the control unit 100 inputs the hydrogen concentration S from the hydrogen concentration sensor 83 (step S610). The hydrogen gas that has flowed into the diluter 82 by opening the on-off valve 36 is diluted by the air from the blower 110 and flows toward the downstream muffler 81 as a mixed gas. The hydrogen concentration sensor 83 detects the hydrogen concentration S in the mixed gas and outputs it to the control unit 100.

  The control unit 100 that has input the hydrogen concentration S determines whether or not the hydrogen concentration S is equal to or less than the predetermined value α (step S620). If it is determined in step S620 that the hydrogen concentration S is not less than or equal to the predetermined value α (No), a command to increase the rotational speed is output to the blower 110 (step S630), and the process returns to step S610 and again the hydrogen concentration S Enter. In response to the command, the blower 110 increases the number of rotations by a predetermined step, and increases the amount of air sent to the diluter 82.

  On the other hand, if it is determined in step S620 that the hydrogen concentration S is less than or equal to the predetermined value α (Yes), a stop command is output to the blower 110 (step S640), and the series of dilution processes is terminated. The on-off valve 36 has a short valve opening time, and is closed before the blower 110 is instructed to stop. Therefore, high-concentration hydrogen gas is not discharged from the diluter 82 after the blower 110 is stopped.

  In the above dilution process, the hydrogen gas is diluted by the operation of the bidirectional blower 110 used for the scavenging process. That is, air for power generation is supplied by the air compressor 48, and air for dilution is supplied by the blower 110. Therefore, an efficient system can be constructed without excessively driving the air compressor 48 for dilution. The air supplied to the diluter 82 by the blower 110 is a dry gas that does not pass through the fuel cell stack 20. Since such dry gas is sent to the exhaust system 80, the humidity of the exhaust gas is reduced, and white smoke can hardly be produced from the exhaust gas discharged to the outside.

C. Third embodiment:
C-1. System configuration:
FIG. 7 is a schematic configuration diagram of a fuel cell system as a third embodiment of the present invention. As shown in the figure, the fuel cell system 15 mainly includes a fuel cell stack 20, a hydrogen system 30, an air system 42, a cooling system 70, an exhaust system 80, an output system 90, a control unit 100, and the like. This fuel cell system 15 differs from the fuel cell system 10 of the first embodiment only in the configuration of the devices of the air system 42. Therefore, parts other than the air system 42 are the same as those in the first embodiment, and the description thereof is omitted.

  The air system 42 in the fuel cell system 15 is composed of three paths, an air supply path 45, an air discharge path 50, an air circulation path 60, and a scavenging path 120, as in the first embodiment.

  The scavenging path 120 is a pipe that connects the air supply path 45 between the intercooler 49 and the fuel cell stack 20 and the air circulation path 60 closer to the air discharge path 50 than the circulation valve 65. Is equipped with a scavenging valve 125. The scavenging valve 125 is a valve that opens and closes the scavenging path 120 and opens only during scavenging described later. By the operation of the scavenging valve 125, the air from the air compressor 48 can be sent to the air circulation path 60 via the scavenging path 120 to perform scavenging. Therefore, the suction blower 55 shown in the first embodiment is not provided on the air discharge path 50.

  In the fuel cell system 15 having the above-described configuration, when generating power from the fuel cell stack 20, the control unit 100 closes the scavenging path 120 by the scavenging valve 125 and activates various actuators to operate. On the other hand, when performing the scavenging process, the control unit 100 controls the operation of various actuators according to the flowchart shown below.

C-2. Scavenging treatment:
FIG. 8 is a flowchart of the scavenging process in the fuel cell system 15 of the third embodiment. This process is executed by the control unit 100 when the fuel cell system 15 is started, stopped, or intermittent.

  When the process is started, the control unit 100 commands the pressure regulating valve 51 to open and the circulation valve 65 to close (step S800). Subsequently, the scavenging valve 125 is instructed to close (step S810). In response to such a command, the pressure regulating valve 51 is fully opened, the circulation valve 65 is fully closed, and the scavenging valve 125 is fully closed.

  The control unit 100 outputs a start command to the air compressor 48 (step S830). In response to this command, the air compressor 48 rotates, sucks air from the outside, and sends the air into the fuel cell stack 20. The fed air flows through the fuel cell stack 20 and the air discharge path 50 and is discharged from the exhaust system 80. By this step, scavenging of the air supply path 45, the fuel cell stack 20, and the air discharge path 50 is performed.

  The control unit 100 determines whether or not a predetermined time for executing scavenging by the air compressor 48 has elapsed (step S8320). Specifically, the elapsed time is counted as the air compressor 48 is started.

  If it is determined in step S830 that the set time has not elapsed (No), this determination process is repeated at a predetermined timing. On the other hand, if it is determined in step S830 that the set time has elapsed (Yes), a valve opening command is output to the scavenging valve 125 (step S840). In response to this command, the scavenging valve 125 is fully opened, and the scavenging path 120 connecting the air supply path 45 and the air circulation path 60 communicates. The air continuously supplied from the air compressor 48 flows in the scavenging path 120 with less pressure loss than the fuel cell stack 20 side, and scavenges in the air circulation path 60.

  The control unit 100 determines whether or not a predetermined time for executing scavenging by opening the scavenging valve 125 has elapsed (step S850). Specifically, the elapsed time is counted together with a command for opening the scavenging valve 125.

  If it is determined in step S850 that the set time has not elapsed (No), this determination process is repeated at a predetermined timing. On the other hand, if it is determined in step S850 that the set time has elapsed (Yes), a stop command is output to the air compressor 48 (step S860), and the series of scavenging processes is terminated. Receiving this command, the air compressor 48 stops rotating.

  As described above, according to the scavenging process of the fuel cell system 15 of the third embodiment, the scavenging path 120 and the scavenging valve 125 are provided to form a new path, and the air by the air compressor 48 is not passed through the fuel cell stack 20. To the air circulation path 60. By doing so, the inside of the air circulation path 60 can be made to flow backward, and the air circulation path 60 can be quickly scavenged as in the first embodiment. In addition, a system for scavenging the air circulation path 60 with a relatively simple configuration can be constructed.

D. Variations:
In the first embodiment, the circulation valve 65 is closed and the scavenging process is executed. However, after the scavenging process for a predetermined time is completed, the circulation valve 65 is opened to drive the blower 55 and the external It is good also as what performs the process which attracts | sucks air. By doing so, air from the outside flows in the air circulation path 60, and moisture can be removed more reliably. The circulation valve 65 may be slightly opened during the scavenging process. Even in this case, it is difficult for the air from the outside to flow into the air circulation path 60, and the same effect as in the first embodiment can be obtained.

  Furthermore, in the fuel cell system 10 of the first embodiment, the blower 55 may be used for the dilution process. For example, the opening degree of the circulation valve 65 may be increased in accordance with the opening timing of the opening / closing valve 36, and the blower 55 may be driven to take in air from the outside and supply it to the diluter 82. By doing so, the hydrogen gas can be diluted without applying a load to the air compressor 48.

  In the dilution process in the second embodiment, the air necessary for diluting the hydrogen gas is supplied by the bidirectional blower 110. However, the air may be co-operated with the air compressor 48, for example. By doing so, the dilution process can be executed efficiently according to the hydrogen concentration.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can of course be implemented in various forms without departing from the spirit of the present invention. . For example, a regenerative motor may be used as the rotary motor of the bidirectional blower 110 in the second embodiment. In such a configuration, when the differential pressure before and after the blower 110 is large and a flow in the circulation direction is possible, the flow rate circulated by the regenerative motor can be adjusted, and the power can be generated using the fluid energy.

1 is a schematic configuration diagram of a fuel cell system as a first embodiment of the present invention. It is a flowchart of the scavenging process in the fuel cell system of 1st Example. FIG. 6 is a timing diagram showing the operation timing of each actuator in a scavenging process at startup. It is a schematic block diagram of the fuel cell system as 2nd Example of this invention. It is a flowchart of the scavenging process in the fuel cell system of 2nd Example. It is a flowchart of the dilution process in the fuel cell system of 2nd Example. It is a schematic block diagram of the fuel cell system as 3rd Example of this invention. It is a flowchart of the scavenging process in the fuel cell system of 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... 1st fuel cell system 12 ... 2nd fuel cell system 15 ... 3rd fuel cell system 20 ... Fuel cell stack 21 ... Single cell 28, 29 ... End Plate 30 ... Hydrogen system 31 ... Hydrogen tank 32 ... Hydrogen supply path 33 ... Hydrogen circulation path 34 ... Circulation pump 35 ... Hydrogen discharge path 36 ... Open / close valve 40, 41, 42 ... Air system 45 ... Air supply path 46 ... Air cleaner 47 ... Air flow meter 48 ... Air compressor 49 ... Intercooler 50 ... Air discharge path 51 ... Pressure control valve 55 ... Blower 56 ... Temperature sensor 57,58 ... Pressure sensor 60 ... Air circulation path 65 ... Circulation valve 70 ... Cooling system 71 ... Radiator 72 ... Pump 80 .. Exhaust system 81 ... Muffler 82 ... Diluter 83 ... Hydrogen concentration sensor 90 ... Output system 91 ... Inverter 92 ... Driving mode 93 ... DC / DC converter 94 ... secondary battery 100 ... control unit 110 ... blower 120 ... scavenging path 125 ... scavenging valve

Claims (7)

An oxidant gas is supplied to the oxygen electrode side of the fuel cell through an oxidant gas supply path, and exhaust gas containing water vapor generated on the oxygen electrode side is exhausted by the operation of the fuel cell using the oxidant gas. A fuel cell system that exhausts through a path,
A circulation control means for circulating the exhaust gas in a circulation direction from the exhaust path side to the supply path side via a circulation path connecting the supply path and the exhaust path;
Direction reversing means for reversing the gas flow in the circulation path from the supply path side to the exhaust path side;
A fuel cell system comprising: scavenging control means for reversing the gas flow using the direction reversing means at a predetermined operation timing of the fuel cell and scavenging the circulation path. The fuel cell system according to claim 1,
The fuel cell system, wherein the direction reversing means is a suction means that is provided on the exhaust path downstream of the connection point between the exhaust path and the circulation path, and sucks the gas flowing through the circulation path. The fuel cell system according to claim 2, wherein
The circulation control means includes a flow rate adjusting valve for adjusting a flow rate of the exhaust gas flowing in the circulation direction on the circulation path,
The scavenging control means reduces the valve opening amount of the flow rate adjusting valve, controls the suction means to suck the gas, and scavenges the circulation path. The fuel cell system according to claim 1,
The direction reversing unit is a fuel cell system that is provided on the circulation path and is a pressure feeding unit that pumps the gas in the circulation direction or the reversal direction. The fuel cell system according to claim 4, further comprising:
A supply unit for sucking oxidant gas from the outside and supplying the fuel cell to the fuel cell through the supply path;
In addition to scavenging the circulation path using the pumping means, the scavenging control means flows the oxidant gas from the supply section to the exhaust path by flowing the oxidant gas through the fuel cell. Fuel cell system for scavenging. The fuel cell system according to claim 1, further comprising:
A supply unit for sucking oxidant gas from the outside and supplying the fuel cell to the fuel cell through the supply path;
The circulation control means includes a flow rate adjusting valve for adjusting a flow rate of the exhaust gas flowing in the circulation direction on the circulation path,
The direction reversing means forms a path for feeding a part or all of the oxidant gas from the supply section toward the fuel cell on the circulation path on the exhaust path side of the flow rate adjusting valve. Path and a scavenging valve for opening and closing the scavenging path,
The scavenging control means reduces a valve opening amount of the flow rate adjusting valve, opens the scavenging valve, sends the oxidant gas into the circulation path, and scavenges the circulation path. The fuel cell system according to any one of claims 1 to 6,
The predetermined operation timing is at least one of predetermined timings during stoppage of intermittent operation of the fuel cell after the start of power generation of the fuel cell, after power generation is stopped.

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