JP2010262824A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of continuous operation, even under a high load in the fuel cell. <P>SOLUTION: The fuel cell system 10 includes a fuel cell stack 12, a fuel gas circulation path 30, connected between a hydrogen-off gas outlet of the fuel cell stack 12 and a fuel gas supply path 24; a hydrogen pump 46 and a gas-liquid separator 32 provided to the fuel gas circulation path 30; a detour 36 connected to both connection parts 38 and 40 on upstream and downstream sides separated in a gas reflux direction of the fuel gas circulation path 30, while bypassing the gas-liquid separator 32, and flow-path switching valves 42 and 44, provided between both the connection parts 38 and 40 on the upstream and downstream sides of at least one path of the fuel gas circulation path 30 and the detour 36. The flow-path switching valves 42 and 44 are opened or closed so that the hydrogen-off gas is sent via the detour 36, to the fuel gas supply path 24, at the high-load operation of the fuel cell stack 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes a fuel cell that generates electricity by an electrochemical reaction between an oxidizing gas and a fuel gas, a fuel gas circulation passage connected between the spent fuel gas outlet and the fuel gas supply passage of the fuel cell, The present invention relates to a fuel cell system including a gas-liquid separator that is provided upstream of a fuel gas circulation device in a gas recirculation direction of a fuel gas circulation channel and removes moisture contained in spent fuel gas.

  The fuel cell stack is configured by stacking a plurality of sets of fuel cell units, for example, a membrane-electrode assembly (MEA) composed of an anode side electrode, an electrolyte membrane and a cathode side electrode and a separator. That is, each fuel cell is configured by arranging an anode side electrode on one side of an electrolyte membrane made of a polymer ion exchange membrane, a cathode side electrode on the other side, and further providing separators on both sides. is doing. A plurality of such fuel battery cells are stacked and sandwiched between current collector plates, insulating plates, and end plates to constitute a fuel cell stack that generates a high voltage.

  In such a fuel cell, a fuel gas, for example, a gas containing hydrogen is supplied to the anode side electrode, and an oxidizing gas, for example, air is supplied to the cathode side electrode. As a result, the fuel gas and the oxidizing gas are subjected to an electrochemical reaction to generate an electromotive force, water is generated at the cathode side electrode, and water may also be contained in the flow path on the anode side electrode side. .

  Conventionally, as described in Patent Document 1, a fuel including a fuel cell main body, a gas flow path for supplying and discharging a reaction gas to and from the fuel cell, and an adjustment component for adjusting a gas flow state in the gas flow path A battery system comprising at least two scavenging paths for scavenging a part of the gas flow path, wherein the first scavenging path is formed to include a fuel cell body, and the second scavenging path is a fuel cell body. A fuel cell system configured to bypass is described. Further, in this fuel cell system, when the fuel cell system is stopped in a low temperature environment, a two-stage moisture removal operation is performed, and in the first-stage moisture removal operation, moisture is removed through the first scavenging path. Then, the fuel cell main body is dried, and then, in the second stage water removal operation, the hydrogen pump water removal operation can be performed in the second scavenging path not including the fuel cell main body. It is supposed to be.

Japanese Patent Laid-Open No. 2007-157489

  In the case of a conventionally known fuel cell system such as the fuel cell system described in Patent Document 1, the fuel cell main body is supplied from the hydrogen gas supply source through the fuel gas supply channel to the fuel cell main body. The hydrogen off-gas discharged from the gas passes through the circulation channel, is returned to the fuel gas supply channel via the hydrogen pump, and is supplied to the fuel cell main body again. In such a configuration, at the time of high load operation of the fuel cell due to an increase in power generation demand for the fuel cell or the like, the load of the motor for driving the hydrogen pump becomes high, so the motor also becomes high load operation. For this reason, a motor tends to become high temperature, and in some cases, the temperature of the motor may tend to exceed a design allowable temperature as a thermal rating. For example, when the coil constituting the motor is hardened by impregnating the varnish, the allowable temperature for heat resistance of the varnish is about 150 to 180 ° C., whereas the temperature of the motor tends to exceed this allowable temperature. There is a possibility. For this reason, conventionally, when the temperature of the motor tends to exceed the allowable temperature, it is possible to reduce the temperature of the motor by intermittently operating the motor. Realizing continuous operation at high load becomes difficult. For this reason, the structure which can implement | achieve continuous driving | running | working at the time of the high load of a fuel cell is desired.

  An object of the present invention is to enable continuous operation in a fuel cell system even when the fuel cell has a high load.

  A fuel cell system according to the present invention includes a fuel cell that generates electricity by an electrochemical reaction between an oxidizing gas and a fuel gas, a fuel gas supply channel that supplies the fuel gas to the fuel cell, and an upstream side of the fuel gas supply channel. The fuel gas supply device provided, the fuel gas circulation passage connected between the spent fuel gas outlet and the fuel gas supply passage of the fuel cell, and the fuel gas circulation passage provided in the fuel gas circulation passage. A fuel gas circulation device driven by a motor that recirculates spent fuel gas from the flow path to the fuel gas supply flow path, and provided upstream of the fuel gas circulation device in the gas recirculation direction of the fuel gas circulation flow path A gas-liquid separator that removes water contained in the spent fuel gas, and a gas-liquid separator that bypasses the upstream-side connection portion and the downstream-side connection portion that are separated in the gas recirculation direction of the fuel gas circulation passage. Connected bypass channel and fuel A flow path switching valve provided between the upstream connection portion and the downstream connection portion of at least one of the gas circulation flow path and the bypass flow path. The fuel cell system is characterized in that opening and closing are switched so that spent fuel gas is sent to the fuel gas supply channel via the bypass channel during the load operation.

  According to the fuel cell system of the present invention, spent fuel gas is sent to the fuel gas supply channel via the detour channel that bypasses the gas-liquid separator during high-load operation of the fuel cell. For this reason, the gas-liquid separation rate of the spent fuel gas sent to the fuel gas circulation device located on the gas downstream side of the detour channel can be intentionally reduced. That is, the amount of water in the gas sent to the fuel gas circulation device can be increased without removing the water present in the spent fuel gas by the gas-liquid separator. This moisture evaporates in the periphery of the drive unit of the fuel gas circulation device, and the heat connected to the drive unit and the drive unit can be cooled by removing the heat of vaporization. For this reason, even when the motor continuously operates during high load operation of the fuel cell, it is possible to prevent the motor from excessively rising in temperature, and it is possible to realize continuous operation at a high load of the fuel cell. In addition, since the water flowing into the fuel gas circulation device evaporates, it does not become a load on the fuel gas circulation device. As a result, the time rating of the fuel gas circulation device can be extended.

It is a figure which shows the basic composition of the fuel cell system of one example of embodiment which concerns on this invention. It is a figure which shows the structure of the A section of FIG. 1 more concretely. It is a figure which shows three examples from which the bypass part structure and the main flow path differ about the B section of FIG.

  Hereinafter, an example of an embodiment according to the present invention will be described in detail with reference to the drawings. 1 to 3 show the present embodiment. FIG. 1 is a diagram showing a basic configuration of an example fuel cell system according to an embodiment of the present invention. FIG. 2 is a diagram more specifically showing the structure of part A of FIG. FIG. 3 is a diagram showing three examples in which the structure of the joining portion between the bypass channel and the main channel is different for the portion B in FIG. As shown in FIG. 1, the fuel cell system 10 is used by being mounted on a fuel cell vehicle, for example, and includes a fuel cell stack 12. The fuel cell stack 12 has a plurality of fuel cells stacked, and a current collector plate and an end plate are provided at both ends of the fuel cell stack 12 in the stacking direction. The plurality of fuel cells, the current collector plate, and the end plate are fastened with tie rods, nuts, and the like. An insulating plate can also be provided between the current collector plate and the end plate.

  Although a detailed view of each fuel cell is omitted, it is assumed that, for example, a membrane assembly in which an electrolyte membrane is sandwiched between an anode side electrode and a cathode side electrode and separators on both sides thereof are provided. Further, hydrogen gas that is a fuel gas can be supplied to the anode side electrode (hereinafter simply referred to as “anode”), and air that is an oxidizing gas is supplied to the cathode side electrode (hereinafter simply referred to as “cathode”). It is possible. Then, hydrogen ions generated by the catalytic reaction at the anode are moved to the cathode through the electrolyte membrane, and water is generated by causing an electrochemical reaction with oxygen at the cathode. Also, an electromotive force is generated by moving electrons from the anode to the cathode through an external circuit. That is, the fuel cell stack 12 in which a plurality of fuel cells shown in FIG. 1 are stacked generates power by an electrochemical reaction between the oxidizing gas and the fuel gas. Further, water existing on the cathode side, such as produced water on the cathode side, also enters the anode-side flow path through the electrolyte membrane.

  In addition, an oxidizing gas supply channel 14 is provided to supply air, which is an oxidizing gas, to the fuel cell stack 12. Further, in order to discharge air off-gas that is used air after being subjected to an electrochemical reaction from the fuel cell stack 12, an oxidizing gas discharge channel 16 is provided. An air compressor 18 that is an oxidizing gas supply device is provided upstream of the oxidizing gas supply flow path 14. The air pressurized by the air compressor 18 is humidified by the humidifier 20 and then supplied to the oxidizing gas flow path on the cathode side of the fuel cell stack 12.

  The air off-gas supplied to the fuel cell stack 12 and subjected to an electrochemical reaction in each fuel cell is discharged from the fuel cell stack 12 through the oxidizing gas system discharge flow path 16 and then passes through the humidifier 20. And then released into the atmosphere via the diluter 22. The humidifier 20 serves to humidify the moisture obtained from the air off-gas discharged from the fuel cell stack 12 to the air before being supplied to the fuel cell stack 12.

On the other hand, a fuel gas supply channel 24 is provided to supply hydrogen gas, which is a fuel gas, to the fuel cell stack 12. In addition, in order to discharge hydrogen off-gas that is used hydrogen gas after being subjected to an electrochemical reaction from the fuel cell stack 12, a fuel gas system discharge passage 26 is provided. The hydrogen off gas includes unreacted hydrogen. Further, the hydrogen off gas may contain moisture. For example, the hydrogen off gas includes hydrogen (H ₂ ), nitrogen (N ₂ ), water (H ₂ O), and the like. A hydrogen gas supply device such as a high-pressure hydrogen tank, which is a fuel gas supply device (not shown), is provided upstream of the fuel gas supply flow path 24. Hydrogen gas is supplied from the hydrogen gas supply device to the fuel cell stack 12 through a fuel gas supply valve 28 that is an electromagnetic valve.

  The hydrogen off-gas supplied to the anode-side fuel gas passage of the fuel cell stack 12 and subjected to the electrochemical reaction is discharged from the fuel cell stack 12 through the fuel gas circulation passage 30. The upstream side of the fuel gas circulation passage 30 serves as a fuel gas discharge passage. The hydrogen gas offflow outlet of the fuel cell stack 12 and the downstream portion of the fuel gas supply passage 24 from the fuel gas supply valve 28. Connected between.

  The fuel gas circulation channel 30 has a main channel 34 including a gas-liquid separator 32 and a bypass channel 36 that bypasses the gas-liquid separator 32. That is, as shown in FIG. 2, the upstream end of the bypass flow path 36 is connected by an upstream connection portion 38 on the gas upstream side of the gas-liquid separator 32 of the main flow path 34, and the downstream end of the bypass flow path 36 is They are connected by a downstream side connecting portion 40 on the gas downstream side of the gas-liquid separator 32 of the main flow path 34. That is, the bypass flow path 36 is connected to the upstream connection section 38 and the downstream connection section 40 that are separated in the gas recirculation direction of the fuel gas circulation flow path 30 so as to bypass the gas-liquid separator 32.

  Further, the first flow path switching valve 42 and the second flow path, which are electromagnetic valves, are disposed between the upstream connection portion 38 and the downstream connection portion 40 of the main flow path 34 and the bypass flow path 36 of the fuel gas circulation flow path 30. A switching valve 44 is provided for each. The fuel gas circulation channel 30 returns the hydrogen off-gas containing unreacted hydrogen gas discharged from the fuel cell stack 12 to the fuel gas supply channel 24, that is, the fuel gas supply from the fuel gas circulation channel 30 It is provided for refluxing to the flow path 24 (FIG. 1). A hydrogen pump 46 that is a fuel gas circulation device is provided in the fuel gas circulation passage 30 on the downstream side of the downstream connection portion 40 in the gas recirculation direction. The hydrogen pump 46 returns the hydrogen off gas to the fuel gas supply flow path 24 through the fuel gas circulation flow path 30, merges it with new hydrogen gas sent from the hydrogen gas supply device, and then supplies the hydrogen off gas to the fuel cell stack 12 again. . The hydrogen pump 46 is, for example, a roots type, scroll type, screw type or the like, and drives a pump rotor 48 provided in the casing by a motor 50. The motor 50 is driven by power supplied from a secondary battery (not shown). As shown in FIG. 1, the driving of the motor 50 is controlled by a controller (ECU) 52 that is a control unit described later. The hydrogen pump 46 can adjust the rotation speed.

  The hydrogen off-gas discharged from the fuel cell stack 12 during a low-load operation of the motor or the like is removed from the water by the gas-liquid separator 32 provided upstream of the hydrogen pump 46 in the gas recirculation direction. 46. An exhaust / drain channel 54 is connected to the gas / liquid separator 32, and a purge valve 56, which is an exhaust / drain valve and is an electromagnetic valve, is provided in the middle of the exhaust / drain channel 54. The gas and moisture sent to the downstream side of the exhaust drainage flow channel 54 merge with the air off-gas sent from the upstream side of the oxidizing gas system discharge flow channel 16 in the diluter 22, and the hydrogen concentration is sufficiently lowered. Is discharged to the outside. It should be noted that a portion separated from the gas-liquid separator 32 between the upstream side connection portion 38 and the downstream side connection portion 40 of the main flow path 34 constituting the fuel gas circulation flow path 30 is separate from the exhaust drainage flow path 54. An exhaust valve, which is an electromagnetic valve, can be provided in this part.

  The controller 52 is connected to the air compressor 18 and the fuel gas supply valve 28 so that a control signal can be transmitted. The controller 52 outputs a control signal for controlling driving to the air compressor 18 and a control signal for controlling opening and closing of the fuel gas supply valve 28. The controller 52 is also connected to the first flow path switching valve 42 and the second flow path switching valve 44, and controls opening and closing of the switching valves 42 and 44. The first flow path switching valve 42 and the second flow path switching valve 44 are selectively opened as will be described later. Such a controller 52 includes a microcomputer having a CPU, a memory and the like.

  The controller 52 is connected to a start switch (not shown) that functions as an ignition switch of the fuel cell system 10, and the power generation start process is executed on condition that a power generation start signal corresponding to the ON state is received from the start switch. Then, each element such as the fuel gas supply valve 28, the air compressor 18, and the hydrogen pump 46 is controlled so that the power generation operation stop process is executed on the condition that the power generation stop signal corresponding to the off state is received.

  FIG. 3A shows a downstream side connection portion 40 that is a joining portion of the bypass channel 36 and the main channel 34. In the example shown in the figure, the bypass channel 36 and the main channel 34 are connected so as to intersect at a substantially right angle. The gas inlet of the hydrogen pump 46 (FIGS. 1 and 2) is connected to the gas downstream side of the downstream side connecting portion 40 of the main flow path 34. As shown in FIG. 2, the hydrogen pump 46 drives a pump rotor 48 provided in the casing by a drive shaft 60 provided integrally with a rotation shaft 58 of the motor 50. For example, when the hydrogen pump 46 is a roots type, the casing has a saddle-shaped rotor that is two pump rotors 48 facing each other, and one saddle-shaped rotor is driven by the drive shaft 60 and the other The saddle type rotor is driven by a driven shaft (not shown) driven by a drive shaft 60 via a gear mechanism (not shown). The rotation shaft 58 of the motor 50 is rotatably supported inside the motor case. Further, the casing and the motor case can be integrally coupled. Moreover, a casing and a motor case can also be comprised by a single casing. A motor rotor 62 is provided on the outer diameter side of the rotating shaft 58 of the motor 50, and the motor rotor 62 is opposed to a motor stator 64 fixed to the motor case. The hydrogen off-gas sucked into the hydrogen pump 46 from the gas inlet and pressurized inside is discharged from the gas outlet and sent to the fuel gas supply channel 24 (FIG. 1).

  Furthermore, the controller 52 shown in FIG. 1 has a flow path switching valve control unit. The flow path switching valve controller controls each flow path switching valve so that the hydrogen off-gas is sent to the fuel gas supply flow path 24 via the bypass flow path 36 instead of the main flow path 34 when the fuel cell stack 12 is operated at a high load. 42 and 44 are controlled. Therefore, the flow path switching valves 42 and 44 are configured so that the hydrogen off gas is sent to the fuel gas supply flow path 24 via the bypass flow path 36 when the fuel cell stack 12 is operated at a high load by the flow path switching valve control unit. Opening and closing is switched.

  For example, when the fuel cell system 10 is used for a fuel cell vehicle, the controller 52 receives a detection signal from an accelerator pedal sensor or the like that detects the depression amount of an accelerator pedal, and the fuel cell stack 12 based on the detection signal. The request output for is calculated. Based on the required output, the controller 52 calculates the rotational speed of the motor 50 for driving the hydrogen pump 46 and the rotational speed of the motor 66 for driving the air compressor 18, and uses the driving of each motor 50, 66 as the calculated value. Control based on. Here, the flow path switching valve control unit determines that the fuel cell stack 12 is in a high load operation when the required output is equal to or higher than a preset set value, and sets the first flow path switching valve 42. The second flow path switching valve 44 is opened while the valve is closed. In this case, the hydrogen off-gas discharged from the fuel cell stack 12 is sent to the hydrogen pump 46 through the bypass channel 36 without passing through the gas-liquid separator 32. On the other hand, when the required output is less than a preset value, the flow path switching valve control unit determines that the fuel cell stack 12 is not in a high load operation, and thus the first flow path switching valve 42. And the second flow path switching valve 44 is closed. In this case, the hydrogen off-gas discharged from the fuel cell stack 12 is sent to the hydrogen pump 46 through the main channel 34 via the gas-liquid separator 32.

  As a first example of another example, the motor 50 for driving the hydrogen pump 46 may be provided with a motor temperature thermistor that is a motor temperature monitoring means, and the detected temperature of the motor temperature thermistor may be input to the controller 52. The flow path switching valve controller stores in advance map data obtained from the relationship between the detected temperature and the required output, and the required output is set in advance by referring to the data from the detected temperature of the motor temperature thermistor. It is determined whether or not it is greater than or equal to the value. When the required output is equal to or higher than the set value, it is determined that the fuel cell stack is operating at a high load, and the opening and closing of the first flow path switching valve and the second flow path switching valve are controlled, and the hydrogen off-gas flows in a detour. Opening and closing is switched so as to be sent to the fuel gas supply passage 24 via the passage 36.

  As another example of the fuel cell stack 12, when the map temperature is not stored in the flow path switching valve control unit and the detected temperature of the motor temperature thermistor exceeds a preset temperature, the fuel cell stack 12 And the opening and closing of the first flow path switching valve 42 and the second flow path switching valve 44 is controlled by the flow path switching valve control unit, so that the hydrogen off gas passes through the bypass flow path 36. It is also possible to switch between opening and closing so as to be sent to the fuel gas supply channel 24.

  As a third example of another example, the controller 52 is not provided with a flow path switching valve control unit, and the first flow path switching valve 42 is provided when the detected temperature of the motor temperature thermistor exceeds a predetermined temperature. By inputting a signal for closing the valve and inputting a signal for opening the second flow path switching valve 44, each flow path is configured such that hydrogen off-gas is sent to the fuel gas supply flow path 24 via the bypass flow path 36. The switching valves 42 and 44 can be switched between open and closed. In the case of the first example to the third example of another example, the motor temperature thermistor that has been conventionally provided for protecting the motor 50 (FIG. 2) can also be used.

  According to the fuel cell system 10 of the present embodiment configured as described above, each of the flow path switching valves 42 and 44 allows the hydrogen off-gas to flow through the bypass flow path 36 during the high load operation of the fuel cell stack 12. Opening and closing is switched so as to be sent to the supply channel 24. For this reason, at the time of high load operation, when water is contained in the hydrogen offgas immediately after being discharged from the fuel cell stack 12, the gas-liquid separator 32 does not remove the water in the hydrogen offgas, and Then, a hydrogen off gas containing moisture is sent to the hydrogen pump 46. Therefore, the gas-liquid separation rate of the hydrogen off-gas sent to the hydrogen pump 46 located on the gas downstream side of the detour channel 36 can be intentionally reduced. That is, the amount of water in the gas sent to the hydrogen pump 46 can be increased without removing the water present in the hydrogen off-gas by the gas-liquid separator 32. The moisture evaporates in the periphery of the pump rotor 48 (FIG. 2), which is a drive unit of the hydrogen pump 46, and the heat 50 is removed from the pump rotor 48 and the motor 50 having the rotary shaft 58 connected to the pump rotor 48. Can be cooled. The pump rotor 48 and the motor rotor 62 are thermally connected via shafts 58 and 60. For this reason, even when the motor 50 continuously operates during high load operation of the fuel cell stack 12, it is possible to prevent the motor 50 from excessively rising in temperature and to realize continuous operation of the fuel cell stack 12 at high load. Become. Moreover, since the water flowing into the hydrogen pump 46 evaporates, it does not become a load on the hydrogen pump 46. As a result, the time rating of the hydrogen pump 46, that is, the time during which the hydrogen pump 46 can be continuously driven at a certain number of rotations can be extended.

  In addition, as the structure of the fourth example of another example, the upstream side connecting portion 38 and the fuel gas circulation passage 30 are not provided with two of the first passage switching valve 42 and the second passage switching valve 44. A three-way valve type flow path switching valve is provided in one or both of the downstream side connection portions 40, and the three-way valve type flow path switching valve allows hydrogen off-gas to flow through the bypass flow path 36 during high load operation of the fuel cell stack 12. The opening and closing can be switched so as to be sent to the gas supply channel 24.

  Further, as a structure of the fifth example of another example, the fuel gas circulation passage 30 is not provided with two of the first flow passage switching valve 42 and the second flow passage switching valve 44, but on the gas-liquid separator 32 side. The first flow path switching valve 42 is provided so that the hydrogen off gas is sent to the fuel gas supply flow path 24 via the bypass flow path 36 when the fuel cell stack 12 is operated at a high load. It is also possible to switch between opening and closing as described.

  According to this configuration, the number of flow path switching valves can be reduced as compared with the case where two flow path switching valves are provided. In addition, when two flow path switching valves are provided, the gas flow is blocked when both switching valves are closed and cannot be driven due to some trouble, so that the durability of the fuel cell system 10 is effective. There is room for improvement in terms of ensuring On the other hand, when only one of the first flow path switching valves 42 is provided as described above, the downstream side of the bypass flow path 36 and the gas inlet of the hydrogen pump 46 are always provided even when a malfunction occurs. Are connected to each other, the flow path is not blocked, and the durability of the fuel cell system 10 can be more effectively ensured. In this case, even if the first flow path switching valve 42 is opened, the hydrogen off gas flows also to the bypass flow path 36 side, so that the gas-liquid separation rate of the hydrogen off gas has two flow path switching valves. It is worse than when it is provided.

  FIG. 3B shows a structure of a sixth example of another example. In the structure of the sixth example, the downstream side connecting portion 40 is connected so that the downstream side of the bypass channel 36 is inclined with respect to the main channel 34. That is, the bypass flow path 36 is inclined with respect to the main flow path at the downstream side connection portion 40 in accordance with the gas-liquid separation performance required at the downstream side connection portion 40. In this case, the downstream side of the bypass flow path 36 is inclined to the upper side of FIG. For this reason, among the hydrogen off-gas containing moisture, the flow rate of the gas toward the hydrogen pump 46 side of the hydrogen pump 46 and the gas-liquid separator 32 becomes high, the gas-liquid separation rate deteriorates, and the gas enters the hydrogen pump 46. Inflow of water will increase. Therefore, the cooling performance of the motor 50 for driving the hydrogen pump 46 can be improved.

  FIG. 3C shows the structure of a seventh example of another example. Also in the structure of the seventh example, the bypass flow path 36 is inclined with respect to the main flow path 34 at the downstream side connection portion 40 according to the gas-liquid separation performance required at the downstream side connection portion 40. In this case, the downstream side of the bypass channel 36 is inclined toward the gas-liquid separator 32. For this reason, in the hydrogen off-gas containing moisture, the flow rate of the gas toward the gas-liquid separator 32 of the hydrogen pump 46 and the gas-liquid separator 32 is increased, and the gas-liquid separation rate is improved. The amount of water flowing into the pump 46 decreases. Therefore, the cooling performance of the motor 50 for driving the hydrogen pump 46 is lowered.

  According to the sixth example or the seventh example of such another example, according to the performance of the hydrogen pump 46, the gas-liquid separation rate can be adjusted only by changing the piping shape, and the amount of water flowing into the hydrogen pump 46 is adjusted. it can. For this reason, if the thermal rating is insufficient, it is more preferable to incline the bypass flow path 36 toward the hydrogen pump 46 at the downstream connection portion 40 as in another sixth example. Further, the amount of water flowing into the hydrogen pump 46 can be finely adjusted only by changing the piping shape. For example, when the performance of the fuel cell stack 12 is worse than expected, the thermal rating can be improved without changing the design of the structure of the hydrogen pump 46 itself.

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 12 Fuel cell stack, 14 Oxidation gas supply flow path, 16 Oxidation gas system discharge flow path, 18 Air compressor, 20 Humidifier, 22 Diluter, 24 Fuel gas supply flow path, 26 Fuel gas system discharge flow 28, fuel gas supply valve, 30 fuel gas circulation channel, 32 gas-liquid separator, 34 main channel, 36 bypass channel, 38 upstream connection, 40 downstream connection, 42 first channel switching valve, 44 Second flow path switching valve, 46 Hydrogen pump, 48 Pump rotor, 50 Controller (ECU), 52 Exhaust drain flow path, 54 Purge valve, 56 Rotating shaft, 58 Drive shaft, 60 Motor rotor, 62 Motor stator, 64 Motor

Claims (1)

A fuel cell that generates electricity by an electrochemical reaction between an oxidizing gas and a fuel gas;
A fuel gas supply channel for supplying fuel gas to the fuel cell;
A fuel gas supply device provided upstream of the fuel gas supply flow path;
A fuel gas circulation passage connected between the spent fuel gas outlet and the fuel gas supply passage of the fuel cell;
A fuel gas circulation device driven by a motor, provided in the fuel gas circulation flow path, for recirculating the spent fuel gas from the fuel gas circulation flow path to the fuel gas supply flow path;
A gas-liquid separator that is provided on the upstream side in the gas recirculation direction from the fuel gas circulation device of the fuel gas circulation flow path and removes moisture contained in the spent fuel gas;
A detour channel connected by bypassing the gas-liquid separator to the upstream side connection portion and the downstream side connection portion separated in the gas recirculation direction of the fuel gas circulation channel;
A flow path switching valve provided between the upstream connection portion and the downstream connection portion of at least one of the fuel gas circulation flow path and the bypass flow path,
The flow path switching valve is switched between open and closed so that spent fuel gas is sent to the fuel gas supply flow path via the bypass flow path during high load operation of the fuel cell.

Images