On-vehicle fuel cell system

A fuel cell includes a cathode side and an anode side. An oxidant gas is fed to the cathode side. In the cathode side, an oxidant exhaust gas is generated by using the oxidant gas. A fuel gas is fed to the anode side. In the anode side, a fuel exhaust gas is generated by using the fuel gas. The oxidant exhaust gas and the fuel exhaust gas are discharged from an outlet of a mixed exhaust gas discharge pipe as a mixed exhaust gas. The dilution apparatus is connected to the outlet of the mixed exhaust gas discharge pipe. The dilution apparatus includes a stirring chamber and an opening. The stirring chamber communicates with the mixed exhaust gas discharge pipe and expands from the outlet of the mixed exhaust gas discharge pipe. The opening is provided in the stirring chamber to take in air.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2015-208053, filed Oct. 22, 2015, entitled “On-Vehicle Fuel Cell System.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to an on-vehicle fuel cell system.

2. Description of the Related Art

For example, a solid polymer electrolyte fuel cell includes an electrolyte membrane electrode assembly (MEA) having an electrolyte membrane that is a polymer ion-exchange membrane, on one face of which an anode electrode is provided, and on the other face of which a cathode electrode is provided. The electrolyte membrane electrode assembly is held between separators to constitute a power generation cell (unit cell). Generally, a predetermined number of power generation cells are stacked to form an on-vehicle fuel cell stack, which is incorporated to a fuel cell vehicle (such as fuel cell electric vehicles).

In the fuel cell vehicle, when used fuel gas that has been supplied to a fuel cell and discharged from the anode electrode (hereinafter also referred to as fuel exhaust gas), is discharged to the outside, the concentration of hydrogen is declined to a predetermined concentration or less, by using a dilution apparatus.

For example, in a dilution apparatus for exhaust gas disclosed in Japanese Unexamined Patent Application Publication No. 2008-123872, fuel exhaust gas discharged from a fuel cell via an fuel gas exhaust pipe is introduced into a dilation container via an exhaust gas inlet pipe. Oxidation gas fed via an oxidation gas exhaust pipe is guided into the dilution container via a dilution gas inlet pipe, and is discharged into the dilution container through a discharge hole.

The fuel exhaust gas introduced via the exhaust gas inlet pipe is mixed and diluted with the oxidation gas discharged through the discharge hole to generate mixed gas. Then, the mixed gas is sucked into a suction hole of the dilution gas inlet pipe, and is mixed with oxidation gas also in the dilution gas inlet pipe. The mixed gas is transported to the outside of the dilution container. In this manner, the mixed gas diluted with the oxidation gas can be discharged to the outside.

SUMMARY

According to one aspect of the present invention, the on-vehicle fuel cell system includes a fuel cell that generate electricity through electrochemical reaction of oxidant gas fed to a cathode side with fuel gas fed to an anode side with an electrolyte membrane being located between the cathode side and the anode side.

The on-vehicle fuel cell system further includes an oxidant gas feeding pipe, an oxidant exhaust gas discharge pipe, a fuel gas feeding pipe, a fuel exhaust gas discharge pipe, a mixed exhaust gas discharge pipe, and a dilution unit. The oxidant gas feeding pipe feeds oxidant gas to the fuel cell, while the oxidant exhaust gas discharge pipe discharges oxidant exhaust gas, which is oxidant gas at least partially used in the cathode side, from the fuel cell.

The fuel gas feeding pipe feeds fuel gas to the fuel cell, while the fuel exhaust gas discharge pipe discharges fuel exhaust gas, which is oxidant gas at least partially used in the anode side, from the fuel cell. The mixed exhaust gas discharge pipe connects the oxidant exhaust gas discharge pipe to the fuel exhaust gas discharge pipe, and discharges mixed exhaust gas of oxidant exhaust gas and fuel exhaust gas, while the dilution unit is connected to the mixed exhaust gas discharge pipe.

The dilution unit includes a stirring chamber that expands from an outlet of the mixed exhaust gas discharge pipe and communicates with the mixed exhaust gas discharge pipe, and an opening for taking air is formed in a lower face of the stirring chamber.

According to another aspect of the present invention, an on-vehicle fuel cell system includes a fuel cell, an oxidant gas feeding pipe, an oxidant exhaust gas discharge pipe, a fuel gas feeding pipe, a fuel exhaust gas discharge pipe, a mixed exhaust gas discharge pipe, and a dilution apparatus. The fuel cell is to generate electricity through electrochemical reaction of an oxidant gas with a fuel gas. The fuel cell includes a cathode side, an anode side, and an electrolyte membrane. The oxidant gas is fed to the cathode side. In the cathode side, an oxidant exhaust gas is generated by using the oxidant gas. The fuel gas is fed to the anode side. In the anode side, a fuel exhaust gas is generated by using the fuel gas. The electrolyte membrane is provided between the cathode side and the anode side. The oxidant gas is fed to the fuel cell through the oxidant gas feeding pipe. The oxidant exhaust gas is discharged from the fuel cell through the oxidant exhaust gas discharge pipe. The fuel gas is fed to the fuel cell through the fuel gas feeding pipe. The fuel exhaust gas is discharged from the fuel cell through the fuel exhaust gas discharge pipe. The mixed exhaust gas discharge pipe connects the oxidant exhaust gas discharge pipe and the fuel exhaust gas discharge pipe. The oxidant exhaust gas and the fuel exhaust gas are discharged from an outlet of the mixed exhaust gas discharge pipe as a mixed exhaust gas. The dilution apparatus is connected to the outlet of the mixed exhaust gas discharge pipe. The dilution apparatus includes a stirring chamber and an opening. The stirring chamber communicates with the mixed exhaust gas discharge pipe and expands from the outlet of the mixed exhaust gas discharge pipe. The opening is provided in the stirring chamber to take in air.

DESCRIPTION OF THE EMBODIMENTS

As illustrated inFIG. 1, an on-vehicle fuel cell system10in accordance with embodiment of the present disclosure is mounted in a fuel cell vehicle12such as a fuel cell electric vehicle. In the fuel cell system10, a fuel cell stack14is disposed in a motor room12M near front wheels15f,15f. A below-mentioned hydrogen tank64and a dilution unit (dilution apparatus)92are disposed between rear wheels15r,15r.

As illustrated inFIG. 2, the fuel cell system10includes the fuel cell stack14, an oxidant gas feeder16for feeding oxidant gas to the fuel cell stack14, and a fuel gas feeder18for feeding fuel gas to the fuel cell stack14. The fuel cell system10further includes a cooling medium feeder (not illustrated) for feeding a cooling medium to the fuel cell stack14.

The fuel cell stack14is configured by stacking a plurality of power generation cells (fuel cells)20in a vehicle width direction (direction indicated by an arrow B) or vehicle longitudinal direction (direction indicated by an arrow A). In the power generation cells20, an electrolyte membrane electrode assembly24is held between a first separator26and a second separator28. The first separator26and the second separator28each are formed of a metal separator or a carbon separator.

The electrolyte membrane electrode assembly24includes a solid polymer electrolyte membrane30such as a thin film made of perfluorosulfonic acid containing moisture, and an anode electrode32and an cathode electrode34, which hold the solid polymer electrolyte membrane30therebetween. The solid polymer electrolyte membrane30is made of a fluorine electrolyte, HC (hydrocarbon) electrolyte, or the like.

A fuel gas channel36for feeding fuel gas to the anode electrode32is provided between the first separator26and the electrolyte membrane electrode assembly24. An oxidant gas channel38for feeding oxidant gas to the cathode electrode34is provided between the second separator28and the electrolyte membrane electrode assembly24. A cooling medium channel40for circulating a cooling medium is provided between the first separator26and the second separator28.

The fuel cell stack14has a fuel gas inlet manifold42a, a fuel gas outlet manifold42b, an oxidant gas inlet manifold44a, and an oxidant gas outlet manifold44b, which communicate with one another in the stacking direction of the power generation cells20. The fuel gas inlet manifold42aand the fuel gas outlet manifold42bserve to circulate fuel gas such a hydrogen-containing gas (hereinafter also referred to as hydrogen gas). The oxidant gas inlet manifold44aand the oxidant gas outlet manifold44bserves to circulate oxidant gas such as oxygen-containing gas (hereinafter also referred to as air).

The oxidant gas feeder16includes an air pump (compressor)46for compressing air from atmosphere and feeding compressed air, and the air pump46is disposed on an air feeding pipe (oxidant gas feeding pipe)48. The air feeding pipe48is provided with a humidifier52and an inlet sealing valve54adownstream of the air pump46, and communicates with the oxidant gas inlet manifold44aof the fuel cell stack14. The air feeding pipe48feed air to the fuel cell stack14.

The oxidant gas outlet manifold44bof the fuel cell stack14communicates with an air discharge pipe (oxidant exhaust gas discharge pipe)56. The air discharge pipe56is provided with the humidifier52, an outlet sealing valve54b, and a back sealing valve58. A bypass channel60is located between the humidifier52and the air pump46, and is connected to the air feeding pipe48and the air discharge pipe56. The bypass channel60is provided with a bypass valve62. The fuel cell stack14discharges oxidant exhaust gas, which is oxidant gas at least partially used in the cathode electrode34, via the air discharge pipe56.

The fuel gas feeder18includes the hydrogen tank64that stores high-pressure hydrogen, and the hydrogen tank64communicates with the fuel gas inlet manifold42aof the fuel cell stack14via a hydrogen feeding pipe (fuel gas feeding pipe)66. The hydrogen feeding pipe66feeds hydrogen to the fuel cell stack14. The hydrogen feeding pipe66is provided with a shutoff valve68and an ejector70.

The fuel gas outlet manifold42bof the fuel cell stack14communicates with an off-gas pipe (fuel exhaust gas discharge pipe)76. The off-gas pipe76derives fuel exhaust gas, which is fuel gas at least partially used in the anode electrode32, from the fuel cell stack14. The off-gas pipe76is connected to a gas-liquid separator78, and is connected to the ejector70via a circulation channel80that branches downstream of the gas-liquid separator78.

The off-gas pipe76is provided with a purge valve84located downstream of the circulation channel80. A drain channel86for discharging fluid mainly containing liquid is formed in the bottom of the gas-liquid separator78. The drain channel86is provided with a drain valve88, and is connected to the off-gas pipe76downstream of the purge valve84. The off-gas pipe76merges with the air discharge pipe56to form a mixed exhaust gas discharge pipe90. The mixed exhaust gas discharge pipe90discharges a mixture of oxidant exhaust gas and fuel exhaust gas, and the mixed exhaust gas discharge pipe90is connected to a dilution unit92made of a conductive material.

As illustrated inFIG. 1, the dilution unit92is disposed in the rear of the hydrogen tank64in the vehicle longitudinal direction (the direction indicated by an arrow Ab), and as illustrated inFIG. 3, is fixed (mounted) to a rear portion of the vehicle using a mount structure94. As illustrated inFIGS. 3 to 6, the dilution unit92is shaped like a bowl opened to the downside, and has a stirring chamber96. An opening96sfor taking air is formed in the lower face of the stirring chamber96.

The stirring chamber96expands from an outlet90eof the mixed exhaust gas discharge pipe90, and communicates with the mixed exhaust gas discharge pipe90. The mixed exhaust gas discharge pipe90is connected to the dilution unit92separated upward from a center of the stirring chamber96in a vertical direction. A stirring plate98is disposed at the outlet90eof the mixed exhaust gas discharge pipe90, and enters a flowing area of mixed exhaust gas. The stirring plate98is disposed to divide the outlet90einto two.

The outlet90eof the mixed exhaust gas discharge pipe90is connected to one end (one end of the stirring chamber96)92fin front of the dilution unit92in the vehicle longitudinal direction. The outlet90eis offset from the stirring chamber96in the vehicle width direction (direction indicated by an arrow B). As illustrated inFIG. 6, a curved opposite face100constituting the stirring chamber96is formed on an inner wall face of the other end92bopposite to the one end of the dilution unit92. A plurality of ribs102are formed on the opposite face100.

As illustrated inFIGS. 3 and 4, a stepped portion104that extends in the vehicle width direction the dilution unit92is formed at the longitudinal center of the upper face of the dilution unit92. The stepped portion104is continuously formed over the upper face and both side faces of the dilution unit92, and is easily broken, for example, when being subjected to an external load. As illustrated inFIG. 5andFIG. 7, a vent hole106through which the stirring chamber96communicates with the outside of the dilution unit92is formed on the upper portion of the one end92fof the dilution unit92above the connection between the dilution unit92and the mixed exhaust gas discharge pipe90.

As illustrated inFIGS. 4 and 7, the mount structure94includes a front flange portion108aprovided on the upper portion of the dilution unit92on the side of the one end92f, and a pair of rear flange portions108bprovided on the upper portion of the dilution unit92on the side of the other end92b. The front flange portion108ahas a substantially cylindrical shape open to the front, and has an aperture110aon its upper face. The aperture110acommunicates with an opening112aopened to the front. Each of the rear flange portions108bhas a substantially cylindrical shape open to the rear, and has an aperture110bon its upper face. The apertures110bcommunicate with respective openings112bopened to the rear.

As illustrated inFIGS. 3 and 8, the mount structure94includes brackets114a,114bprovided in the fuel cell vehicle12. Two rubber mounts (mounts)120are attached to the bracket114bvia a bolt116and two nuts118. The rubber mounts120are attached to the respective apertures110bof the rear flange portions108b. The rubber mounts120can pass through the respective openings112b, and be detached to the rear in the vehicle longitudinal direction (direction indicated by an arrow Ab). One rubber mount120is attached to the bracket114avia the bolt116and the nuts118.

Operation of the fuel cell system10thus configured will be described below.

As illustrated inFIG. 2, oxidant gas (air) is sent to the air feeding pipe48via the air pump46constituting the oxidant gas feeder16. The oxidant gas is humidified by the humidifier52and then, is fed to the oxidant gas inlet manifold44aof the fuel cell stack14.

Meanwhile, in the fuel gas feeder18, during opening of the shutoff valve68, fuel gas (hydrogen gas) is fed from the hydrogen tank64to the hydrogen feeding pipe66. The fuel gas passes through the ejector70and then, is fed to the fuel gas inlet manifold42aof the fuel cell stack14.

Oxidant gas is introduced from the oxidant gas inlet manifold44ainto the oxidant gas channel38of the second separator28, and is fed to the cathode electrode34of the electrolyte membrane electrode assembly24. Fuel gas is introduced from the fuel gas inlet manifold42ainto the fuel gas channel36of the first separator26. Fuel gas moves along the fuel gas channel36, is fed to the anode electrode32of the electrolyte membrane electrode assembly24.

Accordingly, in each electrolyte membrane electrode assembly24, oxidant gas fed to the cathode electrode34and fuel gas fed to the anode electrode32are consumed through electrochemical reaction in an electrode catalyst layer to generate electricity. Cooling medium is fed from a cooling medium feeder not illustrated to the cooling medium channel40.

Next, oxidant exhaust gas, which is oxidant gas that is fed to the cathode electrode34and is partially consumed, is discharged from the oxidant gas outlet manifold44bto the air discharge pipe56. The new oxidant exhaust gas passes through the humidifier52and become humidified. Then, the pressure of the oxidant exhaust gas is raised to a set pressure of the back sealing valve58. After that, the oxidant exhaust gas is discharged to the mixed exhaust gas discharge pipe90.

Similarly, oxidant exhaust gas, which is oxidant gas that is fed to the anode electrode32and is partially consumed, is discharged from the fuel gas outlet manifold42bto the off-gas pipe76. The fuel exhaust gas is introduced from the off-gas pipe76into the gas-liquid separator78, is deprived of moisture, and is sucked to the ejector70via the circulation channel80.

In the off-gas pipe76, the purge valve84is opened as required to pass fuel exhaust gas discharged from an anode line therethrough, and introduce the fuel exhaust gas along with fluid discharged from the gas-liquid separator78via the drain valve88into the mixed exhaust gas discharge pipe90. In the mixed exhaust gas discharge pipe90, the oxidant exhaust gas is mixed with the fuel exhaust gas to generate mixed exhaust gas, and the mixed exhaust gas is discharged to the dilution unit92.

In this case, in the present embodiment, as illustrated inFIGS. 6 and 7, the stirring chamber96of the dilution unit92receives mixed exhaust gas through the mixed exhaust gas discharge pipe90, and air through the opening96sin the lower face of the stirring chamber96. For this reason, the stirring chamber96can take in oxidant exhaust gas as well as external air such as travelling wind, and dilute and stir the exhaust gas with the external air. Therefore, the dilution unit92can reliably dilute fuel exhaust gas with simple and compact structure.

Moreover, as illustrated inFIG. 6, the curved opposite face100is formed at the other end92bopposite to the mixed exhaust gas discharge pipe90of the stirring chamber96. Thus, mixed exhaust gas introduced into the stirring chamber96can smoothly flow along the curved opposite face100, promoting stirring without stopping the flow of the mixed exhaust gas. At this time, the curved opposite face100can absorb a shock caused when mixed exhaust gas discharged from the mixed exhaust gas discharge pipe90is blown against the opposite face100. Therefore, noise and vibration can be effectively suppressed without increasing the weight and strength of the dilution unit92itself.

Further, the plurality of ribs102are formed on the opposite face100. This can properly stir the flow of mixed exhaust gas in the stirring chamber96. Moreover, the mixed exhaust gas discharge pipe90is connected to the dilution unit92at a position separated upward from the center of the stirring chamber96in the vertical direction. This can increase the discharge distance between the outlet90eof the mixed exhaust gas discharge pipe90and the opening96sin the lower face of the stirring chamber96, diluting exhaust gas with a larger quantity of air.

As illustrated inFIG. 7, the dilution unit92has the vent hole106that is located above the connection between the dilution unit92and the mixed exhaust gas discharge pipe90, and communicates the stirring chamber96with the outside of the dilution unit92. Therefore, when a negative pressure occurs in the dilution unit92to suck air through the opening96s, unintended disturbance of gas can be prevented, effectively adjusting the flow.

As illustrated inFIG. 4, the stirring plate98is disposed at the outlet90eof the mixed exhaust gas discharge pipe90, and enters the flowing area of mixed exhaust gas. This can disturb the flow of mixed exhaust gas introduced into the stirring chamber96through the outlet90e, improving the stirring effect.

As illustrated inFIGS. 3 and 4, the dilution unit92is provided with the stepped portion104extending in the vehicle width direction at the longitudinal center of the upper face. At this time, as illustrated inFIG. 9, when an external load F is imposed from the rear of the fuel cell vehicle12, components of the rear portion of the vehicle may contact the other end92bof the dilution unit92. For this reason, in the dilution unit92, stress concentrates on the stepped portion104, and the dilution unit92breaks from the stepped portion104at the longitudinal center. Thus, the dilution unit92does not move forward, preventing the external load F from imposing onto the hydrogen tank64.

The dilution unit92is fixed to the rear portion of the vehicle using the mount structure94. As illustrated inFIG. 8, the mount structure94includes the rear flange portions108bto the bracket114bon the side of the vehicle via the rubber mount120. The rear flange portions108beach have the aperture110bengaging with the rubber mount120, and the apertures110bcommunicate with the respective openings112bto the rear.

Thus, when the external load F is imposed on the dilution unit92from behind, as illustrated inFIG. 9, the rubber mounts120can be detached to the rear in the vehicle longitudinal direction (direction indicated by the arrow Ab) through the openings112communicating with the apertures110b. For this reason, for example, even when the dilution unit92does not break, the other end92bof the dilution unit92can be detached from the bracket114band fall below the vehicle. This can reliably prevent the external load F from imposing on the hydrogen tank64.

The dilution unit92is made of a conductive material. This can prevent the dilution unit92from being charged with electricity.

The outlet90eof the mixed exhaust gas discharge pipe90and the dilution unit92need not be sealed against each other, and may be connected to each other with a clearance therebetween. At this time, the dilution unit92does not necessarily have the vent hole106. This is due to that the clearance can communicate the stirring chamber96to the outside of the dilution unit92.

The on-vehicle fuel cell system of the present disclosure includes a fuel cell that generate electricity through electrochemical reaction of oxidant gas fed to a cathode side with fuel gas fed to an anode side with an electrolyte membrane being located between the cathode side and the anode side.

The on-vehicle fuel cell system further includes an oxidant gas feeding pipe, an oxidant exhaust gas discharge pipe, a fuel gas feeding pipe, a fuel exhaust gas discharge pipe, a mixed exhaust gas discharge pipe, and a dilution unit. The oxidant gas feeding pipe feeds oxidant gas to the fuel cell, while the oxidant exhaust gas discharge pipe discharges oxidant exhaust gas, which is oxidant gas at least partially used in the cathode side, from the fuel cell.

The fuel gas feeding pipe feeds fuel gas to the fuel cell, while the fuel exhaust gas discharge pipe discharges fuel exhaust gas, which is oxidant gas at least partially used in the anode side, from the fuel cell. The mixed exhaust gas discharge pipe connects the oxidant exhaust gas discharge pipe to the fuel exhaust gas discharge pipe, and discharges mixed exhaust gas of oxidant exhaust gas and fuel exhaust gas, while the dilution unit is connected to the mixed exhaust gas discharge pipe.

The dilution unit includes a stirring chamber that expands from an outlet of the mixed exhaust gas discharge pipe and communicates with the mixed exhaust gas discharge pipe, and an opening for taking air is formed in a lower face of the stirring chamber.

Preferably, the mixed exhaust gas discharge pipe is connected to one end of the stirring chamber on a front side in the vehicle longitudinal direction, and a curved opposite face is formed on an inner wall of another end opposite to the one end of the stirring chamber.

Preferably, in the on-vehicle fuel cell system, a rib is formed on the opposite face.

Preferably, a stepped portion extending in a vehicle width direction is provided on an upper face of the dilution unit at a center portion in the vehicle longitudinal direction.

Preferably, the dilution unit includes a flange portion to be fixed to a mount on a vehicle body side, and the flange portion located in the rear of the stepped portion in the vehicle longitudinal direction has an opening from which the mount is detachable to the rear in the vehicle longitudinal direction.

Preferably, the dilution unit has a vent hole formed therein that is located above a connection between the dilution unit and the mixed exhaust gas discharge pipe, and through which the stirring chamber communicates with outside of the dilution unit.

Preferably, a stirring plate is disposed at the outlet of the mixed exhaust gas discharge pipe, and enters a flowing area of mixed exhaust gas.

Preferably, the mixed exhaust gas discharge pipe is connected to the dilution unit at a position separated upward from a center of the stirring chamber in a vertical direction.

Preferably, the dilution unit is made of a conductive material.

According to the present disclosure, the dilution unit receives mixed exhaust gas of fuel exhaust gas and oxidant exhaust gas through the mixed exhaust gas discharge pipe, and takes in air through the opening in the lower face of the stirring chamber. For this reason, the stirring chamber can take in oxidant exhaust gas as well as external air such as travelling wind, and dilute and stir the exhaust gas with the external air. Therefore, the dilution unit can reliably dilute fuel exhaust gas with simple and compact structure.