JP7510908B2 - Fuel Cell Systems - Google Patents

Description

The present invention relates to a fuel cell system.

For example, a fuel cell system installed in a fuel cell vehicle is equipped with a DC/DC converter as an example of a voltage conversion device that includes a reactor. If the temperature of the reactor rises excessively due to heat generation from the reactor, the output performance of the DC/DC converter will decrease, so it is desirable to ensure the cooling performance of the reactor.

For example, in a fuel cell system mounted on a fuel cell vehicle disclosed in Patent Document 1, multiple reactors are arranged on a reactor cooling surface, which is one of the outer surfaces of a cooler. The cooler has a refrigerant flow path that contacts the inner surface opposite the reactor cooling surface. In the cooler, cooling fins are provided on the inner surface opposite the reactor cooling surface. The longitudinal direction of the cooling fins is the same as the direction in which the refrigerant flows in the refrigerant flow path. This makes it possible to reduce pressure loss in the refrigerant flow path while improving the heat transfer coefficient, ensuring the cooling performance of the reactor.

Japanese Patent No. 6390638

The fuel cell system disclosed in Patent Document 1 requires a cooler to ensure the cooling performance of the reactor, and piping to run a refrigerant through the cooler, as well as space to install the cooler in the fuel cell system and space to route the piping. For this reason, the fuel cell system disclosed in Patent Document 1 requires high costs to ensure the cooling performance of the reactor.

The fuel cell system for solving the above problems includes a fuel cell, a switching unit having a heat dissipation unit, and a reactor, a voltage conversion device that converts the output voltage of the fuel cell, a housing that houses the fuel cell and the voltage conversion device, and a bracket that attaches the voltage conversion device to the housing, and the fuel cell system has an airflow inside the housing, the switching unit is attached to the bracket with the heat dissipation unit facing the bracket, the reactor is attached to the bracket downstream of the switching unit in the flow direction of the airflow inside the housing, and a ventilation path extending in the flow direction of the airflow inside the housing is defined between the opposing heat dissipation unit and the bracket, an inlet of the ventilation path is located upstream of the heat dissipation unit in the flow direction of the airflow inside the housing, and an outlet of the ventilation path is located downstream of the heat dissipation unit and upstream of the reactor in the flow direction of the airflow inside the housing.

According to this, air flows from the entrance to the exit of the ventilation passage due to the airflow generated inside the housing. Since the heat dissipation section that defines the ventilation passage is exposed in the ventilation passage, air flows along the heat dissipation section. Then, the heat dissipation section exchanges heat with the air, and the switching section is air-cooled. Also, since the reactor is located downstream of the exit of the ventilation passage, the air that flows through the ventilation passage and then leaves the exit flows along the reactor. Then, the reactor is air-cooled. This air cooling ensures the cooling performance of the reactor. In other words, the reactor is located downstream of the switching section in the flow direction of the airflow, and even though the reactor does not have a dedicated structure for cooling such as a heat dissipation section or a cooler, the cooling performance of the reactor can be ensured.

As a result, the fuel cell system does not require a cooler for water-cooling the reactor, nor piping for running a refrigerant through the cooler, and it also does not require space to install the cooler in the fuel cell system housing, nor space for piping. Therefore, compared to water-cooling the reactor, the cost of ensuring the cooling performance of the reactor can be reduced.

In a fuel cell system, the housing may house a drainage tank into which water produced in conjunction with power generation by the fuel cell is discharged, and the bracket may be connected to the drainage tank so as to enable heat transfer through contact .

As a result, heat generated by the voltage conversion device is easily transferred to the bracket. Since heat from the bracket is transferred to the drainage tank, the drainage tank can be heated by the heat generated by the voltage conversion device. Therefore, when the fuel cell system is placed in a low-temperature environment, freezing of water in the drainage tank can be suppressed.

In the fuel cell system, the bracket may be disposed vertically near the bottom of the drainage tank.
According to this, the drainage tank can be heated from the bottom by the heat generated by the voltage conversion device, so that even if a small amount of water accumulates at the bottom of the drainage tank, freezing of the water in the drainage tank can be suppressed.

For a fuel cell system, the bracket may have a mounting plate to which the switching unit and the reactor are attached, the mounting plate may have a recess extending in the flow direction of the airflow, the recess may house the heat dissipation unit and the reactor aligned in the flow direction of the airflow, and the ventilation passage may be defined in a space surrounded by the heat dissipation unit and the recess.

According to this, the ventilation passage defined by housing the heat dissipation section in the recess is a closed space except for the inlet and outlet. Therefore, the ventilation passage prevents the airflow from diffusing, allowing the air to flow along the heat dissipation section. This makes it easier to air-cool the heat dissipation section. In addition, because the reactor is housed in the recess, diffusion is prevented and the airflow that flows out of the ventilation passage can be directed toward the reactor. This allows the reactor to be cooled efficiently.

In a fuel cell system, the mounting plate may be coupled to the heat sink to enable heat transfer by contact .
According to this, the heat generated in the switching unit is transferred to the mounting plate via the heat dissipation unit. The mounting plate defines an air passage, so that heat is exchanged between the mounting plate and the air flowing through the air passage. As a result, the mounting plate can be air-cooled, and the switching unit can be cooled via the mounting plate.

The fuel cell system may include a heat exchanger that exchanges heat between outside air and a heat exchange medium, a circulation flow path that circulates the heat exchange medium between the fuel cell and the heat exchanger, and a fan that blows air to the heat exchanger, the heat exchanger, the circulation flow path, and the fan being housed in the housing, the housing having an air vent, and the air flow from the air vent toward the fan generated inside the housing by driving the fan, and the ventilation path may be defined between the fan and the air vent in the flow direction of the air flow inside the housing.

According to this, when the fuel cell generates power, the heat exchange medium that circulates through the circulation flow path and flows into the fuel cell absorbs heat generated by the fuel cell and cools the fuel cell. The heat exchange medium that flows from the fuel cell into the heat exchanger is cooled by forced heat exchange with outside air by air blown from the fan. In other words, the fan is an existing component provided in the fuel cell system to cool the heat exchange medium. The fan can then forcefully generate an airflow that flows inside the housing, and can also direct the airflow through the ventilation passage. This makes it possible to ensure the cooling performance of the reactor by effectively utilizing the existing component.

The present invention can reduce the cost of ensuring the cooling performance of the reactor.

1 is a partially cutaway perspective view showing a fuel cell system according to an embodiment; FIG. 1 is a configuration diagram of a fuel cell system. 1 is a side cross-sectional view showing a fuel cell system according to an embodiment from the inlet side of a ventilation passage. 2 is a side cross-sectional view showing the fuel cell system according to the embodiment from the outlet side of the ventilation passage. FIG. 1 is a cross-sectional plan view showing a fuel cell system according to an embodiment; 1 is a perspective view showing a fuel cell system according to an embodiment from the inlet side of a ventilation passage. 1 is a perspective view showing a fuel cell system according to an embodiment, viewed from the outlet side of a ventilation passage.

An embodiment of a fuel cell system will now be described with reference to Figures 1 to 7. The fuel cell system is mounted on an industrial vehicle (not shown).
<Overall configuration of fuel cell system>
As shown in FIGS. 1 and 2, the fuel cell system 10 includes a housing 11 , a fuel cell stack 12 , a hydrogen tank 13 , an air compressor 14 , a gas-liquid separator 15 a , a diluter 15 , and a drain tank 16 .

The fuel cell system 10 also includes a hydrogen supply path 17 that connects the anode (not shown) of the fuel cell stack 12 to the hydrogen tank 13, and an air supply path 18 that connects the cathode (not shown) of the fuel cell stack 12 to the air compressor 14. The fuel cell system 10 also includes a discharge path 19a that connects the fuel cell stack 12 to the diluter 15, and a drainage path 19b that connects the diluter 15 to the drainage tank 16.

The fuel cell system 10 also includes a heat exchanger 21 that exchanges heat between the outside air and the heat exchange medium, a fan 21a that blows air toward the heat exchanger 21, and a circulation flow path 22 that circulates the heat exchange medium between the fuel cell stack 12 and the heat exchanger 21. Cooling water is used as the heat exchange medium, but other media may also be used.

<Case>
As shown in FIG. 1, the housing 11 has a bottom plate 11a, a top plate 11b, and a cylindrical peripheral wall 11c connecting the periphery of the bottom plate 11a and the periphery of the top plate 11b. Assuming that the fuel cell system 10 is placed on a horizontal plane, the direction of gravity is indicated by the Z axis, and the directions along the horizontal plane are indicated by the X axis and the Y axis. The X axis, the Y axis, and the Z axis are perpendicular to each other. In the following description, the direction parallel to the Z axis is also referred to as the vertical direction Z, and the direction parallel to the X axis is also referred to as the horizontal direction X. The direction parallel to the Y axis is also referred to as the depth direction Y. Therefore, the depth direction Y is a direction perpendicular to both the horizontal direction X and the vertical direction Z.

In the housing 11, the bottom plate 11a and the top plate 11b face each other in the vertical direction Z. The peripheral wall 11c has a first side wall 11d and a second side wall 11e that face each other in the horizontal direction X, and a third side wall 11f and a fourth side wall 11g that face each other in the depth direction Y. A plurality of ventilation holes 11h are arranged in the first side wall 11d of the housing 11. Each of the plurality of ventilation holes 11h penetrates the first side wall 11d in the plate thickness direction.

The housing 11 contains a fuel cell stack 12, a hydrogen tank 13, an air compressor 14, a drain tank 16, a heat exchanger 21, and a fan 21a. Although not shown in FIG. 1, the housing 11 also contains a gas-liquid separator 15a, a diluter 15, a hydrogen supply channel 17, an air supply channel 18, a drain channel 19a, and a drain channel 19b.

<Components of fuel cell system>
The fuel cell stack 12 generates power to be supplied to a load mounted on an industrial vehicle (not shown). The fuel cell stack 12 is made up of a plurality of fuel cell cells stacked together. The fuel cell cells are solid molecular fuel cells. The fuel cell stack 12 generates direct current electrical energy by reacting hydrogen supplied from a hydrogen tank 13 via a hydrogen supply path 17 with oxygen in the air supplied from an air compressor 14 via an air supply path 18. The fuel cell stack 12 generates power using hydrogen as the fuel gas and oxygen in the air as the oxidant gas. The fuel cell stack 12 generates water as a result of power generation.

The fuel cell stack 12 and the air compressor 14 are attached to the housing 11 by a battery bracket 40. The battery bracket 40 is attached to the bottom plate 11a. The battery bracket 40 has a support portion 41 and a number of legs 42. The legs 42 are fixed to the bottom plate 11a. Each of the legs 42 protrudes from the bottom plate 11a in the vertical direction Z. The support portion 41 is supported by the upper ends of the legs 42.

The fuel cell stack 12 and the air compressor 14 are supported by the support portion 41. With the fuel cell stack 12 and the air compressor 14 supported by the support portion 41, the fuel cell stack 12 and the air compressor 14 are attached to the housing 11 by the battery bracket 40. The fuel cell stack 12 and the air compressor 14 are positioned above the bottom plate 11a by the battery bracket 40. The hydrogen tank 13 is close to the fourth side wall 11g. The hydrogen tank 13 is supported by the bottom plate 11a.

As shown in FIG. 2, the exhaust passage 19a discharges anode off-gas, which is exhaust gas containing hydrogen discharged from the fuel cell stack 12, to the diluter 15. The exhaust passage 19a also discharges cathode off-gas, which is exhaust gas containing oxygen discharged from the fuel cell stack 12 and water generated during power generation by the fuel cell stack 12, to the diluter 15.

The diluter 15 has a gas-liquid separator 15a therein. The gas-liquid separator 15a has a function of separating oxygen and water from the cathode off-gas discharged to the diluter 15. Furthermore, the gas-liquid separator 15a has a function of separating hydrogen from the anode off-gas discharged to the diluter 15. The water separated by the gas-liquid separator 15a is discharged to the drain tank 16 via the drainage channel 19b. The diluter 15 has a function of diluting the hydrogen separated by the gas-liquid separator 15a. The drain tank 16 is made of metal. The drain tank 16 is disposed below the fuel cell stack 12 in the vertical direction Z.

The circulation flow path 22 circulates the cooling water between the fuel cell stack 12 and the heat exchanger 21. The circulation flow path 22 has an outward path 22a, a return path 22b, a pump (not shown), and a heat exchange flow path (not shown) arranged within the fuel cell stack 12 and the heat exchanger 21. The outward path 22a is a flow path for flowing the cooling water from the heat exchanger 21 toward the fuel cell stack 12. The return path 22b is a flow path for flowing the cooling water from the fuel cell stack 12 toward the heat exchanger 21. The pump (not shown) circulates the cooling water through the circulation flow path 22.

The cooling water circulates through the circulation flow path 22 and flows through the outward path 22a into the heat exchange flow path in the fuel cell stack 12, absorbing heat generated in the fuel cell stack 12 and cooling the fuel cell stack 12. The cooling water flows through the return path 22b into the heat exchange flow path in the heat exchanger 21 and is cooled by heat exchange with the outside air.

As shown in Figures 1 and 5, the heat exchanger 21 is disposed on the second side wall 11e of the housing 11. The fuel cell stack 12 and the heat exchanger 21 are disposed side by side in the horizontal direction X. The fan 21a is disposed closer to the fuel cell stack 12 than the heat exchanger 21 in the horizontal direction X. The heat exchanger 21 and the fan 21a face the vent 11h in the horizontal direction X.

When the fuel cell stack 12 generates power, the fan 21a is driven to draw air from the outside of the housing 11 into the inside of the housing 11 through the vent 11h. Inside the housing 11, an airflow is generated from the vent 11h toward the fan 21a. Inside the housing 11, the direction in which the airflow flows from the vent 11h toward the fan 21a is the airflow direction F. The heat exchanger 21 and the fan 21a are opposed to the vent 11h in the horizontal direction X, so the airflow direction F coincides with the horizontal direction X.

Furthermore, the cooling water that has flowed from the fuel cell stack 12 into the heat exchanger 21 is forcibly exchanged with outside air by air blown from a fan 21a in the heat exchanger 21, and is thereby cooled.
<DC/DC converter and converter bracket>
As shown in Figures 3 to 7, the fuel cell system 10 includes a DC/DC converter 30 as a voltage conversion device that converts the output voltage of the fuel cell stack 12. The DC/DC converter 30 includes, as components, a switching unit 36 having a switching element (not shown), and a plurality of reactors 35. A heat dissipation unit 32 is thermally coupled to the switching unit 36. For this reason, it can be said that the switching unit 36 has the heat dissipation unit 32. The heat dissipation unit 32 has an attachment member 33 for attaching the heat dissipation unit 32 to the switching unit 36, and a plurality of heat dissipation fins 34 that are integrated with the attachment member 33.

The heat dissipation section 32 is made of metal. The mounting member 33 is plate-shaped. The mounting member 33 is fixed to the back surface 36a of the switching section 36 and is thermally coupled to the switching section 36. Each of the multiple heat dissipation fins 34 is a rectangular plate fin. When the heat dissipation fin 34 is viewed from above in the vertical direction Z, the long side of the heat dissipation fin 34 extends in the horizontal direction X and the short side of the heat dissipation fin 34 extends in the depth direction Y. The multiple heat dissipation fins 34 are arranged side by side at intervals in the vertical direction Z. The dimension from the mounting member 33 to the tip 34a of the heat dissipation fin 34 is defined as the height dimension of the heat dissipation fin 34.

The reactor 35 has a core (not shown) and a coil component wound around the core. The DC/DC converter 30 has three reactors 35.
<Converter bracket>
The fuel cell system 10 includes a converter bracket 50. The converter bracket 50 is a bracket for mounting the DC/DC converter 30 to the bottom plate 11a of the housing 11.

The converter bracket 50 is made of a metal plate. The converter bracket 50 is formed by bending a rectangular metal body. The converter bracket 50 has a fixing plate 51 for fixing the converter bracket 50 to the bottom plate 11a, and a mounting plate 61 that protrudes upward from the fixing plate 51 in the vertical direction Z and to which the switching unit 36 and the reactor 35 are attached.

The fixing plate 51 is a rectangular plate in plan view from above in the vertical direction Z. In plan view, the long sides of the fixing plate 51 extend in the horizontal direction X. The fixing plate 51 is fixed to the bottom plate 11a by screwing bolts 51a that penetrate the fixing plate 51 in the plate thickness direction into the bottom plate 11a. Note that the method of fixing the fixing plate 51 to the bottom plate 11a is not limited to fixing with bolts 51a. The fixing plate 51 may be fixed by welding to the bottom plate 11a, or the fixing plate 51 may be fixed by adhering to the bottom plate 11a with an adhesive.

In a plan view of the converter bracket 50 viewed from above in the vertical direction Z, the mounting plate 61 protrudes from one of a pair of long edges of the fixing plate 51 that is closer to the fourth side wall 11g than to the third side wall 11f. The mounting plate 61 is bent and formed so as to have a recess 62 that is recessed in the depth direction Y toward the opposite side to the fixing plate 51.

The mounting plate 61 has a rectangular plate shape in plan view seen from above in the vertical direction Z. In plan view, the longer sides of the mounting plate 61 extend in the horizontal direction X.
The mounting plate 61 has a first mounting piece 63 protruding upward from the fixed plate 51 in the vertical direction Z, and a first extending piece 64 extending from the upper end of the first mounting piece 63 in the depth direction Y toward the opposite side to the fixed plate 51. The mounting plate 61 also has a connecting piece 65 protruding upward from the extension end of the first extending piece 64 in the vertical direction Z, and a second extending piece 66 extending from the upper end of the connecting piece 65 in the depth direction Y toward the fixed plate 51. The mounting plate 61 has a second mounting piece 67 protruding upward from the extension end of the second extending piece 66 in the vertical direction Z. In a plan view of the converter bracket 50 seen from above in the vertical direction Z, the first mounting piece 63, the first extending piece 64, the connecting piece 65, the second extending piece 66, and the second mounting piece 67 are rectangular plates whose long sides extend in the horizontal direction X.

The first mounting piece 63 and the second mounting piece 67 are spaced apart in the vertical direction Z by sandwiching the first extension piece 64, the connecting piece 65, and the second extension piece 66 between them. The connecting piece 65 is located on the opposite side of the fixed plate 51 from the first mounting piece 63 and the second mounting piece 67 by the first extension piece 64 and the second extension piece 66. The metal plate is bent to form the first extension piece 64, the connecting piece 65, and the second extension piece 66, thereby defining a recess 62 in the mounting plate 61. In other words, the recess 62 is defined by bending the metal plate to form the first extension piece 64, the connecting piece 65, and the second extension piece 66. Therefore, it can be said that the mounting plate 61 defines the recess 62 extending in the air flow direction F by being bent. The recess 62 is recessed so as to be away from the first mounting piece 63 and the second mounting piece 67 relative to the fixed plate 51.

As described above, in a plan view, the long sides of the first extension piece 64, the connecting piece 65, and the second extension piece 66 extend in the horizontal direction X. Therefore, the long sides of the recess 62 defined by the first extension piece 64, the connecting piece 65, and the second extension piece 66 extend in the horizontal direction X. As described above, the flow direction F of the airflow generated by driving the fan 21a coincides with the horizontal direction X. Therefore, it can be said that the recess 62 extends in the flow direction F of the airflow. In addition, since the recess 62 is defined by the first extension piece 64, the connecting piece 65, and the second extension piece 66, the recess 62 is closed on both the top and bottom sides in the vertical direction Z and on one side in the depth direction Y, while both ends in the horizontal direction X are open.

The first mounting piece 63 has a first mounting surface 63a on one of the two surfaces in the thickness direction that is closer to the third side wall 11f than the fourth side wall 11g. The second mounting piece 67 has a second mounting surface 67a on one of the two surfaces in the thickness direction that is closer to the third side wall 11f than the fourth side wall 11g. The first mounting surface 63a and the second mounting surface 67a are located on the same imaginary plane. The recess 62 is recessed from the first mounting surface 63a and the second mounting surface 67a.

The connecting piece 65 has an inner surface 65a on the surface facing the recess 62, and an outer surface 65b on the opposite side to the inner surface 65a. The inner surface 65a is the surface of the connecting piece 65 that is closer to the third side wall 11f than the fourth side wall 11g, among both surfaces of the connecting piece 65 in the plate thickness direction. The outer surface 65b is the surface of the connecting piece 65 that is closer to the fourth side wall 11g than the third side wall 11f, among both surfaces of the connecting piece 65 in the plate thickness direction. The shortest distance from the first mounting surface 63a or the second mounting surface 67a to the inner surface 65a is defined as the depth dimension of the recess 62.

The connecting piece 65 is spaced apart from the first mounting piece 63 and the second mounting piece 67 in the depth direction Y. Due to this space, the outer surface 65b of the connecting piece 65 is in contact with the side surface of the drainage tank 16. Therefore, the converter bracket 50 and the drainage tank 16 are thermally coupled. It is preferable that the outer surface 65b of the connecting piece 65 is in contact with the side surface of the drainage tank 16, closer to the bottom 16a of the drainage tank 16. The connecting piece 65 extends above and below both sides in the vertical direction Z with the bottom 16a of the drainage tank 16 as a reference.

The fixing plate 51 of the converter bracket 50 is fixed to the bottom plate 11a below the support portion 41 in the vertical direction Z. Therefore, the converter bracket 50 is disposed below the support portion 41.

<DC/DC Converter Placement>
The DC/DC converter 30 is attached to the bottom plate 11a by a converter bracket 50. With this attachment, the DC/DC converter 30 is disposed below the support portion 41 and to the side of the drain tank 16.

The upper part of the switching unit 36 is attached to the second mounting piece 67 with the upper part of the mounting member 33 in between, and the lower part of the switching unit 36 is attached to the first mounting piece 63 with the lower part of the mounting member 33 in between. The upper part of the switching unit 36 contacts the second mounting surface 67a through the upper part of the mounting member 33, and the lower part of the switching unit 36 contacts the first mounting surface 63a through the lower part of the mounting member 33. Therefore, the heat dissipation unit 32 is thermally coupled to the mounting plate 61. As a result, the switching unit 36 and the mounting plate 61 are thermally coupled.

The switching unit 36 is attached to the converter bracket 50 with the heat dissipation unit 32 facing the mounting plate 61. Therefore, the recess 62 is closed by the heat dissipation unit 32 from the side opposite the connecting piece 65 in the depth direction Y.

All of the heat dissipation fins 34 of the heat dissipation section 32 are housed in the recesses 62. The depth dimension of the recesses 62 is greater than the height dimension of the heat dissipation fins 34. Therefore, the tip 34a of the heat dissipation fins 34 and the inner surface 65a of the connecting piece 65 are spaced apart in the depth direction Y. Ventilation passages 70 are defined between the tip 34a of the heat dissipation fin 34 and the inner surface 65a of the connecting piece 65, and between adjacent heat dissipation fins 34 in the vertical direction Z. In other words, the ventilation passages 70 are defined in the space surrounded by the heat dissipation section 32 and the recesses 62.

As described above, the recess 62 is closed on both the top and bottom sides in the vertical direction Z and on one side in the depth direction Y by the first extension piece 64, the connecting piece 65, and the second extension piece 66, and the other side in the depth direction Y is closed by the heat dissipation section 32. Therefore, the ventilation passage 70 is a space that is closed on both sides in the depth direction Y and on both sides in the vertical direction Z, and is open on both ends in the horizontal direction X. The dimension of the ventilation passage 70 in the horizontal direction X is the same as the dimension of the switching section 36 in the horizontal direction X.

The ventilation passage 70 is a passage that opens on both sides of the horizontal direction X. Furthermore, the flow direction F of the airflow generated by driving the fan 21a coincides with the horizontal direction X. Therefore, it can be said that the ventilation passage 70 extending in the airflow direction F is defined between the heat dissipation section 32 and the mounting plate 61 of the converter bracket 50.

The inlet 70a of the ventilation passage 70 is disposed upstream of the heat dissipation fins 34 of the heat dissipation section 32 in the airflow direction F. The outlet 70b of the ventilation passage 70 is disposed downstream of the heat dissipation fins 34 of the heat dissipation section 32 in the airflow direction F.

The three reactors 35 are housed in the recess 62. Therefore, the heat dissipation unit 32 and the three reactors 35 are housed in the recess 62 lined up in the airflow direction F. The three reactors 35 are attached to the inner surface 65a of the connecting piece 65. The three reactors 35 are thermally coupled to the connecting piece 65. The three reactors 35 are lined up in a row along the longitudinal direction of the mounting plate 61. As described above, since the long side of the mounting plate 61 extends in the horizontal direction X, the three reactors 35 lined up in a row along the longitudinal direction of the mounting plate 61 are lined up in a row in the horizontal direction X. Therefore, the switching unit 36 and the three reactors 35 are lined up in a row in the horizontal direction X. It can also be said that the switching unit 36 and the three reactors 35 are lined up in a row in the airflow direction F.

The three reactors 35 are lined up in a row along the airflow direction F. The three reactors 35 are attached to the center of the inner surface 65a of the connecting piece 65 in the vertical direction Z. Of the three reactors 35, the reactor 35 closest to the switching unit 36 overlaps with the outlet 70b of the ventilation passage 70 in the horizontal direction X. Therefore, the outlet 70b of the ventilation passage 70 opens toward the reactor 35 that is located most upstream of the three reactors 35 in the airflow direction F.

When the DC/DC converter 30 is viewed from the outside in the horizontal direction X, the reactor 35 and the ventilation passage 70 overlap. Since no components are disposed between the outlet 70b of the ventilation passage 70 and the reactor 35 closest to the switching unit 36, the reactor 35 closest to the switching unit 36 faces the outlet 70b of the ventilation passage 70.

<Action>
Next, the operation of the fuel cell system 10 will be described.
When the fuel cell stack 12 generates power, the fan 21a is driven to draw air from the outside of the housing 11 into the inside of the housing 11 through the vent 11h. Inside the housing 11, an airflow is generated that flows from the vent 11h toward the fan 21a.

This airflow causes air to pass through the heat exchanger 21, thereby air-cooling the heat exchanger 21. This increases the cooling efficiency of the coolant in the heat exchange flow path within the heat exchanger 21. As a result, the fuel cell stack 12, which is cooled using coolant, can also be cooled efficiently.

The switching unit 36 and reactor 35 of the DC/DC converter 30 generate heat as the fuel cell stack 12 generates power. The heat generated in the switching unit 36 is transferred to the heat dissipation unit 32 and to the first mounting piece 63 and the second mounting piece 67 via the mounting member 33. That is, the heat generated in the switching unit 36 is transferred to the mounting plate 61. The heat generated in the reactor 35 is transferred to the connecting piece 65. That is, the heat generated in the reactor 35 is transferred to the mounting plate 61.

As airflow is generated from the ventilation opening 11h toward the fan 21a, airflow is generated in the ventilation passage 70 in the flow direction F. Then, air flows from the entrance 70a of the ventilation passage 70 toward the exit 70b. Because the heat dissipation section 32 is exposed in the ventilation passage 70, air flows along the heat dissipation fins 34 and the mounting member 33 of the heat dissipation section 32. Then, the heat dissipation fins 34 and the mounting member 33 exchange heat with the air. As a result, the switching section 36 is air-cooled by the heat dissipation section 32.

In addition, since the ventilation passage 70 is defined by the recess 62 of the mounting plate 61, the mounting plate 61 is exposed in the ventilation passage 70. Therefore, air flows along the mounting plate 61. Then, the mounting plate 61 exchanges heat with the air and the mounting plate 61 is air-cooled, and the switching unit 36 is air-cooled.

The ventilation passage 70 is also defined between the tip 34a of the heat dissipation fin 34 and the inner surface 65a of the connecting piece 65. That is, some air does not come into contact with the heat dissipation fin 34 in the airflow. Since the reactor 35 is located downstream of the outlet 70b of the ventilation passage 70, the air that flows through the ventilation passage 70 and then leaves the outlet 70b flows along the three reactors 35 in the recess 62. In detail, the air that leaves the outlet 70b of the ventilation passage 70 flows along the three reactors 35 in the recess 62 in the following order: The air flows through the reactor 35 located upstream in the flow direction F, the reactor 35 next to the upstream reactor 35, and the reactor 35 located downstream in the flow direction F in the recess 62 in that order. As a result, the three reactors 35 are air-cooled.

Effects of the embodiment
According to the above embodiment, the following effects can be obtained.
(1) The ventilation passage 70 is defined between the mounting plate 61 of the converter bracket 50 and the heat dissipation section 32 of the DC/DC converter 30. The inlet 70a of the ventilation passage 70 is disposed upstream of the heat dissipation section 32 in the airflow direction F, and the outlet 70b of the ventilation passage 70 is disposed downstream of the heat dissipation section 32 in the airflow direction F and upstream of the reactor 35. This allows the airflow generated inside the housing 11 to flow from the inlet 70a to the outlet 70b of the ventilation passage 70. As a result, the airflow generated inside the housing 11 can also flow along the reactor 35 after flowing along the heat dissipation section 32. Therefore, the cooling performance of the reactor 35 can be ensured without adopting a water-cooling method. Therefore, in the fuel cell system 10, a cooler for water-cooling the reactor 35 and piping for flowing a refrigerant to the cooler are not required, and the fuel cell system 10 does not require a space for mounting the cooler and a space for arranging the piping. Therefore, the cost for ensuring the cooling performance of the reactor 35 can be reduced.

(2) A recess 62 is provided in the converter bracket 50 for mounting the DC/DC converter 30 to the housing 11. The gap formed when the heat dissipation fins 34 of the DC/DC converter 30 are housed in this recess 62 is effectively utilized as a ventilation passage 70. This ensures the cooling performance of the reactor 35 without increasing the number of parts.

(3) Because the housing 11 houses many of the components that make up the fuel cell system 10, there are many small gaps between the components. The recess 62 of the converter bracket 50 is formed to house the heat dissipation fins 34 of the DC/DC converter 30, and is a larger space than the gaps. The ventilation passage 70 defined by this recess 62 is relatively large compared to the gaps between the components. For this reason, if airflow is generated inside the housing 11, the airflow will easily flow into the ventilation passage 70. Therefore, by providing the ventilation passage 70, the reactor 35 can be cooled efficiently.

(4) The connecting piece 65 of the converter bracket 50 is thermally coupled to the drainage tank 16. Therefore, the heat generated in the DC/DC converter 30 is transferred to the drainage tank 16 via the converter bracket 50. Therefore, the drainage tank 16 can be heated by the heat generated in the DC/DC converter 30. Therefore, when the fuel cell system 10 is placed in a low-temperature environment, freezing of the water in the drainage tank 16 can be suppressed.

(5) The connecting piece 65 of the converter bracket 50 extends above and below the bottom 16a of the drainage tank 16. In other words, the connecting piece 65 is positioned closer to the bottom 16a of the drainage tank 16. This allows the drainage tank 16 to be heated from the bottom 16a by the heat generated by the DC/DC converter 30. This prevents the water in the drainage tank 16 from freezing when the fuel cell system 10 is placed in a low-temperature environment, even if a small amount of water has accumulated at the bottom 16a of the drainage tank 16.

(6) The fan 21a is an existing component provided in the fuel cell system 10 to cool the cooling water circulating through the circulation flow path 22. The fan 21a can forcibly generate an airflow flowing inside the housing 11, and can also direct the airflow through the ventilation path 70. This makes it possible to effectively use the existing component and ensure the cooling performance of the reactor 35.

(7) The recess 62 is formed on the mounting plate 61 by bending it so as to have a first extension piece 64, a connecting piece 65, and a second extension piece 66. The ventilation passage 70 is defined by the recess 62 and the heat dissipation section 32, and is a closed space except for the inlet 70a and the outlet 70b. This makes it possible to prevent the airflow flowing through the ventilation passage 70 from diffusing. Therefore, the ventilation passage 70 allows the air to flow along the heat dissipation section 32 and also allows the airflow to flow toward the reactor 35.

(8) The converter bracket 50 has a fixed plate 51 and an attachment plate 61. The attachment plate 61 has a recess 62 that defines the ventilation passage 70 together with the heat dissipation section 32. Therefore, the ventilation passage 70 can be formed inside the housing 11 simply by fixing the converter bracket 50, with the switching section 36 and reactor 35 attached to the attachment plate 61, to the bottom plate 11a with the fixed plate 51. In other words, the cooling performance of the reactor 35 can be ensured simply by attaching the DC/DC converter 30 to the housing 11 using the converter bracket 50.

(9) Heat generated in the switching unit 36 is transferred to the heat dissipation unit 32 and to the first mounting piece 63 and the second mounting piece 67 via the mounting member 33. In other words, heat generated in the switching unit 36 is transferred to the mounting plate 61 via the heat dissipation unit 32. The mounting plate 61 defines the ventilation passage 70, so that heat is exchanged between the mounting plate 61 and the air flowing through the ventilation passage 70. As a result, the mounting plate 61 can be air-cooled, and the switching unit 36 can be cooled via the mounting plate 61.

This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.
Although the heat dissipating fins 34 are formed as plate fins in the above embodiment, the heat dissipating fins 34 may be changed to pin fins or corrugated fins.

As long as the DC/DC converter 30 can be attached to the attachment plate 61 of the converter bracket 50 , the second attachment piece 67 may be omitted.
The number of reactors 35 may be changed depending on the switching unit 36 .

The reactors 35 do not have to be aligned in a row in the airflow direction F. Two reactors 35 may be aligned in the vertical direction Z upstream of the airflow direction F, and one reactor 35 may be aligned downstream of the two reactors 35. Alternatively, three reactors 35 may be aligned in the vertical direction Z.

The connecting piece 65 of the converter bracket 50 may be thermally coupled to the upper part of the drainage tank 16 in the vertical direction Z.
The connecting piece 65 of the converter bracket 50 does not have to be thermally coupled to the drainage tank 16 .

The drain tank 16 may be made of resin.
The switching unit 36 may be attached to the mounting plate 61 such that the mounting member 33 is spaced apart from the first mounting piece 63 and the second mounting piece 67 of the mounting plate 61. The heat dissipation unit 32 does not need to be thermally coupled to the mounting plate 61.

The mounting member 33 of the heat dissipation section 32 may be smaller than the dimension of the recess 62 in the vertical direction Z. The mounting member 33 and the heat dissipation fins 34 of the heat dissipation section 32 may be housed in the recess 62.

The mounting plate 61 may be a flat plate without the recess 62. In this case, the mounting member 33 of the switching unit 36 is attached to the mounting plate 61 by interposing an interposition member between the mounting member 33 and the mounting plate 61. Even in this way, a ventilation passage 70 is defined between the heat dissipation unit 32 and the mounting plate 61.

The mounting plate 61 may be formed by joining multiple metal plates. In this case, the first mounting piece 63, the first extending piece 64, the connecting piece 65, the second extending piece 66, and the second mounting piece 67 are manufactured separately. The first mounting piece 63, the first extending piece 64, the connecting piece 65, the second extending piece 66, and the second mounting piece 67 may then be joined together to form the mounting plate 61 having the recess 62.

The converter bracket 50 may have only the mounting plate 61. In this case, since the converter bracket 50 does not have the fixing plate 51, the converter bracket 50 may be attached to the bottom plate 11a by welding the lower end of the first mounting piece 63 to the bottom plate 11a.

○ Airflow is generated inside the housing 11 by drawing air into the housing 11 with the fan 21a, but it is also possible to place the fan 21a on the first side wall 11d and have the fan 21a blow air from the first side wall 11d toward the second side wall 11e to generate an airflow.

Wind generated when the industrial vehicle is traveling may be introduced into the housing 11 to generate an air current.
The fuel cell does not have to be a stack of multiple fuel cells, and may be a single fuel cell.

The fuel cell system 10 does not need to include a gas-liquid separator 15a. In this case, the discharge path 19a is connected to the diluter 15.

10...fuel cell system, 11...housing, 11h...vent, 12...fuel cell stack as fuel cell, 16...drainage tank, 16a...bottom, 21...heat exchanger, 22...circulation flow path, 21a...fan, 30...DC/DC converter as voltage conversion device, 32...heat dissipation section, 35...reactor, 36...switching section, 50...converter bracket, 61...mounting plate, 62...recess, 70...ventilation path, 70a...inlet, 70b...outlet.

Claims (6)

A fuel cell;
a voltage conversion device including a switching unit having a heat dissipation unit and a reactor, and configured to convert an output voltage of the fuel cell;
a housing that houses the fuel cell and the voltage conversion device;
a bracket for attaching the voltage conversion device to the housing,
A fuel cell system in which an airflow is generated inside the housing,
the switching unit is attached to the bracket with the heat dissipation unit facing the bracket,
the reactor is attached to the bracket downstream of the switching unit in a flow direction of the airflow inside the housing,
a ventilation passage extending in a direction in which the airflow inside the housing flows is defined between the heat dissipation portion and the bracket,
a fuel cell system characterized in that an inlet of the ventilation path is positioned upstream of the heat dissipation section in the direction of the airflow inside the housing, and an outlet of the ventilation path is positioned downstream of the heat dissipation section in the direction of the airflow inside the housing and upstream of the reactor. 2. The fuel cell system of claim 1, wherein the housing houses a drainage tank into which water generated by the power generation of the fuel cell is discharged, and the bracket is connected to the drainage tank so as to enable heat transfer through contact with the drainage tank. The fuel cell system according to claim 2, wherein the bracket is positioned vertically toward the bottom of the drainage tank. the bracket has a mounting plate to which the switching unit and the reactor are attached, the mounting plate having a recess extending in a flow direction of the airflow,
The fuel cell system according to any one of claims 1 to 3, wherein the recess accommodates the heat dissipation section and the reactor aligned in the flow direction of the airflow, and the ventilation passage is defined in a space surrounded by the heat dissipation section and the recess. 5. The fuel cell system according to claim 4 , wherein the mounting plate is coupled to the heat sink so as to enable heat transfer through contact with the heat sink. The fuel cell system according to any one of claims 1 to 5, comprising a heat exchanger that exchanges heat between outside air and a heat exchange medium, a circulation flow path that circulates the heat exchange medium between the fuel cell and the heat exchanger, and a fan that blows air to the heat exchanger, the heat exchanger, the circulation flow path, and the fan being housed in the housing, the housing having an air vent, the air flow from the air vent toward the fan being generated inside the housing by driving the fan, and the ventilation path being defined between the fan and the air vent in the flow direction of the air flow inside the housing.

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