WO2012172401A1

WO2012172401A1 - Ventilation structure for fuel cell stack

Info

Publication number: WO2012172401A1
Application number: PCT/IB2012/001056
Authority: WO
Inventors: Makoto Takeyama; Yuichi Yagami
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2011-06-16
Filing date: 2012-05-31
Publication date: 2012-12-20
Also published as: JP2013001231A

Abstract

A fuel cell stack is housed in a housing case. A first opening (16) through which leaked hydrogen is released to the outside of the housing case is formed in the housing case, and a ventilation cover (10) is provided to cover the first opening (16). The first opening (16) extends along a direction in which cells of the fuel cell stack are stacked. With this structure, sufficient rigidity of the housing case is ensured.

Description

VENTILATION STRUCTURE FOR FUEL CELL STACK

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a ventilation structure for a fuel cell stack, and more specifically to a ventilation structure for a fuel cell stack that is mounted in a movable body.

2. Description of Related Art

[0002] When a fuel cell stack is mounted in a movable body such as a hybrid vehicle or an electric vehicle, the fuel cell stack is housed in a dedicated case and mounted in a predetermined position of the vehicle. In a fuel cell, hydrogen gas is used as a reactant gas. Even if the hydrogen gas leaks from the fuel cell stack, stagnation of the leaked hydrogen in the case should be prevented to prevent an increase in the hydrogen concentration. Therefore, the case is provided with a vent for releasing the leaked hydrogen to the outside of the case. In addition, there has been proposed an art for covering a vent of a housing case with a hydrogen pemieable membrane in order to prevent ingress of water into a fuel cell stack.

[0003] Japanese Patent Application Publication No. 2005-149732 (JP 2005-149732 A) describes a fuel cell case that has a gas pemieable membrane (preferably, a hydrogen pemieable membrane) that allows gas to permeate therethrough but does not allow liquid to permeate therethrough. According to JP 2005-149732 A, the fuel cell case is provided with protection means for protecting the gas pemieable membrane. The protection means is configured to prevent stagnation of the gas permeated through the gas permeable membrane in the case, and has a sufficient strength so as not to be broken even if an external force acts thereon.

[0004] Japanese Patent Application Publication No. 2010- 170923 (JP 2010-170923 A) describes a housing case that houses a fuel cell stack that is mounted in a vehicle. According to JP 2010-170923 A, the housing case has a housing that houses the fuel cell stack, and an opening that is formed in an upper portion of the housing. Further, the opening edge of the opening (the edge of a portion of the housing, which defines the opening) is inclined such that the height thereof is reduced from the upstream side to the downstream side in the direction of an airflow (the flow speed of the airflow varies depending on a vehicle speed) generated when the vehicle travels.

[0005] FIG. 4 shows a fuel cell stack case described in JP 2010-170923 A. A housing case 20 that houses a fuel cell stack FC is placed under a floor panel FP of a vehicle and fixed by a supporting member 80. A predetermined amount of clearance is left between the floor panel FP and the housing case 20. When the vehicle travels in its traveling direction, an airflow generated by the travel motion of the vehicle proceeds through the clearance. The housing case 20 has a housing 30 that houses the fuel cell stack FC, and an opening 50 that is formed in an upper portion of the housing 30. A hydrogen permeable membrane 40 is stuck to the opening edge of the opening 50 to cover the entirety of the opening 50. The hydrogen permeable membrane 40 is made of a material that allows gases such as hydrogen and air to permeate theretlirough but does not allow water to permeate therethrough. The opening edge of the opening 50 is inclined such that the height thereof is reduced from the upstream side to the downstream side in the direction of an airflow generated when the vehicle travels. With this structure, even if dust and the like carried by the airflow enter the clearance between the floor panel FP and the housing case 20, the dust and the like are less likely to adhere to an upper surface of the hydrogen permeable membrane 40.

[0006] With an opening formed in a housing case that houses a fuel cell stack, even if hydrogen leaks from the fuel cell stack, the leaked hydrogen is released to the outside of the case through the opening. However, formation of the opening may reduce rigidity of the housing case.

SUMMARY OF THE INVENTION

[0007] The invention provides a ventilation structure that ensures both sufficient rigidity of a housing case and adequate ventilation in a fuel cell stack.

[0008] An aspect of the invention relates to a ventilation structure for a fuel cell stack that is mounted in a movable body. The ventilation structure includes a housing case that houses the fuel cell stack and has a first opening. The first opening extends along a direction in which cells of the fuel cell stack are stacked.

[0009] In the above-described aspect of the invention, a planar shape of the first opening may be an elliptical shape, and a major axis of the elliptical shape may extend along the direction in which the cells of the fuel cell stack are stacked.

[0010] In the above-described aspect of the invention, the movable body may be a vehicle, and the direction in which the cells of the fuel cell stack are stacked may be a vehicle- width direction.

[0011] According to the aspect of the invention, it is possible to ensure both sufficient rigidity of the housing case and adequate ventilation in the fuel cell stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a perspective view showing a ventilation structure for a fuel cell stack according to an embodiment of the invention;

FIG. 2 is plan view showing the ventilation structure for a fuel cell stack according to the embodiment;

FIG. 3 is a sectional view taken along the line III-III in FIG. 2; and

FIG. 4 is a view showing the structure of a device in a related art.

DETAILED DESCRIPTION OF EMBODIMENTS

[0013] Hereafter, an embodiment of the invention will be described with reference to the accompanying drawings.

[0014] A fuel cell stack according to the present embodiment is housed in a housing case and is placed under a floor panel of a vehicle such as a hybrid vehicle or an electric vehicle and fixed by a supporting member, as well as a fuel cell stack in a related art shown in FIG. 4. In addition, a predetermined amount of clearance is left between the floor panel and the housing case. While the vehicle travels in its traveling direction, an airflow generated by the travel motion of the vehicle proceeds through the clearance. The fuel cell stack is formed by stacking a plurality of solid polymer electrolyte fuel cells. Hydrogen gas and air used as reactant gases are supplied to the fuel cell stack.

[0015] The housing case that houses the fuel cell stack has a seal structure. Therefore, the fuel cell stack is sealed in the housing case. An opening is formed in an upper portion of the housing case. Even if the hydrogen gas used as a reactant gas leaks from the fuel cell stack, the leaked hydrogen is released to the outside of the housing case through the opening. Accordingly, stagnation of the leaked hydrogen in the case is prevented, and therefore an increase in the hydrogen concentration is prevented. A hydrogen permeable membrane is stuck to an opening edge of the opening (an edge of a portion of the housing case, which defines the opening) to cover the entirety of the opening. The hydrogen permeable membrane is made of a material that allows gases such as hydrogen and air to permeate therethrough but does not allow water to permeate therethrough.

[0016] FIG. 1 shows a ventilation structure for the fuel cell stack according to the present embodiment. FIG. 1 is a perspective view when the fuel cell stack housed in the housing case is viewed from above.

[0017] A ventilation cover 10 is provided at the top of the housing case, and a total of four second openings, that is, two second openings 12 and two second openings 14, are formed in the ventilation cover 10. Hydrogen permeable membranes are stuck to opening edges of the second openings 12, 14 (edges of portions of the ventilation cover 10, which define the second openings 12, 14). The hydrogen permeable membranes cover the opening of the housing case and the second openings 12, 14 of the ventilation cover 10. The ventilation cover 10 in the present embodiment includes two ventilation cover units 10a, 10b. The ventilation cover 10 is formed by joining the ventilation cover units 10a, 10b together by heat welding. The two ventilation cover units 10a, 10b are not flush with each other but are arranged to incline such that each of ventilation cover units 10a, 10b is highest at its joint surface. More specifically, as shown in FIG. 1 , the two ventilation cover units 10a, 10b are arranged side-by-side in a direction (vehicle-width direction) that is substantially perpendicular to the vehicle traveling direction. The ventilation cover units 10a, 10b are arranged so as to be inclined with respect to the direction (vehicle-width direction) that is substantially perpendicular to the vehicle traveling direction such that each of ventilation cover units 10a, 10b is highest at its joint portion (center portion of the ventilation cover 10 in the vehicle-width direction).

[0018] FIG. 2 is a plan view of the ventilation structure for the fuel cell stack according to the present embodiment as viewed from above. A plurality of first opening 16 is formed at the top of the housing case 15 that houses the fuel cell stack. Each first opening 16 is formed in a substantially elliptical shape that extends in the vehicle-width direction, and the first openings 16 are aligned along the vehicle traveling direction. In FIG. 2, a total of four first openings 16 are aligned along the vehicle traveling direction. However, this is just an example, and the number of first openings 16 is not limited to four. The housing case 15 is made of metal such as stainless steel or aluminum, or reinforced plastic.

[0019] Each first opening 16 is formed in a substantially elliptical shape or an oval shape that extends in the vehicle- width direction, as described above. With regard to the positional relation between the housing case 15 and the fuel cell stack, each first opening 16 extends along a direction in which the cells of the fuel cell stack are stacked. FIG. 2 also shows the direction in which the cells of the fuel cell stack are stacked (hereinafter, referred to as "cell stacking direction" where appropriate). The cell stacking direction extends along the vehicle-width direction, and is substantially perpendicular to the vehicle traveling direction. A constant compression force is applied, in the cell stacking direction, to the fuel cell stack housed in the housing case 15 to restrain the fuel cell stack. Therefore, a stress in the cell stacking direction is generated within the fuel cell stack. Forming each first opening 16 in an elliptical shape and arranging the first opening 16 such that the major axis of the elliptical shape extends along the cell stacking direction suppresses reduction in rigidity of the housing case, which may be caused in the stress direction.

[0020] The ventilation cover 10 is provided at the top of the housing case 15, that is, on a portion of the housing case 15, in which the first openings 16 are formed. The planar shape of the ventilation cover 10 is a rectangular shape. The ventilation cover 10 is fixed at its four comers to the housing case 15. As shown in FIG. 1 , the ventilation cover 10 is formed by joining the two ventilation cover units 10a, 10b together by heat welding. In addition, the two second openings 12 are formed in the ventilation cover unit 10a, and the two second openings 14 are formed in the ventilation cover unit 10b. The planar shape of each of the two second openings 12 is a rectangular shape, and the two second openings 12 are arranged side-by-side in the vehicle traveling direction. Similarly, the planar shape of each of the two second openings 14 is a rectangular shape, and the two second openings 14 are arranged side-by-side in the vehicle traveling direction. The hydrogen permeable membranes are stuck to the opening edges of the second openings 12, 14 to cover the entireties of the second openings 12, 14. Each hydrogen permeable membrane is made of a material, for example, a porous material, which allows gases such as hydrogen and air to permeate therethrough but does not allow water to permeate therethrough. An example of a material of the hydrogen permeable membrane is Poreflon®. However, the material is not limited to this example.

[0021] The second openings 12, 14 are arranged so as to face the first openings 16 of the housing case 15. The region where the second openings 12, 14 are formed at least partially overlaps with the region where the first openings 16 are formed. Therefore, even if a portion of hydrogen leaks from the fuel' cell stack, the leaked hydrogen is released to the outside of the housing case 15 through the first openings 16 of the housing case 15 and the second openings 12, 14 of the ventilation cover 10.

[0022] FIG. 3 shows a sectional view taken along the line III-III in FIG. 2. FIG. 3 also shows a vehicle body 18. The fuel cell stack FC is placed under a vehicle body 18, more specifically, the floor panel, and fixed by the supporting member. The ventilation cover 10 formed by the two ventilation cover units 10a, 10b is provided at the top of the housing case 15. The predetermined amount of clearance is left between the vehicle body 18 and the ventilation cover 10, and various wire harnesses 17 are provided in the clearance.

[0023] The ventilation cover units 10a, 10b are arranged side-by-side in the vehicle- width direction, and the ventilation cover 10 is inclined so as to be highest at its center portion in the vehicle-width direction. An inclination angle Θ of each of the ventilation cover units 10a, 10b is set to at least 5°, for example, 8°.

[0024] Thus, inclined surfaces are formed in the ventilation cover 10. In addition, the inclined surfaces are inclined with respect to the vehicle-width direction that is substantially perpendicular to the vehicle traveling direction instead of being inclined with respect to the vehicle traveling direction. Therefore, it is possible to efficiently release the leaked hydrogen to the outside of the housing case 15, and prevent the airflow generated by the travel motion of the vehicle from excessively entering the housing case 15 through the second openings 12, 14 and the first openings 16. In addition, because the ventilation cover 10 is inclined with respect to the vehicle-width direction, the airflow does not directly contact the inclined surfaces. Therefore, it is possible to suppress vibration of the ventilation cover 10, which may be caused by the airflow, thereby maintaining the durability of the ventilation cover 10.

[0025] The inclined surfaces of the ventilation cover 10 are inclined with respect to the vehicle-width direction. Therefore, there is also an advantage that even if the vehicle travels on an uphill slope, water does not stagnate on the upper surface of the ventilation cover 10.

[0026] The ventilation cover 10 in the present embodiment is formed by integrating the two ventilation cover units 10a, 10b together by heat welding instead of being formed by a single member. Therefore, it is possible to suppress an increase in the height of the ventilation cover 10 in the vertical direction. This means that it is possible to leave a sufficient amount of clearance between the vehicle body 18 and the ventilation cover 10, thereby reliably ensuring a region in which the wire harnesses 17 are provided.

[0027] In the present embodiment, the hydrogen permeable membranes are stuck to the surface of the ventilation cover 10. The hydrogen permeable membranes are stuck to the surface on the vehicle body 18-side in FIG. 3. Accordingly, it is possible to prevent water or the like from stagnating on the hydrogen permeable membranes.

[0028] The present embodiment of the invention has been described above. However, the invention is not limited to the present embodiment, and various modifications may be made to the present embodiment.

[0029] For example, each first opening 16 in the present embodiment is formed in an elliptical shape, and a plurality of the first openings 16 is aligned along the vehicle traveling direction. Each first opening 16 is formed in a so-called slit-like shape. This is to ensure both sufficient strength of the housing cover 15 and adequate ventilation in the fuel cell stack, as described above. Therefore, an opening may be formed in any shape provided that sufficient strength of the housing case 15 is maintained. Examples of the shape of the first opening 16 include a rectangular shape and a rhombus shape in addition to an elliptical shape. However, regardless of the shape of the first opening 16, each first opening 16 should extend along the cell stacking direction.

[0030] In the present embodiment, the inclination angle Θ (see FIG. 3.) of the ventilation cover 10 is 5° or more. As the inclination angle Θ increases, an effect of preventing water and the like from stagnating on the ventilation cover 10 is enhanced. On the other hand, the height of the ventilation cover 10 also increases with an increase in the inclination angle Θ, thereby reducing the amount of clearance between the vehicle body 1 8 and the ventilation cover 1 0. Therefore, the inclination angle Θ may be an appropriate value that is set in consideration of both the advantage and disadvantage of increasing the inclination angle Θ. When there is no need to provide the wire harnesses 17 in the clearance, such consideration is obviously not necessary.

[0031] In the present embodiment, the two ventilation cover units 10a, 10b have the same inclination angle Θ. However, the inclination angles of the ventilation cover units 10a, 10b need not be equal to each other. Asymmetrically inclined surfaces may be formed such that an inclination angle of one of the two ventilation cover units is larger than that of the other ventilation cover unit.

[0032] In the present embodiment, "substantially perpendicular" means not only "strictly perpendicular" but also "perpendicular within a predetermined range of tolerance". In this sense, "the inclined surfaces of the ventilation cover 10 are inclined with respect to the direction substantially perpendicular to the vehicle traveling direction" includes not only "the inclined surfaces are inclined with respect to the direction that intersects at 90° with the vehicle traveling direction" but also "the inclined surfaces are inclined with respect to the direction that intersects at 90°± a with the vehicle traveling direction (a is a predetermined tolerance, and is set to be, for example, 10°)".

[0033] In the present embodiment, the fuel cell stack is provided under the floor panel of the vehicle. However, the fuel cell stack may be mounted in another appropriate position. For example, the fuel cell stack may be mounted in a space (engine compartment) that corresponds to an engine room of a vehicle in which a gasoline engine is used as a power source, or may be mounted in a center tunnel, a trunk, or the like. When the fuel cell stack is mounted in the center tunnel, the vehicle body 18 shown in FIG. 3 corresponds to the center tunnel, and the wire harnesses 17 are provided within the center tunnel. The height of the center tunnel is limited. In this sense, it is understood that the inclination angle Θ of the ventilation cover 10 is limited to a value within a certain range.

Claims

CLAIMS:

1. A ventilation structure for a fuel cell stack that is mounted in a movable body, comprising:

a housing case (15) with a first opening (16), the housing case (15) housing the fuel cell stack, wherein

the first opening ( 16) extends along a direction in which cells of the fuel cell stack are stacked.

2. The ventilation structure according to claim 1 , wherein:

a planar shape of the first opening (16) is an elliptical shape; and

a major axis of the elliptical shape extends along the direction in which the cells of the fuel cell stack are stacked.

3. The ventilation structure according to claim 1 or 2, wherein:

the movable body is a vehicle; and

the direction in which the cells of the fuel cell stack are stacked is a vehicle-width direction.

4. The ventilation structure according to claim 3, further comprising:

a ventilation cover ( 10) that is fixed to a top of the housing case ( 15) and includes ventilation cover units ( 10a, 10b), wherein

each of the ventilation cover units ( 10a, 10b) has a second opening (12, 14), and the ventilation cover units ( 10a, 10b) are arranged side-by-side in the vehicle-width direction and are inclined with respect to the vehicle-width direction.

5. The ventilation structure according to claim 4, wherein:

the second openings ( 12, 14) of the ventilation cover units ( 10a, 10b) face the first opening ( 16) of the housing case ( 15); and the second openings (12, 14) at least partially overlap with the first opening (16).