fuel cells

Abstract

To provide a fuel cell with excellent volumetric efficiency. [Solution] The fuel cell 1 comprises a fuel cell stack 10 in which a plurality of cells 11 are stacked in the stacking direction, and a case 20 having a housing space S in which the fuel cell stack 10 is housed. The case 20 has a bottom wall 21 and opposing side walls 22 that rise from the periphery of the bottom wall 21 and have a first slope θ1. The housing space S is defined by the bottom wall 21 and the opposing side walls 22, and when viewed from the stacking direction, the side edges 18 of the cells 11 have a second slope θ2 that corresponds to the first slope θ1 of the opposing side walls 22.

Description

Technical Field

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[0001] The present disclosure relates to a fuel cell.

Background Art

[0002] A fuel cell is formed by housing a cell stack in which cell elements are stacked in a case. Patent Document 1 discloses a fuel cell including a cell stack body and a case that at least surrounds the side surface of the cell stack body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0007] According to this disclosure, a fuel cell with excellent volumetric efficiency can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the overall structure of a fuel cell according to one embodiment of the present disclosure. [Figure 2] Figure 2 shows the configuration of the cells and cases as viewed from the stacking direction of the cells. [Figure 3] Figure 3 shows an example of the assembly process for a fuel cell. [Figure 4] Figure 4 shows the configuration of a conventional fuel cell cell and case. [Figure 5] Figure 5 shows the configuration of a cell in another embodiment of the present disclosure. [Figure 6] Figure 6 shows the configuration of a cell and case in another embodiment of the present disclosure. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, U represents the upward direction, D represents the downward direction, R represents the right direction, L represents the left direction, F represents the forward direction, and B represents the backward direction.

[0010] Figure 1 is a schematic diagram showing a fuel cell 1 according to one embodiment of the present disclosure. As shown in Figure 1, the fuel cell 1 comprises a fuel cell stack 10 and a case 20. In Figure 1, the fuel cell stack 10 is represented by a dashed line and the case 20 is represented by a solid line. The fuel cell stack 10 is a laminate in which a plurality of cells 11 (see Figure 2) are stacked in the stacking direction. The stacking direction is the direction along the forward or backward direction in Figure 1.

[0011] The case 20 comprises an upper wall 21, opposing side walls 22, a front wall 23, a rear lid 24, and a bottom lid 25. The upper wall 21 is an example of a bottom wall in this disclosure. The case 20 has an internal housing space S (see Figure 2), in which the fuel cell stack 10 is housed. The case 20 is made of aluminum, for example. The fuel cell stack 10 housed in the case 20 is supported by compressive forces applied from end plates (not shown) located at both ends in the stacking direction.

[0012] Figure 2 shows the configuration of cell 11 and case 20 as viewed from the stacking direction of cell 11. As shown in Figure 2, cell 11 comprises a frame 12, a membrane electrode assembly (MEA) 13 located in the center, and manifolds located on the left and right of the membrane electrode assembly 13 and extending in the stacking direction. The manifolds in each cell 11 ensure a flow path for gas or refrigerant to flow along the stacking direction. Specifically, the manifold of cell 11 is provided with a hydrogen inlet 14a, a hydrogen outlet 14b, an air inlet 15a, an air outlet 15b, a cooling water inlet 16a, and a cooling water outlet 16b. The membrane electrode assembly 13 is an assembly that includes a catalyst layer, an electrolyte membrane, and a gas diffusion layer. The fuel cell 1 generates electricity by supplying hydrogen through the hydrogen inlet 14a and oxygen through the air inlet 15a to the membrane electrode assembly 13 of each cell 11. In this specification, the region A1 in cell 11 where the membrane electrode assembly 13 is located is called the power generation region, and the region A2 where each manifold and other elements are located is called the peripheral region. In this embodiment, the cell 11, other than the manifold located in the peripheral region A2, includes notches 171 and holes 172 used for positioning during assembly, a plurality of dimples 173 for evenly distributing gas from the manifold toward the power generation region A1, and a cell monitor terminal 174 for connecting a connector for voltage measurement. Each cell 11 arranged in the stacking direction is separated from adjacent cells 11 by a separator (not shown).

[0013] Figure 3 shows an example of the assembly process for fuel cell 1. The specific configuration of case 20 will also be explained with reference to Figure 3. As shown in Figure 3, fuel cell 1 is formed by the steps of (1) housing the fuel cell stack 10 in a molded body 201 with an open bottom and rear, (2) closing the bottom with a bottom cover 25, and (3) closing the rear with a rear cover 24 while compressing the fuel cell stack 10 in the stacking direction. For illustrative purposes, the orientation of each component in Figure 3 is reversed compared to Figure 1.

[0014] The molded body 201 is integrally formed by casting and comprises an upper wall 21, an opposing side wall 22, and a front wall 23, which are parts of the case 20. The molded body 201 has a housing space S defined by the upper wall 21 and the opposing side wall 22. The front wall 23 is provided with holes 231 for guiding gas or refrigerant to the manifold. In the assembly process of the fuel cell 1, first the fuel cell stack 10 is housed in the housing space S of the molded body 201 (step (1)), and the lower cover 25 is closed (step (2)). Next, the fuel cell stack 10 is compressed in the stacking direction toward the front wall 23 via an end plate (not shown), and the rear cover 24 is closed to fix it in place (step (3)). This results in a fuel cell 1 in which the fuel cell stack 10 is housed in the housing space S within the case 20. As described above, the case 20 is formed from the molded body 201, the lower cover 25, and the rear cover 24.

[0015] Cast products, such as the molded body 201, have a draft angle during the molding process to allow the product to be removed from the mold. More specifically, the molded body 201 is cast using a lower mold that forms the inner surface facing the containment space S and an upper mold that forms the outer surface which is the outside of the case 20. After the molded body 201 is formed, the draft angle is the slope that creates a gap between the mold and the molded body when the molded body is removed from the upper and lower molds. As shown in Figure 2, the case 20 has an upper wall 21 and a pair of opposing side walls 22 rising from the periphery of the upper wall 21, and the opposing side walls 22 have a draft angle θ1 relative to the upper wall 21. The draft angle θ1 is a slope such that the opposing side walls 22 widen downward from the upper wall 21, and its angle is the angle that each of the left and right side walls of the opposing side walls 22 makes with respect to the normal direction of the upper wall 21. Because the opposing side wall 22 has a draft angle θ1, the outer shape of the storage space S defined by the upper wall 21 and the opposing side wall 22 is approximately trapezoidal. In this specification, the slope θ1 of the opposing side wall 22 of case 20 is also referred to as the first slope θ1.

[0016] In this embodiment, the outer shape of the cell 11 is substantially trapezoidal. As shown in FIG. 2, when viewed from the stacking direction, the side edge 18 of the cell 11 has a gradient θ2. In this specification, the gradient θ2 of the side edge 18 of the cell 11 is also referred to as the second gradient θ2. As shown in FIG. 2, the second gradient θ2 of the side edge 18 of the cell 11 corresponds to the first gradient θ1 of the opposing side wall 22, and typically the angles of the first gradient θ1 and the second gradient θ2 are equal. Note that the angle of the second gradient θ2 is the angle formed by the side edge 18 of the cell 11 with respect to the normal direction of the upper side of the cell 11 (the side facing the upper wall 21 of the case 20).

[0017] According to the fuel cell 1 of this embodiment shown in FIG. 2, since the side edge 18 of the cell 11 has a second gradient θ2 corresponding to the first gradient θ1 of the opposing side wall 22 of the case 20, the gap between the cell 11 and the case 20 is small. Therefore, in the fuel cell 1, the ratio of the volume of the fuel cell stack 10 in the accommodation space S of the case 20 is large, and the volumetric efficiency is excellent.

[0018] As a comparative example for this embodiment, the configuration of a conventional fuel cell will be described. FIG. 4 is a diagram showing the configuration of a conventional fuel cell 1A. The fuel cell 1A includes a cell 11A instead of the cell 11 of the fuel cell 1. FIG. 4 shows the cell 11A and the case 20 viewed from the stacking direction. The configuration of the case 20 of the fuel cell 1A is the same as that of the case 20 in the fuel cell 1. As shown in FIG. 4, the outer shape of the cell 11A of the fuel cell 1A is rectangular. That is, the side edge 18A of the cell 11A does not have a gradient. In this case, since the opposing side wall 22 of the case 20 has a first gradient while the side edge 18A of the cell 11A does not have a gradient, an excess space S1 occurs between the cell 11A and the case 20 on the side of the cell 11A.

[0019] According to the fuel cell 1 of the present embodiment shown in FIG. 2 as described above, since the side edge 18 of the cell 11 has a second gradient θ2 corresponding to the first gradient θ1 of the opposing side wall 22 of the case 20, there is no surplus space as in the fuel cell 1A of FIG. 4. As a result, for example, when using cases 20 of the same size in the fuel cell 1 shown in FIG. 2 and the fuel cell 1A shown in FIG. 4, the fuel cell 1 can have a larger power generation area A1 and can increase the power generation amount. Also, when manufacturing fuel cells with the same power generation amount, the fuel cell 1 can make the case 20 smaller than the fuel cell 1A.

[0020] Also, as shown in FIG. 2, in the fuel cell 1 of the present embodiment, in the cell 11 having a substantially trapezoidal outer shape, the power generation area A1 is rectangular, and the peripheral area A2 is substantially trapezoidal along the gradient of the side edge 18. Specifically, that the power generation area A1 is rectangular may be equivalently stated as the membrane electrode assembly 13 being rectangular. Since the electrolyte membrane and the gas diffusion layer disposed in the power generation area A1 are obtained by cutting a roll material, if it is rectangular, cutting is easy and it can be used without material loss. Since the catalyst layer is also formed by coating, if it is rectangular, it is easy to form using a die coater or the like. Therefore, regardless of the shape of the cell 11, if the power generation area A1 is rectangular, the manufacturing efficiency is excellent. In other words, it is preferable to use the non-rectangular area around the side edge 18 of the cell 11 as the peripheral area A2 where the manifold and other accessory elements are disposed.

[0021] In the fuel cell 1 of the present embodiment, both the shape of the accommodation space S viewed from the stacking direction and the shape of the cell 11 are substantially trapezoidal. When manufacturing a case by casting, the ideal shape of the case is a rectangular parallelepiped. However, as described above, since a draft is required for castings, the shape of the case provided with a draft viewed from the stacking direction is typically trapezoidal. Therefore, the case 20 having a trapezoidal accommodation space S is easy to manufacture. By matching the shape of the cell 11 to the trapezoidal accommodation space S, the volume efficiency can be increased.

[0022] When the fuel cell 1 is mounted on a vehicle or power generation device, it is preferable that the gas outlet of the cell 11's flow path is located below the gas inlet. In other words, it is preferable to use the fuel cell 1 with the hydrogen outlet 14b and air outlet 15b located below the hydrogen inlet 14a and air inlet 15a, as shown in Figure 2. Not only gas but also water generated by the reaction of hydrogen and oxygen and condensation is discharged from the gas outlet. By placing the gas outlet lower, water generated in the flow path is more easily guided to the gas outlet by gravity, improving drainage efficiency.

[0023] Furthermore, when the fuel cell 1 is mounted on the device, it is preferable that the distance between the opposing side walls 22 widens downwards. That is, it is preferable to use the fuel cell 1 in an orientation where the upper wall 21 (bottom wall), which has a smaller area, is at the top and the lower cover 25, which has a larger area, is at the bottom, as shown in Figure 2. As shown in Figure 2, the peripheral region A2 of the fuel cell 1 is narrower on the upper wall 21 side and wider on the lower cover 25 side. In the gas distribution of a fuel cell, the gas outlet tends to be designed to be larger than the gas inlet. Therefore, by designing the fuel cell 1 to be mounted in an orientation where the bottom is wider, it is easier to make the gas outlet at the bottom larger and to arrange each component efficiently.

[0024] Next, another embodiment of the cell in this disclosure will be described. In the following description, components already described will be denoted by the same reference numerals and their descriptions will be omitted as appropriate. Figure 5 is a plan view of the cell 511 as seen from the stacking direction. As shown in Figure 5, the cell 511 comprises a frame 12, a membrane electrode composite 13, and each manifold. The cell 511 has a side edge 518R on one end (R side, left side of the paper) and a side edge 518L on the other end (L side, right side of the paper). The side edge 518R has a second slope θ21, and the side edge 518L has a second slope θ22. In this embodiment, the angle of the second slope θ21 of the side edge 518R and the angle of the second slope θ22 of the side edge 518L are different from each other.

[0025] As shown in Figure 5, manifolds are arranged in the peripheral region A2, including the side edges 518R and 518L. The area of ​​each manifold is determined by considering various conditions. For example, hydrogen and air need to flow at flow rates that take into account the flow rate required for power generation and the efficiency of utilization, so the manifold for air is usually designed to be larger than the manifold for hydrogen. Also, in order to distribute the fluid evenly to many stacked cells, the fluid inlet tends to be designed to be small and the outlet to be large. Furthermore, it is also taken into consideration that the mass flow rates at the inlet and outlet differ because hydrogen and air are converted into water during power generation, and that the volume flow rates at the inlet and outlet differ for both fluids due to the effects of temperature and pressure. As an example of an advantageous design that takes the above into consideration, it is possible to make the hydrogen inlet small and the air outlet and cooling water outlet large.

[0026] The manifold provided on the side edge 518L of cell 511, as shown in Figure 5, is based on the above design, with a relatively small hydrogen inlet 14a and relatively large air outlets 15b and cooling water outlets 16b. In this embodiment, the angle of the second slope θ22 of the side edge 518L is large, making it easy to arrange these manifolds with different areas. Specifically, the hydrogen inlet 14a does not become extremely elongated horizontally, and each manifold can be arranged in a balanced manner along the vertical direction, thus avoiding an increase in pressure loss and making it easier to distribute the gas evenly to the power generation area. On the other hand, in this embodiment, there is no large difference in area for the manifold on the side edge 518R, and the slope θ21 of the side edge 518R is set to the minimum slope corresponding to the first slope in the case not shown. In this way, by adjusting the second slope of the cell's side edge according to the manifold design, the manifolds can be appropriately arranged.

[0027] In the above description of the embodiment, we described the case where the second slopes θ21 and θ22 of the side edges 518R and 518L are adjusted according to the design of the manifold. However, the slope of the cell's side edge can be adjusted as appropriate, taking into account any elements to be placed in the peripheral region, not just the manifold. For example, the angle of the slope of the side edge on one end may be made larger or smaller than that on the other end in order to provide notches or holes for positioning (see notches 171 and holes 172 in Figure 2) or cell monitor terminals (see cell monitor terminals 174 in Figure 2). By adjusting the slope of the side edge, elements can be suitably arranged in the peripheral region.

[0028] Next, another embodiment of the fuel cell of the present disclosure will be described. Figure 6 shows a fuel cell 601 according to another embodiment of the present disclosure, showing the configuration of the cell 611 and case 20 as viewed from the stacking direction. Figure 6 is drawn in the orientation in which the fuel cell 601 is mounted on a payload. As shown in Figure 6, the fuel cell 601 has a slope such that the distance between the opposing side walls 22 of the case 20 widens upward, and the top and bottom of the case 20 are inverted compared to the fuel cell 1 in Figure 2. The side edge 618 of the cell 611 has a slope corresponding to the opposing side walls 22 of the case 20. In cell 611, as with cell 11 shown in Figure 2, the gas outlet is located below the gas inlet. Specifically, the hydrogen outlet 14b and air outlet 15b are located below the hydrogen inlet 14a and air inlet 15a. Furthermore, the manifold area is designed such that the hydrogen outlet 14b and air outlet 15b are larger than the hydrogen inlet 14a and air inlet 15a.

[0029] As described above, the side edge 618 of cell 611 has a slope that widens upwards, and the manifold at the bottom of the peripheral region is designed to be large, so there is a surplus area at the top of the peripheral region for arranging elements other than the manifold. As shown in Figure 6, the surplus area of ​​cell 611 is where the positioning notches 171 and holes 172, the cell monitor terminal 174, and the two-dimensional code 175 engraved for cell identification are located. In a fuel cell 601, as in this embodiment, where the distance between the side walls of opposing side walls 22 widens upwards when mounted, it is easy to arrange various elements in the peripheral region of cell 611. Furthermore, in the fuel cell assembly process, there are two methods for storing the stack in the case: placing the case on top of the stack and inserting the stack from above the case. Since the heavy stack is stored suspended, it is preferable to adopt the method of inserting the stack from above the case. The fuel cell 601, which is intended for use in the orientation shown in Figure 6, has the advantage that when the stack is placed on top of the case, the orientation during assembly and the orientation during use are the same, eliminating the need to reverse the top and bottom.

[0030] Although the fuel cell of this disclosure has been described in detail with reference to specific embodiments, this disclosure is not limited to the embodiments described herein.

[0031] In the embodiments described above, the case in which the molded body 201 is manufactured by casting was explained, but the processing method for the case 20 containing the molded body 201 is not particularly limited and may be forging or press forming. In forging and press forming as well, a draft angle is provided to remove the molded product from the mold.

[0032] In the embodiment described above, the first gradient θ1 of the opposing side wall 22 was explained as being due to a draft angle, but the first gradient θ1 is not limited to a draft angle. For example, the first gradient θ1 may be provided on the case 20 to prevent interference with another adjacent fuel cell 1 or other components when the fuel cell 1 is mounted on a vehicle or the like.

[0033] The angle of the first gradient θ1 may be, for example, 0.5° to 22°, or 1.5° to 12°. A draft angle of 0.5° or more is typically provided in casting. If the gradient is 22° or less, the difference between the top and bottom edges of the case will not be excessively large, thus reducing the floor area required for the installation of the fuel cell and avoiding deterioration in the efficiency of the placement of components on the outside of the case. The gradients of the left and right side walls of the opposing side wall 22 may be the same or different. The thickness of the opposing side wall 22 does not have to be uniform, and the thickness of the side wall may gradually decrease or increase from the top wall 21 towards the bottom cover 25. Therefore, the angle made by the inner surface of the opposing side wall 22 with respect to the normal direction of the top wall 21 and the angle made by the outer surface of the opposing side wall 22 may be different from each other. The angle of the second gradient θ2 is not particularly limited, but may be, for example, 0.5° to 22°, or 1.5° to 12°.

[0034] In the embodiments described above, the case where the angles of the first slope θ1 and the second slope θ2 are equal was explained, but this disclosure is not limited to such configurations. That is, even if the angles of the first slope and the second slope are different, if the side edge of the cell has a slope that is aligned with the slope of the opposing side wall, and the volumetric efficiency is improved compared to the case where the side edge has no slope, then it can be said that "the second slope corresponds to the first slope," and this is included within the scope of this disclosure.

[0035] In this disclosure, "approximately trapezoidal" means a shape whose general shape is trapezoidal. Specifically, in addition to shapes like the cell 11 with the notch 171 shown in Figure 2, shapes with small indentations on each side, shapes with chamfered vertices, shapes with a slightly inclined top or bottom edge can also be called approximately trapezoidal if their general shape is trapezoidal.

[0036] In the embodiment described above, a dimple was exemplified as a structure for evenly distributing gas to the power generation area, but the structure for gas distribution is not limited to a dimple. For example, multiple flow paths from the gas inlet to the power generation area may be provided.

[0037] The fuel cell of this disclosure may be a single-cell type or a bipolar type. The single-cell type is a method in which a single cell is fabricated by sandwiching a frame supporting the MEA between two electrode separators and bonding them together, and a fuel cell stack is formed by stacking these single cells. The bipolar type is a method in which a bipolar plate is fabricated by joining a cathode separator and an anode separator, and a fuel cell stack is formed by alternately stacking the bipolar plate and the frame. In other words, the cell in this disclosure is not limited to a single cell that has the configuration of a cell on its own, but may also be a cell in a bipolar type in which the configuration of the cell is completed only when stacked.

[0038] This disclosure includes the following: (1) A fuel cell according to one embodiment of the present disclosure is A fuel cell stack in which multiple cells are stacked in the stacking direction, A fuel cell comprising a case having a housing space in which the fuel cell stack is housed, The case has a bottom wall and a first sloped, opposing side wall rising from the periphery of the bottom wall. The aforementioned containment space is defined by the bottom wall and the opposing side wall. Viewed from the stacking direction, the side edge of the cell has a second slope that corresponds to the first slope of the opposing side wall.

[0039] (2) In (1) above, the cell has a power generation region in which a membrane electrode assembly is arranged and a peripheral region in which a flow path for gas or refrigerant is provided along the stacking direction, and the power generation region of the cell may be rectangular when viewed from the stacking direction.

[0040] (3) In (1) or (2) above, the angle of the second slope on one end edge of the cell and the angle of the second slope on the other end edge may be different from each other.

[0041] (4) In any of (1) to (3) above, the shape of the storage space and the shape of the cell may be substantially trapezoidal when viewed from the stacking direction.

[0042] (5) In any of the above (1) to (4), the gas outlet of the cell may be located below the gas inlet when mounted.

[0043] (6) In the above (5), when mounted, the opposing side walls may have a slope such that the distance between the side walls widens downwards.

[0044] (7) In the above (5), the opposing side walls may have a slope such that the distance between the side walls widens upward when mounted.

[0045] (8) In any of (1) to (7) above, the angle of the first slope may be 0.5° or more and 22° or less. [Explanation of Symbols]

[0046] 1,1A,601 Fuel Cell 10 Fuel Cell Stacks 11,11A,511,611 cells 12 Frame 13 Membrane electrode assembly 14a Hydrogen Inlet 14b Hydrogen outlet 15a Air Inlet 15b Air outlet 16a Cooling water inlet 16b Cooling water outlet 171 Notch 172 holes 173 dimples 174 Cell monitor terminal 175 QR code 18,18A,518L,518R,618 Side edge 20 cases 21 Upper wall (bottom wall) 22 Opposing side wall 23 Front wall 231 hole 24 Rear lid 25 Lower lid 201 Molded body S Containment space S1 Surplus space A1 Power Generation Area A2 Peripheral area

Claims

1. A fuel cell stack in which multiple cells are stacked in the stacking direction, A fuel cell comprising a case having a housing space in which the fuel cell stack is housed, The case has a bottom wall and a first sloped, opposing side wall rising from the periphery of the bottom wall. The aforementioned containment space is defined by the bottom wall and the opposing side wall. A fuel cell in which, when viewed from the stacking direction, the side edge of the cell has a second slope corresponding to the first slope of the opposing side wall.

2. The cell has a power generation region in which a membrane electrode assembly is arranged, and a peripheral region in which a flow path is provided through which gas or coolant flows along the stacking direction. The fuel cell according to claim 1, wherein the power generation region of the cell is rectangular when viewed from the stacking direction.

3. The fuel cell according to claim 1 or claim 2, wherein the angle of the second slope of the side edge on one end of the cell and the angle of the second slope of the side edge on the other end are different from each other.

4. The fuel cell according to claim 1 or claim 2, wherein, when viewed from the stacking direction, the shape of the housing space and the shape of the cell are substantially trapezoidal.

5. The fuel cell according to claim 1 or claim 2, wherein, in the installed state, the gas outlet of the cell is located below the gas inlet.

6. The fuel cell according to claim 5, wherein, in the mounted state, the opposing side walls have a slope such that the distance between the side walls widens downwards.

7. The fuel cell according to claim 5, wherein, in the mounted state, the opposing side walls have a slope such that the distance between the side walls widens upward.

8. The fuel cell according to claim 1 or claim 2, wherein the angle of the first gradient is 0.5° or more and 22° or less.

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