Fuel cell stack

Abstract

It suppresses displacement and peeling of the displacement-suppressing member. [Solution] In a fuel cell stack comprising a plurality of stacked cells, the first cell of the plurality of cells comprises a membrane electrode assembly, a frame that holds the membrane electrode assembly, a pair of separators that sandwich the membrane electrode assembly held by the frame, and one or more elastic bodies having a base and a plurality of columnar portions protruding from the base. The first separator, which is one of the pair of separators comprising the first cell, has one or more grooves on its first surface. The base of one or more elastic bodies is positioned in one or more grooves, the base covers the bottom surface of one or more grooves, and at least a portion of the plurality of columnar portions is positioned along the direction in which one or more grooves extend. In the coolant flow path space formed between the first cell and the second cell adjacent to the first cell, the tips of the plurality of columnar portions of the one or more elastic bodies positioned in one or more grooves of the first separator contact the second separator comprising the second cell.

Description

Technical Field

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

Background Art

[0002] In the technology described in Patent Document 1, a displacement suppressing member is disposed in a coolant flow path space formed by a separator included in one of a plurality of cells constituting a fuel cell stack and a separator included in another cell stacked on the cell. The displacement suppressing member is fixed to the separator included in one cell in order to suppress the occurrence of displacement of the separator due to fluctuations in the pressure of the coolant flowing through the flow path space. This displacement suppressing member has a plurality of protrusions and connecting pieces that connect the plurality of protrusions. The tips of the plurality of protrusions are hitting against the separator facing the separator to which the displacement suppressing member is fixed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology described in Patent Document 1, the pressure of the coolant flowing through the flow path space is applied to the displacement suppressing member. When the pressure of the coolant increases, there is a possibility that the displacement suppressing member may be displaced or peeled off from the separator.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one embodiment of the present disclosure, a fuel cell stack is provided. In this fuel cell stack, a first cell among a plurality of cells comprises a membrane electrode assembly, a frame for holding the membrane electrode assembly, a pair of separators for sandwiching the membrane electrode assembly held by the frame, and one or more elastic bodies having a base and a plurality of columnar portions protruding from the base. The first separator, which is one of the pair of separators in the first cell, has one or more grooves on a first surface which is the surface opposite to the surface facing the other of the pair of separators in the first cell. The base of the one or more elastic bodies is positioned in the one or more grooves, the base covers the bottom surface of the one or more grooves, and at least a portion of the plurality of columnar portions is positioned along the direction in which the one or more grooves extend. In a flow path space for coolant formed between the first cell and a second cell adjacent to the first cell, in a flow path space which is a gap formed by the second separator of the second cell being superimposed on the first surface of the first separator of the first cell, the tips of the plurality of columnar portions of the one or more elastic bodies arranged in the one or more grooves of the first separator are in contact with the second separator of the second cell. In the above configuration, the base portion, which is part of the elastic body, is positioned in the groove so as to cover the bottom surface of the groove formed in the first separator. Therefore, compared to the configuration in which part of the elastic body is not positioned in the groove, the area in which the coolant directly contacts the elastic body can be reduced. As a result, the force that the base portion of the elastic body receives from the coolant can be reduced. Therefore, compared to the configuration in which part of the elastic body is not positioned in the groove, displacement and delamination of the elastic body can be suppressed.

[0007] (2) In the fuel cell stack of the above embodiment, the one or more elastic bodies include a first elastic body and a second elastic body, and each of the first elastic body and the second elastic body has a wall portion protruding from the base portion in addition to the base portion and the plurality of column portions. The first separator has a supply manifold for supplying the coolant to the flow path space and a discharge manifold for discharging the coolant from the flow path space, the first groove of the one or more grooves is formed on the first surface of the first separator so as to surround the supply manifold, and the second groove of the one or more grooves is formed on the first surface of the first separator so as to surround the discharge manifold. By positioning the base of the first elastic body in the first groove, the plurality of columnar portions of the first elastic body may be positioned downstream of the wall portion of the first elastic body in the direction from the supply manifold to the discharge manifold, and by positioning the base of the second elastic body in the second groove, the plurality of columnar portions of the second elastic body may be positioned upstream of the wall portion of the second elastic body in the same direction. According to the above configuration, in the first elastic body arranged to surround the supply manifold that supplies coolant to the flow path space, multiple columnar sections are arranged downstream of the wall section in the direction from the supply manifold to the discharge manifold, and in the second elastic body arranged to surround the discharge manifold that discharges coolant from the flow path space, multiple columnar sections are arranged upstream of the wall section. Therefore, the flow of coolant can be made smooth.

[0008] (3) In the fuel cell stack of the above embodiment, the membrane electrode assembly held by the frame is sandwiched between the first separator and the other of the pair of separators provided in the first cell, and the second surface of the first separator, opposite to the first surface, may be in contact with the frame at a position on the back side of the position where the one or more grooves are provided. In the completed state of the fuel cell stack, the elastic body placed in the flow channel space applies a load to the frame via the first separator in the stacked state of multiple cells, thereby fixing the position of the frame, which is sandwiched between a pair of separators, and the membrane electrode assembly attached to the frame. With this configuration, the occurrence of displacement and delamination of the elastic body can be suppressed compared to the configuration in which a part of the elastic body is not placed in the groove. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram showing a disassembled fuel cell according to this embodiment. [Figure 2] This is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] This is a cross-sectional view showing two fuel cell cells stacked on top of each other. [Figure 4] This is an explanatory diagram showing an example of the external shape of the elastic part. [Figure 5] This is a cross-sectional view taken along the VV line in Figure 1. [Modes for carrying out the invention]

[0010] A. Embodiments: Figure 1 is an explanatory diagram showing an exploded view of the fuel cell cell 100 according to this embodiment. Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. The fuel cell cell 100 is a solid polymer fuel cell that generates electricity by receiving hydrogen and oxygen as reaction gases. A fuel cell stack is formed by stacking multiple fuel cell cells 100.

[0011] As shown in Figure 1, the fuel cell cell 100 comprises a membrane electrode assembly (MEA) 10, a resin sheet 20, a pair of separators 30 and 40, a sealing portion 60, and an elastic portion 70. The fuel cell cell 100 is also simply called the "cell". The elastic portion 70 is also called the "elastic body". The resin sheet 20 is also called the "frame".

[0012] As shown in Figure 2, the membrane electrode assembly 10 comprises an electrolyte membrane 11, a first electrode catalyst layer 12 as a cathode electrode formed on one side of the electrolyte membrane 11, a second electrode catalyst layer 13 as an anode electrode formed on the other side of the electrolyte membrane 11, a first gas diffusion layer 14 formed on the side of the first electrode catalyst layer 12 that is not in contact with the electrolyte membrane 11, and a second gas diffusion layer 15 formed on the side of the second electrode catalyst layer 13 that is not in contact with the electrolyte membrane 11. The electrolyte membrane 11 is composed of, for example, an ion exchange membrane made of a fluororesin. The first electrode catalyst layer 12 and the second electrode catalyst layer 13 are composed of, for example, a carbon carrier supporting a platinum catalyst. The first gas diffusion layer 14 and the second gas diffusion layer 15 are composed of, for example, carbon cloth.

[0013] As shown in Figure 1, the resin sheet 20 is a frame-shaped member that holds the membrane electrode assembly 10. For example, the outer periphery of the membrane electrode assembly 10 is joined to the inner periphery of the central through-hole 20h of the resin sheet 20 by an adhesive film F1 (see Figure 2), which is a sheet-shaped hot-melt adhesive. The membrane electrode assembly 10 is exposed on both the front and back surfaces of the resin sheet 20.

[0014] As shown in Figure 2, the resin sheet 20 comprises a core layer 21 and adhesive layers 22A and 22B provided on both sides of the core layer 21. It is preferable that the materials constituting the core layer 21 and the adhesive layers 22A and 22B are selected such that the melting point of the core layer 21 is higher than the melting points of the adhesive layers 22A and 22B. The core layer 21 is composed of, for example, polyethylene naphthalate (PEN). The adhesive layers 22A and 22B are composed of, for example, modified olefin-based hot-melt adhesives.

[0015] As shown in Figure 1, the separators 30 and 40 sandwich the membrane electrode assembly 10, which is held in the resin sheet 20. The separators 30 and 40 are bonded to the resin sheet 20 by adhesive layers 22A and 22B. The separators 30 and 40 are made of, for example, stainless steel, titanium, or an alloy thereof. The separators 30 and 40 are provided with irregularities formed by press molding. As shown in Figure 2, a channel CF through which oxidizing gas (cathode gas) flows is formed between the separator 30 and the membrane electrode assembly 10 by the irregularities provided in the separator 30. A channel AF through which fuel gas (anode gas) flows is formed between the separator 40 and the membrane electrode assembly 10 by the irregularities provided in the separator 40.

[0016] As shown in Figure 1, multiple through-holes are formed in the resin sheet 20 and the separators 30 and 40. These through-holes form multiple manifolds when the resin sheet 20 is sandwiched between the separators 30 and 40. The multiple manifolds include a supply manifold Mio that supplies oxidizing gas to the membrane electrode assembly 10, a supply manifold Mih that supplies fuel gas to the membrane electrode assembly 10, a supply manifold Miw that supplies coolant, an exhaust manifold Moo that discharges the oxidizing gas used in the reaction in the membrane electrode assembly 10, an exhaust manifold Moh that discharges the fuel gas used in the reaction in the membrane electrode assembly 10, and an exhaust manifold Mow that discharges the coolant that has received heat generated in the membrane electrode assembly 10. In Figure 1, the six through-holes formed in the separator 30 are denoted by the symbols 301 to 306.

[0017] As shown in Fig. 2, two groove portions 31 formed by press molding are provided on the surface S1 of the separator 30. One groove portion 31 is formed so as to surround the through-hole 303 of the separator 30. The other groove portion 31 is formed so as to surround the through-hole 306. Note that the groove portion 31 surrounding the through-hole 306 of the separator 30 in Fig. 2 is not shown. The surface S2 of the separator 30 contacts the resin sheet 20 at a position corresponding to the back side of the position where the groove portion 31 is formed, with the membrane electrode assembly 10 held by the resin sheet 20 sandwiched between the separator 30 and the separator 40. The same applies to the groove portion 31 surrounding the through-hole 306 of the separator 30. The use of the groove portion 31 will be described later. The surface S1 is also referred to as the "first surface". The surface S2 is also referred to as the "second surface".

[0018] Fig. 3 is a partial cross-sectional view showing a state in which two fuel cell units 100 are stacked. The fuel cell unit 100 disposed on the lower side is denoted as the fuel cell unit 100A, and the fuel cell unit 100 disposed on the upper side is denoted as the fuel cell unit 100B. The fuel cell unit 100B is adjacent to the fuel cell unit 100A on the side opposite to the separator 40 of the fuel cell unit 100A with respect to the separator 30 of the fuel cell unit 100A. The gap formed by overlapping the separator 40 of the fuel cell unit 100B with the separator 30 of the fuel cell unit 100A constitutes a flow path space WF through which a coolant for controlling the temperature of the membrane electrode assembly 10 flows. The fuel cell unit 100A is also referred to as the "first cell". The fuel cell unit 100B is also referred to as the "second cell". The separator 30 of the fuel cell unit 100A is also referred to as the "first separator". The separator 40 of the fuel cell unit 100B is also referred to as the "second separator".

[0019] As shown in Figure 1, the seal portion 60 seals the oxidizing gas flow path CF and the fuel gas flow path AF to prevent the oxidizing gas and fuel gas from entering the flow path space WF. The seal portion 60 is made of a rubber gasket, such as EPDM (ethylene propylene diene rubber), or a CIPG (Cured In Place Gasket). The seal portion 60 is joined to surface S1, which is the side of the separator 30 that does not face the membrane electrode assembly 10 and the resin sheet 20. The seal portion 60 is arranged to independently surround through holes 301, 302, 304, and 305. Furthermore, the seal portion 60 is arranged along the outer circumference of the separator 30.

[0020] As shown in Figure 1, the elastic portion 70 includes an elastic portion 71 and an elastic portion 72. As shown in Figure 2, the elastic portions 71 and 72 are bonded to surface S1, which is the side of the separator 30 that does not face the membrane electrode assembly 10 and the resin sheet 20. As shown in Figure 1, the elastic portion 71 is positioned in the groove 31 formed around the through hole 303. Thus, the elastic portion 71 is positioned to surround the through hole 303 that constitutes the supply manifold Miw. Although not shown in Figure 2, the elastic portion 72 is positioned in the groove 31 formed around the through hole 306. Thus, the elastic portion 72 is positioned to surround the through hole 306 that constitutes the discharge manifold Mow (see Figure 1). The elastic portions 71 and 72 are formed, for example, by injection molding onto the separator 30, which has irregularities including the groove 31 formed by press molding.

[0021] The elastic parts 71 and 72 are arranged in the flow path space WF in order to suppress the displacement of the separator 30 of the fuel cell 100A and the separator 40 of the fuel cell 100B. This is because displacement of the separator 30 of the fuel cell 100A and the separator 40 of the fuel cell 100B may occur due to fluctuations in the pressure of the coolant in the flow path space WF, fluctuations in the temperature of the coolant, and warping during cell manufacturing. Displacement of the separators 30 and 40 leads to variations in the flow rate of the coolant in the flow path space WF, and ultimately to a decrease in cooling efficiency and a decrease in power generation efficiency. The groove portion 31 surrounding the through hole 303 is also referred to as the "first groove portion". The groove portion 31 surrounding the through hole 306 is also referred to as the "second groove portion". The elastic part 71 is also referred to as the "first elastic body". The elastic part 72 is also referred to as the "second elastic body".

[0022] In the state where the fuel cell stack is completed, the fuel cells 100 are stacked. In this state, the elastic parts 71 and 72 arranged in the flow path space WF apply a load to the resin sheet 20 via the separator 30. When the cathode gas pressure and the anode gas pressure are higher than the pressure of the coolant, the sealing performance of the joint between the resin sheet 20 and the separators 30 and 40 deteriorates. By applying a load to the resin sheet 20 by the elastic parts 71 and 72, the seal between the resin sheet 20 sandwiched between the separator 30 and the separator 40 and the separators 30 and 40 can be strengthened.

[0023] Figure 4 is an explanatory diagram showing an example of the external shape of the elastic part 71. Figure 4 shows a perspective view of the elastic part 71 in the area enclosed by the rectangular frame IV shown by the dashed line in Figure 1. Figure 5 is a cross-sectional view taken along the line VV in Figure 1. The following explanation will use the elastic part 71 as an example, but the elastic part 72 has a similar configuration. The elastic part 71 includes a base 71A, a plurality of columnar parts 71B, and a wall part 71C. The plurality of columnar parts 71B and the wall part 71C protrude from the base 71A. The base 71A is arranged to cover the bottom surface of the groove 31. It is desirable that the base 71A be arranged over the entire bottom surface of the groove 31, but it is not necessary to have the base 71A on a part of the bottom surface of the groove 31. The plurality of columnar parts 71B are arranged along the direction in which the groove 31 extends. Two adjacent columnar parts 71B are arranged at a predetermined distance from each other. The wall portion 71C is positioned along the direction in which the groove portion 31 extends. As shown in Figure 3, the tip of the column portion 71B of the elastic portion 71 of the fuel cell cell 100A contacts the separator 40 of the fuel cell cell 100B. Although not shown, the tip of the wall portion 71C also contacts the separator 40 of the fuel cell cell 100B.

[0024] A characteristic feature of this embodiment is that the elastic parts 71 and 72 are arranged in corresponding grooves 31 formed in the separator 30. The advantages of arranging the elastic parts 71 and 72 in the grooves 31 will be explained below. The explanation below will use the elastic part 71 as an example, but the same applies to the elastic part 72.

[0025] First, pressure is applied to the elastic parts 71 and 72 by the flow of the coolant in the flow path space WF. If the pressure of the coolant flow increases, the pressure on the elastic parts 71 and 72 also increases. In this case, the possibility of displacement of the elastic parts 71 and 72 relative to the separator 30, or separation of the elastic parts 71 and 72 from the separator 30, increases.

[0026] In this embodiment, the base portion 71A, which is part of the elastic portion 71, is positioned in the groove portion 31 so as to cover the bottom surface of the groove portion 31 formed in the separator 30. Therefore, compared to the embodiment in which the base portion 71A of the elastic portion 71 is not positioned in the groove portion 31, the area in which the coolant directly contacts the elastic portion 71 can be reduced, and the force that the elastic portion 71 receives from the coolant can be reduced. Therefore, displacement and peeling of the elastic portion 71 can be suppressed.

[0027] According to this embodiment, compared to the configuration in which the base portion 71A, which is part of the elastic portion 71, is not arranged in the groove portion 31, the area in which the coolant directly contacts the elastic portion 71 can be reduced. Therefore, the flow of the coolant in the flow path space WF can be made smoother. From the viewpoint of power generation efficiency, it is preferable for the coolant to flow uniformly in the flow path space WF, but the flow of the coolant may be obstructed by the elastic portion 71 arranged in the flow path space WF. According to the above configuration, the occurrence of such problems can be suppressed. Therefore, the increase in pressure loss of the coolant in the flow path space WF can be suppressed. This makes it possible to suppress a decrease in power generation efficiency.

[0028] In this embodiment, the multiple columnar portions 71B of the elastic portion 71 are positioned downstream of the wall portion 71C in the direction from the supply manifold Miw to the discharge manifold Mow (see Figures 1 and 5). On the supply manifold Miw side, the wall portion 71C is positioned upstream, so the flow of coolant is not obstructed. The multiple columnar portions 72B of the elastic portion 72 are positioned upstream of the wall portion 72C in the direction from the supply manifold Miw to the discharge manifold Mow. On the discharge manifold Mow side, the wall portion 72C is positioned downstream, so the flow of coolant is not obstructed. Therefore, the flow of coolant can be made smooth.

[0029] B. Other embodiments: (B1) In the above embodiment, an example was described in which the elastic portion 71 has a wall portion 71C, but the elastic portion 71 does not have to have a wall portion 71C. For example, the elastic portion 71 may include a base portion 71A and a plurality of column portions 71B, and the plurality of column portions 71B may be arranged to surround the supply manifold Miw. The same applies to the elastic portion 72.

[0030] (B2) The elastic portion 71 may be configured such that a part of the column portion 71B of the elastic portion 71 interferes with the side flat portion FA (see Figure 2) adjacent to the groove portion 31. Alternatively, the elastic portion 71 may be configured such that a part of the base portion 71A of the elastic portion 71 interferes with the side flat portion continuous with the groove portion 31. The portion of the base portion 71A of the elastic portion 71 that is exposed to the flow path space WF may have irregularities. Furthermore, the side flat portions on both sides of the groove portion 31 may be configured to have different heights.

[0031] (B3) Furthermore, irregularities may be formed on the bottom surface of the groove 31. By forming irregularities on the bottom surface of the groove 31, the joint between the base 71A and the bottom surface of the groove 31A can be strengthened, and the effect of suppressing displacement and peeling of the elastic part 71 is further improved. The same applies to the groove formed around the through hole 306 and the elastic part 72.

[0032] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0033] 10…Membrane electrode assembly, 11…Electrolyte membrane, 12…First electrode catalyst layer, 13…Second electrode catalyst layer, 14…First gas diffusion layer, 15…Second gas diffusion layer, 20…Resin sheet, 20h…Through hole, 21…Core layer, 22A,22B…Adhesive layer, 30…Separator, 31…Groove, 40…Separator, 60…Seal part, 70,71,72…Elastic part, 71A,72A…Base part, 71B,72B…Column part, 71C,72C…Wall part, 100,100A,100B…Fuel cell cell, 301~306…Through hole, AF,CF…Flow channel, F1…Adhesive film, Mih,Mio,Miw…Supply manifold, Moh,Moo,Mow…Discharge manifold, S1,S2…Surface, WF…Flow channel space

Claims

1. A fuel cell stack comprising multiple stacked cells, The first of the aforementioned plurality of cells is A membrane electrode assembly and A frame that holds the aforementioned membrane electrode assembly, A pair of separators that sandwich the film electrode assembly held in the frame, One or more elastic bodies having a base and a plurality of columnar portions protruding from the base, Equipped with, The first separator, which is one of the pair of separators provided in the first cell, has one or more grooves on its first surface, which is the surface opposite to the surface facing the other of the pair of separators provided in the first cell. The base portion of the one or more elastic bodies is arranged in the one or more grooves, The base covers the bottom surface of one or more grooves, At least a portion of the plurality of columnar portions is arranged along the direction in which one or more groove portions extend, In a flow path space for coolant formed between the first cell and a second cell adjacent to the first cell, in a flow path space which is a gap formed by the second separator of the second cell being superimposed on the first surface of the first separator of the first cell, the tips of the plurality of columnar portions of the one or more elastic bodies arranged in the one or more grooves of the first separator are in contact with the second separator of the second cell. Fuel cell stack.

2. A fuel cell stack according to claim 1, The one or more elastic bodies include a first elastic body and a second elastic body. Each of the first and second elastic bodies has a base and a plurality of columnar portions, as well as a wall portion protruding from the base. The first separator is provided with a supply manifold for supplying the coolant to the flow path space and a discharge manifold for discharging the coolant from the flow path space. The first groove among the one or more grooves is formed on the first surface of the first separator so as to surround the supply manifold. The second groove among the one or more grooves is formed on the first surface of the first separator so as to surround the discharge manifold. By positioning the base of the first elastic body in the first groove, the plurality of columnar portions of the first elastic body are positioned downstream of the wall portion of the first elastic body in the direction from the supply manifold to the discharge manifold. As the base of the second elastic body is positioned in the second groove, the plurality of columnar portions of the second elastic body are positioned upstream of the wall portion of the second elastic body in the direction described above. Fuel cell stack.

3. A fuel cell stack according to claim 2, The film electrode assembly held in the frame is sandwiched between the first separator and the other of the pair of separators provided in the first cell, At a position on the back side of the location where one or more grooves are provided, the second surface of the first separator, opposite to the first surface, contacts the frame. Fuel cell stack.

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