FUEL CELL STACK

Abstract

Fuel cell stack (100), comprising: a fuel cell stack (10); and an end plate (30) arranged at one end of the fuel cell stack, the end plate comprising: a metallic plate-shaped body (32); and a resin layer (60) formed on a surface of the plate-shaped body, the plate-shaped body comprising: flow openings (39) for reaction gas and coolant; a strip-shaped projection (38) extending from the surface, the projection dividing the surface of the plate-shaped body into an interior region comprising the flow openings and an exterior region located outside the interior region, the projection comprising: a vertical section (38a) extending from the surface of the plate-shaped body;and a projecting section (38b) extending from a distal end of the vertical section towards the interior, wherein the resin layer in the interior is formed to cover a surface of the vertical section facing the interior, and at least a part of the projecting section.

Description

CROSS REFERENCE TO RELATED APPLICATIONSThe application claims priority to Japanese Patent Application JP 2016-158502 (published as JP 2018-26 299 A) filed on Aug. 12, 2016, the entire disclosure of which is incorporated herein by reference.BACKGROUNDField of the InventionThe present application relates to a fuel cell stack.Prior ArtAs described in JP 2015-8 086 A, a conventional fuel cell stack includes a fuel cell stack and end plates disposed at both ends of the fuel cell stack. A metallic plate member of the end plate has flow holes for a coolant and a reaction gas, and a resin layer is formed over a region including these flow holes. The resin layer serves to maintain the insulation properties of a surface in contact with the coolant and the reaction gas in the metallic plate member and the chemical resistance thereof.In the fuel cell stack of the above-described related art, there is a tendency that the resin layer may be more likely to be separated from the metal plate member due to a difference in thermal expansion between the metal plate member and the resin when the coolant is introduced through the coolant flow holes of the end plate. The peeling of the resin layer leads to a problem that the insulation properties between the end plate and the fuel cell stack cannot be ensured, as well as another problem that the chemical resistance cannot be ensured, resulting in advancement of metal corrosion.SUMMARYThe present invention has been made to solve at least a part of the above-described problems, and can be embodied in accordance with the following aspect.According to one aspect, a fuel cell stack is proposed. The fuel cell stack includes a fuel cell stack and an end plate disposed at an end of the fuel cell stack. The end plate includes a metal plate-shaped body and a resin layer formed on one surface of the plate-shaped body. The plate-shaped body includes flow openings for reaction gas and coolant, and a strip-shaped protrusion protruding from the surface such that the protrusion divides the surface of the plate-shaped body into an inner region including the flow openings and an outer region that is outside the inner region. The protrusion includes a vertical portion protruding from the surface of the plate-shaped body and a protruding portion protruding from a front and distal end of the vertical portion toward the inner region. The resin layer is formed in the inner region so as to cover a surface of the vertical portion facing the inner region and at least a part of the protruding portion.According to the fuel cell stack of this aspect, the protruding portion of the plate-shaped body of the end plate is configured to penetrate into the resin layer. Due to this, even when a large difference in thermal expansion occurs between the plate-shaped body of the end plate and the resin layer, expansion and contraction of the resin layer can be prevented by the protruding portion, so that detachment of the resin layer from the plate-shaped body of the end plate is prevented. Thus, there is obtained the effect of securing the insulation properties between the end plate and the fuel cell stack and the chemical resistance.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is an explanatory diagram showing a part of a fuel cell stack as an embodiment of the present invention; FIG. 2 is a plan view showing a rear side of the plate-shaped body of the end plate; FIG. 3 is a sectional view taken along line A-A of FIG. 2 ; FIG. 4 is a plan view showing the back surface of the end plate on which a resin layer is formed; FIG. 5 is a sectional view taken along line A-A of FIG. 4 ; FIG. 6 is a flowchart showing a manufacturing process of a protrusion and the resin layer; FIG. 7 is an explanatory diagram showing an aspect in which a plate-shaped body is inserted into a molding die in step 1; FIG. 8 is an explanatory diagram showing the plate-shaped body formed by step 2; FIG. 9 is an explanatory view showing the plate-shaped body after the resin layer is injection-molded in step 3; FIG. 10 is an explanatory diagram showing a modification 1 of the manufacturing process; and FIG. 11 is an explanatory diagram showing a modification 2 of the manufacturing process.DESCRIPTION OF EMBODIMENTSA. Overall Structure of Fuel Cell Unit:FIG. 1 is an explanatory diagram showing a part of a fuel cell stack as an embodiment of the present invention. The fuel cell stack 100 includes a fuel cell stack 10, a housing 20, an end plate 30, and a fixing bolt 40.The fuel cell stack 10 is a multilayer stack body of a plurality of fuel cells CL. Each fuel cell CL has an anode, a cathode, an electrolyte, and separators for performing power generation by electrochemical reaction of hydrogen and oxygen. The fuel cell CL can be implemented in various manners and whiteness, and is a solid polymer fuel cell in this embodiment. In the drawings, x-, y- and z-directions are indicated which perpendicularly intersect each other. The z direction corresponds to the stacking direction of the fuel cell stack 10. an upper side of the z direction is referred to as +z direction, and a lower side of the z direction is referred to as -z direction.The housing 20 is a cylindrically formed container for accommodating the fuel cell stack 10, and the fuel cell stack 10 is accommodated in the housing 20 with its stacking direction (z direction) coincident with the central axis of the housing 20.The end plate 30 is disposed at an end 10 ain the -z direction (the end on the lower side in the figure) of the fuel cell stack 10. The end plate 30 has a plate-shaped body 32 and a resin layer 60 formed on a surface 32 bof the plate-shaped body 32, and the plate-shaped body 32 can be formed of various metal materials that provide corrosion resistance and strength, and is formed of aluminum in this embodiment. The plate-shaped body 32 of the end plate 30 has one surface 32 b(hereinafter referred to as "rear surface 32 b") on which the resin layer 60 is formed, and another surface 32 a(hereinafter referred to as "front surface 32 a") opposite to the rear surface 32 b. The front 32 has accessories (not shown) such as a hydrogen pump, a gas-liquid separator, and an exhaust / drain valve. The fuel cell stack body 10 is disposed on the resin layer 60 on the back surface 32 bof the plate-shaped body 32.An outwardly projecting flange 22 is formed over the entire periphery of the end of the housing 20 on the side in the -z direction. The end plate 30 is attached to this flange 22 with the fastening screw 40. Tightening the bolt 40 enables the fuel cell stack 10 to be fastened by the end plate 30.B. Construction of end plate:FIG. 2 is a plan view showing the back surface 32 bof the plate-shaped body 32 of the end plate 30. FIG. 3 is a sectional view taken along line A-A of FIG. 2 ; a plurality of screw holes 34 are formed at the peripheral edges of the plate-shaped body 32. A fastening bolt 40 (of FIG. 1 ) is inserted into each bolt hole 34.A seal groove 36 (see FIG. 1 ) for placing a seal 50 is formed on the surface of the back surface 32 bof the plate-shaped body 32 inside the screw hole 34. "On the surface... inside" herein denotes a side of the back surface 32 bof the end plate 30 that is closer to a center of the back surface 32 b. The seal groove 36 is formed as a continuous closed strip to divide the rear surface 32 bof the end plate 30 into an inner region and an outer region.On the surface of the back surface 32 bof the plate-shaped body 32 of the end plate 30, a protrusion 38 protruding from the back surface 32 bis formed inside the seal groove 36. The protrusion 38 is formed as a continuous closed strip to further divide the inner region defined by the seal groove 36 into an inner region and an outer region.Flow apertures 39 (see FIG. 2 ) are formed in the interior region defined by the protrusion 38. The flow holes 39 function as flow paths for air (oxygen) as the oxidizing gas, hydrogen gas, and the coolant.FIG. 4 is a plan view of the end plate 30 having the resin layer 60; FIG. 5 is a sectional view taken along line A-A of FIG. 4; as shown in FIGS. 4 and 5, the resin layer 60 is formed in the inner region defined by the protrusion 38. In FIG. 4, the resin layer 60 is shown as a shaded portion. The resin layer 60 covers the inner region defined by the protrusion 38, so that the end plate 30 can be improved in electrical insulation properties as well as chemical resistance in the contact regions with the fluid flowing through the flow holes 39. Here, the resin of the resin layer 60 is not particularly limited as long as it has electrically insulating properties and chemical resistance; therefore, PPS (polyphenylene sulfide) is used in this embodiment.An enlarged view on the upper right side in FIG. 5 shows an enlargement of the portion 38 and its vicinity. As shown in the enlarged view, the protrusion 38 includes a vertical portion 38 athat protrudes from the rear side 32 band a protruding portion 38 bthat protrudes from an end of the vertical portion 38 atoward the inner region defined by the protrusion 38.The protruding portion 38 bof the protrusion 38 penetrates the resin layer 60. More specifically, the resin layer 60 covers the inner region defined by the protrusion 38 to cover an inner region-side surface 38 asof the vertical portion 38 aand at least a part of the protruding portion 38 b. As a result, the protruding portion 38 bof the protrusion 38 penetrates the resin layer 60.C. Production Process with Mold:FIG. 6 is a flowchart showing a manufacturing process of the protrusion 38 and the resin layer 60. As shown in the figure, the process is composed of three steps: Step 1 to Step 3. The respective steps 1 to 3 will be explained in sequence below.In step S 1, the plate-shaped body 32 is inserted into the molding die. The forming tool comprises a lower die and an upper die. Specifically, in step S 1, the plate-shaped body 32 is inserted between the lower die and the upper die.FIG. 7 is an explanatory diagram showing an aspect in which the plate-shaped body 32 is inserted into the molding die in Step 1. The x, y and z directions in this figure coincide with the x, y and z directions of the other figures. To perform the fabrication process, an x-y plane is a horizontal surface and the z-direction is a vertical direction. As shown in the figure, the plate-shaped body 32 is inserted while its surface is located on the upper side with a protrusion T1 protruding therefrom, the lower die (not shown) is located below, and the upper die P1 is located above. The protrusion T 1 serving as a blank for the protrusion 38 (see FIG. 5, etc.) is formed in a continuous closed linear shape like the protrusion 38. In this embodiment, an upper surface T1u of the projection T1 is inclined from upper left to lower right as indicated in the figure. In addition, in this embodiment, the surface of the upper die P 1 facing the lower die is an x-y plane, i.e., a flat surface extending along the horizontal direction.In step S 2, the upper die P 1 is driven to move downward, i.e., toward the lower die. In other words, in FIG. 7, the upper die P 1 is moved in the -z direction as indicated by an arrow A. As a result, the protrusion T 1 of the plate-shaped body 32 is pressed and formed by the upper die P 1.FIG. 8 is an explanatory diagram showing the plate-shaped body 32 formed in step S 2. Since the surface T1u of the protrusion T1 is inclined from upper left to lower right, the surface T1u of the protrusion T1 when pressed by the upper die P1 is flattened, resulting in a leftward protruding state as shown in the figure. Consequently, the protrusion 38 having the shape shown in the enlarged view of FIG. 5 is formed on the plate-shaped body 32, i.e., the protrusion 38 having the protruding portion 38 b. In addition, the left side is the inward side of the area defined by the protrusion 38.In this embodiment, a lateral width (y-direction width) of the upper die P 1 is set such that a left side end surface P 1L of the upper die P 1 is located to the right of a distal end 38 bT of the protruding portion 38 bin the y-direction. Alternatively, the lateral width of the upper die P 1 may be set such that the left side end surface P 1L of the upper die P 1 in the y direction and the distal end 38 bT of the protruding portion 38 bmay be located at the identical position in the y direction.In step S 3, the injection molding of the resin layer 60 is performed.FIG. 9 is an explanatory diagram showing the plate-shaped body 32 after the resin layer 60 is injection-molded in step S 3. Specifically, in step S 3, a resin material is injected toward the left side surface of the protrusion 38, i.e., the side surface thereof having the protruding portion 38 band toward the left side end surface P 1L of the upper die P 1 in the y direction to form the resin layer. The resin material is pressed and injected under an injection pressure when heated to its melting point. Consequently, as shown in FIG. 9, the resin layer 60 is formed so as to cover the left side surface of the vertical portion 38 aas shown in FIG. 9 and at least a part of the protruding portion 38 bof the protrusion 38.D. Effects of the InventionAccording to the fuel cell stack 100 described above, the protruding portion 38 bof the protrusion 38 formed in the plate-shaped body 32 of the end plate 30 is configured to protrude into the resin layer 60. Due to this, even when a large difference in thermal expansion occurs between the plate-shaped body 32 of the end plate 30 and the resin layer 60, expansion and contraction of the resin layer 60 is suppressed by the protruding portion 38 b, so that detachment of the resin layer 60 from the plate-shaped body 32 of the end plate 30 can be suppressed. Thus, it is possible to ensure the insulation properties between the end plate 30 and the fuel cell stack 10, and the chemical resistance.E. Modifications:In the above-described embodiment, the surface T 1 uof the protrusion T 1 (see FIG. 7 ) is formed inclined to form the protruding portion 38 bin the manufacturing process. However, the invention is not limited to this. As Modification 1, for example, a protrusion T 2 having a shape shown in FIG. 10 may be used to form the protruding portion 38 b. That is, as shown in FIG. 10, the protrusion T 2 has a surface T 2 uextending along the horizontal plane and a right-side corner round Rbin the y direction larger than a left-side corner round Rain the y direction. With the plate-shaped body 32 thus formed, pressing the plate-shaped body 32 by the upper die P 1 enables the projection 38 to be formed in a shape having the protruding portion 38 b.Further, as shown in FIG. 11, the protrusion T 2 may be configured such that the surface T 2 uextends along a horizontal plane, while the upper die P 2 has, on the inner side thereof facing the lower die (not illustrated), a surface P 2 swhich is inclined from upper left to lower right as shown in the figure. According to this modification 2, moving the upper die P 2 vertically downward enables the projection 38 to be formed in a shape having the protruding portion 38 b.

Claims

A fuel cell stack (100) comprising: a fuel cell stack (10); and an end plate (30) disposed at an end of the fuel cell stack, the end plate comprising: a metal plate-shaped body (32); and a resin layer (60) formed on a surface of the plate-shaped body, the plate-shaped body comprising: flow holes (39) for reaction gas and coolant; a strip-shaped protrusion (38) protruding from the surface, the protrusion dividing the surface of the plate-shaped body into an inner region comprising the flow holes and an outer region located outside the inner region, the protrusion comprising: a vertical portion (38a) protruding from the surface of the plate-shaped body; and a protruding portion (38b) protruding toward the inside from a distal end of the vertical portion, wherein the resin layer is formed in the inner region to cover a surface of the vertical portion facing the inner region and at least a part of the protruding portion.

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