Fuel cell

Abstract

The present invention is provided with: a membrane electrode assembly (C1) in which a pair of electrodes are disposed on both membrane surfaces of an electrolyte membrane; a separator (C2) made of a plate-shaped member; and a bipolar plate (BP) which is composed of a pair of separators (C2) overlapped and joined in the plate thickness direction and which is laminated in the plate thickness direction alternately with the membrane electrode assembly (C1). The bipolar plate (BP) is provided with a cell voltage measurement unit (20) having a connection terminal (21) on the periphery of each separator (C2), the connection terminal being connectable to an external connector. The cell voltage measurement unit (20) is provided with a reinforcement rib (23) at least at a peripheral portion thereof that is connected to the connection terminal (21), the reinforcement rib protruding in the plate thickness direction of the bipolar plate (BP).

Description

fuel cell

[0001] The present invention relates to a fuel cell in which a plurality of fuel cells are stacked in the thickness direction.

[0002] Some fuel cell units have a membrane electrode assembly sandwiched between a pair of separators. By stacking these fuel cell units, the required power output of the fuel cell is achieved. In this type of fuel cell, the voltage of each fuel cell unit is measured to detect any abnormalities in the individual fuel cell units. To measure the voltage, each separator is provided with a cell voltage measurement terminal, and a connector is connected to the cell voltage measurement terminal. In other words, in the fuel cell described in Patent Document 1, a connector is connected to sandwich both cell voltage measurement terminals of two separators that are back-to-back.

[0003] Japanese Patent Application Laid-Open No. 2014-170667

[0004] However, when the connector is connected so as to sandwich two cell voltage measurement terminals that are back-to-back, if one of the terminals falls over and the terminals become separated, this may hinder assembly of the connector.

[0005] The present invention has been made in view of the above-mentioned points, and has an object to provide a fuel cell that can prevent the connection terminals from falling over and can smoothly connect the connector and the connection terminals.

[0006] In order to achieve the above-mentioned object, the fuel cell of the present invention comprises a membrane electrode assembly in which a pair of electrodes are arranged on both surfaces of an electrolyte membrane, separators made of plate-shaped members, and bipolar plates each consisting of a pair of separators overlapped and joined in the plate thickness direction, and stacked alternately with the membrane electrode assemblies in the plate thickness direction, wherein the bipolar plates are provided with cell voltage measuring units having connection terminals on the periphery of each separator that can be connected to an external connector, and the cell voltage measuring units are provided with reinforcing ribs on the periphery at least at the connection portions with the connection terminals that protrude in the plate thickness direction of the bipolar plates.

[0007] According to the present invention, it is possible to provide a fuel cell that can prevent the connection terminals from falling over and can smoothly connect the connector and the connection terminals.

[0008] Fig. 4 is an exploded perspective view showing a fuel cell of the present embodiment; Fig. 5 is a plan view showing a bipolar plate of the present embodiment; Fig. 6 is an enlarged view of a main part showing part III of Fig. 2; Fig. 7 is a sectional perspective view taken along line IV-IV of Fig. 3; Fig. 8 is a side view showing a state in which fuel cell units are stacked; Fig. 9 is an enlarged view of a main part showing another embodiment of part III of Fig. 2;

[0009] A fuel cell S according to one embodiment of the present invention will be described in detail with reference to Figures 1 to 5. In the description, the same elements are given the same reference numerals, and duplicated descriptions will be omitted.

[0010] The fuel cell S of this embodiment is formed by stacking a plurality of fuel cell units CL in the plate thickness direction (see FIG. 1). Each fuel cell unit CL includes a membrane electrode assembly C1 and a pair of separators C2. In each fuel cell unit CL, the membrane electrode assembly C1 is sandwiched between the pair of separators C2.

[0011] The membrane electrode assembly C1 includes a membrane-shaped polymer electrolyte membrane, an anode diffusion electrode on one side of the polymer electrolyte membrane, and a cathode diffusion electrode on the other side of the polymer electrolyte membrane. Two separators C2 are made of metal plates with concave and convex shapes formed by pressing. Each separator C2 includes a separator body 10 and a cell voltage measurement unit 20. The separator C2 facing the anode diffusion electrode is referred to as the anode separator C2a, and the separator C2 facing the cathode diffusion electrode is referred to as the cathode separator C2b.

[0012] The separator body 10 of the anode (fuel electrode) side separator C2a has a passage for supplying a fuel gas such as hydrogen between the plate surface facing the membrane electrode assembly C1 and the anode side diffusion electrode. The separator body 10 of the cathode (oxygen electrode) side separator C2b has a passage for supplying an oxidant gas such as oxygen between the plate surface facing the membrane electrode assembly C1 and the cathode side diffusion electrode. Furthermore, when the fuel cell units CL are stacked, a passage for circulating a refrigerant is formed between the anode side separator C2a and the cathode side separator C2b, which are back-to-back.

[0013] The anode-side separator C2a and the cathode-side separator C2b, which are back-to-back, are joined to form a bipolar plate BP. That is, the anode-side separator C2a and the cathode-side separator C2b that form the bipolar plate BP constitute separate fuel cell units CL. That is, by stacking the membrane electrode assemblies C1 and the bipolar plates BP alternately in the plate thickness direction, the fuel cell units CL are stacked in the plate thickness direction.

[0014] The cell voltage measuring unit 20 is disposed on the periphery of the separator C2 (the upper left edge in FIG. 2) and is used to measure the voltage of each fuel cell CL. That is, the cell voltage measuring unit 20 is provided to measure the voltage between a pair of adjacent bipolar plates BP sandwiching the membrane electrode assembly C1 (see FIG. 2-5). The cell voltage measuring unit 20 is formed by cutting out the separator body 10, so that it has a concave shape that is recessed downward, and is provided integrally with the separator body 10.

[0015] It is also possible to construct the cell voltage measuring unit 20 as a separate member from the separator body 10 and then form it integrally with the separator body 10 by means of welding or the like. The cell voltage measuring unit 20 includes a connection terminal 21, a guide portion 22, and a reinforcing rib 23 (see FIGS. 3 and 4).

[0016] The connection terminal 21 is a portion to which a terminal (connector terminal TC) of a connector (not shown) used for voltage measurement is electrically connected. The connection terminal 21 is composed of a rectangular piece that protrudes upward in FIG. 3 from the bottom of the recessed shape of the cell voltage measurement unit 20. The connection terminal 21 has an anode-side piece 21a and a cathode-side piece 21b that are joined together by welding.

[0017] The joint portion of the connection terminal 21 is referred to as the terminal joint portion 21c. That is, the pair of separators C2 are welded together at the terminal joint portion 21c. The terminal joint portions 21c are provided on both side edges of the connection terminal 21 along the connecting direction of the connector terminal (the up-and-down direction in FIG. 3). In this embodiment, the connector is inserted and removed along the up-and-down direction. That is, the up-and-down direction coincides with the insertion and removal direction of the connector.

[0018] Furthermore, the terminal joint portion 21c is not provided on the edge portion of the tip of the connection terminal 21. In other words, the terminal joint portion 21c is disposed at a location that does not overlap with the path along which the connector terminal TC slides when the connector is assembled.

[0019] The guide portion 22 is provided to engage with the connector body and maintain the assembled state of the connector when the connector terminal TC is connected to the connection terminal 21. The guide portion 22 constitutes both concave sidewalls of the cell voltage measurement portion 20. The guide portion 22 is formed with rectangular engagement recesses 24, into which the connector body engages. The anode side and cathode side of the guide portion 22 are joined together by welding. The joint portion of the guide portion 22 is referred to as the guide joint portion 22a. The guide joint portion 22a is formed along the side edge of the guide portion 22.

[0020] The reinforcing rib 23 is formed at the boundary between the cell voltage measurement unit 20 and the separator body 10, including the connection portion between the cell voltage measurement unit 20 and the connection terminal 21, so as to surround the periphery of the cell voltage measurement unit 20. The reinforcing rib 23 extends in the stacking direction (plate thickness direction) and protrudes toward the adjacent bipolar plate BP sandwiching the membrane electrode assembly C1, with a generally trapezoidal cross section. When a pair of separators C2 are placed back-to-back, the two reinforcing ribs 23 form a hexagonal hollow cross section. The height (protruding dimension in the stacking direction) of the reinforcing rib 23 is set so that it contacts the membrane electrode assembly C1 (see FIG. 5 ). In other words, the reinforcing rib 23 is formed so that the bipolar plate BP and the membrane electrode assembly C1 support each other to prevent the cell voltage measurement unit 20 from tipping over when stacked.

[0021] The reinforcing rib 23 also has an extension 23a at a location where the cell voltage measurement unit 20 and the connection terminal 21 are connected. The reinforcing rib 23 is located between a pair of terminal joints 21c at the connection between the cell voltage measurement unit 20 and the connection terminal 21. The extension 23a extends toward the tip of the connection terminal 21 so that its upper end is located higher than the lower end of the terminal joint 21c. In other words, the lower end of the terminal joint 21c is arranged to overlap the upper end of the extension 23a. The portion where the terminal joint 21c overlaps the extension 23a is referred to as an overlap portion 25. The protrusion dimension in the stacking direction is set the same as that of the other reinforcing ribs 23.

[0022] Next, the effects of this embodiment will be described. In the fuel cell S of this embodiment, a reinforcing rib 23 is provided at the boundary between the cell voltage measuring unit 20 and the separator body 10, including the connecting portion between the cell voltage measuring unit 20 and the connection terminal 21, so as to surround the outer periphery of the cell voltage measuring unit 20. This configuration increases the rigidity of the cell voltage measuring unit 20. This prevents the connection terminal 21 from collapsing, allowing for smooth connection between the connector and the connection terminal.

[0023] In this embodiment, a terminal joint portion 21c extending along the connecting direction of the connector is provided on a widthwise side edge portion of the connecting terminal 21. The terminal joint portion 21c joins the anode-side piece 21a and the cathode-side piece 21b by welding.

[0024] This configuration prevents the tip portion of the connection terminal 21 from opening, thereby enabling smoother connection between the connector and the connection terminal 21. Furthermore, by providing the terminal joint 21c and joining the anode side piece and the cathode side piece, the rigidity of the connection terminal 21 is increased, making it less likely to tip over. This allows smoother connection between the connector and the connection terminal 21.

[0025] Furthermore, any tilt or bending that occurs during the press working to form the separator C2 before welding the anode-side piece 21a and the cathode-side piece 21b is corrected and rectified. This allows the connection terminals 21 to be positioned more correctly when the bipolar plates BP are stacked. This allows for smooth connection between the connector and the connection terminals 21.

[0026] The terminal joints 21c are provided on both side edges of the connection terminal 21 along the connector terminal connection direction (the vertical direction in FIG. 3 ). In other words, the terminal joints 21c are located in areas that do not overlap with the connector terminals TC when the connector is assembled. If the anode and cathode sides are joined by welding, the surface of the welded area may become rough. Therefore, the terminal joints 21c are located on both side edges of the connection terminal 21 in areas that do not overlap with the sliding path of the connector terminals TC.

[0027] In this embodiment, a guide joint 22a is provided on the edge of the guide portion 22, including the edge along the insertion / removal direction of the connector. The guide joint 22a joins the anode side and the cathode side of the guide portion 22 by welding. This configuration prevents the edge of the guide portion 22 from collapsing or opening. This allows the connector to be smoothly held in the guide portion 22.

[0028] Furthermore, before welding the anode and cathode sides of the guide portion 22 together, any collapse or bending that occurs during the press working to form the separator C2 is straightened and corrected. This allows the guide portion 22 to be positioned more correctly when the bipolar plates BP are stacked. This allows the connector to be held more smoothly in the guide portion 22.

[0029] In this embodiment, the reinforcing rib 23 includes an extension 23a. The extension 23a is disposed between a pair of terminal joints 21c at the connection portion between the cell voltage measurement unit 20 and the connection terminal 21, and the portion of the reinforcing rib 23 located at the connection portion between the cell voltage measurement unit 20 and the connection terminal 21 extends toward the tip of the connection terminal 21. This configuration increases the rigidity of the connection terminal 21, making it less likely to tip over. This allows for smoother connection between the connector and the connection terminal 21.

[0030] In this embodiment, the upper end of the extension 23a is located higher than the lower end of the terminal joint 21c, and the terminal joint 21c is arranged to hang on the extension 23a. This configuration increases the rigidity of the connection terminal 21 and makes it less likely to tip over. This allows for smoother connection between the connector and the connection terminal 21.

[0031] In the present embodiment, the anode and cathode sides of the terminal joint 21c and the guide joint 22a are joined by welding, but this is not a limitation. For example, soldering, brazing, or other techniques can be used, which can provide similar benefits to welding. In the present embodiment, the terminal joint 21c and the guide joint 22a are welded in a linear fashion, but this is not a limitation. For example, corners can be joined by spot welding, which can provide similar benefits to welding.

[0032] Furthermore, although the cell voltage measurement unit 20 in this embodiment has a concave shape, this is not limiting. For example, the cell voltage measurement unit can be configured to have a rectangular base that protrudes upward from the separator body 10, with connection terminals provided on the upper edge of the base and a connector main body engaging with the side edge of the base. Even with this configuration, the same effects as those of this embodiment can be obtained.

[0033] Next, a guide joint 22a according to another embodiment will be described (see FIG. 6). In the description, the same elements as those in the previous embodiment are designated by the same reference numerals, and redundant description will be omitted. In this embodiment, the guide joint 22a is provided only on the edge of the guide portion 22 along the connector insertion / removal direction (the side edge of the guide portion 22 and the recessed bottom of the engagement recess 24). In other words, the edge of the guide portion 22 along the width direction of the separator C2 (the upper edge of the guide portion 22 and the recessed wall of the engagement recess 24) is not welded. This configuration suppresses thermal deformation during welding, thereby preventing the edge of the guide portion 22 from collapsing or opening. This allows the connector to be smoothly held in the guide portion 22.

[0034] S: fuel cell C1: membrane electrode assembly C2: separator BP: bipolar plate 20: cell voltage measuring section 21: connection terminal 21c: terminal joint 22: guide section 22a: guide joint 23: reinforcing rib 23a: extension section

Claims

1. A fuel cell comprising: a membrane electrode assembly in which a pair of electrodes are arranged on both surfaces of an electrolyte membrane; separators made of plate-like members; and bipolar plates each consisting of a pair of separators joined together while being stacked in the thickness direction, the bipolar plates being stacked alternately with the membrane electrode assemblies in the thickness direction, wherein the bipolar plates are provided with cell voltage measuring units having connection terminals on the periphery of each separator that can be connected to an external connector, and the cell voltage measuring units are provided with reinforcing ribs that protrude in the thickness direction of the bipolar plates at least at the connection portions with the connection terminals around the periphery.

2. A fuel cell comprising: a membrane electrode assembly in which a pair of electrodes are arranged on both surfaces of an electrolyte membrane; separators made of plate-like members; and bipolar plates each consisting of a pair of separators joined together while being stacked in the thickness direction, the bipolar plates being stacked alternately with the membrane electrode assemblies in the thickness direction, wherein the bipolar plates are provided with cell voltage measuring units having connection terminals on the periphery of each separator that can be connected to an external connector, and the connection terminals are provided with terminal joining portions on their side edges that join the pair of separators.

3. A fuel cell comprising: a membrane electrode assembly in which a pair of electrodes are arranged on both surfaces of an electrolyte membrane; separators made of plate-like members; and bipolar plates each consisting of a pair of separators joined together while being stacked in the thickness direction, the bipolar plates being stacked alternately with the membrane electrode assemblies in the thickness direction, wherein the bipolar plates are provided with cell voltage measuring units having connection terminals on the periphery of each separator that can be connected to an external connector, the cell voltage measuring units having reinforcing ribs on the periphery at least at the connecting portions with the connection terminals that protrude in the thickness direction of the bipolar plates, and the connection terminals are provided with terminal joining portions on the side edges that join the pair of separators.

4. A fuel cell according to claims 2 and 3, characterized in that the cell voltage measuring section has a guide section that can engage with the connector, and the guide section has guide joint sections at its side edges that extend in the direction in which the connector is inserted and removed and that join the pair of separators.

5. A fuel cell according to claims 1 and 3, characterized in that the reinforcing rib has an extension portion that extends towards the tip of the connection terminal at a portion located at the connection between the connection terminal and the cell voltage measuring portion.

6. A fuel cell according to claim 3, wherein the reinforcing rib has an extension portion that extends toward the tip of the connection terminal at a portion located at the connection between the connection terminal and the cell voltage measuring portion, and the terminal joint portion extends from the tip of the connection terminal to the connection portion with the cell voltage measuring portion so as to overlap the extension portion in the insertion / removal direction of the connector.

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