Fuel cell and fuel cell device having voltage-detection cell coonector receiving portion

A fuel cell that can have a voltage-detection cell connector reliably held thereon without the thickness of the fuel cell increased to a thickness of greater than that originally required to generate power. The fuel cell includes a recess portion in which a cell connector is adapted to be inserted. In the recess portion, a guide portion, which can guide a cell connector being inserted into the recess portion, is formed of a part of a separator (or a second extending portion thereof). In a portion of the recess portion opposite the second extending portion, a protrusion that forms a part of an insulating resin sheet, which is arranged between a pair of separators, protrudes toward the second extending portion. A to-be-crimped portion of the cell connector inserted in the recess portion is pressed against the second extending portion by the protrusion so that its stable posture is held.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2017-227374 filed on Nov. 28, 2017, the content of which is hereby incorporated by reference into this application.

BACKGROUND

Technical Field

The present disclosure relates to a fuel cell that can have attached thereto a voltage-detection cell connector used for detecting a cell voltage, and a fuel cell device including a stack of a plurality of such fuel cells.

Background Art

A fuel cell device is typically formed as a stacked structure of a plurality of fuel cells that are called unit cells. A fuel cell that is a unit cell has a membrane electrode assembly (MEA) including an electrolyte membrane and an anode and a cathode provided on opposite sides of the electrolyte membrane, and is formed in a substantially rectangular shape in a plan view. The fuel cell also includes a pair of separators sandwiching the anode and the cathode therebetween.

The separator includes at least a fuel gas manifold for supplying fuel gas, such as hydrogen gas, to the anode, and an oxidant gas manifold for supplying oxidant gas, such as oxygen gas, to the cathode.

The separator has a function of a cell electrode, and a cell connector with a terminal is attached to a part of the separator (a part extending to the outside from the power-generating region) to detect a voltage of the fuel cell. JP 2007-200633 A or JP 2007-220338 A describes an example of an attachment structure for attaching such a cell connector to a fuel cell.

In the attachment structure described in JP 2007-200633 A, a mating part formed on a cell connector is mated with a mating part on the fuel cell side so that the cell connector can be attached to the fuel cell side. Meanwhile, in the attachment structure described in JP 2007-220338 A, a bulging portion that bulges in the thickness direction of a fuel cell is formed on one of a pair of separators that form the fuel cell, and a cell connector is fixedly inserted between adjacent separators and the bulging portion. That is, the cell connector is fixedly sandwiched in the thickness direction of the fuel cell.

SUMMARY

In the conventional attachment structure for attaching a cell connector to a fuel cell; the thickness of the fuel cell is unavoidably increased. This is because in the attachment structure described in JP 2007-200633 A, since the mating part formed on the cell connector is mated with the mating part on the fuel cell side, the thickness of a resin frame that forms the mating part should be increased to avoid deformation of the mating part. Meanwhile, in the attachment structure described in JP 2007-220338 A, since a cell connector to be inserted between adjacent separators is fixed utilizing a bulging portion, which bulges in the thickness direction, formed on one of the separators, the thickness of the fuel cell is unavoidably increased by an amount corresponding to the width of the bulging portion.

The present disclosure has been made in view of the foregoing, and provides a fuel cell that can have a voltage-detection cell connector reliably held thereon without the thickness of the fuel cell increased to a thickness of greater than that originally required to generate power. In addition, the present disclosure provides a fuel cell device obtained by stacking a plurality of such fuel cells.

A fuel cell in accordance with the present disclosure is a fuel cell adapted to have attached thereto a voltage-detection cell connector used for detecting a cell voltage, the fuel cell including a membrane electrode assembly; a pair of separators sandwiching the membrane electrode assembly therebetween; a recess portion in which the cell connector is adapted to be inserted; a plate-like guide portion located on a side of the recess portion, the plate-like guide portion extending in a direction of insertion of the cell connector and serving as a guide for the cell connector when the cell connector is inserted into the recess portion; a resin sheet arranged between the pair of separators; and a pressing member formed of a part of the resin sheet, the pressing member protruding into the recess portion at a position that is opposite the guide portion and at which the pressing member is adapted to press a part of the cell connector inserted into the recess portion toward the guide portion.

In the fuel cell in accordance with the present disclosure, the lower side of the cell connector inserted into the recess portion is supported by the guide portion formed in the recess portion, and in such a state, a part of the cell connector is pressed by the pressing member that forms a part of the resin sheet arranged between the pair of separators and protrudes into the recess portion. Accordingly, the attached posture of the cell connector is stabilized. In addition, each of the guide portion and the pressing member is in the form of a plate that merely protrudes in the plane direction of the fuel cell, and thus, the thickness of the fuel cell does not increase due to the guide portion or the pressing member.

In some embodiments of the fuel cell of the present disclosure, opposite sides of the proximal side of a portion of the resin sheet that forms the pressing member are sandwiched between the pair of separators.

In some embodiments of the fuel cell in accordance with the present disclosure, the guide portion and the pressing member may be formed as separate dedicated members for the fuel cell. However, in some embodiments, from the perspective of further simplifying the structure, the guide portion is formed of a part of the separator, and the pressing member is formed of a part of an insulating resin sheet arranged between the pair of separators to seal a space between the pair of separators.

In some embodiments of the fuel cell in accordance with the present disclosure, at least a fuel gas manifold and an oxidant gas manifold are provided on the peripheral edge of the fuel cell, and the recess portion is arranged in proximity to the fuel gas manifold.

The present disclosure also discloses a fuel cell device including a stack of a plurality of such fuel cells.

According to the present disclosure, there are provided a fuel cell that can have a voltage-detection cell connector reliably held thereon without the thickness of the fuel cell increased to a thickness of greater than that originally required to generate power, and a fuel cell device obtained by stacking a plurality of such fuel cells.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. First; a schematic structure of a fuel cell system that uses fuel cells of this embodiment will be described.

A fuel cell system100aincludes a fuel cell stack100as a stack of fuel cells. The fuel cell stack100is a stacked structure having an end plate110, an insulating plate120, a current collector130, a plurality of fuel cells140, a current collector130, an insulating plate120, and an end plate110that are stacked in this order. The fuel cell stack100is supplied with hydrogen as fuel gas from a hydrogen tank150that has high-pressure hydrogen stored therein. Fuel gas (anode off-gas) that has not been used in the fuel cell stack100is discharged to the outside of the fuel cell stack100via a discharge pipe151. In addition, air is supplied as oxidant gas to the fuel cell stack100via an air pump160. Oxidant gas (cathode off-gas) that has not been used in the fuel cell stack100is discharged to the outside of the fuel cell stack100via a discharge pipe161.

Further, a cooling medium, which has been cooled by a radiator170, is supplied to the fuel cell stack100via a water pump171so as to cool the fuel cell stack100. The cooling medium discharged from the fuel cell stack100is circulated to the radiator170via a pipe. As the cooling medium, for example, water, unfreezable water such as ethylene glycol, or air is used.

Each fuel cell140of the fuel cell stack100includes, as illustrated inFIG. 3that is a schematic cross-sectional view along line A-A ofFIG. 2described below, a membrane electrode assembly (MEA)10serving as a power-generating module and a pair of separators20,30sandwiching the membrane electrode assembly10therebetween. Diffusion layers12,13are provided between the membrane electrode assembly10and the separators20,30, respectively. In this example, the anode-side separator20includes a plurality of thread-like fuel-gas flow channel grooves14on a plane on the side of the membrane electrode assembly10, and a plurality of thread-like cooling-medium flow channel grooves15on a plane on the side opposite to the membrane electrode assembly10. The cathode-side separator30on the other side includes a plurality of thread-like oxidant-gas flow channel grooves16on a plane on the side of the membrane electrode assembly10.

Each fuel cell140includes an insulating resin sheet40, which is arranged outside (on the outer periphery) of the membrane electrode assembly10sandwiched between the anode-side separator20and the cathode-side separator30, along the plane direction thereof. The resin sheet40is molded into a plate shape and a frame shape using thermoplastic resin, and is used to seal a space between the anode-side separator20and the cathode-side separator30while the membrane electrode assembly10is held in the central region thereof. For the resin sheet40, for example, resin such as PE, PP, PET, or PEN can be used.

FIG. 2is a schematic plan view of the fuel cell140. A region indicated by symbol S of the central portion is a region corresponding to the membrane electrode assembly10, and is a power-generating region S. The aforementioned fuel-gas flow channel grooves14and oxidant-gas flow channel grooves16are formed around regions of the anode-side separator20and the cathode-side separator30, respectively, that are opposite the power-generating region S, thereby forming irregular planes. The aforementioned insulating resin sheet40is located on the outer peripheral side of the power-generating region S. Each of the anode-side separator20and the cathode-side separator30around a region of the resin sheet40has a flat plane17, and the resin sheet40is sandwiched between the pair of separators20,30.

As illustrated inFIG. 3, around an outer peripheral edge of the resin sheet40between the anode-side separator20and the cathode-side separator30, there are provided expanded open portions18that are open in an expanded manner from the portions of the flat planes17up to almost the same heights of the fuel-gas flow channel grooves14and the oxidant-gas flow channel grooves16, and gaps19are formed between the resin sheet40and the expanded open portions18. In addition, the resin sheet40extends outward slightly beyond the tip ends of the expanded open portions18.

In the flat plane17that is a non-power-generating region of the fuel cell140, an inlet-side fuel gas manifold51, a cooling-medium output manifold52, and an inlet-side oxidant gas manifold53are formed on one end side of the fuel cell140. Meanwhile, an outlet-side fuel gas manifold54, a cooling-medium inlet manifold55, and an outlet-side oxidant gas manifold56are formed on the other end side thereof.

Fuel gas supplied via a pipe is distributed to the fuel-gas flow channel grooves14(FIG. 3) of each fuel cell140by the inlet-side fuel gas manifold51. After that, fuel gas that has not been used in the fuel-gas flow channel grooves14is collected by the outlet-side fuel gas manifold54and is discharged to the outside of the fuel cell stack100. Meanwhile, oxidant gas supplied via a pipe is distributed to the oxidant-gas flow channel grooves16(FIG. 3) of each fuel cell140by the inlet-side oxidant gas manifold53. Then, oxidant gas that has not been used in the oxidant-gas flow channel grooves16is collected by the outlet-side oxidant gas manifold56, and is discharged to the outside of the fuel cell stack100via a pipe.

A cooling medium supplied via a cooling medium pipe is distributed to the cooling-medium flow channel grooves15(FIG. 3) of each fuel cell140by the cooling-medium inlet manifold55. After that, the cooling medium is collected by the cooling-medium outlet manifold52, and is discharged to the outside of the fuel cell stack100via a pipe.

Usually, in order to operate a fuel cell device, it is common to use hydrogen gas as fuel gas and air as oxidant gas. Therefore, the amount of air is larger than that of hydrogen gas supplied to the fuel cell during the operation. Thus, the areas of the openings of the fuel gas manifolds51,54can be set smaller than those of the openings of the oxidant gas manifolds53and56. Therefore, larger spaces can be secured around the fuel gas manifolds51and54than those around the oxidant gas manifolds53and56.

In the fuel cell140of this embodiment, a recess portion60that is a cutout portion is formed in a portion of the large space secured around the outlet-side fuel gas manifold54, and a voltage-detection cell connector70used for detecting a cell voltage is inserted into the recess portion60. Hereinafter, the structure thereof will be described in detail.

FIG. 4is an enlarged perspective view of the periphery of the recess portion60of the fuel cell140in which the cell connector70is adapted to be inserted, andFIG. 5is a plan view thereof.FIG. 6is a perspective view of the cell connector70that can be inserted in the recess portion60.

As illustrated inFIG. 4andFIG. 5, in this embodiment, the recess portion60is a region surrounded by a first side portion142inclined obliquely downward at an angle of about 45 degrees from a side (hereinafter referred to as a top side for the sake of convenience)141of the fuel cell140, a second side portion143that rises obliquely upward from the lower end of the first side portion142toward the top side141, and a third side portion144that extends from the upper end side of the second side portion143toward the top side141.

As illustrated inFIG. 4, the separator20on one side is partially cut out along the first side portion142, the second side portion143, and the third side portion144of the recess portion60, and the expanded open portion18is formed along the cutout portion. In addition, as clearly illustrated inFIG. 8that is a cross-sectional view along line B-B ofFIG. 7illustrating the state in which the cell connector70is inserted in the recess portion60, andFIG. 9that is a cross-sectional view along line C-C ofFIG. 7, the resin sheet40partially extends outward along the cutout portion. It should be noted that inFIG. 7, the cell connector70is illustrated in a cross-section, and a conductive wire84for connection to the terminal81is also illustrated.

The expanded open portion18of the separator30on the other side includes a first extending portion31that extends to a region surrounded by the lower portion of the first side portion142, the second side portion143; and the third side portion144of the recess portion60; and a second extending portion32that extends along the first side portion142from the lower region of the first extending portion31. The upper edge32aof the second extending portion32is parallel with the first side portion142. A bulging portion33functioning as a stopper is formed on a portion of the first extending portion31.

A part of the resin sheet40sandwiched between the flat planes17,17of the pair of separators20,30includes a protrusion41that greatly protrudes toward the side of the first side portion142from the tip end side of the third side portion144of the recess portion60, and the lower side of the protrusion41bulges toward the side of the first side portion142. The separator20, the resin sheet40, the protrusion41thereof, and the separator30are stacked in this order from the front surface side to the rear surface side inFIGS. 4 and 5.

Next; the cell connector70adapted to be inserted into the recess portion60will be described.FIG. 6is a perspective view of an example of the cell connector70. The cell connector70includes a flat casing71. The casing71includes a body portion73with a shape conforming to the shape of the recess portion60formed in the fuel cell140, and a knob portion74located at one end of the body portion73.

The body portion73includes a linear base region75, and a tip end region76that is the tip end side of the base region75. The tip end77of the tip end region76has an acute angle. The upper edge side of the tip end region76includes a front inclined plane78that is inclined obliquely upward with respect to the linear base region75, a to-be-crimped portion79that extends from the upper end of the front inclined plane78so as to be in parallel with the linear base region75, and a rear inclined plane80that extends obliquely upward from the rear end of the to-be-crimped portion79. The rear inclined plane80is continuous with the knob portion74. The length of the linear base region75is slightly shorter than that of the first side portion142of the recess portion60.

A space region is formed in the casing71, a terminal81is arranged therein. A gap82, which can receive therein the second extending portion32of the separator30, is formed at the lower end of the base region75along the entire length thereof, and also, a gap83, which can receive therein the first extending portion31of the separator30, is formed in the tip end region76. The distance α from the upper edge32aof the second extending portion32of the separator30to the bottommost end of the protrusion41of the resin sheet40is set shorter than the distance β between the upper edge of the gap82and the to-be-crimped portion79of the cell connector70by about 0.1 to 0.5 mm.

The terminal81is arranged at a portion where a part of the first extending portion31of the separator30can be sandwiched in a state in which the cell connector70is inserted in the recess portion60that is the cutout portion of the separator30, and a conductive wire84(seeFIG. 7) is connected to the rear end of the terminal81.

In order to attach the cell connector70to the fuel cell140, the cell connector70is attached such that it is inserted into the recess portion60as the cutout portion. For the attachment, the second extending portion32of the separator30is inserted into the gap82formed in the base region75of the cell connector70, and in such a state, the cell connector70is slid downward such that it is pressed inside the recess portion60, using the second extending portion32as a guide portion. Through the oblique downward movement of the cell connector70, the tip end77of the tip end region76of the cell connector70reaches a region of the first extending portion31of the separator30, and when the cell connector70is further slid, the first extending portion31is received within the tip end region76, and in such a state, the terminal81in the cell connector70is electrically connected to the first extending portion31of the separator30.

As described above, the distance α from the upper edge32aof the second extending portion32of the separator30to the bottommost end of the protrusion41of the resin sheet40is set shorter than the distance β between the upper edge of the gap82and the to-be-crimped portion79of the cell connector70by about 0.1 to 0.5 mm. Therefore, in a state in which the cell connector70is inserted in the recess portion60formed in the fuel cell140, the to-be-crimped portion79of the cell connector70is pressed downward, that is, toward the second extending portion32of the separator30due to the elastic force of the protrusion41of the resin sheet40. Due to such pressure, the cell connector70is attached to the fuel cell140in a stable posture.

In addition, the proximal side of the protrusion41of the resin sheet40is sandwiched on its right and left sides by the flat planes17,17of the pair of separators20,30, and thus, the posture of the protrusion41can also be maintained stably.

As described above, in the fuel cell140of this embodiment, a part of the insulating resin sheet40, which is usually arranged on the outer side (outer periphery) of the membrane electrode assembly (MEA)10serving as a power-generating module, along the plane direction thereof is made to protrude in the plane direction, and the lower end side of the protrusion41is used as a pressing member for pressing the cell connector70to be attached to the fuel cell140so that the stability of the cell connector70is secured. Therefore, in this embodiment, an insulating resin sheet that is commonly used for typical fuel cells can be used as it is so as to secure the stability of the cell connector, without requiring a thick resin sheet like the conventional means for attaching a cell connector. Consequently, the stability of the cell connector can be secured without the physical size of the fuel cell140increased.

In addition, in this embodiment, as illustrated inFIG. 2, since the aforementioned recess portion60in which the cell connector is adapted to be inserted is formed using an empty, space near the outlet-side fuel gas manifold54and a new space for providing the recess portion60is not required, space saving of the fuel cell140can be achieved, it should be noted that although the recess portion60is formed near the outlet-side fuel gas manifold54inFIG. 2, if an area of the opening of the inlet-side fuel gas manifold51is reduced, a space can be similarly secured near the inlet-side fuel gas manifold51, and thus, the recess portion60in which the cell connector is adapted to be inserted can be formed around the inlet-side fuel gas manifold51.

Further, in this embodiment, the angle of the tip end77along the direction of insertion of the cell connector70into the recess portion60is acute, and thus, the degree of interference between the tip end region76of the cell connector70and the tip end of the first extending portion31of the separator30during the insertion can be reduced, and thus, the cell connector70can be smoothly inserted into the recess portion60.

In this embodiment, although the second extending portion32of the separator30is used as a guide portion for attaching the cell connector70to the fuel cell140, it is also possible to form a member corresponding to the second extending portion32using a different member from the separator30under the condition that the entire thickness is not increased. Further, although a member that presses the cell connector70from above is formed using a part of the insulating resin sheet40for sealing a space between the pair of separators20,30, it is also possible to arrange another resin sheet that is different from the insulating resin sheet40between the pair of separators20,30under the condition that the entire thickness is not increased.

The embodiment described above with reference toFIGS. 2 to 9illustrates a single fuel cell140and a single cell connector70. However, in a structure of the fuel cell stack100including a plurality of fuel cells140like the fuel cell system100aillustrated inFIG. 1, as illustrated inFIG. 10, recess portions60awith the same shape are formed in the same positions of the fuel cells that form a fuel cell group140a, and a cell connector70ain which the same number of cell connectors70as that of the recess portions60aare arranged in parallel is inserted in the recess portions60a.

Finally, the results of comparison between the actual example of the fuel cell140in accordance with this embodiment and a fuel cell having a connector attached thereto in the conventional fashion as described in JP 2007-200633 A will be described. For the fuel cell140in accordance with this embodiment, the resin sheet40with a thickness of 0.2 mm was used, and thus, the stability of the cell connector70attached to the fuel cell140was secured. The thickness of the fuel cell140was 1.0 mm. Meanwhile, in order to attach a cell connector to a fuel cell as in the method described as the conventional art, a resin frame with a thickness of 1.0 mm for forming the aforementioned mating part would be needed, and consequently, the thickness of the fuel cell became 1.8 mm even when the same membrane electrode assembly (MEA) of the fuel cell140in accordance with this embodiment was used. Accordingly, it was found that using the means for attaching the cell connector70in accordance with this embodiment can obtain a fuel cell with the same power-generation level as that of the conventional fuel cell without increasing the thickness of the fuel cell to a thickness of greater than that originally required to generate power.

DESCRIPTION OF SYMBOLS

100aFuel cell system100Fuel cell stack140Fuel cell141Top side of fuel cell142First side portion that forms recess portion143Second side portion that forms recess portion144Third side portion that forms recess portion10Membrane electrode assembly (MEA)17Flat plane of separator18Expanded open portion around separator19Gap of expanded open portion between resin sheet and separator20,30Pair of separators40Insulating resin sheet51Inlet-side fuel gas manifold52Cooling-medium outlet manifold53Inlet-side oxidant gas manifold54Outlet-side fuel gas manifold55Cooling-medium inlet manifold56Outlet-side oxidant gas manifold60Recess portion in which cell connector is adapted to be inserted70Voltage-detection cell connector81Terminal84Conductive wire for connection to terminal31First extending portion of separator3032Second extending portion of separator3041Protrusion that protrudes into recess portion60of resin sheet71Flat casing73Body portion of casing74Knob portion of casing75Linear base region76Tip end region77Tip end of tip end region79To-be-crimped portion82Gap formed at lower end of base region83Gap formed in tip end regionα Distance from upper edge of second extending portion of separator to protrusion of resin sheetβ Distance between upper edge of gap82and to-be-crimped portion79of cell connectorS Power-generating region