JP4910331B2 - Fuel cell stack terminal and method of manufacturing the same - Google Patents

Description

  The present invention relates to a terminal of a fuel cell stack and a manufacturing method thereof.

A unit cell of a fuel cell has a configuration in which a polymer solid electrolyte membrane is sandwiched between an air electrode and a hydrogen electrode. Since sufficient power cannot be ensured with only unit cells, a plurality of unit cells are joined in series to form a fuel cell stack. Such a fuel cell stack is used as a power source for driving a vehicle, for example.
A configuration of a conventional fuel cell stack 1 is shown in FIG.
In FIG. 1, the end cell 2 of the fuel cell stack 1 is laminated with a thick conductive metal plate as a base portion 4 of a terminal 3 in order to reduce electric resistance. A connecting portion 5 protrudes from the side surface of the base portion 4 in the in-plane direction of the base portion 4. An insulator 6 made of a plate-like insulating material is interposed between the base 4 and the end plate 7. The pair of end plates 7, 7 are fastened by four stud bolts 8, and each element constituting the fuel cell stack 1 is fixed.
In such a fuel cell stack 1, the base 4 of the terminal 3 is formed thick, so that its heat capacity is large. As a result, when the fuel cell stack 1 is warmed up in a cold region, the heat of warm air is taken away by the base portion 4 particularly from the end cells 2. Thereby, when the fuel cell stack 1 is started, the temperature of the end cell 2 does not increase moderately. This becomes a factor of deterioration in starting characteristics of the fuel cell stack as a whole.

In the terminal disclosed in Patent Document 1, the connecting portion protrudes from the substantially central portion of the base portion in a substantially vertical direction, thereby comparing with the example shown in FIG. 1 (the connecting portion is formed on the side surface). The base has been made thinner and, consequently, a smaller heat capacity. Since the distance from each area | region of a base to a connection part is shortened, the electrical resistance when taking out electric power from a terminal via a connection part becomes small. Therefore, even if the base is thinned (resistance is increased), the overall electric resistance can be kept within a preferable range.
According to Patent Document 1, a cylindrical member is employed as the connection portion, and this is fixed to the plate-like base portion by a method such as brazing or screwing.

JP 2002-1000039 A

  As described above, in the conventional example, it is necessary to prepare the base portion and the connection portion constituting the terminal separately and to assemble them together, which takes time for manufacturing and eventually increases the manufacturing cost.

The present invention has been made to solve the above problems, and the configuration thereof is as follows.
A terminal connected to an end cell arranged on the outermost side in the fuel cell stack, comprising: a base contacting the end cell; and a connection projecting vertically from the base,
A terminal for a fuel cell stack, characterized in that both the base portion and the connection portion are made of a plate-like or wire mesh-like conductive member, and both are integrated and continuous.

According to the terminal configured as described above, since the base portion and the connection portion are integrally formed, the manufacture becomes easy, and the terminal can be provided at a low cost.
Of course, by adopting a structure in which the connecting portion is vertically projected from the base portion, the base portion can be thinned and its heat capacity is reduced. Therefore, the heat taken from the end cell in contact with the base is reduced, and the low temperature startability of the fuel cell stack is improved.

The second aspect of the present invention is defined as follows. That is,
In the terminal according to the first aspect described above, the connection portion protrudes from the position of the center of gravity of the base portion.
By disposing the connection portion at a substantially center of gravity position of the base portion, the distance from each region of the base portion to the connection portion is minimized. Therefore, the resistance becomes the smallest under the condition where the shape and thickness of the base are the same. In other words, when the shape of the base and the required resistance are the same, the thickness can be made the thinnest. This minimizes the heat capacity of the terminal and minimizes the heat taken away from the end cells. That is, the low temperature startability is further improved.

The third aspect of the present invention is defined as follows. That is,
In the terminal according to the first or second aspect described above, the base portion is entirely formed with irregularities, and the base portion partially contacts the surrounding members.
According to the terminal configured as described above, the base portion is in partial contact with the end cell. Thereby, the heat transferability from the end cell to the base is further lowered, and the low temperature startability is further improved. Furthermore, since the contact between the base portion and the insulator becomes partial, the transfer of heat from the base portion of the terminal to the insulator is also suppressed. That is, in the heat transfer path of the end cell → terminal base → insulator → end plate, the heat transfer performance of the “end cell → terminal base → insulator” portion is reduced, so heat radiation from the end cell is small. Thus, it can be seen that the cold startability is improved.
In addition, regarding the conductivity between the end cell and the base, since the unevenness is formed on the entire base, there is almost no difference from the flat base.

The fourth aspect of the present invention is defined as follows. That is,
In the terminal of the third aspect described above, the unevenness of the base portion forms a waveform, and the top of the wave is formed in the same direction as the connection line between the base portion and the connection portion.
According to the terminal configured in this manner, the bending direction of the connecting portion with respect to the base portion and the bending direction of the corrugation at the base portion coincide with each other, so that the manufacturing method (particularly bending) can be easily performed. Therefore, an inexpensive terminal can be provided.

  According to a fifth aspect of the present invention, the fuel cell stack is provided with the terminals defined in the first to fourth aspects. The same effects as the first to fourth aspects can be obtained.

A sixth aspect of the present invention defines a method for manufacturing a terminal defined in the first to fourth aspects. That is,
A punching process in which the base and the connecting part are continuously punched from a plate-shaped or wire mesh-shaped base material; and
A bending step of bending the connection portion perpendicular to the base portion;
Of manufacturing a terminal for a fuel cell stack, comprising:
According to this manufacturing method, a terminal can be manufactured by performing simple processing of a punching process and a bending process on a plate-shaped or wire mesh-shaped base material. Therefore, the terminal can be manufactured at a low cost.

Hereafter, each element which comprises this invention is demonstrated.
(Fuel cell stack)
The unit cell constituting the fuel cell stack has a structure in which a polymer solid electrolyte membrane is sandwiched between a hydrogen electrode and an air electrode, and this is further sandwiched between separators. A fuel cell stack for a vehicle is formed by stacking such unit cells in units of several tens to several hundreds.
In the fuel cell stack for vehicles, an air supply system and a hydrogen supply system are attached thereto, a cooling device for adjusting the temperature of the fuel cell, and an auxiliary device such as a secondary battery and a capacitor for storing the generated electric power. Optionally provided.
Furthermore, since the usage environment of the vehicle is diverse, it is preferable to attach a heater to the fuel cell stack and its auxiliary equipment, especially assuming use in a cold region.

(Terminal)
In the terminal according to the present invention, both the base portion and the connecting portion are made of a plate-like or wire-like conductive member, and both are integrated and continuous. Such a terminal is formed by processing a single plate-like or wire mesh-like conductive material as a base material. From the viewpoint of ease of processing, the conductive material is preferably a metal material.
The base of the terminal contacts the end cell separator to collect the current generated by the fuel cell stack. An external wiring is connected to the connecting portion, and the current collected by the base is supplied to the external wiring.

The shape and structure of the base portion are not particularly limited as long as the base portion can contact the end cell and collect current from there. In addition to a flat plate or wire mesh, the base can be used as a flat plate and the through holes can be formed evenly in the flat plate as a whole to reduce the contact area between the base and other members.
When unevenness is formed on the base, it is formed on the entire surface. If the unevenness is formed only in a part, the base may come into contact with the end cell and the current collection effect may be reduced.

Examples of the present invention will be described below.
FIG. 2 is a perspective view showing a fuel cell stack 11 according to an embodiment of the present invention. The same elements as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is partially omitted.
FIG. 3 shows an enlarged cross-sectional view of a main part of the fuel cell stack 11 of the embodiment. FIG. 4 is an exploded perspective view of the terminal 13.
As shown in FIG. 4, the terminal 13 of the embodiment is formed by assembling a set of terminal forming pieces 13A and 13B. Each terminal forming piece 13A, 13B includes a rectangular base portion 14A, 14B, and the connection portions 15A, 15B are bent vertically from one edge thereof.
Bolt through holes 19A and 19B are formed in the connecting portions 15A and 15B, and the terminals 13 of the embodiment are formed by overlapping the connecting portions 15A and 15B so that the holes 19A and 19B communicate with each other.

Reference numeral 20 denotes an external wiring, which is bolted to the connecting portion 15.
The base portion 14A and the connecting portion 15A constituting the terminal forming piece 13A are formed from a single flat plate member. As this flat plate member, a copper plate having a thickness of 0.1 to 1 mm plated with gold can be employed. Further, it is also possible to adopt a wire net formed with a copper wire having a diameter of 0.2 to 2 mm and plated with gold. In addition to the metal mesh, punching metal or expanded metal can be used.
The terminal forming piece 13B is also the same member as the terminal forming piece 13A.

The terminal of the embodiment is formed as follows.
This is punched out using a gold-plated copper plate as a base material. At this time, for example, the base portion 14A and the connection portion 15A are on the same plane. Next, the terminal portion 14A shown in FIG. 4 is formed by fixing the base portion 14A and bending the connecting portion 15A vertically. The terminal forming piece 14B is formed in the same manner.
The terminal forming pieces 13 </ b> A and 13 </ b> B are connected to form a terminal 13 using a fastening device (bolt and nut) used to connect the external wiring 20.
Thus, the terminal 13 of this embodiment is formed by a general-purpose and simple processing method. Therefore, the terminal 13 can be provided at a low cost.

In this embodiment, the terminal 13 is divided into two lines symmetrically at the connection portion 15. By dividing line symmetrically in this way, each terminal forming piece has the same shape, and the manufacturing process is simplified.
In addition, when the terminal 13 is enlarged, each terminal formation piece 13A, 13B can be divided | segmented up and down by making an AA line and a BB line into a line symmetry dividing line. In addition, in any terminal formation piece, it has a base part and a connection part, and these shall be integrated and continuous.
As is apparent from FIG. 3, the base portions 14 </ b> A and 14 </ b> B of the terminal 13 of the embodiment contact the end cell 2. Other portions are surrounded by an insulator 16.

Since the terminal 13 of the embodiment thus formed is formed of a thin copper plate plated with gold, its heat capacity is extremely small. Therefore, almost no heat is taken from the end cell 2 when the apparatus is activated. Therefore, the low temperature startability of the fuel cell stack is improved.
Further, it is formed by punching a gold-plated thin copper plate as a base material and then bending it. Therefore, it is easy to manufacture and an inexpensive terminal can be provided.

5 and 6 show a terminal 23 according to another embodiment. The same elements as those in the examples of FIGS. 3 and 4 are denoted by the same reference numerals, and description thereof is partially omitted.
In the terminal 23 of this embodiment, the base 24A and the base 23B are formed in a waveform in the terminal 23 of the previous embodiment. By making the bases 24A and 24B corrugated, the contact area between the bases 24A and 24B and the end cell 2 and the insulator 16 is reduced. As a result, the heat dissipation efficiency of the end cell 2 is reduced, thereby improving the starting characteristics in a cold region.
In this embodiment, the directions of the wave heads in the base portions 24A and 24B coincide with the directions of the connection lines (bending lines) between the base portions 24A and 24B and the connection portions 15A and 15B. As a result, the bending direction of the base material is constant, and bending is facilitated.
In this embodiment, the waveform is adopted as an example of the unevenness formed on the base, but the shape of the unevenness can be arbitrarily designed.
The method of forming the terminal 23 in this embodiment is the same as in the previous embodiment.

7 and 8 show a terminal 33 according to another embodiment. The same elements as those in the examples of FIGS. 5 and 6 are denoted by the same reference numerals, and the description thereof is partially omitted.
In the terminal 33 of this embodiment, the connecting portions 15A and 15B are continuous in the terminal 23 of the previous embodiment. Therefore, the terminal 23 consists of one member, and there is no terminal forming piece. According to the terminal configured in this manner, the alignment work between the terminal forming pieces is omitted, and the manufacturing method is simplified.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

FIG. 1 is a perspective view showing a configuration of a conventional fuel cell stack. FIG. 2 is a perspective view showing a fuel cell stack according to an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the main part of the fuel cell stack. FIG. 4 is an exploded perspective view of the terminal of the embodiment. FIG. 5 is an enlarged cross-sectional view of a main part of a fuel cell stack according to another embodiment. FIG. 6 is an exploded perspective view of the terminal. FIG. 7 is an enlarged cross-sectional view of a main part of a fuel cell stack according to another embodiment. FIG. 8 is a perspective view of the terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 Fuel cell stack 2 End cell 3, 13, 23, 33 Terminal 14, 24, 34 Base part 5, 15 Connection part

Claims (2)

A terminal connected to an end cell arranged on the outermost side of the fuel cell stack, the terminal comprising a base contacting the end cell and a connection projecting vertically from the center of gravity of the base In
The base part and the connection part are both plate-like or wire mesh-like conductive members, and both are integral and continuous ,
A terminal for a fuel cell stack, wherein the base portion is entirely formed with irregularities, and the base portion partially contacts a surrounding member . 2. The terminal according to claim 1 , wherein the unevenness of the base portion forms a waveform, and a wave top portion is formed in the same direction as a connection line between the base portion and the connection portion.