JPS623549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel cell, and particularly to a fuel cell in which a cooler using a non-dielectric liquid as a coolant is provided between unit cells.

As shown in FIG. 1, a conventional fuel cell is constructed by stacking a plurality of unit cells 1 in series. The unit cell 1 has a fuel electrode 4 and an air electrode 5 provided with ribs for supplying fuel and air, respectively, on both sides of matrices 2 and 3 that hold an electrolyte such as phosphoric acid in the center, and further includes: In order to prevent air and fuel from mixing, impermeable separators 6 are provided on both sides of the fuel to create a separated structure. A cooler 7 for absorbing reaction heat generated within the unit cell 1 is disposed every time several unit cells 1 are stacked. This cooler 7 is composed of a cooler holder 8 located between two impermeable separators 6 and a plurality of cooling thin tubes 9 fixed to the center of the cooler holder 8. 9 is connected to a cooling branch pipe 10, and this cooling branch pipe 10 is connected to a main cooling pipe 11, and the fuel cell is cooled by the coolant sent through these pipes.

In such a configuration, if a non-dielectric liquid such as water is used as the cooling liquid and a non-dielectric pipe such as a copper pipe is used as the cooling piping, the cooling system and battery system may be connected. It becomes necessary to electrically separate the cooling tube and the cooling tube holder.

FIG. 2 shows a conventional fuel cell in which cooling thin tubes and a cooling tube holder are insulated. The same parts as in FIG. Cooling water tube connected to 81
and 82 are cooling tube holders designed to sandwich and fix the cooling water thin tubes 9a, and these cooling tube holders 81 and 82 serve to cool the unit cells of the fuel cell and electrically connect adjacent unit cells. The cooling water thin tube 9a, which is constructed of a non-dielectric material so as to be connected with low resistance and is clamped and fixed in the groove, is a pipe whose surface is insulated and coated with a heat-resistant dielectric material such as polytetrafluoroethylene. ing.

Figures 3 and 4 show conventional fuel cells with further enhanced insulation and improved reliability.
Figure 3 is a cross-sectional view in the vertical direction, and Figure 4 is a cross-sectional view in the horizontal direction. The same parts as in Figures 1 and 2 are given the same symbols, 12 is a stack of unit cells, 13 is a tightening plate. It shows. In this fuel cell, the main cooling pipes 11a connecting the cooling branch pipes 10a are electrically isolated by connecting them via the dielectric member 14, resulting in a structure in which the battery system and the cooling system are electrically separated. ing. However, while such a structure is extremely effective in a tube when the cooling medium is dielectric, it is difficult to use a secondary cooling medium when the cooling medium is non-dielectric.
As shown in the figure, it is necessary to provide electrical insulation at the cooling tube holder.

The non-dielectric material constituting this cooling tube holder is a carbon plate that has been subjected to an impermeable firing process and cut into a predetermined size, with grooves formed by machining.

Increasing the number of customers for fuel cells depends on increasing the power generation current density σ per unit area, but since the power generation current density is usually finite at 200 to 400mA/cm ² , a method of increasing the effective area S of the unit cell is needed. is taken. By the way, if the value of (σ) is 300mA/cm ² and the through current between unit cells in series is required to be 1500A, then
The area (S) of the unit cell required for this is ^500cm2 , and the cooling pipe holder to cool it is also 700mm x 700mm.
Large size (mm) is required. For this reason, cooling pipe holders manufactured by carbon plate molding are made of raw materials,
The problem was that it was extremely expensive due to increased construction costs and decreased yield, and was also extremely poor in mass production.

In addition, Fig. 5 shows that grooves are provided in the cooling pipe holder,
This figure shows a cross section of the end of a cooler with a structure in which thin cooling tubes pass through it. The same parts as in Figures 1 and 2 are given the same reference numerals. In order to reduce the contact resistance between the cooling tube 9a and the separator 6, a tightening stress of several kg/cm ² is usually applied. , there is a problem that the cooling tube holder 8 or the separator 6 is mechanically damaged, and in the vicinity of the end of the cooling tube holder 8 (the part indicated by reference numeral 15 in the figure), the dielectric material covering the cooling thin tube 9a is damaged. However, it had the disadvantage of causing poor insulation.

Furthermore, Fig. 6 shows a cross section of a conventional fuel cell stack perpendicular to the cooling thin tubes, and the same parts as in Figs. 1 and 2 are given the same reference numerals, but grooves are provided. When forming the cooling tube 9a by penetrating the cooling tube holder 8, there is a fuel flow passage 16 between the cooling tube 9a and the cooling tube holder 8 due to dimensional accuracy of machining and thermal expansion. This had the disadvantage that parallel voids 17 were formed and the fuel utilization rate was significantly reduced.

The present invention aims to eliminate these problems and provide a fuel cell having a cooler with good thermal conductivity, low resistance, mechanical strength, mass productivity, etc. In a fuel cell stacked with a plurality of unit cells connected in series, and a cooler provided between adjacent unit cells and provided with a non-dielectric cooler, the cooler a plurality of non-dielectric spacers that electrically connect unit cells to each other; and a dielectric member that arranges a non-dielectric cooling pipe between the non-dielectric spacers to electrically separate them from the non-dielectric spacers. It is characterized by the following.

Examples will be described below.

FIG. 7 shows a cross section showing the configuration of a cooler according to an embodiment of the present invention, in which 18 is a non-dielectric cooling pipe carrying a non-dielectric cooling medium, 19 is a non-dielectric cooling pipe 18 A non-dielectric spacer 20 having a U-shaped cross section and electrically connecting adjacent unit cells, which is placed in isolation from the non-dielectric cooling pipe 18 and the non-dielectric spacer 19. Non-dielectric spacers 19, which are dielectric members with good heat conductivity and are separately arranged, are arranged back to back, and their contact surfaces are bonded to be airtight.

This cooler is manufactured by integrally molding a non-dielectric spacer 19 and a non-dielectric cooling pipe 18 that constitute one cooler with a dielectric material that constitutes a dielectric member 20.

Since this cooler is formed by an integral mold, there are problems such as breakage of the cooling tube holder and separator due to compression and pressure concentration as explained in FIG. 5, and deterioration due to damage to the end insulation. Or, the problem of decrease in fuel utilization rate due to the generation of voids as explained in FIG. 6, etc.
There are no drawbacks of conventional products.

In addition, compared to the conventional method of coating and insulating cooling pipes with dielectric materials, insulation separation between the electrical system and the cooling system is possible because dielectric members make up the majority of the cooler and are included as structural materials. , the insulation performance and reliability between the electrical system and the cooling system are extremely high.

Furthermore, the non-dielectric spacer with a U-shaped cross section used in this cooler has higher productivity than the non-dielectric spacer with an I-shaped cross section used in other examples described later, and mass production is easier. It is possible to provide an inexpensive cooler.

In addition, when using a non-dielectric spacer with a U-shaped cross section, the opening sides of the two non-dielectric spacers with a U-shaped cross section are placed opposite each other,
In between, we fabricated a structure in which non-dielectric cooling pipes were held by dielectric members, and connected them in appropriate numbers.
A cooler can be manufactured by joining at a non-dielectric spacer section. When using such a manufacturing method, various manufacturing methods are required, including the case where the number of non-dielectric cooling pipes disposed between two non-dielectric spacers with a U-shaped cross section is zero. Keep it
By appropriately combining these, various coolers with different cooling capacities can be manufactured.

5 and 9 are perspective views of coolers of other different embodiments, and the same parts as in FIG. 7 are given the same reference numerals. The difference from the cooler in FIG. 7 is that in the cooler in FIG. 8, the non-dielectric spacer 18 is eliminated at the end of the cooler. Therefore, insulation performance and reliability are further improved.
The cooler shown in FIG. 9 is different in that the non-dielectric spacer 19 is molded with a dielectric member 20 without being exposed on the side surface of the cooler. Then,
The dimensional accuracy, mechanical strength, and insulation reliability of the mold cooler can be further improved.

FIG. 10 shows the structure of a cooler according to yet another embodiment. The difference from the coolers of FIGS. 7, 8, and 9 is that the non-dielectric spacer has an I-shaped cross section. Since the non-dielectric spacer 21 is used, this cooler can also be manufactured by integrally molding the non-dielectric spacer 21 and the non-dielectric cooling pipe 18 with the dielectric member 20 in the same way as described above. . In this case, unlike the cooler of the embodiment shown in FIG. 7, there is no need to airtightly join the two non-dielectric spacers each having a U-shaped cross section, but the productivity of machining is reduced. Although it is a little lower than the embodiments of FIGS. 7, 8 and 9, and it is not easy to assemble an arbitrary cooling capacity, the other effects can be obtained in exactly the same way.

In addition, when using the non-dielectric spacer of the present invention, the resistance R ₁ between adjacent unit cells
is 700mm ² thick parallel to the cooling capillary in the cooler
Assuming that 40 copper pieces of 10 mm and width 1.0 mm are inserted, R ₁ = 1/40 x ρ ₁ x 1.0/0.1 x 70.0 = 1/
40×(1.72×10 ⁸ )×1.0/0.1×700=6.14×10 ^-11 (Ω).

On the other hand, in the conventional carbon cooling tube holder, the resistance R ₂ between adjacent unit cells is
When the effective area is 700 mm ² and the thickness is 10 mm, R ₂ = ρ ₂ × 1.0/(70.0) ² = 1.0 × 10 ^-3 × 1.0/(70.0) ² = 2.04 × 10 ^-7 (Ω).

As is clear from the comparison of these results,
The value of R ₁ /R ₂ is approximately 3.0×10 ^-4 , which makes it possible to reduce resistance and extremely reduce loss, making it extremely effective for increasing current.

Note that dielectric members with good thermal conductivity include, for example,
It is based on alumina (Al ₂ O ₃ ) powder and can be easily obtained using an organic material such as epoxy resin as a binder, but dielectric members made of Al ₂ O ₃ (80% by weight) and epoxy resin (20% by weight) cannot be used. , the thermal conductivity K ₁ is approximately 4.0×10 ^-3 (cal/deg・cm・sec), and the thermal conductivity K ₂ (=5 to 6 ×10 ^-4 (cal/deg・cm・
sec)), making it possible to provide a cooler with good thermal conductivity. Moreover, the compressive strength of the Al ₂ O ₃ -epoxy resin molded body is about 2000 Kg/cm ² , which is about twice the compressive strength of carbon itself, which is 1000 Kg/cm ² . The stress concentration that occurs near the cooling pipe in the conventional example does not occur, and the design can be made thinner.

That is, in the fuel cell of the example, (1) Electrical insulation of the battery system and cooling system is sufficient.

(2) Connections between adjacent cells have low resistance.

(3) Good thermal conductivity and cooling efficiency.

(4) There is no stress concentration, the compressive strength is high, and the product can be made thinner.

(5) It is easy to mass produce and is inexpensive.

It has the following effects.

As described above, the fuel cell of the present invention has thermal conductivity,
This makes it possible to provide a fuel cell with a cooler that has good low resistance, mechanical strength, mass productivity, etc., and has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the stacked state of a conventional fuel cell, FIG. 2a is a cross-sectional view of the main parts of the fuel cell, and FIG. 3 and 4 are vertical and horizontal cross-sectional views, respectively, of another fuel cell;
5 and 6 are respectively a sectional view of the end of the cooling tube and a sectional view of the side surface on the fuel supply side of different fuel cells, and FIG. 7 is an embodiment of the fuel cell of the present invention. Perspective view of the cooler, No. 8
FIG. 9 and FIG. 9 are perspective views of coolers of other different embodiments, and FIG. 10 is a perspective view of a cooler of another embodiment. DESCRIPTION OF SYMBOLS 1... Unit cell, 7... Cooler, 18... (Non-dielectric) cooling pipe, 19, 21... Non-dielectric spacer, 20... Dielectric member.

Claims (1)

[Scope of Claims] 1. A device comprising a stack of a plurality of unit batteries electrically connected in series and a cooler provided with a non-dielectric cooling pipe arranged between the adjacent unit batteries. In the fuel cell comprising: A fuel cell comprising a spacer and a dielectric member disposed electrically separated from each other. 2. The fuel cell according to claim 1, wherein the non-dielectric spacer is a metal member having a U-shaped cross section and disposed such that both ends thereof are located on both sides of the cooler. 3. The fuel cell according to claim 1, wherein the non-dielectric spacer is a metal member having an I-shaped cross section and disposed such that both ends thereof are located on both sides of the cooler. 4. The cooler includes the non-dielectric spacer;
4. The fuel cell according to claim 1, wherein the non-dielectric cooling pipe is integrally molded with a dielectric material. 5. The fuel cell according to claim 1 or 4, wherein the dielectric material is a mixture of inorganic powder such as alumina and a heat-resistant organic material.