WO2021240723A1 - Fuel cell and fuel cell module - Google Patents

Abstract

A fuel cell 1, 26, 28 comprises a power-generating element and a protective element. The power-generating element is formed by stacking an electrolyte film 5a and one or more electroconductive films 4a, 6a, and receives supplied fuel gas 18, 36, 37 and air 19, 38, 39 to generate power. A protective film is formed on the protective element, to which only one of the fuel gas 18, 36, 37 and the air 19, 38, 39 is supplied. The compressive strength of the protective element is less than that of the power-generating element.

Description

Fuel cell and fuel cell module

The present invention relates to a fuel cell and a fuel cell module.

Patent Document 1 describes that in a fuel cell system, the pressure difference between the fuel electrode and the air electrode is reduced to suppress deterioration of the electrolyte membrane.

In Patent Document 2, anisotropic etching is performed on a single crystal silicon substrate having a (110) plane as a surface, so that the opening angle with the substrate surface in the cross section of the opening in which the battery elements are laminated is approximately 90 °. Is described.

JP-A-2017-183033 Japanese Unexamined Patent Publication No. 2004-288382

However, in the prior art, there is a problem that the power generation element may be damaged when the pressure difference between the fuel gas and the oxidant gas suddenly fluctuates or increases excessively.

The technology of Patent Document 1 is provided with a pressure adjusting device for dealing with the pressure difference between the fuel gas and the oxidant gas, but it is difficult to deal with the momentary pressure fluctuation. Further, this pressure adjusting device is based on the gas pressure difference between a plurality of fuel cell stacks, and it is difficult to cope with the pressure difference in a single fuel cell stack.

Even in the technique of Patent Document 2, since the area of each electrolyte membrane is the same, there is a possibility that any single cell in the substrate may be damaged. Further, when the single cell is damaged, hydrogen and oxygen are mixed, which is not preferable.

The present invention has been made in view of the above problems, and when the pressure difference between the fuel gas and the oxidant gas suddenly fluctuates or excessively increases by providing the protective element portion in the fuel cell. However, it is an object of the present invention to provide a fuel cell and a fuel cell module that prevent damage to the power generation element portion.

An example of a fuel cell according to the present invention is
A power generation element unit formed by laminating an electrolyte membrane and one or more conductive films and supplied with a fuel gas and an oxidant gas to generate power.
A protective element portion on which a protective film is formed and only one of the fuel gas or the oxidant gas is supplied.
Equipped with
It is characterized in that the withstand voltage strength of the protection element portion is lower than the withstand voltage strength of the power generation element portion.

Further, an example of the fuel cell module according to the present invention is
With the above fuel cell
It is characterized in that it is arranged in the fuel cell and includes a separator that separates the fuel gas and the oxidant gas.

According to the fuel cell according to the present invention, even when there is a sudden pressure fluctuation in the air supply of the fuel gas or the oxidant gas, the influence on the power generation element can be reduced and the fuel cell system can be prevented from being damaged.

Other issues, novel features, configurations and effects will become apparent from the description and accompanying drawings herein.

It is a top view of the fuel cell which concerns on Embodiment 1. FIG. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which shows the manufacturing process of the fuel cell of FIG. It is sectional drawing which shows the manufacturing process of the fuel cell of FIG. It is sectional drawing which shows the manufacturing process of the fuel cell of FIG. It is sectional drawing which shows the manufacturing process of the fuel cell of FIG. It is a figure which shows the relationship between the opening area and the withstand voltage of a thin film membrane. It is a top view of the separator for a fuel cell which concerns on Embodiment 1. FIG. FIG. 5 is a cross-sectional view taken along the line BB of FIG. It is sectional drawing of the fuel cell module which concerns on Embodiment 1. FIG. It is the schematic of the fuel cell system which concerns on Embodiment 1. FIG. It is a top view of the fuel cell which concerns on Embodiment 2. FIG. 9 is a cross-sectional view taken along the line CC of FIG. FIG. 3 is a plan view of the fuel cell according to the third embodiment. It is sectional drawing along the DD line of FIG. It is a top view of the separator for a fuel cell which concerns on Embodiment 4. FIG. FIG. 3 is a cross-sectional view taken along the line EE of FIG. It is sectional drawing of the fuel cell module which concerns on Embodiment 4. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The examples are examples for explaining the present invention, and are appropriately omitted and simplified for the sake of clarification of the description. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range and the like disclosed in the drawings.

If there are multiple components with the same or similar functions, the same code may be described with different subscripts. Further, when it is not necessary to distinguish between these a plurality of components, the subscripts may be omitted in the description.

The present invention relates to a fuel cell and a fuel cell module. In recent years, fuel cells have been attracting attention as a clean energy source capable of high energy conversion and not emitting pollutants such as carbon dioxide gas and nitrogen oxides. Among fuel cells, as an example, solid oxide fuel cells (Solid Oxide Fuel Cell, hereinafter abbreviated as SOFC) can use gases such as hydrogen, methane, and carbon monoxide, which have high power generation efficiency and are easy to handle, as fuel. .. As described above, SOFC has many advantages over other types of fuel cells, and is expected as a cogeneration system having excellent energy saving and environmental friendliness.

SOFC has a structure in which a solid electrolyte is sandwiched between a fuel electrode and an air electrode. The electrolyte is a partition wall, and a fuel gas such as hydrogen is supplied to the fuel electrode, and an oxidant gas such as air is supplied to the air electrode.

In the following, air is used as a representative of the oxidant gas, but it is also possible to use a gas other than air as the oxidant gas.

<Embodiment 1>
FIG. 1 is a plan view of the fuel cell 1 according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. For convenience of explanation, the vertical direction of the paper surface in FIG. 2 is the vertical direction of the fuel cell 1, but this direction has nothing to do with the orientation when the fuel cell is actually installed or used.

In the attached drawing, hatching may be added to the part that is not a cross section to facilitate understanding.

The fuel cell 1 has the following configuration.
-Semiconductor substrate 2 (substrate) made of single crystal silicon (Si)
-The first insulating film 3 formed on the semiconductor substrate 2
-The power generation element portion and the protection element portion formed on the first insulating film 3

The configuration of the power generation element unit can be a known configuration, but an example will be described below. The power generation element portion is formed by laminating an electrolyte film and one or more conductive films. In the present embodiment, the electrolyte membrane is the electrolyte membrane 5a, and the conductive film is the first electrode 4a and the second electrode 6a. The power generation element portion is laminated on the first insulating film 3 in the order of the first electrode 4a, the electrolyte film 5a, and the second electrode 6a.

In the present embodiment, the two fuel cell 1s are provided with two protective element units. A protective film is formed on the protective element portion. In the present embodiment, the protective film is configured by laminating the first electrodes 4b and 4c, the electrolyte films 5b and 5c, and the second electrodes 6b and 6c.

The power generation element portion and the protection element portion are formed on the same semiconductor substrate 2. Such a configuration simplifies the manufacturing process.

The semiconductor substrate 2 has a plurality of openings, and the power generation element portion and the protection element portion are formed in the openings. The plurality of openings include a first opening 7 and second openings 8a, 8b. These openings are not visible from above, but are shown by broken lines in the plan view of FIG.

The power generation element portion is formed over a plurality of first openings 7. At least one of the conductive films (first electrode 4a and second electrode 6a in this embodiment) (both in this embodiment) is continuous over the plurality of first openings 7. With such a configuration, the process of forming the conductive film is simplified.

Further, as shown in FIG. 2 as a modified example, one of the conductive films of the power generation element portion (first electrode 4a and second electrode 6a in this modified example) (first electrode 4a in this modified example) and protection. It may be configured so that the conductive film of the element portion (the first electrode 4c in this modification) is continuous. According to such a modification, the process of forming the conductive film is simplified.

The two protective element portions are formed in the second opening 8a and the second opening 8b, respectively.

Fuel gas and air are supplied to the power generation element to generate electricity. At this time, one of the first electrode 4a and the second electrode 6a becomes an anode electrode, and the other becomes a cathode electrode, which are connected to the outside and supply electric power to the outside. Further, the first electrode 4b and the second electrode 6b of the protective element portion can also be connected to the outside, and the capacitance or the resistance value between the first electrode 4b and the second electrode 6b can be measured. ing. The same applies to the first electrode 4c and the second electrode 6c.

The shape and dimensions of the first opening 7 can be arbitrarily designed, but for example, it is rectangular in a plan view (direction in FIG. 1), and the length of one side is about 5 mm. The shapes and dimensions of the second openings 8a and 8b can be arbitrarily designed, but are, for example, rectangular and have a side length of about 6 mm.

Regarding the relationship of the area of each opening, the area of one second opening 8a (or the second opening 8b) related to the protective element portion is larger than the area of one first opening 7 related to the power generation element portion. It's getting bigger. Here, when the area changes depending on the position of the opening (for example, the depth position), the measurement position of the area can be arbitrarily defined. For example, the area may be measured at the lower end of each opening, or the area may be measured at the upper end of each opening. In the present embodiment, the area of the second opening 8a (or the second opening 8b) is larger than the area of the first opening 7 regardless of which of these measuring methods is used.

As shown in FIG. 2, the semiconductor substrate 2 has a plurality of first openings 7 from which the inside has been removed, one second opening 8a, and one second opening 8b. A first insulating film 3 is formed on both surfaces of the semiconductor substrate 2 other than these openings. The first electrodes 4a, 4b, and 4c are formed on the first insulating film 3 so as to cover the first opening 7 and the second openings 8a and 8b, and the electrolyte films 5a, 5b, and 5c are formed on the first electrodes 4a, 4b, and 4c. The second electrodes 6a, 6b, and 6c are formed on the second electrodes 6a, 6b, and 6c.

Therefore, a thin film membrane structure having the same film structure is formed in the first opening 7, the second opening 8a, and the second opening 8b. That is, the power generation element portion and the protection element portion have the same film configuration. With such a configuration, the calculation process when designing the withstand voltage of the power generation element portion and the protection element portion is simplified. The term "film composition" as used herein means, for example, the composition, thickness and stacking order of each layer, and does not necessarily include the area of the film.

3A to 3D are diagrams showing a manufacturing process of the fuel cell 1. These figures are cross-sectional views of a portion corresponding to FIG. First, as shown in FIG. 3A, a semiconductor substrate 2 made of single crystal Si and having a crystal orientation of Si <100> is prepared. The semiconductor substrate 2 has a thickness of, for example, 400 μm or more.

The first insulating film 3 is formed on the surface of the semiconductor substrate 2. As the first insulating film 3, for example, a silicon nitride film having a tensile stress is formed at about 200 nm by a CVD method. In the case of the CVD method, silicon nitride films having the same film thickness are formed on the upper side and the lower side of the semiconductor substrate 2.

Next, a metal film (for example, platinum (Pt) film) is formed to a thickness of about 100 nm by a sputtering method. Next, as shown in FIG. 3A, the first electrodes 4a, 4b, and 4c are formed. This is performed by performing patterning using a photolithography method and using a dry etching method using an argon (Ar) gas or the like.

At this time, it is desirable to modify the surface of the first insulating film 3 in order to improve the adhesive force between the Pt film and the first insulating film 3. The modification is performed, for example, by etching the surface of the first insulating film 3 (for example, etching by about 10 to 15 nm) by sputtering etching with Ar gas before forming the Pt film.

Alternatively, in order to improve the adhesive force between the Pt film and the first insulating film 3, a titanium film (Ti) or an aluminum film (Al) may be formed at about 2 nm as a barrier metal film that assists the adhesion. ..

Next, a negative resist pattern is formed by photolithography technology. Next, using a sputtering method, for example, a YSZ film (zirconium oxide film containing yttrium) as an electrolyte film is formed at about 500 nm. After that, the negative resist is removed. As a result, as shown in FIG. 3B, the electrolyte membranes 5a, 5b, 5c are formed.

Next, a Pt film of about 100 nm is formed by a sputtering method. Next, patterning is performed using a photolithography method, and the second electrodes 6a, 6b, and 6c are formed by dry etching with Ar gas, as shown in FIG. 3C.

Next, as shown in FIG. 3D, a part of the first insulating film 3 on the lower side of the semiconductor substrate 2 is removed by using a photolithography technique and an insulating film etching technique to expose the back surface of the semiconductor substrate 2.

Next, using the first insulating film 3 on the lower surface of the patterned semiconductor substrate 2 as a mask, a plurality of first openings 7 and second openings 8a and 8b are formed. This is done, for example, by wet-etching and removing the Si film of the semiconductor substrate 2 with a KOH (potassium hydroxide) solution or a TMAH (tetramethylamide) solution. Alternatively, it is performed by removing the Si film of the semiconductor substrate 2 by dry etching using a fluorine-based gas as a main component. In this way, the fuel cell 1 shown in FIGS. 1 and 2 is formed.

As suitable materials for the first electrodes 4a, 4b, 4c and the second electrodes 6a, 6b, 6c, the fluorine-based chemical resistance is excellent, the resistivity is low, and the melting point is higher than the operating temperature (for example, 600). A film (° C or higher) can be used. For example, although it is a Pt film, in addition to the Pt film, a silver film (Ag), a nickel film (Ni), a chromium film (Cr), a palladium film (Pd), a ruthenium film (Ru), a rhodium film (Rh), etc. Can be used.

Further, the first insulating film 3 is not limited to the silicon nitride film, but it is preferable to use an insulating film (aluminum nitride film or the like) having a tensile stress with respect to the Si substrate. Further, the first insulating film 3 may be a silicon oxide film containing a silicon nitride film and boron or phosphorus, or may be a laminated film containing a P-TEOS film containing an organic component at a low temperature. ..

FIG. 4 is a diagram showing the relationship between the opening area and the thin film membrane pressure resistance of the fuel cell 1 of FIG. Four rectangular openings are formed, each having a side length of 3 mm (opening area 9 mm ² ), 4 mm (opening area 16 mm ² ), 5 mm (opening area 25 mm ² ), 6 mm (opening area 36 mm). ² ). After forming a thin film membrane having the film structure shown in FIG. 2 on each opening, air was blown and the pressure at which the thin film membrane was damaged (membrane pressure resistance) was measured.

From the results shown in FIG. 4, it can be seen that the pressure resistance of the thin film membrane decreases as the area of the opening increases. In the first embodiment, since the length of one side of the second openings 8a and 8b is 6 mm, the withstand voltage of the protective element portion is about 25 KPa. On the other hand, since the length of one side of the first opening 7 is 5 mm, the withstand voltage of the power generation element portion is about 32 KPa.

In this way, the withstand voltage of the membrane is different, and the withstand voltage of the protective element is lower than the withstand strength of the power generation element. That is, the strength of the film or laminate constituting the protective element portion is lower than the strength of the film or laminate constituting the power generation element portion. Therefore, when a sudden pressure fluctuation occurs, the protective element portion is damaged before the power generation element portion. In the first embodiment, the ratio of compressive strength is about 1.3.

FIG. 5 is a plan view of the separator 9 according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view taken along the line BB of FIG. The separator 9 is arranged in contact with the fuel cell 1.

The separator 9 is formed with an upper groove 11 and a lower groove 13. The upper groove 11 is formed on the upper surface side of the ceramic substrate 10. The upper groove 11 includes a gas inflow port 11a, a gas discharge port 11b, and a through hole 12. The through hole 12 penetrates the ceramic substrate 10 up and down.

The lower groove 13 is formed on the lower surface side of the ceramic substrate 10. The lower gutter 13 includes an air inlet 13a, an air discharge port 13b, and a through hole 14. The through hole 14 penetrates the ceramic substrate 10 up and down.

The external dimensions of the separator 9 are almost the same as the external dimensions of the fuel cell 1. In the present embodiment, the upper groove 11 of the separator 9 extends to a range including the entire first opening 7 of the fuel cell 1 and the entire second opening 8a when viewed from above. Therefore, when the fuel cell 1 is arranged above and below the separator 9 (for example, as will be described later in relation to FIG. 7), the first fuel cell 1 of the upper fuel cell 1 is passed through the upper groove 11. Gas spreads to the electrode 4a, the first electrode 4b of the upper fuel cell 1, and the second electrode 6b of the lower fuel cell 1.

Similarly, in the present embodiment, the lower groove 13 of the separator 9 extends to a range including the entire first opening 7 of the fuel cell 1 and the entire second opening 8b when viewed from above. There is. Therefore, when the fuel cell 1 is arranged above and below the separator 9, the second electrode 6a of the lower fuel cell 1 and the lower fuel cell 1 pass through the lower groove 13. Gas spreads to the second electrode 6c and the first electrode 4c of the upper fuel cell 1.

As shown in FIG. 6, the upper groove 11 includes a through hole 12 and serves as a flow path for a certain gas, and the lower groove 13 includes a through hole 14 and serves as a flow path for another gas. However, since the upper groove 11 and the lower groove 13 are shielded by the substrate of the separator 9, these two gases are not mixed. In particular, since the through hole 12 does not communicate with the lower groove 13 and the through hole 14 does not communicate with the upper groove 11, the fuel gas and air are separated and sent to the fuel cell.

In this way, the separator 9 is arranged in the fuel cell 1 to separate the fuel gas and the air. With such a configuration, it is possible to prevent mixing of the fuel gas and air.

FIG. 7 is a cross-sectional view of the fuel cell module 15 according to the first embodiment. The fuel cell module 15 includes two fuel cell cells 1 and one separator 9. Each fuel cell 1 is arranged above and below the separator 9.

As shown in FIG. 7, in the fuel cell module 15, two fuel cell cells 1 are stacked. The separator 9 is laminated between the two fuel cell 1s. An upper substrate 17 and a lower substrate 16 having a gas flow path are provided at the upper end and the lower end of the fuel cell module 15, respectively.

The flow path of the lower substrate 16 is a groove having the same shape as the portion of the upper groove 11 of the separator 9 excluding the through hole 12. The flow path of the lower substrate 16 is provided with at least two openings on the side surfaces to allow gas inflow and outflow. Similarly, the flow path of the upper substrate 17 is a groove having the same shape as the portion of the lower groove 13 of the separator 9 excluding the through hole 14. The flow path of the upper substrate 17 is also provided with at least two openings on the side surfaces to allow gas inflow and outflow.

The fuel cell module 15 has a mechanism (not shown) for applying pressure to the lower substrate 16 and the upper substrate 17. As a result, the airtightness of the region where the fuel gas and the air flow is maintained, and the mixing of the gas is prevented.

In this structure, the fuel gas 18 is supplied from the right side of the paper in FIG. 7. The fuel gas 18 reaches each of the following electrodes.
-The first electrode 4b and the second electrode 6b of the protective element portion of the fuel cell 1 above.
-First electrode 4a of the power generation element of the fuel cell 1 above
-The first electrode 4b and the second electrode 6b of the protective element portion of the lower fuel cell 1
-First electrode 4a of the power generation element of the lower fuel cell 1
Further, the fuel gas 18 consumed in the power generation is discharged from a gas discharge port (not shown).

Similarly, air 19 is supplied from the left side of the paper in FIG. 7. The air 19 reaches each of the following electrodes.
-The first electrode 4c and the second electrode 6c of the protective element portion of the fuel cell 1 above.
-Second electrode 6a of the power generation element of the fuel cell 1 above
-First electrode 4c and second electrode 6c of the protective element part of the lower fuel cell 1
-Second electrode 6a of the power generation element of the lower fuel cell 1
Further, the air 19 consumed by the power generation is discharged from a gas discharge port (not shown).

Therefore, the fuel gas 18 and the air 19 are supplied, consumed, and discharged while being separated by the separator 9, the lower substrate 16, and the upper substrate 17. Although not shown, pressure is applied to the fuel cell module 15 between the upper substrate 17 and the lower substrate 16 to prevent the fuel gas 18 and the air 19 from leaking.

In FIG. 7, the fuel gas 18 is supplied from the upper, middle, and lower three places on the right side of the paper, but for example, it is assumed that the pressure rises sharply only in the middle stage. In the upper fuel cell 1, the power generation element portion and the right side protection element portion receive a pressure difference, and in the lower fuel cell 1, the right side protection element portion receives a pressure difference. However, since either (or both) of the two protective element portions are damaged before the power generation element portion, which reduces the pressure difference between the stages, the damage of the power generation element portion is avoided.

Further, as is clear from the above, both the fuel gas 18 and the air 19 are supplied to the power generation element portion, and only one of the fuel gas 18 or the air 19 is supplied to the protection element portion. Therefore, although the protective element unit has a configuration capable of generating power in the present embodiment, it does not actually generate power as shown in FIG. 7. As described above, by making the configuration in which the operation of the protective element portion does not affect the power generation, it is possible to avoid the influence on the power generation operation of the fuel cell 1 even if the protective element portion is damaged. Further, in the first embodiment, such a configuration is realized by the separator 9 having through holes 12 and 14 at positions corresponding to the protective element portion.

A heat-resistant sealing material is used between the fuel cell 1 and the separator 9, between the fuel cell 1 and the upper substrate 17, and / or between the fuel cell 1 and the lower substrate 16. May be good. If a material that deforms when pressure is applied is used as the sealing material, damage to the fuel cell 1 when pressure is applied can be reduced.

The fuel cell module 15 of the first embodiment has a structure in which two fuel cell cells 1 are laminated, but a structure in which more stages are laminated by alternately stacking the fuel cell 1 and the separator 9 is also possible. good. In this way, the desired output can be obtained.

FIG. 8 shows a schematic diagram of the fuel cell system according to the first embodiment. The fuel cell system mainly includes a blower 21 for supplying fuel gas 18 and air 19, a reformer 22 having a fuel gas flow rate adjusting mechanism, and a pressure regulator 23 for adjusting the air pressure. The fuel cell module 15 is provided with a housing 24 for keeping the fuel cell module 15 at a constant temperature (300 ° C. to 600 ° C.), and a combustor 25 for burning the discharged fuel gas.

For example, methane can be used as the fuel gas 18. Methane is supplied by the blower 21 and the flow rate and pressure are adjusted in the reformer 22. As a result, a fuel gas having a temperature of about 600 ° C. containing hydrogen is generated. The fuel gas is sent to the fuel cell module 15.

Further, the air 19 is also sent by the blower 21, the pressure and the flow rate are adjusted by the pressure regulator 23, and the air 19 is sent to the fuel cell module 15. The temperature of the air is also set to about 600 ° C. by utilizing the heat of the reformer 22.

The flow rate of fuel gas and air needs to be increased to several liters / minute at the maximum output.

After that, the reformed fuel gas 18 and the heated air 19 pass through the housing 24 kept at about 500 ° C. through piping, are sent to the fuel cell module 15, and are consumed for power generation. After that, each of the consumed gases passes through a pipe, merges with the combustor 25, burns at a high temperature, and is discharged.

Although not shown, a pressure gauge and a flow meter are provided in the fuel gas and air pipes discharged from the fuel cell module 15. As a result, feedback control is performed on the reformer 22 and the pressure regulator 23, and the average pressure and flow rate in the pipe are adjusted.

Since it is difficult to maintain the temperature in the piping before the housing 24, expansion and contraction of the gas due to heat may occur before reaching the fuel cell module 15. Further, since the pipe diameter is narrowed down in the portion entering the fuel cell 1, sudden and instantaneous pressure fluctuations may occur. This tendency appears more strongly as the power generation in the fuel cell 1 is performed with higher efficiency, and the pressure fluctuation due to the temperature change becomes larger.

The pressure fluctuations of the fuel gas 18 and the air 19 are deflected by the thin film membranes (first electrodes 4a, 4b, 4c, electrolyte membranes 5a, 5b, 5c, second electrodes 6a, 6b, 6c) of the power generation element portion and the protection element portion. Causes. It should be noted that this pressure fluctuation often occurs suddenly, and it is often difficult to deal with it even if feedback control is applied to the reformer 22 and the pressure regulator 23.

In the fuel cell 1 of the first embodiment, a protective element portion having a large area is provided near the gas inlet. Further, the withstand voltage strength of the protective element portion is set lower than the withstand voltage strength of the power generation element portion. Therefore, when a sudden pressure fluctuation occurs, the protective element portion is damaged before the power generation element portion is damaged.

When the protective element portion is damaged, a gas flow path is created through the damaged protective element portion, which branches the gas flow, so that the pressure difference becomes small and the pressure fluctuation can be mitigated. Therefore, the influence on the power generation element portion is reduced, and damage to the power generation element portion can be prevented.

Note that the structure of the separator 9 prevents the fuel gas 18 and the air 19 from mixing even if the protective element portion is damaged, so that the adverse effects of gas mixing can be prevented.

As described above, according to the first embodiment, by providing the protective element portion, even when the pressure difference between the fuel gas and the oxidant gas suddenly fluctuates or increases excessively, the power generation element portion is damaged. Can be prevented. This makes it possible to provide a highly reliable and highly efficient fuel cell system.

The limit value of pressure fluctuation can be controlled by designing the opening area of the protective element portion based on the relationship between the opening area shown in FIG. 4 and the pressure resistance of the thin film membrane. When the opening area of the power generation element portion is changed, the opening area of the protective element portion can be changed accordingly.

Further, the protection element portion is damaged by monitoring the capacitance value between the first electrode and the second electrode of the protection element portion, or by monitoring the resistance value of the first electrode or the second electrode. Can be detected. When damage to the protective element is detected, the fuel cell module can be safely stopped. After the stop, only the damaged fuel cell can be replaced and power can be generated again. In this way, maintenance can be easily performed.

When a plurality of fuel cell 1s are stacked, even if one of the protective element portions is damaged, the structure of the power generation element portion is not affected. Further, in the first embodiment, since the fuel gas and the air flow separately, it is possible to continue the power generation operation.

In the first embodiment, methane is mentioned as the fuel gas, but the gas is not particularly limited as long as it can be reformed. For example, as the hydrocarbon fuel, natural gas, LP gas, coal reforming gas, lower hydrocarbon gas (ethane, ethylene, propane, butane), bioethanol and the like can be used. A vaporizer may be provided in front of the reformer 22, and the vaporizer may vaporize water from the raw material gas (or liquid) of the hydrocarbon fuel.

Although the example of the fuel cell module in which the fuel cell 1 is stacked one above the other is given, the fuel cell module may be arranged horizontally. Even in that case, the gas can flow from the bottom to the top.

<Embodiment 2>
FIG. 9 is a plan view of the fuel cell 26 according to the second embodiment of the present invention. FIG. 10 is a cross-sectional view taken along the line CC of FIG. The second electrode of the protective element portion is configured as a temperature sensor 27. The temperature sensor 27 can be wiring arranged on the second openings 8a and 8b. Unlike the first embodiment, the wiring of the temperature sensor 27 is formed only in a part of the second openings 8a and 8b.

Both ends of the wiring of the temperature sensor 27 can be arranged so that they can be connected to the outside. In the fuel cell 26, the configuration other than the protective element portion (including the configuration of the power generation element portion) can be the same as that of the first embodiment.

In the fuel cell 26 according to the second embodiment, the temperature of the protective element portion can be measured by the temperature sensor 27 formed in the protective element portion. The temperature can be measured, for example, by detecting the resistance value of the wiring of the temperature sensor 27 and converting this resistance value into the temperature of the gas. Abnormalities can be detected by monitoring the temperature of the gas. Also, by monitoring the temperature of the gas, feedback can be given to the adjustment of the pressure, flow rate, and / or temperature of the gas. As a result, stable power generation can be performed.

Since the material of the film of the protective element portion is the same as that of the first embodiment and the film structure is almost the same, the effect as a safety valve against sudden pressure fluctuations of fuel gas and the like is exhibited as in the first embodiment.

A flow rate adjusting valve may be provided at the gas inlet into each fuel cell 26 to control the temperature value measured by the temperature sensor 27 so as to be within a certain range. For example, the gas temperature can be measured in a steady state, and when the protective element portion is damaged due to a sudden pressure fluctuation, the wiring of the temperature sensor 27 is broken, so that the damage can be detected. That is, the temperature sensor 27 functions as a detection unit for detecting damage to the protective element unit. As a result, a fuel cell system capable of detecting damage to the protective element portion and performing stable power generation output is provided.

In the second embodiment, the temperature sensor 27 is provided in the protective element portion, but other sensors (for example, a pressure sensor using a piezo element, a vibration sensor, etc.) may be provided, and a plurality of sensors may be provided. May be good. Further, in the second embodiment, the wiring serving as the temperature sensor is formed as the second electrode on the upper side of the electrolyte membrane 5b and 5c, but as a modification, the first electrode 4b and 4c on the lower side of the electrolyte membrane 5b and 5c are formed. It may be formed.

<Embodiment 3>
FIG. 11 is a plan view of the fuel cell 28 according to the third embodiment of the present invention. FIG. 12 is a cross-sectional view taken along the line DD of FIG. In the fuel cell 28 according to the third embodiment, the area of one of the second openings 8a and 8b related to the protective element portion is formed to be substantially the same as the area of one first opening 7 related to the power generation element portion. ing. As a result, the area occupied by the protective element portion becomes smaller as compared with the first embodiment, and more power generation element portions can be arranged.

In the third embodiment, the film structure of the protective element portion is different from the film structure of the power generation element portion. The first electrode and the electrolyte membrane are not formed on the protective element portion. Further, a second insulating film 29 is formed in place of the second electrode, and the same temperature sensor 27 as in the second embodiment is arranged on the second insulating film 29.

The structure of the second insulating film 29 can be appropriately designed based on the relationship between the area of the opening related to the protective element portion and the membrane withstand voltage. For example, for the second insulating film 29 having various structures, the membrane withstand voltage is measured by changing the area of the opening in various ways so that the withstand voltage strength of the protective element portion is lower than the withstand voltage strength of the power generation element portion. 2 The structure of the insulating film 29 and the area of the opening can be determined.

The second insulating film 29 is preferably an insulating film having a tensile stress with respect to the Si substrate, and for example, a silicon nitride film or an aluminum nitride film can be used. Alternatively, the second insulating film 29 may be a laminated film of a film having a tensile stress with respect to the Si substrate and a film having a compressive stress with respect to the Si substrate, for example, a silicon nitride film and boron or phosphorus. It can be a laminated film with a silicon oxide film containing, or it can be a laminated film of a silicon nitride film and a P-TEOS film containing an organic component at a low temperature.

The thin film membrane pressure resistance of the second insulating film 29 can be controlled by changing the film thickness, and it is preferable that the membrane pressure resistance is lower than that of the power generation element portion. Therefore, if the membrane withstand voltage is lower than that of the power generation element portion, the area of the second openings 8a and 8b may be smaller than the area of the first opening 7 related to the power generation element portion.

As a modification of the third embodiment, the second insulating film may be formed of a thinned electrolyte film, or may be formed by leaving the first insulating film 3.

In the third embodiment, by reducing the area of the opening related to the protective element portion as compared with the first embodiment, more power generation element portions in the fuel cell 28 can be arranged, and the area of the power generation region can be increased. Can be wider. This results in higher power output.

<Embodiment 4>
FIG. 13 is a plan view of the separator 30 according to the fourth embodiment of the present invention. FIG. 14 is a cross-sectional view taken along the line EE of FIG. The separator 30 according to the fourth embodiment is composed of, for example, a ceramic substrate 31. An upper groove 32 having a gas inlet 32a and a gas discharge port 32b for fuel gas and an upper groove 33 for air gas are formed on the upper surface side of the ceramic substrate 31. A lower groove 34 having an air inlet 34a and an air discharge port 34b and a lower groove 35 for fuel gas are formed on the lower surface side of the ceramic substrate 31.

Similar to the separator 9 of the first embodiment, the external dimensions of the separator 30 are almost the same as those of the fuel cell 1. In the present embodiment, the upper groove 32 of the separator 30 extends to a range including the entire first opening 7 of the fuel cell 1 and the entire second opening 8a when viewed from above. Therefore, when the fuel cell 1 is arranged above and below the separator 30 (for example, as will be described later in relation to FIG. 15), the first fuel cell 1 of the upper fuel cell 1 is passed through the upper groove 32. Gas spreads to the electrode 4a and the first electrode 4b of the upper fuel cell 1.

Similarly, in the present embodiment, the lower groove 34 of the separator 30 extends to a range including the entire first opening 7 of the fuel cell 1 and the entire second opening 8b when viewed from above. There is. Therefore, when the fuel cell 1 is arranged above and below the separator 30, the second electrode 6a of the lower fuel cell 1 and the lower fuel cell 1 pass through the lower groove 34. Gas spreads to the second electrode 6c.

As shown in FIG. 14, the separator 30 does not have a through hole that penetrates the ceramic substrate 31 up and down, unlike the separator 9 according to the first embodiment. Grooves for supplying fuel gas and air are formed on the upper surface side and the lower surface side of the ceramic substrate 31, respectively. Therefore, each gas is separated and sent to the fuel cell 1.

FIG. 15 is a cross-sectional view of the fuel cell module 40 according to the fourth embodiment. In the fuel cell module 40, two fuel cell cells 1 are stacked. The separator 30 is laminated between the two fuel cell 1s. An upper substrate 17 and a lower substrate 16 having a gas flow path are provided at the upper end and the lower end of the fuel cell module 40, respectively. The lower substrate 16 and the upper substrate 17 have the same configuration as that of the first embodiment.

In this structure, the fuel gas is divided into a fuel gas 36 and a fuel gas 37. The fuel gas 36 is supplied to the first electrodes 4a and 4b via the plurality of first openings 7 and the second openings 8a. The fuel gas 37 is supplied to the second electrode 6b of the protective element portion.

Air is divided into air 38 and air 39. The air 38 is sent to the second electrode 6a of the power generation element portion and the second electrode 6c of the protection element portion. The air 39 is sent to the first electrode 4c of the protective element portion through the second opening 8b.

Therefore, the fuel gas 36 and the air 38 are sent to the power generation element unit to generate electricity. On the other hand, the fuel gas 36 and the fuel gas 37 are sent to the protective element portion, or the air 38 and the air 39 are sent to the protective element portion.

In the fourth embodiment, since the separator 30 does not have a through hole, even if the protection element portion is damaged due to a sudden pressure fluctuation of fuel gas or air, the broken pieces of the protection element portion are further protected in the vertical direction. It does not scatter to the element part. Therefore, damage to one fuel cell does not affect the other fuel cells. Therefore, a highly reliable fuel cell system can be provided.

If the protective element portion is damaged, it is preferable to control the pressure of the fuel gas 37 to be slightly lower than the pressure of the fuel gas 36 so that the debris does not scatter to the power generation element portion. Similarly, for air, it is preferable to control the pressure of the air 39 to be slightly lower than the pressure of the air 38.

<About other modifications>
The present invention is not limited to the above-described embodiments and modifications thereof, and includes various other modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1, 26, 28 ... Fuel cell 2 ... Semiconductor substrate 3 ... First insulating film 4a, 4b, 4c ... First electrode (conductive film)
5a, 5b, 5c ... Electrolyte film 6a, 6b, 6c ... Second electrode (conductive film)
7 ... 1st opening 8a, 8b ... 2nd opening 9,30 ... Separator 10, 31 ... Ceramic substrate 11, 32, 33 ... Upper groove 11a, 32a ... Gas inlet 11b, 32b ... Gas outlet 12, 14 ... Through holes 13a, 34a ... Air inlet 13b, 34b ... Air outlets 13, 34, 35 ... Lower grooves 15, 40 ... Fuel cell module 16 ... Lower substrate 17 ... Upper substrate 18, 36, 37 ... Fuel gas 19 , 38, 39 ... Air (oxidizing agent gas)
21 ... Blower 22 ... Reformer 23 ... Pressure regulator 24 ... Housing 25 ... Combustor 27 ... Temperature sensor (detector)
29 ... Second insulating film

Claims (10)

A power generation element unit formed by laminating an electrolyte membrane and one or more conductive films and supplied with a fuel gas and an oxidant gas to generate power.
A protective element portion on which a protective film is formed and only one of the fuel gas or the oxidant gas is supplied.
Equipped with
A fuel cell cell characterized in that the withstand voltage of the protection element is lower than the withstand strength of the power generation element. The fuel cell according to claim 1, wherein the protective element unit further includes a detection unit that detects damage to the protective element unit. The fuel cell according to claim 1, wherein the power generation element portion and the protection element portion are formed on the same substrate. The power generation element portion and the protection element portion are formed in a plurality of openings in the substrate, and the power generation element portion and the protection element portion are formed in a plurality of openings in the substrate.
The area of one opening related to the protective element portion is larger than the area of one opening related to the power generation element portion.
The fuel cell according to claim 1. The power generation element portion is formed in a plurality of openings in the substrate and is formed.
The power generation element portion includes a plurality of the conductive films, and has a plurality of the conductive films.
At least one of the conductive films is continuous across the plurality of openings.
The fuel cell according to claim 1. The protective element portion is provided with a conductive film and has a conductive film.
One of the conductive films of the power generation element portion and the conductive film of the protective element portion are continuous.
The fuel cell according to claim 1. The fuel cell according to claim 1, wherein the power generation element portion and the protection element portion have the same film configuration. The fuel cell according to claim 1, wherein the protective element unit does not generate electricity. The fuel cell according to claim 1 and the fuel cell.
A fuel cell module arranged in the fuel cell and comprising a separator for separating the fuel gas and the oxidant gas. The separator has a through hole at a position corresponding to the protective element portion.
9. The fuel cell module according to claim 9.

Images