JPH11329465A - Separator for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a fuel cell, advantageous for reducing variations of generated voltage. SOLUTION: Recessed gas passages 30A are formed in a separator 5 for allowing gas including an active material to flow therethrough. The surface roughness of bottom surfaces of the gas passages 30 is 1 μm or less in Rz. The gas passages 30 can be formed. for example, by electrochemical machining. With respect to this separator 5. it is stipulated that the surface roughness of the bottom surfaces of the recessed gas passages 30 should be an extremely small value. This is advantageous for smoothing and uniforming the flow of the gas including the active material and flowing through the gas passage 30. Especially in the event that the depth of the recessed gas passages 30 is small and that gas passage resistance is susceptible to the surface roughness, this is advantageous for smoothing and uniforming the gas flow through the gas passages 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell separator having a gas passage.

[0002]

2. Description of the Related Art There has been provided a fuel cell which supplies fuel gas to generate power. 2. Description of the Related Art A fuel cell is generally configured by stacking a separator for partitioning a gas containing an active material together with a battery cell. By the way, in the industry, conventionally, a metal plate is machined by a cutting tool to cut a groove-shaped gas passage, a separator is formed by pressing a metal plate to form a groove-shaped gas passage, and a metal plate is bent. 2. Description of the Related Art A separator in which a groove-shaped gas passage is dug by performing an etching process is known. A separator having a gas passage formed by etching is disclosed in Japanese Patent Application Laid-Open No. Hei 4-26706.

[0003]

In order to further improve the performance of the fuel cell, it is preferable to reduce the variation in power generation and voltage for each battery cell. Factors of this variation include non-uniform catalyst activity of each electrode, non-uniform contact electric resistance, insufficient control of temperature distribution, and the like. Various improvements have been made, but further development is required. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a fuel cell separator which is advantageous for reducing power generation and voltage variations of each battery cell.

[0005]

Means for Solving the Problems The present inventor has made intensive developments to achieve the above-mentioned objects. Then, the surface roughness of the concave gas passage of the separator is extremely small, that is, Rz
If it is specified to be 1 μm or less, it is advantageous for smoothing and uniforming the flow of the gas containing the active material flowing in the gas passage, and is advantageous for reducing power generation and voltage variation for each battery cell. The present inventors have found out.

In particular, when the depth of the concave gas passage is shallow (for example, 2 mm or less, 10 mm or less), the surface roughness of the bottom surface of the gas passage greatly affects the gas flow, and the surface roughness of the bottom surface of the gas passage. If Rz is defined as 1 μm or less,
The present inventor has found that the flow of the gas containing the active material can be further smoothed and uniformed, and it is advantageous to reduce power generation and voltage variation for each battery cell. Based on this, the separator of the present invention was completed.

By the way, in a separator in which a groove-shaped gas passage is cut by machining with a cutting tool, the surface roughness of the gas passage is large. In a separator in which a groove-shaped gas passage is bent by press working, minute unevenness is likely to be generated under the influence of buckling based on compressive stress and elongation deformation based on tensile stress during bending of the press. In a separator in which a groove-shaped gas passage is dug by performing an etching process, etch pits are easily generated, which is a factor of increasing the surface roughness.

The separator of the present invention is a separator for a fuel cell having a concave gas passage through which a gas containing an active material flows. The surface roughness of the bottom surface of the gas passage is 1 μm in Rz.
m or less. ADVANTAGE OF THE INVENTION According to the separator of this invention, the flow of the gas containing an active material is smoothed.

[0009]

According to the separator of the present invention, the bottom surface of the concave gas passage has a surface roughness Rz of 1 μm or less. In this case, the average value is obtained by measuring the bottom of the gas passage at a plurality of locations. This is because the measurement distance by the surface roughness meter is not so long. According to one aspect of the separator of the present invention, the surface roughness of the bottom surface of the concave gas passage is Rz of 0.8.
μm or less, and 0.5 μm or less. Furthermore, Rz is set to 0.
4 μm or less, 0.3 μm or less, sometimes 0.2 μm
m or less.

[0010] The surface roughness of the bottom surface of the gas passage is Ra of 0.1.
It can be 2 μm or less. Ra can be 0.1 μm or less. According to Rmax, the thickness can be reduced to 2 μm or less, 1 μm or less, 0.8 μm or less, and 0.6 μm or less. These are based on JIS standards, and Ra means center line average roughness, Rmax means maximum height, and Rz means 10 point average roughness.

The depth of the gas passage can be selected according to the type of the fuel cell. For example, the upper limit of the depth of the gas passage is 0.1.
3 mm, 0.5 mm. 0.6mm, 1mm, 3mm, 5
mm, 1 cm, 5 cm or more or less. The lower limit of the depth of the gas passage is 0.05 m
m, 0.1 mm. 0.2mm, 0.5mm, 1mm, 3
mm, 5 mm, 1 cm, or more or less.

As described above, extremely smooth surface roughness
Electrochemical machining is a typical method for premising industrial mass production, which requires cost reduction. Alternatively, electrolytic polishing after rough processing of the gas passage, or composite electrolytic polishing using an extremely fine abrasive may be employed. According to the separator of the present invention, the groove width of the gas passage can be appropriately selected and can be, for example, 0.1 to 5 mm, but is not limited thereto.

In one embodiment of the separator of the present invention, the imaginary line extending along the side of the gas passage can be substantially upright with respect to the surface of the separator. The separator of the present invention can be mainly composed of a non-press-formed metal member. With a non-press molded product, springback can be reduced or avoided, and dimensional change due to springback can be suppressed.

In one embodiment of the separator of the present invention, the separator can be formed by covering the outer edge of a metal member having a gas passage with an elastic coating layer such as rubber or resin. The metal member is generally in the form of a plate and can be made of carbon steel, stainless steel, aluminum, titanium, copper, or the like, but is not limited thereto. The stainless steel system may be an austenitic system, a ferrite system, or a martensitic system.

According to one aspect of the separator of the present invention, the depth of the bottom surface of the gas passage can be changed according to the location of the gas passage. For example, a gas passage having a gradation on the bottom surface and a gas passage having a plurality of depths may be employed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The separator of the present embodiment, together with its manufacturing method, will be described below with reference to the drawings. First, the electrolytic processing apparatus 1 will be described with reference to FIG. Electrolytic processing equipment 1
Is a processing tank 11 in which the electrolyte 10 is stored, and a processing tank 11
A base 12 disposed at the bottom of the base 12 and having an installation surface 12a, an elevating head 13 that can move up and down with respect to the base 12, a driving source 14 that moves the elevating head 13 up and down, a control unit 15 that controls the driving source 14, An electrolytic solution including a processing electrode 16 detachably mounted on the head 13, a processing power supply 17 (DC power supply), a current control unit 18, and an ejection unit 19 having an ejection port 19 a for ejecting the electrolyte 10. Reference numeral 10 denotes a sodium nitrate solution (concentration: 40% by weight). The base 12 is connected to the anode side. The processing electrode 16 is connected to the cathode side. The electrode protrusion 2 having a pattern shape substantially corresponding to the pattern shape of the gas passage 30 is formed on the machining electrode 16.
0 is formed. The tip surface 20c of the electrode projection 20 is coated with a conductive plating film 21 (platinum) for improving corrosion resistance. As schematically shown in FIG.
The ceiling surface 16a of the processing electrode 16, the side surface 20 of the electrode projection 20
a is coated with a masking film 22 (thickness: 3 to 10 μm). The masking film 22 has electric insulation and durability to the electrolyte 10. Therefore, in the processing electrode 16, current flows intensively on the front end surface 20 c of the electrode projection 20.

In this embodiment, a conductive plate 3 (thickness: 1 mm) made of austenitic stainless steel (JIS-SUS304) is used as a conductive member. A portion of the surface 3s of the conductive plate 3 other than the portion serving as the gas passage 30 is covered with a masking film 23. In addition, as in the example schematically shown in FIG.
a, masking film 22 on side surface 20a of electrode projection 20
, But a masking film is applied to the surface 3 of the conductive plate 3.
It is also possible to adopt a method in which s is not coated.

In the electrolytic processing, the conductive plate 3
Is set on the installation surface 12a of the base 12 on the anode side.
In this case, the conductive plate 3 is brought into close contact with the base 12. The conductive plate 3 serves as an anode. In this state, the entire conductive plate 3 is immersed in the electrolyte 10. Then, in a state where the conductive plate 3 and the processing electrode 16 are opposed to each other, the height position of the processing electrode 16 is gradually lowered under precise control so as to keep a gap of 0.2 to 0.3 mm. Conductive plate 3 and processing electrode 1
6 is approaching, but non-contact. Electric power is supplied between the conductive plate 3 and the processing electrode 16 to elute a portion of the conductive plate 3 on the anode side, which becomes the gas passage 30, to perform electrolytic processing. Gas passage 30 (depth: 0.4 mm) having a pattern shape corresponding to electrode projection 20 of processing electrode 16 by electrolytic processing
Is formed. FIG. 2 schematically shows the shape of the gas passage 30 inferred. The gas passage 30 has a bottom surface 30e and a side surface 30f.

In this embodiment, the electrolytic solution 1
The temperature of 0 was about 20 ° C., and a pulse current I having a current density of 40 A / cm ² or more was passed. The pulse current I has a pulse-like waveform having a peak I _m (20 msec) and a valley I _v (5 sec). When the mountain portion I _m of the pulse waveform, the current density was about 40A / cm ^2. At the time of the valley,
No current is being supplied substantially. At Tanibe I _v ,
An electrolytic solution 10 is ejected from the ejecting portion 19, thereby performing a removing operation for removing an electrolytic product. In this embodiment, if necessary, the processing electrode 16 can be appropriately raised so as to increase the gap between the conductive plate 3 and the processing electrode 16 in order to improve the removal of the electrolytic product. The removal operation may be performed at the time of the crest I _m.

According to this embodiment, the masking film 2 is formed on the ceiling surface 16a of the processing electrode 16 and the side surface 20a of the electrode projection 20.
2 is covered, so that the electrode protrusion 20 of the processing electrode 16 is formed.
Since the electrolytic current concentrates on the tip surface 20c of the gas passage 3, the gas passage 3
0 is formed well. Therefore, the processing accuracy of the gas passage 30 is ensured. In addition, the masking film 2 is formed on the surface 3s of the conductive plate 3 other than the portion serving as the gas passage 30.
3, the processing accuracy of the gas passage 30 is further ensured. After the completion of the electrolytic processing, the conductive plate 3 is detached from the processing tank 11 and washed with a cleaning liquid.

According to this embodiment described above, the bottom surface 30e of the gas passage 30 is extremely smoothed, and the variation in the passage resistance of the gas containing the active material can be reduced. In particular, even when the depth of the gas passage 30 is very shallow (0.4 mm) as in this embodiment, the bottom surface 30e of the gas passage 30
Is smoothed, the variation in gas passage resistance in the gas passage 30 can be reduced.

As a result, according to the present embodiment, the gas passage 30
In this case, the gas flow in the fuel cell can be made smooth and uniform, which is advantageous for reducing power generation and voltage variation in each battery cell, and is advantageous for improving the performance of the fuel cell. Moreover, according to the present embodiment, it is possible to suppress the formation of a deteriorated layer, a residual stress layer, or a work hardened layer, which is easily generated by the mechanical polishing method, on the bottom surface 30e. Further, intergranular corrosion due to surface pits is suppressed, and the corrosion resistance in the gas passage 30 is improved.

As a result, according to this embodiment, the gas passage 30
This is more advantageous for smoothing and equalizing the gas flow of the fuel cell, and can further reduce the variation in power generation and voltage in each battery cell, which is advantageous for improving the performance of the fuel cell. According to a test by the inventor, the surface roughness Rz of the bottom surface 30e of the gas passage 30 was extremely small at 1 μm or less. According to the test by the inventor, it was confirmed that the surface roughness Rz of the bottom surface 30 e of the gas passage 30 was reduced by one digit with respect to the surface roughness Rz of the processing electrode 16.

The surface roughness will be further described. That is, when the gas passage 30 was formed in the conductive plate 3 by electrolytic processing, a test for measuring the surface roughness of the bottom surface 30 e of the gas passage 30 was performed. In this test, the surface roughness of the processed electrode 16 was 3.2 μm in Rz, the conductive plate 3 was made of austenitic stainless steel, and the target depth of the gas passage 30 was 0.4 mm to correspond to the current product. . The test results are shown in FIG. The vertical axis in FIG. 4 indicates the surface roughness, and the horizontal axis indicates the distance. As shown in FIG. 4, the characteristic line indicating the surface roughness was flat and smooth. The surface roughness was extremely small, Ra = 0.0861 μm, and Rmax = 0.5320.
μm, Rz = 0.3000 μm. The bottom surface 30e of the gas passage 30 formed by the electrolytic processing in this way was extremely smooth, had a very small surface roughness, and was about 1/10 of the surface roughness of the processing electrode 16.

As a comparative example, a gas passage having the same depth was formed by etching using the same kind of conductive plate. A test for measuring the surface roughness was also performed on the comparative example. The test results are shown in FIG. The vertical axis in FIG. 5 indicates the surface roughness, and the horizontal axis indicates the distance. As shown in FIG. 5, the characteristic line indicating the surface roughness characteristic had large irregularities. The surface roughness is considerably larger than that of electrolytic processing, and Ra = 0.48.
65 μm, Rmax = 3.8160 μm, Rz = 2.84
It was 40 μm.

Based on the above test results, the ratio of Ra by electrolytic processing and Ra by etching is 0.08
61 μm / 0.4865 μm ≒ 0.18 (about 18%). Rmax by electrolytic processing and R by etching
The ratio to max is 0.5320 μm / 3.881610.
μm ≒ 0.14 (about 14%). The ratio of Rz by electrolytic processing to Rz by etching is 0.3000
μm / 2.8440 μm ≒ 0.11 (about 11%). Based on the above test, the surface roughness due to electrolytic processing is 10-20% as compared to the surface roughness due to etching.
It turned out that it becomes extremely small.

In addition, according to the present embodiment, as described above, not only can the surface roughness of the gas passage 30 formed in the conductive plate 3 be reduced, but also it is advantageous in suppressing variations in the depth of the gas passage 30. It is. According to tests by the inventor,
When the target depth dimension of the gas passage 30 is 0.4 mm, the variation in the depth of the gas passage 30 can be reduced with a high accuracy of ± 0.005 mm, that is, 1.25%. For this reason, even in a fuel cell in which a large number of battery cells are stacked, it is possible to reduce the variation in the gas flow including the active material in each battery cell. Therefore, variations in power generation and voltage in each battery cell can be reduced, which is further advantageous in improving the performance of the fuel cell.

Further, according to the present embodiment, the groove width dimension of the gas passage 30 can be made highly accurate. For example, when the target groove width of the gas passage 30 is 1.2 mm, 1.2 mm plus or minus 0.1 mm.
005 mm. Furthermore, according to the present embodiment, FIG.
As schematically shown in FIG. 2, the virtual line PW extending along the side surface 30f of the gas passage 30 is substantially in an upright state with respect to the surface 3s of the conductive plate 30. Therefore, it is advantageous to secure the conductive area SA by the surface 3s of the conductive plate 30 while securing the passage cross-sectional area of the gas passage 30.

The upright form of the side surface 30f is such that the ceiling surface 16a of the processing electrode 16 and the side surface 20a of the electrode projection 20
Based on the fact that the electrically insulating masking film 22 is coated, and that the conductive plate 3 is covered with the electrically insulating masking film 23 on portions other than the portions that will become the gas passages 30, etc. Can be achieved. By the way, when the gas passage 30 is formed by press molding, the press die is worn, and therefore, there is a problem that the depth of the gas passage 30 varies due to the wear. However, according to this embodiment, a high mechanical load does not act on the processing electrode 16 and the processing electrode 1
6 can be suppressed, the electrode projections 20 of the processing electrode 16
Can be used for a long time. For example, it can be used semi-permanently. Also in this sense, it is advantageous to suppress the variation in the depth of the gas passage 30.

When cutting the gas passage 30 by machining, the gas passage 30 having a complicated pattern shape cannot be formed at once, and the gas passage 30 having a complicated pattern shape is formed little by little. Becomes longer. However, according to the present embodiment in which the electrolytic processing is performed, even if the gas passage 30 has a complicated pattern shape, the entire gas passage 30 is formed by the processing electrode 16 having the electrode projection 20 corresponding to the pattern shape of the gas passage 30. Can be formed at the same time, which is advantageous in shortening the time for processing the gas passage 30 and can contribute to improvement in productivity. In the electrolytic processing, the processing speed is affected by the current value. Therefore, if the current value is increased, it is more advantageous to shorten the time for forming the gas passage 30. According to the test by the present inventor, when forming the gas passage 30 having a depth of 0.4 mm on the flat conductive plate 3 of 200 mm × 200 mm, when the above-described pulse current was supplied,
The required time per sheet was as short as several minutes.

In addition, according to the present embodiment, even when the depth of the gas passage 30 differs depending on the position of the gas passage 30, for example, the gas passage 30 may have a plurality of depths. Alternatively, even when the gas passage 30 has a gradient that is inclined, with a small number of electrolytic machining operations,
Normally, the gas passage 30 having a complicated pattern shape can be formed by one electrolytic processing operation, so that productivity can be improved.

(Application Example) FIG. 6 shows a plan view of a separator formed from the above-described conductive plate 3. This separator 5
Is formed by covering the above-described conductive plate 3 with a rubber layer 50 as an elastic layer having a seal projection 50r. In the separator 5, a fuel gas inlet 51 penetrating in the thickness direction,
Fuel gas outlets 52 are formed at diagonal positions. Furthermore,
An air inlet 53 and an air outlet 54 penetrating in the thickness direction are formed at diagonal positions. Further, a cooling medium passage 55 and a cooling medium passage 56 penetrating in the thickness direction are formed at diagonal positions. The fuel gas introduced from the fuel gas inlet 51 is
Basically, arrows K1, K2, K
The fuel gas flows toward the fuel gas outlet 52 along the directions of 3, K4, and K5.

FIG. 7 is a view taken in the direction of arrows W7-W7 in FIG. FIG.
Indicates the view from the arrow W8-W8 when assembled. FIG.
As shown in (1), a battery cell 6 is constituted by sandwiching a positive electrode 61 and a negative electrode 62 on a solid electrolyte membrane 60 made of a polymer material having proton permeability. The separators 5 are stacked on both sides of the battery cell 6. A positive electrode chamber 61c facing the positive electrode 61 is formed, and a negative electrode chamber 62c facing the negative electrode 62 is formed. A gas (hydrogen-containing gas) containing a negative electrode active material flows through the negative electrode chamber 62c. A gas (air) containing a positive electrode active material flows through the positive electrode chamber 61c. Such a large number of battery cells 6 and the separator 5 are stacked to form a fuel cell.

The gas passage 30w on the inlet side directly connected to the fuel gas inlet 51 has a greater depth than the other gas passages 30. The outlet gas passage 30 x directly connected to the fuel gas outlet 52 has a greater depth than the other gas passages 30. Therefore, as shown in FIG. 9, the gas passage 30 on the inlet side of the machining electrode 16 for performing electrolytic machining.
w, the protrusion amount H of the electrode protrusion 20r for forming 30x.
2 is larger than the protrusion amount H1 of the other electrode protrusions 20. This enables two-step digging.

In this application example, the depth of the gas passage 30 may be as shown in FIG. 10 or as shown in FIG.
1 or the embodiment shown in FIG. 12 or the embodiment shown in FIG. 10 to 13, the characteristic lines S1, S2, S
3, S4 indicates the depth of the gas passage 30, and the characteristic lines M1, M
2, M3 and M4 mean the protruding amounts of the electrode protrusions 20 of the processing electrode 16.

In the embodiment shown in FIG. 10, even if the position of the gas passage 30 changes as shown by the characteristic line S1, the gas passage 3
The depth of the bottom of 0 is the same. In this case, the characteristic line M
As shown in FIG. 1, even when the position of the gas passage 30 changes, the amount of protrusion of the electrode projection 20 of the processing electrode 16 is the same. FIG.
In the embodiment shown in FIG. 1, gradation is formed on the bottom surface 30e of the gas passage 30, as shown by the characteristic line S1.
In this embodiment, the fuel gas inlet 51 and the fuel gas outlet 52
The arrows K1, K2, K3, K4
A gradation is formed along the direction of K5, in other words, such that the depth of the bottom surface 30e of the gas passage 30 gradually decreases from the upstream side to the downstream side of the gas flow.
That is, as can be understood from the characteristic line S2 in FIG.
Positions a ₁ , a ₂ , a ₃ → positions b ₁ , b ₂ , b ₃ → positions c ₁ ,
c ₂ , c ₃ → positions d ₁ , d ₂ , d ₃ → positions e ₁ , e ₂ , e ₃ → positions f ₁ , f ₂ , f ₃ The depth of the bottom surface 30 e of the gas passage 30 decreases in this order. .

In this case, the electrode projection 2 of the machining electrode 16
A gradation is formed at a protrusion amount of 0. That is, as can be understood from the characteristic line M2 in FIG.
₁ , a ₂ , a ₃ → positions b ₁ , b ₂ , b ₃ → positions c ₁ , c ₂ , c ₃
→ position d ₁ , d ₂ , d ₃ → position e ₁ , e ₂ , e ₃ → position f ₁ ,
In the order of f ₂ and f ₃ , the projection amount of the electrode projection 20 of the processing electrode 16 decreases.

In the embodiment shown in FIG. 12, gradation is formed on the bottom surface 30e of the gas passage 30, as shown by the characteristic line S3. In this embodiment, as going from the fuel gas inlet 51 to the fuel gas outlet 52, the arrows K1, K
The gradation is formed such that the depth of the bottom surface 30e of the gas passage 30 gradually increases from the upstream side to the downstream side of the gas flow along the directions of K2, K3, K4, and K5. That is, as can be understood from the characteristic line S3 in FIG. 12, the positions a ₁ , a ₂ , a ₃ → the positions b ₁ , b ₂ ,
b ₃ → positions c ₁ , c ₂ , c ₃ → positions d ₁ , d ₂ , d ₃ → positions e ₁ , e ₂ , e ₃ → positions f ₁ , f ₂ , f ₃ in that order.
0 becomes deeper.

In this case, the electrode projection 2 of the machining electrode 16
A gradation is formed at a protrusion amount of 0. That is, as can be understood from the characteristic line M3 in FIG.
₁ , a ₂ , a ₃ → positions b ₁ , b ₂ , b ₃ → positions c ₁ , c ₂ , c ₃
→ position d ₁ , d ₂ , d ₃ → position e ₁ , e ₂ , e ₃ → position f ₁ ,
The protrusion amount of the electrode projection 20 of the processing electrode 16 increases in the order of f ₂ and f ₃ .

In the embodiment shown in FIG. 13, a shallow portion is partially formed in the gas passage 30 as shown by the characteristic line S4. In this case, as shown by the characteristic line M4, the protrusion amount of the electrode protrusion 20 of the processing electrode 16 corresponding to the shallow portion of the gas passage 30 is made smaller than the other protrusion amounts. Unlike the etching process, according to the electrolytic process, the processed electrode 16
By changing the projection amount of the electrode projection 20 according to the position of the gas passage 30, the depth of the gas passage 30 can be easily changed in various modes as described above.

Incidentally, the gas containing the active material is supplied to the gas passage 3.
It is considered that the active material is consumed more on the downstream side than on the upstream side as it flows through 0, so that the concentration of the active material tends to decrease. In this regard, as shown in FIG. 11, by forming a gradation in which the gas passage 30 becomes shallower toward the downstream as shown in FIG. 11, an effect corresponding to a decrease in the concentration of the active material in the gas flowing through the gas passage 30 can be expected. Further, products may be generated in the gas passage 30. For example, when the gas passage 30 is a passage for flowing air, the gas passage 3
Water may be generated at zero, which may increase the downstream passage volume. In this regard, by forming a gradation in which the gas passage 30 becomes deeper toward the downstream as shown in FIG. 12, the downstream passage volume can be increased without changing the width of the gas passage 30.

Further, in the embodiment shown in FIG.
Therefore, it is possible to expect a change in the flow velocity due to a decrease in the cross-sectional area of the passage, and thus it is possible to expect the discharge of the product from the gas passage 30.

[0043]

According to the separator of the present invention, the surface roughness of the bottom surface of the concave gas passage is set to an extremely small value. Therefore, it is advantageous for smoothing and uniforming the flow of the gas containing the active material flowing through the gas passage. In particular, even when the depth of the concave gas passage is small and the gas passage resistance is easily affected by the surface roughness, it is advantageous for smoothing and uniforming the gas flow in the gas passage.

Therefore, according to the separator of the present invention, it is advantageous to reduce variations in power generation and voltage in each battery cell, and can contribute to improvement in performance of a fuel cell. Further, since the gas passage is smooth, improvement of corrosion resistance in the gas passage can be expected. Also in this sense, it is advantageous for smoothing and uniforming the gas flow.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a state in which a gas passage is formed in a conductive plate serving as a separator.

FIG. 2 is an enlarged view near a gas passage.

FIG. 3 is an enlarged view of the vicinity of another gas passage.

FIG. 4 is a graph showing a surface roughness of a bottom surface of a gas passage.

FIG. 5 is a graph showing the surface roughness of the bottom surface of a gas passage as a comparative example.

FIG. 6 is a plan view of a separator according to an application example.

FIG. 7 is an arrow view along the line W7-W7 in FIG. 6;

FIG. 8 is an arrow view along the line W8-W8 in FIG. 6;

9 is a cross-sectional view of a main part schematically showing a state in which the vicinity of a gas passage shown in FIG. 6 is formed.

FIG. 10 is a graph showing a mode of a depth of a gas passage and a projection amount of an electrode projection.

FIG. 11 is a graph showing another aspect of the depth of the gas passage and the amount of protrusion of the electrode protrusion.

FIG. 12 is a graph showing another aspect of the depth of the gas passage and the amount of protrusion of the electrode protrusion.

FIG. 13 is a graph showing another aspect of the depth of the gas passage and the projection amount of the electrode projection.

[Explanation of symbols]

In the figure, 3 is a conductive plate, 30 is a gas passage, 30e is a bottom surface of the gas passage, 30f is a side surface of the gas passage, and 5 is a separator.

Claims (4)

[Claims] 1. A fuel cell separator having a concave gas passage through which a gas containing an active material flows, wherein the surface roughness of the bottom surface of the gas passage is 1 μm or less in Rz. Battery separator. 2. The fuel cell separator according to claim 1, wherein the surface roughness of the bottom surface of the gas passage is 0.5 μm or less in Rz. 3. The fuel cell separator according to claim 1, wherein the surface roughness of the bottom surface of the gas passage is 0.2 μm or less in Ra. 4. The separator according to claim 1, wherein the imaginary line extending along the side surface of the gas passage is substantially upright with respect to the surface of the separator. Fuel cell separator.