Fuel cell stack

Abstract

The challenge is to obtain the required drainage capacity without increasing the size of the fuel cell stack. [Solution] The dry-side end unit 18 has a connecting pipe 80 with both ends open that forms an exhaust water flow path extending in the same direction as the exhaust gas flow path PA2, and a second engaging portion 94 formed on the dry-side end unit 18 with which the end portion 82B of the connecting pipe 80 engages. The dry-side end unit 18 has a shoulder portion 88 in the lower bottom portion of the exhaust gas flow path PA2, which has a first surface 89 facing the upstream open end 83 of the connecting pipe 80 and an upward-facing second surface 90 extending from the upper edge of the first surface 89. The portion 88 has a notch 92 that opens across the first surface 89 and the second surface 90, and the internal passage 85 of the connecting pipe 80 communicates with the exhaust gas flow path PA2 via the notch 92.

Description

Technical Field

[0006] , , , , , , , ,

[0001] The present invention relates to a fuel cell stack.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable and advanced energy, research and development on fuel cells that contribute to energy efficiency have been carried out.

[0003] In order to discharge the generated water that is secondarily generated by the electrochemical reaction of the reaction gas in the fuel cell stack to the outside of the fuel cell stack, a communication pipe for guiding the discharge of the generated water is arranged in the exhaust gas passage of the reaction gas of the fuel cell stack. A fuel cell stack is known (for example, Patent Documents 1 and 2).

[0004] The communication pipe extends in the stacking direction of a plurality of power generation cells provided in the fuel cell stack, and one end side thereof is inserted into an engagement hole provided in an end unit arranged at an end of the fuel cell stack, thereby being supported by the end unit. By this support, positioning of the communication pipe with respect to the end unit in the stacking direction and in a direction orthogonal to the stacking direction is performed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional technology described above, the other end of the engagement hole needs to be open to the exhaust gas passage for the reaction gas in order to introduce the generated water into the connecting pipe. As a result, the length of the connecting pipe in the stacking direction of the end unit of the support part of the connecting pipe becomes longer, and the end unit becomes larger. The increase in the size of the end unit leads to an increase in the overall size of the fuel cell stack, hindering the miniaturization of the fuel cell stack.

[0007] In response to this, one possible solution is to abut the end face of the connecting pipe against the wall surface of the vertical wall provided at the end of the exhaust gas passage that constitutes the end unit.

[0008] In this case, the length of the connecting pipes in the stacking direction of the end units does not increase, but a portion of the connecting pipes is blocked by the end faces due to abutment against the end faces. As a result, the effective passage area of ​​the connecting pipes decreases, and the discharge capacity of the generated water is reduced.

[0009] In view of the above background, the present invention aims to achieve the required drainage capacity without increasing the size of the fuel cell stack. This will ultimately contribute to energy efficiency. [Means for solving the problem]

[0010] To solve the above problems, one aspect of the present invention provides a fuel cell stack comprising a cell stack formed by stacking a plurality of power generation cells including an electrolyte membrane in a predetermined direction, and a first end unit and a second end unit respectively arranged at both ends of the cell stack in the stacking direction, wherein the cell stack is provided with an exhaust gas channel extending in the stacking direction of the cell stack for discharging reaction gas supplied to the power generation cells from the power generation cells, and having open ends arranged in the exhaust gas channel and forming an exhaust product water channel extending in the same direction as the extension direction of the exhaust gas channel. The device comprises a connecting pipe, a first engaging portion formed on the first end unit with one end of the connecting pipe engaging, and a second engaging portion formed on the second end unit with the other end of the connecting pipe engaging. The first end unit has a shoulder portion in the lower bottom portion of the exhaust gas flow path, which has a first surface facing the upstream opening of the connecting pipe and an upward-facing second surface extending from the upper edge of the first surface. The shoulder portion has a notch that opens across the first and second surfaces, and the internal passage of the connecting pipe communicates with the exhaust gas flow path through the notch. [Effects of the Invention]

[0011] According to the present invention, the required drainage capacity can be obtained without increasing the size of the fuel cell stack. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic perspective view showing the overall configuration of the fuel cell stack according to this embodiment. [Figure 2] Longitudinal cross-sectional view of the fuel cell stack according to this embodiment [Figure 3] Enlarged longitudinal cross-sectional view of the main part of the fuel cell stack according to this embodiment. [Figure 4] Perspective view of the main part of the fuel cell stack according to this embodiment. [Figure 5] An explanatory diagram showing the groove shape of the notch in the fuel cell stack according to this embodiment. [Figure 6] Enlarged longitudinal cross-sectional view of the main part of a fuel cell stack according to another embodiment. [Modes for carrying out the invention]

[0013] An embodiment of the fuel cell stack 10 will be described below with reference to the drawings. In the following description, the three orthogonal axes of the front-rear direction, left-right direction, and up-down direction will be defined as shown in the figures.

[0014] First, the overall structure of the fuel cell stack 10 will be described with reference to Figure 1. The fuel cell stack 10 has a cell stack 14 formed by stacking a plurality of power generation cells 12 in the front-to-back direction (a predetermined direction), a wet-side end unit 16 (first end unit) located at one end of the cell stack 14 in the stacking direction, and a dry-side end unit 18 (second end unit) located at the other end of the cell stack 14 in the stacking direction. The cell stack 14, the wet-side end unit 16, and the dry-side end unit 18 are fastened to each other in the stacking direction by fastening members (not shown) and housed in a stack case (not shown).

[0015] The fuel cell stack 10 is supplied with hydrogen gas (fuel gas) and oxidizer gas (air) as reaction gases.

[0016] In the following explanation, the stacking direction of the cell stack 14 may be referred to as the front-to-back direction.

[0017] Each cell stack 14 includes a rectangular plate-shaped electrolyte membrane / electrode structure 20, a first separator 24 positioned on one side of the electrolyte membrane / electrode structure 20, and a second separator 26 positioned on the other side of the electrolyte membrane / electrode structure 20. On the left edge of each power generation cell 12, a hydrogen gas supply opening 30, a refrigerant discharge opening 32, and an oxidizer gas discharge opening 34 are formed, from top to bottom, penetrating in the stacking direction. On the right edge of each power generation cell 12, an oxidizer gas supply opening 36, a refrigerant supply opening 38, and a hydrogen gas discharge opening 40 are formed, from top to bottom, penetrating in the stacking direction.

[0018] The wet-side end unit 16 has a terminal plate 42, an electrical insulation plate 44, and an end plate 46, which are laminated in order from the side of the power generation cell 12. On the left edge of the wet-side end unit 16, a hydrogen gas supply opening 48, a refrigerant discharge opening 50, and an oxidant gas discharge opening 52 are formed penetrating in the front-rear direction in order from above. On the right edge of the wet-side end unit 16, an oxidant gas supply opening 54, a refrigerant supply opening 56, and a hydrogen gas discharge opening 58 are formed penetrating in the front-rear direction in order from above. Each opening provided in the wet-side end unit 16 has the same arrangement as each opening provided in the power generation cell 12, and communicates with the corresponding hydrogen gas supply opening 30, hydrogen gas discharge opening 40, oxidant gas supply opening 36, oxidant gas discharge opening 34, refrigerant supply opening 38, and refrigerant discharge opening 32 of the power generation cell 12.

[0019] The hydrogen gas supply opening 48 communicates with the hydrogen gas supply opening 30 of the cell stack 14. The refrigerant discharge opening 50 communicates with the refrigerant discharge opening 32 of the power generation cell 12. The oxidant gas discharge opening 52 communicates with the oxidant gas discharge opening 34 of the power generation cell 12. The oxidant gas supply opening 54 communicates with the oxidant gas supply opening 36 of the power generation cell 12. The refrigerant supply opening 56 communicates with the refrigerant supply opening 38 of the cell stack 14. The hydrogen gas discharge opening 58 communicates with the hydrogen gas discharge opening 40 of the power generation cell 12.

[0020] The dry-side end unit 18 has a terminal plate 60, an electrical insulation plate 62, and an end plate 64, which are stacked in order from the side of the power generation cell 12. Hydrogen gas supply openings 61, hydrogen gas discharge openings 67, oxidant gas supply openings 63, oxidant gas discharge openings (not shown), refrigerant supply openings 65, and refrigerant discharge openings (not shown) are formed to penetrate in the front-rear direction in the same arrangement as the wet-side end unit 16 in the terminal plate 60 and the electrical insulation plate 62. Note that these openings are not formed in the end plate 64. Each opening provided in the dry-side end unit 18 has the same arrangement as each opening provided in the power generation cell 12, and communicates with the corresponding hydrogen gas supply opening 30, hydrogen gas discharge opening 40, oxidant gas supply opening 36, oxidant gas discharge opening 34, refrigerant supply opening 38, and refrigerant discharge opening 32 of the power generation cell 12.

[0021] Thereby, hydrogen gas flows in the stacking direction of the cell stack 14 through the gas supply flow path PA1 and is supplied to each power generation cell 12. The hydrogen off-gas (exhaust gas) generated in each power generation cell 12 flows from each power generation cell 12 in the stacking direction of the cell stack 14 through the exhaust gas flow path PA2.

[0022] The oxidant gas may be air, and flows in the stacking direction of the cell stack 14 through the gas supply flow path PA3 and is supplied to each power generation cell 12. The oxidant off-gas (exhaust gas) generated in each power generation cell 12 flows from each power generation cell 12 in the stacking direction of the cell stack 14 through the exhaust gas flow path PA4.

[0023] The refrigerant may be water or the like, and flows in the stacking direction of the cell stack 14 through the refrigerant supply flow path PA5 and is supplied to each power generation cell 12 to cool each power generation cell 12. The refrigerant discharged from each power generation cell 12 flows in the stacking direction of the cell stack 14 through the refrigerant discharge flow path PA6.

[0024] The fuel cell stack 10 generates electrons and water through an electrochemical reaction between hydrogen gas and oxidizer gas supplied to each power generation cell 12, and electricity is extracted from terminal plates 42 and 60. The generated water produced in the fuel cell stack 10 is discharged outside the fuel cell stack 10 through exhaust gas channels PA2 and PA4.

[0025] Next, the details of the exhaust gas flow path PA4 of the fuel cell stack 10 will be explained with reference to Figures 2 to 5(A). In Figures 2 to 5(A), parts corresponding to Figure 1 are given the same reference numerals as those used in Figure 1, and their explanations are omitted.

[0026] As shown in Figure 2, the end plate 46 of the wet-side end unit 16 has a port placement plate 45 and a port member 47 attached to the port placement plate 45. An airtight sealing member 66 is provided between the port member 47 and the electrical insulation plate 44. An airtight sealing member 68 is provided between the electrical insulation plate 44 and the terminal plate 42.

[0027] The terminal plate 42, electrical insulation plate 44, and port member 47 of the wet-side end unit 16 each have through holes 72, 74, and 76 that constitute the hydrogen gas discharge opening 58. Through holes 72 and 78 are straight holes having a predetermined cross-sectional shape. Through hole 74 is a throat hole having a constricted portion 74A that protrudes radially inward. The constricted portion 74A is formed by an annular projection 74B that protrudes radially inward from the peripheral wall of the through hole 74 of the electrical insulation plate 44.

[0028] An airtight sealing member 66 is provided between the terminal plate 60 and the electrical insulation plate 62 of the dry-side end unit 18. A gasket 71 is provided between the electrical insulation plate 62 and the end plate 64. A through hole 69 is formed in the terminal plate 60 of the dry-side end unit 18, which constitutes a hydrogen gas discharge opening 67. A non-through hole 86 is formed in the electrical insulation plate 62, which also constitutes a hydrogen gas discharge opening 67.

[0029] The lower bottom surfaces of the hydrogen gas discharge openings 40 and 67 (through-holes 69 and non-through-holes 86) that constitute the exhaust gas flow path PA4 (representatively, as shown in Figure 4, the lower bottom surface 86A of the non-through-hole 86 of the electrical insulation plate 62 will be described) have a pan shape that becomes deeper towards the right side (the outer edge side of the fuel cell stack 10), and the lower bottom surface has a water slope towards the front (see Figure 3).

[0030] The electrical insulation plate 62 of the dry-side end unit 18 has a shoulder portion 88 below the non-through hole 86, as shown in Figures 2 to 4. The shoulder portion 88 comprises a forward-facing, substantially vertical first surface 89 rising from the lower bottom surface 86A of the non-through hole 86, and an upward-facing, substantially horizontal second surface 90 continuous with the upper edge of the first surface 89.

[0031] In other words, the shoulder portion 88 has a first surface 89 facing the upstream opening of the communication pipe 80 and an upward-facing second surface 90 extending from the upper edge of the first surface 89 in the portion that constitutes the lower bottom of the exhaust gas flow path PA2.

[0032] The exhaust gas flow path PA2 has a connecting pipe 80 as a flow path forming section for wastewater generated, which extends in the same direction as the exhaust gas flow path PA2. The connecting pipe 80 extends substantially horizontally along the stacking direction of the cell stack 14, below the hydrogen gas discharge opening 40 of the cell stack 14 (power generation cell 12). The connecting pipe 80 is made of a straight round pipe and has an annular cross-sectional shape as shown in Figure 5(A).

[0033] The connecting pipe 80 has an internal passage 85 and, within the exhaust gas flow path PA4, more specifically at the lower part of the exhaust gas flow path PA4, the internal passage 85 constitutes an exhaust water flow path that extends in the same direction as the exhaust gas flow path PA4.

[0034] The electrical insulation plate 44 of the wet-side end unit 16 has a first engaging portion 82 into which one end 80A of the connecting pipe 80 (sometimes referred to as the outflow-side end 80A in the following description) engages. The electrical insulation plate 62 of the dry-side end unit 18 has a second engaging portion 94 into which the other end 80B of the connecting pipe 80 (sometimes referred to as the inflow-side end 80B in the following description) engages.

[0035] The first engaging portion 82 has an engaging hole 84 that extends in the front-to-back direction (stacking direction) and penetrates the lower side of the annular projection 74B of the electrical insulation plate 44 of the wet-side end unit 16. The engaging hole 84 extends generally in the horizontal direction, is open at both ends, and opens toward both the hydrogen gas discharge opening 40 of the cell stack 14 and the hydrogen gas discharge opening 58 of the end plate 46.

[0036] The outlet end 80A of the communication pipe 80 is inserted into the engagement hole 84 from the cell stack 14 side. This insertion holds the outlet end 80A of the communication pipe 80 to the electrical insulation plate 44. This improves the stability of the communication pipe 80's hold in the fuel cell stack 10.

[0037] The first open end 81 (downstream open end) on the outlet side end 80A of the connecting pipe 80 opens toward the hydrogen gas discharge opening 58 of the end plate 46.

[0038] A through-hole 73 is formed below the through-hole 72 in the terminal plate 42 of the wet-side end unit 16, into which the connecting pipe 80 is fitted. This fitting allows the outlet-side end 80A of the connecting pipe 80 to be supported by the terminal plate 42. As a result, the terminal plate 42 is effectively used to hold the connecting pipe 80.

[0039] A through-hole 59 is formed below the through-hole 69 in the terminal plate 60 of the dry-side end unit 18, into which the connecting pipe 80 is fitted. This fitting allows the inlet end 80B of the connecting pipe 80 to be supported by the terminal plate 60. As a result, the terminal plate 42 is effectively used to hold the connecting pipe 80.

[0040] At the corners of the shoulder portion 88 formed in the electrical insulation plate 62 of the dry-side end unit 18, notches 92 are formed, which constitute groove-shaped spaces 93 that open to the first surface 89 and the second surface 90, respectively. The notches 92 have a box-shaped groove when viewed from either the front-to-back direction or the up-and-down direction. The groove-shaped spaces 93 are open to both the upward and forward directions.

[0041] As shown in Figures 5(A) and 3, the vertical dimension H, horizontal dimension W, and front-to-back dimension D of the notch 92 (groove-shaped space 93) are the same. However, the front-to-back dimension D may be larger than the vertical dimension H and the horizontal dimension W.

[0042] The second engaging portion 94 includes a notch 92. The notch 92 faces the second open end 83 (upstream open end) on the inlet end 80B side of the connecting pipe 80. The inner diameter R of the connecting pipe 80 is slightly larger than or equal to the vertical dimension H and horizontal dimension W of the notch 92, as shown in Figure 5(A). This allows the second open end 83 of the connecting pipe 80 to abut against the vicinity of the outer edge of the notch 92 on the first surface 89. The connecting pipe 80 is restricted from moving in the front-rear direction due to this abutment. The connecting pipe 80 is provided close to the lower bottom surface 86A of the non-through hole 86 of the electrical insulation plate 62.

[0043] The internal passage 85 of the connecting pipe 80 communicates with the groove-shaped space 93 of the notch 92 at the second open end 83 on the inlet end 80B side. As a result, the groove-shaped space 93 of the notch 92 forms a hook-shaped connecting passage that connects the internal passage 85 of the connecting pipe 80 and the hydrogen gas discharge opening 67 (exhaust gas flow path PA2) to each other. The bottom surface 92A of the notch 92 is an inclined surface with a downward slope toward the connecting pipe 80 so that it can be smoothly connected to the inner circumferential surface of the connecting pipe 80.

[0044] As the fuel cell stack 10 operates, the generated water that accumulates at the bottom of the hydrogen gas discharge opening 67 (non-penetrating hole 86) enters the grooved space 93 through the upward opening of the grooved space 93 in the notch 92. The generated water that enters the grooved space 93 flows toward the lateral opening of the grooved space 93 without being subjected to a large throttling action and flows into the internal passage 85 of the connecting pipe 80. The generated water that flows into the internal passage 85 flows toward the outlet end 80A of the connecting pipe 80, and flows out of the internal passage 85 through the engagement hole 84 to the hydrogen gas discharge opening 58.

[0045] According to this structure, the notch 92 is a groove shape with an upward opening, and the flow path corresponding to the groove-shaped space 93 in the notch 92 is formed by a through hole that is closed at the top, allowing for faster discharge of the generated water from the fuel cell stack 10 to the outside of the fuel cell stack 10 without creating significant flow resistance. In other words, the flow resistance at the inflow portion of the generated water to the connecting pipe 80 is reduced, and the space required in the stacking direction of the cell stack 14 can be reduced.

[0046] This makes it possible to obtain the required drainage capacity with the required drainage speed without increasing the size of the dry end unit 18, and consequently the fuel cell stack 10.

[0047] Furthermore, since the degree of freedom in setting the vertical dimension H, horizontal dimension W, and front-to-back dimension D of the notch 92 in the shoulder portion 88 is greater than that of the through hole, it is easier to enlarge the groove-shaped space 93, and the flow resistance of the generated water that is about to flow into the connecting pipe 80 can be reduced.

[0048] Furthermore, the groove shape of the notch 92 may be V-shaped, as shown in Figure 5(B), or U-shaped, as shown in Figure 5(C). This allows for a wider variety of shapes for the notch 92, improving design flexibility.

[0049] The main parts of other embodiments will be described with reference to Figure 6. In Figure 6, the parts corresponding to Figure 3 are given the same reference numerals as those used in Figure 3, and their descriptions are omitted.

[0050] In the embodiment shown in Figure 6, the notch 92 includes a connecting pipe receiving portion 96 into which the inlet end 80B of the connecting pipe 80 is fitted. The connecting pipe receiving portion 96 has a U-shaped groove that is larger than the left-right dimension W of the notch 92 and has a left-right dimension equal to the outer diameter of the connecting pipe 80. A U-shaped stepped wall 97 is formed on the back side of the connecting pipe receiving portion 96. The stepped wall 97 is a vertical surface equivalent to the first surface 89.

[0051] In this embodiment, the inlet end 80B of the connecting pipe 80 is fitted into the connecting pipe receiving section 96, thereby strengthening the support provided by the electrical insulating plate 62. This improves the stability of the holding of the connecting pipe 80 in the fuel cell stack 10. The axial position of the connecting pipe 80 relative to the electrical insulating plate 62 is determined by contact with the second open end 83 of the connecting pipe 80.

[0052] The embodiments are not limited to the above configuration and can be broadly modified. For example, the connecting pipe 80 may be provided in the exhaust gas flow path PA4.

[0053] In conclusion, the above embodiments can be summarized as follows:

[0054] One embodiment of the fuel cell stack 10 comprises a cell stack 14 formed by stacking a plurality of power generation cells 12 in a predetermined direction, and a wet-side end unit 16 (first end unit) and a dry-side end unit 18 (second end unit) respectively arranged at both ends of the cell stack in the stacking direction, wherein the cell stack 14 is provided with an exhaust gas flow path PA2 that extends in the stacking direction of the cell stack 14 and discharges the reaction gas supplied to the power generation cells 12 from the power generation cells 12, and a connecting pipe 80 with openings at both ends arranged in the exhaust gas flow path PA2 and forming an exhaust water flow path that extends in the same direction as the extension direction of the exhaust gas flow path PA2, and the wet-side end unit The unit 16 has a first engaging portion 82 formed therein, into which one end 80A of the communication pipe 80 engages, and the dry-side end unit 18 has a second engaging portion 94 formed therein, into which the other end 80B of the communication pipe 80 engages. The dry-side end unit 18 has a shoulder portion 88 in the lower bottom portion of the exhaust gas flow path PA2, which has a first surface 89 facing the second open end 83 (upstream open end) of the communication pipe 80 and an upward-facing second surface 90 extending from the upper edge of the first surface 89. The shoulder portion 88 has a notch 92 that opens across the first surface 89 and the second surface 90, and the internal passage 85 of the communication pipe 80 communicates with the exhaust gas flow path PA2 via the notch 92.

[0055] According to this embodiment, the flow resistance at the inflow section of the generated water to the connecting pipe 80 is reduced, and the space in the stacking direction of the cell stack 14 can be reduced, thereby obtaining the required drainage capacity without increasing the size of the fuel cell stack 10.

[0056] In the above embodiment, preferably, the first engaging portion 82 is formed in the wet-side end unit 16 extending in the stacking direction and includes an engaging hole 84 with open ends into which one end 80A of the communication pipe 80 is inserted.

[0057] According to this embodiment, the stability of holding the connecting pipe 80 in the fuel cell stack 10 is improved.

[0058] In the above embodiment, preferably, the notch 92 includes a connecting pipe receiving portion 96 into which the other end 80B of the connecting pipe 80 is fitted.

[0059] According to this embodiment, the stability of holding the connecting pipe 80 in the fuel cell stack 10 is improved.

[0060] In the above embodiment, preferably, the connecting pipe 80 has an annular cross-sectional shape, and the notch 92 has a box-shaped, V-shaped, or U-shaped groove when viewed in the stacking direction.

[0061] According to this embodiment, the variations in the shape of the notch 92 become more numerous, improving the degree of design freedom.

[0062] In the above embodiment, preferably, the dry-side end unit 18 includes an electrical insulating plate 62, and the second engaging portion 94 is configured on the electrical insulating plate 62.

[0063] According to this embodiment, the electrical insulating plate 62 is usefully used to constitute the second engaging portion 94.

[0064] In the above embodiment, preferably, the wet-side end unit 16 and the dry-side end unit 18 each have terminal plates 42 and 60, and each terminal plate 42 and 60 has through holes 73 and 59 into which the connecting pipe 80 is fitted.

[0065] In this embodiment, the terminal plates 42 and 60 are effectively used to hold the connecting pipe 80. [Explanation of Symbols]

[0066] 10: Fuel cell stack 12: Power generation cell 14: Cell laminate 16: Wet side end unit (first end unit) 18: Dry side end unit (second end unit) 42: Terminal Plate 44: Electrical insulation plate 59: Through hole 60: Terminal Plate 62: Electrical insulation plate 69: Through hole 72: Through hole 73: Through hole 74: Through hole 76: Through hole 80:Communication pipe 80A: End 80B: End 82: First engaging part 83: Second opening end (upstream opening end) 84: Engagement hole 85: Internal passage 88:Shoulder 89: 1st page 90: 2nd side 92: Notch 94: Second engagement part 96:Communication pipe receiving part PA2: Exhaust gas flow path PA4: Exhaust gas flow path

Claims

1. A cell stack formed by stacking multiple power generation cells in a predetermined direction, The cell laminate has a first end unit and a second end unit, which are respectively arranged at both ends in the stacking direction. The cell stack is provided with an exhaust gas channel that extends in the stacking direction of the cell stack and discharges the reaction gas supplied to the power generation cell from the power generation cell, A connecting pipe with openings at both ends is arranged in the exhaust gas flow path and forms an exhaust water flow path that extends in the same direction as the exhaust gas flow path, A first engagement portion is formed in the first end unit, into which one end of the connecting pipe engages, The second end unit has a second engaging portion formed therein, into which the other end of the connecting pipe engages, The second end unit has a shoulder portion in the lower bottom portion of the exhaust gas flow path, which has a first surface facing the upstream open end of the connecting pipe and an upward-facing second surface extending from the upper edge of the first surface. The shoulder portion has a notch that opens across the first and second surfaces, A fuel cell stack in which the internal passage of the connecting pipe communicates with the exhaust gas flow path via the notch.

2. The fuel cell stack according to claim 1, wherein the first engaging portion is formed in the first end unit extending in the stacking direction and includes an engaging hole with openings at both ends into which one end of the communication pipe is inserted.

3. The fuel cell stack according to claim 1 or 2, wherein the notch includes a connecting pipe receiving portion into which the other end of the connecting pipe is fitted.

4. The fuel cell stack according to claim 1 or 2, wherein the connecting pipe has an annular cross-sectional shape, and the notch has a box-shaped, V-shaped, or U-shaped groove shape when viewed in the stacking direction.

5. The fuel cell stack according to claim 1 or 2, wherein the second end unit includes an electrical insulating plate, and the second engaging portion is configured on the electrical insulating plate.

6. The first end unit and the second end unit each have a terminal plate, The fuel cell stack according to claim 1 or 2, wherein each terminal plate has a through hole into which the connecting pipe is fitted.

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