Fuel cell system

Abstract

Fuel cell system (1), comprising: a gas-liquid separator (40) configured to separate liquid contained in the fuel gas exhaust gas discharged from a fuel cell stack (10) from the fuel gas exhaust gas and to store and discharge the separated liquid; and a fuel gas pump (50) connected to the gas-liquid separator (40) and configured to return the fuel gas exhaust gas in the gas-liquid separator (40) to the fuel cell stack (10); wherein the gas-liquid separator (40) has a first connecting portion (46) which is tubular and extends upwardly; the fuel gas pump (50) has an inner wall surface (55a) forming a pump chamber (550), and a lower part of the inner wall surface (55a) is formed with an opening (51) configured such that the first connecting portion (46) is inserted into the opening (51); and a head end of the first connecting portion (46) is arranged at a height equal to the height of an extension plane extending along the lower part of the inner wall surface (55a); characterized in that the lower part of the inner wall surface (55a) is inclined downwards towards the opening (51); the head end of the first connecting portion (46) is formed with an inclined surface (46b) which adjoins an inner peripheral surface (46a) of the first connecting portion (46) and is inclined downwards towards the inner peripheral surface (46a); and the inclined surface (46b) of the first connecting portion (46) is arranged on the extension plane.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a fuel cell system with a gas-liquid separator and a fuel gas pump. 2. Description of the state of the art

[0002] There is a known fuel cell system with a gas-liquid separator and a hydrogen gas pump (fuel gas pump) (see, for example, Japanese patent application JP 2019 - 16 495 A). The gas-liquid separator separates water contained in the hydrogen off-gas (fuel gas off-gas) from the hydrogen off-gas discharged from the fuel cell stack, stores the separated water, and discharges it. The hydrogen gas pump (fuel gas pump) causes the hydrogen off-gas in the gas-liquid separator to be recirculated to a fuel cell stack.

[0003] In the above-mentioned JP 2019 - 16 495 A, the hydrogen gas pump is arranged on an upper surface of the gas-liquid separator. The hydrogen exhaust gas is sucked in through an opening formed in a lower part of the hydrogen gas pump and supplied to the fuel cell stack via an outlet opening formed in an upper part of the hydrogen gas pump.

[0004] From DE 10 2018 114 079 A1, a fuel cell system according to the preamble of claim 1 is known. Further prior art relating to fuel cell systems and rotary pumps can be found in DE 10 2018 120 601 A1 and US 1 681 796 A. SUMMARY OF THE INVENTION

[0005] The hydrogen exhaust gas that flows from the gas-liquid separator into the hydrogen gas pump contains water. If the water remains in the hydrogen gas pump while the vehicle is stationary, the water may freeze. In particular, if water accumulates at a connection point between the hydrogen gas pump and the gas-liquid separator, the accumulated water may freeze and block the connection point. Or, water droplets may form in the gas-liquid separator due to vibration or other factors after the vehicle stops. The dripped water may freeze and block the outlet path of the gas-liquid separator.

[0006] The invention provides a fuel cell system that can prevent liquid from remaining in a fuel gas pump.

[0007] One aspect of the invention relates to a fuel cell system. The fuel cell system includes a gas-liquid separator and a fuel gas pump. The gas-liquid separator is configured to separate liquid contained in the fuel gas off-gas discharged from the fuel cell stack from the fuel gas off-gas, and to store and discharge the separated liquid. The fuel gas pump is connected to the gas-liquid separator and configured to return the fuel gas off-gas in the gas-liquid separator to the fuel cell stack. The gas-liquid separator has a first connecting portion that is tubular and extends upward. The fuel gas pump has an inner wall surface that forms a pump chamber, and a lower part of the inner wall surface is formed with an opening configured such that the first connecting portion is inserted into the opening.The lower part of the inner wall surface slopes downward toward the opening. A front end of the first connecting portion is positioned at a height equal to the height of an extension plane extending along the lower part of the inner wall surface. The head end of the first connecting portion is formed with an inclined surface that adjoins an inner peripheral surface of the first connecting portion and slopes downward toward the inner peripheral surface.

[0008] In this description and claims, the term “angle of inclination” refers to an angle of inclination with respect to a horizontal plane.

[0009] In the fuel cell system according to the invention, the flow of the fuel gas off-gas around the head end of the first connecting portion can be made uniform. This makes it possible to suppress stagnation of the fuel gas off-gas around the opening of the fuel gas pump. In this way, the liquid in the fuel gas pump can be efficiently pumped to the fuel cell stack along with the fuel gas, thus preventing water from remaining in the fuel gas pump.

[0010] In addition, the tip end of the first connecting portion is formed with the inclined surface that is continuous with the inner peripheral surface of the first connecting portion and inclined downward toward the inner peripheral surface. This facilitates the liquid adhering to the tip end (inclined surface) of the first connecting portion to return to the gas-liquid separator. That is, it is possible to suppress the accumulation of liquid adhering to the orifice of the fuel gas pump. Accordingly, it is possible to prevent the liquid accumulated in the orifice of the fuel gas pump from freezing and blocking the orifice. In addition, it is possible to prevent the liquid accumulated in the orifice of the fuel gas pump from falling into the gas-liquid separator due to vibration or the like after the vehicle stops and freezing to block the outlet path of the gas-liquid separator.

[0011] In the fuel cell system according to the invention, the inclined surface of the first connecting portion is arranged on the extension plane. With this configuration, the flow of the fuel gas off-gas can be made uniform, particularly around the lower part of the inner wall surface and the inclined surface. That is, it is particularly possible to suppress the stagnation of the fuel gas off-gas around the opening of the fuel gas pump. In this way, the liquid in the fuel gas pump can be efficiently conveyed to the fuel cell stack together with the fuel gas off-gas, making it particularly possible to suppress the retention of liquid in the fuel gas pump.

[0012] The fuel cell system of the above aspect may further include an introduction pipe configured to introduce the fuel gas off-gas discharged from the fuel cell stack into the gas-liquid separator. The gas-liquid separator may have a second tubular connecting portion configured such that the introduction pipe is inserted into the second connecting portion and connected to the second connecting portion. At least a lowermost part of an inner peripheral surface of the second connecting portion in a circumferential direction may be formed to smoothly extend downward to a downstream side in a region further downstream from a downstream end of the introduction pipe.With this configuration, liquid droplets attached to the lowest part of the inner peripheral surface of the second connecting portion in the circumferential direction move downstream of the second connecting portion and fall into the reservoir. That is, unlike the case where, for example, a step protruding upward toward the downstream side is formed in the lowest part of the inner peripheral surface of the second connecting portion in the circumferential direction, it is possible to suppress the accumulation of liquid in the second connecting portion of the gas-liquid separator. Accordingly, it is possible to prevent the liquid accumulated in the second connecting portion of the gas-liquid separator from freezing and blocking the second connecting portion.It is also possible to prevent the liquid accumulated in the second connecting portion of the gas-liquid separator from falling into the gas-liquid separator and freezing to block the outlet port of the gas-liquid separator due to vibration or the like after the vehicle stops.

[0013] According to the invention, it is possible to provide a fuel cell system that can prevent liquid from remaining in the fuel gas pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The features and advantages as well as the technical and economic significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, in which: Fig. 1 is a system configuration diagram of a fuel cell system according to an embodiment of the invention; Fig. 2 is a side view showing a structure around a gas-liquid separator and a fuel gas pump of the fuel cell system of the embodiment of the invention; Fig. 3 is a sectional view showing a structure around the gas-liquid separator and the fuel gas pump of the fuel cell system of the embodiment of the invention; Fig. 4 is a sectional view showing a structure around a first connecting portion of the gas-liquid separator of the fuel cell system of the embodiment of the invention; Fig. 5 is a plan view showing a structure around the first connecting portion of the gas-liquid separator of the fuel cell system of the embodiment of the invention; Fig. 6 is a sectional view showing a structure of a connecting part between the gas-liquid separator and an introduction pipe in the fuel cell system of the embodiment of the invention; Fig. 7 a sectional view along the line VII-VII in Fig. 6; Fig. 8 is a diagram showing a step formed in a second connecting portion of the gas-liquid separator of the fuel cell system according to a first modification of the invention; Fig. 9 is a plan view showing a structure around the first connecting portion of the gas-liquid separator of the fuel cell system according to a second modification of the invention; and Fig. 10 a sectional view along the line XX in Fig. 9. DETAILED DESCRIPTION OF EMBODIMENTS

[0015] Hereinafter, a configuration of the invention will be described in detail using an example of an embodiment shown in the drawings. Hereinafter, a case where the invention is applied to a fuel cell mounted on a fuel cell vehicle or to a fuel cell system including the fuel cell will be described as an example.

[0016] A fuel cell system 1 is mounted on a vehicle (not shown) and supplies electrical energy to drive the vehicle. As shown in Fig. As shown in Figure 1, the fuel cell system 1 includes a fuel cell stack 10, an oxidizing gas supply system 20, and a fuel gas supply system 30. The fuel cell stack 10 is formed by stacking a plurality of fuel cells serving as unit cells. The oxidizing gas supply system 20 supplies the fuel cell stack 10 with oxidizing gas such as air. The fuel gas supply system 30 supplies the fuel cell stack 10 with fuel gas such as hydrogen.

[0017] The oxidizing gas supply system 20 includes, for example, an oxidizing gas supply channel 25 and an oxidizing gas outlet channel 29. The oxidizing gas supply channel 25 is used to supply oxidizing gas to the (a cathode electrode of the) fuel cell stack 10. The oxidizing gas outlet channel 29 is used to discharge oxidizing gas off-gas from the fuel cell stack 10, which is produced by subjecting the oxidizing gas supplied to the fuel cell stack 10 to an electrochemical reaction. Each channel of the oxidizing gas supply system 20 can consist of a conduit, e.g., a rubber hose or a metal pipe.

[0018] The oxidizing gas supply passage 25 is formed with an air cleaner 21, a compressor 22, a charge air cooler 23 and the like from an upstream side, and the oxidizing gas outlet passage 29 is formed with a muffler 28 and the like.

[0019] In the oxidizing gas supply channel 25, the air cleaner 21 removes dust in the oxidizing gas (air, etc.) drawn from the atmosphere. The compressor 22 compresses the oxidizing gas introduced through the air cleaner 21 and supplies the compressed oxidizing gas to the intercooler 23. The intercooler 23 cools the oxidizing gas supplied from the compressor 22 through heat exchange, e.g., with a refrigerant, as the oxidizing gas flows through the intercooler 23, and delivers the cooled oxidizing gas to the fuel cell stack 10 (the cathode electrode of the fuel cell stack).

[0020] In the oxidizing gas outlet channel 29, the silencer 28 separates the oxidizing gas exhaust gas (exhaust gas) flowing through the oxidizing gas outlet channel 29, for example, into a gas phase and a liquid phase and discharges them to the outside.

[0021] The fuel gas supply system 30 includes, for example, a fuel gas supply source 31, a fuel gas supply channel 35, a return channel 36, and a fuel gas outlet channel 39. The fuel gas supply source 31 includes a hydrogen tank, etc., for storing high-pressure fuel gas such as hydrogen. The fuel gas supply channel 35 supplies the fuel gas from the fuel gas supply source 31 to the (anode electrode of the) fuel cell stack 10. The return channel 36 returns a portion of the fuel gas off-gas discharged from the fuel cell stack 10 to the fuel gas supply channel 35. The fuel gas outlet channel 39 branches off from the return channel 36 and discharges the fuel gas off-gas to the outside (into the atmosphere) in the return channel 36. Each channel of the fuel gas supply system 30 may consist of a conduit, e.g., a rubber hose or a metal pipe.

[0022] The fuel gas supply channel 35 is formed with a shutoff valve 35V and a regulator 34. The shutoff valve 35V is used to open and close the fuel gas supply channel 35 to interrupt the flow of fuel gas to the fuel cell stack 10. The regulator 34 serves to adjust (reduce) the pressure of the fuel gas flowing through the fuel gas supply channel 35. When the shutoff valve 35V is open, high-pressure fuel gas stored in the fuel gas supply source 31 flows into the fuel gas supply channel 35, and the pressure of the fuel gas is regulated (reduced) by the regulator 34. The fuel gas is then supplied to the (anode electrode of) the fuel cell stack 10.

[0023] The return channel 36 is provided with a gas-liquid separator 40, a fuel gas pump (also called a hydrogen pump) 50, and the like from the upstream side (the side of the fuel cell stack 10). The gas-liquid separator 40 separates the generated water from the fuel gas (e.g., hydrogen) flowing through the return channel 36 and stores the generated water. The fuel gas outlet channel 39 branches off from the gas-liquid separator 40. The fuel gas pump 50 discharges a portion of the fuel gas separated from the generated water by the gas-liquid separator 40 to return this portion to the fuel gas supply channel 35.

[0024] The fuel gas outlet channel 39 is formed with an outlet valve 39V for opening and closing the fuel gas outlet channel 39 to discharge the water separated by the gas-liquid separator 40 and a part of the fuel gas exhaust gas discharged from the fuel cell stack 10.

[0025] In the fuel cell system having the above-described configuration, electric power is generated by an electrochemical reaction between oxidizing gas such as air supplied to (the cathode electrode of) the fuel cell stack 10 through the oxidizing gas supply system 20 and fuel gas such as hydrogen supplied to (the anode electrode of) the fuel cell stack 10 through the fuel gas supply system 30.

[0026] Next, the structures of the gas-liquid separator 40 and the fuel gas pump 50 of the fuel cell system 1 of the present embodiment will be described in detail. The gas-liquid separator 40 separates liquid such as water contained in the fuel gas exhaust gas discharged from the fuel cell stack 10, and stores and discharges the separated liquid.

[0027] As in the Fig. 2 and Fig. 3, the gas-liquid separator 40 includes a housing 41 consisting of an upper housing 41a and a lower housing 41b, sealed with an O-ring (not shown) or the like. An upper right portion of the upper housing 41a in Fig. 3 is formed with an introduction pipe 42. The introduction pipe 42 communicates with an opening (not shown) of the fuel cell stack 10 through which fuel gas off-gas in the fuel cell stack 10 is discharged, and constitutes a part of the return passage 36. The introduction pipe 42 is configured to introduce the fuel gas off-gas after power generation by the fuel cell stack 10 into the casing 41. The introduction pipe 42 slopes downward from the fuel cell stack 10 to the gas-liquid separator 40 and is connected to the gas-liquid separator 40. The detailed structure of a connecting part between the gas-liquid separator 40 and the introduction pipe 42 will be described later.

[0028] As in Fig. 3, a tubular first connecting portion 46 is formed at a predetermined position on an upper surface of the upper casing 41a so as to extend upward (in a direction opposite to the direction of gravity). The first connecting portion 46 is inserted into an opening 51 of the fuel gas pump 50. The fuel gas off-gas separated from the liquid by the gas-liquid separator 40 is sucked into the fuel gas pump 50 and then flows into the fuel gas supply passage 35 via an outlet opening 52 formed in a top surface of the fuel gas pump 50. The detailed structure around the first connecting portion 46 between the fuel gas pump 50 and the gas-liquid separator 40 will be described later.

[0029] The gas-liquid separator 40 is formed with an outlet path 43 for discharging the separated liquid such as water below an outlet opening of the introduction line 42 and a reservoir 44 for storing the separated liquid upstream of the outlet path 43.

[0030] Specifically, the lower housing 41b has a shape that gradually tapers downwards, and the reservoir 44 is formed in a recess at the bottom of the lower housing 41b. The outlet path 43 is a through hole formed at a position slightly higher than the bottom surface of the reservoir 44 and extending in a substantially horizontal direction.

[0031] The through hole serving as the exhaust path 43 extends to the outside of the housing 41 and is connected to the exhaust valve 39V outside the housing 41. The through hole is connected to the fuel gas exhaust channel 39 via the exhaust valve 39V.

[0032] In the fuel cell system 1, the fuel gas exhaust gas exiting the fuel cell stack 10 is introduced through the inlet line 42 into the housing 41 of the gas-liquid separator 40 and separated into gas and liquid. The gas separated by the gas-liquid separator 40 is conveyed by the fuel gas pump 50 to the fuel gas supply channel 35 and fed back to the fuel cell stack 10 during operation of the fuel cell system 1.

[0033] On the other hand, the liquid separated by the gas-liquid separator 40 is stored in the reservoir 44 of the lower casing 41b with the outlet valve 39V closed while the fuel cell system 1 is operating. When a liquid level sensor (not shown) of the reservoir 44 detects that a predetermined amount of liquid has been stored in the reservoir 44, the outlet valve 39V opens, and a portion of the stored liquid is discharged to the outside via the outlet path 43.

[0034] When the fuel cell system 1 is not in operation, the exhaust valve 39V is opened, and the stored liquid and the fuel gas exhaust gas are discharged to the outside via the exhaust path 43.

[0035] Next, the structure around the first connecting portion 46 between the fuel gas pump 50 and the gas-liquid separator 40 will be described in detail. The fuel gas pump 50 consists of a housing 55 and two rotors 56 rotatably arranged in the housing 55. An opening 51 is formed in the center of a lower surface of the housing 55 through which the fuel gas off-gas is introduced. The discharge opening 52 is formed in the center of the upper surface of the housing 55 through which the fuel gas off-gas is supplied. The fuel gas off-gas contains water and water vapor. The two rotors 56 rotate to generate an airflow in the housing 55, so that the fuel gas off-gas, water, and water vapor are sucked in from the gas-liquid separator 40 and discharged through the discharge opening 52. It should be noted that an upper limit for the speed of the rotors 56 is set as noise and vibration damping measures.Therefore, water can normally remain in the housing 55.

[0036] The housing 55 has an inner wall surface 55a which forms a pump chamber S50. As shown in Fig. 4, a lower part of the inner wall surface 55a is formed to be inclined downward (in the direction of gravity) toward the opening 51, and the opening 51 is formed at the lowest part of the inner wall surface 55a.

[0037] An O-ring 49a is formed on an outer peripheral surface of the first connecting portion 46 of the gas-liquid separator 40 so as to seal between the outer peripheral surface of the first connecting portion 46 and an inner peripheral surface of the opening 51.

[0038] Here, in the present embodiment, a front end (top end) of the first connecting portion 46 is located at a height equal to or lower than a height of an extension plane S1 along the lower part of the inner wall surface 55a of the fuel gas pump 50 (a plane defined by the extension of the lower part inclined surface). The extension plane S1 is a virtual plane. The tip end of the first connecting portion 46 is formed with an inclined surface 46b. The inclined surface 46b is formed to be continuous with the top end of an inner peripheral surface 46a of the first connecting portion 46 and to be inclined downward toward the inner peripheral surface 46a. This allows water droplets adhering to the tip end of the first connecting portion 46 to easily fall into the gas-liquid separator 40.A tapered surface 46c is formed radially outside an outer edge of the inclined surface 46b so as to be downwardly inclined in a radially outward direction. The tapered surface 46c is used to facilitate insertion of the first connecting portion 46 into the opening 51 of the fuel gas pump 50. The tip end of the first connecting portion 46 is composed of the inclined surface 46b and the tapered surface 46c. As shown in FIG. Fig. 5, the opening 51 and the first connecting section 46 both have a perfect circular shape when viewed from above.

[0039] As in Fig. As shown in FIG. 4, the inclined surface 46b is shaped to have an inclination angle θ2 equal to or greater than the inclination angle θ1 of the lower part of the inner wall surface 55a. In the present embodiment, the inclined surface 46b is shaped to have an inclination angle θ2 equal to the inclination angle θ1 of the lower part of the inner wall surface 55a. A radial length L1 of the inclined surface 46b is longer than a radial length L2 of the tapered surface 46c.

[0040] The conical surface 46c is shaped to have an inclination angle θ3 that is greater than the inclination angle θ2 of the inclined surface 46b.

[0041] The inclined surface 46b is arranged at a height equal to or lower than a height of the extension plane S1 extending along the lower part of the inner wall surface 55a as described above. In the present embodiment, the inclined surface 46b is arranged on the extension plane S1. The airflow generated during the rotation of the rotors 56 thus flows smoothly and smoothly from the inclined surface 46b to the inner wall surface 55a. This makes it possible to suppress the stagnation of the fuel gas off-gas around the opening 51. As a result, the fuel gas off-gas introduced through the opening 51, water, and water vapor can be efficiently discharged from the discharge port 52, so that the accumulation of water in the lower part of the inner wall surface 55a can be suppressed.

[0042] Next, the structure of the connecting part between the gas-liquid separator 40 and the introduction pipe 42 is described in detail. At the right upper part of the upper casing 41a in Fig. 3, a tubular second connecting section 47 is formed, into which the inlet line 42 is inserted for connection. As shown in Fig. 6, the second connecting portion 47 has an inner peripheral surface 47a extending along an outer peripheral surface 42a of a downstream end 42b of the introduction pipe 42 and slightly inclined downward toward the inside of the housing 41.

[0043] The downstream end 42b of the introduction pipe 42 is inserted into the second connecting portion 47, and the outer peripheral surface 42a of the introduction pipe 42 is in contact with the inner peripheral surface 47a of the second connecting portion 47. An O-ring 49b is arranged on the outer peripheral surface 42a of the introduction pipe 42 to seal between the outer peripheral surface 42a of the introduction pipe 42 and the inner peripheral surface 47a of the second connecting portion 47.

[0044] Here, at least a lowermost part of the inner circumferential surface 47a of the second connecting portion 47 is formed in the circumferential direction so that it extends, at least in a region further downstream (on the left side in Fig. 6) from the downstream end 42b of the introduction pipe 42, extends smoothly downward toward the downstream side. In the present embodiment, at least the lowest part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction is formed to extend smoothly downward toward the downstream side over its entire length. That is, at least the lowest part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction is formed in a linear shape without steps so as to extend along an extension plane S2 of the outer peripheral surface 42a of the introduction pipe 42. The extension plane S2 is a virtual plane. As a result, at least the lowest part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction does not have a portion where the liquid droplets accumulate (recess or upward step).Thus, water droplets adhering to the lowermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction due to water or water vapor contained in the fuel gas exhaust gas move to the downstream side of the second connecting portion 47 and fall into the reservoir 44.

[0045] At least an uppermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction is formed with a step 47b so that at least the uppermost part of the inner peripheral surface 47a of the second connecting portion 47 is flush with the inner peripheral surface of the introduction pipe 42. This can suppress an increase in the difference between an inner surface area of ​​the second connecting portion 47 and an inner surface area of ​​the introduction pipe 42 and can thus suppress an increase in pressure loss. In the present embodiment, the step 47b is formed such that the radial length gradually increases from a lower part to an upper part of the inner peripheral surface 47a of the second connecting portion 47, as shown in Fig. 7. Further, the step 47b is formed to extend upward from a position spaced from the lowermost part of the inner peripheral surface 47a by a predetermined distance (a predetermined angle around a center point of the second connecting portion 47). That is, the step 47b is formed only in a part of the inner peripheral surface 47a located above a region where water drops flow.

[0046] In the present embodiment, as described above, the tip end of the first connecting portion 46 is located at a height equal to or lower than a height of the extension plane S1 extending along the lower part of the inner wall surface 55a, and the tip end of the first connecting portion 46 has the inclined surface 46b formed to be continuous with the inner peripheral surface 46a of the first connecting portion 46 and inclined downward toward the inner peripheral surface 46a. This makes the flow of the fuel gas off-gas around the tip end of the first connecting portion 46 smooth. That is, it is possible to suppress stagnation of the fuel gas off-gas around the opening 51 of the fuel gas pump 50. In this way, the water in the fuel gas pump 50 can be efficiently supplied to the fuel cell stack 10 along with the fuel gas, so that it is possible to prevent water from remaining in the fuel gas pump 50.

[0047] Furthermore, the tip end of the first connecting portion 46 is formed with the inclined surface 46b, which is continuous with the inner peripheral surface 46a of the first connecting portion 46 and inclined downward toward the inner peripheral surface 46a. This facilitates the return of water droplets adhering to the tip end (inclined surface 46b) of the first connecting portion 46 to the gas-liquid separator 40. That is, it is possible to suppress the accumulation of water droplets in the opening 51 of the fuel gas pump 50. Accordingly, it is possible to prevent the freezing of the water droplets accumulated in the opening 51 of the fuel gas pump 50 and the blockage of the opening 51.In addition, the water droplets accumulated in the opening 51 of the fuel gas pump 50 can be prevented from falling into the gas-liquid separator 40 and freezing to block the outlet path 43 of the gas-liquid separator 40 after the vehicle stops due to vibration or the like.

[0048] Furthermore, as described above, the inclined surface 46b is arranged on the extension plane S1 extending along the lower part of the inner wall surface 55a. This allows the flow of the fuel gas off-gas around the lower part of the inner wall surface 55a and the inclined surface 46b to be made particularly uniform. That is, it is particularly possible to suppress the stagnation of the fuel gas off-gas around the opening 51 of the fuel gas pump 50. Thus, the water in the fuel gas pump 50 can be efficiently pumped into the fuel cell stack 10 together with the fuel gas, so that it is particularly possible to suppress the remaining water in the fuel gas pump 50.

[0049] Furthermore, at least the lowermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction is formed to extend smoothly downward toward the downstream side in a region further downstream from the downstream end 42b of the introduction pipe 42. In this way, water droplets adhering to the lowermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction move to the downstream side of the second connecting portion 47 and fall into the reservoir 44. That is, unlike the case where, for example, a step protruding upward toward the downstream side is formed in the lowermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction, it is possible to suppress the accumulation of water droplets in the second connecting portion 47 of the gas-liquid separator 40.Accordingly, it is possible to prevent the water droplets accumulated in the second connecting portion 47 of the gas-liquid separator 40 from freezing and blocking the second connecting portion 47. It is also possible to prevent the water droplets accumulated in the second connecting portion 47 from falling into the gas-liquid separator 40 due to vibration or the like after the vehicle has stopped, and from freezing to block the outlet path 43 of the gas-liquid separator 40.

[0050] For example, in the embodiment described above, the example is shown in which the step 47b is not formed at least in the lowermost part of the inner peripheral surface 47a of the second connecting portion 47 in the circumferential direction. However, the step may also be formed along the entire circumference of the inner peripheral surface 47a.

[0051] Furthermore, in the above-described embodiment, the example in which the step 47b is formed on the inner peripheral surface 47a of the second connecting portion 47 of the gas-liquid separator 40 has been described. However, the step 47b need not be formed on the inner peripheral surface 47a of the second connecting portion 47.

[0052] In addition, for example, as a gas-liquid separator 40 of the fuel cell system according to a Fig. In the first modification of the invention shown in Figure 8, the step 47b may be formed on an upper half of the inner peripheral surface 47a of the second connecting portion 47 and need not be formed on a lower half of the inner peripheral surface 47a. In this case, the radial length of the step 47b may be constant.

[0053] Furthermore, in the above-described embodiment, the example in which the tip end of the first connecting portion 46 is formed with the tapered surface 46c is shown. However, the tip end of the first connecting portion 46 need not be formed with the tapered surface 46c.

[0054] Furthermore, for example, as a gas-liquid separator 40 of the fuel cell system according to a Fig. 9 and Fig. In the second modification of the invention shown in FIG. 10, the tip end of the first connecting portion 46 may be formed with cutouts 46d that slope downward as they extend toward the inner peripheral surface 46a. With this configuration, the water accumulated between the tapered surface 46c and the housing 55 can flow down through the cutouts 46d to the gas-liquid separator 40.

[0055] Furthermore, in the above-described embodiment, the example shown is that at least the lowermost part of the second connecting portion 47 of the gas-liquid separator 40 is formed in a linear shape without steps in the circumferential direction. On the downstream side of the downstream end 42b of the introduction pipe 42, a step may be formed at least in the lowermost part of the second connecting portion 47 in the circumferential direction, which is recessed downward toward the downstream side.

Claims

[1] Fuel cell system (1), comprising: a gas-liquid separator (40) configured to separate liquid contained in the fuel gas exhaust gas discharged from a fuel cell stack (10) from the fuel gas exhaust gas and to store and discharge the separated liquid; and a fuel gas pump (50) connected to the gas-liquid separator (40) and configured to return the fuel gas exhaust gas in the gas-liquid separator (40) to the fuel cell stack (10); wherein the gas-liquid separator (40) has a first connecting portion (46) which is tubular and extends upwardly; the fuel gas pump (50) has an inner wall surface (55a) forming a pump chamber (550), and a lower part of the inner wall surface (55a) is formed with an opening (51) configured such that the first connecting portion (46) is inserted into the opening (51); and a head end of the first connecting portion (46) is arranged at a height equal to the height of an extension plane extending along the lower part of the inner wall surface (55a); characterized by , that the lower part of the inner wall surface (55a) is inclined downwards towards the opening (51); the head end of the first connecting portion (46) is formed with an inclined surface (46b) which adjoins an inner peripheral surface (46a) of the first connecting portion (46) and is inclined downwards towards the inner peripheral surface (46a); and the inclined surface (46b) of the first connecting portion (46) is arranged on the extension plane. [2] Fuel cell system (1) according to claim 1, further comprising: an introduction line (42) configured to introduce the fuel gas exhaust gas discharged from the fuel cell stack (10) into the gas-liquid separator (40), wherein the gas-liquid separator (40) has a second connecting portion (47) which is tubular and is configured such that the introduction line (42) is inserted into the second connecting portion (47) and is connected to the second connecting portion (47); and at least a lowermost part of an inner peripheral surface (47a) of the second connecting portion (47) is formed in a circumferential direction so as to extend smoothly downward to a downstream side in a region further downstream from a downstream end (42b) of the introduction pipe (42).

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