JP2009070641A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing closure of a passage of a check valve at the time of freezing. <P>SOLUTION: The check valve 27 is installed between a piping a6 connected to the exit of an anode pole of a fuel cell and a piping a7 connected to an ejector, and prevents reverse flow of hydrogen to bypass the fuel cell at the time of purging and air to bypass the fuel cell at the time of scavenging. Furthermore, the check valve 27 has a drain hole 27c at the lower part in vertical direction than the opening part 27b1, which communicates inclined in vertical direction. The diameter of this drainage hole 27c is formed smaller than the opening area of the opening part 27b1, and the bypass ratio of the scavenging flux rate bypassing the fuel cell against the scavenging flux rate passing through the fuel cell at scavenging is made to be at least ≤10%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system having a backflow prevention valve in a fuel gas circulation passage.

  In the fuel cell system, in order to effectively use the fuel, the fuel exhaust gas containing unreacted hydrogen discharged from the fuel cell is generally supplied to the fuel cell again through the fuel gas circulation passage. It is. The fuel gas circulation flow path is provided with a backflow prevention valve for preventing the scavenging gas from being discharged by bypassing the fuel cell during scavenging and preventing hydrogen from being discharged by bypassing the fuel cell at the time of purging. ing.

In addition, when the fuel cell system is used in a low-temperature environment that reaches below freezing point, a so-called reed valve having a shape that prevents water from adhering to the valve body is used to prevent the backflow prevention valve from freezing. It has been proposed to use (see, for example, Patent Document 1).
JP 2003-203661 (paragraphs 0017 to 0021, FIG. 2)

  However, in the conventional fuel cell system, when the backflow prevention valve (reed valve) is arranged in the middle of the fuel gas circulation channel rising from the bottom to the top in consideration of drainage, the outlet portion of the backflow prevention valve Water easily collects. A very small amount of water circulates in the ejector and returns to the fuel cell, so there is no problem, but a large amount of water may accumulate at the outlet of the check valve. If the water accumulated in such a large amount does not come out after the operation of the fuel cell system is stopped, there is a problem that the channel is blocked during freezing.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a fuel cell system capable of preventing the flow path of the check valve during freezing from being blocked.

  According to a first aspect of the present invention, there is provided a fuel gas supply path for supplying fuel gas from a fuel gas supply source to an anode electrode of the fuel cell, a fuel exhaust gas discharged from the fuel cell, and a fuel gas from the fuel gas supply source. And a fuel gas circulation channel having an ejector that is re-supplied to the fuel cell, a purge channel having a purge valve that exhausts the fuel exhaust gas discharged from the fuel cell to the outside, and the fuel cell An oxidant gas supply path for supplying an oxidant gas from an oxidant gas supply source to the cathode electrode, and an oxidant gas from the oxidant gas supply source can be introduced into the fuel gas supply path when scavenging the anode electrode The scavenging gas introduction means, the backflow prevention valve for preventing the oxidant gas introduced by the scavenging gas introduction means from bypassing the fuel cell and flowing into the purge flow path, and the backflow prevention valve. A drain hole which is characterized in that it comprises a.

  According to the first aspect of the present invention, the water at the outlet portion of the backflow prevention valve can be completely drained during gravity or scavenging, so that the backflow prevention valve can be prevented from being blocked during freezing. become.

  In the invention according to claim 2, the drain hole has a hole diameter smaller than an opening area when the check valve is opened, and bypasses the fuel cell with respect to a scavenging flow rate passing through the fuel cell during the scavenging. The bypass rate of the scavenging flow rate is configured to be at least 10% or less.

  According to the second aspect of the present invention, by setting the hole diameter of the drain hole so that the bypass rate does not exceed 10%, the reverse flow rate at the time of purging or scavenging can be made small enough to be ignored.

  The invention according to claim 3 is characterized in that the drain hole is provided below the opening of the backflow prevention valve and communicated at least inclined toward the top and bottom direction.

  According to the invention which concerns on Claim 3, it becomes possible to make it easier to drain the water of the exit part of a backflow prevention valve.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can prevent the flow path obstruction | occlusion of the backflow prevention valve at the time of freezing can be provided.

  1 is an overall configuration diagram showing the fuel cell system of the present embodiment, FIG. 2 is a sectional view showing a backflow prevention valve, FIG. 3 is an exploded perspective view showing the backflow prevention valve, and FIG. 4 is a sectional view taken along line AA in FIG. FIG. 5 is a graph showing the relationship between the scavenging flow rate passing through the fuel cell and the bypass rate with respect to the hole diameter of the drain hole. Note that the fuel cell system of the present embodiment can be applied to a vehicle (fuel cell vehicle, etc.), a mobile body such as a ship, an aircraft, and a stationary type such as a household power source.

  As shown in FIG. 1, the fuel cell system 1 of this embodiment includes a fuel cell 10, an anode system 20, a cathode system 30, an anode scavenging means 40, a diluter 50, a control device 60, and the like.

  In the fuel cell 10, for example, one side of an electrolyte membrane 11 made of a solid polymer is sandwiched between an anode 12 and the other side is sandwiched between cathodes 13, and the outside is sandwiched between a pair of conductive separators 14 and 15. It has a structure in which a plurality of configured single cells are stacked. The separator 14 of the fuel cell 10 is formed with an anode flow path 14a through which hydrogen (fuel gas) flows, and the separator 15 is formed with a cathode flow path 15a through which air (oxidant gas) flows. The separator 15 (or 14) is formed with a refrigerant flow path (not shown) through which a refrigerant for cooling the fuel cell 10 flows. Note that FIG. 1 schematically shows a stacked state of single cells for convenience of explanation.

  The anode system 20 is a system for supplying and discharging hydrogen to the fuel cell 10, and includes a hydrogen tank 21, a shutoff valve 22, a regulator 23, a heat exchanger 24, an ejector 25, a purge valve 26, a backflow prevention valve 27, and pipes a1 to a1. a8 or the like.

  The hydrogen tank 21 is made of, for example, an aluminum alloy, and has a tank chamber (not shown) for storing high-purity hydrogen gas at a high pressure therein. The periphery of the tank chamber is CFRP (Carbon Fiber Reinforced Plastic). : Carbon fiber reinforced plastic) or a cover (not shown) formed of GFRP (Glass Fiber Reinforced Plastic) or the like.

  The shut-off valve 22 is an electromagnetically operated ON / OFF valve having a solenoid, for example, and is connected to the hydrogen tank 21 through a pipe a1.

  The regulator 23 has a function of reducing the high-pressure hydrogen supplied from the hydrogen tank 21 to a predetermined pressure, and is connected to the shutoff valve 22 via a pipe a2.

  The heat exchanger 24 operates when the fuel cell 10 is warmed up, has a function of warming and supplying hydrogen supplied from the hydrogen tank 21 to the fuel cell 10, and is connected to the regulator 23 via a pipe a3. Yes. The heat exchanger 24 is warmed up (heat exchange) by circulating, for example, a refrigerant warmed by a heater (electric type, catalytic combustion type).

  The ejector 25 has a function of mixing fuel exhaust gas (including unreacted hydrogen) discharged from the fuel cell 10 with hydrogen supplied from the hydrogen tank 21 and resupplying the fuel cell 10. More specifically, the ejector 25 incorporates a nozzle that injects hydrogen supplied from the hydrogen tank 21, generates a negative pressure by injecting hydrogen from the nozzle, and exhausts the fuel exhaust gas discharged from the fuel cell 10. Then, the hydrogen from the hydrogen tank 21 and the fuel exhaust gas are mixed and supplied to the fuel cell 10 again.

  The ejector 25 is connected to the heat exchanger 24 via a pipe a4 and is connected to the inlet of the anode flow path 14a of the fuel cell 10 via a pipe a5. Moreover, the ejector 25 is connected to the outlet of the anode flow path 14a of the fuel cell 10 through the pipes a6 and a7.

  The purge valve 26 is, for example, an electromagnetically operated ON / OFF valve having a solenoid. When the purge valve 26 is opened (ON), the fuel exhaust gas discharged from the fuel cell 10 is discharged into the anode flow path 14a of the fuel cell 10 and It has a function of discharging (purging) the piping a5 to a8 (anode circulation system) outside (outside of the system). The purge valve 26 is connected to a pipe a8 branched from the pipe a6.

  In this embodiment, the pipes a1 to a5 correspond to the fuel gas supply path, the pipes a6 and a7 correspond to the fuel gas circulation flow path, and the pipe a8 corresponds to the purge flow path.

  The backflow prevention valve 27 is provided in the middle of the fuel gas circulation passage (between the pipe a6 and the pipe a7), and bypasses the fuel cell 10 during purge (when the purge valve 26 is opened) or during scavenging ( It has a function of preventing the pipes a6 and a7 from flowing back and flowing into the pipe a8 (purge flow path).

  As shown in FIG. 2, the backflow prevention valve 27 is a so-called reed valve, and is provided on one surface side (inlet side) of the partition wall 27S having the first valve portion 27A (see FIGS. 3 and 4) and the second valve portion 27B. A housing 28 having a first pressure chamber 28a is provided, and a housing 29 having a second pressure chamber 29a is provided on the other surface side (outlet side). In FIG. 4, the first valve portion 27A and the second valve portion 27B are partially simplified in cross section.

  As shown in FIGS. 3 and 4, the first valve portion 27A includes a rectangular opening 27a1 formed in the partition wall 27S, a strip-shaped reed valve (valve element) 27a2, a stopper 27a3, and a screw 27a5. It consists of and. The reed valve 27a2 can cover the opening 27a1 and is formed longer than the lower edge of the opening 27a1. The stopper 27a3 has a function of limiting the stroke when the reed valve 27a2 is opened. The stopper 27a3 is formed with a long hole 27a4, which is inclined (warped) away from the partition wall 27S upward from the bottom. Yes. The stopper 27a3 is provided on the back side of the reed valve 27a2, and is screwed to the partition wall 27S with a screw 27a5 with the reed valve 27a2 sandwiched in the lower part thereof.

  Similarly to the first valve portion 27A, the second valve portion 27B includes a rectangular opening 27b1 formed in the partition wall 27S, a strip-shaped reed valve 27b2, a stopper 27b3, and a screw 27b5. Has been. The opening 27b1 is formed so as to be displaced in the vertical direction and the horizontal direction (horizontal direction) with respect to the opening 27a1. The reed valve 27b2 can cover the opening 27b1, and is longer than the upper edge of the opening 27b1. The stopper 27b3 has a function of limiting the stroke when the reed valve 27b2 is opened. The stopper 27b3 is formed with an elongated hole 27b4 and inclined (warped) away from the partition wall 27S from the top to the bottom. Yes. The stopper 27b3 is provided on the back side of the reed valve 27b2, and is screwed to the partition wall 27S with screws 27b5 with the reed valve 27b2 sandwiched between the stoppers 27b3.

  The housing 28 has an introduction hole 28b that is introduced from the pipe a6 (see FIG. 2) into the first pressure chamber 28a. The housing 29 is formed with a discharge hole 29b that is discharged from the second pressure chamber 29a to the pipe a7 (see FIG. 2). The first pressure chamber 28a serves as an inlet side during circulation of fuel exhaust gas containing unreacted hydrogen discharged from the fuel cell 10 during normal operation (steady operation), and the second pressure chamber 29a serves as a fuel. It becomes the outlet side when exhaust gas is circulated.

  When the pressure in the first pressure chamber 28a becomes higher than the pressure in the second pressure chamber 29a, the reed valves 27a2 and 27b2 act in the direction of opening, and the valve opens at an opening corresponding to the pressure difference. . As a result, the fuel exhaust gas discharged from the fuel cell 10 flows from the first pressure chamber 28a through the openings 27a1 and 27b1 to the second pressure chamber 29a. Conversely, when the pressure in the second pressure chamber 29a becomes higher than the pressure in the first pressure chamber 28a, the reed valves 27a2 and 27b2 are pressed against the partition wall 27S to close.

  As shown in FIGS. 2 and 3, the partition wall 27S is provided with a drain hole 27C below the openings 27a1 and 27b1. As shown in FIG. 2, the drain hole 27C communicates so as to incline downward from the second pressure chamber 29a (exit side) toward the first pressure chamber 28a (inlet side) with respect to the vertical direction. Is formed.

  In the present embodiment, the case where the drain hole 27C is formed at one place will be described as an example, but the present invention is not limited to this and may be formed at a plurality of places. Further, the drain hole 27C is not limited to being inclined, and may be formed so as to be communicated directly downward along the vertical direction.

  The drain hole 27C has a hole diameter smaller than the opening area (opening area at the time of opening) of the openings 27a1 and 27b1 of the check valve 27. As shown in FIG. 5, the hole diameter has a bypass rate of at least 10% of the scavenging flow rate bypassing the fuel cell 10 with respect to the scavenging flow rate passing through the fuel cell (FC) 10 during scavenging. It is preferable to set to be as follows. In FIG. 5, the maximum possible scavenging flow rate is the maximum possible scavenging flow rate that can be introduced by the air compressor 31 with the scavenging introduction valve 42 opened (when the diameter of the drain hole 27C is 0). The required scavenging flow rate lower limit value is a lower limit value of the required scavenging flow rate that is required when scavenging the anode 12 or the like of the fuel cell 10. That is, with respect to the lower limit value of the required scavenging flow rate, the hole diameter of the drain hole 27C is a scavenging flow rate that does not flow backward even if there is a scavenging flow rate bypassed by the drain hole 27C (maximum possible introduction by the air compressor 31). Set a hole diameter with a margin of (scavenging flow rate−bypass scavenging flow rate) with respect to the lower limit. Thus, by setting the hole diameter of the drain hole 27C to 10% or less with a margin, it is possible to suppress power consumption in the air compressor 31.

  Incidentally, for example, when the hole diameter of the drain hole 27C is φ1 (diameter 1 mm), the total opening area of the openings 27a1 and 27b1 of the check valve 27 is set to φ20 (converted to φ equivalent). In this case, since the area ratio of (hole diameter / opening) is (about 1/400), the reverse flow rate during scavenging or purging is small enough to be ignored.

  The cathode system 30 includes an air compressor 31, a humidifier 32, a back pressure valve 33, pipes c1 to c3, and the like. Note that the pipes c1 and c2 in the present embodiment correspond to an oxidant gas supply path.

  The air compressor 31 includes a supercharger driven by a motor, and has a function of taking in and compressing outside air and supplying the compressed air to the fuel cell 10.

  The humidifier 32 has a function of humidifying the compressed air and supplying it to the cathode electrode 13 of the fuel cell 10. The humidifier 32 uses, for example, generated water discharged from the cathode electrode 13 of the fuel cell 10 as a humidification source. Further, the humidifier 32 is connected to the air compressor 31 via a pipe c1 and is connected to the inlet of the cathode flow path 15a of the fuel cell 10 via a pipe c2.

  The back pressure valve 33 is constituted by a valve such as a butterfly valve capable of adjusting the opening, and has a function of appropriately adjusting the pressure of the cathode system 30 (cathode electrode 13). Further, the back pressure valve 33 is connected to the outlet of the cathode flow path 15a of the fuel cell 10 via the pipe c3.

  The anode scavenging means 40 includes a scavenging introduction pipe 41 and a scavenging introduction valve 42.

  One end (upstream side) of the scavenging air introduction pipe 41 is connected to the upstream pipe c1 of the humidifier 32, and the other end (downstream side) is connected to the downstream pipe a5 of the ejector 25.

  The scavenging introduction valve 42 is provided in the scavenging introduction pipe 41 and is controlled to be opened and closed by a control device 60 described later. The scavenging insertion valve 42 is not limited to the one provided in the middle of the scavenging introduction pipe 41. For example, the scavenging insertion valve 42 may be configured by a three-way valve and provided at the connection portion between the pipe c1 and the scavenging introduction pipe 41.

  The above-described anode scavenging means 40 supplies air from the air compressor 31 as the scavenging gas to the anode system 20 during scavenging performed after the operation of the fuel cell system 1 is stopped, and discharges moisture in the anode system 20 to freeze it. It has a function to prevent. The water in the anode system 20 is generated water that has permeated from the cathode electrode 13 of the fuel cell 10 to the anode electrode 12 through the electrolyte membrane 11.

  In the diluter 50, a pipe 51 connected to the purge valve 26 and a pipe 52 connected to the back pressure valve 33 are connected to each other, and hydrogen discharged from the anode electrode 12 is discharged from the cathode electrode 13. It has the function of being diluted with cathode exhaust gas and discharged outside the system (outside).

  The control device 60 includes a CPU (Central Processing Unit), a memory, various circuits, and the like. The control device 60 is connected to the shutoff valve 22, the purge valve 26, the air compressor 31, the back pressure valve 33, and the scavenging introduction valve 42, and opens and closes the shutoff valve 22, the purge valve 26 and the scavenging introduction valve 42. And the opening degree of the back pressure valve 33 is controlled.

  Next, operation | movement of the fuel cell system 1 of this embodiment is demonstrated. First, during normal operation (during steady operation), the shutoff valve 22 is opened and the anode 12 of the fuel cell 10 from the hydrogen tank 21 is opened with the scavenging introduction valve 42 closed under the control of the control device 60. Then, hydrogen depressurized to a predetermined pressure by the regulator 23 is supplied. Further, the air compressor 31 is driven by the control of the control device 60, and the air humidified by the humidifier 32 is supplied to the cathode 13 of the fuel cell 10. Thereby, in the anode electrode 12, hydrogen is separated into hydrogen ions and electrons by the action of the catalyst, the hydrogen ions are transmitted to the cathode electrode 13 through the electrolyte membrane 11, and the electrons pass through an external load (not shown). By moving to the cathode electrode 13, power generation becomes possible. In the cathode 13, water is generated by the reaction of hydrogen ions, electrons, and oxygen by the action of the catalyst.

  Then, the fuel exhaust gas containing unreacted hydrogen discharged from the fuel cell 10 is supplied to the first pressure chamber 28a and the openings 27a1, 27b1 of the check valve 27 via the pipe a6, as indicated by reference numeral R1 in FIG. The second pressure chamber 29a and the pipe a7 are returned to the ejector 25. The fuel exhaust gas that has returned to the ejector 25 is mixed with hydrogen from the hydrogen tank 21 and re-supplied to the anode electrode 12 of the fuel cell 10. Further, when the fuel exhaust gas circulates through the pipes a6 and a7, a small amount of water remaining in the second pressure chamber 29a of the check valve 27 flows into the anode 12 of the fuel cell 10 together with the flow.

  When power generation is continued in the fuel cell 10, nitrogen contained in the air on the cathode electrode 13 side, water generated at the cathode electrode 13 and the like permeate the electrolyte membrane 11 and move to the anode electrode 12, and the anode The hydrogen concentration on the electrode 12 side (the anode channel 14a, the pipes a5, a6, a7) decreases. For this reason, the purge is executed in the anode system 20. That is, when the purge valve 26 is periodically opened by the control device 60, for example, impurities such as nitrogen are discharged out of the system through the pipe a8 and the pipe 51, and fresh hydrogen is discharged from the hydrogen tank 21. As a result, a decrease in power generation performance due to a decrease in hydrogen concentration is prevented.

  In addition, even when hydrogen flows back through the pipe a7 during the purge, the pressure in the second pressure chamber 29a is higher than the pressure in the first pressure chamber 28a, so that the openings 27a1, 27b1 are opened by the reed valves 27a2, 27b2. The hydrogen from the hydrogen tank 21 does not escape from the second pressure chamber 29a to the first pressure chamber 28a through the openings 27a1 and 27b1. However, although a small amount of hydrogen may leak through the drain hole 27C formed in the check valve 27, the hydrogen leaking from the drain hole 27C at this time is drained as described with reference to FIG. Since the opening diameter (opening area) of the hole 27C is sufficiently small (for example, about 1: 400) with respect to the opening diameter (opening area) of the opening portions 27a1 and 27b1, the anode 12 of the fuel cell 10 is formed. The reverse flow rate of bypassing hydrogen can be made small enough to be ignored. Therefore, a sufficient amount of hydrogen can be reliably supplied to the anode electrode 12 at the time of purging. The hydrogen discharged from the purge valve 26 at the time of purging is diluted by the cathode exhaust gas discharged from the cathode electrode 13 in the diluter 50 and discharged outside the system (outside).

  When an operation stop instruction is issued to the fuel cell system 1, the control device 60 closes the shut-off valve 22 and stops the supply of hydrogen to the anode electrode 12 of the fuel cell 10. In addition, when it is determined that the water remaining in the fuel cell system 1 may freeze, the control device 60 performs scavenging (cathode scavenging, anode scavenging). The condition for determining whether or not to perform scavenging may be determined based on, for example, the outside air temperature, or may be determined based on the weather forecast information of the current location.

  When it is determined that the scavenging is to be performed, the control device 60 first executes the cathode scavenging, for example. That is, when the back pressure valve 33 is fully opened by the control device 60, air (cathode gas) is supplied as a scavenging gas from the air compressor 31, for example, for a predetermined time (predetermined flow rate), and the water remaining in the cathode system 30. Is discharged out of the system.

  Then, the control device 60 opens the purge valve 26 and the scavenging introduction valve 42, controls the back pressure valve 33 in the closing direction, supplies air from the air compressor 31 as scavenging gas, and scavenges the anode system 20. (Anode scavenging). That is, the air supplied to the pipe a5 passes through the anode flow path 14a of the fuel cell 10 and is discharged together with residual water from the purge valve 26 via the pipes a6 and a8. At this time, even if air (scavenging gas) flows back through the pipe a7, the pressure in the second pressure chamber 29a becomes higher than the pressure in the first pressure chamber 28a, so the openings 27a1, 27b1 are connected to the reed valves 27a2, 27b2. Therefore, air does not leak from the second pressure chamber 29a to the first pressure chamber 28a through the openings 27a1 and 27b1. However, a small amount of air escapes from the drain hole 27C formed in the check valve 27. At this time, the air leaking from the drain hole 27C has an opening diameter of the drain hole 27C (see FIG. 5). Since the opening area is sufficiently small (for example, about 1: 400) with respect to the opening diameters (opening areas) of the openings 27a1 and 27b1, the reverse flow rate of air bypassing the anode electrode 12 of the fuel cell 10 Can be made small enough to be ignored. Accordingly, since a sufficient flow rate of air can be supplied to the anode electrode 12 during scavenging, it is possible to reliably discharge the moisture remaining in the anode electrode 12.

  In addition, when a large amount of water is accumulated in the second pressure chamber 29a of the backflow prevention valve 27 during the cathode scavenging at the time of the operation stop command of the fuel cell system 1, the water in the second pressure chamber 29a is removed by gravity. It passes through the hole 27C and exits to the first pressure chamber 28a (see symbol R2 in FIG. 2). On the other hand, when a large amount of water is accumulated in the second pressure chamber 29a of the backflow prevention valve 27 during the scavenging of the anode, the large amount of accumulated water passes through the drain hole 27C by the pressure of the air introduced as the scavenging gas. Then, it is pushed out into the first pressure chamber 28a (see reference numeral R2 in FIG. 2).

  Thus, even if a large amount of water accumulates in the backflow prevention valve 27 (for example, up to the height of the discharge hole 29b of the second pressure chamber 29a), the large amount of water is prevented from flowing back through the drain hole 27C. Since the valve 27 can be completely withdrawn, the blockage of the flow path during freezing can be prevented.

  In this embodiment, since the size (hole diameter) of the drain hole is formed sufficiently smaller than the openings of the openings 27a1 and 27b1, the fuel cell 10 is bypassed at the time of purging or anode scavenging. The discharged gas flow rate can be made small enough to be ignored. Therefore, at the time of purging, hydrogen from the hydrogen tank 21 can be sufficiently supplied to the anode electrode 12 of the fuel cell 10. Further, during the scavenging of the anode, the scavenging gas (air) can be supplied to the anode electrode 12 of the fuel cell 10 to reliably discharge the water remaining in the anode electrode 12.

  Moreover, in this embodiment, since it forms so that it may incline below with respect to the top-and-bottom direction toward the entrance side (1st pressure chamber 28a) from the exit side (2nd pressure chamber 29a) of the drain hole 27C. The water accumulated in the second pressure chamber 29a can be easily discharged by gravity.

  Further, as in this embodiment, at the time of purging and anode scavenging, a rapid flow from the fuel cell 10 through the pipes a6 and a8 to the purge valve 26 is generated in the vicinity of the outlet of the drain hole 27C. A negative pressure is generated in the vicinity of the first pressure chamber 28a side of the vent hole 27C, and the water accumulated in the second pressure chamber 29a is sucked through the drain hole 27C, so that the water accumulated in the backflow prevention valve 27 is sucked. The discharge performance can be further increased.

  The shape of the backflow prevention valve 27 of this embodiment, the connection positions of the pipes a6, a7, and a8 connected to the backflow prevention valve 27 are examples, and may be changed as appropriate according to the layout configuration of the fuel cell system 1. be able to. For example, in the above-described embodiment, the example in which the pipe a8 (purge flow path) including the purge valve 26 is configured to branch with respect to the pipe a6 has been described, but the present invention is not limited thereto. The pipe a6 is connected to the top and bottom of the first pressure chamber 28a of the backflow prevention valve 27 (the state of FIG. 2), and the pipe a8 (purge flow path) provided with the purge valve 26 is connected to the backflow prevention valve 27 of the backflow prevention valve 27. Connection may be made so that the position of the drain hole 27C is located between the pipe a6 and the pipe a8.

  Further, in the present embodiment, the example in which the cathode scavenging is performed and then the anode scavenging is described has been described. However, the present invention is not limited to this. For example, the cathode scavenging and the anode scavenging are performed simultaneously. May be.

It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is sectional drawing which shows a backflow prevention valve. It is a disassembled perspective view which shows a backflow prevention valve. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is a graph which shows the relationship between the scavenging flow rate which passes a fuel cell with respect to the hole diameter of a drain hole, and a bypass rate.

Explanation of symbols

1 Fuel cell system 10 Fuel cell 21 Hydrogen tank (fuel gas supply source)
a1 to a5 piping (fuel gas supply path)
a6, a7 piping (fuel gas circulation flow path)
a8 Piping (Purge flow path)
c1, c2 piping (oxidant gas supply path)
21 Hydrogen tank (fuel gas supply source)
26 Purge valve 27 Backflow prevention valve 27a1, 27b1 Opening 27C Drain hole 31 Air compressor (oxidant gas supply source)
40 Anode scavenging means 41 Scavenging introduction pipe 42 Scavenging introduction valve

Claims (3)

A fuel gas supply path for supplying fuel gas from a fuel gas supply source to the anode electrode of the fuel cell;
A fuel gas circulation passage comprising an ejector for mixing fuel exhaust gas discharged from the fuel cell with fuel gas from the fuel gas supply source and re-supplying the fuel cell;
A purge flow path provided with a purge valve for discharging the fuel exhaust gas discharged from the fuel cell to the outside;
An oxidant gas supply path for supplying an oxidant gas from an oxidant gas supply source to the cathode of the fuel cell;
Scavenging introduction means for allowing an oxidant gas from the oxidant gas supply source to be introduced into the fuel gas supply path when scavenging the anode electrode;
A backflow prevention valve that prevents the oxidant gas introduced by the scavenging gas introduction means from bypassing the fuel cell and flowing into the purge flow path;
A fuel cell system comprising: a drain hole provided in the backflow prevention valve.   The drain hole has a hole diameter smaller than the opening area when the check valve is opened, and the scavenging flow rate bypassing the fuel cell with respect to the scavenging flow rate passing through the fuel cell during the scavenging is at least 10 The fuel cell system according to claim 1, wherein the fuel cell system is configured to be equal to or less than%.   3. The fuel cell according to claim 1, wherein the drain hole is provided below an opening of the backflow prevention valve and communicated with at least an inclination toward the top and bottom. system.

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