Fuel cell system and purging procedure for it

Abstract

Fuel cell system (100, 100a) featuring: a fuel cell (1) comprising an inlet (11) and an outlet (12) for purge gas; a first injection device (31, 32) and a second injection device (33) that inject the purge gas; a gas-liquid separator (5) which separates liquid water from the purge gas which is expelled from the outlet (12) and causes the liquid water to flow out of an opening (52a) which is formed on a vertical, lower side of the gas-liquid separator (5); an outlet valve (6) which expels the liquid water flowing out of the opening (52a) to the outside; an ejector (4), comprising: an inlet opening (45) into which the purge gas from the gas-liquid separator (5) flows; and an outlet opening (46) through which the purge gas injected by the first injection device (31, 32) flows out together with the purge gas flowing from the inlet opening (45); a first connecting path (L30) that is connected between the outlet opening (46) and the inlet (11); an inlet path (L34) which introduces the purge gas injected from the second injection device (33) into the first connecting path (L30) without flowing through the ejector (4); a second connection path (L32) that is connected between the gas-liquid separator (5) and the outlet (12); and a third connection path (L33) which is connected between the gas-liquid separator (5) and the inlet opening (45), and which extends vertically upwards from the gas-liquid separator (5); characterized by a controller (70) which is configured to to purge the ejector (4), the fuel cell (1) and the second connecting path (L32) by performing an injection of the first injection device (31), to purge the third connection path (L33) by stopping the injection of the first injection device (31, 32) and performing an injection of the second injection device (33), and to expel the liquid water in the gas-liquid separator (5) by opening the outlet valve (6).

Description

Field of invention

[0001] The present invention relates to a fuel cell system and a purging method for it. background

[0002] In a purging process for the anode system of a fuel cell system, anode gas is injected by an injection device or injector and then flows through an ejector into the fuel cell. After being expelled from the fuel cell, the anode gas is separated from the liquid water in the gas-liquid separator and then flows from the gas-liquid separator through a circulation path into the ejector. The anode gas thus circulates through the fuel cell (see, for example, JP 2008-021537A). JP 2003-178782A and US 2011 / 0053013A1 disclose a fuel cell system in which a hydrogen pump located on the suction side of the ejector and the associated piping are purged by reverse flow through them during the purging process to remove water. Furthermore, JP 2017 - 147 135 A discloses a fuel cell system according to the preamble of claim 1.

[0003] Even if the anode gas flows in one direction of the circulation described above during the purging process, moisture, such as water vapor contained in the anode gas, is not separated in the gas-liquid separator. Consequently, the moisture in the circulation path is cooled, which can lead to dew formation, and liquid water may remain in the circulation path. For this reason, if the circulation path extends vertically upwards from the gas-liquid separator to the ejector, the remaining liquid water could drip into the gas-liquid separator and then flow through a small opening, for example, on the underside of the gas-liquid separator, to an outlet valve if the fuel cell does not produce power for an extended period after the purging process.If the liquid water freezes below freezing, the outlet valve will jam. This could make it difficult to expel the liquid water from the fuel cell system. Similarly, if liquid water remains in the ejector, circulation path, or any flow path located between the gas-liquid separator and the fuel cell after the purging process and freezes below freezing, the anode gas circulation path will be blocked. This could also make it difficult to expel the liquid water from the fuel cell system. Summary of the invention

[0004] It is therefore an object of the present invention to provide a fuel cell system and a purging method that reduces the amount of liquid water remaining after purging.

[0005] The above problem is solved by a fuel cell system comprising: a fuel cell having an inlet and an outlet for purge gas; a first injection device and a second injection device injecting the purge gas; a gas-liquid separator separating liquid water from the purge gas being expelled from the outlet and causing the liquid water to flow out of an opening formed on a vertical, lower side of the gas-liquid separator; an outlet valve ejecting the liquid water flowing out of the opening; and an ejector comprising: an inlet opening into which the purge gas flows from the gas-liquid separator; and an outlet opening through which the purge gas injected by the first injection device flows out together with the purge gas flowing from the inlet opening.a first connecting path that is connected between the outlet opening and the inlet; an introduction path that introduces the purge gas injected from the second injection device into the first connecting path without flowing through the ejector; a second connecting path that is connected between the gas-liquid separator and the outlet; a third connecting path that is connected between the gas-liquid separator and the inlet opening and that extends vertically upwards from the gas-liquid separator;and a controller configured to purge the ejector, fuel cell, and second connection path by performing an injection from the first injection device, to purge the third connection path by stopping the injection from the first injection device and performing an injection from the second injection device, and to expel the liquid water in the gas-liquid separator by opening the outlet valve.

[0006] In the configuration above, the controller can be set up to flush the third connection path after the ejector has been flushed.

[0007] In the configuration above, the controller can be set up to purge the third connection path after the ejector, fuel cell, and second connection path have been purged.

[0008] The above fuel cell system may further include a temperature sensing device that detects an outside air temperature, the controller being configured to purge the ejector, fuel cell, second connection path and third connection path when the outside air temperature is less than or equal to freezing point.

[0009] In the above configuration, the controller can be set up to purge the ejector, fuel cell, second connection path, and third connection path when the outside air temperature is higher than the freezing point and when it is determined that the temperature of the outlet valve is less than or equal to the freezing point.

[0010] The above fuel cell system can further include a control valve formed in the first connection path, which controls a flow rate of the purge gas flowing from the inlet path through the first connection path into the fuel cell according to an opening degree of the control valve, wherein the controller can be configured to control the opening degree of the control valve such that it is smaller when the third connection path is purged than when the ejector, the fuel cell and the second connection path are purged.

[0011] The above problem is also solved by a purging method for a fuel cell system, wherein the fuel cell system comprises: a fuel cell comprising an inlet and an outlet for purge gas; a first injection device and a second injection device injecting the purge gas; a gas-liquid separator separating liquid water from the purge gas ejected from the outlet and causing the liquid water to flow out of an opening formed on a vertical, lower side of the gas-liquid separator; an outlet valve ejecting the liquid water flowing out of the opening; an ejector comprising: an inlet opening into which the purge gas flows from the gas-liquid separator; and an outlet opening through which the purge gas injected by the first injection device flows out together with the purge gas flowing from the inlet opening;a first connection path connected between the outlet port and the inlet; an inlet path introducing the purge gas injected from the second injection device into the first connection path without flowing through the ejector; a second connection path connected between the gas-liquid separator and the outlet; and a third connection path connected between the gas-liquid separator and the inlet port, extending vertically upwards from the gas-liquid separator, wherein the purging method comprises: purging the ejector, the fuel cell, and the second connection path by injecting fuel from the first injection device; purging the third connection path by stopping injection from the first injection device and injecting fuel from the second injection device;and the expulsion of liquid water in the gas-liquid separator by opening the outlet valve.

[0012] In the above procedure, the flushing of the third connection path can be performed after flushing the ejector.

[0013] In the above procedure, the purging of the third connection path can be carried out after the purging of the ejector, the fuel cell and the second connection path.

[0014] In the above procedure, the fuel cell system may include a temperature sensing device that detects an outside air temperature; purging of the ejector, fuel cell, second connection path and purging of the third connection path may be performed when the outside air temperature is less than or equal to a freezing point.

[0015] In the above procedure, purging of the ejector, fuel cell, second connection path and purging of the third connection path can be carried out when the outside air temperature is higher than the freezing point and when it is determined that the temperature of the outlet valve is less than or equal to the freezing point.

[0016] In the above method, the fuel cell system can include a control valve formed in the first connection path and controlling a flow rate of the purge gas that flows from the inlet path through the first connection path into the fuel cell according to an opening degree of the control valve, and the method can include controlling the opening degree of the control valve such that it is smaller when purging the third connection path than when purging the ejector, the fuel cell and the second connection path. Effects of the invention

[0017] According to the present invention, it is possible to create a fuel cell system and a purging process that reduces the amount of liquid water remaining after purging. Brief description of the drawing Fig. 1 is a configuration view that shows an example of a fuel cell system; Fig. 2 is a view that shows an example of a flushing process for a return pipe; Fig. Figure 3 is a view that illustrates an example of a condition in which liquid water remaining in a return pipe collects in a gas-liquid separator; Fig. Figure 4 is a flowchart that illustrates an example of the operation of an electronic control unit (ECU); Fig. 5 is a flowchart that illustrates an example of the rinsing process; Fig. 6 is a flowchart that provides another example of the rinsing process; Fig. 7 is a configuration view that shows an example of another fuel cell system; Fig. Figure 8 is a view that shows another example of the flushing process for flushing the return pipe; and Fig. Figure 9 is a flowchart illustrating the purging process for another fuel cell system. Detailed description: Fuel cell system configuration 100

[0018] Fig. Figure 1 is a configuration view that illustrates an example of the fuel cell system 100. The fuel cell system 100 is, for example, mounted on a fuel cell vehicle and comprises a fuel cell (FC) 1, an electric motor M, a cathode system 2, an anode system 3, and a control system 7. The electrical configuration for connecting the FC 1 and the electric motor M is not shown.

[0019] The FC 1 comprises a stack of solid polymer electrolyte unit cells. The FC 1 receives a supply of cathode gas and anode gas to generate power in response to a chemical reaction between the cathode and anode gases. In the present embodiment, oxygen-containing air is used as the cathode gas and hydrogen gas as the anode gas. The anode gas is an example of a purge gas used for the purging process of the anode system. The power generated by the FC 1 is supplied to the electric motor M.

[0020] The FC 1 comprises an inlet 11 and an outlet 12 for the anode gas and an inlet 13 and an outlet 14 for the cathode gas. The inlet 11 and outlet 12 for the anode gas are connected via an anode gas flow path L31. The inlet 13 and outlet 14 for the cathode gas are connected via a cathode gas flow path L21. The anode gas flow path L31 and the cathode gas flow path L21 include collector tubes that pass through the stack of unit cells, grooves formed in separators of the unit cells, and the like.

[0021] Cathode system 2 supplies oxygen-containing air to FC 1 as cathode gas. For example, cathode system 2 comprises a cathode supply pipe L20, a cathode discharge pipe L22, and an air compressor (ACP) 20.

[0022] The cathode gas flows through the cathode supply pipe L20 and is fed to the FC 1 as indicated by arrow R20. The air compressor 20 is integrated into the cathode supply pipe L20. The air compressor 20 compresses and blows the cathode gas to the inlet 13 of the FC 1. The cathode gas in the FC 1 flows through the cathode gas flow path L21, as indicated by arrow R21. The FC 1 expels the cathode gas, which is used for power generation, as cathode exhaust from outlet 14 to the cathode discharge pipe L22. The cathode exhaust flows from outlet 14 of the FC 1 through the cathode discharge pipe L22 and is expelled to the outside, as indicated by arrow R22.

[0023] The anode system 3 supplies the FC 1 with the anode gas. The anode system 3 comprises an anode supply pipe L30, an anode discharge pipe L32, a return pipe L33, a bypass pipe L34, an exhaust gas discharge pipe L35, a fuel tank 30, main injectors (Main-INJ) 31 and 32, an auxiliary injector (Aux.-INJ) 33, an ejector 4, a gas-liquid separator 5, and an anode discharge valve 6.

[0024] The anode gas is stored in fuel tank 30 under high pressure. Fuel tank 30 supplies anode gas to the main injection units 31 and 32 and the auxiliary injection unit 33. The main injection units 31 and 32 and the auxiliary injection unit 33 inject the anode gas. The main injection units 31 and 32 are an example of a first injection device. The auxiliary injection unit 33 is an example of a second injection device.

[0025] The main INJs 31 and 32 are connected to the ejector 4. The auxiliary INJ 33 is connected to the anode feed tube L30 via the bypass tube L34.

[0026] Fig. Figure 1 shows a cross-section of the ejector 4 along the direction in which the anode gas flows. The ejector 4 comprises a fixing section 40, which has a disc shape, a large-diameter nozzle 41, a small-diameter nozzle 42, and a diffuser 43. The material of the ejector 4 includes, for example, steel-use stainless (SUS), but is not limited to this.

[0027] The fixing section 40 secures the large-diameter nozzle 41 and the small-diameter nozzle 42. An inlet 410 of the large-diameter nozzle 41 is connected to the main injection port 31. The inlet 420 of the small-diameter nozzle 42 is connected to the main injection port 32. The large-diameter nozzle 41 and the small-diameter nozzle 42 inject the anode gas from their respective injection ports in the main injection ports 31 and 32. The diameter of the injection port of the large-diameter nozzle 41 is larger than that of the injection port of the small-diameter nozzle 42.

[0028] The diffuser 43 comprises an ejector flow path 44 through which the anode gas flows, and an outlet opening 46 connected to the anode supply tube L30. An inlet opening 45, connected to the return tube L33, is formed on a side surface of the diffuser 43.

[0029] The anode gas injected from the main INJs 31 and 32 flows through the ejector flow path 44 to the outlet port 46, as indicated by arrows R1 and R2. The anode exhaust gas expelled from the FC 1 flows from the gas-liquid separator 5 through the return pipe L33 and then through the inlet port 45 into the ejector flow path 44. At this point, the anode gas injected from the large-diameter nozzle 41 and the small-diameter nozzle 42 serves as the propellant fluid, so that the anode exhaust gas is drawn into the ejector flow path 44 from the inlet port 45, as indicated by arrow R33.

[0030] The anode exhaust gas, which flows through the inlet opening 45 into the ejector 4, flows together with the anode gas injected from the main INJs 31 and 32 through the ejector flow path 44 and then flows through the outlet opening 46 to the anode supply tube L30. Thus, the anode exhaust gas and the anode gas flow through the inlet 11 into the FC 1, as shown by arrow R30.

[0031] One end of the anode supply tube L30 is connected to the outlet port 46 of the ejector 4. The other end of the anode supply tube L30 is connected to the anode gas inlet 11 of the FC 1. One end of the bypass tube L34, extending from the auxiliary INJ 33, is connected to a portion of the anode supply tube L30. When at least one of the main INJs 31 and 32 injects the anode gas, the anode gas injected by the auxiliary INJ 33 flows towards the FC 1 at a connection point P, which is positioned between the anode ejection tube L32 and the bypass tube L34.

[0032] Therefore, the anode gas injected from the auxiliary INJ 33 is introduced into the anode supply tube L30 without flowing through the ejector 4, and then flows through the inlet 11 into the FC 1, as indicated by arrow R3. The anode supply tube L30 is an example of a first connection path that is connected between the outlet port 46 and the inlet 11. The bypass tube L34 is an example of a feeder tube that supplies the anode gas injected from the auxiliary INJ 33 to the anode supply tube L30 without flowing through the ejector 4. The anode gas flows from the inlet 11 of the FC 1 through the anode gas flow path L31, as indicated by arrow R31, and then flows from the outlet 12 to the anode discharge tube L32.

[0033] One end of the anode discharge tube L32 is connected to the anode exhaust outlet 12 of the FC 1. The other end of the anode discharge tube L32 is connected to the gas-liquid separator 5. The anode exhaust flows from outlet 12 through the anode discharge tube L32 and then into the gas-liquid separator 5, as indicated by arrow R32. The anode discharge tube L32 is an example of a second connection path that is connected between the gas-liquid separator 5 and outlet 12.

[0034] The gas-liquid separator 5 separates liquid water from the anode exhaust gas discharged from the outlet 12 and discharges the liquid water vertically through an opening formed on a lower side of the gas-liquid separator 5. One end of the exhaust gas discharge pipe L35 is connected to the gas-liquid separator 5. The other end of the exhaust gas discharge pipe L35 is connected to the cathode exhaust pipe L22. The exhaust gas discharge pipe L35 is equipped with an anode discharge valve 6. When the anode discharge valve 6 opens, the liquid water and a portion of the anode exhaust gas flowing out of the opening of the gas-liquid separator 5 are discharged through the exhaust gas drain pipe L35 to the cathode discharge pipe L22 and then expelled to the outside along with the cathode exhaust gas. The anode discharge valve 6 is an example of a discharge valve that expels liquid water flowing out of its opening to the outside.

[0035] One end of the return pipe L33 is connected to the gas-liquid separator 5. The other end of the return pipe L33 is connected to the inlet opening 45 of the ejector 4. The anode exhaust gas flows from the gas-liquid separator 5 through the return pipe L33 and then through the inlet opening 45 into the ejector 4. The return pipe L33 is an example of a third connection path that is connected between the gas-liquid separator 5 and the inlet opening 45 and extends vertically upwards from the gas-liquid separator 5.

[0036] The control system 7 comprises an ECU 70, an ignition switch 71, an accelerator opening sensor 72, and temperature sensors 73 and 74. The ignition switch 71 informs the ECU 70 of instructions to start and stop the fuel cell vehicle. The accelerator opening sensor 72 detects the opening degree of an accelerator (not shown) of the fuel cell vehicle and informs the ECU 70 of this degree. The temperature sensor 73 detects the ambient air temperature and informs the ECU 70 accordingly. The temperature sensor 74 detects the coolant temperature of the FC 1 and informs the ECU 70 accordingly. The temperature sensor 73 is an example of a temperature sensing device.

[0037] The ECU 70 comprises a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The ECU 70 is electrically connected to the ignition switch 71, the accelerator opening sensor 72, the temperature sensors 73 and 74, the air compressor 20, the main INJs 31 and 32, the auxiliary INJ 33, and the anode ejection valve 6.

[0038] The ECU 70 calculates a current value required for the FC 1 according to the accelerator pedal opening degree detected by the accelerator opening sensor 72. The ECU 70 issues a command regarding the cathode gas flow rate to the air compressor 20 and a command regarding the anode gas injection quantity to at least one of the main INJs 31 and 32. When the FC 1 load is at its maximum, the ECU 70 can issue a command regarding the injection quantity to the auxiliary INJ 33 in addition to the main INJs 31 and 32.

[0039] The ECU 70 performs the purging procedure for the fuel cell system 100. When it detects that the ignition switch 71 is off, the ECU 70 performs a purging process for the anode system 3 according to the ambient air temperature and the temperature of the gas-liquid separator 5. The anode gas is used as the purge gas in the purging process. The ECU 70 purges the ejector 4, the anode gas flow path L31 of the FC 1, and the anode discharge tube L32 by injecting the main INJs 31 and 32.

[0040] At this point, the anode gas flows through the paths indicated by arrows R30 and R33. Any remaining liquid water collects in the gas-liquid separator 5 via ejector 4, anode gas flow path L31 of FC 1, and anode discharge pipe L32. Furthermore, the return pipe L33 extends vertically upwards from the gas-liquid separator 5 to the ejector 4. Therefore, any moisture, such as water vapor, that was not separated in the gas-liquid separator 5 could condense in the return pipe L33, potentially leaving liquid water within it. In this case, the liquid water could drip into the gas-liquid separator 5 and, after the purging process, could flow out of the small opening formed on the underside of the gas-liquid separator 5 to the anode discharge valve 6, for example if the FC 1 does not generate power for a long period of time.If the liquid water freezes below the freezing point, the anode ejection valve 6 could jam. This could make it difficult to eject the liquid water from the fuel cell system 100.

[0041] Therefore, the ECU 70 purges the return pipe L33 by stopping the injection of the main INJs 31 and 32 and by performing the injection of the auxiliary INJ 33.

[0042] Fig. Figure 2 is a view that illustrates an example of a flushing process for flushing the return pipe L33. Fig. 2 will be the same components as those from Fig. 1. They are provided with the same reference symbols, and a duplicate description of the same is omitted.

[0043] A large portion of the anode gas injected by the auxiliary INJ 33 flows to the ejector 4 at the connection point P. This is because there is no anode gas flow from the main INJs 31 and 32, and the pressure drop of the ejector 4 is lower than that of the FC 1. Therefore, a large portion of the anode gas flows through the bypass tube L34 and then backslides from the outlet port 46 of the ejector 4 through the anode supply tube L30 into the ejector flow path 44, as indicated by arrow R4. The anode gas flows from the inlet port 45 through the ejector flow path 44 into the return tube L33 and then backslides through the return tube L33 into the gas-liquid separator 5, as indicated by arrow R5. The liquid water that remains in the return pipe L33 collects in the gas-liquid separator 5.

[0044] The anode gas that does not flow to the ejector 4, which is injected by the auxiliary INJ 33, flows through the anode supply pipe L30, the anode gas flow path L31, and the anode discharge pipe L32 into the gas-liquid separator 5, as indicated by arrow R6. Since the cross-sectional area of ​​the anode gas flow path L31 is smaller than the respective cross-sectional areas of the ejector flow path 44 and the return pipe L33, the pressure drop of the anode gas flow path L31 is so high that the anode gas tends not to flow through it.

[0045] The ECU 70 controls the opening and closing of the anode discharge valve 6. When the anode discharge valve 6 opens, the liquid water in the gas-liquid separator 5 flows through the exhaust gas discharge pipe L35 and is then expelled to the outside from the cathode discharge pipe L22, as indicated by arrow R34.

[0046] Fig. Figure 3 is a view that illustrates an example of a condition in which liquid water remaining in the return pipe L33 collects in the gas-liquid separator 5. Fig. 3 will be the same components as those from Fig. 1. They are provided with the same reference symbols, and a duplicate description of the same is omitted.

[0047] The return pipe L33 extends, for example, from the inlet opening 45 of the ejector 4 in the vertical direction V and is connected to an upper part of the gas-liquid separator 5.

[0048] The gas-liquid separator 5 comprises a cylindrical section 51, an upper surface section 50 covering the cylindrical section 51, and a lower section 52 extending continuously from a lower end of the cylindrical section 51 and having a funnel shape. The cylindrical section 51 has a side opening 51a. The upper surface section 50 has an upper opening 50a. One edge of the side opening 51a is connected to the anode discharge tube L32. One edge of the upper opening 50a is connected to the lower end of the return tube L33.

[0049] Furthermore, the lower section 52 has an opening 52a in its center. One edge of the opening 52a is connected to the L-shaped exhaust gas discharge pipe L35. The exhaust gas discharge pipe L35 extends from the lower section 52 in the vertical direction V and is then curved at a right angle to the anode discharge valve 6.

[0050] Moisture contained in the anode gas that has not separated from it in the gas-liquid separator 5 condenses, and water droplets 9 then adhere to an inner wall of the return tube L33. The anode gas flows through the ejector flow path 44 from the anode supply tube L30 and then flows from the inlet opening 45 into the return tube L33, as shown by arrow R5. Thus, the water droplets 9 collect in the gas-liquid separator 5 from the return tube L33.

[0051] The water droplets 9 are stored as liquid water W in the lower section 52 of the gas-liquid separator 5. The liquid water W flows through the exhaust gas discharge pipe L35 and then reaches the anode discharge valve 6, as indicated by arrow R34. When the anode discharge valve 6 opens, the liquid water W is discharged from the gas-liquid separator 5. Operation of the ECU 70

[0052] Fig. Figure 4 is a flowchart illustrating an operating example of the ECU 70. The ECU 70 determines whether the ignition switch 71 is turned on (step St1). If the ignition switch 71 is not turned on (No in step St1), the process from step St1 is repeated.

[0053] When the ignition switch 71 is turned on (Yes in step St1), the ECU 70 starts power generation through the FC 1 (step St2). At this time, the ECU 70, for example, issues an instruction regarding the quantity of anode gas to be supplied to the main INJs 31 and 32 and the auxiliary INJ 33, and issues an instruction regarding the quantity of cathode gas to be supplied to the air compressor 20 according to the accelerator pedal opening degree detected by the accelerator opening sensor 72.

[0054] Next, the ECU 70 determines whether the ignition switch 71 is off (step St3). If the ignition switch 71 remains in an on state (No in step St3), the process from step St3 is repeated.

[0055] When the ignition switch 71 is off (Yes in step St3), the ECU 70 stops the power generation of FC 1 (step St4). At this point, the ECU 70 stops, for example, the supply of cathode gas from the air compressor 20 and the supply of anode gas from the main INJs 31 and 32. Next, the ECU 70 detects an outside air temperature using the temperature sensor 73 (step St5). The ECU 70 determines whether the outside air temperature is less than or equal to the freezing point (step St6).

[0056] If the outside air temperature is less than or equal to freezing (Yes in step St6), the ECU 70 performs a purging process (step St7). That is, if the outside air temperature is less than or equal to freezing, the ECU 70 purges the ejector 4, the anode gas flow path L31 of the FC 1, the anode discharge tube L32, and the return tube L33, as described in the Fig. 1 and Fig. 2 described. For this reason, when the outside air temperature is less than or equal to freezing, the liquid water collects in the ejector 4, the anode gas flow path L31 of the FC 1, the anode discharge tube L32, and the return tube L33 in the gas-liquid separator 5 and is discharged to the outside. This prevents the liquid water from freezing at the anode discharge valve 6.

[0057] If the outside air temperature is higher than freezing (No in step St6), the ECU 70 determines a temperature of the anode ejection valve 6 (step St8). At this point, the ECU 70 determines the temperature of the anode ejection valve 6 based on the outside air temperature, which was measured by temperature sensor 73, the temperature of the cooling water of FC 1, which was measured by temperature sensor 74, and so on.

[0058] If the measured temperature is less than or equal to the freezing point (Yes in step St9), the ECU 70 performs the purging process (step St7). If the measured temperature is higher than the freezing point (No in step St9), the purging process is not performed.

[0059] If the outside air temperature is above freezing and if the temperature of the anode ejection valve 6 is determined to be less than or equal to freezing, the ECU 70 purges the ejector 4, the anode gas flow path L31 of FC 1, the anode ejection tube L32, and the return tube L33. If the outside air temperature is higher than freezing and if the temperature of the anode ejection valve 6 is determined to be less than or equal to freezing, the liquid water collects in the gas-liquid separator 5 from the ejector 4, the anode gas flow path L31 of FC 1, the anode ejection tube L32, and the return tube L33 and is then ejected to the outside. This prevents the liquid water from freezing at the anode ejection valve 6.

[0060] Next, an example of the rinsing process from step St7 is described.

[0061] Fig. Figure 5 is a flowchart illustrating an example of the purging process. The ECU 70 can control the air compressor 20 to supply the cathode gas to the cathode ejection tube L22 to dilute the anode gas ejected there before the purging process. The purging process for the anode system 3 includes a purging process to clean the ejector 4 (step St7a), a purging process to clean the return tube L33 (step St7b), a purging process to clean the FC 1 (step St7c), and a purging process to clean the gas-liquid separator 5 (step St7d).

[0062] First, the ECU 70 performs the purging process for ejector 4 (step St7a). The ECU 70 then starts the injection of the main INJs 31 and 32 (step St71a). At this point, the ECU 70 controls the main INJs 31 and 32 to inject the anode gas at the same frequency. Accordingly, the liquid water remaining in ejector 4g is collected in the gas-liquid separator 5.

[0063] Next, the ECU 70 opens and closes the anode ejection valve 6 at a predetermined frequency (step St72a). This ejects the liquid water from the gas-liquid separator 5. Next, the ECU 70 stops the injection of the main INJs 31 and 32 (step St73a).

[0064] Secondly, the ECU 70 performs the purging process for the return tube L33 (step St7b). The ECU 70 starts the injection of the auxiliary INJ 33 (step St71b). At this point, the ECU 70 controls the auxiliary INJ 33 so that it injects the anode gas when the injection of the main INJs 31 and 32 is stopped. Therefore, the anode gas flows backward into the return tube L33. Accordingly, the liquid water remaining in the return tube L33 is collected in the gas-liquid separator 5.

[0065] Next, the ECU 70 opens and closes the anode ejection valve 6 at a predetermined frequency (step St72b). This ejects the liquid water from the gas-liquid separator 5. Next, the ECU 70 stops the injection of the auxiliary INJ 33 (step St73b).

[0066] In the manner described above, the ECU 70 purges the return tube L33 after the ejector 4 has been purged. This facilitates the flow of anode gas from the ejector 4 to the return tube L33 during the purging process of the return tube L33.

[0067] Thirdly, the ECU 70 performs the purging process for the FC 1 (step St7c). The ECU 70 starts the injection of the main INJs 31 and 32 (step St71c). At this point, the ECU 70 controls the main INJs 31 and 32 to inject the anode gas at, for example, different frequencies. Accordingly, the liquid water remaining in the anode gas flow path L31 and the anode discharge tube L32 on its downstream side is collected in the gas-liquid separator 5.

[0068] Next, the ECU 70 opens and closes the anode ejection valve 6 at a predetermined frequency (step St72c). This ejects the liquid water from the gas-liquid separator 5. Next, the ECU 70 stops the injection of the main INJs 31 and 32 (step St73c).

[0069] Next, the ECU 70 performs the purging process for the gas-liquid separator 5 (step St7d). The ECU 70 then starts the injection of the main INJs 31 and 32 (step St71d). At this point, the ECU 70 controls the main INJs 31 and 32 to inject a large quantity of anode gas compared to the purging process for ejector 4 and FC 1, respectively. Accordingly, the liquid water remaining in the gas-liquid separator 5 is collected in the lower section 52.

[0070] Next, the ECU 70 opens and closes the anode ejection valve 6 at a predetermined frequency (step St72d). This ejects the liquid water from the gas-liquid separator 5. Next, the ECU 70 stops the injection of the main INJs 31 and 32 (step St73d).

[0071] The purging process is carried out in this manner. Furthermore, the purging processes for FC 1 and the gas-liquid separator 5 (steps St7c, St7d) are performed after the purging process for ejector 4 (step St7b). Therefore, the ECU 70 can adjust the liquid water separation rate in the purging process for FC 1 and the gas-liquid separator 5 (steps St7c and St7d) to be higher than in other purging processes, taking into account the decrease in the liquid water remaining in the return pipe L33.

[0072] The ECU 70 can also perform the flushing process for the return pipe L33 (step St7b) last, unlike the sequence of the flushing process described above.

[0073] Fig. Figure 6 is a flowchart that illustrates another example of the rinsing process. Fig. 6. The same processes will be used as those from Fig. 5 are labelled with the same reference symbols and a duplicate description of the same is omitted.

[0074] In the present embodiment, the purging process for the return pipe L33 (step St7b) is carried out last. Thus, the gas-liquid separator 5 is purged in addition to the return pipe L33, so that the purging process for the gas-liquid separator 5 (step St7d) is omitted in the example above.

[0075] In the manner described above, the ECU 70 flushes the return pipe L33 after the ejector 4, the FC 1 and the anode ejection pipe L32 have been flushed. This allows the liquid water to be expelled more efficiently and shortens the entire flushing process. Example of another fuel cell system 100a

[0076] Fig. Figure 7 is a configuration view that shows an example of another fuel cell system, 100a. Fig. 7 will be the same components as those from Fig. 1. They are labelled with the same reference symbols, and a duplicate description of the same is omitted.

[0077] Compared to the example of fuel cell system 100, a control valve 8 is installed in fuel cell system 100a. The control valve 8 is formed in the anode supply tube L30 and controls the flow rate of the anode gas flowing from the bypass tube L34 to the FC 1 according to its degree of opening.

[0078] The ECU 70 controls the opening degree of the control valve 8. The ECU 70 opens the control valve 8 at the time of power generation of the FC 1 and at the time of purging the ejector 4, the anode gas flow path L31 and the anode discharge pipe L32. For this reason, the anode gas injected from the main INJs 31 and 32 and the auxiliary INJ 33 flows into the inlet 11 of the FC 1 through the anode supply pipe L30, as shown by arrows R30 and R3.

[0079] Fig. Figure 8 is a view that shows another example of the flushing process for flushing the return pipe L33. Fig. 8 will be the same components as those from Fig. 2 are provided with the same reference symbols, and a duplicate description of the same is omitted.

[0080] The ECU 70 closes the control valve 8 when the return pipe L33 is flushed. This means the ECU 70 sets the opening degree of the control valve 8 to 0%. Unlike in the Fig. In the example shown in Figure 2, all the anode gas injected from the auxiliary INJ 33 therefore flows into the ejector 4. Thus, the flow rate of the anode gas flowing in the return tube L33 increases compared to that in Figure 2. Fig. 2 shown in the example, and more liquid water is collected from the return pipe L33 in the gas-liquid separator 5.

[0081] Furthermore, the ECU 70 does not always need to set the opening of control valve 8 to 0%. The ECU 70 only needs to reduce the opening of control valve 8 when ejector 4, anode gas flow path L31, and anode discharge pipe L32 are being purged. This reduces the amount of anode gas flowing into inlet 11 of FC 1 from auxiliary inlet 33, which increases the anode gas flow rate indicated by arrow R5. This results in more liquid water being collected from return pipe L33 in the gas-liquid separator 5.

[0082] Fig. Figure 9 is a flowchart illustrating a purging process in the 100a fuel cell system. Fig. 9 will be the same processes as those in Fig. Items 5 are designated with the same reference numerals, and a duplicate description of the same is omitted. It is assumed that the control valve 8 is in an open state when this process is started.

[0083] During the purging process for the return pipe L33 (step St7b'), the ECU 70 closes the control valve 8 (step St70b) and then injects the additional INJ 33 (step St71b). After the injection of the additional INJ 33 has stopped (step St73b), the ECU 70 opens the control valve 8 (step St74b).

[0084] The ECU 70 can reduce the opening degree of control valve 8 in step St70b. Furthermore, the purging process for the return pipe L33 (step St7b') can be performed last, as shown in the example from Fig.6. In this case, the purging process of the gas-liquid separator 5 (step St7d) is not required.

[0085] As described above, the fuel cell systems 100 and 100a each comprise the FC 1, the main INJs 31 and 32, the auxiliary INJ 33, the gas-liquid separator 5, the anode discharge valve 6, the ejector 4, the anode feed tube L30, the bypass tube L34, the anode discharge tube L32, the return tube L33, and the ECU 70. The FC 1 includes the inlet 11 and the outlet 12 for the anode gas. The gas-liquid separator 5 separates the liquid water from the anode gas, which is discharged from the outlet 12, and causes the liquid water to flow out of the opening 52a, which is formed on a vertical, lower side of the gas-liquid separator 5. The anode ejection valve 6 ejects the liquid water flowing out of the opening 52a to the outside.

[0086] The ejector 4 comprises: the inlet opening 45, into which the anode gas flows from the gas-liquid separator 5; and the outlet opening 46, through which the anode gas injected by the main INJs 31 and 32 flows out together with the anode gas flowing from the inlet opening 45. The anode supply pipe L30 is connected between the outlet opening 46 and the inlet 11. The bypass pipe L34 introduces the anode gas injected by the auxiliary INJ 33 into the anode supply pipe L30 without flowing through the ejector 4. The anode discharge pipe L32 is connected between the gas-liquid separator 5 and the outlet 12. The return pipe L33 is connected between the gas-liquid separator 5 and the inlet opening 45 and extends vertically upwards from the gas-liquid separator 5.

[0087] The ECU 70 opens and closes the anode ejection valve 6 to inject fuel from the main INJs 31 and 32 to purge the ejector 4, the FC 1, and the anode ejection tube L32. The ECU 70 then stops injecting fuel from the main INJs 31 and 32 and injects fuel from the auxiliary INJ 33 to purge the return tube L33.

[0088] According to the configuration above, the ECU 70 opens the anode discharge valve 6 to inject fuel from the main INJs 31 and 32 to purge the ejector 4, the FC 1, and the anode discharge tube L32. Thus, the anode gas from the main INJs 31 and 32 enters the ejector 4 and flows from the ejector 4's outlet port 46 into the FC 1's inlet port 11 via the anode supply tube L30. The anode gas is expelled from the outlet 12 of the FC 1 and flows through the anode discharge tube L32 into the gas-liquid separator 5. The gas-liquid separator 5 separates the liquid water from the anode gas and causes the liquid water to flow out of the opening 52a, which is formed on the vertical, lower side of the gas-liquid separator 5.The anode gas flows into the inlet opening 45 of the ejector 4 from the gas-liquid separator 5 through the return pipe L33 and flows from the outlet opening 46 through the anode supply pipe L30 with the anode gas injected through the main INJs 31 and 32. In this way, the anode gas circulates to the FC 1.

[0089] Therefore, the liquid water that remains in the ejector 4, the FC 1 and the anode ejection tube L32 collects in the gas-liquid separator 5.

[0090] Furthermore, the ECU 70 stops the injection of the main INJs 31 and 32, opens the anode discharge valve 6, and initiates the injection of the auxiliary INJ 33 to purge the return pipe L33. Thus, the anode gas is introduced from the auxiliary INJ 33 into the anode supply pipe L30 without flowing through the ejector 4, and flows backward through the anode supply pipe L30 into the ejector 4 via the outlet port 46. The anode gas flows backward from the outlet port 46 of the ejector 4 through the return pipe L33 into the gas-liquid separator 5. The gas-liquid separator 5 separates the liquid water from the anode gas and causes the liquid water to flow out of the opening 52a, which is formed on the vertical, lower side.

[0091] Although the return pipe L33 extends vertically upwards from the gas-liquid separator 5, the anode gas flows backwards through the return pipe L33 due to gravity, so that the liquid water remaining in the return pipe L33 tends to flow towards the gas-liquid separator 5. Therefore, the liquid water remaining in the return pipe L33 collects in the gas-liquid separator 5. Furthermore, the ECU 70 opens the anode discharge valve 6 to discharge the liquid water from the gas-liquid separator 5. Therefore, the fuel cell systems 100 and 100a reduce the amount of liquid water remaining after purging.

Claims

[1] Fuel cell system (100, 100a) comprising: a fuel cell (1) comprising an inlet (11) and an outlet (12) for purge gas; a first injection device (31, 32) and a second injection device (33) that inject the purge gas; a gas-liquid separator (5) which separates liquid water from the purge gas which is expelled from the outlet (12) and causes the liquid water to flow out of an opening (52a) which is formed on a vertical, lower side of the gas-liquid separator (5); an outlet valve (6) which expels the liquid water flowing out of the opening (52a) to the outside; an ejector (4), comprising: an inlet opening (45) into which the purge gas from the gas-liquid separator (5) flows; and an outlet opening (46) through which the purge gas injected by the first injection device (31, 32) flows out together with the purge gas flowing from the inlet opening (45); a first connecting path (L30) that is connected between the outlet opening (46) and the inlet (11); an inlet path (L34) which introduces the purge gas injected from the second injection device (33) into the first connecting path (L30) without flowing through the ejector (4); a second connection path (L32) that is connected between the gas-liquid separator (5) and the outlet (12); and a third connection path (L33) which is connected between the gas-liquid separator (5) and the inlet opening (45), and which extends vertically upwards from the gas-liquid separator (5); characterized by a controller (70) that is configured to to purge the ejector (4), the fuel cell (1) and the second connecting path (L32) by performing an injection of the first injection device (31), to purge the third connection path (L33) by stopping the injection of the first injection device (31, 32) and performing an injection of the second injection device (33), and to expel the liquid water in the gas-liquid separator (5) by opening the outlet valve (6). [2] Fuel cell system (100, 100a) according to claim 1, wherein the controller (70) is configured to purge the third connection path (L33) after the ejector (4) has been purged. [3] Fuel cell system (100, 100a) according to claim 1 or 2, wherein the controller (70) is configured to purge the third connection path (L33) after the ejector (4), the fuel cell (1) and the second connection path (L32) have been purged. [4] Fuel cell system (100, 100a) according to one of claims 1 to 3, further comprising a temperature sensing device (73) which detects an outside air temperature, wherein the controller (70) is configured to purge the ejector (4), the fuel cell (1), the second connection path (L32) and the third connection path (L33) when the outside air temperature is less than or equal to a freezing point. [5] Fuel cell system (100, 100a) according to claim 4, wherein the controller (70) is configured to purge the ejector (4), the fuel cell (1), the second connection path (L32) and the third connection path (L33) when the outside air temperature is higher than the freezing point and when it is determined that a temperature of the outlet valve (6) is less than or equal to the freezing point. [6] Fuel cell system (100a) according to one of claims 1 to 5, further comprising a control valve (8) formed in the first connection path (L30) which controls a flow rate of the purge gas flowing from the inlet path (L34) through the first connection path (L30) to the fuel cell (1) according to an opening degree of the control valve (8), wherein the controller (70) is configured to control the opening degree of the control valve (8) such that it is smaller when purging the third connection path (L33) than when purging the ejector (4), the fuel cell (1) and the second connection path (L32). [7] Purging method for a fuel cell system (100, 100a) comprising the fuel cell system (100, 100a): a fuel cell (1) comprising an inlet (11) and an outlet (12) for purge gas; a first injection device (31, 32) and a second injection device (33) that inject the purge gas; a gas-liquid separator (5) which separates liquid water from the purge gas which is expelled from the outlet (12) and causes the liquid water to flow out of an opening (52a) which is formed on a vertical, lower side of the gas-liquid separator (5); an outlet valve (6) which expels the liquid water flowing out of the opening (52a) to the outside; comprising an ejector (4): an inlet opening (45) into which the purge gas from the gas-liquid separator (5) flows; and an outlet opening (46) through which the purge gas injected by the first injection device (31, 32) flows out together with the purge gas flowing from the inlet opening (45); a first connecting path (L30) that is connected between the outlet opening (46) and the inlet (11); an inlet path (L34) which introduces the purge gas injected from the second injection device (33) into the first connecting path (L30) without flowing through the ejector (4); a second connection path (L32) that is connected between the gas-liquid separator (5) and the outlet (12); and a third connection path (L33) that is connected between the gas-liquid separator (5) and the inlet opening (45), and that extends vertically upwards from the gas-liquid separator (5), characterized by , that the rinsing process exhibits: Purging the ejector (4), the fuel cell (1) and the second connecting path (L32) by injecting the first injection device (31); Purging the third connection path (L33) by stopping the injection of the first injection device (31, 32) and performing an injection of the second injection device (33); and Expulsion of liquid water in the gas-liquid separator (5) by opening the outlet valve (6). [8] Purging method for the fuel cell system (100, 100a) according to claim 7, wherein the purging of the third connection path (L33) is carried out after the purging of the ejector (4). [9] Purging method for the fuel cell system (100, 100a) according to claim 7 or 8, wherein the purging of the third connection path (L33) is carried out after the purging of the ejector (4), the fuel cell (1) and the second connection path (L32). [10] Purging method for the fuel cell system (100, 100a) according to one of claims 7 to 9, wherein the fuel cell system (100, 100a) includes a temperature sensing device (73) that senses an outside air temperature, and The purging of the ejector (4), the fuel cell (1), the second connection path (L32) and the purging of the third connection path (L33) will be carried out when the outside air temperature is less than or equal to the freezing point. [11] Purging method for the fuel cell system (100, 100a) according to claim 10, wherein the purging of the ejector (4), the fuel cell (1), the second connection path (L32) and the purging of the third connection path (L33) is carried out when the outside air temperature is higher than the freezing point and when it is determined that a temperature of the outlet valve (6) is less than or equal to the freezing point. [12] Purging method for the fuel cell system (100a) according to any one of claims 7 to 11, wherein the fuel cell system (100a) comprises a control valve (8) formed in the first connecting path (L30) and which controls a flow rate of the purge gas which flows from the inlet path (L34) through the first connecting path (L30) to the fuel cell (1) according to an opening degree of the control valve (8), and the method comprises controlling the degree of opening of the control valve (8) in such a way that it is smaller when purging the third connection path (L33) than when purging the ejector (4), the fuel cell (1) and the second connection path (L32).

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