Fuel cell system

Abstract

Fuel cell system (100), comprising: a fuel cell (10); a reaction gas supply mechanism (200) designed to supply a reaction gas to the fuel cell (10); an outflow path (23, 24) designed to discharge exhaust gas and water discharged from the fuel cell (10); a valve (29) which is arranged in the outflow path (23, 24); a residual water drainage control unit (66) designed to control a residual water drainage process of the fuel cell (10) using the reaction gas supply mechanism (200) and the valve (29); a heating section (500) designed to heat the valve (29); and a fault detector (52) designed to detect a fault in the heating section (500), wherein, When a fault in the heating section (500) is detected, the residual water drain control unit (66) executes the residual water drain process and increases the water outlet capacity in the residual water drain process compared to the water outlet capacity in the residual water drain process that is executed when no fault in the heating section (500) is detected.

Description

BACKGROUND TECHNICAL AREA

[0001] The present disclosure relates to a residual water drainage process for a fuel cell. STATE OF THE ART

[0002] Water generated during fuel cell operation and water used to humidify the reaction gas are present inside the fuel cell. If the temperature inside the fuel cell drops below zero after a shutdown, any remaining water, for example, in the pores of a catalyst layer or a gas diffusion layer contained in each cell unit, can freeze and impede the flow of reaction gas or exhaust gas upon the next start-up. Therefore, a fuel cell system has been proposed to implement a residual water drainage process after a fuel cell shutdown.A fuel cell system described in JP 2016 - 91 885A estimates the temperature of a valve located in an exhaust path designed to drain exhaust gas and water at regular intervals after a fuel cell has stopped operating, and performs a residual water draining process when the estimated temperature is equal to or below 0 °C.

[0003] However, the fuel cell system described in JP 2016-91885A performs the residual water draining process when the temperature of the valve located in the discharge path is equal to or below 0°C. This makes it likely that the drained water will freeze in the valve, hindering its opening and closing, or that the discharge path will be blocked by ice forming on the valve, preventing any water from being drained. Therefore, there is a need for a technique that reduces the amount of residual water inside a fuel cell while preventing water drained from the fuel cell from freezing in a valve located in the discharge path.

[0004] From DE 10 2016 110 932 A1, a fuel cell system mounted on a vehicle is known. The fuel cell system comprises a gas supply device configured to supply a purge gas to a fuel cell; and a control device configured to control the gas supply device and perform a purge with the purge gas at a vehicle stop time. During a vehicle drive state, the control device receives several ambient temperature readings. If the most recently obtained ambient temperature from the ambient temperatures obtained during the drive state is lower than a predetermined reference value, the control device performs the purge with an increased purge capacity compared to a case where the most recently obtained ambient temperature is higher than the predetermined reference value. SUMMARY (1) According to one aspect of the present disclosure, a fuel cell system is provided. The fuel cell system comprises a fuel cell; a reaction gas supply mechanism configured to supply reaction gas to the fuel cell; an exhaust path configured to discharge exhaust gas and water that is discharged from the fuel cell; a valve arranged in the exhaust path; a residual water drain control unit configured to control a residual water draining process from the fuel cell using the reaction gas supply mechanism and the valve; a heating section configured to heat the valve; and a fault detector configured to detect a fault in the heating section.If a fault in the heating section is detected, the residual water drainage control unit executes the residual water drainage process and increases the water outlet output in the residual water drainage process compared to the water outlet output in the residual water drainage process that is executed when no fault in the heating section is detected.

[0005] The fuel cell system of this aspect includes the heating section, which is designed to heat the valve. This design prevents the drained water in the valve from freezing during the residual water drainage process. If a fault in the heating section is detected, the fuel cell system of this aspect executes the residual water drainage process before the fuel cell shuts down and increases the water outlet rate during this process compared to the rate executed when no fault in the heating section is detected. This design reduces the amount of residual water in the fuel cell after a fuel cell shutdown and prevents water in the valve from freezing after the fuel cell shuts down.

[0006] (2) In the fuel cell system of the aspect described above, the residual water drainage control unit can control a pre-operation-stop residual water drainage process, which can be performed before the fuel cell is shut down, and a post-operation-stop residual water drainage process, which can be performed after the fuel cell is shut down. If a fault in the heating section is detected, the residual water drainage control unit can perform a pre-operation-stop residual water drainage process with a higher water outlet rate compared to a post-operation-stop residual water drainage process, and it can omit the post-operation-stop residual water drainage process.If no fault is detected in the heating section, the residual water drainage control unit executes the post-operational shutdown residual water drainage process and does not execute a pre-operational shutdown residual water drainage process. If a fault is detected in the heating section, the fuel cell system performs the pre-operational shutdown residual water drainage process with a higher water outlet rate than the post-operational shutdown residual water drainage process and does not execute a post-operational shutdown residual water drainage process. This design reduces the amount of residual water in the fuel cell after a shutdown and prevents the drained water from freezing in the valve, unlike a design that performs the residual water drainage process at cold temperatures after a shutdown.If no fault is detected in the heating section, the fuel cell system in this aspect performs the post-operational shutdown residual water drainage process and does not perform a pre-operational shutdown residual water drainage process. This design uses the heating section to prevent the drained water from freezing in the valve and reduces the power consumption required for the residual water drainage process compared to a design that performs both the pre-operational shutdown and post-operational shutdown residual water drainage processes.

[0007] (3) The fuel cell system of the aspect described above may further include a temperature sensor designed to maintain the valve temperature. The residual water drain control unit may be activated at regular intervals after a fuel cell shutdown to check the valve temperature as determined by the temperature sensor and to initiate the post-shutdown residual water drain process if the temperature is above 0 °C, while the post-shutdown residual water drain process is not initiated if the temperature is equal to or below 0 °C. The heating section may heat the valve if the valve temperature as determined by the temperature sensor is equal to or below 0 °C.This aspect of the fuel cell system performs the post-operational shutdown residual water drainage process when the valve temperature is at least 0 °C, while the post-operational shutdown residual water drainage process is not performed if the valve temperature is below 0 °C. This design prevents the drained water from freezing in the valve and reduces the power consumption required for the residual water drainage process compared to a design that performs the post-operational shutdown residual water drainage process regardless of the valve temperature. If the valve temperature is below 0 °C, the heating section serves to warm the valve. This raises the valve temperature above 0 °C.

[0008] (4) In the fuel cell system of the aspect described above, the residual water drainage control unit can cause the valve to repeatedly open and close during the residual water drainage process and controls the water outlet rate in the residual water drainage process by controlling the period during which the valve repeatedly opens and closes, and / or the ratio of open time to closing time in an open-close cycle of the valve. This design enables highly accurate control of the water outlet rate in the residual water drainage process.

[0009] (5) In the fuel cell system of the aspect described above, the reaction gas supply mechanism may include a pump designed to supply the fuel cell with an excess of the reaction gas contained in the exhaust gas. The residual water drainage control unit may drive the pump in the residual water drainage process and controls a water discharge rate in the residual water drainage process by controlling the duration for which the pump is driven and / or the speed of the pump. This design enables the water discharge rate in the residual water drainage process to be controlled with high accuracy.

[0010] The present disclosure can be implemented through various aspects, for example a control device designed to control a residual water emptying process of a fuel cell, a residual water emptying control method for controlling a residual water emptying process of a fuel cell, a computer program designed to implement such a method, and a storage medium on which such a computer program is stored. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram illustrating the schematic design of a fuel cell system according to an embodiment of the present disclosure; Fig. 2 is a flowchart showing the sequence of a residual water drainage process that is carried out in the fuel cell system; Fig. Figure 3 is a diagram illustrating a time graph before and after a post-operational shutdown residual water drainage process; Fig. Figure 4 is a diagram illustrating a time graph during an intensified pre-operational shutdown residual water drainage process; and Fig. Figure 5 is a flowchart showing the sequence of a residual water drainage process according to a second embodiment. DESCRIPTION OF EXECUTION FORMS A. First embodiment A1. System design

[0011] Fig. Figure 1 is a block diagram illustrating the schematic design of a fuel cell system 100 according to an embodiment of the present disclosure. The fuel cell system 100 is mounted in a vehicle to be used as a system for power supply. The fuel cell system 100 comprises a fuel cell 10, a fuel gas supply / outlet mechanism 200, an oxidation gas supply / outlet mechanism 300, a fuel cell circulation cooling mechanism 400, a heating section 500, a control device 60, and a start control device 70.

[0012] The fuel cell 10 comprises several cell units 11 stacked along a stacking direction SD, and a pair of end plates 12 and 13 arranged at respective ends in the stacking direction SD. Each of the cell units 11 is a polymer electrolyte fuel cell and is configured to generate electric current by means of an electrochemical reaction of a fuel gas and an oxidizing gas supplied to an anode-side catalyst electrode layer and a cathode-side catalyst electrode layer, respectively, arranged over a solid polymer electrolyte membrane. According to the embodiment, the fuel gas is hydrogen gas, and the oxidizing gas is air. The catalyst electrode layer is configured to comprise an electrolyte and carbon particles with a catalyst, such as platinum (Pt), arranged thereon.The cell unit 11 also includes gas diffusion layers arranged outside the catalyst electrode layers on the respective electrode sides, and made of a porous material. The porous material used can be, for example, a porous carbon body, such as carbon paper or carbon fabric, or a porous metal body, such as a metal mesh or foamed metal. Manifolds (not shown), through which the fuel gas, the oxidizing gas, and a cooling medium flow, are formed inside the fuel cell 10 along the stacking direction SD.

[0013] The pair of end plates 12 and 13 serves to hold an interposed layered body of the multiple cell units 11. Of the pair of end plates 12 and 13, end plate 12 has the function of supplying the fuel gas, the oxidizing gas, and the cooling medium to the manifolds formed inside the fuel cell 10, and of providing flow paths for the discharge of these gases and the medium. End plate 13, on the other hand, has no such functions. Both end plate 12 and end plate 13 have approximately plate-like outer shapes, the thickness directions of which are identical to the stacking direction SD.

[0014] The fuel gas supply and exhaust mechanism 200 is designed to supply fuel gas to the fuel cell 10 and to discharge an anode exhaust gas from the fuel cell 10. The fuel gas supply and exhaust mechanism 200 comprises a hydrogen tank 20, a shut-off valve 25, an injector 26, a gas-liquid separator 27, a hydrogen pump 28, a drain valve 29, a fuel gas supply path 21, a first fuel gas exhaust path 23, a fuel gas circulation path 22, and a second fuel gas exhaust path 24.

[0015] The hydrogen tank 20 is designed to store high-pressure hydrogen and to supply the hydrogen gas as fuel gas through the fuel gas supply path 21 to the fuel cell 10. The shut-off valve 25 is located near a fuel gas supply port of the hydrogen tank 20 and serves to switch the supply of hydrogen gas from the hydrogen tank 20 between on and off. The injector 26 is located in the fuel gas supply path 21 and serves to regulate the quantity of hydrogen gas supplied to the fuel cell 10 and the pressure of the hydrogen gas. The gas-liquid separator 27 serves to separate water contained in the anode exhaust gas discharged from the fuel cell 10 and to discharge the separated water to the first fuel gas outlet path 23. It also serves to discharge the gas after the water has been separated.of the excess fuel gas to the fuel gas circulation path 22. According to the embodiment, the gas-liquid separator 27 is formed by a part of the end plate 12 and an element provided for covering this part. The hydrogen pump 28 is arranged in the fuel gas circulation path 22 and serves to supply the excess fuel gas, which is discharged from the gas-liquid separator 27, through the fuel gas supply path 21 to the fuel cell 10.

[0016] The drain valve 29 is located at the boundary between the first fuel gas outlet path 23 and the second fuel gas outlet path 24. The drain valve 29 is opened to release the water separated by the gas-liquid separator 27 into the atmosphere. When the drain valve 29 is opened, a portion of the anode exhaust gas discharged from the fuel cell 10, i.e., the remaining gas that is not fed into the fuel gas circulation path 22, is released, along with the water. According to the embodiment, the drain valve 29 is opened and closed at predetermined time intervals during the operation of the fuel cell 10. During a residual water drainage process described later, the drain valve 29 is opened and closed at times and for a period of time determined in response to an instruction from the control device 60.The gas-liquid separator 27 described above communicates with the fuel cell 10 and also with the atmosphere via the second fuel gas outlet path 24 when the drain valve 29 is opened. The internal pressure of the fuel cell 10 is higher than atmospheric pressure. When the drain valve 29 is opened, water that has accumulated in the gas-liquid separator 27 is drained to the second fuel gas outlet path 24 due to the pressure difference between the internal pressure of the fuel cell 10 and atmospheric pressure.

[0017] The fuel gas supply path 21 is designed to connect the hydrogen tank 20 to the fuel cell 10 and to supply the fuel cell 10 with the hydrogen gas stored in the hydrogen tank 20 and the excess hydrogen gas supplied by the hydrogen pump 28. The first fuel gas discharge path 23 is designed to connect the gas-liquid separator 27 to the drain valve 29 and to supply the water separated by the gas-liquid separator 27 and part of the anode exhaust gas to the drain valve 29. The second fuel gas discharge path 24 is designed to connect the drain valve 29 to an oxidation gas discharge path 32 (described later) and to supply the water and the anode exhaust gas supplied to the drain valve 29 to the oxidation gas discharge path 32.The fuel gas circulation path 22 is designed to connect the gas-liquid separator 27 to the fuel gas supply path 21 and to supply the excess hydrogen gas discharged from the gas-liquid separator 27 to the fuel gas supply path 21.

[0018] The oxidation gas supply and exhaust mechanism 300 is designed to supply the fuel cell 10 with oxidation gas and to discharge cathode exhaust gas from the fuel cell 10. The oxidation gas supply and exhaust mechanism 300 comprises an air compressor 30, an oxidation gas supply path 31, an oxidation gas outlet path 32, a three-way valve 33, a check valve 34, and a bypass flow path 35.

[0019] The air compressor 30 is designed to supply air as the oxidizing gas to the fuel cell 10. The oxidizing gas supply path 31 is designed to connect the air compressor 30 to the fuel cell 10 and to supply the fuel cell 10 with the compressed air discharged by the air compressor 30. The oxidizing gas discharge path 32 is connected to a (not shown) cathode-side exhaust distribution pipe located inside the fuel cell 10 to discharge the cathode exhaust and the water discharged from the fuel cell 10 to the atmosphere. As described above, the oxidizing gas discharge path 32 is connected to the second fuel gas discharge path 24, so that the anode exhaust and the water discharged from the second fuel gas discharge path 24 are discharged to the atmosphere along with the cathode exhaust and water.The three-way valve 33 is arranged in the oxidation gas supply path 31 and is designed to regulate the amount of air to be supplied to the oxidation gas supply path 31 and the amount of air to be supplied to the bypass flow path 35 from the total amount of air leaving the air compressor 30. The check valve 34 is arranged near the fuel cell 10 in the oxidation gas outlet path 32 and is designed to regulate a back pressure, which is a pressure on a cathode outlet side of the fuel cell 10, and thereby to set a cathode-side pressure in each of the cell units 11. The bypass flow path 35 has one end connected to the three-way valve 33 and the other end connected to the oxidation gas outlet path 32, so that the oxidation gas supplied by the air compressor 30 via the three-way valve 33 is directed to the oxidation gas outlet path 32 without being supplied to the fuel cell 10.

[0020] The fuel cell circulation cooling mechanism 400 is designed to circulate cooling water through the fuel cell 10 and thereby regulate the temperature of the fuel cell 10 (hereinafter referred to as the "fuel cell temperature"). According to the embodiment, an antifreeze fluid, such as ethylene glycol, is used as the cooling water. However, the cooling medium is not limited to antifreeze fluid but can be any heat-exchangeable medium, such as a gaseous medium like air. The fuel cell circulation cooling mechanism 400 comprises a cooling water outlet path 41, a cooling water inlet path 42, a bypass flow path 43, a cooling water pump 45, a cooler 40, a three-way valve 44, and a temperature sensor 46.

[0021] The cooling water outlet path 41 has one end connected to the fuel cell 10 and the other end connected to the cooler 40, so that the cooling water drained from the fuel cell 10 is directed to the cooler 40. The cooling water inlet path 42 has one end connected to the cooler 40 and the other end connected to the fuel cell 10, so that the cooling water drained from the cooler 40 is directed to the fuel cell 10. The bypass flow path 43 is a flow path designed to return the cooling water drained from the fuel cell 10 to the fuel cell 10 without flowing through the cooler 40 and the heating section 500. The cooler 40 includes a fan (not shown) and is designed to perform heat exchange between the outside air and the cooling water drained from the fuel cell 10 and the cooling water drained from the heating section 500.The three-way valve 44 is located in the center of the cooling water outlet path 41 and is configured to adjust the amount of cooling water to be supplied to the cooling water outlet path 41 and the amount of cooling water to be supplied to the bypass flow path 43 from the total amount of cooling water drained from the fuel cell 10. The temperature sensor 46 is located near the fuel cell 10 in the cooling water outlet path 41 and is configured to measure the temperature of the cooling water in the cooling water outlet path 41 and to transmit information to the control device 60 indicating the measured temperature. According to the embodiment, the temperature of the cooling water measured by the temperature sensor 46 is used as the fuel cell temperature.

[0022] The heating section 500 serves to heat the drain valve 29. According to the embodiment, the heating section 500 is designed by using a part of an air conditioning system used in the vehicle in which the fuel cell system 100 is installed. The heating section 500 comprises a coolant inlet path 51, a heater 50, a coolant outlet path 52, a bypass flow path 53, a coolant pump 54, and a three-way valve 55.

[0023] The cooling water inlet path 51 has one end connected to the cooling water inlet path 42 of the fuel cell circulation cooling mechanism 400 described above and the other end connected to the heater 50, so that the cooling water flowing in the cooling water inlet path 42 is directed to the heater 50. The heater 50 is designed to heat the incoming cooling water and discharge the heated cooling water. The heater 50 directs the heated cooling water to a heater core for air conditioning (not shown) while discharging the heated cooling water to the cooling water outlet path 52. The heater 50 includes a heating unit and a control unit designed to control the heating unit. The cooling water outlet path 52 has one end connected to the heater 50 and the other end connected to the cooling water inlet path 42, so that the cooling water heated by the heater 50 is returned to the cooling water inlet path 42. As shown in Fig. As shown in Figure 1, part of the cooling water outlet path 52 is located near the drain valve 29. Accordingly, the drain valve 29 is heated by the flow of heated cooling water in the cooling water outlet path 52. The cooling water pump 54 is located in the cooling water outlet path 52 and is designed to regulate the flow rate of the cooling water flowing in the heater section 500. The three-way valve 55 is located in the middle of the cooling water outlet path 52 and is designed to adjust the amount of cooling water to be supplied to the heater 50 and the amount of cooling water to be supplied to the bypass flow path 53 from the cooling water flowing from the cooling water outlet path 41 to the cooling water inlet path 51.

[0024] The control device 60 is designed to control the entire fuel cell system 100. The control device 60 comprises a CPU 61 and a memory 68. The CPU 61 executes a control program that has been pre-stored in the memory 68 to serve, for example, as a fault detector 62, a temperature sensor 63, a pre-operation stop residual water drain determination device 64, a post-operation stop residual water drain determination device 65, a residual water drain control unit 66, and an operating control unit 67.

[0025] The fault detector 62 detects a fault in the heating section 500. Expected faults in the heating section 500 include, for example, a fault in the heater 50 and a fault in the cooling water pump 54. The fault detector 62 requests the heater 50 and the cooling water pump 54 to send status information and determines whether or not a fault in the heating section 500 is present based on the status information sent by the heater 50 and the cooling water pump 54 in response to the request.

[0026] The temperature sensor 63 receives the temperature of the drain valve 29. More precisely, the temperature sensor 63 uses the fuel cell temperature transmitted by the temperature sensor 46 to estimate and obtain the temperature of the drain valve 29. The temperature of the drain valve 29 can be estimated, for example, by referring to a table that was experimentally determined beforehand and that contains a correlation between the fuel cell temperature and the temperature of the drain valve 29.

[0027] The pre-operation stop residual water drainage determining device 64 determines whether an enhanced pre-operation stop residual water drainage process, described later, should be executed before the fuel cell 10 stops operating, or more precisely, at the beginning of an operation stop process. The post-operation stop residual water drainage determining device 65 determines whether a post-operation stop residual water drainage process, described later, should be executed after the fuel cell 10 stops operating. According to the embodiment, the determination of whether the enhanced pre-operation stop residual water drainage process should be executed is based on whether the heating section 500 has a fault.More precisely, the pre-operation stop residual water draining determining device 64 determines that the enhanced pre-operation stop residual water draining process should be executed if the heating section 500 has a fault, while it determines that the enhanced pre-operation stop residual water draining process should not be executed if the heating section 500 does not have a fault. According to the embodiment, the determination of whether or not the post-operation stop residual water draining process should be executed is based on the determination of whether the temperature of the drain valve 29 is higher than 0 °C.More precisely, the post-operation stop residual water draining device 65 determines that the post-operation stop residual water draining process should be carried out if the temperature of the drain valve 29 is higher than 0 °C, while it determines that the post-operation stop residual water draining process should not be carried out if the temperature of the drain valve 29 is equal to or below 0 °C. The enhanced pre-operation stop residual water draining process and the post-operation stop residual water draining process can be collectively referred to as the “residual water draining process”.

[0028] The residual water drainage control unit 66 controls the residual water drainage process. According to the embodiment, the residual water drainage process (i.e., the enhanced pre-operation-stop residual water drainage process and the post-operation-stop residual water drainage process) comprises a cathode-side drainage process and an anode-side drainage process. In the cathode-side drainage process, the residual water drainage control unit 66 drives the air compressor 30 to direct the oxidizing gas to the fuel cell 10, thereby draining the cathode exhaust gas and the water remaining in the fuel cell 10. In the anode-side emptying process, the residual water emptying control unit 66 drives the hydrogen pump 28 to supply the hydrogen gas drained from the gas-liquid separator 27 to the fuel cell 10 and thereby drain the anode exhaust gas and the water that has remained in the fuel cell 10.The residual water drain control unit 66 causes the drain valve 29 to open, thereby causing the anode exhaust gas and the water drained from the fuel cell 10 to be discharged to the atmosphere through the second fuel gas outflow path 24 and the oxidizing gas outflow path 32.

[0029] The operating control unit 67 controls the respective functional sections 62 to 66 described above and controls the actuation and stopping of the respective components, such as the air compressor 30 and the hydrogen pump 28, which are electrically connected to the control device 60 in order to control the operating processes of the fuel cell 10 and the control device 60.

[0030] The control device 60 and the auxiliary machines, including the air compressor 30 and the hydrogen pump 28, are powered by a secondary battery (not shown). This secondary battery stores the electrical current generated by the operation of the fuel cell 10. When the power output of the fuel cell 10 is low, additional electrical current is supplied from this secondary battery.

[0031] The start control device 70 is designed to control the power supply to the control device 60 and thereby switch the power supply to the control device 60 between on and off. The start control device 70 includes a timer 71. The start control device 70 initiates the power supply to the control device 60 when the timer expires, thereby switching the state of the control device 60 from the off state to the on state at a predetermined time. The timer 71 is started by the control device 60 in the residual water drainage process described later. According to the embodiment, the start control device 70 is implemented by an ASIC (application-specific integrated circuit). However, like the control device 60, the start control device 70 can also be implemented by a CPU and memory instead of the ASIC.

[0032] The fuel cell system 100, which has the configuration described above, performs the residual water drainage process described below. This reduces the amount of residual water in the fuel cell 10 while preventing the water drained from the fuel cell 10 from freezing in the drain valve 29.

[0033] The first fuel gas discharge path 23 and the second fuel gas discharge path 24 described above correspond to the subordinate concept of the discharge path described in the summary of the invention. The drain valve 29 corresponds to the subordinate concept of the valve described in the summary of the invention, and the hydrogen pump 28 corresponds to the subordinate concept of the pump described in the summary of the invention. A2. Residual water emptying process

[0034] Fig. Figure 2 is a flowchart showing the sequence of a residual water drainage process performed in the fuel cell system 100. The fuel cell system 100 performs the residual water drainage process when a signal indicating a change of ignition from on to off is sent by an ECU (electronic control unit) of the vehicle and received by the control device 60.

[0035] The fault detector 62 determines whether the heating section 500 has a fault (step S105). If it is determined that the heating section 500 does not have a fault (step S105: NO), the operating control unit 67 sets a wake-up timer (step S110). As will be described later, in the fuel cell system 100, after the control device 60 is switched off, the control device 60 is switched on and off at regular intervals. Setting the wake-up timer means that the time period from when the control device 60 is switched off until when it is switched on is counted by the timer 71. The counting of this period is started in step S110. According to the embodiment, one hour is set as the period from when the control device 60 is switched off until when it is switched on. However, this period is not limited to one hour; any desired time can be set as this period.

[0036] The operating control unit 67 then switches off the control device 60 (step S115). The operating control unit 67 switches off the control object devices, such as the air compressor 30 and the hydrogen pump 28, before switching off the control device 60, although this is not illustrated. The start control device 70 waits until the wake-up timer has expired (step S120). When the wake-up timer has expired (step S120: YES), the start control device 70 begins supplying power to the control device 60 to switch it on (step S125). Power is also started to the functional components that discharge the anode side, such as the temperature sensor 46, the hydrogen pump 28, and the discharge valve 29, as well as to the functional components that discharge the cathode side, such as the air compressor 30.

[0037] The post-operation stop residual water drain determination device 65 then determines whether the temperature of the drain valve 29 is higher than 0 °C (step S130). The temperature of the drain valve 29 is obtained from the temperature sensor 63. If it is determined that the temperature of the drain valve 29 is equal to or below 0 °C (step S130: NO), the post-operation stop residual water drain determination device 65 determines that the post-operation stop residual water drain process should not be carried out. The operating control unit 67 then switches on the heating section 500, or more precisely, switches on the heater 50 and the cooling water pump 54 (step S135). After processing step S135, the processing of step S130 described above is carried out again.When the heating section 500 is switched on, the cooling water heated by the heater 50 flows through the cooling water outlet path 52 to heat the drain valve 29 and raise its temperature. During this process, the three-way valve 55 can be caused to stop the circulation of the cooling water between the heating section 500 and the cooling water outlet path 41.

[0038] If it is determined that the temperature of the drain valve 29 is higher than 0 °C (step S130: YES), the post-operation stop residual water drain determination device 65 determines that the post-operation stop residual water drain process is to be executed. The residual water drain control unit 66 then executes the post-operation stop residual water drain process (step S140). The detailed sequence of the post-operation stop residual water drain process is identical to the detailed sequence of the residual water drain process described above and is therefore not described here. The water outlet rate on the anode side in the post-operation stop residual water drain process is lower than the water outlet rate on the anode side in the enhanced pre-operation stop residual water drain process, as will be described later.According to this embodiment, the water outlet capacity is a power that correlates with the amount of water that can be drained per unit of time. Accordingly, a higher water outlet capacity means a larger amount of water that can be drained per unit of time. If the temperature of the drain valve 29 is equal to or below 0 °C, the drain valve 29 is heated by the heating section 500. If the temperature of the drain valve 29 exceeds 0 °C, the post-operational shutdown residual water drainage process is executed. This design therefore prevents the drained water from freezing in the drain valve 29.

[0039] After the completion of the process at step S140, as described above, the residual water drainage process returns to step S100 and executes steps S110 to S140. Accordingly, the post-operational shutdown residual water drainage process is executed at regular intervals.

[0040] Fig. Figure 3 is a diagram illustrating a time graph before and after the post-operational shutdown residual water drainage process. The abscissa of Fig. Figure 3 shows the time. A time 0 denotes a time when, at step S130, it is first determined that the temperature of the drain valve 29 is equal to or below 0 °C, as described above. A top curve of Fig. Figure 3 shows a change in the temperature of the drain valve 29. A second curve below it shows a change in the operating state of the heating section 500. A third, subsequent curve shows a change in the speed of the hydrogen pump 28. A fourth, subsequent curve shows a change in the operating state of the drain valve 29.

[0041] If, at step S130, the temperature of the drain valve 29 is determined to be equal to or below 0 °C, the heating section 500 is switched on, as shown in the second curve. This gradually increases the temperature of the drain valve 29, as shown in the top curve. At time T1, when the temperature of the drain valve 29 exceeds 0 °C, the post-operational shutdown residual water draining process is initiated. This switches on the hydrogen pump 28 to increase its speed and begins opening and closing the drain valve 29. The speed of the hydrogen pump 28 increases to speed r1 and is then maintained at speed r1. At time T1, the heating section 500 is switched off. The temperature of the drain valve 29 remains at a value slightly above 0 °C.At a time T2, after the passage of a previously determined period of time, the hydrogen pump 28 is stopped, and the opening and closing of the drain valve 29 is terminated.

[0042] We return to Fig. 2. If it is determined that the heating section 500 has a fault (step S105: YES), the pre-operation stop residual water drain determination device 64 determines that the enhanced pre-operation stop residual water drain process is to be executed. The operating control unit 67 then executes the enhanced pre-operation stop residual water drain process (step S145). The enhanced pre-operation stop residual water drain process is a residual water drain process that is executed before an operation stop of the fuel cell 10 and that drains the residual water in the fuel cell 10 at a higher water outlet rate than the water outlet rate in the post-operation stop residual water drain process described above. According to the embodiment, the water outlet rate is improved by the following methods (i) to (iv): (i) Extending the period during which the opening and closing of the drain valve is performed repeatedly; (ii) Increasing the ratio of open time within an opening-closing cycle time of the drain valve (hereinafter referred to as the ‘working ratio’); (iii) Increasing the speed of the hydrogen pump 28; and (iv) Extending a period during which the hydrogen pump 28 is driven.

[0043] Methods (i) and (ii) described above extend the overall time that the drain valve 29 is open, thus enabling the draining of a correspondingly larger quantity of water. Methods (iii) and (iv) increase the amount of hydrogen gas supplied to the fuel cell 10 per unit of time, and accordingly enable a larger quantity of water to be drained from the fuel cell 10 by the force of the hydrogen gas.

[0044] Fig. Figure 4 is a diagram illustrating a time graph during the intensified pre-operational shutdown residual water drainage process. The abscissa of Fig. Figure 4 shows the time. A time of 0 indicates the start time of the intensified pre-operational shutdown residual water drainage process. A top curve of Fig. Figure 4 shows a change in the rotational speed of hydrogen pump 28. A solid line curve shows a change in the rotational speed of hydrogen pump 28 during the intensified pre-operation stop residual water drainage process. For reference, a dashed line curve shows a change in the rotational speed of hydrogen pump 28 during the post-operation stop residual water drainage process. For reference, a second, underlying dashed line curve shows... Fig. 4. A change in the operating state of the drain valve 29 in the post-operational shutdown residual water drainage process. A third, subsequent curve with a solid line of Fig. Figure 4 shows a change in the operating state of the drain valve 29 in the enhanced pre-operation stop residual water draining process.

[0045] As in Fig. As shown in Figure 4, the period (T14) in which the opening and closing of the drain valve 29 is repeatedly performed in the enhanced pre-operation stop residual water draining process is longer than the period (T12) in which the opening and closing of the drain valve 29 is repeatedly performed in the post-operation stop residual water draining process. The duty cycle of the drain valve 29 in the enhanced pre-operation stop residual water draining process is higher than the duty cycle of the drain valve 29 in the post-operation stop residual water draining process. The maximum speed r2 of the hydrogen pump 28 in the enhanced pre-operation stop residual water draining process is higher than the maximum speed r1 of the hydrogen pump 28 in the post-operation stop residual water draining process.Furthermore, the period (T13) during which the hydrogen pump 28 is driven in the enhanced pre-operation-stop residual water drainage process is longer than the period (T11) during which the hydrogen pump 28 is driven in the post-operation-stop residual water drainage process. These differences allow for a higher water discharge rate in the enhanced pre-operation-stop residual water drainage process than in the post-operation-stop residual water drainage process. Executing the enhanced pre-operation-stop residual water drainage process, which has the higher water discharge rate, removes a larger quantity of water remaining in the fuel cell 10.

[0046] We return to Fig. 2. After completion of the enhanced pre-operation stop residual water drainage process, the operating control unit 67 switches off the control device 60 (step S150). The processing of step S150 is identical to the processing of step S115 described above, and its detailed description is omitted. After completion of step S150, the residual water drainage process is terminated. Thus, if the enhanced pre-operation stop residual water drainage process is executed, the post-operation stop residual water drainage process is not executed. This is because the enhanced pre-operation stop residual water drainage process has a high water discharge capacity that is sufficient to drain the residual water from the fuel cell 10. Accordingly, there is no need to drain water after an operation stop of the fuel cell 10.

[0047] The fuel cell system 100 of the first embodiment described above includes the heating section 500, which is designed to heat the drain valve 29 and thus prevents the drained water from freezing in the drain valve 29 during the post-operational shutdown residual water drainage process. If a fault in the heating section 500 is detected, the pre-operational shutdown residual water drainage process (i.e., the enhanced pre-operational shutdown residual water drainage process) is executed. The water discharge rate in this residual water drainage process is higher than the water discharge rate in the residual water drainage process that is executed if no fault in the heating section 500 is detected (i.e., the post-operational shutdown residual water drainage process).This design reduces the amount of water remaining in the fuel cell 10 after the fuel cell 10 has been shut down, and thus prevents the water in the drain valve 29 from freezing after the fuel cell 10 has been shut down.

[0048] If a fault in the heating section 500 is detected, the fuel cell system 100 of the first embodiment performs the enhanced pre-operation-stop residual water drainage process, which has a higher water outlet capacity than the water outlet capacity in the post-operation-stop residual water drainage process, and does not perform a post-operation-stop residual water drainage process. This design reduces the amount of water remaining in the fuel cell 10 after an operation stop of the fuel cell 10 and prevents the drained water from freezing in the drain valve 29, in contrast to a design that performs the residual water drainage process at cold temperatures after an operation stop of a fuel cell.If no fault is detected in the heating section 500, the fuel cell system 100 of the first embodiment performs the post-operational shutdown residual water drainage process and does not perform an enhanced pre-operational shutdown residual water drainage process. This embodiment uses the heating section 500 to prevent the drained water from freezing in the drain valve 29 and reduces the power consumption required for the residual water drainage process compared to an embodiment that performs both the enhanced pre-operational shutdown residual water drainage process and the post-operational shutdown residual water drainage process.

[0049] The fuel cell system 100 of the first embodiment does not perform a post-operational shutdown residual water draining process if the temperature of the drain valve 29 is equal to or below 0 °C, whereas it does perform the post-operational shutdown residual water draining process if the temperature of the drain valve 29 is higher than 0 °C. This design prevents the drained water from freezing in the drain valve 29 and reduces the power consumption required for the residual water draining process compared to an embodiment that performs the post-operational shutdown residual water draining process regardless of the temperature of the drain valve 29. If the temperature of the drain valve 29 is equal to or below 0 °C, the heating section 500 serves to heat the drain valve 29. This raises the temperature of the drain valve 29 above 0 °C.

[0050] Controlling the period during which the opening and closing of the drain valve 29 is repeatedly performed, and the operating ratio within an opening-closing cycle time of the drain valve 29, or in other words, the ratio of open time to closing time, results in controlling the water outlet rate in the residual water drainage process. This design makes it possible to control the water outlet rate in the residual water drainage process with high accuracy.

[0051] Controlling the duration and speed of the pump operation directly controls the water outlet rate during the residual water drainage process. This design allows for highly accurate control of the water outlet rate during this process.

[0052] The heating section 500 is designed by using part of an air conditioning system used in the vehicle in which the fuel cell system 100 is installed. This design reduces the manufacturing costs of the fuel cell system 100 compared to a design that includes a mechanism solely for heating the drain valve 29. B. Second embodiment

[0053] Fig. Figure 5 is a flowchart showing the sequence of a residual water drainage process according to a second embodiment. The configuration of a fuel cell system of the second embodiment is comparable to the configuration of fuel cell system 100 of the first embodiment. Fig. The embodiment shown in Figure 1 is identical. Identical components are designated by the same reference numerals, and their detailed description is omitted.

[0054] The residual water drainage process of the second embodiment differs from the residual water drainage process of the one described in Fig. In the first embodiment shown in Figure 2, steps S210 to S235 are performed instead of steps S145 and S150. Otherwise, the residual water drainage process of the second embodiment is identical to that of the first embodiment. Identical steps are designated with the same step numbers, and their detailed description is omitted.

[0055] If it is determined that heating section 500 has a fault (step S105: YES), then steps S210 to S225 are processed. The processing of step S210 is identical to the processing of step S110 described above. The processing of steps S215, S220, and S225 is identical to the processing of steps S115, S120, and S125 described above, and their detailed description is omitted.

[0056] After completion of the processing at step S225, i.e., after the control device 60 has been switched on, the post-operation stop residual water drain determination device 65 determines whether the temperature of the drain valve 29 is higher than 0 °C and lower than 5 °C (step S230). If it is determined that the temperature of the drain valve 29 is higher than 0 °C and lower than 5 °C (step S230: YES), the operating control unit 67 executes a reduced post-operation stop residual water drain process (step S235). The reduced post-operation stop residual water draining process refers to a residual water draining process that is carried out after an operation stop of the fuel cell 10 and that has a lower water outlet capacity than the water outlet capacity in the post-operation stop residual water draining process described above in order to drain the residual water in the fuel cell 10.According to this embodiment, the water outlet rate is reduced by shortening the period during which the drain valve 29 is repeatedly opened and closed, as well as the period during which the hydrogen pump 28 is driven. The water outlet rate can also be reduced by decreasing the duty cycle and / or the speed of the hydrogen pump 28 instead of, or in addition to, shortening the period during which the drain valve 29 is repeatedly opened and closed, and the period during which the hydrogen pump 28 is driven.

[0057] If it is determined that the temperature of the drain valve 29 is not higher than 0 °C or not lower than 5 °C, i.e., if it is determined that the temperature of the drain valve 29 is equal to or below 0 °C or at least 5 °C (step S230: NO), then, on the other hand, the residual water drainage process skips step S235 and returns to step S210. In this case, the residual water drainage process is not executed.

[0058] The attenuated post-operational shutdown residual water draining process is executed when the temperature of the drain valve 29 is higher than 0 °C and lower than 5 °C. This design prevents the water drained from the fuel cell 10 from freezing in the drain valve 29. The attenuated post-operational shutdown residual water draining process has a reduced water discharge rate for the following reason: The temperature of the drain valve 29 is more likely to be higher than 0 °C and lower than 5 °C, so the residual water draining process (the attenuated post-operational shutdown residual water draining process) is more likely to be executed.The fuel cell system of the second embodiment reduces the water outlet capacity of a residual water drainage process, thereby reducing the power consumption required for this process and minimizing the overall increase in power consumption. Performing the residual water drainage process while the vehicle is stationary generates operating noise and vibrations from the hydrogen pump 28, which can be disconcerting for the user. Since the temperature of the drain valve 29 is more likely to be above 0 °C and below 5 °C, this can cause significant discomfort for the user.The fuel cell system of the second embodiment accordingly shortens the period in which the opening and closing of the drain valve 29 is repeatedly performed, as well as the period in which the hydrogen pump 28 is driven in each residual water draining process, in order to reduce the feeling of uncertainty caused to the user.

[0059] The fuel cell system of the second embodiment described above has similar advantageous effects to that of the fuel cell system 100 of the first embodiment. Furthermore, in the event of a malfunction of the heating section 500, the fuel cell system of the second embodiment performs the residual water drainage process if the temperature of the drain valve 29 is higher than 0 °C and lower than 5 °C, for example, before the temperature of the drain valve 29 drops to 0 °C, while the temperature of the drain valve 29 is gradually decreasing due to a shutdown of the fuel cell 10. This design prevents the water drained from the fuel cell 10 from freezing in the drain valve 29. The fuel cell system of the second embodiment does not perform the residual water drainage process if the temperature of the drain valve 29 is higher than 5 °C.This design prevents the residual water drainage process from being performed frequently, thereby reducing the increase in electricity consumption required for the residual water drainage process, while avoiding feelings of uncertainty for the user. C. Modifications C1. Modification 1

[0060] Each of the above embodiments performs the post-operational shutdown residual water draining process at substantially regular intervals when the heating section 500 is not experiencing a fault. However, the present disclosure is not limited to this embodiment. For example, the post-operational shutdown residual water draining process only needs to be performed once after an operational shutdown of the fuel cell 10. One modification can start the control device 60 at regular intervals, as in the respective embodiments above, and does not need to perform the post-operational shutdown residual water draining process if the temperature of the drain valve 29 is higher than 0 °C. If the temperature of the drain valve 29 is equal to or below 0 °C, this modification can use the heating section 500 to heat the drain valve 29 and can then perform the post-operational shutdown residual water draining process.This modified design does not perform the residual water drainage process if the temperature of the drain valve 29 is higher than 0 °C, thereby further reducing power consumption. C2. Modification 2

[0061] The first embodiment uses all of the methods (i) to (iv) described above for the purpose of increasing the water outlet capacity in the enhanced pre-operational shutdown residual water draining process. At least one of these methods may be omitted. For example, a modification may perform at least one of the methods to: (i) extend the period during which the opening and closing of the drain valve is repeatedly performed, and (ii) increase the open-time ratio within an opening-closing cycle time of the drain valve (hereinafter referred to as the "operating ratio"), while omitting methods (iii) and (iv). Another modification may perform at least one of the methods to: (iii) increase the rotational speed of the hydrogen pump 28, and (iv) extend the period during which the hydrogen pump 28 is driven, while omitting methods (i) and (ii).Furthermore, instead of or in addition to the above procedures (i) to (iv), any process for increasing the water outlet capacity from the fuel cell 10 can be carried out. C3. Modification 3

[0062] In the respective embodiments, the heating section 500 is configured by using a part of the air conditioning system used in the vehicle in which the fuel cell system 100 is installed. However, the present disclosure is not limited to this configuration. For example, a heater can be arranged near the drain valve 29 solely for the purpose of heating the drain valve 29. C4. Modification 4

[0063] The second embodiment determines at step S230 in the residual water drainage process whether the temperature of the drain valve 29 is higher than 0 °C and lower than 5 °C. However, the present disclosure is not limited to this embodiment. The upper temperature limit of this determination is not limited to 5 °C, but can be any temperature close to 0 °C. A modification can estimate the temperature of the drain valve 29 at the next wake-up time and determine whether the estimated temperature is within a previously defined temperature range, instead of determining at step S230 whether the instantaneous temperature of the drain valve 29 is within a previously defined temperature range.The temperature of the drain valve 29 at the next wake-up time can be estimated, for example, using at least one piece of information under a change in the temperature of the drain valve 29, the ambient temperature, a change in the ambient temperature, the fuel cell temperature, and a change in the fuel cell temperature. C5. Modification 5

[0064] In the respective embodiments, the temperature sensor 63 is configured to estimate the temperature of the drain valve 29 using the fuel cell temperature transmitted by the temperature sensor 46. However, the present disclosure is not limited to this embodiment. For example, an additional temperature sensor can be arranged which is configured to directly measure the temperature of the drain valve 29, and the temperature sensor 63 can receive temperature information from this additional temperature sensor. A further modification allows a device other than the control device 60, for example, the ECU mounted in the vehicle, to be notified of the fuel cell temperature measured by the temperature sensor 46 and to receive and obtain the temperature of the drain valve 29, which is estimated by the ECU based on the received fuel cell temperature. C6. Modification 6

[0065] In the respective embodiments, the fuel cell system 100 is mounted in the vehicle to be used as the propulsion power supply system. However, the present disclosure is not limited to this embodiment. The fuel cell system 100 can also be mounted and used in any other moving body that requires a propulsion power supply, for example, a ship or an aircraft. The fuel cell system 100 can also be arranged in enclosed spaces or outdoors on company premises or in a private household to be used as a stationary power supply.Each of the cell units 11 contained in the fuel cell 10 is the cell unit for the polymer electrolyte fuel cell in the embodiments described above, but can also be a cell unit for any of various other fuel cells, for example a phosphoric acid fuel cell, a molten carbonate fuel cell or a solid oxide fuel cell. C7. Modification 7

[0066] The configuration of the fuel cell system 100 in each embodiment is for illustrative purposes only and can be modified in various ways. For example, the oxidation gas exhaust path 32 and the second fuel gas exhaust path 24 need not be connected to each other, but can be configured to discharge their respective exhaust gases independently. In another example, the start control device 70 can be configured to include the respective functional components 62 to 67 instead of the control device 60. C8. Modification 8

[0067] In the embodiments described above, a portion of the hardware-implemented design can be replaced by a software-implemented design, while a portion of the software-implemented design can be replaced by a hardware-implemented design. For example, at least one functional component among the respective functional components 62 to 67 can be implemented by an integrated circuit, a discrete circuit, or a combination thereof. If part or all of a particular function in the present disclosure is implemented by a software-implemented design, the software (the computer program) can be provided in the form of memory on a computer-readable recording medium.The term "computer-readable recording medium" is not limited to portable recording media such as flexible disks and CD-ROMs, but also includes internal storage devices, such as various RAMs and ROMs contained within the computer, as well as external storage devices, such as hard drives permanently installed in the computer. Accordingly, the term "computer-readable recording medium" is used in a broad sense, encompassing any recording medium capable of storing data packets in a non-transient manner.

Claims

[1] Fuel cell system (100), comprising: a fuel cell (10); a reaction gas supply mechanism (200) designed to supply a reaction gas to the fuel cell (10); an outflow path (23, 24) designed to discharge exhaust gas and water discharged from the fuel cell (10); a valve (29) which is arranged in the outflow path (23, 24); a residual water drainage control unit (66) designed to control a residual water drainage process of the fuel cell (10) using the reaction gas supply mechanism (200) and the valve (29); a heating section (500) designed to heat the valve (29); and a fault detector (52) designed to detect a fault in the heating section (500), wherein, When a fault in the heating section (500) is detected, the residual water drain control unit (66) executes the residual water drain process and increases the water outlet capacity in the residual water drain process compared to the water outlet capacity in the residual water drain process that is executed when no fault in the heating section (500) is detected. [2] Fuel cell system (100) according to claim 1, wherein the residual water drainage control unit (66) controls a pre-operation stop residual water drainage process, which can be executed before an operation stop of the fuel cell (10), and a post-operation stop residual water drainage process, which can be executed after an operation stop of the fuel cell (10), as the residual water drainage process, wherein, If a fault in the heating section (500) is detected, the residual water drainage control unit (66) performs the pre-operation stop residual water drainage process with a higher water outlet rate than the water outlet rate in the post-operation stop residual water drainage process, and does not perform a post-operation stop residual water drainage process. If no fault is detected in the heating section (500), the residual water drainage control unit (66) performs the post-operation stop residual water drainage process and does not perform a pre-operation stop residual water drainage process. [3] Fuel cell system (100) according to claim 2, further comprising: a temperature sensor designed to obtain the temperature of the valve (29), wherein The residual water drain control unit (66) is activated at regular intervals after a shutdown of the fuel cell (10) to check the temperature of the valve (29) obtained by the temperature sensor and to execute the post-shutdown residual water drain process if the temperature is higher than 0 °C, while the post-shutdown residual water drain process is not executed if the temperature is equal to or below 0 °C, and the heating section (500) heats the valve (29) if the temperature of the valve (29) obtained by the temperature sensor is equal to or below 0 °C. [4] Fuel cell system (100) according to one of claims 1 to 3, wherein the residual water draining control unit (66) causes the valve (29) to repeatedly perform an opening and closing in the residual water draining process, and controls a water outlet capacity in the residual water draining process by controlling a period in which an opening and closing of the valve (29) is repeatedly performed, and / or a ratio of an open time to a closing time in an opening-closing cycle of the valve (29). [5] Fuel cell system (100) according to any one of claims 1 to 4, wherein the reaction gas supply mechanism (200) comprises a pump (28) designed to supply an excess of the reaction gas contained in the exhaust gas of the fuel cell (10), wherein The residual water drainage control unit (66) drives the pump (28) in the residual water drainage process and controls a water outlet capacity in the residual water drainage process by controlling a period in which the pump (28) is driven and / or a speed of the pump (28).

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