Fuel cell system with a valve module between a fuel cell stack and a humidifier

Abstract

Fuel cell system comprising: an air supply unit (33) for supplying oxygen-containing air as an oxidizing gas to a fuel cell stack (10); a humidifier (34) for humidifying the air supplied by the air supply unit (33); an air supply line (35) which is arranged between a cathode inlet of the fuel cell stack (10) and the humidifier (34) and supplies the humidified air to the fuel cell stack (10); a cathode-side exhaust gas line (36) arranged between a cathode outlet of the fuel cell stack (10) and the humidifier (34), and supplying a cathode exhaust gas discharged from a cathode of the fuel cell stack (10) to the humidifier (34) for humidification in the humidifier (34); and a unitary valve module (50) connected to the air supply line (35) and the cathode-side exhaust line (36), comprising: a bypass line (59a) connecting the air supply line (35) to the cathode-side exhaust line (36); and an outwardly directed discharge opening (59b) which discharges the cathode exhaust gas to the outside, and wherein the valve module controls a gas flow between the humidifier (34) and the fuel cell stack (10) and between the bypass line (59a) and the outwardly directed discharge opening (59b), wherein the unitary valve module (50) further comprises: a first valve (51) installed on the air supply line (35); and a second valve (55) installed on the cathode-side exhaust line (36), wherein the bypass line (59a) connects the first valve (51) and the second valve (55), and wherein the outwardly directed discharge opening (59b) is connected to the second valve (55), wherein the first valve (51) selectively opens and closes a first supply line (35a) of the air supply line (35) which is connected to an outlet of the humidifier (34), and opens and closes a second supply line (35b) of the air supply line (35) which is connected to the cathode inlet of the fuel cell stack (10), and opens and closes the bypass line (59a), and wherein the second valve (55) selectively opens and closes a first exhaust line (36a) of the cathode-side exhaust line (36) which is connected to the cathode outlet of the fuel cell stack (10), and opens and closes a second exhaust line (36b) of the cathode-side exhaust line (36) which is connected to an inlet of the humidifier (34), opens and closes the bypass line (59a), and opens and closes the outward discharge opening (59b).

Description

Technical field

[0001] The present disclosure relates to a fuel cell system. In particular, the present disclosure relates to a safe fuel cell system that complies with the Global Technical Regulations (GTRs) in an operating range thereof without fire risk. background

[0002] A fuel cell system for an environmentally friendly hydrogen fuel cell vehicle includes a fuel cell stack that generates electrical energy through an electrochemical reaction of a reactive gas. A hydrogen supply device supplies a fuel gas, i.e., hydrogen, to the fuel cell stack. An air supply device supplies air containing an oxidizing gas, i.e., oxygen. A heat and water management system controls an operating temperature of the fuel cell stack and performs a water management function. A fuel cell system controller controls the overall operation of the fuel cell system.

[0003] Fig. 1 is a diagram illustrating a configuration of a general fuel cell system. In a fuel cell system, a hydrogen supplier thereof includes a hydrogen storage (hydrogen tank) 21, a hydrogen supply pipe 22, a regulator (not shown), a hydrogen pressure control valve 23, and a hydrogen recirculator. An air supplier of the fuel cell system includes an air blower 33 and a humidifier 34. A heat and water management system (not shown) of the fuel cell system includes a water trap, a motor-driven water pump (cooling water pump), a water tank, a heat exchanger, etc.

[0004] High-pressure hydrogen supplied from the hydrogen tank 21 of the hydrogen supply is supplied to the fuel cell stack 10 after being pressure-reduced to a predetermined pressure in the regulator (not shown) by the hydrogen pressure control valve 23 on an inlet side of a cathode. In this case, the pressure-reduced hydrogen is supplied to the fuel cell stack while controlling its amount through pressure control according to the operating conditions of the fuel cell stack 10.

[0005] That is, the hydrogen passing through the regulator, after being supplied from the hydrogen tank 21, is supplied to the fuel cell stack 10 after being pressure-controlled by the hydrogen pressure control valve 23 on the inlet side of the cathode. The hydrogen pressure control valve 23 adjusts the hydrogen pressure-reduced by the regulator to a pressure suitable for a stack operating state.

[0006] In the hydrogen recirculator, an ejector or recirculation fan 25 is connected to a recirculation line 24 at an anode of the fuel cell stack 10 to recirculate unreacted hydrogen that has not been consumed by the anode of the fuel cell stack 10 and to reuse hydrogen.

[0007] The air supplier humidifies air supplied by the air blower 33 with the humidifier 34, and then supplies the humidified air to the fuel cell stack 10 via an air supply line 35.

[0008] Nitrogen contained in the air, which has been supplied to the cathode of the fuel cell stack 10 according to the operation of the fuel cell stack 10, and water (water and steam) generated at the cathode of the fuel cell stack 10 pass through an electrolytic membrane arranged in the fuel cell stack 10 and then reach the anode of the fuel cell stack 10.

[0009] The nitrogen reduces the partial pressure of oxygen, thereby degrading the performance of the fuel cell stack 10. The generated water blocks a flow channel of a partition plate channel, thereby restricting the movement of hydrogen. As the amount of impurities, such as nitrogen, water, and water vapor, supplied to the anode through the electrolytic membrane within the fuel cell stack 10 increases, the amount of hydrogen at the anode decreases, thus decreasing the reaction efficiency.

[0010] Therefore, it is necessary to remove nitrogen from the passing air and liquid droplets in the channel by periodically purging the anode to ensure stable performance of the fuel cell stack 10.

[0011] That is, a purge valve 40 is connected to an outlet line of the anode of the fuel cell stack 10 for purging hydrogen. Hydrogen purging is performed by periodically opening the purge valve 40 at intervals of a predetermined time during vehicle travel to increase the purity of the hydrogen in the fuel cell stack 10. The purge valve 40 is also opened to purge the hydrogen in the fuel cell stack 10 upon shutdown of the fuel cell system or upon startup of the fuel cell system. In this case, the purged hydrogen is discharged to the outside through an exhaust line 41 on an outlet side of the anode in the fuel cell stack 10, through exhaust lines 36 and 37 on the cathode side, and through the humidifier 34.

[0012] When hydrogen is periodically ejected from the anode, impurities such as nitrogen or moisture are removed from the partition plate channel in the fuel cell stack 10 via an outlet. Accordingly, it is possible to achieve an increase in hydrogen concentration and hydrogen consumption rate, and an increase in gas diffusion and reactivity.

[0013] Purge valve 40 is an electromagnetic control valve that is periodically opened or closed in accordance with a command from the fuel cell system controller (not shown) for hydrogen concentration management. When purge valve 40 is open, foreign matter, such as moisture or nitrogen present in fuel cell stack 10, is exhausted into the atmosphere through a vehicle exhaust port connected to exhaust line 37.

[0014] When the purge valve 40 is opened during vehicle travel, the hydrogen can be exhausted into the atmosphere through the exhaust pipes 36 and 37 by a pressure difference between the anode (relatively high pressure) and the cathode in the fuel cell stack 10. In this case, the foreign matter is exhausted together with the hydrogen, thus maintaining a desired performance of the fuel cell stack 10.

[0015] Fig. Figure 2 is a diagram of air flow in a fuel cell system. With reference to Fig. 2, air shut-off valves 32 and 38 are installed on an air supply line 31 at an inlet side of the air blower 33 and on the exhaust line 37 at an outlet side of the humidifier 34, respectively.

[0016] Humid air, which is passed through a cathode-side outlet of the fuel cell stack 10 and the exhaust pipe 36 in the arrangement of the Fig. 2 is discharged, is led outwards via the exhaust gas line 37 together with the hydrogen discharged through the purge valve 40 after passing through the humidifier 34.

[0017] In addition, dry air supplied by the blower 33 is humidified after absorbing moisture from the moist air discharged from the cathode of the fuel cell stack 10 via the exhaust pipe 36, and is then supplied to the cathode of the fuel cell stack 10 via the air supply pipe 35.

[0018] Since the air shutoff valves 32 and 38 are installed on the inlet side of the air blower 33 and the outlet side of the humidifier 34, respectively, air flows along a path including the air shutoff valve 32, the air blower 33, the humidifier 34, the stack (cathode) 10, the humidifier 34, and the air shutoff valve 38.

[0019] Both air shut-off valves 32 and 38 are controlled to be in an open state so as to allow air flow along the path described above.

[0020] The following describes problems that arise in a conventional fuel cell system.

[0021] Initially, both air shut-off valves 32 and 38 are closed when the fuel cell system is shut down. In this state, hydrogen, which has been purged in accordance with the opening of the purge valve 40, not only remains in the humidifier 34, but also, after passing through the anode-side exhaust line (“41” in Fig. 1) and the cathode-side exhaust line 36, but also in the lines 31, 35, 36 and 37 between the air shut-off valves 32 and 38, in the air blower 33, in the humidifier 34 and in the cathode of the fuel cell stack 10.

[0022] If such air remains in the system, performance deterioration and service life shortening of the fuel cell stack 10 may occur.

[0023] In fuel cell vehicles, safety without fire risk can be ensured if the hydrogen concentration released to the outside does not exceed a predetermined level. Generally, the hydrogen concentration released by fuel cell vehicles is set to a peak of 8% or less and an average of 4% or less for 3 seconds.

[0024] In order to comply with such Global Technical Regulations (GTR) by reducing the concentration of emitted hydrogen, vehicle manufacturers use a process in which hydrogen is accumulated in a dilution device and then emitted after dilution by introducing air or a process in which hydrogen is burned.

[0025] However, if the time from the shutdown of the fuel cell system to the next startup is longer (if the shutdown time of the fuel cell stack is longer), a phenomenon may occur in which hydrogen in the fuel cell stack 10 overflows through the electrolytic membrane via the cathode. As the deterioration of the fuel cell stack 10 becomes increasingly problematic, the amount of hydrogen overflowing the cathode increases.

[0026] The hydrogen purged during startup, the hydrogen flowing through the electrolytic membrane in the fuel cell stack 10 via the cathode, and the hydrogen accumulated in the humidifier during shutdown are expelled by the air supplied by the air blower 33 and thus discharged through the exhaust pipe 37. In this case, hydrogen is forced into the exhaust pipe 37 without mixing with air, increasing the hydrogen concentration and the risk of fire. Furthermore, it may be impossible to meet the Global Technical Regulations (GTR).

[0027] In conventional cases, a reduction in hydrogen concentration is achieved by modifying the control software. However, such a hydrogen concentration reduction has limitations. When stack deterioration becomes problematic, a phenomenon in which hydrogen in the fuel cell stack 10 penetrates a cathode, thus increasing the concentration of hydrogen released to the outside. Furthermore, it may be impossible to meet the desired or required regulations.

[0028] When the shutdown state (shutdown) occurs at an ambient temperature of 5°C or less, the air blower 33 is operated to expel water in the fuel cell stack 10 to the exhaust pipes 36 and 37 to prevent freezing of water in the fuel cell stack 10. Thus, a cold start can be achieved at a temperature below the freezing point of water in winter.

[0029] In this case, a lot of the water discharged from the fuel cell stack 10 is returned to the fuel cell stack 10, and therefore, efficient water removal cannot be achieved. If residual water in the fuel cell stack 10 freezes in winter, the start-up time required for cold start may increase, or start-up failure may occur.

[0030] Furthermore, JP 2002 - 343 398 A discloses a fuel cell system comprising: an air supply unit for supplying oxygen-containing air as an oxidizing gas to a fuel cell stack; a humidifier for humidifying the air supplied by the air supply unit; an air supply line arranged between a cathode inlet of the fuel cell stack and the humidifier and supplying the humidified air to the fuel cell stack; a cathode-side exhaust line arranged between a cathode outlet of the fuel cell stack and the humidifier and supplying a cathode exhaust gas discharged from a cathode of the fuel cell stack to the humidifier for humidification in the humidifier;and a unified valve module connected to the air supply line and the cathode-side exhaust line, comprising: a bypass line connected between the air supply line and the cathode-side exhaust line; and an outward discharge port that discharges the cathode exhaust gas to the outside and controls a gas flow between the humidifier and the fuel cell stack and between the bypass line and the outward discharge port.

[0031] US 2012 / 0 141 890 A1 further discloses a fuel cell system comprising an assembly of unit fuel cells, an air supply unit, a humidifier, a hydrogen supply unit, and a valve unit. The valve unit is configured to be connected to a stack and the humidifier. This valve unit prevents outside air from being introduced into an air supply path and an air discharge path through the humidifier when the stack is shut down. More specifically, the valve unit includes a valve body component that forms the air supply path as first and second valve passages and the air discharge path as third and fourth valve passages, as well as an opening and closing component for opening and closing the air supply path and the air discharge path. Overview of Revelation

[0032] The present disclosure has been made in an effort to solve the problems described above in connection with the prior art.

[0033] It is the object of the present inventive concept to provide a safety fuel cell system which satisfies the Global Technical Regulations (GTR) in an operating range thereof without a fire risk, regardless of a deteriorated condition of a fuel cell stack.

[0034] Furthermore, a fuel cell system is to be provided which prevents a deterioration in performance and a shortening of the service life of a fuel cell stack caused by air remaining after the fuel cell system is switched off.

[0035] Furthermore, a fuel cell system is to be provided that solves problems related to cold start, increase in cold start time and freezing of an air shut-off valve due to freezing water in winter.

[0036] The objects are achieved by a fuel cell system having the features of claim 1. Advantageous further developments can be found in the subclaims.

[0037] According to an embodiment of the present inventive concept, a fuel cell system includes an air supply unit for supplying oxygen-containing air as an oxidizing gas to a fuel cell stack. A humidifier humidifies the air supplied by the air supply unit. An air supply line is arranged between a cathode inlet of the fuel cell stack and the humidifier, and supplies the humidified air to the fuel cell stack. A cathode-side exhaust line is arranged between a cathode outlet of the fuel cell stack and the humidifier, and supplies a cathode exhaust gas discharged from a cathode of the fuel cell stack to the humidifier for humidification in the humidifier.A unified valve module is connected to the air supply line and the cathode-side exhaust line, and includes a bypass line connecting the air supply line to the cathode-side exhaust line and an outward discharge port that discharges the cathode exhaust gas to the outside. The valve module controls a gas flow between the humidifier and the fuel cell stack and between the bypass line and the outward discharge port. The unified valve module includes a first valve installed on the air supply line and a second valve installed on the cathode-side exhaust line. The bypass line connects the first valve and the second valve, and the outward discharge port is provided on the second valve.The first valve selectively opens and closes a first supply line of the air supply line connected to an outlet of the humidifier, and opens and closes a second supply line of the air supply line connected to the cathode inlet of the fuel cell stack, and opens and closes the bypass line. The second valve selectively opens and closes a first exhaust line of the cathode-side exhaust line connected to the cathode outlet of the fuel cell stack, and opens and closes a second exhaust line of the cathode-side exhaust line connected to an inlet of the humidifier, opens and closes the bypass line, and opens and closes the outward discharge port.

[0038] Each of the first and second valves may be an electromagnetic valve whose opening or closing operation is independently controlled in accordance with a control signal from a controller.

[0039] Each of the first and second valves may include a valve housing to which the first and second supply lines and the first and second exhaust lines are connected. A valve body is disposed in the valve housing to selectively open and close the first and second supply lines and the first and second exhaust lines connected to the valve housing according to a rotational operation of the valve body. Valve actuators rotate the valve body according to a control signal from a controller to selectively open and close the first and second supply lines and the first and second exhaust lines.

[0040] The first and second valves may have an integrated valve structure in which the valve housings of the first and second valves are integrally connected to each other.

[0041] An anode-side exhaust line of the fuel cell stack, on which a purge valve is installed, may be connected to the first exhaust line to guide purged hydrogen for flow to the first exhaust line during opening of the purge valve.

[0042] In a normal operating mode of the fuel cell system, in which the air supplied by the air supply unit has been supplied to the fuel cell stack after being humidified by the cathode exhaust gas in the humidifier, the first valve may close the bypass passage while the first and second supply passages are open. The second valve may close the bypass passage and the outward discharge port while the first and second exhaust passages are open, in a state where the air supply unit is operating.

[0043] In a startup mode in which startup of the fuel cell system is performed, the first valve may open the first supply line, the second supply line, and the bypass line. The second valve may close the outward discharge port while the first exhaust line, the second exhaust line, and the bypass line are open, in a state where the air supply unit is operated to discharge hydrogen present in the cathode of the fuel cell stack and the cathode-side exhaust line to the outside via the humidifier, and may close an exhaust line connected to the outlet of the humidifier after dilution with the air supplied by the air supply unit.

[0044] The start-up mode may include a first control mode and a second control mode to be executed after the first control mode is executed. In the first control mode, the first valve may close the second supply line while the first supply line and the bypass line are opened, and the second valve may close the first exhaust line and the outward discharge port while the second exhaust line and the bypass line are opened, in a state where the air supply unit is operated. In the second control mode, the first valve may open the first supply line, the second supply line, and the bypass line, and the second valve may close the outward discharge port while the first exhaust line, the second exhaust line, and the bypass line are opened, in a state where the air supply unit is operated.

[0045] In a shutdown state of the fuel cell system, the first valve may close the second supply line, and the second valve may close the first exhaust line.

[0046] In a low-temperature state in which an ambient temperature detected by a temperature sensor in a vehicle during shutdown of the fuel cell system is equal to or lower than a reference temperature, a humidifier bypass mode may be performed in which the first valve closes the bypass passage while the first supply passage and the second supply passage are open. The second valve closes the second exhaust passage and the bypass passage while the first exhaust passage and the outward discharge port are open, in a state where the air supply unit is operated to discharge the air supplied by the air supply unit to the outside through the outward discharge port while bypassing the humidifier after passing through the cathode of the fuel cell stack.

[0047] The humidifier bypass mode may be executed for a predetermined period of time. After the humidifier bypass mode is executed, in a state where the operation of the air supply unit is stopped, a shutdown mode may be executed in which the first valve closes the second supply line and the second valve closes the first exhaust line.

[0048] The term "vehicle" or "vehicle-related" or other similar expression, as used herein, is understood to encompass motor vehicles in general, such as passenger vehicles, including sports utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and to include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels not derived from petroleum). As used herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, vehicles powered by both gasoline and electricity.

[0049] The above and other features of the invention are discussed below. Short description of the drawings

[0050] The above and other features of the present disclosure will now be described in detail with reference to certain exemplary embodiments thereof illustrated in the accompanying drawings, which are given hereinafter for purposes of illustration only and are therefore not intended to be limiting of the present disclosure. Fig. 1 is a diagram showing a configuration of a general fuel cell system. Fig. 2 is a diagram of an air flow in the general fuel cell system. Fig. 3 is a view illustrating a fuel cell system in accordance with an embodiment of the present inventive concept in which a unified valve module is installed. Fig. 4 to 7 are views illustrating valve states in accordance with a control mode of the unified valve module in accordance with an embodiment of the present inventive concept.

[0051] It is understood that the attached drawings are not necessarily to scale, but rather provide a somewhat simplified representation of various features illustrating the basic principles of the invention. The specific design features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and use environment.

[0052] In the figures, reference numerals refer to the same or equivalent elements of the present invention throughout all figures. Detailed description

[0053] Reference will now be made in detail to various embodiments of the present inventive concept, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it is to be understood that the present description is not intended to limit the invention to these exemplary embodiments. Rather, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments which may be included within the spirit and scope of the invention as defined by the appended claims.

[0054] Fig. 3 is a view illustrating a fuel cell system in accordance with an embodiment of the present inventive concept in which a unified valve module is installed.

[0055] As in Fig. 3, a unified valve module 50 is installed between an air supply line 35 and a stack cathode side exhaust line 36 connecting a fuel cell stack 10 and a humidifier 34.

[0056] The air supply line 35 is a line through which dry air is supplied from an air blower 33 as an air supply unit (ASU) to the fuel cell stack 10 after absorbing moisture from the humidifier 34. The cathode-side exhaust line 36 is a line through which cathode exhaust gas, namely, moist air discharged through a cathode outlet of the fuel cell stack 10, is supplied to the humidifier 34 for moisture exchange with the dry air.

[0057] An anode-side exhaust line 41 of the fuel cell stack 10, on which a purge valve 40 is installed, as shown in Fig. 1 is connected to the cathode-side exhaust line 36, thus purged hydrogen flows to the cathode-side exhaust line 36 when the purge valve 40 is opened.

[0058] The unified valve module 50 has a unified module configuration including a bypass line 59a for connecting the air supply line 35 and the cathode-side exhaust line 36, and first and second valves 51 and 55 connected to each other by the bypass line 59a.

[0059] Here, the first valve 51 can be arranged at a central portion of the air supply line 35. The second valve 55 can be arranged at a central portion of the cathode-side exhaust line 36.

[0060] With reference to Fig. 3, the first valve 51, which is a three-way valve, is installed on the air supply line 35 to connect an outlet of the humidifier 34 and a cathode inlet of the fuel cell stack 10. The second valve 55, which is a four-way valve, is installed on the cathode-side exhaust line 36 to connect the cathode outlet of the fuel cell stack 10 to the inlet of the humidifier 34.

[0061] In closer consideration, the first valve 51 selectively opens and closes a first supply line 35a of the air supply line 35 connected to the outlet of the humidifier 34, a second supply line 35b of the air supply line 35 connected to the cathode inlet of the fuel cell stack 10, and the bypass line 59a.

[0062] The second valve 55 additionally includes an outward discharge port 59b for discharging the cathode exhaust gas to the outside. The second valve 55 selectively opens and closes a first exhaust passage 36a of the cathode-side exhaust passage 36 connected to the cathode outlet of the fuel cell stack 10, a second exhaust passage 36b of the cathode-side exhaust passage 36 connected to the inlet of the humidifier 34, the bypass passage 59a, and the outward discharge port 59b.

[0063] Each of the first and second valves 51 and 55 is an electromagnetic valve having an opening or closing operation, each independently controlled in accordance with a control signal from a controller, such as a typical electronic control unit (ECU, not shown). Each of the first and second valves 51 and 55 includes a valve housing 50a to which the above-described conduits are connected. A valve body 54 or 58 is installed in the valve housing 50a to selectively open and close conduits connected to the valve housing 50a according to a rotational operation thereof. Valve actuators (A1, A2) are operated according to the control signal from the controller to rotate the valve body 54 or 58 to selectively open and close the conduits.

[0064] In a particular embodiment, the first and second valves 51 and 55 may have an integrated valve structure in which the valve housings 50a of the first and second valves 51 and 55 are connected to each other.

[0065] In another embodiment, the valve actuators (A1, A2) in each of the valves 51 and 55 may comprise motors (M1, M2) whose operation is controlled according to an electrical signal output from the controller. The valve body 54 or 58 of each valve 51 or 55 is mounted in the corresponding valve housing 50a to rotate by a rotational force received from the motors (M1, M2) during operation of the motors (M1, M2), thus selectively opening and closing the corresponding lines.

[0066] Components for transmitting a rotational force, namely a reduction gear for reducing the speed of the rotational force of the motors (M1, M2), and a power transmission mechanism for transmitting the rotational force reduced in speed by the reduction gear to each valve body 54 or 58, may be arranged between a drive shaft of the motor and a central rotary shaft of the valve body 54 or 58.

[0067] In detail, a drive gear 52 or 56 is fixed to the drive shaft of the motors (M1, M2), and a reduction gear 53 or 57 is meshed with the drive gear 52 or 56. The reduction gear 53 or 57 has more teeth than the drive gear 52 or 56. The power transmission mechanism connects a rotating shaft of the reduction gear 53 or 57 to the rotating shaft of the valve body 54 or 58 in a power transmission manner. According to the power transmission mechanism, a drive belt transmission mechanism for connecting drive pulleys of two rotating shafts by means of a belt or a timing chain transmission mechanism for connecting pinions of two rotating shafts by means of a chain can be used.

[0068] The anode-side exhaust line of the fuel cell stack 10 (“41” in Fig. 1), where the flush valve (“40” in Fig. 1) is connected to the first exhaust line 36a so that purged hydrogen flows to the first exhaust line 36a when the purge valve 40 is opened.

[0069] The unified valve module 50 is controlled according to the control signal output from the controller to operate in a control mode selected from a normal operation mode, a start-up mode, a shutdown mode, and a humidifier bypass mode. Here, the drive of the valve actuators (A1, A2) in each valve is controlled in accordance with the control signal from the controller, and thus the selected control mode is executed when the corresponding valve body rotates to a predetermined position.

[0070] Fig. 4 to 7 are views illustrating valve states according to a control mode of the unified valve module in the present disclosure.

[0071] First, the normal operation mode is a control mode selected under the condition that the fuel cell system is operating normally. As shown in Fig. As shown in Figure 4, in the normal operation mode, the first valve 51 opens the first and second supply lines 35a and 35b, while closing the bypass line 59a in accordance with a control signal from the controller. Additionally, in accordance with the control signal from the controller, the second valve 55 opens the first and second exhaust lines 36a and 36b, while closing the bypass line 59a and the outward discharge port 59b.

[0072] As a result, the air supplied through the air supply line 31 on an inlet side of the humidifier 34 near the air blower 33 is humidified in the humidifier 34 and then supplied to the cathode of the fuel cell stack 10 via the first supply line 35a, the first valve 51, and the second supply line 35b. Air exhausted from the cathode of the fuel cell stack 10 is discharged to the outside after passing through the first exhaust line 36a, the second valve 55, the second exhaust line 36b, the humidifier 34, and an exhaust line 37 on the outlet side of the humidifier 34, together with purged hydrogen (which has been discharged to the first exhaust line 36a via the purge valve).

[0073] Next, the startup mode is executed when the fuel cell system is started. In this mode, hydrogen present in the cathode of the fuel cell stack 10 and the exhaust pipe 36a is exhausted to the outside after being diluted with fresh air supplied by the air blower 33, prior to normal operation of the fuel cell system.

[0074] In the start-up mode, the unified valve module 50 is controlled in two steps in accordance with control signals from the controller. In the first step of the start-up mode, air discharged from the outlet of the humidifier 34 to the first air supply line 35a of the fuel cell stack 10 during operation of the air blower 33 is discharged to the exhaust line 37 after being introduced into the humidifier 34 via the first valve 51, the bypass line 59a, and the second valve 55, without the air being introduced into the fuel cell stack 10.

[0075] As in Fig. 5A, the first valve 51 is controlled to close the second supply line 35b while the first supply line 35a and the bypass line 59a are open.

[0076] In addition, in the first step of the start-up mode, the second valve 55 closes the first exhaust passage 36a and the outward discharge port 59b, while the second exhaust passage 36b and the bypass passage 59a are opened.

[0077] Accordingly, when the air blower 33 is operated in the first step of the start-up mode, air supplied by the air blower 33 is introduced into the humidifier 34, and is then exhausted to the outside via the exhaust pipe 37 on the outlet side of the humidifier 34 after passing through the first supply pipe 35a connected to the outlet of the humidifier 34, the first valve 51, the bypass pipe 59a, the second valve 55, the second exhaust pipe 36b and the humidifier 34.

[0078] Thus, in the first step of the startup mode, the air supplied by the air blower 33 passes through the humidifier 34 and is then discharged to the outside through the exhaust passage 37 after being directed to flow through the humidifier 34 again via the first valve 51 and the second valve 55, without being supplied to the fuel cell stack 10. At this time, no hydrogen is discharged through the exhaust passage 37.

[0079] After a predetermined time has elapsed, the second step of the start-up mode is executed for controlling the unified valve module 50 in accordance with a control signal from the controller. In the second step of the start-up mode, hydrogen present in the cathode of the fuel cell stack 10 and the exhaust passage 36a is exhausted to the outside after being diluted with fresh air supplied by the air blower 33 in the unified valve module 50, before performing normal operation of the fuel cell system.

[0080] As in Fig. 5B, the first valve 51 is controlled to open the first supply line 35a, the bypass line 59a, and the second supply line 35b. The second valve 55 is controlled to open the first exhaust line 36a, the second exhaust line 36b, and the bypass line 59a, while the outward discharge port 59b is closed.

[0081] Accordingly, when the air blower 33 is operated in the second step of the start-up mode, the air supplied by the air blower 33 is introduced into the first valve 51 via the first air supply line 35a connected to the humidifier outlet after passing through the humidifier 34. The air introduced into the first valve 51 is distributed into the second air supply line 35b and the bypass line 59a. Therefore, a quantity of the air is supplied to the cathode of the fuel cell stack 10, and the remaining quantity of the air is supplied to the second valve 55 via the bypass line 59a.

[0082] In addition, in the second step of the startup mode, hydrogen present in the cathode of the fuel cell stack 10 and the first exhaust passage 36a (purged hydrogen, hydrogen flowing over the anode of the fuel cell stack 10, etc.) shifts to the second valve 55 by air supplied to the cathode of the fuel cell stack 10 via the second supply passage 35b after being introduced into the first valve 51. The hydrogen shifted to the second valve 55 is mixed with fresh air introduced into the second valve 55 via the first supply passage 35a, the first valve 51, and the bypass passage 59a for dilution, and is then exhausted to the outside via the second exhaust passage 36b, the humidifier 34, and the exhaust passage 37.

[0083] In accordance with the present disclosure as described above, the concentration of hydrogen discharged to the outside is reduced according to fuel cell start-up and hydrogen dilution so as to satisfy the Global Technical Regulations (GTR) while reducing a fire risk.

[0084] A normal operation mode control is executed after the start-up mode control described above to perform normal operation of the fuel cell system.

[0085] Next, the shutdown mode, which is a control mode for the unified valve module, is executed when the fuel cell system is shut down. In this mode, the unified valve module 50 is controlled to close the cathode inlet and outlet of the fuel cell stack 10.

[0086] As in Fig. 6, the first valve 51 is controlled in the shutdown mode in the same manner as in the first step of the start-up mode according to a control signal from the controller.

[0087] In addition, in the shutdown mode, the second valve 55 is controlled according to a control signal from the controller to open the bypass line 59a and the second exhaust line 36b while closing the first exhaust line 36a and the outward discharge port 59b.

[0088] The shutdown mode control is executed when the fuel cell system is shut down, before the purge operation of the purge valve in an off state of the air blower 33. Accordingly, the hydrogen purged by the purge valve is present in the first exhaust line 36a at the shutdown.

[0089] In this case, the first and second valves 51 and 55 close the second air supply line 35b connected to the cathode inlet of the fuel cell stack 10 and the first exhaust line 36a connected to the cathode outlet of the fuel cell stack 10 to function as conventional air shutoff valves, respectively.

[0090] In addition, in the shutdown state described above, a small amount of air is present in the fuel cell stack 10 and the lines, thereby minimizing performance deterioration and shortening of the service life of the fuel cell stack 10.

[0091] Finally, the humidifier bypass mode is executed when the fuel cell system is shut down under a low-temperature condition where the ambient temperature detected by a temperature sensor installed in the vehicle is equal to or lower than a reference value. That is, the humidifier bypass mode is a control mode for discharging water present in the fuel cell stack 10 and the exhaust passage 36a.

[0092] In the humidifier bypass mode, the unified valve module 50 is controlled to displace air supplied by the air blower 33 during operation of the air blower 33 to the cathode inlet of the fuel cell stack 10 via the humidifier 34 and to the first valve 51 of the unified valve module 50 during discharge, wherein water is present in the cathode of the fuel cell stack 10 and the first exhaust passage 36a due to the air supplied to the cathode of the fuel cell stack 10 through the second valve 55 of the unified valve module 50 and the outward discharge port 59b, while preventing water from passing through the humidifier 34 in a state where the bypass passage 59a is closed.

[0093] With reference to Fig.7, in the humidifier bypass mode, the first valve 51 is controlled to open the first supply line 35a and the second supply line 35b while closing the bypass line 59a during operation of the air blower 33 according to a control signal from the controller.

[0094] The second valve 55 is controlled to open the first exhaust passage 36a and the outward discharge port 59b, while closing the second exhaust passage 36b and the bypass passage 59a in accordance with a control signal from the controller.

[0095] Accordingly, the air supplied through an air supply line 31 on the inlet side of the humidifier 34 is supplied by the air blower 33 to the cathode of the fuel cell stack 10 via the first supply line 35a, the first valve 51 and the second air supply line 35b after passing through the humidifier 34. Here, the supplied air is discharged to the outside through the outwardly directed discharge opening 59b together with the water present in the cathode of the fuel cell stack 10 and the first exhaust line 36a after passing through the second valve 55.

[0096] Thus, the water present in the cathode of the fuel cell stack 10 and the first exhaust passage 36a is expelled to the outside together with the air from the cathode of the fuel cell stack 10 without passing through the humidifier 34. Therefore, it is possible to effectively remove water present in the fuel cell stack 10 during shutdown. As a result, the time required for a cold start can be reduced.

[0097] The humidifier bypass mode control described above is performed for a predetermined time in an on-state of the air blower 33. After the predetermined time has elapsed, the unified valve module 50 is controlled to operate in the shutdown mode to complete the shutdown of the fuel cell system.

[0098] As can be seen from the above description, the fuel cell system according to the present disclosure satisfies the GTRs in the entire operating range, thus reducing the fire risk and ensuring safe operation.

[0099] In addition, since a small amount of air is present in the fuel cell stack after system shutdown (turning off), performance degradation and lifetime shortening of the fuel cell stack are reduced.

[0100] Furthermore, since the unified valve module arranged between the fuel cell stack and the humidifier functions as an air cut-off valve (ACV) to shut off the piping on the inlet and outlet sides of the cathode in the fuel cell stack, it is possible to eliminate the need for a conventional ACV. In particular, it is possible to solve the problems associated with freezing in winter with the ACV arranged on an exhaust piping downstream of one end of the humidifier.

[0101] Additionally, air and water are expelled from the fuel cell stack without passing through the humidifier during shutdown in a low-temperature environment. Therefore, it is possible to achieve effective removal of water from the fuel cell stack and reduce the start-up time required for a vehicle's cold start.

Claims

[1] Fuel cell system comprising: an air supply unit (33) for supplying oxygen-containing air as an oxidizing gas to a fuel cell stack (10); a humidifier (34) for humidifying the air supplied by the air supply unit (33); an air supply line (35) which is arranged between a cathode inlet of the fuel cell stack (10) and the humidifier (34) and supplies the humidified air to the fuel cell stack (10); a cathode-side exhaust gas line (36) arranged between a cathode outlet of the fuel cell stack (10) and the humidifier (34), and supplying a cathode exhaust gas discharged from a cathode of the fuel cell stack (10) to the humidifier (34) for humidification in the humidifier (34); and a unitary valve module (50) connected to the air supply line (35) and the cathode-side exhaust line (36), comprising: a bypass line (59a) connecting the air supply line (35) to the cathode-side exhaust line (36); and an outwardly directed discharge opening (59b) which discharges the cathode exhaust gas to the outside, and wherein the valve module controls a gas flow between the humidifier (34) and the fuel cell stack (10) and between the bypass line (59a) and the outwardly directed discharge opening (59b), wherein the unitary valve module (50) further comprises: a first valve (51) installed on the air supply line (35); and a second valve (55) which is installed on the cathode-side exhaust line (36), wherein the bypass line (59a) connects the first valve (51) and the second valve (55), and wherein the outwardly directed discharge opening (59b) is connected to the second valve (55), wherein the first valve (51) selectively opens and closes a first supply line (35a) of the air supply line (35) which is connected to an outlet of the humidifier (34), and opens and closes a second supply line (35b) of the air supply line (35) which is connected to the cathode inlet of the fuel cell stack (10), and opens and closes the bypass line (59a), and wherein the second valve (55) selectively opens and closes a first exhaust line (36a) of the cathode-side exhaust line (36) connected to the cathode outlet of the fuel cell stack (10), and opens and closes a second exhaust line (36b) of the cathode-side exhaust line (36) connected to an inlet of the humidifier (34), opens and closes the bypass line (59a), and opens and closes the outward discharge opening (59b). [2] A fuel cell system according to claim 1, wherein each of said first and second valves (51, 55) is an electromagnetic valve whose opening or closing operation is independently controllable in accordance with a control signal from a controller. [3] A fuel cell system according to claim 1, wherein each of the first and second valves (51, 55) comprises: a valve housing (50a) to which the first and second supply lines (35a, 35b) and the first and second exhaust lines (36a, 36b) are connected; a valve body (54, 58) installed in the valve housing and selectively closing and opening the first and second supply lines (35a, 35b) and the first and second exhaust lines (36a, 36b) connected to the valve housing in accordance with a rotational operation of the valve body (54, 58); and Valve actuators (A1, A2) which rotate the valve body (54, 58) in accordance with a control signal from a controller to selectively open and close the first and second supply lines (35a, 35b) and the first and second exhaust lines (36a, 36b). [4] A fuel cell system according to claim 3, wherein the first and second valves (51, 55) comprise an integrated valve structure in which the valve housings of the first and second valves (51, 55) are integrally incorporated. [5] The fuel cell system according to claim 1, wherein the first exhaust gas line (36a) is connected to an anode-side exhaust gas line (41) of the fuel cell stack (10), on which a purge valve (40) is installed to guide purge hydrogen to flow to the first exhaust gas line (36a) during opening of the purge valve (40). [6] The fuel cell system according to claim 1, wherein, in a normal operation mode of the fuel cell system in which the air supplied by the air supply unit (33) is supplied to the fuel cell stack (10) after being humidified by the cathode off-gas in the humidifier (34), the first valve (51) closes the bypass passage (59a) while opening the first and second supply passages (35a, 35b), and the second valve (55) closes the bypass passage (59a) and the outward discharge port (59b) under a condition that the air supply unit (33) is operable. [7] The fuel cell system according to claim 1, wherein, in a start-up mode in which a start-up of the fuel cell system is carried out, the first valve (51) opens the first supply line (35a), the second supply line (35b), and the bypass line (59a), and the second valve (55) closes the outward discharge port (59b) while opening the first exhaust line (36a), the second exhaust line (36b), and the bypass line (59a), under a condition that the air supply unit (33) is operable to discharge hydrogen present in the cathode of the fuel cell stack (10) and the cathode-side exhaust line (36) to the outside via the humidifier (34) and an exhaust line (36a, 36b) connected to the outlet of the humidifier (34), after being diluted with the hydrogen supplied by the air supply unit (33). supplied air. [8] The fuel cell system according to claim 7, wherein the start-up mode includes a first control mode and a second control mode for execution after the first control mode has been executed, wherein in the first control operation mode, the first valve (51) closes the second supply line (35b) while opening the first supply line (35a) and the bypass line (59a), and wherein the second valve (55) closes the first exhaust line (36a) and the outward discharge opening (59b) while opening the second exhaust line (36b) and the bypass line (59a), under a condition that the air supply unit (33) is operated, and wherein in the second control operation mode, the first valve (51) opens the first supply line (35a), the second supply line (35a) and the bypass line (59a), and wherein the second valve (55) closes the outward discharge opening (59b) while opening the first exhaust line (36a), the second exhaust line (36b) and the bypass line (59a), under a condition that the air supply unit (33) is operated. [9] The fuel cell system according to claim 1, wherein, in a shutdown state of the fuel cell system, the first valve (51) closes the second supply line (35b), and wherein the second valve (51) closes the first exhaust line (36a). [10] The fuel cell system according to claim 1, wherein, in a low-temperature state in which an ambient temperature measurable with a temperature sensor in a vehicle during shutdown of the fuel cell system is equal to or lower than a reference temperature, a humidifier bypass mode is implemented in which the first valve (51) closes the bypass line (59a) while opening the first supply line (35a) and the second supply line (35b), and the second valve (55) closes the second exhaust line (36b) and the bypass line (59a) while opening the first exhaust line (36a) and the outward discharge port (59b), under a condition that the air supply unit (33) is operated to discharge the air supplied by the air supply unit (33) to the outside through the outward discharge port (59b),while bypassing the humidifier (34) after passing through the cathode of the fuel cell stack (10). [11] The fuel cell system according to claim 10, wherein the humidifier bypass mode is executed for a predetermined period of time, and then a shutdown mode is executed in which the first valve (51) closes the second supply line (35b) and the second valve (51) closes the first exhaust line (36a).

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