JP2008218242A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent water from remaining even after scavenging in a valve arranged in a flow passage in which a reaction gas circulates. <P>SOLUTION: During a standstill of a fuel cell 20, under a condition that outdoor air temperature has fallen 0°C or lower, electromagnetic valves (valves including shut-off valves 43, 46, 52, and a purge valve 63 or the like) 110 arranged in the flow passage 126 including an oxidizing gas flow passage 71, and a fuel gas flow passage 40 are held at a certain opening from a full opening state and retained for a certain period of time, while in the meantime, an air-compressor 75 and a hydrogen pump 55 are scavenging driven to supply the reaction gas to the fuel cell 20 and to the electromagnetic valves 110, so that water droplets adhered inside the electromagnetic valve 110 and the fuel cell 20 are blown off by the reaction gas and exhausted outside, then the electromagnetic valve 110 is driven to the fully closed state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system that performs a scavenging process of a fuel cell.

  An example of a fuel cell that generates electricity using an electrochemical reaction between hydrogen and oxygen is a polymer electrolyte fuel cell. The polymer electrolyte fuel cell includes a stack configured by stacking a plurality of cells. The cell constituting the stack includes an anode (fuel electrode) and a cathode (air electrode), and a solid polymer electrolyte membrane having a sulfone sun group as an ion exchange group is provided between the anode and the cathode. Intervene.

  A fuel gas containing a fuel gas (hydrogen gas or reformed hydrogen made by reforming hydrocarbons to be hydrogen rich) is supplied to the anode, and a gas containing oxygen as an oxidant (oxidant gas), for example, to the cathode. Air is supplied. By supplying the fuel gas to the anode, hydrogen contained in the fuel gas reacts with the catalyst of the catalyst layer constituting the anode, thereby generating hydrogen ions. The generated hydrogen ions pass through the solid polymer electrolyte membrane and cause an electrical reaction with oxygen at the cathode. Power generation is performed by this electrochemical reaction.

  By the way, in a fuel cell system using a polymer electrolyte fuel cell as a power source, when the operation of the system is stopped, the temperature of the fuel cell decreases, and moisture inside the fuel cell that has been in a hot and humid state condenses and dew condensation occurs. Or it may freeze. For this reason, when the operation of the system is stopped, scavenging is performed to discharge water from the reaction gas flow path of the fuel cell.

For example, the fuel cell stack and air discharge system flow control valves and the atomizer attached to the silencer are operated to atomize water remaining in the fuel cell stack and air discharge system, and the supply pipe and discharge pipe are Open and close the gate valve to bypass the humidifier, switch to the bypass supply pipe and bypass discharge pipe, drive the air compressor, and atomize the water remaining in the fuel cell stack, flow control valve and silencer The water remaining in the fuel cell stack, flow control valve and silencer is scavenged with dry air to prevent the water remaining in the fuel cell stack and air exhaust system from freezing. Has been proposed (see Patent Document 1).
Japanese Patent Laying-Open No. 2005-251576

  In the prior art, at the time of scavenging, the gate valves provided in the bypass supply pipe and the bypass discharge pipe are simply opened or closed, so that water may remain in the gate valve even after scavenging and may freeze. is there. That is, since the gate valve has irregularities due to the seat portion, the valve portion, etc., when the gate valve is simply opened or closed during scavenging, the water in the gate valve is not sufficiently removed, and water is not removed after scavenging. May remain. If the fuel cell is stopped while moisture remains in the valve, the remaining moisture may freeze when the temperature becomes below the freezing point and cannot be opened.

  In view of this, an object of the present invention is to prevent water from remaining after scavenging in a valve disposed in a flow path through which a reaction gas flows.

  In order to solve the above problems, a fuel cell system according to the present invention is arranged in a flow path through which a reaction gas flows when the fuel cell system is stopped in a fuel cell system configured to be capable of performing a scavenging process of the fuel cell. If the valve to be controlled is to be fully closed, the valve to be controlled is maintained at an intermediate opening between the fully open state and the fully closed state for a predetermined time and then fully closed. It is characterized by being in a state.

  According to such a configuration, when the valve is closed as a control target when the fuel cell system is stopped, the valve is not suddenly fully closed, but is temporarily maintained at an intermediate opening between the fully open state and the fully closed state. To the fully closed state. When the opening of the valve approaches a fully closed state to some extent, the flow rate of the reaction gas passing through the valve increases according to the opening of the valve and the flow rate of the reaction gas. For this reason, when the valve is maintained at the intermediate opening, the water physically remaining in the valve is removed by the reaction gas whose flow rate has been increased. Accordingly, since the fully closed state is obtained after the moisture is removed, it is possible to suppress a situation in which the residual moisture is frozen by the low temperature at the time of stop and prevents the next valve opening. In other words, even if the valve seat (seat part) or the valve body (valve part) in the valve is uneven, when the reaction gas for scavenging passes through the inside of the valve in the open state, the valve As the flow velocity in the vicinity of the valve seat (seat part) and valve body (valve part) increases, the water remaining in the valve can be reliably discharged to the outside, and water remains in the valve even after scavenging. Or the water in the valve can be prevented from freezing.

  Here, the “intermediate opening” is set so that the reaction gas flowing through the flow path in which the valve to be controlled is disposed has a predetermined flow rate at which moisture can be physically removed. That is, the flow rate of the reaction gas is substantially correlated with the water removal capability in the valve by the reaction gas.

  Here, the “intermediate opening” is not a specific opening but has a width (range) suitable as an intermediate opening. That is, when the opening of the valve approaches the fully closed state, the flow rate tends to increase because the reaction gas tends to flow through the reduced opening, but the opening area also decreases, so the flow resistance of the reaction gas also decreases. To rise. Therefore, when the opening degree is extremely close to the fully closed state, the flow rate of the reaction gas also decreases again. Therefore, a range suitable as the “intermediate opening” is a range of opening where a certain water removal capability is recognized.

  As described above, the “intermediate opening” has a range (range), and the effects of the present invention can be obtained if the opening of the valve is maintained within the range of the intermediate opening for a certain period of time. Therefore, in addition to performing stepwise control such as maintaining the valve opening at a certain intermediate opening for a certain period of time and then shifting to the fully closed state, the valve opening is kept within this intermediate opening over a certain period of time. In other words, the control may be changed, that is, dynamic processing may be performed in which the valve is continuously throttled in the range of the intermediate opening.

  For example, the predetermined flow rate of the reaction gas is set by calculation based on the gas flow rate of the reaction gas flowing through the flow path in which the valve to be controlled is disposed and the valve opening area at the intermediate opening. It has been found that the reaction gas flow rate is a function of the gas flow rate and the valve opening area.

  In the present invention, a temperature detection unit for detecting the temperature of the fuel cell system is provided, and the control unit opens the valve opening when the detected temperature of the fuel cell system is equal to or lower than a predetermined value. It is preferable to maintain the fully closed state after maintaining for a predetermined time each time.

  According to such a configuration, it is possible to prevent the valve from freezing by applying a gradual closing of the valve when the temperature of the fuel cell becomes a predetermined temperature or lower, for example, 0 ° C. or lower. The “temperature of the fuel cell system” is, for example, the outside air temperature, the internal temperature of the fuel cell, or the temperature of the flow path.

Here, for example, the predetermined time for maintaining the intermediate opening is set to the time from the start to the end of the scavenging process. The longer the predetermined time for maintaining the intermediate opening, the longer the moisture can be removed, but the longer it takes to remove the moisture. In this regard, according to this configuration, the scavenging treatment time is a treatment time for reducing the water content of the fuel cell, and is suitable for serving as a moisture removal for the valve. Further, during the scavenging process, it can be expected that the flow rate of the reaction gas is increased by driving the auxiliary equipment with a high driving amount, so that the water removal amount in the valve can also be increased.
The fuel cell system of the present invention includes a flow path for flowing a reaction gas supplied to or discharged from the fuel cell, a valve disposed in the flow path and controlling the flow of the reaction gas, A control unit that controls the opening of the valve, and the control unit sets an intermediate opening between the fully open state and the fully closed state when the valve is fully closed when the fuel cell is stopped. It is characterized by making a transition and then making a transition in stages from the intermediate opening to the fully closed state.

  According to the present invention, when the fuel cell system is stopped, the valve is maintained at the intermediate opening degree for a predetermined time and then fully closed, so that water remains inside the valve or water in the valve freezes at the time of stop. Can be prevented.

Next, a preferred embodiment of the present invention will be described.
FIG. 1 is a system configuration diagram of a fuel cell system to which the present invention is applied.
In FIG. 1, a fuel cell system 10 includes a fuel gas supply system 4 for supplying a fuel gas (hydrogen gas) to the fuel cell 20 and an oxidizing gas supply system for supplying an oxidizing gas (air) to the fuel cell 20. 7, a coolant supply system 3 for cooling the fuel cell 20, and a power system 9 for charging / discharging the generated power from the fuel cell 20.

  The fuel cell 20 is a membrane / electrode assembly in which an anode electrode 22 and a cathode electrode 23 are formed by screen printing or the like on both surfaces of a polymer electrolyte membrane 21 made of a proton conductive ion exchange membrane or the like formed of a fluorine-based resin or the like. 24. Both surfaces of the membrane / electrode assembly 24 are sandwiched by separators (not shown) having flow paths of fuel gas, oxidizing gas, and cooling water, and grooves are respectively formed between the separator and the anode electrode 22 and the cathode electrode 23. An anode gas channel 25 and a cathode gas channel 26 are formed. The anode electrode 22 is configured by providing a fuel electrode catalyst layer on a porous support layer, and the cathode electrode 23 is configured by providing an air electrode catalyst layer on the porous support layer. The catalyst layers of these electrodes are configured by adhering platinum particles, for example.

The anode electrode 22 undergoes an oxidation reaction of the following formula (1), and the cathode electrode 23 undergoes a reduction reaction of the following formula (2). In the fuel cell 20 as a whole, an electromotive reaction of the following formula (3) occurs.
H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  In FIG. 1, for convenience of explanation, the structure of a unit cell composed of a membrane / electrode assembly 24, an anode gas channel 25, and a cathode gas channel 26 is schematically shown. A plurality of unit cells connected in series.

  The coolant supply system 3 of the fuel cell system 10 includes a cooling path 31 for circulating the coolant, a temperature sensor 32 for detecting the temperature of the coolant drained from the fuel cell 20, and a radiator for radiating the heat of the coolant to the outside. (Heat exchanger) 33, a valve 34 for adjusting the amount of coolant flowing into the radiator 33, a coolant pump 35 for pressurizing and circulating the coolant, and a temperature for detecting the temperature of the coolant supplied to the fuel cell 20 A sensor 36 and the like are provided.

  The fuel gas supply system 4 of the fuel cell system 10 includes a fuel gas flow path 40 for supplying fuel gas (anode gas), for example, hydrogen gas, from the fuel gas supply device 42 to the anode gas channel 25, and an anode gas. A circulation passage (circulation passage) 51 for circulating the fuel off-gas exhausted from the channel 25 to the fuel gas passage 40 is piped, and a fuel gas circulation system is constituted by these gas passages.

  In the fuel gas passage 40, a shutoff valve (original valve) 43 that controls the outflow of fuel gas from the fuel gas supply device 42, a pressure sensor 44 that detects the pressure of the fuel gas, and a fuel gas pressure in the circulation path 51 are adjusted. A regulating valve 45 and a shutoff valve 46 for controlling the supply of fuel gas to the fuel cell 20 are installed.

  The fuel gas supply device 42 includes, for example, a high-pressure hydrogen tank, a hydrogen storage alloy, a reformer, and the like. The circulation channel 51 includes a shut-off valve 52 that controls the supply of fuel off-gas from the fuel cell 20 to the circulation channel 51, a gas-liquid separator 53 and a discharge valve 54 that removes water contained in the fuel off-gas, and an anode gas channel 25. The hydrogen pump (circulation pump) 55 that compresses the fuel off-gas that has undergone pressure loss and raises the pressure to an appropriate gas pressure when returning to the fuel gas passage 40 when passing through the fuel gas, and the fuel gas in the fuel gas passage 40 Is provided with a backflow prevention valve 56 for preventing the backflow of the airflow toward the circulation channel 51 side. By driving the hydrogen pump 55 with a motor, the fuel off-gas generated by driving the hydrogen pump 55 merges with the fuel gas supplied from the fuel gas supply device 42 in the fuel gas flow path 40 and then supplied to the fuel cell 20. Reused.

  The hydrogen pump 55 is provided with a rotation speed sensor 57 that detects the rotation speed of the hydrogen pump 55.

  Further, an exhaust passage 61 for branching the fuel off-gas exhausted from the fuel cell 20 to the outside of the vehicle via a diluter (for example, a hydrogen concentration reducing device) 62 is branched and connected to the circulation passage 51. Yes. A purge valve 63 is installed in the exhaust passage 61, and is configured to perform exhaust control of the fuel off gas. By opening and closing the purge valve 63, it is possible to repeatedly circulate in the fuel cell 20, discharge the fuel off-gas having increased impurity concentration to the outside, and introduce new fuel gas to prevent the cell voltage from decreasing. . It is also possible to remove the water accumulated in the gas flow path by causing a pulsation in the internal pressure of the circulation flow path 51.

  On the other hand, the oxidizing gas supply system 7 of the fuel cell system 10 exhausts an oxidizing gas passage 71 for supplying an oxidizing gas (cathode gas) to the cathode gas channel 26 and a cathode off-gas exhausted from the cathode gas channel 26. A cathode off-gas flow path 72 is provided for this purpose. An air cleaner 74 that takes in air from the atmosphere and an air compressor 75 that compresses the taken air and supplies the compressed air as an oxidant gas to the cathode gas channel 26 are set in the oxidizing gas channel 71. The air compressor 75 is provided with a rotation speed sensor 73 that detects the rotation speed of the air compressor 75. A humidifier 76 for exchanging humidity is provided between the oxidizing gas channel 71 and the cathode offgas channel 72. The cathode offgas passage 72 is provided with a pressure regulating valve 77 that adjusts the exhaust pressure of the cathode offgas passage 72, a gas-liquid separator 78 that removes moisture in the cathode offgas, and a muffler 79 that absorbs the exhaust sound of the cathode offgas. ing. The cathode off-gas discharged from the gas-liquid separator 78 is diverted. One of the cathode off-gas flows into the diluter 62 and is mixed and diluted with the fuel off-gas staying in the diluter 62. Is mixed with the gas diluted by the diluter 62 and discharged outside the vehicle.

  Further, the power system 9 of the fuel cell system 10 has a DC-DC converter 90 in which the output terminal of the battery 91 is connected to the primary side and the output terminal of the fuel cell 20 is connected to the secondary side, and a surplus as a secondary battery. A battery 91 that stores electric power, a battery computer 92 that monitors the charging state of the battery 91, an inverter 93 that supplies AC power to a load or driving vehicle 94 of the fuel cell 20, and various high voltages of the fuel cell system 10 An inverter 95 that supplies AC power to the auxiliary machine 96, a voltage sensor 97 that measures the output voltage of the fuel cell 20, and a current sensor 98 that measures the output current are connected.

  The DC-DC converter 90 converts the surplus power of the fuel cell 20 or the regenerative power generated by the braking operation to the vehicle travel motor 94 into a voltage and supplies it to the battery 91 for charging. Further, in order to compensate for the shortage of the generated power of the fuel cell 20 with respect to the required power of the vehicle travel motor 94, the DC-DC converter 90 converts the discharged power from the battery 91 to a secondary side after voltage conversion. .

  Inverters 93 and 95 convert the direct current into a three-phase alternating current and output the three-phase alternating current to vehicle running motor 94 and high voltage auxiliary machine 96, respectively. The vehicle travel motor 94 is provided with a rotational speed sensor 99 that detects the rotational speed of the motor 94. The wheel 94 is mechanically coupled to the motor 94 via a differential, and the rotational force of the motor 94 can be converted into the driving force of the vehicle.

  The voltage sensor 97 and the current sensor 98 are for measuring the AC impedance based on the phase and amplitude of the current with respect to the voltage in the AC signal superimposed on the power system. The AC impedance corresponds to the water content of the fuel cell 20.

  Further, the fuel cell system 10 is provided with a control unit 80 for controlling the power generation of the fuel cell 12. The control unit 80 is configured by a general-purpose computer including a CPU (Central Processing Unit), RAM, ROM, interface circuit, and the like, for example, and includes temperature sensors 32 and 36, a pressure sensor 44, and rotation speed sensors 57, 73, and 99. Sensor signals from the sensor, signals from the voltage sensor 97, current sensor 98, and ignition switch 82, and the motors are driven according to the battery operating state, for example, the electric power load, and the rotation of the hydrogen pump 55 and the air compressor 75. The number is adjusted, and further, opening / closing control of various valves (valves) or adjustment of the valve opening is performed.

  In addition, when the fuel cell system 10 is stopped, the control unit 80 controls the valve disposed in the flow path through which the reaction gas flows and sets the valve to be controlled to a fully closed state. Is maintained at an intermediate opening between the fully open state and the fully closed state for a predetermined time, and then the valve control process for making the fully closed state is performed.

  Specifically, when the scavenging condition is established, the control unit 80 sets each valve to an intermediate opening between the fully open state and the fully closed state before starting the scavenging process. It is throttled from a fully open state to a certain opening, and the certain opening is held for a certain time. During this time, the control unit 80 selects both the hydrogen pump 55 as the fuel gas pump that supplies the fuel gas to the fuel cell 20 and the air compressor 75 as the compressor that supplies the oxidizing gas to the fuel cell 20 as the scavenging drive device. Then, the selected air compressor 75 and the hydrogen pump 55 are scavenged, and after the scavenging of the flow path for the reaction gas and the fuel cell 20 is completed, control is performed to reduce the opening of each valve until it is fully closed. It is supposed to be. In particular, in the present embodiment, the control unit 80 is configured to perform the valve control process when the temperature detected by the temperature sensor 101 that detects the outside air temperature becomes 0 ° C. or less.

  Here, the flow path through which the reaction gas flows is a path through which the fuel gas or the oxidizing gas flows in this embodiment, and the oxidizing gas flow path 71, the cathode offgas flow path 72, the fuel gas flow path 40, the circulation. A flow path such as the flow path 51 and the exhaust flow path 61 corresponds.

  Further, in the present embodiment, the valves arranged in these flow paths correspond to the shutoff valve (original valve) 43, the fuel cell inlet shutoff valve 46, the purge valve 63, the fuel cell outlet shutoff valve 52, and the pressure regulating valve 74. .

  As shown in FIG. 2A, the valve called a shutoff valve is configured by an electromagnetic valve 110 whose energization is controlled by the control unit 80. The electromagnetic valve 110 includes a housing 112 formed in a substantially cylindrical shape. In the housing 112, a cylindrical bobbin 114, a coil 116 wound around the outer periphery of the bobbin 114, a magnet 120 fixed to the outer periphery of the rod 118 and slidably disposed in the bobbin 114, are coupled to the magnet 118. The rod 122 and the spring 122 wound around the upper end in the axial direction of the rod 118 are housed, and the valve body 124 is connected to the lower end in the axial direction of the rod 118. The valve body (valve part) 124 is disposed opposite to the valve port 128 and the valve seat (seat part) 130 of the flow path 126 through which the reaction gas flows.

  In the present embodiment, the electromagnetic valve 110 is controlled so that the opening degree is changed stepwise and the valve is closed. Specifically, when the valve is first opened, as shown in FIG. 2A, the solenoid valve 110 is fully opened with the valve 124 retracted from the valve seat 130 by energization of the coil 116.

  When the valve is closed, as shown in FIG. 2B, the electromagnetic valve 110 narrows the opening from the fully opened state to a certain intermediate opening, holds the certain opening for a certain period of time, and then closes the valve port 128 to close it. A two-stage operation that results in a valve state is performed.

  In the normal valve closing operation, when the electromagnetic valve 110 changes from the fully open state to the fully closed state by energizing the coil 116, the valve body 124 moves by the stroke S. On the other hand, in the stepwise valve control processing of this embodiment, when the intermediate opening degree is reached from the fully opened state, for example, as shown in FIG. 2B, the distance between the valve body 124 and the valve seat 130 is L. At this time, a two-stage operation is performed in which a certain degree of opening is maintained for a certain period of time, and then the valve body 124 is in close contact with the valve seat 130 to close the valve port 128. The distance L corresponding to the intermediate opening varies depending on the opening area of the valve and the flow rate of the reaction gas flowing through the flow path, but is a slight distance of, for example, 0.5 to 1.0 mm.

  The certain degree of opening of the electromagnetic valve 110 depends on the shape of the electromagnetic valve 110, and the flow rate at which water droplets in the flow path 126 can be blown away at a certain flow rate or higher, for example, the reaction gas flowing through the flow path 126 physically absorbs moisture. The flow rate is set to be equal to or higher than a predetermined removable flow rate. This predetermined flow velocity is obtained by calculation based on, for example, the gas flow rate of the reaction gas flowing through the flow path 126 and the opening area of the electromagnetic valve 110 at a certain opening.

FIG. 3 illustrates the relationship between the flow rate V of the reaction gas and the water removal amount Q.
FIG. 3 shows the relationship between the flow rate V of the reaction gas flowing through the flow path 126 and the water removal amount Q when the flow rate of the reaction gas is constant. In this relationship curve, when the flow rate of the reaction gas is equal to or higher than the threshold value Vth, the moisture present in the flow path 126 starts to physically move, and the moisture removal amount per unit time in this case is Q1. And

  FIG. 4 shows the relationship between the flow velocity V of the reaction gas flowing through the flow path 126 and the valve opening D of the electromagnetic valve 110. The flow velocity V tends to increase because the pressure of the reaction gas concentrates on a small opening area as the valve opening decreases, but the flow path resistance increases due to the narrow opening area. Therefore, as shown in FIG. 4, when the opening of the valve is reduced, the flow velocity of the reaction gas becomes Vth or more at a certain valve opening D2 or less, but when the opening is further reduced, there is a certain extreme point. The flow velocity starts to drop at the boundary, and when the bubble opening becomes D1 or less, the flow velocity becomes Vth or less. If the intermediate opening of the present invention is set within a range of valve openings D1 to D2 at which the flow velocity V is equal to or higher than the threshold value Vth, and controlled so as to be maintained within this intermediate opening range for a certain period of time, It can be seen that the valve can be dehydrated.

Next, the valve control processing by the control unit 80 will be described with reference to the flowchart of FIG.
As shown in FIG. 5, first, in step S <b> 1, the control unit 80 determines whether or not the temperature detected by the temperature sensor 101 is 0 ° C. or lower when starting the process associated with the system stop. . When the temperature is 0 ° C. or lower (YES), it is determined that the valve control process of the present invention is to be executed, and the control unit 80 proceeds to step S2 and selects the electromagnetic valve 110 to be controlled. The selected electromagnetic valve (shutoff valve / control valve) is a valve arranged in a flow path through which a reaction gas (oxidizing gas, fuel gas, exhaust gas) flows during the scavenging process.

  Next, the process proceeds to step 3, and the control unit 80 reduces the opening degree of the valve selected as the control target to a predetermined intermediate opening degree. Specifically, as the electromagnetic valve 110 to be controlled, the electromagnetic valve 110 disposed in the flow path 126 (the valve disposed in the flow path including the oxidizing gas flow path 71, the fuel gas flow path 40, and the exhaust flow path 61). After selecting (any), the control unit 80 controls energization to the coil 116 and controls until the opening degree of the selected electromagnetic valve 110 reaches a certain intermediate opening degree from the fully opened state. As described with reference to FIG. 4, the intermediate opening is set in a range in which the flow rate of the reaction gas is equal to or higher than the flow rate Vth at which moisture can be removed.

  On the other hand, when the outside air temperature is higher than 0 ° C. in step S1, the control unit 80 shifts to the scavenging process after step S4 on the assumption that the valve control process of the present invention is not applied.

  In step S4, the control unit 80 selects a scavenging auxiliary machine to prepare for the scavenging process. Specifically, the control unit 80 selects the air compressor 75 and / or the hydrogen pump 55 as a scavenging drive device (scavenging auxiliary device).

  Next, the process proceeds to step S5, and the control unit 80 starts the scavenging process. Specifically, the control unit 80 drives the selected air compressor 75 and / or the hydrogen pump 55 to perform a scavenging process for removing moisture remaining on the electrolyte membrane or the like of the fuel cell.

  Specifically, when the air compressor 75 and the hydrogen pump 55 are driven while the electromagnetic valve 110 is held at a constant opening, the oxidizing gas driven by the air compressor 75 passes through the oxidizing gas passage 71. In addition, the fuel gas accompanying the driving of the hydrogen pump 55 is supplied to the fuel cell 20 through the fuel gas passage 40. Gas containing water evaporated from the fuel cell 20 is discharged to the outside through the cathode off-gas flow path 72, the gas-liquid separator 78, the diluter 62, or the muffler 79, and through the purge valve 63 and the diluter 62. Then, scavenging of the fuel cell 20, the oxidizing gas passage 71, and the fuel gas passage 40 is performed.

  During the scavenging process, since the opening of the valve provided in the flow path through which the reaction gas flows is set to an intermediate opening in step S3, moisture is effectively removed in the scavenging process with a large flow rate. The

  Specifically, since the opening degree of the electromagnetic valve 110 disposed in the flow path 126 is maintained at a constant intermediate opening degree, the reaction gas (oxidizing gas, which passes through the vicinity of the valve body 124 and the valve seat 130 is passed. The flow rate of the fuel gas is increased in the region in the vicinity of the valve body 124 and the valve seat 130, and the discharge of water attached to the valve body 124, the valve seat 130, etc. is promoted. For this reason, the water droplets adhering to the valve body 124, the valve seat 130, and the like are discharged to the outside while being blown off by the reaction gas.

  In step S6, the control unit 80 determines whether or not the scavenging process has ended after a preset time has elapsed. If the scavenging process has not been completed (NO), the control unit 80 continues the scavenging process of step S5.

  On the other hand, when the scavenging process is completed (YES), the process proceeds to step S7, and the control unit 80 reduces the opening degree of the electromagnetic valve 110 held at a constant opening degree until the valve is closed. The control is executed, and the processing in this routine is terminated on condition that the electromagnetic valve 110 is fully closed. At this time, even when the outside air temperature is higher than 0 ° C. or when there are valves that are not selected in step S2, these valves are fully closed. This is to stop the process.

  As described above, according to the present embodiment, when the fuel cell 20 is stopped, the electromagnetic valve 110 is held at a certain opening degree for a certain period of time on the condition that the outside air temperature becomes 0 ° C. or lower, Since the scavenging is performed by supplying the fuel cell 20 through the flow path 126 and discharging the water in the fuel cell 20, and then the electromagnetic valve 110 is fully closed, a large amount of reaction gas in the scavenging process is obtained. Can be used to effectively remove moisture from the valve. In other words, even if there are uneven portions due to the valve body 124, the valve seat 130, etc. in the electromagnetic valve 110, when the reaction gas passes through the inside of the electromagnetic valve 110 in the valve open state, the valve body 124 and the valve Since the flow velocity in the vicinity of the seat 130 increases, the water remaining in the electromagnetic valve 110 can be reliably discharged to the outside, and water remains in the electromagnetic valve 110 even after scavenging, or the water in the electromagnetic valve 110 Can be prevented from freezing.

  Further, in the present embodiment, a certain opening degree related to the electromagnetic valve 110 is set in correspondence with a flow rate at which the reaction gas flowing through the flow path 126 is equal to or higher than a predetermined flow rate Vth at which moisture can be physically removed. As a result, moisture adhering to the flow path 126 and the electromagnetic valve 110 can be reliably removed. On the other hand, since the predetermined flow velocity Vth is obtained from the gas flow rate of the reaction gas flowing through the flow path 126 and the opening area of the valve at a constant opening, by maintaining the electromagnetic valve 110 at a constant opening, The flow rate of the reaction gas passing through the electromagnetic valve 110 can be set to a predetermined flow rate Vth at which water adhering to the flow path 126 and the electromagnetic valve 110 can be physically removed.

  In the present embodiment, the electromagnetic valve 110 that is affected by the water generated in the fuel cell 20 is scavenged when the outside air temperature becomes 0 ° C. or lower. Even when the temperature is 0 ° C. or higher, for example, scavenging of the electromagnetic valve 110 or the like can be performed at predetermined time intervals.

  In the above-described embodiment, the scavenging process period is set to coincide with the intermediate opening degree maintaining time of the valve. However, the present invention is not limited to this. That is, when the valve is closed, the stepwise valve closing process of the present invention can be performed regardless of the scavenging process.

  Moreover, in the said embodiment, although the opening degree of the valve was once set to a certain intermediate opening degree and waited for progress of fixed time, you may change the opening degree of a valve continuously. That is, moisture is removed if there is an opening of the valve in an intermediate opening range where the flow rate of the reaction gas in the valve is equal to or higher than Vth. For example, for a certain period of time while a constant reaction gas flow rate is maintained. It is possible to remove moisture from the valve even if the valve is controlled to be throttled slowly by applying.

  In addition to the electromagnetic valve 110, a stepping motor type valve that opens and closes the flow path 126 by driving a stepping motor can be used as the valve to be controlled. When a stepping motor type valve is used, the valve body moves each time the stepping motor is driven in response to a pulse from the control unit 80. Therefore, the position control of the valve body and the valve position are less than when the electromagnetic valve 110 is used. Control to keep the opening at a constant opening becomes easy.

1 is a system configuration diagram of a fuel cell system showing an embodiment of the present invention. It is sectional drawing when an electromagnetic valve is made into a full open state. It is sectional drawing when an electromagnetic valve is hold | maintained at a fixed opening degree. It is a characteristic view which shows the relationship between the flow rate and moisture removal amount in an electromagnetic valve. It is a characteristic view which shows the relationship between the valve opening degree and flow velocity in an electromagnetic valve. It is a flowchart for demonstrating the scavenging process in a fuel cell system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 20 Fuel cell, 40 Fuel gas flow path, 55 Hydrogen pump, 71 Oxidation gas flow path, 75 Air compressor, 80 Control part, 101 Temperature sensor, 110 Electromagnetic valve, 124 Valve body, 126 Flow path

Claims (6)

In a fuel cell system configured to perform scavenging processing of a fuel cell,
When the fuel cell system is stopped, when a valve disposed in a flow path through which a reaction gas flows is set as a control target, and the control target valve is fully closed,
A fuel cell system, wherein the valve to be controlled is maintained in an intermediate opening between a fully open state and a fully closed state for a predetermined time and then is fully closed. The intermediate opening is set so that the reaction gas flowing through the flow path in which the valve to be controlled is disposed has a predetermined flow rate at which moisture can be physically removed.
The fuel cell system according to claim 1. The predetermined flow rate is
It is set by calculation based on the gas flow rate of the reaction gas flowing through the flow path in which the valve to be controlled is disposed and the opening area of the valve at the intermediate opening,
The fuel cell system according to claim 2. A temperature detector for detecting the temperature of the fuel cell system;
When the detected temperature of the fuel cell system is a predetermined value or less,
The valve opening is maintained at the intermediate opening for a predetermined time before being fully closed.
The fuel cell system according to any one of claims 1 to 3.   The fuel cell system according to claim 1, wherein the predetermined time for maintaining the intermediate opening is set to a time from the start to the end of the scavenging process. A fuel cell;
A flow path for flowing a reaction gas supplied to or discharged from the fuel cell;
A valve disposed in the flow path for controlling the flow of the reaction gas;
A control unit for controlling the opening of the valve,
When the valve is fully closed when the fuel cell is stopped, the controller shifts to an intermediate opening between the fully open state and the fully closed state, and then shifts from the intermediate opening to the fully closed state. , The control unit to shift in stages,
A fuel cell system comprising:

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