JP5276329B2 - FUEL CELL SYSTEM AND METHOD FOR OPERATING FUEL CELL SYSTEM - Google Patents

Description

  The present invention relates to a fuel cell system that performs control for scavenging a fuel cell after power generation is stopped, and a method for operating the fuel cell system.

In the fuel cell system, when the fuel cell system is used in a low temperature environment such as a cold region or winter, there is a problem that water generated during power generation freezes after power generation is stopped. Therefore, in this type of fuel cell system, it is necessary to perform scavenging control in which scavenging gas is introduced into the fuel cell and generation water in the fuel cell is discharged after power generation is stopped. For example, in order to discharge as much water remaining in the fuel cell as possible, a technique has been proposed in which scavenging is performed when the temperature of the fuel cell falls below a predetermined temperature threshold (see Patent Document 1).
JP 2007-35389 (paragraph 0051)

  However, since the water pump of the fuel cell and the auxiliary equipment around the fuel cell is stopped while the system is stopped, the temperature varies due to the influence of the installation environment, thermal mass, and the like. In such a variation system, when the temperature sensor is installed at a relatively low temperature, if the detected value of the temperature sensor is less than or equal to the scavenging execution threshold, there is a portion that is not less than or equal to the scavenging execution threshold. Nevertheless, scavenging is performed. That is, the higher the temperature of the fuel cell membrane (MEA; membrane electrode assembly), the higher the water content of the generated water. is there. In addition, there is a problem that the portion that has been scavenged in a state where the temperature is high causes dew condensation again due to a decrease in temperature while power generation is stopped after scavenging.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a fuel cell system capable of performing scavenging efficiently and a method for operating the fuel cell system.

The invention according to claim 1 is a fuel cell that generates electric power by being supplied with a reaction gas, a refrigerant circulation means that circulates a refrigerant that circulates inside the fuel cell, and a fuel cell temperature detection that detects the temperature of the fuel cell. Means, scavenging means for introducing scavenging gas into the fuel cell to perform scavenging control, and a first predetermined threshold value that is expected to cause the temperature of the fuel cell to fall below freezing point during power generation stoppage of the fuel cell; A scavenging execution determination means for performing scavenging execution determination when the fuel cell temperature is reached. The fuel cell system has a plurality of the fuel cell temperature detection means, and the fuel cell temperature detection means detects any one of the fuel cell temperature detection means . It said refrigerant circulation means when the temperature falls below the first predetermined threshold value is driven for a predetermined time, is detected by any of the fuel cell temperature detecting means is also in the subsequent drive completion state And executes the scavenging when the temperature of the fuel cell is a second predetermined threshold value below the first predetermined threshold value.
According to a fifth aspect of the present invention, there is provided a fuel cell that generates a power by supplying a reactive gas, a refrigerant circulation means that circulates a refrigerant that circulates inside the fuel cell, and a plurality of temperatures that detect the temperature of the fuel cell . A fuel cell temperature detecting means; and a scavenging means for introducing a scavenging gas into the fuel cell to perform scavenging control, and the temperature of the fuel cell is expected to be below freezing point while the power generation of the fuel cell is stopped. In the operation method of the fuel cell system that performs scavenging execution determination when the fuel cell temperature is below a first predetermined threshold, the temperature of the fuel cell detected by any one of the fuel cell temperature detecting means is below the first predetermined threshold. a first step of the refrigerant circulation means when it becomes driven a predetermined time, which is detected by any of the fuel cell temperature detecting means is also in driving completion state after the first step the Characterized in that it comprises a second step of performing scavenging and in case the temperature of the charge the battery is the second predetermined threshold value below the first predetermined threshold value.

According to the first and fifth aspects of the invention, even in the case of a fuel cell (or fuel cell system) having a variation in temperature, when the temperature falls below a predetermined temperature (scavenging temperature threshold), the refrigerant Since the circulation means is driven again, the temperature of the fuel cell can be made uniform. That is, when scavenging is performed, the temperature of the fuel cell is lowered to a uniform state equal to or lower than a predetermined temperature, so that the effects shown in the following (1) and (2) can be obtained. That is, (1) since the MEA temperature is low, the content of produced water in the MEA is reduced, so that the amount discharged as droplets during scavenging can be increased, and (2) the temperature of the fuel cell is low Therefore, the degree of condensation during power generation stop after scavenging can be reduced.
Further, in the conventional fuel cell system, scavenging is performed immediately when the temperature around the fuel cell is low, and thus scavenging may be performed wastefully. Since scavenging is executed after the temperature is lowered as a whole, there is an effect in reducing energy consumption by reducing the scavenging frequency.
According to the first and fifth aspects of the present invention, the temperature of any one of the fuel cells is detected to be equal to or lower than a predetermined threshold even after the refrigerant circulating means is driven, detected by a plurality of fuel cell temperature detecting means (temperature sensors) Since scavenging is executed in such a case, it is possible to prevent moisture from being frozen by the MEA or the like even if such control that delays scavenging is performed.

The invention according to claim 2 and claim 6 is characterized in that the first predetermined threshold and the second predetermined threshold are the same temperature .

According to a third aspect of the present invention, the driving time of the refrigerant circulating means that is driven when the temperature of the fuel cell detected by the fuel cell temperature detecting means falls below a predetermined threshold is lengthened every time driving is repeated. It is characterized by doing.
In the invention according to claim 7, the driving time of the refrigerant circulating means that is driven when the temperature of the fuel cell detected by the fuel cell temperature detecting means becomes a predetermined threshold value or less is repeated each time driving is repeated. The method includes a step of lengthening.

  According to the inventions according to claim 3 and claim 7, by increasing the driving time of the refrigerant circulation means even in a situation where the temperature difference between the refrigerant of the fuel cell temperature detection means and the refrigerant of the other parts is small, The scavenging can be delayed until the temperature of the fuel cell itself becomes lower.

The invention according to claim 4 comprises: a power storage device that supplies power to the scavenging means and the refrigerant circulation means; and a remaining capacity detection means that detects a remaining capacity of the power storage device, wherein the remaining capacity of the power storage device is When it is predicted that the electric power is less than or equal to the electric power required for the scavenging by the scavenging means, the scavenging is performed even when the temperature of the fuel cell does not become the predetermined threshold or less in the driving completion state.
Further, the invention according to claim 8 is characterized in that when the remaining capacity of the power storage device that supplies power to the scavenging means and the refrigerant circulation means is predicted to be less than or equal to the power required for scavenging by the scavenging means, the drive A scavenging step is included even when the temperature of the fuel cell does not fall below a predetermined threshold in the completed state.

  According to the inventions according to claim 4 and claim 8, since it is possible to prevent the remaining capacity of the power storage device from being lowered so that scavenging cannot be performed and it is possible to perform scavenging reliably, it is possible to ensure low-temperature startability. Can be secured.

  ADVANTAGE OF THE INVENTION According to this invention, the operating method of the fuel cell system which can perform efficient scavenging, and a fuel cell system can be provided.

  FIG. 1 is an overall configuration diagram showing the fuel cell system of the present embodiment, FIG. 2 is a flowchart showing scavenging control in the fuel cell system of the present embodiment, and FIG. 3 shows water pump control and scavenging judgment according to temperature changes. FIG. 4A is a time chart, FIG. 4A is a graph showing the relationship between the temperature in the fuel cell and the MEA product water content, and FIG. 4B is the temperature of the fuel cell during scavenging and the dew condensation in the fuel cell after power generation is stopped. It is a graph which shows the relationship with generation amount. In the following, a case where the fuel cell system 1 of the present embodiment is mounted on a fuel cell vehicle (vehicle) will be described as an example. However, the present invention is not limited to a vehicle, and a mobile body such as a ship or an aircraft, Or, it can be applied to anything such as a stationary type such as a household power source.

  As shown in FIG. 1, the fuel cell system 1 of the present embodiment includes a fuel cell 10, an anode system 20, a cathode system 30, a cooling system 40, a high voltage system 50, a control system 60, and the like.

  In the fuel cell 10, for example, an electrolyte membrane made of a solid polymer is sandwiched between an anode and a cathode to form a membrane electrode assembly (MEA), and the membrane electrode assembly is sandwiched between conductive separators. A plurality of unit cells are stacked in the thickness direction. The separator has a channel through which hydrogen (reactive gas, fuel gas) flows on the surface facing the anode, and a channel through which air (reactive gas, oxidant gas) flows on the surface facing the cathode. Is formed.

  The anode system 20 includes a hydrogen tank 21, an ejector 22, a purge valve 23, a drain valve 24, a discharge valve 25, pipes a1 to a7, and the like.

  The hydrogen tank 21 is a container that accumulates high-purity hydrogen at a very high pressure, and includes an electromagnetically operated shut-off valve (not shown).

  The ejector 22 is connected to the hydrogen tank 21 through the pipe a1, returns unreacted hydrogen discharged from the anode outlet of the fuel cell 10 through the pipe a3 to the ejector 22 through the pipe a4, and the pipe. This is a type of vacuum pump that is recirculated back to the anode inlet via a2.

  The purge valve 23 is an electromagnetically actuated on / off valve having a solenoid, and is provided in a pipe a5 connected to the pipe a4. Further, the purge valve 23 is appropriately opened by an ECU (Electric Control Unit) 61 described later, and has a function of discharging impurities (nitrogen and generated water) accumulated in the anode system 20 to the outside.

  The drain valve 24 is an electromagnetically actuated on / off valve having a solenoid, and is provided in a pipe a6 connected to the pipe a4. Further, the drain valve 24 has a function of being appropriately opened by an ECU (Electric Control Unit) 61, which will be described later, and discharging generated water accumulated in a storage unit (not shown) to the outside.

  The discharge valve 25 is an electromagnetically actuated on / off valve having a solenoid, and is provided in a pipe a7 connected to the pipe a4. Further, the discharge valve 25 has a function of discharging scavenging gas introduced into the anode system 20 to the outside, which is opened during anode scavenging by an ECU (Electric Control Unit) 61 described later.

  Further, the drain valve 24 is formed with a smaller flow path diameter than the purge valve 23, and the purge valve 23 is formed with a smaller flow path diameter than the discharge valve 25. That is, a small flow rate gas flows through the drain valve 24, a medium flow rate gas flows through the purge valve 23, and a large flow rate gas flows through the discharge valve 25.

  Although not shown, the anode system 20 is provided with a regulator or the like for decompressing high-pressure hydrogen supplied from the hydrogen tank 21.

  The cathode system 30 includes an air compressor 31, a back pressure control valve 32, pipes c1 and c2, and the like.

  The air compressor 31 is composed of, for example, a supercharger driven by a motor, and has a function of compressing air taken in from the outside and supplying the compressed air to the cathode of the fuel cell 10 via the pipe c1.

  The back pressure control valve 32 is composed of a valve whose opening degree can be adjusted, such as a butterfly valve, and has a function of appropriately adjusting the air pressure supplied to the cathode of the fuel cell 10. The back pressure control valve 32 is connected to the cathode outlet of the fuel cell 10 via a pipe c2.

  Although not shown, the cathode system 30 is provided with a humidifier for humidifying the air supplied from the air compressor 31 and supplying it to the cathode of the fuel cell 10. Further, the downstream of the purge valve 23, the drain valve 24, the discharge valve 25 and the downstream of the back pressure control valve 32 are connected to a diluter (not shown), and hydrogen discharged from the anode system 20 is discharged from the cathode system 30. It is diluted with the discharged air and discharged outside (outside the vehicle).

  The cooling system 40 has a function of appropriately cooling the fuel cell 10 during power generation, and includes a radiator 41, a water pump 42, pipes d1 to d3, and the like.

  The radiator 41 has a function of radiating heat to the refrigerant warmed by the fuel cell 10, and is connected to the refrigerant inlet of the fuel cell 10 via a pipe d1.

  The water pump 42 has a function of circulating the refrigerant, and the rotational speed of the motor is controlled by an ECU 61 which will be described later. Further, the water pump 42 is connected to the refrigerant outlet of the fuel cell 10 through the pipe d2 and is connected to the inlet of the radiator 41 through the pipe d3.

  Further, the fuel cell system 1 of the present embodiment includes an air introduction pipe 55 and an air introduction valve 56 for introducing scavenging air (scavenging gas) into the anode system 20. The air introduction pipe 55 is a flow path for introducing air as a scavenging gas to the anode side, and one end on the upstream side is connected to the pipe c1 and the other end on the downstream side is connected to the pipe a2. The air introduction valve 56 is, for example, an electromagnetically actuated ON / OFF valve, is provided near the anode in the middle of the air introduction pipe 55, and is controlled to be opened and closed by an ECU 61 described later. The upstream of the air introduction pipe 55 is provided on the upstream side of a humidifier (not shown) provided in the pipe c1.

  The high voltage system 50 includes a power storage device 51, a remaining capacity sensor 52, a power distributor 53, and the like.

  The power storage device 51 is composed of, for example, lithium ions, nickel metal hydride, a capacitor, and the like, and can be charged and discharged while receiving power generated from the fuel cell 10.

  The remaining capacity sensor 52 is composed of, for example, an ammeter and a voltmeter, and is a sensor that detects the remaining capacity (charge amount) accumulated in the power storage device 51. Note that the remaining capacity of the power storage device 51 is expressed by, for example, SOC (State Of Charge), but the calculation of the SOC is performed by the ECU 61 described later.

  The power distributor 53 includes a DC / DC converter and the like, and has a function of controlling the generated power of the fuel cell 10 under the control of the ECU 61 described later. The auxiliary machines include the air compressor 31, the water pump 42, a travel motor (not shown), and the like.

  Although not shown, contactors for electrically connecting and disconnecting are provided between the fuel cell 10 and the power distributor 53 and between the power storage device 51 and the power distributor 53, respectively. In addition, the power storage device 51 and the air compressor 31 are connected via, for example, an inverter (not shown) that converts them into three phases, and the power storage device 51 and the water pump 42 include, for example, a DC / DC converter ( (Not shown).

  The control system 60 includes an ECU 61, temperature sensors 62, 63, 64, and the like. These temperature sensors 62 to 64 are sensors that detect the temperature of the fuel cell 10. For example, the temperature sensor 62 is provided at the outlet of the refrigerant circulating in the fuel cell 10, the temperature sensor 63 is provided at the anode outlet of the fuel cell 10, and the temperature sensor 64 is provided at the cathode outlet of the fuel cell 10. It has been.

  The ECU 61 includes a CPU (Central Processing Unit), a RAM, a ROM in which programs are recorded, and the like, and includes scavenging execution determination means. Further, the ECU 61 appropriately opens and closes the purge valve 23, the drain valve 24, the discharge valve 25, and the air introduction valve 56, adjusts the opening degree of the back pressure control valve 32, and rotates the motor speed of the air compressor 31 and the water pump 42. To control. In addition, the scavenging execution determination unit has a function of performing scavenging when it is determined that the temperature of the fuel cell 10 is equal to or lower than the scavenging threshold T0 (predetermined threshold).

  Next, the operation of the fuel cell system 1 of the present embodiment will be described with reference to FIG. During the operation of the fuel cell system 1, the discharge valve 25 and the air introduction valve 56 are closed, and a shut-off valve (not shown) provided in the hydrogen tank 21 is opened to supply hydrogen to the anode of the fuel cell 10. The air compressor 31 is driven and air is supplied to the cathode of the fuel cell 10 to generate power. The power generated by the fuel cell 10 is supplied to an air compressor 31, a water pump 42, a travel motor (not shown), and the like. In operation, the water pump 42 is driven to circulate the refrigerant in the fuel cell 10 so that the fuel cell 10 is appropriately cooled.

  As shown in FIG. 2, when an ignition switch (not shown) is turned off by the driver, the contactor (not shown) on the fuel cell 10 side is shut off (OFF), the shutoff valve of the hydrogen tank 21 is closed, and the air compressor The drive of 31 is stopped. Thereby, the power generation of the fuel cell 10 is stopped.

  In step S100, the ECU 61 starts a timer included therein. The timer operates even when power is supplied from a low-voltage battery provided separately from the power storage device 51 and power generation is stopped.

  In step S110, the ECU 61 determines whether or not a predetermined time has elapsed since the start of measurement by the timer. If it is determined that the predetermined time has not elapsed (No), the ECU 61 repeats step S110 and the predetermined time has elapsed. If it is determined that it has been (Yes), the process proceeds to step S120. The predetermined time here is determined in advance by experiments or the like.

  In step S120, when the temperature of the fuel cell 10 obtained from the temperature sensor 62 is T1, the temperature of the fuel cell 10 obtained from the temperature sensor 63 is T2, and the temperature of the fuel cell 10 obtained from the temperature sensor 64 is T3. It is determined whether any of the temperatures T1, T2, and T3 is equal to or less than the scavenging threshold (T0). In step S120, when the ECU 61 determines that all the temperatures T1, T2, T3 exceed the scavenging threshold T0 (No), the ECU 61 resets the timer in step S130. And it progresses to step S100 and ECU61 starts a timer again. In step S120, if the ECU 61 determines that any of the temperatures T1, T2, and T3 is equal to or less than the scavenging threshold value T0 (Yes), the ECU 61 proceeds to step S140.

  Although not shown, in step S120, if it is predicted that the temperatures T1 to T3 will not fall below the freezing point, the ECU 61 controls to end the process shown in FIG. The case where the temperature is not expected to be below freezing is, for example, the case where the temperature being measured is rising.

  In step S140, the ECU 61 determines whether or not the remaining capacity (SOC; State Of Charge) of the power storage device 51 is greater than or equal to a predetermined value based on the detection value obtained from the remaining capacity sensor 52. The predetermined value is a value corresponding to the power required for scavenging by the scavenging means (such as the air compressor 31), and is determined in advance based on experiments or the like.

  In step S140, if the ECU 61 determines that the SOC is equal to or greater than the predetermined value (Yes), that is, if it is determined that the electric power necessary to perform scavenging remains, the ECU 61 proceeds to step S150, and the water pump (W / P) 42 is driven for a predetermined time s2.

  In step S150, a contactor (not shown) on the power storage device 51 side is connected, power is supplied from the power storage device 51 to the water pump 42, and the water pump 42 is driven. By driving the water pump 42, the partially hot and cold places of the refrigerant are agitated, and the temperature inside the fuel cell 10 can be made uniform. Here, the predetermined time s2 is obtained in advance by experiments or the like.

  In step S160, the ECU 61 drives the water pump 42 for a predetermined time s2, and then again determines whether any of the temperatures T1, T2, and T3 is equal to or lower than the scavenging threshold (T0). In step S160, if the ECU 61 determines that all of the temperatures T1 to T3 exceed the scavenging threshold (T0) (No), the ECU 61 proceeds to step S170, resets the timer in the ECU 61, and proceeds to step S100. Return to. In step S160, when the ECU 61 determines that any of the temperatures T1 to T3 is equal to or less than the scavenging threshold (T0) (Yes), the temperature of the fuel cell 10 is made uniform overall, and Then, it is determined that the temperature of the fuel cell 10 has sufficiently decreased (condensation has sufficiently progressed), and the process proceeds to step S180 to perform scavenging.

  In the scavenging in step S180, for example, the ECU 61 opens the back pressure control valve 32 in a state where the air introduction valve 56 is closed, and the air compressor 31 is driven by the electric power of the power storage device 51. As a result, the air (scavenging gas) introduced from the air compressor 31 passes through the pipe c1, the cathode of the fuel cell 10, and the pipe c2, and water remaining at the cathode in the fuel cell 10 is pushed out and discharged to the outside. Is done.

  Subsequently, the air compressor 31 is driven by the ECU 61 in a state where the air introduction valve 56 and the discharge valve 25 are opened. Thereby, the air (scavenging gas) from the air compressor 31 passes through the pipe c1, the air introduction pipe 55, the pipe a2, the anode of the fuel cell 10, the pipes a3 and a7, and remains in the anode in the fuel cell 10. Water is pushed out and discharged to the outside.

  The scavenging procedure is not limited to scavenging the cathode first, and then scavenging the anode. The scavenging procedure may be performed by scavenging the cathode and the anode at the same time. Thereafter, the cathode may be scavenged. Further, the method is not limited to the method of opening the discharge valve 25 and scavenging the anode. For example, the purge valve 23 and the drain valve 24 may be opened together with the discharge valve 25 to perform scavenging.

  On the other hand, in step S140, when it is predicted that the SOC is not equal to or higher than the predetermined value and lower than the power required for scavenging by the scavenging means (No), the process proceeds to step S180. That is, scavenging is performed even when any of the temperatures T1 to T3 does not fall below the scavenging threshold (T0). In addition, the operation of the timer is stopped after scavenging.

  Further description will be made with reference to the time chart of FIG. That is, when the ignition switch is turned off (IG-OFF) (time t0), the timer is started (S100), and the temperature T1 to T3 of the fuel cell 10 is reached every predetermined time s1 (S110, Yes). It is judged whether any of these is below the scavenging execution threshold T0 (S120). In this case, for example, when the temperature T1 becomes equal to or less than the scavenging threshold value T0 (S120, Yes, time t1), the water pump 42 is driven for s2 for a predetermined time to stir the refrigerant (S150). After the water pump (W / P) 42 is driven for a predetermined time s2, the temperature T1 exceeds the scavenging threshold T0 (S160, No), the timer is reset (S170), and the timer is started again (S100, Time t2). Incidentally, at times t1 to t2, the temperature at the location where the temperature of the fuel cell 10 is measured is low and the other locations are high, so that the temperature of the coolant is increased by driving the water pump 42 and stirring the coolant. To rise.

  Further, every time the predetermined time s1 elapses (S110, Yes), it is determined whether any of the temperatures T1 to T3 of the fuel cell 10 is equal to or lower than the scavenging threshold value T0 (S120). In this case, since the temperature T1 is equal to or lower than the scavenging threshold T0 (S120, Yes, time t3), the water pump 42 is driven for s2 for a predetermined time to stir the refrigerant (S150). After the water pump 42 is driven for a predetermined time, the temperature T1 is not lower than the scavenging threshold value T0 again (S160, No), the timer is reset (S170), and the timer is started again (S100, time t4).

  When the temperature T1 again becomes the scavenging execution threshold T0 or less (S120, Yes, time t5), the water pump 42 is driven for s2 for a predetermined time to stir the refrigerant (S150). In this case, since the temperature T1 after driving for the predetermined time s2 is equal to or less than the scavenging threshold value T0 (S160, Yes), it is determined that the temperature of the refrigerant has become uniform, and scavenging is performed (S180).

  As described above, according to this embodiment, even in the fuel cell 10 (or the fuel cell system 1) having a variation in temperature, any one of the temperatures T1 to T3 is equal to or less than the scavenging threshold (predetermined temperature). At this time, the water pump 42 is driven (re-driven), and the temperature of the fuel cell 10 (or the fuel cell system 1) can be made uniform by stirring the refrigerant. In other words, when scavenging is performed, the temperature of the fuel cell 10 becomes uniform and falls below a predetermined threshold (scavenging threshold). For this reason, the temperature of the MEA is low and the content rate of the produced water in the MEA is low (see FIG. 4A), so that the water in the MEA is discharged as sufficient droplets during scavenging. become.

  Moreover, since scavenging is performed at a low temperature equal to or lower than a predetermined threshold (scavenging execution threshold) (see FIG. 4B), the degree of condensation during power generation stoppage can be reduced. That is, even if the temperature detection position of the fuel cell 10 is located in a relatively low temperature portion as in the prior art and the temperature of a part of the fuel cell 10 falls below a predetermined threshold value, As a result, the temperature rises again during the subsequent power generation stop and the degree of condensation is increased. However, in the present embodiment, scavenging is performed with the temperature of the fuel cell 10 being lowered as a whole, so that the temperature does not rise again during power generation stop after scavenging. It becomes possible to reduce the degree of.

  As described above, scavenging is performed after the temperature of the fuel cell 10 is lowered as a whole, so that the number of scavenging times can be reduced and energy consumption can be reduced.

  Further, according to the present embodiment, when the temperatures T1 to T3 are detected by the plurality of temperature sensors 62 to 64, and any one of the temperatures remains below the predetermined threshold (scavenging threshold) after the water pump 42 is driven. Since the scavenging is executed, the moisture can be prevented from being frozen by the MEA or the like even if the control for delaying the scavenging as in the present embodiment is performed. That is, if scavenging is performed when the temperature of all the temperature sensors 62 to 64 is equal to or lower than the predetermined temperature (scavenging threshold), the fuel cell 10 may reach the freezing temperature, and the MEA or the like may freeze. As described above, scavenging is performed when any of the temperatures T1 to T3 is equal to or lower than a predetermined temperature (scavenging threshold), so that the MEA and the like can be prevented from freezing.

  In addition, according to the present embodiment, by detecting the SOC (remaining capacity) of the power storage device 51, it is possible to prevent the SOC from being lowered to the extent that scavenging cannot be performed, and it is possible to perform scavenging reliably. Become. Therefore, it is possible to reliably ensure the low temperature startability at the next start.

  FIG. 5 is a flowchart showing another scavenging control in the present embodiment, and FIG. 6 is a time chart showing water pump control and scavenging judgment according to a temperature change in another scavenging control. The embodiment shown in FIGS. 5 and 6 differs from the above-described embodiment only in a part of the scavenging control, and the system diagram is the same as FIG. Further, the same processing as that in FIG. 2 is denoted by the same step symbol and description thereof is omitted.

  As shown in FIG. 5, the ECU 61 determines in step S120 that any one of the temperatures T1 to T3 of the fuel cell 10 is equal to or less than the scavenging threshold T0 (Yes), and in step S140, the power storage device 51 If it is determined that the SOC is equal to or higher than the predetermined value (Yes), the water pump 42 is driven for a predetermined time s2 to stir the refrigerant (S150).

  After driving for the predetermined time s2, in step S155, the ECU 61 adds the time α to the predetermined time s2, and sets a new predetermined time s2 as the predetermined time for driving the water pump 42. Note that the time α is a positive number, and is set so that the predetermined time in step S150 becomes longer each time the water pump 42 is driven.

  As shown in FIG. 6, when any temperature T1 becomes equal to or lower than the scavenging threshold value T0 (S120, Yes, time t1), the water pump 42 is driven for a predetermined time s2 to stir the refrigerant (S150). . After the water pump (W / P) 42 is driven for a predetermined time s2, the temperature T1 again exceeds the scavenging threshold value T0 (S160, No), the timer is reset (S170), and the timer is started again (S100, Time t2).

  When the temperature T1 becomes equal to or lower than the scavenging threshold value T0 again (S120, Yes, time t3), the water pump 42 is driven for a predetermined time (s2 + α) to stir the refrigerant (S150). Then, after driving the water pump 42 for a predetermined time (s2 + α), when the temperature T1 again exceeds the scavenging threshold T0 (S160, No), the timer is reset (S170), and the timer is started again (S100, time t4). ).

  When the temperature T1 again becomes the scavenging execution threshold value T0 or less (S120, Yes, time t5), the water pump 42 is driven for a predetermined time (s2 + 2α) to stir the refrigerant (S150). Since the temperature T1 after driving for a predetermined time (s2 + 2α) is equal to or less than the scavenging threshold value T0 (S160, Yes), it is determined that the temperature of the refrigerant has become uniform, and scavenging is performed (S180).

  Thus, according to the embodiment shown in FIG. 5, in addition to the effects of the above-described embodiment, even in a situation where the temperature difference between the refrigerant of the temperature sensor 62 and the refrigerant of other parts is small, Since the driving time of the water pump 42 is lengthened, it is possible to make the temperature of the refrigerant uniform, and it is possible to delay scavenging until the fuel cell 10 itself has a lower temperature.

  In the present embodiment, the temperature of the fuel cell 10 has been described by taking the temperature T1 of the refrigerant, the temperature T2 on the outlet side of the anode, and the temperature T3 on the outlet side of the cathode as examples. However, the present invention is not limited to this. Alternatively, the gas temperature at another position (anode side, cathode side) may be used, or the temperature of the auxiliary device may be used instead.

  In the present embodiment, the drive start temperature (S120) of the water pump 42 and the scavenging temperature (S160) have been described by taking the same temperature (5 ° C.) as an example. For example, the water pump 42 is driven. The starting temperature may be 10 ° C., the scavenging temperature may be 5 ° C., and different temperatures may be set.

  In the present embodiment, the case where the three temperature sensors 62 to 64 are applied has been described as an example. However, the scavenging execution timing is determined by applying a single temperature sensor (for example, the refrigerant temperature T1). May be.

It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is a flowchart which shows the scavenging control in the fuel cell system of this embodiment. It is a time chart which shows water pump control and scavenging judgment according to a temperature change. (A) is a graph showing the relationship between the temperature in the fuel cell and the MEA product water content, and (b) is the relationship between the temperature of the fuel cell during scavenging and the amount of condensed water generated in the fuel cell after power generation is stopped. It is a graph which shows. It is a flowchart which shows another scavenging control in this embodiment. It is a time chart which shows control of the water pump according to the temperature change in another scavenging control, and scavenging judgment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 31 Air compressor (scavenging means)
42 Water pump (refrigerant circulation means)
51 power storage device 52 remaining capacity sensor (remaining capacity detection means)
55 Air introduction piping (scavenging means)
56 Air introduction valve (scavenging means)
61 ECU (scavenging execution determination means)
62-64 temperature sensor (fuel cell temperature detection means)

Claims (8)

A fuel cell that is supplied with a reaction gas to generate power;
Refrigerant circulating means for circulating refrigerant circulating in the fuel cell;
Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
Scavenging means for introducing scavenging gas into the fuel cell and performing scavenging control;
A scavenging execution determination means for performing scavenging execution determination when the temperature of the fuel cell becomes equal to or lower than a first predetermined threshold that is expected to be below freezing point while the fuel cell power generation is stopped .
A plurality of fuel cell temperature detection means;
When the temperature of the fuel cell detected by any one of the fuel cell temperature detecting means falls below the first predetermined threshold value, the refrigerant circulating means is driven for a predetermined time, and any of the fuel cells in the subsequent drive completion state fuel cell system and executes the scavenging when the temperature of the fuel cell is detected is the second predetermined threshold value below the first predetermined threshold value by the fuel cell temperature detecting means. 2. The fuel cell system according to claim 1, wherein the first predetermined threshold and the second predetermined threshold are the same temperature .   The driving time of the refrigerant circulating means that is driven when the temperature of the fuel cell detected by the fuel cell temperature detecting means falls below a predetermined threshold is lengthened each time driving is repeated. The fuel cell system according to claim 1 or 2. A power storage device for supplying electric power to the scavenging means and the refrigerant circulation means;
A remaining capacity detecting means for detecting a remaining capacity of the power storage device,
When the remaining capacity of the power storage device is predicted to be less than or equal to the power required for scavenging by the scavenging means, scavenging is performed even when the temperature of the fuel cell does not fall below a predetermined threshold in the drive completion state. The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell system is characterized in that: A fuel cell that is supplied with a reaction gas to generate power;
Refrigerant circulating means for circulating refrigerant circulating in the fuel cell;
A plurality of fuel cell temperature detecting means for detecting the temperature of the fuel cell;
Scavenging means for introducing scavenging gas into the fuel cell and performing scavenging control, and
In the operation method of the fuel cell system that performs the scavenging execution determination when the temperature of the fuel cell becomes equal to or lower than a first predetermined threshold that is expected to be below freezing point while the power generation of the fuel cell is stopped ,
A first step of driving the refrigerant circulating means for a predetermined time when the temperature of the fuel cell detected by any one of the fuel cell temperature detecting means is not more than the first predetermined threshold;
Even in the driving completion state after the first step, scavenging is performed when the temperature of the fuel cell detected by any one of the fuel cell temperature detecting means is a second predetermined threshold value that is not more than the first predetermined threshold value. A fuel cell system operating method, comprising: a second step. 6. The method of operating a fuel cell system according to claim 5, wherein the first predetermined threshold and the second predetermined threshold are the same temperature .   A step of extending the driving time of the refrigerant circulating means, which is driven when the temperature of the fuel cell detected by the fuel cell temperature detecting means falls below a predetermined threshold, every time the driving is repeated, A method for operating the fuel cell system according to claim 5 or 6. When the remaining capacity of the power storage device that supplies power to the scavenging means and the refrigerant circulation means is predicted to be less than or equal to the power required for scavenging by the scavenging means, the temperature of the fuel cell is predetermined in the drive completion state. The operation method of the fuel cell system according to any one of claims 5 to 7, further comprising a step of executing scavenging even when the value does not become the threshold value or less.

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