JP2010198786A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing deterioration of starting performance at the next starting time. <P>SOLUTION: When the calculated temperature fall rate is less than a prescribed temperature fall rate in which the generated water inside the fuel cell 10 becomes an excessive cooled state during the operation shutdown of a fuel cell system 1, a heater 51 is controlled so that the temperature fall rate may be the prescribed temperature fall rate or more. This control is carried out when the temperature of the fuel cell 10 is a first prescribed temperature higher than a freezing point established below the freezing point (0°C or less). Furthermore, when the temperature of the fuel cell 10 is a second prescribed temperature or more sufficiently higher than 0°C, excessive cooling control is not carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system that prevents freezing of produced water inside a fuel cell.

  If the fuel cell system is used in an environment below freezing (0 ° C or below), the generated water will freeze inside the fuel cell when the fuel cell system is shut down, reducing the effective power generation area and improving the power generation performance at the next startup. May decrease. Moreover, when MEA (Membrane Electrode Assembly) constituting each cell of the fuel cell freezes, the fuel cell may be deteriorated due to damage to the electrolyte membrane. Therefore, a technique has been proposed in which when the fuel cell system is stopped, the inside of the fuel cell is scavenged with a gas that has been dried in advance, and the generated water remaining in the fuel cell is removed (see, for example, Patent Document 1).

JP 2002-208422 (paragraphs 0044 to 0047, FIG. 3)

  However, in the conventional fuel cell system described in Patent Document 1, it is slow that scavenging is performed after the generated water in the fuel cell has been frozen, so the scavenging is started before reaching the freezing temperature. There is a need. As a result, scavenging may be performed even when the temperature does not actually fall below the freezing point (0 ° C. or lower), and thus scavenging is performed wastefully.

  In addition, even when scavenging is performed, if the moisture has not been completely discharged (including the case where water is newly generated due to condensation after scavenging), the water freezes after scavenging, and the startup performance is reduced. There was also a risk of lowering.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a fuel cell system that can suppress a decrease in startup performance during startup.

  The present invention provides a fuel cell comprising a fuel cell that is supplied with a reaction gas to generate power, a temperature detection unit that detects a temperature of the fuel cell, and a temperature decrease rate calculation unit that calculates a temperature decrease rate of the fuel cell. A temperature control means for controlling the temperature of the fuel cell; and the temperature decrease rate calculated by the temperature decrease rate calculation means during the stoppage of the operation of the fuel cell. Supercooling control means for controlling the temperature control means so that the temperature reduction rate is equal to or higher than the predetermined temperature reduction rate when the generated water is less than the predetermined temperature reduction rate at which the product water enters a supercooling state. The control by the supercooling control means is executed until the temperature of the fuel cell reaches a first predetermined temperature higher than the freezing point at which the supercooled product water freezes. That.

  According to this, since the current temperature decrease rate is controlled so that the generated water in the fuel cell is in a supercooled state (supercooled water), the generated water is also in a normal temperature range below freezing (0 ° C. or lower). Freezing can be prevented, and it is possible to suppress a decrease in startability next time. That is, it is possible to generate a supercooled state in which the generated water does not freeze even when the generated water is below normal freezing point (0 ° C. or lower) by slowly decreasing the temperature of the fuel cell so as to be equal to or higher than a predetermined temperature decrease rate. The first predetermined temperature is set to a temperature (eg, minus 4 ° C.) higher than the freezing point (eg, minus 5 ° C. to minus 10 ° C.) at which the supercooled water is frozen at 0 ° C. or less.

  In the present invention, the calculated temperature decrease rate being less than the predetermined temperature decrease rate means that the temperature of the fuel cell is rapidly decreased and the generated water cannot be brought into a supercooled state. Yes. On the other hand, that the calculated temperature decrease rate is equal to or higher than the predetermined temperature decrease rate means that the temperature of the fuel cell decreases slowly (gradually) and the generated water can be brought into a supercooled state. Yes.

  Further, scavenging means for scavenging the fuel cell by introducing scavenging gas into the fuel cell is provided, and scavenging by the scavenging means is executed when the generated water is in a supercooled state.

  According to this, by performing scavenging when the generated water is in a supercooled state, it is possible to delay the scavenging execution timing as compared with the prior art, and the scavenging execution frequency can be reduced. In addition, since scavenging operates using a power source such as a battery as power, the efficiency of scavenging can be reduced, thereby improving energy efficiency.

  The fuel cell further includes scavenging means for introducing a scavenging gas into the fuel cell to scavenge the fuel cell, and after the scavenging by the scavenging means, the control by the supercooling control means is executed.

  According to this, since it is possible to prevent freezing of moisture that could not be removed by scavenging or moisture caused by dew condensation after scavenging, it is possible to suppress a decrease in next-time activation and membrane (MEA) degradation.

  The temperature control means includes a heating means for heating the fuel cell.

  According to this, even when the temperature of the fuel cell is drastically lowered in a low temperature environment, since the control is performed by heating the fuel cell, it is easy to maintain the temperature decrease rate at a predetermined temperature decrease rate. Become.

  Further, the temperature control means includes a refrigerant circulation means for circulating a refrigerant inside the fuel cell.

  According to this, by circulating the refrigerant, the temperature in the plane of the fuel cell and in the stacking direction of the single cells can be made uniform, and it is possible to prevent the temperature decrease rate from being locally maintained. .

  Further, when the temperature of the fuel cell is not lower than the second predetermined temperature, the control by the supercooling control means is not performed.

  According to this, since the temperature decrease rate in the region where the temperature of the fuel cell is high is not related to the supercooling state, the supercooling control is not performed when the temperature exceeds the second predetermined temperature. Energy efficiency can be improved. Note that the second predetermined temperature is set to a temperature (for example, 10 ° C.) at which it is determined that the control to bring the fuel cell into a supercooled state is unnecessary, without fear of freezing.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can suppress the fall of the starting performance at the time of starting can be provided.

It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is a flowchart which shows the operation | movement at the time of the driving | operation stop of the fuel cell system of this embodiment. It is a figure which shows the temperature change of a fuel cell, (a) is an Example, (b) is a comparative example. 6 is another flowchart showing the operation of the fuel cell system according to the present embodiment when the operation is stopped. It is a figure which shows the temperature change of a fuel cell.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following, a case where the fuel cell system 1 of the present embodiment is applied to an automobile (not shown) will be described as an example. However, the present invention is not limited to this, and is not limited to this, for ships, airplanes, etc. It can be applied to anything that needs electricity, such as a stationary type for home use.

  The fuel cell system 1 according to this embodiment includes a fuel cell 10, an anode system 20, a cathode system 30, a refrigerant circulation system 40, a temperature control system 50, a control system 60, and the like.

  The fuel cell 10 is, for example, a polymer electrolyte fuel cell (PEFC), and a MEA (Membrane Electrode Assembly) is sandwiched between conductive separators (not shown). A plurality of unit cells are stacked in the thickness direction, and each unit cell is electrically connected in series.

  The MEA has a structure in which an electrolyte membrane (solid polymer membrane) is sandwiched between an anode and a cathode containing a catalyst. The separator has an anode channel 11 through which hydrogen (reactant gas, fuel gas) flows, a cathode channel 12 through which air (reactant gas, oxidant gas) flows, and a refrigerant channel 13 through which refrigerant flows. Each is formed.

  The anode flow path 11 penetrates in the stacking direction of the single cells, penetrates in the stacking direction of the single cells, the hydrogen introduction communication path for supplying and distributing hydrogen to each anode, the flow path formed on the surface facing the anode, And a hydrogen lead-out communication passage that collects and discharges anode off-gas (such as hydrogen) from each anode.

  The cathode flow path 12 penetrates in the stacking direction of the single cells, the air introduction communication path for supplying and distributing air to each cathode, the flow path formed on the surface facing the cathode, and the stacking direction of the single cells. Thus, the cathode off-gas (wet air or the like) is collectively discharged from each cathode.

  The refrigerant flow path 13 includes a refrigerant introduction communication path that distributes and supplies refrigerant between adjacent separators penetrating in the stacking direction of the single cells, a flow path formed between the adjacent separators, and a stacking direction of the single cells. It is comprised with the refrigerant | coolant derivation | leading-out passage which collects and discharges a refrigerant | coolant from between the separators which penetrate and adjoin.

  In such a fuel cell 10, hydrogen is supplied to the anode and air containing oxygen is supplied to the cathode, so that an electrode reaction occurs on the catalyst included in the anode and the cathode, and the fuel cell 10 can generate power. It becomes.

  The fuel cell 10 is electrically connected to an external load (not shown), and the fuel cell 10 generates power when current is taken out by the external load. The external load includes a traveling motor, a chargeable / dischargeable power storage device such as a battery and a capacitor, an air compressor 31 and a water pump 43 described later.

  The anode system 20 is a system that supplies and discharges hydrogen to and from the anode of the fuel cell 10, and includes a hydrogen tank 21, a shutoff valve 22, an ejector 23, a purge valve 24, a scavenging valve 25, pipes a1 to a6, and the like. Yes.

  The hydrogen tank 21 is a container in which high-purity hydrogen is compressed at a high pressure, and is connected to a downstream shut-off valve 22 via a pipe a1.

  The shut-off valve 22 is, for example, an electromagnetic valve actuated type, and is connected to the downstream ejector 23 via a pipe a2.

  The ejector 23 is a kind of pump that sucks unreacted hydrogen discharged from the fuel cell 10 and returns it to the anode and recirculates it. The ejector 23 is connected to the inlet of the anode channel 11 via a pipe a3. Further, the return port of the ejector 23 is connected to the outlet of the anode flow path 11 via the pipe a4.

  The purge valve 24 is, for example, an electromagnetically operated type, and is connected to a pipe a5 provided by branching from the pipe a4. For example, the purge valve 24 is periodically opened during power generation of the fuel cell 10 to discharge impurities accumulated in the hydrogen circulation paths (pipings a3 and a4, the anode flow path 11) and fresh from the hydrogen tank 21. By supplying fresh hydrogen, the power generation performance is prevented from deteriorating.

  The scavenging valve 25 is connected to a pipe a6 that is branched from the pipe a4. The scavenging valve 25 is opened when scavenging the anode in the fuel cell 10 when power generation of the fuel cell 10 is stopped, and remains inside the fuel cell 10. The generated water is discharged outside the vehicle.

  The cathode system 30 is a system for supplying and discharging air (oxygen) to and from the cathode of the fuel cell 10, and includes an air compressor 31, a back pressure valve 32, a scavenging gas introduction valve 33, pipes b1 and b2, and a scavenging gas introduction pipe b3. b4 and the like.

  The air compressor 31 is, for example, a mechanical supercharger that is driven by a motor (not shown), compresses outside air (air) taken from the outside of the vehicle, and supplies the compressed air to the cathode of the fuel cell 10. The air compressor 31 is connected to the inlet of the cathode channel 12 via a pipe b1.

  The back pressure valve 32 is configured by a valve whose opening degree can be adjusted, such as a butterfly valve, and has a function of appropriately adjusting the pressure of air supplied to the cathode of the fuel cell 10. The back pressure valve 32 is connected to the outlet of the cathode channel 12 via the pipe b2.

  A scavenging gas introduction pipe b3 is branched and connected to the pipe b1, and is connected to the anode side pipe a3 via the scavenging gas introduction pipe b3, the scavenging gas introduction valve 33, and the scavenging gas introduction pipe b4.

  The scavenging gas introduction valve 33 is an on-off valve that opens and closes the flow passages of the scavenging gas introduction pipes b3 and b4, and is controlled to be opened by the ECU 61 described later when scavenging the anode when the operation of the fuel cell system 1 is stopped.

  Although not shown, the downstream of the purge valve 24 and the scavenging valve 25 and the downstream of the back pressure valve 32 are connected to a diluter. The diluter mixes the anode off-gas discharged from the anode channel 11 and the cathode off-gas discharged from the cathode channel 12 to dilute hydrogen contained in the anode off-gas with cathode off-gas (air or the like). It has become. The diluted gas is discharged outside the vehicle.

  Moreover, although not shown in figure, the humidifier is provided in the piping b1 of the cathode system 30. FIG. The humidifier humidifies the air from the air compressor 31 and supplies it to the cathode of the fuel cell 10. Note that the upstream end of the pipe b3 is connected to the upstream side of the humidifier.

  The refrigerant circulation system 40 constitutes a refrigerant circulation means for cooling the fuel cell 10 and includes a radiator 41, a thermostat valve 42, a water pump 43, pipes c1 to c5, and the like.

  The radiator 41 has a function of dissipating the refrigerant warmed by the heat generated during the power generation of the fuel cell 10, and is connected to the outlet of the upstream refrigerant passage 13 via the pipe c1.

  One inlet of the thermostat valve 42 is connected to the refrigerant outlet of the radiator 41 via a pipe c <b> 2, and the other inlet is connected to the pipe c <b> 1 via a pipe c <b> 3 that bypasses the radiator 41. The thermostat valve 42 switches between a flow path passing through the radiator 41 and a flow path bypassing the radiator 41, for example, when the volume of the wax changes with temperature. The thermostat valve 42 may be electrically switched by an electric signal from the ECU 61 described later.

  The water pump (W / P) 43 drives a motor (not shown) to circulate the refrigerant. The water pump (W / P) 43 is connected to the outlet of the thermostat valve 42 on the upstream side via a pipe c4 and passes through the pipe c5. And connected to the inlet of the refrigerant flow path 13.

  The temperature control system 50 is a system that controls the temperature of the fuel cell 10 and includes a heater 51 (temperature control means, heating means) that is a means for heating the fuel cell 10. The heater 51 is, for example, an electric type, and heats the fuel cell 10 from the outside by converting electricity into heat. The heater 51 is constituted by, for example, a sheath heater in which a heating element (such as nichrome wire) is accommodated in a sheath (sheath) via insulating powder, and is disposed so as to surround the periphery of the fuel cell 10. .

  The heater 51 is operated by using electric power of a power storage device (not shown) under the control of the ECU 61 described later when the operation of the fuel cell system 1 is stopped. By operating the heater 51, the fuel cell 10 is warmed, and the temperature decrease rate (decrease rate) when the temperature of the fuel cell 10 decreases is reduced, that is, the temperature of the fuel cell 10 is slowly decreased, and the generated water is excessive. It is controlled to be in a cooling state.

  The control system 60 includes an ECU 61, a temperature sensor 62, a timer 63, and the like.

  The ECU 61 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a program, a RAM (Random Access Memory), and the like. The ECU 61 includes a shutoff valve 22, a purge valve 24, a scavenging valve 25, and a scavenging gas introduction valve 33. It opens and closes, the opening degree of the back pressure valve 32 is adjusted, and the rotational speed of each motor of the air compressor 31 and the water pump 43 is adjusted.

  Further, the ECU 61 includes a temperature decrease rate calculation unit and a supercooling control unit.

  The temperature decrease rate calculating means is a means for calculating a temperature decrease rate when the temperature of the fuel cell 10 decreases. The temperature decrease rate means, for example, a decrease amount (temperature difference) of the temperature of the fuel cell 10 per unit time.

  The supercooling control means is a means for controlling the temperature reduction rate calculated by the temperature reduction rate calculation means so that the generated water in the fuel cell 10 is in a supercooled state (supercooled water). That is, when the calculated temperature decrease rate is less than the predetermined temperature decrease rate, the fuel cell 10 is heated by the heater 51 and the temperature decrease rate is controlled to be equal to or higher than the predetermined temperature decrease rate. The control by the supercooling control means is executed until the temperature of the fuel cell 10 reaches a first predetermined temperature that is higher than the freezing point (eg, minus 5 ° C. to minus 10 ° C.) at which the supercooled product water is frozen. To do.

  The temperature sensor 62 (temperature detection means) detects the temperature of the fuel cell 10 and is provided in the vicinity of the outlet of the refrigerant flow path 13. The position of the temperature sensor 62 is not limited as long as it can detect the temperature of the fuel cell 10, and may be an inlet / outlet of the anode channel 11, an inlet / outlet of the cathode channel 12, or the fuel cell. 10 may be measured directly.

  The timer 63 is used to periodically monitor the temperature of the fuel cell 10 and measure an elapsed time (unit time) when calculating a temperature decrease rate which will be described later.

  Next, the operation of the fuel cell system 1 of the present embodiment will be described with reference to FIGS. First, when the ignition switch (not shown) of the vehicle is turned on (hereinafter referred to as IG-ON) and the fuel cell system 1 is in operation, the ECU 61 closes the scavenging gas introduction valve 33. Then, the shutoff valve 22 is opened, hydrogen is supplied from the hydrogen tank 21 to the anode of the fuel cell 10, and the air compressor 31 is driven to supply air (oxygen) to the cathode of the fuel cell 10. Has been done.

  During power generation, water generated at the cathode of the fuel cell 10 is discharged outside the vehicle through the back pressure valve 32 and permeates to the anode through the electrolyte membrane. When the moisture remaining on the anode becomes excessive, the power generation performance is lowered. Therefore, the ECU 61 opens the purge valve 24 as appropriate, and discharges generated water to the outside of the vehicle.

  Further, during power generation, the ECU 61 controls the fuel cell 10 so as not to become excessively high temperature by driving the water pump 43 and circulating the refrigerant. When the temperature of the refrigerant is equal to or lower than the predetermined value, the thermostat valve 42 is switched so that the refrigerant passes through the pipe c3 that bypasses the radiator 41. When the temperature exceeds the predetermined value, the refrigerant flows to the radiator 41 side. The thermostat valve 42 is switched.

  When the ignition switch is turned off (IG-OFF) and the operation of the fuel cell system 1 is stopped, in step S100, the ECU 61 starts detecting the temperature of the fuel cell 10 (FC: Fuel Cell). The detection of the FC temperature is periodically performed using the timer 63, and the FC temperature is acquired from the temperature sensor 62 when a predetermined time has elapsed after the IG-OFF. Yes. After detecting the FC temperature, the ECU 61 resets the timer 63 and acquires the FC temperature by the temperature sensor 62 when a predetermined time has passed again.

  And it progresses to step S110 and ECU61 judges whether FC temperature is below 2nd predetermined temperature. The second predetermined temperature is a threshold value for determining whether or not the control by the supercooling control means is executed, and is set to a temperature sufficiently higher than 0 ° C., for example, 10 ° C.

  In step S110, if the ECU 61 determines that the FC temperature is equal to or lower than the second predetermined temperature (Yes), the ECU 61 proceeds to step S120, and if the ECU 61 determines that the FC temperature is not equal to or lower than the second predetermined temperature (No) ), Go to step S200.

  In step S200, the ECU 61 determines whether or not it is IG-ON. If it is determined that it is not IG-ON (No), it returns to step S110, and if it is determined that it is IG-ON. (Yes), the series of processing shown in FIG. When the IG-ON is turned on, the fuel cell 10 starts power generation and the FC temperature starts to rise, so that the generated water does not freeze.

  In step S120, the ECU 61 calculates a temperature decrease rate (temperature decrease rate calculation means). The temperature decrease rate indicates the speed of decrease in the FC temperature under a low temperature environment, and is determined by the temperature decrease amount per unit time (−ΔT / t). That is, if the rate of temperature decrease is too low (less than a predetermined value), the rate of FC temperature decrease is rapid, and the generated water freezes immediately at 0 ° C. without being supercooled at 0 ° C. or lower. On the other hand, when the temperature decrease rate is high (when it is above a predetermined value), the FC temperature decrease rate becomes gradual, and a supercooled state in which the generated water does not freeze even at 0 ° C. or less can be achieved.

  In step S130, the ECU 61 determines whether or not the calculated temperature decrease rate is less than a predetermined value (less than a predetermined temperature decrease rate). The predetermined temperature decrease rate is a temperature decrease rate necessary for maintaining the generated water in the fuel cell 10 in a supercooled state, and is determined in advance by experiments or simulations.

  In step S130, if the ECU 61 determines that the calculated temperature decrease rate is less than a predetermined value, that is, the FC temperature decrease rate is too fast (Yes), the process proceeds to step S140. The heater 51 is turned on using the power of the power storage device (battery or the like) that is not used.

  The amount of heat given to the fuel cell 10 when the heater 51 is turned on can be set as appropriate based on the detected FC temperature. That is, when the temperature decrease rate is very low (the temperature decrease rate is abrupt), the amount of heat applied to the fuel cell 10 increases, and when the temperature decrease rate is relatively high (the temperature decrease rate is slow). The amount of heat given to the fuel cell 10 is controlled to be small.

  When the heater 51 is turned on, the fuel cell 10 is heated by the heater 51 and the refrigerant is warmed. As a result, the FC temperature decrease rate is reduced, and the temperature decrease rate is controlled to be equal to or higher than the predetermined temperature decrease rate (to maintain the predetermined temperature decrease rate).

  In step S130, when the ECU 61 determines that the calculated temperature decrease rate is equal to or higher than the predetermined value, that is, the generated water can be in a supercooled state (No), the ECU 61 proceeds to step S150 and turns off the heater 51. .

  In the present embodiment, steps S130 to S150 correspond to the processing executed by the supercooling control means.

  In step S160, the ECU 61 detects the FC temperature with the temperature sensor 62, and determines whether the FC temperature is 0 ° C. or less. In step S160, when the ECU 61 determines that the FC temperature is 0 ° C. or lower (Yes), the ECU 61 proceeds to step S170, and when it is determined that the FC temperature is not 0 ° C. or lower (No), step S180. Proceed to

  In step S170, the ECU 61 determines whether or not the FC temperature is the first predetermined temperature. The first predetermined temperature is a threshold value for determining that the supercooled state of the generated water cannot be maintained, the FC temperature falls to the freezing point at which the supercooled product water is frozen, and that the product is frozen soon thereafter. The temperature is set higher than the freezing point at which water freezes.

  The first predetermined temperature is determined in advance based on experiments, simulations, and the like. For example, when the freezing point is minus 5 ° C. to minus 10 ° C., the first predetermined temperature is set to minus 4 ° C. Further, the first predetermined temperature may be a temperature higher than the freezing point at which the supercooled product water freezes, and may be minus 2 ° C, minus 3 ° C, or the like.

  In step S170, when the ECU 61 determines that the FC temperature is the first predetermined temperature, that is, the supercooled water is frozen soon (or in a predetermined time) (Yes), the ECU 61 proceeds to step S190. Scavenging is performed in a state where the produced water is supercooled. In the present embodiment, the air compressor 31, the scavenging gas introduction valve 33, the scavenging gas introduction pipes b3 and b4, and the ECU 61 constitute scavenging means.

  Scavenging is a process of introducing scavenging gas into the fuel cell 10 and discharging generated water remaining inside the fuel cell 10 to the outside of the vehicle. That is, the ECU 61 drives the air compressor 31 using electric power of a power storage device (not shown) and introduces a predetermined amount of air to the cathode side of the fuel cell 10 in a state where the back pressure valve 32 is fully opened. 12 is discharged outside the vehicle while blowing off the remaining generated water.

  The ECU 61 closes the opening of the back pressure valve 32 and introduces a predetermined amount of air from the air compressor 31 with the scavenging valve 25 and the scavenging gas introduction valve 33 opened. The air introduced from the air compressor 31 is supplied to the anode flow path 11 through the scavenging gas introduction pipes b3 and b4, and is blown out of the vehicle through the scavenging valve 25 while blowing off the generated water remaining in the anode flow path 11. Discharged.

  In the above-described embodiment, the case where scavenging is performed one side at a time so as to scavenge the anode after scavenging the cathode is described as an example. However, the present invention is not limited to this, and the cathode is scavenged after scavenging the anode. Or the cathode and anode may be scavenged simultaneously.

  After the scavenging is executed, the ECU 61 ends the regular monitoring of the FC temperature and ends the series of processes shown in FIG.

  In step S170, if the ECU 61 determines that the FC temperature is not the first predetermined temperature, that is, the generated water is not frozen for a while (No), the ECU 61 proceeds to step S180 and determines whether or not the IG-ON has been performed. to decide.

  In step S180, if the ECU 61 determines that the IG-ON is not performed (No), the ECU 61 returns to step S120. If the ECU 61 determines that the IG-ON is determined (Yes), the series of processes shown in FIG. Exit. Note that when the IG-ON is performed, power generation of the fuel cell 10 is started and the FC temperature rises, so that the generated water is not frozen.

  In step S180, the determination is made based on whether or not the IG-ON has been performed. However, the determination is not limited to this, and the determination may be made based on whether or not the FC temperature has increased. For example, when the temperature rises in the morning and the FC temperature rises, a series of processing ends, and when the FC temperature does not rise, the process returns to step S120.

  Further, as shown in FIG. 3A, when the ECU 61 determines that the FC temperature is equal to or lower than the second predetermined temperature (10 ° C.) (S110, Yes), a process of calculating the temperature decrease rate is started. (S120). When it is determined that the temperature decrease rate (−ΔT1 / t) calculated at this time is less than a predetermined value (less than a predetermined temperature decrease rate) (S130, Yes), the heater 51 is turned on (S140). As a result, the temperature decrease rate is increased and controlled to be equal to or higher than a predetermined temperature decrease rate. Note that the heater 51 is on / off controlled so that the calculated temperature decrease rate (−ΔT2 / t) is not less than a predetermined value (not less than a predetermined temperature decrease rate) at 0 ° C. or less.

  In this way, until the first predetermined temperature (for example, minus 4 ° C.) that is higher than the freezing point of the supercooled product water becomes a temperature higher than the predetermined temperature, that is, the FC temperature is the temperature. It controls so that it falls slowly compared with the case where it is not controlled. As a result, the generated water remaining in the fuel cell 10 enters a supercooled state in which it does not freeze even at 0 ° C. or lower.

  In FIG. 3A, the generated water is in a supercooled state between 0 ° C. and a first predetermined temperature set to a temperature higher than the freezing point at which the supercooled generated water is frozen. The freezing point is a temperature at which the supercooled water is frozen, and is, for example, minus 5 ° C. to minus 10 ° C.

  For example, when the generated water is IG-ON at the time t1 when it is in a supercooled state (S180, Yes), the temperature rises as the fuel cell 10 starts generating power (see the two-dot chain line). The control by the cooling control means becomes unnecessary, and the series of processes shown in FIG.

  Further, when the FC temperature decreases while the generated water is maintained in the supercooled state, scavenging is executed at time t2 when the FC temperature reaches the first predetermined temperature (for example, minus 4 ° C.) (S190). Note that, as shown in the comparative example of FIG. 3B, when the control by the supercooling control means is not executed, the generated water cannot be brought into a supercooled state because the FC temperature rapidly decreases. Moreover, since it is necessary to execute the scavenging timing at time t3 corresponding to a temperature higher than 0 ° C., it is necessary to execute scavenging earlier than the embodiment shown in FIG.

  In the present embodiment, the calculation of the temperature decrease rate is started when the FC temperature is equal to or lower than the second predetermined temperature. However, the present invention is not limited to this, and the generated water can be in a supercooled state. If there is, for example, it may be started immediately before the FC temperature reaches 0 ° C.

  As described above, according to the fuel cell system 1 of the present embodiment, the generated water remaining in the fuel cell 10 when the operation of the fuel cell system 1 is stopped (when the power generation of the fuel cell 10 is stopped) is supercooled ( Since the temperature decrease rate is controlled so that it becomes supercooled water), the generated water can be prevented from freezing even in the region below the freezing point (0 ° C. or lower), and the next decrease in startability can be suppressed.

  Further, according to the present embodiment, scavenging is executed when the generated water is in a supercooled state, so that it is possible to delay the scavenging execution timing as compared with the prior art and reduce the frequency of scavenging. Therefore, energy required for scavenging can be reduced, so that energy efficiency can be improved.

  Further, according to the present embodiment, since the fuel cell 10 is heated using the heater 51 (temperature control means), the temperature decrease rate is set to a predetermined value even when the FC temperature rapidly decreases in a low temperature environment. It becomes easy to maintain the temperature decrease rate.

  In addition, since the temperature decrease rate in the region where the FC temperature is high has low relevance to the supercooling state, when the FC temperature exceeds the second predetermined temperature as in this embodiment, control by the supercooling control means By not performing the above, energy associated with the supercooling control means becomes unnecessary, and energy efficiency can be improved.

  FIG. 4 is another flowchart showing the operation of the fuel cell system of the present embodiment, and FIG. 5 is a diagram showing the temperature change of the fuel cell. In addition, about the process same as the flowchart of FIG. 2, the same step is attached | subjected and the overlapping description is abbreviate | omitted. The control according to the flowchart shown in FIG. 4 is performed so that scavenging is performed first and then the generated water is maintained in a supercooled state. The process of step S115 shown in FIG. 4 is the same as the process of step S190 shown in FIG.

  That is, in step S115, the ECU 61 executes scavenging, thereby discharging generated water (droplets) remaining inside the fuel cell 10 to the outside of the vehicle.

  Further, when the FC temperature is 0 ° C. or lower (S160, Yes), the ECU 61 proceeds to step S170, and when it is determined that the FC temperature has reached the first predetermined temperature (Yes), the ECU 61 proceeds to step S171.

  In step S171, the ECU 61 turns on the heater 51 using the power of the power storage device (not shown). When the heater 51 is turned on, the FC temperature rises before reaching the temperature (freezing point) at which the supercooled product water (supercooled water) freezes (see FIG. 5), and the supercooled product water freezes. Can be prevented.

  Then, the process proceeds to step S172, where the ECU 61 determines whether or not the FC temperature is 0 ° C. or higher. If it is determined that the FC temperature is 0 ° C. or higher (Yes), the ECU 61 proceeds to step S173 and determines the FC temperature. If it is determined that the temperature is not 0 ° C. or higher (No), the process of step S172 is repeated.

  Although not shown in FIG. 4, when it is determined that the FC temperature is not equal to or higher than 0 ° C. (No at S <b> 172), when the IG-ON is performed, the series of processes illustrated in FIG. 4 is terminated.

  In step S173, the ECU 61 turns off the heater 51. By turning off the heater 51, the increase in the FC temperature stops and the FC temperature starts to decrease (see FIG. 5).

  And it progresses to step S180, it is judged whether it was IG-ON, and when it is judged that it was IG-ON (Yes), the control which maintains a supercooling state is complete | finished, and it is not IG-ON. If it is determined (No), the process returns to step S120. Then, the calculation of the temperature decrease rate is started again (S120), and the FC temperature is controlled so that the temperature decrease rate is not less than a predetermined value (not less than a predetermined temperature decrease rate).

  In this way, after the scavenging is performed, the control by the supercooling control means is performed, and the heater 51 is controlled so that the temperature decrease rate becomes a predetermined value or more, and the generated water is maintained in the supercooled state, thereby removing by scavenging. Freezing of moisture that could not be performed or moisture caused by dew condensation after scavenging can be prevented, and deterioration of startability next time and deterioration of MEA can be suppressed.

  In the present embodiment, the heater 51 has been described as an example of the temperature control unit. However, the temperature control unit is not limited to this example. And the temperature of the fuel cell 10 may be controlled by circulating the refrigerant in the fuel cell 10. By circulating the refrigerant, it is possible to circulate the refrigerant that remains in a warm state inside the fuel cell 10 and control the temperature of the fuel cell 10.

  Further, by circulating the refrigerant, the temperature in the plane of the fuel cell 10 and in the stacking direction of the single cells can be made uniform, and it is possible to prevent the temperature decrease rate from being locally maintained. It should be noted that the temperature control means may be configured by combining the refrigerant circulation means for circulating the refrigerant and the heating means by the heater 51.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 31 Air compressor 33 Scavenging gas introduction valve 43 Water pump 51 Heater (temperature control means, heating means)
61 ECU (temperature reduction rate calculation means, supercooling control means)
62 Temperature sensor (temperature detection means)
63 Timer b3, b4 Scavenging gas introduction piping

Claims (6)

A fuel cell that is supplied with a reaction gas to generate power;
Temperature detecting means for detecting the temperature of the fuel cell;
A temperature decrease rate calculating means for calculating a temperature decrease rate of the fuel cell, and a fuel cell system comprising:
Temperature control means for controlling the temperature of the fuel cell;
When the temperature decrease rate calculated by the temperature decrease rate calculation means is less than a predetermined temperature decrease rate at which the generated water inside the fuel cell is in a supercooled state while the fuel cell system is stopped. And a supercooling control means for controlling the temperature control means so that the temperature decrease rate is equal to or higher than a predetermined temperature decrease rate,
The control by the supercooling control means is executed until the temperature of the fuel cell reaches a first predetermined temperature higher than the freezing point at which the supercooled product water freezes. Scavenging means for introducing a scavenging gas into the fuel cell to scavenge the fuel cell;
The fuel cell system according to claim 1, wherein scavenging by the scavenging means is executed when the generated water is in a supercooled state. Scavenging means for introducing a scavenging gas into the fuel cell to scavenge the fuel cell;
2. The fuel cell system according to claim 1, wherein after the scavenging by the scavenging means, control by the supercooling control means is executed.   4. The fuel cell system according to claim 1, wherein the temperature control unit includes a heating unit that heats the fuel cell. 5.   5. The fuel cell system according to claim 1, wherein the temperature control unit includes a refrigerant circulation unit that circulates a refrigerant inside the fuel cell. 6.   6. The fuel cell system according to claim 1, wherein when the temperature of the fuel cell is not equal to or lower than a second predetermined temperature, control by the supercooling control unit is not performed.

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