JP2008123930A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing the freezing of a discharge route after warm-up is completed. <P>SOLUTION: After the warm-up is completed (S105), the convergence temperature of an oxidizer gas discharge flow path where cathode offgas flows is recognized (S110). In the case that the convergence temperature is ≤0°C, it is judged that there is the risk of freezing the oxidizer gas discharge flow path, the heat generation of a fuel cell is increased by increasing the load of the fuel cell, and the exhaust temperature of an offgas discharged from the fuel cell is elevated (S150). Further, control for inhibiting idling stop control is executed (S160). Thus, the cathode offgas passing through the oxidizer gas discharge route is discharged outside a vehicle before freezing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system that can prevent freezing after the start of power generation.

In the fuel cell system, various techniques for warming up the fuel cell have been proposed in order to improve the startability of the fuel cell in a low temperature (below freezing point) environment. Fuel cell vehicles and the like are required to promptly warm up from the standpoint of merchantability. For example, the fuel cell is heated by supplying air heated to a high temperature by the air pressure increased by a compressor. A technique for quickly performing the machine has been proposed (see Patent Document 1).
JP 2002-134150 A (paragraphs 0038 and 0043)

  However, when the fuel cell system is used in an environment where the temperature is below freezing point, the generated water discharged from the fuel cell or the wet water is wet even after the warm-up operation of the fuel cell is completed and the normal operation is started. There was a problem that the moisture in the cathode off-gas in a frozen state freezes in the piping. This is because, even after warming up, the temperature of pipes and the like rapidly decreases depending on the environment, which not only deteriorates the power generation performance but also may cause problems such as piping of the fuel cell system. In other words, in the conventional technology such as Patent Document 1, icing that occurs in piping after the completion of warm-up operation of the fuel cell has not been studied so far.

  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 prevent the freezing of the discharge path after completion of warm-up.

  The invention according to claim 1 is a fuel cell that is supplied with an oxidant gas and a fuel gas to generate electric power, a fuel cell heating value control means that controls a heating value of the fuel cell, and an oxidation gas discharged from the fuel cell. The oxidant gas discharge passage through which the oxidant gas is circulated and discharged, the oxidant gas discharge passage temperature grasping means for grasping the convergence temperature of the oxidant gas discharge passage, and the warm-up of the fuel cell are completed A fuel cell warm-up completion determination unit that determines whether or not the fuel cell warm-up completion determination unit detects completion of warm-up of the fuel cell. When the convergence temperature obtained by the agent gas discharge channel temperature grasping means is equal to or lower than a predetermined temperature, the fuel cell heat generation amount control means raises the temperature of the fuel cell from the temperature at which the convergence temperature is grasped. It is characterized by.

  According to the first aspect of the present invention, when the convergence temperature of the oxidant gas discharge channel is equal to or lower than a predetermined temperature (for example, below the freezing point), the calorific value of the fuel cell is increased. The temperature of the flowing oxidant gas (cathode off-gas) also rises, and the oxidant gas (cathode off-gas) discharged from the fuel cell is discharged to the outside (outside of the fuel cell system) before falling to the freezing temperature. For this reason, it is possible to prevent the water contained in the generated water or the wet oxidant gas discharged from the fuel cell after the start of power generation from icing in the oxidant gas discharge flow path, and the icing progresses, causing problems in the piping and the like. Can be prevented.

  The invention according to claim 2 comprises fuel cell output detection means for detecting the output of the fuel cell, and outside air temperature detection means for detecting the outside air temperature, wherein the oxidant gas discharge flow path temperature grasping means comprises the The convergence temperature is estimated based on the output of the fuel cell detected by the fuel cell output detecting means and the outside air temperature detected by the outside air temperature detecting means.

  According to the second aspect of the present invention, in order to estimate the temperature of the oxidant gas discharge channel from the power generation performance of the fuel cell and the outside air temperature, a device for directly measuring the temperature of the oxidant gas discharge channel is installed. Temperature can be ascertained.

  According to a third aspect of the present invention, a correlation between the calorific value of the fuel cell and the convergence temperature of the oxidant gas discharge passage is obtained in advance, and the correlation is obtained by the oxidant gas discharge passage temperature grasping means. The calorific value of the fuel cell is controlled according to the convergence temperature.

  According to the third aspect of the present invention, the rate of increase in the heat generation amount of the fuel cell can be set according to the convergence temperature using the correlation (map, function, table) obtained in advance by a test or the like. Can be changed.

  The invention according to claim 4 is characterized in that the fuel cell heat generation amount control means increases the heat generation amount of the fuel cell until the convergence temperature becomes higher than a predetermined temperature.

  According to the fourth aspect of the present invention, the heat generation amount of the fuel cell is increased so that the temperature of the oxidant gas passing through the oxidant gas discharge channel is higher than a predetermined temperature. It is possible to suppress adverse effects on the film (for example, electrolyte film) and energy consumption due to excessive heat generation.

  According to a fifth aspect of the present invention, there is provided a fuel cell temperature detecting means for detecting the temperature of the fuel cell, and a fuel cell over-permissible temperature determining means for determining whether or not the temperature of the fuel cell exceeds an allowable range. And when the fuel cell temperature detected by the fuel cell temperature detecting means is determined to have exceeded the allowable temperature of the fuel cell by the fuel cell over-permissible temperature determining means, The control for increasing the heat generation amount is stopped.

  According to the fifth aspect of the present invention, the amount of heat generation is increased so that the fuel cell does not exceed the allowable temperature, so that it is possible to prevent deterioration of the film due to overheating.

  According to the fuel cell system of the present invention, it is possible to prevent icing of the discharge path after the start of power generation.

(First embodiment)
FIG. 1 is an overall configuration diagram of the fuel cell system according to the present embodiment, FIG. 2 is a flowchart illustrating anti-icing control according to the first embodiment, FIG. 3 is a sub-flowchart illustrating control for grasping the convergence temperature, and FIG. FIG. 5 is a map for correcting the convergence temperature, FIG. 6 is a map showing the relationship between the exhaust temperature and the output of the fuel cell, and FIG. 7 is for increasing the load on the fuel cell. It is a graph which shows the relationship between the voltage and current of a fuel cell before and after countermeasures. In the following description, an automobile equipped with a fuel cell system will be described as an example. However, the present invention is not limited to this, and a stationary fuel cell as a power source for ships, aircraft, and households equipped with a fuel cell system is not limited thereto. It may be a system.

  As shown in FIG. 1, the fuel cell system 1 of this embodiment includes a fuel cell FC, an anode system 20, a cathode system 30, a cooling system 35, a dilution system 40, an exhaust system 50, a high voltage system 60, a control system 70, and the like. It is comprised including.

  The fuel cell FC includes a membrane electrode assembly (MEA; Membrane Electrode Assembly) in which an electrolyte membrane 2 made of a solid polymer having proton conductivity is sandwiched between an anode electrode 3 containing a catalyst and a cathode electrode 4 containing a catalyst. ) Is further sandwiched between a pair of conductive separators 5 and 6, and a plurality of single cells are stacked in the thickness direction. In addition, the electrolyte membrane 2 is a membrane having characteristics that can exhibit performance when appropriately humidified. Further, the fuel cell FC is formed with a flow path through which a cooling medium flows. In FIG. 1, for convenience of explanation, one single cell is schematically illustrated.

  The anode system 20 supplies hydrogen as a fuel gas to the anode electrode 3 of the fuel cell FC and discharges hydrogen from the anode electrode 3, and includes a hydrogen tank 21, an ejector 22, a purge valve 23, and a pipe 24a. , 24b, 24c, 24d, and the like.

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

  The ejector 22 is a kind of vacuum pump for circulating unreacted hydrogen discharged from the anode 3 side back to the anode 3 of the fuel cell FC.

  The purge valve 23 is constituted by, for example, a shut-off valve, and is a valve that is appropriately opened during operation and discharges impurities accumulated in the anode system 20. The impurities are nitrogen contained in the air that has permeated from the cathode electrode 4 through the electrolyte membrane 2 to the anode electrode 3.

  One end of the pipe 24 a is connected to the hydrogen tank 21 and the other end is connected to the ejector 22. One end of the pipe 24b is connected to the ejector 22, and the other end is connected to the inlet of the anode 3 of the fuel cell FC. The pipe 24 c is connected to the outlet on the anode electrode 3 side of the fuel cell FC, and the other end is connected to the purge valve 23. One end of the pipe 24 d is connected to the pipe 24 c and the other end is connected to the ejector 22.

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

  The cathode system 30 supplies air (oxygen) as an oxidant gas to the cathode electrode 4 of the fuel cell FC, and discharges air and the like from the cathode electrode 4, and includes an air compressor 31, a humidifier 32, A back pressure valve 33, pipes 34a, 34b, 34c, 34d and the like are provided.

  The air compressor 31 is composed of a supercharger or the like driven by a motor, takes in air outside the vehicle (outside air), compresses it, and supplies it to the cathode 4 of the fuel cell FC.

  The humidifier 32 includes, for example, a hollow fiber membrane module in which a plurality of water permeable membranes are bundled and accommodated in a case, and air from the air compressor 31 is circulated on one side of the inside and outside of the hollow fiber membrane, The cathode off-gas (wet air, generated water) discharged from the cathode electrode 4 of the fuel cell FC is circulated to the other side so that the air from the air compressor 31 is humidified.

  The back pressure valve 33 is constituted by a butterfly valve, for example, and has a function of appropriately adjusting the pressure of air supplied to the cathode electrode 4 of the fuel cell FC.

  The cooling system 35 includes a radiator 36, a thermostat valve 37, a circulation pump 38, pipes 39a, 39b, 39c, and 39d.

  The radiator 36 is composed of tubes, fins, and the like, and has a function of radiating heat from the cooling medium heated by the fuel cell FC.

  The thermostat valve 37 has a function of switching according to the temperature of the cooling medium. When the cooling medium is at a temperature at which the fuel cell FC needs to be cooled, the thermostat valve 37 is switched to a position passing through the radiator 36, and the cooling medium is the fuel. When the temperature is such that the battery FC does not need to be cooled, it is configured to be switched to a position where the radiator 36 is bypassed. This switching is performed, for example, by changing the volume of the wax in the thermostat valve 37 according to the temperature. However, the switching may be performed electrically by a signal from the control unit 71, for example.

  The circulation pump 38 has a function of circulating a cooling medium between the fuel cell FC and the radiator 36.

  The pipe 39 a connects the outlet of the cooling medium of the fuel cell FC and the thermostat valve 37. The pipe 39 b connects the thermostat valve 37 and the inlet of the radiator 36. The pipe 39 c connects the outlet of the radiator 36 and the inlet of the cooling medium of the fuel cell FC via the circulation pump 38. The pipe 39d connects the thermostat valve 37 and a pipe 39c between the radiator and the circulation pump 38.

  The dilution system 40 has a function of diluting the hydrogen discharged from the fuel cell FC, and includes a diluter 41, pipes 42a and 42b, and the like. The diluter 41 is connected to a pipe 42a connected to one end on the downstream side of the purge valve 23 and a pipe 42b connected to one end on the downstream side of the back pressure valve 33, and in the diluter 41, the fuel cell FC is connected. The hydrogen discharged from the anode 3 is mixed with the off-gas (air, water, etc.) discharged from the cathode 4 of the fuel cell FC to be diluted. When the hydrogen discharged from the fuel cell FC passes through the diluter 41, the hydrogen diluted to a concentration below the specified level is discharged outside the vehicle (in the atmosphere).

  The exhaust system 50 includes a silencer 51, a tail pipe 52, a pipe 53, and the like. The silencer 51 has a function of reducing exhaust noise, includes a cylindrical case, and is configured by partitioning the inside into a plurality of parts and providing a sound absorbing material. The tail pipe 52 is a pipe connected to one end of the silencer 51 on the downstream side, and is configured to communicate with the outside of the vehicle (in the atmosphere). The pipe 53 is configured to connect the silencer 51 and the diluter 41.

  Note that the pipe 34c, the flow path on the humidifying side of the humidifier 32, the pipe 42b, the diluter 41, the pipe 53, the silencer 51, and the tail pipe 52 after the outlet of the cathode electrode 4 of the fuel cell FC are used in the first embodiment. An oxidant gas discharge flow path R (see FIG. 1) is also configured (same for other embodiments).

  The high voltage system 60 has a function of supplying power (generated current) obtained by the fuel cell FC to the load 61. The load refers to an electric motor (travel motor), a power storage device such as a battery or a capacitor, various auxiliary machines (including the air compressor 31), and the like.

  The control system 70 includes a control unit 71, a fuel cell temperature sensor S1, an outside air temperature sensor S2, a wind speed sensor S3, a current sensor S4, a voltage sensor S5, and the like.

  The control unit 71 includes a CPU (Central Processing Unit), a memory, an input / output interface, and various electric / electronic circuits, and includes a fuel cell heating value control means, an oxidant gas discharge flow path temperature grasping means, a fuel cell warming means. Machine completion judging means is provided. The control unit 71 is electrically connected to the purge valve 23, the air compressor 31, the back pressure valve 33, the temperature sensors S1 and S2, the wind speed sensor S3, the current sensor S4, and the voltage sensor S5, and opens and closes the purge valve 23. The rotational speed of the air compressor 31 and the opening of the back pressure valve 33 are controlled, the temperatures (° C.) detected by the fuel cell temperature sensor S1 and the outside air temperature sensor S2 are acquired, and the wind speed (m / S), the current value (IFC, ampere) detected by the current sensor S4 is acquired, and the voltage value (VFC, volt) detected by the voltage sensor S5 is acquired.

  The fuel cell temperature sensor S1 is a sensor that detects the temperature of the fuel cell FC, and is provided near the outlet of the anode 3 of the fuel cell FC. It is not limited to the vicinity of the outlet of the anode electrode 3 as long as the temperature of the fuel cell FC can be detected.

  The outside air temperature sensor S2 is a sensor that detects the temperature outside the vehicle (outside air), and is provided in a vehicle body that can directly measure outside air.

  The wind speed sensor S3 detects the wind speed blown to the fuel cell system 1, and is provided in the vicinity of the oxidant gas discharge channel R, for example. Incidentally, as the wind speed increases, the temperature of the oxidant gas discharge passage R decreases. A vehicle speed sensor that detects the traveling speed of the vehicle may be used in place of the wind speed sensor S3.

  The current sensor S4 detects a current value taken from the fuel cell FC toward the load 61, and the voltage sensor S5 detects a voltage value of the fuel cell FC, and is detected by the current sensor S4. The output (power: kW) taken out from the fuel cell FC is obtained by the product of the measured current value and the voltage value detected by the voltage sensor S5.

  Next, icing prevention control in the fuel cell system 1 of the first embodiment will be described with reference to FIGS. 2 to 7 (refer to FIG. 1 as appropriate). The fuel cell vehicle (not shown) shown in the first embodiment (the same applies to the other embodiments) is a vehicle having an idling stop function. For example, the air compressor 31 is stopped when stopping at a signal or the like. Is stopped and the supply of air (oxidant gas) to the fuel cell FC is stopped. The following description is based on the assumption that power generation is started in a low-temperature environment, and control for warming up the fuel cell FC is performed after the power generation is started.

  First, when an ignition switch (not shown) of the fuel cell vehicle (vehicle) is switched from OFF to ON, the control unit 71 opens a shut-off valve (not shown) provided in the hydrogen tank 21 to open the hydrogen tank 21. Then, hydrogen is supplied to the anode electrode 3 of the fuel cell FC, the air compressor 31 is started to be driven, and the air humidified by the humidifier 32 is supplied to the cathode electrode 4 of the fuel cell FC. In the anode electrode 3, hydrogen ions (protons) are generated by the action of the catalyst, and the hydrogen ions pass through the electrolyte membrane 2 and move to the cathode electrode 4. In the cathode electrode 4, water is generated by the reaction of electrons, hydrogen ions, and oxygen that have moved from the anode electrode 3 to the cathode electrode 4 through the load 61 by the action of the catalyst. Thus, in the fuel cell FC, power is generated and water is generated (step S100 in FIG. 2). In order to warm up the fuel cell FC after the start of power generation, for example, air is supplied to the fuel cell FC at a higher flow rate and pressure than in normal operation, and the fuel cell FC is generated with high output.

  Then, the process proceeds to step S105 in FIG. 2, and the control unit 71 determines whether the warm-up is completed. Note that this step S105 corresponds to the fuel cell warm-up completion determination means in the present embodiment. Further, when it is determined that the temperature of the fuel cell FC obtained from the fuel cell temperature sensor S1 exceeds a predetermined temperature (for example, 30 ° C.), it can be determined that the warm-up is completed. In step S105, when it is determined that the warm-up has not been completed (No), the control unit 71 repeats the process of step S105, and when it is determined that the warm-up has been completed (Yes), step S110. Proceed to The temperature of the fuel cell FC for determining the completion of warm-up is, for example, the outlet temperature of hydrogen discharged from the fuel cell FC, the outlet temperature of air discharged from the fuel cell FC, and discharged from the fuel cell FC. This is the outlet temperature of the cooling medium.

  In addition, after starting electric power generation, the control part 71 drives the circulation pump 38, and circulates a cooling medium. When the temperature of the fuel cell FC is low and the temperature of the cooling medium is lower than the predetermined temperature, the thermostat valve 37 is switched to the side bypassing the radiator 36, the cooling medium circulates, and the temperature of the fuel cell FC is excessively high. When the temperature of the cooling medium is higher than the predetermined temperature, the thermostat valve 37 is switched to the radiator 36 side, so that the cooling medium is radiated by the radiator 36 and the fuel cell FC is cooled by the cooled cooling medium. The

  In step S <b> 110, the control unit 71 grasps the temperature of the oxidant gas discharge flow path R after the outlet of the cathode electrode 4. Step S110 corresponds to the oxidant gas discharge channel temperature grasping means in the present embodiment. In step S110, the process proceeds to the subflow of FIG. 3, and in step S111, the control unit 71 estimates the convergence temperature of the oxidant gas discharge flow path R based on the map shown in FIG. The convergence temperature means the temperature at the lowest temperature in the oxidant gas discharge flow path R from the outlet of the cathode electrode 4 to the outlet of the tail pipe 52 of the fuel cell FC. Incidentally, FIG. 4 is a map showing the relationship between the convergence temperature and the output of the fuel cell FC (FC output), and the solid line shows the case where the outside air temperature is minus 10 ° C. When the outside air temperature is a room temperature higher than minus 10 ° C., the convergence temperature is estimated based on the map shown by the broken line shifted upward from the solid line in FIG. 4, and the outside temperature is minus 30 lower than minus 10 ° C. In the case of ° C., the convergence temperature is estimated based on a map indicated by a broken line shifted below the solid line. The outside air temperature at this time is obtained from the temperature (° C.) detected by the outside air temperature sensor S2, and the FC output is the current value (A) detected by the current sensor S4 and the voltage detected by the voltage sensor S5. It is determined by the product of the value (V). However, the FC output is not limited to the product (electric power) of the current and the voltage, but may be a current taken out from the fuel cell FC or a voltage (for example, total cell voltage) applied to the fuel cell FC.

  And it progresses to step S112 of FIG. 3, and the control part 71 correct | amends convergence temperature based on the map shown in FIG. As a condition for correcting the convergence temperature, the wind speed (m / s) detected by the wind speed sensor S3 is used. Incidentally, using the map of FIG. 5, when the wind speed is high, it becomes lower than the convergence temperature estimated in FIG. 4, and when the wind speed is low, it becomes higher than the convergence temperature estimated in FIG. The convergence temperature is corrected. Note that the vehicle speed may be used instead of the wind speed. In this case, the map is shifted downward when the vehicle speed is high, and the map is shifted upward when the vehicle speed is low, as in the case of the wind speed.

  And after step S112, it returns to the flow of FIG. 2 by a return and progresses to step S120, and when the control part 71 judges that the convergence temperature grasped | ascertained in step S110 is 0 degrees C or less (Yes), It is determined that there is a risk of icing in the oxidant gas discharge flow path R, and the process proceeds to step S150 where control is performed to increase the load of the fuel cell FC as the operating condition of the heat generation amount of the fuel cell FC. This step S150 corresponds to the fuel cell heat generation control means in the present embodiment.

  As a means for increasing the load of the fuel cell FC, for example, the electric power taken out from the fuel cell FC may be increased and the power storage device (not shown) may be charged. As shown in FIG. 6, by increasing the load of the fuel cell FC and increasing the FC output, the amount of heat generated by the fuel cell FC increases, and the exhaust temperature of the cathode offgas discharged from the fuel cell FC increases. .

  As another means for increasing the load of the fuel cell FC, the circulation pump 38 (see FIG. 1) may be stopped or the rotational speed may be reduced. As a result, the cooling efficiency for cooling the fuel cell FC decreases, so that the amount of heat generated by the fuel cell FC increases and the exhaust temperature from the fuel cell FC increases.

  As shown in FIG. 7, the IV (current-voltage) characteristic of the fuel cell FC indicated by reference numeral F1 is set to an inefficient operating condition as indicated by reference numeral F2, and the heat generation amount of the fuel cell FC is increased. You may let them. Specifically, the stoichiometry is lowered, the air supply pressure is lowered, and the like. Thus, the calorific value can be increased over the entire output of the fuel cell FC by reducing the IV characteristics.

  And it progresses to step S160 and the control part 71 performs control which prohibits idling stop control. The idling stop control is, for example, control that stops the air compressor 31 and suppresses energy consumption and noise when the vehicle stops due to a signal waiting or the like. If the idling stop control is permitted here, the convergence temperature further decreases due to the stop of the air compressor 31. Therefore, the control to increase the exhaust temperature of the cathode off-gas in step S150 to prevent icing is useless, and oxidation is performed. On the contrary, the possibility that the water contained in the generated gas in the agent gas discharge channel R and the moisture contained in the wet cathode off-gas freeze will increase. Therefore, in this embodiment, when the control unit 71 determines that the convergence temperature is 0 ° C. or less and there is a risk of freezing, the idling stop control is prohibited.

  Thus, in the first embodiment, when applied to a fuel cell vehicle having an idling stop function, the controller 71 is provided with idling stop permission determination means for determining whether or not to allow idling stop control. If there is a risk of icing in the oxidant gas discharge channel R (S120, Yes), the idling stop control is prohibited while increasing the heat generation amount of the fuel cell FC (S160), thereby ensuring the risk of icing. Can be prevented.

  And it progresses to step S170 and the control part 71 judges whether the driving | operation of the fuel cell system 1 is continued. Note that the determination of continuation of operation can be made based on, for example, an on / off state of an ignition switch (not shown). In step S170, when the control unit 71 determines that the operation is continued with the ignition switch turned on (Yes), the control unit 71 returns to step S110 and grasps (estimates and corrects) the convergence temperature again (S111, S111). S112). In step S170, when the control unit 71 determines that the ignition switch is off and the operation is not continued (No), the control unit 71 proceeds to step S180 and performs a shutoff valve (not shown) provided in the hydrogen tank 21. To stop the hydrogen supply to the anode electrode 3 of the fuel cell FC, stop the air compressor 31 to stop the supply of air to the cathode electrode 4 of the fuel cell FC, and terminate the power generation. To do.

  On the other hand, in step S120, when the control unit 71 determines that the convergence temperature is not 0 ° C. or lower (No), the control unit 71 determines that there is no risk of icing in the oxidant gas discharge flow path R (no icing occurs). Then, the process proceeds to step S130, and the operating condition of the calorific value of the fuel cell FC is set to normal control. In other words, normal control refers to an operation that does not increase the load excessively, such as excessively charging the power storage device (not shown) or excessively consuming auxiliary equipment as described above. I mean.

  And it progresses to step S140 and the control part 71 performs control which permits idling stop control. In this case, since it can be determined that there is no risk of icing, idling stop control is permitted to suppress energy consumption and noise during idling stop.

  And it progresses to step S170, and when the control part 71 judges that an ignition switch is an ON state as mentioned above (Yes), it returns to step S110, grasps | ascertains convergence temperature again (S110), and an ignition. If it is determined that the switch is off (No), the process proceeds to step S180 and power generation is terminated.

  As described above, when the fuel cell vehicle is used in a low temperature (below freezing) environment, as shown in the graph A in FIG. The convergence temperature of the flow path R decreases as it moves away from the fuel cell FC, and may reach 0 ° C. or lower before being discharged out of the vehicle. As a result, even if high temperature cathode offgas is discharged from the fuel cell FC, the cathode offgas is cooled to 0 ° C. or lower while being discharged from the tail pipe 52 through the oxidant gas discharge channel R, and the fuel cell The water contained in the FC and water contained in the wet cathode offgas will freeze. Therefore, in the fuel cell system 1 of the first embodiment, as shown in the graph B of FIG. 8, it is estimated that the convergence temperature is 0 ° C. or less, and there is a possibility that icing may occur in the oxidant gas discharge flow path R. If determined, the load of the fuel cell FC is increased, the amount of heat generated by the fuel cell FC is increased, and the exhaust gas temperature of the cathode off-gas discharged from the fuel cell FC is increased, whereby the oxidant gas discharge channel. The temperature rises in all parts of R, and the cathode offgas can be discharged out of the vehicle before the cathode offgas freezes.

(Second Embodiment)
FIG. 9 is a flowchart showing the anti-icing control of the second embodiment, and FIG. 10 is a map showing the relationship between the convergence temperature and the amount of heat generated by the fuel cell. The configuration of the fuel cell system in the second embodiment is the same as that of the fuel cell system 1 in the first embodiment. Moreover, in the flowchart shown in FIG. 9, about the control similar to 1st Embodiment, the same step code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 9, when the control unit 71 determines in step S120 that the convergence temperature is 0 ° C. or lower (Yes), the control unit 71 determines that there is a risk of icing in the oxidant gas discharge flow path R. Then, the process proceeds to step S151, and control is performed to increase (UP) the amount of heat generated by the fuel cell FC based on the map shown in FIG. The map shown in FIG. 10 is obtained in advance by a test or the like for the correlation between the convergence temperature and the heat generation amount of the fuel cell FC (FC heat generation amount). In this way, by using the map shown in FIG. 10, for example, the amount of heat generated by the fuel cell FC becomes Q when the convergence temperature is T1 (<0 ° C.), so only the load on the fuel cell FC is increased. Therefore, the temperature increase of the cathode off gas can be controlled quickly. In this way, using the map (FIG. 10) obtained in advance in the test (test), the rate of increase in the calorific value according to the convergence temperature with reference to the calorific value of the fuel cell FC when the convergence temperature is 0 ° C. Since Δq can be set immediately, the calorific value can be increased instantaneously.

(Third embodiment)
FIG. 11 is a flowchart showing the anti-icing control of the third embodiment. In addition, the structure of the fuel cell system in 3rd Embodiment is the same as that of the fuel cell system 1 in 1st Embodiment. Moreover, in the flowchart shown in FIG. 11, the same step code | symbol is attached | subjected about the control similar to 1st Embodiment, and the description is abbreviate | omitted.

  As shown in FIG. 11, in step S150, the controller 71 increases the amount of heat generated by the fuel cell FC, and then proceeds to step S154 to determine whether or not the convergence temperature is higher than a predetermined temperature. The convergence temperature here is a temperature grasped (estimated and corrected) in the same manner as in step S110. Further, the predetermined temperature in step S154 may be the same value as the predetermined temperature (0 ° C.) in step S120, or may be a value slightly higher (eg, 5 ° C.) than the predetermined temperature (0 ° C.) in step S120. It may be changed as appropriate. In step S154, when the control unit 71 determines that the convergence temperature is not higher than the predetermined temperature (No), the control unit 71 proceeds to step S160 and prohibits the idling stop control. In step S154, when the control unit 71 determines that the convergence temperature is higher than the predetermined temperature (Yes), the control unit 71 proceeds to step S130, and decreases the flow rate of the cathode off gas to the flow rate in the case of normal control, and step S140. As for idling stop control, if it is set to permit, the permission is maintained, and if it is set to prohibit, it is changed to permit.

  Thus, in the third embodiment, the convergence temperature after the heat generation amount of the fuel cell FC is increased and the heat generation amount can be increased by a necessary amount, so that the heat generation amount is not increased excessively. It is possible to reduce adverse effects (drying etc.) and energy consumption on the electrolyte membrane 2 due to excessive temperature rise.

(Fourth embodiment)
FIG. 12 is a flowchart showing the anti-icing control of the fourth embodiment. In addition, the structure of the fuel cell system in 4th Embodiment becomes a structure in which the control part 71 of the fuel cell system 1 in 1st Embodiment further contains a fuel cell over-permissible temperature determination means. Moreover, in the flowchart shown in FIG. 12, the same step code | symbol is attached | subjected about the control similar to 1st Embodiment, and the description is simplified and demonstrated.

  As shown in FIG. 12, when the control unit 71 determines in step S120 that the convergence temperature is 0 ° C. or lower (Yes), the process proceeds to step S121, and the temperature of the fuel cell FC (FC temperature) is allowed. Determine whether the range is exceeded. Note that step S121 corresponds to the fuel cell over-permissible temperature determining means of the present embodiment. Further, exceeding the allowable range means, for example, that the electrolyte membrane 2 is excessively dried and the deterioration of the fuel cell FC proceeds. The temperature of the fuel cell FC is a temperature detected by the fuel cell temperature sensor S1. Further, the temperature of the fuel cell FC at this time can be appropriately changed according to, for example, the type of the electrolyte membrane 2.

  In step S121, when the control unit 71 determines that the temperature of the fuel cell FC does not exceed the allowable range (No), the control unit 71 proceeds to step S150, increases the heat generation amount of the fuel cell FC, and proceeds to step S160. , Idling stop control is prohibited. In step S121, when the control unit 71 determines that the temperature of the fuel cell FC exceeds the allowable range (Yes), the control unit 71 proceeds to step S130 and sets the heat generation amount of the fuel cell FC to normal control. In step S140, idling stop control is permitted.

  As described above, in the fourth embodiment, since the heat generation amount of the fuel cell FC is increased so as not to exceed the allowable temperature of the fuel cell FC, it is possible to prevent the deterioration of the electrolyte membrane 2 due to excessive heating.

  In each of the above-described embodiments, the convergence temperature is grasped (estimated and corrected) using the FC output, the outside air temperature, and the wind speed (vehicle speed). However, when the convergence temperature is the lowest in the oxidant gas discharge flow path R. A temperature sensor may be provided at an expected position. Thus, by directly grasping the convergence temperature, the control by step S110 in FIG. 2 (subflow shown in FIG. 3) can be eliminated.

  The present invention may be configured by selectively combining the first to fourth embodiments as appropriate.

It is a whole block diagram of the fuel cell system of this embodiment. It is a flowchart which shows the anti-icing control of 1st Embodiment. It is a subflow chart which shows control which grasps convergence temperature. It is a map which shows the relationship between convergence temperature and the output of a fuel cell. It is a map for correcting convergence temperature. It is a map which shows the relationship between exhaust temperature and the output of a fuel cell. It is a graph which shows the IV characteristic of the fuel cell before and behind the countermeasure which increases the load of a fuel cell. It is a graph which shows the change of the convergence temperature before and behind a countermeasure. It is a flowchart which shows the anti-icing control of 2nd Embodiment. It is a map which shows the relationship between convergence temperature and the emitted-heat amount of a fuel cell. It is a flowchart which shows the anti-icing control of 3rd Embodiment. It is a flowchart which shows the anti-icing control of 4th Embodiment.

Explanation of symbols

1 Fuel Cell System 71 Control Unit (Oxidant gas temperature grasping means, fuel cell warm-up completion judging means, fuel cell heat generation amount controlling means, fuel cell over-permissible temperature judging means)
FC fuel cell R Oxidant gas discharge flow path S1 Fuel cell temperature sensor (fuel cell temperature detection means)
S2 Outside air temperature sensor (outside air temperature detection means)
S4 Current sensor (fuel cell output detection means)
S5 Voltage sensor (fuel cell output detection means)

Claims (5)

A fuel cell that is supplied with oxidant gas and fuel gas to generate electricity;
Fuel cell heating value control means for controlling the heating value of the fuel cell;
An oxidant gas discharge passage through which the oxidant gas discharged from the fuel cell is circulated and discharged;
An oxidant gas discharge channel temperature grasping means for grasping a convergence temperature of the oxidant gas discharge channel;
Fuel cell warm-up completion determining means for determining whether the fuel cell has been warmed-up;
A fuel cell system comprising:
After the completion of warming-up of the fuel cell is detected by the fuel cell warming-up completion determining means, and the convergence temperature obtained by the oxidant gas discharge channel temperature grasping means is not more than a predetermined temperature, the fuel cell A fuel cell system characterized in that the temperature of the fuel cell is raised by the calorific value control means above the temperature at the time of grasping the convergence temperature. Fuel cell output detection means for detecting the output of the fuel cell;
An outside air temperature detecting means for detecting the outside air temperature,
The oxidant gas discharge channel temperature grasping means estimates the convergence temperature based on the output of the fuel cell detected by the fuel cell output detecting means and the outside air temperature detected by the outside air temperature detecting means. The fuel cell system according to claim 1.   A correlation between the calorific value of the fuel cell and the convergence temperature of the oxidant gas discharge passage is obtained in advance, and the fuel is determined according to the convergence temperature obtained by the oxidant gas discharge passage temperature grasping means. The fuel cell system according to claim 1 or 2, wherein a heat generation amount of the battery is controlled.   The fuel cell according to any one of claims 1 to 3, wherein the fuel cell heat generation amount control means increases the heat generation amount of the fuel cell until the convergence temperature becomes higher than a predetermined temperature. system. Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
A fuel cell over-permissible temperature determining means for determining whether or not the temperature of the fuel cell exceeds an allowable range,
When the temperature of the fuel cell detected by the fuel cell temperature detection means is determined by the fuel cell over-permissible temperature determination means to exceed the allowable temperature of the fuel cell, the amount of heat generated by the fuel cell heat generation amount control means The fuel cell system according to any one of claims 1 to 4, wherein the control for raising the temperature is stopped.

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