JP2008277075A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing freezing of an exhaust channel after finish of warm-up. <P>SOLUTION: After finish of warm-up (S20, Yes), focusing temperature T2 of an oxidant gas exhaust flow channel is detected (S30), and, if the focusing temperature T2 is below 5°C, (a first given temperature), an I/C bypass control supplying air from the air compressor without passing it through a cooling unit is carried out (S50). Then, a focusing temperature T2 is detected (S60), and, if it is above 10°C (S70, Yes), the I/C bypass control is finished (S100). Further, if the focusing temperature T2 is not above 10°C (S70, No), a temperature (FC temperature T1) of the fuel cell is detected, and the I/C bypass control is finished (S100) if the FC temperature T1 is above 95°C as an allowable temperature of the fuel cell (S90, Yes). <P>COPYRIGHT: (C)2009,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.

  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 generates power by being supplied with an oxidant gas and a fuel gas, an oxidant gas supply unit that supplies an oxidant gas to the fuel cell, the oxidant gas supply unit, A heat exchanger that is provided in a gas flow path between the fuel cell and cools the oxidant gas supplied to the fuel cell, and the oxidant gas from the oxidant gas supply means bypasses the heat exchanger. And a heat exchanger bypass flow path that supplies the fuel cell, a switching means that switches between the flow path having the heat exchanger and the bypass flow path, and an oxidant gas discharged from the fuel cell flows. Determining whether or not the warm-up of the fuel cell has been completed; and an oxidant gas discharge passage temperature grasping means for grasping a convergence temperature of the oxidant gas discharge passage; A fuel cell comprising: a fuel cell warm-up completion determining unit The convergence temperature obtained by the oxidant gas discharge passage temperature grasping means is a first predetermined temperature after completion of warming up of the fuel cell is detected by the fuel cell warm-up completion judging means. In the following cases, the switching means bypasses the heat exchanger and controls to supply the oxidant gas to the fuel cell.

  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 the first predetermined temperature (for example, 5 ° C.), the heat exchanger is bypassed, so the oxidant discharged from the fuel cell. Before the gas falls to the freezing temperature, the gas is discharged outside the fuel cell system (outside the system). For this reason, it is possible to prevent the water contained in the generated water or 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 and the piping etc. is blocked and damaged. Can be prevented.

  The invention according to claim 2 is based on the control when the convergence temperature grasped by the oxidant gas discharge channel temperature grasping means is equal to or higher than a second predetermined temperature set higher than the first predetermined temperature. The detouring of the heat exchanger is stopped.

  According to the invention of claim 2, since the second predetermined temperature is set to a value higher than the first predetermined temperature, it is possible to prevent the oxidant gas discharge flow path from becoming below freezing point immediately after the end of the control, It is possible to prevent freezing in the oxidant gas discharge channel.

  The invention according to claim 3 includes fuel cell temperature detecting means for detecting the temperature of the fuel cell, and fuel cell allowable temperature determining means for determining whether or not the fuel cell exceeds an allowable temperature range. When the temperature of the fuel cell detected by the fuel cell temperature detecting means is determined to have exceeded the allowable temperature by the fuel cell allowable temperature determining means, the bypass of the heat exchanger by the control is stopped. It is characterized by.

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

  The invention according to claim 4 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 fourth aspect of the present invention, in order to estimate the temperature of the oxidant gas discharge channel from the power generation performance (output) of the fuel cell and the outside air temperature, the apparatus for directly measuring the temperature of the oxidant gas discharge channel ( The temperature can be grasped without installing a sensor.

  The invention according to claim 5 includes fuel cell heat generation amount control means for controlling the heat generation amount by power generation of the fuel cell, and the fuel cell heat generation amount control means bypasses the heat exchanger by the switching means. The heating value of the fuel cell is increased.

  According to the fifth aspect of the present invention, since the bypass control of the heat exchanger is performed while increasing the calorific value of the fuel cell, the temperature of the off-gas passing through the oxidant gas discharge channel rises, and the oxidant gas discharge flow It is possible to reliably prevent road icing. Also, bypassing the heat exchanger is more responsive to temperature than increasing the amount of heat generation, so the high-temperature oxidant gas can be supplied quickly by performing heat exchanger bypass control in advance. It becomes possible to do.

  According to a sixth aspect of the present invention, when the convergence temperature detected when the heat exchanger bypasses the heat exchanger is equal to or higher than a third predetermined temperature, the fuel by the fuel cell heat generation amount control means It is characterized by not performing control for increasing the amount of heat generated by the battery.

  According to the invention of claim 6, since the heat generation amount increase control is not performed when the convergence temperature exceeds the third predetermined temperature without performing the heat generation amount increase control only by the bypass control of the heat exchanger, the heat generation amount is not performed. It becomes possible to suppress the fuel consumption consumed by the power generation for the rise, and it is possible to prevent icing in the piping while improving the fuel efficiency.

  According to a seventh aspect of the present invention, in the case where a temperature change amount per unit time of the convergence temperature detected when the heat exchanger is bypassed by the switching means is equal to or greater than a predetermined change amount, the fuel cell It is characterized by not performing the increase control of the calorific value of the fuel cell by the calorific value control means.

  According to the invention of claim 7, since the heat generation amount increase control is not performed when the convergence temperature exceeds the third predetermined temperature without performing the heat generation amount increase control only by the bypass control of the heat exchanger, the heat generation amount is not performed. It becomes possible to suppress the fuel consumption consumed by the power generation for the rise, and it is possible to prevent icing in the piping while improving the fuel efficiency.

  According to the fuel cell system of the present invention, it is possible to prevent icing of the discharge path after completion of warm-up.

(First embodiment)
FIG. 1 is an overall configuration diagram of the fuel cell system of the first embodiment, FIG. 2 is a flowchart showing anti-icing control of the first embodiment, and FIG. 3 is a graph showing changes in convergence temperature before and after the countermeasure. In the following, an automobile equipped with a fuel cell system will be described as an example. However, the present invention is not limited to this and may be applied to a ship, an aircraft, a stationary household power source, and the like.

  As shown in FIG. 1, the fuel cell system 1A according to the first embodiment includes a fuel cell FC, an anode system 20, a cathode system 30, a dilution system 40, an exhaust system 50, a control system 70, and the like.

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

  The anode system 20 supplies hydrogen as fuel gas to the anode 3 of the fuel cell FC and discharges hydrogen from the anode 3. The hydrogen tank 21, ejector 22, purge valve 23, and pipes 24 a and 24 b are discharged from the anode 3. 24c, 24d, etc.

  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 of the fuel cell FC 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 out of the system. The impurities are nitrogen contained in the air that has permeated from the cathode 4 to the anode 3 through the electrolyte membrane 2.

  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 an inlet on the anode 3 side of the fuel cell FC. One end of the pipe 24 c is connected to the anode 3 side outlet 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 4 of the fuel cell FC, and discharges air and the like from the cathode 4, and includes an air compressor 31, a cooler 32, and a switching valve. 33, a bypass pipe 34, a humidifier 35, a back pressure valve 36, and the like.

  The air compressor 31 is constituted by 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 cooler 32 is a so-called intercooler (I / C), and has a function of cooling the air that has been compressed by the air compressor 31 to a high temperature. The cooler 32 is connected to the air compressor 31 via the cathode supply pipe 37a. The cooler 32 may be air-cooled or water-cooled.

  The switching valve 33 is provided downstream of the cooler 32, is controlled to be opened and closed by a control unit 71 described later, and is connected to the cooler 32 via a cathode supply pipe 37b.

  The bypass pipe 34 is branched from the cathode supply pipe 37 a, bypasses the cooler 32 and the switching valve 33, and merges with the cathode supply pipe 37 c connected downstream of the switching valve 33. It is connected.

  The humidifier 35 includes 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 air from the air compressor 31 is humidified by circulating a cathode off gas (wet air, generated water) discharged from the cathode 4 of the fuel cell FC. That is, an inlet through which air before humidification is introduced is connected to the cathode supply pipe 37c, and an outlet from which the air after humidification is discharged is connected via the inlet of the cathode 4 of the fuel cell FC and the cathode supply pipe 37d. Are connected to each other through an outlet of the cathode 4 of the fuel cell FC and a cathode discharge pipe 38a. Connected through.

  The back pressure valve 36 is constituted by a butterfly valve, for example, and has a function of appropriately adjusting the pressure of air supplied to the cathode 4 of the fuel cell FC.

  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 42 a connected to one end on the downstream side of the purge valve 23 and a pipe 42 b connected to one end on the downstream side of the back pressure valve 36. Hydrogen discharged from the anode 3 of the FC and cathode off gas (air, water, etc.) discharged from the cathode 4 of the fuel cell FC are mixed and diluted to be discharged. When the hydrogen discharged from the fuel cell FC passes through the diluter 41, the hydrogen diluted to a hydrogen concentration below a 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, and includes, for example, a cylindrical case that is divided into a plurality of interiors and provided with a sound absorbing material. The tail pipe 52 is a pipe connected to one end on the downstream side of the silencer 51, and is configured such that one end on the downstream side communicates 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 cathode discharge pipe 38a, the flow path on the humidifying side of the humidifier 35, the cathode discharge pipe 38b, the pipe 42b, the diluter 41, the pipe 53, the silencer 51, and the tail pipe after the outlet of the cathode 4 of the fuel cell FC. 52 constitutes the oxidant gas discharge flow path R (see FIG. 1) of the present embodiment. Moreover, the cathode supply pipes 37a to 37c correspond to the gas flow paths in the present embodiment.

  The control system 70 includes a control unit 71, a fuel cell temperature sensor 72, a discharge channel temperature sensor 73, 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 warm-up completion determination unit and a fuel cell allowable temperature determination unit. The control unit 71 is electrically connected to the purge valve 23, the air compressor 31, the switching valve 33, the back pressure valve 36, the fuel cell temperature sensor 72, and the discharge flow path temperature sensor 73. The rotational speed of 31 and the opening degree of the back pressure valve 36 are controlled, and each temperature (° C.) detected by a fuel cell temperature sensor 72 and a discharge flow path temperature sensor 73 described later is acquired.

  The fuel cell temperature sensor 72 is a sensor that detects the temperature of the fuel cell FC, and is provided, for example, in the vicinity of the outlet of the anode 3 of the fuel cell FC. As long as the temperature of the fuel cell FC can be detected, the temperature of the fuel cell FC is not limited to the vicinity of the outlet of the anode 3 but may be provided near the outlet of the cathode 4 or the flow path of the refrigerant. It may be provided near the exit.

  The discharge channel temperature sensor 73 has a function of grasping (detecting) the convergence temperature of the present embodiment. For example, the exhaust channel temperature sensor 73 is connected to the tail pipe 52 that is predicted to have the lowest temperature at the position of the oxidant gas discharge channel R. Is provided.

  Next, the anti-icing control in the fuel cell system 1A of the first embodiment will be described with reference to FIG. 2 (refer to FIG. 1 as appropriate). 2 is described on the assumption that the fuel cell FC is started under a low temperature environment in which the fuel cell FC is warmed up.

  First, when an ignition switch (not shown) of the fuel cell vehicle (vehicle) is switched from OFF to ON, the control unit 71 detects the fuel cell temperature (FC temperature in FIG. 2) from the fuel cell temperature sensor 72 in step S10. Notation) T1 is detected. In addition, the control unit 71 opens a shut-off valve (not shown) provided in the hydrogen tank 21, hydrogen is supplied from the hydrogen tank 21 to the anode 3 of the fuel cell FC, and driving of the air compressor 31 is started to drive the fuel. Air that is cooled by the cooler 32 and humidified by the humidifier 35 is supplied to the cathode 4 of the battery FC. In the anode 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 4. In the cathode 4, water is generated by the reaction of electrons transferred from the anode 3 through the load to the cathode 4, hydrogen ions that have passed through the electrolyte membrane 2, and oxygen in the air by the action of the catalyst. Thus, in the fuel cell FC, power is generated and water is generated.

  And it progresses to step S20 and the control part 71 judges whether warming-up was completed. The warm-up is a process executed when the fuel cell system 1A is used in a low temperature environment (below freezing point). For example, air is supplied to the fuel cell FC at a higher flow rate and pressure than in normal operation. This is a process performed by generating power at a high output of the fuel cell FC. Further, as a condition for determining the completion of warm-up, it can be determined that the warm-up is completed when the temperature of the fuel cell FC exceeds a predetermined temperature (for example, 30 ° C.). In addition, this step S20 corresponds to the process performed by the fuel cell warm-up completion determination unit in the present embodiment. In step S20, the control unit 71 returns to step S10 when determining that the warm-up is not completed (No), and proceeds to step S30 when determining that the warm-up is completed (Yes). .

  In step S <b> 30, the control unit 71 grasps the convergence temperature T <b> 2 of the oxidant gas discharge channel R after the outlet of the cathode 4 from the discharge channel temperature sensor 73. Note that step S30 corresponds to the processing performed by the oxidant gas discharge channel temperature grasping means in the present embodiment.

  And it progresses to step S40 and the control part 71 judges whether the convergence temperature T2 is 5 degrees C (1st predetermined temperature) or less. The first predetermined temperature is set to a temperature before freezing. In Step 40, when the control unit 71 determines that the convergence temperature T2 is 5 ° C. or lower (Yes), the control unit 71 proceeds to Step S50 and determines that the convergence temperature T2 is not 5 ° C. or lower (No). To return.

  In step S <b> 50, the control unit 71 starts control for bypassing the cooler (I / C) 32. That is, by closing the switching valve 33, the compressed high-temperature air from the air compressor 31 passes through the bypass pipe 34, and high-temperature air that does not pass through the cooler 32 is supplied to the fuel cell FC.

  Then, the process proceeds to step S <b> 60, and the control unit 71 grasps the convergence temperature T <b> 2 of the oxidant gas discharge channel R from the discharge channel temperature sensor 73. Step S60 corresponds to the process performed by the oxidant gas discharge channel temperature grasping means of the present embodiment.

  Then, the process proceeds to step S70, and if the control unit 71 determines that the convergence temperature T2 is not 10 ° C. (second predetermined temperature) or higher (No), the process proceeds to step S80, where the FC temperature T1 is detected from the fuel cell temperature sensor 72. Is detected. The second predetermined temperature is set to a temperature higher than the first predetermined temperature.

  In Step S70, control part 71 progresses to Step S100, when it judges that convergence temperature T2 is 10 ° C or more (Yes). In step S <b> 100, the control unit 71 ends the control for bypassing the cooler (I / C) 32. That is, by opening the switching valve 33, the compressed high-temperature air from the air compressor 31 is supplied to the fuel cell FC without passing through the bypass pipe 34. Thereby, the air cooled by the cooler 32 and humidified by the humidifier 35 is supplied to the fuel cell FC.

  And it progresses to step S90 and the control part 71 judges whether FC temperature T1 is 95 degreeC or more. The 95 ° C. set here is the allowable temperature of the fuel cell FC. However, the allowable temperature can be variously changed according to the type of the fuel cell FC. Further, this step S90 corresponds to the processing performed by the fuel cell allowable temperature determining means of the present embodiment. In step S90, when the control unit 71 determines that the FC temperature T1 is not 95 ° C. or higher (No), the control unit 71 determines that the fuel cell FC is within the allowable temperature range, returns to step S60, and returns to the I / O. If the C bypass control is continued and it is determined that the FC temperature T1 is 95 ° C. or higher (Yes), it is determined that the allowable temperature of the fuel cell FC is exceeded, and the process proceeds to step S100, where the I / C bypass control is performed. Exit.

  By the way, when the fuel cell vehicle is used in a low temperature (below freezing point) environment, as shown in the graph A of FIG. The convergence temperature of R decreases as it moves away from the fuel cell FC, and may reach 0 ° C. or lower before being discharged outside 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. Thus, in the fuel cell system 1A of the first embodiment, the discharge flow path temperature sensor 73 detects that the convergence temperature is 5 ° C. (not shown) or less, and there is a risk that icing will occur in the oxidant gas discharge flow path R. In some cases, the high temperature air from the air compressor 31 bypasses the cooler 32 and is supplied to the fuel cell FC, so that the cathode off-gas discharged from the fuel cell FC as shown in graph B of FIG. As the exhaust gas temperature rises, the cathode off-gas is discharged outside the vehicle before it freezes. As a result, it is possible to prevent the icing from proceeding and the piping and the like from being blocked and damaged.

  In the first embodiment, the second predetermined temperature higher than the first predetermined temperature is set, and the I / C bypass control is stopped when the temperature is equal to or higher than the second predetermined temperature. It is possible to prevent the discharge flow path R from becoming lower than the first predetermined temperature, and it is possible to prevent the oxidant gas discharge flow path R from freezing.

  In the first embodiment, when the fuel cell FC is at or above the allowable temperature, the control for bypassing the cooler 32 is stopped, so that deterioration of the membrane electrode structure due to excessive heating of the fuel cell FC is prevented. It becomes possible.

(Second Embodiment)
FIG. 4 is a flowchart showing the anti-icing control of the second embodiment, and FIG. 5 is a graph showing an example of a temperature change in the anti-icing control of the second embodiment. In the fuel cell system of the second embodiment, the control unit 71 of the fuel cell system 1A of the first embodiment further includes a fuel cell heat generation amount control means. Also, in the flow of FIG. 4, the same processing as that of the first embodiment of FIG.

  As shown in FIG. 4, in step S70, when the control unit 71 determines that the convergence temperature T2 detected in step S60 is not 10 ° C. (second predetermined temperature) or higher (No), the process proceeds to step S71A. It is determined whether or not the convergence temperature T2 detected in step S60 is 3 ° C. (third predetermined temperature) or higher. In addition, the 3rd predetermined temperature in this embodiment is lower than the 1st predetermined temperature (5 degreeC), for example, and is set to the temperature before freezing.

  In step S71A, when the convergence temperature T2 is not 3 ° C. or higher (No), the control unit 71 proceeds to step S72 and starts control for increasing the amount of heat generated by the fuel cell FC. Note that the heat generation amount increase control is, for example, a process of increasing the amount of electric power extracted from the fuel cell FC by increasing the amount of air supplied from the air compressor 31 and consuming a large amount of oxygen and hydrogen in the air. . Note that the electric power taken out from the fuel cell FC is charged in a power storage device (not shown). By increasing the output of the fuel cell FC in this manner, the amount of heat generated by the fuel cell FC is increased, and the exhaust temperature of the cathode off gas discharged from the fuel cell FC is increased.

  In step S71A, when the convergence temperature T2 is 3 ° C. or higher (Yes), the control unit 71 proceeds to step S73 and does not perform control to increase the amount of heat generated by the fuel cell FC. The convergence temperature T2 of 3 ° C. or higher means that there is no risk of freezing in the oxidant gas discharge flow path R, and it can be covered only by I / C bypass control without increasing the heat generation amount of the fuel cell FC. I mean.

  In step S100, when the I / C bypass control and the heat generation amount increase control are being executed, both controls are terminated, and when only the I / C bypass control is being executed, the I / C is End bypass control.

  As shown in FIG. 5, the I / C bypass control (bypass in FIG. 5) bypasses the cooler 32 when the convergence temperature T2 becomes 5 ° C. (first predetermined temperature) or less at time t1 after completion of warm-up. Control and abbreviation) are started. Even if the I / C bypass control is executed, the convergence temperature T2 is lowered, and when the convergence temperature T2 becomes 3 ° C. (third predetermined temperature) or less at time t2, heat is generated while the I / C bypass control is executed. Start volume increase control. By the I / C bypass control and the heat generation amount increase control, the convergence temperature T2 stops decreasing, and the convergence temperature T2 starts to increase. At time t3, when the convergence temperature T2 exceeds 3 ° C. (third predetermined temperature), the heat generation amount increase control is stopped and only the I / C bypass control is performed. At time t4, the I / C bypass control is ended when the convergence temperature T2 becomes 10 ° C. (second predetermined temperature) or higher set higher than 5 ° C. (first predetermined temperature). Thus, icing in the oxidant gas discharge flow path R can be prevented by switching and controlling the I / C bypass control and the heat generation amount increase control.

  Further, in the second embodiment, since the I / C bypass control is performed while the heat generation amount increase control of the fuel cell FC is performed, it is possible to reliably prevent the oxidant gas discharge channel R from freezing. Moreover, in 2nd Embodiment, since I / C bypass control is performed ahead of calorific value raise control, it becomes possible to supply hot air rapidly. This is because bypassing the cooler 32 is more responsive to temperature than increasing the amount of heat generation.

  In the second embodiment, since the heat generation amount increase control is not performed when the convergence temperature T2 exceeds the third predetermined temperature, the hydrogen consumption (fuel consumption) consumed by the power generation for increasing the heat generation amount is reduced. Therefore, it is possible to prevent icing in the oxidant gas discharge channel R while improving fuel efficiency.

(Third embodiment)
FIG. 6 is a flowchart showing the anti-icing control of the third embodiment, and FIG. 7 is a graph showing an example of a temperature change in the anti-icing control of the third embodiment. In the fuel cell system of the third embodiment, the control unit 71 of the fuel cell system 1A of the first embodiment further includes a fuel cell heat generation amount control means. Further, the flow of FIG. 6 is the same as that of the second embodiment except that step S71B is used instead of step 71A of the flow of the second embodiment.

  As shown in FIG. 6, in step S70, when the convergence temperature T2 detected in step S60 is not 10 ° C. or higher (No), the control unit 71 proceeds to step S71B, and the temperature per unit time of the convergence temperature T2 It is determined whether or not the increase change amount (temperature change amount) is a predetermined value or more. The predetermined value is set to a positive value, for example. In step S71B, when the control unit 71 determines that the temperature increase change amount per unit time of the convergence temperature T2 is equal to or greater than a predetermined value (Yes), the control unit 71 proceeds to step S73 and does not perform the heat generation amount increase control. If the temperature increase change amount per unit time of the convergence temperature T2 is not equal to or greater than the predetermined value (No), the process proceeds to step S72, and the heat generation amount increase control is started.

  As shown in FIG. 7, the I / C bypass control (bypass in FIG. 4) bypasses the cooler 32 when the convergence temperature T2 becomes 5 ° C. (first predetermined temperature) or lower at time t1 after completion of warm-up. Control and abbreviation) are started. Even when the I / C bypass control is executed, the convergence temperature T2 is lowered, and at time t2, the temperature increase change amount (ΔTa / Δt) per unit time of the convergence temperature T2 is negative. The heat generation amount increase control is started while executing. By the I / C bypass control and the heat generation amount increase control, the convergence temperature T2 stops decreasing, and the convergence temperature T2 starts to increase. At time t3, since the temperature rise change amount (ΔTb / Δt) per unit time of the convergence temperature T2 is equal to or greater than a predetermined value, only the I / C bypass control is performed. At time t4, the I / C bypass control is ended when the convergence temperature T2 becomes 10 ° C. (second predetermined temperature) or higher set higher than 5 ° C. (first predetermined temperature).

  As described above, in the third embodiment, as in the second embodiment, the I / C bypass control is performed while the heat generation amount increase control of the fuel cell FC is performed, so that the oxidant gas discharge flow path R is reliably frozen. It becomes possible to prevent. In the third embodiment, since the I / C bypass control is performed prior to the heat generation amount increase control, high-temperature air can be supplied quickly. This is because bypassing the cooler 32 is more responsive to temperature than increasing the amount of heat generation.

(Fourth embodiment)
FIG. 8 is an overall configuration diagram of the fuel cell system of the fourth embodiment, FIG. 9 is a flowchart showing anti-icing control of the fourth embodiment, FIG. 10 is a map showing the relationship between the convergence temperature and the output of the fuel cell, and FIG. Is a map for correcting the convergence temperature based on the wind speed. In the fuel cell system 1B of the fourth embodiment, instead of the discharge channel temperature sensor 73 of the fuel cell system 1A of the first embodiment, a current sensor 74 and a voltage sensor 75 as fuel cell output detection means, an outside air temperature The configuration is the same as that of the first embodiment except that an outside air temperature sensor 76 as a detecting means is provided. That is, in the fourth embodiment, as the oxidant gas discharge channel temperature grasping means, the convergence temperature T2 is estimated based on the output from the fuel cell output detecting means and the outside air temperature from the outside air temperature detecting means. Yes.

  The current sensor 74 detects a current value taken from the fuel cell FC toward the load (see FIG. 8). The voltage sensor 75 detects the voltage value of the fuel cell FC. 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 outside air temperature sensor 76 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 output of the fuel cell FC is not limited to electric power, and may be current or voltage.

  As shown in FIG. 9, after the warm-up is completed (S20, Yes), the process proceeds to step S31, and the control unit 71 detects the output of the fuel cell FC. The output (electric power) at this time is obtained by the product of the current value detected by the current sensor 74 and the voltage value detected by the voltage sensor 75. Then, the process proceeds to step S <b> 32, and the control unit 71 detects the outside temperature by the outside temperature sensor 76.

  And it progresses to step S33 and the control part 71 estimates the convergence temperature T2 based on the map shown in FIG. In FIG. 10, the solid line illustrates 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. 10, and the outside air 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.

  Moreover, you may correct | amend based on the map shown in FIG. 11 about the convergence temperature estimated based on the map of FIG. That is, the corrected convergence temperature is lower than the convergence temperature estimated in FIG. 10 when the wind speed is high, and is higher than the convergence temperature estimated in FIG. 11 when the wind speed is low. The wind speed can be detected by providing a wind speed sensor, but the vehicle speed obtained from the vehicle speed sensor may be used instead of the wind speed.

  Thus, in the fourth embodiment, since the convergence temperature in the oxidant gas discharge channel R is estimated based on the power generation performance (output; power) of the fuel cell FC, the outside air temperature, and the like, the oxidant gas discharge channel The temperature can be grasped without installing a device (temperature sensor) that directly measures the temperature in R.

  Note that step S60A in FIG. 9 estimates the convergence temperature T2 in the same manner as steps S31 to S33. In the fourth embodiment, the case where the present invention is applied to the first embodiment has been described as an example. However, the present invention is not limited to this and may be applied to the second embodiment or the third embodiment.

  The present invention is not limited to the above-described embodiment. For example, the rotational speed of the motor of the air compressor 31 is increased to increase the flow rate of the cathode off-gas flowing through the oxidant gas discharge channel R. May be. By increasing the flow rate, the cathode off-gas can be discharged from the oxidant gas discharge channel R before freezing occurs.

  Further, the first predetermined temperature, the second predetermined temperature, and the third predetermined temperature set in each of the above-described embodiments are examples, and can be appropriately changed.

1 is an overall configuration diagram of a fuel cell system according to a first embodiment. It is a flowchart which shows the anti-icing control of 1st Embodiment. 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. The graph which shows an example of the temperature change in the anti-icing control of 2nd Embodiment. It is a flowchart which shows the anti-icing control of 3rd Embodiment. The graph which shows an example of the temperature change in the anti-icing control of 3rd Embodiment. It is a whole block diagram of the fuel cell system of 4th Embodiment. It is a flowchart which shows the anti-icing control of 4th Embodiment. It is a map which shows the relationship between convergence temperature and the output of a fuel cell. It is a map for correct | amending convergence temperature based on a wind speed.

Explanation of symbols

1A, 1B Fuel cell system 31 Air compressor (oxidant gas supply means)
32 Cooler (heat exchanger)
33 Switching valve (switching means)
34 Bypass piping (heat exchanger bypass flow path)
37a to 37c Cathode supply piping (gas flow path)
71 Control Unit 72 Fuel Cell Temperature Sensor (Fuel Cell Temperature Detection Means)
73 Discharge channel temperature sensor (oxidant gas discharge channel temperature grasping means)
74 Current sensor (fuel cell output detection means)
75 Voltage sensor (fuel cell output detection means)
76 Outside temperature sensor (outside temperature detection means)
FC fuel cell R Oxidant gas discharge flow path

Claims (7)

A fuel cell that is supplied with oxidant gas and fuel gas to generate electricity;
An oxidant gas supply means for supplying an oxidant gas to the fuel cell;
A heat exchanger that is provided in a gas flow path between the oxidant gas supply means and the fuel cell and cools the oxidant gas supplied to the fuel cell;
A heat exchanger bypass flow path for supplying the oxidant gas from the oxidant gas supply means to the fuel cell by bypassing the heat exchanger;
Switching means for switching between the gas flow path having the heat exchanger and the heat exchanger bypass flow path;
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 warm-up of the fuel cell is detected by the fuel cell warm-up completion determination unit, when the convergence temperature obtained by the oxidant gas discharge channel temperature grasping unit is equal to or lower than a first predetermined temperature, A fuel cell system characterized in that control is performed to bypass the heat exchanger by means of switching means and to supply oxidant gas to the fuel cell.   When the convergence temperature obtained by the oxidant gas discharge channel temperature grasping means is equal to or higher than the second predetermined temperature set higher than the first predetermined temperature, the bypass of the heat exchanger by the control is stopped. The fuel cell system according to claim 1, wherein: Fuel cell temperature detecting means for detecting the temperature of the fuel cell;
Fuel cell allowable temperature determination means for determining whether or not the fuel cell exceeds a range of allowable temperature, and
When the temperature of the fuel cell detected by the fuel cell temperature detecting means is determined to have exceeded the allowable temperature by the fuel cell allowable temperature determining means, the bypass of the heat exchanger by the control is stopped. The fuel cell system according to claim 1 or 2, characterized in that 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 any one of claims 1 to 3, wherein the fuel cell system is characterized in that: A fuel cell heat generation amount control means for controlling a heat generation amount by power generation of the fuel cell;
5. The heat generation amount of the fuel cell is increased by the fuel cell heat generation amount control unit after the heat exchanger is detoured by the switching unit. 6. Fuel cell system.   When the convergence temperature detected when the heat exchanger bypasses the heat exchanger is equal to or higher than a third predetermined temperature, the fuel cell heat generation amount control means controls the increase in the heat generation amount of the fuel cell. The fuel cell system according to claim 5, which is not performed.   When the temperature change amount per unit time of the convergence temperature detected when the heat exchanger is bypassed by the switching means is a predetermined value or more, the fuel cell heat generation amount control means 6. The fuel cell system according to claim 5, wherein the control for increasing the calorific value is not performed.

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