JP2007122962A - Fuel cell system, and antifreezing method of cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent freezing by eliminating the deviation of a temperature distribution generated in a cooling system cooling a fuel cell. <P>SOLUTION: The prevention of freezing is realized by detecting the temperature of cooling water in a reservoir tank 43 which is installed at a cooling water supply piping 44 to let the cooling water to cool a fuel cell stack 10 pass through, and which supplies the cooling water to be circulated in the cooling water supply piping 44 by a cooling water pump 41, and by controlling work quantities of the cooling water pump 41 so that a cooling water flow amount of the cooling water to be circulated in the cooling water supply piping 44 will be increased temporarily for a prescribed time as the detected temperature of the cooling water reaches closer to the freezing point at every fixed time or at the timing decided based on the detected temperature of the cooling water in the reservoir tank. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system and a cooling system anti-freezing method that satisfactorily eliminates an uneven temperature distribution in a cooling system of a fuel cell and prevents freezing.

  In response to the fossil fuel depletion crisis, air pollution caused by fossil fuel combustion, and global warming, a vehicle that travels by consuming compressed fuel gas has been devised. As a vehicle that travels by consuming fuel gas in this way, for example, a fuel cell vehicle that uses hydrogen gas as the fuel gas and travels with electric energy generated by a chemical reaction between hydrogen gas and oxygen in the air gas. There is.

  In a fuel cell mounted on such a fuel cell vehicle or the like, moisture always remains inside the fuel cell from the start-up due to its power generation principle. Thus, since residual moisture exists inside the fuel cell, when the temperature falls below freezing point, the moisture freezes and the fuel cell system does not function.

  Therefore, when a moving body such as a vehicle equipped with a fuel cell is used in a cold region, or when the fuel cell is used for stationary use in a cold region, the fuel cell may be exposed to a low temperature environment. In the worst case, the fuel cell cannot be generated due to freezing.

Therefore, when starting the fuel cell in a cold region, in order to prevent the water generated inside the fuel cell from freezing, supply control of cooling water for cooling the fuel cell is performed according to the internal temperature of the fuel cell. Thus, a technique for preventing freezing of generated water generated inside the fuel cell is disclosed (for example, see Patent Document 1).
JP 2003-36874 A

  However, in the method disclosed in Patent Document 1, since the cooling water pump is stopped when the cooling water reaches a temperature at which there is a risk of freezing, the cooling water supply to the fuel cell is stopped. The heat generated by the fuel cell cannot be transmitted to the system. Therefore, for example, some components constituting the cooling system, such as a radiator, are continuously cooled by the outside air temperature, and thus such components are very likely to be frozen. Furthermore, in the technique disclosed in Patent Document 1, since the flow of the cooling water is stopped, the distribution of the internal temperature of the parts constituting the cooling water path and the cooling system is uneven, and the temperature is low. Freezing is also possible.

  Even if the temperature of the cooling water does not decrease until it freezes, when the cooling water temperature is used for operation control of the fuel cell, the cooling system has an uneven temperature distribution. There is also a problem that the temperature cannot be detected and stable operation control cannot be executed. As described above, when the temperature distribution of the fuel cell cooling system is uneven, various adverse effects are caused.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and provides a fuel cell system and a cooling system freezing prevention method for preventing a temperature distribution bias generated in a cooling system for cooling a fuel cell. Objective.

  In order to solve the above-described problems, the present invention provides cooling in a reservoir tank that is provided in a cooling path through which cooling water for cooling a fuel cell passes and supplies cooling water that is circulated in the cooling path by a cooling water circulation device. The temperature of the cooling water is detected, and the cooling water flow rate of the cooling water circulating in the cooling path is temporarily determined for a predetermined time at a fixed time or at a timing determined based on the detected temperature of the cooling water in the reservoir tank. The work of the cooling water circulation device is controlled so as to increase. At this time, the work of the cooling water circulation device increases the amount of increase in the coolant flow rate as the detected coolant temperature approaches the freezing point, and decreases the amount of increase in the coolant flow rate as the coolant temperature becomes farther from the freezing point. This is achieved by controlling the amount.

  According to the present invention, it is possible to satisfactorily prevent uneven temperature distribution that occurs in a cooling system that cools a fuel cell.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of a fuel cell system shown as an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, a fuel cell system includes a fuel cell stack 10 that is a fuel cell body, a hydrogen gas circulation supply system 20 that supplies hydrogen to an anode 11 that is a fuel electrode of the fuel cell stack 10, and a fuel cell stack. An air gas supply system 30 that supplies an air gas that is an oxidant gas to the cathode 12 that is the oxidant electrode 10; and a cooling system 40 that cools the fuel cell stack 10 heated by power generation by circulating cooling water; An output system 50 that takes out the output from the fuel cell stack 10 and supplies it to a load, and a system controller 60 that comprehensively controls the operation of the fuel cell system.

  This fuel cell system prevents the temperature distribution of the cooling system 40 from being biased, and in particular, prevents the cooling system 40 from freezing in the low temperature environment by preventing the temperature distribution of the cooling system 40 from being biased.

  The fuel cell stack 10 is configured by stacking a plurality of single cells, which are power generation units, and generates power by a chemical reaction between hydrogen gas supplied as fuel gas to the anode 11 and oxygen in air gas supplied to the cathode 12. To do. For example, the fuel cell stack 10 is a polymer electrolyte fuel cell (PEFC) using a polymer electrolyte membrane as an electrolyte, and the structure of a single cell has a catalyst layer on both sides of the polymer electrolyte membrane. Are integrated as a MEA (Membrane Electrode Assembly) in which a fuel electrode and an oxidizer electrode are formed.

  The fuel cell stack 10 is provided with a temperature sensor 13 that measures the temperature in the fuel cell stack 10. The temperature in the fuel cell stack 10 measured by the temperature sensor 13 is output to the system controller 60.

  The hydrogen gas circulation supply system 20 is provided with a hydrogen gas supply source 21 such as a high-pressure hydrogen tank for storing hydrogen gas as a fuel gas, and a hydrogen gas pressure adjustment valve 22, and the hydrogen gas stored in the hydrogen gas supply source 21 is supplied to the hydrogen gas circulation supply system 20. A hydrogen gas supply pipe 23 to be supplied to the anode 11 of the fuel cell stack 10, a water separator (not shown) for condensing steam to separate moisture, and a purge valve are provided, and the impurity gas contained in the hydrogen gas of the anode 11 is discharged. A hydrogen gas discharge pipe 24 and a circulation pump 25 for circulating the hydrogen gas are provided, and the hydrogen gas circulation pipe 26 for circulating the hydrogen gas of the anode 11 is circulated by the circulation pump 25 via the hydrogen gas circulation pipe 26. A merging portion (ejector or the like) 27 for merging the hydrogen gas into the hydrogen gas supply pipe 23 is provided.

  The circulation pump 25 is driven and controlled by the system controller 60. The circulation pump 25 is driven by using the electric power generated by the fuel cell stack 10 during operation of the fuel cell system. However, when the fuel cell system is started and when the fuel cell system is stopped, the freeze-fixing prevention process is performed. In this case, the battery is driven by electric power supplied from a secondary battery 53 described later, which is an auxiliary power source for the rechargeable fuel cell stack 10.

  In such a hydrogen gas circulation supply system 20, the hydrogen gas supply source 20 is controlled by controlling the opening degree of the hydrogen gas pressure regulating valve 22 by the control of the system controller 60 according to the hydrogen gas pressure of the hydrogen gas supply pipe 23. The hydrogen gas supplied from 21 through the hydrogen gas supply pipe 23 is adjusted to a predetermined pressure determined within a range where the fuel cell system can be operated, and supplied to the anode 11 of the fuel cell stack 10.

  Further, in the hydrogen gas circulation supply system 20, by controlling the system controller 60, the hydrogen gas flow rate supplied to the anode 11 of the fuel cell stack 10 is made larger than the reaction hydrogen gas flow rate corresponding to the output current, Hydrogen gas can be supplied to each cell of the fuel cell stack 10 composed of a plurality of cells without shortage.

  Furthermore, as power generation is continued, an impurity gas other than hydrogen gas, such as nitrogen, is accumulated in the anode 11 of the fuel cell stack 10 and the hydrogen concentration is reduced. If the hydrogen concentration decreases, power generation efficiency decreases and the fuel cell stack 10 deteriorates. Therefore, the system controller 60 controls the opening of a purge valve (not shown) connected to the hydrogen gas discharge pipe 24 to discharge hydrogen gas. Control is performed to discharge the impurity gas through the pipe 24.

  The air gas supply system 30 includes an air gas supply device 31 such as a compressor that compresses air and supplies it as air gas, and a blower that supplies air gas, and a humidifier 32, and is controlled by a system controller 60. The air gas supply pipe 33 is connected to the cathode 12 of the fuel cell stack 10 by adjusting the air gas to a predetermined pressure determined within a range where the fuel cell system can be operated by controlling the rotation speed of the gas supply device 31. Supply through. Unnecessary air gas is discharged through an air gas discharge pipe 35 provided with a pressure control valve 34 for controlling the pressure of the discharged air gas.

  When the air gas supply device 31 is a compressor, since the air gas is compressed and heated, a cooling device (not shown) for cooling the heated air gas is provided at the subsequent stage of the air gas supply device 31. .

  The humidifier 32 humidifies the air gas supplied to the cathode 12 of the fuel cell stack 10. As described above, the humidifier 32 humidifies the air gas supplied to the cathode 12 to supply moisture to the polymer electrolyte membrane, and has good ion conductivity without reducing the ion transport capability of the polymer electrolyte membrane. Do moisture management to keep.

  The air gas supply pipe 33 of the air gas supply system 30 is provided with an air flow meter 36 for detecting the flow rate of the air gas flowing through the air gas supply pipe 33. The flow rate of the air gas measured by the air flow meter 36 is output to the system controller 60.

  The cooling system 40 includes a cooling water pump 41 that circulates cooling water, a radiator 42 that exchanges heat between outside air and cooling water, a reservoir tank 43 that stores cooling water to be supplied to the radiator 42, and a fuel cell stack. 10 and a cooling water supply pipe 44 for supplying cooling water. Further, a bypass pipe 46 that circulates the cooling water that has cooled the fuel cell stack 10 by bypassing the radiator 42 is connected to the cooling water supply pipe 44 via a three-way valve 45. The ratio between the flow rate of the cooling water passing through the radiator 42 and the flow rate of the cooling water that bypasses the radiator 42 can be arbitrarily adjusted by controlling the opening degree of each valve of the three-way valve 45 by the system controller 60. .

  The reservoir tank 43 is provided with a tank internal temperature detection sensor 47 that measures the temperature of the cooling water in the reservoir tank 43. The coolant temperature in the reservoir tank 43 detected by the tank temperature detection sensor 47 is output to the system controller 60.

  The output system 50 outputs the electric power generated by the fuel cell stack 10 through the output controller 51 and the output controller 51 for taking out the electric power generated while controlling the electric power to be a desired output according to the control of the system controller 60. A load control unit 52 that transmits the power to a load (not shown). The output system 50 includes a secondary battery 53 connected in parallel with the load control unit 52, and is regenerated from the electric power generated by the fuel cell stack 10 taken out via the output controller 51 or from the load. Charge regenerative power.

  Such an output system 50 is provided with an ammeter 54 that detects an output current from the fuel cell stack 10 and a voltmeter 55 that detects an output voltage of the fuel cell stack 10. The output current and output voltage of the fuel cell stack 10 detected by the ammeter 54 and the voltmeter 55 are output to the system controller 60.

  The system controller 60 is a control unit that controls the fuel cell system in an integrated manner. The system controller 60 reads signals output from the temperature sensor 13, the air flow meter 36, the tank temperature detection sensor 47, the ammeter 54, the voltmeter 55, and the outside temperature detection sensor 5 that detects the outside temperature of the fuel cell system. The hydrogen gas circulation supply system 20, the air gas supply system 30, the cooling system 40, and the output so that the optimum operation is performed according to the operation command based on the read various signals and the control logic (program) held inside. Each system 50 is controlled.

  Further, the system controller 60 appropriately controls the flow rate of the cooling water to prevent the temperature distribution of the cooling system 40 from being biased. In particular, the freezing of the cooling system 40 can be prevented by preventing the uneven temperature distribution in a low temperature environment.

  Next, a method for preventing the temperature distribution of the cooling system 40 from being biased by controlling the coolant flow rate by controlling the number of revolutions of the coolant pump 41 by the system controller 60 will be described. In the following description, it is assumed that the fuel cell system is mounted on a vehicle.

[Control processing operation of cooling water pump 41 by system controller 60]
The system controller 60 temporarily controls the number of rotations of the cooling water pump 41, that is, the amount of work of the cooling water pump 41 according to the temperature of the cooling water in the reservoir tank 43 detected by the tank temperature detection sensor 47. The cooling water flow rate is increased to prevent the temperature distribution in the cooling system 40 such as the cooling water pump 41, the radiator 42, the reservoir tank 43, the cooling water supply pipe 44, the three-way valve 45, and the bypass pipe 46. Below, freezing of the cooling system 40 can be prevented.

  At this time, the system controller 60 determines a rotation speed increase time, which is a time for increasing the rotation speed of the cooling water pump 41, and an increase amount of the rotation speed based on various conditions detected from a sensor or the like. Then, the system controller 60 increases the cooling water flow rate of the cooling system 40 by drivingly controlling the cooling water pump 41 so that the determined number of rotations is reached in the determined number of rotations increase time.

(Rotation speed increase time calculation process)
First, the operation for calculating the rotation speed increase time by the system controller 60 will be described with reference to the flowchart shown in FIG. In the description using the flowchart shown in FIG. 2, it is assumed that the system controller 60 includes the rotation speed increase time calculation unit 61 as shown in FIG. 3 as a functional unit. The processing operation of this functional unit is realized by a program held by the system controller 60.

  In step S1, the outside air temperature detection sensor 5 detects the outside air temperature around the vehicle on which the fuel cell system is mounted. The outside air temperature detected by the outside air temperature detection sensor 5 is output to the rotation speed increase time calculation unit 61 of the system controller 60.

  In step S <b> 2, the rotation speed increase time calculation unit 61 calculates a rotation speed increase time that is a time for increasing the rotation speed of the cooling water pump 41 in accordance with the detected outside air temperature. The rotation speed increase time is the time for which the increased rotation speed is continued when the rotation speed is increased from the normal rotation speed. If the increased rotation speed is continued, that is, the rotation speed increase time is increased, the total flow rate of the cooling water circulated in the cooling system 40 is increased, and the uneven temperature distribution in the cooling system 40 is suppressed. Can do.

  Therefore, the rotation speed increase time calculation unit 61 increases the rotation speed increase time as the detected outside air temperature is lower, that is, the higher the possibility of freezing in the cooling system 40, and the temperature distribution of the cooling system 40 is uniform. To be.

  The system controller 60 controls the time for increasing the rotation speed of the cooling water pump 41 using the rotation speed increase time calculated by the rotation speed increase time calculation unit 61. The rotation speed increase time calculated by the rotation speed increase time calculation unit 61 is simply calculated according to the outside air temperature of the vehicle on which the fuel cell system is mounted. It is possible to optimize the rotation speed increase time by correcting the initial value in consideration of the actual cooling water temperature. The method will be described below.

(Optimization of rotation speed increase time)
A processing operation for optimizing the rotation speed increase time will be described with reference to the flowchart shown in FIG. In the description using the flowchart shown in FIG. 4, it is assumed that the system controller 60 includes an increase time correction unit 62, a calculation block 63, and a calculation block 64 as functional units as shown in FIG. The processing operation of this functional unit is realized by a program held by the system controller 60.

  In step S <b> 11, the tank temperature detection sensor 47 detects the coolant temperature in the reservoir tank 43. The coolant temperature in the reservoir tank 43 detected by the tank temperature detection sensor 47 is output to the increase time correction unit 62 of the system controller 60.

  In step S12, the increase time correction unit 62 firstly detects the actual cooling water temperature (hereinafter referred to as the actual cooling water temperature) detected by the in-tank temperature detection sensor 47 and the target temperature of the cooling water (hereinafter referred to as the target). (Referred to as cooling water temperature).

  As a result of the comparison, the increase time correction unit 62 sets the actual cooling water temperature to the target even if the rotation number of the cooling water pump 41 is increased by the rotation number increase time calculated by the rotation number increase time calculation unit 61 described above. When it is estimated that there is a difference between the actual cooling water temperature and the target cooling water temperature so that the cooling water temperature cannot be approached, the process proceeds to step S13. Further, when it is estimated that the increase time correction unit 62 can bring the actual cooling water temperature closer to the target cooling water temperature by increasing the rotation speed of the cooling water pump 41 by the rotation speed increase time. Advances to step S14.

  For the target cooling water temperature used for comparison with the actual cooling water temperature, for example, a value set in advance in the memory of the system controller 60 may be used, or the number of rotations of the cooling water pump 41 may be set. It may be a value obtained by extrapolating the cooling water temperature by time when the temperature distribution is increased, that is, in a state where the temperature distribution of the cooling system 40 is assumed to be uniform, or the rotation speed of the cooling water pump 41 may be A value obtained by adding a predetermined value to the coolant temperature immediately before the increase may be used. Further, the target coolant temperature includes the coolant temperature detected at a place other than the reservoir tank 43, for example, the value of the temperature detection sensor provided at the entrance to the fuel cell stack 10, and the reservoir tank A value detected by a temperature detection sensor closer to 43 may be used.

  In step S13, the increase time correction unit 62 extends the rotation speed increase time calculated by the rotation speed increase time calculation unit 61 so as to increase the coolant flow rate so that the actual cooling water temperature approaches the target cooling water temperature. Correction processing is performed in the direction to be corrected. Specifically, the increase time correction unit 62 calculates extension time information for extending the rotation speed increase time, and outputs it to the calculation block 64.

  In step S14, the calculation block 63 subtracts the actual time in which the number of rotations of the cooling water pump 41 measured by the timer 60T is increased from the number of rotations increasing time calculated by the rotation number increasing time calculating unit 61, The remaining time for increasing the rotational speed of the pump 41 is calculated. In addition, the calculation block 64 adds the extension time indicated by the extension time information calculated by the increase time correction unit 62 to the remaining time for increasing the rotation speed calculated by the calculation block 63, so that the rotation speed of the initial value is obtained. The remaining time for increasing the rotational speed of the cooling water pump 41 when the increase time is corrected and optimized is calculated. Then, the system controller 60 manages a period for increasing the number of revolutions of the cooling water pump 41 based on the remaining time for increasing the number of revolutions calculated in the calculation block 64.

  As described above, the system controller 60 detects the outside air detected by the outside temperature detection sensor 5 based on the extended time information that changes in accordance with the transition of the cooling water temperature in the reservoir tank 43 detected by the tank temperature detection sensor 47. The rotation speed increase time calculated based on the temperature can be corrected and optimized.

  The system controller 60 sets the number of rotations of the cooling water pump 41 for this rotation number increase time at a fixed time or at a timing determined based on the temperature of the cooling water in the reservoir tank 43 detected by the tank temperature detection sensor 47. Increase. The system controller 60 returns the increased number of rotations of the cooling water pump 41 to the normal number of rotations after the elapse of the number of rotations.

  Further, when the system controller 60 determines the timing for increasing the rotation speed based on the temperature of the cooling water in the reservoir tank 43 detected by the tank temperature detection sensor 47, the detected temperature of the cooling water is, for example, The timing at which the predetermined cooling water becomes below the temperature level at which there is no risk of freezing is set as the timing for increasing the rotational speed.

  Note that the cooling water pump 41 is increased in rotation speed by the rotation speed increase time as described above under the control of the system controller 60, but after the rotation speed increase time has elapsed, the normal rotation again It will be controlled by number. As described above, when the cooling water pump 41 is controlled at the normal rotation speed, the system controller 60 resets the measurement of the rotation speed increase time by the timer 60T shown in FIG. 5 to zero.

(Calculation processing of increase in rotation speed)
Next, the calculation processing operation of the increase amount of the rotation speed by the system controller 60 will be described using the flowchart shown in FIG. In the description using the flowchart shown in FIG. 6, the system controller 60 performs the target rotation speed calculation unit 65, the target rotation speed calculation unit 66, the rotation speed limit calculation unit 67, and the generated power calculation as shown in FIG. 7. It is assumed that the unit 68, the rotation speed limit calculation unit 69, the selection block 70, and the selection block 71 are provided as functional units. The processing operation of this functional unit is realized by a program held by the system controller 60.

  In step S <b> 21, the tank temperature detection sensor 47 detects the cooling water temperature in the reservoir tank 43. The coolant temperature in the reservoir tank 43 detected by the tank temperature detection sensor 47 calculates a target rotation speed calculation unit 65 for calculating the first target rotation speed of the system controller 60 and a second target rotation speed. It is output to the target rotational speed calculation unit 66.

  In step S22, the system controller 60 determines whether or not the cooling water temperature in the reservoir tank 43 output to the target rotation speed calculation units 65 and 66 is equal to or lower than a predetermined temperature near 0 ° C. that is the freezing point of the cooling water. To do. The system controller 60 proceeds to step S23 if the cooling water temperature is not below a predetermined temperature near 0 ° C., and proceeds to step S30 if it is below a predetermined value near 0 ° C.

  In step S23, the outside air temperature detection sensor 5 detects the outside air temperature around the vehicle on which the fuel cell system is mounted. The outside air temperature detected by the outside air temperature detection sensor 5 is output to the target rotational speed calculation unit 65 of the system controller 60.

  In step S24, the target rotational speed calculation unit 65 detects the coolant temperature in the reservoir tank 43 detected by the tank internal temperature detection sensor 47 and the surroundings of the vehicle on which the fuel cell system detected by the outside air temperature detection sensor 5 is mounted. Based on the outside air temperature, a first target rotation speed that is a basic rotation speed when the rotation speed of the cooling water pump 41 is increased is calculated. The target rotational speed calculation unit 65 calculates the first target rotational speed in such a manner that the rotational speed of the cooling water pump 41 increases as the cooling water temperature in the reservoir tank 43 approaches the freezing point or the outside air temperature decreases. To do.

  Specifically, the target rotational speed calculation unit 65 calculates the first target rotational speed from an arithmetic expression using as arguments the cooling water temperature in the reservoir tank 43 and the outside air temperature around the vehicle on which the fuel cell system is mounted. . Alternatively, the coolant temperature and the outside air temperature and the first target rotational speed may be stored in advance as a table, and the first target rotational speed may be acquired by referring to this table.

  Thus, the basics for increasing the number of revolutions of the cooling water pump 41 from the cooling water temperature in the reservoir tank 43 detected by the tank internal temperature detection sensor 47 and the outside air temperature detected by the outside air temperature detection sensor 5. The first target rotational speed that is the rotational speed can be obtained. The first target rotational speed calculated by the target rotational speed calculation unit 65 is output to the selection block 70.

  When the target rotational speed calculation unit 65 obtains the first target rotational speed, it is sufficient that at least the coolant temperature in the reservoir tank 43 detected by the tank temperature detection sensor 47 is known, and the outside air temperature detection sensor is not necessarily required. It is not necessary to use the outside temperature detected by 5.

  By the way, when the rotational speed of the cooling water pump 41 is increased so as to be the first target rotational speed thus obtained, the rotational speed increases, that is, depending on the state of the vehicle on which the fuel cell system is mounted. Noise due to the driving sound of the cooling water pump 41, which becomes higher as the work volume increases, becomes a problem. Therefore, the system controller 60 acquires the state of the vehicle in the following steps, and limits the first target rotational speed calculated by the target rotational speed calculation unit 65 based on the state of the vehicle.

  First, in step S25, the current speed of the vehicle is detected by the vehicle speed detection sensor 6 provided in the vehicle on which the fuel cell system is mounted. The vehicle speed detected by the vehicle speed detection sensor 6 is output to the rotation speed limit calculation unit 67 of the system controller 60.

  In step S <b> 26, the rotation speed limit calculation unit 67 calculates a limit rotation speed that limits the first target rotation speed calculated in step S <b> 24 based on the vehicle speed detected by the vehicle speed detection sensor 6.

  In general, the running noise of the vehicle increases as the speed of the vehicle increases. Therefore, when the speed of the vehicle is high, the traveling sound becomes loud, and therefore, there is a low possibility that the driving sound becomes noise even if the rotational speed of the cooling water pump 41 is increased. On the other hand, when the vehicle speed is low, the running noise is small, and therefore the driving sound of the cooling water pump 41 with the increased number of rotations is likely to be noise.

  Therefore, in this step S26, the first target rotation speed is optimized based on the relationship between the vehicle speed and the running sound so that the driving sound of the cooling water pump 41 does not become a noise according to the vehicle speed. Calculate the limited rotational speed. The rotational speed limit calculated by the rotational speed limit calculation unit 67 is output to the selection block 70.

  In step S <b> 27, the generated power calculation unit 68 generates power in the fuel cell stack 10 from the output current of the fuel cell stack 10 detected by the ammeter 54 and the output voltage of the fuel cell stack 10 detected by the voltmeter 55. Find the amount of power to be used

  In step S28, the rotation speed limit calculation unit 69 limits the first target rotation speed calculated in step S24 based on the amount of power generated by the fuel cell stack 10 calculated by the generated power calculation unit 68. Calculate the number of revolutions.

  When the amount of electric power generated by the fuel cell stack 10 is high, the work amount of the air gas supply device 31 that supplies air gas to the cathode 12 of the fuel cell stack 10 increases, and the driving sound of the air gas supply device 31 also increases. That is, in such a situation, even if the rotation speed of the cooling water pump 41 is increased, it can be said that there is a low possibility that the driving sound of the cooling water pump 41 becomes noise. Further, when the amount of power generated by the fuel cell stack 10 is high, the amount of heat generated by the fuel cell stack 10 becomes high.

  Therefore, when the amount of power generated by the fuel cell stack 10 is high, even if the number of revolutions of the cooling water pump 41 is increased in order to suppress the amount of heat generated by the fuel cell stack 10, the driving sound is less likely to be noise.

  On the other hand, when the amount of power generated by the fuel cell stack 10 is low, the work amount of the air gas supply device 31 that supplies air gas to the cathode 12 of the fuel cell stack 10 is reduced, and the driving sound of the air gas supply device 31 is also small. Become. That is, in such a situation, if the rotation speed of the cooling water pump 41 is increased, there is a high possibility that the driving sound of the cooling water pump 41 becomes noise. Further, when the amount of power generated by the fuel cell stack 10 is low, the amount of heat generated by the fuel cell stack 10 also remains low.

  Therefore, when the amount of electric power generated by the fuel cell stack 10 is low, it is not necessary to suppress the heat generation amount of the fuel cell stack 10, and when the number of rotations of the cooling water pump 41 is increased, the driving sound becomes noise. End up.

  Therefore, in step S28, the heat generation of the fuel cell stack 10 is based on the relationship between the amount of power generated by the fuel cell stack 10 and the driving sound of the air gas supply device 31 and the heat generation amount of the fuel cell stack 10. Depending on the amount, a limit rotational speed that optimizes the first target rotational speed so that the driving sound of the cooling water pump 41 does not become noise is calculated. The speed limit calculated by the speed limit calculation unit 69 is output to the selection block 70.

  In step S <b> 29, the selection block 70 determines the limit rotation speed or rotation calculated based on the first target rotation speed calculated by the target rotation speed calculation unit 65 and the vehicle speed calculated by the rotation speed limit calculation unit 67. The lower limit number of rotations is selected by comparing with the limit number of rotations calculated based on the amount of power generated by the fuel cell stack 10 calculated by the number limit calculation unit 69. The selection block 70 outputs the selected number of rotations to the selection block 71.

  Note that only one of the limited rotational speed calculated by the rotational speed limit calculating unit 67 and the limited rotational speed calculated by the rotational speed limit calculating unit 69 may be effective.

  In step S30, the target rotational speed calculation unit 66 becomes the basic rotational speed when the rotational speed of the cooling water pump 41 is increased based on the cooling water temperature in the reservoir tank 43 detected by the tank internal temperature detection sensor 47. A second target rotational speed is calculated. Unlike the first target rotation speed, the second target rotation speed calculated by the target rotation speed calculation unit 66 is limited by comparison with the rotation speeds calculated by the rotation speed limit calculation units 67 and 69. There is no.

  That is, the second target rotational speed calculated by the target rotational speed calculation unit 66 is frozen in the cooling water in the reservoir tank 43 from the temperature of the cooling water in the reservoir tank 43 detected by the tank internal temperature detection sensor 47. When it is determined that there is a risk of this, it is a value calculated for the purpose of increasing the cooling water flow rate by simply increasing the rotation speed of the cooling water pump 41 without limiting it.

  Therefore, if the second target rotational speed is used, it is possible to reduce the deviation of the temperature distribution in the cooling water path and the components constituting the cooling system 40 in a low temperature environment near 0 ° C. The partial freezing of the cooling system 40 including the reservoir tank 43 can be prevented.

  Specifically, the target rotational speed calculation unit 66 uses the predetermined value set in advance as the second target rotational speed, or a predetermined rotational speed that is set in advance for normal control before increasing the rotational speed. The second target rotational speed is calculated by adding the values. The second target rotational speed calculated by the target rotational speed calculation unit 66 is output to the selection block 71.

  In step S31, the selection block 71 sets the second target in consideration of the rotation speed in consideration of the noise based on the vehicle state selected in the selection block 70 and the cooling water freezing calculated in the target rotation speed calculation unit 66. Compared with the rotational speed, the one with the larger rotational speed is selected, and this is output as the third target rotational speed. This selection block 71 preferentially prevents the uneven temperature distribution of the cooling system 40 in a low-temperature environment near 0 ° C. rather than the reduction of noise generated by the increase in the rotation speed of the cooling water pump 41. This is a block for preventing the cooling system 40 from freezing.

  The system controller 60 drives and controls the cooling water pump 41 for the target rotational speed increase time obtained as described above at the third target rotational speed selected in the selection block 71 in this manner, thereby cooling the system. Increase the cooling water flow rate in the system 40.

  Thus, the fuel cell system shown as the embodiment of the present invention is equipped with the fuel cell system detected by the coolant temperature in the reservoir tank 43 detected by the tank internal temperature detection sensor 47 and the outside air temperature detection sensor 5. Based on the outside air temperature of the vehicle, the system controller 60 calculates the rotation speed increase time of the cooling water pump 41 and the third target rotation speed.

  Then, the system controller 60 sets the target at a timing determined based on the temperature of the cooling water in the reservoir tank 43 detected by the tank target temperature detection sensor 47 at regular intervals or at the calculated third target speed. By controlling the drive so that the number of rotations of the cooling water pump 41 is increased by the time for increasing the number of rotations, the flow rate of the cooling water in the cooling system 40 can be increased to an optimal amount for an optimal period at an optimal timing. Therefore, it is possible to prevent the occurrence of bias in the temperature distribution in the reservoir tank 43 constituting the cooling system 40 and the temperature distribution in each cooling path. Therefore, partial freezing of the cooling system 40 caused by the uneven temperature distribution in a low temperature environment can be prevented.

  Further, by limiting and optimizing the number of revolutions of the cooling water pump 41 in accordance with the vehicle speed and the amount of electric power generated by the fuel cell stack 10, it is possible to prevent the driving sound of the cooling water pump 41 from becoming noise. be able to.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

It is a figure for demonstrating the structure of the fuel cell system shown as embodiment of this invention. It is a flowchart for demonstrating the processing operation which calculates rotation speed increase time. It is the figure which showed an example of the function part of the system controller which performs the process which calculates rotation speed increase time. It is a flowchart for demonstrating the processing operation which optimizes rotation speed increase time. It is the figure which showed an example of the function part of the system controller which performs the process which optimizes rotation speed increase time. It is a flowchart for demonstrating the processing operation which calculates rotation speed. It is the figure which showed an example of the function part of the system controller which performs the process which calculates rotation speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell stack 20 Hydrogen gas circulation supply system 30 Air gas supply system 40 Cooling system 41 Cooling water pump 42 Radiator 43 Reservoir tank 44 Cooling water supply piping 47 In-tank temperature detection sensor 50 Output system 60 System controller 60T timer 61 Rotation speed increase Time calculation unit 62 Increase time correction unit 63 Calculation block 64 Calculation block 65 Target rotation number calculation unit 66 Target rotation number calculation unit 67 Speed limit calculation unit 68 Generated power calculation unit 69 Speed limit calculation unit 70 Selection block 71 Selection block

Claims (5)

In a fuel cell system having a fuel cell that generates electricity by a chemical reaction of a supplied gas,
A cooling path through which cooling water for cooling the fuel cell is passed;
A cooling water circulation device for circulating cooling water in the cooling path;
A reservoir tank that is provided in the cooling path and supplies cooling water that circulates in the cooling path;
Cooling water temperature detection means for detecting the temperature of the cooling water in the reservoir tank;
The cooling water flow rate of the cooling water to be circulated in the cooling path is temporarily predetermined at a fixed time interval or at a timing determined based on the cooling water temperature in the reservoir tank detected by the cooling water temperature detecting means. Control means for controlling the amount of work of the cooling water circulation device so as to increase only by time,
The control means increases the increase amount of the cooling water flow rate as the temperature of the cooling water detected by the cooling water temperature detection means approaches the freezing point, and increases the cooling water flow rate as the cooling water temperature becomes far from the freezing point. A fuel cell system, wherein the work amount of the cooling water circulation device is controlled so as to reduce the amount. An outside air temperature detecting means for detecting the outside air temperature of the fuel cell system;
The control means increases the predetermined time for increasing the cooling water flow rate of the cooling water as the outside air temperature is low, and increases the cooling water as the outside air temperature is high, according to the outside air temperature detected by the outside air temperature detecting means. 2. The fuel cell system according to claim 1, wherein control is performed so as to reduce the predetermined time during which the coolant flow rate is increased. The fuel cell system is mounted on a vehicle that travels using power generated by the fuel cell as a power source,
The control means controls the work amount of the cooling water circulation device so that the increase amount of the cooling water flow rate is limited as the speed of the vehicle is slow,
3. The fuel cell system according to claim 1, wherein the work amount of the cooling water circulation device is controlled so that the amount of increase in the cooling water flow rate is limited as the amount of electric power generated by the fuel cell is smaller. . When the cooling water temperature detected by the cooling water temperature detection means is equal to or lower than a predetermined temperature near the freezing point, the control means limits the speed based on the speed of the vehicle and the amount of electric power generated by the fuel cell. 4. The fuel cell system according to claim 3, wherein the work amount of the cooling water circulation device is controlled so that the cooling water flow rate is increased for the predetermined time without being received. In a cooling system freeze prevention method of a fuel cell system having a fuel cell that generates power by a chemical reaction of a supplied gas,
Cooling water temperature detection step of detecting the temperature of cooling water in a reservoir tank that is provided in a cooling path through which cooling water for cooling the fuel cell is passed and supplies cooling water that circulates in the cooling path by a cooling water circulation device. When,
The cooling water flow rate of the cooling water to be circulated in the cooling path is temporarily predetermined at a fixed time interval or at a timing determined based on the cooling water temperature in the reservoir tank detected by the cooling water temperature detection step. A control step of controlling the work of the cooling water circulation device so as to increase only by time,
The control step increases the amount of increase in the cooling water flow rate as the temperature of the cooling water detected by the cooling water temperature detection step approaches the freezing point, and increases the cooling water flow rate as the cooling water temperature becomes far from the freezing point. The cooling system freeze prevention method characterized by controlling the work volume of the cooling water circulation device so as to reduce the amount.

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