JP6071388B2 - Cooling control device for fuel cell system - Google Patents

Description

  The present invention relates to a cooling control device that is applied to a fuel cell system and controls a cooling system for cooling the fuel cell.

  In recent years, development of a vehicle equipped with a fuel cell as a power source has been advanced.

  The fuel cell includes, for example, a membrane / electrode assembly in which an anode (fuel electrode) and a cathode (oxygen electrode) are bonded together on both sides of a solid polymer membrane. When fuel is supplied to the anode and air is supplied to the cathode, a power generation reaction occurs and an electromotive force is generated between the anode and the cathode.

  During power generation by the fuel cell, the fuel cell generates heat, so it is necessary to cool the fuel cell. Therefore, the fuel cell system is provided with a cooling water circulation path, and the fuel cell is cooled by the cooling water circulating in the cooling water circulation path. A water pump for circulating the cooling water and a radiator for cooling the cooling water by blowing air from the radiator fan are interposed in the middle of the cooling water circulation path. The cooling water is cooled by the action of the radiator, and the cooled cooling water is supplied to the fuel cell, whereby the fuel cell is cooled.

  In a fuel cell system using hydrogen as a fuel, various methods for controlling driving of a water pump and a radiator fan have been proposed.

  For example, Patent Document 1 proposes a method for controlling the rotational speeds of the water pump and the radiator fan so that the sum of the power consumption of the water pump and the radiator fan is minimized in order to reduce the power consumption. Yes.

  Patent Document 2 proposes a method of predicting the amount of heat generated per unit time based on the output of the fuel cell and controlling the water pump based on the rotational speed corresponding to the predicted amount of heat generated. .

JP 2004-288516 A JP 2004-253213 A

  However, the methods according to these proposals cannot be applied to a fuel cell system using a liquid fuel such as hydrazine.

  Since the fuel cell system using liquid fuel has a larger heat capacity of the entire fuel cell including liquid fuel than the fuel cell system using hydrogen, the technique proposed in Patent Document 1 aims to reduce power consumption. Even if it is possible, the flow rate of the cooling water is small, so that the fuel cell is insufficiently cooled.

  In a fuel cell system using liquid fuel, so-called cross leak (crossover) occurs in which the liquid fuel moves from the anode through the solid polymer membrane to the cathode. For this reason, the relationship between the output of the fuel cell and the calorific value varies greatly, and it is difficult to predict the calorific value per unit time based on the output of the fuel cell. Therefore, the fuel cell system using liquid fuel and the method proposed in Patent Document 2 cannot be applied.

  An object of the present invention is to provide a cooling control device for a fuel cell system that can reduce power consumption while being able to cool the fuel cell well.

In order to achieve the above object, a cooling control device according to one aspect of the present invention includes a fuel cell including a membrane / electrode assembly, a fuel supply path through which liquid fuel supplied to the fuel cell flows, A fuel discharge path through which liquid fuel discharged from the fuel cell flows; a refrigerant circulation path through which a refrigerant for cooling the fuel cell circulates; a refrigerant pump interposed in the refrigerant circulation path; and the refrigerant circulation path The present invention is applied to a fuel cell system including a radiator that radiates heat of a refrigerant circulating through the radiator. The cooling control device detects a temperature of liquid fuel supplied from the fuel supply path to the fuel cell, and detects a temperature of liquid fuel discharged from the fuel cell to the fuel discharge path. Until the temperature difference between the temperature detected by the fuel outlet temperature detecting means and the temperature detected by the fuel inlet temperature detecting means and the temperature detected by the fuel outlet temperature detecting means exceeds a predetermined switching temperature. When the target rotational speed is kept at the normal rotational speed and the temperature difference is larger than the switching temperature, the target rotational speed is switched to a rotational speed larger than the normal rotational speed, and after the switching, the temperature difference is the switching temperature. It becomes reduced to a lower release temperature than by returning the target rotational speed to the normal rotational speed, and the target rotational speed setting means for setting a target rotational speed of the coolant pump, the eye Based on the target rotational speed set by the revolution speed setting means, and a pump control means for controlling driving of the coolant pump.

  According to this configuration, there is a temperature difference between the fuel inlet temperature, which is the temperature of the liquid fuel supplied from the fuel supply path to the fuel cell, and the fuel outlet temperature, which is the temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path. Desired.

  As the output of the fuel cell changes, the amount of heat generated by the power generation reaction in the fuel cell changes, so the temperature difference between the fuel inlet temperature and the fuel outlet temperature changes. That is, when the output of the fuel cell increases, the amount of heat generated by the power generation reaction in the fuel cell increases, and with this increase, the temperature difference between the fuel inlet temperature and the fuel outlet temperature increases. On the other hand, when the output of the fuel cell decreases, the amount of heat generated by the power generation reaction in the fuel cell decreases, and the temperature difference between the fuel inlet temperature and the fuel outlet temperature decreases with the decrease.

  The target rotational speed of the refrigerant pump is set so that the temperature difference between the fuel inlet temperature and the fuel outlet temperature is within a predetermined allowable range. Then, the driving of the refrigerant pump is controlled based on the target rotational speed.

  Thereby, when the temperature difference between the fuel inlet temperature and the fuel outlet temperature is relatively large, the target rotational speed is set to a relatively large value, and the refrigerant pump is driven at the target rotational speed. As a result, since the refrigerant flows through the refrigerant circulation path at a flow rate sufficient for cooling the fuel cell, the fuel cell can be satisfactorily cooled.

  On the other hand, when the temperature difference between the fuel inlet temperature and the fuel outlet temperature is relatively small, the target rotational speed is set to a relatively small value, and the refrigerant pump is driven at the target rotational speed. As a result, the power consumption of the refrigerant pump can be kept low.

  A fuel cell system includes a radiator fan that blows air to a radiator, a bypass that is branched and connected to a refrigerant circulation path, bypasses the radiator through the refrigerant circulating in the refrigerant circulation path, and the refrigerant circulation path and the bypass path. A three-way flow valve for adjusting the flow rate of the refrigerant that is provided in the branch portion and passes through the radiator and the bypass passage may be further provided.

  In this case, the cooling control device includes a refrigerant inlet temperature detection means for detecting the temperature of the refrigerant flowing into the fuel cell from the refrigerant circulation path, and a target temperature for setting the target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path. A three-way flow valve based on the deviation calculated by the setting means, the deviation calculating means for calculating the temperature difference detected by the fuel outlet temperature detecting means with respect to the target temperature set by the target temperature setting means, When the deviation calculated by the three-way flow valve control means and the deviation calculating means is not less than a predetermined value, the radiator fan is driven, and when the temperature detected by the refrigerant inlet temperature detecting means is not more than the predetermined temperature, It may be configured to further include a radiator fan control means for stopping the radiator fan.

  According to this configuration, based on the deviation of the actual temperature from the target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge passage, specifically, the three-way flow valve is controlled so that the deviation approaches zero. The By controlling the three-way flow valve, the temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path approaches the target temperature.

  The temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path is substantially the same as the temperature of the solid polymer film (reaction film) included in the membrane / electrode assembly of the fuel cell. Therefore, the temperature of the solid polymer membrane can be brought close to the target temperature by controlling the three-way flow valve. As a result, the power generation efficiency in the fuel cell can be improved.

  Further, when the deviation of the actual temperature with respect to the target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path is equal to or larger than a predetermined value, the radiator fan is driven, and the air blown from the radiator fan is supplied to the radiator.

  Thereby, the temperature of the refrigerant | coolant which circulates through a refrigerant circuit can be lowered | hung, and a fuel cell can be cooled favorably. As a result, the temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path can be brought close to the target temperature satisfactorily.

  After driving the radiator fan, confirm that the temperature of the refrigerant flowing out from the fuel cell to the refrigerant circuit has dropped, and if the radiator fan stops driving, the fuel cell will be overcooled by the refrigerant flowing into the fuel cell. There is a risk of being.

  Therefore, it is preferable that the driving of the radiator fan is stopped when the temperature of the refrigerant flowing into the fuel cell from the refrigerant circulation path falls below a predetermined temperature.

  Thereby, overcooling of the fuel cell can be prevented. Moreover, power consumption by the radiator fan can be reduced. When the radiator fan is stopped, the temperature of the refrigerant has fallen below the predetermined temperature. After the radiator fan has stopped, the fuel cell is cooled with the refrigerant whose temperature has been reduced, resulting in insufficient cooling of the fuel cell. There is no risk of causing.

  The cooling control device includes a refrigerant inlet temperature detecting means for detecting a temperature of the refrigerant flowing into the fuel cell from the refrigerant circuit, and a refrigerant outlet temperature for detecting the temperature of the refrigerant flowing out of the fuel cell into the refrigerant circuit. Detection means, target temperature setting means for setting a target temperature of liquid fuel discharged from the fuel cell to the fuel discharge path, temperature detected by the fuel outlet temperature detection means, and detection by the refrigerant inlet temperature detection means , Temperature detected by the refrigerant outlet temperature detection means, target temperature set by the target temperature setting means, flow rate of liquid fuel flowing through the fuel supply path, flow rate of refrigerant circulating through the refrigerant circulation path And a control means for controlling the three-way flow valve and the radiator fan based on the heat capacity of the fuel cell. There.

  According to this configuration, the actual temperature and target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path, the temperature of the refrigerant flowing into the fuel cell from the refrigerant circuit, and the refrigerant flowing out from the fuel cell to the refrigerant circuit The three-way flow valve and the radiator fan are controlled based on the temperature, the flow rate of the liquid fuel flowing through the fuel supply path, the flow rate of the refrigerant circulating in the coolant circulation path, and the heat capacity of the fuel cell.

  Specifically, the actual temperature and target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path, the temperature of the refrigerant flowing into the fuel cell from the refrigerant circuit, and the temperature of the refrigerant flowing out of the fuel cell into the refrigerant circuit The amount of cooling heat required for cooling the fuel cell can be calculated based on the flow rate of liquid fuel flowing through the fuel supply path, the flow rate of refrigerant circulating in the coolant circulation path, and the heat capacity of the fuel cell. The three-way flow valve and the radiator fan are controlled so that

  As a result, the temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path, that is, the temperature of the solid polymer membrane (reaction membrane) included in the membrane / electrode assembly of the fuel cell, is cooled sufficiently. Can be close to the target temperature. As a result, the power generation efficiency in the fuel cell can be improved. Further, when the amount of cooling heat required for cooling the fuel cell is small, the driving of the radiator fan is suppressed, so that the power consumption is reduced.

  According to the present invention, the power consumption can be reduced while the fuel cell can be satisfactorily cooled.

FIG. 1 is a configuration diagram of a fuel cell system to which a cooling control device according to an embodiment of the present invention is applied. FIG. 2 is a block diagram showing the main part of the electrical configuration of the fuel cell system. FIG. 3 is a diagram showing the contents of a map used for water pump control. FIG. 4 is a block diagram showing a configuration for three-way flow valve control. FIG. 5 is a diagram showing the contents of a map used for setting the opening degree of each outlet port of the three-way flow valve. FIG. 6 is a block diagram showing a configuration for controlling the radiator fan. FIG. 7 is a diagram showing a level change of the set signal in the radiator fan control. FIG. 8 is a diagram showing a change in level of the reset signal in the radiator fan control. FIG. 9 is a block diagram showing a configuration for other three-way flow valve control and radiator fan control. FIG. 10 is a diagram showing the contents of a map used for setting the opening degree of each outlet port of the three-way flow valve, and the level change of the set signal and the reset signal in the radiator fan control.

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

<System configuration>

  FIG. 1 is a configuration diagram of a fuel cell system to which a cooling control device according to an embodiment of the present invention is applied.

  The fuel cell system 1 is a fuel cell system (FC system) that uses liquid fuel, and is mounted as a drive source in an automobile, for example.

  The fuel cell system 1 includes a fuel cell 11.

  The fuel cell 11 has a so-called cell stack in which a predetermined number (for example, 100 to 200) of cells are stacked in one direction. Each cell includes a membrane / electrode assembly (MEA), separators disposed on both sides of the membrane / electrode assembly, and a gas diffusion layer (between the membrane / electrode assembly and each separator ( GDL: Gas Diffusion Layer).

The membrane / electrode assembly is an assembly in which an anode (fuel electrode) and a cathode (oxygen electrode) are bonded to both sides of a solid polymer membrane. The solid polymer film has, for example, a property of transmitting anions (OH ⁻ ).

  On both surfaces of the separator, for example, concave grooves (not shown) that are bent in a twisted manner are formed. The concave groove facing the anode of the membrane / electrode assembly is formed as a fuel flow path. One end and the other end of the fuel flow path are connected to a fuel inlet 12 and a fuel outlet 13, respectively. The concave groove facing the cathode of the membrane / electrode assembly is formed as an air flow path. One end and the other end of the air flow path are connected to an air inlet 14 and an air outlet 15, respectively. Moreover, between each cell, the concave groove formed in the separator of one cell and the concave groove formed in the separator of the other cell overlap, and these concave grooves form a cooling water flow path. One end and the other end of the cooling water flow path are connected to a cooling water inlet 16 and a cooling water outlet 17, respectively.

  The fuel cell system 1 includes a fuel circulation system.

  The fuel circulation system includes a first fuel tank 21, a second fuel tank 22, and a fuel sub tank 23.

The first fuel tank 21 stores, for example, room temperature hydrazine (N ₂ H ₄ ) as the liquid fuel. One end of a first fuel supply pipe 24 is connected to the first fuel tank 21. The other end of the first fuel supply pipe 24 is connected to the fuel sub tank 23. A first fuel supply pump 25 is interposed in the middle of the first fuel supply pipe 24.

  The second fuel tank 22 stores, for example, a normal temperature potassium hydroxide aqueous solution (KOH) as an electrolytic solution. One end of a second fuel supply pipe 26 is connected to the second fuel tank 22. The other end of the second fuel supply pipe 26 is connected to the fuel sub tank 23. A second fuel supply pump 27 is interposed in the middle of the second fuel supply pipe 26.

  The fuel sub tank 23 stores liquid fuel mixed with the electrolyte, for example, hydrazine mixed with an aqueous potassium hydroxide solution. One end of a fuel supply pipe 28 is connected to the fuel sub tank 23. The other end of the fuel supply pipe 28 is connected to the fuel inlet 12 of the fuel cell 11. A fuel circulation pump 29 is interposed in the middle of the fuel supply pipe 28. The fuel supply pipe 28 is provided with an FC inlet fuel temperature sensor 30 that detects the temperature of the liquid flowing into the fuel inlet 12 from the fuel supply pipe 28 between the fuel inlet 12 and the fuel circulation pump 29. .

  One end of a fuel discharge pipe 31 is connected to the fuel outlet 13 of the fuel cell 11. The other end of the fuel discharge pipe 31 is connected to the fuel sub tank 23. The fuel discharge pipe 31 is provided with an FC outlet fuel temperature sensor 32 that detects the temperature of the liquid flowing out from the fuel outlet 13 to the fuel discharge pipe 31.

  The fuel cell system 1 includes an air supply system.

  The air supply system includes a compressor 41. One end of an air supply pipe 42 is connected to the air inlet 14 of the fuel cell 11. The compressor 41 is connected to the other end of the air supply pipe 42.

  The fuel cell system 1 includes an exhaust treatment system.

  The exhaust treatment system includes an exhaust treatment device 51. One end of an air discharge pipe 52 is connected to the air outlet 15 of the fuel cell 11. The exhaust treatment device 51 is interposed in the middle of the air discharge pipe 52.

  The fuel cell system 1 includes a cooling system.

  The cooling system includes a cooling water supply pipe 61, a cooling water discharge pipe 62, a radiator 63 and a radiator fan 64.

  One end of the cooling water supply pipe 61 is connected to the radiator 63. The other end of the cooling water supply pipe 61 is connected to the cooling water inlet 16 of the fuel cell 11. In the middle of the cooling water supply pipe 61, a three-way flow valve 65 and a water pump 66 are interposed in this order from the radiator 63 side. The cooling water supply pipe 61 is provided with an FC inlet water temperature sensor 67 that detects the temperature of the cooling water flowing through the cooling water supply pipe 61.

  One end of the cooling water discharge pipe 62 is connected to the cooling water outlet 17 of the fuel cell 11. The other end of the cooling water discharge pipe 62 is connected to the radiator 63. A bypass pipe 68 is branched and connected to a middle portion of the cooling water discharge pipe 62. The tip of the bypass pipe 68 is connected to the three-way flow valve 65. The cooling water discharge pipe 62 is provided with an FC outlet water temperature sensor 69 that detects the temperature of the cooling water flowing through the cooling water discharge pipe 62.

<Power generation operation>

  The fuel circulation pump 29 is driven for power generation by the fuel cell 11. When the fuel circulation pump 29 is driven, the liquid containing the liquid fuel stored in the fuel sub tank 23 is sucked into the fuel supply pipe 28. Then, a liquid flows through the fuel supply pipe 28, and the liquid is supplied from the fuel inlet 12 of the fuel cell 11 to the fuel flow path of the fuel cell 11. The liquid flowing through the fuel flow path is discharged from the fuel outlet 13 to the fuel discharge pipe 31 and returned to the fuel sub tank 23 through the fuel discharge pipe 31.

  Thus, the liquid containing the liquid fuel circulates in the fuel circulation path including the fuel sub tank 23, the fuel supply pipe 28, the fuel flow path of the fuel cell 11 and the fuel discharge pipe 31.

  On the other hand, the compressor 41 is driven for power generation by the fuel cell 11. By driving the compressor 41, air (atmosphere) is sent to the air supply pipe 42. Then, air flows through the air supply pipe 42, and the air is supplied from the air inlet 14 of the fuel cell 11 to the air flow path of the fuel cell 11. The air flowing through the air flow path flows out from the air outlet 15 to the air discharge pipe 52 and is discharged to the atmosphere via the exhaust treatment device 51. As the air passes through the exhaust treatment device 51, harmful substances and the like are removed from the air.

  When liquid containing liquid fuel flows through the fuel flow path of the fuel cell 11 and air flows through the air flow path, a power generation reaction (electrochemical reaction) occurs in the fuel cell 11, and an electromotive force is generated by the electrochemical reaction. To do.

Specifically, the reaction represented by the reaction formula (1) occurs at the anode, and nitrogen gas (N ₂ ), water (H ₂ O), and electrons (e ⁻ ) are generated. The electrons move to the cathode via an external circuit (not shown). Nitrogen gas and water are discharged from the fuel flow path to the fuel discharge pipe 31 through the fuel outlet 13 together with the unreacted liquid fuel. On the other hand, at the cathode, the reaction represented by the reaction formula (2) occurs, and an anion (OH ⁻ ) is generated. The anion passes through the solid polymer membrane and moves to the anode.

NH ₂ NH ₂ + 4OH ⁻ → N ₂ + 4H ₂ O + 4e ⁻ (1)
O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ (2)

  As a result, an electromotive force is generated between the anode and the cathode due to a power generation reaction (electrochemical reaction).

<Refueling operation>

  When the fuel sub-tank 23 needs to be replenished with liquid fuel during operation of the fuel cell system 1, the first fuel supply pump 25 and / or the second fuel supply pump 27 are driven.

  When the first fuel supply pump 25 is driven, liquid fuel (hydrazine) is pumped from the first fuel tank 21 to the first fuel supply pipe 24. Then, the liquid fuel is supplied to the fuel sub tank 23 through the first fuel supply pipe 24.

  When the second fuel supply pump 27 is driven, the electrolytic solution (potassium hydroxide aqueous solution) is pumped from the second fuel tank 22 to the second fuel supply pipe 26. Then, the electrolytic solution is supplied to the fuel sub tank 23 through the second fuel supply pipe 26.

<Cooling operation>

  Cooling water is sealed in the cooling water supply pipe 61 and the cooling water discharge pipe 62.

  When the fuel cell 11 generates power, the water pump 66 is driven. When the water pump 66 is driven, the cooling water flows through the cooling water supply pipe 61 toward the cooling water inlet 16 of the fuel cell 11. The cooling water flowing through the cooling water supply pipe 61 is supplied to the fuel cell 11 through the cooling water inlet 16.

  The cooling water supplied to the fuel cell 11 flows through the cooling water passage and flows out to the cooling water discharge pipe 62 through the cooling water outlet 17. As the cooling water flows through the cooling water flow path, the fuel cell 11 is cooled.

  The cooling water that has flowed out to the cooling water discharge pipe 62 flows through the cooling water discharge pipe 62 toward the radiator 63. When the connection port of the bypass pipe 68 provided in the three-way flow valve 65 is closed, the cooling water flowing through the cooling water discharge pipe 62 passes through the radiator 63 and returns to the cooling water supply pipe 61. The cooling water that passes through the radiator 63 is cooled by running wind and / or air blown from the radiator fan 64. On the other hand, when the connection port of the bypass pipe 68 is opened, the cooling water flowing through the cooling water discharge pipe 62 bypasses the radiator 63, flows through the bypass pipe 68, and returns to the cooling water supply pipe 61.

  Thus, the cooling water circulates in the fuel circulation path including the cooling water supply pipe 61, the cooling water flow path of the fuel cell 11 and the cooling water discharge pipe 62, and one or both of the radiator 63 and the bypass pipe 68.

<Electrical configuration>

  FIG. 2 is a block diagram showing the main part of the electrical configuration of the fuel cell system.

  The fuel cell system 1 includes an FC-ECU (electronic control unit) 71 including a CPU and a memory.

  An FC inlet fuel temperature sensor 30, an FC outlet fuel temperature sensor 32, an FC inlet water temperature sensor 67, and an FC outlet water temperature sensor 69 are connected to the FC-ECU 71.

  The FC-ECU 71 performs a first fuel supply pump 25, a second fuel supply pump 27, a fuel circulation pump 29, a compressor 41, a radiator fan 64, and a radiator based on signals input from various sensors in accordance with a program stored in a memory. The drive of the water pump 66 is controlled, and the opening degree of each outlet port of the three-way flow valve 65 is controlled.

<Water pump control>

  FIG. 3 is a diagram showing the contents of a map used for water pump control.

  During the power generation operation of the fuel cell system 1, the FC-ECU 71 detects the temperature difference between the temperature detected by the FC inlet fuel temperature sensor 30 and the temperature detected by the FC outlet fuel temperature sensor 32, that is, from the fuel supply pipe 28 to the fuel inlet. The temperature difference between the temperature of the liquid supplied to the fuel 12 (hereinafter referred to as “fuel inlet temperature”) and the temperature of the liquid discharged from the fuel outlet 13 to the fuel discharge pipe 31 (hereinafter referred to as “fuel outlet temperature”). Is being monitored. And according to the temperature difference, the rotation speed of the water pump 66 is switched between a normal rotation speed and a higher rotation speed than the normal rotation speed.

  Specifically, until the temperature difference between the fuel inlet temperature and the fuel outlet temperature is greater than or equal to a predetermined switching temperature, the target rotational speed of the water pump 66 is maintained at the normal rotational speed, and the water pump 66 is at the normal rotational speed. Controlled to rotate.

  When the power generation operation continues and heat is generated by the power generation reaction in the fuel cell 11 and the temperature in the fuel cell 11 rises, the temperature difference between the fuel inlet temperature and the fuel outlet temperature increases. When the temperature difference reaches the switching temperature, the target rotational speed of the water pump 66 is switched from the normal rotational speed to a higher rotational speed that is larger than the normal rotational speed, and the water pump 66 is controlled to rotate at a high rotational speed. Is done. As a result, the amount of cooling water flowing through the cooling water flow path of the fuel cell 11 increases, and the ability to cool the fuel cell 11 increases.

  After the target rotational speed of the water pump 66 is switched from the normal rotational speed to the high rotational speed, when the temperature difference between the fuel inlet temperature and the fuel outlet temperature decreases to a release temperature lower than the switching temperature, the target rotational speed of the water pump 66 is reached. The number is returned from the high rotation speed to the normal rotation speed, and the water pump 66 is controlled to rotate at the normal rotation speed. As a result, the amount of cooling water flowing through the cooling water flow path of the fuel cell 11 decreases, and the ability to cool the fuel cell 11 decreases.

<Effects of water pump control>

  In this manner, the target rotational speed of the water pump 66 is set so that the temperature difference between the fuel inlet temperature and the fuel outlet temperature is within the range (allowable range) that is higher than the release temperature and lower than the switching temperature. Based on the target rotational speed, the drive of the water pump 66 is controlled.

  Thus, when the temperature difference between the fuel inlet temperature and the fuel outlet temperature is relatively large, the target rotational speed is set to a relatively large high rotational speed, and the water pump 66 is driven at the target rotational speed. As a result, the cooling water flows through the cooling water flow path of the fuel cell 11 at a flow rate sufficient for cooling the fuel cell 11, so that the fuel cell 11 can be cooled well.

  On the other hand, when the temperature difference between the fuel inlet temperature and the fuel outlet temperature is relatively small, the target rotational speed of the water pump 66 is set to a relatively small normal rotational speed, and the water pump 66 is driven at the target rotational speed. The As a result, the power consumption of the water pump 66 can be kept low.

<3-way flow valve control>

  FIG. 4 is a block diagram showing a configuration for three-way flow valve control.

  During the power generation operation of the fuel cell system 1, the fuel outlet temperature is monitored by the FC-ECU 71. In addition, the target temperature setting unit 72 provided in the FC-ECU 71 allows the fuel cell 11 to generate power efficiently based on the capabilities (rotations) of the fuel circulation pump 29 and the compressor 41, etc. / The temperature of the solid polymer film contained in the electrode assembly) is determined, and the target temperature of the fuel outlet temperature is set to that temperature. Then, a subtractor 73 provided in the FC-ECU 71 obtains a deviation of the actual temperature (temperature detected by the FC outlet fuel temperature sensor 32) from the target temperature of the fuel outlet temperature. Subsequently, the opening degree of each outlet port of the three-way flow valve 65 is set by the three-way valve opening degree setting unit 74 provided in the FC-ECU 71 based on the deviation. The three-way flow valve 65 is controlled so that each outlet port has the set opening.

  FIG. 5 is a diagram showing the contents of a map used for setting the opening degree of each outlet port of the three-way flow valve.

  When the deviation of the actual temperature of the fuel outlet temperature with respect to the target temperature is less than a predetermined negative lower limit value, a connection port of the bypass pipe 68 provided in the three-way flow valve 65 (hereinafter referred to as “bypass side outlet port”). The opening degree is set to fully open, and the opening degree of the connection port of the radiator 63 (hereinafter referred to as “radiator side outlet port”) provided in the three-way flow valve 65 is set to fully closed.

  Thereby, all the cooling water flowing through the cooling water discharge pipe 62 bypasses the radiator 63, flows through the bypass pipe 68, and returns to the cooling water supply pipe 61.

  When the deviation between the target temperature of the fuel outlet temperature and the actual temperature is within the range of the lower limit value and less than 0, as the deviation approaches 0, the opening degree of the bypass side outlet port becomes smaller and the opening of the radiator side outlet port opens. The opening degree of the bypass-side outlet port and the radiator-side outlet port is set so that the degree is increased. When the deviation is 0, the opening degree of the bypass side outlet port and the opening degree of the radiator side outlet port are set to be the same.

  Thereby, a part of the cooling water flowing through the cooling water discharge pipe 62 passes through the radiator 63 and the rest flows through the bypass pipe 68. Then, as the deviation between the target temperature and the actual temperature of the fuel outlet temperature approaches 0, the flow rate of the cooling water passing through the radiator 63 increases, and the flow rate of the cooling water flowing through the bypass pipe 68 decreases.

  When the deviation between the target temperature of the fuel outlet temperature and the actual temperature is within the range of 0 or more and less than the predetermined upper limit value, the opening degree of the bypass side outlet port becomes smaller as the deviation approaches the upper limit value, and the radiator side outlet The opening degree of the bypass side outlet port and the radiator side outlet port is set so that the opening degree of the port becomes large.

  As a result, as the deviation between the target temperature of the fuel outlet temperature and the actual temperature approaches the upper limit value, the flow rate of the cooling water passing through the radiator 63 increases and the flow rate of the cooling water flowing through the bypass pipe 68 decreases.

  When the deviation of the actual temperature of the fuel outlet temperature with respect to the target temperature is equal to or higher than the upper limit value, the opening degree of the bypass side outlet port is set to be fully closed, and the opening degree of the radiator side outlet port is set to be fully open.

  Thereby, all the cooling water flowing through the cooling water discharge pipe 62 returns to the cooling water supply pipe 61 via the radiator 63.

<Effects of three-way flow valve control>

  Thus, based on the deviation of the actual temperature of the fuel outlet temperature with respect to the target temperature, the openings of the bypass side outlet port and the radiator side outlet port of the three-way flow valve are controlled so that the deviation approaches zero. By this control, the actual temperature of the fuel outlet temperature approaches the target temperature.

  The fuel outlet temperature is substantially the same as the temperature of the solid polymer membrane (reaction membrane) included in the membrane / electrode assembly of the fuel cell 11. Therefore, the temperature of the solid polymer membrane can be brought close to the target temperature by the three-way flow valve control. As a result, the power generation efficiency in the fuel cell 11 can be improved.

<Radiator fan control>

  FIG. 6 is a block diagram showing a configuration for controlling the radiator fan. FIG. 7 is a diagram showing a level change of the set signal in the radiator fan control. FIG. 8 is a diagram showing a change in level of the reset signal in the radiator fan control.

  During the power generation operation of the fuel cell system 1, the fuel outlet temperature is monitored by the FC-ECU 71. Further, the target temperature setting unit 72 sets the target temperature of the fuel outlet temperature. Then, the subtractor 73 obtains the deviation of the actual temperature (the temperature detected by the FC outlet fuel temperature sensor 32) from the target temperature of the fuel outlet temperature. When the obtained deviation is input to the set signal output unit 75 provided in the FC-ECU 71, a set signal having a level corresponding to the deviation is output from the set signal output unit 75.

  Specifically, as shown in FIG. 7, when the deviation is less than a predetermined value, a set signal having a level of 0 is output (OFF). When the deviation is greater than or equal to a predetermined value, a set signal having a level of 1 is output (ON).

  During the power generation operation of the fuel cell system 1, the temperature detected by the FC-ECU 71 by the FC inlet water temperature sensor 67, that is, the temperature of the cooling water flowing through the cooling water supply pipe 61 (hereinafter, referred to as the cooling water temperature) "Cooling water inlet temperature") is monitored. And the reset signal of the level according to the coolant inlet temperature is output from the reset signal output part 76 with which FC-ECU71 is equipped.

  Specifically, as shown in FIG. 8, when the coolant inlet temperature is equal to or lower than a predetermined temperature, a set signal having a level of 1 is output (ON). When the cooling water inlet temperature is higher than the predetermined temperature, a set signal whose level is 0 is output (OFF).

  The set signal output from the set signal output unit 75 and the reset signal output from the reset signal output unit 76 are input to the set terminal S and the reset terminal R of the RS flip-flop circuit 77 provided in the FC-ECU 71, respectively. Then, a signal output from the output terminal Q of the RS flip-flop circuit 77 (hereinafter referred to as “output signal”) is used as an ON command signal for the radiator fan 64, and the radiator fan 64 according to the level of the ON command signal. Is driven / stopped.

  When each level of the set signal and the reset signal is 0, the level of the output signal is held. That is, when each level of the set signal and the reset signal is 0, the level of the output signal is held at 0 if it is 0, and is held at 1 if it is 1.

  When the level of the set signal is switched from 0 to 1, that is, when the deviation of the actual temperature of the fuel outlet temperature from the target temperature exceeds a predetermined value, the level of the output signal is switched from 0 to 1. In response to this, the radiator fan 64 is driven.

  When the level of the reset signal is switched from 0 to 1, that is, when the cooling water inlet temperature falls below a predetermined temperature, the level of the output signal is switched from 1 to 0. In response to this, the driving of the radiator fan 64 is stopped.

<Effects of radiator fan control>

  When the deviation of the actual temperature of the fuel outlet temperature with respect to the target temperature is greater than or equal to a predetermined value, the radiator fan 64 is driven, and the blast from the radiator fan 64 is supplied to the radiator 63.

  Thereby, the temperature of the cooling water flowing through the cooling water supply pipe 61 can be lowered, and the fuel cell 11 can be cooled well. As a result, the temperature of the liquid (liquid fuel) discharged from the fuel cell 11 to the fuel discharge pipe 31 can be brought close to the target temperature satisfactorily.

  After driving the radiator fan 64, after confirming a decrease in the temperature of the cooling water flowing out from the fuel cell 11 to the cooling water discharge pipe 62, when the driving of the radiator fan 64 is stopped, the cooling flowing into the fuel cell 11 thereafter The fuel cell 11 may be overcooled by water.

  Therefore, when the cooling water inlet temperature falls below a predetermined temperature, the driving of the radiator fan 64 is stopped.

  Thereby, overcooling of the fuel cell 11 can be prevented. In addition, power consumption by the radiator fan 64 can be reduced. At the time when the radiator fan 64 is stopped, the cooling water inlet temperature is lowered to a predetermined temperature or lower. Therefore, after the radiator fan 64 is stopped, the fuel cell 11 is cooled with the cooling water whose temperature has been reduced. There is no risk of insufficient cooling of the fuel cell 11.

<Other three-way valve opening control and radiator fan control>

  FIG. 9 is a block diagram showing a configuration for other three-way flow valve control and radiator fan control. FIG. 10 is a diagram showing the contents of a map used for setting the opening degree of each outlet port of the three-way flow valve, and the level change of the set signal and the reset signal in the radiator fan control.

  Instead of the above-described three-way valve opening control and radiator fan control, the following three-way valve opening control and radiator fan control may be executed.

  During the power generation operation of the fuel cell system 1, the total cooling that is the total amount of heat for cooling the fuel cell 11 is calculated by the total cooling heat amount calculation unit 81 provided in the FC-ECU 71 for the three-way valve opening control and the radiator fan control. The amount of heat is calculated.

  Specifically, the temperature detected by the cooling water inlet temperature and the FC outlet water temperature sensor 69, that is, the temperature of the cooling water flowing out from the fuel cell 11 to the cooling water discharge pipe 62 (hereinafter referred to as “cooling water outlet temperature”). Is multiplied by the flow rate of the cooling water flowing through the cooling water supply pipe 61, the specific gravity of the cooling water, and the specific heat of the cooling water, so that the amount of heat of the cooling water flowing through the cooling water supply pipe 61 at the present time is A certain amount of cooling water cooling heat is calculated. The flow rate of the cooling water flowing through the cooling water supply pipe 61 is obtained based on, for example, the rotational speed of the water pump 66.

  Further, by multiplying the temperature difference between the target temperature of the fuel outlet temperature and the actual temperature by the flow rate, specific gravity, and specific heat of the liquid (liquid fuel) flowing through the fuel discharge pipe 31, the liquid flowing through the fuel discharge pipe 31 is The liquid cooling heat quantity, which is the heat quantity to be cooled, is calculated. The flow rate of the liquid flowing through the fuel discharge pipe 31 is obtained based on, for example, the rotational speed of the fuel circulation pump 29.

  Further, by multiplying the temperature difference between the target temperature of the fuel outlet temperature and the actual temperature by the amount of heat of the fuel cell 11, a fuel cell cooling heat amount that is a heat amount for cooling the fuel cell 11 is calculated.

  Then, the total cooling heat amount is calculated by adding the cooling water cooling heat amount, the liquid cooling heat amount, and the fuel cell cooling heat amount.

  When the total cooling heat amount is calculated by the total cooling heat amount calculation unit 81, the three-way valve opening setting unit 82 provided in the FC-ECU 71 opens the outlet ports of the three-way flow valve 65 based on the total cooling heat amount. The degree is set. The three-way flow valve 65 is controlled so that each outlet port has the set opening.

  Specifically, as shown in FIG. 10, when the total cooling heat quantity is less than 0, the opening degree of the bypass side outlet port is set to fully open, and the opening degree of the radiator side outlet port is set to fully closed. .

  Thereby, all the cooling water flowing through the cooling water discharge pipe 62 bypasses the radiator 63, flows through the bypass pipe 68, and returns to the cooling water supply pipe 61.

  When the total cooling heat quantity is in the range of 0 or more and less than the predetermined first heat quantity, the opening degree of the bypass side outlet port becomes smaller and the opening degree of the radiator side outlet port becomes smaller as the total cooling heat quantity approaches the first heat quantity. The opening degree of the bypass side outlet port and the radiator side outlet port is set so as to increase.

  Thereby, a part of the cooling water flowing through the cooling water discharge pipe 62 passes through the radiator 63 and the rest flows through the bypass pipe 68. Then, as the total cooling heat amount approaches the first heat amount, the flow rate of the cooling water passing through the radiator 63 increases, and the flow rate of the cooling water flowing through the bypass pipe 68 decreases.

  When the total cooling heat quantity is within the range of the first heat quantity and less than the predetermined second heat quantity, as the total cooling heat quantity approaches the second heat quantity, the opening degree of the bypass side outlet port becomes smaller and the opening of the radiator side outlet port becomes smaller. The opening degree of the bypass-side outlet port and the radiator-side outlet port is set so that the degree is increased. Also, until the total cooling heat amount reaches a third heat amount smaller than the second heat amount, the opening degree with respect to the increase in the total cooling heat amount is greater than when the total cooling heat amount is in the range of 0 or more and less than the predetermined first heat amount. If the total cooling heat amount exceeds the third heat amount, the total cooling heat amount is in the range of 0 or more and less than the predetermined first heat amount, and the opening degree is changed with respect to the increase in the total cooling heat amount. The opening degree of the bypass side outlet port and the radiator side outlet port is set so that the degree is the same.

  As the total amount of cooling heat approaches the second amount of heat, the flow rate of the cooling water passing through the radiator 63 further increases, and the flow rate of the cooling water flowing through the bypass pipe 68 further decreases.

  When the total cooling heat quantity is equal to or greater than the second heat quantity, the opening degree of the bypass side outlet port is set to be fully closed, and the opening degree of the radiator side outlet port is set to be fully open.

  Thereby, all the cooling water flowing through the cooling water discharge pipe 62 returns to the cooling water supply pipe 61 via the radiator 63.

  The total cooling heat amount calculated by the total cooling heat amount calculation unit 81 is input to a set signal output unit 83 provided in the FC-ECU 71. When the total cooling heat amount is input to the set signal output unit 83, a set signal having a level corresponding to the total cooling heat amount is output from the set signal output unit 83.

  Specifically, as shown in FIG. 10, when the total cooling heat quantity is less than the first heat quantity, a set signal whose level is 0 is output (OFF). When the total cooling heat quantity is equal to or greater than the first heat quantity, a set signal having a level of 1 is output (ON).

  The total cooling heat amount calculated by the total cooling heat amount calculation unit 81 is input to the reset signal output unit 84 provided in the FC-ECU 71. When the total cooling heat amount is input to the reset signal output unit 84, a reset signal having a level corresponding to the total cooling heat amount is output from the reset signal output unit 84.

  Specifically, as shown in FIG. 10, when the cold total cooling heat quantity is equal to or less than the fourth heat quantity smaller than the first heat quantity, a set signal having a level of 1 is output (ON). When the total cooling heat quantity is larger than the fourth heat quantity, a set signal whose level is 0 is output (OFF).

  The set signal output from the set signal output unit 83 and the reset signal output from the reset signal output unit 84 are input to the set terminal S and the reset terminal R of the RS flip-flop circuit 85 provided in the FC-ECU 71, respectively. Then, a signal output from the output terminal Q of the RS flip-flop circuit 85 (hereinafter referred to as “output signal”) is used as an on command signal of the radiator fan 64, and the radiator fan 64 according to the level of the on command signal. Is driven / stopped.

  When each level of the set signal and the reset signal is 0, the level of the output signal is held. That is, when each level of the set signal and the reset signal is 0, the level of the output signal is held at 0 if it is 0, and is held at 1 if it is 1.

  When the level of the set signal is switched from 0 to 1, that is, when the deviation of the actual temperature of the fuel outlet temperature from the target temperature exceeds a predetermined value, the level of the output signal is switched from 0 to 1. In response to this, the radiator fan 64 is driven.

  When the level of the reset signal is switched from 0 to 1, that is, when the cooling water inlet temperature falls below a predetermined temperature, the level of the output signal is switched from 1 to 0. In response to this, the driving of the radiator fan 64 is stopped.

<Effects of other three-way valve opening control and radiator fan control>

  By the three-way valve opening control and the radiator fan control, the openings of the bypass-side outlet port and the radiator-side outlet port of the three-way flow valve 65 are controlled so that the total cooling heat amount can be obtained, and the radiator fan 64 is driven. Be controlled. As a result, the fuel cell 11 is cooled well, and the fuel outlet temperature from the fuel cell 11, that is, the temperature of the solid polymer film (reaction film) included in the membrane / electrode assembly of the fuel cell 11 is brought close to the target temperature. Can do. As a result, the power generation efficiency in the fuel cell 11 can be improved. Further, when the amount of cooling heat necessary for cooling the fuel cell 11 is small, the driving of the radiator fan 64 is suppressed, so that power consumption is reduced.

<Modification>

  As mentioned above, although embodiment of this invention was described, this invention can also be implemented with another form. In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 11 Fuel cell 28 Fuel supply pipe (fuel supply path)
30 FC inlet fuel temperature sensor (fuel inlet temperature detection means)
31 Fuel discharge pipe 32 FC outlet fuel temperature sensor (fuel outlet temperature detection means)
61 Cooling water supply pipe (refrigerant circuit)
62 Cooling water discharge pipe (refrigerant circuit)
63 Radiator 64 Radiator fan 65 Three-way flow valve 66 Water pump (refrigerant pump)
67 FC inlet water temperature sensor (refrigerant inlet temperature detection means)
68 Bypass pipe (bypass)
69 FC outlet water temperature sensor (refrigerant outlet temperature detection means)
71 FC-ECU
72 Target temperature setting section (Target temperature setting means)
73 Subtractor (deviation calculation means)
74 Three-way valve opening setting section (three-way flow valve control means)
75 Set signal output unit (radiator fan control means)
76 Reset signal output unit (radiator fan control means)
77 RS flip-flop circuit (radiator fan control means)
81 Total cooling calorie calculation part (control means)
82 Three-way valve opening setting section (control means)
83 Set signal output section (control means)
84 Reset signal output unit (control means)
85 RS flip-flop circuit (control means)

Claims (3)

A fuel cell comprising a membrane / electrode assembly, a fuel supply channel through which liquid fuel supplied to the fuel cell flows, a fuel discharge channel through which liquid fuel discharged from the fuel cell flows, and cooling the fuel cell A cooling control device for a fuel cell system, comprising: a refrigerant circulation path through which a refrigerant for circulation is circulated; a refrigerant pump interposed in the refrigerant circulation path; and a radiator that radiates heat of the refrigerant circulating in the refrigerant circulation path. There,
Fuel inlet temperature detection means for detecting the temperature of the liquid fuel supplied from the fuel supply path to the fuel cell;
Fuel outlet temperature detection means for detecting the temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path;
Until the temperature difference between the temperature detected by the fuel inlet temperature detecting means and the temperature detected by the fuel outlet temperature detecting means opens above a predetermined switching temperature, the target rotational speed of the refrigerant pump is set to the normal rotational speed. When the temperature difference opens more than the switching temperature, the target rotation speed is switched to a rotation speed larger than the normal rotation speed, and after the switching, the temperature difference is reduced to a release temperature lower than the switching temperature. A target rotation speed setting means for setting the target rotation speed of the refrigerant pump by returning the target rotation speed to the normal rotation speed ;
A cooling control device for a fuel cell system, comprising: pump control means for controlling driving of the refrigerant pump based on the target speed set by the target speed setting means. The fuel cell system includes a radiator fan that blows air to the radiator, a bypass that is branched and connected to the refrigerant circulation path, and that bypasses the radiator through the refrigerant circulating in the refrigerant circulation path, the refrigerant circulation path, and the A three-way flow valve for adjusting a flow rate of the refrigerant passing through the radiator and the bypass path, provided at a branch portion with the bypass path;
Refrigerant inlet temperature detection means for detecting the temperature of the refrigerant flowing into the fuel cell from the refrigerant circuit;
Target temperature setting means for setting a target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path;
Deviation calculating means for calculating a deviation of the temperature detected by the fuel outlet temperature detecting means with respect to the target temperature set by the target temperature setting means;
Three-way flow valve control means for controlling the three-way flow valve based on the deviation calculated by the deviation calculation means;
A radiator that drives the radiator fan when the deviation calculated by the deviation calculating means is greater than or equal to a predetermined value and stops the radiator fan when the temperature detected by the refrigerant inlet temperature detecting means is less than or equal to a predetermined temperature. The cooling control apparatus for a fuel cell system according to claim 1, further comprising a fan control means. The fuel cell system includes a radiator fan that blows air to the radiator, a bypass that is branched and connected to the refrigerant circulation path, and that bypasses the radiator through the refrigerant circulating in the refrigerant circulation path, the refrigerant circulation path, and the A three-way flow valve for adjusting a flow rate of the refrigerant passing through the radiator and the bypass path, provided at a branch portion with the bypass path;
Refrigerant inlet temperature detection means for detecting the temperature of the refrigerant flowing into the fuel cell from the refrigerant circuit;
Refrigerant outlet temperature detection means for detecting the temperature of the refrigerant flowing out from the fuel cell to the refrigerant circuit;
Target temperature setting means for setting a target temperature of the liquid fuel discharged from the fuel cell to the fuel discharge path;
A temperature detected by the fuel outlet temperature detecting means, a temperature detected by the refrigerant inlet temperature detecting means, a temperature detected by the refrigerant outlet temperature detecting means, a target temperature set by the target temperature setting means, the fuel And a control means for controlling the three-way flow valve and the radiator fan based on a flow rate of the liquid fuel flowing through the supply path, a flow rate of the refrigerant circulating in the coolant circulation path, and a heat capacity of the fuel cell. 2. A cooling control device for a fuel cell system according to 1.

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