JP4419735B2 - Fuel cell vehicle - Google Patents

Description

  The present invention relates to a fuel cell vehicle equipped with a fuel cell and a power storage device as a power source, and more particularly to an improved technique for efficiently consuming surplus power generated when the fuel cell is overcharged.

In a fuel cell vehicle equipped with a fuel cell and a power storage device as a power source, the vehicle is driven mainly by supplying power generated by the fuel cell to the traction motor, and regenerative braking is performed on the traction motor during deceleration or downhill. The regenerative power collected in this way is charged to the power storage device, and the regenerative power is used for assistance in scenes where the load is high, such as starting acceleration or running uphill, or in driving areas where the fuel cell operating efficiency is poor. Improves fuel economy and driving performance. In this type of fuel cell vehicle, when the SOC (State of Charge) of the power storage device reaches an upper limit during regenerative braking, the traction motor cannot generate deceleration torque due to regenerative braking interruption, and the braking force is reduced. There is a problem of lowering. In order to solve such a problem, Japanese Patent Application Laid-Open No. 2002-204505 describes the operation of auxiliary machinery when surplus power is generated during low load operation such as regenerative braking or idling while the power storage device is overcharged. Techniques for reducing the efficiency and consuming excess power have been proposed.
JP 2002-204505 A

  However, when surplus power is generated when the power storage device is overcharged, it is preferable to consume the surplus power with auxiliary equipment or the like while the low load operation of the fuel cell is continued because fuel efficiency deteriorates. Absent. Also, if surplus power is generated when the power storage device is overcharged, stopping the operation of the fuel cell and consuming surplus power with auxiliary equipment, etc. will cause the fuel cell's self-heating to stop and the influence of traveling wind As a result, the stack temperature decreases, and the IV characteristics may deteriorate. When the IV characteristics deteriorate, even if the fuel cell is restarted in response to a subsequent high load request, the once-reduced cell voltage is not recovered immediately and a response delay occurs, resulting in a decrease in drivability. To do.

  Therefore, the present invention solves such a problem, and a fuel cell vehicle that consumes surplus power generated in a state where the power storage device is overcharged without impairing the drivability of the fuel cell vehicle and can suppress deterioration in fuel consumption. The challenge is to propose.

In order to solve the above problems, a fuel cell vehicle according to the present invention is driven by electric power supplied from at least one of a fuel cell, a power storage device, and a fuel cell or a power storage device, and supplies regenerative power to the power storage device. A traction motor that can be recharged and a temperature adjustment that limits the operation of the fuel cell and adjusts the temperature of the fuel cell when surplus power is generated when the SOC of the power storage device is greater than or equal to a predetermined value. And the temperature adjusting means increases the temperature of the fuel cell as the vehicle traveling speed increases. With this configuration, surplus power generated when the power storage device is overcharged can be consumed without impairing the drivability of the fuel cell vehicle, and deterioration of fuel consumption can be suppressed. Further, the temperature of the fuel cell cooled by the influence of the traveling wind can be raised to an appropriate temperature. “Temperature adjusting means” means a control means (for example, an air conditioner or the like) for controlling the operating state of the fuel cell in addition to means for adjusting the temperature of the fuel cell by converting surplus electricity into heat energy (for example, an air conditioner). Controller etc.).

  The temperature adjusting means desirably pauses the operation of the fuel cell when surplus power is generated when the SOC of the power storage device is equal to or higher than a predetermined value. By temporarily stopping the operation of the fuel cell, overcharge of the power storage device can be suppressed.

  Here, as the surplus power, for example, regenerative power collected by the traction motor during regenerative braking can be cited.

  The temperature adjusting means preferably includes a fuel cell vehicle air conditioner. In addition to consuming excess power by using an air conditioner, the fuel cell can be warmed up by converting it into thermal energy.

  It is desirable that the temperature adjusting means consumes a part of the surplus power as heat energy necessary for adjusting the temperature of the fuel cell, and adjusts the target temperature of the passenger compartment based on the remaining power amount obtained by subtracting this heat energy from the surplus power. . With this configuration, it is possible to appropriately warm up the fuel cell by consuming surplus power.

  In addition to the above-described configuration, the fuel cell vehicle of the present invention preferably further includes a humidity adjusting unit that adjusts the humidity inside the fuel cell in accordance with the temperature adjustment of the fuel cell. Drying of the electrolyte membrane and the like accompanying temperature adjustment of the fuel cell by the temperature adjusting means can be suppressed.

  According to the present invention, surplus power generated when the power storage device is overcharged can be consumed without impairing the drivability of the fuel cell vehicle, and deterioration of fuel consumption can be suppressed.

  FIG. 1 schematically shows the system configuration of a fuel cell vehicle (FCEV). The fuel cell vehicle 10 is configured as a hybrid system (FCHV system) in which a fuel cell 21 and a secondary battery (power storage device) 22 are mounted together as a power supply device. The fuel cell 21 is configured as, for example, a polymer electrolyte fuel cell, and generates electric power upon receiving supply of fuel gas and oxidizing gas. Hydrogen gas released from a hydrogen supply source (not shown) such as a high-pressure hydrogen tank is supplied to the anode electrode of the fuel cell 21 as fuel gas, and air from which dust or the like has been filtered through the air filter 61 is supplied to the cathode electrode. Pressurized air pressurized by the air compressor 62 and moderately humidified by the humidifier 63 is supplied as an oxidizing gas. The humidifier 63 is a high-humidity oxygen off-gas (high-humidity gas) discharged from the fuel cell 21 through the cathode off-gas channel 65 and a low-humidity oxidizing gas (dry) that flows into the fuel cell 21 through the cathode gas channel 64. Moisture exchange with the gas) is performed, and the oxidizing gas flowing into the fuel cell 21 is appropriately overhumidified. The air compressor 62 and the humidifier 63 function as humidity adjusting means MC that adjusts the humidity inside the fuel cell 21 (gas channel, polymer electrolyte membrane, etc.).

  The power generated by the fuel cell 21 is supplied to various power loads via the power lines L1 and L2. In the present embodiment, the inverters INV1 to INV3 that convert DC power into AC power and the DC / DC converter CNV that boosts or lowers DC power are illustrated as power loads. However, the present invention is not limited to this, and is necessary. Various power loads may be connected accordingly. The inverter INV1 supplies AC power to a motor M1 that drives a compressor P1 installed in an air conditioner (air conditioner) 30 that controls the cooling and heating of the passenger compartment. The inverter INV2 supplies AC power to a motor M2 that drives a cooling water pump P2 installed in the cooling water system of the fuel cell 21. The inverter INV3 supplies AC power to a traction motor (vehicle driving motor) M3. The DC / DC converter CNV converts the electric power generated by the fuel cell 21 or the electric power regenerated by the traction motor M3 into an appropriate voltage to charge the secondary battery 22 and adjust the output voltage of the fuel cell 21 Thus, distribution control of power supplied from the fuel cell 21 and the secondary battery 22 to the power load is performed. As the secondary battery 22, for example, a nickel / cadmium storage battery, a nickel / hydrogen storage battery, a lithium secondary battery, or the like is suitable, and its power capacity is designed according to the expected running state of the fuel cell vehicle, load fluctuations, and the like. Is done. However, a power storage device such as a capacitor may be mounted instead of the secondary battery 22.

  In the cooling water system of the fuel cell 21, cooling water passages 52 to 56, a radiator 57, a cooling water pump P2, and three-way valves A4 and A5 are installed. In the cooling state in normal operation, the ports a1 and a2 of the three-way valve A4 are opened and the port a3 is closed, while the ports b1 and b3 of the three-way valve A5 are opened and the port b2 is closed. Then, a closed circuit is formed by the cooling water channels 52 and 53, and the high-temperature cooling water discharged from the fuel cell 21 is cooled by the radiator 57 and then circulates in the cooling water channels 52 and 53. The cooling water temperature can be adjusted by controlling the opening and closing of the ports a1 to a3 of the three-way valve A4 and adjusting the bypass flow rate of the cooling water passage 54 branched from the cooling water passage 52 and bypassing the radiator 57. On the other hand, the cooling water channels 55 and 56 communicate with a heat exchanger 51 installed inside the air conditioner device 30, and perform heat exchange with the air conditioner device 30 to raise the temperature of the cooling water to thereby increase the temperature of the fuel cell. It is comprised so that 21 can be warmed up to moderate temperature. Details of a processing procedure for warming up the fuel cell 21 by heat exchange between the cooling water and the air conditioner 30 will be described later.

  The air conditioner 30 is an apparatus for controlling the heating and cooling of the vehicle interior by a heat pump cycle, and mainly includes an indoor unit (heat exchanger) 41 and an outdoor unit (heat exchanger) 42, and a refrigerant P is circulated by the compressor P1. It is circulated in 43. The circulation passage 43 is provided with expansion valves A1, A2, a four-way valve A3, and a compressor P1, and controls the direction in which the refrigerant flows by controlling the opening and closing of the ports c1 to c4 of the four-way valve A3. The heat pump cycle can be realized without changing the rotation direction of the machine P1. The air conditioner 30 compresses the outside air taken in from the air conditioner duct 31 with the blower fan PN, exchanges heat with the indoor unit 41, and then blows warm air or cold air toward the vehicle interior or the exterior of the vehicle interior. In the case of cooling and heating the passenger compartment, the air passage 33 communicating with the outside of the passenger compartment is closed by the air conditioner duct switching valve A6, and hot air or cold air is guided to the air passage 32 communicating with the passenger compartment. On the other hand, when the vehicle interior is not cooled or heated, the air passage 32 communicating with the vehicle interior is closed by the air conditioner duct switching valve A6, and hot air or cold air is guided to the air passage 33 communicating with the outside of the vehicle interior. The heat exchanger 51 described above is provided with switching valves A7 and A8 for blocking heat exchange between the air conditioner device 30 and the heat exchanger 51, and heat is generated by closing the switching valves A7 and A8. When the exchanger 51 is covered, the heat exchanger 51 is disconnected from the outside air, so that heat exchange with the air conditioner 30 is blocked. On the other hand, when the switching valves A7 and A8 are opened, the heat exchanger 51 can exchange heat with the air conditioner 30.

  The controller (ECU) 70 calculates the required load based on the accelerator opening signal from the accelerator sensor 71, the vehicle speed signal from the vehicle speed sensor, and the like, and controls the operation of the fuel cell 21 so as to obtain the required power generation amount. It is a control means for performing various system controls (for example, surplus power consumption control described later) as necessary. The controller 70 acquires the SOC of the secondary battery 22 detected by the SOC detector C1, the temperature of the fuel cell 21 detected by the temperature detector C2, and the humidity of the fuel cell 21 detected by the humidity detector C3. For example, the internal state (temperature or humidity, etc.) of the fuel cell 21 and the charging state of the secondary battery 22 are monitored, and the above-described compressor P1, cooling water pump P2, various valves A1 to A8, blower fan PN, humidity The entire system is controlled by controlling the adjusting means MC, the DC / DC converter CNV, and the inverters INV1 to INV3. In addition, the controller 70 is configured to temporarily stop the operation of the fuel cell 21 during low load operation and to perform an operation mode (intermittent operation mode) in which the vehicle travels only by supplying power from the secondary battery 22.

  FIG. 3 shows a table in which the system is classified into seven states based on the presence / absence of a cooling / heating request of the air conditioner 30, the charging state of the secondary battery 22, and the presence / absence of a warming-up request of the fuel cell 21. FIG. 2 shows a flowchart of surplus power consumption control corresponding to “state 1” among the seven types of states described above (for convenience of explanation, “state 2” to “state 7” are omitted). Here, “surplus power consumption control” means that surplus power generated during low-load operation (during regenerative braking) is consumed by reducing the operation efficiency of the auxiliary machinery when the secondary battery 22 is overcharged. This control includes control for warming up the fuel cell 21 by converting surplus power into thermal energy when there is a request for warming up the fuel cell 21.

  First, surplus power consumption control in “state 1” will be described. “State 1” is a system state when there is a request for heating in the passenger compartment, the secondary battery 22 is in an overcharged state, and there is a request for warming up the fuel cell 21. In “State 1”, since the secondary battery 22 is in an overcharged state, the operation of the fuel cell 21 is restricted (preferably temporarily suspended), and auxiliary machinery or the like (for example, by the regenerative power collected by the traction motor M3) , Supply operating power to the compressor P1 and the cooling water pump P2. Further, in this system state, since there is a request for heating the vehicle interior and a request for warming up the fuel cell 21, the controller 70 determines the amount of regenerative power (surplus power amount) recovered by the traction motor M3, the target temperature of the fuel cell 21, and the fuel. Thermal energy necessary for temperature adjustment of the fuel cell 21 is calculated based on the traveling speed of the battery vehicle 10 and the like. If the vehicle interior temperature cannot be adjusted to the temperature specified by the driver with the remaining power amount obtained by subtracting the thermal energy necessary for adjusting the temperature of the fuel cell 21 from the surplus power, the operation target temperature of the air conditioner 30 is set to the remaining power. Change to a temperature that can be covered by volume. The controller 70 calculates heat energy required for heating the vehicle interior calculated from the deviation between the vehicle interior temperature and the operation target temperature (required temperature), and heat energy required for warming the fuel cell 21 to the target temperature (air conditioner device). The expansion valves A1 and A2, the four-way valve A3, the compressor P1, and the blower fan PN are controlled so that the total heat energy including the heat exchange amount of 30 and the heat exchanger 51 is released from the indoor unit 41. Specifically, the controller 70 drives the compressor P1 to circulate the refrigerant, fully opens the expansion valve A1, uses the expansion valve A2 as an expansion valve, and brings the ports c2 and c3 of the four-way valve A3 into communication. Ports c1 and c4 are brought into communication. As a result, the indoor unit 41 radiates heat and the outdoor unit 42 absorbs heat, so that the outside air taken in from the air-conditioner duct 31 receives heat from the indoor unit 41 and passes through the heat exchanger 51 in the course of passing through the heat exchanger 51. While exchanging, the air is guided to the ventilation path 32. The cooling water heated by the heat exchanger 51 is circulated through the cooling water passages 52, 55, 56, and 53 by the cooling water pump P2 to warm up the fuel cell 21. At this time, the ports b1 and b2 of the three-way valve A5 are opened and the port b3 is closed. In addition, the valve position of the air conditioner duct switching valve A6 is controlled so as to close the ventilation path 33, and the switching valves A7 and A8 are controlled so that the heat exchanger 51 and the air conditioner 30 can exchange heat. . As described above, the controller 70 and the air conditioner device 30 function as temperature adjusting means for adjusting the temperature of the fuel cell 21 by converting surplus power into heat energy.

  When the fuel cell 21 is warmed up, it is preferable to control the humidity adjusting means MC so that the polymer electrolyte membrane inside the fuel cell 21 can maintain an appropriate wet state. For example, the controller 70 rotates the air compressor 62 at a low speed, supplies a small amount of air humidified by the humidifier 63 to the fuel cell 21, and controls the humidity detected by the humidity detecting means C3 to match the target humidity. To do. However, the wet state of the fuel cell 21 may be controlled based on the dew point as well as the humidity. Further, by controlling the rotation speed of the cooling water pump P2, the cooling capacity of the radiator 57, etc., the temperature increase rate (the rising temperature per unit time) of the cooling water flowing into the fuel cell 21 is moderately controlled. 21 wet states may be controlled. In this way, surplus power is converted into heat energy, and the surcharge is efficiently consumed by warming up the fuel cell 21 using a part of the heat energy, thereby overcharging the secondary battery 22. While suppressing, the deterioration state (output restriction state) of the IV characteristic by cooling of the fuel cell 21 can be suppressed. The target temperature of the fuel cell 21 is desirably set so as to increase as the traveling speed of the fuel cell vehicle 10 increases.

  Here, the surplus electricity consumption control in “state 1” will be described again with reference to FIG. 2 (however, the description overlapping with the above description will be simplified). The controller 70 monitors the SOC of the secondary battery 22, and determines that it is overcharged when the SOC is equal to or greater than a predetermined value (for example, 80% to 90%) (S1; YES). If regenerative braking by the traction motor M3 is performed in a state where the secondary battery 22 is overcharged (S2; YES), the regenerative power can cover the operating power of the in-vehicle auxiliary equipment during low load operation. Is stopped (S3). Next, it is checked whether or not there is a heating request in the vehicle interior (S4). If there is a heating request (S4; YES), the air conditioning device 30 is controlled to heat the vehicle interior (S5), and a heating request is made. When there is no (S4; NO), heating is not performed. Next, it is checked whether or not there is a request for warm-up of the fuel cell 21 (S6). If there is a request for warm-up (S6; YES), the fuel cell 21 is warmed by cooling water via the heat exchanger 51. Machine control is performed (S7). In this warm-up control, the amount of heat dissipated in the indoor unit 41, the amount of heat exchange in the heat exchanger 51, the number of rotations of the cooling water pump P2, so that the temperature inside the fuel cell 21 detected by the temperature detecting means C2 matches the target temperature, The cooling capacity of the radiator 57 is controlled. Further, the wet state is controlled as necessary so that the polymer electrolyte membrane inside the fuel cell 21 does not dry too much (S8).

  Next, an outline of surplus power consumption control in each state of “state 2” to “state 7” will be described. “State 2” is a state in which there is no cooling / heating request in the passenger compartment, the secondary battery 22 is in an overcharged state, and there is a request for warming up the fuel cell 21. In this state, the compressor P1 and the cooling water pump P2 are driven using the regenerative electric power collected by the traction motor M3, and the temperature of the cooling water is raised through the heat exchanger 51 by the heat radiated from the air conditioner 30. The fuel cell 21 is warmed up to the target temperature. The air conditioner duct switching valve A6 is controlled so that the warm air is not guided into the vehicle interior by closing the ventilation passage 32.

  “State 3” is a state in which there is a request for heating the passenger compartment, the secondary battery 22 is not overcharged, and there is a request for warming up the fuel cell 21. In this state, since the secondary battery 22 is not in an overcharged state, auxiliary machinery (for example, the compressor P1 and the cooling water pump P2) is driven by the power generated by the fuel cell 21. The controller 70 controls the expansion valves A1 and A2 and the four-way valve A3 so that heat is radiated by the indoor unit 41 and heat is absorbed by the outdoor unit 42. Further, the cabin temperature and the temperature of the fuel cell 21 are respectively set to the target temperatures. The amount of power consumed by the compressor P1 and the cooling water pump P2 required to reach the value is calculated, and the amount of power generated by the fuel cell 21 is controlled.

  “State 4” is a state in which there is no request for cooling / heating in the passenger compartment, the secondary battery 22 is not overcharged, and there is a request for warm-up of the fuel cell 21. In this state, as in “State 3”, the auxiliary devices (for example, the compressor P1 and the cooling water pump P2) are driven by the power generated by the fuel cell 21, causing the indoor unit 41 to radiate heat, and the outdoor unit 42. To endotherm. The controller 70 calculates the power consumption of the compressor P1 and the cooling water pump P2 necessary for the temperature of the fuel cell 21 to reach the target temperature, and controls the power generation amount of the fuel cell 21. The controller 70 raises the temperature of the cooling water through the heat exchanger 51 by the heat radiated from the air conditioner 30 and warms up the fuel cell 21 to the target temperature. The air conditioner duct switching valve A6 is controlled so that the warm air is not guided into the vehicle interior by closing the ventilation passage 32.

  “State 5” is a state in which there is a cooling request in the vehicle interior, the secondary battery 22 is in an overcharged state, and there is no request for warming up the fuel cell 21. In this state, the regenerative power collected by the traction motor M3 is used to drive the compressor P1 and the cooling water pump P2, and the expansion valves A1, A2, and the four-way valve A3 are controlled to cause the indoor unit 41 to absorb heat, The device 42 generates heat. The cold air generated by the heat absorption operation of the indoor unit 41 is guided to the vehicle interior through the ventilation path 32. The air conditioner duct switching valve A6 is controlled so that the cool air is not guided outside the passenger compartment by closing the ventilation passage 33. Further, the three-way valve A5 is controlled so that the cooling water circulating inside the fuel cell 21 does not flow into the heat exchanger 51. The valve positions of the switching valves A7 and A8 are controlled so that heat exchange is not performed between the heat exchanger 51 and the air conditioner device 30.

  "State 6" is a state in which there is a request for heating the vehicle interior, the secondary battery 22 is in an overcharged state, and there is no request for warming up the fuel cell 21. In this state, the regenerative power collected by the traction motor M3 is used to drive the compressor P1 and the cooling water pump P2, and the expansion valves A1, A2 and the four-way valve A3 are controlled to cause the indoor unit 41 to generate heat, The container 42 is made to absorb heat. The warm air generated by the heat generation operation of the indoor unit 41 is guided to the vehicle interior through the ventilation path 32. The air conditioner duct switching valve A6 is controlled so that the warm air is not guided outside the passenger compartment by closing the ventilation passage 33. Further, the three-way valve A5 is controlled so that the cooling water circulating inside the fuel cell 21 does not flow into the heat exchanger 51. The valve positions of the switching valves A7 and A8 are controlled so that heat exchange is not performed between the heat exchanger 51 and the air conditioner device 30.

  “State 7” is a state in which there is no request for air conditioning in the passenger compartment, the secondary battery 22 is in an overcharged state, and there is no request for warming up the fuel cell 21. In this state, the regenerative power collected by the traction motor M3 is used to drive the compressor P1 and the cooling water pump P2, and the expansion valves A1, A2 and the four-way valve A3 are controlled to cause the indoor unit 41 to generate heat, The container 42 is made to absorb heat. The warm air generated by the heat generation operation of the indoor unit 41 is guided outside the vehicle compartment through the ventilation path 33. The air conditioner duct switching valve A6 is controlled so that the warm air is not guided into the vehicle interior by closing the ventilation passage 32. Further, the three-way valve A5 is controlled so that the cooling water circulating inside the fuel cell 21 does not flow into the heat exchanger 51. The valve positions of the switching valves A7 and A8 are controlled so that heat exchange is not performed between the heat exchanger 51 and the air conditioner device 30.

  As a temperature adjusting means for adjusting the temperature of the fuel cell 21, in addition to the air conditioner 30 described above, for example, an electric heater is installed in the fuel cell 21 (for example, in a separator) or a cooling water channel, and surplus power is provided. Alternatively, the temperature of the fuel cell 21 may be adjusted directly or indirectly through cooling water.

1 is a system configuration diagram of a fuel cell vehicle according to an embodiment. It is a flowchart of the surplus power consumption control of this embodiment. It is a system state table | surface of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell vehicle 21 ... Fuel cell 22 ... Secondary battery 30 ... Air-conditioner apparatus 70 ... Controller INV1-INV3 ... Inverter M1-M3 ... Motor C1 ... SOC detection means C2 ... Temperature detection means C3 ... Humidity detection means MC ... Humidity adjustment means

Claims (6)

A fuel cell, a power storage device, a traction motor that is driven by power supplied from at least one of the fuel cell and the power storage device and that can recharge the power storage device, and a SOC of the power storage device A temperature adjusting means for restricting the operation of the fuel cell when surplus power is generated in a state where the power is greater than or equal to a predetermined value, and adjusting the temperature of the fuel cell by consuming the surplus power, and the temperature adjusting means Is a fuel cell vehicle in which the temperature of the fuel cell is increased as the vehicle traveling speed increases .   2. The fuel cell vehicle according to claim 1, wherein the temperature adjustment unit temporarily stops the operation of the fuel cell when surplus power is generated when the SOC of the power storage device is equal to or higher than a predetermined value. . 3. The fuel cell vehicle according to claim 1 , wherein the surplus power is regenerative power collected by the traction motor during regenerative braking. 4. 4. The fuel cell vehicle according to claim 1 , wherein the temperature adjusting unit includes an air conditioner for the fuel cell vehicle. 5. 5. The fuel cell vehicle according to claim 4 , wherein the temperature adjusting means consumes a part of the surplus power as heat energy necessary for temperature adjustment of the fuel cell, and subtracts the heat energy from the surplus power. A fuel cell vehicle that adjusts a target temperature of a passenger compartment based on the amount of remaining power. 6. The fuel cell vehicle according to any one of claims 1 to 5 , further comprising a humidity adjusting unit that adjusts humidity inside the fuel cell in accordance with temperature adjustment of the fuel cell. .

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