Hybrid vehicles

Abstract

To reduce an amount of heat radiation from a capacitor during EV travel and to continue the EV travel, in a hybrid vehicle including an engine-driven cooling fan.SOLUTION: A hybrid vehicle 100 capable of traveling in an HV mode and an EV mode includes: a radiator 16; an air conditioning device 200 including a capacitor 42 and a pressure sensor 55 and configured to perform air conditioning in a room; a cooling fan 17 configured to operate according to rotation of an engine 11 and to blow cooling air to the radiator 16 and the capacitor 42; and a control unit 80 configured to control an operation of the engine 11 and the air conditioning device 200. The control unit 80 reduces an amount of heat radiation from the capacitor 42 when a cooler high-pressure detected by the pressure sensor 55 during traveling in the EV mode becomes equal to or higher than a first pressure PS1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the control of an air conditioner for a hybrid vehicle.

Background Art

[0002] Vehicles are used in which the heat dissipation of a condenser in a refrigeration cycle is performed by a cooling fan driven by an engine. In such vehicles, when the engine speed is low, the air volume blown to the condenser decreases, and the pressure in the refrigeration cycle may increase, causing the air conditioner to stop. Therefore, in addition to the engine-driven cooling fan, an electric auxiliary fan is provided, and a vehicle has been proposed that is configured to increase the air volume of the auxiliary fan when the engine speed is low so that sufficient heat dissipation of the condenser can be obtained (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in recent years, hybrid vehicles that can travel in an HV mode driven by an engine and a vehicle drive motor and an EV mode in which the engine is stopped and the vehicle travels by the motor have been used. In such hybrid vehicles, an electric cooling fan is provided so that sufficient heat dissipation can be performed from the condenser even when traveling in the EV mode.

[0005] On the other hand, even in hybrid vehicles like those described above, some vehicles are equipped with an engine-driven cooling fan to ensure sufficient heat dissipation from the radiator that cools the engine's coolant when climbing hills or towing. In such vehicles, when driving in EV mode with the engine stopped, the amount of airflow to the condenser decreases, and insufficient heat dissipation from the condenser may not be obtained, causing the pressure in the refrigeration cycle to rise and potentially preventing continued EV driving.

[0006] Therefore, this disclosure aims to reduce the amount of heat dissipated from the capacitor during EV driving in a hybrid vehicle equipped with an engine-driven cooling fan, thereby enabling continued EV driving. [Means for solving the problem]

[0007] The hybrid vehicle of this disclosure is a hybrid vehicle capable of running in an HV mode, which is driven by an engine and a motor for driving the vehicle, and an EV mode, which is driven by the motor with the engine stopped, and comprises an air conditioning system that provides air conditioning to the interior of the vehicle, which includes a radiator for cooling the coolant circulating inside the engine, a compressor and a condenser for condensing the refrigerant compressed by the compressor, and a pressure sensor for detecting the pressure of the refrigerant compressed by the compressor, a cooling fan that operates in accordance with the rotation of the engine and blows cooling air to the radiator and the condenser, the engine, and a control unit that controls the operation of the air conditioning system, wherein the control unit reduces the amount of heat dissipated by the condenser when the pressure of the refrigerant detected by the pressure sensor becomes equal to or greater than a predetermined first pressure while running in EV mode. If, while driving in EV mode, the refrigerant pressure detected by the pressure sensor is equal to or greater than the first pressure and the ambient temperature is below a predetermined first temperature, the driving mode is maintained in EV mode to reduce the amount of heat dissipated by the condenser; if, while driving in EV mode, the refrigerant pressure detected by the pressure sensor is equal to or greater than the first pressure and the ambient temperature is equal to or greater than the first temperature, the engine is started and the driving mode is switched from EV mode to HV mode, and the amount of heat dissipated by the condenser is not reduced. It is characterized by the following.

[0008] Thus, By reducing the amount of heat dissipated by the capacitor during EV driving, the pressure rise of the refrigerant during EV driving is suppressed, allowing EV driving to continue. Furthermore, this suppresses the rise in refrigerant pressure during EV driving, allowing for continued EV operation, and also increases the heat dissipation from the condenser to provide sufficient cooling when the outside temperature is high and cooling is needed.

[0011] In the hybrid vehicle of this disclosure, the air conditioning system includes an interior fan for blowing air into the passenger compartment and a switching damper for switching between outside air intake for introducing outside air into the passenger compartment and internal air circulation for circulating air inside the passenger compartment. The control unit may reduce the amount of heat dissipated by the capacitor by switching the switching damper to internal air circulation and increasing the duty cycle of the interior fan.

[0012] By improving the efficiency of the refrigeration cycle in this way, the amount of heat dissipated by the condenser is reduced, thus reducing the amount of heat dissipated by the condenser without compromising the comfort of the occupants.

[0013] In the hybrid vehicle of this disclosure, the air conditioning system includes an evaporator through which a refrigerant flows to cool the air blown into the passenger compartment, and the control unit may reduce the amount of heat dissipated by the condenser by increasing the set value of the refrigerant temperature at the evaporator outlet and reducing the upper limit rotational speed of the compressor as the refrigerant pressure detected by the pressure sensor increases.

[0014] In this way, by reducing the cooling load on the air conditioning system, the amount of heat dissipated by the condenser is reduced, allowing EV driving to continue.

[0015] In the hybrid vehicle of this disclosure, the control unit may reduce the amount of heat dissipated by the condenser by reducing the duty cycle of the interior fan as the refrigerant temperature at the evaporator outlet increases when the refrigerant pressure detected by the pressure sensor is higher than the first pressure and lower than the engine starting pressure (a second pressure or higher).

[0016] Even after improving the efficiency of the refrigeration cycle and reducing the load on the air conditioning system, if the refrigerant pressure is higher than the second pressure, reducing the duty cycle of the indoor fan further reduces the load on the air conditioning system, thereby more effectively suppressing the rise in refrigerant pressure and allowing the vehicle to continue driving in EV mode. . [Effects of the Invention]

[0017] The present disclosure can reduce the heat dissipation amount of a capacitor during EV driving and continue EV driving in a hybrid vehicle equipped with an engine-driven cooling fan.

Brief Description of the Drawings

[0018] [Figure 1] It is a system diagram showing the configuration of the hybrid vehicle of the embodiment. [Figure 2] It is a map showing the relationship of the set value of the refrigerant temperature at the outlet of the evaporator with respect to the cooler high pressure stored in the memory of the control unit of the hybrid vehicle shown in FIG. 1. [Figure 3] It is a map showing the relationship of the upper limit rotational speed of the compressor with respect to the cooler high pressure stored in the memory of the control unit of the hybrid vehicle shown in FIG. 1. [Figure 4] It is a map showing the relationship of the air volume of the indoor fan with respect to the refrigerant temperature at the outlet of the evaporator stored in the memory of the control unit of the hybrid vehicle shown in FIG. 1. [Figure 5] It is a flowchart showing the operation of the hybrid vehicle shown in FIG. 1. [Figure 6] It is a flowchart showing the operation of the capacitor heat dissipation reduction process shown in FIG. 5.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the hybrid vehicle 100 of the embodiment will be described with reference to the drawings. The hybrid vehicle 100 can travel in an HV mode in which it travels by the engine 11 and the motor 61 for vehicle drive, and an EV mode in which the engine 11 is stopped and it travels by the motor 61.

[0020] As shown in FIG. 1, the hybrid vehicle 100 includes an engine cooling circuit 30, a refrigeration cycle circuit 50, a motor cooling circuit 70, a control unit 80, and an outside air temperature sensor 57. The engine cooling circuit 30 is a circuit that circulates cooling water through the engine 11 to cool the engine 11. The refrigeration cycle circuit 50 is a circuit that compresses and expands a refrigerant to cool the passenger compartment. The motor cooling circuit 70 is a circuit that circulates a coolant through the motor 61 and the PCU 62 to cool the motor 61 and the PCU 62.

[0021] First, the engine cooling circuit 30 will be described. In the engine cooling circuit 30, the engine 11, a three-way flow control valve 20, a heater core 13, an electric pump 14, a water heater 15, a thermostat 18, and a radiator 16 are sequentially provided in series from the upstream side. The engine cooling circuit 30 is a flow path through which cooling water flows through these devices.

[0022] The engine 11 is a drive source of the hybrid vehicle 100. The engine 11 is provided with a cooling water flow path 11a through which cooling water flows inside. Also, an engine-driven pump 12 driven by the engine 11 is attached to the engine 11. The engine-driven pump 12 operates in conjunction with the engine 11. The discharge port of the engine-driven pump 12 is connected to the inlet of the cooling water flow path 11a. The three-way flow control valve 20 is provided between the engine 11 and the heater core 13 in the engine cooling circuit 30. The three-way flow control valve 20 includes three ports: a first port 21, a second port 22, and a third port 23. The three-way flow control valve 20 can switch the flow path of the cooling water by opening and closing each of these three ports.

[0023] The heater core 13 is a heat exchanger that heats the air supplied to the passenger compartment, with a cooling water passage 13a inside through which high-temperature cooling water that has passed through the cooling water passage 11a of the engine 11 flows. The heater core 13 is located inside the discharge duct 47 that blows air into the passenger compartment. Upstream of the heater core 13 inside the discharge duct 47, a flow path switching damper 19 is provided to switch between blocking and opening the airflow to the heater core 13.

[0024] The electric pump 14 is driven by a motor (not shown) and circulates coolant to the engine cooling circuit 30. The water heater 15 is a heater for heating the coolant that flows through the heater core 13 when the hybrid vehicle 100 is running in EV mode. In other words, the water heater 15 is a heat source that heats the passenger compartment when the hybrid vehicle 100 is running in EV mode. The water heater 15 is equipped with a coolant flow path 15a through which coolant flows.

[0025] The thermostat 18 is a switching valve that switches the flow of coolant to the radiator bypass pipe 38 when the coolant temperature is low, and switches the flow path so that the coolant flows to the radiator 16 when the coolant temperature is high.

[0026] The radiator 16 is a heat exchanger that cools the coolant with outside air. The radiator 16 has a coolant passage 16a through which the coolant flows. The radiator 16 is mounted on a radiator support 25 located in the front compartment at the front of the vehicle. The radiator support 25 covers the radiator 16 on all four sides and forms an air intake for outside air. A cooling fan 17 is located at the rear of the radiator 16 of the vehicle, which operates in response to the rotation of the engine 11 and blows cooling air onto the radiator 16.

[0027] The engine cooling circuit 30 consists of an engine-driven pump 12, a cooling water passage 11a for the engine 11, an engine outlet pipe 31, a three-way flow control valve 20, a heater core inlet pipe 32, a cooling water passage 13a for the heater core 13, a heater core outlet pipe 33, an electric pump 14, a cooling water passage 15a for the water heater 15, a water heater outlet pipe 35, a thermostat 18, a radiator inlet pipe 36, a cooling water passage 16a for the radiator 16, a radiator outlet pipe 37, an engine-driven pump inlet pipe 39, a radiator bypass pipe 38, and an engine bypass pipe 34.

[0028] The engine outlet pipe 31 connects the outlet of the cooling water passage 11a of the engine 11 to the first port 21 of the three-way flow control valve 20. The heater core inlet pipe 32 connects the second port 22 of the three-way flow control valve 20 to the inlet of the cooling water passage 13a of the heater core 13. The heater core outlet pipe 33 connects the outlet of the cooling water passage 13a of the heater core 13 to the suction port of the electric pump 14. The discharge port of the electric pump 14 is connected to the inlet of the cooling water passage 15a of the water heater 15. The water heater outlet pipe 35 connects the outlet of the cooling water passage 15a of the water heater 15 to the thermostat 18. The radiator inlet pipe 36 connects the thermostat 18 to the inlet of the cooling water passage 16a of the radiator 16. The radiator outlet pipe 37 connects the outlet of the cooling water passage 16a of the radiator 16 to the engine-driven pump inlet pipe 39. The engine-driven pump inlet pipe 39 is connected to the intake port of the engine-driven pump 12. The radiator bypass pipe 38 bypasses the radiator 16 and connects the thermostat 18 to the engine-driven pump inlet pipe 39. The engine bypass pipe 34 bypasses the engine 11 and connects the water heater outlet pipe 35 of the engine cooling circuit 30 to the third port 23 of the three-way flow control valve 20.

[0029] Next, the refrigeration cycle circuit 50 will be described. The refrigeration cycle circuit 50 consists of a compressor 41, a compressor outlet pipe 51, a condenser 42, a condenser outlet pipe 52, an expansion valve 43, an evaporator inlet pipe 53, an evaporator 44, and an evaporator outlet pipe 54.

[0030] The compressor 41 compresses the refrigerant into a high-temperature, high-pressure gas. The condenser 42 has a refrigerant flow path 42a inside, which exchanges heat with the outside air flowing around it, cooling and condensing the high-temperature, high-pressure gaseous refrigerant compressed by the compressor 41 into a liquid. The discharge port of the compressor 41 and the inlet of the refrigerant flow path 42a of the condenser 42 are connected by the compressor outlet pipe 51. The condenser 42 is mounted on the radiator support 25 upstream of the radiator 16, in series with the radiator 16 in the direction of outside air flow. The cooling fan 17 described earlier also blows cooling air to the condenser 42.

[0031] The expansion valve 43 is a pressure reducing valve that adiabatically expands the refrigerant, which has become a high-pressure liquid in the condenser 42. The expansion valve 43 is connected to the outlet of the refrigerant flow path 42a of the condenser 42 by the condenser outlet pipe 52.

[0032] The evaporator 44 has a refrigerant passage 44a inside, and cools the air flowing outside by vaporizing the refrigerant flowing through the refrigerant passage 44a. The evaporator 44 is connected to the expansion valve 43 by an evaporator inlet pipe 53. Like the heater core 13, the evaporator 44 is located upstream of the heater core 13 in the discharge duct 47 that blows air into the passenger compartment. Upstream of the evaporator 44 in the discharge duct 47 is an interior fan 45 that blows air into the passenger compartment. Upstream of the interior fan 45 is a switching damper 46 that switches between outside air intake, which introduces outside air to the interior fan 45, and internal air circulation, which introduces air from inside the passenger compartment to the interior fan 45. When the switching damper 46 is set to outside air intake, outside air is introduced to the interior fan 45, and the outside air passes through the evaporator 44 and is blown into the passenger compartment as cold air. On the other hand, when the switching damper 46 is set to internal air circulation, the cabin fan 45 receives air from inside the vehicle, and the air from inside the vehicle passes through the evaporator 44 and is blown out into the vehicle as cool air. The outlet of the refrigerant passage 44a of the evaporator 44 is connected to the intake port of the compressor 41 by the evaporator outlet pipe 54.

[0033] The compressor 41, condenser 42, expansion valve 43, and evaporator 44 constitute a refrigeration cycle that compresses and expands the refrigerant to cool the vehicle's interior. The area from the outlet of the compressor 41 to the inlet of the expansion valve 43 is a high-pressure region where the refrigerant pressure is high. On the other hand, the area from the outlet of the expansion valve 43 to the suction port of the compressor 41 is a low-pressure region where the refrigerant pressure is low. A pressure sensor 55 is provided in the compressor outlet pipe 51 to detect the refrigerant pressure in the high-pressure region. The refrigerant pressure detected by the pressure sensor 55 is called the "cooler high pressure." In addition, a temperature sensor 56 is provided in the evaporator outlet pipe 54 to detect the refrigerant temperature at the outlet of the evaporator 44.

[0034] Furthermore, the compressor 41, condenser 42, expansion valve 43, evaporator 44, indoor fan 45, switching damper 46, heater core 13, flow path switching damper 19, pressure sensor 55, and temperature sensor 56 constitute the air conditioning system 200.

[0035] Next, the motor cooling circuit 70 will be described. The motor cooling circuit 70 consists of a motor 61, a motor outlet pipe 73, a PCU 62, a PCU outlet pipe 74, a coolant pump 63, a coolant pump outlet pipe 71, an HEV radiator 64, and a motor inlet pipe 72.

[0036] Motor 61 is a vehicle drive motor that drives the hybrid vehicle 100. Motor 61 has a coolant passage 61a through which coolant flows. PCU 62 converts DC power supplied from a battery (not shown) into AC power and supplies it to motor 61, and also converts the AC power generated by motor 61 into DC power when motor 61 functions as a generator to charge the battery. PCU 62 has a coolant passage 62a through which coolant flows. The coolant passage 62a of PCU 62 is connected to the coolant passage 61a of motor 61 at the motor outlet pipe 73. HEV radiator 64 has a coolant passage 64a through which coolant flows, and exchanges heat with the outside air flowing on the outside to cool the high-temperature coolant. HEV radiator 64 is mounted on the radiator support 25 upstream of radiator 16, in series with radiator 16 and in the direction of outside air flow, and in parallel with capacitor 42. The cooling fan 17 also blows cooling air to the HEV radiator 64. The inlet of the coolant passage 64a of the HEV radiator 64 is connected to the outlet of the coolant pump 63 by the coolant pump outlet pipe 71. The outlet of the coolant passage 64a of the HEV radiator 64 is connected to the coolant passage 61a of the motor 61 by the motor inlet pipe 72. The motor cooling circuit 70 circulates the coolant through the motor 61, PCU 62, and HEV radiator 64 using the coolant pump 63, and cools the motor 61 and PCU 62 by dissipating the heat generated by the motor 61 and PCU 62 through the HEV radiator 64.

[0037] The outside air temperature sensor 57 detects the outside air temperature of the hybrid vehicle 100. The outside air temperature sensor 57 may be installed, for example, near the outside air inlet of the radiator support 25.

[0038] The control unit 80 is a computer equipped with a CPU 81, which is a processor that performs information processing, and a memory 82 that stores operation programs and operation data. The engine 11, the three-way flow control valve 20, the electric pump 14, the water heater 15, the compressor 41, the expansion valve 43, the indoor fan 45, the switching damper 46, the motor 61, the PCU 62, and the coolant pump 63 are connected to the control unit 80 and operate according to commands from the control unit 80. In addition, the cooler high pressure detected by the pressure sensor 55, the refrigerant temperature at the evaporator outlet detected by the temperature sensor 56, and the outside air temperature detected by the outside air temperature sensor 57 are input to the control unit 80. The operation of the control unit 80 is realized by the CPU 81 executing the control program stored in the memory 82.

[0039] The memory 82 of the control unit 80 stores control maps 83 to 85, as shown in Figures 2 to 4. As shown in Figure 2, control map 83 is a map that defines the relationship between the cooler high pressure detected by the pressure sensor 55 and the set value of the refrigerant temperature at the outlet of the evaporator 44. In Figure 2, the first pressure PS1 is a predetermined set pressure at which the condenser heat dissipation reduction process, which will be explained later, begins. The engine start pressure PE is a set pressure at which the engine 11 starts due to the rise in cooler high pressure and the vehicle switches to driving in HV mode. The second pressure PS2 is a pressure higher than the first pressure PS1 and slightly lower than the engine start pressure PE, and is a predetermined set pressure at which the airflow of the interior fan 45 begins to decrease. Control map 83 is a map that raises the set value of the refrigerant temperature at the outlet of the evaporator 44 from the normal set temperature TS1 when the cooler high pressure is equal to or higher than the first pressure, and sets the set value of the refrigerant temperature at the outlet of the evaporator 44 to TS2, which is higher than TS1, when the second pressure PS2 or higher.

[0040] The control map 84 shown in Figure 3 defines the relationship between the cooler high pressure and the upper limit rotational speed of the compressor 41. The control map 84 reduces the upper limit rotational speed of the compressor 41 from the normal upper limit rotational speed R0 when the cooler high pressure is equal to or greater than the first pressure, and sets the upper limit rotational speed of the compressor 41 to R1 when the second pressure is equal to or greater than the second pressure PS2.

[0041] The control map 85 shown in Figure 4 defines the relationship between the refrigerant temperature at the outlet of the evaporator 44, as detected by the temperature sensor 56, and the airflow rate of the indoor fan 45. The control map 85 reduces the airflow rate of the indoor fan 45 from the normal setting Q0 when the refrigerant temperature at the outlet of the evaporator 44 is TS1 or higher, and sets the airflow rate of the indoor fan 45 to Q1 when the refrigerant temperature at the outlet of the evaporator 44 is TS3 or higher.

[0042] Next, with reference to Figure 5, the control of the air conditioning system 200 while the hybrid vehicle 100 is running in EV mode and cooling the passenger compartment with the air conditioning system 200 will be explained. When the driving mode of the hybrid vehicle 100 is EV mode, the engine 11 is stopped, so coolant does not flow through the engine cooling circuit 30, and the cooling fan 17 driven by the engine 11 is stopped. On the other hand, the motor 61 is running, so the coolant pump 63 circulates coolant to the motor 61, PCU 62, and HEV radiator 64 as shown by the arrows in Figure 1, and the motor 61 and PCU 62 are cooled. Also, since the passenger compartment is being cooled, the compressor 41 is operating and the refrigerant is circulating as shown by the arrows in Figure 1, and heat is dissipated from the condenser 42 to the outside air.

[0043] As shown in step 101 of Figure 5, the control unit 80 determines whether the hybrid vehicle 100 is running in EV mode. If the control unit 80 determines NO in step 101 of Figure 5, it waits while repeatedly executing step 101 of Figure 5.

[0044] If the control unit 80 determines YES in step 101 of Figure 5, it proceeds to step 102 of Figure 5 to determine whether the cooler high pressure detected by the pressure sensor 55 is equal to or greater than the first pressure PS1. If the control unit 80 determines NO in step 102 of Figure 5, it returns to step 101 of Figure 5 and repeats steps 101 and 102, then waits. On the other hand, if the control unit 80 determines YES in step 102 of Figure 5, it proceeds to step 103 of Figure 5. Here, the first pressure PS1 is a predetermined set pressure at which the capacitor heat dissipation reduction process begins, and can be freely set, but for example, it may be set to about 70-80% of the engine starting pressure PE.

[0045] In step 103 of Figure 5, the control unit 80 determines whether the ambient temperature detected by the ambient temperature sensor 57 is less than the first temperature Tout1. The first temperature Tout1 is the ambient temperature at which it is necessary to start the engine 11 to increase the amount of heat dissipated from the condenser 42 and prioritize cooling the passenger compartment. The first temperature Tout1 can be set freely, but for example, it may be set to around 40°C to 45°C.

[0046] If the control unit 80 determines YES in step 103 of Figure 5, that is, if the outside air temperature is not high enough to prioritize cooling the passenger compartment, it proceeds to step 104 of Figure 5 to perform the capacitor heat dissipation reduction process, which will be explained later, continues EV driving, and proceeds to step 105 of Figure 5.

[0047] In step 105 of Figure 5, the control unit 80 determines whether the cooler high pressure is equal to or greater than the engine starting pressure PE. As mentioned earlier, the engine starting pressure PE is the pressure at which the engine 11 needs to be started due to the rise in cooler high pressure, the vehicle needs to switch to HV mode, and the amount of heat dissipated by the condenser 42 needs to be increased.

[0048] If the control unit 80 determines NO in step 105 of Figure 5, it returns to step 101 of Figure 5 and repeats steps 101 to 105. During this time, the control unit 80 continues EV driving with the engine 11 stopped.

[0049] On the other hand, if the control unit 80 determines YES in step 105 of Figure 5, it proceeds to step 106 of Figure 5 to start the engine 11 and change the driving mode from EV mode to HV mode, and stops the capacitor heat dissipation reduction process in step 107 of Figure 5. When the engine 11 starts, the cooling fan 17 operates, and the amount of outside air passing through the capacitor 42 increases. This increases the amount of heat dissipated by the capacitor 42 and reduces the cooler high pressure.

[0050] Furthermore, if the control unit 80 determines NO in step 103 of Figure 5, that is, if the outside temperature becomes 1 or higher than the first temperature Tout1, it proceeds to step 106 of Figure 5 to start the engine 11 and switch the driving mode to HV mode, and stops the capacitor heat dissipation reduction process in step 107 of Figure 5.

[0051] Next, referring to Figure 6, we will explain the capacitor heat dissipation reduction process in step 104 of Figure 5.

[0052] As shown in step 201 of Figure 6, the control unit 80 determines whether the switching damper 46 is switched to internal air circulation. If the control unit 80 determines YES in step 201 of Figure 6, it proceeds to step 203 of Figure 6. On the other hand, if the control unit 80 determines NO in step 201 of Figure 6, it proceeds to step 202 of Figure 6, switches the switching damper 46 to internal air circulation, and proceeds to step 203 of Figure 2.

[0053] In step 203 of Figure 6, the control unit 80 increases the duty cycle of the indoor fan 45. The duty cycle may be increased to a level where the occupants do not notice the fan noise, or it may be increased to the maximum duty cycle.

[0054] In this way, by increasing the duty cycle of the interior fan 45 as an internal air circulation system and thereby increasing the airflow rate circulating in the vehicle interior, the amount of heat dissipated by the condenser 42 can be reduced without compromising the comfort of the occupants, and the rise in cooler high pressure can be suppressed.

[0055] Next, the control unit 80 proceeds to step 204 in Figure 6, applying the control map 83 shown in Figure 2 to increase the set value of the refrigerant temperature at the outlet of the evaporator 44 as the cooler high pressure increases. This reduces the amount of heat exchange between the evaporator 44 and the air blown into the passenger compartment, thereby reducing the load on the air conditioning system 200. As a result, the amount of heat dissipated from the condenser 42 to the outside air is reduced, and the cooler high pressure can be lowered.

[0056] Furthermore, the control unit 80 applies the control map 84 shown in Figure 3 to reduce the upper limit rotational speed of the compressor 41 as the cooler high pressure increases. This lowers the refrigerant pressure at the outlet of the compressor 41, and thus lowers the cooler high pressure.

[0057] Then, the control unit 80 proceeds to step 205 in Figure 6 to determine whether the cooler high pressure detected by the pressure sensor 55 is equal to or greater than the second pressure PS2. Here, the second pressure PS2 is slightly lower than the engine starting pressure PE. In other words, if the cooler pressure has risen to just before the engine starting pressure PE even after performing the processes from steps 201 to 204 in Figure 6, the control unit 80 determines YES in step 205 in Figure 6 and proceeds to step 206 in Figure 6. Then, in step 206 in Figure 6, the control unit 80 applies the control map 85 shown in Figure 4 to reduce the duty cycle of the interior fan 45 and reduce the airflow of the interior fan 45 as the refrigerant temperature at the outlet of the evaporator 44 increases. As a result, the amount of heat exchange between the evaporator 44 and the air blown into the passenger compartment is further reduced, and the load on the air conditioning system 200 is reduced. Therefore, the amount of heat dissipated from the condenser 42 to the outside air is reduced, and the cooler high pressure can be further reduced.

[0058] On the other hand, if the control unit 80 determines NO in step 205 of Figure 6, it terminates the evaporator heat dissipation reduction process without performing the process in step 206 of Figure 6.

[0059] As described above, the hybrid vehicle 100 of this embodiment reduces the amount of heat dissipated by the condenser 42 during EV driving, thereby suppressing the rise in cooler high pressure during EV driving and enabling continued EV driving. Furthermore, when the outside temperature is high and cooling is required, the hybrid vehicle 100 of this embodiment can start the engine 11 to increase the amount of heat dissipated by the condenser 42 and provide sufficient cooling.

[0060] Furthermore, the hybrid vehicle 100 of this embodiment improves the efficiency of the refrigeration cycle and reduces the amount of heat dissipated by the condenser 42 by setting the air inflow into the passenger compartment to internal circulation and increasing the duty cycle of the interior fan 45. This makes it possible to reduce the amount of heat dissipated by the condenser 42 without compromising the comfort of the occupants.

[0061] Furthermore, in the hybrid vehicle 100 of this embodiment, as the cooler high pressure increases, the set value of the refrigerant temperature at the outlet of the evaporator 44 is increased, and the upper limit rotational speed of the compressor 41 is reduced. This reduces the cooling load of the air conditioning system 200 and reduces the amount of heat dissipated by the condenser 42.

[0062] Furthermore, in the embodiment, even after improving the efficiency of the refrigeration cycle and reducing the load on the air conditioning system 200, if the cooler high pressure is higher than the second pressure PS2 just before the engine starting pressure PE, the duty cycle of the interior fan 45 is reduced to further reduce the load on the air conditioning system 200. This more effectively suppresses the rise in cooler high pressure and allows the vehicle to continue driving in EV mode. [Explanation of symbols]

[0063] 11 Engine, 11a, 13a, 15a, 16a Cooling water passages, 12 Engine-driven pump, 13 Heater core, 14 Electric pump, 15 Water heater, 16 Radiator, 17 Cooling fan, 18 Thermostat, 19 Flow switching damper, 20 Three-way flow control valve, 25 Radiator support, 30 Engine cooling circuit, 31 Engine outlet pipe, 32 Heater core inlet pipe, 33 Heater core outlet pipe, 34 Engine bypass pipe, 35 Water heater outlet pipe, 36 Radiator inlet pipe, 37 Radiator outlet pipe, 38 Radiator bypass pipe, 39 Engine-driven pump inlet pipe, 41 Compressor, 42 Condenser, 42a, 44a Refrigerant passages, 43 Expansion valve, 44 Evaporator, 45 Interior fan, 46 Switching damper, 47 Discharge duct, 50 Refrigeration cycle circuit, 51 Compressor outlet pipe, 52 Condenser outlet pipe, 53 Evaporator inlet pipe, 54 Evaporator outlet pipe, 55 Pressure sensor, 56 Temperature sensor, 57 Ambient temperature sensor, 61 Motor, 62 PCU, 61a, 62a, 64a Coolant flow path, 63 Coolant pump, 64 HEV radiator, 70 Motor cooling circuit, 71 Coolant pump outlet pipe, 72 Motor inlet pipe, 73 Motor outlet pipe, 74 PCU outlet pipe, 80 Control unit, 81 CPU, 82 Memory, 83, 84, 85 Control map, 100 Hybrid vehicle, 200 Air conditioning system.

Claims

1. A hybrid vehicle capable of operating in an HV mode, which is driven by an engine and a motor for vehicle drive, and an EV mode, which is driven by the motor with the engine stopped, A radiator that cools the coolant circulating inside the engine, An air conditioning system for providing air conditioning inside a vehicle includes a compressor, a condenser for condensing the refrigerant compressed by the compressor, and a pressure sensor for detecting the pressure of the refrigerant compressed by the compressor. A cooling fan that operates in accordance with the rotation of the engine to blow cooling air to the radiator and the condenser, The system comprises the engine and a control unit that controls the operation of the air conditioning system, The control unit reduces the amount of heat dissipated by the condenser when the refrigerant pressure detected by the pressure sensor during driving in EV mode exceeds a predetermined first pressure. When the refrigerant pressure detected by the pressure sensor while driving in EV mode is equal to or greater than the first pressure, and the ambient temperature is less than a predetermined first temperature, the driving mode is maintained in EV mode to reduce the amount of heat dissipated by the condenser. When the refrigerant pressure detected by the pressure sensor while driving in EV mode is equal to or greater than the first pressure, and the ambient temperature is equal to or greater than the first temperature, the engine is started and the driving mode is switched from EV mode to HV mode, without reducing the amount of heat dissipated by the condenser. A hybrid vehicle characterized by the following features.

2. A hybrid vehicle according to claim 1, The aforementioned air conditioning system includes an interior fan for blowing air into the passenger compartment, and a switching damper for switching between outside air intake for introducing outside air into the passenger compartment and internal air circulation for circulating the air inside the passenger compartment. The control unit reduces the amount of heat dissipated by the capacitor by switching the switching damper to internal air circulation and increasing the duty cycle of the indoor fan. A hybrid vehicle characterized by [feature].

3. A hybrid vehicle according to claim 2, The aforementioned air conditioning system includes an evaporator through which a refrigerant flows to cool the air blown into the passenger compartment. The control unit increases the set value of the refrigerant temperature at the evaporator outlet and reduces the upper limit rotational speed of the compressor as the refrigerant pressure detected by the pressure sensor increases, thereby reducing the amount of heat dissipated by the condenser. A hybrid vehicle characterized by [feature].

4. A hybrid vehicle according to claim 3, The control unit reduces the amount of heat dissipated by the condenser by reducing the duty cycle of the indoor fan as the refrigerant temperature at the evaporator outlet increases when the refrigerant pressure detected by the pressure sensor is higher than the first pressure and lower than the engine starting pressure (a second pressure or higher). A hybrid vehicle characterized by [feature].

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