Air conditioning system

Abstract

This suppresses the performance difference between the cooling performance of the front seat air conditioning circuit and the cooling performance of the rear seat air conditioning circuit. [Solution] The control unit calculates the differential front seat fin temperature, which is the difference between the measured front seat fin temperature and the target front seat fin temperature, and calculates the differential rear seat fin temperature, which is the difference between the measured rear seat fin temperature and the target rear seat fin temperature. If the differential front seat fin temperature is higher than the differential rear seat fin temperature, the rotation speed of the rear seat compressor is reduced.

Description

Technical Field

[0001] The present disclosure relates to a vehicle air conditioning system.

Background Art

[0002] Patent Document 1 below discloses a vehicle air conditioning system including a cooling circuit and a high-temperature water circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, the front and rear seats are air-conditioned by a single cooling circuit, but there is no disclosure regarding the case where the front and rear seats are provided with independent cooling circuits. When there are a front-seat cooling circuit mainly responsible for cooling the front seat and a rear-seat cooling circuit mainly responsible for cooling the rear seat, corresponding heat exchangers are provided and arranged front and rear for heat exchange. However, heat may accumulate between the heat exchanger arranged at the rear and the heat exchanger arranged at the front, and the capacity of the cooling circuit corresponding to the heat exchanger arranged at the rear may not be fully exerted.

[0005] An object of the present disclosure is to suppress the occurrence of a performance difference between the cooling performance of the front-seat cooling circuit and the cooling performance of the rear-seat cooling circuit even when there are provided a front-seat cooling circuit mainly responsible for cooling the front seat and a rear-seat cooling circuit mainly responsible for cooling the rear seat.

Means for Solving the Problems

[0006] This disclosure relates to an air conditioning system for a vehicle, comprising: a front seat air conditioning circuit having a front seat compressor and a front seat evaporator for cooling the front seats of the vehicle; a rear seat air conditioning circuit having a rear seat compressor, a rear seat condenser, and a rear seat evaporator for cooling the rear seats of the vehicle; a high-temperature circuit having a front seat heater core for heating the front seats, a rear seat heater core for heating the rear seats, and an HT radiator; a water-cooled condenser for heat exchange between the front seat air conditioning circuit and the high-temperature circuit; and a control unit for controlling the front seat compressor and the rear seat compressor, wherein the rear seat condenser and the HT radiator are arranged in that order from the upstream side of the airflow. The control unit calculates the target front seat evaporator fin temperature, which is the target temperature of the fins on the front seat evaporator, using the target front seat air outlet temperature of the front seat air conditioning circuit. It also measures the actual front seat evaporator fin temperature using a temperature sensor provided to measure the temperature of the fins on the front seat evaporator, and calculates the difference between the actual front seat evaporator fin temperature and the target front seat evaporator fin temperature. The control unit calculates the target rear seat evaporator fin temperature, which is the target temperature of the fins on the rear seat evaporator, using the target rear seat air outlet temperature of the rear seat air conditioning circuit. It also measures the actual rear seat evaporator fin temperature using a temperature sensor provided to measure the temperature of the fins on the rear seat evaporator, and calculates the difference between the actual rear seat evaporator fin temperature and the target rear seat evaporator fin temperature. If the difference front seat evaporator fin temperature is higher than the difference rear seat evaporator fin temperature, the control unit reduces the rotation speed of the rear seat compressor. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress the occurrence of a performance difference between the cooling performance of the front seat air conditioning circuit and the cooling performance of the rear seat air conditioning circuit. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram illustrating the configuration of the air conditioning system in this embodiment. [Figure 2]Figure 2 is a diagram illustrating the configuration of the air conditioning system in this embodiment. [Figure 3] Figure 3 is a diagram illustrating the arrangement of the heat exchangers shown in Figures 1 and 2. [Figure 4] Figure 4 is a flowchart illustrating the processing flow of the control unit shown in Figure 1. [Figure 5] Figure 5 is a flowchart illustrating the processing flow of the control unit shown in Figure 1. [Figure 6] Figure 6 is a diagram illustrating the effects of this embodiment. [Figure 7] Figure 7 shows an example of reducing the rotational speed of the compressor for the rearview mirror (Rr). [Modes for carrying out the invention]

[0009] This embodiment will now be described with reference to the attached drawings. To facilitate understanding of the explanation, the same reference numerals are used for identical components in each drawing whenever possible, and redundant explanations are omitted.

[0010] The following description will use an example of the air conditioning system 2 relating to this disclosure being installed in an electric vehicle (not shown). An electric vehicle is a vehicle equipped with a battery for driving, such as a battery electric vehicle (BEV). An electric vehicle may also be a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV). However, the use of the air conditioning system relating to this disclosure is not limited to vehicles.

[0011] Figure 1 is a diagram showing an example of the configuration of the air conditioning system 2 according to the embodiment of this disclosure. Figure 2 is a diagram showing an example of the configuration of the Rr cooling circuit 29 included in the air conditioning system 2. The air conditioning system 2 will be described with reference to Figures 1 and 2.

[0012] The air conditioning system 2 includes a control unit 20, a high-temperature circuit 21, a low-temperature circuit 22, a Fr (Front) cooling circuit 23, a battery circuit 24, a five-way valve 25, a water-cooled condenser 26, a chiller 27, a reservoir tank (R / T) 28, and a Rr (Rear) cooling circuit 29.

[0013] The control unit 20 is an electronic control unit (ECU) that controls the air conditioning system 2. The control unit 20 includes, for example, a processor, memory, storage, and interfaces. The control unit 20 generates control commands based on sensor values ​​obtained from various sensors (such as temperature sensors) included in the air conditioning system 2, sensor values ​​obtained from the speed sensor of the vehicle on which the air conditioning system 2 is installed, and instruction values ​​based on user operation, and outputs the generated control commands to each part of the air conditioning system 2.

[0014] The high-temperature circuit 21 includes an HT (High Temperature) radiator 211, a reservoir tank (R / T) 212, a water pump (W / P) 213, a three-way valve 214, an electric heater 215, a heater core for the front (Fr) 216, and a heater core for the rear (Rr) 217. The high-temperature circuit 21 shares a water-cooled condenser 26 with the Fr cooling circuit 23.

[0015] The heat transfer medium (usually hot water) circulating in the high-temperature circuit 21 flows through either a first path from water pump 213 - water-cooled condenser 26 - three-way valve 214 - electric heater 215 - heater core 216 for Fr, heater core 217 for Rr - reservoir tank 212 - water pump 213, or a second path from water pump 213 - water-cooled condenser 26 - three-way valve 214 - HT radiator 211 - reservoir tank 212 - water pump 213.

[0016] The three-way valve 214 is configured to switch whether the heat medium flowing through the high-temperature circuit 21 flows through the HT radiator 211. The three-way valve 214 is provided with three ports Pf, Pg, and Ph. The port Pf is an inlet port through which the heat medium flows in from the water-cooled condenser 26. The port Pg is an outlet port through which the heat medium flows out to the electric heater 215, the Fr heater core 216, and the Rr heater core 217. The port Ph is an outlet port through which the heat medium flows out toward the HT radiator 211.

[0017] The low-temperature circuit 22 includes an LT (Low Temperature) radiator 221, a reservoir tank (R / T) 28, a sub-radiator 222, an electricity supply unit (ESU: Electricity Supply Unit) 223, a rear power control unit (Rr-PCU: Rear Power Control Unit) 224, a water pump 225, and an oil cooler (O / C) 226. The electricity supply unit 223 is a unit that integrates a charging function and a power distribution function and includes a DCDC converter. A temperature sensor (not shown) is provided in the low-temperature circuit 22. The temperature sensor detects the water temperature of the LT radiator 221 and outputs it to the control unit 20.

[0018] The heat medium (coolant) circulating in the low-temperature circuit 22 flows through the path of the water pump 225 - oil cooler 226 - five-way valve 25 - LT radiator 221 - reservoir tank 28 - sub-radiator 222 - electricity supply unit 223 - rear power control unit 224 - water pump 225.

[0019] The water pump 225 circulates the heat medium within the low-temperature circuit 22 in accordance with a control command from the control unit 20. The electric power supply unit 223 controls the charging and discharging of the battery 242 in accordance with a control command from the control unit 20. The power control unit for Rr converts the DC power supplied from the battery 242 into AC power in accordance with a control command from the control unit 20, and supplies the AC power to a motor (not shown) built into the transaxle. The oil cooler 226 circulates the lubricating oil of the motor using an electric oil pump (not shown). The electric power supply unit 223, the power control unit 224 for Rr, and the oil cooler 226 are cooled by the heat medium circulating in the low-temperature circuit 22.

[0020] The five-way valve 25 switches the path of the heat medium in the low-temperature circuit 22 and the battery circuit 24 in accordance with a control command from the control unit 20. The LT radiator 221 is arranged in the vicinity of the HT radiator 211 and exchanges heat with the HT radiator 211.

[0021] The five-way valve 25 is connected to the low-temperature circuit 22 and the battery circuit 24. The five-way valve 25 is configured to switch whether the heat medium flowing through the low-temperature circuit 22 flows through the battery 242. The five-way valve 25 is provided with five ports Pa, Pb, Pc, Pd, and Pe. The port Pa is an inlet port through which the heat medium flows in from the electric power supply unit 223, the power control unit 224 for Rr, and the oil cooler 226 in the low-temperature circuit 22. The port Pb is an outlet port through which the heat medium flows out toward the bypass path 244 in the battery circuit 24. The port Pc is an outlet port through which the heat medium flows out toward the electric heater 241 and the battery 242 in the battery circuit 24. The port Pd is an inlet port through which the heat medium flows in from the chiller 27. The port Pe is an outlet port through which the heat medium flows out toward the LT radiator 221.

[0022] The Fr cooling circuit 23 is a refrigeration cycle and includes an Fr compressor 231, a receiver 232, an expansion valve 233, an Fr evaporator 235, an evaporation pressure regulator (EPR) 236, and an expansion valve 234.

[0023] The heat transfer medium (gas-phase or liquid-phase refrigerant) circulating in the Fr cooling circuit 23 flows through one or both of the following paths: a first path from Fr compressor 231 - water-cooled condenser 26 - receiver 232 - expansion valve 233 - Fr evaporator 235 - evaporation pressure regulating valve 236 - Fr compressor 231, and a second path from Fr compressor 231 - water-cooled condenser 26 - receiver 232 - expansion valve 234 - chiller 27 - Fr compressor 231. The chiller 27 is connected to both the Fr cooling circuit 23 and the battery circuit 24.

[0024] The battery circuit 24 includes a water pump 243, a battery 242, an electric heater 241, a bypass path 244, and a reservoir tank 28. The heat transfer medium (coolant) circulating in the battery circuit 24 flows through one or both of the following paths: a first path from water pump 243 - chiller 27 - five-way valve 25 - electric heater 241 - battery 242 - reservoir tank 28 - water pump 243, and a second path from water pump 243 - chiller 27 - five-way valve 25 - bypass path 244 - reservoir tank 28 - water pump 243.

[0025] The water pump 243 circulates the heat transfer medium within the battery circuit 24 according to control commands from the control unit 20. The chiller 27 cools the heat transfer medium circulating in the battery circuit 24 by heat exchange between the heat transfer medium circulating in the Fr cooling circuit 23 and the heat transfer medium circulating in the battery circuit 24. The battery 242 supplies power for driving to the motor built into the transaxle. The battery 242 may be heated using the electric heater 241 or cooled using the chiller 27. A bypass path 244 is provided so that the heat transfer medium bypasses the electric heater 241 and the battery 242. When the heat transfer medium flows through the bypass path 244, temperature changes in the heat transfer medium due to heat absorption / dissipation between the heat transfer medium and the battery 242 can be suppressed. The reservoir tank 28 maintains the pressure and amount of heat transfer medium in the battery circuit 24 by storing a portion of the heat transfer medium in the battery circuit 24.

[0026] As shown in Figure 2, the rear cooling circuit 29 is a refrigeration cycle that includes a rear compressor 291, a rear condenser 292, an expansion valve 293, and a rear evaporator 294. The heat transfer medium (gas-phase or liquid-phase refrigerant) circulating in the rear cooling circuit 29 flows through the path of rear compressor 291 - rear condenser 292 - expansion valve 293 - rear evaporator 294 - rear compressor 291.

[0027] As shown in Figure 3, the rear condenser 292, the hard radiator 211, and the left radiator 221 are arranged in this order from the front of the vehicle. Airflow is introduced from the front of the vehicle along the arrow in Figure 3 and passes through the rear condenser 292, the hard radiator 211, and the left radiator 221 for heat exchange. An electric fan 30 is provided to facilitate this airflow. The electric fan 30 is driven in response to a control command from the control unit 20.

[0028] Next, the control method of the air conditioning system 2 by the control unit 20 will be explained with reference to Figure 4. The air conditioning system 2 is equipped with a front seat air conditioning circuit 23 and a rear seat air conditioning circuit 29. However, since the processing is the same for both circuits within the scope of the explanation with reference to Figure 4, the explanation will be given using the front seat air conditioning circuit 23 as an example.

[0029] In step S01, the control unit 20 calculates the target Fr outlet temperature Tfo. The target Fr outlet temperature Tfo is the target temperature of the air blown into the passenger compartment from the Fr cooling circuit 23.

[0030] In step S02, following step S01, the control unit 20 calculates the target Fr evaporator fin temperature Tfa based on the target Fr blow-out temperature Tfo. The target Fr evaporator fin temperature Tfa is the target fin temperature of the Fr evaporator 235 and is calculated from the target Fr blow-out temperature Tfo when the air that has passed through the fins is blown into the passenger compartment.

[0031] In step S03, following step S02, the control unit 20 acquires the measured Fr evaporator fin temperature Tfb. The measured Fr evaporator fin temperature Tfb is measured using a temperature sensor provided to measure the fin temperature of the Fr evaporator 235.

[0032] In step S04, following step S03, the control unit 20 determines whether the target Fr efferfin temperature Tfa is equal to the measured Fr efferfin temperature Tfb. If the target Fr efferfin temperature Tfa and the measured Fr efferfin temperature Tfb are equal (step S04: YES), the process proceeds to step S06. If the target Fr efferfin temperature Tfa and the measured Fr efferfin temperature Tfb are not equal (step S04: NO), the process proceeds to step S05.

[0033] In step S05, it is determined whether the target Fr efferfin temperature Tfa is higher than the measured Fr efferfin temperature Tfb. If the target Fr efferfin temperature Tfa is higher than the measured Fr efferfin temperature Tfb (step S05: YES), the process proceeds to step S07. If the target Fr efferfin temperature Tfa is not higher than the measured Fr efferfin temperature Tfb (step S05: NO), the process proceeds to step S08.

[0034] In step S06, the control unit 20 maintains the rotational speed of the Fr compressor 231. In step S07, the control unit 20 decreases the rotational speed of the Fr compressor 231. In step S08, the control unit 20 increases the rotational speed of the Fr compressor 231.

[0035] When applying the explanation given with reference to Figure 4 to the Rr cooling circuit 29, the target Fr outlet temperature Tfo is replaced with the target Rr outlet temperature Tro, the target Fr evaporator temperature Tfa is replaced with the target Rr evaporator temperature Tra, and the measured Fr evaporator temperature Tfb is replaced with the measured Rr evaporator temperature Trb. The control target is the Rr compressor 291 instead of the Fr compressor 231.

[0036] The target rear outlet temperature Tro is the target temperature of the air blown into the passenger compartment from the rear air conditioning circuit 29. The target rear evaporator fin temperature Tra is the target fin temperature of the rear evaporator 294, and is calculated from the target rear outlet temperature Tro when the air that has passed through the fins is blown into the passenger compartment. The measured rear evaporator fin temperature Trb is measured using a temperature sensor provided to measure the fin temperature of the rear evaporator 294.

[0037] When controlling the Fr cooling circuit 23 and Rr cooling circuit 29 using only the control method described with reference to Figure 4, the target discharge temperature may not always be achieved. As explained with reference to Figure 3, the HT radiator 211, which indirectly functions as a heat exchanger for the Fr cooling circuit 23, is located behind the Rr condenser 292, which is a heat exchanger in the Rr cooling circuit 29. Therefore, when the Rr cooling circuit 20 is driven, the heat dissipation from the Rr condenser 292 raises the air temperature in front of the HT radiator 211, reducing the heat dissipation capacity of the HT radiator 211 and decreasing the cooling capacity of the Fr cooling circuit 23.

[0038] Therefore, in this embodiment, the control flow illustrated in Figure 5 suppresses the reduction in capacity of the Fr cooling circuit 23. In step S11 of Figure 5, the control unit 20 calculates the differential Fr evafin temperature Tfc and the differential Rr evafin temperature Trc. The differential Fr evafin temperature Tfc is calculated by subtracting the target Rr evafin temperature Tra from the measured Fr evafin temperature Tfb. The differential Rr evafin temperature Trc is calculated by subtracting the target Rr evafin temperature Tra from the measured Rr evafin temperature Trb.

[0039] In step S12, following step S11, the control unit 20 determines whether the differential Fr efferfin temperature Tfc is higher than the differential Rr efferfin temperature Trc. If the differential Fr efferfin temperature Tfc is higher than the differential Rr efferfin temperature Trc (step S12: YES), the process proceeds to step S13. If the differential Fr efferfin temperature Tfc is not higher than the differential Rr efferfin temperature Trc (step S12: NO), the process proceeds to step S13.

[0040] In step S15, the control unit 20 maintains the rotational speeds of the Fr compressor 231 and the Rr compressor 291.

[0041] In step S13, the control unit 20 reduces the rotational speed of the Rr compressor 291. An example of reducing the rotational speed of the Rr compressor 291 is shown in Figure 7. As shown in Figure 7, for example, if the differential Fr efferfin temperature Tfc is 10 [°C] and the differential Rr efferfin temperature Trc is 5 [°C], the rotational speed of the Rr compressor 291 is reduced by 100 [rpm / sec].

[0042] In step S14, following step S13, the control unit 20 increases the rotational speed of the compressor 231 for Fr.

[0043] The effects of this embodiment will be explained with reference to Figure 6. Figure 6 is a diagram illustrating a comparison between a comparative example that does not perform the control flow described with reference to Figure 5 and the present disclosure that performs the control flow described with reference to Figure 5. Figure 6(A) illustrates the temperature transitions in the comparative example and the present disclosure. Figure 6(B) illustrates the transitions of refrigerant pressure and compressor rotation speed in the comparative example and the present disclosure. Figure 6(C) illustrates the transitions of the temperature in front of each heat exchanger in the comparative example and the present disclosure.

[0044] As illustrated in Figure 6(A), the discrepancy between the measured Fr evafin temperature Tfb and the target Fr evafin temperature Tfa is smaller in this disclosure compared to the comparative example. Although the discrepancy between the measured Rr evafin temperature Trb and the target Rr evafin temperature Tra is larger, the reduction in the measured Fr evafin temperature Tfb equalizes the cooling performance between the front and rear seats.

[0045] As illustrated in Figures 6(B) and 6(C), in this disclosure, the rotational speed of the Rr compressor 291 is reduced compared to the comparative example, so the amount of heat dissipated by the Rr condenser 292 is reduced, and the air temperature in front of the HT radiator 211 decreases. When the air temperature in front of the HT radiator 211 decreases, the rotational speed of the Fr compressor 231, which is limited by the discharge pressure, can be increased. As a result, as illustrated in Figure 6(A), the measured Fr evaporator fin temperature Tfb can be reduced, and the Fr outlet temperature can also be reduced.

[0046] The control unit (ECU) and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit (ECU) and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit (ECU) and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0047] The embodiments have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. Modifications made to these specific examples by those skilled in the art are also included within the scope of this disclosure, as long as they retain the features of this disclosure. The elements, their arrangement, conditions, shapes, etc., of each of the aforementioned specific examples are not limited to those illustrated and can be modified as appropriate. The elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise.

[0048] [Note] [Note 1] A front seat air conditioning circuit (Fr air conditioning circuit) has a front seat compressor (Fr compressor 231) and a front seat evaporator (Fr evaporator 235) and provides air conditioning to the front seats of the passenger compartment. A rear seat air conditioning circuit (Rr air conditioning circuit) has a rear seat compressor (Rr compressor 291), a rear seat condenser (Rr condenser 292), and a rear seat evaporator (Rr evaporator 294) and provides air conditioning to the rear seats of the vehicle. A high-temperature circuit 21 having a front seat heater core (Fr heater core 216) for heating the front seats, a rear seat heater core (Rr heater core 217) for heating the rear seats, and a high-temperature radiator (HT radiator 211), A water-cooled condenser 26 performs heat exchange between the front seat air conditioning circuit and the high-temperature circuit, A vehicle air conditioning system 2 is equipped with a control unit 20 that controls the front seat compressor and the rear seat compressor, The rear seat condenser and high-temperature radiator are arranged in that order, from the upstream side of the airflow. The control unit is Using the target front seat air outlet temperature (target Fr air outlet temperature Tfo) of the front seat air conditioning circuit, the target temperature of the fins on the front seat evaporator, the target front seat evaporator fin temperature (target Fr evaporator fin temperature Tfa), is calculated. At the same time, the actual front seat evaporator fin temperature (actual Fr evaporator fin temperature Tfb) is measured using a temperature sensor installed to measure the temperature of the fins on the front seat evaporator, and the difference between the actual front seat evaporator fin temperature and the target front seat evaporator fin temperature, the differential front seat evaporator fin temperature (differential Fr evaporator fin temperature Tfc), is calculated. Using the target rear seat air outlet temperature (target Rr air outlet temperature Tro) of the rear seat air conditioning circuit, the target temperature of the fins on the rear seat evaporator, the target rear seat evaporator fin temperature (target Rr evaporator fin temperature Tra), is calculated. At the same time, the actual rear seat evaporator fin temperature (actual Rr evaporator fin temperature Trb) is measured using a temperature sensor installed to measure the temperature of the fins on the rear seat evaporator, and the difference between the actual rear seat evaporator fin temperature and the target rear seat evaporator fin temperature, the differential rear seat evaporator fin temperature (differential Rr evaporator fin temperature Trc), is calculated. If the differential front seat evaporator temperature becomes higher than the differential rear seat evaporator temperature, the rotation speed of the rear seat compressor is reduced.

[0049] According to Appendix 1, when the differential front seat evaporator temperature becomes higher than the differential rear seat evaporator temperature, the rotation speed of the rear seat compressor is reduced, which decreases the amount of heat dissipated by the rear seat condenser and lowers the air temperature in front of the hot radiator. When the air temperature in front of the hot radiator decreases, the rotation speed of the front seat compressor, which is limited by the discharge pressure, can be increased. As a result, the measured front seat evaporator temperature is lowered, the front seat outlet temperature is also lowered, and the performance difference between the cooling performance of the front seat air conditioning circuit and the rear seat air conditioning circuit can be suppressed. [Explanation of Symbols]

[0050] 2: Air conditioning system 20: Control Unit 21: High temperature circuit 22: Low temperature circuit 23: Front air conditioning circuit (for front seats) 24: Battery Circuit 25: Five-direction dialect 26: Water-cooled condenser 27: Chiller 28: Reservoir Tank (R / T) 29: Rear air conditioning circuit (rear seat air conditioning circuit) 30: Electric fan

Claims

[Claim 1] A front seat air conditioning circuit has a front seat compressor and a front seat evaporator, and provides air conditioning to the front seats of the vehicle. A rear seat air conditioning circuit having a rear seat compressor, a rear seat condenser, and a rear seat evaporator, which provides air conditioning to the rear seats of the vehicle compartment, A heater core for the front seats that provides heating to the front seats, a heater core for the rear seats that provides heating to the rear seats, and a high-temperature circuit having a high-temperature radiator, A water-cooled condenser that performs heat exchange between the front seat air conditioning circuit and the high-temperature circuit, An air conditioning system for a vehicle equipped with a front seat compressor and a control unit for controlling the rear seat compressor, The rear seat condenser and the high-temperature radiator are arranged in that order, from the upstream side of the airflow. The control unit, Using the target front seat air outlet temperature of the front seat air conditioning circuit, the target temperature of the fins of the front seat evaporator is calculated, and the actual front seat evaporator fin temperature is measured using a temperature sensor provided to measure the temperature of the fins of the front seat evaporator. The difference between the actual front seat evaporator fin temperature and the target front seat evaporator fin temperature is then calculated. Using the target rear seat air outlet temperature of the rear seat air conditioning circuit, the target temperature of the fins of the rear seat evaporator is calculated, and the actual rear seat evaporator fin temperature is measured using a temperature sensor provided to measure the temperature of the fins of the rear seat evaporator. The difference between the actual rear seat evaporator fin temperature and the target rear seat evaporator fin temperature is then calculated. An air conditioning system that reduces the rotation speed of the rear seat compressor when the differential front seat evaporator temperature becomes higher than the differential rear seat evaporator temperature.

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