The air conditioning system uses the following controls.
|Control||Function||Air Conditioning Type|
|Neural Network Control||This control is capable of performing complex control by artificially simulating the information processing method of the nervous system of living organisms in order to establish a complex input/output relationship that is similar to a human brain.||-||○|
|Automatic Recirculation Control||Automatically changes the air inlet mode to recirculate mode when the outside temperature exceeds 75°F (23.6°C) with the A/C on.||○||○|
|Manual Control||The air conditioning amplifier assembly controls the damper positions (air inlet control servo motor, air mix control servo motor and mode control servo motor) and blower speed in accordance with the positions of the switches (temperature control switch, blower switch, mode control switch and inlet control switch).||○||○|
|Outlet Air Temperature Control||Based on the temperature set at the temperature control switch, the neural network control calculates the outlet air temperature based on the input signals from various sensors.||-||○|
|Left and Right Independent Control||The temperature setting for the driver and front passenger is controlled independently in order to provide a separate vehicle interior temperature for the right and left sides of the vehicle. Thus, air conditioning control that accommodates occupant preferences has been realized.||-||○|
|Blower Control||Controls the blower motor in accordance with the airflow volume that has been calculated by neural network control based on the input signals from various sensors.||-||○|
|Air Outlet Control||Automatically switches the air outlets in accordance with the outlet mode that has been calculated by neural network control based on the input signals from various sensors.||-||○|
|In accordance with the engine coolant temperature, outside air temperature, amount of sunlight, required blower, outlet temperature, and vehicle speed conditions, this control automatically switches the blower outlet to FOOT/DEF mode to prevent the windows from becoming fogged when the outside air temperature is low.||-||○|
|Air Inlet Control||Automatically controls the air inlet control damper to achieve the calculated outlet air temperature that is required.||-||○|
|Compressor Control||Through the calculation of the target evaporator temperature based on various sensor signals, the air conditioning amplifier assembly optimally controls the discharge capacity by regulating the opening extent of the solenoid valve.||○||○|
|The air conditioning amplifier assembly compares the pulley speed signals (transmitted by the lock sensor located on the compressor) with the engine speed signal (which are transmitted by the ECM (crankshaft position sensor)). When the air conditioning amplifier assembly determines that the pulley is locked, it turns off the magnetic clutch.*||○||○|
|Maximum Air Conditioning Control||
When the temperature control dial tuned to the MAX A/C position, the air conditioning amplifier assembly performs the following control to improve cooling efficiency:
|Refrigerant Shortage Detection Control||When the air conditioning is operating and the engine coolant temperature is above a specified value, the air conditioning amplifier assembly calculates the amount of refrigerant based on signals from the air conditioning pressure sensor, evaporator temperature sensor (No. 1 cooler thermistor) and outside temperature sensor (thermistor assembly).||○||○|
|Defroster Control||Defroster control logic is used to improve defroster performance.||○||○|
|Rear Window Defogger Control||
When the rear defogger switch is pushed, the system is activated to keep the defogger heater on for approx. 15 minutes. However, the operating time of the rear defogger can be extended up to approx. 45 minutes when both of the following requirements are met:
|Diagnosis||A Diagnostic Trouble Code (DTC) is stored in memory when the air conditioning amplifier assembly detects a problem with the air conditioning system.||○||○|
- : Not available
*: Models with 2GR-FE engine
Neural Network Control
Previously, in automatic air conditioning systems without neural network control, the air conditioning amplifier assembly determined the required outlet air temperature and blower air volume in accordance with the calculation formula that has been obtained based on information received from the sensors. However, because the senses of a person are rather complex, a given temperature is sensed differently, depending on the environment in which the person is situated. For example, a given amount of solar radiation can feel comfortably warm in a cold climate, or extremely uncomfortable in a hot climate. Therefore, as a technique for performing a higher level of control, a neural network has been adopted in the automatic air conditioning system. With this technique, the data that has been collected under varying environmental conditions is stored in the air conditioning amplifier assembly. The air conditioning amplifier assembly can then perform control in a way that provides enhanced air conditioning comfort.
The neural network control consists of neurons in the input layer, intermediate layer and output layer. The input layer neurons process the input data of the outside temperature, the amount of sunlight, and the room temperature based on the outputs of the switches and sensors, and output them to the intermediate layer neurons. Based on this data, the intermediate layer neurons adjust the strength of the links among the neurons. The sum of these is then calculated by the output layer neurons in the form of the required outlet temperature, solar correction, target airflow volume and outlet mode control volume. Accordingly, the air conditioning amplifier assembly controls the servo motors and blower motor in accordance with the control volumes that have been calculated by the neural network control.
Air Conditioning Control Assembly
A push-button and dial type air conditioning control assembly is used for both automatic and manual air conditioning.
On models with the automatic air conditioning, the air conditioning control assembly uses a Liquid Crystal Display (LCD).
|*A||Models with Manual Air Conditioning and Mirror Heaters||*B||Models with Automatic Air Conditioning and Mirror Heaters|
Air Conditioning Radiator Assembly
The air conditioning radiator assembly consists of the evaporator, heater radiator unit sub-assembly, servo motors, evaporator temperature sensor (No. 1 cooler thermistor) and blower with fan motor sub-assembly.
A semi-center location air conditioning radiator assembly, in which the evaporator and heater radiator unit sub-assembly are placed in the vehicle's longitudinal direction, is used. As a result, the air conditioning radiator assembly has been made compact and lightweight.
|*1||Evaporator||*2||Heater Radiator Unit Sub-assembly|
|*a||Side View||*b||Top View|
A Revolutionary super-Slim structure (RS) type evaporator is used.
Placing the tanks at the top and the bottom of the evaporator and adopting a micropore tube construction has provided the following benefits:
The heat exchanging efficiency has been improved.
The temperature distribution has been made more uniform.
The evaporator has been made thinner.
Evaporator Temperature Sensor (No. 1 Cooler Thermistor)
The evaporator temperature sensor (No. 1 cooler thermistor) detects the temperature of the cooled air immediately past the evaporator in the form of resistance changes, and outputs this data to the air conditioning amplifier assembly.
Heater Radiator Unit Sub-assembly
The compact, lightweight and highly efficient Straight Flow Aluminum (SFA)-II type heater radiator unit sub-assembly is used for the air conditioning system.
Blower with Fan Motor Sub-assembly
The blower with fan motor sub-assembly has a built-in blower controller which is controlled by the air conditioning amplifier assembly.
Air Conditioning Harness Assembly
An air conditioning harness assembly is used in the wire harness connection that connects the servo motor from the air conditioning amplifier assembly.
|*A||Models with Manual Air Conditioning||*B||Models with Automatic Air Conditioning|
|*1||Bus Connector||*2||Air Conditioning Harness Assembly|
|*a||To Air Conditioning Amplifier Assembly||*b||To Evaporator Temperature Sensor (No. 1 Cooler Thermistor)|
The air conditioning harness assembly has a built-in driver IC with a position detection function that communicates with each servo motor connector and actuates the servo motor. This enables bus communication for the servo motor wire harness with a more lightweight construction and a reduced number of wires.
|*A||Models with Bus Connector||*B||Models without Bus Connector|
|*1||Air Conditioning Amplifier Assembly||*2||Bus Connector|
|*3||Communication Driver IC||*4||Servo Motor|
The pulse pattern type servo motor consists of a printed-circuit board and a servo motor. The printed-circuit board has 3 contact points, and can transmit 2 on-off signals to the air conditioning amplifier assembly based on the difference in the pulse phases. The bus connector can detect damper position and direction of movement with this signal.
Clean Air Filter
A pollen removal type air refiner element is used to remove dust, pollen and other micron particles from air entering from outside the vehicle to provide a comfortable cabin of clean air. The air refiner element is installed in the upper section of the blower with fan motor assembly.
|*1||Air Refiner Element||*2||Pollen|
|*a||Image of Air Refiner Element||*b||Large Foreign Object Filter Layer|
Cooler Condenser Assembly
The cooler condenser assembly consists of 2 cooling portions: a condensing portion and a super-cooling portion. These portions are integrated with a gas-liquid separator (modulator). This cooler condenser assembly uses a sub-cool cycle that offers excellent heat-exchange performance.
In the sub-cool cycle, after the refrigerant passes through the condensing portion of the condenser, both the liquid refrigerant and the gaseous refrigerant that could not be liquefied are cooled again in the super-cooling portion. Thus, the refrigerant is sent to the evaporator in an almost completely liquefied state.
The desiccant and filter at the bottom of the modulator remove moisture and debris from the refrigerant.
|*1||Gaseous Refrigerant||*2||Condensing Portion|
The point at which the air bubbles disappear in the refrigerant of the sub-cool cycle is lower than the proper amount of refrigerant with which the system must be filled. Therefore, if the system is recharged with refrigerant based on the point at which the air bubbles disappear, the amount of refrigerant would be insufficient. As a result, the cooling performance of the system would be affected. Overcharging the system with refrigerant will also lead to reduced performance. For the proper method of verifying the amount of refrigerant and for instructions on how to recharge the system with refrigerant, refer to the Repair Manual.
The compressor is a continuously variable capacity type air conditioning compressor. Its capacity can be varied in accordance with the cooling load of the air conditioning system.
The compressor consists of a pulley, shaft, lug plate, swash plate, piston, shoe, crank chamber, cylinder, air conditioning lock sensor (2GR-FE engine), solenoid valve with built-in Crank chamber to Suction passage (CS) valve, air conditioning mass flow sensor, oil separator and variable suction side throttle.
The oil separator consists of an oil separator chamber and an oil separator cylinder.
|*A||Models with 2AR-FE Engine||*B||Models with 2GR-FE Engine|
|*1||Pulley||*2||Magnetic Clutch Assembly|
|*3||Air Conditioning Lock Sensor||*4||Lug Plate|
|*9||Cylinder||*10||Solenoid Valve with Built-in CS Valve|
|*11||Shaft||*12||Air Conditioning Mass Flow Sensor|
|*13||Oil Separator||*14||Oil Separator Chamber|
|*15||Oil Separator Cylinder||*16||Variable Suction Side Throttle|
A plastic Damper and Limiter (DL) pulley and a steel pulley with magnetic clutch are present.
The plastic DL pulley contains a damper mechanism to absorb the torque fluctuations of the engine and a limiter mechanism to protect the drive belt in case the compressor locks. If the compressor locks, the limiter integrated into the pulley breaks, disconnecting the pulley from the compressor. To reduce weight, the pulley portion is made of plastic.
If the compressor locks, the steel with magnetic clutch pulley turns the magnetic clutch off to protect the drive belt and separates the pulley from the compressor.
|*A||Models with 2AR-FE Engine||*B||Models with 2GR-FE Engine|
|*1||Plastic DL Pulley||*2||Steel with Magnetic Clutch Pulley|
Cooler (Room Temp. Sensor) Thermistor
The cooler (room temp. sensor) thermistor detects the room temperature based on changes in the resistance of its built-in thermistor. This signal is used by the air conditioning amplifier assembly.
Outside Temperature Sensor (Thermistor Assembly)
The outside temperature sensor (thermistor assembly) detects the outside temperature based on changes in the resistance of its built-in thermistor. This signal is used by the air conditioning amplifier assembly.
Solar Sensor (Automatic Light Control Sensor)
The solar sensor (automatic light control sensor) consists of a photo diode, 2 amplifier circuits and a frequency conversion circuit.
The solar sensor (automatic light control sensor) detects (in the form of changes in the current that flows through the built-in photo diode) the changes in the amount of sunlight from its left and right sides (2 directions) and outputs these sunlight strength signals to the air conditioning amplifier assembly for the automatic air conditioning control.
Mode Position and Door Operation
Air Conditioning Unit
|Control Damper||Operation Position||Door Position||Operation|
|Air Inlet Control Damper||FRESH||A||Brings in fresh air.|
|RECIRC||B||Recirculates internal air.|
|Air Mix Control Damper||MAX COLD to MAX HOT Temperature Setting||C - D - E||Varies the mixture ratio of the fresh air and the recirculation air in order to regulate the temperature continuously from HOT to COLD.|
|Mode Control Damper||FACE||I, K, M, O, S||Air blows out of the front center register and side register.|
|BI-LEVEL||I, K, N, O, R||Air blows out of the front center register, side register and front and rear foot well register ducts.|
|FOOT||H, J, L, P, Q||Air blows out of the foot well register duct and side register. In addition, air blows out slightly from the center defroster and side defroster.|
|FOOT/DEF||G, J, L, P, Q||Defrosts the windshield through the center defroster, side defroster, side register, and rear register, while air is also blown out from the front and rear foot well register ducts.|
|DEF||F, J, L, P, S||Defrosts the windshield through the center defroster, side defroster, side register, and rear register.|
|Control Damper||Operation Position||Door Position||Operation|
|Air Inlet Control Damper||FRESH||A||Allows fresh air to enter.|
|RECIRCULATION||B||Causes internal air to recirculate.|
|Air Mix Control Damper||MAX COLD to MAX HOT Temperature Setting||
C - D - E
(C' - D' - E')
T - U - V
|Varies the mixture ratio of the warm air and the cool air in order to regulate the temperature continuously between hot and cold.|
|Mode Control Damper||FACE||I, K, M, O, S, W||Air blows out of the front and rear center registers, and side registers.|
|BI-LEVEL||I, K, N, O, R, X||Air blows out of the front and rear center registers, side register and front and rear footwell registers ducts.|
|FOOT||H, J, L, P, Q, X||Air blows out of the front and rear footwell register duct, and side registers. In addition, air blows out slightly from the center defroster and side defrosters.|
|FOOT/DEF||G, J, L, P, Q, X||Defrosts the windshield through the center defroster, side defrosters, side registers, and rear center register, while air is also blown out from the front and rear footwell register ducts.|
|DEF||F, J, L, P, S, Y||Defrosts the windshield through the center defroster, side defroster, and side registers.|
Air Outlets and Airflow Volume
*1: Regular foot mode (Max. HOT)
*2: Foot mode with large airflow volume from footwell rear ducts (except Max. HOT)
The size of each circle ○ indicates the ratio of airflow volume.
*1: Regular foot mode
*2: Foot mode with large airflow volume from footwell rear ducts
*3: Foot mode with large airflow volume from defrosters
The size of each circle ○ indicates the ratio of airflow volume.
Variable Capacity Operation
A solenoid valve is connected to the suction passage, the discharge passage and the crank chamber passage.
The solenoid valve operates under duty cycle control in accordance with the signals from the air conditioning amplifier assembly.
When the solenoid valve closes (solenoid coil is energized), a difference in pressure is created and the pressure in the crank chamber decreases. Then, the pressure that is applied to the right side of the piston becomes greater than the pressure that is applied to the left side of the piston. This compresses the spring and tilts the lug plate. As a result, the piston stroke increases and the discharge capacity increases.
When the solenoid valve opens (solenoid coil is not energized), the difference in pressure disappears. Then, the pressure that is applied to the left side of the piston becomes the same as the pressure that is applied to the right side of the piston. Thus, the spring elongates and eliminates the tilt of the lug plate. As a result, the piston stroke is small, decreasing the discharge capacity.
Air Conditioning Lock Sensor Operation (Models with 2GR-FE Engine)
The air conditioning lock sensor outputs a pulley rotation signal to the air conditioning amplifier assembly.
The air conditioning amplifier assembly compares this signal with the engine speed signal sent from the ECM to judge if the compressor is locked. If the compressor is locked, the magnetic clutch is turned off.
Air Conditioning Mass Flow Sensor Operation
Using a spool that changes its position according to the amount of refrigerant flow, the air conditioning mass flow sensor detects the amount of refrigerant flow.
The air conditioning mass flow sensor outputs a voltage by converting the change of magnetic flux that occurs due to the magnet that is installed on the spool.
The spool changes its position according to the pressure difference between the pressure before and after the refrigerant flow throttle.
If the amount of refrigerant flow is small, the pressure difference between pressure difference inlet chamber A and B is low, allowing the force of spring B to push up the spool.
If the amount of refrigerant flow is large, the pressure difference between pressure difference inlet chamber A and B is high. The pressure difference overwhelms the force of spring B, and the spool moves down.
Based on the amount of refrigerant flow detected by the air conditioning mass flow sensor, the air conditioning amplifier assembly and ECM cooperatively control the compressor and the engine.
Oil Separator Operation
A mixture of refrigerant and cooler compressor oil flows into the oil separator chamber from the discharge chamber (*a).
The force of the refrigerant and oil mixture flow turns the oil separator cylinder, allowing the oil and refrigerant to be centrifugally separated (*b).
The separated refrigerant flows to the cooler condenser assembly through the discharge port (*c).
The separated oil circulates and lubricates the inside of the compressor by flowing through the oil reservoir chamber, inlet chamber, cylinder and discharge chamber. In addition, the amount of oil that is discharged by the compressor is suppressed (*d).
The oil separator is installed in the refrigerant passage to separate cooler compressor oil from the refrigerant that is discharged. This helps to prevent the cooler compressor oil from flowing into the air conditioning system and reducing cooling effectiveness (*e).
Variable Suction Side Throttle Operation
Refrigerant inlet pressure is applied to the top of the variable suction side throttle and crank chamber pressure to the bottom of the variable suction side throttle.
The pressure difference moves the variable suction side throttle up and down, expanding and contracting the refrigerant inlet passage.
When the refrigerant flow is at a maximum, the refrigerant inlet pressure is greater than the crank chamber pressure. This causes the variable suction side throttle to move down, fully opening the refrigerant inlet passage and lowering the refrigerant inlet resistance.
When the amount of refrigerant flow is controlled, the crank chamber pressure is greater than the refrigerant inlet pressure, raising the variable inlet throttle to contract the flow passage.
These controls suppress noise by reducing pulsation from the refrigerant inlet.
CS Valve Operation
The Crank chamber to Suction passage (CS) valve, built into the solenoid valve, operates in accordance with the suction pressure. The CS valve consists of passage A and passage B.
If the vehicle is left parked for a long period, refrigerant may accumulate in the crank chamber due to the heat capacity difference.
The solenoid valve is controlled by the air conditioning amplifier assembly. While the compressor is operating, the solenoid valve pushes down the CS valve rod and open passage A (*a).
Under the above condition, only if the refrigerant accumulates in the crank chamber, the crank chamber pressure will become high. As a result, the bellows will contract because of the pressure difference with its internal pressure (vacuum), and opens passage B (*b).
This causes the accumulated refrigerant to be drawn in via passage A and B, clearing the accumulated refrigerant earlier and ensuring a more immediate cooling effect.
The air conditioning amplifier assembly has a diagnosis function. It stores a record of any air conditioning system failures in its memory in the form of Diagnostic Trouble Codes (DTCs). For details, refer to the Repair Manual.