LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2007 >> Prius Base >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Air Conditioning >> Air Conditioning System >> System Description
July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

System Description

  1. GENERAL 

    The air conditioning system has the following features:

    • An ES18 type Electric Inverter Compressor is used. This compressor is driven by an alternating current provided by the A/C inverter, which is built into the inverter of the hybrid system.

      As a result, the air conditioning system is actuated without depending on the operation of the engine, thus realizing a comfortable air conditioning system and low fuel consumption.

    • A blower motor controller, which regulates the speed of the blower motor by controlling the output voltage in accordance with the duty cycle signal provided by the air conditioning amplifier, is used.

      As a result, the power loss associated with the heat generation of the conventional blower linear controller is reduced, thus realizing low fuel consumption.

    • A humidity sensor function is added to the room temperature sensor in order to optimize the amount of dehumidification effort during the operation of the air conditioning system.
    • A compact, lightweight and highly efficient RS (Revolutionary Slim) evaporator is used.
    • A compact, lightweight and highly efficient MF-IV (Multi Flow-IV) condenser is used.
    • A compact, lightweight, and highly efficient electrical water pump is used in order to ensure the proper heater performance while the engine is stopped.
    • Fuzzy control is used for calculating the required outlet air temperature (TAO: Temperature Air Outlet) and the blower volume in the automatic air conditioning control system. Accordingly, the air conditioning ECU is able to calculate the outlet air temperature, blower volume, air outlet, and compressor speed that is suited to the operating environment. As a result, the comfort level of the occupants is improved.
  2. AIR CONDITIONING OPERATION 
    • The air conditioning is controlled by using the switches that appear on the air conditioning screen display of the multi-display and the switches provided on the steering pad.
    • In addition to the air conditioning screen display, the operating conditions of the AUTO, RECIRCULATION, front DEF, and rear DEF switches are indicated by the indicator lights in the combination meter.
  3. HEATER CORE AND PTC HEATER 
    • A compact, lightweight, and highly efficient straight flow (full-path flow) aluminum heater core is used. A PTC (Positive Temperature Coefficient) heater is built into the heater core tube.
    • The PTC heater contains electrodes that are interposed with a PTC element, to which current is applied in order to warm the air that passes through the fins.
    • The PTC heater is provided in the air duct at the footwell outlet in front of the air conditioning unit. This PTC heater, which is a honeycomb-shaped PTC thermistor, directly warms the air that flows in the duct.
  4. COMPRESSOR 
    • ES18 Electric Inverter Compressor is actuated by a built-in electric motor.
    • The electric motor is actuated by the alternating current power (201.6 V) supplied by the A/C inverter, which is integrated in the hybrid system inverter. As a result, the air conditioning control system is actuated without depending on the operation of the engine, thus realizing a comfortable air conditioning system and low fuel consumption.
    • The electric inverter compressor controls the compressor speed at the required speed calculated by the air conditioning amplifier. Thus, cooling, dehumidification performance and power consumption are optimized.
    • The suction and discharge hoses at the compressor are low-moisture permeation hoses. This minimizes the entry of moisture into the refrigeration cycle.
    • The compressor uses high-voltage alternating current. If a short or open circuit occurs in the compressor wiring harness, the hybrid control ECU will cut off the A/C inverter circuit in order to stop the power supply to the compressor.
    • The Electric Inverter Compressor consists of a spirally wound fixed scroll and variable scroll that form a pair, a brushless motor, an oil separator, and a motor shaft.
    • The fixed scroll is integrated with the housing. Because the rotation of the shaft causes the variable scroll to revolve while maintaining the same posture, the volume of the space that is partitioned by both scrolls varies to perform the suction, compression, and the discharge of the refrigerant gas.
    • Locating the suction port directly above the scrolls enables direct suction, thus realizing improved suction efficiency.
    • Containing a built-in oil separator, this compressor is able to separate the compressor oil that is intermixed with the refrigerant and circulates in the refrigeration cycle, thus realizing a reduction in the oil circulation rate.

    HINT:

    In order ensure the proper insulation of the internal high-voltage portion of the compressor and the compressor housing, a compressor oil (ND-OIL 11) with a high level of insulation performance is used. Therefore, never use a compressor oil other than the ND-OIL 11 type compressor oil or its equivalent.

    Fig 1: Identifying Oil Separator, Motor Shaft And Brushless Motor
    G04475000Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  5. WATER PUMP 
    • An electrical water pump is used. This provides a stable heater performance even if the engine is stopped because of a function of the THS-ll.
    • A new type of electrical water pump is used in which the water flow resistance has been reduced.
  6. ROOM TEMPERATURE SENSOR AND HUMIDITY SENSOR 
    • A humidity sensor function is used by the room temperature sensor. By enabling the detection of humidity in the vehicle interior, this function optimizes the amount of dehumidification effort during the operation of the air conditioning system. As a result, the power consumption of the compressor has been reduced and a comfortable level of humidity has been realized in the vehicle interior.
      Fig 2: Identifying Water Pump
      G04475001Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    • The humidity-sensing resistance film that is built into the humidity sensor absorbs and releases the humidity in the vehicle interior. During the absorption and releasing processes, the humidity-sensing resistance film expands (during the absorption of humidity) and contracts (during drying). The clearance between the carbon particles in the humidity-sensing resistance film expands and contracts during absorption and drying, thus changing the resistance between the electrodes. The air conditioning amplifier determines the humidity in the vehicle interior through the changes in the output voltage of the humidity sensor that are caused by the resistance between the electrodes.
  7. BLOWER MOTOR CONTROLLER 

    The blower motor controller controls the voltage that is output to the blower motor in accordance with the duty cycle signals that are input by the air conditioning amplifier. It is characterized by a smaller amount of heat generation than the blower controller used on the previous model. As a result, the power loss associated with the heat generation of the conventional blower linear controller has been reduced, thus realizing low fuel consumption.

    Fig 3: Voltage Graph
    G04475002Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  8. AIR CONDITIONING AMPLIFIER 

    The air conditioning ECU has the following controls.

    AIR CONDITIONING AMPLIFIER CONTROLS OUTLINE CHART

    Control Outline
    Fuzzy Control The fuzzy control determines the conformity levels of the temperature deviation, ambient temperature, and solar radiation by defining their respective mathematical functions. In addition, a fuzzy calculation method is used to calculate the required outlet air temperature (TAO) and the blower volume. Based on these calculations, the air conditioning amplifier effects the respective controls for the outlet air temperature, blower volume, compressor, and air outlet.
    Outlet Air Temp. Control Air Mix Damper Control In response to the temperature control switch setting, the required outlet air temperature, evaporator temperature sensor, and engine coolant temperature sensor compensations are used by the air mix control damper control to calculate a tentative damper opening angle, through an arithmetic circuit in the air mix damper, to arrive at a target damper opening angle.
    Blower Control Blower Motor Start Up Control When the blower motor is started up, the air conditioning amplifier transmits a blower motor actuation signal with a low duty cycle ratio to the blower pulse controller, which applies a low voltage to the blower motor, in order to operate the blower motor for 3 seconds at a low speed. This is designed to protect the blower pulse controller from a sudden start-up voltage surge.
    Manual Control Sets the blower speed according to operation of the blower switch.
    Automatic Control Step Less Air Volume Control:
    • When the AUTO switch located on the steering pad switch is pushed, or the air conditioning screen display of the multi-display is touched, the air conditioning amplifier automatically regulates the duty ratio to the blower pulse controller in accordance with a calculation result by the fuzzy control in order to deliver step less air volume.

    Warm-up Control:
    • When the air outlet is in the FOOT, BI-LEVEL, or FOOT/DEF mode, the blower will not operate until the engine coolant temperature increases above a prescribed value. When the temperature increases above a prescribed value, the blower motor operates at the LO speed.

    Time-Lagged Air Flow Control:
    • 2 types of time-lagged air flow control (in accordance with the detected by the evaporator temperature sensor) help prevent hot air from being emitted from FACE or BI-LEVEL vent.

    Sunlight Air Flow Control:
    • Controls the blower speed in accordance with the intensity of the sunlight when the air outlet mode is at FACE or BI-LEVEL. The blower speed can be adjusted in response to the signal received from the solar sensor.
    Air Outlet Control Manual Control Changes the air outlet in accordance with the selected position of the mode select switch.
    Automatic Control Mode Damper Switching Servo motor Control:
    • When the AUTO switch is pushed, automatic control causes the mode servo motor to rotate to a desired position in accordance with the target damper opening, which is based on the calculation of the TAO.

    Low-Temperature FOOT/DEF Control:
    • In accordance with the engine coolant temperature, ambient temperature, amount of sunlight, required outlet temperature (TAO), and vehicle speed conditions, this control automatically switches the blower outlet between the FOOT / DEF modes to prevent the window from becoming fogged when the outside air temperature is low.
    Air Inlet Control Manual Control Drives the air inlet servo motor according to the operation of the air inlet control switch and fixes the dampers in the FRESH or RECIRC position.
    Automatic Control Automatic RECIRC / FRESH Control:
    • When the AUTO switch is pressed, the system controls the servo motor so that the air inlet is as calculated in accordance with the TAO.

    DEF Mode Control:
    • When switching the mode switching switch to DEF mode, air conditioning amplifier turns MAX mode ON forcibly and switched to FRESH mode.
    • When switching the mode switching switch to FOOT / DEF mode, air conditioning amplifier switches to FRESH mode.
    2-Way Flow Mode Control At the time of selecting FRESH mode, the air conditioning amplifier will judge it as 2-way flow mode when the blower outlet is set to FOOT or FOOT / DEF, the tentative air mix damper opening angle is above the specified value (MAX HOT), and either the blower volume is more than the specified volume or the vehicle speed is less than the specified speed.
    Half Inlet Air Mode Control At the time of selecting FRESH mode, the air conditioning amplifier will judge it as half inlet air mode when the blower outlet mode is set to FACE or BI-LEVEL and TAO is more than the specified temperature, and operates both outlet air introduction and inlet air circulation at the same time.
    Electric Inverter Compressor Control Compressor Speed Control
    • The air conditioning amplifier calculates target speed of the compressor based on the target evaporator temperature (which is calculated by the room temperature sensor, humidity sensor, ambient temperature sensor, and the solar sensor) and the actual evaporator temperature that is detected by the evaporator temperature sensor in order to control the compressor speed.
    • The air conditioning amplifier calculates the target evaporator temperature, which includes corrections based on the vehicle interior humidity (which is obtained from the humidity sensor) and the windshield glass inner surface humidity (which is calculated from the humidity sensor, solar sensor, room temperature sensor, mode damper position, and wiper operation condition). Accordingly, the air conditioning amplifier controls the compressor speed to an extent that would not inhibit the proper cooling performance or defogging performance.
    Electrical Water Pump Control The electrical water pump is used in order to ensure the proper heater performance while the blower motor is ON and the engine is stopped.
    Engine Start Request Control To ensure the proper heater performance when the hybrid system is started at low temperatures, the air conditioning amplifier transmits an engine start request to the hybrid control ECU in accordance with the TAO, engine coolant temperature sensor signal, and ambient temperature sensor signal.
    PTC Heater Control When the hybrid system is operating (READY) and the blower motor is turned ON, the air conditioning amplifier turns on the PTC heater if the conditions listed below are met. Heater core integrated PTC heater
    • Air outlet is in the FOOT, FOOT / DEF or DEF mode.
    • Engine coolant temperature is below specified temperature.
    • Ambient temperature is below specified temperature (DEF mode).
    • Tentative air mix damper opening angle is above the specified value (MAX HOT).

    Footwell air duct integrated PTC heater
    • Air outlet is in the FOOT or FOOT / DEF mode.
    • Engine coolant temperature is below specified temperature.
    • Tentative air mix damper opening angle is above the specified value (MAX HOT).
    Electric Cooling Fan Control The air conditioning amplifier control the cooling fan in accordance with the vehicle speed signal and compressor speed signal.
    Rear Window Defogger Control Switches the rear defogger and outside rear view mirror heaters on for 15 minutes when the rear defogger switch is switched on. Switches them off if the switch is pressed while they are operating.
    Outer Temperature Indication Control Based on the signals from the ambient temperature sensor, this control calculates the outside temperature, which is then corrected in the air conditioning ECU, and shown in the multi-display.
    Self-Diagnosis Checks the sensor and A/C inverter in accordance with operation of the air conditioning switches, then the heater control panel displays a DTC (Diagnosis Trouble Code) to indicate if there is a malfunction or not (sensor check function).
    Drives the actuators through a predetermined sequence in accordance with the operation of the air conditioning switches (actuator check function).
  9. ELECTRIC INVERTER COMPRESSOR CONTROL 
    • The air conditioning amplifier calculates the target compressor speed based on the target evaporator temperature (calculated from the room temperature sensor, humidity sensor, ambient temperature sensor, and solar sensor) and the actual evaporator temperature detected by the evaporator temperature sensor. Then, the air conditioning amplifier transmits the target speed to the hybrid control ECU. The hybrid control ECU controls the A/C inverter based on the target speed data in order to control the compressor to a speed that suits the operating condition of the air conditioning system.
    • The air conditioning amplifier calculates the target evaporator temperature, which includes corrections based on the vehicle interior humidity (which is obtained from the humidity sensor) and the windshield glass inner surface humidity (which is calculated from the humidity sensor, solar sensor, room temperature sensor, mode damper position, and wiper operation condition). Accordingly, the air conditioning amplifier controls the compressor speed to an extent that does not inhibit the proper cooling performance or defogging performance. As a result, comfort and low fuel consumption can be realized.
      Fig 4: Communication Diagram Between Evaporator Temperature Sensor And Hybrid Control ECU
      G04475003Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  10. MODEL POSITION AND DAMPER OPERATION 
    Fig 5: Model Position And Damper Operation Diagram
    G04475004Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 6: Identifying A/C AUTO And TEMP Switch
    G04475005Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    Function of main damper 

    Fig 7: Main Damper Functions Chart
    G04475006Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    HINT:

    *1: During 2-way flow control

    *2: Early stage of COOL during AUTO

  11. AIR OUTLETS AND AIR VOLUME RATIOS 
    Fig 8: Identifying Air Outlets
    G04475007Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 9: Air Outlet Modes And Air Outlet Position Symbols Chart
    G04475008Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    HINT:

    1. The circle size (x) indicates the proportion of the airflow volume.
    2. The (-) indicates that the air is not blown out.
    3. The (*) indicates the early stage of COOL during AUTO.
scientia non olet · About LEMON Manuals