Air Conditioning System
System Diagram (Part 1):
System Diagram (Part 2):
System Diagram (Part 3):
SYSTEM DESCRIPTION
1. General
The air conditioning system in the '06 Highlander Hybrid model has the following features:
- A manually controlled air conditioning system is standard equipment and an automatically controlled air conditioning system is optional equipment.
- A manual type rear heater is optional equipment on the 7-seats model.
- An ES27 type electric inverter compressor is used. This compressor is driven by the alternating current that is supplied by the A/C inverter, which is integrated with the compressor. As 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 compact, lightweight, and highly efficient electrical water pump is used in order to ensure the proper heater performance while the engine is stopped.
- A semi-center location air conditioning unit, in which the evaporator and heater core are placed in the vehicle's longitudinal direction, is used.- A compact, lightweight, and highly efficient straight flow (full-path flow) aluminum heater core is used.
- A multi-tank slim structure evaporator is used.
- A clean air filter (standard type particle filter) is used.
- A humidity sensor function has been added to the room temperature sensor in order to optimize the amount of dehumidification effort during the operation of the air conditioning system.
- The air conditioning ECU is equipped with a self-diagnosis function. If there is a malfunction in the system, it stores the DTCs (Diagnostic Trouble Code) in its memory.
2. Mode Position and Damper Operation
3. Air Outlets and Air Volume Rations
The size of the circle indicates the proportion of airflow volume.
4. Compressor
General
- On the '06 Highlander Hybrid model, an ES27 electric inverter compressor that is driven by a motor is used. The basic construction and operation of this compressor are the same as the ordinary scroll compressor, except that it is driven by an electric motor.
- The Air Conditioning (A/C) inverter is integrated with the compressor.
- The electric motor is actuated by 3-phase alternating current (288 V) supplied by the A/C inverter. As a result, the air conditioning control system on the Hybrid model is actuated without depending on the operation of the engine, thus realizing a comfortable air conditioning system and low fuel consumption.
- Due to the use of an electric inverter compressor, the compressor speed can be controlled at the required speed calculated by the A/C ECU. Thus, the cooling and dehumidification performance and power consumption have been optimized.
- Low-moisture permeation hoses are used for the suction and discharge hoses at the compressor in order to minimize 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 vehicle control ECU will cut off the A/C inverter circuit in order to stop the power supply to the compressor.
- For details on the Electric Inverter Compressor control effected by the A/C ECU.
Service Tip:
In order ensure the proper insulation of the internal high-voltage portion of the compressor and the compressor housing, the Highlander Hybrid has adopted a compressor oil (ND11) with a high level of insulation performance. Therefore, never use a compressor oil other than the ND11 type compressor oil or its equivalent.
Construction
- The Electric Inverter Compressor consists of a spirally wound fixed scroll and variable scroll that form a pair, a brushless motor, an oil separator, a motor shaft and A/C inverter.
- The fixed scroll is integrated with the housing. Because the rotation of the shaft causes the variable scroll to remove 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.
- This inverter converts the HV battery's nominal voltage of DC into AC and supplies power to operate the compressor.
System Diagram:
5. Rear Heater Control Switch
- On the models with the rear heater, rear heater main switch has been provided in the instrument panel.
- The rear heater blower switch has been provided on the right deck cover of the rear No.2 seat so that the heater can be controlled and select blower speed (LO or HI).
- The rear heater will not operate even if the rear heater blower switch is operated with the rear heater main switch OFF.
6. Electric Inverter Compressor Control
Compressor Speed Control
- The A/C ECU 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 A/C ECU transmits the target speed to the hybrid vehicle control ECU. The hybrid vehicle controls the A/C operating condition of the air conditioning system.
- The A/C ECU 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, and mode damper position). Accordingly, the A/C ECU 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.