Heating and Air Conditioning: Description and Operation
AIR CONDITIONING SYSTEM:
SYSTEM DIAGRAM
SYSTEM DESCRIPTION
1. General
The air conditioning system has the following features:
- An ES27 type electric inverter compressor is used on the RX400h. This compressor is driven by the alternating current that is supplied by the A/C inverter, which is integrated with the compressor. 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 compact, lightweight, and highly efficient electrical water pump is used in order to ensure the proper heater performance while the engine is stopped.
- A left/right independent temperature control and neural network control have been adopted to make air conditioner control available to suit the perception of the persons in the driver seat and in the passenger seat. Automatic air conditioner is standard in all models.
- A semi-center location air conditioner 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 revolutionary slim structure evaporator 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.
- A deodorizing function that eliminates the exhaust gas smell that enters the cabin from the outside has been added to the conventional clean air filter.
- 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 Codes) in its memory.
2. Mode Position and Damper Operation
Function of Main Damper
*1: Auto FOOT Mode
*2: Manual FOOT Mode
3. Air Outlets and Air Volume Rations
The size of the circle o indicates the proportion of airflow volume.
4. Compressor
General
- Along with the installation of the hybrid unit on the RX400h, an ES27 electric inverter compressor that is driven by a built-in DC 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 A/C inverter has been integrated with the compressor.
- The electric motor is actuated by the alternating current power (288 V) supplied by the A/C inverter. As a result, the air conditioner control system on the RX400h 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 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 to ensure the proper insulation of the internal high-voltage portion of the compressor and the compressor housing, the RX400h 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 288 V into AC 288 V and supplies power to operate the compressor.
System Diagram:
Electric Inverter Compressor 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 (automatic light control 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 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 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 (automatic light control sensor), room temperature sensor, mode damper position, and wiper operation condition). 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.
