Heating and Air Conditioning: Description and Operation
AIR CONDITIONING: AIR CONDITIONING SYSTEM: SYSTEM DIAGRAM
SYSTEM DIAGRAM
AIR CONDITIONING: AIR CONDITIONING SYSTEM: SYSTEM DESCRIPTION
SYSTEM DESCRIPTION
1. GENERAL
(a) The air conditioning system has the following controls:
2. NEURAL NETWORK CONTROL
(a) In previous automatic air conditioning systems, the A/C amplifier 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 effecting 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 A/C amplifier. The A/C amplifier can then effect control to provide enhanced air conditioning comfort.
(b) 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 A/C amplifier controls the servo motors and blower motor in accordance with the control volumes that have been calculated by the neural network control.
3. MODE POSITION AND DAMPER OPERATION
(a) Mode Position and Damper Operation
Functions of Main Dampers:
4. AIR OUTLETS AND AIRFLOW VOLUME
(a) Air Outlets and Airflow Volume
The size of the circle o indicates the proportion of airflow volume.
*1: Greater airflow volume at the upper area
*2: Greater airflow volume at the lower area
*3: Greater airflow volume at the front
*4: Greater airflow volume at the rear
*5: Greater airflow volume at the defroster
5. PTC HEATER
(a) The PTC heater is located above the heater core in the air conditioning unit.
(b) The PTC heater consists of a PTC element, aluminum fin, and brass plate. When current is applied to the PTC element, it generates that to warm the air that passes through the unit.
6. PLASMACLUSTER ION GENERATOR CONTROL
(a) General:
(1) A Plasmacluster ion generator is provided inside the air duct of the side register on the driver seat side to improve the air quality and comfort in the cabin.
(2) This generator is controlled by the A/C amplifier and operates in conjunction with the blower motor.
NOTICE:
- The Plasmacluster ion generator uses a high voltage, which is hazardous. Therefore, if the Plasmacluster ion generator requires repairs, be sure to have them done at a TOYOTA dealer.
- Do not apply any type of spray (such as a cleaning solvent or hair spray) or stick any foreign matter into the Plasmacluster ion outlet, as this could cause improper operation or a malfunction.
- After use, dust may accumulate around the side register on the driver seat side. If this occurs, press the OFF switch on the heater control panel to stop the blower motor before cleaning the area.
- It is normal for the Plasmacluster ion generator to emit a slight sound during operation. This sound is created when electrons collide with the electrode while Plasmacluster ions are being generated.
HINT: PlasmaclusterTM, plasmacluster, and plasmacluster ions are a trademark of the SHARP Corporation.
(b) Operation:
(1) The Plasmacluster ion generator produces positive and negative ions from the water molecules (H2O) and oxygen molecules (O2) in the air, and emits them into the air. These ions reduce airborne germs.
7. BLOWER MOTOR
(a) The blower motor has a built-in blower controller, and is controlled with duty control from the A/C amplifier.
8. BUS CONNECTOR
(a) A BUS connector is used in the wire harness connection that connects the servo motor from the A/C amplifier.
(b) The BUS connector has a built-in communication/driver IC which communicates with each servo motor connector, actuates the servo motor, and has a position detection function. This enables bus communication for the servo motor wire harness, for a more lightweight construction and a reduced number of wires.
9. SERVO MOTOR
(a) The pulse pattern type servo motor consists of a printed circuit board and servo motor. The printed circuit board has three contact points, and transmits to the A/C amplifier two ON-OFF signals for the difference of the pulse phase. The BUS connector detects the damper position and movement direction with this signal.
10. CONDENSER
(a) A MF (Multi-Flow) type condenser is used. The condenser consists of two cooling portions: a condensing portion and a super-cooling portion, and gas-liquid separator (modulator) are integrated together. This condenser uses a sub-cool cycle that offers excellent heat-exchange performance.
(b) 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.
11. A/C COMPRESSOR
(a) General
HINT: In order ensure the proper insulation of the internal high-voltage portion of the compressor and the compressor housing, this vehicle 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.
(1) Along with the installation of the hybrid unit on this vehicle, 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.
(2) The Air Conditioning (A/C) inverter is integrated with the compressor.
(3) The electric motor is actuated by 3-phase alternating current (244.8 V) supplied by the A/C inverter. As a result, the air conditioning control system on this vehicle is actuated without depending on the operation of the engine, thus realizing a comfortable air conditioning system and low fuel consumption.
(4) Due to the use of an electric inverter compressor, the compressor speed can be controlled at the required speed calculated by the A/C amplifier. Thus, the cooling and dehumidification performance and power consumption have been optimized.
(5) 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.
(6) 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.
(b) Compressor Speed Control
(1) The A/C amplifier calculates the target compressor speed based on the target evaporator temperature (calculated from the room temperature sensor, outside temp. sensor, and solar sensor) and the actual evaporator temperature detected by the evaporator temperature sensor. Then, the A/C amplifier transmits the target speed to the hybrid vehicle control ECU. 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.
(2) The A/C amplifier calculates the target evaporator temperature, which includes corrections based on the room temperature sensor, outside temp. sensor, solar sensor, and evaporator temperature sensor. Accordingly, the A/C 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.
12. ELECTRIC WATER PUMP
(a) This vehicle uses an electric water pump for air conditioning. This provides a stable heater performance even if the engine is stopped because of a function of the THS-II system.
(b) This vehicle uses a new type of electrical water pump in which the water flow resistance has been reduced.
13. ROOM TEMPERATURE SENSOR
(a) The room temp. sensor detects the room temperature based on changes in the resistance of its built-in thermistor and sends a signal to the A/C amplifier.
14. AMBIENT TEMPERATURE SENSOR
(a) The outside temp. sensor detects the outside temperature based on changes in the resistance of its built-in thermistor and sends a signal to the A/C amplifier.
15. SOLAR SENSOR
(a) The solar sensor consists of a photo diode, two amplifier circuits for the solar sensor, and frequency converter circuit for the light control sensor.
(b) A solar 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 the LH and RH sides (2 directions) and outputs these sunlight strength signals to the A/C amplifier.
16. EVAPORATOR TEMPERATURE SENSOR
(a) The evaporator temperature sensor detects the temperature of the cool air immediately past the evaporator in the form of resistance changes, and outputs it to the A/C amplifier.
17. A/C PRESSURE SENSOR
(a) The A/C pressure sensor detects the refrigerant pressure and outputs it to the A/C amplifier in the form of voltage changes.
18. ECO MODE CONTROL
NOTICE:
- ECO mode control is performed only when the blower motor is ON. When the ECO switch is turned ON while the blower motor is OFF, the ECO switch indicator light and the heater control panel LCD display illuminate, but ECO mode control is not performed.
- During cooling under ECO mode control, the cabin temperature is maintained at 25°C (77°F) even if the set temperature is below 25°C (77°F). Since the power consumption of the electric inverter compressor is limited under ECO mode control, this does not indicate a malfunction. To decrease the cabin temperature to below 25°C (77°F), the MAX COLD temperature (18°C (64.4°F)) must be selected or ECO mode control must be canceled by turning the ECO switch OFF.
(a) General
(1) ECO mode control limits the air conditioning system performance during heating and cooling and increases the amount of engine OFF time, thus improving the fuel economy.
(2) ECO mode control is activated by pressing the momentary type ECO switch on the instrument panel. "ECO" is displayed on the heater control panel LCD during this control.
(3) ECO mode control during heating and cooling, and its cancel conditions are shown in the table below.
(b) Heating Mode
(1) The required engine coolant temperature when starting the engine when the vehicle is stopped differs from that when the vehicle is running. Therefore, the fuel economy has been improved by increasing the amount of engine-off time when the vehicle is stopped.
(2) When the ECO switch is turned ON during heating, the A/C amplifier stops the PTC heater operation. Therefore, it takes a longer time to reach the set temperature than while the ECO switch is OFF.
(3) Engine coolant temperatures fluctuate greatly between when the vehicle is running and the vehicle is stopped. The blower level changes accordingly.
(4) The hysteresis, which is used while the ECO switch is ON, is provided to prevent the blower level from hunting due to fluctuations in the engine coolant temperature.
(c) Cooling Mode
(1) When the ECO switch is turned ON during cooling, the A/C amplifier limits the power consumption of the electric inverter compressor in accordance with the cabin temperature.
(2) The A/C amplifier does not limit the power consumption very much (C2 shown in the graph below), and prioritizes decreasing the cabin temperature when the cabin temperature is high (T2 or above). When the cabin temperature decreases to T1 or below, the A/C amplifier limits the power consumption of the electric inverter compressor C1 and restrains the cooling performance. This prevents the SOC (state of charge) of the HV battery from decreasing and increases the amount of engine OFF time, improving the fuel economy.