Overview of Automatic Control
Overview of Automatic Control of Automatic Air ConditionerThe full automatic heater and air conditioner on this vehicle has the following features:
- Interior temperature control.
- Air flow control.
- Mode (blow port) control.
- Intake (switching between fresh air and interior air) control.
- Heater start timing control.
- Cooler start timing control.
- Evaporator anti-freeze control.
Interior Temperature Control
The automatic heater/air conditioner control unit operates on the setup temperature signal from the temperature control switch and other sensor signals to derive the total signal. Then, the control unit compares this signal against the signal from the potentiometer to determine rotation direction of the mix actuator. The mix actuator moves the air mix door to the aperture specified by the total signal so that the specified interior temperature is achieved.
If the compressor is turned off in the A/C (air conditioning) mode, aperture of the air mix door is offset according to the outside air temperature or the specified interior temperature. This function removes the difference in the blowing temperature in this state and that of when the compressor is turned on.
When FH or FC is selected for the setup temperature, the air mix door is accordingly fixed to the Full Heat or Full Cool mode.
When the VENT mode is selected, aperture of the air mix door is controlled so that excessively heated air may not be blown from the VENT blow port.
Air Flow Control
In the Auto Mode
The automatic heater/air conditioner control unit operates on the setup temperature signal and other sensor signals to derive the total signal. Then, the control unit adjusts base potential of the power transistor to match it to the voltage pattern of the target fan so that stage-less fan speed control can be achieved.When solar radiation quantity is detected in the VENT or B/L mode, the control unit increases the minimum fan voltage to offset. When FH or FC is selected from the temperature control switch, air flow is accordingly fixed to MAX HI or AUTO HI.
In the Manual Mode
Air flow specified from the fan switch is entered to the automatic heater/air conditioner control unit as the manual signal. The signal modifies the air flow to the level specified from the fan switch so that the required fan voltage is attained.
Mode (Blow Port) Control
The automatic air conditioner control unit operates on the setup temperature from the control switch, and temperature and solar radiation quantify from the sensors to determine the total mode control signal. According to the pattern specified by this signal, the control unit selects either one of the VENT, BI-LEVEL, FOOT or DEF/FOOT mode.
The mode actuator determines the rotation direction comparing the target position against the current position being determined by the position detection signal.
When FH or FC is selected for the temperature from the temperature control switch, mode is accordingly fixed to the VENT or FOOT.
- In the manual operation of the mode switch, you can select a desired blow port mode pressing the corresponding mode switch.
- Operating the DEF mode switch selects the DEF for the blow port mode.
Intake (Fresh air/interior air switching) Control
In the Full Auto mode, the automatic air conditioner control unit operates on the setup temperature signal and other sensor input signals to derive the total signal. According to the pattern specified by this signal, the control unit provides the intake control.
When the fan is turned off or the A/C (air conditioning) is turned off, the intake is fixed to the FRESH mode.
When FC or FH is selected from the control switch, the intake mode is accordingly fixed to the RECIRC or FRESH.
In the Manual Operation
Pressing the FRESH (fresh air intake) or the RECIRC (room air circulation) accordingly selects the FRESH or RECIRC mode.
When the DEF Mode Switch is depressed
The intake mode is fixed to the FRESH. When the MANU REC is selected, however, the mode is fixed the RECIRC.
When the Mode Switch is depressed
If the automatic intake control is selected, the intake is fixed to the currently selected mode.
Compressor Control
In the automatic control mode, the automatic air conditioner control unit turns on or off the compressor with the evaporator anti-freeze mechanism using the evaporation sensor. And, when outside air is detected to be low through the ambient sensor signal, the control unit turns off the compressor using the compressor control function.
Manual Control
- In the automatic control mode, pressing the A/C (air conditioning) switch turns off the compressor.
- Pressing the DEF mode switch automatically turns on the compressor.
Heating Start Timing Control
When the automatic air conditioner is started, heating is turned on under following conditions.
- The detected temperature of thermo unit is 58 °C (136 °F) or less.
- The temperature setting signal and the total signal by each sensor meet the condition of heating.
When the detected temperature by the coolant temperature sensor is 58 °C (136 °F) or less, the blower fan motor is set to work at low speed and the "DEF" mode is selected.
When the detected temperature by the coolant temperature sensor is 25 °C (77 °F) or more, the blow mode changes automatic control. And the blower fan speed is controlled to be lineally up from "LO" to "MAX HI".
Cooling Start Timing Control
When the automatic air conditioner is started, cooling is turned on under following conditions.
- The in car sensor is 30 °C (86 °F) or more.
- The temperature setting signal and the signals from each sensor meet the specified condition.
The blower fan speed is set to "LO" for maximum 7 seconds when cooling start conditions meet, and then, is controlled to be lineally up to "MAX HI" by 5.32%/S.