Air Conditioner Control
AIR CONDITIONER CONTROLDescription of Air Conditioner LAN Control System
The LAN (Local Area Network) system consists of unified meter and A/C amp., mode door motors, air mix door motors, upper ventilator door motor and intake door motor.
A configuration of these components is shown in the figure below.
System Construction
A small network is constructed between the unified meter and A/C amp., mode door motors, air mix door motors, upper ventilator door motor and intake door motor. The unified meter and A/C amp. and motors are connected by data transmission lines and motor power supply lines. The LAN network is built through the ground circuits of each door motor.
Addresses, motor opening angle signals, motor stop signals and error checking messages are all transmitted through the data transmission lines connecting the unified meter and A/C amp. and each door motor.
The following functions are contained in LCUs built into the mode door motors, the air mix door motors, the upper ventilator door motor and the intake door motor.
- Address
- Motor opening angle signals
- Data transmission
- Motor stop and drive decision
- Opening angle sensor (PBR function)
- Comparison
- Decision (Unified meter and A/C amp. indicated value and motor opening angle comparison)
OPERATION
The unified meter and A/C amp. receives data from each of the sensors. The unified meter and A/C amp. sends mode door, air mix door, upper ventilator door and intake door opening angle data to the mode door motor LCUs, air mix door motor LCUs, upper ventilator door motor LCU and intake door motor LCU.
The mode door motors, air mix door motors, upper ventilator door motor and intake door motor read their respective signals according to the address signal. Opening angle indication signals received from the unified meter and A/C amp. and each of the motor position sensors is compared by the LCUs in each door motor with the existing decision and opening angles. Subsequently, HOT/COLD, DEF/VENT, OPEN/SHUT and FRE/REC operation is selected. The new selection data is returned to the unified meter and A/C amp.
TRANSMISSION DATA AND TRANSMISSION ORDER
Unified meter and A/C amp. data is transmitted consecutively to each of the door motors following the form shown in figure below.
Start:
Initial compulsory signal is sent to each of the door motors.
Address:
Data sent from the unified meter and A/C amp. are selected according to data-based decisions made by the mode door motors, air mix door motors, upper ventilator door motor and intake door motor.
If the addresses are identical, the opening angle data and error check signals are received by the door motor LCUs. The LCUs then make the appropriate error decision. If the opening angle data have no error, door control begins.
If an error exists, the received data are rejected and corrected data received. Finally, door control is based upon the corrected opening angle data.
Opening angle:
Data that shows the indicated door opening angle of each door motor.
Error Check:
In this procedure, transmitted and received data is checked for errors. Error data are then compiled. The error check prevents corrupted data from being used by the mode door motors, the air mix door motors, the upper ventilator door motor and the intake door motor. Error data can be related to the following symptoms.
- Malfunction of electrical frequency
- Poor electrical connections
- Signal leakage from transmission lines
- Signal level fluctuation
Stop signal:
At the end of each transmission, a stop operation, in-operation, or internal malfunction message is delivered to the unified meter and A/C amp. This completes one data transmission and control cycle.
AIR MIX DOOR CONTROL (AUTOMATIC TEMPERATURE CONTROL)
The air mix doors are automatically controlled so that in-vehicle temperature is maintained at a predetermined value by the temperature setting, ambient temperature, in-vehicle temperature and amount of sunload.
FAN SPEED CONTROL
Blower speed is automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and air mix door position.
With pressing AUTO switch, the blower motor starts to gradually increase air flow volume.
When engine coolant temperature is low, the blower motor operation is delayed to prevent cool air from flowing.
INTAKE DOOR CONTROL
The intake doors are automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature, amount of sunload and ON/OFF operation of the compressor.
MODE DOOR CONTROL
The mode doors are automatically controlled by the temperature setting, ambient temperature, in-vehicle temperature, intake temperature and amount of sunload.
UPPER VENTILATOR DOOR CONTROL
The upper ventilator door is automatically controlled by the mode setting, and amount of sunload.
MAGNET CLUTCH CONTROL
When A/C switch, AUTO switch or DEF switch is pressed, unified meter and A/C amp. transmits compressor ON signal to ECM, via CAN communication.
ECM judges whether compressor can be turned ON, based on each sensor status (refrigerant-pressure sensor signal, throttle angle, etc.). If it judges compressor can be turned ON, it sends compressor ON signal to IPDM E/R, via CAN communication.
Upon receipt of compressor ON signal from ECM, IPDM E/R turns A/C relay ON to operate compressor.
When sending compressor ON signal to IPDM E/R via CAN communication line, ECM simultaneously sends compressor feedback signal to ECM via CAN communication line.
ECM sends compressor feedback signal to unified meter and A/C amp., then, uses input compressor feedback signal to control air inlet.
SELF-DIAGNOSIS SYSTEM
The self-diagnosis system is built into the unified meter and A/C amp. to quickly locate the cause of malfunctions.
Description of Control System
The control system consists of input sensors, switches, the unified meter and A/C amp. (microcomputer) and outputs. The relationship of these components is shown in the figure below:
Control Operation
DISPLAY SCREEN
MULTIFUNCTION SWITCH
DISPLAY SCREEN
The operation status of the system is displayed on the screen.
MODE SWITCH (DRIVER SIDE)
- Controls the air discharge outlets.
- When the DUAL switch indicator lamp turns OFF, the driver side and passenger side outlets are switched together.
- When the DUAL switch indicator lamp turns ON, only the driver side outlet is switched.
MODE SWITCH (PASSENGER SIDE)
When the MODE switch (passenger side) is pressed, the DUAL switch indicator lamp turns ON, and only the passenger side outlet is switched.
TEMPERATURE CONTROL SWITCH (POTENTIO TEMPERATURE CONTROL) (DRIVER SIDE)
The set temperature is Increased or decreased with this switch.
TEMPERATURE CONTROL SWITCH (POTENTIO TEMPERATURE CONTROL) (PASSENGER SIDE)
- The set temperature is Increased or decreased with this switch.
- When the temperature switch is pressed, the DUAL switch indicator lamp will automatically turns ON.
AUTO SWITCH
- The compressor, intake doors, air mix doors, mode doors and blower speed are automatically controlled so that the in-vehicle temperature will reach, and be maintained at the set temperature selected by the operator.
- When pressing AUTO switch, air inlet, air outlet, fan speed, and discharge air temperature are automatically controlled.
DEFROSTER (DEF) SWITCH
Mode doors are set to the defrost position with this switch. Also, intake doors are set to the outside air position, and compressor turns ON.
UPPER VENT SWITCH
- When UPPER VENT switch is ON, UPPER VENT switch indicator lamp turns ON, and upper ventilator door is automatically controlled.
- When DEFROSTER (DEF) switch is ON, upper ventilator door is shut.
- When MODE position (driver side) is FOOT or D/F, upper ventilation door is shut.
- When UPPER VENT switch is OFF, UPPER VENT switch indicator lamp turns OFF, and upper ventilator door is shut.
A/C SWITCH
Compressor is ON or OFF with this switch.
(Pressing the A/C switch when the A/C switch is ON will turn OFF the A/C switch and compressor.)
FAN SWITCHES
The blower speed is manually controlled with this switch. Seven speeds are available for manual control (as shown on the display screen).
OFF SWITCH
Compressor and blower are OFF, air inlet is set to FRE, and mode position is set to foot position.
REAR WINDOW DEFOGGER SWITCH
When indicator lamp turns ON, rear window is defogged.
INTAKE SWITCH
- When intake switch is ON, FRE indicator lamp turns ON, and air inlet is fixed to FRE.
- When press intake switch again, REC indicator lamp turns ON, and air inlet is fixed to REC.
- When intake switch is pressed for approximately 1.5 seconds or longer, FRE and REC indicator lamps blink twice. Then, automatic control mode is entered. Inlet status is displayed by indicator lamp even during automatic controlled.
- When FRE indicator lamp turned ON, shifting mode position to D/F or DEF, or when compressor is turned from ON to OFF, intake switch is automatically turned OFF (fixed to FRE mode). REC mode can be reentered by pressing intake switch again, and then compressor is turned ON. (Except D/F or DEF position)
DUAL SWITCH
- When the DUAL switch indicator lamp turns ON, the driver side and passenger side temperature can each be set independently.
- When the DUAL switch indicator lamp turns OFF, the driver side outlet and setting temperature is applied to both sides.
Control Operation (Rear Control Switch)
AUTO SWITCH
- When pressing AUTO switch, display for turned on AUTO and fan speed is automatically controlled.
- When pressing AUTO switch, air inlet, air outlet, fan speed, and discharge air temperature are automatically controlled.
FAN SWITCH
The blower speed is manually controlled with this switch. Five speeds are available for manual control (as shown on the display screen).
REAR TEMPERATURE CONTROL SWITCH
- Increases or decreases the set temperature.
- A temperature for the rear seat with respect to a set temperature for the front seat can be adjusted by operating switch.
- Rear temperature control switch allows to select a temperature every 0.5 °C (1 °F) in the 18 °C (60 °F) to 32 °C (90 °F) range.
- When the DUAL switch is ON, temperature for the rear seat changes keeping the temperature difference between two front seats. [e.g. When lowering the set temperature for the rear seat 1 °C (2 °F) by operating rear control switch at a set temperature of 25 °C (77 °F) for the driver's seat and 26 °C (79 °F) for the passenger's seat, the set temperature for the driver's seat and passenger's seat lower 1 °C (2 °F) and become 24 °C (75 °F) for the driver's seat and 25 °C (77 °F) for the passenger's seat.]
NOTE: A set temperature for the rear seat is tied to a set temperature for the passenger's seat. Therefore, a set temperature for the rear seat changes in conjunction with a set temperature for the passenger's seat (When the set temperature of front seats are independent).
Fail-Safe Function
- If a communication error exists between the unified meter and A/C amp.,and the AV control unit and multifunction switch for 30 seconds or longer, air conditioner is controlled under the following conditions:
Compressor : ON
Air outlet : AUTO
Air inlet : FRE (Fresh)
Blower fan speed : AUTO
Set temperature : Setting before communication error occurs
Display : OFF
Discharge Air Flow
System Description
SWITCHES AND THEIR CONTROL FUNCTION
CAN Communication System Description
CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only. For details, refer to LAN-29, "CAN System Specification Chart". CAN System Specification Chart