Automatic Transmission/Transaxle: Description and Operation

OPERATION





1. MECHANICAL OPERATION





2. FUNCTION OF COMPONENTS





Power from the engine transmitted to the input shaft via the torque converter clutch is then transmitted to the planetary gears by the operation of the clutch.
By operation of the brake and one-way clutch, either the planetary carrier or the planetary sun gear are immobilized, altering the speed of revolution of the planetary gear unit.
Shift change is carried out by altering the combination of clutch and brake operation.
Each clutch and brake operates by hydraulic pressure; gear position is decided according to the throttle opening angle and vehicle speed, and shift change automatically occurs.
The conditions of operation for each gear position are shown in the following illustrations:





3. HYDRAULIC CONTROL SYSTEM
TRANSAXLE
The hydraulic control system is composed of the oil pump, the valve body, the solenoid valves, the accumulators, the clutches and brakes as well as the fluid passages which connect all of these components.
Based on the hydraulic pressure created by the oil pump, the hydraulic control system governs the hydraulic pressure acting on the torque converter clutch, clutches and brakes in accordance with the vehicle driving conditions.
There are three solenoid valves on the valve body.
The No.1 and No.2 solenoid valves are tuned on and off by signals from the ECM to operate the shift valves and change the gear shift position.
The lock- up solenoid valve is operated by signals from the ECM to engage or disengage the lock-up clutch of the torque converter clutch.
The 3 way solenoid valve is operated by signals from the ECM to control the line pressure.
TRANSFER
There is a center differential control solenoid on the transfer.
The transfer control solenoid valve is operated by duty cycle signals from the Engine & ECT ECU to modulate the fluid pressure of the center differential clutch control valve.





4. ELECTRONIC CONTROL SYSTEM

GENERAL
The electronic control system of the A540H automatic transaxle provides extremely precise and control of the gear shift timing and lock-up timing in response to driving conditions as sensed by various sensors located throughout the vehicle and in response to the engine's running condition. At the same time, the ECM control reduces vehicle squat when the vehicle starts out and gear shift shock. The electronic control system is also equipped with a self diagnosis system which diagnoses malfunctions of electronically controlled components and warms the driver, a fail-safe system which makes it possible for the vehicle to continue functioning when a malfunction occurs.

CONSTRUCTION
The electronic control system can be broadly divided into three groups; the sensors, ECM and actuators.