With A140L and A140E
DESCRIPTION
The A140L and A140E automatic transaxle described is a lock-up four-speed automatic transaxle developed exclusively for use with a transversely-mounted engine.
The A140E is called an ECT (Electronic Controlled Transaxle). Based on the A140L. the hydraulic control system has been changed, and the shift and lock-up timing are controlled by micro computer.
The construction and operation of the A140L, will first be explained. Then the difference between the A140E and the A140L, and the features of the ECT, will also be explained.
A140L Automatic Transaxle
CONSTRUCTION AND OPERATION
The A140L automatic transaxle can be roughly divided into the automatic transmission section and the differential section. The automatic transmission section is composed of the torque converter, planetary gear unit and the hydraulic control system.
1. Torque Converter
CONSTRUCTION
The torque converter is composed of the pump impeller which is rotated by the engine, the turbine runner and lock-up clutch which are fixed to the transmission input shaft, and the stator which is attached to the stator shaft via the one-way clutch.
The torque converter is filled with ATF.
OPERATION
The pump impeller is rotated by the engine, which causes a flow in the ATF inside the torque converter.
The flow of ATF caused by the pump impeller strikes the turbine runner, providing a force to rotate the turbine runner, and transmits torque to the input shaft.
The flow of ATF which has hit the turbine runner rebounds and tries to flow in the direction opposite to the direction of rotation of the pump impeller, but the stator returns the flow the original direction of rotation. So the ATF becomes a force which supports the pump impeller and increases torque.
HINT: Although the stator is immobilized by the one- way clutch, should the one-way clutch become defective the stator will be rotated by the flow of ATF, the flow of ATF will not be reversed, torque will not be increased and the problem of inadequate acceleration will occur.
The lock-up clutch is pushed against the front cover by fluid pressure so that the engine revolutions are directly transmitted to the input shaft without the medium of the ATF.
2. Planetary Gear Unit
CONSTRUCTION
The planetary gear unit is composed of three sets of planetary gears, three clutches which transmit power to the planetary gears, and four brakes and three one-way clutches which immobilize the planetary carrier and planetary sun gear.
OPERATION
Power from the engine transmitted to the input shaft via the torque converter 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 on the following illustrations:
3. Hydraulic Control System
CONSTRUCTION
The hydraulic control is composed of an oil pump, rotated by the engine, which supplies hydraulic pressure; a valve body which controls the hydraulic pressure and the opening and closing of the fluid passaged; and a governor valve which supplies hydraulic pressure in accordance with vehicle speed.
OPERATION
Hydraulic pressure supplied by the oil pump is controlled by the regulator valve; the resulting oil pressure controlled by the regulator valve is called the line pressure.
Line pressure produces the hydraulic pressure for throttle pressure and governor pressure. Also, line pressure produces hydraulic pressure for the operation of each brake and clutch in the planetary gear unit.
The throttle valve acts to produce hydraulic pressure, called the throttle pressure, which responds to accelerator pedal modulation. Throttle pressure increases as the accelerator pedal is depressed.
The governor valve produces hydraulic pressure, called the governor pressure, in response to vehicle speed. Governor pressure increases as vehicle speed increases.
In accordance with the difference between throttle pressure and governor pressure, each shift valve shifts, the fluid passages to the clutches are brakes in the planetary gear unit are opened and the clutches and brakes operate, and shift change occurs.
The operation of the hydraulic control system, using the 2-3 shift valve as an example, is shown.
A140E Automatic Transaxle (ECT)
WHAT IS THE ECT?
ECT means Electronic Controlled Transaxle. The hydraulic control system of the previous automatic transaxle has been changed, the throttle and governor pressure have been replaced by electronic signals and a micro computer has been used to give precise control of shift timing and lock-up timing.
FEATURES OF THE ECT
a. The shift pattern can be chosen.
In the ECT ECU micro computer used in the A140E, two types of shift pattern, Power and Normal, are recorded in the memory. By operating the pattern select switch, the driver can select the preferred shift pattern.
b. Reduced fuel consumption and reduced shock during shifting is made possible.
Precise control of the shift timing by the ECT ECU, operation of the lock-up clutch from low speeds, and decreased fuel consumption are made possible. Also, shock during ,5hifting is reduced.
c. Self-Diagnostic System
When a malfunction occurs in the electronic control system, the driver is informed of this fact. Also, there is a Self-Diagnostic System which displays the location of the malfunction when the service connector is shorted.
d. Fail-Safe System
A fail-Safe System is included so that, even if a malfunction occurs in the electronic control system, the vehicle will be able to operate.
CONSTRUCTION AND OPERATION
When the A140E (ECT) is compared with the A140L, the automatic transaxle body has the same construction and operation, with the exception of the hydraulic control system, as the A140L.
The electronic control system, which controls the shift timing and lock-up timing, has been added.
1. Hydraulic Control System (Comparison with the A140L)
VALVE BODY - Additions or changes to solenoid valve
In the A140E there are three solenoid valves, the No.1, the No.2 and the lock-up solenoid valves. Shifting occurs according to whether the No.1 and No.2 solenoid valves are ON or OFF, and the lock-up solenoid valve controls the lock-up clutch.
GOVERNOR VALVE - Removed
With the A140E, the governor valve has been replaced with a speed sensor, so that instead of the governor pressure, a speed sensor signal is sent to the ECT ECU.
2. Electronic Control System
COMPONENTS
The electronic control system for controlling the shift timing and the operation of the lock-up clutch is composed of the following three parts:
a. Sensors: These sense the vehicle speed and throttle position and send this data to the ECT ECU in the form of electronic signals.
b. ECT ECU: This determines the shift and lock-up timing based upon the signals from the sensors.
c. Actuators: Solenoid valves divert hydraulic pressure from one circuit of the hydraulic control unit to another, thus controlling shifting and lock-up timing.