Schematic diagram of automatic transmission
Automatic transmission with electronic control
Automatic transmission control unit (TCU)
* Controls shift solenoids, clutches and torque converter lock-up
* Receives signals from sensors and switches
* Generates control signals for solenoids and clutches
Electrical solenoids
* Control turning on and off automatic transmission elements
* Typically includes solenoids for shifting, torque converter lock-up and freewheel
Hydraulic couplings
* Used to transmit torque between automatic transmission elements
* Controlled by solenoids and/or fluid pressure modulation
Sensors
* Monitor the operation of the automatic transmission and provide feedback to the TCU
* Typically includes speed, pressure, temperature and gear position sensors
Switches
* Allow the driver to select automatic transmission modes
* Usually include transmission mode switch and ECO mode switch
Wiring
* Connects all components of the automatic transmission electrical system
Scheme
[TCU] ———————— [Solenoids] —————– [Clutches ]
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[Sensors] —————– [Switches] —————– [Wiring]