System Overview: Notes

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GENERAL

Fig 1: Identifying Transmission Control Module (TCM)

Courtesy of VOLVO CARS CORPORATION

TF-80SC (TF-80SC AWD) is 6-speed electronically controlled automatic transmission with lock-up function on the five highest gears. The Transmission Control Module (TCM) adapts gearshifts so that the correct gear is always selected with respect to driving style, engine load, driver requirements, speed etc. This provides good fuel economy and increased comfort through gentler gearshifts and lower noise level.

The Transmission Control Module (TCM) receives information on required gear position and required driving style (driving program) from the driver. Together with signals from a number of sensors in the transmission and the engine management system, this enables the calculation of optimum gearshift timing and lock-up engagement, in contrast to a gearbox with only a hydraulic control system. The control module takes consideration of small changes in operating conditions and adapts the different transmission functions so that the correct gear is always selected in accordance with the driving program selected by the driver.

The Transmission Control Module (TCM) has an adaptive capacity intended to ensure even gearshift quality during the whole service life of the transmission.

In order to be able to determine gearshift timing and lock-up engagement precisely, based on the selected driving program, the control module receives information on the following:

Selected gear position - from the gear position indicator.
Speed of transmission input shaft - from transmission speed sensor, input shaft.
Speed of transmission output shaft - from transmission speed sensor, output shaft.
Transmission oil temperature - from temperature sensor in the transmission.
Engine speed and torque, and throttle opening - from Engine Control Module (ECM) via the Controller Area Network (CAN).
Whether and how much the accelerator pedal is depressed - from Engine Control Module (ECM) via the Controller Area Network (CAN).
Engine temperature - from Engine Control Module (ECM) via the Controller Area Network (CAN).
Vehicle speed - from Brake Control Module (BCM) via the Controller Area Network.
Whether and how much the brake pedal is depressed - from Brake Control Module via the Controller Area Network.