Torque Converter: Description and Operation

Operation

The Transmission Control Module (TCM) is able to monitor the state of the torque converter clutch at all times.
There are three operating modes for the converter
1. Fully open - Torque converter 'unlocked'
2. Fully closed - Torque converter 'locked'
3. Slip control - The TCM monitors slip and may apply sufficient pressure to allow a small degree of slip. This mode maximizes economy by reducing slip to a minimum whilst providing isolation from drive-line shunt and vibration.

The TCM constantly measures the slip within the torque converter by comparing engine speed (via CAN) and input (turbine speed). Differences in these speeds indicate the amount of slip.

Clutch Hydraulic Pressure Regulation

The TCM supplies an internally switched +12 Volt supply to the #4 pressure regulator. The regulator is operated by switching the other side of the operating winding to ground. Hydraulic pressure is controlled by 'Pulse Width Modulation' (PWM) of the ground switching signal i.e. the duty cycle; the time that the pressure regulator is switched on.