TOD Control

The TOD position usually drives the rear wheels, and transmits the torque to the front wheels with the help of electronically controlled torque split mechanism according to running conditions encountered. The driving force is directly transmitted to the rear wheels. This force is split by the transfer and delivered to the front wheels. The magnitude of the torque transmitted to the front wheels is controlled by changing the pressing force of the multi plate disk clutch built in the transfer unit. The pressing force of the clutch is controlled by changing the duty ratio to the electromagnetic coil mounted to the rear of the clutch. When the clutch is completely disengaged, the rear wheels are driven. When the clutch is completely engaged, a rigid four wheel drive mode is obtained. The torque split status is controlled continuously between the rear wheel and four wheel drive modes. This system includes front and rear speed sensors, and receives throttle position sensor and engine speed information from the PCM, ABS control unit signal, brake switch signal, and shift motor position information.

The control unit receives signals sent from these sensors and changes the pressing force of the multi-plate disk clutch to determine the torque distribution on the front and rear wheels. Therefore, when the slip of the rear wheels is increased against the current torque level in the normal rear wheel drive mode, the control unit detects the slip condition, determines the optimum torque based on the feedback control logic, and increases the torque to the front wheels.

The control unit uses the signal from the throttle position sensor to predict the future vehicle condition and the intention of the driver with respect to acceleration and deceleration, and determines the initial torque distribution using these data and the information from the speed sensors.

In case of small circle turning in the parking lot, for example, the control unit minimizes the clutch pressing force to restrict a braking phenomenon. When the ABS becomes active, the control unit optimizes the clutch pressing force to ensure stable braking.