Limiting braking torque, function

In order to prevent the maximum coolant temperature or retarder oil temperature specified in the retarder control (RS) control unit (A20) being exceeded and to use the cooling capacity of the engine cooling system to the maximum possible extent, the retarder braking torque is reduced to protect the engine cooling system and the retarder accordingly. The actuating pressure is limited and thus a shift of the rotor towards its idle position.

Shifting the rotor means a more rapid reduction in retarder oil temperature or coolant temperature can take place as the retarder oil flow is not braked and no thermal energy is liberated

The RS control unit RS (A20) continuously receives information on retarder oil temperature from the retarder oil temperature sensor (B66) and on the coolant temperature from the coolant temperature sensor (B65).

The retarder brake torque is regulated back at too high coolant temperature, too high retarder oil temperature or too rapid a rise in retarder oil temperature.

As soon as the retarder brake torque is limited, a message with the information about the reason for triggering is placed on the vehicle CAN (CAN 1)

Each measure is evaluated separately and a so-called adaptation factor is determined in the RS control unit (A20). The highest adaptation of all measures determines the limitation of the retarder brake torque up to the complete shutoff of the retarder.