Retarding control apparatus

A retarding control apparatus for controlling operation of a retarder, which is connected to an automatic transmission, by operating a retarder actuating device by manipulation of a retarder changeover switch, comprising:

• vehicle speed detecting means for detecting vehicle speed;
• driving-wheel velocity detecting means for detecting velocity of a driving wheel;
• steering angle detecting means for detecting steering angle of a wheel;
• brake actuation detecting means for detecting actuation of a brake;
• and
• control means to which are inputted a vehicle speed signal from said vehicle speed detecting means, a driving-wheel velocity signal from said driving-wheel velocity detection means, a steering angle signal from said steering angle detection means, a brake actuation signal from said brake actuation detecting means and an ON signal from the retarder changeover switch, for outputting a retarder operating signal to the retarding actuating device;
• said control means having a map in which control characteristics are set such that when a slip rate of the wheel is not more than a fixed value, a retarder braking force is reduced as the slip rate becomes larger;
• when the slip rate exceeds the fixed value and lies in a predetermined range, the retarder braking force is held at a constant value;
• and when the slip rate exceeds the predetermined range, the retarder braking force is reduced as the slip rate becomes larger and is made relatively smaller as the steering angle of the wheel larger becomes;
• wherein when the brake actuation signal and the ON signal from the changeover retarder switch are being inputted to said control means, said control means selects from the map, on the basis of the steering angle signal, a control characteristic of the retarder braking force corresponding to the steering angle, computes the slip rate based upon the vehicle speed signal and the driving-wheel velocity signal, and outputs the retarder operating signal to the retarder actuating device based upon the computed slip rate and the selected control characteristic of the retarder braking force.