Directly Control Pneumatic Clutch for Heavy Duty Vehicles

We have developed an electro-pneumatic control system applied to Daikin Pneumatic Actuated Clutch (D-PAC) for buses and other heavy duty vehicles. This system is a semi-automatic transmission, having a conventional gear train with manual shift lever and the directly controlled pneumatic clutch. In the clutch, the clamping load is proportional to supplied air pressure controlled through an electro-pneumatic proportional valve(EPPV) independent from the wear of clutch facing. To control the valve an electronic control unit is composed of a microcomputer and power amplifier with pulse width modulated (PWM) signals. The most suitable signals are computed considering the engine rotational speed, vehicle speed, gear position and the accelerator pedal stroke. This system is applied to a bus with diesel engine, and we have obtained very smooth feeling at the vehicle starting and gear change in the tests of various road and acceleration conditions.