System for controlling start clutch of automatic transmission

A control system, comprising:

• a vehicular automatic transmission for transmitting power from an engine to wheels of a vehicle, said transmission having at least a start clutch which is engaged by fluid pressure,
• actuator means for varying an engagement force of the start clutch by varying the fluid pressure, said actuator means having a first position for increasing the fluid pressure to engage the start clutch and a second position for decreasing the fluid pressure to disengage the start clutch, said actuator being moved between said first and second positions in response to a control signal having a variable duty factor such that, as the duty factor increases, the actuator remains longer in the first position,
• sensor means responsive to a position of an accelerator member of said engine for producing a start signal representing a start of the vehicle when said accelerator member moves away from an idle position, and
• controller means connected with said sensor means for controlling the fluid pressure supplied to the start clutch by varying said duty factor of said control signal upon receipt of said start signal so that said duty factor of said control signal increases immediately from a low disengage value to a transient high value to increase said fluid pressure, then falls from said transient high value to a transient low value to decrease said fluid pressure, and finally increases gradually and continuously from said transient low value to a high engage value to gradually increase said fluid pressure.