Cruise control system for a vehicle

摘要

A cruise control system for a vehicle having an internal combustion engine provided with a throttle valve operated by a diaphragm actuator irrespective of a depression of an accelerator pedal by an operator of the vehicle. The system is provided with a system for controlling a vehicle speed in a so-called "dead zone" where hunting usually occurs if a normal feedback control is executed. A time-interval integrating unit is provided for integrating the deviation of the acutal speed with respect to the target speed with a time interval as well as a weight factor, so that the integrated value corresponds to the change in the deviation in the dead zone. The integrated value is compared with a predetermined value corresponding to a change in the vehicle speed which is obtainable when the least significant bit in the control signal output to the actuator is changed. When the integrated value becomes equal to or higher than the predetermined value, the least significant bit is incremented or decremented, and thus speed control in the "dead zone" becomes possible.