Engine idling rotational speed control device

Claim 1

An engine idling rotational speed control device for use in an engine having an associated accelerator pedal and air-conditioner and including a main intake passage, a bypass intake passage and a combustion chamber, said device comprising: a throttle valve provided in said main intake passage and substantially fully closed when said accelerator pedal is released; a flow rate control valve provided in said bypass intake passage for controlling the quantity of intake air taken into said combustion chamber through said bypass intake passage; a valve driving means for driving said flow rate control valve; and an electronic control circuit for: controlling said flow rate control valve through said valve driving means for maintaining said engine rotational speed within a target rotational speed range by increasing or decreasing said intake air quantity taken into said bypass intake passage; learning a first value which coincides with a converted value obtained by cancelling an incremental value for an idle up required in accordance with a load on the engine and/or a coolant temperature from a value corresponding to a current opening area of said flow rate control valve; determining a second value during a fast idling control operation, corresponding to a predetermined opening area of said flow rate control valve, in accordance with the coolant temperature from one of a plurality of curves selected in accordance with operational conditions of said air-conditioner, said curves showing a relationship between the second value and the coolant temperature; correcting said second value during the fast idling control operation on the basis of said first value to determine a corrected second value; and controlling said valve driving means by using said corrected second value during the fast idling control operation such that the engine rotational speed becomes a predetermined rotational speed corresponding to said corrected second value.