Control device for controlling air-fuel ratio and spark timing of an integral combustion engine

Claim 1

A control device for controlling the air-fuel ratio and the ignition timing of an internal combustion engine having a fuel injector, a spark plug, and a throttle valve, said device comprising: first sensor mean for sensing engine operating conditions representative of the quantity of the intake air introduced into the engine; second sensor means for sensing whether the opening of the throttle valve is above a predetermined valve; fuel injection control means including means for determining the air-fuel ratio in response to outputs from said first and second sensor means such that the air-fuel ratio is determined in a first fashion with a first predetermined lean limit value when the opening of the throttle valve is below said predetermined value and in a second fashion with a second predetermined lean limit value when the opening of the throttle valve is above said predetermined value, said first predetermined lean limit value being larger than said second predetermined lean limit value; ignition control means including means for determining an ignition timing in response to outputs from said first and said second sensor means such that the ignition timing is determined in a first timing pattern in relation to the air-fuel ratio in said first fashion and in a second timing pattern in relation to the air-fuel ratio in said second fashion, respectively, the first timing pattern being substantially on the spark advance side with respect to said second timing pattern; and delay means which causes a delay in change-over of the ignition timing between said first and said second timing patterns relative to the change-over of the air-fuel ratio between said first and said second fashions when the opening of the throttle valve is changed beyond said predetermined value.