Patent attributes
An internal combustion engine includes a throttle controlling mechanism; a valve characteristic varying mechanism which controls an internal EGR rate by the control of an overlap period Pa and a non-overlap period Pb; and an output setting means which sets a required amount of engine output. The throttle controlling mechanism controls an opening degree of a throttle valve to fully open the throttle valve at a predetermined load Da with an increase in an operating amount D in a first load range Fa which covers load range below the predetermined load Da in a low-load range, and to keeps the throttle valve fully opened in a second load range Fb which covers a load range over the predetermined load Da. The valve characteristic varying mechanism controls the engine output by controlling the overlap period Pa or the non-overlap period Pb according to the required amount D over the entire load range, and controls valve operation characteristics to obtain a maximum internal EGR rate at the predetermined load Da.
