To attain stratified-charge combustion by inhibiting degradation in emission of exhaust gas caused by drop in catalyst temperature in a stratified-charge combustion continued for a long time, or by spark-plug carbon fouling in a center injection-type direct injection engine having a cavity on the piston crown.
In a center injection-type direct injection engine having a cavity on each piston crown, a 1st stratified-charge combustion forming a comparatively small stratified mixture around the spark plug and a 2nd stratified-charge combustion forming a comparatively large stratified mixture around the spark plug can be attained. When judgement conditions are established to perform switching between the 1st stratified-charge combustion and the 2nd stratified-charge combustion in the same engine speed and under the same load conditions, the switching is taken place between the above stratified-charge combustions.
NAKAJIMA SHINICHIRO
HOTTA ISAMU
TANAKA DAISUKE
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