To provide a premixed compression self-ignition internal combustion engine capable of preventing deterioration of thermal efficiency by keeping the inside of a combustion chamber at a high temperature while restraining combustion noise when high load is applied.
This engine repeatedly performs an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke in order. A port injection valve 34 injects fuel to form a mixed gas Gm. An intake valve solenoid driving device 32a opens and closes an intake valve 32 from the beginning of the intake stroke, and thereby, a part of the mixed gas Gm is mixed with a remaining internal EGR gas Gi in the combustion chamber 35, and a first temperature layer Gmi is formed. In the middle of the intake stroke, an exhaust valve solenoid driving device 39a opens and closes an exhaust valve 39, and thereby, another part of the mixed gas Gm is mixed with an external EGR gas Go flowing backward in the combustion chamber 25, and a second temperature layer Gmo is formed. Just before self-ignition in the end of the compression stroke, the second temperature layer Gmo is stratified so as to have a temperature lower than the first temperature layer Gmi.
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