| 摘要 |
PROBLEM TO BE SOLVED: To suppress a friction loss, occurring to a slide part with a piston, to a minimum limit by providing the cylinder wall of an engine with proper temperature distribution. SOLUTION: A gas jacket 20 is situated at the lower part of a cylinder block 11. Exhaust gas in an exhaust passage 17 is fed to the gas jacket 20 through an exhaust gas feed passage 30 having an exhaust gas feed valve 31. Further, by supplying fresh air in an intake passage 16 through a fresh air feed passage 27 having a fresh air feed valve 29, feedback control of a lower cylinder wall temperature Tb to a target lower cylinder wall temperature is executed. A target lower cylinder wall temperature is set to a sufficient high temperature in a range in which an oil film of lubrication oil is insured throughout a portion extending from the intermediate part of a cylinder wall 12a to a piston bottom dead center, whereby lubrication oil viscosity is lowered and the wear loss of a slide part between a cylinder wall 12a and a piston 14 is suppressed to a minimum limit, an engine output is improved, and a fuel consumption amount is saved and a lubrication oil consumption amount is saved. |
