System for controlling the temperature of a cylinder wall in an engine

摘要

A gas jacket is provided in a lower portion of a cylinder block, so that an exhaust gas in an exhaust gas passage is supplied to the gas jacket through an exhaust gas supply passage having an exhaust gas supply valve. Fresh air in an intake passage is supplied to an intake passage through a fresh-air supply passage having a fresh-air supply valve. The temperature of a lower cylinder wall is controlled in a feedback manner to a target temperature for the lower cylinder wall. The target temperature for the lower cylinder wall is set at a sufficiently high temperature in a range in which an oil film of lubricating oil, extending from an intermediate portion of the cylinder wall to a bottom dead center of a piston, can be ensured. Therefore, the viscosity of the lubricating oil can be decreased to minimize the friction loss at slide portions of the cylinder wall and the piston, thereby providing an increase in engine output, a reduction in amount of fuel consumed and a reduction in lubricating oil consumed.