Exhaust gas purification system of internal combustion engines

Abstract

An exhaust gas purification system of internal combustion engine having a branch pipe coupled to the exhaust pipe through a flange and having a first cylindrical case constituting a bypass exhaust gas passage and a second cylindrical case constituting a main exhaust gas passage, whose flow are switched by a switch-over valve by selectively connecting the exhaust pipe to the main exhaust gas passage or the bypass exhaust gas passage, and an adsorbent installed in the bypass exhaust gas passage for adsorbing unburned components of the exhaust gas. The unburned exhaust gas components are recirculated to the air intake system through an EGR pipe. In the system, an inlet of the EGR pipe is formed integrally with the branch pipe flange, thereby enabling to prevent increase in fabrication step and cost and further to facilitate maintenance. Moreover, the first cylindrical case is made displace relative to the second cylindrical case. This can prevent the deformation due to the thermal stress which could occur when they are different in temperature.