Exhaust pipe opening and closing apparatus

Abstract

In an automotive engine exhaust pipe having a main flow passage and a bypass flow passage, the exhaust gas flows through the bypass flow passage having an heater-provided catalyst when an engine starts. After a main catalyst reaches a catalytic activation temperature, a switching valve switches the exhaust gas to flow through the main flow passage. The main shaft is divided into a driven shaft inserted into a bearing hole and a driving shaft inserted into another bearing hole, and therefore, a total length thereof in an axial direction is shorter than a length of the main shaft without having segments. Therefore, even though the driven shaft and the driving shaft are deformed into the arch shape, a deformation amount thereof is reduced so that inner peripheries of the bearing holes are not rubbed against the shafts. Since the driving shaft is smaller in diameter than the driven shaft, even though a cross section of the driving shaft is elliptically strained, the inner periphery of the bearing hole is not rubbed against the driving shaft. As a result, since a clearance between the driving shaft and the bearing hole can be narrowed, the exhaust gas from the clearance can be prevented from leaking.