Exhaust gas purification apparatus

摘要

An improvement in an exhaust gas purification apparatus wherein a detector senses the operation of a device for injecting additional intake air into the intake passage and triggers a timing unit. The timing unit produces a signal for a predetermined amount of time which holds open a control valve for introducing secondary air into the exhaust passage ahead of the catalytic converter. This structure enables the reduction of harmful components of the exhaust gas produced during a gear-change operation of the engine without greatly overheating the catalytic converter.