Catalytic converter for exhaust gas purification

Abstract

A catalytic converter is adapted to retard spark timing to increase the temperature of the converter catalyst when a temperature sensor within the converter senses low exhaust temperature. A vacuum advance mechanism is responsive to intake manifold vacuum conducted thereto via an intake vacuum passageway to advance spark timing for the engine. The temperature of exhaust gas from a catalytic converter for exhaust emissions is sensed. When the sensed temperature of the exhaust is below a predetermined value, a comparator outputs an actuation signal which is used to cause a solenoid valve to open an air passageway to admit atmospheric air into the vacuum advance mechanism so that spark timing will be retarded, thereby increasing the temperature of the catalyst. At least one of a transmission neutral switch, a throttle switch and a clutch switch connected in series may be provided in the circuit between the comparator and the solenoid valve for returning spark timing to a standard value when any of the switches is open. At least one of the intake vacuum passageway and the air passageways may be provided with a member for restricting the internal cross-sectional area of the associated passageway to obtain the desired spark timing relationship.