Engine air:fuel ratio control by exhaust oxygen sensor - actuating solenoid valve in secondary air duct of carburettor

摘要

The air/fuel ratio control is intended for an engine with carburettor containing a venturi (30) with variable free flow area and a main fuel jet (32), and a catalytic converter (2) to purify the exhaust gas. The carburettor comprises a secondary air duct (17) leading to a point upstream of the jet (32), and there is an oxygen sensor (5) in one of the engine exhaust lines (1) and upstream of the converter. A solenoid-operated valve (8) is arranged in the duct (17) which, in response to the sensor signal, adjusts the secondary air flow such that the air/fuel ratio remains constant.