Air-fuel mixture intake apparatus for internal combustion engines

Abstract

An air-fuel mixture intake apparatus for internal combustion engines includes a two-barrel carburetor having a primary venturi for supplying an air-fuel mixture into a combustion chamber under all loads and a secondary venturi for supplying an air-fuel mixture into the combustion chamber under medium and high loads. The primary venturi is of a fixed cross section and the secondary venturi is of a variable cross section. A vacuum-operated actuator controls operation of a secondary throttle valve in response to a vacuum developed in the primary venturi and subsequently in the secondary venturi. The secondary throttle valve is interlinked with a primary throttle valve by a linkage mechanism such that the secondary throttle valve is allowed to open when the primary throttle valve opens to a predetermined degree with the maximum opening of the secondary throttle valve being variably controlled by the opening of the primary throttle valve after the latter has opened beyond the predetermined degree. A delay valve is disposed in a primary vacuum signal passageway or a common vacuum signal passageway connected to a vacuum chamber of the vacuum-operated actuator to delay an air flow through the passageway toward a vacuum pickup probe in the primary venturi. The secondary throttle valve may be mounted on a shaft displaced downstream off the geometric center of the secondary throttle valve.