Method and device for control of internal combustion engine variable

Abstract

An air-fuel mixture intake system of an internal combustion engine includes a helical passage and a straight passage for conducting the air-fuel mixture to an intake port of the engine, the straight passage being selectively closed by a straight passage switchover control valve. A control device for operating the straight passage switchover control valve comprises a valve drive system including a diaphragm adapted to be actuated by intake vacuum of the engine, a vacuum switching valve for selectively either connecting the diaphragm to the intake manifold or releasing the diaphragm to the atmosphere, and a one way valve provided between the vacuum switching valve and the intake manifold so as to hold vacuum on one side thereof toward the diaphragm. Also included is a control system which switches the vacuum switch valve so as to release the diaphragm to the atmosphere when throttle opening increases beyond a certain determinate value thereby to open the straight passage, and which switches the vacuum switching valve so as to connect the diaphragm to the intake manifold when the level of intake vacuum present in the intake manifold rises above a certain determinate level thereby to close the straight passage.