Abstract: An air-fuel ratio control device characterized by the fact that an electromagnetic valve which controls the air bleed quantities for both high- and low-speed fuel systems simultaneously has a pin inserted in a valve disc so as to prevent the rotation of the valve disc but allow it to move axially for open-close operation, so that the valve disc and the seat always contact at the same contacting portion and maintain a perfect seal therebetween. This enables an accurate control of the air bleed quantitiy and therefore of the air-fuel ratio.

Abstract: An improved exhaust gas control apparatus, which utilizes a 3-way catalyst for reducing the contents of harmful components in exhaust gas, incorporates a diaphragm type air pump for supplying secondary air, upstream of the catalyst, to the exhaust gas. A chamber, which is formed on one side of the diaphragm in the air pump, is communicated through an electromagnetic changeover valve with the upstream side of the catalyst.

Abstract: An air-fuel ratio controller for use in an internal combustion engine, of a type having an exhaust gas sensor disposed in the exhaust passage, a control circuit and a solenoid valve having a valve seat in which passages open leading to the air bleeds of the slow and main systems of the carburetor, the controller being adapted to actuate a valve of the solenoid valve, in accordance with a signal derived from the exhaust gas sensor, into and out of contact with the valve seat, so as to simultaneously control the flow rates of bleed air in the air bleeds of the slow and main systems. A recess is formed in the cooperating surface of the valve seat or the valve, at a position between the openings of the passages in the valve seat. This recess communicates with a chamber which in turn communicates with the air inlet.