JPS5584837A - Air-fuel ratio correcting apparatus - Google Patents

Abstract

PURPOSE: To prevent that mixture ratio becomes excessively high at a high land and to obtain an optimal mixture ratio throughout the entire operational range of engine, by transmitting pressure in the air passage of carburetor to a portion of a compenensating-air passage in an apparatus for compensating change in air-fuel ratio of carburetor caused by the change in altitude.

CONSTITUTION: When bellows 9 is expanded at the time of high-speed operation of engine and taper needle 14 is pushed resultantly, clearance is formed between the needle 14 and orifice 13, so that air-fuel ratio compensating air 10 metered by the clearance is supplied through passage 17 to fuel system. Here, if negative pressure 3 at venturi is increased, amount of air passed through main air bleed 16 and passage 17 is increased and fuel flow is reduced by the increase in resistance, so that mixture becomes lean. In order to overcome the above diffuculties, negative pressure 3 at venturi is transmitted to an upstream side of the said compensating-air metering portion to lower pressure at the portion. With such an arrangement, amount of air 10 introduced for compensating air-fuel ratio is reduced by decreasing the pressure difference on the opposite sides of the said metering portion, so that the mixture is prevented from becoming excessively lean.

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