Fuel vapor control system for internal-combustion engine

Abstract

A forward flow region in which forward intake air currents are produced and a reverse flow region in which reverse intake air currents are produced are formed in the throttle bore of a throttle body,included in an internal-combustion engine, and the boundary between those regions extends below a throttle valve,. A fuel vapor control system for an internal-combustion engine has a purge tube,joined to the throttle body,to supply fuel vapor into the throttle body,and is provided with an opening,which acts as a purge port. The opening,is positioned at a distance from the inner surface,of the throttle body,defining a throttle bore on the boundary between the forward intake air currents and the reverse intake air currents. Fuel vapor jetted through the opening,of the purge tube,into the throttle bore flows toward an intake manifold,, diffusing into both the forward intake air currents and the reverse intake air currents from the boundary between the intake air currents. Accordingly, the fuel vapor is distributed evenly through the intake manifold,to the cylinders, so that increase in the difference in air-fuel ratio between the cylinders can be suppressed. The purge port can relatively easily be formed, because the purge tube,provided with the purge port is fitted closely in a bore formed in the throttle body