Air-pollution preventive system for motor vehicles

Claim 1

An air pollution preventive system for a motor vehicle having an internal combustion engine with a carburetor having a throttle valve comprising: a recirculation passage communicating at one end with an exhaust manifold of said engine and at the other with an intake manifold of said engine; a recirculation control valve mounted in said recirculation passage for opening and closing same comprising a casing communicating on one side with the exhaust manifold and on the other side with the intake manifold, a valve seat integral with said casing, a valve head movably mounted in said casing to seat and unseat on said valve seat, a valve stem connected integrally with said valve head with its leading end extending outwardly through said casing, and a compression spring biasing said valve stem to a position in which said valve head is seated on said valve seat; cam means pivotal in response to angular movement of said throttle valve of said carburetor for actuating said control valve to open said recirculation passage when said throttle valveis in a predetermined range of angular positions comprising a pivotal and axially movable cam shaft, a double-action cam fixedly mounted on said cam shaft and having on its periphery a protruded abutment and a radially reduced section merging with said abutment through a conical section, said abutment being so shaped and sized as to contact and depress said valve stem into a position in which said valve head is unseated from said valve seat when said cam is both axially moved by said cam shaft to a position in which the abutment is in line with said valve stem and when said cam is angularly displaced to an angle corresponding to the angular position of the throttle valve within said predetermined range thereby to bring its abutment in abutting engagement with said leading end of said valve stem, and means including an arm fixedly connected with said throttle valve and a rod connecting said cam with said arm for effecting angular displacement of said cam in response to movement of said throttle valve; and means for putting said cam means in an operative condition when vacuum in said intake manifold is under a predetermined level comprising a hollow cylinder fixed relative to said casing and into which said cam shaft is axially slidably inserted to define therebetween a chamber, means communicating said chamber with the intake manifold to enable the vacuum therein to force said cam shaft toward a position in which said reduced section is in line with said valve stem, and a compression spring mounted in said chamber to force said cam shaft against said vacuum drawn into said chamber toward a position in which said abutment is in line with said valve stem whereby as the vacuum in the intake manifold decreases to said predetermined level the last-named compression spring overpowers the thus decreased vacuum to axially move said cam shaft to a position in which said abutment is in line with said valve stem;whereby engine exhaust gases are recirculated through the engine to reduce the concentration of nitrogen oxides in the engine exhaust gases in accordance with varying driving conditions of said motor vehicle.