Exhaust gas recirculation system for automobile engines

Claim 1

In an exhaust gas recirculation system for an automobile engine, comprising an exhaust gas recirculation conduit extending from an exhaust manifold to an intake system of the automobile engine for providing communication of engine exhaust gases between the manifold and carburetor, a flow control valve device disposed midway of said exhaust gas recirculation conduit for controlling the communication of the exhaust gases, said valve device having an intake vacuum chamber and including a valve element normally biased into a closing position of said valve device and movable in said valve device, when actuated, into an opening position of said valve device, an intake vacuum conduit extending from an intake manifold of the automobile engine to the intake vacuum chamber of said valve device for introducing an intake vacuum into said intake vacuum chamber, and actuating diaphragm means extending in said valve device for defining said intake vacuum chamber and connected to said valve element for actuating the same in response to a vacuum which is introduced from the intake manifold, the improvement comprising means including temperature responsive bistable metal spring means, responsive to the operating conditions of the automobile engine in terms of temperatures of both the atmospheric air and the exhaust gases both, for leaving the actuating action of said diaphragm means free only in the case where the temperature of the atmospheric air is higher than a first predetermined value and where the temperature of the exhaust gases is lower than a second predetermined value and for buckling in the remaining operating conditions of the automobile engine to render the actuating action of said diaphragm means inoperative so that said valve element may be held in the closing position even in the presence of the vacuum in the intake vacuum chamber of said valve device.