Secondary air flow rate control device for use in exhaust gas purifying device

Claim 1

A secondary air flow rate control arrangement for use in an exhaust gas purifying device which includes an air pump for delivering secondary air through an air passage to an exhaust gas purifying device in an exhaust system for purifying unburnt components contained in exhaust gases from an internal combustion engine, an air bleeding aperture for bleeding air to the atmosphere, and a valve means provided in said aperture for controlling the amount of secondary air fed to the exhaust gas purifying device, the secondary air flow rate control arrangement comprising: an air flow rate control means for controlling the position of said valve means; an acceleration detecting means for detecting the acceleration condition of the internal combustion engine and providing an output pressure signal in accordance with a pressure prevailing in a suction pipe of the internal combustion engine, said acceleration detecting means and said air flow rate control means forming an integral unit and being operatively connected whereby said air flow rate control means closes said valve means and said air bleeding aperture at the time of acceleration of the engine in response to an output pressure signal of said acceleration detecting means; said valve means being adapted to close the air bleeding aperture by introducing an atmospheric pressure into said air flow rate control means when said acceleration detecting means provides an output signal indicative of an accelerating condition of the internal combustion engine, said valve means bleeds the air delivered from the air pump through said air bleeding aperture by introducing a negative pressure into said air flow rate control means except at the time of acceleration of the internal combustion engine; a first chamber and a second chamber defined by a partition wall in a cylindrical hollow body; a first diaphragm provided within said first chamber, one side of said first diaphragm being in communication with a downstream side of a carburetor of the internal combustion engine; a hollow rod secured to said first diaphragm on the other side thereof; said valve means including a negative pressure valve provided at the tip of said hollow rod, said negative pressure valve being adapted to open and close said air bleeding aperture to the atmosphere; said air bleeding aperture being provided in said partition wall and communicating said second chamber with the atmosphere; said negative pressure valve being adapted to introduce atmospheric pressure into said second chamber when a negative pressure downstream of a throttle valve of the carburetor of the internal combustion engine is relatively low and to introduce a negative pressure through said hollow rod when the negative pressure downstream of the throttle valve is relatively high, a second diaphragm provided in said second chamber, oen side of said second diaphragm being adapted to receive the negative pressure introduced through said hollow rod as well as the atmospheric pressure when said negative pressure is interrupted; a rod secured to said second diaphragm on the other side thereof; and a further valve means for bleeding or interrupting air delivered from said air pump to the atmosphere.