Apparatus for controlling the ignition timing of an internal combustion engine

Claim 1

An internal combustion engine comprising: an air cleaner; a carburetor which includes a throttle valve connected to said air cleaner; an intake manifold located downstream of said carburetor; an engine body connected to said intake manifold; an exahust manifold for receiving the exhaust gas from the engine body; a conduit connecting said exhaust manifold with said intake manifold; a valve in said conduit for controlling the exhaust gas recirculation from said exhaust manifold to said intake manifold; a first pipe connecting said exhuast gas recirculation valve with said carburetor at a position upstream of said throttle valve when said valve is in the closed condition; a vacuum advancer connected to a distributor, said vacuum advancer comprising a casing joined at one end to said distributor body, a longitudinally movable advance shaft extending from said distributor body into said casing, said advance shaft being sealingly connected at a position spaced from its outer end to a first diaphragm which extends across said casing, the outer end portion of said advance shaft passing slidably through a second diaphragm which extends across said casing and is spaced from said first diaphragm and defines a first chamber at the end of said casing remote from said distributor, said advance shaft having an enlargement on the side of said second diaphragm remove from said first diaphragm, which enlargement provides an abutment with said second diaphragm, a cup member sealed to said second diaphragm enclosing said enlargement and allowing displacement of said enlargement away from said second diaphragm, a first spring acting on said second diaphragm so as to urge it towards said distributor, a second spring located between said first and second diaphragms so as to urge said second diaphragm towards abutment with said enlargement on said advance shaft, a bellows member sealingly connecting said first diaphragm with said casing so as to define a second chamber in said casing between said bellows member and said first diaphragm, and a vent hole in said casing between said bellows member and said second diaphragm; a second pipe connecting said first chamber of said vacuum advancer with said carburetor at a position which is always effectively downstream of said throttle valve; a branch pipe connecting said first pipe with said second chamber in said vacuum advancer, and; a vacuum transmitting valve device in said branch pipe, comprising a hollow valve body having first and second ports communicating with said branch pipe on said carburetor side and vacuum advancer side, respectively, a partition extending across said valve body between said ports, said partition having a restricted orifice which allows restricted transmission of a vacuum from said first port to said second port and a check valve which is arranged so as to open and by-pass said restricted orifice when the gas pressure at said first port is greater than the gas pressure at said second port; said engine being arranged so that when said throttle valve is opened said first pipe is exposed to the vacuum in said carburetor, which actuates said valve in said recirculation conduit to provide exhaust gas recirculation to said intake manifold, the vacuum in said first pipe being transmitted at a restricted rate controlled by said restricted orifice to said second chamber in said vacuum advancer, whereby the displacement of said first diaphragm against the action of said second spring, and hence the vacuum advance of the ignition timing, is delayed.