Control system for promoting catalytic removal of noxious components from exhaust gas of internal combustion engine

In an internal combustion engine provided with a carburetor having an air bleed passage opening into a fuel discharge passage and an exhaust system having a catalytic converter containing therein a catalyst which catalyzes both the reduction of oxides of nitrogen and the oxidation of carbon monoxide and hydrocarbons, a system for promoting the catalytic conversion reactions in the catalytic converter comprising:

• means for defining an auxiliary air admitting passage connected to the fuel discharge passage of the carburetor;
• sensing means for sensing the concentration of a particular component of the exhaust gas in the exhaust system at a section upstream of the catalytic converter and for producing an electrical signal representing the concentration of said component sensed, said concentration depending upon the air/fuel ratio of an air/fuel mixture fed to the engine;
• a control circuit having means for continuously producing electrical pulses at a frequency between 5 and 100 Hz, the ratio of the duration of each pulse to the time interval between said each pulse and a next sequential pulse varying or dependance upon a magnitude of a deviation of said air/fuel ratio, corresponding to said electrical signal, from a predetermined ratio which equals at least to a stoichiometric air/fuel ratio;
• and an electromagnetic valve receptive of said pulses and effective to allow admission of auxiliary air to said auxiliary air admitting passage only when each of said pulses is applied thereto, so that the fuel discharge rate to the induction passage of the carburetor varies in response to deviations of said air/fuel ratio from said predetermined ratio.

In an internal combustion engine provided with a carburetor of the fixed venturi type having an air bleed passage opening into a fuel discharge passage and an exhaust system having a catalytic converter containing therein a catalyst which catalyzes both the reduction of oxides of nitrogen and the oxidation of carbon monoxide and hydrocarbons, a system for promoting the catalytic conversion reactions in the catalytic converter comprising:

• means for defining an auxiliary air admitting passage connected to the fuel discharge passage of the carburetor;
• sensing means for sensing the concentration of a particular component of the exhaust gas in the exhaust system at a section upstream of the catalytic converter and for producing an electrical signal representing the concentration sensed, said concentration depending upon the air/fuel ratio of an air/fuel mixture fed to the engine;
• a control circuit having means for continuously producing electrical pulses at a frequency between 5 and 100 Hz, the ratio of the duration of each pulse to the time interval between said each pulse and a next sequential pulse varying in dependance upon a magnitude of a deviation of said air/fuel ratio, corresponding to said electrical signal, from a predetermined ratio which equals at least to a stoichiometric air/fuel ratio;
• and an electromagnetic valve receptive of said pulses and effective to allow admission of auxiliary air to said auxiliary air admitting passage only when each of said pulses is applied thereto, so that the fuel discharge rate to the induction passage of the carburetor varies in response to deviations of said air/fuel ratio from said predetermined ratio.