1.  Field of the Invention:
The present invention relates generally to an internal combustion engine and more particularly to an internal combustion engine having an improved burning mechanism for the air-fuel mixture for reduction of harmful auto emissions. 
2.  Description of the Prior Art:
In order to obtain better combustion and better control of exhaust from the internal combustion engine, the vitally important conditions are that the air/fuel ratio which influences combustion be maintained at a proper value and the supply of mixture to the cylinder be kept even. 
Means for separating the mixture into a rich one and a lean one, supplying the rich and lean mixtures to the cylinder and assuring perfect burning of the lean mixture by ignition of the rich mixture, thereby reducing harmful emissions in the exhaust gas have been developed.  There are two typical modes of such means:
1.  In a type, in which an auxiliary combustion chamber is installed separately from the main combustion chamber; a mixture suction valve is provided in the auxiliary combustion chamber; the rich mixture is introduced into the auxiliary combustion chamber and the lean mixture into the main combustion chamber; spark ignition of the rich mixture takes place in the auxiliary combustion chanber first; and through the flame of the rich mixture, combustion of the lean mixture subsequently takes place in the main combustion chamber. 
2.  In the other mode, in which a rich mixture supply passage is installed within the main passage leading to the main combustion chamber of the cylinder, or along this main passage; the rich mixture supply passage opens just short of the intake valve; and the rich mixture can thereby be supplied close to the spark plug in the main combustion chamber. 
In the first described mode, an additional valve has to be installed in the auxiliary combustion chamber.  Moreover, a valve-operating mechanism for the valve has to be added, which renders the construction extremely complicated.  The latter mode, though the construction is simplified, is hard to realize, because control of the rich mixture distribution becomes poor as a result of pressure pulsations in the suction lines under the effect of other cylinders in the multi-cylinder engine.