Internal combustion engine

摘要

A carburetor for a multi-cylinder internal combustion engine which has for each cylinder a main combustion chamber defined above the piston in the cylinder and a sub-combustion chamber defined above the main combustion chamber and communicating with the latter through a torch nozzle. The carburetor has a main intake passage and a sub-intake passage for supplying a comparatively lean mixture and a comparatively rich mixture to the main and sub-combustion chambers respectively. The carburetor has a single throttle valve shaft extending across the main and sub-intake passages with a main throttle valve and a sub-throttle valve mounted on the valve shaft and disposed in the main and sub-intake passages respectively. The main and sub-throttle valves are attached to the single throttle valve shaft at the same attaching angle and have respective parallel surfaces and outer peripheral edge surface. The angle formed between the outer peripheral edge surface and the parallel surfaces of the main throttle valve and the angle formed between the outer peripheral edge surface and the parallel surfaces of the sub-throttle valve are different from one another so that the ratio of the open areas of the main and sub-intake passages is not constant as the throttle shaft is operated. Thereby, the ratio of weight of air introduced into the sub-combustion chamber to the weight of air introduced into the main combustion chamber can be controlled in accordance with the load condition of the engine.