Carburetor of variable-area venturi type

Claim 1

In a carburetor for an automotive internal combustion engine having a main air passage, a throttle valve, a venturi intervening between said main air passage and said throttle valve and including a constriction and a flow regulating means to continuously reduce the effective sectional area at the venturi as said throttle valve closes, a main upstream mixture passage intervening between said venturi and said throttle valve, a main downstream mixture passage positioned downstream of said throttle valve and leading to an intake manifold of said engine, and a fuel jet opening into said venturi and communicating with a fuel supply passage, the improvement comprising an auxiliary air passage leading from said main air passage, an auxiliary primary mixture passage leading from said upstream mixture passage, said auxiliary passages meeting each other at a junction whereby air drawn from said main air passage through said auxiliary air passage is mixed with a fuel mixture drawn from said upstream mixture passage through said auxiliary primary mixture passage, an auxiliary secondary mixture passage leading from said junction to said intake manifold through said main downstream mixture passage for supplying said fuel mixture to the engine, and a flow control means interposed between said auxiliary air passage and said auxiliary secondary mixture passage and including an air flow adjusting means provided in said auxiliary air passage to control the rate of air passing through said auxiliary air passage for determining an air fuel ratio of said fuel mixture and a fuel mixture adjusting means provided in said auxiliary secondary mixture passage for controlling the rate of said fuel mixture passing therethrough.