Feedback type variable venturi carburetor

Claim 1

A feedback type variable venturi carburetor for an engine comprising an intake manifold and a main fuel jet communicating therewith, a variable venturi including a movable piston movably extending into said intake manifold cooperating with said main fuel jet. means defining an air bleed passage opening into said main fuel jet, said piston of said variable venturi constituting means for controlling a negative pressure to a substantially constant value defining a vacuum source, an exhaust manifold communicating downstream of said engine, an exhaust gas sensor disposed in said exhaust manifold, control valve means for varying an amount of main air bleed through said air bleed passage and disposed at a point along said air bleed passage, a three-way solenoid valve means operatively connected to said control valve means, a control circuit means operatively connected to said exhaust gas sensor for controlling said three-way solenoid valve means to regulate said control valve means and the amount of the main air bleed, said three-way solenoid valve means for performing an ON-OFF operation in accordance with a signal from said exhaust gas sensor via said control circuit means and having a first passage communicating with said vacuum source, a second passage opening to the atmosphere, a third passage communicating with said control valve means and constituting the operative connection thereto, and a movable iron core means operatively controlled by said control circuit means for executing a valve operation, one end of said movable iron core means operatively openingly and closingly respectively cooperating with said second passage and another end of said iron core means operatively closingly and openingly respectively cooperating with said first passage, respectively, and means for biasing said iron core means to close said first passage at all times.