| 摘要 |
PURPOSE:To prevent output drop upon opening of a throttle valve in a secondary side, by providing a variable venturi piston upstream of the throttle valve in a secondary side of a twin carburetor, communicating a vacuum chamber of the variable venturi piston to a venturi portion in a primary side, and permitting the communication therebetween only in a high output operation. CONSTITUTION:A variable venturi piston 13 is provided upstream of a throttle valve 11 in a secondary side which is opened when an opening angle of a throttle valve 4 in a primary side is greater than a predetermined value. A vacuum chamber 15 of the variable venturi piston 13 is communicated through a pipe 18 and a valve 19 to a vacuum port of a venturi 3 in a primary side. When the throttle valve 11 is opened, a large quantity of air tends to flow into a suction passage in the secondary side. However, no vacuum is generated in the vacuum chamber 15 because of closure of the valve 19, thereby suppressing sudden flow of the air and preventing temporary output drop. Thereafter, the valve 19 is opened in concert with an increase in engine rotational speed, and the variable venturi piston 13 is moved by the venturi vacuum in the primary side to supply a desired amount of fuel by means of a needle 12. |
