PURPOSE: To enable a desirable air-fuel ratio control over the whole opening area of the return opening of an air screw without being influenced by the return opening of the air screw and make the sensitivity of the air screw linearly act up to a high opening area.
CONSTITUTION: A low speed air system A is formed of a first low speed air passage 11 provided with a fixed air jet 13, and a second low speed air passage 12 provided with an air screw 21 for variably controlling the effective opening area of the air passage. The second low speed air passage 12 is provided with a normally opened switching valve V for closing the second low speed air passage 12 when negative pressure in ah intake passage 2A more on the engine side than a throttle valve 6 is the fixed value or less. The effective opening area of the second low speed air passage 12 set by the air screw 21 is made larger than the effective opening area of the first low speed air passage 11 set by the fixed air jet 13.
TOMIGUCHI SHIZUO
SATO KIYOTO
NAGAO MASANORI
