PURPOSE: To obtain hysteresis actions of a closing valve and to suppress torque variations by controlling the opening and closing of the closing valve in a branch path connecting the inlet passage section and the volute end section of a suction port in response to the amount of intake air volume.
CONSTITUTION: A helical suction port 6 is composed of a volute section B formed around a suction valve and an inlet passage section A connected at a tangent to the volute section B, and is formed in a cylinder head 3, in which a branch path 14 connecting the inlet passage section A and a volute end section C is further formed, then the branch path 14 is opened or closed by a rotary valve 18. An arm 22 is fixed to the valve shaft 20 of the rotary valve 18, and a rod 29 moved back and forth by a negative pressure diaphragm unit 30 is connected to the arm 22, then the valve 18 is controlled so as to be opened when the intake air volume exceeds the first preset value and to be closed when it becomes less than the second preset value (which is lower than the first preset value).
KATOU KENJI
MATSUSHITA SOUICHI
INOUE TOKUTA
