Rotary-body type throttle valve for spark ignition internal combustion engine

摘要

A rotary-body type throttle valve for a spark ignition internal combustion engine is disclosed. The valve includes a valve casing, an intake passage formed with a rotary-body recess portion, a valve element having a rotary-body shape which is rotatably fitted into the rotary-body recess portion of the valve casing, and a communication passage that permits an upstream intake passage and a downstream intake passage to communicate with each other is formed in the valve element. The upstream intake passage and the downstream intake passage sandwich the rotary-body recess portion of the valve casing. A through hole which is directed from the communication passage of the valve element in a direction intersecting a central axis of the communication passage and reaches only one of rotary outer surfaces of the valve element is formed in the valve element. This arrangement results in a reduced flow resistance by decreasing the size and number of vortices generated during partially opened states of the valve element.