| 摘要 |
The body of the butterfly has a housing (12) in which an intake duct (14) is formed, and a butterfly (20) which is mounted on a rotary shaft (18) which passes through the duct and makes it possible to move the butterfly between a minimum open position and a maximum open position for which the butterfly points parallel to the axis of the duct. The side of the butterfly which points upstream exhibits, on its downstream face, a bulge, the cross section of which, in a plane orthogonal to the axis of rotation, is sufficiently small to allow the butterfly to rotate. The side of the butterfly which points downstream when open and the cross section of the duct downstream of the minimum open position of the said side pointing downstream have shapes which interact in order to give the cross section of the passage for air between them a variation law which is a function of the angle of rotation, the initial slope of which is at least four times smaller than the maximum slope of the variation law during opening. <IMAGE>
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