Patent ID: 7926472

Claim:
An inlet system comprising: an intake manifold connected to a cylinder head of an engine for distributing intake air by turns among cylinders; and an EGR inlet, which projects into an inside of the intake manifold, and through which EGR gas flows to the inside of the intake manifold, wherein: the intake manifold has an insertion portion, which is formed in a generally cylindrical shape, and through which the EGR inlet is received in the inside of the intake manifold; one side of the insertion portion in an axial direction of the insertion portion opens to an outside of the intake manifold, and the other side of the insertion portion in the axial direction opens into the inside of the intake manifold; a leading end portion of the EGR inlet is inserted into the inside of the intake manifold through the insertion portion, thereby projecting to reach a predetermined target position, so that EGR gas flows out of the leading end portion to the inside of the intake manifold; and an insertion portion opening diameter is larger than an insertion maximum occupying diameter, provided that: the insertion portion opening diameter is a diameter of an opening of the one side of the insertion portion; an insertion portion opening depth is a length of the insertion portion in the axial direction between the opening of the one side of the insertion portion and a farthest circumferential position of the insertion portion from the opening of the one side, the farthest circumferential position intersecting with a direction from an axis of the insertion portion toward the predetermined target position; and the insertion maximum occupying diameter is a maximum distance between: a point included in a cutting surface of the EGR inlet on an imaginary reference plane that is perpendicular to the axis of the insertion portion, wherein a distance between the imaginary reference plane and a nearest point of the leading end portion of the EGR inlet to the imaginary reference plane in the axial direction is equal to the insertion portion opening depth; and a point included in a vertical projection view of the leading end portion of the EGR inlet that is a part of the imaginary reference plane, onto which the leading end portion of the EGR inlet is vertically projected; and the intake manifold further includes: a plurality of delivery tubes aligned in a direction from one end toward the other end of the intake manifold, wherein an upstream end of each of the plurality of delivery tubes opens into a surge tank of the engine, and a downstream end of each of the plurality of delivery tubes is connected to the cylinder head, so that the plurality of delivery tubes conducts intake air from the surge tank into the corresponding cylinders; and an introducing pipe connected to one of one end side and the other end side of the surge tank thereby to conduct intake air into the surge tank, wherein the leading end portion of the EGR inlet is disposed at the predetermined target position, where the introducing pipe is connected to the surge tank.