An intake duct for an internal combustion engine includes a plurality of segments coupled together into a tubular shape. The segments include at least a first segment and a second segment. The first segment is formed from a material harder than the second segment. The first segment includes a groove that extends in the extending direction in a portion coupled to the second segment and projections that project from one of two inner surfaces of the groove. The second segment is formed from a material that allows for elastic deformation. The second segment includes a rib. The rib extends in the extending direction and has a projection width that is less than the opening width of the groove. The rib is fitted into the groove so that the projections locally compress the rib in the width direction of the groove.

An inlet duct includes a tubular main body formed by a compression-molded fibrous molded body. The main body includes an alternate layout region in which an air-impermeable high-compression portion and an air-permeable low-compression portion hat is compression-molded at a lower compressibility than a compressibility of the high-compression portion are alternately laid out in an axial direction of the main body. The alternate layout region is configured such that an arbitrary pair of points at an equal distance in the axial direction to a central position in an upstream region and a downstream region of the alternate layout region include only points that are both located in the low-compression portions and points one of which is located in the low-compression portion and the other one of which is located in the high-compression portion.

An intake duct for an internal combustion engine includes a plurality of segments coupled together into a tubular shape. The segments include at least a first segment and a second segment. The first segment is formed from a material harder than the second segment. The first segment includes a groove that extends in the extending direction in a portion coupled to the second segment and projections that project from one of two inner surfaces of the groove. The second segment is formed from a material that allows for elastic deformation. The second segment includes a rib. The rib extends in the extending direction and has a projection width that is less than the opening width of the groove. The rib is fitted into the groove so that the projections locally compress the rib in the width direction of the groove.

An inlet duct includes a tubular main body formed by a compression-molded fibrous molded body. The main body includes an alternate layout region in which an air-impermeable high-compression portion and an air-permeable low-compression portion hat is compression-molded at a lower compressibility than a compressibility of the high-compression portion are alternately laid out in an axial direction of the main body. The alternate layout region is configured such that an arbitrary pair of points at an equal distance in the axial direction to a central position in an upstream region and a downstream region of the alternate layout region include only points that are both located in the low-compression portions and points one of which is located in the low-compression portion and the other one of which is located in the high-compression portion.

An air intake device includes: an air intake port; and a valve that includes an elastically deformable seal portion disposed in Ha side end portion, and switches between flow paths of the air intake port by being turned around a turning shaft, wherein the side end portion of the valve is provided with a curved side end portion that extends from one end portion side to the other end portion side along an extension direction of the turning shaft while being curved.

In this air intake apparatus, a plurality of respective air intake ports include sealing surfaces that include inner wall surfaces with which valve bodies come into contact at the closed positions of the valve bodies, and the rotation angles of valve bodies located on a side relatively close to a drive source from their open positions to their closed positions are larger than the rotation angles of valve bodies located on a side relatively opposite to the drive source when a plurality of valve bodies are rotated from their open positions to their closed positions.

The present air intake control valve includes a valve body and a seal portion being elastically deformable to seal between an inner wall surface of an air intake port and the valve body. The seal portion is formed in a bending configuration including a first hinge portion and a second hinge portion each serving as a supporting point upon elastic deformation of the seal portion. One of the first hinge portion and the second hinge portion is arranged at an upstream side of the air intake port and the other of the first hinge portion and the second hinge portion is arranged at a downstream side in a state where the valve body is at a closed position.

An air intake device includes: an air intake port; and a valve that includes an elastically deformable seal portion disposed in a side end portion, and switches between flow paths of the air intake port by being turned around a turning shaft, wherein the side end portion of the valve is provided with a curved side end portion that extends from one end portion side to the other end portion side along an extension direction of the turning shaft while being curved.