An air intake device for an internal combustion engine of the present invention includes a water discharge passage extending from a bottom surface of a control valve housing part recessed in a housing passage forming part of an air intake passage to an air intake port. The water discharge passage is formed independently from the air intake passage, and includes: a water collection groove recessed in the bottom surface; a water discharge hole formed penetrating a cover of a valve control housing; and a water discharge hole penetrating a flange part of an insert inserted into the air intake port. The downstream end of the water discharge hole is connected to a space defined between an air intake port inner wall surface and an insert cylindrical part.

The disclosure relates to an air inlet system for an internal combustion engine. The air inlet system has a cylinder head having an inlet channel for introducing inlet air into a combustion chamber of the internal combustion engine. The air inlet system has an air supply pipe piece, which is connected to the cylinder head and which at least partially forms an air supply channel, which opens in the inlet channel. The air inlet system additionally has thermal insulation, which is arranged in the air supply channel in order to reduce a heat transfer to the inlet air which flows in the air supply channel.

The present invention provides a die assembly for molding a resin-made insert having a sleeve that is inserted into an intake port of an internal combustion engine. Each sleeve has one inlet and two outlets. The die assembly includes an inner die and an outer die. The inner die includes an inlet side part and an outlet side part. The inlet side part and the outlet side part mold an inner peripheral surface of the sleeve in an assembled state, and are removed in mutually opposite directions. By means of this assembly, a sleeve having a complicated structure and shape can be molded easily.