Abstract: An air intake system for an internal combustion engine comprises an air pipe having at least one communication aperture in a pipe wall and opposite ends, and a resonator formed substantially coaxially about and spaced from an outer circumference of the air pipe and disposed substantially over the entire length of the air pipe. The resonator is connected at the opposite ends to the air pipe. The air intake system further comprises a flexible inner bellows formed at a portion of the air pipe and a flexible outer bellows formed at a portion of the resonator substantially overlying the inner bellows. The material for molding the resonator is changed at an intermediate portion in a longitudinal direction of the resonator from a hard resin to a soft resin, with at least the outer bellows being formed from a soft resin.

Abstract: A process for producing a muffler hose having opposite ends, an intermediate portion having a noise-reducing communication hole, and a noise-reducing expansion chamber. The process includes the steps of fitting a protector at the opposite ends of the hose, and disposing the hose and the protectors in a separable blow-molding mold having a jaw; extruding a tubular parison around the hose and the protectors, closing the blow-molding mold, reducing the parison diametrically at two axially-apart positions by the jaw, clamping the parison around the hose at two axially-opposite positions of the hose, the two axially-opposite positions being intervened by the communication hole, and placing the opposite ends of the parison around the protectors; and blowing air into the parison through one of the protectors, and the communication hole of the hose to expand the parison, thereby forming the expansion chamber.

Abstract: A muffler includes a box-shaped member formed so as to define an inner space therein, and including at least two communication ports. An inner pipe is accommodated in the box shaped member, and includes a fluid passage formed therein. An end of the inner pipe is installed to one of the communication ports, and another end thereof is installed to another one of the communication ports. A separation is provided in the inner pipe which communicates the fluid passage with the inner space. The inner pipe can include a first tubular member, a part thereof formed integrally with the body by injection molding, and a second tubular member having an end. The end is disposed in the inner space so as to face an end of the first tubular member in spaced relation so as to form the separation. A guide and a fixing member can be formed on an inner wall surface of the body so as to connect the inner pipe with the communication port.