The present invention concerns a method for manufacturing an air intake duct connected to an internal combustion engine and an air intake duct manufactured according to this method.
It is known that internal combustion engines have a low-frequency acoustic component ranging from 30 Hz to 1 kHz. This acoustic component is generated by the periodic opening and closure of the valves, as well as by the resonances of the different cavities of the engine (combustion chambers, ducts, . . . ). The low-frequency acoustic component propagates and radiates at the inlet of the air supply circuit of the engine. While propagating inside the air supply ducts of the engine, the low-frequency acoustic component excites the resonance of the ducts, which generates high acoustic emissions.
Furthermore, in the case of turbocharged engines, there is a high-frequency acoustic component ranging from 1 kHz to 15 kHz. This acoustic component is generated by the turbocharger and can also propagate and radiate through the air supply ducts.
Traditionally, mouth noise refers to the acoustic component that propagates in the air supply ducts, and radiated noise refers to the acoustic component radiated by the air supply ducts, themselves.
Currently, to attenuate the noises originating from the air intake ducts, it is known to use a muffler. A muffler usually has a central tube in which air circulates, and whose wall is perforated with several orifices which puts the inside of the tube in communication with a peripheral chamber, delimited by a bell which surrounds the central tube. When stimulated by sound waves, the small volume of air contained in each orifice acts substantially as a small mass, which would be suspended from a spring constituted by the larger volume of air contained in the peripheral chamber. An attenuation of the noise is thus obtained in a spectral band located near the characteristic frequency of this <<mass-spring>> system.
However, the muffler does not allow covering the entire frequency range. Indeed, the muffler does not have a sufficient level of attenuation in the low-frequency field.
Another solution is to use a resonator. The resonator comprises a central tube having a closed bypass at a right angle. This type of resonator is very selective and works only over a very thin frequency band.
To improve the acoustic characteristics of the air intake duct, it is also known to add a porous medium that enhances the acoustic performance. In this regards, the document FR 2788833, filed by the applicant proposes a duct over a portion of which is overmolded a porous medium. Another known solution consists in welding two half-shells, produced by thermoforming, of a porous polyester medium. Mention may also be made to the document JP 2008063970 in which a porous hose is made with two half-shells in a thermos-compressed porous medium. The two half-shells are assembled by an attached clipping system. The implementation of these different techniques requires the use of an expensive tooling, such as an injection mold including a robotic system, to set up the porous medium in the mold. In addition, these techniques do not allow making a 100% porous pipe because of the technical constraints of manufacture.
Another known technique of the document EP 0665404 consists in winding a porous medium around a metallic structure. This technique requires the use of a special filament winding machine, this type of machine being very expensive.
Consequently, the present invention aims at providing a simple and inexpensive method for manufacturing an air intake duct which has a maximum surface area of porous material.
According to a general definition, the invention concerns a method for manufacturing a duct for air intake and for attenuating mouth noises and radiated noises intended to be connected to an internal combustion engine. The method comprises the steps of:
In a particularly advantageous manner, the method according to the invention allows manufacturing, in one single injection phase, an air intake duct having a maximum surface area of porous material. In other words, the method according to the invention allows manufacturing an air intake duct having a maximum surface area of porous material, with a reduced number of manufacturing steps. Thus, the invention proposes a simple and inexpensive method for manufacturing an air intake duct which has a maximum surface area of porous material.
According to a particular arrangement, the method may comprise a step (f) of forcibly removing the molded duct, by pulsed air.
According to a first embodiment, step (a) may comprise the provision of two molding cavities in which the grooves are adapted to mold a helical rib.
According to a second embodiment, step (a) comprises the provision of two molding cavities in which the grooves are adapted to mold several ribs forming a grid.
According to a particular arrangement, step (e) may comprise the injection of a thermoplastic elastomer material.
The invention also concerns a duct for air intake and for attenuating mouth noises and radiated noises intended to be connected to an internal combustion engine. The duct comprises a tubular sheet made of an air-porous material on which are overmolded at least one rib made of a thermoplastic elastomer material and two end sleeves made of a thermoplastic material, a first sleeve being intended to be connected to an internal combustion engine and a second sleeve being intended to be connected to an air intake circuit.
Thus, the duct according to the invention has a maximum surface area of porous medium, allowing attenuating the mouth noises and the radiated noises. In addition, the structure of the air intake duct according to the invention makes it light, thus allowing for a weight saving when the duct is installed in a vehicle. Furthermore, the overmolded ribs allow ensuring the resistance of the duct to the depression forces caused by the suction of air into the duct when the latter is connected to an internal combustion engine and to an air intake circuit.
According to a first embodiment, the duct may comprise a helical rib.
The helical rib may enable the duct to be flexible.
According to a second embodiment, the duct may comprise several ribs forming a grid.
According to a particular arrangement, the tubular sheet may have a porosity comprised between 200 l/m2/s and 600 l/m2/s under a pressure drop of 200 Pascals.
According to a particular arrangement, the thermoplastic material may be a thermoplastic elastomer material.
Other features and advantages of the present invention will emerge come out clearly from the detailed description hereinafter of two embodiments of the invention provided as non-limiting examples, with reference to the appended drawings in which:
The invention concerns a method for manufacturing a duct for air intake and for attenuating mouth noises and radiated noises intended to be connected to an internal combustion engine.
The method according to the invention can be implemented with a mold 1 shown in
According to a first embodiment, the grooves 4 are adapted to mold a helical rib 32.
According to a second embodiment, the grooves 4 are adapted to mold several ribs 32 forming a grid.
Furthermore, according to an embodiment not represented, each cavity 2 may also have elements allowing molding, for example, fastening systems such as support legs, and systems for hooking other elements such as cables or other ducts.
The method according to the invention also uses a core 8 adapted to cooperate with the mold 1. In a known manner, in the field of injection molding, a core allows forming a hollow portion of a part or providing for an opening. In the method according to the invention, the core 8 allows providing for the hollow section of the duct 30. The core 8 can be made of metal. The core 8 is adapted to be positioned between the cavities 2. According to the example presented herein, the core 8 has a substantially cylindrical shape with a longitudinal curvature. According to the embodiment presented herein, the core 8 is fastened to a base 81 adapted to be pressed against the two shells 1a and 1b of the mold 1 in the closed position.
The mold 1 and the core 8 allow implementing the method for manufacturing an air intake duct 30 according to the invention. In addition to a step a of providing the mold 1 and a step b of providing the core 8, the method comprises a step c of positioning on the core 8 a tubular sheet 9. It is specified that by tubular sheet 9 is meant a sheet having two joined edges to substantially form a cylinder with a circular base. The two joined edges of the sheet may be welded, glued or sewn. Referring to
According to a particular arrangement, the tubular sheet 9 may be made from a non-woven material, produced by needling, comprising polyester fibers and bi-component fibers. The bi-component fibers may comprise a core made of polyester and a skin made of copolyester.
Afterwards, the method comprises a step d of positioning the core 8 between the cavities 2 of the mold 1 in the open position. Then, as represented in
Referring to
Thus, the method according to the invention allows manufacturing the duct 30 in one single injection operation. The overmolding of the ribs 32 and the end sleeves 34 on the tubular sheet 9 allows ensuring the cohesion of the duct 30. In other words, the method according to the invention allows manufacturing the duct 30 in one single injection operation without the need to add operations of gluing, clipping or reworking of the different constituents of the duct 30.
The invention also concerns a duct 30 for air intake and for attenuating mouth noises and radiated noises intended to be connected to an internal combustion engine. The duct 30 comprises a tubular sheet 9 made of an air-porous material on which are overmolded one or several ribs 32 made of a thermoplastic elastomer material and two end sleeves 34-36 made of a thermoplastic elastomer material.
The tubular sheet 9 may have a porosity comprised between 200 l/m2/s and 600 l/m2/s. Such a porosity allows for an optimum attenuation of mouth noises and radiated noises.
According to a first embodiment, represented in
According to a second embodiment, represented in
In use condition, a first sleeve 34 is connected to an internal combustion engine and a second sleeve 36 is connected to an air intake circuit. In addition, the rib(s) 32 allow ensuring the resistance of the duct 30 to the depression caused by air suction. The tubular sheet 9, made of a porous material, allows achieving an acoustic impedance break or an adaptation, which allows avoiding the excitation of certain duct modes. Thus, the tubular sheet 9 allows reducing the mouth noises. In addition, because of the porosity of the material of the tubular sheet 9, the tubular sheet 9 allows diffusing a portion of the acoustic energy. The presence of a porous material over almost the entire periphery of the duct 30 allows distributing the radiated energy in an optimum manner, and thus reducing the radiated noises.
Of course, the invention is not limited to the embodiments described hereinabove and illustrated by the different figures, these embodiments having been provided only as examples. Modifications are still possible, in particular with regards to the constitution of the various elements or by the substitution of technical equivalents, yet without departing from the scope of the invention.
Number | Date | Country | Kind |
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17/55189 | Jun 2017 | FR | national |
This application is a National Stage of PCT Application No. PCT/FR2018/051048 filed on Apr. 25, 2018, which claims priority to French Patent Application No. 17/55189 filed on Jun. 9, 2017, the contents each of which are incorporated herein by reference thereto.
Filing Document | Filing Date | Country | Kind |
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PCT/FR2018/051048 | 4/25/2018 | WO | 00 |