WO2015092488A1

WO2015092488A1 - Modular sound absorber

Info

Publication number: WO2015092488A1
Application number: PCT/IB2013/061149
Authority: WO
Inventors: Banu Bicici
Original assignee: TEKLAS KAUCUK SANAYI VE TICARET AS
Current assignee: TEKLAS KAUCUK SANAYI VE TICARET AS
Priority date: 2013-12-19
Filing date: 2013-12-19
Publication date: 2015-06-25
Anticipated expiration: 2016-06-19

Abstract

The present invention relates to a sound absorber that is used for attenuating the noise generated in the air conduits. The present invention particularly relates to a resonator having compact size and low resistance that is used in vehicles for the aim of attenuating the noise in air intake conduits of the internal combustion engines.

Description

MODULAR SOUND ABSORBER

Related Technical Field

The present invention relates to a sound absorber that is used for attenuating the noise generated in the air conduits.

The present invention particularly relates to a resonator having compact size and low back pressure that is used in vehicles for the aim of attenuating the noise in air intake conduits of the internal combustion engines.

Prior Art

In internal combustion engines, sound absorbers are widely used on intake conduits in order to minimize the noise generated while the air received from outside by suction is delivered to the engine.

Although there are many different types of sound absorbers, the perforated pipe resonators are widely used as this type of resonators are effective sound absorbers, and can be easily integrated on the air intake conduits and causes relatively low pressure losses. This type of sound absorbers, of which one example is explained in the Patent No. US5839405, comprises a perforated inner pipe, a casing fitted on the pipe and resonance chambers formed by the walls in the area therebetween. Each chamber communicates with the inner pipe by means of the openings formed on the inner pipe. Thus, each resonance chamber and the openings opening to these chambers together form a Helmholtz resonator and attenuate the noise within a certain frequency range.

One method for producing this type of perforated pipe resonator is to provide the separating walls that form the chambers on the inner pipe and to join the casing with the inner pipe by fitting it over said walls. This method, although practical with respect to assembly, is costly and risky in terms of product performance. The most important point to be paid attention in order for this type of resonator to provide the required performance is that the chambers should be isolated from each other so that there is no passage between the chambers.

In Figure 1, a state of the art sound absorber of this type is shown. As shown in Figure 1-b, the chambers (100') are formed by means of the walls (102') on the perforated inner pipe (10 ). The casing (103') that is fitted over at the top forms the outer borders of the chambers (100'). In the case a sound absorber of this type is produced from metal, it can be operated with precise dimensional tolerances and the desired leak-proofing can be provided between the walls and the casing. However, metal sound absorbers are not preferred due to their weights within the framework of the regulations relating to decrease of fuel consumption and are substituted with plastic equivalents. During production of such a sound absorber from plastic, it is very probable to observe distortions either in the walls or the casing. These distortions can cause various regional gaps (105') as shown in Figure 1 - c between the walls (102') and the casing (103') when the casing (103') and the inner pipe (10 ) are mounted to one another.

In Figure 2, the performance loss of a sound absorber of this type is shown. The curve shown by A shows the noise level attenuated by a suitably manufactured sound absorber while the curve B shows the performance of a model of the same sound absorber having the above mentioned regional gaps (105'). As seen, the noise level attenuated by the sound absorber decreases by a critical amount and the product becomes entirely dysfunctional. Therefore, in this embodiment, it is critical that the surfaces at the region where the walls join with the casing should be connected tightly to one another so that communication between the chambers is not possible. On the other hand, clearance is required between the walls and the casing in order to mount the casing on the component. These two conflicting requirements necessitate the parts to be manufactured within a very narrow interval of tolerance and with high precision. This considerably increases the production costs of the individual components. As an alternative, the walls can be formed on the casing instead of the inner pipe as disclosed in Patent No. US5979598. However, in this case the same problem is still encountered between the inner surfaces of the walls and the inner pipe.

The use of 0-ring is suggested in relation to this problem in Patent No. US6983820. In this design wherein the walls are integrated with the perforated inner pipe, it is disclosed that a circular 0-ring is placed between the wall and the casing on the surface where these two are joined. However, this is not a solution that can be applied effectively in practice since the 0- rings, that are fitted over the outer periphery of the walls having a wall thickness of approximately between 1.5 - 2.5 mm, have difficulty to stay in place during the assembly of the casing. This results in communication between the chambers through the wall peripheries and causes the product to lose its functionality.

On the other hand, in each of these methods, the production of the component whereto the walls are integrated also creates problems. For example, in the arrangement wherein the walls are integrated to the inner pipe, an injection mold that produces the inner pipe with the holes and walls thereon should have a multitude of movable core systems. This requires the production of an extremely complicated mold. Additionally, in such systems, a new mold has to be made for each alternative sound absorber. This creates a great disadvantage in terms of both production flexibility and costs.

Another important point in sound absorber design is that the construction should be adaptable for alternative sound absorber designs. Since the frequency range in which a Helmholtz chamber is active correlates with the volume of the chamber, it is possible to obtain different sound absorbers optimized for different frequency ranges by making modifications only in the chamber volumes. This is a feature that provides important simplifications in the production line by allowing the production of a multitude of different sound absorbers with the same mold and production equipments.

In the state of the art, a great variety of modular sound absorber concepts are known so that the construction is feasible for alternative absorbers. An arrangement again described in Patent No. US6983820 relates to a modular sound absorber that is formed from cylindrical units that are joined end to end. Each unit is a monoblock cylindrical structure having an inner pipe, an outer pipe and a resonance chamber therebetween, and these units form the sound absorber when connected end to end. A gap remaining between the inner pipes at the places where the units are joined together form the opening through which the inner pipe communicates with the resonance chamber. The sound absorber is adjusted for different frequency ranges by changing the distance between the two units. This arrangement eliminates the isolation problem between the walls and the casing. However, the distances between the units, which can slide over one another, should be adjusted in a precise manner and be kept that way during the life of the product. Under the bonnet where high temperature differences and mechanical vibrations are encountered, it is highly probable that these distances change during the product life and hence changing the frequency range whereat the sound absorber is effective. Additionally, by changing the distance between the two units for adjustment to different frequency ranges, the volume of the resonance chamber and the size of the opening that opens into the chamber are also changed. This limits the frequency bands that can be obtained.

In Patent Application No. WO2007101412, another modular sound absorber is described. The units, where each one can be designed differently, are joined to form the inner pipe module having perforated configuration with the walls integrated thereon. This structure is inserted into a housing to form the end product of the sound absorber. Although this arrangement presents a very flexible sound absorber that can be adjusted for alternative frequency ranges, the resonance chambers are again formed by the casing fitted on the outside. Therefore, the design does not provide a solution for the production difficulty arising from the requirement of leak-proofing between the wall and the casing.

In order to eliminate the above-mentioned disadvantages, the present invention discloses a sound absorber which is easy to produce and cost effective, which has a modular structure that can be easily adapted for different frequency bands, and which can be safely isolated against the leakage risk between the resonance chambers of which each is formed from independent units. Definition of the Figures

The present invention is described in detail by referring to the attached figures. In the figures:

Figure 1 shows a state of the art type of perforated pipe sound absorber.

Figure 2 shows the noise attenuation capabilities of the gapped and gapless versions of a model sound absorber of this type.

Figure 3 is the isometric exploded view of the sound absorber of the present invention. Figure 4 is a cross-sectional view of the sound absorber of the present invention.

Figure 5 shows an alternative arrangement of the sound absorber of the present invention. Figure 6 shows an alternative arrangement of the sound absorber of the present invention. Figure 7 shows an example of adapting the sound absorber of the present invention for alternative embodiments.

The elements illustrated in the figures are numbered as follows:

\ 1 i Sound Absorber

\ 10 I Inner pipe

11 i Perforation holes

18 i Inlet end

19 I Outlet end

100 ; Outer surface of the inner pipe

\ 20 i Cylindrical unit

21 i Resonance chamber

27 I Unit outer wall

28 i Unit side walls

280 Mnner surface of the wall 30 i Sealing element

\ 40, 40' i Front fixing element

41 i Lug

400 i Abutment surface of the front fixing element

401 i Outer surface of front fixing element

\ 50, 50' 1 Rear fixing element

51' i Open end of the rear fixing element

52' i Closed end of the rear fixing element

500 i Abutment surface of the rear fixing element

501 ; Inner surface of the rear fixing element

502 i Frontal surface of the rear fixing element

Detailed Description of the Invention

The sound absorber (1) of the present invention shown in exploded view in Figure 3 is essentially composed of a perforated inner pipe (10) and cylindrical units (20) that are fitted thereover and that form the resonance chambers (21). The sound absorber (1) furthermore comprises a front fixing element (40) and a rear fixing element (50) for securing the position of the units (20) and one or more than one sealing elements (30) in order to guarantee the isolation between the chambers (21).

As shown in the cross-sectional view in Figure 4, in the sound absorber (1) of the present invention, the inner pipe (10) has an inlet end (18) and an outlet end (19) to be connected to the other elements in the flow circuit. The perforated structure of the inner pipe (10) is preferably realized by holes (11) with circular cross-sections; however, openings in cut-out or slit form can also be used as an alternative to circular holes (11) or together with these holes (11).

The units (20) are shaped as hollow shells and composed of two side walls (28) and an outer wall (27) that connects these. The inner surface (280) of the side walls (28) is seated peripherally on the outer surface (100) of the inner pipe (10). The side and outer walls (27, 28) of each unit (20) form each resonance chamber (21) together with the outer surface (100) of the inner pipe (10).

Preferably a sealing element (30) is used between the units (20) that form the resonance chambers (21) in order to guarantee leak-proofing between the chambers (21). The sealing element (30) is ring shaped and is fitted over the inner pipe (10). When placed one after the other and moved near one another, two units (20) provide complete isolation by pressing the sealing element (30) therebetween.

The fixing elements (40, 50) are used for fixing the units (20) on the inner pipe (10) at the desired axial position. Of these elements (40, 50), the front fixing element (40) is positioned so as to remain in front of the first chamber (21) in the flow direction and has an abutment surface (40) that supports the side wall (28) of this first chamber (21). The rear fixing element (50) is positioned so as to remain behind the last chamber (21) in the flow direction and has an abutment surface (500) that supports the side wall (28) of the last chamber (21).

The front fixing element (40) can be produced in alternative shapes provided that it has the above-mentioned abutment surface (400); however, it is preferably in disc shape. In the preferred embodiment of the present invention, the front fixing element (40) is integrated with the inner pipe (10) as shown in Figures 3 and 4. However, the front fixing element (40') can also be an independent element as shown in Figure 5 and used by being fitted over the inner pipe (10) during assembly. The independent front fixing element (40') can be fixed on the inner pipe (10) by operations like rotation welding or adhesion, or as shown in Figure 5, can also be positioned by bearing against the lugs (41) formed on the inner pipe (10). Said lugs (41) are preferably protrusions formed on the inner pipe (10) during production and have a planar surface (410) against which the fixing element (40') bears. In this embodiment, at least two, preferably three lugs (41) that are placed on the periphery of the inner pipe (10) at 1205 intervals are used. The rear fixing element (50) can be produced in alternative shapes provided that it has the mentioned abutment surface (500); however, it is preferably in disc shape as shown in Figures 3 and 4. After mounting the units and sealing elements (20, 30) so as to bear against the front fixing element (40), as the last phase of the assembly, the rear fixing element (50) is fitted over the inner pipe (10) and fixed on the inner pipe (10) by operations like rotation welding or adhesion.

Alternatively, the rear fixing element (50') can also be shaped as a shell. This embodiment shown in Figure 6, simplifies the production process by enabling the rear fixing element (50') to be joined with the front fixing element (40). In this embodiment, the rear fixing element (50') is shaped as a cylindrical shell with one end (5 ) entirely open, the other end (52') closed except the central opening enabling the rear fixing element (50') to be fitted over the inner pipe (10) as in Figure 6-a. When the rear fixing element (50') is fitted over the inner pipe and the units (10, 20) from the open end (5 ) thereof, the inner surface (500) of the closed end (52') forms the abutment surface (500) that supports the side wall (28) of the last chamber (21) by remaining behind it. In this position, the rear fixing element (50') is fixed to the inner pipe (10) by joining the open end (51') thereof with the front fixing element (40) and the assembly is completed. The shell-shaped rear fixing element (50') can be joined with the front fixing element (40) by various different methods known in the technique like plastic welding, adhesion, screwing, snap fitting, clipping, etc. In the preferred embodiment of the present invention, this method is plastic welding. Preferably, the rear fixing element (50') is arranged so as to be fitted over the front fixing element (40) as shown in Figure 6-b and the inner surface (501) thereof is joined with the outer surface (401) of the front fixing element (40). Alternatively, the rear fixing element (50') can be arranged to be shorter as shown in Figure 6-c and the frontal surface (502) can be joined with the abutment surface (400) of the front fixing element (40). Rotation welding can be applied for the arrangement in Figure 6-b and butt welding for the arrangement in 6-c.

In order to enable a convenient assembly, the inner diameter (d20) of the unit (20) can be selected to be greater than the outer diameter (dlO) of the inner pipe (10). On the surfaces (280, 100) where the units (20) and the inner pipe (10) are seated onto one another, the clearance required for assembly or the undesired gaps occurring as a result of the manufacturing processes of each component are closed safely by means of the sealing elements (30) used therebetween and passage of air between the adjacent chambers (21) is prevented under any circumstances. The diameter (d30) of the sealing element (30) is preferably selected to be smaller than the diameter (dlO) of the inner pipe (10) in order to compensate the tolerance differences and the warpage of the inner pipe (10).

The most important advantage of this modular design is to easily obtain alternative sound absorbers that are effective within different frequency ranges without changing the perforated pipe (10) which requires complicated and expensive mold designs. Such a model embodiment is shown in Figure 7. In Figure 7-a, a sound absorber is obtained, having three chambers with the volume of each chamber (vl) being equal and a certain number of holes (nl) bored to each chamber by placing three units (ul) of the same type on a certain inner pipe (10). This sound absorber provides the optimum result for a certain frequency range. In Figure 7-b, a new sound absorber is obtained having four chambers with the volume of each chamber (vl, v2, v3, v4) being different and the number of holes (nl, n3, n4) bored to the chambers can be selected differently by placing four different units (ul, u2, u3, u4) on the same inner pipe (10). The frequency range whereat a sound absorber is effective, is determined according to the number and volume of resonance chambers, and the "open area ratio" (the ratio of the total area of the holes opening to the chamber to the cross- sectional area of the inner pipe) for each chamber. Since the number and the volume of each resonance chamber, as well as the number of the holes opening to each one can be changed independently without modifying the inner pipe (10), it is possible with the disclosed invention to obtain alternative sound absorbers with a single inner pipe (10).

Claims

1. A sound absorber (1) that is used for the aim of attenuating the noise in an air intake conduit, characterized by comprising at least one perforated inner pipe (10), one or more independent units (20) that are fitted over the inner pipe (10) and that form the resonance chambers (21) and at least one fixing element (40, 50) used for fixing the position of these units (20) on the inner pipe (10).

2. A sound absorber (1) as in Claim 1, characterized in that at least one sealing element (30) is provided between the said independent units (20) in order to realize isolation between the chambers (21).

3. A sound absorber (1) as in Claim 2, characterized in that said sealing element (30) is ring shaped and can be fitted over the inner pipe (10).

4. A sound absorber (1) as in Claim 1, characterized in that said units (20) are shaped as cylindrical hollow shells and are formed by two side walls (28) and an outer wall (27) connecting the two (28).

5. A sound absorber (1) as in Claim 4, characterized in that the side and outer walls (27, 28) of each of the said units (20) form a resonance chamber (21) together with the outer surface (100) of the inner pipe (10).

6. A sound absorber (1) as in Claim 5, characterized in that the inner surfaces (280) of the side walls (27, 28) of each of the said units (20) are seated on the outer surface (100) of the inner pipe (10) peripherally.

7. A sound absorber (1) as in any one of the above claims, characterized in that the front fixing element (40) of the said fixing elements (40, 50) is positioned so as to remain in front of the first chamber (21) in the flow direction and has an abutment surface (400) to support the side wall (28) of the said first chamber (21).

8. A sound absorber (1) as in Claim 7, characterized in that the said front fixing element (40) is integrated with the inner pipe (10).

9. A sound absorber (1) as in Claim 7, characterized in that the said front fixing element (40) is an independent element that can be fitted and fixed on the inner pipe (10) during assembly.

10. A sound absorber (1) as in Claim 7, characterized in that the said front fixing element (40) is an independent element that is inseparably fixed on the inner pipe (10) by operations like rotation welding or adhesion.

11. A sound absorber (1) as in Claim 7, characterized in that the said front fixing element (40) is an independent element that is positioned by bearing against the lugs (41) formed on the inner pipe (10).

12. A sound absorber (1) as in Claim 7, characterized in that the said front fixing element (40) is disc-shaped.

13. A sound absorber (1) as in any one of the above claims, characterized in that the rear fixing element (50) of the said fixing elements (40, 50) is positioned so as to remain behind the last chamber (21) in the flow direction and has an abutment surface (500) to support the side wall (28) of the said last chamber (21).

14. A sound absorber (1) as in Claim 13, characterized in that the said rear fixing element (50) is fitted over the inner pipe (10) and joined inseparably with the inner pipe (10) or the front fixing element (40).

15. A sound absorber (1) as in Claim 13, characterized in that the said rear fixing element (50) is disc-shaped.

16. A sound absorber (1) as in Claim 13, characterized in that the said rear fixing element (50') is shaped as a cylindrical shell which is entirely open at one end (51') and, except a central opening that allows the rear fixing element (50') to be fitted over the inner pipe (10), closed at the other end (52').

17. A sound absorber (1) as in Claim 13, characterized in that when the said rear fixing element (50') is fitted over the inner pipe and the units (10, 20) through the open end (5 ) thereof, the inner surface (501) of the closed end (52') thereof forms the abutment surface (500) that supports the side wall (28) of the last chamber (21) by remaining behind the last chamber (21).

18. A sound absorber (1) as in Claim 13, characterized in that the said rear fixing element (50') is fixed on the inner pipe (10) by joining the open end (5 ) thereof with the front fixing element (40).

19. A sound absorber (1) as in Claim 18, characterized in that the said rear fixing element (50') is joined with the front fixing element (40) by methods such as plastic welding, adhesion, snap fitting, screwing or clipping.

20. A sound absorber (1) as in Claim 18, characterized in that the inner surface (501) of the said rear fixing element (50') is joined with the outer surface (401) of the front fixing element (40).

21. A sound absorber (1) as in Claim 18, characterized in that the frontal surface (502) of the said rear fixing element (50') is joined with the abutment surface (400) of the front fixing element (40).

22. A sound absorber (1) as in any one of the above claims, characterized in that the inner diameters (d20) of the said units (20) are slightly greater than the outer diameter (dlO) of the inner pipe (10) in order to enable a convenient assembly.

23. A sound absorber (1) as in any one of the above claims, characterized in that the diameter (d30) of the said sealing element (30) is slightly smaller than the outer diameter (dlO) of the inner pipe (10).

24. A sound absorber (1) as in any one of the above claims, characterized in that the said inner pipe (10) has an inlet end (18) and an outlet end (19) in order to be connected to the other elements in the flow conduit.

25. A sound absorber (1) as in any one of the above claims, characterized in that the perforated structure of the said inner pipe (10) is provided by holes (11) with circular cross-sections and/or openings in cut-out or slit form.