EP2541034B1 - Motor vehicle ventilation channel with dampened Helmholtz resonator - Google Patents

Description

The present invention relates to a motor vehicle air duct with a Helmholtz resonator provided thereon according to the preamble of claim 1.

A generic channel is from the US-A-5493080 known. Other relevant channels are the DE-A-10 2004 057 419 . EP-A-0778399 and US-A-5783780 refer to.

Helmholtz resonators are well known in the art as acoustic attenuation devices. Helmholtz resonators are used in air intake tracts of motor vehicles in order to reduce noise occurring in these.

Typically, Helmholtz resonators are designed with respect to their geometry such that they exhibit a sound attenuation effect in a desired frequency range around a target frequency. In this case, Helmholtz resonators usually have a certain bandwidth around the target frequency of the sound damping effect, so that with a specific Helmholtz resonator sound in a frequency range around the desired target frequency around can be effectively damped.

A disadvantage of known Helmholtz resonators are their so-called "side effects", which lead to an undesirable sound amplification in frequency ranges immediately outside the bandwidth in which unfolds the Helmholtz resonator its sound damping effect. As a result, although sound is actually attenuated in the desired target frequency range, sound is undesirably amplified simultaneously in immediately adjacent frequency ranges, which reduces the overall achieved sound-damping effect.

This disadvantage is in a motor vehicle air duct with a provided thereon Helmholtz resonator known US-A-5493080 according to thereby mitigated that in the Helmholtz resonator at least one damping body is provided from sound dissipating material.

Although the sound damping effect is reduced directly at the target frequency by the damping body in the Helmholtz resonator, the sound amplification effect at the edges of the bandwidth is considerably reduced compared to a Helmholtz resonator without damping body. Thus, the aforementioned undesirable "side effects" are at least reduced. The sound level in the air duct is advantageously smoothed or unified over the frequency spectrum. The result is a motor vehicle which emits sound in a uniform frequency spectrum distributed around the target frequency over a frequency range compared to a motor vehicle equipped with conventional Helmholtz resonators.

To increase the sound-damping effect of the Helmholtz resonator on the known motor vehicle air duct described here, this has a plurality of damping bodies.

It is an object of the present invention to improve the sound damping effect of a generic motor vehicle air duct and on. This object is achieved by a motor vehicle air duct with all features of claim 1.

The sound-damping effect of the Helmholtz resonator provided with a plurality of damping bodies can in fact be further increased by providing a filling material between at least two immediately adjacent damping bodies. Such a filling material may, for example, again be a fiber tangle, such as cotton wool, or a foam or the like. However, it should be noted that it is also conceivable that the individual damping body are separated from each other only by a gas, in particular air volume.

Frequently, Helmholtz resonators have a transition region along their depth extension away from the air duct, in which the cross-sectional area of the Helmholtz resonator changes abruptly. It has been found that the achievable with the damping body mitigation of side effects is particularly great when the at least one damping body is provided in the transition region. In this case, material for the damping body can be saved considerably if it is arranged in the transition region on the side of the section with the smaller cross-sectional area.

More specifically, the Helmholtz resonator may have a neck portion of smaller cross-sectional area and a volume portion of larger cross-sectional area. Then advantageously the at least one damping body is provided in the neck portion, more preferably close to the volume portion. It should not be ruled out that the Helmholtz resonator in addition to the sections mentioned has more sections. Nor should it be ruled out that the damping body is arranged in the volume section, close to the neck section.

The damping body can in principle be formed from any sound-damping material or comprise such a material. For example, the at least one sound-damping body may be formed from a closed-cell or open-cell foam, a woven fabric, also a metal mesh, mesh, braid, fiber tangle, perforated or porous material or a composite of at least two of said materials or such to include such.

In order to achieve the desired effect with the present invention, a thin damping body is already sufficient, i. a damping body which has a smaller dimension along the depth extension direction of the Helmholtz resonator than in the direction of the orthogonal to the depth extension direction of the same cross-sectional area. However, in a less preferred embodiment, it is also possible to use thick damping bodies which do not fulfill the previous dimensional condition.

The damping bodies, which in principle may be arranged arbitrarily in the Helmholtz resonator, are preferably provided substantially parallel to one another, so that sound propagating in the Helmholtz resonator must pass through the individual damping bodies in substantially the same way. Preferably, the damping bodies are oriented orthogonal to the sound propagation direction in the Helmholtz resonator. By the arrangement of a plurality of damping body in sound propagation direction one behind the other, the sound-damping effect of the individual switch damping bodies is summed up.

In order to optimize the sound-damping effect, it may be further contemplated that at least two damping bodies comprise different material or even formed of different material. In continuation of this idea, all damping bodies of a Helmholtz resonator may comprise different material or be formed of different material.

However, if a specific frequency spectrum is to be attenuated as selectively as possible by a Helmholtz resonator on the motor vehicle air duct, the Helmholtz resonator can have at least two damping bodies, which comprise the same material or which are even completely formed of the same material. Preferably, in this case, all the damping bodies of a Helmholtz resonator comprise the same material or are formed from the same material.

The above object is achieved according to a further aspect of the present invention also by the use of a Helmholtz resonator with at least one damping body, as described above, on a motor vehicle air duct.

Fig. 1

einen grobschemtischen Längsschnitt durch eine erfindungsgemäße Ausführungsform eines Kraftfahrzeug-Luftleitungskanals und

Fig. 2

einen Vergleich der Schalldämpfungswirkung eines herkömmlichen Helmholtz-Resonators mit jener eines erfindungsgemäßen Helmholtz-Resonators an einem Kraftfahrzeug-Luftleitungskanal.

The present invention will be explained in more detail with reference to the accompanying drawings. It shows:

Fig. 1

a grobschemtischen longitudinal section through an inventive embodiment of a motor vehicle air duct and

Fig. 2

a comparison of the sound damping effect of a conventional Helmholtz resonator with that of a Helmholtz resonator according to the invention on a motor vehicle air duct.

In Fig.1 an embodiment of a motor vehicle air duct according to the invention is generally designated 10. The motor vehicle air duct 10 of the embodiment has a channel section 12, which may be part of an air intake system, for example, and in which air operatively along the arrow L of a respect to a in the Fig.1 Not shown internal combustion engine further lying air inlet side 12a to an internal combustion engine closer lying engine side 12b and finally to the internal combustion engine itself flows.

Starting from the internal combustion engine as a possible sound source, sound may propagate away from the internal combustion engine to the air inlet side 12a in the air-conducting channel section 12. The sound is in the in the Fig. 1 shown embodiment represented by the letter S.

In the prior art, it is generally known to couple to the channel section 12 a Helmholtz resonator 14 such that the enclosed by the Helmholtz resonator 14 inner volume 16 is in continuous fluid communication with the inner volume 18 of the channel section 12. The air in the inner volume 18 of the channel path 12 and the air in the inner volume 16 of the Helmholtz resonator 14 thus form a substantially uniform air continuum.

For this purpose, the Helmholtz resonator 14 comprise a neck portion 14a, by means of which a volume portion 14b, which has a substantially larger transverse surface than the neck portion 14a, may be connected to the channel path 12 to a common fluid space.

In this case, the Helmholtz resonator extends away from the channel path 12 in a depth direction T, whereby the previously designated cross-sectional area of the neck portion 14a and of the volume portion 14b is to be measured orthogonally to the depth extension direction T.

The Helmholtz resonator 14 is in terms of its enclosed volume and shape to a specific target or working frequency, for example, 275 Hz, tuned so that it reflects sound with the operating frequency in the channel section 12 in that it leads to an at least partial extinction of the Sound comes with the working frequency in the channel section 12. Thus, by coupling a Helmholtz resonator to the channel section 12, specifically sound with a specific frequency, namely the operating frequency of the respective Helmholtz resonator, in the channel section 12 can be reduced, which reduces the acoustic emission of the vehicle carrying the channel section 12.

It can also be thought to couple several Helmholtz resonators with different operating frequencies and thus with different shapes to the channel section 12, if the available space allows this. This sound in different frequency ranges in the channel section 12 can be reduced.

In Fig. 2 three sound level curves are shown, of which the curve 20 shows the resonance behavior of a base system of a channel path 12 without a resonator with a resonant frequency of about 275 Hz.

The reflection-based noise reduction by a conventional Helmholtz resonator with an operating frequency corresponding to the above resonant frequency in the channel path 12 leads to the sound level curve 22, in which there is a strong attenuation in the range of the operating frequency of the conventional Helmholtz resonator. This means that in the range of the bandwidth B, a reduction of the sound level can be achieved substantially symmetrically around the operating frequency.

However, the conventional Helmholtz resonator immediately adjacent to the bandwidth range B so-called "side effects", in which there is an undesirable amplification of the sound level. This can be recognized by the two local maxima 24 and 26 of the sound level curve 22 of the sound in the channel section 12.

In order to avoid or at least mitigate these unwanted side effects, in the Helmholtz resonator 14, preferably in the transition region 28 between the neck portion 14a and volume portion 14b of the Helmholtz resonator 14, but preferably still in the neck portion 14a, a damping body 30 of dissipating material intended. This material may be a fabric, a tangle, a foam and the like. For the purposes of the present application, such a material dissipating sound is not regarded as interrupting the fluid connection between the inner volume 16 of the Helmholtz resonator 14 and the inner volume 18 of the channel section 12.

Preferably, precisely in order to endanger the fluid connection as little as possible, the dimension of the damping body 30 in the depth direction T is smaller than its extension in one of the cross-sectional surface extension directions, which in the Fig. 1 aligned orthogonal to the depth extension plane.

To reinforce the sound dissipating effect of the damping body more than one damping body is provided, for example as shown by the dashed second damping body 32 in the neck portion 14a in Fig. 1 is indicated.

In this case, between the first and the further damping body 30 and 32, an air volume 34 may be included.

The number of possible damping bodies in the Helmholtz resonator 14, in particular in its neck portion 14a, is not limited to two. Likewise, three, four or five or more damping body may be provided. The proposed damping body may be formed of different or the same materials. Likewise, it can be provided that with a plurality of damping bodies provided in one and the same Helmholtz resonator, a first group of damping bodies is formed from a first material and a second group of damping bodies is formed from a second material which is different from the first damping material.

These groups can be entangled, partially cross-linked or arranged in blocks.

The sound-reducing effect of a Helmholtz resonator 14 with at least one damping body 30 is in the sound level curve 32 in Fig. 2 shown.

As can be seen there, due to the intended damping body 30, although the maximum damping at the working frequency decreases. However, the unwanted side effects are significantly reduced.

Overall, the sound level in the channel section 12 is uniformed in the desired manner, so that the sound level fluctuations on the in the channel route 12 occurring frequencies are compensated, which is a desired effect on the noise reduction of motor vehicles.

Also is in Fig. 2 to recognize that the bandwidth range B is not changed in amount by the provision of the damping body 30. There may be a slight frequency shift, but this is negligible compared to the entire frequency bandwidth of the bandwidth range.

Claims (9)

1. Motor vehicle air duct (12) provided with a Helmholtz resonator (14) in which a plurality of damping elements (30, 32) made of a sound-dissipating material is provided, characterised in that a filler material (34) is provided between at least two immediately adjacent damping elements (30, 32).
2. Motor vehicle air duct according to claim 1, characterised in that the Helmholtz resonator (14) comprises a transition region (28) with an abrupt change in cross-sectional area set away from the air duct (12) in the direction of the depth extension (T) of the resonator, the damping elements (30, 32) being provided in the transition region (28), preferably on the side of the portion (14a) having the smaller cross-sectional area.
3. Motor vehicle air duct according to either claim 1 or claim 2, characterised in that the Helmholtz resonator (14) comprises a neck portion (14a) having a smaller cross-sectional area and a volume portion (14b) having a larger cross-sectional area, the damping elements (30, 32) being provided in the neck portion (14a).
4. Motor vehicle air duct according to any of the preceding claims, characterised in that the damping elements (30, 32) are formed from a closed-cell foam or an open-cell foam, from a woven material, from a fibre mesh, from a perforated or porous material or from a composite of at least two of these materials.
5. Motor vehicle air duct according to any of the preceding claims, characterised in that the damping elements (30, 32) are of a smaller dimension in a depth direction of the Helmholtz resonator orthogonal to the cross-sectional area of said Helmholtz resonator (14) than in the direction of the cross-sectional area.
6. Motor vehicle air duct according to any of the preceding claims, characterised in that the damping elements (30, 32) from the plurality of damping elements (30, 32) are provided substantially parallel to one another.
7. Motor vehicle air duct according to any of the preceding claims, characterised in that at least two damping elements (30, 32), and preferably in that all damping elements (30, 32), of a Helmholtz resonator (14) comprise different material, and are preferably made entirely of different material.
8. Motor vehicle air duct according to any of claims 1 to 6, characterised in that at least two damping elements (30, 32), and preferably in that all damping elements (30, 32), of a Helmholtz resonator (14) comprise the same material, and are preferably made entirely of the same material.
9. Use of a Helmholtz resonator (14) comprising a plurality of damping elements (30, 32) as defined in one or more of the preceding claims for damping sound at an air duct (12) in a motor vehicle, in particular at an intake duct of the internal combustion engine or at an air conditioning duct.

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