JP2009250183A - Air intake duct of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce sound pressure of a comparatively low frequency region made impossible to be reduced by only a sound absorbing material, in an air intake duct 1 causing air flow sound as a problem. <P>SOLUTION: In this air intake duct 1 made of synthetic resin, an extension part 14 expanded upward is provided in a part of the air intake duct 1, and an intermediate wall 16 for partitioning between the extension part 14 and a main air intake passage 10 is provided. The intermediate wall 16 is provided with a plurality of slits 17. In a space in the extension part 14, a sound absorbing material layer 18 made of foamed polyurethane, etc. is provided along an inner wall surface of an upper part wall 14a, and the sound absorbing material layer 18 is away from the intermediate wall 16. A space layer 19 is remained between a surface of the sound absorbing layer 18 and the intermediate wall 16. The space layer 19 functions as a kind of resonator in addition to a sound absorbing action of the sound absorbing layer 18 to reduce sound pressure of a specified frequency. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an intake duct made of a synthetic resin used for an intake system of an internal combustion engine, and more particularly to an improvement of an intake duct designed to reduce airflow noise.

For example, synthetic resin intake ducts are often used as intake ducts from the intake port of an internal combustion engine for automobiles to the air cleaner and intake ducts from the air cleaner to the intake manifold. Since the flow flows at a high speed, airflow sounds including high-frequency sounds are likely to occur. For this reason, conventionally, as disclosed in Patent Document 1, an expanded portion in which the passage cross-sectional area is partially expanded is provided, or a sound absorbing material is disposed on the inner peripheral surface of the intake duct to reduce airflow noise. Attempts have been made. Patent Document 1 discloses a configuration in which an outer periphery of a pipe provided with a large number of openings is covered with an expansion duct portion, and a space between them is filled with a sound absorbing material.
JP-A-8-286673

  However, in the configuration of Patent Document 1, since the inside of the expansion duct portion is filled with the sound absorbing material, actually, this portion does not function as a so-called expansion element, and the sound absorbing material is practically disposed on the inner peripheral surface of the duct. There is no essential difference in the adhered structure and noise reduction effect. Therefore, as a characteristic of the sound absorbing material, although the sound pressure in a relatively high frequency region can be reduced, for example, a sound pressure reducing action for a sound of 2500 Hz or less cannot be sufficiently obtained.

  Therefore, in the present invention, a space serving as a kind of resonator is provided in the expansion portion in addition to the sound absorbing material layer to reduce the specific frequency. That is, in an intake duct of an internal combustion engine in which two synthetic resin parts molded in two are joined together, at least one of the synthetic resin parts has a partial passage cross-sectional area at a part of the passage length. The expansion part bulges outward so as to expand to a large number, and an intermediate wall that divides the space in the expansion part and the main intake passage part is formed with a large number of openings that communicate with both. In the space in the section, a sound absorbing material layer is provided along the inner wall surface of the extended portion, and the sound absorbing material layer is separated from the intermediate wall, and the surface of the sound absorbing material layer and the intermediate wall A space is provided between the layers.

  As the sound absorbing material constituting the sound absorbing material layer, for example, various known sound absorbing materials such as foamed synthetic resin materials such as foamed polyurethane, fiber materials such as felt, glass wool, and the like can be used. In one example, the sound-absorbing material layer is preliminarily formed into a three-dimensional shape along the inner wall surface of the extended portion, and is attached to the inner wall surface with a double-sided tape. Further, the sound absorbing material layer may be fixed to the inner wall surface of the extension part through an appropriate holding member that does not excessively cover the surface area of the sound absorbing material. For example, a sound absorbing material layer using a long coil spring as a holding member along the longitudinal direction of the intake duct. And the intermediate wall, and the sound absorbing material may be pressed against the inner wall surface of the expansion portion by utilizing the radial deformation of the coil spring.

  Moreover, in one aspect of the present invention, the thickness of the sound absorbing material layer is partially different. In this case, desirably, the position of the inner wall surface of the extension portion is changed in accordance with the thickness of the sound absorbing material layer, and the distance between the surface of the sound absorbing material layer that forms the layered space and the intermediate wall is Is almost constant.

  In this configuration, since the frequency of the sound that can be reduced varies depending on the thickness of the sound absorbing material layer, the sound pressure is reduced over a wide frequency band as a whole by varying the thickness of the sound absorbing material layer.

  According to this invention, the sound pressure of the airflow sound is reduced by the sound absorbing material layer exposed toward the inside of the air intake duct, and the space secured between the intermediate wall and the sound absorbing material layer functions as a kind of resonator. Therefore, it is possible to reduce a predetermined frequency region, for example, a region of 2500 Hz or less where the sound pressure reduction is insufficient with the sound absorbing material, and the noise can be further reduced as a whole.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an air cleaner 2 for an automobile internal combustion engine having an intake duct 1 made of a synthetic resin according to an embodiment of the present invention. The intake duct 1 has a base end connected to the side surface on the dust side of the air cleaner 2, is gently curved so as to form an elongated, substantially S-shape, and the tip opens as an intake intake 3. Yes.

  2 to 4 show a specific configuration of the intake duct 1, FIG. 2 is a cross-sectional view taken along the central longitudinal direction of a substantially S shape, and FIG. 3 is a part of the intake duct 1. FIG. 4 is a cross-sectional view taken along a plane orthogonal to the cut surface of FIG. 2. The intake duct 1 is divided into two parts along the central axis of the main intake passage 10 inside, and the first duct half 11 and the upper part, which are the lower part in the figure, are shown. The second duct half 12 is generally composed of the two, and both are integrally bonded or joined together along the joining line 13 on the side edge thereof. The second duct half 12 that is the upper portion is provided with an extended portion 14 that bulges upward so that the passage cross-sectional area partially expands at a part of the passage length.

  More specifically, the extended portion 14 is formed as a cover-like component different from the main body portion of the second duct half portion 12 for convenience of molding, and the second duct half portion is formed along the peripheral joining line 15. It is bonded or joined to the part 12. In the main body portion of the second duct half portion 12 covered by the cover-like extension portion 14, an intermediate wall 16 that partitions the space in the extension portion 14 from the original main intake passage 10 portion remains. That is, a main intake passage 10 having a substantially constant cross-sectional area that is basically equal to the passage cross-sectional area at both ends of the intake duct 1 is formed between the intermediate wall 16 and the first duct half 11, and this passage An extension portion 14 is added to enlarge the cross-sectional area. The intermediate wall 16 is provided with a plurality of elongated slits 17 along the longitudinal direction of the intake duct 1 as openings that communicate the space in the extended portion 14 with the main intake passage 10. Note that a large number of holes may be formed in place of the slits 17. As apparent from FIGS. 3 and 4, the main intake passage 10 has a substantially rectangular cross-sectional shape with rounded corners, and the extended portion 14 has a pair of parallel portions constituting the main intake passage 10. The side walls 12a, 12a are formed so as to extend upward. In addition, in the cross-sectional shape as shown in FIG. 4, the upper wall 14a of the extended portion 14 has a substantially straight line parallel to the bottom wall 11a of the first duct half 11, and therefore, the upper wall 14a and the intermediate wall The space in the extended portion 14 formed between the two and the whole 16 has a flat and substantially rectangular shape. The height of this space hardly changes along the longitudinal direction of the intake duct 1 and is substantially constant.

  The first duct half part 11, the second duct half part 12, and the cover-like extension part 14 constituting the intake duct 1 are all injection-molded using a hard synthetic resin such as nylon or polypropylene. The extended portion 14 may be integrally formed as a part of the second duct half 12, and the intermediate wall 16 portion may be formed as a separate part and bonded or joined together.

  Here, a sound absorbing material layer 18 is provided along the inner wall surface of the upper wall 14 a in the space in the extension portion 14. The sound absorbing material layer 18 has a thickness that is approximately half of the height (thickness) of the space in the extended portion 14 and occupies the upper portion of the space. The remaining portion, that is, the lower portion is occupied by a layered space that becomes a substantial expansion space, that is, the space layer 19. In other words, the sound absorbing material layer 18 is separated from the intermediate wall 16, and the space layer 19 remains between the surface of the sound absorbing material layer 18 and the intermediate wall 16. For example, the space in the extended portion 14 has a height of about 20 mm, and the thickness of the sound absorbing material layer 18 is about 10 mm. Therefore, the space layer 19 having a thickness of about 10 mm is secured. Yes.

  The sound-absorbing material layer 18 is made of, for example, a foamed synthetic resin material such as foamed polyurethane, and is molded in advance into a three-dimensional shape along the inner wall surface of the upper wall 14a of the extended portion 14, as shown in FIG. And it is attached to the said inner wall surface with the double-sided tape 20 arrange | positioned, for example at six places of both ends and an intermediate part. Note that a fiber material such as felt or a sound absorbing material such as glass wool may be formed in a predetermined shape together with an appropriate binder, for example, and attached in the same manner.

  In the configuration as described above, in addition to the sound pressure level being reduced by the action of the sound absorbing material layer 18 against the sound of airflow caused by the intake air flowing through the main intake passage 10, the space layer 19 functions as a kind of resonator. Further reduction in sound pressure can be achieved. Moreover, since the sound absorbing material layer 18 is separated from the intermediate wall 16 and the surface area thereof is not covered by the intermediate wall 16, the sound absorbing action by the sound absorbing material layer 18 is excellent. FIG. 6 shows an example of the sound pressure reduction effect on the airflow sound of the intake duct 1. As a conventional example, the sound pressure is reduced when only the 10 mm-thick sound absorbing material layer is provided without the space layer 19. The effect (solid line) and the sound pressure reduction effect (one-dot chain line) of the present embodiment including the 10 mm-thick sound absorbing material layer 18 through the 10 mm-thick space layer 19 are shown in comparison. As shown in the figure, the addition of the space layer 19 makes it possible to reduce the sound in the vicinity of 2000 Hz to 2500 Hz, which is likely to result in insufficient sound pressure reduction particularly with a sound absorbing material. It is possible to tune the frequency region for reducing the sound pressure by changing the size of the space layer 19 or the like.

  In the above embodiment, the space layer 19 and the sound absorbing material layer 18 are provided only on one side of the main intake passage 10 (that is, the second duct half 12 side). Alternatively, the extended portions 14 may be formed on both sides, that is, both the first and second duct halves 11 and 12, and the space layer 19 and the sound absorbing material layer 18 may be provided respectively. Also good.

  Further, in the above embodiment, the sound absorbing material layer 18 is fixed with the double-sided tape 20, but the sound absorbing material layer 18 and the intermediate wall 16 are formed using a long and thin coil spring as a holding member along the longitudinal direction of the intake duct 1. The sound absorbing material layer 16 can be fixed and held by pressing it against the upper wall 14a of the expansion portion 14 by using the bending deformation in the radial direction of the coil spring. With such a coil spring, the surface of the sound absorbing material layer 18 serving as the sound absorbing surface is not excessively covered, and good sound pressure reduction can be achieved as in the above embodiment.

  Next, FIGS. 7 and 8 show a second embodiment of the present invention. In this embodiment, the height of the upper wall 14a of the extended portion 14 is changed in three steps in a stepwise manner, and the thickness of the sound absorbing material layer 18 disposed therein is 3 correspondingly. Different in stages. Specifically, among the sound-absorbing material layer 18 disposed along the longitudinal direction of the intake duct 1, the most downstream portion, that is, the first portion 18a close to the air cleaner 2 side has the smallest thickness. For example, the thickness is about 10 mm. The intermediate second portion 18b upstream of this has an intermediate thickness, for example, a thickness of about 15 mm. The most upstream third portion 18c has the largest thickness, for example, a thickness of about 30 mm. The sound-absorbing material layer 18 composed of these three portions 18a to 18c is formed in advance in a predetermined three-dimensional shape along the inner wall surface of the upper wall 14a of the extended portion 14, for example, as in the above-described embodiment. The double-sided tape 20 as shown in FIG. 5 is attached to the inner wall surface. Alternatively, the three portions 18a to 18c may be separately formed and attached individually. As the sound absorbing material, a foamed synthetic resin material such as foamed polyurethane is used, for example, as in the above-described embodiments. In addition, fiber materials such as felt or various materials such as glass wool can be used. .

  Although the sound absorbing material layer 18 has three portions 18a to 18c having different thicknesses, the lower surface of each portion is continuous without a step, and the lower surface of the sound absorbing material layer 18 and the intermediate wall 16 are connected to each other. In the meantime, the space layer 19 having a substantially constant thickness remains. The thickness of the space layer 19 is about 10 mm as an example.

  When absorbing sound using a sound absorbing material, if the thickness of the sound absorbing material is different, the frequency band of the sound to be absorbed is different. FIG. 9 shows the frequency characteristics of the sound absorption coefficient with respect to the normal incident sound for the sound absorbing materials having different thicknesses. The characteristics (solid line) of the sound absorbing material having a thickness of 10 mm and the characteristics of the sound absorbing material having a thickness of 15 mm ( A dot-dash line) is compared with a characteristic of the sound absorbing material having a thickness of 30 mm (two-dot chain line). As shown in the figure, the sound absorbing material having the thinnest thickness of 10 mm effectively absorbs sound in the vicinity of 4000 Hz to 5000 Hz, and the sound absorbing material having the thickest thickness of 30 mm effectively absorbs sound of 2000 Hz or less. In the sound absorbing material having an intermediate thickness of 15 mm, sound in the vicinity of 2000 Hz to 4000 Hz is effectively absorbed.

  Therefore, by combining these sound absorbing materials having different thicknesses, airflow noise can be reduced over a wide frequency range. FIG. 10 shows an example of the sound pressure reduction effect on the airflow sound of the intake duct 1. As a conventional example, the sound pressure is reduced when only the 10 mm-thick sound absorbing material layer is provided without the space layer 19. The effect (solid line) and the sound pressure reduction effect (one point) of the present embodiment provided with the sound absorbing material layer 18 having different thicknesses in three stages (10 mm, 15 mm, and 30 mm) through the space layer 19 having a thickness of 10 mm as described above. (Dotted line). As shown in the figure, this embodiment has an advantage that the sound pressure is reduced over a wide frequency range. In addition, since the area occupied by the thin sound absorbing material portion 18a effective in the high frequency region is relatively reduced, the sound pressure reduction in the high frequency region is worsened. Noise can be reduced at a substantially uniform level over the entire frequency range.

  In the above-described embodiment, the thickness of the sound absorbing material layer 18 is sequentially decreased from the upstream side of the intake air flow. However, the present invention is not limited to such an arrangement, and each portion having a different thickness is provided. It is possible to arrange them appropriately. Further, the thickness may be changed more finely than in three stages, and the thickness may be changed continuously.

The perspective view of the air cleaner provided with the air intake duct of the present invention. Sectional drawing along the longitudinal direction of this intake duct. The perspective view which cuts and shows a part of upper surface of this intake duct. Fig. 3 is a cross-sectional view of the intake duct. The top view which looked at the sound-absorbing material layer from the back side. The characteristic view which shows the sound pressure reduction effect of the intake duct of this Example compared with a prior art example. Sectional drawing along the longitudinal direction of the air intake duct of 2nd Example. The perspective view of the intake duct of 2nd Example. The characteristic view which shows the frequency characteristic of the sound absorption coefficient of the sound-absorbing material from which thickness differs. The characteristic view which shows the sound pressure reduction effect of the air intake duct of 2nd Example compared with a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Intake duct 10 ... Main intake passage 14 ... Expansion part 16 ... Intermediate | middle wall 17 ... Slit 18 ... Sound-absorbing material layer 19 ... Spatial layer

Claims (4)

In an intake duct of an internal combustion engine in which two synthetic resin parts molded in two are joined together,
At least one of the synthetic resin parts includes an extended portion that bulges outward so that the passage cross-sectional area partially expands at a part of the passage length,
In the intermediate wall that partitions the space in the extended portion and the main intake passage portion, a large number of openings that communicate both are formed.
A sound absorbing material layer is provided along the inner wall surface of the expanding portion in the space in the expanding portion, and the sound absorbing material layer is separated from the intermediate wall, and the surface of the sound absorbing material layer and the intermediate wall are separated. An air intake duct of an internal combustion engine, wherein a space is provided in a layered manner between   2. The internal combustion engine according to claim 1, wherein the sound-absorbing material layer is formed in advance in a three-dimensional shape along an inner wall surface of the extension portion, and is attached to the inner wall surface by a double-sided tape. Intake duct.   The intake duct for an internal combustion engine according to claim 1 or 2, wherein the thickness of the sound absorbing material layer is partially different.   The position of the inner wall surface of the extended portion changes corresponding to the thickness of the sound absorbing material layer, and the distance between the surface of the sound absorbing material layer that forms the layered space and the intermediate wall is substantially constant. The intake duct for an internal combustion engine according to claim 3.

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