JP7374848B2 - Sound deadening structure and sound deadening method - Google Patents

Description

The present disclosure relates to a noise reduction structure and a noise reduction method that can reduce engine noise leaking to the outside of a vehicle.

As this type of noise reduction structure, one that covers the engine from below is known (for example, Patent Document 1).

JP 2004-170584 A (paragraphs [0013], [0014], Figure 1)

By the way, there is an opening on the side of the engine room of a vehicle to allow the drive shafts and tie rods of the wheels to pass through, so the engine noise leaks through the opening, passing under the side member and to the side of the vehicle. . However, since such engine noise leaking to the sides cannot be suppressed by the above-mentioned conventional noise reduction structure, there is a need for the development of a technique for suppressing engine noise leaking to the sides.

The invention according to claim 1, which has been made to solve the above problem, is a noise reduction structure that reduces engine noise passing below a side member of a vehicle and leaking to the side of the vehicle, the noise reduction structure being provided on the lower surface of the side member. The noise reflecting part has a sound reflecting surface that is inclined with respect to the vertical direction so as to go downward as it moves away from the engine laterally, and the engine sound received by the sound reflecting surface is This is a noise reduction structure that reflects the sound downward and interferes with the engine sound passing below the side member. Here, the side members include both a side member that extends over substantially the entire longitudinal direction of the vehicle, and a front side member that extends in the longitudinal direction in the engine compartment of the vehicle.

The invention of claim 2 is the sound-reducing structure according to claim 1, wherein the sound reflecting surface is an arcuate surface having a radius of curvature of 20 to 30 [mm] and a circumference of 30 to 50 [mm]. .

The invention according to claim 3 is the sound reflecting surface according to claim 1, wherein the sound reflecting surface is a flat surface having an inclination angle of 40 to 50 [DEG] in the vertical direction and a dimension in the vertical direction of 20 to 30 [mm]. It has a sound deadening structure.

The invention according to claim 4 is a sound damping device according to any one of claims 1 to 3, which includes a pair of side projecting walls that protrude from both ends of the sound reflecting surface in the front and back direction and oppose each other in the front and back direction. It is a structure.

According to a fifth aspect of the invention, the noise reflecting section includes a sound reflecting plate having the sound reflecting surface as one of the front and back surfaces, and a mounting plate projecting from an edge of the sound reflecting plate to a side opposite to the sound reflecting surface. The mounting plate is a resin molded product that integrally includes a mounting plate part on the lower surface of the side member or the lower edge of the fender liner that overlaps the side surface of the side member and projects downward from the side member. 5. The sound deadening structure according to claim 4, wherein the two are fixed in an overlapping manner.

The invention according to claim 6 is a sound damping device according to any one of claims 1 to 5, which includes a partition projecting wall that protrudes from an intermediate position in the front-rear direction of the sound-reflecting surface and partitions the sound-reflecting surface in the front-rear direction. It is a structure.

The invention according to claim 7 is a noise reduction method for reducing engine noise passing below a side member of a vehicle and leaking to the side of the vehicle, wherein a noise reflecting portion provided overlapping the side member reduces the engine noise downward. This is a method of muffling noise by interfering with the engine sound that is reflected by the side member and passes below the side member.

According to an eighth aspect of the invention, the engine sound reflected by the noise reflecting portion and the lower part of the side member are arranged so as to reduce the noise level of the sound having the highest frequency among the engine sounds leaking to the side of the vehicle. 8. The noise reduction method according to claim 7, wherein the phase is shifted from the passing engine sound.

According to the noise reduction structure and the noise reduction method of claims 1 and 7, a part of the engine sound directed from the engine to the side is reflected by the sound reflection surface of the noise reflection part provided overlappingly on the lower surface of the side member. It travels downward, and below the noise reflecting section, it intersects and interferes with the engine sound that has gone straight to the side from the engine, out of phase. This suppresses engine noise that passes below the side members and leaks to the sides.

Here, the phase of the engine sound reflected by the noise reflector and the engine sound passing below the side member is determined to reduce the noise level of the highest frequency sound among the engine sounds leaking to the sides of the vehicle. It is preferable to shift (Claim 8). For this purpose, when the vehicle is a regular car, the sound reflecting surface may be either an arcuate surface or a flat surface as long as it is inclined with respect to the vertical direction so as to go downward as it moves away from the engine laterally. Further, when the sound reflecting surface is an arcuate surface, it is preferably an arcuate surface with a radius of curvature of 20 to 30 [mm] and a circumferential length of 30 to 50 [mm] (invention of claim 2). ), When the sound reflecting surface is a flat surface, it is preferably a flat surface with an inclination angle of 40 to 50 [DEG] in the vertical direction and a dimension of 20 to 30 [mm] in the vertical direction ( Invention of Claim 3).

As in the configurations of claims 4 and 6, a structure in which a pair of side protruding walls protrudes from both ends of the sound reflecting surface in the front and back direction, or a structure in which a partition protruding wall protrudes from an intermediate position in the front and back direction of the sound reflecting surface. By doing so, the spread of the engine sound reflected by the sound reflecting surface in the longitudinal direction of the vehicle is suppressed.

In the noise reduction structure of claim 5, since the noise reflecting part is a part fixed to the side member or fender liner, the noise reflecting part can be made common among vehicle models with different shapes of the side member or fender liner. can be achieved.

Front sectional view of the front part of the vehicle according to the first embodiment Plan view of the wheel house viewed from above the vehicle Perspective view of the wheel house seen from the front side of the vehicle Perspective view of the fender liner seen from the rear of the vehicle (A) Perspective view of the noise reflector as seen from the sound reflecting surface side, (B) Perspective view as seen from the side opposite to the sound reflecting surface. Diagram showing the flow of engine sound from the side opening to the side A diagram schematically showing the structure of the noise reflector of (A) Example 1, (B) Example 2, and (C) Comparative Example 1. Plan view of the test track viewed from above Graph showing the results of the confirmation experiment (A), (B) Front sectional views of noise reflectors according to other embodiments

[First embodiment]
Hereinafter, a first embodiment of a vehicle 90 having a noise reduction structure according to the present disclosure will be described with reference to FIGS. 1 to 6. A vehicle 90 according to the present embodiment shown in FIG. 1 is, for example, a passenger car in which an engine 95 is mounted at the front and front wheels 91 are driven. The engine room 93 of this vehicle 90 has cover walls 92A and 92B at the lower part and both sides, thereby suppressing sound leakage to the sides and downwards. Further, as shown in FIG. 2, side openings 92C are formed in the cover walls 92A on both sides to lead out the drive shaft 31 and tie rod 32 of the front wheel 91 from the engine room 93. In order to suppress sound leakage from the side opening 92C to the side, a sound deadening structure according to the present disclosure is provided on the lower surface of the front side member 20.

Specifically, the surroundings of the silencing structure are as follows. As shown in FIG. 1, the front side member 20 is located outside the side cover wall 92A, has a rectangular tube structure, and extends in the front-rear direction. Further, as shown in FIG. 3, the front side member 20 forms a substantially horizontal horizontal part 20A from the front end to a position near the rear end, and a slope part 20B that slopes backward downward from the horizontal part 20A. It has become. The wheel house 96 is arranged in a range extending from the rear of the horizontal portion 20A of the front side member 20 to the front of the inclined portion 20B.

As shown in FIG. 1, the fender liner 22 in the wheel house 96 is provided with an inner wall 22B that is fixed to overlap the outer surface of the front side member 20. Furthermore, a shock absorber 33 for the front wheel 91 passes through the top of the arcuate wall 22A that covers the front wheel 91 from above in the fender liner 22. A notch 23 for passing through extends from the top of the arcuate wall 22A to the lower end of the inner wall 22B, as shown in FIG.

As shown in FIG. 3, a subframe 21 is provided at a position downwardly away from the front side member 20. Furthermore, the aforementioned cover wall 92B is superimposed on the lower surface of the subframe 21. The aforementioned side opening 92C opens between the front side member 20 and the subframe 21 within the wheel house 96.

In order to suppress sound leakage to the side from the side opening 92C, a plurality of (for example, three) noise reflectors 10 are fixed to the lower surface of the front side member 20 in a row in the front-rear direction. is coming. The silencing structure of this embodiment is composed of these plurality of noise reflectors 10. In addition, in this embodiment, each noise reflector 10 corresponds to the "noise reflection part" of a claim.

The noise reflector 10 is, for example, an injection molded product made of resin, and is shown as a single unit in FIG. 5 . As shown in FIG. 5(A), the noise reflector 10 includes a strip-shaped mounting plate portion 12 extending in the longitudinal direction of the front side member 20 (the longitudinal direction of the vehicle 90). As shown in FIG. 5(B), rectangular side projecting walls 14 having the same width as the mounting plate section 12 are suspended from positions near both ends in the longitudinal direction of the mounting plate section 12, and there is a space between the side projecting walls 14. A sound reflecting plate 11 is provided.

The sound reflecting plate 11 has a cross-sectional shape of 1/4 circle and extends in the longitudinal direction of the front side member 20. Further, the radius of the outer circumferential surface of the sound reflecting plate 11 is approximately the same size as the width of the mounting plate portion 12. One side of the mounting plate 12 and the upper part of the sound reflecting plate 11 are connected so that one thickness side of the mounting plate 12 in the width direction and the upper part of the sound reflecting plate 11 are shared. are integrated, and both ends of the sound reflecting plate 11 are connected to a pair of side projecting walls 14.

The arcuate inner surface of the sound reflecting plate 11 constitutes a sound reflecting surface 11A according to the present disclosure. Note that the radius of curvature of the sound reflecting surface 11A is preferably 20 to 30 [mm], and the circumference thereof is preferably 30 to 50 [mm], for example. Moreover, a pair of partition projecting walls 15 are provided on the sound reflecting surface 11A at positions that partition the sound reflecting plate 11 into three equal parts in the longitudinal direction. Each partition projecting wall 15 has the same shape as the portion of the side projecting wall 14 that projects from the inner surface of the sound reflecting plate 11.

The end portion of the mounting plate portion 12 that is closer to the side projecting wall 14 forms a fixed portion 12A, in which a mounting hole 12B is formed. The noise reflector 10 is fixed to the front side member 20 by tightening a bolt passed through the mounting hole 12B into a screw hole (not shown) formed on the lower surface of the front side member 20.

Although the noise reflector 10 of this embodiment is, for example, an injection molded product of resin, it may be a vacuum molded product. Further, the noise reflector 10 is not limited to being made of resin, and may be made of metal, for example. Furthermore, the method for fixing the front side member 20 to the lower surface is not limited to bolts, but may be rivets, adhesives, or welding if the material is metal.

Next, the effects of the noise reflector 10 of this embodiment will be explained. Engine noise generated in the engine room 91 and directed to the side leaks to the outside of the vehicle through the side opening 92C, passing between the front side member 20 and the subframe 21. In this embodiment, a plurality of noise reflectors 10 are attached to the lower surface of the front side member 20, and the sound reflecting surface 11A of the noise reflector 10 is arranged so as to face the side opening 92C. There is. Therefore, as shown in FIG. 6, the path of the engine sound going to the side from the side opening 92C is a first path 16R passing through the sound reflecting surface 11A, and a first path 16R passing through the sound reflecting surface 11A. It passes through the lower part, goes straight, and is divided into a second route 17R, which is discharged outside the vehicle.

The engine sound passing through the first path 16R is reflected by the sound reflecting surface 11A of the noise reflector 10 and heads downward. Then, it merges with the engine sound traveling straight through the second route 17R. The wavelength of the engine sound reflected by the sound reflecting surface 11A is out of phase with the wavelength of the engine sound traveling straight, so when they merge, they interfere with each other. Thereby, engine noise is reduced below the front side member 20 before it leaks outside the vehicle.

Here, by lowering the noise level of the sound with the highest frequency among the engine sounds leaking outside the vehicle, the overall noise level of the engine sound can be lowered. Therefore, it is desirable to reduce the sound in the frequency band of 800 to 1250 [Hz], which is the peak of engine sound. As in this embodiment, if the radius of curvature of the sound reflecting surface 11A is 20 to 30 [mm] and the circumference is 30 to 50 [mm], the frequency range centered on the frequency band 800 to 1250 [Hz] A good reduction effect can be obtained.

Further, since the noise reflector 10 is provided with a pair of side protruding walls 14, when the engine sound is reflected at the ends of the sound reflecting plate 11A in the longitudinal direction of the vehicle 90, the engine sound is reflected by the noise. Escape from the container 10 in the longitudinal direction of the vehicle 90 can be prevented. Thereby, the engine sound passing through the first path 16R can be directed downward without waste, and can be caused to interfere with the engine sound passing through the second path 17R, thereby increasing the efficiency of reducing the engine sound leaking from outside the vehicle.

Furthermore, since the noise reflector 10 is provided with the pair of partition walls 15, it is possible to suppress the engine sound reflected by the sound reflecting surface 11A from spreading in the longitudinal direction of the vehicle 90. Thereby, the engine sound passing through the first path 16R can be directed downward without waste, and can be made to efficiently interfere with the engine sound passing through the second path 17R.

Here, if the noise reflector 10 is placed inside the front side member 20, it may interfere with various auxiliary equipment, and if it is placed outside the front side member 20, it may interfere with the shock absorber 33. Since the noise reflector 10 is arranged below the front side member 20, there is no possibility of interference with these parts, and the degree of freedom in the shape of the noise reflector 10 is increased.

Furthermore, since the noise reflector 10 is a separate component, the noise reflector 10 can be used in common among vehicle models with different shapes of the front side members 20. Furthermore, the positions and number of attachments can be changed as appropriate depending on the positions and sizes of the drive shaft 31, tie rods 32, and the like. Further, since the mounting plate portion 12 is provided, the mounting work becomes easy.

[Confirmation experiment]
An experiment to confirm the silencing effect of the silencing structure of the present disclosure will be described. In this experiment, the following Examples 1 and 2, which are vehicles that have the noise reduction structure of the present disclosure, and the following Comparative Examples 1 and 2, which are vehicles that do not have the noise reduction structure of the present disclosure, were prepared. The main body of the vehicle used in Examples 1 and 2 and Comparative Examples 1 and 2 is the same, for example, a 2000cc front engine four-wheel drive passenger car, and the side opening 92C has a width of approximately 250 mm. ], and the height is approximately 150 [mm].

(Structures of Examples and Comparative Examples)
Embodiment 1 is shown in FIG. 7A, and includes three noise reflectors 10 described in the first embodiment on the lower surface of the front side member 20 of the vehicle. Further, the front side member 20 is wider than the noise reflector 10, and the noise reflector 10 is arranged closer to the outer side of the lower surface of the front side member 20. The radius of curvature of the sound reflecting surface 11A of this noise reflector 10 is 25 [mm]. Further, in the noise reflector 10, the front side member 20 has a length along the longitudinal direction of 240 [mm], a width of 26 [mm], and a height of 26 [mm].

Example 2 is shown in FIG. 7(B) and has a structure in which the noise reflector 10 of Example 1 is replaced with a noise reflector 10V. The noise reflector 10V differs from the noise reflector 10 only in the structure of the sound reflection plate 11V. That is, the sound reflecting plate 11V of the noise reflector 10V has a flat plate shape inclined at an inclination angle of, for example, 45 [DEG] with respect to the vertical direction, and the sound reflecting surface 11A of the sound reflecting plate 11V increases as it goes downward. It is a flat surface that slopes away from the engine 30.

Comparative example 1 is shown in FIG. 7(C), and has a structure in which the noise reflector 10 of Example 1 is replaced with a noise reflector 10W instead of the noise reflector 10 of the first embodiment. . The noise reflector 10W differs from the noise reflector 10 only in the structure of the sound reflection plate 11W. That is, the sound reflecting plate 11W of the noise reflector 10W has a flat plate shape so as to be orthogonal to the lower surface of the mounting plate portion 12.

Although not shown, Comparative Example 2 has a structure in which a noise reflector is not provided on the lower surface of the front side member 20.

(experimental method)
The experiment was conducted using each of the vehicles of Examples 1 and 2 and Comparative Examples 1 and 2 described above, on an ISO road specified by ISO 10844, at a speed of 50 [km/h] at point A, which is the acceleration line, as shown in FIG. The vehicle entered the vehicle at point B, which is the acceleration end line, after driving for 20 meters after starting acceleration with the throttle fully open. The microphone position is at point P, which is the midpoint between the lines of point A and point B, and is installed at a distance of 7.5 [m] from the center of the vehicle 90 and at a height of 1.2 [m], and is located within the measurement area. The maximum noise level was taken as the measurement result.

FIG. 9 shows the measurement results of Examples 1 and 2 and Comparative Examples 1 and 2. The measurement results show that Examples 1 and 2 have lower noise levels in the frequency band 800 to 1250 [Hz] than Comparative Examples 1 and 2. As a result, in the noise reflectors 10 and 10V of Examples 1 and 2, the range of the path difference between the first path 16R and the second path 17R is 1/2 times the wavelength in the frequency band 800 to 1250 [Hz]. It is thought that it is defined as the center. In other words, it was confirmed that by providing the noise reflectors 10 and 10V of Examples 1 and 2, the noise level of the sound having the highest frequency was reduced.

Further, it can be seen that in the noise reflector 10W of Comparative Example 1, there is a region where the noise level is higher than that of Comparative Example 2 in the frequency band 800 to 1250 [Hz]. This confirms that the structure of the sound reflecting surface that directs engine sound downward is preferably such that it slopes further away from the engine 30 as it goes further downward than the upright wall facing the side opening 92C. Ta.

[Other embodiments]
(1) In the above embodiment, the sound reflecting surface 11A of the noise reflector 10 was an arcuate surface, but it is a flat surface that faces the side opening 92C and slopes away from the engine 30 as it goes downward. (see FIG. 7(B)). It is preferable that this flat surface has an inclination angle of 40 to 50 [DEG] with respect to the vertical direction and a dimension of 20 to 30 [mm] in the vertical direction. Even with such a configuration, the noise level in the frequency band of 800 to 1250 [Hz] can be reduced, as shown in Example 2 of FIG.

(2) In the above embodiment, the mounting plate portion 12 of the noise reflector 10 is stacked on the lower surface of the front side member 20, but as shown in FIG. The lower end portion may be configured to protrude below the lower surface of the front side member 20, and the mounting plate portion 12 of the noise reflector 10 may be stacked on the inner wall 22XB.

Alternatively, as shown in FIG. 10(B), the lower end portion of the inner wall 22YB that protrudes below the lower surface of the front side member 20 may be bent and overlapped with the lower surface of the front side member 20. . At this time, the mounting plate portion 12 of the noise reflector 10 may be fixed to a portion of the inner wall 22YB that overlaps the lower surface of the front side member 20.

(3) In the embodiment (2) above, the noise reflector 10 was a separate part attached to the fender liners 22X, 22Y, but it is formed integrally with the fender liners 22X, 22Y via an integral hinge. Good too.

(4) In the above embodiment, the noise reflector 10 is provided on the front side member 20 extending in the longitudinal direction in the engine compartment 93 of the vehicle 90 in which the engine 30 is mounted at the front. The vehicle 90 may have a configuration in which the noise reflector 10 is provided on a side member extending substantially over the entire length of the vehicle 90 in the front-rear direction.

(5) In the above embodiment, the distance between the pair of partition walls 15 that partitions the sound reflecting surface 11A is approximately the same as the radius of curvature of the sound reflecting surface 11A, but even if it is larger than the radius of curvature, It's fine, and it can be smaller. Further, the partition projecting wall 15 may not be provided, or one, or three or more may be provided.

(6) In the above embodiment, the noise reflector 10 was provided so as to face substantially the entire upper part of the side opening 92C, but it was provided so as to face a part of the upper part of the side opening 92C. Good too. That is, although three noise reflectors 10 were provided, there may be two or less. Moreover, four or more may be provided according to the width of the side opening 92C in the front-rear direction.

(7) In the above embodiment, the present invention is applied to the vehicle 90 equipped with the engine 30, but it may also be applied to an electric vehicle equipped with a motor or a hybrid vehicle equipped with a motor and an engine.

10 Noise reflecting part 11A Sound reflecting surface 20 Side member 90 Vehicle

Claims (8)

A noise-reducing structure that reduces engine noise passing below the side member of the vehicle and leaking to the side of the vehicle,
A noise reflecting section is provided overlappingly on the lower surface of the side member, and the noise reflecting section has a sound reflecting surface that is inclined with respect to the vertical direction so as to go downward as it moves away from the engine laterally, and the sound reflecting section A noise reduction structure that reflects engine sound received by the side member downward and interferes with engine sound passing below the side member. The sound-reducing structure according to claim 1, wherein the sound reflecting surface is an arcuate surface having a radius of curvature of 20 to 30 [mm] and a circumferential length of 30 to 50 [mm]. The sound-reducing structure according to claim 1, wherein the sound reflecting surface is a flat surface having an inclination angle of 40 to 50 [DEG] in the vertical direction and a dimension of 20 to 30 [mm] in the vertical direction. The sound deadening structure according to any one of claims 1 to 3, comprising a pair of side protruding walls that protrude from both ends of the sound reflecting surface in the front-back direction and face each other in the front-back direction. The noise reflecting section integrally includes a sound reflecting plate having the sound reflecting surface as one of the front and back surfaces, and a mounting plate extending from an edge of the sound reflecting plate to the opposite side of the sound reflecting surface. It is a resin molded product,
5. The noise reduction device according to claim 4, wherein the mounting plate portion is fixed to a lower surface of the side member or a lower edge of a fender liner that overlaps the side surface of the side member and projects downward from the side member. structure. The noise reduction structure according to any one of claims 1 to 5, further comprising a partition projecting wall that protrudes from an intermediate position in the front-rear direction of the sound-reflecting surface and partitions the sound-reflecting surface in the front-rear direction. A noise reduction method for reducing engine noise passing below a side member of a vehicle and leaking to the side of the vehicle,
A noise reduction method in which engine sound is reflected downward by a noise reflecting portion provided overlappingly on the side member and interferes with engine sound passing below the side member. The phase between the engine sound reflected by the noise reflecting section and the engine sound passing below the side member so as to reduce the noise level of the highest frequency sound among the engine sounds leaking to the side of the vehicle. 8. The noise reduction method according to claim 7, wherein

Images