JP2008126698A - Noise reducing structure of vehicle roof part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise reducing structure of a vehicle roof part capable of effectively reducing noise in a cabin and suppressing generation of intrinsic vibration sound at abutting parts between a roof panel and a roof trim. <P>SOLUTION: This structure is in a vehicle roof part 10 provided with the roof panel 11 and the roof trim 21 having the plurality of abutting parts 33a, 33b, 33c and 33d abutting on the roof panel 11 and disposed on the cabin side of the roof panel 11. The roof trim 21 is provided with a substrate layer 22, a low ventilation layer 32 located on an upper side of the substrate layer 22 and having the plurality of abutting parts, and a plurality of first sound absorbing materials 25a, 25b, 25c and 25d interposed between the substrate layer 22 and the low ventilation layer 32 and provided on each of the cabin sides of the abutting parts. The plurality of first sound absorbing materials 25a, 25b, 25c, and 25d is disposed in each separated state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise reduction structure for a vehicle roof portion that includes a roof panel that constitutes a vehicle body and a roof trim that is disposed on a vehicle cabin side of the roof panel.

  2. Description of the Related Art Conventionally, in vehicles such as automobiles, a noise absorbing material is applied to the roof portion (roof portion) of the vehicle to reduce the noise in the passenger compartment. The roof panel constituting the vehicle body and the roof panel 2. Description of the Related Art A noise reduction structure for a vehicle roof portion is known in which a sound absorbing material is disposed in a space portion formed between a roof trim disposed on the vehicle interior side to reduce noise in the vehicle interior.

  For example, Patent Document 1 discloses a vehicle soundproofing material in which a skin layer is laminated on the surface side of a sound absorbing layer and a sound insulating layer is laminated on at least one side of the sound absorbing layer. A soundproofing material for a vehicle is disclosed which has a multiple wall sound insulation structure between the sound insulation layer and the vehicle body panel.

In the present specification, the Young's modulus of a sound absorbing material to be described later is measured based on the techniques disclosed in Non-Patent Documents 1 to 3. In this Young's modulus measurement, a vibrator that is connected to a sound card via a power amplifier is attached to one end of a test piece made of a sound absorbing material processed into a rod shape, and a charge amplifier is attached to both ends of the test piece. A vibration pickup connected to the sound card is attached. A computer is connected to such a sound card, and a transfer function is obtained based on the vibration acceleration at both ends of the test piece measured when the test piece is vibrated, and the Young's modulus is calculated from the transfer function. The
Japanese Patent Laid-Open No. 2002-2408 Hiroshi Nakagawa, “About Acoustic Materials (2)”, [online], Internet <URL: http://www.noe.jp/news/21/21meca2.html> L.kelders, W.Lauriks, etc. “Experimental Study of the Dynamic Elastic Moduli of Porous Materials”, 11th International FASE Symposium, pp15-17 T. Pritz, etc. “Transfer Function Method for Investigating the Complex Mudulous of Acoustic Materials: Rod-Like Specimen”, Journal of Sound and Vibration (1982) 81 (3), pp359-376

  By the way, the roof trim provided in the vehicle roof portion includes a low ventilation layer (corresponding to the sound insulation layer of Patent Document 1) having low air permeability from the viewpoint of preventing dust and dirt from adhering to the roof trim. . In a vehicle having a vehicle roof portion in which a sound absorbing material for reducing noise in the vehicle interior is disposed above the low ventilation layer, noise generated in the vehicle interior, for example, high frequency sound of 800 Hz to 10 kHz is low. Since it is reflected by the ventilation layer, it is difficult to obtain a sound absorbing effect by the sound absorbing material, and it is desired to reduce the noise in the passenger compartment.

  Further, in a vehicle having a vehicle roof portion in which a sound absorbing material is disposed above the low ventilation layer, the above sound absorption is also applied to a cavity resonance sound generated in the passenger compartment, for example, a cavity resonance frequency sound of 50 Hz to 500 Hz. Since it is difficult to obtain a sound absorption effect by the material, the vehicle is required to reduce noise such as high-frequency sound in the passenger compartment and cavity resonance sound.

  On the other hand, it is possible to reduce noise in the passenger compartment, such as high-frequency sound and cavity resonance noise, by arranging a sound absorbing material on the passenger compartment side of the low vent layer. When the sound absorbing material disposed on the vehicle compartment side of the layer is formed integrally and continuously over the entire roof trim, when the roof panel vibrates, such as when the vehicle is running, There is a possibility that new natural vibration sound caused by the vibration of the roof panel is generated at the contact portion with the roof trim, and this natural vibration sound is propagated into the vehicle interior to cause new noise in the vehicle interior.

  Accordingly, the present invention has been made in view of the above technical problem, and can effectively reduce noise in the vehicle interior and generate natural vibration noise at the contact portion between the roof panel and the roof trim. It is an object of the present invention to provide a noise reduction structure for a vehicle roof portion that can suppress this.

  Therefore, the noise reduction structure for a vehicle roof portion according to claim 1 of the present application has a roof panel constituting the vehicle body and a plurality of abutting portions that abut against the roof panel, and is arranged on the vehicle compartment side of the roof panel. A noise reduction structure for a vehicle roof part provided with a roof trim provided, wherein the roof trim is located above the base material layer and has a plurality of contact parts located above the base material layer. And a low ventilation layer having a lower air permeability than the base material layer, and a plurality of the air gaps interposed between the base material layer and the low air permeability layer and provided on the vehicle compartment side of the plurality of contact portions, respectively. A plurality of first sound absorbing materials, wherein the first sound absorbing materials are arranged in a state of being separated from each other.

  Further, in the invention according to claim 2 of the present application, in the invention according to claim 1, there is a space between the roof panel and the roof trim at a portion where the roof panel and the roof trim do not contact each other. It is formed, and the second sound absorbing material is disposed in the space portion.

  Furthermore, in the invention according to claim 3 of the present application, in the invention according to claim 2, the amount of vibration is low in the base material layer due to low / medium frequency sound of 100 Hz to 799 Hz. The vibration part which increases more is provided, At least one part of the said 2nd sound-absorbing material is arrange | positioned in the position corresponding to the said vibration part, It is characterized by the above-mentioned.

  Still further, the invention according to claim 4 of the present application is characterized in that, in the invention according to any one of claims 1 to 3, the first sound absorbing material absorbs a high frequency sound of 800 Hz to 10 kHz. It is a thing.

  Still further, the invention according to claim 5 of the present application is the invention according to any one of claims 1 to 3, wherein the first sound absorbing material emits a cavity resonance frequency sound of 50 Hz or more and 500 Hz or less generated in the vehicle interior. It is characterized by absorbing sound.

  Furthermore, the invention according to claim 6 of the present application is the invention according to any one of claims 2 to 5, wherein the second sound absorbing material absorbs low / medium frequency sound of 100 Hz to 799 Hz. It is a feature.

  Still further, the invention according to claim 7 of the present application is the invention according to any one of claims 1 to 6, wherein the first sound absorbing material has a length in the vehicle front-rear direction of 85 cm or more. It is what.

  Here, the length of the first sound absorbing material in the vehicle front-rear direction is set to 85 cm or more because when the cavity resonance frequency sound of 50 Hz to 500 Hz is absorbed by the first sound absorbing material, at least 1 / By using the first sound-absorbing material having a length of 85 cm or more, which is 1/8 wavelength of 50 Hz having the largest wavelength in the range of 8 wavelengths or more, that is, 50 Hz to 500 Hz, the sound-absorbing effect by the first sound-absorbing material It is because it can be obtained substantially.

  Still further, the invention according to claim 8 of the present application is the invention according to any one of claims 2 to 7, wherein the second sound absorbing material has a length in the vehicle front-rear direction of 43 cm or more. It is what.

  Here, the length of the second sound absorbing material in the vehicle front-rear direction is set to 43 cm or more when at least one of the sound waves when absorbing the low / medium frequency sound of 100 Hz to 799 Hz by the second sound absorbing material. By using the second sound absorbing material having a length of 43 cm or more corresponding to 1/8 wavelength of 100 Hz having the largest wavelength in the range of / 8 wavelengths or more, that is, 100 Hz or more and 799 Hz or less, the second sound absorbing material is used. This is because a sound absorption effect can be substantially obtained.

  According to the noise reduction structure for a vehicle roof portion according to claim 1 of the present application, since the first sound absorbing material is provided on the vehicle interior side of the low ventilation layer, noise in the vehicle interior can be effectively reduced. Since the first sound-absorbing material is disposed in the vehicle compartment side of the abutting portion of the low ventilation layer that abuts against the roof panel, natural vibration noise is generated at the abutting portion between the roof panel and the roof trim. Generation | occurrence | production can be suppressed.

  According to the second aspect of the present invention, since the second sound absorbing material is disposed in the space formed between the roof panel and the roof trim, the second sound absorbing material is disposed from the vehicle interior via the roof trim. Noise propagated in the space can be absorbed, and noise in the passenger compartment can be further reduced.

  Furthermore, according to the invention of claim 3 of the present application, the distribution of the particle velocities of the low / medium frequency sound propagated in the space is directed from the substantially vertical direction to the substantially parallel direction of the roof trim so that the low / medium frequency sound is directed. The sound-abdominal portion of the sound wave can be effectively taken in by the second sound-absorbing material, and the sound-absorbing performance of the low / medium frequency sound can be improved, and the noise in the passenger compartment can be further reduced.

  Furthermore, according to the invention which concerns on Claim 4 of this application, the sound absorption property with respect to the high frequency sound of 800 Hz or more and 10 kHz or less of a vehicle interior can be improved, and the said effect can be show | played effectively.

  Still further, according to the invention of claim 5 of the present application, it is possible to improve the sound absorption for the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less generated in the vehicle interior, and the above effect can be effectively achieved.

  Furthermore, according to the invention according to claim 6 of the present application, it is possible to improve sound absorption for low / medium frequency sound of 100 Hz or more and 799 Hz or less propagated from the vehicle interior through the roof trim into the space portion, The said effect can be show | played more effectively.

  Furthermore, according to the invention according to claim 7 of the present application, when the length of the first sound absorbing material in the longitudinal direction of the vehicle is 85 cm or more, the energy is maximum in the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less. The abdominal portion of the sound wave can be effectively taken in by the first sound absorbing material, and the above effect can be obtained effectively.

  When the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less is absorbed by the first sound absorbing material, the first sound absorbing material having a length of at least 1/8 wavelength of the sound wave of the cavity resonance frequency sound, that is, a length of 85 cm or more is used. By using, the sound absorbing effect by the first sound absorbing material can be substantially obtained.

  Furthermore, according to the invention according to claim 8 of the present application, the length of the second sound absorbing material in the vehicle front-rear direction is set to 43 cm or more, so that the energy is maximum in low / medium frequency sound of 100 Hz to 799 Hz. The abdominal part of a certain sound wave can be taken in effectively by the second sound absorbing material, and the above effect can be obtained effectively.

  When a low / medium frequency sound of 100 Hz or more and 799 Hz or less is absorbed by the second sound absorbing material, a second sound absorbing material having a length of at least 1/8 wavelength of the sound wave of the low / medium frequency sound, that is, a length of 43 cm or more. By using the material, the sound absorbing effect by the second sound absorbing material can be substantially obtained.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an explanatory plan view of a vehicle including a vehicle roof portion according to a first embodiment of the present invention, FIG. 2 is an explanatory cross-sectional view of the vehicle in the longitudinal direction of the vehicle, and FIG. FIG. 4 is an explanatory plan view showing a roof trim of the vehicle.

  As shown in FIGS. 1 and 2, the vehicle 1 including the vehicle roof portion according to the present embodiment is a vehicle such as a one-box vehicle, and a vehicle interior space 3 is formed in the vehicle body 2 of the vehicle 1. ing. A vehicle roof portion 10 that forms a roof portion (roof portion) of the passenger compartment space 3 includes a roof panel 11 that constitutes the vehicle body 2 and a roof trim 21 that is disposed on the passenger compartment space 3 side of the roof panel 11. I have.

  The roof panel 11 is formed in a substantially flat plate shape, and is formed in a substantially rectangular shape elongated in the vehicle front-rear direction as shown in FIG. As shown in FIG. 3, the roof panel 11 is formed with bulging portions 12a, 12b, 12c, and 12d that bulge from the roof panel 11 to the vehicle body lower side. The bulging portions 12a, 12b, 12c, 12d extends in the vehicle width direction. Further, the bulging portions 12a, 12b, 12c, and 12d are provided on the roof panel 11 in a state of being separated from each other in the vehicle front-rear direction.

  On the other hand, as shown in FIG. 2, the roof trim 21 includes a base material layer 22 that is positioned above the seat 4 and the like disposed in the passenger compartment space 3 and defines the upper portion of the passenger compartment space 3. The material layer 22 has air permeability. As shown in FIG. 3, the substantially flat base material layer 22 is formed to be curved upward and convex, and both ends in the vehicle front-rear direction are bent upward.

  In addition, the roof trim 21 includes a low ventilation layer 32 having a lower air permeability than the base material layer 22 above the base material layer 22. As shown in FIG. 3, the low ventilation layer 32 formed in a substantially flat plate shape is overlapped with the base material layer 22 and protrudes upward, specifically, the roof panel 11, specifically, the bulging portion 12 a of the roof panel 11. , 12b, 12c, 12d are provided with contact portions 33a, 33b, 33c, 33d. The contact portions 33a, 33b, 33c, and 33d extend in the vehicle width direction corresponding to the bulging portions 12a, 12b, 12c, and 12d, respectively.

  In the vehicle roof portion 10 according to the present embodiment, first sound absorbing materials 25 a, 25 b, 25 c, and 25 d are disposed between the base material layer 22 and the low ventilation layer 32 that constitute the roof trim 21. The first sound absorbing materials 25a, 25b, 25c, and 25d are disposed in a state of being separated from the abutting portions 33a, 33b, 33c, and 33d of the low ventilation layer 32, respectively, and extend in the vehicle width direction. .

  As said 1st sound-absorbing material 25a, 25b, 25c, 25d, what absorbs the high frequency sound of 800 Hz or more and 10 kHz or less of a vehicle interior can be used, Thereby, 800 Hz or more and 10 kHz or less of vehicle interior space are used. Sound absorption for high frequency sound can be improved.

  As shown in FIG. 4, the roof trim 21 has a rear mirror opening 41, a room lamp opening 42, a sun visor opening 43, an assist grip opening 44, a fastener opening 45, and the like. Is formed.

  FIG. 5 is an explanatory diagram for explaining the noise generated in the passenger compartment space of the vehicle. As shown in this figure, when the vehicle 1 travels on an uneven road surface 5, vibrations from the road surface 5 are transmitted to the vehicle body 2 via tires 6 and suspensions (not shown), and the vehicle interior space 3 Road noise.

  In the passenger compartment 3 of the vehicle 1, noise having various frequencies including road noise is generated. Low and medium frequency noises of 100 Hz to 799 Hz, high frequency noises of 800 Hz to 10 kHz, etc. Has occurred. Further, low / medium frequency sounds having relatively long wavelengths resonate with each other according to the shape of the vehicle body 2, for example, the shape of the passenger compartment space 3, and the particle velocity distribution as indicated by a two-dot chain line L1 in FIG. A cavity resonance frequency sound of 50 Hz to 500 Hz is generated.

In this embodiment, the test for measuring the cavity resonance frequency sound generated in the passenger compartment 3 in the vehicle 1 was performed.
FIG. 6 is an explanatory diagram for explaining a method for measuring the cavity resonance frequency sound generated in the passenger compartment space. As shown in FIG. 6, a speaker 8 is arranged on the floor 7 on the front side of the vehicle body in the passenger compartment space 3 of the vehicle 1 to generate various frequency sounds from the speaker 8 at a position indicated by a two-dot chain line L2. The cavity resonance frequency sound generated in the passenger compartment 3 was measured.

  FIG. 7 is a graph showing the measurement result of the cavity resonance frequency sound generated in the passenger compartment space. In FIG. 7, the horizontal axis represents the measurement position and the vertical axis represents the particle velocity of the cavity resonance frequency sound, and various frequency sounds generated from the speaker 8, specifically, 308 Hz, 360 Hz, 430 Hz, 500 Hz, The measurement results measured for a frequency sound of 550 Hz are shown by a thick solid line A1, a broken line A2, a one-dot chain line A3, a two-dot chain line A4, and a thin solid line A5. In FIG. 7, the position P1 shown in FIG.

  As shown in FIG. 7, the particle velocity of the cavity resonance frequency sound generated in the passenger compartment space 3 is 308 Hz (A 1), 360 Hz (A 2), 430 Hz (A 3) frequency sound with low frequency sound from the speaker 8. In this case, it was found that the peak of the particle velocity distribution of the cavity resonance frequency sound is larger than that of the frequency sound of 500 Hz (A4) and 550 Hz (A5) where the frequency sound from the speaker 8 is high.

  Further, the particle velocity of the cavity resonance frequency sound generated in the passenger compartment space 3 becomes large at a predetermined measurement position. In this embodiment, the regions S1, S2, and S3 surrounded by the two-dot chain line in FIG. It turned out that it has become large in the position of 60-80 cm, 170-200 cm, and 220-250 cm.

  Therefore, in the vehicle roof portion 10, specifically, the measurement position at which the peak of the particle velocity distribution increases corresponding to the portion where the peak of the particle velocity distribution of the cavity resonance frequency sound generated in the passenger compartment space 3 increases. 1st sound-absorbing material 25a, 25c, 25d is arrange | positioned at the roof trim 21 in the upper side. That is, the first sound absorbing material 25a is disposed above the vicinity of the measurement position 60 to 80 cm, the first sound absorbing material 25c is disposed above the vicinity of the measurement position 170 to 200 cm, and above the measurement position 220 to 250 cm. The first sound-absorbing material 25d is disposed at the bottom. In the present embodiment, the first sound absorbing material 25b is also provided above the vicinity of the measurement position 110 to 130 cm.

  Thus, in the present embodiment, the first sound absorbing materials 25a, 25c, and 25d are located at positions corresponding to the peaks of the particle velocity distribution of the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less generated in the passenger compartment space 3. It is arranged. In addition, as the first sound absorbing material 25a, 25c, 25d, by using a material that absorbs a cavity resonance frequency sound of 50 Hz or more and 500 Hz or less generated in the passenger compartment space, 50 Hz or more and 500 Hz or less generated in the passenger compartment space is used. Sound absorption with respect to the cavity resonance frequency sound can be improved.

  Further, the first sound absorbing materials 25a, 25c, and 25d are formed such that their lengths W1, W2, and W3 in the vehicle front-rear direction are 85 cm or more. Thereby, the antinode part of the sound wave with the maximum energy in the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less can be effectively taken in by the first sound absorbing material.

  When the cavity resonance frequency sound of 50 Hz or more and 500 Hz or less is absorbed by the first sound absorbing material 25a, 25c, 25d, at least 1/8 wavelength of the sound wave of the cavity resonance frequency sound, that is, in the range of 50 Hz or more and 500 Hz or less. By using the first sound absorbing material having a length of 85 cm or more corresponding to 1/8 wavelength of 50 Hz having the largest wavelength, the sound absorbing effect by the first sound absorbing material can be substantially obtained.

In the present embodiment, the base layer 22 of the roof trim 21 has a Young's modulus of, for example, 1.4E + 05 (N / m) at the portion where the first sound absorbing materials 25a, 25b, 25c, and 25d are disposed. ² ) to 1.9E + 05 (N / m ² ), and can be molded using, for example, urethane or a fiber material.

On the other hand, the low air permeability layer 32 of the roof trim 21 has lower air permeability than the base material layer 22, and when the air permeability is expressed by flow resistance, the flow is 4.0E + 07 (N · s / m ⁴ ) or more. It preferably has a resistance. As this low air permeability layer, for example, a nonwoven fabric or a resin thin film material can be used.

The first sound absorbing materials 25a, 25b, 25c, and 25d preferably have a flow resistance of 10,000 (N · s / m ⁴ ) or less with respect to the cavity resonance frequency sound, and with respect to the high frequency sound. It is preferable that it has a flow resistance of 100,000 to 1,000,000 (N · s / m ⁴ ). When the flow resistance is 100,000 (N · s / m ⁴ ) or less, the sound absorbing material is deteriorated in sound insulation, and when it is 1,000,000 (N · s / m ⁴ ) or more. This is because the sound absorption is deteriorated. As the first sound absorbing materials 25a, 25b, 25c, and 25d, for example, urethane or a fiber material can be used.

  Thus, according to the noise reduction structure of the vehicle roof portion 10 according to the present embodiment, the first sound absorbing members 25a, 25c, and 25d are provided on the vehicle interior side of the low ventilation layer 32. The first sound-absorbing materials 25a, 25b, 25c, and 25d can be effectively reduced and the vehicle interior side of the abutting portions 33a, 33b, 33c, and 33d of the low ventilation layer 32 that abuts against the roof panel 11 is provided. Since it arrange | positions in the state spaced apart, it can suppress that a natural vibration sound generate | occur | produces in the contact part of a roof panel and a roof trim.

  For example, when the roof panel vibrates, such as when the vehicle is running, when the first sound absorbing material is arranged in a continuous state, the rigidity of the first sound absorbing material and the base material layer is large and the roof trim is compared. However, when the first sound absorbing material is divided and disposed, the base material layer on which the first sound absorbing material is not disposed has a low rigidity and a low roof trim.・ Can be vibrated at medium frequency.

  FIG. 8 is a cross-sectional explanatory view in the vehicle front-rear direction of the vehicle roof portion according to the second embodiment of the present invention, and FIG. 9 is a plan explanatory view showing the roof trim of the vehicle. FIG. 9 also shows a second sound absorbing material interposed between the roof panel and the roof trim. About the vehicle roof part which concerns on 2nd Embodiment, the same code | symbol is attached | subjected about what has the structure similar to the vehicle roof part which concerns on 1st Embodiment, and performs the same effect | action, and the further description is abbreviate | omitted. .

  As shown in FIG. 8, the vehicle roof portion 50 according to the second embodiment includes a roof panel 11 and a roof trim 51, like the vehicle roof portion 10 according to the first embodiment. The base material layer 52, the low ventilation layer 32, and the first sound absorbing materials 25a, 25b, 25c, and 25d are provided. In the vehicle roof portion 50, the roof panel is provided between the roof panel 11 and the roof trim 51. The second sound absorbing materials 36a, 36b, and 36c are disposed in the space portions 35a, 35b, and 35c formed in the portions where the 11 and the roof trim 51 do not contact each other. In addition, as the second sound absorbing material 36a, 36b, 36c, for example, urethane or fiber material can be used, and it is preferable to use fiber material for low / medium frequency sound.

  Further, in the vehicle roof portion 50, the base material layer 52 is provided with vibration portions 53 a, 53 b, and 53 c in which the amount of vibration due to low / medium frequency sound of 100 Hz to 799 is greater than other portions of the base material layer 52. Yes. The vibration parts 53a, 53b, and 53c are formed in portions where the base material layer 52 and the low ventilation layer 32 are overlapped, and the second sound absorbing material 36a and the vibration parts 53a, 53b, and 53c are disposed above the vibration parts 53a, 53b, and 53c, respectively. 36 b and 36 c are arranged via the low air-permeable layer 32.

  Thus, in this embodiment, the vibration parts 53a, 53b, and 53c in which the vibration amount is increased in the base material layer 52 by the low / medium frequency sound of 100 Hz or more and 799 Hz or less than other parts of the base material layer 52. And at least a part of the second sound absorbing material 36a, 36b, 36c is disposed at a position corresponding to the vibrating portions 53a, 53b, 53c. As the second sound absorbing material 36a, 36b, 36c, a material that absorbs low / medium frequency sound of 100 Hz or more and 799 Hz or less in the vehicle interior is used and is transmitted from the vehicle interior to the space through the roof trim. In addition, it is possible to improve sound absorption for low and medium frequency sounds.

  The second sound absorbing materials 36a, 36b, and 36c are formed such that their lengths W11, W12, and W13 in the vehicle front-rear direction are 43 cm or more, respectively. Thereby, the antinode part of the sound wave with the maximum energy in the low / medium frequency sound of 100 Hz to 799 Hz can be effectively taken in by the second sound absorbing material.

  When low / medium frequency sound of 100 Hz to 799 Hz is absorbed by the second sound absorbing material 36a, 36b, 36c, at least 1/8 wavelength of the sound wave of the low / medium frequency sound, that is, a range of 100 Hz to 799Hz or less. Among them, by using the second sound absorbing material having a length of 43 cm or more corresponding to 1/8 wavelength of 100 Hz having the largest wavelength, the sound absorbing effect by the second sound absorbing material can be substantially obtained.

The base material layer 52 of the roof trim 51 preferably has a Young's modulus of, for example, 1.4E + 05 (N / m ² ) to a portion where the first sound absorbing materials 25a, 25b, 25c, and 25d are disposed. Although it is set to 1.9E + 05 (N / m ² ), the Young's modulus of the portion where the second sound absorbing materials 36a, 36b, 36c are disposed, for example, the vibrating portions 53a, 53b, 53c is, for example, 8. It is preferably set to 0E + 04 (N / m ² ) to 1.1E + 04 (N / m ² ). In addition, the base material layer 52 distributes the particle velocity distribution of low and medium frequency sound in the vehicle interior transmitted to the base material layer 52 in a substantially vertical direction from the base material layer 52 and, in turn, the roof trim 51 in a substantially vertical direction. The Young's modulus is suitably set so as to be directed in the direction.

  As described above, according to the noise reduction structure of the vehicle roof portion 50 according to the present embodiment, the second sound absorbing material 36a and the space portions 35a, 35b, and 35c formed between the roof panel 11 and the roof trim 51 are provided. Since 36b and 36c are arrange | positioned, the noise propagated in the said space part via the roof trim from the vehicle interior can be absorbed, and the noise in a vehicle interior can further be reduced.

  Further, the particle velocity distribution of the low / medium frequency sound propagated in the space portion is directed from the substantially vertical direction to the substantially parallel direction of the roof trim, and the antinode portion of the sound wave of the low / medium frequency sound is caused by the second sound absorbing material. It can be taken in effectively, improving the sound absorption performance of low / medium frequency sound and further reducing the noise in the passenger compartment.

  In the case where low and medium frequency sound in the passenger compartment is effectively absorbed by the second sound absorbing material, the second sound absorbing material is arranged substantially in the vertical direction of the roof trim because the wavelength of the sound wave of the low and medium frequency sound is relatively long. In the present embodiment, the second sound absorption in the substantially vertical direction of the roof trim is achieved by directing the low / medium frequency sound in the vehicle interior from the substantially vertical direction of the roof trim to the substantially parallel direction. Without increasing the thickness of the material, it is possible to effectively take in the antinodes of low and medium frequency sound waves directed in the substantially parallel direction of the roof trim by the second sound absorbing material.

  In the present embodiment, in the vehicle roof portion 10 according to the first embodiment, the base material layer 22 and the low ventilation layer 32 are overlapped at portions where the first sound absorbing materials 25a, 25b, and 25c are not provided. However, a sound absorbing space may be provided between the base material layer 22 and the low ventilation layer 32.

  In this embodiment, the roof panel 11 is provided with the bulging portions 12a, 12b, 12c, and 12d, and the bulging portions 12a, 12b, 12c, and 12d and the roof trim 21 are in contact with each other. Further, a roof panel reinforcement for reinforcing the roof panel may be provided so as to bulge downward from the roof panel, and the roof panel reinforcement and the roof trim may be brought into contact with each other.

  As described above, the present invention is not limited to the illustrated embodiments, and it goes without saying that various improvements and design changes can be made without departing from the gist of the present invention.

  The present invention can effectively reduce noise in a vehicle interior and can reduce noise generated in a vehicle roof portion that can suppress generation of natural vibration noise at a contact portion between a roof panel and a roof trim. For example, it can be suitably applied to a roof portion of a vehicle such as a one-box vehicle.

It is plane explanatory drawing of the vehicle provided with the vehicle roof part which concerns on the 1st Embodiment of this invention. It is a cross-sectional explanatory drawing in the vehicle body front-back direction of the said vehicle. It is sectional explanatory drawing which shows the roof part of the said vehicle. It is a plane explanatory view showing the roof trim of the above-mentioned vehicle. It is explanatory drawing for demonstrating the noise which arises in the vehicle interior space of the said vehicle. It is explanatory drawing for demonstrating the measuring method of the cavity resonance frequency sound which arises in vehicle interior space. It is a graph which shows the measurement result of the cavity resonance frequency sound which arises in vehicle interior space. It is a section explanatory view in the direction of vehicles body of a vehicle roof part concerning a 2nd embodiment of the present invention. It is a plane explanatory view showing the roof trim of the above-mentioned vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Car body 10, 50 Vehicle roof part 11 Roof panel 21, 51 Roof trim 22, 52 Base material layer 25a, 25b, 25c, 25d 1st sound-absorbing material 32 Low ventilation layer 33a, 33b, 33c, 33d Contact part 35a, 35b, 35c Space portion 36a, 36b, 36c Second sound absorbing material 53a, 53b, 53c Vibrating portion

Claims (8)

  A noise reduction structure for a vehicle roof portion comprising a roof panel constituting a vehicle body, and a roof trim having a plurality of abutting portions that abut against the roof panel and disposed on a cabin side of the roof panel. The roof trim includes a base material layer having air permeability, a low air permeability layer positioned above the base material layer, having the plurality of contact portions and having lower air permeability than the base material layer, and A plurality of first sound absorbing materials interposed between the base material layer and the low ventilation layer and provided on the vehicle compartment side of the plurality of contact portions, respectively. A noise reduction structure for a vehicle roof portion, wherein the first sound absorbing materials are disposed in a state of being separated from each other.   2. The noise reduction structure for a vehicle roof portion according to claim 1, wherein a space portion is formed between the roof panel and the roof trim at a portion where the roof panel and the roof trim are not in contact with each other. A noise reduction structure for a vehicle roof part, wherein a second sound absorbing material is disposed in the part.   3. The vehicle roof noise reduction structure according to claim 2, wherein the base material layer has a vibration in which a vibration amount is increased more than other parts of the base material layer due to low / medium frequency sound of 100 Hz to 799 Hz. And a noise reduction structure for a vehicle roof portion, wherein at least a part of the second sound absorbing material is disposed at a position corresponding to the vibration portion.   4. The vehicle roof portion noise reduction structure according to claim 1, wherein the first sound absorbing material absorbs a high frequency sound of 800 Hz to 10 kHz. 5. Noise reduction structure.   The noise reduction structure for a vehicle roof part according to any one of claims 1 to 3, wherein the first sound absorbing material absorbs a cavity resonance frequency sound of 50 Hz or more and 500 Hz or less generated in the vehicle interior. A noise reduction structure for the vehicle roof.   6. The vehicle roof noise reduction structure according to claim 2, wherein the second sound absorbing material absorbs low / medium frequency sound of 100 Hz to 799 Hz. Noise reduction structure of the part.   7. The vehicle roof portion noise reduction structure according to claim 1, wherein the first sound absorbing material has a length of 85 cm or more in the vehicle front-rear direction. 8. Noise reduction structure.   The vehicle roof part noise reduction structure according to any one of claims 2 to 7, wherein the second sound absorbing material has a length in the vehicle front-rear direction of 43 cm or more. Noise reduction structure.

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