JPH10100812A - Lower part structure of car body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for reducing out-car noises by attenuating sound generated from a car at the lower part of a car body. SOLUTION: A transmission 3, etc., is interposed at a space between the floor pane 9 of a car body and an undercover 8 at the lower part of the floor panel. Stand surfaces 16 are formed at the undercover 8 at its both the edges, respectively. Each frame is fixed at spaced intervals. Each screen 10 is sandwiched between each stand surface and each frame and is suspended from the floor panel 9 to form each snaked gap 17. Emitting a driving noise and an exhaust noise from the gaps 17 reduces out-car noises. Extending a side sill 18 to increase the distance between the gap 17 evolves a noise reduction effect. Mounting a sound absorbing material on the reflecting surface of emitting sound enhances noise reduction effect. This structure has air permeability, eliminating the user of a member having high heat resistance. Costs are reduced owing to the simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Since engine sounds and running sounds of a vehicle are noises for a driver, clearances on the floor are eliminated and rigidity is increased so as to improve sound insulation in the vehicle. Also, an under cover is mounted below the engine of the vehicle body so that noise does not leak outside the vehicle. The present invention relates to a lower body structure for dealing with the noise transmitted to the outside.

[0002]

2. Description of the Related Art Conventionally, noise in an automobile is reduced by shielding an engine, a transmission, an exhaust pipe, and the like to cut off sound and prevent sound leakage. As an example, in the automobile shown in FIG. 5, an engine 2, a transmission 3, and an exhaust muffler 4 are mounted on a frame 1, and a sound absorbing material 7 is mounted on a dash panel 5 and a hood 6, so that noise does not enter the vehicle. I have. In addition, there is also a type in which a noise absorbing material is attached to the floor panel to prevent noise inside the vehicle body (Japanese Patent Laid-open No. Hei 7-1995).
277102).

In FIG. 5, an under cover 8 is provided below the frame 1 so that these noises are reflected on the ground and do not leak outside. The sound absorbing material 7 is attached to the under cover 8 to lower the sound pressure level of the reflected sound, thereby reducing the radiation outside the vehicle such as engine noise, drive system noise, and exhaust system noise. As shown in FIG. 6, an under cover 8 is provided below the transmission 3 and the exhaust muffler 4 on a frame 1 disposed on both sides of a lower portion of the vehicle body in the front-rear direction, and a sound absorbing material 7 is provided on an upper portion of the under cover. In addition, a floor panel (iron plate) 9 covering the transmission 3 and the exhaust muffler 4 is connected to the frame 1 with another member, and a partition 10 is provided at this location to close a gap therebetween. There is. In this configuration, the area around the sound source is closed, which is effective in preventing noise. Reference numeral 11 denotes the propeller shaft of the engine, and reference numeral
Reference numeral 12 denotes a tire, and reference numeral 13 denotes a steering.

In the above configuration, since the entire sound source is covered, the sound source becomes large, the weight increases, and the cost increases. Therefore, there is also a noise prevention structure in which a vehicle body frame is attached to the lower surface of the floor panel via a sound absorbing material and a sound insulating material ( See JP-A-7-285396). As shown in FIG. 7, the sound absorbing material 7 mounted on the lower surface of the floor panel 9 and the sound insulating material 14 and the sound absorbing material 7 mounted on the lower part of the frame 1 prevent noise inside the vehicle, and radiate and radiate noise outside the vehicle. The level will be reduced.

[0005]

However, in the above-described noise prevention structure in a closed state, since the surroundings of the sound source are tightly shielded, the effect of reducing noise outside the vehicle is large, but the heat radiation to the outside of the vehicle is poor and the noise prevention structure is overheated. There is a danger that a member having high heat resistance will be used at this location. Further, the noise prevention structure shown in FIG. 7 is such that the sound radiated from the transmission 3, the exhaust muffler 4, and the engine (propeller shaft 11) is reflected on the road surface 15 or the floor panel 9 as shown by the arrow, and the sound is emitted outside the vehicle. Because of the emission, the effect of reducing noise outside the vehicle is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle body lower structure capable of attenuating sound generated in a vehicle and reducing noise outside the vehicle.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pair of undercovers provided at the lower part of a vehicle body, which are provided with upright surfaces at both ends on the vehicle width side, and which extend on both sides of the vehicle body in the front-rear direction. The frame is mounted on the undercover inside the upright surface, and a screen is mounted on the floor panel above the undercover so as to hang between the frame and the upright surface.

Further, a side sill communicating with an end of the floor panel in the vehicle width direction is extended downward so as to cover an upright surface of the undercover.

Further, a sound absorbing material is attached to each of the side sill, the undercover, and the screen at a position inside the vehicle body.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An under cover of an automobile according to the present invention is provided with an under cover below a floor panel covering an engine, a transmission and the like, that is, below an engine and a transmission. (In this state, driving noise (including exhaust noise) generated by the engine, transmission, and the like is emitted to the outside of the vehicle body while being reflected by the undercover and the floor panel.)

An upright surface is formed at an end of the undercover in the vehicle width direction, and a frame is provided at an interval inside the upright surface. A partition is provided between the upright surface and the frame from a floor panel. It is hung down and the gap at this point is in a meandering state. Therefore, the driving sound radiated outward is radiated while being reflected on the frame, the screen, and the upright surface. Thereby, the noise outside the vehicle can be reduced.

Further, when the side sill is extended downward and the gap in the meandering state is lengthened, the number of reflections of the driving sound increases, and the noise outside the vehicle is reduced. Therefore, by providing the partition inside the frame, the gap in the meandering state becomes longer. Further, by attaching a sound absorbing material to the surface on which the driving sound is reflected, the driving sound is absorbed on the reflecting surface.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, frames 1 arranged on both sides of the vehicle body extend in the front-rear direction of the vehicle body, and a floor panel 9 is disposed above the frame 1 via a member (not shown). An undercover 8 provided between the frames 1 and 1 is fixed to a lower portion of the frame 1. Thus, the transmission 3, the exhaust muffler 4, and the propeller shaft 11 are located between the floor panel 9 and the under cover 8. Reference numeral 12 denotes a tire, and reference numeral 13 denotes a steering.

Undercover 8 fixed to frame 1
Is extended laterally, and the end is bent upward to form an upright surface 16. From the floor panel 9, a partition 10 is hung between the frame 1 and the upright surface 16, and a meandering gap 17 is formed at this location. Driving noises and the like are radiated from the gap 17 and become external noise. The frequency (f) characteristic of the external noise peak value generally spreads around 1 kHz as shown in FIG. Therefore, in consideration of sound diffraction, it is necessary to set the meandering gap passage to a wavelength or more. Here, the wavelength λ is represented by the following equation. .lambda. = C / f C: sound speed The frequency (f) of the noise peak value outside the vehicle is relatively high frequency, so that the passage length can be short, so that it is sandwiched between the undercover 8 and the floor panel 9. In the space,
The frame 1, the partition 10, and the upright surface 16 protrude as obstacles to form a meandering gap (passage) 17.

As described above, by forming the structure of the lower part of the vehicle body, the drive sound (exhaust sound) generated by the engine, the transmission and the like is reflected by the under cover 8 and the floor panel 9 while the frame 1, the partition 10 and the , Standing face
It is released to the outside of the vehicle body through the space between the vehicle and the vehicle, whereby the driving noise is reduced and the noise outside the vehicle can be reduced.
Also, since the lower structure has ventilation, unlike the closed type, a member having low heat resistance can be used, and the cost can be reduced because of the simple structure.

In FIG. 1, the drive sound is reflected by the side sill 18 and radiated to the outside by making the side sill 18 extend downward from the prior art. Therefore, external noise is further reduced.

In addition, as shown in FIG.
The sound absorbing material 7 is mounted on the upper surface of the under cover 8, inside the partition 10, and inside the side sill 18. As a result, the driving sound is absorbed by the reflection surface, and the driving sound is reduced, thereby increasing the effect of reducing the noise outside the vehicle.

[0018]

Since the present invention is constructed as described above, the diffraction of driving sound, exhaust sound, etc. is taken into account in the lateral gap between the floor panel and the undercover,
Since the gap is formed in the meandering passage, noise outside the vehicle can be reduced. In addition, since the number of reflections is increased by the side sill and the sound absorbing material is provided on the reflection surface, noise outside the vehicle can be further reduced. In addition, since the lower body structure can reduce radiation noise outside the vehicle without tightly shielding around the sound source, there is no need to use a member having high air permeability and high heat resistance. By structure
Cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a vehicle body lower structure according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a sound absorbing material is arranged in the lower body structure shown in FIG.

FIG. 3 is a graph showing a frequency distribution of peak values of outside noise of the vehicle body shown in FIG. 1;

FIG. 4 is a graph showing the noise reduction effect outside the vehicle according to the present invention.

FIG. 5 is a side sectional view showing a vehicle body lower structure of a conventional automobile.

6 is a cross-sectional view of the lower body structure shown in FIG.

FIG. 7 is a cross-sectional view showing another conventional vehicle body lower structure.

[Explanation of symbols]

 1 Frame 7 Sound absorbing material 8 Under cover 9 Floor panel 10 Screen 16 Standing surface 18 Side sill

Claims (3)

[Claims] 1. An undercover provided at a lower part of a vehicle body is provided with upright surfaces at both ends on a vehicle width side, and a pair of frames extending in the front-rear direction on both sides of the vehicle body are mounted on the undercover inside the upright surface. A lower body structure of a vehicle, wherein a partition is attached to a floor panel above the undercover so as to hang between the frame and the upright surface. 2. The underbody structure according to claim 1, wherein a side sill communicating with an end of the floor panel in the vehicle width direction is extended downward so as to cover an upright surface of the undercover. 3. The lower body structure according to claim 1, wherein a sound absorbing material is mounted on each of the side sill, the undercover, and the screen at a position inside the vehicle body.