JPH0428857Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an engine noise reduction device for a cab-over type vehicle.

[Prior Art] As shown in Fig. 4, in a cab-over type truck in which a cab 8 and a loading platform 5 are supported separately from a vehicle frame 3, the engine is disposed under the floor of the cab 8, so engine noise is reduced. It is propagated from under the floor in the front-rear and left-right directions, especially towards the rear.

As shown in Figures 5 and 6, in the conventional soundproofing device,
In order to suppress engine noise from propagating backwards,
An inverted U-shaped support frame 4 that supports the rear of the cab 8
A sound insulating plate 6 is supported, and the rear side of the engine or the lower side of the rear wall of the cab 8 is closed by the sound insulating plate 6.
A sound insulating plate 6 that closes the lower opening of the rear wall of the cab 8
The flange 6b formed on the periphery is placed on the support frame 4 and fixed with bolts. The sound insulating plate 6 has a main body 6a formed with a louver having an eave-shaped air guide hole 7, and is lined with a sound absorbing material. Engine noise under the floor of the cab 8 can be suppressed from propagating rearward by the louvers of the main body 6a. A part of the outside air that has flowed into the underfloor of the cab 8 flows out to the rear through the air guide hole 7 of the main body 6a.

However, in the above-mentioned soundproofing device, the noise propagated to the rear is only reduced by the sound absorbing material of the sound insulating plate, and the noise reduction effect cannot be said to be sufficient.
Since the passage area of the louver is considerably reduced, the flow of outside air becomes poor and the cooling performance of the engine is reduced.

A soundproofing device has also been proposed in which an undercover lined with a sound-absorbing material such as polyurethane is supported on the vehicle frame to cover the engine's oil pan, but this also obstructs the flow of outside air, increasing the ambient temperature around the engine. It also affects the heat resistance of auxiliary equipment such as generators.

[Problems to be solved by the invention] In view of the above-mentioned problems, the purpose of the invention is to intensively capture engine noise waves without interfering with the flow of outside air.
An object of the present invention is to provide an engine noise reduction device for a cab-over type vehicle that effectively attenuates sound by applying it to a sound absorbing member.

[Means for solving the problem] In order to achieve the above object, the configuration of the present invention is to connect an inverted U-shaped support frame to the lower part of the rear wall of the cab of the vehicle frame, and to attach a convex lens type acoustic prism to the support frame. A sound absorbing member is provided on the front wall of the loading platform facing the acoustic prism, and the acoustic prism has a number of guide plates that are inclined diagonally downward toward the rear and are arranged at equal intervals above and below;
A large number of crescent-shaped partition plates lined up at equal intervals on the left and right,
It is divided into a large number of passages that are interconnected and intersected and become gradually shorter towards the bottom.

[Operation] Most of the engine noise is reflected by the cab walls and propagated to the ground or to the rear. Noise waves propagating rearward from the engine are narrowed down by an acoustic prism, a high sound pressure portion is radiated to a sound absorbing member, and the noise waves are attenuated and absorbed by the sound absorbing member. The outside air that flows into the floor from the front of the cab to cool the engine flows out to the rear through the acoustic prism passage, so it does not have much effect on the cooling performance of the engine.

[Embodiment of the invention] As shown in FIG. 1, a support frame 4 bent in an inverted U-shape is fixed to a vehicle frame 3, and the inside of the support frame 4 has a large number of passages 19 as shown in FIG. An acoustic prism 1 is provided. One end of the acoustic prism 1 with a flat envelope surface is directed toward the engine body, and the other end with a curved envelope surface in the shape of a convex lens is directed toward the loading platform 5.
Sound absorbing member 2 made of polyurethane supported on the front wall of
is faced with.

As shown in FIGS. 2 and 3, the acoustic prism 1 includes a rectangular frame 10 that is fixed to a support frame 4, and has bolt holes 16 in both flanges 14 of the frame 10.
However, bolt holes 15 are provided in the upper and lower flanges 13, respectively.

The acoustic prism 1 has a large number of guide plates 17 that are inclined diagonally downward toward the rear and are arranged at equal intervals vertically and a large number of crescent-shaped partition plates 18 that are arranged at equal intervals on the left and right sides, and are joined together by crossing each other. It is divided into a large number of passages 19 that become gradually shorter toward the sides. That is, between the left and right crescent-shaped side wall plates 12 provided with the flanges 14, a large number of guide plates 17, which are inclined obliquely downward toward the rear, are coupled at equal intervals vertically. A plurality of partition plates 18 parallel to the side wall plates 12 are arranged between the guide plates 17 at equal intervals in the lateral direction. In reality, the partition plate 18 and the guide plate 17 are combined in a grid pattern to form a large number of passages 19.

The acoustic prism 1 may be constructed by bonding metal plates such as steel or aluminum, but it can also be integrally molded from synthetic resin, and is fixed to the support frame 4 with bolts inserted through bolt holes 15 and 16.

With the above-described configuration of the present invention, the noise waves propagating rearward from the engine are condensed by the passage 19 of the acoustic prism 1, radiated to the sound absorbing member 2, and attenuated or absorbed. The passages 19 of the acoustic prism 1 are longer on the upper side and shorter on the lower side, so that engine noise waves that enter the lower passage 19 exit from the passage 19 more quickly, It interferes with the noise waves that come out later, and pushes up the noise waves that come later. As mentioned above, the noise waves in the upper passage interfere with the noise waves emitted from the lower passage and are pushed up, and eventually the noise waves with a high noise level that have passed through the acoustic prism 1 are narrowed to the center and the noise waves are pushed up by the sound absorbing member. 2.

In a cab-over type vehicle, the upper half of the engine under the floor of the cab 8 is covered by the bottom wall, front wall, and side walls of the cab 8, so most of the engine noise is reflected by the walls of the cab 8. Propagates to the road surface or backwards. The noise waves reflected rearward and the noise waves propagated directly rearward from the engine are narrowed down by the acoustic prism 1, and the high sound pressure portion hits the sound absorbing member 2, where they are attenuated and absorbed.

The outside air that flows into the underfloor from the front of the cab 8 and cools the engine flows out to the rear through the passage 19 of the acoustic prism 1.

[Effects of the invention] As described above, the present invention connects an inverted U-shaped support frame to the lower part of the rear wall of the cab of the vehicle frame, supports a convex lens type acoustic prism on the support frame, and attaches an acoustic prism to the front wall of the cargo bed. A sound absorbing member is provided opposite the prism, and the acoustic prism has a number of guide plates that are inclined diagonally downward toward the rear and are arranged at equal intervals vertically, and a number of crescent-shaped partition plates that are arranged at equal intervals on the left and right sides. Since we have divided a number of passages that are intersected and connected and gradually become shorter toward the bottom, engine noise waves propagating backwards are narrowed down by the acoustic prism, and the high sound pressure part hits the sound absorption member, causing attenuation and absorption. be done.

The acoustic prism allows outside air that flows into the underfloor of the cab to cool the engine and then flows out to the rear through the acoustic prism passage, so it does not adversely affect the cooling performance of the engine.

Since the acoustic prism does not impair the ventilation that helps dissipate heat, placing an undercover under the engine will further improve the effect of reducing engine noise.

[Brief explanation of the drawing]

Fig. 1 is a side view of an engine noise reduction device for a cab-over type vehicle according to the present invention, Fig. 2 is a perspective view of an acoustic prism, Fig. 3 is a side sectional view of the same, and Fig. 4 is a side view of the cab-over type vehicle. FIG. 5 is a rear view showing a conventional soundproofing device for a cab-over type vehicle, and FIG. 6 is a perspective view thereof. 1...Acoustic prism, 2...Sound absorbing member, 4...
Support frame, 5... Loading platform, 17... Guide plate, 18...
Partition plate, 19...Aisle.

Claims (1)

[Scope of utility model registration request] An inverted U-shaped support frame is connected to the lower part of the rear wall of the vehicle frame, a convex lens type acoustic prism is supported on the support frame, and a sound absorbing member is provided on the front wall of the loading platform opposite to the acoustic prism. A large number of guide plates that slope diagonally downward toward the rear and are lined up at equal intervals vertically and a large number of crescent-shaped partition plates lined up at equal intervals on the left and right are combined in a way that intersects, and the lower ones are gradually An engine noise reduction device for a cab-over type vehicle, characterized by dividing a number of shorter passages.