JP2002129974A - Engine cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce noise from an engine by reducing resonance sound in addition to sound absorption by an acoustic material. SOLUTION: A cover body 10 has a through-hole 12 passing through the top side and rear faces thereof at a portion opposed to a resonance space 3 generating resonance sound, and the opening of the through-hole 12 is closed by an acoustic material layer 11. Thereby, since a part of the resonance space 3 is opened, resonance sound generating in the space 3 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cover used for an automobile or the like, and more particularly, to a structure of an engine cover capable of further reducing noise.

[0002]

2. Description of the Related Art In an engine room of a recent automobile, an engine cover is provided above a cylinder head cover of an engine. The engine cover is formed in a plate shape from a thermoplastic resin or the like, and the design is enhanced by, for example, design letters and patterns being drawn on the surface and the color tone being a warm color tone.

It is also required that the engine cover shield the sound radiated from the engine to reduce the noise leaking from the engine room. A hard cover body and a sound absorbing material laminated on the surface of the cover body facing the engine are also required. An engine cover composed of layers is also used. By laminating the sound absorbing material layers in this manner, the sound absorbing material layers absorb the sound radiated from the engine, so that the sound absorption by the sound absorbing material layers and the sound insulation by the cover body synergistically suppress the leakage of noise outside the vehicle. can do.

As a sound absorbing material used in such a sound absorbing material layer, a non-woven fabric made of PET or the like made of synthetic resin fiber, a non-woven fabric made of natural fiber, a fibrous sound absorbing material such as a glass wool laminate, or a urethane foam Foam-type sound-absorbing materials such as foam and olefin are known.

[0005]

However, according to the measurement of noise from a position at a predetermined distance from the surface of the engine cover, 300 to 80 by providing the engine cover.
In many cases, the sound pressure level of noise in a relatively low sound frequency band of about 0 Hz increases. It is difficult to sufficiently absorb noise in such a frequency band with a conventionally used sound absorbing material layer.

It is believed that this phenomenon is caused by resonance in a somewhat closed space formed between the engine cover and the engine member.

The present invention has been made in view of such circumstances, and an object of the present invention is to further reduce the noise from the engine by reducing the resonance sound.

[0008]

The feature of the engine cover according to the present invention that solves the above-mentioned problems is that the engine cover is held by an engine member, and the engine cover is laminated on a plate-shaped cover body and a rear surface of the cover body. The cover body has a through-hole that penetrates the front and back of the cover body in a portion facing a resonance space that generates a resonance sound formed between the cover body and the engine member. The opening of the through hole on the back side of the cover body is closed by the sound absorbing material layer.

The sound absorbing material layer desirably has air permeability.

The opening area of the through hole is 100.
mm ² or more and the aperture ratio is desirably 45% or less.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an engine cover according to the present invention, the cover body penetrates the front and back of the cover body into a portion opposed to a resonance space formed between the cover body and the engine member, which generates a resonance sound. Has a through hole. Thereby, a part of the resonance space is opened, so that the resonance sound generated in the resonance space is reduced.

The opening of the through hole on the back side of the cover body is closed by a sound absorbing material layer,
Noise leaking from the through hole can be reduced, and 1000
It is possible to reduce noise in a relatively high frequency range in a frequency band of not less than Hz.

The engine member is a general term for an engine body including a cylinder and a piston, a device for supplying fuel and air to the engine body, a cam device for controlling intake and exhaust, an oil circulation device, and the like. Is assembled so as to cover at least a part of them.

The resonance space is exemplified by a space formed between the engine body and the engine cover, a space formed between the intake manifold and the engine cover, and the like. This resonance space can be easily detected by measuring the sound pressure distribution on the surface of the driven engine using a noise meter or the like.

The cover body is formed in a plate shape that covers the upper part of the engine member as in the prior art. The surface shape, decoration, color tone, and the like are not particularly limited. The material is not particularly limited, such as various thermoplastic resins, fiber-reinforced thermoplastic resins, powder-reinforced thermoplastic resins, thermosetting resins, and metals.

It is preferable that the entire periphery of the back surface side of the cover main body covers as much of the upper surface of the engine member as possible. Thereby, the sound insulation performance is further improved. It is also preferable that the peripheral portion on the back side of the cover main body abuts on the engine member to form a closed space between the cover main body and the surface of the engine member. This further improves the sound insulation performance. In order to achieve this, the entire periphery of the peripheral portion on the back side of the cover body may be brought into contact with the surface of the engine member via a sealing member such as a urethane foam or a rubber seal. In addition, since such a closed space may become a resonance space, in such a case, a through-hole may be formed facing the closed space.

The sound absorbing material layer may be any material as long as it has air permeability and absorbs the energy of the sound wave by vibration of fibers of the sound absorbing material layer when the sound wave passes through the pores. Examples of such a sound absorbing material include a synthetic resin fiber non-woven fabric, a natural fiber non-woven fabric, a fiber-based sound absorbing material such as a glass wool laminate, a urethane foam, a foamed olefin, and the like. And the like. The thickness and the degree of air permeability can be variously selected depending on the purpose.

It is desirable that the opening area of the through hole is not less than 100 mm ² and the opening ratio is not more than 45%. When a plurality of through holes are formed, the total value may be within this range. If the opening area is smaller than 100 mm ^2, the effect of providing the through-hole will not be exhibited, and it will be difficult to reduce noise due to resonance. More preferably, it is 400 mm ² or more. When the aperture ratio exceeds 45%, 1000 Hz
It becomes difficult to reduce the noise in the high frequency band described above. More preferably, the aperture ratio is 30% or less.

It is desirable that the design of the opening area and the opening ratio is determined by trial and error, since it is affected by the air permeability and the thickness of the sound absorbing material layer. Further, the shape of the through-hole is not particularly limited, such as a perfect circle, an ellipse, a square hole, and a slit.

It is also preferable that a partition wall protruding from the cover main body and facing a high sound pressure portion having a relatively high sound pressure level on the surface of the engine member is formed on the back side of the cover main body. This further improves the sound insulation performance. However, when a resonance space is formed by the presence of the partition wall, it is desirable to form a through hole also in that portion.

It is desirable that the partition is formed such that a space surrounded by the partition and the cover body completely covers the high sound pressure portion. When there are a plurality of high sound pressure parts, it is desirable to form a plurality of partitions and to form each space so as to cover each high sound pressure part. If even a part of the high sound pressure part protrudes from the space, the sound insulation performance is reduced accordingly.

The tip of the partition may be in contact with the surface of the engine member or may be separated from the surface of the engine member by a predetermined distance. The highest sound insulation performance is obtained when the end of the partition wall is in contact with the engine surface and the partition wall, the cover body, and the engine member form a closed space. However, in order to form a closed space, it is necessary to dispose a soft sealing member such as a urethane foam or a rubber seal at the interface between the tip of the partition wall and the surface of the engine member, which increases the cost. Therefore, it is realistic to arrange the partition wall at a predetermined distance from the surface of the engine member, and the distance is desirably within 10 mm. When the distance between the tip of the partition and the surface of the engine member exceeds 10 mm, the probability that sound waves from the engine member escape to the outside of the partition increases, and the sound insulation performance decreases.

[0023]

The present invention will be specifically described below with reference to examples and comparative examples.

(Embodiment 1) Engine cover 1 shown in FIG.
Is made of ABS, and is composed of a plate-shaped cover main body 10 and a sound absorbing material layer 11 made of PET non-woven fabric that is integrally laminated on the back side of the cover main body 10.

The engine member 2 covered by the engine cover includes an engine body 20, a cylinder head cover 21 fixed on the upper part of the engine body 20, an intake manifold 22 for supplying combustion air to the engine body 20, and a plug. 23 and a harness member 24. A resonance space 3 is formed between the engine cover 1 and the cylinder head cover 21 and the intake manifold 22.

In the portion of the cover body 10 facing the resonance space 3, one through hole 12 penetrating the front and back is provided, and the opening of the through hole 12 on the back side of the cover body 10 is a sound absorbing material layer 11. It is blocked. The through-hole 12 has a substantially elliptical shape that is long in the longitudinal direction (perpendicular to the paper surface) of the cover body 10, and its minor axis is approximately 20% of the length in the width direction (the left-right direction of the paper surface) of the cover body 10. The major axis is about 40% of the length of the cover body 10 in the longitudinal direction, the opening area is 14400 mm ² , and the opening ratio is 8%.

In this embodiment, since the engine cover 1 is disposed on the engine member 2 as described above, the noise generated from the engine member 2 can be effectively shielded by the sound absorbing material layer 11 and the through hole 12. it can.

(Embodiment 2) In this embodiment, as shown in FIG. 2, a portion of the cover body 10 facing the resonance space 3 is
The configuration is the same as that of the first embodiment except that a plurality of circular through holes 13 penetrating the front and back are formed.

The diameter of the through-hole 13 is 4 mm, and a plurality of the through-holes 13 are uniformly formed in a portion corresponding to the through-hole 12 in the first embodiment so as to have a total opening area of 7200 mm ² and a total opening ratio of about 40%. .

(Comparative Example 1) The structure is the same as that of Example 1 except that the cover main body 10 does not have the through hole 12.

<Test / Evaluation> The engine cover 1 of the first, second and comparative examples 1 was replaced with stud bolts (not shown) provided on the cylinder head cover 21.
Each was fixed by a nut via a collar. Then, a microphone was arranged at a position 1 m above the center of the engine cover 1 and the engine was driven to measure a sound pressure level in an idling state.

In the measurement, a sound wave transmitted through the engine cover 1 was detected by a microphone, and the sound wave was measured by a real-time analyzer to measure a sound pressure level at each frequency. For comparison, the sound pressure level was similarly measured only for the engine member 1 without the engine cover. The results are shown in FIG. In FIG. 3, the vertical axis represents the sound pressure level (dB).
, The scale is 5 dB, and the higher the vertical axis, the higher the sound pressure level and the lower the vertical axis, the lower the sound pressure level.

FIG. 3 shows that when the engine covers 1 of the first, second and comparative examples 1 are mounted, the noise is reduced in a frequency band of 1000 Hz or more as compared with the case where no engine cover is provided. . This is considered to be due to the sound insulation effect of the cover body 10 and the sound absorption effect of the sound absorbing material layer 11.

In the frequency band of 1000 Hz or more, the noise reduction effect of the second embodiment is smaller than that of the first comparative example.
This is because the sound transmitted through the sound absorbing material layer 11 cannot be blocked because the cover main body 10 does not exist in the portion of the through hole 13. However, in Example 1, since the aperture ratio was smaller than that in Example 2, although the sound insulation performance of the cover body 10 was inferior to that of Comparative Example 1, it was recognized that it was almost equal to that of Comparative Example 1.

On the other hand, in the frequency band of less than 1000 Hz, in Comparative Example 1, 50
It can be seen that a large resonance sound is generated near 0 Hz. Example 1 and Example 2 have an effect of suppressing this resonance sound, and it is clear that this is the effect of providing the through holes 12 and 13.

(Example 3) Using the same engine cover 1 as in Example 1 except that the shape of the through hole 12 was different, the difference in noise level due to the difference in the opening area of the through hole 12 was measured. One through hole 12 is formed in a slit shape, and its width is three levels of 1 mm, 2 mm and 4 mm, and its length is 50 mm and 1 mm.
The width and length were formed by various combinations of three levels of 00 mm and 200 mm. In addition, the through hole 12
As shown in FIG. 1, the cover body 10 was formed at the position of the front end, and the start end was formed to extend to the left from the start end as the center in the longitudinal direction. The maximum aperture ratio is 0.1.
4%.

(Comparative Example 3) The same as Example 3 except that the sound absorbing material layer 11 was not provided.

<Test / Evaluation> Then, in the same manner as in the above test, the noise levels at 500 Hz, 800 Hz and 2000 Hz during idling were measured for each engine cover. The result is shown in FIG. 4 as a relative value to the opening area of the through hole 12. One scale of the noise level is 5 dB.

FIG. 4 shows that in order to reduce noise in the low frequency range of about 500 Hz, the opening area of
may preferably be mm ² or more, it can be seen that it is more desirable that the 400 mm ² or more. As for the noise in the high frequency range, the through hole 12
It can be seen that the noise level can be reduced by providing the sound absorbing material layer 11 irrespective of the presence or absence and the opening area.

(Embodiment 4) Therefore, the width 2 in the embodiment 3
Example 3 A cover main body 10 having slit-shaped through holes 12 (opening area 400 mm ² , opening ratio 0.2%) having a length of 200 mm and a length of 200 mm was used to determine the difference in noise level due to the difference in the material of the sound absorbing material layer 11. It measured similarly to. The material of the sound absorbing material layer 11 is a PET nonwoven fabric (500 g / m ² ,
mm). FIG. 5 shows the results. One scale of the noise level is 5 dB.

Example 5 The material of the sound absorbing material layer 11 was P
Same as Example 4 except that ET nonwoven fabric (500 g / m ² , thickness 20 mm) was used.

Example 6 The same as Example 4 except that a closed cell urethane foam (thickness: 15 mm) was used as the material of the sound absorbing material layer 11.

Comparative Example 4 The same as Example 4 except that the sound absorbing material layer 11 was not formed.

(Comparative Example 5) The same as Example 4 except that the through hole 12 was not formed.

<Evaluation> As shown in FIG. 5, the engine cover of Comparative Example 4 has a high noise level in a high frequency range, and the sound absorbing material layer 11
It can be seen that there is no sound leakage from the through-hole 12 because of the absence of the noise. Further, in the engine cover of Comparative Example 5, since there is no through hole 12, it is difficult to reduce the resonance sound, and the noise level in the low frequency range is large. In the engine cover of Example 6, since the noise level in the low frequency range is almost the same as that of Comparative Example 5, it is considered that the function of the through hole 12 does not work because the closed cell urethane has no air permeability.

In the engine covers of Examples 4 and 5, noise can be reduced from a low frequency range to a high frequency range. This is because the through holes 12 are formed, and the opening area and the opening ratio of the through holes 12 are optimally set. It is clear that this is due to the fact that the sound absorbing material layer 11 is formed and that the sound absorbing material layer 11 is made of a material having air permeability.

Since there is no significant difference between Example 4 and Example 5, no difference in the effect due to the difference in the thickness of the sound absorbing material layer 11 is observed under this test condition.

[0048]

That is, according to the engine cover of the present invention, the noise due to the resonance sound in the resonance space can be reduced well, and the noise from the engine can be further reduced together with the sound absorbing action by the sound absorbing material layer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an engine member and an engine cover, showing one embodiment of the present invention.

FIG. 2 is a schematic sectional view showing an engine member and an engine cover according to a second embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a frequency and a sound pressure level.

FIG. 4 is a graph showing a relationship between an opening area of a through hole and a noise level.

FIG. 5 is a graph showing the relationship between frequency and noise level in the engine covers of Examples 4 to 6 and Comparative Examples 4 and 5.

[Explanation of symbols]

1: engine cover 2: engine components 3:
Resonance space 10: Cover body 11: Sound absorbing material layer 1
2: Through hole 13: Through hole 20: Engine body 2
1: Cylinder head cover 22: Intake manifold

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Hirose 1 Ochiai Nagahata, Kasuga-machi, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. Address Toyoda Gosei Co., Ltd. (72) Inventor Masahiro Ogata 1 Ochiai Ogata, Kasuga-cho, Nishi-Kasugai-gun, Aichi F-term (reference) 3D003 AA07 BB02 CA03 CA08 DA02 DA03 3D023 BA02 BA03 BB16 BB21 BB29 BD21 BE06 BE20

Claims (3)

[Claims] 1. An engine cover held by an engine member, the engine cover comprising a plate-shaped cover main body and a sound absorbing material layer laminated on a back surface of the cover main body, wherein the cover main body is provided with a cover. A portion facing the resonance space that generates the resonance sound formed between the main body and the engine member has a through hole penetrating the front and back of the cover main body,
An engine cover, wherein an opening of the through-hole on the back surface side of the cover body is closed by the sound absorbing material layer. 2. The engine cover according to claim 1, wherein the sound absorbing material layer has air permeability. 3. The engine cover according to claim 1, wherein an opening area of the through hole is 100 mm ² or more, and an opening ratio is 45% or less.