JPH10205352A - Engine cover - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an engine cover capable of obtaining a large sound absorption and sound insulation effect from a low frequency range to a high frequency range. The engine cover has a shape that covers the top surface, the top surface and one side surface, or the top surface and many side surfaces of the engine, and the cover has a shape that covers the entire surface or a part of the area. Therefore, in the space formed by the engine and the cover, the overall value of the average sound pressure level during normal operation is at least 1.3 times as large as the value without the cover, and the average of the engine and the cover The interval is in the range of 5 to 100 mm, a sound absorbing material is installed in the space between the engine and the cover, and the sound absorbing material is composed of the internal material and the skin material, and the skin material is the engine side surface of the internal material or the entire surface of the internal material. a shape covering the tensile strength of 1 to 10 kgf / mm ^2, a polymer nonwoven and / or tensile strength 5~30Kgf / mm ² with a thickness of 0.1 to 5 mm, thickness 5
It is characterized by including a polymer film of 50 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cover, and more particularly to an engine cover used in an engine room for the purpose of absorbing and insulating engine sounds.

[0002]

2. Description of the Related Art In order to reduce noise generated by an engine as a sound source, various sound and vibration components are used in an engine room. Examples of the sound vibration component include a hood insulator installed on the back of the hood, a resonator for reducing intake noise, and an in-engine insulator installed on a wall.

[0003] One of them is an engine proximity shield cover (hereinafter referred to as an engine cover), which is one of the parts located closest to the engine and is made of only a material having sufficient heat resistance. In order to satisfy this requirement, class wool is used for most of the components including only a resin plate or a component provided with a sound absorbing material, and tuning of sound absorption and sound insulation frequency is impossible.

A conventional engine cover is of a type having a thin rigid plate for improving the sound insulation performance in terms of structure, and having a Helmholtz resonator in a part of the plate (Japanese Utility Model Application Laid-Open No. 57-25 / 1982).
No. 144, JP-A-54-47020), a type having a weatherstrip at the grounding portion to prevent water leakage on the engine (Japanese Utility Model Laid-Open No. 57-25143), and installed directly in a portion where sound is generated. Type (Japanese Utility Model 63-402)
No. 32, Japanese Utility Model Application Laid-Open No. 64-51738), a Helmholtz type having both air permeability and sound insulation performance (Japanese Unexamined Patent Publication No.
JP-A-13573, JP-A-7-64564) and the like have been proposed. . However, in these types, the effect is mainly applied only to a specific frequency, and it is difficult to provide an effect over the entire frequency range.

[0005] Further, a type in which a general sound absorbing material is used to improve sound insulation performance and sound absorption performance (Japanese Patent Laid-Open No. 53-9000).
No. 1, JP-A-56-176388, JP-A-6-176388
However, these have some effects in the whole region in contrast to the above-mentioned structure type, but it is difficult to give an effect particularly in a low frequency region.

[0006]

In particular, although the engine noise of a vehicle varies depending on the number of revolutions of the engine, the noise in the low frequency range of 500 Hz or less basically poses a problem. It is an issue to obtain a sound absorbing or sound insulating structure having a particularly large effect over the entire region. At the same time, the space in the engine room of the vehicle is limited,
Achieving a high performance and compact structure is also a significant challenge. Further, since the interior of the engine room has a relatively high temperature atmosphere, the sound absorbing material also requires some heat resistance. Accordingly, an object of the present invention is to provide an engine cover that is installed mainly to reduce the radiation sound of an engine and that can obtain a large sound absorption and sound insulation effect from a low frequency range to a high frequency range.

[0007]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
For the purpose of sound insulation of the engine sound, in an engine cover installed near the engine, the shape of the engine cover is a shape that covers at least the upper surface of the engine, the upper surface of the engine and one side surface, or the upper surface of the engine and many side surfaces. The cover installed on the surface has a shape that covers the entire surface of the surface or a part of the area, and by installing the engine cover, in a space formed by the engine and the engine cover, during normal engine operation. The overall value of the average sound pressure level is at least 1.3 times the value without the engine cover, the average distance between the engine and the engine cover is in the range of 5 to 100 mm, Installing a sound absorbing material in the space formed by the engine and the engine cover, Sound absorbing material is composed of inner material and a skin material, the tensile strength of the shaped skin material covers the engine side of the inner material or the entire surface of the inner material, 1 to 10 kgf /
mm ^2, a thickness of 0.1~5mm polymeric nonwoven and / or tensile strength 5~30Kgf / mm ^2, is achieved by an engine cover, which comprises a polymer film having a thickness of 0.1~5mm Was.

[0008] The shape of the engine cover is such that it is installed only on the top surface of the engine, the top surface of the engine (Fig. 1) and one side surface (Fig. 2), two side surfaces (Figs. 3 and 4) and three side surfaces (Fig. 5). ) Or on four sides (FIG. 6). In this case, there is a type that covers the entire surface or a type that partially covers the surface. At this time, the greater the installation area, the greater the effect of sound absorption and sound insulation. Therefore, the larger the area of the engine cover of the present invention, which is intended for sound absorption and sound insulation, is better. However, it is often difficult to set a large area due to the layout of the engine room, so it is important to improve the performance of the sound absorbing material set in the engine cover.

The present invention has been made by paying attention to this point, and improves the performance of the sound absorbing material, particularly in the low frequency range. Generally used sound absorbing materials are basically in the form of a porous sound absorbing material, but it is difficult to impart sound absorbing performance to a low frequency region with this type of sound absorbing material.

Therefore, attention is paid to a skin material used to protect the sound absorbing material from heat, water, oil, or external physical obstacles, and a film sound absorbing form set to a target frequency for the skin material is used as the sound absorbing material. The material was formed.

[0011] However, in general, the film sound absorbing form can easily obtain a sound absorbing effect if it can be used in a large area for use in a building or the like, but is used for a small part such as an engine cover. Even so, the effect was not so much obtained.

Generally, in a pseudo-closed space separated by an engine cover and an engine, the sound pressure energy generated when the engine operates normally increases the ambient sound pressure level in the space. Does not leak its sound pressure energy to the outside, so that sound absorption and sound insulation can be achieved as a whole.

[0013] The present inventors consider that when the sound pressure level of the space after the installation of the engine cover is at least 1.3 times or more the sound pressure level without the installation of the engine cover at this time, It was confirmed that performance was remarkably exhibited even in the form of sound absorption.

In order to form an atmosphere having a high sound pressure level in the space between the engine cover and the engine, it is necessary that the average distance between the engine and the engine cover is 5 to 100 mm. If the average interval is less than 5 mm, it is impossible to actually install the sound absorbing material, and there is no point in improving the effect of the sound absorbing material. On the other hand, a space exceeding 100 mm is not so different from an open space, so that the sound pressure level cannot be increased to a target level. Therefore, it is necessary to set the space to this high sound pressure atmosphere and to install a sound absorbing material in a film sound absorbing form.

In order to form the sound absorbing material into a film sound absorbing form, the skin material is installed so as to cover the engine side surface of the inner member of the sound absorbing material or the entire inner member of the sound absorbing material, and the skin material has a tensile strength of 5 to 5. 30 kgf / mm ² , a polymer film having a thickness of 5 to 50 μm, and / or a tensile strength of 1 to 10 kgf / mm
^2. A polymer nonwoven fabric having a thickness of 0.1 to 5 mm is suitable. Membrane sound absorption form is due to the presence of a skin material that suppresses ventilation to some extent,
It is formed, but its formation requires the thickness and tensile strength of the skin material to be limited.

When using a polymer film for the skin material
Has a tensile strength of 5 to 30 kgf / mm^Two, Thickness 5-50μm
 Must be in the range of Tensile strength is 5kgf
 / Mm ^TwoWhen the value is less than the above range, membrane sound absorption is also caused by the presence of the skin material.
It does not shift to the form and maintains the porous sound absorbing form. Reverse
And 30Kgf / mm^TwoOver the
To achieve the sound absorption performance that the inherent sound absorbing material in the high frequency range holds.
I can't do that. Also, if the film thickness is less than 5 μm
In this case, the mechanical strength of the film itself is insufficient,
Is meaningless. Conversely, if it exceeds 50 μm,
Extremely high-frequency sound absorption performance due to stoppage of ventilation of the skin
Will decrease.

The case of using a polymer nonwoven fabric for the skin material is basically the same as the case of a polymer film, and the tensile strength is in the range of 1 to 10 kgf / mm ² and the thickness is in the range of 0.1 to 5 mm. Is suitable.

Since a polymer nonwoven fabric has a smaller airflow resistance than a polymer film, the tensile strength and the thickness are different from the polymer film. If the tensile strength is less than 1 kgf / mm ^{2, the} film does not shift to the film sound absorbing form due to the presence of the skin material, and the porous sound absorbing form is maintained. Conversely, 10Kgf /
Beyond mm ^2, the nonwoven fabric is not suitable for circulation member for uncommon. Further, when the thickness of the nonwoven fabric is less than 0.1 μm, the mechanical strength of the nonwoven fabric itself becomes insufficient, and it becomes meaningless to set the skin material. On the other hand, when the thickness exceeds 5 mm, the airflow resistance increases extremely, so that the sound absorption performance in a high frequency range is extremely lowered.

As the polymer film and the polymer nonwoven fabric, it is effective to use polyester, polypropylene, nylon, polyacrylonitrile, polyacetate, polyethylene, linear polyester, polyamide or the like, but there is no particular limitation.

The purpose of the engine cover of the present invention is to improve sound absorption and sound insulation performance in a low frequency range. Frequency tuning in the low frequency range will be described. To set the sound absorbing frequency in the low frequency range, the dynamic spring constant of the material constituting the sound absorbing material is 2 × 10 ^{5 to} 20 × 10 ⁵ N / m, and the surface density of the skin material is 50 to 500 g / m ^2. , The Young's modulus of the skin material is 3 to 500 N / m ² , and the Poisson's ratio of the skin material is 0.2 to
By setting it to 0.4, in a film sound absorbing mode in which the skin material is a film, a vibration system having at least one degree of freedom is formed in which the skin material is a mass part and the internal sound absorbing material is a spring part, and the primary resonance frequency is reduced. It is suitable to be able to set variably from 100 Hz to 1 kHz.

Equation (1) is used to set a target frequency (f) for general membrane sound absorption. FIG. 7 shows a model of the one-degree-of-freedom vibration system.

(Equation 1) C: sound velocity (m / sec) K1: spring constant of sound absorbing material (N / m) K2: rigidity of skin material (Nsec / m ³ ) m: mass per unit area of skin material (kg)

Here, the rigidity K2 of the skin material varies depending on the installation condition of the skin material on the sound absorbing material, and thus cannot be simply determined. Therefore, as determined by experiments, when the Young's modulus of the skin material is not limited to at least 3 to 500 N / m ² and the Poisson's ratio of the skin material is not limited to the range of 0.2 to 0.4, the primary resonance frequency is set to 100 Hz to 1 kHz. Cannot be set in the range.

The dynamic spring constant of the sound absorbing material is set to 2 × 10 ⁵
５０50 × 10 ⁵ N / m, surface density of skin material 50-500
If not limited to the range of g / m ^2, the primary resonance frequency cannot be set in the range of 100 Hz to 1 kHz as described above.

Further, since the sound absorbing material of the present invention does not form a complete film sound absorbing form, the frequency cannot be completely set only by the above equation (1). Therefore, rough frequency setting is performed using Equation 1 as a guide. However, if the material is experimentally out of the above-mentioned limited range, sound absorption performance cannot be imparted to the target frequency region. The polymer nonwoven fabric used as the skin material of the sound absorbing material used in the engine cover of the present invention has an average fiber length of 1 to 100 cm and an average diameter of 1 to 30 μm.
It is preferable to use a needle-punched spun bond made of the above polymer fiber or an embossed spun bond for forming a part of the cloth by heat fusion.

The sound absorbing material used in the engine cover of the present invention is mainly intended to protect the sound absorbing material. Therefore, in order to impart mechanical strength, it is effective to provide a polymer nonwoven fabric for preventing fibers from coming off from the sound absorbing material. Therefore, if the average fiber length is less than 1 cm, mechanical performance cannot be satisfied. Conversely, if it exceeds 100 cm, it is difficult to disperse the fibers uniformly and maintain uniform mechanical performance.

As long as it is within the above range, short fibers of 10 cm or less or long fibers of more than 10 cm may be used. These fibers are
It is molded into a cloth-like nonwoven fabric or woven fabric, but in the case of nonwoven fabric, the needle punching method or the method of molding by heat-sealing a part of the cloth increases the rigidity of the cloth and secures air permeability Can and is effective. It is particularly effective to use only long fibers of 10 cm or more as the constituent fibers because the rigidity of the cloth can be further improved. It is also possible to apply a water-repellent or oil-repellent treatment to the skin material, which is very effective in protecting the sound absorbing material in the vicinity of the engine, but is not limited.

The fibers to be constituted are suitably polymer fibers having an average diameter in the range of 1 to 30 μm. If the average diameter is less than 1 μm, the rigidity of the fiber itself is insufficient,
Unsatisfactory mechanical strength. Conversely, if the average diameter exceeds 30 μm, the airflow resistance decreases, and it is difficult to provide effective sound absorption performance in a low frequency range. In order to further increase the mechanical strength of the nonwoven fabric, it is particularly preferable to use a needle punch spunbond or an embossed spunbond in which a part of the fabric is heat-sealed and formed.

Hereinafter, the internal base material of the sound absorbing material will be described. The internal material forming the sound absorbing material is constituted by a fiber aggregate composed of a woven fabric or a nonwoven fabric composed of short fibers and / or long fibers, and the fibers constituting the fiber aggregate have a circular cross section having a diameter of 10 to 40 μm; Or a fiber made of polyester having a shape other than a circle,
0% by weight is a binder fiber having a double core portion and a surface portion in the cross-sectional direction, and has a high softening point in the core portion and a low softening point in the surface portion, and the difference between these softening points is 50 to 80 ° C. Fibers in the range, average thickness 3-30 mm, area density 200-2
A sound absorbing material in the range of 000 g / m ² is suitable.

The fiber aggregate constituting the sound absorbing material may be in the form of a woven cloth or a non-woven cloth. This is because the sound absorbing performance does not depend on the form of the fiber aggregate. However, since the form of the fiber aggregate strongly depends on securing the bulkiness and the mechanical strength of the sound absorbing material, it is necessary to determine the form of the sound absorbing material in consideration of the environment around the installation of the sound absorbing material. is there. At this time, a non-woven fabric is desirable when the bulkiness is important, and a woven fabric is desirable when the mechanical strength is important, but there is no particular limitation.

The fibers constituting the sound absorbing material have an average diameter of 10 to 10.
The thickness must be in the range of 40 μm. The performance of the sound absorbing material depends on the average fiber diameter of the fiber assembly constituting the sound absorbing material, and the smaller the fiber diameter, the higher the sound absorbing performance. However, thin fibers are not common, and the rigidity of the fibers themselves is low, so that it is difficult to use them as components. Further, if the rigidity of the fiber is small, it is difficult to impart bulkiness, which is one of the performances of the sound absorbing material, and the bonding force of the fiber itself is also reduced. As described above, the use of fibers having a size of less than 10 μm cannot satisfy the sound absorbing performance. On the other hand, if the fiber is thickened, the sound absorbing performance is reduced, so that if the fiber is 40 μm or more, the sound absorbing performance cannot be satisfied.

The fibers constituting the fiber assembly can be used without any problem, even if they have a round cross-section fiber or a non-circular cross-section fiber. In particular, since the sound absorbing performance depends on the surface area of the fiber, the use of a fiber having a modified cross section is effective but not particularly limited.

The fibers constituting the sound absorbing material must be made of polyester. This is because polyester contains many polymers having a relatively high melting point and is suitable as a material of a sound absorbing material used in a relatively high temperature atmosphere for use in an engine room of an automobile. Particularly, polyethylene terephthalate, a general polyester, has a melting point of about 250 ° C.
Which is particularly appropriate but not limiting. In addition, polyester has high recyclability, and it is possible to produce a nonwoven fabric again by opening the cut material cut out as a sound absorbing material again. It is also possible to melt the polyester fiber such as scraps and spin the fiber again.

10 to 50% by weight of the fiber constituting the sound absorbing material
Is a binder fiber having a double core-sheath structure in the cross-sectional direction, and it is necessary that the core has a high softening point and the surface has a low softening point. Binder fibers are used to impart moldability to the nonwoven fabric,
The portions having a low softening point on the fiber surface fuse with each other at the time of heat molding, so that molding suitable for the mold is possible.

As described above, when the sound-absorbing material is used in the intake system of an engine room, a surface such as a spun bond is provided on the surface of the sound-absorbing material so that the fibers of the sound absorbing material do not come off by the intake air. Attached to protect the sound absorbing material.
Here, when the binder fiber is used in the skin in the range of 10 to 50% by weight, the fiber on the surface is bonded by the binder fiber, so that there is an advantage that the above-mentioned problem hardly occurs.

At this time, if the amount of the binder fiber is less than 10% by weight, it is difficult to form the sound absorbing material itself and a part of the surface fiber may be scattered. If it exceeds 50% by weight,
Since the sound absorbing material itself hardens, it is difficult to satisfy the dynamic spring constant of the sound absorbing material.

It is necessary that the melting point of the low softening point on the surface of the binder fiber is low within the range of 50 to 80 ° C. with respect to the core. This is because it is necessary for imparting formability to the sound absorbing material. Therefore, according to the difference in the softening point, in a temperature range in which only some of the fibers are softened,
By using the softening fiber as a binder, the fiber aggregate can be given moldability.
If the difference in softening point is less than 50 ° C., it becomes difficult to control the temperature during hot molding, and the practicality is reduced. On the other hand, if the difference in softening point exceeds 80 ° C., the temperature of the softening point decreases, and it may be difficult to secure the shape of the sound absorbing material used at normal temperature or high temperature.

It is considered that polyester fibers other than the binder fiber have a melting point substantially similar to that of the core material of the binder fiber. Therefore, the larger the temperature difference of the softening point of the binder fiber, the easier the molding. However, if the surface portion melts out in a high-temperature atmosphere, the shape of the molded sound absorbing material returns to the original sheet shape of the sound absorbing material, which is a problem.

Particularly, the sound absorbing material used for the engine cover is
High heat resistance is required to withstand the radiant heat of the engine. Therefore, in the case of a binder fiber using polyethylene terephthalate, which is the most common polyester, as a core material, the melting point of the core material is about 250 ° C., and the softening point of the surface is in the range of about 170 to 200 ° C. You need to be there.

The sound-absorbing material must be made of a single fiber having a fiber length of 100 mm or less and / or a fiber aggregate composed of long fibers having a fiber length of 100 mm or more. Since sound absorption converts sound energy into heat energy or the like, it is necessary to improve energy conversion efficiency in order to improve this performance. This efficiency can be improved by increasing the friction with the air,
For this purpose, it is effective to increase the surface area of the sound absorbing material. From this point, among various types of sound absorbing materials, a fiber aggregate having a large surface area per unit weight is suitable. Further, since the sound absorbing performance does not depend on the length of the constituent fibers, there is almost no need to define the fiber length to ensure the sound absorbing performance.

Depending on the purpose of use of the sound absorbing material, it may be better to use a single fiber or to use a long fiber. For example, monofilaments themselves are short, so when molded into a sound-absorbing material, the sound-absorbing material has good followability of the mold and high shape retention, and long fibers have high mechanical strength. It is good when rigidity is required for the material, but there is no particular limitation.

However, when considering the manufacturing of the sound absorbing material and the rigidity of the sound absorbing material itself, the mechanical strength of the sound absorbing material is influenced by the fiber length, and therefore, it is meaningful to specify these. When forming the fiber into a sound absorbing material, it is important that the fiber length is in the range of 30 to 100 mm, but there is no particular limitation.

If the fiber length is less than 30 mm, the fiber length is too short, and it is difficult to form a sound absorbing material. Further, it is difficult for a general fiber sound absorbing material manufacturing apparatus to uniformly disperse and form fibers having a size of more than 100 mm.
Therefore, there is a high possibility that a part of the fibrous body becomes a one-sided sound absorbing material in the sound absorbing material, and it is difficult to always maintain a constant performance.

The areal density of the sound absorbing material is 200 to 2000 g / m ^2.
It is effective to be within the range. Area density 200g /
If it is less than m ² , rigidity as a sound absorbing material cannot be secured. On the other hand, in the region exceeding 2,000 g / m ² , not only the performance is not improved but the efficiency is high despite the excess weight and the accompanying cost, and the ventilation volume of the sound absorbing material itself is increased due to the increase in the surface density. Due to the decrease, sound may be reflected.

It is necessary that the thickness of the sound absorbing material be in the range of 3 to 30 mm. If the thickness is less than 3 mm, sound absorption performance cannot be secured, and if it exceeds 30 mm, it is too thick as a sound absorbing material,
Since a space for installation is required, there are many cases where the layout is not satisfied, and the use route may be narrowed.

It is composed of a polymer film or a polymer non-woven fabric.
10-200g between the skin material and the sound absorbing material inside
/ M^Two, Air pressure 0.1kg / cm^Two1-100cc ventilation volume
/cm ^Twomin hot-melt adhesive
Suitable to be.

When the skin material is installed on the sound absorbing material, a certain level of mechanical strength is required. Therefore, installation of a hot melt in the form of a film is effective. Further, in order to provide sound absorption performance in a low frequency range, 10 to 200 g / m ² and an air pressure of 0.
It is preferable that the air flow rate at 1 kg / cm ² is 1 to 100 cc / cm ² min.

The area density of the hot melt adhesive is 10 g / m ²
If it is less than 30, the adhesive strength cannot be satisfied, and there is no point in using a hot melt. On the other hand, if it exceeds 200 g / m ² , the airflow resistance together with the skin material becomes too high, so that the sound absorbing performance in a high frequency range cannot be secured.

The hot melt adhesive has an air flow rate of 1 cc / cm ²
If it is less than min, the airflow resistance becomes too high, so that sound absorbing performance in a high frequency range cannot be secured. If it exceeds 100 cc / cm ² min, it is difficult to improve the sound absorbing performance in a low frequency range because the film has low airflow resistance.

Regarding the installation form of the sound absorbing material, it is suitable to form a back air layer of 5 to 20 mm between the engine cover and the sound absorbing material. The presence of the back air layer is effective for the purpose of the invention, because the presence of the back air layer improves sound absorption performance in a low frequency range. Here, if the back air layer is less than 5 mm, there is no point in installing the back air layer because the sound absorption performance in the low frequency range is not appropriately improved. Conversely, if it exceeds 20 mm,
Since the entire thickness of the engine cover is increased, layout problems when installing the engine cover in the engine room are significant.

In order to improve the sound absorbing performance in the low frequency range over a wide range, the specifications of the sound absorbing material to be installed on the engine cover should be at least two or more, and the desired sound absorbing frequency in the low frequency region should be at least two or more. Is valid.
By installing sound absorbing materials set at different frequencies on each surface of the engine cover, an engine cover having high sound absorbing performance in a wide range can be obtained. Further, since the sound absorbing performance is proportional to the installation area of the sound absorbing material, it is particularly effective to change the area of the sound absorbing material in the order in which the sound absorbing effect is required and to install the sound absorbing material on the back surface of the engine cover.

It is effective to use the sound absorbing material installed on the engine cover of the present invention in the engine room. In the engine room, high sound pressure parts using the engine as a vibration source are distributed over a wide area, so that the effect of the sound absorbing material of the present invention can be sufficiently exhibited. In particular, it is effective to apply to the periphery of the engine, but there is no particular limitation.

[0052]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 The engine cover was shaped 1 (see FIG. 1), and the engine cover was installed on the upper surface of the engine such that the average distance between the engine and the engine cover was 20 mm. At this time, in the normal operation state, the sound pressure level ratio of the space between the engine and the engine cover after the engine cover is installed is about 1.5 times that of the sound pressure level on the upper surface of the engine without the engine cover. became. Here, the specification of the sound absorbing material is such that the inner sound absorbing material has a round cross-section polyester with an average diameter of about 15 μm
20% of the total weight of the sound absorbing material is made of a binder fiber having a softening point difference of about 50 ° C., and has a thickness of 10 mm and a surface density of 1.0 kg / m ^2. used. The dynamic spring constant of this sound absorbing material is 2 × 10 ⁵ N / m. As the skin material, a spunbond nonwoven fabric having an area density of 0.2 kg / m ² , a thickness of 0.6 mm, a tensile strength of 8 kgf / mm ² , a Young's modulus of 70 N / m ² , and a Poisson's ratio of about 0.3 was used. The skin material was adhered to the sound absorbing material base material in the presence of the binder fiber to be mixed with the sound absorbing material base material, whereby the sound absorbing material 1 was manufactured. The primary resonance frequency of the sound absorbing material 1 at this time is about 160 Hz. The engine cover 1 was obtained by combining the shape 1 engine cover and the sound absorbing material 1.

Example 2 An engine cover was installed on an engine so that the average interval between the engine and the engine cover was 100 mm, and a sound absorbing material 2 having a ratio of sound pressure levels under the atmosphere of 1.3 was used. Except for the above, an engine cover 2 was obtained in exactly the same manner as in Example 1.

Example 3 An engine cover was installed on an engine such that the average distance between the engine and the engine cover was 10 mm, and a sound absorbing material 3 having a ratio of sound pressure levels under the atmosphere of 2 was used. The engine cover 3 was obtained in the same manner as in Example 1.

Example 4 The skin material to be installed on the sound absorbing material was made to have a surface density of 0.05 kg / m ² , a thickness of 0.2 mm, a tensile strength of ² kgf / mm ² , and a Young's modulus of 18
An engine cover 4 was obtained in exactly the same manner as in Example 1, except that a spunbond nonwoven fabric having an N / m ² and a Poisson's ratio of about 0.3 was used, and the primary resonance frequency of the sound absorbing material 4 was about 320 Hz. .

Example 5 A skin material installed on a sound-absorbing material had a surface density of 0.4 kg / m ² , a thickness of 1.2 mm, a tensile strength of 9 kgf / mm ² , and a Young's modulus of 15.
Using a spun-pound nonwoven fabric of 0 N / m ² and a Poisson's ratio of about 0.3, the primary resonance frequency of this sound absorbing material 5 is about 110 Hz.
An engine cover 5 was obtained in exactly the same manner as in Example 1 except that the above conditions were satisfied.

Example 6 A skin material to be installed on a sound absorbing material was provided with a surface density of 0.05 kg / m ² , a thickness of 15 μm, a tensile strength of 21 kg / mm ² and a Young's modulus of 20
An engine cover 6 was obtained in exactly the same manner as in Example 1 except that a polymer film having 0 N / m ² and a Poisson's ratio of about 0.25 was used, and the primary resonance frequency of the sound absorbing material 6 was about 500 Hz. .

Example 7 A skin material to be installed on a sound absorbing material was prepared to have a surface density of 0.07 kg / m ² , a thickness of 40 μm, a tensile strength of 22 kgf / mm ² , and a Young's modulus of 2
Using a polymer film of 00N / m ² and a Poisson's ratio of about 0.25, the primary resonance frequency of this sound absorbing material 7 is about 360 Hz.
Except for that, an engine cover 7 was obtained in exactly the same manner as in Example 1.

Example 8 The surface density of the sound absorbing material was 0.2 kg / m ² , its dynamic spring constant was 4 × 10 ⁴ N / m, and the primary resonance frequency of this sound absorbing material 8 was about 80 Hz. An engine cover 8 was obtained in exactly the same manner as in Example 1.

Example 9 The surface density of the sound absorbing material was 1.8 kg / m ² , the dynamic spring constant was 3.2 × 10 ⁵ N / m, and the primary resonance frequency of the sound absorbing material 9 was about 200 Hz. The engine cover 9 was obtained in the same manner as in Example 1.

Example 10 A PET fiber having a Y-shaped cross section with an average diameter of about 15 μm was used as an internal sound absorbing material.
20% of the total weight of the sound-absorbing material is softened at a difference of about 50 ° C.
Blended with certain binder fiber, thickness 10mm, area density
1.0 kg / m^TwoUse the dynamic spring constant
Is 1.8 × 10 ^FiveN / m, the primary resonance frequency of the sound absorbing material 10
Exactly the same as Example 1 except that the wave number was set to about 150 Hz.
Thus, an engine cover 10 was obtained.

Example 11 The thickness of the internal sound absorbing material was 5 mm, and the dynamic spring constant was 4.
An engine cover 11 was obtained in exactly the same manner as in Example 1, except that the primary resonance frequency of this sound absorbing material 11 was set to approximately 230 Hz, and the same was set to 0 × 10 ⁵ N / m.

Example 12 Example 12 was repeated except that the thickness of the internal sound absorbing material was 25 mm, the dynamic spring constant was 1.0 × 10 ⁵ N / m, and the primary resonance frequency of the sound absorbing material 12 was about 110 Hz. An engine cover 12 was obtained in exactly the same manner as in Example 1.

Example 13 The average diameter of the PET fiber constituting the internal sound absorbing material was about 30 μm.
An engine cover 13 was obtained in exactly the same manner as in Example 1 except that the dynamic spring constant was 2.0 × 10 ⁵ N / m, and the primary resonance frequency of the sound absorbing material 13 was about 160 Hz.

Example 14 The amount of the PET fiber constituting the internal sound absorbing material was 10% by weight, and the dynamic spring constant was 1.5 × 1.
0 ⁵ N / m, the primary resonance frequency of this sound absorbing material 14 is about 14
An engine cover 14 was obtained in exactly the same manner as in Example 1 except that the frequency was set to 0 Hz.

Example 15 The amount of the PET fiber constituting the internal sound absorbing material was 50% by weight, and the dynamic spring constant was 2.5 × 1.
0 ⁵ N / m, the primary resonance frequency of this sound absorbing material 15 is approximately 18
An engine cover 15 was obtained in exactly the same manner as in Example 1 except that the frequency was set to 0 Hz.

Example 16 In order to bond the internal sound absorbing material and the skin material, the surface density was set to 0.0
5 kg / m ² , air flow rate of 10 cc / cm ² at air pressure of 0.1 kg / cm ²
cm ² using a film-shaped hot melt is min, and the dynamic spring constant 2.0 × 10 ⁵ N / m, the sound-absorbing material 1
An engine cover 16 was obtained in exactly the same manner as in Example 1 except that the primary resonance frequency of the No. 6 was set to about 160 Hz.

Example 17 A 10 mm back air layer was set between the engine cover and the sound absorbing material 1 and its dynamic spring constant was 1.8 × 10 ⁵ N / m,
An engine cover 17 was obtained in exactly the same manner as in Example 1 except that the primary resonance frequency of the sound absorbing material 17 was set to about 150 Hz.

Example 18 An engine cover 18 was obtained in exactly the same manner as in Example 1 except that the shape of the engine cover was changed to shape 2 (see FIG. 2) and the ratio of the sound pressure levels was set to about 1.7.

Example 19 An engine cover 19 was obtained in exactly the same manner as in Example 1 except that the shape of the engine cover was 3 (see FIG. 3) and the ratio of the sound pressure levels was about 1.8.

Example 20 An engine cover 20 was obtained in exactly the same manner as in Example 1 except that the shape of the engine cover was 4 (see FIG. 4) and the ratio of the sound pressure levels was about 1.9.

Example 21 An engine cover 21 was obtained in exactly the same manner as in Example 1 except that the shape of the engine cover was changed to 5 (see FIG. 5) and the ratio of the sound pressure levels was set to about 2.2.

Example 22 An engine cover 22 was obtained in exactly the same manner as in Example 1 except that the shape of the engine cover was 6 (see FIG. 6) and the ratio of the sound pressure levels was about 2.4 times.

Comparative Example 1 The engine cover was installed on the engine with the space between the engine and the engine cover being 3 mm. However, due to the space, an effective sound absorbing material could not be installed in the low frequency range, and the sound pressure ratio could be measured. Did not.

Comparative Example 2 The engine cover was installed on the engine with the space between the engine and the engine cover set to 120 mm.
As a result, it was not possible to form an atmosphere in which the effect of the sound absorbing material effective in the low frequency range was exhibited.

COMPARATIVE EXAMPLE 3 The skin material to be installed on the sound absorbing material had a surface density of 0.01 kg / m ² , a thickness of 0.1 mm, a tensile strength of 0.8 kgf / mm ² , a Young's modulus of 13 N / m ² , and a Poisson's ratio. Using a spun pound non-woven fabric of about 0.3, the primary resonance frequency of this sound absorbing material is about 200 Hz.
An engine cover was obtained in exactly the same manner as in Example 1 except that the above conditions were satisfied.

COMPARATIVE EXAMPLE 4 A skin material to be installed on a sound-absorbing material had a surface density of 0.6 kg / m ² , a thickness of 1.0 mm, a tensile strength of 1.2 kgf / mm ² , a Young's modulus of 92 N / m ² , and a Poisson's ratio. Using a spunbond nonwoven fabric of about 0.3, the primary resonance frequency of this sound absorbing material is about 200Hz
An engine cover was obtained in exactly the same manner as in Example 1 except that the above conditions were satisfied.

COMPARATIVE EXAMPLE 5 A skin material to be installed on a sound-absorbing material had a surface density of 0.01 kg / m ² , a thickness of 5 μm, a tensile strength of 1.2 kgf / mm ² , and a Young's modulus of 1
A spunbond non-woven fabric with 5 N / m ² and a Poisson's ratio of about 0.25 is used, and the primary resonance frequency of this sound absorbing material is about 200 Hz.
An engine cover was formed in exactly the same manner as in Example 1, except that the surface was broken, but the skin was broken during the experiment due to insufficient rigidity of the skin.

Comparative Example 6 The skin material to be installed on the sound absorbing material was 0.07 kg / m ² in area density, 60 μm in thickness, 23 kgf / mm ² in tensile strength, and ² in Young's modulus.
A spunbonded non-woven fabric having 20 N / m ² and a Poisson's ratio of about 0.25 is used.
Except for Hz, an attempt was made to form the engine cover in exactly the same manner as in Example 1, but the skin was torn during the experiment due to insufficient rigidity of the skin.

Comparative Example 7 Except that the areal density of the sound absorbing material was 0.1 kg / m ² , the dynamic spring constant was 1 × 10 ⁴ N / m, and the primary resonance frequency of the sound absorbing material was about 80 Hz. An engine cover was obtained in exactly the same manner as in Example 1.

Comparative Example 8 The surface density of the sound absorbing material was 3.0 kg / m ² and its dynamic spring constant was 6 × 10 ⁴ N / m. However, the primary resonance frequency of this sound absorbing material was about 1100 Hz, A sound absorbing material suitable for the frequency range could not be formed.

Comparative Example 9 The thickness of the internal sound absorbing material was 2 mm, and the dynamic spring constant was 2.
Although it was set to 0 × 10 ⁶ N / m, the primary resonance frequency of this sound absorbing material was about 1200 Hz, and an effective sound absorbing material could not be formed in a low frequency range.

Comparative Example 10 Although the thickness of the internal sound absorbing material was set to 40 mm, an experiment could not be performed with an engine cover provided with the sound absorbing material in terms of layout.

Comparative Example 11 Although the average diameter of the PET fiber constituting the internal sound absorbing material was set to about 8 μm, the fiber itself did not have rigidity and a fiber aggregate could not be formed.

Comparative Example 12 The average diameter of the PET fibers constituting the internal sound absorbing material was about 50 μm.
An engine cover was obtained in exactly the same manner as in Example 1, except that the dynamic spring constant was 3.0 × 10 ⁵ N / m, and the primary resonance frequency of this sound absorbing material was about 250 Hz.

Comparative Example 13 The blending amount of the PET fiber constituting the internal sound absorbing material was set to 7% by weight.
A fiber aggregate could not be formed.

Comparative Example 14 The blending amount of the PET fiber constituting the internal sound absorbing material was 70% by weight, and the dynamic spring constant was 1.0 × 1.
0 was ⁶ N / m, but the primary resonance frequency of the sound absorbing material 15 is about 1100Hz, and the could not form large sound absorbing material effect on the low frequency range.

Conventional Example 1 Surface Density 1.0 kg / m ² , Thickness 10 Consisting of Natural Fiber and Synthetic Fiber Spread on an Engine Cover of Shape 1
An engine cover was obtained in the same manner as in Example 1 except that a molded felt of mm was used as a sound absorbing material.

Reference Example 1 The engine cover of Example 1 was installed near the engine of an actual vehicle, and the sound pressure level at each frequency was measured using the engine. The rigidity of the sound absorbing material itself was sufficient, and It was confirmed that the sound absorbing effect was almost the same as the result of the above.

Test Examples The following experiments were performed on the engine covers obtained in the above Examples, Comparative Examples and Conventional Examples.

Test Example 1 The engine covers obtained by the methods of the respective examples and comparative examples were mounted near a four-cylinder engine installed in a semi-anechoic chamber. For this system, an actual engine firing experiment was performed, and four directions, front, rear, left and right
m and the sound pressure level at 1m above the engine,
The four positions were averaged, and the difference from the sound pressure level when no sound absorbing material was used was shown in dB for each frequency. At this time, 50-300
Hz is low frequency, 300-500Hz is middle frequency, and 500-
The high frequency was 2 kHz, and the average value is shown in Table 1. The test results are shown in Tables 1 and 2.

[0093]

[Table 1]

[0094]

[Table 2]

[0095]

[Table 3]

[0096]

[Table 4]

From Tables 1 and 2, each of the high-rigidity sound absorbing materials prepared in Examples of the present invention has a lower frequency (50%) than that of the conventional example.
It has been confirmed that the engine cover has excellent sound absorption characteristics in a region of about 300 Hz), a medium frequency (300 to 500 Hz), and a high frequency (500 to 2 kHz), requires little space, and has excellent mounting properties.

On the other hand, the comparative example prepared with the specification out of the specified range of the present invention has a particularly required sound absorption performance in the low frequency region and the medium frequency region (all the frequencies are 10 dB or more as a criterion). It was confirmed that the sound absorption performance of the vehicle was not satisfied, and that the space was not satisfactory (it was not possible to fit in the space in the engine room of the actual vehicle).

[0099]

As described above, according to the engine cover of the present invention, the radiation noise of the vehicle engine can be mainly reduced, particularly in the low frequency range, and the noise can be reduced in places where space is limited. It is very effective as an engine cover with high performance to improve sound absorption performance in the frequency range.

[Brief description of the drawings]

FIG. 1 is a schematic view and a side view of an engine cover shape 1. FIG.

FIG. 2 is a schematic view and a side view of an engine cover shape 2;

FIG. 3 is a schematic view and a side view of an engine cover shape 3;

FIG. 4 is a schematic view and a side view of an engine cover shape 4;

FIG. 5 is a schematic view and a side view of an engine cover shape 5;

FIG. 6 is a schematic view and a side view of an engine cover shape 6;

FIG. 7 is a schematic diagram of a film sound absorbing mode.

[Explanation of symbols]

 1 Shape 1 engine cover 2,6,10,14,18,22 Sound absorbing material 3,7,11,15,19,23,26 Skin material 4,8,12,16,20,24,25 Inner member 5 Shape 2 engine cover 9 Shape 3 engine cover 13 Shape 4 engine cover 17 Shape 5 engine cover 21 Shape 6 engine cover 27 Spring part 28 Mass part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Fig10K 11/16 A

Claims (7)

[Claims] 1. An engine cover installed near an engine for the purpose of isolating engine sound, wherein the shape of the engine cover covers at least the upper surface of the engine, the upper surface and one side surface of the engine, or the upper surface and many side surfaces of the engine. The shape, the cover installed on each surface is a shape that covers the entire surface of the surface, or a part of the area, by installing the engine cover, in the space formed by the engine and the engine cover, The overall value of the average sound pressure level during normal engine operation is at least 1.3 times the value without the engine cover, and the average distance between the engine and the engine cover is 5 to 100 mm. Sound absorption in the space formed by the engine and the engine cover Was placed, sound absorbing material is composed of inner material and a skin material, the engine side of the inner material is the skin material or a shape that covers the entire surface of the inner material tensile strength 1,
~10Kgf / mm ^2, a thickness of 0.1~5mm polymeric nonwoven and / or tensile strength 5~30Kgf / mm ^2, a thickness of 5
An engine cover comprising a polymer film of about 50 μm. 2. The dynamic spring constant of the internal material constituting the sound absorbing material is 2 × 10 ⁵ to 50 × 10 ⁵ N / m, and the surface density of the skin material is 50 to 500 g / m ² . Young's modulus is 3
５００500 N / m ² , and the Poisson's ratio of the skin material is 0.2-0.
4, a vibration system having at least one degree of freedom using the skin material as a mass part and the internal material as a spring part is formed in a film-absorbing mode in which the skin material is used as a film.
2. The engine cover according to claim 1, wherein the engine cover can be variably set between 0 Hz and 1 kHz. 3. A needle-punched spunbond or a part of a fabric in which a skin material composed of a polymer nonwoven fabric is composed of a polymer fiber having an average fiber length of 1 to 100 cm and an average diameter of 1 to 30 μm. The engine cover according to claim 1, wherein the engine cover is an embossed spun bond formed by fusing. 4. The internal material forming the sound-absorbing material is constituted by a fiber aggregate made of a woven or non-woven fabric composed of short fibers and / or long fibers, and the fibers constituting the fiber aggregate have a diameter of 10 to 40 μm. And a binder fiber having a double core portion and a surface portion in a cross-sectional direction, wherein 10% to 50% by weight of the fiber assembly is a binder fiber having a double core portion and a surface portion. With a high softening point and a low softening point on the surface, the difference between these softening points is 50 to
Fibers in the range of 80 ° C., average thickness 3 to 30 mm,
Engine cover according to any one of claims 1 to 3, characterized in that a sound absorbing material in the range of surface density 200 to 2000 g / m ^2. 5. An intermediate between a skin material composed of a polymer film and / or a non-woven fabric of a polymer and an inner material.
0 g / m ² , air flow rate at air pressure 0.1 kg / cm ² is 1-10
The engine cover according to any one of claims 1 to 4, further comprising a film-like hot melt adhesive of 0 cc / cm ² min. 6. Between the engine cover and the sound absorbing material, 5 to 2
6. The engine cover according to claim 1, wherein the engine cover has a back air layer in a range of 0 mm. 7. The engine cover according to claim 1, wherein at least two or more specifications of the sound absorbing material installed on the engine cover are set, and at least two or more sound absorbing frequencies in a target low frequency region can be set.