Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
1994-09-01
2001-06-26
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S198000, C428S920000, C442S013000, C442S016000, C442S229000, C442S319000, C442S377000, C442S378000
Reexamination Certificate
active
06251498
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a soundproof heat shield member having a three-dimensional shape, and more particularly to a soundproof heat shield member suitable for an exhaust manifold.
2. Description of the Related Art
In an engine room of an automobile are arranged various electronic parts for conducting engine control, run control and the like in addition to an engine. These electronic parts are exposed to a higher temperature from the engine as a heat source, so that they are protected by arranging a heat shield member onto the heat source. That is, the heat shield member is arranged around an exhaust manifold of the engine at a given distance separated therefrom to insulate heat from the electronic parts. Furthermore, the exhaust manifold is generally a noise source, so that the heat shield member is required to have a soundproof function.
As the conventional soundproof heat shield member, there have been known a single metal plate, a laminate of plural metal plates, a laminate of plural metal plates sandwiching an asbestos sheet therebetween and the like. However, the conventional soundproof heat shield members do not yet develop satisfactory soundproof function. In the conventional soundproof heat shield member, noise becomes frequently high due to solid-borne sound from the exhaust manifold. Furthermore, a space between the exhaust manifold and the soundproof heat shield member serves as a resonator, in which noise from the exhaust manifold is repeatedly reflected in the space to amplify the noise and hence the noise level in the soundproof heat shield member rises. Moreover, when the asbestos sheet is sandwiched as a sound absorbing material between the metal plates, the outer surface of the metal plate reflects noise and hence the sufficient sound absorbing effect is not obtained.
On the other hand, JP-U-1-158513 discloses a cover for exhaust manifold covering the exhaust manifold. This cover comprises an inner plate facing the exhaust manifold, an outer plate located outside the inner plate and a sound absorbing member sandwiching between the inner plate and the outer plate, in which plural openings are formed in the inner plate. In the cover of such a construction, the noise from the exhaust manifold is absorbed by the sound absorbing member through the openings of the inner plate. However, there is no consideration that the noise is repeatedly reflected on the portion of the inner plate other than the openings to amplitude the noise. In this cover, therefore, the noise control effect is low, and particularly the effect of controlling high-frequency noise is very low.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the aforementioned problems of the conventional techniques and to provide a three-dimensionally shaped soundproof heat shield member for an exhaust manifold having excellent soundproofness, heat shielding property and durability.
According to the invention, there is the provision of a soundproof heat shield member for an exhaust manifold comprising a metal substrate formed into a given three-dimensional shape, a nonwoven fabric disposed on a surface of the metal substrate facing an exhaust manifold, and a woven wire cloth of metal wires disposed on a surface of the nonwoven fabric and fixed to the metal substrate and having a wire diameter of 0.1-1 mm and an interstice of 5-100 mesh.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As the metal substrate, use may be made of steel sheet, plated steel sheet and stainless sheet having a thickness of 0.5-2 mm. When the thickness of the metal substrate is less than 0.5 mm, noise amplified by vibrations of the engine is generated and cracks are apt to be caused, while when it exceeds 2 mm, the weight becomes considerably heavy as a whole and it is difficult to reduce the weight.
The nonwoven fabric is made from inorganic fibers. As the inorganic fiber, use may be made of ceramic fiber, glass wool, silica fiber and rock wool. As the ceramic fiber, it is favorable to use alumina ceramic fiber or silica-alumina ceramic fiber. The ceramic fiber is most popular among the nonwoven fabrics capable of satisfying conditions such as density and the like as mentioned later, and is cheap in the cost and high in the safety. In case of the ceramic fiber, it is preferable to have an average fiber diameter of 1.5-20 &mgr;m and an average fiber length of not less than 5 mm. Furthermore, the ceramic fiber is excellent in the heat resistance and durability. If the demand on the heat resistance is not important, the use of glass wool is favorable from a viewpoint of the cost.
The nonwoven fabric is preferable to have an average bulk density of 0.05-0.5 g/cm
3
, an average thickness of 0.5-15 mm and an average compressibility of not less than 1% in the assembling thereof. Moreover, the term “average compressibility” used herein means a volume ratio of the nonwoven fabric decreased by compression.
When the average bulk density is less than 0.05 g/cm
3
, problems are caused in the durability, while when it exceeds 0.5 g/cm
3
, there is a fear of causing poor sound absorption. When the average thickness is less than 0.5 mm, the sound absorption and heat shielding property are insufficient, while when it exceeds 15 mm, the soundproof heat shield member cannot frequently be mounted onto the engine in a restricted space of the engine room. On the other hand, when the nonwoven fabric is assembled at an average compressibility of not less than 1%, it can effectively be fixed, and consequently the position shifting or the powdering of the nonwoven fabric through vibrations of the engine can effectively be prevented.
According to the invention, the nonwoven fabric made from the inorganic fibers absorbs noise as follows: that is, gaps between the inorganic fibers in the nonwoven fabric convert sound energy entered therein into heat energy through viscous resistance of capillary action, or the fibers themselves are vibrated by sound entered to convert sound into heat energy. Thus, the inorganic fibers serve as a sound absorbing member.
On the other hand, the nonwoven fabric absorbs vibrations as follows: that is, vibration energy transmitted from the engine to the soundproof heat shield member is converted into heat energy through internal friction of the inorganic fibers. Thus, the nonwoven fabric also serves as a damping material.
The woven wire cloth is located nearest to the exhaust manifold of the engine, so that it is required to be excellent in the heat resistance and flexibility. The flexibility is required for closely fixing the nonwoven fabric to a curved surface of the three-dimensionally shaped metal substrate. Further, when the woven wire cloth is compared with the metal plate, noise from the exhaust manifold can effectively be absorbed by the nonwoven fabric through the interstices of the woven wire cloth without reflection, and also vibrations transmitted to the metal substrate can effectively be damped by the woven wire cloth.
From viewpoints of the heat resistance and flexibility, the metal wire constituting the woven wire cloth is preferable to be made from stainless steel (SUS 304), brass or galvanized steel.
In the woven wire cloth, the wire diameter is within a range of 0.1-1.0 mm, and the interstice is within a range of 5-100 mesh. When the wire diameter is less than 0.1 mm, the flexibility is excellent but the durability is insufficient, while when it exceeds 1.0 mm, the durability is excellent but the flexibility and workability are poor. Particularly, the wire diameter is preferable to be 0.2-0.3 mm.
When the interstice is less than 5 mesh, the nonwoven fabric falls off and scatters from the interstices of the woven wire cloth due to vibrations and run wind of an automobile and the like, while when it exceeds 100 mesh, noise from the exhaust manifold is reflected to decrease the sound absorbing effect. The interstice is favorable to be within a range of 40-50 mesh.
In the soundproof heat shield member according to the invention, an outermost pe
Fukushima Koji
Sakashita Keiichi
Cole Elizabeth M.
Ibiden Co. Ltd.
Oliff & Berridg,e PLC
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