Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
1998-03-11
2001-06-19
Gray, David M. (Department: 2851)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C029S890080, C060S323000
Reexamination Certificate
active
06247552
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to an air gap-insulated exhaust manifold with an end-side outlet opening, a collection pipe, and lateral inlet openings, wherein the outer pipe and the inner pipe are shaped parts made of sheet metal.
BACKGROUND OF THE INVENTION
Air gap-insulated, double-walled exhaust manifolds have been increasingly used especially in exhaust systems of motor vehicles which together with other air gap-insulated, double-walled exhaust pipes provide for the optimal operation of an emission control device (catalytic converter) arranged downstream of them. They bring about a reduction in the amount of heat released from the exhaust gas to the environment, so that the exhaust gas flows to the emission control device at a higher temperature than in single-walled exhaust manifolds and exhaust pipes. This is significant especially during the warm-up phase of the internal combustion engine, because the catalyst will thus rapidly reach its working temperature.
Prior-art double-walled exhaust manifolds have an outer pipe and a one-part or multipart inner pipe, which are shaped parts made of sheet metal in a half-shell design. After the pressing of the sheet metal, the blanks are assembled, and the outer half shells of the outer pipe are welded together. Such a manufacturing process is relatively expensive and requires many individual parts, along with an increased material consumption.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the present invention to provide an air gap-insulated exhaust manifold of the type described in the introduction, which has a very simple and especially material-saving design and has an unlimited, full ability to function.
According to the invention, an air gap-insulated exhaust manifold is provided including an end-side outlet opening, a collection pipe and lateral inlet openings. The exhaust manifold is formed by an outer pipe and an inner pipe which are shaped parts made of sheet metal. The inner pipe is gas-carrying and is provided only in the area of the collection pipe. Gas-carrying outer pipe sections are provided in the area of the inlet openings with the outer pipe defining an air gap with the gas carrying inner pipe in the area of the collection pipe.
The inner pipe is preferably formed of partial sections, the partial sections preferably overlapping at a point of connection.
Preferably the inner pipe is designed as a thin-walled pipe. The inner pipe is preferably manufactured according to a hydrostatic pressing process. The inner pipe may include the one-piece of pipe section with at least a pipe branch which points in the direction of the inlet opening. Each of these pipe branches may be mounted in a snug fit in the outer pipe. The inner pipe is preferably mounted in a sliding seat in the outer pipe.
A two-dimensional local spacing structure is arranged between the outer pipe and the inner pipe. The spacing structure may be in the form of depressions of the outer pipe or the inner pipe. The spacing structure may also be in the form of shaped wire mesh parts.
The one part or multipart inner pipe is fixed or even more preferably welded at least at one point in relation to the outer pipe. Gas carrying outer pipe sections may be provided as the separate sections.
The essence of the present invention is to provide the gas-carrying inner pipe only in the area of the collection pipe, while gas-carrying outer pipe sections are provided in the area of the inlet openings.
Thus, the present invention provides for a double-walled exhaust manifold in partial areas only, namely, in the areas which are subject to a high thermal load during the operation of the internal combustion engine. The zones of an exhaust manifold which are subject to high thermal load are especially the outside, which is located opposite the lateral inlet openings of the exhaust manifold, and generally the collection pipe of the exhaust manifold itself, because the throughput is substantially higher there than in the individual pipes, which are fastened to the cylinder head flange of an internal combustion engine. The individual pipes arranged downstream of the cylinder head are consequently subject to a lower thermal load.
As can be seen, a considerable amount of material can be saved by designing a double-walled exhaust manifold only partially. In addition, the zones of the inner pipe which are subject to high thermal load may be designed as very thin-walled zones, which are supported on the outer pipe. A small “thermal mass” is formed as a result, which is advantageous during operation especially during the warm-up phase of an engine. The exhaust gases are thus sent to a catalytic converter rapidly and with a very high temperature in the case of a cold start. The use of a reduced amount of material not only leads to advantages in terms of costs, but it also ensures a low overall weight of an exhaust manifold.
It is particularly advantageous for the inner pipe to be manufactured according to a hydrostatic pressing process. The one-part or multipart inner pipe is manufactured in such a process from circumferentially closed pipe sections, which are preferably straight. A pipe section is placed into a two-part calibrating mold, whose interior space is the desired contour of the completed, manufactured inner pipe. The two pipe ends are closed by sealing mandrels in a pressure-sealed manner, and at least one sealing mandrel communicates with a pressure source. With a pressurized medium, especially an aqueous emulsion, the pressure source exerts a very high pressure in the interior of the inner pipe, which undergoes deformation corresponding to the calibrating mold.
The application of an above-mentioned inner high-pressure process for deforming the inner pipe is particularly suitable because the inner pipes according to the present invention have relatively short branches, which point in the direction of the inlet openings of the exhaust manifold. Only a small amount of pipe material must be deformed, so that the wall thickness of the inner pipe can be selected to be very thin even for the blank, because the inner high-pressure deformation technique has its limits in the dome (curvature) height and in the direction of the domes, which can be pulled out of the pipe as branches. In exhaust manifolds, these branches usually have acute angles for reasons of proper flow guidance, which is an unfavorable condition concerning the attainable dome height. If a great dome height is required, it is also necessary, in principle, to have a starting material of great wall thickness, which is precisely untrue in the case of the present invention. An acute-angle pipe routing can be achieved substantially better due to the shorter dome height in the present invention. The guidance of the exhaust gas flow is more favorable as a result, which leads to a further optimization of the output of the engine.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
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Kovar Oliver
Nording Thomas
Gray David M.
J. Eberspacher GmbH & Co.
McGlew and Tuttle , P.C.
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