Exhaust manifold for internal combustion engines

Details Exhaust manifold for internal combustion engines Exhaust manifold for internal combustion engines

2000-12-26

2001-12-04

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

Common receiver having inlets from plural cylinder

C060S324000

Reexamination Certificate

active

06324839

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to exhaust manifolds for internal combustion engines, and more particularly to those installed in internal combustion engines in association with a means for cleaning the exhaust gases, in particular a start catalyst, which for example is mounted on the manifold.
SUMMARY OF THE INVENTION
One object of the invention is to provide such a manifold whose heat loss is as small as possible in order to shorten the time for starting the cleaning means.
Another object of the invention is to ensure that the gas velocity field over the inlet face of the cleaning means is as uniform as possible.
Yet another object of the invention is to permit easy assembly of the manifold in the factory.
The invention therefore provides an exhaust manifold for internal combustion engines. According to one general characteristic of the invention, this manifold comprises a flange for fixation on the engine cylinder head, a wide exhaust-gas collecting cavity joined to the flange to receive the exhaust gases delivered by the cylinder head exhaust pipes, this wide collecting cavity having a reentrant wall element subdividing the said cavity into two mutually communicating sub-cavities. The manifold also comprises an end portion joined to the collecting cavity outlet and having an outlet orifice for the exhaust gases.
The combination of the “plenum” form of the manifold (wide exhaust-gas collecting cavity) subdivided into two “lungs” ensures that the heat loss will be minimal and contributes to achieving a uniform velocity field and uniform distribution of the exhaust gases at the inlet of a gas cleaning means.
According to one embodiment of the invention, the reentrant wall element provides, on the outside surface of the collecting cavity, a central indentation extending substantially perpendicular to the flange fixation plane, the two sub-cavities being symmetric with respect to the central plane of this central indentation.
This embodiment thus not only makes it possible easily to construct the wide cavity formed by these two lungs but also permits, by virtue of the central indentation, easy introduction of a wrench for establishing a point for fixation of the manifold on the cylinder head.
The wide collecting cavity has an appropriate internal volume. More particularly, it has been found that it is advantageous for the volume of the collecting cavity to be greater than about 0.8 times the cubic capacity of the engine in order to achieve a noteworthy reduction of heat loss as well as good uniformity of the velocity field at the inlet of the cleaning means. In addition, and especially for reasons of overall size, it is preferable that the volume of the collecting cavity be smaller than about 1.5 times the cubic capacity of the engine.
According to a preferred embodiment of the invention, the volume of the collecting cavity is chosen substantially equal to the cubic capacity of the engine, thus permitting an optimal compromise between the criteria of heat loss and uniformity of the velocity field and distribution, and overall manifold size.
It is also particularly advantageous for the end portion to have substantially the form of a bowl, thus permitting the uniformity of the velocity field to be further improved.
In addition, the end portion is preferably provided with an elliptical throttle plate, the major axis of the ellipse being parallel to the plane of fixation of the fixation flange. This also contributes to obtaining better uniformity of the velocity field.
The fixation flange is advantageously provided with four inlet ports to receive the exhaust gases and with five points of fixation on the cylinder head, those points being disposed in crisscross arrangement around the four inlet ports. Furthermore, the line segment connecting the respective centers of two consecutive fixation zones passes substantially through the center of the port situated between these two fixation zones.
Such an embodiment makes it possible to minimize the number of bolts for fixation of the manifold on the cylinder head and thus to minimize the assembly stresses associated with the introduction of wrenches. In addition, the criss-cross disposition of the fixation bolts relative to the centers of two consecutive fixation zones aligned with the center of the inlet port situated between these two fixation zones contributes to ensuring excellent leaktightness of fixation of the manifold on the cylinder head.
According to another embodiment of the invention, the manifold also comprises an intermediate connecting portion which connects the fixation flange to the collecting cavity and is provided with exhaust conduits joined respectively to the inlet ports of the fixation flange. Advantageously, the exhaust conduits disposed at the ends of the intermediate connecting portion are convergent. Consequently, all the exhaust conduits make it possible to force the exhaust-gas streams toward the manifold center, thus additionally contributing to achievement of a uniform velocity field over the inlet face of the cleaning means. In addition, this intermediate connecting portion contributes to increasing the rigidity of the manifold.


REFERENCES:
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patent: 5572868 (1996-11-01), Okamoto et al.
patent: 5953912 (1999-09-01), Kaiho et al.
patent: 3815408 (1988-12-01), None
patent: 4315086 (1994-11-01), None
patent: 58-51214 (1983-03-01), None
patent: 09-025841 (1997-01-01), None

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