Power plants – Internal combustion engine with treatment or handling of... – Common receiver having inlets from plural cylinder
Reexamination Certificate
2000-04-20
2001-10-09
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Common receiver having inlets from plural cylinder
C060S322000, C060S282000
Reexamination Certificate
active
06298660
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle gas-directing component, and more particularly to a non-metallic exhaust manifold with an inner surface having a plurality of embedded ceramic members.
Various types of exhaust manifolds have been used in the field of internal combustion engines. Known exhaust manifolds are typically manufactured of a heat resistance metal such as cast iron to resist the high temperature exhaust gas emitted from the vehicle engine. However, these known manifolds are relatively heavy and tend to absorb much of the thermal energy generated by the exhaust gases.
In order to reduce their weight, some known exhaust manifolds are constructed of a light metal such as aluminum. When using such a material for an exhaust manifold, it becomes necessary to line or coat the inner surface with a heat insulating material such as a ceramic. In one known exhaust manifold, a ceramic fiber layer coats the inner surface of the aluminum exhaust manifold. However, because of the great difference in the thermal expansion properties of metals and ceramics, prolonged use tends to induce undesirable separation of the ceramic layer from the metallic surface. Separation of the ceramic fiber layer typically results in the destruction of the light metal surface by the high temperature exhaust gas.
Known iron exhaust manifolds have a high thermal conductivity and tend to immediately absorb much of the thermal energy generated by the exhaust gases. High thermal conductivity can be a disadvantage as the exhaust system catalyst can not immediately “light off” and a high percentage of total emissions occur before the catalysts are active. It would therefore be further desirable to prevent the exhaust manifold from absorbing the heat of the exhaust gases and allow the residual heat to activate the downstream catalytic converter. The catalytic converter will then “light off” earlier and will operate with higher efficiency which may effectively reduce the emission levels of the engine.
Accordingly, it is desirable to provide a lightweight vehicle gas-directing component which can resist the highly heated exhaust gas emitted from the vehicle engine.
SUMMARY OF THE INVENTION
The present invention provides a non-metallic vehicle gas-directing component having a plurality of ceramic members embedded within an inner surface and a method for producing the same. The inner surface preferably defines an exhaust passageway within an exhaust manifold for directing exhaust gas away from a vehicle engine.
The ceramic members are embedded within the inner surface to be in direct contact with the exhaust gas. Notably, the ceramic members need not form a completely continuous layer along the inner surface. Because the ceramic members extend into the exhaust passageway, a boundary layer is formed between the flow of exhaust gas and exposed portions of the inner surface. The exhaust gas, although impacting the ceramic members, tends to flow over the exposed inner surface portions because of the boundary layer.
The method for producing a vehicle gas-directing component preferably includes temporarily attaching a plurality of ceramic members to an inner mold core during a lost core molding process. In one disclosed embodiment, the ceramic members are temporarily attached directly to the inner mold core by an adhesive. In another disclosed embodiment, the plurality of ceramic members are attached to an inner contour of a core casting cavity by an adhesive. By temporarily tacking the ceramic members to the inner contour, the ceramic members will be transferred to the outer contour of the inner mold core.
The next step includes placing the inner mold core having the ceramic members attached to its outer contour within an outer core casting cavity and overmolding a non-metallic material over the surface of the inner mold core. The outer mold is sealed and the non-metallic material for forming finished component is injected or otherwise filled in between the inner mold core and outer core casting cavity of the outer mold. During the setting of non-metallic material, the ceramic members become embedded within what will become the inner surface of the finished component.
After the non-metallic material is set within the outer core casting cavity, the finished component is removed and the inner mold core is destructively removed leaving the ceramic members embedded in the inner surface of the finished component. The inner surface of the finished component now includes the plurality of embedded ceramic members to provide, for example, a highly heat resistant and lightweight exhaust passageway for directing the exhaust gas as described above.
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Denion Thomas
Siemens Canada Limited
Tran Binh
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