Exhaust manifold with integral catalytic converter

A pollutant reducing exhaust manifold for an internal combustion engine incorporating a catalytic converter therein. The manifold has a plurality of header pipes connected to and receiving exhaust gases from respective ones of a plurality of exhaust ports of an internal combustion engine. The header pipes are connected to a single chamber with an outlet therefrom connected to an exhaust pipe as well as a catalytic converter structure having a catalyst disposed on a supporting substrate disposed in the chamber between the inlet(s) and the outlet so that all exhaust gases from the engine must pass through the catalytic converter structure. The catalytic converter operates at higher temperatures for increased efficiency and comes to operating temperature virtually immediately.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to methods and apparatus for removing pollutants 
from the exhaust emissions of internal combustion engines and, more 
particularly, to a pollutant reducing exhaust manifold for an internal 
combustion engine comprising, a plurality of header pipes connected to and 
receiving exhaust gases from respective ones of a plurality of exhaust 
ports of the engine; a catalytic chamber having inlet(s) connected to 
receive exhaust gases from the plurality of header pipes and an outlet 
therefrom connected to an exhaust system; and, a catalytic converter 
structure having a catalyst disposed on a supporting substrate disposed in 
the catalytic chamber between the inlet(s) and the outlet so that all 
exhaust gases from the engine must pass through the catalytic converter 
structure. 
2. Background Art 
For many years, the exhaust systems of automobiles and other vehicles 
powered by internal combustion engines have remained substantially 
unchanged. There is an exhaust manifold that collects the exhaust gases 
emitted from the exhaust ports of the engine and outputs them into an 
exhaust pipe which conducts the gases to the rear of the automobile. 
Typically, a muffler is disposed in-line with the exhaust pipe to muffle 
the sounds of the gases to an acceptable level. More recently (after 1974 
in the United States), modern exhaust systems have included a catalytic 
converter to remove emitted pollutants from the exhaust gases. A typical 
prior art exhaust system of such design is depicted in FIG. 1. The exhaust 
manifold 10 is bolted or clamped to the engine (not shown) with the 
flanges 12. The catalytic converter 14 is positioned in-line in the 
exhaust pipe 16, typically some two to ten feet from the manifold 10. The 
muffler 18 is typically located at the rear of exhaust system. 
The above-described placement of the catalytic converter 14 creates several 
problems completely contrary to the intent thereof which is to reduce 
pollutants. Once it is operational, it works fairly well for its intended 
purpose. Because of its placement, however, it does not work as well as it 
could and, moreover, until it attains its operating temperature, it does 
not work at all. A catalytic converter is nothing more than a catalyst 
disposed on a substrate. When hot enough, the catalyst causes the unburned 
pollutants to be further oxidized. Until that time, the pollutants pass 
through unaffected. Since it is placed well down the exhaust pipe 16, when 
the engine is started the catalytic converter 14 is cold. And, it takes 
time for heat to build up in the catalytic converter 14 to a sufficient 
level that it begins to work. Unfortunately, starting is the time when the 
most pollutants are produced since a choke or similar mechanism typically 
increases the fuel-to-air ratio to enhance the combustion process in a 
cold engine. Thus, the partially burned fuel products pass virtually 
unhindered into the atmosphere. When one considers the number of engines 
started in a cold condition in a major city on any normal day, it can be 
seen that there are a lot of unburned pollutants poured into the 
atmosphere each and every day. 
It has been suggested to add a heating element to the catalytic converter 
to get it to operating temperature more quickly; but, that is a stop-gap 
measure that is not overly effective. Typically, a operator expects 
his/her vehicle to start immediately when the ignition key is turned and 
will object if he/she must wait until the catalytic converter warms up 
before the engine will start. Like the bell or other alarm that warns that 
the seatbelt is not fastened, if a car will not start until the catalytic 
converter reaches temperature, based on human nature and prior experience 
many drivers will simply have their vehicles modified to bypass that 
feature, thereby eliminating the results intended to be attained thereby. 
Wherefore, it is an object of the present invention to provide a catalytic 
converter which begins effective operation virtually immediately. 
It is another object of the present invention to provide a catalytic 
converter which is highly effective in eliminating pollutants from exhaust 
gases. 
Other objects and benefits of this invention will become apparent from the 
description which follows hereinafter when read in conjunction with the 
drawing figures which accompany it. 
SUMMARY OF THE DISCLOSURE 
The foregoing objects have been achieved in an exhaust manifold for an 
internal combustion engine having a plurality of header pipes connected to 
and receiving exhaust gases from respective ones of a plurality of exhaust 
ports of the engine and a single chamber inlet(s) connected to the 
plurality of header pipes and an outlet connected to an exhaust system, by 
the improvement of the present invention for reducing pollutants emitted 
by the engine comprising disposing a catalytic chamber between the 
inlet(s) and outlet thereof and disposing a catalytic converter structure 
having a catalyst disposed on a supporting substrate in the catalytic 
chamber between the inlet(s) and the outlet so that all exhaust gases from 
the engine must pass through the catalytic converter structure. 
Preferably, the plurality of header pipes and the catalytic chamber are of 
a structural fiber reinforced ceramic matrix composite (FRCMC) material 
comprising fibers of a generic fiber system disposed throughout a 
pre-ceramic resin in its ceramic state. The preferred pre-ceramic resin 
comprises either a polymer-derived ceramic resin such as Silicon-Carboxyl 
or Alumina Silicate resins or a cementatous resin that has been modified 
to emulate polymer composite processing techniques such as Monoaluminum 
Phosphate (AKA Monoalumino Phosphate) resin; and, the preferred generic 
fiber system comprises Alumina, Altex, Nextel 312, Nextel 440, Nextel 510, 
Nextel 550, Silicon Nitride, Silicon Carbide, HPZ, Graphite, Carbon, and 
Peat 
The preferred supporting catalyst substrate is an open cell Silicon Carbide 
foam, Silicon Carboxyl foam, Oxide Ceramic foam, or similar ceramic foam 
material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In a co-pending application entitled FIBER REINFORCED CERAMIC MATRIX 
COMPOSITE INTERNAL COMBUSTION ENGINE EXHAUST MANIFOLD by the inventors, 
herein Ser. No. 08/515,925 filed on Aug. 16, 1995 and assigned to the 
common assignee of this application, an improved structural fiber 
reinforced ceramic matrix composite material is disclosed having high 
breakage resistance, high temperature resistance, corrosion resistance, 
low heat rejection, and "tailorable" thermal expansion characteristics 
which makes it particularly suited for an exhaust manifold material for an 
internal combustion engine. The present invention is particularly intended 
for use with that manifold design as the catalytic converter substrate can 
be co-cured with the manifold itself. Additionally in the previously 
mentioned ceramic manifold invention, an expendable mandrel is employed to 
form the inner contours of the FRCMC exhaust manifold structure and, as 
described therein, by employing the present invention herein described the 
expendable mandrel can be eliminated and be replaced by the catalytic 
converter substrate material which acts as an internal tool during the 
forming process of the FRCMC manifold structure. 
As depicted in FIG. 2, in the present invention the catalytic converter 
substrate material 14' is incorporated directly into the exhaust manifold 
10'. The header pipes 22, chamber 24, and single connecting pipe 28 all 
contain the catalytic substrate and therefore, act as the catalytic 
converter chamber. The outlet 30 is the outlet of the manifold 10' to 
which the standard exhaust pipe 16 of FIG. 1 is connected. Thus, all the 
hot exhaust gases from the engine immediately impinge on and pass through 
the catalytic substrate 26 to be cleaned thereby. Not only are the gases 
hotter than in a conventional prior art catalytic converter; but, 
additionally, the catalytic substrate 26 of this invention achieves 
sufficient operating temperature almost immediately because of the heat 
insulating/containment effect of the outer FRCMC structure that is 
inherently low thermal conductivity and low specific heat capacity. 
While any structure capable of withstanding the temperatures involved may 
be employed for the manifold 10' of this invention, an all-ceramic 
structure as described in the co-pending application entitled FIBER 
REINFORCED CERAMIC MATRIX COMPOSITE INTERNAL COMBUSTION ENGINE EXHAUST 
MANIFOLD by the inventors herein Ser. No. 08/515,925, filed on Aug. 16, 
1995, herewith and assigned to the common assignee of this application is 
preferred. Thus, it is preferred that the header pipes 22, the chamber 24, 
the connecting pipe 28, and the outlet 30 be of a fiber reinforced ceramic 
matrix composite (FRCMC) material comprising a pre-ceramic resin having 
fibers of a generic fiber system disposed throughout. 
The preferred FRCMC material used in this invention employs either polymer 
derived ceramic resins commercially available such as Silicon-Carboxyl 
resin (sold by Allied-Signal under the trade name Blackglas), Alumina 
Silicate resin (sold by Applied Poleramics under the product designation 
CO2) or cementatous resins that have been modified to emulate polymer 
composite processing techniques such as Monoaluminum Phosphate (also known 
as Monoalumino Phosphate) resin combined with a generic fiber system such 
as, but are not limited to, Alumina, Altex, Nextel 312, Nextel 440, Nextel 
510, Nextel 550, Silicon Nitride, Silicon Carbide, HPZ, Graphite, Carbon, 
and Peat. To add toughness qualities to the material, the fiber system is 
first coated to a few microns thickness with an interface material such as 
Carbon, Silicon Nitride, Silicon Carbide, Silicon Carboxide, Boron Nitride 
or multiple layers of one or more of these interfacial materials. The 
interface material prevents the resin from adhering directly to the fibers 
of the fiber system. Thus, after the resin has been converted to a ceramic 
as per the resin manufacturer's recommended cure cycle, there is a weak 
interface between the ceramic matrix and the fibers thereby imparting the 
desired qualities to the final component. Additionally, while any type of 
structure capable of withstanding the temperatures involved can be 
employed for the catalytic converter substrate 26, a high temperature 
resistant foam structure such as a Silicon Carbide, Silicon Carboxyl, or 
an equivalent oxide ceramic foam is preferred due to it's high surface 
area to volume ratio and low specific heat capacity.