Metal working – Method of mechanical manufacture – Catalytic device making
Reexamination Certificate
1999-03-01
2001-09-25
Tran, Hien (Department: 1764)
Metal working
Method of mechanical manufacture
Catalytic device making
C029S508000, C029S515000, C029S516000, C422S177000
Reexamination Certificate
active
06293010
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust treatment device, which may, for example comprise a catalytic device having a one-piece cylindrical housing, preferably formed of metal, with integral inlet gas shields and diffusers which may be spin-formed.
2. Disclosure Information
The tailpipe emission control laws applicable to automotive vehicles in various countries are becoming increasingly stringent. Tighter standards demand more precise air/fuel ratio control. This is possible only if air leaks in the exhaust system are kept to an absolute minimum, because air leaks cause a loss of air/fuel ratio control capability. A second important consideration relates to the need to rapidly “light off” exhaust treatment devices. Rapid light off requires that certain exhaust treatment devices be located close to the vehicle's engine. Thus, it is highly desirable to have an exhaust treatment device which packages in an extremely small volume, and which, therefore, may be mounted in engine compartment or the toeboard area of a vehicle, or in other areas which do not offer much space for an exhaust treatment device.
Another objective of automotive manufacturers is to reduce cost of vehicles; engine exhaust treatment systems comprise an expensive vehicle system. The present exhaust treatment device, while allowing much more flexible packaging, also allows lower cost because welding and additional parts are eliminated.
U.S. Pat. No. 4,969,264 discloses a catalytic converter and substrate support having a swaged center section and ram-formed ends. Unfortunately, the design of the '264 patent is not suitable for use as an automotive catalytic converter because the ram-formed ends do not provide any protection against undercutting of the support system by the exhaust gases. And, ram forming in close proximity to a catalyst substrate may have the unfortunate consequence of breaking the substrate.
The inventors of the present device have determined that a segmented inlet gas shield and diffuser may be spin-formed rather than ram-formed so as to provide a gas shield, greatly reducing exhaust gas impingement upon the catalytic substrate sealing and support system, while also producing a device of leakproof construction and with a reduced package volume. Additionally, an exhaust treatment device, according to the present invention, having integral diffusers, may be mated with exhaust pipes without a need for additional extensions.
SUMMARY OF THE INVENTION
An exhaust treatment device for an internal combustion engine includes a substrate, generally cylindrical in shape and having a cylindrical outer surface extending between an inlet surface and an outlet surface, and a sealing system applied to the cylindrical outer surface. A one-piece, generally cylindrical housing containing the substrate and for directing the flow of exhaust gas to and from the substrate, includes a center portion swaged upon the substrate such that the sealing system is uniformly compressed and a segmented inlet gas shield and diffuser. The inlet gas shield and diffuser includes a first concave segment extending between the center portion of the housing and a first convex segment which is tangential to the inlet surface of the substrate such that impingement of exhaust gas upon the sealing system is inhibited. The gas shield and diffuser further comprises a second concave segment extending between the first convex segment and a second convex segment having a termination to which an exhaust inlet pipe may be attached. A segmented outlet gas shield and diffuser comprises a first concave segment extending between the center portion of the housing and a first convex segment which is tangential to the outlet surface of the substrate such that impingement of exhaust gas upon the sealing system adjacent the outlet surface of the substrate is inhibited, with the outlet shield and diffuser further comprising a second concave segment extending between the first convex segment and a second convex segment having a termination to which an exhaust outlet pipe may be attached.
The first concave segment of the inlet gas shield and diffuser has a radius of curvature which is approximately twice the radius of curvature of the first convex portion. The first concave segment of the inlet gas shield and diffuser has a radius of curvature with a length which is about one-tenth of the maximum diameter of the generally cylindrical housing. Also, the first convex segment of the inlet gas shield and diffuser has a radius of curvature with a length which is about one-fifth of the maximum diameter of the generally cylindrical housing.
According to another aspect of the present invention, a sealing system comprises a wire mesh mat extending substantially the entire length of the substrate with the mat terminating at both ends with a metallic Z-shaped seal. The inlet gas shield and diffuser and outlet gas shield and diffuser may be spin-formed after the substrate has been swaged and placed within the housing. Other alternatives are possible for the spin-forming, regarding the precise sequence of locating a substrate within the housing prior to spin-forming one end of the housing. In either event, the first concave segment of the inlet gas shield and diffuser extends inwardly at approximately 45° to the cylindrical outer surface of the substrate.
According to yet another aspect of the present invention, a process for assembling an exhaust treatment device comprises the steps of inserting an exhaust treatment substrate into a cylindrical metallic tube, reducing the diameter of the tube by swaging such that the substrate is held firmly in place within the tubing, and spin-forming gas shielding diffusers from the tube at opposite ends of the exhaust treatment device. It is an advantage of the present invention that an exhaust treatment device made according to this invention will be of one-piece, leak-proof construction.
It is a further advantage of the present invention that an exhaust treatment device made according to this invention will be economical to produce.
It is yet another advantage of the present invention that an exhaust treatment device made according to this invention will have small package volume and therefore will be able to fit into smaller locations in all types of automotive vehicles.
It is yet another advantage of the present invention that an exhaust treatment device made according to this invention may be produced with flexible manufacturing systems, lending themselves readily to changes in length and diameter of the exhaust treatment device.
It is yet another advantage of the present invention that an exhaust treatment device made according to this invention may be produced without the need for either welding or any other high temperature operation.
Other advantages and features of the present invention will become apparent to the reader of this specification.
REFERENCES:
patent: 4969264 (1990-11-01), Dryer et al.
patent: 5724735 (1998-03-01), Ickes et al.
patent: 768451 (1997-04-01), None
Albrecht Michael Blake
Harold Vincent
Morrow Timothy D.
Nowka Erich James
Umin Edward A.
Drouillard Jerome R.
Ford Global Technologies Inc.
Tran Hien
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