RELATED APPLICATION

[0001] This application claims priority to United States Provisional Application No. 61/088,045, which was filed on August 12, 2008.

TECHNICAL FIELD

[0002] This invention generally relates to a vehicle exhaust system component, such as a catalytic converter for example, that has an improved interface between an outer shell and associated substrate assembly.

BACKGROUND OF THE INVENTION

[0003] Exhaust components such as catalytic converters for example, include an outer shell with a catalytic substrate assembly that is received within an internal cavity defined by the outer shell. The outer shell has a smooth inner surface that engages the substrate assembly when installed.

[0004] In passenger car applications, catalytic converters are typically sized to be long and thin for packaging purposes. This provides an aspect ratio (a ratio of the length to diameter of the substrate) that is greater than 1. In this configuration, the catalytic converter operates effectively.

[0005] However, when catalytic converters are used in heavy-duty applications, such as commercial vehicle applications, a failure mode can develop at an interface between the catalytic substrate assembly and the outer shell. The failure mode occurs due to relative movement between the substrate assembly and the outer shell caused by vibration. This movement can cause the catalytic converter to prematurely wear or fail.

[0006] For packaging purposes, in commercial vehicle applications, the substrate assembly is sized to have a greater diameter than length, i.e. an aspect ratio that is less than 1. The combination of a shorter length and increased diameter makes the substrate assembly more susceptible to damage from vibration. SUMMARY OF THE INVENTION

[0007] An outer shell of an exhaust component includes an external surface and an internal surface defining an inner cavity. At least a portion of the internal surface has a non-smooth finish. A substrate assembly is received within the inner cavity and is in contact with this non-smooth portion. The resulting contact prevents relative movement between the substrate assembly and the outer shell.

[0008] In one example, the vehicle exhaust component comprises a catalytic converter and the substrate assembly comprises a catalyst member that is wrapped within a fiber mat.

[0009] In one example, the substrate assembly is defined by a diameter D and a length L where the diameter D is significantly greater than the length L to provide an aspect ratio that is less than 1.

[0010] In one example, the non-smooth surface comprises a textured, roughened surface that extends about a center axis defined by the outer shell, and which is roughened to include a series of peaks and valleys. The inner surface can be roughened by acid etching, sand blasting, or shot peening for example.

[0011] These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic representation of a vehicle exhaust system.

[0013] Figure 2 is a side view of a converter incorporating the subject invention.

[0014] Figure 3 is an end view of the converter of Figure 2.

[0015] Figure 4 is a cross-sectional view taken along line 4-4 as indicated in Figure 3.

[0016] Figure 5 is a perspective view of the converter of Figure 2

[0017] Figure 6 is a schematic representation of a roughened inner surface of an outer shell of the converter of Figure 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] A vehicle exhaust system is shown at 10 in Figure 1. The vehicle exhaust system is comprised of various exhaust components. In one example, the vehicle exhaust system includes 10 includes at least an engine 12, a catalytic converter 14, and other exhaust system components schematically indicated at 16. Further, while the additional exhaust system components 16 are shown downstream of the catalytic converter 14, it should be understood that additional exhaust components could also be positioned upstream of the catalytic converter. The catalytic converter 14 includes a catalyst that causes decomposition of exhaust gases into products such as water and carbon dioxide. The operation of the catalytic converter 14 is well known and will not be discussed in detail.

[0019] The catalytic converter 14 is shown in greater detail in Figures 2-6. The catalytic converter 14 has an outer shell 18 within an inlet 20 that is downstream of the engine 12 and an outlet 22 as shown in Figure 2. The outer shell 18, in one example, is made from a stainless steel material and is formed into a desired shape by stamping, for example. As shown in Figure 3, the outer shell 18 has an external surface 24 and an internal surface 26 that defines an inner cavity 28. The internal surface 26 extends circumferentially around a center axis A (Figure 2) of the catalytic converter 14.

[0020] As shown in Figure 4, a substrate assembly 30 is inserted within the inner cavity 28. The substrate assembly 30 includes a substrate body 32 (catalyst) and a mat 34 that is wrapped around the substrate body 32. The mat 34, in one example, is formed from a plurality of fibers that are compressed together to form a single-piece structure that is wrapped around the substrate body 32. The mat 34 includes an outer surface 38a and an inner surface 38b. The outer surface 38a is in direct contact with the internal surface 26 of the outer shell 18. The inner surface 38b is in direct contact with an outer surface of the substrate body 32.

[0021] When assembled, the substrate assembly 30 may not fill the entire length of the inner cavity 28 and can include an open area 36 for facilitating insertion as shown in Figure 5. Any type of insertion method can be used to install the substrate assembly 30. Further, leaving an open area at an end of the outer shell facilitates connection to other exhaust components. [0022] The substrate assembly 30 is defined by a diameter D and a length L. As shown, the diameter D of the substrate assembly 30 is significantly greater than the length L as best shown in Figure 4. This provides an aspect ratio, i.e. a ratio of length to diameter, which is less than 1. When the aspect ratio is less than 1, vibrations experienced by the catalytic converter 14 can be of concern.

[0023] The substrate assembly 30 defines an outer peripheral surface 40 that abuts against the internal surface 26 of the outer shell 18. The internal surface 26 has a non- smooth, textured, or roughened surface finish that provides peaks 42 and valleys 44 as shown in Figure 6. As the outer peripheral surface 40 of the substrate assembly 30 contacts this roughened surface, the substrate assembly 30 bites or grabs into the outer shell 18 to prevent relative movement between the outer shell 18 and the substrate assembly 30.

[0024] The internal surface 26 can be roughened using any of various chemical and/or mechanical processes. For example, the internal surface 26 can be roughed by acid etching to create the peaks 42 and valleys 44. In another example, sand blasting or shot peening could be used to create the roughened surface. In one example, the entire internal surface 26 is roughened. However, only a portion of the internal surface 26 may have to be roughened to provide a sufficient holding force. In one example, the roughened surface is formed to extends circumferentially around the center axis A.

[0025] Roughening the internal surface 26 of the outer shell 18 increases the coefficient of friction at the contact interface and thereby prevents the relative movement. One advantage with this configuration is that larger fiber mats can be used to increase durability because these larger fibers now have a roughened or textured surface to bite into. Further, while the example of a catalytic converter is shown, it should be understood that the combination of an inner exhaust component assembly and roughened inner surface of an associated outer shell could also be utilized in other types of exhaust components.

[0026] Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.