Patent Application
20070271786
Catalytic converters have been employed to catalyze exhaust fluids in vehicles for more than twenty years and have been manufactured in a number of ways. Catalytic converters play a critical role in ensuring that fuel rich fluids are reduced down to acceptable levels, and are a comparatively expensive article within an exhaust system. The materials are expensive, and manufacture is labor intensive. Furthermore, design packages that increase durability and improve overall system performance for reductions in emissions are at a premium. Accordingly, methods of manufacture have been put forth in attempts to reduce manufacturing costs, while at the same time, increasing durability and stabilizing system performance.
One method of manufacturing catalytic converters is to provide a pre-made canister and stuff it with the catalyst substrate and the insulation/support pad. In this method, the catalyst substrate is wrapped with an intumescent or non-intumescent mat of a selected thickness and weight (various weights are employed for various applications and desired properties). Generally, the wrapped substrate material will create an assembly having outer dimensions that measure about 8 mm larger than the inside dimensions of the converter shell or canister. The assembly as described is then forced through a reduction cone and into the converter shell. Up to about 20,000 lbs of force may be used to accomplish the insertion of the assembly into the can. More particularly, within this range a force up to 7,000 lbs may be used. The method is costly.
A catalytic converter may be produced by a method referred to as “the tourniquet method.” The tourniquet method dispenses with the reducing cone and thus avoids the high insertion pressures on the substrate and mat materials. The method places the substrate and mat assembly into a canister open on one longitudinal edge. The canister is closed around the assembly by straps and compressed to the desired size. The open ends of the canister will, in this position, be overlapping and then are welded together. This method is also expensive and labor intensive. Further, due to this overlap, engineering design consideration must be given to the space alteration inside the canister due to the overlapped edge. The overlapped edge causes a mat density change in the local area of the overlap. This is a further cost addition.
Further, both of the above described catalyst and shell assemblies may have transitional areas to accommodate any difference in diameter between the catalyst shell diameter and the diameter of inlet and outlet pipes. These transitions, e.g., endcones, may be affixed to the shell by Metal Inert Gas (MIG) welding, which may result in a significant amount of cycle time and heat addition to the parts. An alternative to MIG welding is spinforming of the ends of a shell that extends beyond the ends of the catalyst. This process is also high in cycle time and also results in parts having a large area of heated surface. Accordingly, there remains a need in the art for a catalytic converter that is easily and inexpensively manufactured, that increases durability, and does not restrict design choice.
Disclosed herein is a catalytic converter including a shell having a welding deformation detail; a catalyst substrate inserted within the shell; a mat support material disposed between the catalyst substrate and the shell; an end cone having a flange; and wherein the flange is deformation welded to the shell at the welding deformation detail.
Further disclosed herein is a method of making a catalytic converter including forming a shell having a welding deformation detail; inserting and housing a catalyst substrate inside the shell, wherein a mat support material is disposed between the shell and the catalyst substrate; welding an end cone having a flange to the shell by applying a deformation force to the flange causing deformation of welding deformation detail.
The above-described and other features will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike:
A method of welding end-cones to a converter assembly is described below. Although the method is described in relation to welding end-cones to a converter assembly, this method may also be used in other welding applications, e.g., tube to tube, converter to tube, and the like.
Annular Deformation Resistance Welding (ADRW), as used herein, refers generally to a welding method, wherein a joint is formed through the deformation and displacement of material at the weld interface. Annular Deformation Resistance Welding is also described in U.S. Pat. No. 6,552,294 to Ananthanarayanan et al., which is herein incorporated by reference. Although ADRW is similar to “Resistance Welding,” it is a distinct welding method as will be discussed in greater detail. Resistance welding, as used herein, refers generally to a method used to join metallic parts with electric current. There are several forms of resistance welding, including, for example, spot welding, seam selding, projection welding, butt welding, and the like. In all forms of resistance welding, the parts are locally heated until a molten pool forms. The parts are then allowed to cool, and the pool solidifies to form a weld bond. Generally, during resistance welding, an operator of resistance welding equipment has control over, for example, current setting, electrode force, and weld time.
In resistance welding, heat is created by electrode(s) passing an electric current through the work pieces. The heat generated may depend on electrical resistance and thermal conductivity of the metal, and the time that the current is applied. The heat generated may be expressed by the following equation:
E=I2·R·t
where E is the heat energy, I is the current, R is the electrical resistance and t is the time that the current is applied. Copper may be used for electrodes, because it has a low resistance and high thermal conductivity compared to most metals. This promotes heat generation in the work pieces instead of the electrodes. The electrodes may be cooled with water, removing excess heat, to prevent the electrodes from overheating.
Furthermore, in resistance welding, the electrodes are held under a controlled force during welding. The resistance across the interfaces between the work pieces and the electrodes may be affected by the amount of the force applied. The force may be adjusted to immediately create heat at the interface between the work pieces. Moreover, if the force is too low expulsion, weld splash, and/or the like can occur. The heat used to produce the molten pool may depend on, for example, the thermal conductivity and melting point of the metal being welded. A material with a relatively high thermal conductivity will quickly conduct heat away from the weld pool, thus increasing the total heat used to melt the pool compared to a material with a relatively low melting point.
In ADRW, at least one of the work pieces comprises a deformation detail, for example, a rib portion, wherein welding occurs at the deformation detail. As will be discussed in greater detail, the deformation detail facilitates deformation under a deformation force. Like simple resistance welding, an electrode is applied to the work piece. For example, a current of about 5,000 amperes to about 20,000 amperes is applied for less than 1 second. More particularly, a current of about 15,000 amperes to 20,000 amperes is used. Further, the electrode(s) apply a force of about 300 to 800 pounds to the work piece. Unlike simple resistance welding, however, in ADRW, the force applied by the electrode causes deformation of the deformation detail. For example, if the deformation detail is a rib portion, the force applied by the electrode causes the rib to compress, i.e., deform. Furthermore, the welding surfaces are deformed under the heat generated by the current across the welding surfaces and the force of the electrodes. A weld bond is formed while the materials are in this plastic-like state, which allows impurities in the metal to be displaced away from the weld bond as the welding surfaces are placed in intimate contact with each other under the electrode force. In other words, impurities are pushed radially away from the weld area, i.e., the material is ejected away from the area that forms the weld bond, allowing for a metal-to-metal weld bond relatively free of contaminates. In the ADRW method, the deformation has an action linear distance about equal to the desired weld bond. For example, the weld bond is about equal to the thickness of one material thickness in order to be of equal load bearing capacity as the parent material.
Further, the deformation detail is not limited to embodiments depicting a rib portion; rather the deformation detail may be a detail (i.e., feature) that facilitates deformation as described above. Moreover, the ADRW method may be used to create leak-tight joints with uniform circumferential weld strength. The term “leak-tight”, as used herein, refers to a joint that generally prohibits the passage of fluid therethrough.
Additionally, the heat-affected zone of the weld in the ADRW method is much smaller, resulting in less strength reduction of the parent materials when compared to, for example, Gas Metal Arc Welding (GMAW), and the like. GMAW may also be referred to as Metal Inert Gas (MIG) welding. In MIG welding the “inert gas” refers to a shielding gas, which is generally supplied from a cylinder or other gas source and then piped to the welding gun. Further, a metal wire is used to start the arc, and then is fed into the puddle of molten metal to continuously replenish the metal in the puddle that is used to join the materials.
The ADRW method allows the weld to be monitored to indicate quality of the finished product, which is advantageous in that it may reduce weld repair, and may have potential for reducing capital expenditure for inspection equipment (e.g., elimination of leak tester). Moreover, this method may reduce cycle time to less than about 5 seconds and even a cycle time of about 1 second (s) in some embodiments. Thus, an increased capacity of a production cell may be realized, while using substantially the same capital.
Several combinations of catalytic converters are discussed hereunder with reference to individual drawing figures. One of skill in the art will easily recognize that many of the components of each of the embodiments are similar or identical to the others. Each of these elements is introduced in the discussion of
Referring now to
End cone 20 comprises an opening 22, a flange 24, and an inner cone 26. As will be discussed in greater detail, end cone 20 is joined to shell 16 at ribbed portion 18 using the ADRW method. End cone 20 is blanked, i.e., the sheet metal forming process by which the part is removed from the strip of parent metal. This blanking process leaves flange 24, which then fits over shell 16, wherein ribbed portion 18 of shell 16 abuts flange 24 of end cone 20. Since end cone 20 is cut from the parent metal by blanking instead of blanking and pinch trimming a comparatively more simple end cone 20 form may be used. The term “pinch trimming” as used herein refers an additional process where a flange (e.g., 24), which is formed by a previous blanking process is then pushed through an additional die detail that wipes the short flange, left from blanking, along the centerline leaving a longer skirt. This type of endcone may be used, for example, on stuffed shells. Flange 24 comprises a mating surface sufficient for an electrode (not shown). During the ADRW method, an electrode applies a force to flange 24, wherein deformation occurs in the weld area under the force and heat generated by the current flow across the interface from rib portion 18 to flange 24. Moreover, the force applied by the electrode is sufficient to cause deformation between rib portion 18 and flange 24. The deformation is accomplished in
As mentioned above, the distinct elements of each embodiment are discussed in each figure, for example,
Examples of suitable insulating materials include formed ceramic fiber materials comprising vermiculite, refractory ceramic fibers, organic binders, combinations thereof, and the like. The insulating material may be a non-expanding ceramic material, an intumescent material, or a material comprising both. Examples of non-expanding ceramic fiber material includes, but is not limited to, ceramic materials such as those sold under the trademarks “NEXTEL” and “SAFFIL” by the “3M” Company, Minneapolis, Minn., or those sold under the trademark, “FIBERFRAX” and “CC-MAX” by the Unifrax Co., Niagara Falls, N.Y., and the like. Examples of intumescent ceramic material include, but is not limited to, ceramic materials such as those sold under the trademark “INTERAM” by the “3M” Company, Minneapolis, Minn., as well as those intumescents which are also sold under the aforementioned “FIBERFRAX” trademark, as well as combinations thereof and others.
Referring now to
Further embodiments are envisioned, where the two part converter with central weldment may be used to create a converter that has inlet and outlet angles to the centerline of the part. First, a shell tube is cut at half the desired angle between snorkels. New tube ends are then formed to add features that facilitate the ADRW method (e.g., rib portion and/or flange). The tube sections are stuffed with catalyst in mat support and then joined together again after being rotated 180 degrees. This process produces a converter that has an angled body with the angle equal to about 2 times the original angle cut in the tube. This embodiment may be useful for close packaging in under hood and/or underbody areas. Embodiments are also envisioned where greater than two catalysts are canned separately and joined together using the ADRW method. The advantage of this type of construction is that each catalyst is individually stuffed into each container, which may eliminate the potential for high mat density caused by face angles between adjoining catalysts leading to potential breakage of the catalyst.
The same type of weld interface used in the ADRW method to form converter to tube joints, cone to shell joints, and the like may also be used for tube to tube joins. For example, in tube-to-tube joints, a first tube comprises a rib portion and second tube comprises a flange.
Catalyst substrate 12 comprises any ceramic material or “high temperature material” capable of operating under exhaust system conditions, i.e., temperatures up to about 1,100° C. and exposure to hydrocarbons, nitrous oxides, carbon monoxide, carbon dioxide, and/or sulfur in, for example, a spark ignition or diesel engine environment. These high temperature materials may be ceramic, metallic foils, combinations thereof, and other materials, that are capable of supporting the desired catalyst coating. Some possible ceramic materials include cordierite, silicon carbide, and the like, and mixtures thereof. One such material, “Cordierite”, is commercially available from Corning, Inc., Corning, N.Y..
Catalyst substrate 12 may have any geometry, which provides a sufficient surface area for the catalyst, with a honeycomb structure being desirable. The honeycomb structure may have cells shaped like triangles, squares, rectangles, hexagons, octagons, diamonds and the like. In consideration of the tooling costs for extrusion molding or the like, however, the cells are generally square in shape. Moreover, it is desirable that catalyst substrate 12 has the greatest number of cells that is structurally feasible such that the inner surface area of catalyst substrate 12 is maximized. The surface area of the substrate should also be sufficient to support a sufficient amount of catalyst(s) to effectively catalyze exhaust fluid streams flowing therethrough, with the surface area being a function of the surface design of fluid passages, the volume of the substrate, and the effective density of the substrate. These parameters may be adjusted according to design specifications, taking into account both the desired shape of the catalytic converter and optimal paths for exhaust fluid flow. Additionally, it is desirable that catalyst substrate 12 is formed in geometric shapes such that mat support material 14 may be wrap around substrate 12 properly without delaminating or cracking, which may occur when bending the material around sharp radii, e.g., radii less than about 25 mm.
Catalyst substrate 12 may comprise any catalyst material sufficient to convert exhaust fluids to acceptable emission levels. Catalyst substrate 12 may be wash coated and/or imbibed with a catalyst, which may comprise a high surface area material, having one or more possible catalyst materials including noble metals such as platinum, palladium, rhodium, iridium, osmium and ruthenium; and other metals such as tantalum, zirconium, yttrium, cerium, nickel, and copper; and mixtures and alloys thereof, and other conventional catalysts.
The mat support 14 may comprise a material that enhances the structural integrity of the substrate by applying compressive radial forces about it, reducing its axial movement, and retaining it in place, is concentrically disposed around the substrate. Mat support material 14 may be a formed ceramic fiber material comprising vermiculite, refractory ceramic fibers, organic binders, combinations thereof, and the like. Mat support material 14 may be a non-expanding ceramic material, an intumescent material, or a material comprising both. Examples of non-expanding ceramic fiber material includes, but is not limited to, ceramic materials such as those sold under the trademarks “NEXTEL” and “SAFFIL” by the “3M” Company, Minneapolis, Minn., or those sold under the trademark, “FIBERFRAX” and “CC-MAX” by the Unifrax Co., Niagara Falls, N.Y., and the like. Examples of intumescent ceramic material include, but is not limited to, ceramic materials such as those sold under the trademark “INTERAM” by the “3M” Company, Minneapolis, Minn., as well as those intumescents which are also sold under the aforementioned “FIBERFRAX” trademark, as well as combinations thereof and others.
The thickness of mat support material 14 may depend upon the temperature of the exhaust fluid, as well as the application of catalytic converter. For example, the thickness of mat support material used in catalytic converter for a spark ignition environment may differ from that used in a diesel environment. Moreover, as the exhaust fluid temperature range increases, the thickness of mat material 14 may also increase accordingly to meet customer skin temperature requirements. Generally, the mat support material thickness is about 2 mm to about 12 mm for most automotive applications, within this range it is also desirable to have a thickness of about 4 mm to about 8 mm.
The choice of material for the shell 16 depends upon the type of exhaust fluid, the maximum temperature reached by the catalyst substrate, the maximum temperature of the exhaust fluid stream, and the like. Suitable materials for the shell 16 may comprise any material that is capable of resisting under-car salt, temperature and corrosion. For example, ferrous materials may be employed such as ferritic stainless steels. Ferritic stainless steels may include stainless steels such as, e.g., the 400-Series such as SS-409, SS-439, and SS-441, with SS-409 particularly desirable. Acceptable SS type stainless steel may include stainless steels such as those sold under the trademarks “Type S40900” by Armco, Inc., in Pittsburgh, Pa.
Possible materials for the end-cone 20 include any material capable of maintaining the desired structural integrity in an operating environment consistent with exhaust fluid treatment, e.g., temperatures up to about 1,000° C., exposure to exhaust fluids, and extreme weather conditions. Although numerous materials and alloys can be employed, ferrous materials and alloys are typically used. High temperature, corrosion resistant, stainless steel is desirable, with stainless steel 400 series, e.g., type 409 and the like, being more desirable.
Advantageously, the Annular Deformation Resistance Welding (ADRW) method reduces weld time compared to other welding methods, e.g., MIG welding. The cycle time for ADRW is about 1 second. Therefore, an increased cell capacity may be realized, while using approximately the same capital. The ADRW method allows the weld to be monitored to indicate quality of the finished product, which is advantageous in that it may reduce weld repair, and may have potential for reducing capital expenditure for inspection equipment (e.g., elimination of leak tester). Further, welds made to end cones may have a greater load bearing capacity compared to welds using other methods, because full thickness materials are being joined, i.e., materials that have not been thinned by, for example, extrusion.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This application is a divisional of U.S. Ser. No. 10/465,356, filed Jun. 18, 2003.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10465356 | Jun 2003 | US |
| Child | 11825685 | Jul 2007 | US |
