STRUCTURE

CROSS REFERENCE TO RELATED APPLICATION The present application is a continuation-in-part of U.S. application Ser. No. 08/501,755, filed July 12, 1995 by David T. Sheller and William A. Whittenberger, and related to concurrently filed U.S. applications, entitled Assembly and Method for Making Catalytic Converter Structures, as follows: Ser. No. (Atty Dkt. 04605.0078) by William A. Whittenberger, John J. Chlebus, Joseph E. Kubsh, and Boris Y. Brodsky; Ser. No. (Atty Dkt. 04605.0079) by David T. Sheller and William A. Whittenberger; Ser. No. (Atty Dkt. 04605.0081) by David T. Sheller, Steven Edson and William A.

Whittenberger; Ser. No. (Atty Dkt. 04605.0082) by William A. Whittenberger, David T. Sheller, and Gordon W. Brunson; Ser. No. (Atty Dkt. 04605.0083) by David T. Sheller, William A. Whittenberger and Joseph E. Kubsh; Ser. No. (Atty Dkt. 04605.0084) by William A.

Whittenberger, Gordon W. Brunson, and Boris Y. Brodsky; and Ser. No. (Atty Dkt. 04605.0087) by William A. Whittenberger and Gordon W. Brunson; The complete disclosure of all of these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to methods for the manufacture of metallic catalytic converters, and, more particularly, to such converters especially adapted for use in vehicular engines to control exhaust emissions, and to foil subassemblies useful in the practice of such methods.

Description of the Related Art

Catalytic converters containing a corrugated thin metal (stainless steel) monolith typically have been formed of a plurality of thin metal strips or foil leaves wound about a central pin or about spaced

"fixation" points. Such prior catalytic converters bodies, have supported both the outer and inner end of the individual layers by fixing them to the housing for the converter body and a central pin or post. In certain instances, the interior support has been provided by looping the foil leaves about a fixed point or portions whereby the inner ends of the leaves have been supported by other foil leaves. The thin metal strips or leaves forming the multicellular honeycomb body also have been brazed together at points intermediate the ends to form a rigid honeycomb

monolith. Various techniques such as soldering, welding, brazing, riveting, clamping, reverse wrapping or folding, or the like, have been used to secure the inner and outer ends , and usually the intermediate 5 portion, of the leaves or strips to the support member. While many techniques have been used to assemble the leaves into the housing and many leaf arrangements have been constructed, many arrangements have been unable to survive severe automotive industry tests known as the

10. Hot Shake Test, the Hot Cycling Test, combinations of these tests, cold vibration testing, water quench testing, and impact testing.

The Hot Shake test involves oscillating (50 to 200 Hertz and 28 to 80 G inertial loading) the device in a

15 vertical, radial or angular attitude at a high temperature (between 800 and 1050 degrees C . ; 1472 to 1922 degrees F. , respectively) with exhaust gas from a gas burner or a running internal combustion engine simultaneously passing through the device. If the 0 device telescopes, or displays separation or folding over of the leading or upstream edges of the foil leaves, or shows other mechanical deformation or breakage up to a predetermined time, e.g. , 5 to 200 hours, the device is said to fail the test. 5 The Hot Cycling Test is run with exhaust flowing at 800 to 1050 degrees C; (1472 to 1922 degrees F.) and

cycled to 120 to 200 degrees C. once every 13 to 20 minutes for up to 300 hours. Telescoping or separation of the leading edges of the thin metal foil strips, or mechanical deformation, cracking or breakage is considered a failure.

Also, the Hot Shake Test and the Hot Cycling Test are sometimes combined, that is, the two tests are conducted simultaneously or superimposed one on the other. The Hot Shake Test and the Hot Cycling Test are hereinafter called "Hot Tests." While they have proved very difficult to survive, the structures of the present invention are designed to survive these Hot Tests and other tests similar in nature and effect that are known in the industry.

From the foregoing, it will be appreciated that catalytic converter bodies and their method of manufacture have received considerable attention, particularly by the automotive industry, are complex in design and manufacture, and are in need of improvement.

SUMMARY OF THE INVENTION

The advantages and purpose of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages

and purpose of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

To attain the advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a catalytic converter is provided, comprising an outer jacket, and at least one nonradiating parallel grouping of non-nestable foil leaves having ends defining a leaf length to provide flow passages generally transverse to a leaf length. One end of each foil leaf is connected to the outer jacket and the other end of each leaf is unconnected to the outer jacket.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. In the drawings.

Fig. 1 is a partial end view of an embodiment of a catalytic converter incorporating the teachings of the present invention;

Fig. 2 is a partial end view of an alternative embodiment of a catalytic converter incorporating the teachings of the present invention;

Fig. 2a is an alternative arrangement for the structure shown in Fig. 2;

Fig. 3 is a partial end view of an alternative embodiment of a catalytic converter incorporating the 5 teachings of the present invention;

Fig. 3a is an alternative arrangement for the structure shown in Fig. 3;

Fig. 4 is a partial end view in cross section of an alternative embodiment of a catalytic converter 10. incorporating the teachings of the present invention;

Fig. 4a is an alternative arrangement for the structure shown in Fig. 4;

Fig. 5 is a perspective view of a continuous sheet of segments usable to construct catalytic converters 15 according to the claimed invention;

Fig. 6 is an end view of a pair of continuous strips shown in Fig. 5 and braised together;

Fig. 7 is a partial end view in cross section of an alternative embodiment of a catalytic converter 0 incorporating the teachings of the present invention;

Fig. 8 is a partial end view in cross section of an alternative embodiment of a catalytic converter incorporating the teachings of the present invention;

Fig. 9 is a partial end view in cross section of 5 an alternative embodiment of a catalytic converter

incorporating the teachings of the present invention; and

Fig. 10 is a partial end view in cross section of an alternative embodiment of a catalytic converter incorporating the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

One aspect of the present invention is based on a finding by the inventors that the structure of a metallic catalytic converter body can be improved by allowing the metal sheets, referred to as foil leaf core elements or foil leaves, to be compliant, move, flex, or float in the fluid stream. Whereas it was previously thought that rigidity was essential to prevent failure in the "Hot Tests, " it has been discovered that flexure or compliance of the foil heat core elements in response to thermal and fluid flow variations as well as mechanical vibration were desirable attributes in converter bodies used in various applications.

This discovery has given rise to what is termed a "cantilever" converter body, namely, one in which the foil leaf elements forming the core are secured at one end only or are secured at their second end in a manner, so the individual foil leaf core elements are

"compliant", that is, they move or yield to stresses within the elastic limit of the thin metal.

The foil leaf arrangement may be constructed from "ferritic" stainless steel such as that described in U.S. Patent 4,414,023 to Aggen. One usable ferritic stainless steel alloy contains 20% chromium, 5% aluminum, and from 0.002% to 0.05% of at least one rare earth metal selected from cerium, lanthanum, neodymium, yttrium, and praseodymium, or a mixture of two or more of such rare earth metals, balance iron and trace steel making impurities. A ferritic stainless steel is commercially available from Allegheny Ludlum Steel Co. under the trademark "Alfa IV.

Another usable commercially available stainless steel metal alloy is identified as Haynes 214 alloy. This alloy and other useful nickeliferous alloys are described in U.S. Patent 4,671,931 dated 9 June 1987 to Herchenroeder et al . These alloys are characterized by high resistance to oxidation and high temperatures. A specific example contains 75% nickel, 16% chromium, 4.5% aluminum, 3% iron, optionally trace amounts of one or

more rare earth metals except yttrium, 0.05% carbon, and steel making impurities. Haynes 230 alloy, also useful herein has a composition containing 22% chromium, 14% tungsten, 2% molybdenum, 0.10% carbon, a trace amount of lanthanum, balance nickel.

The ferritic stainless steels, and the Haynes alloys 214 and 230, all of which are considered to be stainless steels, are examples of high temperature resistive, oxidation resistant (or corrosion resistant) metal alloys that are useful for use in making the foil leaf core elements or leaves of the present invention, as well as the multicellular honeycomb converter bodies thereof. Suitable metal alloys must be able to withstand "high" temperature, e.g., from 900 degrees C. to 1200 degrees C. (1652 degrees F. to 2012 degrees F.) over prolonged periods.

Other high temperature resistive, oxidation resistant metal alloys are known and may be used herein. For most applications, and particularly automotive applications, these alloys are used as "thin" metal or foil, that is, having a thickness of from about 0.001" to about 0.005", and preferably from 0.0015" to about 0.0037". The housings, or jacket, hereof are of stainless steel and have a thickness of from about 0.03" to about 0.08", preferably, 0.04" to 0.06".

The multicellular converter bodies of the present invention preferably are formed from foil leaves precoated before assembly, such as described in U.S. Patent 4,711,009 Cornelison et al . The converter bodies of the invention may be made solely of corrugated foil core elements which are non-nesting, or of alternating corrugated and flat foil core elements, or of other non¬ nesting arrangements or of other arrangements providing cells, flow passages, or a honeycomb structure when assembled. In the preferred embodiments, the foil leaves, which will be used as core elements, are precoated before assembly. The ends are masked or cleansed to maintain them free of any coating so as to facilitate brazing or welding to the housing or to an intermediate sleeve.

As indicated in U.S. Patent 4,911,007, supra, the coating is desirably a refractory metal oxide, e.g., alumina, alumina/ceria, titania, titania/alumina, silica, zirconia, etc., and if desired, a catalyst may be supported on the refractory metal oxide coating. For use in catalytic converters, the catalyst is normally a noble metal, e.g., platinum, palladium, rhodium, ruthenium, indium, or a mixture of two or more of such metals, e.g., platinum/rhodium. The refractory metal oxide coating is generally applied in an amount ranging

from about 10 mgs/square inch to about 80 mgs/ square inch.

In some applications, corrugations preferably have an amplitude of from about 0.01 inch to about 0.15 inch, and a pitch of from about 0.02 inch to about 0.25 inch. The amplitude and pitch of the corrugations determine cell density, that is, the number of cells per unit of cross-sectional area in the converter body. Typically, the cell density is expressed in cells per square inch (cpsi) and may vary from about 50 cpsi to 2-000 cpsi. Where a non-nesting corrugated foil leaf core element is used, the corrugations are generally patterned, e.g., a herringbone pattern or a chevron pattern, or skewed pattern. in a "skewed pattern", the corrugations are straight, but at an angle of from 3 degrees to about 10 degrees to the parallel marginal edges of the strips. The latter foil leaf core elements may be layered without nesting.

Where alternating corrugated and flat foil leaf core elements are used in a non-nesting arrangement to form the multicellular bodies, straight-through corrugations may be conveniently used, these exhibiting the lowest pressure drop at high flow in fluid flowing through the converter body. The straight-through corrugations are usually oriented along a line normal to the longitudinal marginal edges of the foil leaves,

although, as indicated above, the corrugations may be oriented along a line oblique to the longitudinal marginal edges of the leaves.

To reduce stress, the "flat" foil leaf core elements preferably are lightly corrugated to have corrugations with an amplitude of from about 0.002" to about 0.01", e.g., 0.005" and a pitch of from about 0.02" to about 0.2", e.g., 0.1".

The coated corrugated and flat foil leaves that form the working gas flow passageways in the converter body of the invention constitute the major metal foil content thereof and are preferably formed of the lower cost ferritic stainless steel alloys. Because of its greater strength, albeit higher cost, he nickeliferous stainless steel alloys may be used in the converter of the invention particularly in the center area and other areas where the requirement for foil strength justifies the higher cost of these alloys. In the ensuing description and in the appended claims, the latter foil alloys may be referred to generically as "high strength" foil and may be uncoated to facilitate joining by spot welding, for example.

According to the present invention, a honeycomb structure for use as a catalytic convertor structure or catalyst carrier body is provided including a jacket and at least one non-radiating parallel grouping of

non-nestable foil leaves having ends defining a leaf length to provide flow passage to its generally transverse to the leaf length. One end of each foil leaf is connected to the jacket tube, and the other end of each leaf is unconnected to the jacket. As shown in Fig. 1, a catalytic converter structure 20 includes an jacket, 22, preferably made from a metal sheet formed into a tube. The non-nestable foil leaves preferably include an alternating series of corrugated metal strips 24 and flat metal strips 26, which together are non-nestable and provide flow passages 28 generally transverse to a leaf length. Each sheet has two ends. In the embodiment shown in Fig. 1, the left end 30 of each flat leaf 26 is connected to the left side of the jacket 22 and the right end 32 of each flat leaf 64 is proximate to but spaced from and unconnected to the right side 33 of jacket 22.

As shown in Fig. 1, a stack of foil leaves 24 and 26 form a single nonradiating parallel grouping of metal sheets that extend along flat paths. The leaves extend along nonradiating paths because the paths of the leaves do not generally radiate from a center or central area. The remaining portion inside the jacket 22 of the arrangement shown in Fig. 1 is filled with flat and corrugated sheets in a manner similar to those shown in place. Alternatively, the remaining space may be filled

with another arrangement of sheets. A completed arrangement of non-nestable sheets in a jacket may be used alone as a catalytic converter structure or it may be used as a catalytic converter structure within a larger catalytic converter structure. For example, one use of the structure shown in Fig. 1 could be central core of a catalytic converter from which additional foil leaves may be attached and radiate outward to another j cket. Although the following preferred embodiment discloses a resulting body that can be inserted into a cylindrical jacket, bodies of other shapes, such as elliptical shapes, may also be constructed according to the teachings of the invention. A number of methods may be used to construct the arrangement shown in Fig. 1. As shown in Fig. 5 and as disclosed in more detail in the applications incorporated by reference, a continuous sheet of metal may be formed into alternating corrugated and flat pieces with intermediate segments, which are either masked when the sheet is coated with catalytic material, or subsequently cleaned of the catalytic coating before assembly and connection to the jacket. The alternating corrugated and flat pieces may be either cut to the proper lengths for any geometric configuration such as various chord lengths spanning a jacket, or folded to

form that geometric configuration, and the stack is inserted into a jacket lined with brazing foil. The foil leaves may also be individually inserted into a jacket. As described in more detail in the applications incorporated by reference, the ends of the alternating strips are then secured to the jacket, preferably by a brazing method using induction heat.

In a folded arrangement, the folded portions on one side of the jacket may be brazed while the portions on the other side of the jacket are not brazed, to allow a cantilevered arrangement. Alternatively, every other folded portion around the periphery of the outer jacket may be connected to allow for folded ends that cantilever in alternating left and right directions. An example of an accordion folded stack of foils is shown in Fig. 2 where folded portions 138 can be selectively connected to outer jacket 122 by brazing in a manner to obtain the desired amount of compliance for a particular application according to the present invention. For example, folds 138a, c, e, and g, can be connected to outer jacket 122, while folds 138 b, d, f, and h are left free and unconnected to outer jacket 122. Alternatively, folds 138a, d, e, and h may be connected to outer jacket 122 while folds 138b, c, f, and g are allowed to be free from connection to outer jacket 123. The folds 138 are made at the areas where catalytic

coating is not present, either by masking during the coating process or removal after the coating process.

The foil arrangement shown in Fig. 3 is formed to provide a flat and corrugated segment in each leaf length and each leaf length is configured so that when juxtaposed, a flat segment in one leaf length is coextensive with a corrugated segment in an adjacent leaf length. For example, in leaf length a, flat segment 226a extends over the left half of the body and continues to provide corrugated segment 224a over the right half of the body. The right end of leaf segment 224a is folded at fold 238a and continues back as a flat segment 226b juxtaposed to adjacent corrugated leaf segment 224a. Flat segment 226b of leaf length b continues to the left and becomes corrugated leaf segment 224b, which is juxtaposed to flat leaf segment 226a.

A similar arrangement appears in Fig. 4, where there are three leaf segments for each leaf length. For instance, leaf length a starts with corrugated section 324a, becomes flat section 326a and then corrugated section 324a', which is folded at fold 328a to form leaf lenth b, where it becomes flat segment 326b, corrugated section 324b and flat section 326b" , and then folds again at 328b to form the next row. In the arrangements shown in Figs . 3 and 4, the same kind of selective

connection process can be employed to braze the foil ends to the outer jacket where desired for the proper amount of compliancy. In some applications, both foil ends of all or selected leaf lengths may be connected to 5 the jacket in a rigid and/or compliant manner, either by the design of the connection and/or the end portions of the leaves themselves. For example, in Figs. 3, 4, 9, and 10 it may be desirable to connect both ends in some applications. It is preferable in a number of

10. applications that the compliancy is such that the natural frequency of the catalytic converter is between 10 Hertz and 100 Hertz.

As shown in Fig. 5, a continuous strip of metal sheet, which forms the foil leaves, includes several

15 corrugated portions 424 which alternate with flat portions 426. Each of these segments may be separated by a margin 425, which has no catalytic material and which forms a good surface for brazing to an outer jacket. In other alternatives, some margins may contain 0 catalytic material. As shown in Fig. 6, two sets of leaves made by the process of Fig. 5 can be juxtaposed and brazed together at 427 in some or all of margins 425 in a desired manner to change the stiffness and compliancy of the leaf structure. Figs. 2a, 3a, and 4a, 5 show these arrangements relating to the respective figures with brazing 227 and 327 respectively in the

margins. Figs. 2a, 3a, and 4a, also show an arrangement of folds 138, 238, and 338 along respective margins 125, 225, and 325.

Fig. 7 shows a catalytic converter with two groupings of leaves, group 531 on the left half and group 532 on the right half. One end 530 and 534 of each of the leaves 524 and 526 are connected to the left side 531 of outer jacket 532. One end 532 and 536 of the leaves 524 and 526a are connected to the other opposite side of jacket 522, namely the right side 533. As shown in Fig. 7, the leaves in both groupings extend across the outer jacket to a common diametral line 540 where the cantilevered ends are narrowly spaced from each other. Another arrangement is shown in Fig. 8, where the leaves are in four groupings, 640, 641, 642, and 643. One end of each of the leaves is connected to outer jacket 622 and the free ends of the leaves extend to perpendicular diametral lines 650 and 651, where they are spaced from the leaves of the adjacent segment.

Other variations within the scope and spirit of the invention as claimed are also possible. Examples include additional groupings or segments, and other patterns for positions where the cantilevered ends terminate. These structures may be used both for the

catalytic converter as a whole as well as a subassembly in the converter.

Fig. 9 shows a catalytic converter where the leaves 724 and 726 extend along curved paths that are parallel and nonradiating, in that they do not radiate to or from a central point or define a central point in the converter. Fig. 10 shows a catalytic converter in which the nonradiating parallel grouping of foil leaves extend along reversely curved paths. In these two instances, the foils are symmetric along center lines

750 and 850. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.