GB2047562A - Catalytic converters for internal combustion engine exhaust gases - Google Patents

Abstract

The converters have two end- to-end arranged catalyst beds 14, 16 wherein all of the joints of the flanges 50, 52 of the housing 12 and the joints of the flanges 82, 106 of the retaining members of the two catalyst beds may be joined and sealed externally and are readily available for inspection. <IMAGE>

Description

SPECIFICATION Catalytic converters for internal combustion engine exhaust gases This invention relates to dual bed catalytic converters for internal combustion engine exhaust gases, and more particularly to catalytic converters with catalyst beds arranged end-toend.

In known end-to-end catalyst bed arrangements, the joints of the members forming the two catalyst beds are inside the converter housing and as a result require that at least some of the joints must first be made and sealed prior to the assembly of the housing thereabout, which then conceals these joints from view and inhibits access thereto. Then there remains the problem of how to join the catalyst retainer members to the interior of the housing so as to hold them in place and also provide the necessary internal sealing at these joints. Thus, such end-to-end catalyst bed arrangements, in addition to being difficult to assemble, have internal joints which are difficult to join and which cannot readily be inspected for proper sealing after final assembly of the converter.

These problems are solved, according to the present invention, by a catalytic converter with end-to-end arranged catalyst beds with a small number of different, simply formed and assembled parts. In the preferred embodiment, the converter housing is formed with four stampings, which may be similar, and each of the catalyst beds is formed with two stampings which are different from each other but may be similar to those forming the other bed. The housing members co-operatively form the housing with an inlet and outlet and the two pairs of catalyst retainer members respectively co-operatively form the two catalyst beds in end-to-end relationship and together with the housing also form the required series-flow arrangement of the beds between the inlet and outlet of the housing with downflow through each bed.The peripheries of the co-operating pairs of catalyst retainer members have mating flanges which extend outwardly and are sandwiched between outwardly extending flanges of the housing members so that all the joints therebetween can then be joined and sealed exter nally of the housing at final assembly, either by roll welding of the flanges or by welding of the flange edges. As a result, the catalytic converter is a compact, easily assembled, rigid yet simple structure of few different parts and with all the joints external of the housing and later inspection.

The invention is hereinafter particularly described with reference to the accompanying drawings in which: Figure 1 is a side elevation of a dual bed catalytic converter according to the present invention; Figure 2 is a view on the line 2-2 of Fig.

1; Figure 3 is a section on the line 3-3 of Fig.

2; Figure 4 is a section on the line 4-4 of Fig.

3; and Figure 5 is an exploded view of the converter in Fig. 1.

Figs. 1-3 show a dual bed catalytic converter 10 having a housing 1 2 enclosing two catalyst beds or retainer 14 and 1 6 which are arranged end-to-end for series-flow therethrough between an inlet 1 8 and an outlet 20 in the housing. The converter is intended for use in a vehicle to purify the exhaust gases from an internal combustion engine and for that purpose and in an underfloor installation the housing 1 2 has a rectangular box shape with a low profile compared to width, as shown in Figs. 1 and 2, permitted by the endto-end arrangement of the catalyst beds 1 4 and 1 6 as shown in Fig. 3.The respective beds 14 and 1 6 retain pellets 22 and 24 respectively coated with a suitable reducing or 3-way catalyst and an oxidizing catalyst for purifying by reduction and oxidation and exhaust gases which enter the inlet 18, before they pass out of the outlet 20. Air, which is the primary source for the oxidation process promoted by the oxidizing catalyst, is introduced into the exhaust gas stream between the two catalyst beds by an air injection tube 26 which is inserted through a hole in one side of the housing 1 2 below the reducing bed 14 and sealed to the housing by a weld, the tube extending across this bed and being attached, as by welding, to the opposite inner side of the housing.As shown in Figs. 4 and 5, the tube 26 has orifices 27 spaced along the length thereof for injecting air directly into the passing exhaust gases so as to be mixed therewith prior to entering the oxidizing bed 16.

In a preferred embodiment of the present invention, the housing comprises four housing members 30 which may be similar, except as described later, and are manufactured by stamping to have a generally rectangular box shape with both an open end and an open side as shown in Fig. 5, so as to form a portion, that is, one quarter beds. In addition, each of the housing members 30 has a semicylindrical portion 32 which projects outwardly from the otherwise closed end wall 34 of the housing member 30 and on its concave side forms a part, that is, one half, of the inlet 1 8 or outlet 20 of the housing.The enclosure portion of each housing member 30 in addition to the end wall 34 comprises a flat, horizontal wall 38, which serves as the top or bottom of the housing, and parallel, flat, vertical, side walls 40 and 42 which serve as opposite, quarter-side portions of the housing.

In addition, each housing member 30 has abouts its periphery an integral, outwardly extending, right-angle flange 46 comprising a planar, transverse, flange portion 48, of angular C-shape, which intersects at right angles with co-planar, longitudinal, flange portions 50 and 52 of generally L-shape. The flange portion 48 extends along the open end of the housing member horizontally across the horizontal wall 38 and vertically along the side walls 40 and 42. The two longitudinally extending flange portions 50 and 52 extend from opposite ends of the transverse flange portion 48 and parallel to each other horizontally along the vertical sides 40 and 42 and converge to extend along the end wall 34 on opposite sides of the projection 32 from whence they continue along opposite sides of the projection 32 to the end thereof.

Each of the catalyst beds 1 4 and 1 6 comprises only two catalyst retainer members 60 and 62 formed by stamping and having generally the shape of shallow rectangular scoops, as shown in Fig. 5. The retainer members 60 and 62 are not of exactly similar shape but may be of the same shape as those forming the other catalyst bed, except as hereinafter described. The catalyst retainers 60 each form one half of each of the catalyst beds and have a catalyst retainer portion comprising a flat perforated wall 64 which serves as a bottom or top, parallel righttriangle shaped, imperforate, vertical, side walls 70 and 72, and a rectangular shaped, imperforate end wall 74 which joins with one end of the perforated wall 64 and corresponding vertical ends of the triangular side walls 70 and 72.In addition, the catalyst retainer members 60 have a semi-cylindrical projection 78 which extends outwardly from the otherwise closed end wall 74 and, its convex side, is adapted to nest with the concave side of the semi-cylindrical projection 32 of one of the housing members 30 at the inlet or outlet, as the case may be. The concave side of the semi-cylindrical projection 78 is sealed from the interior of the retainer member 60 and the catalyst bed by the other retainer member 62 so as to prevent exhaust gas leakage and loss of catalyst as will be hereinafter described in more detail. At the opposite end of each catalyst retainer 60, there is formed an imperforate, rectangular end wall 80 which extends generally parallel to end wall 74 and joins with corresponding apices of the triangular side walls 70 and 72 and the end of the perforated wall 64 which extends thereacross.

In addition, the retainer members 60 are formed with an outwardly extending flange 82 about their catalyst retainer portion, said flange comprising a transverse planar, flange portion 84 which extends along the periphery of the end wall 80 and intersects at right angles at its opposite ends with a pair of coplanar, flange portions 86 and 88 which extend along the periphery of the respective side walls 70 and 72, the end wall 74 and the opposite sides of projection 78.Moreover, the flange portions 86 and 88 of the retainer members 60 correspond to, and are adapted to abut on their external bed side with the flange portions 50 and 52 of the housing member 30 in which they are received, and the remaining flange portion 84 of each of the retainer members 60 corresponds to and is adapted to abut on its external bed side with the flange portion 48 of the diagonally opposite housing member 30 in which another retainer member 60 is received.

The other catalyst retainer members 62 complete the formation of the catalyst beds and each comprises a flat, perforated wall 92 which serves as a top or bottom and parallel triangular-shaped, imperforate, vertical, side walls 94 amd 96, but only one imperforate end wall 98 which is located by the shallow end of this half of the retainer bed. A semicylindrical projection 100 projects from but is blocked at the closed end wall 98 and on its convex side is adapted to nest with the concave side of the semi-cylindrical projection 78 of one of the retainer members 60 at the inlet or outlet, as the case may be, so that the end wall 98 closes off the interior of the catalyst bed at that end.In addition, the catalyst retainer members 62 are formed with an outwardly extending right-angle flange 106 about their catalyst retainer portion, the flange comprising a transverse, planar, flange portion 108 which extends along the periphery of the open end of the catalyst retainer portion and intersects at right angles at its opposite ends with a pair of co-planar flange portions 110 and 11 2 which extend along the periphery of the respective side walls 94 and 96, the end wall 98 and the opposite sides of projection 100. Moreover, the flange portions 110 and 11 2 of the retainer members 62 correspond to and are adapted to abut on opposite sides with the flange portions 86 and 88 of the retainer member 60 with which they are paired and the flange portion 50 and 52 of the housing members 30 in which they are received. In addition, the remaining flange portion 108 of the retainer members 62 corresponds to and is adapted to abut on opposite sides with the flange portion 84 of the retainer member 60 with which they are paired and the flange portion 48 of the housing members 30 in which they are received.

Filling of the beds formed by the pairs of retainers 60, 62 after assembly of the converter, as described, in more detail hereinafter, is provided by an opening 114 formed in the perforated wall 64 of each of the retainer members 60 and an opening 11 6 which is formed in only two of the housing members 30, these housing members being those which are directly opposite and enclose the retainer members 60 and which are similar to the other two housing members in all other respects.The housing member fill opening 11 6 aligns with the respective retainer member fill opening 11 4 at assembly and has a flange 11 8 which projects through and is crimped about the latter, whereafter a plug 1 20 formed by stamping is then secured in place after the beds have been filled as shown in Fig. 3.

In the assembly of the converter, its parts are arrangeable relative to each other as shown in Fig. 5 with two of the housing members 30 located above and the other two located below the four catalyst retainer members 60 and 62. In these relative positions, the interior sides of the upper housing members 30 face downwards and these sides, of the lower housing members face upwards.

The flanged open ends of the upper housing members face each other, as do the lower housing members, and the concave sides of their respective semi-cylindrical projections face each other at the inlet and outlet. At the inlet end of the assembly a catalyst retainer member 62 is located over a catalyst retainer member 60 with their interior sides facing each other while at the outlet end of the assembly the other two retainer members are arranged in reverse manner with the catalyst retainer member 60 on top and the catalyst retainer member 62 underneath. Furthermore, the catalyst retainer members 60 and 62 are arranged with their respective semi-cylindrical projections 78 and 100 between the oppositely facing semi-cylindrical projections 32 of the housing members 30 at the inlet and outlet.The relatively elevated pairs of catalyst retainer members 60 and 62 can then abut at the interior sides of their respective flanges 82 and 106 with the portions 84, 86 and 88 of the lower retainer members respectively engaging portions 108, 110 and 11 2 of the latter while their respective semi-cylindrical projections 78 and 100 are brought into nesting engagement at their respective concave and convex sides so that each pair of retainer members 60 and 62 thus engaged complete one of the catalyst beds 14 and 1 6 with their perforated walls 64 and 92 spaced opposite each other while their sides and ends are completely closed along their abutted flanges and nesting projections.

The two pairs of retainer members 60 and 62 thus engaged are then positioned edge-toedge at their inner closed ends at the corner 121 of the retainer members 60 whereafter the housing members 30 are brought into engagement, with their oppositely facing, transverse flange portions 48 sandwiching the previously engaged transverse flange portions 84 and 108 of the respective retainer members 60 and 62. At the same time, the oppositely facing, longitudinal, flange portions 50 and 52 of the housing members 30 are caused to sandwich the previously engaged longitudinal flange portions 86, 88 and 110, 11 2 of the respective retainer members 60 and 62. In addition, the vertical sides of the housing and catalyst retainer members are laterally located as shown in Fig. 4 so as to abut each other, thus increasing their rigidity in the horizontal direction.

At the inlet end of the converter the previously nested semi-cylindrical projections 78 and 100 of the pair of retainer members 60 and 62 at this end are nested with the semicylindrical projection 32 of the lower housing member so as to form the inlet 1 8 in cooperation with the oppositely facing semicylindrical projection 32 of the upper housing member at this end. Furthermore, the closed end wall 34 of the housing members 30 is tapered from its projection 32 and in cooperation with the imperforate end wall 98 of the upper catalyst retainer member 62 at this end provides a path from the converter inlet to the upper side of the reducing bed 1 4.

Conversely, the counterpart components form the outlet opening 20, with a path for gas flow leading from the bottom side of the oxidizing bed 1 6. Intermediate the ends of the two beds, the imperforate end walls 80 of the retainer members 60 have similar oppositely facing, recessed portions 1 22 providing therebetween a flow path within the housing which requires the gases leaving from the underside of the reducing bed 1 4 to flow upwards to the upper side of the oxidizing bed 1 6.

Thus, the exhaust gases are forced to flow downwards through both beds 14 and 16, as shown by the arrows in Fig. 3, and such flow contributes to catalyst life, as is well known in the art. Furthermore, because of the triangular shaped side walls 70, 72 and 94, 96 of the respective retainer members 60 and 62 and their parallelogram-forming arrangement, both beds have a uniform depth and are inclined at the same angle and in the same direction relative to the top or bottom wall 38 of the housing member 30 which they face. As a result, the gas flow path along the inlet side of each of the beds 1 4 and 1 6 converges as it proceeds toward the closed end of the bed on this side, thereby preventing excess gas flow through the rear of the bed and promoting even distribution of the gases downwardly into the bed.

With the housing and retainer members engaged in the manner described above, a four-layer sandwich of flanges is formed which includes all the external joints of the converter, and these flanges may then be simply edge-welded together, as shown, with a weld bead 1 24 or roll-welded completely externally of the housing. Thus, the gas joints of both the catalyst beds and the housing are simply joined and sealed and remain externally visible for easy inspection. Furthermore, such welding results in a very rigid structure with the retainer members reinforcing the housing members and vice versa.

It will also be appreciated by those skilled in the art that while the four housing members and the two pairs of retainer members may be man-ufactured as identical parts except for the catalyst fill openings, as indicated above, they may also differ in other respects to meet different installation and/or operating requirements while still retaining their co-operative relationship with each other. For example, the housing members could have different forms to avoid obstructions. Furthermore, the perforated wall of the retainer members could be formed as a separate flat piece for ease of manufacture of the perforations therein and then be welded to a one-piece stamping forming the remainder of the retainer member. In addition, the catalyst retainer members may still have co-operating mating flanges with respect to each other about their catalyst retaining portion but only one of these members have its flange extend ing between the flanges of the housing members for joining therewith. In that case, however, the pairs of retainer members must first be sealingly joined before assembly of the housing members. And in a similar manner, it is also contemplated that only one of the retainer members may have a semi-cylindrical or similarly formed projections which extends into either the inlet or outlet so as to properly direct gas flow to or from one side of the catalyst bed of which it forms a part.

Claims (4)

1. A dual bed catalytic converter having a housing enclosing two catalyst beds arranged end-to-end for series flow therethrough from an inlet to an outlet in the housing, said converter comprising: four housing members each having an enclosure portion of the housing and also a portion projecting outwardly therefrom to form a part of either said inlet or outlet, each said housing member having, projecting outwardly from the periphery of its said portions, a flange adapted to be engaged with and sealed to complementary portions of the flanges on two other of said housing members, so as completely to join and seal said housing along the flanges of the four housing members thereof, except across said inlet and outlet; and four catalyst retainer members each having a perforated portion around which the retainer member is adapted to be engaged with and sealed to one complementary other retainer member so that each catalyst bed is com pletely formed by two of the catalyst retainer members, with spaced-apart oppositely facing perforated sides, at least one of said catalyst retainer members of both catalyst beds also having an imperforate outwardly projecting portion adapted to form a part of said inlet or outlet, and at least one of said catalyst retainer members of both catalyst beds also having a peripheral flange adapted to be engaged between corresponding portions of the flanges on two of the housing members and also between corresponding portions of the flanges on one af these two housing members and one of the other housing members, so as to be externally joined and sealed thereto with each of the catalyst beds enclosed betweentwo of the housing members and in end-toend arrangement with the other catalyst beds, both the catalyst beds being peripherally supported by the housing and said imperforate outwardly projecting portions of the retainer members compelling gas flow from said inlet to pass in series through the perforate sides of one catalyst bed and then through the perforate sides of the other bed to said outlet.

2. A catalytic converter according to claim 1, in which the catalyst retainer members of both catalyst beds have said peripheral flanges.

3. A catalytic converter according to claim 1 or 2, in which said four housing members are similarly shaped.

4. A catalytic copnverter constructed and adapted to operate substantially as hereinbefore particularly described with reference to and as shown in the accompanying drawings.