Title of Invention	A CATALYTIC CONVERTER FOR A SILENCER OF A SMALL ENGINE
Abstract	The invention relates to a catalytic converter (7) for controlling emissions, particularly from a small engine, having a converter housing {6) and at least one honeycomb element (12) which is arranged therein and which contains layers of sheet metal (19) which have catalytically active material, the converter (7) being arranged on a dividing wall (5), provided with at least one opening (9), of a silencer housing (1) for a small engine, said housing (1) having an upper housing component (3) and a lower housing component {2). According to the invention, the converter housing (6) is shaped in such a way that emissions can flow successively through the honeycomb element (12) and the opening (9), the converter housing (6) being spaced apart from the silencer housing (1). Such a converter can be manufactured cost-effectively, can easily be integrated into existing structures, and during operation does not lead to unacceptable temperatures of the outer wall of the silencer housing.

Title of Invention

A CATALYTIC CONVERTER FOR A SILENCER OF A SMALL ENGINE

Abstract

The invention relates to a catalytic converter (7) for controlling emissions, particularly from a small engine, having a converter housing {6) and at least one honeycomb element (12) which is arranged therein and which contains layers of sheet metal (19) which have catalytically active material, the converter (7) being arranged on a dividing wall (5), provided with at least one opening (9), of a silencer housing (1) for a small engine, said housing (1) having an upper housing component (3) and a lower housing component {2). According to the invention, the converter housing (6) is shaped in such a way that emissions can flow successively through the honeycomb element (12) and the opening (9), the converter housing (6) being spaced apart from the silencer housing (1). Such a converter can be manufactured cost-effectively, can easily be integrated into existing structures, and during operation does not lead to unacceptable temperatures of the outer wall of the silencer housing.

Full Text	E 41003 PC (literal translation identical to priority document) Catalytic converter for a silencer of a small engine The present invention relates to a catalytic converter for a silencer of a small engine Reternic to claim in ollso NotNov claim correcty ward As environment consciousness has become stronger and emissions regulations relating to the exhaust gases of internal combustion engines have become stricter, a need has arisen to provide catalytic emissions control in small engines. Small engines are understood below to be internal-combustion engines with an engine capacity of less than 200 cm3, in particular less than 50 cm3. Such.engines are found in particular in lawnmowers, powered saws, transportable power packs, two-wheeled vehicles and such applications. In particular in powered saws, lawnmowers and other garden implements driven by internal-combustion engines, someone using such an implement is frequently located directly in the region of the exhaust gases of the small engine over a relatively long period of time, for which reason catalytic emissions control is particularly important. EP The emissions which enter a silencer near to the engine are, as a rule, already at a high temperature of, for example, over 600°C. As a result of exothermal reactions in the catalytic converter, its temperature may also rise considerably, for example to 1000°C. DE-A 38 29 668 discloses a protection -1- mechanism for an exhaust gas silencer for two-stroke engines, in particular for portable implements such as powered saws or the like, having a housing, a catalytic converter and an exhaust gas end pipe, the catalytic converter being arranged in a hollow element which is provided in the silencer housing with spacing on all sides and whose output has a tapering cross section in the direction of flow of the treated exhaust gas and leads the treated exhaust gas out of the housing. The mechanical structure of this exhaust gas silencer is very complex and requires a specifically designed adaptation of the catalytic converter for the respective purpose of use. Furthermore, the exhaust gas silencer has a large volume. The described arrangements for the catalytic emissions control of small engines require, in addition, specially fabricated honeycomb elements whose manufacture, catalytic coating and installation require a relatively large number of working steps and are therefore relatively expensive in comparison with equipment provided with a small engine. For this reason, the provision of a catalytic converter for a small engine is frequently dispensed with. In contrast, the invention is based on the object of providing a small engine catalytic converter which is very cost-effective to manufacture and requires the smallest possible changes to already existing small engines and their emission systems and nevertheless catalytically removes a considerable portion of the noxious substance from the emissions without, however, generating unacceptably high temperatures, at the outer surfaces of the emission system. Such a catalytic converter according to the invention having a converter housing and at least one honeycomb element which is arranged therein and which contains layers of sheet metal which have catalytically active material, the converter -2- being arranged on a dividing wall, provided with at least one opening, of a silencer housing, having an upper housing component and a lower hpusing component, for a small engine, is distinguished by the fact that the converter housing is shaped in such a way that gases flowing through the opening in the dividing wall flow completely through the honeycomb element, and that the converter housing is spaced apart from the silencer housing. The emissions which are to be controlled flow, in a manner known per se, into a housing component of the silencer housing and from there out through the opening provided in the dividing wall into the converter housing in which there are located the layers of sheet metal which are coated with catalytic material and which are configured as a honeycomb element. The inverse, firstly through the converter housing and then through the opening in the dividing wall, is possible. Since the converter housing of the catalytic converter according to the invention does not bear against the silencer housing, heating of the silencer housing by the catalytic converter is reduced or even avoided. Since the converter housing of the catalytic converter according to the invention can be attached to the dividing wall of the silencer housing, a particularly simple and therefore cost-effective adaptation of the catalytic converter according to the invention to existing emission systems is possible. Said converter has, in fact, merely to be mounted on the dividing wall without any need for changes to the upper and/or lower housing component of the silencer housing. The catalytic converter and dividing wall can thus be prefabricated together and introduced into the usual process for fabricating the silencer. The catalytic converter advantageously has a converter housing which has at least one side wall and one end wall, there being ¦3- a free space in the converter housing in the region of the end wall, which free space communicates with the opening in the dividing wall. This makes it possible to design the catalytic converter as a separate component which a manufacturer of catalytic converters can supply as an assembly to a manufacturer of silencers. The latter can then mount the catalytic converter according to the invention in a silencer housing. In a particularly advantageous fashion, the dividing wall of the silencer simultaneously forms the bottom wall of the converter housing. As a result, easier fabrication of a silencer which is equipped with the catalytic converter is made possible, since the converter and the dividing wall are designed as one component which simply then has to be introduced between the lower and the upper housing components of the silencer housing and attached. The layers of sheet metal which are provided for the honeycomb element can be squeezed, with plastic deformation, into the converter housing. As a result, a configuration of the catalytic converter according to the invention is obtained which-is particularly' simple in terms of production technology. Furthermore, it is possible for a casing to be arranged around the honeycomb element. The casing serves as a support element for the individual layers of sheet metal of the honeycomb element so that said layers can be prefabricated and introduced into the casing before said casing is placed in the honeycomb element. The honeycomb element and converter housing are thus designed as separate components which can be connected to one another in a particularly simple way. The casing does not need to enclose the entire outer surface of the honeycomb element as long as it simply ensures that the honeycomb element holds together. The catalytic converter according to the invention has in the -4- region of its end wall a free space into which emissions which are to be controlled can flow. The controlled emissions can flow out of the catalytic converter out of another opening provided in the converter housing, preferably on the opposite end side which may be completely open. Alternatively, there may be provision that an intermediate wall which divides the opening in the converter housing and the honeycomb element into two spaces in each case, the two spaces having a fluidic connection to one another such that the opening in the converter housing constitutes an inlet opening for the emissions to be controlled and an outlet opening for controlled emmisions. This means that just one opening has to be provided in the converter housing and/or the dividing wall. The same advantage is achieved if not one honeycomb element but rather two honeycomb elements are located in the converter housing. Here, the intermediate wall can divide the two honeycomb elements into two spaces in each case, these spaces also having a fluidic connection to one another such that the opening again constitutes both an inlet opening and an outlet opening for emissions. Further features, advantages and refinements of the present invention are explained in more detail in the following description of the accompanying drawings, in which: Fig. 1 shows a longitudinal section through a silencer housing in which a catalytic converter is located, Fig. 2 shows a catalytic converter in a perspective view, the layers of sheet metal of which converter are squeezed into the converter housing, Fig. 3 shows a catalytic converter in a front view, the layers of sheet metal of which catalytic converter are squeezed, Fig. 4 shows a catalytic converter with two layers of sheet . metal which are divided from one another by an intermediate -5- wall, Fig. 5 shows a longitudinal section through a silencer housing in which a catalytic converter is installed, Fig. 6 shows a catalytic converter which is enclosed by a casing, Fig. 7 shows a catalytic converter having an uncoated flat layer, and Fig. 8 shows a honeycomb element surrounded by a casing. Figure 1 shows a schematic view of a longitudinal section of a silencer housing 1 for a small engine, which housing 1 has a lower ho.using component 2 and an upper housing component 3. Emissions enter through an emissions inlet 4 into the lower housing component 2, from where they enter a converter housing 6 of a catalytic converter 7 through openings 9 in a dividing wall 5 which runs over the entire length of the silencer housing 1. The flow path of the emissions is indicated by the arrows 8. The emissions flow through openings 9, provided in the dividing wall 5, into a free space which is bounded by an end wall 10 of the converter housing 6, and then through ducts 11 of a honeycomb element 12 and then arrive at an emissions outlet 13 located in the upper housing component 3. The lower housing component 2 and the upper housing component 3 of the silencer housing 1 are connected to one another in gas-tight fashion. In the example shown here, the connection is made by means of attachment elements 14 which are provided on the left-hand and right-hand end of the silencer housing 1 in Figure 1. However, it is self-evident that other types of connections of the lower housing component 2 to the upper housing component 3 may also be provided, such as, for example, a common chamfering of the two housing components 2, 3. As is clear from Figure 1, the converter housing 6 of the -6- catalytic converter 7 does not touch the silencer housing 1. Instead, between the converter housing 6 and the upper housing component 3 there is an insulation space 15 in which emissions are located during operation. These emissions which are located in the insulation space 15 serve, as it were, as an insulator by means of which the transmission of heat from the catalytic converter 7 to the silencer housing 1 is reduced. Of course, it is possible, as an alternative or in addition to the emissions located in the insulation space 15, to provide insulation materials such as ceramic elements which reduce the conduction and convection of heat and/or a protective insulating layer which reduces thermal radiation and is composed of metal, for example. At the left-hand end of the converter housing 6 in Figure 1, said housing 6 is open so that at this point emissions may flow out of the end openings 16 of the ducts 11. Figure 2 shows an embodiment of a catalytic converter 7. The catalytic converter 7 has an approximately half-cylinder-shaped converter housing 6 which has an essentially rectangular bottom wall 17 which is formed as a base surface (which may also be formed by the dividing wall 5) which is adjoined by an essentially half-shell-shaped housing component 18. Within the converter housing 6 is a plurality of layers of sheet metal 19 which are coated with a catalytic material. In the example shown here, the layers of sheet metal 19 are formed from alternately arranged, individual flat layers of sheet metal and corrugated layers of sheet metal which together form a plurality of ducts 11 through which emissions can pass. It is to be noted that the coating may either already be applied to the layers of sheet metal 19 in a continuous process before all the other processing steps or else may be applied to all of the layers of sheet metal 19 together after they have been layered one on top of the other. The path of the emissions through the catalytic converter 7 which is shown in Figure 2 by means of arrow 8 corresponds to the path shown in Figure 1: -7- Emissions which are to be controlled enter the converter housing 6 in the region of the end wall 10 and pass form there into the ducts 11. After catalytic emissions control, the controlled emissions emerge from the end openings 16 again. The emissions can also flow in the opposite direction. In this case, the catalytic converter more quickly reaches the temperature it needs for conversion, which is desirable, but it also becomes hotter during continuous operation, which may be undesirable. This must be taken into account when selecting the direction of flow. The converter housing 6 has an edge 20 which extends over each side of the bottom wall 17. Said edge 20 is used for the secure mounting of the catalytic converter 7 on the dividing wall 5. It can be secured in a detachable or nondetachable fashion. This makes it possible to attach the edge 20 to the dividing wall 5 by welding, soldering, riveting or some other means-While Figure 2 has shown a catalytic converter which is essentially semicircular in cross section, Figure 3 shows a catalytic converter 7 which has an essentially rectangular cross section. Both the honeycomb element 12 which is shown in Figure 2 and the honeycomb element 12 which is shown in cross section in Figure 3 have layers of sheet metal 19 which are configured with squeezed-in layers of sheet metal 19 running in the, in Figure 3, left-hand and right-hand ends in the longitudinal direction of the silencer housing 1. Whereas the layers of sheet metal 19 are plastically deformed on the left-hand end 21 and the right-hand end 22, a high number of non plastically deformed ducts 11, which allow for the catalytic conversion of emissions which have been passed through, remain, in particular in the inner region of the honeycomb element 12. The ducts 11 are deformed considerably more elastically by the squeezing forces exerted on the entire honeycomb element 12, so that the entire element is under prestress. For this reason, an attachment element 23, for -8- example a rivet; is provided on the left-hand end 21 and a chamfer 24 on the right-hand end 22, so that the honeycomb element 12 is reliably mounted in the converter housing 6. Figure 4 shows an alternative embodiment of a catalytic converter 7. The catalytic converter which is shown there has an essentially parallelepiped-shaped converter housing 6 in which there is a rectangular honeycomb element 12. The layers of sheet metal 19 which are provided are attached to the converter housing 6 in a manner known per se, for example by spot welding. The flow path 8 which the emissions which are to be cleaned will take is identical to that shown in Figure 2. The catalytic converter 7 which is shown in Figure 4 is attached to the dividing wall 5 by means of seven attachment webs 25, for example. The attachment webs 25 are plugged through corresponding openings provided in the dividing wall 5, and are bent or twisted through approximately 90°, so that the converter housing 6 is secured to the dividing wall 5. In the silencer housing shown in Figure 1, the emissions inlet 4 and the emissions outlet 13 are arranged opposite one another, viewed in the longitudinal direction of the silencer housing 1. However, this is not imperative, as illustrated in Figure 5. Here, the emissions inlet 4 and the emissions outlet 13 are located one directly next to the other in the upper housing component 3 of the silencer housing 1. The emissions inlet 4 and the emissions outlet 13 are separated from one another fluidically by a dividing wall 26, so that an exchange between the incoming emissions and outgoing emissions is prevented. The incoming emissions enter the converter housing 6 of the catalytic converter 7 through the emissions inlet 4 and the openings 9 of the dividing wall 5, and through the converter housing openings 10. In the example shown in Figure 5, the catalytic converter 7 is in the lower housing component 2. The catalytic converter 7 has an intermediate wall 27 which runs - 9 - in the longitudinal direction of the silencer housing 1 and extends to the, in Figure 5, left-hand end of the catalytic converter 7 as far as the dividing wall 26, so that two sections 28 and 29 are formed in the catalytic converter 7, the sections 28 and 29 having a fluidic connection to one another at the right-hand end (shown in Figure 5) of the catalytic converter 7 by virtue of the fact that the intermediate wall 27 does not extend completely as far as the, in Figure 5, right-hand side of the catalytic converter 7. The emissions which are to be controlled enter an emissions inlet section 28 and leave again from an emissions outlet section' 29. It is to be noted that the intermediate wall 27 separates an individual honeycomb element 12 into the two sections 28, 29, said honeycomb element 12 being accommodated in the converter housing 6. However, it is also possible to accommodate two or more separate honeycomb elements (not shown here) in the converter housing, which elements are separated by any desired number of intermediate walls. In thi£ way, at least one emissions inlet section and one emissions outlet section, which communicate fluidically with one another, are also respectively provided. The catalytic converter 7 which is illustrated in Figure 5 is shown again in more detail in Figure 6. The converter housing 6 is an essentially parallelepiped-shaped element in which a honeycomb element 12 is accommodated. In the honeycomb element 12 there are layers of sheet metal 19 which form ducts 11. Provided parallel to the dividing wall 5 is an intermediate wall 27 which is arranged approximately centrally in the converter housing 6 and which extends from the, in Figure 6, front end of the converter housing 6 along essentially one quarter of the length of the converter housing 6, as indicated by the broken lines. The intermediate wall 27 is secured by means of projections 30 which protrude from it and latch into corresponding openings in the converter housing 6. -10- The converter housing 6 has, in the longitudinal direction, two edges 31 which - as already described in Figure 2 - can be fastened to the dividing wall 5 in the lower housing component in a detachable or nondetachable fashion. Here, the part of the dividing wall 27 which can be seen in Figure 6 comes into contact with a dividing end wall 26 in such a way that the sections 28, 29 which are shown in Figure 5 are separated from one another. A further embodiment of the catalytic converter 7 according to the invention is illustrated in Figure 7. The catalytic converter 7 has an essentially parallelepiped-shaped converter housing 6, in which a honeycomb element 12 which is composed of layers of sheet metal 19 is arranged. In the honeycomb element 12 there is a flat layer 32. which runs essentially parallel to the dividing wall 5. In addition, part of the flat layer 32 bears against the side walls 33 of the converter housing 6 and, with its ends which are designed as wings 34 and which run in the longitudinal direction of the silencer, bears on edges 35 of the converter housing 6 which protrude perpendicularly from the side walls 33. Holes 36 are provided both in the wings 34 and in the edges 35, it being possible to insert through said holes attachment elements, such as rivets, into corresponding openings in the dividing wall 5 in order to fix the catalytic converter 7, together with the flat layer 32, securely to the dividing wall 5. The attachment of the individual layers of sheet metal 19 can be carried out in a manner known per se. Thus, it is possible to solder or weld said layers to one another or to attach them in some other manner which is known per se. In addition, it is possible to attach said layers by means of attachment elements, for example rivets, staples, or by spot welding to the converter housing 6. Preferably, the points of attachment by welding or soldering must be free of catalytically active -11- coating. The honeycomb elements 12 which are shown above may be surrounded by a casing. In Figure 8, the honeycomb element 12 illustrated in Figure 4 is surrounded by a casing 38 in such a way that the emissions can flow freely through the ducts 11, as is also the case in the other exemplary embodiments. By means of the casing 38, the honeycomb element 12 is designed as a module which can be inserted into the converter housing 6 and it can be attached there in a detachable or nondetachable fashion. This has the advantage that honeycomb elements can, be prefabricated individually. The casing 38 may be here a very thin piece of sheet metal which does not necessarily have to surround the entire outer surface of the honeycomb element either, as long as it is ensured that the pieces of sheet metal are held together in a dimensionally stable way. It is to be noted that any catalytic converter 7 may be provided with the insulation material for thermal insulation. Furthermore, it is also possible to line the silencer housing 1 entirely or partially with insulation material 37, as is indicated in Figure 5. The present invention is particularly suitable for the simple manufacture of cost-effective catalytic converters for small engines whose emissions contain considerable portions of hydrocarbons, at least some of which is to be removed catalytic-ally, during which process other noxious substances such as carbon monoxide or nitrogen oxides, for example, can also simultaneously be reduced. -12- List of reference numerals 1 Silencer housing 2 Lower housing component 3 Upper housing component 4 Emissions inlet 5 Dividing wall 6 Converter housing 7 Catalytic converter 8 Flow path 9 Openings in the dividing wall 10 End wall 11 Ducts 12 Honeycomb element 13 Emissions outlet 14 Attachment elements 15 Insulation space 16 end openings 17 Bottom wall 18 Half-shell-shaped housing component 19 Layers of sheet metal 20 Edge 21 Left-hand end 22 Right-hand end 23 Attachment element 24 Chamfer 25 Attachment webs 26 Dividing end wall 27 Intermediate wall 28 Emissions inlet section 29 Emissions outlet section 30 Projections 31 Edges 32 Flat layer 33 Side walls 34 Wing 35 Edges 36 Holes 37 Insulation material -13- 38 Casing WE CLAIM: 1. A catalytic converter (7) for a silencer of a small engine for controlling emissions, having a converter housing (6) and at least one honeycomb element (12) which is arranged therein and which contains layers of sheet metal (19) which have catalystically active material, the converter (7) being arranged on a dividing wall (5). provided with at least one opening (9), of a silencer housing (1) for a small engine, said housing (1) having an upper housing component (3) and a lower housing component (2). characterised in that a) the converter housing (6) is shaped whereby emissions can flow sucessively through the honeycomb element (12) and the opening (9). and b) the coverter housing (6) is spaced apart from the silencer housing (1) and fixed to the dividing wall. 2. The converter (7) as claimed in claim 1, wherein the coverter housing (6) is attached to the dividing wall (5). 3. The converter (7) as claimed in claim 1 or 2. wherein the converter housing (6) has at least one side wall (33) and an end wall (10). 4. The converter (7) as claimed in one of claims 1 to 3. wherein one wall of the converter housing (6) is formed by the dividing wall (5). 5. The converter (7) as claimed in one of claims 1 to 4, wherein the converter housing (6) has an essentially rectangular or semicircular cross section which corresponds to the cross section of the honeycomb element (12). 6. The converter (7) as claimed in one of claims 1 to 5, wherein the converter housing (6) is composed of deep-drawn sheet metal, 7. The converter (7) as claimed in one of claims 1 lo 6. wherein the converter housing (6) has attachment webs (25) -15- which engage in corresponding openings which are provided in the dividing wall (5). 8. The converter (7) as claimed in one of claims 1 to 7, wherein the converter housing (6) is attached to the dividing wall (5), preferably by spot welding or mechanical clamping. 9. The converter (7) as claimed in one of claims 1 to 8, wherein the layers of sheet metal (19) are squeezed, with plastic deformation, into the converter housing (6). 10. The converter (7) as claimed in one of claims 1 to 9, wherein a casing (38) is provided around the honeycomb element (12) . 11. The converter (7) as claimed in claim 10, wherein the layers of sheet metal (19) are attached in the casing (38). 12. The converter (7) as claimed in one of claims 1 to 11, wherein the casing (38) is attached to the dividing wall (5) and/or to the converter housing (6). 13. The converter (7) as claimed in one of claims 1 to 12, wherein the layers of sheet metal (19) already have a catalytically active surface layer before the converter is assembled. 14. The converter (7) as claimed in one of claims 1 to 13, wherein a flat layer (32) is provided within the layers of sheet metal (19), the ends of which flat layer are formed as wings (34) which are located between the converter housing (6) and the dividing wall (5). 15. The converter (7) as claimed in one of claims 1 to 13, wherein the layers of sheet metal (19) are wound or folded. 16. The converter (7) as claimed in one of claims 1 to 15, wherein an intermediate wall (27) which divides the converter -16- housing (6) and the honeycomb element (12) into two spaces (28, 29) in each case is provided, the two spaces (28, 29) having a fluidic connection to one another such that the openings (9) in the dividing wall (5) form an inlet opening for the emissions to be controlled and an outlet opening for controlled emissions. The invention relates to a catalytic converter (7) for controlling emissions, particularly from a small engine, having a converter housing {6) and at least one honeycomb element (12) which is arranged therein and which contains layers of sheet metal (19) which have catalytically active material, the converter (7) being arranged on a dividing wall (5), provided with at least one opening (9), of a silencer housing (1) for a small engine, said housing (1) having an upper housing component (3) and a lower housing component {2). According to the invention, the converter housing (6) is shaped in such a way that emissions can flow successively through the honeycomb element (12) and the opening (9), the converter housing (6) being spaced apart from the silencer housing (1). Such a converter can be manufactured cost-effectively, can easily be integrated into existing structures, and during operation does not lead to unacceptable temperatures of the outer wall of the silencer housing.

Full Text

E 41003 PC
(literal translation identical to priority document)

Catalytic converter for a silencer of
a small engine
The present invention relates to a catalytic converter for a silencer of a small engine Reternic to claim in ollso NotNov claim correcty ward
As environment consciousness has become stronger and emissions regulations relating to the exhaust gases of internal combustion engines have become stricter, a need has arisen to provide catalytic emissions control in small engines. Small engines are understood below to be internal-combustion engines with an engine capacity of less than 200 cm3, in particular less than 50 cm3. Such.engines are found in particular in lawnmowers, powered saws, transportable power packs, two-wheeled vehicles and such applications. In particular in powered saws, lawnmowers and other garden implements driven by internal-combustion engines, someone using such an implement is frequently located directly in the region of the exhaust gases of the small engine over a relatively long period of time, for which reason catalytic emissions control is particularly important.
EP The emissions which enter a silencer near to the engine are, as a rule, already at a high temperature of, for example, over
600°C. As a result of exothermal reactions in the catalytic converter, its temperature may also rise considerably, for example to 1000°C. DE-A 38 29 668 discloses a protection
-1-

mechanism for an exhaust gas silencer for two-stroke engines, in particular for portable implements such as powered saws or the like, having a housing, a catalytic converter and an exhaust gas end pipe, the catalytic converter being arranged in a hollow element which is provided in the silencer housing with spacing on all sides and whose output has a tapering cross section in the direction of flow of the treated exhaust gas and leads the treated exhaust gas out of the housing. The mechanical structure of this exhaust gas silencer is very complex and requires a specifically designed adaptation of the catalytic converter for the respective purpose of use. Furthermore, the exhaust gas silencer has a large volume.
The described arrangements for the catalytic emissions control of small engines require, in addition, specially fabricated honeycomb elements whose manufacture, catalytic coating and installation require a relatively large number of working steps and are therefore relatively expensive in comparison with equipment provided with a small engine. For this reason, the provision of a catalytic converter for a small engine is frequently dispensed with.
In contrast, the invention is based on the object of providing a small engine catalytic converter which is very cost-effective to manufacture and requires the smallest possible changes to already existing small engines and their emission systems and nevertheless catalytically removes a considerable portion of the noxious substance from the emissions without, however, generating unacceptably high temperatures, at the outer surfaces of the emission system.
Such a catalytic converter according to the invention having a converter housing and at least one honeycomb element which is arranged therein and which contains layers of sheet metal which have catalytically active material, the converter
-2-

being arranged on a dividing wall, provided with at least one opening, of a silencer housing, having an upper housing component and a lower hpusing component, for a small engine, is distinguished by the fact that the converter housing is shaped in such a way that gases flowing through the opening in the dividing wall flow completely through the honeycomb element, and that the converter housing is spaced apart from the silencer housing.
The emissions which are to be controlled flow, in a manner known per se, into a housing component of the silencer housing and from there out through the opening provided in the dividing wall into the converter housing in which there are located the layers of sheet metal which are coated with catalytic material and which are configured as a honeycomb element. The inverse, firstly through the converter housing and then through the opening in the dividing wall, is possible.
Since the converter housing of the catalytic converter according to the invention does not bear against the silencer housing, heating of the silencer housing by the catalytic converter is reduced or even avoided.
Since the converter housing of the catalytic converter according to the invention can be attached to the dividing wall of the silencer housing, a particularly simple and therefore cost-effective adaptation of the catalytic converter according to the invention to existing emission systems is possible. Said converter has, in fact, merely to be mounted on
the dividing wall without any need for changes to the upper and/or lower housing component of the silencer housing. The catalytic converter and dividing wall can thus be prefabricated together and introduced into the usual process for fabricating the silencer.
The catalytic converter advantageously has a converter housing which has at least one side wall and one end wall, there being
¦3-

a free space in the converter housing in the region of the end wall, which free space communicates with the opening in the dividing wall. This makes it possible to design the catalytic converter as a separate component which a manufacturer of catalytic converters can supply as an assembly to a manufacturer of silencers. The latter can then mount the catalytic converter according to the invention in a silencer housing.
In a particularly advantageous fashion, the dividing wall of the silencer simultaneously forms the bottom wall of the converter housing. As a result, easier fabrication of a silencer which is equipped with the catalytic converter is made possible, since the converter and the dividing wall are designed as one component which simply then has to be introduced between the lower and the upper housing components of the silencer housing and attached.
The layers of sheet metal which are provided for the honeycomb element can be squeezed, with plastic deformation, into the converter housing. As a result, a configuration of the catalytic converter according to the invention is obtained which-is particularly' simple in terms of production technology.
Furthermore, it is possible for a casing to be arranged around the honeycomb element. The casing serves as a support element for the individual layers of sheet metal of the honeycomb element so that said layers can be prefabricated and introduced into the casing before said casing is placed in the honeycomb element. The honeycomb element and converter housing are thus designed as separate components which can be connected to one another in a particularly simple way. The casing does not need to enclose the entire outer surface of the honeycomb element as long as it simply ensures that the honeycomb element holds together.
The catalytic converter according to the invention has in the
-4-

region of its end wall a free space into which emissions which are to be controlled can flow. The controlled emissions can flow out of the catalytic converter out of another opening provided in the converter housing, preferably on the opposite end side which may be completely open. Alternatively, there may be provision that an intermediate wall which divides the opening in the converter housing and the honeycomb element into two spaces in each case, the two spaces having a fluidic connection to one another such that the opening in the converter housing constitutes an inlet opening for the emissions to be controlled and an outlet opening for controlled emmisions. This means that just one opening has to be provided in the converter housing and/or the dividing wall.
The same advantage is achieved if not one honeycomb element but rather two honeycomb elements are located in the converter housing. Here, the intermediate wall can divide the two honeycomb elements into two spaces in each case, these spaces also having a fluidic connection to one another such that the opening again constitutes both an inlet opening and an outlet opening for emissions.
Further features, advantages and refinements of the present invention are explained in more detail in the following description of the accompanying drawings, in which:
Fig. 1 shows a longitudinal section through a silencer housing in which a catalytic converter is located,
Fig. 2 shows a catalytic converter in a perspective view, the layers of sheet metal of which converter are squeezed into the converter housing,
Fig. 3 shows a catalytic converter in a front view, the layers of sheet metal of which catalytic converter are squeezed,
Fig. 4 shows a catalytic converter with two layers of sheet . metal which are divided from one another by an intermediate
-5-

wall,
Fig. 5 shows a longitudinal section through a silencer housing in which a catalytic converter is installed,
Fig. 6 shows a catalytic converter which is enclosed by a casing,
Fig. 7 shows a catalytic converter having an uncoated flat layer, and
Fig. 8 shows a honeycomb element surrounded by a casing.
Figure 1 shows a schematic view of a longitudinal section of a silencer housing 1 for a small engine, which housing 1 has a lower ho.using component 2 and an upper housing component 3. Emissions enter through an emissions inlet 4 into the lower housing component 2, from where they enter a converter housing 6 of a catalytic converter 7 through openings 9 in a dividing wall 5 which runs over the entire length of the silencer housing 1. The flow path of the emissions is indicated by the arrows 8. The emissions flow through openings 9, provided in the dividing wall 5, into a free space which is bounded by an end wall 10 of the converter housing 6, and then through ducts 11 of a honeycomb element 12 and then arrive at an emissions outlet 13 located in the upper housing component 3. The lower housing component 2 and the upper housing component 3 of the silencer housing 1 are connected to one another in gas-tight fashion. In the example shown here, the connection is made by means of attachment elements 14 which are provided on the left-hand and right-hand end of the silencer housing 1 in Figure 1. However, it is self-evident that other types of connections of the lower housing component 2 to the upper housing component 3 may also be provided, such as, for example, a common chamfering of the two housing components 2, 3.
As is clear from Figure 1, the converter housing 6 of the
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catalytic converter 7 does not touch the silencer housing 1. Instead, between the converter housing 6 and the upper housing component 3 there is an insulation space 15 in which emissions are located during operation. These emissions which are located in the insulation space 15 serve, as it were, as an insulator by means of which the transmission of heat from the catalytic converter 7 to the silencer housing 1 is reduced. Of course, it is possible, as an alternative or in addition to the emissions located in the insulation space 15, to provide insulation materials such as ceramic elements which reduce the conduction and convection of heat and/or a protective insulating layer which reduces thermal radiation and is composed of metal, for example. At the left-hand end of the converter housing 6 in Figure 1, said housing 6 is open so that at this point emissions may flow out of the end openings 16 of the ducts 11.
Figure 2 shows an embodiment of a catalytic converter 7. The catalytic converter 7 has an approximately half-cylinder-shaped converter housing 6 which has an essentially rectangular bottom wall 17 which is formed as a base surface (which may also be formed by the dividing wall 5) which is adjoined by an essentially half-shell-shaped housing component 18. Within the converter housing 6 is a plurality of layers of sheet metal 19 which are coated with a catalytic material. In the example shown here, the layers of sheet metal 19 are formed from alternately arranged, individual flat layers of sheet metal and corrugated layers of sheet metal which together form a plurality of ducts 11 through which emissions can pass. It is to be noted that the coating may either already be applied to the layers of sheet metal 19 in a continuous process before all the other processing steps or else may be applied to all of the layers of sheet metal 19 together after they have been layered one on top of the other.
The path of the emissions through the catalytic converter 7 which is shown in Figure 2 by means of arrow 8 corresponds to the path shown in Figure 1:
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Emissions which are to be controlled enter the converter housing 6 in the region of the end wall 10 and pass form there into the ducts 11. After catalytic emissions control, the controlled emissions emerge from the end openings 16 again. The emissions can also flow in the opposite direction. In this case, the catalytic converter more quickly reaches the temperature it needs for conversion, which is desirable, but it also becomes hotter during continuous operation, which may be undesirable. This must be taken into account when selecting the direction of flow.
The converter housing 6 has an edge 20 which extends over each side of the bottom wall 17. Said edge 20 is used for the secure mounting of the catalytic converter 7 on the dividing wall 5. It can be secured in a detachable or nondetachable fashion. This makes it possible to attach the edge 20 to the dividing wall 5 by welding, soldering, riveting or some other means-While Figure 2 has shown a catalytic converter which is essentially semicircular in cross section, Figure 3 shows a catalytic converter 7 which has an essentially rectangular cross section. Both the honeycomb element 12 which is shown in Figure 2 and the honeycomb element 12 which is shown in cross section in Figure 3 have layers of sheet metal 19 which are configured with squeezed-in layers of sheet metal 19 running in the, in Figure 3, left-hand and right-hand ends in the longitudinal direction of the silencer housing 1. Whereas the layers of sheet metal 19 are plastically deformed on the left-hand end 21 and the right-hand end 22, a high number of non plastically deformed ducts 11, which allow for the catalytic conversion of emissions which have been passed through, remain, in particular in the inner region of the honeycomb element 12. The ducts 11 are deformed considerably more elastically by the squeezing forces exerted on the entire honeycomb element 12, so that the entire element is under prestress. For this reason, an attachment element 23, for
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example a rivet; is provided on the left-hand end 21 and a chamfer 24 on the right-hand end 22, so that the honeycomb element 12 is reliably mounted in the converter housing 6.
Figure 4 shows an alternative embodiment of a catalytic converter 7. The catalytic converter which is shown there has an essentially parallelepiped-shaped converter housing 6 in which there is a rectangular honeycomb element 12. The layers of sheet metal 19 which are provided are attached to the converter housing 6 in a manner known per se, for example by spot welding. The flow path 8 which the emissions which are to be cleaned will take is identical to that shown in Figure 2.
The catalytic converter 7 which is shown in Figure 4 is attached to the dividing wall 5 by means of seven attachment webs 25, for example. The attachment webs 25 are plugged through corresponding openings provided in the dividing wall 5, and are bent or twisted through approximately 90°, so that the converter housing 6 is secured to the dividing wall 5.
In the silencer housing shown in Figure 1, the emissions inlet 4 and the emissions outlet 13 are arranged opposite one another, viewed in the longitudinal direction of the silencer housing 1. However, this is not imperative, as illustrated in Figure 5. Here, the emissions inlet 4 and the emissions outlet 13 are located one directly next to the other in the upper housing component 3 of the silencer housing 1. The emissions inlet 4 and the emissions outlet 13 are separated from one another fluidically by a dividing wall 26, so that an exchange between the incoming emissions and outgoing emissions is prevented.
The incoming emissions enter the converter housing 6 of the catalytic converter 7 through the emissions inlet 4 and the openings 9 of the dividing wall 5, and through the converter housing openings 10. In the example shown in Figure 5, the catalytic converter 7 is in the lower housing component 2. The catalytic converter 7 has an intermediate wall 27 which runs
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in the longitudinal direction of the silencer housing 1 and extends to the, in Figure 5, left-hand end of the catalytic converter 7 as far as the dividing wall 26, so that two sections 28 and 29 are formed in the catalytic converter 7, the sections 28 and 29 having a fluidic connection to one another at the right-hand end (shown in Figure 5) of the catalytic converter 7 by virtue of the fact that the intermediate wall 27 does not extend completely as far as the, in Figure 5, right-hand side of the catalytic converter 7. The emissions which are to be controlled enter an emissions inlet section 28 and leave again from an emissions outlet section' 29.
It is to be noted that the intermediate wall 27 separates an individual honeycomb element 12 into the two sections 28, 29, said honeycomb element 12 being accommodated in the converter housing 6. However, it is also possible to accommodate two or more separate honeycomb elements (not shown here) in the converter housing, which elements are separated by any desired number of intermediate walls.
In thi£ way, at least one emissions inlet section and one emissions outlet section, which communicate fluidically with one another, are also respectively provided.
The catalytic converter 7 which is illustrated in Figure 5 is shown again in more detail in Figure 6. The converter housing 6 is an essentially parallelepiped-shaped element in which a honeycomb element 12 is accommodated. In the honeycomb element 12 there are layers of sheet metal 19 which form ducts 11. Provided parallel to the dividing wall 5 is an intermediate wall 27 which is arranged approximately centrally in the converter housing 6 and which extends from the, in Figure 6, front end of the converter housing 6 along essentially one quarter of the length of the converter housing 6, as indicated by the broken lines. The intermediate wall 27 is secured by means of projections 30 which protrude from it and latch into corresponding openings in the converter housing 6.
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The converter housing 6 has, in the longitudinal direction, two edges 31 which - as already described in Figure 2 - can be fastened to the dividing wall 5 in the lower housing component in a detachable or nondetachable fashion. Here, the part of the dividing wall 27 which can be seen in Figure 6 comes into contact with a dividing end wall 26 in such a way that the sections 28, 29 which are shown in Figure 5 are separated from one another.
A further embodiment of the catalytic converter 7 according to the invention is illustrated in Figure 7. The catalytic converter 7 has an essentially parallelepiped-shaped converter housing 6, in which a honeycomb element 12 which is composed of layers of sheet metal 19 is arranged. In the honeycomb element 12 there is a flat layer 32. which runs essentially parallel to the dividing wall 5. In addition, part of the flat layer 32 bears against the side walls 33 of the converter housing 6 and, with its ends which are designed as wings 34 and which run in the longitudinal direction of the silencer, bears on edges 35 of the converter housing 6 which protrude perpendicularly from the side walls 33.
Holes 36 are provided both in the wings 34 and in the edges 35, it being possible to insert through said holes attachment elements, such as rivets, into corresponding openings in the dividing wall 5 in order to fix the catalytic converter 7, together with the flat layer 32, securely to the dividing wall 5.
The attachment of the individual layers of sheet metal 19 can be carried out in a manner known per se. Thus, it is possible to solder or weld said layers to one another or to attach them in some other manner which is known per se. In addition, it is possible to attach said layers by means of attachment elements, for example rivets, staples, or by spot welding to the converter housing 6. Preferably, the points of attachment by welding or soldering must be free of catalytically active
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coating.
The honeycomb elements 12 which are shown above may be surrounded by a casing. In Figure 8, the honeycomb element 12 illustrated in Figure 4 is surrounded by a casing 38 in such a way that the emissions can flow freely through the ducts 11, as is also the case in the other exemplary embodiments. By means of the casing 38, the honeycomb element 12 is designed as a module which can be inserted into the converter housing 6 and it can be attached there in a detachable or nondetachable fashion. This has the advantage that honeycomb elements can, be prefabricated individually. The casing 38 may be here a very thin piece of sheet metal which does not necessarily have to surround the entire outer surface of the honeycomb element either, as long as it is ensured that the pieces of sheet metal are held together in a dimensionally stable way.
It is to be noted that any catalytic converter 7 may be provided with the insulation material for thermal insulation. Furthermore, it is also possible to line the silencer housing 1 entirely or partially with insulation material 37, as is indicated in Figure 5.
The present invention is particularly suitable for the simple manufacture of cost-effective catalytic converters for small engines whose emissions contain considerable portions of hydrocarbons, at least some of which is to be removed catalytic-ally, during which process other noxious substances such as carbon monoxide or nitrogen oxides, for example, can also simultaneously be reduced.
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List of reference numerals
1 Silencer housing
2 Lower housing component
3 Upper housing component
4 Emissions inlet
5 Dividing wall
6 Converter housing
7 Catalytic converter
8 Flow path
9 Openings in the dividing wall
10 End wall
11 Ducts
12 Honeycomb element
13 Emissions outlet
14 Attachment elements
15 Insulation space
16 end openings
17 Bottom wall
18 Half-shell-shaped housing component
19 Layers of sheet metal
20 Edge
21 Left-hand end
22 Right-hand end
23 Attachment element
24 Chamfer
25 Attachment webs
26 Dividing end wall
27 Intermediate wall
28 Emissions inlet section
29 Emissions outlet section
30 Projections
31 Edges
32 Flat layer
33 Side walls
34 Wing
35 Edges
36 Holes
37 Insulation material
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38 Casing

WE CLAIM:
1. A catalytic converter (7) for a silencer of a small engine for controlling
emissions, having a converter housing (6) and at least one honeycomb element
(12) which is arranged therein and which contains layers of sheet metal (19)
which have catalystically active material, the converter (7) being arranged on
a dividing wall (5). provided with at least one opening (9), of a silencer
housing (1) for a small engine, said housing (1) having an upper housing
component (3) and a lower housing component (2). characterised in that
a) the converter housing (6) is shaped whereby emissions can flow
sucessively through the honeycomb element (12) and the opening (9).
and
b) the coverter housing (6) is spaced apart from the silencer housing (1)
and fixed to the dividing wall.

2. The converter (7) as claimed in claim 1, wherein the coverter housing (6) is
attached to the dividing wall (5).
3. The converter (7) as claimed in claim 1 or 2. wherein the converter housing
(6) has at least one side wall (33) and an end wall (10).
4. The converter (7) as claimed in one of claims 1 to 3. wherein one wall of the
converter housing (6) is formed by the dividing wall (5).
5. The converter (7) as claimed in one of claims 1 to 4, wherein the converter
housing (6) has an essentially rectangular or semicircular cross section which
corresponds to the cross section of the honeycomb element (12).
6. The converter (7) as claimed in one of claims 1 to 5, wherein the converter
housing (6) is composed of deep-drawn sheet metal,
7. The converter (7) as claimed in one of claims 1 lo 6. wherein the converter
housing (6) has attachment webs (25)
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which engage in corresponding openings which are provided in the dividing wall (5).
8. The converter (7) as claimed in one of claims 1 to 7,
wherein the converter housing (6) is attached to the dividing
wall (5), preferably by spot welding or mechanical clamping.
9. The converter (7) as claimed in one of claims 1 to 8,
wherein the layers of sheet metal (19) are squeezed, with
plastic deformation, into the converter housing (6).
10. The converter (7) as claimed in one of claims 1 to 9,
wherein a casing (38) is provided around the honeycomb element
(12) .
11. The converter (7) as claimed in claim 10, wherein the
layers of sheet metal (19) are attached in the casing (38).
12. The converter (7) as claimed in one of claims 1 to 11,
wherein the casing (38) is attached to the dividing wall (5)
and/or to the converter housing (6).
13. The converter (7) as claimed in one of claims 1 to 12,
wherein the layers of sheet metal (19) already have a
catalytically active surface layer before the converter is assembled.
14. The converter (7) as claimed in one of claims 1 to 13,
wherein a flat layer (32) is provided within the layers of
sheet metal (19), the ends of which flat layer are formed as
wings (34) which are located between the converter housing (6)
and the dividing wall (5).
15. The converter (7) as claimed in one of claims 1 to 13,
wherein the layers of sheet metal (19) are wound or folded.
16. The converter (7) as claimed in one of claims 1 to 15,
wherein an intermediate wall (27) which divides the converter
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housing (6) and the honeycomb element (12) into two spaces (28, 29) in each case is provided, the two spaces (28, 29) having a fluidic connection to one another such that the openings (9) in the dividing wall (5) form an inlet opening for the emissions to be controlled and an outlet opening for controlled emissions.

The invention relates to a catalytic converter (7) for controlling emissions, particularly from a small engine, having a converter housing {6) and at least one honeycomb element (12) which is arranged therein and which contains layers of sheet metal (19) which have catalytically active material, the converter (7) being arranged on a dividing wall (5), provided with at least one opening (9), of a silencer housing (1) for a small engine, said housing (1) having an upper housing component (3) and a lower housing component {2). According to the invention, the converter housing (6) is shaped in such a way that emissions can flow successively through the honeycomb element (12) and the opening (9), the converter housing (6) being spaced apart from the silencer housing (1). Such a converter can be manufactured cost-effectively, can easily be integrated into existing structures, and during operation does not lead to unacceptable temperatures of the outer wall of the silencer housing.

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Patent Number

203594

Indian Patent Application Number

IN/PCT/2000/0068/KOL

PG Journal Number

11/2007

Publication Date

16-Mar-2007

Grant Date

16-Mar-2007

Date of Filing

09-Jun-2000

Name of Patentee

EMITEC GESELLSCHAFT FUR EMISSONTECH NOLOGIE MBH

Applicant Address

Hauptstrasse 150, D-53797 Lohmar,

Inventors:

#	Inventor's Name	Inventor's Address
1	BRUCK , ROLF	FROBELSTRASSE 12, D-51429 , BERGISCH GLADBACH,
2	KONIECZNY, JORG-ROMAN,	BAHNHOFSTRASSE 17, D-53721 SIEBURG,

PCT International Classification Number

FOIN 3/28 ,7/00

PCT International Application Number

PCT/EP99/00044

PCT International Filing date

1999-01-07

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	19801122.9	1998-01-14	Germany