EP1012455A2

EP1012455A2 - Catalytic converter for a small-size engine

Info

Publication number: EP1012455A2
Application number: EP97950069A
Authority: EP
Inventors: Rolf BRÜCK; Wolfgang Maus
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH
Current assignee: Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 1996-11-08
Filing date: 1997-11-03
Publication date: 2000-06-28
Anticipated expiration: 2017-11-03
Also published as: RU2160371C1; CN1093908C; KR100495383B1; ES2174315T3; DE59706715D1; JP2001505274A; WO1998021453A2; KR20000053136A; WO1998021453A3; US6403039B1; AU5316098A; TW364038B; MY122028A; EP1012455B1; CN1258336A; JP3251299B2; DE19646242A1; DE19646242C2

Abstract

The present invention relates to a catalytic converter for a small-size engine and a method for the production thereof. In order to cut production costs, a honeycomb shaped body, coated with a catalytically active material made out of at least partially structured metal sheets (5, 6) with exhaust gas conduits (7), is placed in the housing of a silencer located close to the engine in order to enable at least the greater part of the exhaust gas from the engine to flow through the honeycomb body. The honeycomb body is a layered, wound or folded pile of metal sheets (5,6) which is squeezed into the silencer housing (3.1, 3.2, 3.3) with a plastic deformation of at least 10 %, preferably 20-30 % of the conduits (7), whereby said body entirely fills at least a partial volume. The considerable deformation that occurs in part of the conduits (7) also leads to high elastic deformation in the rest of the honeycomb body, thereby guaranteeing the stability of the honeycomb body even in the case of alternating thermal strains.

Description

Catalytic converter for a small engine

The present invention relates to a catalytic converter for a small motor, in which a honeycomb body coated with catalytically active material is arranged in a silencer housing arranged close to the motor.

In the course of increasing environmental awareness and stricter emission regulations in many countries, the need has increased to carry out catalytic exhaust gas cleaning not only for motor vehicles but also for small engines. Small engines in the following mean engines with a displacement of less than 250 ccm, in particular less than 50 ccm. Such engines occur particularly in lawn mowers, chain saws, portable power units, two-wheelers and similar applications. In the case of chainsaws, lawn mowers and other garden tools in particular, the person operating the device is often in the exhaust area of the small engine for a longer period of time, which is why catalytic exhaust gas cleaning is particularly important.

DE-OS 38 29 668 already provides an example of an exhaust silencer for two-stroke engines, which contains a catalytic converter for exhaust gas purification in its interior.

EP 0 470 113 B1 also discloses a metallic catalyst carrier body which is particularly suitable for fastening in the partition of a silencer housing.

The described arrangements for the catalytic exhaust gas purification of small engines require specially manufactured honeycomb bodies, their manufacture, Catalytic coating and installation require a relatively large number of work steps and are therefore relatively expensive in comparison with the small motor itself and an associated device. However, in order to further spread catalytic exhaust gas purification in small engines, it is necessary to drastically reduce the cost of such exhaust gas purification devices.

The object of the present invention is therefore a catalytic converter for a small engine, which is very inexpensive to manufacture, requires the smallest possible design changes to existing small engines and their exhaust systems, and yet can remove a considerable proportion of the pollutants from the exhaust gas catalytically.

A catalytic converter according to claim 1 is used to achieve this object, a corresponding manufacturing method being specified in claim 11. Advantageous refinements are specified in the respective dependent claims.

Catalytic converters usually contain honeycomb bodies in order to provide a sufficiently large surface for a catalytic conversion in a partial volume of the exhaust system. Such honeycomb bodies are produced in particular from metal sheets, at least some of these metal sheets being structured in such a way that channels which are permeable to exhaust gas result overall. In the simplest case, alternating smooth and corrugated sheet layers are used. However, a large number of structures come into consideration for the present invention, so that sheet metal layers with two different corrugations or sheet metal layers with corrugations arranged alternately obliquely to one another can also be used. In the prior art it has been customary to fill a partial volume provided for the honeycomb body as evenly as possible with channels, all known ones If possible, manufacturing processes avoid deforming or destroying a larger proportion of ducts when installing the honeycomb body in an exhaust system. Although honeycomb bodies are occasionally inserted into a jacket tube or a housing under a prestress, the channels are generally not plastically deformed or only to a small extent. According to the solution according to the invention, this path is left for catalytic converters of small motors in order to drastically simplify production. Silencer housings for small engines generally have a larger volume than is necessary to accommodate a catalyst carrier body for complete exhaust gas purification. It is therefore not a matter of making optimal use of the available volume or minimizing a housing. It can therefore be accepted that part of the volume is partially blocked by plastically deformed channels without this affecting the function or the exhaust gas cleaning. This opens up the possibility, as a honeycomb body, of simply using a layered, wound or otherwise folded stack of sheet metal layers coated with catalytically active material, which plastically deform a large proportion of the cells, for example 10, 20 or up to 30%, into the muffler housing is squeezed so that it completely fills at least a partial volume of the muffler housing.

As will be described below with the aid of preferred exemplary embodiments, this method has many advantages in terms of production technology and leads to a simple, but durable catalytic converter.

In general, a silencer housing for small engines consists of two or more individual parts, in particular half-shells and a partition, which can be connected by means of a simple connection process, e.g. B. flanging or welding. These housing parts can Assembling can be used simultaneously for the shaping of the honeycomb body, without the need for additional tools. A stack of sheet metal layers with a larger volume than the partial volume to be filled in the muffler housing is simply placed in the intended position when the housing is assembled and squeezed into its final position and shape when the housing parts are assembled. Even if 15 to 30% of the channels are plastically and / or elastically deformed, namely at the lateral ends of the stack and in the outer edge areas, enough cells remain gas-permeable, so that effective catalytic cleaning is ensured.

In order to prevent the honeycomb body from slipping in the silencer housing in the gas flow direction, the lateral ends of the stack should be held on or in the walls of the housing in a preferred embodiment.

It is also important for a simple manufacturing process that the sheets are already coated with catalytically active material before being fitted in the silencer housing, either by using sheets already coated for the entire production process or by coating a prefabricated stack of sheet metal layers as a whole.

A major advantage of the catalytic converter according to the invention is that the considerable deformation of the channels is partly plastic and partly elastic, so that the honeycomb body remains under a pretension which prevents the sheet metal layers from loosening under all operating conditions, in particular thermal alternating loads. In general, the honeycomb body will be under maximum prestress in a catalytic converter manufactured according to the invention, since it is deformed everywhere beyond the elastic limit. This prevents relative movements between the sheet layers even with decreasing elasticity with increasing temperature.

At this point it should be pointed out that sheet metal layers with so-called transverse microstructures, which are known in the prior art, are also particularly suitable for the present invention. These microstructures increase the effectiveness of the catalytic conversion and also cause the sheet metal layers to be clamped together, so that they cannot move against each other, especially under the high elastic preload, even under the most unfavorable conditions. This also applies if not all sheet metal layers, but only a part of them, are attached to the silencer housing with their ends.

It is particularly expedient if the stack to be squeezed into the muffler housing is adapted in its initial form to the shape of the partial volume to be filled and to the degree of deformation of the individual regions to be expected during the crushing, although the volume of the stack is preferably at least 5%, preferably should be at least 10% larger than the partial volume to be filled.

Therefore, different shapes can be considered as cross-sectional shapes for a stack, in particular rectangular, trapezoidal, oval or, in individual cases, more irregular shapes. It should also be noted that individual sheet layers, the ends of which are bent along the ends of the stack, should be longer than less bent sheet layers if their ends are to extend to the housing wall or a parting joint after the crimping process.

It is particularly preferred, in the case of silencer housings composed of at least two parts, to clamp the crimped ends of the stack in the joint between these parts in order to enclose the honeycomb body to fix overall. This can be carried out both in the case of stacks formed from individual sheets, and in the case of stacks which are wound, folded or laid in a meandering shape from one or more sheets after the ends have been squeezed together. The ends of the stack can be included in the technology previously used for assembling the silencer housing, so that the attachment can be carried out, for example, by flanging, welding with a weld seam or spot welding. In particular when flanging, but also when incorporating into a weld seam, the catalytically active coating on the metal sheets generally does not interfere, so that no additional processing steps are necessary to remove them.

Advantageous refinements and exemplary embodiments of the invention are explained below with reference to the drawing, but the invention is not restricted to the exemplary embodiments shown. Show it:

FIG. 1 shows a longitudinal section through a muffler housing with a schematically indicated installation location of a catalytic converter,

FIG. 2 shows in cross section the parts of a silencer housing, including a stack, shortly before assembly,

3 shows a cross section along the section line III-III in Figure 1 by a silencer housing after assembly and

Figures 4, 5, 6, 7 and 8 different forms of stacks of at least partially structured sheet metal layers.

Figure 1 shows schematically in longitudinal section a silencer housing 3 for a small engine. The exhaust gas enters the exhaust gas inlet 1 Lower part 3.2 of the muffler housing, from where it reaches the upper part 3.1 of the muffler housing through openings in a partition 3.3. From here it flows through the channels 7 of a honeycomb body 4 and then reaches the exhaust gas outlet 2. Upper part 3.1 and lower part 3.2 of the muffler housing and the partition 3.3 are connected to one another in the area of a parting joint 3.4, for example by flanging or by a weld.

FIG. 2 schematically illustrates in cross section the joining of upper part 3.1, lower part 3.2, partition 3.3 of the muffler housing and a stack 8 of sheet metal layers 5, 6, the process of joining being indicated by arrows. In the present exemplary embodiment, the stack 8 is formed from alternately arranged individual smooth sheet metal layers 5 and corrugated sheet metal layers 6, which together form a multiplicity of channels 7 which are permeable to the exhaust gas. The sheet metal layers 5, 6 are coated with catalytically active material 10. This coating can either be applied to the sheet metal layers 5, 6 in a continuous process before all other processing steps, or else can be applied together after the stack 8 has been layered.

Figure 3 shows in cross section along the line III-III in Figure 1 an essentially completely assembled silencer housing with a crimped honeycomb body. It can be seen that the lateral ends 9 of the stack 8, which is still undeformed in FIG. 2, are now squeezed together, with numerous channels 7.1 also being plastically deformed in the edge regions of the honeycomb body. Nevertheless, especially in the inner region of the honeycomb body, there remain sufficient channels which are not plastically deformed and which are sufficient for the catalytic conversion of exhaust gas passed therethrough. However, these channels 7 are deformed considerably elastically by the squeezing forces exerted on the entire honeycomb body, so that the whole honeycomb body is under considerable pretension. The crimped lateral ends 9 of the stack of sheets are clamped between the upper part 3.1 and the partition 3.3 of the muffler housing and can be included in the usual connection technology of the muffler housing. As shown on the right side of FIG. 3, this can be a flanging 3.5. However, a welded connection 3.6 indicated on the left side of FIG. 3 is also possible, which also includes the ends of the sheet metal layers 5, 6 of the upper part 3.1, the lower part 3.2 and the partition 3.3.

FIGS. 4, 5, 6, 7 and 8 show different initial shapes for the honeycomb body 4 to be integrated into the silencer housing 3 as a selection of the shapes that are possible overall. Figure 4 shows a trapezoidal sheet metal stack 11, made of smooth sheet metal layers 5 and corrugated sheet metal layers 6, in the lateral end regions 9 of the sheet metal stack 11 those sheet metal layers are longer, the ends of which have a longer path to the parting joint after assembly. In this way it is ensured that the ends of practically all sheet metal layers can be held reliably. FIG. 5 shows a meandering stack of sheets 12.1 in which a corrugated sheet layer 6 is layered in a meandering manner, with individual smooth sheets 5 being arranged between the individual layers. A similar configuration is shown in FIG. 6, but only a single sheet, which is smooth and corrugated in sections, was layered into a meandering sheet stack 12.2. FIG. 7 shows an oval sheet stack 13 made of a smooth 5 and a corrugated sheet 6 as the starting stack. Such a stack can be achieved in a conventional manner by flattening a spiral sheet stack stacked with a cylindrical cavity. Figure 8 finally shows a particularly preferred embodiment in which only the smooth sheet metal layers 5 are to be included in the connection of the parting line. For this reason, the ends of the smooth sheet metal layers protrude to different degrees, depending on their way to the parting line. The corrugated sheet metal layers 6 are shorter and in their respective lengths adapted to the cross-sectional shape of the muffler housing and in turn equipped with a certain excess of volume, which is later reduced by plastic deformation. In order to prevent the corrugated sheet metal layers 6 from slipping in the finished honeycomb body in the gas flow direction, the smooth 5 and the corrugated sheet metal layers 6 are equipped with interlocking structures. Microstructures extending transversely to the direction of flow, as are known from the prior art, are particularly suitable for this purpose.

By means of inexpensive manufacturing technology, the present invention creates the possibility of being able to apply exhaust gas catalysts to small engines on a broad basis in order to relieve the environment and the operating personnel of the small engines.

Reference list

1 exhaust gas inlet

2 Exhaust gas outlet 3 Muffler housing

3.1 Upper part of the silencer housing

3.2 Lower part of the silencer housing

3.3 Partition in the silencer housing

3.4 Joint 3.5 Flanging

3.6 Connection welding

4 honeycomb bodies

5 smooth sheet metal layer

6 corrugated sheet metal layer 7 channel

7.1 deformed channel

8 stacks of sheet metal layers

9 crushed side end of the sheet stack

10 catalytically active material (coating) 11 trapezoidal sheet stack

12.1 meandering stack of sheets with inserted smooth sheet layers

12.2 meandering stack of sheets from different sections

13 oval stack of sheets

14 sheet stacks with protruding smooth sheet layers

Claims

claims

1. Catalytic converter for a small engine, in which a honeycomb body (4) coated with catalytically active material (10) and at least partially structured sheet metal layers (5, 6) with channels (7) permeable to exhaust gas are arranged in a silencer housing (3) close to the engine is arranged that at least a predominant portion of the exhaust gas of the small engine must flow through the honeycomb body (4), characterized in that the honeycomb body (4) is a layered, wound or folded

Stack of sheet metal layers (8), which is squeezed with plastic deformation of at least 10%, preferably 20 to 30%, of the channels (7) into the silencer housing (3), so that it completely fills at least a partial volume of the silencer housing (3) .

2. Catalytic converter according to claim 1, characterized in that the lateral ends (9) of the stack (8) on or in the walls of the housing (3) are held.

3. Catalytic converter according to claim 1 or 2, characterized in that the sheet metal layers (5, 6) are coated with catalytically active material (10) before mounting in the silencer housing (3).

4. Catalytic converter according to claim 1, 2 or 3, characterized in that the deformation of the channels (7.1) is partly plastic and partly elastic, so that the honeycomb body (4) remains under a pretension, which in all operating conditions , in particular thermal alternating loads, prevents loosening of the sheet metal layers (4, 5).

5. Catalytic converter according to one of the preceding claims, characterized in that the stack (8) has a shape adapted to the shape of the partial volume of the muffler housing (3) to be filled, but with a volume which is at least 5%, preferably at least 10%, larger.

6. Catalytic converter according to one of the preceding claims, characterized in that the stack (8) is rectangular in cross section before being introduced into the muffler housing (3).

7. Catalytic converter according to one of claims 1 to 6, characterized in that the stack (11) is trapezoidal in cross section before being introduced into the muffler housing (3).

8. Catalytic converter according to one of claims 1 to 6, characterized in that the stack (13) is oval in cross section before being introduced into the muffler housing (3).

9. Catalytic converter according to one of the preceding claims, characterized in that the stack (8; 11; 14) is layered from individual, at least partially structured sheet metal layers (4, 5), the ends of which are squeezed together (9) and on the muffler housing (3) are fixed, preferably clamped in a joint (3.4) between two parts (3.1, 3.3) of the muffler housing (3).

10. Catalytic converter according to one of claims 1 to 8, characterized in that the stack (11; 12.1; 12.2; 13) is formed from one or more at least partially structured, meandering or oval-wound sheets (5, 6), wherein the lateral ends (9) of the stack (11; 12.1; 12.2; 13) are each squeezed together and are fixed to the muffler housing (3), preferably clamped in a joint (3.4) between two parts (3.1, 3.3) of the muffler housing (3).

11. A method for producing a catalytic converter in a silencer housing (3) for a small engine with the following steps:

a stack (8; 11; 12.1; 12.2; 13; 14) of at least partially structured sheet metal layers (5, 6) is formed, which has passages (7) permeable to an exhaust gas,

the stack (8; 11; 12.1; 12.2; 13; 14) is squeezed into a partial volume of the muffler housing (3) with plastic deformation of at least 15%, preferably 20 to 30%, the partial volume being completely filled becomes,

the lateral ends (9) of the crushed stack (8; 11; 12.1; 12.2; 13; 14) are fixed on or in the wall of the silencer housing (3).

12. The method according to claim 11, characterized in that the sheets (5, 6) before forming the stack (8; 11; 12.1; 12.2; 13; 14) or at least before installation in the silencer housing (3) with catalytically active Material (10) are coated.

13. The method according to claim 11 or 12, characterized in that the crushing of the stack (8; 11; 12.1; 12.2; 13; 14) by assembling two or more housing parts (3.1, 3.2, 3.3) of the silencer housing (3) between which the stack (8; 11; 12.1; 12.2; 13; 14) is inserted.

4. The method according to claim 11, 12 or 13, characterized in that the stack (8; 11; 12.1; 12.2; 13; 14) is made somewhat wider than the muffler housing (3), so that its lateral ends (9) after The squeezing and joining of the silencer housing (3) protrude from the housing (3) on one or two sides and are included in the connection of the silencer housing parts (3.1, 3.2, 3.3) by flanging (3.5) or a joining technology connection (3.6) can.