Hand-held power tool and exhaust gas aftertreatment device for hand-held power tool

Abstract

A hand-held work appliance comprises an internal combustion engine (A8) and an exhaust gas muffler (A23). A first muffler chamber (A47) and a second muffler chamber (A48) are formed in the exhaust gas muffler (A23). The exhaust gas silencer (A23) comprises an exhaust gas aftertreatment device (A26) which comprises at least one flow-through unit (A31). The flow-through unit (A31) is arranged in a flow path from the first muffler chamber (A47) into the second muffler chamber (A48). The thickness (b) of the flow-through unit (A31), measured from the upstream end face (A36) to the downstream end face (A37) of the flow-through unit (A31), is at least 10 mm in the region of the flow-through unit (A31) through which the exhaust gas flows at least in the range of 70% of the cross-section. The exhaust gas aftertreatment device (A26) is not provided with a catalytic coating.

Description

Technical Field

[0001] The invention relates to a hand-held power tool of the type specified in the preamble of claim 1 and to an exhaust gas aftertreatment device for a hand-held power tool. Background Art

[0002] A hand-held work tool having an exhaust muffler with a catalyst is known from JP 2009-156158 A. The catalyst can be formed from a wire and coated with a catalyst material such as platinum.

[0003] Combustion-driven hand-held working tools, such as motor saws, cutting machines, brush cutters, blowers, lawn mowers or the like, need to continue to meet increasingly stringent legal requirements on exhaust gas composition. In order to meet these requirements, it is also known in such small engines that catalysts are used for exhaust gas aftertreatment. The framework conditions for such catalysts in hand-held working tools differ from the framework conditions in the automotive industry in various aspects. Due to the limited available structural space, the exhaust gas muffler in such hand-held working tools must be relatively small. At the same time, the contact between the operator and the hot parts of the working tool must be avoided. Therefore, strict requirements are also applicable in terms of exhaust gas temperature. Usually, the internal combustion engine used is a mixed lubrication motor. Since the fuel is at least partially supplied to the crankshaft housing of the internal combustion engine in the mixed lubrication motor, it is impossible to achieve accurate cyclic dosing of the fuel. Therefore, compared with, for example, in the automotive industry, the composition of the exhaust gas fluctuates significantly more violently in such small engines, where accurate cyclic control of the amount of fuel injected directly into the combustion chamber is achieved.

[0004] Therefore, compared to exhaust mufflers such as are used in the automotive industry or for diesel engines or for separately lubricated four-stroke engines, different requirements are placed on exhaust mufflers for such hand-held work tools not only with regard to temperature and weight, but also with regard to fluctuating exhaust gas compositions, so that solutions from this field cannot be easily transferred to exhaust mufflers for hand-held work tools. Summary of the invention

[0005] The invention is based on the object of creating a handheld power tool of the generic type which is of simple and robust construction. A further object of the invention is to provide an exhaust gas aftertreatment device for an exhaust gas muffler of a handheld power tool.

[0006] With regard to the handheld power tool, this object is achieved by a power tool having the features of claim 1. With regard to the exhaust gas aftertreatment device, this object is achieved by an exhaust gas aftertreatment device having the features of claim 16 .

[0007] According to the invention, it is provided that the exhaust gas aftertreatment device is free of a catalytic coating. A catalytic coating is a coating which acts as a catalyst in this context, which then reduces the activation energy for chemically converting the exhaust gases and thus increases the reaction rate. The catalytic coating is in particular a coating of a noble metal. The catalytic coating is in particular a coating which serves primarily to convert hydrocarbons and / or nitrogen oxides.

[0008] Since the exhaust gas aftertreatment device does not have a catalytic coating, the exhaust gas in the exhaust gas muffler is heated significantly less than in an exhaust gas aftertreatment device with a catalytic coating. Since a shorter cooling path is required for the exhaust gas in the muffler, a smaller structural space of the exhaust gas muffler can be achieved. Since the exhaust gas aftertreatment device does not have a catalytic coating, the raw materials for the catalytic coating, especially precious metals, are saved, and the cost for manufacturing the exhaust gas aftertreatment device is reduced. Unexpectedly, it has been shown that in an internal combustion engine in a handheld work tool, even without a catalytic coating of the exhaust gas aftertreatment device, it is possible to fully treat the exhaust gas in the exhaust gas aftertreatment device, especially in terms of conversion particles. In particular, the flow-through unit, preferably the wire body of the flow-through unit, does not have a catalytic coating.

[0009] The flow-through unit must have a minimum thickness in order to achieve a sufficient residence time of the exhaust gas in the flow-through unit so that the exhaust gas can be adequately converted. The flow-through unit for particle conversion has a thickness of at least 10 mm in the region through which the exhaust gas flows. The flow-through unit can have a smaller thickness in the edge region. For example, the flow-through unit can be rounded or have chamfered edges in the edge region. The indicated thickness of at least 10 mm is obtained in the range of at least 70% of the maximum cross section, in particular in the range of at least 80% of the maximum cross section.

[0010] The high stability of the flow-through unit results from the relatively large thickness of the flow-through unit. The cross section is perpendicular to the main flow direction through the exhaust gas aftertreatment device. The maximum cross section is the largest cross section of the flow-through unit perpendicular to the main flow direction. The thickness is advantageously measured parallel to the main flow direction. The thickness is preferably perpendicular to the first, upstream end side of the flow-through unit.

[0011] Preferably, the thickness of the flow unit in the region of the flow unit through which the exhaust gas flows is at least 15 mm, particularly preferably at least 20 mm, at least within the range of 70% of the maximum cross section. Advantageously, the thickness of the flow unit in the region of the flow unit through which the exhaust gas flows is at least 10 mm, particularly at least 15 mm, within the range of the entire maximum cross section.

[0012] Advantageously, all flow-through units of the exhaust gas aftertreatment unit of the exhaust gas silencer have a thickness of at least 10 mm in the region of the flow-through unit through which the exhaust gas flows, at least in the region of 70% of the maximum cross section.

[0013] Advantageously, at least one flow-through unit is at least partially, in particular completely, coated with a carrier coating. In this context, a carrier coating is a coating that increases the surface without reducing the activation energy for the chemical conversion. For example, the carrier coating can consist of aluminum oxide. The carrier coating leads to an improved effect on the particle conversion. Advantageously, the flow-through unit comprises at least one wire body consisting of metal. Since the flow-through unit comprises at least one wire body consisting of metal, the flow-through unit acts as a particle converter. Oil droplets in the exhaust gas flow are converted in the wire body at a sufficiently high temperature, thereby achieving a particle reduction.

[0014] It has been found that, in particular for the wire bodies, a coating with a washcoat is advantageous in order to achieve good results during particle conversion.

[0015] A wire body is understood herein as a shape-stable body, which is formed by at least one wire made of metal. Here, the wire is a thin, elongated, bendable metal piece. The wire has a preferably circular cross section. An angular cross section or other suitable cross-sectional shapes can also be advantageous. The cross section of the wire is advantageously constant within the scope of its length within the framework of common processing tolerances. The wire is preferably manufactured by elongation.

[0016] In alternative embodiments, the flow-through unit can also have a differently designed flow-through unit instead of a wire body.

[0017] Advantageously, the wire cross section of at least one wire body, in particular all wire bodies, of the exhaust gas aftertreatment device is at least 0.07 mm 2 If the wire has a circular wire cross section, the wire diameter is advantageously at least 0.3 mm. This results in sufficient stability of the wire body. At the same time, a large surface area of ​​the wire body is obtained, so that good particle reduction is achieved. The wire cross section of the wire body is advantageously no greater than 0.8 mm. 2 Advantageously, in the case of a circular wire cross section, the wire diameter is no greater than 1 mm.

[0018] Advantageously, the wires of the wire body consist at least partially, in particular completely, of a nickel alloy or of stainless steel. In this context, stainless steel is in particular stainless steel according to DIN EN 10 088.

[0019] Advantageously, the density of the at least one wire body is 0.6 g / cm 3 Up to 2.0g / cm 3The density of all wire bodies of the exhaust gas aftertreatment device is preferably 0.6 g / cm 3 Up to 2.0g / cm 3 It has been shown that a good particle reduction can be achieved when the density of the wire body is within a specified range. The density of the wire body is closely related to the proportion of the hollow space of the wire body relative to the entire volume of the wire body. The density of the wire body thus influences the flow resistance and the residence time of the exhaust gas in the wire body. If the density is within a specified range, favorable values ​​for the flow resistance and the residence time can be obtained.

[0020] It has been shown that the volume of the wire body is important for a good particle reduction. Advantageously, the sum of the volumes of the flow-through regions of all wire bodies of the flow-through unit is at least 0.6 times the displacement of the internal combustion engine.

[0021] The wire body is preferably constructed from a metal braided mesh. The wire body is preferably wound helically. It is particularly preferred that the wire body is a metal braided mesh mat wound helically. In an advantageous design, the wire body is arranged in the exhaust gas silencer in such a way that the winding axis extends through the upstream end side and the downstream end side of the wire body. In the case of an approximately cylindrical shape of the wire body, it is then possible to easily achieve a constant thickness of the wire body within the framework of common processing tolerances within the range of a large part of the cross section, in particular within the range of the entire cross section. Advantageously, the winding axis extends perpendicularly to the upstream end side and / or the downstream end side of the wire body.

[0022] The minimum cross section of the flow unit in the region of the flow unit through which the exhaust gas flows is advantageously at least 8 mm per cubic centimeter of the displacement of the internal combustion engine. 2 , especially at least 12mm 2 .

[0023] Advantageously, it is provided that the exhaust gas silencer has an exhaust gas inlet into the exhaust gas silencer and an exhaust gas outlet from the exhaust gas silencer. Advantageously, at least one flow-through unit, in particular at least one wire body of an exhaust gas aftertreatment device, is arranged in each flow route from the exhaust gas inlet to the exhaust gas outlet. Therefore, the exhaust gas silencer has no bypass relative to the at least one wire body in a preferred design. The exhaust gas must therefore be forced to flow through at least one flow-through unit, in particular through at least one wire body of the exhaust gas aftertreatment device. This ensures a good reduction of particles. Advantageously, there is no flow route from the exhaust gas inlet to the exhaust gas outlet, which does not lead through at least one flow-through unit. A flow route is understood in this article as a fluid connection from the exhaust gas inlet to the exhaust gas outlet of the exhaust gas silencer. Multiple flow routes from the exhaust gas inlet to the exhaust gas outlet can be formed in the exhaust gas silencer.

[0024] In order to ensure that the exhaust gases flowing out of the exhaust gas aftertreatment device can be adequately cooled in the exhaust gas muffler, it is advantageously provided that the second muffler chamber has a volume of at least 80% of the displacement of the internal combustion engine.

[0025] The internal combustion engine is in particular a mixed lubricated internal combustion engine. It is particularly preferred that the internal combustion engine is a two-stroke engine. In a mixed lubricated internal combustion engine, the exhaust gas includes oil droplets, which can be converted in the wire body. The working device is advantageously constructed so that the temperature of the exhaust gas flow at the upstream side of the exhaust gas aftertreatment device is 450° C. to 750° C. after at least 2 minutes of operation of the internal combustion engine under full load. This temperature can be achieved, for example, by appropriately designing the internal combustion engine and / or appropriately arranging the exhaust gas aftertreatment device. Such temperatures are especially achieved in mixed lubricated internal combustion engines in handheld working tools, especially in two-stroke engines. It has been shown that in the case of temperatures in this temperature range, there is a sufficient temperature for good particle reduction at the upstream side of the exhaust gas aftertreatment device. For example, additional heating of the exhaust gas aftertreatment device caused by a catalytic reaction of a catalytic coating of a component of the exhaust gas aftertreatment device is not mandatory. Thus, a simple structure of the working tool is obtained.

[0026] It is advantageously provided for an exhaust gas aftertreatment device for a handheld work tool that the exhaust gas aftertreatment device comprises at least one flow-through unit, in particular at least one flow-through unit having at least one wire body made of metal. The exhaust gas aftertreatment device has no catalytic coating. The wire body made of metal is therefore not coated with a catalytic material. The wire body has no coating or the coating of the wire body does not have a catalytic effect. The coating of the wire body in particular does not comprise precious metals. This results in a simple, cost-effective design and the exhaust gas leaving the wire body has a relatively low temperature.

[0027] The invention further relates to an exhaust gas silencer of the type specified in the preamble of claim 17 and to an internal combustion engine having an exhaust gas silencer.

[0028] DE 101 47 338 A1 discloses a ceramic catalyst body for an exhaust gas muffler. In one embodiment, the catalyst body has a central region that has a higher amount of catalytic coating per volume unit than the peripheral region. Compared to full-load operation, a higher proportion of the exhaust gas flow should be cleaned during idling due to the arrangement of the central region in the projection plane of the gas inlet.

[0029] It has been found that the exhaust gas silencer can overheat during operation if an excessively large partial flow of the exhaust gas is subjected to catalytic aftertreatment.

[0030] The invention is based on the object of creating an exhaust gas silencer of the generic type which has a simple structure and which allows adjustment of the temperatures which occur during operation.

[0031] This object is achieved by an exhaust gas silencer having the features of claim 17 .

[0032] A further object of the present invention is to provide an internal combustion engine having an exhaust muffler. This object is achieved by an internal combustion engine having the features of claim 34 .

[0033] It is provided that the exhaust gas silencer has a first flow unit and a second flow unit for exhaust gas aftertreatment. The flow units have different amounts of catalytic coatings. Here, the amount of catalytic coating in this article refers to the mass of the catalytic coating. As a result, the flow units are heated to different degrees during operation. Multiple flow paths for the exhaust gas are formed in the exhaust gas silencer, wherein the first flow path is only guided through the first flow unit and the second flow path is only guided through the second flow unit. By appropriately designing the flow paths, the amount of exhaust gas flowing through the first flow path and guided through the second flow path can be predetermined in terms of structure. The flow cross section of the flow path is predetermined in terms of structure and cannot be changed. This results in a simple structure of the exhaust gas silencer. In particular, no mechanical devices such as flaps, slides or the like are provided for controlling and changing the flow path.

[0034] In order to achieve a good setting of the amount of exhaust gas flowing through the first flow unit and the amount of exhaust gas flowing through the second flow unit, the present invention provides that the first flow unit and the second flow unit are arranged spatially separately from each other. The spatially separated arrangement causes a partial flow of the exhaust gas to flow through the first flow unit or through the second flow unit. Due to the spatially separated arrangement, a lateral flow between the flow units is prevented. As a result, a prescribed flow condition is achieved in the exhaust silencer, which is set in particular depending on the rotational speed. The spatial separation can better predetermine in terms of structure than in the prior art: which proportion of exhaust gas flows through which flow unit in which total exhaust gas flow.

[0035] The setting can be implemented, for example, in such a way that at low speeds a greater proportion of the exhaust gas flows through the second flow-through unit having a greater amount of catalytically active coating than at high speeds. As a result, rapid heating of the exhaust gas silencer can be achieved at low speeds, so that the exhaust gas aftertreatment becomes fully effective quickly after starting, and overheating of the exhaust gas silencer can be prevented at high speeds.

[0036] The spatial separation is advantageously configured in such a way that a transverse flow between the flow-through units is not possible. The spatial separation is advantageously configured in such a way that a partial flow of the exhaust gas flows only through the first flow-through unit or only through the second flow-through unit. As an additional option, one or more further flow-through units can be provided. For example, a third flow-through unit can be provided, by which a third flow path is formed, and a further partial flow of the exhaust gas flows only through the third flow-through unit and bypasses the first flow-through unit and the second flow-through unit.

[0037] It has been shown that an exhaust muffler with a catalytic coating can overheat, in particular, if an internal combustion engine in which the exhaust muffler is arranged is operated under high load in stationary operation. In such operation, a maximum mass flow through the internal combustion engine occurs, since the throttle element in the intake channel of the internal combustion engine is completely open. According to the invention, a spatially separated first and second flow-through unit with different amounts of catalytically active coatings makes it possible to dimension, position and / or construct the flow-through units in such a way that, in particular in the case of a high exhaust gas mass flow through the exhaust muffler, a smaller partial flow is generated through the second flow-through unit than in the case of a lower exhaust gas mass flow. As a result, overheating of the exhaust muffler can be prevented, in particular in stationary operation under high load.

[0038] At least one flow-through unit, i.e., in particular the first flow-through unit and / or the second flow-through unit, is advantageously coated with a carrier coating and / or a catalytic coating. Advantageously, each flow-through unit is provided with a carrier coating and / or a catalytic coating. However, it can also be provided that at least one flow-through unit has no carrier coating and no catalytic coating. The flow-through unit that is not provided with a carrier coating and is not provided with a catalytic coating is preferably mainly used to reduce particles. The exhaust gas of a mixed-lubricated internal combustion engine includes lubricating oil in the form of droplets, which are converted by the flow-through unit. Once the temperature required for this is reached, the oil droplets are converted by the first flow-through unit. Particles are thereby reduced. The second flow-through unit coated with a catalytic coating, in particular a precious metal, is preferably mainly used to convert hydrocarbons and / or nitrogen oxides.

[0039] A catalytic coating is defined in this context as a coating that acts as a catalyst, which then reduces the activation energy for chemically converting the exhaust gases and thus increases the reaction rate. A washcoat is not considered a catalytic coating in this context. Washcoats are considered to be coatings that increase the surface of a substrate, for example of the first flow-through unit and / or the second flow-through unit, without reducing the activation energy for the chemical conversion. The first flow-through unit does not necessarily have to have a catalytic coating, but can have a washcoat.

[0040] Advantageously, the first flow unit and the second flow unit are spaced apart from one another, thereby making it easy to spatially separate the flow units and in particular avoid transverse flows from the first flow unit into the second flow unit or from the second flow unit into the first flow unit.

[0041] A simple design results when the first flow unit and the second flow unit are arranged in a partition wall between the first and second silencer chambers of the exhaust gas silencer. The first flow unit and the second flow unit are in particular spaced apart from one another in the partition wall.

[0042] In an advantageous embodiment variant, it is provided that the first silencer chamber at least partially surrounds the second silencer chamber. The first silencer chamber is advantageously separated from the second silencer chamber by a separation portion, in which the first flow-through unit and the second flow-through unit are arranged. The separation portion can be constructed, for example, in a tubular shape. The separation portion can be formed, for example, by a pipe or by one or more separation walls. Preferably, the separation portion is constructed as a unilaterally closed pipe, into which the exhaust gas flows from the first silencer chamber through the first flow-through unit or through the second flow-through unit. The exhaust gas preferably flows from the second silencer chamber through the open end of the tubular separation portion.

[0043] In an advantageous alternative embodiment, it is provided that the exhaust gas silencer has a third silencer chamber. The first flow-through unit is advantageously arranged in a first dividing wall, which separates the first silencer chamber and the second silencer chamber from each other. The second flow-through unit is advantageously arranged in a second dividing wall, which separates the third silencer chamber from the second silencer chamber. The third silencer chamber is advantageously arranged in a second flow path between the first silencer chamber and the second silencer chamber along the flow direction. If a third silencer chamber is provided, the exhaust gas can therefore flow from the first silencer chamber through the first flow-through unit into the second silencer chamber or from the first silencer chamber first flow into the third silencer chamber and from there flow into the second silencer chamber through the second flow-through unit.

[0044] Advantageously, a passage is provided through the first dividing wall and the second dividing wall, which leads from the first muffler chamber into the third muffler chamber. The throttling of the second flow path can be set by the arrangement and size of the passage. The distribution of the exhaust gas flow to the first and second flow paths can then be easily set. Advantageously, the volumes of the first muffler chamber and the third muffler chamber are not the same. It can be provided that the first muffler chamber is larger than the third muffler chamber. However, it can also be advantageous that the third muffler chamber is larger than the first muffler chamber. In an advantageous alternative design, the first muffler chamber and the third muffler chamber can be approximately the same size.

[0045] In a particularly advantageous embodiment, the outflow direction from the first flow unit and the outflow direction from the second flow unit are directed in opposite directions to one another. The flow of the exhaust gas through the partial flows of the first and second flow units influences one another due to the mutually opposite outflow directions in the second muffler chamber. The degree of influence depends on the volume flow of the exhaust gas. This makes it possible to easily implement different distributions of the partial flows to the flow paths for different rotational speeds of the internal combustion engine.

[0046] Advantageously, the outflow surface from the first flow unit and the outflow surface from the second flow unit overlap at least partially along the outflow direction from the first flow unit. Flows directed in opposite directions from the flow units are throttled according to the total exhaust gas mass flow and the partial exhaust gas mass flow passing through the flow units. The mutual influence can be set by appropriately selecting the degree of overlap and the spacing of the outflow surfaces. The influence on the mass flow can be easily achieved through the flow path, so that different exhaust gas distributions to the flow path are generated depending on the rotational speed. A compact structure is thereby achieved at the same time. Advantageously, the exhaust gas escaping from the first flow unit throttles the exhaust gas flow flowing through the second flow unit. As a result, the exhaust gas flow flowing through the second flow unit is reduced by the exhaust gas silencer in the case of an increased total exhaust gas mass flow.

[0047] It has proven to be advantageous if the distance between the outflow surface of the first flow unit and the second flow unit in the second silencer chamber is less than 3 cm, in particular less than 2 cm.

[0048] If at least one flow-through unit comprises at least one wire body, a simple structure of the exhaust gas silencer is achieved. In particular, it is known that coated wire bodies are used as catalysts for hand-held working tools, such as motor-driven saws, cutting machines, brush cutters or the like. Such wire bodies can be very robust and easy to manufacture and are therefore well suited for use in such working tools. It is particularly preferred that the wire body is formed by extruded metal wire. Here, each flow-through unit can include one or more wire bodies. The individual wire bodies of the flow-through unit can be in contact with each other or spaced apart relative to each other. The flow-through bodies of the flow-through units can advantageously be arranged in a common housing, which is, for example, held in a dividing wall or a dividing portion. Here, the housing can be constructed at least partially in one piece with the dividing wall or the dividing portion, or can be constructed separately from the dividing wall or the dividing portion and firmly connected thereto.

[0049] Advantageously, each flow path through the exhaust gas silencer is led through a flow-through unit. Therefore, no exhaust gas can leave the exhaust gas silencer without passing through at least one flow-through unit. This makes it possible to easily ensure effective exhaust gas aftertreatment.

[0050] Advantageously, the first flow path leads directly from the first flow-through unit into the second muffler chamber. Advantageously, the second flow path leads directly from the second flow-through unit into the second muffler chamber. Therefore, the exhaust gas reaches the common muffler chamber directly after flowing through the flow-through unit. In this second muffler chamber, the exhaust gas flows can appropriately influence each other according to the position and size of the flow-through unit. In addition, sufficient mixing of the exhaust gas advantageously occurs in the second muffler chamber. Advantageously, a vortex is formed in the second muffler chamber, which facilitates sufficient mixing of the exhaust gas. The exhaust gas flow leaving the second muffler chamber thus advantageously has a uniform temperature.

[0051] Preferably, the volumes of the first and second muffler chambers are not the same. It can be provided that the first muffler chamber is smaller than the second muffler chamber. In an advantageous embodiment variant, the first muffler chamber is larger than the second muffler chamber. In an advantageous alternative embodiment, the first muffler chamber and the second muffler chamber can be the same size.

[0052] It can be provided that the outflow surfaces from the first flow-through unit and the second flow-through unit are not the same size. By appropriately selecting the outflow surface, the amount and speed of the exhaust gas flowing through the corresponding flow-through unit into the second silencer chamber can be appropriately influenced. Advantageously, as an alternative or in addition, the flow-through units have different volumes and / or different densities. As an alternative or in addition, different thicknesses of the flow-through units measured along the flow direction can be provided. The outflow surface, volume, thickness and density are parameters that can be appropriately adapted by a person skilled in the art in order to set the desired flow conditions through the exhaust silencer for different rotational speeds.

[0053] The exhaust gas inlet of the exhaust gas silencer is connected to the exhaust channel of an internal combustion engine, for which it is advantageously provided that the first flow unit and the second flow unit are designed and arranged in such a way that in at least one operating state of the internal combustion engine more than 50%, in particular more than 70%, of the entire exhaust gas flow is conducted through the first flow path. Thus, it is provided for the internal combustion engine that more than half of the exhaust gas flow flows through the first flow unit. In this case, the first flow unit has a smaller amount of catalytically active coating in terms of volume than the second flow unit.

[0054] Since a greater proportion of the exhaust gas flow flows through the flow-through unit coated with a smaller amount of catalytic coating, excessive heating of the exhaust gas silencer can be prevented during operation of the internal combustion engine. In an operating state of the internal combustion engine, more than 50% of the exhaust gas flow flows through the first flow path, which operating state is in particular full-load operation. As a result, overheating of the exhaust gas silencer can be easily prevented in full-load operation. It can be provided that more than 50%, in particular more than 70%, of the exhaust gas flow also flows through the first flow path in partial load operation and / or at no load. Alternatively, it can be provided that at most 70%, in particular at most 50% of the exhaust gas flow flows through the first flow path in partial load operation and / or at no load.

[0055] Advantageously, the first flow unit adjoins the first muffler chamber and at least partially overlaps the projection of the inlet opening into the first muffler chamber along the inflow direction. This makes it easy to ensure that a large proportion of the exhaust gas flowing into the exhaust gas inlet flows to the first flow unit.

[0056] The second flow unit is advantageously completely outside the projection of the exhaust gas inlet in the central outflow direction from the exhaust channel. The second flow unit is thus arranged such that the exhaust gas from the exhaust channel cannot enter the second flow unit in the outflow direction but is first deflected.

[0057] The inflow opening is in particular an exhaust gas inlet. The inflow direction is in particular an outflow direction from the middle of the exhaust channel. In an alternative design, the inflow opening can be a transfer opening from another muffler chamber arranged upstream of the first muffler chamber, and the inflow direction can be an inflow direction through the middle of the transfer opening.

[0058] By suitably positioning the first flow-through unit and the second flow-through unit, a desired distribution of the exhaust gas flow to the first flow path and the second flow path can be easily achieved.

[0059] As an alternative or in addition, at least one flow-guiding element can be provided which brings about a desired distribution of the exhaust-gas flow to the first flow-through unit and to the second flow-through unit.

[0060] The invention further relates to an exhaust gas aftertreatment device of the type specified in the preamble of claim 37 and to an exhaust gas silencer.

[0061] US Pat. No. 7,552,585 B2 discloses an exhaust gas aftertreatment device for a diesel engine, namely a particle filter, which comprises a plurality of flow-through units with different amounts of catalytic coating. The flow-through units with a smaller amount of catalytic coating surround the flow-through units with a larger amount of catalytic coating. This results in a relatively complex structure.

[0062] The invention is based on the object of realizing an exhaust gas aftertreatment device of the generic type having a simple structure. A further object of the invention is to realize an exhaust gas silencer having a simple structure.

[0063] With regard to the exhaust gas aftertreatment device, this object is achieved by an exhaust gas aftertreatment device having the features of claim 37. With regard to the exhaust gas silencer, this object is achieved by an exhaust gas silencer having the features of claim 50.

[0064] It is provided that the exhaust gas aftertreatment device has a first and a second flow-through unit. The first flow-through unit has a catalytic coating, and the second flow-through unit has no catalytic coating or has a catalytic coating with a smaller mass per volume unit than the first flow-through unit. The first flow-through unit has an outflow surface, and the second flow-through unit has an inflow surface. It is provided that the inflow surface of the second flow-through unit does not protrude beyond a plane containing the outflow surface. In particular, the inflow surface of the second flow-through unit does not protrude beyond a plane containing the outflow surface in the opposite direction of the outflow.

[0065] The outflow direction is the direction perpendicular to the outflow surface of the first flow unit, from the first flow unit to the second flow unit. The actual direction in which the exhaust gas flows out of the first flow unit can coincide with the mentioned outflow direction or deviate therefrom. The second flow unit does not protrude in a direction opposite to the outflow direction beyond the plane defined by the outflow surface in the direction of the inflow surface of the first flow unit. The second flow unit is arranged completely downstream of the first flow unit with respect to the outflow direction.

[0066] The housing has at least one first inlet opening into the first flow-through unit, at least one second inlet opening into the second flow-through unit, and at least one transfer opening from the first flow-through unit to the second flow-through unit. A partial flow of the exhaust gas flowing into the exhaust gas aftertreatment device can therefore flow into the first flow-through unit and from there into the second flow-through unit through the at least one transfer opening. Another partial flow of the exhaust gas flow can flow directly into the second flow-through unit through the at least one second inlet opening. The at least one second inlet opening forms a bypass relative to the first flow-through unit. The exhaust gas flowing into the exhaust gas aftertreatment device through the at least one second inlet opening bypasses the first flow-through unit.

[0067] In the first flow unit, rapid and intense heating is achieved during operation due to the catalytic coating during the chemical conversion of exhaust gas components. Since the second flow unit does not protrude beyond a plane containing the outflow surface of the first flow unit, the first flow unit is not surrounded by the second flow unit in its circumferential direction, so that if the second flow unit also has a catalytic coating, no additional heating due to the heat generated in the second flow unit occurs here.

[0068] Due to the arrangement of the second flow-through unit downstream of the first flow-through unit, a transverse flow from the second flow-through unit into the first flow-through unit can be easily avoided. This makes it possible to dispense with the structurally complex separation of the flow-through units. The proportion of the two partial flows relative to the entire exhaust gas flow can be easily determined by the geometric design of the exhaust gas aftertreatment device. Since the proportion of the exhaust gas flow flowing through the first flow-through unit can be predetermined within a strict range in terms of structure, the heating of the exhaust gas flow and thus the exhaust gas escape temperature from the exhaust gas aftertreatment device can also be predetermined within a relatively strict range for different operating states of the internal combustion engine. This makes it possible to structurally prevent unwanted overheating of the exhaust gas aftertreatment device and the escaping exhaust gas in an easy manner.

[0069] Advantageously, provision is made for the second flow unit to be arranged completely downstream of the first flow unit with respect to the main flow direction through the exhaust gas aftertreatment device.

[0070] The main flow direction is advantageously a flow direction which is perpendicular to the respective inflow surface at each inflow surface of the flow-through unit. The main flow direction is particularly perpendicular to the flow direction which is perpendicular to the respective outflow surface at each outflow surface of the flow-through unit.

[0071] The maximum cross-section of the second flow-through unit is advantageously greater than the maximum cross-section of the first flow-through unit. The maximum cross-section of the second flow-through unit is advantageously at least 130%, in particular at least 150%, of the maximum cross-section of the first flow-through unit. Here, the cross-section is perpendicular to the main flow direction through the exhaust gas aftertreatment device. The maximum cross-section is the maximum cross-section of the corresponding flow-through unit perpendicular to the main flow direction. Preferably, the cross-section is perpendicular to the outflow direction of the first flow-through unit. Preferably, the first flow-through unit and the second flow-through unit are arranged in such a way that only a portion of the exhaust gas flow flows through the first flow-through unit and the entire exhaust gas flow flows through the second flow-through unit. Preferably, the inflow surface of the second flow-through unit is flat within the framework of the usual manufacturing tolerances. This results in a simple structure, and the second flow-through unit can be easily arranged completely downstream of the first flow-through unit with respect to the main flow direction.

[0072] Preferably, at least one transfer opening is the only opening that fluidically connects the first flow-through unit to the second flow-through unit. Thus, no opening is led out of the first flow-through unit, which does not lead to the second flow-through unit. In this case, one or more transfer openings can be provided, which fluidically connect the first flow-through unit to the second flow-through unit. As a result, the exhaust gas flowing out of the first flow-through unit must be forced to flow through the second flow-through unit before it can leave the exhaust gas aftertreatment device.

[0073] Advantageously, the first flow-through unit has an inflow surface opposite to the outflow surface. Advantageously, the first inlet opening is arranged only at the inflow surface of the first flow-through unit. For example, advantageously no further inlet openings are arranged at the circumferential side of the first flow-through unit. Since the exhaust gas aftertreatment unit has the first inlet opening only at the inflow surface of the first flow-through unit, the proportion of the exhaust gas flow flowing through the first flow-through unit relative to the total exhaust gas flow can be easily set within the range of the maximum cross-section of the flow-through unit. A bypass flow through an inlet opening is avoided, which is not arranged at an end side that is located upstream with respect to the outflow direction of the first flow-through unit, in particular at the front with respect to the main flow direction.

[0074] Advantageously, the first flow-through unit has the first inlet opening only at the end side of the first flow-through unit which is located upstream with respect to the main flow direction.

[0075] Advantageously, the first flow-through unit has a constant thickness measured along the outflow direction of the first flow-through unit within a range of at least 80% of its maximum cross-section, in particular within a range of at least 90%. Preferably, the second flow-through unit has a constant thickness measured along the outflow direction of the first flow-through unit within a range of at least 80% of its maximum cross-section, in particular within a range of at least 90%. Here, the thickness is constant within the framework of usual manufacturing tolerances. The first flow-through unit and / or the second flow-through unit are advantageously constructed in an approximately disk-shaped manner. The flow-through unit can have a rounding or chamfer in the edge region, so that good fixation of the flow-through unit can be achieved. Alternatively, other shapes of the first and / or second flow-through unit, such as a cuboid shape, can also be advantageous.

[0076] A simple structure is obtained when the housing of the exhaust gas aftertreatment device comprises at least two housing parts connected to one another. The housing parts are formed in particular from sheet metal, for example as deep-drawn parts. One of the housing parts can be designed in one piece with a partition wall of the exhaust gas silencer. Alternatively, both housing parts can be connected to a partition wall of the exhaust gas silencer. Other arrangements of the housing of the exhaust gas aftertreatment device can also be advantageous.

[0077] Advantageously, the first flow-through unit is at least partially, in particular predominantly, arranged in the first housing section. Advantageously, the second flow-through unit is at least partially, in particular predominantly, arranged in the second housing section. Preferably, the flow-through unit is pressed into the housing section. This makes it possible to dispense with additional fastening elements.

[0078] Preferably, the first housing section has all inflow openings and the second housing section has all outflow openings. Advantageously, the first inflow opening and the second inflow opening do not overlap with the outflow opening when viewed in the outflow direction of the first flow-through unit. This ensures that the exhaust gas remains in the exhaust gas aftertreatment device for a sufficiently long time.

[0079] The housing preferably has a step. In this case, the step is advantageously produced in a cross section of the housing parallel to the outflow direction of the first flow-through unit. The step is formed in particular by a change in the cross section of the housing of the exhaust gas aftertreatment device. The second inlet opening is preferably arranged at the step. The step is preferably used to fix the two flow-through units and to orient the flow-through units relative to each other. The step section advantageously abuts against the first flow-through unit, and a further step section extending transversely to, in particular perpendicularly to, the first step section advantageously abuts against the second flow-through unit.

[0080] Advantageously, at least one flow-through unit is at least partially formed by metal wires. Preferably, the metal wires are in the form of a wire mesh. In a preferred design, two flow-through units are at least partially formed by metal wires, in particular by a wire mesh. In an alternative embodiment, at least one flow-through unit is formed by a carrier material having a defined, elongated channel. In particular, the first flow-through unit is formed by a carrier material having a defined channel.

[0081] Advantageously, at least one flow-through unit, in particular two flow-through units, are each formed by at least one flow-through body. In this context, a body which is inherently dimensionally stable is considered to be a flow-through body, which is designed in such a way that the exhaust gas can flow through it. In a particularly preferred embodiment, each flow-through unit is formed by exactly one flow-through body. This results in a simple structure of the exhaust gas aftertreatment device. In a particularly preferred embodiment, the exhaust gas aftertreatment unit has exactly two flow-through bodies, namely a first flow-through body forming a first flow-through unit and a second flow-through body forming a second flow-through unit.

[0082] The first flow-through unit and the second flow-through unit can therefore be formed by one or more bodies that are separate from each other. Alternatively, it can be provided that the first and second flow-through units are constructed integrally with each other. The first flow-through unit can be formed by a first region of the body and the second flow-through unit by a further second region of the same body.

[0083] The exhaust gas muffler is provided so that the exhaust gas muffler comprises a first muffler chamber and a second muffler chamber separated by a partition wall. An exhaust gas aftertreatment unit is arranged in the connecting opening between the first muffler chamber and the second muffler chamber. The exhaust gas muffler is especially an exhaust gas muffler of a mixed lubrication internal combustion engine, especially a two-stroke engine or a mixed lubrication four-stroke engine. In particular, for a mixed lubrication internal combustion engine, a combination of a first flow-through unit and a second flow-through unit in the aftertreatment device is advantageous.

[0084] Advantageously, the exhaust gas aftertreatment unit is arranged in such a way that the exhaust gas flowing into the muffler chamber through the inlet opening does not flow directly into the exhaust gas aftertreatment unit. For this purpose, it is advantageously provided that the inlet opening into the first muffler chamber does not overlap with the inlet opening of the exhaust gas aftertreatment unit in a direction parallel to the outflow direction of the first flow-through unit through the exhaust gas aftertreatment unit. Preferably, the projection of the inlet opening in a direction parallel to the outflow direction of the first flow-through unit through the exhaust gas aftertreatment unit does not overlap with the exhaust gas aftertreatment unit. As a result, the exhaust gas flowing into the first muffler chamber through the inlet opening is first diverted before it can flow into the exhaust gas aftertreatment unit.

[0085] It can be advantageous that not the entire exhaust gas flow flows through the exhaust gas aftertreatment device. Advantageously, the exhaust gas silencer has a bypass channel, which forms a flow path through the exhaust gas silencer, which flow path bypasses the exhaust gas aftertreatment device. Therefore, the exhaust gas flowing through the bypass channel does not flow through the exhaust gas aftertreatment device. In a preferred design, the bypass channel does not open into the second muffler chamber. Advantageously, the exhaust gas silencer has an escape opening for the exhaust gas flowing through the exhaust gas aftertreatment device. Particularly preferably, the exhaust gas silencer has a further escape opening for the exhaust gas flowing through the bypass channel. Preferably, the bypass channel opens into a further discharge opening. The bypass channel can also be advantageous for an exhaust gas silencer that does not have an exhaust gas aftertreatment device according to the invention, but rather has an exhaust gas aftertreatment device of a different construction. The bypass channel is particularly advantageous in exhaust gas aftertreatment devices in which the entire exhaust gas flow flowing through the exhaust gas aftertreatment device flows through a flow-through unit coated with a catalytically active material.

[0086] The concept of providing an exhaust gas silencer with a bypass channel represents an independent concept according to the invention, which is independent of the design of the exhaust gas aftertreatment device. The exhaust gas silencer advantageously comprises a first silencer chamber and a second silencer chamber separated by a dividing wall, wherein an exhaust gas aftertreatment device is arranged in a connecting opening between the first silencer chamber and the second silencer chamber, the exhaust gas aftertreatment device comprising at least one flow-through unit, wherein the exhaust gas silencer has a bypass channel, which forms a flow path through the exhaust gas silencer, which flow path bypasses the exhaust gas aftertreatment device.

[0087] The invention further relates to an exhaust gas aftertreatment device of the type specified in the preamble of claim 53 and to an exhaust gas silencer.

[0088] US Pat. No. 7,552,585 B2 discloses a particle filter for a diesel engine, which can have a region with a greater amount of catalytic coating and a region with a lesser amount of catalytic coating. The region with the lesser amount of catalytic coating surrounds the region with the greater amount of catalytic coating. In addition, the region with the lesser amount of catalytic coating can be arranged downstream of the region with the greater amount of catalytic coating.

[0089] The object of the present invention is to provide an exhaust gas aftertreatment device having an advantageous structure. Another object of the present invention is to provide an exhaust gas silencer having an advantageous structure.

[0090] With regard to the exhaust gas aftertreatment device, this object is achieved by an exhaust gas aftertreatment device having the features of claim 53. With regard to the exhaust gas silencer, this object is achieved by an exhaust gas silencer having the features of claim 65.

[0091] The exhaust gas aftertreatment device has a first and a second flow-through unit. The second flow-through unit has a catalytic coating. The first flow-through unit has no catalytic coating or has a catalytic coating with a smaller mass per volume unit than the second flow-through unit. In the second flow-through unit with the catalytic coating, the exhaust gas is heated very strongly due to the catalytic conversion. It has now been shown that this heating can be so strong that the first flow-through unit arranged downstream of the second flow-through unit can be damaged during operation due to the high temperature.

[0092] The first flow-through unit is preferably used for particle reduction. It has been shown that an exhaust gas aftertreatment device comprising a first and a second flow-through unit leads to good results with regard to particle reduction and catalytic conversion even when the first flow-through unit is arranged upstream of the second flow-through unit. This is particularly true if the first flow-through unit is already sufficiently heated, in particular by the exhaust gas flow flowing through or by heat generated in a second flow-through unit arranged downstream. Overheating of the first flow-through unit can be easily avoided.

[0093] It has been shown that flow-through units with a catalytically active coating can age prematurely during operation when exhaust gas containing oil droplets flows through them. Premature aging can be avoided if a second flow-through unit is arranged downstream of a first flow-through unit. The second flow-through unit is protected from premature aging by the first flow-through unit arranged upstream.

[0094] The exhaust gas leaving the second flow-through unit has a very high temperature. In order to prevent an excessively high temperature of the exhaust gas flow escaping from the exhaust gas aftertreatment device, it is provided according to the present invention that the entire exhaust gas flow is not guided through the second flow-through unit. For this purpose, the housing has at least one outflow opening through which the exhaust gas can escape from the housing from the first flow-through unit without previously passing through the second flow-through unit. A partial flow of the exhaust gas flow can flow from the first flow-through unit, in particular through the outflow surface, to the second flow-through unit. Another partial flow of the exhaust gas flow can escape from the housing from the first flow-through unit, in particular through the outflow surface, based on the design of the housing according to the present invention, without previously passing through the second flow-through unit.

[0095] Since only a portion of the exhaust gas flow flows through the second flow-through unit, an excessively high temperature of the total exhaust gas flow leaving the exhaust gas aftertreatment device is avoided. The exhaust gas can escape from the housing from the first flow-through unit through at least one outflow opening without previously passing through the second flow-through unit, and the at least one outflow opening enables a bypass flow for the exhaust gas, which bypasses the second flow-through unit. A simple structural design can be achieved.

[0096] Advantageously, the housing of the exhaust gas aftertreatment device has at least one further outflow opening, through which the exhaust gas can flow out of the housing from the second flow-through unit. Thus, the exhaust gas can advantageously leave the exhaust gas aftertreatment device from the first flow-through unit, in particular via an outflow surface of the first flow-through unit, or from the second flow-through unit, in particular via an outflow surface of the second flow-through unit.

[0097] If the first flow-through unit completely covers the second flow-through unit in the line of sight along the outflow direction of the first flow-through unit, a simple and compact structure is obtained. Preferably, in the line of sight opposite to the outflow direction of the first flow-through unit, in particular in the line of sight along the main flow direction, the first flow-through unit protrudes at least 3 mm beyond the second flow-through unit at each position of the circumference of the second flow-through unit. Preferably, the exhaust gas can escape from the first flow-through unit through a plurality of outflow openings from the housing of the exhaust gas aftertreatment device, and the plurality of outflow openings are distributedly arranged around the second flow-through unit in the line of sight opposite to the outflow direction of the first flow-through unit. The outflow openings are preferably distributedly arranged near the circumference of the second flow-through unit. As a result, the exhaust gas with a cooler temperature flows from the first flow-through unit along the entire circumference of the second flow-through unit and is thereby cooled. At the same time, a simple and compact structure is obtained.

[0098] Here, the outflow direction of the first flow unit is a direction perpendicular to the outflow surface of the first flow unit from the first flow unit to the second flow unit. The actual direction in which the exhaust gas flows out of the first flow unit can coincide with or deviate from the aforementioned outflow direction.

[0099] The maximum cross-section of the first flow unit is preferably greater than the maximum cross-section of the second flow unit. The maximum cross-section of the first flow unit is preferably at least 130%, preferably at least 150% of the maximum cross-section of the second flow unit. Here, the cross-section is perpendicular to the main flow direction through the exhaust gas aftertreatment device. The maximum cross-section is the maximum cross-section of the corresponding flow unit perpendicular to the main flow direction. On the one hand, this can avoid overheating of the exhaust gas, and on the other hand, it is possible to achieve sufficient cooling of the second flow unit by the exhaust gas flowing along the circumference of the second flow unit from the first flow unit. Preferably, the cross-section is perpendicular to the outflow direction of the first flow unit.

[0100] Advantageously, the housing of the exhaust gas aftertreatment device has at least one inlet opening. Particularly preferably, the at least one inlet opening opens into the inlet surface of the first flow-through unit.

[0101] If the housing of the exhaust gas aftertreatment device includes at least two partial shells connected to each other, an advantageous simple structure is obtained. In a preferred design, the first flow-through unit is mainly arranged in the first partial shell and the second flow-through unit is mainly arranged in the second partial shell. A simple and compact structure is thus achieved. Preferably, the second flow-through unit is completely arranged in the second partial shell. As a result, the two partial shells can be easily manufactured without a back cut, for example as deep-drawn parts. The first flow-through unit can be completely arranged in the first partial shell or protrude into the second partial shell. In an alternative design, it can be provided that the second flow-through unit protrudes into the first partial shell. In another alternative design, it can be provided that the housing is constructed in one piece and is closed, for example by bending the protruding edge. Alternatively, it can be provided that the housing is formed by a shell, the two flow-through units are arranged in the shell and the shell is closed with a cover. Other designs of the housing of the exhaust gas aftertreatment device can also be advantageous.

[0102] A preferably simple design results if the first housing subshell has all inflow openings of the housing of the exhaust gas aftertreatment device and the second housing subshell has all outflow openings of the housing of the exhaust gas aftertreatment device.

[0103] Advantageously, at least one flow-through unit, in particular at least the first flow-through unit, is at least partially made of metal wires, in particular of a wire mesh. This results in a simple structure of the first flow-through unit. A flow-through unit made of metal wires has proven to be a simple and robust structure for a flow-through unit for particle conversion.

[0104] Advantageously, the second flow-through unit has a carrier having channels for the exhaust gas separated from one another. The carrier can be made of metal or ceramic material, for example. The carrier can be a sintered body, for example. In a design consisting of metal, the carrier can be formed by a plurality of wound sheets, wherein at least one of the sheets undulates in a corrugated sheet-like manner and thus forms channels. Other structures of the second flow-through unit can also be advantageous. In an alternative design, the second flow-through unit can also be at least partially made of metal wires, in particular of a wire mesh.

[0105] The metal wire which can form the first and / or the second flow-through unit consists, in particular, of steel or of a nickel alloy.

[0106] Advantageously, at least one flow-through unit, in particular two flow-through units, are each formed by at least one flow-through body. In this context, a body which is inherently dimensionally stable is considered to be a flow-through body, which is designed in such a way that the exhaust gas can flow through it. Preferably, at least one flow-through unit, in particular two flow-through units, are each formed by exactly one flow-through body. In a particularly preferred embodiment, the exhaust gas aftertreatment unit has exactly two flow-through bodies, namely a first flow-through body forming a first flow-through unit and a second flow-through body forming a second flow-through unit.

[0107] The first flow-through unit and the second flow-through unit can therefore be formed by one or more bodies that are separate from each other. Alternatively, it can be provided that the first and second flow-through units are constructed integrally with each other. The first flow-through unit can be formed by a first region of the body, and the second flow-through unit can be formed by a further second region of the same body.

[0108] It is particularly preferred that the exhaust gas aftertreatment device is arranged in the exhaust gas silencer. The exhaust gas silencer is in particular an exhaust gas silencer of a mixed lubricated internal combustion engine, in particular a two-stroke engine or a mixed lubricated four-stroke engine. In particular, for mixed lubricated internal combustion engines, a combination of a first flow-through unit and a second flow-through unit in the aftertreatment device is advantageous. The exhaust gas silencer has a first silencer chamber and a second silencer chamber separated by a dividing wall, wherein the exhaust gas aftertreatment device is arranged in a connecting opening between the first silencer chamber and the second silencer chamber. Advantageously, at least one outflow opening leads from the first flow-through unit into the second silencer chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] Next, embodiments of the present invention will be explained with reference to the accompanying drawings.

[0110] Figure A1 shows a schematic cross-sectional view of a motor-driven saw,

[0111] Figure A2 Shows Figure A1 Schematic cross-sectional view of an exhaust muffler of a motor-driven saw,

[0112] Figure A3 Shows Figure A2 A schematic perspective illustration of an exhaust gas aftertreatment device of an exhaust gas muffler,

[0113] Figure A4 A schematic diagram of a wire body is shown,

[0114] Figure A5 Shows Figure A4 A schematic cross-sectional view of a wire body of a wire,

[0115] Figure A6 A schematic diagram of manufacturing a wire body is shown.

[0116] Figure B1 shows a schematic cross-sectional view of a motor-driven saw,

[0117] Figures B2 to B9 Shows Figure B1 A schematic sectional view of an embodiment of an exhaust muffler for a motor-driven saw,

[0118] Figure B10 Shown along Figure B9 A schematic cross-sectional view of line XX in FIG.

[0119] Figure B11 , B12 Shows Figure B1 A schematic sectional view of a further exemplary embodiment of an exhaust muffler for a motor-driven saw,

[0120] Figure B13 shows an exemplary schematic sectional view of a flow-through unit,

[0121] Figure C1 shows a schematic sectional view of a hand-held power tool having an exhaust gas muffler with an exhaust gas aftertreatment device,

[0122] Figure C2 Shows Figure C1 A cross-sectional view of an exhaust gas aftertreatment unit of a working tool,

[0123] Figure C3 Shows Figure C2 The exhaust gas aftertreatment device is along Figure C2 A schematic side view in the direction of arrow III,

[0124] Figure C4 A schematic diagram showing a possible structure of a flow-through body of a flow-through unit,

[0125] Figure C5 A schematic diagram showing an alternative design of an exhaust silencer,

[0126] Figure D1 shows a schematic cross-sectional view of a motor-driven saw,

[0127] Figure D2 Shows Figure D1 A cross-sectional view of an exhaust gas aftertreatment device of an exhaust gas muffler of a motor-driven saw,

[0128] Figure D3 Shown along Figure D2 A schematic side view in the direction of arrow III,

[0129] Figure D4 , D5 A schematic diagram of a possible design of a flow-through unit is shown. DETAILED DESCRIPTION

[0130] exist Figures A1 to A6 The reference numerals mentioned below are shown in each case without the preceding letter A.

[0131] Figure A1 A motor-driven saw A1 is shown as an embodiment for a hand-held working tool. Instead of the motor-driven saw A1, the working tool can also be a brush cutter, a cutting machine, a blower, a lawn mower or the like. The hand-held working tool is in particular a portable working tool. The motor-driven saw A1 has a housing A2, on which a handle A3 is held. On the handle A3, operating elements for the motor-driven saw A1 are arranged, in this embodiment, a throttle lever A4 and a throttle lever lock A5. The motor-driven saw A1 has a guide rail A6, on which a saw chain A7 is arranged to rotate. During operation, the saw chain A7 is driven by an internal combustion engine A8 arranged in the housing A2. The internal combustion engine A8 is advantageously a mixed-lubricated internal combustion engine A8, in this embodiment, a two-stroke engine. The internal combustion engine A8 can also be another internal combustion engine A8, in particular a mixed-lubricated four-stroke engine.

[0132] The internal combustion engine A8 comprises an air filter A9, through which air is sucked in during operation. The air enters the crankcase A15 of the internal combustion engine A8 through an intake channel A11. A section of the intake channel A11 is formed in a fuel supply device A10, for example, a carburetor. Other types of fuel supply, for example, supply via a fuel valve, can also be provided. Other locations for fuel input, for example, into the crankcase A15, can also be provided.

[0133] The internal combustion engine A8 includes a cylinder A12 in which a piston A13 is supported to move back and forth. The piston A13 defines a combustion chamber A14 constructed in the cylinder A12. The combustion chamber A14 is located at the position of the piston A13. Figure A1The region of the lower dead center shown in the figure is connected to the inner cavity of the crank housing A15 via an overflow channel A19. The piston A13 drives a crankshaft A17 rotatably supported in the crank housing A15 via a connecting rod A16. The crankshaft A17 is rotatably supported around an axis of rotation A18. The spark plug A20 protrudes into the combustion chamber A14. The motor saw A1 includes an exhaust muffler A23. An exhaust opening A21 is led out from the combustion chamber A14, which is connected to an exhaust gas inlet A24 of the exhaust muffler A23 via an exhaust channel A22.

[0134] During operation, the internal combustion engine A8, which is constructed as a two-stroke engine, draws the fuel / air mixture into the inner chamber of the crankshaft housing A15 through the intake passage A11 during the upward stroke of the piston A13. The fuel / air mixture is compressed in the crankshaft housing A15 during the downward stroke of the piston A15. Once the overflow passage A19 from the piston A13 to the combustion chamber A14 is opened, the fuel / air mixture flows from the inner chamber of the crankshaft housing A15 into the combustion chamber A14. The spark plug A20 ignites the mixture in the combustion chamber in the area of ​​the top dead center. Based on the combustion that follows, the piston A13 returns to accelerate in the direction of the crankshaft housing A15. Once the piston A13 opens the discharge opening A21, the exhaust gas can flow out of the combustion chamber A14 and flow to the exhaust muffler A23. Once the overflow passage A19 from the piston A13 to the combustion chamber A14 is opened, a fresh fuel / air mixture flows in again for the next combustion.

[0135] Alternatively, the internal combustion engine A8 can also be operated in a scavenging pre-storage mode and include, in addition to the intake channel A11, one or more air channels, through which largely fuel-free air is pre-stored in the overflow channel A19. The pre-stored air separates the exhaust gases from the previous combustion from the fresh fuel / air mixture flowing into the combustion chamber A14 during the downward stroke of the piston A13.

[0136] The exhaust gas silencer A23 has a silencer housing A32, in which a first silencer chamber A47 and a second silencer chamber A48 are constructed. The first silencer chamber A47 is arranged upstream of the second silencer chamber A48. In the present embodiment, the exhaust gas inlet A24 leads to the first silencer chamber A47. However, it can also be provided that, upstream of the first silencer chamber, another silencer chamber is constructed in the silencer housing A32 or in another unit. The exhaust gas silencer A23 has an exhaust gas outlet A25, from which the exhaust gas can flow out of the exhaust gas silencer A23 into the surrounding environment. In the present embodiment, a fireproof screen A33 is arranged in at least one flow route, in particular in all flow routes, between the second silencer chamber A48 and the escape opening A25. The fireproof screen A33 can be, for example, a single-layer fabric composed of metal wire. In the present embodiment, the exhaust gas outlet A25 is derived from the second silencer chamber A48. In an alternative embodiment, a further muffler chamber can be arranged downstream of the second muffler chamber A48. Alternatively or additionally, it can be provided that the further muffler chamber is arranged between the first muffler chamber A47 and the exhaust gas aftertreatment device A26 and / or between the exhaust gas aftertreatment device A26 and the second muffler chamber A48.

[0137] In the present embodiment, the first muffler chamber A47 and the second muffler chamber A48 are separated by a partition wall A28. The exhaust muffler A23 has an exhaust gas aftertreatment unit A26. In the present embodiment, the exhaust gas aftertreatment device A26 is held at the partition wall A28. The exhaust gas flows from the first muffler chamber A47 to the second muffler chamber A48 through the exhaust gas aftertreatment unit A26. In the present embodiment, exactly one exhaust gas aftertreatment device A26 is provided, through which the exhaust gas can flow from the first muffler chamber A47 to the second muffler chamber A48. In an alternative advantageous embodiment, a plurality of exhaust gas aftertreatment devices A26 can be provided. In an advantageous embodiment variant, a plurality of exhaust gas aftertreatment devices A26 are arranged parallel to each other. In the parallel arrangement of two exhaust gas aftertreatment devices A26, a partial flow of the exhaust gas flow flows through one of the exhaust gas aftertreatment devices A26, and another partial flow of the exhaust gas flow flows through the other of the exhaust gas aftertreatment devices A26. As an alternative or in addition, it can also be advantageous to arrange a plurality of exhaust gas aftertreatment devices A26 one behind the other, so that at least one partial flow of the exhaust gas flow first flows through one exhaust gas aftertreatment device A26 and then flows through the other exhaust gas aftertreatment device.

[0138] Partition wall A28 has an opening A34 which establishes a fluid connection between muffler chambers A47 and A48. In the present exemplary embodiment, exhaust gas aftertreatment device A26 projects through opening A34. Other arrangements of exhaust gas aftertreatment device A26 at partition wall A28 can also be advantageous.

[0139] Internal combustion engine A8 and exhaust silencer A23 are designed such that the temperature of the exhaust gas flow on the upstream side of exhaust gas aftertreatment device A26 at full load after an operating time of A2 minutes of internal combustion engine A8 is 450° C. to 750° C. This results in a temperature that is favorable for the conversion of the exhaust gas in the exhaust gas aftertreatment device.

[0140] The exhaust gas aftertreatment device A26 includes a flow-through unit A31, which is described in more detail below. In the present exemplary embodiment, the exhaust gas aftertreatment device A26 includes exactly one flow-through unit A31. In alternative embodiments, the exhaust gas aftertreatment device A26 can include a plurality of flow-through units A31.

[0141] The flow-through unit A31 serves to reduce particles, ie, as a particle converter. The exhaust gas of a mixed-lubrication internal combustion engine contains lubricating oil in the form of droplets, which are at least partially converted in the flow-through unit A31.

[0142] The volume of the silencer chamber A47 and / or A48 is advantageously greater than the volume of the flow-through unit A31. Advantageously, the second silencer chamber A48 has a volume of at least 80% of the displacement of the internal combustion engine A8. This makes it possible to easily cool the exhaust gas downstream of the exhaust gas aftertreatment device A26 before the exhaust gas leaves the exhaust silencer A23 through the exhaust gas outlet A25. As an alternative or in addition, it is advantageously provided that the first silencer chamber A47 has a volume of at least 80% of the displacement of the internal combustion engine A8.

[0143] Next, according to Figure A2 Describe the structure of the exhaust muffler A23. Figure A2As shown, the silencer housing A32 in this embodiment is constructed of two partial shells A49 and A50, which are connected to each other at a circumferential edge A51. The partial shells A49 and A50 can be, for example, deep-drawn parts made of sheet metal, which are curled at the edge A51. The dividing wall A28 extends in the silencer housing A32. In this embodiment, the dividing wall A28 is constructed as a sheet metal and is also fixed at the edge A51. The exhaust gas aftertreatment device A26 is arranged in the opening A34 of the dividing wall A28. A first silencer chamber A47 is constructed in the silencer housing A32, and a second silencer chamber A48 is constructed downstream of the first silencer chamber A47. The exhaust gas aftertreatment device A26 is arranged in at least one flow route from the first silencer chamber A47 to the second silencer chamber A48. The exhaust gas aftertreatment device A26 is arranged in this embodiment so that each flow path from the first muffler chamber A47 to the second muffler chamber A48 is led through the exhaust gas aftertreatment device A26. The exhaust gas aftertreatment device A26 has a housing A27. In this embodiment, multiple inlet openings A29 are led into the housing A27. A single inlet opening A29 can also be provided. In this embodiment, the inlet opening A29 is adjacent to the first muffler chamber A47. Multiple outlet openings A30 are derived from the housing A27 of the exhaust gas aftertreatment device A26. A single outlet opening A30 can also be provided.

[0144] The flow-through unit A31 is arranged in the housing A27 of the exhaust gas aftertreatment device A26. In the present embodiment, the flow-through unit A31 is formed by a single wire body A41. Figure A2 As shown, the flow-through unit A31 has a first end side A36 located upstream and a second end side A37 located downstream. The exhaust gas flows through the exhaust gas aftertreatment device A26 along the main flow direction A35. The main flow direction A35 points from the first end side A36 to the second end side A37. Due to the structure of the wire body A41, a transverse flow occurs in the wire body A41. As a result, multiple flow routes can be realized through the wire body A41.

[0145] In this embodiment, the exhaust gas flows through the entire wire body A41. In alternative embodiments in which the exhaust gas does not flow through the entire wire body A41, the dimensions specified below only relate to the area through which the exhaust gas flows. Areas of the wire body A41 or of the flow unit A31 that are not flowed through by the exhaust gas are not considered.

[0146] The thickness b of the flow-through unit A31 in the area through which the exhaust gas flows is advantageously at least A10 mm, in particular at least A15 mm, preferably at least A20 mm. In this case, the thickness b is measured from the end side A36 located upstream to the end side A37 located downstream. The thickness b is advantageously measured parallel to the main flow direction A35. In an embodiment in which the end sides A36 and A37 extend parallel to one another within the framework of manufacturing tolerances, the thickness b is measured perpendicular to the end sides A36 and A37. In this case, the flow-through unit A31 does not need to have the stated thickness b over its entire cross section. The flow-through unit A31 has a thickness b of 1.1 mm. Figure A2 The maximum cross section E is indicated by a dashed line in FIG. The flow-through unit A31 has an area A45. In the area A45, the thickness b is constant within the framework of the usual manufacturing tolerances in this embodiment. Figure A2 Schematically shown in a limited manner by dashed lines. Advantageously, the flow unit A31 has a thickness b of at least A10 mm within the range of at least 70%, in particular at least 80%, of the maximum cross section E of the flow unit in the area through which flow is passed. In the present embodiment, the flow unit A31 has a thickness b within the range of the entire area A45. In the area through which exhaust gas flows through the flow unit A31, the thickness b of the flow unit A31 is particularly preferably at least A10 mm, in particular at least A15 mm, within the range of the entire cross section. The maximum cross section E advantageously extends perpendicularly to the main flow direction A35.

[0147] Preferably, the flow-through unit A31 is formed by a single flow-through body A41. However, it can also be provided that the flow-through unit A31 is formed by a plurality of flow-through bodies A41.

[0148] The through-body A41 has a plurality of cavities that allow through-flow. Figure A4 The through-body A41 does not have a closed surface at least at the end sides A36 and A37. Figure A4 As shown. In this embodiment, the flow unit A31 includes a wire of an associated flow body A41 and a cavity formed between the segments of the wire. The flow unit A31 represents a sheath that surrounds the flow body A41, and the flow body A41 uniformly rests against the sheath within the framework of the processing accuracy of the cavity and the uniformity of the size and distribution.

[0149] like Figure A2 and A3 As shown, the housing A27 of the exhaust gas aftertreatment device A26 is formed by two housing parts A38 and A39. The housing parts A38 and A39 are firmly, in particular tightly, connected to one another. The flow-through unit A31 is advantageously pressed into the housing A27 of the exhaust gas aftertreatment device A26.

[0150] like Figure A3 As shown, the inlet opening A29 and the outlet opening A30 do not overlap along the main flow direction A35. As a result, the exhaust gas must also flow transversely to the main flow direction A35 on its way through the exhaust gas aftertreatment device A26. This increases the residence time of the exhaust gas in the exhaust gas aftertreatment device A29. Other arrangements of the inlet opening A29 and the outlet opening A30 can also be advantageous.

[0151] The flow-through unit A31 is formed by at least one wire body A41. Figure A4 A feasible design of the wire body A41 is schematically shown. The wire body A41 is constructed of a metal braided mesh A42 in this embodiment, which is pressed into a suitable shape. Alternatively, the wire body A41 can also be constructed of a wire knitted fabric, a wire braided fabric or the like. The metal braided mesh A42 is constructed of wire A43.

[0152] exist Figure A5 Wire A43 is schematically shown in cross section in FIG. Wire A43 in this embodiment has a circular cross section with a diameter d. The diameter d is advantageously at least 0.3 mm. The cross-sectional area A of wire A43 is advantageously at least 0.07 mm 2 This cross-sectional area is also advantageous for wire A43 having a cross-sectional shape that deviates from a circular shape. Wire A43 is advantageously at least partially, in particular completely, made of a nickel alloy or of stainless steel.

[0153] The wire body A41 is advantageously constructed from a wound metal braided mesh A42, as schematically shown in FIG. Figure A6 As shown in FIG. As illustrated by arrow A44, the metal woven mesh A42 is wound around a winding axis A46. Here, the metal woven mesh A42 is, for example, in the shape of a mat before winding.

[0154] like Figure A4 As shown, the winding axis A46 advantageously extends from the first end side A36 of the flow-through unit A31 to the second end side A37. The main flow direction A35 advantageously extends parallel to the winding axis A46. The wire body A41 has a cylindrical shape approximately in a preferred design. However, other shapes of the wire body A41 can also be advantageous. Here, the wire body A41 is advantageously pressed into a suitable shape.

[0155] In order to achieve sufficient particle reduction, it is provided that the sum of the volumes of all wire bodies A41 of the flow-through unit A31 is at least 0.6 times the displacement of the internal combustion engine A8. In the present embodiment, the volume of the wire body A41 of the flow-through unit A31 is at least 0.6 times the displacement of the internal combustion engine A8. If not all areas of the wire body A41 are flowed through, the sum of the volumes of the areas through which the flow is flowed through of all wire bodies A41 of the flow-through unit A31 is at least 0.6 times the displacement of the internal combustion engine A8.

[0156] The density of the wire body A41 is 0.6 g / cm at least in the region through which the exhaust gas flows. 3 Up to 2g / cm 3 This ensures that the exhaust gas has sufficient contact with the surface of the wire body A41. Advantageously, the density of all the wire bodies A41 of the exhaust silencer A23 is within a specified range. In this embodiment, the exhaust gas flows through the entire wire body A41.

[0157] According to the invention, the flow-through unit A31 has no catalytic coating. A catalytic coating is a coating that acts as a catalyst in this context, which then reduces the activation energy for the chemical conversion of the exhaust gas and thus increases the reaction rate. The catalytic coating is in particular a coating with precious metals, which serves primarily to convert hydrocarbons and / or nitrogen oxides. The flow-through unit A41 of the exhaust gas aftertreatment device A26 is not provided with a catalytic coating.

[0158] In the present embodiment, the wire body A41 of the flow-through unit A31 is coated with a washcoat. Washcoats in this context are coatings that increase the surface without reducing the activation energy for chemical conversion. Washcoats are therefore not catalytic coatings in the sense of this context. Washcoats can consist, for example, of aluminum oxide.

[0159] exist Figures B1 to B13 The reference numerals mentioned below are shown in each case without the preceding letter B.

[0160] Figure B1 A motor saw B1 is shown as an embodiment for a work tool. However, the exhaust gas silencer according to the invention can also be used in other work tools, in particular hand-held work tools such as brush cutters, cutting machines, lawn mowers or the like. The motor saw B1 has a housing B2, to which a rear handle B3 is fixed. The rear handle B3 is used to guide the motor saw B1 during operation. In the present embodiment, operating elements, namely a throttle lever B4 and a throttle lever lock B5 are arranged on the rear handle B3. A guide rail B6 is fixed to the housing B2, on which a saw chain B7 is guided in a rotatable manner. The saw chain B7 is driven by an internal combustion engine B8 arranged in the housing B2.

[0161] During operation, the internal combustion engine B8 draws in combustion air via an air filter B9 through an intake channel B11. A section of the intake channel B11 is formed in a fuel supply device B10, such as a carburetor. The internal combustion engine B8 has a cylinder B12 in which a piston B13 is guided back and forth. The piston B13 defines a combustion chamber B14 formed in the cylinder B12.

[0162] The intake channel B11 opens into a crankshaft housing B15 in which a crankshaft B17 is rotatably mounted about an axis of rotation B18. The crankshaft B17 is rotationally driven by a piston B13 that moves back and forth via a connecting rod B16.

[0163] In the present embodiment, the internal combustion engine B8 is a single-cylinder engine. In the present embodiment, the internal combustion engine B8 is a two-stroke engine. However, it can also be provided that the internal combustion engine B8 is a four-stroke engine. The internal combustion engine B8 is advantageously a mixed lubrication internal combustion engine.

[0164] The internal combustion engine B8 has a plurality of overflow channels B19, which open into the combustion chamber B14 with overflow windows controlled by the piston B13. Figure B1 The crankshaft housing B15 is fluidly connected to the combustion chamber B14 in the region of the lower dead center shown in the figure, so that air and fuel can flow from the crankshaft housing B15 into the combustion chamber B14. The spark plug B20 protrudes into the combustion chamber B14, which ignites the fuel / air mixture in the combustion chamber B14 in the region of the upper dead center of the piston B13. In the subsequent downward stroke of the piston B13, the exhaust opening B21 from the cylinder B12 is opened by the piston B13, and the exhaust gas flows through the exhaust channel B22 constructed in the cylinder B12 to the exhaust muffler B23 connected to the exhaust channel B22. The exhaust muffler B23 is advantageously connected directly to the exhaust channel B22 of the cylinder B12, if necessary with a seal, a heat-resistant plate or the like placed in between. However, it can also be provided that the exhaust muffler B23 is indirectly connected to the exhaust channel B22 through another intermediately connected component.

[0165] The exhaust silencer B23 has an exhaust inlet B24 into which the exhaust gas flows from the cylinder B12. An exhaust outlet B25 is led out from the exhaust silencer B23, through which the exhaust gas flows into the surrounding environment. A fire screen B26 can be arranged at the exhaust outlet B25. Figure B2 It is schematically shown in Figure B2 The figure also schematically shows a heat protection plate B27 arranged between the cylinder B12 and the exhaust muffler B23.

[0166] like Figure B2As shown, the exhaust gas flows out of the cylinder B12 from the outlet channel B22 along the outflow direction B34 and flows into the exhaust muffler B23. The exhaust muffler B23 is advantageously formed in the usual manner by a plurality of deep-drawn sheets, which can be connected to each other, for example, by crimping their edges. A plurality of muffler chambers B31 and B32 are formed in the interior of the exhaust muffler B23. Figure B2 The exhaust gas silencer B23 has a partition wall B28, which divides the inner cavity of the exhaust gas silencer B23 into a first silencer chamber B31 and a second silencer chamber B32. The first silencer chamber B31 and the second silencer chamber B32 are fluidically connected to each other via two flow-through units B35 and B36.

[0167] In the present embodiment, a first flow unit B35 is provided, which advantageously has no catalytic coating. The second flow unit B36 has a catalytic coating. Compared with the second flow unit B36, the first flow unit B35 has a smaller amount of catalytic coating in terms of volume. Therefore, the mass of the catalytic coating is smaller in volume in the first flow unit B35 than in the second flow unit B36. The mass of the catalytic coating of the first flow unit B35 can be zero. It can be provided that the first flow unit B35 and / or the second flow unit B36 have a carrier coating. The carrier coating is used to increase the surface of the first flow unit B35 and / or the second flow unit B36 and does not appear as a catalytic coating.

[0168] Preferably, the flow-through units B35 and B36 are respectively formed by one or more wire bodies. The flow-through units B35 and / or B36 are advantageously formed by a metal braided mesh or a metal fabric. It can also be provided that the flow-through units B35 and B36 respectively have regions with different amounts of catalytic coatings. For example, it can be provided that the second flow-through unit B36 does not have a catalytic coating in its circumferential region in order to avoid wear when the wire body is pressed into the housing B29 of the flow-through unit B36. It can also be provided that at least one flow-through unit B35, B36 has a plurality of wire bodies, which have different amounts of catalytic coatings in terms of volume. Here, the amount of the catalytic coating is taken into account for each flow-through unit in terms of the total volume of the flow-through unit.

[0169] The flow cells B35 and B36 form two separate flow paths B37 and B38 from the first silencer chamber B31 into the second silencer chamber B32. A partial flow of the exhaust gas flow flows through the first flow cell B35 or through the second flow cell B36. The flow cells B35 and B36 have a spacing a relative to each other in this embodiment. Figure B2In the embodiment of the present invention, the spacing a can be several centimeters. The two flow-through units B35 and B36 are arranged in the partition wall B28. The spacing a is measured at the partition wall B28.

[0170] In accordance with Figure B2 In the embodiment of the present invention, the flow-through units B35 and B36 have approximately the same shape and size. However, different sizes of the flow-through units B35 and B36 can also be advantageous. The flow-through units B35 and B36 each have a thickness e measured along the flow direction. The flow-through units B35 and B36 each have a diameter d measured perpendicular to the flow direction.

[0171] The first flow path B37 extends through the first flow unit B35. The second flow path B38 extends through the second flow unit B36. The two flow paths B37 and B38 lead from the first muffler chamber B31 to the second muffler chamber B32. Figure B2 In the exemplary embodiment of FIG. 5 , the exhaust gas flow is distributed to the flow paths B37 and B38 based on the positioning of the flow-through units B35 and B36 relative to the exhaust gas inlet B24 into the exhaust gas silencer B23 .

[0172] exist Figure B2 The projection P of the exhaust gas inlet B24 along the outflow direction B34 onto the partition wall B28 is marked. Figure B2 As shown, the first flow unit B35 is partially located within the projection P. The second flow unit B36 is completely outside the projection P, or more precisely, in the present embodiment, at a distance B relative to the projection P. In the present embodiment, the distance B is smaller than the distance a. However, the distance B can also correspond to the distance a or be larger than the distance a. Since the first flow unit B35 is partially located in the extension of the outflow direction B34, more exhaust gas flows through the first flow unit B35 than through the second flow unit B36. If a further silencer chamber is arranged between the exhaust gas inlet B24 and the first silencer chamber B31, the projection P and the flow direction along which the projection P is observed advantageously relate to the inlet opening in the first silencer chamber B31.

[0173] Figure B3 A further embodiment of an exhaust gas silencer B23 is shown. In this case, identical reference numerals in all the figures denote mutually corresponding elements. Figure B3The exhaust silencer B23 shown in the figure has a third silencer chamber B33 in addition to the first silencer chamber B31 and the second silencer chamber B32. The third silencer chamber B33 is located between the first silencer chamber B31 and the second silencer chamber B32 along the flow direction. The exhaust gas is advantageously divided into at least two partial flows. A partial flow of the exhaust gas flows from the first silencer chamber B31 along the first flow path B37 through the first flow unit B35 to the second silencer chamber B32. The first flow path B37 bypasses the third silencer chamber B33. Another partial flow of the exhaust gas flows from the first silencer chamber B31 along the second flow path B38 to the third silencer chamber B33 and from there through the second flow unit B36 to the second silencer chamber B32. The passage B42 leads from the first silencer chamber B31 to the third silencer chamber B33. The second flow path B38 leads only through the second flow unit B36 and bypasses the first flow unit B35. The exhaust gas thus flows on its way through the first flow unit B35 or through the second flow unit B36 into the second silencer chamber B32.

[0174] In accordance with Figure B3 In the embodiment of the present invention, the muffler chamber is separated by a first separating wall B40 and a second separating wall B41. The first separating wall B40 separates the first muffler chamber B31 from the second muffler chamber B32. The second separating wall B41 separates the second muffler chamber B32 from the third muffler chamber B33. In the present embodiment, the second muffler chamber B32 is arranged between the first muffler chamber B31 and the third muffler chamber B33. The passage B42 extends through two separating walls B40 and B41. However, other arrangements and designs of the separating walls B40 and B41 can also be advantageous.

[0175] The position and size of the passage B42 and the third silencer chamber B33 can also be used to structurally predetermine how much of the entire exhaust gas flow flows through the first flow path B37 with the first flow unit B35, and how much of the exhaust gas flow flows along the second flow path B38 through the second flow unit B36. This distribution of the exhaust gas flow also depends on the entire exhaust gas mass flow and therefore on the speed and load of the internal combustion engine.

[0176] In accordance with Figure B3 In the embodiment of the present invention, the first flow-through unit B35 is completely in the projection P of the exhaust gas inlet B24. In this embodiment, the passage B42 is completely outside the projection P. There is a spacing f between the passage B42 and the projection P. The spacing f is measured at the partition wall B40. Thus, in at least one operating state, preferably at least in full-load operation, and in particular in all operating states, more than 50%, in particular more than 70%, of the entire exhaust gas flow flows through the first flow path B37 and flows through the first flow-through unit B35.

[0177] like Figure B3 As shown, the exhaust gas flows out from the first flow unit B35 along the first outflow direction B43. The exhaust gas flows out from the second flow unit along the second outflow direction B44. Figure B3 As shown, the first outflow direction B43 and the second outflow direction B44 point in opposite directions to each other. In the present embodiment, the outflow directions B43 and B44 are oriented parallel to each other. The first flow unit B35 has a first outflow surface B45. The first outflow surface is the surface of the first flow unit B35 through which the exhaust gas escapes from the first flow unit B35 along the first outflow direction B43. The first outflow surface B45 is adjacent to the second muffler chamber B32. The second flow unit B36 has a second outflow surface B46. The second outflow surface B46 is the surface through which the exhaust gas flows out from the second flow unit B36 along the second outflow direction B44.

[0178] In accordance with Figure B3 In the embodiment of the present invention, the flow units B35 and B36 are of the same size and are constructed with the same cross-sectional area. In the present embodiment, a circular cross-sectional area is provided for the flow units B35 and B36. However, other cross-sectional areas, such as rectangular, in particular square cross-sectional areas or irregular cross-sectional areas, can also be advantageous. Figure B3 In the embodiment of , the outflow surfaces B45 and B46 completely overlap along the outflow direction B43 and correspondingly along the outflow direction B44. Figure B3 Schematically indicated in FIG is an overlap U of the outflow surfaces B45 and B46 . The overlap U results from the projection of one of the outflow surfaces B45 , B46 along the associated outflow direction B43 or B44 onto the other of the outflow surfaces B45 and B46 .

[0179] Due to the orientation of the outflow directions B43 and B44 and the arrangement of the outflow surfaces B45 and B46, the exhaust gas flows flowing out of the flow units B35 and B36 along the outflow directions B43 and B44 influence each other during operation. In the case of a low total exhaust gas mass flow through the exhaust silencer B23, then at low speeds, the partial flow flowing out of the first flow unit B35 along the outflow direction B43 only slightly influences the partial exhaust gas flow flowing through the second flow path B38.

[0180] In the case of a higher total exhaust gas mass flow, a larger exhaust gas mass flow flows through the first flow path B37. The partial exhaust gas flow escaping from the first flow unit B35 affects the partial exhaust gas flow escaping from the second flow unit B36 and throttles it due to the partial exhaust gas flow flowing out along the outflow direction B43. As a result, in the case of a higher total exhaust gas mass flow, especially in the case of a fully open throttle element in the intake channel B11 of the internal combustion engine B8 when operating at full load, the proportion of the exhaust gas flow flowing through the second flow path B38 is reduced. According to the design, the proportion of the partial exhaust gas flow flowing through the second flow path B38 can be less than 70%, especially 50%, of the total exhaust gas mass flow under full load.

[0181] The distribution of the exhaust gas flow can be set by appropriately designing and arranging the outflow surfaces B45 and B46, the spacing a, and the position and size of the passage B42. The arrangement of the first flow unit B35 with respect to the exhaust gas inlet B24 also affects the distribution of the exhaust gas to the flow paths B37 and B38. Since the proportion of the partial exhaust gas flow flowing through the second flow unit B36 at full load is reduced, the heat generation in the second flow unit B36 coated with the catalytic material is reduced, so that overheating of the exhaust gas silencer B23 can be avoided at full load. Since a larger proportion of the exhaust gas flow flows through the second flow unit B36 at no load and advantageously also at partial load, improved exhaust gas aftertreatment is achieved in these operating states. At the same time, faster heating of the second flow unit B36 is achieved at no load, so that the exhaust gas silencer B23 achieves the temperature for the optimal catalytic aftertreatment of the exhaust gas more quickly when operating at no load after startup.

[0182] Typically, the dimensions of passage B42 are Figure B3 The height c of the passage B42 is indicated in FIG. The height c schematically illustrates the flow cross section of the passage B42. The geometrical adaptation of the passage B42 can be achieved by adapting the minimum flow cross section. Figure B4 Here, the passage B42 has a height c that is less than that in accordance with Figure B3 Therefore, according to the embodiment of Figure B4 In the embodiment of the invention, the minimum flow cross section of the passage B42 is smaller than that in the embodiment according to Figure B3 Thus, in accordance with Figure B4 In the embodiment of the present invention, the partial flow along the second flow path B38 is smaller than that in the embodiment according to Figure B3 In the embodiment of the present invention, the partial flow and the partial exhaust gas flow flowing through the first flow path B37 are greater than that in the embodiment according to Figure B3 According to the partial exhaust gas flow of the embodiment of Figure B4 The embodiment of the invention corresponds to the embodiment according to Figure B3, and thus refer to Figure B3 Description.

[0183] In accordance with Figure B3 and Figure B4 In the embodiment of the invention, the flow-through units B35 and B36 have the same outer diameter d. The outflow surfaces B45 and B46 are of the same size. In the following, the size of the outflow surfaces B45 and B46 is typically referred to as the outer diameter d.

[0184] The flow-through units B35 and B36 each have a thickness e measured along the flow direction. Figure B3 and Figure B4 In the embodiment of the present invention, the thickness e of the flow-through units B35 and B36 is the same. The different thicknesses e of the flow-through units B35 and B36 can also advantageously affect the distribution of the flows on the flow paths B37 and B38.

[0185] Figure B5 An embodiment is shown, in which the first flow unit B35 has an outer diameter d1 and the second flow unit B36 has an outer diameter d2. The cross-sectional area of ​​the first flow unit B35 is thus significantly larger than the cross-sectional area of ​​the second flow unit B36. The first outer diameter d1 is significantly larger than the second outer diameter d2. As a result, the second outflow surface B46 is significantly larger than the first outflow surface B45. The first outflow surface B45 is advantageously at least 1.2 times, in particular at least 1.5 times, and preferably at least 2 times, the second outflow surface B46. As a result, during operation in at least one operating state, in particular in all operating states, at least 50%, preferably at least 70%, of the entire exhaust gas flow flows through the first flow path B37. In accordance with Figure B5 In the embodiment of the present invention, the outflow directions B43 and B44 point in opposite directions to each other. The second outflow surface B46 is completely located in the overlapping portion U relative to the first outflow surface B45.

[0186] In accordance with Figure B6 In the embodiment of the present invention, the flow-through units B35 and B36 are arranged offset relative to each other at the partition walls B40 and B41. In this embodiment, the two flow-through units B35 and B36 have the same outer diameter d and preferably the same cross-sectional area. However, the outflow surfaces B45 and B46 only partially overlap. Figure B6 The overlapping portion U of the outflow surfaces B45 and B46 is schematically marked in FIG. The overlapping portion U is obtained when one of the outflow surfaces B45 and B46 is projected onto the other outflow surface in the associated outflow direction B43 or B44. Figure B3 and Figure B4 The embodiment of the reduced overlap U results in a smaller influence of the partial exhaust gas flow flowing along the second flow path B38 on the partial exhaust gas flow flowing through the first flow path B37.

[0187] Figure B7 Another embodiment is shown, in which the spacing between the walls B40 and B41 is relative to the spacing between the walls B40 and B41 according to Figures B3 to B6 The embodiment of the invention is significantly reduced. The flow-through units B35 and B36 are as shown in Figure B3 and B4 However, the flow-through units B35 and B36 have a spacing a relative to each other that is smaller than in Figures B3 to B6 However, a different arrangement and / or size of the flow-through units B35 and B36, for example as in one of the other exemplary embodiments, can also be advantageous. Due to the reduced spacing a, the influence of the partial exhaust gas flow flowing through the first flow path B37 on the partial exhaust gas flow flowing through the second flow path B38 is greater than according to Figures B3 to B6 The influence of the previous embodiment. Figure B7 In the embodiment according to Figure B3 , thereby achieving a greater reduction in the partial exhaust gas flow flowing through the second flow path B38 while increasing the total exhaust gas mass flow.

[0188] Figure B8 A further embodiment is shown, in which the first silencer chamber B31 is significantly smaller than the third silencer chamber B33. The first dividing wall B40 is arranged relatively close to the exhaust gas inlet B24. The first flow-through unit B35 is arranged completely in the projection P of the exhaust gas inlet B24 in this embodiment, so that a very large proportion of the total exhaust gas mass flow flows through the first flow-through unit B35. As a supplementary solution, in accordance with Figure B8 In the embodiment of the present invention, the outer diameter d2 of the second flow-through unit B36 is configured to be smaller than the outer diameter d1 of the first flow-through unit B35. The first flow-through unit B35 has a larger cross-sectional area than the second flow-through unit B36. This also reduces the partial exhaust gas flow flowing through the second flow path B38.

[0189] Figure B9 and B10 Another embodiment is shown, in which the second muffler chamber B32 is separated from the first muffler chamber B31 by a separation portion B47. Figure B10 As shown, the first muffler chamber B31 in this embodiment completely surrounds the second muffler chamber B32 at its periphery. It can also be advantageous to partially surround the second muffler chamber B32 by the first muffler chamber B31. Figure B9 and B10In the embodiment of the present invention, the split portion B47 is tubularly constructed. Here, the cross section of the split portion B47 can be appropriately adapted to the size of the flow-through units B35 and B36 and the desired spacing a between the outflow surfaces B45 and B46 of the flow-through units B35 and B36 and to the desired flow cross section. In the present embodiment, the split portion B47 has an approximately elliptical shape. A circular or polygonal cross-sectional shape can also be advantageous. An irregular cross-sectional shape of the split portion B47 is also feasible.

[0190] Alternatively, the partition B47 can be formed by one or more partition walls between the housing shells of the exhaust gas silencer B23.

[0191] In the present embodiment, the flow units B35 and B36 have the same outer diameter d and the same cross-sectional area. Different cross-sectional areas of the flow units B35 and B36 can also be provided to influence the proportion of the exhaust gas flow. Figure B10 In the embodiment of the present invention, since the first flow-through unit B35 is arranged in the projection P of the exhaust gas inlet B24 into the exhaust gas silencer B23, a larger proportion of the exhaust gas flows through the first flow path B37. As an additional solution or alternative, the distribution of the exhaust gas flow can also be influenced by other measures, in particular by other measures described in relation to other embodiments.

[0192] Figure B11 A further embodiment of an exhaust gas silencer B23 is shown, in which two flow-through units B35, B36 are arranged in a partition wall B28. Figure B11 The embodiment of Figure B2 In accordance with Figure B11 As a supplementary solution in the embodiment of the present invention, a flow guide element B48 is arranged in the exhaust gas silencer B23 adjacent to the exhaust gas inlet B24 into the exhaust gas silencer B23. The flow guide element B48 is arranged and oriented in such a way that the exhaust gas flow flowing into the exhaust gas silencer B23 is guided to the first flow unit B35. For the second flow unit B36, the exhaust gas flow must flow around the flow guide element B48. As a result, the proportion of the partial exhaust gas flow flowing through the first flow unit B35 to the total exhaust gas mass flow is greater than 50%, in particular greater than 70%. The distribution of the partial exhaust gas flow to the flow units B35 and B36 can be structurally set in a desired manner by appropriately arranging and designing the flow guide element B48. In accordance with Figure B11 In the embodiment of the present invention, the flow-through units B35 and B36 are constructed identically. However, it is also possible to provide that the flow-through units B35 and B36 have different cross-sectional areas, thicknesses, volumes and / or densities in order to influence the distribution of the exhaust gas flow.

[0193] Figure B12Another embodiment of the exhaust gas silencer B23 is shown, in which the supplementary silencer chamber B49 is arranged between the exhaust gas inlet B24 and the first silencer chamber B31 along the flow direction. The entire exhaust gas flow flows through the supplementary silencer chamber B49 in this embodiment. The exhaust gas silencer B23 has a dividing wall B28, which separates the first silencer chamber B31 from the second silencer chamber B32, and two flow-through units B35 and B36 are arranged in the dividing wall. A supplementary dividing wall B50 is arranged upstream of the first silencer chamber B31, which separates the supplementary silencer chamber B49 from the first silencer chamber B31. The supplementary dividing wall B50 has a transfer opening B51, through which the exhaust gas can flow from the supplementary silencer chamber B49 into the first silencer chamber B31. The first flow-through unit B35 is arranged in the projection V relative to the transfer opening B51 in this embodiment. In the present exemplary embodiment, a projection V of the transfer opening B51 along the flow direction B52 through the transfer opening B51 largely covers the flow-through unit B35. A complete covering solution can also be provided.

[0194] The second flow unit B36 is spaced a relative to the first flow unit B35. In the present embodiment, the spacing a also corresponds to the spacing of the second flow unit B36 relative to the projection V. The second flow unit B36 is arranged completely outside the projection V. The second flow unit B36 is therefore not directly flowed by the exhaust gas flow that flows into the first muffler chamber B31 through the transfer opening B51. In order to reach the second flow unit B36, the exhaust gas flow must first be turned several times. This reduces the proportion of the exhaust gas flow that flows through the second flow unit B36. The flow units B35 and B36 are arranged according to Figure B12 In the embodiment of the invention, the size of the structure is approximately the same. Figure B12 In the embodiment of the present invention, flow-through units B35 and B36 designed to be of different sizes and different densities can also be provided.

[0195] Figure B13 The structure of the flow-through unit B35 and B36 is schematically shown. The flow-through unit B35 and B36 include a wire body B39. The wire body B39 is a main body that is stable in itself. It can also be arranged that the flow-through unit B35 and B36 include a plurality of wire bodies B39. In the present embodiment, the wire body B39 is formed by extruded metal wire, preferably by a metal braided mesh or a metal fabric. The wire body B39 of the first flow-through unit B35 advantageously has no catalytic coating. In an alternative embodiment, it can be arranged that the wire body B39 of the first flow-through unit B35 is coated with a catalytic coating. Compared with the first flow-through unit B35, the second flow-through unit B36 advantageously has a larger amount of catalytic coating per volume unit. The two flow-through units B35 and B36 can have a carrier coating.

[0196] In such a wire body B39, eddies are obtained during operation within the flow-through unit B35 or B36. The exhaust gas flow is not laminar as in a honeycomb catalyst such as ceramic. As a result, a transverse flow through the flow-through units B35 and B36 is obtained during operation. Since the flow-through units B35 and B36 are spatially separated, such a transverse flow between the flow-through units B35 and B36 can be easily prevented, so that a prescribed flow condition is obtained through the area provided with the catalytic coating and in the area provided with no or little catalytic coating in terms of volume. As a result, a prescribed flow condition is easily achieved during operation.

[0197] The flow-through units B35, B36 have a housing B29. The housing B29 can be tubular, for example. The flow-through units B35 or B36 can be pressed into the housing B29, for example, and thus be held in the housing B29.

[0198] Each embodiment describes different feasible schemes for influencing the distribution of the exhaust gas flow to the flow-through unit. These different feasible schemes can be appropriately combined with each other in any manner to achieve the desired distribution of the exhaust gas flow to the flow paths B37 and B38. This results in another advantageous embodiment of the present invention. Another advantageous embodiment is obtained by arranging one or more additional flow-through units and / or by arranging one or more additional silencer chambers. In all embodiments, a fire screen can be provided in addition, especially adjacent to the exhaust gas outlet. The volumes of the first silencer chamber and the third silencer chamber, the first silencer chamber and the second silencer chamber, and the second silencer chamber and the third silencer chamber can be the same or different. In all embodiments in which the outflow directions B43 and B44 point in opposite directions to each other, the spacing between the flow-through units B35 and B36 is preferably less than 3 cm, especially less than 2 cm, so as to be able to achieve the influence on the exhaust gas flows pointing in opposite directions to each other. The flow-through units B35 and B36 preferably have different volumes and / or different thicknesses.

[0199] The amount of catalytically active coating in all examples relates to the mass of the catalytically active coating.

[0200] exist Figure C1 In C6 to C6 the reference numerals mentioned below are shown in each case without the preceding letter C.

[0201] Figure C1A motor-driven saw C1 is shown as an embodiment for a hand-held working tool. Instead of the motor-driven saw C1, the working tool can also be a brush cutter, a cutting machine, a blower, a lawn mower or the like. The hand-held working tool is, in particular, a portable working tool. The motor-driven saw C1 has a housing C2, on which a handle C3 is held. On the handle C3, operating elements for the motor-driven saw C1 are arranged, in this embodiment, a throttle lever C4 and a throttle lever lock C5. The motor-driven saw C1 has a guide rail C6, on which a saw chain C7 is rotatably arranged. During operation, the saw chain C7 is driven by an internal combustion engine arranged in the housing C2, in this embodiment, a two-stroke engine C8. The internal combustion engine can also be another mixed-lubricated internal combustion engine, in particular a mixed-lubricated four-stroke engine.

[0202] The two-stroke engine C8 comprises an air filter C9, through which air is sucked in during operation. The air enters the crankcase C15 of the two-stroke engine C8 via the intake channel C11. A section of the intake channel C11 is formed in the fuel supply device C10, for example, a carburetor. Another type of supply of fuel can also be provided, for example, by a fuel valve. Another location for the fuel input can also be provided, for example, into the crankcase C15.

[0203] The two-stroke engine C8 includes a cylinder C12 in which a piston C13 is supported back and forth. The piston C13 defines a combustion chamber C14 constructed in the cylinder C12. The combustion chamber C14 is formed by the piston C13 moving in the cylinder. Figure C1 The overflow channel C19 in the region of the lower dead center shown in FIG. 1 is connected to the inner cavity of the crankshaft housing C15. The piston C13 drives the crankshaft C17 rotatably supported in the crankshaft housing C15 via the connecting rod C16. The crankshaft C17 is rotatably supported around the rotation axis C18. The spark plug C20 protrudes into the combustion chamber C14. The discharge opening C21 is led out from the combustion chamber C14, and the discharge opening is connected to the inlet opening C24 of the exhaust muffler C23 via the discharge channel C22.

[0204] During operation, the two-stroke engine C8 draws the fuel / air mixture into the inner cavity of the crankshaft housing C15 through the intake channel C11 during the upward stroke of the piston C13. The fuel / air mixture is compressed in the crankshaft housing C15 during the downward stroke of the piston C15. Once the overflow channel C19 from the piston C13 to the combustion chamber C14 is opened, the fuel / air mixture flows from the inner cavity of the crankshaft housing C15 into the combustion chamber C14. In the area of ​​the top dead center, the spark plug C20 ignites the mixture in the combustion chamber. Due to the subsequent combustion, the piston C13 returns to accelerate in the direction of the crankshaft housing C15. Once the piston C13 opens the discharge opening C21, the exhaust gas can flow out of the combustion chamber C14 and flow to the exhaust muffler C23. Once the overflow channel C19 from the piston C13 to the combustion chamber C14 is opened, a fresh fuel / air mixture flows in again for the next combustion.

[0205] Alternatively, the two-stroke engine C8 can also be operated with scavenging pre-storage and include, in addition to the intake channel C11, one or more air channels which pre-storage a large amount of fuel-free air in the overflow channel C19. The pre-storage air separates the exhaust gases from the previous combustion from the fuel / air mixture flowing into the combustion chamber C14 during the downward stroke of the piston C13.

[0206] The exhaust silencer C23 has a housing C27, in which a first silencer chamber C47 and a second silencer chamber C48 are constructed. The first silencer chamber C47 is arranged upstream of the second silencer chamber C48. In the present embodiment, the inlet opening C24 leads to the first silencer chamber C47. However, it can also be provided that, upstream of the first silencer chamber, another silencer chamber is constructed in the housing C27 or in another unit. The exhaust silencer C23 has an escape opening C25, through which the exhaust gas flows out of the exhaust silencer C23 into the surrounding environment. In the present embodiment, the escape opening C25 is derived from the second silencer chamber C48. In an alternative embodiment, another silencer chamber can be provided downstream of the second silencer chamber C48.

[0207] The first muffler chamber C47 and the second muffler chamber C48 are separated by a partition wall C28. In the present embodiment, the exhaust gas aftertreatment unit C26 is held at the partition wall C28, through which the exhaust gas can flow from the first muffler chamber C47 to the second muffler chamber C48. For this purpose, the partition wall C28 has a connecting opening C50 in the area of ​​the exhaust gas aftertreatment device C26. The exhaust gas aftertreatment unit C26 includes a first flow-through unit C29 and a second flow-through unit C30, which will be described in more detail below.

[0208] Figure C1The arrangement of the exhaust gas aftertreatment unit C26 is schematically shown with respect to the arrangement of the inlet opening C24 into the exhaust gas silencer C23. The exhaust gas flows through the exhaust gas aftertreatment unit C26 along a main flow direction C35. In the present exemplary embodiment, the main flow direction C35 is approximately perpendicular to the partition wall C28. The main flow direction C35 preferably corresponds to the outflow direction C67 from the first flow-through unit C29, which is described in more detail below. Figure C1 The projection C49 of the inlet opening C24 parallel to the main flow direction C35 onto the partition wall C28 is schematically indicated in FIG. Figure C1 As shown, projection C49 is outside exhaust gas aftertreatment unit C26. Projection C49 and exhaust gas aftertreatment unit C26 do not overlap. As a result, the exhaust gas flowing into exhaust gas silencer C23 must be diverted before it can flow through exhaust gas aftertreatment unit C26. This achieves a more uniform distribution of the exhaust gas and exhaust gas aftertreatment unit C26 is loaded with exhaust gas to a large extent evenly.

[0209] Next, according to Figure C2 and C3 Explain the structure of the exhaust gas aftertreatment unit C26. Figure C2 As shown, the exhaust gas aftertreatment unit C26 comprises a housing C37. In the present embodiment, the housing C37 is formed by two partial shells C38 and C39. The partial shells C38 and C39 are preferably manufactured from bent sheet metal, for example as deep-drawn parts. In the present embodiment, the partial shells C38 and C39 are connected to each other in a sealing manner at the circumferential edge C43 of the exhaust gas aftertreatment unit C26.

[0210] The first partial housing C38 of the housing C37 is arranged adjacent to the first muffler chamber C47. The first partial housing C38 has all inflow openings of the exhaust gas aftertreatment unit C26. The exhaust gas aftertreatment unit C26 includes a first inflow opening C31, through which the exhaust gas flows into the first flow-through unit C29. The first partial housing C38 also has a second inflow opening C32, through which the exhaust gas directly enters the second flow-through unit C30.

[0211] The first flow-through unit C29 has an inflow surface C42, through which the exhaust gas can flow into the first flow-through unit C29. The inflow surface C42 is configured at the upstream end side C40 of the first flow-through unit C29. The first flow-through unit C29 has an outflow surface C57 located downstream, through which the exhaust gas can escape from the first flow-through unit C29. In the present embodiment, the inflow surface C42 and the outflow surface C57 are parallel to each other. However, other arrangements of the inflow surface C42 and the outflow surface C57 can also be advantageous.

[0212] The second flow-through unit C30 has an inflow surface C58. The inflow surface C58 is configured at the upstream end side C46 of the second flow-through unit C30. The inflow surface C58 is configured flatly in the present embodiment. The term "flat" in this article means flat within the framework of usual processing tolerances. The second inflow opening C32 leads to the end side C46 of the second flow-through unit C30. The transfer opening C34 also leads to the inflow surface C58. The second flow-through unit C30 has an outflow surface C64 located downstream. The outflow surface C64 is oriented parallel to the inflow surface C58 in the present embodiment. However, other positions may also be advantageous.

[0213] The outflow surface C57 of the first flow-through unit C29 has an outflow direction C67. The outflow direction C67 is perpendicular to the outflow surface C57 and points from the first flow-through unit C29 to the second flow-through unit C30.

[0214] exist Figure C3 The arrangement of the first inlet opening C31 and the second inlet opening C32 is shown in FIG. The first partial housing C38 comprises a central region C44 having the first inlet opening C31. In the present embodiment, five first inlet openings C31 are provided. Another number of first inlet openings C31 can also be advantageous. The central region C44 is Figure C3 In the top view shown in the figure, i.e. in the line of sight along the outflow direction C67 of the first flow-through unit C29, the central region C44 is completely surrounded by the surrounding region C45. In the present embodiment, the central region C44 is approximately circular, and the surrounding region C45 forms a ring around the central region C44. The surrounding region C45 has a second inflow opening C32. In the present embodiment, eight second inflow openings C32 are provided. Another number of second inflow openings C32 can also be advantageous.

[0215] like Figure C2 As shown, the exhaust gas aftertreatment device C26 has two sections C51 and C52 that are arranged one after the other along the outflow direction C67 of the first flow-through unit C29. The first flow-through unit C29 is arranged in the first section C51, and the second flow-through unit C30 is arranged in the second section C52. The second flow-through unit C30 does not protrude into the first section C51. The first flow-through unit C29 does not protrude into the second section C52. The second flow-through unit C30 is therefore arranged completely downstream of the first flow-through unit C29 with respect to the main flow direction C35 or with respect to the outflow direction C67 of the first flow-through unit C29.

[0216] The outflow surface C57 of the first flow-through unit C29 is located in an imaginary plane C66. Figure C2. The plane C66 is arranged perpendicular to the main flow direction C35. The second flow-through unit C30, in particular, does not protrude beyond the plane C66 in the opposite direction of the outflow direction C67 of the first flow-through unit C29, but is completely located downstream of the plane C66 or contacts the plane. The plane C66 does not intersect the second flow-through unit C30. The first flow-through unit C29 is completely located upstream of the plane C66 and does not protrude beyond the plane C66 along the outflow direction C67. The flow-through units C29 and C30 extend on opposite sides of the plane C66.

[0217] The first flow-through unit C29 has a maximum cross section C69. The second flow-through unit C30 has a maximum cross section C70. The maximum cross sections C69 and C70 are perpendicular to the main flow direction C35 and perpendicular to the outflow direction C67. In the present embodiment, the maximum cross section C69 corresponds to the square of half the outer diameter f of the first flow-through unit C29 multiplied by π. Correspondingly, the maximum cross section C70 corresponds to the square of half the outer diameter g of the second flow-through unit C30 multiplied by π.

[0218] The first section C51 extends from the inflow surface C42 of the first flow-through unit C29 to the outflow surface C57 of the first flow-through unit C29. The second section C52 extends from the inflow surface C58 of the second flow-through unit C30 to the outflow surface C64 of the second flow-through unit C30.

[0219] The first inlet opening C31 leads to the first flow-through unit C29. The first inlet opening C31 leads to the first section C51. The second inlet opening C32 leads to the second section C52. The inlet openings C31 and C32 are offset relative to each other with respect to the outflow direction C67 of the first flow-through unit C29, more precisely, the thickness a of the first section C51 measured in the direction of the outflow direction C67 of the first flow-through unit C29 is offset. The thickness of the first section C51 corresponds to the thickness a of the first flow-through unit C29 in the middle region. At its edge region located upstream, the first flow-through unit C29 has rounded corners, so that a slightly smaller thickness is obtained here. The first flow-through unit C29 has the same thickness a within the range of at least 80%, in particular at least 90%, of its maximum cross section C69. Here, the thickness a is constant within the framework of the usual manufacturing tolerances within the range of at least 80%, in particular at least 90%, of its maximum cross section.

[0220] The second flow-through unit C30 has a thickness b in its central region measured along the outflow direction C67 of the first flow-through unit C29. At its downstream edge region, the second flow-through unit C30 has chamfered corners, resulting in a slightly smaller thickness here. The second flow-through unit C30 has the same thickness b over at least 80%, in particular over at least 90%, of its maximum cross section C70.

[0221] The first flow cell C29 advantageously has a constant thickness a measured along the outflow direction C67 of the first flow cell C29 over at least 80% of its maximum cross section C69. The second flow cell C30 advantageously has a constant thickness b measured along the outflow direction C67 of the first flow cell C29 over at least 80% of its maximum cross section.

[0222] Thickness a and b can be approximately the same size. Advantageously, thickness a is half to twice the thickness b. Sections C51 and C52 are connected to each other in the shell C37 so that the exhaust gas flowing out of the outflow surface C57 of the first flow unit C29 can flow into the inflow surface C58 of the second flow unit C30. For this purpose, a transfer opening C34 of the shell C37 is provided. In the present embodiment, the transfer opening C34 extends within the range of the entire maximum cross-section C69 of the first flow unit C29. However, it can also be provided that one or more smaller transfer openings C34 connect the two flow units C29 and C30 to each other fluidically.

[0223] A step C36 is constructed at the first partial cover C38, which abuts against the outer periphery of the first flow unit C29 with a first step section C53. A second inlet opening C32 is constructed in the second step section C54. The second step section C54 extends transversely to, in particular perpendicularly to, the first step section C53. Preferably, the first step section C53 extends approximately parallel to the outflow direction C67 or the main flow direction C35 of the first flow unit C29, and the second step section C54 extends approximately perpendicularly to the main flow direction C35 or the outflow direction C67 of the first flow unit C29. In the present embodiment, the step C36 is formed by a change in the cross section of the shell C37 of the exhaust gas aftertreatment device C26. In the first section, the shell C37 has an outer diameter d, such as Figure C3 As shown. At the step C36, the outer diameter of the housing C37 increases to the outer diameter e in the second section C52. In this embodiment, the housing C37 is configured with a circular cross section along the main flow direction C35. Other cross-sectional shapes can also be advantageous. The step C36 can be formed by a correspondingly abrupt increase in the outer dimensions of the housing C37.

[0224] The first section C51 is completely formed in the first partial shell C38. The second section C52 is formed by the first partial shell C38 and the second partial shell C39. In the present embodiment, the first flow-through unit C29 is completely arranged in the first partial shell C38. The second flow-through unit C30 is mainly arranged in the second partial shell C39. In the present embodiment, the second flow-through unit C30 protrudes into the first partial shell C38 with a section that is less than 50%, in particular 80%, of the thickness b of the second flow-through unit C30. Another arrangement of the flow-through units C29 and C30 in the partial shells C38 and C39 can also be advantageous. In an alternative design, it can be provided, for example, that the first flow-through unit C29 protrudes into the second partial shell C39. Another structure of the housing C37 consisting of a single sheet or a shell-shaped sheet part and a cover can also be advantageous, for example.

[0225] The end side C40 of the first flow-through unit C29 is the side of the first flow-through unit C29 that is located upstream with respect to the main flow direction C35. The exhaust gas aftertreatment device C26 has the first inlet opening C31 only at the end side C40.

[0226] The maximum cross section C70 of the second flow cell C30 is advantageously greater than the maximum cross section C69 of the first flow cell C29. The maximum cross section C70 of the second flow cell C30 is advantageously at least 130%, in particular at least 150%, of the maximum cross section C69 of the first flow cell C29.

[0227] like Figure C2 As shown, the second flow unit C30 extends beyond the first flow unit C29 in the line of sight along the outflow direction C67 of the first flow unit C29. The protrusion c of the second flow unit C30 extending beyond the first flow unit C29 is advantageously at least 3 mm, in particular at least 5 mm. Preferably, the protrusion C extends over the entire circumference of the first flow unit C29 in the line of sight along the outflow direction C67 of the first flow unit C29. Here, the size of the protrusion C can be constant or vary within the circumference. However, the protrusion C is preferably at least 3 mm at each position of the circumference of the first flow unit C29.

[0228] In this embodiment, the flow-through units C29 and C30 are each cylindrically configured. Figure C3 The first flow-through unit C29 has an outer diameter f( Figure C2 The second flow-through unit C30 has an outer diameter g( Figure C2 ). The flow-through units C29 and C30 are respectively connected by the flow-through body C41 ( Figure C4 ) is formed. The through-flow body C41 has a plurality of cavities that allow through-flow. Figure C4The through-body C41 is at least at its inflow surface C42 and C58 and at its outflow surface C57 and C64 ( Figure C2 ) does not have a closed surface. In this embodiment, the flow-through units C29 and C30 each include a wire of the associated flow-through body C41 and a cavity formed between the segments of the wire. The flow-through units C29 and C30 represent a sheath that surrounds the flow-through body C41 and that the flow-through body C41 uniformly abuts against within the framework of the processing accuracy and uniformity of the size and distribution of the cavity.

[0229] An outflow opening C33 is led out of the exhaust gas aftertreatment unit C26. The outflow opening C33 is arranged in such a way that the exhaust gas must first flow through the second flow-through unit C30 in order to reach the outflow opening C33. In the present embodiment, the outflow opening C33 is configured in the second housing part C39. The outflow opening C33 can overlap with the inflow openings C31, C32 or be arranged offset thereto in a viewing direction opposite to the outflow direction C67 of the first flow-through unit C29.

[0230] In this embodiment, the first flow-through unit C29 and the second flow-through unit C30 are respectively formed by the flow-through body C41. Figure C4 A possible structure for the through-flow body C41 is shown in FIG. In the present embodiment, the through-flow body C41 is formed by a metal wire. The through-flow body C41 is dimensionally stable. An opening is formed between the ferrules of the metal wire, through which the exhaust gas can flow through the through-flow body C41. The through-flow body C41 is in particular a wire mesh. In the present embodiment, each through-flow unit C29, C30 is formed by exactly one through-flow body C41. However, it can also be provided that at least one through-flow unit C29, C30 is formed by more than one through-flow body C41.

[0231] The at least one transfer opening C34 is advantageously the only opening which fluidically connects the first flow-through unit C29 to the second flow-through unit C30. As a result, the exhaust gas can flow through the exhaust gas aftertreatment unit C26 via the first inlet opening C31 into the first flow-through unit C29, from there via the transfer opening C34 into the second flow-through unit C30 and from there via the outlet opening C33 into the second muffler chamber C48. Figure C3 Alternatively, a partial flow of the exhaust gas can flow directly into the second flow-through unit C30 through the second inlet opening C32 and from there into the second muffler chamber C48 through the outlet opening C33, as shown in FIG. Figure C3 As shown by the arrow C56 in FIG. 1 , no additional flow path is provided through the exhaust gas aftertreatment unit C26 .

[0232] The first flow-through unit C29 is coated with a catalytic material. In addition, a coating with a so-called carrier coating can be provided. Therefore, catalytic conversion of the exhaust gas is carried out in the first flow-through unit C29. The second flow-through unit C30 has no catalytic coating or has a catalytic coating with less mass per volume unit than the first flow-through unit C29. Therefore, the second flow-through unit C30 mainly acts as a particle filter. Since the first flow-through unit C29 is arranged upstream of the second flow-through unit C30, the exhaust gas in the first flow-through unit C29 is heated up sharply due to the catalytic conversion. The second flow-through unit C30 is preferably mainly used to reduce particles. The exhaust gas of a mixed lubrication internal combustion engine includes lubricating oil in the shape of droplets. These droplets form particles in the exhaust gas flow. The droplet-shaped lubricating oil is converted in the second flow-through unit C30. For this purpose, a sufficiently high temperature of the second flow-through unit C30 is necessary. In addition, a sufficiently long residence time of the oil droplets in the second flow-through unit C30 is necessary. The second flow-through unit C30 is preferably heated quickly by the first flow-through unit C29. This improves the particle reduction effect of the second flow-through unit C30. Once the temperature required for this is reached, the oil droplets are converted. In the currently commonly used lubricating oils, the temperature required for the conversion can be, for example, in the order of 600° to 700°.

[0233] The first flow cell C29 coated with a catalytic coating, in particular a noble metal, is preferably used primarily for converting hydrocarbons and / or nitrogen oxides. The second flow cell C30 can be designed without a catalytic coating or with a smaller amount of catalytic coating per volume unit than the first flow cell C29.

[0234] In this context, a catalytic coating is a coating that acts as a catalyst, which then reduces the activation energy for the chemical conversion of the exhaust gas and thus increases the reaction rate. The second flow-through unit C30 can be coated in particular with a washcoat. Washcoats are not considered catalytic coatings in this context. Washcoats are considered coatings that increase the surface without reducing the activation energy for the chemical conversion.

[0235] Since the second flow cell C30 is completely arranged behind the first flow cell C29 with respect to the outflow direction C67 of the first flow cell C29 through the exhaust gas aftertreatment unit C26, a transverse flow between the first flow cell C29 and the second flow cell C30 is not feasible. The exhaust gas flowing into the second flow cell C30 advantageously does not flow back into the first flow cell C29 due to the arrangement. As a result, the proportion of the exhaust gas flow flowing through the first flow cell C29 can be very well controlled by the design of the maximum cross-sections C69 and C70 and by the design of the inflow openings C31 and C32. The proportion of the exhaust gas flow flowing through the first flow cell C29 mainly affects the temperature of the exhaust gas flowing out of the exhaust gas aftertreatment device C26.

[0236] For the flow through both flow cells C29, C30, a higher fluid dynamic resistance for the exhaust gas is obtained than for the flow through only the second flow cell C30. The distribution of the exhaust gas flow to the first and second inlet openings C31 and C32 can be easily predetermined by the thicknesses a and b of the flow cells C29 and C30 and the maximum cross sections C69 and C70.

[0237] Figure C5 An alternative embodiment for an exhaust gas silencer C23 is shown. The exhaust gas silencer C23 has a housing C27, in which a first silencer chamber C47 and a second silencer chamber C48 are constructed. The silencer chambers C47 and C48 are separated by a partition wall C28. An exhaust gas aftertreatment device C26 is arranged in a connecting opening C50 of the partition wall C28. In this case, the same reference numerals represent corresponding elements in all exemplary embodiments. The exhaust gas aftertreatment device C26 can be as in Figures C1 to C3 , as shown in FIG. 1 , by two flow-through units C29 and C30. The exhaust gas aftertreatment device C26 can be constructed in such a way that a part of the exhaust gas flow flows through the two flow-through units C29 and C30, and another part of the exhaust gas flow flows only through the flow-through unit C30. Alternatively, the exhaust gas aftertreatment device C26 can be constructed in such a way that the entire exhaust gas flow flowing through the exhaust gas aftertreatment device C26 flows through all the flow-through units C29, C30 of the exhaust gas aftertreatment device C26. It can be provided here that the exhaust gas aftertreatment device C26 has only a single flow-through unit.

[0238] In an advantageous embodiment, the exhaust gas aftertreatment device C26 has the same amount of catalytic coating per volume unit in all regions of the at least one flow-through unit, so that the entire exhaust gas flow flowing through the exhaust gas aftertreatment device C26 flows through the catalytic coating.

[0239] In order to prevent excessive heating of the exhaust gas flow, Figure C5 In the embodiment of the invention, it is provided that part of the exhaust gas flow does not flow through the exhaust gas aftertreatment device C26. Figure C5 In the embodiment of the invention, a bypass channel C61 is provided, through which a part of the exhaust gas flow flows. The exhaust gas part flow flowing through the bypass channel C61 is illustrated by arrow C63. This part flow does not flow through the exhaust gas aftertreatment device C26.

[0240] The flow of the exhaust gas flow through the partial flow of the exhaust gas aftertreatment device C26 is illustrated by arrow C62. In the present embodiment, the bypass channel C61 has a connecting opening C59, which connects the first silencer chamber C27 with the bypass channel C61, and the exhaust gas flows into the bypass channel C61 through the connecting opening. The bypass channel C61 also has an escape opening C60, through which the exhaust gas leaves the exhaust silencer C23 from the bypass channel C61. In the present embodiment, the exhaust gas flowing through the bypass channel C61 does not flow through the inner cavity of the second silencer chamber C48. In the present embodiment, the bypass channel C61 is spatially guided through the second silencer chamber C48, but is fluidically separated from it. As a result, no mixing occurs between the partial flow (arrow C63) of the exhaust gas flow flowing through the bypass channel C61 and the partial flow (arrow C62) flowing through the second silencer chamber C48. The bypass channel C61 is arranged in such a way that it is heated by the exhaust gas arranged in the muffler chamber C48 . This makes it possible to convert the exhaust gas components in the bypass channel C61 even without catalytically active materials.

[0241] The bypass channel C61 is preferably guided adjacent to the outer wall of the exhaust gas silencer C23. The partial flow flowing through the bypass channel C61 is advantageously smaller than the partial flow flowing through the exhaust gas aftertreatment device C26. Advantageously, the partial flow flowing through the bypass channel C61 is less than 40%, in particular less than 30%, preferably less than 20% of the entire exhaust gas flow. The amount of exhaust gas flowing through the bypass channel C61 is preferably set by the flow cross section of the exhaust gas aftertreatment device C26 and the bypass channel C61.

[0242] In the present embodiment, the flow-through units C29, C30 have a flow-through body C41 made of metal wire. The metal wire that can form the first and / or second flow-through units C29, C30 is especially made of steel or a nickel alloy. Other carriers (e.g. metal fibers, foamed materials) or carriers that form elongated, geometrically defined channels (e.g. carriers made of sintered ceramics) can also be advantageous.

[0243] The terms “constant” and “flat” in this document always denote a constant or flat shape within the framework of usual manufacturing tolerances.

[0244] exist Figures D1 to D5 The reference numerals mentioned below are respectively shown without the preceding letter D.

[0245] Figure D1A motor-driven saw D1 is shown as an embodiment for a hand-held working tool. Instead of the motor-driven saw D1, the working tool can also be a brush cutter, a cutting machine, a blower, a lawn mower or the like. The hand-held working tool is, in particular, a hand-held working tool. The motor-driven saw D1 has a housing D2, on which a handle D3 is held. On the handle D3, operating elements for the motor-driven saw D1 are arranged, in the present embodiment, a throttle lever D4 and a throttle lever lock D5. The motor-driven saw D1 has a guide rail D6, on which a saw chain D7 is rotatably arranged. During operation, the saw chain D7 is driven by an internal combustion engine arranged in the housing D2, in the present embodiment, by a two-stroke engine D8. The internal combustion engine can also be another mixed-lubricated internal combustion engine, in particular a mixed-lubricated four-stroke engine.

[0246] The two-stroke engine D8 comprises an air filter D9, through which air is sucked in during operation. The air enters the crankcase D15 of the two-stroke engine D8 via the intake channel D11. A section of the intake channel D11 is formed in a fuel supply device D10, for example a carburetor. Another type of supply of fuel can also be provided, for example, supply via a fuel valve. Another location for the fuel input can also be provided, for example, a fuel input into the crankcase D15.

[0247] The two-stroke engine D8 includes a cylinder D12 in which a piston D13 is supported to and fro. The piston D13 defines a combustion chamber D14 formed in the cylinder D12. The combustion chamber D14 is filled with water by the piston D13. Figure D1 The overflow channel D19 in the region of the lower dead center shown in FIG. 1 is connected to the inner cavity of the crankshaft housing D15. The piston D13 drives the crankshaft D17 rotatably supported in the crankshaft housing D15 via the connecting rod D16. The crankshaft D17 is rotatably supported around the rotation axis D18. The spark plug D20 protrudes into the combustion chamber D14. The discharge opening D21 is led out from the combustion chamber D14, and the discharge opening is connected to the inlet opening D24 of the exhaust muffler D23 via the discharge channel D22.

[0248] During operation, the two-stroke engine D8 draws the fuel / air mixture into the inner cavity of the crankshaft housing D15 through the intake passage D11 during the upward stroke of the piston D13. The fuel / air mixture in the crankshaft housing D15 is compressed during the downward stroke of the piston D13. Once the overflow passage D19 from the piston D13 to the combustion chamber D14 is opened, the fuel / air mixture flows from the inner cavity of the crankshaft housing D15 into the combustion chamber D14. In the area of ​​the top dead center, the spark plug D20 ignites the mixture in the combustion chamber. Due to the subsequent combustion, the piston D13 returns to accelerate in the direction of the crankshaft housing D15. Once the piston D13 opens the discharge opening D21, the exhaust gas can flow out of the combustion chamber D14 and flow to the exhaust muffler D23. Once the overflow passage D19 from the piston D13 to the combustion chamber D14 is opened, a fresh fuel / air mixture flows in again for the next combustion.

[0249] Alternatively, the two-stroke engine D8 can also operate with scavenging pre-storage and include, in addition to the intake channel D11, one or more air channels which pre-store largely fuel-free air in the overflow channel D19. The pre-stored air separates the exhaust gases from the previous combustion from the fuel / air mixture flowing into the combustion chamber D14 during the downward stroke of the piston D13.

[0250] The exhaust silencer D23 has a silencer housing D27, in which a first silencer chamber D47 and a second silencer chamber D48 are constructed. The first silencer chamber D47 is arranged upstream of the second silencer chamber D48. In the present embodiment, the inlet opening D24 leads to the first silencer chamber D47. However, it can also be provided that, upstream of the first silencer chamber, another silencer chamber is constructed in the silencer housing D27 or in another unit. The exhaust silencer D23 has an escape opening D25, from which the exhaust gas flows out of the exhaust silencer D23 into the surrounding environment. In the present embodiment, the escape opening D25 is derived from the second silencer chamber D48. In an alternative embodiment, another silencer chamber can be provided downstream of the second silencer chamber D48.

[0251] The first muffler chamber D47 and the second muffler chamber D48 are separated by a partition wall D28. In the present embodiment, the exhaust gas aftertreatment device D26 is held at the partition wall D28, through which the exhaust gas can flow from the first muffler chamber D47 to the second muffler chamber D48. For this purpose, the partition wall D28 has an opening in the region of the exhaust gas aftertreatment device D26. The exhaust gas aftertreatment device D26 includes a first flow-through unit D29 and a second flow-through unit D30, which are described in more detail below.

[0252] Figure D1The arrangement of the exhaust gas aftertreatment device D26 schematically shows the arrangement of the inlet opening D24 in the exhaust gas silencer D23. The exhaust gas flows through the exhaust gas aftertreatment device D26 along the main flow direction D35. In the present embodiment, the main flow direction D35 is approximately perpendicular to the partition wall D28. The main flow direction D35 preferably corresponds to the outflow direction D64 from the first flow-through unit D29 described in more detail below. Figure D1 The projection D59 of the inlet opening D24 parallel to the main flow direction D35 onto the partition wall D28 is schematically indicated in FIG. Figure D1 As shown, projection D59 is located outside exhaust gas aftertreatment device D26. Projection D59 and exhaust gas aftertreatment device D26 do not overlap. As a result, the exhaust gas flowing into exhaust muffler D23 must be deflected before it can flow through exhaust gas aftertreatment device D26. As a result, a more uniform distribution of the exhaust gas is achieved, and exhaust gas aftertreatment device D26 is loaded with exhaust gas to a large extent evenly.

[0253] Next, according to Figure D2 and D3 To explain the structure of the exhaust gas after-treatment device D26. Figure D3 A side view of the exhaust gas aftertreatment device D26 is shown opposite to the outflow direction D64 of the first flow-through unit D29, which will be explained in more detail below. Figure D2 As shown, the exhaust gas aftertreatment device D26 comprises a housing D37. In the present embodiment, the housing D37 is formed by two partial housings D38 and D39. The partial housings D38 and D39 can be manufactured, for example, as deep-drawn parts. In the present embodiment, the partial housings D38 and D39 are connected to each other in a sealing manner at the circumferential edge D50 of the exhaust gas aftertreatment device D26. Other structures of the housing D37, for example, consisting of a single sheet metal or a shell-shaped sheet metal part and a cover, can also be advantageous.

[0254] The first partial housing D38 of the housing D37 is arranged adjacent to the first muffler chamber D47. Figure D1 As shown. The first housing part D38 has an inflow opening D31 of the exhaust gas aftertreatment device D26. The exhaust gas flows into the first flow-through unit D29 through the inflow opening D31. Figure D2As shown, the exhaust gas aftertreatment device D26 has two sections D51 and D52 that are arranged one after the other with respect to the main flow direction D35. A first flow unit D29 is arranged in the first section D51. A second flow unit D30 is arranged in the second section D52. The second flow unit D30 does not protrude into the first section D51. The first flow unit D29 does not protrude into the second section D52. Therefore, the second flow unit D30 is completely arranged downstream of the first flow unit D29 with respect to the outflow direction D64 of the first flow unit D29, especially with respect to the main flow direction D35. The first inlet opening D31 is arranged at the upstream end side D40 of the first flow unit D29. No inlet opening D31 is provided at the circumference of the first flow unit D29.

[0255] The outflow surface D61 of the first flow-through unit D29 is located in an imaginary plane D66. Figure D2 . Plane D66 is arranged perpendicular to the main flow direction D35. The second flow-through unit D30 does not protrude beyond plane D66, especially opposite to the outflow direction D64, but is completely located downstream of plane D66 or contacts the plane. Plane D66 does not intersect with the second flow-through unit D30. The first flow-through unit D29 is completely located upstream of plane D66 and does not protrude beyond plane D66 along the outflow direction D64. The flow-through units D29 and D30 extend on opposite sides of plane D66. The second flow-through unit D30 is advantageously arranged completely downstream of the first flow-through unit D29 with respect to the outflow direction D64.

[0256] The first flow unit D29 has a downstream end side D41 through which the exhaust gas leaves the first flow unit D29. The downstream end side D41 of the first flow unit D29 covers the second flow unit D30 in a partial area in the line of sight along the main flow direction D35. The exhaust gas can be transferred from the first flow unit D29 to the second flow unit D30 through the transfer opening D34 of the housing D37. At least one transfer opening D34 is advantageously the only opening that connects the first flow unit D29 to the second flow unit D30 fluid. Therefore, the exhaust gas escaping from the first flow unit D29 must flow into the second flow unit D30.

[0257] The first flow-through unit D29 has an inflow surface D60, through which the exhaust gas can flow into the first flow-through unit D29. The inflow surface D60 is configured at the upstream end side D40 of the first flow-through unit D29. The first flow-through unit D29 has an outflow surface D61 located downstream, through which the exhaust gas can escape from the first flow-through unit D29. In the present embodiment, the inflow surface D60 and the outflow surface D61 are parallel to each other. However, other arrangements of the inflow surface D60 and the outflow surface D61 can also be advantageous.

[0258] The second flow-through unit D30 has an inflow surface D62. The inflow surface D62 is configured at the upstream end side D42 of the second flow-through unit D30. In the present embodiment, the inflow surface D62 is configured flat within the framework of the usual processing tolerances. The transfer opening D34 leads to the inflow surface D62. The second flow-through unit D30 has an outflow surface D63 located downstream. In the present embodiment, the outflow surface D63 is oriented parallel to the inflow surface D62. However, other positions can also be advantageous.

[0259] The outflow surface D61 of the first flow-through unit D29 has an outflow direction D64. The outflow direction D64 is perpendicular to the outflow surface D61 and points from the first flow-through unit D29 to the second flow-through unit D30.

[0260] like Figure D2 As shown, the first flow unit D29 extends beyond the second flow unit D30 in the viewing direction opposite to the outflow direction D64. The protrusion c of the first flow unit D29 extending beyond the second flow unit D30 is advantageously at least 3 mm, in particular at least 5 mm. Preferably, the protrusion c extends over the entire circumference of the second flow unit D30 in the viewing direction opposite to the outflow direction D64 or opposite to the main flow direction D35. Here, the size of the protrusion c can be constant or vary within the circumference within the framework of normal manufacturing tolerances. However, the protrusion c is preferably at least 3 mm at each position on the circumference of the second flow unit D30.

[0261] In this embodiment, the flow-through units D29 and D30 are each cylindrically constructed. Figure D3 The cylindrical outer contours of the flow-through units D29 and D30 are shown by dashed lines. The first flow-through unit D29 has an outer diameter f( Figure D2 The second flow-through unit D30 has an outer diameter g( Figure D2 ). The flow-through units D29 and D30 are respectively formed by a flow-through body D46. The flow-through body D46 has a plurality of cavities that allow flow through. Figure D4 The through-body D46 is at least at its inflow surface D60 and D62 and at its outflow surface D61 and D63 ( Figure D2 ) does not have a closed surface. In the present embodiment, the flow-through units D29 and D30 respectively include a wire of the associated flow-through body D46 and a cavity formed between the segments of the wire. The flow-through units D29 and D30 represent a sheath that surrounds the flow-through body D46 and against which the flow-through body D46 rests evenly within the framework of the processing accuracy and uniformity of the size and distribution of the cavity.

[0262] The first flow-through unit D29 has a maximum cross section D69. The second flow-through unit D30 has a maximum cross section D70. The maximum cross sections D69 and D70 are perpendicular to the main flow direction D35 and perpendicular to the outflow direction D64. In the present embodiment, the maximum cross section D69 corresponds to the square of half the outer diameter f of the first flow-through unit D29 multiplied by π. Correspondingly, the maximum cross section D70 corresponds to the square of half the outer diameter g of the second flow-through unit D30 multiplied by π.

[0263] like Figure D2 As shown, the housing D37 has an outflow opening D32 at the downstream end side D41 of the first flow-through unit D29. The partial flow D45 escaping from the first flow-through unit D29 can flow out of the housing D37 from the outflow opening D32 without first flowing through the second flow-through unit D30. Figure D2 The partial flow D45 of the exhaust gas flow is schematically shown by arrows in FIG. Figure D2 The other partial flow D44, which is also schematically indicated by an arrow, flows into the first flow unit D29 at the upstream end side D40 of the first flow unit D29, leaves the first flow unit D29 at the downstream end side D41, flows into the second flow unit D30 through the upstream end side D42 of the second flow unit D30, flows through the second flow unit D30, and leaves the second flow unit D30 at the downstream end side D43 of the second flow unit D30. At the downstream end side D43 of the second flow unit D30, the housing D37 has at least one outflow opening D33, through which the partial flow D44 can leave the housing D37. No other flow route is provided through the exhaust gas aftertreatment device D26. The entire exhaust gas flow is divided into partial flows D44 and D45 in the flow through the exhaust gas aftertreatment device D26.

[0264] In the present embodiment, a plurality of outflow openings D32 and a plurality of outflow openings D33 are provided. However, just one outflow opening D32 and / or just one outflow opening D33 can also be advantageous.

[0265] The outflow openings D32 and D33 are offset relative to each other with respect to the outflow direction D64, in particular with respect to the main flow direction D35, more precisely, the thickness b of the second section D52 measured along the outflow direction is offset. The thickness of the first section D51 corresponds to the thickness a of the first flow-through unit D29 in the middle area. The thickness a is measured along the outflow direction D64, i.e. perpendicularly to the outflow surface D61. The first flow-through unit D29 has a chamfered edge at its upstream edge area, so that a slightly smaller thickness is obtained here. The first flow-through unit D29 has the same thickness a within the scope of at least 80% of its maximum cross-section D69, in particular within the scope of at least 90%, within the framework of normal manufacturing tolerances.

[0266] The second flow-through unit D30 has a thickness b in its central region measured along the outflow direction D64 or along the main flow direction D35. The second flow-through unit D30 has rounded corners at its downstream edge region, resulting in a slightly smaller thickness here. The second flow-through unit D30 has the same thickness b within the scope of customary manufacturing tolerances over at least 80%, in particular over at least 90%, of its maximum cross section D70.

[0267] In the present embodiment, the thickness of the first section D51 corresponds approximately to the thickness a of the first flow-through unit D29. The thickness b can correspond approximately to the thickness of the second section D52. The thickness a and b can be approximately the same, especially within the framework of usual manufacturing tolerances. Advantageously, the thickness a is half to twice the thickness b.

[0268] The transfer opening D34 of the housing D37 leads from the first section D51 to the second section D52. In the present embodiment, the transfer opening D34 extends at least within the entire maximum cross-section D70 of the second flow-through unit D30. However, it can also be provided that one or more smaller transfer openings D34 connect the two flow-through units D29 and D30 to each other fluidically.

[0269] A step D36 is formed on the second housing part D39, which with a first step section D53 abuts against the downstream end side D41 of the first flow-through unit D29. The step D36 is formed in particular by a change in the cross section of the housing D37 of the exhaust gas aftertreatment device D26. In the first section D51, the housing D37 has an outer diameter D such as Figure D3 As shown. At the step D36, the outer diameter of the housing D37 is reduced to the outer diameter e in the second section D52. In the present embodiment, the housing D37 is constructed with a circular cross section. Other cross-sectional shapes can also be advantageous. The step D36 can be formed by a corresponding abrupt reduction in the external dimensions of the housing D37. An outflow opening D32 is constructed in the first step section D53. The second step section D54 extends transversely to, in particular perpendicularly to, the first step section D53. The second step section D54 abuts against the outer periphery of the second flow-through unit D30. Preferably, the first step section D53 extends approximately perpendicular to the main flow direction D35. The second step section D54 advantageously extends approximately parallel to the main flow direction D35. Advantageously, no outflow opening is constructed at the second step section D54. The exhaust gas aftertreatment device D26 has an outflow opening D32 or D33 only at the downstream end sides D41 and D43 of the flow-through units D29 and D30.

[0270] The maximum cross section D69 of the first flow unit D29 is advantageously greater than the maximum cross section D70 of the second flow unit D30. The maximum cross section D69 of the first flow unit D29 is advantageously at least 130%, in particular at least 150%, of the maximum cross section D70 of the second flow unit D30.

[0271] In the present embodiment, the first flow-through unit D29 and the second flow-through unit D30 are respectively formed by the flow-through body D46. Alternatively, it can be provided that one or two flow-through units D29, D30 are formed by two or more flow-through bodies D46. Alternatively, it can also be provided that the first flow-through unit D29 and the second flow-through unit D30 are formed by different regions of a single flow-through body D46.

[0272] Figure D4 and D5 A possible design for the through-body D46 is shown. Figure D4 The penetrating body D46 is shown, and the penetrating body is formed by metal wires. The penetrating body D46 is particularly a wire braided mesh. Figure D4 The structure shown in FIG. 1 is particularly provided for the first flow-through unit D29. However, it is also possible to provide that the second flow-through unit D30 is connected to the Figure D4 A corresponding penetrating body D46 is formed.

[0273] Figure D5 An alternative design for the through-body D46 is shown. Figure D5 The flow-through body D46 shown in the figure comprises a carrier D58 in which a plurality of channels D57 are formed. In the present embodiment, the channels D57 extend parallel to each other and are preferably formed separately from each other. The carrier D58 is advantageously coated with a catalytic material, which preferably comprises a precious metal. Figure D5 The through-flow body D46 shown in FIG. 1 is preferably provided for the second through-flow unit D30 . Figure D5 The flow-through body D46 can be formed, for example, from a ceramic material or from a metal. The carrier D58 can preferably be formed from a plurality of wound sheets. One of the sheets is preferably wavy in shape like a corrugated sheet, so as to form a channel D57.

[0274] Other supports D58 (for example metal fibers, foamed materials) or other supports D58 which form elongated, geometrically defined channels (for example supports D58 composed of sintered ceramic) may also be advantageous.

[0275] Figure D3The arrangement of the outflow openings D32 and D33 in the second partial housing D38 is shown. The second partial housing D38 has a central region D55, which has an outflow opening D33. The central region D55 is arranged downstream of the second flow-through unit D30. The central region D55 is surrounded by a surrounding region D56 in the direction of sight opposite to the main flow direction D35. The surrounding region D56 forms a first section D53 of the step D36. The outflow opening D32 is arranged in the surrounding region D56. Figure D3 As shown, the outflow openings D32 are arranged uniformly around the central region D55. As a result, the exhaust gas flowing out of the outflow openings D32 flows along the region of the housing D37 where the second flow-through unit D30 is arranged, thereby cooling it well.

[0276] The second flow-through unit D30 is coated with a catalytic material. In addition, a coating with a so-called carrier coating can be provided. In the second flow-through unit D30, a catalytic conversion of the exhaust gas is thus performed. The first flow-through unit D29 has no catalytic coating or has a smaller amount of catalytic coating per volume unit than the second flow-through unit D30.

[0277] The first flow-through unit D29 is preferably used primarily for particle reduction. The exhaust gas of a mixed-lubrication internal combustion engine contains lubricating oil in the form of droplets, which are converted in the first flow-through unit D29.

[0278] The second flow cell D30 coated with a catalytic coating, in particular a noble metal, is preferably used primarily for converting hydrocarbons and / or nitrogen oxides. The first flow cell D29 can be designed without a catalytic coating or with a catalytic coating of a lower mass per volume unit than the second flow cell D30.

[0279] In this context, a catalytic coating is a coating that acts as a catalyst, which then reduces the activation energy for chemically converting the exhaust gas and thus increases the reaction rate. The first flow-through unit D29 can be coated in particular with a washcoat. Washcoats are not considered catalytic coatings in this context. Washcoats are considered coatings that increase the surface of their carrier without reducing the activation energy for chemical conversion.

[0280] Since the second flow-through unit D30 is arranged completely downstream of the first flow-through unit D29 with respect to the main flow direction D35 through the exhaust gas aftertreatment unit D26, a transverse flow between the first flow-through unit D29 and the second flow-through unit D30 is not possible. As a result, the proportion of the exhaust gas flow flowing through the second flow-through unit D30 can be very well controlled by the design of the cross section and the inflow opening. The proportion of the exhaust gas flow flowing through the second flow-through unit D30 mainly affects the temperature of the exhaust gas flowing out of the exhaust gas aftertreatment device D26.

[0281] Compared to the flow through only the first flow unit D29, a higher fluid dynamic resistance for the exhaust gas is obtained for the flow through the two flow units D29, D30. The distribution of the exhaust gas flow to the first and second outflow openings D32 and D33 can be easily predetermined by the thickness a and b and the cross section of the flow units D29 and D30.

[0282] The terms “constant” and “flat” in this document always denote a constant or flat shape within the framework of usual manufacturing tolerances.

Claims

1. A hand-held work tool having an internal combustion engine (A8) and an exhaust gas silencer (A23), in which a first silencer chamber (A47) and a second silencer chamber (A48) are formed, wherein: The exhaust gas silencer (A23) comprises an exhaust gas aftertreatment device (A26), which comprises at least one flow-through unit (A31), wherein the flow-through unit (A31) is arranged in a flow path from the first muffler chamber (A47) to the second muffler chamber (A48), wherein a thickness (b) of the flow-through unit (A31) measured from an upstream end side (A36) to a downstream end side (A37) of the flow-through unit (A31) is at least 10 mm in a region of the flow-through unit (A31) through which the exhaust gas flows, at least within the range of 70% of the maximum cross section (E), The invention is characterized in that the exhaust gas aftertreatment device (A26) has no catalytic coating.

2. The working tool according to claim 1, It is characterized in that The at least one flow-through unit (A31) is at least partially coated with a washcoat.

3. The working tool according to claim 1 or 2, It is characterized in that The flow-through unit (A31) includes at least one wire body (A41) made of metal.

4. The working tool according to claim 3, It is characterized in that At least one wire body (A41), in particular all wire bodies (A41) of the exhaust gas aftertreatment device (A26) have a wire cross section of at least 0.07 mm 2 .

5. The working tool according to claim 3 or 4, It is characterized in that The wires of the wire body (A41) are at least partially made of a nickel alloy or stainless steel.

6. The working tool according to any one of claims 3 to 5, It is characterized in that At least one, in particular all, of the wire bodies (A41) have a density of 0.6 g / cm at least in the region through which the exhaust gas flows. 3 Up to 2g / cm 3 .

7. The working tool according to any one of claims 3 to 6, It is characterized in that The sum of the volumes of the regions through which flow passes of all the wire bodies (A41) of the flow-through unit (A31) is at least 0.6 times the displacement of the internal combustion engine (A8).

8. The working tool according to any one of claims 3 to 7, It is characterized in that The wire body (A41) is constructed of a metal braided mesh (A42).

9. The working tool according to any one of claims 3 to 8, It is characterized in that The wire body (A41) is spirally wound.

10. The working tool according to claim 9, It is characterized in that The wire body (A41) is arranged in the exhaust gas silencer (A23) such that a winding axis (A46) extends through an upstream end side (A36) and a downstream end side (A47) of the wire body (A41).

11. The working tool according to any one of claims 1 to 10, It is characterized in that The minimum cross section of the flow-through unit (A31) in the region of the flow-through unit (A31) through which the exhaust gas flows is at least 8 mm per cubic centimeter of displacement of the internal combustion engine (A8). 2 .

12. The work tool according to any one of claims 1 to 11, It is characterized in that The exhaust gas silencer (A23) has an exhaust gas inlet (A24) into the exhaust gas silencer (A23) and an exhaust gas outlet (A25) out of the exhaust gas silencer (A23), and at least one flow-through unit (A31), in particular at least one wire body (A41) of the exhaust gas aftertreatment device (A26), is arranged in each flow path from the exhaust gas inlet (A24) to the exhaust gas outlet (A25).

13. The working tool according to any one of claims 1 to 12, It is characterized in that The second muffler chamber (A48) has a volume of at least 80% of the displacement of the internal combustion engine (A8).

14. The work tool according to any one of claims 1 to 13, It is characterized in that The internal combustion engine (A8) is a mixture-lubricated internal combustion engine (A8), in particular a two-stroke engine.

15. The work tool according to any one of claims 1 to 14, It is characterized in that The power tool (A1) is designed such that the temperature of the exhaust gas flow on the upstream side of the exhaust gas aftertreatment device (A26) is 450° C. to 750° C. at full load after an operating time of at least 2 minutes of the internal combustion engine (A8).

16. An exhaust gas aftertreatment device, used for a handheld working tool according to any one of claims 1 to 15, wherein: The exhaust gas aftertreatment device (A26) comprises at least one flow-through unit (A31), in particular at least one flow-through unit (A31) having at least one wire body (A41) made of metal, Characterized in that the exhaust gas after-treatment device (A26) has no catalytic coating.

17. An exhaust muffler, in particular for a mixture-lubricated internal combustion engine in a handheld work tool, comprising: an exhaust gas inlet (B24) and an exhaust gas outlet (B25); First muffler chamber (B31); Second muffler chamber (B32); A first flow-through unit (B35) for exhaust gas aftertreatment; as well as A second flow-through unit (B36) for exhaust gas aftertreatment, wherein the first muffler chamber (B31) is arranged upstream of the second muffler chamber (B32), wherein the second flow-through unit (B36) has a catalytic coating in at least one section, and wherein the first flow-through unit (B35) has a smaller volume of the catalytic coating or has no catalytic coating than the second flow-through unit (B36), wherein a flow path from the first muffler chamber (B31) to the second muffler chamber (B32) is formed in the exhaust gas muffler (B23). 2), wherein the flow cross sections of the first flow path (B37) and the second flow path (B38) are predetermined in terms of structure and cannot be changed, wherein the first flow path (B37) is guided through the first flow unit (B35) and bypasses the second flow unit (B36), and wherein the second flow path (B38) is guided through the second flow unit (B36) and bypasses the first flow unit (B35), It is characterized in that the first flow-through unit (B35) and the second flow-through unit (B36) are arranged spatially separated from each other.

18. The exhaust muffler according to claim 17, It is characterized in that The first flow-through unit (B35) and the second flow-through unit (B36) have a distance (Ba) relative to each other.

19. The exhaust muffler according to claim 17 or 18, It is characterized in that The first flow-through unit (B35) and the second flow-through unit (B36) are arranged in a partition wall (B28) of the exhaust silencer (B23) between the first silencer chamber (B31) and the second silencer chamber (B32) and have a distance (Ba) relative to each other in the partition wall (B28).

20. The exhaust muffler according to any one of claims 17 to 19, It is characterized in that The first muffler chamber (B31) at least partially surrounds the second muffler chamber (B32), wherein the first muffler chamber (B31) is separated from the second muffler chamber (B32) by a separation portion (B47), and the first flow-through unit (B35) and the second flow-through unit (B36) are arranged in the separation portion.

21. The exhaust muffler according to claim 17 or 18, It is characterized in that The first flow-through unit (B35) is arranged in a first separating wall (B40), which separates the first silencer chamber (B31) and the second silencer chamber (B32) from each other, and the second flow-through unit (B36) is arranged in a second separating wall (B41), which separates the third silencer chamber (B33) from the second silencer chamber (B32), wherein the third silencer chamber (B33) is arranged between the first silencer chamber (B31) and the second silencer chamber (B32) along the flow direction in the second flow path (B38).

22. The exhaust muffler according to claim 21, It is characterized in that A passage (B42) is provided which passes through the first partition wall (B40) and the second partition wall (B41) and leads from the first muffler chamber (B31) to the third muffler chamber (B33).

23. The exhaust muffler according to claim 21 or 22, It is characterized in that The volumes of the first muffler chamber (B31) and the third muffler chamber (B33) are different.

24. The exhaust muffler according to any one of claims 20 to 23, It is characterized in that A first outflow direction (B43) from the first flow-through unit (B35) and a second outflow direction (B44) from the second flow-through unit (B36) point in opposite directions to each other.

25. The exhaust muffler according to any one of claims 20 to 24, It is characterized in that The first outflow surface (B45) of the first flow-through unit (B35) and the second outflow surface (B46) of the second flow-through unit (B36) at least partially overlap along the first outflow direction (B43).

26. The exhaust muffler according to any one of claims 20 to 25, It is characterized in that In the second muffler chamber (B32), a distance (Ba) between the first flow-through unit (B35) and the second flow-through unit (B36) is less than 3 cm, in particular less than 2 cm.

27. An exhaust muffler according to any one of claims 17 to 26, It is characterized in that At least one flow-through unit (B35, 36) includes at least one wire body (B39).

28. The exhaust muffler according to claim 27, It is characterized in that The wire body (B39) is formed of an extruded metal wire.

29. The exhaust muffler according to any one of claims 17 to 28, It is characterized in that The first flow path (B37) leads directly from the first flow-through unit (B35) into the second muffler chamber (B32), and the second flow path (B38) leads directly from the second flow-through unit (B36) into the second muffler chamber (B32).

30. An exhaust muffler according to any one of claims 17 to 29, It is characterized in that The volumes of the first muffler chamber (B31) and the second muffler chamber (B32) are different.

31. An exhaust muffler according to any one of claims 17 to 30, It is characterized in that Outflow surfaces (B45, 46) from the first flow-through unit (B35) and the second flow-through unit (B36) are different in size.

32. An exhaust muffler according to any one of claims 17 to 31, It is characterized in that The first flow-through unit (B35) and the second flow-through unit (B36) have different volumes.

33. An exhaust muffler according to any one of claims 17 to 32, It is characterized in that The first flow-through unit (B35) and the second flow-through unit (B36) have different densities.

34. An internal combustion engine having an exhaust passage (B22) connected to an exhaust gas inlet (B24) of an exhaust muffler (B23) according to any one of claims 17 to 33, wherein: The first flow unit (B35) and the second flow unit (B36) are constructed and arranged such that in at least one operating state of the internal combustion engine (B8), more than 50%, in particular more than 70%, of the entire exhaust gas flow flows through the first flow path (B37).

35. An internal combustion engine according to claim 34, It is characterized in that The first flow-through unit (B35) is adjacent to the first muffler chamber (B31) and at least partially overlaps with a projection (BP, V) of the inlet opening along the inlet direction into the first muffler chamber (B31).

36. An internal combustion engine according to claim 34 or 35, It is characterized in that The second flow-through unit (B36) is adjacent to the first silencer chamber (B31) and is completely outside a projection (P, V) of the inlet opening along the inlet direction into the first silencer chamber (B31).

37. An exhaust gas aftertreatment device, comprising a first flow-through unit (C29) and a second flow-through unit (C30) arranged in a housing (C37) of the exhaust gas aftertreatment device (C26), wherein: The first flow-through unit (C29) has a catalytic coating, and wherein the second flow-through unit (C30) has no catalytic coating or has a catalytic coating of a smaller mass per volume unit than the first flow-through unit (C29), wherein the housing (C37) has at least one first inlet opening (C31) into the first flow-through unit (C29), at least one second inlet opening (C32) into the second flow-through unit (C30), and at least one transfer opening (C34) from the first flow-through unit (C29) to the second flow-through unit (C30), wherein the first flow-through unit (C29) has an outflow surface (C57) and an outflow direction (C67) perpendicular to the outflow surface (C57) from the first flow-through unit (C29) to the second flow-through unit (C30), and wherein the second flow-through unit (C30) has an inflow surface (C58), It is characterized in that the inflow surface (C58) of the second flow-through unit (C30) does not protrude beyond the plane (C66) containing the outflow surface (C57), and in particular does not protrude beyond the plane (C66) opposite to the outflow direction (C67).

38. The exhaust gas aftertreatment device according to claim 37, It is characterized in that The maximum cross section (C69) of the second flow-through unit (C30) is greater than the maximum cross section (C70) of the first flow-through unit (C29), in particular at least 130% of the maximum cross section (C70) of the first flow-through unit (C29).

39. The exhaust gas aftertreatment device according to claim 37 or 38, It is characterized in that The inflow surface (C58) of the second flow-through unit (C30) is flat.

40. The exhaust gas aftertreatment device according to any one of claims 37 to 39, It is characterized in that The at least one transfer opening (C34) is the only opening that fluidically connects the first flow-through unit (C29) and the second flow-through unit (C30).

41. The exhaust gas aftertreatment device according to any one of claims 37 to 40, It is characterized in that The first flow-through unit (C29) has an inflow surface (C42) opposite to the outflow surface (C57), and the first inlet opening (C31) is arranged only at the inflow surface (C42) of the first flow-through unit (C29).

42. The exhaust gas aftertreatment device according to any one of claims 37 to 41, It is characterized in that The first flow-through unit (C29) has, over at least 80% of its maximum cross section (C69), a constant thickness (a) measured along an outflow direction (C67) of the first flow-through unit (C29).

43. An exhaust gas aftertreatment device according to any one of claims 37 to 42, It is characterized in that The second flow-through unit (C30) has, over at least 80% of its maximum cross section (C70), a constant thickness (b) measured along the outflow direction (C67) of the first flow-through unit (C29).

44. The exhaust gas aftertreatment device according to any one of claims 37 to 43, It is characterized in that The housing (C27) comprises two partial shells (C38, 39) connected to each other, and the first flow-through unit (C29) is at least partially arranged in the first partial shell (C38), and the second flow-through unit (C30) is at least partially arranged in the second partial shell (C39).

45. The exhaust gas aftertreatment device according to claim 44, It is characterized in that The first housing section (C38) has all inflow openings (C31, 32) of the exhaust gas aftertreatment device (C26), and the second housing section (C39) has all outflow openings (C33).

46. ​​An exhaust gas aftertreatment device according to any one of claims 37 to 45, It is characterized in that The first inlet opening (C31) and the second inlet opening (C32) do not overlap with the outlet opening (C33) when viewed along the outflow direction (C67) of the first flow-through unit (C29).

47. An exhaust gas aftertreatment device according to any one of claims 37 to 46, It is characterized in that The housing (C30) has a step (C36) at which the second inflow opening (C32) is arranged.

48. An exhaust gas aftertreatment device according to any one of claims 37 to 47, It is characterized in that At least one flow-through unit (C29, C30), in particular both flow-through units (C29, C30), are at least partially formed from metal wires, in particular from a wire mesh.

49. The exhaust gas aftertreatment device according to any one of claims 37 to 48, It is characterized in that At least one flow-through unit (C29, C30), in particular two flow-through units (C29, C30), are each formed by at least one flow-through body (C41).

50. An exhaust muffler having a first muffler chamber (C47) and a second muffler chamber (C48) separated by a separation wall (C28), wherein: An exhaust gas aftertreatment device (C26) according to any one of claims 37 to 49 is arranged in a connecting opening (C50) between the first muffler chamber (C47) and the second muffler chamber (C48).

51. The exhaust muffler according to claim 50, It is characterized in that An inlet opening (C24) into the first muffler chamber (C47) does not overlap with an inlet opening (C31, C32) of the exhaust gas after-treatment device (C26) in a direction parallel to an outflow direction (C67) of the first flow-through unit (C29) through the exhaust gas after-treatment device (C26).

52. The exhaust muffler according to claim 50 or 51, It is characterized in that The exhaust muffler (C23) has a bypass passage (C61) which forms a flow route through the exhaust muffler (C23) and bypasses the exhaust after-treatment device (C26).

53. An exhaust gas aftertreatment device, comprising a first flow-through unit (D29) and a second flow-through unit (D30) arranged in a housing (D37) of the exhaust gas aftertreatment device (D26), wherein: The second flow-through unit (D30) has a catalytic coating, and the first flow-through unit (D29) has no catalytic coating or has a catalytic coating with a smaller mass per volume unit than the second flow-through unit (D30), wherein the first flow-through unit (D29) has an outflow surface (D61), It is characterized in that the shell (D37) has at least one transfer opening (D34) through which the exhaust gas can flow from the first flow unit (D29), especially through the outflow surface (D61) to the second flow unit (D30), and the shell (D37) has at least one outflow opening (D32) through which the exhaust gas can escape from the first flow unit (D29), especially through the outflow surface (D61) from the shell (D37) without first passing through the second flow unit (D30).

54. The exhaust gas after-treatment device according to claim 53, It is characterized in that The housing (D37) of the exhaust gas aftertreatment device (D26) has at least one further outflow opening (D33) through which the exhaust gas can flow out of the housing (D37) from the second flow-through unit (D30).

55. The exhaust gas aftertreatment device according to claim 53 or 54, It is characterized in that The first flow-through unit (D29) completely covers the second flow-through unit (D30) in the viewing direction along the outflow direction (D64).

56. An exhaust gas aftertreatment device according to any one of claims 53 to 55, It is characterized in that In a viewing direction opposite to an outflow direction (D64) directed from the first flow unit (D29) to the second flow unit (D30) from an outflow surface (D61) perpendicular to the first flow unit (D29), the first flow unit (D29) protrudes beyond the second flow unit (D29) by at least 3 mm at each circumferential position of the second flow unit (D30).

57. An exhaust gas aftertreatment device according to any one of claims 53 to 56, It is characterized in that Exhaust gas can escape from the first flow-through unit (D29) through a plurality of outflow openings (D32) of a housing (D37) of the exhaust gas aftertreatment device (D26), wherein the plurality of outflow openings are distributedly arranged around the second flow-through unit (D30) in a viewing direction opposite to an outflow direction (D64) of the first flow-through unit (D29).

58. An exhaust gas aftertreatment device according to any one of claims 53 to 57, It is characterized in that The maximum cross-section (D69) of the first flow-through unit (D29) is greater than the maximum cross-section (D70) of the second flow-through unit (D30), in particular at least 130% of the maximum cross-section (D70) of the second flow-through unit (D30), wherein the cross-sections (D69, D70) are perpendicular to the main flow direction (D35) through the exhaust gas aftertreatment device (D26).

59. An exhaust gas aftertreatment device according to any one of claims 53 to 58, It is characterized in that The housing (D37) of the exhaust gas aftertreatment device (D26) comprises two partial housings (D38, D39) connected to each other, wherein in particular the first flow-through unit (D29) is mainly arranged in the first partial housing (D38), and the second flow-through unit (D30) is mainly arranged in the second partial housing (D39).

60. An exhaust gas aftertreatment device according to any one of claims 53 to 59, It is characterized in that The housing (D37) of the exhaust gas aftertreatment device (D26) has at least one inflow opening (D31).

61. The exhaust gas aftertreatment device according to claims 59 and 60, It is characterized in that The first partial housing (D38) has all inflow openings (D31) of the housing (D37) of the exhaust gas aftertreatment device (D26), and the second partial housing (D39) has all outflow openings (D32, D33) of the housing (D37) of the exhaust gas aftertreatment device (D26).

62. An exhaust gas aftertreatment device according to any one of claims 53 to 60, It is characterized in that At least one flow-through unit (D29, D30), in particular at least the first flow-through unit (D29), is at least partially composed of metal wires, in particular a wire mesh.

63. An exhaust gas aftertreatment device according to any one of claims 53 to 62, It is characterized in that The second flow-through unit (D30) has a carrier (D58) having channels (D57) for the exhaust gas that are separated from one another.

64. An exhaust gas aftertreatment device according to any one of claims 53 to 63, It is characterized in that At least one flow-through unit (D29, D30) is formed by at least one flow-through body (D46), wherein in particular two flow-through units (D29, D30) are each formed by a flow-through body (D46).

65. An exhaust muffler having a first muffler chamber (D47) and a second muffler chamber (D48) separated by a separation wall (D28), wherein: An exhaust gas aftertreatment device according to any one of claims 53 to 64 is arranged in a connecting opening (D49) between the first muffler chamber (D47) and the second muffler chamber (D48).

66. The exhaust muffler according to claim 65, It is characterized in that The at least one outflow opening (D32) leads from the first flow-through unit (D29) into the second silencer chamber (D48).

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