exhaust silencer

Abstract

An exhaust silencer comprises a silencer housing (126) with an exhaust gas inlet (124) and an exhaust gas outlet (125), as well as a coated flow-through body (131) arranged in the flow path from the exhaust gas inlet (124) to the exhaust gas outlet (125), and an exhaust gas guide device (136) arranged downstream of the flow-through body (131). The flow-through body has a longitudinal axis (137). The longitudinal axis runs parallel to a main flow direction through the flow-through body (131). In a silencer section (152), which extends between two planes (156, 157) running perpendicular to the longitudinal axis (137), the exhaust gas guide device (136) has a first flow-through chamber (138) which extends at least partially around the outer circumference (171) of the flow-through body (131).A second flow space (139) extends in the silencer section (152) at least partially around the outer circumference (145) of the first flow space (138) and is arranged downstream of the first flow space (138).

Description

[0001] The invention relates to an exhaust silencer of the type specified in the preamble of claim 1.

[0002] From US Patent 5,612,006 A, an exhaust silencer with a catalytic converter is known. A sheet metal plate wound spirally around the catalytic converter is arranged on its outer circumference. The exhaust gases flow through a perforated plate at the end face into the space formed between the turns of the spiral plate and from there out of the exhaust silencer.

[0003] CN 102 400 755 A discloses an exhaust silencer with a labyrinth structure formed by nested cups.

[0004] The invention is based on the objective of creating an exhaust silencer of the generic type with a simple design, with which good exhaust emission values ​​can be achieved.

[0005] This problem is solved by an exhaust silencer with the features of claim 1.

[0006] The exhaust silencer comprises a coated flow element. Downstream of the flow element, an exhaust guide is arranged within the silencer housing. In internal combustion engines, particularly premixed-lubricated engines, particles can be present in the exhaust gas. In premixed-lubricated engines, these particles originate predominantly from the oil mixed with the fuel. To reduce the number and size of the particles, a sufficiently long residence time of the particles in a sufficiently high temperature is advantageous. Here, the particles can be broken down and / or partially combusted.

[0007] In exhaust silencers, heat is generated, particularly in a coated flow chamber. To utilize this heat for further exhaust gas treatment, especially for reducing particulate matter, the exhaust guide assembly comprises a first flow chamber and a second flow chamber. The first flow chamber extends at least partially around the outer circumference of the flow chamber. The second flow chamber extends at least partially around the outer circumference of the first flow chamber within the same silencer section. The second flow chamber is located downstream of the first flow chamber.

[0008] The flow chambers are arranged around the outer circumference of the flow body, with the downstream second flow chamber extending along the outer circumference of the first flow chamber. This creates a nested arrangement of the flow chambers. As a result, the exhaust gases can be heated by the flow body and, due to the arrangement of at least two flow chambers, retained in the hot zone of the exhaust silencer for a comparatively long time.

[0009] The fact that the second flow chamber is located downstream of the first flow chamber means that exhaust gases must first flow through the first flow chamber before they can enter the second flow chamber.

[0010] The first flow chamber extends at least partially around the outer circumference of the flow body. In particular, the first flow chamber extends over at least 80% of the outer circumference of the flow body. In particular, the second flow chamber extends completely around the outer circumference of the first flow chamber. In particular, the second flow chamber extends completely around the outer circumference of the first flow chamber. In particular, the second flow chamber forms a closed ring around the outer circumference of the first flow chamber.

[0011] The first flow space extends in the silencer section, in particular from one plane to the other that bounds the silencer section.

[0012] In particular, a first transfer zone is formed at a downstream end face of the first flow chamber, through which exhaust gases from the first flow chamber can pass into the second flow chamber. The flow chambers are directly connected to each other via the transfer zone. This allows for a compact design and enables the exhaust gas temperature to be maintained at a comparatively high level.

[0013] In particular, the exhaust gas guide includes a third flow chamber. This third flow chamber extends at least partially around the outer circumference of the second flow chamber within the silencer section and is located downstream of the second flow chamber. The third flow chamber further increases the residence time of the exhaust gases in the area of ​​the outer circumference of the flow chamber. It prevents the rapid dissipation of heat from the exhaust gases to the environment, thus forming thermal insulation around the first and second flow chambers. The third flow chamber extends over at least 80% of the outer circumference of the second flow chamber. Specifically, the third flow chamber extends completely around the outer circumference of the second flow chamber.The third flow chamber extends in the silencer section, in particular in a ring shape around the outer circumference of the second flow chamber.

[0014] The first flow chamber, the second flow chamber, and the third flow chamber extend, in particular, within the same region of the outer circumference of the flow body. The first flow chamber, the second flow chamber, and the third flow chamber are, in particular, nested within one another.

[0015] A simple design results when at least one flow chamber is at least partially bounded by a pipe section. This pipe section runs completely around the flow body. The pipe section is a longitudinal segment of a pipe that is closed on its circumference. The cross-sectional shape of the pipe can be arbitrary and can be selected to suit the dimensions of the exhaust silencer.

[0016] At least one flow chamber is bounded by two pipe sections. One pipe section bounds the flow chamber, particularly on the inner side facing the flow body, and the other pipe section bounds the flow chamber, particularly on the outer side furthest from the flow body. This results in a simple design for the exhaust silencer.

[0017] An advantageous design results when the exhaust gas guide is configured such that the exhaust gas flows in opposite main flow directions on at least one pipe section: on the inner side facing the flow body and on the outer side facing away from the flow body. The opposing flow direction allows for a simple design and good heat transfer through the pipe section.

[0018] A simple exhaust silencer design is achieved when at least two pipe sections, defining a flow space, are connected to the silencer housing at opposite ends. Connecting the pipe sections to the silencer housing at opposite ends allows for easy installation, as each pipe section can be fixed to a housing shell of the silencer at one end. Once all pipe sections are fixed, the two housing shells can be slid together, forming the exhaust guide.

[0019] In particular, the flow chamber has a partition wall that separates a first silencer chamber from a second silencer chamber. Specifically, the flow body and at least one pipe section are held against the partition wall. Specifically, the second pipe section is also held against the partition wall.

[0020] An advantageous design results when the silencer housing comprises a first housing shell and a second housing shell. The first housing shell, in particular, has the exhaust gas inlet. Specifically, at least one pipe section is held to the second housing shell. A simpler design results when a first pipe section is held to one of the housing shells and a second pipe section is held to the other housing shell. Specifically, the first pipe section and a third pipe section are held to the second housing shell.

[0021] In particular, at least one pipe section lacks a catalytically active coating. This at least one pipe section serves solely to guide the exhaust gas flow, not for catalytic conversion. The conversion of the exhaust gas in the area of ​​the exhaust gas guide device occurs solely due to the temperature and residence time in this area. Specifically, all pipe sections lack a catalytically active coating.

[0022] To prevent the heat from the flow element from radiating to components located at the inlet of the exhaust silencer, particularly an internal combustion engine, a shielding device is arranged upstream of the flow element. The shielding device is specifically designed to ensure direct radiative contact between the flow element and adjacent components, such as an exhaust port or piston assembly of an internal combustion engine. This prevents excessive heating of the internal combustion engine during operation with the exhaust silencer.

[0023] Advantageously, the exhaust silencer features a restrictor upstream of the exhaust outlet. This restrictor serves to adjust the desired exhaust backpressure within the silencer, ensuring a sufficiently long residence time for the exhaust gases. This allows for simple and effective particle conversion within the exhaust system. A simpler design is achieved when the restrictor is integrated into the second housing shell.

[0024] In particular, the flow body is coated with a catalytically active coating and / or a washcoat. This ensures efficient exhaust gas conversion within the flow body. Due to the catalytically active coating and / or the washcoat, high temperatures are achieved within the flow body, which can be utilized in the exhaust gas ducting system to further maintain the high temperature of the exhaust gases.

[0025] In particular, the elements limiting the flow spaces, especially the pipe sections, are not coated with a catalytically effective coating and not with washcoat.

[0026] Exemplary embodiments of the invention are explained below with reference to the drawing. The drawing shows: Fig. 1 a schematic sectional view of a chainsaw, Fig. 2 a perspective view of the exhaust silencer of the chainsaw made of Fig. 1, Fig. 3 a sectional view of the exhaust silencer, Fig. 4. a cut along line IV-IV in Fig. 3, Fig. 5 a cutaway perspective exploded view of the exhaust silencer, Fig. 6 a perspective exploded view of the exhaust silencer, Fig. 7 another cutaway perspective exploded view of the exhaust silencer, Fig. 8 a perspective exploded view of the exhaust silencer, Fig. 9 a sectional view of an exemplary embodiment of the exhaust silencer, Fig. 10 a cutaway perspective exploded view of the exhaust silencer made of Fig. 9, Fig. 11 an exploded view of parts of the exhaust silencer from the Fig. 9 and Fig. 10, Fig. 12 a cutaway exploded view of the parts from Fig. 11.

[0027] Fig. Figure 1 shows a chainsaw 101 as an embodiment of a hand-held tool. Instead of the chainsaw 101, the hand-held tool can also be another tool such as an angle grinder, a brush cutter, a lawnmower, or the like. The hand-held tool is, in particular, a tool carried by the operator during operation.

[0028] The chainsaw 101 has a housing 102 that includes a rear handle 103. Operating elements, in this exemplary embodiment a throttle lever 104 and a throttle lever lock 105, are arranged on the rear handle 103. A guide bar 106 projects from the housing 102, on which a saw chain 107 (shown schematically) is arranged circumferentially. The saw chain 107 is driven by a drive motor arranged in the housing 102, in this exemplary embodiment an internal combustion engine, namely a two-stroke engine 108. Instead of the two-stroke engine 108, another internal combustion engine, in particular a four-stroke engine with mixture lubrication, can also be provided.

[0029] The two-stroke engine 108 includes an air filter 109 through which air is drawn in during operation. Fuel is supplied via a fuel supply device 110, for example a carburetor. A mixture of fuel and two-stroke oil is supplied to the two-stroke engine 108 via the fuel supply device 110.

[0030] The two-stroke engine 108 has an intake port 111 through which air is drawn from the air filter 109 into a crankcase 115 of the two-stroke engine 108. In the exemplary embodiment, the fuel supply device 110 supplies the fuel to the intake port 111. However, the fuel supply can be located elsewhere, for example, in the crankcase 115.

[0031] The two-stroke engine 108 has a cylinder 112 in which a piston 113 is mounted to reciprocate. The piston defines a combustion chamber 114 formed in the cylinder 112. The piston 113 drives a crankshaft 117, which is rotatably mounted in the crankcase 115 about a pivot axis 118, via a connecting rod 116. The interior of the crankcase 115 is fluidically connected to the combustion chamber 114, at least in the region of the piston 113's bottom dead center, via transfer ports 119. A spark plug 120 protrudes into the combustion chamber 114. An exhaust port 121 leads from the combustion chamber 114. The exhaust port 121 is connected via an exhaust channel 122 to an exhaust inlet 124 of an exhaust silencer 123. The exhaust silencer 123 has an exhaust outlet 125 through which exhaust gases escape into the environment.

[0032] During operation, the two-stroke engine 108 draws a fuel / oil / air mixture into the crankcase 115 during the upward stroke of the piston 105. During the downward stroke of the piston 113, the mixture is compressed in the crankcase 115. As soon as the transfer ports 119 open to the combustion chamber 114 during the downward stroke of the piston 113, the mixture flows from the crankcase 115 into the combustion chamber 114. During the upward stroke of the piston 113, the mixture is compressed in the combustion chamber 114 and ignited by the spark plug 120 near the top dead center of the piston 113. The subsequent combustion of the mixture accelerates the piston 113 towards the crankcase 115. As soon as the exhaust port 121 is opened by the piston 113, the exhaust gases flow from the combustion chamber 114 into the exhaust silencer 123. Fresh fuel / oil / air mixture then flows into the combustion chamber 114 via the transfer ports 119 for the next engine cycle.

[0033] The two-stroke engine 108 can also be a scavenging-type two-stroke engine, in which air is pre-positioned in the transfer ports 119 to assist in scavenging the exhaust gases from the previous engine cycle and to separate the incoming fresh mixture from the exhaust gases. The two-stroke engine 108 can also be a premixed-lubricated four-stroke engine.

[0034] Particles are produced during the combustion of the fuel / oil / air mixture. These particles are to be reduced in the exhaust silencer 123.

[0035] Fig. Figure 2 shows an embodiment of the exhaust silencer 123 in a perspective view. The exhaust silencer 123 has a silencer housing 126. In this embodiment, the silencer housing 126 is constructed from two housing shells, namely a first housing shell 127 and a second housing shell 128. A different construction of the silencer housing 126 may also be advantageous. The two housing shells 127 and 128 are connected to each other at a circumferential rim 130. In this embodiment, fastening screws 172 are provided for connecting the housing shells 127 and 128. It is also possible for the housing shells 127 and 128 to be crimped at the rim 130 and thus connected to each other.

[0036] How Fig. Figure 2 shows that the exhaust gas outlet 125 is formed on an outlet plate 129, which is held on the second housing shell 128. In the exemplary embodiment, the exhaust gas outlet 125 is formed by several openings in the outlet plate 129.

[0037] The Fig. 3 and Fig. Figure 4 shows the detailed construction of the exhaust silencer 123. Fig. Figure 3 shows a section through exhaust inlet 124 and exhaust outlet 125.

[0038] A flow-through element 131 is arranged in the silencer housing 126. The flow-through element 131 can, for example, be a body made of pressed metal wire, such as a knitted metal mesh. The flow-through element 131 can also consist of wound flat and corrugated sheets that form a plurality of passage channels through the flow-through element 131 between them.

[0039] The flow body 131 is coated. Specifically, the flow body 131 is coated with a washcoat and / or a catalytically active coating. In this context, a catalytically active coating is defined as a coating that acts as a catalyst, thus lowering the activation energy for the chemical reaction of the exhaust gases and thereby increasing the reaction rate. A washcoat is not considered a catalytic coating in this context. A washcoat is defined as a coating that increases the surface area without lowering the activation energy for the chemical reaction. The flow body 131 can be coated with only a washcoat, only a catalytically active coating, or with both a washcoat and a catalytically active coating. Due to the coating of the flow body 131, efficient exhaust gas conversion is achieved within the flow body 131. The flow body 131 heats up considerably during operation.

[0040] The flow body 131 has an inlet area 178 through which the exhaust gases enter the flow body 131. The flow body 131 has an outlet area 179 through which the exhaust gases exit the flow body 131.

[0041] In the exemplary embodiment, the flow body 131 has an approximately cylindrical shape. A different shape for the flow body 131 may also be advantageous. The flow body 131 has a longitudinal direction 137. The longitudinal direction 137 runs parallel to a main flow direction 180 through the flow body 131. The main flow direction 180 through the flow body 131 runs, in particular, from the inlet surface 178 to the outlet surface 179. The main flow direction 180 runs, in particular, perpendicular to the inlet surface 178. However, a different orientation of the main flow direction 180 may also be advantageous. The longitudinal direction 137 runs, in particular, parallel to a longitudinal center axis of the flow body 131.

[0042] The flow body 131 has a length a. The length a is measured in the main flow direction 180 from the inlet surface 178 to the outlet surface 179. With an irregular surface structure of the flow body 131, the inlet surface 178 and the outlet surface 179 are surfaces of a surrounding body.

[0043] The flow body 131 is surrounded on its outer circumference by several flow chambers 138, 139, 140, 141. In the exemplary embodiment, the flow chambers 138 to 141 extend completely around the flow body 131. The flow chambers 138 to 141 are arranged one after the other with respect to the direction of flow of the exhaust gases through the exhaust silencer 123. In particular, exhaust gases cannot enter a flow chamber located downstream of another flow chamber without first flowing through that other flow chamber. This means, for example, that for the second flow chamber 139 located downstream of the first flow chamber 138, exhaust gases must first flow through the flow chamber 138 in order to enter the second flow chamber 139 located downstream of it.

[0044] The flow-through element 131 is held in a partition 132 of the exhaust silencer 123. The partition 132 separates a first silencer chamber 133 from a second silencer chamber 134. In the exemplary embodiment, the flow passages 138 to 141 are arranged in the second silencer chamber 134. In the exemplary embodiment, the exhaust gas inlet 124 opens into the first silencer chamber 133.

[0045] In the exemplary embodiment, a shielding device 151 is arranged between the inlet surface 178 and the exhaust gas inlet 124, which will be explained in more detail below. A throttle 135 leads from the second silencer chamber 134. Exhaust gases from the second housing shell 128 pass through the throttle 135 into an area covered by the outlet plate 129 and from there through the exhaust gas inlet 124 into the environment.

[0046] The flow chambers 138 to 141 are formed in an exhaust gas guide device 136, which is arranged downstream of the flow body 131. The throttle 135 serves to set a suitable exhaust gas back pressure in order to achieve a desired residence time of the exhaust gases in the exhaust gas guide device 136.

[0047] In the exemplary embodiment, the exhaust gases from the flow body 131 pass directly into the first flow chamber 138. The first flow chamber 138 is connected to the second flow chamber 139 via a transition area 142. The second flow chamber 139 is connected to the third flow chamber 140 via a transition area 143. The third flow chamber 140 is connected to the fourth flow chamber 141 via a transition area 144. From the fourth flow chamber 141, the exhaust gases pass to the throttle 135.

[0048] The transition area 142 is formed at a downstream end face 153 of the first flow chamber 138. The transition area 143 is formed at a downstream end face 154 of the second flow chamber 139. The transition area 144 is formed at a downstream end face 155 of the third flow chamber 140. Through the transition areas 142, 143, 144, exhaust gases from a flow chamber 138, 139, 140 pass into the downstream flow chamber 139, 140, 141.

[0049] In the exemplary embodiment, the flow spaces 138 to 141 are nested within one another. In this embodiment, the flow spaces 138 to 141 surround the flow body 131 as annular spaces running around each other.

[0050] In the exemplary embodiment, the flow spaces 138 to 141 are bounded by pipe sections 148, 149 and 150. The pipe sections 148, 149 and 150 are nested within each other.

[0051] The first flow chamber 138 is formed between an outer circumference 171 of the flow body 131 and an inner surface 158 of the first pipe section 148. The first transition area 142 extends along an open end face 168 of the first pipe section 148. The exhaust gases flow in the first flow chamber 138 in a main flow direction 164. In the exemplary embodiment, the main flow direction 164 is opposite to the main flow direction 180 in the flow body 131.

[0052] The second flow chamber 139 extends along an outer circumference 145 of the first flow chamber 138. How Fig. As shown in Figure 4, the second flow chamber 139 is bounded by an outer surface 159 of the first pipe section 148 and an inner surface 160 of the second pipe section 149. Fig. Figure 3 shows that a main flow direction 165 in the second flow chamber 139 runs approximately parallel to the main flow direction 180 in the flow body 131. The main flow directions 164 and 165 are opposite to each other.

[0053] The second transition area 143 extends along an open end face 169 of the second pipe section 149. The third flow space 140 is bounded by an outer surface 161 of the second pipe section 149 and an inner surface 162 of the third pipe section 150, as shown. Fig. Figure 4 shows that a main flow direction 166 in the third flow chamber 140 runs as follows: Fig. Figure 3 shows, opposite to the main flow direction 180 in the flow body 131.

[0054] The third transition area 144 is formed on an end face 170 of the third pipe section 150. The fourth flow chamber 141 runs along an outer surface 163 of the third pipe section 150. In the exemplary embodiment, the fourth flow chamber 141 is bounded by the partition 132, the third pipe section 150, and the second housing shell 128. A main flow direction 167 in the fourth flow chamber 141 runs as follows: Fig. Figure 3 shows, parallel to the main flow direction 180 in the flow body 131.

[0055] In the exemplary embodiment, the third pipe section 150 is formed on a pot-shaped sheet metal part. The bottom 187 of the pot defines the area of ​​the first flow chamber 138 adjacent to the outlet surface 179.

[0056] The third flow chamber 140 extends along the outer circumference 146 of the second flow chamber 139. The fourth flow chamber 141 extends at least partially along the outer circumference 147 of the third flow chamber 140. In the exemplary embodiment, the outer flow chambers 139, 140, 141 each extend completely around the outer circumference of the inner flow chambers 138, 139, 140.

[0057] The first flow passage 138 extends completely around the outer circumference 171 of the flow body 131. However, it is also possible for the flow passages 138 to 141 to be interrupted in the circumferential direction. This can be particularly advantageous for reasons of space.

[0058] In this embodiment, the term "pipe section" means a continuous, closed wall. The cross-sectional shape can be largely arbitrary. In particular, a round or rounded rectangular cross-sectional shape can be provided for one or more pipe sections 148 to 150. Specifically, the cross-sectional shape is irregular and adapted to the available installation space. The pipe sections 148, 149, and 150 each run completely around the flow body 131. The pipe sections 148, 149, and 150 are designed as circumferentially closed tubes.

[0059] In this embodiment, the first flow chamber 138 does not extend over the entire length a of the flow body 131 at its outer circumference 171, but rather over a length b of a silencer section 152. The silencer section 152 extends from a first imaginary plane 156 to a second imaginary plane 157. The planes 156 and 157 run parallel to each other and perpendicular to the longitudinal direction 137 of the flow body 131. In this embodiment, the first plane 156 lies between the inlet surface 178 and the outlet surface 179. The second plane 157 coincides with the outlet surface 179 in this embodiment. Other positions of the planes 156 and 157 may also be advantageous. The planes 156 and 157 are spaced apart by a distance corresponding to the length b of the silencer section 152.The length b is in particular at least 20%, in particular at least 50%, in particular at least 75% of the length a of the flow body 131.

[0060] In the first level 156, in particular, an end face of a pipe section is located, specifically an end face 168 of the first pipe section 148. The end face 168 forms a free end of the pipe section 148. At an opposite end face 188, the first pipe section 148 is fixed to the base 187 of the pot, which forms the third pipe section 150. The fixing is effected in particular by a welded connection.

[0061] In the silencer section 152, the first flow chamber 138, the second flow chamber 139, the third flow chamber 140, and the fourth flow chamber 141 extend in at least one section plane containing the longitudinal direction 137. One such section plane is, for example, the section plane in Fig. 3. The flow spaces 138, 139, 140, 141 extend continuously from the first level 156 to the second level 157. In particular, the flow spaces 138, 139, 140, 141 extend completely around the longitudinal direction 137 continuously from the first level 156 to the second level 157.

[0062] The Fig. 5 and Fig. Figure 6 shows the structure of the exhaust silencer 123. The first housing shell 127 and a stiffening plate 192 fixed to the first housing shell 127 form a first assembly of the exhaust silencer 123. A second assembly is formed by the partition 132 with the flow element 131 arranged in the partition 132. The partition 132 has a mounting area to which the second pipe section 149 is fixed.

[0063] A third assembly comprises the second housing shell 128 and the pipe sections 148 and 150. Pipe section 148 is fixed at its end face 188 to the base 187 formed on pipe section 150. Pipe section 149 is fixed at its end face 189 to the partition 132. The base 187 abuts the end face 190 of pipe section 150. The end faces 168, 169, and 170 of the pipe sections are exposed and do not touch any other components.

[0064] The three assemblies are connected to each other via the fastening screws 172. The pipe section 149 has a fastening rim 173 on its end face 189. The pipe section 148 has a fastening rim 174 on its end face 188. Fastening studs 175 are arranged on the base 187. The pipe section 150 is held to the second housing shell 128 at a distance from the second housing shell 128 by the fastening studs 175.

[0065] The Fig. 7 and Fig. Figure 8 shows the design of the components in detail. How the Fig. 7 and Fig. As shown in Figure 8, a seal 176 is arranged between the first housing shell 127 and the partition 132. As the Fig. 7 and Fig. As also shown in Figure 8, the shielding device 151 has outwardly projecting mounting arms 177. The mounting arms 177 are intended for fixing to the partition wall 132.

[0066] The Fig. Figures 9 to 12 show an alternative embodiment of an exhaust silencer 123. The design of the exhaust silencer 123 corresponds, except for the design of the shielding device 181, to the design of the preceding embodiment, to whose description reference is made. In the Fig. A shielding device 181, consisting of two sheets, is arranged between the exhaust gas inlet 124 and the inlet surface 178 of the flow body 131, from 9 to 12. The sheets are spaced a distance d apart from each other, measured parallel to the longitudinal axis 137. Due to the distance d between the two sheets 182 and 183, the shielding device 181 requires more installation space than the shielding device 151.

[0067] As the Fig. 10, Fig. 11 and Fig. As shown in Figure 12, the shielding device 181 comprises a first sheet 182 and a second sheet 183, each having openings 184. The openings 184 of the two sheets 182 and 183 are not aligned relative to each other when viewed from the exhaust gas inlet 124 to the flow body 131. The openings 184 are offset from each other. As a result, the inlet area 178 is covered by the shielding device 181.

[0068] As the Fig. 11 and Fig. Figure 12 shows that the first sheet 182 has fastening arms 185. The second sheet 183 has fastening arms 186. Both sheets 182 and 183 are fixed to the partition 132 by the fastening arms 185 and 186.

[0069] In both embodiments, the shielding devices 151, 181 have a distance c to the inflow surface 178 of the flow body 131, as shown by the Fig. 3 and Fig. Figure 9 shows. The distance c is particularly large enough to ensure that the flow body 131 is uniformly supplied with exhaust gas.

[0070] In the illustrated embodiments, the flow chambers 138 to 141 are arranged approximately cylindrically around the flow body 131. The pipe sections 148, 149 and 150 are not connected to each other within the silencer section 152, but rather outside the silencer section 152, in particular via the partition 132 and the housing shell 128.

[0071] In an alternative embodiment, not shown, the flow chambers can be formed in pipes wound spirally around the flow body. A first flow chamber, spirally extending around the flow body 131, extends particularly directly along the outer circumference 171 of the flow body 131. A second pipe section, arranged downstream of the first pipe section, extends radially outside the first pipe section with respect to the longitudinal direction 137. The second pipe section is particularly spirally wound around the first pipe section.

[0072] The first pipe section forms a first flow chamber, and the second pipe section forms a second flow chamber that extends around the outer circumference of the first flow chamber. Further flow chambers can also be formed in a similar manner.

[0073] The shielding devices 151 and 181 form radiation barriers between the two-stroke engine and the flow body 131. Due to the multiple flow chambers 138, 139, 140, 141 arranged in series, the exhaust gases have a very long flow path in the exhaust guide device 136. Because of its position on the outer circumference of the flow body 131, high exhaust gas temperatures can be achieved in the exhaust guide device 136. Due to the high temperature and the long residence time of the exhaust gases resulting from the long flow path, good particle conversion can be achieved in the exhaust guide device 136.

[0074] Because the pipe sections 148 to 150 in the silencer section 152 are not connected to each other, there is no direct heat conduction between the pipe sections. In particular, at least one flow space 138, 139, 140, 141 is a free, unfilled space. In particular, all flow spaces 138, 139, 140, 141 are free, unfilled spaces.

[0075] In particular, the individual parts of the exhaust silencer 123 are connected to each other via spot welds. This ensures low heat transfer between the individual elements. Because the transition areas 142, 143, 144 are formed in the region of the end faces 168, 169, 170 of the pipe sections 148, 149, 150, the free flow cross-section of the transition areas 142 to 144 can be easily adjusted by selecting a suitable position for the end faces 168, 169, 170. This allows for simple structural adaptation of the exhaust silencer 123 to specific requirements without having to fundamentally change its geometry.

Claims

[1] Exhaust silencer comprising a silencer housing (126) with an exhaust inlet (124) and an exhaust outlet (125), with a coated flow element (131) arranged in the flow path from the exhaust inlet (124) to the exhaust outlet (125), and with an exhaust guide device (136) arranged downstream of the flow element (131) in the silencer housing (126), wherein the flow element (131) has a longitudinal direction (137) corresponding to a main flow direction through the flow element (131), wherein the exhaust silencer (123) has a silencer section (152) extending between two imaginary planes (156, 157) perpendicular to the longitudinal direction (137) of the flow element (131) and in which at least a part of the flow element (131) runs, wherein the exhaust guide device (136) has a first flow space (138) includes,which extends at least partially around the outer circumference (171) of the flow body (131) in the silencer section (152), characterized by , that the exhaust gas guide device (136) comprises a second flow chamber (139) which extends at least partially around the outer circumference (145) of the first flow chamber (138) in the silencer section (152) and which is arranged downstream of the first flow chamber (138). [2] Exhaust silencer according to claim 1, characterized by , that a first transfer area (142) is formed on a downstream end face (153) of the first flow chamber (138), through which exhaust gases from the first flow chamber (138) can pass into the second flow chamber (139). [3] Exhaust silencer according to claim 1 or 2, characterized by, that the exhaust gas guide device (136) comprises a third flow chamber (140) which extends at least partially around the outer circumference (146) of the second flow chamber (139) in the silencer section (152) and which is arranged downstream of the second flow chamber (139). [4] Exhaust silencer according to any one of claims 1 to 3, characterized by , that at least one flow space (138, 139, 140) is at least partially bounded by a pipe section (148, 149, 150) that runs completely around the flow body (131). [5] Exhaust silencer according to claim 4, characterized by , that at least one flow space (139, 140) is bounded by two pipe sections (148, 149, 150). [6] Exhaust silencer according to claim 4 or 5, characterized by, that the exhaust gas guide device (136) is designed such that the exhaust gas flows in opposite main flow directions (164, 165, 166, 167) on at least one pipe section (148, 149, 150) on an inner side (158, 160, 162) facing the flow body (131) and on an outer side (159, 161, 163) facing away from the flow body (131). [7] Exhaust silencer according to any one of claims 4 to 6, characterized by , that at least two pipe sections (148, 149, 150) defining a flow space (139, 140) are connected to the silencer housing (126) at different, opposite end faces (188, 189, 190). [8] Exhaust silencer according to any one of claims 4 to 7, characterized by, that the exhaust silencer (123) has a partition (132) that separates a first silencer chamber (133) from a second silencer chamber (134), wherein the flow body (131) and at least one pipe section (149) are held on the partition (132). [9] Exhaust silencer according to claim 8, characterized by , that the second pipe section (149) is held against the partition wall (132). [10] Exhaust silencer according to any one of claims 4 to 9, characterized by , that the silencer housing (126) comprises a first housing shell (127) and a second housing shell (128), wherein the first housing shell (127) has the exhaust gas inlet (124) and wherein at least one pipe section (148, 150) is held on the second housing shell (128).

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