Handheld work apparatus, and exhaust gas after-treatment unit for a handheld work apparatus, and exhaust muffler

Abstract

A handheld work apparatus includes a combustion engine and an exhaust muffler. A first muffler chamber and a second muffler chamber are formed in the exhaust muffler. The exhaust muffler includes an exhaust gas after-treatment unit which includes at least one through-flow unit. The through-flow unit is disposed in a flow path from the first muffler chamber into the second muffler chamber. The thickness of the through-flow unit measured from an upstream end face to a downstream end face of the through-flow unit in the region of the through-flow unit passed through by a flow of exhaust gas is at least 10 mm across at least 70% of the cross section. The exhaust gas after-treatment unit does not have a catalytically effective coating.

1 . A handheld work apparatus comprising:
 a combustion engine;   an exhaust muffler having a first muffler chamber and a second muffler chamber formed therein;   said exhaust muffler including an exhaust gas after-treatment unit which includes at least one through-flow unit;   said at least one through-flow unit being disposed in a flow path from said first muffler chamber into said second muffler chamber and having a thickness measured from an upstream end face to a downstream end face of said at least one through-flow unit in a region of said at least one through-flow unit passed through by a flow of exhaust gas of at least 10 mm across at least 70% of a largest cross section; and,   wherein said exhaust gas after-treatment unit does not have a catalytically effective coating.   
     
     
         2 . The work apparatus of  claim 1 , wherein said at least one through-flow unit is at least partially coated with a washcoat. 
     
     
         3 . The work apparatus of  claim 1 , wherein said at least one through-flow unit includes at least one wire element of metal. 
     
     
         4 . The work apparatus of  claim 3 , wherein a wire cross section of said at least one wire element of the exhaust gas after-treatment unit is at least 0.07 mm 2 . 
     
     
         5 . The work apparatus of  claim 3 , wherein a wire of said at least one wire element is made at least partially of a nickel alloy or of stainless steel. 
     
     
         6 . The work apparatus of  claim 3 , wherein a density of said at least one wire element at least in the region passed through by a flow of exhaust gas is 0.6 g/cm 3  to 2 g/cm 3 . 
     
     
         7 . The work apparatus of  claim 3 , wherein a sum of volumes of regions passed through by a flow of all of said at least one wire element of said through-flow unit is at least 0.6 times a cubic capacity of said combustion engine. 
     
     
         8 . The work apparatus of  claim 3 , wherein said at least one wire element is formed from a knitted metal mesh. 
     
     
         9 . The work apparatus of  claim 3 , wherein said at least one wire element is helically wound. 
     
     
         10 . The work apparatus of  claim 9 , wherein said at least one wire element is disposed in said exhaust muffler such that a winding axis extends through an upstream end face and a downstream end face of said at least one wire element. 
     
     
         11 . The work apparatus of  claim 1 , wherein a smallest cross section of said at least one through-flow unit in the region of the at least one through-flow unit passed through by a flow of exhaust gas is at least 8 mm 2  per cubic centimeter of a cubic capacity of said combustion engine. 
     
     
         12 . The work apparatus of  claim 1 , wherein said exhaust muffler has an exhaust inlet into said exhaust muffler and an exhaust outlet from said exhaust muffler; and, at least one of said at least one through-flow unit is disposed in each flow path from said exhaust inlet to said exhaust gas outlet. 
     
     
         13 . The work apparatus of  claim 1 , wherein said exhaust muffler has an exhaust inlet into said exhaust muffler and an exhaust outlet from said exhaust muffler; and, at least one of wire element of the exhaust gas after-treatment unit is disposed in each flow path from said exhaust inlet to said exhaust gas outlet. 
     
     
         14 . The work apparatus of  claim 1 , wherein said second muffler chamber has a volume which is at least 80% of a cubic capacity of said combustion engine. 
     
     
         15 . The work apparatus of  claim 1 , wherein said combustion engine is a mixture-lubricated combustion engine. 
     
     
         16 . The work apparatus of  claim 1 , wherein the work apparatus is configured such that a temperature of an exhaust gas flow on an upstream side of said exhaust gas after-treatment unit after at least 2 minutes of operating time of said combustion engine under full load is 450° C. to 750° C. 
     
     
         17 . The work apparatus of  claim 1 , wherein said combustion engine is a two-stroke engine. 
     
     
         18 . An exhaust muffler, in particular for a mixture-lubricated combustion engine in a handheld work apparatus, comprising:
 an exhaust inlet;   an exhaust outlet;   a first muffler chamber;   a second muffler chamber;   a first through-flow unit for exhaust gas after-treatment;   a second through-flow unit for exhaust gas after-treatment;   said first muffler chamber being disposed upstream of said second muffler chamber;   said second through-flow unit having a catalytically effective coating in at least one portion;   said first through-flow unit having a smaller quantity of catalytically effective coating in terms of volume than said second through-flow unit or no catalytically effective coating;   wherein a first flow path and a second flow path from said first muffler chamber into said second muffler chamber are formed in the exhaust muffler;   wherein flow cross sections of said first flow path and said second flow path are structurally predefined and invariable;   said first flow path leading through said first through-flow unit and bypassing said second through-flow unit;   said second flow path leading through said second through-flow unit and bypassing said first through-flow unit; and,   said first through-flow unit and said second through-flow unit being disposed so as to be spatially separated from one another.   
     
     
         19 . An exhaust gas after-treatment unit comprising:
 a housing;   a first through-flow unit and a second through-flow unit disposed in said housing;   said first through-flow unit having a catalytic coating;   said second through-flow unit not having a catalytic coating or having a smaller mass of catalytic coating per volumetric unit than said first through-flow unit;   said housing defining at least one first inflow opening into said first through-flow unit, at least one second inflow opening into said second through-flow unit, and at least one transfer opening from said first through-flow unit into said second through-flow unit;   said first through-flow unit having an outflow surface and an outflow direction which is oriented perpendicularly to said outflow surface from said first through-flow unit to said second through-flow unit;   said second through-flow unit having an inflow surface; and,   said inflow surface of said second through-flow unit does not protrude beyond a plane containing said outflow surface.   
     
     
         20 . An exhaust gas after-treatment unit comprising:
 a housing;   a first through-flow unit and a second through-flow unit which are disposed in said housing;   said second through-flow unit having a catalytic coating;   said first through-flow unit not having a catalytic coating or having a smaller mass of catalytic coating per volumetric unit than said second through-flow unit;   said first through-flow unit having an outflow surface;   said housing having at least one transfer opening through which exhaust gas from said first through-flow unit can flow to said second through-flow unit; and,   said housing having at least one outflow opening through which exhaust gas from said first through-flow unit can exit said housing without having previously passed through said second through-flow unit.