Exhaust gas purification apparatus for an internal combustion engine of motor vehicles

Claim 1

In an exhaust gas purification apparatus for an internal combustion engine including a catalyst chamber containing a catalyst composition comprising noble metals of the platinum group for the catalytic conversion of harmful substances contained in the exhaust gases of the internal combustion engine deposited on a catalyst carrier therefor, which chamber is connected to one end of an exhaust pipe, the other end of said exhaust pipe being connected to the internal combustion engine, said exhaust pipe having relatively thin walls, wherein the catalyst carrier is susceptible to melting and damage at incompatibly high temperatures in said catalyst chamber caused by ignition and combustion of unburned hydrocarbon fuel resulting from improper or incomplete burning in the combustion engine of the fuel-air-mixture produced in the carburetor and the inability of said carrier to sufficiently rapidly conduct away the heat generated as a result of said ignition and combustion. the improvement which prevents large quantities of non-ignited fuel-air mixtures from reaching the catalyst chamber containing said carrier, and comprising at least a part of the inside wall of the exhaust pipe connecting the internal combustion engine with the catalyst chamber being coated with a noble metal of the platinum group containing layer wherein the exterior and interior surfaces of said exhaust pipe do not have any other coating applied thereto, whereby any fuel-air mixtures leaving the internal combustion engine in a non-ignited or unburned condition will be ignited and burned in said part of the exhaust pipe which is coated with said catalytically active coating, and the substantial quantities of heat released by the combustion in said exhaust pipe being radiated to a relatively large extent to the atmosphere through the relatively thin walls of the exhaust pipe, so that the temperature in the catalyst chamber is not raised sufficiently high to fuse or melt the catalyst carrier, and whereby the catalyst carrier containing the catalyst composition is protected against overheating due to unwanted ignition and burning.