Process of manufacturing an air-gap-insulating exhaust elbow of a vehicle exhaust system

Abstract

A process for manufacturing an air-gap-insulated exhaust elbow of a motor vehicle exhaust system achieves in a simple manner a manufacturing of space-saving air-gap-insulating exhaust elbows which is reliable with respect to the process and can be precisely reproduced. The exhaust elbow is joined together from several air-gap-insulated exhaust pipes as well as the pertaining entry flanges and the exit flange, which, by way of an internal high-pressure metal forming process, are shaped in an air-gap-insulating manner from one double pipe respectively. The ends of the air-gap-insulated exhaust pipes which are to be connected with one another are first trimmed while opening the respective air insulating gap and are then fitted into one another. In such case, the ends are shaped such that the fitted connections of the outer pipes and of the inner pipes of the exhaust pipes to be connected are made with play. The mutually connected outer pipe ends of the exhaust pipes are welded together at the point of their fitted connection while forming a circular bead. The connection-free ends of the exhaust pipes to be connected to the cylinder head are fitted together with the respective pertaining entry flanges and are welded together and the connection-free end, which faces away from the cylinder head, of the last one of the branched exhaust pipes arranged in a row side-by-side, is fitted together with the exit flange and is welded to the latter.