Membrane pump, in particular for use in an exhaust tract of a combustion engine, and combustion engine with membrane pump

A membrane pump (1, 1', 1"), in particular for use in the exhaust tract of an internal combustion engine (70), with a pressure housing (2), whose internal volume (4) is divided by a number of elastically deformable membranes (6) into a plurality of gas-side separated partial volumes (8, 10), wherein the or each membrane (6) is subjected to a bias force such that in the unpressurized state the partial volume (8) forming the primary side has a minimum value within the limits of the deformability of the or each membrane (6), is intended to have a particularly efficiency-enhancing effect when used in the exhaust system of an internal combustion engine (70). For this purpose, according to the invention, the inner side (36) of the partial volume (8) forming the primary side has a continuously expanding cross-section in a diffuser region (40) extending from an inflow surface (23) towards the membrane (6), wherein in the unpressurized state the point of the membrane (6) projecting furthest into the partial volume (8) forming the primary side is spaced at least 5 mm from the inflow surface.