Arrangement at a piston engine and method of controlling the pistons

Abstract

A piston engine in the form of a piston pump or a piston engine (motor) comprises two or more piston cylinders (), preferably positioned with the same angular distances of 180 degrees for two cylinders, 120 degrees for three cylinders etc. with regards to an axis, and each comprising a reciprocating piston with a projecting piston rod (). Via the piston rods (), each piston is given a controlled displacement matched to the controlled, given displacement of another or other pistons. The control means is rotatable and influences the projecting outer end portions of the piston rods or parts fitted to these, for instance rotatable rollers (). By a piston pump of this type, the pistons are to contribute to impelling a fluid flow, while a piston engine of this type shall be designed to be driven by a fluid flow. Operating conditions are aimed at which give a more even volume flow, i.e. without any significant fluctuations. For this purpose, said rotatable control means is designed with an encircling cam surface () which the piston rod ends abut via the peripheral surface of said rotatable rollers (). According to a feature of a method associated with the application of such a piston engine, each piston may with advantage be driven at a constant speed through part of its power stroke.