Roller vane pump

Abstract

A roller vane pump, in particular suited for pumping fluid in a continuously variable automatic transmission of a motor vehicle, is provided with a pump housing ( ) accommodating a carrier ( ) rotatable around a central axis ( ) of the carrier in a direction of rotation by a pump shaft ( ), on the periphery of the carrier ( ) there is provided a slot ( ), which extends in a substantially radial direction and accommodates an essentially cylindrically shaped roller element ( ) having a roller diameter (D ) for interaction with a radially inner cam surface ( ) of a cam ring ( ) encompassing the carrier ( ) in radial direction. The cam surface ( ) is located at a radial distance (R) from the central axis ( ) that varies in dependence on an angular rotation (&phgr;) according to a cam curve (R{&phgr;}). The cam ring ( ) is shaped such that a second order mathematical derivative of the cam curve (R″{&phgr;}) shows a maximum value (R″ ) at a value for the angular rotation (&phgr;), which is smaller than a radial distance (R) at the value of the angular rotation according to the cam curve (R{&phgr;}) minus half the value of the roller diameter (D ).