Patent ID: 6699025
Filing Date: 2004-03-02
Classification: F01C

Abstract:
Roller vane pump for pumping fluid in a continuously variable automatic transmission of a motor vehicle, provided with a pump housing (12) accommodating a carrier (4) rotatable around a central axis (4a) of the carrier in a direction of rotation by a pump shaft (5), on the periphery of the carrier (4) there is provided a slot (6), which extends in a substantially radial direction and which accommodates an essentially cylindrically shaped roller element (7) having a roller diameter (DR) for interaction with a radially inner cam surface (2a) of a cam ring (2) encompassing the carrier (4) in radial direction, which cam surface (2a) is located at a radial distance (R) from the central axis (4a) that varies in dependence on an angular rotation (&phgr;) according to a cam curve (R{&phgr;}), characterised in that the cam ring (2) is shaped such that a second order mathematical derivative of the cam curve (Râ€³{&phgr;}) shows a maximum value (Râ€³MAX) at a value for the angular rotation (&phgr;), which is smaller than a radial distance (R) at said value of the angular rotation according to the cam curve (R{&phgr;})) minus half the value of the roller diameter (DR).