COMPARISON OF HELICAL AND SKEWED AXIS GEROTOR PUMPS

The gerotor is a planar mechanism consisting of two surfaces whose rel ative motion can be described by the kinematics of orbiting pitch circ les. Typically, gerotor surfaces are prismatic with the axes of rotati on parallel to the ruled surfaces. For a given position, the generated cross section of the mechanism in the plane of motion is independent of the location of the section along the axis of rotation. In this wor k, a mathematical derivation for producing gerotors with non-prismatic surfaces is presented. The implementation results in two types of ger otors, mechanisms with conical surfaces relative to the rotor axis, an d mechanisms with helical surfaces. These are relatively new invention s and this is the first publication of the mathematical model describi ng these mechanisms. The derivations of the mathematics associated wit h each mechanism are presented. Comparisons of the mechanisms are pres ented based on the displacement, compression ratio and surface area to volume ratio. (C) 1997 Elsevier Science Ltd.