Effect of Interference on a Floating Axis Epitrochoidal Hydrostatic Unit

Abstract

In the present work, the effect of inclusion of interference on the performance of an Epitrochoidal Hydrostatic Rotary Piston Machine, namely Orbit motor is studied by building its mathematical model and implementing the algorithm in MATLAB. In this approach, the rotor is rigid, rollers are elastic and interference between the rotor and the stator is provided by changing the roller radius, chordal thickness and the pitch circle radius. In an Orbit motor of interference-fit type, the contact points and the rotor center deviate from their original position as found in an Orbit motor of perfect-fit type. A corrective technique based on minimum potential energy of the system is used to obtain the rotor center of an interference-fit motor, starting from the geometrically obtained rotor center of a perfect-fit motor, correcting itself to its final position. For various positions of the output shaft, the forces and torque acting on the rotor are calculated. For positions other than those corresponding to that of maximum compression and maximum expansion of chambers, it is found that a net unbalanced torque acts on the rotor. This torque tends to bring the rotor back to the nearest position of maximum compression. Apart from the determination of the unbalanced torque, the variation of deformation and maximum contact pressure at the contact points between the rotor and the stator due to sole inclusion of interference, for the first two phases of the rotor rotation is also investigated.