Design of Rotor for Internal Gear Pump Using Cycloid and Circular-Arc Curves

Abstract

In the case of internal gear pumps, the eccentricity of the outer rotor, which resembles a circular lobe, must be limited to a certain value in order to avoid the formation of cusps and loops; furthermore, the tip width of the inner rotor, which has a hypocycloid curve and an epicycloid curve, should not be allowed to exceed the limit value. In this study, we suggest that the tip width of the inner rotor be controlled by inserting a circular-arc curve between the hypocycloid and epicycloid curves. We also suggest that the outer rotor be designed using the closed-form equation for the inner rotor and the width correction coefficient. Thus, it is possible to design a gerotor for which there is no upper limit on the eccentricity, as in this case, undercut is prevented and there is no restriction on the tip width. We also develop an automated program for rotor design and calculation of the flow rate and flow rate irregularity. We demonstrate the superior performance of the gerotor developed in this study by analyzing the internal fluid flow using a commercial computational fluid dynamics (CFD)-code.

The Influence of the form Error after Rotor Manufacturing on the Output Characteristics of an Orbital Hydraulic Motor

“…The relationship between the design features of the rotors and the output characteristics of hydraulic machines has not been studied. The issues associated with wear of the rotors working surfaces in orbital hydraulic motors [6] were investigated. The model which describes the tribological changes in the geometry of the working surfaces of the rotors in those hydraulic motors has been developed.…”

“…The limiting deviations in the form of manufacturing of the gearing surfaces of the inner and outer rotors in the orbital hydraulic motor were not substantiated. The recent studies on displacement kinematics, power interaction and the design of internal and external rotors of orbital hydraulic machines [3][4][5][6][7][8] show one of the main limitations. The fact is that the interaction between rotors was considered as a theoretical (gapless) connection where there are no form errors of the rotor gear surfaces.…”

“…The difficulties provide a certain error in the shape of the gears surface of the rotors (Figure 1). It leads to oscillations of the diametrical gap between the outer (Figure 1, a) and inner (Figure 1, b) rotors [4][5][6][7][8]. During operation, oscillations of the gap have a negative effect on the changes in the output characteristics of an orbital hydraulic motor.…”

Justification of the Kinematic Diagrams for the Distribution System of a Planetary Hydraulic Motor

“…The change in the crosssectional area of the distribution system occurs cyclically and depends on the angle of rotation of the distributor. In the literature [7][8][9] the questions connected with designing of working surfaces of rotors in gerotor machines are considered. The theoretical and practical aspects of the problem were studied, and the mathematical models, which described the design process, were developed.…”

Optimization of Gerotor Pumps with Asymmetric Profiles through an Evolutionary Strategy Algorithm

“…To achieve similar objectives, Hsieh recently published an original solution that makes use of variable clearance designs [25]. A significant amount of research on multiple profiles geometries to optimize the pressure angle during the whole contact cycle can be found in [26][27][28][29][30][31][32][33], while a different approach to rotor design, based on straight-line-conjugated profiles can be found in [33][34][35][36]. Other significant contributions to this research field can be found in [37], while a particularly interesting development on a magnetically-driven gerotor is proposed in [38].…”