Research On Miniature Magnetic Planetary Gear

As a new non-contact transmission mechanism, the permanent magnetgearbox (MPG) has advantages of complete isolation between different gears,noise elimination, free of lubrication and maintenance, low starting torque andauto-protection against overload in comparison with the traditional mechanicalgearbox. Besides these advantages as mentioned above, MPG also has meritsincluding large transmission power, wide range of transmission ratio, compactstructure and strong overload ability, which is absolutely worth researching.In this paper, the miniature MPG has been studied. The main aspects are asfollows: parameter constraint and its basic equations, special problems ofpermanent magnetic gearbox coupling, three excitation methods of ring gear,winding analysis and design of electro-magnetic structure, and structureanalysis of hybrid excitation.Firstly, the operation principle and speed reduction ratio of MPG areanalyzed. The torque equation between sun gear and planetary gear, the torqueequation between ring gear and planetary gear and the torque of drive systemare derived, respectively. Parameter constraints of drive system are studied, andthe pole pairs allocation plan and its variation law of each magnetic gear arediscussed and analyzed. In this way, the design parameter of MPG is obtainedso that simulation model is built.Secondly, special problems of magnetic coupling are simulated andanalyzed, including the research value of coupling particularity. In comparisonwith the condition that polar distance of sun gear is equal to that of planetarygear, the condition that polar distance of sun gear is unequal to that of planetarygear, and that polar distance of north magnetic pole is unequal to that of southmagnetic pole on planetary gear, and the effects of magnetic steel shape ontransmitted torque are analyzed respectively in this article.Thirdly, three excitation methods of ring gear on MPG are analyzed usingfinite element method. The MPG model is simulated, including value andvariation law of transmitted torque and cogging torque, and followingcharacteristic between input angle and output angle. Moreover, structure designand flux density analysis of hybrid excitation MPG are studied, includingcomparison of flux density of MPG under three different excitation of ring gear,and feasibility analysis of hybrid excitation structure.At last, operation principle of modulating speed reduction ratio is analyzed.And distribution and connection of electrical excitation winding is designed in corresponding with three types of speed reduction. Operating characteristics ofelectrical excitation MPG are analyzed, including the static torquecharacteristic, load analysis of MPG and following characteristic between inputangle and output angle.