In view of problems that are the screw and nut in the trans-rotary magnetic gear (TRMG) has no direct mechanical contact and the motion transformation between rotation of screw and linear motion of nut achieves through magnetic coupling, the transmission principle, ratio and thrust force of TRMG were analyzed, and the relationships of ratio and thrust force to pole pitch, number of pole pair, pole width, and screw diameter were derived respectively.The constraint condition between pole width, number of pole pair, and screw diameter was established.The influences of pole pitch, airgap, thickness of pole and steel yoke both in screw and nut to stall force (maximum thrust force) were investigated by means of 3D FEM.The result shows that airgap has the greatest influence to stall force, and it almost decreases linear when airgap increases.When pole pitch increases, stall force changes in approximate parabolic relationship, and it gets the maximum value when pole pitch is 8 mm.The influence of thickness of poles both in screw and nut is similar, that is the larger the thickness of poles, the greater the stall force.When pole thicknesses is ≤5 mm, the stall force changes fast, and when it exceeds 5 mm, stall force changes tended to be gentle.The thickness of steel yokes in both screw and nut has no influence to stall force.%针对永磁丝杠的丝杠和螺母之间不存在机械接触,两者依靠永磁体磁场的耦合实现丝杠旋转运动与螺母直线运动之间的运动变换等问题,对永磁丝杠的传动原理、传动比及推力进行理论分析,推导出传动比和推力与磁极节距、磁极对数、磁极宽度及丝杠直径等结构参数之间的关系式,提出磁极宽度、磁极对数和丝杠直径3者的约束条件.通过有限元仿真,对磁极节距、气隙长度、磁极厚度及轭铁厚度等因素对推力的影响进行研究.结果表明,气隙长度对推力的影响最大,且随着气隙长度增大,推力近乎线性减小.推力随磁极节增大以近似抛物线的关系变化,且在磁极节距8 mm时推力达到最大值.丝杠和螺母的磁极厚度变化对推力的影响基本相同,即磁极厚度越大推力越大;但在磁极厚度≤5 mm时推力变化较快,当磁极厚度超过5 mm后推力变化趋于平缓.丝杠和螺母轭铁厚度的变化对推力没有影响.
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