摘要:
Based on the transmission principle of cycloidal pinwheel drive,the tooth profile of pinwheel is regarded as a special constant curvature elliptic curve with overlapped focuses.Then a new high-performance small tooth difference planetary drive,which takes the variable curvature elliptical curve as internal tooth profile,is proposed.The axial length coefficient λ is introduced to analyze the geometric principle of variable curvature elliptical curve,an elliptical internal tooth profile equation is derived based on differential geometry and conjugate engagement theory,and accordingly the conjugate profile equation is deduced.The meshing line,undercutting condition,meshing boundary,pressure angle,induced normal curvature and sliding ratio of this new gear drive are analyzed.Results show that this new gear drive has multi-teeth meshing property,and the theoretical methods for the conjugate profile undercutting judgment and elliptical tooth root optimal design are provided separately by undercutting boundary function and meshing boundary.Compared with cycloidal drive,when the tooth height is determined,the pressure angle,induced normal curvature and sliding ratio in sensitive sliding range can be reduced by decreasing axial length coefficient λ.Further,the reducer unit of variable valve timing system is designed by applying this new gear drive,and simulation analysis of the reducer unit is conducted.Results indicate that the superior transmission efficiency and high transmission precision of this new gear drive are demonstrated compared with the same type of cycloidal drive.Finally,a prototype is produced,and its backlash is tested,which meets the design requirements well,suggesting that the simulation model and simulation result of this new reducer unit are reasonable.%根据摆线针轮少齿差行星传动原理,把圆形针齿齿廓看作两焦点重合的特殊定曲率椭圆曲线,在此基础上提出了一种新型高性能变曲率椭圆内齿型少齿差行星齿轮副:引入轴长系数λ分析了变曲率椭圆齿廓曲线的几何原理;基于微分几何和齿轮啮合原理,建立了新型变曲率椭圆内齿齿廓方程,并推导了与其共轭的少齿差行星齿廓方程;分析了该新型齿轮副的啮合线、根切条件、啮合界限、压力角、诱导法曲率和滑动率等啮合特性.研究表明:新型齿轮副具有多齿啮合特性;根切界限方程和啮合界限模型分别为共轭齿廓的根切判定、椭圆内齿的齿根优化提供了有效的理论设计方法;相对于摆线行星传动,当齿高确定时,减小轴长系数λ可降低齿轮副压力角、诱导法曲率以及滑动率敏感区间的滑动率幅值和平均值.应用该新型齿轮副对发动机可变气门正时系统的减速装置进行了机构设计与传动性能仿真分析,结果表明:相对于同类型的摆线行星传动,新型齿轮副在传动效率与传动精度方面具有优势.最后加工出了减速装置的物理样机,并测试了样机的回差.测得的回差能很好地满足设计要求,表明回差仿真模型与仿真结果具有合理性.