Geometric Characteristics of Tooth Profile and Meshing Properties Changing Laws of Composite Cycloid Planetary Drive with Small Tooth Difference

Aimed at the problems of bigger engaging angle of cycloid-pin gear, lower reliability of turning arm bearing and higher uniform position precision of pinwheel, the composite cycloid, that has a relatively strong controllability in geometry, was utilized to establish the internal tooth profile of small tooth difference planetary drive (STDPD), then a new high-performance STDPD with composite cycloid internal tooth profile (CCITP) was proposed. Based on the geometry principle of traditional cycloid pinwheel drive, the geometrical design method of CCITP was presented, and the impacts of c2 on geometrical shape and curvature were analyzed. Using kinematic conjugate theory of gear meshing, the profile equation of CCITP, the meshing equation of conjugate gear drive, the conjugate profile equation with small tooth difference and action line equation were established. The analysis of meshing boundary properties based on parameter transformation was conducted. According to the mathematic princple that singularity appeared on conjugate profile, the judgement equation for determining whether undercutting occurred or not was derived. Meshing properties including action line, contact ratio, pressure angle, induced normal curvature and sliding ratio of this new gear drive (TNGD) were investigated, sensitivity analysis methods on induced normal curvature and sliding ratio in certain meshing range were put forward. The results indicated that meshing boundary point existed on composite cycloid internal profile, furthermore the effective theoretical methods of both the transition-curve geometry design of internal tooth dedendum and the non-undercutting design of conjugate profile were provided on account of meshing boundary model and undercutting judgement equation. Meanwhile, the analysis result of action line and contact ratio showed that the multi-teeth meshing property of TNGD could be carried out. When the tooth number, eccentricity, tooth height and internal tooth distribution circle of TNGD were determined, c2 was the only gear parameter that really could impact the pressure angle, induced normal curvature and sliding ratio. The minimum and average of planet gear pressure angle decreased with c2, the impacts of c2 on induced normal curvature and sliding ratio were classified into non-sensitive and sensitive ranges in one meshing cycle. The impacts in non-sensitive range could be ignored, while both the average of induced normal curvature and the amplitude and average of sliding ratio in sensitive range were decreased with c2.Compared with the traditional cycloid drive having the same parameters, the advantages on pressure angle, induced normal curvature and sliding ratio of TNGD were shown. Accordingly, better meshing performances in multi-tooth meshing, force transmitting, lubrication, capacity and anti-wear were achieved.Therefore, a certain effect in engineering application of TNGD was showed. © 2017, Editorial Department of Advanced Engineering Sciences. All right reserved.