design and analysis of logarithmic spiral type sprag one-way clutch

LIU Zhi-hui(刘志辉)^{1, 2, 3}, YAN Hong-zhi(严宏志)^{1, 2}, CAO Yu-ming(曹煜明)^{1, 2}

(1. State Key Laboratory of High-performance and Complex Manufacturing
(Central South University), Changsha 410083, China;
2. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;
3. Department of Mechanical and Energy Engineering, Shaoyang University, Shaoyang 422000, China)

Abstract:A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given. It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing. It takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races, and it can be used for optimization of design and comparison with other types of sprag clutches. A good deal of analysis shows that the parameters of the steady windup angle, the steady contact force, the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race, while the parameters of the maximum transient windup angle, the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of clutch. It is also shown that the strut angle has great influence on the dynamic engagement performance of clutch. The parameters of the steady windup angle, the maximum transient windup angle, the steady engaging time, the steady contact force, the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle, while the natural frequency of the system increases linearly with the inner strut angle.

Key words:mathematical model; logarithmic spiral; one-way clutch; hunt-crossley; windup angle; steady contact force; transient impact force