A Thermal EHI Investigation For Infinite/Finite Line Contacts On Hinge Pairs In Chain Drive

In this thesis,the thermal elastohydrodynamic lubrication(EHL)theory is used to evaluate the lubrication state of bush chain,roller chain and silent chain in the contact zone of their hinge pairs through numerical analyses.The main contents of this thesis include:(1)Geometric analyses of bush-pin hinge pair in bush chain and roller chain was carried out by established a corresponding thermal EHL model of infinite line contact.It is found that the radius of equivalent curvature is very large,and the increase of the radius of equivalent curvature will increase the oil film thickness and temperature rise of the contact zone.The great influence of the change of the equivalent radius of curvature on the lubrication state in the contact zone has been revealed and the effects of load,velocity and lubricant fluid properties on contact zone pressure,film thickness,temperature and friction coefficient were studied.It is found that the existence of surface waviness may cause the increase of film thickness in contact zone,and a reasonable explanation is given through further research.(2)The infinite-length model was extended to a finite-length linear contact EHL model.On this basis,the effects of the equivalent curvature radius,the length of the contact zone and the size of the modified fillet on the lubrication state of contact zone were studied.In addition,a method to reduce stress concentration by changing the size of the modified fillet is proposed,and the simulated results show that the method is effective and feasible.The results show that the lubrication between the bush and the pin of the chain should be considered in the design.(3)Aiming at the chain plate-pin hinge pair in silent chain,a short finite line contact EHL model was established.The effects of equivalent curvature radius,chain plate thickness,modification fillet size and chain plate sliding speed on lubrication state of contact area were studied.The results show that the lubrication condition of the hinge pair of silent chain is better than that of the sleeve chain and the roller chain with the same maximum Hertzian pressure.