Thermal Elastohydrodynamic Lubrication Analysis Of Gear And Rack Transmission In Reciprocating Motion

Gear rack mechanism was widely used in modern machinery,but when it was subjected to large load and large sliding speed,it was easy to produce surface wear,gluing and other failure behavior.In this paper,the infinite line-contact elastohydrodynamic lubrication model was established for the reciprocating gear rack mechanism,and the numerical solution of the elastohydrodynamic lubrication of reciprocating gear rack mechanism was obtained.The factors that considered include:parameters,rough texture shape,load changes along the meshing cycle,displacement coefficient,commutation process duration,commutation process in the meshing line position and so on.First,the influence of different parameters on the numerical solution of steady-state elastohydrodynamic lubrication of gear and rack mechanism was analyzed.The distribution law of oil film pressure and film thickness in the contact zone of gear rack mechanism under different parameters was obtained,including the meshing point position,modulus,line angle transmission ratio and other parameters on the impact of lubrication,and the effects of three rough textures on the oil film pressure,film thickness and temperature were compared.Secondly,the unsteady elastohydrodynamic lubrication numerical solution of the gear rack mechanism was calculated by considering the variation of load time between the single and double teeth alternating meshing,the effects of the variation of load time between the single and double teeth alternating meshing and the displacement coefficient on the center pressure,the central film thickness,the minimum film thickness,the maximum temperature and the change of oil film pressure,film thickness of the contact area at different meshing points were discussed.Then,considering the thermal effect,the non-Newton effect and the load time-varying effect of the reciprocating motion was compared with the unidirectional motion,the elastohydrodynamic lubrication of reciprocating motion and unidirectional motion was compared,the center pressure,central film thickness,theminimum film thickness and the maximum temperature in a meshing cycle were compared,furthermore,the pressure and film thickness of contact zone at the same position on the meshing line of unidirectional motion were compared;The influence of load changes on the center pressure,central film thickness,the minimum film thickness and the maximum temperature of the reciprocating gear rack mechanism was studied,the influence of the load size on the pressure and film thickness at the contact zone of the reciprocating point was analyzed.Then,using the unsteady elastohydrodynamic lubrication model of gear rack mechanism,the change of load during gear transmission and the change of surface velocity in the process of reciprocating were considered,the influence of the load varies with the single and double teeth engagement was discussed,and the influence of the duration of reciprocating motion process on the lubrication state of the gear rack was also discussed in the process of gear rack engagement.The minimum film thickness,maximum temperature,central pressure and the central film thickness in an engaged period were calculated,and the pressure and film thickness in different instantaneous of the commutation process were calculated.Finally,on the basis of transient EHL of reciprocating gear rack mechanism,the influence was discussed when the commutation process of reciprocating motion occurs at different position along the meshing line.The change of the minimum film thickness,maximum temperature,central pressure and the central film thickness during a meshing cycle was calculated when the commutation process of reciprocating motion occurs at different position along the meshing line,and the film thickness of reversing process was compared for different commutation positions to obtain a more favorable commutation position for the lubrication of the mechanism.