Lubrication And Wear Of Spherical Roller Sleeve Bearings For Roller Cones

At present,the international oil industry is turbulence.In order to save the drilling cost,oil drilling companies have higher and higher requirements on the service life of the drill bit.The performance of sliding bearing is essential for the working life of roller bit.As the key factors that improve the performance and life of bearing,lubrication and wear are always the study core of many scholors.Spherical floating ring bearing in roller bit is a new type of bearing that is applied in the field of oil and gas exploitation.Based on the common floating ring bearing,the outer contact of the bearing is designed as a spherical surface fit,which not only keeps the double oil film mechanism of the floating ring bearing,but also effectively increases the contact area of the outer spherical contact pair.At the same time,it has the self-aligning function of the spherical surface.Using the new type of spherical floating ring bearing in roller bit as the research object,this paper studied the lubrication and friction wear law of it.The main achievements are as follows:(1)In terms of the lubrication theory of radial sliding bearing,when the roller bit is under the condition of RB grease lubrication,this paper,based on spherical coordinate system,establised Reynolds equations of the inner and outer oil film of spherical floating ring bearing in roller bit.And the internal and external oil film thickness equation is also deduced for the two kinds of offset.Then,the influence of pressure difference on the boundary conditions is discussed,and the method of solving the model is studied,which lays the theoretical foundation of spherical floating ring bearing.(2)On the theory of the spherical floating ring bering,the comparative analysis of the influence of the radial offset and the compound offset is carried out,and the conclusion show that the compound migration has a negative influence on the bearing performance.So,the spherical floating ring journal bearings in the work process should avoid compound migration.The influence of special boundary conditons was discussed.It is concluded that the special boundary conditions can improve the internal and external oil film bearing capacity,and the special boundary condition is more in line with cone bit.At the same time,the influence of various parameters on the oil film pressure is studied under the special boundary conditions.(3)In terms of the Fang contact theory for spherical contact,the spherical surface contact analysis of spherical floating ring bearing in roller bit is conducted,and the effects of external load,radius gap and material on the contact are discussed.(4)Under compound motion,this paper established a combined wear mathematical model of spherical floating ring bearing in roller bit.The model can be applied to spherical floating ring bearing in roller bit wear calculation under complex working conditons including vibration.It can make up the deficiency of the existing floating ring bearing wear formula which only considers the lack of rotational motion.Some reference can be provided for the calculation of floating ring bearing friction theory.