Cone Bit Variable Curvature Modification Sliding Bearing Analysis

Roller cone bit plays an important role in oil drilling and are used extensively. The revolution of bit and the rotation of cone cause rock to be broken. The rotation of cone is realized with bearing system, so the quality of bearing has a direct influence on performance and working life of bits. As far as the widely-used journal bearing is concerned, the forepart wear failure of journal bearing is the main source of the failure of the cone bit, suffering with high temperature from friction and bearing enormous load and being in bad hydrodynamic lubrication. Consequently in order to prolong bearing's life the structure improvement of journal bearing is a more efficient way than the material improvement, that's to say, to design a more reasonable diameter clearance and therefore increasing the load-undertaking area, avoiding abnormal distribution of the local peak contact stress.Based on those reasons mentioned above, this thesis has developed a way to improve the load-undertaking capacity by improving the structure of claw, in more detail, to adopt curvature-changing design along the radial direction and crowned design along the axis direction. According to such an idea, four kinds of different structure on claw, such as the straight-lined curvature-changing claw, corrected curvature-changing claw, full crowned curvature-changing claw and logarithmic curvature-changing claw, has been studied. Applying the elastic contact theory, lubrication theory and wear theory those curvature-changing crowned claw has been studied on the contact pressure and oil pressure distribution, dynamic wear analysis and life estimation. We can also carry out the analysis and calculation on the O-ring seal, which is used in the cone bit as well.The analysis results indicate that the curvature-changing crowned claw can effectively improve the contact pressure distribution and prolong the working life of journal bearing. According to the certain operating condition,the crown shape and the size of crown about the claw can be optimized on the basis of the analysis results. And the O-ring seal analysis results would be helpful to the structural design of O-ring seal.