Theoretical and Experimental Research on the Floating-Sleeve Bearing Applied in Roller-Cone Bit

In oil and gas drilling, the roller-cone bit and the hybrid bit configured with roller cones are two commonly used rock-breaking tools; however, service lives of the bits are limited by the sliding bearings therein. In order to improve the performance and reliability of the bearing in the roller cone, a novel bearing with a floating sleeve is researched in this paper. Firstly, motion characteristics of the bearing are researched, and motion relations between the elements in the bearing are analyzed, respectively. Then, on the basis of the motion relations, three motion statuses of the float sleeve are clarified, including the sleeve start to rotate, the sleeve rotates stably with the pushing force exerted by the rollers, and the sleeve rotates stably with the opposing force exerted by the rollers. At last, bearing performances in three different conditions are respectively tested in the experiment. The results, with the specific speed value being in the range of 0.375∼0.833 and the average value in 0.613∼0.618, show that the sleeves with 6∼12 rollers are able to start and rotate stably under 5 kN radial load, indicating that the sleeves can be started to rotate and work stably, whereas, for the sleeve with less than 4 rollers, the specific speed value varies in the large range of 0∼1.176, indicating that this sleeve cannot rotate stably in the bearing. This research revealed that the amount of rollers is an important factor that determines whether the sleeve is able to float stably in the bearing; therefore, roller quantity should be focused in the bearing design to optimize its performance