Joint bearing structure is simpler than the rolling bearing structure. its consist mostly of an inner ring with external sphere and an outer ring with internal sphere. Joint bearing is generally used in low speed swinging motion (namely, the angular motion. Due to the spherical sliding surface, it can make tilting motion in a certain angle range (namely, the heart movement), even if the non-concentricity between the supporting shaft and the shaft shell hole is bigger, it can still work normally.