Spherical roller bearings have two rows of drum shaped rollers, with a shared spherical raceway on the outer ring and two raceways on the inner ring, forming an angle with the vertical axis of the bearing. This structure enables the bearing to have automatic centering performance, which can compensate for errors or shaft bending caused by the angle between the shaft and the bearing housing. The centering angle is generally 1 ° -2.5 °.