The Relationship Between The Contact Between The Ball Base Surface And The Large Rib Of A Tapered Roller Bearing And The Bearing Life

1. Problems existing in the contact between the base surface of the tapered roller ball and the large rib

In large taper angle tapered roller bearings, the three surfaces of the inner ring raceway, outer ring raceway and roller outer diameter mainly bear radial load and are theoretically in a pure rolling state. The angle between the outer ring raceway busbar and the axis center line of the bearing studied in this article is approximately α = 25° ~ 29°, so it is called a large taper angle tapered roller bearing. This type of bearing has a higher ability to withstand axial loads than ordinary tapered roller bearings, and is mainly used to bear combined radial and axial loads, mainly axial loads in one direction.

The design and processing methods of conventional tapered roller ball base surfaces do not meet the service life requirements of tapered roller bearings. The main issues are:

(1) The surface of the large rib of the inner ring and the base surface of the roller ball are unevenly worn, and the SR value of the base surface of the roller ball has a large dispersion;

(2) Abnormal temperature rises often occur during bearing use;

(3) The contact position between the base surface of the tapered roller with a large taper angle and the large rib of the inner ring is abnormal. The contact position sometimes appears between the outside of the large rib of the inner ring and the edge of the hole diameter of the base surface of the roller ball, and sometimes appears within The contact position between the inner side of the ring’s large rib and the radial chamfered edge of the roller ball base surface, that is, the contact position between the roller ball base surface and the inner ring’s large rib often appears erratic;

(4) The large rib of the bearing inner ring sometimes breaks. Therefore, in order to effectively improve the service life of this kind of large taper angle tapered roller bearing, we must first solve the problem of the influence of the shape of the roller ball base surface on the bearing performance.

2. Analysis of the contact state between the base surface of the tapered roller ball and the large rib of the inner ring

The base surface of the roller ball and the large rib of the inner ring are both working surfaces. The sliding friction they generate during operation will cause severe friction and wear, burns or stress concentration when the lubrication is poor or the contact position is unreasonable, which will lead to bearing failure. Failure due to early fatigue spalling of the raceway, roller ball base surface and outer diameter. The shape of the tapered roller ball base surface, the hole diameter of the ball base surface and
The shape of the large rib of the inner ring is the main factor that affects the abnormal temperature rise of the large rib of the inner ring and the bearing capacity of the bearing. The contact position between the base surface of the tapered roller ball and the large rib of the inner ring is also a very important link.

The abnormal contact position and wear condition between the large rib of the inner ring and the base surface of the roller ball also affect the service life of the bearing. Uneven wear, especially the bulging edge of the hole diameter caused by the small hole diameter of the tapered roller ball base surface (as shown in Figure 1b), can cause poor contact between the roller ball base surface and the large rib of the inner ring. If it is also accompanied by problems such as excessive angle difference and surface roughness of the inner ring’s large rib, uneven wear will cause spiral wear on the surface of the inner ring’s large rib. Therefore, appropriately increasing the hole diameter of the tapered roller spherical base surface according to the condition of the large rib of the inner ring of the bearing will, on the one hand, facilitate equal-area grinding of both end surfaces of the tapered roller, and effectively ensure the chamfer coordinate dimensions of both ends of the tapered roller; On the one hand, it is also helpful to improve the uneven wear degree of the large rib surface of the inner ring and the roller ball base surface caused by factors such as the large axial load of the bearing and the large SR value dispersion of the roller ball base surface.

In addition, at the contact point, the size of the sliding friction is related to the position of the contact point: when the diameter of the circle where the contact point is located is small, the sliding friction is small; otherwise, the sliding friction is large. Therefore, the contact position between the base surface of the roller ball and the large rib is in the middle, which can effectively avoid or reduce the occurrence of cracking of the large rib.