Thrust roller bearings

Thrust roller bearings includes self-aligning thrust roller bearings, tapered roller thrust bearings, cylindrical roller thrust bearings and needle roller thrust bearings.

Structures:

1. 29000 type thrust self-aligning roller bearings, this type of bearings can carry both axial and radial load in which mainly is axial load. And it has low friction coefficient and fine self-aligning property. The roller of this bearing is unsymmetrical spherical roller, which can reduce relatively slip between roller and raceway in the operating. Also the long roller has big diameter and much quantity, so the load capacity is high. Generally it adopts oil lubrication, but under low speed circs will be grease lubrication.

NXZ mainly produce the following structures:

2.80000 type thrust cylindrical roller bearings and 90000 type thrust tapered roller bearings, this type can accommodate single-direction axial load, they have much higher axial carrying-capacity than thrust ball bearings; in additional, they have high rigidity and take up smaller space.. The thrust cylindrical roller bearings are applied in operation with low rotation speed; the rotation speed of thrust tapered roller bearings is a little higher than thrust cylindrical roller bearings.

3.350000 type double-directions thrust tapered roller bearings (SKF code), this type

can accommodate larger double-direction axial load.

4. TTSV and TTSX type thrust full tapered roller bearings used on pressing-down

device of mill, this type is full complement roller, can accommodate larger single-direction axial load.

Cage materials

Brass, brozen or steel solid cages are adopted.

Permissible tilt angle

The bearing axis of thrust tapered roller bearings and thrust cylindrical roller bearings are not permitted to be inclined. The bearing axis of thrust self-aligning roller bearing is permitted to be inclined, when the equivalent static load P_0a≤0.05C_0a, and when the shaft washer is slewing, the permissible tilt angle is:  

Bearing series   Permissible tilt angle

292 series        1.5°

293 series          2°

294 series        2.5°

The permissible tilt angle will decrease with the increase of the load.

Minimum axial load

When the bearings are slewing, as the rolling bodies are acted by centrifugal moment, the rolling bodies will slid with reference to the raceway, which will cause the shaft washer and housing washer to be separated. In order to ensure the normal operation of the bearings, certain axial load must be put on the bearing. The minimum axial load required is:   

Thrust tapered roller bearings and thrust cylindrical roller bearings

C_0a/1000≤F_amin>A(n/1000)²

Thrust self-aligning roller bearings

C_0a/1000≤F_amin>1.8F_r+A(n/1000)²

In the equation: F_amin    Minimum axial load （kN）

            F_r        Radial load （kN）

            C_0a    Basic static load rating (see bearing dimension table) （kN）

            A      Minimum load constant (see bearing dimension table)

            n      Rotational speed （r/min）

When the actual load acted on a bearing is less than the minimum axial load computed, a spring or other measures must be used to preload the bearing.

Dynamic equivalent axial load

P_a=F_a      (Thrust tapered roller bearings and thrust cylindrical roller bearings)

When F_r≤0.55F_a      P_a=F_a+1.2F_r    （Thrust self-aligning roller bearings）

Static equivalent axial load

        P_0a=F_a        (Thrust tapered roller bearings and thrust cylindrical roller bearings)

When F_r≤0.55F_a   P_0a=F_a+2.7F_r   （Thrust self-aligning roller bearings）