Thrust roller bearings include self-aligning thrust roller bearings, tapered roller thrust bearings cylindrical roller thrust bearings and needle roller thrust bearings.
Structures
1. Thrust self-aligning roller bearings
Thrust self-aligning roller bearings are separable bearings, as there is an angle between the load action line and bearing axis, this type of bearings can carry both axial and radial loads, and they can be applied in the operations with heavy load, the permissible rotation speed is higher. The thrust self-aligning roller bearings have fine self-aligning property and the allowable angular error is 2°~3°, but such error will decrease with the increase of load on the bearings. For example, bearing series 292, 293 and 294, when Fa+2.7Fr=0.15Ca, the allowable angular error is decreased to 1.5°. Shaft washer comprises two types of structures, with bushing and without bushing.
2. Thrust tapered roller bearings
Thrust tapered roller bearings can accommodate single-direction axial load, and restrain single-direction axial displacement. They have much higher axial carrying-capacity than thrust ball bearings; in addition, they have high rigidity and take up smaller space. They are applied in operations with low rotation speed.
3. Thrust tapered roller bearings
Thrust tapered roller bearings can accommodate single-direction axial load, and restrain single-direction axial displacement. They have much higher axial carrying-capacity than thrust cylindrical bearings; their limit rotational speed is a little higher than that of thrust cylindrical roller bearings.
4. Thrust full tapered roller bearings used on pressing-down device of mill
Thrust full tapered roller bearings used on pressing-down device of mill, full components, can accommodate large single-direction axial load.
Cages
Copper (steel) solid lathed cages are adopted.
Rolling elements
The rolling elements of thrust self-aligning roller bearings are non-asymmetric spherical rollers, and the space for asymmetric spherical rollers is also reserved for the users.
Permissible tilt angle
1. The bearing axis of thrust tapered roller bearings and thrust cylindrical roller bearings are not permitted to be inclined.
2. The bearing axis of thrust self-aligning roller bearings is permitted to be inclined, when the equivalent static laod Poa*0.05Coa and when the shaft washer is slewing, the permissible tilt angle is:
292 series 1.5* 293 series 2* 294 series 2.5*
The permissible tilt angle will decrease with the increase of the load.
Equivalent load
1. Thrust tapered roller bearings and thrust cylindrical roller bearings Dynamic equivalent axial load: Pa=Fa Static equivalent axial load: Poa=Fa In the equation: Fa Actual axial load of the bearing (kN)
Fr Actual radial load of the bearing (kN)
2. Thrust self-aligning roller bearings Dynamic equivalent axial load: Pa=Fa+1.2Fr When Fr*0.55Fa Static equivalent axial load: Poa=Fa+2.7Fr When Fr*0.55Fa In the equation: Fa Actual axial load of the bearing (kN)
Fr Actual radial load of the bearing (kN)
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:
1. Thrust tapered roller bearings and thrust cylindrical roller bearings
Famin=Coa/1000 In the equation:Famin Minimum axial load (kN) Coa Basic static load rating (See Bearing Dimensions Table) (kN)
2. Thrust self-aligning roller bearings
Famin=Coa/1400+A(DHn/106)2
In the equation:Famin Minimum axial load (kN) Coa Basic static load rating (See Bearing Dimensions Table) (kN)A Minimum load constant
292series A=0.0026 293series A=0.0030 294series A=0.0020
D Housing washer outer diameter H Height of bearing assembly n Limit rotational speed (r/min)
When the actual load acted on a bearing is less than the minimum axial load computed, must a spring or other measures to preload the bearing.
3. Screw-down bearings
This type of bearings is specially designed for the pressing-down device of mill. There is no cage on the bearing, the whole raceway is full of rollers, so it can carry larger single-direction axial load. To meet the requirements of the pressing-down device of mill, the top ring of the bearing is processed as a convex sphere, TTSX type (439000 type) or a concave sphere TTSV type (429000 type), they are evenly contacted with corresponding non-conventional type of end faces, which can guarantee the bearings to receive even force when certain inclination is generated by the pressing-down device of mill with reference to the bearing axis. As this type of bearings has inferior CPT, pay attention not to mix the rollers when mounting and the bearings must be filled with grease.
Operating temperature
-20*~ +120* When the operating temperature exceeds +120*, please contact with Technical Department.
Safety coefficient
The allowable equivalent static load of a bearing depends on the basic static load rating of the bearing. While permanent deformation quantity said above (local depressed quantity) decides bearing performance and service conditions. So, safety coefficient is made out for analyzing the safety degree of the basic static load rating.
So=Cor/Pormax In the equation: Pormax The maximum static equivalent radial load permitted to be acted on the bearing (N)
Cor Basic static radial load rating (N)
So See Table 1 for Operational safety coefficient
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