The Influencing Factors Of Bearing Friction Torque

In order to reduce the friction torque of bearings and accurately measure the friction torque of bearings, it is necessary to analyze various influencing factors of friction torque.
1.Design factors:
The torque of a bearing is influenced by its size and design parameters, such as groove curvature, radial clearance, and cage parameters. It is important to note that the impact of these factors on torque varies depending on the bearing structure and design.
2.Machining accuracy factors：
The stability of the bearing friction torque largely depends on machining accuracy, including surface roughness, geometric accuracy, dimensional accuracy, and rotational accuracy of the finished product. The lower the machining accuracy, the greater the friction torque.

3.Measurement condition factors
(1) Measurement load: Bearings are working under load conditions, so the measurement of torque is also required to be carried out in the presence of a load, when the size and direction of the applied measurement load (axial or radial) are different while the value of its frictional torque is not the same.

(2) Lubricant: The viscosity, quantity, and cleanliness of the lubricant significantly affect the torque of the sensitive bearing. Therefore, it is crucial to specify the quality and quantity of the lubricant when measuring the bearing.
(3) Rotation speed: The bearing rotation needs to overcome air resistance and increase the power loss of the mixing lubricant, so the higher the bearing speed the greater the torque. When measuring the torque at medium and high speeds, the instantaneous peak value will be exceeded by the moment of inertia of the rotating parts or absorbed by the measuring system and cannot be truly reflected, so only the average friction torque can be measured. The maximum friction torque can only be measured at very low speeds and under conditions where the inertia of the measuring system is very small.
(4) Measurement position: Measurement position refers to whether the axis of the measured bearing is in the vertical position or in the water position. Generally, when the domestic and foreign instruments apply radial load to the bearing, the measured bearing is in the horizontal position, while when the axial load is applied to the bearing, the measured bearing is in the vertical position.
The motion state of different parts varies with the measurement position of the bearing, and their torque values not only differ in magnitude but also have essential differences.
(5) Cleanliness of the tested bearing: The residual magnetism of the bearing before measurement, the lack of cleaning, and environmental pollution during the measurement process may all cause abnormal friction, resulting in poor friction performance of the bearing. This is an important aspect of production management that cannot be ignored by manufacturers. For sensitive bearings, strict cleaning procedures must be followed before measuring the torque, and the assembly and measurement of the bearing should be carried out in a clean room. Generally, foreign regulations stipulate that the dust particle count per cubic foot of the clean room should not exceed 100 particles with a size greater than 0.5μ.
In short, bearing friction torque is a random variable, where the relatively stable torque component is due to design factors and measurement conditions, while the torque due to factors such as processing conditions and cleanliness is quite dispersed and has a significant impact on the measured value, which should be eliminated as much as possible. Therefore, bearing friction torque is a comprehensive indicator of various influencing factors, which must be fully considered by bearing designers, bearing manufacturers, test operators, and instrument researchers to provide products with qualified torque.