Metric Taper Roller Bearingshttps://www.deepgroveballbearings.com/taper-roller-bearing-1/
The pre-tightening of the bearing is to use a certain method to generate a certain axial pressing force in the bearing to eliminate the axial clearance in the bearing and to produce certain deformation in the contact between the inner and outer rings of the tapered roller. When the rear bearing is subjected to the working load, the radial and axial deformation of the inner and outer rings are much smaller than when there is no preload, so that the transmission is accurate and can withstand a certain load. At the same time, the bearing preload can improve the bearing stiffness and ensure the rotation precision of the shaft movement. The preload force of the bearing has a great influence on the running quality of the support shaft. If the pre-tightening force is small, the relative starting is relatively easy, the friction is small, but the rotation precision is not high; if the pre-tightening force is increased, the bearing can be effectively improved. Rotational accuracy and load carrying capacity, but the bearing is difficult to start, the friction is larger, and the efficiency is lower. There is an optimum value for the bearing preload, which has an important relationship with the bearing speed, temperature rise, load, spindle deformation, bearing life, lubrication conditions, etc.
A large number of experiments must be carried out to determine the optimum preload of the bearing. In view of the importance of bearing pre-tightening force, this paper focuses on the common pre-tightening method of tapered bearings, the measurement of pre-tightening force and the pre-tightening force adjustment and control methods.
1Common bearing preload method
(1) Outer ring or inner ring pressing method
After fixing the inner ring of the bearing, pre-tighten by clamping the outer ring of the bearing, such as using the bearing end cover; or after positioning the outer ring, pre-tighten by pressing the inner ring, such as using a round nut. The method is easy to operate and has the widest range of use, but the preload force cannot be changed, and is usually used when the external load is fixed, such as a reducer, a machine tool spindle, etc.
(2) spacer or collar adjustment method
The bearing preload can be effectively adjusted by increasing or decreasing the thickness of the gasket at the inner and outer circumferences. The specific method is as follows: when a pair of tapered roller bearings are installed, a spacer of a certain thickness is placed between the inner and outer rings, and then pads of different thicknesses are placed to achieve the purpose of adjusting the preload of the bearing.
(3) Spring preloading method
Use a spring to hold the outer ring or inner ring that does not rotate, to compress the bearing and pre-tighten. This method is easy to operate and a stable preload can be obtained. However, since the spring has a certain fatigue life, after a certain time, the spring elasticity is reduced and the pre-tightening force is reduced. Therefore, the reliability of the method is inferior to the above method, and a spring with a special rigidity must be designed, and the cost is high.
2 Preload force measurement
Since the magnitude of the preload force has an important influence on the bearing and the quality of its bearing shaft rotation, it is necessary to know the actual magnitude of the preload force of the bearing after preloading. There are two common methods.
(1) Direct measurement method
A method of placing a strain gauge on the outer ring to measure the force applied to the outer ring and obtain the preload force. The measurement method can directly obtain the pre-tightening result, but the cost is high due to the need to damage the structure of the outer ring, so it is not easy to be practically applied.
(2) Indirect measurement method
Since the bearing preload force and its axial load satisfy a certain relationship, and the axial load has a certain relationship with the friction torque of the bearing, the bearing preload can be obtained through a series of calculation formulas by measuring the bearing friction torque. Magnitude of the force.