Purpose and rolling bearing preload bearing pre-tightening direction

A, what is the bearing pre-tightening? Rolling bearing preloaded, refers to installing a bearing the rolling element bearing between the inner and outer ring and produce certain initial stress and deformation, to keep the bearing inner and outer ring is in a state of compression, the bearing under working load, under a state of negative clearance operation. Second, what is the purpose of bearing preload? Increases the bearing preload is the purpose of the bearing stiffness; Make the axis of rotation in the axial and radial orientation, right the axis of rotation accuracy; Lower shaft vibration and noise, reduce caused by inertia moment of rolling element relative to the inner and outer ring raceway of sliding; Compensation caused by the wear of bearing internal clearance change; Extend the life of the bearing. What are the three direction, bearing preload way? Bearing can be divided by pre load in the direction of the radial and axial preload preload, in practical applications, the ball bearing with axial pre-tightening, cylindrical roller bearings for radial preload. Two identical models of angular contact ball bearing or tapered roller bearing installed in pairs, exerted load according to the method, and points locating preloaded and axial preload constant pressure preload. 1, positioning of prestressing is refers to the bearing pre-tightening positioning of axial position in use process remains the same way, a kind of axial preload are shown in figure 1 below, can adjust the width of the spacer between the two bearings in order to obtain a certain amount of preloaded. Figure 1 positioning preloaded when two same model of angular contact ball bearing in pairs when installation, its axial load - Deformation curve is shown in figure 2. Preloaded, within the inner ring with two bearing clearance between gasket, after applying Fa0 axial pre-tightening force, eliminating axial clearance, bearing axial generated inside ( Preloaded) Deformation of the delta a Ⅰ, delta a Ⅱ are delta a0. Figure in the two bearing load - The formation of deformation curve intersection point. When coupled with axial load Fa, acting on the shaft of two bearing axial deformation and axial load changes, shaft move along the direction of the Fa to delta a displacement; At this point, the deformation of bearing Ⅰ increased by delta a bearing Ⅱ deformation reduces the delta a. Figure 2 & emsp; Angular contact ball bearing positioning of pre-tightening load - Deformation curve prestressing quantity is too small to reach the purpose of preloaded, but pre-tightening load is too big, stiffness of the bearing does not significantly improved, on the contrary make bearing increases the friction, temperature, lower bearing life. The size of the pre-tightening load, should according to the requirement of load condition and use. Generally speaking, under the condition of high speed light load, or in order to reduce the vibration of the supporting system and improve the rotation accuracy, then choose lighter pre-tightening load; Load in the medium or low speed heavy load conditions, and to increase the stiffness of the supporting system, the selection of pre-tightening load and heavy pre-tightening load. General should be calculated and combined with experience with pre-tightening load size. Two constant pressure and constant pressure preload preload refers to make through spring bearing axial pre-tightening load remains the same in using a way of axial preload. As shown in figure 3, can by adjusting the amount of compression spring for a certain amount of preloaded. Figure 3 constant pressure preload when two same model of angular contact ball bearing installed in pairs, and USES the constant pressure preload its synthetic load - Deformation curve as shown in figure 4. See from the diagram, the load bearing Ⅰ, Ⅱ in preload Fa0, deformation are the preload delta a0, when coupled with axial load Fa, acting on the shaft axis along the Fa to move the delta a. Ⅱ bearing outer ring in the spring under the action of pressure inner ring all the time. Because of the spring stiffness compared with the bearing stiffness is very small, so it can approximate that under the effect of applied axial load, the bearing Ⅰ deformation increase the delta a, and Ⅱ deformation and bearing pre-tightening load remains constant. Figure 4 constant pressure when pre-tightening load - Deformation compared with positioning preloaded, deformation, in the same preload constant pressure pre-tightening axial stiffness of supporting system increase was not significant. But when positioning preloaded, shaft and bearing temperature difference caused by the axial length, inner and outer ring radial expansion caused by temperature difference, etc all can affect the amount of preloaded deformation, and the constant pressure preload, are not affected. Therefore, must choose pre-tightening methods according to specific technical requirements. Usually, when high stiffness, choose preloaded positioning; Choose in high speed, constant pressure preload. Using 3, radial preload of the bearing and shaft neck, make the bearing inner ring expansion, in order to eliminate the radial clearance and produce certain prestressing method, called bearing radial preload. Can improve the radial preload bearing stiffness. In the high speed cylindrical roller bearing, can reduce the radial preload under the action of centrifugal force, rolling element and raceway skid phenomenon. For bearing cone hole, lock nut, is used to adjust inner ring and set set of the relative position, reduce the radial preload bearing radial clearance of the implementation.