Test of bearings and precision of pre-tightening methods

Preloaded, refers to the bearing load, through changing the relative position of inner and outer ring, make bearing clearance usage. For household appliances bearing preloaded main role is to improve the bearing stiffness, vibration noise control. Preloaded bearing noise impact bearing the radial load, due to the radial clearance, only part of the steel ball under load, known as the bearing area, the other is called the load bearing area. In steel ball bearing the D motion from a to D ', in the process of steel ball size and direction of gravity and centrifugal force change constantly, steel ball collisions with inner and outer ring raceway alternately, thus bearing internal produce different sound. This kind of different sound can be avoided through the bearing preloaded. But a pretightening ambassador bearing friction increases, the temperature rise, the noise of the bearing life. So is very important to choose suitable pre-tightening force. ( 1) Measuring the size of the shaft and bearing hole, to determine with precision of the bearing, cooperate with requirements as follows: take the interference fit, inner ring on the shaft interference was 0 ~ + 4 microns ( At light load, high precision of 0) ; Outer ring and bearing hole clearance fit, the interval 0 ~ + 6 microns ( But on the free end bearing with angular contact ball bearing, still can increase the clearance) ; Shaft and hole surface roundness error in under 2 microns, bearing the face of baffle used parallelism in under 2 microns, shaft shoulder end foreign face beat in under 2 microns; Axis bearing hole block shoulder to beat under 4 microns; Spindle axis inside the front cover end face beat under 4 microns. ( 2) Fixed end before the installation of the bearings on the shaft bearing with clean to clean a thorough cleaning of kerosene, the grease lubrication, to contain 3% ~ 5% of organic solvent injection bearing grease for degreasing, cleaning and quantitative grease oil gun will fill in the bearing inner ( Accounts for 10% ~ 15%) of the bearing space volume ; Heat bearing the heat up 20 ~ 30 ℃, using hydraulic press the bearing into shaft end; Will set casing pressure on the shaft and with appropriate pressure against bearing face makes its axial positioning; The lace will spring balance volume on the bearing outer ring, use the method of measuring start torque check is the preload of the regulation for substantial changes ( Even if the bearing is correct, but due to cooperate or cage, the deformation of the preload is also has the potential to change) 。