The influencing factors of the combination of NTN bearing tolerance and solution

(1) the influence of temperature, NTN bearing because of friction heat at work, and other sources of heat, the temperature of the ring will be higher than the temperature of the phase components, the thermal expansion of the inner circle to that of the journal of cooperate to come loose, while the thermal expansion of the outer ring with the casing hole with tight. Therefore, when the bearing temperature higher than 100 ℃, deal with proper correction of coordination, to ensure the normal operation of combined bearing. (2) shaft neck and the influence of the structure and material of shell hole: split the shell holes and integral with the bearing outer ring with elastic shell hole difference, the former is a bit loose, to avoid the clip flat outer ring; Thin-walled shell or hollow shaft and bearing ring should match than thick wall shell or solid shaft with combination of bearing ring with some tight, in order to make sure there is enough of the connection strength. (3) bearing axial moving components: from the content, the NTN bearing components in the process of operation, the journal heated easy extension, therefore, bearing assembly shall ensure that certain axial movement at the end of the room, then the end bearing ring with phase accessories should be loose, to ensure that the axial can swim. (4) the rotation precision and the influence of rotating speed: when the rotation of the NTN bearing accuracy requirement is high, should choose higher accuracy level of the bearing, and a higher level of shaft and the hole tolerance; To load the combined bearing large and high rotation accuracy requirement, to eliminate the influence of elastic deformation and vibration, rotating ring should avoid using clearance fit, but also shoulds not be too tight; To load small high precision bearings for precision machine tool, in order to avoid the parts form error on the accuracy of rotation effect, regardless of the rotating ring or a rotating ring, cooperate with shaft or hole often want to have a smaller gap. When the rotation of the bearing is too high, and work under impact dynamic load, bearing and shaft neck and the matching between the shell hole is best to choose the interference fit. In all other things being equal, the higher the bearing rotating speed, cooperation should be tight. (5) tolerance grade coordination: choose the journal and the shell hole tolerance grade should be coordinated with the tolerance grade of the bearing. Such as the level 0 bearings with journal generally choose IT6, shell hole general choose IT7; Have higher request for rotating accuracy and operational stability of occasions ( Such as motor) , journal generally choose IT5, generally choose IT6 shell hole. 6 bearing installation and removal, for the convenience of the installation and dismantling, combination bearings should consider adopting a loose fit. Such as convenient operation requirements but also urgent to cooperate, this type of bearings can be used to separate, or inner ring with cone hole, with tight sleeves and withdrawal of NTN bearing. To sum up, there are many influence factors of rolling bearing with, is often difficult to determine maneuver algorithm, so the analogy method can be used in practical production choose bearing. Bearing failure of the main reason is that defects and overload two factors. When the loads more than material strength limit fracture caused by parts called overload fracture. Overload reason mainly is the main engine failure or improper installation. NTN bearing parts of micro crack, shrinkage cavity, bubbles and large foreign impurities, overheating organizations and local burns and other defects during the impact overload or violent vibration will cause fracture in defect, known as defect fracture. It should be pointed out that combination of bearing in the process of manufacturing, for raw materials into the factory reinspection, forging and heat treatment quality control, process control through instrument analysis of the existence of the above defects and correct still must strengthen control in the future. But in general, usually bearing fracture failure of most for overload failure. NTN bearing in the work, because of the influence of the external or internal factors, change the original fit clearance, lower accuracy, and the change of 'killed' called clearance failure. , large amount of the external factors such as interference of installation does not reach the designated position, temperature rise caused by the expansion, instantaneous overload, etc. , internal factors such as residual austenite and the residual stress in a state of flux and so on all is the main reason for the failure caused by clearance changes.