KM bearing knowledge: Purpose and method of bearing matching
1. Bearing fit
Rolling bearing is a kind of standardized component, which has the advantages of low friction, easy to start and easy to replace. When we are engaged in routine maintenance or mechanical design, reasonable and correct choice of bearing mating is crucial.
2. Purpose of bearing fitting
The purpose of bearing matching is to make the inner ring of the bearing firmly fixed with the shaft or outer ring and housing, so as to avoid adverse circumferential sliding on the matching surface. This kind of unfavorable circumferential sliding (called creep) will cause abnormal heating, surface wear, wear iron powder into the bearing interior, vibration and other problems, so that the bearing can not play its full role. For bearings, therefore, due to load rotation, it is generally necessary to let the ring band interfere so that it is firmly fixed to the shaft or housing.
3. Common mating methods of bearings
Bearing common two mating methods, respectively: press fit and heating fit.
1) Press fit
Bearing inner ring and shaft tight fit, outer ring and bearing hole is a loose fit, press the bearing to be pressed on the shaft are available, and then put the shaft together with the bearing load bearing hole, when pressed on the bearing inner ring end face, cushion the assembling casing made of a soft metal material (copper or mild steel), the inner diameter of the casing assembly should be slightly larger than the diameter of a journal, outside diameter than the bearing inner ring guard slightly smaller, in order to avoid pressure in keeping the frame. Bearing outer ring and bearing seat hole are tightly matched. When the inner ring and shaft are loose, the bearing can be first pressed into the bearing seat hole. At this time, the outer diameter of the sleeve assembly should be slightly smaller than the diameter of the seat hole. If the bearing ring is closely matched with the shaft and the seat hole, the inner ring and outer ring shall be pressed into the shaft and seat hole at the same time, and the structure of the sleeve shall be able to tighten the end face of the inner ring and outer ring at the same time.
2) Heating fit
It is a common and labor-saving installation method to change the tight fit into loose fit by heating the bearing or bearing seat and using thermal expansion. This method is suitable for the installation of bearing with large interference. Before hot loading, the ring of the bearing or separable bearing is put into the oil tank and heated evenly at 80-100℃. Then, it is taken out from the oil and installed on the shaft as soon as possible. When the bearing outer ring is tightly matched with the bearing seat made of light metal, the hot loading method of heating the bearing seat can avoid the abrasion of the bearing surface. Heating tank with bearing and should be at a certain distance from the bottom of a mesh, or hanging hooks in the bearings, bearing on the bottom, in case of heavy impurities into the bearing or uneven heating, fuel tank must have a thermometer, strictly control the oil temperature shall not exceed 100 ℃, in order to prevent the tempering effect, reduce the hardness of the ring.