Needle roller bearings are a kind of roller bearings with cylindrical rollers. They are commonly used in automobiles or motorcycles in our daily life. Needle roller bearings will inevitably have some failures in use. According to the understanding of needle roller bearings , Tell you about some common failure factors of needle roller bearings, and related methods to eliminate bearing failures. picture Common faults of needle roller bearings and their causes: 1. Fault form: (1) The bearing is difficult to rotate and generates heat; (2) There is abnormal sound in the bearing operation; (3) The bearing generates vibration; (4) Peeling and cracking of the inner race; (5) Peeling and cracking of the outer race; (6) The bearing raceways and rolling elements produce indentations. 2. Failure cause analysis: (1) The inspection before assembly is not careful. The bearing should be cleaned before assembly and carefully inspect the inner and outer races, rolling elements and cage of the bearing for rust, burrs, bruises and cracks; check whether the bearing clearance is appropriate, whether the rotation is brisk and free, and whether there is sudden blocking At the same time, check the size, roundness and cylindricity of the shaft diameter and bearing seat hole, and whether there are burrs or unevenness on the surface. For split bearing housings, it is required to leave a gap of 0.1mm~0.25mm between the joint surface of the bearing cover and the bearing base and the outer circular surface of the outer race to prevent “clamping” at the “tile mouth” on both sides of the outer housing. The gap caused by the “gang” phenomenon is reduced, the wear is accelerated, and the bearing is damaged prematurely. (2) Improper assembly. Improper assembly will lead to the above-mentioned various failure modes of the bearing, as well as the following situations: A. Improper coordination: The cooperation between the inner hole of the bearing and the shaft adopts the base hole system, and the cooperation between the outer circle of the bearing and the housing hole adopts the base shaft system. Generally, the shafts and bearing inner races of centrifugal pumps, centrifuges, reducers, motors and centrifugal compressors working under normal load conditions adopt J5, js5, js6, k5, k6, m6 to match, and the bearing seat hole and bearing The outer race adopts j6, J7 fit. The rotating seat ring (the inner race of most bearings is a rotating race, the outer race is not a rotating race, and a few bearings are the opposite), usually using interference fit, which can avoid the seat ring under the load. Rolling and sliding occurs on the mating surface with the housing bore. picture However, sometimes due to the inaccurate measurement of the shaft diameter and the bearing seat hole or the roughness of the mating surface does not meet the standard requirements, excessive interference fit is caused, and the bearing race is greatly squeezed, resulting in radial clearance of the bearing itself. The reduction will make the bearing difficult to rotate, generate heat, increase wear or get stuck, and in severe cases, it will cause the inner and outer races of the bearing to crack when they are installed. The non-rotating seat ring often adopts a fit with a small gap or interference, so that the non-rotating seat ring may produce slight creep, so that the contact surface between the seat ring and the rolling body is constantly replaced, and the raceway of the seat ring wears evenly. At the same time, it can also eliminate the axial jamming of the rolling elements in the bearing due to the thermal elongation of the shaft. However, excessive clearance fit will cause the non-rotating seat ring to rotate with the rolling elements, resulting in severe wear of the shaft (or bearing housing hole) and the inner race (or outer race), and friction will cause the bearing to heat up and vibrate. B. Improper assembly method: When the interference between the bearing and the shaft diameter or the housing hole is small, the press-fit method is often used for assembly. The easiest way is to use a copper rod and a hand hammer to symmetrically tap the seat ring with the interference fit of the bearing in a certain order, so that the bearing can be pressed in smoothly. In addition, a casing made of soft metal can also be hammered in or pressed in with a press. If the operation is not done properly, the seat ring will be deformed and cracked, or the hand hammer on the non-interference fit seat ring will cause indentation on the raceway and rolling elements or the bearing will be indirectly damaged. C. Improper temperature control during assembly: When assembling needle roller bearings, if the interference with the shaft diameter is large, they are generally assembled by shrink fitting. That is to say, the bearing is put into an oil barrel filled with organic oil, and the outside of the oil barrel is heated with hot water or flame. The process requires that the temperature of the heated oil be controlled at 80°C~90°C, generally not exceeding 100°C, and at most not exceeding 120°C. After the bearing is heated, quickly take it out and fit it on the journal. If the heating temperature is too high due to improper temperature control, the bearing will be tempered and the hardness will be reduced, and the bearing will be easily worn, peeled off, or even cracked during operation.