In the automobile transmission, most of the traditional systems use rolling bearings to support the rotating axle to ensure the rotation stability of the rotating axle. Here, the cylindrical roller bearing is used to support the stable transmission of the rotating axle. The circle appears to come out. What causes the inner ring of a cylindrical roller bearing to come out? If the solution is the best solution? The following is based on the understanding of bearing knowledge, to share relevant content. 1. The phenomenon of the inner ring of the cylindrical roller bearing falling out and the influence of the faulty parts are removed from the whole box for inspection. As shown in Figure 1, it is found that the inner ring of the cylindrical roller bearing of the driving axle is 3mm away from the plane on which the internal measurement is attached. If the inner ring of the cylindrical roller bearing is out of a certain distance, the roller and the raceway surface of the inner ring of the bearing are not in full-length contact, and the bearing will vibrate abnormally under load, and the vibration will directly affect the operation of the entire gearbox, resulting in bad noise. , thus affecting normal use. Figure 1. The inner ring of the cylindrical roller bearing is pulled out. 2. Analysis of the failure of the inner ring of the cylindrical roller bearing. Groove ball bearing with cylindrical roller bearing at the free end. The deep groove ball bearing is subjected to the radial force generated by the steel belt and the axial force generated by the oil pressure of the main shaft. Cylindrical roller bearings are only subjected to the tensile force of the steel belt transmitted from the axle, and no axial force is applied to this bearing, that is, the cylindrical roller bearing will not be pulled out by the axial force. Figure 2 Schematic diagram of the bearing force of the pulley system 2. Reason analysis: From the mechanical principle, it can be known from the mechanical principle that the two parts with interference fit are separated during the use process. Either the parts are manufactured out of tolerance and the tightening force is insufficiently reduced, or It is because the designed interference is too small that the tightening force generated is insufficient, and the thrust generated during the work of the parts is greater than the tightening force, so that the parts are moved and dislodged. The reason for the bearing's escape is based on this idea to explore. 1) Dimensional inspection: If the scale of the part is unqualified, there is a risk that the inner ring of the bearing will come out. The bearing fittings of the two prototypes are measured, and the results are shown in Table 1. The dimensions of the parts meet the design requirements, and the influence of this factor can be excluded. 2) Calculation of binding force: The inner ring of the bearing and the axle are in an interference fit, and the reason for the inner ring falling out may be the insufficient amount of designed interference. Check the dimensional design of the axle and the bearing, and find that the minimum interference between the two under the limit state is 0.002mm. At this time, the combination of the inner ring of the bearing and the axle can be calculated by the following formula (1): where: p - inner The binding force between the ring and the shaft, nd1 - the diameter of the shaft, mmd2 - the inner diameter of the bearing, mmb - the contact width between the bearing and the inner ring, mme - the elastic modulus of the shaft, mpa According to the calculation, the interference between the bearing and the axle is 0.002mm When , the combined tightening force p is 23.73n, this value is too small, it is easy to cause insufficient tightening and fixing of the driving axle to the inner ring of the bearing, resulting in the bearing coming out. However, in the previous structural analysis, the cylindrical roller bearing is not subject to axial force. It seems that it cannot be explained that a small binding force will cause the problem of prolapse, and the problem needs to be further explored. 3) Analysis of the cae of the axle and bearing stress Build a model according to the structure in Figure 2, and use computer software to conduct cae analysis. According to the cae calculation and analysis results, the state of the axle when it is not subjected to the tension of the steel strip is shown in Figure 3; the state of the axle under the action of the tension of the steel strip is shown in Figure 4. When the axle is stressed, a certain bending deformation will occur, and then Axial forces are applied to the bearing. Fig.3 Schematic diagram of the state of the axle when it is not under the tension of the steel beltFig.4 Schematic diagram of the deformation of the axle under the tension of the steel belt At the same time, the cae analysis results of the driving axle show that the tapered flange contacting the steel belt is also deformed, as shown in Fig. 5, The bearing position deformation caused by the maximum strip tension is 0.084mm. The deformation of the tapered flange also produces axial forces on the bearing. Figure 5. Cloud diagram of the cae analysis of the buckling of the pulley shaft And the error of assembly, the axial force will increase. When the total axial force caused by the forced operation of the axle and the manufacturing error is greater than the combined tightening force of the bearing, the bearing will slip at the original position on the axle. The numerical calculation of the axial force generated by the deformation of the wheel axle is relatively complicated, and the specific derivation calculation is not made here. From the results of the cae analysis - the 0.084mm deformation of the tapered flange bearing position of the driving axle, it can be seen that the axial force is not too small, and the minimum interference between the bearing and the shaft combined with the tightening force of 23.73n is definitely negligible compared to it. Therefore, it can be confirmed that the cause of the failure of the inner ring of the cylindrical roller bearing of the driving axle in the bench test of this cvt product is the insufficient interference between the bearing and the axle given by the part design, and there is no structural design. The limit and anti-drop structure of the bearing on the axle. 3. The solution is for the two reasons confirmed above,Two measures were formulated to solve the problem: a) Increase the interference between the inner ring of the bearing and the axle. Adjusting the diameter tolerance of the axle-to-bearing fit will increase the minimum fit interference between the axle and the cylindrical roller bearing from 0.002mm to 0.011mm. b) Add a limit stop structure to the inner ring of the bearing. Add a retaining ring groove to the outer position of the bearing on the axle, install the retaining ring, and limit the inner ring of the bearing to prevent the inner ring from coming out, as shown in Figure 6. Figure 6 Schematic diagram of the installation position of the retaining ring
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