In 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? How to solve it as the best solution? The following editor will share relevant content based on the understanding of bearing knowledge.
1. The phenomenon and influence of the inner ring of the cylindrical roller bearing falling out
The faulty part was removed from the whole box for inspection, and it was found that the inner ring of the cylindrical roller bearing of the driving axle was 3mm away from the plane position on which the internal measurement was 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.
2. Analysis of the cause of the failure of the inner ring of the cylindrical roller bearing
1）. System structure analysis: According to the structural design, the two ends of the driving axle are bearings, the fixed end adopts deep groove ball bearings, and the free end adopts cylindrical roller bearings. 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.
2）. Reason analysis: It can be known from the mechanical principle that the two parts with interference fit are separated during the use process, either because the parts are manufactured out of tolerance, so that the tightening force is insufficiently reduced, or the designed interference is too small. The generated tightening force is insufficient, and the thrust generated during the work of the parts is greater than the tightening force so that the parts are loosened and dislodged. The reason for the bearing's escape is based on this idea to explore.
1. Size detection:
If the scale of the part is not qualified, 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 show that the dimensions of the parts meet the design requirements, and the influence of this factor can be excluded.
2. Binding force calculation:
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 size design of the axle and the bearing, and find that the minimum interference between the two under the limit state is 0.002mm.
3. Cause confirmation
According to the above analysis, under the action of the steel belt tension, there will be no axial force between the axle and the cylindrical roller bearing. In addition to the errors in product manufacturing and 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 CAE analysis—the tapered flange bearing position of the driving axle has a deformation of 0.084mm, 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 with it.
Therefore, it can be confirmed that the reason for the failure of the inner ring of the cylindrical roller bearing of the driving axle in the bench test of this CVT product is that the interference between the bearing and the axle given by the part design is insufficient, and there is no structural design. The limit and anti-drop structure of the bearing on the axle.
3. Solutions
For the two reasons identified above, two measures to solve the problem have been formulated:
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. A retaining ring groove is added to the outer position of the bearing on the axle, and the retaining ring is installed to limit the inner ring of the bearing to prevent the inner ring from coming out.
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