Effect of profile modification on dynamic load of involute spur gear under different profile modification lengths

With parabolic modification, the dynamic load coefficient changes with the modification amount under different modification lengths as shown in the figure.From the qualitative point of view, the analytical conclusions of parabolic modification and straight line modification are basically the same, for example, the dynamic load coefficient changes in the form of’V’; the optimal modification quantity, the critical modification quantity and the minimum dynamic load coefficient corresponding to different modification lengths are obviously different; the critical modification quantity exists for short modification, while the critical modification quantity does not exist for long modification, etc.From the quantitative point of view, the minimum load coefficient of linear modification is smaller than that of parabolic modification, whether it is short or long.

In the figure, when the modification length is 8.4 mm and the modification quantity is 0.044 mm, the dynamic load coefficient of the gear reaches the minimum value of 1.68 under the condition of long modification.In the case of short modification, when the modification length is 4.2mm and the modification quantity is 0.016mm, the dynamic load coefficient of the gear reaches the minimum value of 1.87.The meshing force and meshing stiffness time-domain curves under the above two modification parameters are compared and analyzed with those of non-modification gears as shown in the figure.It can also be seen that the overlap of gears remains basically unchanged in the case of short modification while it decreases in the case of long modification when the meshing force is small.

The analysis shows that with the increase of modification quantity, the dynamic load coefficient changes in the form of’, but there are obvious differences between the optimal modification quantity, the critical modification quantity and the minimum dynamic load coefficient under different modification lengths.The optimum modification quantity of short modification is less than that of the highest point of single tooth engagement under the average engine torque, and the modification length should not be too short, otherwise the dynamic load reduction is not obvious, and critical modification quantity exists for both short modifications.The optimum modification amount for long modification is greater than the deformation amount at the highest point of single tooth engagement under the average engine torque, and it can reduce the dynamic load of the gear more effectively without the critical modification amount.Under the optimum modification corresponding to the short modification, the gear overlap basically remains unchanged, while under the optimum modification corresponding to the long modification, the gear overlap decreases when the meshing force is small.

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