The effect of inch-type gear metric conversion on the transmission mechanism
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Dongfang Steam Turbine Works (Deyang 618201, Sichuan) Wang Zhaoyuan 15 and a = 14.5 gear or worm gear damaged. Because there is no tool, the production is urgently needed to convert them into a metric gear of a=20. After the pair is replaced, it is feasible to realize the transmission, but the influence on the relevant shaft and bearing after redistributing the transmission quality and load can not be ignored.
As the pressure angle increases, the actual meshing line segments of the gears (or worm gears) will shrink and the degree of coincidence will decrease. As shown, A52 is the actual meshing segment of the gear teeth, and the coincidence degree of the /2 pairs of gears is calculated as follows: The example shows the reduction of the coincidence degree after the modification: the basic coincidence degree of a pair of gears reduces the coincidence degree, and at the same time meshes The number of teeth is large, and the load per unit area of ​​each pair of gears is small, and the amount of change in load is also small. Therefore, the operation is stable, the noise is small, and the life is long. The current coincidence is reduced by nearly 1/6, and the transmission will be greatly affected.
15 increases to a = 20% of the gear teeth will change, as shown.
32%, the circumferential force Ft decreases and the 3 bending moment increases. As a result, the bending strength of the shaft is reduced by 32% compared to a = 15, especially in the case of an asymmetrical arrangement or a cantilever arrangement, as the bending moment increases, the deformation of the shaft increases. This will deteriorate the gear mesh quality and the transmission quality.
For rolling bearings, the rated life is used in the actual calculation for cylindrical spur gears, single row radial bearings, which are subjected to radial loads. Therefore, =1, as the pressure angle increases, the radial component increases by 32%, that is, the bearing equivalent load increases by 32%. Therefore, the bearing life is shortened according to the rated dynamic load and the cube when the load ratio is set.
The life of a rolling bearing is quite discrete. Changing the pressure angle increases the bearing load, leading to early damage of the bearing and reducing the rotation accuracy, so the downtime loss is considerable.
It is possible to change the gear pressure angle without a tool as a short-term emergency. However, the amount of cutting should be reduced, especially under heavy load conditions. Once there is a tool, the original parameter c diagram should be restored.