What are the advantages of helical gears over ordinary gears?

When the transmission power and torque are the same, the size and weight of the helical gear reducer will be smaller. This is because the number of teeth on the helical gear is less than that on the spur gear; the overlap coefficient of the helical gear is larger than that of the spur gear (the helical gear has an additional axial overlap coefficient than the spur gear), and a smaller module can be selected.