According to the transmission score:
Fixed transmission ratio-circular gear mechanism (cylindrical, cone)
Variable transmission ratio-non-circular gear mechanism (elliptical gear)
According to the relative position of the axle
Plane gear mechanism, spur gear transmission, external gear transmission, internal gear transmission, rack and pinion transmission, helical cylindrical gear transmission, herringbone gear transmission, space gear mechanism, bevel gear transmission, cross-axis helical gear transmission, Worm gear drive
According to the process
Bevel gears, semi-finished gears, helical gears, internal gears, spur gears, worm gears
