There are many mechanical transmission methods used in various machines, the most important one is belt transmission, chain transmission, friction
Wheel drive, gear drive and sash bar nut drive, etc.
Where the gear drive, in general, that is to make one axis in rotation can drive another axis rotation;Or you can change the rotation of an axis into a straight line.
Its main characteristics are: teeth compact mesh between each other, the transfer of torque is much larger than the belt and chain drive;Its transmission efficiency is also higher than other mechanical transmission;And it can keep the speed ratio between the two axes constant under a large transmission force.
There are many types of gear, generally according to the shape of the tooth surface, divided into cylindrical gear, conical gear and worm gear and other types.The commonly used spur and helical gears are cylindrical gears, which are used to drive the rotation of two parallel shafts, while bevel gears (conical gears) are used to drive the rotation of two intersecting shafts.When the teeth of a pair of bevel gears engage for transmission, the situation is similar to that of two semi-conical friction wheels, as shown in figure 3.However, the friction wheel drive, if the force driven by the driven shaft is greater than the friction between the two wheels, the two wheel surface will occur sliding phenomenon, or even make a slave wheel can not be driven.If the friction wheel is made into a toothed wheel and the teeth on the gear are used to drive the teeth on the other axis, the rotation force of this axis can be transferred to the other axis, as shown in FIG. 4.Bevel gear meshing transmission is based on this basis.
Bevel gear is used for a wide range of purposes, especially when the two shafts intersect, the distance between the two shafts is very close, the power of transmission is very large, the ratio of revolution and play fixed, the use of bevel gear is most suitable.