Types and characteristics of worm gear transmission

Worm gear transmission is a transmission mechanism that transmits motion and power between two axes interlaced in space. The angle between the two axes can be any value, and the commonly used angle is 90°. This type of transmission has the advantages of compact structure, large transmission ratio, smooth transmission and reliable self-locking under certain conditions, so it is widely used; its disadvantages are low transmission efficiency and the frequent consumption of non-ferrous metals. Worm gear transmission is usually used for speed reduction devices, but some machines are also used as speed increase devices.
With the increase in machine power, many new types of worm gear transmission have emerged in recent years, and the disadvantage of low efficiency is gradually improving.
(I) Types of worm gear transmission

According to the different shapes of the worm, worm gear transmission can be divided into cylindrical worm gear transmission, toroidal worm gear transmission and bevel worm gear transmission.
Cylindrical worm gear transmission includes ordinary cylindrical worm gear transmission and arc cylindrical worm gear transmission.

(II) Characteristics of worm gear transmission

1) It can achieve a large transmission ratio. In power transmission, the general transmission ratio i=5~80; in the transmission of indexing mechanism or manual mechanism, the transmission ratio can reach 300; if only motion is transmitted, the transmission ratio can reach 1000. Due to the large transmission ratio and the small number of parts, the structure is very compact.
2) In worm transmission, since the worm teeth are continuous helical teeth, they gradually enter and exit the meshing with the worm wheel teeth, and there are more meshing tooth pairs at the same time, so the impact load is small, the transmission is stable, and the noise is low.
3) When the helix angle of the worm is less than the equivalent friction angle of the meshing surface, the worm transmission has self-locking properties.
4) The worm transmission is similar to the helical gear transmission, and there is relative sliding at the meshing point. When the sliding speed is very large and the working conditions are not good enough, more serious friction and wear will occur, causing excessive heat dissipation and worsening the lubrication condition. Therefore, the friction loss is large and the efficiency is low; when the transmission has self-locking properties, the efficiency is only about 0.4.