Worm drive is a transmission mechanism that transmits motion and power between two interlaced axes in space. The included Angle between two interlaced axes can be any value, commonly used is 90°.This kind of transmission has many advantages, such as compact structure, large transmission ratio, smooth transmission and reliable self-locking under certain conditions.Its inadequacy is drive efficiency is low, often need to consume nonferrous metal to wait.Worm drive is usually used for deceleration, but some machines are also used for acceleration.

With the improvement of machine power, a variety of new worm drives have appeared in recent years.

(I) type of worm drive

According to the different shape of worm, worm drive can be divided into cylindrical worm drive, toroidal worm drive and worm drive.

Cylindrical worm drive includes two types: ordinary cylindrical worm drive and circular cylindrical worm drive.

(2) characteristics of worm drive

1) can achieve a large transmission ratio.In power transmission, the general transmission ratio I =5 ~ 80;In the transmission of dividing mechanism or manual mechanism, the transmission ratio can reach 300;If only motion is transmitted, the transmission ratio may be up to 1000.Due to the large transmission ratio and the small number of parts, the structure is very compact.

2) in worm drive, because the worm tooth is a continuous spiral tooth, it and the worm tooth are gradually into engagement and gradually out of engagement, at the same time, the tooth meshing more, so the impact load is small, the transmission is stable, low noise.

3) when the spiral rise Angle of the worm is less than the equivalent friction Angle of the meshing surface, the worm drive is self-locking.

4) worm drive is similar to spiral gear drive, with relative sliding in the meshing.When the sliding speed is large and the working conditions are not good enough, serious friction and wear will occur, which will cause excessive heat and make the lubrication situation worse.Therefore, the friction loss is large and the efficiency is low.When the transmission has self-locking, the efficiency is only about 0.4.