Worm gear structures are often used to transmit motion and power between two staggered shafts. The worm gear and worm are equivalent to gears and racks in their mid-plane, and the worm is similar in shape to the screw.
Features
1. A large transmission ratio can be obtained, which is more compact than the staggered shaft helical gear mechanism. 2. There is line contact between the meshing tooth surfaces of the two wheels, and its load-bearing capacity is much higher than that of the staggered-axis helical gear mechanism. 3. Worm transmission is equivalent to screw transmission and is a multi-tooth meshing transmission, so the transmission is stable and the noise is small. 4. Self-locking. When the lead angle of the worm is less than the equivalent friction angle between the meshing gear teeth, the mechanism is self-locking and can achieve reverse self-locking, that is, only the worm can drive the worm gear, but not the worm gear. For example, the self-locking worm mechanism used in lifting machinery has a reverse self-locking function that can provide safety protection. 5. The transmission efficiency is low and the wear is serious. When the worm gear is engaged in transmission, the relative sliding speed between the meshing gear teeth is large, so the friction loss is large and the efficiency is low. On the other hand, the relative sliding speed increases the tooth surface wear and heat seriously. In order to dissipate heat and reduce wear, more expensive materials with good friction reduction and anti-wear properties and good lubrication devices are often used, so the cost is high. . 6. The axial force of the worm is large.