The worm drive of the screw elevator is a type of drive that transmits motion and power between two axes that are spatially staggered. The angle between the two axes can be any value, and the commonly used is 90°.
The transmission system used by the screw lifter is widely used in machine tools, automobiles, instruments, and lifting transportation machinery due to its advantages of compact structure, large transmission ratio, smooth transmission, and reliable self-locking under certain conditions. , Metallurgical machinery and other machines or equipment.
The number of worm heads in the design of the worm gear can be selected according to the required transmission ratio and efficiency. Generally, z1=1-10 is recommended, and z1=1, 2, 4, 6 is recommended.
The selection principle is: when the transmission is required to be relatively large, or a large torque is required to be transmitted, z1 takes a small value; when the transmission is required to be self-locking, z1=1; when high transmission efficiency is required, or when high-speed transmission is required, z1 Take a larger value.
The recommended values of z1 and z2 are shown in the table below:
The number of worm gear teeth affects the stability of operation, and is subject to two restrictions: the minimum number of teeth should avoid undercutting and interference. In theory, z2min≥17, but when z2<26, the meshing area is significantly reduced, affecting stability , And when z2≥30, it can always keep more than two pairs of teeth meshing, so usually z2>28.
On the other hand, z2 should not be too much. When z2>80 (for power transmission), the diameter of the worm gear will increase too much. In the structure, the span between the two supporting points of the worm must be increased accordingly, which affects the rigidity of the worm shaft. And meshing accuracy; for a worm gear of a certain diameter, if z2 is too much, the modulus m will be greatly reduced, which will affect the bending strength of the gear teeth; so for power transmission, the commonly used range is z2≈28-70. For transmission of motion transmission, z2 can reach 200, 300, or even 1000.