In the worm drive, the selection of the number of worm gear teeth and the number of worm heads
The worm drive of the screw elevator is a transmission that transmits motion and power between two axes that are staggered in space. The angle between the two axes can be any value, and the commonly used one is 90°.
This kind of transmission system used by the screw elevator has the advantages of compact structure, large transmission ratio, stable transmission and reliable self-locking under certain conditions. It is widely used in machine tools, automobiles, instruments, lifting and transportation machinery. , metallurgical machinery and other machinery or equipment.
The number of worm heads in the worm gear and worm design can be selected according to the required transmission ratio and efficiency. Generally, z1=1-10, and z1=1, 2, 4, and 6 are recommended.
The selection principle is: when the transmission is required to be relatively large, or the transmission of large torque is required, then z1 takes a small value; when the transmission self-locking is required, take z1=1; when high transmission efficiency is required, or high-speed transmission is required, then z1 Take the larger value.
The recommended values of z1 and z2 are shown in the table below:
The number of worm gear teeth affects the smoothness of operation, and is subject to two restrictions: the minimum number of teeth should avoid undercutting and interference. In theory, z2min should be ≥17, but when z2<26, the meshing area is significantly reduced, affecting the stability. , and when z2 ≥ 30, more than two pairs of teeth can always be meshed, so z2 > 28 is usually specified.
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, and the span between the two support points of the worm must be increased accordingly in terms of structure, which will affect the stiffness of the worm shaft. and meshing accuracy; for a worm gear of a certain diameter, if z2 is obtained too much, the modulus m will be greatly reduced, which will affect the bending strength of the gear teeth; therefore, for power transmission, the commonly used range is z2≈28-70. For transmissions that transmit motion, z2 can reach 200, 300, or even 1000.
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