The worm drive consists of a worm and a worm gear, and the worm is usually an active part. The worm has the same right-handed and left-handed points as the thread.
The worm drive is called a right-handed worm and a left-handed worm.
1. Large transmission ratio and compact structure. The number of worm heads is represented by Z1 (generally Z1 = 1~4), and the number of worm gear teeth is represented by Z2. It can be seen from the gear ratio formula I=Z2/Z1 that when Z1=1, that is, the worm is a single head, the worm must turn to the Z2 worm wheel to turn one turn, so that a large gear ratio can be obtained, generally in the power transmission, The transmission ratio is I=10-80; in the indexing mechanism, I can reach 1000. Such a large transmission, such as gear transmission, requires multi-stage transmission, so the worm transmission is compact, small in size and light in weight.
2. The drive is smooth and noise free. Because the worm tooth is a continuous uninterrupted helical tooth, it is continuous with the worm gear teeth, and the worm tooth does not enter and exit the meshing process, so the work is stable, and the impact, vibration and noise are relatively small.
3. Self-locking. When the worm's helix angle is small, the worm can only drive the worm gear, and the worm wheel can't drive the worm to rotate.
4. The efficiency of the worm drive is low. It is generally considered that the efficiency of the worm drive is lower than that of the gear drive. In particular, the self-locking worm drive has an efficiency of less than 0.5 and a general efficiency of only 0.7 to 0.9.
5. The heat is large, the tooth surface is easy to wear and the cost is high.
According to the shape of the worm can be divided:
Cylindrical worm drive
2. Toroidal worm drive
3. Conical worm drive
Worm drives are often used in applications where the two axes are staggered, the drive is relatively large, the transmission power is not too large, or intermittent operation.
When it is required to transmit a large power, in order to improve the transmission efficiency, Z1=2~4 is often taken. In addition, since the transmission has self-locking property when γ1 is small, it is often used as a safety protection function in a hoisting machine such as a hoist. It is also widely used in machine tools, automobiles, instruments, metallurgical machinery and other machines or equipment. The reason is that the use of axle motion can reduce the consumption of force and promote it.