The principle and self-locking function of worm gear reducer

What is the self-locking function of the worm gear reducer? Any object has a friction angle. When the direction of the resultant external force on the object is within the friction angle, no matter how large the force is, the reducer will not move. This is called the self-locking of the worm gear reducer.

What is the principle of self-locking of the worm gear reducer?

Worm gear reducer self-locking needs to meet some conditions

Adding a reverse torque to the worm gear reducer will generate a reverse efficiency η'=2-1/η, which is significantly smaller than the forward efficiency η. If the forward efficiency η≤0.5, then the worm gear reducer will self-lock. There are only a small number of worm gear reducers with large speed ratios that are statically self-locking.

The self-locking principle of the worm gear reducer is: 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 realize reverse self-locking, that is, the worm can only be driven by the worm, not by the worm gear. The worm gear drives the worm. Such as the self-locking worm mechanism used in other machinery, its reverse self-locking can play a role in safety protection.

Application of self-locking function of worm gear reducer:

In the transmission mode of the reducer, the worm gear transmission has the characteristics that other gear transmissions do not have, that is, the worm can easily rotate the worm gear, but the worm gear cannot rotate the worm. This is because the structure and transmission of worm gears are achieved through friction.

The self-locking function of the worm gear drive is very useful in mechanical applications, such as hoists, conveying equipment, etc. However, it is also because of the friction transmission mode of the worm gear that the transmission efficiency of the worm gear is much lower than that of the gear transmission.

However, not all worm gear reducers have a good self-locking function, and the self-locking function of the worm gear can only be realized if it reaches a certain speed ratio. This is related to the lead angle, that is, the self-locking function of the worm gear with a small speed ratio is not so ideal.

For the occasions where the self-locking property of worm gear reducer needs to be applied, it is particularly important to determine its self-locking property, but in practical applications, it is often difficult to determine the self-locking property. For example, in the process of designing a high-voltage vacuum switch tube exhaust table, its reducer is a worm and worm gear mechanism (without brakes). However, when the motor is turned off during the descending movement, the mechanism can sometimes self-lock, sometimes not, and even accelerate the descent, and completely lose the self-locking ability.