Introduction to the Principle and Self-Locking Function of Worm Gear Reducers

Release time:

2022-10-10

What is the self-locking function of a worm gear reducer? Every object has a friction angle. When the external force acting on an object is within the friction angle, no matter how large the force is, the reducer will remain stationary.

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

　　Self-locking requires the fulfillment of certain conditions. When a reverse torque is applied to a worm gear reducer, the reverse efficiency becomes η' = 2 - 1/η, which is significantly lower than the forward efficiency. If the forward efficiency is less than or equal to 0.5, the worm gear reducer will become self-locking. Only a small number of worm gear reducers with high reduction ratios exhibit static self-locking.

　　The self-locking principle of worm gear reducers is as follows: When the lead angle of the worm is smaller than the equivalent friction angle between the meshing gear teeth, the mechanism exhibits self-locking capability, enabling reverse self-locking—meaning that the worm can only drive the worm wheel but cannot be driven by it. Like other machines that employ self-locking worm mechanisms, this reverse self-locking feature serves as a safety safeguard.

　Application of the self-locking function in worm gear reducers:

　　In the transmission methods of reducers, worm gear transmission possesses characteristics that other gear transmissions lack: the worm can easily rotate the worm wheel, but the worm wheel cannot rotate the worm. This is because the structure and transmission of the worm gear pair rely entirely on friction.

　　The self-locking function of worm gear drives is highly useful in mechanical applications, such as winches and conveying equipment. However, due to the friction-based transmission mechanism of worms, their transmission efficiency is significantly lower than that of gear drives. Moreover, not all worm gear reducers possess a strong self-locking capability; the self-locking function of a worm gear can only be effectively achieved when a certain speed ratio is reached. This is related to the lead angle—specifically, worm gears with small speed ratios exhibit less-than-ideal self-locking performance.

　　When it comes to practical applications, determining the self-locking performance of worm gear reducers is particularly important. However, in actual applications, it is often quite difficult to ascertain this self-locking performance. For example, in the design of a vacuum switch tube exhaust platform operating at high pressure, the reducer used is a worm-gear mechanism (without a brake). When the thermal insulation cover is lifted, the motor power is switched off, and the mechanism immediately locks itself, preventing the cover from descending. Yet, when the cover is lowered and the motor power is then turned off, sometimes the mechanism does lock itself, while other times it fails to do so—and in some cases, it even accelerates its descent, completely losing its self-locking capability.

　　The Seven Key Features of Worm Gear Reducers

　　1. It is a high-tech mechanical device. The helical gear and worm gear are integrated for drive, enhancing the machine’s torque and efficiency.

　　2. The uneven surface features heat dissipation capabilities. In addition, worm gear reducers also boast strong shock absorption, low temperature rise, and low noise levels.

　　3. It features excellent sealing performance and strong adaptability to various working environments, allowing it to operate continuously even in harsh conditions such as high humidity, and can be stored for long periods.

　　4. High transmission accuracy with self-locking function.

　　5. After special heat treatment, it features high machining accuracy, small size, large load-carrying capacity, and a long service life.

　　6. It can be paired with various motors to form electromechanical integration, fully ensuring the quality characteristics of the product.