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Power Transmission and Gearing Systems
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
It should be pointed out that the motion of the worm and worm wheel is a mixture of sliding and rolling actions. The high rate of sliding friction tends to cause a temperature rise at sliding surfaces, wipe the lubricant along the convergent zone, and in a worse case, make the sliding surfaces stick together. This is especially true if the materials of the worm and worm wheel are the same. To reduce the sliding friction between the worm pair, the worm and worm wheel are always made of different materials. Practically, the worm is commonly made of steel and the worm gear is made of bronze, where the static coefficients of friction are 0.34 and 0.16 for dry and lubricated contacts, respectively. When gearing systems are used under high loads or high speeds, it is common to harden and grind worms. On the contrary, low loads or low life rotating components may use plastic or nylon materials for worm gears.
Gears
Published in Asok Kumar Mallik, Amitabha Ghosh, Günter Dittrich, Kinematic Analysis and Synthesis of Mechanisms, 1994
Asok Kumar Mallik, Amitabha Ghosh, Günter Dittrich
A worm-gear set is usually not reversible and the input motion needs to be given to the worm. This is very useful in many situations where self locking is necessary to prevent bodies from coming down under gravity after vertical positioning has taken place. Therefore, in hoists and cranes worm gears are used frequently. Equation (10.10.5) shows that by making Ng sufficiently large and using a single-thread worm, a large speed reduction is possible in one stage. Such speed reduction units are quite popular. Since the relative sliding motion between the threads of a worm and the teeth of a meshing worm gear is substantial, energy loss through friction is greater compared to other types of gearing.
Gear Types and Nomenclature
Published in Stephen P. Radzevich, Dudley's Handbook of Practical Gear Design and Manufacture, 2016
Worm gear efficiency is quite dependent on operating speed. The same set may show an efficiency of, say, 75% at a low speed and 85% at a higher speed. Ratio, material, accuracy, and geometric design all affect worm gear efficiency. Typical efficiencies run from 35% to 90%, with higher or lower values occurring in special cases.
Hydraulic-pressure-following control of an electronic hydraulic brake system based on a fuzzy proportional and integral controller
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Qiping Chen, Hao Shao, Yu Liu, Yuan Xiao, Ning Wang, Qiang Shu
On the one hand, the worm gear combination has high structural strength, safety and reliability, and long service life. On the other hand, it has been used in EPS system for many years. The established friction model is shown in formula (2). The friction characteristics of worm gear and rack gear reduction mechanism are analyzed by using the friction model of Yuan et al. (2016). Here, is the friction, is the static friction, is the dynamic friction, and is the speed of movement.