Full definition
A speed reducer, commonly known as a gearbox, is an enclosed gear mechanism designed to decrease the input rotational speed while simultaneously increasing the output torque. This device operates under the principle of conservation of energy, taking into account inherent losses such as friction and heat dissipation. Speed reducers are pivotal in various industrial applications to optimize performance and enhance the efficiency of machinery. The main types of speed reducers include worm, helical, planetary (or epicyclic), and cycloidal gear systems, each offering unique advantages based on the application's requirements.
Worm gear reducers are compact and typically provide reduction ratios between 5:1 and 100:1, with efficiencies ranging from 45% to 90%. They are particularly valued for their self-locking capabilities at higher ratios (≥50:1), making them suitable for applications requiring a holding function without back-driving. Helical gear reducers, which can be configured for parallel or right-angle drives, offer higher efficiencies (95% to 98%) and are available in reduction ratios from 3:1 to 25:1 per stage, making them ideal for high-speed applications with moderate torque demands.
Planetary gear systems are renowned for their compact design and high torque density, achieving reduction ratios from 3:1 to 10:1 per stage with efficiencies of 95% to 97%. They are particularly advantageous in applications where space is limited but high torque output is necessary. Cycloidal reducers, on the other hand, showcase high shock resistance and can achieve reduction ratios from 6:1 to 119:1, with efficiencies between 85% and 95%, making them suitable for heavy-duty applications. Selection criteria for speed reducers include power requirements, desired reduction ratio, duty cycle, mounting configurations, and the output torque capacity needed for the application. Standards such as AGMA 6013 and ISO 6336 provide guidelines for the design and rating of speed reducers, ensuring they meet the required performance specifications. Proper lubrication is essential for optimal operation, with options including mineral or synthetic oils, applied via splash or forced methods. Brands recognized for their reliable speed reducers include SEW-Eurodrive, Nord, Flender (Siemens), Bonfiglioli, Sumitomo, and Dodge (ABB). The service factor is critical as it applies to the rated torque of the reducer, ensuring it can handle the operational demands effectively.