How to choose coupling

When selecting couplings, designers should first choose couplings that have been formulated as national standards and mechanical industry standards and obtained national patents. Only when the existing standard couplings and patented couplings cannot meet the design needs can they design their own couplings. At present, China has formulated a considerable number of different types of standard couplings, which can basically meet different torque, speed and working conditions of different structural types and specifications. Some of the standard couplings have been developed by our country and passed industrial tests. Some have been reformed according to the relevant standards of foreign industrialized countries; Some are digested and absorbed with reference to imported prototypes and developed by themselves. Some standard couplings are not only new and high-performance in China, but also advanced internationally, such as diaphragm couplings. When formulating standards, they usually go through strict procedures to ensure the quality of standards. Standard couplings are mature and usually reliable. The key is the right choice. National patent couplings such as elastic pin coupling and sector elastic coupling absorb the advantages of many old-fashioned elastic couplings and overcome their respective shortcomings. It is a new high-performance technology at home and abroad, and it is an updated coupling.

Steps/Methods Select the kind and type of coupling.

Understand the comprehensive function of coupling (especially flexible coupling) in transmission system, and choose the variety and type of coupling from the overall design of transmission system. According to the type of prime mover, working load, working speed, transmission accuracy, two-axis deviation, temperature, humidity, working environment and other comprehensive factors, the variety of coupling is selected. Select the structure type of coupling according to the need of supporting the main engine. When the coupling and brake are used together, the coupling with brake wheel or brake disc should be selected. When overload protection is needed; Safety coupling should be selected; When connecting with flanges, the flange type should be selected; For long-distance transmission, when the axial size of the connection is large, the intermediate connection or the intermediate sleeve connection should be selected. Calculation of coupling torque

The power of the power machine in the transmission system should be greater than the power required by the workpiece machine. According to the power and speed of the power machine, the theoretical torque t of the high-speed end connected to the power machine can be calculated; According to the working condition coefficient K and other related coefficients, the calculated torque Tc of the coupling can be calculated. The coupling t is inversely proportional to n, so the low-speed end t is greater than the high-speed end t. Coupling model primary selection

According to the calculated torque Tc, similar nominal torque Tn can be selected from the standard series, and Tn ≥ Tc should be satisfied when selecting the model. Select the model (specification) of the coupling preliminarily. The alLowable rotational speed [n], the maximum radial dimension d and the axial dimension lo of the coupling can be found from the standard, and the rotational speed of the coupling should be n ≤ [n]. Adjust the model according to the shaft diameter

The shaft hole diameter d and the shaft hole length l initially selected should meet the requirements of the shaft diameters of the driving end and the driven end, otherwise, the specifications of the coupling should be adjusted according to the shaft diameter d, and it is common that the shaft diameters of the driving end and the driven end are different. When the torque and speed are the same and the shaft diameters of the driving and driven ends are different, the coupling model should be selected according to the large shaft diameter. In the newly designed transmission system, seven shaft hole types conforming to GB/T 3852 should be selected, and J 1 shaft hole type is recommended to improve universality and interchangeability, and the length of shaft hole should meet the requirements of coupling product standard. Select the connection style

The choice of coupling connection mode depends on the connection mode of driving end and driven end with shaft. Generally, key connection is adopted. In order to unify the key connection types and codes, GB/T 3852 stipulates seven types of keyways and four types of keyless connections, and A-type keys (Ping Jian single key slot) are widely used. Type and specification (model) of fixed coupling

According to the load category, rotating speed, working environment and other comprehensive factors of power machine and coupling, the type of coupling is selected according to the matching and connection of coupling. According to the nominal torque, shaft hole diameter and shaft hole length, the type of coupling is finally determined. In shafting transmission, there are generally different degrees of relative deviation between the two shafts, so elastic coupling should be selected; When the working load in shafting transmission produces impact and vibration, elastic coupling should be selected. Considering vibration reduction, cushioning effect and economy, elastic coupling with nonmetallic elastic elements should be selected.

Improper selection of coupling is common in China, such as gear coupling is widely used in shafting transmission of metallurgical machinery and heavy machinery. Impact, vibration and two-axis deviation are quite prominent unfavorable factors in low-speed and heavy-load shafting transmission of metallurgical machinery and heavy machinery. Only the elastic coupling with good damping effect can improve the working state of the transmission system, while the toothed coupling, whether it is drum tooth or straight tooth, is a rigid movable coupling. According to a series of shortcomings of drum gear coupling, such as no damping function, need of lubrication and sealing, need of regular maintenance, complex manufacturing process, high cost, etc., all teeth of drum gear coupling should mesh (point contact), but it is impossible to mesh all teeth due to manufacturing errors, so the large bearing capacity is a theoretical value. In the past, there were few types of coupling and little choice. At present, there are many elastic couplings, among which sector elastic coupling and elastic pin coupling are one of the reasonable choices to replace tooth coupling.