Coupling selection reference (XNUMX)
Time: 2018-04-15 Browse:
There are many types, types, and specifications of couplings. Based on the correct understanding of the respective concepts of types, types, and specifications, the coupling should be selected according to the needs of transmission. First, choose from the couplings that have been formulated as a standard. At present, I have There are dozens of types of couplings formulated as international and industry standards. Most of these standard couplings are universal couplings. Each type of coupling has its own characteristics and suitable range, and can basically meet a variety of working conditions. In general, designers do not need to design the coupling by themselves, and only design the coupling when the existing standard coupling cannot meet the needs.Standard couplings are easy to purchase, and the price is much cheaper than self-designed non-standard couplings.Among the many standard couplings, the correct choice of the best coupling that suits your needs is related to the working performance, reliability, service life, vibration, noise, energy saving, transmission efficiency, transmission accuracy, A series of issues such as economy are also related to the quality of mechanical products.
When selecting a coupling, the designer should choose the coupling based on the angle and needs of the slave shaft transmission, and should avoid simply considering the coupling of the main and driven ends.
XNUMX. Factors to be considered when choosing a coupling
(XNUMX) Mechanical characteristics of power machine
Between the power machine and the working machine, the main and driven ends are connected through one or several couplings of different types and specifications to form a shaft transmission system.In mechanical transmission, power machines are nothing more than electric motors, internal combustion engines and gas turbines.Due to the different working principles and mechanisms of the power machine, its mechanical characteristics are quite different, some run smoothly, and some run with shocks, which have unequal effects on the transmission system.According to the mechanical characteristics of power machines, power machines are divided into four categories.See Table 1.
Table 1 Power machine coefficient Kw
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Power engine category code
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Power machine name
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Power machine coefficient Kw
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Power engine category code
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Power machine name
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Power machine coefficient Kw
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I
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Motor, turbine
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1.0
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Ⅲ
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Two-cylinder internal combustion engine
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1.4
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Ⅱ
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Four-cylinder and more than four-cylinder internal combustion engine
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1.2
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Ⅳ
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Single cylinder internal combustion engine
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1.6
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The mechanical characteristics of the power machine have a certain influence on the entire transmission system. For different types of power machines, due to their different mechanical characteristics, the corresponding power machine coefficient Kw should be selected, and the best coupling suitable for the system should be selected.The type of power machine is the basic factor for selecting the type of coupling. The power of the power machine is one of the main basis for determining the size of the coupling, which is proportional to the torque of the coupling.
Most of the power machines in the transmission system of fixed mechanical products are electric motors. The power machines in the transmission systems of mechanical products (such as ships, various vehicles, etc.) are mostly internal combustion engines. When the power machine is an internal combustion engine with a different number of cylinders, the torsional vibration must be considered. The influence of the transmission system is related to the number of cylinders of the internal combustion engine and whether each cylinder is working normally.In this case, flexible couplings should generally be selected to adjust the natural frequency of the shafting, reduce the torsional vibration amplitude, thereby damping, buffering, and protecting the transmission device components, improving the centering performance, and increasing the stability of the output power.
(XNUMX) Load category
Due to different structures and materials, the load capacity of couplings used in the transmission system of various mechanical products varies greatly.The load category is mainly for the impact, vibration, forward and reverse rotation, braking, frequent start and other reasons of the working load of the working machine to form different types of loads.In order to facilitate selection and calculation, the load of the transmission system is divided into four categories, as shown in Table 2.
Table 2 Load category
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Load category
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Load condition
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Working condition factor K
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Load category
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Load condition
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Working condition factor K
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I
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Uniform load, stable work
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1 ~ 1.5
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Ⅲ
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Heavy impact load, frequent forward and reverse rotation
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2.5 ~ 2.75
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Ⅱ
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Medium shock load
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1.5 ~ 2.5
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Ⅳ
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Extremely heavy impact load, frequent forward and reverse rotation
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> 2.75
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The load category of the transmission system is the basic basis for selecting the coupling type.For working loads with large changes in shock, vibration and torque, flexible couplings with elastic elements, that is, elastic couplings, should be selected to buffer, reduce vibration, compensate for axis deviation, and improve the performance of the transmission system.The torque during frequent starting, forward and reverse rotation, and braking is several times the torque during normal and stable operation. It is overload work, which will inevitably shorten the service life of the coupling elastic element. The coupling only allows short-term overload, generally short-term The overload shall not exceed 2~3 times of the nominal torque, ie [Tmax] ≥ 2~3T n.
Low-speed working conditions should avoid the use of couplings that are only suitable for small and medium power, such as: elastic sleeve pin coupling, core-type elastic coupling, polygonal rubber coupling, tire coupling, etc.; overload control is required For safety-protected shafting systems, safety couplings should be used; for shafting systems with large load changes and impacts and vibrations, flexible couplings with elastic elements and better cushioning and damping effects should be selected.The load-bearing capacity of the elastic coupling of the metal elastic element is higher than that of the elastic coupling of the non-metal elastic element; the reliability of the elastic coupling of the elastic element being compressed is higher than that of the elastic coupling of the elastic element being sheared.
