Coupling selection method
The coupling is one of the components in the hydraulic system, due to the use of a wider area, there are many varieties, in the classification of coupling models and specifications, so there are many requirements in the choice of small, collecting some of the choice of coupling method, and to share with you a.
In many standard couplings, the correct choice for your needs best coupling, and the machinery shaft drive performance, reliability, service life, vibration, noise, energy saving, transmission efficiency, transmission accuracy and economy are closely related, but also related to the quality of mechanical products. When choosing the coupling, the designer should choose the shaft coupling from the angle of shaft drive and need to choose the coupling which only considers the main and driven end connection.
The factors that should be considered in the selection of couplings:
1. Mechanical characteristics of the power machine
The mechanical characteristics of the power machine have certain influence on the whole transmission system. Because of the different mechanical characteristics of different types of power machine, the corresponding power machine coefficient Kw should be selected, and the best coupling suitable for the system is selected. The category of the power machine is the basic factor to select the coupling type, and the power of the power machine is one of the main basis to determine the size of the coupling, and is directly proportional to the torque of the coupling.
Between the power machine and the working machine, the main and driven ends are connected by one or several couplings of different types and sizes to form a shaft transmission system. In the mechanical drive, the power machine is no more than motor, internal combustion engine and gas turbine. Because of the different working principle and mechanism of the power machine, its mechanical characteristics vary greatly, some of them run smoothly, some of them have shock when they are running, and they have different effects on the transmission system. According to the mechanical characteristics of the power machine, the power machine is divided into four categories.
2. Classification of loads
The load category of the transmission system is the basic basis for selecting the coupling varieties. In order to improve the working performance of the transmission system, the flexible coupling with elastic elements, i.e. the elastic coupling, should be chosen to buffer, reduce vibration and compensate the axial offset. Frequently, start reversing, the braking torque is normal working torque several times, overload work, shorten the service life of the inevitable coupling elastic element, coupling allows only short-term overload, generally not more than twice the nominal 2~3 short-term overload torque, i.e. [Tmax] = 2~ 3T n.
The power transmission system of mechanical products are fixed to the motor drive system of mechanical products (such as ships, vehicles etc.) in power machine for internal combustion engine, when the engine is the cylinder of internal combustion engine with different numbers, must consider the torsional vibration of the drive system's influence, the influence factors and the internal combustion engine cylinder number each cylinder is working on. The elastic coupling should be used in order to adjust the natural frequency of the shafting and reduce the amplitude of the torsional vibration, so as to reduce the vibration, buffer and protect the transmission parts, improve the performance and improve the stability of the output power.
The low speed coupling should be avoided, choose only applicable to small and medium power such as pin coupling with elastic sleeve and core type elastic coupling, coupling, polygonal rubber tire coupling; control needs of the shafting of overload protection, should use safe coupling; great change of shaft load and shock and vibration, should choose a elastic coupling elastic element and buffer and good damping effect. The bearing capacity of metal elastic component elastic coupling is higher than the elastic coupling of nonmetal elastic element; the elastic coupling of the elastic element squeezed is higher than the elastic coupling of the elastic element being sheared.
3, the allowable rotation speed of the coupling
The allowable rotational speed range of the coupling is determined according to the allowable line speed and the maximum outer dimension of the coupling materials. The range of allowable rotational speed of the couplings of different materials and varieties and specifications is different. Changing the material of the coupling can increase the allowable rotational speed range of the coupling. The allowable rotation speed of the material is greater than the allowable speed of the material as cast iron.
For the coupling of n>5000r/min working condition, the centrifugal force of the outer edge of the coupling and the deformation of the elastic element should be taken into account, and dynamic balance should be taken. High speed should not use non-metallic elastic components elastic coupling, high speed deformation of elastic components, it is advisable to use high precision flexible coupling. At present, foreign high-speed coupling is more than diaphragm coupling and high precision drum gear coupling. Universal coupling
4, the coupling of the two axis relative displacement
Due to the manufacturing error, assembly error, installation error, shaft deformation, base deformation, bearing damage, temperature change (thermal expansion, cold contraction), relative movement between components, relative displacement of the two shafts is relative to the two axes. Generally, the relative displacement between two axes is difficult to avoid, but the displacement direction produced by shafting transmission under different operating conditions, namely axial (x), radial (y), angular (alpha) and displacement magnitude, is different.
Flexible coupling has the ability to compensate the relative displacement between two shafts, so flexible couplings are widely used in practical applications. The rigid coupling has no compensation performance, and the application range is limited, so the amount is very little. Angle (alpha) only large shaft drive should adopt universal coupling, axial movement, and the need to control the drive shaft axial displacement, should be used only for diaphragm coupling; high precision under the condition of the rigid coupling, flexible coupling the standard allowable amount of compensation.
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