Choice of coupling

CouplingThe selection mainly considers the speed of the required transmission shaft, the size of the load, the installation accuracy of the connected two parts, the stability of rotation, the price, etc., refer to the characteristics of various couplings, and choose a suitable coupling Types of.

The following points can be considered when making specific choices:
1.Due to reasons such as manufacturing, installation, load deformation and temperature changes, it is difficult to maintain strict and precise alignment of the two shafts after installation and adjustment.There is a certain degree of displacement in the x and Y directions and the deflection angle CI.When the radial displacement is large, you can choose a slider coupling, and when the angular displacement is large or the connection of two intersecting shafts, you can choose a universal coupling.When the two shafts produce a large additional relative displacement during the working process, a flexible coupling should be used.
2.The working speed of the coupling and the centrifugal force caused by it.For high-speed transmission shafts, couplings with high balance accuracy, such as diaphragm couplings, should be used instead of eccentric slider couplings.
3.The size and nature of the torque to be transmitted and the requirements for the function of damping vibration.For example, for high-power heavy-duty transmission, gear couplings can be used.For severe impact loads or transmissions requiring the elimination of shaft torsional vibration, tire couplings can be used.
Most couplings have been standardized or standardized.The designer's task is to choose, not design.The basic steps for selecting a coupling are as follows:
Select the type of coupling
According to the size of the transmitted load, the speed of the shaft, the installation accuracy of the two parts to be connected, etc., refer to the characteristics of various couplings and select a suitable coupling type.

The following points can be considered when making specific choices:
　　1) The size and nature of the torque to be transmitted and the requirements for the buffer and vibration reduction function.For example, for high-power and heavy-duty transmissions, gear couplings can be selected; for transmissions that require severe impact loads or to eliminate shaft torsional vibrations, tire couplings and other couplings with high elasticity can be selected.
2) The working speed of the coupling and the centrifugal force caused by it.For high-speed transmission shafts, couplings with high balance accuracy, such as diaphragm couplings, should be selected, rather than slider couplings with eccentricity.
3) The magnitude and direction of the relative displacement of the two axes.When it is difficult to maintain strict and precise alignment of the two shafts after installation and adjustment, or when the two shafts will have a large additional relative displacement during the working process, a flexible coupling should be used.For example, when the radial displacement is large, you can choose a slider coupling, and when the angular displacement is large or the connection of two intersecting shafts, you can choose a universal coupling.
4) The reliability and working environment of the coupling.Generally, couplings made of metal elements that do not require lubrication are more reliable; couplings that require lubrication are easily affected by the perfect degree of lubrication and may pollute the environment.Couplings containing non-metallic components such as rubber are more sensitive to temperature, corrosive media and strong light, and are prone to aging.
5) The manufacturing, installation, maintenance and cost of the coupling.Under the premise of meeting the convenience of use, couplings that are convenient for assembly and disassembly, simple maintenance, and low cost should be selected.For example, the rigid coupling is not only simple in structure, but also easy to assemble and disassemble, and can be used for low-speed, rigid drive shafts.General non-metal elastic element couplings (such as elastic sleeve pin couplings, elastic pin couplings, plum-shaped elastic couplings, etc.), due to their good comprehensive capabilities, are widely used in general medium and small Power transmission.

universalCouplingOptional calculation
Calculated torque of universal coupling:
Tc=TKnKhK Ka≤Tn(N·m)
Under alternating load: Tc≤Tf (N·m)
In the formula, Tn——the nominal torque of the universal joint, N·m, (it is the theoretically calculated value under the given conditions, that is, the speed of the coupling, n≈10r/min. Bearing life Ln=5000h, Axis angle = 3°, the value when the load is stable);
Tf——Fatigue torque of universal joint, N·m
T——Theoretical torque of universal coupling, N·m
T = 9550
Pw——drive power, kw
N——Universal coupling speed, r/min
Kn——The speed correction coefficient of universal coupling,
Kh-bearing life correction factor of universal coupling
K ——The correction coefficient of the two-axis angle of the universal coupling
Ka——load correction factor.When the load is uniform and the work is stable, Ka=1.0; when the load is uneven, when the impact is medium, Ka=1.1～1.3; when the large impact load and frequent forward and reverse rotation, Ka=1.3～1.5, extra large impact load and frequent forward and reverse rotation When Ka>1.5.
For universal joints with high rotation speed, large folding angles, or lengths exceeding the regulations, in addition to the above calculations, the rotation flexibility must be checked. The rotation flexibility is represented by n. In general: n> 18000.
In the formula-the axis angle of the universal coupling, (°); n-the speed of the universal coupling, r/min