Whether there is a transmission device between the prime mover and the universal coupling.If there is a transmission ratio, it will be output by several shafts after passing through the intermediate transmission device, that is, whether there is power split.Consider the type, power and speed of the prime mover.
It is necessary to consider the type of prime mover and the load category of the optional cross-shaft universal coupling to transmit load: one-way constant load, pulsating load or two-way alternating load.What is the installation status of the universal coupling?Horizontal, vertical or inclined installation.It is necessary to make the axis bend angle less than 3 degrees as much as possible, if oblique installation is necessary, determine the horizontal and vertical angle.
Taking into account the working environment of the prime mover, whether it is affected by harsh environmental conditions such as high temperature, dust, water spray, chemical corrosion, etc., choose the corresponding type of universal coupling according to the different use environment.
It is necessary to know the connection form and specific installation dimensions required at both ends of the universal coupling, as well as whether there are special requirements such as mounting brackets.
What is the speed of the cross shaft universal coupling itself?Whether it needs to be dynamically balanced.Dynamic balance or balance is required, and which level of balance quality level is required.
Are there restrictions on the installation location?What is the specific installation length and whether it needs to be telescopic.When it is required to expand and contract, what is the outward extension of the universal joint in the short state.For universal joints that do not require expansion or contraction, the compensation of axial dimensional errors must be considered, and the position for compensation in the system should be determined.
Through the understanding of the above prerequisites, gradually determine the specifications of the universal joint shaft, and then determine which structure to choose.The structural forms of universal couplings are cross shaft type, ball cage type, ball fork type, bump type, ball pin type, ball hinge type, ball hinge plunger type, three pin type, three fork rod type, three ball pin Type, hinge type, etc., commonly used is the cross shaft type, followed by the ball cage dragon. In actual applications, it is divided into heavy, medium, light and small according to the transmitted torque.To choose a coupling suitable for the prime mover from so many universal couplings, it is necessary to have a deep understanding of the prerequisites mentioned above and the external influence factors. The selection and calculation of universal couplings:
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; where T=9550Pw/ N (N·m)
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 bend angle, or length beyond the regulation, in addition to the above calculations, the rotation flexibility must also be checked. The rotation flexibility is represented by n, under normal circumstances: n>18000.
Where-the axis of the universal coupling, (°); n-the speed of the universal coupling, r/min.