The pin lug coupling is made of several non-metallic elastic materials, which are placed in the flange holes of the two halves of the coupling, and the two half couplings are connected through the pin lugs. The coupling is simple in structure and easy to manufacture. It is convenient to assemble and disassemble and replace the elastic elements without moving the two couplings.
There are two types of pin lug couplings: key connection and flange connection. The key connection is generally divided into keyway connection, splined connection and clamping keyway connection.
Common keyway connection is commonly used. When the key coupling is assembled, it should be noted that the hub and shaft are not coaxial due to improper assembly of the key.
The heating method is mostly used in temperature difference assembly method for gear coupling, and the cooling method is used less. The correct installation of the pin lug coupling should make the two sides of the key closely fit with the wall of the keyway. Generally, it is checked by coloring during assembly. If it is not suitable, it can be repaired with a file or a shovel to meet the requirements.
There is generally a gap on the upper part of the key, about 0.1-0.2mm. High-speed rotating machinery has high requirements on the coaxiality between the hub and the shaft. The single-key connection cannot achieve high coaxiality, and the double-key connection or spline connection can improve the coaxiality of the two.
Due to the elastic element of the pin lug coupling, the elastic element can produce large elastic deformation and damping effect, so the pin lug coupling can not only compensate the relative displacement of the two shafts, but also cause buffering and vibration absorption.
In the process of mechanical transmission, the load transferred by the shaft system often changes, causing the change of load for different reasons, such as the motor speed instability, the load instability of the working mechanism and the centrifugal force caused by the imbalance of rotating parts in the shaft system.
The change of load is often reflected as cyclic load, shock load and irregularly changing load. The pin lug coupling can adapt to the fluctuation of the load, and has the ability of buffering and damping, which is mainly related to the stiffness and damping of the pin lug coupling.
The stiffness of coupling includes radial stiffness, axial stiffness and torsional stiffness. In practical engineering, load variation is often caused by torsional vibration caused by torque fluctuation, so the main stiffness of coupling is torsional stiffness.
In general, in pin lug coupling shafting drive, the stiffness of other parts of the system will be much greater than the stiffness of pin lug coupling.
Therefore, in the simplified case, it is assumed that the elasticity of other components is zero, and only the elasticity of the coupling is considered. The torsional stiffness of the coupling is used as the torsional stiffness of the transmission shaft.
Although the pin lug coupling generally has the functions of buffering and vibration absorption, the pin lug coupling with a certain value of stiffness does not have the effect of damping vibration under the action of arbitrary torque change, but sometimes causes strong vibration.
Therefore, the damping effect can only be produced when the stiffness of the coupling is coordinated with other parameters and loads of the entire drive shaft.
For a given transmission shafting, the rotational inertia and natural frequency can be obtained. If the variation law of the transmitted torque, such as amplitude and frequency, is known, the differential equation of the torsional vibration of the shafting can be established, and the required coupling stiffness can be obtained by solving the equation.
In order to solve the differential equations of motion, it is necessary to simplify the mechanical models of inertia and stiffness of the active and driven sides of the pin lug coupling in the transmission shaft system.
It is typically simplified to two equivalent disks, arranged on either side of the coupling. In the operation of coupling, the periodic load is a typical load form in mechanical transmission.
