The working principle of the coupling diaphragm

The diaphragm is the core component of the diaphragm coupling. According to the shape of the diaphragm, it can be divided into a beam waist type, a ring type, a separate connecting rod type, a spoke type, and a polygon type.The diaphragm coupling relies on the elastic deformation of the diaphragm to compensate for the relative displacement of the two shafts connected. It is a high-performance flexible coupling with metal elastic elements. It does not require lubrication, has a compact structure, high strength and long service life. There is no rotation gap, and it is not affected by temperature and oil pollution. It has the characteristics of acid resistance, alkali resistance, and corrosion resistance. It is suitable for shaft transmission in high temperature, high speed, and corrosive medium conditions. It is widely used in shaft transmission of various mechanical devices, such as Water pumps (especially high-power and chemical pumps), fans, compressors, hydraulic machinery, petroleum machinery, printing machinery, textile machinery, chemical machinery, mining machinery, metallurgical machinery, aviation (helicopters), high-speed power transmission systems for ships, After being dynamically balanced, it is relatively common to apply to high-speed transmission shafting. 

According to the working condition of the coupling, we can summarize the forces of the coupling into the following four types, and give the calculation methods of various forces, taking the eight-hole waist diaphragm as the object.

(1) Bending stress caused by angular installation error.Due to the actual installation error in the axial angular direction, the diaphragm is periodically bent and deformed along the axial direction, and it is the main reason that determines the fatigue life of the coupling diaphragm.Calculate the displacement of the middle bolt hole in the axial direction caused by the angular deviation. The radial displacement and the axial displacement are fixed.The magnitude of the restoring moment H can be obtained by the angle tilt. Generally, the angular displacement of the coupling diaphragm is very small, so the diaphragm deformation is a small deformation, which can be analyzed by the small deflection bending theory of the thin plate.

(2) Due to the error of the axial installation, the diaphragm is bent and deformed along the axial direction.The displacement is loaded in the axial direction of the middle bolt hole, and the radial displacement and the axial displacement are fixed.The two middle holes at both ends are used for restraint, and the middle hole is used to bear the load.In this way, treat it as a statically determinate simply supported mechanism.

(3) Centrifugal stress due to inertia during high-speed rotation.Assuming that the bolt and the coupling diaphragm are of the same material, the respective masses can be calculated. According to the position and the spiral angle, the centrifugal force can be calculated and acted on the total center of mass.The centrifugal inertia force of high-speed machinery is very important in the stress calculation of the structure. The centrifugal inertia force can be loaded according to the radial force F=(2∏n/60)2rp, the direction is radially outward, and the diameter of the middle bolt hole is fixed. There is no other load around the displacement, circumferential displacement and axial displacement.

(4) Film stress generated by torque.Suppose the transmitted torque is T(Nm), and the total number of pieces is m. For 8-hole bolts, the simplified conditions are: the torque of a single diaphragm is T1=T/m, and the force on each main bolt is F =T/4mR.