There are many types of couplings, which can be divided into two categories according to their compensation capacity and working principle:
I. Rigid coupling:
Features: Simple structure, low cost, large torque transmission, no elastic elements. Requires strict and accurate alignment of the two connected shafts. Very sensitive to installation errors and shaft deformation, and cannot compensate for any deviation. Transmits vibration and impact.
· Main types:
Sleeve coupling: The simplest form, a sleeve is sleeved on the two ends of the shaft and fixed with a key or pin.
Flange coupling: The most commonly used. Two hubs with flanges are installed on the shafts respectively, and then the flanges are connected and fastened with bolts. There is a centering tenon structure to ensure the centering accuracy.
Clamp shell coupling: It consists of two longitudinally split half-cylindrical clamp shells and fixing bolts, which is easy to install and disassemble (the shaft does not need to move axially).
II. Flexible coupling:
Features: It can compensate for a certain amount of relative displacement and angular deviation between the two shafts. Usually contains elastic elements (metal or non-metal) or uses the gap/movement between parts to absorb deviations. Can buffer and absorb vibration. Most widely used.
· Main types (subdivided by compensation elements and working principles):
Flexible coupling without elastic elements (metal flexibility): Use the relative mobility between metal elements to compensate for deviations.
Gear coupling: Internal and external teeth mesh to transmit torque, allowing large comprehensive displacement compensation, high load capacity, lubrication required, often used in heavy machinery (rolling mills, ships).
Slider coupling/cross slider coupling: The middle slider slides in the grooves of the hubs on both sides to compensate for radial displacement. It has a simple structure and is resistant to high temperatures, but has wear and clearance.
Universal coupling: Mainly used for transmission between two intersecting shafts (large angular displacement), the output speed of a single universal joint is uneven, and it is often used in pairs (double universal joints) to maintain constant speed. Widely used in automobiles and engineering machinery.
Chain coupling: It uses a double-row roller chain to mesh with two identical parallel sprockets at the same time. It has a simple structure, is easy to assemble and disassemble, and has a certain compensation capacity.
Diaphragm coupling: One of the mainstream choices in modern industry. It uses a multi-layer metal diaphragm group as an elastic element to compensate for displacement through the flexible deformation of the diaphragm. It is wear-free, maintenance-free, has a long life, is resistant to oil pollution, has high torsional stiffness, has zero clearance, and has extremely high reliability. It is widely used in occasions requiring high speed, precision, and long life (pumps, fans, compressors, generators, turbomachinery, high-speed wire rolling mills).
Bellows coupling: Metal thin-walled bellows are used as elastic elements to mainly compensate for angular and axial displacements. They are particularly suitable for occasions with small torque, high precision, and high speed (servo motors, encoders, small precision equipment).
Ball cage universal coupling: A special constant velocity universal joint with a large transmission angle, high efficiency, and strong load-bearing capacity. It is widely used in automotive drive shafts and front-wheel drive systems.
Flexible coupling with elastic element: Use the deformation of non-metallic (rubber, polyurethane, engineering plastics, etc.) or metal (reed, diaphragm) elastic elements to compensate displacement, buffer and absorb vibration.
Elastic sleeve pin coupling: The pin is covered with rubber (or nylon) elastic sleeve and inserted into the holes of the two halves of the coupling. It has a simple structure, is easy to manufacture, easy to assemble and disassemble, has low cost, and has average compensation capacity. It is widely used (small and medium-power general machinery).
Elastic pin coupling: Use nylon (or other engineering plastic) pins to connect the two halves of the coupling. It transmits greater torque than the elastic sleeve pin, allows a certain axial displacement, and needs to be replaced after the pin is worn.
Plum blossom elastic coupling: The middle is a plum blossom-shaped elastomer (polyurethane or rubber), and the wheel hub claws on both sides are embedded with it. It has a compact structure, strong displacement compensation capacity, good buffering and vibration absorption, easy maintenance, and is widely used (various general machinery).
Tire coupling: A tire-shaped elastic element made of rubber or polyurethane, connected to the two halves of the coupling with bolts. It has strong displacement compensation capability (especially angular), excellent vibration absorption performance, and is suitable for damp, dusty, and high-impact situations (crushers, cranes). Low torsional stiffness.
Leaf coupling: A set of spring steel sheets are stacked, one end is fixed, and the other end is clamped in the hub, and the displacement is compensated by the bending deformation of the leaf. It has high torsional stiffness and good damping performance, and is often used in situations driven by high-power diesel engines (ships, generator sets).
Safety coupling:
Shear pin type: When overloaded, the pin is sheared off, disconnecting the power transmission.
Friction type: When overloaded, the friction surface slips.
Magnetic type: Use magnetic force to transmit torque and disengage when overloaded.