Cardan Couplings
As a key component in mechanical transmission systems, cardan couplings play an irreplaceable role in modern industrial equipment. It can effectively solve the power transmission problem in the case of axis misalignment and angular deviation, and is widely used in various fields from precision automotive transmission to heavy metallurgical machinery.
Cardan coupling is a mechanical device that can achieve continuous rotation and reliably transmit torque and motion in the presence of an angle between two axes. Its core function is to compensate for axial, radial, and angular deviations in the transmission system, and solve the problem of shaft misalignment caused by manufacturing errors, installation deviations, load deformation, or thermal expansion. This unique performance makes universal couplings an indispensable component in complex mechanical transmission systems.
Structurally, the cardan coupling utilizes the principle of hinge mechanism to achieve multi-directional rotational freedom through special structures such as cross shafts and ball cages. When the driving shaft rotates, power is transmitted to the driven shaft through an intermediate transmission mechanism, which maintains the continuity of motion even if there is a certain angle between the two shafts. This design not only solves the problem of axis misalignment, but also buffers and reduces vibration, improving the dynamic performance of the entire shaft system. The transmission efficiency of universal couplings is usually high, the structure is relatively compact, and it can achieve power transmission with large angle deflection in a limited space.
From a material perspective, universal couplings are often made of high-strength alloy steel, carbon steel, or special composite materials. Key components undergo precision machining and heat treatment to ensure sufficient strength, wear resistance, and fatigue life. The bearing part usually uses needle or roller bearings to reduce friction losses, and some high-speed products also undergo dynamic balancing treatment to ensure smooth operation. The design of the lubrication system is also crucial, as good lubrication can significantly extend the service life of the coupling. Modern high-end products are often equipped with automatic lubrication systems or adopt maintenance free designs.
The development of universal couplings has formed diverse structural forms, each with its unique advantages and application scenarios. According to the transmission principle and structural characteristics, common universal couplings in the market can be divided into various types such as cross shaft type, ball cage type, ball fork type, three pin type, etc. They each have their own emphasis on compensation ability, transmission efficiency, speed limit, and service life. A deep understanding of the characteristic differences among these structural types is the foundation for correct selection and application.
The cross axis cardan coupling is the most traditional and common type, consisting of two Y-shaped or U-shaped cardan coupling forks and a cross axis. The four necks of the cross shaft are connected to two forks through needle roller bearings, forming a hinge structure. The advantages of this design are simple structure, low manufacturing cost, easy maintenance, and the ability to adapt to larger torque transmission requirements. Its disadvantage is that the output speed is uneven when used in a single section, which can generate additional dynamic loads. Therefore, in practical applications, a double coupling structure is often used to eliminate speed fluctuations by reasonably arranging the phase relationship between the two cross couplings. The allowable angle between the two axes of the cross axis cardan coupling is usually 15 ° -25 °, and can reach 45 ° in heavy-duty designs. It is widely used in industrial fields such as metallurgy, mining, and construction machinery. According to the different bearing seat structures, the cross shaft type can be divided into various forms such as SWC type integral fork head type, SWP type partial bearing seat type, and SWZ type integral bearing seat type, which are suitable for different load conditions and installation space limitations.
The ball cage cardan coupling (also known as the constant velocity cardan coupling) uses spherical raceways and steel balls as transmission components, ensuring that the instantaneous angular velocity of the input and output shafts is always consistent through precise geometric relationships. This structure has smooth transmission and low vibration noise, making it particularly suitable for high-speed operation. The most common application is in automotive drive shafts. The ball cage cardan coupling usually allows a working angle of up to 22 ° -25 °, and special designs can reach up to 47 °. The internal steel balls move along the precision machined raceway under the guidance of the cage, with low friction loss and high efficiency. According to the different shapes of the raceway, the cage type is divided into fixed type (RF) and telescopic type (VL). The former is used for the wheel end, while the latter is used for the differential end, together forming a complete automotive drive shaft system. In addition to the automotive industry, ball cage cardan couplings are gradually being applied in fields such as industrial robots and precision machine tools that require high transmission stability.
The ball joint plunger cardan coupling represents another innovative design concept, which adopts a spherical hinge structure and a plunger type force transmission mechanism, combining large angle compensation capability and compact structural dimensions. This type of coupling usually consists of two connecting plates and three or more force transmitting arm pairs, and power transmission is achieved through a ball joint socket connection. Its single section swing angle can reach 42.5 °, and special models even support high tilt angle operation of 75 °, far higher than traditional cross axis products. Another significant advantage of the ball joint plunger type is its compact structure. Under the same rotation diameter conditions, its axial size is much smaller than that of the cross shaft coupling, making it very suitable for installation in situations where space is limited. At the same time, this design naturally has good dynamic balance performance and can adapt to high-speed operation requirements. In heavy load and limited space scenarios such as metallurgical rolling mills and mining hoisting machinery, ball joint plunger universal couplings demonstrate significant advantages.
In addition to the three mainstream types mentioned above, the cardan coupling family also includes various variants such as ball fork type, three pin type, and convex block type. The ball fork transmission is achieved through a spherical fork head and a groove, with a simple structure but fast wear and tear; The three pin type adopts three pin shafts and a special contour cam plate, which can achieve constant speed transmission and is mainly used for the inner cardan coupling of front wheel drive vehicles; The convex block type utilizes the engagement between the convex block and the groove to transmit torque, and has overload protection function. Each structural type has its own advantages, and in practical selection, multiple factors such as torque capacity, speed range, compensation capability, space limitations, and cost budget need to be comprehensively considered.
