A cardan shaft also known as a Cardan Joint, Hooke's Joint, or U-Joint)is a fundamental component widely used in mechanical drive systems. Its primary function is to connect two shafts whose axes are not collinear and to transmit torque and rotational motion between them.Its operating principle is based on a spherical linkage mechanism, allowing the connected shafts to form a certain included angle (typically up to 15°-20°) within a plane and compensating for minor axial, radial, and angular misalignment.
A typical single universal joint coupling mainly consists of the following components:
Yoke (Driving Yoke and Driven Yoke): The U-shaped or yoke-shaped fork ends attached to the shafts.
Cross Shaft/Spider (Cruciform): The core component, featuring four trunnion journals arranged in a cross shape.
Needle Roller Bearings / Plain Bearings: Installed between the cross shaft journals and the yoke bores to reduce friction and wear.
Bearing Cap / Retaining Ring (Circlip): Used to secure and seal the bearings, preventing disassembly.
To overcome the inherent velocity fluctuation of a single joint, engineering practice commonly employs a "double universal joint" arrangement in series. This setup must adhere to the installation rule that "the input shaft and output shaft angles relative to the intermediate shaft are equal, and the yokes at both ends of the intermediate shaft lie in the same plane" to achieve constant velocity transmission.
Compensates for Large Angular Misalignment:
Its most prominent advantage. A single joint can accommodate a relatively large working angle (typically 15°-25°, up to 35°+ with special designs), making it ideal for connecting shafts with significant installation errors or those subject to relative movement during operation.
Compact Design with High Load Capacity:
Relatively simple yet robust construction, often forged from high-strength alloy steel. Capable of transmitting very high torque, suitable for heavy-duty machinery (e.g., rolling mills, ships, mining equipment).
High Transmission Efficiency:
With needle roller bearings, friction loss is minimal, achieving efficiency rates of 98%-99.9%.
High Reliability and Relatively Simple Maintenance:
Rugged and durable with a long service life when properly lubricated. Failures typically manifest as wear on the cross shaft or bearings, which are relatively straightforward to replace.
Suitable for Harsh Environments:
Can operate in dusty, damp, or environments with temperature variations when equipped with protective covers or seals.
Primary Application Fields:
Automotive Industry: Driveshaft systems, connecting the transmission to the drive axle.
Metallurgical Machinery: Drive mechanisms for rolling mills, straightening machines.
Construction Machinery: Locations requiring large-angle power transmission in cranes, excavators, concrete pump trucks, etc.
Paper Machinery, Marine Industry, Heavy-Duty Mining Machinery: Equipment that transmits high torque and involves shaft misalignment.