Universaalinivelinen

Universaalinivelinen, also known as a universal joint or U-joint, is a mechanical coupling that connects rigid rotating shafts where the shafts are not aligned. Its primary function is to transmit rotational motion and torque between shafts that are at an angle to each other. This allows for flexibility in the drivetrain of vehicles and other machinery.

The most common design of a universal joint consists of two yoke-shaped ends, each attached to one of the shafts. These yokes are connected by a cross-shaped spider, with four bearings or trunnions that fit into the bores of the yokes. The spider allows the yokes, and thus the shafts, to pivot relative to each other, accommodating the angle between them.

Universal joints are essential in applications where the angle between rotating components changes during operation. For example, in rear-wheel-drive vehicles, they are used in the driveshaft to connect the transmission output shaft to the differential. As the suspension moves, the angle of the driveshaft changes, and the universal joints compensate for this variation. Similarly, in steering columns, they allow for a comfortable and adjustable driving position by connecting the steering wheel shaft to the steering rack at an angle.

While simple and effective, standard universal joints have a characteristic known as "non-uniform velocity." This means that when operating at an angle, the output shaft does not rotate at a perfectly constant speed relative to the input shaft. This can lead to vibrations and wear, especially at higher angles and speeds. To counteract this, often two universal joints are used in series, with their angles configured to cancel out the non-uniform velocity effect.