Kreuzgelenk

Kreuzgelenk, also known as a universal joint or Cardan joint, is a mechanical coupling that connects rigid rotating shafts that are not aligned. It is designed to transmit rotary motion between shafts that are at an angle to each other. The most common form of a Kreuzgelenk consists of a pair of hinges oriented at 90 degrees to each other, connected by a spider piece. This spider has four trunnions, each of which pivots in a yoke attached to the end of a shaft.

The primary function of a Kreuzgelenk is to allow for changes in the relative angle between the driving and driven shafts. This is particularly useful in applications where the distance between components is not constant or where there are vibrations or movements. Examples include the driveshafts of rear-wheel-drive vehicles, where the angle between the transmission and the rear axle changes as the suspension moves, and in steering systems.

While effective, a single Kreuzgelenk transmits motion with a fluctuating velocity if the angle between the shafts is not zero. This means the driven shaft speeds up and slows down twice per revolution. To overcome this, two Kreuzgelenks are often used in series, with the second joint oriented to compensate for the velocity variations of the first, resulting in a constant velocity output. This double-cardan joint configuration is common in automotive applications. The design is relatively simple and robust, making it a widely adopted solution for transmitting power between angled shafts.