In motor vehicles, steering columns transform steering wheel rotation to steering rack translation and thence to the wheels of the vehicle. In particular, steering columns transmit a steering angle and steering torque from a steering wheel to a steering gear, e.g., to a rack and pinion steering gear, in a known manner. Steering columns that are commonly used today are generally bent, including multiple shafts connected to one another by universal joints to form the transmission path. The configuration of the steering column promotes safety and space conservation. The universal joints or Hooke's joints, allow even offset paths of the steering column connection. The rotation of the steering wheel and the steering wheel torque may be considered input into the system. A constant rotational velocity at the input shaft results in a variable output shaft velocity. The steering ratio of the steering column is generally a periodic function of the steering wheel angle (SWA), leading to a rotary motion which is transmitted non-uniformly by the steering column and which can be described by means of a transfer function. The function has a period of 180° SWA. This means the steering column transfer characteristic is exactly the same after half a rotation.
One known practice is to design the steering ratio either for a fast or a slow ratio in the central steering position or to select the steering ratio in such a way that the overall non-uniformity of the steering column is minimized.
In small passenger vehicles, a faster ratio in the central steering position can help to improve the feel of the steering, especially when traveling straight ahead. However, a slower steering ratio can improve the steering behavior of the vehicle when towing trailers, for example, especially in the case of small trucks.
In certain steering columns having conventional universal joints in the transmission path thereof, there are, however, certain limits to the adaptation of the transmission ratio since the transfer function of such steering columns has, as noted above, a period of 180° as a result of the universal joints used. For comfort, the non-uniformity of the rotary motion of the steering column should always be kept below a certain level so as to not obtain undesirable, perceptible torque fluctuations, e.g., when parking the vehicle. In some cases, adaptation of the non-uniformity of the transmission ratio of conventional steering columns can also lead to an undesirable high steering torque in the region of the respective steering lock.
It may be desirable, therefore, to provide a universal joint for connecting torque transmitting shafts, which significantly widens the scope for the design of the transmission of the rotary motion and to provide a steering column constructed with a universal joint of this kind.