Planetary screw drives (PWGs) (also referred to as rolling planetary screw drives) have been the state of the art for many years, and are described for example in DD 0277308 A5. A planetary screw drive is known, for example, from published patent DE 10 2010 047 800 A1, which is contained in a hydrostatic actuator in the form of a hydrostatic clutch actuator in order to convert a rotary motion produced by means of an electric motor to an axial motion.
From a heretofore unpublished application, rolling planetary transmissions for use in an actuator are also known. Here, a rotor of an e-motor (electric motor) is connected non-rotatingly to a spindle of a PWG. At the same time, the spindle nut of the PWG is secured against turning, in order to guarantee an axial motion which ultimately results in a piston stroke of the actuator. The position of the piston can be determined using sensor technology that is integrated into the disengaging system. To that end, the position of an electrically conductive object that is to be detected (target) is ascertainable using an inductive sensor that is fixed relative to the housing, the target being integrated into the piston or into a component of the disengaging system which is movable axially complementarily to the piston, or being shaped in the form of at least one region of a component that is movable complementarily to the piston. This solution turns out to be very expensive.
A device for converting a rotary motion into an axial motion, having a threaded spindle with a nut that encircles the screw spindle and is rotatable relative to the latter, with inside profiling and with a number of profiled rolling elements positioned in between, is also known from publication EP 320 621 A1. The threaded spindle has single-course or multi-course fine threading on its outside, and the inner profiling of the nut, which is rotatable relative to the threaded spindle, is executed in the form of relatively coarse grooves. In addition, a covering is provided on both sides, which serves to secure the rollers.
Furthermore, it is also known to connect a rotor of a drive to a spindle by means of a compression connection or in some other way so that it cannot turn.
Disadvantages here are the high construction expense and the sometimes expensive assembly.