The invention relates to a ball screw nut that is provided for a ball screw drive and comprises a tubular sheet-metal part with a thread profile functioning as a load section for roller bodies.
As a ball screw drive, a rolling element, helical raceway drive is defined, which includes balls as the rolling elements. The rolling elements traverse a helical-shaped load section that is formed by profiled sections of nut and spindle of the ball screw drive. After completely traversing the load section, the balls are fed through a deflection section located in the nut back into the load section. Ball screw drives are distinguished by high efficiencies of typically greater than 80% and can convert both rotational motion into a translational motion and also a translational motion into a rotational motion. With regard to standardization, reference is made to DIN ISO 3408-1:2011-04 and also the older standard DIN 69 051 part 1.
A ball screw nut according to the prior art is known, for example, from DE 28 29 433 C2. This ball screw nut consists of an outer sleeve that can be made from plastic and an inner sleeve-like component. The sleeve-like component has a screw-shaped groove and is provided with a plurality of radial passage holes on which ball return elements are set. The sleeve-like component also has, on its outer side, a helical-shaped groove that has the same pitch as the groove on the inner side, so that the sleeve wall essentially has the same strength everywhere. The ball return element consists of a cylindrical projection and a curved plate that has a grooved surface that corresponds to the outer contour of the sleeve-like component.
Another ball screw nut is known from DE 30 32 955 C2. This ball screw nut is produced using a compression molding method and is comprised of two halves each of which are produced from a metal band. In one of the halves, a return recess is formed, that is, a deflection section that feeds the balls of the rolling-element, helical raceway drive back into the load section after exactly one revolution around the spindle.
Another ball screw drive that has a ball rolling spindle, and a spindle nut arranged on this spindle, that is, a ball screw nut, is known, for example, from DE 10 2004 040 362 A1. In this case, the ball rolling spindle and the spindle nut also define a ball channel for the endless circulating of the balls. The ball channel comprises a helical-shaped, wound load section and a load-free deflection section with ends contacting the load section. The deflection section here describes two legs arranged at angles to each other viewed in the axial direction. An angle that is measured on the spindle axis and reaches from one end up to the other end of the deflection section preferably equals 140 to 150 degrees according to DE 10 2004 040 362 A1.
From DE 10 2011 081 966 A1, a rolling-element helical raceway drive is known that comprises a thread part constructed as a composite part. Thread pitches are here produced from metal by shaping processes and encapsulated with tubular carrier parts made from plastic. The rolling-element helical-raceway drive should be suitable for use in an electromechanical braking force booster.
A thread nut of a maintenance-free thread drive with sliding surfaces is known, for example, from DE 100 28 968 A1. This thread nut is a sleeve-shaped sheet-metal part that is produced, for example, from steel, copper, brass, or aluminum. On the metallic material of the sleeve there is a sliding coating that can contain polytetrafluoroethylene.