Ball-screw drive with integrated ball return for brake actuator assembly
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Solution Overview
Problem
Conventional ball-screw drives for electromechanical brakes with a screw nut closed on one side cannot be assembled conventionally due to the inability to push out the assembly rod and pre-assemble balls in the ball return system.
Innovation Solution
A ball-screw drive with a recirculating ball screw and an integrated ball return system, where the balls are pre-assembled on the screw, allowing a screw nut closed on one side to be used, enabling axial displacement and a shorter design by integrating the ball return system into the recirculating ball screw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a screw nut closed on one side is used, then the brake piston can directly place the brake pad on the brake rotor without additional intermediate elements, but the conventional assembly method cannot be applied since the assembly rod cannot be pushed out
Solution Approach 1:
The ball return system is pre-filled with balls before the screw nut is closed. The balls are inserted into the ball return system through the open end of the screw nut while it is still accessible, and then the screw nut is closed. This preliminary action allows the closed screw nut design to be manufactured without compromising the ball return function.
2Length of moving object
If a screw nut closed on one side is used, then a more compact design is achieved, but pre-assembly of balls in the ball return system becomes impossible with conventional methods
Solution Approach 1:
The balls are preliminarily inserted into the ball return system before the screw nut is closed. The ball return system is designed with an open end that allows ball insertion, and after the balls are in place, the screw nut is closed to seal the balls inside. This enables the compact closed design while maintaining the ability to pre-assemble the balls.
Solution Approach 2:
The ball return system acts as an intermediary structure that temporarily allows ball insertion from the outside. It provides a pathway for the balls to be introduced into the closed screw nut design, serving as a mediator between the closed structure and the ball filling requirement.
3Length of moving object
If the ball return system is integrated into the recirculating ball screw, then a shorter axial design is achieved, but the structure becomes more complex
Solution Approach 1:
The ball return system is merged with the recirculating ball screw structure. Instead of being separate components, the ball return system is integrated into the screw itself, allowing balls to return to the thread start position through the screw structure. This merging eliminates the need for separate ball return channels in the screw nut, reducing axial length.
Solution Approach 2:
The ball return system utilizes the radial dimension of the ball screw by forming ball return channels that extend radially into the screw. This dimensional approach allows the ball return function to be achieved within the existing screw volume, reducing the need for additional axial space.
Data Source
AI summary
A ball-screw drive for an actuator assembly of a vehicle brake is disclosed, comprising a rotatably mounted recirculating ball screw on which a screw nut which is closed on one side is mounted, at least one thread being formed on the circumferential surface of the recirculating ball screw, in which thread a plurality of balls are guided in such a way that a rotation of the recirculating ball screw brings about an axial displacement of the screw nut along an axis of rotation of the recirculating ball screw. A ball return system is integrated in the recirculating ball screw. Furthermore, an actuator assembly comprising a ball-screw drive and a method for producing a ball-screw drive are indicated.