Axial Ball Return Sleeve for Power Steering Reliability
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Solution Overview
Problem
Existing power steering systems with ball screw mechanisms face challenges in minimizing installation space and production complexity, and ensuring steerability when the toothed belt snaps.
Innovation Solution
A power steering system with a ball screw mechanism featuring a U-shaped ball return means formed by a deflector and a sleeve, where the sleeve axially surrounds the ball nut and deflector, providing a simple and compact design that maintains steerability even if the toothed belt snaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic sleeve with arcuate and resilient supporting regions is used to secure the ball return means, then the ball return means is radially secured, but the production process becomes complex
Solution Approach 1:
The invention extracts the fastening function from a complex resilient sleeve structure and implements it through a simple axial insertion of the ball return means into the ball nut housing. The ball return means is secured by being received within the housing in the axial direction, eliminating the need for complex resilient supporting regions and arcuate structures.
2Reliability
If a tubular deflector is used to convey balls back into the ball nut, then the ball return function is achieved, but additional installation space is required
Solution Approach 1:
The invention merges the deflector and ball return means into a single integrated component. The ball return means serves both as the structural element and the ball conveying path, eliminating the need for a separate tubular deflector and reducing installation space requirements.
Solution Approach 2:
The ball return means is designed to perform multiple functions: it provides the structural framework for ball return, creates the ball conveying path through its internal geometry, and secures itself axially within the housing. This multi-functional design eliminates the need for separate components.
3Reliability
If apertures are provided in the toothed belt pulley to fasten deflectors, then the deflectors can be secured in the ball nut, but parts of the pulley can get between the main body and deflectors and block rotation if the belt snaps
Solution Approach 1:
The invention removes the toothed belt pulley from the fastening system entirely. The ball return means is secured through axial reception within the ball nut housing, independent of the pulley structure. This eliminates the risk of pulley parts interfering with ball nut rotation during belt failure.
Solution Approach 2:
The ball nut housing serves as an intermediary structure that provides the fastening function. The ball return means is axially received and secured within this housing, creating a reliable connection that is independent of the toothed belt pulley and eliminates interference risks.
Data Source
AI summary
A power steering system for a motor vehicle may include a servomotor, which drives an axially-movable rack via a ball nut. The ball nut may be mounted in a bearing such that the ball nut can be rotated in a housing. The ball nut engages with a threaded spindle formed on the axially-movable rack and has a ball screw thread on an inside thereof for balls to roll on. An external ball return means may connect a beginning of the ball screw thread to an end of the ball screw thread to allow endless circulation of the balls. A deflector and a sleeve may form a return channel of the ball return means.