Steering Ball Nut Return Tube Coupling for Leak-Free Circulation
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Solution Overview
Problem
Conventional vehicle steering devices face issues with the return tube falling off, deformation, or damage due to continuous steering, leading to improper ball circulation and lubricant leakage, which affects steering assistance force and power transfer efficiency.
Innovation Solution
A vehicle steering device design featuring a ball nut with inner and outer screw grooves and a return tube composed of symmetrical body portions with coupling flanges and protrusions, along with an elastic member for secure coupling and enhanced watertightness, to prevent the return tube from falling off and ensure proper ball circulation and lubricant retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the return tube is continuously circulated during driving, then the ball circulation function is maintained, but the return tube falls off, is deformed, or is damaged due to vibration and impact
Solution Approach 1:
The return tube is divided into multiple body portions (first body portion, second body portion, etc.) that are coupled together through coupling flanges. This segmentation allows each section to be independently secured while maintaining overall structural integrity during continuous operation and vibration.
Solution Approach 2:
Coupling protrusions and coupling holes are pre-formed on the coupling flanges of each body portion before assembly. This preliminary preparation ensures that when the body portions are coupled together, the connection is immediately secure and resistant to vibration-induced separation during continuous steering operation.
2Reliability
If the return tube is securely fixed to prevent falling off, then fixation reliability is improved, but the structure becomes more complex with multiple coupling flanges and protrusions
Solution Approach 1:
Multiple functions are merged into the coupling flange structure: it provides both the coupling protrusions for mechanical connection and the sealing surface for lubricant retention. This integration achieves secure fixation without adding separate complex components.
Solution Approach 2:
The coupling flange structure serves multiple purposes: it connects adjacent body portions, prevents separation during vibration, and provides sealing for lubricant retention. This multi-functionality reduces the need for additional specialized components.
3Ease of manufacture
If the return tube structure is simplified for ease of manufacture, then manufacturing becomes easier, but the tube may not correctly circulate balls or may leak lubricant
Solution Approach 1:
The return tube is segmented into multiple body portions that can be manufactured separately using standard molding processes, then assembled through coupling flanges. This approach maintains manufacturing simplicity while ensuring proper ball circulation paths are formed in each section.
Solution Approach 2:
The coupling protrusion fits into the coupling hole like a nested structure, creating a secure mechanical connection that ensures proper alignment of the ball circulation path across multiple body portions without requiring complex manufacturing.
4Reliability
If the coupling flanges are designed with protrusions and holes for secure connection, then fixation reliability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The coupling flange structure concentrates the connection function at specific localized areas (coupling protrusions and holes) rather than requiring precision across the entire surface. This allows standard manufacturing tolerances to be used in most areas while achieving reliable connection at the coupling points.
Data Source
AI summary
A vehicle steering device may prevent a return tube from falling off from a ball nut, being deformed or being damaged despite continuous steering during driving, allow a ball to correctly circulate to the ball nut through the return tube, and prevent the lubricant from leaking from the return tube to correctly transfer steering assistance force.