Rack-Driven Steering Ball Return Tube for Vibration-Stable Circulation

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Solution Overview

Problem

Conventional rack-driven power assisted steering apparatuses face issues with the return tube detaching, deforming, or damaging due to vibrations and impact during continuous steering, leading to improper ball circulation and reduced steering assistance power.

Innovation Solution

The apparatus includes a rack bar with an outer screw groove, a ball nut with an inner screw groove, and a return tube coupled between the ball nut and nut pulley, with specific ball circulation holes to ensure precise ball circulation and secure attachment, preventing separation and damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the return tube is coupled to the ball nut for ball circulation, then the steering assistance power is transmitted, but the return tube is detached, deformed, or damaged due to vibration and impact during continuous steering

Engineering Contradiction:

Improvereturn tube attachment stabilityVSAvoidvibration and impact

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The return tube is divided into multiple sections with intermediate support portions that can independently deflect, allowing each segment to absorb vibration and impact separately rather than transmitting forces throughout the entire tube structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate support portions are designed to provide preemptive cushioning against vibration and impact forces before they can cause detachment or damage to the return tube during continuous steering operations

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Ease of manufacture

If the return tube is not accurately fixed to the ball nut, then assembly is easier, but the ball is not circulated properly, reducing steering assistance power and power transmission efficiency

Engineering Contradiction:

Improveassembly easeVSAvoidball circulation accuracy

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The return tube's intermediate support portions automatically position and support themselves during assembly and operation, ensuring accurate ball circulation without requiring complex external fixing mechanisms or additional assembly steps

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11840291B2Rack-driven power assisted steering apparatus

Publication Date: 2023.12.12 HL MANDO CORP

AI summary

A steering apparatus with an assistance of a rack-driven power includes a rack bar having an outer circumferential screw groove formed, a ball nut having an inner circumferential screw groove and a pair of first and second ball circulation holes, a nut pulley provided with a space on the inner circumferential surface spaced apart from the outer circumferential surface of the ball nut and coupled to an end of the ball nut, and a return tube disposed between the outer circumferential surface of the ball nut and the inner circumferential surface of the nut pulley.