Rack Driven Power Steering Ball Nut Noise Reduction

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Solution Overview

Problem

Conventional rack driven electric power steering apparatuses experience increased impact and friction noise due to rapid ball direction changes and require a separate assembling device for ball introduction, making the manufacturing and assembly process inefficient.

Innovation Solution

The apparatus features a ball nut with an inner screw groove and end caps with ball introducing passages, allowing balls to be introduced while end caps are assembled within the nut, reducing noise and eliminating the need for a separate assembling device by using end cap rings to prevent ball separation and facilitate smooth circulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a separate assembling device is used for ball introduction, then balls can be introduced into the ball nut, but the manufacturing and assembly process becomes complex and inefficient

Engineering Contradiction:

Improveassembly process efficiencyVSAvoidassembling device complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The ball introduction function is extracted from a separate assembling device and integrated into the end cap structure itself. The end cap includes a ball introduction passage that allows balls to be introduced directly during the assembly process, eliminating the need for complex external ball introduction devices and simplifying the overall manufacturing process.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The end cap structure serves itself by incorporating the ball introduction passage directly into its design. This allows the end cap to perform both its primary function of sealing the ball nut and the secondary function of facilitating ball introduction, making the assembly process self-sufficient and eliminating dependency on separate specialized tools.

Inventive Principle:

Principle #25Self-service

2Speed

If balls circulate rapidly in the ball nut, then steering response is improved, but impact noise and friction noise increase

Engineering Contradiction:

Improveball circulation speedVSAvoidimpact noise and friction noise

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The end cap is designed with localized features including a ball introduction passage and specific geometric configurations that create favorable local conditions for ball circulation. These local structural qualities guide ball movement smoothly, reducing impact and friction noise while maintaining high circulation speed for responsive steering.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The end cap structure is designed to cushion and absorb impacts before they propagate through the ball nut. The geometric configuration of the end cap and its integration with the ball nut creates a cushioning effect that mitigates impact noise and friction noise generated during rapid ball circulation, while still allowing high-speed operation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8783409B2Rack driven electric power steering apparatus

Publication Date: 2014.07.22 HL MANDO CORP

AI summary

Disclosed is a rack driven electric power steering apparatus in which balls can be introduced in a state where end caps are assembled within a ball nut, impact noise and friction noise can be reduced when the balls circulate, and a separate assembling device for injection of the balls is not required, making it possible to shorten a manufacturing and assembling process.