Rack Assist EPS Ball Nut Vibration Absorption

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Solution Overview

Problem

Conventional rack-assist type electric power steering apparatuses generate noise and vibration when the ball nut slides the rack bar, which are transferred to the driver, reducing the steering comfort.

Innovation Solution

The apparatus incorporates a bearing-mounted ball nut, a connecting ring between the bearing and the rack housing, and an axial or radial damper with projections to absorb vibrations and noise, facilitating smooth operation and reducing noise and vibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a ball nut slides a rack bar while rotating, then the steering power is transmitted, but vibration and noise are generated in the axis direction and radial direction

Engineering Contradiction:

Improvesteering power transmissionVSAvoidvibration and noise

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

A damper is introduced as an intermediary component between the rack bar and rack housing to absorb vibrations and noise generated during power transmission, without interfering with the ball nut's sliding and rotating motion

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The physical state of vibration and noise is changed by introducing a damper that converts mechanical vibrations into other forms of energy, thereby reducing the harmful vibrations and noise while maintaining power transmission

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the ball nut and rack bar operate directly, then the structure is simple, but the operation is not smooth due to vibration and noise

Engineering Contradiction:

Improvestructural simplicityVSAvoidsmooth operation

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The damper provides beforehand cushioning by being pre-installed in the rack housing to absorb and mitigate vibrations and noise before they can propagate through the steering system, ensuring smooth operation from the start

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively absorbs axis and radial direction vibrations and noise, enhancing the steering comfort by reducing unwanted vibrations and noise, thus improving the overall steering experience.

Implementation Method 1

a bearing which is mounted on an outer circumferential surface of the ball nut to support rotation

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

an axial damper which is combined at both sides of the connecting ring and is provided with lateral side projections protruding in a direction of a central axis of the rack bar

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 3

a radial damper which is combined between an outer circumferential surface of the connecting ring and the rack housing

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentUS8540258B2Rack assist type electric power steering apparatus

Publication Date: 2013.09.24 HL MANDO CORP

AI summary

A rack-assist type electric power steering apparatus, in which when a ball nut slides a rack bar while rotating, a vibration and a noise in the axis direction and the radial direction, generated from the rack bar and a rack housing, are absorbed. This facilitates the operation of the ball nut and the rack bar, and reduces the vibration and the noise, thereby resulting in an effect for providing a comfortable steering feeling to a driver.