Rear-Axle Steering Spindle Drive With Elastomer Preload

Solution Overview

Problem

Existing spindle drives in rear-axle steering systems experience axial play between the spindle nut and spindle due to production tolerances, which affects the precision and efficiency of the actuator.

Innovation Solution

Incorporating an elastomeric spring element, such as an elastomeric disc, to provide a constant preload on the threaded ring and flanks of the motion thread, combined with an adjusting ring and locking mechanism to eliminate axial play and allow for continuous preload adjustment, while preventing lubricant leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a metallic spring element is used to eliminate axial play, then the precision and reliability are improved, but the weight and manufacturing cost increase

Engineering Contradiction:

Improveaxial play eliminationVSAvoidspring element weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

The patent changes the material parameter from metallic to elastomeric, transforming the spring element from a rigid metal component to a flexible polymer component. This material substitution maintains the elastic deformation capability needed for preload while significantly reducing weight and manufacturing cost.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs elastomeric material as a composite alternative to traditional metallic springs. The elastomeric disc combines flexibility, elasticity, and light weight properties, creating a composite solution that eliminates axial play without the drawbacks of metallic springs.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If a metallic spring element is used to eliminate axial play, then the precision and reliability are improved, but the manufacturing cost increases

Engineering Contradiction:

Improveaxial play eliminationVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from metallic to elastomeric, transforming the spring element from a rigid metal component to a flexible polymer component. This material substitution maintains the elastic deformation capability needed for preload while significantly reducing weight and manufacturing cost.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The elastomeric disc serves as a cost-effective alternative to expensive metallic springs. The elastomeric material can be manufactured through simpler, less costly processes such as molding, making the overall assembly more economical while achieving the same functional goal of eliminating axial play.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of manufacture

If production tolerances are relaxed, then the manufacturing cost decreases, but axial play increases affecting precision

Engineering Contradiction:

Improvemanufacturing costVSAvoidaxial play

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The elastomeric disc acts as a cushioning element that compensates for dimensional variations and tolerances in the threaded ring and spindle nut. By incorporating this compliant element, the system can accommodate relaxed production tolerances while maintaining precise axial positioning and eliminating play through the elastomer's deformable nature.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent changes the material parameter from metallic to elastomeric, transforming the spring element from a rigid metal component to a flexible polymer component. This material substitution maintains the elastic deformation capability needed for preload while significantly reducing weight and manufacturing cost.

Inventive Principle:

Principle #35Parameter changes

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 eliminates axial play, enhances the precision and efficiency of the spindle drive, and maintains the preload during operation, offering weight and cost advantages over metallic springs.

Implementation Method 1

The elastomer is elastically deformable and exerts an elastic restoring force or preload when deformed

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP3635276B1Actuator with a spindle drive and rear-axle steering system

Publication Date: 2022.06.15 ZF FRIEDRICHSHAFEN AG

Figure 1~2

AI summary

An actuator having a spindle drive (1) for a rear-axle steering system, comprising a spindle (2) with a spindle thread (2a) and comprising a spindle nut (3) with a nut thread (3a), wherein the spindle thread (2a) and the nut thread (3a) are designed as motion threads, and the spindle nut (3), which can be driven in a direction of rotation, engages with the axially displaceable spindle (2) via the motion thread, wherein the spindle thread (2a) and the nut thread (3a) are braced against one another in a longitudinal direction of the spindle (2) by means of a bracing element (4), characterized in that the bracing element is designed as a threaded ring (4) with an internal thread (4a) which engages with the spindle thread (2a), wherein the threaded ring (4) is supported via at least one spring element (5, 6) relative to the spindle nut (3), and wherein the at least one spring element (5, 6) is formed from an elastomer.