Elastically Deformable Rolling Bearing Cage for Power Steering

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Solution Overview

Problem

Conventional retaining cages for rolling bearings in motor vehicle electric power steering systems face deformation and damage under low rotational speeds and reversing load directions, leading to reliability issues and potential destruction.

Innovation Solution

A cage design with elastically deformable connecting portions between pockets allows for relative movement in the circumferential direction, featuring elastic tabs forming a spring with undulations and notches for reduced material usage and enhanced flexibility, made from lightweight synthetic materials like polymers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional rigid retaining cage is used, then the cage maintains structural integrity under normal conditions, but the cage suffers extensive deformation and damage under low rotational speeds and reversing load directions

Engineering Contradiction:

Improvecage dependabilityVSAvoidcage resistance to deformation

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The cage transitions from a rigid structure to a dynamic structure with elastically deformable connecting portions that allow controlled deformation under load. The connecting portions act as springs that can flex to accommodate ball movement while maintaining overall cage integrity, resolving the contradiction between rigidity for structural strength and flexibility for deformation resistance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cage's mechanical parameters are changed by introducing elastic deformability in the connecting portions while maintaining rigidity in the pockets. This selective parameter change allows the cage to adapt its stiffness characteristics based on operational conditions, improving reliability without sacrificing necessary structural strength.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the cage structure is made more flexible to prevent deformation, then the cage can accommodate ball movement, but the cage bulk and weight increase

Engineering Contradiction:

Improvecage resistance to damageVSAvoidcage weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The cage is segmented into rigid pockets and flexible connecting portions, with only the necessary connecting sections made elastically deformable. This segmentation allows the cage to gain flexibility where needed while minimizing overall material usage and weight, avoiding the penalty of making the entire cage structure flexible.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the cage have different mechanical properties: the pockets maintain rigidity to hold balls securely, while the connecting portions have local elastic deformability to accommodate movement. This local quality differentiation achieves damage resistance without requiring overall structural flexibility that would increase weight.

Inventive Principle:

Principle #3Local quality

3Force

If axial retention claws are provided in all pockets, then the cage is securely retained on the balls, but the cage is severely deformed when adjacent balls move in opposite directions under high axial and radial loads

Engineering Contradiction:

Improveaxial retention forceVSAvoidcage resistance to severe deformation

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The connecting portions provide dynamic flexibility that complements the static axial retention claws. When balls move in opposite directions under high loads, the elastic connecting portions can deform to accommodate this movement while the retention claws maintain axial positioning, preventing severe cage deformation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cage structure changes its effective stiffness parameter through elastic deformation of connecting portions under load, allowing it to accommodate ball movement while maintaining retention force. This parameter adaptation prevents the severe deformation that would occur with a completely rigid structure.

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 design significantly reduces the risk of cage degradation and damage by allowing balls to move freely, maintaining even spacing and reducing material usage while maintaining structural integrity under varying loads and rotational conditions.

Implementation Method 1

At least one of the said connecting portions is elastically deformable at least in the circumferential direction so as to allow the two associated pockets to move relative to one another in the said circumferential direction

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS9709096B2Cage for a rolling bearing, notably for a motor vehicle electric power steering bearing

Publication Date: 2017.07.18 AB SKF SKF PATENT DEPARTMENT

AI summary

A cage for a rolling bearing, wherein the cage is intended to ensure the circumferential spacing of a row of rolling elements. The cage comprises pockets for the rolling elements and connecting portions, each connecting portion connecting two successive pockets. At least one of the connecting portions is elastically deformable at least in a circumferential direction so as to allow the two associated pockets to move relative to one another in the circumferential direction.