Locking Differential Holdout Ring Arrangement

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Solution Overview

Problem

Existing locking differentials require complex parts, are costly to manufacture and assemble, and are prone to failure due to holdout ring displacement issues, leading to clutch damage.

Innovation Solution

A simplified locking differential design with smooth, continuous surfaces between the center cam and central driver members, using helical compression springs for biasing and resilient holdout rings with integral lugs to prevent relative displacement and ensure proper engagement of clutch teeth, eliminating the need for snap rings and reducing manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If snap rings or keying devices are used to connect the center cam member and central driver member, then relative axial displacement is prevented, but the construction becomes complicated and assembly becomes difficult

Engineering Contradiction:
Improverelative axial displacement preventionVSAvoidconstruction complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent removes the snap ring or keying device from the differential mechanism. The center cam member and central driver member are connected without any keying device, using only smooth continuous circumferential surfaces to prevent relative axial displacement. This extraction of the keying device simplifies the construction while maintaining the stability function.

Inventive Principle:
Principle #2Taking out (Extraction)

2Force

If spring biasing means are arranged concentrically within the clutch members and center cam member, then the clutch members are biased inwardly, but the assembly and servicing become complicated

Engineering Contradiction:
Improveinward biasing forceVSAvoidassembly complexity
Core Design Contradiction:
ForceVSDevice complexity

Solution Approach 1:

The spring biasing means are relocated from a concentric arrangement within the clutch members and center cam member to an external arrangement. The springs are positioned in axially-spaced concentric relation about the central driver member, with outer ends engaging the clutch members and inner ends engaging the center cam member. This dimensional relocation simplifies assembly and servicing while maintaining the required biasing force.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Reliability

If holdout rings are mounted in grooves between cam teeth and driving teeth, then the clutch members are held during operation, but the holdout ring can jump over the spider key during speed variation, causing clutch damage

Engineering Contradiction:
Improveclutch engagement stabilityVSAvoidholdout ring displacement
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent eliminates the spider key from the mechanism. The holdout rings are mounted in grooves in the clutch member faces, and the center cam member has smooth continuous circumferential surfaces without keys or protrusions. This prevents the holdout ring from jumping over a key during speed variations, eliminating the source of clutch damage while maintaining engagement stability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The holdout rings are made of resilient material and are biased radially outwardly into engagement with the counterbore wall surfaces. This resilient construction provides beforehand cushioning that allows the holdout rings to accommodate speed variations without jumping, preventing clutch tooth damage before it can occur.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

4Adaptability or versatility

If cam teeth and driving teeth are arranged in circular patterns on opposite faces of clutch members, then the clutch members can engage and disengage, but the manufacturing cost increases

Engineering Contradiction:
Improveengagement and disengagement capabilityVSAvoidmanufacturing cost
Core Design Contradiction:
Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent combines the cam teeth and driving teeth into a single integrated structure on the clutch members. The clutch members have camming surfaces and driving surfaces formed as continuous unitary features rather than separate components. This merging reduces the number of parts and simplifies manufacturing, lowering production costs while maintaining the engagement and disengagement capability.

Inventive Principle:
Principle #5Merging (Combining)

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 reduces part count, simplifies assembly, enhances durability, and prevents clutch damage by ensuring continuous engagement and disengagement of clutch teeth during speed variations, while eliminating the risk of holdout ring jumping.

Implementation Method 1

The biasing spring means include a pair of helical compression springs arranged concentrically externally about the side gears, respectively, thereby to bias the clutch members inwardly together toward the central driving member

Methodology Applied
Scientific EffectHelical compression spring: Spring

Implementation Method 2

The holdout rings are resiliently biased radially outwardly into engagement with the counterbore wall surfaces of the clutch members, respectively

Methodology Applied
Scientific EffectResilient biasing: Elasticity

Data Source

PatentEP2240708B1Improved differential holdout ring arrangement
Publication Date: 2011.05.18 EATON CORP
  • EP2240708B1 patent drawingFigure 1~3
  • EP2240708B1 patent drawingFigure 4~7
  • EP2240708B1 patent drawingFigure 8

AI summary

A locking differential includes an annular center cam member freely rotatably supported within an annular central driver member without the use of any keying device, such as a snap ring, thereby to simply the construction and assembly of the differential, and to reduce cost. The center cam member is longitudinally maintained in place by the biasing forces applied to the clutch members arranged on opposite sides of the central driver member by helical compression springs arranged externally concentrically about the side gears, respectively, and by the holdout rings that are connected with the clutch members. The center cam member and the central driver member have adjacent outer and inner circumferential surfaces, respectively, that are smooth, continuous, and uninterrupted. The holdout rings are rotatably connected at their remote ends with the clutch members by integral annular outer ribs that extend within corresponding grooves contained in the counterbore wall surfaces.