Differential Case Window Layout for Thrust Load Rigidity

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Solution Overview

Problem

Conventional differential devices face issues with insufficient rigidity and stress concentration at the peripheral parts of the working window due to a long gap between joining parts, leading to potential collapse and reduced rigidity balance under thrust loads.

Innovation Solution

The differential device incorporates a specific joining part placement strategy where the closest joining part to the working window is positioned further outward than the inner end of the window, with the working window extending to the outer peripheral end and the flange portion discontinued at the outer end, ensuring a shorter support span and avoiding stress concentration by transmitting loads through larger diameter parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If two large working windows are formed in the case main body to simplify the joining part and lighten the weight, then the weight and complexity are reduced, but the gap between joining parts becomes too long, reducing rigidity

Engineering Contradiction:

Improveweight of differential caseVSAvoidrigidity toward thrust load

Core Design Contradiction:

Weight of stationary objectVSStrength

Solution Approach 1:

The patent applies local quality by making the flange portion discontinuous only in the region corresponding to the working window, while maintaining continuity in other regions. This localized modification reduces weight where it is least needed (at the working window area) while preserving structural integrity and rigidity in critical load-bearing areas.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The flange portion is segmented into continuous and discontinuous regions based on functional requirements. The discontinuous section at the working window area removes unnecessary material, while the continuous sections maintain structural strength. This segmentation allows the case to achieve both weight reduction and adequate rigidity.

Inventive Principle:

Principle #1Segmentation

2Weight of stationary object

If the flange portion is made discontinuous at the working window region to reduce weight, then weight is reduced, but stress concentration may occur at the peripheral part of the working window

Engineering Contradiction:

Improveweight of differential caseVSAvoidstress concentration at working window periphery

Core Design Contradiction:

Weight of stationary objectVSStress or pressure

Solution Approach 1:

The patent applies preliminary anti-action by strategically positioning joining parts at specific locations that preemptively counteract stress concentration. The joining parts are arranged to provide structural support at critical points near the working window, preventing stress concentration before it can occur during thrust load application.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The joining parts serve as intermediaries that transfer and distribute loads away from the working window periphery. By positioning joining parts at specific locations, the patent creates intermediate support points that mediate the stress distribution, preventing direct stress concentration at the working window edges.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If the gap between joining parts is reduced to improve rigidity, then rigidity is improved, but the structure becomes more complex and heavier

Engineering Contradiction:

Improverigidity of differential caseVSAvoidcomplexity of joining part arrangement

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies partial action by making the flange portion discontinuous only in the specific region corresponding to the working window, rather than throughout the entire circumference. This partial modification achieves the necessary weight reduction and rigidity balance without requiring complete redesign of the entire flange structure, thus avoiding excessive complexity.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11300189B2Differential device

Publication Date: 2022.04.12 MUSASHI SEIMITSU INDUSTRY CO LTD

AI summary

In a differential device in which a working window is provided in a case main body of a differential case that can rotate around a first axis, when viewed on the projection plane, orthogonal to the first axis, among joining parts between a flange portion of the differential case and a ring gear, a specific joining part that is the closest to the working window is positioned further outward than an inner end part of the working window in a direction along a third axis orthogonal to the first axis and a pinion axis, and the working window is positioned further outward, in the direction along the third axis, than an imaginary straight line joining the specific joining part and the first axis. Accordingly, rigidity strength of the differential case is enhanced and concentration of stress is prevented from occurring in the working window of the case main body.