Differential Gear Shaft Fixing for Pre-Weld Inspection Access

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Solution Overview

Problem

Existing differential gear assemblies face challenges in ensuring a stable connection between the gear shaft and casing before the crown wheel is attached, making quality control and correction difficult, especially when the connection is permanently sealed by welding.

Innovation Solution

The design includes gear shafts with specific end surfaces and flats that allow for visible inspection and engagement of fastening members, such as pins, which are protected by the casing and can be inspected before the crown wheel is attached, ensuring a secure connection and simplifying quality control processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the crown wheel is permanently attached to the casing by welding, then the structural integrity is improved, but the ability to inspect and correct the connection between the casing and gear shafts is lost

Engineering Contradiction:
Improvestructural integrityVSAvoidinspection capability
Core Design Contradiction:
StrengthVSDifficulty of detecting and measuring

Solution Approach 1:

The patent provides for inspection of the connection between the casing and gear shafts before the crown wheel is permanently attached by welding. This preliminary inspection allows detection and correction of connection issues before they are locked in by the permanent attachment, thus resolving the contradiction between structural integrity and inspection capability.

Inventive Principle:
Principle #10Preliminary action

2Ease of manufacture

If the fastening member engages the gear shaft at its outer end surface, then the assembly process is simplified, but the fastening member is exposed to environmental conditions

Engineering Contradiction:
Improveassembly simplicityVSAvoidenvironmental exposure
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent introduces the casing as an intermediary protective structure that encloses the fastening member and gear shaft connection. The casing acts as a barrier between the fastening member and environmental conditions, while still allowing the fastening member to engage the gear shaft effectively. This resolves the contradiction by protecting the connection from environmental factors while maintaining assembly simplicity.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If the gear shaft connection is made before attaching the crown wheel, then inspection and correction are possible, but the assembly sequence becomes more complex

Engineering Contradiction:
Improveconnection reliabilityVSAvoidassembly sequence
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent establishes a specific assembly sequence where the gear shaft connection with fastening members is made and inspected before the crown wheel is permanently attached. This preliminary completion of the connection allows for verification and correction, improving reliability. The sequence is structured to minimize complexity by performing critical connections early when access is available.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3299666B1Differential gear assembly and components thereof
Publication Date: 2022.08.17 MERITOR HEAVY VEHICLE SYST CAMERI
  • EP3299666B1 patent drawingFigure 1
  • EP3299666B1 patent drawingFigure 2a~2c

AI summary

A differential gear assembly, comprising: • a casing extending along a longitudinal drive axis and adapted to receive end gears of first and second half shafts of a vehicle drive axle, the casing comprising at least one opening extending perpendicular to the drive axis between outer and inner bearing surfaces of the casing; • a first gear shaft received within the at least one opening of the casing; • a first differential side gear adapted to mesh with end gears of said first and second half shafts, the side gear being rotatably mounted on the first gear shaft; wherein the gear assembly further comprises at least one fastening member adapted to fix the first gear shaft with respect to the casing, and wherein the assembly is arranged in such a way that the at least one fastening member is visible from the outer bearing surface of the casing.