Differential Device Ring Gear Welding Thermal Distortion
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Solution Overview
Problem
Conventional differential devices face issues with thermal distortion due to welding, leading to degradation in strength and durability, and increased costs and complexity in reducing the ring gear diameter.
Innovation Solution
A differential device design where the ring gear is fitted non-welded onto the barrel part with a weld area positioned axially inward, and a recessed area on the barrel part to absorb thermal distortion, reducing the welded area and minimizing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the ring gear diameter is reduced by eliminating the inward-facing flange and directly welding the rim portion to the barrel part, then the device complexity and material usage are reduced, but thermal distortion occurs causing degradation in gear portion strength and durability
Solution Approach 1:
The ring gear is segmented into a gear portion and a rim portion that are integrally formed but functionally separated. The rim portion is fitted onto the barrel part while the gear portion remains spaced away, allowing the welding operation to be isolated from the critical gear meshing area. This segmentation enables reduced device complexity through integral formation while protecting gear portion strength by spatial separation from thermal distortion zones.
Solution Approach 2:
The patent applies local quality by creating a specific structural configuration where only the rim portion is welded to the barrel part, while the gear portion maintains a non-welded state with spacing from the weld zone. This localized welding approach concentrates the thermal effect to a specific area (the rim portion) while preserving the quality and strength of the gear portion, thus reducing overall device complexity without compromising critical functional areas.
2Device complexity
If the ring gear diameter is reduced by direct fitting and welding, then material usage and device complexity are reduced, but manufacturing precision deteriorates due to thermal distortion affecting the gear portion
Solution Approach 1:
The ring gear is divided into a gear portion and a rim portion that are integrally formed but spatially separated in function. The rim portion accepts the welding connection to the barrel part, while the gear portion is positioned away from the weld zone. This segmentation reduces device complexity by eliminating the inward-facing flange structure while preserving manufacturing precision of the gear portion through spatial isolation from thermal distortion.
Solution Approach 2:
The rim portion acts as an intermediary element between the barrel part and the gear portion. It absorbs the thermal distortion effects of welding while maintaining the structural integrity and dimensional precision of the gear portion. The integral formation of the rim portion with the gear portion allows stress and thermal effects to be contained in the rim area, protecting the gear meshing surfaces from precision degradation.
3Productivity
If welding is performed close to the gear portion to reduce ring gear diameter, then productivity and cost are improved, but thermal distortion increases causing durability degradation
Solution Approach 1:
The ring gear structure is segmented into a gear portion and a rim portion that are integrally formed. The rim portion is designed to be welded to the barrel part while the gear portion is spaced away from the weld zone. This segmentation improves productivity by enabling direct welding without complex flange structures, while simultaneously protecting gear portion durability through spatial separation from thermal distortion zones.
Solution Approach 2:
The patent implements local quality by concentrating the welding operation exclusively on the rim portion, which is integrally connected to but spatially separated from the gear portion. This localized welding approach enhances productivity by simplifying the overall structure and reducing welding complexity, while preserving gear portion durability by isolating it from the high-temperature thermal field and associated distortion effects.
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
This design effectively suppresses thermal distortion, maintains strength and durability, reduces costs, and improves productivity by allowing a smaller ring gear diameter while minimizing the impact of welding on the gear portion.
Implementation Method 1
a rim portion that is formed integrally with an inner periphery of the gear portion and is fitted, in a non-welded state, onto a maximum diameter outer peripheral portion of the barrel part
Implementation Method 2
the rim portion has a to-be-fixed portion that is welded to the barrel part at a position that is spaced in an axial direction from a fitting part via which the rim portion and the barrel part are fitted
Implementation Method 3
the gear portion can be spaced from the weld part between the ring gear and the differential case, it becomes possible to suppress the influence of thermal distortion due to welding on the gear portion
Data Source
AI summary
A differential device includes a ring gear receiving a rotational driving force from a drive gear, a differential case rotating integrally with the ring gear around a predetermined axis, and a differential mechanism installed within a barrel part of the differential case. The ring gear includes a gear portion meshing with the drive gear, and a rim portion that is formed integrally with an inner periphery of the gear portion and is fitted, in a non-welded state, onto a maximum diameter outer peripheral portion of the barrel part or a predetermined outer peripheral portion having a smaller diameter than the maximum diameter outer peripheral portion. The rim portion has a to-be-fixed portion welded to the barrel part at a position spaced in an axial direction from a fitting part via which the rim portion and the barrel part are fitted, the position being further radially inward than the fitting part.