Differential Case Recesses for Load Distribution
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Solution Overview
Problem
Conventional differential devices face durability issues when thinned in the axial direction due to concentrated loads on specific shafts, leading to potential deterioration of the differential case.
Innovation Solution
The differential device incorporates recessed portions on the input member and cover portions to deviate the shafts, ensuring even load distribution and improved durability, with specific ratios of teeth numbers and pitch cone distances to maintain gear strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the differential device is thinned in the axial direction by making the side gear diameter sufficiently larger than the pinion diameter, then the axial thickness is reduced, but load concentration occurs on overlapping shaft portions leading to deteriorated durability
Solution Approach 1:
The patent resolves the contradiction by changing the spatial arrangement from a conventional aligned configuration to a staggered configuration in the peripheral direction. By positioning the pinion support shaft and planetary gear support shafts at different peripheral positions, the patent eliminates load concentration while maintaining the thinned axial design. This dimensional rearrangement in the peripheral direction solves the durability issue without compromising the axial thickness reduction.
Solution Approach 2:
The patent applies asymmetry by deliberately creating an offset arrangement between the pinion support shaft and planetary gear support shafts in the peripheral direction. This asymmetric positioning ensures that the shafts do not overlap, distributing loads more evenly across the differential case structure. The asymmetric configuration prevents the load concentration that would occur in a symmetric, aligned arrangement, thereby maintaining durability in the thinned design.
2Device complexity
If the shaft for supporting a differential gear and the shaft for supporting a planetary gear are arranged at the same position in the peripheral direction, then the structure is simplified, but load concentration occurs leading to potential deterioration of the differential case
Solution Approach 1:
The patent maintains structural simplicity while improving durability by utilizing the peripheral direction dimension. Instead of complicating the axial or radial arrangements, the patent positions the shafts at different peripheral locations, effectively using the circumferential space to avoid overlap. This approach preserves the simplicity of the overall structure while eliminating the load concentration problem through spatial separation in the peripheral dimension.
Solution Approach 2:
The patent segments the shaft support positions by separating the pinion support shaft and planetary gear support shaft into distinct peripheral locations. This segmentation prevents the overlapping of load paths and distributes mechanical stresses across different areas of the differential case. By segmenting the support positions rather than concentrating them at the same location, the patent enhances durability without significantly increasing structural complexity.
Data Source
AI summary
In a differential device including: an input member capable of being joined to a carrier supporting a plurality of planetary gears via a plurality of first shafts that respectively support the plurality of planetary gears; a differential gear supported on the input member via at least one second shaft and being able to rotate and revolve; and a pair of output gears each meshing with the differential gear, the input member includes a plurality of recessed portions on a wall of the input member facing the carrier, the plurality of recessed portions being able to be respectively fitted with the plurality of first shafts and being each arranged at a position deviated in a peripheral direction of the input member with respect to the at least one second shaft. Accordingly, deterioration in durability of a differential case due to formation of the recessed portions is suppressed.