Planetary Transaxle Layout for High Reduction in Compact Space
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Solution Overview
Problem
Existing transaxles face a challenge in achieving a large driving force while maintaining a compact size, as increasing the radial body size to accommodate larger reduction ratios leads to an overall increase in size.
Innovation Solution
The transaxle incorporates a planetary gear mechanism with a stepped pinion gear and a differential device, where the large-diameter pinion gear is integrated and positioned radially inward, allowing for a larger reduction ratio without increasing the radial body size by optimizing the arrangement of the outer pinion gear and ring gear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the radial body size is increased to accommodate larger reduction ratios, then the driving force is improved, but the overall size of the transaxle increases
Solution Approach 1:
The differential device is disposed radially inward of the small-diameter pinion gear, nesting it within the existing gear structure. This allows the differential device to utilize the radial space already occupied by the pinion gear, avoiding additional radial expansion while maintaining the large reduction ratio capability
Solution Approach 2:
The stepped pinion gear uses two different diameters (large-diameter and small-diameter portions) to achieve a large reduction ratio without increasing the radial body size. By varying the diameter dimension at different angular positions, the design accomplishes high reduction ratio in a compact radial footprint
2Productivity
If a large reduction ratio is achieved, then the driving force is improved, but the transaxle size increases
Solution Approach 1:
The differential device is nested within the radial space of the pinion gear structure, allowing the transaxle to achieve a large reduction ratio without proportionally increasing the overall transaxle volume. The nested arrangement enables compact packaging of multiple functional components
Solution Approach 2:
The large-diameter pinion gear and small-diameter pinion gear are integrated into a single stepped pinion gear component. This merging of functions into one component achieves the large reduction ratio while reducing the number of separate parts and minimizing the overall transaxle volume
Data Source
AI summary
A transaxle includes: a planetary gear mechanism having a stepped pinion gear in which a large-diameter pinion gear and a small-diameter pinion gear are integrated; a differential device disposed radially inward of the small-diameter pinion gear; and a transaxle case for accommodating the planetary gear mechanism and the differential device. Further, the planetary gear mechanism includes a sun gear, provided on an output shaft of the electric motor, which meshes with the large-diameter pinion gear, a ring gear which rotates at a same rotational speed as a differential case of the differential device rotates, a carrier, fixed to the transaxle case, which rotatably supports the stepped pinion gear, and an outer pinion gear which is rotatably supported by the carrier and meshes with the small diameter pinion gear and the ring gear.