Planetary Transmission Bearing Boss Layout for Rigid Sun Gear Support
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Solution Overview
Problem
The existing transmission device has insufficient spatial room around the differential case, leading to reduced rigidity in supporting the output shaft and sun gear, due to the integration of the differential case and carrier, which limits the structural support and axial dimension.
Innovation Solution
A transmission device with a divided carrier structure, where the differential case and second carrier portion are integrated into the power-transmission case main body, and a bearing boss portion is projectingly provided on the sun gear side to support the output shaft and sun gear, allowing for enhanced rigidity and reduced axial dimension, along with an oil passage system to ensure lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the differential case and carrier are integrated, then the structure is simplified, but the spatial room around the differential case becomes insufficient, reducing the rigidity for supporting the output shaft and sun gear
Solution Approach 1:
The carrier is divided into a first carrier portion and a second carrier portion. The first carrier portion supports one end of the pivot shaft, while the second carrier portion supports the other end. This segmentation allows the bearing boss portion to be provided on the power-transmission case main body at a position that overlaps the sun gear in the axial direction, thereby enhancing the rigidity for supporting the output shaft and sun gear while maintaining structural simplification through integration of the differential case and second carrier portion.
2Strength
If the bearing boss portion is extended lengthwise from the differential case toward the sun gear side, then the rigidity for supporting the output shaft and sun gear is enhanced, but the axial dimension increases
Solution Approach 1:
The bearing boss portion is provided on the power-transmission case main body at a position that overlaps the sun gear in the axial direction, and the outer peripheral part of the bearing boss portion is fitted into the center hole of the sun gear. This utilizes the radial dimension (fitted structure) to provide support rigidity without extending the axial dimension, thereby resolving the contradiction between enhancing rigidity and increasing axial length.
3Strength
If the carrier is divided into first and second carrier portions, then the rigidity for supporting the output shaft and sun gear is enhanced, but the device complexity increases
Solution Approach 1:
The differential case and the second carrier portion are integrated into the power-transmission case main body. This merging reduces the number of separate components and assembly steps, thereby maintaining structural simplicity while the first carrier portion is joined to the power-transmission case main body to provide the necessary support rigidity through the bearing boss portion.
Data Source
AI summary
A transmission device includes a planetary reduction gear and a differential device, wherein a carrier of the reduction gear is dividedly formed from a first carrier portion that supports one end side of a pivot shaft and a second carrier portion that supports the other end side of the pivot shaft, and has a power-transmission case that is supported on a transmission case and includes a power-transmission case main body in which the differential case and the second carrier portion are integrated and the first carrier portion, which is joined to one end wall of the power-transmission case main body, a bearing boss portion is integrally and projectingly provided on a side face, on the sun gear side, of the one end wall, the bearing boss portion extending toward the sun gear side and having an outer peripheral part of one of output shafts rotatably fitted into and supported thereby, the bearing boss portion is present at a position where it overlaps the sun gear at least partially in an axial direction, and an outer peripheral part of the bearing boss portion is relatively rotatably fitted into a center hole of the sun gear.