Planetary Gear Unit Radial Downsizing via Integrated Case
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Solution Overview
Problem
Conventional planetary gear units used in electric motor driving devices, particularly in electric motorcycles, face challenges in reducing size both radially and axially while maintaining structural support, especially when used as wheel motor devices.
Innovation Solution
The design incorporates a planetary gear unit with a sun gear, planetary gears, a carrier pin, internal gear, and a carrier member, where the internal gear is formed with fastening holes and the covers are connected using these holes to form a peripheral wall, allowing for a compact configuration by reducing the size of the internal gear and optimizing the placement of mounting holes for enhanced structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the planetary gear unit uses a conventional structure with separate covers and internal gear, then the structural strength is maintained, but the size in radial direction cannot be reduced further
Solution Approach 1:
The patent merges the internal gear with the planetary case by forming the internal gear as an integral part of the case structure. This eliminates the need for separate internal gear components and reduces the radial size while maintaining structural strength through the unified design.
Solution Approach 2:
The planetary case is designed to serve multiple functions: it provides structural support, contains the gear mechanism, and forms the peripheral wall of the housing. This multi-functionality allows reduction of overall radial dimension by eliminating redundant structural elements.
2Volume of moving object
If the internal gear is reduced in size to downsize the planetary gear unit, then the radial size is reduced, but the structural integrity may be compromised
Solution Approach 1:
By integrating the internal gear with the planetary case, the structural integrity is maintained through the case's inherent strength while allowing the internal gear portion to be optimized for minimal size. The unified structure ensures load paths are maintained without requiring a large separate internal gear component.
3Volume of moving object
If the planetary gear unit is downsized for use in electric motorcycles, then the space requirement is reduced, but the supporting strength for the motor output shaft may be insufficient
Solution Approach 1:
The planetary case is merged with the housing structure to form a unified support system. This integration allows the case to provide both the gear containment function and the structural support for the motor output shaft, maintaining supporting strength while reducing overall size.
Solution Approach 2:
The planetary case serves dual purposes: housing the gear mechanism and providing structural support for the motor output shaft. This multi-functionality enables the compact design to maintain adequate supporting strength without requiring additional separate support structures.
Data Source
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AI summary
A planetary-side first side wall includes an input opening into which a power transmission shaft transmitting rotative power from an electric motor body to a sun gear is inserted, an inner region extending radially outward from an outer peripheral edge of the input opening, an axially extending region extending in the direction toward the sun gear from an inner end in the radial direction of the inner region, and an outer region extending radially outward from the inner region via a transitional region. A carrier-side first side wall of a carrier member is rotatably supported via a bearing member by the axially extending region. At least a part of the inner region enters a motor case via an output opening formed in a motor-side first side wall of the motor case.