Split Pivot Shaft Swing Arm for Motorcycle Frame Weight Reduction
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Solution Overview
Problem
The existing swing arm structure for saddle riding type vehicles requires a thicker vehicle body frame and large-sized cross members to withstand tightening, hindering efforts to reduce size and weight.
Innovation Solution
The swing arm structure incorporates a pivot shaft that is split into two sections, with a non-pass-through portion in the middle, and a bearing system that is directly fixed to the pivot shaft and interposed portion, allowing for reduced length and weight, and a nut member that is housed within the swing arm to provide protection and additional support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pivot shaft is passed through the entire width direction of the vehicle body frame elements to tighten the vehicle body frame, then the vehicle body frame strength is improved, but the swing arm structure size and weight increase
Solution Approach 1:
The patent divides the single long pivot shaft into multiple shorter pivot shafts that are arranged in parallel. Each pivot shaft spans only a portion of the width direction rather than the entire width, which reduces the length and weight of each individual shaft while collectively providing the necessary structural support through their distributed arrangement
Solution Approach 2:
The patent places the pivot shafts within hollow portions of the swing arm structure. The pivot shafts are nested inside the hollow portions of the swing arm, which protects them and allows for a more compact integrated design without increasing external dimensions
2Stability of the object's composition
If the pivot shaft is passed through the entire width direction of the vehicle body frame elements, then the vehicle body frame can be tightened, but the vehicle body frame requires thicker walls and large-sized cross members
Solution Approach 1:
The vehicle body frame is divided into multiple separate frame elements (first and second frame elements) with the pivot shafts positioned between them. This segmentation allows each frame element to be optimized independently and eliminates the need for a single large cross member spanning the entire width
Solution Approach 2:
Instead of using a single long pivot shaft extending in the width direction, the patent transitions to multiple shorter pivot shafts arranged in parallel. This dimensional redistribution provides equivalent structural support through a different spatial configuration, reducing the volume requirements of individual components
Data Source
AI summary
A swing arm structure includes pivot shafts extending in a vehicle width direction and disposed in a vehicle body frame, a pair of wall portions disposed in the vehicle width direction in the vehicle body frame, and an interposed portion disposed between the wall portions in a swing arm. The wall portions have wall portion-side pass-through portions, which receive the pivot shafts passed therethrough. The interposed portion has interposed portion-side pass-through portions formed therein at, out of both end portions in the vehicle width direction, portions facing the wall portion-side pass-through portions. The interposed portion-side pass-through portions receive the pivot shafts passed therethrough. The interposed portion has a non-pass-through portion formed therein at a middle portion in the vehicle width direction of the interposed portion. The non-pass-through portion does not receive the pivot shafts.