Straddle-Type Vehicle Power Unit Shift Mechanism Friction Reduction
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Solution Overview
Problem
The frictional force generated between the torsion spring and the support shaft and/or stopper lever in conventional gear change mechanisms causes resistance during rotation, preventing smooth speed changes in straddle-type vehicles.
Innovation Solution
A power unit design where the elastic member is attached to the stopper lever instead of the support shaft, preventing frictional forces and allowing smooth rotation, while utilizing a tension spring to simplify the spring structure and compactly dispose the stopper lever, reducing the size and weight of the gear change mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a torsion spring is wound around the support shaft to hold the stopper lever, then the gear change mechanism is reduced in size, but frictional force is generated between the spring and support shaft/stopper lever causing resistance during rotation
Solution Approach 1:
The invention divides the spring support structure into separate components: the stopper lever is supported by the support shaft, while the elastic member is attached to the stopper lever itself rather than being wound around the support shaft. This segmentation eliminates the friction problem while maintaining compactness.
Solution Approach 2:
Instead of attaching the elastic member to the support shaft (conventional approach), the invention inverts the attachment relationship by fixing the elastic member to the stopper lever. This reversal eliminates the frictional contact between the spring and support shaft, allowing smooth rotation.
2Device complexity
If the elastic member is attached to the support shaft, then the structure is compact, but frictional resistance prevents smooth rotation of the stopper lever
Solution Approach 1:
The invention extracts the elastic member from the support shaft and reattaches it to the stopper lever. This extraction removes the source of frictional energy loss while preserving the compact tension spring structure.
Solution Approach 2:
The invention converts the potential harm of friction into a benefit by repositioning the elastic member attachment point. The tension spring continues to provide compactness, while its new attachment location eliminates friction, turning a problematic configuration into an optimized one.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables smooth rotation of the stopper lever during speed changes without increasing the gear change mechanism's size, achieving compactness and efficiency by eliminating frictional resistance and optimizing the layout of components.
Implementation Method 1
an elastic member including a first engagement end portion that is configured to engage with the first end portion of the stopper lever, and a second engagement end portion that is configured to engage with the crankcase, so as to apply a force to the stopper lever
Implementation Method 2
The frictional force generated between the torsion spring and the support shaft and/or stopper lever in conventional gear change mechanisms causes resistance during rotation
Data Source
AI summary
A power unit includes: a rotation plate 62 that is fixed to an end of a shift drum 50, includes a plurality of recessed portions 63, and rotates together with the shift drum 50; a shift lever 66 that engages with the rotation plate 62; a shift shaft 74 fixed to the shift lever 66; a support shaft 76 disposed substantially in parallel with the shift drum 50; a stopper lever 78 rotatably supported by the support shaft 76; and a stopper roller 88 that is provided in the stopper lever 78 and engages with the recessed portion 63 of the rotation plate 62. When viewed in an axial direction of the shift shaft 74, the stopper lever 78 is disposed to intersect a first line segment A that connects a center 74C of the shift shaft 74 and a center 62C of the rotation plate 62 to each other.