Motorcycle Engine Unit Width Reduction via Vertical CVT Layout
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Solution Overview
Problem
The installation of a belt type continuously variable transmission (CVT) in a motorcycle engine unit often results in a wider vehicle body, making it difficult to maintain a compact width.
Innovation Solution
The engine unit is designed with the primary sheave on one side of the crankshaft, the secondary sheave shaft positioned behind it, and the clutch and rotation motor arranged to allow the center axis of the secondary sheave shaft to be higher than the crankshaft axis, with the footstep located behind the generator and under the secondary sheave, thereby reducing the vehicle width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a belt type continuously variable transmission is located on the outer side of a piston in the vehicle width direction, then the engine unit can be assembled, but the footstep projects greatly in the vehicle width direction making it difficult to keep down the vehicle body width
Solution Approach 1:
The patent repositions the belt type CVT components from a horizontal arrangement (width direction) to a vertical arrangement (height direction). Specifically, the secondary sheave shaft is positioned above the crankshaft axis, and the belt type CVT is arranged in the vertical direction rather than extending outward in the width direction. This dimensional change allows the footstep to be positioned inward without projecting outward, resolving the contradiction between assembly feasibility and vehicle width reduction.
2Length of moving object
If the secondary sheave shaft is positioned higher than the crankshaft axis, then the vehicle width is reduced, but the footstep must be positioned under the secondary sheave which requires careful spatial arrangement
Solution Approach 1:
The patent positions the footstep within the spatial envelope created by the elevated secondary sheave arrangement. Specifically, the footstep is located behind the generator and under the lower end of the secondary sheave, effectively nesting the footstep in the vertical space beneath the CVT components. This nesting approach allows the footstep to be positioned inward for width reduction while maintaining proper clearance and spatial relationships among all components.
Data Source
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AI summary
A motorcycle 1 includes an engine unit 12 and a pair of right and left footsteps 30. The engine unit 12 includes an engine 13 having a crankshaft 20, a belt type CVT 14, a clutch 15, an output shaft 16a and a generator 29. The belt type CVT 14 has a primary sheave 36, a secondary sheave shaft 38 and a secondary sheave 37. The primary sheave 36 is provided on one side of the crankshaft 20 in a vehicle width direction. The clutch 15 is provided on another side in the vehicle width direction with respect to the secondary sheave 37 on the secondary sheave shaft 38. The output shaft 16a is provided on a side opposite to the clutch on the secondary sheave shaft 38 in the vehicle width direction. The generator 29 is provided on the other side of the crankshaft 20 in the vehicle width direction.