Parallel Shaft Engine Layout for Motorcycle Width Reduction
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Solution Overview
Problem
Conventional engines with torque converters, oil pumps, and primary shafts coaxially disposed with the crankshaft are too wide to be mounted on straddle-type vehicles, such as motorcycles, due to their extended axis arrangement.
Innovation Solution
The engine design features a crankshaft, drive pulley shaft, driven pulley shaft, output shaft, and pump drive shaft disposed in parallel, with the pump drive shaft positioned closer to a flat plane than the pulley shafts, allowing for a more compact layout that includes a transmission with drive and driven pulleys and an oil pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque converter, oil pump, and primary shaft are disposed on an extended axis of the crankshaft, then good transmission efficiency is achieved, but the engine becomes too wide to be mounted on straddle-type vehicles
Solution Approach 1:
The patent transitions from a conventional axial arrangement (all components on the crankshaft extended axis) to a parallel shaft arrangement where the crankshaft, drive pulley shaft, driven pulley shaft, and pump drive shaft are disposed parallel to each other. This dimensional reconfiguration reduces engine width while maintaining functional relationships through belt-driven power transmission between parallel shafts
2Length of moving object
If the crankshaft, drive pulley shaft, driven pulley shaft, and output shaft are arranged in parallel, then engine width is reduced, but the spatial arrangement becomes more complex
Solution Approach 1:
The patent combines multiple shafts (crankshaft, drive pulley shaft, driven pulley shaft, and pump drive shaft) into a compact parallel arrangement within a unified engine structure. The belt-driven connection system merges the power transmission function across all shafts, simplifying the overall spatial configuration while maintaining reduced engine width
3Volume of moving object
If the pump drive shaft is positioned closer to the flat plane than the pulley shafts, then engine compactness is improved, but the oil pump placement becomes more constrained
Solution Approach 1:
The patent positions the pump drive shaft at a different vertical level (closer to the flat plane) compared to the pulley shafts, creating localized spatial differentiation. This allows the oil pump to be positioned in a specific zone within the engine structure, optimizing both compactness and manufacturability through targeted spatial allocation
Data Source
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AI summary
An engine 2 includes: a crankshaft 40; a drive pulley shaft 62 of a transmission 60; a driven pulley 64; an output shaft 70; and a pump drive shaft 81 for driving an oil pump 80 for supplying oil to the transmission 60. The crankshaft 40, the drive pulley shaft 62, the driven pulley shaft 64, the output shaft 70, and the pump drive shaft 81 are dispose in parallel. The drive pulley shaft 62 and the driven pulley shaft 64 are disposed between the crankshaft 40 and the output shaft 70 above a flat plane passing through an axial center P1 of the crankshaft 40 and an axial center P4 of the output shaft 70. The pump drive shaft 81 is disposed between the crankshaft 40 and the output shaft 70 and is disposed closer to the flat plane than the drive pulley shaft 62 and the driven pulley shaft 64.