Motorcycle Engine Case Widthwise Shaft Arrangement
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Solution Overview
Problem
Existing motorcycle engine designs with multiple split sections and arranged rotation shafts in the front-rear direction lead to increased engine size and compromised workability and mountability due to complex shaft arrangements.
Innovation Solution
An engine case split into an upper and lower section with rotation shafts, such as the crankshaft, transmission input shaft, and balancer shaft, supported in the width direction, and a transmission output shaft positioned below, reducing the engine's longitudinal length and improving workability by simplifying the mating surface and shaft arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotation shafts are arranged in the front-rear direction at multiple mating surfaces, then the engine can support multiple shafts, but the engine case becomes lengthened and total size increases
Solution Approach 1:
The patent transitions from arranging shafts in the front-rear direction (longitudinal dimension) to arranging them in the width direction (lateral dimension). By supporting the crankshaft, transmission input shaft, and balancer shaft in the width direction at a single mating surface, and the transmission output shaft in the width direction within the lower case section, the engine case length in the front-rear direction is reduced while still accommodating all necessary shafts.
2Adaptability or versatility
If the engine case is split into three sections, then multiple shafts can be supported at different mating surfaces, but the workability and mountability deteriorate
Solution Approach 1:
The engine case is divided into an upper case section and a lower case section, forming a two-split structure. The upper case section supports the crankshaft, transmission input shaft, and balancer shaft, while the lower case section supports the transmission output shaft. This segmentation provides sufficient flexibility for shaft arrangement while improving workability and mountability compared to a three-split structure.
3Adaptability or versatility
If four rotation shafts are arranged in the front-rear direction, then all shafts can be supported, but the engine total size increases
Solution Approach 1:
The patent arranges four rotation shafts (crankshaft, transmission input shaft, balancer shaft, and transmission output shaft) in the width direction rather than the front-rear direction. The crankshaft, transmission input shaft, and balancer shaft are positioned in the width direction at the mating surface between upper and lower case sections, while the transmission output shaft is positioned in the width direction within the lower case section. This dimensional reorganization reduces the engine's longitudinal length and overall volume.
Data Source
AI summary
An engine for a motorcycle includes an engine case split in an upper case section and a lower case section. A mating surface between the upper case section and the lower case section extends linearly and inclines forward downward in a side view of the motorcycle. A crankshaft, a transmission input shaft, and a balancer shaft extending in the width direction of the motorcycle are rotatably supported at the mating surface, and a transmission output shaft rotated by the transmission input shaft is supported in the lower case section. The balancer shaft, the crankshaft, and the transmission input shaft are arranged in that order from the front side in the running direction of the motorcycle. The transmission output shaft is disposed below the transmission input shaft.