Power Unit Compact Design via External Gearshift Shaft Support
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Solution Overview
Problem
The existing power units with first and second gearshift clutches face challenges in maintaining a compact design due to the increased center distance between the crankshaft and gearshift shaft, leading to potential interference and instability in gearshift operations.
Innovation Solution
The power unit design includes a gearshift shaft extending from the crankcase, with first and second gearshift clutches supported by an extending shaft portion and a bearing portion, allowing the clutches to be positioned outside the crankcase, reducing the center distance and enhancing support and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gearshift clutches are disposed inside the crankcase, then the gearshift shaft is reliably supported, but the center distance between the crankshaft and gearshift shaft becomes greater, making the power unit larger
Solution Approach 1:
The gearshift clutches are extracted from the interior of the crankcase and positioned on its exterior. The gearshift shaft extends from the crankcase to support these externally positioned clutches, thereby reducing the center distance between the crankshaft and gearshift shaft while maintaining reliable support through the extended shaft structure
Solution Approach 2:
The gearshift shaft is extended in the axial direction perpendicular to the crankshaft rotation plane, creating a three-dimensional support structure. This dimensional extension allows the clutches to be positioned outside the crankcase while maintaining proper support, effectively resolving the spatial conflict between compactness and support reliability
2Volume of moving object
If the center distance between crankshaft and gearshift shaft is reduced, then the power unit becomes compact, but the gearshift clutches may interfere with the crankshaft
Solution Approach 1:
The gearshift shaft extends axially from the crankcase in a direction perpendicular to the crankshaft rotation plane, positioning the clutches in a different spatial dimension. This dimensional separation eliminates interference between the clutches and crankshaft while maintaining a compact center distance
3Volume of moving object
If the gearshift shaft extends outside the crankcase to support clutches, then the power unit becomes compact, but shaft runout may increase
Solution Approach 1:
The gearshift shaft is pre-supported at multiple locations including within the crankcase and at the exterior end. These preliminary support positions are strategically placed to prevent shaft runout before it can affect clutch operation, ensuring stability while maintaining compact dimensions
Data Source
AI summary
A small center distance is provided between a crankshaft and a gearshift shaft disposed in parallel. A power unit is built compactly in a direction of arrangement of the crankshaft and the gearshift shaft for supporting reliably the gearshift shaft on which heavy, first and second gearshift clutches are supported. A transmission includes a main shaft, disposed in parallel with a crankshaft and rotatably supported in a crankcase, and first and second gearshift clutches. The first and second gearshift clutches change a gearshift position in a first gearshift portion and a gearshift position in a second gearshift portion, respectively. The main shaft includes an outer shaft portion that extends from the crankcase and supports the first and second gearshift clutches. The outer shaft portion is supported by a bearing portion disposed in a front cover on a side opposite to the crankcase across the first and second gearshift clutches.