Motorcycle Starter Motor Link Gear Layout
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Solution Overview
Problem
In motorcycles with engines having a cylinder body that extends upward and rearward, placing a starter motor above the crankcase and rearward of the cylinder body is challenging due to space constraints and interference with the exhaust pipe, leading to increased power unit size and difficulty in achieving mass centralization.
Innovation Solution
A motorcycle design where the starter motor is linked to the second gear via link gears, including a one-way clutch and torque limiter, allowing it to be positioned above the crankcase and rearward of the cylinder body without increasing the axial dimensions of the main shaft or crankshaft, and avoiding interference with the exhaust pipe, thus achieving mass centralization without enlarging the power unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the starter motor is placed above the crankcase and rearward of the cylinder body to achieve mass centralization, then the maneuverability is improved, but the power unit size increases due to space constraints and exhaust pipe interference
Solution Approach 1:
The starter motor is positioned in the vehicle width direction (lateral dimension) rather than only in the longitudinal or vertical dimensions. By placing the starter motor laterally outward from the power unit and linking it via link gears, the design utilizes the width direction to resolve spatial conflicts, allowing mass centralization without increasing the power unit's longitudinal or vertical footprint.
Solution Approach 2:
Link gears are introduced as intermediary components to transmit rotational force from the starter motor to the crankshaft. This intermediary mechanism allows the starter motor to be positioned laterally outward from the power unit while still effectively engaging the crankshaft, resolving the conflict between starter motor placement and exhaust pipe positioning.
2Ease of operation
If the starting gear is provided on the main shaft closer to the center than the clutch, then the starter motor can be positioned rearward, but the main shaft axial dimension increases causing clutch protrusion
Solution Approach 1:
The starting gear function is extracted from the main shaft and relocated to the crankshaft. By providing the starting gear directly on the crankshaft rather than on the main shaft, the design eliminates the need for extended main shaft axial dimensions, preventing clutch protrusion while enabling proper starter motor positioning.
Solution Approach 2:
The starting gear is merged with the crankshaft structure, combining the rotation function of the crankshaft with the starting gear engagement function. This integration allows the starter motor to drive the crankshaft directly without requiring additional axial space on the main shaft.
3Ease of operation
If the starting gear is provided on the crankshaft closer to the center than the generator, then the starter motor can be positioned rearward, but the crankshaft axial dimension increases causing generator protrusion
Solution Approach 1:
The starting gear function is extracted from the crankshaft and relocated to a position where it can be driven laterally by the starter motor. By positioning the starting gear laterally outward from the power unit rather than extending the crankshaft axially, the design prevents generator protrusion while enabling starter motor engagement.
4Volume of moving object
If the exhaust pipe extends in a downward-rearward diagonal direction from the cylinder head, then the exhaust system is compact, but the starter motor placement space is reduced
Solution Approach 1:
The starter motor is positioned in the vehicle width direction (lateral dimension) rather than in the longitudinal or vertical dimensions where the exhaust pipe occupies space. By utilizing the lateral dimension for starter motor placement, the design resolves the spatial conflict with the downward-rearward extending exhaust pipe while maintaining a compact exhaust system.
Data Source
AI summary
A motorcycle includes a first gear provided on a crankshaft, a second gear provided on a second clutch member of a clutch that meshes with the first gear, a starter motor located above the crankcase and rearward of the cylinder body, and a link gear that links together the second gear and the starter motor. The starter motor is located above a transmission. The starter motor includes an overlapping portion that overlaps with the clutch, as the vehicle is seen from the side, and a front portion located forward of a center axis of a main shaft, as the vehicle is seen from the side.