General-Purpose Engine Starter Device Crankcase Integration
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Solution Overview
Problem
General-purpose engines face challenges in downsizing while minimizing gear wear and noise due to the large size required for pinion and driven gears with a significant speed reduction ratio, especially when these gears are disposed inside the crankcase.
Innovation Solution
A starting device configuration that includes a starter motor, pinion gear, camshaft gear, crankshaft gear, and a gear assembly where the pinion gear meshes with a gear within the assembly, all disposed inside the crankcase, allowing for a reduced size by transmitting the driving force from the starter motor to the camshaft gear without transmitting back to the pinion gear, utilizing a one-way clutch to manage torque and prevent kickback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the pinion gear and driven gear are disposed outside the crankcase, then the size of the crankcase can be reduced, but wear of the pinion gear or driven gear increases and noise at startup becomes relatively large
Solution Approach 1:
The patent merges the pinion gear and driven gear into a single integrated gear assembly that is disposed inside the crankcase. This combination allows both gears to be protected within the crankcase environment while maintaining a compact overall structure, thus reducing crankcase size without sacrificing gear protection or increasing noise.
Solution Approach 2:
The gear assembly is nested within the crankcase interior space, utilizing the available volume efficiently. The pinion gear and driven gear are positioned in a nested arrangement where the driven gear is disposed inside the crankcase and the pinion gear meshes with it, allowing both components to occupy minimal space while remaining protected from foreign matter.
2Reliability
If the pinion gear and driven gear are disposed inside the crankcase, then wear and noise are suppressed, but the size of the engine increases due to increased crankcase size
Solution Approach 1:
The gear system is segmented into two distinct gears (pinion gear and driven gear) that are positioned at different locations within the crankcase. The pinion gear is disposed on the output shaft of the starter motor, while the driven gear is disposed inside the crankcase. This segmentation allows for optimized space utilization and protects both gears within the crankcase without significantly increasing its overall size.
Solution Approach 2:
The patent utilizes the three-dimensional space within the crankcase by positioning the pinion gear and driven gear in different spatial dimensions and orientations. The gears are arranged to mesh with each other in a compact configuration that maximizes the use of available interior space, thereby accommodating protected gears without proportionally increasing crankcase volume.
3Power
If a large speed reduction ratio is used to rotate the crankshaft, then the starter motor can effectively crank the engine, but a relatively large gear is required which increases the size of the starting device
Solution Approach 1:
The patent introduces an intermediary gear mechanism where the pinion gear on the starter motor output shaft meshes with the driven gear inside the crankcase. This intermediary arrangement allows for effective speed reduction and torque multiplication without requiring a single excessively large gear, thereby maintaining cranking capability while controlling the overall size of the starting device.
Data Source
AI summary
A starting device for a general-purpose engine according to one embodiment includes: a starter motor; a pinion gear mounted on an output shaft of the starter motor; a camshaft gear mounted on a camshaft; a crankshaft gear mounted on a crankshaft and meshing with the camshaft gear; and a gear assembly configured to transmit a driving force of the starter motor via the pinion gear to the camshaft gear and configured not to transmit a driving force of the camshaft gear to the pinion gear. The pinion gear, the camshaft gear, the crankshaft gear, and the gear assembly are disposed in a crankcase in a state where the pinion gear meshes with a gear included in the gear assembly.