Offset-Center Pinion Gear Layout for Compact Speed Reduction
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Solution Overview
Problem
Conventional speed reduction mechanisms for in-vehicle drive sources, such as wiper devices, face a trade-off between ensuring the strength of the pinion and helical gears, where increasing the thickness of the helical gear's oblique teeth reduces the diameter, compromising the strength of the pinion gear's core, and vice versa, affecting power transmission efficiency and speed reduction ratio.
Innovation Solution
The design features a pinion gear with a crescent-shaped helical tooth and a helical gear with oblique teeth, where the center of the pinion main body is offset from the helical tooth, allowing the pinion gear to protrude outside the imaginary circle of the helical tooth's outer shape, enhancing strength while maintaining a compact size and improving meshing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the speed reduction ratio is increased, then the power transmission capability is improved, but the meshing strength between gears must be increased, complicating the design
Solution Approach 1:
The asymmetric configuration with offset centers allows for optimized meshing geometry that improves power transmission capability. The protrusion of the pinion main body outside the imaginary circle creates favorable engagement conditions between teeth, enabling higher speed reduction ratios while maintaining adequate meshing strength without requiring excessive tooth thickness
2Volume of moving object
If the pinion gear is made compact, then the overall size is reduced, but the core portion may become thin, reducing strength
Solution Approach 1:
The patent resolves this contradiction by making the pinion main body asymmetric with respect to the helical tooth center, allowing the pinion to be compact in overall dimensions while the core portion maintains sufficient thickness. The offset configuration enables the core to extend appropriately to maintain strength even in a compact design
Data Source
AI summary
When viewed in the axial direction of a pinion gear (31), the center (C1) of a pinion main body (31b) and the center (C2) of a helical tooth (31c) are offset from each other, the helical tooth (31c) has a larger diameter than the pinion main body (31b), and the pinion main body (31b) partially protrudes outside an imaginary circle (VC) that forms the outer shape of the helical tooth (31c). A cross-sectional shape of the pinion gear (31) can be made non-circular with the pinion main body (31b) partially protruding outside the imaginary circle (VC) that forms the outer shape of the helical tooth (31c).