Resin Helical Gear Axial Bending Restriction
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Solution Overview
Problem
Conventional drive devices with resin helical gears face issues of insufficient meshing due to axial bending of helical gears under high loads, which is difficult to address with existing support structures.
Innovation Solution
A drive device design that includes a gear housing with a housing cover featuring a restriction portion allowing slidable contact with the output-side helical gear to prevent axial bending, ensuring proper meshing of helical gears by supporting both gears rotatably and using a resin material for the gears and housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resin helical gears are used in reduction drive, then manufacturing cost is reduced and vibration/noise are decreased, but axial bending occurs under high load causing insufficient meshing
Solution Approach 1:
A thrust bearing is introduced as an intermediary component between the helical gear and the housing. The thrust bearing mediates the axial load by converting it into radial load on the gear shaft, preventing axial bending of the gear while maintaining the benefits of resin helical gears. This resolves the contradiction by adding a specific structural element that addresses the meshing insufficiency problem without changing the gear material.
Solution Approach 2:
The patent changes the structural parameters of the gear support system by adding axial support through thrust bearings and designing specific housing structures (such as ribs or support projections) that provide axial positioning. This parameter change in the support system allows resin helical gears to withstand axial loads without bending, resolving the reliability issue while maintaining cost-effectiveness.
2Device complexity
If the helical gear near the output unit is supported only by a support projection, then device complexity is reduced, but axial bending occurs under load
Solution Approach 1:
The support function is segmented into multiple components: the support projection provides basic positioning, while additional features such as ribs, flanges, or integrated thrust bearing mounts provide axial support. This segmentation of support functions allows the structure to handle axial loads without requiring a completely complex support system, balancing simplicity with strength.
Solution Approach 2:
The housing structure merges multiple functions into unified elements. For example, the housing simultaneously provides gear mounting, axial support through integrated ribs or projections, and thrust bearing mounting. This merging reduces the number of separate components while providing comprehensive support that prevents axial bending, resolving the contradiction between complexity and strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents axial bending of helical gears, maintaining sufficient meshing and reducing manufacturing costs, while allowing for efficient torque transmission without increasing the device's size or risk of gear breakage.
Implementation Method 1
The restriction portion is configured to allow for slidable contact with the output-side helical gear to restrict axial bending of the output-side helical gear
Data Source
AI summary
A drive device includes a reduction drive, an accommodation portion, and an output unit. The reduction drive includes at least two resin helical gears meshed with each other. The at least two helical gears include an output-side helical gear and another helical gear. The output-side helical gear is located closer to the output unit than the other helical gear in a power transmission path of the reduction drive. The housing cover includes a restriction portion located within a range that includes a straight line intersecting the first center axis and the second center axis. The restriction portion projects toward a bottom of the gear accommodation portion. The restriction portion is configured to allow for slidable contact with the output-side helical gear to restrict axial bending of the output-side helical gear.