Gear Assembly Plateau Surface Polishing for Torque Transmission
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Solution Overview
Problem
Conventional gear manufacturing methods increase production costs and reduce yield by requiring extensive man-hours for tooth surface treatment, and existing solutions are not suitable for high-strength gears used in automotive powertrains to efficiently transmit large torque.
Innovation Solution
The tooth surfaces of the gear rotated at the highest speed are finished into a plateau surface with a smaller surface roughness parameter, specifically an arithmetic mean roughness Ra smaller than 0.15 μm and a reduced peak height Rpk between 0.01 μm and 0.1 μm, through polishing, to enhance transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If tooth surfaces of all gears are polished to reduce surface roughness, then transmission efficiency is improved, but production time and cost increase significantly
Solution Approach 1:
The patent applies different surface roughness requirements to different gears based on their rotational speed. Specifically, the gear rotating at the highest speed (first gear) receives intensive polishing treatment with Ra < 0.15 μm, while other gears have less stringent requirements. This local differentiation optimizes transmission efficiency where it matters most (high-speed gears contribute more to energy loss) while reducing overall production time and cost.
2Strength
If conventional tooth forming method is used with subsequent hardening and surface treatment, then gear strength is sufficient, but man-hour increases and production yield decreases
Solution Approach 1:
The patent performs surface polishing treatment on the high-speed gear before hardening treatment. By conducting the polishing operation while the gear material is still in its softer state, the process becomes more efficient and requires less subsequent rework. This preliminary action maintains adequate gear strength while significantly reducing total production time and improving yield.
3Object-generated harmful factors
If resin driven gear is used to reduce engagement friction, then friction is reduced, but it is not suitable for automotive powertrains requiring high-strength gears for large torque transmission
Solution Approach 1:
The patent changes the surface parameters (roughness) of metal gears to achieve low-friction operation comparable to resin gears, while maintaining the high strength requirements for automotive powertrains. By controlling the arithmetic mean roughness Ra to be less than 0.15 μm on the high-speed gear, the patent achieves reduced engagement friction without sacrificing the torque transmission capability required in automotive applications.
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
This approach reduces loss torque and enhances transmission efficiency by polishing only the tooth surfaces of the gear involved in torque transmission most frequently, comparable to polishing all gear surfaces, while minimizing the number of gears that need to be polished.
Implementation Method 1
tooth surfaces of a first gear that is rotated at a highest speed are individually finished into a plateau surface
Data Source
AI summary
A gear assembly wherein transmission efficiency is enhanced by a simple treatment is provided. The gear assembly includes a plurality of gears to transmit torque of a prime mover to an output member. Tooth surfaces of a first gear rotated at a highest speed are individually finished into a plateau surface, and a parameter representing a surface roughness of each of the plateau surface is smaller than those of the tooth surfaces of the other gears.