In-Wheel Motor Gear Case Structure for Helical Gear Thrust Loads
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Solution Overview
Problem
Existing in-wheel motor drive devices face challenges in withstanding thrust loads generated by helical gears without increasing the weight of the gear case, as increasing wall thickness adds weight while reducing it may lead to deformation.
Innovation Solution
The in-wheel motor drive device incorporates a gear case with strategically placed thrust bearings and a rib on the motor case to distribute and support thrust loads, allowing the gear case to maintain strength without excessive weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the wall thickness of the gear case is increased to withstand thrust loads, then the strength is improved, but the weight increases
Solution Approach 1:
The gear case has different wall thicknesses at different locations: the first wall (inner wall) has a smaller thickness, while the second wall (outer wall) has a larger thickness. This local differentiation allows the gear case to withstand thrust loads at critical locations without uniformly increasing weight across the entire structure.
Solution Approach 2:
The gear case employs asymmetric wall thickness design where the first wall and second wall have different thicknesses. The first wall thickness is smaller than the second wall thickness, creating an asymmetric structure that optimizes strength distribution according to the actual load patterns of helical gears.
2Weight of stationary object
If the wall thickness of the gear case is reduced to decrease weight, then the weight is decreased, but the gear case may deform under thrust loads
Solution Approach 1:
The gear case has different wall thicknesses at different locations: the first wall (inner wall) has a smaller thickness, while the second wall (outer wall) has a larger thickness. This local differentiation allows the gear case to withstand thrust loads at critical locations without uniformly increasing weight across the entire structure.
Solution Approach 2:
The gear case employs asymmetric wall thickness design where the first wall and second wall have different thicknesses. The first wall thickness is smaller than the second wall thickness, creating an asymmetric structure that optimizes strength distribution according to the actual load patterns of helical gears.
Data Source
AI summary
A gear case of an in-wheel motor drive device houses first and second helical gears, has a first opening in its inner wall through which a motor main shaft passes, and has a second opening in its outer wall through which an axle passes. The in-wheel motor drive device further includes a first thrust bearing attached to the outer wall and supporting the first helical gear, and a second thrust bearing attached to the inner wall and supporting the second helical gear. The directions of helical teeth of the first and second helical gears are set so that when a motor vehicle travels forward, a thrust load directed outward in the vehicle width direction is applied to the first helical gear, and a thrust load directed toward the middle in the vehicle width direction is applied to the second helical gear.