Stepped Positioning Holes for Scratch-Free Electric Drive Gearbox Assembly
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Solution Overview
Problem
Existing powertrain assembly methods using positioning pins and holes result in scratches on bearing raceways due to insufficient offset space, leading to performance issues and reduced assembly efficiency.
Innovation Solution
Implementing stepped hole positioning in the electric drive gearbox assembly with guiding and engaging sections in the positioning holes to facilitate pre-positioning and radial adjustment of housings, using ventilation grooves and guide slopes to ensure smooth assembly and prevent scratches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If positioning pins and positioning holes are used to connect housing assemblies, then the housings can be positioned and connected, but there is not enough offset space between the positioning pin and positioning hole, causing the bearing roller and bearing inner ring to compress each other during assembly, which results in scratches on the bearing raceway surface
Solution Approach 1:
The positioning hole is divided into two sections: a guiding section with a larger aperture and an engaging section with a smaller aperture. This segmentation allows the positioning pin to first pass through the guiding section without compressing the bearing components, and then engage with the engaging section to secure the housing assemblies, thus preventing scratches while maintaining connection reliability
Solution Approach 2:
The guiding section acts as an intermediary structure between the positioning pin and the engaging section. It provides a transition zone with larger aperture that allows the positioning pin to enter without directly compressing the bearing roller and inner ring, thereby mediating the assembly process to prevent damage to the bearing raceway surface
2Reliability
If a stepped pin is used to prevent scratches on the bearing raceway, then the bearing surface is protected, but the structures of two ends of the stepped pin are different, making it easy for the ends to be installed in reverse during batch assembly, which reduces assembly efficiency
Solution Approach 1:
Instead of making the positioning pin stepped with different structures at both ends (which causes confusion during assembly), the invention inverts the approach by making the positioning hole stepped while keeping the positioning pin simple and uniform. This reversal eliminates the risk of incorrect installation while still achieving the protective function, thereby maintaining high assembly efficiency
3Reliability
If the aperture of the positioning hole is reduced to prevent bearing compression, then the bearing raceway is protected from scratches, but the positioning pin cannot be properly inserted, reducing assembly feasibility
Solution Approach 1:
The positioning hole is segmented into a guiding section with larger aperture for easy pin insertion and an engaging section with smaller aperture for bearing protection. This segmentation resolves the contradiction by providing different aperture sizes at different sections of the same positioning hole, enabling both proper pin insertion and bearing raceway protection
Data Source
AI summary
The utility model discloses a stepped hole positioning electric drive gearbox assembly. The stepped hole positioning electric drive gearbox assembly specifically comprises a first shell, a second shell and a positioning pin. A first positioning hole is formed in the connecting surface of the first shell, a second positioning hole corresponding to the first positioning hole is formed in the second shell, and the first shell and the second shell are in positioning connection through the first positioning hole, the second positioning hole and a positioning pin; the first positioning hole and/or the second positioning hole are/is stepped holes, each stepped hole comprises a guiding section close to the hole opening and a matching section away from the hole opening, the hole diameter of the guiding section is larger than that of the matching section, and the guiding section is used for guiding the positioning pin to enter the matching section. In the electric drive gearbox assembly, the first shell can be pre-positioned when being assembled with the second shell, and the first shell can be radially adjusted relative to the second shell during pre-positioning, so that the first shell and the second shell can be conveniently positioned and assembled, and the electric drive gearbox assembly can be automatically and massively assembled.