Electromechanical Assembly Centering Shafts Eliminate Spline Misalignment
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Solution Overview
Problem
Existing electromechanical assemblies with splined connections between electric motors and reduction gears face issues of misalignment, wear, and noise due to radial forces, leading to premature wear and reduced lifespan, particularly exacerbated by the presence of fretting corrosion.
Innovation Solution
The solution involves centering reliefs with zero clearance, where the shafts are fitted together without play, allowing the casings to be fixed in the assembled position using screws or bolts, eliminating the need for precise positioning reliefs and minimizing noise by ensuring the splines interlock without angular displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If radial clearance is provided at the centering seat to allow shaft assembly, then ease of assembly is improved, but angular displacement and spline misalignment occur leading to wear and noise
Solution Approach 1:
A centering element is introduced as an intermediary component between the first shaft and the second shaft. This centering element features a centering portion that fits into a centering seat on the first shaft, providing precise alignment and eliminating angular displacement while maintaining ease of assembly through the intermediary structure.
2Reliability
If damping elements such as O-rings are interposed radially to damp displacement between shafts, then spline wear is reduced, but device complexity increases
Solution Approach 1:
The centering element serves as a mediator that provides both centering function and damping capability through its structural design. The centering portion with centering seat creates a precise fitting interface that inherently dampens displacement between shafts without requiring additional O-rings or damping elements, thus maintaining reliability while reducing complexity.
3Reliability
If a motor with two bearings is coupled to a reducer with two bearings, then shaft co-axiality is improved, but manufacturing and assembly difficulty increase due to rigorous positioning requirements
Solution Approach 1:
The centering element acts as a mediator that transfers and maintains precise co-axial alignment between the motor shaft and reducer shaft during assembly. By providing a centering portion that fits into the centering seat, it ensures rigorous positioning is achieved automatically through the fitting interface, eliminating the need for complex external positioning fixtures or procedures.
Solution Approach 2:
The centering seat and centering portion are pre-formed during manufacturing with precise tolerances. This preliminary action of creating the centering interface during production allows the shafts to be automatically aligned when assembled, eliminating the need for rigorous positioning during the actual assembly process and reducing manufacturing and assembly difficulty.
4Ease of operation
If play is left at the splines to allow assembly, then ease of assembly is improved, but wear by fretting corrosion occurs reducing service life
Solution Approach 1:
The centering element serves as an intermediary that establishes precise co-axial alignment between shafts before the splined connection engages. By providing the centering portion and centering seat interface, it eliminates angular displacement and fretting corrosion at the spline interface, ensuring long service life while still allowing straightforward assembly through the centering mechanism.
Data Source
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Figure 4~6
AI summary
The present invention concerns an electromechanical assembly (10) comprising an electric machine (20) coupled to a reducing gear (30), the electric machine (20) comprising two bearings or rollers, the reducing gear (30) comprising two bearings or rollers, the reducing gear (30) and the electric machine (20) each comprising a housing (31; 21) comprising means (35) for attachment to the other housing (21; 31), the electric machine (20) and the reducing gear (30) each comprising a shaft (23; 33) engaged in the other, each shaft (23; 33) comprising centring projections (41, 42) produced in such a way that the mutual engagement of the shafts (23, 33) has a centring effect that positions the housings (21, 31) correctly in order for them to be attached by means of the attachment means (35).