Rotor Sleeve Installation Using a Conical Mandrel
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Solution Overview
Problem
The challenge in manufacturing electric machines is the difficulty in installing a reinforcing sleeve onto the rotor without causing damage due to manufacturing tolerances and material strain, particularly in electric vehicles where the sleeve expansion during operation is critical.
Innovation Solution
A mandrel with specific geometrical features, including cylindrical and conical portions, is used to align and press-fit the sleeve onto the rotor assembly, utilizing a polymeric ring and lubrication to minimize damage and ensure a smooth installation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reinforcing sleeve is installed onto the rotor using conventional press-fit methods, then the rotor expansion during operation can be prevented, but the sleeve installation may cause damage to the rotor assembly due to manufacturing tolerances and material strain
Solution Approach 1:
A mandrel is introduced as an intermediary tool between the sleeve and rotor assembly during installation. The mandrel provides a controlled interface that distributes installation forces evenly, preventing direct damage to the rotor while enabling proper sleeve expansion and seating. The mandrel acts as a mediator that facilitates the press-fit process without transferring harmful stresses to the rotor components.
Solution Approach 2:
The mandrel geometry is specifically designed with varying diameters (cylindrical and conical portions) to control the expansion parameters of the sleeve during installation. By changing the mandrel diameter along its length, the installation process gradually expands the sleeve to the required dimensions, preventing sudden stress concentration and material damage while achieving the necessary fit on the rotor assembly.
2Productivity
If the sleeve is pressed directly onto the rotor assembly, then installation can be completed, but manufacturing tolerances cause misalignment and potential damage
Solution Approach 1:
The mandrel serves as a precision intermediary that compensates for manufacturing tolerances in both the sleeve and rotor assembly. By providing a standardized, precisely manufactured interface, the mandrel ensures proper alignment during installation even when component tolerances vary, enabling successful installation without sacrificing productivity.
3Strength
If the sleeve expansion is constrained during installation, then rotor integrity is maintained, but the sleeve cannot achieve proper fit and function
Solution Approach 1:
The mandrel's varying diameter profile (cylindrical to conical transitions) controls the expansion parameters of the sleeve in a gradual, controlled manner. This allows the sleeve to expand sufficiently to achieve proper fit and function while the mandrel's structured geometry prevents excessive or uncontrolled expansion that would compromise rotor integrity. The parameter changes in mandrel diameter enable precise control over the deformation state of the sleeve throughout installation.
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 method allows for the successful installation of the sleeve without damaging the rotor assembly, ensuring proper alignment and expansion, thereby enhancing the rotor's structural integrity and operational reliability.
Implementation Method 1
pressing the sleeve over the outer mandrel diameter and onto the rotor assembly with a driver on a press with the sleeve configured to apply a compressive force to a portion of the rotor assembly surrounded by the sleeve
Implementation Method 2
utilizing a polymeric ring and lubrication to minimize damage and ensure a smooth installation process
Data Source
AI summary
An assembly includes a rotor assembly having a rotor stack with an outer rotor diameter and a rotor shaft extending along a rotational axis of the rotor assembly. A mandrel includes an outer mandrel diameter extending between a proximal end and a distal end with a rotor engaging surface at the distal end of mandrel. The outer mandrel diameter includes a first cylindrical portion adjacent the proximal end, a conical portion distal of the first cylindrical portion with a first transitional portion connecting the first cylindrical portion to the conical portion. The assembly also includes a sleeve having an inner sleeve diameter that is less than the outer rotor diameter when in an unexpanded state.