Preloaded Shaft Assembly for Bearing Axial Load Stability
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Solution Overview
Problem
High-speed electric motor shaft assemblies with semi-floating bearing configurations experience axial load shifts, leading to unwanted noise, vibration, and harshness (NVH), which existing preload methods like shimming or using springs are time-consuming and require additional assembly steps.
Innovation Solution
A simplified shaft assembly with a preload spring featuring a washer body and axially extending flange, where the flange contacts both the outer housing and bearing assembly, providing preloading without the need for shims or additional components, and is formed as a unitary component for easier installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shimming or preloading components are added to address NVH issues, then the axial load stability is improved, but the assembly complexity and time increase
Solution Approach 1:
The preload spring integrates the washer body and flange into a single unitary component, combining multiple functions (preload application, axial positioning, and load distribution) into one element that is installed as a single unit, eliminating the need for separate shims or preload components
Solution Approach 2:
The preload spring serves multiple functions simultaneously: it provides axial preload to the bearing assembly, positions the bearing assembly axially within the housing, and distributes loads across the bearing and housing interfaces, replacing what would traditionally require multiple separate components
2Reliability
If traditional preload methods are used, then axial load distribution is improved, but installation time and measurement steps increase
Solution Approach 1:
The preload spring is pre-configured with a specific curvature (R = 90° to 220°) and dimensions during manufacturing, establishing the required preload characteristics before installation, eliminating the need for on-site measurement and adjustment of stack-up lengths
Solution Approach 2:
The preload spring's geometric parameters (curvature radius, flange thickness, outer diameter) are specifically designed to provide the necessary preload force and axial positioning, allowing consistent load distribution to be achieved through manufacturing precision rather than assembly adjustment
3Ease of operation
If a unitary preload spring is used, then ease of installation is improved, but manufacturing complexity may increase
Solution Approach 1:
The preload spring is formed from a flexible material (steel) that can be elastically deformed during installation to fit into the annular groove, then returns to its predetermined curvature to provide preload, allowing a single-piece construction to achieve functions that would otherwise require multiple rigid components
Solution Approach 2:
The washer body is given a curved profile with a circumferential curvature radius (R) of 90° to 220° in its uncompressed state, which provides the elastic compliance needed for easy installation while maintaining the structural integrity and load-bearing capability required for reliable preload application
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 solution effectively addresses NVH issues by providing a direct preload contact between the bearing assembly and housing, simplifying installation by eliminating the need for additional measurement and assembly steps, and ensuring consistent axial load distribution.
Implementation Method 1
a preload spring. The preload spring includes a washer body positioned or arranged within an annular groove of an outer ring of the bearing assembly, and a flange extending axially from the washer body and contacting the outer housing
Data Source
AI summary
A shaft assembly is disclosed herein. The assembly includes a shaft, an outer housing, a bearing assembly, and a preload spring. The bearing assembly includes an inner ring mounted on the shaft and defining an inner raceway. An outer ring defines an outer raceway and an annular groove, and the outer ring is arranged within the outer housing. A plurality of rolling elements are arranged between the inner raceway and the outer raceway. The preload spring includes: a washer body positioned within the annular groove of the outer ring, and a flange extending axially from the washer body and contacting the outer housing.