Driven Pulley Spindle Bearing Layout for Low Axial Runout
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Solution Overview
Problem
Existing belt-driven pulley systems face challenges with high axial runout due to overhanging components like fan clutches, which cause imbalance and structural stress, especially in heavy-duty applications, where precise mounting is required to minimize wobble and ensure proper lubrication, often leading to costly machining and increased reject rates.
Innovation Solution
The use of multiple sets of bearings with radial clearance on a spindle shaft, including at least one set of double-row bearings, with a sleeve providing a minimum 0.005 mm diametral clearance, allows for precise assembly and clamping to achieve low axial runout without press fitting, which reduces distortion and assembly variations, enabling direct mounting of overhanging components like fan clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If press fitting is used to assemble bearings to the shaft, then assembly is simplified, but distortion of the mounting surface occurs which increases axial runout
Solution Approach 1:
The assembly is divided into separate components: the shaft with precision-machined mounting face, the bearing assemblies with interference fits to the shaft, and the pulley mounted separately. This segmentation allows the mounting face to be precision-machined before bearing assembly, avoiding distortion from press-fitting the pulley, while still enabling simplified assembly through pre-assembled bearing units.
Solution Approach 2:
The bearing assemblies are pre-assembled to the shaft with interference fits before the final pulley mounting. The mounting face is precision-machined in advance before bearing assembly. This preliminary action ensures the mounting face is precisely formed before any press-fitting operations that could cause distortion, while still maintaining ease of final assembly.
2Manufacturing precision
If the distance between bearing raceways is increased to reduce axial runout, then precision of rotation axis improves, but bearing size and complexity increase
Solution Approach 1:
Instead of increasing the axial distance between bearings along the rotation axis, the patent uses multiple bearing assemblies positioned at different radial locations on the shaft. This dimensional change allows precision control of the rotation axis through radial bearing arrangement rather than axial spacing, avoiding the complexity of very long bearing spans.
Solution Approach 2:
Multiple bearing assemblies are combined on a single shaft with precision-machined mounting faces. This merging of multiple bearing units at optimized locations achieves the precision of a long-span bearing system while maintaining compact overall dimensions and avoiding the complexity of oversized individual bearings.
3Manufacturing precision
If machining is performed after assembly to reduce axial runout, then precision improves, but contamination risk and cost increase
Solution Approach 1:
The mounting face is precision-machined to the required precision before any assembly operations. This preliminary machining ensures the face is formed to exact tolerances before bearings and pulleys are assembled, eliminating the need for post-assembly machining and avoiding contamination from machining operations on assembled components.
Solution Approach 2:
The machining operation is extracted from the post-assembly process and performed separately on the shaft before assembly. This separation allows precision machining to be completed in a clean environment without risk of contaminating bearing grease or damaging seals, while still achieving the required axial runout precision.
4Ease of manufacture
If standardized bearing assemblies are used, then ease of manufacture improves, but customization for specific runout requirements decreases
Solution Approach 1:
The shaft design with precision-machined mounting faces serves multiple functions: it provides standardized interfaces for bearing assemblies, ensures precise axial runout control through careful machining, and allows flexibility in bearing selection. This universal shaft design accommodates both standardized bearing units and specific precision requirements through the quality of the machined mounting surfaces rather than custom bearing designs.
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
This solution achieves very low axial runout, supports high loading, and provides a more precise axis of rotation, reducing the need for costly machining and minimizing contamination risks, while allowing for standardized bearing assemblies and reduced scrap rates.
Implementation Method 1
multiple sets of bearings with radial clearance to the shaft
Implementation Method 2
at least one set of double-row bearings
Data Source
AI summary
A low axial runout driven pulley through the application of a spindle shaft utilizing multiple sets of bearings with radial clearance to the shaft. Utilizing a belt-driven pulley supporting overhanging loads with low axial runout provided by a spindle shaft with radial clearance to supporting bearings. Further axial clamp loading may be provided through multiple sets of bearings by the application of a fastener, such as a shaft bolt and a sleeve that press against the inner races of the bearings in the axial direction with this clamp load. The belt-driven pulley with low axial runout through the application of a spindle shaft utilizing at least two sets of bearings with radial clearance to the shaft may be utilized with heavy-duty trucking, marine, industrial, and other systems that utilize an overhung driven component.