Two-Piece Zero Distortion Pulley Assembly Axial Clamping
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Solution Overview
Problem
Existing pulley designs for vehicle engines often result in distortion of the outer bearing raceway during assembly, leading to irregular internal radial clearance and reduced bearing durability, contributing to NVH issues.
Innovation Solution
A two-piece pulley design that axially clamps the outer bearing raceway, using a stamped pulley body with a slip pocket and a disc-shaped bearing retainer with tabs that fold over to secure the bearing, maintaining the roundness and radial internal clearance of the bearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If press-fit or over-molding operation is used to retain the ball bearing in the pulley body, then the bearing is securely retained in the pulley, but the outer race of the ball bearing is distorted, resulting in irregular internal radial clearance and reduced bearing durability
Solution Approach 1:
The pulley is divided into two separate pieces: the pulley body and the bearing retainer. The bearing retainer is a separate component that axially clamps the bearing, while the pulley body provides the belt running surface. This segmentation allows the bearing to be retained without distorting the outer race, as the retainer applies axial force rather than radial press-fit force.
Solution Approach 2:
Instead of retaining the bearing radially through press-fit or over-molding (conventional approach), the invention inverts the retention direction by using axial clamping force from the bearing retainer. This inversion of the retention mechanism eliminates distortion of the bearing outer race while maintaining secure bearing retention.
2Reliability
If press-fit or over-molding operation is used to retain the ball bearing, then the bearing is fixed in position, but the average radial internal clearance of the bearing changes during assembly, making it difficult to control the radial internal clearance tolerance
Solution Approach 1:
The invention inverts the retention direction from radial to axial. The bearing retainer applies axial clamping force to secure the bearing in position without affecting the radial internal clearance. This allows the radial internal clearance tolerance to be tightly controlled during bearing assembly, as the axial retention process does not compress or distort the bearing radially.
3Reliability
If a two-piece pulley design with axial clamping is used to prevent bearing distortion, then the bearing durability is improved, but the device complexity increases due to additional components and assembly steps
Solution Approach 1:
The pulley is segmented into two functional pieces: the pulley body (providing belt running surface) and the bearing retainer (providing bearing retention). This segmentation allows each component to be optimized for its specific function, improving bearing durability while maintaining a relatively simple overall structure.
Solution Approach 2:
The bearing retainer is designed to fit over the pulley body, with the bearing nested between the retainer and pulley body. The tabs of the retainer fold over to secure the assembly, creating a compact nested structure that minimizes complexity while achieving the desired bearing retention.
Data Source
AI summary
A zero distortion bearing pulley including a bearing is provided. The bearing clamps axially on the outer bearing raceway instead of radially. The pulley includes a stamped pulley body having a central axis, a pulley face having a periphery, a belt running surface extending perpendicularly from the periphery of the pulley face, a bearing slip pocket formed in the face coaxially with the axis of the pulley body, and a plurality of slots formed between the bearing pocket and the periphery of the pulley face. The slip pocket has a rear stop for retaining the bearing. A disc-shaped, stamped bearing retainer is provided having tabs that fit into the slots in the pulley body. The tabs may be folded over. Optionally, each tab may have an end hook allowing attachment of the stamped retainer bearing to the pulley body face by rotation following insertion of the tabs into the slots.