Molded Bearing Cage Geometry for Precision and Low Friction
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Solution Overview
Problem
Molded plastic cages for high-speed rolling bearings suffer from manufacturing tolerances that are not comparable to machined cages, leading to high costs and long production times, and result in excessive friction and unwanted heating due to surface contact with the outer ring.
Innovation Solution
Designing the radially outer lateral portion of the cage with reduced contact surfaces and blind recesses to control shrinkage during molding, ensuring constant section walls and minimizing friction with the outer ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plastic cages are made by molding, then manufacturing cost and production time are reduced, but manufacturing precision and dimensional tolerance deteriorate compared to machined cages
Solution Approach 1:
The patent changes the geometric parameters of the cage design, specifically introducing blind recesses in the radially outer lateral portion and designing constant section walls. These parameter changes allow the molded cage to achieve dimensional stability and precision comparable to machined cages while maintaining the advantages of injection molding production
Solution Approach 2:
The blind recesses are pre-designed into the cage structure before assembly. These recesses accommodate the shrinkage of plastic material during molding and serve as preliminary compensation for dimensional variations, enabling the molded cage to achieve the required precision without post-machining operations
2Stability of the object's composition
If traditional cage design with larger contact surfaces is used, then structural stability is improved, but friction and heat generation increase
Solution Approach 1:
The patent applies local quality by creating blind recesses in specific locations of the radially outer lateral portion of the cage. This local modification reduces the contact surface area between the cage and outer ring at critical locations while maintaining overall cage structural stability, thereby reducing friction and heat generation without compromising cage integrity
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
Achieves high dimensional precision, reduces friction and unwanted heating, and optimizes manufacturing efficiency by using injection molding instead of machining.
Implementation Method 1
enabling greater control over the shrinkage of the plastic material during and after the molding phase
Data Source
AI summary
A rolling bearing unit includes a rolling bearing and an annular cage including an annular body molded from a synthetic plastic material and a plurality of seats or pockets to accommodate the respective rolling bodies. The annular body has a radially outer annular lateral surface including an annular shallow recess extending axially between a pair of opposing end edges of the annular body and a pair of annular guide reliefs designed to cooperate when in use with an outer ring of a bearing. The radially outer lateral surface of the annular body is provided with a plurality of sets of four recesses arranged around each one of the plurality of pockets, each recess preferably being formed as a blind recess.