Radial Cage Crossbar Thickness Variation for Centrifugal Load Management
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Solution Overview
Problem
Conventional needle roller and cage assemblies experience crossbar breakage due to high centrifugal forces at high rotational speeds, leading to malfunction and damage in automatic transmissions, despite previous design modifications aimed at reducing bending and wear.
Innovation Solution
The radial cage design features increased material thickness in the straight side sections of axial crossbars for enhanced strength, reduced material thickness in the axial center sections to minimize centrifugal mass, and tapered intermediate sections for uniform force transmission, along with enlarged stop faces and optional center subsections for improved support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the material thickness of axial crossbars is increased to reduce bending under centrifugal forces, then the strength and stability of the radial cage is improved, but the centrifugal mass and rotational inertia of the crossbars increases, leading to higher centrifugal forces and potential breakage at high speeds
Solution Approach 1:
The patent applies local quality by differentiating the material thickness across different sections of the axial crossbars. The side sections (4a, 4b) have increased material thickness to provide strength against bending, while the center section (4e) has reduced material thickness to minimize centrifugal mass. This localized variation in material properties resolves the contradiction between needing strength and minimizing weight.
Solution Approach 2:
The axial crossbars are segmented into distinct sections with different material thicknesses: side sections (4a, 4b) with greater thickness for strength, intermediate sections (4c, 4d) with tapered thickness, and center sections (4e) with reduced thickness. This segmentation allows each part to be optimized for its specific functional requirements, balancing strength and centrifugal mass.
2Reliability
If the material thickness of side sections is increased to prevent breakage, then the reliability of the radial cage is improved, but the manufacturing complexity and material consumption increases
Solution Approach 1:
Instead of uniformly increasing the thickness of entire axial crossbars, the patent applies local quality by selectively thickening only the side sections (4a, 4b) that are subject to bending stresses. This localized reinforcement improves reliability where needed while avoiding unnecessary material consumption and manufacturing complexity in other sections.
3Reliability
If the material thickness of center sections is reduced to minimize centrifugal mass, then the reliability at high speeds is improved, but the structural strength and support capability of the crossbars decreases
Solution Approach 1:
The patent applies local quality by selectively thinning only the center sections (4e) of axial crossbars, which are located farthest from the rotation axis and thus contribute most to centrifugal mass. This localized thinning reduces centrifugal forces and improves high-speed reliability while the thicker side sections maintain the necessary structural strength for supporting rolling elements.
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 design effectively prevents crossbar breakage and consequential damage by distributing loads more evenly, ensuring reliable operation at high speeds and reducing wear, particularly in applications like planetary gear bearings and connecting rod bearings.
Implementation Method 1
the increased loads resulting from the high rotational speeds have led to increased crossbar breakage in the vicinity of the straight side sections of the axial crossbars of the radial cage, and thus to failure of the needle roller and cage assemblies. The cause of this was identified as the fact that the radial cage is so strongly loaded by the intermittently acting, extremely high centrifugal forces
Data Source
AI summary
A radial cage in which side rings have a material thickness of a starting material for the radial cage, straight side sections of each axial crossbar are implemented with a greater material thickness that increases their strength, and an axial center section of each axial crossbar is implemented with a smaller material thickness than the material thickness of the side rings, thus reducing centrifugal mass.