Necked Impeller Shell Torque Converter Stress Reduction
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Solution Overview
Problem
Existing torque converters face challenges in reducing rotary bend stresses at the weld toe and effectively supporting high-torque applications, particularly in the integration of bearings for improved durability and centering.
Innovation Solution
The design incorporates an axially extending necked portion in the impeller shell, formed by extrusion or stamping, which connects to the radial wall at a 90-degree angle, reducing stresses at the weld toe and supporting a bearing for enhanced durability and centering, while allowing for cost and time savings by eliminating alternative machining methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flanged covers or hubs are used to support bearings in torque converters, then the structure is simple and easy to manufacture, but rotary bend stresses at the weld toe increase and durability decreases
Solution Approach 1:
The impeller shell is segmented into distinct functional portions: a radial wall portion for structural support, an elbow portion for stress redistribution, and an axially extending necked portion for bearing support. This segmentation allows each portion to be optimized for its specific function, reducing overall stress concentrations while maintaining manufacturability.
Solution Approach 2:
The bearing support function is moved from a radial/flange-based structure to an axial dimension through the necked portion extending parallel to the rotation axis. This dimensional shift allows the bearing to be supported away from high-stress weld zones, reducing rotary bend stresses at critical weld toes while maintaining structural integrity.
2Reliability
If bearings are supported directly on the impeller shell in traditional designs, then the structure is simpler, but centering accuracy and durability in high-torque applications deteriorate
Solution Approach 1:
The axially extending necked portion acts as an intermediary element between the impeller shell and the bearing. It provides a dedicated, precision-machined support surface that ensures accurate bearing centering while distributing loads away from critical weld zones, thereby improving durability without significantly complicating manufacturing.
Solution Approach 2:
The necked portion features localized geometric characteristics (reduced cross-section, specific length-to-diameter ratio) that are optimized specifically for bearing support and centering functions. This local quality enhancement allows the bearing to be precisely positioned and supported without requiring the entire impeller shell to be overly complex.
3Duration of action of stationary object
If the impeller shell uses traditional flange designs, then manufacturing is easier and faster, but stress concentrations at weld toes reduce component life
Solution Approach 1:
The elbow portion introduces a curved, transitional geometry between the radial wall and the axial necked portion. This curvature distributes stress more evenly through the structure, eliminating sharp corners and stress concentrations at weld toes, thereby extending service life while remaining compatible with standard forming processes.
Data Source
AI summary
An impeller for a torque converter comprising: an axis of rotation; an impeller shell comprising: a torus portion; a radial wall portion; an elbow portion; an interior portion; and, an axially extending necked portion, extending about the axis of rotation and into the interior portion, having: a first circumferential surface; and, a second circumferential surface.