Torque Converter Impeller Weld Root Machining

Solution Overview

Problem

Existing torque converter impeller designs often suffer from stress concentration points at the weld root, which can lead to crack propagation during operation, reducing the reliability and longevity of the component.

Innovation Solution

A method of forming an impeller for a torque converter that involves machining both the impeller shell and hub at the weld location to remove the weld root, creating a smooth transition and reducing stress concentrations, and forming an s-shape from the impeller shell to the hub flange to enhance structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If welding is used to join impeller shell and hub, then structural integrity is improved, but stress concentration points are created at the weld root

Engineering Contradiction:

Improvestructural integrityVSAvoidcrack propagation resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The machining operation is performed after welding to remove the weld root and create a smooth transition surface. This preliminary action eliminates stress concentration points that would otherwise exist at the weld root, preventing future crack propagation while maintaining the structural integrity provided by the weld.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The weld root, which initially creates stress concentration and potential crack initiation sites, is converted into a beneficial smooth transition surface through machining. The harmful stress concentration is eliminated by removing the weld root and creating a radiused surface that distributes stress evenly, transforming the weld from a potential failure point to a strengthened joint.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Ease of manufacture

If weld root is left as-is, then manufacturing complexity is reduced, but stress concentration points remain that reduce reliability

Engineering Contradiction:

Improvewelding process simplicityVSAvoidoperational reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The machining operation is performed after welding to remove the weld root and create a smooth transition surface. This preliminary action eliminates stress concentration points that would otherwise exist at the weld root, preventing future crack propagation while maintaining the structural integrity provided by the weld.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If machining is performed to remove weld root, then reliability is improved by eliminating stress concentration, but manufacturing complexity increases

Engineering Contradiction:

Improvecrack propagation resistanceVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The machining operation is performed after welding to remove the weld root and create a smooth transition surface. This preliminary action eliminates stress concentration points that would otherwise exist at the weld root, preventing future crack propagation while maintaining the structural integrity provided by the weld.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10197142B2Method of forming a torque converter impeller including machining a weld root

Publication Date: 2019.02.05 SCHAEFFLER TECHNOLOGIES AG & CO KG

AI summary

A method of forming an impeller for a torque converter is provided. The method includes providing an impeller shell including a back axial surface for facing away from an interior of the torque converter, providing an impeller hub including an outer circumferential surface and forming a weld joining the impeller shell and the impeller hub. The weld is contiguous with the back axial surface of the impeller shell. The weld is also contiguous with the outer circumferential surface of the impeller hub. The weld includes a root where the impeller shell and the impeller hub meet the weld. The method also includes machining the root. An impeller for a torque converter is also provided.