Gear Tooth Rolling with Dual Shaping Tools for Fatigue Strength
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Solution Overview
Problem
Existing methods for enhancing the fatigue strength of toothing in gear wheels, such as shot blasting and hydrostatic pressing, are complex and result in low productivity or surface roughness, failing to effectively induce compressive residual stresses.
Innovation Solution
A rolling device with multiple shaping tools, including rollers and sliding elements, is used to induce compressive residual stresses and improve surface quality, allowing for guided movement to process gear wheels efficiently, especially in mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shot blasting is used to induce compressive residual stresses, then fatigue strength of toothings is improved, but surface smoothness deteriorates and process complexity increases
Solution Approach 1:
The patent replaces the shot blasting process (which uses discrete particles) with a rolling process using continuous cylindrical tools. The rolling tools apply controlled mechanical pressure through rotation, inducing compressive residual stresses without the random impact of shot blasting, thereby maintaining surface smoothness while improving fatigue strength.
Solution Approach 2:
The patent changes the fundamental parameter of the processing method from particle impact (shot blasting) to controlled rolling pressure. By adjusting rolling force, rotation speed, and tool geometry, the process achieves compressive residual stress induction with controlled surface quality, resolving the contradiction between strength improvement and surface smoothness.
2Productivity
If a single shaping tool is used, then device complexity is reduced, but productivity decreases
Solution Approach 1:
The patent divides the work piece processing into multiple independent shaping tools, each responsible for specific tooth flanks. This segmentation allows parallel processing of multiple features simultaneously, increasing overall productivity while keeping each individual tool relatively simple in design.
Solution Approach 2:
The patent combines multiple shaping tools into a single integrated device structure with common support and control mechanisms. This merging approach enables simultaneous operation of multiple tools on different tooth flanks, achieving high productivity without proportionally increasing device complexity, as shared components reduce the net complexity increase.
3Strength
If hydrostatic pressing with high liquid pressure is used, then compressive residual stresses are induced, but device complexity increases due to extreme pressure requirements
Solution Approach 1:
The patent replaces the hydrostatic pressing system (which requires complex high-pressure liquid delivery infrastructure) with a direct mechanical rolling system. The rolling tools transmit force through controlled rotation and mechanical contact, achieving comparable or superior compressive residual stresses without the infrastructure complexity of extreme pressure hydraulic systems.
Solution Approach 2:
The patent transforms the static high-pressure application of hydrostatic pressing into a dynamic rolling process. The rolling tools apply varying pressure through rotation, allowing controlled stress induction through motion rather than requiring sustained extreme static pressure, thereby simplifying the overall system while achieving the desired residual stress state.
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
The solution enables quick and effective processing of gear wheels with improved wear resistance and surface quality, enhancing the fatigue strength of toothing while maintaining minimal thickness change.
Implementation Method 1
induce compressive residual stresses into a cylindrical external surface of a component
Implementation Method 2
a first shaping tool and at least a second shaping tool are moved jointly and in a guided way relative to the work piece
Data Source
AI summary
A rolling device for work pieces with toothing, in particular gear wheels, includes first and second shaping tools which are guided by a guide relative to the work pieces. With respect to the work pieces, a first region of a tooth flank is shaped with the first shaping tool and a second region of the tooth flank is shaped by the second shaping tool. The first and second shaping tools are respectively mounted on first and second rollers. The second roller has an axial thickness on the circumference, which differs from the axial thickness of the first roller such that the second region of the tooth flank is different from the first region.