Screw-like Grindstone Axis Angle Adjustment for Internal Gear Machining

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Solution Overview

Problem

The machining accuracy of internal gears is compromised due to changes in the diameter of screw-like grindstones during dressing, affecting the state of contact and resulting tooth flank shape, especially in large-scale machining.

Innovation Solution

An internal gear machining method that synchronously rotates the gear and a barrel-shaped screw-like tool, setting the axis intersection angle based on the outer diameter of the tool after dressing, and gradually decreasing this angle with each dressing to maintain consistent contact and slip velocity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the grindstone is dressed with a constant axis intersection angle, then the dressing process is simple and quick, but the diameter change of the screw-like grindstone affects the contact state and machining accuracy

Engineering Contradiction:
Improvedressing process simplicityVSAvoidtooth flank shape accuracy
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by adjusting the axis intersection angle based on the grindstone diameter. Before dressing, the axis intersection angle is set to a first value; after dressing when the diameter decreases, the angle is changed to a second value that is smaller than the first value. This dynamic parameter adjustment compensates for the diameter change and maintains consistent contact conditions, resolving the contradiction between simple dressing and machining precision.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If the axis intersection angle is decreased after dressing, then the contact state is maintained consistent, but the dressing process becomes more complex

Engineering Contradiction:
Improvegrinding contact state consistencyVSAvoiddressing process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements feedback control by measuring the grindstone diameter before and after dressing, then using this information to determine the appropriate axis intersection angle for subsequent grinding operations. The system automatically adjusts the angle parameter based on the actual diameter change, ensuring consistent contact conditions while managing complexity through automated control.

Inventive Principle:
Principle #23Feedback

3Duration of action of stationary object

If the grindstone diameter decreases after dressing, then the grindstone can be reused, but the change in diameter alters the contact state and affects machining accuracy

Engineering Contradiction:
Improvegrindstone service lifeVSAvoidtooth flank shape consistency
Core Design Contradiction:
Duration of action of stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by making the axis intersection angle adjustable and variable rather than fixed. The angle is dynamically changed from a first value before dressing to a second value after dressing, adapting to the changed grindstone diameter. This dynamic adjustment allows the system to maintain optimal contact conditions throughout the grindstone's service life, extending usable duration while preserving machining precision.

Inventive Principle:
Principle #15Dynamics

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 method stabilizes the machining accuracy by ensuring the same state of grinding before and after dressing, minimizing changes in the tooth flank shape and maintaining consistent grinding properties.

Implementation Method 1

grinding the tooth flanks of an internal gear, which is a workpiece, with a screw-like grindstone

Methodology Applied
Scientific EffectAbrasion: Abrasion

Data Source

PatentEP2460625B1Method for machining internally toothed gear
Publication Date: 2019.11.20 MITSUBISHI HEAVY IND MACHINE TOOL CO LTD
  • EP2460625B1 patent drawingFigure 1
  • EP2460625B1 patent drawingFigure 2~3
  • EP2460625B1 patent drawingFigure 4

AI summary

A method for dressing a tool used for a method for machining an internally toothed gear, the method for machining an internally toothed gear being capable of, even if the grindstone of the tool has a regenerated grinding surface, machining with stable accuracy the internally toothed gear to be machined. A method for dressing a screw-like tool, configured for dressing the screw-like tool by meshing an internally toothed gear-like dressing gear (14), which is rotatable about the dressing gear rotation axis (C2), with the barrel-shaped, screw-like grindstone (11) which has a diameter gradually increasing from both ends thereof in the axial direction thereof toward the intermediate section in the axial direction thereof and which is used for machining an internally toothed gear to be machined. The outer diameter of the screw-like grindstone (11) after dressing is estimated before the dressing, the angle (Σ2) of intersection between the dressing gear rotation axis (C2) and the screw-like tool rotation axis (B1) of the screw-like grindstone (11) is set on the basis of the estimated outer diameter of the screw-like grindstone (11) after dressing, and dressing is performed with the dressing gear (14) and the screw-like grindstone (11) meshed with each other at the set angle (Σ2) of intersection between the axes.