Two-Region Shaft Mating Structure for Precise Inclined Entry

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Solution Overview

Problem

Conventional torque sensors attached to robot arms face detection accuracy issues due to bending moments and loads when aligned over long distances, leading to reduced precision.

Innovation Solution

A machine-part mating structure with two mating regions in the axial direction, where the inner diameter of the second region is larger than the first, allowing the shaft to enter smoothly even when inclined, preventing galling and maintaining high positioning accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the inner diameter of the mating hole is reduced to improve radial positioning accuracy, then positioning accuracy is improved, but the shaft cannot enter smoothly when inclined

Engineering Contradiction:

Improveradial positioning accuracyVSAvoidease of entry

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The mating hole is segmented into two regions with different inner diameters. The first mating region has a smaller inner diameter to provide high radial positioning accuracy, while the second mating region has a larger inner diameter to facilitate smooth entry of the shaft even when inclined, thus resolving the contradiction between positioning accuracy and ease of entry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second mating region with the larger inner diameter is positioned at the inlet side of the mating hole, allowing the shaft to enter smoothly first. This preliminary action of providing clearance at the entry point enables the shaft to be guided into the first mating region with smaller inner diameter for precise positioning without causing galling.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the clearance between the inner surface of the mating hole and outer surface of the shaft is increased to allow smooth entry when inclined, then ease of entry is improved, but radial positioning accuracy is reduced

Engineering Contradiction:

Improveease of entryVSAvoidradial positioning accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The mating hole is divided into two regions: the second mating region with larger inner diameter provides increased clearance for smooth entry when the shaft is inclined, while the first mating region with smaller inner diameter provides the tight fit necessary for high radial positioning accuracy. This segmentation resolves the contradiction between ease of entry and positioning accuracy.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20250102001A1Machine-part mating structure

Publication Date: 2025.03.27 FANUC LTD

AI summary

A machine-part mating structure is for mating a columnar shaft with a mating hole in an axial direction. The mating hole includes at least two mating regions arranged side-by-side in the axial direction in a mating area, in which the mating hole is mated with the shaft, extending in the axial direction. Of the mating regions, an inner diameter, at an upper tolerance limit, of a first mating region located on an inner side of the mating hole is smaller than an inner diameter, at a lower tolerance limit, of a second mating region located closer to an inlet of the mating hole than the first mating region. The second mating region is dimensioned in the axial direction so that the shaft is allowed to smoothly enter the first mating region even if the shaft is inclined to a maximum angle with respect to an axis of the mating hole.