Angle Measuring Disc Adhesive Bonding Thermal Stress

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Solution Overview

Problem

Conventional angle measuring devices face challenges in achieving precise and long-term accurate measurements due to thermal influences, as soft adhesives with low modulus of elasticity fail to reliably fix the graduation disc, leading to deformations and inadmissible eccentricities.

Innovation Solution

A structural unit for an angle measuring device featuring a graduation disc made from a material with a specific coefficient of linear expansion, attached to a carrier element with a differing coefficient using an adhesive connection with axial and radial adhesive layers, where the radial adhesive layer has a higher modulus of elasticity than the axial layer, and the materials are chosen to have a significant difference in thermal expansion coefficients, typically greater than 3×10^-6 K^-1, ensuring a robust and precise connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a soft adhesive with low modulus of elasticity is used to fix the graduation disc, then thermal stresses can be absorbed, but precise fixing of the graduation disc is not reliably guaranteed in the long term

Engineering Contradiction:
Improvethermal stress absorptionVSAvoidlong-term fixation precision
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies parameter changes by selecting materials with specific thermal expansion coefficients. The carrier element is made from a material with a higher coefficient of linear expansion than the graduation disc material, creating a controlled thermal expansion difference that compensates for adhesive deformation under thermal stress, thereby maintaining long-term fixation precision.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by combining the graduation disc material (with lower thermal expansion coefficient) and the carrier element material (with higher thermal expansion coefficient) in a specific configuration. This composite structure leverages the differential thermal expansion properties to counteract the effects of thermal stress on the adhesive bond, ensuring both stress absorption and reliable long-term fixation.

Inventive Principle:
Principle #40Composite materials

2Object-affected harmful factors

If the difference between the coefficients of linear expansion of the carrier element and graduation disc is large, then thermal expansion mismatches are significant, but precise connection is no longer guaranteed when the difference exceeds 3×10^-6

Engineering Contradiction:
Improvethermal expansion mismatch managementVSAvoidconnection precision
Core Design Contradiction:
Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent optimizes the thermal expansion coefficient difference parameter within a specific range (at least 3×10^-6 but not exceeding 3.10^-6). This controlled parameter change ensures that thermal expansion mismatches are managed to compensate for adhesive deformation while maintaining connection precision through proper material selection.

Inventive Principle:
Principle #35Parameter changes

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 configuration significantly reduces deformations caused by thermal changes and maintains precise fixation of the graduation disc over time, ensuring accurate angle measurements by minimizing thermal expansion mismatches between the disc and carrier element.

Implementation Method 1

The graduation disc is made from a first material with a first coefficient of linear expansion and the carrier element from a second material with a second coefficient of linear expansion. The second coefficient of linear expansion of the material of the carrier element differs from the first coefficient of linear expansion of the material of the graduation disk to a comparatively large extent, so that the difference between the second coefficient of linear expansion and the first coefficient of linear expansion is at least 3×10^-6

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP2401585B1Assembly for angle measuring apparatus and corresponding angle measuring apparatus
Publication Date: 2014.01.15 DR JOHANNES HEIDENHAIN GMBH
  • EP2401585B1 patent drawingFigure 1
  • EP2401585B1 patent drawingFigure 2~3

AI summary

The invention relates to a module for an angle measuring device, comprising a dividing disc (1.3) made of a first material having a first longitudinal expansion coefficient (a1.3) and a carrier element (1.4, 1.4') made of a second material having a second longitudinal expansion coefficient (a1.4). The difference between the second longitudinal expansion coefficient (a1.4) and the first longitudinal coefficient (a1.3) is at least 3-10-6-K-1. The dividing disc (1.3) is attached to the carrier element (1.4, 1.4') by means of an adhesive bond, wherein the adhesive bond comprises an axial adhesive layer (1.1, 1.1') and a radial adhesive layer (1.2). The axial adhesive layer (1.1, 1.1') and the radial adhesive layer (1.2) disposed in an axial gap (Sa, Sa') and radial gap (Sr) respectively, each between the carrier element (1.4, 1.4') and the dividing disc (1.3). The two adhesive layers (1.1, 1.2) comprise different adhesives. The invention further relates to an angle measuring device having said module.