Bottom-Touching Detection Standard Using Direct Axial Force Measurement

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Solution Overview

Problem

Existing screw tightening devices, such as those with axial force meters, face increased part count and cost issues, and suffer from low precision in detecting bottom-touching defects due to indirect axial force measurement methods.

Innovation Solution

A method utilizing a measuring system with a screw hole member and an axial force measuring device to directly measure compressive forces between the screw hole member and a measurement screw, allowing for precise determination of bottom-touching based on acquired parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a probe with vibration generator and vibration detector is used to measure axial force, then axial force measurement capability is achieved, but the number of parts and cost increase

Engineering Contradiction:

Improveaxial force measurement capabilityVSAvoidnumber of parts

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the axial force measurement function from a separate probe assembly and integrates it into the existing torque meter of the nut runner. By utilizing the existing torque sensor and adapting it to measure axial force through mathematical transformation of measurement data, the invention eliminates the need for additional vibration generators, detectors, and probes, thereby reducing part count while maintaining measurement capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The torque meter in the nut runner is made multi-functional by enabling it to measure both torque and axial force. Through mathematical transformation of the torque meter's measurement data, the same sensor serves dual purposes: traditional torque measurement and axial force measurement, eliminating the need for separate measurement devices

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If vibration generation and detection method is used to indirectly measure axial force, then axial force can be determined, but measurement precision decreases due to indirect measurement

Engineering Contradiction:

Improveaxial force measurement accuracyVSAvoidmeasurement method complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical vibration-based indirect measurement system with a computational approach. Instead of using vibration generators and detectors to physically measure axial force, the invention uses mathematical transformation of torque meter data to calculate axial force, substituting a complex mechanical measurement system with a simpler computational method that achieves direct measurement accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the measurement parameters by transforming the torque measurement data into axial force information through mathematical relationships. By establishing a correlation between torque measurements and axial force based on screw geometry and material properties, the system converts one type of measurement parameter into another, achieving direct axial force measurement without physical contact or vibration

Inventive Principle:

Principle #35Parameter changes

3Reliability

If bottom-touching is determined by checking gap between bearing surface and object, then obvious bottom-touching can be detected, but bottom-touching without gap cannot be detected

Engineering Contradiction:

Improvebottom-touching detection capabilityVSAvoiddetection method limitation

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces axial force measurement as an intermediary parameter to detect bottom-touching. Instead of directly observing the gap between the bearing surface and object (which may be invisible), the system measures axial force as an intermediate physical quantity that reflects the presence or absence of bottom-touching, enabling detection of both obvious and subtle bottom-touching conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention replaces the visual or mechanical gap-checking method with a force-based detection method. By measuring axial force and comparing it against threshold values, the system substitutes direct gap measurement with an indirect but more reliable force-based indication of bottom-touching, enabling detection of cases where no visible gap exists

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3875935B1Method for setting bottom-touching-determination standard and program therefor

Publication Date: 2024.11.27 OMRON CORP

Figure 1~2(b)
Figure 3(a)~4
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AI summary

Provided is a method for setting a bottom-touching-determination standard that makes it possible to highly reliably set a parameter-based bottom-touching-determination standard. This method for setting a bottom-touching-determination standard includes a screwing step for screwing a measurement screw (11) into a measurement screw hole (13a), a parameter acquisition step for acquiring a parameter from the screwing step, a bottom touching determination step for determining whether the measurement screw has touched the bottom on the basis of the axial force of the measurement screw, and a determination standard setting step for setting a bottom-touching-determination standard by comparing the parameter and the result of the determination in the bottom touching determination step.