Power Tool Torque Stop Control Using Magnetic Polarity Detection

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Solution Overview

Problem

Conventional electric power tools face challenges in accurately controlling torque, leading to overtightening and potential damage to workpieces due to complex computations and uncertain environmental conditions.

Innovation Solution

An electric power tool design featuring a magnetic ring with alternating magnetic polarities, a magnetic polarity detector circuit, and a controller that stops the motor based on a predetermined inter-change time interval of magnetic polarity changes, simplifying torque control and reducing computational load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional approaches use complicated computations and multiple sensors to control torque, then torque control capability is improved, but device complexity increases

Engineering Contradiction:

Improvetorque control capabilityVSAvoidcontroller complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex computational torque control systems with a magnetic field-based detection system. A magnetic ring with alternating polarities is attached to the fastener, and a magnetic sensor detects its position to directly determine torque levels, substituting mechanical/computational control with magnetic field detection

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from measuring physical characteristics (sounds, oscillations, deformations) to detecting magnetic polarity changes. This parameter change simplifies the detection mechanism while maintaining torque control capability

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If conventional approaches use multiple sensors to detect physical characteristics, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvetightening state detection precisionVSAvoidsensor quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential detection function by using a single magnetic sensor to detect magnetic polarity changes, eliminating the need for multiple sensors (sound sensors, vibration sensors, deformation sensors) while maintaining measurement precision

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The magnetic ring with alternating polarities serves multiple functions: it provides a detectable signal for torque measurement, indicates fastener rotation position, and enables simple binary detection of tightening states, making a single sensor sufficient for what previously required multiple specialized sensors

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If conventional approaches rely on uncertain environmental conditions for detection, then adaptability is improved, but measurement precision deteriorates

Engineering Contradiction:

Improveworking environment adaptabilityVSAvoidtightening state detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent replaces acoustic and vibration-based detection (which are sensitive to environmental noise) with magnetic field detection, which is inherently more stable and less affected by environmental conditions such as noise, vibration, and temperature variations

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes from detecting analog physical characteristics (sound waves, vibration frequencies) that are easily influenced by environmental factors to detecting discrete magnetic polarity changes, which provide clear binary signals resistant to environmental interference

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

Effectively prevents overtightening by directly determining the torque level through magnetic polarity detection, enhancing precision and reducing the risk of workpiece damage while simplifying the control process.

Implementation Method 1

The magnetic ring has a plurality of magnetic portions surrounding the output shaft. Every adjoining two of the magnetic portions have different magnetic polarities.

Methodology Applied

Scientific EffectMagnetic polarity alternation: Magnetism

Implementation Method 2

The magnetic polarity detector circuit is configured to detect a change of magnetic polarities at the predetermined position.

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentUS20240413714A1Electric power tool

Publication Date: 2024.12.12 BASSO IND CORP

AI summary

An electric power tool includes a housing, a motor disposed in the housing, an output shaft connected to the motor and extending out of the housing, a magnetic ring sleeved on the output shaft, a magnetic polarity detector circuit disposed in proximity to the magnetic ring, and a controller connected to the motor and the magnetic polarity detector circuit. The output shaft is driven by the motor to rotate about its axis. The magnetic ring synchronously rotates with the output shaft, and has magnetic portions surrounding the output shaft. Every adjoining two of the magnetic portions have different magnetic polarities. The magnetic polarity detector circuit detects a change of magnetic polarities. The controller controls the motor to stop operating when an inter-change time interval satisfies a predetermined condition.