Impact Wrench Torque Control via Angular Acceleration

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Solution Overview

Problem

Existing impact tightening tools either require expensive strain gauges for accurate torque measurement, leading to increased size and weight, or fail to account for transmission losses, resulting in premature torque cessation and improper tightening.

Innovation Solution

An impact tightening tool with angular acceleration detection and torque value calculation means that uses an approximation formula to calculate actual torque, accounting for losses without a strain gauge, allowing for precise torque management and tool miniaturization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a strain gauge is provided in the power transmission shaft to determine tightening torque, then torque measurement accuracy is improved, but device complexity, size, and cost increase

Engineering Contradiction:
Improvetorque measurement accuracyVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts the torque measurement function from the mechanical transmission shaft by using angular acceleration detection means on the rotary power source. Instead of measuring torque directly in the power transmission shaft with a strain gauge, the system calculates torque based on angular acceleration data from the rotary power source, thereby removing the need for strain gauges in the transmission path and reducing device complexity

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces the mechanical strain gauge measurement system with an angular acceleration detection and calculation system. By detecting angular acceleration of the rotary power source and calculating torque values through mathematical relationships, the system substitutes direct mechanical torque measurement with a dynamic measurement approach, reducing device complexity while maintaining measurement capability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If angular acceleration detection is used to calculate torque without strain gauges, then device size and cost are reduced, but torque measurement accuracy deteriorates due to unaccounted transmission losses

Engineering Contradiction:
Improvedevice complexityVSAvoidtorque measurement accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The invention introduces feedback mechanisms where the calculated torque values are continuously monitored and used to control the tightening process. The system detects angular acceleration, calculates torque values, and uses this feedback information to determine when the preset tightening torque has been reached, allowing for automatic stopping of the tightening operation

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The invention changes the measurement parameter from direct torque measurement to angular acceleration measurement. By detecting angular acceleration of the rotary power source and using mathematical relationships to derive torque values, the system measures a different parameter that is easier to obtain without strain gauges, then transforms this data into useful torque information through calculation

Inventive Principle:
Principle #35Parameter changes

3Productivity

If torque transmission is stopped when calculated torque reaches preset value, then proper tightening torque is achieved, but tightening precision deteriorates due to unaccounted loss torques

Engineering Contradiction:
Improvetightening efficiencyVSAvoidtightening precision
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The invention performs preliminary calibration to establish the relationship between angular acceleration and actual torque values. By pre-determining the characteristics of the transmission system and the correlation between angular acceleration and torque, the system creates a foundation for more accurate torque calculation that compensates for transmission losses

Inventive Principle:
Principle #10Preliminary action

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

Enables accurate and efficient torque management, reducing tool size, weight, and cost while ensuring proper tightening, by calculating actual torque values considering transmission losses.

Implementation Method 1

angular acceleration detection means (3) configured to detect an angular acceleration value of the rotary power source (21)

Methodology Applied
Scientific EffectAngular acceleration detection: Accelerometer

Implementation Method 2

torque value calculation means (4) configured to calculate an actual torque approximate value of the output shaft (23) based on the angular acceleration value

Methodology Applied
Scientific EffectTorque calculation from angular acceleration: Torque

Data Source

PatentEP2895300B1Impact tightening tool
Publication Date: 2018.04.04 YOKOTA IND
  • EP2895300B1 patent drawingFigure 1~2
  • EP2895300B1 patent drawingFigure 3~5
  • EP2895300B1 patent drawing

AI summary

An impact tightening tool (1), including a rotating part (2), angular acceleration detection means (3), torque value calculation means (4), and a storage section (5), wherein: the rotating part (2) includes a rotary power source (21), an impact tightening generation mechanism (22), and an output shaft (23); the angular acceleration detection means (3) is configured to detect an angular acceleration value of the rotary power source (21); the torque value calculation means (4) is configured to calculate an actual torque approximate value of the output shaft (23) by using an approximation formula stored in the storage section (5); and the approximation formula stored in the storage section (5) is a formula which correlates an angular acceleration value detected by the angular acceleration detection means (3) at the time of torque transmission to a screw with an actual torque value of the output shaft (23) at the time of torque transmission to the screw, and is a formula based on a torque measured value of the output shaft (23) measured before the torque transmission to the screw.