Impact Tool Seating Detection Using Motor Current and Speed
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Solution Overview
Problem
Existing impact tools face issues with motor control when seating occurs before impacting starts, leading to potential over-tightening or under-tightening and poor workability due to reliance on electric current-based seating determination.
Innovation Solution
An impact tool equipped with a control unit that measures motor current and rotation speed to determine seating, allowing for motor stop or deceleration, and includes modes for screw tightening depth control and machining amount estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If seating determination is performed based on electric current only, then the control system is simple, but the seating detection accuracy is poor leading to over-tightening or under-tightening
Solution Approach 1:
The patent combines multiple measurement methods (electric current measurement and rotation speed detection) into a unified seating determination system. The control unit integrates signals from both the current measuring means and rotation speed measuring means to comprehensively judge seating status, thereby improving detection accuracy while maintaining reasonable system complexity through functional integration.
Solution Approach 2:
The control unit serves multiple functions: it processes current measurement data, processes rotation speed data, performs seating determination, and controls motor operation. This multi-functional design allows the system to achieve high seating detection accuracy without requiring separate dedicated systems for each function, thus managing complexity effectively.
2Ease of operation
If seating determination is performed only after impacting starts, then the control logic is simple, but the motor cannot be stopped or decelerated if seating occurs before impacting
Solution Approach 1:
The patent enables seating determination to be performed at any time point before or after impacting starts, including during the pre-impact phase. This preliminary detection capability allows the system to identify seating conditions early and initiate appropriate motor control actions (stopping or deceleration) before impacting begins, providing flexible motor control while managing logic complexity through timely detection.
Solution Approach 2:
The system continuously monitors motor current and rotation speed, providing real-time feedback to the control unit. This feedback mechanism enables the control unit to detect seating conditions dynamically and adjust motor operation accordingly, whether before or after impacting starts, thereby improving operational flexibility while maintaining manageable control logic through continuous monitoring.
3Productivity
If multiple measurement parameters are used for seating determination, then the workability is improved, but the measurement and control complexity increases
Solution Approach 1:
The patent merges multiple measurement parameters (current and rotation speed) into a unified seating determination process handled by a single control unit. This integration approach improves workability by enabling accurate seating detection for better tightening control, while managing complexity through centralized processing rather than separate independent systems.
Solution Approach 2:
The system monitors changes in multiple parameters (current magnitude and rotation speed variations) to determine seating status. By analyzing parameter changes rather than relying on fixed thresholds, the system improves workability through adaptive detection that accounts for varying operating conditions, while managing complexity through change-based detection logic.
Data Source
AI summary
Provided is an impact tool capable of stopping or decelerating a motor even if seating has occurred before impacting starts. An electric tool, which is an impact tool, includes: a motor; an impact mechanism driven by the motor; a current measuring means for measuring a motor current; a rotation speed measuring means for detecting a motor rotation speed; and a control unit for controlling the motor. The control unit includes a seating determination mode configured to determine whether a screw is seated, in accordance with the measured motor current and motor rotation speed, at any time point before or after impacting by the impact mechanism is started in a screw tightening operation having multiple different work conditions, and to stop or decelerate the motor after it has been determined that the screw is seated.