Impact Tool Control Modes for Fastener Torque Accuracy
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Solution Overview
Problem
Impact drivers and impact wrenches often overdrive fasteners or fail to apply sufficient torque, leading to stripped threads or slow installation, as they lack precise control over power delivery and torque management.
Innovation Solution
A brushless impact power tool with a controller that switches between open loop and closed loop control based on motor parameters, allowing for optimized power delivery and torque management by adjusting conduction band and advance angle values, and featuring a mode switch for different operational modes suited to hard or soft joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If impact tools are used at full power, then fastening speed is improved, but fasteners may be overdriven or stripped
Solution Approach 1:
The system dynamically transitions between open-loop and closed-loop control modes based on real-time motor parameter monitoring. When motor parameters indicate approaching torque thresholds, the system switches to closed-loop control to precisely maintain desired torque levels, preventing overdriving while maximizing fastening speed during lower torque conditions
Solution Approach 2:
The closed-loop control mode continuously monitors motor parameters and adjusts power delivery to maintain precise torque control. This feedback mechanism allows the system to respond to changing load conditions and prevent fastener damage while optimizing fastening speed across different operational phases
2Manufacturing precision
If impact tools are used at less than full power, then fastener torque control is improved, but application speed becomes too slow
Solution Approach 1:
The system employs dynamic control mode switching that allows high-speed operation in open-loop mode during phases where precise torque control is less critical, then transitions to closed-loop mode when precise torque control becomes necessary, thereby maintaining both speed and precision across different operational phases
Solution Approach 2:
The control system periodically monitors motor parameters and switches between control modes as needed during the fastening process. This periodic assessment allows the system to optimize for speed during initial phases and switch to precision control when torque thresholds are approached, maximizing overall productivity while ensuring quality
3Device complexity
If single control mode is used, then system simplicity is maintained, but adaptability to different joint conditions is reduced
Solution Approach 1:
The control system integrates both open-loop and closed-loop control capabilities within a single unified controller, allowing it to adapt to different joint conditions (hard or soft) by selecting the appropriate control mode. This multi-functional approach enables the system to handle diverse fastening scenarios without requiring separate dedicated systems for each condition
Data Source
AI summary
An impact power tool includes a housing, a motor, a controller, an output member configured to be rotated when the motor is energized, and an impact mechanism configured to rotationally drive the output member. The impact mechanism is configured to selectively apply rotational impacts to the output member when a torque on the output member exceeds a torque threshold. The controller is configured to control the motor during a first phase of operation with open loop control and a baseline conduction band and advance angle setting when a sensed tool operation parameter is one of above or below a threshold value. The controller is configured to control the motor during a second phase of operation with closed speed loop control and an increased conduction band and advance angle setting when the sensed tool operation parameter is the other of above or below the threshold value.