Rotary Impact Tool Controller Duty Ratio Speed Control
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Solution Overview
Problem
Rotary impact tools experience reduced workability and increased time to tighten screws due to limited motor rotational speed during no-load or low-load operations, leading to potential impact failures and component deterioration.
Innovation Solution
Incorporating a motor with an impact mechanism, an impact detector, and a controller that employs constant duty ratio control and constant rotation speed control to manage motor speed, ensuring high-speed operation before impacts and reducing the likelihood of impact failures by adjusting control modes based on load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the motor is configured to be driven at a constant rotational speed after start, then the tightening torque of the screw can be controlled to a desired torque, but the rotational speed of the motor is limited during no-load or low-load operation before impact application
Solution Approach 1:
The patent applies dynamics by switching between two control modes: constant duty ratio control for no-load/low-load operations (allowing high speed) and constant rotation speed control during impact operations (ensuring torque accuracy). This dynamic adaptation of control strategy resolves the contradiction between speed and torque control precision.
Solution Approach 2:
The control system changes the operational parameters of the motor based on load conditions. During no-load operation, the duty ratio is maintained constant allowing maximum speed. When impact is detected, the system transitions to constant rotation speed control to maintain precise torque. This parameter change strategy allows the system to optimize performance for different operational phases.
2Productivity
If the motor is rotated at higher speed before impact is applied, then work efficiency is improved, but the hammer may jump over the anvil and rotate without applying impact, causing impact failure
Solution Approach 1:
The patent employs feedback through an impact detection device that monitors whether the hammer successfully applies impact to the anvil. Based on this feedback, the control system adjusts the motor operation - maintaining high speed when impacts are successful, and reducing speed or adjusting timing when impact failure is detected. This feedback mechanism resolves the contradiction between high-speed operation and reliable impact application.
3Manufacturing precision
If constant rotation speed control is applied from motor start, then torque accuracy is maintained, but time required to tighten screw increases due to limited motor speed during no-load operation
Solution Approach 1:
The system performs preliminary high-speed rotation during the no-load phase (before impact is needed) by applying constant duty ratio control. This preliminary action allows the screw to be quickly positioned and the motor to reach optimal operating conditions. Once impact is detected, the system transitions to constant rotation speed control to ensure torque accuracy during the actual tightening operation. This preliminary action strategy reduces total tightening time while maintaining torque precision.
Data Source
AI summary
A rotary impact tool in one aspect of the present disclosure includes a motor, an impact mechanism, an impact detector, and a controller. The controller executes constant duty ratio control from when the motor is started until an impact is detected by the impact detector. The controller executes constant rotation speed control in response to detection of an impact by the impact detector.