Brushless Power Tool Load-Adaptive Speed Control for Noise Reduction
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Solution Overview
Problem
Electric power tools, such as circular saws and grinders, face issues with increased vibration, noise, and power consumption when attempting to enhance cutting efficiency by increasing rotation speed during no-load conditions.
Innovation Solution
The implementation of a brushless motor control system that allows for multiple rotation speed settings through a control unit, which switches between constant-speed control and duty ratio control based on detected load values, optimizing duty ratio to balance efficiency and power usage, and includes soft start control for smooth motor engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed during no-load increases to increase cutting efficiency, then productivity is improved, but vibration and noise increase
Solution Approach 1:
The patent implements dynamic rotation speed control that adapts to load conditions. The control unit automatically adjusts the rotation speed of the brushless motor based on detected load values, switching between high-speed mode (4500-5500 rpm) for light loads to maximize cutting efficiency, and low-speed mode (2500-3500 rpm) for heavy loads to reduce vibration and noise. This dynamic adaptation resolves the contradiction by making the rotation speed flexible rather than fixed.
Solution Approach 2:
The patent changes the operational parameters of the motor by implementing multiple rotation speed modes. The control unit can set the rotation speed to different ranges (2500-3500 rpm or 4500-5500 rpm) depending on the work conditions and load detection. This parameter change allows the system to optimize between productivity and harmful factors by selecting appropriate speed levels for different operating scenarios.
2Productivity
If the rotation speed during no-load increases to increase cutting efficiency, then productivity is improved, but power consumption unnecessarily increases
Solution Approach 1:
The system dynamically adjusts power consumption by varying rotation speed according to actual load requirements. The control unit monitors load conditions and automatically selects the appropriate rotation speed mode, ensuring that the motor operates at high speed (4500-5500 rpm) only when necessary for light-load cutting operations, and reduces to low speed (2500-3500 rpm) under heavy loads or no-load conditions, thereby optimizing energy usage while maintaining productivity when needed.
Solution Approach 2:
The patent implements parameter changes in rotation speed to optimize energy consumption. By providing multiple speed modes (2500-3500 rpm and 4500-5500 rpm) and automatically selecting between them based on load detection, the system changes its operational parameters to match actual work demands, preventing unnecessary power consumption during light-load or no-load conditions while maintaining high productivity when required.
3Use of energy by moving object
If constant-speed control is used with duty ratio smaller than 100%, then power consumption is reduced, but work efficiency decreases when load increases
Solution Approach 1:
The patent implements a dynamic control strategy that transitions between constant-speed control and duty ratio control based on load conditions. When the load is light, the system uses constant-speed control with duty ratio less than 100% to reduce power consumption. When the load increases beyond a predetermined threshold, the system automatically switches to duty ratio control, gradually increasing the duty ratio to 100% to maximize work efficiency. This dynamic switching resolves the contradiction by adapting the control method to actual load requirements.
Solution Approach 2:
The patent changes the control parameter from constant duty ratio to variable duty ratio based on load detection. The control unit monitors load values and switches between two control modes: constant-speed control with fixed duty ratio for light loads, and duty ratio control with gradually increasing duty ratio for heavy loads. This parameter change enables the system to optimize between power consumption and work efficiency by selecting the appropriate control strategy for each operating condition.
Data Source
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AI summary
An electric power tool includes a brushless motor, a control unit configured to control power supply to the brushless motor, a rotary tool configured to be rotated by the brushless motor, a rotation speed detecting unit configured to detect a rotation speed of the brushless motor, a main switch configured to transmit, to the control unit, an ON/OFF signal for switching between driving and stopping of the brushless motor, and a mode switching unit configured to transmit, to the control unit, a mode switching signal for switching between multiple modes of rotation control of the brushless motor, the control unit is configured to perform the rotation control of the brushless motor in any one of the multiple modes including at least a high-speed mode and a low-speed mode.