Electric Power Tool Speed-Torque Control via Conduction Angle
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Solution Overview
Problem
Existing electric power tools with three-phase brushless motors struggle to adjust speed-torque characteristics effectively for various work types, requiring either high speed or high torque, as they lack the ability to finely tune conduction angles and reduction ratios simultaneously.
Innovation Solution
The electric power tool incorporates a three-phase brushless motor with a gear reducer that can change reduction ratios and a motor controller that adjusts conduction angles between 120 and 180 degrees, allowing for precise adjustment of speed-torque characteristics by combining these changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the conduction angle is increased to drive the tool at high speed, then the rotational speed is improved, but the torque decreases
Solution Approach 1:
The patent applies dynamics by making the conduction angle adjustable rather than fixed. The motor controller can selectively change the conduction angle between at least two different angles, allowing the system to dynamically optimize between speed and torque based on the specific work requirements. This resolves the contradiction by enabling the conduction angle to adapt to different operational conditions.
Solution Approach 2:
The patent changes the electrical parameter (conduction angle) to resolve the speed-torque contradiction. By adjusting the conduction angle parameter between different values, the motor can achieve different speed-torque characteristics, allowing high speed when the conduction angle is increased and high torque when it is decreased.
2Force
If the conduction angle is decreased to drive the tool with high torque, then the torque is improved, but the rotational speed decreases
Solution Approach 1:
The motor controller dynamically adjusts the conduction angle based on the required torque output. When high torque is needed, the controller decreases the conduction angle, and when high speed is needed, it increases the conduction angle, making the system adaptable to different work conditions.
Solution Approach 2:
The patent utilizes parameter changes by varying the conduction angle to achieve different torque-speed characteristics. This allows the motor to be optimized for either high torque or high speed depending on the specific application requirements.
3Adaptability or versatility
If a single reduction ratio is used in the gear reducer, then the device complexity is reduced, but the adaptability to different work types decreases
Solution Approach 1:
The gear reducer is designed with adjustable reduction ratios rather than a fixed single ratio. This allows the system to adapt to different work types by changing the reduction ratio, providing versatility while maintaining a relatively simple gear reducer structure through selective adjustment.
Data Source
AI summary
An electric power tool may include a three-phase brushless motor configured to drive a tool, a gear reducer provided between the motor and the tool. The gear reducer is configured to selectively change a reduction ratio from the motor to the tool between a first reduction ratio and a second reduction ratio. The electric power tool may further include a motor controller configured to drive the motor with rectangular waves. The motor controller is configured to selectively change a conduction angle of each rectangular wave between at least a first conduction angle and a second conduction angle.