Brushless Power Tool Motor Balancing for Vibration Reduction
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Solution Overview
Problem
Brushless DC motors in power tools often vibrate or shake due to imbalances, which can lead to unwanted vibrations and reduced performance.
Innovation Solution
The implementation of balancing members, such as brass bushings or overmolds with balancing features, coupled to the output shaft of the brushless DC motor to correct imbalances and reduce vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotor rotates at high speed relative to the stator, then the motor produces sufficient power, but the motor generates vibrations and shaking due to imbalance
Solution Approach 1:
A balancing member with a specific mass is coupled to the output shaft at a predetermined location to counterbalance the rotor's imbalance. The balancing member's mass and position are calculated to generate a counteracting centrifugal force that offsets the vibrations caused by the rotor's eccentricity, thereby reducing harmful vibrations while maintaining high-speed rotation and power output
2Stability of the object's composition
If a balancing member is added to reduce vibrations, then motor stability improves, but device complexity increases
Solution Approach 1:
The balancing member is integrated with existing motor components such as the output shaft or fan assembly, rather than being a completely separate component. This merging approach allows the balancing function to be achieved while minimizing additional parts and assembly steps, thus improving stability without significantly increasing device complexity
Data Source
AI summary
A brushless DC motor for use with a power tool includes a stator surrounding a rotor, an output shaft with first and second ends that is fixed to the rotor to transmit movement of the rotor to the output shaft, first and second bearings positioned on the output shaft adjacent the first and second ends, a fan coupled to the output shaft between the first and second bearings to rotate with the output shaft relative to the stator, and a brass bushing with an outer diameter coupled to the output shaft and positioned between the first and second bearings closer to the first bearing than to the second bearing. A hub portion of the fan is coupled to the output shaft and fins extend radially outward away from the hub portion. An outer diameter of the brass bushing is less than the outer diameter of the hub portion.