Outer Rotor Brushless Motor Direct Drive for Circular Saw Noise Reduction
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Solution Overview
Problem
Conventional cutting tools face challenges in enhancing motor power while minimizing wind noise and vibration, which are exacerbated by high-rotation motors.
Innovation Solution
A portable circular saw employing an outer rotor type brushless motor is designed to operate at low rotation-high torque settings, maintaining output and size equivalence with inner rotor type motors, using direct drive systems or shaft displacement mechanisms to reduce noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a motor of high rotation is employed to enhance motor power, then the motor power is improved, but the wind noise and vibration of the motor itself increase
Solution Approach 1:
The patent changes the rotational speed parameter of the motor from high rotation to low rotation while compensating with increased torque through the outer rotor configuration. This parameter change allows the motor to deliver equivalent or enhanced power output without generating the wind noise and vibration associated with high-speed operation
Solution Approach 2:
The patent inverts the conventional motor configuration by using an outer rotor type brushless motor instead of the traditional inner rotor type. This inversion places the rotor on the outside and stator on the inside, enabling the motor to achieve low rotation-high torque characteristics that reduce wind noise and vibration while maintaining power output
2Object-generated harmful factors
If an outer rotor type brushless motor is used to achieve low rotation-high torque, then wind noise and vibration are reduced, but the motor size may increase compared to inner rotor type
Solution Approach 1:
The patent optimizes the physical dimensions and magnetic properties of the outer rotor configuration to achieve compact size. By adjusting parameters such as magnet strength, rotor thickness, and stator winding density, the motor maintains equivalent volume to inner rotor type motors while delivering low rotation-high torque performance
Solution Approach 2:
The patent employs high-performance composite materials in the rotor and stator construction, including advanced permanent magnets and optimized winding materials, to increase power density. This allows the outer rotor motor to achieve the required torque output in a compact size without increasing overall motor volume
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively enhances motor power while significantly reducing wind noise and vibration, improving the operational efficiency and usability of the cutting tool.
Implementation Method 1
the outer rotor type brushless motor has, on the outer side of the motor, a rotor including permanents magnet including N-poles and S-poles, and, on the inner side of the motor, a stator constituted by a three-phase stator winding
Data Source
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AI summary
In a portable cutting tool configured to perform a cutting operation through movement along the upper surface of a workpiece, when an ordinary inner rotor type motor is used as the drive source, the motor is rotated at high speed to obtain a high output, which is reduced in speed by a speed reduction device to thereby secure an appropriate rotational speed for a rotary cutter. Since the electric motor is rotated at high speed in this construction, there have been problems of noise, vibration, etc. The present invention aims to achieve a reduction in the noise and vibration of the cutting tool. A direct drive system is incorporated with an outer rotor type electric motor (11) used as the drive source and with a rotary cutter (12) directly mounted to an output shaft (11d) of the motor, and the electric motor (11) is rotated at an appropriate rotational speed for the rotary cutter (12), for example, at approximately 6,000 RPM, whereby it is possible to achieve a reduction in the noise and vibration of the cutting tool 1.