Brushless DC Motor Direct Drive Power Tool
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Solution Overview
Problem
Existing hand-held power tools, such as chainsaws and trimmers, face issues with weight, maintenance, and operational efficiency due to the use of brush type DC motors and gear assemblies, which increase cost, weight, and require periodic maintenance, while also posing safety risks from sparks during high-speed operation.
Innovation Solution
The implementation of a brushless DC motor with a direct drive mechanism to the cutting device, eliminating the need for intermediate gear assemblies and incorporating a self-locking worm gear assembly for the oil pump, resulting in a more compact, efficient, and simpler power tool design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a brush type DC motor is used, then the power tool can be made compact and light weight, but the speed is limited to a pre-determined range and requires periodic maintenance
Solution Approach 1:
The patent replaces the brush type DC motor with a brushless DC motor, eliminating mechanical brushes and commutators. This substitution enables a wider speed range while maintaining compact size and reducing maintenance requirements, as the brushless motor has no wear-prone mechanical contact components.
2Productivity
If a gear assembly is added between the motor and cutting device, then the speed range can be expanded, but the overall cost and weight increase
Solution Approach 1:
The patent extracts and eliminates the gear assembly from the power tool design by using a brushless DC motor that can directly provide the required speed range. This removal reduces overall weight, cost, and complexity while maintaining the necessary productivity.
3Reliability
If an oil pump driven by an auxiliary electric motor is added, then lubrication can be provided to moving parts, but the weight, running costs, and power requirements increase
Solution Approach 1:
The patent merges the oil pump function into the existing brushless DC motor system by driving the pump from the motor's output shaft. This integration eliminates the need for a separate auxiliary electric motor, reducing weight, power consumption, and overall system complexity while maintaining reliable lubrication.
4Duration of action of moving object
If a brush assembly is used in the DC motor, then commutation can be achieved for continuous rotation, but the brushes wear out over time and cause sparks at high speeds
Solution Approach 1:
The patent replaces the brush and commutator mechanical system with an electronic commutation system in the brushless DC motor. This substitution eliminates brush wear and spark generation while maintaining continuous rotation capability, significantly improving reliability and reducing maintenance requirements.
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
This solution reduces the weight and maintenance needs of power tools, enhances operational efficiency, and minimizes heat generation, while providing improved handling and safety through reduced spark risks and optimized battery placement for better grip and handling.
Implementation Method 1
The power source includes a brushless DC motor
Implementation Method 2
incorporating a self-locking worm gear assembly for the oil pump
Data Source
AI summary
An electric power tool (100) includes a power source (102) enclosed in a casing (104). The power source (102) is a brushless DC motor (202) which drives a drive mechanism (106) for a cutting device. Further, an oil pump is at least partly housed in the casing (104) of the electric power tool (100). The oil pump is also driven by the brushless DC motor (202).