Brushless Motor Sensor Isolation from Cooling Wind
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Solution Overview
Problem
Conventional electric tools with brushless DC motors are prone to anomalies and reduced lifespan due to dust and moisture entering the motor and sensor magnet areas via the cooling wind, leading to magnetic anomalies and potential motor shutdown.
Innovation Solution
The electric tool is designed with a housing that isolates the magnetic detection unit and magnetic body from the cooling wind path, using a non-magnetic material and a sealed structure with a water-resistant coating, and features a cylindrical casing with ventilating windows on opposite sides to prevent dust and moisture from entering the motor and sensor magnet areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the cooling wind path is designed to flow through the motor and control circuit areas for effective cooling, then the cooling efficiency is improved, but dust and moisture enter the motor and sensor magnet areas causing magnetic anomalies and reduced reliability
Solution Approach 1:
The patent divides the internal space into multiple sealed compartments using partition walls. The motor area, control circuit area, and sensor magnet area are separated into distinct sealed spaces, preventing dust and moisture from traveling between areas while maintaining independent cooling paths for each component
Solution Approach 2:
The patent introduces sealed compartments and partition walls as intermediary structures between the cooling wind path and sensitive components. These intermediaries allow cooling air to flow past components without directly exposing the motor and sensor magnet areas to dust-laden cooling winds
2Ease of operation
If the motor casing is made thin and cylindrical for ease of gripping, then the ease of operation is improved, but the structural strength and protection against dust and moisture penetration deteriorate
Solution Approach 1:
The patent employs thin-walled cylindrical motor casing that maintains structural integrity through optimized geometry and material selection. The thin casing provides adequate protection while enabling easy gripping, complemented by sealed joints and gaskets that prevent dust and moisture penetration without requiring thick walls
3Temperature
If ventilating windows are disposed on the rear cover for cooling, then the cooling performance is improved, but the entry points for dust and moisture into the control circuit and motor areas increase
Solution Approach 1:
The patent uses sealed compartments with integrated ventilation structures. The partition walls and sealed spaces act as barriers that allow controlled air flow through ventilating windows while preventing dust and moisture from entering the control circuit and motor areas
Solution Approach 2:
The patent segments the internal space so that ventilating windows are positioned in areas where air flow is needed, while sealed partition walls prevent harmful particles from reaching sensitive components. Each sealed space has its own controlled ventilation path
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 configuration effectively prevents dust and moisture from attaching to the magnetic components, ensuring reliable operation and extending the tool's lifespan by isolating the cooling wind from the motor and sensor magnet, thus maintaining precise rotational control and preventing malfunctions.
Implementation Method 1
a cooling fan 120 configured to generate a cooling wind
Implementation Method 2
a sensor magnet 114 in a cylindrical shape is disposed to detect a rotational position of the rotor
Implementation Method 3
a sealed structure with a water-resistant coating
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An electric tool is provided. The electric tool prevents anomalies in motor rotation due to dust and moisture sucked in together with a cooling wind, and is configured such that rotational position detection operations and switch operations are not affected. In the electric tool which drives a brushless DC motor using a controller, a magnetic body (14) for rotational position detection is provided on a rotation shaft (10) which can rotate integrally with a rotor (7), Hall ICs (41 to 43) are provided to detect the rotational position of the magnetic body and output a position signal to the controller, and the magnetic body (14) and the Hall ICs (41 to 43) mounted on a substrate (44) are arranged in a region isolated from the wind path of the cooling wind generated by rotation of a cooling fan. The Hall ICs (41 to 43) are accommodated in a housing (61) filled with resin.