Brushless Motor Sensor Substrate Mounting Structure
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Solution Overview
Problem
In electrically powered tools using brushless DC motors, the integration of sensor magnets and substrates leads to increased motor housing size due to the need for accurate rotor position detection, which complicates size management and mounting structures.
Innovation Solution
An improved sensor substrate mounting structure where the sensor substrate is sandwiched between the stator and housing, secured by an insulating member and a base unit, allowing for orthogonal placement and reduced size, eliminating the need for dedicated sensor magnets and screw bosses, thereby curbing the overall housing size increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated sensor magnet is provided at the end of the rotational shaft with three Hall ICs mounted on a dedicated sensor substrate, then accurate rotor position detection is achieved, but the entire length in the rotor axial direction increases
Solution Approach 1:
The sensor substrate is merged with the stator structure by mounting it on the rear surface of the stator. This integration eliminates the need for a separate dedicated sensor substrate and sensor magnet assembly, thereby reducing the rotor axial length while maintaining accurate rotor position detection capability through the Hall ICs.
Solution Approach 2:
Instead of extending the sensor detection system in the axial direction (rotor shaft end), the solution repositions the sensor substrate to the stator's rear surface, utilizing a different spatial dimension. This dimensional shift allows rotor position detection without increasing the rotor axial length.
2Reliability
If screw bosses are provided on the sensor substrate and insulator for securing the sensor substrate, then secure mounting is achieved, but the housing size increases in the radial direction
Solution Approach 1:
The sensor substrate mounting structure is merged with the stator by directly mounting the sensor substrate on the stator's rear surface. This eliminates the need for separate screw bosses on both the sensor substrate and insulator, reducing the radial size of the housing while maintaining secure mounting through the integrated stator structure.
Solution Approach 2:
The stator structure serves multiple functions: it provides the magnetic circuit for the motor and simultaneously serves as the mounting base for the sensor substrate. This multi-functionality eliminates the need for dedicated mounting features like screw bosses, thereby reducing radial housing size.
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 facilitates precise rotor position detection without increasing the tool's size, simplifies sensor substrate mounting, and reduces the motor housing dimensions, enhancing design flexibility and cost-effectiveness.
Implementation Method 1
a sensor substrate that has a sensor mounted thereon for detecting a rotational position of the rotor
Data Source
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AI summary
Provided is an electrically powered tool having an improved sensor substrate mounting structure, the electrically powered tool being configured so that a brushless type motor is axially contained in a cylindrical housing. The electrically powered tool has: a cylindrical housing 100 for axially containing a motor; a control unit for controlling the motor; and a sensor substrate 11 having mounted thereon a plurality of position detecting elements for detecting the rotational position of a rotor. The sensor substrate is gripped between the insulator 6 of the motor and the housing 100 and held on the housing 100 side when axially mounting the motor. The sensor substrate 11 is annularly shaped and has formed at the center thereof a through-hole 12a through which a bearing for the motor is passed. The portion of the sensor substrate, on which a Hall IC is mounted, is provided with a synthetic resin cover member 14 for protecting the Hall IC against dust or the like.