Brushless Motor Sensor Circuit Board Bearing Overlap Design
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Solution Overview
Problem
The durability of power tools driven by brushless motors is limited due to the bearing life being constrained by the size of the sensor circuit board's through-hole, which restricts the bearing's diameter and affects the tool's overall durability.
Innovation Solution
The design includes a sensor circuit board with a through-hole that allows the rotational shaft to extend through, and an interference avoidance hole with a larger diameter than the bearing, enabling the bearing to overlap the rotation detecting elements axially, thus accommodating a larger bearing diameter and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bearing diameter is increased to improve durability, then the bearing life is extended, but the sensor circuit board's through-hole must be enlarged which may interfere with the rotation detecting element
Solution Approach 1:
The sensor circuit board's hole structure is divided into two separate functional zones: a through-hole for the rotational shaft and a separate interference avoidance hole for the bearing. This segmentation allows each hole to be optimized independently - the through-hole maintains its original size for shaft passage while the interference avoidance hole provides the necessary clearance for the larger bearing, thus resolving the contradiction between bearing size and sensor board integrity
Solution Approach 2:
The interference avoidance hole acts as an intermediary structural element that mediates between the bearing and the rotation detecting element. By providing this intermediate clearance passage, the bearing can be enlarged for improved durability without directly interfering with the rotation detecting element's position and function, thus resolving the spatial conflict
2Duration of action of stationary object
If the bearing diameter is increased to improve durability, then the bearing life is extended, but the through-hole diameter must be enlarged which complicates the assembly structure
Solution Approach 1:
The hole structure is segmented into two distinct openings: the through-hole for shaft passage and the interference avoidance hole for bearing clearance. This segmentation allows the bearing to have a larger diameter for improved life without requiring the through-hole to be enlarged, thereby simplifying the manufacturing process and assembly structure while still achieving the durability improvement
3Length of moving object
If the through-hole diameter is enlarged to accommodate a larger bearing, then the bearing diameter can be increased, but the rotation detecting element may be interfered with
Solution Approach 1:
The opening structure is segmented into two separate holes: the through-hole positioned to allow shaft passage without interfering with the rotation detecting element, and the interference avoidance hole positioned to provide clearance for the bearing. This spatial segmentation enables the bearing diameter to be increased while maintaining the through-hole dimensions that protect the rotation detecting element from interference, thus resolving the contradiction between bearing size and detection accuracy
Solution Approach 2:
The interference avoidance hole serves as an intermediary clearance zone that allows the bearing to extend radially without encroaching on the rotation detecting element's operational space. This intermediate structure enables the bearing to be larger for improved durability while the rotation detecting element maintains its original position and detection accuracy
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 allows for a longer bearing life and improved durability of the power tool by enabling a larger bearing diameter without interfering with the sensor circuit board's functionality, enhancing the tool's operational lifespan.
Implementation Method 1
three magnetic sensors (rotation detecting elements such as Hall elements). The magnetic sensors detect the position of a permanent magnet included in the rotor
Data Source
AI summary
A power tool including a brushless motor having a sensor circuit board has higher durability. The power tool includes a housing, a brushless motor including a rotor having a rotational shaft, a stator, and a sensor circuit board fixed to the stator and having a rotation detecting element that detects rotation of the rotor, and receiving the rotational shaft through the sensor circuit board, and a bearing held in the housing and supporting the rotational shaft. The bearing is located to overlap the rotation detecting element in an axial direction of the rotational shaft.