Brushless Motor Stator Temperature Sensing for Timely Thermal Protection
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Solution Overview
Problem
Existing power tools with brushless motors and electronic controllers are sensitive to current fluctuations, leading to reduced rotational speed during heavy loads and inadequate thermal protection due to the placement of NTC thermistors on the outer surface, which are affected by external temperatures, causing premature protection states.
Innovation Solution
The placement of a temperature sensor on a tooth surface of the stator lamination, with a fixing coating to secure it, and an avoidance structure for lead-out wires, allowing for timely temperature detection and improved thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NTC thermistor is added to the outer surface of iron core for temperature monitoring, then the electric motor can be protected from excessive temperature rise, but the thermal conduction path becomes excessively long and protection is not timely
Solution Approach 1:
The patent introduces an insulating end cover as an intermediary component that integrates the temperature sensor directly into the stator structure. This intermediary structure provides a thermal conduction path from the heating winding to the temperature sensor without requiring the sensor to be on the outer surface, thus reducing the thermal conduction distance and improving response time while maintaining protection reliability.
2Device complexity
If NTC thermistor is placed on the outer surface for temperature monitoring, then the structure is simple, but the sensor is greatly affected by external temperature causing premature protection state
Solution Approach 1:
The patent extracts the temperature sensor from the outer surface environment and integrates it directly into the stator structure through the insulating end cover. This extraction removes the sensor from the harmful external temperature environment while maintaining its temperature monitoring function, eliminating premature protection states caused by ambient temperature interference.
3Reliability
If constant-current control is performed by electronic controller to protect motor during heavy load, then overcurrent protection is achieved, but rotational speed is significantly reduced due to input power limitation
Solution Approach 1:
The patent implements a feedback mechanism where the temperature sensor continuously monitors the actual temperature of the heating winding and provides real-time feedback to the control system. This allows the controller to adjust operating parameters based on actual thermal conditions rather than relying solely on constant-current control, enabling the motor to maintain higher rotational speeds during heavy loads while still providing reliable protection through accurate temperature monitoring.
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
Enhances thermal protection by providing accurate temperature monitoring and reducing the impact of external temperatures on the motor's performance, maintaining consistent rotational speed during heavy loads.
Implementation Method 1
a temperature sensor configured to detect a temperature of the electric motor
Implementation Method 2
a fixing coating is applied between the temperature sensor and the first tooth surface to fix the temperature sensor on the first tooth surface
Data Source
AI summary
A power tool includes an electric motor, a transmission mechanism, and a temperature sensor. The electric motor includes a stator and a rotor. The stator includes a stator lamination, an insulating end cover, and coils. The insulating end cover includes an end cover body and multiple wound teeth. The temperature sensor is placed on a first tooth surface of any wound tooth. The first tooth surface is a plane substantially perpendicular to a rotating shaft of the rotor.