Fan Guide Air Recirculation for Power Tool Idling Noise
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Solution Overview
Problem
Conventional power tools face challenges in controlling motor speed during idling, leading to increased noise due to high fan exhaust rates, which is costly to address with complex speed detection and control systems.
Innovation Solution
A power tool design featuring a fan guide that diverges and recirculates cooling air within the housing, using branching passages to manage airflow and reduce motor speed during idling without the need for expensive controllers, by guiding cooling air to re-enter the fan path before discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor speed is increased to raise output, then the output increases, but the idling speed becomes high and noise increases
Solution Approach 1:
A fan guide is introduced as an intermediary component between the fan and the motor. The fan guide includes a guide portion that redirects airflow and a blocking portion that restricts air passage, thereby mediating the relationship between fan rotation and motor cooling efficiency to suppress idling speed and noise
Solution Approach 2:
The airflow characteristics are changed by introducing the fan guide with specific geometric features (guide portion and blocking portion). This modifies the air passage cross-sectional area and airflow direction, changing the cooling efficiency parameter to suppress motor speed during idling while maintaining operational performance
2Object-generated harmful factors
If a controller is added to limit idling speed, then noise is reduced, but the product cost increases
Solution Approach 1:
The fan guide structure enables self-regulation of motor cooling based on operational state. During idling, the guide and blocking portions naturally restrict airflow to reduce cooling efficiency and suppress speed. During operation, sufficient airflow is maintained for proper cooling, eliminating the need for external control systems
Solution Approach 2:
The control function is extracted from the motor system and integrated into the passive aerodynamic design of the fan guide. The speed regulation capability is removed from active electronic control and embedded in the geometric configuration of the air passage structure
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 approach effectively suppresses motor speed and noise during idling with a simple, cost-effective structure, maintaining high output torque while reducing the fan's workload and noise levels, enhancing the reliability and efficiency of the power tool.
Implementation Method 1
A fan for cooling is arranged on a front end side of the rotation axis of the motor, and a ventilation port introducing an external air and an exhaust port for discharging an internal air are arranged on the housing. The cooling air flows from the ventilation port to the exhaust port due to the rotation of the fan and cools the heat-generating motor.
Implementation Method 2
a fan guide, which straightens the flow of cooling air generated by the fan
Implementation Method 3
a branching passage for diverging a portion of the cooling air drawn by the fan and discharging it to a drawing side is arranged, and a portion of the cooling air circulates inside the housing instead of being discharged from the exhaust port owing to the branching passage
Data Source
AI summary
A power tool has a fan guide for straightening the flow of cooling air generated by a fan, wherein the branching passages through are provided for causing a portion of the cooling air drawn into the fan from a ventilation hole to diverge from a flow toward an exhaust port formed on a bearing guide side, and the portion of the cooling air flows toward an inlet and thereby circulates inside a housing. The branching passages through provided to the fan guide are formed so as to be inclined in the same direction as a circumferential direction so that air path resistance during actual operation (in an intermediate-speed region) does not increase.