Brushless Motor Terminal Layout for Direct Coil Cooling

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Solution Overview

Problem

Existing brushless motors suffer from insufficient cooling efficiency, particularly for the coils, as the cooling wind primarily passes through gaps between the rotor and stator, failing to directly cool the coils generating heat.

Innovation Solution

A brushless motor design with phase coils of multiple phases arranged around a rotation axis and terminals connected to a switching circuit, where the terminals are located inside a circumscribed circle of the phase coils, enhancing the cooling efficiency by allowing unobstructed airflow to reach the coils.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the cooling wind passes through the gap between rotor and stator, then the motor structure is simple and compact, but the cooling efficiency of the coil is insufficient

Engineering Contradiction:

Improvecoil temperatureVSAvoidmotor structure

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The cooling air path is segmented into multiple regions: a first cooling air path that directly reaches the coil winding from the air intake, and a second cooling air path for other motor components. This segmentation allows the cooling wind to be directed specifically to the coil area, improving cooling efficiency without requiring a completely redesigned motor structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A partition wall is introduced as an intermediary structure to separate and direct the cooling air flow. The partition wall includes a first opening facing the air intake and a second opening facing the coil winding, acting as a mediator to channel the cooling wind directly to the coil area while maintaining the overall motor structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If the terminals are arranged outside the circumscribed circle of phase coils, then the wiring is simpler, but the cooling airflow is obstructed

Engineering Contradiction:

Improvecoil temperatureVSAvoidwiring simplicity

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The terminals are repositioned from an external arrangement (outside the circumscribed circle of phase coils) to an internal arrangement (inside the circumscribed circle). This dimensional repositioning in the radial direction allows the cooling air to flow unobstructed through the coil area, while the terminals remain electrically connected to the phase coils through the stator core.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 design improves the cooling efficiency of the coils, reducing joule heat generation and enhancing the overall efficiency of the brushless motor.

Implementation Method 1

a coil that generates heat due to a current flowing therethrough

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS12266986B2Brushless motor and electrically-powered tool

Publication Date: 2025.04.01 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A brushless motor is an inner rotor type brushless motor. The brushless motor includes a plurality of phase coils of multiple phases arranged around a rotation axis, and a plurality of terminals configured to connect the plurality of phase coils of multiple phases to a switching circuit. The plurality of terminals are located inside a circumscribed circle of the plurality of phase coils of multiple phases.