Brushless Motor Rectifier Airflow Inversion for Thermal Management

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Solution Overview

Problem

The electric work machine described in Patent Document 1 experiences a temperature increase issue in the switching circuit when alternating current voltage is applied to the stator of the brushless motor via the switching circuit.

Innovation Solution

Incorporating a rectification circuit that converts alternating current voltage to direct current voltage, positioned upstream of the switching circuit in the airflow path for cooling, allowing heat from the rectification circuit to be effectively transmitted to the air and reducing temperature increases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the rectification circuit is positioned downstream of the switching circuit in the airflow path, then the switching circuit can be cooled effectively, but the rectification circuit experiences temperature increase

Engineering Contradiction:

Improvetemperature of rectification circuitVSAvoidreliability of rectification circuit

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent inverts the conventional arrangement by placing the rectification circuit upstream of the switching circuit in the airflow path. This reversal allows the rectification circuit to receive cool air first, effectively cooling the rectification circuit before the air proceeds to cool the switching circuit, thereby resolving the temperature increase issue while maintaining reliability

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If alternating current voltage is applied to the stator via the switching circuit, then the motor operates, but the switching circuit temperature increases

Engineering Contradiction:

Improvemotor operationVSAvoidtemperature of switching circuit

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent introduces an intermediary cooling airflow that passes through both the rectification circuit and switching circuit in sequence. This intermediary air current acts as a heat transfer medium, carrying heat away from the rectification circuit first, then continuing to cool the switching circuit, enabling motor operation while controlling temperature rise

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively suppresses the temperature increase of the rectification circuit and ensures efficient cooling, maintaining the performance and reliability of the electric work machine.

Implementation Method 1

a rectification circuit converting a voltage to be applied to the electric motor from an alternating current voltage to a direct current voltage

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

a circulation direction of air that cools the rectification circuit and the switching circuit

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

heat of the rectification circuit can be transmitted to the air

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS11052530B2Electric work machine

Publication Date: 2021.07.06 KOKI HLDG CO LTD

AI summary

Provided is an electric work machine that can suppress a temperature increase of a component controlling an electric motor. The electric work machine including a brushless motor that operates a tip tool includes a rectification circuit that converts a voltage to be applied to the brushless motor from an alternating current voltage to a direct current voltage, and a switching circuit that controls the brushless motor, and the rectification circuit is arranged upstream of the switching circuit in a circulation path of the air that cools the rectification circuit and the switching circuit.