BLDC Power Tool Circuit Layout for Compact Cooling and Reliability

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Solution Overview

Problem

Handheld power tools with brushless electric motors face issues of increased volume, reliability concerns due to multiple circuit boards, and excessive heat generation from capacitors and power switches.

Innovation Solution

A compact handheld grinder design featuring a single circuit board with integrated components such as a rectifier, DC bus capacitors, motor switches, and a power switch, minimizing inter-board connections and using heat sinks for efficient cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple circuit boards are used to support capacitor, power switch and control circuitry, then the power tool can perform required functions, but the volume of the power tool increases and reliability decreases due to susceptible connections

Engineering Contradiction:

ImprovereliabilityVSAvoidvolume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent combines the capacitor, power switch, and control circuitry onto a single circuit board, eliminating the need for multiple separate circuit boards. This integration reduces the overall volume of the power tool while improving reliability by minimizing the number of inter-board connections that could wear out or break.

Inventive Principle:

Principle #5Merging (Combining)

2Power

If capacitor and power switch are used to control current flow, then the brushless electric motor can be driven, but excessive heat is generated

Engineering Contradiction:

ImprovepowerVSAvoidtemperature

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent introduces a heat sink as an intermediary component between the power switch and the environment. The heat sink absorbs and dissipates the heat generated by the capacitor and power switch during current control operations, allowing the motor to receive full power while preventing excessive temperature rise that would compromise reliability.

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

The solution reduces the tool's volume, enhances reliability by minimizing connection vulnerabilities, and decreases heat generation, resulting in a more compact and durable power tool.

Implementation Method 1

a rectifier configured to receive power from an alternating current (AC) power source and operable to convert an alternating current to a direct current

Methodology Applied

Scientific EffectRectification: Diode

Implementation Method 2

a capacitor connected electrically between the rectifier and the switching arrangement, wherein the capacitor is coupled in parallel across the rectifier

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

using heat sinks for efficient cooling

Methodology Applied

Scientific EffectHeat dissipation: Heat Sink

Data Source

PatentUS11770048B2Handheld power tool with a brushless electric motor

Publication Date: 2023.09.26 BLACK & DECKER CORP

AI summary

A power tool comprising a housing and a brushless direct-current (BLDC) motor disposed within the housing. The motor includes a stator and a rotor rotatable relative to the stator. The power tool is configured to generate a power output from the motor such that a quotient obtained by the power output measured in Watts (Wout), divided by an input measured in Volt-Amperes (Vain), and further divided by a diameter of the motor measured in meters (m), is greater than 10 Wout/Vain/m.