Brushless Power Tool Motor PCB Layout for Heat and Insulation

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Solution Overview

Problem

Brushless DC motors in power tools face challenges in heat management and electrical insulation, leading to potential short-circuits and corrosion, particularly due to the complexity of manufacturing and assembly processes.

Innovation Solution

A motor assembly with a heat sink and PCB assembly that includes a power PCB and position sensor PCB, where coil contact plates are overmolded within end caps to prevent short-circuits and ensure insulation, using spacers to maintain gaps between plates and employing a multi-piece heat sink for efficient heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional manufacturing methods are used for brushless DC motors, then production complexity is reduced, but heat management and electrical insulation performance deteriorate

Engineering Contradiction:

Improveelectrical insulation performanceVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The coil contact plates are overmolded with insulating material during the manufacturing process before final assembly. This preliminary insulation action ensures electrical isolation is built into the structure from the outset, preventing short-circuits between diagonally opposite coils without requiring additional insulation steps or complex assembly procedures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent combines the coil contact plates with the end cap structure by overmolding them as an integrated assembly. This merging of components simplifies the overall manufacturing process while ensuring proper electrical insulation, as the insulating material is applied directly to the contact plates in their final position within the end cap.

Inventive Principle:

Principle #5Merging (Combining)

2Temperature

If adequate heat dissipation structures are added to the motor, then heat management improves, but device complexity increases

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidstructural complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The heat sink is integrated with the existing end cap structure that houses the coil contact plates. By merging the thermal management function with the structural component already present in the motor design, the patent achieves effective heat dissipation without adding separate, complex heat management systems.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The end cap structure serves multiple functions: it provides structural support for the stator, houses the overmolded coil contact plates for electrical insulation, and incorporates the heat sink for thermal management. This multi-functionality reduces overall device complexity while addressing both electrical and thermal requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If coil contact plates are insulated with overmolding, then short-circuit prevention improves, but manufacturing time increases

Engineering Contradiction:

Improveshort-circuit preventionVSAvoidmanufacturing cycle time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The overmolding of insulating material onto the coil contact plates is performed as a preliminary step during the manufacturing process, before final assembly. This timing allows the insulation to be applied while components are still in an accessible state, and the insulating material can begin curing or setting before subsequent assembly operations begin.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The overmolding process is combined with the end cap manufacturing process, creating an integrated component assembly. By merging these operations, the patent eliminates separate insulation application steps and reduces the total number of manufacturing cycles required, thereby maintaining productivity while ensuring reliable electrical insulation.

Inventive Principle:

Principle #5Merging (Combining)

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 effectively manages heat and prevents short-circuits and corrosion, enhancing the reliability and durability of brushless DC motors in power tools by ensuring proper insulation and reducing the risk of internal shorts during manufacturing.

Implementation Method 1

The PCB assembly includes a heat sink

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

employing a multi-piece heat sink for efficient heat dissipation

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 3

coil contact plates are overmolded within end caps to prevent short-circuits and ensure insulation

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS11881750B2Brushless direct current motor for power tools

Publication Date: 2024.01.23 MILWAUKEE ELECTRIC TOOL CORP

AI summary

A motor assembly for use with a power tool includes a motor housing, a brushless electric motor disposed at least partially in the motor housing, and a PCB assembly coupled to the motor housing. The PCB assembly includes a heat sink, a power PCB coupled to a first side of the heat sink, and a position sensor PCB coupled to a second side of the heat sink opposite the first side and in facing relationship with the motor.