Actuator EMI Reduction via Spring Contact Grounding

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Solution Overview

Problem

Brushed DC motors face challenges in efficiently reducing electromagnetic interference (EMI) due to arcing within the motor case, making it difficult to implement effective EMI reduction mechanisms, and existing solutions like grounding wires or common mode chokes are either unreliable or costly with low EMI reduction performance.

Innovation Solution

A circuit board with an EMI reduction circuit and a resilient conductive spring contact that automatically connects the motor case to the EMI reduction circuit when the motor is mounted, eliminating the need for hand soldering and providing a reliable conductive path using capacitors referenced to ground.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a brushed DC motor is used for low cost and simple control, then cost and control simplicity are improved, but electromagnetic interference increases due to arcing within the motor case

Engineering Contradiction:

Improvecost and control simplicityVSAvoidelectromagnetic interference

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

A spring contact serves as an intermediary component that automatically establishes an electrical connection between the motor case and the circuit board. This spring contact acts as a mediator to ground the motor case, providing a path for EMI currents without requiring complex additional components or assembly steps.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The spring contact is designed to automatically make contact with the motor case upon mounting, eliminating the need for manual wiring or additional assembly steps. The motor mounting process itself serves to establish the EMI reduction connection, making the system self-configuring.

Inventive Principle:

Principle #25Self-service

2Object-generated harmful factors

If grounding wires or common mode chokes are used to reduce EMI, then EMI reduction performance is improved, but device complexity and cost increase

Engineering Contradiction:

ImproveEMI reduction performanceVSAvoiddevice complexity and cost

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The spring contact is a simple, inexpensive component that provides effective EMI reduction without the cost and complexity of common mode chokes or extensive grounding wire assemblies. It uses a basic elastic conductive element that can be easily manufactured and replaced if needed.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention extracts the essential EMI reduction function from complex grounding systems and implements it through a single spring contact component. This isolates the EMI mitigation capability from the motor itself and provides it through a separate, simple interface element.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If hand soldering is used to connect EMI reduction components, then connection reliability is improved, but manufacturing time and complexity increase

Engineering Contradiction:

Improveconnection reliabilityVSAvoidmanufacturing time and complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The spring contact is designed to be mounted using standard surface mount techniques that are automatically performed by pick-and-place machines. The mounting process itself establishes the electrical connection, eliminating the need for separate hand soldering operations while maintaining reliable electrical contact.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention replaces manual hand soldering operations with an automated spring contact mounting system. The elastic mechanical property of the spring contact ensures reliable electrical connection through contact pressure rather than relying solely on solder joint integrity, and this can be automatically assembled by standard SMT equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 reduces EMI emissions by automatically and reliably connecting the motor case to the EMI reduction circuit, improving EMI reduction performance without additional assembly steps or costly components.

Implementation Method 1

a resilient conductive spring contact that automatically connects the motor case to the EMI reduction circuit when the motor is mounted

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

providing a reliable conductive path using capacitors referenced to ground

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Implementation Method 3

providing a reliable conductive path using capacitors referenced to ground

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9941773B2Actuator with electric motor and EMI reduction circuit

Publication Date: 2018.04.10 TYCO FIRE & SECURITY GMBH

AI summary

An actuator includes a circuit board having an electromagnetic interference (EMI) reduction circuit. The actuator includes a motor having a motor casing mounted on the circuit board. A portion of the motor casing contacts a surface of the circuit board. The actuator includes an electrical contact conductively coupled to the EMI reduction circuit and mounted on the surface of the circuit board. The electrical contact establishes a conductive path between the EMI reduction circuit and the motor casing when the motor casing is mounted on the circuit board.