Flexible PCB Interconnection for Combustion Engine Pressure Plug

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Solution Overview

Problem

Existing piezo-resistive pressure-measuring plugs for combustion engines face challenges in maintaining reliable electrical connections that can withstand high temperatures and vibrations, while also being cost-effective and suitable for high-volume production.

Innovation Solution

The solution involves an interconnection structure within the measuring plug's hollow body, utilizing a flexible PCB with bonding wires and an elongated support structure to establish a durable electrical connection between the sensing element and conditioning electronics, which can span over 100mm, and includes a ring-shaped support structure for alignment and protection, allowing for pre-assembly and reduced manufacturing complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bonding wires are used to electrically couple sensing elements with sensor electronics, then electrical connection is achieved, but reliability under high temperature and vibration conditions deteriorates

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidhigh temperature and vibration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A flexible PCB is introduced as an intermediary structure between the sensing elements and sensor electronics. The flexible PCB provides a robust electrical connection path that can withstand high temperature and vibration conditions better than bonding wires alone, while still allowing for the necessary electrical coupling between components.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The flexible PCB is pre-positioned and secured within the plug body before final assembly. This preliminary positioning ensures that the electrical connection path is established and protected before the component undergoes thermal and mechanical stress during operation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If connector terminals are arranged in a housing attached to the plug body, then electrical connection is provided, but device complexity increases

Engineering Contradiction:

Improveelectrical connectionVSAvoidhousing and connector structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The flexible PCB integrates multiple functions into a single structure: it serves as both the electrical connection path and the structural support for mounting sensor electronics. This merging eliminates the need for separate connector terminals and housing structures, reducing overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The flexible PCB performs multiple functions simultaneously: electrical connection, mechanical support, and structural integration within the plug body. This multi-functionality reduces the number of separate components needed, simplifying the overall device design.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If sensing elements are placed near the combustion side, then measurement precision is improved, but manufacturing and assembly difficulty increases

Engineering Contradiction:

Improvepressure feedback accuracyVSAvoidassembly difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The sensing system is segmented into modular components: sensing elements mounted on a sensing structure, flexible PCB for electrical connection, and sensor electronics mounted separately on the plug body. This segmentation allows each component to be manufactured and tested independently, then assembled together, reducing overall manufacturing and assembly difficulty.

Inventive Principle:

Principle #1Segmentation

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 provides a reliable, cost-effective, and robust electrical connection capable of withstanding automotive engine conditions, facilitating high-volume production and reducing stress on components, while protecting the sensing elements from corrosion.

Implementation Method 1

The interconnection structure comprises a flexible PCB with first contact areas at a proximal end part of the flexible PCB and second contact areas at a distal end part of the flexible PCB. The first contact areas are electrically coupled to the electrical sensing element by means of bonding wires.

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

The sensor electronics is arranged to measure a resistance change of the piezo-resistive elements mounted on a sensing structure and to generate a conditioned measurement signal therefrom.

Methodology Applied

Scientific EffectPiezo-resistive effect: Piezoresistive Effect

Data Source

PatentEP2781903B1A measuring plug and method for assembling a measuring plug

Publication Date: 2016.05.25 SENSATA TECHNOLOGIES INC

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AI summary

Disclosed is a pressure-measuring plug (100) for a combustion engine. An interconnection structure in the plug body electrically couples by means of a flexible PCB (108A) an electrical sensing element (104A) at one end of the plug body (102) to connector terminals (118) of the plug at the other end of the plug body. An elongated support structure (108B) fixates a part of the flexible PCB (108A) in the plug body to enable the flexible PCB to withstand automotive conditions and to facilitate during assembly to put the flexible PCB through the hollow plug body.