Pressure Sensor Flow Channel Inversion for Freezing Protection

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Solution Overview

Problem

Piezoresistive pressure sensor systems risk destruction when exposed to freezing media due to ice formation, which can cause pressure buildup and damage to the flexible membrane.

Innovation Solution

The pressure sensor system features a flow channel design without undercuts, where the medium flows perpendicularly to the flexible plate, and includes a compressible element like silicone foam to divert pressure away from the sensor element, minimizing ice column height and preventing solid abutment during freezing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional flow channel with undercuts is used, then the pressure sensor system can be compactly designed, but the freezing medium can build up pressure against the flexible plate causing destruction

Engineering Contradiction:

Improveprotection against freezing mediumVSAvoidflow channel design

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of having the flow channel narrow down towards the flexible plate (conventional design), the channel is designed to widen away from the plate, creating an inverted geometry that prevents ice buildup pressure. The channel cross-section increases in the direction away from the flexible plate, eliminating undercuts and ensuring freezing medium pressure is diverted away from the sensor element.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The harmful feature (undercuts in the flow channel) is completely removed from the design. The flow channel is designed without any material projections or narrowings that could create pressure buildup zones, extracting the problematic geometric feature that caused the freezing damage issue.

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If a thin flexible plate is used for the membrane, then the pressure sensor system achieves high sensitivity, but the membrane becomes vulnerable to damage from freezing medium pressure

Engineering Contradiction:

Improvepressure measurement sensitivityVSAvoidmembrane resistance to freezing damage

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The flow channel geometry acts as an intermediary protective structure between the freezing medium and the thin flexible plate. By designing the channel to widen away from the plate without undercuts, it prevents the medium from building up pressure that could damage the membrane, while still allowing the thin plate to maintain its high sensitivity for pressure measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the flow channel cross section is reduced to minimize ice column height, then protection against freezing improves, but the channel may create bottlenecks causing pressure buildup

Engineering Contradiction:

Improvefreezing protectionVSAvoidmedium flow capability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Rather than reducing the channel cross-section to minimize ice height (which would create bottlenecks), the design inverts the approach by ensuring the channel cross-section increases in the direction away from the flexible plate. This inverted geometry simultaneously minimizes ice column height and maintains excellent flow capability by eliminating bottlenecks.

Inventive Principle:

Principle #13The other way round (Inversion)

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 effectively protects the pressure sensor system from damage by ice formation, allowing it to operate in freezing conditions without oil-filled systems and enabling integration into automotive housings.

Implementation Method 1

The pressure sensor element is formed as a piezoresistive sensor element... Depending on the pressure of the medium or the bending of the flexible plate, a change in resistance can be measured at connecting contacts of the pressure sensor element

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Implementation Method 2

a compressible element can be installed in a hollow space of the support element below the at least one sub-section of the flow channel... the expanding medium presses against the compressible element... prevents a solid abutment from arising below the at least one sub-section of the flow channel during the ice formation during freezing of the medium

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS11561146B2Pressure sensor system having protection against freezing medium

Publication Date: 2023.01.24 TDK ELECTRONICS AG

AI summary

In an embodiment, a pressure sensor system includes a pressure sensor element with a flexible plate, wherein the pressure sensor element is a piezoresistive sensor element and a support element on which the pressure sensor element is arranged, wherein a flow channel configured to supply a medium to the flexible plate runs in the support element, wherein the flow channel has at least one sub-section, a longitudinal direction of which running perpendicularly below the flexible plate, and wherein a channel cross section of the at least one sub-section of the flow channel is at no point within the sub-section of the flow channel smaller than an area of the flexible plate.