Temperature Sensor Dual-Layer Insulation Thermal Expansion

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Solution Overview

Problem

Temperature sensors used in wet environments are prone to moisture ingress, leading to electrical short circuits due to gaps formed by thermal expansion and contraction of conductive wires, which increases the likelihood of moisture reaching the wires.

Innovation Solution

A temperature sensor design featuring a thermosensitive body and conductive wires covered by a first silicone rubber layer with a lower elastic modulus and a second epoxy resin layer, where the first layer acts as a buffer to prevent gaps and ensure insulation, and the epoxy resin layer provides additional insulation and bonding with the filler and protection tube.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conductive wires are used to connect the thermosensitive body, then electrical connection is achieved, but gaps occur around the wires due to thermal expansion and contraction, leading to moisture ingress and short circuits

Engineering Contradiction:

Improveelectrical insulation reliabilityVSAvoidstructural stability of wire connections

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies a flexible insulation covering made of rubber material that elastically conforms to the conductive wires. This flexible covering maintains continuous contact with the wires even during thermal expansion and contraction, preventing gap formation and moisture ingress while preserving electrical insulation.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent uses a composite structure combining the conductive wire core with a rubber insulation covering. This composite design integrates the electrical conductivity of the wire with the elastic, moisture-resistant properties of rubber, creating a unified component that simultaneously provides electrical connection and environmental protection.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a single insulation layer is used to cover conductive wires, then manufacturing is simplified, but insufficient protection against moisture and thermal stress results

Engineering Contradiction:

Improveprotection against moisture and thermal stressVSAvoidstructure of insulation layers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies different materials with specific local properties: the inner rubber covering provides elastic conformity and primary insulation, while the outer resin coating provides environmental resistance and sealing. Each layer is optimized for its specific function, creating localized protection where each material performs best.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements a nested multi-layer insulation structure where the rubber covering is embedded within the resin coating. This nested arrangement allows the inner elastic layer to handle thermal expansion while the outer resin layer provides environmental protection, with each layer supporting the other's function.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 design effectively prevents or minimizes gaps around conductive wires, thereby preventing short circuits even in wet environments by using the silicone rubber layer's elasticity to absorb thermal expansion and contraction, and ensuring reliable electrical insulation with the epoxy resin layer.

Implementation Method 1

a first covering layer made of a first electrical insulator, the first covering layer covering from the thermosensitive body to predetermined positions of the pair of conductive wires... The first covering layer has elastic modulus smaller than elastic modulus of the second covering layer

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a second covering layer made of a second electrical insulator, the second covering layer covering the first covering layer

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 3

the case contains a metal material excellent in thermal conductivity more than the filler in order to rapidly transfer ambient temperature to the thermosensitive body

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11428584B2Temperature sensor, sensor element and manufacturing method of temperature sensor

Publication Date: 2022.08.30 SHIBAURA ELECTRONICS CO LTD

AI summary

A temperature sensor includes a sensor element including a thermosensitive body, a protection tube accommodating the thermosensitive body part of the sensor element, and a filler filling a space between the protection tube and the sensor element inside the protection tube. The sensor element includes a first covering layer made of a first electrical insulator, the first covering layer covering the thermosensitive body, and a second covering layer made of a second electrical insulator, the second covering layer covering the first covering layer. The first covering layer has elastic modulus smaller than elastic modulus of the second covering layer.