Temperature Sensor Intermediate Member Reduces Thermal Stress

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Solution Overview

Problem

Temperature sensors for exhaust gas purifiers face issues with stress concentration and reduced durability due to thermal expansion differences between element electrode wires and leads, particularly under increased exhaust gas temperatures.

Innovation Solution

A temperature sensor design featuring element electrode wires made of noble metals or alloys with intermediate members of Ni-based or Fe-based alloys, where the wires and intermediate members are aligned and bonded on opposing surfaces, reducing the bonding area and thermal expansion differences, and leads and intermediate members are formed from the same high-strength alloys to enhance bonding strength and reduce stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If element electrode wires are overlapped with leads for laser welding, then electrical connection is achieved, but stress concentration occurs at the bonding interface due to thermal expansion differences

Engineering Contradiction:

Improvebonding reliabilityVSAvoidstress concentration

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

An intermediate member made of Fe-based alloy or Ni-based alloy is introduced between the element electrode wire and the lead. This intermediate member serves as a mediator that facilitates bonding while reducing stress concentration. The intermediate member has thermal expansion characteristics that bridge the gap between the noble metal wire and the stainless steel lead, thereby reducing stress at the bonding interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The direct bonding interface between element electrode wire and lead is segmented into two separate bonding interfaces: one between the wire and intermediate member, and another between the intermediate member and lead. This segmentation distributes the thermal expansion stress across multiple interfaces rather than concentrating it at a single bonding point.

Inventive Principle:

Principle #1Segmentation

2Strength

If element electrode wires are bonded to leads in an axially wide area, then bonding strength is improved, but thermal expansion differences cause greater stress

Engineering Contradiction:

Improvebonding strengthVSAvoidthermal expansion stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The intermediate member acts as a buffer that accommodates thermal expansion differences between the element electrode wire and the lead. By positioning this intermediate member at the bonding interface, the structure can maintain adequate bonding strength while the intermediate member absorbs the differential thermal expansion stress.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If exhaust gas temperature increases for higher engine output, then engine performance is improved, but temperature sensor durability decreases due to increased thermal stress

Engineering Contradiction:

Improveengine outputVSAvoidtemperature sensor durability

Core Design Contradiction:

PowerVSDuration of action of stationary object

Solution Approach 1:

The intermediate member made of Fe-based alloy or Ni-based alloy serves as a thermal buffer between the element electrode wire and the lead. This intermediate member reduces the transmission of thermal stress to the bonding interfaces, thereby improving the temperature sensor's durability under high exhaust gas temperature conditions associated with higher engine output.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces stress concentration and improves the reliability and heat resistance of the temperature sensor, enhancing its durability and performance under varying temperatures and vibrations.

Implementation Method 1

the element electrode wires are overlapped with the respective leads, for laser welding

Methodology Applied

Scientific EffectLaser welding: Laser Beam Welding

Implementation Method 2

The material used for the element electrode wires has a thermal expansion coefficient different from that of the leads

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10024726B2Temperature sensor having intermediate member connecting leads to element electrode wires extending from temperature detector

Publication Date: 2018.07.17 DENSO CORP

AI summary

A temperature sensor includes a temperature detector having a thermosensitive element, element electrode wires, leads, and intermediate members. The temperature sensor is formed such that ends of the element electrode wires are embedded in the temperature detector, the leads are electrically connected to the respective element electrode wires, and the intermediate members electrically connect the element electrode wires to the respective leads. Each element electrode wire and the corresponding intermediate member are arranged being aligned in the extending direction, and bonded to each other, with opposing surfaces facing each other being abutted each other. The intermediate member and the corresponding lead are juxtaposed in a direction perpendicular to the extending direction, and bonded being overlapped with each other.