Glow Plug Coil Connection via Laser Welding

Solution Overview

Problem

Glow plugs with tungsten (W) or molybdenum (Mo) front end coils face embrittlement and connection breakage due to high temperature recrystallization, leading to potential failure at the connection point between the front and rear coils.

Innovation Solution

A method involving laser welding, where the rear end coil is melted to embed and surround the rear end portion of the front end coil, using a material with a lower melting point than the front end coil, thereby minimizing the melting of the front end coil and reducing embrittlement and connection breakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the front end coil is made of tungsten (W) or molybdenum (Mo) to withstand high temperatures, then the temperature resistance is improved, but embrittlement occurs due to recrystallization after melting at high temperature

Engineering Contradiction:

Improvetemperature resistanceVSAvoidembrittlement

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent changes the material parameter by selecting a front end coil material with a melting point higher than the rear end coil (e.g., tungsten, molybdenum, or their alloys). This parameter change allows the front end coil to maintain structural integrity at high temperatures without recrystallization-induced embrittlement, while the rear end coil melts first to enable the embedding connection method.

Inventive Principle:

Principle #35Parameter changes

2Strength

If the front end coil is melted by a large amount to connect with the rear end coil, then the connection strength is improved, but breakage occurs at the connection portion due to embrittlement

Engineering Contradiction:

Improveconnection strengthVSAvoidbreakage resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent inverts the conventional welding approach by melting the rear end coil instead of the front end coil. The rear end coil material is specifically selected to have a lower melting point than the front end coil, allowing it to melt and form a connection without causing the front end coil to undergo harmful recrystallization and embrittlement.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the material parameter by selecting a front end coil material with a melting point higher than the rear end coil (e.g., tungsten, molybdenum, or their alloys). This parameter change allows the front end coil to maintain structural integrity at high temperatures without recrystallization-induced embrittlement, while the rear end coil melts first to enable the embedding connection method.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If laser welding is performed by irradiating the front end portion of the rear end coil, then the melting precision is improved, but the front end coil may be damaged by excessive heat

Engineering Contradiction:

Improvemelting precisionVSAvoidfront end coil integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the material parameter by selecting a front end coil material with a melting point higher than the rear end coil (e.g., tungsten, molybdenum, or their alloys). This parameter change allows the front end coil to maintain structural integrity at high temperatures without recrystallization-induced embrittlement, while the rear end coil melts first to enable the embedding connection method.

Inventive Principle:

Principle #35Parameter changes

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 approach effectively suppresses embrittlement and breakage of the connection region by reducing the melting amount of the front end coil, ensuring a strong and durable connection between the coils, and allows for efficient temperature rise characteristics in glow plugs.

Implementation Method 1

a welding step of, by melting a front end portion of the rear end coil, welding the rear end portion of the front end coil and the front end portion of the rear end coil

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

by melting a front end portion of the rear end coil

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentEP3163170B1Method of producing glow plug and the glow plug

Publication Date: 2018.03.21 NITERRA CO LTD

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AI summary

To suppress breakage at a connection region where a front end coil and a rear end coil are connected, provided is a method of producing a glow plug including a sheath tube that extends in an axial direction and whose front end is closed, a front end coil that is disposed in the sheath tube and that is connected to a front end portion of the sheath tube, and a rear end coil that is disposed in the sheath tube and that is connected to a rear end portion of the front end coil. The method includes a welding step of, by melting a front end portion of the rear end coil, welding the rear end portion of the front end coil and the front end portion of the rear end coil such that at least part of the rear end portion of the front end coil is embedded in the front end portion of the rear end coil while being surrounded by the front end portion of the rear end coil. In the method, a main component of the front end coil is tungsten (W) or molybdenum (Mo), and a melting point of the rear end coil is lower than a melting point of the front end coil.