Glow Plug Fusion Zone Spacing for Thermal Consistency
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Solution Overview
Problem
Glow plugs with tungsten-based heat generation elements exhibit variations in thermal performance due to differences in resistance ratios and material amounts, leading to inconsistent heating capabilities among individual units.
Innovation Solution
A glow plug design where the distance between specific cross-sections of the heat generation element is optimized to ensure consistent insertion into the fusion zone, reducing variations in resistance and thermal performance, with a relational expression of 1.30≤A/B≤4.00 to maintain sufficient heat-up performance and durability by preventing exposure of the heat generation element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat generation element is inserted into the fusion zone during manufacturing, then the heat generation element is joined to the tubular member, but the amount of material melted varies causing variation in insertion amount and resistance among individual glow plugs
Solution Approach 1:
The patent applies preliminary action by pre-forming the fusion zone with a predetermined volume and shape before inserting the heat generation element. The fusion zone is created by melting and solidifying the tubular member material in advance, establishing a standardized receptacle that ensures consistent insertion depth and resistance values across all glow plugs, eliminating variation caused by inconsistent melting during assembly.
2Temperature
If tungsten is used as the main component of the heat generation element, then high heating-up temperature is achieved, but large resistance ratio causes thermal performance variation among individual glow plugs
Solution Approach 1:
The patent applies parameter changes by precisely controlling the resistance value of the heat generation element within a specific range (0.25Ω to 0.45Ω at room temperature) and managing the insertion depth into the fusion zone. By adjusting these parameters and maintaining them within defined limits, the patent achieves both high heating-up temperature and reduced thermal performance variation among individual glow plugs.
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 optimized design reduces thermal performance variations among individual glow plugs, ensures reliable heat generation, and enhances durability by preventing the heat generation element from being exposed during wear.
Implementation Method 1
a glow plug in which a heat generation element containing tungsten (W) as a main component is disposed in a tubular member
Implementation Method 2
the forward end of the tubular member is melted and then solidified to thereby fix the heat generation element in the fusion zone
Data Source
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AI summary
To reduce variation in thermal performance among individual glow plugs. A glow plug 10 includes a sheath tube (tubular member) 810 whose forward end is closed with a fusion zone 891, and a heat generation coil (coiled heat generation element) 820. The heat generation coil 820 contains W as a main component. The distance A between a first heat-generation-element cross section 902a and a second heat-generation-element cross section 903a is rendered greater than the distance B between the second heat-generation-element cross section 903a and a third heat-generation-element cross section 904a. Namely, the distance A (i.e., space) between the first heat-generation-element cross section 902a and the second heat-generation-element cross section 903a is increased such that the rear end surface 895 of the fusion zone 891 is disposed in the space. Accordingly, even when the amount of the melted material of the sheath tube 810 varies and thus the position of the rear end surface 895 of the fusion zone 891 varies in the axial direction, the position of the rear end surface 895 is located between the first heat-generation-element cross section 902a and the second heat-generation-element cross section 903a without fail.