Electrode Crystal Grain Control for Extra-High Pressure Discharge Lamps
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Solution Overview
Problem
Extra-high pressure discharge lamps face breakage issues at the boundaries of the electrode and axis portion due to crystal grain coarsening caused by heat generated during lighting, particularly exacerbated by higher purity tungsten materials and increased lighting voltage, leading to premature failure.
Innovation Solution
The design incorporates a pair of electrodes with a thick, thin, and intermediate portion, featuring three crystal grains on a cross-sectional line, a curved intermediate portion with a 0.1 mm or more curvature radius, and a closed space for tungsten evaporation, which suppresses breakage by managing heat distribution and grain growth, using high-purity tungsten (99.999%) and controlled halogen levels to prevent material deposition and strengthen the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high electric power is applied to increase output, then lighting output is improved, but electrode breakage occurs due to heat-induced crystal grain coarsening
Solution Approach 1:
The electrode is designed with varying crystal grain sizes in different regions: finer grains in the intermediate portion (boundary region) to resist breakage, and coarser grains in the axis portion for structural stability. This local differentiation allows the electrode to withstand high electric power while preventing breakage at vulnerable boundary regions.
Solution Approach 2:
The invention controls crystal grain size as a critical parameter by specifying that the intermediate portion has a smaller crystal grain size than the axis portion. This parameter change optimizes the electrode's resistance to heat-induced coarsening and mechanical stress during high-power operation.
2Volume of moving object
If miniaturization of electrode is performed to reduce lamp size, then projector miniaturization is achieved, but electrode fracture occurs more frequently
Solution Approach 1:
The electrode structure implements local quality differentiation where the intermediate portion has finer crystal grains to provide enhanced strength at the smallest diameter section, while the axis portion maintains larger grains for structural integrity. This allows miniaturization without compromising electrode strength at critical regions.
Solution Approach 2:
The intermediate portion is designed with a curved transition (radius of curvature 0.5mm or more) between the axis portion and working portion, eliminating sharp corners that would concentrate stress. This curvature design prevents stress concentration during miniaturization while maintaining electrode strength.
3Loss of substance
If higher purity tungsten material is used to prevent material deposition, then light transmission is improved, but crystal grain coarsening accelerates under heat
Solution Approach 1:
The electrode uses high-purity tungsten (99.999% or more) specifically in the intermediate portion to prevent material deposition in the light path, while accepting that the axis portion may have slightly different properties. This localized high-purity material prevents deposition without requiring the entire electrode to have uniform properties that would accelerate grain coarsening.
Solution Approach 2:
The invention controls the crystal grain size parameter by specifying that the intermediate portion has a smaller grain size (0.1mm or less) compared to the axis portion. This parameter control compensates for the heat-induced coarsening tendency of high-purity tungsten by creating a fine-grained structure that is more resistant to coarsening.
4Length of moving object
If the intermediate portion is miniaturized to reduce overall electrode size, then lamp compactness is improved, but breakage at boundaries increases
Solution Approach 1:
The intermediate portion is designed with a curved transition (radius of curvature 0.5mm or more) instead of sharp corners, which eliminates stress concentration points. This allows miniaturization of the electrode while maintaining boundary strength by distributing stress more evenly across the curved surface.
Solution Approach 2:
The intermediate portion has finer crystal grains and high-purity tungsten material specifically at the boundary regions to enhance local strength, while the overall electrode size is minimized. This localized quality enhancement prevents breakage at boundaries even when the electrode is miniaturized.
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 configuration effectively prolongs the lifespan of the lamp by reducing breakage risks, maintaining high reliability and output while preventing strength deterioration and material deposition, ensuring a stable light source for miniaturized projector applications.
Implementation Method 1
heat generated by lighting of the extra-high pressure discharge lamp
Implementation Method 2
crystal grain coarsening of the electrode itself or at an axis portion of the electrode due to heat generated by lighting
Implementation Method 3
an approximately closed space section which is surrounded by the electrode and an inner wall of the light emission section, and in which tungsten material evaporated from the electrode stays
Data Source
AI summary
An extra-high pressure discharge lamp, comprises an optical transparent light emitting section, sealing sections connected to the light emitting section, a pair of electrodes which face each other in the light emitting section, wherein one of the electrodes having a thick portion, a thin portion and an intermediate portion which is formed between the thick portion and the thin portion, wherein 0.15 mg/mm3 of mercury is enclosed in the light emitting portion, and wherein the number of crystal grains which exist on a cross section perpendicular to an axis of the one of the electrodes is three.