JP2005122958A - High pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide structure of a high pressure discharge lamp capable of suppressing progress of a chemical reaction of a ceramic which is a material for a discharge vessel with a metal halide sealed in the discharge vessel for reducing the probability of occurrence of a fade-away phenomenon during lighting. <P>SOLUTION: This high pressure discharge lamp is provided with a protrusion part 1a made of a ceramic material and the discharge vessel 1 having a thin tube part 1b connected with both ends of the protrusion part 1a and made of a ceramic material. The electrode part 3 has a tip part 101 maintaining discharge and an intermediate part 100 connected with the tip part 101 and made of a conductive material having lower heat conductivity than the tip part 101. The intermediate part 100 is located at least in the protrusion part 1a so that progress of the chemical reaction of the ceramic near a joint part of the protrusion part 1a and the thin tube part 1b of the discharge container 1 with the metal halide sealed in the discharge vessel 1 can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-pressure discharge lamp using a discharge vessel made of a ceramic material, and more particularly to a technique for suppressing the reaction between the discharge vessel and a luminescent metal.

  A high pressure discharge lamp using a conventional discharge vessel made of a ceramic material is superior in heat resistance and corrosion resistance compared to a discharge vessel made of quartz glass. For this reason, it is widely used for metal halide lamps in which a metal halide is enclosed as a light emitting metal (see, for example, Patent Document 1 and Patent Document 2).

  FIG. 5 shows a cross-sectional view of the configuration of a conventional discharge lamp described in Patent Document 1. As shown in FIG. In FIG. 5, the discharge vessel 1 includes a bulging portion 1a and a pair of end portions 1b, and the bulging portion 1a is made of alumina ceramic. The thin tube portion 1b seals the sealing metal portion 2a of the power supply conductor 2 with a ceramic sealing compound seal 4 at the sealing portion 1b1 portion. The halide resistant portion 2b is made of a tungsten rod, and a coil 2b1 made of molybdenum wire is wound thereon. The electrode 3 is configured by winding a tungsten wire around the tip of the halide resistant portion 2b. The seal 4 of the ceramic sealing compound hermetically seals between the sealing portion 1b1 of the thin tube portion 1b of the discharge vessel 1 and the sealing metal portion 2a of the power supply conductor 2 to a predetermined position. A slight gap 5 is formed between the inner surface of the narrow tube portion 1 b of the discharge vessel 1 and the coil 2 b 1 wound around the halide-resistant portion 2 b of the power supply conductor 2. In Patent Document 1, the sealing portion 1b1 of the thin tube portion 1b is made of a cermet material, so that the portion sealed by the seal 4 of the ceramic sealing compound is translucent due to thermal shock during lamp lighting. This prevents cracks in the ceramic.

In Patent Document 2, attention is paid to hydrogen and oxygen present in the discharge vessel. A configuration is disclosed in which hydrogen and oxygen permeable materials are used for the power supply conductor so that they can escape outside the discharge vessel during lamp operation. This is intended to suppress the blackening of the discharge vessel and the rise of the ignition voltage.
Japanese Patent Laid-Open No. 11-213952 (page 8, FIG. 1) JP-A-6-196131 (page 9, FIG. 1)

  In Patent Document 1, it is reported that in a metal halide lamp using a metal halide as a light emitting metal, the metal halide chemically reacts with a metal material (for example, niobium) serving as a power supply conductor and corrodes.

  However, as the tube wall load in the discharge vessel (ratio of input power to the discharge vessel per unit inner surface area of the discharge vessel) increases, it has been found that the metal halide also reacts with the alumina ceramic that is the discharge vessel. It was. The chemical reaction between the metal halide and the alumina ceramic directly increases the amount of free halogen present in the discharge vessel during lamp operation and does not directly affect the light emission phenomenon, thereby increasing the ignition voltage during lamp operation. When the ignition voltage rises, the “extinction phenomenon” that the discharge sustaining voltage cannot be supplied and turns off becomes obvious.

  The chemical reaction between the metal halide and the alumina ceramic is the portion where the metal halide sealed in the discharge vessel aggregates on the inner surface of the alumina ceramic discharge vessel, and the portion where the surface temperature of the discharge vessel is the highest. The chemical reaction begins. The inventor of the present application does not cause this chemical reaction in the vicinity of the end of the thin tube sealed by the ceramic sealing compound as described in Patent Document 1, but the bulging portion (generally “ It has been noticed that there are many in the vicinity of the junction between the light emitting part) and the narrow tube part connected to the bulging part. Note that the vicinity of the joint between the bulging portion and the narrow tube portion is a portion where the metal halide aggregates and the inner surface of the alumina ceramic discharge vessel has a relatively high temperature.

  The object of the present invention is to solve the above-mentioned conventional problems, and in order to reduce the probability of occurrence of the extinction phenomenon during lighting, the ceramic that is the material of the discharge vessel and the metal halide enclosed in the discharge vessel Is to provide a configuration of a high-pressure discharge lamp capable of suppressing the progress of the chemical reaction.

  In order to solve the above problems, a high-pressure discharge lamp of the present invention is a discharge having a bulging portion made of a ceramic material and a thin tube portion connected to both ends of the bulging portion and made of a ceramic material. A container, a pair of electrode parts partially located in the bulging part, a pair of power supply conductors connected to each of the electrode parts and supplying power to the electrode part, and enclosed in the discharge container A light emitting metal, and the electrode portion includes a tip portion that maintains discharge, and an intermediate portion that is connected to the tip portion and is formed of a conductive material that is lower in thermal conductivity than the tip portion. And the intermediate portion is located at least in the bulging portion.

  As one preferred embodiment, a gap is formed between the narrow tube portion and the electrode portion.

  In one preferred embodiment, the tip portion is made of a tungsten material, and the intermediate portion is made of a conductive cermet material.

Furthermore, the tube wall load in the discharge vessel is 0.37 W / mm ² or more.

  In one preferred embodiment, the light emitting metal includes a metal halide.

  With the above configuration, the high-pressure discharge lamp according to the present invention allows the chemical reaction between the bulging portion of the discharge vessel and the joint near the tubule connected to the bulging portion to proceed with the chemical reaction between the metal halide sealed in the discharge vessel. Can be suppressed. Since the progress of the chemical reaction can be suppressed, an increase in the amount of free halogen in the discharge vessel can be suppressed, and the occurrence of the extinction of the high-pressure discharge lamp caused by the free halogen can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
1 is a cross-sectional view of a high-pressure discharge lamp according to Embodiment 1 of the present invention. The discharge vessel 1 has a bulging portion 1a and a narrow tube portion 1b connected to both ends of the bulging portion 1a. The bulging portion 1a and the thin tube portion 1b are made of a ceramic material made of translucent alumina. The bulging portion 1a can have an inner diameter of 3.6 mm to 7.0 mm and a total length of 20 mm to 50 mm. In this embodiment, the inside diameter of the bulging portion 1a is 4.0 mm and the total length is 30 mm. The inner diameter of the thin tube portion 1b can be 0.8 mm to 2.0 mm, and the total length can be 10 mm to 20 mm. In this embodiment, the inside diameter of the thin tube portion 1b is 1.0 mm and the total length is 15 mm.

  A part of the pair of electrode portions 3 is located in the bulging portion 1 a so as to face each other, and an arc discharge is generated between the electrode portions 3. Furthermore, an electrode coil is wound around the tip of the electrode part 3 located in the bulging part 1b.

  A pair of power supply conductors 2 is connected to each of the electrode portions 3. The power supply conductor 2 serves to supply power to the electrode unit 3. Further, the power supply conductor 2 is hermetically sealed by a seal 4 of a ceramic sealing compound at a sealing portion 1 b 1 of the thin tube portion 2. The feed conductor 2 is connected to a lighting circuit, and is lit with a lamp power of 150 W in this embodiment.

  In the discharge vessel 1, a metal halide (sodium iodide, praseodymium iodide, etc.) and mercury are enclosed as a light emitting metal (not shown). Further, argon is sealed in the discharge vessel 1 as a buffer gas.

  Furthermore, the electrode part 3 is demonstrated.

  In the present embodiment, the electrode portion 3 includes a front end portion 101 that maintains discharge, an intermediate portion 100 that is connected to the front end portion 101, and a rear end portion 102 that connects the intermediate portion 100 and the power supply conductor 2. The The intermediate part 100 is formed from a conductive material having a thermal conductivity lower than that of the tip part 101. In the present embodiment, the tip portion 101 is made of a tungsten material, and the intermediate portion 100 is made of a conductive cermet material. The rear end portion 102 is made of a tungsten material and has a halide-resistant portion 2b. A coil 2b1 made of molybdenum, for example, is wound around the halide resistant portion 2b. The diameter of the shaft of the electrode part 3 is 0.3 mm to 0.8 mm, and the total length is 12 mm to 24 mm. In this embodiment, the one having a diameter of 0.5 mm and a total length of 17 mm was used. Further, the tip portion 101 can have a length of 0.1 mm to 1.0 mm. In this embodiment, the tip portion 101 has a length of 0.2 mm. The intermediate part 100 having a length of 1.0 mm to 3.0 mm can be used, and in this embodiment, a part having a length of 2.0 mm is used.

  Furthermore, a slight gap 5 exists between the thin tube portion 1b and the electrode portion 3, and is continuously connected from the space in the bulging portion 1a.

  In general, the above-described high-pressure discharge lamp (metal halide lamp) is in the order of several hundred hours after the start of lighting, and the light-emitting metal sealed in the bulging portion 1a gradually enters the inner part of the gap 5 gradually. Go. At this time, for example, if the feed conductor 2 is made of a material such as niobium, a minute crack is generated between the niobium and the seal 4 of the ceramic sealing compound due to the reaction between niobium and the halide, and the sealing portion A failure mode such as a leak occurs. Therefore, in this embodiment, a conductive cermet made of alumina ceramic and molybdenum is used for the power supply conductor 2 so that such cracks do not occur. As can be seen from the fact that the coil 2b1 of the halogen-resistant portion 2b is made of molybdenum, molybdenum has a property that it is less susceptible to halides than niobium.

<Calculation results by simulation>
When the lamp shown in FIG. 1 is turned on, the metal halide gradually enters the inner part of the slight gap 5. What is important at this time is the temperature design of the discharge vessel 1, particularly the narrow tube portion 1b. In the case of a high-pressure discharge lamp (hereinafter also referred to as a “metal halide lamp”) having a narrow tube portion 1b structure having a slight gap as usual, the amount of metal halide that enters during the lamp life is estimated in advance at the time of design. The amount of metal halide enclosed is determined so that the change in emission color during the lamp life caused by the decrease in the amount of metal halide in the outlet 1a falls within the specification range. This is because the metal halide that has once entered the back of the slight gap 5 cannot sufficiently contribute to light emission thereafter. The degree of progress of the reaction between the metal halide that has entered at this time and the material to be reacted (for example, when the power supply conductor 2 is made of niobium) proceeds as the temperature at that portion increases. For this reason, the length of the narrow tube portion 1b is often designed so that the back portion of the slight gap 5 where these reactions usually occur is sufficiently spaced from the bulging portion of the discharge vessel that becomes high temperature. In the present embodiment, the length of the narrow tube portion 1b is 15 mm. In the case of the present embodiment, no reaction between the metal halide and the halide-resistant portion 2b, the feed conductor 2 or the ceramic sealing compound seal 4 was confirmed in the slight gap depth.

  However, it has been found that a portion that reacts significantly with the metal halide is generated separately. This will be described with reference to FIG. FIG. 2 is an enlarged sectional view of a part of FIG. Note that the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  The portion that reacts remarkably with the metal halide is the joint between the bulging portion 1a and the thin tube portion 1b, that is, the portion that can be said to be the thin tube introduction portion 110. The narrow tube introduction portion 110 corresponds to an entrance through which the metal halide existing in the bulging portion 1a during lamp operation enters the thin tube portion 1b. Since the temperature in the narrow tube portion 1b is lower than that in the bulging portion 1a, the metal halide enters the narrow tube portion 1b by diffusion or convection. In this case, since the gap 5 is abruptly narrowed due to the presence of the coil 2 b 1, much of the metal halide that has entered first stays in the narrow tube introduction part 110. At this time, if the temperature of the ceramic in the portion of the narrow tube introduction portion 110 is too high, the reaction between the ceramic and the metal halide proceeds rapidly.

  Therefore, the present inventor has found a configuration in which the entering metal halide does not aggregate on the ceramic surface of the capillary tube introduction portion 110 in order to suppress the reaction between the metal halide and the alumina ceramic in the capillary tube introduction portion 110. The configuration is the configuration of the electrode unit 3 of the present embodiment. In the electrode part 3 partially located in the bulging part 1a, the electrode part 3 is connected to the tip part 101 for maintaining the discharge and the tip part 101, and the conductive material is lower than the thermal conductivity of the tip part 101. And an intermediate portion 100 formed of

  A discharge arc is generated between the tip portions 101 of the opposing electrode portions 3, and thermal energy and charged particle collision energy generated therein flow mainly into the tip portion 101. The temperature distribution of the electrode portion 3, the halogenated portion 2 b connected to the electrode portion 3, and the power supply conductor 2 is determined by the heat transfer of the energy flowing into the tip portion 101.

  The principle of preventing the metal halide entering the thin tube introducing portion 110 from aggregating on the ceramic surface of the thin tube introducing portion 110 according to the configuration of the present embodiment will be described with reference to FIG. In addition, the same structure attaches | subjects the same code | symbol and abbreviate | omits description.

  If the temperature of the electrode portion surface portion 103 of the electrode portion 3 facing the ceramic surface 112 of the thin tube introduction portion 110 becomes relatively low, the aggregation of metal halides on the ceramic surface 112 can be reduced. When the front end portion 101 and the rear end portion 102 use tungsten and the intermediate portion 100 uses conductive cermet, the electrode portion surface 113 (B -B ') The temperature around the top was calculated using the finite element method. The result is shown in FIG. FIG. 4 also shows the temperature distribution near the ceramic surface 112 (C-C ′). In this calculation, the diameter of the shaft of the electrode portion 3 was 0.5 mm, the length was 17 mm, the tip portion 101 was 0.2 mm in length, and the intermediate portion 100 was 2.0 mm in length. The coil wire diameter of the tip 101 was 0.2 mm. Moreover, the thermal conductivity of tungsten was calculated as 102.6 [W / mK], and the thermal conductivity of the conductive cermet was calculated as 34.3 [W / mK].

  In FIG. 4, the horizontal axis indicates the position of the electrode portion 3 in the axial direction, and the vertical axis indicates the temperature. In addition, in order to clarify the reference | standard of a horizontal axis, the position of the electrode part 3 in the surface where the thin tube part 1b is exposed to the bulging part 1a is shown in FIG. 4 as A-A '. In FIG. 4, the calculated temperature of the electrode surface 113 is indicated by a solid line, and the calculated temperature of the ceramic surface 112 is indicated by a broken line. As shown in FIG. 4, by providing the intermediate portion 100, the bulging portion 1a has a steep inclination of temperature decrease with respect to the position, and the temperature is rapidly lowered. In the thin tube portion 1b, the temperature of the electrode portion surface of the electrode portion 3 is lower when the intermediate portion 100 is present. On the other hand, it can be seen that there is almost no change in the temperature distribution of the ceramic surface 112.

  The reason why the temperature distribution on the ceramic surface 102 hardly changes is as follows.

  Compared with FIG. 5 which is the conventional example, the lamp of FIG. 1 which is the present embodiment has a smaller inner diameter (the inner diameter of the bulge portion of the conventional example is 9 mm, whereas the bulge portion 1a of the present embodiment is The inner diameter is 4 mm). Therefore, the bulging portion 1a of the present embodiment is closer to a discharge arc that is a heating element. The closer the inner wall of the bulging portion 1a is to the discharge arc, the greater the amount of heat transfer from the discharge arc to the ceramic. In other words, the temperature distribution of the ceramic surface 112 in the narrow tube introduction portion 110 is dominated by the contribution determined by further transferring the energy transferred from the discharge arc to the bulging portion 1a. This means that heat transfer and heat radiation are not affected.

  Moreover, in order to reduce the temperature of the electrode part surface 113 as compared with a state where the intermediate part 100 is not provided, the intermediate part 100 is at least on the bulging part 1a side (from AA ′ in FIG. 2 to the bulging part 1a side). It is preferable to substitute in. That is, the intermediate part should just be arrange | positioned so that it may be located at least in a bulging part. With such a configuration, the energy flowing from the tip portion 101 is inhibited from being conducted by the substituted intermediate portion 100 having a material with low thermal conductivity, and the temperature of the electrode portion surface 112 in the capillary tube introduction portion 110 is not replaced. Reduced compared to the case.

<Experimental result>
In order to verify the calculation result by such a finite element method, the temperature of the end 2c of the feed conductor 2 shown in FIG. 1 is measured in a lamp in which a part of the electrode part 3 is replaced with the intermediate part 100. did. The difference between the two lamps is that the middle part 100 is replaced with a part of the electrode part 3, and the other structures of the measured high-pressure discharge lamp are those described in the first half of this embodiment. . Compared to 545 ° C. for the high-pressure discharge lamp without the intermediate portion 100, the temperature of the lamp replaced with the intermediate portion 100 was confirmed to be 535 ° C. and 10 ° C. This is considered to support the temperature reduction effect of the replacement of the conductive cermet in the calculation.

  Furthermore, it was confirmed that the chemical reaction between the ceramic and the metal halide generated in the capillary tube introduction portion 110 was reduced by analyzing the sample. In addition, when a lighting life test was performed using a lamp with and without the intermediate part 100, it was confirmed that the probability of extinction during the lighting life test was reduced for the lamp with the intermediate part 100. It was done.

<Other special notes>
In the present invention, the reason why the tip portion is not replaced when the intermediate portion 100 is replaced with the electrode portion 3 is as follows. In general, since the discharge arc of the high-pressure discharge lamp is maintained by thermionic emission of the electrode surface supporting the discharge arc, the electrode surface becomes very hot. Therefore, since a high melting point material such as tungsten is required for the electrode material, it is not preferable to replace the tip portion with a conductive cermet having a melting point lower than that of tungsten in this application.

  In addition, if the chemical reaction generated in the narrow tube introduction part 110 is a problem, the idea of extending the coil 2b1 to the bulging part side by the idea of closing the part comes out. However, if this is done, heat dissipation from the coil 2b1 is increased, and as a result, the temperature of the tip portion 101 is unnecessarily lowered.

In FIG. 1, the amount of tube wall load was calculated. The tube wall load is obtained by dividing the lamp power by the surface area of the bulging portion in the discharge vessel 1, and is a measure of the thermal load that the discharge vessel receives. In FIG. 1, since the inner diameter of the bulging portion is 4 mm and the total length is 30 mm, the tube wall load is 150 W / (4π × 30 + 2 × 2 × 2 × π) mm ² = 0.37 [W / mm ² ], In the conventional lamp of FIG. 5 (the inner diameter of the bulging portion is 9 mm and the total length is 13 mm), 150 W / (9π × 13 + 2 × 4.5 × 4.5 × π) mm ² = 0.303 [W / mm ² ], The load is greater than 23%. This suggests that the temperature of the ceramic is increased, and the present invention shows that the present invention is effective for a lamp having a large tube wall load as compared with the prior art.

In the same manner as described above, the comparison with and without the conductive cermet replacement was also performed in a discharge vessel having an inner diameter of 5.2 mm and a total length of 22 mm inside the bulging portion 1a (tube wall load was 150 W / (5.2π). × 22 + 2 × 2.6 × 2.6 × π) mm ² = 0.37 [W / mm ² ]). As in the configuration example of FIG. 1, it was confirmed by destructive analysis that the chemical reaction between the ceramic and the metal halide generated in the narrow tube introduction portion 110 was reduced. At this time, as described above, when a lighting life test was performed using a lamp with and without a conductive cermet, the probability of occurrence of extinction during the lighting life test was higher for the lamp with a conductive cermet. Has been confirmed to be reduced.

From the above two examples, it is envisioned that if at least the tube wall load is 0.37 [W / mm ² ] or more, the thermal load is further increased and the temperature of the ceramic is further increased, and the reaction is promoted. Obviously. In such a high-pressure discharge lamp having a high tube wall load, the configuration of the present application is effective.

  Since the high-pressure discharge lamp according to the present invention relates to a technique for suppressing the reaction between the discharge vessel and the luminescent metal, it is particularly useful for a high tube wall load type high-pressure discharge lamp employing a ceramic material as the discharge vessel.

Sectional drawing of the high pressure discharge lamp in Embodiment 1 of this invention The expanded sectional view of the high-pressure discharge lamp in Embodiment 1 of the present invention The expanded sectional view of the high-pressure discharge lamp in Embodiment 1 of the present invention The figure which shows temperature distribution of the thin tube introduction part 110 grade | etc., Of the high pressure discharge lamp in Embodiment 1 of this invention. Cross section of a conventional high pressure discharge lamp

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Discharge vessel 1a Expansion part 1b Narrow tube part 100 Middle part 101 Front-end | tip part 102 Rear end part 110 Narrow tube introduction part 112 Ceramic surface 113 Electrode part surface 2 Feeding conductor 2b Halogen-resistant part 2b1 Coil 2c End part of feeding conductor 3 Electrode part 4 Seal 5 Clearance

Claims (5)

A discharge vessel having a bulging portion made of a ceramic material and a thin tube portion connected to both ends of the bulging portion and made of a ceramic material;
A pair of electrode portions partially located in the bulging portion;
A pair of power supply conductors connected to each of the electrode portions and supplying power to the electrode portions;
A light emitting metal enclosed in the discharge vessel,
The electrode part has a tip part for maintaining discharge, and an intermediate part connected to the tip part and formed from a conductive material lower than the thermal conductivity of the tip part,
The intermediate portion is a high pressure discharge lamp located at least in the bulging portion. The high pressure discharge lamp according to claim 1, wherein a gap is formed between the narrow tube portion and the electrode portion. The tip is made of a tungsten material;
The high-pressure discharge lamp according to claim 1 or 2, wherein the intermediate portion is made of a conductive cermet material. The high-pressure discharge lamp according to any one of claims 1 to 3, wherein a tube wall load in the discharge vessel is 0.37 W / mm ² or more. The high-pressure discharge lamp according to any one of claims 1 to 4, wherein the luminescent metal includes a metal halide.

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