JP3576133B2 - High pressure discharge lamp - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-pressure discharge lamp such as a metal halide lamp.
[0002]
[Prior art]
In recent years, a high-pressure discharge lamp using a translucent ceramic, mainly a polycrystalline alumina ceramic, instead of quartz as an arc tube material, particularly a metal halide lamp, has been developed. Since the alumina ceramic arc tube has higher heat resistance than that of quartz, it can emit light at a higher temperature, and has a characteristic that lamp characteristics with higher efficiency and higher color rendering properties than quartz can be obtained.
[0003]
This metal halide lamp is generally used in which a narrow tube portion is provided at both ends of a main tube portion in which a discharge space is formed, and a conductive holding member such as molybdenum for holding an electrode is sealed in a thin tube portion with a sealing material. And joining the holding member and the thin tube portion to hermetically seal the arc tube. As this joining technique, a frit sealing technique (see, for example, JP-A-6-196131) has been put to practical use.
[0004]
However, this frit sealing is relatively weak in bonding force due to physical bonding, so that the hermeticity of the sealing portion is low, and rare gas sealed in the arc tube leaks to shorten the life in some cases. In addition, since the frit easily reacts with the metal halide as a luminescent substance at a high temperature, it is necessary to increase the length of the thin tube portion in the tube axis direction to separate the sealed portion from the discharge space in order to avoid such a problem. The loss is large and the lamp efficiency is not good. Further, even if the sealing portion is separated from the discharge space, there are still problems to be solved in terms of quality, such as the emission color may change due to the reaction.
[0005]
On the other hand, as a technique for joining a ceramic member and a conductive member such as a metal, a metallized sealing technique (see, for example, JP-A-2000-100385, JP-A-20001-58882, etc.) has recently attracted attention. ing. The metallized sealing is based on chemical bonding, and therefore has an advantage that the bonding strength is stronger than that of frit sealing and that there is less reaction with a luminescent material than frit.
[0006]
Then, the inventor of the present application worked on practical development of a metal halide lamp in which the thin tube portion and the holding member were joined by the metallized sealing. As a development goal, a lamp efficiency was set to be higher than that of a conventional metal halide lamp with frit sealing. As described above, according to the metallized sealing, the bonding strength is strong, and the reaction with the luminescent substance is small, so that the area of the sealed portion can be made smaller than in the case of frit sealing, and the sealed portion needs to be separated from the discharge space. There is no. Therefore, it is possible to reduce the length of the thin tube portion in the tube axis direction as compared with the case of frit sealing, and if the length can be shortened, the heat loss can be reduced accordingly, so that the vapor pressure of the metal halide in the arc tube can be reduced. And the lamp efficiency can be increased.
[0007]
[Problems to be solved by the invention]
However, a configuration in which the length of the thin tube portion is actually shortened as much as possible (a configuration in which the frit sealing in a 150 W lamp was reduced from 16.8 (mm) to 4.0 (mm)). When a metal halide lamp was prototyped and subjected to a life test, although the lamp efficiency was increased as expected, a new problem occurred that the inner surface of the main pipe was blackened and the lamp luminous flux was significantly reduced at an initial stage of about 500 hours.
[0008]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a high-pressure discharge lamp that can prevent a reduction in luminous flux due to blackening of an arc tube.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an arc tube comprising a main tube portion forming a discharge space and thin tube portions provided at both ends of the main tube portion, and an arc tube formed of a translucent ceramic material. It has a shaft portion supported by the thin tube portion, and has a pair of electrodes provided so that the tip portions face each other at an interval in the discharge space, and at least one of the pair of electrodes is provided. The electrode is supported by the thin tube portion in a state where a shaft portion of the electrode is inserted into a cylindrical holding member made of a halide-resistant metal. A high-pressure discharge lamp sealed via a bonded body including a glass body and a mixed glass impregnated in open pores of the sintered body, wherein the tip of the electrode and a discharge space side of the holding member are provided. Let Lme (mm) be the distance in the pipe axis direction from the tip When the up power was P (W), the holding member is characterized in that the distance Lme is disposed at a position where the 0.012P + 2.5 (mm) or more.
[0010]
Accordingly, glow discharge does not occur from the discharge space side end of the conductive holding member when the lamp is started, and the blackening of the inner surface of the arc tube during the life can be prevented. Then, in the range of the distance Lme obtained by the above equation, it is possible to improve the lamp efficiency by shortening the narrow tube portion as compared with the conventional frit sealing.
[0011]
Further, a winding member made of a halide-resistant metal is wound around at least a part of a portion of the shaft portion of the electrode that is inserted into the holding member.
This makes it difficult for the light-emitting substance made of metal halide to enter the cylindrical holding member, so that the amount of the light-emitting substance enclosed can be reduced as compared with the case where the winding member is not wound around the shaft of the electrode.
[0012]
Further, the discharge space side end of the winding member is located between the discharge space side tip of the holding member in the tube axis direction and the discharge space side tip of the thin tube portion of the shaft of the electrode, The winding member is wound around a shaft of the electrode such that an end opposite to the discharge space is located in the holding member.
In this case, the amount of the luminescent substance that is going to enter not only the holding member but also the capillary portion can be reduced.
[0013]
Furthermore, a proximity conductor for starting assistance is attached to the outer periphery of the arc tube, and at least one mounting end of the proximity conductor is connected to an end of the winding member on the discharge space side in the tube axis direction and the holding member. And a discharge space side tip.
Thus, at the time of starting the lamp, discharge starts from between the mounting end of the proximity conductor and the winding member, and the startability can be improved by attaching the proximity conductor.
[0014]
Further, the halide-resistant metal sintered body is a metal sintered body containing molybdenum, and the mixed glass is a glass containing alumina.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a high-pressure discharge lamp according to the present invention will be described with reference to the drawings, taking a metal halide lamp as an example.
(First Embodiment)
FIG. 1 is a local sectional view showing the overall configuration of a 150 W type metal halide lamp (hereinafter simply referred to as “lamp”) 21 according to the first embodiment. The lamp 21 emits light when supplied with AC power, and is used for general indoor lighting of a store or the like.
[0016]
As shown in FIG. 1, the lamp 21 has an arc tube unit 2 having an arc tube 1 installed in an outer tube glass bulb 22 made of quartz or hard glass, and a cap 23 is attached to the outer tube glass bulb 22. It is configured. A gas mainly composed of nitrogen is sealed in the outer glass bulb 22, and a shield quartz tube 24 for preventing the outer glass bulb 22 from being damaged is provided around the arc tube 1.
[0017]
FIG. 2 is a sectional view showing the arc tube unit 2 of the lamp 21.
As shown in FIG. 1, the arc tube unit 2 includes an arc tube 1, tungsten electrodes 10, 11, and the like.
The arc tube 1 is composed of a main tube portion 3 forming a discharge space 25 and a pair of thin tube portions 4 and 5 sintered at both ends thereof, and a light-transmitting alumina ceramic having a heat resistance of about 1200 ° C. Made of material. The thin tube portion 4 supports the tungsten electrode 10, and the thin tube portion 5 supports the tungsten electrode 11.
[0018]
In the arc tube 1, for example, a metal halide (DyI ₃ + TmI ₃ + HoI ₃ + TlI + NaI), a predetermined amount of mercury as a buffer gas, and a predetermined amount of argon as a starting auxiliary rare gas.
The tungsten electrode 10 has a tungsten coil 14 wound around a tip of a tungsten electrode shaft 12, and the tungsten electrode 11 has a tungsten coil 15 wound around a tip of a tungsten electrode shaft 13. The tungsten electrodes 10 and 11 are provided such that the distal ends thereof face each other with an interval (Le) therebetween in the discharge space 25.
[0019]
The tungsten electrodes 10 and 11 are inserted through molybdenum thin tubes 6 and 7 which are holding members for holding the tungsten electrode shafts 12 and 13, and are supported by the thin tube portions 4 and 5 via the molybdenum thin tubes 6 and 7. Is done.
The molybdenum tubes 6 and 7 are sealed by laser welding in a state in which the tungsten electrode shafts 12 and 13 are inserted in the openings on the side opposite to the discharge space 25. The shafts 12 and 13 are held. The shafts protruding outward from the sealing portions 18 and 19 are used as external lead wires, respectively.
[0020]
Further, the molybdenum thin tubes 6, 7 are sealed by the above-described metallization sealing technique via the joined bodies 8, 9 in a state where they are inserted into the inside portions of the ends of the thin tube portions 4, 5 opposite to the discharge space 25. Is being worn.
FIG. 3 is an enlarged cross-sectional view of a part of the sealing portion formed by the bonded body 8, showing a bonding (sealing) state of the thin tube portion 4 (alumina ceramic) and the molybdenum fine tube 6 (molybdenum) by the bonded body 8. It is a figure shown in detail. Since the other joined body 9 is the same as the joined body 8, the joined body 8 will be described here as a representative.
[0021]
As shown in the figure, the joined body 8 is composed of a main layer 81 in contact with the molybdenum thin tube 6 and Dy existing at an interface between the thin tube portion 4 and the main layer 81. ₂ O ₃ -Al ₂ O ₃ And an interface glass layer 82 made of a system glass. The main layer 81 is made of a sintered body of a metal powder such as molybdenum, and has a porous skeleton 83 having open pores and Dy impregnated in the open pores. ₂ O ₃ -Al ₂ O ₃ Dy whose main component is ₂ O ₃ -Al ₂ O ₃ And an impregnated glass layer 84 of a mixed glass. Dy ₂ O ₃ -Al ₂ O ₃ La mixed glass ₂ O ₃ And Y ₂ O ₃ And the like. The metal powder may be selected from, for example, tungsten and alloys thereof in addition to molybdenum.
[0022]
According to the joined body 8 having the above configuration, the mixed glass impregnated in the open pores functions as a kind of cushioning material, so that the impact resistance is improved. That is, the joined body 8 includes a metal sintered body having open pores and a mixed glass impregnated in the open pores. In addition, since the said joined body 8 and its manufacturing method, and the joining method using the said joined body are disclosed in detail in Unexamined-Japanese-Patent No. 2001-58882, the further description is abbreviate | omitted.
[0023]
As described above, the arc tube unit 2 is sealed by joining the thin tube portions 4, 5 and the molybdenum thin tubes 6, 7 by metallizing sealing and sealing the openings of the molybdenum thin tubes 6, 7 on the side opposite to the discharge space 25. Will be.
Returning to FIG. 2, the dimensions of the main part of the arc tube unit 2 are as follows. That is, the inner diameter φi of the central portion of the main tube portion 3 is 10.7 (mm), the overall inner length is 15.4 (mm), the electrode tube distance Le is 10.0 (mm), and the outer portions of the thin tube portions 4 and 5 are outside. The diameter is 3.2 (mm), the hole diameter is 1.30 (mm), the total length Ls is 7.0 (mm), the outer diameter of the molybdenum thin tubes 6, 7 is 1.2 (mm), and the wall thickness is 0.10 (mm), and the wire diameter of the tungsten electrode shafts 12 and 13 is 0.5 (mm). The tube wall load we of the arc tube 1 is about 27 (W / cm). ² ) Is set to
[0024]
In the lamp 21, the separation distance in the tube axis direction (vertical direction in the figure) from the tip of the tungsten electrode 10 to the discharge space side tip 61 of the molybdenum thin tube 6, and the distance between the tip of the tungsten electrode 11 and the molybdenum thin tube 7. Is set to 5.5 (mm). Hereinafter, the reason why the value of the separation distance Lme is set in this manner will be described.
[0025]
The inventor of the present application shortened the length Ls of the thin tube portions 4 and 5 to 4.0 (mm) in order to improve the lamp efficiency by using the metallized sealing technology, as described in the above "Conventional Technology". Prototype of lamp. The distance Lme in this prototype lamp was 2.5 (mm).
Then, when the lamp was subjected to a life test of 5.5 hours on and 0.5 hours off, the initial lamp efficiency was 97 (lm / W) as compared to 90 (lm / W) of the lamp with the conventional frit sealing. The expected high rise of about 8% was achieved. In addition, the general color rendering index Ra was about 92, compared to about 90 for a conventional frit-sealed lamp, which was also found to be improved. Further, when the temperature Tc of the root end portion C of the main pipe portion 3 was measured, the value was increased by about 250 ° C. as compared with the case of the lamp by frit sealing.
[0026]
From this, the lamp efficiency increases due to the heat loss reduction due to the shortened narrow tube portion, and the general color rendering index Ra value increases in addition to the lamp efficiency increase due to the increase in the vapor pressure of the luminescent material 20 mainly composed of metal halide. It can be said that it has been improved.
However, 500 hours after the start of the test, the inner surface of the main tube 3 was blackened, and the luminous flux was reduced to about 70% of the value after 100 hours. The inventor of the present application observed the state of discharge at the time of starting the lamp in order to investigate the cause, and found that the discharge was started from the molybdenum thin tubes 6 and 7 used as the conductive members. That is, in the prototyped lamp, since the discharge space side tips 61 and 71 of the molybdenum tubes 6 and 7 are extremely close to the discharge space 25, heat escapes outside through the cross sections of the molybdenum tubes 6 and 7 and arc discharge occurs. Before the transition to the arc discharge, the molybdenum is scattered by the spatter at the time of the glow discharge started from the distal end portion of the molybdenum thin tubes 6, 7 during the transition to the arc discharge, and It was clarified that the blackening phenomenon occurred by adhering to the inner surface of the portion 3 and the light flux was reduced during the life.
[0027]
Then, the inventor of the present application took various measures to solve this problem, and if the distal ends 61 and 71 of the molybdenum thin tubes 6 and 7 on the discharge space side were separated from the discharge space 25 to some extent in the tube axis direction, the present invention was concerned. It has been found that glow discharge is not started from the tips 61 and 71. Specifically, among the various dimensions of the lamp, an attempt was made to extend the length Ls of the thin tube portions 4 and 5 while keeping the length Lm of the thin molybdenum tubes 6 and 7 such that the distance Lme was long. Was. That is, lamps were prepared in which Ls was sequentially increased from 4.0 (mm) (Lme was 2.5 mm), and these were subjected to the same life test as described above.
[0028]
FIG. 4 is a graph showing the relationship between the luminous flux maintenance rate after 500 hours and the Lme obtained from the result of the life test.
As shown in the figure, it can be seen that the luminous flux maintenance ratio increases as Lme increases, indicating that the blackening phenomenon has decreased. When the distance Lme is 4.3 (mm) or more, it is confirmed that no glow discharge is generated from the tips of the thin molybdenum tubes 6 and 7, and when Lme is 4.3 (mm), 500 hours elapse. The luminous flux maintenance ratio is 93% of the value after 100 hours, which is compared with the luminous flux maintenance ratio of the initial lamp (when the separation distance Lme is 2.5 (mm)) was about 70%. It was confirmed that it was significantly improved. The luminous flux maintenance ratio after 6000 hours had passed was 75%. The initial lamp efficiency is 94.5 (lm / W), which is about 5% higher than that of the conventional lamps. It was confirmed that the purpose of improving the lamp efficiency was also achieved.
[0029]
That is, in the case of a 150 W lamp, it was found that when Lme was shorter than 4.3 (mm), the lamp efficiency was improved, but on the other hand, the blackening phenomenon occurred.
The inventor of the present application performed a life test similar to that described above for lamps having a wattage other than the 150 W lamp, and determined the minimum value of Lme that can prevent the blackening phenomenon. As a result, for 20 W, 35 W, 70 W, 100 W, 250 W, and 400 W lamps, the Lme minimum value of the lamps is 2.6 (mm), 2.9 (mm), 3.3 (mm), and 3. 7 (mm), 5.4 (mm), and 7.2 (mm).
[0030]
FIG. 5 is a graph showing the relationship between the lamp power and Lme obtained from the results of the life test.
As shown in the figure, when the values of Lme for each lamp power (W) are plotted, they can be almost connected by a straight line 28, and the relational expression between the value of Lme and the value of lamp power is substantially a linear function. It can be seen that the expression of this linear function is Lme = 0.012P + 2.5 (mm).
[0031]
From this equation, it can be seen that the value of Lme increases as the lamp power increases. This is due to the following reasons. That is, in a high-pressure discharge lamp such as a metal halide lamp, the distance Le between the electrodes is generally short when the wattage (lamp power) of the lamp is small, and long when the wattage of the lamp is large. The shorter the distance Le between the electrodes, the higher the probability of starting arc discharge from the tip of the tungsten electrode. In other words, the longer the distance Le between the electrodes, the higher the probability of starting glow discharge. Therefore, in the lamp of small wattage, since the distance Le between the electrodes is short, the glow discharge is not started from the discharge space side tips 61, 71 of the molybdenum thin tubes 6, 7 even if the separation distance Lme is shortened. This is because the distance Le between the electrodes increases as the lamp has a larger wattage, and the probability of glow discharge increases unless the value of the separation distance Lme is increased.
[0032]
As described above, if the value of the separation distance Lme is set to be equal to or greater than the value calculated by the above equation in the lamp of each wattage, the blackening phenomenon can be prevented. Since the lamp efficiency is conversely reduced due to the loss, for example, an optimum value should be selected within the shaded area in FIG. 5 while considering the lamp dimensions, the lamp efficiency during the lamp life, the luminous flux maintenance factor, and the like. Is preferred.
[0033]
The inventor of the present invention set the Lme to 5.5 (mm) and the Ls to 7.0 (mm) for the 150 W lamp, and performed the measurement of the initial lamp characteristics and the same life test as described above. As a result, characteristics of an initial lamp efficiency of 95 (lm / W) and a general color rendering index of 91.4 are obtained, and a blackening phenomenon, breakage and leakage of the thin tube portions 4, 5 and a change in emission color are obtained until 6000 hours. It was confirmed that it did not occur.
[0034]
As described above, by setting the value of the separation distance Lme between the tip of the tungsten electrode and the tip of the molybdenum thin tube on the discharge space side to an appropriate value based on the above equation, the inner surface of the arc tube during the life of the lamp can be improved. Can be prevented, and the lamp efficiency can be improved.
In the present embodiment, the arc tube 1 is obtained by sintering the thin tube portions 4 and 5 at both ends of the main tube portion 3. However, the light emission tube is formed by integrally molding the main tube portion 3 and the thin tube portions 4 and 5. It can also be a tube.
[0035]
Further, the relational expression between the lamp power (W) and the value of Lme (mm) is not limited to a lamp having a lamp power of 400 (W). Although not shown in FIG. 5, the relational expression can be applied to a lamp whose lamp power is larger than 400 (W), for example, 1 (KW) or 2 (KW).
(Second embodiment)
The present embodiment has a configuration in which a member made of molybdenum as a halide-resistant metal (hereinafter, referred to as a “molybdenum coil”) is wound around the tungsten electrode shafts 12 and 13, and only this portion is a first molybdenum coil. Is different from the embodiment of FIG. Here, a description will be given mainly of a portion different from the first embodiment, and the description of the same portion will be omitted and the same reference numerals will be given to the drawings.
[0036]
FIG. 6 is a diagram illustrating a configuration of the arc tube unit 30 according to the present embodiment.
As shown in the figure, a molybdenum coil 32 is wound around a tungsten electrode shaft 12 and a molybdenum coil 33 is wound around a tungsten electrode shaft 13, respectively. The gap between the tungsten electrode shafts is filled. This is done for the following reason.
[0037]
That is, in the case of the configuration in which the narrow tube portions 4 and 5 are provided at both ends of the main tube portion 3 as in the present embodiment, the luminescent substance 20 sealed in the arc tube 1 accumulates in a liquid state in the main tube portion 3. Some of them are aggregated in the thin tube portions 4 and 5 and the thin molybdenum tubes 6 and 7. Since these aggregated substances will not be used for the original light emission, if a stable emission color is to be obtained, the light emitting substance is preliminarily encapsulated in anticipation of the amount of aggregation. This necessitates the use of a luminescent material.
[0038]
In order to reduce the amount of these luminescent substances to be aggregated and to reduce the total encapsulation amount, the gap between the tungsten electrode shaft 12 and the thin tube portion 4 and the gap between the tungsten electrode shaft 13 and the thin tube portion 5 and the thin molybdenum thin tube 7 are formed. The gap may be filled with a member made of a halide-resistant metal so that the light-emitting substance does not enter. Then, if a coil-shaped member is used as a member for filling the gap, the cross-sectional area is smaller than in the case of, for example, a cylindrical shape, and heat is less likely to escape to the outside through the member, so that the time required for transition to arc discharge is reduced. It is because it does not become long.
[0039]
In actual life test results, there was almost no influence by sputtering, and no blackening phenomenon due to scattering of molybdenum occurred. Also, the amount of sealing can be reduced by about 30% as compared with the case where the molybdenum coils 32 and 33 are not provided.
In the case of a coil shape, it can be easily manufactured simply by winding it around the tungsten electrode shafts 12 and 13. For example, in the case of a cylindrical shape, the inner diameter is larger than the outer diameter of the tungsten electrode shafts 12 and 13. Since it is necessary to strictly manufacture a tube whose diameter is smaller than the inner diameter of the thin molybdenum tubes 6, 7, it is not easy.
[0040]
In order to prevent the light-emitting substance from entering the thin tube portions 4, 5 and the like as much as possible, as shown in FIG. It is desirable that the molybdenum coils 32 and 33 are wound around all the portions.
In addition, the ends 321 and 331 of the molybdenum coils 32 and 33 on the discharge space side are connected to the discharge space side ends 41 and 41 of the thin tube portions 4 and 5 from the discharge space side ends 61 and 71 of the molybdenum thin tubes 6 and 7 in the tube axis direction. , 51, there is an effect that it is possible to reduce the amount of the luminescent substance entering not only the molybdenum thin tubes 6, 7 but also the thin tube portions 4, 5.
[0041]
Furthermore, even when the molybdenum coil is wound around at least a part of the molybdenum thin tubes 6 and 7 of the tungsten electrode shafts 12 and 13 as compared with the case where the coil is not provided at all. There is an effect that the total amount of the light emitting substance can be reduced.
The base end of the molybdenum coil 32 (the end opposite to the discharge space 25) is a sealed portion 18 in the thin molybdenum tube 6, and the base end of the molybdenum coil 33 is a sealed portion in the thin molybdenum tube 7. 19 and joined together during laser welding.
[0042]
Further, in the present embodiment, a member made of molybdenum is used as a winding member wound around the electrode shaft, but this member may be made of a halide-resistant metal, and for example, a member made of tungsten may be used. . Needless to say, the diameter of the member is within a range in which the member can enter a gap formed between the surfaces of the tungsten electrode shafts 12 and 13 and the inner surfaces of the molybdenum thin tubes 6 and 7. In order to minimize the amount of the luminescent substance entering the thin tube, it is better to make the gap as small as possible. Therefore, when the member is wound around the electrode shaft, the surface of the member becomes molybdenum thin tubes 6, 7 It is preferable that the thickness be such that it comes into contact with the inner surface. Further, the winding pitch is determined based on the degree of the penetration amount and the like.
[0043]
(Third embodiment)
As shown in FIG. 7, an arc tube unit 50 according to the present embodiment has a configuration in which a known starting conductor 51 is provided to the arc tube 1 according to the second embodiment.
As shown in the figure, the proximity conductor 51 attached to the arc tube 1 has a wire shape, and one of the mounting ends 511 is wound around the thin tube portion 4, and the other mounting end. The portion 512 is wound around the thin tube portion 5.
[0044]
The winding position of one of the attachment ends 511 around the thin tube portion 4 in the tube axis direction is a position 2 (mm) away from the discharge space side tip 61 of the molybdenum thin tube 6 toward the discharge space in the tube axis direction. Similarly, the winding position of the other mounting end portion 512 around the thin tube portion 5 in the tube axis direction is also a position 2 (mm) apart from the discharge space side tip portion 71 of the molybdenum thin tube 7. I have.
[0045]
This is because, when the proximity conductor is provided, the discharge starts from the position closest to the proximity conductor at the time of starting the lamp, and the mounting end 511 of the proximity conductor 51 is temporarily set to A in FIG. If it is wound around the position, glow discharge at the time of starting the lamp is generated between the mounting end portion 511 and the thin molybdenum tube 6, and the above-described blackening phenomenon of the arc tube may occur.
[0046]
Therefore, the proximity conductor 51 is provided at a position where no glow discharge occurs between the molybdenum thin tubes 6 and 7, that is, the mounting end 511 of the molybdenum thin tube 6 on the discharge space side tip 61 and the molybdenum coil 32 is wound around a position between the discharge space side end 321 of the molybdenum thin tube 7 and the discharge space side end 331 of the molybdenum coil 33 on the discharge space side. In such a configuration, the discharge is started from the position of the molybdenum coils 33 and 34 closest to the adjacent conductor 51, that is, the glow discharge is not started from the molybdenum tubes 6 and 7.
[0047]
In this case, since the molybdenum coils 32 and 33 are coil-shaped, spattering of molybdenum hardly occurs due to spatter for the above-described reason, and the effect of improving the lamp startability by providing the proximity conductor can be obtained. . Considering that the lamp startability is better when the discharge at the start of the lamp is closer to the discharge space 25, in order to further improve the lamp startability, it is necessary to use the thin tube portions 4 and 5 of the mounting ends 511 and 512. Is preferably positioned as close to the discharge space 25 as possible.
[0048]
Further, here, one of the mounting ends 511 of the proximity conductor 51 is wound around the narrow tube portion 4 and the other mounting end 512 is wound around the narrow tube portion 5. Therefore, for example, a configuration in which one mounting end 511 is wound around the narrow tube portion 4 and the other mounting end 512 is connected to the sealing portion 19 may be adopted. Note that the proximity conductor 51 may be, for example, a plate-like material instead of a wire-like material.
[0049]
(Modification)
As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modified examples can be considered.
(1) In the above embodiment, the configuration example in which the molybdenum thin tubes 6 and 7 as the conductive members are metallized and sealed to both the thin tube portions 4 and 5 has been described. It is also possible to adopt a configuration in which the conductive members are joined by attachment. If metallized sealing is performed on at least one of the thin tube portions, an improvement in lamp efficiency can be expected because the length of the thin tube portion metallized and sealed can be shortened as compared with the case where both are formed by frit sealing.
[0050]
(2) In the above embodiment, an example in which the present invention is applied to a metal halide lamp has been described. However, the same applies to other high-pressure discharge lamps such as a high-pressure mercury lamp, and the present invention can be applied to these general high-pressure discharge lamps. it can.
[0051]
【The invention's effect】
As described above, in the high-pressure discharge lamp of the present invention, the distance in the tube axis direction between the tip of the electrode and the tip of the holding member on the discharge space side is Lme (mm), and the lamp power is P (W). Then, the holding member is arranged at a position where the distance Lme is equal to or greater than 0.012P + 2.5 (mm). Accordingly, glow discharge does not occur from the discharge space side end of the conductive member when the lamp is started, and the blackening phenomenon of the inner surface of the arc tube during the life of the lamp can be prevented. Then, within the range of the distance L obtained by the above equation, it is possible to improve the lamp efficiency by shortening the narrow tube portion as compared with the conventional frit sealing.
[Brief description of the drawings]
FIG. 1 is a local sectional view showing an overall configuration of a 150 W type metal halide lamp 21 according to a first embodiment.
FIG. 2 is a sectional view showing a configuration of an arc tube unit 2 of the metal halide lamp 21.
FIG. 3 is an enlarged cross-sectional view of a part of a sealing portion formed by a bonded body 8;
FIG. 4 is a graph showing a relationship between a luminous flux maintenance factor and Lme obtained from a result of a life test.
FIG. 5 is a graph showing the relationship between lamp power and Lme obtained from the results of a life test.
FIG. 6 is a diagram illustrating a configuration of an arc tube unit 30 according to a second embodiment.
FIG. 7 is a diagram illustrating a configuration of an arc tube unit 50 according to a third embodiment.
[Explanation of symbols]
1 arc tube
2, 30, 50 arc tube unit
3 Main section
4, 5 thin tube section
6, 7 Molybdenum thin tube
8, 9 joint
10, 11 Tungsten electrode
12, 13 Tungsten electrode shaft
18, 19 Sealed part
21 Metal halide lamp
25 Discharge space
32,33 molybdenum coil
51 Proximity conductor
61, 71 Discharge space side tip
321, 331 Discharge space side end
511, 512 Mounting end

Claims (5)

An arc tube comprising a main tube portion forming a discharge space and thin tube portions provided at both ends of the main tube portion, and formed of a translucent ceramic material;
Having a shaft portion supported by the thin tube portion, and having a pair of electrodes provided so that tip portions thereof face each other at intervals in the discharge space,
Of the pair of electrodes, at least one of the electrodes is supported by the thin tube portion in a state where the shaft portion is inserted into a cylindrical holding member made of a halide-resistant metal,
A high-pressure discharge lamp in which the holding member and the thin tube portion are sealed via a joined body including a halide-resistant metal sintered body and a mixed glass impregnated in open pores of the sintered body. So,
When the distance in the tube axis direction between the tip of the electrode and the tip of the holding member on the discharge space side is Lme (mm) and the lamp power is P (W), the holding member has a distance Lme. A high-pressure discharge lamp, which is arranged at a position of 0.012P + 2.5 (mm) or more. The high-pressure discharge according to claim 1, wherein a winding member made of a halide-resistant metal is wound around at least a part of a portion of the shaft portion of the electrode that is inserted into the holding member. lamp. The discharge space side end of the winding member is located between the discharge space side end of the holding member in the tube axis direction and the discharge space side end of the thin tube portion of the shaft of the electrode. The high-pressure discharge lamp according to claim 2, wherein the winding member is wound around a shaft portion of the electrode such that an end opposite to a space is located inside the holding member. A proximity conductor for assisting starting is attached to the outer periphery of the arc tube, and at least one mounting end of the proximity conductor is connected to an end of the winding member on the discharge space side in the tube axis direction and discharge of the holding member. 4. The high-pressure discharge lamp according to claim 3, wherein the high-pressure discharge lamp is arranged at a position between the space-side front end portion. The high-pressure discharge lamp according to any one of claims 1 to 4, wherein the halide-resistant metal sintered body is a metal sintered body containing molybdenum, and the mixed glass is a glass containing alumina. .

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