JP2010238368A - Ceramic metal halide lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic metal halide lamp restraining a crack of a sealed part generated at a sealing process of a light-emitting tube. <P>SOLUTION: The ceramic metal halide lamp is provided with the light-emitting tube forming a pair of narrow tube portions at both ends of its luminous portion into each of which an electrode assembly composed of at least a sealable conductive member, a rod-like molybdenum member and an electrode is inserted, and being sealed with heat-molten frit inpoured into a gap between the narrow-tube portion and the sealable conductive member. A wall thickness of the narrow tube portion in contact with the frit is specified to be ten times or more as thick as the maximum sealing width at a position where the molybdenum rod-like member and the frit are in contact with each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ceramic metal halide lamp, and more particularly to a ceramic metal halide lamp having a ceramic arc tube having a narrow tube portion at both ends, an electrode assembly inserted from an open end of the narrow tube portion, and a gap sealed with a frit. It is. When simply described as “lamp” in the following text, it means a ceramic metal halide lamp with the above specifications. Further, when simply described as “arc tube”, it means a ceramic arc tube having the above specifications.

  When manufacturing an arc tube of a ceramic metal halide lamp in this type of lamp, in the arc tube sealing process, an electrode assembly comprising at least a tungsten electrode, a molybdenum rod-shaped member, and a sealing conductive member is inserted from the opening end of the narrow tube portion. The airtight sealing is achieved by pouring heated and melted frit into the gap between the sealing conductive member and the narrow tube to cool and solidify.

  The arc tube is mainly made of alumina, and the sealing conductive member of the electrode assembly is made of niobium, which is a refractory metal having a coefficient of thermal expansion relatively close to that of alumina, or a conductive cermet rod made of molybdenum and alumina. ing. The frit is mainly composed of oxides of dysprosium, aluminum, and silicon, and the thermal expansion coefficient is relatively close to that of a sealing conductive member. Further, the seal layer is made as thin as possible in order to suppress cracks in the seal layer due to deterioration of the seal layer that occurs when the lamp is lit for a long time.

  However, recently, it is known that cracks in the seal layer due to deterioration of the seal layer can be prevented by lowering the temperature of the end surface on the discharge space side of the seal layer (Patent Document 1). Moreover, paying attention to the inner diameter of the small-diameter cylindrical portion (narrow tube portion) of the discharge vessel and the diameter of the sealing portion of the power supply conductor, the relationship between them is defined by a relational expression to prevent cracks in the discharge vessel ( There is also Patent Document 2).

  However, the crack in the seal portion that occurs during the sealing process is due to the thermal shock when the frit is heated and melted and cooled, and the arc is not a crack in the seal layer filled with the frit, but is a crystal arc tube Cracks occur from the part. The sealing conductive member uses a material having a coefficient of thermal expansion relatively close to that of the thin tube portion, but is not exactly the same coefficient of thermal expansion. When the seal layer is thinned, the distance between the narrow tube portion and the current introduction body becomes very close, and cracks in the seal portion due to thermal shock are likely to occur. The inner diameter of the narrow tube portion is mainly determined by the maximum outer diameter of the electrode. When the lamp power is increased, the maximum outer diameter of the electrode is increased, and the inner diameter of the arc tube narrow tube portion must be increased. Here, in order to make the seal layer thin, it is necessary to increase the outer diameter of the sealing conductive member, and the stress of the seal portion is increased. As a result, a crack in the seal portion is more likely to occur during the sealing process.

  In order to solve such problems, the sealing conductive member is a conductive cermet made of molybdenum and alumina, and the thickness of the thin tube portion, the thickness of the seal layer, and the maximum outer diameter of the sealing conductive member are 3 A technique that suppresses cracks in the seal portion during the arc tube sealing process by optimizing the number of persons is also disclosed (Patent Document 3).

Japanese Patent No. 3246463 JP 2000-353597 A JP 2004-179006 A

  However, the inventors of the present invention describe an arc tube having an electrode assembly in which a tungsten electrode, a molybdenum coil rod, and a conductive cermet rod are joined on the same axis, as described in Patent Document 3, using arc tubes of various design specifications. It was found that even when arc tubes were manufactured according to the numerical values specified, arc tubes that had cracks in the seal portion during the sealing process were present to some extent.

  As a result of failure analysis of the arc tube in which the seal portion crack occurred, it was found that the seal portion crack was caused by a cause different from that assumed in Patent Document 3. That is, Patent Document 3 discusses a sealing layer between a sealing conductive member, for example, a conductive cermet rod and the inner surface of the arc tube capillary, and the seal layer is formed between the arc tube and the sealing conductive member. The optimum range of the seal width is derived in consideration of the role as a buffer for the thermal stress generated between them and the mechanical strength of the seal layer itself. On the other hand, it was found that the position where the molybdenum rod-shaped member is arranged is the starting point of the crack in the seal part crack this time.

  In the arc tube of the same kind as the present invention, in the arc tube sealing step, an electrode assembly in which a tungsten electrode, a molybdenum rod-shaped member, and a sealing conductive member are coaxially joined in series is inserted from the open end of the arc tube thin tube portion. A frit heated and melted is poured into the gap between the sealing conductive member and the narrow tube to hermetically seal it. As the sealing conductive member, it is necessary to use a material having a thermal expansion coefficient close to that of alumina, which is the material of the arc tube narrow tube part, so niobium metal wire or alumina and molybdenum are usually mixed and sintered. Conductive cermet rods are used. Since niobium is susceptible to erosion when it comes into contact with a metal halide sealed in a ceramic metal halide lamp arc tube at high temperature, the frit needs to completely cover niobium during sealing. The normal seal portion is in a state where the molybdenum rod-shaped member and the frit are in direct contact with each other beyond the joint portion with the molybdenum rod-shaped member. Even when a conductive cermet is used as the sealing conductive member, the alumina part of the conductive cermet rod may be eroded depending on the arc tube specifications, so the frit is poured to a position where it directly contacts the molybdenum rod-shaped member. Sometimes. Of course, it is a well-known fact that the seal between the molybdenum rod-shaped member and the frit is prone to generate cracks due to the large difference in the coefficient of thermal expansion. In general, the generation of thermal stress in the inside is reduced as much as possible.

  However, it is difficult to accurately control the amount of frit poured in the sealing process. Even if the arc tube has the same design specifications, the actually produced arc tube can be either a product with a contact length between the molybdenum rod-like member and the frit of 0.5 mm or a product with a length of 1.5 mm. The longer the contact length, the higher the probability of occurrence of a seal crack. Cracks due to thermal stress during the lamp life do not occur in products where the contact length between the molybdenum rod-like member and the frit is about 1.5 mm, but in the sealing process it is cooled from about three times the temperature when the lamp is lit to room temperature. Therefore, the narrow tube portion made of alumina cannot withstand the stress generated during cooling, and defects due to cracks in the seal portion are generated at a ratio that cannot be ignored.

  Furthermore, as a result of many analyzes of defective products in the sealing process, it has been found that the defective rate due to the above cause is almost the same for each arc tube specification. In order to ensure that the crack of the seal portion is zero when the arc tube of the same kind as that of the present invention is used by further study, the ratio between the seal width and the arc tube capillary thickness is a constant value. It turned out that it was necessary to set above. However, when the thickness of the thin tube portion is increased, the heat conduction from the light emitting portion increases, and the heat retention of the light emitting portion decreases. In particular, when trying to realize a high color rendering and high efficiency ceramic metal halide lamp as required by the market in recent years, it is desired to make the wall thickness of the narrow tube portion as small as possible. On the other hand, as disclosed in Patent Document 3, an electrode assembly in which a tungsten electrode, a molybdenum rod-shaped member, and a sealing conductive member are coaxially joined in series is inserted from the open end of the arc tube capillary tube, and the sealing is performed. In a light emitting tube that is hermetically sealed by pouring heated and melted frit into the gap between the conductive member and the narrow tube, if the seal width is reduced without increasing the outer diameter of the narrow tube portion, the sealing conductive member is disposed. The probability of occurrence of a crack at the seal portion at a certain position increases.

  In order to solve the above problems, a light emitting portion and a thin tube portion having an outer diameter smaller than the light emitting portion outer diameter provided at both ends thereof are formed of ceramics, and at least the sealing conductive member and the molybdenum rod-like member are formed in the thin tube portion. In a ceramic metal halide lamp having an arc tube sealed by pouring a heated and melted frit into a gap between the narrow tube portion and the sealing conductive member, The thickness of the portion in contact with the frit may be a ceramic metal halide lamp having an arc tube that is defined to be 10 times or more the maximum seal width at the position where the molybdenum rod-shaped member and the frit are in contact. The maximum seal width is the difference between the inner diameter of the narrow tube portion and the outer diameter of the molybdenum rod-shaped member. In the case of a member whose outer diameter varies depending on the location, such as a molybdenum coil rod, the maximum outer diameter of the molybdenum coil rod is defined as the outer diameter as a molybdenum rod-shaped member.

  Further, as a preferable condition of the present invention, the light emitting portion side end of the thin tube thick portion is 1 mm from the central position of the molybdenum rod member of the electrode assembly to the arc tube side from the junction point of the molybdenum rod member and the sealing conductive member. Set to be in the range up to the position of.

  Further, the maximum outer diameter of the thin tube thick portion is set to be equal to or smaller than the outer diameter of the arc tube, and more preferably less than twice the outer diameter of the thin tube portion on the light emitting portion side.

Ceramic metal halide lamps manufactured with the above specifications do not cause seal cracks during lamp manufacture, and naturally do not generate seal cracks during the life of the lamp, resulting in a long-life lamp. Since the thickness and the outer diameter are the same as the conventional one, it is possible to exhibit the effect of keeping the light-emitting part warm and generating highly efficient color rendering light.

Schematic which shows an example of the ceramic metal halide lamp to which this invention is applied. Schematic which shows an example of the ceramic arc tube to which this invention is applied. The enlarged view which shows an example of the ceramic arc tube to which this invention is applied. The schematic sectional drawing which shows the relationship between the seal width maximum value in a molybdenum rod-shaped member position, and a thin tube part thickness. The figure which shows the relationship between a seal part crack incidence and [thin tube part thickness / seal width maximum value]. The figure which shows the relationship between a thin tube thick part edge part position and an average color rendering index.

  In order to carry out the present invention, an arc tube main body and thin tube portions having an outer diameter smaller than the outer diameter of the arc tube main body provided at both ends thereof are formed of ceramics, and at least the sealing conductive member and molybdenum are formed in the thin tube portion. An electrode assembly comprising a rod-shaped member and an electrode is inserted, and in the ceramic metal halide lamp having an arc tube sealed by pouring heated and melted frit into a gap between the thin tube portion and the sealing conductive member, the thin tube portion The thickness of the portion in contact with the frit is at least 10 times the maximum seal width at the position where the molybdenum rod-shaped member and the frit are in contact. Since the arc tube design determines where the frit flows into the narrow tube part, when designing the shape of the ceramic envelope in advance, the thickness and length of the thin tube thick part should be taken into account. Can be decided. Naturally, it is necessary to set a dimension having a margin with respect to the assumed maximum value in consideration of the variation in the outer diameter of the molybdenum rod-shaped member and the variation in the frit flow amount.

  When the length of the thin tube thick portion is defined from another point of view, the light emitting portion side end of the thin tube thick portion is located from the central position of the molybdenum rod-shaped member in a state where the electrode assembly is disposed when the arc tube is completed. It suffices if it is located in a range from the junction point of the molybdenum rod-shaped member and the sealing conductive member to a position on the 1 mm arc tube side. When the thin tube thick portion continues from the central position of the molybdenum rod-shaped member to the light emitting portion side, the heat transfer rate from the light emitting portion to the end of the thin tube portion increases, and the amount of evaporation of the light emitting substance enclosed in the light emitting portion Reduces the luminescent properties.

  An example of a ceramic metal halide lamp to which the present invention is applied is shown in FIG. FIG. 2 shows an enlarged view of the arc tube portion in the same lamp as FIG. Further, FIG. 3 shows a positional relationship between the arc tube thin tube portion and the electrode assembly sealed and fixed to the thin tube portion. 4 is a cross-sectional view perpendicular to the major axis of the arc tube at the position where the molybdenum coil rod 104 and the frit 106 are in contact with each other in FIG.

  An arc tube 101 is provided at the approximate center of the lamp, and a translucent sleeve 108 is fixed to a metal frame 109 via a translucent sleeve fixing plate around the arc tube 101. The frame 109 is fixed in position in the translucent outer tube 111 by connecting to the mounting support plate 114 and the introduction line of the stem 115. The frame 109 is a member for fixing the position, and also serves as a member for electrical connection. Power from an external power supply system (not shown) is supplied to the external lead 107 of the arc tube via the lead 112 and the introduction line of the stem 115. I tell you.

  A pair of electrode assemblies 120 are inserted into the narrow tube portions 101b at both ends of the arc tube as members for supplying power to the inside of the arc tube. Each electrode assembly 120 includes a tungsten electrode 103, a molybdenum coil rod 104 as a molybdenum rod-shaped member, and a conductive cermet rod 105 as a sealing conductive member. Between the conductive cermet rod 105 and the arc tube capillary 101b, A frit 106 is poured and hermetically sealed. The frit 106 is poured into the light emitting portion side by about 1 mm from the connection portion between the conductive cermet 105 and the molybdenum coil rod 104.

  As a constituent member of the electrode assembly that can be used in the present invention, a molybdenum rod-like member includes a molybdenum pipe, a molybdenum wire, and a conductive cermet rod in addition to the molybdenum coil rod, and a sealing conductive member. In addition to the conductive cermet rod, niobium wire and tantalum wire are known.

  The thin tube portion 101b is a thin tube thick portion 101c in a region where the inner wall surface is in contact with the frit 106. The thin tube thick portion 101c has the same inner diameter as the other portions of the thin tube portion, but the outer diameter is larger than the other portions, and is 11 times as thick as the maximum seal width (tf) shown in FIG. (Tc) is secured.

  In the case of a ceramic metal halide lamp with an internal starter, an internal starter circuit including the starter 110 can be incorporated into the frame 109. Further, in the case of a lamp specification in which the temperature of the arc tube 101 needs to be kept relatively high, the inside of the translucent outer tube 111 is evacuated and then the getter 113 is activated to keep the arc tube warm by vacuum insulation. .

Inside the arc tube 101, a predetermined amount of holmium iodide, thulium iodide, dysprosium iodide, sodium iodide, thallium iodide, and cesium iodide is sealed as the luminescent material 102, and discharge in the arc tube is started. However, mercury and Ar gas are enclosed for maintenance. The structure of the arc tube 101 itself is not particularly different from that of a known ceramic metal halide lamp, and light having a continuous wavelength including ultraviolet rays and infrared rays centering on visible light is emitted from the arc tube at the time of lighting.

  When a lamp having such an arc tube is turned on vertically with the base 112 facing upward, the luminescent substance 102 is heated by the discharge in the arc tube, and part of the light is evaporated and excited by the discharge to emit light. The remaining part of the luminescent material 102 is pooled in the coldest part in the arc tube in a liquid phase state, and after a part of it is evaporated, the cycle of returning to the coldest part by convection in the arc tube is repeated.

  When the lamp is lit vertically, the end of the arc tube light emitting part is the coldest part. In the vicinity of this, there is a connecting portion between the tungsten electrode 103 and the molybdenum coil rod 104, and 90% or more of the luminescent encapsulating material in the liquid phase stays here. A few percent of the luminescent material enters the gap between the molybdenum coil rod and the arc tube narrow tube portion, but almost no luminescent material 102 penetrates to the position of the conductive cermet rod 105.

  On the other hand, the heat generated by the light emitting unit 101a is radiated from the light emitting unit in the form of infrared rays or the like, or is conducted to the narrow tube unit 101b and is radiated from the surface of the narrow tube unit as radiant heat. To go. Therefore, the thickness of the thin tube portion 101b affects the light emission state of the arc tube. In general, the larger the outer diameter of the narrow tube portion and the thicker the wall, the greater the mechanical strength and the less likely it will be to crack or break, but it will escape to the end of the arc tube because the cross-sectional area of the narrow tube portion will increase. The heat flow rate is also increased, and the temperature of the light emitting portion is lowered, so that desired light emission characteristics are not achieved.

  FIG. 5 shows the results of examining the rate of occurrence of seal cracks in the sealing process for various types of arc tubes from 40W to 400W. Different marker shapes have different lamp power, and there are two or three types of arc tube specifications for each lamp power. Data for thousands of each type are compiled. When organized by “thin tube portion / maximum seal width value” (tc / tf shown in FIG. 4), even if the arc tube has a different lamp power, there is no difference depending on the lamp power, and the value of tc / tf is The smaller the smaller, the greater the occurrence rate of the seal portion crack, and no seal portion crack occurred in the arc tube having a value of tc / tf of 10 or more.

  From the results shown in FIG. 5, for example, in the case of an arc tube having a dimensional difference of 0.2 mm between the inner diameter of the thin tube portion and the maximum outer diameter of the molybdenum coil rod, cracks in the seal portion can be prevented if the thickness of the thin tube portion is 2 mm or more. I understand. However, since the heat flux that escapes to the end of the light-emitting tube increases in proportion to the cross-sectional area of the thin-tube portion connected to the light-emitting portion as described above, the cross-sectional area of the thin-tube portion near the light-emitting portion cannot be increased.

  For the arc tube 101 having the configuration shown in FIG. 3 as shown in FIG. 6, an arc tube in which the light emitting portion side end position of the thin tube thick portion 101c is set to the positions 1 to 6 in FIG. The results are shown when the light emission characteristics are measured by assembling the lamp as shown in FIG. The thin tube thickness of the thin tube thick portion 101c was 2 mm, and the thickness of the other thin tube portion 101b was 1 mm. In FIG. 3, the prototype corresponding to number 1 has a thin tube portion thickness of 2 mm continuously to the light emitting portion 101a, and the prototype corresponding to number 3 is the thin tube thick portion within the scope of the present invention. The long one, the prototype corresponding to the number 4 has the shortest thin tube portion within the scope of the present invention, and the prototype corresponding to the number 6 has no thin tube thick portion and has a thickness of 1 mm over the entire length of the thin tube portion. It is the same as the prior art. In addition, 5 data was measured for each specification.

  As is apparent from the results shown in FIG. 6, the light emission characteristics represented by the average color rendering index Ra of the lamp are the prototype No. 3, that is, the light emitting part side end of the thin tube thick part 101c is the molybdenum coil rod 104. If it is in the center position, the same characteristics as conventional products can be obtained. In this way, if the cross-sectional area of the narrow tube portion 101b connected to the light emitting portion 101a is small, the heat flux escaping from the light emitting portion to the end of the thin tube becomes small, and then the cross-sectional area of the thin tube portion at a lower temperature than the light emitting portion side. Even if is increased, the influence on the light emission characteristics of the lamp is small.

As described above, the thickness of the thin tube portion in the thin tube thick portion 101c is set to 10 times or more of the maximum seal width tf at the position where the molybdenum coil rod 104 and the frit 106 are in contact with each other at the time of manufacturing the arc tube. In this sealing step, an arc tube that does not cause cracks in the seal portion can be obtained, but according to requirements other than suppression of cracks in the seal portion, the outer diameter of the thin tube thick portion should not be so large. For example, considering the light distribution when assembled as a lamp, it is necessary to make the outer diameter of the thin tube thick portion smaller than the maximum diameter of the light emitting portion. Furthermore, as a practical condition, it is preferable that the outer diameter of the thin tube portion 101c is not more than twice the outer diameter of the thin tube portion 101b when good light emission characteristics are obtained.

The present invention provides a ceramic metal halide lamp that does not cause cracks in the seal portion during the arc tube sealing process while ensuring high efficiency and high color rendering properties equivalent to those of conventional products.

DESCRIPTION OF SYMBOLS 101 Light emission tube 101a Light emission part 101b Thin tube part 101c Thin tube thick part 102 Luminescent substance 103 Tungsten electrode 104 Molybdenum coil rod 105 Conductive cermet rod 106 Frit

Claims (4)

An arc tube main body and a thin tube portion having an outer diameter smaller than the outer diameter of the arc tube main body provided at both ends thereof are formed of ceramics, and an electrode assembly including at least a sealing conductive member, a molybdenum rod-shaped member, and an electrode is formed on the thin tube portion. In a ceramic metal halide lamp having an arc tube that is inserted and sealed by pouring a frit heated and melted into a gap between the narrow tube portion and the sealing conductive member,
A ceramic metal halide lamp characterized in that a thickness of a portion of the thin tube portion in contact with the frit is 10 times or more a maximum seal width at a position where the molybdenum rod-shaped member and the frit are in contact. In the ceramic metal halide lamp according to claim 1,
The light emitting portion side end portion of the thin tube thick portion is located in a range from the central position of the molybdenum rod-shaped member of the electrode assembly to the position on the 1 mm arc tube side from the junction point of the molybdenum rod-shaped member and the sealing conductive member. This is a ceramic metal halide lamp. In the ceramic metal halide lamp according to claim 1 or 2,
The ceramic metal halide lamp according to claim 1, wherein a maximum outer diameter of the thin tube thick portion is equal to or less than an outer diameter of the arc tube. In the ceramic metal halide lamp according to claim 1 or 2,
The ceramic metal halide lamp according to claim 1, wherein a maximum outer diameter of the thin tube thick portion is not more than twice a light emitting portion side outer diameter of the thin tube portion.

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