Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/30—Vessels; Containers
  • H01J61/34—Double-wall vessels or containers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/02—Details
  • H01J61/12—Selection of substances for gas fillings; Specified operating pressure or temperature
  • H01J61/125—Selection of substances for gas fillings; Specified operating pressure or temperature having an halogenide as principal component
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J61/00—Gas-discharge or vapour-discharge lamps
  • H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
  • H01J61/827—Metal halide arc lamps

Definitions

• the present invention relates to a metal halide lamp and a luminaire.
• the arc tube has an elongated shape ⁇ L/D > 5, when the internal diameter of the arc tube is D and the length of the space (i.e. distance) between the electrodes is L) , and cerium iodide (Cel 3 ) and sodium iodide (Nal) are enclosed therein. It is said that this ceramic metal halide lamp is capable of achieving extremely high luminous efficiency of 111 lm/W - 177 Im/ .
• an arc tube is housed in, for example, a hard-glass outer tube.
• a quartz-glass sleeve is placed between the outer tube and the arc tube so as to surround the arc tube.
• the sleeve is provided in order to protect the outer tube from being damaged by broken pieces in the case of rupture of the arc tube (see, e.g. Japanese Laid-Open Patent Application Publication No.H05-258724) .
• some conventional metal halide lamps have a structure with no sleeve.
• fluorocarbon resin coating is applied to the outer tube in order to prevent the outer tube breakage.
• these conventional metal halide lamps are necessarily used with a luminaire equipped with a front glass so that, in the case of breakage of the outer tube, the broken pieces would not fly off, and thus they are never used with a luminaire having no such a frontal shield facing the floor.
• the present inventors found traces that, in the burnt-out lamps, the internal surface of the arc tube intensely reacted with the metal halides enclosed in the arc tube. Accordingly, the rise in lamp voltage is thought to be attributable to a significant increase in liberated halides in the arc tube as a result of the reaction between the metal halides and the ceramic forming the envelope of the arc tube. Then, the cause of the intensive reaction between the metal halides and the ceramic was examined, and the following was found.
• the ceramic was used to form the envelope because it is a material that is supposed to withstand use at a high temperature.
• the arc tube was made in an elongated shape (e.g.
• the fluorocarbon resin coating has limits in its heat resistance, and therefore cannot be applied to all lamps.
• the outer tube may possibly break as a result of the arc tube rupture as described above. This was considered to cause a restriction on the applicability of the metal halide lamp to luminaires.
• the present invention aims at providing a metal halide lamp and a luminaire using the same, bothhaving a configurationto achieve the following goals : (i) toprevent themetal halide lamp fromburning out due to a rise in lamp voltage during the rated life, and at thesametime (ii) toobtainhighluminous efficiencyandcompactness.
• the metal halide lamp of the present invention comprises: an arc tube made of translucent ceramic and having a main tube part in which a pair of electrodes are disposed; and an outer tube housing the arc tube therein.
• L is a length of a space between the electrodes and D is an internal diameter of the main tube part.
• M M ⁇ 4.0, where M (mg/cc) is a density of mercury enclosed in the arc tube.
• the "internal diameter” phrased in this specification means an average internal diameter of, in the main tube part, a portion across the region positionally corresponding to the space between the electrodes.
• the "region positionally corresponding to, in a radial direction of the outer tube and the arc tube, the space between the electrodes” means a region sandwiched by two imaginary planes . Each of the imaginary planes lies at a tip of one of the electrodes, and is perpendicular to a central axis in a longitudinal direction of the electrode.
• R/r may be at 7.0 or smaller.
• the above configuration facilitates the maintenance of the discharge while obtaining high luminous efficiency.
• a sodium halide and at least one of a ceriumhalide and a praseodymiumhalide maybe enclosed in the arc tube.
• a sodium (Na) halide and at least one of a cerium (Ce) halide and a praseodymium (Pr) halide are enclosed in the arc tube in order to obtain higher luminous efficiency
• the arc tube is adequately kept heated and therefore the vapor pressures of the enclosedmetals were maintained at high levels without any downturns.
• a degree of vacuum inside the outer tube may be no more than lxlO 3 Pa at 300 K.
• the luminaire of the present invention comprises: a metal halide lamp recited in one of Claims 1 to 7 of the present invention; and a lighting circuit for illuminating the metal halide lamp. According to the above configuration, the occurrence of burnt-out lamps during the rated life due to a lamp voltage rise can be prevented while high luminous efficiency is obtained.
• FIG. 1 is a front view of a metal halide lamp according to a first embodiment of the present invention, with a part cut away to reveal the internal arrangements
• FIG. 2 is a front cross-sectional view of an arc tube used in the metal halide lamp
• FIG. 3 shows results of experiments conducted in order to determine the operational effectiveness of the metal halide lamp
• FIG.4 shows results of another experiment conducted in order to determine the operational effectiveness of the metal halide lamp
• FIG. 5 is a front view of a metal halide lamp whose outer tube has a different shape
• FIG. 6 is a front view of a metal halide lamp whose arc tube has a different shape, with a part cut away to reveal the internal arrangements
• FIG. 7 is a schematic diagram of a luminaire according to a second embodiment of the present invention.
• FIG.1 shows a metal halide lamp (a ceramic metal halide lamp) 1 according to a first embodiment of the present invention.
• the metal halide lamp 1 with rated lamp wattage of 150 W has an overall length T of 160 mm - 200 mm (e.g. 180 mm) .
• the metal halide lamp 1 comprises an outer tube 3, an arc tube 4, and a base 5.
• the outer tube 3 is cylindrical, and an end of the outer tube 3 is closed and round in shape while the other end is closed by fixing a stem tube 2 thereto.
• the arc tube 4 is made of translucent ceramic such as polycrystalline alumina, and disposed in the outer tube 3.
• the base 5 is a screw base (Edison screw base) , and fixed to the outer tube 3 at the end on the stem tube 2 side. Note that the central axis in the longitudinal direction of the arc tube 4 substantially coincides with the central axis Y in the longitudinal direction of the outer tube 3.
• the outer tube 3 is made of, for example, hard glass.
• a wall thickness ti of the outer tube 3 should be determined so as to provide strength to withstand an external shock incurred during replacement of the lamp and transportation. Yet, the wall thickness ti should be limited to the degree that does not leadtohighproduction costs andan excessive increase in weight of the lamp. In view of these conditions, it is desirable the wall thickness t of the outer tube 3 be determined case by case within the range of, for example, 0.6 mm - 1.2 mm.
• the inside of the outer tube 3 is kept in vacuum at a pressure of lxlO 3 Pa or lower (e.g. IxlO "2 Pa) at 300 K.
• one or more getters are provided at appropriate locations in order to maintain the high vacuum condition during the life.
• Two stem wires 7 and 8 are single metal wires, each formed by joining together a plurality of metal wires made of different materials. A part of each the stem wires 7 and 8 is fixed onto the stem tube 2. One ends of the respective stem wires 7 and 8 are led into the inside of the outer tube 3, while the other ends are led out from the outer tube 3. The one end of the stem wire 7 is electrically connected, via an electric power supply wire 9, to an external lead wire 10, which is one of two external lead wires 10 and 11 (to be hereinafter described) of the arc tube 3. The one endofthe other stemwire 8 is directlyandelectricallyconnected to the other external lead wire 11.
• the arc tube 4 is composed of a main tube part 6 and two cylindrical thin tube parts 16. Within the main tube part 6, a discharge space 15 is formed and a pair of electrodes 14 is placed substantially opposite one another on the approximately same axis Z. Each of the thin tube parts 16 is formed on each end of the main tube part 6. In the example shown in FIG. 2, the main tube part 6 and thin tube parts 16, making up the ceramic envelope of the arc tube 4, are integrally formed in one piece with no joints.
• the main tube part and thin tube parts may be made of different materials and joined each other by shrink-fit process, and an envelope formed by this means can be used instead.
• the materials used to form the envelope of the arc tube 4 other kinds of translucent ceramics, such as yttrium aluminum garnet (YAG) , aluminum nitride, yttria, and zirconia, can be used besides polycrystalline alumina.
• the main tube part 6 is made up of a circular cylinder 17 and two rounded portions 18. Each of the rounded portions 18 is formed on each end of the circular cylinder 17.
• the circular cylinder 17 has: an external diameter r ranging, e.g., 5.0 mm - 12.8 mm; an internal diameter D ranging, e.g., 3 mm - 10 mm; and a wall thickness t ⁇ ranging, e.g., 1.0 mm - 1.4 mm. Each of these dimensions is determined case by case within the above range. In the example depicted in FIGs.
• the central axis in the longitudinal direction of the outer tube 3 and that of the arc tube 4 substantially coincide with each other, and both the outer tube 3 and the main tube part 6 of the arc tube 4 are cylindrical . Therefore, where the outer circumference of the main tube part 6 comes closest to the inner circumference of the outer tube 3 corresponds, in this case, to the entire circular cylinder 17.
• the electrode lead-in units 19 are fixed by glass frit 20 poured from the other ends of the thin tube parts 16 (each located further from the main tube part 6) into the space left between the inside of the thin tube parts 16 and the electrode lead-in units 19 inserted therein.
• Each of the electrodes 14 has a tungsten electrode shaft 21, and a tungsten electrode coil 22 mounted on the tip of the electrode shaft 21.
• the electrode shaft 21 is 0.5 mm in external diameter and 16.5 mm in length.
• a length L of the space between the electrodes 14 is set so as to satisfy a relational expression of L/D ⁇ 4. For instance, when the internal diameter D of the arc tube 4 is set within the range of 3 mm - 10 mm, the length L is determined case by case within the range of 12 mm - 40 mm.
• the electrode lead-in units 19 are each composed of: a conductive cermet 23; an external lead wire 10 or 11 made of, e.g. , niobium; and a molybdenum coil 24.
• the conductive cermet 23 has an external diameter of 0.92 mmand a length of 18.3mm.
• the electrode shaft 21 is connected to one end of the conductive cermet 23, and the other end is led to the outside of the thin tube part 16.
• One end of the external lead wire 10 or 11 is electrically connected to either the stem wire 8 or the electric power supply wire 9.
• the coil 24 is wound around the middle portion of the conductive cermet 23.
• the conductive cermet 23 is made by mixing metallic powder and ceramic powder and sintering the mixture.
• the metallic powder is made, e.g., of molybdenum while the ceramic powder, e.g., alumina.
• the coil 23 is 7.0xl0 ⁇ 6 (/°C), which is substantially equal to the thermal expansion coefficient of the ceramic forming the envelope of the arc tube 4.
• the coil 24 is provided in order to substantially fill spaces left between the thin tube part 16 and the conductive cermet 23 and make it harder for the metal halides enclosed in the arc tube 4 to seep out into the spaces.
• the electrode lead-in unit 19 used here comprising the external lead wire 10 or 11, the conductive cermet 23, and the coil 24, is merely an example, and various publicly known electrode lead-in units can be used instead.
• metal halides, mercury, and a rare gas are enclosed in the arc tube 4.
• the enclosedmetal halides are composedof a sodium (Na) halide and at least either one of a cerium (Ce) halide and a praseodymium (Pr) halide.
• publicly known metal halides may be enclosed instead of the above metal halides, or may be added together with the above metal halides.
• the mercury to be enclosed can take either form of an elemental mercury or a mercury compound. The mercury is enclosed so as to satisfy a relational expression of M ⁇ 4.0, where Mis the density of mercury enclosed in the arc tube 4.
• the density M (mg/cc) here is defined as the mass of the mercury divided by the inner volume of the arc tube 4.
• the density M can be 0 mg/cc, except for mercury that will be inevitably mixed in.
• the rare gas for example, a pure argon gas, a pure xenon gas, or a mix of these is enclosed.
• the amount of the rare gas to be enclosed is set appropriately case by case within the range of 10 kPa - 50 kPa regardless of the constituent materials and their ratio. The following explains experiments conducted in order to determine the operational effectiveness of the metal halide lamp 1. 1 . 1 R/r and Density M of Mercury The lamp' s operational effectiveness in terms of R/r and the density M of mercury enclosed in the arc tube 4 was examined.
• a plurality of the above metal halide lamps 1 were prepared as follows .
• Five different categories were set up on the basis of R/r. Specifically speaking, these categories were created by variously changing the internal diameter R of the outer tube 3 with 20 mm, 22 mm, 30mm, 45 mm, and 50 mm, while setting the external diameter r of the main tube part 6 at a constant of 6.4 mm.
• the internal diameter R is a measurement obtained, within the region sandwiched by the two imaginary planes, on a cross-sectional surface where the outer circumference of the arc tube 4 comes closest to the inner circumference of the outer tube 3.
• various classes were set up by changing the density M of enclosed mercury.
• these classes were set up by changing the inner volume of the arc tube 4 in stages, ranging from 0.2 cc to 1.0 cc as well as changing the amount of enclosed mercury in stages, ranging from 0.5 mg to 2.0 mg.
• Ten lamps were made for each class. With five out of the ten lamps for each class, the color temperature at the beginning stage of lighting (i.e. approximately after a 100-hour lighting period) and a rise in lamp voltage (V) from the beginning stage to the end of a 9000-hour lighting period were examined. Each lamp was lit, with the central axis of the lamp being horizontal, using a lighting circuit (for instance, one having a publicly known electronic ballast) . The results of the examination are shown in FIG. 3.
• Values in "VARIATION OF COLOR TEMPERATURE" are obtained by subtracting the minimum from the maximum.
• FIG. 3 when a relational expression of R/r > 3.4 was satisfied, i.e. lamps of all Classes from E to T, a rise in lamp voltage from the beginning stage to the end of a 9000-hour lighting period was suppressed to 27 V or lower, and the occurrence of burnt-out lamps due to the rise in lamp voltage was not observed in these classes.
• a relational expression of R/r ⁇ 3.4 i.e. lamps of all Classes from A to D, the rise in lamp voltage became 35 V or higher. It was observed that some of the lamps in these classes burned out due to the lamp voltage rise.
• the gas pressure within the lamp is reduced when the density Mof mercury is 4.0 mg/cc or lower, or namely when the amount of the enclosed mercury is reduced. Then, the lamp voltage and the lamp power decrease accordingly, which in turn could result in a reduction in the vapor pressures of the enclosed metals.
• individual lamps have different degrees of variation in lamp power, which naturally leads to variation in the vapor pressures of the enclosed metals . Therefore, the present inventors expected that the color temperature would consequently vary.
• the present invention is capable of preventing the occurrence of burnt-out lamps caused by a rise in lamp voltage during the life. This is because the metal halide lamp 1 also satisfies relational expressions of 3.4 ⁇ R/r ⁇ 7.0 and M ⁇ 4.0.
• the present invention allows for obtaining desired characteristics in the color temperature at the beginning stage of lighting, and further suppresses variations in color temperature among individual lamps. Since the amount of mercury enclosed in the arc tube 4 is reduced, the amount of ultraviolet emitted from the metal halide lamp 1 is cut down, which in turn leads to reducing the effects on the environment.
• thepresent invention is capable ofpreventing, without using a sleeve and such, the breakage of the outer tube 3 caused by the arc tube 4 rupture. Additionally, since the metal halide lamp 1 of the present invention does not require a sleeve, the cost ofmaterials for the sleeve as well as formembers supporting the sleeve in the lamp can be eliminated, and this further leads to a reduction in operation cost. Thus, low-cost production can be realized. Furthermore, because there is no sleeve intercepting light emitted from the arc tube 4 , a decrease in the total luminous flux of the lamp as well as a degradation of the luminous intensity distribution characteristics can be prevented.
• the present invention is free from the problem of the occurrence of defective productions due to the sleeve breakage during transportation of the lamps .
• the present invention achieves a lighter and smaller metal halide lamp. This results in an improvement of the impact resistance of the metal halide lamp.
• the degree of vacuum inside the outer tube 3 be IxlO 3 Pa or lower at 300 K.
• the heat of the arc tube 4 is transferred to the outer tube 3 through the gas enclosed in the outer tube 3 and then released to the outside of the metal halide lamp 1. This, in turn, prevents a decrease in luminous efficiency.
• the heat of the arc tube 4 is transferred to the outer tube 3 through the gas and released to the outside, and consequently the luminous efficiency may possibly decrease.
• the outer tube 3 is cylindrical, however, the present invention is not confined to this shape.
• the same operational effectiveness can be accomplished with, for example, a teardrop-shaped outer tube 3a having a bulging portion as shown in FIG. 5.
• the first embodiment above describes the case in which the arc tube 4 has a cylindrical main tube part 6, however, the present invention is not confined to this.
• FIG. 7 shows a luminaire 25 according to a second embodiment of the present invention.
• the luminaire 25 is used, for instance, for ceiling lighting, and comprises a main lighting body 30, the metalhalide lamp 1 (ratedlampwattage: 150W) ofthe first embodiment, and a lighting circuit 31.
• the main lighting body 30 is composed of a reflector 27, a base unit 28, and a socket 29.
• the reflector 27 has an umbrella shape, and is set in a ceiling 26.
• the base unit 28 has a plate-like shape, and is attached to the bottom plane of the reflector 27.
• the socket 29 is placed on this bottom plane within the reflector 27.
• the metal halide lamp 1 is attached to the socket 29 in a manner that the central axis Y substantially coincides with the central axis W of the reflector 27.
• the lighting circuit 31 is placed, on the base unit 28, at a position apart from the reflector 27. Note that a shape and such of a reflection surface 32 of the reflector 27 are determined case by case in view of the applications and use conditions of the luminaire 25. Although, in the example depicted in FIG. 7, there is no front glass set in front of the reflector 27, such a front glass may be employed according to the uses.
• the lighting circuit 31 uses a publicly known electronic ballast. Here, the use of a commonly-usedmagnetic ballast, instead of the electronic ballast, is not appropriate. As described above, a reduction in the amount of the enclosed mercury leads to a decrease in the lamp voltage, which, in turn, could lead to a decrease in the lamp power.
• the lamp power is more susceptible to the influence of the decrease in the lamp voltage, and tends to decrease more readily. Besides, a degree of variation in lamp power is different from lamp to lamp. As a result, the vapor pressures of the metals enclosed in the arc tube (not shown) may vary among the lamps, which may lead to variations in color temperature .
• the lamp electric power is kept at constant in a vast range of voltage.
• the temperature of the arc tube is controlled to be constant and the vapor pressures of the enclosed metals are stabilized. This further prevents variations in color temperature among individual lamps.
• the configuration of the luminaire 25 according to the second embodiment prevents the occurrence of burnt-out lamps due to a rise in lamp voltage during the life while obtaining high luminous efficiency since the metal halide lamp 1 of the first embodiment above is used.
• this configuration allows for obtaining desired characteristics in the color temperature at the beginning state of lighting and suppressing variations in color temperature among individual luminaires.
• the luminaires are capable of making the entire space having a unified color temperature . Since the amount ofmercuryenclosed inthe arctube is reduced, the amount of ultraviolet emitted from the lamp 1 is cut down.
• the luminaire 25 of the present invention uses the metal halide lamp 1, which does not require a sleeve. Therefore, the cost of materials for the sleeve as well as members supporting the sleeve in the metal halide lamp 1 can be eliminated, and this leads to a reduction in operation cost. Thus, low-cost production can be realized. Furthermore, because there is no sleeve intercepting light emitted from the arc tube, a decrease in the total luminous flux of themetal halide lamp 1 as well as a degradation of the luminous intensity distribution characteristics can be prevented.
• the second embodiment exemplifies a case in which the luminaire 25 is used for ceiling lighting.
• the present invention is not confined to this use, and can also be applied to othertypes of interior lighting, store lighting, and street lighting.
• the luminaire 25 of the present invention can adopt avarietyofpublicly knownmainlightingbodies andlighting circuits according to the uses.
• the metal halide lamp and the luminaire of the present invention are applicable to situations where it is necessary to prevent the occurrence of burnt-out lamp during the life due to a rise in lamp voltage as well as to obtain high luminous efficiency at the same time.

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• Vessels And Coating Films For Discharge Lamps (AREA)
• Discharge Lamps And Accessories Thereof (AREA)
• Discharge Lamp (AREA)

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• 2003
  • 2003-12-22 JP JP2003424169A patent/JP4832717B2/ja not_active Expired - Lifetime
• 2004
  • 2004-12-20 WO PCT/JP2004/019478 patent/WO2005062341A2/en not_active Ceased
  • 2004-12-20 DE DE602004025286T patent/DE602004025286D1/de not_active Expired - Lifetime
  • 2004-12-20 CN CN200480038412A patent/CN100583381C/zh not_active Expired - Fee Related
  • 2004-12-20 EP EP04807833A patent/EP1709667B1/en not_active Expired - Lifetime
  • 2004-12-20 US US10/582,844 patent/US7348730B2/en not_active Expired - Fee Related

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