JP2006093046A - High-pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-pressure discharge lamp satisfying light emission characteristics, such as light distribution, when a completed discharge lamp is combined with a reflecting mirror of a car or the like, by constituting an arc tube discharge container with a material in which the average linear transmittance of ceramic material for a container body part and an end cap part, blocking an end part of the body part, is selected. <P>SOLUTION: The high pressure discharge lamp L1 is equipped with a discharge container 10, in which end caps 2A, 2A made of polycrystalline alumina having an average linear transmittance of T<SB>2</SB>%, having a small diameter cylindrical part 3 to which an electrode structure is fixed are airtightly jointed to both ends of a cylindrical vessel body 11 made of polycrystalline alumina, having an average linear transmittance of T<SB>1</SB>% in a visible light region to form a discharge space on the inside, the relation between the average linear transmittances T<SB>1</SB>, T<SB>2</SB>satisfies the condition T<SB>1</SB>≥15%>T<SB>2</SB>, an arc tube 1A having a discharge medium containing a metal halide and starting gas sealed in the discharge vessel 10, and an outer tube 5 with the arc tube 1A arranged along the tube axis on the inside, and closed airtightly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-pressure discharge lamp used for a vehicle headlamp or the like in which a metal halide is enclosed in an arc tube composed of a discharge vessel made of polycrystalline alumina, which is a translucent ceramic.

  High-pressure discharge lamps, such as metal halide lamps, are widely used as light sources for optical equipment such as overhead projectors and liquid crystal projectors, as well as lighting for buildings, roads, plazas, and stadiums, as well as stores and vehicles. Has been.

  A metal halide lamp is a discharge lamp in which a discharge medium composed of an electrode structure and a metal halide, mercury, and a rare gas is enclosed in an arc tube, and utilizes emission light of a spectrum line of encapsulated metal atoms and a molecular spectrum of metal halide. Thus, the lamp can obtain higher luminous efficiency, correlated color temperature, and color rendering than a mercury lamp.

  This metal halide lamp is a light emitting metal, such as Na, In, Tl, Li, Cs, or rare earth metals such as Dy, Ho, Tm, Sc, Nd, Ce as halides such as iodine and bromine. If necessary, Hg is enclosed in the arc tube container together with the chemical compound, and is lit with high luminous efficiency or desired lamp characteristics.

  Recently, the use of metal halide lamps has been expanded, and the lighting directions of arc tubes have been diversified. For example, when used for automobile headlamps, etc., since the light emission tube is turned on in the horizontal direction, the arc generated between the electrodes arranged opposite to each other in the discharge space is horizontal due to the convection phenomenon. It has a curved shape with a raised center, leading to a rise in temperature at the center of the arc tube container, causing significant changes in lamp characteristics, resulting in decreased efficiency and uneven color on the irradiated surface, lamp extinction, short life, etc. In some cases, this could cause problems.

  For this reason, a miniaturized discharge vessel for an arc tube has been developed that is made of a material made of a light-transmitting ceramic that has less reaction with the metal halide than quartz glass and has excellent corrosion resistance and heat resistance.

  For example, Patent Document 1 discloses an arc tube (light-emitting tube) for an automobile headlamp in which a halide as a light-emitting metal is enclosed in a light-emitting tube made of a light-transmitting ceramic container with a small diameter and a reduced size.

  According to Patent Document 1, first, even if the arc tube is made compact by regulating the ratio between the outer diameter and the total length of the arc tube made of translucent ceramics, it is desirable without thermal deformation or thermal deterioration. It is described that the luminous flux of can be obtained.

  Secondly, the linear transmittance and the total luminous flux transmittance of the translucent ceramic forming the arc tube are regulated. That is, by making the arc tube container milky white with a linear transmittance of 20% or less and a total light transmittance of 85% or more, the light emitted from the arc tube is diffused and the entire tube emits light relatively uniformly. It is described that a light-emitting portion that does not generate unevenness in brightness or color can be formed.

  However, as described above, when the arc tube container has a linear transmittance of 20% or less and is milky white, there is an advantage that the entire arc tube can emit light uniformly, but the light emitting part becomes large and the point light source becomes large. May not be acceptable.

  In particular, reflecting mirrors such as automotive headlamps are designed to obtain optimal light distribution characteristics by arranging and lighting a light emitting part at a focal position or the like, so if this light emitting part is too large Since light is emitted from a region other than the focal point, desired light distribution characteristics cannot be obtained, and optical design may be very difficult.

  In this type of headlamp, for example, the low-pass beam has severe restrictions (standards) on the light irradiation above the horizon and toward the opposite lane, and if the light emitting part is large, a complicated reflector, front lens, etc. Optical design must be performed, and light leakage in an undesired direction may occur, which makes it difficult to reliably obtain a desired light distribution characteristic.

  Further, Patent Document 2 discloses a metal halide lamp using an arc tube container made of translucent ceramic mainly composed of polycrystalline YAG having an average linear transmittance of 60 to 85%. That is, by setting the average linear transmittance at the center of the arc tube container to 60 to 85%, the light collection rate is increased to prevent unevenness in the illuminance of the irradiated light, and the change over time in the emission spectrum of the lamp is suppressed. It is a lamp.

  However, the arc tube container shown in Patent Document 2 is formed by integrally forming a small-diameter cylindrical portion at both ends of a substantially spherical body in which the center of the arc tube bulges. The electrode assembly is directly joined via an alumina sleeve.

  Therefore, the surface treatment for setting the linear transmittance to 60 to 85% is very complicated, and there are problems in economical efficiency and mass productivity.

In addition, a discharge vessel in which a small-diameter cylindrical portion is integrally formed as in the metal halide lamp of Patent Document 2 has a high linear transmittance in the arc tube axial direction, so light emission in the same direction cannot be ignored, and for automobiles. In the case of a lamp, it is not preferable.
JP 2004-103461 A (paragraph [0025] column) JP-A-10-255719

  In the present invention, when the above-mentioned arc tube container is formed of a milky white ceramic material having high heat resistance and corrosion resistance, the light diffusibility becomes high and light emission characteristics such as severe light distribution for automobiles cannot be satisfied, This is to cope with the improvement of productivity by easily polishing the inner surface of the discharge vessel in order to increase the average linear transmittance.

  That is, the arc tube discharge vessel is configured by selecting the average linear transmittance of each ceramic material of the vessel body portion and the end cap portion that closes the end portion of the body, and configuring the arc tube discharge vessel. An object of the present invention is to provide a high-pressure discharge lamp that can satisfy light emission characteristics such as a light distribution when used in combination with a reflector such as the above.

The high-pressure discharge lamp according to the first aspect of the invention has an average having a small-diameter cylindrical portion in which an electrode assembly is fixed to both ends of a cylindrical container body made of polycrystalline alumina having an average linear transmittance T ₁ % in the visible light region. An end cap made of polycrystalline alumina having a linear transmittance of T ₂ % is hermetically joined to form a discharge space therein, and the relationship between the average linear transmittances T ₁ and T ₂ is T ₁ ≧ 15%> T ₂ . A discharge vessel configured to satisfy the conditions, an arc tube having a discharge medium containing a metal halide and a starter gas enclosed in the discharge vessel, and the arc tube is disposed along the tube axis and hermetically sealed And a closed outer tube.

  By forming the container body and the end cap with fine particles, preferably polycrystalline alumina having an average particle size of 10 μm or less or ceramics mainly composed of this alumina, it can be manufactured at a lower cost than other ceramics and lamp discharge is performed from room temperature. Mechanical strength can be improved over time. That is, the thickness of the ceramic of the container body can be reduced, and a discharge container having a high average linear transmittance can be obtained.

  The cylindrical body that forms the main body of the discharge vessel has an average linear transmittance in the visible light region of 15% or more, exhibits high brightness and high luminous flux, and has a small arc image diameter (light emitting part) when used in a reflector. Since there is little diffusion, horizontal lines can be cut easily.

  Also, the end cap that closes the end face of the container body is made of alumina with an average linear transmittance of less than 15%, which is lower than that of the body, so that light emission in the direction of the arc tube axis is suppressed and used. In such a case, light emission in an undesired direction such as lateral spread can be reduced, and in combination with the above, desired light distribution characteristics can be easily obtained.

  In the present invention and each of the following inventions, the definitions and technical meanings of terms are as follows unless otherwise specified.

Formed using polycrystalline alumina (aluminum oxide-Al ₂ O ₃ ), which has high translucency, heat resistance, and corrosion resistance from halides, as the material of the cylindrical container body that forms the main body of the discharge vessel of the arc tube To do.

Since the cylindrical container body is formed of polycrystalline alumina, it is easy to realize an arbitrary shape as compared with other polycrystalline ceramics such as yttrium oxide (Y ₂ O ₃ ) and aluminum nitride (AlN). Manufacturing cost can be reduced. In addition, there is an advantage that, compared with single crystal ceramics such as sapphire (Al ₂ O ₃ ), processing time is not required and manufacturing cost can be reduced.

  And the said container main body by a polycrystalline alumina can be easily manufactured by means, such as casting molding, extrusion molding, and hot isostatic pressing (HIP) shaping | molding, for example.

  The shape of the discharge vessel is a cylindrical shape such as a straight tube, or an oval or spherical shape with a bulged center portion, and both ends are cylindrical, and the opening at both ends is a disc made of polycrystalline alumina. Air-tightly closed with an end cap.

  This disk-shaped end cap is formed by integrating a small-diameter small-diameter cylindrical portion that is inserted and supported at the center into the center by integral molding or by separately fitting another body.

When this end cap is formed of polycrystalline ceramics such as yttrium oxide (Y ₂ O ₃ ) or aluminum nitride (AlN), the manufacturing cost increases or the bonding strength decreases due to the difference in thermal expansion coefficient. In addition, when formed of single crystal ceramics such as sapphire (Al ₂ O ₃ ), there is a problem that undesired light emission in the axial direction of the arc tube increases due to high linear transmittance.

Further, the means for increasing the average linear transmittance T ₁ of the molded container body is performed by mechanically polishing both the inner and outer surfaces using diamond powder or a grindstone containing diamond powder, and at least one of the inner and outer surfaces of the container body is provided. This can be realized by making the surface a smooth surface with few irregularities, and the higher the smoothness, the higher the average linear transmittance T ₁ .

When the average linear transmittance T _{1 of the} container body made of this ceramic is less than 15%, the internal high-intensity arc image becomes faint, while the container portion other than the one corresponding to the arc looks bright. However, it is difficult to design the light distribution, and the maximum light intensity on the light distribution surface is lowered, and there is a problem that stray light (glare) increases. Although this linear transmittance T ₁ is preferably as high as possible, there is no practical problem if the minimum is 15% or more in consideration of variations, etc., but 30% or more is considered in consideration of downsizing of lamps or further reduction of glare. Considering bringing these levels close to the level of transparent glass, it is preferably 50% or more.

In addition, when the average linear transmittance T _{2 of} the end cap is 15% or more, the amount of light in an undesired direction (light ray toward the end cap side) increases, and there are problems such as generation of glare and uneven distribution of light distribution. However, the lower the value, the less stray light is preferable.

  In addition, the average linear transmittance referred to in the present invention is the transmittance of light in the visible light region (380 to 780 nm).

In the present invention, although not limited depending on the rating of the lamp, the maximum inner diameter of the container main body forming the discharge space of the small arc tube is about 2 to 7 mm as the high-pressure discharge lamp, and the total inner length is 2 About 10 to 10 mm and an internal volume of about 0.02 to 0.3 cc, preferably about 0.05 to 0.20 cc, and a tube wall load (unit inner surface area (cm ² ) of the discharge space portion). The per lamp power (W) is about ²⁰ to 50 W / cm ² with a relatively high load.

  The pair of electrode structures are formed in a rod-like body, a pipe-like body, a coil-like body, etc., and function to introduce an electric current from the outside, and the introduction conductors are opposed to each other with a predetermined gap substantially on the central axis in the container. It is inserted and sealed in a small-diameter cylindrical part at both ends of the discharge vessel, and the materials are tungsten (W), doped tungsten, molybdenum (Mo), niobium (Nb), cermet (fired body of metal powder and ceramics), etc. One type or a plurality of types are connected.

  Further, the tip of the electrode structure serves as a discharge electrode portion, and a coil made of tungsten W wire or the like can be wound as necessary in order to increase the surface area and improve heat dissipation. The lead conductor portion led out from the end of the small diameter cylindrical portion of the electrode assembly is used to support the arc tube.

Further, the means for fixing the electrode assembly in the small diameter cylindrical part is that metal oxides such as Al ₂ O ₃ , SiO _2, and Dy ₂ O ₃ are provided at the opening of the small diameter cylindrical part that is separated from the discharge electrode part and has a lower temperature than the end cap. Airtight joining is performed via an adhesive made of frit glass composed of at least one kind of material.

  The discharge medium is sodium (Na), thallium (Tl), indium (In), thulium (Tm), lithium (Li), cesium (Cs), dysprosium (Dy), holmium (Ho), thulium (Tm) as the luminescent metal. ), Mercury (Hg) containing at least one halide such as scandium (Sc), neodymium (Nd), cerium (Ce) and amalgam as necessary.

  As the halogen, one or more of iodine (I), bromine (Br), chlorine (Cl), and fluorine (F) can be used. The amount of metal halide enclosed is about 0.2 to 20 mg per 0.1 cc of the container internal volume, but is determined according to the light emission characteristics, the lamp power, the internal volume of the discharge container, or the like.

  Further, a rare gas such as argon (Ar), xenon (Xe), or neon (Ne) is enclosed as a starting and buffer gas at a normal temperature of about 8 kPa to 2000 kPa (Pascal), and exhibits a pressure of about 500 kPa or more during lighting. In addition, when the enclosure pressure of this rare gas is less than 8 kPa, it becomes difficult to start discharge as shown in the Paschen curve, and when it exceeds 2000 kPa, the starting voltage increases and exceeds the pressure resistance of the base. In addition, when the xenon (Xe) is enclosed, the arc tube can enhance the rising characteristics of the luminous flux by the emission of xenon (Xe) immediately after starting.

The outer tube is formed of a light-transmitting and heat-resistant material made of glass or ceramics such as quartz glass, borosilicate glass or semi-rigid glass, and even if the inside of the outer tube is in a vacuum atmosphere, nitrogen is used. A rare gas such as (N ₂ ) or argon (Ar) may be enclosed.

  In addition, a heat-resistant film such as grayish black is formed on a part of the outer tube surface to shield light radiation in an undesired direction, or a shield that covers a part of the arc tube from the outside is provided. May be.

  Furthermore, a getter such as a zirconium (Zr) -aluminum (Al) alloy that cleans the inside of the outer tube may be provided on a power supply line in the outer tube.

  Furthermore, the high-pressure discharge lamp of the present invention can be used, for example, in a vehicle headlamp device such as an automobile or an optical device.

  The high-pressure discharge lamp of the invention of claim 2 is characterized in that the container body has an average linear transmittance T1 of 30% or more.

By setting the average linear transmittance T ₁ of the container main body to 30% or more, a small and bright headlamp device can be realized as a result of less glare and higher luminous intensity on the light distribution surface. (If the same average linear transmittance T ₁ value, the larger the lamp, the less the glare and the higher the brightness.)
The high-pressure discharge lamp of the invention of claim 3 is characterized in that an average linear transmittance T _{1 of the} container body is 50% or more.

By setting the average linear transmittance T ₁ of the container body to 50% or more, the glare and the luminous intensity are further improved, and can be improved to the same level as a conventional lamp made of quartz glass.

  The high-pressure discharge lamp of the invention of claim 4 is characterized in that an end cap is hermetically joined to the end portion of the container body by shrink fitting.

  By joining the polycrystalline alumina ceramics by shrink fitting, the heat resistance is improved compared to the case where an adhesive such as ceramic paste or frit glass is used, and there is no generation of impure gas from the adhesive. As a result, it is possible to suppress the decrease in luminous flux and the occurrence of short life.

  By shrink-fitting, using polycrystalline alumina with different raw materials, using alumina with different molding pressure at the time of molding, or pre-baking one and different shrinkage ratios of both, At the time of firing, pressure is applied to both contact portions due to shrinkage, and the contact portions become a single phase, and strong bonding with high airtightness is performed.

  The high-pressure discharge lamp of the invention of claim 5 is characterized in that the inner peripheral surface of the projecting portion of the peripheral edge forming the disc shape of the end cap and the outer peripheral surface of the container body are hermetically joined.

  A state where the outer peripheral surface of the end of the container body is tightened by applying pressure from the outside to the outer peripheral surface of the container body during firing, such as using a polycrystalline alumina ceramic material that has a higher thermal shrinkage on the end cap side than the container body A strong airtight connection is made by contact with.

  The high pressure discharge lamp of the invention of claim 6 is characterized in that the outer peripheral surface portion of the peripheral edge forming the disc shape of the end cap and the inner peripheral surface portion of the container main body are hermetically joined.

  The inner peripheral surface of the container body end is tightened by applying pressure from the outside to the outer peripheral surface of the end cap during firing, such as using a polycrystalline alumina ceramic material that has a higher thermal shrinkage on the container body side than the end cap. In this state, contact is made and strong bonding is performed.

  The end cap is formed with a step portion having a small-diameter portion that fits on the inner peripheral surface of the container body and a large-diameter portion that can be placed on the end surface of the container body, even if the outer peripheral surface portion of the peripheral edge is a straight surface. It may be of a different structure.

  According to the first to third aspects of the present invention, the container main body is formed from the fine particles of polycrystalline alumina to increase the mechanical strength of the main body, and the container main body is thinned. A high pressure discharge lamp having a discharge vessel having

  In addition, when the lamp is incorporated in a reflector, the arc image diameter (light emitting part) is small and light emission in the direction of the arc tube axis is prevented and suppressed, so light diffusion is small and horizontal line light cuts are easy. Therefore, it is possible to provide a high-pressure discharge lamp suitable for a vehicle headlamp or the like that can easily obtain desired light distribution characteristics.

  According to the invention of claim 4, in addition to the effects described in claims 1 to 3, the mutual joining is shrink-fit, not only the heat resistance is increased compared to the case of using an adhesive, but also the generation of impure gas. Therefore, it is possible to provide a high-pressure discharge lamp that can reduce the luminous flux and suppress the short life.

  According to the invention of claim 5, in addition to the effects of claims 1 to 3, the end cap side is in contact with the container body in a state where pressure is applied from the outside, so that the high pressure discharge lamp can be firmly joined. Can be provided.

  According to invention of Claim 6, since the container main body side is contacting the outer peripheral surface of an end cap in the state which applied the pressure from the outside with the effect of the said Claims 1-3, it is a high pressure | pressure in which strong joining is performed A discharge lamp can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially sectional front view showing an embodiment of a high-pressure discharge lamp for an automobile headlamp, FIG. 2 is an enlarged longitudinal front view showing an arc tube portion in FIG. 1, and FIG. 3 is a high-pressure in FIG. It is a partial cross section front view which shows embodiment of the lamp | ramp of vehicle headlamps, such as a motor vehicle equipped with the discharge lamp.

  In the figure, a high-pressure discharge lamp L1 is mainly composed of an arc tube 1A, an outer tube 5 that accommodates the arc tube 1A, and a base 7 that supports the outer tube 5 and connects a pair of power feeding members 6A and 6B that feed power. It is configured.

The arc tube 1A is a discharge vessel in which end caps 2A and 2A made of ceramics having protrusions 21 formed on the periphery of a disk-like base 20 are joined to both ends of a cylindrical vessel body 11 made of translucent ceramics. 10, a small-diameter cylindrical portion 3 extending outward from the center of the end caps 2A, 2A, an electrode assembly 4 fixedly supported in the small-diameter cylindrical portion 3, and argon (Ar as a discharge medium in the discharge vessel 1) ) And xenon (Xe) and other rare gases such as starter and buffer gases, and sodium iodide (NaI), thallium iodide (TlI), indium iodide (InI) and thulium iodide (TmI ₃ ) as luminescent metals The metal halide and mercury are enclosed.

In the present invention, the ceramic forming the vessel body 11 of the discharge vessel 10 is mainly composed of polycrystalline alumina or polycrystalline alumina having an average linear transmittance T ₁ of 15% or more in the visible light region (380 to 780 nm). Made of material. Further, the end cap 2A and the small diameter cylindrical portion 3 have an average linear transmittance mainly composed of polycrystalline alumina or polycrystalline alumina whose average linear transmittance T ₂ is lower than the ceramic forming the container main body 11 and is less than 15%. It is made of a material having a relationship of T ₁ ≧ 15%> T ₂ .

  Further, the end cap 2A is fitted with the protruding portion 21 at the end of the container body 11 and fired (baked), whereby the outer peripheral surface portion of the container main body 11 and the inner peripheral surface of the protruding portion are airtightly joined.

  The electrode structures 4 and 4 include a linear lead conductor 41 penetrating the inside of the small-diameter cylindrical portion 3 in which one or more kinds of metal wire materials such as tungsten (W), molybdenum (Mo), and niobium (Nb) are connected. A light emitting (light source) portion is formed between the ends of the opposed discharge electrode portions 42 and 42 facing the inside of the main body 11, and is airtight through the glass adhesive 43 at the opening of the small diameter cylindrical portion 3. It has a sealed symmetrical structure.

  At this time, if there is a gap between the inner surface of the small-diameter cylindrical portion 3 and the outer surface of the introduction conductor 41, the introduction conductor 41 is wound with a thin wire such as tungsten (W) or molybdenum (Mo) to reduce the gap. Is desirable. Further, a portion of the introduction conductor 41 that is led out from the opening of the small diameter cylindrical portion 3 may be connected to a separate conductive wire as an external introduction conductor. Further, the discharge electrode portion 42 may be a coiled electrode having a tungsten (W) wire wound around the tip.

The outer tube 5 in which the arc tube 1A is housed has a cylindrical shape made of transparent quartz glass, aluminosilicate glass, or the like, and the introduction conductor 41 led out from the arc tube 1A is attached to both ends directly or to the introduction conductor 41 with the glass. A metal member 51 such as molybdenum molybdenum wire or foil is interposed, and the outer tube 5 is heated and contracted from the outside to form hermetic sealing portions 52 and 52. The outer tube 5 is in a vacuum atmosphere or a rare gas atmosphere in which nitrogen (N ₂ ), argon (Ar), or the like is sealed.

  The outer tube 5 is formed by spot welding or the like on an annular metal piece 73 provided in an annular shape in the recess 72 of the base shell 71 via a metal band 70 fixed by winding or the like in the vicinity of the sealing portion 52 on one end side. It is fixed and held by means.

  Further, the metal wire 61 constituting one power supply member 6A led out from both ends of the outer tube 5 passes through the recess 72 of the base shell 71 and the through hole 74 formed in the insulator, and the tip thereof is a terminal member at the top of the base 7. 75 is connected by welding, caulking or brazing.

  The metal wire 62 constituting the other power supply member 6B on the side opposite to the base 7 has a through hole 75 disposed substantially in parallel with the outer tube 5 and provided in the recess 72 of the base shell 71 with a partition wall therebetween. The other terminal member 76 provided in an annular shape on the outer surface of the street shell 71 is connected by welding, caulking, or brazing. In the figure, 63 is an insulating tube made of ceramics which covers the exposed portion of the other metal wire 62 passing outside the outer tube 5 and provides electrical protection, and 77 is a flange portion provided at the outer end of the shell 71. .

  Further, when the arc tube L1 and the base 7 are fixed, for example, the locking piece side of the metal band 70 holding the outer tube 5 is placed on the annular metal piece 73 with reference to the flange portion 77 of the base 7. After the light emitting tube L1 is temporarily turned on and the light emitting tube L1 is moved to adjust the balance with the focal position, the light emitting (light source) unit is aligned, and then the locking piece of the metal band 70 is an annular metal piece. The high-pressure discharge lamp L1 is completed by fixing and integrating with 73 by spot welding or the like.

  FIG. 3 shows a lamp 8 for a headlamp of an automobile or the like equipped with the high pressure discharge lamp L1. In the figure, reference numeral 81 denotes a reflecting mirror, and a light reflecting film (not shown) such as aluminum is formed on the inner surface formed of heat-resistant synthetic resin, hard glass or metal plate, and a front opening of the reflecting mirror 81. Is provided with a light control body 82 typified by a lens designed to exhibit a predetermined light distribution characteristic.

  And the spring which inserted and positioned the flange part 77 of the discharge lamp L1 shown in the said embodiment in the through-hole of the holder 83 provided in the center of the back surface of the reflective mirror 81, and latched the back surface of the flange part 77 to the holder 83 The lamp 84 is pressed and fixed by the member 84, and the socket 9 is connected to the base 7 to complete the lamp 8.

  The lamp 8 having such a configuration has high accuracy in the dimensional position relationship between the light emitting (light source) portion and the base 7 and the positional relationship between the light emitting (light source) portion and the focal point of the reflecting mirror 81. Therefore, when the discharge lamp L1 is lit through a lighting circuit device (not shown), it is possible to obtain a light distribution characteristic with a small predetermined variation.

That is, the discharge lamp L1 exhibits a high luminance and a high luminous flux when the average linear transmittance T ₁ in the visible light region of the main body 11 constituting the main body of the discharge vessel 10 is 15% or more, and is incorporated in a reflecting mirror. Since the image diameter (light emission (light source) portion) is small and light diffusion is small, horizontal lines can be easily cut and desired light distribution characteristics are easily obtained.

Further, the end caps 2A and 2A for closing the end face of the container body 11 are made of ceramics having an average linear transmittance T ₂ lower than the main body 11 and less than 15%, thereby preventing light emission in the axial direction of the arc tube 1A. In addition, when incorporated in a reflecting mirror, light emission in an undesired direction can be reduced, and a desired light distribution characteristic can be easily obtained.

FIG. 4 is an enlarged longitudinal sectional front view showing another embodiment of the arc tube of the present invention. In FIG. 4, the same parts as those in FIG. In addition, the arc tube shown in these embodiments is also formed of ceramics in which the container main body 11 and the end cap have the average linear transmittances T ₁ and T ₂ under the same conditions as those in the above embodiment.

  FIG. 4 is different from FIG. 2 in the shape of the end cap, and the end cap 2B having a disc shape has a stepped portion 24 formed at the periphery having a small diameter portion 22 and a large diameter portion 23, and is formed in the container body 11. The arc tube 1 </ b> B is hermetically joined by sintering the outer peripheral surface portion of the small-diameter side 22 and the inner peripheral surface portion of the main body 11 that are fitted.

  And it has confirmed that the arc tube 1B shown in this FIG. 4 had the same effect as the said arc tube 1A. In addition, in this end cap 2B, you may make it fit in the container main body 11 as a straight structure, without forming the step part 24, and shrink-fit.

  Example 1 is an arc tube 1A having an end cap 2A having the same structure as that shown in FIG. 2, and Comparative Example 1 is a conventional arc tube made of polycrystalline alumina having an average linear transmittance of less than 10%. It consists of a container. Comparative Example 2 is a conventional arc tube, which is an arc tube made of a quartz glass container having an average linear transmittance of 90% or more. Each of these arc tubes is placed in an outer tube having the same structure as that shown in FIG. A high pressure discharge lamp for an automobile headlamp was manufactured by sealing.

Then, the discharge lamp for this vehicle headlamp is mounted in the same left-hand drive vehicle headlamp, and the main light distribution point based on the light emission efficiency and the ECE Regulation 98 (European headlight distribution standard) ( HV point etc. The numerical values are shifted from the front center of the lamp to the upper U in the vertical direction, the lower D in the vertical direction, the left L in the horizontal (horizontal) direction, and the right direction R. The emission characteristics such as illuminance (Lx) at a point 25 m away from the angle are shown. (N = 10)

  The headlamp equipped with the high pressure discharge lamp of Example 1 according to the present invention has a total luminous flux value almost equal to that of the luminous tube (Comparative Example 2) of the alumina container as compared with the high pressure discharge lamps shown in Comparative Examples 1 and 2. Equivalent, about 9% higher than the quartz glass arc tube. Moreover, it has confirmed that the glare in a center (0-0) point was less than the comparative example 2, and the light distribution surface was bright, and can provide the headlamp with better visibility than before.

1 is a partial cross-sectional front view showing an embodiment of a high-pressure discharge lamp for an automobile headlamp according to the present invention. It is an enlarged vertical front view which shows the arc_tube | light_emitting_tube part in FIG. It is a partial cross section front view which shows embodiment of the lamp | ramp of vehicle headlamps, such as a motor vehicle equipped with the high voltage | pressure discharge lamp in FIG. It is an enlarged vertical front view which shows other embodiment of the arc tube of this invention.

Explanation of symbols

  L1: High-pressure discharge lamp (metal halide lamp), 1A, 1B: arc tube, 10: discharge vessel, 11: vessel body, 2A, 2B: end cap, 21: protrusion, 3: small diameter cylindrical portion, 4: electrode assembly, 5: Outer tube, 6A, 6B: Power supply member, 8: Lamp,

Claims (6)

Polycrystalline alumina having an average linear transmittance of T ₂ % having a small-diameter cylindrical portion with an electrode assembly fixed at both ends of a cylindrical container body made of polycrystalline alumina having an average linear transmittance of T ₁ % in the visible light region A discharge vessel formed by hermetically joining end caps made of metal to form a discharge space therein, wherein the relationship between the average linear transmittances T ₁ and T ₂ satisfies the condition of T ₁ ≧ 15%> T ₂ , An arc tube having a discharge medium comprising a metal halide and a starting gas enclosed in a discharge vessel;
An outer tube having the arc tube disposed therein along the tube axis and hermetically closed;
A high-pressure discharge lamp comprising: High-pressure discharge lamp according to claim 1, wherein the average linear transmittance T ₁ of the said container body is 30% or more. High-pressure discharge lamp according to claim 1, wherein the average linear transmittance T ₁ of the said container body is equal to or less than 50%.   The high-pressure discharge lamp according to any one of claims 1 to 3, wherein an end cap is hermetically joined to the end of the container body by shrink fitting.   The high pressure discharge lamp according to any one of claims 1 to 4, wherein an inner peripheral surface of the protruding portion of the peripheral edge of the end cap that is disk-shaped and an outer peripheral surface of the container body are hermetically joined.   The high-pressure discharge lamp according to any one of claims 1 to 4, wherein an outer peripheral surface portion of a peripheral edge forming a disc shape of the end cap and an inner peripheral surface portion of the container main body are hermetically joined.

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