JP4494224B2 - Seal for lamp and discharge lamp - Google Patents

Description

  The present invention relates to a discharge lamp used for an automotive headlamp, a liquid crystal projector, and the like.

  The discharge lamp is formed by sealing a metal foil in which electrodes and external lead wires are connected to both ends by welding to sealing portions formed at both ends of a light-transmitting hermetic container in which an arc tube portion is formed. Is generally arranged to face each other in the discharge space in the hermetic vessel.

Resistance welding has been mainly used as a method for connecting the metal foil to the electrode and the external lead wire. However, in resistance welding, suitable welding conditions vary depending on the physical properties such as the resistance value and melting point of the electrode and metal foil material, which may result in poor bonding or perforation of the metal foil. Therefore, laser welding has been attempted. (For example, Patent Document 1 and Patent Document 2)
JP-A-8-50882 (pages 2 and 3, FIGS. 1 and 2) JP 2000-288755 A (pages 3 and 7, FIGS. 11, 14, and 15)

  However, as shown in FIG. 1 of Patent Document 1 above, in the lamp sealing body welded by irradiating the electrode with a laser from the back surface of the metal foil, after sealing the lamp sealing body in a sealing step, There is a problem that the electrode is cracked or broken.

  An object of the present invention is to reduce defects of cracks and breaks that occur in electrodes.

  In order to achieve the above object, the lamp sealing body of the present invention is a lamp sealing body in which an electrode is connected to one end of a metal foil and an external lead wire is connected to the other end by welding, and is formed on the electrode. The relationship d / r between the depth d (mm) of the welded portion and the diameter r (mm) of the electrode is d / r ≦ 0.3.

  According to the present invention, it is possible to reduce defects such as cracks and breaks occurring in the electrode.

(First embodiment)
Hereinafter, a discharge lamp according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view of a discharge lamp according to a first embodiment of the present invention.

  The hermetic container 1 is made of, for example, fire-resistant and light-transmitting quartz glass, and the arc tube shape is an elliptical arc tube portion 11 and the same material as the arc tube portion 11, and both ends in the longitudinal direction are crushed. It consists of the formed plate-shaped sealing parts 131 and 132. Inside the arc tube portion 11, a discharge space 12 having an axial shape of a substantially cylindrical shape and an internal volume of 0.1 cc or less is formed. The discharge space 12 is a metal halide as a discharge medium. Sodium iodide, scandium iodide, zinc iodide, and xenon which is a rare gas are enclosed.

  Metal sodium contained in sodium iodide and metal scandium contained in scandium iodide mainly act as luminescent metals, and the metal zinc contained in zinc iodide is mainly a lamp voltage instead of mercury. Acts as a forming medium. As the halide bonded to these luminescent metals, iodine having the lower reactivity than other halides is most suitable, but other halogens such as bromine and chlorine may be used. Also, xenon, which is a rare gas, mainly acts as a starting gas because of its high luminous efficiency immediately after starting.

  Here, the discharge medium sealed in the arc tube portion 11 essentially does not contain mercury. This “essentially free of mercury” means that it does not contain any mercury, or accepts an amount of mercury of less than 2 mg per cc, preferably 1 mg or less. That is, when the discharge lamp voltage is increased to a required level with mercury vapor as in the case of a conventional short arc lamp containing mercury, 20 to 40 mg per cc, or 50 mg or more in some cases, is sealed. Then, it can be said that the amount of mercury of less than 2 mg is overwhelmingly small and essentially contains no mercury.

  Inside the sealing portions 131 and 132, lamp sealing bodies 21 and 22 are sealed. The lamp sealing bodies 21 and 22 are made of tungsten at both ends of the metal foils 211 and 212 made of molybdenum with a thickness of 18 μm to 25 μm, and the diameter of the distal end is larger than the diameter of the proximal end. It comprises stepped electrodes 221 and 222 having a base end diameter of 0.28 mm to 0.32 mm and external lead wires 231 and 232 made of molybdenum having a diameter of 0.38 mm to 0.42 mm.

  FIG. 2 is a cross-sectional view for explaining a welded portion between the metal foil and the electrode. Here, (a) is a cross-sectional view perpendicular to the tube axis direction, and (b) is a cross-sectional view parallel to the tube axis direction.

  When the lamp sealing body 21 is viewed in a cross section perpendicular to the tube axis direction, an electrode 221 is disposed on the metal foil 211, and the cross section is a substantially triangular weld from a surface opposite to the electrode arrangement surface of the metal foil 211. A portion 31 is formed. This “welded part” is a part in which a large crystal lump is formed because crystallization by heat is more advanced than other parts, and can be regarded as a recrystallized part. Further, when viewed in a cross section parallel to the tube axis direction, a plurality of welded portions are formed in the axial direction, which are welded portions 31 to 33, respectively. The welded portions 31 to 33 each have a cross-sectional shape of a triangle, a quadrangle, and a triangle with a tip portion extending. The three-dimensional shape is a substantially cone and a substantially truncated cone. The shape of these welding parts 31-33 can be formed in various shapes by the heating at the time of welding, and forms other than the above, for example, a shape in which a plurality of welding parts are connected and connected are formed. Can do. Here, in the welded portions 31 to 33, the surface of the welded portion on the metal foil 211 side is slightly curved, which is formed by melting during the welding process.

  Here, among the formed welds 31 to 33, the weld with the deepest depth in the axial center direction of the electrode 221 (the weld 31 in FIG. 2) has its depth d (mm) and the diameter of the electrode 221. The relationship d / r with r (mm) is formed so that d / r ≦ 0.3. As a method of adjusting the depth d of the welded portion so as to be in this relationship, in the welding process described later, the welding energy of the laser irradiation apparatus is changed, specifically, the welding current and the welding time are changed. Therefore, the desired depth can be easily adjusted.

  A method for manufacturing the lamp sealing body will be described with reference to FIG. (A) is a general view, and (b) is a cross-sectional view taken along the dotted line A-A ′ as seen from the direction of the arrow.

  As a first step, the electrode 221 and the external lead wire 231 are placed on a substantially straight line in the groove 412 of the table 41 in which the V-shaped groove 412 is formed on the mounting surface 411, and the metal foil 211 is placed on the predetermined surface. Arrange according to the position. And as a 2nd process, in order to prevent the position shift at the time of welding, the four corners of the metal foil 211 are pressed and fixed with the fixing tools 421-424. Here, in FIG. 3B, the metal foil 211 is fixed in a bent state, but this is an error due to the depth of the V-shaped groove 412 and the diameter of the electrode 221 to be used. Even if it is the lamp sealing body 21 manufactured by welding in this state, there is no problem on the product.

  Then, as a third step, a laser irradiation device is arranged at a position penetrating the electrode 221 etc. from the surface of the opposite metal foil 211 with respect to the surface on which the electrodes 221 etc. are arranged, and laser light is irradiated between these metals. Are fused together to form the lamp sealing body 21 integrally. Here, since the laser welding is spot welding, for example, about three locations in the axial direction of the electrode 221 and the external lead wire 231 that are in contact with the metal foil 211 are continuously or separated from each other. The bonding strength can be kept sufficiently.

  The above-described method for manufacturing a lamp sealing body does not require the use of other metals for welding, is easy to manufacture, and can be reliably fixed to a metal foil such as an electrode.

  The lamp sealing bodies 21 and 22 sealed in the sealing portions 131 and 132 are such that the tip portions of the electrodes 221 and 222 are kept at a predetermined distance between the electrodes in the discharge space 12 and the tips thereof are opposed to each other. Are arranged as follows. Here, the “predetermined” is about 4.2 mm when used for an automobile headlamp, and about 2 mm when used for a projection. That is, in a short arc type lamp, it is suitable to be 5 mm or less.

  The other ends of the external lead wires 231 and 232 connected to the opposite ends of the metal foils 211 and 212 extend to the outside of the sealing portions 131 and 132, and the external lead wire 232 has an L-shape. One end of the power supply terminal 233 formed in the above is connected so as to be substantially perpendicular. A part of the power supply terminal 233 is covered with, for example, an insulating tube 5 made of ceramic so that the potential of the external lead wire 232 portion does not affect.

  On the outside of the hermetic container 1 having these, for example, a translucent cylindrical outer tube 6 made of a material that blocks ultraviolet rays is provided so as to cover most of the hermetic container 1 along its longitudinal direction. It has been. A welded portion 61 connected to the sealing portion 132 by glass welding is formed at the end of the outer tube 6 in the longitudinal direction. (Here, the welded portion on the sealing portion 131 side is not shown.) The space formed by the airtight container 1 and the outer tube 6 is in an atmospheric atmosphere. Further, this space can be filled with argon or in a vacuum atmosphere as desired.

  The outer tube 6 that covers the airtight container 1 is connected to the socket 8 by a fixed metal tool 7 that is formed so as to sandwich the outer peripheral surface thereof. Near the end of the socket 8, a metal terminal 81 for supplying power from the lighting circuit is formed along the outer peripheral surface, and the metal terminal 81 is connected via an external lead wire 232 and a power supply terminal 233. Electrically connected. Although not shown, the other terminal for supplying power is formed at the bottom portion of the socket 8, and this terminal is electrically connected to the external lead wire 231.

  FIG. 4 is a diagram for explaining the number of occurrences of electrode breakage after sealing a lamp sealing body having a depth of a welded portion to quartz glass heated to a high temperature of about 1800 ° C. with a water oxygen burner. FIG. Here, for the lamp sealing body 21, a metal foil 211 having a thickness of 20 μm, an electrode 221 having a welded portion diameter of 0.30 mm, and an external lead wire 231 having a diameter of 0.40 mm are used. Then, 100 samples each having a relation d / r between the depth d (mm) of the welded portion and the diameter r (mm) of the electrode changed in the range of 0.10 to 0.50 were prepared, and the test was performed. I did it. The presence or absence of electrode breakage was confirmed visually by X-ray transmission imaging.

  FIG. 4 shows that the number of occurrences of bending in the electrode 221 increases as d / r increases. Here, looking at the graph of FIG. 5 showing the relationship between d / r and the rate of electrode breakage, the rate of electrode breakage increases when d / r becomes greater than 0.30. There is a tendency to From this, it is preferable that the relationship d / r between the depth d (mm) of the welded portion and the diameter r (mm) of the electrode is 0.30 or less. More preferably, d / r where the rate of occurrence of electrode breakage remains at 0% is 0.15 or less. By the way, the conditions such as the dimensions of the metal foil and the like are the same, and the same test was performed on the lamp sealing body manufactured by resistance welding. As a result, electrode breakage occurred in 15 out of 100 tests, and d It was also confirmed that if / r is 0.30 or less, it is more effective against electrode breakage than resistance welding.

  The relationship d / r between the depth d (mm) of the weld and the diameter r (mm) of the electrode and the cause of electrode breakage are estimated as follows.

  The welding method of the metal foil and the electrode (and external lead wire) of the present invention is formed by melting a part of the metal foil and the electrode with a laser at a high temperature, and the materials used are different, but they are formed so as to be melted together. The metal foil and the electrode are connected by the welded portion. Therefore, in this welding process, it is necessary to input welding energy that is at least connected to each other, and it has been thought that it is better to input more energy in order to strengthen the mutual connection. This is because when a large amount of energy is applied, a weld is formed deeper in the electrode, and the mutual bond becomes stronger. However, in the sealing process, the result was that electrode breakage was more likely to occur in the lamp sealing body in which a large amount of energy was input and the welded portion was deeply formed.

  This cause is considered to be related to a heat affected zone (also known as HAZ: Heat Affect Zone) that does not melt and changes in mechanical properties, which occurs at the boundary between the welded portion and the non-welded portion of the electrode.

  Therefore, the mechanism of electrode breakage will be described with reference to the schematic diagram of FIG.

In the sealing process of the lamp sealing body 21, first, the lamp sealing body 21 is positioned and arranged in the cylindrical sealing portion 131 before sealing. (FIG. 6A) Thereafter, the atmosphere in the glass tube is evacuated to vacuum and heated, so that the cylindrical sealing portion 131 is necked, and the quartz glass is used as the metal foil 211 of the lamp sealing body 21. Or the electrode 221 is contacted to form a sealing portion 131 having a non-uniform surface. Then, the sealing portion 131 is completed by pressurizing with the pincher 15. In the pressing process of the pincher 15 at this time, the contact condition between the pinch surface of the pincher 15 and the quartz glass. As a result, quartz glass flows, and microscopic bending stress is generated in the electrode 221 and the like. This bending stress causes a tensile stress in the axial direction of the lamp sealing body 21. (Fig. 6 (c))
The tensile stress is strong because the non-welded portion of the electrode 221 has a fiber structure, and the welded portions 311 to 313 are also strong because one crystal grain is large and single crystallized. The existing heat-affected zone is relatively weak because the mechanical properties have changed and deteriorated. Therefore, stress is applied to the material-affected heat-affected zone formed at the boundary between the welded portions 311 to 313 and the non-welded portion, and a crack occurs in the heat-affected zone near the proximal end of the welded portion, and then the crack It is thought that the stress was concentrated, so that the crack occurred so as to cut through the fiber structure of the electrode starting from the crack occurrence point, which led to the bending of the electrode.

  That is, it can be said that the direction in which the heat-affected zone is not formed so large can prevent the occurrence of electrode breakage during the sealing process. Here, the size of the heat affected zone is greatly related to the size of the welded portion, particularly in the case of spot welding the electrode and the metal foil as in the present embodiment. It can be seen that it is important to reduce the depth of the heat affected zone.

  From the above, in the present invention, the relationship d / r between the depth d (mm) of the welded portion and the diameter r (mm) of the electrode is d / r ≦ 0.3, but the lower limit is particularly set. Not done. This is because it is important to reduce the depth of the weld for reducing electrode breakage, and the minimum weld depth at which the electrode and the metal foil are mechanically connected is formed. If it is, the effect of this invention can fully be acquired.

  Also, on the external lead wire side, which is the welding point of the other end of the metal foil, cracks and breaks may occur during the sealing process, although less than on the electrode side. Therefore, it is desirable to form the depth of the welded portion by laser welding to 30% or less with respect to the diameter of the external lead wire as well as the electrode.

  In the present embodiment, electrodes 221 and 222 are connected to one end of metal foils 211 and 212, and external lead wires 231 and 232 are connected to the other end by welding, and the depth of the welded portion formed on the electrodes 221 and 222 is reduced. The lamp sealing bodies 21 and 22 in which the relationship d / r between d (mm) and the electrode diameter r (mm) is d / r ≦ 0.3 are sealed in the sealing portions 131 and 132 of the airtight container 1. By stopping, it is possible to reduce defects of electrode breakage and cracks that are likely to occur in the sealing process.

(Second Embodiment)
FIG. 7 is a cross-sectional view for explaining a discharge lamp according to a second embodiment of the present invention. About each part of this 2nd Embodiment, the same part as each part of the discharge lamp of 1st Embodiment of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. In the second embodiment, the lamp welded body 21 in which the electrode 221 and the external lead wire 231 are welded to the metal foil 211 whose surface is coated with the metal layer 213 made of titanium oxide is used.

  FIG. 8 is a diagram for explaining the number of occurrences of leak in the discharge lamp depending on the presence or absence of titanium oxide coating on the metal foil. Here, one of the lamp sealing bodies was coated with titanium oxide having a thickness of 20 μm on the surface and the other was not coated with titanium oxide, and 30 discharge lamps each including them were manufactured. Further, the leak occurrence rate was confirmed every 6 hours in a high temperature furnace maintained at 900 ° C.

  As is apparent from the results, about 80% of discharge lamps having a lamp sealant coated with titanium oxide were normal after 24 hours, whereas discharge without titanium oxide coating. In the lamps, leaks had already occurred in all the lamps after 6 hours. In other words, it can be seen that when titanium oxide coating is performed, a high effect on leakage can be obtained. The reason why this effect was obtained is considered to be that the sealing property with the sealing portion was improved by coating titanium oxide on the metal foil.

  FIG. 9 is a diagram for explaining the number of occurrences of electrode breakage when a test similar to that of FIG. 4 is performed on a lamp sealing body in which a metal foil is coated with titanium oxide having a thickness of 20 μm.

  FIG. 9 shows that even when a lamp sealing body coated with titanium oxide is used, as the relationship d / r between the weld depth d (mm) and the electrode diameter r (mm) increases, the electrode 221 increases. It can be seen that the number of occurrences of creases in is increasing. Here, looking at the graph of FIG. 10 showing the relationship between d / r and the rate of electrode breakage, the rate of electrode breakage increases when d / r is greater than 0.30. There is a tendency to Therefore, the relationship d / r between the depth d (mm) of the welded portion and the diameter r (mm) of the electrode is preferably 0.30 or less, and more preferably the rate of occurrence of electrode breakage. It is preferable that d / r staying at 0% is 0.15 or less. By the way, when the same test was performed on the lamp sealing body manufactured by resistance welding, electrode breakage occurred in 23 pieces out of 100 test pieces. Even in this case, the electrode breakage occurred rather than resistance welding. It was also confirmed that it was effective.

  Here, in resistance welding, the number of occurrences of electrode breakage of the lamp sealant coated with titanium oxide is increasing. This is a welding in which the joining state changes greatly depending on the physical properties such as the resistance value and melting point of the materials to be welded by resistance welding, so the joining is achieved by interposing titanium oxide between the electrode and the metal foil. This is probably because the strength was weakened and the bonding itself was not successful. That is, in the case of welding a metal foil coated with titanium oxide, it means that laser welding which is not easily influenced by the physical properties of the welding material is preferably performed.

  In this embodiment, electrodes 221 and 222 are connected to one end of metal foils 211 and 212 coated with a metal layer 213 made of titanium oxide, and external lead wires 231 and 232 are connected to the other end by welding. The lamp seals 21 and 22 having a relationship d / r between the depth d (mm) of the weld formed in 222 and the electrode diameter r (mm) satisfying d / r ≦ 0.3 are hermetically sealed. By sealing in the sealing parts 131 and 132 of the container 1, the malfunction of the electrode breakage and crack which are easy to generate | occur | produce in a sealing process similarly to 1st Embodiment can be reduced.

  In this embodiment, since the metal foil is coated with titanium oxide as the metal layer 213, the occurrence of leakage during lamp lighting can also be reduced.

  Here, as the metal layer 213, the same effect can be obtained by applying a halogen material such as rhenium in addition to titanium oxide.

  In addition, embodiment is not necessarily restricted above, For example, you may change as follows.

  Means for welding at the time of manufacturing the metal foils 211 and 212 of the lamp sealing bodies 21 and 22 and the electrodes 221 and 222 are not limited to lasers, and welding is performed by heating with an electron beam or an arc. You may do it.

  As shown in FIG. 11, as the electrodes of the lamp sealing bodies 21 and 22, a coil 223 is wound as a covering body around the shafts of the electrodes 221 and 222 in order to reduce the occurrence of cracks leading to leakage, and in this state, a metal foil 211 and 212 may be welded. As in the case of the electrode that does not wind the coil 223, the relationship d / r between the depth d (mm) of the welded portion 37 having the deepest depth and the electrode diameter r (mm) is 0.3 or more. This is because it has been confirmed that the same can be obtained for electrode breakage. Further, the covering body may be a cylindrical metal body made of tungsten.

  Here, it was confirmed that when the lamp sealing body 21 in which the coil 223 is wound around the shaft of the electrode 221 is sealed, further electrode breakage occurs. It is expected that a slight gap formed between the electrode 221 and the coil 223 is related. That is, when the lamp sealing body 21 is sealed, a mechanism as shown in FIG. 6 is generated. In addition, the electrode portion around which the coil 223 is wound is applied when the pincher is pressed in the sealing process. It can be considered that the electrode portion around which the coil 223 is not wound serves as a fulcrum of the “lever” and a strong bending stress is generated because it can operate relatively by the gap between the electrode and the coil. Therefore, when the lamp sealing body 21 around which the coil 223 is wound is used, it is more effective to implement the present invention.

The whole figure for demonstrating 1st Embodiment of the discharge lamp of this invention. Sectional drawing for demonstrating the welding part part of metal foil and an electrode. The figure for demonstrating the manufacturing method of the sealing body for lamps of this invention. The figure for demonstrating the number of generation | occurrence | production of the electrode bending after sealing the sealing body for lamps which changed the depth of the welding part. The figure for demonstrating the relationship between d / r and an electrode bending incidence. The schematic diagram for demonstrating the mechanism of electrode breakage generation | occurrence | production. The whole figure for demonstrating 2nd Embodiment of the discharge lamp of this invention. The figure for demonstrating the leak incidence rate of the discharge lamp by the presence or absence of the titanium oxide coating of metal foil. The figure for demonstrating the number of generation | occurrence | production of the electrode bending after sealing the sealing body for lamps which changed the depth of the welding part. The figure for demonstrating the relationship between d / r and an electrode bending incidence. Sectional drawing for demonstrating the welding part part of metal foil and an electrode with a coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Airtight container 11 Light emission tube part 12 Discharge space 131,132 Sealing part 21,22 Lamp sealing body 211,212 Metal foil 213 Metal layer 221,222 Electrode 223 Coil 231,232 External lead wire 233 Feed terminal 31-39 Welded part 5 Insulating tube 6 Outer tube 7 Fixed metal fixture 8 Socket

Claims (3)

  A lamp sealing body in which an electrode is connected to one end of a metal foil and an external lead wire is connected to the other end by welding, and a depth d (mm) of a welded portion formed on the electrode and a diameter r ( mm)) d / r, d / r ≦ 0.3. 2. The lamp sealing body according to claim 1, wherein a layer made of a metal oxide is coated on a surface of the metal foil. A translucent airtight container having an arc tube portion in which a discharge medium is enclosed, and sealing portions formed at both ends of the arc tube portion;
A discharge lamp comprising the lamp sealing body according to claim 1 or 2, which is sealed to the sealing portion.

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