JP4878984B2 - Discharge lamp and discharge lamp manufacturing method - Google Patents

Description

  The present invention relates to a discharge lamp used for an automobile headlamp and the like, and a method for manufacturing the discharge lamp.

  A discharge lamp used for an automotive headlamp or the like includes an arc tube and a socket. Furthermore, the arc tube generally has a double tube configuration for the purpose of keeping warm and the like. An example of such a discharge lamp is Japanese Patent No. 3596812 (hereinafter referred to as Patent Document 1). As described in this invention, a rare gas or the like is enclosed in the space of the inner and outer tubes constituting the arc tube. There is also.

  As a method for connecting the inner tube and the outer tube, there is a method disclosed in Japanese Patent Laid-Open No. 2002-163980 (hereinafter referred to as Patent Document 2). The method of Patent Document 2 will be described in detail. First, the outer tube is heated and welded to a circular flange portion formed at the end of the inner tube on the rear end side. Then, with the space between the inner tube and the outer tube kept at a negative pressure, the outer tube on the distal end side is heated to reduce the diameter of the outer tube in the direction of the inner tube (shrink seal), thereby The pipe is connected. Japanese Patent Laid-Open No. 2005-327487 (hereinafter referred to as Patent Document 3) also describes a similar connection method.

Japanese Patent No. 3596812 JP 2002-163980 A JP 2005-327487 A

  However, in the connection method of the inner tube and the outer tube as in Patent Document 2 and Patent Document 3, there is a problem that the welded portion on the distal end side subjected to shrink sealing becomes long and lacks compactness. This is because the shrink seal tends to have a large variation in welding, and it is necessary to form a long welded portion in order to ensure airtightness that does not cause the internal gas to leak for a long time.

  On the other hand, the method of mechanically pressing the outer tube against the inner tube with a molding roller or the like as described in the prior art of Patent Document 2 is easy to make the welded shape compact, but it is formed during the second welding. When a roller was used, it was found that the strain remained in the vicinity of the welded portion on the side welded for the first time, causing crack leakage during lighting, which is not suitable.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a compact discharge lamp and a discharge lamp manufacturing method in which distortion hardly remains.

In order to achieve the above object, the discharge lamp of the present invention has an outer tube connected so as to surround an inner tube having a discharge portion, and a first end and a second end are respectively provided on the front end side and the rear end side. An arc tube in which a welded portion is formed; and a socket for inserting and holding the second welded portion of the arc tube, wherein the first welded portion heats the first welded portion formation scheduled portion The second welded portion is formed by pressing the outer tube against the inner tube, and the second welded portion forms a space between the inner tube and the outer tube after forming the first welded portion. It is formed by heating and shrinking the second weld portion formation scheduled portion.

In order to achieve the above object, according to the discharge lamp manufacturing method of the present invention, an outer tube is connected so as to surround an inner tube having a discharge part, and a front end side and a rear end side are respectively 1. An arc tube in which a second weld portion is formed, and a socket for inserting and holding the second weld portion of the arc tube, wherein the first weld portion is to form the first weld portion. After the portion is heated, the outer tube is formed by pressing the outer tube against the inner tube by mechanical means, and the second welded portion forms the first welded portion, and then the inner tube and the The space between the outer tubes is formed in a negative pressure, and the second welded portion formation scheduled portion is formed by a process of heating and shrinking.

  According to the present invention, it is possible to provide a compact discharge lamp and a discharge lamp manufacturing method in which distortion hardly remains.

(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 axial sectional view for explaining a first embodiment of a discharge lamp of the present invention, and FIG. 2 is an overall view of an arc tube.

  The discharge lamp has an arc tube LB as a main part. The arc tube LB has a double tube configuration, and the inner tube 1 is located inside. The inner tube 1 is made of quartz glass having heat resistance and translucency, and has an elongated shape in the tube axis direction of the arc tube LB. A substantially elliptical discharge portion 11 is formed at the approximate center. Plate-shaped pinch seal portions 12 a and 12 b are formed at both ends of the discharge portion 11. Further, cylindrical non-pinch seal portions 14a and 14b are formed at both ends via tapered shrink seal portions 13a and 13b.

  Inside the discharge part 11, a discharge space 15 having a substantially cylindrical shape at the center and a tapered shape at both ends in the tube axis direction of the arc tube LB is formed. The volume of the discharge space 15 is preferably 100 μl or less for a short arc type discharge lamp, and the volume of the discharge space is preferably 10 μl to 40 μl when an application is specified for an automobile headlamp.

  The discharge space 15 is filled with a discharge medium composed of the metal halide 2 and a rare gas. The metal halide 2 is composed of a halide of sodium, scandium, zinc, or indium. In addition, halides such as tin and cesium can be added or substituted. In addition, iodine is most suitable for the halide bonded to these metals. However, bromine, chlorine, or a combination of multiple halides may be used.

  As the rare gas, xenon which has high luminous efficiency immediately after starting and mainly acts as a starting gas is enclosed. The pressure of xenon is preferably 5 atm or more, more preferably 10 to 15 atm at normal temperature (25 ° C.). In addition to xenon, neon, argon, krypton, or the like may be used, or a combination thereof may be used.

  Here, the discharge space 15 essentially does not contain mercury. This “essentially mercury-free” means that it contains no mercury at all, or an amount equivalent to that which is hardly enclosed even when compared with a conventional mercury-containing discharge lamp, for example, less than 2 mg per ml, preferably Shall be allowed even in the presence of mercury of 1 mg or less.

  Mounts 3a and 3b are sealed inside the pinch seal portions 12a and 12b. The mounts 3a and 3b include metal foils 3a1 and 3b1, electrodes 3a2 and 3b2, coils 3a3 and 3b3, and lead wires 3a4 and 3b4.

  The metal foils 3a1 and 3b1 are thin metal plates made of, for example, molybdenum.

  The electrodes 3a2, 3b2 are made of a material mainly composed of tungsten, for example, a material obtained by doping tungsten with a small amount of thorium oxide, such as about 1.0% by weight. One end thereof is connected to the metal foils 3 a 1 and 3 b 1, and the other end is arranged in the discharge space 15 so as to face each other with a predetermined distance between the electrodes. Here, the above-mentioned “predetermined interelectrode distance” is desirably 5 mm or less in terms of the apparent distance in a short arc type lamp, and further about 4.2 mm in the case of being used for an automotive headlamp.

  The coils 3a3 and 3b3 are made of, for example, doped tungsten, and are wound spirally around the electrodes 3a2 and 3b2. The coils 3a3 and 3b3 are sealed in pinch seal portions 12a and 12b in the direction of the discharge space 15 from the end of the foil, avoiding contact portions between the metal foils 3a1 and 3b1 and the electrodes 3a2 and 3b2.

  The lead wires 3a4 and 3b4 are made of, for example, molybdenum, and one end is connected to the end portions of the metal foils 3a1 and 3b1, and the other ends extend outside the pinch seal portions 12a and 12b along the tube axis. . Note that one end of an L-shaped support wire 3c made of nickel is connected to the lead wire 3a4 on the front end side extending to the outside. The other end of the support wire 3c extends in the direction of a socket 6 described later. The portion of the support wire 3c parallel to the tube axis is covered with an insulating sleeve 4 made of ceramic.

  On the outside of the inner tube 1, a cylindrical outer tube 5 is provided substantially concentrically with the inner tube 1 along the tube axis. In the outer tube 5, an oxide such as titanium, cerium, or aluminum is added to quartz glass. As a result, the action of blocking ultraviolet rays occurs, and the melting point is lower than that of the inner tube, making it easier to weld. In addition, a gas or the like can be sealed in the space 51 formed by the inner tube 1 and the outer tube 5, and for example, a rare gas such as nitrogen, neon, argon, xenon, or the like can be sealed or mixed. Is possible. The inner tube 1 and the outer tube 5 are welded and fixed by first and second welded portions 52a and 52b.

  A socket 6 is mounted on the rear end side of the arc tube LB configured as described above. A cylindrical wall 61 is formed in the socket 6. The second welded portion 52b of the arc tube LB is inserted into the cylindrical wall 61. Further, a bottom terminal 7a and a bottom terminal 7b are formed at the bottom and side of the socket 6, respectively. A lead wire 3b4 is connected to the bottom terminal 7a, and a support wire 3c is connected to the bottom terminal 7b. The arc tube LB and the socket 6 are connected by connecting a metal band 81 attached to the outer peripheral surface of the outer end of the outer tube 5 to four metal tongues formed at the opening end of the front end of the socket 6. This is performed by sandwiching them with a piece 82 (two are shown in FIG. 1). In order to strengthen the connection, the contact points of the metal band 81 and the tongue piece 82 may be welded with a laser or the like.

  The discharge lamp constituted by these is arranged with the tube axis in a substantially horizontal state, and by connecting a lighting circuit to the bottom terminal 7a and the side terminal 7b, about 35 W at the stable time, and at the stable power at the start time On the other hand, it is lit at about 75 W, which is twice or more.

  Here, the welding state of the inner tube 1 and the outer tube 5 will be described in detail.

  The first and second welded portions 52a and 52b that weld and fix the inner tube 1 and the outer tube 5 are formed at both ends of the arc tube LB. Specifically, the first welded portion 52a is located on the distal end side of the discharge lamp, and the outer tube 5 is welded so as to straddle the shrink seal portion 13a and the non-pinch seal portion 14a of the inner tube 1. Thus, the boundary region 53a is square. The second welded portion 52b is located on the rear end side of the discharge lamp, and is welded so that the outer tube 5 extends to the end of the non-pinch seal portion 14b of the inner tube 1, and the boundary region 53b is a curved surface. Is. As can be seen from FIGS. 1 and 2, the second welded portion 52 b has a substantially flat outer peripheral surface. Here, “substantially flat” means that there is almost no unevenness on the surface, and the height difference W of the outer peripheral surface is within 0.5 mm.

  The welded state of the inner pipe 1 and the outer pipe 5 of the first and second welded parts 52a and 52b may be mixed with each other, and there may be almost no boundary between them, or there may be a boundary. good.

  Next, the formation method of the 1st, 2nd welding part is demonstrated using FIG. 3 and FIG. In addition, about the formation process of the inner tube | pipe 1, since it is substantially the same as the conventional method, it abbreviate | omits.

  In the step of forming the first welded portion 52a, first, as shown in FIG. 3 (a), the inner tube 1 is arranged at the approximate center in the outer tube 5, and then the portion on the rear end side of the arc tube LB is held. The first welded portion formation scheduled portion 52a ′ (the outer tube 5 near the shrink portion 13a) is heated and melted by the burner 92 while being held by the means 91. Then, as shown in (b), the outer tube 5 of the first welded portion formation scheduled portion 52 a ′ melted by using the forming roller 93 is pressed against the inner tube 1. For example, the forming roller 93 is configured to be attached to a donut-shaped turntable, and the forming roller 93 rotates around the first welded portion formation scheduled portion 52a 'by the rotation of the turntable. Therefore, as shown in (c), it is possible to form the first welded portion 52a having a substantially uniform thickness and a flat outer peripheral surface.

  In the step of forming the second welded portion 52b, first, as shown in FIG. 4A, the front and rear of the second welded portion formation scheduled portion are held by the first and second holding means 95a and 95b. Specifically, the first holding means 95a holds the outer tube 5 portion on the distal end side of the arc tube LB, and the second holding means 95b holds the opening portion of the outer tube 5 on the rear end side of the arc tube LB. After being held by the first and second holding means 95a and 95b, the space 51 is evacuated from the opening of the outer tube 5 of the second holding means 95b, and the inside is made a nitrogen atmosphere of 76 torr or less. That is, the space 51 has a negative pressure.

  Thereafter, as shown in (b), the second welded portion formation scheduled portion 52b '(non-pinch seal portion 14b) is heated and melted by the burner 96. When the second welded portion formation scheduled portion 52 b ′ is heated by the burner 96, the space 51 has a negative pressure, and thus the melted outer tube 5 shrinks to the inner tube 1. At the same time as the shrinkage of the outer tube 5 starts, the first holding means 95a is moved in the direction of the anti-discharge portion 11, and the second welded portion 52b is pulled in the tube axis direction. By the pulling process while shrinking, the outer peripheral surface of the second welded portion 52b can be made substantially flat as shown in (d). And if an unnecessary part is cut | disconnected, the arc tube LB will be completed. The outer peripheral surface of the second welded portion 52b can be adjusted by changing the heating temperature, the pulling speed, and the pulling distance d by the burner 96. Incidentally, in this embodiment, the pulling distance d is about 3.0 mm. Here, unlike the patent document 3, the series of steps described above has a structure in which the burners 92 and 96 and the molding roller 93 rotate around the lamp while the lamp is fixed. Therefore, the pulling process can be easily performed.

  Here, as shown in FIG. 5, the test which forms the 1st, 2nd welding part by various means and order was performed, and generation | occurrence | production of leak and compactness were test | inspected about each. The “leak” is determined when 70 torr of nitrogen is sealed in each discharge lamp space 51 and when the discharge lamp is turned on, the nitrogen leaks. In addition, the compactness is determined from the ease of mounting when the socket 6 is mounted on the rear end side, and the protruding length of the arc tube LB from the reference surface of the socket 6 as in FIG.

  As a result, Example 1 was the most excellent with respect to leakage, followed by Example 2 and Comparative Examples 2 and 5, and Comparative Examples 1, 3, and 4 were very likely to cause leakage. . This is largely related to the fact that distortion remained in a lamp that was prone to leak. That is, when each of the lamps was inspected for distortion using a sensitive color plate method (a method for identifying the state of distortion occurring in the glass by the optical path difference of light), Distortion was confirmed on the first welded portion side. This strain was found to be caused by performing the second welding using a mechanical means such as a molding roller while holding the first welding portion side. On the other hand, almost no distortion was observed in the lamps of Examples 1 and 2 and Comparative Examples 2 and 5 in which the second welding was performed by the shrink seal. In Example 1, it was considered that the leak was most unlikely to occur because the inner and outer tubes of the second welded portion 52b were brought into close contact with each other and the gap was filled by performing the pulling process while shrink-sealing.

  Regarding compactness, Example 1 and Comparative Example 4 were the best, followed by Example 2 and Comparative Example 3, and Comparative Examples 1, 2, and 5 lacked compactness. When the welded part is formed by shrink seal, the contact length of the actual inner and outer pipes tends to be smaller than the case of forming the welded part by the forming roller, and manufacturing variations are likely to occur. . Therefore, a sufficient welding length is required to ensure the reliability of welding, and it is difficult to make it compact. However, the rear end side of the arc tube LB can accommodate the welded portion in the socket, so that any method is used without affecting the compactness. That is, Examples 1 and 2 and Comparative Examples 3 and 4 in which the welded portion by the molding roller is on the tip side are compact, and Comparative Examples 1, 2, and 5 in which the welded portion by the shrink seal is on the tip side are lacking in compactness. It became the result.

  Therefore, Examples 1 and 2 were excellent from the viewpoint of leakage and compactness, and it was found that the effects of the production method of the present invention were high.

  In the case of a discharge lamp that does not enclose mercury as in the present embodiment, the temperature of the metal foils 3a1 and 3b1 tends to increase as compared with a discharge lamp containing mercury. Therefore, in order to improve the durability of the metal foils 3a1, 3b1, a design is generally made to increase the distance between the metal foils 3a1, 3b1 and the discharge part 11, but this design results in a long tip side, which is preferable. Absent. Therefore, it is desirable to apply the present invention to a discharge lamp that does not enclose mercury in order to realize compactness comparable to that of a discharge lamp containing mercury.

  In the case of a discharge lamp that does not contain mercury, xenon is sealed in the discharge space 15 at a high pressure. When xenon is sealed at a high voltage, the discharge start voltage becomes very high, and a high voltage pulse of about 20 kV is required to start the discharge. Therefore, in a discharge lamp that does not enclose mercury, the application of a high-pressure pulse at the time of start-up causes a pulse leak between the lead wire 3b4 and the support wire 3c. For this pulse leak, there are measures such as improving the structure of the socket 6, and our company has proposed to increase the thickness of the cylindrical wall 61 in the socket 6 (Japanese Patent Application No. 2006-463). However, these measures are accompanied by a demerit that the degree of freedom inside the socket 6 is reduced. For example, in the present embodiment, the space in which the second welded part 52b can be inserted is reduced, and the distance between the outer peripheral surface of the second welded part 52b and the cylindrical wall 61 is only about 0.7 mm. When the welded portion on the rear end side of the arc tube LB is inserted into such a socket 6, in Example 2 in which the welded portion on the rear end side is formed by a shrink seal, there is a problem that the welded portion cannot be inserted well. There is. On the other hand, in Example 1, since the outer peripheral surface is managed to be substantially flat, it can be concluded that the arc tube LB of Example 1 is the best if the above-mentioned problem does not occur.

  It is possible to determine by what means the first and second welds 52a and 52b are formed. For example, when the welded portion is formed by mechanical means such as a molding roller, the outer tube 5 is strongly pressed against the inner tube 1 by the surface, so that the surface shape is transferred. Therefore, the outer peripheral surface of the welded portion has a substantially flat shape. Further, depending on the forming roller, a square portion like the boundary region 53a in FIGS. On the other hand, when the welded portion is formed only by the shrink seal, the welded portion 52b has a gently curved shape. Further, since the cross section is difficult to be a perfect circle (for example, a shape close to an ellipse), the thickness of the welded portion tends to be uneven and the outer peripheral surface tends to be uneven. On the other hand, when the welded portion is pulled while shrink-sealing as in the present embodiment, the boundary region is curved as in the case of only the shrink seal, but the outer peripheral surface of the welded portion is substantially flat.

  It is also possible to determine in what order the first and second welds 52a and 52b are formed. For example, if one is formed with a forming roller and the other is formed with a shrink seal from the weld shape, if the second welding is performed with the forming roller, the distortion should be confirmed on the welded portion side where the shrink seal is performed as described above. Can do. On the other hand, when the second weld is pulled while shrinking or shrink-sealing, no distortion is observed near either welded part.

  From the above, it is possible to objectively estimate what welding means is used to connect the inner pipe and the outer pipe and in what order.

  Therefore, in the present embodiment, the arc tube LB of the discharge lamp causes the first welded portion 52a to press the outer tube 5 against the inner tube 1 after heating the first welded portion formation scheduled portion 52a ′. The second welded portion 52b is formed by applying a negative pressure to the space 51 between the inner tube 1 and the outer tube 5 and heating and shrinking the second welded portion formation scheduled portion 52b ′. Therefore, since it is difficult for distortion to remain, a discharge lamp in which leakage does not easily occur even when gas is sealed in the space 51 or the like and the length of the arc tube LB from the socket 6 is compact can be realized.

  At that time, after the second welded portion 52b is made negative in the space 51 between the inner tube 1 and the outer tube 5, the second welded portion formation scheduled portion 52b ′ is heated and shrunk in the tube axis direction. Since the outer peripheral surface of the second welded portion 52b can be made substantially flat, specifically, the height difference W can be made within 0.5 mm, for example, a discharge lamp that does not enclose mercury Thus, it is possible to reliably insert and hold the socket 6 with a low degree of freedom inside the socket 6. Further, the adhesion between the inner and outer tubes is improved, and it is possible to make it difficult for leaks to occur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial cross-sectional view for explaining a first embodiment of a discharge lamp according to the present invention. FIG. The figure for demonstrating the manufacturing method of a 1st welding part. The figure for demonstrating the manufacturing method of a 2nd welding part. FIG. 6 is a diagram showing a result of conducting a test for forming first and second welded portions in various means and order, and inspecting the occurrence of leak and compactness for each.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner tube 11 Discharge part 12a, 12b Pinch seal part 13a, 13b Shrink part 14a, 14b Non-pinch seal part 15 Discharge space 2 Metal halide 3a, 3b Mount 3a1, 3b1 Metal foil 3a2, 3b2 Electrode 3a3, 3b3 Coil 3a4, 3b4 Lead wire 3c Support wire 4 Insulating tube 5 Outer tube 51 Spaces 52a, 52b First and second welded portions 52a ′, 52b ′ First and second welded portion formation planned portions 53a, 53b Boundary region 6 Socket 61 Cylinder Wall 7a Bottom terminal 7b Side terminal 81 Metal band 82 Tongue piece 93 Forming rollers 95a, 95b First and second holding means

Claims (3)

An outer tube is connected so as to surround an inner tube having a discharge part, and an arc tube having first and second welds formed on the front end side and the rear end side thereof, and a first tube of the arc tube A socket for inserting and holding the two welds;
The first welded portion is formed by pressing the outer tube against the inner tube after heating the first welded portion formation scheduled portion,
The second welded portion, after forming the first welded portion, creates a negative pressure in the space between the inner tube and the outer tube, and heats and shrinks the second welded portion formation scheduled portion. A discharge lamp characterized by being formed by the following.   The second welded portion is formed by pulling in the tube axis direction while heating and shrinking the second welded portion formation scheduled portion after making the space between the inner tube and the outer tube a negative pressure. The discharge lamp according to claim 1, wherein An outer tube is connected so as to surround an inner tube having a discharge part, and an arc tube having first and second welds formed on the front end side and the rear end side thereof, and a first tube of the arc tube A socket for inserting and holding the two welds;
The first welded portion is formed by a step of pressing the outer tube against the inner tube by mechanical means after heating the first welded portion formation scheduled portion,
The step of forming the first welded portion, then forming a negative pressure in the space between the inner tube and the outer tube, and heating and shrinking the second welded portion formation scheduled portion after the second welded portion forms the first welded portion. A method of manufacturing a discharge lamp, characterized by comprising:

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