JP2007220350A - High-pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems in a conventional configuration: loss in a terminal portion increases when formation of an electric discharge lamp of 50 W or less is achieved, thereby decreasing its efficiency; purity of a gas sealed inside a discharge tube is deteriorated when the gas is sealed; and miniaturization that deserves electric power can not be achieved, thereby causing enlargement. <P>SOLUTION: Translucent ceramics constituting the discharge tube 2 has a cylindrical electrode-mounting part 2c formed at either end of a likewise cylindrical light-emitting part 2b. A diameter of one end of a metal pipe 3 capable of insertion-coupling with the electrode-mounting part is narrowed down beforehand so as to be insertion-coupled with electrode shafts 5b constituting a part of an electrode structure, the translucent ceramics and the metal pipe 3 are fused with a compound 4 made of cermets or ceramics as an adhesive, and the electrode shafts and the metal pipe are sealed by welding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a relatively small discharge lamp whose power consumption is in the vicinity of 50 W or less, such as a metal halide discharge lamp used as a light source of a vehicle headlight.

  FIG. 5 shows an example of the configuration of a conventional discharge lamp 90 of this type, in particular, the configuration of the electrode portion. First, a substantially cylindrical opening is formed at both ends of the arc tube 91 formed of transparent ceramics. An end portion 92 which is a portion is provided at both ends, and the end portion 92 is closed by an end plug 93 made of aluminum and tungsten.

  In the end plug 93, a molybdenum tube 94 is directly sintered and fitted. Subsequently, after a molybdenum pin 96 having a projecting portion 97, a center electrode 98, a filament 99 and the like attached in the molybdenum tube 94 is inserted into the molybdenum tube 94 and exhausted, filled with gas, and the like, Laser welding is performed in a circumferential direction as indicated by an arrow L at a portion where the molybdenum tube 94 and the molybdenum pin 96 protrude from the end plug 93 to the outside, and sealing is performed.

  At this time, the molybdenum tube 94 and the molybdenum pin 96 on either side are sealed in advance, and the other side of the molybdenum tube 94 and the molybdenum pin 96 on the other side that has not been sealed yet. The above-described exhaust and gas filling are performed.

  Further, in the high-pressure discharge lamp 80 shown in FIG. 6, a metal pipe 82 is hermetically connected to both ends of the translucent ceramic container 81 and the electrode 83 is passed through substantially the center of the metal pipe 82. The metal pipe 82 and the electrode 83 are joined with a metal brazing material 84.

Further, the high-pressure discharge lamp 70 shown in FIG. 7 is a general sealing method, and is heated until a metal 72 (here, an electrode) and a ceramic tube 73 (such as a discharge tube) to which the cermet 71 is to be melted and bonded become familiar. The two are welded together.
Japanese Patent Laid-Open No. 06-318435 JP 2004-055149 A Japanese Patent No. 3209752

  However, in the sealing method of Patent Document 1 described above, the discharge chamber 91a of the discharge tube 91 and the sealing portion are relatively close to each other, and the sealing portion includes the end plug 93, the molybdenum tube 94, Since it is formed using a metal member with relatively good thermal conductivity, such as a molybdenum pin 96, for example, in a high pressure discharge lamp with a low power consumption of about 45 W, such as for a light source of an automobile headlight. There is a high possibility that the heat loss from the terminal portion increases, for example, causing a problem that a desired light amount cannot be obtained.

  Further, in the sealing method shown in Patent Document 2, a large amount of the metal brazing material 84 must be used at the time of sealing, so that the gas generated at the time of brazing enters the translucent ceramic container 81. As a result, the inside of the discharge tube is contaminated, and as a result, the lamp life may be lost, or the starting voltage may vary.

  Furthermore, in the thing of patent document 3, if it heats until an electrode and a ceramic tube become accustomed uniformly, a heating amount will become a thing for a long time and heat will be carried out to the other electrode which is not heated. It will be affected. As a result, the enclosed material evaporates. In addition, in order to prevent the influence of heat up to the other electrode, it is necessary to provide an appropriate distance between the two electrodes so that they are not affected by each other. This is a difficult problem.

  The present invention provides, as a specific means for solving the above-described conventional problems, a discharge lamp having a discharge electrode, a light-transmitting ceramic, and an enclosed filling gas, and the light-transmitting ceramic constituting the discharge tube. The electrode attachment part which forms an opening part in the light emitting part and both ends is formed, and the electrode part provided with a metal pipe inside the electrode attachment part is hermetically attached to the electrode attachment part. The part provides a discharge lamp characterized in that the outer diameter of one end is substantially the same as the inner diameter of the opening, and the other end is a narrow-diameter part that fixes the electrode. Even in a small discharge lamp, the thermal efficiency can be improved, and the manufacturing method of the present invention can reduce the size of the discharge lamp itself, thereby solving the problem.

  According to the present invention, a gap is formed between the electrode shaft and the metal pipe for holding the electrode shaft in the discharge tube, and the connection between the electrode shaft and the metal pipe is made from the position where the discharge is performed. By adopting a shape that is performed at a remote location, the heat transfer from the inside of the discharge tube to the outside is reduced, the thermal efficiency is improved, and it is possible to provide a brighter high-pressure discharge lamp with the same power consumption. Play.

  Below, this invention is demonstrated in detail based on embodiment shown in a figure. FIG. 1 is a side view of a high-pressure discharge lamp 1 according to the present invention, and FIG. 2 is a cross-sectional view of the same high-pressure discharge lamp 1. Also in the present invention, the discharge tube 2 is formed in a substantially pipe shape by translucent ceramics, as in the conventional example.

  In this embodiment, the through hole 2a passing through the discharge tube 2 in the direction of the axis X (see FIG. 2) has the same inner diameter over the entire length of the discharge tube 2, and this inner diameter is a metal pipe described later. The outer diameter of 3 is an inner diameter that can be inserted with an appropriate gap.

  A compound 4 made of cermet or ceramics is applied to the outer diameter of the metal pipe 3 or an appropriate portion of the through-hole 2a of the discharge tube 2 as a sealing adhesive in a predetermined range, and the through-hole 2a and the metal pipe 3 It is heated and melted until it becomes familiar, and both ends are hermetically sealed. Therefore, the central part of the through hole 2a where the metal pipe 3 is not attached becomes the light emitting part 2b, and the part where the metal pipe 3 is attached becomes the electrode attaching part 2c. The metal pipe 3 is made of a refractory metal such as tantalum, tungsten, or molybdenum.

  Thus, after the metal pipes 3 were attached to both ends, the tip electrode portion 5a and the electrode shaft 5b were formed of the same high melting point metal as the metal pipe 3, for example, tantalum, tungsten, molybdenum, etc. The electrode 5 is inserted into the inner diameter of the metal pipe 3, and the outer diameter of the metal pipe 3 is appropriately narrowed down by machining or the like so that the inner diameter can be fitted with the outer diameter of the electrode shaft 5b. A diameter portion 3a is formed.

  The narrow-diameter portion 3a formed at this time is partially formed with protrusions 3b as shown in an enlarged view in FIG. 3, and the electrode shaft 5b is temporarily sealed by the narrow-diameter portion 3a. However, there is still a gap through which gas or the like flows, and the gap can be used to exhaust, replace with gas, or seal metal halide gas into the discharge tube 2. .

  Furthermore, the force with which the projection 3b supports the electrode shaft 5b is also appropriate, and by allowing the electrode shaft 5b to be moved back and forth by applying a force from the outside, the gap between the tip electrode portions 5a is maintained. If the distance can be adjusted, the accuracy of the high-pressure discharge lamp 1 to be obtained can be further improved, the uniformity can be improved, and the quality can be made uniform.

  For forming the narrow-diameter portion 3a, it is desirable to draw the electrode shaft 5b so as to have the substantially same diameter, but press caulking can also be used. In the case where a refractory metal such as molybdenum is used as the metal pipe material, it is desirable to perform the heating under a temperature that does not cause recrystallization of the metal pipe when the narrow diameter portion 3a is formed. The narrow-diameter portion 3a may be formed on either side of the discharge tube 2 for temporary sealing, and the other side may be completely sealed without temporary sealing.

  In the above description, the narrow pipe 3a is formed in the metal pipe 3 and then the exhaust gas and the gas are replaced. However, the present invention does not limit the above procedure. The narrow diameter portion 3a may be formed in a gas atmosphere, and in this case, since the gap between the metal pipe 3 and the electrode shaft 5b is large, the atmosphere in the discharge tube 2 is replaced with the gas. There is an advantage that can be done quickly.

  As described above, by any method, after the substance of the prescribed type and amount is sealed in the discharge tube 2, laser welding between the metal pipe 3 and the electrode shaft 5b is performed in the narrow diameter portion 3a. Thus, complete sealing is performed, and the high-pressure discharge lamp 1 according to the present invention is completed. In the above description, the example in which the metal halide gas is sealed inside through the temporarily sealed gap of the electrode shaft 5b has been described. However, before the temporary sealing is performed, an enclosure such as a metal halide in a solid or liquid state is used. Can be introduced into the interior, followed by temporary sealing. For example, metal iodide is used as the metal halide.

  Here, according to the present invention, in the small high-pressure discharge lamp 1 having this type of rating of around 45 W, in order to improve the performance, for example, the distance between the tip electrode portions 5a, gas, or metal iodide is used. It is required that the accuracy of each part, such as the amount of addition, is high, and optimization of the terminal loss in the sealing part is also required.

  Therefore, according to the configuration of the present invention, the thickness of the metal pipe 3 can be easily changed. For example, the shape of the discharge tube 2 of the small high-pressure discharge lamp 1 is changed or the internal gas is changed. Therefore, optimization setting becomes easy.

  Further, as described above, the portion of the narrow-diameter portion 3a can be adjusted in size between the two tip electrode portions 5a before welding, and the variation between the individual small high-pressure discharge lamps 1 is reduced. This facilitates mass production of the compact high-pressure discharge lamp 1 with uniform performance.

  Furthermore, by welding at the narrow diameter portion 3a, it is possible to extremely reduce the entry of impure gas (metal vapor) generated during metal welding into the discharge tube 2, thereby shortening the service life, etc. The occurrence of characteristic deterioration can be suppressed. Also, since the welding time can be short, in order to reduce problems caused by heat applied to the gas, electrodes, etc. in the discharge tube 2, the discharge tube 2 must be used longer than necessary, and a small high-pressure discharge is required. It is possible to prevent the lamp 1 from becoming larger than necessary.

  FIG. 4 shows another embodiment of the present invention. In the present invention, the shape of the discharge tube 21 is such that the light emitting portion 2b has a large diameter as shown in the figure, and the metal pipe 3 and the metal pipe 3 are fitted. The portion of the through-hole 2a of the discharge tube 21 to be combined, that is, the portion of the electrode mounting portion 2c has the same diameter as that of the previous embodiment. Therefore, the same parts can be adopted without changing the parts other than the discharge tube 21.

  As described above, according to the present invention, a compact high-pressure discharge lamp 1 having a small size of 50 W or less and therefore requiring high assembly accuracy can be easily produced, and productivity is improved. It is possible to achieve excellent effects in improving quality and promoting cost reduction. In addition, it is free to apply a technique used in this type of small high-pressure discharge lamp, such as applying a phosphor on the inner surface of the discharge tube to obtain a desired emission color.

1 is a side view showing an embodiment of a small high-pressure discharge lamp 1 according to the present invention. It is a sectional view of small high-pressure discharge lamp 1 according to the present invention. It is sectional drawing which expands and shows the principal part of another embodiment of the narrow diameter part of the small high-pressure discharge lamp 1 which similarly concerns on this invention. It is sectional drawing which similarly shows another embodiment of the small high-pressure discharge lamp 1 which similarly concerns on this invention. It is sectional drawing which shows a prior art example by the principal part. It is sectional drawing which shows another prior art example. It is sectional drawing which shows another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Small high pressure discharge lamp 2, 21 ... Discharge tube 2a ... Through-hole 2b ... Light emission part 2c ... Electrode attaching part 3 ... Metal pipe 3a ... Narrow diameter part 3b ... Protrusion 4 ... Compound 5 ... Electrode 5a ... Tip electrode part 5b ... Electrode shaft

Claims (3)

A discharge lamp having a discharge electrode, a light-transmitting ceramic, and an enclosed filling gas,
The translucent ceramic constituting the discharge tube has a light emitting portion and an electrode mounting portion having openings at both ends, and the electrode mounting portion has an electrode portion having a metal pipe inside the electrode mounting portion. Installed airtight,
The discharge lamp according to claim 1, wherein an outer diameter of one end of the electrode portion substantially coincides with an inner diameter of the opening, and the other end is a narrow-diameter portion that fixes the electrode. The electrode part includes a metal pipe made of a refractory metal material and a discharge electrode,
The metal pipe has a cylindrical shape in which the outer diameter of one end is substantially the same as the inner diameter of the electrode mounting portion, and the other end is a narrow-diameter portion having a protrusion on the inner surface,
The electrode includes an electrode rod and a tip electrode portion having a diameter larger than that of the electrode rod, and the electrode rod and the metal pipe are welded to each other. A method of manufacturing a discharge lamp having a pair of opposed discharge electrodes, translucent ceramics, and an enclosed filling gas,
a) preparing a translucent ceramic having openings at both ends, inserting a metal pipe into each of the openings and fixing the metal pipe to the ceramic;
b) After inserting the electrode into a metal pipe having a protrusion inside, the diameter of one end side of the metal pipe is reduced to form a narrow diameter portion, and the protrusion comes into contact with the electrode to temporarily A diameter-reducing step for sealing;
c) a filling gas filling step of filling a filling gas from the gap between the protrusion and the electrode inside the ceramic after attaching the electrode parts that have undergone the pipe fixing step and the diameter reduction step to both ends of the translucent ceramic; ,
d) heating the temporarily-sealed narrow-diameter portion to perform complete sealing;
A method for manufacturing a discharge lamp, comprising:

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